(43a) Thermal Energy Production and Heat Exchange between an Electrochemical Cell and Its Surroundings

Information regarding the heat exchange between an electrochemical cell and its surroundings is of great utility for the planet earth and deep space probe applications. Thermal energy production must be controlled in an electrochemical cell to avoid thermal runaway and cell rupture. For the operation of a cell at a desired temperature, even under reversible operational conditions, the generated thermal energy must be removed as heat transfer from the cell interior to its surroundings. Here, a theoretical scheme has been developed to determine the cell temperature for any desired cell discharge current. This scheme incorporates both the reversible production of thermal energy due to the change in entropy of the system and the irreversible production of thermal energy due to the cell voltage losses associated with the species transport in the cell electrolyte, electrode components, current collectors, and the electrochemical reactions involving charge transfer at the electrolyte-electrode interfaces. Assumptions for this model include that natural convection heat transfer may be neglected in a perfect vacuum and that the cell temperature throughout its body is constant at any time during the cell discharge. The information on dT/dt versus t (i.e., rate of change of the cell temperature versus time) generated by this scheme can be integrated either graphically or by the use of a numerical procedure, such as the Euler method, to obtain the cell temperature versus time data. Then, plots of temperature versus time can be prepared for each desired current value. Currently, we are in the process of calculating temperature versus time data. It is anticipated that such data will become available in the near future.