Rechargeable lithium metal batteries are next generation energy storage devices with high energy density, but face challenges in achieving high energy density, high safety, and long cycle life. Here, lithium metal batteries in a novel nonflammable ionic‐liquid (IL) electrolyte composed of 1‐ethyl‐3‐methylimidazolium (EMIm) cations and high‐concentration bis(fluorosulfonyl)imide (FSI) anions, with sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as a key additive are reported. The Na ion participates in the formation of hybrid passivation interphases and contributes to dendrite‐free Li deposition and reversible cathode electrochemistry. The electrolyte of low viscosity allows practically useful cathode mass loading up to ≈16 mg cm⁻². Li anodes paired with lithium cobalt oxide (LiCoO₂) and lithium nickel cobalt manganese oxide (LiNi_0.8Co_0.1Mn_0.1O₂, NCM 811) cathodes exhibit 99.6–99.9% Coulombic efficiencies, high discharge voltages up to 4.4 V, high specific capacity and energy density up to ≈199 mAh g⁻¹ and ≈765 Wh kg⁻¹ respectively, with impressive cycling performances over up to 1200 cycles. Highly stable passivation interphases formed on both electrodes in the novel IL electrolyte are the key to highly reversible lithium metal batteries, especially for Li–NMC 811 full batteries.

中文翻译：

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新型离子液体电解质中的高安全性和高能量密度锂金属电池。

可充电锂金属电池是具有高能量密度的下一代能量存储设备，但是在实现高能量密度，高安全性和长循环寿命方面面临挑战。在这里，锂金属电池是一种新型的不可燃离子液体（IL）电解质，它由1-乙基-3-甲基咪唑鎓（EMIm）阳离子和高浓度双（氟磺酰基）酰亚胺（FSI）阴离子与双（三氟甲烷磺酰基）酰亚胺钠组成报告了（NaTFSI）作为关键添加剂。Na离子参与混合钝化中间相的形成，并有助于无枝晶的Li沉积和可逆的阴极电化学。低粘度的电解质允许实际有用的阴极质量加载量高达≈16mg cm ^-2。锂阳极与钴酸锂（LiCoO ₂）和锂镍钴锰氧化物（LiNi _0.8 Co _0.1 Mn _0.1 O ₂，NCM 811）阴极具有99.6–99.9％的库仑效率，高达4.4 V的高放电电压，高比容量和高达≈199mAh g的能量密度^-分别为¹和≈765Wh kg ^-1，在高达1200个循环中具有令人印象深刻的循环性能。新型IL电解质中两个电极上形成的高度稳定的钝化相是高度可逆锂金属电池的关键，特别是对于Li-NMC 811完整电池。