Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer – spacer or materials for use therewith
Reexamination Certificate
2001-02-09
2003-01-14
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer, spacer or materials for use therewith
C429S249000, C429S247000, C429S204000, C429S225000, C429S228000, C429S145000
Reexamination Certificate
active
06506522
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an improved lead acid battery element containing metal impurity inhibiting polymeric additives, which are added to the positive active material, negative active material and/or battery separator to inhibit the detrimental effects of certain metals on the efficiency of a lead acid battery, particularly the negative plate battery element and to macroporous additives that enhance active material utilization efficiency and improvement in the utilization of sulfuric acid electrolyte necessary for the discharge reaction of a lead acid battery.
Further the present invention relates to a recombinant battery separator element, which improves utilization efficiency of the sulfuric acid electrolyte in a valve regulated recombinant lead acid battery. In brief the separator battery elements include the addition of porous containing particle additives to the separator of a valve regulated recombinant lead acid battery to improve the overall utilization efficiency and the utilization of sulfuric acid electrolyte during charge/discharge of the battery.
Separators used for valve regulated or as also referred to sealed lead-acid batteries operating on the oxygen recombination principle, i.e. oxygen recombinant batteries, typically operate with a limited amount of sulfuric acid electrolyte, i.e. only having electrolyte within the separator and the pores of the negative and positive active material. Unlike flooded batteries which have excess electrolyte and generally means for water addition, the design of valve regulated recombinant batteries do not have provisions for the addition of water during the life of the battery. Further, the battery is designed so that the oxygen generated at the positive electrode during charging is recombined to form water at the negative electrode. Separators used for valve regulated lead acid batteries typically include one or more layers of highly absorptive porous mats typically having a mix of fibers. The porosity of the separator is designed such to allow oxygen to transport directly through the separator for reaction at the negative electrode. The design requirements of limited sulfuric acid electrolyte and oxygen recombination at the negative electrode gives rise to a number of serious problems affecting valve regulated lead acid batteries including electrolyte stratification in the separator particularly in the vertical direction and excessive transport of oxygen to the negative plate before the negative plate can be fully recharged. Thus, published studies have shown that the stratification of the electrolyte brings about a difference in the electrolyte concentration between the upper and lower portions of the separator thereby reducing the amount of sulfate ion required for the electrochemical reactions during discharge of the battery, i.e. both positive and negative plate active material are converted to lead sulfate. Further, the properties of the separator can affect the height at which the electrolyte rises and the speed or rate of electrolyte absorption and diffusion both upward and downward particularly during electrolyte initial fill of the battery and sulfate reaction during discharge particularly high rate discharges. Thus, the separator for valve regulated batteries should minimize stratification effects particularly during repeated charge/discharge cycles and provide for rapid wicking of the electrolyte during fill of the battery. Further, the separator should allow control of the oxygen from the positive electrode to the negative electrode in order to improve the charging efficiency of the negative plate as it approaches full charge. In addition the separator must provide for controlled wetability in order to minimize stratification, provide for ease of electrolyte filling and to control oxygen recombination transport for improved negative plate charging.
Metal impurities can be introduced into a lead acid battery through the use of any of the materials used in the manufacture of the battery. For example, metal impurities can be introduced in the lead and leady oxides used in the manufacture of the active material, the materials of construction including the lead grids, alloying agents, electrolyte and water. Nearly all metallic impurities, if they are nobler than lead, have a smaller hydrogen overvoltage than pure lead. Therefore, they increase hydrogen evolution even if they are deposited in minute concentrations on the surface of the negative plates. These metals cause a continued gas evolution even after charging is completed. Hydrogen is evolved on the deposited metal with low hydrogen overvoltage, which can be short-circuited with lead. The effect of metal on the gassing particularly postcharge gassing decreases in the following sequence: Pt, Au, Te, Ni, Co, Fe, Cu, Sb, Ag, Bi and Sn. The presence of 0.3 ppm of platinum in the acid can cause a doubling of the self-discharge rate. Tin can produce this effect at 0.1%. Freshly deposited antimony is especially active. Besides the discharge of the negative plates with concomitant hydrogen evolution, these materials also move the end of charge voltage of the negative plates toward more positive values. The hydrogen evolution increases with rising acid density. Because the hydrogen overvoltage decreases with temperature, the self-discharge increases.
SUMMARY OF THE INVENTION
A new battery element which inhibits the detrimental effect of soluble metal impurity on the negative plate has been discovered. In brief, the battery elements include the addition of an organic polymer having functional groups with a preferential affinity for the metal impurity in the cation or anion state, to the positive active material, the negative active material or the separator which separates the positive and negative plates within a lead acid battery and which typically is a reservoir for sulfuric acid electrolyte.
A new recombinant battery separator element, which improves utilization efficiency of the sulfuric acid electrolyte in a lead acid battery, has been discovered. In brief the separator battery element includes the addition of porous organic particle additives having functional groups, which associate with the sulfuric acid electrolyte to control oxygen diffusion through the separator, improve electrolyte distribution in the separator and improve overall battery utilization efficiency, particularly the utilization of sulfuric acid electrolyte during repeated charge/discharge cycles of the battery.
A new battery element, which improves utilization efficiency of the active material in a lead acid battery has been discovered. In brief, the battery elements include the addition of macroporous containing particle additives to the active material in the positive or negative plates of a lead acid battery to improve overall utilization efficiency and the utilization of sulfuric acid electrolyte during discharge of the battery.
A new recombinant battery separator element, which improves utilization efficiency of the battery, particularly the utilization of the sulfuric acid electrolyte in a lead acid battery, has been discovered. In brief the separator element includes the addition of macroporous containing particle additives to the separator of a lead acid battery to improve overall battery utilization efficiency, particularly the utilization of sulfuric acid electrolyte during repeated charge/discharge cycles of the battery.
DETAILED DESCRIPTION OF THE INVENTION
In one broad aspect, the present battery elements comprise the addition of an organic polymer containing functional groups with a preferential affinity for metal impurity in the cation or anion state to the positive active material, the negative active material and/or the separator which separates the positive plates from the negative plates in a lead acid battery. In a preferred embodiment, the organic polymers are porous, i.e. the porosity of the polymer allows the soluble metal impurity in the electrolyte to contact both the outer surface of the polymers and the internal surfaces created by
Ensci Inc.
Uxa Frank J.
Weiner Laura
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