A preparation method and application of pre-magnesium silicon oxide

Abstract

The present invention discloses a preparation method and application of pre-magnesium silicon oxide, belonging to the technical field of lithium ion batteries. The steps of the preparation method include: S1, weighing silicon oxide, magnesium source and carbon source according to the mass ratio, grinding and mixing to obtain a precursor; S2, placing the precursor on a carrier of a Joule heating device, connecting the power supply of the electrode in the Joule heat treatment device under a protective atmosphere, performing thermal shock treatment, and obtaining pre-magnesium silicon oxide. Rapid heating is achieved by Joule heating, and the reaction of magnesium source and silicon oxide is precisely controlled, so that the reaction is more sufficient and efficient, and the initial charge and discharge efficiency, charge and discharge rate performance and cycle stability of the battery capacity of the lithium battery are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a preparation method and application of pre-magnesium silicon oxide. Background Art

[0002] Lithium-ion batteries have achieved rapid development due to their high energy density and good cycle stability. Under the current trend of lithium-ion batteries pursuing high capacity density, graphite anode materials are limited in their further development due to low specific capacity (theoretical capacity is 372mAh / g) and poor rate performance. Silicon-based materials have attracted widespread attention due to their extremely high theoretical specific capacity (4200mAh / g). However, the inherent low conductivity (10-5S / cm) and slow ion diffusion rate (10-14cm 2 / s), resulting in low cycle efficiency during the cycle and poor charge and discharge performance at high current density, which seriously hinders the large-scale application of silicon anode in lithium-ion batteries.

[0003] Among silicon-based negative electrode materials, silicon-oxygen negative electrode materials have obvious advantages in long-cycle stability. Although they have a lower theoretical specific capacity (2400mAh / g), they are still much higher than the specific capacity of graphite negative electrode materials, and have become the focus of researchers. In view of the fact that silicon-oxygen negative electrode materials still have low first coulombic efficiency and large volume expansion (about 200%) during the process of lithium removal and lithium insertion, many scholars at home and abroad currently mainly use different strategies such as disproportionation reaction, carbon material coating, pre-magnesiation and pre-lithiation to modify silicon-oxygen negative electrode materials. These modification measures have significantly improved the charge and discharge cycle performance, first coulombic efficiency and rate performance of negative electrode materials.

[0004] There is no report on the use of rapid Joule heating to prepare pre-magnesium silicon oxide negative electrode materials. In view of this, it is urgent to develop a method for preparing high-first-efficiency pre-magnesium silicon oxide negative electrode materials based on rapid heating Joule heating. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of pre-magnesium silicon oxide to improve the initial charge and discharge efficiency, charge and discharge rate performance and cycle stability of lithium batteries.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The present invention provides a method for preparing pre-magnesium silicon oxide, comprising the following steps:

[0008] S1. Weigh silicon dioxide, a magnesium source and a carbon source according to a mass ratio, grind and mix them in a mortar to obtain a precursor;

[0009] S2, placing the precursor on a carrier of a Joule heating device, connecting the power supply of the electrode in the Joule heat treatment device under a protective atmosphere, and subjecting the precursor to a thermal shock treatment to obtain a silicon negative electrode material with high initial efficiency and gram capacity;

[0010] The magnesium source is at least one of magnesium powder and magnesium silicide;

[0011] The mass ratio of silicon dioxide, magnesium source and carbon source is (1-15):1:(0.1-3).

[0012] Preferably, the mass ratio of silicon dioxide, magnesium source and carbon source is (10-15):1:(0.3-1).

[0013] Preferably, the silicon dioxide particles in S1 have a particle size of 1 to 20 μm, more preferably, a particle size of 5 μm;

[0014] The carbon source in S1 is at least one of asphalt, glucose, sucrose, and phenolic resin.

[0015] Preferably, the grinding time in S1 is 5 to 60 min, more preferably, the grinding time is 30 min.

[0016] Preferably, the Joule heating device in S2 comprises a vacuum pump, a positive electrode, a negative electrode, an infrared thermometer, a carrier and a power supply.

[0017] Preferably, the carrier of the Joule heating device in S2 is one of a graphite sheet and carbon paper.

[0018] Preferably, the protective atmosphere in S2 is one of nitrogen and argon.

[0019] Preferably, the number of thermal shock treatments in S2 is 2 to 50 times, and the duration of a single thermal shock treatment is 5 to 20 seconds.

[0020] Preferably, the current of the power supply in S2 is 20-50A, and the voltage is 20-30V.

[0021] Preferably, the temperature of the thermal shock treatment in S2 is 1000-2000°C.

[0022] The present invention also provides an application of pre-magnesium silicon oxide, wherein the pre-magnesium silicon oxide prepared above is used as a negative electrode material for a lithium ion battery;

[0023] The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, and the negative electrode sheet contains the pre-prepared magnesium silicon oxide.

[0024] Beneficial effects of the present invention:

[0025] (1) The present invention generates magnesium silicate compound and silicon element by reacting a part of oxygen in silicon oxide with reducing magnesium. The magnesium silicate compound can alleviate volume expansion and improve cycle performance, and the silicon element can improve energy density. At the same time, an amorphous carbon layer is coated on the surface of the material particles to improve conductivity while effectively buffering the volume change generated during lithium insertion and extraction, avoiding the generation of irreversible capacity during the first lithium insertion and extraction process, and improving the first coulombic efficiency.

[0026] (2) The preparation equipment for pre-magnesium silicon oxide in the present invention adopts a Joule heating device, which can accurately control and utilize thermal reactions and phase changes in time and space dimensions. It is an efficient, low-energy, and high-throughput preparation technology.

[0027] (3) The pre-magnesium silicon oxide of the present invention is used as a negative electrode material for a lithium battery, which has a higher gram capacity, improves the electron transportability of the negative electrode material, optimizes the channels for lithium insertion and extraction, and alleviates the volume expansion of silicon during the cycle, thereby improving the initial charge and discharge efficiency of the lithium battery, the charge and discharge rate performance and the cycle stability of the battery capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 is the XRD pattern of the material prepared in Example 1;

[0030] Figure 2 This is a comparison of XRD patterns of materials prepared in Example 1 and Comparative Example 1;

[0031] Figure 3 This is a comparison chart of the rate performance of button-type half-cells when the materials prepared in Example 1 and Comparative Example 1 are used as negative electrode materials;

[0032] Figure 4 It is a comparison chart of the room temperature cycle performance of button-type half-cells using the materials prepared in Example 1 and Comparative Example 1 as negative electrode materials. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0035] Example 1

[0036] The preparation method of magnesium silicon oxide in this embodiment comprises the following steps:

[0037] S1. Weigh 10 g of silicon oxide with a particle size of 5 μm, 1 g of magnesium powder and 1 g of glucose in a mass ratio of 10:1:1, place them in a mortar and grind them for 30 min to mix them evenly to obtain a precursor;

[0038] S2. Place the precursor in a carrier graphite sheet of a Joule heating device, connect it to the positive electrode and the negative electrode respectively through wires, pass argon for 30 minutes, turn on the power supply in the Joule heat treatment device, set the current to 35A, and the voltage to 25V, perform Joule heat shock treatment on the precursor on the graphite sheet, the single Joule heat shock treatment time is 10s, the number of Joule heat shock treatments is 20 times, and the temperature of the Joule heat shock treatment is 1300°C, to obtain pre-magnesium silicon dioxide. Take the pre-magnesium silicon dioxide prepared in this example for XRD detection, and the detection spectrum is shown in Figure 1 The XRD spectrum of Example 1 shows that Si, Mg2SiO4 and amorphous carbon peaks exist and are relatively sharp, indicating that the preparation method of this example achieves pre-magnesiation reaction and carbon coating.

[0039] Example 2

[0040] The preparation method of magnesium silicon oxide in this embodiment comprises the following steps:

[0041] S1. Weigh 10 g of silicon dioxide with a particle size of 5 μm, 1 g of magnesium silicide powder and 1 g of glucose in a mass ratio of 10:1:1, place them in a mortar and grind them for 30 min to mix them evenly to obtain a precursor;

[0042] S2. Place the precursor in a carrier graphite sheet in a Joule heating device, connect it to the positive electrode and the negative electrode respectively through wires, pass argon for 30 minutes, turn on the power supply in the Joule heat treatment device, set the current to 35A, and the voltage to 25V, perform Joule thermal shock treatment on the precursor on the graphite sheet, the single Joule thermal shock treatment lasts 10 seconds, the number of Joule thermal shock treatments is 20 times, and the temperature of the Joule thermal shock treatment is 1300°C to obtain pre-magnesium silicon oxide.

[0043] Example 3

[0044] The preparation method of magnesium silicon oxide in this embodiment comprises the following steps:

[0045] S1. Weigh 10 g of silicon oxide with a particle size of 5 μm, 1 g of magnesium powder and 1 g of glucose in a mass ratio of 10:1:1, place them in a mortar and grind them for 30 min to mix them evenly to obtain a precursor;

[0046] S2. Place the precursor in a carrier graphite sheet in a Joule heating device, connect it to the positive electrode and the negative electrode respectively through wires, pass argon gas for 30 minutes, turn on the power supply in the Joule heat treatment device, set the current to 50A, and the voltage to 30V, perform Joule thermal shock treatment on the precursor on the graphite sheet, the single Joule thermal shock treatment time is 20s, the number of Joule thermal shock treatments is 50 times, and the temperature of the Joule thermal shock treatment is 1800°C to obtain pre-magnesium silicon oxide.

[0047] Example 4

[0048] The preparation method of magnesium silicon oxide in this embodiment comprises the following steps:

[0049] S1. Weigh 10 g of silicon oxide with a particle size of 5 μm, 1 g of magnesium powder and 1 g of asphalt in a mass ratio of 10:1:1, place them in a mortar and grind them for 30 minutes to mix them evenly to obtain a precursor;

[0050] S2. Place the precursor in a carrier graphite sheet in a Joule heating device, connect it to the positive electrode and the negative electrode respectively through wires, pass argon for 30 minutes, turn on the power supply in the Joule heat treatment device, set the current to 20A, and the voltage to 20V, perform Joule thermal shock treatment on the precursor on the graphite sheet, the single Joule thermal shock treatment time is 5s, the number of Joule thermal shock treatments is 2 times, and the temperature of the Joule thermal shock treatment is 1000°C to obtain pre-magnesium silicon oxide.

[0051] Example 5

[0052] The preparation method of magnesium silicon oxide in this embodiment comprises the following steps:

[0053] S1. Weigh 15 g of silicon oxide with a particle size of 5 μm, 1 g of magnesium powder and 0.3 g of asphalt in a mass ratio of 15:1:0.3, place them in a mortar and grind them for 30 minutes to mix them evenly to obtain a precursor;

[0054] S2. Place the precursor in a carrier graphite sheet in a Joule heating device, connect it to the positive electrode and the negative electrode respectively through wires, pass argon gas for 30 minutes, turn on the power supply in the Joule heat treatment device, set the current to 35A, and the voltage to 25V, perform Joule thermal shock treatment on the precursor on the graphite sheet, the single Joule thermal shock treatment time is 10s, the number of Joule thermal shock treatments is 20 times, and the temperature of the Joule thermal shock treatment is 1300°C to obtain pre-magnesium silicon oxide.

[0055] Example 6

[0056] The preparation method of magnesium silicon oxide in this embodiment comprises the following steps:

[0057] S1. Weigh 12 g of silicon dioxide with a particle size of 5 μm, 1 g of magnesium silicide and 0.5 g of polyvinyl pyrrolidone in a mass ratio of 12:1:3, place them in a mortar and grind them for 30 min to mix them evenly to obtain a precursor;

[0058] S2. Place the precursor in a carrier graphite sheet in a Joule heating device, connect it to the positive electrode and the negative electrode respectively through wires, pass argon gas for 30 minutes, turn on the power supply in the Joule heat treatment device, set the current to 35A, and the voltage to 25V, perform Joule thermal shock treatment on the precursor on the graphite sheet, the single Joule thermal shock treatment time is 10s, the number of Joule thermal shock treatments is 20 times, and the temperature of the Joule thermal shock treatment is 1300°C to obtain pre-magnesium silicon oxide.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that the carbon-coated pre-magnesium silicon oxide is prepared by a conventional heating method.

[0061] The preparation method of carbon-coated pre-magnesium silicon oxide comprises the following steps:

[0062] S1. Weigh 10 g of silicon dioxide with a particle size of 5 μm, 1 g of magnesium powder and 1 g of glucose in a mass ratio of 10:1:1, place them in a mortar and grind them for 30 min to mix them evenly to obtain a precursor;

[0063] S2. Sintering the precursor in a nitrogen atmosphere, raising the temperature to 950°C at 5°C / min, keeping the temperature for 5 hours, and obtaining carbon-coated pre-magnesium silicon oxide after cooling.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Example 2 is that the carbon-coated pre-magnesium silicon oxide is prepared by conventional heating method.

[0066] The preparation method of carbon-coated pre-magnesium silicon oxide comprises the following steps:

[0067] S1. Weigh 10 g of silicon dioxide with a particle size of 5 μm, 1 g of magnesium silicide powder and 1 g of glucose in a mass ratio of 10:1:1, place them in a mortar and grind them for 30 min to mix them evenly to obtain a precursor;

[0068] S2. Sintering the precursor in a nitrogen atmosphere, raising the temperature to 950°C at 5°C / min, keeping the temperature for 5 hours, and obtaining carbon-coated pre-magnesium silicon oxide after cooling.

[0069] The materials prepared in Examples 1 to 6 and Comparative Examples 1 to 2 were used as negative electrode materials, and lithium sheets were used as positive electrode materials. Button-type half-cells were assembled to conduct electrochemical performance tests. The results are shown in Table 1. The pre-magnesium silicon oxide prepared in Example 1 and the materials prepared in Comparative Example 1 were subjected to XRD tests. The test results are shown in Table 1. Figure 1 The magnesium silicon oxide prepared in Example 1 and the material prepared in Comparative Example 1 were used to assemble button-type half-cells, and the battery rate performance and cycle performance at room temperature were tested. The test results are shown in Figure 3 and Figure 4 .

[0070] The materials prepared in Example 1 and Comparative Example 1 were subjected to XRD testing. The test results are shown in Figure 2 .

[0071] Table 1

[0072]

[0073] It can be seen from Table 1 that the pre-magnesium silicon oxide prepared by the present invention as the negative electrode material has good comprehensive electrochemical properties, and its first charge and discharge efficiency is more than 78%, and the 50-week cycle capacity retention rate is more than 93%. The first charge and discharge efficiency of the negative electrode material of Comparative Example 1 is 68.7%, and the 50-week cycle capacity retention rate is 88.5%. The first charge and discharge efficiency of the negative electrode material of Comparative Example 2 is 73.5%, and the 50-week cycle capacity retention rate is 89.3%. Compared with the embodiment, the first irreversible capacity loss of the comparative example is larger, and the cycle performance is poor.

[0074] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0075] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing magnesium silicon oxide, characterized in that: The steps include: S1. Weigh silicon dioxide, a magnesium source and a carbon source according to a mass ratio, grind and mix them to obtain a precursor; S2, placing the precursor on a carrier of a Joule heating device, connecting the power supply of the electrodes in the Joule heat treatment device under a protective atmosphere, and performing a thermal shock treatment to obtain pre-magnesium silicon oxide; The magnesium source is at least one of magnesium powder and magnesium silicide; The mass ratio of silicon dioxide, magnesium source and carbon source is (1-15):1:(0.1-3); The number of heat shock treatments in S2 is 2 to 50 times, and the single heat shock treatment time is 5 to 20 seconds; The temperature of the thermal shock treatment in S2 is 1000-2000°C.

2. The method for preparing magnesium silicon oxide according to claim 1, characterized in that: The particle size of silicon 2 oxide in S1 is 1 to 20 μm.

3. The method for preparing magnesium silicon oxide according to claim 1, characterized in that: The carbon source in S1 is at least one of asphalt, glucose, sucrose, and phenolic resin.

4. The method for preparing magnesium silicon oxide according to claim 1, characterized in that: The grinding time in S1 is 5 to 60 minutes.

5. The method for preparing pre-magnesium silicon oxide according to claim 1, characterized in that: The current of the power supply in S2 is 20-50A, and the voltage is 20-30V.

6. An application of pre-magnesium silicon oxide, characterized in that: The pre-magnesium silicon oxide prepared by the preparation method according to any one of claims 1 to 5 is used as a negative electrode material for a lithium ion battery.

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