Patent ID: 8323815
Filing Date: 2012-12-04
Classification: H01M,Y02E,Y10T

Abstract:
1. A method for improving battery capacity, using an electrochemical cell, the steps comprising: (a) making a positive high density electrode; (b) making a negative high density electrode; (c) producing a symmetric, strong, highly porous, microporous polymer membrane by: (a) preparing a solution of one or more polymers in a mixture of a principal liquid which is a solvent for the polymer and a second liquid which is miscible with the principal liquid, wherein (i) the principal liquid has a surface tension at least 5% lower than the surface energy of the polymer, (ii) the second liquid has a surface tension at least 5% higher than the surface energy of the polymer, (iii) the normal boiling point of the principal liquid is less than 125° C. and the normal boiling point of the second liquid is less than about 160° C., (iv) the polymer has a lower solubility in the second liquid than in the principal liquid, and (v) the solution is prepared at a temperature less than about 20° C. above the normal boiling point of the principal liquid and while precluding any substantial evaporation of the principal liquid, (b) reducing the temperature of the solution by at least 5° C. to between the normal boiling point of the principal liquid and the temperature of the substrate upon the solution is to be cast, (c) casting the polymer solution onto a high surface energy substrate to form a liquid coating thereon, said substrate having a surface energy greater than the surface energy of the polymer, and (d) removing the principal liquid and the second liquid from the coating by unidirectional mass transfer without use of an extraction bath, (ii) without redissolving the polymer, and (iii) at a maximum air temperature of less than about 100° C. in a period of about 5 minutes, to form the strong, highly porous, thin, symmetric polymer membrane; (d) discharging ions from second active material of the negative high density electrode through the aprotic ion conducting liquid of the second chamber; (e) increasing rate capability of the ion flow by reducing interfacial resistance to ion flow by increasing porosity of the polymer membrane by controlling pore size and solids distribution; and (f) accepting ions into the first active material of the positive high density electrode of the first chamber through the protogenous ion conducting liquid; producing a symmetric, strong, highly porous, microporous polymer membrane said electrochemical cell comprising: