Lipo Batteries.

I have just found this interesting article on the net. it give a little insight in to the latest development in batteries for the radio control market, due to their light weight and fairly compact sizes.
I hope it is of interest to you also.

Pouch Cells

Pouch cells

Valence pouch cells
Pouch cell
Pouch casings are typically used for Lithium Polymer cells with solid electrolytes, providing a low cost "flexible" (sometimes in unintended ways) construction. The the electrodes and the solid electrolyte are usually stacked in layers or laminations and enclosed in a foil envelope. The solid electrolyte permits safer, leak-proof cells. The foil construction allows very thin and light weight cell designs suitable for high power applications but because of the lack of rigidity of the casing the cells are prone to swelling as the cell temperature rises. Allowance must be made for the possibility of swelling when choosing cells to fit a particular cavity specified for the battery compartment. The cells are also vulnerable to external mechanical damage and battery pack designs should be designed to prevent such possibilities.
The GS-Melcotec example illustrated uses spiral wound electrodes and a solid polymer electrolyte.

This construction, using stacked electrodes is suitable for making odd shaped cells but few applications make use of this opportunity.