Lithium ion battery SiO composite material as well as preparation method and application thereof

Abstract

The invention relates to a lithium ion battery SiO composite material which comprises powder and a conductive carbon coating layer, wherein the chemical formula of the powder is SiOx; x is greater than 0.9 and less than 1.1; the volume of powder with particle diameters below 1.0mu m accounts for less than 15.0% of that of all the SiOx powder; D90 / D10 is greater than 3.0 and less than 15.0; D90 is less than 25.0mu m; Dmax is less than 50.0mu m; and the median particle diameterD50 of the SiOx changes within 0.5-2.0mu m before and after carbon coating. When the composite material charges and discharges at 0-1.5V as a lithium ion battery cathode material, the reversible specific capacity is high (over 1,650mAh / g), the initial coulomb efficiency is up to a theoretical value (over 79.0%), and meanwhile the composite material has excellent cycle performance, excellent conductive performance and low volume expansion, is suitable for high-rate charge and discharge, and can be applied to the power market.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery composite materials. Specifically, the invention relates to a lithium-ion battery silicon oxide composite material, 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 a lithium-ion battery composite material. It is generally believed that the charging and discharging mechanism of the 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 composite 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 silicon oxides and organic electrolytes consume more lithium ...

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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] CN 103236517A discloses a silicon-based composite material for lithium-ion batteries and a preparation method thereof. The silicon-based composite material for lithium-ion batteries is made of silicon monoxide, the macroscopic particle size is 10-25 μm, and the microscopic structure is silicon dioxide Coated nano-silicon particles, the particle size of the inner silicon particles is 20-30nm; the composite material has an initial discharge capacity of 2010-2640mAh / g at a rate of 0.1C, and 420-790mAh / g after 50 cycles; The reversible capacity of SiO 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 Seriously, 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 material has improved to a certain extent the specific capacity (>1600mAh / g) and the first coulombic efficiency (>80%) of the SiO composite material, the silicon oxide composite material is 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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