Construction, lithium polymer batterie

Fig. 7.21 Schematic illustration of the construction of a lithium polymer battery (LPB)...

Scale-up from laboratory test cells to EV module is the next challenge for the LPB technology. There are three general areas which need to be addressed when considering scale-up, namely (1) raw materials, (2) component fabrication, and (3) cell and battery construction. In general, the raw materials employed in the various forms of lithium polymer batteries can easily be obtained in large quantities. The key areas are the lithium metal foil and the active positive material. Lithium metal foils are commercially available in a range of thicknesses down to 50 pm. However, thinner... 

Electrodes and cell components must be thin to minimise the internal resistance of the batteries the total cell can be less than 0.2 mm thick. Figure 12.11 shows the construction of a multi-layer film, rechargeable lithium polymer battery, using a solid polymer electrolyte. A thin lithium metal foil acts as an anode. The electrolyte is polyethylene oxide containing a lithium salt, and the cathode is a composite of the electrolyte and a... 

Work at Harwell has concentrated on scaling up the lithium polymer battery technology for use in electric vehicle traction batteries. The project, supported by the Commission of the European Communities, has systematically scaled up the cell active area. The various cell sizes are shown in Figure 6.33. The larger cells were used to construct two 80 A h units which are shown in Figure 6.34. The results of the project have highlighted the need for capacity balance and excellent cell-to-cell reproducibility. 

Sec color insert.) Pouch cell design for solid electrolyte lithium polymer battery. Design is easily adaptable to ECs made with organic electrolyte. Source ElectropecUa Cell Construction (online). http //wwwjnpoweruk.com/ceU construction.htm [accessed AprU 5, 2012]. With permission.)... 

The lithium sulfur dioxide and the lithium thionyl chloride systems are specialty batteries. Both have liquid cathode reactants where the electrolyte solvent is the cathode-active material. Both use polymer-bonded carbon cathode constructions. The Li-S02 is a military battery, and the Li-SOCl2 system is used to power automatic meter readers and for down-hole oil well logging. The lithium primary battery market is estimated to be about 1.5 billion in 2007. 

Lithium s 47% fraction of the 3.61 bilUon rechargeable battery market in 1999s had become 52% and 3 billion by itself in 2002. Sony Corp. had about 33% of this market, and Sanyo Electric Company 23% in 2000. Sony originally developed the lithium-ion batteries, but in 2000 began converting much of its manufacturing capacity to the more profitable lithium polymer type. Sanyo Electric also produced about 32% of the nickel-cadmium, and 46% of the nickel hydride batteries in 2000 (Lerner, 2001 Jarvis, 2000). Considerable research has been conducted on rechargeable lithium batteries for automobiles, but by 2002 there were still major safety and construction problems. 

The majority of electrochemical cells to have been constructed are based on PEO, PAN, or PVdF [101]. Recently, the Yuasa Corporation have commercialized solid polymer electrolyte batteries, primarily for use in devices such as smart cards, ID cards, etc. To date, the batteries which have been manufactured and marketed are primary lithium batteries based on a plasticized polymer electrolyte, but a similar secondary battery is expected [120]. 

A second class of important electrolytes for rechaigeable lithium batteries are solid electrolytes. Of particular importance is the class known as solid polymer electrolytes (SPEs). SPEs are polymers capable of forming complexes with lithium salts to yield ionic conductivity. The best known of the SPEs are the lithium salt complexes of poly (ethylene oxide) [25322-68-3] (PEO), — (CH2CH20)k—, and poly(propylene oxide) [25322-69 4] (PPO) (11—13). Whereas a number of experimental battery systems have been constructed using PEO and PPO dectrolytes, these systems have not exhibited suitable conductivities at or near room temperature. Advances in the 1980s included a new dass of SPE based on polyphosphazene complexes suggesting that room temperature SPE batteries may be achievable (14,15). 

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. 

Since both neutral and reduced forms of (CH) have good stability in a battery employing lithium perchlorate in tetrahydrofuran solvent, a cell was constructed using the above polymer electrodes. It is the first stable, fully polymer, rechargeable battery with Coulombic efficiencies greater than 99%. A cell of this type, using 7% doped anode, has an open-circuit potential of 1 V and current of approximately 30 Am of (CH). ... 

In the development of batteries to date, the most notable are those containing n and p type polymer, e.g., the perchlorate-doped polyacetylene in conjunction with the lithium doped polyacetylene, and acetonitrile. Aqueous polyacetylene battereis are under construction. Theoretical work has been done here by Will (56), who has derived equations for the slow change of a battery potential resulting from dopant diffusion within the solid. Mermilliod and co-workers (59) have demonstrated that much of the electrical capacity of the batteries arise not because of the conversion of chemical to electrical work as with normal batteries, but because of the storage of electricity in the double layer, very large because of the high surface area to bulk ratio in many polymers. 

Figure 17 Illustration of lithium battery construction. Reprinted with permission from Hanser Gardner Publications Robeson, L. M. Polymer Blends A Comprehensive Review, Hanser Garner Publication, Cincinnati, CT, 2007.2 ...

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