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 (LiNi0.8Co0.1Mn0.1O2, 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.
The construction of nanoporous conductive polymer membranes has potential applications in catalysts and energy-conversion devices. In this letter, we present a facile method to prepare free-standing polypyrrole (PPy) nanotube films by simply heating pulp-like homogeneous suspensions at a low temperature, which can be employed as a novel counter electrode (CE) to substitute for the expensive fluorine-doped tin oxide (FTO) glass and Pt used in dye-sensitized solar cells (DSSCs). The DSSCs assembled with these paper-like PPy membranes show an impressive conversion efficiency of 5.27%, which is about 84% of the cell with a conventional Pt/FTO CE (6.25%).
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