Truth and mechanism of high safety and long durability in Fe-rich lithium ferromanganese silicate (LFMS) cathode-based Li-ion batteries: A first principles and experiment study

The cathodes containing SiO44− system possess a higher energy density, so it can greatly reduce energy consumption and enable the prepared Li-ion batteries to have a longer durability. The representative is Li2FeSiO4, which has great development potential in the domain of large-scale Li-ion power batteries on account of the truth that it features high safety, low cost and environmental friendliness, etc. However, its mass and charge transport delay hinder the further application of Li2FeSiO4, and it needs to be modified before it can be popularized. In this paper, the Li2Fe1-xMnxSiO4/C (x = 0, 1/24, 1/12, 1/8, 1/4) in Pmn21 space group has been successfully made by chemical co-precipitation method. The crystal structure, bonding condition, mechanical properties, energy band, state density, local charge density and differential charge density of Li2Fe1-xMnxSiO4 system were calculated and discussed by first principles, and their effects on the electrochemical performances of materials were analyzed. A theoretical foundation for further enhancing the electrochemical performance of Li2FeSiO4 cathode materials is provided by the revelation of the modification of crystal/electronic structure and electron transport in the charging-discharging process. Both calculation and experiment show that Li2Fe23/24Mn1/24SiO4/C cathode has the best performance. This material has excellent dynamic characteristics because of its minimal band gap. It has a discharge capacity of 153.1 mAh/g at 0.5C. After 100 charge and discharge cycles, it still maintains 149.5 mAh/g, and the capacity retention rate is 97.65 %. •The Li2Fe1-xMnxSiO4/C in Pmn21 was prepared by the chemical co-precipitation method.•The first principle provides a theoretical basis for improving property of Li2FeSiO4.•The 1/24 content Mn is optimum as conductive additive.