Pseudocapacitive Li+ intercalation in ZnO/ZnO@C composites enables high-rate lithium-ion storage and stable cyclability

Metallic oxide ZnO is considered to be a promising alternative anode material for lithium ion battery because of its high theoretical capacities (978 mA h g−1). However, its inherent low electronic conductivity and undesirable large volume change result in inferior electrochemical performances and hinder its practical application. Herein, ZnO/ZnO@C composites are prepared by a simple carbonization process of ZnO/ZnO@ZIFs-8, which are constructed by using ZnO particles as both template and zinc sources for zeolitic imidazolate frameworks-8 (ZIF-8) preparation via a facile solution reaction. When evaluated as anode for lithium ion batteries, the as-prepared composites show an initial capacity of 878 mA h g−1 at current density of 0.1 A g−1 with high capacity retention of 95.6% after 50 cycles, and an initial capacity of 359 mA h g−1 tested at 5.0 A g−1 with a capacity retention of 85.3% after 500 cycles, exhibiting outstanding cycling stability and excellent rate capability. The ameliorated electrochemical performances are mainly attributed to the elevated conductivity and cushioning effects provided by carbon framework derived from ZIF-8, and the enhanced pseudocapacitance behavior originated from the decreased size of ZnO particles and high surface area of ZIFs-derived carbon.