Carbon interconnected microsized Si film toward high energy room temperature solid-state lithium-ion batteries

Solid-state batteries (SSBs) with high-capacity Si anodes have been regarded as one of the most promising candidates to meet the large scale energy storage and electrical vehicles due to its intrinsic safety and potential high energy density. However, Si suffers from poor electrical conductivity and huge volume change and particles fracture during lithiaiotn and delithiation, which induces low practical energy density. In addition, the SSBs are often operated at high temperature due to the poor physical contact and huge resistance between Si and SSE. To improve the bulk electronic/ionic conductivity of Si and its interfacial compatibility with SSE, herein, a binder free and self-supporting Si/C film was developed. The monolithic carbon not only enhance the electric conductivity but also release huge stress during lithiation and delithiation. In addition, paired with the flexible and soft PVDF-HFP/LATP solid-state electrolyte, a LiF-rich and electrochemical stable SEI layer is in-situ engineered. The fast bulk and interfacial ionic transportation as well as the mechanical integrity of MSi enable high performance SSBs at room temperature. As a result, high specific capacity of 2137 mAh/g with an initial Coulombic efficiency of 83.2% is obtained at a rate of 0.5 A/g. Even at a high rate of 3 A/g, the specific capacity is 1793 mAh/g. At a rate of 1 A/g, the Si/C anode delivers a long cycling performance over 500 cycles while maintains a capacity of 1135 mAh/g. This work provides a new strategy that combines charge transfer kinetics and interfacial chemistry design toward high energy density Si-based SSBs.