Regulating the Local Spin States in Spinel Oxides to Promote the Activity of Li-CO₂ Batteries.

Abstract

Due to the high energy barrier, slow reaction kinetics, and complex reaction environments of Li-CO₂ batteries, the development of durable and efficient catalysts is essential. Transition metal oxides are promising for their availability, stability, and 3d electronic features, with spin states playing an important role in CO₂ activation. In this study, the local spin states are regulated by incorporating Ni into Co₃O₄ and its impact on activity in Li-CO₂ batteries is explored. The results show that Ni atoms with high spin states in Ni_0.1Co_2.9O₄ facilitate electron transfer from the catalyst to the unoccupied orbitals of CO₂, providing sufficient active sites for the nucleation and growth of small Li₂CO₃ crystals. These small crystals have a low decomposition barrier, leading to improved battery efficiency. Therefore, Ni_0.1Co_2.9O₄ shows superior catalytic performance with an overpotential of 0.72 V and an energy efficiency of ≈70% after 500 h. This work provides insights into the relationship between spin states and CO₂ reactions, highlighting a promising avenue for developing high-performance metal-CO₂ batteries.