Portable electronic devices are powered by batteries. With the rapid development of portable products, the use of various batteries, and the development of many new types of batteries. In addition to the familiar high-performance alkaline batteries, rechargeable nickel-cadmium batteries, and nickel-hydrogen batteries, there are also lithium-ion batteries developed in recent years. This article mainly introduces the basic knowledge of lithium ion batteries. Including its characteristics, important parameters, the meaning of the model, the scope of application and the precautions for the use of large-capacity lithium-ion batteries.
Lithium-ion batteries are also divided into two categories: non-rechargeable batteries and rechargeable batteries. Non-rechargeable batteries are called disposable batteries. Chemical energy can only be converted into electrical energy at a time, and electrical energy cannot be reduced to chemical energy (or the reduction performance is very poor). Rechargeable batteries are called secondary batteries. It can convert electrical energy into chemical energy and store it. When used, the conversion of chemical energy into electrical energy is reversible, which is an important feature of electrochemical lithium-ion batteries.
The positive electrode of a lithium ion battery is usually composed of the active compound lithium, while the negative electrode is carbon with a special molecular structure. The important component of commonly used anode materials is LiCoO2. When charging, the electric potential on the electrode forces the anode compound to release lithium ions and insert them into the carbon. The anode molecules are arranged in a laminar structure. Lithium ions are separated from the layered structure of carbon during discharge and recombine with the positive electrode compound. The movement of lithium ions appeared in large-capacity lithium-ion batteries.
Although the principle of chemical reaction is simple, there are still many practical problems to be considered in actual industrial production. The positive electrode material needs to add additives to maintain the activity of repeated charges, while the negative electrode material needs to be designed on the molecular structure level to accommodate more lithium ions. In addition to maintaining stability, the electrolyte between the positive and negative electrodes should also have good conductivity to reduce the internal resistance of the battery.
Although lithium-ion batteries rarely have the memory effect of nickel-cadmium batteries, the memory effect is based on crystallization, and there is almost no such reaction in lithium-ion batteries. However, the capacity of a lithium-ion battery will still decrease after repeated charging, and the reasons are complex and diverse. The important reason is the changes in the anode and cathode materials themselves. From a molecular level, the positive and negative holes containing lithium ions will gradually collapse and block. From a chemical point of view, it is the active passivation of anode and cathode materials, and other stable compounds occur in side reactions. There are also some practical situations where the anode material gradually falls off, ultimately reducing the number of lithium ions that can move freely during the charge and discharge process in the battery.
Important types of lithium-ion batteries
According to different electrolyte materials used in lithium ion batteries, lithium ion batteries are divided into liquid lithium ion batteries (liquified lithiumion batteries, referred to as LIB) and polymer lithium ion batteries (polymer lithiumion batteries, referred to as PLB) large-capacity lithium ion batteries.