Silicon dioxide composite anode material for lithium ion battery, as well as preparation method and application of silicon dioxide composite anode material

Abstract

The invention discloses a silicon dioxide composite anode material for a lithium ion battery, as well as a preparation method and an application of the silicon dioxide composite anode material. The silicon dioxide composite anode material is prepared from the components of silicon dioxide powder and a conductive carbon layer with the surface of the silicon dioxide powder is uniformly and densely coated. With the adoption of the silicon dioxide composite anode material, the original component structure of an SiO material system is kept, so that the lower volume effect is ensured; the silicon dioxide dense carbon layer coating structure is successfully realized by adopting the technologies of mixing kneading, sheet rolling, press forming and the like, and thus the first coulombic efficiency of the silicon dioxide composite anode material is remarkably increased, and can reach a theoretical value being larger than 77 percent, and the cycle performance and the conductive characteristic are also remarkably improved, so that the silicon dioxide composite anode material is suitable for being charged and discharged with the large rate and can be applied to the power market.

Description

technical field [0001] The invention belongs to the field of negative electrode materials for lithium ion batteries, in particular, the invention relates to a silicon oxide composite negative electrode material for lithium ion batteries, a preparation method and an application thereof. Background technique [0002] For a long time, due to the good volume effect of silicon oxide (SiO), people have tried to use it as the negative electrode material of lithium-ion batteries. It is generally believed that the charging and discharging mechanism of SiO negative electrode is as follows: [0003] SiO+Li→Li 2 O+Si (1) [0004] SiO+Li→Li 4 SiO 4 +Si (2) [0005] Si+Li→Li 4.4 Si (3) [0006] When SiO is used as a negative electrode material, its first Coulombic efficiency is low, mainly because the first step reactions (Formula 1) and (Formula 2) are irreversible reactions, and the generated Li 2 O. Li 4 SiO 4 And reactions such as the contact decomposition and condensation of...

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Problems solved by technology

[0011] As far as the SiO materials used in previous literature and patent reports are concerned, the capacity is generally less than 1500mAh / g, and the efficiency is lower than 75.0%. Compared with the theoretical value, there is still room for improvement; at the same time, related literature reports that the electrical conductivity of SiO materials is extremely poor. , the order of magnitude of conductivity is in the range of insulators (-12 S / cm)

[0012] CN103236517A discloses a silicon-based negative electrode material for a lithium-ion battery and a preparation method thereof. The silicon-based negative electrode material for a lithium-ion battery is made of silicon monoxide, the macroscopic particle size is 10-25 μm, and the microscopic structure is silicon dioxide-coated Covered with nano-silicon particles, the particle size of the inner silicon particles is 20-30nm; the negative electrode material has an initial discharge capacity of 2010-2640mAh / g at a rate of 0.1C, and 420-790mAh / g after 50 cycles; the SiO The reversible capacity of the material is less than 1500mAh / g, and the initial efficiency is obviously less than 75% (0-2.0V). It can be seen that the efficiency will be lower under the conventional 0-1.5V, and the conductivity of the material has not been improved, and the electrochemical polarization is serious. , poor rate performance

The invention patent uses silicon oxide (SiO) as the raw material to make the material. Although the cycle and conductivity characteristics have been improved, the reversible capacity is around 650mAh / g, and the first-time efficiency is less than 70%.

Although the silicon oxide composite negative electrode material has improved the specific capacity (>1600mAh / g) and the first Coulombic efficiency (>80%) of the SiO composite material to a certain extent, the silicon oxide composite material is based on the original SiO material. On the basis of the component structure, artificially introduced nano-silicon materials with large volume expansion on the surface of SiO particles by physical combination, the large grains are difficult to control, and the dispersion is poor. The huge volume brought by the Si material itself Bloat problem cannot be avoided without effective buffering and poor cycle performance

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