A designer fast Li-ion conductor Li6.25PS5.25Cl0.75 and its contribution to the polyethylene oxide based electrolyte

The composite polymer electrolytes , consisting of a flexible matrix and superb fast ion conductor are promising for large-scale practical application in safer lithium metal batteries . The quantification of polymer structure evolution induced by the inorganic filler was rarely reported. Here, a designer cubic argyrodite Li 6 PS 5 X sulfide electrolyte was fabricated by a solid reaction. A stoichiometry deviation by increasing S and Li, reducing Cl contents, leads to a novel electrolyte of Li 6.25 PS 5.25 Cl 0.75 with high conductivity of 1.0 mS cm −1 and low activation energy of 0.14 eV at room temperature . The off-stoichiometry Li 6 PS 5 X sulfide electrolyte Li 6.25 PS 5.25 Cl 0.75 was used as active filler for polyethylene oxide . Small angle X-ray scattering experiment indicates that the Li 6.25 PS 5.25 Cl 0.75 triggers a pronounced structure evolution in the matrix. As a result, Li-ion diffusion pathway is expanded significantly by the Li 6.25 PS 5.25 Cl 0.75 additives. An optimum ionic conductivity of 1.4 mS cm −1 at 70 °C for CPEs-1 was obtained, and a LFP/Li demo battery delivers a high capacity retention of 91.1% for 100 cycles at 0.2 C.