Sodium ion battery, positive pole piece and electric equipment

Abstract

The invention provides a sodium ion battery, a positive pole piece and electric equipment, the sodium ion battery comprises the positive pole piece, the positive pole piece comprises a positive pole material layer, the positive pole material layer comprises a positive pole material and a conductive agent, and the conductive agent comprises graphene; the average particle size D50 of the positive electrode material is recorded as a, the number of layers of the graphene is recorded as n, and the following conditions are met: a is more than or equal to 1 mu m and less than or equal to 9 mu m, and n is more than or equal to 10 and less than or equal to 20. The sodium ion battery provided by the invention has improved cycle performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a sodium ion battery, a positive electrode sheet and an electrical device. Background Art

[0002] Sodium-ion batteries have attracted widespread attention due to their abundant sodium reserves, low price, and uniform distribution. They may replace lithium-ion batteries in certain areas in the future, and are expected to be used in portable electronic devices, electric vehicles, hybrid vehicles, etc. However, current sodium-ion batteries often have the risk of sodium precipitation due to the large migration impedance of sodium ions on the negative electrode side, resulting in reduced cycle performance. Summary of the invention

[0003] Based on this, the present application provides a sodium ion battery, a positive electrode plate and an electrical device, which can enable the sodium ion battery to obtain improved cycle performance.

[0004] A first aspect of the present application provides a sodium ion battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode material and a conductive agent, wherein the conductive agent comprises graphene;

[0005] The average particle size D50 of the positive electrode material is denoted as a, and the number of graphene layers is denoted as n, which satisfies the following conditions: 1 μm≤a≤9 μm, 10≤n≤20.

[0006] In some embodiments of the present application, the following conditions are met: a 1 / 2 ≤0.2×n.

[0007] In some embodiments of the present application, the following conditions are met: a 1 / 2 ≤0.15×n.

[0008] In some embodiments of the present application, the mass proportion of the graphene in the positive electrode material layer is w, satisfying one or more of the following conditions:

[0009] (1)1.2a≤100w×n≤1.6a;

[0010] (2) 0.1%≤w≤0.6%.

[0011] In some embodiments of the present application, the following condition is satisfied: 0.5a≤100w×n≤0.8a.

[0012] In some embodiments of the present application, one or more of the following conditions are met:

[0013] (1) The conductive agent further comprises one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black and Ketjen black;

[0014] (2) The positive electrode material includes one or more of Prussian blue compounds, layered oxides, and polyanion-type compounds, and may be a layered oxide;

[0015] Optionally, the layered oxide satisfies the chemical formula Na x M y O 2 , where 0 < x ≤ 1, 0.9 < y ≤ 1, and M includes transition metal elements of the 3d group.

[0016] In some embodiments of the present application, the positive electrode material layer further contains a binder;

[0017] Optionally, the mass ratio of the positive electrode material, the conductive agent, and the binder is (90% - 98%):(1% - 5%):(1% - 5%);

[0018] Optionally, the binder includes one or more of polyacrylonitrile, hydrogenated nitrile, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene, and polyolefin compounds.

[0019] The second aspect of the present application provides a positive electrode tab, including a positive electrode material layer, the positive electrode material layer containing a positive electrode material and a conductive agent, and the conductive agent including graphene;

[0020] Denote the average particle size D50 of the positive electrode material as a, and the number of layers of the graphene as n, satisfying the following conditions: 1 μm ≤ a ≤ 9 μm, 10 ≤ n ≤ 20.

[0021] In some embodiments of the present application, the positive electrode tab is the positive electrode tab in the sodium-ion battery described in the first aspect of the present application.

[0022] The third aspect of the present application provides an electrical device, including the sodium-ion battery described in the first aspect of the present application.

[0023] The electrical device of the present application includes the sodium-ion battery provided by the present application, and thus has at least the same advantages as the sodium-ion battery.

[0024] By appropriately controlling the volume average particle size D50 of the positive electrode material and the number of layers of the conductive agent graphene, the present application enables them to form an effective combination. On the one hand, it can improve the positive electrode electron kinetics and appropriately weaken the positive electrode sodium ion kinetics, making the sodium ion insertion / extraction speeds on the positive and negative electrode sides match, reducing the risk of sodium deposition on the negative electrode, and improving the cycle performance; on the other hand, it can also increase the contact area between the graphene network structure and the positive electrode material, improve the electron conductivity of the positive electrode, reduce polarization, and improve the high-temperature cycle performance of the battery cell. Specific Embodiments

[0025] In order to facilitate understanding of the present application, the present application will be described more comprehensively below. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0026] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. It should be noted that, unless otherwise specified, the term "and / or" used herein includes any and all combinations of one or more related listed items, and "above" and "below" are inclusive of the number, and the meaning of "multiple" in "one or more" is more than two.

[0028] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0029] In this article, if there are multiple steps involved in the method flow, unless there is a clear different description in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders than described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0030] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0031] In traditional sodium-ion batteries, the negative electrode material is usually made of carbon-based materials, especially hard carbon, as the main material. However, the negative electrode with carbon-based materials, especially hard carbon as the main negative electrode material, usually has the problem of low kinetics. Therefore, at the same rate, the negative electrode faces a higher risk of sodium precipitation, such as low sodium precipitation window rates at room temperature and low temperature; in addition, it has been reported that the negative electrode DC resistance (DCR) accounts for about 75% of the entire battery cell, which is significantly higher than the positive electrode DCR. The sodium ion migration impedance determined by the structure of the negative electrode material is large, resulting in mismatched sodium ion deintercalation speeds at the positive and negative electrodes, resulting in a high risk of sodium precipitation and low cycle performance. Based on this, the present application proposes a sodium-ion battery, which, by appropriately designing the material on the positive electrode side, can improve the electronic conductivity on the positive electrode side while appropriately weakening the sodium ion migration ability on the positive electrode side, so that the sodium ion kinetics of the positive and negative electrodes are closer, which is conducive to reducing the risk of sodium precipitation on the negative electrode side, and can effectively improve the battery's cycle performance and safety of use.

[0032] In a first aspect, the present application provides a sodium ion battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode material and a conductive agent, wherein the conductive agent comprises graphene;

[0033] The average particle size D50 of the positive electrode material is denoted as a, and the number of graphene layers is denoted as n, which satisfies the following conditions: 1 μm≤a≤9 μm, 10≤n≤20.

[0034] The sodium ion battery provided in the present application adopts a graphene conductive agent in the positive electrode plate, and controls the number of graphene layers to 10 to 20 layers, while controlling the average particle size D50 of the positive electrode material to 1 μm to 9 μm, so that the contact area between the two-dimensional network structure of the graphene and the positive electrode material can be larger, so that the positive electrode has better electronic conduction ability, reduces polarization, effectively improves the electronic dynamics of the positive electrode, and improves the high-temperature cycle performance of the battery cell.

[0035] At the same time, the number of graphene layers and the average particle size D50 of the positive electrode material are controlled within a suitable range, so that the number of graphene layers and the average particle size D50 of the positive electrode material can be appropriately matched, so that the multilayer graphene is attached to a larger area on the surface of the positive electrode material, and the surface of the positive electrode material is more attached and coated, thereby having a proper hindering effect on the deintercalation of positive electrode sodium ions, and appropriately reducing the sodium ion desorption rate on the positive electrode side during charging, so that it can match the relatively slow sodium ion kinetics on the negative electrode side, thereby reducing the risk of sodium precipitation on the negative electrode side and improving the battery cycle performance and cell safety performance.

[0036] In this way, the present application appropriately controls the volume average particle size D50 of the positive electrode material and the number of layers of the conductive agent graphene to form an effective combination of the two. On the one hand, it can improve the positive electrode electron dynamics and appropriately weaken the positive electrode sodium ion dynamics, so that the sodium ion deintercalation speeds on the positive and negative electrode sides are matched, reducing the risk of sodium precipitation at the negative electrode and improving the cycle performance; on the other hand, it can also increase the contact area between the graphene network structure and the positive electrode material, improve the electronic conductivity of the positive electrode, reduce polarization, and improve the high-temperature cycle performance of the battery cell.

[0037] In some embodiments, the average particle size D50 of the positive electrode material may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or within a range consisting of any of the above values.

[0038] As an example, the volume average particle size D50 of the positive electrode material can be tested with a laser particle size analyzer according to the particle size distribution laser diffraction method specified in GB / T 19077-2016.

[0039] In some embodiments, the number of graphene layers can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or within a range consisting of any of the above values.

[0040] As an example, the number of graphene layers can be tested using a Raman spectrometer.

[0041] In some embodiments, the following conditions are met: a 1 / 2 ≤0.2×n; optionally, a 1 / 2≤0.15×n. In this way, the positive electrode material and graphene are better matched, which is conducive to further reducing the risk of sodium precipitation at the negative electrode and further improving the battery cycle performance; at the same time, when the positive electrode material that meets this condition is matched with graphene, the electrochemical performance and structural stability of the battery can be better balanced.

[0042] In some embodiments, the mass proportion of the graphene in the positive electrode material layer is w, which satisfies the following conditions: 1.2a≤100w×n≤1.6a; optionally, 0.5a≤100w×n≤0.8a.

[0043] The appropriate number of graphene layers is conducive to moderately reducing the positive electrode sodium ion deintercalation speed and reducing the risk of negative electrode sodium precipitation. However, when the number of graphene layers is relatively high, it is easy to excessively weaken the positive electrode sodium ion deintercalation speed, which is easy to increase the polarization internal resistance of the battery and the battery cell cycle retention rate. In view of this, by controlling the volume average particle size a of the positive electrode material, the mass proportion w of graphene in the positive electrode material layer, and the number of graphene layers n to satisfy the above relationship, not only can the positive electrode sodium ion deintercalation speed be appropriately weakened and the risk of negative electrode sodium precipitation be reduced, but also graphene can play a better conductivity and mechanical support role in the positive electrode material; in this way, through reasonable design and optimization, a better balance can be found between conductivity, mechanical properties and energy density.

[0044] If the product of the mass percentage of graphene and the number of layers is relatively small, the graphene may not provide sufficient conductivity and mechanical support, affecting the performance of the battery; if the product of the mass percentage of graphene and the number of layers is relatively large, too much graphene may occupy too much space, reducing the proportion of the positive electrode material, thereby affecting the energy density of the battery.

[0045] In some embodiments, the mass proportion of the graphene in the positive electrode material layer is w, which satisfies the following condition: 0.1%≤w≤0.6%. For example, the mass proportion of graphene in the positive electrode material layer can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% or within the range of any of the above values. In this way, it is beneficial to further reduce the risk of sodium precipitation at the negative electrode and further improve the battery cycle performance.

[0046] In some embodiments, the conductive agent further includes one or more of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, acetylene black (SP), and Ketjen black.

[0047] In some embodiments, the positive electrode material layer further includes a binder.

[0048] In some embodiments, the mass ratio of the positive electrode material, the conductive agent, and the binder is (90% - 98%):(1% - 5%):(1% - 5%). For example, the mass ratio can be 90%:5%:5%, 91%:4%:5%, 92%:4%:4%, 93%:3%:4%, 94%:3%:3%, 95%:3%:2%, 96%:2%:2%, 97%:2%:1%, 98%:1%:1% or within the range composed of any of the above values.

[0049] In some embodiments, the binder includes one or more of polyacrylonitrile, hydrogenated nitrile butadiene, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene, and polyolefin compounds.

[0050] In some embodiments, the positive electrode material includes one or more of Prussian blue compounds, layered oxides, and polyanion-type compounds, and may be optionally a layered oxide.

[0051] In some embodiments, the layered oxide satisfies the chemical formula Na x M y O 2 , where 0 < x ≤ 1, 0.9 < y ≤ 1, and M includes 3d group transition metal elements; for example, M may include, but is not limited to, one or more of Ni, Mn, Fe, Co, and Cu. When the positive electrode material is a layered oxide, it has a better matching effect with the conductive agent multi-layer graphene, can further reduce the risk of sodium deposition on the negative electrode, and can further improve the cycling performance of the battery.

[0052] In some embodiments, the positive electrode plate further includes a positive electrode current collector, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0053] In some embodiments, the sodium-ion battery further includes a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process of the battery, sodium ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate; the electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate; the separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows sodium ions to pass through.

[0054] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0055] In some embodiments, the negative electrode material includes a carbon-based material and one or more of the optional alloy materials; optionally, the carbon-based material includes one or more of hard carbon, soft carbon and graphite; the alloy material includes one or more of tin alloy, titanium alloy and lead alloy. When the negative electrode material includes a carbon-based material, especially a hard carbon material, the number of graphene layers is matched with the average particle size D50 of the positive electrode material to improve the negative electrode sodium precipitation and battery cycle performance.

[0056] In a second aspect, the present application provides a positive electrode sheet, comprising a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode material and a conductive agent, wherein the conductive agent comprises graphene;

[0057] The average particle size D50 of the positive electrode material is denoted as a, and the number of graphene layers is denoted as n, which satisfies the following conditions: 1 μm≤a≤9 μm, 10≤n≤20.

[0058] In some embodiments, the positive electrode plate is the positive electrode plate in the sodium ion battery described in the first aspect of the present application.

[0059] The role played by the positive electrode plate of the second aspect of the present application in the battery is the same as that of the first aspect of the present application, and will not be elaborated here.

[0060] In a third aspect, the present application provides an electrical device comprising the sodium ion battery described in the first aspect of the present application.

[0061] In some embodiments, the type of the electric device is not particularly limited, and it can be any electronic device known in the prior art. For example, the electric device can include, but is not limited to, power tools, electric cars, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, etc.

[0062] Example

[0063] The following are specific examples, which more specifically describe the contents disclosed in this application, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0064] Example 1

[0065] (1) The sodium layer oxygen positive electrode NaNi 0.33 Fe 0.33Mn 0.33 O 2 The conductive agent and the binder PVDF were homogenized in N-methylpyrrolidone at a mass ratio of 93%: (0.2% graphene + 1.5% CNTs + 1.3% SP): 4% to prepare a positive electrode slurry, and the positive electrode slurry was coated on the opposite surfaces of the aluminum foil, and the positive electrode sheet was obtained after drying, roller baking and slicing, wherein the number of graphene layers was n=10, and the average particle size D50 of the positive electrode material was a=4μm; the single-sided coating surface density of the positive electrode sheet was 160mg / m 2 The compaction density after roller pressing is 1.6g / cm 3 .

[0066] (2) Hard carbon, conductive carbon black and binder are homogenized in a mass ratio of 96%:1%:3% to prepare negative electrode slurry, and the negative electrode slurry is coated on the opposite sides of the copper foil. After drying, roller pressing and baking, and slicing, the negative electrode sheet is obtained; the single-sided coating surface density of the positive electrode sheet is 80g / m 2 The compaction density after roller pressing is 0.95g / cm 3 .

[0067] (3) The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound into a square bare cell, loaded with aluminum plastic film, and then injected with non-aqueous electrolyte, sealed, and after standing, hot and cold pressing, and chemical formation, a sodium ion battery is obtained; wherein the solvent in the non-aqueous electrolyte includes PC (propylene carbonate) and EMC (ethyl methyl carbonate), the volume ratio of the two is 1:1, and the solute is sodium salt NaPF 6 , its molar concentration is 1 mol / L.

[0068] Embodiments 2 to 7

[0069] The preparation method is similar to that of Example 1, with the main difference being that in step (1), at least one of the average particle size D50 of the positive electrode material, the number of graphene layers n, and the mass proportion w of graphene in the positive electrode material layer is changed, as shown in Table 1 below.

[0070] Example 8

[0071] The preparation method is similar to that of Example 2, except that in step (1), an equal mass percentage of polyanionic positive electrode NaFePO 4 Replace the sodium electrode with oxygen positive electrode.

[0072] Comparative Example 1

[0073] The preparation method is similar to that of Example 1, with the main difference being that in step (1), graphene is replaced by SP in an equal mass ratio, so that the positive electrode material layer does not contain graphene.

[0074] Comparative Examples 2 to 4

[0075] The preparation method is similar to that of Example 1, with the main difference being that in step (1), at least one of the average particle size D50 of the positive electrode material, the number of graphene layers n, and the mass proportion w of graphene in the positive electrode material layer is changed, as shown in Table 1 below.

[0076] The sodium ion batteries prepared in Examples 1 to 8 and Comparative Examples 1 to 4 were subjected to relevant performance tests, and the test results are shown in Table 1 below.

[0077] Among them, the test conditions or test standards for each performance test item are as follows:

[0078] (1) Capacity retention rate and sodium precipitation

[0079] At 25℃, the sodium-ion battery is left for 10 minutes, then charged to 3.65V at 1C constant current and constant voltage; left for 10 minutes, discharged to 2.0V at 1C constant current, this is one cycle; if it is cycled continuously for 1500 times, the Nth capacity retention rate = Nth discharge capacity / third discharge capacity*100%.

[0080] After disassembling the sodium-ion battery after 1500 cycles, the sodium precipitation on the negative electrode side was observed.

[0081] Table 1

[0082]

[0083] In Table 1, it can be seen from the comparison between Examples 1 to 8 and Comparative Example 1 that the conductive agent contains graphene, which is beneficial to reducing sodium precipitation and improving the cycle performance. It can be seen from the comparison between Examples 1 to 8 and Comparative Examples 2 to 4 that controlling a or n within a suitable range is beneficial to improving the cycle performance.

[0084] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A sodium ion battery, characterized in that: A positive electrode sheet is included, wherein the positive electrode sheet includes a positive electrode material layer, wherein the positive electrode material layer includes a positive electrode material and a conductive agent, and wherein the conductive agent includes graphene; The average particle size D50 of the positive electrode material is denoted as a, and the number of graphene layers is denoted as n, which satisfies the following conditions: 1 μm≤a≤9 μm, 10≤n≤20.

2. The sodium ion battery according to claim 1, characterized in that The following conditions are met: a. 1 / 2 ≤0.2×n.

3. The sodium ion battery according to claim 2, characterized in that: Meet the following conditions: a 1 / 2 ≤0.15×n.

4. The sodium ion battery according to any one of claims 1 to 3, characterized in that: The mass proportion of the graphene in the positive electrode material layer is w, and satisfies one or more of the following conditions: (1)1.2a≤100w×n≤1.6a; （2）0.1%≤w≤0.6%。 5. The sodium ion battery according to claim 4, characterized in that: The following conditions are met: 0.5a≤100w×n≤0.8a.

6. The sodium ion battery according to any one of claims 1 to 3, characterized in that: One or more of the following conditions are met: (1) The conductive agent further comprises one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black and Ketjen black; (2) The positive electrode material includes one or more of a Prussian blue compound, a layered oxide, and a polyanion compound, and the layered oxide may be selected; Optionally, the layered oxide satisfies the chemical formula Na x M y O2, where 0 < x ≤ 1, 0.9 < y ≤ 1, and M comprises a Group 3d transition metal element.

7. The sodium ion battery according to any one of claims 1 to 3, characterized in that: The positive electrode material layer further comprises a binder; Optionally, the mass ratio of the positive electrode material, the conductive agent and the binder is (90%~98%):(1%~5%):(1%~5%); Optionally, the binder includes one or more of polyacrylonitrile, hydrogenated butyronitrile, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene and polyolefin compounds.

8. A positive electrode sheet, characterized in that: The positive electrode material layer comprises a positive electrode material and a conductive agent, wherein the conductive agent comprises graphene; The average particle size D50 of the positive electrode material is denoted as a, and the number of graphene layers is denoted as n, which satisfies the following conditions: 1 μm≤a≤9 μm, 10≤n≤20.

9. The positive electrode sheet according to claim 8, characterized in that: The positive electrode sheet is the positive electrode sheet in the sodium ion battery according to any one of claims 2 to 7.

10. An electrical device, characterized in that: A sodium ion battery comprising the sodium ion battery according to any one of claims 1 to 7.

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