This review article, titled "Li Alloys in All Solid-State Lithium Batteries: A Review of Fundamentals and Applications," provides an in-depth examination of the role of Li-alloy materials in all solid-state lithium batteries (ASSLBs). The authors, Jingru Li, Han Su, Yu Liu, Yu Zhong, Xiuli Wang, and Jiangping Tu, highlight the safety and high energy density advantages of ASSLBs over traditional lithium-ion batteries (LIBs), particularly in the context of Li metal anodes. However, the interface instability between the anode and solid-state electrolyte (SSE) remains a significant challenge. To address this, the article explores various strategies, including using Li-alloy materials as anodes, interlayers, and within the anode itself, to enhance interface performance and stability. The review begins with a detailed analysis of the fundamental kinetics, thermodynamics, and mechanics of Li-alloy materials, emphasizing their potential to mitigate side reactions and Li metal intrusions. It then systematically connects these material properties with their practical applications, providing a comprehensive understanding of the operational principles governing Li alloys in ASSLBs. Finally, the article concludes by discussing the future prospects and potential of Li-alloy materials in advancing the field of ASSLBs, aiming to fill the gap in the literature regarding the physicochemical concepts and practical applications of these materials.This review article, titled "Li Alloys in All Solid-State Lithium Batteries: A Review of Fundamentals and Applications," provides an in-depth examination of the role of Li-alloy materials in all solid-state lithium batteries (ASSLBs). The authors, Jingru Li, Han Su, Yu Liu, Yu Zhong, Xiuli Wang, and Jiangping Tu, highlight the safety and high energy density advantages of ASSLBs over traditional lithium-ion batteries (LIBs), particularly in the context of Li metal anodes. However, the interface instability between the anode and solid-state electrolyte (SSE) remains a significant challenge. To address this, the article explores various strategies, including using Li-alloy materials as anodes, interlayers, and within the anode itself, to enhance interface performance and stability. The review begins with a detailed analysis of the fundamental kinetics, thermodynamics, and mechanics of Li-alloy materials, emphasizing their potential to mitigate side reactions and Li metal intrusions. It then systematically connects these material properties with their practical applications, providing a comprehensive understanding of the operational principles governing Li alloys in ASSLBs. Finally, the article concludes by discussing the future prospects and potential of Li-alloy materials in advancing the field of ASSLBs, aiming to fill the gap in the literature regarding the physicochemical concepts and practical applications of these materials.