Effect of Different Charging Protocols on the High-Temperature Cycling Performance and Failure Analysis of LMFP Batteries

Due to manganese dissolution, the cycling performance of lithium manganese iron phosphate (LMFP) batteries is significantly inferior to that of lithium iron phosphate (LFP) batteries.In this study, 5 Ah LMFP/C pouch cells were used to investigate the effects of different charging protocols on the high temperature cycling performance, followed by failure analysis.The results show that when the constant current-constant voltage with negative pulse (CC-CVNP) charging protocol was applied, the cell achieved 80% capacity retention after 897 cycles at 45C.Under this protocol, the manganese deposition on the anode surface (534 ppm) was significantly lower than that under the stepwise charging (CC-CC) (827 ppm) and Constant current-constant voltage charging (CC-CV) (1102 ppm) charging protocols.Furthermore, the Li diffusion coefficient (D Li + ) of the cathode material was only slightly lower than that of the fresh cell.These findings indicate that the CC-CVNP charging protocol with negative pulses not only effectively prevents the deterioration of Li + diffusion kinetics but also mitigates material degradation, thereby extending the cell's lifespan.