Separators nonwoven

Nonwoven materials have also been developed for lithium-ion cells but have not been widely accepted, in part due to the difficulty in fabricating thin materials with good uniformity and high strength. Nonwoven separators have been used in button cells and bobbin cells when thicker separators and low discharge rates are acceptable. 

Cho, T., Sakai, T., Iknase, S., Kimura, K., Kondo, Y, Tarao, T., Tanaka, M., 2007. Electrochemical performances of polyacrylonitrile nanofiber-based nonwoven separator for lithium-ion battery. Electrochem. Solid-State Lett. 10, A159-A162. 

Because of its toughness, nylon fiber is suitable for nonwoven needle-punched floorcovering products. Nylon nonwoven fiber can be found in garment interlinings and wipes for its strength and resilience. It is also used Ni/H and Ni/Cd batteries as nonwoven separators in high performance wipes, synthetic suede, heat insulators, battery separators, and specialty papers and in automotive products, athletic wear, and conveyor belts. 

The materials used in nonwoven fabrics include a single polyolefin, or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), polytetrafluoroethylene (PTFE), polyvinylidine fluoride (PVdF), and polyvinyl chloride (PVC). Nonwoven fabrics have not been able to compete with microporous films in lithium-ion cells. This is primarily because of the inadequate pore-size structure and difficulty in making thin (<25 pm) nonwoven fabrics with acceptable physical properties. However, nonwoven separators have been used in button cells and bobbin cells when thicker separators and low discharge rates are acceptable. 

Typically, carbon zinc and alkaline cells use nonwoven separators. In these cases, cost is an important design consideration, and the high conductivity of the electrolyte enables thicker separator materials. However, the thickness of the separator also defines the gap or distance between electrodes, which can impact the cell s ability to support high current densities. Pores are not well defined and are typically on the order of... 

Most nanofiber nonwoven separators are made through electrospinning. However, a few other approaches have been tried as well. 

Core-sheath nanofibers of PVDF (polyvinylidiene fluoride) around a polyimide core The nonwoven separators show better wettability with polar solvents, better thermal stability, better rate capability, and better cycle life compared to conventional PP separators. 

Electrospun PET nanofiber nonwovens The nonwoven separators showed excellent thermal stability, thermal stability of the cell, and rate capability compared to conventional PE separators. 

Electrospun polyacrylonitrile nonwoven separators with nanofiber size between 250 and 380 nm The separators showed higher porosity, better wettability, and small and uniform pore sizes. The cells made with the separator showed better cycle life and faster rate capabilities than the conventional separators. Cells also showed that the separator was stable to 120°C, but not to 150°C, which is similar to conventional separators. 

Fibrillated, wet-laid nanofibers of paraphenylene teraphthalamide They were able to make nonwoven separators with pore size <0.5 pm, which showed good separator properties and low impedance. 

Here, more than 20 different approaches to making nonwoven separators for LIB are shown to make functioning batteries, which show consistent advantages of ... 

Because of the consistency of the performance of the various approaches, these may be taken to be general trends among nonwoven separators that are suitable for use in lithium-ion cells. But that being the case, what are the diHiculties that still remain There are several, which largely have to do with cost and mass production uniformity. Namely, the separators that are able to exhibit the following characteristics in addition to those above can be expected to take a place in the market among those currently being used ... 

F. Zhang, X. Ma, C. Cao, J. li, Y. Zhu, Poly(vinlyidiene fluoride)/Si02 composite membranes prepared by electrospinning and their excellent properties for nonwoven separators for lithium ion batteries, J Power Sour 251 (2014) 423—431. 

T. Cho, M. Tanaka, H. Ohnishi, Y. Kondo, T. Nakamura, H. Yamazaki, et al.. Battery perforamnces and thermals stabihty of polyacrylonitrile nano-fiber-based nonwoven separators for Li-ion battery, J Power Sour 181 (2008) 155—160. 

Yi et al. [33] made a wet-laid, nonwoven separator using fibrillated fibers made of polyparaphenylene terephthalamide and PE terephthalate fibers used as binder. The membranes were 30-40 gm thick and had maximum pore sizes greater than 1 gm, so were stiU not suitable for hthium-ion cells. 

The pore sizes of separators made from nonwoven fibers vary from 1 to 100 pm. The fibers for this type of separator are manufactured primarily for the textile industry and include polyolefins, cellulose, and polyvinyl alcohol. The fibers are bonded by friction, cohesion, or adhesion into sheets, webs, or mats. The nonwoven separators have highly desirable properties such as uniform weight, thickness, and porosity and they exhibit superior stabihty to electrolytes. This type of separator... 

Cho T-H, Tanaka M, Onishi H, Kondo Y, Ntikamura T, Yamazald H, Tanase S, Sakai T (2008) Battery performances and thermal stability of polyacrylonitrile nanofiber-based nonwoven separators for Li-ion battery. J Power Sources 181(1) 155-160. doi 10.1016/j.jpowsour.2008.03.010... 

Tanaka M, Cho T-H, Nakamura T, Tarao T, Kawabe M, Sakai T (2010) Electrochemical performances of polyacrylonitrile nano-fiber based nonwoven separator for lithium ion battery. Electrochemistry 78(12) 982-987... 

Cho T-H, Tanaka M, Ohnishi H, Kondo Y, Yoshikazu M, Nakamura T, Sakai T (2010) Composite nonwoven separator for lithium-ion battery development and characterization. J Power Sources 195(13) 4272-4277, http //dx.doi.Org/10.1016/j.jpowsour.2010.01.018... 

Miao YE, Zhu GN, Hou HQ, Xia YY, Liu TX (2013) Electrospun polyimide nanofiber-based nonwoven separators for lithium-ion batteries. J Power Sources 226 82-86... 

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