Dependence of lithium metal battery performances on inherent separator porous structure regulation

Abstract

Boosting of rechargeable lithium metal batteries (LMBs) holds challenges because of lithium dendrites germination and high-reactive surface feature. Separators may experience structure-determined chemical deterioration and worsen Li plating-stripping behaviors when smoothly shifting from lithium-ion batteries (LIBs) to LMBs. This study precisely regulations the crystal structure of β-polypropylene and separator porous construction to investigate the intrinsic porous structure and mechanical properties determined electrochemical performances and cycling durability of LMBs. Crystal structure characterizations, porous structure analyses, and electrochemical cycling tests uncover appropriate annealing thermal stimulation concentrates β-lamellae thickness and enhances lamellae thermal stability by rearranging molecular chain in inferior β-lamellae, maximally homogenizing biaxial tensile deformation and resultant porous constructions. These even pores with high connectivity lower ion migration barriers, alleviate heterogeneous Li+ flux dispersion, stabilize reversible Li plating-stripping behaviors, and hinder coursing and branching of Li dendrites, endowing steady cell cycling durability, especially at higher currents due to the highlighted uncontrollable cumulation of dead Li, which offers new insights for the current pursuit of high-power density battery and fast charging technology. The suggested separator structure-chemical nature functions in ensuring cyclic cell stability and builds reliable relationships between separator structure design and practical LMBs applications.