丨Source: Network
In recent years, lithium-ion batteries have developed rapidly, and their applications have developed from mobile phones and laptops to electric vehicles, energy reserve systems and other fields. The rapid development of lithium batteries has put forward new requirements for large-scale technology, high energy isal density, rapid charging and discharging, cycle stability and environmental protection and safety. Adhesives are inactive substances in positive and negative electrode materials and have a great impact on the overall performance of lithium-ion batteries. The amount of adhesive used is usually 2-5% of the total battery material, and the cost accounts for less than 1% of the battery manufacturing cost, but it can improve the battery performance by 5-10%, which is one of the necessary materials for lithium-ion battery production. Its main function is to connect the electrode active substance, conductive agent and electrode collector fluid, so that the electrode active substance, conductive agent and collector have an overall connection, thereby reducing the impedance of the electrode.
Lithium-ion battery modules
Characteristics of water-based adhesives for lithium-ion batteries
The adhesive requirements in lithium-ion batteries are different from ordinary adhesives, mainly including: (1) good electrochemical stability; (2) resistance to electrolyte corrosion; (3) good solubility in a certain solvent; (4) good adhesion performance to metals; (5) good flexibility. At present, the main adhesive used is a solvent-based PVDF (polyvinylidene fluoride) adhesive with NMP (N-methylpyrrolidone) as the dispersant. PVDF adhesive in battery applications has been exposed to a high modulus of elasticity (1-4GPa) so that the pole piece toughness is insufficient, there is a certain degree of swelling in the electrolyte used, for particles and electrons have insulation, will increase the battery internal resistance and other defects, in addition, NMP dispersant is expensive, high volatility temperature, large dosage, high recovery cost, harmful to human health. Therefore, the selection of water-based adhesives with water as the dispersion medium in lithium-ion anode materials has become the mainstream direction.
The development of water-based adhesives for lithium-ion batteries in China
At present, the main water-based adhesives are SBR (styrene-butadiene latex), CMC (hydroxymethyl cellulose), PTFE (polytetrafluoroethylene emulsion), PAA (polyacrylate emulsion) and PUA (waterborne polyurethane). According to the survey, the overall demand for water-based adhesives in 2017 is about 2,000 tons, and it is expected to be 4,000-5,000 tons in 2020, and the demand increase will mainly come from the power battery field. At present, the high-end water-based adhesive market for power batteries has formed a highly concentrated situation, almost mainly occupied by Japanese companies such as Ruiweng, JSR, and Shuangri, while the more well-known domestic water-based adhesive brand is Chengdu Indile Company. The high-end price of water-based adhesive is 300-400 yuan / kg, and the low end is only 20-30 yuan / kg, and the price difference is more than ten times. The fundamental reason for the formation of the gap between domestic water-based adhesives and Japanese enterprises is that it started late, the basic research and development strength is weak, and it is also related to the ecological environment of the entire domestic industrial chain. Domestic supporting raw materials and equipment need to be improved, and domestically purchased raw materials need to be processed and purified before they can be used. The raw materials purchased in Japan are of high purity and are difficult to purchase in the domestic market.
Lithium-ion battery modules for electric vehicles
The expanded application of water-based adhesives in positive and negative electrode materials is an inevitable trend for lithium-ion batteries to achieve high-quality and low-cost and green pollution-free production. With the large-scale production of lithium-ion batteries in the mainland, as one of the important auxiliary materials, a large number of raw materials for lithium-ion batteries with water-based adhesives will begin to gradually localize, which will enable domestic enterprises to have the natural advantage of meeting the customized needs of downstream battery enterprises (foreign companies usually reflect slowly). The current research has fully shown that it has a good role in reducing the interfacial impedance between the electrode / electrolyte and the internal resistance of the battery, improving and improving the electrochemical properties, and the selection, modification and performance improvement of waterborne polymer adhesive materials with different structures and properties in the future, the study of the mechanism of action and the application process method of the adhesive have to be systematically deepened, and the market prospect of water-based adhesives for lithium-ion batteries is very bright.
(Disclaimer: We respect originality, but also pay attention to sharing, thank each author for their hard work and creation.) The copyright of this article belongs to the author of the article, which only represents the views of the author, does not represent the views of this public account, and is for learning and reference only. This article is not for commercial use, only for learning and communication purposes, such as the content, pictures, audio, video, etc. in the text there are third parties' prior intellectual property rights, please contact us in time to delete, thank you! ）