Lamination, lithium polymer batterie

In the following section, the manufacturing process of a lithium polymer battery and a lithium-ion battery, which use a laminated film as the exterior case, will be briefly explained. The methods of coating the positive electrode and the negative electrode are the same as previously described. The following methods are now being used for making the cell core or electrode stack ... 

The discovery and the characterization of ionically conducting polymeric membranes (see Chapters 1 and 2) have provided the interesting possibility of developing new types of lithium batteries having a thin-layer, laminated structure. Various academic and industrial laboratories [1-5] are presently engaged in the development of this revolutionary type of battery, i.e. the so-called Lithium Polymer Battery (LPB). The key component of the LPB is the polymeric ionic membrane which acts both as electrolyte and separator furthermore, the membrane can be easily fabricated in the form of a thin film (typically 50 jum thickness) by a number of convenient casting techniques. 

These polymer electrol5rtes were exploited in the late 1990s for the fabrication of large-sized, laminated battery modules based on cells formed by a lithium foil anode and a vanadium oxide cathode, developed jointly by Hydro Quebec in Canada and 3M company in the United States [7,8]. The battery module had very good performance in terms of energy density (155 Wh kg ) and cycle life (600 cycles at 80% depth of discharge (DOD)), and it was proposed as a power source for EVs, a very futuristic concept back in 1996. However, despite this and other successful demonstration projects, the lithium polymer battery project was abandoned and only very recently reconsidered for use in an EV produced in France [9]. 

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. 

Lithium ion polymer batteries and laminated solid-state redox supercapacitors have also been fabricated [271]. In these plastic power sources, a highly conducting gel-type membrane electrolyte is placed between a PP-PANI electrode combination. 

They are fabricated from a variety of inorganic, organic, and naturally occurring materials and generally contain pores that are greater than 50—100 A in diameter. Materials such as nonwoven fibers (e.g. nylon, cotton, polyesters, glass), polymer films (e.g. polyethylene (PE), polypropylene (PP), poly(tetrafluo-roethylene) (PTFE), poly (vinyl chloride) (PVC)), and naturally occurring substances (e.g. rubber, asbestos, wood) have been used for microporous separators in batteries that operate at ambient and low temperatures (<100 °C). The microporous polyolefins (PP, PE, or laminates of PP and PE) are widely used in lithium based nonaqueous batteries (section 6.1), and filled polyethylene separators in lead-acid batteries (section 7.3), respectively. 

Lithium ion cells serve the smaU-sealed rechargeable battery market and compete mainly with the Ni-Cd and Ni-MH cells for the various applications. The Li-Ion cells are available in cylindrical and prismatic format as well as flat plate constructions. The cylindrical and prismatic constructions use a spiral-wrap cell core where the ceU case maintains pressure to hold and maintain compression on the anode, separator, and cathode. The lighter-weight polymer constructions utilize the adhesive nature of a polymer/laminate-based electrolyte to bond the anode to the cathode. 

The technology of rechargeable lithium batteries is being developed continuously. Goals are larger batteries, e.g. for the hybrid propulsion system of vehicles, environmentally more compatible components, especially for the cathode, lower priced materials, longer cycle lives, more inert electrodes, etc. So-called solid-state batteries with polymeric electrolyte are also to be mentioned here. They are lithium-ion cells with an inert polymer matrix or a gel, which contains the electrolytic solvent-conductive salt mix. Herewith, the use of the normal heavy steel containers, which cannot be manufactured with heavily reduced wall thickness anyway, can be abandoned and a plastic laminated aluminum foil can be applied instead. In this way lightweight and very thin cells of a card format can be made. 

At the time of writing, the solid-state alkali metal battery is by far the most important projected application of a polymer electrolyte. This is based on a thin film laminated structure containing a lithium-metal negative electrode, a polymer film electrolyte, and a positive electrode made of an oxidizing agent capable of inserting alkali ions into its structure (Figure 7). 

---