Modeling of commercial, primary Li/MnO2 coin cells - Embedded.com

Modeling of commercial, primary Li/MnO2 coin cells

Li/MnO2 coin cells are used for many low-drain, low-cost, long-life consumer applications and constitute roughly about 80% of the lithium primary battery market. They are suitable for use in devices such as wrist watches, calculators, computer memory backup, home electronics instruments, alarm systems, CD/MD players etc.

The electrodes in these cells consist of a lithium metal foil as negative electrode and MnO2 combined with a binder and some carbon black as the positive electrode. The electrodes along with a non-woven separator are crimp-sealed with metal cups at either end.

Coin-type Li/MnO2 batteries are made in a number of sizes and by a number of manufacturers including Sony, Panasonic, Gold Peak, Varta and Maxell. Limited battery performance data is available from their manufacturers, often at a given temperature and load.

A software model that accounts for a wide variety of use conditions – user specified load and temperature would greatly help electronic device manufacturers to evaluate and understand the battery for a given application.

The objective of the work described here is to determine if a macro-homogenous model can be used to predict the discharge behavior of coin-type primary manganese dioxide batteries.

This is the first study to examine the capability of a macro-homogeneous model to fit a range of cell designs over a wide range of conditions. The results indicate that, using the same set of fitted kinetic parameters, the discrepancy between the model and data increases as the thickness of the positive electrode increases, especially at low temperatures.

This may be a result of using an inaccurate electrolyte composition or ignoring edge effects due to mismatched cathode and anode diameters. Alternatively, the model may not be accounting for the agglomerated nature of the cathode particles that introduces another diffusion process (liquid-phase transport in the agglomerated particles).

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