High-performance PVDF/Sepiolite composite separator for Li-ion batteries

PVDF has a relatively high polarity leading to better affinity with electrolyte, and its relatively high dielectric constant promotes the dissociation of lithium ions. Sepiolite has a unique fibrous morphology, forming a rich pore structure, which can enhance the specific surface area and thermal stability of separators. In this work, the PVDF/sepiolite composite separator is prepared by electrospinning technology. Benefiting from the high polarity and dielectric constant of PVDF and the special structure of sepiolite, the composite separator reveals excellent electrolyte adsorption and electrochemical performance. It shows a high ionic conductivity (3.04 × 10^-3 S·cm⁻¹) and a high lithium-ion transference number (${\text{t}}_{{\text{L}\text{i}}^{+}}$ = 0.781), With excellent rate capacity (110mAh g⁻¹ even at 5C) and cycle performance (∼165mAh g⁻¹ after 250 cycles at 0.5C with a capacity retention of 99 %). The thermal stability and electrochemical performance of the composite separator is enhanced by adding appropriate amount of sepiolite.