Improved Rate Capability of Layered Li-Rich Cathode for Lithium Ion Battery by Electrochemical Treatment

Markedly enhanced rate performance of Li-rich (Li 1.2 Ni 0.4/3 Co 0.4/3 Mn 1.6/3 O 2 ) 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 Ni 3+ to Li + vacancies as well as the higher charge-transfer resistance by a partially insulating Li 2 O layer, which are created when a slower first charge/discharge rate is applied, result in the capacity loss upon prolonged cycling.