Lithium Polymer Battery - Technical Specifications

Technical Specifications

There are currently two commercialized technologies, both lithium-ion-polymer (where "polymer" stands for "polymer electrolyte/separator") cells. These are collectively referred to as "polymer electrolyte batteries".

The battery is constructed as:

• positive electrode: LiCoO₂ or LiMn₂O₄
• Separator: Conducting polymer electrolyte (e.g., polyethyleneoxide, PEO)
• negative electrode: Li or carbon-Li intercalation compound

Typical reaction:

• Negative electrode: carbon–Li_x → C + xLi+ + xe−
• Separator: Li+ conduction
• Positive electrode: Li_1−xCoO₂ + xLi+ + xe− → LiCoO₂

Polymer electrolytes/separators can be solid polymers (e.g., polyethyleneoxide, PEO) plus LiPF₆, or other conducting salts plus SiO₂, or other fillers for better mechanical properties (such systems are not available commercially yet). Some manufacturers like Avestor (since merged with Batscap) are using metallic Li as the negative electrode (these are the lithium-metal polymer batteries), whereas others wish to go with the proven safe carbon intercalation negative electrode.

Both currently commercialized technologies use PVdF (a polymer) gelled with conventional solvents and salts, like EC/DMC/DEC. The difference between the two technologies is that one (Bellcore/Telcordia technology) uses LiMn₂O₄ as the positive electrode, and the other the more conventional LiCoO₂.

Other, more exotic (although not yet commercially available) Li-polymer batteries use a polymer positive electrode. For example, Moltech is developing a battery with a plastic conducting carbon-sulfur positive electrode. However, as of 2005 this technology seems to have had problems with self-discharge and manufacturing cost.

Yet another proposal is to use organic sulfur-containing compounds for the positive electrode in combination with an electrically conductive polymer such as polyaniline. This approach promises high power capability (i.e., low internal resistance) and high discharge capacity, but has problems with cycleability and cost.