CR2032 button cell battery

Analysis of the development of production technology of positive electrode materials for CR2032 button cell battery

This paper reviews the development history of production and preparation technology of positive electrode materials for CR2032 button cell battery and analyzes the development direction of positive electrode materials for CR2032 button cell battery. At the end of the last century, from the perspective of processing performance and battery performance of positive electrode materials for CR2032 button cell battery, the research team of Tsinghua University proposed a technology for preparing high-density spherical precursors by controlled crystallization, and combined with the subsequent solid-phase sintering process, proposed an industrial technology for preparing lithium-containing electrode materials. Among them, the controlled crystallization method can be used to prepare precursors, which can regulate and optimize the performance of materials at four levels: unit cell structure, primary particle composition and morphology, secondary particle size and morphology, and particle surface chemistry. The materials produced by this technology process have the characteristics of easy control of particle size and morphology, good uniformity, batch consistency and stability, and can simultaneously meet the comprehensive requirements of batteries for material electrochemical properties and processing performance. Due to the high packing density of the material, it is particularly suitable for high specific energy batteries. This technology process is applicable to a variety of positive electrode materials and is suitable for large-scale production. As time goes by, it has gradually been proven to be the best production technology process for positive electrode materials for CR2032 button cell battery, and has been widely accepted and recognized by the current industry. This is also one of the important contributions made by Chinese scientists to the international lithium-ion battery industry. CR2032 button cell battery have the advantages of high specific energy, high energy storage efficiency and long life. In recent years, they have gradually occupied the main market share of electric vehicles, energy storage systems and mobile electronic devices. Since Sony Corporation of Japan first commercialized CR2032 button cell battery in 1990, the negative electrode material has always been a carbon-based material, while the positive electrode material has made great progress and is the most critical material to promote the performance of CR2032 button cell battery. The research and development of positive electrode materials for CR2032 button cell battery are mainly carried out in three aspects: 1) At the basic science level, it is mainly to discover new materials, or to calculate, design and synthesize and explore the composition, crystal structure and defect structure of materials, in order to discover new positive electrode materials with excellent electrochemical performance; 2) At the material chemistry level, it mainly explores synthesis technology, in order to optimize the material structure factors such as material crystal structure, orientation, particle morphology, interface, etc., to obtain the best match of electrochemical performance, processing performance and battery performance, with the purpose of developing material structures and synthesis methods that can achieve the best comprehensive performance of positive electrode materials; 3) At the material engineering technology level, it is mainly to develop large-scale, low-cost and stable equipment and processes, in order to develop reasonable engineering technology to meet market demand. In order for positive electrode materials of CR2032 button cell battery to achieve the best performance in the whole battery, it is necessary to further optimize the physical and chemical properties of the materials, such as crystal structure, particle structure and morphology, particle surface chemistry, material stacking density and compaction density, on the premise of optimizing the material composition. At the same time, it is also necessary to strictly prevent the introduction of trace metal impurities during the process. Of course, stable and high-quality large-scale production is an important guarantee for the stable performance of materials in battery manufacturing. With the continuous improvement of lithium battery technology and the increasing maturity of the lithium battery market, the application fields of different positive electrode materials have gradually become divided, that is, the performance requirements of CR2032 button cell battery for various positive electrode materials are also different. Therefore, the mainstream synthesis technology and process of positive electrode materials have also experienced different development paths. 1. Performance requirements of CR2032 button cell battery for positive electrode materials (1) Industry performance requirements for CR2032 button cell battery To understand the technical indicators of positive electrode materials, we need to start with the technical indicators of batteries. In the early days of the lithium-ion battery industry, it mainly served the development of mobile electronic products, such as laptops, tablets, mobile smart terminals (mobile phones), etc. In recent years, the new energy industry and the electric vehicle industry have risen rapidly, and the demand for CR2032 button cell battery has grown rapidly, stimulating the lithium battery industry to accelerate its development. Therefore, CR2032 button cell battery need to meet many technical performance indicators in order to be recognized by the industry and further developed. Among these technical indicators, the most basic ones are specific energy, cycle stability, specific power, cost, safety and reliability, durability, manufacturing efficiency, sustainability, etc. The indicators are interrelated, and different application fields have different priorities for lithium-ion battery indicators. Compared with CR2032 button cell battery in portable electronic products, the biggest difference between CR2032 button cell battery used in energy storage and electric vehicle industries is that the capacity of single cells has increased by ten times or even dozens of times, and the function, structure and application complexity of battery modules have increased significantly, which puts higher requirements on the consistency and reliability of CR2032 button cell battery. Based on more than 20 years of research and engineering practice experience, it is believed that the most important technical indicators of CR2032 button cell battery are specific energy and cycle performance, followed by specific power, safety, reliability, cost and consistency. The higher the specific energy, the lower the material cost per unit energy (Wh); the longer the cycle life, the lower the actual cost of the battery. At present, CR2032 button cell battery for mobile smart terminals need to meet the requirements of specific energy of more than 700Wh/L and cycle performance of more than 200 times, while CR2032 button cell battery for electric vehicles need to meet the requirements of specific energy of more than 140Wh/kg (lithium iron phosphate or lithium manganese oxide positive electrode materials) or 200Wh/kg (layered oxide positive electrode materials) and cycle performance of more than 1,500 times. Lithium-ion battery positive electrode materials must meet the above battery indicators before they can be accepted by the mainstream battery market. At present, the specific energy and cycle performance of CR2032 button cell battery mainly depend on the positive electrode materials [1-6]. Therefore, the main research and development goals of lithium-ion battery positive electrode materials are high specific energy and long cycle life. For CR2032 button cell battery for laptops, tablets, and mobile smart terminals, volume specific energy is the most important indicator. Of course, batteries with high volume specific energy usually have high mass specific energy. Because customers want to put more battery energy in a device of a specific volume (such as a mobile phone), the graphite/lithium cobalt oxide system CR2032 button cell battery are currently the most mature in industrialization and have the highest volume specific energy. It is difficult for CR2032 button cell battery of other material systems to shake the dominant position of CR2032 button cell battery of this system in the mobile electronic products industry. Safety, reliability and certain cycle performance are also important for this type of battery. Since it is mainly used in a single-cell mode, the consistency and cost of the battery are not so important. For CR2032 button cell battery for electric vehicles, although the requirements for volume energy are not as stringent as those for portable electronic product batteries, after all, the space in passenger cars is limited and the weight of the car body will affect the mileage of electric vehicles. Therefore, the mass energy and volume energy of the battery are still very important. In addition, the requirements for almost all other performance of CR2032 button cell battery for vehicles are almost stringent, far higher than the performance requirements of portable electronic product batteries. There are three biggest differences between them and portable electronic product batteries. First, electric vehicle power requires higher voltage and current, and a large number of single cells are required to be connected in series and parallel. This makes the specific energy that can be actually used by the battery pack depend not only on the specific energy of the single cell, but also on the consistency of the single cell, especially the dynamic consistency. The consistency of power batteries has gradually attracted people's attention in recent years [7]. Second, the scale of single cells has increased significantly, which makes the price of single cells higher and the harm caused by thermal runaway is more serious. Therefore, the market is more sensitive to the safety and reliability of batteries. Third, since electric vehicles need a service life of 10-15 years, the requirements for cycle performance are very high, generally requiring more than 1,500 times. In addition, since electric vehicles need to start and accelerate, there are certain requirements for the specific power of power batteries. With the rapid development of the electric vehicle industry, power CR2032 button cell battery will become the mainstream products of the lithium battery industry together with portable electronic product batteries in the future. Specific energy and cycle performance are the most important performance indicators that are always pursued in the development of lithium-ion battery technology. With the increasing attention paid to safety, reliability, specific power and consistency, the technology in this area is expected to develop rapidly. It should be noted that as CR2032 button cell battery gradually penetrate into various fields of the national economy, there will be more and more non-mainstream lithium-ion battery market segments, which have special requirements for battery performance indicators and are not within the scope of this article. (2) Positive electrode materials that meet the needs of the mainstream lithium-ion battery industry. At present, the positive electrode materials that meet the battery performance requirements of the mainstream lithium-ion battery market mainly include layered lithium cobalt oxide LiCoO2 material (LCO), spinel lithium manganese oxide LiMn2O4 material (LMO), olivine lithium iron phosphate LiFePO4 material (LFP), olivine lithium manganese iron phosphate LiMn0.8Fe0.2PO4 material (LMFP), layered ternary material LiNi1/3Mn1/3Co1/3O2 material (NMC333), Layered ternary materials include LiNi0.4Mn0.4Co0.2O2 (NMC442), LiNi0.5Mn0.3Co0.2O2 (NMC532), LiNi0.6Mn0.2Co0.2O2 (NMC622), LiNi0.7Mn0.2Co0.1O2 (NMC721), LiNi0.8Mn0.1Co0.1O2 (NMC811) and layered high-nickel materials LiNi0.8Co0.15Al0.05O2 (NCA), etc. From the perspective of industrial application, the above materials have different physical and chemical characteristics and are suitable for CR2032 button cell battery in different application fields, so the key performance indicators of material products are also different. Lithium cobalt oxide LiCoO2 (LCO) material is currently the positive electrode material with the highest compaction density, so the prepared lithium-ion battery has the highest volume energy ratio, making it the main positive electrode material for CR2032 button cell battery for tablets and mobile smart terminals. Its main disadvantages are limited cobalt resources and high costs, which restrict its widespread application in the field of electric vehicles. The structure and reaction characteristics of this material are that as the charging voltage gradually increases, the amount of lithium released gradually increases, and the available capacity of LCO gradually increases. However, when the amount of lithium released exceeds 55% (that is, the charging potential relative to metallic lithium is 4.25V, and the charging voltage relative to the graphite|LCO full battery is 4.2V), the structural stability of the material decreases rapidly, and the life and safety deteriorate rapidly. Therefore, LCO positive electrode materials that can withstand higher charging voltages and have chemical stability that meets the requirements of battery applications are the main development direction of current material preparation technology. LCO has a stable structure and is relatively easy to synthesize. Its preparation technology is simple and relatively mature. Before 2000, LCO was mainly produced by solid-phase sintering technology of cobalt oxide/lithium carbonate mixtures. With people's extreme pursuit of product bulk density, specific surface modification, etc., the method of controlling crystallization to prepare lithium cobalt oxide precursors has gradually become the main industrial preparation technology due to its advantages in material morphology control [8-11]. The main advantages of spinel lithium manganese oxide LiMn2O4 (LMO) materials are abundant raw material resources, low cost, and good battery safety; its recognized main disadvantages are low battery specific energy and poor cycle stability. Since the 1990s, people have explored the application of LMO in electric buses, passenger cars, special vehicles, power tools and other fields due to its low raw material and process costs and good safety. Traditional solid-phase sintering preparation technology cannot achieve the regulation of material structure. In order to improve its cycle stability and material tap density, the author's team introduced the liquid phase process to prepare precursors in 2004 [12-14], and further improved the material performance through surface coating, lattice doping, surface gradient and other technologies [15-22]. However, due to the high solubility of the material, the cycle stability of the battery has not been well met. Only by further cooperating with the electrolyte can the battery life meet the demand. At present, although LMO is rarely used in automotive power batteries, it has been widely used in small power battery industries such as electric bicycles that are more sensitive to cost. In addition, with people's concern about the safety of large-scale power batteries for vehicles, blending with ternary materials has also become one of the main uses of LMO materials. The main advantages of olivine lithium iron phosphate LiFePO4 (LFP) materials are abundant raw material resources, low cost, good battery safety and cycle performance, and its main disadvantage is low battery specific energy. This material has been widely used not only in electric bicycles, electric buses, electric buses, and special vehicle industries, but also in large-scale energy storage industries. Since lithium ions in this material are transmitted along a one-dimensional channel, the material has significant anisotropy and is extremely sensitive to defective structures. The preparation process needs to ensure the high uniformity of the synthesis reaction and the precise Fe:P ratio in order to obtain better capacity and rate performance. Based on the complexity of the material structure and the synthesis reaction, there are two main difficulties in the preparation of this material: first, the process requires a reducing atmosphere. The reaction raw materials have different requirements for the reducing atmosphere due to different types and particle sizes. Local reducibility that is too high or too low will cause impurities to remain in the product; second, the material needs to be carbon-coated on the surface or compounded with other types of conductive agents, which makes it difficult to control the impurities and compaction density of the material. In 2005, the author's research group proposed to use controlled crystallization technology to prepare high-performance iron phosphate precursor (FP), and then prepare LFP through carbon thermal reduction with lithium source and carbon source[11]. The above process route has been further improved and has become the mainstream lithium iron phosphate material preparation technology[23-29]. In order to meet people's continuous pursuit of LFP battery performance, high uniformity and high batch stability have become the most concerned product indicators of LFP positive electrode materials. On the one hand, traditional solid-phase sintering technology is difficult to achieve efficient consistency control in principle, and on the other hand, consistency control will lead to a significant increase in process costs. Compared with solid-phase processes, precursors prepared by liquid-phase processes or positive electrode materials prepared by hydrothermal/solvothermal processes have better structural adjustability and controllability[30], as well as good batch stability and reaction uniformity. Similar to large chemical plants, continuous solvothermal processes can easily achieve ultra-large-scale production. Therefore, liquid-phase technology has gradually become the development trend of the next generation of high-quality LFP positive electrode material preparation technology[31-37]. Olivine manganese iron phosphate lithium LiMn0.8Fe0.2PO4 (LMFP) material is an upgraded version of LFP material, with a specific energy 10% higher than LFP; due to the differences in the reaction kinetics of Mn and Fe raw materials and the requirements for reducing atmosphere, the main disadvantage of this material is that it is difficult to prepare. At present, the industrial preparation process based on the solid phase method is still immature and has not yet been widely used. If the liquid phase preparation technology of LFP is industrially applied[38-41], the preparation difficulties of this type of material are expected to be solved. The development of ternary materials began at the beginning of this century. In the late 1990s, with the large-scale application of LCO, due to the limitation of cobalt resources, people hoped to replace cobalt with nickel, which is more abundant in resources. Compared with LCO, LiNiO2 material (LNO) was once considered the most promising lithium-ion battery material because of its abundant resources, low price and higher capacity[42-46]. However, as a positive electrode material, LNO also has difficult problems such as difficulty in preparation, unstable material structure and poor battery cycle performance. In order to solve the problem of structural stability and thermal stability of LNO, people doped cobalt and manganese into the bulk phase of LNO, and the earliest nickel-cobalt-manganese ternary material NCM came into being [47,48]. In order to improve the tap density of the material, in 2005, the author's research group proposed to use controlled crystallization technology to prepare high-density spherical nickel-cobalt-manganese hydroxide precursors, and then sinter them together with lithium sources to produce

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