18650 lithium rechargeable battery

Application of 18650 lithium rechargeable battery interface film coating technology

The goal of reaching 300wh/kg for power 18650 lithium rechargeable battery cells has been achieved, but many difficulties need to be overcome in order to mass-produce and apply them. Recently, the major science and technology project of Beijing, "Development of 300Wh/kg-level ternary high-energy lithium-ion batteries for electric vehicles", led by CITIC Guoan Mengguli Power Technology Co., Ltd., has passed the acceptance of the expert group of Beijing Science and Technology Commission. It is understood that the project was approved by the Beijing Science and Technology Commission in January 2017, aiming to promote the research and development and promotion of high-energy power batteries for new energy vehicles. The single 18650 lithium rechargeable battery developed by the project team this time has a mass specific energy of 310.3Wh/kg, a volume specific energy of 659.3Wh/L, and a 18650 lithium rechargeable battery cycle life of 1,000 times. The project also developed high-energy-specific power lithium 18650 lithium rechargeable battery positive electrode materials, new high-safety, high-voltage-resistant electrolytes and other matching lithium 18650 lithium rechargeable battery materials, which have a positive effect on promoting the industrialization of high-energy-specific single batteries above 300Wh/kg. Prior to this, many 18650 lithium rechargeable battery companies including Guoxuan High-tech, Lishen 18650 lithium rechargeable battery, and CATL have also developed 300wh/kg high-energy-density 18650 lithium rechargeable battery samples. Specifically, almost all of the above-mentioned 18650 lithium rechargeable battery companies have adopted a high-nickel positive electrode + silicon-carbon negative electrode material system, matched and developed a new high-voltage electrolyte to solve problems such as internal 18650 lithium rechargeable battery expansion and low cycle life, and adopted a soft-pack technology route to develop a 300wh/kg single cell. In fact, under the guidance of subsidy policies, the energy density of domestic power batteries has risen rapidly in the past two years. The average specific energy of lithium iron phosphate 18650 lithium rechargeable battery monomers is 160wh/kg, and the system is about 140wh/kg; the specific energy of ternary 18650 lithium rechargeable battery monomers is about 220-240wh/kg, and the system energy density is about 140-160wh/kg. In 2019, the energy density of power batteries has a further upward trend. The mass-produced lithium iron phosphate 18650 lithium rechargeable battery is expected to reach 190wh/kg, and the system is 160wh/kg; the high-energy ternary 18650 lithium rechargeable battery monomer reaches 260wh/kg, and the system reaches more than 180wh/kg. Judging from the current rising trend of power 18650 lithium rechargeable battery energy density, power batteries with a monomer of 300wh/kg are expected to be industrialized in 2020, but the scale will not be too large. Since high-nickel batteries are still facing problems such as immature high-nickel materials, to-be-improved manufacturing processes, and imperfect industrial chain coordination, there is still a certain distance from large-scale mass production applications. At the same time, as the energy density of power batteries continues to increase, the safety and consistency reliability of batteries have become loose. If the energy density is increased at the expense of 18650 lithium rechargeable battery safety and cycle life, it may cause a series of safety accidents, which will in turn have a fatal blow to the new energy vehicle industry. Therefore, both OEMs and 18650 lithium rechargeable battery manufacturers are currently discussing the energy density level of power batteries in 2019, and it is generally believed that it is not appropriate to increase blindly. Instead, it is necessary to carry out diversified development and design on the basis of ensuring 18650 lithium rechargeable battery safety, give full play to the performance advantages of lithium iron phosphate and ternary batteries, and enhance the product competitiveness of electric vehicles. Let's take a look at the new technologies and major events in the lithium 18650 lithium rechargeable battery industry this week. 1. Disruptive innovation in the United States helps lithium 18650 lithium rechargeable battery technology break through. A report on the development of the global lithium 18650 lithium rechargeable battery industry released by the Fraunhofer Association for the Promotion of Applied Research in Germany specifically mentioned the disruptive innovation of the United States in the fields of research and development and industry, that is, the technology that achieves at least one performance parameter, such as energy density, which is significantly improved over existing lithium-ion batteries. Starting this year, several start-ups including SilaNanotechnologies, SolidPower, and QuantumScape will bring their batteries to the commercial market. Gene Berdichevsky, CEO of SilaNanotechnologies, said: "It took us eight years and about 35,000 material synthesizers to have something commercialized." SilaNanotechnologies previously received $70 million in Series D financing from world-renowned companies such as Siemens to continue to adjust 18650 lithium rechargeable battery technology and build its first commercial production line for silicon negative electrode batteries. One of Sila's current automotive partners is BMW. Comment: There is no shortage of innovative lithium 18650 lithium rechargeable battery technologies in the laboratory, such as lithium-air batteries, graphene batteries, and all-solid-state batteries. However, judging from the existing technology, the industrialization time of the above-mentioned new 18650 lithium rechargeable battery technology is still far away, mainly because the preparation technology of raw materials is still immature and the cost of 18650 lithium rechargeable battery manufacturing is difficult to reduce. Lithium-ion batteries are still a relatively mature and reliable solution. 2. Power batteries will be included in the "three guarantees" of electric vehicles. On March 14, the "Regulations on the Responsibility for Repair, Replacement and Return of Household Automobile Products (Draft for Comments)" (hereinafter referred to as the "Three Guarantees for Automobiles" revised draft) was published on the Ministry of Justice's China Government Legal Information Network and the State Administration for Market Regulation website at the same time, soliciting public opinions. Any unit or individual can feedback opinions and suggestions to the State Administration for Market Regulation through the Internet, e-mail, letter, etc. before April 13. The revised draft of the "Three Guarantees for Automobiles" supplements and improves the "Three Guarantees" responsibilities of household electric vehicles: 1) The power 18650 lithium rechargeable battery and driving motor are included in the scope of free replacement of the assembly as the main systems of household automobiles on par with the engine and transmission; 2) The repeated quality problems of the power 18650 lithium rechargeable battery, driving motor and their main parts are included in the terms of return and replacement of vehicles; 3) The manufacturer is required to clearly indicate the limit of power 18650 lithium rechargeable battery discharge capacity attenuation and the corresponding test method on the "Three Guarantees" certificate; the failure of power 18650 lithium rechargeable battery fire in household electric vehicles is supplemented in the terms of return and replacement of vehicles. 4) The power 18650 lithium rechargeable battery and driving motor in hybrid electric vehicles are subject to this regulation. Other new energy vehicles such as hydrogen energy have not yet been put on the market in batches, and this revision does not involve relevant content for the time being. At the same time, the revised draft of the "Three Guarantees for Automobiles" further strengthens the protection of consumers' legitimate rights and interests. In response to the current problem of high compensation fees paid by consumers for returning and replacing vehicles, through comparative research and calculation of similar foreign regulations and calculations, the compensation coefficient n is adjusted from 0.5% to 0.8% in the current "Three Guarantees for Automobiles" to an upper limit of no more than 0.7% and a lower limit. Taking into account that the current "three guarantees" start date is calculated from the date of issuing the purchase invoice, and there are situations in actual sales activities where the product is delivered to consumers later than the date of invoice issuance, the provision of calculating the "three guarantees" period from the actual delivery date is added. Comment: At present, due to a series of immature and imperfect reasons such as lithium 18650 lithium rechargeable battery technology, three-electric system and charging network, electric vehicles have a series of quality problems, and the quality problems of power batteries are particularly prominent. The inclusion of power batteries in the scope of the "three guarantees" for electric vehicles provides a guarantee for consumers, and also puts a hoop on the OEM and 18650 lithium rechargeable battery factories to avoid infringement of consumers' rights and interests. 3. CATL uses interface film coating to solve silicon-carbon hard injuries. Silicon-based materials are regarded as the next generation of materials to replace graphite. According to calculations, the specific capacity of silicon-based negative electrode materials can reach 10 times that of graphite negative electrodes, and are regarded as the "substitute" of the latter. The application of traditional silicon-based materials mainly adopts carbon coating technology, that is, a layer of carbon material is compounded on the surface of silicon materials. However, due to the volume change of silicon materials during charging and discharging, the carbon material coated on the surface will break and fall off after multiple cycles, and the protective effect on silicon materials will be greatly weakened, resulting in poor 18650 lithium rechargeable battery cycle performance. Wu Kai, chief scientist of CATL, introduced that CATL abandoned the traditional carbon coating technology and turned to the research of artificial electrolyte interface membrane coating technology. It took more than two years to apply this technology to the preparation of silicon materials and develop a new type of artificial electrolyte interface membrane coated silicon-carbon composite negative electrode material with independent intellectual property rights, and its cycle performance is significantly better than foreign products. "Compared with carbon materials, the artificial electrolyte interface membrane has a stronger binding force with silicon materials, better elasticity, and is not easy to break or pulverize, which plays a good protective role on silicon materials. Therefore, it can greatly improve the interface stability of silicon materials in the cycle, thereby improving the cycle life of the 18650 lithium rechargeable battery." Comment: Based on this technology, CATL has taken the lead in developing 18650 lithium rechargeable battery samples with a specific energy (mass energy density) of 304Wh/kg, which shows that the artificial electrolyte interface membrane coating technology it uses has solved the expansion problem of silicon-carbon materials to a certain extent. This move will promote the full mastery of core technologies in many aspects such as material modification and precursor synthesis in China, realize the localization of key material technologies, and provide important guarantees for the gradual commercialization and promotion of silicon-carbon composite negative electrodes.

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