Sodium-ion battery separator and preparation method and application thereof

Abstract

The application provides a sodium ion battery diaphragm and a preparation method and application thereof, and relates to the technical field of batteries.The sodium ion battery diaphragm provided by the application comprises a diaphragm base body and a coating layer coated on the diaphragm base body; the coating layer is mainly composed of Ni-MOF loaded with aluminum-doped zinc oxide and a binder.The Ni-MOF can guide the uniform deposition of sodium ions and inhibit the growth of sodium dendrites; the Ni-MOF can store high-energy charges in a smaller volume, realize dense cation hopping sites, minimize the activation energy of ion transmission, and thus improve the ion conductance; and the Ni-MOF can reduce the gas production of the battery.The aluminum-doped zinc oxide is loaded in the Ni-MOF, which can improve the conductive performance of the battery cell, make the battery cell have better cycle performance and rate performance, improve the melting point of the diaphragm, improve the safety performance, and improve the wettability of the electrolyte and the high liquid absorption rate.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a sodium-ion battery separator, its preparation method, and its application. Background Technology

[0002] With the continuous rise in the price of raw materials for lithium-ion batteries, it is imperative to find alternative or alternative energy storage technologies for lithium-ion batteries. In recent years, sodium-ion batteries, which have a similar working principle to lithium-ion batteries, have received increasing attention from researchers. Due to the abundant reserves of sodium in the Earth's crust and its wide distribution globally, sodium-ion batteries have enormous potential for large-scale application.

[0003] Sodium-ion batteries offer numerous advantages, including abundant sodium resources, excellent high and low temperature performance, high safety, and the ability to use low-salt-concentration electrolytes. However, current sodium-ion batteries suffer from issues such as sodium deposition, poor cycle performance, and gas generation. Furthermore, using PP or PE separators presents risks such as poor wettability, sodium deposition, and separator puncture / short circuits.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The first objective of this invention is to provide a sodium-ion battery separator to solve at least one of the above-mentioned problems.

[0006] A second objective of this invention is to provide a method for preparing the above-mentioned sodium-ion battery separator.

[0007] A third objective of this invention is to provide the application of the above-mentioned sodium-ion battery separator in the preparation of sodium-ion batteries.

[0008] In a first aspect, the present invention provides a sodium-ion battery separator, comprising a separator substrate and a coating applied to the separator substrate;

[0009] The coating is mainly composed of Ni-MOF (nickel metal-organic framework) and binder;

[0010] The Ni-MOF is supported on aluminum-doped zinc oxide (AZO).

[0011] As a further technical solution, the membrane substrate includes a PP membrane (polypropylene membrane) or a PE membrane (polyethylene membrane).

[0012] As a further technical solution, the mass percentage of Ni-MOF in the coating is 92%-98%;

[0013] And / or, in Ni-MOF, the mass percentage of aluminum-doped zinc oxide is 8%-12%;

[0014] And / or, in aluminum-doped zinc oxide, the mass percentage of aluminum is 1%-3%.

[0015] As a further technical solution, the preparation method of the Ni-MOF includes the following steps:

[0016] Ni-MOF was prepared by mixing nickel acetate tetrahydrate, aluminum-doped zinc oxide, L-malic acid and 4,4-bipyridine in a methanol solution and then heating the mixture in a reactor.

[0017] The reactants, by mass fraction, consist of 1-1.5 parts nickel acetate tetrahydrate, 0.1-0.3 parts aluminum-doped zinc oxide, 0.6-1 parts L-malic acid, and 0.3-0.4 parts 4,4-bipyridine.

[0018] As a further technical solution, the temperature of the heating reaction is 140-160℃;

[0019] The heating reaction takes 25-35 hours.

[0020] As a further technical solution, the method for preparing aluminum-doped zinc oxide includes the following steps:

[0021] Zinc acetate dihydrate, sodium hydroxide, and aluminum nitrate were mixed in ethanol and then heated in a reaction vessel to prepare aluminum-doped zinc oxide.

[0022] The molar ratio of zinc acetate dihydrate, sodium hydroxide, and aluminum nitrate is 1:(8-12):(0.015-0.035).

[0023] As a further technical solution, the temperature of the heating reaction is 140-160℃;

[0024] The heating reaction takes 20-28 hours.

[0025] As a further technical solution, the adhesive includes polyvinylidene fluoride;

[0026] And / or, the coating further includes a dispersant; the dispersant includes 1-methyl-2-pyridinone; the content of the dispersant is 1%-3% of the coating mass.

[0027] Secondly, the present invention provides a method for preparing a sodium-ion battery separator, comprising the following steps:

[0028] Ni-MOF and binder, along with an optional dispersant, are mixed, coated onto a separator substrate, and dried to prepare a sodium-ion battery separator.

[0029] Thirdly, the present invention provides the application of the above-mentioned sodium-ion battery separator in the preparation of sodium-ion batteries.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The sodium-ion battery separator provided by this invention includes a separator substrate and a coating applied to the separator substrate. The coating mainly consists of Ni-MOF loaded with aluminum-doped zinc oxide and a binder. Ni-MOF provides a better environment for ion diffusion channels, guiding the uniform deposition of sodium ions and thus inhibiting the growth of sodium dendrites. Ni-MOF has a porous structure and high specific surface area, enabling it to store high-energy charges in a small volume, achieving dense cation jumping sites, minimizing the activation energy of ion transport, and thus improving ionic conductivity. Ni-MOF has abundant cavity structures that can act as a host to accommodate various gases, absorbing gases generated by the battery and reducing gas production. The aluminum-doped zinc oxide loaded in Ni-MOF improves the conductivity of the battery cell, promotes ion transport, and gives the battery cell better cycle performance and rate performance. It also increases the melting point of the separator, providing good thermal stability, low thermal shrinkage, and improved safety performance. Furthermore, it enhances the wettability of the electrolyte, resulting in good compatibility and high electrolyte absorption. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a flowchart of the sodium-ion battery separator preparation process in Example 1;

[0034] Figure 2 The charge-discharge curves of the negative electrode hard carbon coin cell prepared using PP base film and sodium ion battery separator of Example 1 are shown.

[0035] Figure 3 A graph showing the high-temperature cycle capacity retention rate of cells using PP separators and sodium-ion battery separators from Example 1;

[0036] Figure 4 A trend chart showing the high-temperature cycle capacity retention rate of the separator provided in Comparative Example 2 and the sodium-ion battery separator cell of Example 1;

[0037] Figure 5 A trend chart of high-temperature cycle capacity retention rate of the separator provided in Comparative Example 3 and the sodium-ion battery separator cell of Example 1;

[0038] Figure 6A trend chart showing the high-temperature cycle capacity retention rate of the separator provided in Comparative Example 4 and the sodium-ion battery separator cell in Example 1. Detailed Implementation

[0039] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0040] In a first aspect, the present invention provides a sodium-ion battery separator, comprising a separator substrate and a coating applied to the separator substrate;

[0041] The coating is mainly composed of Ni-MOF and a binder;

[0042] The Ni-MOF is supported on aluminum-doped zinc oxide.

[0043] The sodium-ion battery separator provided by this invention has good electrical properties and excellent safety performance.

[0044] The inventors discovered that Ni-MOF possesses an ordered porous structure that can serve as a channel for ion diffusion; its high specific surface area provides a favorable environment for redox reactions; it can guide the uniform deposition of sodium ions, thereby inhibiting the growth of sodium dendrites; the porous structure and high specific surface area of ​​Ni-MOF enable it to store high-energy charges in a small volume, achieving dense cation jumping sites, minimizing the activation energy of ion transport, and thus improving ionic conductivity; Ni-MOF has abundant cavity structures that can serve as a host to accommodate various gases, and it can absorb gases generated by the battery, reducing gas production.

[0045] Aluminum-doped zinc oxide (AZO) is an environmentally friendly, transparent conductive material with good conductivity and low cost, offering high cost-effectiveness. Loading AZO onto Ni-MOF can improve the conductivity of the battery cell, promote ion transport, and give the cell better cycle performance and rate capability. Furthermore, AZO can withstand temperatures up to 1975℃, exhibiting strong high-temperature stability. Adding AZO can increase the melting point of the separator, giving it good thermal stability and low thermal shrinkage, preventing thermal runaway and improving its safety performance. AZO-modified separators can also improve electrolyte wettability, resulting in better compatibility and increased electrolyte absorption.

[0046] In some alternative embodiments, the membrane substrate includes, but is not limited to, PP membranes or PE membranes.

[0047] In some alternative embodiments, the mass percentage of Ni-MOF in the coating may be, for example, but not limited to, 92%, 94%, 96% or 98%, preferably 95%;

[0048] And / or, in Ni-MOF, the mass percentage of aluminum-doped zinc oxide can be, for example, but not limited to, 1%.

[0049] 8%, 9%, 10%, 11% or 12%, preferably 10%;

[0050] And / or, in aluminum-doped zinc oxide, the mass percentage of aluminum can be, for example, but not limited to, 1%, 2%, or 3%, preferably 2%.

[0051] In some optional embodiments, the preparation method of the Ni-MOF includes the following steps:

[0052] Ni-MOF was prepared by mixing nickel acetate tetrahydrate, aluminum-doped zinc oxide, L-malic acid and 4,4-bipyridine in a methanol solution and then heating the mixture in a reactor.

[0053] The reactants, by mass fraction, consist of 1-1.5 parts nickel acetate tetrahydrate, 0.1-0.3 parts aluminum-doped zinc oxide, 0.6-1 parts L-malic acid, and 0.3-0.4 parts 4,4-bipyridine.

[0054] The preparation method is simple and convenient, and the prepared Ni-MOF has an ordered porous structure and a high specific surface area.

[0055] In some alternative embodiments, the volume ratio of methanol to water in the methanol solution is 1:1.

[0056] In some alternative embodiments, the temperature of the heating reaction can be, for example, but not limited to, 140°C, 144°C, 148°C, 152°C, 156°C or 160°C, preferably 150°C;

[0057] The heating reaction time can be, for example, but not limited to, 25h, 27h, 29h, 31h, 33h or 35h, preferably 30h.

[0058] In some optional embodiments, the method for preparing aluminum-doped zinc oxide includes the following steps:

[0059] Zinc acetate dihydrate, sodium hydroxide, and aluminum nitrate were mixed in ethanol and then heated in a reaction vessel to prepare aluminum-doped zinc oxide.

[0060] The molar ratio of zinc acetate dihydrate, sodium hydroxide, and aluminum nitrate can be, for example, but is not limited to, 1:8:0.035, 1:10:0.02, or 1:12:0.015.

[0061] In some alternative embodiments, the temperature of the heating reaction can be, for example, but not limited to, 140°C, 144°C, 148°C, 152°C, 156°C or 160°C, preferably 150°C;

[0062] The heating reaction time can be, for example, but not limited to, 20h, 22h, 24h, 26h or 28h.

[0063] In some alternative embodiments, the adhesive includes, but is not limited to, polyvinylidene fluoride, or other adhesives well known to those skilled in the art.

[0064] In some alternative embodiments, the coating further includes a dispersant; the dispersant includes 1-methyl-2-pyridinyl ketone; the dispersant content is 1%-3% of the coating mass, and the dispersant helps to ensure uniform dispersion of the various components in the coating.

[0065] Secondly, the present invention provides a method for preparing a sodium-ion battery separator, comprising the following steps:

[0066] Ni-MOF and binder, along with an optional dispersant, are mixed, coated onto a separator substrate, and dried to prepare a sodium-ion battery separator.

[0067] The preparation method is simple and convenient, and the sodium-ion battery separator prepared has good electrical properties and excellent safety performance.

[0068] Thirdly, the present invention provides the application of the above-mentioned sodium-ion battery separator in the preparation of sodium-ion batteries.

[0069] The present invention will be further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0070] Example 1

[0071] A sodium-ion battery separator (Ni-MOF / AZO modified PP separator), the preparation process is as follows: Figure 1 As shown, the preparation method is as follows:

[0072] Step 1, Preparation of AZO (aluminum doping content of 2%):

[0073] 2.5 mmol of zinc acetate (Zn(Ac)₂·2H₂O), 25 mmol of sodium hydroxide (NaOH), and 0.05 mmol of aluminum nitrate (Al(NO₃)₃) were added to 75 mL of anhydrous ethanol and stirred until homogeneous. The mixture was then placed in a 200 mL polytetrafluoroethylene (PTFE) reactor and reacted at 150 °C for 24 hours. After the reactants cooled to room temperature, they were washed three times each with anhydrous ethanol and ultrapure water, and then dried at 80 °C for 24 hours to obtain aluminum-doped zinc oxide.

[0074] Step 2: Synthesis of Ni-MOF / AZO (10%):

[0075] 1.2 g Ni(CH3COO)2·4H2O, 0.2 g AZO, 0.8 g L-malic acid, and 0.37 g 4,4-bipyridine were dissolved in 20 mL of a mixed solvent (V water:V methanol = 1:1). The mixed solution was placed in a polytetrafluoroethylene reaction vessel and reacted at 150 °C for 30 hours. Then, the mixture was washed several times with methanol and dried at 60 °C for 24 hours to obtain the green solid product Ni-MOF / AZO.

[0076] Step 3: Preparation of Ni-MOF / AZO modified PP membrane:

[0077] 94% Ni-MOF / AZO and 4% PVDF were mixed evenly, and then 2% 1-methyl-2-pyridinyl ketone was added, followed by stirring. Subsequently, a layer of Ni-MOF / AZO (4 μm thick) was uniformly coated on a 12 μm PP base film, and then vacuum dried for 12 h to obtain a Ni-MOF / AZO modified PP membrane.

[0078] Example 2

[0079] A sodium-ion battery separator is prepared by the following method:

[0080] Step 1, Preparation of AZO (aluminum doping content 1%):

[0081] The preparation method is the same as in Example 1, except that the mass percentage of aluminum in the prepared AZO is 1%.

[0082] Step 2: Synthesis of Ni-MOF / AZO (8%):

[0083] The preparation method is the same as in Example 1, except that the mass percentage of AZO in the prepared Ni-MOF / AZO is 8%.

[0084] Step 3: Preparation of Ni-MOF / AZO modified PP membrane:

[0085] 92% Ni-MOF / AZO and 5% PVDF were mixed evenly, and then 3% 1-methyl-2-pyridinyl ketone was added, followed by stirring. Subsequently, a layer of Ni-MOF / AZO (4 μm thick) was uniformly coated on a 12 μm PP base film, and then vacuum dried for 12 h to obtain a Ni-MOF / AZO modified PP membrane.

[0086] Example 3

[0087] A sodium-ion battery separator is prepared by the following method:

[0088] Step 1, Preparation of AZO (aluminum doping content 3%):

[0089] The preparation method is the same as in Example 1, except that the mass percentage of aluminum in the prepared AZO is 3%.

[0090] Step 2: Synthesis of Ni-MOF / AZO (12%):

[0091] The preparation method is the same as in Example 1, except that the mass percentage of AZO in the prepared Ni-MOF / AZO is 12%.

[0092] Step 3: Preparation of Ni-MOF / AZO modified PP membrane:

[0093] 98% Ni-MOF / AZO and 1% PVDF were mixed evenly, and then 1% 1-methyl-2-pyridinyl ketone was added, followed by stirring. Subsequently, a layer of Ni-MOF / AZO (4 μm thick) was uniformly coated on a 12 μm PP base film, and then vacuum dried for 12 h to obtain a Ni-MOF / AZO modified PP membrane.

[0094] Comparative Example 1

[0095] A battery separator (PP separator) differs from Example 1 in that the battery separator is a PP separator and does not contain a coating.

[0096] Comparative Example 2

[0097] A battery separator (Ni-MOF modified PP separator) differs from Example 1 in that it does not contain AZO.

[0098] Comparative Example 3

[0099] A battery separator (Ni-MOF / ZnO modified PP separator) differs from Example 1 in that AZO is replaced with an equal amount of zinc oxide.

[0100] Comparative Example 4

[0101] A battery separator (Ni-MOF / CNTs modified PP separator) differs from Example 1 in that AZO is replaced with an equal amount of carbon nanotubes.

[0102] Test case

[0103] 1. Coin cells were prepared using the same method with PP base film and Ni-MOF / AZO modified PP separator (the positive electrode material of this battery is sodium iron sulfate (NFS), the negative electrode is hard carbon (Bestig YHC-1), and the electrolyte is (1M NaPF6 EC:PC:EMC = 2:3:5; 0.5% VC; 1.5% PS)). The charge-discharge curves of the batteries were then compared, with the voltage range being 0-2V. Figure 2 As shown, the specific capacity of the PP membrane modified with Ni-MOF / AZO is significantly higher than that of the PP base membrane, approximately 1.5 times that of the PP membrane.

[0104] 2. The melting point of the battery separators provided in Example 1 and Comparative Examples 1-4 was tested. The results are shown in Table 1. It was found that the melting point of the Ni-MOF / AZO modified PP separator was significantly increased, which can prevent the separator short circuit problem caused by the rise of cell temperature and improve cell safety.

[0105] Table 1. Melting points of PP membranes and Ni-MOF / AZO modified PP membranes.

[0106]

[0107]

[0108] 3. The poor high-temperature cycle performance of sodium-ion batteries is a problem that needs to be solved at present. Batteries (20 Ah, positive electrode material is sodium iron sulfate (NFS), negative electrode is hard carbon (Bestig YHC-1), electrolyte is (1M NaPF6 EC:PC:EMC = 2:3:5; 0.5% VC; 1.5% PS)) were prepared using the same method with the battery separators provided in Example 1 and Comparative Examples 1-4. The high-temperature cycle performance (45℃, 1C, -2.6~4.2V) of the batteries was tested, and the results are as follows: Figures 3-6 As shown in the figure. Trend of 1C / 1C capacity retention rate of PP membrane cells modified with PP membrane and Ni-MOF / AZO at high temperature cycling (1C / 1C). Figure 3 The results show that the Ni-MOF / AZO modified PP membrane has a good capacity retention rate. The capacity retention rate of the Ni-MOF / AZO modified PP membrane is 95.2% after 360cls of high-temperature cycling, while the capacity retention rate of the PP membrane is 86.5% after 183cls of cycling. This indicates that the performance of the Ni-MOF / AZO modified PP membrane is much better than that of the PP membrane.

[0109] High-temperature cycling 1C / 1C capacity retention trend of Ni-MOF modified PP separator and Ni-MOF / AZO modified PP separator cells ( Figure 4 The results show that the Ni-MOF / AZO modified PP membrane retains 95.2% of its capacity after 360 cls of high-temperature cycling, while the Ni-MOF modified PP membrane retains 84.4% of its capacity after 360 cls of cycling. This indicates that the Ni-MOF / AZO modified PP membrane performs better than the Ni-MOF modified PP membrane.

[0110] High-temperature cycling 1C / 1C capacity retention trend of PP separator cells modified with Ni-MOF / ZnO and Ni-MOF / AZO ( Figure 5 The results show that the capacity retention rate of the Ni-MOF / AZO modified PP membrane after 360cls of high-temperature cycling is 95.2%, while that of the Ni-MOF / ZnO modified PP membrane after 352cls of cycling is 91.3%, indicating that the performance of the AZO modified PP membrane is better than that of the ZnO modified PP membrane.

[0111] High-temperature cycling 1C / 1C capacity retention trend of PP separator cells modified with Ni-MOF / CNTs and Ni-MOF / AZO modified with PP separator ( Figure 6 The results show that the capacity retention rate of the Ni-MOF / AZO modified PP membrane after 360cls of high-temperature cycling is 95.2%, while the capacity retention rate of the Ni-MOF / CNTs modified PP membrane after 367cls of cycling is 88.7%, indicating that the performance of the Ni-MOF / CNTs modified PP membrane is not as good as that of the Ni-MOF / AZO modified PP membrane.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sodium-ion battery separator, characterized in that, Includes the membrane substrate and the coating applied to the membrane substrate; The coating is mainly composed of Ni-MOF and a binder; The Ni-MOF is supported on aluminum-doped zinc oxide.

2. The sodium-ion battery separator according to claim 1, characterized in that, The membrane substrate includes PP membrane or PE membrane.

3. The sodium-ion battery separator according to claim 1, characterized in that, In the coating, Ni-MOF accounts for 92%-98% of the mass; And / or, in Ni-MOF, the mass percentage of aluminum-doped zinc oxide is 8%-12%; And / or, in aluminum-doped zinc oxide, the mass percentage of aluminum is 1%-3%.

4. The sodium-ion battery separator according to claim 1, characterized in that, The preparation method of the Ni-MOF includes the following steps: Ni-MOF was prepared by mixing nickel acetate tetrahydrate, aluminum-doped zinc oxide, L-malic acid and 4,4-bipyridine in a methanol solution and then heating the mixture in a reactor. The reactants, by mass fraction, consist of 1-1.5 parts nickel acetate tetrahydrate, 0.1-0.3 parts aluminum-doped zinc oxide, 0.6-1 parts L-malic acid, and 0.3-0.4 parts 4,4-bipyridine.

5. The sodium-ion battery separator according to claim 4, characterized in that, The temperature of the heating reaction is 140-160℃; The heating reaction takes 25-35 hours.

6. The sodium-ion battery separator according to claim 1, characterized in that, The method for preparing aluminum-doped zinc oxide includes the following steps: Zinc acetate dihydrate, sodium hydroxide, and aluminum nitrate were mixed in ethanol and then heated in a reaction vessel to prepare aluminum-doped zinc oxide. The molar ratio of zinc acetate dihydrate, sodium hydroxide, and aluminum nitrate is 1:(8-12):(0.015-0.035).

7. The sodium-ion battery separator according to claim 6, characterized in that, The temperature of the heating reaction is 140-160℃; The heating reaction takes 20-28 hours.

8. The sodium-ion battery separator according to claim 1, characterized in that, The adhesive includes polyvinylidene fluoride; And / or, the coating further includes a dispersant; the dispersant includes 1-methyl-2-pyridinone; the content of the dispersant is 1%-3% of the coating mass.

9. A method for preparing the sodium-ion battery separator according to any one of claims 1-8, characterized in that, Includes the following steps: Ni-MOF and binder, along with an optional dispersant, are mixed, coated onto a separator substrate, and dried to prepare a sodium-ion battery separator.

10. The use of the sodium-ion battery separator according to any one of claims 1-8 in the preparation of sodium-ion batteries.

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