Ni-doped Bi2O2CO3 nanosheet with H+/Zn2+ co-insertion for "rocking chair" zinc-ion battery.

Developing insertion-type anode is key to advancing "rocking chair" zinc-ion batteries, though there are few reported insertion-type anodes. Herein, the Bi2O2CO3 is a high-potential anode, with a special layered structure. A one-step hydrothermal method was used to prepare Ni-doped Bi2O2CO3 nanosheet, and also a free-standing electrode consisting of Ni-Bi2O2CO3 and CNTs was designed. Both cross-linked CNTs conductive networks and Ni doping improve charge transfer. Ex situ tests (XRD, XPS, TEM, etc.) reveal the H+/Zn2+ co-insertion mechanism of Bi2O2CO3 and that Ni doping improves its electrochemical reversibility and structural stability. Therefore, this optimized electrode offers a high specific capacity of 159 mAh g-1 at 100 mA g-1, a suitable average discharge voltage of ≈0.400 V, and a long-term cycling stability of 2200 cycles at 700 mA g-1. Besides, the Ni-Bi2O2CO3//MnO2 "rocking chair" zinc-ion battery (based on the total mass of cathode and anode) delivers a high capacity of ≈100 mAh g-1 at 50.0 mA g-1. This work provides a reference for designing high-performance anode in zinc-ion batteries.