CN109273680B

CN109273680B - Porous silicon-carbon negative electrode material, preparation method thereof and lithium ion battery

Info

Publication number: CN109273680B
Application number: CN201810998286.5A
Authority: CN
Inventors: 叶柏青; 张蕾
Original assignee: Sichuan X Danfu Energy Technology Co ltd
Current assignee: Sichuan X Danfu Energy Technology Co ltd
Priority date: 2018-08-29
Filing date: 2018-08-29
Publication date: 2020-10-20
Anticipated expiration: 2038-08-29
Also published as: CN109273680A

Abstract

The invention relates to the technical field of lithium ion battery materials, in particular to a porous silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery, wherein the porous silicon-carbon negative electrode material comprises a porous silicon-carbon material and a graphite material; the porous silicon carbon material is of a core-shell type three-layer composite structure and comprises an inner core, and an intermediate layer and an outermost layer which are sequentially coated on the inner core, wherein the inner core is an amorphous porous silicon oxygen material SiO_xThe intermediate layer is a mesh conductive agent coating layer, and the outermost layer is an amorphous carbon coating layer. Compared with the prior art, the porous silicon-carbon material has the advantages that the volume expansion of the porous silicon-carbon material is greatly reduced, and the first efficiency and the cycle performance are remarkably improved through the design of a core-shell type three-layer composite structure; after the porous silicon-carbon negative electrode material is mixed with a graphite material, the first reversible specific capacity of the porous silicon-carbon negative electrode material is not less than 487.8mAh/g, the first efficiency is not less than 87.86%, the capacity retention rate is not less than 94.6% after 500 times of circulation, and the volume expansion rate is not more than 19.51%.

Description

Porous silicon-carbon negative electrode material, preparation method thereof and lithium ion battery

Technical Field

The invention relates to the technical field of lithium ion battery materials, in particular to a porous silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery.

Background

The lithium ion battery has the advantages of high energy density, good safety performance, good cycle performance, no memory effect, high working voltage, environmental friendliness, small self-discharge and the like, and is widely applied to various fields. Along with the publication of 'notice about 2016 + 2020 new energy automobile popularization and application financial support policy', the national ministry of finance publishes that the lithium ion battery has higher energy density, the energy density of the lithium ion battery is mainly influenced by positive and negative electrode active materials, the negative electrode active material which is commercially applied at present is mainly artificial graphite, but the actual specific capacity of the negative electrode active material is close to the theoretical specific capacity 372mAh/g, the space is difficult to be improved, the requirement of the lithium ion battery on the energy density is higher and higher, and the development of a new high-energy density material is urgent.

The silicon material has extremely high theoretical specific capacity (4200mAh/g), abundant resources and low delithiation potential (< 0.5V), and is one of effective materials for replacing graphite. However, the silicon material has a large volume change during the intercalation and deintercalation of lithium ions, and has a low first efficiency and an extremely poor cycle performance, which makes it difficult to realize practical production applications.

In view of the above problems, many methods for modifying silicon-based materials have been developed, such as three-dimensional porous Si particles, core-shell crystal/amorphous Si nanowires, Si-metal oxide composites, Si-carbon core-shell structures, and graphene as a buffer. Although the scheme has certain improvement on the expansion of the silicon-based material, the modification mode is single, the effect is not obvious, the problems of difficult preparation, poor electric contact, high cost and the like still exist, and compared with the graphite material, the first efficiency, the cycle performance and the volume expansion rate of the graphite material have larger differences and need to be further improved.

The patent publication No. CN 102903896B, which is a Chinese invention patent, discloses a silicon-carbon composite negative electrode material for a lithium ion battery, a preparation method and an application thereof, wherein the negative electrode material is of a core-shell structure and comprises a core body, an intermediate layer and an outermost layer, the intermediate layer and the outermost layer are sequentially coated on the core body, the core body is made of nano silicon, the intermediate layer is made of amorphous carbon, and the outermost layer is made of a one-dimensional nano carbon material.

Disclosure of Invention

One of the objects of the present invention is: aiming at the defects of the prior art, the porous silicon-carbon anode material is provided to solve the problems of low first efficiency, large volume expansion and poor cycle performance of the conventional silicon-based anode material.

The second purpose of the invention is: provides a preparation method of a porous silicon-carbon negative electrode material.

The third purpose of the invention is that: a lithium ion battery is provided.

In order to achieve the purpose, the invention adopts the following technical scheme:

a porous silicon carbon negative electrode material comprises a porous silicon carbon material and a graphite material; the porous silicon carbon material is of a core-shell structure and comprises an inner core, an intermediate layer and an outermost layer, wherein the intermediate layer and the outermost layer are sequentially coated on the inner core, and the inner core is amorphousSiO porous silicon oxide material_xWherein x is more than 0 and less than or equal to 2, the middle layer is a reticular conductive agent coating layer, and the outermost layer is an amorphous carbon coating layer.

Preferably, the porous silica material SiO_xThe porosity of the porous material is 20 to 80%, and more preferably 40 to 80%. SiO can be effectively controlled in the pore range_xThe volume expands, allowing it to expand and fill with its own pores. If the porosity is too low, effective control of SiO is not possible_xVolume expansion; if the porosity is too high, SiO will be affected_xThe structural stability of (2).

Preferably, the porous silica material SiO_xMedian particle diameter D of₅₀Is 3 to 7 μm.

Preferably, the thickness of the conductive agent coating layer is 10-100 nm, the conductive agent comprises a conductive agent A and a conductive agent B, the conductive agent A is at least one of a carbon nanotube and graphene, and the conductive agent B is conductive carbon black. Wherein the conductive agent is coated on the porous SiO_xThe surface forms a conductive network coating structure which takes conductive carbon black as a node and carbon nano tube/graphene as a connecting network.

Preferably, the thickness of the amorphous carbon coating layer is 0.5-2 μm, and the amorphous carbon is formed by carbonizing one or more of petroleum pitch and coal tar pitch.

Preferably, the mass ratio of the porous silicon-carbon material to the graphite material is 5-50%: 50-95%; the porous silica material SiO_xAnd the mass ratio of the conductive agent to the amorphous carbon is 20-50%: 5-20%: 30-75%.

Preferably, the graphite material is at least one of natural graphite, artificial graphite, microcrystalline graphite, mesocarbon microbeads and soft carbon.

The invention also provides a preparation method of the porous silicon-carbon negative electrode material, which comprises the following steps:

step 1) preparing silicon oxide SiO_xAnd the active metal powder according to the mass ratio of (0.5-2): 1, ball milling for 1-4 h in a ball milling tank to mix uniformly, and carrying out heat treatment at 650-1000 ℃ under inert atmosphere for 4-24h, crushing and grading to obtain D₅₀Silicon oxide SiO of 3 to 7 μm_xAnd a metal oxide composite material, wherein x is more than 0 and less than or equal to 2;

step 2), adopting hydrochloric acid to carry out acid washing on the material prepared in the step 1), removing metal oxide, further carrying out water washing and drying to obtain porous SiO_xA material;

step 3), using a dispersing agent to mix the conductive agent A and the conductive agent B according to the mass ratio of (1-20): 1, preparing a uniform conductive agent solution, wherein the conductive agent A is at least one of carbon nano tube and graphene, and the conductive agent B is conductive carbon black;

step 4) preparing the porous SiO prepared in the step 2)_xAdding the material into the conductive agent solution prepared in the step 3), and preparing porous SiO_xThe molar ratio of the material to the conductive agent is 10: (0.5-2), stirring for 0.5-3 h at a stirring speed of 500-1500 r/min to uniformly mix, and vacuum drying to remove the solvent to obtain the porous SiO with the surface coated with the conductive agent_xParticles;

step 5) mixing the asphalt and the porous SiO coated with the conductive agent prepared in the step 4)_xThe particles are (1-5) by mass: 1, performing ball milling fusion for 1-3 h, heating to 260-270 ℃ in an inert atmosphere to complete coating, continuously heating to 500-600 ℃ to complete preliminary carbonization, and then heating to 1000-1100 ℃ to perform high-temperature carbonization for 8-24 h to obtain a porous silicon-carbon material with a three-layer core-shell structure;

step 6), mixing the porous silicon-carbon material prepared in the step 5) with a graphite material according to a mass ratio of 5-50%: mixing 50-95% of the raw materials, and performing ball milling in a ball milling tank for 1-4 hours to uniformly mix the raw materials to obtain the porous silicon-carbon negative electrode material.

Preferably, in step 1), the active metal powder is one or more of magnesium, zinc and iron.

Preferably, in step 1), the silicon oxide SiO_xAnd the mass ratio of the active metal powder to the active metal powder is (0.8-1.2): 1. if the addition amount of the active metal powder is too small, the generated pore structure is too small, and the volume expansion of the material cannot be effectively reduced; if the amount of the active metal powder added is too large, the pore structure formed becomes too large, and the structural strength of the material is loweredAnd a compacted density.

Preferably, in step 1) and step 5), the inert atmosphere is one of nitrogen, argon and helium.

Preferably, in step 2), the porous silica material SiO_xThe porosity of the porous material is 20 to 80%, and more preferably 40 to 80%. SiO can be effectively controlled in the pore range_xThe volume expands, allowing it to expand and fill with its own pores. If the porosity is too low, effective control of SiO is not possible_xVolume expansion; if the porosity is too high, SiO will be affected_xThe structural stability of (2).

Preferably, in step 3), the dispersant is polyvinylpyrrolidone (PVP).

Preferably, in the step 3), the carbon nanotube is one or more of a single-walled carbon nanotube, a multi-walled carbon nanotube, a single-walled carbon nanotube conductive liquid, and a multi-walled carbon nanotube conductive liquid.

Preferably, in the step 4), the vacuum drying temperature is 60-150 ℃, and the drying time is 1-3 h.

Preferably, in the step 5), the asphalt is one or more of petroleum asphalt and coal tar asphalt.

Preferably, in step 6), the graphite material is at least one of natural graphite, artificial graphite, microcrystalline graphite, mesocarbon microbeads and soft carbon.

The invention also provides a lithium ion battery which comprises the porous silicon carbon negative electrode material in any section.

The invention has the beneficial effects that: the invention relates to a porous silicon-carbon negative electrode material, which comprises a porous silicon-carbon material and a graphite material; the porous silicon carbon material is of a core-shell type three-layer composite structure and comprises an inner core, and an intermediate layer and an outermost layer which are sequentially coated on the inner core, wherein the inner core is an amorphous porous silicon oxygen material SiO_xThe intermediate layer is a mesh conductive agent coating layer, and the outermost layer is an amorphous carbon coating layer. Wherein, porous SiO_xFormation of Li by the first lithium insertion reaction of the core₄SiO₄Effectively buffering the volume expansion effect of the silicon material, and the reserved space of the porous structure can be used for filling the materialThe volume change in the discharging process is absorbed, so that the volume change of the whole material is reduced; the conductive agent coating layer is coated on the porous SiO in a net form_xThe network structure limits the porous SiO while improving the conductivity_xThe inner core expands outwardly in volume; the outermost amorphous carbon coating layer functions to form a uniform and stable SEI film while preventing an electrolyte from contacting porous SiO_xThe inner core contacts and limits its expansion to the outside. Therefore, through the design of a core-shell type three-layer composite structure, the volume expansion of the porous silicon-carbon material is greatly reduced, and the first efficiency and the cycle performance are obviously improved; after the porous silicon-carbon negative electrode material is mixed with a graphite material, the first reversible specific capacity of the porous silicon-carbon negative electrode material is not less than 487.8mAh/g, the first efficiency is not less than 87.86%, the capacity retention rate is not less than 94.6% after 500 times of circulation, and the volume expansion rate is not more than 19.51%.

Drawings

FIG. 1 is a schematic view of a preparation method of a porous Si-C material according to the present invention.

Fig. 2 is a scanning electron microscope image of the porous silicon carbon negative electrode material obtained in example 1 at a magnification of 1 k.

Fig. 3 is a first charge-discharge curve diagram of the porous silicon carbon negative electrode material obtained in example 1.

Fig. 4 is a charge-discharge cycle curve diagram of the porous silicon carbon negative electrode material obtained in example 1 at a charge-discharge rate of 0.5C.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Preparing a porous silicon carbon negative electrode material:

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Powder and metallic Mg powder, with the addition ofBall milling for 1h in a ball milling tank, heating to 650 ℃ at a heating rate of 10 ℃/min in nitrogen atmosphere, carrying out heat preservation treatment for 4h, and naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 50% and no impurities and moisture_x；

(3) Using a dispersant PVP 30 to mix carbon nanotubes and conductive carbon black according to a mass ratio of 10: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution obtained in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 1h at the stirring speed of 800r/min to uniformly mix the components, putting the mixture into a vacuum drying oven for vacuum drying for 2h at the temperature of 85 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 3: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 550 ℃ to finish primary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 24 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with artificial graphite according to the mass ratio of the components of 30%: mixing the components in a proportion of 70 percent, and ball-milling the mixture in a ball-milling tank at a low speed for 4 hours to uniformly mix the mixture to obtain the porous silicon-carbon cathode material.

Wherein, porous SiO_xThe pore-forming mechanism of (a) is as follows: using SiO₂And active metal MgHigh temperature oxidation reduction reaction to prepare synthetic porous silicon. Magnesium becomes molten at 648.9 deg.C, and is easily volatilized to form magnesium vapor when SiO₂: the mass ratio of Mg is 1: 2, the reaction is as follows:

when SiO is present₂In excess, the reaction is:

removing MgO by hydrochloric acid to prepare the porous SiO_x。

The preparation process of the porous silicon carbon material of the present embodiment is shown in fig. 1.

Preparing a lithium ion battery:

preparing a porous silicon-carbon negative electrode material: Super-P: LA133 ═ 96: 1: 3 preparing slurry, and coating the slurry on the microporous copper foil to prepare a silicon-carbon negative pole piece;

cutting the silicon-carbon negative pole piece, testing the thickness of the pole piece, taking the metal lithium piece as a counter electrode and a reference electrode of the button cell, and taking 1mol/L LiFP as electrolyte₆And assembling the button cell in a glove box filled with argon by using the + EC/DEC (1: 1) + 2% VC solution and a PP microporous membrane as a diaphragm.

The microscopic morphology of the porous silicon carbon negative electrode material prepared in example 1 was observed by a scanning electron microscope. As shown in fig. 2, it can be seen by a scanning electron microscope that the particles of the material obtained in example 1 are divided into large artificial graphite particles and small porous silicon carbon particles, and the surface topography of the porous silicon carbon material is uniform.

The first charge-discharge efficiency test was performed on the porous silicon carbon negative electrode material prepared in example 1. The test result is shown in fig. 3, and through a first charge-discharge efficiency test, the first delithiation capacity of the material of example 1 is 487.8mAh/g, and the first charge-discharge efficiency is 87.86%, which indicates that the porous silicon-carbon negative electrode material of the present invention has a higher delithiation capacity and a higher first charge-discharge efficiency.

The porous silicon carbon anode material prepared in example 1 was subjected to cycle performance test. The test result is shown in fig. 4, and the capacity retention rate of the material of example 1 after 500 cycles is 94.6%, which indicates that the porous silicon-carbon anode material of the invention has good cycle performance.

The porous silicon carbon negative material prepared in example 1 was subjected to a volume expansion rate test. The result shows that the volume expansion rate of the fully embedded lithium pole piece in example 1 is 19.51%, which indicates that the volume expansion rate of the porous silicon-carbon negative electrode material is lower.

Example 2

The difference between the present embodiment and embodiment 1 is the preparation of the porous silicon carbon negative electrode material:

(1) according to the mass ratio of 1.2: 1 weighing SiO with a certain mass₂Adding the powder and metal Zn powder into a ball milling tank for ball milling for 1h, heating to 650 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 4h, naturally cooling to room temperature to generate SiO_xAnd ZnO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_xAnd ZnO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting with ZnO mixture particles in hydrochloric acid, filtering, repeating the acid washing step once again to remove ZnO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with 80% porosity and no impurities and moisture_x；

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 1h at the stirring speed of 800r/min to uniformly mix, and putting the mixture into a vacuum drying oven for vacuum drying at the temperature of 85 DEG CDrying for 2h to remove the solvent to obtain the porous SiO with the surface coated with the conductive agent_xParticles;

The rest is the same as embodiment 1, and the description is omitted here.

Example 3

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Mg powder into a ball milling tank for ball milling for 1h, heating to 650 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 4h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 60% and no impurities and moisture_x；

(3) Using a dispersant PVP 30 to mix graphene and conductive carbon black according to a mass ratio of 5: 1 preparing a uniform conductive agent solution;

(4) obtained in the step (2)To porous SiO_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 8: 1, stirring for 1h at the stirring speed of 800r/min to uniformly mix the components, putting the mixture into a vacuum drying oven for vacuum drying for 2h at the temperature of 85 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with microcrystalline graphite according to the mass ratio of the components of 30%: mixing the components in a proportion of 70 percent, and ball-milling the mixture in a ball-milling tank at a low speed for 4 hours to uniformly mix the mixture to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 4

(1) according to the mass ratio of 1.1: 1 weighing SiO with a certain mass₂Adding the powder and metal Zn powder into a ball milling tank, ball milling for 1h, heating to 650 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 4h, naturally cooling to room temperature, and obtaining SiOx and ZnO with the molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_xAnd ZnO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting with ZnO mixture particles in hydrochloric acid, filtering, repeating the acid washing step once again to remove ZnO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 70% and no impurities and moisture_x；

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 1h at the stirring speed of 800r/min to uniformly mix the components, putting the mixture into a vacuum drying oven for vacuum drying for 2h at the temperature of 85 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing petroleum asphalt and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 2.8: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 550 ℃ to finish primary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 24 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with soft carbon according to the mass ratio of the components of 30%: mixing the components in a proportion of 70 percent, and ball-milling the mixture in a ball-milling tank at a low speed for 4 hours to uniformly mix the mixture to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 5

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xIs arranged atUltrasonically cleaning for 10min in ionized water, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 40% and no impurities and moisture_x；

(3) Using a dispersant PVP 30 to mix graphene and conductive carbon black according to a mass ratio of 10: 1 preparing a uniform conductive agent solution;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 40%: mixing the components in a proportion of 60 percent, and performing low-speed ball milling in a ball milling tank for 4 hours to uniformly mix the components so as to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 6

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Mg powder into a ball milling tank, ball milling for 1h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the argon atmosphere, carrying out heat preservation treatment for 10h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(2)preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 30% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing the carbon nano tube, the graphene and the conductive carbon black according to the mass ratio of 5: 5: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 2, stirring for 3 hours at the stirring speed of 1500r/min to uniformly mix the materials, putting the materials into a vacuum drying oven for vacuum drying for 1 hour at the temperature of 150 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 5: 1, ball-milling and fusing for 1h, heating to 270 ℃ in an inert atmosphere to complete coating, continuing to heat to 600 ℃ to complete preliminary carbonization, and then heating to 1000 ℃ to perform high-temperature carbonization for 16h to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 20%: mixing 80 percent of the raw materials, and performing low-speed ball milling in a ball milling tank for 2 hours to uniformly mix the raw materials to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 7

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Fe powder into a ball milling tank for ball milling for 1h, heating to 1000 ℃ at a heating rate of 10 ℃/min under the argon atmosphere, and keeping the temperature at a hot positionConditioning for 20h, naturally cooling to room temperature to generate SiO_x(x. apprxeq.1) and Fe₂O₃The molecular weight ratio is about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x. apprxeq.1) and Fe₂O₃Particles of the mixture;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xAnd Fe₂O₃The mixture particles were reacted in hydrochloric acid, filtered and the acid washing step was repeated once more to remove Fe₂O₃Impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 20% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing carbon nano tube, graphene and conductive carbon black according to the mass ratio of 10: 10: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 0.5, stirring for 3h at a stirring speed of 500r/min to uniformly mix the components, putting the mixture into a vacuum drying oven for vacuum drying for 1h at the temperature of 150 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 4: 1, ball-milling and fusing for 3 hours, heating to 270 ℃ in an inert atmosphere to complete coating, continuing to heat to 500 ℃ to complete preliminary carbonization, and then heating to 1000 ℃ to perform high-temperature carbonization for 10 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 10%: mixing the components in a proportion of 90 percent, and performing low-speed ball milling in a ball milling tank for 2 hours to uniformly mix the components so as to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 8

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Fe powder into a ball milling tank for ball milling for 1h, heating to 650 ℃ at the heating rate of 10 ℃/min under the atmosphere of helium, carrying out heat preservation treatment for 8h, naturally cooling to room temperature to generate SiO_x(x. apprxeq.1) and Fe₂O₃The molecular weight ratio is about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x. apprxeq.1) and Fe₂O₃Particles of the mixture;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xAnd Fe₂O₃The mixture particles were reacted in hydrochloric acid, filtered and the acid washing step was repeated once more to remove Fe₂O₃Impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 45% and no impurities and moisture_x；

(3) Using a dispersant PVP 30 to mix graphene and conductive carbon black according to a mass ratio of 15: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1.5, stirring for 3 hours at the stirring speed of 500r/min to uniformly mix the components, putting the mixture into a vacuum drying oven for vacuum drying for 1 hour at the temperature of 60 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 4: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 550 ℃ to finish primary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 15 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 5%: mixing the components in a proportion of 95 percent, and performing low-speed ball milling in a ball milling tank for 4 hours to uniformly mix the components so as to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 9

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Mg powder into a ball milling tank, ball milling for 1h, heating to 750 ℃ at the heating rate of 10 ℃/min under the atmosphere of helium, carrying out heat preservation treatment for 12h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 55% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing carbon nano tubes and conductive carbon black according to the mass ratio of 12: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 2, stirring for 0.5h at the stirring speed of 1000r/min to uniformly mix, putting the mixture into a vacuum drying oven for vacuum drying for 2.5h at the temperature of 80 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 3: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 550 ℃ to finish primary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 15 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 15%: 85 percent of the mixture is mixed, and the mixture is ball milled for 4 hours in a ball milling tank at low speed to be uniformly mixed, thus obtaining the porous silicon carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 10

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Mg powder into a ball milling tank, ball milling for 1h, heating to 850 ℃ at the heating rate of 10 ℃/min under the atmosphere of helium, carrying out heat preservation treatment for 16h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 65% and no impurities and moisture_x；

(3) Using a dispersant PVP 30 to mix graphene and conductive carbon black according to a mass ratio of 18: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 2, stirring for 0.5h at the stirring speed of 1000r/min to uniformly mixVacuum drying at 80 deg.C for 2.5h in a vacuum drying oven to remove solvent to obtain porous SiO coated with conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 3: 1, ball-milling and fusing for 3 hours, heating to 265 ℃ in an inert atmosphere to finish coating, continuously heating to 580 ℃ to finish primary carbonization, and then heating to 1050 ℃ to perform high-temperature carbonization for 18 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 20%: mixing 80 percent of the raw materials, and performing low-speed ball milling in a ball milling tank for 4 hours to uniformly mix the raw materials to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 11

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Zn powder into a ball milling tank for ball milling for 1h, heating to 950 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 18h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and ZnO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and ZnO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting with ZnO mixture particles in hydrochloric acid, filtering, repeating the acid washing step once again to remove ZnO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with 75% porosity and no impurities and moisture_x；

(3) Using a dispersant PVP 30 to mix graphene and conductive carbon black according to a mass ratio of 20: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 0.5h at the stirring speed of 1000r/min to uniformly mix, putting the mixture into a vacuum drying oven for vacuum drying for 2.5h at the temperature of 100 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 1: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 600 ℃ to finish primary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 20 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 40%: mixing the components in a proportion of 60 percent, and carrying out low-speed ball milling in a ball milling tank for 2 hours to uniformly mix the components so as to obtain the porous silicon-carbon negative electrode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 12

(1) according to the mass ratio of 1: 1 weighing SiO with a certain mass₂Adding the powder and metal Zn powder into a ball milling tank for ball milling for 1h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 20h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and ZnO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and ZnO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting with ZnO mixture particles in hydrochloric acid, filtering, repeating the acid washing step once again to remove ZnO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xPut into a vacuum drying ovenVacuum drying at 85 deg.C for 2h to obtain porous SiO with porosity of 40% and no impurities and moisture_x；

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1.5, stirring for 2.5h at the stirring speed of 1000r/min to uniformly mix, putting into a vacuum drying oven, and vacuum drying for 3h at the temperature of 120 ℃ to remove the solvent to obtain the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 1: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 500 ℃ to finish primary carbonization, and then heating to 1000 ℃ to perform high-temperature carbonization for 22 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components: mixing the components in a proportion of 50 percent, and performing low-speed ball milling in a ball milling tank for 4 hours to uniformly mix the components so as to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 13

(1) according to the mass ratio of 0.8: 1 weighing SiO with a certain mass₂Adding the powder and metal Zn powder into a ball milling tank, ball milling for 2.5h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 22h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and ZnO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and ZnO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting with ZnO mixture particles in hydrochloric acid, filtering, and repeating the reactionOne acid washing step is carried out to remove ZnO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 50% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing carbon nano tube, graphene and conductive carbon black according to the mass ratio of 10: 5: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 2, stirring for 2.5h at the stirring speed of 1000r/min to uniformly mix, putting the mixture into a vacuum drying oven for vacuum drying for 2h at the temperature of 130 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 1: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 550 ℃ to finish primary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 24 hours to obtain a porous silicon-carbon material with a three-layer structure;

The rest is the same as embodiment 1, and the description is omitted here.

Example 14

(1) according to the mass ratio of 1.2: 1 weighing SiO with a certain mass₂Adding the powder and metal Zn powder into a ball milling tank, ball milling for 3h, heating to 1000 ℃ at a heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 24h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and ZnO molecular weight ratio of about 1: 1, the product ofCrushing and grading the material to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and ZnO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting with ZnO mixture particles in hydrochloric acid, filtering, repeating the acid washing step once again to remove ZnO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 60% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing the carbon nano tube, the graphene and the conductive carbon black according to the mass ratio of 5: 3: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 3 hours at the stirring speed of 1000r/min to uniformly mix the materials, putting the materials into a vacuum drying oven for vacuum drying for 2 hours at the temperature of 130 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

The rest is the same as embodiment 1, and the description is omitted here.

Example 15

(1) according to the mass ratio of 0.9: 1 weighing SiO with a certain mass₂Adding the powder and the metal Fe powder into a ball milling tank for ball milling for 4h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 24h, naturally cooling to room temperature to generate SiO_x(x. apprxeq.1) and Fe₂O₃The molecular weight ratio is about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x. apprxeq.1) and Fe₂O₃Particles of the mixture;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xAnd Fe₂O₃The mixture particles were reacted in hydrochloric acid, filtered and the acid washing step was repeated once more to remove Fe₂O₃Impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 70% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing the carbon nano tube, the graphene and the conductive carbon black according to the mass ratio of 5: 10: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 2.5h at the stirring speed of 1000r/min to uniformly mix, putting the mixture into a vacuum drying oven for vacuum drying for 2h at the temperature of 140 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

The rest is the same as embodiment 1, and the description is omitted here.

Example 16

(1) according to the mass ratio of 1.1: 1 weighing SiO with a certain mass₂Adding the powder and the metal Fe powder into a ball milling tank for ball milling for 4h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 10h, naturally cooling to room temperature to generate SiO_x(x. apprxeq.1) and Fe₂O₃The molecular weight ratio is about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x. apprxeq.1) and Fe₂O₃Particles of the mixture;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xAnd Fe₂O₃The mixture particles were reacted in hydrochloric acid, filtered and the acid washing step was repeated once more to remove Fe₂O₃Impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with 80% porosity and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing carbon nano tube, graphene and conductive carbon black according to the mass ratio of 10: 8: 1 preparing a uniform conductive agent solution;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 2.5h at the stirring speed of 1000r/min to uniformly mix, putting the mixture into a vacuum drying oven for vacuum drying for 1h at the temperature of 150 ℃ to remove the solvent, and obtaining the porous SiO with the surface coated with the conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 1: 1, ball milling and fusing for 3 hours in inert atmosphereHeating to 260 ℃ to complete coating, continuously heating to 550 ℃ to complete preliminary carbonization, and then heating to 1100 ℃ to perform high-temperature carbonization for 20 hours to obtain a porous silicon-carbon material with a three-layer structure;

(6) and (3) mixing the porous silicon-carbon material prepared in the step (5) with the mesocarbon microbeads according to the mass ratio of the components of 30%: mixing the components in a proportion of 70 percent, and ball-milling the mixture in a ball-milling tank at a low speed for 4 hours to uniformly mix the mixture to obtain the porous silicon-carbon cathode material.

The rest is the same as embodiment 1, and the description is omitted here.

Example 17

(1) according to the mass ratio of 1.1: 1 weighing SiO with a certain mass₂Adding the powder and metal Mg powder into a ball milling tank for ball milling for 4h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 24h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(4) the porous SiO obtained in the step (2) is treated_xAdding into the conductive agent solution prepared in the step (3), wherein SiO is_xThe component ratio to the conductive agent is 10: 1, stirring for 2.5h at the stirring speed of 1000r/min to mix uniformly, and putting the mixture into a vacuum drying oven for vacuum drying for 1h at the temperature of 150 ℃ to remove the solventPreparing a porous SiO with the surface coated with a conductive agent_xParticles;

(5) mixing the coal tar pitch and the porous SiO coated with the conductive agent prepared in the step (4)_xThe mass ratio of the particles is 1: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ under an inert atmosphere to finish coating, continuously heating to 600 ℃ to finish primary carbonization, and then heating to 1000 ℃ to perform high-temperature carbonization for 24 hours to obtain a porous silicon-carbon material with a three-layer structure;

The rest is the same as embodiment 1, and the description is omitted here.

Example 18

(1) according to the mass ratio of 1.2: 1 weighing SiO with a certain mass₂Adding the powder and metal Mg powder into a ball milling tank for ball milling for 4h, heating to 1000 ℃ at the heating rate of 10 ℃/min under the nitrogen atmosphere, carrying out heat preservation treatment for 24h, naturally cooling to room temperature to generate SiO_x(x ≈ 1) and a MgO molecular weight ratio of about 1: 1, crushing and classifying the product to obtain D₅₀SiO in 3-7 μm_x(x ≈ 1) and MgO mixture particles;

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO with porosity of 70% and no impurities and moisture_x；

(3) Dispersing agent PVP 30 is used for mixing the carbon nano tube, the graphene and the conductive carbon black according to the mass ratio of 8: 5: 1 preparing a uniform conductive agent solution;

The rest is the same as embodiment 1, and the description is omitted here.

Comparative example 1

The difference from the examples is that the preparation of the silicon-carbon anode material of the comparative example does not carry out the step (1) and the step (2), and SiO with a non-porous structure is adopted_xSubstituted porous SiO_x. The preparation method comprises the following steps:

(1) using a dispersant PVP 30 to mix carbon nanotubes and conductive carbon black according to a mass ratio of 10: 1 preparing a solution;

(2) mixing non-porous SiO_xAdding into the mixed conductive agent solution, wherein SiO_xThe component ratio to the conductive agent is 10: 1, stirring for 1 hour at the stirring speed of 800r/min to uniformly mix the components, putting the mixture into a vacuum drying oven for vacuum drying for 2 hours at the temperature of 85 ℃ to remove the solvent, and obtaining the nonporous SiO with the surface coated with the conductive agent_xParticles;

(3) mixing coal tar pitch and SiO coated with conductive agent_xThe mass ratio of the particles is 3: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ in an inert atmosphere to complete coating, heating to 550 ℃ to complete preliminary carbonization, and heating to 1100 ℃ to perform high-temperature carbonization for 24 hours to obtain a silicon-carbon material with a three-layer structure;

(4) the silicon-carbon material and the artificial graphite are mixed according to the mass ratio of 30%: mixing the components in a proportion of 70 percent, and performing low-speed ball milling for 4 hours in a ball milling tank to uniformly mix the components to obtain the silicon-carbon negative electrode material of the comparative example 1.

Comparative example 2

The difference from the examples is that the preparation of the silicon carbon anode material of the present comparative example does not perform the coating step of the conductive agent of the step (3) and the step (4). The preparation method comprises the following steps:

(2) preparing hydrochloric acid with the concentration of 1mol/L, and reacting SiO_xReacting the mixture with MgO granules in hydrochloric acid, filtering, repeating the acid washing step once again to remove MgO impurities to obtain porous SiO_x(ii) a The porous SiO after acid washing_xPlacing the mixture in deionized water, carrying out ultrasonic cleaning for 10min, filtering, and repeating the step for 3-5 times; washing the porous SiO_xVacuum drying in a vacuum drying oven at 85 deg.C for 2 hr to obtain porous SiO without impurities and moisture_x；

(3) Mixing coal tar pitch and porous SiO_xThe mass ratio of the particles is 3: 1, ball-milling and fusing for 3 hours, heating to 260 ℃ in an inert atmosphere to complete coating, heating to 550 ℃ to complete preliminary carbonization, and heating to 1100 ℃ to perform high-temperature carbonization for 24 hours to obtain a porous silicon-carbon material with a core-shell structure;

(4) the porous silicon-carbon material and the artificial graphite are mixed according to the mass ratio of 30%: mixing the components in a proportion of 70 percent, and ball-milling the mixture in a ball-milling tank at a low speed for 4 hours to uniformly mix the mixture to obtain the porous silicon-carbon negative electrode material.

Electrochemical performance tests were performed on the silicon-carbon anode materials prepared in examples 1 to 18 and comparative examples 1 to 2, and the test results are shown in table 1.

Table 1 electrochemical performance test results of silicon carbon anode materials prepared in examples and comparative examples

From the test results of table 1, it can be seen that:

1) the initial reversible specific capacity of the porous silicon carbon anode material is not less than 487.8mAh/g, and the first efficiency is not less than 87.86%, which shows that the porous silicon carbon anode material has higher lithium removal capacity and higher first charge-discharge efficiency. Because the internal porous structure reserves the space of volume expansion, the stress generated by the volume expansion of the material is reduced, the material is broken and pulverized, the loss of electric contact between the materials is effectively avoided, and meanwhile, SiO_xThe carbon nano tube/graphene + Super P covered on the surface improves the conductivity of the material, and greatly reduces the capacity loss caused by the obstruction of ion transmission.

Electrolyte and Li consumed in SEI film forming process of amorphous carbon coated on material surface in first charge-discharge process⁺Less consumption than silicon material, and the formed SEI film is more uniform and stable, and can avoid SiO inside_xContact with and reaction with the electrolyte. The structure and the carbon nano tube/graphene + Super P covered on the surface limit SiO of the inner core_xThe expansion and the generation of cracks during lithium intercalation can avoid the electrolyte from entering the cracks to generate new phases, thereby reducing the influence on the electrolyte and Li⁺The consumption of (c).

2) The volume expansion rate of the porous silicon-carbon negative pole piece is less than or equal to 19.51 percent, is far lower than 300 percent when pure Si is fully embedded with lithium, and is lower than that of SiO with a nonporous structure_x37.25% of the total weight of the conductive paste, which is slightly lower than 22.66% of the total weight of the conductive paste without the conductive agent coating. The analysis reasons are as follows:

(a)SiO_xthe volume change rate is reduced correspondingly although the volume of the inner core is lower than that of pure Si;

(b) SiO of porous structure_xThe inner core reserves a certain space for the volume expansion during lithium intercalation, and can basically meet the volume during lithium intercalationExpanding;

(c) coated conductive agent network and outer layer amorphous carbon limited SiO_xThe inner core is expanded to the outside;

(d) the porous silicon carbon material and the graphite material are mixed to prepare the porous silicon carbon negative electrode material, so that the volume expansion of the negative electrode is further reduced.

3) The capacity retention rate of the porous silicon-carbon negative electrode plate is more than or equal to 94.6% after the electrode plate is cycled for 500 times, which shows that the porous silicon-carbon negative electrode material has good cycle performance.

The capacity loss of the silicon-carbon cathode is mainly caused by the following reasons: the volume expansion and contraction causes the cracking and pulverization of the material, and the irreversible capacity caused by the obstruction of ion transmission after the loss of electric contact; the SEI film caused by volume expansion-contraction is repeatedly cracked and generated, and lithium ions and electrolyte are continuously consumed; after the SEI film is broken, the electrolyte and HF in the electrolyte and the silicon-carbon negative electrode generate side reaction, and Si and Li are consumed⁺And an electrolyte, and the product generated by the side reaction further deteriorates the battery performance. The invention adopts a core-shell type three-layer composite structure design, and effectively inhibits the occurrence of the above conditions.

During multiple charge-discharge cycles, due to the porous SiO of the material_xThe structure is present, a space for material expansion is provided, and simultaneously, due to the carbon nano tube/graphene + Super P network and the amorphous carbon on the surface, the conductivity is enhanced, the obstruction of ion transmission caused by the deterioration of electrical contact due to the crushing and pulverization of the material in the cyclic process is inhibited, and the irreversible capacity caused by the obstruction of ion transmission in the cyclic process is reduced.

Because the surface is coated with the amorphous carbon, a good SEI film is formed on the surface of the amorphous carbon in the first circulation process, and because of the structural design of the porous and coated structure, the continuous rupture-regeneration process of the SEI film on the surface caused by the huge volume change of the material during lithium extraction is avoided, and the SiO is also avoided_xThe micro-cracks exposed in the electrolyte and the particles react with the electrolyte to form a new phase, thereby reducing the electrolyte and Li caused in the circulation process⁺A large consumption of energy.

The three-layer structure is providedThe measured silicon-carbon cathode solves the problems of volume change rate, electric contact among particles and SiO_xThe problem of reaction with electrolyte reduces the capacity loss caused by the obstruction of ion transmission, the capacity loss caused by the continuous crack generation of SEI film and SiO_xConsuming electrolyte and Li by reaction with electrolyte⁺The resulting capacity loss, thereby improving the cycle performance of the material.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A porous silicon carbon negative electrode material is characterized in that: comprises a porous silicon carbon material and a graphite material; the porous silicon carbon material is of a core-shell structure and comprises an inner core, and an intermediate layer and an outermost layer which are sequentially coated on the inner core, wherein the inner core is an amorphous porous silicon oxygen material SiO_xWherein x is more than 0 and less than or equal to 2, the middle layer is a reticular conductive agent coating layer, the outermost layer is an amorphous carbon coating layer, and the porous silicon-carbon negative electrode material is coated on the surface of the microporous copper foil to form a silicon-carbon negative electrode plate.

2. The porous silicon carbon anode material of claim 1, wherein: the porous silica material SiO_xThe porosity of the porous material is 20-80%.

3. The porous silicon carbon anode material of claim 1, wherein: the porous silica material SiO_xMedian particle diameter D of₅₀Is 3 to 7 μm.

4. The porous silicon carbon anode material of claim 1, wherein: the thickness of the conductive agent coating layer is 10-100 nm.

5. The porous silicon carbon anode material of claim 1, wherein: the conductive agent comprises a conductive agent A and a conductive agent B, wherein the conductive agent A is at least one of carbon nano tubes and graphene, and the conductive agent B is conductive carbon black.

6. The porous silicon carbon anode material of claim 1, wherein: the thickness of the amorphous carbon coating layer is 0.5 to 2 μm.

7. The porous silicon carbon anode material of claim 1, wherein: the amorphous carbon is formed by carbonizing at least one of petroleum pitch and coal tar pitch.

8. The porous silicon carbon anode material of claim 1, wherein: the mass ratio of the porous silicon-carbon material to the graphite material is 5-50%: 50-95%.

9. The porous silicon carbon anode material of claim 1, wherein: the porous silica material SiO_xAnd the mass ratio of the conductive agent to the amorphous carbon is 20-50%: 5-20%: 30-75%.

10. The porous silicon carbon anode material of claim 1, wherein: the graphite material is at least one of natural graphite, artificial graphite, microcrystalline graphite, mesocarbon microbeads and soft carbon.

11. The preparation method of the porous silicon-carbon negative electrode material is characterized by comprising the following steps of:

step 1) preparing silicon oxide SiO_xAnd the active metal powder according to the mass ratio of (0.5-2): 1, ball milling for 1-4 h in a ball milling tank to uniformly mix, carrying out heat treatment for 4-24 h at 650-1000 ℃ under inert atmosphere, and crushing and grading to obtain the productD₅₀Silicon oxide SiO of 3 to 7 μm_xAnd a metal oxide composite material, wherein x is more than 0 and less than or equal to 2;

12. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in the step 1), the active metal powder is at least one of magnesium, zinc and iron.

13. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in step 1), the silicon oxide SiO_xThe mass ratio of the active metal powder to the active metal powder is（0.8~1.2）：1。

14. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in the step 1) and the step 5), the inert atmosphere is one of nitrogen, argon and helium.

15. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in step 2), the porous SiO_xThe porosity of the material is 20-80%.

16. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in the step 3), the dispersant is polyvinylpyrrolidone.

17. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in the step 4), the vacuum drying temperature is 60-150 ℃, and the drying time is 1-3 h.

18. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in the step 5), the asphalt is at least one of petroleum asphalt and coal tar asphalt.

19. The method for preparing the porous silicon-carbon anode material according to claim 11, wherein: in the step 6), the graphite material is at least one of natural graphite, artificial graphite, microcrystalline graphite, mesocarbon microbeads and soft carbon.

20. A lithium ion battery, characterized by: the porous silicon carbon negative electrode material comprises the porous silicon carbon negative electrode material as claimed in any one of claims 1 to 10.