Rechargeable, Alkaline Zinc-based battery
to Potentially Double
Laptop Run Times
Information compiled by Donald and Shirley Georgi
based on information from Zinc Matrix Power’s website, Skip Zeiler (CEO and President) and the U.S. Patent Office
The patent 6,743,548 uses cutaways of the layers of the Alkaline-zinc battery to illustrate the use of cellulose metal silver plating and zinc dendrite formation. Salt filled cellulose are reinforced by the presence of particulate fillers providing mechanical strength and superior ionic transport.
Figure 1 is an isometric view of the battery. Figure 2 is a cross-section illustrating a battery containing three films of hydrogen-permeable cellulose separator films of the same type. Figure 3 is a cross-sectional view of a stack of hydrogen-permeable regenerated cellulose separator film interspersed with hydrocarbon separator films.
The photo shows a prototype cell employing the patented technology. +
Zinc Matrix Power, Inc. is developing a polymer-based rechargeable Alkaline-zinc battery technology that is similar to the common flashlight battery chemistry, but in laboratory testing, the battery has demonstrated about two times the energy to volume of today’s Lithium-based chemistry. The Company states that this new zinc-based rechargeable could potentially double run times in the same package size as current laptop batteries.
In speaking with Skip Zeiler, President and CEO of Zinc Matrix Power, he commented on his great hopes for the technology which has an energy density of approximately 600 Watt hours/ liter compared with 275 or 285 Watt-hours/liter for Lithium-ion.
This technology, like that of common flashlight batteries, uses a water-based electrolyte (KOH) which, together with its low pressure flexible plastic case work, minimizes the risk of fire or explosion due to abuse.
A schematic view of a stack of separator films (152) containing a regenerated cellulose separator film placed adjacent to the cathode, which retards cathode metal deposition. It contains particles of a fluoride salt which prevents silver plating. Hydrogen permeable cellulose separators (16, 18 & 20) are closest to the anode. +
Intel Corporation has shown interest in this technology and has signed a technology collaboration agreement with Zinc Matrix Power, Inc. Mr. Zeiler is thrilled with having Intel as a partner. The “pot at the end of this rainbow” is a new battery technology which could result in a laptop runtimes of up to ten hours. Together, the two companies will work together to develop several aspects of this technology, including the battery packaging, charging circuits and fuel gauges, which could enable computer manufacturers to build plans to introduce this technology commercially in 2006. However, for those who want to catch the first public introduction, it will be previewed at Intel’s upcoming developer forum to be held early this September in San Francisco.
Product field test
The rechargeable Alkaline-zinc battery was tested in a small handheld computer on the floor of the Chicago Commodity Exchange for two years. The setting proved to be a rugged environment for testing since the battery had to work Monday through Friday and reliably connect in a Wi-fi environment. Skip Zeiler was pleased with the performance and noted that the unit had to undergo 200 cycles of deep discharge during the year.
A schematic view of a stack of hydrogen permeable separator layers, the first having a dispersion of particles for cathode metal deposition retardation, the second containing a salt which retards zinc dendrite formation and the third containing a salt which controls the concentration of the second salt. +
Solving the problems to create a rechargeable zinc battery
According to Zinc Matrix Power, zinc metal has two characteristics which have made it extremely difficult to recharge. Why?
First, there is the solubility issue. Zinc oxide is highly soluble in alkaline electrolyte. As the zinc anode discharges, the zinc oxide dissolves in the electrolyte and tends to leave the immediate vicinity of the anode, moving around in the battery. On recharge, the reforming zinc typically takes on a radically different shape than the original anode. And the zinc tends to reform as spikes (dendrites) which can penetrate the separator. Dendrites lead to short circuits.
Zinc Matrix says that the problem can be even more difficult because in order to achieve reasonable power levels, modern battery anodes need to be collections of highly powered metal with a very high surface area. For recycling to maintain consistency, the anode material must always reform exactly where it was on the last cycle and thus maintain consistent surface area.
Zinc Matrix technology has fundamentally addressed the issue by containing zinc granules in a patented polymer matrix. This matrix is highly permeable to hydroxide ions, but blocks zinc oxide from leaving the immediate vicinity of each zinc grain. Thus, each zinc granule of a high surface area powder electrode is locked in place such that the surface area does not significantly change over 100 charge/discharge cycles or more.
The second phenomenon to address is hydrogen recombinance. Zinc recharges approximately at the same Voltage that breaks down water into hydrogen and oxygen. An Alkaline-zinc battery incorporating pure zinc will tend to break down water on recharge at nearly the same rate as it reforms zinc. The liberated oxygen will attack the fresh zinc forming zinc oxide and the hydrogen will bubble out of the battery.
Until the 1980’s, various heavy metals were added to zinc to suppress this gassing phenomenon. New low toxicity additives have been found which work adequately in non-rechargeable batteries but do not work perfectly in rechargeables. The hydrogen gas, at this very low rate, is not toxic or hazardous, but it gradually consumes the water in the electrolyte causing capacity loss. Materials which are effective in blocking zinc oxide are highly impervious to hydrogen, making a sealed recombinant rechargeable zinc battery a challenge.
Zinc Matrix solved this problem with their invention of a new class of polymers which are both hydrogen permeable and impermeable to zinc oxide in solution. These new polymers are incorporated in the zinc matrix anode and in the batteries’ separators resulting in a totally sealed highly recombinant and rechargeable battery.
A schematic of a stack of separator films with the addition of a hydrocarbon layer to the middle of the stack to further reduce zinc migration is shown. A regenerated separator (120) contains particles of a fluoride salt and is placed next to the cathode. An unfilled cellulose film is placed next to the anode (12) and a Celgard film (119) is placed between copper containing film 122 and sulfide containing film 124. +
Combinations for the Zinc Matrix Anode System
The most common system is the Alkaline zinc manganese dioxide battery for which Zinc Matrix Power has a rechargeable version. However, the Zinc Matrix Anode System can be combined with many battery oxidizers such as manganese dioxide, nickel hydroxide and air cathodes.
Currently, Zinc Matrix’s most advanced design is the Silver PolymerR battery which utilizes divalent silver oxide to achieve very high energy and power, yielding up to twice the energy to volume of current Lithium-ion and Lithium-polymer batteries.
Zinc Matrix Power, Inc.’s patents revolve around a thin zero pressure zinc-alkaline battery geometry. The system has an advanced polymer matrix to confine the zinc such that it maintains approximately the same shape and surface area from cycle to cycle. Patents also cover internal and external gas recombination pathways via highly advanced plastic alloy and hydrogen permeable inner cases. This rechargeable and recombinant zinc electrode system can be used with manganese dioxide, nickel hydroxide, mono and divalent silver oxide, air cathodes and the emerging family of super oxides.
Zinc Matrix Power’s most recent U. S. patent received on June 1, 2004 discusses the Silver-zinc Alkaline rechargeable battery which contains a stack of hydrogen permeable cellulose-based films, each one optionally containing a dispersion or metal salts. A film may contain copper salt that reacts with cellulose to prevent zinc dispersion. A second film may contain fluoride salts that react with silver ions to prevent silver plating. A third optional film contains sulfide salts that react with cooper ions to form copper sulfide salts to lower cooper ion concentration in the electrolyte. The stack may also contain at least one hydrogen-permeable generated cellulose film and at least one hydrogen permeable hydrocarbon film such as polypropylene.
2006 - A vision of a milestone
Mr. Zieler has a definite goal to have Zinc Matrix Power’s rechargeable zinc-based batteries powering laptops, tablet PCs, handheld computers and other portable communication devices for 8 to 10 hours a day, before recharge, by 2006. He is also quick to note that his company’s rechargeable zinc-based chemistry is nontoxic to the environment, and because the chemsitry is also “well behaved,” it is not subject to special regulations for safety. Finally, he was asekd, “Can this new technology be cost competetive with such chemistries as Lithium-ion and Lithium-polymer? Mr. Zieler was positive it could! BD