A Safe Separator with Heat-Dispersing Channels for High-Rate Lithium-Ion Batteries

Separators are becoming increasingly important in both academic research and industrial production as a means of enhancing the performance of lithium-ion batteries (LIBs), particularly at a high rate. However, fast charge-discharge processes will produce local heat accumulation, which accelerates the local reaction rate of Li+ to form lithium dendrites. Commercial polyolefin separators fail to tackle the above issue due to inferior thermal stability. Herein, a core-shell structure is proposed to reinforce the polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) matrix through encircling carbon nanotube (CNT) by adherent polydopamine (PDA). The core-shell 3D structure with PDA avoids the short circuits caused by the electrically conductive CNT, and meantime, the CNT serves as an effective radiator for dispersing local heat sources verified through finite element analysis. The composite separator allows LIBs to achieve high Li+ conductivity (0.49 x 10-3 S cm-1) and Li+ transfer number (0.74), resulting in a high capacity retention of 87.35% after 800 cycles at 5C. In particular, the safety is confirmed that the composite separator avoids violent growth of lithium dendrites caused by local heat accumulation through phase-field simulations. This work suggests a promising approach for the fabrication of core-shell nanotube composite separators for high-rate and safe LIBs. In this study, a core-shell structure is proposed to reinforce the polyvinylidene fluoride-hexafluoropropylene through encircling carbon nanotube (CNT) by adherent polydopamine. The CNT serves as an effective radiator for dispersing local heat sources. The composite separator avoids the violent growth of lithium dendrites caused by local heat accumulation, thus giving rise to high-rate and safe lithium-ion batteries.image