Construction of internal electric field to suppress oxygen evolution of Ni-rich cathode materials at a high cutoff voltage

The Nickel-rich layered cathode materials have been considered as promising cathode for lithium-ion batteries (LIBs), which due to it can achieve a high capacity of than 200 mAh g_1 under a high cutoff voltage of 4.5 V. However, the nickel-rich layered cathode materials show severely capacity fading at high voltage cycling, induced by the hybrid O anion and cation redox promote Oa_ (a< 2) migration in the crystal lattice under high charge voltage, lead to the instability of the oxygen skeleton and oxygen evolution, promote the phase transition and electrolyte decomposition. Here, Li1_xTMO2_y/Li2SO4 hybrid layer is designed by a simple pyrolysis method to enhance the high voltage cycle stability of NCM. In such constructed hybrid layer, the inner spinel structure of Li1_xTMO2_y layer is the electron-rich state, which could form an electron cloud coupling with the NCM with surface oxygen vacancies, while Li2SO4 is p-type semiconductors, thus constructing a heterojunction interface of Li1_xTMO2_y//Li2SO4 and Li1_xTMO2_y//NCM, thereby generating internal self-built electric fields to inhibit the outward migration of bulk oxygen anions. Moreover, the internal self-built electric fields could not only strengthen the bonding force between the Li1_xTMO2_y/Li2SO4 hybrid layer and host NCM material, but also boost the charge transfer. As consequence, the modified NCM materials show excellent electrochemical performance with capacity retention of 97.7% and 90.1% after 200 cycles at 4.3 V and 4.5 V, respectively. This work provides a new idea for the development of high energy density applications of Nickel-rich layered cathode materials.(c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press All rights reserved.

Automated summary

The study enhances the high voltage cycle stability of nickel-rich layered cathode materials by designing a Li1_xTMO2_y/Li2SO4 hybrid layer, which suppresses the outward migration of oxygen anions through the construction of internal self-built electric fields and improves the bonding and charge transfer between the hybrid layer and the host material, resulting in excellent electrochemical performance of the modified materials.