Ni2+ crossover effect induced by electron delocalization to construct corrosion-resistant interface for Li metal battery

Abstract

In order to maximize the advantages of high energy density in Li metal batteries, it is necessary to match cathode materials with high specific capacities. Ni-rich layered oxides have been shown to reversibly embed more Li⁺ during charge and discharge processes due to the increased Ni content in their crystal structure, thereby providing higher energy density. However, a significant challenge associated with Ni-rich layered oxide cathodes is the crossover effect, which arises from the dissolution of Ni²⁺ from the cathode, leading to a rapid decline in battery capacity. Through the delocalization-induced effect of solvent molecules, Ni²⁺ is transformed into a fluorinated transition metal inorganic phase layer, thereby forming a corrosion-resistant Li metal interface. This prevents solvent molecules from being reduced and degraded by Li metal anode. The surface of the Li metal anode exhibits a smooth and flat deposition morphology after long-term cycling. Furthermore, the introduction of Ni²⁺ can enhance the concentration gradient of transition metal ions near the cathode, thereby suppressing the dissolution process of transition metal ions. Even the NCM955 cathode with a mass load of 22 mg cm⁻² also has great capacity retention after cycling. The Ni²⁺ induced by high electronegative functional groups of solvent under the electron delocalization effect, preventing the Ni ions dissolution of cathode and constructing a corrosion-resistant Li metal interface layer. This work provides new insights into suppressing crossover effects in Li metal batteries with high nickel cathodes.