Pseudocapacitance effect in Al-C batteries with expanded graphite positive electrode at different temperatures

摘要

In Al-C batteries, graphite and aluminum are used as positive electrode and negative electrode in room temperature ionic liquid AlCl3/1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), respectively. Due to that the electrochemical energy storage is performed by the anions and cations in the electrolyte, the electrochemical properties and pseudocapacitance characteristics of Al-C batteries at different temperatures are systematically analyzed. At 1 mV s(-1), the ratio of pseudocapacitance are 36.9%, 19.8% and 15.2% at 20 degrees C, 40 degrees C and 60 degrees C, respectively. In addition, the diffusion coefficient of polyaluminium anions improved with the increase of temperature. This interesting phenomenon can be attributed to the fact that high temperature accelerates the diffusion and transmission of polyaluminium anions in the electrolyte and takes full advantages of electrode materials. This will increase the discharge capacity, accelerate the transport of ions and electrons and show more dominant traditional battery characteristics. However, too high temperature may accelerate the corrosion effect of electrolyte to aluminum metal, so expanded graphite shows excellent cycling performance in Al-C batteries at 40 degrees C. This work plays a guiding role in the development of aluminum secondary batteries.