Li3BO3 decoration endows fast reaction kinetics of LiFePO4 cathode for lithium ion batteries

Abstract

Olivine-type lithium iron phosphate is widely used as a cathode material for lithium-ion batteries because of its moderate operating voltage, excellent stability, and high safety. However, the high rate capability of LiFePO₄ is limited by its low electrical conductivity. Additionally, its interface and internal structure would degrade under high-rate conditions. To address these issues, Li₃BO₃ was prepared via sol-gel method as the surface decoration to enhance the rate performance of LiFePO₄. The Li₃BO₃ decorated LiFePO₄ (B-LiFePO₄) maintains the structural integrity during cycling under large current densities, furthermore, it induces the formation of favorable cathode-electrolyte interface (CEI) with less Li₂CO₃ and more Li₂O contents, and reduces the activation energy of Li⁺ diffusion in the CEI layer and charge transfer, thus the high capacity and long cycle performances of LiFePO₄ are achieved when cycled at high current densities. At ambient environment and 30C, B-LiFePO₄ delivers a high reversible capacity of 63.1 mAh g⁻¹, and a capacity retention of 90 % can be realized over 600 cycles at 1C. In contrast, the original LiFePO₄ delivers only 27.8 mAh g⁻¹ at 30C and a capacity retention of 67.2 % after 600 cycles at 1C. Besides, B-LiFePO₄ demonstrates good low temperature performance, it exhibits high capacities of 122.1 and 80.7 mAh g⁻¹ at 1C, 0 °C and − 20 °C, respectively. This study provides a simple method to enhance the reaction kinetics of LiFePO₄ cathode, which would benefit the development of LiFePO₄ based lithium ion batteries with high rate performance.