86 Chapter 7 hardware” to integrate into the complete ESS when compared to a polymer-type cell and they come in quite high capacity ratings. And as mentioned earlier, there are fewer cell-to-cell connections that need to be made so the reliability is expected to be higher. I say expected to here since there are few of these applications that have reached their EOL yet, so the reliabil- ity calculations are still estimates for most of them. The third format for lithium-ion cells is the lithium-ion polymer cells (LiPo, LIP, or Li-poly), also called “pouch” or “laminate” cells because they use a soft polymer laminate casing.
The term polymer was originally used in reference to the use of a polymer-based electrolyte instead of a liquid-based electrolyte. However, today the term has become a general moniker used to refer to the physical form factor of the pouch-type cell. This does on occasion cause some confusion when discussing lithium polymer cells as some people refer to them in the polymer electrolyte aspect and others in the form factor. The pouch type cell has become the standard in many of the portable power applications such as cell phones and tablets due to their thin form factor.
It is also a very flexible cell-type solution because it is relatively easy to create many size variations of this cell, making it relatively easier to design into unique pack solutions. One of the challenges of this form factor is that it is more difficult to integrate some of the safety features mentioned earlier. Cell venting is much more difficult to predict and manage, and it is generally not possible to integrate things like CIDs and PTCs into this form factor. It is also generally necessary to design the cells into modules that can manage the “stack pressure” of the cells.
In most cases, the pouch-type cell will perform better over life, if a consistent pressure is applied over the face of the cell. It is also very important to ensure that the pressure is uniformly applied. If the pressure is not applied uniformly, it can affect the cell’s ability to pass the lithium-ions back and forth within the cell and eventually cause them to begin getting stuck. This is known as lithium plating, or in some areas it is referred to as “white out” when the lithium-ions become fixed and no longer pass back and forth; this increases the impedance of the cell and reduces the cell life.
The other challenge of the polymer-type cell is that it must be handled with some care because the packaging is a soft-type laminate or polymer enclosure. So it is relatively easy to damage during cell assembly. Cells in this size can range from milliampere hours (mAh) all the way up to about 100 Ah in capacity. Lithium-Ion Cell Manufacturers Today, there are hundreds of lithium-ion cell manufacturers in the marketplace. In this section, I will briefly review what are generally considered to be some of the top players in this market.
This is only intended to be a short introduction to a handful of manufacturers, there are plenty more out there that I will not cover, so do not assume this is an all-inclu- sive list. I will leave some of the start-ups with innovative chemistries for the final chapter. A123/Wanxiang—A123 was a start-up based in Waltham, Massachusetts and founded as a spin-off from a group of MIT researchers. A123 made some very significant early