Direct Ink Writing of Polymer Composite Electrolytes with Enhanced Thermal Conductivities

Proper distribution of thermally conductive nanomaterials in polymer batteries offers new opportunities to mitigate performance degradations associated with local hot spots and safety concerns in batteries. Herein, a direct ink writing (DIW) method is utilized to fabricate polyethylene oxide (PEO) composite polymers electrolytes (CPE) embedded with silane‐treated hexagonal boron nitride (S‐hBN) platelets and free of any volatile organic solvents. It is observed that the S‐hBN platelets are well aligned in the printed CPE during the DIW process. The in‐plane thermal conductivity of the printed CPE with the aligned S‐hBN platelets is 1.031 W −1 K−1, which is about 1.7 times that of the pristine CPE with the randomly dispersed S‐hBN platelets (0.612 W −1 K−1). Thermal imaging shows that the peak temperature (°C) of the printed electrolytes is 24.2% lower than that of the CPE without S‐hBN, and 10.6% lower than that of the CPE with the randomly dispersed S‐hBN, indicating a superior thermal transport property. Lithium‐ion half‐cells made with the printed CPE and LiFePO4 cathode displayed high specific discharge capacity of 146.0 mAh g−1 and stable Coulombic efficiency of 91% for 100 cycles at room temperature. This work facilitates the development of printable thermally‐conductive polymers for safer battery operations. The silane‐treated hexagonal boron nitride (S‐hBN) platelets are well aligned in the polyethylene oxide composite polymers electrolytes (CPE) via a direct ink writing technique. The aligned S‐hBN platelets improve the thermal transport properties and electrochemical performances of the printed CPE. This work facilitates the development of thermally conductive polymer batteries enabled by printing techniques.