Controllable oxygen vacancies (in surface and bulk) to suppress the voltage decay of Li-rich layered cathode

Abstract

Li-rich Mn-Based layered oxide is defined as a potential cathode material for its high specific capacity while several significant drawbacks such as inferior cycling stability and voltage decay limit its wide application. In this work, a suite of characterization techniques is employed to comprehensively investigate the crystal structure, surface morphology and chemical state of materials. The results suggest the successful preparation of layered oxide with controllable oxygen vacancies. Specifically, 1) Surface oxygen vacancies can act as a deterrent to irreversible oxygen release, consequently suppressing the voltage decay. 2) Stable lattice oxygen can enhance structural stability during cycling. 3) Swing-like sintering methodology and inducing surface oxygen vacancies technique are connected to synthesize the layered oxide with little lattice oxygen vacancies and abundant surface oxygen vacancies. The as-prepared cathode exhibits a commendable capacity retention of 85 %, and managed to alleviate the voltage attenuation significantly to 3.81 mV/cycle over 150 cycles at 0.5C. This concept of pre-constructing controllable oxygen vacancies provides important groundwork for developing Li-rich cathode with mitigated voltage decay and enhanced cycle life.