Lithium-Ion Gel Polymer Battery

Sony is number one worldwide in production of lithium-ion gel polymer batteries, especially the relatively small-sized (below 1 Ah) battery. Sanyo-GS (Japan) and Samsung SDI (Korea) also are producing this kind of battery. Recently, a Chinese manufacturer started to produce lithium-ion gel polymer battery. ATL, one of the largest battery manufacturers, is producing a polymer battery based on Bellcore technologies. However, those manufacturers still continue their production in the small-sized battery field. 

In recent years there has been a strong demand for higher-capacity lithium-ion cells because of the strong growth in portable electronics. One way to achieve higher capacity is by reducing the thickness of separators. At present, battery manufacturers routinely use separators 16 pm or thinner in higher-capacity (>2.6 Ah) cylindrical cells and 9 pm separators in lithium-ion gel polymer cells. 

Lithium-Ion Cel Polymer Battery The Hthium-ion gel polymer batteries offer better performance than that of solid polymer electrolyte batteries. The gel electrolyte is a polymer matrix swollen with a liquid electrolyte, and the batteries that employ gel electrolyte are known as gel polymer batteries. The detailed information on this type of battery can be found in other chapters of this book and in a review [33]. Most of the gel electrolytes have been made employing PEO, poly(acrylonitrile) (PAN) [34], poly(methyl methacrylate) (PMMA) [35, 36], and PVdF [37, 38]. The poor mechanical properties of polymer and gel polymer electrolytes have led to an alternative approach where microporous membranes are impregnated with gel polymer electrolytes [39-42]. The process builds upon the work of Abraham et al. who saturated commercial polyolefin separators with a solution of lithium salt in a photopolymerizable monomer and a nonvolatile... 

A. Guerfi, M. Gontigny, Y. Kobayashi, A. 5jh, K. Zaghib, J. Solid State Electrochem. 2009, 13,1003-1014. Investigations on some electrochemical aspects of lithium-ion ionic hquid/gel polymer battery systems. 

The electrochemically active electrode materials in Li-ion batteries are a lithium metal oxide for the positive electrode and lithiated carbon for the negative electrode. These materials are adhered to a metal foil current collector with a binder, typically polyvinylidene fluoride (PVDF) or the copolymer polyvinylidene fluoride-hexafluroropropylene (PVDF-HFP), and a conductive diluent, typically a high-surface-area carbon black or graphite. The positive and negative electrodes are electrically isolated by a microporous polyethylene or polypropylene separator film in products that employ a liquid electrolyte, a layer of gel-polymer electrolyte in gel-polymer batteries, or a layer of solid electrolyte in solid-state batteries. 

As discussed in previous chapters, the separators are an integral part of liquid electrolyte batteries including nonaqueous batteries such as lithium-ion, lithium-polymer, hthium-ion gel polymer, and aqueous batteries such as zinc-carbon, zinc-manganese oxide, lead-acid, nickel-based batteries, and zinc-based batteries. 

Many think the future moves toward solvent free systems Scrosati presents a chapter on polymer electrolytes, most of which are solvent-containing gel-polymers in practical systems, and Nishi discusses gel-polymer battery properties and production. Webber and Blomgren give extensive treatment of ionic hquids (otherwise known as ambient-temperature molten salts) and their use in lithium-ion and other battery systems. 

It is manipulation of the rate-limiting step that will lead to increased rates of charge for a lithium-ion cell (and battery). The processes occurring in a lithium-ion-polymer (ak.a lithium-polymer), and a lithium-ion-gel (ak.a... 

These types of separators consist of a solid matrix and a liquid phase, which is retained in the microporous structure by capillary forces. To be effective for batteries, the liquid in the microporous separator, which generally contains an organic phase, must be insoluble in the electrolyte, chemically stable, and still provide adequate ionic conductivity. Several types of polymers, such as polypropylene, polysulfone, poly(tetrafluoroethylene), and cellulose acetate, have been used for porous substrates for supported-liquid membranes. The PVdF coated polyolefin-based microporous membranes used in gel—polymer lithium-ion battery fall into this category. Gel polymer... 

Lithium secondary batteries can be classified into three types, a liquid type battery using liquid electrolytes, a gel type battery using gel electrolytes mixed with polymer and liquid, and a solid type battery using polymer electrolytes. The types of separators used in different types of secondary lithium batteries are shown in Table 1. The liquid lithium-ion cell uses microporous polyolefin separators while the gel polymer lithium-ion cells either use a PVdF separator (e.g. PLION cells) or PVdF coated microporous polyolefin separators. The PLION cells use PVdF loaded with silica and plasticizer as separator. The microporous structure is formed by removing the plasticizer and then filling with liquid electrolyte. They are also characterized as plasticized electrolyte. In solid polymer lithium-ion cells, the solid electrolyte acts as both electrolyte and separator. 

Development efforts are under way to displace the use of microporous membranes as battery separators and instead use gel electrolytes or polymer electrolytes. Polymer electrolytes, in particular, promise enhanced safety by eliminating organic volatile solvents. The next two sections are devoted to solid polymer and gel polymer type lithium-ion cells with focus on their separator/electrolyte requirements. 

The solid polymer electrolyte approach provides enhanced safety, but the poor ambient temperature conductivity excludes their use for battery applications. which require good ambient temperature performance. In contrast, the liquid lithium-ion technology provides better performance over a wider temperature range, but electrolyte leakage remains a constant risk. Midway between the solid polymer electrolyte and the liquid electrolyte is the hybrid polymer electrolyte concept leading to the so-called gel polymer lithium-ion batteries. Gel electrolyte is a two-component system, viz., a polymer matrix... 

Gel polymer lithium-ion batteries replace the conventional liquid electrolytes with an advanced polymer electrolyte membrane. These cells can be packed in lightweight plastic packages as they do not have any free electrolytes and they can be fabricated in any desired shape and size. They are now increasingly becoming an alternative to liquid-electrolyte lithium-ion batteries, and several battery manufacturers. such as Sanyo. Sony, and Panasonic have started commercial production.Song et al. have recently reviewed the present state of gel-type polymer electrolyte technology for lithium-ion batteries. They focused on four plasticized systems, which have received particular attention from a practical viewpoint, i.e.. poly(ethylene oxide) (PEO). poly (acrylonitrile) (PAN). ° poly (methyl methacrylate) (PMMA). - and poly(vinylidene fluoride) (PVdF) based electrolytes. ... 

Ion conducting polymers may be preferable in these devices electrolytes because of their flexibility, moldability, easy fabrication and chemical stability (for the same reasons that they have been applied to lithium secondary batteries [19,48,49]). The gel electrolyte systems, which consist of a polymeric matrix, organic solvent (plasticizer) and supporting electrolyte, show high ionic conductivity about 10 5 S cnr1 at ambient temperature and have sufficient mechanical strength [5,7,50,51], Therefore, the gel electrolyte systems are superior to solid polymer electrolytes and organic solvent-based electrolytes as batteries and capacitor materials for ambient temperature operation. 

The strategy of hybrid and gel electrolytes is very promising for lithium-ion batteries, but it seems less viable for lithium-metal batteries due to the reactivity of lithium metal with the encapsulated solvent. In fact, high conductivity is not the only parameter in selecting a successful polymer electrolyte for the development of lithium batteries a low interface resistance and a high interface stability over time are also required to assure good cyclability and long life. 

Saunier, AUoin, E, Sanchez, J.-Y., Maniguet, L, 2004. Plasticized microporous PVdF separators for lithium ions batteries. Part 111 gel properties and irreversible modifications of PolyfvinyUdene fluoride) membranes under swelling in liquid electrolyte. J. Polym. Sci. Part B 42,2308-2317. 

Alternative routes to obtain lithium-ion plastic batteries have considered the use of PAN-based gel-type polymer electrolytes as separators. These electrolyte membranes, although macroscopically solid, contain in their structure the active liquid electrolyte (Figure 7.7). Therefore, they have a configuration which in principle allows a single lamination process for the fabrication of the lithium-ion battery, i.e., a process that avoids intermediate liquid extraction-soaking activation steps. 

The feasibility of the gel electrolytes for lithium-ion batteries development has been tested by first examining their compatibility with appropriate electrode materials, i.e., the carbonaceous anode and the lithium metal oxide cathode. This has been carried out by examining the characteristics of the lithium intercalation-deintercalation processes in the electrode materials using cells based on the given polymer as the electrolyte and lithium metal as the counter electrode. 

Once the compatibility of the gel-type electrolyte with both anode and cathode materials is ascertained, one can proceed with the combination of the two for the fabrication of polymer-based lithium-ion battery prototypes. A few examples of these prototypes have been reported at the laboratory level scale. One is provided by a battery of the type C/ LiC104-EC-PC-PAN/LiCryMn2.y04. 

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