1675 mA h g −1 ), low-toxicity, high natural abundance of sulfur, as well as environmental friendliness. [1][2][3][4][5] However, two major challenges closely associated with the electrolytes prevented any immediate commercialization of LSB: 1) the incessant reaction between Li-metal and electrolytes, leading to the constant growth of Li dendrite and inactive Li [6][7][8] and 2) the dissolution of the intermediate polysulfides and their subsequent shuttling. [9][10] These irreversible and parasitic processes result in fast capacity degradation, persistent loss of active materials (both Li and S), severe self-discharge and even catastrophic safety hazard. [11][12] Aiming to resolve these parasitic reactions, significant efforts have been made to develop new electrolyte formulations, including electrolyte additives [13][14][15] solvents, [16][17] and Li salts, with structures of either unsaturation or fluorination that can contribute unique interphasial chemistries to protect Li-metal or suppress polysulfide dissolution and shuttling. [18][19] Among these components, new anionic compounds (counterions of Li + in the salts) are rather rare as compared with new molecular compounds (solvents and additives), mainly due to the much higher difficulty associated with their designing and synthesis. Hence, how anions contribute to interphases remains little understood, although a few successful examples of anionderived interphases, as represented by LiBOB and LiDFOB in nonaqueous and LiTFSI in aqueous electrolytes, suggests that the protections provided by such interphases often outperform their molecular counterparts. In particular, for the interphase protecting Li-metal anode, the anion-derived interphase seems to be more effective than those formed by solvents or additives. [20][21][22][23] One challenge presented for anion-derived interphases is their negatively charged nature, which discourages their presence in the inner-Helmholtz layer at anode surface. [24] In the case of water-in-salt electrolytes (WiSE), such "anode challenge" was partially offset by superconcentration, which compresses the anions into the inner-Helmholtz layer and forces an interphasial chemistry that is otherwise impossible in diluted aqueous electrolyte. The astonishing benefit brought by such anion-derived interphase is an electrochemical stability window of 3-4 V. [25][26] Superconcentration concept has also been applied on both Li-metal anode [27] and sulfur-cathode, [28] in the hope that the interphasial chemistries formed by the existing Lithium-sulfur batteries (LSBs) are considered promising candidates for the next-generation energy-storage systems due to their high theoretical capacity and prevalent abundance of sulfur. Their reversible operation, however, encounters challenges from both the anode, where dendritic and dead Li-metal form, and the cathode, where polysulfides dissolve and become parasitic shuttles. Both issues arise from the imperfection of interphases between electrolyte and electrode. Herein, a new lithium salt based on ...

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Tin-based materials have been intensively studied as attractive candidates for high-capacity and long-cycle-life anodes in Li-ion batteries (LIBs) owing to their low cost and high energy density. However, they all suffer from severe structural decay during the lithium ion insertion/extraction process, which results in deterioration in the overall performance of the batteries. To mitigate this problem, we have synthesized a Mo-doped SnO2 nanostructure via a facile hydrothermal method, which then fragmented into ultrafine particles after dozens of cycles. The fracture-resistant size and ample contact with Super-P and Li2O greatly improved the electrochemical kinetics and cyclability to deliver a reversible capacity of 670 mA h g-1 after 700 cycles, which demonstrated the potential suitability of Mo-doped SnO2 nanoparticles as a long-cycle-life anode material. Then, the compounds were uniformly dispersed in carbon nanofibers and reduced in situ to prepare a free-standing anode via electrospinning and carbonization. When used directly as an anode in LIBs (without a polymeric binder or conductive agent, as well as a current collector), the nanofiber membrane anode delivered comparable cycling performance and capacity to that of a slurry-coated electrode.