A simple analysis of lithium batteries

Lithium battery is a kind of rechargeable battery, it mainly depends on the movement of lithium ions between the positive electrode and the negative electrode to work. During the charging and discharging process, Li+ intercalates and deintercalates back and forth between the two electrodes: when recharging the battery, Li+ deintercalates from the positive electrode and inserts into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. Batteries that generally use materials containing lithium as electrodes are representative of modern high-performance batteries. Lithium batteries use carbon material as the negative electrode and lithium-containing compounds as the positive electrode. There is no metal lithium, only lithium ions, which is a lithium battery. Lithium battery refers to the general term for batteries with lithium ion intercalation compound as the cathode material. The charging and discharging process of lithium batteries is the process of intercalation and deintercalation of lithium ions. In the process of intercalation and deintercalation of lithium ions, it is accompanied by the intercalation and deintercalation of electrons equivalent to that of lithium ions (the positive electrode is usually represented by intercalation or deintercalation, and the negative electrode is denoted by insertion or deintercalation). During the charging and discharging process, lithium ions are intercalated/deintercalated and intercalated/deintercalated back and forth between the positive and negative electrodes, which is vividly called the rocking chair battery. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon as the negative electrode has a layered structure. It has many micropores. The lithium ions reaching the negative electrode are embedded in the micropores of the carbon layer. The more lithium ions are inserted, the higher the charging capacity. Similarly, when the battery is discharged (that is, the process we use the battery), the lithium ions embedded in the carbon layer of the negative electrode are released and move back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity. Generally, the charging current of lithium batteries is set between 0.2C and 1C. The larger the current, the faster the charging and the greater the battery heat. Moreover, charging with an excessive current will result in insufficient capacity because the electrochemical reaction inside the battery takes time. It's the same as pouring beer. If you pour it too fast, foam will appear, but you will be dissatisfied. For batteries, normal use is the process of discharging. There are several points to pay attention to when discharging lithium batteries: First, the discharge current should not be too large. Excessive current will cause the internal heating of the battery, which may cause permanent damage. On mobile phones, this is not a problem, so you don't need to consider it. Second, it must not be over-discharged! Lithium 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 battery of the mobile phone, and the voltage is not low enough to damage the battery, the protection circuit will be used to stop the discharge. It can be seen from the figure that the larger the battery discharge current, the smaller the discharge capacity and the faster the voltage drop. Lithium battery structure positive electrode: active material, conductive agent, solvent, binder, matrix. An electrode that obtains electrons from an external circuit when the battery is discharged. At this time, the electrode undergoes a reduction reaction. It is usually an electrode with a high potential. Lithium cobalt oxide, lithium manganate electrode, etc. in lithium batteries. Negative electrode: active material (graphite, MCMB, CMS), binder, solvent, matrix. An electrode that transports electrons to an external circuit when the battery is discharged. At this time, the electrode undergoes an oxidation reaction. Usually the electrode with low potential, graphite electrode in lithium battery. Diaphragm Diaphragm is placed between the two poles as a device to isolate the electrodes, so as to prevent the active material on the two poles from directly contacting and causing short circuits inside the battery. But the diaphragm still needs to allow charged ions to pass through in order to form a pathway. Disclaimer: The articles published on this website are all from the Internet. 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