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.

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