This review discusses the critical role of fundamentals of battery recycling in addressing the challenges posed by the increasing number of spent lithium-ion batteries (LIBs) due to the widespread use of electric vehicles and portable electronics, by providing the theoretical basis and technical support for recycling spent LIBs, including battery classification, ultrasonic flaw detection, pretreatment (e.g., discharging, mechanical crushing, and physical separation), electrolyte recovery, direct regeneration, and theoretical calculations and simulations. Physical chemistry principles are essential for achieving effective separation of different components through methods like screening, magnetic separation, and flotation. Electrolyte recovery involves separation and purification of electrolytes through advanced physical and chemical techniques. Direct regeneration technology restores the structure of electrode materials at the microscopic scale, requiring precise control of the physical state and crystal structure of the material. Physical processes such as phase changes, solubility, and diffusion are fundamental to techniques like solid-state sintering, eutectic-salt treatment, and hydrothermal methods. Theoretical calculations and simulations help predict the behaviour of materials during recycling, guiding process optimization. This review provides insights into understanding and improving the recycling process, emphasizing the central role of physical chemistry principles in addressing environmental and energy issues. It is valuable for promoting innovation in spent LIB recycling processes and is expected to stimulate interest among researchers and manufacturers.

Potassium-ion batteries (PIBs) have been considered as a promising new-generation energy storage device because they can be used as a replacement or complement to lithium-ion batteries. However, the large radius and the sluggish diffusion kinetics of K⁺ make it a great challenge to develop high-performance electrode materials for PIBs. Herein, a novel nanocomposite of SnSb alloy confined in N-doped three-dimensional porous carbon (3D SnSb@NC) is fabricated by using the NaCl template-assisted in situ pyrolysis strategy and investigated as an anode for PIBs based on dimethoxyethane (DME)-based and conventional ester-based (EC/DEC) electrolytes. The uniformly anchored SnSb nanoparticles could effectively alleviate dramatic volume variation during potassiation/depotassiation owing to the synergistic effect of Sn and Sb. N-doped 3D porous carbon prevents the aggregation of SnSb nanoparticles, provides abundant active sites for K⁺, facilitates sufficient infiltration of the electrolyte, and serves as a conductive network to accelerate the electron transport. Moreover, the DME-based electrolyte shows superior wettability to the 3D SnSb@NC electrode and forms a thinner SEI film, resulting in negligible surface film impedance and reduced charge transfer impedance. Consequently, the rational 3D SnSb@NC structure coupled with an optimized DME-based electrolyte makes PIBs deliver a high reversible capacity of 357.2 mA h g⁻¹ at 50 mA g⁻¹, an remarkable initial coulombic efficiency (ICE) of 90.1%, good rate capability, and excellent cycling stability with a capacity retention of 80% after 200 cycles at 0.5 A g⁻¹. This work presents an advanced concept for designing multifunctional anode materials with compatible electrolytes for high-performance PIBs.