Portable electronics use batteries as a power source. With the rapid development of portable products, the use of various batteries has increased significantly, and many new batteries have been developed. In addition to the familiar high-performance alkaline batteries, rechargeable nickel-cadmium batteries, and nickel-metal hydride batteries, there are also lithium batteries developed in recent years. Here mainly introduces the basic knowledge about lithium batteries. This includes its large-capacity lithium batteries, including its characteristics, main parameters, meaning of models, scope of application, and precautions for use.
Energy density of various battery types
Lithium is a metal element. Its chemical symbol is Li (its English name is lithium). It is a silver-white, very soft, and chemically active metal. It is the lightest metal. In addition to its application in the atomic energy industry, it can manufacture special alloys, special glass (fluorescent screen glass for televisions), and lithium batteries. It is used as the anode of a battery in a lithium battery.
Lithium batteries are also divided into two categories: non-rechargeable and rechargeable. A non-rechargeable battery is called a disposable battery. It can only convert chemical energy into electrical energy at one time, and cannot restore electrical energy back to chemical energy (or has extremely poor reduction performance). The rechargeable battery is called a secondary battery (also called a storage battery). It can convert electric energy into chemical energy and store it. When in use, it converts chemical energy into electric energy. It is reversible, such as the main characteristics of electric chemical lithium batteries.
The positive electrode material of a lithium-ion battery is usually composed of an active compound of lithium, and the negative electrode is carbon with a special molecular structure. The main component of a common positive electrode material is LiCoO2. During charging, the potential applied to the battery's poles forces the positive electrode compound to release lithium ions, which are embedded in the carbon of the negative electrode molecules arranged in a sheet structure. During discharge, lithium ions are precipitated from the carbon of the sheet structure and recombined with the compounds of the positive electrode. The movement of lithium ions has produced a large-capacity lithium battery.
Although the chemical reaction principle is very simple, in actual industrial production, there are many more practical issues to be considered: the material of the positive electrode needs additives to maintain the activity of multiple charge and discharge, and the material of the negative electrode needs to be designed at the molecular structure level to Hold more lithium ions; in addition to the electrolyte filled between the positive and negative electrodes, it needs to have good conductivity and reduce the internal resistance of the battery.
Although lithium-ion batteries rarely have the memory effect of nickel-cadmium batteries, the principle of memory effect is crystallization, and almost no such reaction occurs in lithium batteries. However, the capacity of lithium-ion batteries will still decrease after multiple charging and discharging. The reasons are complex and diverse. It is mainly the change of the positive and negative electrode materials. From the molecular level, the hole structure that contains lithium ions on the positive and negative electrodes will gradually collapse and block. From a chemical point of view, the positive and negative electrode materials are activated and passivated. Other compounds. Physically, the positive electrode material gradually peels off, etc. In short, the number of lithium ions in the battery that can be freely moved during the charge and discharge process is eventually reduced.