Electrochemical Properties of High Nickel NMCA Materials

Abstract

Lithium nickel manganese cobalt oxides (NMC) with high nickel composition are considered as the most promising candidates for the next-generation cathode because of their high reversible capacities (180−250 mAh g−1), high voltage window, and reasonable rate capability. However, the highly reactive Ni4+ ions tend to cause unfavorable side reactions with the electrolyte, which leads to an electrochemical inactive NiO-type rock-salt phase associated with oxygen loss on the surface at the highly delithiated state, degrading the structure of materials. Furthermore, the dramatic lattice contraction in a rather short period after charging to high voltage (>4V) causes cracks along the grain boundaries, which damages the particle integrity, delivering a gradual fading of the reversible capacity and thermal stability during cycling.Aluminum substitution is an effective strategy to stabilize the lattice structure and suppress oxygen release due to the Al-O bonds are stronger compared to other transition metal-oxygen bonds. To maximum the impact of the Al, a uniform substitution in the host structure is essential. Here we report an in-situ Al substitution strategy for NMC811, which leads to robust layered structures, reducing the phase transition and side reactions on the surface of high nickel NMC materials at the highly delithiated state. This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy, through the Advanced Battery Materials Research Program (Battery500 Consortium)