Understanding Particle-Size-Dependent Electrochemical Properties of Li2MnO3-Based Positive Electrode Materials for Rechargeable Lithium Batteries

Abstract

Electrochemical properties of Li-excess electrode materials, Li1.2Co0.13Ni0.13Mn0.54O2, with different primary particle sizes are studied in Li cells, and phase transition behavior on continuous electrochemical cycles is systematically examined. Although the nanosize (<100 nm) sample delivers a large reversible capacity of 300 mAh g–1 at the initial cycle, capacity retention is not sufficient as a positive electrode material. Moreover, unfavorable phase transition, gradual enrichment of trivalent manganese ions, and lowering structural symmetry is not avoidable on electrochemical cycles for a nanosize sample, which is confirmed by combined techniques of synchrotron X-ray diffraction, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. A submicrosize sample also delivers a large reversible capacity of 250 mAh g–1 even though a slow activation process is observed accompanied with partial oxygen loss and migration oxide ions in the crystal lattice coupled with transition metal migration on t...