Ultrafine Co-Doped NiO Nanoparticles Decorated on Carbon Nanotubes Improving the Electrochemical Performance and Cycling Stability of Li–CO₂ Batteries

Rechargeable Li–CO2 batteries offer a sustainable strategy for CO2 utilization and energy storage in an environmentally friendly way. However, the current Li–CO2 batteries are restrained by unsatisfactory electrochemical performance and lack of cost-effectiveness in practical application. Thus, developing low-cost and highly effective electrode materials is crucial. Inspired by the concept of high nickel and low cobalt content in the electrode material, ultrafine Co0.1Ni0.9Ox nanoparticles decorated on carbon nanotubes (Co0.1Ni0.9Ox/CNT) are first developed in this work. Through various characterization techniques, the effects of doping Co2+ cations on the properties and electrochemical performance are systematically studied. At a current density of 100 mA g–1, a battery with the Co0.1Ni0.9Ox/CNT electrode delivers a high capacity of 5871.41 mA h g–1 with a Coulombic efficiency of 92.91% and a low overpotential of 3.94 V with an energy efficiency of 68%. At a cutoff capacity of 500 mA h g–1, the battery based on the Co0.1Ni0.9Ox/CNT electrode can be easily operated for 50 cycles without the trace of capacity degradation, which is nearly twice more than those with the NiO/CNT and CNT electrodes. Compared with the NiO/CNT electrode, the Co0.1Ni0.9Ox/CNT electrode exhibits superior electrocatalytic activity in oxidation and evolution reactions of CO2, which results from doping Co2+ cations in the NiO lattice to improve the p-type electronic conductivity. In addition, the polymer-like discharge products affected by doping Co2+ provide better reaction interfaces, curtailing the overpotential and reducing the life span. The results enlighten new ideas of fabricating high-performance and cost-effective electrode materials for prolonging the cycling life of Li–CO2 batteries toward practical applications.