Safety properties of liquid state soft pack high power batteries with carbon-coated LiFePO4/graphite electrodes

The carbon-coated LiFePO(4) materials were synthesized, and their structure and morphology were characterized by X-ray diffraction and transmission electron microscopy. The safety and heating mechanism of the 066094-type liquid state soft pack high power batteries with carbon-coated LiFePO(4)/graphite electrodes under abusive conditions, such as overcharge, overdischarge, and short current were extensively investigated. It was found that the increase in the temperature of the LiFePO(4)/graphite high power batteries during overcharge was attributed to the reaction of the electrolyte decomposition and the Joule heat. The batteries were heated rapidly by the irreversible heat generated from the current passing through the electrodes during short current. The temperature rise of the batteries which were overdischarged to 0 V was mainly due to the Joule heat. The overdischarge at 1 C/0 V almost did not influence the cycling performance of the batteries. The batteries did not fire, smoke, and explode under the above-mentioned abusive conditions. Therefore, the 066094-type liquid state soft film pack high power batteries with carbon-coated LiFePO(4)/graphite electrodes showed excellent safety performance.