Self-standing Li1.2Mn0.6Ni0.2O2/graphene membrane as a binder-free cathode for Li-ion batteries

Yang Puheng; Wang Wenxu; Zhang Xiaoliang; Li Honglei; Zhang Shichao; Xing Yalan

doi:10.1039/c8ra06086j

Self-standing Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane as a binder-free cathode for Li-ion batteries

RSC Adv. 2018 Nov 28;8(69):39769-39776. doi: 10.1039/c8ra06086j. eCollection 2018 Nov 23.

Authors

Yang Puheng¹, Wang Wenxu¹, Zhang Xiaoliang¹, Li Honglei¹, Zhang Shichao¹, Xing Yalan¹

Affiliation

¹ School of Materials Science and Engineering, Beihang University Beijing 100191 PR China csc@buaa.edu.cn xingyalan@buaa.edu.cn +86 01082338148 +86 01082339319.

Abstract

Lithium-rich transition-metal layered oxides (LROs), such as Li_1.2Mn_0.6Ni_0.2O₂, are promising cathode materials for application in Li-ion batteries, but the low initial coulombic efficiency, severe voltage fade and poor rate performance of the LROs restrict their commercial application. Herein, a self-standing Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane was synthesized as a binder-free cathode for Li-ion batteries. Integrating the graphene membrane with Li_1.2Mn_0.6Ni_0.2O₂ forming a Li_1.2Mn_0.6Ni_0.2O₂/graphene structure significantly increases the surface areas and pore volumes of the cathode, as well as the reversibility of oxygen redox during the charge-discharge process. The initial discharge capacity of the Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane is ∼270 mA h g^-1 (∼240 mA h g^-1 for Li_1.2Mn_0.6Ni_0.2O₂) and its initial coulombic efficiency is 90% (72% for Li_1.2Mn_0.6Ni_0.2O₂) at a current density of 40 mA g^-1. The capacity retention of the Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane remains at 88% at 40 mA g^-1 after 80 cycles, and the rate performance is largely improved compared with that of the pristine Li_1.2Mn_0.6Ni_0.2O₂. The improved performance of the Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane is ascribed to the lower charge-transfer resistance and solid electrolyte interphase resistance of the Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane compared to that of Li_1.2Mn_0.6Ni_0.2O₂. Moreover, the lithium ion diffusion of the Li_1.2Mn_0.6Ni_0.2O₂/graphene membrane is enhanced by three orders of magnitude compared to that of Li_1.2Mn_0.6Ni_0.2O₂. This work may provide a new avenue to improve the electrochemical performance of LROs through tuning the oxygen redox progress during cycling.