Do you know what are the negative electrode materials for lithium-ion batteries? How much do you know about their characteristics? Today, Winshinepower will lead you to learn more about the negative electrode materials of lithium-ion batteries and solve the above doubts for everyone.
Introduction to Lithium-ion Battery Anode Materials
Lithium-ion battery anode material The anode of a lithium-ion battery is an acceptor of lithium ions. At present, common anode materials include carbon anode materials, tin-based anode materials, lithium-containing transition metal nitride anode materials, silicon anode materials, etc., but only carbon anode materials are really commercially available. Carbon anode materials that can be used as anode materials for lithium-ion batteries include graphite, coke, mesh carbon microspheres, and hard carbon.
Lithium-ion battery anode materials follow the principles
Generally speaking, the selection of a good anode material should follow the following principles:
①Low lithium intercalation potential, as close as possible to the redox potential of lithium;
②High lithium storage capacity per unit mass and unit volume;
③ The intercalation and deintercalation reaction of lithium in it is fast, that is, the diffusion coefficient of lithium ions in the solid phase is large, and the moving impedance at the electrode-electrolyte interface is small;
④High electronic conductivity;
⑤ The existence of lithium ions in the electrode material is stable;
⑥ The deformation of the material is small in the process of intercalation and deintercalation of lithium ions;
⑦Insoluble in an electrolyte.
A detailed explanation of anode materials for lithium-ion batteries
1 Lithium-ion battery anode material graphite
Graphite has a wide range of sources and low price and is an early carbon material used as a negative electrode for lithium-ion batteries. There are two main types of graphite: natural graphite and artificial graphite. The reversible charge-discharge capacity of graphite, a lithium-ion battery material, can reach more than 350 mA h/g, which is close to the theoretical specific capacity of LiC6, which is 372 mA h/g. For Li/Li+), it has a good charge-discharge platform and stable voltage. However, due to the high crystallinity of lithium-ion battery material graphite and its highly oriented layered structure, it is sensitive to electrolytes and has poor compatibility with solvents. In addition, the lithium-ion battery material graphite has poor high-current charge and discharge capabilities. At the same time, since the graphite interlayer spacing of lithium-ion battery materials is smaller than that of the graphite interlayer compound LixC6 formed after lithium is inserted into the graphite layer, the graphite interlayer spacing changes greatly during the charge-discharge cycle; The co-insertion of the solvent between the graphite layers and the decomposition of the organic solvent can easily cause the graphite layer to gradually peel off, and the graphite particles to crack and pulverize, thereby reducing the cycle life of the graphite material for lithium-ion batteries.
2 Lithium-ion battery anode material coke
Coke has the advantages of abundant resources and low prices. Lithium-ion battery materials are a class of carbon materials formed by liquid-phase carbonization. Depending on the raw materials, they can be divided into pitch coke and petroleum coke. Coke has strong adaptability to various electrolytes, better resistance to overcharge and over-discharge, and longer cycle life. Li-ion battery material coke has the characteristics of low heat treatment temperature, low cost, and good compatibility with PC, so it can reduce battery cost. However, since the voltage of the lithium-ion battery material is not stable during charging and discharging, and the average discharge voltage is relatively high, this is unfavorable for the practical voltage and capacity of the battery. In addition, the tap density of coke, a lithium-ion battery material, is about 80% that of graphite, so the volumetric specific capacity is lower.
3 Lithium-ion battery anode material hard carbon
Hard carbon is a carbon material close to an amorphous structure, and generally has a high reversible lithium intercalation capacity, but the disadvantage is that the voltage lags significantly, that is, lithium ions are intercalated at around 0V (vs. Li+/Li) during charging while discharging. It is deintercalated at 1V, so the working voltage in the full battery system is only 3V. In addition, the cycle performance of hard carbon, a negative material for lithium-ion batteries, is poor, and its energy density is not as good as that of graphite. Considering the comprehensive performance, it is still unable to replace graphite materials, which makes it difficult to apply hard carbon to commercial lithium-ion batteries.
4 Mesophase carbon microspheres as anode materials for lithium-ion batteries
Mesocarbon microspheres (MCMB) are the most studied soft carbon anode materials for lithium-ion batteries. Its particles are spherical, with a high packing density, a highly ordered layered structure, and a large volume of specific energy. Lithium-ion battery anode material MCMB has a small specific surface area, which can reduce the occurrence of electrode boundary side reactions during the charging and discharging process, thereby reducing the capacity loss during the first charging process. In addition, the negative electrode material MCMB of lithium-ion battery has a lamellar structure, which is conducive to the insertion and extraction of lithium ions from all directions of the ball and solves the problem of graphite sheet swelling, collapse, and The problem of not being able to discharge large currents. The commercialized negative electrode material MCMB for lithium-ion batteries has excellent cyclability and is one of the main negative electrode materials currently used in long-life small lithium-ion batteries and power batteries. Its main problem is that its mass-specific capacity is not high (300mA·h/g), especially when mesophase pitch carbon microspheres are used as electrode materials for lithium-ion batteries, graphitization at 2800°C is required, which undoubtedly greatly Increased the cost of mesophase pitch carbon microspheres.
The above is the whole content of lithium-ion battery negative electrode materials brought to you by Winshinepower today. I believe that you have read the whole text and have an understanding of the four materials of lithium-ion battery graphite, coke, hard carbon, and mesh carbon microspheres. I hope The above content is helpful to you, more information will be continuously updated, we will see you in the next issue.
