Regulating local chemical environment in O_(3)-type layered sodium oxides by dual-site Mg^(2+)/B^(3+)substitution achieves durable and high-rate cathode

The O_(3)-Na_(0.85)Ni_(0.2)Fe_(0.4)Mn_(0.4)O_(2)layered oxide cathode material possesses the advantages of high specific capacity,low cost,and simple synthesis.However,sluggish kinetics and complicated phase transition caused by the large size difference between Na+and tetrahedral gaps lead to poor rate and cycling performance.Therefore,a scalable and feasible strategy was proposed to modulate local chemical environment by introducing Mg^(2+)and B^(3+)into O_(3)-Na_(0.85)Ni_(0.2)Fe_(0.4)Mn0.4O_(2),which can distinctly improve kinetic transport rate as well as electrochemical performance.The capacity retention of O_(3)-(Na_(0.82)Mg_(0.04))(Ni_(0.2)Fe_(0.4)Mn_(0.4))B_(0.02)O_(2)(NFMB)increases from 43.3%and 12.4%to 89.5%and 89.0%at 1 C and 3 C after 200 cycles,respectively.Moreover,the electrode still delivers high rate capacity of 93.9 mAh/g when current density increases to 10 C.Mg^(2+)ions riveted on Na layer act as a“pillar”to stabilize crystal structure and inhibit structural change during the desodiumization process.B^(3+)ions entering tetrahedral interstice of the TM layer strengthen the TM-O bond,lower Na+diffusion energy barrier and inhibits the slip of TM layer.Furthermore,the assembled full batteries with the modified cathode material deliver a high energy density of 278.2Wh/kg with commercial hard carbon as anode.This work provides a strategy for the modification of high-performance SIB layered oxide materials to develop the next-generation cost-effective energy storage grid systems.