Mechanical behaviors and ion transport variation of lithium-ion battery separators under various compression conditions

Separators exhibit harsh mechanical degradation as encounter various compression conditions within lithium-ion batteries (LIBs), deteriorating ion migration and cell performance directly. To appraise the crucial role of the separator in raising the ion migration barrier as LIBs operate, this research investigates the separator compression behavior and separator-deterministic ion transport evolution under varied compression conditions. Dry-processed separator with bulk shish-kebab structure along the thickness direction exhibits excellent compression resistance and higher ionic conductivity retention under compression stress, mitigating ion migration deterioration and discharge capacity fade caused by the creep of porous skeleton. The luxuriant supporting structure also generates a stronger hardening effect for electrolyte-filled separators. The multi-stacked structure of the wet-processed separator cannot offer valid support, causing much poorer compression resistance and feeble rate-dependence. The flow and creep of micropores at excessive compression caused by LIBs component swelling lessen ion transport channels, deteriorating ion migration and lowering discharge capacity severely. This research proposes some new sights for the separator design philosophy for pragmatic LIBs in terms of mechanical stability to LIBs that it is necessary to balance the separator compression resistance when focusing on the micropore homogeneity during the separator manufacture, which is crucial for exploiting LIBs with long circular life.