Solid-state batteries have become a critical growth area for next-generation energy storage systems, driven by their inherent benefits of superior operational safety, exceptional theoretical energy density, and extended cycle life. This work provides a systematic overview of recent progress in solid-state battery research, organized around three core components: electrode materials, electrolytes, and interphase engineering. In terms of electrode design, commercially dominant cathode systems primarily include lithium iron phosphate (LiFePO4) and high-nickel nickel-cobalt-manganese (NCM) oxides, while anode development is heavily concentrated on lithium metal and carbon-based architectures. Each material class offers unique technical advantages but also suffers from intrinsic drawbacks, requiring tailored modification approaches to overcome their respective performance limitations. Electrolyte platforms are broadly categorized into three main families: polymer, oxide, and sulfide-based systems. For polymer electrolytes in particular, this review analyzes both free-standing electrolyte membranes and cathode-integrated coating layers, two configurations that exhibit distinct suitability for diverse application requirements. Interphase regulation represents the most significant barrier to the practical deployment of solid-state batteries. Longstanding challenges including poor solid-solid interfacial contact, elevated interfacial resistance, and undesired parasitic reactions severely degrade cell performance. These issues can be effectively alleviated through monolithic manufacturing techniques and targeted interphase modification strategies.



