Author ：Iflowpower – Portable Power Station Supplier
Lithium-ion battery is the fastest secondary battery after cadmium and hydrogen-nickel battery. Users used should all know that the lithium battery will reduce the capacity after using a period of time. This article summarizes and analyzes the possible reasons for the working principle of lithium ion batteries, and the capacity attenuation, I hope to help you.
Lithium ion battery work principle Lithium ion battery is a secondary battery (rechargeable battery), which mainly relies on lithium ions to move between positive and negative electrodes. During the charge and discharge process, Li + is inserted and deserted between the two electrodes: When charging, Li + is escaled from the positive electrode, and the electrolyte is embedded in the negative electrode, the negative pole is in a lithium state; the discharge is reverse. Lithium battery discharge is based on chemical oxidation reactions.
When discharge is discharged, it is when we use the battery to consume power, its positive electrode will embed lithium ions, negative electrode lithium ions. When charging is, the opposite is. He has a certain voltage to form a certain amount of voltage so that the battery generates electricity.
During each charge and discharge cycle, lithium ion (Li) acts as a handling carrier of the electric energy, the movement from the positive electrode → negative electrode → the positive electrode from the positive and negative electrode materials, and converts chemical and electrical energy to each other. Implementing the transfer of charge, this is the basic principle of "lithium ion battery". Due to the electrolyte, the isolation film, etc.
is an electron insulator, so this circulation is not moved back and forth between the positive and negative poles, and they only participate in the chemical reaction of the electrode. Causes of lithium battery capacity attenuation is the fastest secondary battery after cadmium battery and hydrogen nickel batteries. The application of lithium-ion batteries is largely dependent on its stability of the charge and discharge cycle, and other secondary batteries , Lithium-ion batteries are inevitable during cycle.
1 Composition of components. The transformation of components can easily lead to changes in phase transfer and physical phase structure. The electrode material phase transition can cause changes in the lattice parameters and lattice mismatch, thereby generating induced stress causes the crushing of the grain, and causes crack propagation, resulting in mechanical damage to the structure of the material, thereby causing electrochemical performance attenuation.
2. The negative electrode material commonly used in the negative electrode material structure is carbon material, lithium titanate, etc., this paper analyzes the typical negative graphite.
The attenuation of lithium battery capacity occurs for the first time, in this stage, SEI is formed on the surface of the negative electrode, consuming part of lithium ions. As the lithium battery is used, the change in graphite structure can also cause a decrease in battery capacity. Although the morphology of graphite is maintained, the half of its (002) crystal surface is large, resulting in a small grain size in the C-axis direction, and the change in the crystal structure causes cracks in the carbon material, which in turn disrupts the surface of the negative surface.
The film and promotes the repair of the SEI film, the excessive growth of the SEI film consumes active lithium, thus causing the non-reversible capacity attenuation of lithium batteries. 3. The electrolyte mainly includes three parts of solvent, electrolyte and additives.
The decomposition of the solvent, the decomposition of electrolytes can cause lithium battery capacity loss. The decomposition and side reaction of the electrolyte is the main factor of lithium battery capacity attenuation. Regardless of the positive and negative electrode material, which process, with the lithium battery circulation, the decomposition of the electrolyte and the interface between the normal and negative electrode material The reaction can cause the capacity attenuation.
4, the positive precision reaction is too low when the positive electrode active relative to the negative electrode active is too low, it is easy to charge. The lithium battery positive transition caused capacity loss mainly due to the generation of electrochemical inert substances (such as CO3O4, MN2O3, etc.), destroying the capacity balance between electrodes, and its capacity loss is irreversible.
5, electrode instability in the positive electrode active material instability during charging, reacting with electrolyte reactions. It affects the unstable factors of the positive electrode material, the structural defect of the positive electrode material, the carbon black content, too high of the charging potential, where the positive electrode material structure defect is the weight in the factors. As the available area of the lithium battery is reduced, the filling energy is lowered, and the charging time is gradually shortened.
In most cases, the capacity of lithium battery is linearly decay due to cycle cycle and aging. 6. The storage temperature charge and discharge cycle is not the only reason for lithium battery capacity attenuation, and the lithium battery in high temperature can also cause capacity attenuation.
A full-charged lithium battery will cause 35% capacity loss in the case of 40 ° C (104 ° F) for one year without being used. Super fast charge is also harmful to the battery, which will reduce battery life, which is very obvious for monomer lithium batteries. Lithium battery pack is higher than energy, but it is particularly subtle due to differences in cell batteries.
Lithium battery needs often calculates its capacity attenuation and final life. Capacity attenuation to 80% requires replacement of battery packs, and the ultimate life limit of lithium battery pack should change according to the application of the application, and the user's preferences and the company's guarantee.
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