Improved rate capability of layered li-rich cathode for lithium ion battery by electrochemical treatment

Markedly enhanced rate performance of Li-rich (Li1.2Ni0.4/3Co0.4/3Mn1.6/ 3O2) cathode material is observed after a simple electrochemical pretreatment. The cathode material can deliver discharge capacities of 196, 124 and 86 mAh g?1, under current densities of 2, 20 and 40 C, respectively. The capacity retention reaches 60% after 1000 cycles even at 20 C. Analysis of dQ/dV plot and impedance spectroscopy prove that more migration of Ni3+ to Li+ vacancies as well as the higher charge-transfer resistance by a partially insulating Li2O layer, which are created when a slower first charge/discharge rate is applied, result in the capacity loss upon prolonged cycling. © 2013 The Electrochemical Society