High-performance aqueous Zn–MnO2 batteries enabled by the coupling engineering of K+ pre-intercalation and oxygen defects

Abstract

Aqueous zinc–manganese dioxide (Zn–MnO₂) batteries show great promise for grid-scale energy storage but suffer from sluggish reaction kinetics and severe structural instability of the MnO₂ cathode. Herein, a K⁺-pre-intercalated α-MnO₂ cathode with oxygen defects (KMO_d) is designed, guided by a new coupling engineering strategy, demonstrating boosted reaction kinetics and improved structural stability of MnO₂. Closely coupled first-principles calculations and experiments reveal that the synergy effects of pre-intercalated K⁺ and oxygen defects are key to the high electronic conductivity, favorable H⁺ diffusion kinetics, enhanced H⁺/Zn²⁺ adsorption/intercalation capability, and improved structural stability of the KMO_d cathode. A high energy density of 518 W h kg⁻¹ calculated based on the mass of the cathode and outstanding long-term cycling performance of over 2500 cycles at 2.0 A g⁻¹ with a capacity of 203 mA h g⁻¹ and a retention of 81.3% are achieved. New insights into the structural stabilization effect by adding K₂SO₄ additive into the aqueous electrolyte are also revealed. A hybrid charge storage mechanism of non-diffusion controlled Zn²⁺ intercalation and diffusion controlled H⁺ intercalation is proposed.