Improving structure stability of single-crystalline Ni-rich cathode at high voltage by element gradient doping and interfacial modifcation

Single-crystalline Ni-rich cathodes can provide high energy density and capacity retention rates for lithium-ion batteries（LIBs）.However,single-crystalline Ni-rich cathodes experience severe transition metal dissolution,irreversible phase transitions,and reduced structural stability during prolonged cycling at high voltage,which will significantly hinder their practical application.Herein,a Li4TeO5 surface coating along with bulk Te-gradient doping strategy is proposed and developed to solve these issues for single-crystalline Ni-rich LiNi0.90Co0.05Mn0.05O2 cathode（LTeO-1.0）.It has been found that the bulk Te6+ gradient doping can lead to the formation of robust Te-O bonds that effectively inhibit H2-H3 phase transformations and reinforce the lattice framework,and the in-situ Li4TeO5 coating layer can act as a protective layer that suppresses the parasitic reactions and grain fragmentation.Besides,the modified material exhibits a higher Young's modulus,which will be conducive to maintaining significant structural and electrochemical stability under high-voltage conditions,Especially,the LTeO-1.0 electrode shows the improved Li+ diffusion kinetics and thermodynamic stability as well as high capacity retention of 95.83%and 82.12% after 200 cycles at the cut-off voltage of 4.3 and 4,5 V.Therefore,the efficacious dualmodification strategy will definitely contribute to enhancing the structural and electrochemical stability of single-crystalline Ni-rich cathodes and developing their application in LIBs.