CN116154123A

CN116154123A - Silicon composite material and preparation method and application thereof

Info

Publication number: CN116154123A
Application number: CN202211411525.5A
Authority: CN
Inventors: 白文龙; 王育文; 游兴艳; 武宝珍; 郑蔚; 叶永煌; 金海族; 吴凯
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-11-11
Filing date: 2022-11-11
Publication date: 2023-05-23

Abstract

The application provides a silicon composite material and a preparation method thereof, a negative electrode composition, negative electrode slurry, a negative electrode plate, a secondary battery and an electric device. The silicon composite material comprises a doped silicon-containing substrate and a lithium-containing layer positioned on the surface of the doped silicon-containing substrate, wherein the doped silicon-containing substrate comprises a silicon-containing substrate and doping elements doped into the silicon-containing substrate; the conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon-containing substrate. According to the silicon composite material, the silicon substrate is doped, and the lithium-containing layer is arranged on the surface of the doped silicon-containing substrate, so that the lithium ion battery can be promoted to be embedded into the silicon composite material, the capacity of the silicon composite material is fully exerted, and the performance of the secondary battery is improved.

Description

Silicon composite material and preparation method and application thereof

Technical Field

The application relates to the technical field of secondary batteries, in particular to a silicon composite material and a preparation method thereof, a negative electrode composition, negative electrode slurry, a negative electrode plate, a secondary battery and an electric device.

Background

As research on secondary batteries continues to be advanced, a wide variety of materials are applied to the preparation of secondary batteries to improve the performance of the secondary batteries. Among them, the use of a silicon material in the negative electrode of the secondary battery has a certain improvement effect on the performance of the battery. However, the conventional silicon material is difficult to be well matched with the negative electrode of the secondary battery, so that the capacity of the silicon material is difficult to be fully exerted, and further improvement of the performance of the secondary battery is restricted.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a silicon composite material, a method for producing the same, a negative electrode composition, a negative electrode slurry, a negative electrode tab, a secondary battery, and an electric device, in which the silicon composite material can be better matched with the negative electrode of the battery by improving the silicon material, and further, the performance of the lithium ion battery can be improved.

A first aspect of the present application provides a silicon composite material comprising a doped silicon-containing substrate and a lithium-containing layer on a surface of the doped silicon-containing substrate, the doped silicon-containing substrate comprising a silicon substrate and a doping element doped into the silicon substrate; the conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon substrate.

According to the silicon composite material, the silicon substrate is doped, so that the conductivity of the doped silicon-containing substrate is larger than that of the silicon substrate, and the lithium-containing layer is arranged on the surface of the doped silicon-containing substrate, so that the lithium ion battery can be promoted to be embedded into the silicon composite material, the capacity of the silicon composite material can be fully exerted, and the performance of the secondary battery can be improved.

A second aspect of the present application provides a method for preparing a silicon composite material, comprising the steps of: forming a lithium-containing layer on a surface of a doped silicon-containing substrate, the doped silicon-containing substrate comprising a silicon substrate and a doping element doped into the silicon substrate; the conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon-containing substrate.

A third aspect of the present application provides a negative electrode composition comprising the silicon composite material or a silicon composite material prepared by the method of preparing a silicon composite material.

A fourth aspect of the present application provides a negative electrode slurry comprising a solvent and the negative electrode composition.

A fifth aspect of the present application provides a negative electrode tab comprising a current collector and a negative electrode active layer on at least one surface of the current collector, the negative electrode active layer comprising the negative electrode composition or formed by solidifying a material comprising the negative electrode slurry on the current collector and then drying.

A sixth aspect of the present application provides a secondary battery comprising the negative electrode tab.

A seventh aspect of the present application provides an electric device including the secondary battery.

Drawings

Fig. 1 is a schematic structural diagram of a silicon composite material according to an embodiment of the present application.

Fig. 2 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 3 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 2.

Fig. 4 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 5 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 6 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 5.

Fig. 7 is a schematic view of an electric device in which the secondary battery according to an embodiment of the present application is used as a power source.

Fig. 8 is a graph of particle morphology of the silicon composite material of example 2 of the present application.

Fig. 9 is an XRD pattern of the silicon composite in example 2 of the present application.

Fig. 10 is an elemental distribution diagram of a silicon composite material in example 2 of the present application.

Fig. 11 is a graph showing the comparison of the fast charge performance of the secondary batteries in example 2 and comparative example 4 of the present application.

Reference numerals illustrate:

100. a lithium-containing layer; 200. a doped silicon-containing substrate; 1. a battery pack; 2. an upper case; 3. a lower box body; 4. a battery module; 5. a secondary battery; 51. a housing; 52. an electrode assembly; 53. and a top cover assembly.

Detailed Description

Hereinafter, embodiments of a battery pack, a battery cell, a secondary battery, and an electric device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

Unless otherwise indicated, the terms "positive electrode sheet" and "positive electrode sheet" are used interchangeably in this application. The terms "negative electrode sheet" and "negative electrode sheet" have the same meaning and are used interchangeably. The terms "separator membrane" and "separator membrane" have the same meaning and are used interchangeably.

In the design of the secondary battery, when a conventional silicon material is applied to the negative electrode, since the lithium intercalation platform of the silicon material is high, the capacity of the silicon material is difficult to be sufficiently exerted in the presence of electrochemical polarization, which may cause a decrease in the initial coulombic efficiency and cycle performance of the battery. Especially in the rapid charge and discharge process, the improvement of the traditional silicon material on the battery performance is restricted more obviously.

The traditional silicon material is difficult to be well matched with the negative electrode of the secondary battery, so that the capacity of the silicon material is difficult to be fully exerted, and the further improvement of the performance of the secondary battery is restricted.

The application provides a silicon composite material, which comprises a doped silicon-containing substrate and a lithium-containing layer positioned on the surface of the doped silicon-containing substrate, wherein the doped silicon-containing substrate comprises a silicon-containing substrate and doping elements doped into the silicon-containing substrate; the conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon-containing substrate. In the silicon composite material, the silicon-containing substrate is doped, so that the conductivity of the doped silicon-containing substrate is larger than that of the silicon-containing substrate, and the lithium-containing layer is arranged on the surface of the doped silicon-containing substrate, so that the lithium ion battery can be promoted to be embedded into the silicon composite material, the capacity of the silicon composite material can be fully exerted, and the performance of the secondary battery can be improved.

Referring to fig. 1, a structure of a silicon composite material according to an embodiment of the present application is shown, wherein the silicon composite material includes a doped silicon-containing substrate 200 and a lithium-containing layer 100 on a surface of the doped silicon-containing substrate, and the doped silicon-containing substrate 200 includes a silicon-containing substrate and a doping element doped into the silicon-containing substrate.

It is understood that the lithium-containing layer is located on the surface of the doped silicon-containing substrate, meaning that the lithium-containing layer is located on a portion of the surface or the entire surface of the doped silicon-containing substrate. In the schematic structure shown in fig. 1, the lithium-containing layer is located over the entire surface of the doped silicon-containing substrate.

In one embodiment, the doping element includes at least one of a P-type doping element and an N-type doping element. In the embodiment, at least one of the P-type doping element and the N-type doping element is selected, so that the conductivity of the silicon composite material can be effectively improved, the quick charge performance and the cycle life of the secondary battery are further improved, and the silicon composite material can be better applied to scenes with high requirements on the quick charge performance. More specifically, the silicon material is generally crystalline, silicon atoms are connected through covalent bonds, 8 electrons are arranged on the silicon outer layer, and the electrons are not easy to lose and migrate. When the P-type doping element is selected, redundant holes can be formed in the crystal lattice of the silicon-containing substrate, and when the N-type doping element is selected, redundant electrons can be formed in the crystal lattice of the silicon-containing substrate, so that free moving electrons or ions exist on the surface of the silicon-containing substrate, the conductivity of the silicon-containing substrate can be effectively improved, and the quick charge performance and the cycle life of the secondary battery can be further improved. Optionally, the P-type doping element includes at least one of boron element and aluminum element, and the N-type doping element includes phosphorus element.

In one embodiment, the molar ratio of silicon in the doped silicon-containing substrate to lithium in the lithium-containing layer is from 10:1 to 2:1. Optionally, the molar ratio of silicon in the doped silicon-containing substrate to lithium in the lithium-containing layer is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, etc.

In one embodiment, the doping element doping amount is less than or equal to 10 percent in percentage by mass of the silicon composite material. When the doping amount of the doping element is too high, the amount of the active material in the electrode tab may be reduced, resulting in a decrease in the energy density of the electrode tab. Optionally, the doping amount is less than or equal to 8 percent. Optionally, the doping amount is less than or equal to 6 percent. Optionally, the doping amount is less than or equal to 5 percent. Optionally, the doping amount is 0.5% -5%. Alternatively, the doping amount may be, but is not limited to, 0.5%, 1%, 3%, 5%, 8%, 10%, or the like.

In one embodiment, the doped silicon-containing substrate is particulate. Optionally, the particle size distribution Dv50 of the doped silicon-containing substrate is less than or equal to 10 μm. Optionally, the particle size distribution Dv50 of the doped silicon-containing substrate is less than or equal to 8 μm. The grain size distribution Dv50 of the doped silicon-containing substrate is less than or equal to 6 mu m. Alternatively, the particle size distribution Dv50 of the doped silicon-containing substrate is from 5 μm to 10 μm. For example, the particle size distribution Dv50 of the doped silicon-containing substrate may be, but is not limited to, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

In this application, dv50 refers to: in the volume cumulative distribution curve, the particle size corresponding to the cumulative particle size distribution number of the particles reaching 50% is physically defined as having a particle size less than (or greater than) 50% of its particles. By way of example, dv50 may be conveniently determined by reference to the GB/T19077-2016 particle size distribution laser diffraction method using a laser particle size analyzer, such as the Mastersizer 2000E type laser particle size analyzer from Markov instruments, UK.

In one embodiment, the silicon-containing substrate comprises one or more of silicon, silicon oxide, and silicon dioxide. Alternatively, the silicon-containing substrate comprises silicon, or the silicon-containing substrate comprises silicon and silicon dioxide, or the silicon-containing substrate comprises silicon and silicon oxide, or the silicon-containing substrate comprises silicon, silicon oxide, and silicon dioxide.

In one embodiment, the silicon-containing substrate includes elemental silicon and elemental oxygen. Optionally, the atomic number ratio of elemental silicon to elemental oxygen in the silicon-containing substrate is from 1:0.1 to 1:2. Optionally, the atomic number ratio of elemental silicon to elemental oxygen in the silicon-containing substrate is 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc.

In one embodiment, the doping element is doped into the silicon substrate from the surface of the silicon substrate, and the doping element is doped into a portion of the silicon-containing substrate or the entire silicon-containing substrate.

In one embodiment, the silicon composite further comprises a carbon cladding layer on the surface of the lithium-containing layer. Through set up the carbon coating at the surface on lithium layer, on the one hand can make silicon composite's inner structure more stable, on the other hand can isolate water, reduce the gas production, improve silicon composite's security in the use. Meanwhile, the arrangement of the carbon coating layer can also improve the conductivity of the silicon composite material. Optionally, the carbon coating layer coats all or part of the surface of the lithium-containing layer.

In one embodiment, the mass ratio of the carbon coating layer to the doped silicon-containing substrate is 1:6 to 1:1. Optionally, the mass ratio of the carbon coating layer to the doped silicon-containing substrate is 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, etc.

In one embodiment, the silicon composite is in the form of particles. Alternatively, the particle size distribution Dv50 of the silicon composite material is 5 μm to 15 μm. Alternatively, the particle size distribution Dv50 of the silicon composite material is 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, or the like.

In one embodiment, the lithium-containing layer includes elemental silicon. Optionally, the lithium-containing layer comprises at least one of lithium silicate, lithium hydride, lithium fluoride, lithium sulfite, and a lithium silicon alloy.

The application also provides a preparation method of the silicon composite material. The preparation method comprises the following steps: a lithium-containing layer is formed on a surface of a doped silicon-containing substrate that includes a silicon substrate and a doping element doped into the silicon substrate. The conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon-containing substrate.

In one embodiment, forming a lithium-containing layer on a surface of a doped silicon-containing substrate comprises the steps of: mixing a doped silicon-containing substrate with a lithium source to prepare a mixture; the mixture is subjected to a heat treatment under a protective gas atmosphere. By heat-treating the mixture after the doped silicon-containing substrate and the lithium source are mixed, the lithium source can be reacted with the silicon-containing substrate in the doped silicon-containing substrate to form a lithium-containing layer on the surface of the doped silicon-containing substrate.

In one embodiment, the molar ratio of silicon in the doped silicon-containing substrate to lithium in the lithium source is from 10:1 to 2:1. Optionally, the molar ratio of silicon in the doped silicon-containing substrate to lithium in the lithium source is 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, etc.

In one embodiment, the lithium source comprises at least one of elemental lithium, lithium hydroxide, lithium hydride, biphenyl lithium, naphthalene lithium, and phenanthrene lithium. Alternatively, the lithium source may be in powder form or in foil form. Alternatively, the elemental lithium may be at least one of lithium powder and lithium foil.

In one embodiment, the heat treatment includes a heating stage and a holding stage that are performed sequentially. At this time, forming the lithium-containing layer on the surface of the doped silicon-containing substrate includes the steps of: mixing a doped silicon-containing substrate with a lithium source to prepare a first mixture; and (3) heating the first mixture in a protective gas atmosphere, and then carrying out heat preservation treatment.

Alternatively, the heating rate of the heating stage is 1 to 10 ℃ per minute, for example, the heating rate of the heating stage may be, but not limited to, 1, 3, 5, 7, 9, 10, etc. Alternatively, the temperature of the incubation period is 550 ℃ to 750 ℃, for example, the temperature of the incubation period may be, but is not limited to 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, and the like. Alternatively, the time of the incubation period is 1h to 5h, for example, the time of the incubation period may be, but not limited to, 1h, 2h, 3h, 4h, 5h, etc. It will be appreciated that during the heating process, the temperature is raised to the soak temperature and then soak is performed at that soak temperature.

It is understood that mixing the doped silicon-containing substrate with the lithium source may be performed in a blender. The protective atmosphere may be at least one of nitrogen, helium, argon, neon, krypton, and xenon.

In one embodiment, the doped silicon-containing substrate is prepared by vapor deposition of a vapor phase silicon-containing substrate and a vapor phase dopant material in a protective gas atmosphere.

Optionally, the gas phase doping material comprises one or more of borane, alane, and phosphane. Alternatively, the gas phase silicon-containing substrate may be prepared from a solid silicon-containing substrate by heating.

In one embodiment, the vapor deposition temperature is 1000 ℃ to 1400 ℃. For example, the temperature of vapor deposition may be, but is not limited to, 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, 1400 ℃, and the like. Alternatively, the vapor deposition time is 2 to 10 hours. For example, the time of vapor deposition may be, but is not limited to, 2h, 3h, 5h, 7h, 9h, 10h, etc. Alternatively, the pressure of the vapor deposition is 0.05Pa to 10Pa. For example, the pressure of vapor deposition may be, but is not limited to, 0.05Pa, 0.1Pa, 0.3Pa, 0.5Pa, 0.8Pa, 1Pa, 2Pa, 3Pa, 5Pa, 8Pa, 10Pa, etc.

It is understood that the shielding gas may be at least one of hydrogen, nitrogen, helium, argon, neon, krypton, and xenon during vapor deposition. Optionally, during vapor deposition, the shielding gas comprises hydrogen.

In one embodiment, the method of preparing a silicon composite further comprises the step of collecting the product after vapor deposition. Alternatively, the collection is by precipitation. Alternatively, the temperature of the precipitate is 600℃to 700 ℃. The product after vapor deposition was collected by precipitation. Alternatively, the temperature of the precipitation may be, but is not limited to, 600 ℃, 610 ℃, 620 ℃, 650 ℃, 680 ℃, 690 ℃, 700 ℃, etc.

In one embodiment, the method further comprises, prior to forming the lithium-containing layer on the surface of the doped silicon-containing substrate: a carbon coating layer is formed on the surface of the doped silicon-containing substrate. Optionally, the carbon coating is formed on the surface of the doped silicon-containing substrate by vapor phase cladding. Optionally, the carbon coating layer coats all or part of the surface of the lithium-containing layer.

It is understood that the doped silicon-containing substrate is polished prior to forming the carbon cladding layer on the surface of the doped silicon-containing substrate.

In one embodiment, the vapor phase cladding comprises the steps of: preheating a doped silicon-containing substrate in a protective gas atmosphere; mixing the doped silicon-containing substrate after the preheating treatment with a carbon source to obtain a mixture; the mixture is subjected to a heat-preserving treatment. Optionally, the shielding gas in the gas phase cladding may be at least one of nitrogen, helium, argon, neon, krypton, and xenon.

Alternatively, the heating rate of the preheating treatment is 1 to 10 ℃ per minute, for example, the heating rate of the preheating treatment may be, but not limited to, 1, 3, 5, 7, 9, 10, etc. Alternatively, the temperature after the pre-heat treatment is 700 ℃ to 900 ℃, for example, the temperature after the pre-treatment may be, but not limited to, 700 ℃, 720 ℃, 750 ℃, 780 ℃, 800 ℃, 820 ℃, 850 ℃, 880 ℃, 900 ℃, and the like. Alternatively, the temperature of the incubation treatment is 700 ℃ to 900 ℃, for example, the temperature of the incubation treatment may be, but not limited to, 700 ℃, 720 ℃, 750 ℃, 780 ℃, 800 ℃, 820 ℃, 850 ℃, 880 ℃, 900 ℃, and the like. It will be appreciated that the mixture is subjected to a soak treatment at a temperature subsequent to the pre-heat treatment. Alternatively, the time of the incubation treatment is 8h to 20h, for example, the time of the incubation treatment may be, but not limited to, 8h, 10h, 12h, 15h, 18h, 20h, etc.

In one embodiment, the mass ratio of the carbon source to the doped silicon-containing substrate is 1:6 to 1:1. Optionally, the mass ratio of the carbon source to the doped silicon-containing substrate is 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, etc. Optionally, the carbon source comprises one or more of alcohol, glucose, sucrose, cellulose, and glycogen. Optionally, the alcohol comprises at least one of propanol, methanol and ethanol.

In one embodiment, the mixing of the pre-heat treated doped silicon-containing substrate with the carbon source is by adding the carbon source to the pre-heat treated doped silicon-containing substrate. Optionally, the carbon source is added at a rate of 0.5L/min to 2L/min. For example, the carbon source may be added at a rate of, but not limited to, 0.5L/min, 0.8L/min, 1L/min, 1.2L/min, 1.5L/min, 1.8L/min, 2L/min, etc. Optionally, the carbon source is added in gaseous form.

In one embodiment, a method of preparing a silicon composite material includes the steps of: forming a carbon coating layer on the surface of the doped silicon-containing substrate; mixing a doped silicon-containing substrate after forming a carbon coating layer with a lithium source; the mixture after mixing was subjected to heat treatment under a protective gas atmosphere. It is understood that when forming the lithium-containing layer, lithium passes through the carbon cladding layer to the surface of the doped silicon-containing substrate and reacts with the surface of the doped silicon-containing substrate to form a lithium-containing layer on the surface of the doped silicon-containing substrate.

The application also provides a negative electrode composition. The negative electrode composition comprises the silicon composite material or the silicon composite material prepared by the preparation method of the silicon composite material.

In one embodiment, the mass percent of the silicon composite material is 1-34% based on the mass percent of the negative electrode composition. Alternatively, the mass percent of the silicon composite material may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 33%, 34%, etc.

In one embodiment, the negative electrode composition further includes a negative electrode active material. Optionally, the negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon; optionally, the mass ratio of the anode active material to the silicon composite material is 3:1-99:1. For example, the mass ratio of the anode active material to the silicon composite material may be, but is not limited to, 3:1, 5:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, etc.

In one embodiment, the anode active material is in the form of particles. Alternatively, the particle size distribution Dv50 of the anode active material is 10 μm or less; alternatively, the particle size distribution Dv50 of the anode active material is 8 μm or less. Alternatively, the particle size distribution Dv50 of the negative electrode active material is 3 μm or less and 8 μm or less. For example, the particle size distribution Dv50 of the anode active material may be, but is not limited to, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

In one embodiment, the negative electrode composition further includes a conductive agent. Optionally, the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In one embodiment, the negative electrode composition further comprises a binder. Optionally, the binder includes at least one of polyacrylic acid (PA a), styrene-butadiene rubber (SBR), polyamideimide (PAI), polyvinyl alcohol (PVA), polyethylenimine (PEI), polyimide (PI), and poly-t-butyl acrylate-triethoxysilane (TBATEVS). Optionally, the weight average molecular weight of the binder is 100 to 200 tens of thousands. For example, the weight average molecular weight of the binder may be, but is not limited to, 110 ten thousand, 120 ten thousand, 150 ten thousand, 180 ten thousand, 200 ten thousand, etc.

The application also provides a negative electrode slurry. The negative electrode slurry includes a solvent and the above negative electrode composition.

The application also provides a negative pole piece. The negative electrode plate comprises a current collector and a negative electrode active layer, wherein the negative electrode active layer is positioned on at least one surface of the current collector, and the negative electrode active layer comprises the negative electrode composition or is formed by solidifying and drying a material comprising the negative electrode slurry on the current collector.

The application also provides a secondary battery. The secondary battery comprises the negative electrode plate.

The application also provides an electric device. The electricity utilization device comprises the secondary battery.

The secondary battery will be described below with reference to the related drawings.

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.

[ Positive electrode sheet ]

The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, wherein the positive film layer comprises the positive active material of the first aspect of the application.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, when the secondary battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for a lithium ion battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/ ₃ Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFe PO ₄ (may also beAbbreviated as LFP)), a composite of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.

In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material may employ a positive electrode active material for a sodium-ion battery, which is well known in the art. As an example, the positive electrode active material may be used alone, or two or more kinds may be combined. Wherein the positive electrode active material is selected from sodium-iron composite oxide (NaFeO) ₂ ) Sodium cobalt composite oxide (NaCoO) ₂ ) Sodium chromium composite oxide (NaCrO) ₂ ) Sodium manganese composite oxide (NaMnO) ₂ ) Sodium nickel composite oxide (NaNiO) ₂ ) Sodium nickel titanium composite oxide (NaNi) _1/2 Ti _1/2 O ₂ ) Sodium nickel manganese composite oxide (NaNi) _1/2 Mn _1/2 O ₂ ) Sodium iron manganese composite oxide (Na _2/3 Fe _1/3 Mn _2/3 O ₂ ) Sodium nickel cobalt manganese composite oxide (NaNi) _1/3 Co _1/3 Mn _1/3 O ₂ ) Sodium iron phosphate compound (NaFePO) ₄ ) Sodium manganese phosphate compound (NaMn) _P O ₄ ) Sodium cobalt phosphate compound (NaCoPO) ₄ ) Prussian blue type materials, polyanionic materials (phosphates, fluorophosphates, pyrophosphates, sulfates), etc., but the present application is not limited to these materials, other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used herein.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

[ negative electrode sheet ]

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material. The negative electrode tab may be the negative electrode tab described above.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyamideimide (PAI), polyethylenimine (PEI), polyimide (PI), and poly-t-butyl acrylate-triethoxyvinylsilane (TBATEVS).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The type of the electrolyte is not particularly limited, and may be selected according to the need.

In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

[ isolation Membrane ]

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.

In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte as described above.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 2 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 3, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 5 and 6 are battery packs 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device, which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 7 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

(1) Preparation of a silicon composite material.

(1) 1kg of silicon powder and silicon dioxide powder are uniformly mixed, wherein the atomic ratio of silicon to oxygen is 1:1. then introducing borane and hydrogen at the temperature of between 1000 and 1400 ℃ under the pressure of between 0.05 and 10Pa, reacting for 5 hours to carry out vapor deposition, and then depositing at the temperature of between 600 and 700 ℃ to obtain the doped silicon-containing substrate. Wherein, the doping amount of boron element is 0.5 percent in terms of mass percent of the silicon composite material in the embodiment.

(2) The doped silicon-containing substrate is ball-milled in a ball mill for 6 hours under the condition of 1000r/min until the particle size distribution Dv50 of the doped silicon-containing substrate is 8 mu m.

(3) And (3) putting the ball-milled doped silicon-containing substrate into a rotary furnace, adopting a gas phase cladding method, heating to 850 ℃ at a speed of 5 ℃/min under a nitrogen atmosphere, then introducing propanol gas at a speed of 1.0L/min, and preserving heat for 12 hours to obtain the carbon-clad doped silicon-containing substrate. Wherein, the mass ratio of the propanol to the doped silicon-containing substrate is 3:100.

(4) uniformly mixing the carbon-coated doped silicon-containing substrate and lithium hydroxide in a mixer according to the molar ratio of silicon to lithium of 10:1, then placing the mixture into a crucible, placing the crucible into an atmosphere furnace, heating to 650 ℃ at a speed of 5 ℃/min under argon atmosphere, and preserving heat for 3 hours at 650 ℃. Then naturally cooling to room temperature, and sieving to obtain the silicon composite material with the particle size distribution Dv50 of 5 mu m.

(2) And (3) preparing a negative electrode plate.

And (3) dissolving the silicon composite material obtained in the step (1), artificial graphite, a conductive agent acetylene black, a binder styrene-butadiene rubber (weight average molecular weight is 200 ten thousand) and a dispersing agent sodium carboxymethyl cellulose (CMC) in a solvent deionized water according to a weight ratio of 10:87:1:1:1, and uniformly stirring and mixing to prepare the negative electrode slurry. The cathode slurry was mixed at a concentration of 9.7mg/cm ² The coating density of the alloy is uniformly coated on a 7 mu m negative current collector copper foil, and the negative electrode plate is obtained through drying, cold pressing and cutting.

(3) And (3) preparing a positive electrode plate.

The positive electrode active material lithium nickel cobalt manganese oxide (NCM 523, liNi _0.5 Co _0.2 Mn _0.3 O ₂ ) The adhesive polyvinylidene fluoride PVDF and the conductive agent acetylene black SP are prepared according to the weight ratio of 98:1:1, adding N-methyl pyrrolidone (NMP) as a solvent, and stirring the slurry in a vacuum state until the slurry is uniform. The resulting slurry was subjected to a treatment of 13.7mg/cm ² Coating the surface density of the alloy on an aluminum foil with the thickness of 13 mu m by using a scraper, drying at 140 ℃, cold pressing, and cutting to obtain the positive electrode plate.

(4) And (3) preparing an electrolyte.

In an argon atmosphere glove box (H ₂ O<0.1ppm，O ₂ <0.1 ppm), the organic solvent Ethylene Carbonate (EC)/ethylmethyl carbonate (EMC) was mixed uniformly in a volume ratio of 3/7, and 12.5% by weight (based on the weight of ethylene carbonate/ethylmethyl carbonate solvent) of LiPF was added ₆ Dissolving in the organic solvent, and stirring uniformly to obtain electrolyte.

(5) And a separation film.

A commercially available PP-PE copolymer microporous film (from Highway electronic technologies Co., ltd., model No. 20) having a thickness of 7 μm and an average pore diameter of 80nm was used.

(6) And (3) preparation of a secondary battery.

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, so that the isolating film is positioned in the middle of the positive electrode and the negative electrode to play a role in isolation, and winding to obtain the bare cell. And placing the bare cell in an outer package, injecting electrolyte and packaging to obtain the secondary battery.

Examples 2 to 6

Examples 2 to 6 are different in the mass percentage of boron element based on the mass percentage of the silicon composite material and/or in the particle size distribution Dv50 of the silicon composite material from example 1, as shown in table 1.

Wherein the particle morphology of the silicon composite material in example 2 is shown in fig. 8, the XRD pattern of the silicon composite material in example 2 is shown in fig. 9, and the elemental distribution of the silicon composite material in example 2 is shown in fig. 10. As can be seen from fig. 8 to 10, in the silicon composite material of example 2, the distribution of B element is relatively uniform, and the lithium-containing layer has obvious lithium silicate.

Comparative examples 1 to 4

Comparative examples 1 to 4 differ from example 1 in the mass percentage of boron element based on the mass percentage of the silicon composite material and/or in the particle size distribution Dv50 of the silicon composite material as shown in table 1.

Test case

(1) 25 ℃ quick charge cycle life/number of turns.

The capacity retention performance of the secondary battery was evaluated by a 25 ℃ fast charge cycle life/turn number. The secondary batteries prepared in examples and comparative examples were charged at a rate of 4C at 25C, discharged at a rate of 1C, and subjected to continuous cycle test in a 3% -97% soc interval until the capacity of the secondary battery was less than 80% of the initial capacity, and the number of cycles was recorded as cycle performance.

(2) 4C charging resistor.

The kinetic performance of the secondary battery was evaluated by a 4C charging resistance at 25 ℃. At 25 ℃, the secondary batteries prepared in the examples and the comparative examples are discharged to a 50% capacity state, kept stand for 30min, the voltage value V1 is recorded, the secondary batteries are charged for 10s by the current A0 corresponding to the 4C multiplying power, the voltage value V2 corresponding to the end of charging is recorded, and the charging resistance is calculated in the following manner: r= (V2-V1)/A0.

(3) Negative gram capacity.

And assembling the prepared negative electrode plate into a button cell, and charging and discharging at the rate of 0.04A/g to obtain the total capacity. Gram capacity is the total capacity divided by the mass of the active layer of the negative electrode sheet.

(4) Charging time.

At 35 ℃, the secondary battery is discharged to a state of 0% SOC, and is kept stand for 30min, the SOC when the anode potential reaches 0V is monitored by a three-electrode battery, charging is started from 5C until 2.3C is cut off, charging time and corresponding SOC are recorded at intervals of 0.3C, and the time from the start of charging to the cut-off of charging is taken as the fast charging time of the secondary battery.

(5) The fast charge performance of the secondary batteries in example 2 and comparative example 4 were compared, and the results are shown in fig. 11. As can be seen from fig. 11, the secondary battery of example 2 was charged at 5C, 10-80% soc, and the rapid charge at 35 ℃ was improved by 9% as compared with comparative example 1, showing excellent rapid charge performance.

(6) The silicon composite materials obtained in example 2 and comparative example 4 were tested for powder resistance, and the results are shown in table 2, indicating that the silicon composite material in example 2 has a significantly reduced powder resistance.

(7) The silicon composite material obtained in example 2 was subjected to an element percentage content test, which showed that the mass percentage of the element was 1%.

The results of the above part of the test are shown in table 1.

TABLE 1

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TABLE 2

Silicon composite material	Powder resistor/omega
		Comparative example 4	0.08
Example 2	0.04

TABLE 3 Table 3

Test element	Element percentage/wt%
		Boron (B)	1
Lithium ion battery	4.55
		Silicon (Si)	12.2

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. A silicon composite comprising a doped silicon-containing substrate and a lithium-containing layer on a surface of the doped silicon-containing substrate, the doped silicon-containing substrate comprising a silicon-containing substrate and a doping element doped into the silicon-containing substrate; the conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon-containing substrate.

2. The silicon composite of claim 1, wherein the doping element comprises at least one of a P-type doping element and an N-type doping element;

optionally, the P-type doping element comprises at least one of boron element and aluminum element;

optionally, the N-type doping element includes a phosphorus element.

3. The silicon composite of claim 1, wherein the silicon composite meets one or more of the following characteristics:

(1) The molar ratio of silicon in the doped silicon-containing substrate to lithium in the lithium-containing layer is 10:1-2:1;

(2) The doping amount of the doping element is less than or equal to 10 percent based on the mass percentage of the silicon composite material;

optionally, the doping amount is 0.5% -5%;

(3) The doped silicon-containing substrate is granular;

optionally, the particle size distribution Dv50 of the doped silicon-containing substrate is less than or equal to 10 mu m;

optionally, the doped silicon-containing substrate has a particle size distribution Dv50 of 5 μm to 10 μm;

(4) The silicon-containing substrate comprises one or more of silicon, silicon oxide and silicon dioxide;

optionally, the silicon-containing substrate includes a silicon element and an oxygen element;

optionally, the silicon-containing substrate comprises silicon element and oxygen element, wherein the atomic number ratio of the silicon element to the oxygen element is 1:0.1-1:2.

4. The silicon composite of claim 1, further comprising a carbon cladding layer on a surface of the lithium-containing layer;

optionally, the carbon coating layer coats all or part of the surface of the lithium-containing layer;

optionally, the mass ratio of the carbon coating layer to the doped silicon-containing substrate is 1:6-1:1.

5. The silicon composite according to any one of claims 1 to 4, further satisfying one or more of the following characteristics:

(1) The silicon composite material is granular;

optionally, the particle size distribution Dv50 of the silicon composite material is 5 μm to 15 μm;

(2) The lithium-containing layer includes elemental silicon;

optionally, the lithium-containing layer comprises at least one of lithium silicate, lithium hydride, lithium fluoride, lithium sulfite, and lithium silicon alloy.

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

forming a lithium-containing layer on a surface of a doped silicon-containing substrate, the doped silicon-containing substrate comprising a silicon substrate and a doping element doped into the silicon substrate; the conductivity of the doped silicon-containing substrate is greater than the conductivity of the silicon-containing substrate.

7. The method of producing a silicon composite material according to claim 6, wherein forming the lithium-containing layer on the surface of the doped silicon-containing substrate comprises the steps of:

mixing the doped silicon-containing substrate with a lithium source to prepare a mixture;

the mixture is subjected to a heat treatment under a protective gas atmosphere.

8. The method of preparing a silicon composite according to claim 7, wherein one or more of the following characteristics are satisfied:

(1) The molar ratio of silicon in the doped silicon-containing substrate to lithium in the lithium source is 10:1-2:1;

(2) The lithium source comprises at least one of elemental lithium, lithium hydroxide, lithium hydride, biphenyl lithium, naphthalene lithium and phenanthrene lithium;

(3) The heat treatment comprises a heating stage and a heat preservation stage which are sequentially carried out;

optionally, the heating rate of the heating stage is 1-10 ℃/min;

optionally, the temperature of the heat preservation stage is 550-750 ℃;

optionally, the time of the heat preservation stage is 1 h-5 h.

9. The method according to any one of claims 6 to 8, wherein the doped silicon-containing substrate is prepared by vapor deposition of a vapor phase silicon-containing substrate and a vapor phase doping material in a protective gas atmosphere;

Optionally, the gas phase doping material comprises one or more of borane, alane, and phosphane.

10. The method of preparing a silicon composite according to claim 9, wherein the vapor deposition satisfies one or more of the following characteristics:

(1) The temperature of the vapor deposition is 1000-1400 ℃;

(2) The vapor deposition time is 2-10 hours;

(3) The pressure of the vapor deposition is 0.05 Pa-10 Pa.

11. The method of producing a silicon composite according to claim 9, further comprising a step of collecting a product after the vapor deposition;

optionally, the collecting adopts a precipitation mode;

optionally, the temperature of the precipitate is 600 ℃ to 700 ℃.

12. The method of producing a silicon composite material according to any one of claims 6 to 11, further comprising, before forming the lithium-containing layer on the surface of the doped silicon-containing substrate: forming a carbon coating layer on the surface of the doped silicon-containing substrate;

optionally, a carbon coating layer is formed on the surface of the doped silicon-containing substrate by gas phase coating.

13. A negative electrode composition comprising the silicon composite material according to any one of claims 1 to 5 or the silicon composite material produced by the method for producing a silicon composite material according to any one of claims 6 to 12.

14. The negative electrode composition according to claim 13, wherein the mass percentage of the silicon composite material is 1 to 34% based on the mass percentage of the negative electrode composition.

15. The anode composition according to claim 13 or 14, further comprising an anode active material;

optionally, the negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon;

optionally, the mass ratio of the anode active material to the silicon composite material is 99:1-3:1;

optionally, the particle size distribution Dv50 of the negative electrode active material is less than or equal to 10 mu m;

alternatively, the particle size distribution Dv50 of the anode active material is 3 μm to 8 μm.

16. A negative electrode slurry comprising a solvent and the negative electrode composition of any one of claims 13 to 15.

17. A negative electrode tab comprising a current collector and a negative electrode active layer on at least one surface of the current collector, the negative electrode active layer comprising the negative electrode composition of any one of claims 13-15 or formed from a material comprising the negative electrode slurry of claim 16 cured on the current collector and dried.

18. A secondary battery comprising the negative electrode tab of claim 17.

19. An electric device comprising the secondary battery according to claim 18.