A Novel Lithium‐Doping Approach for an Advanced Lithium Ion Capacitor

Abstract

Although electrochemical double-layer capacitors (EDLC) have the advantages of high rate capability, good durability, and superior cycle life over presently available secondary batteries, they have drawbacks in terms of energy density and cost. Especially, their relatively low energy storage capacity is mainly responsible for their limited usage. [ 1 ] To overcome this limitation, various types of hybrid capacitors have been developed and successfully commercialized. The lithium ion capacitor (LIC), one of the hybrid capacitors under development, has a specifi c energy and energy density of around 30 Whkg − 1 and 20 WhL − 1 , respectively. These values are more than three times higher than the values of a conventional EDLC. [ 2 ] LICs consist of an activated carbon cathode (positive electrode) and a carbonaceous lithium-intercalating anode (negative electrode). The fl at discharge profi le of the negative electrode enables improvement of LICs by allowing higher utilization of the cathode within an expanded voltage window. In fabrication, lithium doping of the anode is necessary process prior to charge the capacitor. During the doping process, metallic lithium is oxidized to release lithium ion, while the reduction of the lithium ion occurs at the surface of the anode. Throughout the process, the voltage of the anode decreases until it is close to 0 V (vs. Li/Li + ). The lithium doping is a necessary process for LICs and metallic lithium is currently used as the lithium source. The metallic lithium has to be handled with caution to minimize risks since lithium metal reacts violently with moisture, causing fi re and explosion. [ 3 ] We therefore propose a new lithium-doping method that uses a stable lithium metal oxide, Li 2 MoO 3 as an alternative lithium source, thanks to its huge charge capacity and the irreversibility of the fi rst cycle. [ 4 ] The innovative use of Li 2 MoO 3 simplifi es the lithium-doping process and meets the stringent safety requirements for use of LICs. Herein, the advantages of our novel concept will be discussed in detail.Schematic diagrams comparing different lithium-doping methods are given in Figure 1 . According to the cell confi guration of a conventional LIC, metallic lithium is incorporated in the cell, as illustrated in Figure 1 a. By means of electrical short-circuiting, lithium ions can be inserted into anode materials. In this way, it would be diffi cult to load the amount of desired lithium precisely during cell fabrication because the loaded metallic lithium cannot be fully inserted into the anode materials. Moreover, any remaining metallic lithium in the LIC would cause safety issues. In contrast, our proposed concept for LICs is that Li 2 MoO 3 is integrated into the cathode, as presented in Figure 1 b. Lithium ion can be electrochemically extracted from the Li 2 MoO 3 and then effectively inserted into the anode. The inserted lithium ions are only partially recovered to the Li 2 MoO 3 within the operating-voltage range of LICs. After lithium ion extraction, the delithiate...

Pre-lithiation design and lithium ion intercalation plateaus utilization of mesocarbon microbeads anode for lithium-ion capacitors

“…Therefore, it is particularly of interest to develop an electrochemical energy storage device, which can overcome the conflicts of energy and power density in a single device. Under the circumstances, the hybrid energy storage device lithium-ion capacitor (LIC), which combines the EDLC positive electrode and LIB negative electrode, has emerged and attracted tremendous attention [8][9][10][11][12][13][14][15].…”

Electrochemical Performance of Lithium-Ion Capacitors Using Pre-Lithiated Multiwalled Carbon Nanotubes as Anode

“…For example, EC process requires repeated assembly and disassembly of batteries, which resulted in unnecessary waste of human and material resources. [16][17][18][19][20][21] Internal shortcircuit (ISC) method is also called direct contact (DC) method. The pre-lithiation can be achieved through direct physical contact between negative electrode and lithium metal with electrolyte in pressure.…”

Remanufacturing cathode from end-of-life of lithium-ion secondary batteries by Nd:YAG laser radiation

“…included in the cathode materials (Park et al 2011). The theoretical recovered ratio of capacity (g) is defined in Eq.…”