Electrospun Polyacrylonitrile/Polyvinylidene Fluoride/Boehmite Separator and Gel Polymer Electrolyte Polyethylene Oxide/Polyvinylidene Fluoride‐hexafluoropropylene/Lithium Bis(trifluoromethanesulfonyl)imide/Boehmite Composite Separator Are Used for Fast Charging
Haowen Tan, Shaojin Jia
Abstract
Abstract With the increasing popularity of electric vehicles, the fast charging of lithium (Li) batteries is attracting increasing attention. However, the rapid decline in battery capacity caused by fast charging and accidents caused by Li dendrites piercing the separator greatly restrict fast‐charging applications. Herein, an electrospun polyacrylonitrile/polyvinylidene fluoride/boehmite (PAN/PVDF/12 wt.% AlO(OH)) and gel polymer polyethylene oxide/polyvinylidene fluoride‐hexafluoropropylene/lithium bis(trifluoromethanesulfonyl)imide/boehmite (PEO/PVDF‐HFP/12.6 wt.% LiTFSI /10 wt.% AlO(OH)) pressed together to form a two‐layer functional separator is designed. The electrospun separator improves the high‐temperature resistance of the entire separator due to its special structure. After the 1 h heat treatment at 220 °C, the thermal shrinkage rate of the double‐layer separator reaches 10.1%, showing good thermal stability. At 0.2 C, the discharge capacity retention rate is 99.4% after 100 cycles. After 1000 cycles at a rate of 10 C, the discharge capacity remains at 88% of the initial value. The two‐layer separator exhibits better capacity retention and superior rate performance than PP, providing an effective approach for commercializing fast‐charging functional separators.