Improved Discharge Capacity of Zinc Particles by Applying Bismuth-Doped Silica Coating for Zinc-Based Batteries Batteries

Corrosion and discharge behavior of battery-grade zinc particles coated with a silica layer doped with bismuth was investigated and compared with untreated zinc powder. Electrochemical investigations were carried out in half-cell configuration. The electrolyte was 6 M KOH in excess. Coated zinc particles provided a discharge capacity of 737 mAh g−1 (89.9% DoD) versus 633 mAh g−1 (77.2% DoD) of untreated zinc particles after a dwell time of 1 h in KOH. The silica coating reduced the direct contact of the zinc surface with the electrolyte and thus minimized the hydrogen evolution reaction, which led to an increased discharge capacity. Additionally, bismuth doping enhanced conductivity within the silica coating and increased zinc utilization. Those coated zinc particles inhibited corrosion, i.e., corrosion efficiency reached 87.9% compared to uncoated zinc. Additionally, the coating achieved a capacity retention of 90.9% (670 mAh g−1) after 48 h dwell time in 6 M KOH. The coatings were prepared by sol-gel technology and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface determination

Mechanical Coating of Zinc Particles with Bi2O3-Li2O-ZnO Glasses as Anode Material for Rechargeable Zinc-Based Batteries

The electrochemical performance of zinc particles with 250 μm and 30 μm diameters, coated with Bi2O3-Li2O-ZnO glass is investigated and compared with noncoated zinc particles. Galvanostatic investigations were conducted in the form of complete discharge and charging cycles in electrolyte excess. Coated 30 μm zinc particles provide the best rechargeability after complete discharge. The coatings reached an average charge capacity over 20 cycles of 113 mAh/g compared to the known zero rechargeability of uncoated zinc particles. Proposed reasons for the prolonged cycle life are effective immobilization of discharge products in the glass layer and the formation of percolating metallic bismuth and zinc phases, forming a conductive network through the glass matrix. The coating itself is carried out by mechanical ball milling. Different coating parameters and the resulting coating quality as well as their influence on the passivation and on the rechargeability of zinc–glass composites is investigated. Optimized coating qualities with respect to adhesion, homogeneity and compactness of the glass layer are achieved at defined preparation conditions, providing a glass coating content of almost 5 wt % for 250 μm zinc particles and almost 11 wt % for 30 μm zinc particles