Bulky steric hindrance effect-mediated weakly solvating electrolytes for highly reversible potassium-metal batteries

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Abstract:The implementation of sustainable and high capacity potassium metal anodes relies heavily on the uniform and stable components in solid electrolyte interphases (SEIs) that are closely associated with K+ solvation structures. Here, a bulky and weakly solvating cosolvent of tris(trimethylsilyl) phosphate (TMSP) has been introduced into 3.0 M potassium bis(fluoroslufonyl)imide (KFSI)/dimethoxyethane (DME) electrolyte to improve the K plating/ stripping reversibility. As revealed by spectroscopy results and first-principle calculations, TMSP is unable to participate in the first solvation sheath due to its steric hindrance effect, instead it shows a solvent-drag function to weaken the interaction between K+ and DME solvent. As a result, F-rich and Si-containing SEIs derived from salt decomposition and trace TMSP show superior uniformity and stability. Cryogenic scanning transmission electron microscopy (Cryo-STEM) images reveal a bulk-like particle without non-dendritic growth. The K plating/stripping reversibility has been also greatly improved (420 cycles vs. 17 cycles and 65 mV vs. 105 mV). The as-designed electrolyte also displays good compatibility towards Prussian blue cathode (100 cycles with an average Columbic efficiency of 93.0 %).

Volume:511

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