FeS2@TiO2 nanorods as high-performance anode for sodium ion battery

Sodium-ion battery(SIB)is an ideal device that could replace lithium-ion battery(LIB)in grid-scale energy storage system for power because of the low cost and rich reserve of raw material.The key challenge lies in developing electrode materials enabling reversible Na+insertion/desertion and fast reaction kinetics.Herein,a core-shell structure,FeS2 nanoparticles encapsulated in biphase TiO2 shell(FeS2@TiO2),is developed towards the improvement of sodium storage.The diphase TiO2 coating supplies abundant anatase/rutile interface and oxygen vacancies which will enhance the charge transfer,and avoid severe volume variation of FeS2 caused by the Na+insertion.The FeS2 core will deliver high theoretical capacity through its conversion reaction mechanism.Consequently,the FeS2@TiO2 nanorods display notable performance as anode for SIBs including long-term cycling performance(637.8 m A·h·g^-1 at 0.2 A·g^-1 after 300 cycles,374.9 m A·h·g^-1 at 5.0 A·g^-1 after 600 cycles)and outstanding rate capability(222.2 m A·h·g^-1 at 10 A·g^-1).Furthermore,the synthesized FeS2@TiO2 demonstrates significant pseudocapacitive behavior which accounts for 90.7%of the Na+storage,and efficiently boosts the rate capability.This work provides a new pathway to fabricate anode material with an optimized structure and crystal phase for SIBs.