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Detailed analysis of the structure and working principle of lithium-ion batteries

by:Vglory      2021-04-11
Detailed analysis of the structure and working principle of lithium-ion batteries Lithium-ion batteries are divided into lithium-ion batteries and lithium-ion batteries. Both mobile phones and laptops use lithium-ion batteries. Real lithium-ion batteries are very dangerous and are rarely used in everyday electronic products. Lithium-ion battery is a rechargeable battery whose working principle is that lithium ions move between the positive and negative electrodes. During charging and discharging, Li+ intercalates and deintercalates back and forth between the two electrodes. In rechargeable batteries, lithium ions are extracted from the positive electrode and inserted into the negative electrode through the electrolyte. The negative electrode is in a state rich in lithium. When unloading, the situation is just the opposite. Generally speaking, batteries with lithium as the electrode are representative of modern high-performance batteries. How does a lithium-ion battery work? A lithium-ion battery uses carbon material as the negative electrode and a lithium-containing compound as the positive electrode. There is no metal lithium, only lithium ions. This is a lithium ion battery. Lithium ion battery refers to a battery with lithium ion intercalation compound as the cathode material. The charging and discharging process of lithium ion batteries is the process of intercalation and deintercalation of lithium ions. The embedding and de-embedding of lithium ions is accompanied by the embedding and de-embedding of lithium ions and equivalent electrons (traditionally, the positive electrode is represented by embedding or de-embedding, and the negative electrode is represented by embedding or de-embedding). During the charging and discharging process, lithium ions are inserted/de-intercalated and inserted/de-intercalated back and forth between the positive electrode and the negative electrode, which is commonly known as the rocking chair battery. When the battery is charged, lithium ions are formed at the positive electrode of the battery, and the lithium ions reach the negative electrode through the electrolyte. Negative carbon has a layered structure with many micropores. Lithium ions reaching the negative electrode are inserted into the micropores of the carbon layer. The more lithium ions are inserted, the greater the charging capacity. Similarly, when the battery is discharged (the process we use the battery), the lithium ions embedded in the carbon of the negative electrode will come out and return to the positive electrode. The more lithium ions in the cathode, the greater the discharge capacity. The charging current of lithium-ion batteries is generally set between 0.2c and 1C. The higher the current, the faster the charging and the higher the battery heat. More importantly, if the battery is charged with too much current, the capacity is not enough, because the electrochemical reaction inside the battery takes time. Just like pouring beer, pouring too fast will cause foam and dissatisfaction. Regarding the battery, normal use is the process of discharging. Pay attention to the following points when discharging lithium-ion batteries: First, the discharge current should not be too large, otherwise it will cause permanent damage due to the internal heat of the battery. On mobile phones, this is no problem and cannot be considered. Second, don't over-discharge! Lithium-ion batteries are most afraid of over-discharge. Once the discharge voltage is lower than 2.7V, the battery may be scrapped. Fortunately, a protection circuit has been installed inside the mobile phone battery. The voltage is not low enough to damage the battery. The protection circuit will function and stop discharging. It can be seen from the figure that the larger the discharge current of the battery, the smaller the discharge capacity and the faster the voltage drop. Lithium-ion battery structure positive electrode: active material, conductive agent, solvent, binder, matrix. When the battery is discharged, an electrode that receives electrons from an external circuit, and a reduction reaction occurs. It is usually a high-potential electrode. Lithium cobalt oxide lithium ion battery, lithium manganese oxide lithium electrode. Negative electrode: active material (graphite, MCMB, CMS), binder, solvent, matrix. When the battery is discharged, the electrodes that carry electrons to the external circuit are oxidized. It is usually a low-potential electrode, which is the graphite electrode in lithium-ion batteries. The diaphragm membrane is a device that is placed between the two poles as a barrier between the electrodes to prevent the direct contact between the active materials of the two poles from causing a short circuit in the battery. But the film still needs to be able to allow charged ions to pass through to form a channel. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: Why do lithium-ion battery packs have broad application prospects?
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