Polyvinylidene fluoride‐co‐chlorotrifluoroethylene and polyvinylidene fluoride‐co‐hexafluoropropylene nanofiber‐coated polypropylene microporous battery separator membranes

Abstract

Nanofiber-coated polypropylene (PP) separator membranes were prepared by coating a Celgard V R microporous PP membrane with electrospun polyvinylidene fluorideco-chlorotrifluoroethylene (PVDF-co-CTFE) and PVDF-co-CTFE/ polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) nanofibers. Three PVDF polymer solutions of varying compositions were used in the preparation of the nanofiber coatings. Two of the polymer solutions were PVDF-co-CTFE blends made using different types of PVDF-co-HFP copolymers. The PVDF-co-CTFE and PVDF-co-CTFE/PVDF-co-HFP blend nanofiber coatings have been found to have comparable adhesion to the PP microporous membrane substrate. The electrolyte uptakes and separator-electrode adhesion properties of nanofibercoated membranes were evaluated. Both the electrolyte uptake and the separator-electrode adhesion were improved by the nanofiber coatings. The improvement in electrolyte update capacity is not only related to the gelation capability of the PVDF copolymer nanofibers, but also attributed to the increased porosity and capillary effect on nanofibrous structure of the electrospun nanofiber coatings. Enhancement of the separatorelectrode adhesion was owing to the adhesion properties of the copolymer nanofiber coatings. Compared with the PVDF-co-CTFE/PVDF-co-HFP blend nanofiber coatings studied, the PVDF-co-CTFE coating was more effective in improving the electrolyte uptake and separator-electrode adhesion.

ForceSpinning of polyacrylonitrile for mass production of lithium‐ion battery separators

“…The fibrous structure of the PAN membrane plays a key role in its ion transport and conductivity behavior. 39 The electrolyte uptake results shown in Figure 3(a), showed that the PAN membrane has a large mass electrolyte uptake of about 328% compared to the PP Celgard separator value of 82%. Factors such as viscosity, surface tension, solution concentration had a direct influence on the fiber diameters of the Forcespun V R fibers; however, the effect of these factors were minimized through heating of the solution in the silicon oil bath, choosing the appropriate needle gauge (i.e., 30Gx 1 = 2 00 ), and the spinneret speed.…”

“…[36][37][38][39] To further elucidate, the effects of membrane microstructural properties like; porosity, pore size and thickness on the electrolyte capacity, future experiments will be designed to investigate the effect of Forcespun polymer and nanocomposite membranes on these microstructural properties with the aim to improve the separator performance, mechanical strength, thermal, and shutdown properties. The electrolyte uptake, which is a measure of the amount of liquid electrolyte absorbed per unit area of the membrane, is one key performance index of a good lithium ion battery separator.…”

“…have designed and developed commercial separators for the over $4billion lithium ion batteries market, 5 these mostly consist of polymer materials such as polyolefin microporous membranes developed by Celgard, DSM, and Asahi and a tri-layer of polypropylene/ polyethylene/polypropylene from Celgard and Ube industries. [36][37][38][39][40][41][42] As many researchers identify the short comings of these microporous polymer separators, have paved the way for many research efforts aimed at improving their electrochemical performance. 5,25,27 However, several studies [27][28][29][30][31][32][33] have pointed to these polymer-based battery separators to having less impressive key performance indices such as: high interface resistance, low thermal stability, and low electrolyte uptake.…”

A sandwich‐structured separator based on in situ coated polyaniline on polypropylene membrane for improving the electrolyte wettability in lithium‐ion batteries

“…8,[11][12][13] Recently, several strategies have been proposed to improve the electrolyte wettability of polyolefin separators including physical coating and chemical modification. [14][15][16] For example, Lee et al coated polypropylene (PP) separators with polyvinylidene fluoride (PVDF) copolymer nanofiber using electrospinning technology, which largely improved the electrolyte wettability and the corresponding electrochemical performance of LIBs. 14 However, the physical coating layers are normally unstable in the electrolyte, which could easily delaminate from the separator.…”

Tailoring poly(vinylidene fluoride-co-chlorotrifluoroethylene) microstructure and physicochemical properties by exploring its binary phase diagram with dimethylformamide

“…The pseudo‐block structure of PVDF‐CTFE offers feasibility for possible grafting modification via atom transfer radical polymerization (ATRP) preserving the high mechanical, thermal, and chemical stabilities . Intense research efforts are underway on the use of the materials for electrical energy storage, as high energy materials, and the development of gel electrolyte membranes. In particular, its key features for energy storage application are its high ionic conductivity and good compatibility with lithium metal electrodes …”