Phosphorus-carbon negative electrode plate and preparation method thereof, sodium-ion battery and electric equipment

Abstract

The invention relates to the technical field of sodium-ion batteries, in particular to a phosphorus-carbon negative electrode plate, a preparation method thereof, a sodium-ion battery and electric equipment. The phosphorus-carbon negative plate comprises a negative current collector and a negative coating arranged on the surface of the negative current collector; the negative coating is mainly composed of a phosphorus-carbon negative material, a conductive agent and a binder; the conductive agent comprises conductive carbon black and a linear conductive agent, the linear conductive agent has a fibrous structure, and the linear conductive agent comprises single-walled carbon nanotubes and / or carbon fibers; and the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material is greater than or equal to 1. According to the invention, the linear conductive agent is added into the phosphorus-carbon negative electrode sheet of the sodium-ion battery, and the ratio of the average length of the linear conductive agent to the particle size D50 of the phosphorus-carbon negative electrode material is controlled to be greater than or equal to 1, so that powdered phosphorus particles can be effectively communicated, and the cycle capacity retention rate is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a phosphorus-carbon negative electrode sheet and a preparation method thereof, a sodium ion battery and electrical equipment. Background Art

[0002] Because sodium resources account for 2.74% of the earth's crust, which is about 420 times the lithium reserves, sodium-ion batteries have huge market potential in the long run.

[0003] Currently, there is a significant energy density gap between sodium-ion batteries and lithium-ion batteries. Compared to traditional hard carbon materials for sodium-ion batteries, phosphorus-carbon materials have a higher energy density. Their application in sodium-ion battery anodes can effectively improve the energy density of these batteries.

[0004] However, the phosphorus component in the phosphorus-carbon material expands by about 300% during the charge and discharge process, causing the particles to break and fail, resulting in a capacity decay of about 12% in the first 100 cycles of the sodium-ion battery with the phosphorus-carbon material as the negative electrode.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The first objective of the present invention is to provide a phosphorus-carbon negative electrode sheet. By adding a linear conductive agent and controlling the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material to be ≥1, the sheet effectively connects the pulverized phosphorus particles, thereby improving the cycle capacity retention rate. This solves the problem of phosphorus expansion in existing phosphorus-carbon materials during charge and discharge, which causes particle breakage and failure, leading to severe capacity decay in the first 100 cycles of sodium-ion batteries.

[0007] The second object of the present invention is to provide a method for preparing a phosphorus-carbon negative electrode sheet, which has the advantages of simple operation, short process, low cost and suitability for mass production.

[0008] A third object of the present invention is to provide a sodium ion battery having excellent cycle performance.

[0009] A fourth object of the present invention is to provide an electrical device.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0011] The present invention first provides a phosphorus-carbon negative electrode sheet, which includes a negative electrode current collector and a negative electrode coating arranged on the surface of the negative electrode current collector, wherein the negative electrode coating is mainly composed of a phosphorus-carbon negative electrode material, a conductive agent and a binder; wherein the conductive agent includes conductive carbon black and a linear conductive agent, the linear conductive agent has a fibrous structure, and the linear conductive agent includes single-walled carbon nanotubes and / or carbon fibers; the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material is ≥1, wherein the units of the average length of the linear conductive agent and the D50 particle size of the phosphorus-carbon negative electrode material are both μm.

[0012] Furthermore, the linear conductive agent is a single-walled carbon nanotube, or the linear conductive agent is composed of single-walled carbon nanotubes and carbon fibers; wherein the mass ratio of the conductive carbon black, the single-walled carbon nanotubes and the carbon fibers is 1-3.5:0-1.5:0.05-0.3.

[0013] Furthermore, the mass ratio of phosphorus element to carbon element in the phosphorus-carbon negative electrode material is 1-10:90-99.

[0014] Furthermore, the mass ratio of the phosphorus-carbon negative electrode material, the conductive agent, and the binder in the negative electrode coating is 93-94.5:2-4:3-4.5.

[0015] Furthermore, the binder includes polyacrylic acid and / or sodium polyacrylate.

[0016] The present invention further provides a method for preparing a phosphorus-carbon negative electrode sheet, comprising the following steps: mixing a phosphorus-carbon negative electrode material, a conductive agent, a binder and a solvent to obtain a negative electrode slurry; coating the negative electrode slurry on the surface of a negative electrode current collector, and drying to obtain the phosphorus-carbon negative electrode sheet.

[0017] The present invention further provides a sodium ion battery comprising the above-mentioned phosphorus-carbon negative electrode sheet.

[0018] Furthermore, the capacity retention rate of the sodium ion battery after 100 cycles at 25° C. and 1C is ≥95%.

[0019] Furthermore, the capacity retention rate of the sodium ion battery after 1000 cycles at 25° C. and 1C is ≥88%.

[0020] The present invention also provides an electrical device comprising the above-mentioned sodium ion battery.

[0021] Compared with existing technologies, the present invention offers the following advantages: By adding a linear conductive agent and controlling the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material to be ≥1, the phosphorus-carbon negative electrode sheet forms a network of conductive pathways that effectively connect the pulverized phosphorus particles, thereby improving cycle capacity retention. This solves the problem of phosphorus expansion in existing phosphorus-carbon materials during charge and discharge, which causes particle breakage and failure, leading to severe capacity decay in the first 100 cycles of sodium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 is the SEM image of carbon fiber;

[0024] Figure 2 This is the SEM image of single-walled carbon nanotubes. DETAILED DESCRIPTION

[0025] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0026] Unless otherwise specified, in the present invention, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," "third," and "fourth" serve only as non-exhaustive enumeration and description, and should not constitute closed-ended limitations on quantity.

[0027] Unless otherwise specified, the terms "include" and "comprising" used in the present invention may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0028] Unless otherwise specified, in the present invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. Among them, "several" refers to any two or any two or more.

[0029] In a first aspect, the present invention provides a phosphorus-carbon negative electrode sheet for a sodium ion battery, comprising a negative electrode current collector and a negative electrode coating arranged on at least one surface of the negative electrode current collector, wherein the negative electrode coating is mainly composed of a phosphorus-carbon negative electrode material, a conductive agent and a binder.

[0030] Preferably, the phosphorus-carbon negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on both side surfaces of the negative electrode current collector.

[0031] The conductive agent includes conductive carbon black (SP) and a linear conductive agent, the linear conductive agent has a fibrous structure (i.e., the microstructure of the linear conductive agent is fibrous, or filamentous, or rod-like), and the linear conductive agent includes single-walled carbon nanotubes (SWCNTs) and / or carbon fibers (VGCFs).

[0032] The ratio of the average length L (in μm) of the linear conductive agent to the D50 particle size (abbreviated as D50, in μm) of the phosphorus-carbon negative electrode material satisfies: L / D50 ≥ 1, wherein the value of L / D50 includes but is not limited to any one of 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.5 or a range between any two of the values.

[0033] The present invention significantly improves the cycle performance of a sodium ion battery made from the phosphorus-carbon negative electrode sheet by adding a linear conductive agent to the phosphorus-carbon negative electrode sheet and controlling the multiple relationship between the average length of the linear conductive agent and the D50 particle size of the phosphorus-carbon negative electrode material to be ≥1. The capacity decay of the sodium ion battery over the first 100 cycles is reduced from about 12% to about 3%.

[0034] Specifically, VGCF and SWCNT are linear conductive agents that can achieve point contact and line contact. Among them, the microscopic morphology of VGCF is rod-shaped, such as Figure 1 As shown in Figure 2, it can bridge phosphorus particles. The microscopic morphology of SWCNT is filamentous, as shown in Figure 2. Figure 2 As shown in the figure, it can entangle the phosphorus particles. The two form a network of conductive paths, which can effectively connect the pulverized phosphorus particles and improve the cycle capacity retention rate.

[0035] It is understood that the average length of VGCF refers to the average length of the VGCF particles.

[0036] Average Length of SWCNTs Transmission electron microscopy (TEM) was used to collect images of SWCNT samples, and then ImageJ graphic analysis software was used to collect statistical SWCNT length data.

[0037] In some specific embodiments, the linear conductive agent is a single-walled carbon nanotube, or the linear conductive agent is composed of single-walled carbon nanotubes and carbon fibers.

[0038] The mass ratio of the conductive carbon black, the single-walled carbon nanotubes, and the carbon fibers is 1-3.5 (e.g., 1.3, 1.5, 1.8, 2, 2.2, 2.5, 2.7, 3, or 3.1): 0-1.5 (e.g., 0.2, 0.3, 0.5, 0.8, 1.0, or 1.3): 0.05-0.3 (e.g., 0.06, 0.08, 0.1, 0.15, 0.2, 0.25, or 0.3). This helps further improve the cycle capacity retention rate of the sodium ion battery made with the phosphorus-carbon negative electrode sheet.

[0039] In some specific embodiments, the mass ratio of phosphorus to carbon in the phosphorus-carbon negative electrode material is 1-10:90-99, for example, 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92 or 9:91.

[0040] In some specific embodiments, the mass ratio of the phosphorus-carbon negative electrode material, the conductive agent, and the binder in the negative electrode coating is 93-94.5 (e.g., 93.2, 93.5, 93.7, 93.9, 94.0, 94.2, or 94.4): 2-4 (e.g., 2.3, 2.5, 2.8, 3, 3.2, 3.5, or 3.7): 3-4.5 (e.g., 3.2, 3.3, 3.5, 3.7, 3.9, 4, 4.2, or 4.4). This helps to further improve the cycle capacity retention rate of the sodium ion battery made with the phosphorus-carbon negative electrode sheet.

[0041] In some specific embodiments, the binder includes polyacrylic acid (PAA) and / or sodium polyacrylate (PAANa).

[0042] In a second aspect, the present invention provides a method for preparing a phosphorus-carbon negative electrode sheet, comprising the following steps: mixing a phosphorus-carbon negative electrode material, a conductive agent, a binder, and a solvent to obtain a negative electrode slurry; coating the negative electrode slurry on the surface of a negative electrode current collector, and drying to obtain the phosphorus-carbon negative electrode sheet.

[0043] The preparation method has the advantages of simple operation, short process, low cost, and suitability for mass production.

[0044] In some specific embodiments, the preparation method of the phosphorus-carbon negative electrode sheet specifically includes: mixing the conductive agent and the binder in a certain mass ratio uniformly in deionized water (i.e., solvent), stirring at room temperature and vacuum for 1 hour to obtain a uniform conductive adhesive; adding the phosphorus-carbon negative electrode material to the conductive adhesive, stirring at room temperature and vacuum for 1 hour to obtain a negative electrode slurry; evenly applying the above-mentioned negative electrode slurry on both sides of the negative electrode aluminum foil current collector, and obtaining a phosphorus-carbon negative electrode sheet after drying.

[0045] In a third aspect, the present invention provides a sodium ion battery comprising a phosphorus-carbon negative electrode sheet.

[0046] This sodium ion battery has high energy density, low cost and excellent cycle performance.

[0047] In some specific embodiments, the capacity retention rate of the sodium ion battery after 100 cycles at 25°C and 1C is ≥95%, including but not limited to any one of 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, and 99%, or a range between any two of the values.

[0048] In some specific embodiments, the capacity retention rate of the sodium ion battery after 1000 cycles at 25°C and 1C is ≥88%, including but not limited to 88%, 88.5%, 89%, 89.5%, 90%, 91%, 92%, 93%, 94%, 95%, or any one of the point values ​​or the range value between any two of them.

[0049] In a fourth aspect, the present invention provides an electrical device comprising a sodium ion battery.

[0050] It is understood that the above-mentioned electrical equipment includes any equipment, device or system using the above-mentioned sodium ion battery, including but not limited to: laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, and large household batteries.

[0051] The embodiments of the present invention will be described in detail below with reference to the examples. However, it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0052] Example 1

[0053] The method for preparing a phosphorus-carbon negative electrode sheet provided in this embodiment includes the following steps: weighing a phosphorus-carbon negative electrode material, a conductive agent, and a binder, PAANa, in a mass ratio of 93.2:3.3:3.5, wherein the mass ratio of phosphorus to carbon in the phosphorus-carbon negative electrode material is 6:94. The conductive agent comprises conductive carbon black SP and SWCNT in a mass ratio of 3.1:0.2, with an average SWCNT length of 5.3 μm. The D50 particle size of the phosphorus-carbon negative electrode material is 5.3 μm, meaning that the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material is 1. The conductive agent and binder are uniformly dispersed in deionized water (solvent) and stirred at room temperature (25°C) under vacuum for 1 hour to produce a uniform conductive adhesive. The phosphorus-carbon negative electrode material is added to the conductive adhesive and stirred at room temperature (25°C) under vacuum for 1 hour to produce a phosphorus-carbon negative electrode slurry. The negative electrode slurry is evenly coated on both sides of a negative aluminum foil current collector and dried to produce a phosphorus-carbon negative electrode sheet.

[0054] The phosphorus-carbon negative electrode sheet comprises a negative electrode aluminum foil current collector and a negative electrode coating arranged on both side surfaces of the negative electrode aluminum foil current collector.

[0055] Example 2

[0056] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 1, except that: the conductive agent is conductive carbon black SP, VGCF and SWCNT in a mass ratio of 2.6:0.5:0.2, wherein the average length of SWCNT is 5.3 μm, the average length of VGCF is 6.0 μm, and the D50 particle size of the phosphorus-carbon negative electrode material is 5.3 μm, that is, the ratio of the average length of SWCNT to the D50 particle size of the phosphorus-carbon negative electrode material is 1, and the ratio of the average length of VGCF to the D50 particle size of the phosphorus-carbon negative electrode material is 1.1.

[0057] Example 3

[0058] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 1, except that the average length of the SWCNT is 6.9 μm, that is, the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material is 1.3.

[0059] Example 4

[0060] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 2, except that the average length of SWCNT is 6.9 μm, that is, the ratio of the average length of SWCNT to the D50 particle size of the phosphorus-carbon negative electrode material is 1.3.

[0061] Example 5

[0062] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 2, except that the mass ratio of the conductive carbon black SP, VGCF and SWCNT is replaced with 1:1.5:0.3.

[0063] Example 6

[0064] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 2, except that the mass ratio of the conductive carbon black SP, VGCF and SWCNT is replaced with 2:1:0.05.

[0065] Example 7

[0066] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 1, except that the mass ratio of the phosphorus-carbon negative electrode material, the conductive agent, and the binder PAANa is replaced with 94.5:2.5:3.

[0067] Example 8

[0068] The preparation method of the phosphorus-carbon negative electrode sheet provided in this embodiment is basically the same as that in Example 1, except that the mass ratio of phosphorus to carbon in the phosphorus-carbon negative electrode material is replaced with 10:90.

[0069] Comparative Example 1

[0070] The preparation method of the phosphorus-carbon negative electrode sheet provided in this comparative example is basically the same as that in Example 1, except that the conductive agent is only conductive carbon black SP and does not contain SWCNT.

[0071] Comparative Example 2

[0072] The preparation method of the phosphorus-carbon negative electrode sheet provided in this comparative example is basically the same as that in Example 1, except that the average length of the SWCNT is 2.33 μm, that is, the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material is 0.44.

[0073] Comparative Example 3

[0074] The preparation method of the phosphorus-carbon negative electrode sheet provided in this comparative example is basically the same as that of Example 2, except that the average length of SWCNT is 2.65 μm, that is, the ratio of the average length of SWCNT to the D50 particle size of the phosphorus-carbon negative electrode material is 0.5.

[0075] Experimental example

[0076] The phosphorus-carbon negative electrode sheets prepared in each embodiment and each comparative example were assembled into battery cells, and 1C cycle tests were performed at 25°C and a voltage window of 2.0V to 4.0V. The test results are shown in Table 1.

[0077] Among them, when preparing the battery cell: the positive electrode of each embodiment and the comparative example uses the same model and batch of layered oxygen positive electrode material; the diaphragm of each embodiment and the comparative example uses the same model and batch of 9+3 ceramic diaphragm, PE base film 9μm, ceramic coating 3μm; the electrolyte of each embodiment and the comparative example uses the same model and batch of sodium ion battery electrolyte; the positive electrode sheet, negative electrode sheet, diaphragm and electrolyte are assembled into a 26700 cylindrical battery cell for testing.

[0078] Table 1 Cyclic performance test results

[0079]

[0080] As can be seen from Table 1 above, compared with Comparative Example 1, Example 1 and Example 2 add a linear conductive agent and control the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material to be ≥1. The 25°C / 1C capacity retention rate increases by 8.8% and 9.4% after 100 cycles, and by 7.6% and 10.1% after 1000 cycles. This is because the phosphorus in the phosphorus-carbon negative electrode exists in the form of red phosphorus, and the conductivity of red phosphorus (about 10-12 S·m -1 ) is extremely low, and the volume expansion rate of phosphorus particles during charge and discharge is about 300%, causing the particles to break and pulverize, trapping the circulating sodium in an extremely low conductivity environment, resulting in a decrease in capacity retention. SP is a granular conductive agent that can only achieve point contact and cannot effectively connect the powdered phosphorus particles. Therefore, increasing SP cannot effectively improve the capacity retention of the phosphorus-carbon negative electrode. VGCF and SWCNT are linear conductive agents that can achieve point contact and line contact. VGCF is rod-shaped and can bridge phosphorus particles, and SWCNT is filamentous and can wrap around phosphorus particles. The two form a mesh-like conductive path, effectively connecting the powdered phosphorus particles and achieving an improvement in the cycle capacity retention rate.

[0081] In Comparative Examples 2 and 3, although linear conductive agents were also added, the ratio of the average length of SWCNT to the D50 particle size of the phosphorus-carbon negative electrode material was less than 1. As a result, the negative electrode particles were too large, and the VGCF and SWCNT were attached to a single particle. The inter-particle connectivity efficiency was greatly reduced, and an effective conductive network could not be formed, thus limiting the improvement in the cycle capacity retention rate.

[0082] In summary, the present invention can effectively connect the pulverized phosphorus particles by adding a linear conductive agent to the phosphorus-carbon negative electrode sheet of the sodium ion battery and controlling the ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material to be ≥1, thereby effectively improving the cycle capacity retention rate.

[0083] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A phosphorus-carbon negative electrode sheet, characterized in that: It includes a negative electrode current collector and a negative electrode coating provided on the surface of the negative electrode current collector, wherein the negative electrode coating is mainly composed of a phosphorus-carbon negative electrode material, a conductive agent and a binder; Wherein, the conductive agent includes conductive carbon black and a linear conductive agent, the linear conductive agent has a fibrous structure, and the linear conductive agent includes single-walled carbon nanotubes and / or carbon fibers; The ratio of the average length of the linear conductive agent to the D50 particle size of the phosphorus-carbon negative electrode material is ≥1, wherein the units of the average length of the linear conductive agent and the D50 particle size of the phosphorus-carbon negative electrode material are both μm.

2. The phosphorus-carbon negative electrode sheet according to claim 1, characterized in that: The linear conductive agent is a single-walled carbon nanotube, or the linear conductive agent is composed of single-walled carbon nanotubes and carbon fibers; wherein the mass ratio of the conductive carbon black, the single-walled carbon nanotubes and the carbon fibers is 1-3.5:0-1.5:0.05-0.

3.

3. The phosphorus-carbon negative electrode sheet according to claim 1, characterized in that: The mass ratio of phosphorus element to carbon element in the phosphorus-carbon negative electrode material is 1-10:90-99.

4. The phosphorus-carbon negative electrode sheet according to claim 1, characterized in that: The mass ratio of the phosphorus-carbon negative electrode material, the conductive agent, and the binder in the negative electrode coating is 93-94.5:2-4:3-4.

5.

5. The phosphorus-carbon negative electrode sheet according to claim 1, characterized in that: The binder includes polyacrylic acid and / or sodium polyacrylate.

6. The method for preparing a phosphorus-carbon negative electrode sheet according to any one of claims 1 to 5, characterized in that: The steps include: A negative electrode slurry is obtained by mixing a phosphorus-carbon negative electrode material, a conductive agent, a binder and a solvent; The negative electrode slurry is coated on the surface of the negative electrode current collector, and dried to obtain the phosphorus-carbon negative electrode sheet.

7. A sodium ion battery, characterized in that: The invention comprises the phosphorus-carbon negative electrode sheet as claimed in any one of claims 1 to 5.

8. The sodium ion battery according to claim 7, characterized in that: The capacity retention rate of the sodium ion battery after 100 cycles at 25° C. and 1C is ≥95%.

9. The sodium ion battery according to claim 7, characterized in that: The capacity retention rate of the sodium ion battery after 1000 cycles at 25° C. and 1C is ≥88%.

10. An electrical device, characterized in that: Comprising the sodium ion battery as claimed in claim 7.

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