Do you know the working principle of lithium-ion batteries?

Composition material

Lithium-ion batteries are mainly composed of four basic parts: electrode, electrolyte, separator and container.

(1) The electrode is further divided into a positive electrode material and a negative electrode material by its polarity. The most common anode material is graphite; there are many types of cathode materials, and Shaowei Cai has made a comprehensive summary of the types and characteristics of cathode materials.

(2) Electrolytes can be divided into two categories: one is an aqueous solution of an acid, a base, or a salt; the other is an organic electrolyte solution. The electrolyte is the carrier for the transfer of lithium ions between the positive and negative electrodes, so it determines the capacity, cycle efficiency, rate, high and low temperature discharge, high temperature storage, longevity and safety of the battery [23, 24]. The organic electrolyte generally has the following composition: a solvent, an electrolyte lithium salt, and an additive. Commonly used organic solvents are ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Different solvents have great influence on the performance of the battery. For example, a solvent with a large dielectric constant can reduce the attraction between lithium ions and fully liberalize lithium ions; the flash point of the solvent determines the maximum operating temperature of lithium ions [25, 26]. Lithium ion salts are substances that provide lithium ions, and they mainly have two series of inorganic salts and organic salts. Additives are substances that significantly improve the performance of lithium ions. For example, the film forming additive can prevent the destruction of the electrode by the solvent, and improve the capacity and cycle life of the lithium insertion and delithiation of the electrode. In addition to this, there are anti-overcharge additives, conductivity additives, flame retardant additives, and the like.

(3) The separation layer is a film of organic matter, and the film has abundant zigzag micropores. Such micropores can prevent the passage of a large particle size electrolyte, but lithium ions having a small particle size can pass freely, forming an energization loop inside the battery. Therefore, the isolation layer divides the positive and negative electrodes into two parts, which can prevent short circuit inside the battery and provide isolation [27-29].

(4) The container is a packaging metal casing of the battery, which mainly functions to maintain the shape of the battery and protect the internal battery. The outer casing of the battery is connected to the positive and negative poles of the battery.

The working principle of

Lithium ion battery charge and discharge process is Li + and embedded on anode materials are embedded and take off with the process of absorption and release energy. For lithium ion battery, Li + from the anode materials embedded, via the electrolyte to the cathode, anode materials after absorption of electronic embedded in the formation of high energy embedded compounds. Lithium ion battery discharge:

Li + embedded off and release electrons from the anode materials, Li + via the electrolyte to the anode, the absorption of electronic embedded after embedding the anode material form relatively stable compounds.

The positive and negative materials of lithium ion batteries are mixed conductors of ions and electrons embedded in compounds, and electrons can only move in the positive and negative materials. The charging and discharging process requires lithium ions and electrons to work together. This requires the lithium ion electrode material to have good conductivity and ion diffusion capacity to ensure that electrons are quickly conducted to the external circuit through the electrode tab during discharge, and lithium ions are in the negative electrode. After the material is deintercalated, it rapidly diffuses into the electrolyte; the lithium ions in the electrolyte are transported to the positive electrode material by the carrier, and combined with electrons to form an intercalation compound.

The page contains the contents of the machine translation.