High C-Rate Lithium Ion Batteries with Niobium Tungsten Oxide

Abstract

Lithium ion batteries are heavily investigated as storage devices, in order to obtain high energy density and high power density. However, there are still many problems to be solved; high rate and low temperature cycling of graphite-based electrode leading to lithium plating, for example. Recently, our group has introduced niobium tungsten oxide (NWO) as a high-rate electrode material for lithium ion batteries[1]. As an extension of this study, Nb16W5O55 is electrochemically tested with commercial cathode materials and the feasibility for high C-rate lithium ion batteries is confirmed. For this purpose, the Ni-rich NMC622 (Li(Ni0.6Mn0.2Co0.2)O2) compound and LFP (LiFePO4) cathode material are coupled with the crystallographic shear structured Nb16W5O55 anode, and 1.0 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate (EC)/dimethyl carbonate (DMC) (1/1 vol.%) is used as electrolyte. From the full cell test with NMC622, NWO shows 86.8% capacity retention at 5C/5C charge/discharge after 500 cycles with high coulombic efficiency. Moreover, with LFP cathodes, an excellent stable performance of 89% of capacity retention at 10C/10C after 1000 cycles is confirmed. Electrolyte analyses are performed by solution NMR, and the full cell degradation is thoroughly investigated by EIS, SEM and XRD. Electrochemical performance at high temperatures is also discussed in detail. Keywords: niobium tungsten oxide, lithium ion battery, anode, high c-rate material Reference [1] K.J. Griffith, K.M. Wiaderek, G. Cibin, L.E. Marbella and C.P. Grey, Nature, 559, 556 (2018).