Dressing Paraffin Wax/Boron Nitride Phase Change Composite with a Polyethylene “Underwear” for the Reliable Battery Safety Management

Phase change material (PCM) can provide a battery system with a buffer platform to respond to thermal failure problems. However, current PCMs through compositing inorganics still suffer from insufficient thermal‐transport behavior and safety reliability against external force. Herein, a best‐of‐both‐worlds method is reported to allow the PCM out of this predicament. It is conducted by combining a traditional PCM (i.e., paraffin wax/boron nitride) with a spirally weaved polyethylene fiber fabric, just like the traditional PCM is wearing functional underwear. On the one hand, the spirally continuous thermal pathways of polyethylene fibers in the fabric collaborate with the boron nitride network in the PCM, enhancing the through‐plane and in‐plane thermal conductivity to 10.05 and 7.92 W m−1 K, respectively. On the other, strong polyethylene fibers allow the PCM to withstand a high puncture strength of 47.13 N and tensile strength of 18.45 MPa although above the phase transition temperature. After this typical PCM packs a triple Li‐ion battery system, the battery can be promised reliable safety management against both thermal and mechanical abuse. An obvious temperature drop of >10 °C is observed in the battery electrode during the cycling charging and discharging process. A spirally weaved organic fiber fabric is employed into a traditional paraffin wax/boron nitride matrix, just like this material is wearing functional underwear, leading the original insufficiently thermo‐conductive and weak phase change material to be highly thermally conductive and mechanically robust. This material successfully provides a triple Li‐ion battery system with reliable safety management against both thermal and mechanical abuse.