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Poor interfacial compatibility between the solid polymer electrolyte and lithium anode is one of bottleneck issues for the wide application of solid-state lithium batteries. In this work, a strategy to improve the stability of a solid electrolyte/anode interface by applying graphene oxide (GO) coating on the surface of the poly(propylene carbonate) (PPC) solid electrolyte membrane to react with metal Li and spontaneously reducing in situ to form a reduced graphene oxide (rGO) interface-modified layer was proposed. The rGO interlayer contributes to the combination of an interface and inhibition of lithium dendrites. The GO-modified composite solid electrolyte (GO-SE) shows a wide electrochemical window of up to 4.8 V, high room temperature ionic conductivity reaching 2.22 × 10 −4 S•cm −1 , and a high ion migration number of 0.9. This GO-SE is suitable for high-voltage solid-state lithium batteries, and the assembled NCM622/GO-SE/Li cells have an initial specific capacity of about 160 mA h/g at 0.5 C, and the specific capacity remains above 100 mA h/g after 200 cycles, much more stable than that of the battery with an unmodified SE membrane at different rates from 0.1 to 2 C. This interface modification method is promising to be widely applied in the solid-state lithium batteries.

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Composite solid electrolytes (CSEs) with high ionic conductivity and good interfacial compatibility are the basis for the practical application of solidstate lithium batteries. The combination of suitable polymers and inorganic fillers is the key to the preparation of CSEs with excellent performance. In this work, a flexible-rigid composite solid electrolyte film was prepared by incorporating different weight ratios (5−20 wt %) of γ-Al 2 O 3 fibers into flexible polypropylene oxide (PPO) polymer electrolytes. Due to the addition of γ-Al 2 O 3 fibers, the ion migration path is shortened and the ion migration rate is effectively improved. At the same time, the Lewis acid groups of γ-Al 2 O 3 fibers react with TFSI − to release more Li + , which increases the number of lithium-ion migration. Therefore, when the content of γ-Al 2 O 3 fibers is 15 wt %, the room-temperature ionic conductivity reaches 3.38 × 10 −4 S cm −1 , the ion migration number is 0.70, and the electrochemical window is 5.6 V. In addition, lithiophilic γ-Al 2 O 3 reacts with Li metal to generate a Li−Al−O transition layer, which promotes Li + interfacial transport and Li uniform deposition, and further inhibits the growth of Li dendrites. This Al 2 O 3 fiber-reinforced CSE improves the lithium-ion transport properties and interface stability between lithium and the electrolyte and has positive practical applications in solid-state lithium batteries.

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