Abstract:Driven by the global energy transition and the "dual-carbon" goals, the efficient recycling of spent lithium-ion batteries (LIBs) is of great significance for securing critical metal resources and mitigating environmental impacts. Pressurized technology, which alters reaction thermodynamic equilibria and enhances kinetics under elevated temperature and pressure, offers a promising approach for spent LIB recycling and has garnered significant attention in this field. This review systematically summarizes recent advances in the application of pressurized technology for recycling spent LIBs, with a particular focus on three key areas: valuable metal extraction, synthesis of high-value materials, and direct regeneration of electrode materials. In terms of valuable metal extraction, technologies such as pressurized acid leaching, ammonia leaching, and oxidative leaching exhibit remarkable effectiveness in enhancing the extraction of valuable metals. These methods significantly improve the leaching efficiency and selectivity of critical metals such as lithium, cobalt, and nickel. The high-temperature, high-pressure environment accelerates reaction rates, enables reactions that are non-spontaneous under ambient conditions, and reduces reagent consumption. Beyond metal extraction, pressurized technology, primarily the hydrothermal method, facilitates the short-path, high-value utilization of spent LIBs. Purified leachates can be directly employed as precursors for the synthesis of functional materials, such as cathode precursors and metal oxides, thereby upgrading waste into valuable products. Regarding direct regeneration, hydrothermal repair presents a compelling alternative to traditional energy-intensive solid-state calcination. This approach allows for an effective relithiation of degraded cathodes such as LiFePO4, LiCoO2, and ternary materials (e.g., NMC) under milder conditions. The liquid-phase environment ensures uniform lithium-ion diffusion, leading to more homogeneous repair, superior recovery of electrochemical performance, lower energy consumption, and specific capacities comparable to those of pristine materials. Furthermore, to address current challenges such as the difficulty of in-situ characterization and the lack of suitable characterization technologies for pressurized processes, this review also highlights advancements in in-situ characterization techniques. The integration of specialized reactors with powerful tools such as synchrotron radiation X-ray diffraction (XRD), X-ray absorption spectroscopy (XANES), and Raman spectroscopy enables real-time observation of phase transitions, valence changes, and crystal growth during pressurized processes, offering unprecedented insights into reaction mechanisms. Despite the promising laboratory-scale successes, the industrial application of pressurized technologies still faces challenges, including insufficient thermodynamic data for novel and mixed materials, inadequate mechanistic understanding, lack of robust in-situ characterization techniques, and high equipment costs. Future development should prioritize establishing comprehensive thermodynamic databases, developing multi-dimensional and multi-scale in-situ characterization methods, innovating reactor designs for lower energy consumption and cost, integrating pressurized processes with clean energy sources to reduce the carbon footprint, and developing low-cost, corrosion-resistant materials for reactors. This review concludes that pressurized technology holds significant potential for enabling closed-loop and sustainable recycling of spent LIBs. Close-