Internal thermal management for electrochemical batteries

摘要

Secondary (rechargeable) electrochemical batteries provide a means for supplying electrical power to equipment. Thermal management is needed to reduce the temperatures caused by internal energy generation inside the batteries, a direct consequence of the chemical reactions required to produce the electrochemical potential. Depending on the electrolyte, anode and cathode materials, energy generation can occur during discharge, recharge, or both. For particular electrochemical battery systems, internal heat generation caused by 12R losses can be considerable as well. Energy generation is a detriment to the operation of the battery, reducing life, increasing recharge time, and/or limiting output due to restricted discharge rates. We consider a strategy for thermal management of rechargeable electrochemical batteries. The strategy consists of thermoelectric (TE) elements placed at the battery boundary connected to a heat conducting plate in contact with the energy-generating electrolyte region of the battery. Quasi-steady, two-dimensional analytical and numerical models have been developed for a Ni-Zn battery system. Ni-Zn batteries are susceptible to thermal build-up during excessive discharge; the increased temperatures cause damage to cell structure components. The models include heat generation due to the chemical reaction in the Ni-Zn cell, and heat transfer in the cold junction plate of the TE cooler in thermal contact with the electrolyte and the electrodes inside the battery. The thermal models provide the temperature distribution throughout the battery electrolyte region, as well as the temperature distribution in the cold-junction plate. The results have shown that better internal thermal management in electrochemical batteries utilizing TE coolers will improve battery performance in the demanding applications required for the automotive industry and small battery-powered bicycles. In particular, the ratio of the discharge time for a TE-cooled Ni-Zn battery operating at a peak temperature of 332 K to that for a non-TE-cooled battery at the same peak temperature w as calculated. The results showed that TE cooling of the battery allows the discharge time to be educed by more than a factor of two over that for an un-cooled battery.