A composite silicon oxide negative electrode material and its preparation method and application

Abstract

The present invention relates to a composite silicon oxide negative electrode material and a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing a binder; (2) preparing an auxiliary material obtained by mixing conductive carbon black, aqueous single-walled carbon nanotube slurry and the binder; (3) preparing an active material obtained by mixing SiO and artificial graphite; (4) compounding the active material, the auxiliary material and the piezoelectric material lead titanate to finally obtain a composite silicon oxide negative electrode material. The method uses graphite and silicon oxide to compound, and through the piezoelectric effect of the doped lead titanate, the volume expansion of the silicon-based material is slowed down, the charge diffusion resistance is reduced, and the lithium ion migration rate is accelerated, thereby preparing a composite silicon oxide negative electrode material with high specific capacity and high cyclability. In addition, the method has a simple process, a short production cycle, strong repeatability, low equipment requirements, and great application potential.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery electrode materials, and in particular to a composite silicon oxide negative electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are widely used in electric vehicles, information technology, aerospace and other fields. They are the mainstream technology of the new generation of energy storage power sources. However, with the continuous development of portable electronic devices and new energy vehicles, higher requirements are placed on the specific energy and cycle performance of power batteries. As one of the important components of lithium-ion batteries, the performance of negative electrode materials directly affects the overall energy density of the battery. At present, the negative electrode material of commercial lithium-ion batteries is mainly graphite, and the theoretical specific capacity of graphite is low, only 372mAh / g, which is difficult to meet the development needs of lithium-ion batteries with high specific energy and high cycle performance in the current market. Compared with graphite, silicon dioxide (SiO) as a negative electrode material has high specific capacity (theoretical specific capacity is 2100mAh / g), abundant reserves, and easy processing. It is considered to be a high-power, ideal negative electrode material for lithium-ion batteries that can replace graphite materials. However, SiO has a large volume expansion during the cycle process, which easily leads to material pulverization and capacity decay, resulting in poor cycle performance of lithium-ion batteries. In addition, SiO has low intrinsic conductivity, which restricts its wide range of practical applications. Summary of the invention

[0003] To solve the above problems, the purpose of the present invention is to provide a composite silicon oxide negative electrode material and a preparation method and application thereof. The method uses a composite of graphite and silicon oxide to improve the specific capacity of the composite material, and uses the piezoelectric effect of doped lead titanate to slow down the volume expansion of the silicon-based material, reduce the charge diffusion resistance, and accelerate the lithium ion migration rate, thereby preparing a lithium ion battery negative electrode material with high specific capacity and high cyclability.

[0004] In order to achieve the above object, the present invention discloses a method for preparing a composite silicon oxide negative electrode material, comprising the following steps:

[0005] (1) preparing a binder: adding sodium carboxymethyl cellulose to deionized water, stirring at room temperature for a certain period of time until the sodium carboxymethyl cellulose is completely dissolved, thereby obtaining a binder;

[0006] (2) Preparing auxiliary materials: drying the conductive carbon black (Super P) for a certain period of time, then grinding it in a mortar until it is uniform, adding the aqueous single-walled carbon nanotube slurry to the uniformly ground conductive carbon black, and continuing to grind until the two raw materials are fully mixed to obtain a mixture A, adding the mixture A to the binder obtained in step (1), grinding until it is uniform, and obtaining an auxiliary material;

[0007] (3) Preparation of active material: SiO and artificial graphite are dried and put into a mortar and ground until uniform to obtain active material;

[0008] (4) Preparing a composite negative electrode material: adding the active material obtained in step (3) to the auxiliary material obtained in step (2), grinding them evenly to obtain a mixture B, then adding the piezoelectric material to the mixture B, continuing to grind them evenly, transferring them to a beaker and stirring to finally obtain a composite silicon oxide negative electrode material;

[0009] In step (1), the stirring time is 2 to 3 hours, and the mass fraction of sodium carboxymethyl cellulose in the binder is 1.5%.

[0010] In step (2), the drying temperature is 60-80° C., the drying time is 12 h, the grinding time is 0.5 h to 1.0 h each time, and the solid content of the aqueous single-walled carbon nanotube slurry is 0.4%.

[0011] The mass ratio of the conductive carbon black in step (2), the single-walled carbon nanotubes, and the sodium carboxymethyl cellulose in step (1) is 8.5:1.5:10;

[0012] In step (3), the mass ratio of SiO2 to artificial graphite is 1:3, the drying temperature is 60-80°C, the drying time is 12h, and the grinding time is 0.5h-1.0h.

[0013] In step (4), the mass ratio of the active material to the auxiliary material is 16:1 to 16:4, the mass ratio of the active material to the piezoelectric material is 16:1 to 16:3, and the above two mass ratios do not include the mass of water and other solvents, and the piezoelectric material is lead titanate; the grinding time is 0.5h to 1.0h, and the stirring time is 3 to 4h.

[0014] The theoretical specific capacity of graphite is low, while SiO has low intrinsic conductivity and large volume expansion during the cycle, which easily leads to material pulverization and capacity decay. If graphite and silicon oxide are compounded, good conductivity and high specific capacity of the material can be achieved. Conductive carbon black is added to the material to improve the conductivity of the material; single-walled carbon nanotubes have a flexible network and strong van der Waals force, which can improve the cycle performance of the composite material as a negative electrode material; and lead titanate piezoelectric materials will generate local micro-electric fields under the action of mechanical stress, which can accelerate the migration speed of lithium ions, and at the same time can inhibit the volume expansion of silicon oxide during the charge and discharge process, improve the cyclability of the composite material, and thus improve the lithium storage performance of the negative electrode material.

[0015] Based on this, the preparation method proposed in the present invention utilizes the piezoelectric effect of lead titanate to prepare a composite silicon oxide negative electrode material by compounding it with graphite, silicon oxide, single-walled carbon nanotubes, etc.

[0016] The present invention also aims to provide a composite silicon oxide negative electrode material prepared according to the above preparation method and the application of the material as a negative electrode material for lithium ion batteries.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The preparation method has simple process, short production cycle, strong repeatability, low equipment requirements, and great application potential.

[0019] (2) It shortens the diffusion distance of lithium ions and electrons, improves the lithium storage performance of the material, inhibits the volume change of the material during the cycle, improves the cycle stability, and thus effectively improves the electrochemical properties of the material, including conductivity, specific capacity of lithium-ion batteries, and cycle stability.

[0020] (3) When the prepared composite silicon oxide negative electrode material is used as a negative electrode material for lithium-ion batteries, it is tested at a current density of 0.1C. The first discharge specific capacity can reach 1264.13mAh / g, and the first coulombic efficiency can reach 83.45%, which has a high specific capacity. After 50 cycles, the discharge specific capacity is still as high as 1323.6mAh / g, which has a good capacity retention rate. The coulombic efficiency after 50 cycles is as high as 99.09%, showing excellent cycle performance. The above test results show that the composite silicon oxide negative electrode material has excellent high capacity and high cyclability, and is expected to meet the current commercial needs of high energy density lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the cycle performance curve of the composite silicon oxide negative electrode material prepared in Example 1;

[0022] Figure 2 This is the cycle performance curve of the composite silicon dioxide negative electrode material prepared in Example 2;

[0023] Figure 3 This is the cycle performance curve of the composite silicon oxide negative electrode material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0024] In order to better understand the content of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings. The following embodiments are implemented based on the technology of the present invention, and detailed implementation methods and operating steps are given, but the protection scope of the present invention is not limited to the following embodiments.

[0025] The water-based single-walled carbon nanotube slurry in the embodiment is purchased from outside, and the solid content of the water-based single-walled carbon nanotube slurry is 0.4%;

[0026] Embodiment 1:

[0027] (1) Preparation of a binder: 0.025 g of sodium carboxymethyl cellulose was added to 1.642 g of deionized water and stirred at room temperature for 2 h until the sodium carboxymethyl cellulose was completely dissolved to obtain a binder with a mass fraction of 1.5%;

[0028] (2) Preparation of auxiliary materials: Dry 0.0213 g of conductive carbon black (Super P) at 80° C. for 12 h, then grind in a mortar for 0.5 h until uniform, add 0.938 g of aqueous single-walled carbon nanotube slurry (solid content of 0.4%) to the uniformly ground conductive carbon black, and continue grinding for 0.5 h until the two raw materials are fully mixed to obtain a mixture A, add the mixture A to the binder obtained in step (1), and grind in a mortar for 1.0 h until the mixture is uniformly mixed to obtain an auxiliary material;

[0029] (3) Preparation of active material: 0.1 g SiO and 0.3 g artificial graphite were dried at 80 °C for 12 h, and then ground in a mortar for 1.0 h until mixed uniformly to obtain an active material;

[0030] (4) Preparation of composite negative electrode material: adding the active material obtained in step (3) to the auxiliary material obtained in step (2), grinding for 0.5 h until the mixture is uniformly mixed, to obtain a mixture B, then adding 0.05 g of piezoelectric material lead titanate to the mixture B, continuing to grind for 0.5 h until the mixture is uniformly mixed, then transferring it to a beaker and stirring and mixing it with an electromagnetic stirring device for 3 h, finally obtaining a composite silicon oxide negative electrode material;

[0031] In this embodiment, the mass ratio of the active material (SiO and artificial graphite) to the auxiliary material (conductive carbon black, single-walled carbon nanotubes, sodium carboxymethyl cellulose) is 8:1, and the mass ratio of the active material to the piezoelectric material (lead titanate) is also 8:1, that is, the above two mass ratios do not include the deionized water and other solvents used, and the mass fraction of the active material to the total mass of the obtained composite negative electrode material (excluding the mass of water and other solvents) is 80%.

[0032] Electrochemical performance test: The prepared composite silicon oxide negative electrode material was coated on copper foil and dried at 80°C for 12h, cut into circular pole pieces with a diameter of 12mm as working electrodes, and assembled into batteries in a glove box using Cellgard 2300 microporous polypropylene component separators and Li wafer counter electrodes. The battery performance of the lithium-ion battery negative electrode was measured using CR2025 coin-type battery test materials. Battery charge / discharge tests were performed on a LANHE battery test system (CT2001A, Wuhan, China) with a voltage window of 0.01-3V (relative to Li+ / Li).

[0033] Figure 1 This is the cycle performance curve of the composite silicon oxide negative electrode material prepared in this embodiment. Figure 1It shows that the composite silicon oxide negative electrode material is tested as a negative electrode material for lithium-ion batteries at a current density of 0.1C. The first discharge specific capacity can reach 1264.1mAh / g, the first charge specific capacity can reach 1055mAh / g, and the first coulombic efficiency can reach 83.45%. It has a high specific capacity. After 50 cycles, the discharge specific capacity is still as high as 1323.6mAh / g, the charge specific capacity can reach 1311.6mAh / g, and the coulombic efficiency is 99.09%. It has a good capacity retention rate and shows excellent cycle performance.

[0034] Embodiment 2:

[0035] (1) Preparation of a binder: 0.0125 g of sodium carboxymethyl cellulose was added to 0.82 g of deionized water and stirred at room temperature for 2 h until the sodium carboxymethyl cellulose was completely dissolved to obtain a binder with a mass fraction of 1.5%;

[0036] (2) Preparation of auxiliary materials: Dry 0.0107 g of conductive carbon black (Super P) at 80° C. for 12 h, then grind in a mortar for 0.5 h until uniform, add 0.469 g of aqueous single-walled carbon nanotube slurry (solid content of 0.4%) to the uniformly ground conductive carbon black, and continue grinding for 0.5 h until the two raw materials are fully mixed to obtain a mixture A, add the mixture A to the binder obtained in step (1), and grind in a mortar for 1.0 h until the mixture is uniformly mixed to obtain an auxiliary material;

[0037] (3) Preparation of active material: 0.1 g SiO and 0.3 g artificial graphite were dried at 80 °C for 12 h, and then ground in a mortar for 1.0 h until mixed uniformly to obtain an active material;

[0038] (4) Preparation of composite negative electrode material: The active material obtained in step (3) is added to the auxiliary material obtained in step (2), and the mixture is ground for 0.5 h until it is uniformly mixed to obtain a mixture B. Then, 0.075 g of piezoelectric material lead titanate is added to the mixture B, and the mixture is further ground for 1.0 h until it is uniformly mixed. The mixture is then transferred to a beaker and stirred for 3 h using an electromagnetic stirring device to finally obtain a composite silicon oxide negative electrode material.

[0039] In this embodiment, the mass ratio of the active material to the auxiliary material is 16:1, and the mass ratio of the active material to the piezoelectric material is 16:3, that is, the above two mass ratios do not include the deionized water and other solvents used, and the mass fraction of the active material to the total mass of the obtained composite negative electrode material (excluding the mass of water and other solvents) is 80%.

[0040] The composite silicon dioxide negative electrode material obtained in this embodiment was tested using the same electrochemical performance test method as in Example 1. Figure 2This is the cycle performance curve of the composite silicon oxide negative electrode material prepared in this embodiment. Figure 2 It shows that when the composite silicon oxide negative electrode material is tested as a negative electrode material for lithium-ion batteries at a current density of 0.1C, the first discharge specific capacity can reach 914mAh / g, the first charge specific capacity can reach 777mAh / g, the first coulombic efficiency can reach 85.00%, and after 30 cycles, the discharge specific capacity is 742.9mAh / g, the charge specific capacity can reach 739.3mAh / g, and the coulombic efficiency can reach 99.53%.

[0041] Comparative Example 1:

[0042] (1) Preparation of a binder: 0.05 g of sodium carboxymethyl cellulose was added to 3.28 g of deionized water and stirred at room temperature for 3 h until the sodium carboxymethyl cellulose was completely dissolved to obtain a binder with a mass fraction of 1.5%;

[0043] (2) Preparation of auxiliary materials: Dry 0.0425 g of conductive carbon black (Super P) at 80° C. for 12 h, then grind in a mortar for 0.5 h until uniform, add 1.875 g of aqueous single-walled carbon nanotube slurry (solid content of 0.4%) to the uniformly ground conductive carbon black, and continue grinding for 0.5 h until the two raw materials are fully mixed to obtain a mixture A, add the mixture A to the binder obtained in step (1), and grind in a mortar for 1.0 h until the mixture is uniformly mixed to obtain an auxiliary material;

[0044] (3) Preparation of active material: 0.1 g SiO and 0.3 g artificial graphite were dried at 80 °C for 12 h, and then ground in a mortar for 1.0 h until mixed uniformly to obtain an active material;

[0045] (4) Preparation of composite negative electrode material: The active material obtained in step (3) is added to the auxiliary material obtained in step (2), and the mixture is ground for 1.0 h until the mixture is uniformly mixed. The mixture is then transferred to a beaker and stirred for 3 h using an electromagnetic stirring device to finally obtain a composite silicon oxide negative electrode material.

[0046] In this comparative example, the mass ratio of active materials (SiO and artificial graphite) to auxiliary materials (conductive carbon black, single-walled carbon nanotubes, sodium carboxymethyl cellulose) is 4:1, that is, the above two mass ratios do not include the deionized water and other solvents used, and the mass fraction of the active material to the total mass of the obtained composite negative electrode material (excluding the mass of water and other solvents) is 80%.

[0047] The composite silicon dioxide negative electrode material obtained in this comparative example was tested using the same electrochemical performance test method as in Example 1. Figure 3 The cycle performance curve of the composite silicon oxide negative electrode material of the undoped lead titanate piezoelectric material prepared in this comparative example is: Figure 3It shows that when the composite silicon oxide negative electrode material is tested as a negative electrode material for lithium-ion batteries at a current density of 0.1C, the first discharge specific capacity can reach 748.7mAh / g, the first charge specific capacity can reach 573.4mAh / g, the first coulombic efficiency can reach 76.59%, and after 30 cycles, the discharge specific capacity is 752.9mAh / g, the charge specific capacity can reach 749.1mAh / g, and the coulombic efficiency can reach 99.50%.

[0048] Depend on Figure 1-Figure 3 It can be clearly seen that the materials in Examples 1 and 2 are superior to the material in Comparative Example 1 in terms of charge and discharge specific capacity and first coulombic efficiency, and the overall performance of Example 1 is significantly better than that of the material in Comparative Example 1.

[0049] The above is only an embodiment of the present invention, and does not limit the present invention in any form. The present invention can also have other forms of embodiments according to the above structures and functions, which are not listed one by one. Therefore, any simple modification, equivalent change and modification made by any technician familiar with the profession to the above embodiment according to the technical essence of the present invention without departing from the scope of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite silicon oxide negative electrode material, characterized in that The specific steps include: (1) preparing a binder: adding sodium carboxymethyl cellulose to deionized water, stirring at room temperature for a certain period of time until the sodium carboxymethyl cellulose is completely dissolved, to obtain a binder, wherein the mass fraction of the sodium carboxymethyl cellulose in the binder is 1.5%; (2) preparing auxiliary materials: drying the conductive carbon black for a certain period of time, then grinding it in a mortar until it is uniform, adding the aqueous single-walled carbon nanotube slurry to the uniformly ground conductive carbon black, and continuing to grind until the two raw materials are fully mixed to obtain a mixture A, adding the mixture A to the binder obtained in step (1), and grinding until it is uniform to obtain an auxiliary material; (3) Preparation of active material: SiO and artificial graphite are dried and put into a mortar and ground until uniform to obtain active material; (4) Preparing a composite negative electrode material: adding the active material obtained in step (3) to the auxiliary material obtained in step (2), grinding them evenly to obtain a mixture B, then adding the piezoelectric material to the mixture B, continuing to grind them evenly, transferring them to a beaker and stirring to finally obtain a composite silicon oxide negative electrode material; In step (2), the solid content of the aqueous single-walled carbon nanotube slurry is 0.4%, and the mass ratio of the conductive carbon black, the single-walled carbon nanotubes, and the sodium carboxymethyl cellulose in step (1) is 8.5:1.5:10; In step (3), the mass ratio of SiO to artificial graphite is 1:3; In step (4), the mass ratio of the active material to the auxiliary material is 16:1 to 16:4, the mass ratio of the active material to the piezoelectric material is 16:1 to 16:3, and the above two mass ratios do not include the mass of water and other solvents. The piezoelectric material is lead titanate, the grinding time is 0.5h to 1.0h, and the stirring time is 3 to 4h.

2. The method for preparing the composite silicon oxide negative electrode material according to claim 1, characterized in that: In step (1), the stirring time is 2 to 3 hours.

3. The method for preparing the composite silicon oxide negative electrode material according to claim 1, characterized in that: In step (2), the drying temperature is 60-80° C., and the drying time is 12 h; and the grinding time each time is 0.5 h to 1.0 h.

4. The method for preparing the composite silicon dioxide negative electrode material according to claim 1, characterized in that: In step (3), the drying temperature is 60-80° C., the drying time is 12 h, and the grinding time is 0.5 h to 1.0 h.

5. The composite silicon 2 oxide negative electrode material obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the composite silicon oxide negative electrode material as claimed in claim 5 as a negative electrode material for lithium ion batteries.

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