TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: A portion of the main chain silicons are linked to a cross-linker having a moiety of O-(CH2CH2O)q or Si-O-(Si-O)k-Si, where q = at least 4 and less than 30, and k = at least 5 and less than 30. Each of the silicons in the -Si-O-(SiO)k-Si- is also linked to two methyl groups. Fewer than 20% of the silicons in the main chain are linked to a cross linker. m of the silicons are linked to the side chain and n of the silicons are linked to a cross linker, a ratio of n:m is 1:6 to 1 :70. The cross-linking agent may also include two unsaturated carbon-carbon bonds. It further includes CH2=CH-CH2-O-(CH2CH2O)q-CH2-CH=CH2 or CH2=CH-CH2-O-Si-O-(Si-O)k-Si-CH2-CH=CH2.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The polysiloxane and cross-linking agent are transported into a battery housing. They are reacted within the battery housing to form a solid cross-linked polysiloxane in the presence of platinum catalyst. They are elevated to above 50 degrees C and below 150 degrees C while reacting the polysiloxane and crosslinking agent. A carbon from the crosslinking agent is linked to the main chain silicon that was linked to a hydrogen before the reaction. EXAMPLE - A viscous branched polysiloxane precursor (0.55 g) was pipetted into an oven dried flask, then diallyl terminated poly(ethylene glycol) (molecular weight of 1080) cross-linker (0.136 g) and lithium bis(trifluoromethanesulfonyl)imide (7.6 ml of 0.0367 mol/L tetrahydrofuran (THF) solution) were syringed into the flask. The mixture was stirred vigorously, resulting in a homogeneous and colorless THF solution. The resulting solution was evacuated on a high-vacuum line (5- approximately 10 torr) for 24 hours to completely remove the solvent and trace moisture. The flask was transferred into a glove-box filled with pure argon, where the liquid sample was loaded into the conductivity cell. The well-sealed conductivity cell was placed in an oven at 80 degrees C. After 5 hours a solid polysiloxane film resulted, which showed no silicon-hydrogen absorption at 2100 cm-1 in the FTIR spectrum.