Engineering a manganese-based oxide heterostructure cathode for high-performance aqueous potassium-ion storage

Abstract

Advances in aqueous potassium-ion batteries (APIBs) are hindered by the lack of cathode materials with fast K⁺ transport kinetics and stable structures during K⁺ intercalation/deintercalation. Herein, a birnessite/spinel Mn₃O₄ heterostructure cathode is rationally fabricated via a two-step hydrothermal method for aqueous K⁺ storage. Such structure design provides sufficient heterointerfaces and regulates the electronic structure of the Mn atoms in the material, which greatly facilitates the adsorption of K⁺. Meanwhile, the Mn d_z² orbital disrupts the long-range collinear Jahn–Teller order of the pure layered birnessite or spinel Mn₃O₄ phase, leading to the remission of Mn dissolution. Due to these merits, the K_0.52MnO₂·0.22H₂O/Mn₃O₄ cathode exhibits a high reversible capacity of 147 mA h g⁻¹ at 100 mA g⁻¹ in mild K₂SO₄ electrolyte, a superior rate capability of 99 mA h g⁻¹ at 2 A g⁻¹, and 91.7% capacity retention after 2000 charge/discharge cycles. This work may provide an efficient strategy for the rational design of heterostructures and suppressing the dissolution of Mn to obtain high-performance cathodes for APIBs.