Annealing determined β-phase polypropylene crystal texture, separator porous channels after biaxial stretching, and lithium-ion battery performances

Abstract

Abstract Uneven porous channels tend to undergo structure-determined chemical deterioration as lithium-ion battery (LIB) operates, which may restrict lithium-ion migration behaviors within the separator and deteriorate cell performances. This research precisely regulates β-phase polypropylene crystal texture and porous channels after biaxial stretching based on the systematic annealing process to explore annealing decided separator porous channels and subsequent electrochemical performances of LIB. Suitable annealing temperature maximally concentrates lamellae layer dispersion and enhances thermal stability, which homogenizes biaxial tensile deformation and subsequent porous channels. Identical crystal and porous channel optimizations are also achieved by synchronously rising annealing temperature and shortening annealing time, especially annealing at 155℃ for only 10s, which lowers the Li+ migration barrier and strengthens cell C-rate and cycling stability. This desirable improvement does not require the sacrifice of time cost to achieve, which verifies separator structure-chemical affected LIB performance and the application feasibility of annealing in the actual production of the dry double-drawn separator.