Designing of multilevel-nanofibers-based organic–inorganic hybrid gel electrolyte enabling an innovative lithium-ion battery with superior ionic transport capability and advanced security

Abstract

Separator plays a key background role in maintaining excellent ionic flux and avoiding the subject of internal short-circuit faults, which is thought as the key-part of lithium-ion battery. Hence, the characteristics of prominent thermal stability, eminent electrolyte affinity and laudable mechanical strength are of vital importance to guarantee energy density and security for lithium-ion cells. In this study, a natty poly(vinylidene fluoridehexafluoropropylene) (PVDF-HFP)-based gel membrane with multi-level nanofibers was resoundingly prepared for the first time through blend electrospinning of manganese dioxide (MnO2) particles and poly-m-phenyleneisophthalamide (PMIA) solution. The organic–inorganic hybrid multi-level gel electrolyte presented relatively high porosity, small aperture, superior electrolyte uptake and outstanding heat-resistance. Moreover, the mutual overlaps between the coarse fibers and the fine fibers within the multi-level nanofiber membrane provided a strong skeleton support to suppress the lithium-dendrites growth, resulting in an appealing safety for the resulting batteries. And the existence of the multi-level nanofibers can significantly accommodate more sufficient active sites and shorter diffusion channels to accelerate lithium ions migration. Depend on these benefits, the as-assembled cells using the hybrid PMIA separator delivered superior ionic conductivity (2.27 × 10−3 S cm−1) and steady anodic stability window (~5.01 V). The most extraordinary was that the capacity retention of the resulting lithium-ion cell reached up to 90.5% after 200 cycles at 0.5 C, while the Celgard PP separator merely achieved to 70.2%. This work proved that the addition of functional inorganic particles similar with MnO2 in gel PVDF-HFP-doped PMIA membrane with multi-level structure could enhance the lithium ions transport capability and resist the growth of lithium dendrites, which would prompt a great development of lithium-ion cells with reassuring safety and high energy.