Synthesis and lithium storage performance of Mg/Nb dual-doped LiMn0.7Fe0.3PO4/C cathodes

Lithium manganese iron phosphate (LiMn x Fe 1- x PO 4 , 0 <  x  < 1) is regarded as an upgraded cathode material compared to lithium iron phosphate (LiFePO 4 ), owing to its higher voltage plateau and superior energy density. However, its commercial application has been hindered by inherent poor electronic conductivity, abysmal Jahn–Teller effect and manganese dissolution associated with the Mn 3+ , which simultaneously degrades the rate capability and cycling performance. In this study, a dual-doping modification strategy based on a co-precipitation and high-temperature solid-state reaction method is proposed, successfully yielding magnesium and niobium dual-doped LiMn 0.7 Fe 0.3 PO 4 /C composites. The results demonstrate that an appropriate amount of Mg and Nb dual-doping can effectively enhance the electronic/ionic conductivity, improve structural stability, and accelerate lithium-ion migration kinetics of the manganese-enriched lithium manganese iron phosphate. The as-prepared LMFP-Mg2Nb2 sample exhibits optimal rate performance and cycling stability. It maintains a reversible capacity of 145.27 mAh g −1 even at a high current rate of 4C. Furthermore, after 100 cycles at 1C, it demonstrates an excellent discharge capacity of 149.97 mAh g −1 with a high-capacity retention of 98.29%. The synthetic strategy by co-precipitation and solid-state method involved in this work is analogous to the mainstream commercial technical approach for LiFePO 4 -based cathode material and compatibility with commercial LiFePO 4 -production equipment, thereby laying a significant foundation for the industrial application of high-energy-density lithium manganese iron phosphate.