CR2450 battery

Analysis of the current status and trend of key materials for CR2450 battery

With the continuous development of the global economy, the energy crisis has gradually deepened and environmental awareness has been continuously enhanced. As a new energy and environmentally friendly low-carbon power battery industry has developed rapidly, and lithium-ion batteries have become the mainstream development direction of many power batteries with their excellent performance and mature technology. Lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes, and diaphragms. They work by moving lithium ions between the positive and negative electrodes and have the ability to be recharged repeatedly. With the continuous breakthroughs in material types, performance technologies, and effective control of production costs, the advantages of lithium-ion batteries, such as light weight, long driving range, wide application range, high energy density, and high output power, will gradually be reflected. They are developed as the main power batteries and are the main type of power batteries for new energy vehicles today.

1. Lithium-ion battery positive electrode materials

At present, the positive electrode materials of lithium-ion power batteries used in industrial applications at home and abroad include lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary (nickel cobalt manganese oxide, nickel cobalt aluminum oxide), and lithium nickel oxide materials; the main manufacturers include Hunan Shanshan New Materials Co., Ltd., Hunan Ruixiang New Materials Co., Ltd., Peking University Pioneer Technology Industry Co., Ltd., Beijing Dangsheng Materials Technology Co., Ltd., Tianjin Bamo Technology Co., Ltd., Ningbo Jinhe New Materials Co., Ltd., Shenzhen Tianjiao Technology Co., Ltd., etc.

1. Main positive electrode materials

The capacity of lithium cobalt oxide can reach 140mAh/g, with light weight, small size, stable charge and discharge voltage, high conductivity, and simple production process; the preparation methods include high-temperature solid phase method, sol-gel method, precipitation method, spray drying method, and hydrothermal synthesis method; but the high price of raw materials, poor thermal stability and serious pollution problems limit its application in electric vehicles.

The capacity of lithium nickel oxide reaches 190-210mAh/g, with little environmental pollution and low self-discharge rate. The synthesis methods include high-temperature solid phase method and sol-gel method; but the thermal stability is poor and the capacity decays quickly.

Lithium manganate is rich in resources, low in cost, and safe. It has spinel and layered structures, with a specific energy of 80-120Wh/kg and a cycle life of about 1500 times. The three-dimensional tunnel structure of spinel lithium manganate is more suitable for the insertion and extraction of lithium ions. It has low cost, stable performance, mature production technology, and is easy to achieve industrial production, but the capacity decays quickly and the high-temperature cycle performance is poor; layered lithium manganate has a high capacity of 250mA? h/g, but poor sequential performance, instability at high temperature, and serious capacity decay problems, making industrial production difficult to achieve.

Lithium iron phosphate is an olivine structure with a specific energy of 100-120Wh/kg and a cycle life of up to 2,000 times. It has good thermal stability and safety, and is rich in raw materials. It also has low manufacturing costs and long cycle life. It is widely used in current electric vehicles. However, its low specific energy and specific power limit its application in large pure electric vehicles. It is currently developing in the direction of nano-sized and high-density lithium iron phosphate energy type to meet the needs of new energy vehicles, especially buses and special vehicles.

Nickel-cobalt-manganese and nickel-cobalt-aluminum ternary materials are currently more promising positive electrode materials. They make good use of the advantages of lithium manganese oxide, lithium cobalt oxide, and lithium nickel oxide, and to a certain extent make up for the shortcomings of the three materials. The performance of ternary materials is relatively balanced, with high energy density and capacity, and the capacity can reach 180-190mAh/g, good cycle performance, up to 2,000 times, strong endurance, and relatively cheap price; but the safety and low temperature performance are poor, synthesis is difficult, and the charging and discharging efficiency is low.

2. Research and development of positive electrode materials

The research and development of nickel-cobalt-manganese and nickel-cobalt-aluminum ternary materials is mainly to improve the volumetric energy of the materials, improve low-temperature performance, and improve battery safety; and to achieve performance regulation by adjusting the composition ratio of the materials. In order to continue to improve the energy density of the battery, positive electrode materials will develop towards silicate composite materials, layered lithium-rich manganese-based materials, and sulfur-based materials; and towards reversible materials with higher lithium insertion capacity and good lithium deinsertion performance. Material structure research tends to be layered structure and spinel structure.

3. Development trend of positive electrode materials

(1) Material modification

The stability of the surface structure of the electrode material is mainly achieved through graphene modification and surface modification, so as to improve the conductivity of the material, high-temperature cycle performance, and reduce the capacity decay of the material.

(2) Ion doping

Ion doping mainly involves doping metal elements such as aluminum (Al), chromium (Cr), and magnesium (Mg) into transition metals and non-metallic elements at the oxygen position, doping metal ions with good conductivity into positive electrode materials, improving the lithium ion diffusion rate, conductivity, electrochemical performance, and stability. It is necessary to study the specific mechanism of doping modification in depth so as to better utilize doping to improve material performance.

(3) Material nanomaterials

By reducing the particle size of the positive electrode material, shortening the diffusion path, and increasing the diffusion rate, while increasing the specific surface area of the material, adding more diffusion channels, accelerating the reaction, increasing the deintercalation rate and specific power of the positive electrode material, and improving the electrochemical activity.

(4) Composite positive electrode materials

With the continuous improvement of the requirements for lithium-ion power batteries, the trend of selecting positive electrode materials with complementary performance for composite is becoming increasingly obvious, such as sulfur/graphene composite positive electrode materials. The key point is how to give full play to the performance advantages of various composite materials.

2. Lithium-ion battery negative electrode materials

The negative electrode materials of lithium-ion power batteries should have high conductivity, be able to accommodate a large number of lithium ions, and have good stability. At present, most negative electrode materials use carbon materials with graphite structure, which are generally made by mixing carbon materials, adhesives, and additives in a certain proportion and coating them on copper foil, drying and rolling them; in addition, there are silicon-based materials, tin-based materials, lithium titanate materials, etc. Domestic manufacturers of negative electrode materials for lithium-ion batteries mainly include Shenzhen Barrett Technology Co., Ltd., Shanghai Shanshan Technology Co., Ltd., Jiangxi Zichen Technology Co., Ltd., Shenzhen Snow Industrial Development Co., Ltd., Hunan Xingyuan Technology Development Co., Ltd., Jiangxi Zhengtuo New Energy Technology Co., Ltd., etc.

1. Main negative electrode materials

The negative electrode materials of lithium-ion batteries are mainly graphite materials, mainly including artificial graphite, natural graphite, soft/hard carbon and mesophase carbon microspheres, and lithium titanate; the negative electrode materials under research include titanium oxide, tin-carbon composites, silicon composites, carbon nanotubes, and new graphite materials.

Natural graphite is rich in resources and low in cost. Its own lamellar structure can realize the reversible insertion and extraction of lithium ions. The preparation technology of artificial graphite is mature, and the pore structure formed by the random arrangement of secondary particles during the preparation process is conducive to the penetration of electrolyte and the diffusion of lithium ions, improving the charging and discharging capacity of the battery and having good cycle performance. It has a large proportion advantage in the current negative electrode production. Mesophase carbon microspheres are spherical lamellar particles with good cycle performance and high electrode density, but low capacity and high manufacturing cost. Although soft carbon materials have high capacity values, their fast decay rate causes obstacles to practical application. Hard carbon materials are easier to prepare and have a high cycle life, and have been partially applied in practice.

Lithium titanate negative electrode materials have high power characteristics, good safety, good structural stability, fast charge and discharge, good cycle performance, excellent high and low temperature performance, and the volume of the material hardly changes during the process of lithium ion insertion or extraction, and does not react with the electrolyte. It has high safety and is likely to become the main development direction of the negative electrode materials of the new generation of lithium-ion power batteries; however, the cost is high, the energy density and conductivity are low, and the process technology is immature.

Carbon-silicon composite materials can effectively improve the cycle performance of silicon negative electrodes and alleviate the volume expansion of electrodes during the cycle process; vanadium oxide negative electrode materials have high energy efficiency, excellent cycle performance, and reduced capacity decay; transition metal oxide negative electrodes have received increasing attention due to their high theoretical capacity, but during the discharge process, the generation of low-density lithium oxide will cause the electrode volume to expand, causing the battery capacity to decay. Ferroferric oxide (Fe3O4) has attracted widespread attention among transition metal oxide negative electrode materials due to its good conductivity and cycle stability. The material has a high theoretical capacity, abundant resources, and is safe and non-toxic; Li3V2(PO4)3 negative electrode materials have excellent capacity stability and low-temperature performance.

2. Research and development of negative electrode materials

Currently, the research on negative electrode materials mainly focuses on embedded type, alloy type and conversion type; the main research and development materials are hard carbon, soft carbon and silicon carbon; improve process maturity, stability and efficiency; the negative electrode materials that are currently studied more are nanoscale silicon and silicon alloys (mainly to solve the problem of fast capacity decay caused by large volume change of silicon negative electrode materials), metal oxides (iron oxide, titanium oxide) replace graphite, and improve its conductivity by coating or controlling its material particle size and morphology. Alloy research mainly focuses on nano-materials and multi-component composites. Carbon nanotubes and graphite new negative electrode materials are under research, which will bring new opportunities and challenges to the development of lithium-ion batteries.

3. Development trend of negative electrode materials

(1) Optimization of graphite negative electrode

Ion doping can effectively improve the power characteristics and cycle stability of materials, and coating treatment can effectively inhibit particle growth, while improving electronic conductivity and obtaining good electrochemical performance

(2) Material nano-materials

Carbon nanotubes and graphene are representatives of them. The dispersed spherical nanostructure has a high specific surface area, which can significantly improve the specific capacity, cycle performance and rate performance of materials.

(3) New type

In order to continuously improve the energy density of lithium-ion power batteries, the key development direction of negative electrode materials in the future will turn to new carbon active materials, alloy materials, and silicon-carbon composite materials; improve lithium insertion capacity.

III. Lithium-ion battery electrolyte materials

The electrolyte transports ions and conducts current between the positive and negative poles of the battery. It is one of the key factors for the battery to obtain high energy, long life and safety, and must have good stability. The main manufacturers include Zhangjiagang Guotai Huarong Chemical New Materials Co., Ltd., Shenzhen Xinzhoubang Technology Co., Ltd., Tianjin Jinniu Power Materials Co., Ltd., Guangzhou Tianci High-tech Materials Co., Ltd., and Saiwei (Shenzhen) Electronics Co., Ltd.

1. Main electrolyte materials

The electrolyte of lithium-ion power batteries participates in all reactions inside the battery. If the battery system is overcharged, over-discharged, short-circuited, or thermally shocked, the battery temperature will rise, the electrolyte will burn, and the battery will catch fire or even explode. Therefore, the safety of the electrolyte is crucial. It is mainly a solution of lithium salts dissolved in organic solvents. The main lithium salts are lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), and lithium hexafluoroarsenate (LiAsF6); organic solvents are usually carbonates, mainly dimethyl phosphate, ethyl methyl carbonate, ethylene carbonate, and ethyl methyl carbonate; there are also sulfonates, borates, cyclic ethers, polyethers, sulfones, nitriles, and nitro compounds. In order to maintain the conductivity of the electrolyte, lithium salts are easily soluble in organic solvents and have good thermal stability, but they also have their own limitations. LiPF6 has poor stability at high temperatures, LiBF4 has low ionic conductivity at room temperature, and LiClO4 has strong oxidizing properties.

2. Research and development of electrolyte materials

The research on new lithium salts mainly focuses on lithium bis(oxalatoborate) (LiBOB), lithium difluoro(oxalatoborate) (LiDFOB), and lithium bis(imide) (LiFSI).

3. Development trend of electrolyte materials

(1) Solidification

In order to prevent safety issues such as leakage, combustion, and explosion of lithium-ion battery electrolytes, electrolyte materials are developing towards solidification. The main research directions are inorganic solid electrolytes, solid polymer electrolytes, and solid-liquid composite electrolytes.

(2) New solvent systems

Nitrile and sulfone solvents are less compatible with graphite negative electrodes than commonly used carbonate solvents. The main research direction is to reduce the cost of new solvent systems and improve their compatibility with existing negative electrode materials.

(3) High-voltage electrolytes

The main research direction of high-voltage electrolytes is to simultaneously increase the voltage level of positive electrode materials and electrolytes.

4. Lithium-ion battery diaphragm materials

The diaphragm cost accounts for about 20% of the battery cost and is an important component of battery materials. Its main function is to isolate the positive and negative electrodes of the battery, ensure battery safety, and realize charging and discharging functions. The main requirement is good insulation. As a polymer functional material, the diaphragm has broad development prospects, high added value, low cost, and considerable benefit prospects. Domestic diaphragm manufacturers mainly include Xingyuan Electronic Technology (Shenzhen) Co., Ltd., Beijing Taihe Zhongke Technology Co., Ltd., Foshan Jinhui High-tech Optoelectronic Materials Co., Ltd., Chongqing Mingzhu Plastic Co., Ltd., Henan Yiteng New Energy Technology Co., Ltd., and Nantong Tianfeng Electronic New Materials Co., Ltd.

1. Main diaphragm materials

In order to facilitate gas diffusion, a lithium-ion power battery diaphragm material with good air permeability and thinness should be selected. It is generally a polyolefin microporous film material, including a polyethylene monolayer film, a polypropylene monolayer film, and a double-layer or three-layer composite film of two materials. The film thickness is about 10 to 20 μm. The research direction of the diaphragm is mainly focused on improving strength, stability, and porosity.

2. Research and development of diaphragm materials

Currently, the low-end diaphragm market has overcapacity, but the high-end diaphragm market still has a certain gap in quality with foreign products. There are problems with quality uniformity and stability. The market is in short supply and heavily relies on imports from a few countries such as Japan and the United States.

3. Development trend of diaphragm materials

(1) Surface modification

By applying inorganic ceramic coatings or organic coatings to modify and enhance the surface of diaphragm materials, the physical properties of diaphragms are improved, such as puncture strength, tensile strength, thermal shrinkage, high temperature resistance, high pressure resistance, etc.

(2) Thinning of diaphragm materials

To increase the capacity of lithium-ion batteries, the diaphragm must be developed in the direction of lightness and thinness. Mastering the production technology of thin diaphragms will be in a favorable position in future competition, but this also puts higher requirements on the production and preparation of diaphragm materials and the process level, which requires continuous research and development and breakthroughs.

V. Conclusion

With the continuous development of battery research and industry in Japan, South Korea and the United States, the Chinese government has also introduced a series of policies to promote the development of the battery industry. The major lithium-ion power battery manufacturers that have developed rapidly in recent years include AVIC Lithium Battery (Luoyang) Co., Ltd., BYD Co., Ltd., Tianjin Lishen Battery Co., Ltd., Zhejiang Wanxiang Yineng Power Battery Co., Ltd., Guangyu International Group Co., Ltd., Shenzhen BAK Battery Co., Ltd., Shenzhen Watma New Energy Vehicle Power Battery Co., Ltd., Hefei Guoxuan High-tech Power Energy Co., Ltd., and CITIC Guoan Mengguli Power Technology Co., Ltd.; However, there is still a certain gap with the international advanced level in key materials and overall battery production.

In recent years, in order to reduce dependence on traditional petrochemical energy, save energy and reduce emissions to reduce the generation of greenhouse effects, the large-scale promotion and application of electric vehicles has become an inevitable trend. Therefore, improving the overall performance of power batteries and reducing costs within the consumer's tolerance range have become the main goals of competition among battery manufacturers. With the continuous breakthrough of lithium-ion power battery technology bottlenecks and the continuous reduction of costs, it can be foreseen that lithium-ion power batteries will become the direction of battery technology development in the future and become the goal pursued by more and more automobile manufacturers.

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