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From 1981 to 2021: How exciting is the history of lithium-ion capacitors?
Lithium-ion capacitor (LIC) is a hybrid capacitor that combines the energy storage mechanism of lithium-ion batteries with the structural characteristics of supercapacitors. Since its first introduction in 1981, the development of lithium-ion capacitors has been as full of innovations and breakthroughs as the capacitor itself. Over the past four decades, this technology has not only driven changes in electrical energy storage, but also triggered extensive research in related fields. Let us explore this exciting historical journey together.
Historical BackgroundIn 1981, Dr. Yamabe of Kyoto University collaborated with Dr. Yata of Kanebo Corporation to create a material called PAS, a technology that laid the foundation for the birth of lithium-ion capacitors.
In the early 1980s, Kanebo filed several patents and began to focus on the commercialization of PAS capacitors and lithium-ion capacitors. The first PAS capacitor was commercially available in 1986, and lithium-ion capacitors followed in 1991. Over time, academia and industry have begun to appreciate the potential of lithium-ion capacitors, and research teams have worked hard to improve the performance of electrodes and electrolytes and extend their cycle life. In 2010, Naoi et al. successfully developed a composite material of nanostructured lithium titanium oxide (LTO) and carbon nanofibers, bringing the technology to a new level.
Concept of lithium-ion capacitors
Lithium-ion capacitors are hybrid electrochemical energy storage devices that combine the intercalation mechanism of lithium-ion battery negative electrodes with the double-layer mechanism of electric double-layer capacitors. As a result of this structure, the energy density of lithium-ion capacitors reaches about 20 W⋅h/kg, which is four to five times that of conventional electric double-layer capacitors. Despite their high energy density, lithium-ion capacitors have a power density comparable to that of electric double-layer capacitors because they can be discharged in just a few seconds.
Electrode structure
The negative electrode of a lithium-ion capacitor is a battery-like electrode with high energy density that can store large amounts of electrical energy through the reversible intercalation reaction of lithium ions. However, electrode degradation becomes an important design consideration. With the advancement of technology, more and more new electrode materials have been proposed, among which lithium titanium oxide (LTO) has attracted widespread attention due to its excellent performance.
The advantages of lithium titanium oxide include high coulombic efficiency, a stable operating voltage platform and minimal volume change during lithium intercalation.
Electrolyte and Isolator
A kinetically sound electrolyte is crucial to the performance of lithium-ion capacitors. An ideal electrolyte should have high ionic conductivity to facilitate lithium ions to reach the electrode sites efficiently. Therefore, non-aqueous lithium ion salt solutions are usually used to avoid performance degradation caused by the reaction of water with lithium ions.
Advantages and characteristics of lithium-ion capacitors
Lithium-ion capacitors generally have higher permittivity and better energy density than traditional capacitors, but their energy density is still lower than that of lithium-ion batteries. Lithium-ion capacitors exhibit good performance in operating temperature range, low self-discharge rate and cycle life, making them an ideal choice in a variety of applications.
Comparison with other technologies
Lithium-ion capacitors exceed traditional lithium-ion batteries in power density and safety, and of course they also have higher output voltages. Compared with electric double layer capacitors, lithium ion capacitors have higher energy density but are inferior to the latter in cycle life. Overall, lithium-ion capacitors are an independent technology that is suitable for many specific application scenarios.
Future Development and Applications
As technology continues to advance, the potential applications of lithium-ion capacitors are increasing. Whether in wind power generation systems, UPS uninterruptible power supplies, photovoltaic power generation systems, or regenerative braking of heavy vehicles, lithium-ion capacitors have demonstrated superior performance. The upward trend of these applications shows the huge market potential.
The development of lithium-ion capacitors is the result of the intersection of materials science and electrochemical technology, and each step has brought us new possibilities. Facing the future, whether lithium-ion capacitors can meet the growing energy demand and the concept of sustainable development has become a topic we need to think deeply about?
