Cooperative Jahn-Teller effect and engineered long-range strain in manganese oxide/graphene superlattice for aqueous zinc-ion batteries

The Jahn-Teller and cooperative Jahn-Teller effects are phenomena that induce asymmetry in individual ions and solid-state lattices and are commonly observed in structures containing specific transition metals, such as copper and manganese. Although the Jahn-Teller effect causes lattice distortions that stress electrode materials in rechargeable batteries, strategically utilising the strain generated by cooperative Jahn-Teller distortions can enhance structural stability. Here we introduce the cooperative Jahn-Teller effect on MnO₂ by constructing a two-dimensional superlattice structure with graphene crated in the bulk MnO₂/graphene composite material. The strong interaction between MnO₂ and graphene increases the concentration of high-spin Mn³⁺ ions, creating orderly long-range biaxial strains that are compressive in the out-of-plane direction and tensile in the in-plane direction. These strains mitigate Zn²⁺ intercalation stress and proton corrosion, enabling over 5000 cycles with 165 mAh g^-1 capacity retention at 5 C (1 C = 308 mA g^-1) in aqueous zinc-ion batteries. Our approach offers an effective strategy to significantly enhance the lifetime of rechargeable batteries by introducing the cooperative Jahn-Teller effect that overcomes the stress of ion insertion in electrode materials.