Effect of Mn and Na Additives in 1 M ZnSO ₄ Electrolyte on Performance of a Zinc–Manganese Battery With High δ‐MnO ₂ Loading

Many publications have demonstrated the beneficial effects of Mn and Na ions as additives in ZnSO 4 electrolyte on zinc manganese batteries (ZMB) performance with low cathode loadings (<5 mg cm −2 ). For commercial applications, however, higher loadings are needed. This work investigates the effects of MnSO 4 and Na 2 SO 4 concentration in 1 M ZnSO 4 on the ZMB performance with a high δ‐MnO 2 cathode loading of 10 mg cm −2 . After the addition of 0.3 M MnSO 4 and 1 M Na 2 SO 4 into base electrolyte, ZMB capacity increased from 96 to 178 mAh g −1 . In XRD spectra, no major phase change was observed besides the emergence of a layered Mn 7 O 13 ·5H 2 O phase that grew with increasing cycle number. XPS analysis of MnO 2 cathode after partial discharge step of ZMB until 1.3 V revealed predominance of Mn(III) species compared to Mn(IV), confirming its reduced state due to intercalated Zn 2+ ions. The addition of Na 2 SO 4 improved electrolyte conductivity, allowing for 100 charge/discharge cycles (1000 h) at C/5. Capacity fading was assigned to zinc corrosion and irreversible zinc sulfate hydroxide (ZSH) within the cathode. After chemical ZSH removal step, ZMB with reused MnO 2 cathode delivered 151 mAh g −1 in ZM 0.3 NS, confirming positive effect of both additives on MnO 2 structure stability.