Thermal runaway problems of lead-acid batteries


Battery deformation is not unexpected, often there is a process. Battery in charging capacity to 80%, about to enter the high voltage charging area, then the positive plate precipitated oxygen, oxygen through the bulkhead hole to negative electrode of oxygen in the reaction of resurrection on negative plate: 2Pb+O2 (oxygen) =2PbO+Q (heat); PbO+H2SO4=PbSO4+H2O+ Q (heat). The heat generated during the reaction, when the charging capacity reaches 90%, the oxygen generating speed increases, the negative to produce hydrogen gas, increase the number of the battery internal pressure exceeds the pressure valve, safety valve open, gas, for the final performance loss. 2H2O=2H2 = +O2 =. With the increase of the number of battery cycles, the water gradually decreases. As a result, the following conditions occur in the storage battery:
The oxygen channel becomes smooth, easy to produce oxide cathode anode through the "channel";
The heat capacity decreases, in the battery heat capacity is the largest water, water loss, the battery capacity is greatly reduced, the heat generated by the battery temperature rise quickly;
Because of fine glass fiber separator after dehydration shrinkage in the battery, and make the positive and negative electrode adhesion variation, resistance increases, the charge and discharge process of calorific value increase. Through the above process, the internal heat generated by the battery can only be dissipated by the cell, such as the heat is less than the heat, that is, the phenomenon of temperature rise. The temperature rise of the battery gassing overpotential decreased, gas volume increased, a large number of positive oxidation through the channel, on the surface of the anode reaction, a large amount of heat, the temperature rises rapidly, forming a vicious spiral, the so-called "thermal runaway".