Study On Synthesis And Electrochemical Properties Of Li₂FeSiO₄ Cathode Materials For Lithium-ion Batteries

In recent years,Li₂FeSiO₄ cathode material has been widely tested due to its excellent properties.Li₂FeSiO₄ cathode material has many advantages such as abundant raw materials,high theoretical capacity,stable working voltage,good thermal stability,large reserves of earth crust and environmental friendliness.However,the electroconductivity of Li₂FeSiO₄ electrode material is very poor,which makes it difficult to exert the advantages.Therefore,it becomes an important topic to improve the electrode conductivity and lithium ion diffusion coefficient.In this article,the effects of synthesis conditions,coating and doping on the structure,morphology and electrochemical properties of Li₂FeSiO₄ were studied.In this report,Orthorombic crystal system Li₂FeSiO₄ electrode materials coated with carbon?from glucose and ascorbic acid?were synthesized from sol-gel method based on solvothermal and further coated another layer of hierarchical porous carbon?from cornstalk?by ball-milling method.And the iron substitution of rare earth ions Sm3+ was studied.Effect of cornstalk carbon on microstructure and electrochemical performances of Li₂FeSiO₄/C/BC composite electrode materials have been investigated using XRD,SEM and TEM,C v and EIS.Result shows that all the samples of Li₂FeSiO₄/C synthesized are orthorombic structure,the carbon source coating and Sm3+ substitution can regulate the Li₂FeSiO₄ cell parameters,which can effectively inhibit the agglomeration of particles.The partical size of the as prepared Li₂FeSiO₄/C composite materials are very uniform and distributed from 50 to 200 nm with 10 wt% glucose.Li₂FeSiO₄/C/BC composite materials are about 100 nm with 20 wt% cornstalk carbon.The results of electrochemical performance show that glucose can improve the discharge capacity of the electrode material and cyclic stability.The maximum discharge capacity of the sample with 10 wt% glucose is 158.4 mAh·g-1,after 10 cycles,the discharge specific capacity was stable at 142.6 mAh·g-1;The maximum discharge capacity of the sample with 8 wt% ascorbic acid is 132.5 mAh·g-1,after 10 cycles,the discharge specific capacity was stable at 118.2 mAh·g-1;The maximum discharge capacity of the sample with 20 wt% cornstalk carbon is 237.2 mAh·g-1,when the Sm3+ content is 0.01,the charge transfer resistance of Li₂Fe0.99Sm0.01SiO₄/C is the smallest.