A lithium-ion capacitor (LIC) is a hybrid energy storage device combining the energy storage mechanisms of lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), which incorporates the advantages of both technologies and eliminates their drawbacks. This article presents a novel semi-empirical electro-thermal equivalent circuit model (ECM) for LIC technology up to 500 A and from −20 to +60 °C. The performance of two ECMs, a first- and second-order model, is thoroughly evaluated and compared. The second-order model was selected due to its higher accuracy and superior voltage behaviour prediction for all temperatures. The parameter extraction techniques and governing equations are explained in detail. Since temperature highly affects an LIC's performance and electrochemical behaviour, influencing all presented parameters, a 1D thermal model was combined with the ECM model to further study the effect of temperature. The first order electrical circuit of the 1D thermal model is successfully capable of predicting the thermal behaviour. The thermal model's parameters were extracted and comprehensively explained. Finally, the presented model was validated through experiments for continuous dynamic currents up to 300 A and for pulse currents up to 500 A at different temperatures with an acceptable error of less than 5%.