Weak Li-O bonds and small grains enable fast ion diffusion and electron transport for LiFePO4 cathode

Abstract

The LiFePO4 material continue to suffer from poor rate performance. Nanosized LFP can improve rate performance; however, nanofabrication typically requires expensive organic matter and high-pressure-resistant equipment. The current widely used solid-phase sintering methods employ FePO4 as the precursor, but it is difficult to suppress grain growth. Here, we propose a W–Ti codoping strategy to suppress grain growth during sintering, thereby improving rate performance of Li-ion batteries. W and Ti doping shrinks grains during the sintering process and make the Li-O bond more ionized. Li0.36WO3 accumulates at grain boundaries, hindering grain boundary diffusion and inhibiting grain growth during sintering. The resulting material exhibits refined grains and suppressed polarization growth, resulting in improved rate performance while maintaining a specific capacity of 117 mAh g−1 at a rate of 10 C. After 1000 cycles at a rate of 1 C, 91.0 % of the initial capacity was retained. In summary, this research provides a method for large-scale production of LFP with excellent rate performance.

Keywords

• Li-ion battery
• Cathode
• LiFePO4
• Doping
• Rate performance