The internal resistance of cylindrical lithium-ion batteries changes significantly after training (14,500). The internal resistance after training is tens or even hundreds of milliohms higher than before. In some cases, the internal resistance after training is inversely lower than before. training? What are the reasons? THANKS. This is not a manufacturing problem. Most batteries in the same batch are normal. Charge and discharge at 0.2C, lithium iron phosphate material
Is polyvinylidene fluoride soluble in organic solvents
Lithium battery is a " lithium-ion battery" (lithium-ion battery, LIB for short)); lithium polymer batteries, most of which are “lithium-ion polymer/polymer batteries” (lithium-ion polymer battery, called LPB).
LIB and LPB use similar chemical materials and electrochemical properties. The princeThe main difference is that certain colloidal substances are used to help the battery plate adapt or absorb the electrolyte, thereby reducing the amount of liquid electrolyte used. Battery packaging can change from metal shell to aluminum foil packaging.
Electrode materials and battery structure
1. Cathode materials
(1) Lithium cathode materials: mainly LiCoO2, LiNiO2 and LiMnO2.
(2) Polymeric cathode materials: mainly heterocyclic polymers such as polypyrrole (Ppy), polythiophene (PTh) and their derivatives.
2. Negative electrode materials
(1) Carbon materials: mainly natural graphite, coke and carbon fiber, etc. At present, more advanced negative electrode layered graphite particles have adopted nanocarbon. .
(2) Tin oxide negative electrode material: usedez a mixture of SnO, SiO2 and a small amount of Al2O3, B2O3, P2O3, etc., and gradually heat it to 1000°C or slightly higher temperature for 12 hours in an argon atmosphere. Mixed oxides containing divalent tin can be produced.
3. Structure of the positive electrode
LiCoO2 (lithium cobalt oxide) + conductive agent (acetylene black) + adhesive (PVDF) + current collector (foil aluminum or aluminum strip) positive electrode< /p>
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4. Negative electrode structure
Graphite + conductive agent (acetylene black) + thickener ( CMC) + binder (SBR) + current collector (copper foil or nickel strip) negative electrode The actual ingredients and production process are quite detailed and complex.
Polyvinylidene fluorideis soluble in organic solvents. Polyvinylidene fluoride is a semi-crystalline fluoropolymer soluble in polar organic solvents. The lithium battery electrode binder material prepared therewith has good chemical stability, good temperature stability and good electrolyte affinity.
Use of polyvinylidene fluoride
However, the binder must remain in a special environment for a long time and must be able to withstand the influence of various environments. Currently, PVDF is mainly used as a positive electrode binder and lithium battery in the market. The separator is used as a separator between the positive and negative electrodes of the battery, to prevent positive and negative active materials from contacting each other and causing a short circuit. During the electrochemical reaction, the necessary electrolyte is maintained to form a channel. movement of ions.
In order to increase the specific surface of the electrode and reduce the resistance, theThe active material of the electrode consists mainly of a powder material, so a binder is required for bonding. Its main function is to firmly. Bind the active electrode material and the conductive agent. On the current collector, it prevents active material particles from falling due to swelling during battery charging and discharging, and reduces the impedance between the current collector and the electrode material.