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

• Published in: RSC advances Vol. 8; no. 69; pp. 39769 - 39776
• Main Authors: Yang Puheng, Wang, Wenxu, Zhang, Xiaoliang, Li, Honglei, Zhang, Shichao, Xing Yalan
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2018; The Royal Society of Chemistry
• Subjects: Cathodes; Charge transfer; Chemical synthesis; Chemistry; Discharge; Electrochemical analysis; Electrode materials; Graphene; Ion diffusion; Lithium; Lithium-ion batteries; Rechargeable batteries; Solid electrolytes; Transition metals
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c8ra06086j

Lithium-rich transition-metal layered oxides (LROs), such as Li1.2Mn0.6Ni0.2O2, 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 Li1.2Mn0.6Ni0.2O2/graphene membrane was synthesized as a binder-free cathode for Li-ion batteries. Integrating the graphene membrane with Li1.2Mn0.6Ni0.2O2 forming a Li1.2Mn0.6Ni0.2O2/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 Li1.2Mn0.6Ni0.2O2/graphene membrane is ∼270 mA h g−1 (∼240 mA h g−1 for Li1.2Mn0.6Ni0.2O2) and its initial coulombic efficiency is 90% (72% for Li1.2Mn0.6Ni0.2O2) at a current density of 40 mA g−1. The capacity retention of the Li1.2Mn0.6Ni0.2O2/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 Li1.2Mn0.6Ni0.2O2. The improved performance of the Li1.2Mn0.6Ni0.2O2/graphene membrane is ascribed to the lower charge-transfer resistance and solid electrolyte interphase resistance of the Li1.2Mn0.6Ni0.2O2/graphene membrane compared to that of Li1.2Mn0.6Ni0.2O2. Moreover, the lithium ion diffusion of the Li1.2Mn0.6Ni0.2O2/graphene membrane is enhanced by three orders of magnitude compared to that of Li1.2Mn0.6Ni0.2O2. This work may provide a new avenue to improve the electrochemical performance of LROs through tuning the oxygen redox progress during cycling.