A positive electrode sheet, a method for manufacturing the same, and a sodium-ion battery

Abstract

The application relates to a positive electrode sheet and a preparation method thereof and a sodium ion battery. The positive electrode comprises a current collector and an active material layer, and the active material layer is a single directional active material layer or the outermost layer is a single directional active material layer. The single directional active material slurry containing a magnetic sodium positive electrode active material is prepared first, and is dried in a magnetic field environment, so that the positive electrode active material in the active layer of the positive electrode sheet is vertically oriented or the surface layer active material of the positive electrode sheet is vertically oriented, the positive electrode sheet presents a three-dimensional cluster arrangement structure, has a bundle-shaped hole feature, the electrolyte and the electrode are more fully contacted, the active points are more fully exposed, the sodium ion transmission channel is widened, the transmission capacity of the sodium ion between the electrodes is effectively improved, the polarization internal resistance of the battery is reduced, the energy density, the rate and the cycle performance of the battery are improved, and the purpose of improving the battery performance by only regulating the positive electrode sheet structure is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a positive plate, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] With the attention of the state to energy security and environmental pollution prevention, batteries have been widely used in consumer batteries, power batteries and energy storage batteries. The existing large-scale chemical energy storage batteries are mainly lithium ion batteries, but due to the poor combination of high and low discharge capacity, high manufacturing cost and poor safety, its large-scale application is limited. Sodium ion batteries have similar working principles to lithium ion batteries and are secondary batteries. They have good high and low temperature performance, high safety and low cost, and are expected to become an important supplement to the future large-scale energy storage market of lithium ion batteries, providing strong support for the development of low-speed vehicles. However, the existing sodium ion batteries have low energy density and poor cycle performance. Among them, thick electrode technology is one of the important ways to improve the energy density of the battery. However, thick electrodes often increase the diffusion transmission path of sodium ions between electrodes, thereby increasing the transmission impedance of sodium ions and the polarization of the battery. At the same time, with the increase of the thickness of the electrode, the difficulty of the electrolyte to infiltrate the electrode increases, and the active site decreases. This will further affect the improvement of the energy density, rate and cycle performance of the battery.

[0003] The invention patent with the application publication number CN108417839A provides a method for improving the rate performance of lithium battery negative electrode by magnetic effect. A one-dimensional nanometer negative electrode material is loaded with a ferromagnetic fluid and a ferrite material to form a directional structure under a magnetic field, which is combined vertically with a copper current collector to form a three-dimensional dense array structure of the negative electrode. The active point of the material is exposed more fully to form a lithium ion transmission channel, effectively improving the deintercalation and migration ability of lithium ions in the negative electrode material, improving the rate performance of the battery, and achieving the purpose of improving the electrical performance of the negative electrode material by controlling the structure rather than the composition. The invention patent with the application publication number CN114744160A discloses a preparation method of a lithium ion battery. A high-nickel positive electrode slurry is obtained by mechanically stirring and mixing a magnetic material and a high-nickel material. The slurry is coated on the surface of the current collector, and the magnetic material is arranged in the high-nickel positive electrode material by alternating loading and removing. At the same time, an ice crystal effect is used to prepare a thick electrode plate with multi-level stacked through channels. Then, the magnetic material in the thick electrode plate is recycled by a magnetic recovery device to prepare a lithium ion battery positive plate. A thick electrode with hierarchical multi-dimensional through channels is constructed, which realizes the rapid charging and discharging of the lithium ion battery without sacrificing the utilization rate and capacity of the active material. Although the above researchers have achieved the purpose of widening the ion transmission channel by different strategies, the introduction of non-active magnetic substances has an impact on the electrical performance and safety performance of the battery. SUMMARY

[0004] To solve the above technical problems, the application provides a positive electrode sheet, a preparation method thereof and a sodium ion battery.

[0005] The technical scheme adopted by the application is as follows: a positive electrode sheet comprises,

[0006] a current collector;

[0007] a single-direction active material layer coated on one side or both sides of the current collector, and the single-direction active material layer comprises a magnetic sodium positive electrode active material.

[0008] Preferably, the positive electrode sheet further comprises a non-directional active material layer coated on one side or both sides of the current collector, and the non-directional active material layer is coated outside the single-direction active material layer, and the non-directional active material layer comprises a non-magnetic sodium positive electrode active material.

[0009] Preferably, when the positive electrode sheet comprises the non-directional active material and the single-direction active material, the mass ratio of the non-directional active material to the single-direction active material is 1-4:6-9.

[0010] The preparation method of the positive electrode sheet comprises the following steps: preparing a single-direction active material slurry containing a magnetic sodium positive electrode active material, coating the single-direction active material slurry on the surface of a current collector, and drying the coated positive electrode sheet in a magnetic field environment.

[0011] Preferably, the specific steps are as follows:

[0012] mixing the magnetic sodium positive electrode active material, the conductive agent, the binder and the solvent to obtain the single-direction active material slurry;

[0013] coating the single-direction active material slurry on at least one surface of the current collector;

[0014] drying the coated positive electrode sheet in a magnetic field environment to obtain the positive electrode sheet.

[0015] Preferably, before the single-direction active material slurry is coated, a non-directional active material slurry containing a non-magnetic sodium positive electrode active material is first coated.

[0016] Preferably, the single-direction active material slurry comprises 91-97% of the magnetic sodium positive electrode active material, 2.0-4.5% of the conductive agent and 1.0-4.5% of the binder by weight.

[0017] The non-directional active material slurry comprises 91-97% of the non-magnetic sodium positive electrode active material, 2.0-4.5% of the conductive agent and 1.0-4.5% of the binder by weight.

[0018] Preferably, the non-magnetic sodium positive electrode active material is a layered oxide positive electrode material, and the molecular formula is Na x Ni yFe z Mn k M m O2, 0≤y≤0.1, 0≤z≤0.1, 0≤k≤0.8, 0≤m≤0.2, y+z+k+m=1, 0.6 x Ni y Fe z Mn k M m O2, 0.1

[0019] M is one or more of Mg, Al, Cu, Zn, K, Ca, Co, Zr, Nb, Li, B, Ti, V, Cr, and Sn.

[0020] Preferably, the conductive agent comprises a combination of one or more of conductive carbon black, carbon nanotubes, graphene;

[0021] The binder comprises PVDF and / or PAN.

[0022] A sodium ion battery comprising the above cathode sheet.

[0023] The present application has the advantages and positive effects that: the active material of the active layer surface is vertically oriented, forming a three-dimensional cluster structure with a bundle-shaped hole feature, making the contact between the electrolyte and the electrode active material more sufficient, and the active point is more fully exposed; by vertically orienting the active material layer, the sodium ion transmission channel is widened, effectively improving the transmission capacity of sodium ions between electrodes, reducing the polarization resistance of the battery, improving the energy density, rate performance and cycle performance of the battery, achieving the purpose of improving the battery performance by only adjusting the cathode electrode sheet structure, and having important promoting significance for the industrialization of actual sodium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of the cathode sheet structure of an embodiment of the present application;

[0025] Figure 2 is a schematic diagram of the cathode sheet structure of an embodiment of the present application;

[0026] Figure 3 is a schematic diagram of the cathode sheet structure of a comparative example of the present application;

[0027] 1, current collector, 2, single directional active material layer, 3, sodium ion diffusion transmission path, 4, non-directional active material layer;

[0028] Figure 4 Figure 2 is a rate discharge performance comparison curve of the positive electrode sheet of the present application and a sodium ion battery positive electrode sheet of the prior art;

[0029] Figure 5 Figure 3 is a cycle performance comparison curve of the positive electrode sheet of the present application and a sodium ion battery positive electrode sheet of the prior art. DETAILED DESCRIPTION

[0030] Embodiments of the present application will be described below with reference to the accompanying drawings.

[0031] The present application relates to a positive electrode sheet, comprising a current collector and an active material layer, the active material layer being coated on at least one surface of the current collector, and the active material layer comprising a single directional active material layer or comprising a non-directional active material layer and a single directional active material layer. The single directional active material layer can generate directional perpendicular orientation of the positive electrode active material or directional perpendicular orientation of the surface active material of the positive electrode sheet, and the positive electrode sheet presents a three-dimensional cluster arrangement structure with a bundle-shaped hole feature, so that the electrolyte and the electrode are more fully contacted, the active points are more fully exposed, and the sodium ion transmission channel is widened.

[0032] A single directional active material layer is provided on one side or both sides of the current collector; or a non-directional active material layer and a single directional active material layer are sequentially provided on one side or both sides of the current collector; or a single directional active material layer is provided on one side of the current collector, and a non-directional active material layer and a single directional active material layer are sequentially provided on the other side; or a non-directional active material layer is provided on one side of the current collector alone, and a non-directional active material layer and a single directional active material layer are sequentially provided on the other side. When a non-directional active material layer and a single directional active material layer are sequentially provided on one side of the current collector, the mass ratio of the non-directional active material and the single directional active material is 1-4:6-9; specifically, it can be 1:9, 1.5:8.5, 2:8, 2.5:7.5, 3:7, 3.5:6.5, or 4:6. More vertical orientation of the sodium positive electrode active material on the surface layer is more conducive to forming a sodium ion transmission channel. If the mass ratio of the first active material layer on the bottom layer is too high, it will be not conducive to electrolyte infiltration, active point exposure, and sodium ion transmission, and will affect the performance of the battery.

[0033] In preparation, a single directional active material slurry is first prepared, and is coated on the current collector by using a single layer coating process technology; if a non-directional active material layer and a single directional active material layer are sequentially provided, the non-directional active material slurry is first coated on the current collector, and then the single directional active material slurry is coated. The current collector with the coated slurry is dried in a magnetic field environment. Under the influence of the magnetic field, the magnetic sodium positive electrode active material is vertically or approximately vertically arranged on the current collector, forming a single directional magnetic sodium positive electrode active material. The specific preparation method is as follows:

[0034] Step 1: stirring and mixing magnetic sodium positive active material, conductive agent, binder and solvent uniformly and stably to obtain single directional active material slurry; the single directional active material slurry includes 91-97% of magnetic sodium positive active material, 2.0-4.5% of conductive agent and 1.0-4.5% of binder by weight;

[0035] Step 2: coating the single directional active material slurry on at least one surface of the current collector;

[0036] Step 3: setting a magnetic field emitting device in an oven, and drying the coated pole piece under the action of the magnetic field to obtain a positive pole piece, the drying temperature is 80-120℃, and specifically can be 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃.

[0037] Alternatively, the specific steps are as follows:

[0038] Step 1: stirring and mixing magnetic sodium positive active material, conductive agent, binder and solvent uniformly and stably to obtain single directional active material slurry; stirring and mixing non-magnetic sodium positive active material, conductive agent, binder and solvent uniformly and stably to obtain non-directional active material slurry; the single directional active material slurry includes 91-97% of magnetic sodium positive active material, 2.0-4.5% of conductive agent and 1.0-4.5% of binder by weight; the non-directional active material slurry includes 91-97% of non-magnetic sodium positive active material, 2.0-4.5% of conductive agent and 1.0-4.5% of binder by weight;

[0039] Step 2: using a double-layer coating process technology, coating the non-directional active material slurry on at least one surface of the current collector, and then coating the single directional active material slurry on the surface of the non-directional active material slurry;

[0040] Step 3: setting a magnetic field emitting device in an oven, and drying the coated pole piece under the action of the magnetic field to obtain a positive pole piece, the drying temperature is 80-120℃, and specifically can be 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃.

[0041] In some embodiments of the present application, the current collector includes at least one of aluminum foil, carbon-coated foil and composite aluminum foil, and the thickness of the current collector is 4-30um, and specifically can be 4um, 5um, 8um, 10um, 12um, 15um, 20um, 25um or 28um.

[0042] The non-magnetic sodium positive active material is a layered oxide positive material, and its molecular formula is Na x Ni y Fe z Mn k Mm O2, wherein M is one or more of Mg, Al, Cu, Zn, K, Ca, Co, Zr, Nb, Li, B, Ti, V, Cr, and Sn; y, z, k, m are molar ratios of the corresponding elements, and satisfy 0≤y≤0.1, 0≤z≤0.1, 0≤k≤0.8, 0≤m≤0.2, y+z+k+m=1, 0.6<x≤1; the magnetic sodium cathode active material is a layered oxide cathode material, and its molecular formula is Na x Ni y Fe z Mn k M m O2, wherein M is one or more of Mg, Al, Cu, Zn, K, Ca, Co, Zr, Nb, Li, B, Ti, V, Cr, and Sn; y, z, k, m are molar ratios of the corresponding elements, and satisfy 0.1<y≤0.6, 0.1<z≤0.6, 0≤k<0.8, 0≤m≤0.2, y+z+k+m=1, 0.6<x≤1; when the sodium cathode active material contains more Fe-based, Co-based, and Ni-based, the obtained sodium cathode active material is magnetic; when the sodium cathode active material contains less Fe-based, Co-based, and Ni-based, the obtained sodium cathode active material is non-magnetic.

[0043] The conductive agent includes a combination of one or more of conductive carbon black, carbon nanotubes, and graphene; and the binder includes PVDF and / or PAN. In some embodiments of the present application, the weight ratio of the cathode active material, the conductive agent, and the binder is 91-97:2.0-4.5:1.0-4.5, preferably 95:2:3; within the mass control range of the above components, the electronic conduction between the active material particles can be ensured, and the bonding strength between the components and between the active material layer and the current collector can be ensured, thereby ensuring the performance of the battery.

[0044] By setting a magnetic field emitting device in the oven, adjusting the electrode structure of the cathode sheet, forming a three-dimensional cluster structure, widening the pore channel between the active material particles, improving the infiltration ability between the electrolyte and the electrode active material, and solving the problem of large sodium ion diffusion transmission impedance, the energy density, rate, and cycle performance of the battery are improved.

[0045] The application also relates to a sodium ion battery comprising a positive electrode sheet containing a single-directional active material layer. The aforementioned positive electrode sheet is subjected to rolling, shearing, die cutting, dust removal and drying; a negative electrode sheet is prepared through the steps of homogenizing, coating, rolling, shearing, die cutting, dust removal and drying; the positive electrode sheet, the negative electrode sheet and a diaphragm are stacked or wound to obtain a bare electrode group of the battery; the bare electrode group is subjected to tab welding, packaging, electrolyte injection, formation and sorting to obtain the sodium ion battery. The active material in the negative electrode sheet includes but is not limited to one or a mixture of several of hard carbon, soft carbon, artificial graphite and natural graphite; the diaphragm is one or several multilayer composite diaphragms of a polyethylene diaphragm, a polypropylene diaphragm, an aramid diaphragm and a non-woven fabric diaphragm; the electrolyte includes a sodium-containing electrolyte salt, an organic solvent and an additive, and the specific types and components of the sodium-containing electrolyte salt, the organic solvent and the additive are not limited in particular, for example, the sodium-containing electrolyte salt includes common NaPF6, NaClO4 and the like, the organic solvent includes EC, DEC, EMC, PC and the like, and the additive includes FEC, VC, PS, DTD and the like.

[0046] Without introducing other non-active magnetic substances, the directional vertical orientation of the positive active material in the active layer of the positive electrode sheet or the directional vertical orientation of the active material on the surface layer of the positive electrode sheet is realized by arranging a magnetic field emitting device in an oven, the positive electrode sheet presents a three-dimensional cluster arrangement structure with a bundle-shaped hole feature, the contact between the electrolyte and the electrode active material is more sufficient, the active points are more fully exposed, and the sodium ion transmission channel is widened. When the positive electrode is used in a sodium ion battery, the transmission capacity of sodium ions between electrodes can be effectively improved, the polarization resistance of the battery is reduced, the energy density, the rate performance and the cycle performance of the battery are improved, the purpose of improving the battery performance by only regulating the structure of the positive electrode sheet is achieved, and the actual industrialization of the sodium ion battery has important promoting significance.

[0047] The application scheme will be described below in combination with the drawings, wherein the experimental methods of the operation steps not specifically described are performed according to the corresponding product instructions, and the instruments, reagents and consumables used in the examples can be purchased from commercial companies if not specifically stated.

[0048] Example 1:

[0049] A positive electrode sheet, as shown in Figure 1 , comprises a current collector and a single-directional active material layer coated on both sides of the current collector. The preparation comprises the following steps:

[0050] Preparation of the single-directional active material slurry: magnetic sodium positive active material Na 2 / 3 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3O2, acetylene black conductive agent, carbon nanotube conductive agent, PVDF binder are stirred and mixed uniformly and stably according to a mass ratio of 95%:0.8%:1.2%:3% and NMP solvent to form a single directional active material slurry;

[0051] A single directional active material slurry is coated on the front and back surfaces of a 12um thick aluminum foil current collector by using a single layer coating process technology, and the coating amount is 30mg / cm 2 A magnetic field emitting device is arranged in the drying air box, and the pole piece is dried at 110℃ in a magnetic field environment to obtain a positive pole piece. Under the action of the magnetic field, the magnetic sodium positive active material in the single directional active material layer slurry is distributed on the current collector in a single direction under the action of the magnetic field.

[0052] Example 2:

[0053] A positive pole piece, as shown in Figure 2 , includes a current collector, and a non-directional active material layer and a single directional active material layer arranged on both sides of the current collector respectively. The specific preparation steps are as follows:

[0054] Preparation of a non-directional active material slurry: non-magnetic sodium positive active material Na 2 / 3 Ni 1 / 10 Fe 1 / 10 Mn 3 / 5 Cu 1 / 10 Mg 1 / 10 O2, acetylene black conductive agent, carbon nanotube conductive agent, PVDF binder are stirred and mixed uniformly and stably according to a mass ratio of 95%:0.8%:1.2%:3% and NMP solvent to form a non-directional active material slurry;

[0055] Preparation of a single directional active material slurry: magnetic sodium positive active material Na 2 / 3 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, acetylene black conductive agent, carbon nanotube conductive agent, PVDF binder are stirred and mixed uniformly and stably according to a mass ratio of 95%:0.8%:1.2%:3% and NMP solvent to form a single directional active material slurry;

[0056] A non-directional active material slurry is coated on the front and back surfaces of a 10um aluminum foil current collector by using a double layer coating process technology, and then a single directional active material slurry is coated on the surface of the non-directional active material slurry. The mass ratio of the non-directional active material slurry to the single directional active material slurry is 3:7; a magnetic field emitting device is arranged in the drying air box, and the pole piece is dried at 110℃ in a magnetic field environment to obtain a positive pole piece. Under the action of the magnetic field, the magnetic sodium positive active material in the single directional active material layer slurry is distributed on the current collector in a single direction under the action of the magnetic field.

[0057] Example 3:

[0058] A positive electrode sheet, as shown in the structure of Figure 2 includes a current collector, and a non-oriented active material layer and a single-oriented active material layer respectively arranged on both sides of the current collector. The specific preparation steps are as follows:

[0059] Preparation of non-oriented active material slurry: non-magnetic sodium positive active material Na 2 / 3 Ni 1 / 10 Mn 7 / 10 Cu 1 / 5 O2, acetylene black conductive agent, carbon nanotube conductive agent, PVDF binder, PAN binder are stirred and mixed uniformly and stably according to the mass ratio of 95.4%:0.6%:1.0%:2.5%:0.5% and NMP solvent to form a non-oriented active material slurry;

[0060] Preparation of single-oriented active material slurry: magnetic sodium positive active material Na 2 / 3 Ni 1 / 5 Fe 1 / 5 Mn 9 / 20 Cu 1 / 10 Zn 1 / 20 O2, acetylene black conductive agent, carbon nanotube conductive agent, PVDF binder: PAN binder are stirred and mixed uniformly and stably according to the mass ratio of 96%:0.8%:1.2%:1.5%:0.5% and NMP solvent to form a single-oriented active material slurry;

[0061] Using a double-layer coating process technology, the non-oriented active material slurry is coated on the positive and negative surfaces of the 12um aluminum foil current collector, and then the single-oriented active material slurry is coated on the surface of the non-oriented active material slurry, and the mass ratio of the non-oriented active material slurry to the single-oriented active material slurry is 3:7; The magnetic field emitting device is arranged in the drying air bellow, and the electrode sheet is dried at 110°C in the magnetic field environment to obtain a positive electrode sheet. Under the action of the magnetic field, the magnetic sodium positive active material in the single-oriented active material layer slurry is distributed on the current collector in a single direction under the action of the magnetic field.

[0062] Example 4:

[0063] The difference between this embodiment and Example 1 is that the coating amount of the active material layer is different, and the coating amount is 40mg / cm 2 , and the rest is the same as Example 1.

[0064] Example 5:

[0065] The embodiment differs from example 2 in that the mass ratio of the first active material layer to the second active material layer is different, and the mass ratio is 2:8, and the rest is the same as example 2.

[0066] Comparative example 1:

[0067] A positive electrode sheet, as shown in the structure of Figure 3 , includes a current collector and an active material layer coated on the current collector. Different from example 1, the magnetic field emitting device is not arranged in the oven, and the magnetic sodium positive active material in the active material layer slurry is randomly distributed in the active material layer.

[0068] Example 6:

[0069] The positive electrode sheet prepared in example 1 and comparative example 1 is respectively rolled, sheared, die cut, dusted and dried; the negative electrode includes homogenizing, coating, rolling, shearing, die cutting, dusting and drying; the positive electrode sheet, the negative electrode sheet and the separator are stacked to obtain a bare electrode group of the battery; the bare electrode group is subjected to tab welding, packaging, electrolyte injection, formation and sorting to obtain a sodium ion battery. The capacity retention rate and the cycle number of the prepared sodium ion battery are detected respectively. Figure 4 and Figure 5 The rate and cycle performance comparison data of example 1 and comparative example 1 are respectively shown in the table, and it can be seen from the data comparison that the sodium ion battery of example 1 is superior to the sodium ion battery of comparative example 1 in rate and cycle performance.

[0070] The above embodiments of the present application are described in detail, but the content described is only the preferred embodiment of the present application, and cannot be considered to limit the scope of the present application. Any equivalent changes and improvements made within the scope of the present application should still belong to the scope of the present application.

Claims

1. A positive electrode plate, characterized in that: include, current collector; A single oriented active material layer is coated on one or both sides of the current collector; the single oriented active material layer includes magnetic sodium positive electrode active material, and the positive electrode sheet presents a three-dimensional clustered structure with bundle-shaped pores. The magnetic sodium cathode active material is a layered oxide cathode material with the molecular formula Na. x Ni y Fe z Mn k M m O2, 0.1<y≤0.6, 0.1<z≤0.6, 0≤k<0.8, 0≤m≤0.2, y+z+k+m=1, 0.6 <x≤1; Wherein, M is one or more of Mg, Al, Cu, Zn, K, Ca, Zr, Nb, Li, B, Ti, V, Cr, and Sn.

2. The positive electrode sheet according to claim 1, characterized in that: It also includes a non-directional active material layer coated on one or both sides of the current collector, with the single directional active material layer coated on the outside. The non-directional active material layer includes a non-magnetic sodium positive electrode active material. The non-magnetic sodium cathode active material is a layered oxide cathode material with the molecular formula Na. x Ni y Fe z Mn k M m O2, 0≤y≤0.1, 0≤z≤0.1, 0≤k≤0.8, 0≤m≤0.2, y+z+k+m=1, 0.6 <x≤1。 3. The positive electrode sheet according to claim 2, characterized in that: When the positive electrode includes non-directional active material and single directional active material, the mass ratio of non-directional active material to single directional active material is 1-4:6-9.

4. The method for preparing the positive electrode sheet according to any one of claims 1-3, characterized in that: A single-directed active material slurry containing magnetic sodium positive electrode active material was prepared, coated on the surface of the current collector, and dried in a magnetic field environment to obtain a positive electrode sheet.

5. The method for preparing the positive electrode sheet according to claim 4, characterized in that: The specific steps are as follows: The magnetic sodium positive electrode active material, conductive agent, binder and solvent are stirred and mixed to obtain a single directional active material slurry; A single directional active substance slurry is coated on at least one surface of the current collector; The coated electrode is dried in an environment with a magnetic field to obtain a positive electrode.

6. The method for preparing the positive electrode sheet according to claim 4, characterized in that: Before coating a single positive active material slurry, a layer of non-directional active material slurry containing non-magnetic sodium positive active material is first coated.

7. The method for preparing the positive electrode sheet according to any one of claims 4-6, characterized in that: The single-directed active material slurry includes 91-97% magnetic sodium positive electrode active material, 2.0-4.5% conductive agent and 1.0-4.5% binder by weight; The non-directional active material slurry includes 91-97% non-magnetic sodium positive electrode active material, 2.0-4.5% conductive agent and 1.0-4.5% binder by weight.

8. The method for preparing the positive electrode sheet according to claim 7, characterized in that: Conductive agents include one or more combinations of conductive carbon black, carbon nanotubes, and graphene. The adhesive includes PVDF and / or PAN.

9. A sodium-ion battery, characterized in that: Includes the positive electrode sheet as described in any one of claims 1-3.

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