703048 polymer battery.Research progress on functional additives for lithium-ion battery electrolytes

Research on lithium-ion battery electrolytes and functional additives has become a focus of current lithium-ion battery research. The properties of organic solvents and electrolytes directly affect the performance of lithium-ion batteries. Among them, the safety performance of lithium-ion batteries has received more and more attention, and seeking additives to improve the safety performance of lithium-ion batteries has become a top priority in our research. At present, research on functional additives for lithium-ion battery electrolytes mainly focuses on the following aspects: improving the stability of the SEI film. The quality of the SEI film formed by the carbon negative electrode plays an important role in improving the cycle life of the lithium-ion battery. It is very necessary to select appropriate additives to improve the chemical composition and interface properties of the negative SEI film and form a stable SEI film between the electrode and the electrolyte. To improve the conductivity of the electrolyte, the additives vinylene carbonate (VC) and fluoroethylene carbonate (FEC) were studied using electrochemical methods and spectroscopy methods. It was found that VC and FEC can improve the cycle performance of the battery, especially at high temperatures. When the cycle performance is high, the irreversible capacity is reduced. The main reason is that VC can polymerize on the surface of graphite to form a polyalkyl lithium carbonate film, thereby inhibiting the reduction of solvent and salt anions, thus forming an SEI film on the surface of the graphite anode. Improving the safety performance of batteries Lithium-ion batteries themselves have many potential safety hazards. Protection methods include: mechanical circuit cutting method, electronic circuit method, diaphragm self-melting closing method, etc. These methods improve the safety of lithium-ion batteries to a certain extent. Adding additives to the electrolyte is also a simple and effective way to improve the safety of lithium-ion batteries. 1. Additives that reduce the flammability of solvents. The reason why the solvent in the electrolyte burns is because it itself undergoes a chain reaction. If additives that inhibit the occurrence of these chain reactions can be found, the safety of lithium-ion batteries will be effectively improved. sex. 2 Overcharge additives: Overcharge protection is achieved by adding additives, which is extremely important for simplifying the battery manufacturing process and reducing battery production costs. At present, there are two main types of additives to solve the overcharging problem: ① Oxidation/reduction couple additives ② Polymer monomer additives. 3 Additives to improve the conductivity of the electrolyte 4 Additives to control the acid and water content in the electrolyte The water and acid (HF) present in the organic electrolyte can interact with the lithium salt in the electrolyte to form lithium fluoride and other deposits on the surface of the negative electrode , plays an important role in the formation of SEI film; too high content of water and acid (HF) will not only cause the decomposition of LiPF6, but also destroy the SEI film. 5 Sulfonate additives In view of the instability of LiMn2O4 in the lithium-ion battery electrolyte, stabilizing additives are usually added to the electrolyte to improve the thermal stability and cycle life of the battery. The solid electrolyte interphase interface (SEI) film is of great significance in lithium-ion batteries. The quality of the SEI film plays an important role in improving the cycle life of lithium-ion batteries. 6. Lithium salt additive Lithium bisoxaloborate (LiBOB) is a new type of organic borate. 7LiPF6 stabilizer LiPF6 is currently the most commonly used lithium salt in commercial lithium-ion batteries. However, LiPF6 has poor thermal stability, and the following decomposition reaction may occur even at room temperature: Gaseous PF5 has strong Lewis acidity, which will interact with the lone electron pair on the oxygen atom in the solvent molecule to cause the solvent to decompose. LiPF6 is very sensitive to moisture, and will react as follows when encountering trace amounts of water. HF will corrode the cathode material, especially LiMn2O4. Conclusion In summary, research on functional additives plays a very important role in improving battery performance, because the addition of improved new additives can greatly make up for the deficiencies in the compatibility of electrolyte and positive and negative electrode materials. In power lithium Battery performance pursues characteristics such as longer battery life and longer life. New functional additives are also one of the keys to lithium battery material research.

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