Silicon is the preferred cathode for lithium-ion batteries with high energy density because of the highest theoretical lithium storage capacity, but its low cycle life seriously hinders its commercial application. Silicon The low cycle life of silicon cathode is due to its huge volume expansion during charging and discharging. The volume expansion of the silicon anode makes the mechanical stability of the silicon particle and the electrode, Silicon the electrical contact between the active particles and the stability of the SEI film worse. In order to improve the cyclic stability of the adverse factors, the researchers in the preparation of polar tablets, Silicon electrolyte selection and battery design has done a lot of efforts, and achieved some success. The research work is reviewed in order to provide feasible technical thinking for the practical process of silicon cathode.
Increasing the energy density of lithium-ion batteries is an urgent requirement for the development of portable electronic products, electric vehicles and storage power stations. The theoretical intercalation capacity of existing graphite anode is only $number Mah G, which severely limits the energy density of lithium ion battery. Silicon is considered to be the ideal cathode for the next generation lithium-ion batteries because of its lithium storage capacity of 10 times times that of graphite cathode. However, the silicon cathode in the lithium/lithium-ion process involves huge volume changes, resulting in poor circulation stability, limiting the actual application of the silicon cathode.
In response to this problem, researchers have done a lot of research to improve their cyclic performance. Part of the work focuses on the design of the composition and structure of silicon materials, such as the ability to provide cushioning space for composite materials, or the use of nanotechnology to reduce the volume swelling effect of active particles. Magasinskia and other people adopt two-step vapor deposition method to prepare Nano-Si composites, Silicon and the ratio of material to 100 weeks after circulation is still above 1500mah, which shows excellent cyclic performance. Cui Yi and other people through the template method prepared hollow silicon nanotubes, Silicon the material showed a 6,000-week cycle life.
The structural design of the silicon material can keep the individual active particles intact in the repeated volume changes, thus improving the cyclic performance of the material. However, the volume expansion of silicon also leads to the mechanical stability of the electrodes, the electrical contact of the active particles in the electrode and the stability of the SEI film on the electrode surface are affected, Silicon so the properties of the silicon anode are not only related to the composition and structure of the material itself, but also to the preparation process of the polar chip, the selection of electrolyte and the design of the battery.
The preparation process of a silicon base cathode is usually a mixture of active material, conductive agent and binder, which is coated on a set of fluids to form an electrode. Among them, the conductive agent can maintain good electrical contact between the active powders, thus ensuring that the active particles in each part of the electrode are fully electrochemical. Therefore, the electrical conductivity, dispersion, Silicon particle size, surface and other physical and chemical indicators, as well as the addition and dispersion of the method will significantly affect the electrochemical properties of silicon-based cathode. The commonly used conductive agents are acetylene black, Superp, Ke Qin black, vapor deposition carbon fiber and so on, they are reviewed with different morphology, conductivity and the ability of absorbing liquid, so different conductive agents are suitable for different structures and morphologies of silicon materials.