A water-in-salt electrolyte (WiSE) offers an electrochemical stability window much wider than typical aqueous electrolytes but still falls short in accommodating high-energy anode materials, mainly because of the enrichment of water molecules in the primary solvation sheath of Li⁺. Herein, we report a new strategy in which a non-Li cosalt was introduced to alter the Li⁺-solvation sheath structure. The presence of an asymmetric ammonium salt (Me₃EtN·TFSI) in water increases the solubility of LiTFSI by two times, pushes the salt/water molar ratio from 0.37 in WiSE to an unprecedented value of 1.13, and significantly suppresses the water activity in both bulk electrolyte and the Li⁺-solvation sheath. This new 63 m (mol kg_solvent^–1) aqueous electrolyte (42 m LiTFSI + 21 m Me₃EtN·TFSI) offers a wide potential window of 3.25 V and supports a 2.5 V aqueous Li-ion battery (LiMn₂O₄//Li₄Ti₅O₁₂) to deliver a high energy density of 145 Wh kg^–1 stably over 150 cycles.

中文翻译：

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用于高能锂离子电池的63 m超浓缩水电解质

盐包水电解质（WiSE）的电化学稳定性窗口比典型的水性电解质要宽得多，但在容纳高能阳极材料方面仍然不足，主要是因为Li ⁺的主要溶剂化鞘中的水分子富集。在本文中，我们报道了一种新的策略，其中引入了非锂盐来改变Li ⁺溶剂化鞘结构。水中不对称铵盐（Me ₃ EtN·TFSI）的存在将LiTFSI的溶解度提高了两倍，将盐/水摩尔比从WiSE中的0.37推升至前所未有的1.13，并显着抑制了水中的活度。整体电解质和Li ^+-溶剂化鞘。这个新的63 m（mol kg_溶剂^–1）水性电解质（42 m LiTFSI + 21 m Me ₃ EtN·TFSI）提供3.25 V的宽电位窗口并支持2.5 V水性锂离子电池（LiMn ₂ O ₄ // Li ₄ Ti ₅ O ₁₂）可在150个循环中稳定地提供145 Wh kg ^–1的高能量密度。