Polydopamine-boron nitride nanosheet composites with core-shell structures modified PMIA separator for enhanced performance of high-power lithium-ion batteries

Current commercial polyolefin separators suffer from poor electrolyte affinity and thermal stability, which seriously affect the electrochemical performance and safety of lithium-ion batteries (LIBs). In this work, supramolecular self-assembly by π-π stacking interaction was utilized in combination with the self-polymerization of dopamine (DA) to achieve a homogeneous cladding of poly-dopamine (PDA) functional layer on the surface of boron nitride (BN) nanosheets. PDA-BN/poly (m-phenylene isophalamide) (PMIA) composite separators for high-safety LIBs were synthesized using a non-solvent-induced phase separation process. The combination of PMIA and PDA-BN nanomaterials formed a hierarchical porous structure, which enhanced the porosity of PMIA separators. The excellent thermal conductivity of BN nanosheets enhanced the thermal conductivity of the PMIA separator, which facilitated the heat dissipation of the LIBs during the battery operation, and enhanced the cycling stability of the LIBs. The evidence of the results, which were assembled with PDA-BN/PMIA composite separator LiFePO4||Li battery achieved a capacity retention of 95 % after 100 cycles at 0.5 C high-rate cycling. In addition, the PDA-BN/PMIA composite separator did not undergo significant thermal shrinkage at 250 °C, which provides better safety performance than commercial PP separators. The non-solvent-induced phase separation process is not only simple but also inexpensive, and the good electrochemical performance and excellent safety of the as-prepared PDA-BN/PMIA composite separators are expected to be applied in the high-power energy field. •Polydopamine-boron nitride (PDA-BN) composites with core-shell structure were successfully prepared using self-polymerization of dopamine (DA).•The PDA-BN/PMIA composite separator did not exhibit thermal shrinkage below 250 °C.•The polar group of the PDA promotes the desolvation of Li+.•After 100 cycles at 0.5 C, the discharge specific capacity of the PDA-BN/PMIA composite separator was still 133.5 mAh∙g-1 and capacity retention rate of 95%.