1. Lead acidAccumulatorThe structure and composition of lead-acid batteries Generally speaking, lead-acid batteries are mainly composed of positive plate, negative plate, separator, battery tank cover (Guy) (container), electrolyte and other parts. (1) Polar plate: An electrode composed of an active material and a supporting conductive grid, which is divided into a positive plate and a negative plate. The grid is generally composed of lead-antimony alloy and lead-calcium alloy. The active material of the positive plate is PbO2 and the color is Brown, tan, reddish brown, the active material of the negative plate is spongy metallic lead (Pb), the color is gray, light gray, and dark gray. (2) Separator: It is placed between the positive and negative plates of the battery and is composed of an electrical insulating material that allows ions to pass through. It can completely block the short circuit of the positive and negative electrodes. PE separators, rubber, plastics, composite glass fiber separators, 10G, AGM separators, etc. are usually used. (3) Electrolyte (substance): liquid or solid phase substance containing mobile ion conduction. It has a conductive effect and participates in the flow reaction. The density of lead-acid battery electrolyte is related to the place where it is used. Relatively speaking, the density of electrolyte used in electric vehicle batteries is higher. (4) Battery tank: a container that contains the electrolyte of the battery group without being corroded by the electrolyte, generally made of hard rubber or plastic. (5) Components: battery cover (Guy), threaded liquid hole plug, safety valve, top cover (Guy), positive and negative poles, etc. 2. Theoretical basis of lead-acid batteries In 1859, French physicist Gplante first prepared lead-acid batteries, but they have not yet formed the batteries in the current sense, but formed batteries, also known as "Plant batteries." In 1880, Fuer used the paste-c
1. Lead acidAccumulatorThe structure and composition of lead-acid batteries Generally speaking, lead-acid batteries are mainly composed of positive plate, negative plate, separator, battery tank cover (Guy) (container), electrolyte and other parts. (1) Polar plate: An electrode composed of an active material and a supporting conductive grid, which is divided into a positive plate and a negative plate. The grid is generally composed of lead-antimony alloy and lead-calcium alloy. The active material of the positive plate is PbO2 and the color is Brown, tan, reddish brown, the active material of the negative plate is spongy metallic lead (Pb), the color is gray, light gray, and dark gray. (2) Separator: It is placed between the positive and negative plates of the battery and is composed of an electrical insulating material that allows ions to pass through. It can completely block the short circuit of the positive and negative electrodes. PE separators, rubber, plastics, composite glass fiber separators, 10G, AGM separators, etc. are usually used. (3) Electrolyte (substance): liquid or solid phase substance containing mobile ion conduction. It has a conductive effect and participates in the flow reaction. The density of lead-acid battery electrolyte is related to the place where it is used. Relatively speaking, the density of electrolyte used in electric vehicle batteries is higher. (4) Battery tank: a container that contains the electrolyte of the battery group without being corroded by the electrolyte, generally made of hard rubber or plastic. (5) Components: battery cover (Guy), threaded liquid hole plug, safety valve, top cover (Guy), positive and negative poles, etc. 2. Theoretical basis of lead-acid batteries In 1859, French physicist Gplante first prepared lead-acid batteries, but they have not yet formed the batteries in the current sense, but formed batteries, also known as "Plant batteries." In 1880, Fuer used the paste-coating method to prepare the plates, and only today's paste-coated lead-acid batteries are available. In 1882, Glaston and Treber proposed the "bissulfation" theory to explain the flow reaction of lead-acid batteries. According to this theory, the electrode reaction and battery reaction of lead-acid batteries are as follows: negative electrode: Pb-2e+SHO4→PbSO4+H+ positive electrode: PbO2+2e+3H++HSO4-→PbSO4+2H2O battery reaction: PbO2+Pb+2H2SO4 (Positive) (Negative) PbSO4+2H2O has been tested by time and practice, and through rigorous scientific physical and chemical analysis, it is proved that the "bipolar sulfation" theory is correct. 3. The battery of an electric vehicle. What I talked about in the front is the common things of common lead-acid batteries. For electric vehicle batteries, it has its own characteristics. General requirements for batteries for electric vehicles (1) High volume ratio capacity (2) Long lifespan (3) Less gas evolution (4) Low self-discharge rate (5) High safety performance and high volume ratio capacity. Actually, here The above is the pursuit of high capacity within the same volume. For this problem, different manufacturers have different solutions, such as increasing the amount of acid, improving grid alloys, improving the formulation of lead paste, adjusting the proportion of acid, and so on. There are many methods. However, due to high-tech means such as improving grid alloys and improving lead paste formulations, factories of average scale do not yet have this capability. They often use simpler methods such as increasing the amount of acid and increasing the proportion of acid, but simple methods have their own shortcomings that cannot be ignored. There should be a limit on the amount of acid. Free acid is not allowed. Batteries with free acid can only be placed on the front side and are likely to leak acid, causing damage to the battery and even the electric vehicle. Some factories also believe that increasing the proportion of acid can increase the capacity of the battery. This phenomenon does occur in the early stage of battery use, but the proportion of acid is also closely related to the battery life. The density of battery electrolyte (acid specific gravity) has a significant impact on battery capacity and life. Usually, the density is high, the capacity is large, and the life is short; the density is small, the capacity is small, and the life is long. Of course, this is only relative. The electrolyte density is high, the active material can exert more efficiency, that is, the utilization rate is high, and the capacity is relatively large. However, as the number of cycles increases, due to the high electrolysis density, the positive electrode PbO2 particles can be slurried, and the binding force will decrease.resistanceIf it becomes larger, the active material will fall off quickly under the condition of frequent use, and the life of the battery will end early. Controlling the gas evolution of the battery is actually controlling its internal composition. The gas is decomposed by H2O, and the loss of water will directly affect the specific gravity of the acid and the conductivity of the electrolyte. After severe water loss, the battery will soon be sulfated , Thus ending the battery life. This also has to start with the structural design of the battery and internal improvements. Sealed battery (maintenance-free): also known as "cathode absorption valve-regulated sealed battery", in a strict sense, the sealed battery does not need to add water for maintenance during the entire life, which is determined by its own characteristics: a. Special alloy Electrode material: Metal with higher hydrogen evolution potential is used as the negative grid, such as lead-calcium alloy, which is used as a conductor and a carrier. b. Glass wool separator with strong adsorption force: It absorbs the electrolyte in the battery tank to make the battery lean and no free electrolyte. c. Safety valve: The outside air cannot enter, and the gas inside can be released when the pressure exceeds a certain pressure of 0.03-0.04Mpa to prevent explosion. The safety valve is also called "check valve", "air pressure valve", "rubber cap", and the valve top cover (Guy) has a polytetrafluoroethylene filter. d. Cathode O2: When the charging voltage is greater than 2.4V, water electrolysis: 2H2O→2H2↑＋O2↑Because the separator lean liquid has a gas channel, the positive electrode will start to produce O2 when it is charged to about 70% of the electricity (negative electrode) When charged to 90-100%, H2 is produced. O2 passes through the separator channel to the negative electrode. The following reaction occurs on the negative plate: O2+2Pb (negative electrode)→2PbOPbO+H2SO4→PbSO4+H2O to complete the "oxygen cycle", and the gas is combined into water . e. Of course, the smaller the self-discharge, the better, and the higher the safety performance, the better.
