Exceptionally long-cycle all-solid-state lithium metal batteries enabled by a 3D aluminum foam interlayers

All-solid-state lithium metal batteries (ASSLMBs) with sulfide solid electrolytes (SSEs) are next-generation energy storage technology offering high theoretical energy density. However, interface issues between the SSEs and lithium (Li) metal have plagued the performance of ASSLMBs. In this study, a three-dimensional (3D) aluminum (Al) foam coating with fine alumina (Al₂O₃) particles was introduced as an interlayer between the SSE and Li metal to mitigate physical and chemical degradation of SSEs and offer ample space for Li deposition. The exceptional lithiophilicity of Al₂O₃-coated Al enables the in-situ formation of an LiAl/LiAlO₂ composite layer, which facilitates the uniform Li metal nucleation and plating. Additionally, the 3D framework provides a host with an increased surface area for the Li plating, thereby preventing the formation of Li dendrites. ASSLMBs incorporating the 3D Al foam (Al₂O₃@Al@Ni) interlayer demonstrate outstanding electrochemical performance, retaining 90 % of their initial capacity after 500 cycles with a high cathode active material loading of 17.8 mg/cm². Due to the ample space and superior Li affinity with the Al₂O₃@Al@Ni structure, the ASSLMB with cathode loading of 36 mg/cm² achieves a high areal capacity of 6 mAh/cm² at room temperature, and remains 93 % of capacity after 100 cycles at 0.2 C. Moreover, an ASSLMB with cathode loading of 3.6 mg/cm² demonstrates an ultra-long cycle life over 5000 cycles at a high current density of 1 C, which is an outstanding achievement for ASSLMBs. The use of 3D Al₂O₃@Al@Ni interlayer effectively addresses interface challenges in ASSLMBs, enabling record-long cycle life and high energy density ASSLMBs for practical energy storage applications.