High-wettability sodium ion battery separator, preparation method therefor and use thereof

Abstract

A high-wettability sodium ion battery separator, a preparation method therefor and a use thereof. The sodium ion battery separator comprises a base material layer and a coating arranged on at least one surface of the base material layer. The coating comprises a filler and a polyamino acid additive; the base material layer serves as a carrier of the coating and can achieve the effects of supporting and isolating; the polyamino acid additive in the coating has rich amide bond structures, and has good amphipathicity, enabling the filler in the coating to be well dispersed; and the amphiphilic chain structure of the polyamino acid additive forms a skeleton structure in the coating, and the filler is filled and connected in the skeleton structure to form a stable coating structure. The separator prepared by coating with the coating has better electrolyte wettability, and can reduce the internal resistance of the battery, thereby improving the rate performance of the battery.

Description

Highly wettable sodium-ion battery separator, preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium-ion batteries, and more particularly to a highly wettable sodium-ion battery separator, a preparation method and application thereof. BACKGROUND

[0002] With the continuous development of energy storage technology, as one of the main means of energy storage, the performance of the battery directly affects the operation effect of the equipment. The performance of the battery is affected by many factors, and the internal resistance is one of the important indicators for measuring the performance of the battery. The size of the internal resistance directly affects the energy density and the charging and discharging efficiency of the battery. Therefore, reducing the internal resistance of the battery is one of the keys to improving the performance of the battery. How to reduce the internal resistance of the battery has become a technical problem to be solved.

[0003] SUMMARY

[0004] The present application mainly provides a highly wettable sodium-ion battery separator, a preparation method and application thereof, which can significantly reduce the internal resistance of the battery, thereby improving the rate performance of the battery.

[0005] According to a first aspect, the present application provides a highly wettable sodium-ion battery separator, comprising a substrate layer and a coating layer arranged on at least one surface of the substrate layer.

[0006] The coating layer comprises a filler and a polyamino acid additive.

[0007] In an optional embodiment, the polyamino acid additive comprises an amino acid polymer or an amino acid polymer salt composed of at least one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrolysine.

[0008] Optionally, the polyamino acid additive comprises at least one of polyaspartic acid, polyglutamic acid and polyornithine.

[0009] Optionally, the amino acid polymer salt comprises at least one of an amino acid polymer sodium salt and an amino acid polymer potassium salt.

[0010] Optionally, the polyamino acid additive comprises at least one of polyaspartic acid sodium and polyglutamic acid sodium.

[0011] In an optional embodiment, the molecular molar mass of the polyamino acid additive is 2000 g / mol-60000 g / mol according to the molar mass of the molecule.

[0012] In an optional embodiment, the substrate layer satisfies at least one of (1)-(3):

[0013] (1) the substrate layer is a polyolefin porous substrate;

[0014] (2) the thickness of the substrate layer is 5-30 μm;

[0015] (3) the porosity of the substrate layer is 30-60%.

[0016] In an optional embodiment, the substrate layer comprises one of a single-layer polyolefin porous substrate, a double-layer polyolefin porous substrate or a multi-layer polyolefin porous substrate.

[0017] In an optional embodiment, the filler comprises at least one of an inorganic filler or an organic filler.

[0018] In an optional embodiment, the inorganic filler comprises at least one of calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomite, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, aluminum oxide, boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide and titanium nitride;

[0019] The organic filler comprises at least one of polyvinylidene fluoride, polyethylene, polyethylene wax and polymethyl methacrylate.

[0020] In an optional embodiment, the coating satisfies at least one of (1)-(5):

[0021] (1) the content of the polyamino acid additive in the coating is 1-20% of the total weight of the coating;

[0022] (2) the content of the filler in the coating is 60-90% of the total weight of the coating;

[0023] (3) the coating further comprises nanocellulose;

[0024] (4) the coating further comprises a binder;

[0025] (5) the coating further comprises a dispersant;

[0026] Optionally, the amount of the nanocellulose is 5-15% of the total weight of the coating;

[0027] Optionally, the binder comprises at least one of polyacrylonitrile, acrylic resin, polyurethane and styrene butadiene rubber;

[0028] Optionally, the amount of the binder is 1-20% of the total weight of the coating;

[0029] Optionally, the dispersant comprises at least one of sodium carboxymethyl cellulose, sodium polyacrylate, ammonium polyacrylate, n-butanol and cyclohexanol.

[0030] Optionally, the dispersant is used in an amount of 0.1% to 5% of the total weight of the coating.

[0031] According to a second aspect, the application provides a method for preparing a high-wetting sodium ion battery separator, the separator being the separator described above, and the steps comprising:

[0032] The coating raw material is dispersed in deionized water and stirred uniformly to prepare a coating slurry;

[0033] The coating slurry is coated on at least one surface of the substrate layer, and the sodium ion battery separator is obtained after drying.

[0034] According to a third aspect, the application provides a sodium ion battery comprising the high-wetting sodium ion battery separator described above or prepared by the method described above.

[0035] The high-wetting sodium ion battery separator according to the above embodiment comprises a substrate layer and a coating layer arranged on at least one surface of the substrate layer; the coating layer comprises fillers and amino acid additives; the substrate layer serves as a carrier for the coating layer and can play a supporting and isolating role; the amino acid additives in the coating layer have abundant amide bond structures and good amphiphilicity, which can make the fillers in the coating layer disperse well, and the amphiphilic chain structure of the amino acid additives forms a skeleton structure in the coating layer, and the fillers are filled and connected to the skeleton structure to form a stable coating structure. The separator prepared by coating the coating layer has good electrolyte wetting property, which can reduce the internal resistance of the battery and thus improve the rate performance of the battery. DETAILED DESCRIPTION

[0036] The application will be further described in detail below with reference to the specific embodiments and the accompanying drawings. In different embodiments, similar elements are denoted by similar reference numerals. In the following embodiments, many details are described in order to make the application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different cases, or can be replaced by other elements, materials or methods. In some cases, some operations related to the application are not shown or described in the specification in order to avoid the core part of the application being overwhelmed by too much description, and it is not necessary to describe these related operations in detail for those skilled in the art based on the description in the specification and the general technical knowledge in the art.

[0037] In addition, features described in the specification, operations or characteristics can be combined in any appropriate manner to form various embodiments. Meanwhile, the steps or actions in the method description can also be sequentially changed or adjusted in a manner that can be apparent to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment, and do not mean that the sequence is necessary, unless otherwise stated that a certain sequence must be followed.

[0038] The serial numbers of components in the present application, such as "first", "second", etc., are only used to distinguish the described objects, and do not have any order or technical meaning. Unless otherwise specified, "connection" and "coupling" in the present application include direct and indirect connections (couplings).

[0039] The present application provides a high-wetting sodium ion battery separator, comprising a substrate layer and a coating layer arranged on at least one surface of the substrate layer; the coating layer comprises a filler and a polyamino acid additive.

[0040] The above-mentioned substrate layer serves as a carrier for the coating layer, which can play a supporting and isolating role. The above-mentioned coating layer is mainly composed of a filler and a polyamino acid additive. The polyamino acid additive has a rich amide bond structure and good amphiphilicity, which can make the filler in the coating layer disperse well. The amphiphilic chain structure of the polyamino acid additive forms a skeleton structure in the coating layer, and the filler is filled and connected in the skeleton structure to form a stable coating structure. The separator prepared by coating with the coating layer has better electrolyte wetting property, which can reduce the internal resistance of the battery, thereby improving the rate performance of the battery.

[0041] In an optional embodiment, the polyamino acid additive comprises an amino acid polymer, an amino acid polymer salt, or a copolymer formed by an amino acid polymer and other monomers.

[0042] In an optional embodiment, the polyamino acid additive comprises an amino acid polymer, and the amino acid polymer comprises a polymer or an amino acid polymer salt composed of at least one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine, or pyrrolysine.

[0043] In an optional embodiment, the amino acid polymer comprises at least one of polyaspartic acid, polyglutamic acid, or polyornithine.

[0044] In an alternative embodiment, the polyamino acid additive comprises an amino acid polymer salt, such as a polyamino acid sodium salt or a polyamino acid potassium salt. Alternatively, the polyamino acid additive comprises polyaspartic acid sodium or polyglutamic acid sodium. Amino acid polymer salts have better ionic conductivity in the coating than amino acid polymers.

[0045] In an alternative embodiment, the polyamino acid additive comprises a copolymer of an amino acid and another monomer. For example, the other monomer comprises ethylene glycol, forming a PEG-polyaspartic acid copolymer, a PEG-polyleucine copolymer, a PEG-polylysine copolymer, etc.

[0046] In an alternative embodiment, the polyamino acid additive has a molecular weight of 2000 g / mol to 60000 g / mol, according to the molar mass of the molecule.

[0047] In an alternative embodiment, the substrate layer is a polyolefin porous substrate; the polyolefin porous substrate comprises one or more copolymers or one or more blends selected from polyethylene, polypropylene, polybutylene, poly 4-methylpentene.

[0048] Further, the substrate layer comprises one of a single-layer polyolefin porous substrate, a double-layer polyolefin porous substrate, or a multi-layer polyolefin porous substrate.

[0049] In an alternative embodiment, the substrate layer has a thickness of 5 μm to 30 μm. Alternatively, the substrate layer has a thickness of 8 μm to 20 μm, such as a thickness of 8 μm, 9 μm, 10 μm, 15 μm, or 20 μm, or a range defined by any of the foregoing.

[0050] In an alternative embodiment, the substrate layer has a porosity of 30% to 60%. Alternatively, the substrate layer has a porosity of 40% to 60%, such as a porosity of 40%, 45%, 50%, 55%, or 60%, or a range defined by any of the foregoing. The higher the porosity of the porous substrate, the more conducive to the transport of conductive particles, such as sodium ions in a sodium ion battery, thereby reducing the internal resistance of the battery and improving the conductivity of the battery.

[0051] In an alternative embodiment, the filler comprises at least one of an inorganic filler or an organic filler.

[0052] In an alternative embodiment, the inorganic filler comprises at least one of calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomite, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, aluminum oxide, boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, and titanium nitride.

[0053] In optional embodiments, the organic filler includes at least one of polyvinylidene fluoride, polyethylene, polyethylene wax, and polymethyl methacrylate.

[0054] In optional embodiments, the content of the polyamino acid additive in the coating is 1-20% of the total weight of the coating. For example, the mass percentage of the amino acid additive is 1%, 2%, 3%, 5%, 9%, 10%, 12%, 15%, 17%, 19%, or 20%, or within a range consisting of any of the foregoing values.

[0055] In optional embodiments, the content of the filler in the coating is 60-90% of the total weight of the coating. For example, the mass percentage of the filler is 60%, 65%, 70%, 75%, 80%, 85%, or 90%, or within a range consisting of any of the foregoing values.

[0056] In optional embodiments, the coating further includes nanocellulose, and the amount of the nanocellulose is 5-15% of the total weight of the coating. For example, the mass percentage of the nanocellulose is 5%, 8%, 10%, 11%, 12%, 13%, 14%, or 15%, or within a range consisting of any of the foregoing values. The nanocellulose cooperates with the inorganic filler to improve the heat resistance of the prepared separator.

[0057] In optional embodiments, the coating further includes a binder to facilitate bonding of the materials to form a slurry that is convenient for coating. The amount of the binder is 1-20% of the total weight of the coating. For example, the mass percentage of the binder is 1%, 2%, 3%, 5%, 7%, 9%, 10%, 15%, or 20%, or within a range consisting of any of the foregoing values.

[0058] Optionally, the binder includes at least one of polyacrylonitrile, acrylic resin, polyurethane, and styrene butadiene rubber.

[0059] In optional embodiments, the coating further includes a dispersant to facilitate uniform dispersion of the materials when preparing the coating slurry, thereby improving the consistency of the performance of the separator. The amount of the dispersant is 0.1-5% of the total weight of the coating. The mass percentage of the dispersant is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, or 5%, or within a range consisting of any of the foregoing values.

[0060] Optionally, the dispersant includes at least one of sodium carboxymethyl cellulose, sodium polyacrylate, ammonium polyacrylate, n-butanol, and cyclohexanol.

[0061] The application also provides a preparation method of the high-wettability sodium ion battery separator.

[0062] The coating raw materials are dispersed in deionized water and stirred uniformly to prepare a coating slurry.

[0063] The coating slurry is coated on at least one surface of the substrate layer, and dried to obtain the separator.

[0064] The at least one surface of the substrate layer includes coating the coating slurry on any surface of the substrate layer and drying to obtain the separator, and also includes coating the coating slurry on both surfaces of the substrate layer and drying to obtain the high-wettability sodium ion battery separator. Preferably, coating is performed on both surfaces.

[0065] Specifically, the coating slurry is coated on the surface of the substrate by using a gravure roll. Optionally, the gravure roll is a double-sided gravure roll.

[0066] The application also provides a sodium ion battery comprising the high-wettability sodium ion battery separator or the high-wettability sodium ion battery separator prepared by the preparation method.

[0067] In order to illustrate the effects of the application, the following more specific embodiments are provided.

[0068] Embodiment One

[0069] The raw materials for preparing the coating slurry are prepared according to the proportions, wherein the raw materials include deionized water, Al2O3 as a filler, polyaspartic acid sodium salt as a polyamino acid additive, polyacrylate as a binder, and sodium carboxymethyl cellulose as a dispersant.

[0070] The mass ratio of the deionized water, Al2O3 (200 nm), polyaspartic acid sodium salt (2000 g / mol-11000 g / mol), binder polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:75:15:9.8:0.2. The above materials are uniformly mixed to prepare a coating slurry with a solid content of 50%.

[0071] The substrate layer is selected to be a PP microporous membrane with a thickness of 14 μm and a porosity of 48%.

[0072] The coating slurry is coated on both surfaces of the substrate layer by using a double-sided roll, and then dried to obtain the separator. The total thickness of the coating of the final separator is 4 μm.

[0073] Embodiment Two

[0074] The raw materials for preparing the coating slurry are prepared according to the proportion, wherein the raw materials include deionized water, Al2O3 as filler, nanocellulose, polyaspartic acid sodium salt as polyamino acid additive, polyacrylate as binder, and sodium carboxymethyl cellulose as dispersant.

[0075] The mass ratio of deionized water, nanocellulose, Al2O3 (200 nm), polyaspartic acid sodium salt (2000 g / mol-11000 g / mol), binder polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:10:75:5:9.8:0.2. The above materials are uniformly mixed to prepare a coating slurry with a solid content of 50%.

[0076] The size of the above nanocellulose is 10 nm×200 nm.

[0077] The substrate layer is selected as a PP microporous membrane with a thickness of 14 μm and a porosity of 48%.

[0078] The above coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating of the finally obtained separator is 4 μm.

[0079] Example Three

[0080] The raw materials for preparing the coating slurry are prepared according to the proportion, wherein the raw materials include deionized water, Al2O3 as filler, polyaspartic acid sodium salt as polyamino acid additive, polyacrylate as binder, and sodium carboxymethyl cellulose as dispersant.

[0081] The mass ratio of deionized water, Al2O3 (200 nm), polyaspartic acid (5000 g / mol-11000 g / mol), binder polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:75:15:9.8:0.2. The above materials are uniformly mixed to prepare a coating slurry with a solid content of 50%.

[0082] The substrate layer is selected as a PP microporous membrane with a thickness of 14 μm and a porosity of 48%.

[0083] The above coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating of the finally obtained separator is 4 μm.

[0084] Example Four

[0085] The raw materials for preparing the coating slurry are prepared according to the proportion, wherein the raw materials include deionized water, Al2O3 as filler, poly-D-glutamic acid sodium salt as polyamino acid additive, polyacrylate as binder, and sodium carboxymethyl cellulose as dispersant.

[0086] The mass ratio of deionized water, AI2O3 (200 nm), poly-D-glutamic acid sodium salt (15000 g / mol-50000 g / mol), adhesive polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:75:15:9.8:0.2. The above materials are mixed uniformly to prepare a coating slurry with a solid content of 50%.

[0087] The substrate layer is selected from a PP microporous membrane with a thickness of 14 μm and a porosity of 48%.

[0088] The above coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating of the obtained separator is 4 μm.

[0089] Example Five

[0090] The raw materials for preparing the coating slurry are prepared according to the ratio, wherein the raw materials include deionized water, AI2O3 as a filler, polyaspartic acid sodium salt as a polyamino acid additive, polyacrylate as an adhesive, and sodium carboxymethyl cellulose as a dispersant.

[0091] The mass ratio of deionized water, AI2O3 (200 nm), polyaspartic acid sodium salt (2000 g / mol-11000 g / mol), adhesive polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:60:20:15.8:4.2. The above materials are mixed uniformly to prepare a coating slurry with a solid content of 50%.

[0092] The substrate layer is selected from a PP microporous membrane with a thickness of 14 μm and a porosity of 48%.

[0093] The above coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating of the obtained separator is 4 μm.

[0094] Example Six

[0095] The raw materials for preparing the coating slurry are prepared according to the ratio, wherein the raw materials include deionized water, AI2O3 as a filler, polyaspartic acid sodium salt as a polyamino acid additive, polyacrylate as an adhesive, and sodium carboxymethyl cellulose as a dispersant.

[0096] The mass ratio of deionized water, AI2O3 (200 nm), polyaspartic acid sodium salt (2000 g / mol-11000 g / mol), adhesive polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:90:1:8.8:0.2. The above materials are mixed uniformly to prepare a coating slurry with a solid content of 50%.

[0097] The substrate layer is selected from a PP microporous membrane having a thickness of 14 μm and a porosity of 48%.

[0098] The coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating layer of the finally obtained separator is 4 μm.

[0099] Example Seven

[0100] The raw materials for preparing the coating slurry are prepared according to the proportions, wherein the raw materials include deionized water, AI2O3 as a filler, polyaspartic acid sodium salt as a polyamino acid additive, polyacrylate as a binder, and sodium carboxymethyl cellulose as a dispersant.

[0101] The mass ratio of the deionized water, AI2O3 (200 nm), polyaspartic acid sodium salt, binder polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:55:35:9.8:0.2. The above materials are uniformly mixed to prepare a coating slurry having a solid content of 50%.

[0102] The substrate layer is selected from a PP microporous membrane having a thickness of 14 μm and a porosity of 48%.

[0103] The coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating layer of the finally obtained separator is 4 μm.

[0104] Comparative Example One

[0105] The raw materials for preparing the coating slurry are prepared according to the proportions, wherein the raw materials include deionized water, AI2O3 as a filler, polyaspartic acid sodium salt as a polyamino acid additive, polyacrylate as a binder, and sodium carboxymethyl cellulose as a dispersant.

[0106] The mass ratio of the deionized water, AI2O3 (200 nm), polyaspartic acid sodium salt, binder polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:55:35:9.8:0.2. The above materials are uniformly mixed to prepare a coating slurry having a solid content of 50%.

[0107] The substrate layer is selected from a PP microporous membrane having a thickness of 14 μm and a porosity of 48%.

[0108] The coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating layer of the finally obtained separator is 4 μm.

[0109] Comparative Example Two

[0110] The raw materials for preparing the coating slurry are prepared according to the proportion, wherein the raw materials include deionized water, Al2O3 as filler, polyacrylic acid sodium salt as additive, polyacrylate as binder, and sodium carboxymethyl cellulose as dispersant.

[0111] The mass ratio of deionized water, Al2O3 (200 nm), polyacrylic acid sodium salt (2000 g / mol-6000 g / mol), binder polyacrylate, and dispersant sodium carboxymethyl cellulose is 100:90:1:8.8:0.2, and the above materials are uniformly mixed to prepare a coating slurry with a solid content of 50%.

[0112] The substrate layer is selected as a PP microporous membrane with a thickness of 14 μm and a porosity of 48%.

[0113] The above coating slurry is coated on both surfaces of the substrate layer using a double-sided roller, and then dried to obtain a separator. The total thickness of the coating of the finally obtained separator is 4 μm.

[0114] The performance of the separators prepared in Examples 1 to 7 and Comparative Examples 1 and 2 is tested, and the comparison is evaluated from three dimensions of liquid climbing length, ion conductivity, and contact angle.

[0115] The ion conductivity test is performed using inert stainless steel electrodes to make a symmetric cell. As the number of separator layers increases, the cell resistance also increases linearly, and the corresponding slope is the resistance of the separator. The ion conductivity of the separator is calculated by the following formula (1): σS=d / (RS×A×10) (1)

[0116] Wherein, σS is the ion conductivity of the separator, unit: mS / cm; d is the thickness of the separator, unit: μm, measured by a thickness gauge; RS is the resistance of the separator, unit: Ω; A is the effective area of the separator in the symmetric cell, taking the value of 6 cm 2 ; 10 is the dimension conversion ratio.

[0117] The liquid climbing length test is performed by configuring a test electrolyte: dissolving sodium hexafluorophosphate (NaPF6) in a non-aqueous organic solvent of ethylene carbonate EC: dimethyl carbonate DMC: fluoroethylene carbonate FEC = 47.5:47.5:5 (volume ratio) to prepare an electrolyte with a NaPF6 concentration of 1 mol / L. Take three 0.5*10 cm sample separators, drop the test electrolyte in the middle of the sample separator, and measure the moving distance of the electrolyte in the length direction of the separator after 20 s.

[0118] The specific test results are shown in Table 1 below.

[0119] Table 1

[0120] From the data in Table 1, it can be seen that the performance of the separator prepared in Examples 1 to 7 is obviously better than that of the separators prepared in Comparative Example 1 and Comparative Example 2. The wicking length in Examples 1 to 6 is more than 20 mm, and the wicking length in Example 7 is 18 mm, which is obviously better than the wicking length of 6 mm in Comparative Example 1 and the wicking length of 12 mm in Comparative Example 2. The ionic conductivity in Examples 1 to 6 is greater than that in Comparative Example 1 and Comparative Example 2, so it can be seen that the addition of the polyamino acid additive can obviously increase the wettability and ionic conductivity, so as to improve the rate performance of the battery.

[0121] From the comparison of Example 1, Example 4 and Example 3, it can be seen that the amino acid polymer salt has better ion conductivity when used in the coating compared with the amino acid polymer.

[0122] From the comparison of Example 6 and Comparative Example 2, it can be seen that the use of the polyamino acid additive increases the wicking length of the prepared separator and obviously reduces the contact angle, so as to obviously improve the wettability of the separator, and the ionic conductivity is increased, so as to improve the ion conductivity of the separator.

[0123] From the comparison of Examples 1 to 6 and Example 7, it can be seen that the content of the polyamino acid additive in the coating will affect the wettability of the separator. Controlling the mass content of the polyamino acid additive in the coating to be 1% to 20% can obtain a high-wettability separator with excellent performance. Increasing the mass content of the polyamino acid additive will improve the amphiphilicity of the separator, and then increase the wicking performance of the separator and reduce the contact angle, so as to improve the wettability of the separator.

[0124] Although the principles herein have been illustrated in various embodiments, many modifications of structure, arrangement, proportion, elements, materials, and components specifically adapted to particular environments and operating requirements can be used without departing from the principles and scope of the present disclosure. The above modifications and other changes or modifications will be included within the scope of the present disclosure.

[0125] The foregoing detailed description has been presented for purposes of illustration and description. However, various modifications and changes are possible in the implementation of the disclosure. Accordingly, the disclosure is intended to embrace all modifications and alterations within the scope and spirit of the disclosure. Thus, the scope of the disclosure is not intended to be limited to the particular form set forth herein, but includes all features that might be provided within the scope and spirit of the disclosure. Likewise, the benefits and advantages of the various embodiments, other advantages, and solutions to problems have been presented in the foregoing detailed description. However, the scope of the disclosure should not be limited by the recitation of these benefits and advantages, since the application can be practiced without these benefits and advantages, or other benefits and advantages can be realized. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The use of the terms "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Furthermore, the use of the term "coupled" and variations thereof herein is meant to encompass a direct connection between two elements, an indirect connection between two elements through one or more intermediaries, and / or a functional connection between two elements wherein one or more intermediaries are not present.

[0126] Those skilled in the art will recognize that many modifications can be made to the details of the above-described embodiments without departing from the underlying principles of the present application. The scope of the present application should, therefore, be determined only by the following claims.

Claims

1. A high wettability sodium-ion battery separator, characterized in that, The coating layer is coated on at least one surface of the substrate layer. The coating layer contains a filler and a polyamino acid additive.

2. The high wettability sodium-ion battery separator of claim 1, wherein, The polyamino acid additive includes an amino acid polymer or an amino acid polymer salt composed of at least one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine, and pyrrolysine. Optionally, the polyamino acid additive includes at least one of polyaspartic acid, polyglutamic acid, and polyornithine. Optionally, the amino acid polymer salt includes at least one of an amino acid polymer sodium salt and an amino acid polymer potassium salt. Optionally, the polyamino acid additive includes at least one of polyaspartic acid sodium and polyglutamic acid sodium.

3. The high wettability sodium-ion battery separator of claim 1, wherein, The polyamino acid additive has a molecular molar mass of 2000 g / mol-60000 g / mol.

4. The high wettability sodium-ion battery separator of claim 1, wherein, The substrate layer satisfies at least one of (1)-(3): (1) The substrate layer is a polyolefin porous substrate. (2) The thickness of the substrate layer is 5 μm-30 μm. (3) The porosity of the substrate layer is 30%-60%.

5. The high wettability sodium-ion battery separator of claim 4, wherein, The substrate layer includes one of a single-layer polyolefin porous substrate, a double-layer polyolefin porous substrate, or a multi-layer polyolefin porous substrate.

6. The high wettability sodium-ion battery separator of claim 1, wherein, The filler includes at least one of an inorganic filler or an organic filler.

7. The high wettability sodium-ion battery separator of claim 6, wherein, The inorganic filler includes at least one of calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomite, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, aluminum oxide, boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, and titanium nitride. The organic filler includes at least one of polyvinylidene fluoride, polyethylene, polyethylene wax, and polymethyl methacrylate.

8. The high wettability sodium-ion battery separator of claim 1, wherein, The coating layer satisfies at least one of (1)-(5): (1) The content of the polyamino acid additive in the coating layer is 1%-20% of the total weight of the coating layer. (2) The content of the filler in the coating layer is 60%-90% of the total weight of the coating layer. (3) The coating layer further contains nanocellulose. (4) The coating layer further contains a binder. (5) The coating layer further contains a dispersant. Optionally, the nanocellulose is used in an amount of 5%-15% of the total weight of the coating layer. Optionally, the binder includes at least one of polyacrylonitrile, an acrylic resin, polyurethane, and styrene butadiene rubber. Optionally, the binder is used in an amount of 1%-20% of the total weight of the coating layer. Optionally, the dispersant includes at least one of sodium carboxymethyl cellulose, sodium polyacrylate, ammonium polyacrylate, n-butanol, and cyclohexanol. Optionally, the dispersant is used in an amount of 0.1%-5% of the total weight of the coating layer.

9. A method of making a high wettability sodium-ion battery separator, characterized in that, The separator is the separator according to any one of claims 1-8, and the steps include: dispersing coating layer raw materials in deionized water to uniformly stir and prepare a coating layer slurry; coating the coating layer slurry on at least one surface of the substrate layer, and drying to obtain the sodium ion battery separator.

10. A sodium-ion battery, characterized in that, A high wettability sodium-ion battery separator comprising or prepared by the method of any one of claims 1-8 or 9.

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