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A “Magic Box” that has Evolved So Far
The Lithium Ion Polymer
Rechargeable Battery
According to Japan’s Ministry of Posts and Telecommunications, as of July batteries are no longer acceptable. The thick- 1999, there were over 50 million PHS (Personal Handyphone System) ness of most of the lithium ion rechargeable and cellular telephone subscribers in Japan.
batteries currently used in cellular telephones Thus two out of every five Japanese citizens are taking advantage of mobile is 5 or 6 mm. However, the lithium ion poly- One important product that has supported miniaturization and weight released is only 3.8 mm thick. The conceptbehind this development effort was ‘thin and reduction in mobile equipment is the lithium ion rechargeable battery, which light’, and we put everything we had towards In this article, we introduced a further evolutionary step in batteries, the lithium Of the samples we were shown, some were a ion polymer rechargeable battery, in which the electrolyte has a gel form.
mere 0.5 mm thick, like the thickness of thincardboard. These could be stacked and placedin a 2 mm gap behind the LCD in a notebookPC.
“The point was that we switched from an Leisurely Evolution
device that could not operate for extended pe-riods, but it was here that the principles of electrolyte to a polymer electrolyte in a gel over 2000 Years
battery operation were discovered. However, given that there was an 1800 year blank, we achieved by solidifying the liquid as a gel.
Do you know what the world’s first battery must say that the battery is not a simple con- Since there is no possibility of leakage, it was was? It was called the Baghdad battery and possible to create a battery in the form of a consisted of a clay jar into which a copper Tracing history a bit further, the lead-acid vessel and an iron rod were inserted. It is battery, which is a storage battery (i.e. a Since the laminated film pack is lighter than thought that it was used by being filled with rechargeable battery) whose energy can be the metal outer casing used in earlier batter- wine. In experiments, the copper acts as the ies, it is possible to increase the weight positive electrode, the iron acts as the nega- energy density (the amount of energy that can was finally invented in 1866. The nickel-cad- be taken from a unit volume of battery) by electrolyte, thus forming a fully functional battery. It is thought to have been used to known as the Ni-Cd battery, first appeared “Users have three requirements for these bat- create electroplated ornaments, and to date in 1899. The manganese and Ni-Cd batteries teries: the first is the capacity, the second is from around the beginning of the western cal- are still used, 100 years later, with the same the cycle characteristics, and the third is the endar. Thus this battery existed about 2000 low temperature characteristics. Functionally, We can see that the impact and value of these we increased the priority of the cycle charac- “A battery is really a rather simple device, batteries were extremely large, even consid- teristics when we designed these batteries.” consisting of positive and negative electrodes ering the social conditions of the times, and Concretely, we aimed for a residual capacity and an electrolyte. If you want to call it a the next revolutionary developments in bat- ratio of 80% after 1000 cycles. This means “classic technology” then, I suppose I’d have teries, the primary lithium metal battery and that the per cycle degradation is so low that a typical user would not notice a difference if This was Kiyokazu Oiyama’s comment.
battery, were developed and put into practi- they recharged the batteries once a day for 3 Oiyama is a manager in the Battery R&D De- cal use quite recently. However, there are as- partment at Energy Company’s Nishi Battery pects of recent battery evolution that are cause These batteries also have superlative tempera- Laboratories. First, let’s discuss the history for interest. One of these is the lithium ion ture characteristics. For example, a cellular of the battery. The next device that appeared telephone using these batteries would oper- in battery history after the Baghdad battery viable commercial product by Sony in 1991.
ate correctly in an environment with a tem- was the Volta Battery, invented in 1800. It This battery was well received due to its light perature of –20°C. Really? Minus 20 degrees used copper for the positive electrode, zinc weight and long life, and its use has been Centigrade? “Cellular telephones are ex- for the negative electrode, and sulfuric acid growing rapidly as the power supply for mo- for the electrolyte. It was, of course, a crude bile equipment such as cellular telephones other northern European countries. Users in and notebook PCs. The lithium ion recharge- able battery ushered in the most significant about being able to make emergency calls in epoch in battery history since the Baghdad I see. The point is that the use of polymers This brings us to the topic of this article, the gives these batteries their superlative cycle lithium ion polymer rechargeable battery.
and temperature characteristics, right?“However, it turns out that polymer electro-lytes have a lower ion conductance, that is their Thin because of Gel,
capacity to move ions between the positive High Performance Despite Gel
and negative electrodes, than liquid electro-lytes. This is because the liquid is solidified “It is certainly true that batteries did not into a gel. If we created these batteries in a Kiyokazu Oiyama
evolve continuously. Perhaps products with normal manner, their performance would be this level of functionality were simply not nowhere near that of liquid-electrolyte bat- required prior to Japan’s period of rapid eco- teries. Our struggle was to get the perfor- Nishi Battery Laboratories Energy Company mance of these new batteries as close to that Core Technology & Network CompanySony Corpoation where mobility is everything, and large heavy of the liquid-electrolyte ones as possible.” Newly-developed gel poly-
mer electrolyte.
Sony Corporate Culture: Focusing on the Future Ion permeability was in-
creased by applying this ma-
■ Lithium Ion Polymer Rechargeable
terial in a layer only a few mi-
Battery (UP383562) Main Specifications
crons thick.
Two prototype lithium
ion polymer recharge-
able batteries that
weigh only 30 grams
are installed in the
back of the wings of a
model airplane.
Disposable Diapers and a Jelly Confection
The development of the lithium ion polymer rechargeablebattery started in July 1996 as part of a project that aimed at improvingproduct safety.
“At first there were 20 or 30 researchers working on polymer electrolytes.
Although all of us spent a lot of time working with gels, the gels were quiteuncooperative about functioning in batteries. We were unable to come up This was a test to see
with any concrete content, let alone numbers for our progress reports, and if this “dream” would
handed in tables and graphs that were empty. We spent a lot of time apolo- gizing and promising results later.” (Laughs.) “This was my first report as aproject leader.”Anyway, no one had ever heard of a gel battery before. We even tried usingbread-making equipment and sausage stuffers. It is said that, from an elec-trochemical standpoint, it has been understood for over ten years what ma-terials to use for electrodes and what materials to use for the electrolyte toget the best performance. However, in this development project, we had torun experiment after experiment, day and night, to allow us to adopt a gelelectrolyte to achieve thinner, lighter, and safer batteries while still main- The UP383562 was shipped
taining high quality standards despite using a gel electrolyte.
in sample quantities in March
“What we were aiming for is something like disposable diaper material.
1999. The model number
Instead of absorbing and holding moisture, the material has to absorb and used in battery products
hold the electrolyte. In particular, if the material is squeezed, it must not often indicates the size of
allow any electrolyte to leak out. We racked our brains for ideas for appro- the device, which is 3.8 × 35
priate materials. We tried everything that was available in the lab; rubber, × 62 mm in this case.
plastic, polymers. These experiments determined what sort of polymer ma-terial could best hold the electrolyte.”Once we determined that an electrolyte in a gel form would work, we werefaced with the problem of packaging.
“The packaging, is, if you insist, the key to the whole system. Although wehad a rough idea of using a laminated film, this was an area in which we hadno experience. One day I was eating a jelly confection. Looking closely, Irealized that the container it came in was quite strong. I learned quite a bit With Yumi Mizuno,
from that candy. Anyway, I went to the nearest supermarket and purchased Assistant Manager,
every vacuum-packed food product in the so-called “retort pouch” package Lithium Ion Battery
I could find, and analyzed the packaging technology. Although these retort Sales Dept.
pouch packages initial all seemed similar to each other, they actually are “Our customers’ de-
quite different, for example frozen food packages and the packages used for mands for lithium ion
foods that can be boiled in the package. Since it would have been wasteful rechargeable batter-
not to, we ate the contents. Of course, that left the laboratory reeking of ies are increasing
curry.” (Laughs.) (Many readers may not be aware that the Japanese ver-sion of curry is the most commonly served meal in Japanese homes, and every year.”
widely available in a wide range of instant, ready-to-eat, and partially pre-pared forms.)In addition to cellular telephones, this new battery can also be used in widerange of products including PDAs, digital cameras, IC cards, games, andclocks. Their thinness alone opens a whole range of unforeseen applica-tions.
“Lithium ion rechargeable batteries do not use environmentally harmfulheavy metals such as cadmium and lead, and thus can be said to be environ-mentally friendly. However, the cobalt used in the positive electrode mate-rial is a limited resource, and we are still not satisfied with the performance.
As a long term goal, our dream is a battery that can be inserted as a page inFilofax or other notebook and then connected.”

Source: http://www.sony.net/Products/SC-HP/cx_news/vol18/pdf/cxeye.pdf