Thermal and economic analysis of hybrid energy storage system based on lithium-ion battery and supercapacitor for electric vehicle application

Abstract

A hybrid electrical energy storage system (EESS) consisting of supercapacitor (SC) in combination with lithium-ion (Li-ion) battery has been studied through theoretical simulation and experiments to address thermal runaway in an electric vehicle. In theoretical simulation, the working temperature of Li-ion battery and SC has been varied from 0 to 75 °C in steps of 25 °C and the effect of the variation is observed on the output current, voltage and power of Li-ion battery and SC for a calculated load using the standard driving cycle. Further, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) have been performed to investigate the effect of temperature on SC. EIS measurements of SC indicate a low equivalent series resistance of 0.095 Ω at 25 °C. CV measurements indicate a high value of capacitance of 56.65 F/g at 25 °C for a scan rate of 5 mV s−1. Through theoretical simulation of EESS, a temperature increase ( $$ \Delta T $$ ) of 0.41 °C is calculated considering an initial peak of 10-s duration for the case of EESS without SC, whereas the use of SC reduces $$ \Delta T $$ to 0.025 °C. Further, optimal size calculation for hybrid EESS is done to achieve the least cost, wherein Li-ion battery capacity has been varied from 0 to 200 Ah and the SC capacity has been varied from 0 to 5 F in MATLAB simulation. The optimal combination is obtained as 30 Ah capacity of Li-ion battery and 3 F capacity of SC by connecting load across hybrid EESS for a duration of 3600 s.