| abstract |
A lithium ion polymer cell comprises an anode layer and a cathode layer each comprising respective lithium ion insertion materials, separated by a porous polymeric membrane, wherein the anode layer and the cathode layer each incorporates a polymeric binder. The cell is made by coating a thin porous layer of a copolymer material onto the face of the anode layer and onto the face of the cathode layer, before assembling the anode layer, the porous polymeric membrane, and the cathode layer to form a cell assembly, and enclosing the cell assembly in an enclosure. A small quantity of a liquid such as acetone is introduced into the enclosure, this being a solvating liquid for the copolymer material but not for the polymeric material of the membrane, and then holding the temperature at a slightly elevated level such as 30°C, so the surfaces of the thin porous copolymer layers become tacky and adhere to the membrane. The solvating liquid can then be evaporated from the cell assembly, and an electrolyte solution introduced into the cell assembly to form a cell. This technique enables the cell components to be laminated together without requiring the application of pressure, and enables very thin membranes (e.g. 20 νm) to be used, which are of low resistance. |