Amorphous silicon monoxide and preparation method thereof, negative active material, negative pole piece and lithium ion battery

Abstract

The invention provides amorphous silicon monoxide and a preparation method thereof, a negative active material, a negative pole piece and a lithium ion battery, and belongs to the technical field of lithium ion batteries. The preparation method comprises the following steps: by taking nitrogen and / or rare gas as a gas source, carrying out plasma bombardment treatment on crystalline silicon monoxide by adopting a plasma treatment instrument to obtain amorphous silicon monoxide. According to the preparation method, crystalline silicon oxide is bombarded by using a high-energy shielding gas plasma beam to be amorphized so as to obtain amorphous silicon oxide, so that the volume expansion of silicon oxide in a lithium intercalation process can be reduced, and the cycle performance of a battery when the amorphous silicon oxide is used as a negative electrode active material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to amorphous silicon oxide and a preparation method thereof, a negative electrode active material, a negative electrode plate and a lithium ion battery. Background Art

[0002] Crystalline silicon oxide, as the negative electrode active material of lithium-ion batteries, can be alloyed with Li + The reaction contributes to the capacity and has a high energy density. Its theoretical gram capacity can reach 4-5 times the gram capacity of the traditional negative electrode active material graphite. However, due to the high average Si-O coordination number of crystalline silicon oxide, the volume expansion is anisotropic when lithium is inserted, and it has a high lithiation energy barrier, resulting in the crystalline silicon oxide and Li + There is a large volume expansion during the electrochemical reaction, which will deteriorate the cycle performance of the battery. Therefore, it is necessary to modify the crystalline silicon oxide to alleviate its volume expansion during the cycle and improve the cycle performance of the battery. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the embodiments of the present invention provide an amorphous silicon oxide and a preparation method thereof, a negative electrode active material, a negative electrode sheet and a lithium ion battery.

[0004] The embodiment of the present invention provides a method for preparing amorphous silicon oxide, comprising the following steps: using nitrogen and / or a rare gas as a gas source, using a plasma treatment apparatus to perform plasma bombardment treatment on crystalline silicon oxide to obtain amorphous silicon oxide.

[0005] The advantages and technical effects of the method for preparing amorphous silicon dioxide in the embodiment of the present invention are as follows:

[0006] The preparation method of the embodiment of the present invention uses a high-energy gas source plasma beam to bombard crystalline silicon oxide, physically and chemically modify it, and make it amorphous to obtain amorphous silicon oxide, which can reduce the volume expansion of silicon oxide during lithium insertion and improve the cycle performance of the battery when it is used as a negative electrode active material;

[0007] Preferably, the power of the plasma treatment apparatus is 100-300W.

[0008] Preferably, the power of the plasma treatment apparatus is 100-200W.

[0009] Preferably, the plasma bombardment treatment is performed for 10-70 minutes.

[0010] Preferably, the flow rate of the gas source is 400-800 mL / min.

[0011] More preferably, the flow rate of the gas source is 400-600 mL / min.

[0012] The embodiment of the present invention further provides an amorphous silicon dioxide, which is obtained by the preparation method of the embodiment of the present invention.

[0013] The advantages and technical effects brought by the amorphous silicon dioxide of the embodiment of the present invention are as follows:

[0014] (1) Compared with crystalline silicon oxide, the amorphous silicon oxide of the embodiment of the present invention has a lower average Si-O coordination number, that is, it has an unsaturated Si-O coordination structure, which can alleviate the volume expansion of the negative electrode active material during the electrochemical reaction process and maintain the stability of the negative electrode structure and the cycle performance;

[0015] (2) The volume expansion of crystalline silicon oxide when embedded with lithium is anisotropic, while the volume expansion of amorphous silicon oxide obtained by the preparation method of the embodiment of the present invention when embedded with lithium is isotropic. Therefore, compared with crystalline silicon oxide, the amorphous silicon oxide of the embodiment of the present invention has smaller volume expansion during the cycle process, which can improve the cycle performance of the battery;

[0016] (3) In addition, the amorphous silicon oxide in the embodiment of the present invention has the characteristics of "long-range order and short-range disorder", and its structure has many "dangling bonds" and "voids", and has a lower lithiation energy barrier than crystalline silicon oxide. Therefore, compared with crystalline silicon oxide, the amorphous silicon oxide in the embodiment of the present invention has a smaller volume expansion during the cycle process, which can improve the cycle performance of the battery.

[0017] The embodiment of the present invention further provides a negative electrode active material, comprising the amorphous silicon oxide of the embodiment of the present invention.

[0018] The advantages and technical effects brought by the negative electrode active material of the embodiment of the present invention are:

[0019] Compared with the negative electrode active material containing crystalline silicon iodine, the negative electrode active material containing amorphous silicon iodine in the embodiment of the present invention has smaller volume expansion during the cycle process and better cycle performance of the battery.

[0020] The embodiment of the present invention further provides a negative electrode plate, comprising the negative electrode active material of the embodiment of the present invention.

[0021] The advantages and technical effects brought by the negative electrode sheet of the embodiment of the present invention are as follows:

[0022] Compared with the negative electrode plate containing crystalline silicon iodine oxide, the negative electrode plate containing amorphous silicon iodine oxide in the embodiment of the present invention has smaller volume expansion during the cycle process and better cycle performance of the battery.

[0023] The embodiment of the present invention further provides a lithium ion battery, including the negative electrode sheet of the embodiment of the present invention. The advantages and technical effects brought by the lithium ion battery of the embodiment of the present invention are:

[0024] Compared with a lithium-ion battery containing a negative electrode plate of crystalline silicon oxidase, the lithium-ion battery containing a negative electrode plate of amorphous silicon oxidase according to the embodiment of the present invention has better cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the XRD pattern of amorphous silicon dioxide obtained by the preparation method of Example 1;

[0026] Figure 2 This is the XRD pattern of crystalline silicon oxide in Comparative Example 1. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0028] The embodiment of the present invention provides a method for preparing amorphous silicon oxide, comprising the following steps: using nitrogen and / or a rare gas as a gas source, using a plasma treatment apparatus to perform plasma bombardment treatment on crystalline silicon oxide to obtain amorphous silicon oxide.

[0029] The preparation method of the embodiment of the present invention uses a high-energy gas source plasma beam to bombard crystalline silicon oxide, physically and chemically modify it, and amorphize it to obtain amorphous silicon oxide, which can reduce the volume expansion of silicon oxide during lithium insertion and improve the cycle performance of the battery when it is used as a negative electrode active material. In addition, the preparation method of the embodiment of the present invention is easy to operate, low in cost, and is conducive to large-scale industrial production.

[0030] In the preparation method of the embodiment of the present invention, the time of plasma bombardment treatment is adjusted according to the power set by the plasma treatment instrument. When the power of the plasma treatment instrument is too low, in order to ensure that the crystalline silicon oxide is completely transformed into amorphous silicon oxide, a longer bombardment treatment time is required, which is not conducive to improving production efficiency. When the power of the plasma surface treatment instrument is too high, the temperature will also be too high, which is not conducive to reducing the damage to the characteristics such as material structure and morphology. Therefore, the power of the plasma treatment instrument is preferably 100-300W, more preferably 100-200W, and the time of the modification treatment is preferably 5-70min, more preferably 10-70min.

[0031] Preferably, the flow rate of the gas source is 400-800 mL / min. When the flow rate of the gas source is too small, it is not conducive to obtaining sufficient high-energy gas source plasma, and it is not conducive to the complete transformation of crystalline silicon oxide into amorphous silicon oxide. When the flow rate of the gas source is too large, the modification effect will no longer be significantly improved. In order to reduce costs and increase efficiency, more preferably, the flow rate of the gas source is 400-600 mL / min.

[0032] Preferably, the gas source is a rare gas, which may include helium, neon, argon, krypton, xenon, etc. Compared with nitrogen, rare gases have better inertness and are more conducive to obtaining amorphous silicon dioxide. In order to reduce costs and increase efficiency, more preferably, the rare gas is argon.

[0033] Amorphous silicon dioxide is obtained by the preparation method of the embodiment of the present invention.

[0034] Compared with crystalline silicon oxide, the amorphous silicon oxide of the embodiment of the present invention has a lower average Si-O coordination number, that is, it has an unsaturated Si-O coordination structure, which can alleviate the volume expansion of the negative electrode active material during the electrochemical reaction and maintain the stability of the negative electrode structure and the cycle performance; the volume expansion of crystalline silicon oxide is anisotropic when embedded in lithium, while the volume expansion of the amorphous silicon oxide of the embodiment of the present invention is isotropic when embedded in lithium. Therefore, compared with crystalline silicon oxide, the volume expansion of amorphous silicon oxide is smaller during the cycle; in addition, amorphous silicon oxide has the characteristics of "long-range order and short-range disorder", and its structure has many "dangling bonds" and "voids", which has a lower lithiation energy barrier than crystalline silicon oxide. Therefore, compared with crystalline silicon oxide, the volume expansion of amorphous silicon oxide is also smaller during the cycle. Therefore, the amorphous silicon oxide of the embodiment of the present invention can effectively improve the cycle performance of the battery.

[0035] In addition, compared with crystalline silicon oxide, the amorphous silicon oxide of the embodiment of the present invention also has a larger specific surface area and a rich pore structure, which is conducive to the exposure of the active sites of the negative electrode material.

[0036] A negative electrode active material includes amorphous silicon oxide according to an embodiment of the present invention. The negative electrode active material according to the embodiment of the present invention can be all amorphous silicon oxide, or a mixture of amorphous silicon oxide and other types of negative electrode active materials. Compared with the negative electrode active material containing crystalline silicon oxide, the negative electrode active material containing amorphous silicon oxide according to the embodiment of the present invention has smaller volume expansion during the cycle process and better cycle performance of the battery.

[0037] A negative electrode plate includes the negative electrode active material of the embodiment of the present invention. Compared with the negative electrode plate containing crystalline silicon monoxide, the negative electrode plate containing amorphous silicon monoxide in the embodiment of the present invention has smaller volume expansion during the cycle process and better cycle performance of the battery.

[0038] A lithium-ion battery includes a negative electrode plate according to an embodiment of the present invention. Compared with a lithium-ion battery including a negative electrode plate of crystalline silicon oxide, a lithium-ion battery including a negative electrode plate of amorphous silicon oxide according to an embodiment of the present invention has better cycle performance.

[0039] The present invention is described in detail below with reference to the embodiments and the accompanying drawings.

[0040] Example 1

[0041] A method for preparing an amorphous silicon oxide negative electrode active material comprises the following steps: using a plasma treatment instrument to perform plasma bombardment treatment on crystalline silicon oxide (commercially available), the treatment atmosphere is argon (Ar), the power of the plasma treatment instrument is set to 200W, the flow rate of argon is set to 800mL / min, the sample is taken out after the treatment time is 10min, and amorphous silicon oxide is obtained.

[0042] Example 2

[0043] A method for preparing an amorphous silicon oxide negative electrode active material comprises the following steps: using a plasma treatment instrument to perform plasma bombardment treatment on crystalline silicon oxide (commercially available), the treatment atmosphere is argon (Ar), the power of the plasma treatment instrument is set to 150W, the flow rate of argon is set to 400mL / min, the sample is taken out after the treatment time is 55min, and amorphous silicon oxide is obtained.

[0044] Example 3

[0045] A method for preparing an amorphous silicon oxide negative electrode active material comprises the following steps: using a plasma treatment instrument to perform plasma bombardment treatment on crystalline silicon oxide (commercially available), the treatment atmosphere is argon (Ar), the power of the plasma surface treatment instrument is set to 100W, the flow rate of argon is set to 500mL / min, the sample is taken out after the treatment time is 70min, and amorphous silicon oxide is obtained.

[0046] Comparative Example 1

[0047] Crystalline silicon oxide is used as the negative electrode active material.

[0048] Electrochemical performance test: The negative electrode active materials of Examples 1-3 and Comparative Example 1 were mixed with the conductive agent carbon nanotubes and the binder polyvinylidene fluoride in a mass ratio of 7:1:2, and N-methylpyrrolidone (NMP) was added and stirred for 6 hours to obtain a uniform slurry, which was coated on copper foil, and the negative electrode was obtained after vacuum drying, rolling and cutting; the positive electrode used a metal lithium sheet; the electrolyte was a 1 mol / L LiPF6 electrolyte, and the solvent used in the electrolyte was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and fluoroethylene carbonate (FEC), wherein the volume ratio EC:EMC:FEC=3:6:1; the diaphragm was Celgard2400. The battery was assembled into a CR2430 battery in a glove box filled with argon. The battery test was carried out on the Shenzhen Xinwei battery test system. Charge and discharge were carried out at room temperature at 0.1C in the voltage range of 5mV-1.5V.

[0049] Table 1. Specific surface areas of negative electrode active materials of Examples 1-3 and Comparative Example 1

[0050]

[0051] Table 2. Electrochemical performance test results of negative electrode active materials of Examples 1-3 and Comparative Example 1

[0052] Number of cycles Capacity retention rate (%) Example 1 100 87 Example 2 100 83 Example 3 100 92 Comparative Example 1 100 75

[0053] Figure 1 is the XRD pattern of amorphous silicon dioxide of Example 1; Figure 2 This is the XRD pattern of crystalline silicon oxide in Comparative Example 1. Figure 1 The characteristic peaks belonging to crystalline silicon oxide are not seen in the spectrum of amorphous silicon oxide, indicating that the crystalline silicon oxide has been completely transformed into amorphous silicon oxide.

[0054] Table 1 shows the specific surface areas of the amorphous silicon oxide of Examples 1-3 and the crystalline silicon oxide of Comparative Example 4. By comparison, it can be seen that after argon plasma treatment, the specific surface area of ​​the material increases and more negative electrode active sites are exposed.

[0055] Table 2 lists the cycle performances measured after assembling test batteries using the amorphous silicon oxide of Examples 1-3 and the crystalline silicon oxide of Comparative Example 1 as negative electrode active materials. By comparison, it can be seen that when crystalline silicon oxide is used as the negative electrode active material, the capacity retention rate of the test battery after 100 cycles is only 75%, while when amorphous silicon oxide is used as the negative electrode active material, the capacity retention rate of the test battery can reach 83-92%, achieving a significant improvement.

[0056] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0057] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing amorphous silicon dioxide, characterized in that: The following steps are involved: Using nitrogen and / or rare gas as gas source, a plasma treatment apparatus is used to perform plasma bombardment treatment on crystalline silicon oxide to obtain amorphous silicon oxide.

2. The method for preparing amorphous silicon dioxide according to claim 1, characterized in that: The power of the plasma treatment instrument is 100-300W.

3. The method for preparing amorphous silicon dioxide according to claim 2, characterized in that: The power of the plasma treatment instrument is 100-200W.

4. The method for preparing amorphous silicon dioxide according to claim 3, characterized in that: The plasma bombardment treatment time is 10-70 minutes.

5. The method for preparing amorphous silicon dioxide according to claim 1, characterized in that: The flow rate of the gas source is 400-800 mL / min.

6. The method for preparing amorphous silicon dioxide according to claim 5, characterized in that: The flow rate of the gas source is 400-600 mL / min.

7. Amorphous silicon dioxide, characterized in that: Obtained by the preparation method according to any one of claims 1 to 6.

8. A negative electrode active material, characterized in that: Comprising the amorphous silicon oxide as described in claim 7.

9. A negative electrode plate, characterized in that: Comprising the negative electrode active material according to claim 8.

10. A lithium ion battery, characterized in that: Including the negative electrode sheet as described in claim 9.

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