Synthesis and electrochemical behavior of K+ and Mn2+ co-doped LiFePO4/C as a cathode material for lithium-ion batteries and the mechanism of modification

Abstract

Mn and K co-doped lithium iron phosphate (LFP) cathode materials are obtained by an expedient solvothermal method. The contributions of the two doped elements to the LFP are discussed in detail by density functional theory (DFT) calculations and several characterizations. The presence of Mn improves the energy band and diffusion kinetics, while the stabilized structure and the widened diffusion channel are attributed to K. Benefiting from the expanded ion channels and stable structure that resulting from the doping treatment, the LFP cathode exhibits a remarkable capacity of 145 mAh·g−1 at 5 C and demonstrates a 96% retention rate after 400 cycles. In particular, the interaction between the two doping elements, which is less mentioned in other literature is discussed by building a failure model of the control group. The samples co-doped with K and Mn (KLMFP) showed better electrochemical performance than the other groups in cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge–discharge cycling tests.