Laminated oxidation protected separator
A battery separator for a lead acid battery addresses the issues of acid stratification and separator oxidation arising from contaminants. The separator includes a microporous membrane and a diffusive mat affixed thereto. The diffusive mat has a three hour wick of: at least about 2.5 cm. The diffusive mat may be made of synthetic fibers, glass fibers, natural fibers, and combinations thereof. The diffusive mat may include silica. The separator may include a rubber.
1 . A flooded lead acid battery comprising a battery separator that comprises:
a microporous membrane comprising a microporous sheet of polyolefin, and wherein the microporous membrane is impregnated with uncured rubber, meaning that the uncured rubber is incorporated with a processing oil into the microporous membrane and is not a layer formed onto the microporous membrane; and
a diffusive mat affixed to the microporous membrane, wherein said diffusive mat is made of natural fibers and optionally also includes synthetic fibers or glass fibers or combinations of glass and synthetic fibers; said diffusive mat further comprising a particulate filler and having an electrolyte wicking defined by a three hour wick of at least 2.5 cm and wherein the separator does not comprise a layer of rubber, wherein the diffusive mat faces or is in contact with a positive electrode or positive plate to improve oxidation resistance of the battery.
2 . The flooded lead acid battery of claim 1 wherein said diffusive mat has a three hour wick in a range of 2.5-10.0 cm.
3 . The flooded lead acid battery of claim 1 wherein said diffusive mat has: a MD stiffness of greater than 90 mN, and a CMD stiffness of greater than 45 mN.
4 . The flooded lead acid battery of claim 1 wherein said diffusive mat is made of synthetic fibers, glass fibers, or a combination of both.
5 . The flooded lead acid battery of claim 1 wherein said rubber comprises no more than 12% by weight of the separator.
6 . The flooded lead acid battery of claim 1 wherein said rubber comprises 2.5-3.5% by weight of the separator.
7 . The flooded lead acid battery of claim 1 wherein said rubber is a latex.
8 . The flooded lead acid battery of claim 1 wherein said rubber is a natural or a synthetic latex.
9 . The flooded lead acid battery of claim 1 wherein said rubber is a natural rubber.
10 . The flooded lead acid battery of claim 1 wherein said microporous membrane is a microporous sheet of filled polyethylene.
11 . The flooded lead acid battery of claim 1 wherein said diffusive mat further comprises glass fibers.
12 . The flooded lead acid battery of claim 1 wherein said diffusive mat further comprises a natural fiber.
13 . The flooded lead acid battery of claim 1 wherein said diffusive mat has an electrical resistance of 12 mohm cm 2 or greater.
14 . The flooded lead acid battery of claim 1 selected from inverter batteries, enhanced flood batteries (EFB), ISS batteries, stationary batteries, or golf cart batteries.
15 . The flooded lead acid battery of claim 1 , wherein the particulate filler is particulate silica.
16 . The flooded lead acid battery of claim 1 , wherein the flooded lead acid battery is a dry charge flooded lead acid battery comprising contaminated water or acid, wherein the contaminated water or acid comprises contaminants that are transition metals.
17 . The flooded lead acid of claim 16 , wherein the transition metals are one or more selected from chromium, manganese, titanium, and copper.
18 . The flooded lead acid battery of claim 17 , wherein chromium, manganese, and/or titanium are present in amounts greater than 2.0 ppm.
19 . The flooded lead acid battery of claim 17 , wherein copper is present in an amount more than 26 ppm.