Electrochemically Activated Highly Reversible Sulfate Conversion Enables High-Voltage and Large-Volumetric-Capacity...

Aqueous dual-ion batteries (DIBs) are becoming one of the most compelling choices for large-scale stationary energy storage owing to the excellent safety performance, high power density, and cost-effectiveness. However, their low output voltage leads to insufficient energy density. Here, we design a highly reversible pH-neutral Ag↔Ag₂SO₄ electrochemistry and construct a novel Zn-based conversion-type aqueous anion-cation shuttle DIB. A dendrite-free Zn anode with functional graphite layer is prepared to improve cycle life. Benefitting from the synchronous effect of Zn²⁺/SO₄ ^2- dual charge carries and dendrite-free anode, the DIB delivers a high output voltage of 1.41 V, volumetric energy density of 3295.4 Wh L^-1 at 0.5 A g^-1, and 95.9% capacity retention over 300 cycles at 1 A g^-1, superior to most reported DIBs. As a proof of concept, we fabricate a quasi-solid-state aqueous DIB with remarkable mechanical strength, flexibility, and impressive temperature resistance. With working temperature decreasing from 20 to -10°C, it shows only a very low-capacity loss (8.4%) and negligible polarization change (0.05 V). This work overcomes the bottleneck of low output voltage in aqueous DIBs and offers a promising pathway for the development of future aqueous batteries with high energy density.