Sandwich-like dual carbon layers coated NiO hollow spheres with superior lithium storage performances

Transition metal oxides (e.g. NiO) have been considered as promising high-capacity anode in lithium ion batteries (LIBs). However, the low electronic conductivity and huge volume change during cycling lead to rapid capacity fading and poor rate capability. To solve those drawbacks, we design a sandwich-like dual carbon layers coated hollow structured NiO (C@NiO@NC). The NiO nanosheets are anchored on the surface of hollow carbon nanospheres and then coated with N-doped porous carbon layer, which confine them between two carbon shells. Such hierarchical architecture with high surface area increases the contact between the electrode and electrolyte, resulting in decreased Li⁺ diffusion pathway. Moreover, the dual carbon layers enhance the electronic conductivity of C@NiO@NC and effectively buffer the volume changes of NiO during cycling. Therefore, this sample delivers a high capacity (1189 mA h g⁻¹ at 100 mA g⁻¹), superior rate capability (420 mA h g⁻¹ at ultrahigh rate of 10000 mA g⁻¹) and outstanding cycling stability (96.1% at 1000 mA g⁻¹ after 1000 cycles) when used as LIBs anode. The density functional theoretical calculation further proves the enhanced electronic conductivity and more energetic favorable capability of C@NiO@NC. This facile method can be extended to other transition-metal oxides with superior electrochemical performance.