Homogeneous CoO on graphene for binder-free and ultralong-life lithium ion batteries

Ultralong cycle life, high energy, and power density rechargeable lithium-ion batteries are crucial to the ever-increasing large-scale electric energy storage for renewable energy and sustainable road transport. However, the commercial graphite anode cannot perform this challenging task due to its low theoretical capacity and poor rate-capability performance. Metal oxides hold much higher capacity but still are plagued by low rate capability and serious capacity degradation. Here, a novel strategy is developed to prepare binder-free and mechanically robust CoO/graphene electrodes, wherein homogenous and full coating of β-Co(OH)₂ nanosheets on graphene, through a novel electrostatic induced spread growth method, plays a key role. The combined advantages of large 2D surface and moderate inflexibility of the as-obtained β-Co(OH)₂/graphene hybrid enables its easy coating on Cu foil by a simple layer-by-layer stacking process. Devices made with these electrodes exhibit high rate capability over a temperature range from 0 to 55 °C and, most importantly, maintain excellent cycle stability up to 5000 cycles even at a high current density.