Hydrothermal Synthesis And Performance Study Of Li₂FeSiO₄ As Cathode Material For Li-ion Batteries

The cathode material is the sole provider of Li⁺ and is a key factor in limiting the specific capacity of the battery.Li₂FeSiO₄ as a lithium-ion battery cathode material,because of its high theoretical capacity,in which each Li₂FeSiO₄ molecule can possess two lithium ions,when a lithium-ion reversible intercalation or deintercalation is completed,its specific capacity is 166mAh/g,when two reversible lithium ions intercalation or deintercalation is carried out,its theoretical specific capacity can reach 332mAh/g.At the same time,Li₂FeSiO₄ has a stable cycle performance,but also has a good safety performance and friendly to the environment,is growing concern,showing a promising application.Li₂FeSiO₄ crystal structure,lithium ion intercalation and deintercalation mechanism of the relevant research in the continuous maturity,and its synthesis method of exploration is also constantly research and development.There are many Li₂FeSiO₄ synthesis methods,including high-temperature solid-phase method,sol-gel method,hydrothermal synthesis methods are reported in succession.However,high-temperature solid-phase and sol-gel methods have been tried in the more common synthetic methods suitable for large quantities in industry but the progress of hydrothermal synthesis is relatively difficult.In this paper,nano-sized Li₂FeSiO₄ with a certain morphology was controlled by hydrothermal synthesis method,and its electrochemical performance was investigated.The main contents of the paper are divided into the following three parts: Li₂FeSiO₄ particles containing carbon?LFS-C?were synthesized by hydrothermal method.The growth of LFS-C was investigated under different temperature conditions,and then the comparative conditions were analyzed.Finally,it was found that the optimum temperature of LFS-C cathode material was 200 ?,the size of the sample prepared by this method is probably distributed between 100 400 nm,and the nanoscale LFS-C cathode material was obtained well,but the LFS-C cathode material contains a small amount of Fe3O4 impurity;Li₂FeSiO₄ particles without carbon?LFS?were synthesized by high temperature solid-phase method and hydrothermal method.The growth of LFS was investigated under different alkaline conditions.The results showed that the best conditions for preparing LFS cathode materials were pH = 10,the size of the sample prepared by this method is about 100 300 nm,and the synthesized nanoscale LFS cathode material was pure and had no impurity peak;The electrochemical characteristics of Li₂FeSiO₄ cathode materials were studied,and he electrochemical characteristics of LFS and LFS-C were analyzed and compared by the method of charge and discharge specific capacity,charge and discharge cycle characteristics,magnification characteristics and AC impedance.It is found that Li₂FeSiO₄ containing carbon has better electrochemical properties than Li₂FeSiO₄ without carbon,This is because the addition of carbon can improve the ionic conductivity and electron conductivity of the material,which makes the material have better electrochemical performance.