Based on first-principles calculation, study on the synthesis, and performance of Fe–Ni co-doped LiMnPO4/C as cathode material for lithium-ion batteries

Olivine-structured LiMnPO4 is one of the cathode materials with great application prospects for lithium-ion batteries in that it possesses the characteristics of abundant raw materials, low price, stable structure, high energy density, and good cycling stability. In this paper, the electronic structure of LiMn1-x-yFexNiyPO4 (x = 0, y = 0; x = 1/4, y = 1/4) system is calculated by using MS (Material Studio) software. The calculated results show that the band gap width of LiMn1/2Fe1/4Ni1/4PO4/C system is 0.105 eV, which has a great change compared with LiMnPO4. Thus, it is speculated that the Fe–Ni co-doped LiMnPO4 material has better electrochemical performance. The LiMn1-x-yFexNiyPO4 (x = 0, y = 0; x = 1/4, y = 1/4) composite materials were synthesized by co-precipitation method, and the optimum synthesis conditions also was explored. The electrochemical test indicates that the LiMn1/2Fe1/4Ni1/4PO4/C cathode material has excellent electrochemical properties, and its initial charge–discharge capacity is 143.8 mAh/g, which is significantly higher than that of LiMnPO4 material. The discharge capacity of this sample remains at about 152 mAh/g after 100 cycles at 0.05 C rate, showing good cyclic stability. The results of theoretical calculation and experimental test confirm each other, so as to prepare the LiMn1/2Fe1/4Ni1/4PO4/C materials with excellent electrochemical performance.