Preparation method of magnesium-containing silicon monoxide/silicon@resin carbon/CVD carbon material

Abstract

A preparation method of a magnesium-containing silicon monoxide / silicon@resin carbon / CVD carbon material comprises the following steps: adding silicon monoxide particles and silicon particles into absolute ethyl alcohol, mixing, and carrying out ultrasonic dispersion; adding resin, heating to dissolve the resin, stirring and grinding, and carrying out spray drying; carrying out heat treatment to foam and carbonize the resin; placing a magnesium sheet on the surface, and performing heat treatment under a vacuum condition; and putting into a chemical vapor deposition furnace, and carrying out surface carbon deposition. The obtained magnesium-containing silicon monoxide / silicon@resin carbon / CVD carbon material has a unique double-layer coating structure, and small-particle-size silicon monoxide and magnesium silicide are uniformly dispersed in the carbon material, so when the material is used for manufacturing a lithium ion battery negative electrode, and the lithiation rate is increasedby 3-4.5 times; the preparation method is simple to operate, low in cost and easy for industrial production; and the obtained battery negative electrode material can greatly improve the initial coulombic efficiency of the lithium ion battery and prolong the service life of the lithium ion battery.

Description

technical field [0001] The invention relates to a preparation method of magnesium-containing silicon / carbon material, in particular to a preparation method of magnesium-containing silicon monoxide / silicon carbon material. Background technique [0002] Lithium-ion batteries are widely used due to their advantages of high voltage, high specific energy, and long cycle life; but at the same time, lithium-ion batteries using graphite and other materials as negative electrodes have a theoretical capacity of only 375 mAh g -1 . As the performance of portable electronic devices becomes more and more powerful, improving the energy density and cycle life of lithium-ion batteries has become an increasingly urgent demand. [0003] Compared with traditional graphite anodes, silicon has an ultra-high theoretical specific capacity (4200 mAh g -1 ), is one of the potential options for upgrading lithium-ion batteries. However, there are still some other problems in using silicon-based mat...

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Problems solved by technology

[0006]In addition, silicon-based materials also have the problem of low initial coulombic efficiency (charge-discharge efficiency), which means that when the positive electrode material and silicon-based negative electrode material are matched to form a battery, it is relatively difficult After the first charge and discharge is completed, more lithium ions become the SEI film components of the negative electrode or are consumed in other aspects, and cannot return to the positive electrode, resulting in a decrease in specific capacity.

[0007] CN110176601A discloses a carbon-coated silicon oxide negative electrode material and its preparation method and application. The obtained carbon-coated silicon oxide negative electrode material has a core-shell structure, including The core body, buffer layer and outer layer are distributed sequentially from the inside to the outside; the core body is silicon oxide with low oxygen value, the buffer layer is carbon nanotubes, and the outer layer is carbon coating layer; this method uses carbon nanotubes as a flexible buffer layer to suppress the volume change of the entire negative electrode material particles, but it cannot suppress the volume change of the silicon oxide nuclei. After many charge-discharge cycles, the silicon oxide will still appear pulverized; this modification method can improve the first Coulombic efficiency of the material. no obvious effect

Magnesium metal and silicon metal in the material are heated and recombined in a rotary heating furnace to form magnesium silicide, but due to the uneven mixing degree, the amount of magnesium silicide formed is limited, which cannot play a good role in improving the first Coulombic efficiency of the material

[0009] CN103219504A discloses a silicon monoxide composite negative electrode material for lithium-ion batteries and a preparation method thereof. The outer layer of silicon monoxide is coated with carbon nanotubes and amorphous The carbon coating prevents the pulverization of silicon particles; however, in each particle of the obtained negative electrode material, silicon monoxide is aggregated together to form a larger inner core, and after many charge-discharge cycles, silicon monoxide remains There will be pulverization, and at the same time, the silicon content of the negative electrode material is too small, and the specific capacity is small; this modification method has no obvious effect on improving the first Coulombic efficiency of the material

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