Negative pole piece, preparation method thereof and battery

Abstract

The invention relates to a negative pole piece as well as a preparation method and application thereof, and belongs to the technical field of secondary batteries. The negative pole piece comprises a negative active material layer and a negative current collector, and the negative active material layer is attached to the negative current collector; the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a first material and a second material, the first material comprises a pre-magnesium silica material, the pre-magnesium silica material is a pre-magnesium silica body of which the surface is modified with nitrogen, and the second material comprises graphite; nitrogen modification is carried out on the surface of a pre-magnesium silica material, more Li3N components are generated when SEI is generated on the surface of the pre-magnesium silica material in the charging and discharging process, and Li3N generated in situ is a stable inorganic substance with high ion conductivity, so that the problem of poor lithium ion conductivity caused by magnesium silicate on the original surface of the material can be solved; furthermore, the rate and the cycle performance of the battery are improved, and the effect of improving the electrochemical performance of the pre-magnesium silica material is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a negative electrode plate and a preparation method thereof, and a battery. Background Art

[0002] Silicon negative electrode has been widely used in high-energy-density batteries due to its advantages such as high capacity, wide source and low price. However, the silicon negative electrode has the disadvantage of high expansion rate, which will lead to problems such as particle pulverization, electrode structure destruction, and repeated growth of SEI film, affecting the long-cycle stability of the battery. In order to solve the problem of silicon negative electrode expansion, silicon oxide materials came into being. The inert buffer provided by silicon oxide materials can greatly inhibit the expansion of silicon negative electrodes, but they also have the problem of low initial efficiency. In order to solve this problem, they will be pre-lithiated or pre-magnesiated. Among them, pre-magnesiated silicon oxide does not require expensive lithium raw materials and has low cost, so it has received widespread attention. However, since the surface of pre-magnesiated silicon oxide is coated with a layer of magnesium silicate, the lithium ion conductivity of this layer of magnesium silicate is very poor, which has an adverse effect on the rate and cycle performance of the battery, so the electrochemical performance is poor. Summary of the invention

[0003] The present application provides a negative electrode plate and a preparation method thereof and a battery to improve the electrochemical performance of pre-magnesiumized silicon oxide materials.

[0004] In the first aspect, the present application provides a negative electrode plate, which includes a negative electrode active material layer and a negative electrode current collector, wherein the negative electrode active material layer is attached to the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material, wherein the negative electrode active material includes a first material and a second material, wherein the first material includes a pre-magnesiumized silicon oxide material, wherein the pre-magnesiumized silicon oxide material is a pre-magnesiumized silicon oxide body whose surface is modified with nitrogen, and the second material includes graphite.

[0005] As an optional implementation, in the pre-magnesiumized silicon oxide material, the mass ratio of nitrogen to the pre-magnesiumized silicon oxide body is (1:27) to (1:72).

[0006] As an optional implementation, the mass ratio of the pre-magnesiumized silicon oxide material to graphite is (30-40): (60-70).

[0007] As an optional embodiment, the negative electrode active material layer further includes a conductive agent and a binder, and the mass ratio of the negative electrode active material, the conductive agent and the binder is (93-95): (0.5-1.5): (4-6).

[0008] As an optional embodiment, the conductive agent includes carbon black and carbon nanotubes, and the mass ratio of carbon black to carbon nanotubes is (5-7): (3-5); and / or

[0009] The binder comprises PAA and SBR, and the mass ratio of PAA to SBR is (0.5-1.5):(0.5-1.5).

[0010] In a second aspect, the present application provides a method for preparing a negative electrode sheet, the method comprising:

[0011] Obtaining a pre-magnesiumized silicon-oxygen material, wherein the pre-magnesiumized silicon-oxygen material is a pre-magnesiumized silicon-oxygen body with nitrogen modified on the surface;

[0012] The pre-magnesiumized silicon oxide material and graphite are prepared into a slurry, which is then coated on the negative electrode current collector to obtain a negative electrode plate.

[0013] As an optional embodiment, obtaining the pre-magnesiumized silicon-oxygen material includes:

[0014] Mixing the pre-magnesiumized silicon oxide body, the nitrogen source and the carbon source to obtain a mixed solution;

[0015] The mixed solution is heated and dispersed, and then cooled and precipitated to obtain an intermediate;

[0016] The intermediate is calcined to obtain a pre-magnesium-containing silicon-oxygen material.

[0017] As an optional embodiment, the nitrogen source includes at least one of melamine, dicyandiamide and thiourea; and / or

[0018] The carbon source comprises citric acid; and / or

[0019] The mass ratio of the pre-magnesiumized silicon oxide body to the nitrogen source is (5-8):1; and / or

[0020] The mass ratio of the pre-magnesiumized silicon oxide body to the carbon source is (6-10):1; and / or

[0021] The heating temperature is 60°C to 80°C; and / or

[0022] The heating time is 0.5h to 1h; and / or

[0023] Dispersing is performed by ultrasonic dispersion; and / or

[0024] The dispersion time is 4 to 6 minutes; and / or

[0025] The calcination temperature is 700°C to 800°C; and / or

[0026] The calcination time is 2h to 5h.

[0027] In a third aspect, the present application provides a battery, comprising the negative electrode plate provided in the first aspect.

[0028] In a fourth aspect, the present application provides a battery, the battery comprising a negative electrode plate, the negative electrode plate comprising a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer being attached to the negative electrode current collector; the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising a first material and a second material, the first material comprising a pre-magnesiumized silicon oxide material, the pre-magnesiumized silicon oxide material comprising a pre-magnesiumized silicon oxide body and a coating layer coated on the pre-magnesiumized silicon oxide body, the material of the coating layer comprising Li3N, and the second material comprising graphite.

[0029] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0030] The negative electrode plate provided in the embodiment of the present application, by nitrogen modification of the surface of the pre-magnesiumized silicon oxide material, generates a large amount of Li3N component when SEI is generated on the surface of the pre-magnesiumized silicon oxide material during the charge and discharge process. The in-situ generated Li3N is a stable inorganic substance with high ion conductivity, which can improve the problem of poor lithium ion conductivity caused by magnesium silicate on the original surface of the material, thereby improving the rate and cycle performance of the battery, and improving the electrochemical performance of the pre-magnesiumized silicon oxide material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 A schematic diagram of a process for a method provided in an embodiment of the present application;

[0034] Figure 2 A graph of the cycle performance test results of a half-cell is provided for Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] The present application intends to provide a method for preparing a long-cycle pre-magnesiumized silicon oxide negative electrode and a pole piece, by nitrogen-modifying the surface of the pre-magnesiumized silicon oxide material, in-situ constructing a Li3N layer with high ionic conductivity during charging and discharging. The in-situ generated Li3N is a stable inorganic substance with high ionic conductivity, which can improve the problem of poor lithium ion conductivity caused by magnesium silicate on the original surface of the material.

[0038] An embodiment of the present application provides a negative electrode plate, which includes a negative electrode active material layer and a negative electrode current collector, wherein the negative electrode active material layer is attached to the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material, wherein the negative electrode active material includes a first material and a second material, wherein the first material includes a pre-magnesiumized silicon oxide material, wherein the pre-magnesiumized silicon oxide material is a pre-magnesiumized silicon oxide body whose surface is modified with nitrogen, and the second material includes graphite.

[0039] The negative electrode plate is prepared by nitrogen modification of the surface of the pre-magnesiumized silicon oxide material. During the charge and discharge process, a large amount of Li3N components are generated when SEI is generated on the surface of the pre-magnesiumized silicon oxide material. The in-situ generated Li3N is a stable inorganic substance with high ion conductivity, which can improve the poor lithium ion conductivity caused by magnesium silicate on the original surface of the material, thereby improving the rate and cycle performance of the battery, and improving the electrochemical performance of the pre-magnesiumized silicon oxide material.

[0040] In some embodiments, in the pre-magnesiumized silicon oxide material, the mass ratio of nitrogen to the pre-magnesiumized silicon oxide body is (1:27) to (1:72). By controlling the ratio of nitrogen in the pre-magnesiumized silicon oxide material, it is beneficial to form an appropriate amount of Li3N, which is beneficial to the ion conduction of the pre-magnesiumized silicon oxide material. The silicon oxide body can be a carbon-coated silicon oxide material.

[0041] In some embodiments, the mass ratio of the pre-magnesiumized silicon oxide material to graphite is (30-40): (60-70).

[0042] Exemplarily, the mass ratio of pre-magnesiumized silicon oxide material to graphite can be 30:70, 31:69, 32:68, 33:67, 34:66, 35:65, 36:64, 37:63, 38:62, 39:61 or 40:60, etc., and it can also be any value in the range of (30-40): (60-70).

[0043] In some embodiments, the negative electrode active material layer further includes a conductive agent and a binder, and the mass ratio of the negative electrode active material, the conductive agent and the binder is (93-95): (0.5-1.5): (4-6). Exemplarily, the mass ratio of the negative electrode active material, the conductive agent and the binder can be 94:1:5, and it can also be any value within the range of (93-95): (0.5-1.5): (4-6).

[0044] In some embodiments, the conductive agent includes carbon black and carbon nanotubes, and the mass ratio of carbon black to carbon nanotubes is (5-7): (3-5).

[0045] For example, the mass ratio of carbon black to carbon nanotubes can be 5:5, 5.5:4.5, 6:4, 6.5:3.5 or 7:3, etc. It can also be any value in the range of (5-7):(3-5).

[0046] In some embodiments, the binder includes PAA and SBR, and the mass ratio of PAA to SBR is (0.5-1.5):(0.5-1.5).

[0047] Illustratively, the mass ratio of PAA to SBR can be 0.5:0.5, 1:0.5, 1.5:0.5, 0.5:1, 0.5:1.5, 1:0.5 or 1:1.5, etc., and it can also be any value in the range of (0.5-1.5):(0.5-1.5).

[0048] Figure 1 A flow chart of the method provided in the embodiment of the present application is as follows: Figure 1 As shown, based on a general inventive concept, an embodiment of the present application also provides a method for preparing a negative electrode plate.

[0049] The method is used for preparing the above-mentioned negative electrode plate. The specific content of the negative electrode plate can refer to the above-mentioned embodiment. Since the method adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here one by one.

[0050] In some embodiments, the method comprises:

[0051] S1. Obtaining a pre-magnesiumized silicon-oxygen material, the pre-magnesiumized silicon-oxygen material is a pre-magnesiumized silicon-oxygen body whose surface is modified with nitrogen;

[0052] In some embodiments, obtaining the pre-magnesiumized silicon-oxygen material comprises:

[0053] S1.1. The pre-magnesium-containing silicon oxide body, the nitrogen source and the carbon source are mixed to obtain a mixed solution;

[0054] In some embodiments, the nitrogen source includes at least one of melamine, dicyandiamide, and thiourea.

[0055] In some embodiments, the carbon source comprises citric acid.

[0056] In some embodiments, the mass ratio of the pre-magnesiumized silicon oxide body to the nitrogen source is (5-8):1.

[0057] Exemplarily, the mass ratio of the pre-magnesiumized silicon oxide body to the nitrogen source can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1 or 8:1, etc., and can also be any value in the range of (5-8):1.

[0058] In some embodiments, the mass ratio of the pre-magnesiumized silicon oxide body to the carbon source is (6-10):1.

[0059] Exemplarily, the mass ratio of the pre-magnesiumized silicon oxide body to the carbon source can be 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, etc., and it can also be any value in the range of (6-10):1.

[0060] S1.2. The mixed solution is heated and dispersed, and then cooled and precipitated to obtain an intermediate;

[0061] In some embodiments, the heating temperature is 60° C. to 80° C. Exemplarily, the heating temperature can be 60° C., 61° C., 62° C., 63° C., 64° C., 65° C., 66° C., 67° C., 68° C., 69° C., 70° C., 71° C., 72° C., 73° C., 74° C., 75° C., 76° C., 77° C., 78° C., 79° C. or 80° C., etc., and it can also be any value within the range of 60° C. to 80° C.

[0062] In some embodiments, the heating time is 0.5 h to 1 h. For example, the heating time can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h, etc., and can also be any value within the range of 0.5 h to 1 h.

[0063] In some embodiments, the dispersion is carried out by ultrasonic dispersion, and the dispersion time is 4 min to 6 min. Exemplarily, the dispersion time can be 4 min, 4.2 min, 4.4 min, 4.6 min, 4.8 min, 5 min, 5.2 min, 5.4 min, 5.6 min, 5.8 min or 6 min, etc., and it can also be any value within the range of 4 min to 6 min.

[0064] S1.3. Calcine the intermediate to obtain a pre-magnesiumized silicon-oxygen material.

[0065] In some embodiments, the calcination temperature is 700° C. to 800° C. For example, the calcination temperature may be 700° C., 710° C., 720° C., 730° C., 740° C., 750° C., 760° C., 770° C., 780° C., 790° C. or 800° C., etc., and may also be any value within the range of 700° C. to 800° C.

[0066] In some embodiments, the calcination time is 2 h to 5 h. For example, the calcination time can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., and can also be any value within the range of 2 h to 5 h.

[0067] Specifically, in this embodiment, the preparation process of the pre-magnesiumized silicon oxide material can be: first, the pre-magnesiumized silicon oxide material is dispersed in desalted water in which a nitrogen source and citric acid are heated and dissolved. Among them, the nitrogen source can be one of melamine, dicyandiamide, and thiourea, and citric acid is used as a carbon source; the mass ratio of pre-magnesiumized silicon oxide to the nitrogen source ranges from 5:1 to 8:1, and the mass ratio of pre-magnesiumized silicon oxide to citric acid ranges from 6:1 to 10:1; the heating temperature is 60°C to 80°C, and the heating time is 0.5 to 1h; ultrasonic dispersion is used, and the dispersion time is 4 to 6min. Then, the solid precipitated after the solution is cooled is calcined at high temperature in an argon-hydrogen mixture to obtain a pre-magnesiumized silicon oxide material with surface nitrogen modification. The method comprises the following steps: firstly cooling the solution in which the pre-magnesiumized silicon-oxygen material is dispersed after being heated to room temperature, and solid will precipitate; the turbid liquid is centrifuged, washed with deionized water and ethanol, and then dried; and the dried solid is calcined at high temperature in an argon-hydrogen mixed gas with a hydrogen content of 10%, the calcination temperature being 700° C. to 800° C., and the calcination time being 2 to 5 hours, to obtain a pre-magnesiumized silicon-oxygen material with surface nitrogen modification.

[0068] S2. Pre-magnesiumized silicon oxide material and graphite are prepared into a slurry, and then coated on the negative electrode current collector to obtain a negative electrode plate.

[0069] Specifically, in this embodiment, the preparation of the negative electrode sheet can be: the obtained surface nitrogen-modified pre-magnesiumized silicon oxide material is used as the negative electrode main material and matched with a certain binder and conductive agent to make a negative electrode sheet. Among them, the negative electrode formula contains the main material, the conductive agent, and the binder, and the ratio is 94:1:5; the ratio of the surface nitrogen-modified pre-magnesiumized silicon oxide material to graphite in the main material is 35:65, the ratio of carbon black to carbon tube in the conductive agent is 6:4, and the ratio of PAA to SBR in the binder is 1:1; desalted water is added to the raw materials for slurrying, coating, drying, rolling, and die cutting to obtain the negative electrode sheet.

[0070] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0071] Example 1

[0072] A negative electrode sheet, the preparation process of which is as follows:

[0073] 1) Add melamine and citric acid to deionized water, heat at 80°C for 1 hour to dissolve, and then add pre-magnesiumized silica material and ultrasonically disperse for 5 minutes. The mass ratio of pre-magnesiumized silica material to melamine is 5:1, and the mass ratio to citric acid is 8:1. After the dispersion is cooled to room temperature, it is centrifuged, washed with deionized water and ethanol, and then dried. The obtained solid is calcined at high temperature in an argon-hydrogen mixture with a hydrogen content of 10%, and calcined at 750°C for 3 hours to obtain a pre-magnesiumized silica material with surface nitrogen modification.

[0074] 2) The obtained surface nitrogen-modified pre-magnesium-containing silicon oxide material is used as the negative electrode main material and matched with a certain binder and conductive agent to make a negative electrode plate. Among them, the negative electrode formula contains the main material, conductive agent, and binder in a ratio of 94:1:5; the ratio of the surface nitrogen-modified pre-magnesium-containing silicon oxide material to graphite in the main material is 35:65, the ratio of carbon black to carbon tube in the conductive agent is 6:4, and the ratio of PAA to SBR in the binder is 1:1; deionized water is added to the raw materials for slurry mixing, coating, drying, rolling, and die cutting to obtain a negative electrode plate.

[0075] Example 2

[0076] A negative electrode sheet, the preparation process of which is as follows:

[0077] 1) Add thiourea and citric acid to deionized water, heat at 80°C for 1 hour to dissolve, then add pre-magnesiumized silica material and ultrasonically disperse for 5 minutes. The mass ratio of pre-magnesiumized silica material to melamine is 5:1, and the mass ratio to citric acid is 8:1. After the dispersion is cooled to room temperature, it is centrifuged, washed with deionized water and ethanol, and then dried. The obtained solid is calcined at high temperature in an argon-hydrogen mixture with a hydrogen content of 10%, and calcined at 750°C for 3 hours to obtain a pre-magnesiumized silica material with surface nitrogen modification.

[0078] 2) The obtained surface nitrogen-modified pre-magnesium-containing silicon oxide material is used as the negative electrode main material and matched with a certain binder and conductive agent to make a negative electrode plate. Among them, the negative electrode formula contains the main material, conductive agent, and binder in a ratio of 94:1:5; the ratio of the surface nitrogen-modified pre-magnesium-containing silicon oxide material to graphite in the main material is 35:65, the ratio of carbon black to carbon tube in the conductive agent is 6:4, and the ratio of PAA to SBR in the binder is 1:1; deionized water is added to the raw materials for slurry mixing, coating, drying, rolling, and die cutting to obtain a negative electrode plate.

[0079] Example 3

[0080] A negative electrode sheet, the preparation process of which is as follows:

[0081] 1) Add dicyandiamide and citric acid to deionized water, heat at 65°C for 1 hour to dissolve, and then add pre-magnesiumized silica material and ultrasonically disperse for 5 minutes. The mass ratio of pre-magnesiumized silica material to melamine is 8:1, and the mass ratio to citric acid is 10:1. After the dispersion is cooled to room temperature, it is centrifuged, washed with deionized water and ethanol, and then dried. The obtained solid is calcined at high temperature in an argon-hydrogen mixture with a hydrogen content of 10%, and calcined at 800°C for 5 hours to obtain a pre-magnesiumized silica material with surface nitrogen modification.

[0082] 2) The obtained surface nitrogen-modified pre-magnesium-containing silicon oxide material is used as the negative electrode main material and matched with a certain binder and conductive agent to make a negative electrode plate. Among them, the negative electrode formula contains the main material, conductive agent, and binder in a ratio of 94:1:5; the ratio of the surface nitrogen-modified pre-magnesium-containing silicon oxide material to graphite in the main material is 35:65, the ratio of carbon black to carbon tube in the conductive agent is 6:4, and the ratio of PAA to SBR in the binder is 1:1; deionized water is added to the raw materials for slurry mixing, coating, drying, rolling, and die cutting to obtain a negative electrode plate.

[0083] Comparative Example 1

[0084] A negative electrode sheet, the preparation process of which is as follows:

[0085] The pre-magnesiumized silicon oxide material is used as the main negative electrode material and matched with a certain binder and conductive agent to make a negative electrode plate. Among them, the negative electrode formula contains the main material, conductive agent, and binder in a ratio of 94:1:5; the ratio of the pre-magnesiumized silicon oxide material with surface nitrogen modification to graphite in the main material is 35:65, the ratio of carbon black to carbon tube in the conductive agent is 6:4, and the ratio of PAA to SBR in the binder is 1:1; desalted water is added to the raw materials for slurry mixing, coating, drying, rolling, and die cutting to obtain a negative electrode plate.

[0086] The negative electrode sheets provided in each embodiment and comparative example were cut into discs with a diameter of 12 mm, button-type half-cells (the counter electrode was lithium metal) were assembled, and cycle performance tests were performed. The results are shown in Figure 2. It should be noted that since the results of Examples 1 to 3 are similar, only the results of Example 1 are shown in the accompanying drawings.

[0087] Depend on Figure 2 It can be seen that the battery composed of negative electrode sheets prepared by the method provided in the embodiment of the present application has significantly higher cycle performance while meeting the high capacity requirement.

[0088] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0089] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b and c can be single or multiple.

[0090] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate includes a negative electrode active material layer and a negative electrode current collector, wherein the negative electrode active material layer is attached to the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material, wherein the negative electrode active material includes a first material and a second material, wherein the first material includes a pre-magnesiumized silicon oxide material, wherein the pre-magnesiumized silicon oxide material is a pre-magnesiumized silicon oxide body with nitrogen modified on the surface, and the second material includes graphite.

2. The negative electrode sheet according to claim 1, characterized in that: In the pre-magnesiumized silicon oxide material, the mass ratio of nitrogen to the pre-magnesiumized silicon oxide body is (1:27) to (1:72).

3. The negative electrode sheet according to claim 1, characterized in that: The mass ratio of the pre-magnesiumized silicon oxide material to the graphite is (30-40): (60-70).

4. The negative electrode sheet according to claim 1, characterized in that: The negative electrode active material layer further includes a conductive agent and a binder, and the mass ratio of the negative electrode active material, the conductive agent and the binder is (93-95): (0.5-1.5): (4-6).

5. The negative electrode sheet according to claim 4, characterized in that: The conductive agent comprises carbon black and carbon nanotubes, and the mass ratio of the carbon black to the carbon nanotubes is (5-7): (3-5); and / or The binder comprises PAA and SBR, and the mass ratio of PAA to SBR is (0.5-1.5):(0.5-1.5).

6. A method for preparing a negative electrode sheet, characterized in that: The method comprises: Obtaining a pre-magnesiumized silicon-oxygen material, wherein the pre-magnesiumized silicon-oxygen material is a pre-magnesiumized silicon-oxygen body with nitrogen modified on the surface; The pre-magnesiumized silicon oxide material and graphite are prepared into a slurry, which is then coated on a negative electrode current collector to obtain a negative electrode plate.

7. The method for preparing a negative electrode sheet according to claim 6, characterized in that: The obtaining of the pre-magnesiumized silicon-oxygen material comprises: Mixing the pre-magnesiumized silicon oxide body, the nitrogen source and the carbon source to obtain a mixed solution; The mixed solution is heated and dispersed, and then cooled and precipitated to obtain an intermediate; The intermediate is calcined to obtain a pre-magnesium-containing silicon-oxygen material.

8. The method for preparing a negative electrode sheet according to claim 7, characterized in that: The nitrogen source comprises at least one of melamine, dicyandiamide and thiourea; and / or The carbon source comprises citric acid; and / or The mass ratio of the pre-magnesiumized silicon oxide body to the nitrogen source is (5-8):1; and / or The mass ratio of the pre-magnesiumized silicon oxide body to the carbon source is (6-10):1; and / or The heating temperature is 60°C to 80°C; and / or The heating time is 0.5h to 1h; and / or The dispersion is carried out by ultrasonic dispersion; and / or The dispersion time is 4 to 6 minutes; and / or The calcination temperature is 700°C to 800°C; and / or The calcination time is 2h to 5h.

9. A battery, characterized in that: The battery comprises the negative electrode sheet according to any one of claims 1 to 5.

10. A battery, characterized in that: The battery comprises a negative electrode plate, the negative electrode plate comprises a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer is attached to the negative electrode current collector; the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a first material and a second material, the first material comprises a pre-magnesiumized silicon oxide material, the pre-magnesiumized silicon oxide material comprises a pre-magnesiumized silicon oxide body and a coating layer coated on the pre-magnesiumized silicon oxide body, the material of the coating layer comprises Li3N, and the second material comprises graphite.

Images