Electrochemical Study on a Hybrid Device of a Lithium-Ion Capacitor and a Lithium-Ion Battery using 8-Reference Electrodes

Abstract

We have developed a hybrid device (HLIC: Hybrid Lithium-Ion Capacitor) which combined a lithium ion capacitor (LIC) element and a lithium ion battery (LIB) element in the electrode components. The HLIC has a common negative electrode and two positive ones. The common negative electrode is including a negative electrode collector foil having through-holes. The two positive electrodes are; the first positive electrode (AC) containing particles of activated carbon and the second positive electrode (LFP) containing particles of a lithium-containing metal compound (LiFePO₄) as an active material. The HLIC has a life-extending effect to the cycle life of a LIB. A HLIC cell which has a common negative electrode and two set of AC and LFP positive electrodes were studied using eight reference electrodes embedded around the common negative electrode. The electric current through the AC1 and LFP1 was measured separately by using two ammeters. The AC2 and LFP2 were not connected. Sharing of total current to the AC1 and LFP1 positive electrodes was occurred during charge-discharge tests. The sharing of current can be one of the life-extending effects of the HLIC. The potentials in the horizontal plane of the AC2 and LFP2 side were uniform during the charge-discharge tests, but a little change was observed at the area close to the AC1 and LFP1.