Effect of Mn and Na Additives in 1 M ZnSO4 Electrolyte on Performance of a Zinc–Manganese Battery With High δ-MnO2 Loading

Batteries & Supercaps, 2026 

Abstract

Many publications have demonstrated the beneficial effects of Mn and Na ions as additives in ZnSO₄ 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 MnSO₄ and Na₂SO₄ concentration in 1 M ZnSO₄ on the ZMB performance with a high δ-MnO₂ cathode loading of 10 mg cm⁻². After the addition of 0.3 M MnSO₄ and 1 M Na₂SO₄ 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 Mn₇O₁₃·5H₂O phase that grew with increasing cycle number. XPS analysis of MnO₂ 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 Zn²⁺ ions. The addition of Na₂SO₄ 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 MnO₂ cathode delivered 151 mAh g⁻¹ in ZM_0.3NS, confirming positive effect of both additives on MnO₂ structure stability.