4:00pm - 4:30pmInvited
Transition Metal Monoxides for Positive Electrodes In Lithium-ion Batteries
1Seoul National University, South Korea; 2Center for Nanoparticle Research, Institute for Basic Science (IBS), South Korea
Lithium ion batteries based on intercalation compounds have dominated the advanced portable energy storage. Positive electrode materials in these batteries belong to a material group of lithium-conducting crystals that contain redox-active transition metal and lithium. Materials without lithium conducting paths or lithium-free compounds could be rarely used as positive electrodes due to the incapability of reversible lithium intercalation or the necessity of using metallic lithium as negative electrodes. These constraints have significantly limited the choice of materials and retarded the development of new positive electrodes in lithium ion batteries. Here, we demonstrated that lithium-free transition metal monoxides that do not contain lithium-conducting paths in their crystal structure can be converted into high-capacity positive electrodes in the electrochemical cell by initially decorating the monoxide surface with nano-sized lithium fluoride. This unusual electrochemical behavior is attributed a ‘surface conversion reaction mechanism’ in contrast with the classic lithium intercalation reaction. Our findings will offer a potential new path in the design of positive electrode materials in lithium ion batteries.
4:30pm - 5:00pmInvited
Synthesis, Structure and Electrochemical Properties of New Lithium Iron Vanadates
1Université de Montreal, Canada; 2Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux, France
Iron vanadates have been widely explored as possible electrode material for Li batteries. Up to now, the ternary Li2O-Fe2O3-V2O5 phase diagram only displays two lithium iron vanadium oxides with a similar spinel structure. Our recent investigations allowed us to identify two new phases in this system. These two compounds will be discussed in this presentation starting with their synthesis and their thermal properties. Single crystal diffraction data were collected at room temperature and the structure was refined with JANA-2000 program package. Mössbauer and magnetic measurements were also used to check the oxidation state of iron ions, to support the obtained crystal structure and to consider any possible structural/magnetic transitions. A specific emphasis will be given to the interesting electrochemical properties of these new phases.
5:00pm - 5:15pmOral
Sonochemical Synthesis with Controlled Stoichiometry of Na0.7MnO2 and Na0.44MnO2 as Cathode materials for Na-ion Batteries and Na-ion Capacitors
Indian Institute of Science, India
Energy storage technologies are imperative these days for myriads of applications. Among various energy storage technologies, Lithium-ion batteries (LIBs) and Lithium-ion capacitors (LICs) have attracted much attention due to their high energy and power density respectively. The constraint in the lithium resource impels us to replace Li with other abundant elements. Sodium seems to be the most attractive element to replace lithium with comparable standard electrode potential (-2.71 V vs SHE) and practically unlimited resources making this technology cost effective. Cathode plays an important role in storage devices (batteries and supercapacitors). Various transition metal oxides and polyanionic compounds can be employed as efficient cathode materials, but oxides are favourable owing to their high energy density and ease of synthesis. Current work explores two manganese based oxides as cathodes for Na-ion batteries (NIBs) and Na-ion Capacitors (NICs): (i) Na0.7MnO2 and (ii) Na0.44MnO2.
Sodium manganese oxides mainly have two kinds of structures: (i) layered structure (e.g. Na0.7MnO2) or (ii) tunnel structure (e.g. Na0.44MnO2), both having large number of vacancies accommodating constituent Na-ions. Na0.44MnO2 is particularly attractive as cathode in NIB because of its unique 3D crystal structure, which greatly facilitates Na+ mobility whereas Na0.7MnO2 is good candidate for cathode in NICs owing to its sloppy discharge profile. In the current work, we focused on (ultrasonic) sonochemical synthesis of above target compounds, which restricts the final high-temperature annealing duration within 1-2 h. Herein, we will present (i) single crystalline Na0.7MnO2 nanoplates with preferential growth in (100) direction facilitating efficient Na+ (de)insertion leading to capacity over 140 mAh/g (average voltage = 2.6 V) and (ii) orthorhombic Na0.44MnO2 having a reversible capacity of 110 mAh/g (average voltage = 2.8 V). The salient features of sonochemical synthesis, structure, morphology and final electrochemical performance (both as NIB and NIC) will be presented.
5:15pm - 5:30pmOral
Non-flammable and Inexpensive Non-aqueous Sodium-ion Batteries
1Department of Mechanical Engineering, National University of Singapore, Singapore; 2Department of Materials Science and Engineering, National University of Singapore, Singapore
Sodium-ion batteries (NIBs) are poised to become a viable energy storage option for large-scale electrochemical energy storage. In fact, aqueous NIBs have already been commercialized for such grid-storage applications. Non-aqueous NIBs would be attractive due to the promise of higher energy densities due to the higher operating voltage. In this context, reducing costs of such grid-storage NIBs would be critical. While NIBs benefit from the globally abundant Na resources, such benefits would translate to cost reductions only if the Na based cathode and anode materials also employ other abundant elements. Furthermore, these non-aqueous NIBs should also be extremely safe and durable.
Therefore, in this presentation, we will firstly reveal the sodium storage characteristics of an extremely Na-rich phase of an all Fe-based Prussian Blue Analogue (PBA) cathode. This new phase, the monoclinic Na2Fe2(CN)6.2H2O, synthesized from a very scalable and ambient pressure-based reflux reaction, can deliver moderate capacity of 85 mAh/g at an attractive potential of 3 V vs Na/Na+ together with long cycle life of 3,000 cycles. We shall discuss the effect of structural water on its electrochemical performance and its conversion to the dehydrated Na2Fe2(CN)6 phase which possesses a very high capacity approaching 170 mAh/g.
From a holistic view of battery development, it should be remembered that the type of electrolyte used may be more important in determining battery performance and stability than simply considering that of cathodes and anodes. Hence, we will also reveal a newly developed non-aqueous liquid electrolyte which will be shown to be compatible with low voltage anodes and also high voltage cathodes. Most impressively, this electrolyte is non-flammable. We shall finally reveal various types of durable full cells by pairing the PBA cathodes mentioned above with different types of earth-abundant anodes to yield attractive contenders for future grid-storage NIBs.
5:30pm - 5:45pmOral
Carbon Coated Na4Co3(PO4)2P2O7: A Multifunctional Cathode Material for Hybrid Sodium-air Battery
Indian Institute of Science (IISc), India
In recent years, sodium-air batteries (Na-air) are getting prominent interest as an effective alternate to Li-air batteries, given the facts that Na-air batteries are much safer, economic and have high power density arising from much higher ionic conductivity of Na-ion based solid electrolyte and high solubility of discharge product [1-3]. Based on cell design and electrolyte type, Na-air batteries can be classified into two major types: Non-aqueous and Aqueous (hybrid) batteries [3-5]. Recent studies have shown that hybrid Na-air batteries hold some edges over non-aqueous systems, including low overpotential, higher rate capability, improved energy efficiency, and higher power density [4,5]. Bifunctional catalysts are prominent to attain high capacity, maximum energy efficiency and long cycle-life for aqueous rechargeable Na-air batteries [4,5]. In this work, nanostructured carbon coated Na4Co3(PO4)2P2O7 is exploited as a multifunctional cathode material for hybrid Na-air battery. The material is prepared by solution combustion synthesis using citric acid as fuel. Crystal structure of Na4Co3(PO4)2P2O7 is analyzed using neutron diffraction studies and it has a space group of Pn21a. The structure consists of 3D conducting path ways for Na-ion and exhibits a theoretical capacity of 170 mAh/g. We have attained a maximum discharge capacity of 108 mAh/g in the first cycle. The electrocatalytic properties of the pristine and Na+ de-intercalated structures of the material have been investigated. Hybrid Na-air batteries have been fabricated using the material as air cathode. The multidimensional charge storage capability and bi-functional (OER/ORR) electrocatalytic activity of this material will be presented. The performances of the air battery will be discussed.
 P. Hartmann et al., Nat. Mater. 12(2013)228-232.
 S. K. Das et al., J. Mater. Chem. A2(2014)12623-12629.
 P. G. Bruce et al., Nat. Mater., 11(2012)19-29.
 K. Hayashi et al., J. Electrochem. Soc., 160(2013)A1467-A1472.
 B. Senthilkumar et al., J. Power Sources, 311(2016)29-34.
5:45pm - 6:00pmOral
Building Freestanding Electrode Materials for High-Performance Li-Ion Batteries
Northwestern Polytechnical University, China
With the booming development of flexible electronics, it is necessary to explore flexible energy storage devices based on freestanding electrodes. In this talk, we will present two kinds of freestanding electrode materials. Coaxial ultralong MnO/C hybrid nanowires are developed via a novel strategy of interfacial polymerization method. The entanglement of MnO/C nanowires enables the formation of a robust freestanding paper for Li-ion batteries. A high specific capacity of 803 mAh g-1 is obtained for the hybrid electrodes after 100 cycles without the assistance of conductive agents and binders. To improve the flexibility of the nanocomposite, a new 1D/2D architecture of graphene/Mn3O4 nanowire is reported to demonstrate excellent mechanical deformability, such as rolling, folding, and twisting. The flexible graphene/Mn3O4 electrode could deliver a stable specific capacity of 800 mAh g-1 along with superior rate capability and cycling stability. The electrode is further to construct a flexible full Li-ion battery, which shows excellent electrochemical properties and high flexibility, demonstrating its great potential for high-performance flexible energy storage devices.
6:00pm - 6:15pmOral
Pseudocapacitive Na-Ion Storage Boosts High-Rate and Areal Capacity of Self-Branched 2D Layered Metal Chalcogenide Nanoarrays
Nanyang Technological University, Singapore
The abundant reservation and low cost of sodium have provoked tremendous evolution of Na-ion batteries (SIBs) in the past few years, but their performances were still limited either by the specific capacity or rate capability. Attempts to pursuit high-rate ability with maintained high-capacity in a single electrode remains even more challenging. Here, an elaborate self-branched 2D SnS2 (B-SnS2) nanoarrays electrode is designed by a facile hot bath method for Na storage. This interesting electrode exhibits unprecedented areal reversible capacity of ca. 3.7 mAh cm-2 (900 mAh g-1), and rate capability of 1.6 mAh cm-2 (400 mAh g-1) at 40 mA cm-2 (10 A g-1). Improved extrinsic pseudocapacitive contribution is demonstrated as the origin of fast kinetics of alloying-based SnS2 electrode. Sodiation dynamics analysis based on first-principle calculations, ex-situ HRTEM, in-situ impedance, and in-situ Raman technologies verify the S-edge effect to the fast Na+ migration, reversible and sensitive structure evolution during high-rate charge/discharge. The excellent alloying-based pseudocapacitance and unsaturated edge-effect enabled by self-branched surface nanoengineering could be a promising strategy for promoting development of SIBs with both high capacity and rate response.
6:15pm - 6:30pmOral
Increased Cyclic Stability of Uniform Carbon Coated Lithium Stoichiometric Layered and Li-Excess Mn-Based Transition Metal Oxide Materials
International Advanced Research Centre for Powder Metallurgy and New Materials, ARCI, India
Layered lithium transition metal oxide LiNi1-x-yCoxMnyO2 (LNMC), is an extensively used cathode material in lithium ion batteries for electric vehicle applications . However, the cyclic stability of pristine layered oxides is poor due to the unwanted secondary reaction with the electrolyte. Though the cyclic stability and electrochemical characteristics of NMC can be improved by having uniform carbon coating, there is a industrial challenge to achieve it. We have developed an in-situ technique to coat uniformly carbon on oxide material. This has been done by the solid-state reaction of carbon precursor pillared transition metal hydroxide with lithium hydroxide. Pillaring of carbon precursor in between the layers of hydroxide reduces the reaction rate between oxygen and carbon precursor leading to uniform carbon coating on oxides even when heat-treated in air ambient. The mechanism of in-situ carbon coating on oxide material and its implication on the electrochemical characteristic of LNMC will be presented. This technique can be easily extended to any of the oxide active materials for lithium ion battery material. As an example, the effect of having uniform carbon coating on lithium excess Mn-based layered oxide (LLO) on its electrochemical properties will be discussed. It is observed that uniform carbon coating on LNMC and LLO increases the cyclic stability and decreases the average voltage decay with repeated charging/discharging cycle drastically compared to pristine LLO. The fabrication of lithium ion batteries for electric vehicle applications in our Centre will also be presented.
 Shumei Dou, J Solid State Electrochem (2013) 17:911–926