Safety issues in lithium‐ion batteries (LIBs) have aroused great interest owing to their wide applications, from miniaturized devices to large‐scale storage plants. Separators are a vital component to ensure the safety of LIBs; they prevent direct electric contact between the cathode and anode while allowing ion transport. In this study, the first design is reported for a thermoregulating separator that responds to heat stimuli. The separator with a phase‐change material (PCM) of paraffin wax encapsulated in hollow polyacrylonitrile nanofibers renders a wide range of enthalpy (0–135.3 J g−1), capable of alleviating the internal temperature rise of LIBs in a timely manner. Under abuse conditions, the generated heat in batteries stimulates the melting of the encapsulated PCM, which absorbs large amounts of heat without creating a significant rise in temperature. Experimental simulation of the inner short‐circuit in prototype pouch cells through nail penetration demonstrates that the PCM‐based separator can effectively suppress the temperature rise due to cell failure. Meanwhile, a cell penetrated by a nail promptly cools down to room temperature within 35 s, benefiting from the latent heat‐storage of the unique PCM separator. The present design of separators featuring latent heat‐storage provides effective strategies for overheat protection and enhanced safety of LIBs.

With the rapid development of lithium‐ion batteries (LIBs), safety problems are the great obstacles that restrict large‐scale applications of LIBs, especially for the high‐energy‐density electric vehicle industry. Developing component materials (e.g., cathode, anode, electrolyte, and separator) with high thermal stability and intrinsic safety is the ultimate solution to improve the safety of LIBs. Separators are crucial components that do not directly participate in electrochemical reactions during charging/discharging processes, but play a vital role in determining the electrochemical performance and safety of LIBs. In this review, the recent advances on traditional separators modified with ceramic materials and multifunctional separators ranging from the prevention of the thermal runaway to the flame retardant are summarized. The component–structure–performance relationship of separators and their effect on the comprehensive performance of LIBs are discussed in detail. Furthermore, the research challenges and future directions toward the advancement in separators for high‐safety LIBs are also proposed.

Aqueous Zn-based energy-storage devices have aroused much interest in recent years. However, uncontrollable dendrite growth in the Zn anode significantly limits their cycle life. Moreover, the poor low-temperature performance arising from the freezing of aqueous electrolytes at sub-zero temperatures restricts their practical applications in cold regions. Here, we fabricated low-temperature-tolerant and durable Zn-ion hybrid supercapacitors (ZHSCs) via modulating a co-solvent water/ethylene glycol electrolyte. The interaction of intermolecular hydrogen bonds between water and ethylene glycol as well as cation solvation was systematically investigated by tuning the co-solvent composition. The results illustrate that the ZnSO 4 /water/ethylene glycol (65%) electrolyte possesses high ionic conductivity at low temperatures and effectively prevents the dendrite formation of the Zn anode. The as-fabricated ZHSCs exhibit long-term cyclability and are capable of working at sub-zero temperatures as low as −40°C. The present ZHSCs are anti-freezing and cost-effective, which may find new applications in the fields of next-generation electrochemical energy storage devices.

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