Lithium-ion capacitors (LiCs) are hybrid energy storage systems that combine the advantages of lithium-ion batteries (LiB) and electric double-layer capacitors (EDLC). Therefore, LiCs have higher power capability and longer lifetime compared to LiBs. LiCs have also higher energy density and higher voltage range than EDLCs. Based on the mentioned advantages, LiCs are perfect solutions for high power applications where high charge and discharge currents are applied. Nevertheless, LiCs' performance highly depends on temperature. Therefore, a robust thermal management system (TMS) is indispensable to ensure reliability. Such a system-level management is linked to robust modeling tools, which are called electro-thermal models. The need for a validated electro-thermal model is trivial in high power applications where LiCs are subjected to high current rate of 150 A, which is typical for fast acceleration of electric vehicles.
In this PhD dissertation, the target cell is a commercial prismatic 2300 F LiC with 1 Ah capacity. A holistic methodology has been considered for electrical, thermal, and lifetime models that are developed in MATLAB/SIMULINK environment for high dynamic current rates under a wide range of temperatures from -30°C to +60°C. The electrical model is validated against the experiments considering the voltage measurements. The thermal model is validated against the experiments considering the capacity degradation. A critical parameter from the developed 1D model is the LiCs' power loss that is an input for the 3D thermal analysis of the proposed active, passive, and hybrid thermal management systems (TMS). The calculated power loss enables us to investigate the heat dissipation and temperature pattern inside the LiC cell. Such a coupled 1D/3D model for the LiC technology was not found during the comprehensive literature review.
The proposed TMSs in this PhD thesis are active, passive, and hybrid cooling methods including air cooled TMS (ACTMS), liquid cooled TMS (LCTMS), heat sink cooling system (HSCS), phase change materials (PCM), and heat pipe cooling system (HPCS). Test benches for all of the proposed TMSs are made experimentally, and analyzed and verified numerically employing COMSOL Mulitphysics software package. The main case study that all the proposed TMSs are being compared with, is natural convection (NC), in which the thermal behavior of the cell is studied under a 150 A continious current rate without any rest that is considered as super-fast charging/discharging that is unique. After investigation of the NC case study, the cooling performance of the proposed active and passive TMSs have been investigated under the super-fast driving profile. Then, hybrid solutions comprising different combinations of the proposed active/passive TMSs are developed and tested experimentally and numerically. Finally, the best thermal solutions are chosen and compared to be implemented for a module of LiC cells to study their performance.