Cathodes, lithium polymer batteries

This type of Li battery has already widely diffused in the electronic consumer market, however for automotive applications the presence of a liquid electrolyte is not considered the best solution in terms of safety, then for this type of utilization the so-called lithium polymer batteries appear more convenient. They are based on a polymeric electrolyte which permits the transfer of lithium ions between the electrodes [21]. The anode can be composed either of a lithium metal foil (in this case the device is known as lithium metal polymer battery) or of lithium supported on carbon (lithium ion polymer battery), while the cathode is constituted by an oxide of lithium and other metals, of the same type used in lithium-ion batteries, in which the lithium reversible intercalation can occur. For lithium metal polymer batteries the overall cycling process involves the lithium stripping-deposition at the anode, and the deintercalation-intercalation at the anode, according to the following electrochemical reaction, written for a Mn-based cathode ... 

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... 

Sivakkumar, S., Kim, D.-W., 2007. Polyanfline/carbon nano tube composite cathode for rechargeable lithium polymer batteries assembled with gel polymer electrolyte. J. Electrochem. Soc. 154, A134-A139. 

Park, J.E., S.G. Park, A. Koukitu, O. Hatozaki, and N. Oyama. 2004. Effect of adding Pd nanoparticles to dimercaptan-polyaniline cathodes for lithium polymer battery. Synth Met 140 (2-3) 121-126. 

In general the raw materials employed in the various forms of lithium polymer batteries can easily be obtained in larger quantities. The key areas will be the lithium metal foil and the active cathode material. Lithium metal foils are commercially available in a range of thicknesses down to 50 im. However, thin (< 30 pm) and wide (> 10 cm) foils will be very difficult to achieve at reasonable rates and low cost. Present lithium foil manufacturers are rising to the challenge [53] and several groups are exploring... 

Doeff MM, Peng MY, Ma Y, De Jonghe LC (1994) Orthorhombie NaxMn02 as a cathode material for secondary sodium and lithium polymer batteries. J Electroehem Soc 141 L145-L147... 

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]. 

The lithium-ion-polymer battery, which uses a cathode that contains lithium instead of cobalt, is likely to eventually replace lithium-ion. Lithium-ion-polymer batteries boast a longer life expectancy (over 500 charge-and-discharge cycles as opposed to around 400), much more versatility (they are flat and flexible and can be cut to fit almost any shape), and better safety (far less likely to vent flames while recharging). 

As to anodes, in most of the research work a generously dimensioned sheet of lithium metal has been used. Such an electrode is rather irreversible, but this is not noticed when a large excess of lithium is employed. Li-Al alloys and carbon materials inserting lithium cathodically during recharging can be used as anodes in nonaqueous solutions. Zinc has been used in polymer batteries with aqueous electrolyte (on the basis of polyaniline). 

The molecular orbital (MO) calculations within the PM3 method, using a MOP AC package, provided an explanation of the advantages of a new redox system, poly(l,4-phenylene-l,2,4-dithiazolium-3, 5 -yl) (PPDTA), as a cathode material for high-capacity lithium secondary batteries in comparison with three typical polymer conductors (poly-/>-phenylene, polypyrrole, and polythiophene). The MO calculation revealed that the S-S bond in the 1,2,4-dithiazo-lium moiety of PPDTA caused gap narrowing and a downshift of HOMO and LUMO levels, which is consistent with the electrochemical experiment (HOMO = highest occupied molecular orbital LUMO = lowest unoccupied molecular orbital) <2001MI2305>. 

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. 

A battery cell where both the electrodes consist of dopable polymer is shown in Figure 5.23. The electrolyte in this case consists of Li+ClO 4 dissolved in an inert organic solvent, usually tetrahydro-furan or propylene carbonate. When two sheets of polyacetylene or PPP are separated by an insulating film of polycarbonate saturated in an electrolyte (lithium perchlorate), and completely encapsulated in a plastic casing, a plastic battery can be made. The two sheets of polyacetylene or PPP act as both anode and cathode for the battery. A schematic is shown in Figure 5.24. Although doped polyacetylene and polyaniline electrodes have been developed, polypyrrole-salt films are the most promising for practical appKcation. 

Chao, D., Xia, X., Liu, J., Fan, Z., Ng, C.F., Lin, J., Zhang, H., Shen, ZX, Fan, H.J., 2014. A V205/Conductive-polymer core/shell nanobelt array on three-dimensional graphite foam a high-rate, ultrastable, and freestanding cathode for lithium-ion batteries. Adv. Mater. 26,5794-5800. 

Kim, Y, Jo, C., Lee, J., Lee, C.W., Yoon, S., 2012. An ordered nanocomposite of organic radical polymer and mesoceUular carbon foam as cathode material in lithium ion batteries. J. Mater. Chem. 22,1453-1458. 

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