3.5.1 Batteries Including Lithium Polymer Types

The use of polymers in battery construction can be categorised in three distinct ways. For example the polymer may be used in the manufacture of the battery separators used in traditional cells to provide physical separation of the positive and negative plates whilst permitting electron flow through the electrolyte. Polyester and polypropylene fibres may also be used to reinforce the battery plates themselves in traditional cells. The second function is as a battery container material which must resist chemical attack by the electrolyte and give the container mechanical strength.

Rechargeable lithium-ion polymer cells are also available from IBT, for use in such portable applications as mobile communications and hand-held instrumentation, with a nominal voltage of 3.7 V and capacities ranging from 100 mAh to 4500 mAh at the five hour discharge rate. The polymer may be part of the electrochemical operation of the battery as in the case of lithium polymer designs.

The performance of traditional lithium-ion cells has more than doubled over the past ten years from 280 Wh/l (watt hour per litre) in 1995 to 580 Wh/l in 2005 as a result of changing the chemical formulation of anode and cathode. In current designs the anode is typically a graphite mixture, the cathode being composed of a blend of lithium, nickel and cobalt. Cost has been reduced and the robustness of the cells improved. These cells are now the dominant power sources in such portable...