Conference Programme

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Overview
Session
D-05: Poster Session
Time:
Tuesday, 20/Jun/2017:
4:00pm - 6:15pm

Location: Foyer

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Presentations
Poster

A Novel Proton Electrolyte Membrane to Eliminate Ionic Cross-over for Redox Flow Battery System

Mei Lin CHNG, Lijun LIU, Ming HAN

Temasek Polytechnic, Singapore

Vanadium redox flow battery (VRB) has been acknowledged as one of the leading electrochemical energy storage systems for large scale energy storage due to its long cycle life, flexible design, deep-discharge capability, and low cost in energy storage. Even for the most popular V/V flow battery which utilise costly commercial Nafion membrane, swelling issues leading to serious water transfer across the membrane during the charge–discharge processes of VRB is still unavoidable. It is therefore important to understand how to minimize, or even eliminate, this effect to reduce the electrochemical energy loss and energy efficiency reduction of the battery.

An especial matrix structure synergizing the properties of both hydrophilic and hydrophobic polymer segments was chosen to form the resultant ion exchange membrane. The hydrophilic polymer segment containing sulfonic acid group provide the proton conductivity while the hydrophobic fluorine-containing polymer was chosen as the structural component because of its good mechanical strength and chemical stability. The series of copolymers with different monomer unit ratios was synthesized via free radical solution polymerization. Comparing with post-sulfonated materials like SPEEK, sulfonic acid group in this study is more stable during operation of flow battery. Preliminary performance shows that the energy efficiency of the battery can reach 80%@50mA/cm². The capacity drops only 6% after 110 runs@50mA/cm². It is a promising membrane for flow battery having comparable energy efficiency with Nafion 117 with less crossover of vanadium ions.


Poster

All-solid-state Lithium ion Batteries using Li6PS5Br:LiTFSI Electrolyte

Prasada Rao RAYAVARAPU, Stefan ADAMS

National University of Singapore, Singapore

Rechargeable all-solid-state, Li-ion batteries are attractive power sources for applications like “smart” cards and medical implants and can work at room as well as elevated temperatures. They need a Li-fast ion conductor as the solid electrolyte. The purpose is to improve safety and stability over conventional batteries with liquid electrolyte. Finding a suitable solid electrolyte with high ionic conductivity is a pivotal issue for building practical solid-state batteries. Many research groups including us focus in developing such high conducting solid electrolytes. There have been numerous developments on materials such as lithium rich sulfide glasses as solid electrolyte. However, limited current density remains a major impediment in these electrolyte systems. Argyrodites form a class of chalcogenide structures related to the mineral Ag8GeS6, which includes various fast Ag+ or Cu+ ion conductors such as A7PS5X (A = Ag+, Cu+). Recently, many groups could synthesize the analogue cubic Li+ argyrodytes with formula Li6PS5X (X = Cl, Br, I), Li7PS6 and Li10GeP2S12. 7Li-NMR relaxation and impedance experiments find an intrinsic local lithium mobility of the Li-argyrodite crystals as high as 10−3 S/cm at room temperature close to the mobility in liquid electrolytes comprising of LiPF6 salt in various carbonates. With such high lithium mobilities, these materials may be ideal for use as solid electrolytes in lithium ion batteries. We prepared the argyrodite-type Li6PS5X (X = Cl, Br) using mechanical milling followed by annealing of the samples. The batteries prepared using these solid electrolytes suffer major capacity fading due to the electrode electrolyte interface resistance after few cycles. More over preparation of thin pellets about 100 μm is difficult. To overcome such problems we prepared Li6PS5Br:LiTFSI:PVDF with 85:10:5 weight ratios. Monoglyme is used as dispersant for the preparation. Nyquist plots for both Li6PS5Br:LiTFSI and Li6PS5Br indicated that the composite has more ionic conductivity ~9×10-4 S/cm when compared with Li6PS5Br which is ~7×10-4 S/cm.


Poster

Aluminium and Magnesium Insertion in Sulfide Spinels: A First-Principles Study

Vadym KULISH, Sergei MANZHOS

National University of Singapore, Singapore

Wide-spread use of hybrid electric vehicles and grid integration of renewable sources require reliable and affordable energy storage. Currently, Li-ion batteries provide the highest energy density among commercial battery technologies, but their long-term and large-scale application faces some serious concerns, such as limited lithium resources and their increasing price. Among the non-Li technologies, Mg and Al-ion batteries provide an attractive energy solution with the benefits of low cost, elemental abundance, environment-friendly chemistry and multivalency. However, the practical development of electrode materials is hindered by slow Mg/Al diffusion and undesirable conversion reactions. Despite the recent progress, identification of suitable cathode materials is still a challenge.

In search of potential electrode materials for Al and Mg-ion batteries, we computationally screen a range of sulfides with spinel crystal structure. We evaluate the effect of transition-metal substitution (TM=Ti, Cr, Mn, Fe, Co, Ni) on the key properties determining electrode performance. We systematically calculate the thermodynamic stability, average voltage, binding energy, volume expansion, and Al/Mg diffusion for all compounds. Ti2S4 has been previously shown to operate as a cathode with voltages 0.9-1.2 V and capacities 200 mAh/g in Mg-ion batteries. The low voltage of Ti2S4 implies a low energy density, and diffusion barriers about 0.70 eV imply that rate capability, although improved over the layered counterpart, remains limited. Our calculations show that it is possible to improve the voltage and rate performance by TM substitution. Specifically, the Ni-based spinel shows a relatively high Mg insertion voltage of 1.71 V and low Mg diffusion barrier of 0.46 eV, and thus is a promising candidate cathode material for Al and Mg-ion batteries.


Poster

Aqueous Lithium-Metal Chloride Rechargeable Battery

Shinya WATANABE, Yoshinori MORITA, Osamu YAMAMOTO, Yasuo TAKEDA, Nobuyuki IMANISHI

Mie University, Japan

Electric vehicles with rechargeable batteries are considered to reduce CO2 emissions and the consumption of fossil fuels, because the total energy conversation efficiency of batteries is higher than that of internal combustion (IC) engines. However, the driving range of commercialized EVs with current lithium ion batteries is much lower than that of vehicles with IC engines, because specific energy density of lithium ion batteries is low compared to IC engines. New battery systems with higher theoretical energy densities have been proposed, such as lithium-sulphur and lithium-air rechargeable batteries. However, they have several inherent problems in the cell chemistry and still need breakthroughs for further development.

Lithium metal anode and liquid cathode couples have a potential ability to develop a rechargeable battery with high specific energy and power density, because a high areal specific capacity of the liquid cathode can be realized at a high current density due to a high diffusion rate of reaction ions in the catholyte. Here we demonstrate the feasibility of a novel aqueous lithium rechargeable battery with an aqueous solution of MCl2 (M = Fe, Co, Ni, Cu and Zn) using a high lithium-ion conducting solid electrolyte of Li1.4Al0.4Ge0.2Ti1.4(PO4)3 film as the separator between lithium anode and the aqueous catholyte.

Li/MCl2 (M=Co, Ni, Zn) cells were successfully charged and discharged, while the Li/MCl2 (M=Fe, Cu) cells were discharged but could not be charged, because FeCl2 and CuCl2 reacted with lithium ions to produce an insoluble compound. The Li/CoCl2, Li/NiCl2, and Li/ZnCl2 cells showed high reversible capacities at 60 °C and 4.0 mA cm-2. The estimated specific energy density calculated using the mass of the cell components was 574 Wh kg-1 for the Li/NiCl2 cell, which is ca. 1.7 times higher than that of the conventional lithium ion batteries.


Poster

Array of Nanosheets Render Ultrafast and High Capacity Na-ion Storage by Tunable Pseudocapacitance

DongLiang CHAO, Ze Xiang SHEN

Nanyang Technological University, Singapore

Sodium ion battery (SIB) is a potentially low-cost and safe alternative to the prevailing lithium ion battery (LIB) technology. It is a great challenge to achieve fast charging and high power density for most SIB electrodes because of the sluggish sodiation kinetics. Here we demonstrate a high-capacity and high-rate SIB anode based on ultrathin layered SnS nanostructures, in which a maximized extrinsic pseudocapacitance contribution is first identified and verified by kinetics analysis. The graphene foam supported SnS nanoarray SIB anode delivers a high reversible capacity of ~1100 mAh g-1 at 30 mA g-1 and ~420 mAh g-1 at 30 A g-1, which even outperforms its Li ion storage performance. The surface-dominated redox reaction rendered by our tailored ultrathin SnS nanostructures may also work in other layered materials for high-performance Na ion storage.


Poster

Catalyst Engineering Towards High Energy Density SnX2 (X = O, S, Se) Lithium-ion Battery Anode Through Reversible Conversion and Alloying Process

ZhiXiang HUANG1,2, Ye WANG1, Hui Ying YANG1

1Singapore University of Technology and Design, Singapore; 2Airbus Group Innovations Singapore, Singapore

Tin-based anode are well poised to replace traditional graphite anode materials in Lithium-ion Batteries (LIBs) owing to its high energy density and suitable discharge potential. However, lithiation of pure Sn undergoes an alloy process that results in significant volume change leading to poor stability. In this regard, SnX2(X = O, S, Se) provides more stable cycling owing to presence of Li2X that is able to buffer volume changes during Li-Sn alloy. Li2X is formed in the initial lithiation of SnX2 through a conversion process that also produces Sn (equation 1). In subsequent lithiation, Sn alloys reversible with Li+ (equation 2).

Initial Conversion: SnX2 + 4 Li++ 4e- -> Sn + 2 Li2X (X = O, S, Se) (1)

Alloy-Dealloy: Sn + 4.4Li+ + 4.4e-<-> Li4.4Sn (2)

From the above equations, it can be observed that 4 moles of Li is lost in the initial conversion reaction. This results in poor initial coulombic efficiency (ICE) in SnX2 anode materials. Hence, if equation 1 is made reversible, not only will the ICE be improved, the reversible decomposition of Li2X increases lithium storage of SnX2 significantly (8.4 mol from 4.4 mol Li); this results in a substantial increase in theoretical capacity of SnX2 (e.g. SnO2: 1493 from 872 mAh g-1). In our recent work, we introduced catalyst engineering in an attempt to promote the reversible decomposition of Li2X in SnX2/carbon based nanocomposites. In SnO2/rGO nanocomposites, we demonstrated the use of GeO2 and Co3O4 as catalyst while MoS2 was used in SnS2/3D graphene. In these instances, the catalyst were successfully able to induce reversible decomposition of Li2X, leading to significant capacity enhancements in the nanocomposites. In SnSe2/rGO, Sn nanoparticles released from SnSe2 acted as the catalyst. Hence, these examples demonstrate a clear direction towards high energy density SnX2 based anode for LIBs.


Poster

Cycle Performance and Electrochemical Diagnostics of Commercial High-Energy Lithium-Ion Batteries

Joongpyo SHIM1, Gyungse PARK1, Yoojin LEE1, Euney JUNG2, Hong-Ki LEE3, Hyung-Ryul RIM3, Heesuk JEONG3

1Kunsan National University, South Korea; 2Ruby Co. Ltd., South Korea; 3Fuel Cell Regional Innovation Center, Woosuk University, South Korea

Lithium-ion batteries have been intensively studied for application in electric vehicles (EV) and energy storage systems (ESS) because of their high-power and energy densities. Extensive research on the rechargeable lithium-ion battery has been carried out with the goal of the development of power sources. We are focusing on the development of a high-energy battery for ESS and our group is studying the cycling performance and power fade mechanism of various battery chemistries during constant current cycling over 100% of the cell capacity. Part of our goal is to elucidate differences in the capacity and power fade mechanisms during long cycles. In this work, we report on the performance of cells, containing electrodes designed for high-energy operation, cycled at 100%DOD at 25oC. In order to aid in identification of failure mechanisms, several diagnostic techniques were used to analyze cell components. The performance of 53Ah pouch cells during extended (1000 cycles) room temperature cycling over different capacity ranges was examined. The capacity fade was monitored during different depth of discharge cycling. As before, the cell components were examined with electrochemical diagnostics to help to define the performance fade mechanisms. The overall cell impedance increased with cycling, although the ohmic resistance from the electrolyte was almost constant. From electrochemical analysis of each electrode after cycling, structural and/or impedance changes in the cathode are responsible for most of the capacity and power fade, not the consumption of cycleable Li from side-reactions. The large capacity and power losses in this cell chemistry come mainly from increases in the bulk and/or interfacial impedance of the cathode.


Poster

Effect of Copper Charge Subtraction Ability in CuxFe1-x[Fe(CN)6] on the Electrochemical Behavior as Cathode in Aqueous Sodium Ion Batteries

Miguel Angel OLIVER-TOLENTINO, Ariel GUZMÁN-VARGAS

Instituto Politécnico Nacional (IPN), Mexico

In recent years, aqueous rechargeable sodium-ion batteries (ARSBs) have attracted considerable attention because of their relative safety, lower environmental impact, low cost, and an abundance of the necessary raw materials. Additionally, aqueous-based electrolytes have both better ionic transportation capabilities and improved kinetics compared with conventional organic electrolytes.

To building an aqueous Na ion battery, a severe challenge is to find a qualified cathode that have sufficiently high potential and capacity as well as cycling stability in aqueous electrolytes. For these purpose the hexacyanoferrates (MeHCFs) have demonstrated certain Na-storage performance in aqueous electrolytes. The iron hexacyanferrate (FeHCF) is under most investigation due to its two-electron-redox processes and the corresponding high theoretical capacity of ~170 mAh g-1, from oxidation of prussian white to Prussian yellow. On the other hand, the Copper hexacyanoferrate (CuHCF) exhibited a good capacity retention and stability however the specific capacity reported is near to 60 mAh g-1; in this work the electrochemical performance of CuxFe1-x[Fe(CN)6] is studied the results are related with the copper ability to receive charge in its partially free eg orbital.

The structural results reveal that every material crystallized in a face-centered cubic structure with space group Fm-3m; the Thermogravimetric analysis indicate that copper ions tend to locate in the surface pores; on the other hand the vibrational spectroscopy suggest the presences of Cu3+, this was verify by Mossbauer spectroscopy where the IS value of FeII (LS) in the chain FeII-CN-Cu3+ is very low, due to the ability of copper to charge substation attributed to its partially free eg orbital; inducing an increase in the π- back donation which reduces the 3d electron on the FeII. This copper ability have an important effect over electrochemical behavior improve the stability and rate capability of system with same amount of copper and iron in high spin.


Poster

Electrical and Thermal Studies on a Sodium Based Polymer Electrolyte

Varuni SENEVIRATNE1,2, Anjula HERATH2

1Department of Physics, University of Peradeniya, Sri Lanka; 2Postgraduate Institute of Science, University of Peradeniya, Sri Lanka

Polymer electrolytes (PEs) have attracted much attention due to their numerous applications such as rechargeable batteries, sensors, electrochromic devices, super capacitors, etc. A series of poly(ethylene oxide) (PEO) and sodium iodide (NaI) based PEs were prepared with different concentrations, hereafter referred to as the number of oxygen atoms (n) to a sodium (n:1). In this study samples with n = 7.5,10,15,20,30,40,50,60 and 80 were prepared. In this study, PEO was used as the polymer. Acetronitrile, sodium iodide was used as solvent and salt, respectively. Free standing films of polymer electrolytes were prepared using solvent casting method. Samples were characterized by different experimental techniques like complex impedance spectroscopy, DC conductivity, polarized light microscopy and Differential Scanning Calorimetry (DSC). The dependence of salt concentration on ionic conductivity of PEO-NaI PEs was investigated using complex impedance spectroscopy whereas the changes in the spherulite formation of PEs, was observed using Polarized light microscopy. DC polarization test was used to calculate ionic transference numbers. The melting temperature and melting enthalpy were studied using DSC. The ionic conductivity increased with increasing salt concentration and the sample temperature. The amorphous nature was increased with the increasing salt concentration. This is evident from the slight reduction in the onset and the maximum temperature of the pure PEO melting peaks in samples with high salt concentrations. This is supported by the images of spherulites obtained using the polarized light microscope. Fourier Transform Infrared (FTIR) spectroscopy studies show the cation-polymer interactions; an important concept in ionic transport mechanism.


Poster

Electrolyte Salt Effect on Electrochemical Performance of Lithium Metal Electrode

Sho EIJIMA, Mitsuhiro MATSUMOTO, Nobuyuki IMANISHI

Mie University, Japan

Electric Vehicles play a crucial role to reduce consumption of fossil fuels and thus, carbon dioxide emission. Vehicles driving range per one charge is largely determined by the limitation of electric energy stored in batteries. In this regard, there is a strong demand for developing a new battery system with higher energy density than conventional lithium ion battery. Lithium metal is a potential anode material for such batteries with its low electrode potential and high specific capacity. However, as generally known, low cycle performance has been a serious issue, which can be attributed to its dendritic growth in the plating process. In this presentation, electrolyte salt effect is discussed to improve lithium metal anode for organic lithium-air secondary battery.

Organic lithium-air battery usually uses electrolyte comprising dimethylsulfoxide (DMSO) as solvent, since it shows not only good chemical stability against super oxide anions, but also high dissolving ability of their lithium salt. In this study, lithium bis(fluorosulfonyl)imide (LiFSI) and lithium nitrate (LiNO3) were examined as the salt for DMSO solution, in which the ratios of LiNO3:LiFSI (x:10-x in mole) were changed in the range of 0≤x≤10. The electrochemical lithium plating/stripping were tested in a Li/Cu two-electrode coin-type cell. From the results obtained, LiNO3 was found effective to have small polarizations in the early cycles. However, the polarization grew with cycle numbers continuously. On the other hand, LiFSI showed larger but stable polarizations, which were kept in a similar magnitude during extended cycles. Compared to these single salt electrolytes, salt mixtures gave better cycle performance with low and stable polarizations. This work indicates that salt anions play an important role in determining nature of solid electrolyte interphase (SEI) formed on lithium metal anode.


Poster

Enhanced Reversible Li-storage of Mo/MoO3/Graphene Nanocomposite Anodes Prepared by Pulsed Electrical Wire Explosion Route

Hack-Jun LEE, Hyun-Woo SHIM, Dong-Wan KIM

Korea University, South Korea

Because of an intrinsic limitation of electrical conductivity of metal oxides as anode materials in Li-ion battery, great efforts have been steadily applied based on nanostructuring, a doping of conductive metals, and/or composite with carbonaceous materials (e.g., CNTs, graphene, and carbon coating). Herein, we demonstrate a simple method to prepare MoO3-based nanocomposite (i.e., both Mo/MoO3 and Mo/MoO3/graphene) showing an enhanced electrochemical performance of Li-ion battery anodes with improved electrical conductivity. This facile process involves the synthesis of highly uniform Mo metal nanoparticles (20 ~ 50 nm in diameter) by the pulsed-electrical wire explosion (PWE) in methanol media, which can synthesize high-quality conductive metals and/or metal oxides nanoparticles at room temperature, and subsequently partial oxidation of Mo metal nanoparticles by annealing process in air. Furthermore, the ratio of Mo metal to MoO3 in nanocomposite was controlled along with a change of annealing temperature (300, 400, and 500 oC). The Mo/MoO3/graphene nanocomposite was also prepared through the PWE process in the well-dispersed graphene and after a heat-treatment in air, and the result shows that Mo/MoO3 nanoparticles are anchored on the graphene with a high distribution. The all products obtained were characterized by power X-ray diffraction (P-XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM), and the electrochemical properties of all samples were investigated by means of cyclic voltammograms and galvanostatic charge/discharge cycles. In addition, we also evaluated the electrochemical impedance spectroscopy (EIS) analyses to show the electrical conductivity corresponding to the electrochemical performance of all samples, and thereby Mo/MoO3/graphene nanocomposite exhibited the improved reversible capacity with cycling stability, compared to other anodes. This enhanced electrochemical performance in Mo/MoO3/graphene nanocomposite can be attributed to the section of improved electrical conductivity by both conductive Mo metals and graphene as well as structural properties without the aggregation of Mo/MoO3 nanoparticles.


Poster

Fluoroethylene Carbonate Additives to Render Uniform Li Deposits in Lithium Metal Batteries

Xue-Qiang ZHANG

Tsinghua University, China

Lithium (Li) metal has been strongly considered as a critically important substitution of graphite anode to further boost the energy density of Li ion batteries. However, Li dendrite growth during Li plating/stripping induces safety concern and poor lifespan of Li metal batteries (LMB). Herein, fluoroethylene carbonate (FEC) additives were employed to form a LiF-rich solid electrolyte interphase (SEI). The FEC induced SEI layer is compact and stable, thus beneficial to obtain a uniform morphology of Li deposits. This uniform and dendrite-free morphology renders a significantly improved Coulombic efficiency of 98 % within 100 cycles in a Li | Cu half-cell. When the FEC-protected Li metal anode matched high loading LiNi0.5Co0.2Mn0.3O2 (NMC) cathode (12 mg cm-2), a high initial capacity of 154 mAh g-1 (1.9 mAh cm-2) at 180.0 mA g-1 was obtained. This LMB with conversion-type Li metal anode and intercalation-type NMC cathode affords an emerging energy storage system to probe the energy chemistry of Li metal protection and demonstrate the material engineering of batteries with very high energy density.


Poster

Graphical User Interface Visualizing Ion Conduction Pathways in Battery Materials

Wee Shin CHEW, Lee Loong WONG, Haomin CHEN, Stefan ADAMS

National University of Singapore, Singapore

Understanding pathways for ionic conductivity in battery materials is of utmost importance in the pursuit of high power battery systems. This includes both solid electrolytes and insertion-type mixed-conducting electrodes, for which we recently showed how the rate capability is in most cases quantitatively controlled by the characteristics of the ion transport pathways. To identify promising materials for high rate capability batteries and to engineer materials with optimised performance, a clear picture of the pathway characteristics is essential.

To this end we developed a Python-based GUI-interface to facilitate the usage of our softBV pathway software tools. Starting from the crystal structure file in standard cif format and the choice of the mobile species as its only input, it generates the corresponding bond valence site energy landscape of the selected mobile ion (e.g. Li+, Na+ etc.). This includes all occupied or unoccupied local energy minimum sites for the ions, the location of saddle points and the height of migration barriers for local pathways. Therefrom, it analyses the dimensionality, topology and tortuosity of the pathways for dc ionic conduction, and automatically generates a reaction pathway representing the migration barriers along the relevant conduction pathway of the mobile ion. The program also allows users to modify the visualisation of the reaction pathway.

The usefulness of the tool will be demonstrated in selected case studies of local pathway models of disordered battery materials.


Poster

Hexa-peri-hexabenzacoronene Based Materials for Anolyte Applications in Secondary Batteries

Andrey LUNCHEV, Kim Seng TAN, Rachid YAZAMI, Andrew Clive GRIMSDALE

School of Materials Science and Engineering, Nanyang Technological University, Singapore

A possible option to overcome some limitations of Li-ionic batteries, including slow rate of charge and discharge, relatively low energy density, high cost, and safety issues, is to use electrodes based on liquids due to their fast ion transport, high solubility of active components, and complete elimination of such solid based electrode drawbacks as metal dendrite formation.

While some types of non-solid based cathodes (like air cathode) have already been investigated, utilization of liquid based anodes is a relatively new approach.

One promising concept for a liquid based anode uses solvated electron solutions (SES), which are formed by the reaction between polycyclic aromatic hydrocarbons (PAH) and alkali metals in organic solvents. This concept has been successfully demonstrated with biphenyl and naphthalene as the PAH.[1]

Enlarging of PAH systems with aromatic rings would increase the amount of alkali metal atoms per PAH in SES, and make positive influence on conductivity of the system due to π-stacking effect, which should lead to improvement of SES electrochemical properties. Substituents with different nature incorporated in PAH molecules may also have an impact on SES characteristics, as well as electron withdrawing anti-aromatic systems (e.g. cyclopentadienone).[2]

After preliminary studies on relatively simple polyaromatic compounds and their derivatives (triphenylbenzene, anthracene and simple heteroaromatic systems), we have started our investigations on large polyaromatic systems based on hexa-peri-hexabenzocoronene framework.

Here we report our recent progress on synthesis and studies of Li-SESs based on large PAHs for possible use in batteries.

References:

[1] K. S. Tan, A. C. Grimsdale, R. Yazami, J. Phys. Chem. B, 2012, 116, 9056.

]2] Z. B. Lim, K. S. Tan, A. V. Lunchev, H. Li, S. J. Cho, A. C. Grimsdale, R. Yazami, Synth. Met.,2015, 200, 85.


Poster

Hierarchical Porous Yolk-shell-like Architecture LiNi1/3Co1/3Mn1/3O2 with Superior Long-term Energy Retention and High Rate Capability for Lithium-Ion Batteries

Zhen CHEN, Dongliang CHAO, Jilei LIU, Jin WANG, Linyi BAI, Shi CHEN, Yanli ZHAO, Tze Chien SUM, Jianyi LIN, Zexiang SHEN

Nanyang Technological University, Singapore

The sluggish lithium ions diffusion of LiNi1/3Co1/3Mn1/3O2 (NCM) is one of the fatal factors which can significantly prevent its sustainability and usage in high power applicants. In this work, the monodisperse hierarchical nano-/micro yolk-shell-like NCM (YS-NCM) with exposure to {010} electrochemical active facets was successfully synthesized, aiming to elevate the lithium ion diffusion ability and thus to enhance the electrochemical performance. The hierarchical porous nano-/microsphere structure can increase the contact area with electrolyte, shorten Li+ diffusion length and thus improve the Li+ mobility. The exposure of {010} electrochemical active facets provides more open structure for unimpeded Li+ migration. Therefore, by this design strategy, the lithium ion transport kinetics is greatly improved, yielding superior electrochemical performances. When examined as the cathode material for LIBs, the YS-NCM delivers initial reversible discharge of 187.12 mA h g-1 at 0.1 C with a high capacity retention ratio of 85.99 % after 100 cycles. Even tested at higher current density, YS-NCM can achieve 91.08 % (1 C) and 93.23 % (2 C) capacity retention ratio after 100 cycles, respectively. The discharge capacities of YS-NCM at 1, 2, 5, 10, 15, 20 and 30 C are 145.93, 126.01, 109.58, 93.61, 79.16, 69.22 and 64.50 mA h g-1, respectively. The YS-NCM with superior long-term capacity retention and excellent high C-rates capability is expected to be a highly potential candidate for practical lithium ion battery applications.


Poster

Ions Size-dependent Phase Transformations in TiS2 during Intercalation with Li, Na and K Alkali Ions: In-situ XRD Combined TEM Study

Bingbing TIAN, Kian Ping LOH

National University of Singapore, Singapore

The individual layers of TiS2 provide ion channels and prompt it as a cathode material in rechargeable batteries. In this work, we have investigated the electrochemical properties, phase transformations and stability of alkali metal intercalated in hexagonal TiS2 (MxTiS2), for 0≤x≤1 and M = Li, Na, and K using electrochemical method combined in-situ XRD and ex-situ TEM techniques. We found that K ions, with larger ionic radius, successfully realized reversible discharge/charge in the bulk TiS2 host. As shown by in-situ XRD results, five phase stages are observed in the K ions intercalation caused phase transformations process, which are different from that of Li and Na ions. Then via a strategy of chemical pre-potassiation for the bulk TiS2, a nano-crystallization TiS2 with improved electrochemical performance is observed. This study provides more comprehensive understanding of insertion of Li, Na and K alkali ions into layered TiS2, which is of essential importance for both alkali ion batteries and intercalation type TMDs.


Poster

Li4SnS4 and Li2SnS3 Solid Electrolytes for all Solid State Rechargeable Batteries

Prasada Rao RAYAVARAPU, Stefan ADAMS

National University of Singapore, Singapore

Rechargeable batteries play an important role in conversion of chemical energy to electrical energy and energy storage. Lithium batteries have been considered as promising power supply for various portable applications, electric vehicles and grid storage systems. However, the presently available lithium-ion technology still suffers limitations due to the use of organic flammable electrolytes. Replacing liquid electrolytes with high conducting solid electrolyse can minimise such safety issues. Here we prepared Li4SnS4 and Li2SnS3 solid electrolytes using solid state reaction in sealed quartz tubes filled with Ar at 450˚C for 20h. XRD data for Li4SnS4 indicated the formation of the targeted compound with space group Pnma and lattice parameters a= 14.310(5) Å, b=7.881(3) Å, c=6.331(3) Å. XRD data for Li2SnS3 indicated the formation of the targeted compound with space group C2/c and lattice parameters a= 6.394(2), b=11.076(4), c=12.395(1) Å and β=99.85(3)°. Li2SnS3 exhibited high ionic conductivity of 7.3 ×10-4 S/cm at room temperature. The ionic conductivity of Li4SnS4 is 5.2×10-4 S/cm at room temperature.More details of Li/Li2SnS3/LiCoO2 all solid state rechargeable batteries will be discussed.


Poster

Metal (M = Ni, Fe, and Cu)-Combined Ultra-fine SnO2 Nanoparticles for Large Reversible Capacity of Li-ion Battery Anodes: A Case Study for SnO2 Conversion Reaction

Da-Sol KIM, Hyun-Woo SHIM, Dong-Wan KIM

Korea University, South Korea

Tin oxide (SnO2) is considered as one of high-capacity anode materials versus Li+, by following two-step reactions; i) the conversion reaction (SnO2 + 4Li+ + 4e- → Sn + 2Li2O), which is usually accepted to be completely irreversible, and ii) Li-alloying/dealloying process (Sn + xLi+ + xe- ↔ LixSn (0 ≤ x ≤ 4.4)), which is recognized to be more reversible and thus theoretical capacity of 782 mA h g-1. However, some of the recent reports suggest that such conversion reaction is partially reversible, when applied nanometer-sized SnO2 particles (< 5 nm), resulted in leading to a higher reversible capacity. Herein, we describe a synthesis of M-SnO2 nanocomposite (M = Ni, Fe, and Cu) based on the ultra-fine SnO2 nanoparticles, and electrochemical properties of M-SnO2 nanocomposite as a model material to deal with the conversion reaction that can lead to the extra capacity. The M-SnO2 nanocomposite is prepared through a series of facile methods; first, the synthesis of SnO2 nanoparticles by hydrothermal at 150 oC for 24 hr, and then the electrical explosion process of metal wires in the well-dispersed SnO2 nanoparticles in ethanol media at room temperature. The as-synthesized SnO2 nanoparticles exhibited ultra-fine and uniformly small size of ~5 nm in diameter. Additionally, each metal content in M-SnO2 nanocomposite was also investigated through EDS analysis, which is determined to be 5 – 10 wt%. Li-electroactivity of all samples was analyzed with CV profiles to discuss the conversion reaction, which were further determined with both ex-situ XRD and HR-TEM analyses after charge/discharge tests. We also evaluated galvanostatic charge/discharge cycles to compare the capacity and cyclability. In particular, M-SnO2 nanocomposite indicated relatively improved cycle stability with the large capacity, compared to pristine SnO2 nanoparticles, and this result can be further discussed based on the enhanced electrical conductivity in combination with conducting metal.


Poster

MnO2 Nanofiber/Single-Walled Carbon Nanotube Hybrid Film for All-Solid-State Flexible Supercapacitors with High Energy Density

Zong-Huai LIU, Liping KANG

Shaanxi Normal University, China

Well-dispersed ultralong δ-MnO2 nanofibers with smooth surface, good dispersibility, and large length-to-width ratio are firstly controllably prepared by hydrothermally treating δ-MnO2 with low crystalline at 150 °C for 20 h in 1 M NaOH. δ-MnO2 nanofiber/single-walled carbon nanotubes (SWCNT) hybrid film electrodes with good flexibility and high capacitance are obtained between d-MnO2 nanofibers and SWCNT via a simple vacuum filtration method. When a suitable amount of SWCNT is added in δ-MnO2 nanofiber/SWCNT hybrid film electrodes, regular fibrous network structure is formed and a synergistic effect takes place between SWCNT and δ-MnO2 nanofiber. The δ-MnO2/SWCNT-15 hybrid film electrode shows larger areal specific capacitance of 964 mF cm−2 at current density of 1 mA cm−2 and an excellent capacity retention rate of 81 % when the current density increases from 1 to 10 mA cm−2. By using δ-MnO2/SWCNT-15 film electrodes, a flexible all-solid-state δ-MnO2/SWCNT-15 hybrid supercapacitor is assembled by sandwiching PVA-KOH solid-state electrolyte without using other conductive additives, binders, and current collector. The assembled flexible all-solid-state δ-MnO2/SWCNT-15 hybrid supercapacitor not only shows good flexibility and mechanical property, but also gives a high areal capacitance of 358 mF cm-2 at a current density of 2 mA cm-2, good capacitance retention of 90 %, excellent Coulombic efficiency of 96 % after 2,000 cycles, and high energy density of 31.8 μWh cm−2 at a power density of 0.815 mW cm−2. Because of its integration of flexibility, high energy density, good cycle life and Columbic efficiency, δ-MnO2 nanofiber/SWCNT hybrid film flexible supercapacitors have great potential in future portable and wearable electronic application.


Poster

Morphological Influence of SiO2 on Magnesiothermic Reduction to Si and its Impact on Si-SiO2-MWCNTs as LIBs Anode

Vincent Ming Hong NG1, Pin Han LIM1, Jason Zhichuan XU1, Hui HUANG2, Ling Bing KONG1

1School of Materials Science and Engineering, Nanyang Technological University, Singapore; 2Singapore Institute of Manufacturing Technologies (SIMTech), Agency for Science, Technology and Research (A*STAR), Singapore

Amongst many alternative high specific capacity anode materials for lithium-ion batteries (LIBs), silicon (Si) possesses the highest theoretical capacity of exceeding 4000 mAh g-1 and low operating voltage (ca. 0.3 V vs. Li/Li+). Although various nanostructured Si and Si-based composites have been identified to be more resistant against the cyclic volumetric expansion/contraction during lithiation/delithiation, much room for improvement on its cycling performance and Coulombic efficiency (CE) remains. With silica (SiO2) as initial template materials, magnesiothermic reduction of SiO2 to Si has been explored by various groups to obtain nanostructured Si [1]. However, the effects of morphology of the precursory SiO2 and size of the magnesium (Mg) on the eventual yield of Si through magnesiothermic reduction have yet been well-elucidated. Additionally, multiwalled carbon nanotubes (MWCNTs) could be used as spacers and conductivity enhancer. Si-SiO2-MWCNTs composites were obtained through dry pressing [2]. Then, SiO2 was removed by using HF etching, thus leaving behind voids in the remnant Si-MWCNTs clusters, to further improve cyclability of the materials [3].

A series of amorphous silica nanoparticles with varying sizes and shapes (particulate, elongated and hollow) were synthesized through aqueous ammonia (NH3.H2O) catalyzed condensation of tetraethyl orthosilicate (TEOS), with the presence of cetyltrimethylammonium bromide (CTAB) at various concentrations. To retain the nanostructures even after magnesiothermic reduction, NaCl was added to the mixture of nano-SiO2 and MWCNTs [4]. It was found that the size of SiO2 had an interesting effect on eventual morphology, composition, microstructure and electrochemical performance of the Si-SiO2-MWCNTs composites as anode of LIBs.


Poster

MoSe2 Thin Layer Dispersed on Hierarchical Carbon Nanoparticles for Na-ion Storage

Guichong JIA, Hong Jin FAN

Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore

The severe environmental pollution and the rapid development of renewable energy have stimulated the research of energy storage in recent years. Lithium ion battery has huge demand for all kinds of electronics and energy storage devices. However, the lithium resource is rare, which can result in high cost. An alternative but much more earth-abundant material than lithium is sodium. Thus, development of sodium-based energy storage devices become necessary and significant.

High energy density and good rate performance have always been the motivation for researchers in energy storage field. Herein, we synthesized MoSe2 thin layer dispersed on hierarchical carbon nanoparticles with a simple method. The nanoparticle has nanosheet structure on the surface. The composite displayed initial charge and discharge specific capacities of 503 and 857 mA h g-1 at the current density of 0.1 A g-1 in sodium ion half-cell. It also displayed good rate performance, delivering specific capacity of 480 mA h g-1 at 0.1 A g-1, even delivering 110 mA h g-1 at 10 A g-1. It also exhibited a good cycle stability at a current density of 8 A g-1, it had a discharge specific capacity of 130 mA h g-1 even after 250 cycles with a high capacitance retention of 94 %.


Poster

Nanostructured Li4Ti5O12 Anode Material for Secondary Batteries: A Green Synthesis Route

Swatilekha GHOSH1, Sagar MITRA2, Prabeer BARPANDA3

1Dr M.N. Dastur School of Materials Science and Engineering, Indian Institute of Engineering Science and Technology, India; 2Department of Energy Science and Engineering, Indian Institute of Technology Bombay (IITB), India; 3Faraday Materials Laboratory, Materials Research Centre, Indian Institute of Science, India

For commercial batteries, graphite-based anodes have been extensively employed due to their high energy density and low working voltage. However, these anodes suffer from limited capacity, poor energy efficiency and safety issues. To overcome these problems, Li-Ti-O based anodes were introduced for secondary batteries. These anodes offer desirable characteristics such as high reversible capacity, descent thermal stability and good cycle life.This Li-Ti-O material particularly Li4Ti5O12 recently showed to act as a host for reversible Li+ and Na+ (de)intercalation, making it suitable for Li and Na both the systems.The present work is focused on sonochemical synthesis, an energy-savvy green synthesis route for Li4Ti5O12 (1.5 V vs. Li+/Li and 0.9 V vs. Na+/Na).

Li4Ti5O12 was prepared by sonochemical synthesis from the mixture of LiOH.H2O and TiO2. This synthesis was carried out in an ultrasonic probe sonicator of 20 kHz-500 W by applying sonication irradiation for 10-40 min (at 25 °C). Using this energy-savvy synthesis route enormous reduction in calcination duration was observed. The final products were obtained after calcination at 750-800 °C for 2 h in air. Due to reduction in calcinations duration uniform, spherical and nano scale products (100 to 300 nm) were accomplished. This material delivered excellent reversible electrochemical performance acting as a 1.5 V anode for Li-ion batteries (reversible capacity upto 130 mA h/g) and 0.9 V anode for Na-ion batteries (reversible capacity upto 60 mA h/g).

The detail study on the influence of various synthetic parameters on the structural, morphological and final electrochemical performance of this Li-Ti-O system for secondary batteries will be presented.


Poster

Phosphate-based Polyanionic Insertion Materials for Na-ion and K-ion Batteries: Four Case Studies

Ritambhara GOND, Prabeer BARPANDA

Indian Institute of Science Bangalore, India

Successful commercialization of triphylite LiFePO4 has ushered extensive research on phosphate (PO43-) based polyanionic insertion materials for secondary batteries. These compounds offer robust framework, fast ion migration and chemical/ thermal stability. Suites of phosphate-containing polyanionic materials have been unraveled for secondary Li-ion and Na-ion batteries. While Li-ion batteries target suave portable electronics and automobile sectors, Na-ion batteries are suitable for large-scale grid storage sector. In both case, it is crucial to implement new insertion chemistry with improved performance.

On another note, transition metals (TM) are crucial for insertion materials, where low cost and multiple redox activity is desirable. Fe based insertion materials are attractive due to the elemental abundance of Fe on the earth crust. In the present work, we have explored four Fe-containing PO4-based polyanionic insertion compounds: namely (i) fluorophosphate (Na2-xFePO4F), (ii) metaphosphate [NaFe(PO3)3], (iii) pyrophosphate (A2FeP2O7, A= Na, K) and (iv) layered polyphosphate [Na3Fe3(PO4)4]. These compounds were prepared by carbothermal assisted solution combustion synthesis using low cost Fe(III)-based precursors [Fe(NO3)3.9H2O]. The combustion synthesis allows us to develop nanostructured particles with carbon coating with final annealing step restricted to 1-6 h.

We will showcase the role of synthetic condition, particle morphology and crystal structure in Na+ and K+-ion insertion into these PO4 compounds having layered or three-dimensional frameworks. Salient features of our study include (i) one minute synthesis of Na2FePO4F acting as a 3 V (vs. Na) insertion host with 110 mAh/g reversible capacity, (ii) the first demonstration of electrochemical activity in NaFe(PO3)3 metaphosphate at 2.86 V (vs. Na), (iii) polymorphism and electrochemical activity in K2FeP2O7 pyrophosphate based on various synthesis conditions and (iv) observation of near-theoretical capacity in layered structure Na3Fe3(PO4)4. The presence and degree of electrochemical activity in these PO4-based materials will be correlated to their underlying crystal structure.


Poster

Preparation & Study of Lithium Solvated Electron Solutions (LiSES) using Benzimidazole Derivatives as Electron Receptors

Kim Seng TAN, Animesh GHOSH, Andrew Clive GRIMSDALE, Rachid YAZAMI

School of Materials Science & Engineering, Nanyang Technological University, Singapore

The lithium solvated electrons solution (Li-SES) is made up of metallic lithium dissolved in an anhydrous solution of poly-aromatic hydrocarbon (PAH) electron receptors at ambient temperature. Our previous studies on biphenyl and naphthalene-based LiSES demonstrate the feasibility of using these solutions as a liquid anode material (anolyte). Both biphenyl and naphthalene are simple two-ring PAHs which are utilized as the electron receptors in the LiSES. Unlike solutions containing only ions, conductivity measurements reveal that the LiSES is metal-like and is a mixed conductor, consisting of 2 types of charge carriers: solvated electrons and lithium ions.

Moving on, our studies progressed to testing more complex PAHs as electron receptors. This poster will present the preparation and conductivity results of LiSES solutions prepared using two types of benzimidazole derivatives, namely 1-hexyl-5,6-dimethyl-2-phenyl-1H-benzo[d]imidazole and 2-hexyl-5,6-dimethyl-1-phenyl-1H-benzo[d]imidazole.


Poster

Preparation and Characterization of Nanostructured CuCo2O4 for Hybrid Li-air Batteries

Dickson Jun Jie NG, M V REDDY, Stefan ADAMS

Department of Materials Science and Engineering, National University of Singapore, Singapore

We will discuss the preparation of nanostructured CuCo2O4 material by simple chemical preparative techniques like molten salt, sol gel and hydrothermal methods. We studied the effect of different Cu and Co salts and surfactant on the resulting CuCo2O4 structure and morphology. Differences in the particle morphology were noted using scanning electron microscopy and also Transmission electron Microscopy. The crystal structure and oxidation states were evaluated using X-ray diffraction (XRD), Raman spectroscopy and X-ray photo electron spectroscopy (XPS) techniques. XRD studies shows pure single phase cubic structure with a lattice parameter value of a = 8.145Å and XPS studies shows presence of Cu 2p and Co2p and O1s binding energy levels with +2 and +3 oxidation state of Cu and Co -ion respectively. Specific surface area of nanostructured samples was analyzed by the Brunauer-Emmett-Teller (BET) method. Pore volume and pore-size distributions were obtained using the Barrett-Joyner-Halenda (BJH) model. We will discuss the stability test with aqueous acidified LiCl, LiOH and bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) in DME and H2O / DME. Preliminary electrochemical studies were conducted with optimized Li1 + xAlxGe2 − x(PO4)3 (LAGP) anode protecting membrane with aqueous electrolyte . Cycling performance with different catholytes will be discussed and we also present the effect of coating on the above mentioned material with different substrates (carbon, Ni mesh or Cu-mesh) and effect of surface area on electrochemical properties. Electrochemical impedance spectroscopy and Raman spectroscopy studies were conducted on fresh cells and after few cycles in order to understand the reaction mechanism.


Poster

Proton Enhanced Battery Kinetics for Aprotic Li-O2 Cells

Yunguang ZHU1, Qi LIU2, Yangchun RONG2, Haomin CHEN1, Jing YANG1, Chuankun JIA1, Li-Juan YU3, Amir KARTON3, Yang REN2, Xiaoxiong XU4, Stefan ADAMS1, Qing WANG1

1Department of Materials Science and Engineering, Faculty of Engineering, National University of Singapore, Singapore; 2X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, United States; 3School of Chemistry and Biochemistry, The University of Western Australia, Australia; 4Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, China

The aprotic Li-O2 battery attracts tremendous attention due to its high theoretical energy density. However, the open system of aprotic Li-O2 battery is vulnerable to species such as H2O, CO2, etc. from air. While water is generally believed to undermine the performance of the cell, some recent studies have shown that trace amount of water may be beneficial to the kinetics of oxygen evolution reaction (OER).1-3 Therefore, it is critical to scrutinize the role of water and the battery chemistry of water-contaminated aprotic Li-O2 batteries. Here, we demonstrated a Li-O2 battery with charging overpotential as low as 0.20 V in the presence of water as electrolyte additive and LiI as OER redox catalyst.4 Interestingly, an unprecedented compound LiOOH was identified in the discharge products, which exhibits much faster kinetics than Li2O2 toward the oxidation by I3-. This mechanistic study unequivocally discloses the role of water, and that the moisture fed into the cell does not pose immediate adverse impact to the battery operation, so long as the lithium anode is properly protected.

References:

[1] Li, F.; Wu, S.; Li, D.; Zhang, T.; He, P.; Yamada, A.; Zhou, H. Nat Commun 2015, 6, 7843.

[2] Kwak, W.-J.; Hirshberg, D.; Sharon, D.; Shin, H.-J.; Afri, M.; Park, J.-B.; Garsuch, A.; Chesneau, F. F.; Frimer, A. A.; Aurbach, D.; Sun, Y.-K. Journal of Materials Chemistry A 2015, 3, (16), 8855-8864.

[3] Liu, T.; Leskes, M.; Yu, W.; Moore, A. J.; Zhou, L.; Bayley, P. M.; Kim, G.; Grey, C. P. Science 2015, 350, (6260), 530-533.

[4] Zhu, Y. G.; Liu, Q.; Rong, Y.; Chen, H.; Yang, J.; Jia, C.; Yu, L.-J.; Karton, A.; Ren, Y.; Xu, X.; Adams, S.; Wang, Q. Nature Communications 2017, 8, 14308.


Poster

Sn-Co/Graphene Nanosheets as Anode Materials for High Performance Lithium-ion Batteries

Yewei YANG, Zhongtao JIANG, Chunling LIU, Xiaoshan LI, Wensheng DONG

Key Laboratory of Applied Surface and Colloid Chemistry (SNNU), MOE, School of Chemistry and Chemical Engineering, Shaanxi Normal University, China

Novel structural Sn-Co/graphene nanosheets (GNS) with a layered sandwich nanostructure were prepared using a solution polymerization route followed by high-temperature carbon thermal reduction. The composites were characterized using various characterization techniques including powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy and the electrochemical performance test. The results show that the compositions of Sn and Co have strong influence on the electrochemical performance of the Sn-Co/GNS composites. With increasing the ratio of Sn to Co the capacities of the Sn-Co/GNS composite electrodes gradually increase, after reaching the highest value it drops. The composite with the ratio of Sn:Co of 3:1 reveals the best electrochemical performance with an initial charge capacity of 845 mAh g−1 at a constant current density of 50 mAg−1, and even after 100 cycles the electrode maintains a capacity of 762 mAh g−1. In such stable layered structure, GNS firmly fix the isolated Sn-Co nanoparticles with an average size of ~7 nm and prevent them from aggregation, and Sn-Co nanoparticles, as the spacers, prevent the GNS from restacking, leaving a stable channel for ion transport during the charge–discharge process. Moreover, a sandwich-like network provides a strain buffer for volume changes of the Sn-Co nanoparticles due to the electrochemical reaction. The first coulombic efficiency and cycle performance of the Sn-Co/GNS composites electrode can be further improved by optimizing the carbonization temperature and the precise control of Sn-Co nanoparticle size.


Poster

Space-confinement and Chemisorption Co-involved in Encapsulation of Sulfur for Lithium-Sulfur Batteries with Exceptional Cycling Stability

Jin WANG1,2, Jianyi LIN1, Zexiang SHEN2

1Energy Research Institute (ERI@N), Nanyang Technological University, Singapore; 2Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore

Rechargeable lithium–sulfur (Li–S) batteries have attracted an enormous amount of interest owing to their various advantages, including high–energy density with low costs, high natural abundance of sulfur, and environmental friendliness. However, the commercialization of Li–S batteries has been hampered by the three major obstacles: (i) low electrical conductivity of sulfur (5*10–30 S cm–1) and its intermediate polysulfide products (Li2S and Li2S2), (ii) the shuttling of dissolved lithium polysulfide (Li2Sx, 3≤x≤8) between the sulfur cathode and lithium anode, and (iii) large volumetric expansion (∼79%) between sulfur and the final product Li2S during the lithiation/delithiation processes. Herein, we present an effective strategy to dually confine sulfur and lithium polysulfide, as well as alleviate the volume variation of sulfur during discharge process, by using porous N-doped carbon layer coated carbon nanotubes with internal nanogap, which is formed via a thin sacrificial layer of Al2O3. The unique nanostructured carbon tubes with internal nanogap are directly supported on a conductive three-dimensional graphene foam as the additive/binder-free electrode structure to accommodate large amounts of dissolved lithium polysulphides. The nitrogen heteroatoms are induced into the out layer of nanostructured carbon tube, which can create reactive sites for fast charge transfer and facilitate better immobilization of the polysulfide ions. As a result, high specific capacity, good rate performance and excellent cycling stability are achieved.


Poster

Study of Electrode Structures and Redox Kinectics in Bio Fuel Cells

Aashray NARLA, Siddarth DURGA, Dhruv UPADHYAYA, Sivakumar AMARVATHY, Subramaniam CHITTUR KRISHNASWAMY

VIT University Vellore, India

Selection of material for anode, cathode and their structure is one of the critical challenges of bio fuel cell. They can affect the power density and Coulombic efficiency. Two types of bio fuel cells were studied, the Microbial Fuel Cell (MFC) and the Enzymatic Fuel Cell (EFC), where the electrode structure and kinetics are similar except for the rates of respective redox reactions. The electrochemical characteristics of the electrodes were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and polarization profiles. Carbon and blends with graphene were used for developing the electrode structure. In the MFC the anode was inoculated with MRS broth containing Lactobacillus Cesai Shirota. Complete characterisation and optimisation of the redox kinetics will be presented. Mediators will be used to enhance electron transfer between the fuel, bacteria and electrodes to enhance the electrode reactions. A fast and convenient bacterial immobilization method will be proposed as an attempt to improve the anode efficiency of a microbial fuel cell, in which bacteria will be entrapped. The electron transfer characteristics with the mediators and immobilizers will be studied by cyclic voltammetry and SEM imaging. A low power of about 3.0 micro watts was obtained in the preliminary experiment using a 5 cm2 cell MFC. This glucose EFC cell features a 3-D porous carbon as anode and cathode for high surface area facilitating the reaction, a suitable immobilizer for the enzyme immobilization and mediators like ferrocene for optimal electron transfer. The achievable cell potential varies between 0.6-0.8V. The achieved power density is still below theoretical value. A cell potential of around 0.5 V for 50 hours was achieved in the EFC. The EFC will be optimized for enzyme loading; conductive loss minimization, both electronic and ionic, direct charge transfer for improving charge transfer efficiency, and pore channel and size profile


Poster

Study of Reactivity for Cu@Pt Core/shell Nanoparticles as Fuel Cell Anode Material

Ji LIU1, Xiaofeng FAN1,2, Changqing SUN1, Weiguang ZHU1

1Nanyang Technological University, Singapore; 2Jilin University, China

The proton exchange membrane fuel cell (PEMFC) is regarded as one of the most promising green technologies to achieve commercialization for automotive, portable and stable applications. Platinum (Pt) is a good anode material for fuel cell if pure H2 is used. However, the poor CO-tolerance ability has hindered the applications for fuel cell. Usually, the anode H2 is produced by reforming hydrocarbons and CO is one of the inevitable byproducts, which is extremely difficult to be removed completely. Processes such as water gas shift (WGS) and preferential oxidation (PROX) can reduce the concentration of CO down to ppm levels, which can still easily deactivate the fuel cells with pure Pt-anode. Thus for decades, researchers have been searching for suitable anode materials with better CO-tolerance ability. Based on density functional theory (DFT) calculations, we have proposed a core/shell structure Cu@Pt nanoparticle to serve as anode material. We have then calculated the CO surface saturation coverage to check the CO-tolerance ability and compared with pure Pt surface. A barrier calculation by nudged elastic band (NEB) method is performed to investigate the hydrogen dissociation ability with various surface CO and H2 coverage. The results show that the proposed Cu@Pt core/shell structure have much better CO-tolerance ability than pure Pt and H2 can dissociate easily on the surface. With the evidence of greater reactivity, Cu@Pt core/shell nanoparticle is very promising to be an alternate anode material for fuel cell.


Poster

Synthesis of Co-containing Metal-Organic Frameworks and their Application to Cathode Materials in Zn-air Batteries

Joongpyo SHIM, Kangjong KIM, Jin-Hyun YANG, Ho-Jung SUN, Gyungse PARK

Kunsan National University, South Korea

Although zinc-air rechargeable batteries (ZARB) have received much attention due to its low cost, high stability, non-explosion and environmental benignity, they have not shown any advantages because their poor cycleability, high solubility of zinc compounds and low rate of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of air electrode. The catalytic activities of perovskite type materials, such as lanthanum based oxide, and related compounds have also received much attention because of relatively high catalytic activity for the ORR & OER, and low cost synthetic process.

In this study, the materials prepared from Co-containing metal-organic framework (Co-MOF) as a new catalyst were investigated for ORR and OER in alkaline solution. MOF consist of transition metal surrounded by organic molecules. MOF is highly porous material having micro pore in powder.

To prepared Co-MOF, a mixture of Co(NO3)2·6H2O, 1,4-bdcH2 (1,4-benzenedicarboxylic acid) and DMF was stirred for 30 min in air at room temperature. The mixture was transferred and sealed in a Teflon reactor and heated at 100 °C for three days. After the mixture cooled to room temperature, purple hexagonal-plate crystals of [Me2NH2]2[Co3(1,4-bdc)4]·4DMF were obtained. The Co-MOF powder was heat-treated under N2 atmosphere at different temperatures.

The Co-MOF powders were mixed with carbon black, Ni powder and PTFE in a solution of isopropyl alcohol. The resulting mixture was rolled on glass plate and dried at 60oC for 2h. The obtained sheet was transferred onto a wet-proofed carbon paper by pressing at 10 MPa for 1 min at 350 oC. The bifunctional electrodes were electrochemically characterized for the ORR and OER in an 8M KOH solution using a three-electrode system. The cell potential was measured using a linear sweep voltammetry (LSV) method at a scan rate of 1 mV s-1. The scan was conducted between 0.5 and 2.5 V vs. Zn/Zn2+.


Poster

Synthesis of Hierarchical Porous Carbon Materials for Lithium-ion Batteries

Ke ZHANG, Jian PEI, Mengyuan LI, Zhiling LI, Chunling LIU, Wensheng DONG

Key Laboratory of Applied Surface and Colloid Chemistry (SNNU), MOE, School of Chemistry and Chemical Engineering, Shaanxi Normal University, China

3D hierarchical porous carbons with different pore size distributions were prepared using Ni(OH)2 template. The morphology, crystalline features, pore structure and surface composition of the hierarchical porous carbons are characterized using various analytic techniques including scanning electron microscopy, transmission electron microscopy, N2 physical adsorption, powder X-ray diffraction and X-ray photoelectron spectroscopy. The pore size distributions of the hierarchical porous carbons were controlled through changing the amount of template. It was found that the pore size distributions of the 3DCs play an important role in the lithium-storage capacity. The micropores with size of 0.6~0.9 nm are confirmed to be able to promote effectively the lithium storage capacity. The typical sample that has a BET surface area of 568 m2 g-1, a micropore surface area of 425 m2 g-1, a pore volume of 0.39 cm3 g-1, and a micropore volume of 0.19 cm3 g-1 shows a good electrochemical performance with a specific reversible capacity of about 630 mAh g-1 in the first cycle and 363 mAh g-1 after 50 cycles. The good electrochemical performance of this sample can be attributed to the existence of the largest amount of micropores with size of 0.6~0.9 nm which increase the lithium storage capacity; in addition the existence of mesoporous and macroporous effectively shortens the distance for charge diffusion, the turbostratic graphite structure low resistance for electron conduction.


Poster

The Surface Treatment of Cathode Current Collector and Its Electrochemical Behavior for Lithium-ion Batteries

Sukeun YOON, Nam-Chul KIM

Kongju National University, South Korea

The commercial batteries industry is not still satisfied to adopt in the rapid advances for mobile, automotive, and stationary storage applications markets. These markets desire further gravimetric/volumetric energy densities, long-term use, and safety. These challenging requirements make it need alternative active electrode materials beyond the typical LiCoO2 and graphite. In this regards, many researcher has explored new generation active cathode and anode materials for Li-ion batteries, and besides they has suggest new electrical energy storage, such as Li-S batteries, Na-ion batteries, and metal-air batteries, etc. Although these attempts are so ingenious, the developments of them are too tardy and difficult to employ the commonly batteries industry due to they cannot meet the in terms of high chemical/electrochemical stability, durability, stable cycle life, safety concerns, and cost of starting materials. In addition, in order to use novel materials, it takes a long research time and supplies high expenses. Among the solution excluded from core materials in Li-ion batteries for improving energy density, parts materials, such as current collector, lead tab, and exterior case, can simply enhance the energy density in the cell by reducing theirs weight or volume. Particularly, current collectors for cathode and anode can easily raise batteries performance through the thickness control without change of existing materials. However, there have been only few studies about current collectors in Li-ion batteries because it looked like less novelty and impact in the battery technologies compared with the core materials.

The aim of this study was to investigate the correlation between roughened thin Al current collector and electrochemical properties for Li-ion batteries. In order to increase the adhesiveness, we employed wet chemical etching as surface modification on the Al current collector.


Poster

Vertical Graphene Composites for the High Performance Energy Storage Applications

Yadong WANG, Xinhui XIA

Nanyang Polytechnic, Singapore

Smart hybridization of active materials into tailored electrode structure is highly important for developing advanced electrochemical energy storage devices. Here, we report a directional synthetic strategy for fabrication of integrated arrays of vertical graphene/active materials by combination of hydrothermal, atomic layer deposition and chemical vapor deposition methods. Active materials are uniformly coated on vertical graphene backbone and interesting advantages including high electrical conductivity, strong mechanical stability, and large porosity are combined in the hybrid arrays. The synthesized nanostructures are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy; transmission electron microscopy (TEM) techniques and the electrochemical performance of these hybrid nanostructures will be evaluated.


Poster

Dendrite-Free Nanostructured Li Metal Anode in Safe Li-Metal Batteries

Qiang ZHANG

Tsinghua University, China

Li metal is considered as the “Holy Grail” of energy storage systems. The bright prospects give rise to worldwide interests in the metallic Li for the next generation energy storage systems, including highly considered rechargeable metallic Li batteries such as Li-O2 and Li-sulfur (Li–S) batteries. However, the formation of Li dendrites induced by inhomogeneous distribution of current density on the Li metal anode and the concentration gradient of Li ions at the electrolyte/electrode interface is a crucial issue that hinders the practical demonstration of high-energy-density metallic Li batteries.

Free-standing graphene foam provides several promising features as underneath layer for Li anode, including (1) relative larger surface area than 2D substrates to lower the real specific surface current density and the possibility of dendrite growth, (2) interconnected framework to support and recycle dead Li, and (3) good flexibility to sustain the volume fluctuation during repeated incorporation/extraction of Li. The synergy between the LiNO3 and polysulfides provides the feasibility to the formation of robust SEI in an ether-based electrolyte. The efficient in-situ formed SEI-coated graphene structure allows stable Li metal anode with the cycling Coulombic efficiency of ∼97 % with high safety and efficiency performance. These results indicated that interfacial engineering of nanostructured electrode were a promising strategy to handle the intrinsic problems of Li metal anodes, thus shed a new light toward LMBs, such as Li-S and Li-O2 batteries with high energy density.

References:

[1] X. B. Cheng, et al, Small 2014, 10, 4257

[2] X. B. Cheng, et al, ACS Nano 2015, 9, 6373.

[3] R. Zhang, et al. Adv Mater 2016, 28, 2155.

[4] X.B. Cheng, et al, Adv Mater 2016, 28, 2888.

[5] X.Q. Zhang, et al, Adv Funct Mater 2017, 27, 1605989


Poster

Enhanced Stability of ALD-coated LAGP Solid Electrolytes

Kia Chai PHUAH, Prasada Rao RAYAVARAPU, Stefan ADAMS

National University of Singapore, Singapore

The push towards renewable energy usage today currently drives demand for high-density energy storage devices. Lithium-based electrochemical energy storage is able to provide high theoretical energy densities and has thus been an area of research interest. In particular, the replacement of graphitic anodes in today’s lithium-ion batteries with lithium metal anodes should provide a significant increase in the energy density available. However, the reactivity of lithium metal limits the number of available compatible electrolytes. For solid electrolytes, the electropositive nature of lithium metal tends to cause reduction of other cations in the electrolyte it is in contact with. One example is the NASICON-type lithium aluminium germanium phosphate (LAGP) ionic conductor, where the germanium atoms are reduced in contact with Li metal and degradation of the electrolyte occurs.

One possible way to circumvent this problem would be to fabricate a thin buffer interlayer between the Li metal anode and the solid electrolyte. Atomic layer deposition (ALD) is a technique used to deposit thin films with a precise number of layers. By alternating pulses of different precursors, precise control on the number of layers can be obtained. In addition, the ability of ALD to fabricate conformal layers with good coverage makes it ideal for membrane applications. We coat buffer oxide layers (Ta2O5, ZrO2, Al2O3) via ALD onto LAGP samples to improve the stability of LAGP towards Li metal contact. Characterization of the ALD-coated samples is performed using techniques such as X-ray diffraction and Raman spectroscopy. Time-dependent electrochemical impedance spectroscopy is then used to observe the effect of the ALD coating on the stability and ionic conductance of the coated samples as compared to pristine LAGP.



 
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