CN116706013A - Composite negative electrode material, preparation method thereof and lithium ion battery - Google Patents

Composite negative electrode material, preparation method thereof and lithium ion battery Download PDF

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Publication number
CN116706013A
CN116706013A CN202310678886.4A CN202310678886A CN116706013A CN 116706013 A CN116706013 A CN 116706013A CN 202310678886 A CN202310678886 A CN 202310678886A CN 116706013 A CN116706013 A CN 116706013A
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coating layer
anode material
composite anode
mixture
negative electrode
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郝雪纯
别晓非
姜涛
翟喜民
杨贺捷
杨晶博
何丽红
赵孟迪
张笑鸣
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FAW Group Corp
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FAW Group Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The application provides a composite anode material, a preparation method thereof and a lithium ion battery. The composite anode material comprises an inner core, wherein the inner core is a secondary particle formed by elemental silicon and/or silicon oxide; the composite anode material further comprises a first coating layer and a second coating layer, wherein the material of the first coating layer is selected from tin dioxide, at least part of the first coating layer is coated on the surface of the inner core, and the optional rest part of the first coating layer is positioned between the secondary particles; the second coating layer is made of carbon, is coated outside the first coating layer on the surface of the inner core, and is chemically bonded with the first coating layer through carbon-oxygen single bonds. The composite anode material has excellent conductivity and structural stability, and can improve the rate performance and the cycle performance of the composite anode material when being applied to lithium ion batteries. The first coating layer and the second coating layer are chemically bonded through carbon-oxygen single bonds, so that the mechanical connection strength between the two layers is enhanced, the structural stability of the composite anode material is improved, and the cycle performance of the lithium ion battery is improved.

Description

Composite negative electrode material, preparation method thereof and lithium ion battery
Technical Field
The application relates to the technical field of preparation of negative electrode materials, in particular to a composite negative electrode material, a preparation method thereof and a lithium ion battery.
Background
With the further popularization of electric vehicles, the market has created a higher demand for the performance of power batteries, wherein the development of key electrode materials is critical to improving battery performance. Silicon anodes have received extensive attention from the scientific and industrial community due to their high specific capacity. However, silicon often accompanies large volume changes (about 300%) during lithiation or delithiation, which can lead to cracking and chalking of the bulk silicon particles, limiting the practical use of silicon cathodes, and in addition, the poor conductivity of silicon limits the performance of the electrode. SnO (SnO) 2 As a potential negative electrode material with high theoretical capacity (about 1493 mAh/g), low cost and environmental friendliness, the material has been widely focused on the aspects of lithium storage mechanism and practical application, and is similar to a silicon negative electrode, snO 2 The negative electrode also has a problem of volume expansion and low conductivity. At the same time, snO 2 Tin particles generated during lithiation are easily aggregated, resulting in a sharp drop in capacity.
It has been reported that Si and SnO 2 Multiple effects of (3)It should be advantageous to improve the storage performance of lithium. By compounding the two components, the conductivity of the electrode can be effectively improved. However, the conventional hydrothermal method is complex in operation and high in cost, and is not beneficial to industrial mass preparation.
Chinese patent application (publication No. CN113314702 a) discloses a carbon-silicon coated tin dioxide compound, a preparation method thereof and application thereof as a negative electrode material of a lithium ion battery. The method comprises the following steps: mixing the ground biomass with an ionic liquid, and carbonizing to obtain biochar; silicon powder and SnO 2 Mixing the nano particles, and performing ball milling to obtain silicon oxygen compound coated tin dioxide nano particles; adding biological carbon into the silicon oxide coated tin dioxide nano particles, and continuing ball milling to obtain a biological carbon silicon coated tin dioxide compound; and finally sieving the biological carbon-silicon coated tin dioxide compound. The patent has complicated steps, and three materials are physically mixed, so that the acting force is weak, and the improvement on the cycle performance and the multiplying power performance of the lithium ion battery is not obvious.
Therefore, a preparation method of the composite anode material with simple preparation flow and a prepared composite anode material with excellent structural stability, difficult volume expansion and excellent conductivity are researched and developed, and the preparation method has important significance for improving the cycle stability and the rate capability of the lithium ion battery.
Disclosure of Invention
The application mainly aims to provide a composite anode material, a preparation method thereof and a lithium ion battery, which are used for solving the problems of poor cycling stability and rate capability of the lithium ion battery caused by high volume expansion rate and poor conductivity of the anode material in the prior art.
In order to achieve the above object, according to one aspect of the present application, there is provided a composite anode material including an inner core, the inner core being secondary particles formed of elemental silicon and/or silicon oxide; the composite anode material further comprises a first coating layer and a second coating layer, wherein the material of the first coating layer is selected from tin dioxide, at least part of the first coating layer is coated on the surface of the inner core, and the optional rest part of the first coating layer is positioned between the secondary particles; the second coating layer is made of carbon, is coated outside the first coating layer on the surface of the inner core, and is chemically bonded with the first coating layer through carbon-oxygen single bonds.
Further, the coating amount of the first coating layer is 5 to 20wt%, preferably 2 to 10wt%, based on the weight percentage of the core; preferably, the first coating layer is coated in an amount of 10 to 15wt%, preferably 4 to 6wt%, based on the weight percentage of the core; preferably, the secondary particles have a particle size of 100 to 500nm.
Further, the thickness of the first coating layer is 5-20 nm; preferably, the thickness of the second coating layer is 10-20 nm; preferably, the second coating layer has a porous structure with a porosity of 5 to 15%; preferably, the material of the second cladding layer is amorphous carbon.
In order to achieve the above object, another aspect of the present application further provides a method for preparing the above composite anode material, where the method for preparing the composite anode material includes: mixing elemental silicon and/or silicon oxide with elemental tin to obtain a first mixture; carrying out heat treatment on the first mixture in an inert atmosphere to enable elemental tin in the first mixture to be melted, so as to obtain a second mixture; and (3) carrying out oxidation-reduction reaction on the second mixture and carbon dioxide gas to obtain the composite anode material.
Further, the weight ratio of elemental silicon and/or silicon oxide to elemental tin is 1 (0.1 to 5), preferably 1 (0.2 to 1).
Further, the temperature of the heat treatment is 300-500 ℃, the time is 2-3 h, and the heating rate is 2-10 ℃/min.
Further, the inert atmosphere is selected from one or more of the group consisting of nitrogen, helium, argon and neon.
Further, the redox reaction process includes: introducing carbon dioxide gas into the vacuum tube furnace to oxidize molten tin in the second mixture by the carbon dioxide gas, so as to obtain a composite anode material; preferably, the carbon dioxide gas is introduced at a rate of 0.05 to 0.1L/min, and the weight of the second mixture is 0.6 to 1g.
Further, the temperature of the oxidation-reduction reaction is 600-800 ℃ and the time is 5-8 h; preferably, the temperature of the redox reaction is the same as the temperature of the heat treatment.
In yet another aspect, the present application provides a lithium ion battery, which includes a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, where the negative electrode includes the above-mentioned composite negative electrode material provided by the present application, or a composite negative electrode material prepared by the preparation method of the above-mentioned composite negative electrode material provided by the present application.
By applying the technical scheme of the application, the silicon-based anode material has no hidden danger of lithium precipitation, low cost and higher theoretical specific capacity. Under the lithiation effect, the first coating layer coated on the surface of the inner core is gradually converted into a tin simple substance along with the deepening of the lithium intercalation degree, so that an excellent electronic conductor is formed, and the theoretical specific capacity of the composite anode material can be improved. The second cladding layer, which is outside the first cladding layer on the surface of the core, limits the elemental silicon and/or silicon oxide in the core and the SnO in the first cladding layer 2 At the same time as Li + Volume expansion during the reaction process, while fixing SnO during the lithiation process 2 Is converted into Sn, so that the structural stability of the composite anode material is improved, and the cycle performance of the lithium ion battery is improved; meanwhile, carbon has better conductivity, and the carbon serving as a material of the second coating layer can improve the conductivity of the composite anode material, so that the rate performance of the lithium ion battery can be improved. And moreover, the first coating layer and the second coating layer are chemically bonded through carbon-oxygen single bonds, so that the mechanical connection strength between the two layers is enhanced, the structural stability of the composite anode material is improved, and the cycle performance of the lithium ion battery is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
fig. 1 shows an SEM image of the composite anode material prepared in example 1.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The present application will be described in detail with reference to examples.
As described in the background art, the existing negative electrode material has the problems of high volume expansion rate and poor conductivity, and the cycle stability and the rate capability of the lithium ion battery are poor. In order to solve the technical problems, the application provides a composite anode material, which comprises an inner core, wherein the inner core is secondary particles formed by elemental silicon and/or silicon oxide; the composite anode material further comprises a first coating layer and a second coating layer, wherein the material of the first coating layer comprises, but is not limited to, tin dioxide, at least part of the material is coated on the surface of the inner core, and the optional rest part of the material is positioned between the secondary particles; the second coating layer is made of carbon, is coated outside the first coating layer on the surface of the inner core, and is chemically bonded with the first coating layer through carbon-oxygen single bonds.
The silicon-based anode material has no hidden danger of lithium precipitation, low cost and higher theoretical specific capacity. Under the lithiation effect, the first coating layer coated on the surface of the inner core is gradually converted into a tin simple substance along with the deepening of the lithium intercalation degree, so that an excellent electronic conductor can be formed, and the theoretical specific capacity of the composite anode material can be improved. The second cladding layer, which is outside the first cladding layer on the surface of the core, limits the elemental silicon and/or silicon oxide in the core and the SnO in the first cladding layer 2 At the same time as Li + Volume expansion during the reaction process, while fixing SnO during the lithiation process 2 Is converted into Sn, so that the structural stability of the composite anode material is improved, and the cycle performance of the lithium ion battery is improved; meanwhile, carbon has better conductivity, and the carbon serving as a material of the second coating layer can improve the conductivity of the composite anode material, so that the rate performance of the lithium ion battery can be improved. And moreover, the first coating layer and the second coating layer are chemically bonded through carbon-oxygen single bonds, so that the mechanical connection strength between the two layers is enhanced, the structural stability of the composite anode material is improved, and the cycle performance of the lithium ion battery is improved.
In a preferred embodiment, the first cladding layer is present in an amount of 5 to 20wt% based on the weight of the core, preferably the second cladding layer is present in an amount of 2 to 10wt%. Compared with other ranges, the coating amount of the first coating layer is limited in the range, so that the theoretical specific capacity of the composite anode material is improved, and the coating amount of the second coating layer is limited in the range, so that the volume expansion of the composite anode material is restrained, and the structural stability of the composite anode material is improved; on the other hand, the conductivity of the composite anode material is improved, so that the multiplying power performance of the composite anode material is improved.
In order to further increase the theoretical specific capacity of the composite anode material and to further increase the electrical conductivity thereof, and to suppress the volume expansion of the composite anode material, it is preferable that the coating amount of the first coating layer is 10 to 15wt% and the coating amount of the second coating layer is 4 to 6wt% in terms of the weight percentage of the core.
In a preferred embodiment, the secondary particles have a particle size of 100 to 500nm. The particle size of the secondary particles includes, but is not limited to, the above-mentioned ranges, and limiting it to the above-mentioned ranges is advantageous in improving contact between particles, in increasing electron transport paths, and in improving electrochemical properties of the composite anode material.
In a preferred embodiment, the thickness of the first cladding layer is 5 to 20nm; the thickness of the second coating layer is preferably 10 to 20nm. Compared with other ranges, the thickness of the first coating layer is limited in the range, so that the theoretical specific capacity of the composite anode material is improved, and the thickness of the second coating layer is limited in the range, on one hand, the volume expansion of the composite anode material is restrained, and the structural stability of the composite anode material is improved; on the other hand, the conductivity of the composite anode material is improved, so that the multiplying power performance of the composite anode material is improved.
Compared with a compact second coating layer, the second coating layer with the porous structure is beneficial to inhibiting the direct contact of the inner core and the first coating layer with electrolyte, simultaneously enabling lithium ions to be more easily inserted and extracted, and improving the transportation rate of the lithium ions and electrons. In a preferred embodiment, the second cladding layer has a porous structure with a porosity of 5 to 15%. Compared with other ranges, the porosity of the second coating layer is limited in the range, so that the effect of direct contact between the inner core and the first coating layer and the electrolyte is further restrained, and meanwhile, the transportation rate of lithium ions and electrons is improved, and the structural stability and the electrochemical specific capacity of the composite anode material are improved.
The preparation method of the amorphous carbon is simple and easy to obtain, and the amorphous carbon has the advantage of good conductivity. In a preferred embodiment, the material of the second cladding layer is amorphous carbon.
The second aspect of the present application also provides a method for preparing the composite anode material provided by the present application, where the method for preparing the composite anode material includes: mixing elemental silicon and/or silicon oxide with elemental tin to obtain a first mixture; carrying out heat treatment on the first mixture in an inert atmosphere to enable elemental tin in the first mixture to be melted, so as to obtain a second mixture; and (3) carrying out oxidation-reduction reaction on the second mixture and carbon dioxide gas to obtain the composite anode material.
Mixing elemental silicon and/or silicon oxide with elemental tin, wherein in the process, the elemental silicon and/or silicon oxide form secondary particles and are mixed and dispersed with the elemental tin to obtain a first mixture; carrying out heat treatment on the first mixture in an inert atmosphere to enable elemental tin in the first mixture to be molten, and coating molten tin on the surfaces of the secondary particles to obtain a second mixture; and (2) carrying out oxidation-reduction reaction on the second mixture and carbon dioxide gas, wherein the carbon dioxide gas is used as an oxide in the process, and can oxidize molten tin, so that tin dioxide and carbon are generated in situ, and carbon-oxygen single bonds exist between the tin dioxide and the carbon, and the following reaction occurs in the process: sn+CO 2 →SnO 2 And +C, obtaining the composite anode material. During the heat treatment of the first mixture, the molten elemental tin coats the surfaces of the secondary particles, and the amount of elemental tin between the secondary particles is small and therefore negligible.
Compared with the prior art, the method has the advantages that silicon powder, snO 2 According to the method for preparing the carbon-silicon coated tin dioxide composite by performing the first ball milling on the nano particles and adding the biochar into the nano particles to perform the second ball milling, the tin dioxide and the carbon can be generated in situ, and a carbon-oxygen single bond exists between the tin dioxide and the carbon, so that the first coating layer and the second coating layer have stronger mechanical connection strength, and the prepared composite negative electrode material has better structural stability, and can obviously improve the cycle performance of a lithium ion battery when the composite negative electrode material is applied to the lithium ion battery. In addition, the preparation method provided by the application has the advantages of short process flow and easiness in operation and control.
In a preferred embodiment, the weight ratio of elemental silicon and/or silicon oxide to elemental tin is 1 (0.1 to 5), preferably 1 (0.2 to 1). The weight ratio of the materials includes but is not limited to the above range, and the limitation of the weight ratio in the above range is beneficial to the subsequent preparation of the first coating layer with more proper thickness and coating amount, thereby being beneficial to improving the structural stability of the composite anode material and further being beneficial to improving the cycle performance of the lithium ion battery.
In a preferred embodiment, the heat treatment is carried out at a temperature of 300 to 500℃for a period of 2 to 3 hours and at a rate of 2 to 10℃per minute. The temperature, time and heating rate of the heat treatment include, but are not limited to, the ranges described above, and limiting the ranges described above advantageously increases the melting efficiency of the elemental tin, while inhibiting the melting of the elemental silicon and/or silicon oxide under the conditions described above, advantageously maintains the original solid phase structure of the elemental silicon and/or silicon oxide, and provides a more suitable second mixture for the subsequent formation of the first and second cladding layers.
In a preferred embodiment, the inert atmosphere includes, but is not limited to, one or more of the group consisting of nitrogen, helium, argon, and neon. The heat treatment process by adopting the inert atmosphere is beneficial to inhibiting the oxidation of the simple substance tin and reducing the introduction of impurities.
In a preferred embodiment, the redox reaction process comprises: introducing carbon dioxide gas into the vacuum tube furnace to oxidize molten tin in the second mixture by the carbon dioxide gas, thereby obtaining the composite anode material.
In a preferred embodiment, the carbon dioxide gas is introduced at a rate of 0.05 to 0.1L/min and the weight of the second mixture is 0.7 to 1g. Compared with other ranges, the carbon dioxide gas introducing rate and the weight of the second mixture are limited in the ranges, so that the efficiency of the oxidation-reduction reaction is improved, and the porosity of the second coating layer is regulated and controlled in a proper range, so that the structural stability and the electrochemical specific capacity of the composite anode material are improved.
In a preferred embodiment, the temperature of the redox reaction is 600 to 800℃and the time is 5 to 8 hours. The temperature and time of the oxidation-reduction reaction include, but are not limited to, the above ranges, and limiting them to the above ranges is advantageous in improving the utilization ratio of the raw materials, while being advantageous in improving the rate of the oxidation-reduction reaction, and also in improving the purity of each of the first coating layer and the second coating layer.
Preferably, the temperature of the redox reaction is the same as the temperature of the heat treatment.
The third aspect of the application also provides a lithium ion battery, which comprises a positive electrode, a negative electrode, electrolyte and a diaphragm arranged between the positive electrode and the negative electrode, wherein the negative electrode comprises the composite negative electrode material provided by the application or a composite negative electrode material prepared by the preparation method of the composite negative electrode material provided by the application.
The composite anode material provided by the application has excellent structural stability and electrochemical specific capacity, and can have excellent cycle performance and rate performance when being applied to a lithium ion battery.
The application is described in further detail below in connection with specific examples which are not to be construed as limiting the scope of the application as claimed.
Example 1
A preparation method of a composite anode material comprises the following steps:
(1) Weighing 0.2g of silicon powder (the component is pure silicon, the granularity is 200 nm) and 0.5g of tin powder, putting the silicon powder and the tin powder into a porcelain boat, and slightly shaking the silicon powder and the tin powder to uniformly mix the silicon powder and the porcelain boat to obtain 0.7g of first mixture;
(2) Transferring the porcelain boat to a vacuum tube furnace, placing the porcelain boat in an open place, introducing argon, heating to 400 ℃ at a heating rate of 5 ℃/min for heat treatment, and preserving the heat for 2 hours to obtain a second mixture;
(3) CO is introduced into the vacuum tube furnace at an introduction rate of 0.05L/min 2 And heating the gas to 700 ℃, and continuing to perform heating reaction for 5 hours to obtain a powder product, wherein the powder product is the composite anode material.
As shown in the SEM image of fig. 1, it can be seen that the composite anode material is in a spherical particle shape, the surface has many folds, and the pores on the surface of the particle are moderate in size and uniform in distribution. The first cladding layer was coated in an amount of 16.3wt% and the second cladding layer was coated in an amount of 5.1wt% based on the weight percentage of the core.
Example 2
A preparation method of a composite anode material comprises the following steps:
(1) Weighing 0.5g of silicon powder (the component is pure silicon, the granularity is 200 nm) and 0.5g of tin powder, putting the silicon powder and the tin powder into a porcelain boat, and slightly shaking the silicon powder and the tin powder to uniformly mix the silicon powder and the porcelain boat to obtain 1.0g of first mixture;
(2) The same as in step (2) of example 1, a second mixture was obtained;
(3) A composite anode material was obtained in the same manner as in step (3) in example 1.
Example 3
A preparation method of a composite anode material comprises the following steps:
(1) 1.0g of silicon powder (the component is pure silicon, the granularity is 200 nm) and 0.5g of tin powder are weighed and put into a porcelain boat, and the porcelain boat and the tin powder are gently rocked to be uniformly mixed, so as to obtain 1.5g of first mixture;
(2) The same as in step (2) of example 1, a second mixture was obtained;
(3) A composite anode material was obtained in the same manner as in step (3) in example 1.
Example 4
The difference from example 1 is that: the weight ratio of the silicon powder to the tin powder is 1:5.
Example 5
The difference from example 1 is that: the weight ratio of the silicon powder to the tin powder is 1:0.05.
Example 6
The difference from example 3 is that: the weight ratio of the silicon powder to the tin powder is 1:0.2.
Example 7
The difference from example 3 is that: the temperature of the heat treatment was 300 ℃.
Example 8
The difference from example 3 is that: the temperature of the heat treatment was 500 ℃.
Example 9
The difference from example 3 is that: the heat treatment was carried out at 250℃for 1 hour.
Example 10
The difference from example 1 is that: CO 2 The gas feed rate was 0.15L/min.
Example 11
The difference from example 1 is that: CO 2 The gas feed rate was 0.1L/min.
Example 12
The difference from example 1 is that: CO 2 The gas feed rate was 0.02L/min.
Example 13
The difference from example 1 is that: the temperature of the oxidation-reduction reaction was 500℃for 2 hours.
Comparative example 1
The difference from example 1 is that: in the step (1), no silicon powder was added, and only 0.5g of tin powder was added, and in the steps (2) and (3), the same as in example 1, snO was obtained 2 @ C negative electrode material.
Comparative example 2
The difference from example 1 is that: in the step (1), no tin powder was added, and only 0.5g of silicon powder was added, and in the steps (2) and (3), the same as in example 1, respectively, to obtain a Si negative electrode material.
The coating amounts of the first coating layer, the second coating layer, and the porosity of the second coating layer in the composite anode materials or anode materials prepared in all of the above examples and comparative examples of the present application are shown in table 1.
The composite anode materials or anode materials prepared in all the above examples and comparative examples of the present application were assembled into CR2032 button cells for electrochemical performance and cycle performance testing.
The CR2032 button cell was assembled as follows: mixing the anode material prepared in the embodiment or the comparative example with conductive agent acetylene black and polyvinylidene fluoride respectively in a weight ratio of 8:1:1, preparing the mixture into slurry by using N-methyl pyrrolidone, coating the slurry on a copper foil, and placing the prepared slurry coating in a vacuum drying oven and drying at 90 ℃ for 24 hours; cutting the dried electrode into small discs with the diameter of 1cm by using a cutting machine to serve as a negative electrode, taking a metal lithium sheet as a counter electrode, celgard2500 as a diaphragm, and EC/DMC/EMC 1:1:1 (W/W) +1mol/L LiPF 6 As an electrolyte, a CR2032 button cell was assembled in a glove box under argon atmosphere.
The electrochemical performance test conditions were as follows: and carrying out constant current charge and discharge test on the assembled battery by using a LANDCT 2001A tester (Wuhan city blue electric power electronic Co., ltd.) at a test temperature of 25 ℃, a test voltage range of 0.01-1.5V, a test current density of 1/3C and a nominal specific capacity of 2000mAh/g.
The cycle performance test conditions were as follows: the current density is 0.1A/g, the test voltage range is 0.01-3V, and the cycle is 50 circles.
The test results are shown in Table 2.
TABLE 1
Coating amount of the first coating layer/wt% Coating amount/wt% of the second coating layer Porosity/%of the second coating layer
Example 1 16.3 5.1 10.4
Example 2 13.8 4.2 11.2
Example 3 10.1 3.6 9.8
Example 4 25.7 9.4 12.3
Example 5 3.7 1.4 9.4
Example 6 8.8 3.3 10.5
Example 7 6.3 2.1 4.5
Example 8 12.7 4.0 11.6
Example 9 4.6 1.9 12.3
Example 10 10.5 3.5 5.6
Example 11 15.4 4.6 13.9
Example 12 8.5 3.3 4.7
Example 13 6.6 2.4 3.6
Comparative example 1 / / /
Comparative example 2 0 0 /
TABLE 2
Specific first discharge capacity (mAh/g) at 1/3C rate 50 cycle capacity retention (%)
Example 1 1456 62.6
Example 2 1876 88.1
Example 3 2156 57.6
Example 4 1398 63.6
Example 5 1175 57.4
Example 6 1433 64.6
Example 7 1690 74.4
Example 8 1764 69.5
Example 9 1045 43.5
Example 10 1532 60.3
Example 11 1425 61.4
Example 12 1067 42.3
Example 13 965 48.7
Comparative example 1 865 35.8
Comparative example 2 2665 52.6
From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:
as can be seen from comparative example 1 and comparative example 1, snO was used as a core material compared with silicon 2 The cathode material obtained by coating the core material with the carbon layer has lower initial discharge specific capacity (only 865 mAh/g), and the capacity retention rate is also obviously reduced (from 62.6% to 35.8%).
As can be seen from comparative example 1 and comparative example 2, the lithium ion battery prepared from the composite anode material provided by the application exhibits better cycle performance (from 52.6% to 62.6%) compared to the uncoated Si anode material.
As can be seen from comparative examples 1, 4 and 5 and comparative examples 1, 3 and 6, the weight ratio of the silicon powder to the tin powder includes, but is not limited to, the preferred range of the present application, and the preferred range of the present application is limited to facilitate the subsequent preparation of the first coating layer having a more suitable thickness and coating amount, thereby facilitating the improvement of the structural stability of the composite anode material, and thus facilitating the improvement of the cycle performance of the lithium ion battery.
As can be seen from comparing examples 1, 7 to 9, the temperature, time and heating rate of the heat treatment, including but not limited to the preferred ranges of the present application, are limited to the preferred ranges of the present application, which is advantageous for improving the melting efficiency of elemental tin, while suppressing melting of elemental silicon and/or silicon oxide under the above conditions, which is advantageous for maintaining the original solid phase structure of elemental silicon and/or silicon oxide, and for providing a more suitable second mixture for the subsequent formation of the first coating layer and the second coating layer.
As can be seen from comparing examples 1, 10 to 12, limiting the rate of introduction of carbon dioxide gas and the weight of the second mixture within the preferred ranges of the present application is advantageous in improving the efficiency of the redox reaction, while being advantageous in controlling the porosity of the second coating layer within a suitable range, thereby being advantageous in improving the structural stability and electrochemical specific capacity of the composite anode material, as compared with other ranges.
As can be seen from comparing examples 1 and 13, the temperature and time of the redox reaction include, but are not limited to, the preferred ranges of the present application, and limiting them to the preferred ranges of the present application facilitates the improvement of the raw material utilization rate, and also facilitates the improvement of the redox reaction rate, and also facilitates the improvement of the respective purities of the first coating layer and the second coating layer, thereby facilitating the improvement of the electrochemical properties of the composite anode material.
It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those described herein.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (10)

1. The composite anode material is characterized by comprising an inner core, wherein the inner core is secondary particles formed by elemental silicon and/or silicon oxide; the composite anode material further comprises a first coating layer and a second coating layer, wherein the material of the first coating layer is selected from tin dioxide, at least part of the first coating layer is coated on the surface of the inner core, and the optional rest part of the first coating layer is positioned between the secondary particles; the second coating layer is made of carbon, is coated outside the first coating layer on the surface of the inner core, and is chemically bonded with the first coating layer through carbon-oxygen single bonds.
2. The composite anode material according to claim 1, wherein the first coating layer is coated in an amount of 5 to 20wt%, preferably the second coating layer is coated in an amount of 2 to 10wt%, based on the weight percentage of the core;
preferably, the coating amount of the first coating layer is 10-15 wt%, preferably the coating amount of the second coating layer is 4-6 wt%, based on the weight percentage of the core;
preferably, the secondary particles have a particle size of 100 to 500nm.
3. The composite anode material according to claim 1 or 2, wherein the thickness of the first coating layer is 5 to 20nm; preferably, the thickness of the second coating layer is 10-20 nm;
preferably, the second coating layer has a porous structure with a porosity of 5 to 15%;
preferably, the material of the second coating layer is amorphous carbon.
4. A method of preparing the composite anode material of claim 1, comprising:
mixing elemental silicon and/or silicon oxide with elemental tin to obtain a first mixture;
carrying out heat treatment on the first mixture in an inert atmosphere so as to enable elemental tin in the first mixture to be melted and obtain a second mixture;
and (3) carrying out oxidation-reduction reaction on the second mixture and carbon dioxide gas to obtain the composite anode material.
5. The method according to claim 4, wherein the weight ratio of the elemental silicon and/or the silicon oxide to the elemental tin is 1 (0.1-5), preferably 1 (0.2-1).
6. The method for producing a composite anode material according to claim 4 or 5, wherein the heat treatment is performed at a temperature of 300 to 500 ℃ for 2 to 3 hours at a temperature rise rate of 2 to 10 ℃/min.
7. The method for producing a composite anode material according to any one of claims 4 to 6, wherein the inert atmosphere is one or more selected from the group consisting of nitrogen, helium, argon, and neon.
8. The method for producing a composite anode material according to any one of claims 4 to 7, characterized in that the process of the oxidation-reduction reaction includes: introducing the carbon dioxide gas into a vacuum tube furnace to oxidize molten tin in the second mixture by the carbon dioxide gas, so as to obtain the composite anode material;
preferably, the carbon dioxide gas is introduced at a rate of 0.05 to 0.1L/min, and the weight of the second mixture is 0.7 to 1g.
9. The method for preparing a composite anode material according to claim 8, wherein the temperature of the oxidation-reduction reaction is 600-800 ℃ for 5-8 hours; preferably, the temperature of the redox reaction is the same as the temperature of the heat treatment.
10. A lithium ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator provided between the positive electrode and the negative electrode, characterized in that the negative electrode comprises the composite negative electrode material according to any one of claims 1 to 3, or the composite negative electrode material produced by the production method of the composite negative electrode material according to any one of claims 4 to 9.
CN202310678886.4A 2023-06-08 2023-06-08 Composite negative electrode material, preparation method thereof and lithium ion battery Pending CN116706013A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117476920A (en) * 2023-12-28 2024-01-30 贝特瑞新材料集团股份有限公司 Negative electrode material, preparation method thereof and lithium ion battery

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117476920A (en) * 2023-12-28 2024-01-30 贝特瑞新材料集团股份有限公司 Negative electrode material, preparation method thereof and lithium ion battery

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