Although employing solid polymer electrolyte (SPE) in all-solid-state lithium/ sulfur (ASSLS) batteries is a promising approach to obtain a power source with both high energy density and safety, the actual performance of SPE-ASSLS batteries still lag behind conventional lithium/sulfur batteries with liquid ether electrolyte. In this work, combining characterization methods of X-ray photoelectron spectroscopy, in situ optical microscopy, and three-electrode measurement, a direct comparison between these two battery systems is made to reveal the mechanism behind their performance differences. In addition to polysulfides, it is found that the initial elemental sulfur can also dissolve into and diffuse through the SPE to reach the anode. Different from the shuttle effect that causes uniform corrosion on the anode in a liquid electrolyte, dissolved sulfur species in SPE unevenly passivate the anode surface and lead to the inhomogeneous Li + plating/stripping at the anode/SPE solid-solid interface. Such inhomogeneity eventually causes void formation at the interface, which leads to the failure of SPE-ASSLS batteries. Based on this understanding, a protection interlayer is designed to inhibit the shuttling of sulfur species, and the modified SPE-ASSLS batteries show much-improved performance in cycle life.

By employing in situ/operando X‐ray absorption characterization, the veritable shuttle effect and its suppression/conversion strategy using bismuth‐based nanomaterials as electrocatalytic layer in lithium/sulfur cells are unraveled.

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High‐performance magnesium electrolyte is crucial for the practical application of rechargeable Mg batteries. Herein, a bis(2,2,2‐trifluoroethyl) ether (BTFE) cosolvent is introduced into the chlorine‐containing Mg electrolytes. Theoretical calculations and experimental characterizations reveal that the positive electrostatic potential distributed around the hydrogen atoms in a BTFE molecule could interact with Cl− and facilitate the formation of charged, instead of neutral, ion‐solvent clusters in the BTFE cosolvated magnesium lithium chloride complex (MLCC) electrolyte, which helps to lift its ionic conductivity. The modified solvation structure also lowers the lowest unoccupied molecular orbital energy level of the ion‐solvent clusters, facilitating the in situ formation of solid electrolyte interphase. Using the BTFE cosolvated MLCC electrolyte, reversible Mg plating/stripping can be achieved at 20 mA cm−2 in a Mg//Mg cell, and an ultra‐long cycle life of 1200 h can be achieved at 5 mA cm−2. The new electrolyte also enables high capacity retention of 160 mAh g−1 after 800 cycles for a Mg//CuS full cell, or super‐long cycle life of over 10 000 cycles at 80 C for a Mg//Mo6S8 full cell. The merits of BTFE cosolvent, universally applicable to other chlorine‐containing Mg electrolytes, open a way to develop practical Mg battery electrolytes.