A negative electrode sheet, a method for manufacturing the same, and a battery

Abstract

The application relates to a negative pole piece and a preparation method and application thereof, and belongs to the technical field of secondary batteries. The negative pole piece comprises a negative pole active material layer and a negative pole current collector, and the negative pole active material layer is attached to the negative pole current collector. The negative pole active material layer comprises a negative pole active material, the negative pole active material comprises a first material and a second material, the first material comprises a pre-magnesia silicon-oxygen material, the pre-magnesia silicon-oxygen material is a pre-magnesia silicon-oxygen body with a nitrogen surface modification, and the second material comprises graphite. The surface of the pre-magnesia silicon-oxygen material is modified with nitrogen. In the charging and discharging process, more Li3N components are generated on the surface of the pre-magnesia silicon-oxygen material when an SEI is generated. The in-situ generated Li3N is a stable inorganic substance with high ion conductivity, can improve the poor lithium ion conductivity caused by the original surface magnesium silicate of the material, and further improves the rate and cycle performance of the battery, thereby improving the electrochemical performance of the pre-magnesia silicon-oxygen material.

Description

TECHNICAL FIELD

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

[0002] Silicon negative electrodes have been widely used in high-energy batteries due to their high capacity, wide source and low price. However, the silicon negative electrode has the disadvantage of high expansion rate, which can cause particle pulverization, electrode structure damage, SEI film regrowth and other problems, affecting the long cycle stability of the battery. In order to solve the problem of silicon negative electrode expansion, silicon-oxygen material emerges as the times require. The inert buffer provided by silicon-oxygen material can greatly inhibit the expansion of silicon negative electrode, but it also has the problem of low initial efficiency. In order to solve this problem, pre-lithiation or pre-magnesium operation is performed. Among them, pre-magnesium silicon-oxygen does not need to use expensive lithium raw materials, and the cost is low, so it has been widely concerned. However, since the pre-magnesium silicon-oxygen 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

[0003] The present application provides a negative electrode sheet, a preparation method thereof and a battery to improve the electrochemical performance of pre-magnesium silicon-oxygen material.

[0004] In a first aspect, the present application provides a negative electrode sheet, which comprises a negative electrode active material layer and a negative electrode current collector, and 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, and the negative electrode active material comprises a first material and a second material, the first material comprises a pre-magnesium silicon-oxygen material, and the pre-magnesium silicon-oxygen material is a pre-magnesium silicon-oxygen body with a surface modified with nitrogen, and the second material comprises graphite.

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

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

[0007] As an optional implementation, the negative electrode active material layer further comprises 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 implementation, 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

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

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

[0011] obtaining a pre-magnesia silicon-oxygen material, the pre-magnesia silicon-oxygen material being a pre-magnesia silicon-oxygen body modified with nitrogen on the surface;

[0012] preparing a slurry of the pre-magnesia silicon-oxygen material and graphite, and then coating the slurry on a negative electrode current collector to obtain the negative electrode sheet.

[0013] As an optional implementation, obtaining the pre-magnesia silicon-oxygen material comprises:

[0014] mixing the pre-magnesia silicon-oxygen body, a nitrogen source, and a carbon source to obtain a mixed solution;

[0015] heating and dispersing the mixed solution, and then cooling and precipitating to obtain an intermediate;

[0016] calcining the intermediate to obtain the pre-magnesia silicon-oxygen material.

[0017] As an optional implementation, the nitrogen source comprises 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-magnesia silicon-oxygen body and the nitrogen source is (5-8):1; and / or

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

[0021] the heating temperature is 60-80℃; and / or

[0022] the heating time is 0.5-1h; and / or

[0023] the dispersing is ultrasonic dispersing; and / or

[0024] the dispersing time is 4-6min; and / or

[0025] the calcining temperature is 700-800℃; and / or

[0026] the calcining time is 2-5h.

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

[0028] In a fourth aspect, the present application provides a battery, the battery comprising a negative electrode sheet, the negative electrode sheet 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-magnesia silicon-oxygen material, the pre-magnesia silicon-oxygen material comprising a pre-magnesia silicon-oxygen body and a coating layer coated on the pre-magnesia silicon-oxygen body, the material of the coating layer comprising Li3N, the second material comprising graphite.

[0029] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0030] The negative electrode sheet provided by the embodiments of the present application has the following advantages: the surface of the pre-magnesia silicon-oxygen material is modified by nitrogen, and more Li3N components are generated on the surface of the pre-magnesia silicon-oxygen material when the SEI is generated in the charging and discharging process. The in-situ generated Li3N is a stable inorganic substance with high ion conductivity, which can improve the poor lithium ion conductivity caused by the original surface magnesium silicate of the material, and further improve the rate and cycle performance of the battery, thereby improving the electrochemical performance of the pre-magnesia silicon-oxygen material. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0033] Figure 1 The flowchart of the method provided by the embodiments of the present application is shown in the figure.

[0034] Figure 2 The cycle performance test results of the half-cell provided by the embodiment 1 and the comparative example 1 of the present application are shown in the figure. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0036] Unless otherwise specifically indicated, each of the various materials, reagents, instruments and equipment that are used in the present application are commercially available or can be prepared by known methods.

[0037] The present application intends to provide a long-circulation pre-magnesium silicon-oxygen negative electrode and a preparation method of an electrode sheet. A Li3N layer with high ion conductivity is constructed in situ during charging and discharging by nitrogen modification of the surface of the pre-magnesium silicon-oxygen 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 the original surface magnesium silicate of the material.

[0038] The negative electrode sheet provided by the present application includes a negative electrode active material layer and a negative electrode current collector, and 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, and the negative electrode active material includes a first material and a second material. The first material includes a pre-magnesium silicon-oxygen material, and the pre-magnesium silicon-oxygen material is a pre-magnesium silicon-oxygen body with nitrogen modification on the surface. The second material includes graphite.

[0039] The negative electrode sheet generates more Li3N components on the surface of the pre-magnesium silicon-oxygen material during the formation of SEI on the surface of the pre-magnesium silicon-oxygen material during the charging and discharging process. The in-situ generated Li3N is a stable inorganic substance with high ion conductivity, which can improve the poor lithium ion conductivity caused by the original surface magnesium silicate of the material, thereby improving the rate and cycle performance of the battery and improving the electrochemical performance of the pre-magnesium silicon-oxygen material.

[0040] In some embodiments, the mass ratio of nitrogen to the pre-magnesium silicon-oxygen body in the pre-magnesium silicon-oxygen material is (1:27) to (1:72). By controlling the proportion of nitrogen in the pre-magnesium silicon-oxygen material, an appropriate amount of Li3N is formed, which is conducive to the ion conduction of the pre-magnesium silicon-oxygen material. The silicon-oxygen body can be a carbon-coated silicon monoxide material.

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

[0042] For example, the mass ratio of the pre-magnesium silicon-oxygen 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. It can also be any value within the range of (30-40):(60-70).

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

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

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

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

[0047] For example, the mass ratio of the PAA and the 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, and can also be any value within the range of (0.5-1.5):(0.5-1.5).

[0048] Figure 1 A flowchart of the method provided by the embodiments of the present application is shown in Figure 1 Based on the overall inventive concept, the embodiments of the present application also provide a preparation method of a negative electrode sheet.

[0049] The method is used for the preparation of the negative electrode sheet described above, and the specific content of the negative electrode sheet can refer to the above embodiments. Since the method adopts part or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0050] In some embodiments, the method comprises:

[0051] S1. obtaining a pre-magnesia silicon-oxygen material, the pre-magnesia silicon-oxygen material being a pre-magnesia silicon-oxygen body modified with nitrogen on the surface;

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

[0053] S1.1. mixing the pre-magnesia silicon-oxygen body, a nitrogen source and a carbon source to obtain a mixed solution;

[0054] In some embodiments, the nitrogen source comprises 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-magnesia silicon-oxygen bulk and the nitrogen source is (5-8):1.

[0057] For example, the mass ratio of the pre-magnesia silicon-oxygen bulk and the nitrogen source can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, or 8:1, etc., which can also be any value within the range of (5-8):1.

[0058] In some embodiments, the mass ratio of the pre-magnesia silicon-oxygen bulk and the carbon source is (6-10):1.

[0059] For example, the mass ratio of the pre-magnesia silicon-oxygen bulk and 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., which can also be any value within the range of (6-10):1.

[0060] S1.2. Heating and dispersing the mixed solution, and then cooling and precipitating to obtain an intermediate;

[0061] In some embodiments, the heating temperature is 60-80℃. For example, the heating temperature can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, or 80℃, etc., which can also be any value within the range of 60-80℃.

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

[0063] In some embodiments, the dispersion is ultrasonic dispersion, and the dispersion time is 4-6min. For example, the dispersion time can be 4min, 4.2min, 4.4min, 4.6min, 4.8min, 5min, 5.2min, 5.4min, 5.6min, 5.8min, or 6min, etc., which can also be any value within the range of 4-6min.

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

[0065] In some embodiments, the temperature of the calcination is 700-800 °C. Illustratively, the temperature of the calcination can 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., which can also be any value within the range of 700-800 °C.

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

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

[0068] S2. The pre-magnesia silicon-oxygen material and graphite are prepared into a slurry, which is then coated on the negative current collector to obtain a negative electrode sheet.

[0069] Specifically, in this embodiment, the preparation of the negative electrode sheet can be as follows: the obtained pre-magnesia silicon-oxygen material with surface nitrogen modification is used as a negative electrode main material, and is combined with a certain amount of binder and conductive agent to make a negative electrode sheet. The negative electrode formula contains a main material, a conductive agent, and a binder, and the ratio is 94:1:5; the ratio of the pre-magnesia silicon-oxygen 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 preparation, coating, drying, rolling, and die cutting, to obtain the negative electrode sheet.

[0070] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. The experimental methods in the following examples, if no specific conditions are noted, are generally determined according to national standards. If there is no corresponding national standard, the general international standards, conventional conditions, or the conditions suggested by the manufacturer are used.

[0071] Example 1

[0072] A negative electrode sheet is prepared as follows:

[0073] 1) Melamine and citric acid are added to the desalted water, heated at 80°C for 1 h to dissolve, and then pre-magnesium siliceous material is added and ultrasonically dispersed for 5 min. The mass ratio of the pre-magnesium siliceous material to melamine is 5:1, and the mass ratio to citric acid is 8:1. After the dispersion is cooled to room temperature, centrifugal separation is performed, and the desalted water and ethanol are washed and dried. The obtained solid is calcined at high temperature in argon-hydrogen mixed gas with a hydrogen content of 10%, and calcined at 750°C for 3 h to obtain a pre-magnesium siliceous material modified by surface nitrogen.

[0074] 2) The obtained pre-magnesium siliceous material modified by surface nitrogen is used as a negative electrode main material to make a negative electrode sheet together with a certain amount of binder and conductive agent. In the negative electrode formula, the main material, conductive agent, and binder are in a ratio of 94:1:5; the ratio of the pre-magnesium siliceous material modified by surface nitrogen 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; the raw materials are mixed with desalted water, coated, dried, rolled, and die-cut to obtain the negative electrode sheet.

[0075] Example 2

[0076] A negative electrode sheet is prepared as follows:

[0077] 1) Thiourea and citric acid are added to the desalted water, heated at 80°C for 1 h to dissolve, and then pre-magnesium siliceous material is added and ultrasonically dispersed for 5 min. The mass ratio of the pre-magnesium siliceous material to melamine is 5:1, and the mass ratio to citric acid is 8:1. After the dispersion is cooled to room temperature, centrifugal separation is performed, and the desalted water and ethanol are washed and dried. The obtained solid is calcined at high temperature in argon-hydrogen mixed gas with a hydrogen content of 10%, and calcined at 750°C for 3 h to obtain a pre-magnesium siliceous material modified by surface nitrogen.

[0078] 2) The obtained surface nitrogen modified pre-magnesia silicon-oxygen material is used as a negative electrode main material to make a negative electrode sheet together with a certain binder and conductive agent. 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-magnesia silicon-oxygen 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; salt-free water is added to the raw materials for slurry mixing, coating, drying, rolling, die cutting, and the negative electrode sheet is obtained.

[0079] Example 3

[0080] A negative electrode sheet is prepared as follows:

[0081] 1) Dicyandiamide and citric acid are added to salt-free water, heated at 65°C for 1h to dissolve, and then pre-magnesia silicon-oxygen material is added and ultrasonically dispersed for 5min. The mass ratio of pre-magnesia silicon-oxygen material to melamine is 8:1, and the mass ratio of pre-magnesia silicon-oxygen material to citric acid is 10:1. After the dispersion is cooled to room temperature, centrifugal separation is performed, and the salt-free water and ethanol are washed and dried. The obtained solid is calcined at high temperature in argon-hydrogen mixed gas with a hydrogen content of 10%, and calcined at 800°C for 5h to obtain the surface nitrogen modified pre-magnesia silicon-oxygen material.

[0082] 2) The obtained surface nitrogen modified pre-magnesia silicon-oxygen material is used as a negative electrode main material to make a negative electrode sheet together with a certain binder and conductive agent. 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-magnesia silicon-oxygen 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; salt-free water is added to the raw materials for slurry mixing, coating, drying, rolling, die cutting, and the negative electrode sheet is obtained.

[0083] Comparative Example 1

[0084] A negative electrode sheet is prepared as follows:

[0085] The pre-magnesia silicon-oxygen material is used as a negative electrode main material to make a negative electrode sheet together with a certain binder and conductive agent. 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-magnesia silicon-oxygen 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; salt-free water is added to the raw materials for slurry mixing, coating, drying, rolling, die cutting, and the negative electrode sheet is obtained.

[0086] The negative electrode sheets provided in each embodiment and comparative example were cut into 12mm diameter circular pieces, assembled into coin cell half-cells (with lithium metal as the counter electrode), and subjected to cycle performance testing. 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 figures.

[0087] Depend on Figure 2 It is evident that the battery composed of the negative electrode sheet prepared by the method provided in the embodiments of this application has significantly higher cycle performance while meeting the requirement of high capacity.

[0088] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0089] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely 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. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means 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 single 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 a single or multiple.

[0090] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A negative electrode sheet, characterized by, The negative electrode sheet 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-magnesia silicon-oxygen material, the pre-magnesia silicon-oxygen material is a pre-magnesia silicon-oxygen body with a surface modified with nitrogen, and the second material comprises graphite; The pre-magnesia silicon-oxygen body with the surface modified with nitrogen generates Li3N in situ on the surface of the pre-magnesia silicon-oxygen material during the charging and discharging process of the battery; The pre-magnesia silicon-oxygen material is prepared by the following method: mixing a pre-magnesia silicon-oxygen body, a nitrogen source and a carbon source to obtain a mixed solution; heating and dispersing the mixed solution, and then cooling and precipitating to obtain an intermediate; calcining the intermediate to obtain the pre-magnesia silicon-oxygen material, the nitrogen source comprises at least one of melamine, dicyandiamide and thiourea, the carbon source comprises citric acid, and the calcination temperature is 700-800 DEG C.

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

3. The negative electrode sheet according to claim 1, wherein The mass ratio of the pre-magnesia silicon-oxygen material to the graphite is (30-40):(60-70).

4. The negative electrode sheet according to claim 1, wherein The negative electrode active material layer further comprises 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 by 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 the PAA to the SBR is (0.5-1.5):(0.5-1.5).

6. A method of producing the negative electrode sheet according to any one of claims 1 to 5, characterized by, The method comprises: obtaining a pre-magnesia silicon-oxygen material, the pre-magnesia silicon-oxygen material being a pre-magnesia silicon-oxygen body with a surface modified with nitrogen; preparing a slurry of the pre-magnesia silicon-oxygen material and graphite, and then coating the slurry on a negative electrode current collector to obtain a negative electrode sheet.

7. The method for preparing the negative electrode sheet according to claim 6, wherein: the mass ratio of the pre-magnesia silicon-oxygen body to the nitrogen source is (5-8):1; and / or the mass ratio of the pre-magnesia silicon-oxygen body to the carbon source is (6-10):1; and / or the heating temperature is 60-80 DEG C; and / or the heating time is 0.5-1 h; and / or the dispersion is ultrasonic dispersion; and / or the dispersion time is 4-6 min; and / or the calcination time is 2-5 h.

8. A battery, characterized by The battery comprises the negative electrode sheet according to any one of claims 1-5.

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