Solid particle volatilization pore-forming type sodium battery positive electrode sheet and preparation method and application thereof

Abstract

The application belongs to the technical field of sodium ion batteries, and particularly relates to a solid-state particle volatile pore-forming type sodium battery dry-method positive electrode sheet and a preparation method and application thereof. The positive electrode sheet is prepared by compounding a positive electrode film sheet made of a dry-method positive electrode material on both sides of a current collector, the positive electrode material comprises a positive electrode active material, a conductive agent, a binder and a pore-forming agent, the pore-forming agent is solid particle hexachloroethane, and the D50 particle size of the solid particle hexachloroethane is less than or equal to 0.3 microns. After the solid pore-forming agent is added to the positive electrode and sublimated at high temperature, small pores are formed, the porosity of the electrode sheet is improved, the electrolyte retention amount is increased, the concentration polarization is reduced, the rate performance is improved at a high area density, and thus the energy density of the sodium ion battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a solid particle volatilization pore-forming sodium dry cathode sheet, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries can be divided into energy storage type and high-power type according to different application scenarios. High-power type requires high charge and discharge rate. In order to achieve high rate, the positive electrode surface density is usually reduced at the coating end to reduce ion transport distance and reduce concentration polarization. However, a smaller surface density will lead to a decrease in energy density. Low energy density will increase watt-hour cost and reduce the price advantage of sodium-ion batteries.

[0003] Dry electrode technology is an electrode preparation process that involves mixing active materials, conductive agents, and binders at high speed to obtain fibrous electrode powder, which is then continuously rolled and formed, and finally compounded with a current collector to obtain an electrode sheet. Dry electrode production is characterized by low cost, high efficiency, and environmental friendliness. Applying this technology in sodium-ion batteries can reduce watt-hour costs.

[0004] In existing technologies, controlling the porosity of electrodes fabricated using dry electrode technology is difficult. Excessive porosity can lead to a loose electrode structure and insufficient mechanical strength, while insufficient porosity results in insufficient ion channels and limited electrochemical performance. Currently, pore-forming agents used in cathode material production include carbon, starch, and resins, which decompose and generate gas during high-temperature calcination to create pores. This method is unsuitable for dry electrode preparation without high-temperature calcination. Furthermore, ammonium bicarbonate is also used as a pore-forming agent in cathode material production. Ammonium bicarbonate is easily decomposed when heated above 60 degrees Celsius, leading to surface defects during the wet coating process and the release of gases such as NH3, CO2, and H2O. Rapid gas generation can create localized pressure within the electrode, easily causing microcracks, interlayer delamination, or pore closure, thus affecting structural integrity. Summary of the Invention

[0005] This invention provides a solid particle volatile pore-forming sodium dry-process positive electrode sheet, its preparation method, and its application. A solid pore-forming agent is added to the positive electrode and sublimated at high temperature to form micropores, which increases the porosity of the electrode sheet, increases the electrolyte retention capacity, reduces concentration polarization, and improves rate performance under high areal density, thereby improving the energy density of sodium-ion batteries.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a solid particle volatile pore-forming sodium dry-process positive electrode sheet, wherein the positive electrode sheet is prepared by laminating a positive electrode film made of a positive electrode material made by dry process onto both sides of a current collector, the positive electrode material comprising a positive electrode active material, a conductive agent, a binder and a pore-forming agent, the pore-forming agent being solid particles hexachloroethane, wherein the solid particles hexachloroethane have a D50 particle size ≤ 0.3 μm.

[0007] Preferably, the porosity of the sodium-ion dry-process positive electrode is 30%–60%; the areal density of the sodium-ion dry-process positive electrode is 200–600 g / m³. 2 .

[0008] Preferably, the sodium-ion dry-process positive electrode sheet further includes a positive electrode active material and a binder, wherein the ratio of the positive electrode active material, conductive agent, binder and pore-forming agent is (93%~98%): (1%~4%): (0.5%~1.5%): (0.1%~0.5%).

[0009] Preferably, the positive electrode active material is at least one of sodium-ion layered oxide, polyanionic compound, and Prussian blue / white positive electrode material; the conductive agent is at least one of carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, and graphene; and the binder is PTFE.

[0010] Preferably, the ratio of the particle size of the conductive agent to the particle size of the hexachloroethane is 1:(2-4).

[0011] Preferably, the solid particles of hexachloroethane D50 have a particle size range of 0.10 μm to 0.2 μm, and the conductive agent has a particle size range of 50 nm to 60 nm; the specific surface area of ​​the conductive agent is 70 m². 2 / g.

[0012] Preferably, the mass ratio of the polyanionic compound, sodium-ionized layered oxide and Prussian blue / white cathode material in the positive electrode active material is (10~90):(10~90):(10~90).

[0013] Secondly, the present invention provides a method for preparing a solid particle volatile porous sodium dry electrode, comprising the following steps:

[0014] Step A: Stir and mix the positive electrode active material, conductive agent, binder and pore-forming agent to obtain a uniformly mixed dry powder. Shear and mix the dry powder evenly to obtain fibrous powder.

[0015] Step B: The fibrous powder obtained in Step A is extruded and molded to obtain an initial membrane. Then, it is repeatedly rolled to obtain a positive electrode membrane. The positive electrode membrane and the current collector are rolled together to obtain a dry electrode positive electrode precursor.

[0016] Step C: The dry electrode positive sheet precursor obtained in step B is baked to create holes, and then cooled to obtain the dry electrode sheet.

[0017] Preferably, in step A, the stirring speed is 100-300 r / min and the stirring time is 0.5-2 h;

[0018] In step B, the extrusion molding temperature is 40–120°C; the current collector is at least one of aluminum foil, carbon-coated aluminum foil, metal mesh current collector, and composite current collector; the areal density of the dry electrode positive electrode precursor is 200–600 g / m³. 2 ;

[0019] In step C, the baking of the dry electrode positive electrode precursor is divided into three stages: the first stage is baking at 140~155℃ for 2~3 hours; the second stage is baking at 175-185℃ for 2~3 hours with a heating rate of 0.5~0.8℃ / min; and the third stage is baking at 187-195℃ for 30~45 minutes.

[0020] Thirdly, the present invention provides a sodium-ion battery, the sodium-ion battery comprising the sodium dry-process positive electrode sheet or a positive electrode sheet prepared by the method for preparing the sodium dry-process positive electrode sheet.

[0021] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0022] In this embodiment of the invention, the provided positive electrode sheet is prepared by laminating a positive electrode film made of positive electrode material using a dry process onto both sides of a current collector. The positive electrode material includes a positive electrode active material, a conductive agent, a binder, and a pore-forming agent. The pore-forming agent volatilizes during the subsequent baking and pore-forming step, leaving uniform micropores, thus forming pores inside the electrode. These pores provide channels for the electrolyte, significantly improving the electrode's permeability. This invention uses solid particulate hexachloroethane as the pore-forming agent. It is solid at room temperature, structurally stable, and does not react at high temperatures. Its sublimation point at normal pressure is 187°C, but it sublimates at high temperatures. Adding the solid pore-forming agent to the mixture and allowing it to sublimate at high temperatures creates micropores, increasing the porosity of the electrode sheet, increasing the electrolyte retention capacity, reducing concentration polarization, and improving rate performance under high areal density, thereby increasing the energy density of the sodium-ion battery. Hexachloroethane is stable and can be recycled and reused after high-temperature sublimation through condensation. The sublimation products do not react with the sodium-ion battery cathode material, making the cathode material more stable and avoiding chemical corrosion of the cathode sheet. During the high-temperature sublimation process, the pores are formed by the gradual sublimation of the pore-forming agent solid particles from the outside to the inside. Unlike other pore-forming agents that rely on material decomposition and carbonization at different locations, or simultaneous irregular vaporization at multiple locations such as the surface and core, the sublimation process of solid-particle hexachloroethane as a pore-forming agent is more controllable, which is conducive to the uniform formation and stability of the pores. The preparation method of the solid-particle volatilization pore-forming sodium-ion battery dry cathode sheet of this invention has the advantages of high safety, high rate performance, and low cost. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram showing the particle size of the pore-forming agent and conductive agent in the solid particle volatile pore-forming sodium dry electrode sheet provided in an embodiment of the present invention.

[0025] Figure 2 The image shows a scanning electron microscope (SEM) image of the microstructure of a solid particle volatile porous sodium electrode provided in an embodiment of the present invention. Detailed Implementation

[0026] In this invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" are generally understood in conjunction with the accompanying drawings and the directions shown in actual applications.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "discretionary" mean that they may or may not be included (or may or may not be present).

[0030] The applicant of this invention has observed that dry electrode fabrication technology has attracted significant attention in recent years, showing broad application prospects in supercapacitors, lithium-ion batteries, and sodium-ion batteries. Dry electrode technology is an emerging electrode manufacturing method that eliminates the need for solvents, energy-intensive drying equipment, and N-methylpyrrolidone (NMP) recovery devices. It also requires less equipment investment, lower energy consumption, and a smaller footprint. The prepared dry electrodes exhibit advantages such as high areal density, excellent rate and cycle performance, and low internal resistance. However, controlling the porosity of electrodes prepared using dry electrode technology is challenging. Excessive porosity can lead to a loose electrode structure and insufficient mechanical strength, while insufficient porosity results in insufficient ion channels and limited electrochemical performance. Currently, pore-forming agents used in the production of cathode materials include carbon, starch, and resins, which decompose and generate gas during high-temperature calcination to create pores. This method is not suitable for dry electrode preparation without high-temperature calcination. Ammonium bicarbonate is also used as a pore-forming agent in the production of cathode materials. Ammonium bicarbonate is easily decomposed when heated above 60 degrees Celsius, which can easily cause surface defects during the wet coating process and release gases such as NH3, CO2, and H2O. Rapid gas generation can create local pressure inside the electrode, which can easily lead to microcracks, interlayer delamination, or pore closure, thereby affecting the structural integrity.

[0031] To address the aforementioned problems, this invention provides a solid particle volatile porous sodium dry-process positive electrode sheet. The positive electrode sheet is prepared by laminating a positive electrode film made of a positive electrode material made by dry processing onto both sides of a current collector. The positive electrode material comprises a positive electrode active material, a conductive agent, a binder, and a pore-forming agent. The pore-forming agent is solid hexachloroethane particles with a D50 particle size ≤ 0.3 μm.

[0032] The positive electrode material of this invention comprises a positive electrode active material, a conductive agent, a binder, and a pore-forming agent. The pore-forming agent volatilizes during the subsequent baking and pore-forming step, leaving uniform micropores that create pores within the electrode. These pores provide channels for the electrolyte, significantly improving the electrode's permeability. This invention uses solid particulate hexachloroethane as the pore-forming agent. It is solid at room temperature, structurally stable, and does not react at high temperatures. Its sublimation point at normal pressure is 187°C, but it sublimates at high temperatures. Adding the solid pore-forming agent to the positive electrode material mixture and allowing it to sublimate at high temperatures creates micropores, increasing the porosity of the electrode, increasing the electrolyte retention capacity, reducing concentration polarization, and improving rate performance under high areal density, thereby increasing the energy density of the sodium-ion battery. Hexachloroethane is stable and can be recycled by condensation after high-temperature sublimation. The products after high-temperature sublimation do not react with the sodium-ion battery positive electrode material, making the positive electrode material more stable and avoiding chemical corrosion of the positive electrode sheet. During the high-temperature sublimation process, pores are formed by the gradual sublimation of solid particles of the pore-forming agent from the outside to the inside. Unlike other pore-forming agents that rely on material decomposition and carbonization at different locations, or random vaporization at multiple points including the surface and core, the sublimation process of hexachloroethane solid particles as a pore-forming agent is more controllable, which is beneficial for the uniform formation and stability of pores. The preparation method of the solid particle volatilization pore-forming sodium electrode dry process of this invention has the advantages of high safety, high rate performance, and low cost.

[0033] In this embodiment, the D50 particle size of the aforementioned solid hexachloroethane particles is ≤0.3 μm. The particle size of the pore-forming agent affects the ion transport efficiency of the battery. Small-particle-size pore-forming agents produce a more uniform microporous structure, maintaining a certain porosity while preserving high compaction density and strength. A suitable pore structure helps alleviate electrode volume expansion and reduces the generation of microcracks during cycling, thereby extending cycle life. The selected solid hexachloroethane particles, within their particle size range, provide sufficient porosity while maintaining high compaction density, balancing energy density, rate performance, and cycle life. By appropriately selecting the particle size of the pore-forming agent, it is beneficial to reduce the tendency of conductive agent particles to agglomerate due to van der Waals forces during the dry preparation process, forming "conductive dead zones" (where charge cannot be transferred within the agglomerates). At the same time, hexachloroethane particles can act as "spacers." The appropriate particle size and suitable spacing between the spacers help maintain a suitable porosity in the prepared electrode, physically preventing the further growth of conductive agent agglomerates such as conductive carbon black, and avoiding the formation of large-sized agglomerates. In addition, the weakly polar surface of hexachloroethane can form a weak interaction with the defect sites on the carbon black surface (such as oxygen-containing functional groups -OH, -COOH), reducing the surface energy of carbon black, suppressing the attraction between particles, and forming a "three-dimensional continuous conductive network" within the electrode, reducing charge transfer resistance (Rct), and significantly improving rate performance.

[0034] This invention adds a pore-forming agent to the dry electrode, which forms micropores after high-temperature sublimation. When the electrode is filled with electrolyte, it can increase the electrolyte retention and reduce the migration path length of sodium ions. It can also reduce concentration polarization during high-rate charge and discharge. Compared with existing electrodes, it can improve rate performance at the same areal density or improve areal density while maintaining the same rate performance.

[0035] Optionally, in one embodiment, the porosity of the above-mentioned sodium-ion dry-process positive electrode sheet is 30% to 60%, and can be a value within the range of one or any two of 30%, 35%, 40%, 45%, 50%, 55%, and 60%. The areal density of the above-mentioned sodium-ion dry-process positive electrode sheet is 200 to 600 g / m³. 2 It can be 200g / m 2 250g / m 2 300g / m 2 350g / m 2 400g / m 2 450g / m 2 500g / m 2 550g / m 2 600g / m 2 The porosity of a sodium-ion dry electrode is within a range of one or both of these values. Within this range, the electrolyte level is moderate, ensuring ion channels without reducing energy density due to excessive liquid. When the porosity is too low, insufficient electrolyte penetration leads to increased ion resistance; when the porosity is too high, the volume fraction of active material decreases, limiting electron conduction. Too low a porosity can cause electrode brittleness and particle breakage, reducing cycle life. Too high a porosity allows positive and negative electrode particles to penetrate the separator, leading to dendrite formation or short circuit risks. The areal density of a sodium-ion dry electrode refers to the mass of active material per unit area of ​​the positive electrode. Within this range, the areal density significantly improves the battery's energy density. When the areal density is too high, the battery capacity increase is limited, ion / electron transport is hindered, the rate capability and cycle life of sodium-ion batteries decrease, and the internal resistance during fast charging increases. When the areal density is too low, the battery capacity is insufficient, and the energy density is limited, but the rate capability and internal resistance of sodium-ion batteries are better.

[0036] Optionally, in one embodiment, the sodium-ion dry-process positive electrode sheet further includes a positive electrode active material and a binder, wherein the ratio of the positive electrode active material, conductive agent, binder, and pore-forming agent is (93%–98%):(1%–4%):(0.5%–1.5%):(0.1%–0.5%). The ratio can be one or any two of the following: (93%:1%:0.5%:0.1%), (95%:2%:1%:0.2%), (97%:3%:1.2%:0.3%), and (98%:4%:1.5%:0.5%). The positive electrode material is uniformly mixed and stirred into fibrous powder agglomerates by positive electrode active material, conductive agent, binder and pore-forming agent. The fibrous powder agglomerates are then extruded and pressed into dry electrode films. The dry electrode films are then rolled and compounded with current collectors to prepare the positive electrode precursor. The positive electrode precursor is baked at high temperature to allow the pore-forming agent inside the electrode to slowly volatilize and form pores, thereby preparing a dry positive electrode with high areal density and high porosity. The resulting dry positive electrode has uniform pore size and pore distribution, and high areal density, which reduces concentration polarization caused by high areal density during high-rate charge and discharge. It is beneficial for sodium ion insertion and extraction, and significantly improves the rate performance of the battery electrode at high areal density. Moreover, this preparation method has simple processing equipment, more reliable and easier on-site process control, and is more conducive to large-scale production. It avoids the use of solvents and complex coating processes in wet electrode processes, and the production energy consumption is low.

[0037] Optionally, in one embodiment, the positive electrode active material is at least one of sodium-ion layered oxides, polyanionic compounds, and Prussian blue / white positive electrode materials; layered oxides have the characteristics of high capacity, high energy density, mature technology, and good rate capability, and the layered structure (O3, P2, etc.) provides two-dimensional Na+. + Migration channels enable Na + It can be inserted / extracted over a wide range, with a significantly higher energy density than tunnel-type or polyanionic materials. The layered oxide is produced by high-temperature solid-state sintering or co-precipitation. dry A one-step compaction process yields a high-tap-density powder, which can be directly used for the high-loading, high-tap-rate preparation of dry-process cathode sheets. In polyanionic compounds, the polyanionic units are linked by strong covalent bonds, forming a rigid three-dimensional network structure. The crystal framework is located in Na... + / Li + Almost no structural rearrangement occurs during the insertion / extraction process, which significantly improves battery safety and cycle life. The main advantages of using polyanionic compounds as the positive electrode active material in sodium-ion dry-process cathode sheets are: [The text abruptly shifts to a seemingly unrelated topic about PO4 and polyanionic compounds, which appears to be a fragment from a different context.] n- SO4 n-The three-dimensional network structure with a face-centered cubic (fcc) framework exhibits minimal volume change during charging and discharging, effectively suppressing structural collapse and providing excellent cycle life and thermal stability. The Prussian blue / white cathode material possesses a face-centered cubic (fcc) framework structure, and Na... + The wide three-dimensional tunnels within the crystal lattice enable rapid insertion / extraction, imparting excellent rate performance and structural stability to the material. Compared to high-energy-density cathodes in lithium-ion batteries, Prussian blue-based materials exhibit higher thermal stability and do not involve high-voltage oxidants, reducing the risk of thermal runaway. Prussian blue / white cathode materials are naturally compatible with dry electrode processes, enabling the production of solvent-free, low-binder-content, high-energy-density sodium-ion battery cathode sheets.

[0038] Optionally, in one embodiment, the conductive agent is at least one selected from carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, and graphene. The carbon black particles are uniformly dispersed during dry mixing and, together with the binder, construct continuous conductive channels, significantly reducing the electron transport impedance between active materials. The carbon black fills the pore walls created by the pore-forming agent, maintaining the openness of the pores while providing continuous electronic pathways, achieving efficient coupling of electrons and ions within the same structure. This efficient coupling structure of electrons and ions within the same structure maintains high conductivity while avoiding mechanical weakening due to excessively large pores. Acetylene black itself has extremely low volume resistivity, enabling the formation of a continuous conductive network inside the positive electrode. The pore-forming agent generates uniform micro / macro channels during the dry process, reducing the path resistance for ion migration. The large specific surface area of ​​acetylene black can "fill" these pore walls, forming a three-dimensional conductive network, allowing for the synchronous distribution of electron and ion channels. Ketjenblack possesses a branched, high-specific-surface-area structure, forming numerous conductive contact points. A small amount added is sufficient to construct a continuous electronic pathway, significantly reducing the overall electrode resistance. Ketjenblack provides a highly efficient electronic conductive network, while the pore-forming agent enhances ion transport and structural stability by forming uniform micropores. The synergy between these two agents significantly improves the conductivity, ion permeability, mechanical strength, and energy / power performance of dry-process cathode sheets. Simultaneous use of carbon nanotube conductive agents and pore-forming agents in dry-process cathode sheets achieves highly efficient electronic conduction with extremely low addition amounts, while also enhancing electrolyte permeation and ion diffusion through micropores. This results in multi-dimensional improvements in key indicators such as energy density, power performance, cycle life, and safety. Carbon fiber conductive agents provide efficient electronic pathways and structural flexibility, while pore-forming agents generate a highly permeable porous network. The combination of these two agents in dry-process cathode sheets optimizes the electron-ion dual-channel system, significantly improving the rate performance, initial capacity, cycle life, and overall energy density of sodium-ion batteries. The synergistic effect of graphene and pore-forming agents not only solves the problem of insufficient electronic conductivity in dry cathode sheets, but also significantly improves ion transport and electrolyte penetration through the pore structure, thereby bringing higher rate performance, cycle life and safety.

[0039] Preferably, based on the total mass of the conductive agent, the ratio of carbon black: acetylene black: carbon fiber conductive agent: graphene is (2-6): (1-3): (0.1-0.6): (0.01-0.09). By compounding the conductive agents, the conductivity can be improved. At the same time, the conductive agents are less likely to agglomerate due to the spacing of the pore-forming agent. A more stable conductive pathway is formed by compounding the dot-shaped one-dimensional carbon black and acetylene black, the two-dimensional carbon fiber conductive agent, and the sheet-like graphene. The pore structure significantly improves ion transport and electrolyte penetration, thereby bringing higher rate performance, cycle life and safety.

[0040] Optionally, in one embodiment, the binder is PTFE. The pore-forming agent forms a uniform microporous network in the PTFE matrix, allowing Na inside the electrode to... + Shorter diffusion paths and higher porosity significantly reduce ion migration resistance. PTFE itself possesses excellent adhesion and chemical resistance, enabling it to firmly bond active materials, conductive agents, and current collectors. The addition of pore-forming agents maintains bonding strength while creating a porous structure, alleviating shrinkage stress during drying and improving the sheet's crack resistance and flexibility. The pore structure of the pore-forming agent increases the stacking density of active materials without increasing the volume of additional binder. Combined with PTFE's high compressive strength, this achieves higher compaction density and greater capacity per unit area. Blending the pore-forming agent with PTFE allows for precise control of pore size, porosity, and pore distribution, meeting the specific requirements of different cathode materials (such as Na3V2(PO4)2F3, layered oxides, etc.).

[0041] Optionally, in one embodiment, the ratio of the particle size of the conductive agent to the particle size of the hexachloroethane is 1:(1~6), which can be one or any two of the following: 1:1, 1:2, 1:3, 1:4, 1:5, 1:6. By selecting a suitable particle size, the formation of "conductive dead zones" (where charge cannot be transferred within the agglomerates) due to van der Waals forces can be further reduced. By matching the particle size of the conductive agent with that of the hexachloroethane, the weakly polar surface of the hexachloroethane can be enhanced to form weak interactions with the defect sites (such as oxygen-containing functional groups -OH, -COOH) on the carbon black surface. This is more conducive to enhancing the particle barrier effect while reducing the surface energy of the carbon black, suppressing the attraction between particles, forming a "three-dimensional continuous conductive network" within the electrode, reducing the charge transfer resistance (Rct), and further improving the rate performance.

[0042] Optionally, in one embodiment, the particle size range of the aforementioned solid hexachloroethane D50 particles is 0.10 μm to 0.2 μm, and can be one or any two of 0.1 μm, 0.12 μm, 0.14 μm, 0.16 μm, 0.18 μm, and 0.2 μm. The particle size range of the aforementioned conductive agent is 50 nm to 60 nm, and can be one or any two of 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, and 60 nm; the specific surface area of ​​the aforementioned conductive agent is 70 m². 2 / g. Conductive agents (such as SP) have a large specific surface area and high surface energy, making them prone to agglomeration due to van der Waals forces, forming "conductive dead zones" (where charge cannot be transferred within the agglomerates). Hexachloroethane particles can act as "spacers," physically blocking the further growth of carbon black agglomerates and preventing the formation of large-sized agglomerates. At the same time, the weakly polar surface of hexachloroethane can form weak interactions with defect sites on the carbon black surface (such as oxygen-containing functional groups -OH, -COOH), reducing the surface energy of the carbon black, suppressing the attraction between particles, and forming a "three-dimensional continuous conductive network" within the electrode, reducing charge transfer resistance (Rct), and significantly improving rate performance.

[0043] Optionally, in one embodiment, the mass ratio of the polyanionic compound, sodium-ionized layered oxide, and Prussian blue / white cathode material in the positive electrode active material is (10~90):(10~90):(10~90); preferably, the mass ratio of the polyanionic compound, sodium-ionized layered oxide, and Prussian blue / white cathode material in the positive electrode active material is (30~70):(20~60):(10~50), (45~65):(30~45):(12~35), (52~61):(34~42):(14~27), ​​(55~60):(37~39):(15~21). The electronic / ionic conductivity of the three materials in the sodium-ionized cathode material—polyanionic, layered oxide, and Prussian blue—differs significantly, and after compounding, mismatch in transport rates can easily lead to Na+ / Na+ / white cathode material defects. + Migration is hindered, and the sublimation of hexachloroethane forms a three-dimensional, uniform, and regularly connected pore structure, which can also act as a source of Na. + The rapid channel allows the ion transport paths of the composite cathode to be interconnected, preventing a decrease in overall rate performance due to transport lag in one material. The addition of hexachloroethane as a pore-forming agent reduces the charge transfer resistance of the composite cathode, thereby improving high-rate performance. On the other hand, sodium-ion cathode materials exhibit large differences in volume change rates during charge and discharge. If stress concentration occurs after composite formation, it can easily lead to electrode cracking and active material shedding. The porous structure provides a volume buffer space; the addition of hexachloroethane as a pore-forming agent significantly improves the cycle stability of the composite cathode.

[0044] This invention also provides a method for preparing a solid particle volatile porous sodium dry electrode, including steps 201 to 203:

[0045] Step 201: Stir and mix the positive electrode active material, conductive agent, binder and pore-forming agent to obtain a uniformly mixed dry powder. Shear and mix the dry powder evenly to obtain fibrous powder.

[0046] In one embodiment of the present invention, the stirring speed is 100–300 r / min, which can be any one or any two of 100 r / min, 150 r / min, 200 r / min, 250 r / min, and 300 r / min; the stirring time is 0.5–2 h, which can be any one or any two of 0.5 h, 1 h, 1.5 h, and 2 h. This range represents a suitable stirring speed and time, which is crucial for achieving uniform mixing of the powder. It indirectly determines the stability of the electrode porosity by affecting the dispersion uniformity of the pore-forming agent, and ultimately significantly affects the consistency and quality of the cell rate performance. Too low a stirring speed results in insufficient friction and shear force between powder particles, making it impossible to break up local agglomerates. Pore-forming agents are prone to "local aggregation" or "dispersion blank areas," resulting in poor overall powder uniformity. Excessive stirring speed generates strong shear forces, potentially causing active material particles to break or leading to electrostatic agglomeration due to frictional heat, thus compromising uniformity. Insufficient stirring time results in incomplete mixing, preventing the pore-forming agent from forming a homogeneous system with other powders and causing localized component imbalances. Excessive stirring time can lead to excessive particle wear, altering the powder's particle size distribution; furthermore, prolonged stirring may cause evenly mixed powders to stratify due to "excessive tumbling," further reducing uniformity.

[0047] Step 202: Extrude the fibrous powder obtained in step A to form an initial film, and then repeatedly roll it to obtain a positive electrode film. Roll press the positive electrode film and the current collector together to obtain a dry electrode positive electrode precursor.

[0048] In one embodiment of the present invention, the extrusion molding temperature is 40-120°C, which can be one or any two of the following values: 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C. If the temperature is too low, insufficient PTFE fiberization leads to weak powder adhesion, with an initial porosity as high as 55%-60%. After subsequent baking and pore formation, the porosity further increases to over 65%. Although there are sufficient ion transport channels, the active material loading decreases by 10%-15%, reducing the cell energy density. The large number of large pores leads to excessively long ion transport paths and excessive impedance, affecting rate performance. If the temperature is too high, PTFE softens sufficiently at high temperatures, and the powder is easily over-compacted during extrusion, reducing the initial porosity to 20%-30%. Even if hexachloroethane is completely decomposed, the porosity can only be increased to 30%-35% after baking, resulting in narrow sodium ion transport channels and affecting rate performance.

[0049] The current collector can be any one or a combination of several of the following: aluminum foil, carbon-coated aluminum foil, metal mesh current collector, and composite current collector. Conventional aluminum foil has a dense surface, which slightly hinders gas escape. Compared to other current collectors, its porosity is 1%–3% lower, and its surface is smoother, resulting in lower adhesion to the main material. It is well-suited for use with spherical layered oxides. Carbon-coated aluminum foil has a layer of conductive carbon on its surface, providing good conductivity, but poor conductivity with polyanionic materials, making it well-suited for use with carbon-coated aluminum foil. Metal mesh current collectors have perforated mesh openings that allow gas to pass through directly and quickly. Furthermore, the "supporting effect" of the mesh prevents excessive compaction during electrode extrusion, reserving sufficient space for pore formation. Simultaneously, the nesting effect of the mesh provides greater adhesion. Prussian blue material, due to its cubic shape, is difficult to bond sufficiently with ordinary current collectors, making it a better match for mesh current collectors. Common main materials include polyanionic polymers, layered oxides, and Prussian blue. Among these, layered oxides have the highest true density, are spherical, easy to compact, and have high ion mobility, providing significant porosity even at high areal densities. They are suitable for areal densities of 400–600 g / m³. 2 Polyanionic poly ... 2 Prussian blue has the lowest true density, a cubic morphology, low compaction, and a porosity distribution that is prone to unevenness. Its suitable areal density is 200–400 g / m³. 2 .

[0050] Step 203: The dry electrode positive sheet precursor obtained in step B is baked to create holes, and then cooled to obtain the dry electrode positive sheet.

[0051] In one embodiment of the present invention, the baking of the dry electrode positive electrode precursor is divided into three stages: the first stage is baking at 140~155℃ for 2~3 hours; it can be baking at 140℃ for 2 hours, 145℃ for 2 hours, 150℃ for 2.5 hours, or 155℃ for 3 hours; the second stage is baking at 175-185℃ for 2~3 hours; it can be baking at 175℃ for 2 hours, 180℃ for 2 hours, 180℃ for 2.5 hours, or 185℃ for 3 hours; the heating rate is 0.5~0.8℃ / min; it can be one or any two of 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, or 0.8℃ / min; the third stage is baking at 187-195℃ for 30~45 minutes; it can be baking at 187℃ for 30 minutes, 190℃ for 35 minutes, 192℃ for 40 minutes, or 195℃ for 45 minutes. This ensures complete removal of the pore-forming agent and avoids trace amounts of hexachloroethane residue, which may slowly decompose during battery cycling (releasing Cl-). - Hexachloroethane (HCH) corrodes the current collector or cathode material, causing capacity decay. When HCH sublimates, its volume expands rapidly, causing a sudden increase in localized temperature inside the electrode. This leads to a sudden, large-scale sublimation of the pore-forming agent, preventing the gas from escaping slowly and potentially causing the electrode to break down, forming large pores or cracks, or causing edge warping. Gradual heating allows the pore-forming agent to escape slowly, forming interconnected pores with uniform pore size. If the holding time is insufficient, residual HCH will result in a porosity lower than the design value. The residual HCH may slowly decompose during battery cycling (releasing Cl-). - This corrodes the current collector or cathode material, causing capacity decay.

[0052] First, bake at 140℃ for 2 hours. This low-temperature baking pretreatment, which is much lower than the sublimation temperature of the pore-forming agent, is beneficial for the weakly polar surface of the hexachloroethane particles to form weak interactions with the defect sites (such as oxygen-containing functional groups -OH and -COOH) on the carbon black surface. This reduces the surface energy of the carbon black, inhibits the attraction between particles, reduces the aggregation tendency of the conductive agent, and facilitates the formation of stable and uniform pores after the pore-forming agent sublimates. At the same time, it is beneficial for the formation of a three-dimensional continuous conductive network in the electrode, reducing the charge transfer resistance (Rct) and further improving the rate performance.

[0053] Dry particle mixing results in varying inter-particle spacing and thermal conductivity, leading to differences in local particle temperature and inter-particle micro-pressure. This causes some particles to sublimate. They are then baked at near-sublimation temperatures (e.g., 175-185℃) for 2 hours. Slow sublimation at higher temperatures prevents the pore-forming agent from overflowing too quickly. Before a stable three-dimensional network structure is formed, the particles are affected, impacting pore uniformity and stability, and consequently, material stability. Finally, baking at an even higher temperature (187-195℃) for 30 minutes allows the pore-forming agent to partially sublimate and escape, while simultaneously creating a stable structure between other particles at high temperatures. This strengthens and stabilizes the pore structure, completely removing the pore-forming agent and preventing trace amounts of hexachloroethane residue. Residual hexachloroethane may slowly decompose during battery cycling (releasing Cl-). - Corrosion of the current collector or cathode material can lead to capacity decay. Baking at temperatures lower or higher than the pore-forming agent's sublimation temperature near its sublimation point helps control the sublimation process, improves porosity, increases pore stability, and further enhances rate performance.

[0054] This invention involves uniformly mixing and stirring positive electrode materials, conductive agents, binders, and pore-forming agents to form fibrous powder agglomerates. These agglomerates are then extruded and pressed into dry electrode films. The dry electrode films are then rolled and compounded with current collectors to prepare a positive electrode precursor. The precursor is then subjected to high-temperature baking, causing the pore-forming agent inside the electrode to slowly volatilize and form pores. This process produces a dry positive electrode with high areal density and high porosity. The resulting dry positive electrode exhibits uniform pore size and pore distribution, and its high areal density reduces concentration polarization during high-rate charge and discharge, which is beneficial for sodium ion insertion and extraction. This significantly improves the rate performance of the battery electrode at high areal density. Furthermore, this preparation method requires simple processing equipment, allows for more reliable and easier on-site process control, and is more conducive to large-scale production. It avoids the use of solvents and complex coating processes required in wet electrode processes, while also having lower energy consumption.

[0055] The dry electrode prepared by this invention can significantly improve the energy density of the battery, thus obtaining an electrode structure with excellent energy density and rate performance. Moreover, the preparation method has simpler processing equipment, more reliable and easier on-site process control, and is more conducive to large-scale production. It also reduces the production cost and energy consumption of sodium-ion battery motors.

[0056] This invention provides a sodium-ion battery, which includes the above-described sodium dry-process positive electrode sheet or the positive electrode sheet prepared by the above-described method for preparing sodium dry-process positive electrode sheet.

[0057] The dry sodium ion cathode of the present invention has the advantages of low cost, high loading capacity, high rate capability, and high safety.

[0058] The sodium-ion battery provided in this embodiment of the invention also includes a negative electrode, a separator, and an electrolyte.

[0059] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector. The negative active material layer may include at least one of artificial graphite, natural graphite, hard carbon, soft carbon, and carbon black.

[0060] The electrolyte plays a role in conducting ions between the positive and negative electrode plates. The electrolyte can be liquid, gel, or solid.

[0061] In some implementations, the electrolyte uses EC:PC:EMC:NaPF6:NaFSI:FEC = 30%:20%:36%:8%:5%:1%, and the electrolyte salt is a lithium salt.

[0062] The present invention will be described in detail below through embodiments.

[0063] Example 1

[0064] A method for preparing a sodium-ion battery positive electrode sheet, comprising the following steps:

[0065] (1) Sodium iron phosphate pyrophosphate, SP, preferred binder PTFE, and hexachloroethane are mixed evenly at a mass ratio of 95:3:1.8:0.2, and then subjected to high-speed shear mixing to obtain fibrous powder; the D50 particle size of the solid hexachloroethane particles is 0.20 μm; the SP particle size is 50 nm; and the specific surface area of ​​the conductive agent is 70 m². 2 / g; The stirring speed is 200r / min, and the stirring time is 1h;

[0066] (2) The fibrous powder agglomerates are extruded to obtain an initial film; the extrusion temperature is 100℃; the initial film is repeatedly rolled to obtain a dry electrode film; two dry electrode films are respectively placed on both sides of an aluminum foil, and then rolled together, adjusting the roller gap of the dry electrode rolling process to 190μm to obtain an areal density of 400g / m³. 2 Dry electrode positive electrode precursor;

[0067] (3) The dry-process electrode positive electrode precursor was baked in an oven at 140℃ for 2 hours in the first stage; at 175℃ for 2 hours in the second stage, with a heating rate of 0.5℃ / min; and at 190℃ for 30 minutes in the third stage. After cooling, the sodium-ion battery dry-process positive electrode was obtained. The porosity of the sodium-ion battery dry-process positive electrode was 40%, and the areal density of the sodium-ion battery dry-process positive electrode was 400 g / m³. 2 .

[0068] Example 2

[0069] The only difference from Example 1 is that in the preparation of the fibrous powder in step (1), the mass ratio of sodium iron phosphate pyrophosphate, SP, PTFE and hexachloroethane is adjusted to 93:4:1.9:0.1.

[0070] Example 3

[0071] The only difference from Example 1 is that in the preparation of the fibrous powder in step (1), the mass ratio of sodium iron phosphate pyrophosphate, SP, PTFE and hexachloroethane is adjusted to 97:1.2:1.5:0.3.

[0072] Example 4

[0073] The only difference from Example 1 is that, in the process of preparing the fibrous powder in step (1), the D50 particle size of the solid hexachloroethane particles is adjusted to 0.25 μm.

[0074] Example 5

[0075] The only difference from Example 1 is that in the preparation of the fibrous powder in step (1), the ratio of the particle size of the conductive agent to that of hexachloroethane is adjusted to 1:6, the particle size of hexachloroethane D50 is 0.18 μm, and the particle size of the conductive agent is 30 nm.

[0076] Example 6

[0077] The only difference from Example 1 is that in the preparation of the fibrous powder in step (1), the conductive agent is adjusted to carbon black: acetylene black: carbon fiber conductive agent: graphene in a ratio of 5:2:0.2:0.01.

[0078] Example 7

[0079] The only difference from Example 1 is that, in the preparation of the fibrous powder in step (1), the mass ratio of the polyanionic compound, sodium-ionized layered oxide, and Prussian blue / white cathode material in the positive electrode active material is adjusted to 60:20:20, the polyanionic compound is Na4Fe3(PO4)2P2O7, and the sodium-ionized layered oxide is NaNi. 0.33 Fe 0.33 Mn 0.33 O2, Prussian blue / white cathode material is Na2Fe[Fe(CN)6]4.

[0080] Example 8

[0081] The only difference from Example 1 is that, in step (2) of preparing the dry electrode positive electrode precursor, the areal density of the dry electrode positive electrode precursor is adjusted to 500 g / m³. 2 The method to adjust the areal density of the precursor of the dry electrode positive sheet is to adjust the gap between the rolls in the dry electrode rolling process to 240 μm.

[0082] Example 9

[0083] The only difference from Example 1 is that in step (2) during the preparation of the dry electrode positive electrode precursor, the current collector is adjusted to a mesh current collector, which is a nickel mesh.

[0084] Example 10

[0085] The only difference from Example 1 is that, in the preparation process of the dry cathode sheet in step (3), the baking temperature of the dry cathode sheet precursor is adjusted. The first stage is baking at 150°C for 3 hours; the second stage is baking at 170°C for 3 hours with a heating rate of 0.6°C / min; the third stage is baking at 195°C for 40 minutes; after cooling, the sodium-ion battery dry cathode is obtained.

[0086] Comparative Example 1

[0087] A method for preparing a sodium-ion battery positive electrode sheet, differing from Example 1 in that a pore-forming agent is not added, and the steps include:

[0088] (1) Mix sodium iron phosphate pyrophosphate, SP and PTFE in a mass ratio of 95:3:2 until uniform, and then perform high-speed shearing to mix evenly to obtain fibrous powder.

[0089] (2) The fibrous powder agglomerates are extruded to form an initial film; the initial film is repeatedly rolled to obtain a dry electrode film; two dry electrode films are respectively placed on both sides of an aluminum foil, and then rolled together to obtain a surface density of 400 g / m³. 2 Dry electrode.

[0090] Comparative Example 2

[0091] A method for preparing a sodium-ion battery positive electrode sheet, differing from Example 1 in that no pore-forming agent is added, and the areal density is reduced to 150 g / m². 2 The steps include:

[0092] (1) Mix sodium iron phosphate pyrophosphate, SP and PTFE in a mass ratio of 95:3:2 until uniform, and then perform high-speed shearing to mix evenly to obtain fibrous powder.

[0093] (2) The fibrous powder agglomerates are extruded to form an initial film; the initial film is repeatedly rolled to obtain a dry electrode film; two dry electrode films are respectively placed on both sides of an aluminum foil, and then rolled together to obtain a surface density of 150 g / m³. 2 Dry electrode.

[0094] Comparative Example 3

[0095] The only difference from Example 1 is that in the preparation of the fibrous powder in step (1), the pore-forming agent solid particles hexachloroethane are replaced with polyethylene glycol.

[0096] Comparative Example 4

[0097] The only difference from Example 1 is that, in the preparation of the fibrous powder in step (1), the particle size of the pore-forming agent solid particles hexachloroethane is 0.5 μm.

[0098] Depend on Figure 1 It can be seen that the pore-forming agent volatilizes at high temperature to form micropores and generate pores.

[0099] Depend on Figure 2 As can be seen from the figure, the porous electrode prepared by Example 1 has a large number of pores, which can improve the liquid retention, reduce concentration polarization, and improve rate performance; the electrode has a large number of pores.

[0100] (1) Pouch battery

[0101] The electrodes prepared in each embodiment and comparative example were used as positive electrodes for sodium-ion batteries. Negative electrodes for sodium-ion batteries were prepared by coating a slurry using a hard carbon:SP:CMC:SBR ratio of 94%:2%:1.5:2.5. The cell's NP ratio was designed to be 1.2. A ceramic separator was selected, and a 1Ah soft-pack cell was fabricated using a stacking technique. The electrolyte used was EC:PC:EMC:NaPF6:NaFSI:FEC = 30%:20%:36%:8%:5%:1%.

[0102] (2) Electrical performance testing

[0103] Electrical performance tests were conducted using the Xinwei CT / CTE-4000 cell testing equipment.

[0104] (3) Mass energy density

[0105] This is calculated by dividing the cell's 0.2C discharge energy by the cell's mass.

[0106] Table 1 Results of performance tests

[0107]

[0108] As shown in Table 1, the sodium-ion batteries prepared by the dry-process positive electrode sheet of the present invention have high energy density and high rate capability.

[0109] As can be seen from the comparison between Example 1 and Example 2, reducing the pore-forming agent content to 0.1% will slightly reduce the rate performance.

[0110] As can be seen from the comparison between Example 1 and Example 3, increasing the content of main materials and increasing the amount of pore-forming agent can increase the energy density of the battery cell, but the rate performance is slightly reduced.

[0111] Comparing Example 1 and Example 4, it can be seen that when the particle size of the pore-forming agent is controlled at 0.25 μm, the rate performance is slightly reduced.

[0112] Comparing Example 1 and Example 5, it can be seen that when the ratio of conductive agent to pore-forming agent is 1:6, it has little effect on rate performance and energy density.

[0113] As can be seen from the comparison between Example 1 and Example 6, replacing the conductive agent with a composite conductive agent has little impact on the rate performance.

[0114] As can be seen from the comparison between Example 1 and Example 7, the composite main material improves the rate performance and energy density of the battery cell.

[0115] As can be seen from the comparison between Example 1 and Example 8, increasing the areal density can increase the energy density, but it will affect the rate performance.

[0116] Comparing Example 1 and Example 9, it can be seen that replacing the aluminum foil with a mesh current collector has little impact on the rate performance and energy density.

[0117] Comparing Example 1 and Example 10, it can be seen that changing the hole-forming drying temperature has little impact on the rate performance and energy density.

[0118] As can be seen from the comparison between Example 1 and Comparative Example 1, when the areal density is consistent, the addition of a pore-forming agent can improve the rate performance of the battery cell.

[0119] As can be seen from the comparison between Example 1 and Comparative Example 2, when the rate performance is not much different, the electrode with added pore-forming agent can increase the areal density, thereby increasing the energy density of the battery cell.

[0120] As can be seen from the comparison between Example 1 and Comparative Example 3, the use of hexachloroethane pore-forming agent has higher rate performance and energy density than polyethylene glycol.

[0121] As can be seen from the comparison between Example 1 and Comparative Example 4, a larger pore-forming agent will lead to a decrease in rate performance, and using a pore-forming agent with an appropriate particle size will result in better rate performance.

[0122] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A solid particle volatile porous sodium dry-process positive electrode, characterized in that, The positive electrode sheet is prepared by laminating a positive electrode film made of positive electrode material by dry process onto both sides of the current collector. The positive electrode material includes positive electrode active material, conductive agent, binder and pore-forming agent. The pore-forming agent is solid particulate hexachloroethane, and the D50 particle size of the solid particulate hexachloroethane is ≤0.3μm. The sodium-ion dry-process positive electrode sheet further includes a positive electrode active material and a binder, wherein the ratio of the positive electrode active material, conductive agent, binder, and pore-forming agent is (93%–98%): (1%–4%): (0.5%–1.5%): (0.1%–0.5%). The positive electrode active material is at least one of sodium-ion layered oxide, polyanionic compound, and Prussian blue / white positive electrode material; the conductive agent is at least one of carbon black, carbon nanotubes, carbon fiber, and graphene; and the binder is PTFE. The ratio of the particle size of the conductive agent to the particle size of the hexachloroethane is 1:(1~6).

2. The solid particle volatilization porous sodium dry electrode sheet according to claim 1, characterized in that, The porosity of the sodium-ion dry-process positive electrode is 30%–60%; the areal density of the sodium-ion dry-process positive electrode is 200–600 g / m³. 2 .

3. The solid particle volatilization porous sodium dry electrode sheet according to claim 1, characterized in that, The solid particles of hexachloroethane D50 have a particle size range of 0.10 μm to 0.2 μm, and the conductive agent has a particle size range of 50 nm to 60 nm; the specific surface area of ​​the conductive agent is 70 m². 2 / g.

4. The solid particle volatilization porous sodium dry electrode sheet according to claim 1, characterized in that, The mass ratio of the polyanionic compound, sodium-ionized layered oxide and Prussian blue / white cathode material in the cathode active material is (10~90):(10~90):(10~90).

5. The method for preparing a solid particle volatile porous sodium dry electrode according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step A: Stir and mix the positive electrode active material, conductive agent, binder and pore-forming agent to obtain a uniformly mixed dry powder. Shear and mix the dry powder evenly to obtain fibrous powder. Step B: The fibrous powder obtained in Step A is extruded and molded to obtain an initial membrane. Then, it is repeatedly rolled to obtain a positive electrode membrane. The positive electrode membrane and the current collector are rolled together to obtain a dry electrode positive electrode precursor. Step C: The dry electrode precursor obtained in step B is baked to create holes, and then cooled to obtain the dry positive electrode.

6. The method for preparing a solid particle volatile porous sodium dry electrode according to claim 5, characterized in that, In step A, the stirring speed is 100-300 r / min, and the stirring time is 0.5-2 h. In step B, the extrusion molding temperature is 40–120°C; the current collector is at least one of aluminum foil, carbon-coated aluminum foil, metal mesh current collector, and composite current collector; the areal density of the dry electrode positive electrode precursor is 200–600 g / m³. 2 ; In step C, the baking of the dry electrode precursor is divided into three stages: the first stage is baking at 140~155℃ for 2~3 hours; the second stage is baking at 175-185℃ for 2~3 hours with a heating rate of 0.5~0.8℃ / min; and the third stage is baking at 187-195℃ for 30~45 minutes.

7. A sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode sheet prepared by the method described in any one of claims 1 to 4 or the method described in any one of claims 5 to 6.

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