The negative electrode material of lithium ion batteries is an important part of rechargeable lithium batteries. It not only needs to be used as an electrode material but also needs to participate in electrochemical reactions. It must have stable safety performance and sustainable charge and discharge. Therefore, we need to consider comprehensively when designing and selecting anode materials for lithium-ion batteries. The ideal lithium battery anode material should meet the following conditions:
①The structure and chemical stability of the negative electrode material in the process of inserting and removing lithium ions are better, so that the battery has a higher cycle life and safety;
②The material needs to have good lithium ion conductivity and electronic conductivity in order to obtain a higher charge-discharge rate and low-temperature charge-discharge performance;
③The material needs to have a high reversible specific capacity;
④The required material has a low oxidation-reduction potential in the intercalation and deintercalation reaction of lithium ions, so that the lithium ion battery has a higher output voltage. During the deintercalation of lithium ions, the electrode potential changes little to ensure small voltage fluctuations during charging and discharging. ；
⑤ If the lithium ion potential is below 1.2V, a dense and stable solid electrolyte membrane should be formed on the surface of the negative electrode to prevent the electrolyte from continuously reducing on the negative electrode surface and irreversibly consume the lithium ions of the positive electrode;
⑥Rich production resources, no pollution to the environment, can be mass-produced and easily obtained, and the manufacturing and use costs are low;
According to the reaction mechanism of lithium and negative electrode, many negative electrode materials can be divided into three categories: alloy reaction electrode, insertion reaction electrode and conversion reaction electrode. Among them, the alloy reaction electrode refers specifically to tin or silicon-based alloys and compounds; the conversion reaction electrode refers to metal oxides, metal sulfides, metal hydrides, metal nitrides, metal phosphides, and metals that are active to lithium through conversion reactions. Fluoride, etc.; inserting the reactive electrode mainly refers to carbon anode and TiO2-based anode materials.
At present, the use of anode materials is mainly concentrated on carbon anodes, lithium titanate and silicon-based alloy materials. The use of traditional carbon anodes basically meets the requirements of consumer electronics, power batteries, and energy storage batteries. The use of lithium titanate as the anode can meet the high battery requirements. Power density and long cycle life are required. Of course, we have been looking for more suitable materials that are expected to further increase the energy density of the battery.
The current commercial lithium-ion battery negative electrodes can be divided into two categories: one is carbon materials, such as natural graphite, synthetic graphite, mesophase carbon microspheres (MCMB), and so on. Compared with natural graphite, MCMB has superior electrochemical performance. The main reason is that the outer surface of the particles is the edge surface of the graphite structure, and the reaction activity is uniform, and it is easy to form a stable SEI film, which is conducive to the insertion and deintercalation of lithium ions.
There is also a type of Li4Ti5O12 negative electrode material with spinel structure, its theoretical specific capacity is 175mA·h·g-1, and the actual specific capacity can reach 160mA·h·g-1. Although Li4Ti5O12 has a higher working voltage, its cycle performance and rate performance are particularly excellent. Compared with carbon materials, it has safety advantages. Therefore, this material will also be used more, so this material is in power and There are strong application requirements for energy storage lithium-ion batteries. However, it is easy for the electrolyte to undergo chemical reactions, causing flatulence and causing battery bulging.
According to the current situation, the next generation of high-capacity anode materials include Si anodes and Sn-based alloys. However, alloy anode materials face the problem of high capacity changes with high volume. In order to solve the problem of material powdering caused by volume expansion, they are often used Alloy and carbon composite materials, composite materials can improve the energy density of existing lithium-ion batteries to a certain extent.