Bulk and surface reconstructed Li-rich Mn-based cathode material for lithium ion batteries with eliminating irreversible capacity loss

Abstract

Bulk and surface reconstructed Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode materials induced by spinel embedment and γ-MnO2 modification were synthesized by a one-step hydrothermal method. The results of XRD, XPS and SEM confirmed the introduction of γ-MnO2. The analysis of XPS, TEM images, dQ/dV curves and CV curves demonstrated that a spinel phase is embedded synchronously in the bulk of layered structure during the process of γ-MnO2 modification. The results of charge-discharge profiles and dQ/dV curves demonstrated the irreversible discharge capacity loss in the initial cycle is reduced with the introduction and collaboration of spinel and γ-MnO2. Namely, the initial coulombic efficiency is improved up to approximately 100%. Furthermore, the specific discharge capacity and rate performances are enhanced by a structure breakthrough for Li+ transport through blending with electrochemical active spinel-phase and γ-MnO2. In addition, the capacity retention of the material is enhanced from 64% up to 85% after 200 cycles. The main reasons are that the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is stabilized and the phase transformation from surface to bulk is mitigated under the protection of γ-MnO2 coating layer.