The global energy transition toward sustainable and green energy systems have intensified a demand for advanced electrochemical energy storage technologies. Lithium-ion batteries (LIBs), while being dominant in portable electronics and electric vehicles, face some challenges, including safety risks from flammable liquid electrolytes and limited energy density. These limitations hinder their application in emerging fields such as electric aviation, high-performance drones, and long-range electric vehicles. Recent incidents of LIB thermal runaway and combustion further highlight an urgency for safe and high-energy-density alternatives. In this context, all-solid-state lithium metal batteries (ASSLMBs) emerge as a promising next-generation energy storage solution, offering enhanced safety and superior energy density.ASSLMBs replace volatile liquid electrolytes with solid-state electrolytes (SSEs), thereby eliminating combustion risks and improving thermal stability. Also, the use of lithium metal anodes with an ultrahigh theoretical capacity (i.e., 3860mA·h/g) and a minimum electrochemical potential (i.e., −3.04V vs. SHE) significantly boosts energy density, compared to conventional graphite anodes. These advantages make ASSLMBs a focal point of research and development. However, despite their theoretical potential, ASSLMBs face some practical challenges, particularly the electrochemo-mechanical issues induced by volume expansion during charge and discharge cycles.Volume changes in ASSLMBs stem from the expansion and contraction of electrode materials during lithium (de)intercalation. Cathode materials, such as lithium-rich manganese-based oxides, typically exhibit volume changes of 2%–10%. In contrast, lithium metal anodes can experience extreme volume expansion of up to 1000% when operating at a low negative-to-positive capacity ratio (i.e., N/P=1.1). In high-energy-density configurations, such as ASSLMBs targeting about 600 W·h/kg, the overall cell-level volume change can reach 18%. Unlike conventional LIBs that use liquid electrolytes to accommodate strain, the rigid solid-solid interfaces in ASSLMBs cannot self-adjust to such deformations. This rigidity leads to significant mechanical stresses, including stack-level stresses in the MPa range and localized stress concentrations in the GPa range, caused by heterogeneous current distribution, lithium dendrite growth, and particle cracking. These stresses can result in interfacial delamination, active material fracture, and ion transport blockages, severely degrading the battery performance and cycle life.This review provides a comprehensive analysis of the electrochemo–mechanical challenges in all-solid-state lithium metal batteries (ASSLMBs) and explores some strategies to mitigate these issues. First, we examine the fundamental mechanisms of mechanical-electrochemical coupling, emphasizing a relationship between material properties (i.e., modulus, fracture toughness), operational parameters (i.e., current density, pressure), and stress generation. Advanced characterization techniques, such as in-situ stress sensors, X-ray computed tomography, and finite element modeling, are employed to reveal multi-scale stress evolution and its impact on the battery performance. These tools enable to visualize and quantify stress distribution in micro- and macro-scale, providing insights into the dynamic interplay between mechanical and electrochemical processes. Second, we analyze the consequences of volumetric strain on key performance metrics, including interface stability, lithium deposition behavior, and cathode degradation.To address these challenges, we evaluate strategic approaches such as material innovation, interface engineering, and structural optimization. Material innovation focuses on designing SSEs with balanced ionic conductivity and mechanical compliance. Strain-tolerant cathode architectures, including single-crystal particles and composite electrodes with buffer matrices, are also explored to mitigate volume changes. Interface engineering involves introducing functional interlayers, such as Li₃N coatings, to enhance adhesion and redistribute interfacial stresses. Artificial solid-electrolyte interphases (SEI) with self-healing properties are highlighted for stabilizing lithium anodes and preventing dendrite formation. Structural optimization explores cell-level designs, including pre-stress mechanisms and gradient porosity electrodes, to mitigate strain accumulation and improve the overall battery performance. Pressure management strategies for stack assemblies are also discussed to balance contact maintenance with stress relaxation. ASSLMBs with enhanced mechanical stability, improved electrochemical performance and extended cycle life are developed via integrating these approaches, paving a way for their practical application in next-generation energy storage systems.Finally, we outline future research directions, emphasizing a need for multi-physics models that integrate electrochemical, thermal, and mechanical dynamics across scales. Advanced manufacturing techniques and novel diagnostic tools for real-time stress monitoring are identified as critical enablers for advancing ASSLMB technology. In addition, we also analyze the existing technical challenges and potential solutions, which can provide theoretical support and practical guidance.Summary and prospectsOne of the core challenges faced by all-solid-state lithium metal batteries during their development is a mechanical-electrochemical coupling effect caused by volumetric changes. The volumetric changes of active materials during charge and discharge, especially under high energy density conditions, can significantly negatively impact the structural stability and electrochemical performance of the battery, leading to some problems such as interface delamination and crack formation. These problems severely limit the cycle life and high-rate performance of all-solid-state lithium metal batteries, becoming a major obstacle to their practical application. To address these challenges, some strategies such as optimizing cell module structures, material modification, and structural regulation have been proposed. Future research should focus on four key directions, i.e., exploring the mechanical-electrochemical coupling mechanism using advanced experimental techniques and multiscale modeling to better understand the interactions between stress, ion transport, and electrochemical reactions, developing advanced characterization and testing methods to cope with the complexity of mechanical-electrochemical coupling mechanism, developing volumetric expansion suppression strategies for practical applications (i.e., the development of zero-strain electrode materials and interface engineering designs) to mitigate the adverse effects of volumetric changes during cell cycling while reducing the high stack pressure demands of all-solid-state lithium metal batteries, and leveraging machine learning and artificial intelligence to accelerate the discovery of high-performance materials and optimize the battery structure design.