Efficient Preparation of Li2FeSiO4/C with High Purity and Excellent Electrochemical Performance in Li-Ion Batteries

One method to enhance the electrochemical performance of carbon-coated Li₂FeSiO₄ cathode material in lithium-ion batteries is to produce an ideal Li₂FeSiO₄ precursor with minimal impurities. A novel precursor for Li₂FeSiO₄ (Li₂O·FeCO₃·CH₃OSiO₂H) was synthesized through a methanol solvothermal reaction under stringent conditions (180 °C and 2.7 MPa), achieving a purity level of 93.2%. During synthesis, the new Li₂FeSiO₄ precursor exhibits unique self-purification properties and maintains a fine morphology after annealing. The resulting carbon-coated Li₂FeSiO₄ composites demonstrate a Brunauer-Emmett-Teller specific surface area of 102.4 m²/g and approximately 81% mesoporous volume, with 90% of the pore sizes measuring less than 39 nm. As a cathode material for lithium-ion batteries, this carbon-coated Li₂FeSiO₄ exhibits initial specific capacities of 172.3 mAh/g (charge) and 159.3 mAh/g (discharge). Remarkably, nearly 50% of the theoretical specific capacity remains after 1300 cycles at a rate of 0.1 C. The excellent electrochemical performance of the carbon-coated Li₂FeSiO₄ materials is demonstrated by their high lithium-ion diffusivity (D_Li+) value of 1.26 × 10^-11 cm²/s. Additionally, the enormous capacities-controlled diffusion contribution, which accounts for 70% of the total diffusion at a rate of 1C, is noteworthy. This performance can be attributed to the high purity of the carbon-free Li₂FeSiO₄ composite, which contains 91% Li₂FeSiO₄, as well as its favorable morphology.