CN116632212A - Silicon-carbon negative electrode material, preparation method thereof, lithium ion battery and power utilization device - Google Patents

Silicon-carbon negative electrode material, preparation method thereof, lithium ion battery and power utilization device Download PDF

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CN116632212A
CN116632212A CN202310795105.XA CN202310795105A CN116632212A CN 116632212 A CN116632212 A CN 116632212A CN 202310795105 A CN202310795105 A CN 202310795105A CN 116632212 A CN116632212 A CN 116632212A
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silicon
negative electrode
carbon
graphite
electrode material
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罗汉卿
蔡奕金
刘鹏
褚春波
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Xinwangda Power Technology Co ltd
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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
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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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
    • 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
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    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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    • H01M4/00—Electrodes
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    • 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
    • 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
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    • 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
    • H—ELECTRICITY
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    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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Abstract

The invention provides a silicon-carbon negative electrode material, a preparation method thereof, a lithium ion battery and an electric device. The silicon-carbon anode material comprises an inner core and a functional layer arranged on the surface of the inner core: the inner core comprises graphite with silicon carbide and silicon arranged on the surface, and the functional layer comprises amorphous carbon; the silicon-carbon anode material meets the following conditions: i a /I b ＝0.02～0.10，I c /I a =0.10 to 0.30; wherein I is a Is the (111) crystal plane peak intensity of silicon, I b Is the (002) crystal face peak intensity of graphite, I c Is silicon carbide(111) crystal plane peak intensity. According to the invention, the amorphous carbon is coated on the surface, so that the cycling stability of the lithium ion battery is improved, and meanwhile, the material collocation proportion of the graphite-silicon carbide-silicon core material of the silicon-carbon negative electrode material is regulated, so that the cycling stability and the multiplying power performance of the prepared lithium ion battery can be remarkably improved.

Description

Silicon-carbon negative electrode material, preparation method thereof, lithium ion battery and power utilization device
Technical Field
The invention relates to the technical field of negative electrode materials, in particular to a silicon-carbon negative electrode material, a preparation method thereof, a lithium ion battery and an electric device.
Background
In recent years, with the rapid development of the new energy automobile industry, higher requirements are put on the energy density of rechargeable lithium ion batteries. The traditional graphite negative electrode material has the advantages of strong electronic conductivity, excellent cycle performance, economy, environmental protection and the like, but the lower theoretical specific capacity (372 mAh/g) limits the further improvement of the energy density of the lithium ion battery.
In the existing few lithium ion battery cathode materials, silicon becomes the first choice of the high-energy lithium ion battery cathode materials because of the theoretical specific capacity of up to 4200mAh/g, and the energy density of the battery can be effectively improved by mixing a small amount of silicon into graphite. However, the silicon anode material has the problems of poor electronic conductivity, large volume expansion (about 300%), and the like, so that the pulverization failure of silicon particles, the loss of electrical contact of a current collector, the continuous generation of a solid electrolyte film on the surface of particles, and the like, the reduction of the capacity of a battery is caused, and the rate performance and the cycle performance of the battery are seriously influenced.
Therefore, there is a need for further optimization of the negative electrode material of lithium ion batteries, providing a silicon-carbon negative electrode material for lithium ion batteries with excellent cycle performance and higher discharge rate performance.
Disclosure of Invention
The invention aims to solve the problem that the cycle stability and the multiplying power performance of the existing lithium ion battery are required to be further improved, and provides a silicon-carbon anode material for the lithium ion battery, which has excellent cycle performance and higher discharge multiplying power performance. According to the invention, the amorphous carbon is coated on the surface, so that the cycle stability of the lithium ion battery is improved, the material collocation proportion of the graphite-silicon carbide-silicon core material of the silicon-carbon negative electrode material is regulated, the structural stability of the negative electrode material is further improved, the capacity exertion of the negative electrode material is improved, and the cycle stability and the multiplying power performance of the prepared lithium ion battery can be remarkably improved.
According to a first aspect of the invention, a silicon-carbon anode material is provided, and comprises an inner core and a functional layer coated on the surface of the inner core: the inner core comprises graphite with silicon carbide and silicon arranged on the surface, and the functional layer comprises amorphous carbon;
the silicon-carbon anode material meets the following conditions: i a /I b ＝0.02～0.10，I c /I a ＝0.10～0.30；
Wherein I is a Is the (111) crystal plane peak intensity of silicon, I b Is the (002) crystal face peak intensity of graphite, I c The (111) plane peak intensity of silicon carbide.
In the silicon carbon anode material, I is a /I b ＝0.04～0.08。
In the silicon carbon anode material, I is c /I a ＝0.15～0.25。
As an embodiment of the present invention, in the silicon-carbon negative electrode material, the weight ratio of graphite, silicon carbide to silicon is 1: (0.9-1.8): (0.1-0.2).
As an embodiment of the invention, the specific surface area of the silicon-carbon anode material is 1-3 m 2 /g。
As an embodiment of the invention, the silicon carbon anode material has a powder compaction density of 1.5-2.0 g/cm under 3T pressure 3 。
As an embodiment of the present invention, the silicon carbon negative electrode material has a powder resistivity of 0.003 to 0.005 Ω×cm under a 2T pressure.
As an embodiment of the present invention, the silicon carbon negative electrode material D V50 Is 5-25 mu m, D v50 And accumulating the particle size corresponding to the volume percentage of the silicon-carbon anode material reaching 50 percent.
As an embodiment of the present invention, the functional layer has a thickness of 10 to 80nm.
As an embodiment of the present invention, the functional layer has a thickness of 30 to 70nm.
In a second aspect of the present invention, a preparation method of the silicon-carbon negative electrode material is provided, including the following steps:
s1, mixing graphite and silicon, and embedding silicon carbide and silicon on the surface of the graphite through a melting reaction in an inert atmosphere;
s2, mixing the product obtained in the step S1 and the precursor of amorphous carbon, and carbonizing in an inert atmosphere to obtain the silicon-carbon anode material.
As an embodiment of the present invention, the specific flow of the melting in step S1 is: heating to 1500-1600 ℃ at a heating rate of 1-10 ℃/min, keeping the temperature for 1-3 hours, and then cooling to 20-30 ℃ at a speed of 10-20 ℃/min.
As an embodiment of the present invention, the specific flow of the carbonization treatment in step S2 is as follows: heating to 800-1000 ℃ at a heating rate of 1-10 ℃, preserving heat for 1-3 h, and then naturally cooling.
As an embodiment of the present invention, the precursor of amorphous carbon includes at least one of glucose, sucrose, soluble starch, cyclodextrin, pitch, phenolic resin, epoxy resin, carboxymethyl cellulose, and citric acid.
The invention provides a lithium ion battery, which comprises a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode membrane arranged on at least one side of the negative electrode current collector, and the negative electrode membrane comprises the silicon-carbon negative electrode material or the silicon-carbon negative electrode material prepared by the preparation method.
In a fourth aspect of the present invention, an electrical device is provided, comprising the lithium ion battery.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the amorphous carbon is coated on the surface, so that the cycle stability of the lithium ion battery is improved, the material collocation proportion of the graphite-silicon carbide-silicon core material of the silicon-carbon negative electrode material is regulated, the structural stability of the negative electrode material is further improved, the capacity exertion of the negative electrode material is improved, and the cycle stability and the multiplying power performance of the prepared lithium ion battery can be remarkably improved.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-carbon negative electrode material according to the present invention, in which 1 represents graphite, 2 represents silicon carbide, 3 represents silicon, and 4 represents amorphous carbon.
Detailed Description
For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples and the accompanying drawings, but the examples are not intended to limit the present invention in any way. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art. The reagents and materials used in the present invention are commercially available unless otherwise specified.
The embodiment of the invention provides a silicon-carbon anode material, which comprises an inner core and a functional layer coated on the surface of the inner core: the inner core comprises graphite with silicon carbide and silicon inlaid on the surface, and the functional layer comprises amorphous carbon;
the silicon-carbon anode material meets the following conditions: i a /I b ＝0.02～0.10，I c /I a ＝0.10～0.30；
Wherein I is a Is the (111) crystal plane peak intensity of silicon, I b Is the (002) crystal face peak intensity of graphite, I c The (111) plane peak intensity of silicon carbide.
The amorphous carbon in the silicon-carbon anode material coating layer can be identified by raman spectrum test. Crystal face peak intensity I a 、I b 、I c Can be calculated from XRD patterns obtained by CuK alpha ray scanning. In XRD spectrum, 2 theta is the (111) crystal face peak intensity of silicon at 28.2-28.6 degrees, and is marked as I a The method comprises the steps of carrying out a first treatment on the surface of the The intensity of the (002) crystal face peak of the graphite at the position of 26.2-26.8 degrees is recorded as I b The method comprises the steps of carrying out a first treatment on the surface of the The (111) crystal face peak intensity of the silicon carbide at the position of 35.3-35.9 degrees of 2 theta is recorded as I c 。
According to the invention, the amorphous carbon is coated on the surface, so that the cycling stability of the lithium ion battery is improved, and specifically: 1) Silicon carbide and silicon are inlaid on the surface of graphite in a condensation state, and can keep a relatively stable structure in the lithium intercalation and deintercalation process, which is not similar to the traditional silicon particles and is easy to pulverize and lose efficacy, thus having better electrochemical cycle performance; 2) Part of silicon can react with graphite to generate silicon carbide, so that the volume expansion of the whole silicon-carbon anode material can be reduced, the structural stability of the silicon-carbon anode material is enhanced, the electrochemical cycle performance of the silicon-carbon anode material is further improved, but the generation of the silicon carbide causes a small amount of silicon to lose electrochemical activity and the capacity of a battery to be lost; 3) The amorphous carbon shell layer is added to further strengthen the structure of the silicon-carbon negative electrode material, the volume change of the core graphite and silicon in the lithium intercalation and deintercalation process is relieved by providing an expansion space, the electrochemical cycle performance of the silicon-carbon negative electrode material is improved, meanwhile, the amorphous carbon shell layer can construct a three-dimensional electronic conductive network on the surface of the material, and the isotropic structure is favorable for lithium ion intercalation, so that the rate capability of the silicon-carbon negative electrode material can be improved.
The inventor of the invention also discovers through further research that the substance collocation proportion of the graphite-silicon carbide-silicon core material in the silicon-carbon anode material is regulated and controlled at the same time, so that the capacity exertion of the anode material can be improved, and the capacity loss caused by a small amount of silicon deactivation can be compensated; meanwhile, the structural stability of the anode material can be further improved, and the cycle stability and the multiplying power performance of the prepared lithium ion battery are obviously improved.
In the silicon-carbon anode material, the use amount of silicon carbide, silicon and amorphous carbon can influence the performance of the prepared battery:
although the silicon carbide can improve the structural stability of the silicon-carbon anode material, if the content is too high, a large amount of silicon loses electrochemical activity, the capacity of the material is reduced, the impedance is increased, and the improvement of the electrochemical performance of the material is not facilitated; if the silicon carbide content is too low, the active silicon content in the material is too high, the volume change in the lithium intercalation and deintercalation process is too large, and the structural stability is poor.
If the silicon content is too high, the silicon layer on the surface of the graphite is too thick, and the volume change generated in the lithium intercalation and deintercalation process is too large, so that the material structure is easy to damage; if the silicon content is too small, the capacity of the battery is not improved.
Therefore, in the silicon-carbon negative electrode material of the present invention, the weight ratio of graphite, silicon carbide and silicon is 1: (0.9-1.8): (0.1-0.2).
By reasonably controlling the ratio of the specific crystal face in the silicon carbide to the specific crystal face in the silicon crystal (I c /I a ) The influence of silicon carbide on the capacity of the silicon-carbon anode material can be obviously reduced, the capacity exertion of the anode material is obviously improved, and the capacity loss caused by a small amount of silicon deactivation is compensated; meanwhile, the structural stability of the anode material can be further improved, and the cycle stability and the multiplying power performance of the prepared lithium ion battery are obviously improved.
In some embodiments of the invention, the I c /I a 0.15 to 0.25. For example, I c /I a May be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25 or a range consisting of any two of the foregoing values.
In some embodiments of the invention, the I a /I b 0.04 to 0.08. For example, I a /I b May be 0.04, 0.05, 0.06, 0.07, 0.08 or any two of the above values.
The amorphous carbon coating is carried out on the graphite core embedded with the condensed silicon carbide and the silicon, an amorphous carbon layer can be formed on the surface of the graphite core, the direct contact of the silicon and electrolyte is avoided, a relatively stable solid electrolyte membrane is generated on the surface of the material, the consumption of reversible lithium is reduced, and the electrochemical cycle performance of the cathode material is improved. In addition, the amorphous carbon layer can construct a three-dimensional electronic conductive network on the surface of the material, and lithium ions are allowed to be simultaneously embedded into silicon-carbon anode material particles from all directions, so that the rate capability of the silicon-carbon anode material is effectively improved.
The amorphous carbon layer is too thin or too thick, which is not beneficial to the improvement of the multiplying power performance of the silicon-carbon anode material. When the amorphous carbon layer is too thin, the amorphous carbon cannot fully cover the surface of the inner core, and a large-area three-dimensional electronic conductive network cannot be formed; when the amorphous carbon layer is too thick, the diffusion path of lithium ions in the particle shell is prolonged, the lithium ion diffusion coefficient of the silicon-carbon negative electrode material is reduced, and the capacity retention rate of the lithium ion battery prepared by the amorphous carbon layer at high multiplying power is obviously reduced. Thus, in some embodiments of the invention, the amorphous carbon layer has a thickness of 10 to 80nm, for example, the amorphous carbon layer may have a thickness of 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, or a range of any two values recited above.
In some embodiments of the invention, the amorphous carbon layer has a thickness of 30 to 70nm.
In some embodiments of the invention, D of the silicon carbon anode material V50 Specifically, the D is 5 to 25 μm, specifically 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm or a range of any two values thereof v50 And accumulating the particle size corresponding to the volume percentage of the silicon-carbon anode material reaching 50 percent.
In some embodiments of the invention, the silicon carbon anode material has a powder compaction density of 1.5 to 2.0g/cm at 3T pressure 3 . For example, the powder compaction density of the silicon carbon anode material at 3T pressure may be 1.5g/cm 3 、1.6g/cm 3 、1.7g/cm 3 、1.8g/cm 3 、1.9g/cm 3 、2.0g/cm 3 Or a range of any two values recited above.
In some embodiments of the invention, the specific surface area of the silicon-carbon anode material is 1-3 m 2 And/g. For example, the specific surface area of the silicon carbon anode material may be 1m 2 /g、1.5m 2 /g、2.0m 2 /g、2.5m 2 /g、3.0m 2 /g or any two values above.
In some embodiments of the invention, the silicon carbon anode material has a powder resistivity of 0.003 to 0.005 Ω×cm at a 2T pressure. For example, the powder resistivity of the silicon carbon anode material at 2T pressure may be 0.003 Ω cm, 0.0035 Ω cm, 0.004 Ω cm, 0.0045 Ω cm, 0.005 Ω cm, or a range of any two of the foregoing values.
The embodiment of the invention also provides a preparation method of the silicon-carbon anode material, which comprises the following steps:
s1, mixing graphite and silicon, and embedding silicon carbide and silicon on the surface of the graphite through a melting reaction in an inert atmosphere;
s2, mixing the product obtained in the step S1 and the precursor of amorphous carbon, and carbonizing in an inert atmosphere to obtain the silicon-carbon anode material.
In an embodiment of the present invention, the silicon in step S1 is nano silicon having a particle size of 30 to 500nm, preferably 50 to 100nm.
In the embodiment of the present invention, the specific flow of melting in step S1 is as follows: heating to 1500-1600 ℃ at a heating rate of 1-10 ℃/min, keeping the temperature for 1-3 hours, and then cooling to 20-30 ℃ at a speed of 10-20 ℃/min.
In the embodiment of the present invention, the specific flow of the carbonization treatment in step S2 is as follows: heating to 800-1000 ℃ at a heating rate of 1-10 ℃, preserving heat for 1-3 h, and then naturally cooling.
In an embodiment of the present invention, the inert atmosphere in the step S2 is an atmosphere formed of at least one gas selected from helium, neon, argon and nitrogen.
In an embodiment of the present invention, the precursor of amorphous carbon includes at least one of glucose, sucrose, soluble starch, cyclodextrin, pitch, phenolic resin, epoxy resin, carboxymethyl cellulose, citric acid.
The embodiment of the invention also provides a lithium ion battery, which comprises a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode membrane arranged on at least one side of the negative electrode current collector, and the negative electrode membrane comprises the silicon-carbon negative electrode material or the silicon-carbon negative electrode material prepared by the preparation method.
The invention also provides an electric device comprising the lithium ion battery.
The following examples are provided to facilitate an understanding of the present invention. These examples are not provided to limit the scope of the claims.
Example 1
The embodiment provides a silicon-carbon anode material, which is prepared by a method comprising the following steps:
s1 10g of graphite (D v50 13 μm of) And 1g of nano-silicon (D) v50 10 nm) is placed in a ball milling tank, ball milling and mixing are carried out for 2 hours at a rotating speed of 300r/min to obtain a mixture, the mixture is heated to 1500 ℃ at a heating rate of 10 ℃/min in a nitrogen atmosphere, the temperature is kept for 2 hours, and then the mixture is slowly cooled to room temperature (25 ℃) at a cooling rate of 15 ℃/min to prepare graphite inlaid with silicon carbide and silicon;
s2, mixing the product obtained in the step S1 and 2g of asphalt, placing the mixture in a ball milling tank, ball milling and mixing for 2 hours at a rotating speed of 300r/min, then heating to 800 ℃ at a heating rate of 10 ℃/min under a nitrogen atmosphere, and preserving heat for 2 hours, and obtaining the silicon-carbon anode material after the material is naturally cooled to room temperature (below 30 ℃), for example, 25 ℃).
Examples 2 to 4
A series of silicon-carbon negative electrode materials are provided, and are prepared according to the preparation method of the example 1, and the difference from the example 1 is that the addition amount of the nano silicon in the step S1 is 0.5g, 1.5g and 2.0g in sequence.
Examples 5 to 10
A series of silicon carbon negative electrode materials were provided, prepared according to the preparation method of example 1, which is different from example 1 in that the addition amount of the amorphous carbon precursor in step S2 was changed to change the thickness of the amorphous carbon layer in the silicon carbon negative electrode material (specific thickness parameters are detailed in table 1).
Examples 11 to 15
A series of silicon-carbon negative electrode materials are provided, which are prepared according to the preparation method of example 1, and are different from example 1 in that the mass of nano-silicon in step S1 is replaced by the particle size (D v50 ) Nano silicon of 25nm, 30nm, 50nm, 150nm and 500nm respectively, and other preparation process conditions (such as temperature rising rate and the like) are changed to ensure I c /I a The value of (2) is unchanged.
Examples 16 to 17
A series of silicon carbon negative electrode materials are provided, and are prepared according to the preparation method of example 1, which is different from example 1 in that in step S2, the types of amorphous carbon precursors are respectively replaced by phenolic resin and sucrose, and the addition amount is changed to ensure that the thickness of the amorphous carbon layer is the same as that of example 1.
Examples 18 to 24 and comparative examples 1 to 5
Providing a series of silicon-carbon anode materials, preparing according to the preparation method of the example 1, and adjusting parameters of the preparation process (such as heating rate, reaction temperature, time and the like) in the example 1 to obtain different I a /I b 、I c /I a Silicon carbon negative electrode material of (2).
Examples 25 to 26
A series of silicon carbon negative electrode materials are provided and prepared according to the preparation method of example 1, differing from example 1 in the graphite D v50 5 μm and 25 μm respectively.
Parameters of the silicon-carbon anode material prepared by the above embodiment of the present invention are shown in table 1 in detail.
In Table 1, particle diameter D of the silicon carbon negative electrode material v50 The test method specifically comprises the following steps: dispersing a silicon-carbon negative electrode material sample in dispersing agent ethanol, performing ultrasonic treatment for 30min, adding the sample into a Markov particle size tester, and testing the D of the silicon-carbon negative electrode material v50 。
Crystal face peak intensity I a 、I b 、I c Calculated from the XRD pattern obtained by cukα ray scanning. In the XRD pattern, the (111) plane peak intensity of silicon at 2θ=28.4° is denoted as I a The method comprises the steps of carrying out a first treatment on the surface of the The (002) plane peak intensity of graphite at 2θ=26.5°, denoted as I b The method comprises the steps of carrying out a first treatment on the surface of the The (111) plane peak intensity of silicon carbide at 2θ=35.6° is denoted as I c 。
Powder compaction density (in g/cm) of silicon carbon negative electrode material 3 ): the test is carried out by referring to a test method in a standard GB/T24533-2009, wherein the test pressure is 3T, and the test time is 30s.
Powder resistivity (unit: Ω×cm) of the silicon carbon anode material: the test was performed using a resistivity tester, wherein the test pressure was 2T.
Specific surface area of the silicon carbon negative electrode material (BET for short, unit is m 2 /g): and testing by using a specific surface area analyzer.
Table 1 parameters of the silicon carbon anode materials prepared in examples and comparative examples
Performance testing
The silicon-carbon anode materials prepared in the above examples and comparative examples are assembled into a lithium ion battery, and the electrochemical performance of the lithium ion battery is tested, and specific test items and test methods are as follows:
the specific assembly process of the lithium ion battery comprises the following steps: mixing the prepared anode material with SP, SBR, CMC according to a mass ratio of 80:10:5:5, using ultrapure water as a solvent to mix the mixture into slurry, uniformly coating the slurry on copper foil, and carrying out vacuum drying at 120 ℃ for 12 hours to prepare a battery pole piece; then lithium sheet is used as a counter electrode, and the molar concentration is 1mol/L of LiPF 6 The four-component mixed solvent (according to the mass ratio EC: DMC: EMC: fec=3:4:2:1) is an electrolyte, a polypropylene film is used as a diaphragm, and the CR2032 button half cell is assembled in a vacuum glove box.
1. And (3) testing the cycle performance: discharging the button half cell to 5mV at constant current 0.1C, charging the constant current 0.1C to 1.5V, likewise discharging the button half cell to 5mV at constant current 0.1C, charging the button half cell to 1.5V at constant current 0.1C, recording the first-turn discharge capacity C1 (mAh/g) at the moment, and calculating the first coulomb efficiency (%); the discharge capacity of the cells was tested after 99 repetitions, recorded as C100 (mAh/g), and the capacity retention (100%) over 100 weeks of cycling was calculated = (C1-C100)/C1 x 100%, see in particular table 2.
2. And (3) multiplying power performance test: (1) discharging the button half cell to 5mV at constant current of 0.1C, charging the button half cell to 1.5V at constant current of 0.1C, and recording discharge capacity C1 (mAh/g) of the cell at the moment; (2) performing cyclic charge and discharge according to the step (1), testing the discharge capacity C2 (mAh/g) of the battery at the moment after 10 cycles, then increasing the current to 0.2C, testing the discharge capacity C3 (mAh/g) of the battery at the moment after 20 cycles (calculated by taking the first cycle as the initial cycle number), then increasing the current to 0.3C, testing the discharge capacity C4 (mAh/g) of the battery at the moment after 30 cycles, then increasing the current to 0.5C, testing the discharge capacity C5 (mAh/g) of the battery at the moment after 40 cycles, then increasing the current to 1C, and testing the discharge capacity C6 (mAh/g) of the battery at the moment after 10 cycles; (3) calculating a capacity retention (%) = (C1-C2)/C1 of 100% of the battery after 10 cycles at 0.1C; capacity retention (%) = (C2-C3)/C2 of the battery 100% after 10 cycles at 0.2C; the capacity retention (%) = (C3-C4)/C3 of the battery after 10 cycles of 0.3C down-cycle is 100%; the capacity retention (%) = (C4-C5)/C4 =100% of the battery after 10 cycles of 0.5C down cycle; the capacity retention (%) = (C5-C6)/C5 x 100% of the cells after 10 cycles at 1C, and the test results are shown in table 2.
Table 2 performance of lithium ion batteries prepared using the silicon carbon negative electrode materials of examples and comparative examples
From the results of the above examples and comparative examples, it can be seen that:
according to the invention, the amorphous carbon is coated on the surface, so that the cycling stability of the lithium ion battery is improved. The first-circle discharge capacity of the lithium ion battery prepared by the silicon-carbon negative electrode material is more than 500 mAh/g; after 100 circles of circulation, the capacity retention rate of the battery is still above 80%, and can reach 93%; the capacity retention rate of the battery is above 30% and can reach 42% under the condition of 5C current density.
The results of comparative examples 1 to 5 show that the ratio relationship between specific crystal plane intensities in graphite, silicon carbide and carbon materials is not in the protection scope of the invention, and the capacity, the cycle stability or the rate capability of the lithium ion battery prepared by the silicon-carbon negative electrode material is significantly inferior to that of each example of the invention.
The comparison results of the above comparative examples and examples further demonstrate that: the crystal structure composition of the graphite-silicon carbide-silicon core material of the silicon-carbon anode material is regulated, so that the structural stability of the anode material can be further improved, the capacity exertion of the anode material is improved, and the cycle stability and the multiplying power performance of the prepared lithium ion battery are obviously improved.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. The silicon-carbon anode material is characterized by comprising an inner core and a functional layer, wherein the functional layer is arranged on the surface of the inner core, the inner core comprises graphite, the surface of the graphite is provided with silicon carbide and silicon, and the functional layer comprises amorphous carbon;
the silicon-carbon anode material meets the following conditions: i a /I b ＝0.02～0.10，I c /I a ＝0.10～0.30；
Wherein I is a Is the (111) crystal plane peak intensity of silicon, I b Is the (002) crystal face peak intensity of graphite, I c The (111) plane peak intensity of silicon carbide.
2. The silicon-carbon negative electrode material according to claim 1, wherein the silicon-carbon negative electrode material satisfies at least one of the following conditions:
(1)I a /I b ＝0.04～0.08；
(2)I c /I a ＝0.15～0.25；
(3) The weight ratio of graphite, silicon carbide and silicon is 1: (0.9-1.8): (0.1 to 0.2);
(4) Specific surface area of 1-3 m 2 /g；
(5) The compacted density of the powder under the pressure of 3T is 1.5 to 2.0g/cm 3 ；
(6) The powder resistivity under the pressure of 2T is 0.003-0.005 omega cm;
(7)D V50 is 5-25 mu m, D v50 And accumulating the particle size corresponding to the volume percentage of the silicon-carbon anode material reaching 50 percent.
3. The silicon-carbon negative electrode material according to claim 1, wherein the functional layer has a thickness of 10 to 80nm.
4. A silicon-carbon anode material according to claim 3, wherein the functional layer has a thickness of 30 to 70nm.
5. The method for preparing a silicon-carbon anode material as claimed in any one of claims 1 to 4, comprising the steps of:
s1, mixing graphite and silicon, and embedding silicon carbide and silicon on the surface of the graphite through a melting reaction in an inert atmosphere;
s2, mixing the product obtained in the step S1 and the precursor of amorphous carbon, and carbonizing in an inert atmosphere to obtain the silicon-carbon anode material.
6. The method for preparing a silicon-carbon negative electrode material according to claim 5, wherein the specific flow of melting in step S1 is: heating to 1500-1600 ℃ at a heating rate of 1-10 ℃/min, keeping the temperature for 1-3 hours, and then cooling to 20-30 ℃ at a speed of 10-20 ℃/min.
7. The method for preparing a silicon-carbon negative electrode material according to claim 5, wherein the specific process of the carbonization treatment in step S2 is as follows: heating to 800-1000 ℃ at a heating rate of 1-10 ℃/min, preserving heat for 1-3 h, and then naturally cooling.
8. The method of claim 5, wherein the amorphous carbon precursor comprises at least one of glucose, sucrose, soluble starch, cyclodextrin, pitch, phenolic resin, epoxy resin, carboxymethyl cellulose, and citric acid.
9. A lithium ion battery comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode membrane disposed on at least one side of the negative electrode current collector, wherein the negative electrode membrane comprises the silicon-carbon negative electrode material of any one of claims 1 to 4 or the silicon-carbon negative electrode material prepared by the preparation method of any one of claims 5 to 8.
10. An electrical device comprising the lithium-ion battery of claim 9.
CN202310795105.XA 2023-06-30 2023-06-30 Silicon-carbon negative electrode material, preparation method thereof, lithium ion battery and power utilization device Pending CN116632212A (en)

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