Sodium-ion battery diaphragm and preparation method thereof

Abstract

The main purpose of the invention is to develop the sodium ion battery diaphragm, the wettability and liquid retention of the diaphragm to electrolyte are improved by coating the sodium ion conductor material and the metal oxide on one side or two sides of the surface of the diaphragm base membrane, a stable SEI membrane is formed, the cycle performance of the battery is improved, and the service life of the battery is prolonged. And sodium precipitation and sodium dendrite generation in the charging, discharging and circulating processes are obviously inhibited.

Description

Technical Field

[0001] The invention relates to a sodium ion battery separator. Background Art

[0002] Research on sodium-ion batteries began in the 1970s, and the layout of related industries has begun in the past 10 years. Its working principle is similar to that of lithium-ion batteries, mainly relying on the movement of sodium ions between the positive and negative electrodes. In the current era of energy transformation, sodium-ion batteries have obvious advantages in terms of resource abundance and cost. As the technology matures and the industrial chain gradually improves, it has excellent application prospects in the field of energy storage and power batteries, and at the same time complements mature energy storage technologies such as lithium-ion batteries and lead-acid batteries.

[0003] Compared with lithium-ion batteries, sodium-ion batteries have the following advantages: (1) Sodium resources are more abundant in the earth's crust than lithium resources, and the resource cost advantage is huge; (2) Sodium-ion batteries have more stable electrochemical properties and better safety; (3) Both the positive and negative current collectors of sodium-ion batteries can be made of aluminum foil, which further reduces costs; (4) The solvation energy of sodium ions is lower than that of lithium ions, and the interfacial ion diffusion capacity is better; (5) The ion conductivity is higher; and (6) The high and low temperature performance is better.

[0004] However, compared with lithium-ion batteries, sodium-ion batteries also have disadvantages such as lower energy density and poor cycle life. They are also prone to sodium precipitation and sodium dendrites, which is mainly due to the sodium storage mechanism and structural instability of the negative electrode material hard carbon. As a disordered graphitic carbon material, hard carbon has an irregular polycrystalline microstructure and a large number of topological defects, prismatic surfaces and closed pores. Its sodium storage methods mainly include interlayer intercalation, bulk chemical adsorption and nanoclusters. This unstable sodium storage method causes sodium-ion batteries to easily experience sodium precipitation and sodium dendrites during the cycle, which seriously affects the cycle life and safety of the battery. On the other hand, the SEI film on the surface of the negative electrode hard carbon has poor stability during the cycle and is constantly decomposed and generated. This leads to interface instability and consumes a large amount of active sodium, which will cause the battery cycle performance to deteriorate.

[0005] Sodium ion conductor diaphragm can accelerate the transmission rate of sodium ions during the battery charging and discharging process, and at the same time help the negative electrode to form a more stable SEI film. In addition, it can easily form a smooth and dense interface with the electrode, and it itself has a certain sodium storage capacity, which can improve the wettability and liquid retention of the diaphragm to the electrolyte, which has a significant effect on inhibiting the formation of sodium dendrites and improving circulation.

[0006] Some metal oxides MOx (such as M is Fe, Co, Ni, Cu, Sn, Sb, etc.) can react chemically with sodium dendrites to regulate Na +The deposition of sodium dendrites can be significantly inhibited, thereby significantly inhibiting the formation and growth of sodium dendrites and improving the wettability and liquid retention of the separator to the electrolyte, so as to achieve the purpose of inhibiting sodium dendrites and improving the cycle performance. Summary of the invention

[0007] Therefore, one of the purposes of the present invention is to provide a sodium ion battery separator in view of the shortcomings of the prior art, by coating sodium ion conductor materials and metal oxides on one side or both sides of the surface of the separator base film, thereby improving the wettability and liquid retention of the separator to the electrolyte, and forming a stable SEI film, thereby improving the battery cycle performance, and significantly inhibiting the formation of sodium precipitation and sodium dendrites during charging and discharging and cycling.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A sodium ion battery separator, characterized by comprising: A base film; and a coating located on at least one side of the base film, comprising a sodium ion conductor and a metal oxide.

[0010] Preferably, the coating further comprises a binder.

[0011] Preferably, the sodium ion conductor comprises NaZr 2 (PO 4 ) 3 、Na 3 Zr 2 Si 2 PO 12 、Na 2 O- 11 Al 2 O 3 、Na 3 OBr 0.5 I 0.5 、Na 2 B 12 H 12 、Na 2 B 10 H 10 , NaB 11 H 14 One or more of the .

[0012] Preferably, the metal oxide comprises Fe 2 O 3 、Co 3 O 4 、NiO、CuO、SnO 2 , Sb 2 O 3 One or more of the .

[0013] Preferably, the adhesive comprises a first adhesive and a second adhesive, and the second adhesive is different from the first adhesive.

[0014] Preferably, the binder type includes one or more of polyacrylates, polyacrylonitriles, polyacrylic amides, styrenes, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol.

[0015] Preferably, the thickness of the coating is between 0.5-5 μm.

[0016] Preferably, the content of the sodium ion conductor in the coating is between 25wt% and 97wt%, the content of the metal oxide is between 2wt% and 74wt%, and the content of the binder is between 1wt% and 12wt%.

[0017] The second object of the present invention is to provide a method for manufacturing the above-mentioned sodium ion battery separator, comprising the following steps: Mixing a binder, a sodium ion conductor, and a metal oxide in a solvent to form a first mixed solution; The first mixed solution is applied to one side of the base film, and after drying, a first coating is formed to obtain the sodium ion battery separator.

[0018] Preferably, the adhesive further comprises a first adhesive and a second adhesive, and the second adhesive is different from the first adhesive; The sodium ion battery separator manufacturing method may further include: The first binder is mixed with the solvent to obtain a first solution, and the first solution is mixed with the sodium ion conductor and the metal oxide to form the first mixed solution.

[0019] Preferably, in the manufacturing method, the first binder and the second binder are dissolved in the solvent and mixed to form the first solution.

[0020] Preferably, the manufacturing method further comprises: Before obtaining the diaphragm, the first mixed solution is further coated on the other side of the base film relative to the first coating layer, and a second coating layer is obtained after drying.

[0021] Preferably, in the manufacturing method, the first binder includes one or more of polyacrylates, polyacrylonitrile, polyacrylamide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol, and the second binder includes one or more of polyacrylates, polyacrylonitrile, polyacrylamide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol.

[0022] The present invention coats the above two types of materials on the surface of the sodium ion battery separator. The two types of materials play a synergistic role in effectively inhibiting the formation of sodium precipitation and sodium dendrites, while improving the cycle performance of the battery, solving the problem that sodium precipitation and sodium dendrites are very likely to occur during the cycle, and the battery cycle performance deteriorates, seriously affecting the cycle life and safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The first coating layer is applied to one side of the base film.

[0024] Figure 2 The first coating is applied on one side of the base film, and the second coating is applied on the other side of the base film.

[0025] Figure 3 The battery of the present invention was disassembled after 500 cycles, and the sodium precipitation and sodium dendrite phenomenon at the negative electrode interface of the embodiment and the comparative example were actually photographed.

[0026] Figure 4 The present invention is a flow chart of the method for preparing a sodium ion battery separator.

[0027] Figure 5 The flowchart is for preparing the first mixed solution. DETAILED DESCRIPTION

[0028] In order to achieve the above object, according to one of the objects of the present invention, a method for preparing a sodium ion battery separator is provided, which comprises: The binder, the sodium ion conductor and the metal oxide are mixed in a solvent to form a first mixed liquid.

[0029] In the implementation manner of the present application, the adhesive includes a first adhesive and a second adhesive, and the second adhesive is different from the first adhesive.

[0030] In the embodiment of the present application, the first mixed solution is coated on one side of a base film to form a first coating layer, and the sodium ion battery separator is obtained after the first coating layer is dried.

[0031] In the embodiment of the present application, the base film further includes a second coating layer, which is relative to the first coating layer. Located on the other side of the base film, the second coating layer includes a sodium ion conductor, a metal oxide, and a binder.

[0032] In the embodiment of the present application, the sodium ion conductor comprises NaZr 2 (PO 4 ) 3 、Na 3 Zr 2 Si 2 PO 12 , Na 2 O- 11 Al 2 O 3 、Na 3 OBr 0.5 I 0.5 、Na 2 B 12 H 12 、Na 2 B 10 H 10 , NaB 11 H 14 One or more of the following, preferably, the sodium ion conductor is NaZr 2 (PO 4 ) 3 Or Na 3 OB r0.5 I 0.5 .

[0033] In the embodiment of the present application, preferably, the metal oxide comprises Fe 2 O 3 、Co 3 O 4 , NiO, CuO, SnO 2 , Sb 2 O 3 Preferably, the metal oxide is SnO 2 , NiO or CuO.

[0034] In the embodiment of the present application, the binder includes one or more of polyacrylates, polyacrylonitrile, polyacrylamide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol. Preferably, the binder is sodium carboxymethyl cellulose or polyacrylonitrile.

[0035] In the embodiment of the present application, the thickness of the first coating layer is between 0.5-5 μm, and preferably the thickness ranges between 0.8-4.5 μm.

[0036] In the embodiment of the present application, the thickness of the second coating layer is between 0.5-5 μm, and preferably the thickness ranges between 0.8-4.5 μm.

[0037] In the embodiment of the present application, the content of the sodium ion conductor in the first coating is between 25wt% and 97wt%, the content of the metal oxide is between 2wt% and 74wt%, and the content of the binder is between 1wt% and 12wt%. Preferably, the content of the sodium ion conductor is between 27wt% and 55wt% or 65wt% and 94wt%, the content of the metal oxide is between 5wt% and 30wt% or 40wt% and 65wt%, and the content of the binder is between 1wt% and 12wt%. Between wt%-10wt%.

[0038] In the embodiment of the present application, the content of the sodium ion conductor in the second coating is between 25wt% and 97wt%, the content of the metal oxide is between 2wt% and 74wt%, and the content of the binder is between 1wt% and 12wt%. Preferably, the content of the sodium ion conductor is between 27wt% and 55wt% or 65wt% and 94wt%, the content of the metal oxide is between 5wt% and 30wt% or 40wt% and 65wt%, and the content of the binder is between 1wt% and 12wt%. Between wt%-10wt%.

[0039] The second object of the present invention is to provide a method for manufacturing the above-mentioned sodium ion battery separator, such as Figure 4 or Figure 5 As shown, the following steps are included: (S1) mixing a binder, a sodium ion conductor, and a metal oxide in a solvent to form a first mixed solution; (S2) applying the first mixed solution to one side of the base film, and forming a first coating after drying to obtain the sodium ion battery separator.

[0040] In the embodiment of the present application, the adhesive may further include a first adhesive and a second adhesive. The second binder is different from the first binder; The sodium ion battery separator manufacturing method may further include: (S1A) mixing a first binder with the solvent to obtain a first solution; (S1B) Mixing the first solution, the sodium ion conductor, and the metal oxide to form the first mixed solution.

[0041] In the embodiment of the present application, in step (S1A), the first binder is further dissolved in the solvent and mixed with the second binder to form the first solution.

[0042] In the embodiment of the present application, the manufacturing method further comprises: (S3) Before obtaining the diaphragm, the first mixed solution is further applied to the other side of the base film relative to the first coating layer, and a second coating layer is obtained after drying.

[0043] In the embodiment of the present application, the first binder includes one or more of polyacrylates, polyacrylonitrile, polyacrylamide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol. Preferably, the first binder is sodium carboxymethyl cellulose or polyacrylonitrile.

[0044] In the embodiment of the present application, the second binder includes one or more of polyacrylates, polyacrylonitrile, polyacrylamide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol. The second binder is different from the first binder. Preferably, The second binder is sodium carboxymethyl cellulose or polyacrylonitrile.

[0045] The present invention is further described in detail below by means of several embodiments, but it is not intended to limit the protection scope of the present invention. Figure 1 to Figure 2 .

[0046] Example 1

[0047] Sodium carboxymethyl cellulose is fully dissolved in deionized water to form a first solution, and then polyacrylate, NaZr 2 (PO 4 ) 3 and NiO are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 The mass ratio of NiO, sodium carboxymethyl cellulose and polyacrylate is 88:8:1:3. The first mixed solution is stirred and coated on one side of a 12 μm thick PE base film. The thickness of the first coating after drying is 2 μm, and the sodium ion battery separator can be obtained. In this embodiment, NaZr 2 (PO 4 ) 3 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improve the wettability and liquid retention of the film to the electrolyte; NiO, as a metal oxide, reacts chemically with sodium dendrites, which can inhibit the formation and growth of sodium dendrites and improve the cycle performance of sodium ion batteries.

[0048] Example 2

[0049] Sodium carboxymethyl cellulose is fully dissolved in deionized water to form a first solution, and then polyacrylonitrile, NaZr2 (PO 4 ) 3 and SnO 2 are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 , SnO 2 The mass ratio of sodium carboxymethyl cellulose and polyacrylonitrile is 90:5:2:3. The first mixed liquid is evenly coated on one side of a 9μm thick PE base film after stirring, and dried to form a first coating with a thickness of 1μm. The first mixed liquid is then evenly coated on the other side of the base film. After drying, the second coating has a thickness of 1 μm, the sodium ion battery separator can be obtained; in this embodiment, NaZr 2 (PO 4 ) 3 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; SnO 2 As a metal oxide, it reacts chemically with sodium dendrites, inhibiting the formation and growth of sodium dendrites to improve the cycle performance of sodium-ion batteries.

[0050] Example 3

[0051] Polyvinylidene fluoride was dissolved in deionized water to form a first solution, and then Na 2 B 10 H 10 and Co 3 O 4 are sequentially added to the first solution to form a first mixed solution, wherein Na 2 B 10 H 10 、Co 3 O 4 The mass ratio of polyvinylidene fluoride is 92:5:3. The first mixed liquid is stirred and coated on one side of a 9 μm thick PE base film. After drying, the thickness of the first coating is 4 μm, and the sodium ion battery separator can be obtained. In this embodiment, Na 2 B 10 H 10 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; Co 3 O 4 As a metal oxide, it reacts chemically with sodium dendrites, inhibiting the formation and growth of sodium dendrites to improve the cycle performance of sodium-ion batteries.

[0052] Example 4

[0053] Sodium carboxymethyl cellulose and polyvinyl alcohol are fully dissolved in deionized water to form a first solution, and then Na 2 O-11Al 2 O 3 and Fe 2 O 3 are sequentially added to the first solution to form a first mixed solution, wherein Na 2 O-11Al 2 O 3 , Fe 2 O 3 , sodium carboxymethyl cellulose, and polyvinyl alcohol in a mass ratio of 50:42:3: 5, the first mixed solution is stirred and coated on one side of a PE base film having a thickness of 7 μm. After drying, the thickness of the first coating layer is 3 μm, and the sodium ion battery separator is obtained. In this embodiment, Na 2 O-11Al 2 O 3 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; Fe 2 O 3 As a metal oxide, it reacts chemically with sodium dendrites, inhibiting the formation and growth of sodium dendrites to improve the cycle performance of sodium-ion batteries.

[0054] Example 5

[0055] Sodium carboxymethyl cellulose and styrene ester are fully dissolved in deionized water to form a first solution, and then Na 3 OB r0.5 I 0.5 and Sb 2 O 3 are sequentially added to the first solution to form a first mixed solution, wherein Na 3 OB r0.5 I 0.5 , Sb 2 O 3 , sodium carboxymethyl cellulose, and styrene ester in a mass ratio of 37:56:2: 5, the first mixed solution is stirred and coated on one side of the PP base film with a thickness of 16 μm, and the thickness of the first coating layer after drying is 1 μm, and the sodium ion battery separator can be obtained; in this embodiment, Na 3 OB r0.5 I 0.5 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; Sb 2 O 3As a metal oxide, it reacts chemically with sodium dendrites, inhibiting the formation and growth of sodium dendrites to improve the cycle performance of sodium-ion batteries.

[0056] Example 6

[0057] The polyvinylidene fluoride, sodium carboxymethyl cellulose and polyvinyl alcohol are fully dissolved in deionized water to form a first solution, and then NaZr 2 (PO 4 ) 3 and CuO are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 , CuO, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl alcohol in a mass ratio of 88:6:2:2:2, the first mixed solution is stirred and coated on one side of a PE base film with a thickness of 12 μm, and the thickness of the first coating is 2 μm after drying, and the sodium ion battery separator can be obtained; in this embodiment, NaZr 2 (PO 4 ) 3 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improve the wettability and liquid retention of the film to the electrolyte; CuO, as a metal oxide, reacts chemically with sodium dendrites, which can inhibit the formation and growth of sodium dendrites and improve the cycle performance of sodium ion batteries.

[0058] Example 7

[0059] The polyacrylic acid amide and styrene ester are fully dissolved in deionized water to form a first solution, and then NaZr 2 (PO 4 ) 3 and NiO are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 The mass ratio of NiO, polyacrylic acid amide and styrene ester is 70:22:4:4. The first mixed liquid is stirred and coated on one side of the PP base film with a thickness of 12 μm. After drying, the thickness of the first coating layer is 2 μm, and the sodium ion battery separator can be obtained. In this embodiment, NaZr 2 (PO 4 ) 3 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improve the wettability and liquid retention of the film to the electrolyte; NiO, as a metal oxide, reacts chemically with sodium dendrites, which can inhibit the formation and growth of sodium dendrites and improve the cycle performance of sodium ion batteries.

[0060] Example 8

[0061] Sodium carboxymethyl cellulose is fully dissolved in deionized water to form a first solution, and then polyacrylonitrile, NaZr 2 (PO 4 ) 3 , CuO, SnO 2 are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 , CuO, SnO 2 , sodium carboxymethyl cellulose, and polyacrylonitrile in a mass ratio of 80:10: 5:2:3, the first mixed liquid is stirred and evenly coated on one side of the PE base film with a thickness of 9 μm, and dried to form a first coating with a thickness of 1 μm, and then the first mixed liquid is evenly coated on the other side of the base film, and the thickness of the second coating after drying is 2 μm, and the sodium ion battery separator can be obtained; in this embodiment, NaZr 2 (PO 4 ) 3 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; CuO and SnO 2 As a metal oxide, it reacts chemically with sodium dendrites, inhibiting the formation and growth of sodium dendrites to improve the cycle performance of sodium-ion batteries.

[0062] Example 9

[0063] Sodium carboxymethyl cellulose and polyvinyl alcohol are fully dissolved in deionized water to form a first solution, and then NaZr 2 (PO 4 ) 3 、Na 3 OB r0.5 I 0.5 and Co 3 O 4 are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 、Na 3 OB r0.5 I 0.5 、Co 3 O 4The mass ratio of sodium carboxymethyl cellulose and polyvinyl alcohol is 50:32:10:3:5. The first mixed liquid is stirred and evenly coated on one side of a PP base film with a thickness of 14 μm, and dried to form a first coating with a thickness of 1 μm. The first mixed liquid is then evenly coated on the other side of the base film. After drying, the thickness of the second coating is 1 μm, and the sodium ion battery separator is obtained. In this embodiment, NaZr 2 (PO 4 ) 3 And Na 3 OB r0.5 I 0.5 As a sodium ion conductor, it helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; Co 3 O 4 As a metal oxide, it reacts chemically with sodium dendrites, inhibiting the formation and growth of sodium dendrites to improve the cycle performance of sodium-ion batteries.

[0064] Example 10

[0065] The polyvinylidene fluoride is fully dissolved in deionized water to form a first solution, and then polyacrylonitrile, NaZr 2 (PO 4 ) 3 and SnO 2 are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 , SnO 2 The mass ratio of polyvinylidene fluoride and polyacrylonitrile is 30:60:5:5. The first mixed liquid is stirred and evenly coated on one side of the 9 μm thick PE base film, and dried to form a first coating layer with a thickness of 2 μm. The first mixed solution is then evenly coated on the other side of the base film. After drying, the thickness of the second coating is 2 μm, and the sodium ion battery separator is obtained. In this embodiment, NaZr 2 (PO 4 ) 3 As a sodium ion conductor, It helps to form a stable SEI film at the negative electrode and improves the wettability and liquid retention of the film to the electrolyte; SnO 2 As a metal oxide, it reacts chemically with sodium dendrites to inhibit the formation and growth of sodium dendrites. To improve the cycle performance of sodium ion batteries.

[0066] Comparative Example 1

[0067] In order to confirm whether the first coating layer or the second coating layer has the effect of inhibiting sodium precipitation and the formation of sodium dendrites, a PE base film with a thickness of 12 μm is used as the comparative example.

[0068] Comparative Example 2

[0069] In order to confirm whether the first coating layer or the second coating layer has the effect of inhibiting sodium precipitation and the formation of sodium dendrites, a PP base film with a thickness of 16 μm is used as the comparative example.

[0070] Comparative Example 3

[0071] Sodium carboxymethyl cellulose is fully dissolved in deionized water to form a first solution, and then polyacrylate, NaZr 2 (PO 4 ) 3 are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 The mass ratio of sodium carboxymethyl cellulose and polyacrylate is 95:2:3. The first mixed liquid is stirred and coated on one side of a 9 μm thick PE base film. After drying, the thickness of the first coating is 2 μm, and the sodium ion battery separator can be obtained.

[0072] Comparative Example 4

[0073] Sodium carboxymethyl cellulose and polyvinyl alcohol are fully dissolved in deionized water to form a first solution, and then NaZr 2 (PO 4 ) 3 、Na 3 OB r0.5 I 0.5 are sequentially added to the first solution to form a first mixed solution, wherein NaZr 2 (PO 4 ) 3 、Na 3 OB r0.5 I 0.5 , sodium carboxymethyl cellulose, and polyvinyl alcohol in a mass ratio of 50:42: 3:5, the first mixed liquid is stirred and evenly coated on one side of the PP base film with a thickness of 14 μm, and dried to form a first coating with a thickness of 1 μm, and then the first mixed liquid is evenly coated on the other side of the base film. After drying, the thickness of the second coating is 1 μm, and the sodium ion battery separator can be obtained.

[0074] Comparative Example 5

[0075] Sodium carboxymethyl cellulose is fully dissolved in deionized water to form a first solution, and then polyacrylonitrile, CuO、SnO2 are sequentially added to the first solution to form a first mixed solution, wherein CuO, SnO 2 The mass ratio of sodium carboxymethyl cellulose and polyacrylonitrile is 60:35:2:3. The mixed suspension B is fully stirred and evenly coated on one side of a 9 μm thick PE base film, and dried to form a first coating with a thickness of 1 μm. The mixed liquid B is then evenly coated on the other side of the base film. After drying, the thickness of the second coating is 2 μm, and the sodium ion battery separator can be obtained.

[0076] Comparative Example 6

[0077] Fully dissolve polyacrylamide and styrene ester in deionized water to form a first solution, and then add NiO to the first solution to form the first mixed solution, wherein the mass ratio of NiO, polyacrylamide and styrene ester is 92:4:4. After fully stirring, the first mixed solution is coated on one side of a PP base film with a thickness of 12 μm. After drying, the thickness of the first coating is 2 μm, and the sodium ion battery separator can be obtained.

[0078] Battery cycle capacity test

[0079] The sodium ion battery separator of the present invention can be used to make sodium ion batteries. First, the positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 , conductive agent Super P, and binder PVDF are dissolved in NMP at a ratio of 95:2:3, mixed evenly and applied on aluminum foil, and dried to obtain a positive electrode sheet; hard carbon, conductive agent Super P, sodium carboxymethyl cellulose, and styrene-butadiene rubber are dissolved in deionized water at a ratio of 94.5:2:1.5:2, mixed evenly and applied on aluminum foil, and dried to obtain a negative electrode sheet; wherein the positive and negative electrode coating mass ratio is 1:1.1. The positive and negative electrode sheets are cut into pieces of suitable size, and the sodium ion battery separator prepared by the present invention is used. After lamination, the electrolyte is injected, and then packaged to make a sodium ion soft-pack battery with a designed capacity of 1Ah.

[0080] The battery was cycled tested with a charge and discharge voltage range of 1.5 to 3.9V and a current of 0.5A. The test temperature is 25°C and the cycle test data can be seen in Table 1. Table 1

[0082] As can be seen from Table 1, after 500 cycles of the sodium ion battery using the sodium ion battery of Examples 1 and 2, Its negative electrode capacity retention rate is significantly better than that of the negative electrode capacity retention rate of the sodium ion battery using comparative examples 1 and 2; In addition, from Figure 3 It can be seen that when the battery after the cycle is disassembled, the negative electrode interface of the sodium ion battery using Examples 1 and 2 is smooth, and no sodium precipitation and sodium dendrites appear, while the negative electrode interface of the sodium ion battery using Comparative Examples 1 and 2 has serious sodium precipitation and sodium dendrites, which proves that the sodium ion battery separator provided by the present invention has an obvious effect on inhibiting sodium dendrites and improving the cycle performance of sodium ion batteries.

[0083] As can be seen from Table 1, Example 1 is compared with Example 8, Example 2 is compared with Example 10, and Example 4 is compared with Example 6. The comparison results of the sodium ion batteries of the three groups of examples after 500 cycles show that when only the type or combination of the binder is changed, there is no obvious difference in the effect of the battery cycle.

[0084] Comparative Example 3 is compared with Example 1 to compare whether the capacity retention rate of the sodium ion conductor battery can be close to that of Example 1 when NiO is removed from the diaphragm coating. As can be seen from Table 1, the capacity retention rate of the sodium ion conductor battery can be close to that of Example 1. After 500 cycles, the negative electrode capacity retention rate of the sodium ion battery prepared by the coating material is less than that of the sodium ion battery prepared by the coating material in Example 1; and Comparative Example 4 is compared with Example 9 to compare the negative electrode capacity retention rate of the sodium ion battery prepared by the coating material in Example 1 when the diaphragm coating removes CuO and SnO 2 When the capacity retention rate of the sodium ion conductor battery is close to that of Example 9, it can be seen from Table 1 that after 500 cycles of the sodium ion battery prepared by the coating material of Comparative Example 4, the negative electrode capacity retention rate is less than that of the sodium ion battery prepared by the coating material of Example 9; and the capacity retention rate of the negative electrode of the sodium ion battery prepared by the coating material of Comparative Example 3, After 500 cycles of the sodium ion battery prepared by the coating material, the negative electrode capacity retention rate is similar to that of the comparative example 1, 2 have similar results in terms of negative electrode capacity retention of sodium ion batteries, with no significant difference. This result indicates that if only sodium ion conductor is used as the coating of the diaphragm, it will not be effective in inhibiting sodium precipitation and sodium dendrite formation and improving the cycle performance of sodium ion batteries.

[0085] Comparative Example 5 is compared with Example 8 to compare the effect of removing NaZr from the diaphragm coating. 2 (PO 4 ) 3 When the capacity retention rate of the sodium ion conductor battery is similar to that of Example 8, it can be seen from Table 1 that after 500 cycles of the sodium ion battery prepared by the coating material of Comparative Example 5, its negative electrode capacity retention rate is less than that of the sodium ion battery prepared by the coating material of Example 8; and Comparative Example 6 is compared with Example 7, the purpose is to compare the capacity retention rate of the negative electrode when the diaphragm coating removes NaZr 2 (PO4 ) 3 When the capacity retention rate of the sodium ion conductor battery is similar to that of Example 7, it can be seen from Table 1 that after the sodium ion battery prepared by the coating material of Comparative Example 6 is cycled 500 times, its negative electrode capacity retention rate is less than that of the sodium ion battery prepared by the coating material of Example 7; and after the sodium ion batteries prepared by the coating materials of Comparative Examples 5 and 6 are cycled 500 times, their negative electrode capacity retention rates are similar to the negative electrode capacity retention rates of the sodium ion batteries of Comparative Examples 1 and 2, and there is no obvious difference; it can be explained by the results that if only metal oxide is used as the coating of the diaphragm, it has no obvious effect on inhibiting sodium precipitation and sodium dendrite generation and improving the cycle performance of the sodium ion battery.

[0086] The negative electrode capacity retention results from Comparative Examples 3 to 6 show that when only sodium ion conductors or metal oxides are used as the coating of the diaphragm, the effect of inhibiting sodium precipitation and sodium dendrite generation is similar to that of the base membrane without a coating, and the problems of the prior art cannot be solved. Figure 3 It can be seen that the sodium ion battery separator provided by the present invention solves the technical problems of sodium precipitation and generation of sodium dendrites during the cycle of existing sodium ion batteries, and has a significant effect on improving the cycle performance of sodium ion batteries.

[0087] The above contents involving common knowledge are not described in detail, and those skilled in the art can understand them.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A sodium ion battery separator, characterized in that: include: Basement membrane; and The coating layer located on at least one side of the base film comprises a sodium ion conductor and a metal oxide.

2. The sodium ion battery separator according to claim 1, wherein the coating further comprises a binder.

3. The sodium ion battery separator according to claim 1, wherein the sodium ion conductor comprises <h2 style=";text-align:left;direction:ltr">NaZr2(PO4)3, Na3Zr2Si2PO<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> Na2O-11Al2O3 Na3OB<h2 style=";text-align:left;direction:ltr"> r0.5 <h2 style=";text-align:left;direction:ltr"> I<h2 style=";text-align:left;direction:ltr"> 0.5 <h2 style=";text-align:left;direction:ltr"> 、 Na2B 12 H 12 , Na2B 10 H 10 , NaB 11 H 14 One or more of the .

4. The sodium ion battery separator according to claim 1, wherein the metal oxide comprises one or more of Fe2O3, Co3O4, NiO, CuO, SnO2, and Sb2O3.

5. The sodium ion battery separator according to claim 2, wherein the binder comprises a first binder and a second binder, and the second binder is different from the first binder.

6. The sodium ion battery separator according to claim 2, wherein the binder type comprises one or more of polyacrylates, polyacrylonitriles, polyacrylic acids, styrenes, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol.

7. The sodium ion battery separator according to claim 1, wherein the content of the sodium ion conductor in the coating is between 25wt% and 97wt%, the content of the metal oxide is between 2wt% and 74wt%, and the content of the binder is between 1wt% and 12wt%.

8. A method for manufacturing a sodium ion battery separator, comprising the steps of: Mixing a binder, a sodium ion conductor, and a metal oxide in a solvent to form a first mixed solution; The first mixed solution is applied to one side of the base film, and after drying, a first coating is formed to obtain the sodium ion battery separator.

9. The method for manufacturing a sodium ion battery separator according to claim 8, wherein the binder further comprises a first binder and a second binder, and the second binder is different from the first binder; The sodium ion battery separator manufacturing method further comprises: The first binder is mixed with the solvent to obtain a first solution, and the first solution is mixed with the sodium ion conductor and the metal oxide to form the first mixed solution.

10. The method for manufacturing a sodium ion battery separator according to claim 9, wherein: The first binder and the second binder are further dissolved in the solvent and mixed to form the first solution.

11. The method for manufacturing a sodium ion battery separator according to claim 9, further comprising: Before obtaining the diaphragm, the first mixed solution is further coated on the other side of the base film relative to the first coating layer, and a second coating layer is obtained after drying.

12. The method for manufacturing a sodium ion battery separator according to claim 9, wherein the first binder comprises one or more of polyacrylates, polyacrylonitrile, polyacrylic acid amide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol, and the second binder comprises one or more of polyacrylates, polyacrylonitrile, polyacrylic acid amide, styrene esters, polyvinylidene fluoride, sodium carboxymethyl cellulose, and polyvinyl alcohol.

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