Li-Polymer: to charge, or not to charge

My cell phone is powered by a Li-Polymer rechargeable battery. It’s a Sony Ericsson Z500a. It has gotten its initial charge, and, according to the battery meter, it looks like it’s beginning to run low. I’ve been using it for several days now without a charge.

Should I wait until it’s dead before I charge it? or should I just charge it now?

This is an old article I found when searching for info on Li-Polymer:

Li-Polymer: Practical, Or Just Promising?

David G. Morrison
ED Online ID #1629
March 18, 2002

Almost five years have passed since Sony began large-scale commercialization of Li-polymer technology with the introduction of its 3.2- by 53- by 85-mm cell. Since then, a number of other cell makers have joined them in producing Li-polymer. But so far, all of these cells have captured only a small fraction of the market for rechargeable batteries. The slow growth in the adoption of Li-polymer batteries has tempered initial enthusiasm that surrounded its introduction. Some question its current value, even as they look forward to its future development.

Using a polymer or gelled form of electrolyte, rather than the liquid electrolyte found in standard Li-ion cells, has many potential advantages. A gelled electrolyte eliminates the need for the metal that a liquid electrolyte requires for generating the stack pressure within the cell. So, Li-polymer cells could be encased in the very thin foil pouches that help to reduce cell thickness, and are simpler and less expensive to make than aluminum or steel cans.

But stack pressure wasn’t the only concern in changing cell packaging from a metal can to a foil pouch. Leakage was another issue addressed via the gelled electrolyte. By eliminating liquid electrolyte within the cell, the Li-polymer technology would prevent leakage in the event of a punctured package. So, Li-polymer cells could be housed in foil pouches, while Li-ion cells would generally require the more durable cans.

Eliminating electrolyte leakage—ideally via fully solid polymer electrolyte—also raises the possibility that cell protection devices, either the PTC or IC, can be eliminated. This reduces cost and frees up space for active battery materials.

However, it’s thin cell design and light weight are key benefits of Li-polymer and the polymer approach to thinning the cell’s internal construction and packaging. Within the cell, the polymer electrolyte permits layering of electrode, electrolyte, and separators in a flat sandwich-like stack, as opposed to the wound stack or “jellyroll” normally employed in Li-ion cells. The stacked approach allows fabrication of 1-mm or thinner cells.

These characteristics endow Li-ion polymer cells with the potential for great design flexibility. In theory, cell makers could produce Li-polymer cells in varying voltages and capacities, with varying thicknesses, different form factors, and custom shapes. So, cell manufacturers are pursuing development of Li-polymer cells with the hope that their flexibility will open doors to new applications.

But the promise of Li-polymer has yet to be realized. Michael Mummert, senior product manager of GS-Melcotec, has noted, “Most manufacturers are relying on gel chemistry approaching a solid. Therefore, protection circuitry remains a requirement due to outgassing at high temperatures.”

“Custom sizes and configurations haven’t been achieved either. Even when the advent of solid polymer arrives, the costs of these custom formed and configured cells will be far too expensive to meet the market cost requirements. Mass production of the cells keeps price points and competition keen to allow wireless manufacturers competitive pricing.”

At the moment, Li-polymer technology has lost some of its luster because thinness—one of Li-polymer’s main claims to fame—doesn’t seem like such a great advantage now that Li-ion cells are available in 3- to 4-mm thicknesses. Although Li-polymer cells can be manufactured in even thinner dimensions, no great demand for such cells exists yet.

Despite the current obstacles to Li-polymer deployment, GS-Melcotec and other vendors continue to commercialize the technology, confident that the ideal of the Li-polymer cell can ultimately be achieved. Probably its biggest proponent is Sony, the company that first ramped up production for Li-polymer. It now offers at least 13 models in a range of sizes and capacities.

Sony’s Sage Nishimura cites some reasons why Sony still views Li-polymer as the better technology. Although, Li-ion and Li-polymer now offer almost the same energy density, Nishimura claims that the capacity of Li-polymer cells could easily rise another 50% in the next few years, pushing its performance ahead of Li-ion.

Safety is another concern. While vendors strive to increase cell capacity, they also are trying to make the cell safer, particularly because the newer cell contains more energy. According to Nishimura, use of polymer electrolyte enables Sony to offer the safest battery.

Some recent consumer product introductions serve as proof of the industry’s interest in Li-polymer. Two major laptop makers have already introduced models powered by Li-polymer batteries, and Apple’s iPod MP3 player contains one as well. In addition, Li-polymer also is being considered for more futuristic applications, such as wearable devices.

Some companies also see hope for Li-polymer in niche applications that some of the big cell vendors may not have addressed. One company, NewTurn Energ of Soowon Kyonggi-Do, Korea, plans to develop custom Li-polymer batteries in low volumes. These batteries are expected to have odd sizes and shapes with larger than usual capacities above 2500 mAh.

Another vendor, Electrovaya (formerly Electrofuel) of Mississauga, Ontario, is pursuing niche battery markets by developing its Li-polymer technology into standard and custom products with very high energy density—better than 200 Wh/kg (gravimetric) and up to 500 Wh/l (volumetric) (see Table 2 of “Li-Ion Batteries Reach For Higher Performance,” p. 62).

Despite the high performance numbers, the materials employed don’t appear to be anything exotic. Electrovaya’s Li-polymer cells contain graphite anodes and lithium-cobalt-oxide cathodes, as do most other cells. But as President Sankar Das Gupta notes, “We’re pushing the technology closer to its theoretical limits.”

As standard product, the company offers external batteries that extend the runtimes of laptops by adding 160 or 120 Wh of capacity (PowerPad 160/120) with packs that weigh less than 2.5 and 2 lbs, respectively. Beyond these products, the company wants to be a flexible custom cell manufacturer. According to Das Gupta, the company designs its own production equipment. Using this flexibility, Li-polymer batteries can be built with capacities in the tens of ampere-hours for a range of applications.

Update the battery meter went into the red zone, so I decided to charge it.

3 Responses to “Li-Polymer: to charge, or not to charge”

  1. F Ross says:

    MIght be a bit late in responding…… You can treat a “Li Polymer” battery the same was as Li-ion. I.e. you don’t have to let it run down. Li Polymer is largely a marketing ploy. For all practical purposes your battery is Li-ion.

  2. B Burton says:

    The articles at this site should be of interest to you if you haven’t found them yourself already. Lithium- Ion Batteries do not have memory like the Nickel-Cadmium chemistry does. It is however important to let the battery drop low enough to cause the device to cut off at least once every 30 cycles. This ensures that the batteries internal safety switch resets, which is supposed to add life to its over all cycles. Lithium batteries don’t mind if you use them for a short time and then recharge to maximum. The internal resistance of the lithium ion battery is moderate unlike its counter parts the alkaline and nickel based batteries which is high. Note that the lead -acid batteries found in cars and other devices have the lowest internal resistance which means they can run longer and deliver more of the power stored in them per second there just bulky and toxic. However lithium based batteries have the highest stored energy 4.2v(initial charge) per cell instead of 1.5 volts per cell as with other batteries. (standard AA type) There flat construction is possible due to extremely thin layers stacked upon each other instead of being rolled into a can. Perfect for cell phones and PDA’s, not so good for power tools and medical equipment. Lithium Ions exhaust rapidly under heavy current loads and the battery can vent gas if operated or left in temperatures over 120F and if charged improperly. (ie. hot cars with windows rolled up) An internal safety circuit is built into them to insure the battery is forced open in case of overheating to prevent it from corroding internally which can destroy it. Solid lithium plating can occur in excessive temperatures or if foreign metals like copper, iron and others left over from manufacture come in contact with the active materials inside. If the battery is left in a “dead” state for to long then a recharge is no longer possible from a regular wall or car charger.

    That happened to my AT&T 8525 when I first bought it from the previous owner. The phone was brand new and he had only had it for about a week. When I bought the phone, it wouldn’t power on at first. I figured “Oh well, it probably just needs to be recharged.” I was mad when the next morning I woke up and had, had the phone on charge all night but the phone still would not turn on. I had used the charger that plugs in the wall, and it was charging at .5 amps or .5C. I was beginning to think I had bought a piece of crap. I then used the USB charger that links it to my computer (a USB cable with a special end for the phone) to charge it, the battery was so dead it wouldn’t even turn on with it plugged to the computer. I said, “Well I will let it sit for an while and see what happens” Later on I checked it and the light had went from red to orange/yellow. I pushed the power button and BAM it came to life. I could then see the charge status of the battery and it was at 90% and at 100% the charge light turned green. When I first got the phone I didn’t know anything about lithium ion polymer or lithium anything really. It was after that incident I became interested in there construction, and chemical composition. The site I learned all this from and more is at the top of this reply.

  3. Geek Mother says:

    yeah, use it as if it were just Li-ion. Pretty much the same to be honest

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