隨著超級電容器的發(fā)展不斷地推陳出新,其技術(shù)水平日新月異,應(yīng)用范圍也不斷擴大。超級電容也稱電化學(xué)電容,一種新型儲能器件,與傳統(tǒng)靜電電容器不同,主要表現(xiàn)在儲存能量的多少上。
With the development of supercapacitor, its technology level is changing with each passing day, and its application scope is also expanding. Supercapacitor, also known as electrochemical capacitor, is a new type of energy storage device, which is different from the traditional electrostatic capacitor in terms of energy storage.
作為能量的儲存或輸出裝置,其儲能的多少表現(xiàn)為電容量的大小。根據(jù)超級電容器儲能的機理,其原理可分為以下兩類:
As an energy storage or output device, the amount of energy storage is expressed as the size of capacitance. According to the energy storage mechanism of supercapacitors, the principles can be divided into the following two categories:
1.在電極P溶液界面通過電子和離子或偶極子的定向排列所產(chǎn)生的雙電層電容器。該模型認為金屬表面上的靜電荷將從溶液中吸收部分不規(guī)則的分配離子,使它們在電極P 溶液界面的溶液一側(cè),離電極一定距離排成一排,形成一個電荷數(shù)量與電極表面剩余電荷數(shù)量相等而符號相反的界面層。
Electric double layer capacitor produced by the directional arrangement of electrons and ions or dipoles at the interface of electrode P solution. According to the model, the static charge on the metal surface will absorb some irregular distribution ions from the solution, so that they will be arranged in a row at a certain distance from the electrode on the solution side of the electrode P solution interface, forming an interface layer with the same number of charges as the remaining charges on the electrode surface, but the sign is opposite.
于是,在電極上和溶液中就形成了兩個電荷層,這就是我們通常所講的雙電層。雙電層有儲存電能量的作用,電容器的容量可以利用以下公式來計算:
Thus, two charge layers are formed on the electrode and in the solution, which is what we usually call the electric double layer. The capacity of capacitor can be calculated by the following formula:
式中,E為電容器的儲能大小;C為電容器的電容量;V 為電容器的工作電壓。由此可見,雙電層電容器的容量與電極電勢和材料本身的屬性有關(guān)。通常為了形成穩(wěn)定的雙電層,一般采用導(dǎo)電性能良好的極化電極。
Where e is the energy storage capacity of the capacitor; C is the capacitance of the capacitor; V is the working voltage of the capacitor. It can be seen that the capacity of the electric double layer capacitor is related to the electrode potential and the properties of the material itself. In order to form a stable electric double layer, polarization electrode with good conductivity is usually used.
雙層電容器的工作原理
2.在電極表面或體相中的二維與準(zhǔn)二維空間,電活性物質(zhì)進行欠電位沉積,發(fā)生高度可逆的化學(xué)吸附、脫附或氧化還原反應(yīng),產(chǎn)生與電極充電電位有關(guān)的法拉第準(zhǔn)電容器。
On the electrode surface or in the two-dimensional and quasi-two-dimensional space in the bulk phase, the electroactive substances underpotential deposition, and highly reversible chemical adsorption, desorption or redox reactions occur, resulting in Faraday quasi capacitors related to the electrode charging potential.
在電活性物質(zhì)中,隨著存在于法拉第電荷傳遞化學(xué)變化的電化學(xué)過程的進行,極化電極上發(fā)生欠電位沉積或發(fā)生氧化還原反應(yīng),充放電行為類似于電容器,而不同于二次電池,不同之處為:
In electroactive materials, with the development of electrochemical process existing in Faraday charge transfer chemistry, under potential deposition or redox reaction occurs on the polarization electrode. The charge discharge behavior is similar to that of capacitor, but different from secondary battery
(1)極化電極上的電壓與電量幾乎呈線性關(guān)系;
The voltage on the polarization electrode is almost linear with the electric quantity;
(2)當(dāng)電壓與時間成線性關(guān)系d V/d t=K時,電容器的充放電電流為一恒定值I=Cd V/d t=CK.此過程為動力學(xué)可逆過程,與二次電池不同但與靜電類似。法拉第電容和雙電層電容的區(qū)別在于:雙電層電容在充電過程中需要消耗電解液,而法拉第電容在整個充放電過程中電解液的濃度保持相對穩(wěn)定。
When the voltage is linear with time DV / dt = k, the charge discharge current of the capacitor is a constant value, I = CD V / d t = CK. This process is a dynamic reversible process, different from the secondary battery, but similar to static electricity. The difference between Faraday capacitance and electric double-layer capacitor is that the electric double-layer capacitor consumes electrolyte during the charging process, while the concentration of electrolyte keeps relatively stable in the whole charging and discharging process.
法拉第準(zhǔn)電容不僅在電極表面產(chǎn)生,而且還可以在電極內(nèi)部產(chǎn)生,其最大充放電能力由電活性物質(zhì)表面的離子取向和電荷轉(zhuǎn)移速度控制,因此可以在短時間內(nèi)進行電荷轉(zhuǎn)移,即可以獲得更高的比功率(比功率大于500W /kg )。
Faraday quasi capacitance can be generated not only on the surface of the electrode, but also inside the electrode. Its maximum charge discharge capacity is controlled by the ion orientation and charge transfer speed of the surface of the electroactive material. Therefore, the charge transfer can be carried out in a short time, that is, higher specific power (more than 500W / kg) can be obtained.