Supercapacitors are mainly composed of four parts: electrode, current collector, electrolyte and diaphragm. The electrode material is the most important factor affecting the performance and production cost of supercapacitor. Research and development of high-performance, low-cost electrode materials is an important part of the development of supercapacitors. At present, many supercapacitor electrode materials are mainly carbon materials, metal oxides (or hydroxides), conductive polymers, etc., and the commercialization of carbon materials and metal oxide electrode materials is relatively mature, which is a hot spot of current research. .
1. What is a supercapacitor?
Supercapacitors or ultracapacitors, also known as electrochemi calcapacitors, are new energy storage devices between secondary batteries and conventional capacitors. They combine high secondary battery energy density with conventional capacitor power density. In addition, supercapacitors have the characteristics of no pollution to the environment, high efficiency, long cycle life, wide temperature range, high safety, etc., and are widely used in electric vehicles, new energy power generation, information technology, aerospace and other fields. prospect.
The supercapacitor can also form a composite power system with the rechargeable battery, which can meet the high power requirements of the electric vehicle during starting, accelerating and climbing, and can prolong the cycle life of the rechargeable battery, thereby optimizing the performance of the electric vehicle power system. At present, commercial production of supercapacitors has been realized at home and abroad, but there are also problems of high price and low energy density, which greatly limits the large-scale application of supercapacitors.
Supercapacitors are mainly composed of four parts: electrode, current collector, electrolyte and diaphragm. The electrode material is the most important factor affecting the performance and production cost of supercapacitor. Research and development of high-performance, low-cost electrode materials is an important part of the development of supercapacitors.
At present, many supercapacitor electrode materials are mainly carbon materials, metal oxides (or hydroxides), conductive polymers, etc., and the commercialization of carbon materials and metal oxide electrode materials is relatively mature, which is a hot spot of current research. . Therefore, this paper will focus on the latest research progress and commercial application prospects of high-performance electrode materials such as carbon materials, metal oxides and their composite materials.
2. The latest research progress of carbon materials as electrode materials for supercapacitors
History of carbon materials
Carbon materials are currently the most widely studied and widely used supercapacitor electrode materials, including activated carbon, template carbon, carbon nanotubes, activated carbon fibers, carbon aerogels and graphene. The carbon material has the advantages of high electrical conductivity, large specific surface area, good electrolyte wettability, wide potential window, and the like, but its specific capacitance is low. The carbon material mainly uses the electric double layer formed by the electrode/solution interface to store energy, which is called the electric double layer capacitor. Increasing the specific surface area of ​​the electrode active material can increase the area of ​​the interface double layer, thereby increasing the electric double layer capacitance.
Carbon nanotube
Carbon nanotubes were discovered in the early 1990s as a nano-conductivity and chemical stability, a large specific surface area, pores suitable for electrolyte ion migration, and cross-winding to form a nano-scale network structure, which was once considered It is the ideal electrode material for high power supercapacitors.
Niu et al. first reported the use of carbon nanotubes as electrode materials for supercapacitors. They used catalytic pyrolysis to form hydrocarbons into multiwalled carbon nanotube film electrodes in a mass fraction of 38% H2SO4 electrolyte. At different frequencies from 0.001 to 100 Hz, the specific capacitance reaches 50-110 F/g, and its power density exceeds 8 kW/kg. However, the free-growth carbon nanotubes have different shapes, disordered orientations, and even inclusions with amorphous carbon, which is difficult to purify, which increases the difficulty of practical application.
In recent years, research on highly ordered carbon nanotube arrays has once again attracted attention. This array of carbon nanotubes grown directly on the current collector not only reduces the contact resistance between the active material and the current collector, but also simplifies the electrode. Preparation process.
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