Hard carbon composite negative electrode material, preparation method thereof and lithium ion battery

Abstract

The application provides a hard carbon composite negative electrode material and a preparation method and a lithium ion battery thereof, and relates to the technical field of lithium ion batteries.The preparation method comprises the following steps: adding nano silicon, a boron source and a surfactant into an alcohol solvent, performing ultrasonic dispersion, and obtaining a suspension; adding a titanium source into the suspension, and obtaining a mixed reaction solution; placing the mixed reaction solution into a hydrothermal kettle, performing hydrothermal treatment at 180-250 DEG C, and obtaining a hydrothermal product; mixing the hydrothermal product with a hard carbon precursor, and obtaining a mixture; performing calcination on the mixture at 1000-1500 DEG C under an inert atmosphere, and obtaining the hard carbon composite negative electrode material.The preparation method of the hard carbon composite negative electrode material provided by the application uses nano silicon, a boron source and a titanium source as raw materials, and the prepared composite negative electrode material is coated with TiC on the outside of the nano silicon, which not only helps to improve the conductivity of the composite negative electrode material, but also effectively alleviates the volume effect of silicon in the charging and discharging process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a hard carbon composite negative electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] At present, lithium ion batteries are widely used in portable electronic devices, communication devices, electric vehicles and other fields due to their high energy density, no memory effect and other advantages. With the development and progress of science and technology, the commercial graphite negative electrode of lithium ion batteries is difficult to meet the user's demand for high performance of lithium ion batteries, and finding a new generation of negative electrode material with high capacity, high safety and low manufacturing and using cost has become the focus of research in the academic and industrial circles.

[0003] Among them, silicon is widely concerned due to its high specific capacity and abundant reserves; however, when silicon is used as a negative electrode material for lithium ion batteries, the volume effect is significant during charging and discharging, and serious volume change easily causes the negative electrode material to pulverize, resulting in poor cycle performance. SUMMARY

[0004] The technical problem to be solved by the present application is to solve the problem of poor cycle performance of silicon-based negative electrode materials in the prior art. The present application provides a preparation method of a hard carbon composite negative electrode material, which uses nanosilicon, a boron source and a titanium source as raw materials, first prepares a hydrothermal product by a hydrothermal method, then mixes the hydrothermal product with a hard carbon precursor and calcines to obtain a hard carbon Si / TiC-TiB2 composite negative electrode material. The composite negative electrode material has small volume effect, solving the problem of poor cycle performance of silicon-based negative electrode materials in the prior art.

[0005] The technical solution adopted by the present application to solve the technical problem is:

[0006] A preparation method of a hard carbon composite negative electrode material, comprising the following steps:

[0007] S1: adding nanosilicon, a boron source and a surfactant into an alcohol solvent, ultrasonic dispersion to obtain a suspension;

[0008] S2: adding a titanium source into the suspension to obtain a mixed reaction liquid;

[0009] S3: placing the mixed reaction liquid in a hydrothermal kettle and performing hydrothermal treatment at 180-250 DEG C to obtain a hydrothermal product;

[0010] S4: mixing the hydrothermal product with a hard carbon precursor to obtain a mixture;

[0011] S5: calcining the mixture at 1000-1500 DEG C under an inert atmosphere to obtain a hard carbon composite negative electrode material.

[0012] Optionally, the titanium source is selected from at least one of tetrabutyl titanate and isopropyl titanate.

[0013] Optionally, the boron source is boric acid.

[0014] Optionally, the hard carbon precursor is selected from at least one of starch, sucrose and phenolic resin.

[0015] Optionally, the surfactant is selected from at least one of CTAB, P123 and PVP.

[0016] Optionally, the molar ratio of the nano-silicon, the boron source and the titanium source is (3-5):(3.5-6.5):(4-7).

[0017] Optionally, the mass ratio of the surfactant and the nano-silicon is (2-7.5):(3-16.5).

[0018] Optionally, the mass ratio of the hard carbon precursor and the nano-silicon is (30-45):(1-3).

[0019] Another object of the present application is to provide a hard carbon composite negative electrode material prepared by the preparation method of the hard carbon composite negative electrode material as described above.

[0020] Still another object of the present application is to provide a lithium ion battery comprising the hard carbon composite negative electrode material as described above,

[0021] The present application has the following beneficial effects:

[0022] The preparation method of the hard carbon composite negative electrode material provided by the present application uses nano-silicon, a boron source and a titanium source as raw materials, first prepares a hydrothermal product by a hydrothermal method, then mixes the hydrothermal product with a hard carbon precursor and calcines to obtain a hard carbon Si / TiC-TiB2 composite negative electrode material. The composite negative electrode material, by introducing nano-silicon to improve the capacity, and by the TiC coated on the outside of the nano-silicon, not only helps to improve the conductivity of the composite negative electrode material, but also effectively alleviates the volume effect of silicon in the charging and discharging process, avoids the pulverization of the negative electrode material, and improves the cycle performance of the composite negative electrode material. In addition, the introduction of TiB2 in the composite negative electrode material helps to further improve its electrochemical performance and the stability of the structure, and further improves the stability of the cycle performance. DETAILED DESCRIPTION

[0023] The present application will now be further described in detail. The examples described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application. Based on the examples of the present application, all other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0024] To address the poor cycle performance of silicon-based anode materials in existing technologies, this invention provides a method for preparing a hard carbon composite anode material, which includes the following steps:

[0025] S1: Add nano-silicon, boron source and surfactant to alcohol solvent, disperse by ultrasonication to obtain suspension;

[0026] S2: Add a titanium source to the suspension to obtain a mixed reaction solution;

[0027] S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 180-250℃ to obtain the hydrothermal product;

[0028] S4: Mix the hydrothermal products with the hard carbon precursor to obtain a mixture;

[0029] S5: The mixture is calcined at 1000-1500℃ under an inert atmosphere to obtain a hard carbon composite anode material.

[0030] In this invention, the preferred alcohol solvent in step S1 is ethanol. By adding nano-silicon, boron source, and surfactant to the ethanol solvent and ultrasonically dispersing them, the nano-silicon and boron source are uniformly mixed. Furthermore, during the hydrothermal treatment, the titanium source reacts to generate titanium dioxide. Due to the presence of the surfactant, the generated titanium dioxide can uniformly coat the surface of the nano-silicon. Specifically, the hydrothermal product obtained in step S3 is a Si / TiO2-boron source composite material, which includes nano-silicon coated with a TiO2 layer and boric acid. Because step S1 simultaneously mixes the nano-silicon, boron source, and surfactant... The activator is ultrasonically dispersed, and the nano-silicon and boron source are uniformly dispersed. Therefore, after the hydrothermal reaction, the boron source is uniformly dispersed in the hydrothermal product. The hydrothermal product is further mixed with the hard carbon precursor, and during calcination in an inert atmosphere, the hydrothermal product reacts with the hard carbon precursor. The nano-silicon avoids the reaction of titanium dioxide with carbon to form TiC, resulting in a TiC coating layer on the surface of the nano-silicon. With the increase of calcination time, the unreacted carbon dioxide in the hydrothermal product further reacts with the boron source to form TiB2, thereby obtaining a hard carbon Si / TiC-TiB2 composite material, denoted as hard carbon composite anode material.

[0031] The present invention provides a method for preparing a hard carbon composite anode material. Using nano-silicon, boron source, and titanium source as raw materials, a hydrothermal product is first prepared via a hydrothermal method. Then, the hydrothermal product is mixed with a hard carbon precursor and calcined to obtain a hard carbon Si / TiC-TiB2 composite anode material. This composite anode material improves capacity by introducing nano-silicon. Furthermore, the TiC coating on the outside of the nano-silicon not only enhances the conductivity of the composite anode material but also effectively mitigates the volume effect of silicon during charge and discharge, preventing pulverization of the anode material and improving its cycle performance. In addition, the introduction of TiB2 further improves its electrochemical performance, structural stability, and cycle performance stability.

[0032] Specifically, the titanium source of the present invention is preferably selected from at least one of tetrabutyl titanate and isopropyl titanate, so as to generate titanium dioxide through the titanium source during hydrothermal treatment.

[0033] The preferred boron source in this invention is boric acid. On the one hand, boron is introduced into the system through this boron source. On the other hand, boric acid inhibits the hydrolysis of the titanium source, so that the titanium source can be hydrothermally treated to obtain titanium dioxide with a nanostructure and uniform dispersion, thereby improving the stability of the composite anode material performance.

[0034] To balance the electrochemical performance and cycle performance of the composite anode material, the present invention preferably selects the hard carbon precursor from at least one of starch, sucrose, and phenolic resin.

[0035] To ensure the uniformity of the dispersion of nano-silicon and boron source, the surfactant of the present invention is preferably selected from at least one of CTAB, P123, and PVP.

[0036] Furthermore, the present invention preferably has a molar ratio of nano-silicon, boron source and titanium source of (3-5):(3.5-6.5):(4-7), a preferred mass ratio of surfactant to nano-silicon of (2-7.5):(3-16.5), and a preferred mass ratio of hard carbon precursor to nano-silicon of (30-45):(1-3).

[0037] Another object of the present invention is to provide a hard carbon composite anode material, which is prepared by the preparation method of hard carbon composite anode material as described above.

[0038] The hard carbon composite anode material provided by this invention uses nano-silicon, boron source, and titanium source as raw materials. First, a hydrothermal product is prepared via a hydrothermal method. Then, the hydrothermal product is mixed with a hard carbon precursor and calcined to obtain a hard carbon Si / TiC-TiB2 composite anode material. This composite anode material improves capacity by introducing nano-silicon. Furthermore, the TiC coating on the outside of the nano-silicon not only helps improve the conductivity of the composite anode material but also effectively alleviates the volume effect of silicon during charge and discharge, preventing pulverization of the anode material and improving its cycle performance. In addition, the introduction of TiB2 further enhances its conductivity, structural stability, and cycle performance stability.

[0039] Another object of the present invention is to provide a lithium-ion battery comprising the hard carbon composite anode material as described above.

[0040] The lithium-ion battery provided by this invention uses the hard carbon composite anode material described above. This hard carbon composite anode material uses nano-silicon, boron source, and titanium source as raw materials. First, hydrothermal products are prepared by hydrothermal method. Then, the hydrothermal products are mixed with hard carbon precursor and calcined to obtain a hard carbon Si / TiC-TiB2 composite anode material. This composite anode material improves capacity by introducing nano-silicon. The TiC coating on the outside of the nano-silicon not only helps to improve the conductivity of the composite anode material, but also effectively alleviates the volume effect of silicon during charge and discharge, avoids pulverization of the anode material, and improves the cycle performance of the composite anode material. In addition, the introduction of TiB2 into this composite anode material helps to further improve its electrochemical performance, improve structural stability, and further improve cycle performance stability, thereby improving the conductivity and cycle performance of the lithium-ion battery.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0042] Example 1

[0043] This embodiment provides a method for preparing a hard carbon composite anode material, including the following steps:

[0044] S1: 2.1 g (0.075 mol) of nano-silicon, 9.28 g (0.15 mol) of boric acid and 1.02 g of PVP were added to ethanol solvent and ultrasonically dispersed for 2 h to obtain a suspension;

[0045] S2: Add 51g (0.15mol) tetrabutyl titanate to the suspension and sonicate for 2h to obtain a mixed reaction solution;

[0046] S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 220℃ for 36 hours to obtain the hydrothermal product;

[0047] S4: Mix the hydrothermal product with 31.5g of starch and ball mill for 4 hours to obtain a mixture;

[0048] S5: The mixture was calcined at 1200℃ for 2 hours under a nitrogen atmosphere to obtain a hard carbon composite anode material.

[0049] Example 2

[0050] This embodiment provides a method for preparing a hard carbon composite anode material, including the following steps:

[0051] S1: 2.1g (0.075mol) of nano-silicon, 9.28g (0.15mol) of boric acid and 0.78g of surfactant P123 were added to ethanol solvent and ultrasonically dispersed for 2h to obtain a suspension;

[0052] S2: Add 42.6 g (0.15 mol) of isopropyl titanate to the suspension and sonicate for 2 h to obtain a mixed reaction solution;

[0053] S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 250℃ for 24 hours to obtain the hydrothermal product;

[0054] S4: Mix the hydrothermal product with 31.5g of starch and ball mill for 2 hours to obtain a mixture;

[0055] S5: The mixture was calcined at 1500℃ for 1 hour under a nitrogen atmosphere to obtain a hard carbon composite anode material.

[0056] Example 3

[0057] This embodiment provides a method for preparing a hard carbon composite anode material, including the following steps:

[0058] S1: 2.1g (0.075mol) of nano-silicon, 9.28g (0.15mol) of boric acid and 0.86g of surfactant CTAB were added to ethanol solvent and ultrasonically dispersed for 2h to obtain a suspension;

[0059] S2: Add 51g (0.15mol) tetrabutyl titanate to the suspension and sonicate for 2h to obtain a mixed reaction solution;

[0060] S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 180℃ for 48 hours to obtain the hydrothermal product;

[0061] S4: Mix the hydrothermal product with 31.5g of starch and ball mill for 6 hours to obtain a mixture;

[0062] S5: The mixture was calcined at 1000℃ for 3 hours under a nitrogen atmosphere to obtain a hard carbon composite anode material.

[0063] Comparative Example 1

[0064] This comparative example provides a method for preparing a composite anode material, including the following steps:

[0065] S1: Add 2.1g of nano-silicon and 1.02g of PVP to ethanol solvent and disperse by ultrasonication for 2h to obtain a suspension;

[0066] S2: Add 51g of tetrabutyl titanate to the suspension and sonicate for 2 hours to obtain a mixed reaction solution;

[0067] S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 220℃ for 36 hours to obtain the hydrothermal product;

[0068] S4: Mix the hydrothermal product with 31.5g of starch and ball mill for 4 hours to obtain a mixture;

[0069] S5: The mixture was calcined at 1200℃ for 2 hours under a nitrogen atmosphere to obtain a hard carbon composite anode material.

[0070] Comparative Example 2

[0071] This comparative example provides a method for preparing a composite anode material, including the following steps:

[0072] S1: Add 2.1g of nano-silicon and 1.02g of PVP to ethanol solvent and disperse by ultrasonication for 2h to obtain a suspension;

[0073] S2: Add 51g of tetrabutyl titanate to the suspension and sonicate for 2 hours to obtain a mixed reaction solution;

[0074] S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 220℃ for 36 hours to obtain the hydrothermal product;

[0075] S4: Mix the hydrothermal product with 9.28g boric acid and 31.5g starch, and ball mill for 4 hours to obtain a mixture;

[0076] S5: The mixture was calcined at 1200℃ for 2 hours under a nitrogen atmosphere to obtain a hard carbon composite anode material.

[0077] Comparative Example 3

[0078] The difference between this comparative example and Example 1 is that sodium borate was used as the boron source.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 1 is that the amount of tetrabutyl titanate added is 25.5g.

[0081] The composite negative electrode materials prepared in each embodiment and comparative example were mixed with conductive agent acetylene black and binder CMC at a mass ratio of 70:10:20. This mixture was then prepared into a slurry with distilled water and uniformly coated onto copper foil. The slurry was then vacuum-dried at 60°C for 8 hours to obtain the electrode sheet for the experimental battery. Using a lithium sheet as the counter electrode, a 1 mol / L LiPF6 EC+DEC solution as the electrolyte, and a Celgard 2400 membrane as the separator, an LIR2430 coin cell was assembled in a glove box filled with argon atmosphere. The battery performance was then tested, and the test results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from the data in Table 1, the composite anode materials provided in Examples 1-3 all have excellent charge-discharge capacity and cycle performance.

[0085] The difference between Comparative Example 1 and Example 1 is that boric acid was not added during the preparation process, and the resulting composite anode material was a hard carbon Si / TiC composite anode material. The electrochemical performance of this composite anode material was lower than that of Example 1, and the cycle performance was significantly reduced.

[0086] Although boric acid was added in Comparative Example 2, it was added after the hydrothermal reaction. The charge-discharge capacity, first-time efficiency, and capacity retention of the prepared hard carbon composite anode material were significantly lower than those in Example 1.

[0087] Comparative Example 3, which used sodium borate as the boron source, showed weaker electrochemical performance in its hard carbon composite anode material compared to Example 1.

[0088] In Comparative Example 4, the amount of tetrabutyl titanate added was reduced, and the capacity and cycle performance of the prepared composite anode material were significantly lower than those in Example 1. It is speculated that the reason may be that the amount of titanium source added was insufficient, and TiB2 was not generated during the reaction process.

[0089] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a hard carbon composite negative electrode material, characterized in that, Includes the following steps: S1: Add nano-silicon, boron source and surfactant to alcohol solvent, disperse by ultrasonication to obtain suspension; S2: Add a titanium source to the suspension to obtain a mixed reaction solution; S3: Place the mixed reaction solution in a hydrothermal reactor and perform hydrothermal treatment at 180-250℃ to obtain a hydrothermal product; S4: Mix the hydrothermal product with the hard carbon precursor to obtain a mixture; S5: The mixture is calcined at 1000-1500℃ under an inert atmosphere to obtain a hard carbon Si / TiC-TiB2 composite anode material.

2. The preparation method of the hard carbon composite negative electrode material as described in claim 1, characterized in that, The titanium source is selected from at least one of tetrabutyl titanate and isopropyl titanate.

3. The method for preparing the hard carbon composite negative electrode material as described in claim 2, characterized in that, The boron source is boric acid.

4. The method for preparing the hard carbon composite negative electrode material as described in claim 2, characterized in that, The hard carbon precursor is selected from at least one of starch, sucrose, and phenolic resin.

5. The method for preparing the hard carbon composite negative electrode material as described in claim 2, characterized in that, The surfactant is selected from at least one of CTAB, P123, and PVP.

6. The method for preparing the hard carbon composite negative electrode material according to any one of claims 1-5, characterized in that, The molar ratio of the nano-silicon, the boron source, and the titanium source is (3-5):(3.5-6.5):(4-7).

7. The method for preparing the hard carbon composite negative electrode material as described in claim 6, characterized in that, The mass ratio of the surfactant to the nano-silicon is (2-7.5):(3-16.5).

8. The method for preparing the hard carbon composite negative electrode material as described in claim 6, characterized in that, The mass ratio of the hard carbon precursor to the nano-silicon is (30-45):(1-3).

9. A hard carbon composite anode material, characterized in that, The hard carbon composite anode material is prepared by the preparation method described in any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Including the hard carbon composite anode material as described in claim 9.

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