Cyclic Life Analysis of Lead-acid Batteries

The factors affecting the life of lead-acid batteries are various, including the internal factors of the battery, such as battery structure, positive and negative grid materials, positive and negative active materials, separators, electrolyte concentration, etc., and also depend on a series of external Factors such as discharge current density, temperature, depth of discharge, maintenance conditions, and storage time. The deeper the discharge, the shorter the service life. Overcharging also shortens life. As the acid concentration increases, battery life decreases. In the research process of large-capacity lead-acid batteries, we found that the lead-slip short circuit is an important cause of battery performance degradation and failure. In addition, the corrosion deformation of the positive grid, the positive active material shedding, softening, Irreversible sulfation, and the serious accumulation of cerium on the active material are all key factors affecting the life of the battery.

Cyclic Life Analysis of Lead-acid Batteries

In order to prevent corrosion of the positive grid, a multi-component low tantalum alloy was developed. The corrosion resistance of this multi-alloy is greatly improved. The negative grid is made of lead-plated copper. The ratio of the weight of the copper grid to the active material is 1:3, and the specific energy of the reservoir is significantly improved. Moreover, due to the good electrical performance of the copper grid negative electrode, the charging acceptance capability is strong, and the battery charge and discharge cycle life are raised. Adding additives to the positive and negative active materials increases the utilization rate of the active materials and prolongs the service life. In order to prevent the lead-free short circuit, comprehensive short-circuit prevention measures are taken. High-performance boards and a range of new assembly processes are used.

Introduction to the development of lead-acid batteries

The lead-acid battery was first produced by Gastron Prandt in 1860 and has a history of more than 140 years. Over the past 100 years, with the development of science and technology, the process, structure, production mechanization and automation of lead-acid batteries have been continuously improved, and the performance has been continuously improved. Due to its excellent performance and price ratio, the production and application of lead-acid batteries are still at the top of various chemical power sources until today. Applications include power, start-up, emergency and working power, including vehicles, ships, aircraft, and telecommunications. Systems, computers, instruments, and other equipment and facilities, especially in automotive batteries and industrial batteries, lead-acid batteries account for more than 90% of the market share, with an absolute advantage. 121. The original Valta stack appeared for the first time in 1800. Gotti 1801 Roth has observed the so-called "secondary current", that is, the current opposite to the direction of the charging current can be obtained after charging. Della·Weiwei studied the primary battery of Pb02 as a positive electrode in sulfuric acid solution from 1836 to 1843. Several electrode forms of the acid battery and the manufacturing process of the main process were gradually determined in the half century from 1860 to 1910. The earliest appeared was the formed plate. In 1881, Fore first proposed the pasted plate. Xielang first used Pb.sb alloy casting grids to improve the fluidity of liquid alloys and the hardness in the solid state. 1924 R Rendaojin invented the ball mill and replaced the red and yellow powder with the ball powder as the active material of the battery. The use of lignin as the negative electrode active material additive effectively prevented the lead sulfate crystal from becoming thicker and prolong the life of the battery. It appeared in the 1920s. Microporous rubber separators, resin-paper separators in the 1940s, which gradually replaced wood partitions during the 20 years from the 1950s to the 1960s. Lead-acid batteries have made significant advances in manufacturing processes: plastics Replacement of hard rubber to make battery slots and covers; use of thin plates and improved grid design; through-wall welding technology for start-up batteries; low-twist or untwisted alloy cast grids are generally used; Active material utilization rate; dry-type battery manufacturing process. After the 1970s, countries have vigorously developed maintenance-free and sealed lead-acid batteries. In basic theory, physics, especially electronics achievements and means are widely used: stable potential Instrument, scanning current meter, scanning electron microscope, x. ray and neutron diffraction,special magnetic resonance and electronic spectroscopy, etc. plus rotating disk electrode and meter Technical research focus from thermodynamics to the electrode kinetics.

The main producers of lead-acid batteries are distributed in several developed countries including the United States, Europe (UK, Germany, France, etc.) and Japan, and their total output accounts for about 70% of the world's total output. The United States has EXIDE Technologies, the world's largest producer of lead-acid batteries (with annual global sales of $2.8 billion), and other very large lead-acid battery manufacturers such as JOHNSON, CONTROL, DEKA, and DELPHI. The output value of lead-acid batteries in the United States accounts for about 20% of the world's total. However, in recent years, with the changes in factors such as technology and labor costs, some lead-acid battery companies have experienced a decline. The production of lead-acid batteries is transferred to countries such as India, Southeast Asia and other countries where labor costs are low. There are many large lead-acid battery manufacturers in Europe, such as CHLORIDE, HOPPECKE, F1AMM, DETA, HAWKER, etc. Lead-acid batteries in Europe play an important role in the world, with a well-established technology-leading lead-acid battery manufacturer such as Sunshine (now a subsidiary of EXIDE). In 2001, the output of lead-acid batteries in Europe was 48.1 million, and in 2002 it was estimated to be 49.1 million. In 2005, it will reach 51.8 million. In terms of industrial batteries, the number of spare batteries in 2000 was 130,000, the number of sealed batteries less than 24 Ah was 110,000, and the number of sealed batteries larger than 24 Ah was 430,000. The producers of lead-acid batteries in Japan mainly include Yuasa Battery Co., Ltd., Matsushita Battery Co., Ltd., Furukawa Battery Co., Ltd., Shin-Kobe Electric Co., Ltd., and Japan Battery (GS). According to statistics from relevant parties, in 2002, the output value of lead-acid batteries in Japan was about 1.16 billion US dollars, the starting batteries of lead-acid batteries accounted for 55.7%, and the industrial batteries (fixed lead-acid batteries) accounted for 6.7%. Small lead acid The battery accounts for 8. O%, the other accounted for 29.7%. Since the 1990s, the proportion of lead-acid batteries in the total output value of secondary batteries has remained at around 20% and has increased in recent years.

In recent years, the performance of lead-acid batteries in China has been greatly improved, and the energy of weight ratio and volume ratio have been greatly improved. Less maintenance and maintenance-free, valve-regulated sealed lead-acid batteries are growing rapidly.

Lead-acid battery structure, composition and classification

The electrochemical expression of a lead-acid battery is (1) PbIH2SO·IPb02(+).

The main structure of the lead-acid battery includes a positive electrode, a negative electrode, a separator, a sulfuric acid electrolyte, a battery tank, and a cover. The positive and negative electrodes are respectively welded into a pole group, and the large-capacity battery is led out from the bus bar to form a pole. The electrolyte used in the lead-acid battery is a certain concentration of sulfuric acid electrolyte. The function of the rain separator is to separate the positive and negative electrodes. It is an electrical insulator (such as rubber, plastic, fiberglass, etc.), resistant to sulfuric acid corrosion, oxidation resistant, and has sufficient porosity and pore size to allow electrolyte and The ions pass freely. The tank body is also an electrical insulator, which is resistant to acid and temperature and has high mechanical strength. Generally, hard rubber or plastic is used as the tank body.

Lead acid battery cycle life analysis

1.2.1 Positive active material

The positive electrode active material is lead dioxide. The crystal forms of Pb02 are d--Pb02 and 0--Pb02. In a sulfuric acid solution,

The Pb02 electrode reaction is:

Pb02+HS04"+3H++2e=PbS04+2H20

Tests have shown that the discharge capacity of B-Pb02 is always greater than the discharge capacity of a--Pb02. This is because the true specific surface area of ??B-Pb02 is larger than that of Q--Pb02, which directly affects the growth and diffusion of lead sulfate on its surface, thus affecting the utilization rate of active substances. During charge and discharge, n--Pb02 and B-Pb02 are transformed into each other, mainly a--Pb02 is converted to 13--Pb02. The charge and discharge reaction mechanism of the positive electrode can be divided into a dissolution deposition mechanism and a solid state mechanism.

In order to improve the utilization rate of the active material of the positive electrode, various additives, including conductive additives, inorganic additives such as barium, calcium sulfate, aluminum sulfate, zeolite, and the like, and organic and polymer additives are used. Wei Guolin believes that the BD additive can greatly improve the battery capacity. Significantly improve the utilization rate of active materials, can form a microstructure with more pores, thereby improving the mass transfer process and significantly improving the charge and discharge performance of the positive electrode. The combination of BD and PII can significantly increase the battery capacity and the utilization rate of the positive active material.

Ramanthanll41 studies have shown that calcium sulphate is added to the positive active material to improve battery performance at high discharge rates and low temperatures. The addition of RS03H to the positive electrode active material improves the diffusion condition of H+ in the positive electrode micropores, and greatly increases the positive electrode discharge capacity and the positive electrode active material utilization rate 115]. D. Pavlov and N. CopkOV mixes Pb, 04 and lead powder, and obtains 4PbO·PbS04 paste as a positive electrode after high-temperature curing. The cycle life of the battery is increased by 30% because of the active substance a. The content of Pb02 is significantly increased by I". Document 1171 introduces a high-performance positive electrode plate with persulfate added to the common lead paste composition, the active material has high porosity and specific surface area, and the discharge power is at least 1 W/cm2. The material has a porosity of 55% and a specific surface area of ?? at least 4 m2/g. The literature [181 proposes to add PbF2 to the lead paste and add fluororesin latex as a binder, which does not require curing, which is beneficial to the high power output of the battery. It is proposed to use propylene and propylene styrene while adding carbon to the active material, which is mainly beneficial to the formation of a network and increases the porosity.

1.2.6 Classification

Lead-acid batteries are customarily used in three classifications.

1) Classified by purpose

China's lead-acid battery products are classified according to their use. Mainly divided into starting, fixed, power and other aspects. Among them, the starting battery is mainly used for various automobiles, locomotives, ship starting, and lighting. It is required to discharge at high current, can start at a low temperature, the internal resistance of the battery should be small, and the positive and negative plates should be thin. The fixed lead-acid battery is mainly used as a backup power source for various large-scale equipment systems, the plate is thick, the electrolyte is thin, and the service life is long. The power battery mainly provides power for various power systems, and the long-term and short-time performance requirements are better.

2) Classification by plate structure

Mainly divided into paste, tube, and formation. The lead oxide is adjusted into a lead paste with a sulfuric acid solution, coated on a grid cast with a lead alloy, and dried and formed into a paste-like plate. The skeleton is made of a lead alloy, and the fibrous tube is prepared in the skeleton outer casing, and the tube is filled with an active material. This electrode plate is called a tubular plate. The polar plate is cast from pure lead and is called a formation.

3) Classified by electrolyte and charge maintenance

Mainly divided into dry discharge battery, dry-charge battery, wet charge battery, maintenance-free, less maintenance battery, valve-controlled sealed battery.

Electromotive force, open circuit voltage, working voltage

The electromotive force of the battery is the difference between the equilibrium electrode potentials of the two electrodes. The battery electromotive force is a function of the concentration of sulfuric acid. The open circuit voltage of the battery is the potential difference between the electrodes when no current flows through the external circuit, and is generally smaller than the battery electromotive force, which is directly related to the state of charge of the battery. The operating voltage of the battery, also known as the discharge voltage or load voltage, refers to the potential difference between the two poles of the battery when there is an external current. The operating voltage is always lower than the open circuit voltage because the resistance caused by the polarization resistance and the ohmic resistance must be overcome when the current is passed through the interior of the battery. As the discharge of the battery progresses, the positive and negative active materials and sulfuric acid are gradually consumed, the amount of water increases, the acid concentration decreases, and the voltage of the battery decreases.

Lead-acid battery life

The service life of lead-acid batteries is one of its important performance indicators. The life of a battery is generally expressed in cycles. The battery undergoes a charge and discharge, which is called a cycle. In a certain charging and discharging system or working mode, the number of cycles that the battery is subjected to before the battery capacity drops to the specified value is called the service life, that is, the battery life. Life can also be expressed in terms of the time of use. In practical applications, battery life has a variety of expressions such as bench test period, assumed period, and actual use time, which are mainly determined by the way the battery is used. Factors affecting battery life include the internal factors of the battery, including the structure of the battery, the material of the grid, the performance of the active material, etc., and also depend on a series of external factors such as discharge current density, temperature, depth of discharge, maintenance status and storage time. Wait. The deeper the depth of discharge, the shorter the service life. Overcharging also shortens life. Battery life increases with increasing temperature. As the acid concentration increases, battery life decreases. The internal factors of the battery affect its service life mainly in the following aspects.

Lead short circuit

In the research of large-capacity lead-acid batteries, we found that the lead-slip short circuit is an important cause of battery performance degradation and ultimately failure. During the recycling of the battery, the active material and the fiber additive on the positive and negative plates are peeled off, a part of which is present in a solid form, and a part of which is dissolved in the electrolyte. As the charge and discharge process progresses, the dissolved material is reduced and precipitated in the negative electrode, and the undissolved substances and additives can also be precipitated in the positive and negative plates and other places of the polar group. As time elapses, the battery charge and discharge cycle increases, more and more substances are deposited, and eventually, the positive and negative electrodes are locally connected, resulting in a micro short circuit, called a lead short circuit. The short circuit point increases self-discharge and the temperature rises. With the accumulation of time, the lead short-circuit area is increased, the charging efficiency is greatly reduced, the battery capacity is decreased, and the hydrogen evolution amount is increased. Moreover, the local high temperature may cause the separator to burn through, lose the isolation effect, the positive and negative electrodes are connected in one body, the structure is damaged, the function is lost, and finally the battery life is terminated.

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