lithium 18650 battery

　　What are the new breakthroughs in the research progress of lithium 18650 battery materials?

　　What are the new breakthroughs in the research progress of lithium 18650 battery materials - "The country's major needs have promoted a new leap forward in the development of power batteries. On the premise of ensuring safety, new power sources with high energy, high power, long life, low cost and no pollution have been developed. Batteries are forming industries and going to the market according to different user needs," Wu Feng said, "The technological integration between nickel-metal hydride batteries, lithium-ion batteries, high-energy new system batteries and supercapacitors is very important. The integration of this technology is very important. It is also a technological innovation in itself, and together with the Internet, it will open a new chapter for the development of new secondary batteries in our country!”

　　Limited by the technical level of power batteries, new energy vehicles have low cruising range, short lifespan (low number of charges and discharges), and high attenuation rate, which hinders the large-scale application of new energy vehicles. Recently, South Korea and Japan have successively announced breakthroughs in lithium 18650 battery material technology, and the cost of power batteries will drop in the future.

　　At the 5th Guoxuan Hi-Tech Science and Technology Innovation Conference and the 4th Power Energy Summit Forum, Professor Wu Feng from Beijing Institute of Technology shared the research progress of power batteries and related materials with the guests.

　　The country's major needs have promoted a new leap forward in the development of power batteries. Under the premise of ensuring safety, new power batteries with high energy, high power, long life, low cost and no pollution are forming industries according to different user needs and heading towards market. Wu Feng said that the technological integration between nickel-metal hydride batteries, lithium-ion batteries, high-specific energy new system batteries and supercapacitors is very important. This technological integration itself is also a technological innovation. Together with the Internet, it will provide my country with a new type of secondary battery. The development of batteries opens a new chapter!

　　Wu Feng said that the development of power batteries faces the following problems: Can a new generation of high-specific-energy batteries be constructed? Can the problem of battery safety and reliability be solved? Can long battery life be achieved? Can the cost performance of batteries be improved?

　　Wu Feng introduced that the energy density index of power lithium-ion batteries in 2015 was 120-180Wh/kg, and the material system was mainly lithium iron phosphate-graphite and ternary graphite. The energy density index of the new generation of power lithium-ion batteries in 2020 is: lithium-rich (250mAh/g) - silicon carbon anode: battery cell 300Wh/kg.

　　The increase in the energy density of power lithium-ion batteries is not only related to the positive and negative electrode materials, but also has higher and higher requirements for the electrolyte used. Wu Feng said that using NCM ternary cathode material and Si/C anode material, a high specific energy lithium-ion battery with an energy density of 319Wh/kg can be prepared.

　　Regarding the research progress of 300Wh/kg lithium 18650 battery material system, Wu Feng said that he studied the impact of divalent nickel content on the mixed arrangement of lithium and nickel in the high-nickel ternary cathode material NCM811, and found that increasing the stoichiometric ratio of lithium can increase the content of the material. The content of divalent nickel can reduce the mixing of lithium and nickel in the material and improve the cycle stability of the material. In addition, a high-nickel ternary cathode material (LiNi0.7Co0.15Mn0.15O2) with dominant growth of 010 crystal plane was prepared. Electrochemical measurements showed that the material has good rate performance. We also designed and developed a spherical hierarchical structure with dominant growth of the electrochemical active surface, which significantly improved the rate cycle characteristics and rate performance of lithium-rich manganese-based materials for lithium-ion batteries.

　　In terms of negative electrode material research, SiO/CNx composite electrodes without binders are synthesized through direct coating methods. The nitrogen-containing carbon network can buffer its volume change during cycling, form a better conductive network on the SiO surface, and provide a stable channel for electron transmission. And a high-energy ball milling method was used to synthesize Si/Ni/graphite composite materials. Metal Ni and graphite are interlaced to form a good conductive network. Nanocrystalline Si is embedded in the SiOx matrix in situ, which improves the electrochemical activity of SiOx.

　　For the research on functional electrolytes, a new slurry electrolyte containing lithium silicate was designed and developed, which significantly improved the safety and cycle stability of high-voltage lithium-ion battery cathode materials. In addition, safety functional electrolytes and additives have been developed: imidazolinones, piperidine ring ionic liquids, and flame-retardant phosphate additives were combined with the film-forming additive butylene sulfite to develop a series of flame-retardant products. The functional electrolyte system with electrochemical compatibility significantly improves the safety, reliability and temperature adaptability of lithium-ion batteries (expanding the operating temperature range from -20°C to +60°C to -40°C to +80°C). And developed a solid-state electrolyte with a mesoporous SiO2+ ionic liquid network structure with a wide electrochemical window, high thermal stability and room temperature ionic conductivity of 10-3S/cm, which provides a solution to the safety problem of new high-specific energy batteries. Material support.

　　In addition to the research on battery materials, Wu Feng also introduced the research progress of battery recycling technology. He said that secondary batteries have now penetrated into all areas of the national economy and people's lives. Battery production has increased sharply, which has exerted huge environmental and resource pressure on society. According to my country's new energy vehicle sales forecast, in 2020 only the demand for power batteries will be It will reach 30 billion watt hours, the negative impact on the environment will become increasingly serious, and lithium resources will become increasingly scarce. The new environmentally friendly natural organic acid recycling technology is used to achieve green and efficient recycling of used lithium-ion batteries (lithium and cobalt leaching rates are 98% and 94% respectively), which is superior to foreign processes using strong acid and avoids strong acid recycling Secondary pollution during treatment.

　　Progress in R&D of New Materials for Power Batteries

　　We very much hope to be positive in terms of materials, which is relatively difficult for us. From an enterprise's perspective, the first is safety, reliability, and cost technical indicators that put forward a series of requirements. The bottom-line indicators and long-term development indicators are both very high. The government and the country have put forward very high energy density requirements for power batteries. Like the new energy vehicle project released this year, for basic research projects, it is hoped that the energy density of lithium-ion batteries will reach 400Wh/kg, and the energy density of new system battery samples will reach 500Wh/kg. It is not easy for enterprises to achieve 300Wh/kg, and many new systems need to be developed. "Made in China 2025" requires 400wh/kg or more, and the key words in some of the proposed plans are mainly batteries. The gap between the two is still relatively large.

　　Considering this issue from the perspective of product indicators, let's compare the relevant requirements of various national governments. I just mentioned "Made in China 2025". The bottom one is Japan's. What's more tiring is the competition between China and the United States. This year, three special projects were launched, all involving power batteries.

　　Everyone hopes that it will be 400wh/kg in the future. Why do we set this indicator? Mostly due to safety considerations of lithium-ion batteries. Take the BAIC New Energy EV200 as an example. Its energy consumption per 100 kilometers is 14kwh, and its life requirement is 10 years and 200,000 kilometers. However, the cost has now been reduced a lot. In the future development of power batteries, the cost of achieving the same cruising range will be much higher than at present. Therefore, if the power batteries of electric vehicles do not develop to high energy, they will face more fierce competition in pure electric vehicles in the future, and may even be crushed by fuel cells. Case.

　　From an actual development perspective, the entire development is very slow and relatively stable, mainly due to the upgrading of technology and materials. Even if we look at it according to the route, if we can keep up with the current development speed, you will be able to reach 2020 The goal is to achieve 300 by 2030, and 390 watt-hours per kilogram in 2030. How can this roadmap be realized step by step? Can the second one achieve 400 watt-hours per kilogram or even higher?

　　Liquid electrolyte lithium batteries have been developed for three generations. There was a detailed introduction last year. The main thing is that each of the positive electrode materials is being upgraded, increasing the voltage or capacity; the main changes in the negative electrode are in the energetics of the battery. Introduce nano-silicon carbon into the electrolyte and add some technologies, including ceramic-coated separators and so on. How high can the lithium batteries we look at now go? The low-energy density is indeed very good, but it sacrifices cyclicity, not to mention safety, to achieve high energy. However, this does not mean that the cyclicity cannot be improved. Some detailed and basic research is needed. This is what a French survey company saw. There are more and more opinions on materials. Now many teams and colleagues are familiar with it, so I won’t go into details.

　　But for battery materials, there are many problems and performance requirements. At least 13 or more technologies have been adopted to comprehensively solve this technology. Each line has a lot of detailed technology and content. You can replace it. When using one material, the entire battery will change very complexly. The development of this battery material is very slow. It usually takes more than ten years. Many teams and companies are now developing lithium batteries with a capacity of 300 watt hours per kilogram. One of the most difficult problems in this aspect is that high negative electrode capacity brings high volume expansion, which is very difficult to deal with at the battery cell level. The core problem is how to solve the problem of volume expansion after charging to meet the needs of current battery cells. Enterprise requirements, in addition, the realization of these high energy densities is possible, but can its comprehensive access indicators meet the application requirements? It's not clear what the upper limit is. There are some solutions in this, so I won't discuss it in detail due to time constraints. We welcome everyone to have the opportunity to exchange technology in this area.

　　In addition, the government wants to make 400wh/kg and 500wh/kg. After calculation, there is a model. The current graphite anode and silicon anode metal lithium are also placed here. If it can reach more than 800 watts, there is still a chance, 400wh/kg, 500wh/ There are some solutions for kg, but it is very difficult to implement. NC can reach up to 200, and negative lithium can reach 300. This is a systematic calculation of different anode materials. From the calculation point of view, it seems that there are some positive and negative electrode materials. To achieve high matching density, the previous steps are all virtual calculations, and the Academy of Sciences is working in this area. In order to strengthen research and development results to promote economic development and solve practical problems, the Academy of Sciences has launched strategic pilot A projects. Among them is a nano project, which is to provide centralized support for the nanotechnology studied by the Academy of Sciences over the past 20 years, hoping to have a positive impact on the industry. Help, the first of these projects is the lithium 18650 battery, and nanomaterials and nanotechnology are likely to be used.

　　Regarding the requirements for this type of project, Vice Minister Yin Hejun, who was originally in charge of this project, proposed that what we do has clear goals, can be used, can be assessed, and has been assessed by a third party, and the materials and technologies must be used. Finally, There are many indicators to assess the level of use, whether there is any impact, and the impact ability, so such a project is very difficult. He put forward specific indicators. The country has proposed to achieve 300 watt-hours per kilogram by 2020 and 150 watt-hours per kilogram by 2015. Related battery materials, cathode electrolyte separators, etc. also need to be industrialized. In order to complete this project, several main contents have been set. One is that 60% to 70% of the funds will be spent on lithium batteries, developing high-energy positive and negative electrodes, high-voltage electrolytes, and high-safety separators, integrated in Regarding power batteries, in the long run we need to lay out solid-state batteries, and air batteries are also planned in this regard. In addition, Teacher Chen mentioned the testing level this morning. The domestic testing level is still good, but two platforms have been built. I will briefly report the results. There are 12 units and a R&D team of about 300 people, covering all aspects. One is silicon anode, and I have been doing scientific and technological research and development in this area for 19 years, which is quite difficult. Recently, this matter has been developed from the perspective of application. The main technical routes include two categories, one is SiOx/C and the other is Nano-Si. It is mainly based on continuous iteration of comprehensive technical indicators. After receiving support in 2013, The ability to achieve a batch size of 500 kilograms is probably due to comprehensive design considerations. What I show here is that our thinking is not a real thing. It is still very difficult to introduce additives, etc. The difficulty in the nano talk is how to get nano silicon that costs 100 yuan per kilogram.

　　Second, how to disperse nano-silicon evenly among the particles?

　　What is being done now is such a material, which is about dispersing nano-silicon in particles, which can be put into mass production. Among 450 mA/h materials, it is generally a high-capacity load that can be cycled about 500 times, but the previously developed Silicone oxide is being developed, but its low efficiency and high capacity of nano-silicon carbon are not satisfactory solutions, so we are developing a new generation of silicon-rich oxide materials to reduce the challenges it brings.

　　This new material company is currently ranked third or second in the country. It has solved a series of technical problems. I will not go into details. There is progress in negative electrode materials, but we have accumulated relatively few positive electrode materials. After the support of this project, it is mainly aimed at high-capacity levels. The difficult part of this material is voltage attenuation. In this work, the problem of voltage attenuation is mainly solved through the reconstruction of the surface structure, so the trial can be started. This year In the 500kg range.

　　Another material is high-voltage spinel, which is relatively easy to switch over. The most difficult thing is that after using this material, the electrolyte and so on need to be fully upgraded, so this aspect still needs to be improved, especially the issue of high temperature of 55 degrees. In order to solve the problem of high-voltage lithium-rich materials, this is very important and also very challenging in China. Now it can cycle relatively stably in high voltage, and there are additives in the electrolyte. We feel that there are still some problems with the direct use of separators, so we are developing ceramic separators with cellulose substrates and high temperature resistance. However, this does not seem to be able to be used in our batteries. The main thing is consistent stability. It is now a small trial. It has reached the pilot test stage, but the prospects shown are promising. Cellulose separators plus ceramic particles. In fact, we have also developed ion conductive coating separators.

　　Graphene has been developed for a long time, and the coating technology can achieve the level of mass production of dozens of tons. We used the materials just now to make a preliminary battery. This battery can achieve 375 watt-hours per kilogram, but The cycleability is not good, but the circulation is good at low capacity. The main problem is how to solve the problem of a series of auxiliary materials under high volume expansion.

　　Finally, I will introduce solid metal lithium. Considering theoretical calculations, with the improvement of lithium batteries, there is another possibility to use lithium batteries, metal lithium batteries, and air batteries, including oxygen, water, carbon dioxide and other different batteries. System, from the calculation results just now, we can see that the green metallic lithium is relatively high, and the silicon anode is more powerful. If 2000 mA of silicon expands above 200, relatively speaking, the expansion of lithium is easier to solve. If the impact is greater High-energy electricity can also be used as a battery, but there are still some challenges in terms of mechanics and so on.

　　Metal lithium batteries have been developed for more than 50 years. Especially in the 1980s and 1990s, there were serious problems. There is currently no evidence that metal lithium batteries are safe. The main problem with using metal lithium batteries is that non-uniform deposition and precipitation are different from graphite and silicon. The second one is that the SEI film is unstable, so many people still hope to use solid state to solve this problem. A key point of the solid state is that it can be solved theoretically, so it has a lot of safety and benefits, as well as the benefits of cycle coefficient. In addition, it can also be used for internal series, such as polymers, and adding some liquid electrolytes. There are many companies in the world that have invested a lot, but from a practical point of view, the target of batteries with high energy density isIt has not been done before. The key issue here is how to solve the problem of the resistance of the positive electrode.

　　From the perspective of industrial development, the difference between solid-state batteries is the solid-state electrolyte. Metal lithium batteries may be used. Lithium batteries are also very powerful. This is actually in the development of the industry. Once the key materials of battery technology can be broken through, they can quickly enter the market. to the market, so we have put forward some roadmaps. Perhaps the battery pack will be available as soon as 2019. It is possible to test the water to the level of commercialization in 2020. Some all-solid-state ones are relatively slow. Real all-solid-state It may take longer, and batteries containing a little liquid will be faster because of the balance between energy density and safety.

　　South Korea: lithium 18650 battery capacity increased by 45%

　　Information from the online version of the academic magazine "Natural Energy" shows that a research team at South Korea's Ulsan Institute of Science and Technology (UNIST) recently developed a cathode material for secondary batteries that can increase the existing battery capacity by 45%, which is the cruising range of electric vehicles. At least 100 kilometers will be added to the current more than 200 kilometers.

　　The research group succeeded in increasing battery capacity by developing graphite-silicon composite materials that could replace graphite electrodes used in existing batteries. The new electrode is made by injecting 20-nanometer (billionths of a meter) silicon particles between graphite molecules. In addition to improving the cruising range, the new technology greatly shortens the charging and discharging time, and the battery charging and discharging speed is more than 30% faster than existing batteries.

　　The industry predicts that this type of new battery will be easier to mass produce and will have strong price competitiveness in the future.

　　Japan: Developed lithium battery that does not require cobalt

　　Information from Japan's Panasonic shows that Japan has developed new lithium battery materials that do not require the rare metal cobalt, and has trial-produced new lithium batteries.

　　A research team headed by Junichi Yoshida, a professor at Panasonic Kyoto University in Japan, developed a new organic material using lithium and carbon, and successfully trial-produced a new lithium battery that does not use cobalt as an electrode material. Test results show that batteries produced from new materials have the same capacity as lithium batteries using cobalt-containing materials as electrodes. This kind of lithium battery is expected to get rid of dependence on cobalt and greatly reduce production costs.

　　Another advantage of lithium batteries produced from this new material is longer battery life and lower degradation rate. Experimental results show that the lithium battery produced by this new material can be charged and discharged 100 times, but the battery capacity attenuation does not exceed 20%. Panasonic plans to improve this new material, hoping to increase the battery charge and discharge times to 500 to 1,000 times, and then commercialize it.

　　Technology Zone 220V AC to 12V DC reference design The current status of domestic lithium battery ternary material patent technology layout What is the echelon utilization of automotive power batteries? It will become a hot issue for a long time. New energy vehicle design cannot be ignored Cells and battery materials 2020 China’s automotive lithium 18650 battery pack shipments and forecasts in 2020

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