Batteries may get boost from new development
March 23, 1994
RICHLAND, Wash. –
Energizer Bunny take note, if you're feeling drained, the Pacific Northwest Laboratory may have the technology to juice up your power source.
The U.S Department of Energy's laboratory has developed and patented a technology that may revolutionize the battery market. By using this new technology to produce thin film material for making a lithium polymer battery, it's projected that batteries used in electronic components including flashlights, smoke alarms, computers and electric cars, will be able to hold their charges longer and be recharged a significantly greater number of times. And, since lithium is a lighter metal than nickel or cadmium, two heavy metals currently used in batteries, lithium batteries will provide more power with less weight.
Known as web-coating by vacuum deposition, PNL's new technology represents a breakthrough in the rapid and cost-effective fabrication of electrodes and electrolytes -- the basic components of batteries. The new technology also improves the bonding quality of the various layers -- current- collecting metals, polymers (thin film material composed of two or more molecules) and lithium -- that make up a lithium polymer battery.
The efficiency of a battery and its ability to hold a charge depend upon the bonding quality between the various polymer and metal layers. With conventional bonding processes, mechanical presses are used to bring the layers into close contact. However, these types of bonding processes allow pockets of trapped gas and other impurities to form between the various layers, which reduces the interlayer adhesion.
A major problem in the development of lithium batteries has been the inability to form a complete bond between the lithium and polymer layers. Current technology for making the lithium layer seems to produce a visually smooth surface. However, it actually produces one that, at the microscopic level, is extremely rough, pitted and highly oxidized, which significantly reduces the electrical life of the battery.
With PNL's technology, the polymer and metal layers are deposited molecule by molecule and form a bond without microscopic voids, contaminants or trapped gas between the layers. This larger area of electrical contact between the layers improves the battery's efficiency.
Unlike conventional battery manufacturing methods where the polymer and metal layers are produced in several stages, PNL's vacuum deposition process deposits all of the layers that make up a lithium polymer battery sequentially on a moving roll of flexible plastic called a web. The web of plastic is similar to a roll of paper towels but without perforations.
When the layers have been deposited, an insulating polymer layer is applied that seals the layers and creates an airtight bond between the layers and the atmosphere. This airtight bond prevents contaminants from penetrating between the layers.
The vacuum deposition process has proven itself in the laboratory, and PNL is now looking for industrial partners to take the technology to the commercial market.
Tags: Energy, Batteries