A brief discussion on the technical principle of 18650 battery 3.7v 6000mah

Fuel-powered batteries are power generation devices that directly convert the chemical energy of fuel into electrical energy. The principle of fuel-powered batteries is an electrochemical device, and its composition is the same as that of general batteries. Its single cell consists of two positive and negative electrodes (negative electrode, namely the fuel electrode, and positive electrode, namely the oxidant electrode) and an electrolyte. The difference is that the active substances of general batteries are stored inside the battery, thus limiting the battery capacity. The positive and negative electrodes of fuel-powered batteries do not contain active substances themselves, but are only catalytic conversion elements. Therefore, fuel-powered batteries are truly energy conversion machines that convert chemical energy into electrical energy. When the battery is working, fuel and oxidant are supplied from the outside to react. In principle, as long as the reactants are continuously input and the reaction products are continuously removed, the fuel-powered battery can generate electricity continuously. Here, the hydrogen-oxygen fuel-powered battery is taken as an example to illustrate the fuel-powered battery

The reaction principle of hydrogen-oxygen fuel-powered batteries This reaction is the reverse process of water electrolysis. The electrodes should be: negative electrode: H2+2OH-→2H2O+2e-

positive electrode: 1/2O2+H2O+2e-→2OH-

battery reaction: H2+1/2O2==H2O

In addition, the fuel cell body alone cannot work,

there must be a set of corresponding auxiliary systems, including reactant supply system, heat removal system, drainage system, electrical performance control system and safety devices.

Fuel cells are usually composed of electrolyte plates that form ion conductors and fuel electrodes (anodes) and air electrodes (cathodes) arranged on both sides, and gas flow paths on both sides. The purpose of the gas flow path is to allow fuel gas and air (oxidant gas) to pass through the flow path.

In practical fuel cells, due to different working electrolytes, the types of ions related to the reaction passing through the electrolyte are also different. The PAFC and PEMFC reactions are related to hydrogen ions (H+), and the reactions that occur are:

Fuel electrode: H2==2H++2e- (1)

Air electrode: 2H++1/2O2+2e-==H2O (2)

Total: H2+1/2O2==H2O (3)

In the fuel electrode, H2 in the supplied fuel gas is separated into H+ and e-, and H+ moves to the electrolyte to react with O2 supplied from the air electrode. e- passes through the external load circuit and then returns to the air electrode to participate in the reaction on the air electrode side. A series of reactions facilitate e- to pass through the external circuit uninterruptedly, thus constituting power generation. And from the reaction formula (3) in the above formula, it can be seen that H2O generated from H2 and O2 has no other reactions except this, and the chemical energy of H2 is converted into electrical energy. But in fact, there is a certain resistance accompanying the electrode reaction, which will cause some heat energy to be generated, thereby reducing the proportion of conversion into electrical energy. A group of cells that cause these reactions is called a component, and the voltage generated is usually less than one volt. Therefore, in order to obtain a large output, a high-voltage stack must be obtained by stacking multiple components. The electrical connection between components and the separation between fuel gas and air use a component called a separator with gas flow paths on the upper and lower surfaces. The separators of PAFC and PEMFC are both made of carbon materials. The output of the stack is determined by the product of the total voltage and current, and the current is proportional to the reaction area in the battery.

The electrolyte of PAFC is a concentrated phosphoric acid aqueous solution, while the electrolyte of PEMFC is a membrane of a proton conductive polymer system. The electrodes are all made of porous carbon. In order to promote the reaction, Pt is used as a catalyst. CO in the fuel gas will cause poisoning and reduce the performance of the electrode. For this reason, the amount of CO contained in the fuel gas must be limited in the use of PAFC and PEMFC, especially for PEMFC working at low temperatures. It should be strictly limited.

The basic composition and reaction principle of phosphoric acid fuel cell are: fuel gas or city gas is added with water vapor and sent to the reformer to convert the fuel into a mixture of H2, CO and water vapor. CO and water are further converted into H2 and CO2 in the shift reactor by a catalyst. The fuel gas after such treatment enters the negative electrode (fuel electrode) of the fuel pile, and oxygen is transported to the positive electrode (air electrode) of the fuel pile for chemical reaction, and electric energy and heat energy are quickly generated with the help of the catalyst.

Compared with PAFC and PEMFC, high-temperature fuel cell MCFC and SOFC do not need catalysts. The coal gasification gas with CO as the main component can be used directly as fuel, and it also has the characteristics of easy use of its high-quality exhaust gas to form combined cycle power generation.

MCFC main components. Contains electrolytes related to electrode reactions (usually carbonates mixed with Li and K) and two electrode plates (fuel electrode and air electrode) connected to each other from top to bottom, as well as gas chambers and electrode clamps for the flow of fuel gas and oxidant gas outside the two electrodes. The electrolyte is a molten liquid at the operating temperature of MCFC, about 600~700℃, forming an ion conductor. The electrode is a nickel-based porous body, and the formation of the gas chamber is made of corrosion-resistant metal.

MCFC working principle. O2 (air) and CO2 at the air electrode combine with electricity to generate CO32- (carbonate ions). The electrolyte moves CO32- to the fuel electrode side, combines with H+ supplied as fuel, releases e-, and generates H2O and CO2 at the same time. The chemical reaction formula is as follows:

Fuel electrode: H2+CO32-==H2O+CO2+2e-(4)

Air electrode: CO2+1/2O2+2e-==CO32-(5)

Total: H2+1/2O2==H2O(6)

In this reaction, e- is released from the fuel electrode and returned to the air electrode through an external circuit, just like in PAFC. The uninterrupted flow of e- in the external circuit enables the fuel cell to generate electricity. In addition, the biggest feature of MCFC is that CO32- ions that contribute to the reaction must be present, so the supplied oxidant gas must contain carbon dioxide gas. In addition, a method has been developed to fill the cell with a catalyst to reform CH4, the main component of natural gas, inside the cell and directly generate H2 inside the cell. When the fuel is coal gas, its main component CO reacts with H2O to generate H2, so CO can be used as fuel equivalently. In order to obtain greater output, the separator is usually made of Ni and stainless steel.

SOFC is mainly composed of ceramic materials. The electrolyte is usually ZrO2 (zirconium oxide), which constitutes the conductor Y2O3 (yttrium oxide) of O2- and is used as stabilized YSZ (stabilized zirconium oxide). The fuel electrode in the electrode uses Ni and YSZ composite porous body to form metal ceramics, and the air electrode uses LaMnO3 (lanthanum manganese oxide). The separator uses LaCrO3 (lanthanum chromium oxide). In order to prevent crack initiation caused by thermal expansion differences between electrolytes due to different battery shapes, SOFCs that work at lower temperatures have been developed. In addition to the flat type of battery shape that is the same as other fuel cells, a cylindrical type has also been developed to prevent stress accumulation. The reaction equation of SOFC is as follows:

Fuel electrode: H2+O2-==H2O+2e-(7)

Air electrode: 1/2O2+2e-==O2-(8)

Overall: H2+1/2O2==H2O(9)

At the fuel electrode, H2 moves through the electrolyte and reacts with O2- to generate H2O and e-. At the air electrode, O2 and e- generate O2-. Overall, H2O is generated from H2 and O2 in the same way as other fuel cells. In SOFC, because it is a high-temperature working type, the main component of natural gas, CH4, can be directly reformed into H2 for use without the use of other catalysts, and CO, an important component of coal gas, can be directly used as fuel.

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