Deep ion mass transfer addressing the capacity shrink challenge of aqueous Zn‖MnO2 batteries during the cathode scaleup†

Abstract

MnO₂ is considered a promising cathode for aqueous zinc ion batteries (AZIBs), however there is a dilemma that it demonstrates high specific capacities at small mass loadings but sharp capacity shrikage at large mass loadings. Here, we uncover this dilemma and develop a deep ion mass transfer (DIMS) strategy. Alkaline zincate (ZHS) forms with the H⁺/Zn²⁺ co-intercalation, which partially covers the cathode surface at small mass loading while fully covers the cathode surface under large mass loading. DIMS involves regulating MnO₂ by interstitial carbon (IC@MnO₂) to suppress the affinity toward OH⁻/SO₄²⁻, thus impeding ZHS coverage. We develop an accurate method to quantify the zinc storage amount normalized by manganese, which shows that IC@MnO₂ exhibits zinc storage enhancement by 182.4% compared to bare MnO₂. IC@MnO₂ exhibits remarkable capacity enhancement of 162% compared to bare MnO₂ at 10 mg cm⁻². This study presents a promising direction for the lab-to-market transition of AZIBs.