Aqueous hybrid supercapacitors are attracting increasing attention due to their potential low cost, high safety and eco-friendliness. However, the narrow operating potential window of aqueous electrolyte and the lack of suitable negative electrode materials seriously hinder its future applications. Here, we explore high concentrated lithium acetate with high ionic conductivity of 65.5 mS cm⁻¹ as a green “water-in-salt” electrolyte, providing wide voltage window up to 2.8 V. It facilitates the reversible function of niobium tungsten oxide, Nb₁₈W₁₆O₉₃, that otherwise only operations in organic electrolytes previously. The Nb₁₈W₁₆O₉₃ with lithium-ion intercalation pseudocapacitive behavior exhibits excellent rate performance, high areal capacity, and ultra-long cycling stability. An aqueous lithium-ion hybrid capacitor is developed by using Nb₁₈W₁₆O₉₃ as negative electrode combined with graphene as positive electrode in lithium acetate-based “water-in-salt” electrolyte, delivering a high energy density of 41.9 W kg⁻¹, high power density of 20,000 W kg⁻¹ and unexceptionable stability of 50,000 cycles.

水性混合超级电容器由于其潜在的低成本，高安全性和生态友好性而受到越来越多的关注。然而，水性电解质的工作电位窗口狭窄以及缺少合适的负极材料严重阻碍了其未来的应用。在这里，我们探索高浓度乙酸锂，其离子电导率为65.5 mS cm ^-1，是绿色的“盐包水”电解质，提供高达2.8 V的宽电压窗口。它促进了铌酸钨铌Nb的可逆功能₁₈ W ₁₆ O ₉₃，否则以前只能在有机电解质中运行。Nb ₁₈ W ₁₆ O ₉₃具有锂离子嵌入作用的假电容行为具有出色的倍率性能，高面容量和超长循环稳定性。水性锂离子混合式电容器是通过使用Nb的开发₁₈ w ^ ₁₆ ö ₉₃作为负极使用的石墨烯作为正极中的锂结合醋酸酯基“水包盐”电解质，提供41.9W¯¯kg的高能量密度^{-如图1所示}，具有20,000 W kg ^-1的高功率密度和50,000个循环的无与伦比的稳定性。