NEGATIVE POLE PLATE OF LEAD ACID BATTERY

PROBLEM TO BE SOLVED: To restrict dispersion of high efficiency discharge capacity at a low temperature by specifying the average molecular weight of lignin sulfonate and the factor of sulfonation. SOLUTION: The average molecular weight of lignin sulfonate used in the present negative pole plate is defined to be 4,000 to 10,000 and a sulfonation factor to be 90% or more, then dispersion of high efficiency discharge capacity at low temperatures can be restricted. This situation suggests some eccentric existence of sulfone group on the surface of the lignin sulfonate and phenomenon takes place as the result of improved surface activity and enhanced dispersion property into an active substance of sulfonate. Meantime, when the quantity of lignin sulfonate powder is included by 0.1 to 0.5wt.% in relation to lead powder which is the main material of the active substance, the active substance using factor is enhanced. If it is below the lower limit value, sufficient contraction proof effect of the active material can not be realized, but when it exceeds the upper limit value, sulfonate covers the active points of electrically conductive surface too much to disturb electric discharge, so that the active material using factor may be decreased.