Graphene-wrapped CoNi-layered double hydroxide microspheres as a new anode material for lithium-ion batteries.

High-performance electrode materials that can be easily prepared are imperative for obtaining highly efficient lithium-ion batteries (LIBs). In this study, graphene-wrapped CoNi-layered double hydroxide (LDH) microspheres were first fabricated and used as an anode material for LIBs. The composite electrode with a mass ratio of 2.5 : 1 (CoNi-LDH/graphene) showed a high reversible specific capacity of 1428.0 mA h g-1 at 0.05 A g-1, excellent rate performances (977.5, 670.8 and 328.1 mA h g-1 at 0.5, 2 and 10 A g-1, respectively) and long-cycling performance (75% retention at 10 A g-1 after 10 000 cycles). The excellent electrochemical performances could be due to the following reasons: CoNi-LDHs had high chemical reactivity, and the graphene shell improved the electrical conductivity of CoNi-LDHs, which facilitated charge transfer; the graphene shell also suppressed the volume expansion of metal hydroxides during charge-discharge cycling and enhanced the cycle stability of the electrode. More importantly, this is a significant study to directly use LDHs as a potential electrode for LIBs, which can promote applications of electro-active LDHs in energy storage and conversion fields.