Secondary cells

Abstract

The invention relates to a secondary cell having zinc electrodes in which there is provided an auxiliary electrode having a surface of electrocatalyst having a low overvoltage for hydrogen evolution, which is resistant to deposition of zinc thereon, means for connecting said auxiliary electrode to the negative electrodes during charging, the arrangement being such that the auxiliary electrode takes up the excessive current at the negative electrodes over that of the positive ones, thus eliminating or substantially reducing shape-change phenomena of the negative electrodes. It further relates to a Ni-Zn cell of the minimum electrolyte type having teflonized -ZnO electrodes, wherein there is provided a U-shaped electrocatalytically active auxiliary electrode in the shape of a bent-over ribbon of suitable catalytically active surface, positioned adjacent to the edges of the lower end of the plates of the cell and its lateral sides and a further rectangular similar material adjacent to the upper edge of the plates of the cell, said auxiliary electrode being separated from the edges of the plates by a suitable pervious insulator, said auxiliary electrode being adapted to be connected with the zinc plates during the charges, the arrangement being such that the auxiliary takes up about 5 to 10 per cent of the current during charging.

Dependencies are inferred from the claim text.