Lithium-ion battery overview
Lithium-ion battery is a secondary battery. Its working principle is: during the charge and discharge process, lithium ions are in a state of movement from positive electrode → negative electrode → positive electrode. During the charge and discharge process, lithium ions are intercalated and deintercalated back and forth between the two electrodes. That is, during charging, lithium ions are deintercalated from the positive electrode and intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state. The opposite is true during discharge.
Lithium-ion batteries are complex systems consisting of positive electrode materials, negative electrode materials, electrolytes, separators, conductive agents, binders and packaging materials. Due to their high operating voltage, high specific energy density, long cycle life and wide operating temperature range, lithium-ion batteries have been widely used in new energy vehicles, energy storage and consumer electronics.
The lithium-ion battery electrolyte is composed of high-purity solvents, electrolytes and additives according to a certain formula ratio. Its preparation process includes the synthesis, preparation and purification of solvents, electrolytes and additives, the design and development of electrolyte formulas and the production and preparation of electrolytes. The synthesis, preparation and purification of solvents, electrolytes and additives are the material basis for the design of electrolyte formulas; the design and development of electrolyte formulas is the technical prerequisite for the preparation of electrolytes. The process technology of the production and preparation of electrolytes is mainly reflected in improving the production efficiency and product quality of electrolytes. It mainly includes processes such as organic solvent impurity removal, additives, electrolyte preparation and electrolyte filling, as follows:
1. Organic solvent removal
Main raw materials: organic solvents (dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, etc.)
Main equipment: horizontal storage tanks, pumps, condensers, vertical storage tanks, impurity removal towers
The main process technology is impurity removal technology, which can reduce the solvent moisture to less than 10ppm.
2. Additive removal
The main raw materials are additives (vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate and lithium bis(trifluoromethylsulfonyl)imide, etc.)
Main equipment: vertical storage tank, impurity removal tower
The main process impurity removal technology can reduce the moisture content of additives to less than 50ppm and increase the purity of raw materials to more than 99.9%.
3. Electrolyte preparation
Main raw materials: lithium salt, organic solvent, additives
Main equipment: mixing kettle, vertical storage tank, weighing system, module, industrial automation control system
The main process mixing technology can realize the automated feeding and production of electrolyte, effectively reducing the introduction of environmental moisture and impurities.
4. Electrolyte filling
Main raw materialsElectrolyteFinished products
Main equipment: packaging barrel, automatic filling machine
The main process is automatic filling technology, and the filling accuracy can be controlled within ±0.05kg.
Overview of Lithium-ion Battery Electrolyte
Lithium-ion battery electrolyte is the carrier of ion transmission in the battery. It plays the role of conducting ions between the positive and negative electrodes of the lithium battery and is one of the main raw materials of lithium-ion batteries. Lithium-ion battery electrolyte is made of electrolyte, high-purity organic solvent, necessary additives and other materials under certain conditions and in a certain proportion.
Since the electrolyte continuously interacts with positive electrode materials, negative electrode materials, separators, binders and other materials in the battery, it plays an important role in battery performance. The electrolyte is crucial to improving the initial efficiency, cycle life, power performance, storage performance and safety performance of the battery. Changes, optimizations and upgrades to any raw materials such as positive electrode materials, negative electrode materials, separators, etc. require electrolyte conduction and interaction to the entire battery system. With the improvement of performance requirements for power batteries, energy storage batteries and high-end digital batteries, research on the matching of electrolytes with material systems, battery design and application scenarios will become increasingly important.
The main features of lithium-ion battery electrolyte are as follows:
① Wide voltage resistance range, less decomposition in the range of 2.5V~5V.
② Good chemical stability, with little reaction and dissolution with positive and negative electrode materials, separators, binders, conductive agents, current collectors and conductive glues.
③ Low viscosity, high ion conductivity, weak solvation ability for lithium ions, and low resistance to ion migration.
④The liquid range is wide, with less crystallization and volatilization in the range of -20℃～70℃.
⑤Environmentally friendly and low cost.
Lithium-ion battery electrolyte is mainly composed of three parts: lithium salt, organic solvent and additives. According to the quality, organic solvent usually accounts for 80-90%, lithium salt accounts for 10-15%, and additives account for about 5%. The specific composition and classification of lithium-ion battery electrolyte are as follows:
Lithium salts
Ensure that lithium-ion batteries have sufficient lithium ions to travel back and forth between the positive and negative electrodes during the charge and discharge cycle, thereby achieving reversible circulation
(1) Small degree of association, easy to dissolve in organic solvents, ensuring high ionic conductivity of the electrolyte;
(2) Having a reasonable electrochemical window;
(3) Good chemical stability, no harmful side reactions with electrode materials, organic solvents, diaphragms, etc.;
(4) The preparation process is simple and the cost is low;
(5) Relatively good environmental friendliness.
The role of lithium salts is to ensure that lithium-ion batteries have sufficient lithium ions to travel back and forth between the positive and negative electrodes during the charge and discharge cycle, thereby achieving reversible cycles. At present, the commonly used lithium salts used in lithium-ion battery electrolytes are mainly lithium hexafluorophosphate (LiPF6). Lithium hexafluorophosphate has outstanding advantages such as suitable solubility and high ionic conductivity, aluminum foil passivation ability, and easy formation of SEI (Solid Electrolyte Interphase, i.e. solid electrolyte interface membrane). However, lithium hexafluorophosphate also has certain shortcomings. Currently, companies in the industry are actively trying new lithium salts to optimize the performance of lithium-ion battery electrolytes. At present, the main advantages and disadvantages of common lithium salts for lithium-ion battery electrolytes are compared as follows:
Organic solvents
As a carrier of lithium ions, it is the main part of the electrolyte
(1) High dielectric constant and strong solubility for lithium salts;
(2) Low melting point, high boiling point, and remains liquid over a wide temperature range;
(3) Low viscosity, which facilitates the transmission of lithium ions;
(4) Good chemical stability, does not destroy the positive and negative electrode structure or dissolve the positive and negative electrode materials;
(5) Good safety and low cost;
(6) Relatively good environmental friendliness.
Organic solvents, as carriers of lithium ions, are the main part of the electrolyte. According to their structures, they are mainly divided into chain carbonate organic solvents and cyclic carbonate organic solvents. Chain carbonate organic solvents mainly include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), while cyclic carbonate organic solvents mainly include ethylene carbonate (EC) and propylene carbonate (PC).
Additive
Small amounts of functional substances that improve the stability of the electrolyte and enhance the electrochemical performance of the battery can significantly improve key properties of lithium-ion batteries, such as gas generation, cycling stability, low-temperature charge and discharge performance, and safety, despite their minimal usage.
(1) High solubility in organic solvents;
(2) A small amount of addition can significantly improve one or several properties;
(3) Do not produce harmful side reactions with other components of the battery, affecting battery performance;
(4) Relatively good environmental friendliness.
Additives are small amounts of functional substances introduced to improve the stability of electrolytes and enhance the electrochemical performance of batteries. Based on their functions, they can be categorized into film-forming additives, overcharge protection additives, flame retardant additives, electrolyte stabilizers, and more. Despite their minimal usage, these additives can significantly improve key properties of lithium-ion batteries, such as gas generation, cycling stability, low-temperature charge and discharge performance, and safety. They represent one of the core areas showcasing the competitive strength of electrolyte and raw material manufacturers.
Canrd Brief Introduce
Canrd use high battery R&D technology(core members are from CATL) and strong Chinese supply chain to help many foreign companies with fast R&D. We provide lab materials, electrodes, custom dry cells, material evaluation, perfomance and test, coin/pouch/cylindrical cell equipment line, and other R&D services.
Email： contact@canrd.com Phone/Wechat/WhatsApp： +86 19867737979
Canrd Official Web Canrd Company Vedio Canrd Company profile
Website : www.canrud.com
Comments
Post a Comment