Separator structural-chemical features dependency on lithium-ion battery performances

Abstract

Rechargeable lithium-ion batteries (LIBs) increasingly attract emphasis. Porous construction evolutions during LIBs operation inevitably deteriorate separators mechanical and electrochemical performances. In this research, separators with serial porous constructions are prepared accurately to reveal the dependency mechanism of separator porous structure design on LIB performances. Porous structure analyses, mechanical properties, orientation parameters, and thermal stability diagnosis verify uniform drawing deformations of casting films centralize pore size, optimize pore channel linearity, and retain isotropic texture. Heterogeneous pores with coarse fibrils emphasize under asynchronous drawing, causing worse permeability and anisotropic features, which likely suffered from potential safety hazards caused by excessive unidirectional shrinkage. Electrochemical and battery performance measurements uncover that concentrated pores with superior connectivity determine homogeneous Li+ fluxes, uniformly expand electrodes to impose even compressive stress on separators, and thus reserve initial porous structure maximally to ensure cycling stability. Heterogeneous Li+ fluxes derived from uneven pores with inferior connectivity cause excessive local compression stress on separators. Consequently, mechanically deteriorated porous structure highlight, in reverse impedes Li+ transfer and worsens cell performances. This study suggests separator structural-chemical features function in ensuring LIB performances, which lays solid foundations for separator industrial manufacturing with suitable porous structures for LIBs.