Novel preparation of lithium‐ion battery wet‐processed separator based on the synergistic effect of porous skeleton <scp>nano‐Al<sub>2</sub>O<sub>3</sub></scp><i>in situ</i> blending and synchro‐draw
Lei Ding, Dandan Li, Fanghui Du, Daoxin Zhang, Sihang Zhang, Tong Wu
Abstract
Abstract Routine lithium‐ion battery separators with uneven micropores and poor electrolyte affinity raise ion transport barriers and become the battery‐performance‐limiting factors. A wet‐processed separator with homogeneous porous structure and porous skeleton nano‐Al 2 O 3 in situ blending is readily prepared by thermally induced phase separation of paraffin, nano‐Al 2 O 3 and ultra‐high molecular weight polyethylene (UHMWPE) in this work. SEM, ImageJ statistical analysis, porosity and Gurley calculation show that a separator that has undergone asynchronous drawing exhibits ample sturdy fibrils, heterogeneous pore size dispersion, poor permeability and strong anisotropy. However, UHMWPE deforms much more uniformly under a synchro‐draw, which distinctly lessens coarse fibrils, centralizes porous construction after stretching and brings better isotropy for the separator. Additionally, nano‐Al 2 O 3 scattered in the cast film further weakens the heterogeneity of micropores stemming from the uneven thermally induced phase separation. Wettability tests and thermal diagnoses also show that nano‐Al 2 O 3 on the porous skeleton strengthens the thermal stability and electrolyte affinity of the separator. Consequently, batteries containing nano‐Al 2 O 3 composite separators show much higher electrochemical stability, ionic conductivity and Li + transport number because of the synergistic effect of the even microvoids and nano‐Al 2 O 3 on the porous skeleton, which expedites Li + transport and endows superior lithium‐ion battery performance. © 2022 Society of Industrial Chemistry.