CN115986114A

CN115986114A - Silicon-oxygen-carbon composite material and preparation method thereof, negative electrode raw material, negative electrode plate and lithium ion battery

Info

Publication number: CN115986114A
Application number: CN202111204150.0A
Authority: CN
Inventors: 庞春雷; 沙玉静; 谢维; 邓志强; 任建国; 夏圣安; 贺雪琴
Original assignee: Huawei Technologies Co Ltd; BTR New Material Group Co Ltd
Current assignee: Huawei Technologies Co Ltd; BTR New Material Group Co Ltd
Priority date: 2021-10-15
Filing date: 2021-10-15
Publication date: 2023-04-18

Abstract

The application discloses a silicon-oxygen-carbon composite material, a preparation method of the silicon-oxygen-carbon composite material, a negative electrode raw material, a negative electrode plate and a lithium ion battery, and belongs to the field of electrode materials. The silicon-oxygen-carbon composite material comprises: an inner core and an outer layer, the outer layer comprising: a carbon coating layer and a plurality of carbon protrusions; the inner core is a silicon-oxygen material doped with metal; the carbon coating layer is coated outside the inner core, and a plurality of carbon protrusions are formed on the outer surface of the carbon coating layer. The application discloses silicon-oxygen-carbon composite material, based on the bellied synergism of a plurality of carbons of metallization kernel, the even carbon coating of thickness and distribution in carbon coating outside, can show reversible capacity, first effect, rate capability and the circulation stability that improves lithium ion battery.

Description

Silicon-oxygen-carbon composite material and preparation method thereof, negative electrode raw material, negative electrode pole piece and lithium ion battery

Technical Field

The disclosure relates to the field of electrode materials, in particular to a silicon-oxygen-carbon composite material, a preparation method thereof, a negative electrode raw material, a negative electrode plate and a lithium ion battery.

Background

Silicon has the theoretical specific capacity as high as 4200mAh/g, and the silicon-based negative electrode material has important significance for developing a lithium ion battery with high energy density. However, the silicon-based negative electrode material has a large volume expansion coefficient, and the volume change amount of the silicon-based negative electrode material is up to 300% in the lithiation/delithiation process, so that the silicon-based negative electrode material is pulverized and crushed due to the volume change in the charge-discharge cycle process, and the reversible capacity, the coulombic efficiency and the cycle stability of the lithium ion battery are restricted.

The silica material belongs to one of silicon-based cathode materials, and the silica material has higher oxygen content, so that more irreversible capacity and lower coulombic efficiency can be generated in the process of lithium intercalation for the first time. In the related technology, a carbon source is used for constructing a carbon coating layer outside a silica material to form a carbon-coated silicon-based anode material, the volume effect of silicon is relieved through the carbon coating layer, the direct interface contact and side reaction of the silicon and electrolyte are reduced, the surface conductivity of the silicon is increased, and therefore the volume expansion of the silicon is reduced, and the first efficiency and the capacity of the silicon-based anode material are increased. The construction method of the carbon coating layer comprises the following steps: examples of the solid/liquid phase mixed carbonization method include a solid/liquid phase mixed carbonization method (for example, the carbon source is pitch or resin), a gas phase cracking method (for example, the carbon source is acetylene or methane), an emulsion polymerization method (for example, the carbon source is polyacrylonitrile), and a high temperature pyrolysis method (for example, the carbon source is polyvinyl alcohol or polyvinylidene fluoride).

However, the carbon-coated silicon-based anode material provided by the related art has a limited effect on improving the reversible capacity, the first coulombic efficiency, the rate capability and the cycling stability of the silicon-based anode material.

BRIEF SUMMARY OF THE PRESENT DISCLOSURE

In view of the above, the present disclosure provides a silicon-oxygen-carbon composite material, a preparation method thereof, a negative electrode raw material, a negative electrode sheet, and a lithium ion battery, which can solve the above technical problems.

Specifically, the method comprises the following technical scheme:

in one aspect, a silicon oxygen carbon composite is provided, the silicon oxygen carbon composite comprising: an inner core and an outer layer, the outer layer comprising: a carbon coating layer and a plurality of carbon protrusions;

the inner core is a silicon-oxygen material doped with metal;

the carbon coating layer is coated outside the inner core, and the plurality of carbon protrusions are formed on the outer surface of the carbon coating layer.

According to the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure, the inner core is a silicon-oxygen material doped with metal, and the metal is doped into the silicon-oxygen material, so that the silicon-oxygen material is metallized, the conductivity and the rate capability of the inner core are improved, meanwhile, part of doped metal can be stably combined with oxygen in the silicon-oxygen material, the irreversible loss of oxygen elements to lithium ions in the electrochemical lithium intercalation process of the silicon-based negative electrode material is avoided, and the reversible capacity, the first effect and the cycling stability of the silicon-based lithium ion battery are further improved.

The silicon-oxygen-carbon composite material provided by the embodiment of the disclosure comprises a carbon coating layer and a plurality of carbon protrusions formed outside the carbon coating layer, wherein the wettability of the outer layer and electrolyte is improved by increasing the specific surface area of the outer layer, and the lithium ion diffusion and charge transfer performance of the surface of a silicon-based negative electrode material are promoted, so that the interface charge transfer capacity of the silicon-oxygen-carbon composite material is enhanced, and the rate capability and the cycle stability of a lithium ion battery are improved.

The silicon-oxygen-carbon composite material provided by the embodiment of the disclosure simultaneously comprises a carbon element and a metal element, so that when the silicon-oxygen-carbon composite material is prepared, a carbon source and a metal source can be mixed with a silicon-oxygen material in the form of a metal-carbon source complex, metal atoms in the metal source can react with the silicon-oxygen material to form a metal-doped silicon-oxygen material, and the carbon source can be adsorbed and deposited on the surface of the silicon-oxygen material by taking the metal atoms as active sites to form a carbon coating layer. The strong deposition and adsorption of the carbon source on the surface of the silica material is beneficial to enabling the carbon coating layer to be uniformly deposited on the surface of the silica material to form the carbon coating layer with uniform thickness and compactness. The uniform coating of the carbon coating layer can avoid side reaction caused by exposure of silicon in electrolyte due to nonuniform coating, and improve the circulation stability of the silicon-based negative electrode material. When the carbon coating layer with uniform thickness is used in a lithium ion battery, the carbon coating layer with uniform thickness can not only effectively avoid the contact of electrolyte and a silica material, but also ensure uniform lithium embedding, and is favorable for improving the reversible capacity, the first effect, the rate capability and the cycling stability of the lithium ion battery.

Therefore, the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure can significantly improve the reversible capacity, the first effect, the rate capability and the cycle stability of the lithium ion battery based on the synergistic effect of the metalized inner core, the carbon coating layer with uniform thickness and the plurality of carbon protrusions distributed outside the carbon coating layer.

In some possible implementations, the carbon protrusions have a size of 5nm to 50nm;

wherein the size of the carbon protrusion is a size of the carbon protrusion in a direction parallel to the surface of the inner core.

In some possible implementations, the average difference in distance MD between any two adjacent carbon protrusions is <20%;

wherein the content of the first and second substances,

r is the center distance between any two adjacent carbon protrusions, and n is the total number of the carbon protrusions on the carbon coating layer.

In some possible implementations, the silicon oxycarbide composite has an average particle size D50 of less than or equal to 10um;

the thickness of the carbon coating layer is 1nm-100nm.

For the silicon-oxygen-carbon composite material, the sizes of all parts are limited, so that the silicon-oxygen-carbon composite material has good electrical property and mechanical property, and is suitable for being used as a negative electrode material for manufacturing a negative electrode plate.

In some possible implementations, the silicon oxygen material has a chemical formula of SiO _x Wherein x is more than or equal to 0.5 and less than 2. For example, if x is 1, the silicon oxide material is a silicon monoxide SiO, and silicon oxide materials having such a chemical formula are particularly suitable for obtaining the core of the above-described metallized silicon oxide material.

In some possible implementations, the metal includes at least one of Li, na, K, mg, cu, ag, al.

When the metal M is at least one of Li, na, K and Mg, the metal M reacts with part of the silica material to form silicate, so that the material of the inner core 1 is silicate/SiO _x /Si/SiO ₂ Wherein 0.5. Ltoreq. X < 2.

The metal element M is combined with oxygen in the silicon-oxygen material to form silicate, so that oxygen in the silicon-oxygen material is consumed in advance, and irreversible lithium consumption in the electrochemical lithium intercalation process of the lithium ion battery is avoided, and the positive effect on improving the reversible capacity and the first effect of the silicon-based negative electrode material is achieved. In addition, the formed silicate also has abundant lithium ion channels, which is beneficial to the migration and diffusion of lithium ions and has a positive effect on improving the rate capability of the silicon-based negative electrode material.

When the metal M is at least one of Cu, ag and Al, the metal M reacts with partial silica material in the form of metal complex to form metal M-silicon alloy, so that the material of the inner core 1 is presented as metal M-silicon alloy/SiO _x /Si/SiO ₂ In a combination of (1) and (2) (wherein 0.5. Ltoreq. X).

The metal element M reacts with the silica material to form the metal M-silicon alloy, and the metal M-silicon alloy has good electronic conductivity, which has important significance for improving the electronic conductivity and rate capability of the silicon-based anode material.

The various metals can achieve the purpose of improving the conductivity and the rate capability of the core, and can also improve the diffusion depth of active lithium in the core, thereby achieving the purpose of improving the reversible capacity, the first effect, the rate capability and the cycle stability of the lithium ion battery.

On the other hand, the embodiment of the disclosure also provides a preparation method of the silicon-oxygen-carbon composite material, wherein the silicon-oxygen-carbon composite material is as shown above;

the preparation method of the silicon-oxygen-carbon composite material comprises the following steps:

stirring a carbon source, a metal source and a silicon-oxygen material in a dispersion solvent for a first set time, and then carrying out solid-liquid separation treatment to obtain a precursor of the silicon-oxygen-carbon composite material; wherein the solid-liquid separation treatment comprises: volatilizing and drying or distilling;

and calcining the precursor of the silicon-oxygen-carbon composite material under a protective atmosphere to obtain the silicon-oxygen-carbon composite material.

According to the preparation method of the silicon-oxygen-carbon composite material, the carbon source, the metal source and the silicon-oxygen material are fully and uniformly stirred in the dispersing solvent, in the process, the carbon source and the metal source can be mutually complexed to form a metal source-carbon source complex, and the metal source-carbon source complex is uniformly dissociated in the dispersing solvent.

After the stirring is completed, solid-liquid separation is performed by a volatilization drying treatment or a distillation treatment, and in this solid-liquid separation method, the metal source-carbon source complex free in the dispersion solvent can be promoted to be deposited layer by layer on the surface of the silica material as the dispersion solvent is gradually reduced, so that crystal clusters are formed, and finally, a precursor of the silica-oxygen-carbon composite material is formed. In the precursor of the silicon-oxygen-carbon composite material, the metal source in the metal source-carbon source complex can be adsorbed on the surface of the silicon-oxygen material, so that the precursor of the silicon-oxygen-carbon composite material is in a form that the silicon-oxygen material, the metal source and the carbon source are sequentially distributed from inside to outside.

By calcining the precursor of the silicon-oxygen-carbon composite material under the protective atmosphere, the metal source can spontaneously enter the interior of the silicon-oxygen material to react with the silicon-oxygen material and leave a vacancy on the surface of the silicon-oxygen material, and the remaining carbon source takes the silicon-oxygen material as an inner core to collapse and contract and enter the vacancy, so that a carbon layer structure with a bulge on the surface can be formed. After calcination, the silica material reacts with the metal source to form a metallized core of silica material, while the carbon layer structure is carbonized to form an outer layer having a carbon coating and a plurality of carbon protrusions.

In some possible implementation manners, the solid-liquid separation treatment is performed under the condition of continuous stirring, so that a precursor of the silicon-oxygen-carbon composite material is prevented from depositing in a dispersion solvent, the dispersion degree of the precursor of the silicon-oxygen-carbon composite material is favorably improved, and the clustering phenomenon is prevented.

In some possible implementations, the stirring the carbon source, the metal source, and the silica material in the dispersion solvent for a first set time includes:

allowing the carbon source and the metal source to undergo a complexation reaction in the dispersion solvent to form a feedstock system containing a metal source-carbon source complex;

and adding the silica material into the raw material system, and stirring for the first set time.

In some possible implementations, the metal source includes at least one of elemental Li, elemental Na, elemental K, and elemental Mg.

In some possible implementations, the metal source is a carbon-containing metal complex.

In some possible implementations, the carbon-containing metal complex includes at least one of methyllithium, copper phthalocyanine, and aluminum acetylacetonate.

In some possible implementations, the dispersion solvent includes at least one of dimethyl carbonate, tetrahydrofuran, toluene, benzene, diethyl ether, propylene oxide, ketones, ethylene glycol dimethyl ether.

In some possible implementations, the first set time is between 3 hours and 24 hours.

In some possible implementations, the calcining treatment includes:

heating the precursor of the silicon-oxygen-carbon composite material to a calcination temperature under the condition that the heating rate is greater than or equal to 5 ℃/min, and calcining the silicon-oxygen-carbon composite material at the calcination temperature for a second set time.

By controlling the heating rate to be more than or equal to 5 ℃/min during calcination, the phenomenon that carbon layer structures with bulges on the surfaces in the precursor of the silicon-oxygen-carbon composite material are randomly connected into a whole under the drive of thermal motion due to the overlong carbonization heating process can be avoided, so that irregular, non-uniform, different-size and broken carbon layers are avoided, the formed outer layer is ensured to have a compact carbon coating layer and a plurality of carbon bulges which are uniformly distributed, and the excellent electrochemical performance brought by the outer layer is ensured.

In some possible implementations, the calcination temperature is 400 ℃ to 1200 ℃ and the second set time is 0.5h to 10h to ensure that the silica material can be sufficiently metallized and to ensure that the outer layer obtains the desired morphology.

In another aspect, a negative electrode material is provided, where the negative electrode material includes: silicon-based negative electrode material, conductive agent and binder;

the silicon-based negative electrode material is any one of the silicon-oxygen-carbon composite materials shown above.

On the other hand, the negative pole piece is prepared from the negative pole raw material.

Illustratively, the preparation method of the negative electrode plate is as follows: dissolving a binder in a polar solvent to obtain a glue solution; mixing the glue solution with the silicon-based negative electrode material and the conductive agent, and uniformly stirring to obtain negative electrode slurry; and coating the negative electrode slurry on two opposite surfaces of the current collector, and sequentially drying and rolling to obtain the negative electrode piece.

In another aspect, a lithium ion battery is also provided, and the lithium ion battery comprises the negative electrode plate.

The lithium ion battery provided by the embodiment of the disclosure further comprises a positive electrode plate, electrolyte, a diaphragm and an encapsulation layer besides the negative electrode plate.

The electrolyte is filled in the space between the negative pole piece and the positive pole piece, and the diaphragm is positioned in the electrolyte and used for isolating the negative pole piece from the positive pole piece. The packaging layer is used for integrally packaging the negative pole piece, the positive pole piece, the electrolyte and the diaphragm.

The lithium ion battery realizes the storage and release of energy through the de-intercalation of lithium ions between the negative pole piece and the positive pole piece, the electrolyte is a carrier for the transmission of the lithium ions between the negative pole piece and the positive pole piece, the diaphragm is ion-conductive but electronically insulated, and the negative pole piece and the positive pole piece are separated to prevent short circuit while the migration of the lithium ions is ensured by the diaphragm.

Drawings

Fig. 1 is a schematic structural diagram of an exemplary silicon-oxygen-carbon composite material provided in an embodiment of the present disclosure;

fig. 2 is a first process schematic diagram for illustrating a structure synthesis mechanism of a silicon-oxygen-carbon composite material provided by an embodiment of the disclosure;

fig. 3 is a schematic diagram of a second process for illustrating a structure synthesis mechanism of a silicon-oxygen-carbon composite material provided by an embodiment of the disclosure;

fig. 4 is a schematic diagram of a third process for illustrating a structure synthesis mechanism of a silicon-oxygen-carbon composite material according to an embodiment of the disclosure;

fig. 5 is a fourth process diagram for illustrating a structure synthesis mechanism of a silicon-oxygen-carbon composite material provided by an embodiment of the disclosure;

fig. 6 is a fifth process diagram for illustrating a structure synthesis mechanism of a silicon-oxygen-carbon composite material according to an embodiment of the disclosure;

fig. 7 is a schematic structural diagram of an exemplary lithium ion battery provided in an embodiment of the present disclosure;

figure 8 is an EDS diagram for a silicon oxygen carbon composite provided in example 1 of the present disclosure;

figure 9 is an EDS plot of a silicon-oxygen-carbon composite provided by comparative example 2 of the present disclosure;

fig. 10 is an SEM image at different magnifications of a conventional carbon coating based resulting siloxycarbon composite provided by embodiments of the disclosure;

fig. 11 is an SEM image at different magnifications of a conventional carbon cladding + prelithiation based silicon-oxygen-carbon composite provided by embodiments of the disclosure;

fig. 12 is an SEM image at different magnifications of a silicon-oxygen-carbon composite material obtained based on the present disclosure provided in an example of the present disclosure.

In the SEM images shown in fig. 10 to 12, S4800 denotes a model of a SEM, 3.0kv denotes an acceleration voltage of the SEM, 8.1mm denotes a focal length, 10k and 50k denote different magnifications, respectively, and 1.00 μm and 5.00 μm denote different scales, respectively.

The reference numerals denote:

1-the core of the kernel,

2-an outer layer of a polymer,

a 21-carbon coating layer, wherein,

the 22-carbon bump is formed by the following steps,

100-a negative pole piece, wherein the negative pole piece,

200-a positive pole piece, wherein the positive pole piece is provided with a positive electrode,

300-an electrolyte solution, wherein the electrolyte solution comprises a base,

400-a membrane, which is provided with a membrane,

500-encapsulation layer.

Detailed Description

In order to make the technical solutions and advantages of the present disclosure clearer, the following will describe embodiments of the present disclosure in further detail with reference to the accompanying drawings.

For example, a silicon oxide material is a common silicon-based negative electrode material and has an important meaning for developing a super-large-capacity lithium ion battery, however, as described above, since the silicon-based negative electrode material has a large volume expansion coefficient, and in addition, the oxygen content in the silicon oxygen material is high, a large irreversible capacity and a low coulombic efficiency are generated in the first lithium intercalation process, and the natural disadvantage causes that the silicon-based negative electrode material represented by the silicon oxide material cannot be applied in a large scale at present.

In the related technology, a carbon source is used for constructing a carbon coating layer outside a silica material to form a carbon-coated silicon-based anode material, the volume effect of silicon is relieved through the carbon coating layer, the direct interface contact and side reaction of the silicon and electrolyte are reduced, the surface conductivity of the silicon is increased, and therefore the volume expansion of the silicon is reduced, and the first efficiency and the capacity of the silicon-based anode material are increased. The construction method of the carbon coating layer comprises the following steps: examples of the solid/liquid phase mixed carbonization method include a solid/liquid phase mixed carbonization method (for example, the carbon source is pitch or resin), a gas phase cracking method (for example, the carbon source is acetylene or methane), an emulsion polymerization method (for example, the carbon source is polyacrylonitrile), and a high temperature pyrolysis method (for example, the carbon source is polyvinyl alcohol or polyvinylidene fluoride).

However, in the related art, when the carbon coating layer is constructed, the adsorption of the carbon source on the surface of the silicon-oxygen anode material is weak, only van der waals force is weak in interaction force, uniform deposition on the surface of the silicon-oxygen anode material cannot be achieved, a stably adsorbed carbon coating layer is difficult to obtain, or the thickness of the carbon coating layer is uneven, for example, a part of the carbon coating layer is thick, and a part of the carbon coating layer is thin. Therefore, when the silica negative electrode material provided by the related technology is used in a lithium ion battery, the electrolyte is easily contacted with the silicon-based negative electrode material due to the carbon coating layer with uneven thickness, so that interface side reaction and continuous consumption of the electrolyte are caused, and the problems of low initial coulomb efficiency (first effect for short), quick cycle attenuation and the like of the lithium ion battery are caused. In addition, the carbon coating layer with uneven thickness can also cause inconsistent stress release after local lithium intercalation, thereby further causing internal stress imbalance and particle pulverization caused by local expansion of silicon-based negative electrode material particles, and causing the problems of low capacity, low first effect, quick cycle attenuation and the like of the lithium ion battery. In addition, the carbon coating layer designed by the related technology has poor infiltration effect with electrolyte, so that the interface charge transfer capability of the lithium ion battery is reduced and the rate capability is poor.

Therefore, the carbon-coated silicon-based negative electrode material provided by the related technology has limited improvement effects on reversible capacity, first coulombic efficiency and cycle stability of the lithium ion battery.

According to an aspect of an embodiment of the present disclosure, there is provided a silicon-oxygen-carbon composite material, as shown in fig. 1, including: an inner core 1 and an outer layer 2, the outer layer 2 comprising: a carbon coating layer 21 and a plurality of carbon protrusions 22. The inner core 1 is a silicon-oxygen material doped with metal, the carbon coating layer 21 is coated outside the inner core 1, and the plurality of carbon protrusions 22 are formed on the outer surface of the carbon coating layer 21.

According to the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure, the inner core 1 is a silicon-oxygen material doped with metal, and the metal is doped into the silicon-oxygen material, so that the silicon-oxygen material is metallized, the conductivity and the rate capability of the inner core 1 are improved, meanwhile, part of doped metal is stably combined with oxygen in the silicon-oxygen material, irreversible loss of oxygen elements to lithium ions in the electrochemical lithium intercalation process of the silicon-based negative electrode material is avoided, and the reversible capacity, the first effect and the cycling stability of the silicon-based lithium ion battery are further improved.

According to the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure, the outer layer 2 comprises the carbon coating layer 21 and the plurality of carbon protrusions 22 formed outside the carbon coating layer 21, the wettability of the outer layer 2 and an electrolyte is improved by increasing the specific surface area of the outer layer 2, and the lithium ion diffusion and charge transfer performance of the surface of the silicon-based negative electrode material is promoted, so that the interface charge transfer capacity of the silicon-oxygen-carbon composite material is enhanced, and the rate capability and the cycle stability of a lithium ion battery are improved.

The silicon-oxygen-carbon composite material provided by the embodiment of the disclosure simultaneously comprises a carbon element and a metal element, so that when the silicon-oxygen-carbon composite material is prepared, a carbon source and a metal source can be mixed with a silicon-oxygen material in the form of a metal-carbon source complex, metal atoms in the metal source can react with the silicon-oxygen material to form a metal-doped silicon-oxygen material, and the carbon source can be adsorbed and deposited on the surface of the silicon-oxygen material by taking the metal atoms as active sites to form a carbon coating layer 21. The strong deposition and adsorption of the carbon source on the surface of the silicon oxygen material is beneficial to uniformly depositing the carbon coating layer 21 on the surface of the silicon oxygen material to form the carbon coating layer 21 with uniform and compact thickness. The uniform coating of the carbon coating layer 21 can avoid side reaction caused by exposure of silicon in electrolyte due to nonuniform coating, and improve the circulation stability of the silicon-based negative electrode material. When the carbon coating layer 21 with uniform thickness is used in a lithium ion battery, the contact between electrolyte and a silica material can be effectively avoided, uniform lithium embedding can be ensured, and the capacity, the first effect, the rate performance and the cycling stability of the lithium ion battery can be improved.

Therefore, the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure can significantly improve the reversible capacity, the first effect, the rate capability and the cycle stability of the lithium ion battery based on the synergistic effect of the metalized core 1, the carbon coating layer 21 with uniform thickness and the plurality of carbon protrusions 22 distributed outside the carbon coating layer 21.

In the embodiment of the disclosure, the average particle diameter D50 of the silicon-oxygen-carbon composite material is less than or equal to 10um, wherein the average particle diameter D50 of the silicon-oxygen-carbon composite material is a size obtained by observing the whole silicon-oxygen-carbon composite material under an electron microscope, and the average particle diameter D50 refers to an equivalent diameter of the largest particle when the cumulative distribution in a particle size distribution curve is 50%. For example, the average particle diameter D50 of the silicon-oxygen-carbon composite material is 1um to 10um, and further for example, the average particle diameter D50 of the silicon-oxygen-carbon composite material includes but is not limited to: 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, etc.

In some examples, the thickness of the carbon coating layer 21 is 1nm to 100nm, wherein the thickness of the carbon coating layer 21 is a dimension of the carbon coating layer 21 in a diameter direction of the core 1. For example, the thickness of the carbon coating layer 21 includes, but is not limited to: 1nm, 10nm, 15nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.

The plurality of carbon protrusions 22 are uniformly distributed on the outer portion of the carbon coating layer 21, so that the outer surface of the carbon coating layer 21 is uneven, and the structure of the carbon protrusions 22 includes, but is not limited to: arc convex block, conical convex block such as cone or pyramid, cylindrical convex block such as cylinder or prism, and other geometric shapes. The structural arrangement of the carbon protrusions 22 on the carbon coating layer 21 can improve the contact area of the silicon-oxygen-carbon composite material and the electrolyte, and facilitates deep lithium insertion.

In some examples, the size of the carbon bumps 22 is 5nm-50nm; wherein the size of the carbon bump 22 is the size of the carbon bump 22 in the direction along the surface of the core 1.

The above-mentioned dimensions at the respective positions on the carbon protrusion 22 may be changed in the diameter direction of the inner core 1, but still remain in the above-mentioned range of 5nm to 50 nm. For example, the size of carbon protrusions 22 is 10nm-50nm, 20nm-50nm, 30nm-50nm, 40nm-50nm, 10nm-20nm, 10nm-30nm, 10nm-40nm, 20nm-30nm, 20nm-40nm, etc., and further, the size of carbon protrusions 22 includes, but is not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc.

Further, the average difference MD in distance between any two adjacent carbon protrusions 22<20 percent of the total weight of the mixture, wherein,

r is the center-to-center distance between any two adjacent carbon protrusions 22, and n is the total number of carbon protrusions 22 on the carbon cladding layer 21.

In the embodiment of the present disclosure, the carbon coating layer 21 is uniformly distributed on the outer surface of the core 1, and the carbon coating layer 21 has at least the following advantages:

the carbon coating layer 21 has a certain mechanical strength, can ensure the integrity of silicon-oxygen particles in the process of lithium desorption from active silicon, inhibit the pulverization of the silicon-oxygen particles, promote the structural stability and integrally improve the cycle performance of the lithium ion battery. The carbon coating layer 21 is dense enough so that the electrolyte cannot contact the silicon oxide material through the carbon coating layer 21, thereby suppressing the occurrence of side reactions between the electrolyte and the silicon oxide material. The carbon coating layer 21 has good conductivity, can greatly improve the electron gaining and losing capacity of active silica, improves the lithium releasing and embedding efficiency of silica materials, promotes capacity exertion and deep lithium embedding, and improves the reversible capacity and the first effect of the lithium ion battery.

The outer layer 2 including the carbon coating layer 21 and the carbon protrusions 22 is made of carbon, that is, the raw material for preparing the outer layer 2 at least includes carbon element, and further, the raw material for preparing the outer layer 2 may further include doping element to further improve the conductivity and stability of the outer layer 2.

In some examples, the raw materials for preparing the outer layer 2 include: carbon and a doping element, wherein the weight percentage of the doping element is less than or equal to 5%. For example, the doping element includes, but is not limited to, an N element, a P element, and a F element, and the doping element not only can improve the conductivity of the outer layer 2, but also can reduce the lithium ion transport energy barrier on the surface of the core 1, thereby improving the transport efficiency of lithium ions.

For core 1, which is a silicon-oxygen material doped with a metal, there may be different coordination forms between the metal and the silicon-oxygen material depending on the specific metal species, for example, there are some metals that are more prone to react with silicon dioxide to form silicates; for example, there are also metals that are more prone to react with elemental silicon to form alloys.

In some examples, the metal includes at least one of Li, na, K, mg, cu, ag, al.

Wherein, when the metal M is at least one selected from Li, na, K, mg and Al, the metal M reacts with at least part of the silica material to form silicate, so that the material of the inner core 1 is silicate/SiO _x /Si/SiO ₂ Wherein 0.5. Ltoreq. X < 2.

When the metal M is at least one of Cu and Ag, the metal M reacts with part of the silicon oxygen material in the form of metal complex to form metal M-silicon alloy, so that the material of the inner core 1 is metal M-silicon alloy/SiO _x /Si/SiO ₂ In a combination of (1) and (2) (wherein 0.5. Ltoreq. X).

The metal element M reacts with the silicon oxygen material to form the metal M-silicon alloy, and the metal M-silicon alloy has good electronic conductivity, so that the metal M-silicon alloy has important significance for improving the electronic conductivity and rate capability of the silicon-based cathode material.

The above metals can improve the conductivity and rate performance of the core 1, and can also improve the diffusion depth of active lithium in the core 1, thereby improving the reversible capacity, first effect, rate performance and cycle stability of the lithium ion battery.

The reason why the diffusion depth of the active lithium in the core 1 can be increased by the above-mentioned metals is that the diffusion depth of the active lithium in the core 1 is related to the diffusion coefficient of lithium ions in the core 1, and the higher the diffusion coefficient of lithium ions is, the higher the diffusion depth of lithium ions is under the same driving force. In the present disclosure, if a metal and a silica material form a silicate, the silicate has a multi-dimensional lithium ion diffusion channel, and thus the purpose of increasing the lithium ion diffusion coefficient can be achieved; if the metal and the silicon-oxygen material form an alloy, the conductivity of the alloy is increased, the charge transfer resistance is reduced, the lithium ion diffusion resistance is reduced, and the purpose of improving the lithium ion diffusion coefficient can be achieved.

In the embodiment of the disclosure, the chemical formula of the silicon oxide material is SiO _x Wherein x is 0.5 ≦ x <2, for example, x is 1, the silica material is a silica SiO, silica materials having this formula are particularly suitable for obtaining the core 1 of the above-described metallized silica material.

In some examples, embodiments of the present disclosure provide that the silicone material is in a powder form, and the average particle size D50 of the silicone material is less than or equal to 10 μm, including but not limited to: less than or equal to 9.5 μm, less than or equal to 9 μm, less than or equal to 8 μm, less than or equal to 7 μm, less than or equal to 6 μm, less than or equal to 5 μm, and the like.

According to another aspect of the embodiments of the present disclosure, there is also provided a method for preparing a silicon-oxygen-carbon composite material, the method for preparing a silicon-oxygen-carbon composite material including:

step 1: and stirring the carbon source, the metal source and the silicon-oxygen material in a dispersion solvent for a first set time, and then carrying out solid-liquid separation treatment to obtain a precursor of the silicon-oxygen-carbon composite material. Wherein the solid-liquid separation treatment comprises: volatilization drying treatment or distillation treatment.

And 2, step: and calcining the precursor of the silicon-oxygen-carbon composite material under a protective atmosphere to obtain the silicon-oxygen-carbon composite material.

In some examples, the molar ratio of the silicon oxygen material (e.g., silica) to the metal source is 1:0.05 to 1:1 (e.g., 1;

in some examples, the molar ratio of the silicon oxygen material (e.g., silica) to the carbon source is 1:0.05 to 1:0.5 (e.g., 1;

in some examples, the mass ratio of the silicon oxygen material (e.g., silica) to the dispersing solvent is 1:0.5 to 1:1 (e.g., 1.

The proportion of the raw materials is in the range, so that the carbon outer layer with proper thickness and size can be obtained.

After completion of the stirring, solid-liquid separation is performed by a volatilization drying treatment or a distillation treatment, and in this solid-liquid separation method, as the dispersion solvent is gradually decreased (that is, the dispersion solvent is gradually decreased), the layer-by-layer deposition of the metal source-carbon source complex free in the dispersion solvent on the surface of the silica material is promoted, and a crystal cluster is formed, and finally a precursor of the silica-oxygen-carbon composite material is formed. In the precursor of the silicon-oxygen-carbon composite material, the metal source in the metal source-carbon source complex can be adsorbed on the surface of the silicon-oxygen material, so that the precursor of the silicon-oxygen-carbon composite material is in a form that the silicon-oxygen material, the metal source and the carbon source are sequentially distributed from inside to outside.

In the disclosed embodiments, the carbon source, the metal source, and the silica material are stirred in the dispersion solvent for a first set time, illustratively, the first set time is 3 hours to 24 hours, for example, this includes, but is not limited to, 3 hours, 5 hours, 7 hours, 8 hours, 10 hours, 13 hours, 15 hours, 17 hours, 20 hours, 22 hours, 24 hours, and the like. In this time range, the carbon source is sufficiently complexed with the metal source to form a desired metal source-carbon source complex, and the metal source-carbon source complex is sufficiently adsorbed on the surface of the silica material to form a precursor of the highly dispersed silica-carbon composite material.

In some examples, the carbon source, the metal source, and the silica material are stirred in the dispersion solvent at a temperature of between room temperature and 60 ℃, e.g., between 20 ℃ and 28 ℃.

In the embodiment of the present disclosure, the volatilization drying or distillation treatment may be performed in various ways as long as it is ensured that the carbon source adsorbed to the silica material is not carried away during the removal process of the dispersion solvent. For example, natural evaporation drying at room temperature, or air blowing assisted evaporation drying at a certain temperature, or vacuum pumping assisted evaporation drying at a certain temperature, and the like.

Further, in the embodiments of the present disclosure, the solid-liquid separation further includes: and performing suction filtration treatment or drying treatment, wherein the suction filtration treatment or the drying treatment is configured to improve the efficiency of solid-liquid separation, and does not influence the stacking adsorption of the carbon source on the surface of the silica material.

In some examples, a suction filtration process or a drying process may be performed for a certain time before the evaporation drying or distillation process to remove most of the surplus solvent, and then the remaining part of the dispersion solvent may be removed by the evaporation drying or distillation process, for example, when the amount of the solvent is separated into the remaining half, the evaporation drying or distillation process may be performed again.

In other examples, after the volatilization drying or distillation treatment, the residual dispersion solvent can be removed by suction filtration or drying treatment after ensuring that the carbon source is completely stacked and adsorbed on the surface of the silica material.

Therefore, the suction filtration treatment or the drying treatment firstly ensures that the carbon source is fully stacked and adsorbed on the surface of the silica material, and secondly improves the solid-liquid separation efficiency.

In the solid-liquid separation, the stacking of the carbon source on the surface of the silica material is assisted and promoted by a volatilization drying treatment or a distillation treatment step, rather than completely performing the solid-liquid separation by a conventional filtration means (for example, reduced pressure filtration, suction filtration, heat filtration, etc.), because it is found that if the conventional filtration means is used throughout the solid-liquid separation, a protruding prototype (i.e., carbon protrusion) is not formed on the carbon coating layer. When the conventional filtration means is used, the dispersion solvent reaches a removal state from an initial sufficient state in a short time, and in the process of rapid loss of the dispersion solvent, the carbon source completely dispersed in the dispersion solvent flows with the flow of the dispersion solvent, and for example, the carbon source such as an aromatic compound is completely dispersed and dissolved in the dispersion solvent in the initial state, and with rapid removal of the dispersion solvent, the carbon source flows without spontaneously forming pi-pi conjugated crystal deposition and precipitation from the dispersion solvent, and therefore, stacked crystal clusters cannot be formed on the surface of the silica material, and further, a special morphology such as carbon protrusions cannot be synthesized on the carbon coating layer after calcination treatment. By adopting the solid-liquid separation means in the embodiment of the disclosure, the technical problems are effectively avoided, and the formation of carbon protrusions is effectively promoted.

In some possible implementation manners, the solid-liquid separation treatment is performed under the condition of continuous stirring to prevent the precursor of the silicon-oxygen-carbon composite material from depositing in the dispersion solvent, so that the dispersion degree of the precursor of the silicon-oxygen-carbon composite material is improved, and the clustering phenomenon is prevented.

In the embodiment of the present disclosure, the implementation manners of all the stirring processes involved include, but are not limited to: magnetic stirring, paddle stirring, and the like.

In some possible implementations, stirring the carbon source, the metal source, and the silica material in the dispersion solvent for a first set time includes: performing a complex reaction of a carbon source and a metal source in a dispersion solvent to form a raw material system containing a metal source-carbon source complex; and adding the silica material into the raw material system, and stirring for a first set time.

The metal source and the carbon source are mixed with the silica material in a metal source-carbon source complex form, and after the metal source and the carbon source are added into a dispersion solvent and stirred for a certain time, the metal source in the metal source-carbon source complex can be adsorbed on the surface of the silica material, so that the precursor of the silica-carbon composite material is in a form that the silica material, the metal source and the carbon source are sequentially distributed from inside to outside.

In embodiments of the present disclosure, carbon sources include, but are not limited to: ethers, alcohols, carboxylic acids, ketones, aromatics, polymers, and the like, for example, polymers include, but are not limited to: polyethylene glycol, polyacrylic acid, and the like. For example, aromatic compounds include, but are not limited to: biphenyl, terphenyl, naphthalene, anthracene, phenanthrene, pyrene, tetracene and their branched modification product derivatives, for example, these modification products are aromatic compounds modified with: alkane groups, alcohol groups, nitride groups, sulfide groups, ether groups, ketone groups, ester groups, and the like.

(1) In some implementations, the metal source includes at least one of elemental Li, elemental Na, elemental K, elemental Mg.

The metal is a metal element capable of realizing metal solvation, the metal source and the carbon source can be fully dissolved in a dispersing solvent, and in a solvent environment provided by the dispersing solvent, active groups in the carbon source can be subjected to complexation with the metal in the metal source to form a metal source-carbon source complex.

The following description will be given by taking an example in which the metal source is a Li simple substance, the carbon source is an aromatic compound, and the silica material is Silica (SiO):

as shown in fig. 2, in a solvent environment provided by a dispersion solvent, an aromatic compound contacts with metallic lithium and performs a complex reaction to form a metal source-carbon source complex having a metallic lithium end and an aromatic carbon end, wherein the metallic lithium is used as a doping element of an inner core, and the aromatic carbon end is used as a carbon source.

As shown in fig. 3, after the metal source-carbon source complex is contacted with the SiO material in the dispersion solvent, the metal lithium end is adsorbed on the surface of the SiO material to form a precursor of the silicon-oxygen-carbon composite material and make it present a form in which SiO-Li-aromatic compounds are distributed in sequence from inside to outside. In the precursor of the silicon-oxygen-carbon composite material, the interaction among the molecules is changed according to different orientations among the molecules, wherein after the metal lithium end is adsorbed on the surface of the SiO material, the orientations of the aromatic compound molecules are consistent, and the different aromatic compound molecules are mutually in the side direction, so that the different aromatic compound molecules are mutually repelled, and the respective independent adsorption structures are formed on the surface of the SiO material, thereby effectively preventing the aromatic compound from clustering on the surface of the SiO material and uniformly distributing on the surface of the SiO material, and being beneficial to obtaining a carbon coating layer with uniform thickness later.

As shown in fig. 4, the metal source-carbon source complex adsorbed on the surface of the SiO material is used as a base layer, and the rest of the metal source-carbon source complexes are adsorbed and stacked on the surface of the base layer, and so on, the metal source-carbon source complexes are sequentially stacked to form a stacked structure of "SiO-Li-aromatic …". Because the volume of the aromatic compound molecules is smaller than that of the SiO material, the stacking direction of the aromatic compound molecules is variable and irregular, and random stacking growth is realized.

As shown in fig. 5, the potential of the metal source-carbon source complex (i.e., li-aromatic complex) is between metal lithium and the SiO material due to the potential difference, and therefore, lithium at the metal lithium end of the metal source-carbon source complex spontaneously enters the SiO material, and a vacancy is left on the surface of the SiO material after the lithium enters the SiO material, so that the remaining aromatic compound enters the vacancy as a carbon source, so that the aromatic compound collapses and contracts around the center of the base layer, and a carbon layer structure with a protrusion on the surface is formed.

As shown in FIG. 6, during the calcination process (i.e., high temperature carbonization process), the SiO material reacts with lithium to form lithium silicate, forming a core of metal-doped silica material (the core is lithium silicate/SiO/Si/SiO) ₂ In combination with (b) and, at the same time, the carbon layer structure is carbonized according to its structural embryonic form to form a carbonaceous outer layer, such that the outer layer has a carbon coating layer and a plurality of carbon protrusions (the location of the carbon coating layer in fig. 6 illustrates its formation on the surface of the inner core, and the location of the plurality of carbon protrusions illustrates their location on the surface of the carbon coating layer).

(2) In other implementations, the metal source is a carbon-containing metal complex, for example, the carbon-containing metal complex includes at least one of methyllithium, copper phthalocyanine, and aluminum acetylacetonate. Methyl lithium, for example, has lithium as the metal source and a methyl group as the carbon source.

In this implementation, the finished product of the metal complex containing carbon is directly screened as a metal source, which can provide not only the metal source but also a carbon source. The metal in the carbon-containing metal complex reacts with the silica material to form a metal-silicon alloy. In some examples, the carbon source used herein is also the carbon-containing metal complex described above, that is, the metal source and the carbon source are provided simultaneously using the carbon-containing metal complex.

Embodiments of the present disclosure utilize a dispersing solvent to provide a solvent environment, which in some possible implementations includes at least one of dimethyl carbonate, tetrahydrofuran, toluene, benzene, diethyl ether, propylene oxide, ketones, ethylene glycol dimethyl ether. For example, ketones include, but are not limited to, acetone and the like.

In embodiments of the present disclosure, the radial thickness of the carbon cladding layer may be controlled by at least one of the following reaction conditions: the concentration of the metal source and the carbon source, the ratio of the carbon source to the silica material, the reaction time and the like;

the radial dimension of the carbon protrusions may be controlled by at least one of the following reaction conditions: the types of the metal source and the carbon source (this is because different metal sources and carbon sources affect the molecular charge and the interaction force thereof, and further affect the stacking morphology of the carbon source on the surface of the silica material), the reaction time, the reaction temperature, and the like.

And 2, calcining the precursor of the silicon-oxygen-carbon composite material in a protective atmosphere to obtain the silicon-oxygen-carbon composite material. In some examples, the calcination treatment includes: and under the condition that the heating rate is greater than or equal to 5 ℃/min, heating the precursor of the silicon-oxygen-carbon composite material to the calcining temperature, and calcining the silicon-oxygen-carbon composite material at the calcining temperature for a second set time.

For example, the ramp rate is from 5 ℃/min to 10 ℃/min, further by way of example, this includes, but is not limited to: 5.2 ℃/min, 5.5 ℃/min, 5.8 ℃/min, 6 ℃/min, 6.5 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min, and the like.

By controlling the heating rate during calcination to be more than or equal to 5 ℃/min, the situation that a carbon layer structure with bulges on the surface in a precursor of the silicon-oxygen-carbon composite material is randomly connected into a piece under the drive of thermal motion due to the overlong carbonization heating process can be avoided, further, the formation of irregular, non-uniform and broken carbon layers is avoided, the formed outer layer is ensured to have a compact carbon coating layer and a plurality of carbon bulges which are uniformly distributed, and the excellent electrochemical performance brought by the outer layer is ensured. In addition, in order to improve the safety of the calcining process, some measures for preventing temperature runaway can be arranged in the temperature rising process.

In order to ensure that the silicon oxygen material can be fully metalized and ensure that the outer layer obtains a desired morphology structure, the calcining temperature is 400-1200 ℃ and the second set time, namely the calcining time, is 0.5-10 h.

For example, calcination temperatures include, but are not limited to: 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, etc., for a time period including, but not limited to: 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h and the like.

The above calcination process is carried out under a protective atmosphere using an inert gas as long as it does not react with the metal source and the carbon source, for example, the inert gas includes, but is not limited to: argon, nitrogen, and the like. For the protective atmosphere, O is required therein ₂ The content is less than 0.1ppm ₂ The O content is less than 0.01ppm. In addition, the precursors of the silicon-oxygen-carbon composite material are brought to the dew point before calcination<-40 ℃ in a reaction environment.

In some examples, the calcination process described above is performed in a firing furnace provided with a protective atmosphere as described above.

According to yet another aspect of the embodiments of the present disclosure, there is also provided an anode raw material including a silicon-based anode material, a conductive agent, and a binder; the silicon-based negative electrode material is any one of the silicon-oxygen-carbon composite materials shown in the embodiment of the disclosure.

In some examples, the weight percentage of the conductive agent in the anode raw material is 0.02% to 2%, for example, this includes but is not limited to: 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, etc. Suitable conductive agents are those that do not provide additional reversible capacity, do not cause additional chemical reactions, and are electronically conductive, and in some examples, include, but are not limited to: at least one of conductive graphite, conductive carbon black, acetylene black, carbon nanotubes and graphene. By using the conductive agent, the purposes of reducing the impedance of the negative pole piece and improving the multiplying power performance can be achieved.

The binder can ensure adhesiveness and can suppress expansion of the silicon active material while reducing the internal resistance of the negative electrode tab, and in some examples, the binder includes, but is not limited to: polyimides, polyether imides, polyacrylic acids, polyvinyl alcohols, polyacrylonitriles, and the like. In some examples, the weight percentage of the binder in the anode raw material is 0.05% -5%, for example, this includes but is not limited to: 0.05%, 0.1%, 0.5%, 0.6%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc.;

the balance is the silicon-based anode material, namely, the amount of the silicon-based anode material is 100 percent of the total weight percentage of the binder, the silicon-based anode material and the conductive agent.

According to still another aspect of the embodiment of the present disclosure, an embodiment of the present disclosure further provides a negative electrode plate, which is prepared by using the negative electrode raw material.

Illustratively, the preparation method of the negative electrode plate is as follows: dissolving a binder in a polar solvent to obtain a glue solution; mixing the glue solution with the silicon-based negative electrode material and the conductive agent, and uniformly stirring to obtain negative electrode slurry; and coating the negative electrode slurry on two opposite surfaces of the current collector, and sequentially drying and rolling to obtain the negative electrode plate.

In order to improve the quality of the negative pole piece, the negative pole slurry can be defoamed and sieved, and then the negative pole slurry is coated on two opposite surfaces of the current collector.

Exemplary current collectors include, but are not limited to: at least one of copper foil, copper mesh, carbon-coated copper foil, stainless steel mesh, carbon-coated stainless steel foil and nickel foil.

Exemplary polar solvents include, but are not limited to: at least one of N-methyl pyrrolidone, dimethyl acetamide, N-dimethyl formamide, dimethyl sulfoxide and cyclohexanone.

According to still another aspect of the embodiments of the present disclosure, there is also provided a lithium ion battery including the above negative electrode tab.

Based on the negative pole piece provided by the embodiment of the disclosure, the lithium ion battery has high reversible capacity, first effect, rate capability and high cycling stability.

As shown in fig. 7, the lithium ion battery provided in the embodiment of the present disclosure includes, in addition to the negative electrode tab 100, a positive electrode tab 200, an electrolyte 300, a separator 400, and a packaging layer 500.

The electrolyte 300 is filled in the space between the negative electrode tab 100 and the positive electrode tab 200, and the diaphragm 400 is located in the electrolyte 300 and used for isolating the negative electrode tab 100 from the positive electrode tab 200. The encapsulation layer 500 is used for integrally encapsulating the negative electrode tab 100, the positive electrode tab 200, the electrolyte 300, and the separator 400.

The lithium ion battery realizes energy storage and release through the de-intercalation of lithium ions between the negative pole piece 100 and the positive pole piece 200, the electrolyte 300 is a carrier for the transmission of the lithium ions between the negative pole piece 100 and the positive pole piece 200, the diaphragm 400 is ion-conductive but electron-insulating, and the negative pole piece 100 and the positive pole piece 200 are separated to prevent short circuit while the migration of the lithium ions is ensured by the diaphragm 400.

The positive pole piece comprises a positive active material, a conductive agent, a current collector and a positive adhesive, wherein the positive active material can be selected from at least one of lithium-containing layered metal oxide, lithium-containing spinel structure metal oxide, lithium metal phosphate, lithium metal fluoride sulfate and lithium metal vanadate.

For example, lithium-containing layered metal oxides include, but are not limited to: lithium cobaltate (LiCoO) ₂ ) At least one of nickel-cobalt-manganese ternary material (NCM) and nickel-cobalt-aluminum ternary material (NCA); spinel structure metal oxides containing lithium include, but are not limited to: lithium manganate (LiMn) ₂ O ₄ ) Etc.; lithium metal phosphates include, but are not limited to: lithium iron phosphate (LiFePO) ₄ ) Etc.; lithium metal fluorosulfates include, but are not limited to: fluorinated lithium cobalt sulfate (LiCoFSO) ₄ ) Etc.; lithium metal vanadates include, but are not limited to: nickel lithium vanadate (LiNiVO) ₄ ) And so on.

The conductive agent used for the positive electrode plate includes but is not limited to: at least one of conductive graphite, conductive carbon black, acetylene black, carbon nanotubes and graphene.

The present disclosure will be further described by the following more specific examples, and although some specific embodiments are described below, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the examples set forth herein. The reagents and apparatuses used in the examples are those which are not specified as specific techniques or conditions, those which are described in the literature in the field or those which are specified as product specifications, and those which are not specified as manufacturers, and are commercially available. The silicon oxide materials referred to in the following examples are all SiO raw materials.

Example 1

This example 1 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of metal lithium and 5g of biphenyl were uniformly dispersed in 10g of ethylene glycol dimethyl ether, and after uniform magnetic stirring, a lithium-biphenyl complex was formed in the ethylene glycol dimethyl ether. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 12 hours, and removing ethylene glycol dimethyl ether at room temperature in a volatilization drying mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment in an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 1. Wherein the calcination treatment comprises: under the condition that the heating rate is 5 ℃/min, the precursor of the silicon-oxygen-carbon composite material is heated to 900 ℃, and the silicon-oxygen-carbon composite material is calcined for 2 hours at 900 ℃.

Example 2

This example 2 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of metal lithium and 5g of 4,4' -dimethylbiphenyl are uniformly dispersed in 10g of ethylene glycol dimethyl ether, and after uniform magnetic stirring, a lithium-dimethylbiphenyl complex is formed in the ethylene glycol dimethyl ether. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 15 hours, and removing ethylene glycol dimethyl ether at room temperature in a volatilization drying mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment in an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 2. Wherein the calcination treatment comprises: under the condition that the heating rate is 5.5 ℃/min, the precursor of the silicon-oxygen-carbon composite material is heated to 900 ℃, and the silicon-oxygen-carbon composite material is calcined for 2 hours at 900 ℃.

Example 3

This example 3 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of metallic lithium and 3g of biphenyl were uniformly dispersed in 10g of tetrahydrofuran, and after uniform magnetic stirring, a lithium-biphenyl complex was formed in ethylene glycol dimethyl ether. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 12 hours, and then removing ethylene glycol dimethyl ether at room temperature in a distillation mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment in an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 3. Wherein the calcination treatment comprises: heating the precursor of the silicon-oxygen-carbon composite material to 950 ℃ under the condition that the heating rate is 6 ℃/min, and calcining the silicon-oxygen-carbon composite material for 2 hours at 950 ℃.

Example 4

This example 4 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of metal lithium and 5g of biphenyl are uniformly dispersed in 10g of ethylene glycol dimethyl ether, and a lithium-biphenyl complex is formed in the ethylene glycol dimethyl ether after uniform magnetic stirring. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 13 hours, and removing ethylene glycol dimethyl ether at room temperature in a volatilization drying mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment in an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 4. Wherein the calcination treatment comprises: heating the precursor of the silicon-oxygen-carbon composite material to 500 ℃ under the condition that the heating rate is 5.8 ℃/min, and calcining the silicon-oxygen-carbon composite material for 6 hours at 500 ℃.

Example 5

This example 5 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of metal sodium and 5g of biphenyl are uniformly dispersed in 10g of ethylene glycol dimethyl ether, and after uniform magnetic stirring, a sodium-biphenyl complex is formed in the ethylene glycol dimethyl ether. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 13 hours, and removing ethylene glycol dimethyl ether at room temperature in a volatilization drying mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment in an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 5. Wherein the calcination treatment comprises: heating the precursor of the silicon-oxygen-carbon composite material to 900 ℃ under the condition that the heating rate is 5.5 ℃/min, and calcining the silicon-oxygen-carbon composite material for 3 hours at 900 ℃.

Example 6

This example 6 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of copper phthalocyanine and 5g of biphenyl are uniformly dispersed in 10g of ethylene glycol dimethyl ether, and after uniform magnetic stirring, a copper phthalocyanine-biphenyl complex is formed in the ethylene glycol dimethyl ether. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 12 hours, and then removing ethylene glycol dimethyl ether at room temperature in a distillation mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment in an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 6. Wherein the calcination treatment comprises: heating the precursor of the silicon-oxygen-carbon composite material to 1000 ℃ under the condition that the heating rate is 7 ℃/min, and calcining the silicon-oxygen-carbon composite material for 2 hours at 1000 ℃.

Example 7

Example 7 provides a silicon-oxygen-carbon composite material, which is prepared by the following method:

1g of aluminum acetylacetonate and 5g of biphenyl were uniformly dispersed in 10g of ethylene glycol dimethyl ether, and after uniform magnetic stirring, an aluminum acetylacetonate-biphenyl complex was formed in the ethylene glycol dimethyl ether. And continuously adding 10g of SiO raw material into the raw material system, magnetically stirring for 12 hours, and removing ethylene glycol dimethyl ether at room temperature in a volatilization drying mode to obtain a precursor of the silicon-oxygen-carbon composite material.

The precursor of the silicon-oxygen-carbon composite material was subjected to calcination treatment under an argon atmosphere, to obtain the desired silicon-oxygen-carbon composite material of example 7. Wherein the calcination treatment comprises: heating the precursor of the silicon-oxygen-carbon composite material to 1100 ℃ under the condition that the heating rate is 8 ℃/min, and calcining the silicon-oxygen-carbon composite material for 1 hour at 1100 ℃.

Comparative example 1

This comparative example 1 provides a SiO feedstock that was not treated at all.

Comparative example 2

This comparative example 2 provides a silicon-oxygen-carbon composite material without any metal doping, which is prepared by the following method:

5g of biphenyl is dissolved in 10g of ethylene glycol dimethyl ether, 10g of SiO raw material is added into a raw material system after the biphenyl is completely dissolved, magnetically stirring for 12h, volatilizing and drying at normal temperature, and calcining at 900 ℃ for 2h under Ar atmosphere to obtain the silicon-oxygen-carbon composite material.

Comparative example 3

The comparative example 3 provides a silicon-oxygen-carbon composite material with a carbon coating layer obtained by a chemical vapor deposition method, which is prepared by the following method:

placing SiO raw material in a tube furnace, vacuumizing and replacing air in the tube with inert gas N ₂ Repeating the steps for three times, starting a power supply, heating to 800 ℃ at a speed of 3 ℃/min, keeping the temperature constant for 20min, introducing mixed gas of ethylene and nitrogen into the tubular furnace, and continuously introducing the mixed gas for 30minAnd obtaining the silicon-oxygen-carbon composite material.

Test example

In this test example, the improvement effects of the silicon-oxygen-carbon composite material and the SiO raw material on the first effect and the reversible capacity of the button cell are tested through a button cell test, and the carbon layer coating and uniformity of each silicon-oxygen-carbon composite material are obtained through trace carbon, a Scanning Electron Microscope (SEM) and an Energy Spectrometer (EDS). The charge and discharge schedule involved in the power-off test is as follows: discharging to 10mV at constant current of 0.05C, and then discharging to 5mV at constant current of 0.02C; charging to 1.5V at a constant current of 0.05C; wherein the standard of 1C is 1500mAh/g.

The test results are shown in table 1:

TABLE 1

In table 1, rate@0.1C, rate@0.2C and Rate@0.5C refer to corresponding multiplying ratios under different constant current discharge tests, and the percentage value obtained by comparing the reversible capacity of the corresponding 0.1c,0.2c and 0.5c constant current discharge section with the reversible capacity of the first 0.05C constant current discharge section is the multiplying ratio data.

As can be seen from table 1, the carbon content of the materials provided in comparative examples 1 and 2 was about 0.45%, the carbon content was low, and no carbon layer was found in the SEM electron micrograph and the EDS element distribution. This is because in comparative example 2, the organic carbon source was not efficiently deposited on the surface of SiO, and thus a stable carbon coating layer was not formed.

The silicon-oxygen-carbon composite materials provided in examples 1 to 7 are prepared by the method provided in the embodiments of the present disclosure, so that the carbon content of the silicon-oxygen-carbon composite materials is effectively increased, and the carbon outer layer is already covered on the surfaces of the silicon-oxygen-carbon composite materials provided in examples 1 to 7 in combination with the EDS element distribution structure.

Fig. 8 illustrates an EDS diagram of the siloxycarbon composite material provided in example 1, which represents the distribution state of carbon, oxygen and silicon in the siloxycarbon composite material, and as can be seen from the C k α l-2 image in fig. 8, the carbon is a white bright point uniformly distributed therein, and it can be seen that, under the same carbon source content, the deposition amount and char formation rate on the surface of the siloxycarbon material after the metal source and the carbon source are complexed are higher, and the carbon coating layer formed by the metal carbon source is more uniform.

FIG. 9 illustrates an EDS diagram of the silicon-oxygen-carbon composite material provided by comparative example 2, which represents the distribution state of carbon element, oxygen element and silicon element in the silicon-oxygen-carbon composite material, and as can be seen from the C k alpha l-2 image in FIG. 9, the signal of the carbon element is not obvious, which indicates that the deposition amount of the carbon source in the silicon-oxygen material is low and a uniform carbon coating layer cannot be formed in the comparative example 2.

Fig. 10 illustrates SEM images at different magnifications of a siloxycarbon composite obtained based on a conventional carbon coating, wherein the siloxycarbon composite is the siloxycarbon composite provided in comparative example 3.

Fig. 11 illustrates SEM images at different magnifications of a silicon-oxygen-carbon composite material based on conventional carbon cladding + prelithiation, wherein the silicon-oxygen-carbon composite material is a commercial product of silicon-oxygen-carbon composite material.

Fig. 12 illustrates SEM images at different magnifications of a silicon-oxygen-carbon composite material obtained based on an embodiment of the disclosure, wherein the silicon-oxygen-carbon composite material is the silicon-oxygen-carbon composite material provided in example 1.

As shown in fig. 10 to fig. 12, in the conventional carbon-coated and conventional carbon-coated + pre-lithiated silicon-oxygen-carbon composite materials, a complete carbon coating layer is not obtained on the surface of a part of the silicon-oxygen material, so that the surface of the part of the silicon-oxygen material is exposed (which is easily exposed to an electrolyte solution and thus causes more side reactions), while the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure obtains a complete and dense carbon coating layer, and in addition, the silicon-oxygen-carbon composite material provided by the embodiment of the disclosure can observe obvious carbon protrusions in a synaptic morphology.

As can be seen from table 1, the first efficiency of the silicon-oxygen-carbon composite materials provided in examples 1 to 7 is effectively improved compared with that of comparative examples 1 to 3, which indicates that the silicon-oxygen-carbon composite materials prepared by the method provided in the embodiments of the present disclosure enable both the metal source and the carbon source to play a positive role.

Compared with the example 1, the type of the organic carbon source is changed in the example 2, and therefore, the carbon content of the silicon-oxygen-carbon composite material is improved by changing the type of the carbon source, the possibility of optimization between the organic carbon source and an organic solvent is suggested, and the silicon-oxygen-carbon composite material with better comprehensive performance is obtained by selecting and matching similar organic matters.

Example 3 compared with example 1, the amount of the organic carbon source is reduced, however, the carbon content of the silicon-oxygen-carbon composite material provided by example 3 is not significantly reduced, which indicates that the deposition amount of the same organic carbon source has a limit value, the excessive carbon source part is also dispersed in the dispersing solvent, and the residual carbon source can be collected for recycling by a method such as filtration, so that the material consumption cost is reduced.

Example 4 compared to example 1, the reduction of the calcination temperature has an effect on the overall performance of the silica-carbon composite due to the different disproportionation degrees caused by different temperatures, but the carbon content of the silica-carbon composite is not very different, which confirms that calcination at relatively low temperature is also feasible.

It is confirmed by example 5 that the same kind of alkali metal sodium can be used as the metal source to achieve substantially the same effect, because the atomic weight of sodium is different from that of lithium, and the metal sodium is slightly lower than that of lithium in the reversible capacity and first effect improvement effect on the silicon-oxygen-carbon composite material, but the carbon content of the silicon-oxygen-carbon composite material is still significantly improved.

Examples 6 and 7 both adopt the carbon-containing metal complex to synthesize the silicon-oxygen-carbon composite material, and the carbon-containing metal complex also plays a positive role in increasing the carbon content, which indicates that the direct utilization of the carbon-containing metal complex is feasible, and can also solve the problem that some metals are difficult to disperse, for example, metals such as Cu, al and the like cannot synthesize a metal source-carbon source complex by dissolving bulk metals.

The lithium intercalation performance tests of comparative example 3 and example 1 at different rates show that the rate performance of the silicon-oxygen-carbon composite material provided by example 1 is obviously improved relative to the rate performance of the silicon-oxygen-carbon composite material provided by comparative example 3 even under the condition of similar carbon coating amount. This is because the outer layer of the silicon-oxygen-carbon composite material provided in example 1 includes not only the carbon coating layer but also further has carbon protrusions formed on the surface of the carbon coating layer, which can increase the wettability of the carbon outer layer of the silicon-oxygen-carbon composite material and the electrolyte solution, and promote the interfacial transport of lithium ions.

As used with respect to the disclosed embodiments, the terms "each," "a plurality," and "any," and the like, a plurality includes two or more, each referring to each of the corresponding plurality, and any referring to any one of the corresponding plurality.

The above description is only for facilitating the understanding of the technical solutions of the present disclosure by those skilled in the art, and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A silicon-oxygen-carbon composite material, comprising: an inner core (1) and an outer layer (2), the outer layer (2) comprising: a carbon coating layer (21) and a plurality of carbon protrusions (22);

the inner core (1) is a silicon-oxygen material doped with metal;

the carbon coating layer (21) is coated outside the inner core (1), and the plurality of carbon protrusions (22) are formed on the outer surface of the carbon coating layer (21).

2. The siloxycarbon composite material according to claim 1, characterized in that the size of the carbon protrusions (22) is comprised between 5nm and 50nm;

wherein the size of the carbon protrusion (22) is the size of the carbon protrusion (22) in a direction parallel to the surface of the core (1).

3. The silicone-carbon composite material according to claim 1, characterized in that the average difference in distance MD between any two adjacent carbon protrusions (22) is <20%;

wherein, the first and the second end of the pipe are connected with each other,

r is the center-to-center distance between any two adjacent carbon protrusions (22), and n is the total number of the carbon protrusions (22) on the carbon coating layer (21).

4. The silicon oxycarbon composite of claim 1 wherein the silicon oxycarbon composite has an average particle size D50 of less than or equal to 10um;

the thickness of the carbon coating layer (21) is 1nm-100nm.

5. The silicon oxycarbon composite material according to any one of claims 1 to 4, wherein the silicon oxycarbon material has the chemical formula SiO _x Wherein x is more than or equal to 0.5 and less than 2.

6. The silicon oxycarbon composite material according to any one of claims 1 to 5, wherein the metal comprises at least one of Li, na, K, mg, cu, ag, al.

7. A method for preparing a silicon-oxygen-carbon composite material, wherein the silicon-oxygen-carbon composite material is as defined in any one of claims 1 to 6;

8. The method for producing a silicon oxycarbon composite material according to claim 7, wherein the solid-liquid separation treatment is performed under continuous stirring.

9. The method of producing a silicon oxycarbide composite material according to any one of claims 7 to 8, wherein the stirring the carbon source, the metal source and the silicon oxycarbide material in the dispersion solvent for a first set time comprises:

and adding the silicon-oxygen material into the raw material system, and stirring for the first set time.

10. The method for preparing a silicon-oxygen-carbon composite material according to claim 9, wherein the metal source comprises at least one of a simple substance Li, a simple substance Na, a simple substance K and a simple substance Mg.

11. The method of producing a silicon-oxygen-carbon composite material according to claim 9, wherein the metal source is a carbon-containing metal complex.

12. The method of making a silicon-oxygen-carbon composite material according to claim 11, wherein the carbon-containing metal complex comprises at least one of methyllithium, copper phthalocyanine, and aluminum acetylacetonate.

13. The method for producing a siloxane-carbon composite material according to any one of claims 7 to 12, wherein the dispersion solvent comprises at least one of dimethyl carbonate, tetrahydrofuran, toluene, benzene, diethyl ether, propylene oxide, ketones, and ethylene glycol dimethyl ether.

14. The method for producing a silicon-oxygen-carbon composite material according to any one of claims 7 to 13, wherein the first set time is 3 hours to 24 hours.

15. The method for the preparation of a silica-carbon composite material according to any one of claims 7 to 14, characterized in that said calcination treatment comprises:

16. The method for preparing a silicon-oxygen-carbon composite material according to claim 15, wherein the calcination temperature is 400 ℃ to 1200 ℃, and the second set time is 0.5h to 10h.

17. An anode raw material, characterized by comprising: silicon-based negative electrode material, conductive agent and binder;

wherein the silicon-based negative electrode material is the silicon-oxygen-carbon composite material as defined in any one of claims 1 to 6.

18. A negative pole piece is characterized in that the negative pole piece is prepared by adopting the negative pole raw material of claim 17.

19. A lithium ion battery comprising the negative electrode sheet of claim 18.