Morphology optimizing of polyvinylidene fluoride (PVDF) nanofiber separator for safe lithium‐ion battery

Abstract

Commercial polyolefin separator cannot guarantee the safety of lithium-ion batteries at high temperatures due to their poor thermal stability. All kinds of nanofiber membranes with high thermal stability become the focus. In this paper, we have prepared PVDF nanofiber membrane by electrospinning method and have studied the relationship between the electrochemical performance and nanofiber morphology in detail. It is found that the morphology of PVDF is transformed from ball-like to various nanofiber with increasing the concentration of spinning solution. As a result, the PVDF nanofiber membrane (24 wt%-HP) prepared from spinning solution with the concentration of 24 wt% is composed of coarse nanofiber and fine nanofiber, which exhibits better electrochemical properties, such as cycling stability (300 cycles) and ionic conductivity (1.65 mS cm À1 ). LiCoO 2 /Li cells based on PVDF nanofiber separators have higher discharge capacity even at the current density of 5 C-rate, superior than the cells based on PE separator. It is inspiring for high-energy-density battery safety to use this PVDF nanofiber separator.

Flame-Retardant Nano-TiO2/Polyimide Composite Separator for the Safety of a Lithium-Ion Battery

“…The ionic conductivity of separators was calculated by the following equation, eq : For specific test details, it could refer to our previous work . The electrochemical stability of the separator was characterized by linear sweep voltammetry (LSV) analysis (5 mV s –1 , 2.5–6.5 V (vs Li/Li + )) of the assembled SS//Li cells.…”

“…The meaning of ΔW (%), W 0 (g), and W (g) can be found in our previous work. 23 The separator was placed in an oven at 160 °C for 0.5 h, and the thermal stability of the separator was tested by comparing the dimensional changes before and after. The measure-ment method of separator porosity is the N-butanol absorption method.…”

“…For specific test details, it could refer to our previous work. 23 The electrochemical stability of the separator was characterized by linear sweep voltammetry (LSV) analysis (5 mV s −1 , 2.5−6.5 V (vs Li/Li + )) of the assembled SS//Li cells. The procedure and equipment for LiCoO 2 /liquid electrolyte-separator/Li battery analysis (cycling performance, discharge capacity, electrochemical impedance, and discharge C rate capability) have been described in detail in our previous work.…”

“…The procedure and equipment for LiCoO 2 /liquid electrolyte-separator/Li battery analysis (cycling performance, discharge capacity, electrochemical impedance, and discharge C rate capability) have been described in detail in our previous work. 23…”

Recent Development in Novel Lithium-Sulfur Nanofiber Separators: A Review of the Latest Fabrication and Performance Optimizations

“…Nanofiber (NF) separators are highly porous, thermally stable, low cost, and easily modifiable alternatives to polyolefin separators [ 18 , 19 , 20 ]. Because NFs have high porosity and polar functional groups (in some polymer NFs), they also have higher electrolyte affinity and LiPS-adsorbing properties [ 21 ].…”