A lithium ion battery negative electrode material beta-SnSb / HCS / C and a preparation method thereof

Abstract

The application discloses a kind of lithium ion battery negative electrode material β-SnSb / HCS / C and preparation method thereof, it is related to lithium ion battery material technical field, the negative electrode material is the carbon layer obtained after β-SnSb alloy and spherical hard carbon are blended;Its preparation method is as follows: preparation carbon source aqueous solution, stirring reaction is added dehydrating agent, after appearing colloidal substance in solution, continue to add dehydrating agent and heat, stirring reaction, filtration, carbonization treatment, obtain HCS;Tin, antimony-containing metal ion solution is added dropwise to alkaline NaBH4 solution, water bath reaction, obtain β-SnSb alloy;Under inert atmosphere, HCS and β-SnSb are mixed and ground, to obtain β-SnSb / HCS composite material;Coated carbon source is mixed with β-SnSb / HCS composite material, and carbonization reaction is carried out under inert atmosphere, to obtain β-SnSb / HCS / C composite material.The application is simple to prepare, and stable in performance, and excellent electrochemical performance is shown when it is applied to lithium ion battery, with the advantages of high specific capacity, high first charge-discharge efficiency, excellent rate performance, good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery anode material β-SnSb / HCS / C and its preparation method. Background Technology

[0002] Compared to other rechargeable batteries, lithium-ion batteries have gained widespread application in various portable electronic products and electric vehicles due to their advantages such as high specific capacity, high charging efficiency, good temperature characteristics, low self-discharge rate, small charging heat effect, and no memory effect. They have attracted considerable attention in today's society and have a very bright application prospect. The performance of lithium-ion batteries is determined by factors such as the performance of their electrode materials, electrolyte performance, and battery structure. Among these, the electrode materials directly determine the capacity and cycle life of the lithium battery. Although the commonly used graphite anode material has approached its theoretical specific capacity (372 mAh / g), it still cannot meet the growing demand of human society for high-energy-density and environmentally friendly rechargeable batteries. Existing low-capacity anode materials have gradually become one of the limiting factors for improving the energy density of lithium-ion batteries.

[0003] Silicon-based, tin-based, and antimony-based anode materials all exhibit high charge-discharge specific capacities. Tin's theoretical lithium intercalation specific capacity is 994 mAh / g, three times that of commercial graphite carbon materials. The final product of Sn-Li alloying is Li. 22 Sn5, with a lithium intercalation potential between 0.3-0.6V, avoids the formation of lithium dendrites. However, due to the significant volume effect of elemental Sn during the intercalation / deintercalation process, and the decreased toughness of the alloy formed by Sn and lithium, lithium ions are difficult to extract. Furthermore, the active material is prone to pulverization and detachment during the intercalation / deintercalation process, ultimately losing electrical contact with the current collector and becoming deactivated. Therefore, directly using metallic Sn as a negative electrode material for lithium-ion batteries is severely limited. Antimony metal has a theoretical specific capacity of 660mAh / g and an intercalation / deintercalation voltage plateau of approximately 0.8V, providing a relatively stable operating voltage and high charge / discharge specific capacity. However, antimony metal as a negative electrode material for lithium-ion batteries also faces serious volume expansion problems, large irreversible capacity, low initial efficiency, and poor cycle stability, similarly limiting its application in lithium-ion battery negative electrode materials.

[0004] Tin-antimony alloys combine the advantages of both tin-based and antimony-based anode materials, possessing the former's high specific capacity and the latter's stable voltage plateau. Different lithium insertion / extraction potentials allow the two materials to act as buffers for each other during charge and discharge, improving both the charge / discharge specific capacity and cycle stability. However, the preparation of this alloy generates tin oxide and antimony oxide, leading to an irreversible increase in capacity and a decrease in initial efficiency.

[0005] Hard carbon materials exhibit a high specific capacity of 200-600 mAh / g within a voltage range of 1.5-0 V. The potential of hard carbon mainly consists of two states: a sloping state with a specific capacity of approximately 150-250 mAh / g between 1.0-0.1 V, and a stable region with a specific capacity of approximately 100-400 mAh / g. Furthermore, hard carbon materials do not have a significant lithium insertion / extraction potential, so lithium plating does not occur at the negative electrode during charge and discharge. From a microscopic perspective, when lithium ions enter hard carbon, they are mainly stored in the porous structure of hard carbon, rather than the layered structure similar to graphite. Hard carbon materials have excellent rate performance, but their drawbacks include low initial efficiency and low tap density. Therefore, preparing ideal hard carbon materials with high initial efficiency and high tap density is of great significance. Spherical hard carbon materials are ideal. However, spherical hard carbon materials are difficult to prepare through the direct pyrolysis of organic or polymer precursors. Summary of the Invention

[0006] Based on the technical problems existing in the background technology, the present invention proposes a lithium-ion battery anode material β-SnSb / HCS / C and its preparation method.

[0007] The lithium-ion battery anode material β-SnSb / HCS / C proposed in this invention is obtained by blending β-SnSb alloy and spherical hard carbon, and then coating the surface of the blend with a carbon layer.

[0008] Preferably, the mass ratio of the β-SnSb alloy to the spherical hard carbon is 1:5-10.

[0009] This invention also proposes a method for preparing the above-mentioned lithium-ion battery anode material β-SnSb / HCS / C, comprising the following steps:

[0010] S1, HCS preparation: Prepare a carbon source aqueous solution, add a dehydrating agent to it and stir to react. After a gel-like substance appears in the solution, continue to add the dehydrating agent and heat up, stir to react, cool to room temperature, filter, vacuum dry, and then carbonize to obtain spherical hard carbon material HCS.

[0011] Preparation of S2 and β-SnSb: NaBH4 was dissolved in NaOH solution to obtain an alkaline NaBH4 solution; tin source and antimony source were dissolved in water to obtain a metal ion solution, which was ultrasonically dispersed and then added dropwise to the alkaline NaBH4 solution. The mixture was stirred, reacted in a water bath, filtered, washed, and dried to obtain the β-SnSb alloy.

[0012] S3, β-SnSb / HCS preparation: Under an inert atmosphere, spherical hard carbon material HCS and β-SnSb alloy were mixed and ground to obtain β-SnSb / HCS composite material;

[0013] S4, Preparation of β-SnSb / HCS / C: The coated carbon source is mixed with the β-SnSb / HCS composite material and subjected to a high-temperature carbonization reaction under an inert atmosphere to coat the surface of the β-SnSb / HCS composite material with a carbon layer, thus obtaining the β-SnSb / HCS / C composite material.

[0014] Preferably, in S1, the carbon source is one or more of glucose, sucrose, fructose, and lactose; and the dehydrating agent is one or more of ethanol, acetone, glycerol, n-butanol, and tert-butanol.

[0015] Preferably, in S1, the amount of dehydrating agent added is 12-18 vt% of the volume of the carbon source aqueous solution; the mass ratio of the two additions of dehydrating agent is 1:1.8-2.5; after the second addition of dehydrating agent, the temperature is raised to 380-420℃ and the reaction is stirred for 1-2 hours.

[0016] Preferably, in S1, the carbonization treatment is carried out under an inert atmosphere by heating to 800-1000℃ at a rate of 2-3℃ / min and holding for 12-20 hours.

[0017] Preferably, in S2, the tin source is SnCl2·2H2O, the antimony source is SbCl3, and the concentration of the metal ion solution is 0.07-0.15 mol / L. Sn :n Sb = 1:1; the pH of the alkaline NaBH4 solution is 9-12, and the concentration of NaBH4 in the solution is 0.07-0.15 mol / L; preferably, the reaction temperature of the water bath reaction is 80-90℃, and the reaction time is 4-6h.

[0018] Preferably, in S3, the mass ratio of HCS to β-SnSb is 5-10:1.

[0019] Preferably, in S4, the carbon source for coating is one or more of coal tar pitch, petroleum residue asphalt, mesophase asphalt, polyacrylonitrile, epoxy resin, and phenolic resin; preferably, the amount of carbon source added is 5-8 wt% of the mass of the β-SnSb / HCS composite material.

[0020] Preferably, in S4, the carbonization reaction is carried out under an inert atmosphere, with the temperature increased to 1000-1200℃ at a rate of 2-3℃ / min, and held at that temperature for 10-20 hours.

[0021] Beneficial Effects: This invention prepares nanoscale spherical hard carbon HCS via a hydrothermal method, and β-SnSb nanoalloy materials via a chemical reduction co-precipitation method. HCS and β-SnSb are then mixed through grinding, and finally coated with carbon to form a carbon shell on the material surface, resulting in the composite anode material β-SnSb / HCS / C. While existing technologies show high capacity for Sn and Sb, material pulverization during cycling leads to poor cycle performance. The β-SnSb prepared in this invention alleviates the pulverization problem. However, the oxides produced by the reaction reduce the initial efficiency of the material. Utilizing HCS and carbon coating can effectively improve the initial efficiency and suppress the poor cycle performance caused by material volume expansion and pulverization. This invention is simple to prepare, has stable performance, and shows good application prospects. When this β-SnSb / HCS / C composite anode material is applied to lithium-ion batteries, it exhibits excellent electrochemical performance, with advantages such as high specific capacity, high initial charge-discharge efficiency, excellent rate performance, and good cycle performance. Attached Figure Description

[0022] Figure 1 The first charge-discharge curves of lithium-ion batteries prepared using the negative electrode materials of Example 1 and Comparative Example 1 are shown.

[0023] Figure 2 The graphs show the cycle retention rates of lithium-ion batteries using the negative electrode materials prepared in Example 1 and Comparative Example 2, respectively. Detailed Implementation

[0024] The technical solution of the present invention will now be described in detail through specific embodiments.

[0025] Example 1

[0026] 1) Preparation of β-SnSb / HCS / C anode material for lithium-ion batteries

[0027] 1.1) Preparation of spherical hard carbon HCS by hydrothermal method: Glucose was added to deionized water and stirred to prepare a 1 mol / L glucose solution. 1 L of glucose solution was added to 50 mL of ethanol solution with a mass fraction of more than 90% for dehydration. The mixture was stirred and reacted for 30 min. After a gel-like substance appeared in the solution, 100 mL of the ethanol solution was added. The mixture was heated to 400℃ and reacted for 1.5 h. After cooling to room temperature, the precipitate was stirred, filtered, and dried under vacuum. Then, under an inert atmosphere, the temperature was increased to 900℃ at 2.5℃ / min and maintained for 15 h for carbonization treatment to obtain the desired spherical hard carbon material HCS.

[0028] 1.2) Preparation of β-SnSb by chemical reduction coprecipitation: SnCl2·2H2O and SbCl3 were weighed out in a 1:1 molar ratio and dissolved in deionized water to prepare 0.1 mol / L solutions. At the same time, a 0.1 mol / L alkaline NaBH4 solution was prepared (the pH was adjusted to 11 by adding NaOH). The SnCl2·2H2O and SbCl3 mixed solution was ultrasonically vibrated for 40 min and then added dropwise to the NaBH4 solution with stirring to form a suspension. Stirring was continued for 20-40 min to form a black precipitate. The mixed solution was placed in a constant temperature water bath at 85℃ for 5 h. The precipitate was filtered and washed several times with deionized water and ethanol solution. The black precipitate was vacuum dried at 105℃ for 10 h to obtain the target product β-SnSb.

[0029] 1.3) Grinding, mixing, coating and carbonization: The prepared HCS sample and β-SnSb sample were placed in a mortar at a mass ratio of 10:1, placed in a glove box, and ground and mixed evenly under inert conditions. The evenly mixed β-SnSb / HCS sample was taken and mixed evenly with epoxy resin at a mass ratio of 100:5. After carbonization and cooling at 1050℃, the desired β-SnSb / HCS / C composite anode material was obtained.

[0030] 2) Preparation of the negative electrode and assembly and testing of the half-cell

[0031] 2.1) The prepared β-SnSb / HCS / C composite negative electrode material was mixed with conductive carbon black in a ratio of 8:2, and then ground in a mortar until the mixture was homogeneous.

[0032] 2.2) Take the binder into the mixing tank, add the ground mixed powder from 2.1), and mix.

[0033] 2.3) Coat the slurry evenly on the copper foil, dry at 80°C for 12 hours, and prepare the negative electrode sheet using a tablet press;

[0034] 2.4) The negative electrode obtained in (2.3) is used to assemble a half cell in a glove box under an argon atmosphere with lithium metal sheet, nickel foam, separator, positive and negative electrode shells.

[0035] 2.5) Electrochemical performance analysis was performed on the assembled half-cell to obtain the charge-discharge curves of the prepared material.

[0036] The material obtained in this embodiment has an initial charge capacity of 441 mAh / g and an initial efficiency of 89% at a 0.1C rate. After 100 cycles, the reversible capacity reaches as high as 439 mAh / g.

[0037] Example 2

[0038] 1) Preparation of β-SnSb / HCS / C anode material for lithium-ion batteries

[0039] Compared with Example 1, the only difference is that in step 1.3), the mass ratio of HCS sample to β-SnSb sample is 5:1.

[0040] 2) Preparation of the negative electrode and assembly and testing of the half-cell: Same as in Example 1.

[0041] Compared with Example 1, the material obtained in this example has an initial charge capacity of 591 mAh / g and an initial efficiency of 85% at a 0.1C rate. After 100 cycles, the reversible capacity is 576 mAh / g.

[0042] Example 3

[0043] 1) Compared with Example 1, the only difference is that in step 1.3), the mass ratio of HCS sample to β-SnSb sample is 8:1; the carbon source for coating is coal tar pitch, and the mass ratio of β-SnSb / HCS sample to coal tar pitch is 100:5.

[0044] 2) Preparation of the negative electrode and assembly and testing of the half-cell: Same as in Example 1.

[0045] Example 4

[0046] 1) Compared with Example 1, the only difference is that in step 1.3), the carbon source for coating is phenolic resin, and the mass ratio of β-SnSb / HCS sample to phenolic resin is 100:8.

[0047] 2) Preparation of the negative electrode and assembly and testing of the half-cell: Same as in Example 1.

[0048] Comparative Example 1

[0049] 1) Compared with Example 1, the only difference is that step 1.2) is not included. The specific step is to mix the spherical hard carbon material HCS obtained in step 1.1) with epoxy resin in a ratio of 100:5, carbonize and cool at 1050°C to obtain the desired HCS / C composite negative electrode material.

[0050] 2) Preparation of the negative electrode and assembly and testing of the half-cell: Same as in Example 1.

[0051] Comparative Example 2

[0052] 1) Compared with Example 1, the only difference is that step 1.1) is not included. The specific step is to mix the β-SnSb obtained in step 1.2) with epoxy resin in a ratio of 100:5, carbonize and cool at 1050°C to obtain the desired HCS / C composite negative electrode material.

[0053] 2) Preparation of the negative electrode and assembly and testing of the half-cell: Same as in Example 1.

[0054] The raw material ratios and electrochemical performance test results in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1; the first charge-discharge curves of the lithium-ion batteries prepared with the negative electrode materials in Examples 1 and Comparative Example 1 are shown in Figure 1. Figure 1 As shown, the cycle retention rate curves of Example 1 and Comparative Example 2 are as follows. Figure 2 As shown.

[0055] Table 1. Raw material ratios and electrochemical performance test results in the examples and comparative examples.

[0056]

[0057] From Table 1 and Figure 1-2 Electrochemical performance tests showed that spherical hard carbon HCS alone exhibited excellent cycle performance but suffered from low capacity; SnSb composite anode materials had high specific capacity but poor cycle performance. By combining spherical hard carbon HCS and β-SnSb, and then modifying the surface of the materials through coating, the resulting β-SnSb / HCS / C material exhibited high capacity and excellent cycle performance.

[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium-ion battery anode material β-SnSb / HCS / C, characterized in that, It is obtained by blending β-SnSb alloy with spherical hard carbon and then coating its surface with a carbon layer; The mass ratio of the β-SnSb alloy to the spherical hard carbon is 1:5-10; The amount of carbon source added is 5-8 wt% of the mass of the β-SnSb / HCS composite material; Includes the following steps: S1, HCS preparation: Prepare a carbon source aqueous solution, add a dehydrating agent to it and stir to react. After a gel-like substance appears in the solution, continue to add the dehydrating agent and heat up, stir to react, cool to room temperature, filter, vacuum dry, and then carbonize to obtain spherical hard carbon material HCS. Preparation of S2 and β-SnSb: NaBH4 was dissolved in NaOH solution to obtain an alkaline NaBH4 solution; tin source and antimony source were dissolved in water to obtain a metal ion solution, which was ultrasonically dispersed and then added dropwise to the alkaline NaBH4 solution. The mixture was stirred, reacted in a water bath, filtered, washed, and dried to obtain the β-SnSb alloy. S3, β-SnSb / HCS preparation: Under an inert atmosphere, spherical hard carbon material HCS and β-SnSb alloy were mixed and ground to obtain β-SnSb / HCS composite material; S4, Preparation of β-SnSb / HCS / C: The coated carbon source is mixed with the β-SnSb / HCS composite material and subjected to a high-temperature carbonization reaction under an inert atmosphere to coat the surface of the β-SnSb / HCS composite material with a carbon layer, thus obtaining the β-SnSb / HCS / C composite material.

2. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S1, the carbon source is one or more of glucose, sucrose, fructose, and lactose; the dehydrating agent is one or more of ethanol, acetone, glycerol, n-butanol, and tert-butanol.

3. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S1, the amount of dehydrating agent added is 12-18 vt of the volume of the carbon source aqueous solution; the mass ratio of the dehydrating agent added before and after is 1:1.8-2.5; after the second addition of the dehydrating agent, the temperature is raised to 380-420℃ and the reaction is stirred for 1-2 hours.

4. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S1, the carbonization process involves heating to 800-1000℃ at a rate of 2-3℃ / min under an inert atmosphere and holding for 12-20 hours.

5. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S2, the tin source is SnCl2·2H2O, the antimony source is SbCl3, and the concentration of the metal ion solution is 0.07-0.15 mol / L. Sn :n Sb =1:1; the pH of the alkaline NaBH4 solution is 9-12, and the concentration of NaBH4 in the solution is 0.07-0.15 mol / L; the reaction temperature of the water bath reaction is 80-90℃, and the reaction time is 4-6h.

6. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S3, the mass ratio of HCS to β-SnSb is 5-10:

1.

7. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S4, the carbon source being coated is one or more of the following: coal tar pitch, petroleum residue asphalt, mesophase asphalt, polyacrylonitrile, epoxy resin, and phenolic resin.

8. The method for preparing the lithium-ion battery anode material β-SnSb / HCS / C according to claim 1, characterized in that, In S4, the carbonization reaction is carried out under an inert atmosphere, with the temperature increased to 1000-1200℃ at a rate of 2-3℃ / min, and held for 10-20 hours.

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