Bitumen battery grade
To reduce the leakage of electrolyte from alkaline cells, bitumen battery grade is used between the gasket and the metal surface. Typically asphaltic compounds such as bitumen are used. However, such seals are only marginally satisfactory, and then only when the steel cans are plated with nickel. When the steel can is unplated, such seals are very poor. The poorer seals noticed with unplated steel cans are probably due to differences in the bonding strength of bitumen to steel and bitumen to nickel-plated steel.
Oxidized bitumen in battery
Others, attempting to improve upon the seals of alkaline batteries have used sealants consisting of fatty polyamides or both oxidized bitumen and fatty polyamide resins, all of these solutions have the same drawback--leakage still occurs since these materials do not always completely seal the interface of the metal surface and the gasket. It is hypothesized that leakage results from the inability of the sealant, or sealants, to adequately bond to the metal surface. Moreover, sealants such as oxidized bitumen and fatty polyamides are soft, somewhat tacky materials at and above room temperature and so are subject to damage and contamination during the assembly of electrochemical cells. Even cured epoxy-polyamine resins, though non-tacky, are relatively soft and can cause problems during cell assembly.
Bitumen is sealing of battery
The battery seal set forth in solves many of the processing problems as described above. However, as with cells incorporating bitumen and polyamides in the seal area, extreme care must be taken to confine the organosilane resin of the van Lier patent to the immediate area of the seal, otherwise the electrical operation of the cell will be adversely affected by the introduction of a non-conductive layer between the electrode and current collector.