Lead-acid battery separators, electrodes, batteries, and methods of manufacture and use thereof
New or improved battery separators for lead-acid batteries that include a carbon or mineral additive applied to the separator. In possibly preferred embodiments, the battery separator may include engineered carbon materials applied to the battery separator to modify sulfate crystal formation while decreasing the detrimental consequences of excessive gas evolution into the negative electrode itself. In one embodiment, a method of enhancing the lead-acid energy storage performance of a lead-acid battery may include delivering carbon to the negative active material surface of the battery separator where the carbon may effectively enhance charge acceptance and improve life cycle performance of a lead-acid battery.
1. A battery separator for a lead-acid battery with enhanced lead-acid energy storage performance, the battery separator comprising a polyolefin layer or a polyolefin layer and a non-woven mat, the separator formed into an envelope for enclosing an electrode of a battery, wherein a porous sheet formed from a carbon material and comprising from greater than 50% carbon material is placed inside the envelope.
2. The battery separator of claim 1 wherein the carbon material is an engineered carbon material.
3. The battery separator of claim 1 wherein the carbon material is at least one selected from the group consisting of carbon black, graphite, activated carbon, graphenes and associated analogs, dendritic forms of carbon, nanocarbon materials derived from various manufacturing methods, highly-structured carbonaceous materials including fullerene, bucky-balls, etc., carbon monolithic sol gel materials, and carbon multi-component sol gel materials.
4. The battery separator of claim 1 wherein the engineered carbon material is selected from the group consisting of: carbon black; graphite; activated carbon; and combinations thereof.
5. The battery separator of claim 1 wherein the carbon material is further applied to a negative active material (NAM) surface of the battery separator.
6. The battery separator of claim 1 wherein the carbon material slows the sulfation effect under partial state of charge (PSoC) conditions, wherein:
sulfate crystal growth is directly influenced by available surface area (nucleation sites) within a plate of the battery;
increased surface area provides a driving force
for the establishment of small less stable crystals with less impact on the porous nature of the negative electrode;
under typical and PSoC conditions, the electrode produces gas as the over-potential of hydrogen is reached;
as high surface area carbons are introduced directly into the NAM, acceleration of both gas and sulfate nucleation occurs, where the typical gas evolution is dramatically increased and gas is liberated within the porous plate structure;
gas is introduced into the interstitial region of the electrode, which results in insufficient electrolyte penetration, increased corrosion of the grids, increased consumption of water from the electrolyte, increased ionic resistance, the like, or combinations thereof;
charge acceptance may be limited due to the blocking effect of trapped gas; or combinations thereof.
7. The battery separator of claim 1 wherein the carbon material has a surface area selected from the group consisting of: 10-5000 sqm/g; 500-1500 sqm/g; and 1500-3000 sqm/g.
8. The battery separator of claim 1 wherein the carbon sheet comprises greater than 70% carbon material, greater than 80% carbon material, or greater than 85% carbon material.
9. The battery separator of claim 8 wherein the carbon sheet comprises about 87% carbon material.
10. The battery separator of claim 9 wherein the electrode enclosed I the envelope is a negative electrode.
11. The battery separator of claim 8 wherein adequate pressure exists between the plate, the sheet, and the separator to maintain contact between [plate<->sheet<->separator].
12. The battery separator of claim 11 wherein an inside surface of the envelope may include a profile or topological property selected from the group consisting of ribs, mini-ribs, cross-ribs, and ay combination thereof.