A Dissolution-Tolerant Trilayer Cathode for Aqueous Zinc-Ion Batteries

Manganese dissolution is the dominant degradation mechanism limiting cycle life in aqueous zinc–manganese dioxide batteries, yet existing mitigation strategies operate downstream of dissolution and are not structurally encoded within the electrode. A proof-of-concept trilayer cathode is demonstrated here that couples electrode-embedded dissolution compensation with interfacial resistance reduction within a single sequential brush-painted, earth-abundant architecture: a turbostratic graphene conductive interlayer on copper; a semi-crystalline γ-MnOOH/MnCl 2 /MWCNT reservoir layer that simultaneously supplies a co-deposited electrode-embedded Mn 2+ source and additional intercalation capacity; and a 3 mol% Mg-doped β-MnO 2 /MWCNT outer layer. Three-electrode evaluation in buffered 1 M ZnCl 2 /1 M NH 4 Cl shows that the trilayer delivers 315.3 mAh g −1 at 5 A g −1 and 201.0 Wh kg −1 at 10 A g −1 , representing 2.32 × and 2.59 × improvements over the single-layer control. Post-cycling EDAX reveals 15.6 × greater retained Mn, strongly supported by an elevated post-cycling Cl signal consistent with reservoir consumption, and Trasatti analysis attributes a 145% increase in bulk intercalation charge to the MnOOH underlayer. EIS resolves distinct relaxation kinetics for each electrode (f 0 = 122.1 Hz control vs. 97.66 Hz trilayer), consistent with the additional reservoir interface introduced by the trilayer stack. Extended cycling (150 cycles, 20 A g⁻¹) shows that, over the fade-dominated regime beyond initial activation, the trilayer retains 93.1% of its peak capacity versus 72.2% for the control. These results establish the trilayer architecture as a viable dissolution-mitigating design strategy for aqueous zinc-ion storage.