Enhancement of the high potential specific charge in layered electrode materials for lithium-ion batteries

Abstract

Among the layered transition metal oxide electrodes, the NCA (Li(Ni_1−x−yCo_xAl_y)O₂) and the NMC (Li_1+a(Ni_xMn_yCo_z)_1−aO₂) families with working potentials ranging from 4 V to close to 5 V against Li metal are nowadays identified as potential high specific energy materials. The present candidates have their advantages and drawbacks, i.e. NCA is a high energy density material but safety is of major concern while NMC has a lower energy density but exhibits improved safety. Recently, overlithiated layered transition metal oxides have proved to deliver reversible specific charge over 200 mA h g⁻¹. The high specific charge is associated with a complex reaction mechanism that involves the activation of the material at high potentials. However, further R&D is needed for the current technology to meet the needs, in terms of safety, cost, energy and power capabilities, of the emerging HEV and EV market. A review of the state-of-the-art of these families of compounds together with current approaches for their future development is presented.