A new symmetrical lead-based battery using a “water-in-salt” electrolyte

Lead–acid batteries are widely used in medium and large energy storage systems, but their application in emerging technologies has been limited by shortcomings in practical applications, such as low specific capacity and irreversible sulfation. We tried to apply “water-in-salt” electrolytes to novel symmetric lead-based batteries, exploring a variety of active material substrates to show that graphite foil current collector batteries perform best. An elevated concentration of water-in-salt electrolyte can broaden the electrochemical stability window, which enables these batteries to show excellent discharge performance, with a reversible specific capacity of 167 mAh g⁻¹ at a discharge current density of 0.1 A g⁻¹, increasing the active material utilization to 69.6% of theoretical capacity. In addition, the batteries maintained a discharge capacity of 152 mAh g⁻¹ after 800 cycles, with a capacity retention rate of 91%, which is better than most pre-reported values. The charging and discharging mechanisms of the positive electrode were analyzed using Raman, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy.