Negative electrode active materials and their preparation methods, negative electrode sheets, sodium-ion batteries and related electrical equipment

Abstract

This application provides a negative electrode active material and its preparation method, a negative electrode sheet, a sodium-ion battery, and electrical devices, relating to the field of sodium-ion batteries. The negative electrode active material includes a carbon matrix and phosphorus, nitrogen, sulfur, and boron doped into the carbon matrix; based on the total mass of the negative electrode active material, the phosphorus content is 1-10 wt%, the nitrogen content is 1-10 wt%, the sulfur content is 1-3 wt%, and the boron content is 1-3 wt%. The specific doping amounts of phosphorus, nitrogen, sulfur, and boron in this application, combined with the carbon matrix, enable the negative electrode active material to possess excellent cycle stability, excellent rate performance, and high capacity, while reducing volume expansion during cycling and minimizing adverse problems such as electrode breakage.

Description

Technical Field

[0001] This application relates to the field of sodium-ion batteries, and more particularly to a negative electrode active material and its preparation method, a negative electrode sheet, a sodium-ion battery, and electrical equipment. Background Technology

[0002] Existing sodium-ion batteries and anode technologies still have some problems that limit their large-scale application.

[0003] While using ultrathin metallic sodium as the negative electrode material can significantly improve the energy density of sodium-ion batteries, the flexibility and viscosity of metallic sodium itself make it very difficult to produce ultrathin sodium foil. At the same time, sodium metal is prone to dendrite growth, infinite volume expansion and low coulombic efficiency during cycling, which may lead to internal short circuits or performance degradation in the battery, thereby reducing the cycle life and safety of the battery.

[0004] When hard carbon materials are used as anode materials for sodium-ion batteries, they suffer from problems such as low capacity, which limits the widespread application of sodium-ion batteries.

[0005] Therefore, it is necessary to improve the active materials of the negative electrode in sodium-ion batteries. Summary of the Invention

[0006] The purpose of this application is to provide a negative electrode active material and its preparation method, a negative electrode sheet, a sodium-ion battery, and electrical equipment to solve the above-mentioned problems.

[0007] To achieve the above objectives, this application adopts the following technical solution: A negative electrode active material, the negative electrode active material comprising a carbon matrix and phosphorus, nitrogen, sulfur and boron doped in the carbon matrix; Based on the total mass of the negative electrode active material, the phosphorus content is 1-10 wt%, the nitrogen content is 1-10 wt%, the sulfur content is 1-3 wt%, and the boron content is 1-3 wt%.

[0008] According to embodiments of this application, the structure of the carbon matrix includes at least one of graphitized carbon and amorphous carbon.

[0009] This application also provides a method for preparing the negative electrode active material as described above, including: A mixed raw material is obtained by mixing a carbon source, a nitrogen source, thiourea, and potassium tetraborate. The mixed raw materials were carbonized under an inert atmosphere to obtain an intermediate. The intermediate was ball-milled with elemental phosphorus to obtain the negative electrode active material.

[0010] According to embodiments of this application, the carbon source includes at least one of resin and biomass raw materials; the resin includes at least one of thermoplastic resin and thermosetting resin; the thermosetting resin includes thermosetting phenolic resin; and the biomass raw materials include at least one of coconut shell, bamboo, walnut shell, and straw. And / or, the nitrogen source includes at least one of melamine, polydopamine, and polypyridine; And / or, the elemental phosphorus includes at least one of red phosphorus, white phosphorus, and black phosphorus.

[0011] According to an embodiment of this application, the mass ratio of the carbon source to the nitrogen source, thiourea, and potassium tetraborate is (1-10):(1-10):(1-3):(1-3). And / or, the carbonization treatment temperature is 800-1600℃, the carbonization treatment heating rate is 2-10℃ / min, and the carbonization treatment time is 6-12h.

[0012] According to an embodiment of this application, the mass ratio of the intermediate to the elemental phosphorus is (1-10):(1-10).

[0013] According to an embodiment of this application, the ball milling rotation speed is 100-500 rpm / min, and the ball milling time is 12-24 h; And / or, the ball milling process is carried out in an inert gas atmosphere.

[0014] This application also provides a negative electrode sheet, which includes a negative electrode active material, wherein the negative electrode active material is the negative electrode active material described above or a negative electrode active material prepared by the preparation method described above.

[0015] This application also provides a sodium-ion battery, including the negative electrode sheet described above.

[0016] This application also provides an electrical device, including the sodium-ion battery described above.

[0017] Compared with the prior art, the beneficial effects of this application include: The negative electrode active material provided in this application includes a carbon matrix and phosphorus, nitrogen, sulfur, and boron doped into the carbon matrix. The carbon matrix restricts the volume expansion of deposited sodium metal, improving battery safety and cycle life. Nitrogen doping increases the electrochemical active sites in the material, enhances the adsorption capacity for sodium ions, and promotes rapid electron transport, thus improving the battery's rate performance and cycle life. Compared to nitrogen atoms, sulfur and boron atoms have higher electron-donating capabilities. Sulfur and boron doping can cause wrinkling of the carbon material's edge planes, providing abundant defects and electrochemical active sites for ion adsorption, which helps enrich nitrogen. Phosphorus, as a sodium-loving nucleation site, can effectively reduce the sodium ion nucleation barrier, decrease internal polarization, promote uniform sodium ion deposition, effectively prevent sodium dendrite growth, and improve battery safety. Phosphorus-nitrogen co-doping expands the interlayer distance of the carbon matrix, generating a large number of active sites and improving electronic conductivity. The specific doping amounts of phosphorus, nitrogen, sulfur, and boron in this application work in conjunction with the carbon matrix to give the negative electrode active material excellent cycle stability, excellent rate performance, and high capacity. This can reduce volume expansion during cycling and reduce the occurrence of adverse problems such as electrode breakage.

[0018] The preparation method of the negative electrode active material provided in this application is simple, easy to industrialize, and has broad application prospects.

[0019] The negative electrode sheet provided in this application, using the aforementioned negative electrode active material as raw material, can effectively improve safety performance, cycle performance, and battery stability.

[0020] The sodium-ion battery and electrical equipment provided in this application have excellent electrochemical performance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0022] Figure 1 This is a SEM image of the negative electrode active material prepared in Example 1. Detailed Implementation

[0023] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0024] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0025] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0026] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0027] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0028] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0029] A negative electrode active material, the negative electrode active material comprising a carbon matrix and phosphorus, nitrogen, sulfur and boron doped in the carbon matrix; Based on the total mass of the negative electrode active material, the phosphorus content is 1-10 wt%, the nitrogen content is 1-10 wt%, the sulfur content is 1-3 wt%, and the boron content is 1-3 wt%.

[0030] Nitrogen atoms contain lone pairs of electrons. Doping a carbon matrix with nitrogen can improve the conductivity and wettability of the carbon material in the electrolyte. This helps to reduce the contact resistance between the porous carbon material and the electrolyte, thereby improving electrochemical performance. When the nitrogen content in the negative electrode active material is within the above-mentioned range, it ensures that the negative electrode active material maintains good structural stability and cycle performance while maintaining high electrochemical performance. If the nitrogen content in the negative electrode active material is too high, it may lead to a decrease in the structural stability of the porous carbon material, thus affecting its cycle performance and service life.

[0031] For example, the phosphorus content in the negative electrode active material is any value between 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or 1-10wt%; the nitrogen content in the negative electrode active material is any value between 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or 1-10wt%; the sulfur content in the negative electrode active material is any value between 1wt%, 2wt%, 3wt%, or 1-3wt%; and the boron content in the negative electrode active material is any value between 1wt%, 2wt%, 3wt%, or 1-3wt%.

[0032] According to embodiments of this application, the structure of the carbon matrix includes at least one of graphitized carbon and amorphous carbon.

[0033] This application also provides a method for preparing the negative electrode active material as described above, including: A mixed raw material is obtained by mixing a carbon source, a nitrogen source, thiourea, and potassium tetraborate. The mixed raw materials were carbonized under an inert atmosphere to obtain an intermediate. The intermediate was ball-milled with elemental phosphorus to obtain the negative electrode active material.

[0034] According to embodiments of this application, the carbon source includes at least one of resin and biomass raw materials; the resin includes at least one of thermoplastic resin and thermosetting resin; the thermosetting resin includes thermosetting phenolic resin; and the biomass raw materials include at least one of coconut shell, bamboo, walnut shell, and straw. The nitrogen source includes at least one of melamine, polydopamine, and polypyridine; The elemental phosphorus includes at least one of red phosphorus, white phosphorus, and black phosphorus.

[0035] According to an embodiment of this application, the mass ratio of the carbon source to the nitrogen source, thiourea, and potassium tetraborate is (1-10):(1-10):(1-3):(1-3). For example, the mass ratio of carbon source to nitrogen source, thiourea, and potassium tetraborate can be any value between 1:1:1:1, 5.5:5.5:2:2, 6:2:1:1, 10:10:3:3, or (1-10):(1-10):(1-3):(1-3).

[0036] The carbonization treatment temperature is 800-1600℃, the carbonization treatment heating rate is 2-10℃ / min, and the carbonization treatment time is 6-12h.

[0037] For example, the carbonization temperature is 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, or any value between 800℃ and 1600℃. The heating rate of the carbonization process is 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or any value between 2℃ and 10℃ / min; the carbonization time is 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any value between 6h and 12h.

[0038] In some embodiments, the inert atmosphere for carbonization includes at least one of nitrogen and argon.

[0039] According to an embodiment of this application, the mass ratio of the intermediate to the elemental phosphorus is (1-10):(1-10). For example, the mass ratio of the intermediate to the elemental phosphorus is any value between 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or (1-10):(1-10).

[0040] According to an embodiment of this application, the ball milling rotation speed is 100-500 rpm / min, and the ball milling time is 12-24 h; For example, the ball milling speed can be any value between 100 rpm / min, 200 rpm / min, 300 rpm / min, 400 rpm / min, 500 rpm / min, or 100-500 rpm / min. The ball milling time can be any value between 12h, 14h, 16h, 18h, 20h, 22h, 24h, or 12-24h.

[0041] The ball milling process is carried out in an inert gas atmosphere.

[0042] Furthermore, the inert atmosphere for ball milling includes at least one of nitrogen and argon.

[0043] This application also provides a negative electrode sheet, which includes a negative electrode active material, wherein the negative electrode active material is the negative electrode active material described above or a negative electrode active material prepared by the preparation method described above.

[0044] Furthermore, the negative electrode sheet includes a negative current collector and a negative active layer located on the negative current collector.

[0045] The raw materials for the negative electrode active layer also include sodium ion-conducting components, binders, and conductive agents.

[0046] The sodium-conducting ion component includes at least one of a sodium halide compound and a sodium chalcogenide compound, wherein the sodium chalcogenide compound includes Na3PS4.

[0047] The mass ratio of the negative electrode active material to the sodium ion-conducting component, binder, and conductive agent is (70-80):(10-20):(5-10):(5-10); for example, the mass ratio of the negative electrode active material to the sodium ion-conducting component, binder, and conductive agent is any value between 70:10:5:5, 70:10:10:10, 80:10:5:5, 80:20:10:10, or (70-80):(10-20):(5-10):(5-10).

[0048] The adhesive includes at least one of styrene-butadiene rubber and polyvinylidene fluoride; The conductive agent includes at least one of acetylene black, conductive porous carbon, and graphene.

[0049] The negative electrode current collector is aluminum foil or copper foil; The thickness of the negative electrode current collector is 10μm-20μm; for example, the thickness of the negative electrode current collector is any value between 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or 10μm-20μm.

[0050] The thickness of the negative electrode active layer is 5μm-50μm. For example, the thickness of the negative electrode active layer is any value between 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, or 5μm-50μm.

[0051] This application also provides a sodium-ion battery, including the negative electrode sheet described above.

[0052] This application also provides an electrical device, including the sodium-ion battery described above.

[0053] Electrical equipment includes, but is not limited to, electric vehicles, electric bicycles, smartphones, tablets, smartwatches, health monitors, and drones.

[0054] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0055] Example 1 Example 1 provides a negative electrode active material, the preparation method of which includes: (1) Thermosetting phenolic resin, polydopamine, thiourea and potassium tetraborate are mixed in a mass ratio of 6:2:1:1 to obtain mixed raw materials; The mixed raw materials were placed in a tubular furnace for carbonization under an argon atmosphere. The carbonization temperature was 1000℃, the heating rate was 2℃ / min, and the carbonization time was 4h. After cooling to room temperature, an intermediate was obtained.

[0056] (2) The intermediate and nano-red phosphorus with D50 of 50 nm were mixed at a mass ratio of 9:1 and ball-milled. The ball milling speed was 200 rpm / min, the maximum temperature of the ball milling jar was 50 °C, the atmosphere was argon, and the ball milling time was 16 h. The negative electrode active material was obtained after ball milling.

[0057] Example 1: The negative electrode active material includes a carbon matrix and phosphorus, nitrogen, sulfur and boron doped in the carbon matrix. The structure of the carbon matrix is ​​amorphous carbon. The phosphorus content in the negative electrode active material is 8 wt%, the nitrogen content is 4.5 wt%, the sulfur content is 1.8 wt%, and the boron content is 1.8 wt%.

[0058] The SEM image of the negative electrode active material prepared in Example 1 is shown below. Figure 1 As shown.

[0059] Example 2 The difference between Example 2 and Example 1 is that the thermosetting phenolic resin in step (1) is replaced with an equal mass of coconut shell. Everything else is the same as in Example 1.

[0060] Example 2: The negative electrode active material includes a carbon matrix and phosphorus, nitrogen, sulfur and boron doped in the carbon matrix. The carbon matrix has an amorphous carbon structure. The negative electrode active material contains 8 wt% phosphorus, 5.5 wt% nitrogen, 2.2 wt% sulfur and 1.5 wt% boron.

[0061] Example 3 The difference between Example 3 and Example 1 is that the nano red phosphorus in step (2) is replaced with an equal mass of black phosphorus. Everything else is the same as in Example 1.

[0062] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that polydopamine, thiourea, and potassium tetraborate are not added in step (1). Everything else is the same as in Example 1.

[0063] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that step (2) is omitted, and the intermediate obtained in step (1) is used as the negative electrode active material. Everything else is the same as in Example 1.

[0064] Comparative Example 3 The negative electrode of Comparative Example 3 uses commercial sodium sheet (manufacturer: Dongguan Kelude Experimental Equipment Technology Co., Ltd., product batch number: 20240610).

[0065] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that polydopamine is not added in step (1). Everything else is the same as in Example 1.

[0066] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that thiourea is not added in step (1). Everything else is the same as in Example 1.

[0067] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that potassium tetraborate is not added in step (1). Everything else is the same as in Example 1.

[0068] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that step (2) is omitted, and the same mass of nano-red phosphorus as in Example 1 is added in step (1) to prepare the negative electrode active material in one step through carbonization treatment. Everything else is the same as in Example 1.

[0069] The negative electrode sheets were prepared under the same conditions using the negative electrode active materials of the examples and comparative examples. Specifically, the following steps were taken: the negative electrode active materials of the examples or comparative examples, Na3PS4, acetylene black, and polyvinylidene fluoride were mixed uniformly in a mass ratio of 70%:10%:10%:10%, N-methylpyrrolidone was added, and the solid content was 30%. The mixture was then ball-milled at high speed to obtain a mixed slurry. The mixed slurry was coated onto an aluminum foil current collector with a thickness of 10 μm using a coating machine, and after vacuum drying, it was rolled to obtain a sodium-ion battery negative electrode sheet with a negative electrode active layer thickness of 20 μm.

[0070] The negative electrode sheets of the examples or comparative examples are assembled into batteries under the same conditions. Specifically, the negative electrode sheets are prepared using the negative electrode sheets of the examples or comparative examples prepared by the above method, the positive electrode sheets are O3-type layered oxides, and the electrolyte is commercial sodium battery electrolyte (manufacturer: Dongguan Kelude Experimental Equipment Technology Co., Ltd., product batch number: 20240812). They are assembled into 2032 coin-type sodium full cells according to conventional methods.

[0071] Electrochemical performance tests were conducted on the batteries under the same test conditions, specifically including: at room temperature, the sodium-ion batteries prepared in the examples and comparative examples were activated at a rate of 0.1C for the first cycle, and then charged and discharged cycles were conducted at a rate of 0.5C and the corresponding voltage window. The test was terminated when the discharge capacity of the battery decreased to 95% of the initial capacity, and the number of cycles was recorded.

[0072] The 5C rate capacity retention is calculated using the following formula: 5C rate capacity retention rate (%) = ×100% The test results are shown in Table 1.

[0073] Table 1. Comparison of electrochemical performance of sodium-ion batteries prepared in the examples and comparative examples.

[0074] As can be seen from Table 1, the number of cycles and 5C rate capacity retention of Examples 1-3 are significantly higher than those of Comparative Examples 1-7, indicating that Examples 1-3 have both high cycle stability and excellent rate performance. Moreover, Examples 1-3 also have good reversible specific capacity, and their overall performance is significantly better than that of Comparative Examples 1-7.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0076] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A negative electrode active material, characterized in that, The negative electrode active material includes a carbon matrix and phosphorus, nitrogen, sulfur and boron doped in the carbon matrix; Based on the total mass of the negative electrode active material, the phosphorus content is 1-10 wt%, the nitrogen content is 1-10 wt%, the sulfur content is 1-3 wt%, and the boron content is 1-3 wt%.

2. The negative electrode active material according to claim 1, characterized in that, The structure of the carbon matrix includes at least one of graphitized carbon and amorphous carbon.

3. A method for preparing the negative electrode active material as described in claim 1 or 2, characterized in that, include: A mixed raw material is obtained by mixing a carbon source, a nitrogen source, thiourea, and potassium tetraborate. The mixed raw materials were carbonized under an inert atmosphere to obtain an intermediate. The intermediate was ball-milled with elemental phosphorus to obtain the negative electrode active material.

4. The method for preparing the negative electrode active material according to claim 3, characterized in that, The carbon source includes at least one of resin and biomass raw materials; the resin includes at least one of thermoplastic resin and thermosetting resin; the thermosetting resin includes thermosetting phenolic resin; the biomass raw materials include at least one of coconut shell, bamboo, walnut shell, and straw. And / or, the nitrogen source includes at least one of melamine, polydopamine, and polypyridine; And / or, the elemental phosphorus includes at least one of red phosphorus, white phosphorus, and black phosphorus.

5. The method for preparing the negative electrode active material according to claim 3, characterized in that, The mass ratio of the carbon source to the nitrogen source, thiourea, and potassium tetraborate is (1-10):(1-10):(1-3):(1-3). And / or, the carbonization treatment temperature is 800-1600℃, the carbonization treatment heating rate is 2-10℃ / min, and the carbonization treatment time is 6-12h.

6. The method for preparing the negative electrode active material according to claim 5, characterized in that, The mass ratio of the intermediate to the elemental phosphorus is (1-10):(1-10).

7. The method for preparing the negative electrode active material according to any one of claims 3-6, characterized in that, The ball milling speed is 100-500 rpm / min, and the ball milling time is 12-24 h; And / or, the ball milling process is carried out in an inert gas atmosphere.

8. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative electrode active material, which is the negative electrode active material according to claim 1 or 2, or a negative electrode active material prepared by the preparation method according to any one of claims 3-7.

9. A sodium-ion battery, characterized in that, Includes the negative electrode sheet as described in claim 8.

10. An electrical-related device, characterized in that, Including the sodium-ion battery as described in claim 9.

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