10 μm-Level TiNb₂ O₇ Secondary Particles for Fast-Charging Lithium-Ion Batteries

TiNb₂ O₇ with Wadsley-Roth phase delivers double theoretical specific capacity and similar working potential in comparison to spinel Li₄ Ti₅ O₁₂ , the commercial high-rate anode material, and thus can enable much higher energy density of lithium-ion batteries. However, the inter-particle resistance within the high-mass-loading TiNb₂ O₇ electrode would impede the capacity release for practical application, especially under fast-charging conditions. Herein, 10-20 μm-size carbon-coated TiNb₂ O₇ secondary particle (SP-TiNb₂ O₇ ) consisting of initial micro-scale TiNb₂ O₇ particles (MP-TiNb₂ O₇ ) was fabricated. The high crystallinity of active material could enable fast-charge diffusion and electrochemical reaction rate within particles, and the small number of stacking layers of SP-TiNb₂ O₇ could reduce the large inter-particle resistance that regular particle electrode often possess and achieve high compaction density of electrodes with high mass loading. The investigation on materials structure and electrochemical reaction kinetics verified the advances of the as-fabricated SP-TiNb₂ O₇ in achieving superior electrochemical performance. The SP-TiNb₂ O₇ exhibited high reversible capacity of 292.7 mAh g^-1 in the potential range of 1-3 V (Li⁺ /Li) at 0.1 C, delivering high-capacity release of 94.3 %, and high capacity retention of 86 % at 0.5 C for 250 cycles in half cell configuration. Particularly, the advances of such an anode were verified in practical 5 Ah-level laminated full pouch cell. The as-assembled LiFePO₄ ||TiNb₂ O₇ full cell exhibited a high capacity of 5.08 Ah at high charging rate of 6 C (77.9 % of that at 0.2 C of 6.52 Ah), as well as an ultralow capacity decay rate of 0.0352 % for 250 cycles at 1 C, suggesting the great potential for practical fast-charging lithium-ion batteries.