First-Principles Theory Calculation And Material Modification Prediction Of Lithium Iron Silicate

In the context of new energy applications,we optimized the performance of a lithium-ion battery cathode material through first-principles calculations.A rational structural model was established to investigate the influence of the microscopic properties of the material on the electrochemical performance of the battery.The lithium iron silicate（Li₂Fe Si O₄）is exactly the matrix structure to be carried the class-elements doping modification study.The doped elements include Ti with its congeners,Zr,Hf,and iron’s same-period elements,V,Mn,Co,Ni,and main group elements,Al,Mg.All of them are used to replace the iron atom.At first,the suitable doping scheme is obtained by comparing the formation energy and band gap of the material structures with different doping ratios.Then,the migration network of lithium ions in the material was calculated.On this basis,the effects of the doping element on energy barrier of the lithium-ion migration path was compared,and the performance of lithium migration in the modified cathode materials was evaluated.After comparing the data from different doping proportions of Ti series,we found the5%doping is sufficient to present the impact of heteroatoms on the formation energy and the electronic structure.Therefore,the other two series are calculated on association attributes.The main results is summarized as following:（1）The selected doping materials are not only feasible in the experimental synthesis,but also are benificial to fully release the theoretical lithium capacity of the battery.（2）The majority of metals doping increases the conductivity of the material significantly via changing the electronic structure.The frontier orbital contribution of impurity atoms is the main reason.（3）NEB transition state search was applied in the representative lithium migration path,B01-04,B02-25 of the matrix structure.It’s found that Ti-,Zr-,Hf-and Mn-doping enlarge the barrier difference of two lithium migration paths,and thus improve the overall performance of the lithium migration because the lithium ion tends to choose the lower energy barrier path.Moreover,the doping of Ni,Mg and Al reduces the energy barrier of the lithium migration path directly and thus prompt the lithium migration in the material.These studies analyzed the electronic structure and lithium ion migration performance of lithium iron silicate and its doped materials,aiming to point out the feasible way to optimize the materials and provide theoretical reference for the subsequent experimental preparation.