Separators for industrial batteries

Separators for Industrial Batteries 11.2.3.1 Separators for Traction Batteries... 

Very different microporous separators for alkaline batteries are included in Table 11.16. The very thin ( 25 xm) films of stretched polypropylene ( Celgard ) are generally employed in combination with fleeces, while separators of sintered PVC or filled UHMW PE find use also in single separation of alkaline industrial batteries. Their production process corresponds to the analogous version for lead-acid batteries and is described in detail in Sections 11.2.2.1 and 11.2.2.2 respectively. 

Aprotic electrolytes of an adequate high conductivity are necessary for lithium batteries and super capacitors. Therefore, recently, much industrial research has been done in this area and highly sophisticated electrolyte systems have been developed (e.g. [64]). The supporting electrolytes for aprotic solvents generally are more or less expensive and toxic. After the reaction, their separation and recycling is inevitable and frequently needs considerable efforts. 

Asahi Chemical Industry carried out an exploratory investigation to determine the requirements for cellulose based separators for lithium-ion batteries. In an attempt to obtain an acceptable balance of lithium-ion conductivity, mechanical strength, and resistance to pinhole formation, they fabricated a composite separator (39—85 /cellulosic fibers (diameter 0.5—5.0 /pore diameter 10—200 nm) film. The fibers can reduce the possibility of separator meltdown under exposure to heat generated by overcharging or internal short-circuiting. The resistance of these films was equal to or lower than the conventional polyolefin-based microporous separators. The long-term cycling performance was also very comparable. 

Lead-acid batteries can be classified into three major types or categories, namely, automotive (SLI), stationary, and motive power (industrial). In addition, there are many special batteries that cannot be easily categorized as either of the above types. As these types of batteries are constructed with different materials and design to meet the requirements of their intended end uses, each requires a particular separator with specific material composition, mechanical design, and physical, chemical, and electrochemical properties that are tailored for the battery and its relevant specific uses. These batteries are generally available in flooded electrolyte or valve regulated (sealed) versions. In this section the types... 

For battery separators, regenerated cellulose is placed on the surface of nonwoven so that the nonwoven is available to promote the wicking of the electrolyte. The nonwovens should not allow the penetration of viscose into itself. Suitable nonwovens are made from polypropylene, poly(vinyl alcohol), and hardwood hemps. Regenerated cellulose films are commonly used in alkaline manganese cells, both primary and secondary, in NiCd industrial batteries, as well as in silver—zinc batteries. 

A related situation we ll call piggyback markets. By this we mean industries in which extensive recycling exists for some material other than polymers, but in which polymers are easily separated for recycle as well. We earlier mentioned the recycling of polypropylene battery cases. Infrastructure was already in place to recover valuable lead metal from the electrodes. It was easy to also recover the plastic cases when polymer recycling became feasible. Table 9-3 summarizes a few examples. 

Shirai, H., Spotnitz, R., Atsushi, A. Characterization of Separators for Lithium Ion Batteries -A Review, Chemical Industry, 48 (1997) 47 (in Japanese)... 

Nonwovens have been well established as traditional materials for alkaline batteries, NiCd and NiMH cells, and for absorbed glass matt (AGM) lead—acid batteries. Alkaline batteries use a variety of materials, mostly composed of wet-laid cellulose and polyvinyl alcohol (PVA). NiCd and NiMH use a variety of materials, from spunbond and melt blown to dry-laid materials. Lead—acid AGM batteries use a wet-laid glass matt as the separator, often in conjunction with another membrane. These materials range in thickness from 100 to 300 pm. One review article in 2007 even states that for lithium ion cells, nonwoven not possible. However, these traditional nonwovens are a significant industrial market for several manufacturers, with total sales into these types of cells of 450 million globally. 

In August 2015, it was announced that Freudenberg and Toray will purchase all of the shares of Japan Vilene. Japan Vilene has automotive, industrial, apparel, and electrical products. In electrical, they are well established as a supplier of separators for NMH and NiCd batteries. In 2006, they built a pilot facility to produce nanofibers in web widths as wide as 1 m. The fiber diameter ranges from 0.1 to 1.0 pm, while the pore size of the nonwovens ranges from 0.4 to 2.0 pm. The materials they can produce ranges from 5 to 25 g/m. They are targeting applications in filtration, separators, and medical materials. In their 2013 annual report, they mention using nonwovens with nanofibers in a cell culture scaffold, in filtration, and in separators for LIB. 

---