This review discusses the challenges and advancements in interfacial engineering for garnet-based solid-state lithium batteries (SSLBs), focusing on LLZO (Li7La3Zr2O12) electrolytes. Solid-state batteries offer improved safety and energy density compared to traditional lithium-ion batteries. However, the practical deployment of SSLBs is hindered by interfacial challenges, including high interfacial impedance, chemical incompatibility, and lithium dendrite formation. The review highlights the importance of designing stable and compatible interfaces between the electrolyte and electrodes to enhance performance and safety. LLZO-based electrolytes are attractive due to their high ionic conductivity and chemical stability with lithium metal. However, their rigid structure leads to poor solid-solid contact with electrodes, increasing interfacial resistance. Additionally, chemical incompatibility between LLZO and electrodes can cause side reactions, increasing impedance and reducing battery life. Lithium dendrites, which can cause short circuits, are also a significant challenge, as they form due to uneven lithium deposition and high electronic conductivity of the electrolyte. To address these challenges, various interfacial engineering strategies have been developed. These include modifying the electrolyte surface with lithiophilic layers, using alloying reactions to improve wettability, and converting inorganic layers into lithiophilic ones. Techniques such as carbon thermal reduction, liquid-phase reduction, and solid-state conversion have been explored to remove surface contaminants like Li2CO3 and improve interfacial stability. Additionally, conformal interface designs, such as nanoscale metal buffer layers, have been proposed to enhance wettability and reduce interfacial resistance. The review emphasizes the need for further research into interfacial engineering to achieve high-performance SSLBs with long-term stability and safety. Strategies such as optimizing interfacial contact, reducing electronic conductivity, and enhancing ion transport are critical for overcoming the challenges associated with LLZO-based electrolytes. The development of stable and compatible interfaces is essential for the successful commercialization of solid-state lithium batteries.This review discusses the challenges and advancements in interfacial engineering for garnet-based solid-state lithium batteries (SSLBs), focusing on LLZO (Li7La3Zr2O12) electrolytes. Solid-state batteries offer improved safety and energy density compared to traditional lithium-ion batteries. However, the practical deployment of SSLBs is hindered by interfacial challenges, including high interfacial impedance, chemical incompatibility, and lithium dendrite formation. The review highlights the importance of designing stable and compatible interfaces between the electrolyte and electrodes to enhance performance and safety. LLZO-based electrolytes are attractive due to their high ionic conductivity and chemical stability with lithium metal. However, their rigid structure leads to poor solid-solid contact with electrodes, increasing interfacial resistance. Additionally, chemical incompatibility between LLZO and electrodes can cause side reactions, increasing impedance and reducing battery life. Lithium dendrites, which can cause short circuits, are also a significant challenge, as they form due to uneven lithium deposition and high electronic conductivity of the electrolyte. To address these challenges, various interfacial engineering strategies have been developed. These include modifying the electrolyte surface with lithiophilic layers, using alloying reactions to improve wettability, and converting inorganic layers into lithiophilic ones. Techniques such as carbon thermal reduction, liquid-phase reduction, and solid-state conversion have been explored to remove surface contaminants like Li2CO3 and improve interfacial stability. Additionally, conformal interface designs, such as nanoscale metal buffer layers, have been proposed to enhance wettability and reduce interfacial resistance. The review emphasizes the need for further research into interfacial engineering to achieve high-performance SSLBs with long-term stability and safety. Strategies such as optimizing interfacial contact, reducing electronic conductivity, and enhancing ion transport are critical for overcoming the challenges associated with LLZO-based electrolytes. The development of stable and compatible interfaces is essential for the successful commercialization of solid-state lithium batteries.