Probing current contribution of lithium-ion battery/lithium-ion capacitor multi-structure hybrid systems

Abstract

Lithium-ion battery capacitors (LIBC), as a hybrid device combining Lithium-ion capacitor (LIC) and Lithium-ion battery (LIB) on the electrode level, has been widely studied due to its advantages of both LIC and LIB. To study the energy storage mechanism of parallel hybrid systems, the current contribution of LIBC and external parallel system (EPS) have been comparatively analyzed. LIBC and EPS display similar variation trends, i.e., upon galvanostatic charge/discharge process, the current mainly flows through the capacitor part in the low voltage range and the battery part in the high voltage range. During the rest period after the discharge process, the battery part will charge the capacitor part, which is called the recharging phenomenon. Due to the recharging mechanism, the battery part of the LIBC cell used in this work provides a capacity of 1.663 mAh to the capacitor part during all rest periods at 10C pulsed discharge, accounting for 35.9% of the pulsed discharge capacity provided by AC electrode. In addition, the LIBC cell has no capacity loss after 1000 cycles at 10C, showing better cycle performance than EPS. This study is helpful for obtaining in-depth insights on the mechanisms of current distribution and synergistic effects of LIBCs.