Niobium Tungsten Oxides as Anodes for High-Power and Low-Temperature Li-ion Batteries

Space-limited and low-temperature environments demand battery materials with both high volumetric capacity and fast charge-storage kinetics. To address this need, we investigate the electrochemical Li⁺-insertion behavior of high-density niobium–tungsten oxide (NWO) Wadsley–Roth compounds at room temperature and 0 °C. These compounds contain orthogonal crystallographic shear planes that form an m × n block structure around a corner-sharing network. We compare three NWO materials: Nb12WO33 (3 × 4), Nb14W3O44 (4 × 4), and Nb16W5O55 (4 × 5). Operando electrochemical X-ray diffraction shows that structural evolution during Li⁺ insertion becomes more complex as block size increases. At a C/10 rate and 25 °C, all three compounds store more than 1 Li⁺/e⁻ per transition metal (T.M.), with Nb14W3O44 (4 × 4) and Nb16W5O55 (4 × 5) reaching volumetric capacities of 1,315 mAh/cm³ and 1,247 mAh/cm³, respectively. Rate-capability measurements at 25 °C and 0 °C show that larger block sizes maintain higher capacity at slow (dis)charge rates, whereas asymmetric block sizes (m ≠ n) deliver greater rate capability. All three materials outperform a commercial graphite anode in volumetric capacity, rate capability, and long-term cycling with each material retaining over 90% of capacity at 25 °C and 95% at 0 °C after 500 cycles. These results highlight NWO phases as promising candidates for lithium-ion batteries that require high volumetric energy density, high power, and reliable low-temperature operation.