Li-polymer cells

PANI-NFA 2O5 is promising nanocomposite material for utilization as a cathode for ion-Li batteries [292,293]. PANI-NFs have been used as a cathode material for rechargeable Li-polymer cells assembled with a gel polymer electrolyte [152], and in an aqueous PANI-Zn rechargeable battery [261]. Dispersions of dedoped PANI-NFs in poly(vinyhdene fluoride-hexafluoropropylene)-based gel polymers can be used as electrolyte membranes for rechargeable Li batteries [513]. PANI-NF and PANI-NT arrays, which show superior electrochemical properties to the bulk counterpart, can be applied to Li-polymer thin-film batteries, which are shape-flexible and specifically suitable for powering integrated circuit cards and microelectromechanical systems [514,515]. 

FIGURE 7.4 The 24 kWh Nissan Leaf Li-ion battery pack with AESC Li-polymer cells. (For color version of this figure, the reader is referred to the online version of this book.)... 

The Ford Focus BEV was launched in December 2011 for fleet sales, and in May 2012, for consumers in California, New York, and New Jersey, with the release scheduled for Q3 2012 in 16 other US markets. The Focus is a BEV with a 23 kWh Li-ion battery system using Li-polymer cells provided by LG Chem and the battery system, including cell, modules and controls, provided by Compact Power (LG Chem s US subsidiary). 

The number of recalls and failures is small in comparison to production volumes. In 2005, 1.7 billion Li-ion and li Polymer cells were made worldwide [8] with a projected volume of 2.2 billion cells per year by 2008. Estimates are that safety incidents involving Li-ion rechargeable batteries occur in less than 1 in a milUon cells, and probably in less than 1 in 10 million cells [9]. However, even though the frequency is small on a percentage basis, it has gained the attention of the CPSC and other consumer and transportation safety regulatory agencies [10]. 

Li-ion and Li-polymer cells have poor response to overcharge abuse compared to aqueous electrolyte cells because they contain more energy and have potentially flammable electrolyte solvents. Instabihty of certain cathode materials (typically containing nickel oxide) at elevated voltages will produce oxygen that exothermically reacts with organic materials within the cell [27]. Newer cathode materials have improved the situation. 

Figure 20. Construction of (A) cylindrical, (B) prismatic, and (C) polymer Li ion cells. (Reprinted with permission from a brochure by Sony Corporation).

In 1995, West and Crespi studied the reversibility of the lithium insertion process in a polymer electrolyte Li/Ag2V4On cell, cycled between 2.2 and 3.5 V at 100°C... 

Both the lithium sulfur dioxide (Li-SO and lithium thionyl chloride (Li-SOCy cells may be classified as liquid cathode systems. In these systems, S02 and SOCl2 function as solvents for the electrolyte, and as the active materials at the cathode to provide voltage and ampere capacity. As liquids, these solvents permeate the porous carbon cathode material. Lithium metal serves as the anode, and a polymer-bonded porous carbon is the cathode current collector in both systems. Both cells use a Teflon-bonded acetylene black cathode structure with metallic lithium as the anode. The Li-S02 is used in a spirally wound, jelly-roll construction to increase the surface area and improve... 

Albeit these are preliminary, illustrative results, and system optimization is still ongoing, PEGnMg(CI04)2lPN are likely to become an alternative to Li-polymer electrolytes for low-temperature devices, not only in terms of specific cell features,... 

H.-Y. Chen, J. Hou, S. Zhang, Y. Liang, G. Yang, Y. Yang, L. Yu, Y. Wu, G. Li, Polymer Solar Cells with Enhanced Open-Circuit Voltage and Efficiency. Nat. Photonics 2009, 3, 649-653. 

Peramunage and Abraham have recently reported an advanced lithium-ion polymer cell [106, 107]. In this case, a material of the Li [Lij/3Tij/3]04 family [108, 109], e.g., the Li4Ti50i2, intercalation compound, has been used as an anode. The lithium intercalation-deintercalation process in this compound is shown in Equation 7.14. 

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. 

Once the cell assembly process is complete, the final step in the overall production process shifts to the formation and aging of the cells. This applies to cylindrical, prismatic, flat plate, and polymer cell constructions. Li-Ion cells are assembled in the discharged condition and must be activated by charging. The first charge is called formation, which activates the active materials in the cells and establishes... 

Safety is a key issue for Li-Ion batteries. The U.S. Department of Transportation (DOT) and the United Nations classify Li-Ion and Li-Ion polymer batteries as hazardous materials for shipping. The DOT grants exemptions for shipping small Li-Ion cells, provided that the cells/battery with limited lithium-equivalent content... 

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 20.1. The liquid Li-Ion cell uses microporous polyolefin separators while the gel polymer Li-Ion cells either use polyvinylidene difluoiide (PVdF) separator (e.g., PLION cells) or PVdF-coated microporous polyolefin separators. The PLION cells use PVdF loaded with silica and a plasticizer as the separator. The microporous structure is formed by removing the plasticizer and then filling with liquid electrolyte. They also are characterized as plasticized electrolyte. In solid polymer Li-Ion cells, the soM electrolyte acts as both electrolyte and separator. This chapter focuses only on the conventional liquid Li-Ion systems. 

Progress is also being made in the fabrication and testing of polymer electrolyte-based solid-state Li batteries. Capacity degradation with continuous cycling has been identified in most of the studies reported to date. The underlying cause of this is not well understood. However, the Li/polymer electrolyte interfacial behaviour is believed to be a contributor to the capacity decline of cells with cycling [46]. The evidence presently... 

Polycarbazole and polyiminodibenzyl were chemically synthesized and tested in Li/LiC104 in PC/polymer cells [29]. The charge-discharge coulombic efficiencies were 68% for polycarbazole and 88% for polyiminodibenzyl at a charge depth of 33 Ah kg" Poly(triphenylamine) can also be used as the positive electrode material [80]. A Li/LiC104 in PC/poly(triphenylamine) cell produces an open circuit voltage of 3.9 V. 

Table 5.7 Characteristics of various Li/conductive polymer cells... 

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