Carbon Nanotube/Hygroscopic Salt Nanocomposites with Dual‐Functionality of Effective Cooling and Fire Resistance for Safe and Ultrahigh‐Rate Operation of Practical Lithium‐Ion Batteries

Abstract Fire and explosion accidents and reduced energy utilization due to poor cycling stability of lithium‐ion batteries (LIBs) caused by inevitable internal temperature rise during high‐rate operations have become a growing concern. Herein, a dual‐functional carbon nanotube/hygroscopic salt (DFCNT/HS) film with effective passive cooling performance and fire insulation for the safe usage of practical LIBs under extremely fast discharging conditions is reported. The DFCNT/HS film based on the cooling mechanism of self‐adaptive moisture absorption/desorption delivers a high cooling power of 32.9 W m −2 K −1 , which can reduce the maximum temperature of a 18650–3.6 V/2.0 Ah LIB by 11.2 and 17.4 °C at discharging rates of 10 and 15 C, respectively. Covering the cooling film, the battery discharges 23.6 Ah more total capacity at 10 within 500 cycles. What is challenging, almost three‐fold extended lifetime of 425 cycles is achieved at 15 C with an extra total capacity of 467.2 Ah. Meanwhile, the developed film also shows an excellent high‐temperature resistance up to 540 °C, which can alleviate the devastating fire propagation. The fast heat dissipation and excellent fire insulation as well as the mechanical flexibility and manufacturing scalability make this new material promising for safe usage of high‐rate LIBs with zero energy consumption.