CN116565206A

CN116565206A - Silicon-based anode material and preparation method and application thereof

Info

Publication number: CN116565206A
Application number: CN202310553433.9A
Authority: CN
Inventors: 薛山; 万远鑫; 李意能; 陈燕玉; 刘厅; 王鹏
Original assignee: Shenzhen Dynanonic Co ltd
Current assignee: Shenzhen Dynanonic Co ltd
Priority date: 2023-05-16
Filing date: 2023-05-16
Publication date: 2023-08-08

Abstract

The application relates to the technical field of negative electrode materials, and provides a silicon-based negative electrode material, a preparation method and application thereof, wherein the silicon-based negative electrode material comprises a core body and a shell layer for coating the core body; the material of the core body comprises a silicon-based material, the material of the shell layer comprises a black phosphorus and carbon material, and the black phosphorus and the carbon material form a composite structure which is stacked and inlaid in a staggered mode. The silicon-based negative electrode material provided by the application adopts the staggered stacked and inlaid composite structure formed by the black phosphorus and the carbon material to coat the silicon-based material, can effectively isolate the direct contact between the silicon-based material and electrolyte to form a more stable and compact SEI film, so that the stability of the negative electrode material is improved, the volume expansion of the silicon-based material can be effectively buffered, the volume expansion of the silicon-based material can be limited to a certain extent, the lithium storage performance of silicon oxide can be exerted to the greatest extent, and the negative electrode material is endowed with higher gram capacity, first coulombic efficiency and multiplying power performance.

Description

Silicon-based anode material and preparation method and application thereof

Technical Field

The application belongs to the technical field of negative electrode materials, and particularly relates to a silicon-based negative electrode material, and a preparation method and application thereof.

Background

The advent and use of lithium ion batteries brings innovation and convenience to the production and life of people, and the lithium ion batteries are still in the vigorous development stage at present, so that the lithium ion batteries have great application markets in the fields of new energy automobiles and energy storage. The properties of the positive and negative electrode materials of lithium ion batteries have a critical effect on the capacity, energy density, cycle life and other properties of the batteries. The ideal negative electrode material needs to have the characteristics of low working point, high capacity, high first effect, low cost, good cycle stability and the like. Graphite-based carbon materials are currently widely used as negative electrodes of lithium ion batteries due to excellent cycle stability. However, the lithium storage theoretical capacity of graphite is 370mAh/g, which greatly limits the proportion of the positive electrode material in the battery, and the requirements of people on high-power and high-energy density batteries are not met. In the study, it was found that Si and Li can form a series of Li _x Si alloy compound with theoretical capacity up to 4200mAh/g and low working voltage<0.4V vs Li/Li ⁺ ) The method comprises the steps of carrying out a first treatment on the surface of the And silicon is abundant in the crust, safe and pollution-free, and is considered as one of the most potential anode materials. However, silicon undergoes great volume expansion during the alloying reaction with lithium>300%) and poor conductivity of silicon are major factors restricting the development of silicon-based materials.

Silicon oxide (SiO) _x ,0<x<2) Is a mature industrial raw material, belongs to the incomplete oxide of Si, and is a multiphase material. SiO (SiO) _x Is not only amorphous Si and SiO ₂ The phase also has an incomplete oxide SiO between the two _x It is embedded with Li ⁺ The mechanism is still competing at presentAmong the theory. SiO (SiO) _x Unique structure makes it possible to insert Li in the Li-removing process ⁺ The volume expansion is weaker than that of Si in the process, so that the silicon-containing composite material has better circulation stability, the theoretical capacity is still kept at a higher level (1965 mAh/g-4200 mAh/g), and the silicon-containing composite material has better application prospect. Nevertheless, siO _x There are some drawbacks that are difficult to compensate, such as a large volume expansion, a possibility of pulverization of the electrode material, a low initial coulombic efficiency, a low electrical conductivity, etc.

Disclosure of Invention

The invention aims to provide a silicon-based negative electrode material and a preparation method thereof, and aims to solve the problems of non-ideal specific capacity and first coulombic efficiency of the silicon-based negative electrode material and poor circulation in the use process.

Another object of the present application is to provide a negative electrode and a secondary battery including the same, so as to solve the technical problems of low energy density and low power of the existing secondary battery.

In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:

in a first aspect, the present application provides a silicon-based anode material comprising a core and a shell layer coating the core; the material of the core body comprises a silicon-based material, the material of the shell layer comprises a black phosphorus and carbon material, and the black phosphorus and the carbon material form a composite structure which is stacked and inlaid in a staggered mode.

In a second aspect, the present application provides a method for preparing a silicon-based anode material, including the steps of:

step S10, providing a silicon-based material, black phosphorus, a carbon source and a solvent;

step S20, mixing and grinding the silicon-based material, black phosphorus, a carbon source and a solvent to coat an initial shell layer on the surface of the silicon-based material, so as to obtain an intermediate material;

and step S30, sequentially performing drying treatment and carbonization treatment on the intermediate material to enable the initial shell layer to generate a shell layer with a staggered stacking and inlaid composite structure, and obtaining the silicon-based anode material.

In a third aspect, the present application provides a negative electrode, including a current collector and a negative electrode active layer bonded to a surface of the current collector, where the negative electrode active layer contains the silicon-based negative electrode material of the present application or the silicon-based negative electrode material prepared by the preparation method of the silicon-based negative electrode material of the present application.

In a fourth aspect, the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the negative electrode sheet being the negative electrode of the present application.

According to the silicon-based anode material provided by the first aspect of the application, the silicon-based material is taken as a nucleus body, the anode material is endowed with higher gram capacity and cycle stability, and is coated by adopting a staggered stacked and inlaid composite structure formed by black phosphorus and carbon materials, so that on one hand, the direct contact between the silicon-based material and electrolyte can be effectively isolated, the continuous growth and active lithium consumption of an SEI film (Solid Electrolyte Interface, solid electrolyte interface film) can be effectively avoided, the formation of a more stable and compact SEI film is facilitated, the stability of the anode material is improved, and the Li is promoted ⁺ The charge transfer impedance of the electrode is reduced, and the conductivity of the cathode material is effectively improved; on the other hand, the shell layer can also provide effective buffer for the volume expansion of the silicon-based material, can limit the volume expansion of the silicon-based material to a certain extent, and remarkably improves the structural stability of the anode material in the charge and discharge process, so that the lithium storage performance of the silicon oxide is exerted to the greatest extent, and the anode material is endowed with higher gram capacity, first coulombic efficiency and rate capability. In addition, the staggered stacked and inlaid composite structure formed by the black phosphorus and the carbon material has higher mechanical property, so that the volume expansion of the silicon-based material can be effectively relieved, and the lithium storage performance of the black phosphorus and the carbon material can be fully exerted, thereby further improving the cycle stability and gram capacity of the silicon-based negative electrode composite material.

According to the preparation method of the silicon-based anode material, provided by the second aspect, the shell layer which is formed by black phosphorus and carbon materials and has a staggered stacking and inlaid composite structure is effectively formed on the surface of the silicon-based material, and has higher mechanical properties, so that the volume expansion of the silicon-based material can be effectively inhibited, the structural stability of the anode material is ensured, and the anode material is endowed with higher gram capacity, first coulomb efficiency and cycle stability. In addition, the preparation method of the anode material can effectively prepare the silicon-based anode material with stable structure and electrochemical performance, and the process condition is easy to control, thus being applicable to large-scale industrial production and application.

The negative electrode provided in the third aspect of the application fully exerts the lithium storage performance of the silicon oxide, the black phosphorus and the carbon material due to the inclusion of the negative electrode material, and effectively improves the first coulombic efficiency, the specific capacity and the cycle performance of the negative electrode.

The secondary battery provided by the fourth aspect of the application has higher energy density, first coulombic efficiency and larger power due to the negative electrode provided by the application, and has the advantages of good cycle stability, long service life and stable electrochemical performance.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly introduce the drawings that are needed in the embodiments or the description of the prior art, it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a flowchart of a method for preparing a silicon-based anode material according to an embodiment of the present application;

FIG. 2 is an X-ray diffraction analysis chart of a silicon-based anode material provided in example 1 of the present application;

fig. 3 is a specific capacity-voltage curve of a button cell containing a silicon-based negative electrode material of example 1 of the present application.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

In this application, the term "and/or" describes an association relationship of an association object, which means that there may be three relationships, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

It should be understood that, in various embodiments of the present application, the sequence number of each process does not mean that the sequence of execution is sequential, and some or all of the steps may be executed in parallel or sequentially, where the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The weights of the relevant components mentioned in the embodiments of the present application may refer not only to specific contents of the components, but also to the proportional relationship between the weights of the components, and thus, any ratio of the contents of the relevant components according to the embodiments of the present application may be enlarged or reduced within the scope disclosed in the embodiments of the present application. Specifically, the mass described in the specification of the examples of the present application may be a mass unit known in the chemical industry such as μ g, mg, g, kg.

The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

A first aspect of embodiments of the present application provides a silicon-based anode material, including a core body and a shell layer covering the core body; the material of the core body comprises a silicon-based material, the material of the shell layer comprises a black phosphorus and carbon material, and the black phosphorus and the carbon material form a composite structure which is stacked and inlaid in a staggered mode.

According to the silicon-based anode material provided by the first aspect of the embodiment of the application, the silicon-based material is taken as a nucleus body, the anode material is endowed with higher gram capacity and cycle stability, and the anode material is coated by adopting a staggered stacked and inlaid composite structure formed by black phosphorus and carbon materials, so that on one hand, the direct contact between the silicon-based material and electrolyte can be effectively isolated, the continuous growth and active lithium consumption of an SEI film (Solid Electrolyte Interface, solid electrolyte interface film) can be effectively avoided, the formation of a more stable and compact SEI film is facilitated, the stability of the anode material is improved, and the Li is promoted ⁺ The charge transfer impedance of the electrode is reduced, and the conductivity of the cathode material is effectively improved; on the other hand, the shell layer can also provide effective buffer for the volume expansion of the silicon-based material, can limit the volume expansion of the silicon-based material to a certain extent, and remarkably improves the structural stability of the anode material in the charge and discharge process, so that the lithium storage performance of the silicon oxide is exerted to the greatest extent, and the anode material is endowed with higher gram capacity, first coulombic efficiency and rate capability. In addition, the staggered stacked and inlaid composite structure formed by the black phosphorus and the carbon material has higher mechanical property, so that the volume expansion of the silicon-based material can be effectively relieved, and the lithium storage performance of the black phosphorus and the carbon material can be fully exerted, thereby further improving the cycle stability and gram capacity of the silicon-based negative electrode composite material.

In some embodiments, the staggered stacked and inlaid composite structure includes: part of the black phosphorus and the carbon material form a structure of which the two are mutually staggered and stacked, and part of the black phosphorus is embedded into the carbon material to form another structure of which the two are embedded.

It should be understood that the black phosphorus has a two-dimensional layered orthorhombic crystal structure, and the carbon material also has a two-dimensional layered structure, so that the black phosphorus and the carbon material can be physically doped under the action of van der waals force to form a structure by alternately stacking part of the black phosphorus and the carbon material, and the structure enables the shell layers to be coated on the surface of the silicon-based material in the form of a multi-layer overlapped composite shell layer. And embedding part of black phosphorus into the carbon material in the form of nano black phosphorus sheets to form another embedded structure, wherein the structure enables the shell layer to be coated on the surface of the silicon-based material in the form of a composite shell layer. The staggered stacking and inlaying composite structure provided by the embodiment of the application can effectively relieve the volume expansion of the silicon-based material, is also beneficial to the intercalation and deintercalation of lithium ions, and further endows the anode material with higher gram capacity and cycle stability.

In some embodiments, in the shell layer, a portion of the black phosphorus is doped in the carbon material in the form of clusters or monoatoms. In the embodiment of the application, the carbon material and the black phosphorus are distributed in the shell layer in a mutually doped mode, the doped mode comprises physical doping and chemical doping, wherein part of the black phosphorus is substituted for part of carbon atoms in the carbon material in an atomic cluster or single atom mode through the chemical doping mode to form the carbon material doped with the phosphorus atoms, the formed carbon-phosphorus bond endows the shell layer with higher mechanical property, the surface of the silicon-based material can be effectively protected, the carbon-phosphorus bond serves as a buffer layer for generating a volume effect in the lithium intercalation process of the silicon-based material, the direct contact between the silicon-based material and electrolyte is effectively isolated, the transmission of lithium ions is promoted, and the gram capacity and the cycle stability of the cathode material are remarkably improved.

In some embodiments, chemical bonds exist at the interface of the black phosphorus and the carbon material. The carbon-phosphorus bond at the joint of the black phosphorus and the carbon material can effectively improve the mechanical property of the shell layer, further effectively inhibit the volume expansion of the silicon-based material, and remarkably improve the gram capacity, the structural stability and the cycle performance of the anode material.

In some embodiments, the silicon-based material includes SiO _x WhereinX is more than 0 and less than 2. Specifically, x may satisfy 0 < x < 0.5, or 0.5 < x < 1, or 1 < x < 1.5, or 1.5 < x < 2.

Specifically, siO _x At least one of the materials in the form of particles, blocks, cakes and powders, preferably SiO _x The material is provided in powder form.

In some embodiments, the silicon-based material includes SiO _x The material of the shell layer coating the silicon-based material comprises black phosphorus and carbon material, and the silicon-based anode material can be understood as SiO _x Ternary composite material @ BP @ C.

In some embodiments, the shell layer comprises 30wt% to 80wt% of the total mass of the silicon-based anode material. Specifically, the shell layer accounts for 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt% or any of the above values. The composite shell layer with the staggered stacking and inlaid composite structure can be used as a buffer layer for volume expansion of the silicon-based material, so that pulverization of the electrode structure is effectively avoided, higher cycle stability and structural stability of the anode material are endowed, and the composite shell layer can also be used as a place for storing lithium, so that gram capacity and primary charge-discharge efficiency of the anode material are improved. In the content range of the shell layer provided by the embodiment of the application, the lithium storage performance of the silicon-based material, the carbon material and the black phosphorus can be fully exerted, so that the anode material is endowed with excellent electrochemical performance.

In some embodiments, the carbon material comprises 70wt% to 95wt% of the total mass of the shell layer. Specifically, the carbon material may account for 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt% or be in a range composed of any of the above values, based on the total mass of the shell layer. After the silicon-based material core is coated by a shell layer formed by a carbon material and black phosphorus, the volume effect of the silicon-based material can be effectively inhibited, the structural stability of the anode material is maintained, and the cycle stability and the rate capability of the anode material can be improved. In the carbon content range provided by the embodiment of the application, the carbon material can effectively relieve the anisotropic expansion effect caused by the silicon-based material and the black phosphorus, and endows the anode material with higher specific capacity, first coulombic efficiency and cycle stability.

In some embodiments, the black phosphorus comprises 5wt% to 30wt% of the total mass of the shell layer. Specifically, the black phosphorus accounts for 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt% or is in the range of any of the above values. The black phosphorus has higher conductivity and charge transmission performance, has lithium intercalation removal activity, can utilize the difference of lithiation potential of the black phosphorus and the silicon-based material, can improve the conductivity of the negative electrode material, and can relieve the mechanical internal stress generated by the silicon-based material and the black phosphorus, thereby improving the cycling stability of the negative electrode material. In the content range of the black phosphorus provided by the embodiment of the application, the addition improvement effect can be achieved on the inhibition of the volume expansion effect of the silicon-based material and the improvement of the conductivity.

In some embodiments, the particle size of the core satisfies: d50 is more than or equal to 50nm and less than or equal to 300nm. In particular, the particle size of the nucleus may be, but is not limited to, 50nm to 100nm, or 80nm to 120nm, or 150nm to 200nm, or 180nm to 250nm, or 250nm to 300nm. The D50 particle size is the particle size corresponding to a cumulative particle size distribution percentage of the particles of up to 50%. The smaller the particle size of the nuclear body is, the larger the specific surface area of the nuclear body is, so that atoms on the surface of the nuclear body material have higher binding energy, the stress generated in the volume expansion process of the silicon-based material can be better released, the influence of the volume expansion of the silicon-based material is effectively reduced, the lithium storage performance of the silicon-based material is fully exerted, and the cathode material is endowed with higher gram capacity, first coulombic efficiency and cycle performance. In the particle size range of the nuclear body provided by the embodiment of the application, the lithiation of the anode material can be ensured to be more sufficient, and the stability of the core-shell structure can be improved.

In some embodiments, the shell layer has a thickness of 10nm to 100nm. Specifically, the thickness of the shell layer may be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or within a range composed of any of the above values. In the thickness range of the shell layer provided by the embodiment of the application, the shell layer can provide effective buffer for the volume expansion of the silicon-based material, effectively inhibit the volume expansion effect of the silicon-based material, further improve the conductivity of the silicon-based material, and further improve the structural stability of the coating layer, thereby endowing the anode material with excellent electrochemical performance.

In some embodiments, the primary particle size of the silicon-based anode material satisfies: d50 is more than or equal to 0.05 mu m and less than or equal to 0.7 mu m, and the secondary particle size satisfies the following conditions: d50 is more than or equal to 0.5 μm and less than or equal to 10 μm. Specifically, the primary particle diameter of the silicon-based anode material may be, but not limited to, 0.05 μm to 0.1 μm, or 0.1 μm to 0.3 μm, or 0.2 μm to 0.5 μm, or 0.4 μm to 0.7 μm, and the secondary particle diameter may be, but not limited to, 0.5 μm to 1.0 μm, or 1 μm to 3 μm, or 2 μm to 5 μm, or 4 μm to 8 μm, or 6 μm to 10 μm.

In some embodiments, the silicon-based anode material has a specific surface area of 8m ² /g～30m ² And/g. Specifically, the specific surface area of the silicon-based anode material may be 8m ² /g～15m ² /g, or 10m ² /g～25m ² /g, or 15m ² /g～30m ² And/g. The specific surface area refers to the total area of the mass of the substance. In the particle size and specific surface area range of the silicon-based anode material provided by the embodiment of the application, the absolute volume expansion of the silicon-based material can be reduced, and the volume effect of the silicon-based material is effectively inhibited, so that the electrochemical performance of the silicon-based anode material is greatly improved, and the anode material is endowed with higher first coulombic efficiency and structural stability.

A second aspect of the embodiments of the present application provides a method for preparing a silicon-based anode material, where the flow is shown in FIG. 1, and the method includes the following steps:

According to the preparation method of the silicon-based anode material, provided by the second aspect of the embodiment, the shell layer which is made of black phosphorus and carbon materials and has a staggered stacking and embedding composite structure is effectively formed on the surface of the silicon-based material, has high mechanical properties, can effectively inhibit volume expansion of the silicon-based material, and ensures structural stability of the anode material, so that the anode material is endowed with high gram capacity, first coulombic efficiency and cycle stability. In addition, the preparation method of the anode material can effectively prepare the silicon-based anode material with stable structure and electrochemical performance, and the process condition is easy to control, so that the method is suitable for large-scale industrial production and application.

In some embodiments, in step S10, the silicon-based material forms a nucleus of the upper Wen Guiji anode material, and the carbon material generated by carbonizing the carbon source and black phosphorus may be coated on the surface of the silicon-based material to form a shell of the upper Wen Guiji anode material.

In some embodiments, in step S10, the silicon-based material includes SiO _x The material, wherein 0 < x < 2. Specifically, x may satisfy 0 < x < 0.5, or 0.5 < x < 1, or 1 < x < 1.5, or 1.5 < x < 2.

In some embodiments, in step S10, the carbon source comprises at least one of pitch, resin, rubber, starch, glucose, sucrose, polyvinylpyrrolidone, and polyethylene glycol. The carbon material obtained by carbonizing the carbon source can form a staggered stacked and inlaid composite shell layer with black phosphorus for coating the silicon-based material.

In some embodiments, in step S10, the solvent includes ethanol and water. Specifically, the ethanol accounts for 10% -90% of the total volume of the solvent. The solvent should be added in an amount sufficient to enable the silicon-based material, black phosphorus and carbon source to be ball-milled to obtain a viscous mixture, which is advantageous for subsequent spray drying.

In some embodiments, the mass to volume ratio of carbon source to solvent is 1-3:1, the mass is in grams (g) and the volume is in milliliters (mL).

In some embodiments, in step S10, the mass ratio of the carbon source to the silicon-based material is 1-15:1. Specifically, the mass ratio of the carbon source to the silicon-based material may be 1-2:1, or 3-5:1, or 4-10:1, or 8-12:1, or 9-15:1. According to the embodiment of the application, through optimization and regulation of the addition amount of the carbon source, the formation of the carbon material which is matched with the particle size of the silicon-based material and has unique morphology is ensured, so that the high gram capacity of the cathode material is provided.

In some embodiments, the mass ratio of silicon-based material to black phosphorus is 2-5:1. Specifically, the mass ratio of the silicon-based material to the black phosphorus may be 2:1, or 3:1, or 4:1, or 5:1. According to the embodiment of the application, through optimization and control of the mass ratio of the silicon-based material to the black phosphorus, the black phosphorus with moderate thickness is coated on the surface of the silicon-based material, the direct contact between the silicon-based material and the electrolyte can be effectively isolated, and a more stable, compact and thin SEI film is obtained, so that the stability and electrochemical performance of the cathode material are improved.

In some embodiments, in step S20, the step of performing the mixed grinding treatment on the silicon-based material, the black phosphorus, the carbon source, and the solvent includes:

step S210, mixing a silicon-based material with black phosphorus for a first ball milling treatment to obtain a mixture;

step S220, mixing the mixture with a carbon source and a solvent for performing a second ball milling treatment.

According to the embodiment of the application, the silicon-based material and the black phosphorus are subjected to ball milling treatment, so that the silicon-based material can be subjected to nanocrystallization, the purposes of reducing the particle size and inhibiting the volume effect are achieved, the lithium storage performance and the cycle stability of the anode material are improved, meanwhile, the black phosphorus can be stripped to form two-dimensional nano black phosphorus flakes (black phosphane), the stability of the core-shell structure of the anode material is improved by utilizing the negative Poisson ratio characteristic of the black phosphorus, the specific surface area of the anode material can be increased, the ion diffusion path is reduced, and the anode material is endowed with excellent electrochemical performance; and ball milling the silicon-based material with reduced size, black phosphorus (containing black phosphazene) and a carbon source, and coating an initial shell layer on the surface of the silicon-based material, so that the gram capacity and the first coulomb efficiency of the anode material are further improved.

In some embodiments, in step S210, after the black phosphorus is subjected to the first ball milling treatment, a portion of the black phosphorus is stripped to form two-dimensional nano black flakes, and the nano black flakes may be embedded in a carbon material to form a shell layer of the mosaic structure.

Wherein the average thickness of the nano black phosphorus sheet is 1 nm-5 nm, and the ratio of the average length/width is 10-50. In particular, the average thickness may be 1nm, 2nm, 3nm, 4nm or 5nm, and the average length/width ratio may be 10 to 15, or 20 to 25, or 30 to 40, or 45 to 50.

In some embodiments, in step S210, the first ball milling process is performed at a rotational speed of 500rpm to 1000rpm for a period of 3 hours to 12 hours, and the ball to material ratio is 15 to 20:1. Specifically, the rotation speed of the first ball milling treatment may be 500rpm to 600rpm, or 500rpm to 800rpm, or 600rpm to 1000rpm, or 400rpm to 700rpm; the time is 3 to 5 hours, or 6 to 10 hours, or 8 to 12 hours, or 7 to 9 hours, or 4 to 6 hours; the ball to material ratio may be 15-17:1, or 18-20:1, or 16-19:1.

In some embodiments, in step S220, the second ball milling process is performed at a rotational speed of 300rpm to 700rpm for a period of 3 hours to 6 hours. Specifically, the rotation speed of the second ball milling treatment is 300 rpm-400 rpm, or 400 rpm-500 rpm, or 600 rpm-700 rpm; the time is 3 to 4 hours, or 4 to 6 hours, or 3.5 to 5.5 hours, or 5 to 6 hours.

In some embodiments, in step S20, the mixed grinding treatment is performed under a protective atmosphere, wherein the protective atmosphere may be nitrogen or argon.

In some embodiments, in step S30, the carbonization treatment is performed at a temperature of 500 ℃ to 1000 ℃ for a time of 2 hours to 12 hours. Specifically, the carbonization treatment temperature can be 500-700 ℃, or 700-800 ℃, or 800-1000 ℃, and the carbonization treatment time can be 2-4 hours, or 4-6 hours, or 4-8 hours, or 6-12 hours, or 8-10 hours.

According to the embodiment of the application, the intermediate material is subjected to spray drying and carbonization treatment, so that the carbon material formed by carbonizing the carbon source and black phosphorus can form the shell layer of the coated silicon-based material, which has a staggered stacking and inlaid composite structure, thereby improving the lithium storage performance of the anode material and effectively improving the gram capacity and the cycle stability of the anode material.

In some embodiments, in step S30, the carbonization process is performed at a heating rate of 1 ℃/min to 5 ℃/min. Specifically, the heating rate may be 1 to 3℃per minute, or 2 to 4℃per minute, or 3 to 5℃per minute, or 2 to 5℃per minute.

A third aspect of the embodiments of the present application provides a negative electrode, including a current collector and a negative electrode active layer bonded to a surface of the current collector, where the negative electrode active layer contains the silicon-based negative electrode material of the present application or the silicon-based negative electrode material prepared by the preparation method of the silicon-based negative electrode material of the present application.

The negative electrode provided in the third aspect of the embodiment of the application fully exerts the lithium storage performance of the silicon oxide, the black phosphorus and the carbon material due to the inclusion of the negative electrode material, and effectively improves the first coulomb efficiency, the specific capacity and the cycle performance of the negative electrode.

In some embodiments, the material of the negative electrode current collector includes one of aluminum foil, copper foil, titanium foil, stainless steel, and nickel foil.

In some embodiments, the anode active layer includes an anode active material, a binder, and a conductive agent. The anode active material comprises the silicon-based anode material provided by the embodiment of the application. Specifically, the silicon-based anode material accounts for 85-95 wt% of the total mass of the anode active layer.

Specifically, the binder accounts for 1-5 wt% of the total mass of the anode active layer. Illustratively, the binder includes at least one of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

Specifically, the conductive agent accounts for 1-5 wt% of the total mass of the anode active layer. Illustratively, the conductive agent includes at least one of graphite, carbon black, acetylene black, graphene, carbon fiber, soccer graphene, and carbon nanotubes.

Specifically, the preparation process of the negative electrode comprises the following steps:

adding deionized water into the negative electrode active material, the binder and the conductive agent, mixing, stirring and ball milling to obtain electrode slurry;

and coating the electrode slurry on a current collector, and obtaining the negative electrode through drying, rolling and die cutting processes.

The drying, rolling and die cutting processes are all those known to those skilled in the art.

The fourth aspect of the embodiment of the application provides a secondary battery, which comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the negative plate is a negative electrode of the application.

The secondary battery provided by the fourth aspect of the embodiment of the application has higher energy density, first coulombic efficiency and larger power due to the negative electrode provided by the application, and has the advantages of good cycle stability, long service life and stable electrochemical performance.

In some specific embodiments, the secondary battery is a lithium ion battery, the first coulombic efficiency of the lithium ion battery at 0.1C rate is greater than 75%, the capacity retention rate for 100 cycles is greater than 80%, and the first discharge specific capacity is greater than 1400mAh/g.

The silicon-based anode material, the preparation method and the application thereof and the like according to the embodiment of the invention are exemplified by a plurality of specific examples. For comparison, siO in each of examples and comparative examples _x In (0 < x < 2), x=1, namely, silicon oxide.

Example 1

The embodiment provides a silicon-based anode material and a preparation method thereof.

A silicon-based anode material comprises an SiO core and a shell layer which is coated on the surface of the SiO core and is formed by black phosphorus and a carbon material and has a staggered stacking and inlaid composite structure. The secondary particle diameter (D50 particle diameter) of the silicon-based anode material is 4.5 μm, and the specific surface area is 18.2m ² And/g, wherein the shell layer accounts for 50wt% of the total mass of the silicon-based anode material (the carbon yield of asphalt is calculated as 95%), the carbon material accounts for 94wt% of the total mass of the shell layer, the thickness of the shell layer is 45nm, and the D50 particle size of the SiO core is 200nm.

A preparation method of a silicon-based anode material comprises the following steps:

step S1, weighing 10g of silicon-based material (SiO powder) and 0.6g of black phosphorus, putting into a ball milling tank, adding 180g of ball milling beads with different sizes, sealing the ball milling tank in a glove box filled with nitrogen, and performing high-energy ball milling for 6 hours under the condition of rotating at 700rpm to obtain a mixture comprising the silicon-based material with reduced size and the black phosphorus (containing two-dimensional nano black phosphorus flakes);

step S2, adding 10g of asphalt, 10mL of absolute ethyl alcohol and 10mL of water into the ball milling tank in the step S1, sealing the ball milling tank in a nitrogen glove box, and ball milling for 4 hours under the condition of 400rpm of rotating speed, so that the surface of the silicon-based material is coated with an initial shell layer to obtain a viscous intermediate material;

step S3, performing spray drying on the intermediate material to obtain precursor powder;

and S4, placing the precursor powder into a tube furnace, heating to 700 ℃ at a speed of 5 ℃/min under the protection of nitrogen, calcining for 6 hours, and taking out after the precursor powder is recovered to room temperature to obtain the silicon-based anode material.

Example 2

A silicon-based anode material comprises an SiO core and a shell layer which is coated on the surface of the SiO core and is formed by black phosphorus and a carbon material and has a staggered stacking and inlaid composite structure. The secondary particle diameter (D50 particle diameter) of the silicon-based anode material is 6.2 μm, and the specific surface area is 8.5m ² And/g, wherein the shell layer accounts for 30wt% of the total mass of the silicon-based anode material (the carbon yield of the resin is calculated as 70%), the carbon material accounts for 93.3wt% of the total mass of the shell layer, the thickness of the shell layer is 23nm, and the D50 particle size of the SiO core is 270nm.

step S1, weighing 35g of silicon-based material (SiO powder) and 1g of black phosphorus, putting into a ball milling tank, adding 200g of ball milling beads with different sizes, sealing the ball milling tank in a glove box filled with nitrogen, and performing high-energy ball milling for 6 hours under the condition of 900rpm of rotating speed to obtain a mixture comprising the silicon-based material with reduced size and the black phosphorus (containing two-dimensional nano black phosphorus flakes);

step S2, adding 20g of resin, 10mL of absolute ethyl alcohol and 15mL of water into the ball milling tank in the step S1, sealing the ball milling tank in a nitrogen glove box, and ball milling for 4 hours under the condition of 500rpm of rotating speed, so that the surface of the silicon-based material is coated with an initial shell layer to obtain a viscous intermediate material;

and S4, placing the precursor powder into a tube furnace, heating to 800 ℃ at a speed of 5 ℃/min under the protection of nitrogen, calcining for 4 hours, and taking out after the precursor powder is recovered to room temperature to obtain the silicon-based anode material.

Example 3

A silicon-based anode material comprises an SiO core and a shell layer which is coated on the surface of the SiO core and is formed by black phosphorus and a carbon material and has a staggered stacking and inlaid composite structure. The secondary particle diameter (D50 particle diameter) of the silicon-based anode material is 4.2 μm, and the specific surface area is 23.7m ² And/g, wherein the shell layer accounts for 80wt% of the total mass of the silicon-based anode material (the carbon yield of starch is calculated as 40%), the carbon material accounts for 70.6wt% of the total mass of the shell layer, the thickness of the shell layer is 78nm, and the D50 particle size of the SiO core is 156nm.

step S1, weighing 4.25g of silicon-based material (SiO powder) and 5g of black phosphorus, putting into a ball milling tank, adding 250g of ball milling beads with different sizes, sealing the ball milling tank in a glove box filled with nitrogen, and performing high-energy ball milling for 8 hours under the condition of 900rpm of rotating speed to obtain a mixture comprising the silicon-based material with reduced size and the black phosphorus (containing two-dimensional nano black phosphorus flakes);

step S2, adding 30g of starch, 10mL of absolute ethyl alcohol and 10mL of water into the ball milling tank in the step S1, sealing the ball milling tank in a nitrogen glove box, and ball milling for 6 hours under the condition of 500rpm of rotating speed, so that the surface of the silicon-based material is coated with an initial shell layer to obtain a viscous intermediate material;

step S4, the same as step S4 in example 2, a silicon-based negative electrode material was obtained.

Example 4

A silicon-based anode material comprises SiOThe SiO core is coated with a shell layer which is formed by black phosphorus and carbon materials and has a staggered stacking and inlaid composite structure. The secondary particle diameter (D50 particle diameter) of the silicon-based anode material is 4.3 μm, and the specific surface area is 21.5m ² And/g, wherein the shell layer accounts for 48.7wt% (the carbon yield of polyvinylpyrrolidone is 67%) of the total mass of the silicon-based anode material, the carbon material accounts for 70.5wt% of the total mass of the shell layer, the thickness of the shell layer is 40nm, and the D50 particle size of the SiO core is 170nm.

step S1, weighing 10g of silicon-based material (SiO powder) and 2.8g of black phosphorus, putting into a ball milling tank, adding 280g of ball milling beads with different sizes, sealing the ball milling tank in a glove box filled with nitrogen, and performing high-energy ball milling for 8 hours under the condition of 900rpm of rotating speed to obtain a mixture comprising the silicon-based material with reduced size and the black phosphorus (containing two-dimensional nano black phosphorus flakes);

step S2, adding 10g of polyvinylpyrrolidone, 10mL of absolute ethyl alcohol and 10mL of water into the ball milling tank in the step S1, sealing the ball milling tank in a nitrogen glove box, and ball milling for 6 hours under the condition of 500rpm of rotating speed, so that the surface of the silicon-based material is coated with an initial shell layer to obtain a viscous intermediate material;

Example 5

A silicon-based anode material comprises an SiO core and a shell layer which is coated on the surface of the SiO core and is formed by black phosphorus and a carbon material and has a staggered stacking and inlaid composite structure. The secondary particle diameter (D50 particle diameter) of the silicon-based anode material is 4.6 μm, and the specific surface area is 20m ² And/g, wherein the shell layer accounts for 80wt% of the total mass of the silicon-based anode material (the carbon yield of asphalt is calculated as 95%), the carbon material accounts for 94.5wt% of the total mass of the shell layer, the thickness of the shell layer is 72nm, and the D50 particle size of the SiO core is 210nm.

step S1, weighing 10g of silicon-based material (SiO powder) and 2.2g of black phosphorus, putting into a ball milling tank, adding 180g of ball milling beads with different sizes, sealing the ball milling tank in a glove box filled with nitrogen, and performing high-energy ball milling for 6 hours under the condition of rotating at 700rpm to obtain a mixture comprising the silicon-based material with reduced size and the black phosphorus (containing two-dimensional nano black phosphorus flakes);

step S2, adding 40g of asphalt, 30mL of absolute ethyl alcohol and 20mL of water into the ball milling tank in the step S1, sealing the ball milling tank in a nitrogen glove box, and ball milling for 4 hours under the condition of 700rpm of rotating speed, so that the surface of the silicon-based material is coated with an initial shell layer to obtain a viscous intermediate material;

and S4, placing the precursor powder into a tube furnace, heating to 1000 ℃ at a speed of 3 ℃/min under the protection of nitrogen, calcining for 8 hours, and taking out after the precursor powder is recovered to room temperature to obtain the silicon-based anode material.

Comparative example 1

This comparative example provides a silicon-based negative electrode material and a method for producing the same.

A silicon-based anode material (SiO@BP composite material) having a secondary particle diameter (D50 particle diameter) of 3.8 μm and a specific surface area of 12m ² /g。

step S1 is the same as step S1 in example 1;

step S2, the same as step S2 in example 1, except that no asphalt was added;

step S3, step S3 in example 1;

and step S4, the step S4 in the embodiment 1 is the same to obtain the SiO@BP composite material.

Comparative example 2

A silicon-based negative electrode material (SiO@C ternary composite material) comprises a SiO core and a carbon layer coated on the surface of the SiO core. The silicon-based negative electrode materialThe secondary particle diameter (D50 particle diameter) of the material was 4.5. Mu.m, and the specific surface area was 18.1m ² /g。

step S1, weighing 10g of silicon-based material (SiO powder), 10g of asphalt 2g, 10mL of absolute ethyl alcohol and 10mL of water black phosphorus, putting into a ball milling tank, adding 180g of ball milling beads with different sizes, sealing the ball milling tank in a glove box filled with nitrogen, and performing ball milling for 4 hours under the condition of 400rpm of rotating speed, so that the surface of the silicon-based material is coated with an initial shell layer to obtain a viscous intermediate material;

step S2, performing spray drying on the intermediate material to obtain precursor powder;

and step S3, placing the precursor powder into a tube furnace, heating to 700 ℃ at a speed of 5 ℃/min under the protection of nitrogen, calcining for 6 hours, and taking out after the temperature is restored to the room temperature to obtain the SiO@C ternary composite material.

Performance detection

(1) Characterization of physical Properties

The silicon-based anode material prepared in example 1 was subjected to X-ray diffraction analysis (XRD), and the results are shown in fig. 2. As can be seen from fig. 2, four phases of SiO, si, C and black phosphorus exist in the XRD spectrum, thereby illustrating that the anode material prepared in example 1 is a sio@bp@c ternary composite material.

(2) Characterization of electrochemical Performance

The electrochemical properties of the CR 2032-button half cells were evaluated by assembling the silicon-based negative electrode materials provided in examples 1 to 5 and comparative examples 1 to 2 described above. The button cell manufacturing process is as follows:

negative electrode plate: the mass ratio of the silicon-based anode material to the acetylene black to the sodium carboxymethylcellulose CMC to the styrene butadiene rubber SBR is 80:10:4:6, wherein CMC is 1wt% aqueous solution. The dispersion slurry was stirred. The homogenized slurry was then uniformly coated on a 15 μm thick copper foil. After naturally airing, placing the copper foil in a vacuum drying oven at 80 ℃ for drying for 10 hours, and compacting the dried copper foil by a roller press; and punching and cutting the pole piece into a circular piece with the diameter of 13mm, namely the negative pole piece.

A counter electrode: a metallic lithium foil.

A diaphragm: a polypropylene porous membrane.

Lithium battery electrolyte: 1M LiPF ₆ The volume ratio of the ethylene carbonate to the dimethyl carbonate to the ethylmethyl carbonate is 1:1:1 to the resulting mixed solution was added 1M LiPF6 and 5wt% fluoroethylene carbonate.

Assembling the button cell: and assembling the lithium ion battery in a glove box protected by high-purity argon according to the assembling sequence of the lithium metal foil, the diaphragm, the electrolyte and the negative plate.

The batteries of the negative electrode sheets of the silicon-based negative electrode materials provided in examples 1 to 5 were respectively referred to as examples S1 to S5, and the batteries including the silicon-based negative electrode materials of comparative examples 1 to 2 were respectively referred to as comparative examples DS1 to DS2.

The button cell having the composition of example S1 was subjected to a constant current charge-discharge test of 0 to 2.0V, and a current of 0.1C, and the result is shown in FIG. 3. As can be seen from fig. 3, the lithium secondary battery having the composition of example S1 had a specific capacity for initial discharge of 1498mAh/g, a specific capacity for charge of 1268mAh/g, and a coulombic efficiency of 84.6%.

The results of constant current charge and discharge tests of lithium secondary batteries containing the silicon-based negative electrode materials of examples S2 to S5 were also similar to those of fig. 3. Therefore, according to the first charge-discharge capacity-voltage test result, the silicon-based anode material has higher first coulombic efficiency and gram capacity.

The electrochemical properties of lithium secondary batteries each composed of examples S1 to S5 and comparative examples DS1 to DS2 were tested. The button cell was charged and discharged at a rate of 0.5C, and after 100 cycles, the results of the electrochemical performance test of the lithium secondary battery are shown in table 1 below.

As can be seen from table 1, the secondary batteries containing the silicon-based negative electrode materials prepared in this example application were higher in initial coulombic efficiency, initial charge-discharge specific capacity, and capacity retention than the comparative examples.

Table 1 test results

The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.

Claims

1. A silicon-based anode material, characterized in that the silicon-based anode material comprises a core body and a shell layer coating the core body; the material of the core body comprises a silicon-based material, the material of the shell layer comprises black phosphorus and a carbon material, and the black phosphorus and the carbon material form a composite structure with staggered stacking and inlaying.

2. The silicon-based anode material of claim 1, wherein the staggered stack and mosaic composite structure comprises: part of the black phosphorus and the carbon material form a structure of a type which is mutually staggered and stacked, and part of the black phosphorus is embedded into the carbon material to form another type of embedded structure.

3. The silicon-based anode material according to claim 1, wherein part of the black phosphorus in the shell layer is doped in the carbon material in the form of atomic clusters or monoatoms.

4. The silicon-based anode material of claim 1, wherein the silicon-based material comprises SiO _x Wherein x is more than 0 and less than 2; and/or

The shell layer accounts for 30-80 wt% of the total mass of the silicon-based anode material; and/or

The carbon material accounts for 70-95 wt% of the total mass of the shell layer; and/or

The black phosphorus accounts for 5-30wt% of the total mass of the shell layer.

5. A silicon-based anode material according to any one of claims 1 to 4, wherein the particle size of the core satisfies: d50 is more than or equal to 50nm and less than or equal to 300nm; and/or

The thickness of the shell layer is 10 nm-100 nm; and/or

The primary particle size of the silicon-based anode material meets the following conditions: d50 is more than or equal to 0.05 mu m and less than or equal to 0.7 mu m, and the secondary particle size satisfies the following conditions: d50 is more than or equal to 0.5 mu m and less than or equal to 10 mu m; and/or

The specific surface area of the silicon-based anode material is 8m ² /g～30m ² /g。

6. The preparation method of the silicon-based anode material is characterized by comprising the following steps of:

providing a silicon-based material, black phosphorus, a carbon source and a solvent;

mixing and grinding the silicon-based material, the black phosphorus, the carbon source and the solvent to coat an initial shell layer on the surface of the silicon-based material, so as to obtain an intermediate material;

and sequentially carrying out drying treatment and carbonization treatment on the intermediate material to enable the initial shell layer to generate a shell layer with a staggered stacking and inlaid composite structure, thereby obtaining the silicon-based anode material.

7. The method for preparing a silicon-based anode material as claimed in claim 6, wherein,

the step of carrying out mixed grinding ball milling treatment on the silicon-based material, the black phosphorus, the carbon source and the solvent comprises the following steps:

mixing the silicon-based material with the black phosphorus for a first ball milling treatment to obtain a mixture;

and mixing the mixture with the carbon source and the solvent for performing a second ball milling treatment.

8. The method for preparing a silicon-based anode material according to claim 7, wherein the rotation speed of the first ball milling treatment is 500 rpm-1000 rpm, the time is 3 h-12 h, and the ball-to-material ratio is 15-20:1; and/or

The rotating speed of the second ball milling treatment is 300 rpm-700 rpm, and the time is 3 h-6 h; and/or

The mass ratio of the carbon source to the silicon-based material is 1-15:1; and/or

The mass ratio of the silicon-based material to the black phosphorus is 2-5:1; and/or

The carbonization treatment is carried out at 500-1000 ℃ for 2-12 h; and/or

The heating rate of the carbonization treatment is 1-5 ℃/min.

9. A negative electrode comprising a current collector and a negative electrode active layer bonded to the surface of the current collector, wherein the negative electrode active layer contains the silicon-based negative electrode material according to any one of claims 1 to 5 or the silicon-based negative electrode material produced by the method for producing a silicon-based negative electrode material according to any one of claims 6 to 8.

10. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the negative electrode sheet is the negative electrode of claim 9.