CN115632126A

CN115632126A - Composite negative electrode material, preparation method thereof, negative electrode plate, secondary battery and power utilization device

Info

Publication number: CN115632126A
Application number: CN202211528353.XA
Authority: CN
Inventors: 梁静爽; 滕国鹏; 王欣; 练震; 蒋丽君
Original assignee: Jiangsu Contemporary Amperex Technology Ltd
Current assignee: Jiangsu Contemporary Amperex Technology Ltd
Priority date: 2022-12-01
Filing date: 2022-12-01
Publication date: 2023-01-20

Abstract

The application provides a composite negative electrode material and a preparation method thereof, a negative electrode pole piece, a secondary battery and an electric device, wherein the composite negative electrode material comprises a silicon nanowire and silicon-based M metal compound nanoparticles loaded on the silicon nanowire, the mass proportion of the silicon-based M metal compound nanoparticles in the composite negative electrode material is 5% -15%, and M comprises one or more of Cu, fe and Ni. The composite negative electrode material provided by the application can improve the rate capability and the cycle performance of a secondary battery.

Description

Composite negative electrode material, preparation method thereof, negative electrode plate, secondary battery and power utilization device

Technical Field

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

Background

In recent years, secondary batteries represented by lithium ion batteries have been applied more and more widely, and they are widely used in energy storage power systems such as hydraulic power, thermal power, wind power, and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, and aerospace. As the development of secondary batteries has been greatly advanced, higher demands have been made on rate performance, cycle performance, and the like. At present, in the traditional lithium ion battery, a silicon-based material is widely applied to a negative electrode due to higher capacity and moderate lithium intercalation potential. However, the problems of volume expansion and the like commonly exist in the silicon-based materials in the circulating process, so that the circulating performance of the secondary battery is reduced, and the practical use requirement is difficult to meet.

Disclosure of Invention

The application aims to provide a composite negative electrode material, a preparation method thereof, a negative electrode pole piece, a secondary battery and an electric device, and the cycle performance and the rate capability of the secondary battery can be improved.

In order to achieve the above object, a first aspect of the present application provides a composite anode material comprising:

a silicon nanowire; and silicon-based M metal compound nanoparticles supported on the silicon nanowires, wherein M comprises one or more of Cu, fe, and Ni.

The composite cathode material comprises a silicon nanowire and silicon-based M metal compound nanoparticles loaded on the silicon nanowire, wherein the silicon nanowire can reduce the volume expansion of the silicon-based material in the radial direction, a one-dimensional electron migration path and an active ion (such as lithium ion) transmission channel are provided, the diffusion distance of the active ion is obviously shortened, the diffusion rate of the active ion is improved, and the rate capability of a secondary battery is improved. In addition, in the circulation process, the M element in the silicon-based M metal compound nano particles loaded on the silicon nanowire can be released in situ, and a simple substance of the M element is formed and stays in the negative electrode, so that the electronic conductivity of the silicon nanowire is improved, the volume expansion of the silicon material is buffered, the rebound of a negative electrode pole piece is reduced, the circulation performance of the secondary battery is improved, and the multiplying power performance of the secondary battery is further improved.

In some embodiments of the present application, at least a portion of the silicon-based M-metal compound nanoparticles are encapsulated in at least one end of the silicon nanowires.

The silicon-based M metal compound nanoparticles are positioned at the end parts of the silicon nanowires, and the in-situ release of the M element in the silicon-based M metal compound nanoparticles in the circulation process is facilitated, so that a simple substance of metal M is formed and stays in the negative electrode, the electronic conductivity of the silicon nanowires is facilitated to be improved, and the rate capability of the secondary battery is improved.

In some embodiments of the present application, the silicon-based M metal compound comprises Cu ₃ Si、Fe ₃ Si and Ni ₃ One or more of Si.

The application provides a silica-based M metal compound of above-mentioned kind can easily M element in the normal position release of cyclic process, forms M element's simple substance and stops in the negative pole to be favorable to improving the electron conductivity of silicon nanowire, the volume expansion of buffering silicon reduces the bounce-back of negative pole piece, and then promotes secondary battery's cyclicity performance and multiplying power performance.

In some embodiments of the present application, the silicon-based M-metal compound nanoparticles satisfy at least one of the following conditions:

(1) The mass ratio of the silicon-based M metal compound nanoparticles in the composite negative electrode material is 5% -15%;

(2) The average particle size of the silicon-based M metal compound nanoparticles is 5nm to 15nm.

The mass ratio of the silicon-based M metal compound nano particles in the composite negative electrode material is in a proper range, so that the silicon-based M metal compound nano particles can play an effective catalytic role in the growth of silicon nano wires in the preparation process of the composite negative electrode material, and the formation of the silicon nano wires is promoted. Meanwhile, the mass ratio of the silicon-based M metal compound nanoparticles in the composite cathode material is in a proper range, so that the electron conductivity of the composite cathode material can be improved after M element is released in situ to form a simple substance of metal M in the circulation process, and the capacity of the composite cathode material cannot be influenced.

In some embodiments of the present application, the composite anode material satisfies at least one of the following conditions:

(1) The average diameter of the silicon nanowire is 5nm to 15nm;

(2) The length-diameter ratio of the silicon nanowire is 10 to 13;

(3) The average particle size of the powder of the composite negative electrode material is 15nm to 50nm.

The average diameter and the length-diameter ratio of the silicon nanowire are in a proper range, so that the volume expansion of silicon in the radial direction is further reduced, and the cycle performance of the secondary battery is improved; meanwhile, the diffusion distance of active ions (such as lithium ions) is further shortened, the transmission channel of the active ions in unit volume is increased, the diffusion rate of the active ions is improved, and the rate capability of the secondary battery is further improved.

A first aspect of the present application provides a method for preparing a composite anode material, comprising:

and carrying out direct current arc discharge treatment on the mixture containing the elemental silicon and the elemental metal M to form a silicon nanowire and silicon-based M metal compound nanoparticles loaded on the silicon nanowire, so as to obtain the composite cathode material, wherein the metal M comprises one or more of Cu, fe and Ni.

The silicon nanowire can be generated and obtained in one step by adopting an arc method, the operation is simple, the time consumption is short, and higher yield can be obtained; meanwhile, the silicon-based M metal compound nanoparticles formed in the reaction process can be directly used as a catalyst to promote the transient growth of the silicon nanowires, so that no additional noble metal is required to be added as the catalyst, and the preparation cost is favorably reduced.

In some embodiments of the present application, the dc arc discharge treatment of the mixture containing the elemental silicon and the elemental metal M includes:

taking the mixture of the elemental silicon and the elemental metal M as an anode for direct current arc discharge treatment;

discharging the anode in a mixed gas of hydrogen and inert gas to generate silicon-based M metal compound nanoparticles and silicon nanowires epitaxially grown at ends formed by wrapping at least part of the silicon-based M metal compound nanoparticles, so as to obtain the deposited powder of the composite anode material, wherein the silicon-based M metal compound comprises Cu ₃ Si、Fe ₃ Si and Ni ₃ One or more of Si.

The direct current arc discharge in the above steps may include the following reaction processes: firstly, a mixture containing a simple substance of silicon and a simple substance of metal M is evaporated into gaseous silicon atoms and M atoms in an arc flame, and in the process of outward diffusion, the silicon reaches the melting point (about 1414 ℃) of the silicon along with the reduction of the temperature, and the silicon starts to nucleate; then the melting point of the metal M (such as Cu, the melting point is about 1085 ℃) is reached, the metal M starts to nucleate, then as the temperature continues to decrease, the silicon nucleus and the metal M nucleus can react to generate an intermetallic compound silicon-based M metal compound, and the generated silicon-based M metal compound can be used as a catalyst for growing the silicon nanowire. When the temperature is reduced to the eutectic point of the silicon and the silicon-based M metal compound, the silicon in a supersaturated state in the mixed liquid drop consisting of the silicon and the silicon-based M metal compound is separated out, at least one part of the silicon-based M metal compound nano particles is taken as an end part, and the continuous growth of the one-dimensional silicon nano wires is realized by following the VLS growth mechanism.

In some embodiments of the present application, the method satisfies at least one of the following conditions:

(1) The voltage of the direct current arc discharge treatment is 5V to 30V;

(2) The current of the direct current arc discharge treatment is 10A to 200A;

(3) The inert gas comprises argon and/or helium;

(4) The pressure ratio of the inert gas to the hydrogen in the mixed gas is (5:3) - (2:1).

The current and voltage of the direct current arc discharge treatment are in a proper range, which is beneficial to improving the yield of the prepared composite cathode material. The gas pressure ratio of hydrogen to inert gas in the mixed gas is in a proper range, and the average particle size of the prepared composite negative electrode material powder can be controlled in a proper range, so that the composite negative electrode material is in close contact arrangement when a negative electrode film layer is formed, the content of the composite negative electrode material in the unit volume of the negative electrode film layer is increased, and the energy density of the secondary battery is increased.

In some embodiments of the present application, before performing the dc arc discharge treatment on the mixture containing the elemental silicon and the elemental metal M, the method further includes:

and mixing silicon powder and metal M powder, and then pressing and forming to obtain the mixture containing the elemental silicon and the elemental metal M.

The silicon powder and the metal M powder are pressed and formed to obtain a mixture with a three-dimensional macroscopic structure, which is beneficial to obtaining mixed steam of silicon atoms and M atoms in the direct current arc discharge process, and further provides reactants for the subsequent formation of silicon-based M metal compound nanoparticles and silicon nanowires.

(1) The mass ratio of the silicon powder to the metal M powder is (9~1): 1;

(2) The average particle size of the silicon powder is 20-80 μm;

(3) The average particle size of the metal M powder is 20-80 μ M.

The mass ratio of the silicon powder to the metal M powder is in a proper range, which is beneficial to the generation of the silicon nanowire and the silicon-based M metal compound nano particles, and the mass of the silicon powder is far higher than that of the metal M powder, which is beneficial to ensuring that the silicon nanowire can be used as the main body of the composite cathode material.

In some embodiments of the present application, after obtaining the deposited powder of the composite anode material, the method further includes:

and exposing the deposition powder to an oxygen-containing gas atmosphere to passivate the deposition powder.

The passivation treatment is carried out on the deposition powder in the steps, so that a passivation film can be generated on the surface of the deposition powder, and the corrosion resistance of the composite cathode material is enhanced.

A third aspect of the present application provides a secondary battery comprising a composite anode material according to the first aspect of the present application or a composite anode material produced by the method according to the second aspect of the present application.

A fourth aspect of the present application provides an electric device including the secondary battery according to the third aspect of the present application.

The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

Drawings

Fig. 1 is a TEM image of a composite anode material in example 1.

Fig. 2 is an XRD pattern of the composite anode material in example 1.

Fig. 3 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 3.

Fig. 5 is a schematic view of a secondary battery according to still another embodiment of the present application.

Fig. 6 is a schematic view of a secondary battery according to another embodiment of the present application.

Fig. 7 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 6.

Fig. 8 is a schematic diagram of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Description of reference numerals:

1, a battery pack; 2, putting the box body on the box body; 3, discharging the box body; 4 a battery module; 5 a secondary battery; 51 a housing; 52 an electrode assembly; 53 a cap assembly.

Detailed Description

Hereinafter, embodiments of the composite negative electrode material, the method for producing the same, the negative electrode sheet, the secondary battery, and the electrical device according to the present application are specifically disclosed in detail with reference to the accompanying drawings as appropriate. But detailed description thereof will be omitted unnecessarily. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the following description, and to facilitate understanding by those skilled in the art. The drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

The "ranges" disclosed herein are defined in terms of lower limits and upper limits, with a given range being defined by a selection of one lower limit and one upper limit that define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may 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. Further, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 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 stated, 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, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose 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, if not specifically stated.

All technical and optional features of the present application may be combined with each other to form new solutions, if not otherwise specified.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, if not specifically stated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.

The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that additional components not listed may also be included or included, or that only listed components may be included or included.

In this application, the term "or" is inclusive, if not 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 not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).

At present, in order to meet market demands, the energy density of secondary batteries represented by lithium ion batteries is increasing, and in order to increase the energy density, silicon-based materials are introduced into the secondary batteries in terms of selection of negative electrode active materials. The inventor finds that the silicon-based material can generate volume expansion in the cycle process of the secondary battery, so that the rebound quantity of a negative pole piece in the direction vertical to the plane (Z direction) is continuously accumulated, and the shell entering quantity of a negative pole active material can be influenced in a short term, thereby influencing the capacity of the secondary battery; and the battery core has overlarge expansion force caused by the rebound of the pole piece for a long time, so that the cycle life of the secondary battery is influenced. Meanwhile, the silicon-based material generally has the problem of low electronic conductivity, so that the rate performance of the secondary battery is not high.

In order to solve the technical problems, the inventor starts with the improvement of the existing silicon-based material, and provides a composite negative electrode material through a large amount of researches, wherein the composite negative electrode material can enable the silicon nanowire and the silicon-based M metal compound nanoparticle to play a role in the circulation process by compounding the silicon nanowire and the silicon-based M metal compound nanoparticle, and simultaneously improves the rate capability and the circulation performance of the secondary battery.

Composite negative electrode material

A first aspect of an embodiment of the present application provides a composite anode material, including a silicon nanowire and a silicon-based M metal compound nanoparticle supported on the silicon nanowire, where M includes one or more of Cu, fe, and Ni.

In the embodiment of the application, the composite cathode material comprises a silicon nanowire and silicon-based M metal compound nanoparticles loaded on the silicon nanowire, wherein the silicon nanowire can reduce the volume expansion of the silicon-based material in the radial direction, a one-dimensional electron migration path and an active ion (such as lithium ion) transmission channel are provided, the diffusion distance of the active ion is remarkably shortened, the diffusion rate of the active ion is improved, and the rate capability of the secondary battery is improved. In addition, in the circulation process, the M element in the silicon-based M metal compound nano particles loaded on the silicon nanowire can be released in situ, and a simple substance of the M element is formed and stays in the negative electrode, so that the electronic conductivity of the silicon nanowire is improved, the volume expansion of silicon is buffered, the rebound of a negative electrode plate is reduced, the circulation performance of the secondary battery is improved, and the rate capability of the secondary battery is further improved.

It should be noted that, in the above cycle process, the in-situ release of the M element in the si-based M metal compound nanoparticles may be understood as that, in the first lithium intercalation process of the secondary battery, the si-based M metal compound reacts with active ions (such as lithium ions) to generate a simple substance of the metal M and a si-li alloy compound, and then, in the battery charge-discharge cycle process, the simple substance of the metal M stably exists and stays in the negative electrode and does not participate in the electrochemical reaction.

In some embodiments, at least a portion of the silicon-based M-metal compound nanoparticles are encapsulated in at least one end of the silicon nanowires.

It is understood that at least a portion of the silicon-based M-metal compound nanoparticles are wrapped in at least one end of the silicon nanowire, and any one end of the silicon nanowire wraps at least a portion of the silicon-based M-metal compound nanoparticles, a portion of the end of the silicon nanowire wraps at least a portion of the silicon-based M-metal compound nanoparticles, or all ends of the silicon nanowire wrap at least a portion of the silicon-based M-metal compound nanoparticles.

In the embodiment of the application, the structure that at least a part of the silicon-based M metal compound nanoparticles are wrapped in at least one end of the silicon nanowire is formed by performing epitaxial growth on the silicon nanowire with the silicon-based M metal compound nanoparticles as the end in the preparation process of the composite anode material. The silicon-based M metal compound nanoparticles are positioned at the end parts of the silicon nanowires, and the in-situ release of the M element in the silicon-based M metal compound nanoparticles in the circulation process is facilitated, so that a simple substance of metal M is formed and stays in the negative electrode, the electronic conductivity of the silicon nanowires is facilitated to be improved, and the rate capability of the secondary battery is improved.

In some embodiments, the silicon-based M metal compound comprises Cu ₃ Si、Fe ₃ Si and Ni ₃ One or more of Si. The application provides a silica-based M metal compound of above-mentioned kind can easily M element in the normal position release of cyclic process, forms M element's simple substance and stops in the negative pole to be favorable to improving the electron conductivity of silicon nanowire, the volume expansion of buffering silicon reduces the bounce-back of negative pole piece, and then promotes secondary battery's cyclicity performance and multiplying power performance.

In some embodiments, the silicon-based M metal compound nanoparticles are present in the composite anode material in an amount of 5% to 15% by mass. For example, the mass ratio of the silicon-based M metal compound nanoparticles in the composite anode material may be 6%,7%,8%,9%,10%,11%,12%,13%,14% or in a range composed of any of the above values. Optionally, the mass ratio of the silicon-based M metal compound nanoparticles in the composite negative electrode material is 8-12%.

The mass ratio of the silicon-based M metal compound nanoparticles in the composite anode material is known in the art, and can be determined by using instruments and methods known in the art. For example, an EDS spectrometer can be used for measurement, that is, an EDS test can be performed on the composite negative electrode material, and the mass ratio of the silicon-based M metal compound nanoparticles can be quantitatively analyzed.

In some embodiments, the silicon-based M metal compound nanoparticles have an average particle size of 5nm to 15nm. For example, the average particle diameter of the silica-based M metal compound nanoparticles may be 7nm,9nm,11nm,13nm, or any range of values thereof. Alternatively, the average particle size of the silicon-based M metal compound nanoparticles is 7nm to 13nm.

The average particle size of the silica-based M metal compound nanoparticles is a well-known meaning in the art and can be determined using instruments and methods well known in the art. For example, it may conveniently be determined by a laser particle size analyser such as the Mastersizer2000E laser particle size analyser from Malvern instruments Ltd, UK, by reference to the GB/T19077-2016 particle size distribution laser diffraction method.

The average particle size of the silicon-based M metal compound nanoparticles is in a proper range, which is beneficial to loading the silicon-based M metal compound nanoparticles on the silicon nanowires, so that the in-situ release of an M element in a circulation process can be realized, the electronic conductivity of the silicon nanowires is improved, the volume expansion of silicon is buffered, and the rate capability and the circulation performance of the secondary battery are improved.

In some embodiments, the silicon nanowires have an average diameter of 5nm to 15nm. For example, the average diameter of the silicon nanowires may be 7nm,9nm,11nm,13nm, or in a range consisting of any of the above values. Optionally, the average diameter of the silicon nanowires is from 9nm to 13nm.

The average diameter of the silicon nanowires is well known in the art and can be determined using instruments and methods well known in the art. For example, the measurement may be performed using a Transmission Electron Microscope (TEM).

In some embodiments, the aspect ratio of the silicon nanowire is 10 to 13. For example, the aspect ratio of the silicon nanowires can be 10.5, 11, 11.5, 12.5 or within any of the above ranges. Optionally, the aspect ratio of the silicon nanowire is 10.5 to 12.5.

The aspect ratio of silicon nanowires is well known in the art and can be determined using instruments and methods well known in the art. For example, the measurement may be performed using a Transmission Electron Microscope (TEM).

The average diameter and the length-diameter ratio of the silicon nanowire are in a proper range, so that the volume expansion of silicon in the radial direction is further reduced, and the cycle performance of the secondary battery is improved; meanwhile, the diffusion distance of active ions (such as lithium ions) is further shortened, the number of transmission channels of the active ions in unit volume is increased, the diffusion rate of the active ions is improved, and the rate capability of the secondary battery is further improved.

In some embodiments, the average particle diameter of the powder of the composite anode material is 15nm to 50nm. For example, the average particle size of the powder of the composite anode material may be 20nm,25nm,30nm,35nm,40nm,45nm, or a range consisting of any of the above values. Optionally, the average particle size of the powder of the composite negative electrode material is 20nm to 45nm.

The average particle size of the powder of the composite negative electrode material is controlled within a proper range, so that the composite negative electrode material is in close contact arrangement when a negative electrode film layer is formed, the content of the composite negative electrode material in the unit volume of the negative electrode film layer is increased, and the energy density of the secondary battery is increased.

A second aspect of embodiments of the present application provides a method for preparing a composite anode material, which may include the steps of:

s10, performing direct current arc discharge treatment on the mixture containing the elemental silicon and the elemental metal M to form a silicon nanowire and silicon-based M metal compound nanoparticles loaded on the silicon nanowire, and obtaining the composite cathode material, wherein the metal M comprises one or more of Cu, fe and Ni.

The inventor finds in the research process that most of the silicon nanowires are prepared by a chemical vapor deposition method or a template method at present, and the methods usually have the defects of complex operation, difficult process control, low yield and the like; in addition, in the process of preparing the silicon nanowire by using the methods, noble metal gold and the like are generally used as a catalyst, so that the preparation cost of the silicon nanowire is high.

In order to overcome the defects of the existing preparation method, the silicon nanowire is prepared by adopting a direct current arc method for the first time, the silicon nanowire can be generated and obtained in one step by adopting the arc method, the operation is simple, the time consumption is short, and higher yield can be obtained. Meanwhile, the silicon-based M metal compound nanoparticles can be formed in the direct current arc discharge process by selecting the appropriate metal M, and the silicon-based M metal compound nanoparticles are directly used as a catalyst to promote the transient growth of the silicon nanowires, so that additional precious metals such as gold and the like are not required to be used as the catalyst, and the preparation cost is favorably reduced.

It can be understood that the above-mentioned dc arc discharge used in the present application is a conventional dc arc discharge method, and the method uses a conventional apparatus for performing dc arc discharge, which is not described herein again.

In some embodiments, the performing the dc arc discharge treatment on the mixture containing the elemental silicon and the elemental metal M in step S10 may include the following steps:

s100, taking the mixture of the elemental silicon and the elemental metal M as an anode for direct current arc discharge treatment;

s110, performing discharge treatment on the anode in mixed gas of hydrogen and inert gas to generate silicon-based M metal compound nanoparticles and silicon nanowires epitaxially grown at end parts formed by wrapping at least part of the silicon-based M metal compound nanoparticles, so as to obtain deposited powder of the composite cathode material, wherein the silicon-based M metal compound comprises Cu ₃ Si、Fe ₃ Si and Ni ₃ One or more of Si.

The dc arc discharge performed in steps S100 to S110 may include the following reaction processes: the arc flame of the direct current arc is used as a heat source for supplying high-energy-state growth substances, mainly comprises an inner part, a middle part and an outer part, a certain temperature gradient exists from inside to outside, the temperature is gradually reduced from inside to outside, and the growth process of the silicon-based M metal compound nano particles and the silicon nano wires is completed in the heat source region. Firstly, a mixture containing a simple substance of silicon and a simple substance of metal M is evaporated into gaseous silicon atoms and M atoms in an arc flame, and in the process of outward diffusion, the silicon reaches the melting point (about 1414 ℃) of the silicon along with the reduction of the temperature, and the silicon starts to nucleate; then the melting point of the metal M (such as Cu, the melting point is about 1085 ℃) is reached, the metal M starts to nucleate, and then as the temperature continues to decrease, the silicon nuclei and the metal M nuclei can react to generate the intermetallic compound silicon-based M metal compound M ₃ Si, the resulting Si-based M metal compound M ₃ Si can be used as a catalyst for growing the silicon nanowire. When the temperature is reduced to silicon and silicon-based M metal compound M ₃ Eutectic point of Si, si and Si-based M metal compound M ₃ Silicon in a supersaturated state in the mixed liquid drop consisting of Si is precipitated and is converted into a silicon-based M metal compound M ₃ At least a portion of the Si nanoparticles are end-capped while enabling continuous growth of one-dimensional silicon nanowires following the VLS growth mechanism.

In some embodiments, the voltage of the dc arc discharge treatment is 5v to 30v. For example, the voltage of the DC arc discharge treatment may be 10V,15V,20V,25V or in a range of any of the above values. Optionally, the voltage of the direct current arc discharge treatment is 8V to 28V.

In some embodiments, the current of the dc arc discharge treatment is 10a to 200a. For example, the current for the DC arc discharge process may be 30A,50A,70A,90A,110A,130A,150A,180A or within a range consisting of any of the above values. Alternatively, the current of the direct current arc discharge treatment is 40A to 190A.

The current and voltage of the direct current arc discharge treatment are in a proper range, which is beneficial to improving the yield of the prepared composite cathode material. The higher the current and the voltage, the easier the electric arc is excited, the higher the energy of the electric arc is, the gasification and evaporation of the excitation source material target material are facilitated, and the yield of the composite cathode material is higher. However, in consideration of electrical safety during the manufacturing process, current and voltage need to be controlled.

In some embodiments, the gas pressure ratio of the inert gas to the hydrogen gas in the mixed gas is (5:3) - (2:1). For example, the pressure ratio of inert gas to hydrogen in the mixed gas may be 7:4, 11. The hydrogen has high heat conductivity coefficient and enthalpy value, and is easily ionized into hydrogen plasma in the arc zone, small-sized hydrogen atoms or hydrogen ions enter the molten silicon, and in the subsequent escape process, the silicon atoms are taken away from the matrix, so that the reaction is accelerated. The inert atmosphere does not participate in the reaction after ionization, and is mainly used for reducing energy through collision in the nucleation and growth process of the substances.

The gas pressure ratio of hydrogen to inert gas in the mixed gas is in a proper range, and the average particle size of the prepared composite negative electrode material powder can be controlled in a proper range, so that the composite negative electrode material is in close contact arrangement when a negative electrode film layer is formed, the content of the composite negative electrode material in the unit volume of the negative electrode film layer is increased, and the energy density of the secondary battery is increased.

In some embodiments, the kind of the inert gas is not particularly limited, and may be selected according to actual requirements. For example, the inert gas may include argon and/or helium.

In some embodiments, before the step S10 of performing the dc arc discharge treatment on the mixture containing the elemental silicon and the elemental metal M, the following steps may be further included:

s20, mixing silicon powder and metal M powder, and then pressing and forming to obtain the mixture containing the elemental silicon and the elemental metal M.

The metal M powder includes copper powder, iron powder, and nickel powder. The metal powders are selected by the application because the inventor finds that the metal powders can form an intermetallic compound silicon-based M metal compound in the process of carrying out direct current arc discharge together with silicon powder, and the intermetallic compound silicon-based M metal compound can be directly used as a catalyst to play a role in promoting the growth of silicon nanowires, so that the use of other catalysts can be saved, the preparation process is facilitated, and the cost is saved.

In some embodiments, the mass ratio of the silicon powder to the metal M powder is (9~1): 1. For example, the mass ratio of silicon powder to metal M powder may be 8. Optionally, the mass ratio of the silicon powder to the metal M powder is (8~2): 1.

The mass ratio of the silicon powder to the metal M powder is in a proper range, which is beneficial to the generation of silicon nanowires and silicon-based M metal compound nanoparticles, and the mass of the silicon powder is far higher than that of the metal M powder, which is beneficial to ensuring that the formed silicon nanowires can be used as the main body of the composite cathode material.

In some embodiments, the silicon powder has an average particle size of 20 μm to 80 μm. For example, the silicon powder may have an average particle diameter of 30 μm,40 μm,50 μm,60 μm,70 μm or any range of values above.

In some embodiments, the metal M powder has an average particle size of 20 μ M to 80 μ M. For example, the average particle size of the metal M powder may be 30 μ M,40 μ M,50 μ M,60 μ M,70 μ M or any range therebetween. The average particle size of the silicon powder and the metal M powder is in a proper range, and the pressing into a mixture with a three-dimensional macroscopic structure is facilitated.

In some embodiments, after obtaining the deposition powder of the composite anode material in step S110, the following steps may be further included:

and S120, exposing the deposition powder to an oxygen-containing gas atmosphere to passivate the deposition powder.

It is to be understood that the oxygen-containing atmosphere may be a pure oxygen atmosphere or an air atmosphere as long as oxygen is contained therein.

As a non-limiting example of passivating the deposition powder, after the direct current arc discharge reaction is finished, the deposition powder is cooled for 3h to 5h, and after the temperature is reduced to room temperature, the deposition powder is exposed to trace air or oxygen for passivating for 8h.

In the step S120, the passivation treatment is performed on the deposited powder, so that a passivation film can be formed on the surface of the deposited powder, and the corrosion resistance of the composite negative electrode material is enhanced.

Secondary battery

The secondary battery and the electric device according to the present invention will be described below with reference to the drawings as appropriate.

In one embodiment of the present application, there is provided a secondary battery including any device in which an electrochemical reaction occurs to convert chemical energy and electrical energy into each other, for example, a lithium ion secondary battery or a sodium ion secondary battery.

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through.

[ Positive electrode sheet ]

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

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

In some embodiments, the positive electrode 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 polymer material base layer and a metal layer formed on at least one surface of the polymer 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 base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the positive active material may employ a positive active material for a 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 positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g., liNiO) ₂ ) Lithium manganese oxides (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 (may also be abbreviated as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM) ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (may also be abbreviated as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (may also be abbreviated as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (may also be abbreviated as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxides (e.g., liNi) _0.85 Co _0.15 Al _0.05 O ₂ ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) ₄ (may also be simplifiedCalled LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., liMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

In some embodiments, the positive active material may also include at least one of the following materials: sodium transition metal oxides, polyanionic compounds and prussian blue compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more.

As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal may be at least one of Mn, fe, ni, co, cr, cu, ti, zn, V, zr, and Ce. The sodium transition metal oxide is, for example, na _x MO ₂ Wherein M is one or more of Ti, V, mn, co, ni, fe, cr and Cu, and x is more than 0 and less than or equal to 1.

As an alternative embodiment of the present invention, the polyanionic compound may have a sodium ion, a transition metal ion, and a tetrahedral type (YO) ₄ ) ^n- A class of compounds of anionic units. The transition metal can be at least one of Mn, fe, ni, co, cr, cu, ti, zn, V, zr and Ce; y can be at least one of P, S and Si; n represents (YO) ₄ ) ^n- The valence of (c).

The polyanionic compound may have sodium ion, transition metal ion, and tetrahedral (YO) ₄ ) ^n- Anionic units and halide anions. The transition metal can be at least one of Mn, fe, ni, co, cr, cu, ti, zn, V, zr and Ce; y may be P, S or at least one of Si, and n represents (YO) ₄ ) ^n- The valence of (a); the halogen may be at least one of F, cl and Br.

The polyanionic compound may have sodium ion or tetrahedral (YO) ₄ ) ^n- Anion cell, polyhedral cell (ZO) _y ) ^m+ And optionally a halide anion.Y may be P, S or at least one of Si, and n represents (YO) ₄ ) ^n- The valence of (a); z represents a transition metal, and may be at least one of Mn, fe, ni, co, cr, cu, ti, zn, V, zr and Ce, and m represents (ZO) _y ) ^m+ The valence of (a); the halogen may be at least one of F, cl and Br.

The polyanionic compound being, for example, naFePO ₄ 、Na ₃ V ₂ (PO4) ₃ (sodium vanadium phosphate, NVP for short), na ₄ Fe ₃ (PO ₄ ) ₂ (P ₂ O ₇ ) NaM 'PO4F (M' is one or more of V, fe, mn and Ni) and Na ₃ (VO _y ) ₂ (PO ₄ ) ₂ F _3-2y (0. Ltoreq. Y. Ltoreq.1).

The Prussian blue compound may be sodium ion, transition metal ion and cyanide ion (CN) ^- ) A class of compounds of (1). The transition metal may be at least one of Mn, fe, ni, co, cr, cu, ti, zn, V, zr and Ce. Prussian blue compounds, e.g. Na _a Me _b Me’ _c (CN) ₆ Wherein Me and Me' are respectively and independently at least one of Ni, cu, fe, mn, co and Zn, and a is more than 0 and less than or equal to 2,0 and less than b and less than 1,0 and less than 1.

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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and 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 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 coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

The positive electrode sheet of the present application does not exclude other additional functional layers than the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the present application further comprises a conductive primer layer (e.g., consisting of a conductive agent and a binder) interposed between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In some other embodiments, the positive electrode sheet of the present application further comprises a protective layer covering the surface of the positive electrode film layer.

[ negative electrode sheet ]

The negative pole piece comprises a negative pole current collector and a negative pole film layer arranged on at least one surface of the negative pole current collector, wherein the negative pole film layer comprises the composite negative pole material of the first aspect of the application or the composite negative pole material prepared by the method of the second aspect of the application.

As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode 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 can be used. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer 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 base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode film layer does not exclude an anode active material other than the composite anode material of the present application, for example, an anode active material known in the art for a battery may be used as the anode active material. 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 can be at least one selected from the group consisting of elemental silicon, a silicon oxy compound, a silicon carbon compound, a silicon nitrogen compound and a silicon alloy. The tin-based material may be selected from at least one of elemental tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material may also be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the anode 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), and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent may be selected from at least one of 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 further optionally include other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet can be prepared by: dispersing the components for preparing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (such as deionized water) to form negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.

The negative electrode sheet of the present application does not exclude other additional functional layers than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present application further comprises a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer, disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[ electrolyte ]

The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The kind of the electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolytic solution. 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-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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 ethyl sulfone, and diethyl sulfone.

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

[ separator ]

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

In some embodiments, the material of the isolation 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 exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.

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 outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other shape. For example, fig. 3 is a secondary battery 5 of a square structure as an example.

In some embodiments, referring to fig. 4, the overwrap may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodating chamber, and a cover plate 53 can be provided to cover the opening to close the accommodating 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. An electrode assembly 52 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and those skilled in the art can select them according to the actual needs.

In some embodiments, the secondary battery may also be a battery module assembled by a plurality of battery cells, and the number of the battery cells contained in the battery module may be plural, and the specific number may be adjusted by those skilled in the art according to the application and the capacity of the battery module.

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

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

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

In some embodiments, the battery cells can also be directly assembled into a battery pack, and the number of the battery cells contained in the battery pack can be adjusted according to the application and the capacity of the battery pack.

Fig. 6 and 7 are a battery pack 1 as an example. Referring to fig. 6 and 7, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein 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. A plurality of battery modules 4 may be arranged in any manner in the battery box.

Electric device

In addition, this application still provides a power consumption device, power consumption device includes at least one in secondary battery, battery module or the battery package that this application provided. The secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The powered device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

As the electricity-using device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirement thereof.

Fig. 8 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack or a battery module may be used.

As another example, the device may be a cell phone, tablet, laptop, etc. The device is generally required to be thin and light, and a secondary battery may be used as a power source.

Examples

Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are conventional products which are commercially available, and are not indicated by manufacturers.

Example 1

Preparation of composite anode material

(1) And (2) sufficiently grinding and uniformly mixing micron-sized (20-80 microns) silicon powder and copper powder in a mass ratio of 9:1, pressing into a cylindrical block, placing the cylindrical block on a copper base to serve as an arc discharge anode, using a tungsten rod as a cathode, and adjusting the distance between the two electrodes to 30mm.

(2) The reaction chamber was evacuated to about 10 deg.f ^-2 Pa, filling argon and hydrogen according to the proportion of 2:1 to reach 2 x 10 respectively ⁴ Pa and 1X 10 ⁴ Pa。

(3) Starting a cooling water system, switching on a power supply, starting an arc, adjusting current and the distance between two electrodes, and stabilizing the arc, wherein the evaporation block target material is silicon atoms and copper atoms; silicon atoms react with copper atoms to form the intermetallic compound Cu ₃ Si as a catalyst to catalyze the one-dimensional growth of excess silicon atoms, followed by Cu ₃ The Si @ Si nanowire composite anode material powder is deposited on the wall of the reaction chamber.

(4) After the direct current arc discharge reaction is finished, cooling for 3h to 5h, introducing a trace amount of passivation gas air to perform passivation treatment for 8h when the reaction chamber is lowered to the room temperature, and then collecting composite negative electrode material powder attached to the inner wall of the direct current arc reaction chamber to obtain Cu ₃ Si @ Si nanowire composite anode material.

Preparation of negative electrode plate

Prepared Cu ₃ The Si @ Si nanowire composite negative electrode material is used as an active substance, is mixed with acetylene black serving as a conductive agent and SBR into negative electrode slurry according to the mass ratio of 80 to 10.

Preparation of positive pole piece

Dissolving a positive electrode active material NCM, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF) in a solvent N-methyl pyrrolidone (NMP) according to a weight ratio of 96.5; and uniformly coating the positive electrode slurry on a positive electrode current collector, and drying and cold pressing to obtain the positive electrode piece.

Preparation of the electrolyte

Mixing Ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 1; mixing LiPF ₆ Dissolving in the organic solvent, adding fluoroethylene carbonate (FEC), and uniformly mixing to obtain an electrolyte; wherein, liPF ₆ The concentration of (2) is 1mol/L.

Preparation of the separator

A PE porous film is used as a separation film.

Preparation of lithium ion battery

And respectively cutting the positive pole piece and the negative pole piece into round pieces with the diameter of 14mm, then sequentially stacking the cut positive pole piece, negative pole piece and isolating membrane for assembly, and enabling the isolating membrane to be positioned between the positive pole piece and the negative pole piece to play an isolating role, thereby obtaining the button type lithium ion battery.

Examples 2 to 16

The lithium ion battery was prepared similarly to example 1, except that: relevant parameters of the composite cathode material and the preparation process thereof are adjusted, and the specific parameters are detailed in the following table 1. Where "/" indicates that no corresponding parameter exists.

Comparative example 1

The silicon nanowire is prepared by adopting a traditional chemical vapor deposition method. The surface treatment is carried out on the stainless steel substrate to remove impurities such as an oxide layer, oil stain and the like, a layer of gold is evaporated on the surface, and then the stainless steel substrate is placed into a quartz tube of a tube furnace. After protective gas is introduced into the quartz tube, the temperature is raised to 700 ℃ according to the heating rate of 5 ℃/min, the temperature is kept, mixed gas of silane and hydrogen is introduced, the volume fraction of the silane is 10 percent, the flow rate of the mixed gas is 80sccm, the gas is continuously introduced, and a layer of silicon nanowires can be deposited on the surface of the stainless steel substrate.

Comparative example 2

When preparing the negative pole piece, silicon powder is used for replacing Cu ₃ The Si @ Si nanowire composite anode material.

TABLE 1

In addition, the composite negative electrode materials and the lithium ion battery obtained in the above examples 1 to 16 and comparative example 1~2 were subjected to related performance tests, and the test results are shown in table 2 below.

Test section

(1) Composite anode material TEM test

Dispersing the prepared composite material in a dispersing agent ethanol, performing ultrasonic treatment for 40 minutes to form a dilute suspension, taking a small amount of suspension by using a capillary tube, dripping the suspension on a copper micro-grid attached with a carbon film, drying at room temperature for 2 hours, and then placing the copper micro-grid in a transmission electron microscope (Tecnai G2F 30S-TWIN) sample rod for observation to obtain a TEM image of the composite material.

(2) XRD test of composite anode material

The XRD test is carried out on a D/max 2500VL/PC type XRD diffractometer of Japan science company, a copper target is adopted, the test precision is +/-0.02 degrees, and the scanning range is from 5 degrees to 90 degrees.

(3) Lithium ion battery coulombic efficiency and rate capability test

And (3) carrying out rate performance test on the prepared button lithium ion battery by adopting a Wuhan blue electricity (LAND 2001A) electrochemical performance tester. The voltage range is 0.01V to 2.00V (vs. Li/Li +), and the current density is 0.1C to 2C (1C. The coulombic efficiency is obtained by dividing the specific discharge capacity by the specific charge capacity.

(4) Cycle performance testing of lithium ion batteries

Charging the lithium ion battery to 3.65V at a constant current of 0.33C, then charging at a constant voltage until the current is 0.05C, standing for 5min, then discharging at a constant current of 0.33C to 2.5V, wherein the process is a circle of charge-discharge cycle, and testing and recording the discharge capacity at the moment as D01; the above charging and discharging process is repeated for 100 circles, and the capacity of the 100 th circle is recorded as D1. Then disassembling the battery, taking out the negative pole piece, soaking the negative pole piece in DMC (dimethyl carbonate) for 30min, removing the electrolyte and byproducts on the surface of the negative pole piece, then drying the negative pole piece in a fume hood for 4 hours, firing the pole piece into powder at 400 ℃ in vacuum, and weighing the weight of the pole piece to be m1.

The specific discharge capacity of the lithium ion battery after 100 cycles = D1/m1.

The capacity retention ratio = D1/D01 × 100% after the lithium ion battery is cycled for 100 cycles.

TABLE 2

Comparing examples 1 to 16 with comparative example 1, it can be seen that the specific discharge capacity, capacity retention rate, coulombic efficiency and rate capability of the lithium ion batteries in examples 1 to 16 are generally higher than those in comparative example 1, which shows that compared with the conventional chemical vapor deposition method, the cycle performance and rate capability of the secondary battery can be effectively improved by the composite anode material containing the silicon nanowire prepared by the direct current arc method provided by the application.

Comparing examples 1 to 16 with comparative example 2, it can be seen that the specific discharge capacity, capacity retention rate, coulombic efficiency and rate capability of the lithium ion batteries in examples 1 to 16 are generally higher than those of comparative example 2, which shows that compared with conventional negative electrode materials such as silicon, the composite negative electrode material provided by the present application can improve the cycle performance and rate capability of a secondary battery.

The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are all included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, within the scope not departing from the gist of the present application.

Claims

1. A composite anode material, comprising:

a silicon nanowire; and

the silicon-based M metal compound nano particles are loaded on the silicon nanowires, wherein the mass ratio of the silicon-based M metal compound nano particles in the composite negative electrode material is 5% -15%, and M comprises one or more of Cu, fe and Ni.

2. The composite anode material of claim 1, wherein at least a portion of the silicon-based M-metal compound nanoparticles are encapsulated in at least one end of the silicon nanowires.

3. The composite anode material according to claim 1 or 2, wherein the silicon-based M metal compound comprises Cu ₃ Si、Fe ₃ Si and Ni ₃ One or more of Si.

4. The composite negative electrode material according to any one of claims 1 to 3, wherein the silicon-based M metal compound nanoparticles have an average particle diameter of 5nm to 15nm.

5. The composite anode material according to any one of claims 1 to 3, wherein the composite anode material satisfies at least one of the following conditions:

(1) The average diameter of the silicon nanowire is 5nm to 15nm;

(2) The length-diameter ratio of the silicon nanowire is 10 to 13;

6. A method for preparing a composite anode material, comprising:

the method comprises the following steps of carrying out direct current arc discharge treatment on a mixture containing a silicon simple substance and a metal M simple substance to form a silicon nanowire and silicon-based M metal compound nanoparticles loaded on the silicon nanowire, and obtaining a composite anode material, wherein the mass ratio of the silicon-based M metal compound nanoparticles in the composite anode material is 5% -15%, and the metal M comprises one or more of Cu, fe and Ni.

7. The method according to claim 6, wherein the performing the direct current arc discharge treatment on the mixture containing the elemental silicon and the elemental metal M comprises:

8. The method of claim 7, wherein the method satisfies at least one of the following conditions:

(1) The voltage of the direct current arc discharge treatment is 5V to 30V;

(2) The current of the direct current arc discharge treatment is 10A to 200A;

(3) The inert gas comprises argon and/or helium;

9. The method according to any one of claims 6 to 8, wherein before the direct current arc discharge treatment of the mixture containing the elemental silicon and the elemental metal M, the method further comprises:

and mixing silicon powder and metal M powder, and then pressing and forming to obtain the mixture containing the simple substance of silicon and the simple substance of metal M.

10. The method of claim 9, wherein the method satisfies at least one of the following conditions:

(1) The mass ratio of the silicon powder to the metal M powder is (9~1): 1;

(2) The average particle size of the silicon powder is 20-80 μm;

(3) The average particle size of the metal M powder is 20-80 μ M.

11. The method according to any one of claims 7 to 10, further comprising, after obtaining the deposited powder of the composite anode material:

12. A negative electrode plate, characterized by comprising the composite negative electrode material of any one of claims 1 to 5 or the composite negative electrode material prepared by the method of any one of claims 6 to 11.

13. A secondary battery comprising the negative electrode sheet according to claim 12.

14. An electric device comprising the secondary battery according to claim 13.