Recent Advances in Ex Situ Surface Treatments for Lithium Metal Negative Electrodes in Secondary Batteries

Lithium metal negative electrodes are pivotal for next-generation batteries because of their exceptionally high theoretical capacity and low redox potential. However, their commercialization is constrained by critical challenges, including dendrite formation, volumetric instability, and the fragility of the solid electrolyte interphase (SEI). In this context, this review highlights the transformative potential of ex situ surface treatments, which stabilize lithium metal electrodes before cell assembly. Key advancements include inorganic and polymer-based coatings that enhance SEI stability and mitigate dendrite growth, three-dimensional host architectures that manage volumetric changes and improve lithium diffusion, and liquid-phase chemical modifications that enable uniform lithium deposition. These strategies are critically evaluated for their scalability, environmental sustainability, and long-term stability, paying particular attention to cost, complexity, and ecological considerations. In addition, their potential contributions to the development of advanced battery technologies are discussed, providing insights into pathways toward enhanced commercial viability. By synthesizing cutting-edge research and identifying unresolved challenges, this review provides a comprehensive roadmap for advancing safer, more efficient, and more durable lithium metal batteries, thereby bridging the gap between laboratory research and commercial adoption.