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), whereas suffering from the dilemma that it demonstrates high specific capacities at small loading masses but sharp capacity shrinks at large loading masses. 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 loading mass while wholly covering the cathode surface under large loading mass. DIMS involves regulating MnO2 by interstitial carbon (IC@MnO2) to suppress the affinity toward OH–/SO42–, thus impeding ZHS coverage. We design an accurate method to quantify the zinc storage amount normalized by manganese, which shows that IC@MnO2 achieves zinc storage enhancement by 182.4% than bare MnO2. IC@MnO2 achieves remarkable capacity enhancement of 162% than bare MnO2 at 10 mg cm-2. This study presents a promising direction for the lab-to-market transition of AZIBs.