Asymmetric functional sodium battery diaphragm as well as preparation method and application thereof

Abstract

The invention discloses an asymmetric functional sodium battery diaphragm as well as a preparation method and application thereof, and belongs to the technical field of sodium batteries, the asymmetric functional sodium battery diaphragm structurally comprises a base membrane and a negative electrode sodium supplement / semiconductor mixed layer coated on the surface of one side of the base membrane; or the structure comprises a base film, a negative electrode sodium supplementing layer and a semiconductor coating, the negative electrode sodium supplementing layer and the semiconductor coating are arranged on the surfaces of the two sides of the base film respectively, or the negative electrode sodium supplementing layer and the semiconductor coating are arranged on the surface of the same side of the base film, and a laminated structure is formed; the negative electrode sodium supplement / semiconductor mixed layer comprises the following components: a sodium supplement material, a semiconductor material, a conductive agent and an auxiliary agent; the components of the negative electrode sodium supplementing layer comprise a sodium supplementing material, a conductive agent and an auxiliary agent; the semiconductor coating comprises the following components: a semiconductor material, a conductive agent and an auxiliary agent. The asymmetric functional sodium battery diaphragm is easy to prepare, and can enhance the fast charge characteristic of a sodium ion battery, improve the first charge-discharge efficiency and capacity by supplementing sodium, and enhance the safety characteristics of overcharge resistance, overheating resistance, thermal runaway resistance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium batteries, and in particular to an asymmetric functional sodium battery separator and a preparation method and application thereof. Background Art

[0002] Sodium battery is a secondary battery with sodium ions as charge carriers. It has high theoretical energy density, abundant raw material resources, high safety, low cost and good environmental adaptability. It has become one of the hot spots in the field of new energy research. The diaphragm is one of the important components of sodium battery. It is located between the positive electrode and the negative electrode and can provide a channel for the transport of sodium ions. The physical and chemical properties of the diaphragm affect the electrochemical performance and safety of sodium battery.

[0003] In order to improve the capacity of sodium ion batteries, the prior art usually applies a functional coating on the positive electrode side or the negative electrode side of the diaphragm. The Chinese patent document with publication number CN117352954A discloses a sodium-supplementing electrolyte diaphragm, and the preparation method of the sodium-supplementing electrolyte diaphragm includes: dissolving a polymer matrix in a solvent to obtain a polymer gel; dispersing a sodium-supplementing agent in the polymer gel, heating and mixing to obtain a doped gel; removing the solvent in the doped gel to obtain a polymer film; placing the polymer film in a sodium ion electrolyte for activation to obtain a gel-state sodium-supplementing electrolyte diaphragm. The safety of the sodium-supplementing electrolyte diaphragm is better than that of a liquid electrolyte, and can alleviate sodium electricity gas production to a certain extent. The Chinese patent document with publication number CN116526066A discloses a sodium battery diaphragm coating, which includes a core-shell structured conductive material coated solid electrolyte particles, the solid electrolyte is the core layer, and the conductive material layer is the shell layer; the material of the solid electrolyte core is selected from β-Al2O3 and Na 1+x Zr2Si x P 3-x O 12 (0≤x≤3), the conductive material layer is made of a binary composite material of carbon and aluminum-doped zinc oxide; the invention simultaneously introduces sodium ion conductivity and electronic conductivity into the diaphragm material, reduces the ion migration impedance during the sodium battery cycle, and improves the battery formation efficiency. The sodium-containing compound or mixture used in the above patents is coated on at least one side of the diaphragm, and its role is to provide an additional sodium ion source to enhance sodium ion conductivity and enhance the sodium supplementation effect.

[0004] Semiconductor materials have certain band gaps and forbidden band widths, as well as high critical magnetic fields and high electron saturation velocities. Under certain conditions, they have high electron migration rates, and therefore have characteristics such as resistance to high temperatures, high power, high voltage, high frequency, and high radiation. The corresponding characteristics are also highly consistent with the requirements of cells that are resistant to high temperatures, high voltages, and high rates, and have great potential application value in the field of secondary batteries. In order to improve the electrochemical performance and safety of sodium batteries, it is necessary to develop a functional sodium battery separator in combination with semiconductor materials. Summary of the invention

[0005] The present invention provides an asymmetric functional sodium battery separator, which has a simple structure, is easy to prepare, and has easy-to-obtain raw materials. It can enhance the fast charging characteristics of sodium ion batteries, supplement sodium to improve the initial charge and discharge efficiency and capacity, and can enhance safety characteristics such as resistance to overcharging, resistance to overheating, and resistance to thermal runaway.

[0006] The specific technical solutions adopted are as follows: An asymmetric functional sodium battery separator, The structure includes a base film and a negative electrode sodium supplement / semiconductor mixed layer coated on one side of the base film; Or the structure includes a base film, a negative electrode sodium replenishing layer and a semiconductor coating, wherein the negative electrode sodium replenishing layer and the semiconductor coating are respectively arranged on both sides of the base film, or the negative electrode sodium replenishing layer and the semiconductor coating are both arranged on the same side of the base film to form a laminated structure; The thickness of the base film is 5 μm to 35 μm; The thickness of the negative electrode sodium supplement / semiconductor mixed layer is 0.5 μm to 19 μm, and the components include sodium supplement material, semiconductor material, conductive agent and auxiliary agent; The thickness of the negative electrode sodium supplement layer is 0.5 μm to 10 μm, and the components include sodium supplement material, conductive agent and auxiliary agent; The thickness of the semiconductor coating is 0.2 μm to 20 μm, and the components include semiconductor material, conductive agent and auxiliary agent.

[0007] In the asymmetric functional sodium battery diaphragm of the present invention, the sodium supplement material arranged on the negative electrode side corresponding to the diaphragm has a sodium conductive property. At the same time, the sodium supplement material can store sodium to provide additional space for sodium ion charging, thereby improving the utilization efficiency of sodium ions, and further improving the initial efficiency, capacity and energy density of the battery cell; during the cycle process, the sodium supplement material with the sodium storage function can slowly release sodium ions, thereby achieving a good sodium supplement effect on the negative electrode side, thereby improving the cycle performance; the introduction of semiconductor materials can improve the heat resistance and pressure resistance of the diaphragm, and ensure safety in use.

[0008] Preferably, in the asymmetric functional sodium battery separator, the thickness of the base membrane is 9μm to 12μm; the thickness of the negative electrode sodium supplement / semiconductor mixed layer is 4μm to 15μm; the thickness of the negative electrode sodium supplement layer is 3μm to 6μm; and the thickness of the semiconductor coating is 1μm to 5μm.

[0009] A sodium supplement layer or a sodium supplement / semiconductor mixed layer is coated on the negative electrode side corresponding to the diaphragm, which can not only accept the sodium from the positive electrode and have certain sodium storage characteristics and overcharge resistance characteristics, but also provide an additional sodium source to reasonably supplement sodium to improve the initial charge and discharge efficiency, and also have certain safety performance.

[0010] Preferably, the asymmetric functional sodium battery diaphragm comprises a base film, a negative electrode sodium replenishing layer and a semiconductor coating, wherein the negative electrode sodium replenishing layer and the semiconductor coating are respectively arranged on the negative electrode side and the positive electrode side surface corresponding to the base film. The asymmetric functional coating is coated on both sides of the diaphragm, the semiconductor coating is coated on the positive electrode side corresponding to the diaphragm, and the negative electrode sodium replenishing layer is coated on the corresponding negative electrode side. The negative electrode sodium replenishing layer and the semiconductor coating work together to enhance the fast charging characteristics of the sodium ion battery, improve the initial charge and discharge efficiency and capacity by sodium replenishment, and enhance the safety characteristics such as resistance to overcharging, overheating, and thermal runaway.

[0011] The base film material includes but is not limited to at least one of polypropylene (PP), polyethylene (PE), polypropylene / polyethylene composite (PP / PE), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), polyimide (PI), aramid, glass fiber (CF), and lignin fiber.

[0012] Optionally, the sodium supplement material is selected from Na2Ti3O7, NaTi3O6OH, Na 0.66 [Li 0.22 Ti 0.78 ]O2、Li4Ti5O 12 、NaTi2(PO4)3、Na 1.4 Al 0.4 Ti 1.6 At least one of (PO4)3. The Dv50 particle size of the sodium supplementing material is 100 nm-5 μm, further 350 nm-5.5 μm.

[0013] Optionally, the semiconductor material is selected from at least one of Si, GaAs, InP, SiC, GaN, ZnO, diamond, and AlN.

[0014] The conductive agent is selected from at least one of conductive graphite, fibrous conductive agent or flaky conductive agent; the conductive graphite includes carbon black SP, acetylene black AB or Ketjen black KB; the fibrous conductive agent includes vapor grown carbon fiber VGCF or carbon nanotubes CNTs; the flaky conductive agent includes graphene GN.

[0015] Preferably, in the negative electrode sodium supplement / semiconductor mixed layer, based on the total mass of the sodium supplement material, the semiconductor material, the conductive agent and the auxiliary agent as 100%, the content of the sodium supplement material is 5% to 30%, the content of the semiconductor material is 7% to 40%, the content of the conductive agent is 1% to 5%, and the auxiliary agent includes a binder and a dispersant, the content of the binder is 3% to 5%, and the content of the dispersant is 25% to 55%.

[0016] Preferably, in the negative electrode sodium supplement layer, based on the total mass of the sodium supplement material, the conductive agent and the auxiliary agent as 100%, the content of the sodium supplement material is 82% to 95%, the content of the conductive agent is 1% to 5%, the auxiliary agent includes a binder and a dispersant, the content of the binder is 3.5% to 10%, and the content of the dispersant is 0.5% to 3%; the content of the conductive agent is ≤ the content of the binder.

[0017] Preferably, in the semiconductor coating, based on the total mass of the semiconductor material, the conductive agent and the auxiliary agent as 100%, the content of the semiconductor material is 87% to 97.5%, the content of the conductive agent is 0.5% to 2%, and the auxiliary agent includes a binder and a dispersant, the content of the binder is 1% to 8%, and the content of the dispersant is 1% to 3%.

[0018] The present invention also provides a method for preparing the asymmetric functional sodium battery separator, comprising the following steps: S10: dissolving a binder, a dispersant and a conductive agent in an oily solvent to obtain a first mixed solution; dissolving a sodium supplement material and a dispersant in an oily solvent to obtain a second mixed solution; and fully mixing the first mixed solution and the second mixed solution to obtain a sodium supplement slurry; dissolving a semiconductor material, a conductive agent, a binder and a dispersant in water to obtain a semiconductor material slurry; S11 dissolving a binder, a dispersant and a conductive agent in an oily solvent to obtain a third mixed solution, dissolving a sodium supplement material, a semiconductor material and a dispersant in an oily solvent to obtain a fourth mixed solution, and fully mixing the third mixed solution and the fourth mixed solution to obtain a sodium supplement slurry containing a semiconductor material; S2: coating the sodium supplement slurry, semiconductor material slurry or sodium supplement slurry containing semiconductor material in S10 onto the base film to obtain the asymmetric functional sodium battery separator.

[0019] Preferably, the oily solvent includes at least one of N-methylpyrrolidone, ethanol, acetone, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0020] Preferably, the dispersant includes at least one of sodium carboxymethyl cellulose, sodium hexametaphosphate, sodium alginate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and disodium ethylenediaminetetraacetate (EDTA).

[0021] Preferably, the binder is selected from at least one of polymethyl methacrylate butadiene styrene rubber, polyvinylidene fluoride, polystyrene acrylic emulsion, polyvinyl alcohol, ethylene vinyl acetate copolymer, polytetrafluoroethylene, polyvinyl acetate, polyurethane, polyvinylidene fluoride hexafluoropropylene copolymer, polyacrylic acid, and polyacrylate.

[0022] Preferably, the solid content of the sodium supplement slurry is 45wt% to 70wt%, the solid content of the semiconductor material slurry is 30wt% to 50wt%, and the solid content of the sodium supplement slurry containing the semiconductor material is 45wt% to 75wt%.

[0023] The present invention also provides a sodium ion battery, which comprises the asymmetric functional sodium battery separator.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention, through the design of an asymmetric functional sodium battery diaphragm, can not only play a reasonable role in sodium supplementation and improve overcharge resistance, but also improve the high temperature and high pressure resistance of the diaphragm, build a safety barrier for the diaphragm, thereby improving the energy density of the battery cell and enhancing the safety of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the asymmetric functional sodium battery membrane in Example 1.

[0026] Figure 2 This is a schematic diagram of the structure of the asymmetric functional sodium battery membrane in Example 2.

[0027] Figure 3 This is a schematic diagram of the structure of the asymmetric functional sodium battery membrane in Example 3.

[0028] Figure 4 This is a schematic diagram of the structure of the asymmetric functional sodium battery membrane in Example 4.

[0029] Figure 5 This is a schematic diagram of the first formation curve of the sodium ion battery made of the diaphragm in Comparative Example 1.

[0030] Figure 6 This is a schematic diagram of the first formation curve of the sodium ion battery cell made of the asymmetric functional sodium battery membrane in Example 4. DETAILED DESCRIPTION

[0031] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description through specific embodiments. In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0032] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The contents not described in detail in this specification belong to the prior art known to professionals in the field. The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0033] Example 1 22 kg of polyvinylidene fluoride, 3 kg of sodium carboxymethyl cellulose, and 10 kg of conductive carbon black were fully stirred and mixed in 150 kg of N-methylpyrrolidone to form a conductive glue; 200 kg of sodium supplement material Li4Ti5O 12 (Dv50 particle size is 350nm) and 0.2kg sodium alginate are mixed evenly in 100kg N-methylpyrrolidone to form a suspension; conductive glue is added to the suspension and then sand-milled and stirred to obtain a sodium supplement slurry; 91.5 kg of Si, 0.5 kg of conductive carbon black SP, 5 kg of binder (the mass ratio of polyacrylic acid PPA to SBR is 1:4), and 3 kg of dispersant sodium carboxymethyl cellulose are stirred and dispersed in 100 kg of solvent H2O to obtain a semiconductor material slurry; The sodium supplement slurry is coated on one side of the base film, and then rolled up for use after drying to form a negative electrode sodium supplement layer, and then the semiconductor material slurry is coated on the other side of the base film to form a semiconductor coating to obtain the asymmetric functional sodium battery separator; like Figure 1 As shown, the asymmetric functional sodium battery separator includes a base membrane, a semiconductor coating corresponding to the positive electrode side, and a negative electrode sodium supplement layer corresponding to the negative electrode side; the base membrane adopts a PE separator with a thickness of 9 μm, the thickness of the negative electrode sodium supplement layer is 5 μm, and the thickness of the semiconductor coating is 3 μm.

[0034] Example 2 23 kg of polyvinylidene fluoride, 3 kg of sodium carboxymethyl cellulose, and 10 kg of conductive carbon black were fully stirred and mixed in 200 kg of N-methylpyrrolidone to form a conductive glue; 200 kg of sodium supplement material Na2Ti3O7 (Dv50 particle size is 550nm) and 0.2 kg of sodium alginate were mixed in 85 kg of N-methylpyrrolidone to form a suspension; the conductive glue was added to the suspension and sand-milled and fully stirred to obtain a sodium supplement slurry; 91.5 kg of diamond C, 0.5 kg of conductive carbon black SP, 5 kg of binder (the mass ratio of polyacrylic acid PPA to SBR is 1:4), and 3 kg of dispersant carboxymethyl cellulose CMC are stirred and dispersed in 200 kg of solvent H2O to obtain a semiconductor material slurry; The sodium supplement slurry is coated on one side of the base film, and then rolled up for standby use after drying to form a negative electrode sodium supplement layer, and a semiconductor material slurry is coated on the negative electrode sodium supplement layer to form a semiconductor coating to obtain the asymmetric functional sodium battery separator; like Figure 2 As shown, the asymmetric functional sodium battery separator includes a base membrane and a negative electrode sodium supplement layer and a semiconductor coating on the negative electrode side; the base membrane adopts a PE separator with a thickness of 12 μm, the thickness of the negative electrode sodium supplement layer is 5 μm, and the thickness of the semiconductor coating is 3 μm.

[0035] Example 3 23 kg of polyvinylidene fluoride, 3 kg of sodium carboxymethyl cellulose, and 10 kg of conductive carbon black were fully stirred and mixed in 200 kg of N-methylpyrrolidone to form a conductive glue; 200 kg of sodium supplement material NaTi2(PO4)3 (Dv50 particle size is 350nm) and 0.2 kg of sodium alginate were mixed in 80 kg of N-methylpyrrolidone to form a suspension; the conductive glue was added to the suspension and sand-milled and fully stirred to obtain a sodium supplement slurry; 91.5 kg of AlN, 0.5 kg of conductive carbon black SP, 5 kg of binder (the mass ratio of polyacrylic acid PPA to SBR is 1:4), and 3 kg of dispersant carboxymethyl cellulose CMC are stirred and dispersed in 200 kg of solvent H2O to obtain a semiconductor material slurry; The semiconductor material slurry is coated on one side of the base film to form a semiconductor coating, and the sodium supplement slurry is coated on the semiconductor coating to form a negative electrode sodium supplement layer to obtain the asymmetric functional sodium battery separator.

[0036] like Figure 3 As shown, the asymmetric functional sodium battery separator includes a base membrane, a semiconductor coating on the negative electrode side, and a negative electrode sodium supplement layer; the base membrane adopts a PE separator with a thickness of 9 μm, the thickness of the semiconductor coating is 3 μm, and the thickness of the negative electrode sodium supplement layer is 5 μm.

[0037] Example 4 3 kg of polyvinylidene fluoride, 18 kg of sodium carboxymethyl cellulose, and 2 kg of conductive carbon black were fully stirred and mixed in 40 kg of N-methylpyrrolidone to form a conductive glue; 18 kg of sodium supplement material Na 0.66 [Li 0.22 Ti 0.78 ]O2 (Dv50 particle size is 5.5 μm), 25 kg semiconductor material ZnO, and 0.2 kg sodium alginate are mixed evenly in 40 kg N-methylpyrrolidone to form a suspension; conductive glue is added to the suspension and then sand-milled and stirred to obtain a sodium supplement slurry containing semiconductor materials; A sodium supplement slurry containing semiconductor material is coated on one side of the base film to form a negative electrode sodium supplement / semiconductor mixed layer to obtain the asymmetric functional sodium battery separator.

[0038] like Figure 4 As shown, the asymmetric functional sodium battery separator includes a base membrane and a negative electrode sodium supplement / semiconductor mixed layer on the negative electrode side; the base membrane adopts a PE separator with a thickness of 12μm, and the thickness of the negative electrode sodium supplement / semiconductor mixed layer is 10μm.

[0039] Comparative Example 1 Comparative Example 1 is a commercially available 9 (PE base film, thickness of 9 μm) + 3 (single-layer alumina ceramic layer, thickness of 3 microns) + 3 (PVDF coating, thickness of 3 μm) + 3 (PVDF coating, thickness of 3 μm) with a total thickness of 18 μm.

[0040] Comparative Example 2 Among them, Comparative Example 2 is a commercially available 12 (PP base film, thickness of 12μm) + 3 (single-layer alumina ceramic layer, thickness of 3μm) + 3 (PVDF coating, thickness of 3μm) + 3 (PVDF coating, thickness of 3μm) with a total thickness of 21μm.

[0041] Comparative Example 3 Comparative Example 3 is a commercially available 20 (PP base film, thickness is 20 μm) + 3 (single-layer alumina ceramic layer, thickness is 3 microns) diaphragm product, with a total thickness of 24 microns.

[0042] Sample analysis Test method description: The thickness of the diaphragm is tested according to GB / T36363-2018 6.4; the thermal shrinkage rate is tested according to GB / T36363-2018 6.5.2; the puncture strength is tested according to GB / T36363-2018 6.5.3.

[0043] The first charge and discharge efficiency needs to be achieved by making a sodium ion full cell, in which the positive electrode material is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2 (Xiangying XN33S), the negative electrode material is hard carbon (Bai Te Rui BSHC360); the electrolyte is 1 mol / L NaPF6+EC:DEC=1:1+5%FEC+1.5%VC+0.5%DDT+0.5%MSDS; the diaphragm adopts the diaphragm in the embodiment or the comparative example, and the diaphragm-negative electrode sheet-diaphragm-positive electrode sheet-diaphragm is stacked to form a roll core, and then the positive and negative electrode ears are welded and led out and laser-sealed in an aluminum shell package, the dry battery cell is baked at 90℃ for 18h and then cooled and injected with liquid, and the battery cell is left to stand for 24h after injection for formation (the formation adopts step-by-step formation, that is, 0.05C is charged to 2.8V, 0.1C is charged to 3.0V, and 0.2C is charged to 3.2V, and the charging capacity C1 at this time is recorded), and the liquid is injected again after formation, and the same electrolyte is used for the two injections (the ratio of the first injection is 95% and the second injection has the remaining 5%) and laser sealed.

[0044] The cell is charged to 4.0V at 0.2C, and the charging capacity at this time is recorded as C2. After standing for 30 minutes, the cell is discharged to 0V at 0.2C, and the discharge capacity at this time is recorded as C3. The first efficiency is: C3 / (C1+C2). By comparing the first efficiencies of the embodiment and the comparative example, it can be seen that the first efficiency of the asymmetric functional sodium battery separator is 4.5%~6.8% higher than that of the comparative example (the first efficiency of the embodiment 4 is 4.5%~6.8% higher than that of the comparative example). Figure 6 Compared with the comparative example 1 Figure 5 Compared with the first effect, it is improved by 6.8%), and the heat shrinkage resistance and puncture resistance at 130°C are also greatly improved, as shown in Table 1; Table 1 Test results of membrane performance in examples and comparative examples

[0045] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An asymmetric functional sodium battery separator, characterized in that: The structure includes a base film and a negative electrode sodium supplement / semiconductor mixed layer coated on one side of the base film; Or the structure includes a base film, a negative electrode sodium replenishing layer and a semiconductor coating, wherein the negative electrode sodium replenishing layer and the semiconductor coating are respectively arranged on both sides of the base film, or the negative electrode sodium replenishing layer and the semiconductor coating are both arranged on the same side of the base film to form a laminated structure; The thickness of the base film is 5 μm to 35 μm; The thickness of the negative electrode sodium supplement / semiconductor mixed layer is 0.5 μm to 19 μm, and the components include sodium supplement material, semiconductor material, conductive agent and auxiliary agent; The thickness of the negative electrode sodium supplement layer is 0.5 μm to 10 μm, and the components include sodium supplement material, conductive agent and auxiliary agent; The thickness of the semiconductor coating is 0.2 μm to 20 μm, and the components include semiconductor material, conductive agent and auxiliary agent.

2. The asymmetric functional sodium battery separator according to claim 1, characterized in that: The asymmetric functional sodium battery separator comprises a base film, a negative electrode sodium supplement layer and a semiconductor coating, wherein the negative electrode sodium supplement layer and the semiconductor coating are respectively arranged on the negative electrode side and the positive electrode side surfaces corresponding to the base film.

3. The asymmetric functional sodium battery separator according to claim 1, characterized in that: The sodium supplement material is selected from Na2Ti3O7, NaTi3O6OH, Na 0.66 [Li 0.22 Ti 0.78 ]O2、Li4Ti5O 12 、NaTi2(PO4)3、Na 1.4 Al 0.4 Ti 1.6 At least one of (PO4)3.

4. The asymmetric functional sodium battery separator according to claim 1, characterized in that: The base film material includes at least one of polypropylene, polyethylene, polypropylene / polyethylene, polyethylene terephthalate, polyvinylidene fluoride, polyphenylene sulfide, polyimide, aramid, glass fiber, and lignin fiber.

5. The asymmetric functional sodium battery separator according to claim 1, characterized in that: The semiconductor material is selected from at least one of Si, GaAs, InP, SiC, GaN, ZnO, diamond and AlN.

6. The asymmetric functional sodium battery separator according to claim 1, characterized in that: The conductive agent is selected from at least one of conductive graphite, fibrous conductive agent or flaky conductive agent; the conductive graphite includes carbon black SP, acetylene black AB or Ketjen black KB; the fibrous conductive agent includes vapor grown carbon fiber VGCF or carbon nanotubes CNTs; the flaky conductive agent includes graphene GN.

7. The asymmetric functional sodium battery separator according to claim 1, characterized in that: In the negative electrode sodium supplement / semiconductor mixed layer, based on the total mass of the sodium supplement material, the semiconductor material, the conductive agent and the auxiliary agent as 100%, the content of the sodium supplement material is 5% to 30%, the content of the semiconductor material is 7% to 40%, the content of the conductive agent is 1% to 5%, the auxiliary agent includes a binder and a dispersant, the content of the binder is 3% to 5%, and the content of the dispersant is 25% to 55%; And / or, in the negative electrode sodium supplement layer, based on the total mass of the sodium supplement material, the conductive agent and the auxiliary agent as 100%, the content of the sodium supplement material is 82% to 95%, the content of the conductive agent is 1% to 5%, the auxiliary agent includes a binder and a dispersant, the content of the binder is 3.5% to 10%, and the content of the dispersant is 0.5% to 3%; the content of the conductive agent is ≤ the content of the binder; And / or, in the semiconductor coating, based on the total mass of the semiconductor material, the conductive agent and the auxiliary agent as 100%, the content of the semiconductor material is 87% to 97.5%, the content of the conductive agent is 0.5% to 2%, the auxiliary agent includes a binder and a dispersant, the content of the binder is 1% to 8%, and the content of the dispersant is 1% to 3%.

8. The method for preparing an asymmetric functional sodium battery separator according to any one of claims 1 to 7, characterized in that: The following steps are involved: S10: dissolving a binder, a dispersant and a conductive agent in an oily solvent to obtain a first mixed solution; dissolving a sodium supplement material and a dispersant in an oily solvent to obtain a second mixed solution; and fully mixing the first mixed solution and the second mixed solution to obtain a sodium supplement slurry; dissolving a semiconductor material, a conductive agent, a binder and a dispersant in water to obtain a semiconductor material slurry; S11 dissolving a binder, a dispersant and a conductive agent in an oily solvent to obtain a third mixed solution, dissolving a sodium supplement material, a semiconductor material and a dispersant in an oily solvent to obtain a fourth mixed solution, and fully mixing the third mixed solution and the fourth mixed solution to obtain a sodium supplement slurry containing a semiconductor material; S2: coating the sodium supplement slurry, semiconductor material slurry or sodium supplement slurry containing semiconductor material in S10 onto the base film to obtain the asymmetric functional sodium battery separator.

9. The method for preparing an asymmetric functional sodium battery separator according to claim 8, characterized in that: The solid content of the sodium supplement slurry is 45wt% to 70wt%, the solid content of the semiconductor material slurry is 30wt% to 50wt%, and the solid content of the sodium supplement slurry containing the semiconductor material is 45wt% to 75wt%.

10. A sodium ion battery, characterized in that: It comprises the asymmetric functional sodium battery separator described in any one of claims 1 to 7.

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