BiPO4/hard-carbon composite anode enables 10C fast-charging for lithium-ion battery applications

Abstract

Post-transition metal phosphates are promising alternatives to traditional anodes for lithium-ion batteries (LIBs), offering higher energy and power density without concerns of lithium plating. However, their practical applications are hindered by challenges, such as volume expansion, poor rate capability, and capacity degradation, particularly in fast-charging applications. This study presents a strategy to mitigate these challenges and enhance the rate performance of bismuth phosphate (BiPO₄) by creating a BiPO₄/hard carbon composite anode.

BiPO₄ nanoparticles are synthesized via a cost-effective, co-precipitation method at 350 °C (ramp of 10 °C/min). The influence of heating rates on crystallite size is also investigated. The HC sheet accelerates reaction kinetics and Li⁺ diffusion within the BiPO₄/HC composite. Consequently, the BiPO₄/HC anode demonstrates superior rate performance and cycling stability. It delivers a reversible capacity of 212.2 mAh g⁻¹ (67% retention after 500 cycles at a current rate 6C) and 200 mAh g⁻¹ (62% retention after 500 cycles at a current rate 10C), with a consistent 99.9% coulombic efficiency. Furthermore, a full cell assembled with a composite anode and lithium iron phosphate (LiFePO₄) cathode exhibits 70% capacity retention at a current density of 200 mA g⁻¹ over 250 cycles, confirming its potential for high-performance applications in LIBs.