A battery separator and method of making the same

Abstract

The application discloses a battery separator, which comprises a base film, at least one layer of the base film is coated with a functional coating, raw materials of the functional coating comprise inorganic solid electrolyte and acrylate multi-copolymer, the mass ratio of the inorganic solid electrolyte to the acrylate multi-copolymer is (20 parts-30 parts):(10 parts-40 parts), and the acrylate multi-copolymer has a structure of chemical formula (I): wherein n and m are selected from integers not less than 1; R is selected from one or more of C2-C4 alkyl having a pyridine ring. The separator of the application is beneficial to improving the heat resistance of the separator, thereby improving the safety performance of the battery. The separator of the application is beneficial to improving the ionic conductivity of the battery, thereby being beneficial to improving the cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery separators, and more specifically to a battery separator and its preparation method. Background Technology

[0002] Lithium-ion batteries have high energy density and high output power, can be repeatedly charged and discharged, and have no memory effect. They have become an ideal portable energy storage device and power source in people's lives.

[0003] In existing lithium battery technologies, the battery separator isolates the positive and negative electrodes, reducing internal short circuits caused by contact between them and thus improving battery safety. Current technologies often use ceramic particles for coating, which, while improving the separator's thermal shrinkage to some extent, still presents several problems. First, the ceramic coating is prone to detachment during battery cycling due to electrode expansion, exhibiting low volumetric shrinkage. Second, it ages easily after prolonged charge-discharge cycles, impacting battery safety. Third, the ceramic particle coating often hinders lithium-ion transport within the separator, causing the lithium-ion diffusion rate at the separator to mismatch with the electrochemical reaction rate within the battery, leading to polarization and negatively affecting electrical performance. Summary of the Invention

[0004] This invention addresses the problems in the prior art by disclosing a battery separator and its preparation method. The battery separator of this invention has good heat insulation performance, as well as good lithium-ion conductivity and adhesion between electrodes, thereby helping to reduce electrode polarization caused by lithium-ion transport obstruction. The battery separator of this invention is beneficial to improving the electrical performance and safety performance of the battery.

[0005] This invention is achieved through the following technical solution:

[0006] This invention provides a battery separator, the separator comprising a base membrane, at least one layer of the base membrane being coated with a functional coating, the raw materials of the functional coating comprising an inorganic solid electrolyte and an acrylate multi-component copolymer, wherein, by mass, the ratio of the inorganic solid electrolyte to the acrylate multi-component copolymer is (20-30 parts):(10-40 parts), and the acrylate multi-component copolymer has a structure of chemical formula (Ⅰ):

[0007]

[0008] Wherein, n and m are selected from integers not less than 1; R is selected from one or more C2-C4 alkyl groups having a pyridine ring.

[0009] In the above design of this invention, the pyridine ring in the acrylate multi-element copolymer is a planar ring with a closed conjugated system within the molecule. Since the electronegativity of the nitrogen atom is greater than that of the carbon atom, the pyridine ring is a typical electron-donating group. The pyridine ring and carboxyl group are interleaved, which is beneficial to the structural stability of the acrylate multi-element copolymer. During battery cycling, the π electrons in the aromatic ring can move around the benzene ring under the combined action of the pyridine ring and the benzene ring, thereby promoting ion migration in the separator and improving the ionic conductivity of the separator. Adding an inorganic solid electrolyte to the separator of this invention has two advantages: firstly, the inorganic solid electrolyte has good heat resistance, which can improve the thermal stability of the separator; secondly, the combination of the inorganic solid electrolyte and the acrylate multi-element copolymer in the separator can form a functional membrane in the battery separator with functions and ionic conductivity very similar to the SEI membrane. This functional membrane can promote the ionic conductivity of the separator and facilitate the construction of a bridge for ion transport between the separator and the electrolyte, thereby improving the electrical performance and safety performance of the battery.

[0010] As a further embodiment, the raw materials for the functional coating also include dispersant A, dispersant B, binder, and wetting agent. By mass, the ratio of inorganic solid electrolyte: acrylate multi-component copolymer: dispersant A: dispersant B: binder: wetting agent is (20-30 parts): (10-40 parts): (0.3-0.8 parts): (0.5-1.2 parts): (3-4 parts): (0.3-0.9 parts). Adding dispersant A and dispersant B to the functional coating improves the dispersibility between substances in the slurry, thus facilitating the obtaining of a uniformly dispersed slurry. The binder improves the adhesion between particles in the slurry, as well as the adhesion between the functional coating and the base film and the positive and negative electrodes. The wetting agent enhances the wettability of the inorganic solid electrolyte in the slurry.

[0011] As a further embodiment, the raw material for the functional coating also includes a solution, wherein the solution accounts for 47%-69% of the raw material by mass. The solution in this invention is not limited to deionized water or pure water, but can also be an organic solvent.

[0012] As a further embodiment, the inorganic solid electrolyte includes one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum titanium oxide (LLTO), and lithium titanium aluminum phosphate (LATP).

[0013] As a further embodiment, the inorganic solid electrolyte particles have a D50 particle size of 0.2 μm-1.8 μm and a D100 particle size of 1.7 μm-3.5 μm. The significant difference in particle size among the inorganic solid electrolyte particles is beneficial for constructing ion transport channels.

[0014] As a further embodiment, the inorganic solid electrolyte particles have a D50 particle size of 0.2 μm-1.5 μm and a D100 particle size of 2 μm-3.5 μm. The differences in the inorganic solid electrolyte particles within this range are more conducive to constructing suitable ion transport channels.

[0015] As a further embodiment, the dispersant A comprises one or more of sodium phosphate, citrate, alkylbenzene sulfonate, and ammonium salt. Alkylbenzene sulfonate has good solubility, is relatively non-volatile, and has a stable structure; alkylbenzene sulfonate adsorbs on the surface of the inorganic solid electrolyte and disperses the inorganic solid electrolyte in the slurry through steric hindrance.

[0016] As a further embodiment, the sodium phosphate salt includes one or more of sodium hexametaphosphate and sodium tripolyphosphate.

[0017] As a further embodiment, the citrate includes sodium citrate.

[0018] As a further embodiment, the alkylbenzene sulfonate includes sodium dodecylbenzene sulfonate.

[0019] As a further embodiment, the ammonium salt includes ammonium polyacrylate.

[0020] As a further embodiment, the dispersant B comprises one or more of the following: fatty acid ethylene oxide adducts, polyethylene glycol-type polyols, polyethyleneimine derivatives, aryl ether sulfonates, polyoxyethylene ethers, modified polyether polymers, and polyacrylates. The pyridine ring in the acrylate copolymer exhibits an electron-donating effect, and the sulfonate group in the aryl ether sulfonate reduces the electron cloud density on the benzene ring, enhancing the electron-withdrawing effect of the sulfonate group. This allows for better coordination with the acrylate copolymer, thereby facilitating its dispersion in the slurry.

[0021] As a further embodiment, the aryl ether sulfonate includes sodium polyethylene glycol alkyl aryl ether sulfonate.

[0022] As a further embodiment, the polyoxyethylene ether includes one or more of polyoxyethylene alkylphenol ether and alkylphenol polyoxyethylene ether.

[0023] As a further embodiment, the polyacrylate includes sodium polyacrylate.

[0024] As a further embodiment, the binder includes one or more of the following: carboxymethylated cellulose derivative binders, polyester binders, rubber binders, polysaccharide binders, polyol binders, amino ester binders, and nitrile binders. Polysaccharide binders are substances with multiple hydroxyl and carboxyl groups, possessing strong electron-withdrawing capabilities, which is beneficial for the dispersion of acrylate copolymers and inorganic solid electrolytes in the adhesive slurry, thereby improving the adhesion of the functional coating.

[0025] As a further embodiment, the carboxymethylated derivative binder includes sodium carboxymethyl cellulose.

[0026] As a further embodiment, the polyester adhesive includes one or more of polyacrylate and polymethyl acrylate.

[0027] As a further option, the rubber-based adhesive includes styrene-butadiene rubber.

[0028] As a further option, the polyol adhesive includes polyvinyl alcohol.

[0029] As a further option, the amino ester adhesive includes polyurethane.

[0030] As a further embodiment, the polysaccharide binder includes one or more of xanthan gum and sodium alginate.

[0031] As a further embodiment, the nitrile adhesive includes polyacrylonitrile.

[0032] As a further embodiment, the wetting agent includes one or more of the following: polyester wetting agents, ether wetting agents, monohydroxy alcohol wetting agents, polyhydroxy alcohol wetting agents, alkyl sulfate wetting agents, sulfone wetting agents, and sulfonate wetting agents. In polyhydroxy alcohol wetting agents, the polyhydroxy structure can be more easily adsorbed onto the surface of the inorganic solid electrolyte, thereby improving the wettability of the inorganic solid electrolyte.

[0033] As a further option, the polyester wetting agent includes methyl acrylate.

[0034] As a further option, the ether wetting agent includes dodecylphenol polyoxyethylene ether.

[0035] As a further option, the monohydroxy alcohol wetting agent includes ethanol.

[0036] As a further embodiment, the polyhydroxy alcohol wetting agent includes one or more of propylene glycol and glycerin.

[0037] As a further embodiment, the sulfone-based wetting agent includes dimethyl sulfoxide.

[0038] As a further embodiment, the raw materials for the functional coating include an inorganic solid electrolyte with a particle size of 0.2μm-1.5μm for D50 and 2μm-3.5μm for D100, an acrylate multi-component copolymer, an alkylbenzene sulfonate, an aryl ether sulfonate, a polysaccharide binder, and a polyhydroxy alcohol wetting agent. By mass, the ratio of the inorganic solid electrolyte with a particle size of 0.2μm-1.5μm for D50 to 2μm-3.5μm for D100 to the acrylate multi-component copolymer is (20-30 parts):(10-40 parts):(0.3-0.8 parts):(0.5-1.2 parts):(3-4 parts):(0.3-0.9 parts), where R in the acrylate multi-component copolymer is a C2-C4 alkyl group having a pyridine ring. Building upon the above, we further discovered that polysaccharide binders and polyhydroxy alcohol wetting agents possess similar substituent groups, which facilitates uniform mixing of the two substances in the slurry, thus exerting a synergistic effect. Alkylbenzene sulfonates and aryl ether sulfonates also have similar structures and can play a synergistic role in the slurry, thereby promoting the dispersibility of the inorganic solid electrolyte and acrylate copolymer in the slurry, which is beneficial for obtaining a uniformly dispersed slurry. This, in turn, contributes to obtaining a membrane with uniform thermal insulation and the formation of a uniform functional membrane. Alkylbenzene sulfonates, aryl ether sulfonates, polysaccharide binders, and polyhydroxy alcohol wetting agents all possess electron-withdrawing groups and can effectively cooperate with acrylate copolymers.

[0039] As a further embodiment, the raw materials for the functional coating include lithium lanthanum zirconium oxide compound with a particle size of 0.2μm-1.5μm for D50 and 2μm-3.5μm for D100, acrylate multi-component copolymer, sodium dodecylbenzene sulfonate, polyethylene glycol alkyl aryl ether sulfonate, xanthan gum, and glycerin. By mass, the ratio of the lithium lanthanum zirconium oxide compound with a particle size of 0.2μm-1.5μm for D50, to the acrylate multi-component copolymer with a particle size of 2μm-3.5μm for D100 is (20-30 parts):(10-40 parts):(0.3-0.8 parts):(0.5-1.2 parts):(3-4 parts):(0.3-0.9 parts), where R in the acrylate multi-component copolymer is a C4 alkyl group having a pyridine ring. Building upon the above, we further discovered that lithium lanthanum zirconium oxide compounds exhibit good thermal stability, while sodium dodecylbenzene sulfonate demonstrates superior flexibility, allowing for better adsorption onto the lithium lanthanum zirconium oxide compounds. Furthermore, its longer alkyl chain provides better steric hindrance, promoting uniform dispersion of the lithium lanthanum zirconium oxide compounds. Xanthan gum possesses unique rheological properties and exhibits good stability against heat and acids / alkalis, improving the texture of the slurry and thus enhancing coating uniformity. The three hydroxyl groups in glycerol reduce the probability of intermolecular hydrogen bonding due to excessive hydroxyl groups, promoting the wettability of the inorganic solid electrolyte. The addition of hydroxyl groups to sodium polyethylene glycol alkyl aryl ether sulfonate further improves the solubility of the dispersant in the slurry and enhances its compatibility with xanthan gum and glycerol, thereby contributing to the stability of the various components in the slurry.

[0040] As a further option, the base film includes one of PP base film and PE base film.

[0041] As a further improvement, the thickness of the base film is 9μm-12μm.

[0042] As a further option, the thickness of the functional coating is 2μm-5μm.

[0043] The present invention also provides a method for preparing the diaphragm, the method comprising:

[0044] S1: Weigh out the inorganic solid electrolyte, dispersant A, wetting agent, and solution according to the mass ratio, and stir and disperse them.

[0045] S2: Add acrylate copolymer and dispersant B to S1 according to the mass ratio, and stir to disperse evenly;

[0046] S3: Mix S1 and S2 evenly, add binder, stir evenly, and obtain the slurry of functional coating;

[0047] S4: Coat the slurry onto at least one side of the base membrane and dry it under vacuum to obtain a diaphragm.

[0048] In the method of this invention, the inorganic solid electrolyte has poor wettability, which leads to poor particle dispersibility in the solution. The acrylate copolymer has a large molecular weight, therefore, the inorganic solid electrolyte and the acrylate copolymer are added separately. To improve the wettability and dispersibility of the inorganic solid electrolyte, dispersant A and a wetting agent are added in step S1 to promote its wettability and dispersion, resulting in a uniform slurry. Adding dispersant B in step S2 further promotes the dispersion of the acrylate copolymer. The two uniformly dispersed slurries are then bonded together using a binder to improve the adhesion of the functional coating.

[0049] As a further embodiment, in step S1, the stirring and dispersion time is 30-40 minutes, and the stirring and dispersion speed is 2000-3000 r / min; in step S2, the stirring and dispersion time is 30-90 minutes, and the stirring and dispersion speed is 500-2000 r / min; in step S3, the stirring and homogenization time is 20-30 minutes, and the stirring and homogenization speed is 500-800 r / min; in step S4, the vacuum drying temperature is 60℃-130℃, and the vacuum drying time is 5-40 minutes.

[0050] In this invention, the optimal coating method is rotary spraying, with a coating speed of 40m / min-100m / min. This promotes uniformity of the slurry coating.

[0051] The features and beneficial effects of this invention are as follows:

[0052] (1) The separator of the present invention is beneficial to improving the heat resistance of the separator, thereby improving the safety performance of the battery.

[0053] (2) The separator of the present invention is beneficial to improving the ionic conductivity of the battery, thereby improving the cycle performance of the battery.

[0054] (3) The separator of the present invention is not limited to lithium-ion batteries, but can also be used in sodium batteries and potassium batteries.

[0055] (4) The solution in the slurry of the functional coating of the diaphragm of the present invention can be an aqueous solution, which helps to reduce production costs. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 The preparation method provided in Example 1 of the present invention. Detailed Implementation

[0058] To facilitate understanding of the battery separator and its preparation method according to the present invention, the separator of the present invention will be described more comprehensively below, and embodiments of the present invention will be given, but this does not limit the scope of the present invention.

[0059] In the embodiments of this invention, the base film is coated with PE base film.

[0060] The preparation method of the diaphragm of the present invention will be described using the preparation process of Example 1 as an example:

[0061] Example 1:

[0062] S1: Weigh out lithium lanthanum zirconium oxide compound (particle D50 with a particle size of 0.2μm-1.5μm) and sodium dodecylbenzenesulfonate (particle D100 with a particle size of 2μm-3.5μm) according to the mass ratio, and stir and disperse them for 30min-40min. The stirring and dispersion speed is 2000r / min-3000r / min.

[0063] S2: Add acrylate multi-polymer, R being a C4 alkyl group with a pyridine ring, and sodium polyethylene glycol alkyl aryl ether sulfonate to S1 according to the mass ratio, stir and disperse evenly for 30 min-90 min, and the stirring speed is 500 r / min-2000 r / min.

[0064] S3: Mix S1 and S2 evenly, add xanthan gum, stir evenly to obtain the slurry of the functional coating. The stirring time is 20min-30min, and the stirring speed is 500r / min-800r / min.

[0065] S4: Coat the slurry onto at least one side of the base membrane, and vacuum dry to obtain a diaphragm. The vacuum drying temperature is 60℃-130℃, and the vacuum drying time is 5min-40min.

[0066] The method for obtaining the C4 alkyl acrylate multi-component copolymer with a pyridine ring in Example 1 is as follows: Figure 1 As shown.

[0067] The composition, by mass, of the lithium lanthanum zirconium oxide compound: acrylate multi-component copolymer: sodium dodecylbenzenesulfonate: sodium polyethylene glycol alkyl aryl ether sulfonate: xanthan gum: glycerol, consisting of lithium lanthanum zirconium oxide compound (D50 particle size 0.2μm-1.5μm) : sodium acrylate alkyl ether sulfonate (D100 particle size 2μm-3.5μm) in the following ratio: (20-30 parts): (10-40 parts): (0.3-0.8 parts): (0.5-1.2 parts): (3-4 parts): (0.3-0.9 parts), comprises 47%-69% of the raw materials in the slurry.

[0068] The optimal coating method is rotary spraying at a speed of 40-100 m / min. The obtained separator is then hot-pressed with the battery electrode to bond them together. The hot-pressing temperature is 80-100℃, and the pressing time is 60-100 seconds.

[0069] We will also use the prepared battery separator in the battery. The battery preparation process includes:

[0070] We will also obtain the battery separator for testing, including adhesion, etc. The battery separator of this invention was used in a battery, and electrical performance tests were also conducted. The testing process included:

[0071] (1) Battery preparation: The positive electrode is a ternary material (nickel-cobalt-manganese), the negative electrode is graphite, and the electrolyte is a standard electrolyte with EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) = 1:1:1 and lithium hexafluorophosphate concentration of 1 mol / L.

[0072] (2) Adhesion test: The 180-degree peel test was used.

[0073] Validation Result Analysis

[0074] Table 1. Embodiments and Comparative Examples of the Invention

[0075]

[0076] Table 2. Amounts of each substance added in the embodiments of the present invention

[0077]

[0078] Table 3 Test results of embodiments and comparative examples of the present invention

[0079] — Capacity retention rate (%) Peel strength (N / m) Hot-press bonding strength (N / m) Example 1 98.05 92 15 Example 2 97.8 82 12 Example 3 97.79 90 11 Example 4 97.78 83 14 Example 5 97.77 85 12 Example 6 97.66 85 11 Example 7 97.65 89 10 Comparative Example 1 75 40 5 Comparative Example 2 65 55 4

[0080] We successfully obtained battery separators according to the formulations of the embodiments in Tables 1-2 and the method of the present invention. We conducted a series of tests on the obtained battery separators, and the test results are shown in Table 3. We can see that the performance (adhesion, etc.) of the separators in Examples 1-15 of the present invention and the electrical performance of the batteries are superior to those in Comparative Examples 1-2. We believe that the inorganic solid electrolyte in the functional coating material on the separator base film of the present invention has thermal stability, which can improve the thermal stability of the separator during battery cycling and reduce the decrease in adhesion caused by heat. The slurry also includes an acrylate multi-electrode copolymer. The π electrons in the benzene and pyridine rings of the acrylate multi-electrode copolymer can move around the benzene ring, promoting ion migration in the separator and thus improving the separator's ion migration capability. The pyridine ring is a planar ring with a closed conjugated system within the molecule. Since the electronegativity of the nitrogen atom is greater than that of the carbon atom, the pyridine ring is a typical electron-donating group. The ester groups in the acrylate multi-electrode copolymer have electron-withdrawing capabilities. The interaction between the pyridine ring and the ester groups is beneficial to the structural stability of the acrylate multi-electrode copolymer, thus better synergizing with the inorganic solid electrolyte. During battery formation, a functional membrane with functions and ionic conductivity very similar to the SEI membrane is formed on the surface of the separator. On the one hand, the functional membrane can improve the ion conductivity of the battery separator; on the other hand, the functional membrane can act as a bridge for ion transport between the battery separator and the electrolyte. Therefore, the slurry for obtaining the battery separator of this invention can improve the battery's safety performance and electrical performance.

[0081] First, we investigated inorganic solid-state electrolytes. Our selection of inorganic solid-state electrolytes considered both their optimization of the ion migration capability of the separator and their impact on the thermal stability of the separator. Through a comparison of Examples 1-3, we found that Example 1 achieved the best battery cycle performance. We believe this is because the particle size of the inorganic solid-state electrolyte selected in Example 1 creates abundant channels conducive to lithium-ion migration. If the particle size difference is too small, it may lead to fewer channels forming, causing the lithium-ion migration rate to not match the electrochemical reaction, resulting in electrode polarization. Furthermore, it may lead to overly narrow lithium-ion migration channels, hindering lithium-ion migration. We further optimized the inorganic solid-state electrolyte by selecting particles with a D50 particle size of 0.2 μm-1.5 μm and a D100 particle size of 2 μm-3.5 μm.

[0082] Based on this, in order to promote the wetting of inorganic solid electrolyte in the slurry and its uniform dispersion, we further added dispersant A and wetting agent to the slurry. In order to promote the uniform dispersion of acrylate copolymer in the slurry, we also added dispersant B. In order to improve the bonding ability between the particles in the slurry, we further added binder. On the one hand, this promotes the increase of the bonding force inside the functional coating, and on the other hand, it can improve the bonding force between the separator and the positive and negative electrode sheets of the battery.

[0083] Therefore, we further investigated the combination of inorganic solid electrolyte, acrylate multi-electrolyte copolymer, dispersant A, dispersant B, binder and wetting agent in the slurry of the separator of the present invention, and how to further optimize the battery separator of the present invention.

[0084] Based on the above, we selected the polyhydroxy alcohol wetting agent from Example 1. First, polyhydroxy alcohol wetting agents are more likely to adsorb onto the surface of the inorganic solid electrolyte, thereby improving the wettability of the inorganic solid electrolyte. Second, polyhydroxy alcohol wetting agents have good solubility and can dissolve well in solution. In order to improve the dispersibility of the inorganic solid electrolyte while wetting it, we further selected alkylbenzene sulfonate dispersant A from Example 1. On the one hand, alkylbenzene sulfonates have good solubility, are less volatile, and have a more stable structure. When the diaphragm is dried, it can stabilize the dispersibility of the inorganic solid electrolyte in the coating. On the other hand, alkylbenzene sulfonates adsorb onto the surface of the inorganic solid electrolyte and disperse the inorganic solid electrolyte in the slurry through steric hindrance. Furthermore, the alkyl group in the alkylbenzene sulfonate has a weak electron-donating group, which, in combination with the hydroxyl group in the polyhydroxy alcohol wetting agent, can simultaneously improve the dispersibility and wettability of the inorganic solid electrolyte. To further promote the dispersion of acrylate multi-component copolymers, we also added aryl ether sulfonate dispersant B from Example 1. On the one hand, the pyridine ring in the acrylate multi-component copolymer has an electron-donating effect, and the sulfonate group in the aryl ether sulfonate can reduce the electron cloud density on the benzene ring, enhancing the electron-withdrawing effect of the sulfonate group. The aryl ether sulfonate can better cooperate with the acrylate multi-component copolymer, thus facilitating the dispersion of the acrylate multi-component copolymer in the slurry. On the other hand, aryl ether sulfonate and alkylbenzene sulfonate have similar structures and can be better dissolved in the slurry. Furthermore, the combination of aryl ether sulfonate and polyhydroxy alcohol wetting agents can promote the dispersion and wetting of inorganic solid electrolytes. Alkylbenzene sulfonate can promote the dispersion of acrylate multi-component copolymers. When the slurry is mixed during the preparation process, a uniformly dispersed slurry can also be obtained. To improve the adhesion between the various substances in the slurry and between the separator and the positive and negative electrode sheets of the battery, we also selected a polysaccharide binder. First, polysaccharide binders are substances with multiple hydroxyl and carboxyl groups, which have a strong electron-withdrawing ability, which is beneficial to the adhesion of the acrylate multi-component copolymer and inorganic solid electrolyte dispersed in the slurry, thereby improving the adhesion of the functional coating. Second, polysaccharide binders and the polyhydroxy alcohol wetting agent of Example 1 have similar substituent groups, which is beneficial to the uniform mixing of the two substances in the slurry, thereby playing a synergistic role in the slurry.We can verify this by comparing Example 1 with Examples 5-7. Example 1 shows that the battery exhibits the best electrical performance, and the battery separator also demonstrates the best performance. We further optimize the following components: inorganic solid electrolyte with a particle size of 0.2 μm-1.5 μm and a particle size of 2 μm-3.5 μm; acrylate multi-component copolymer; alkylbenzene sulfonate; aryl ether sulfonate; polysaccharide binder; and polyhydroxy alcohol wetting agent. By mass, the particle size of the D50 component is 0.2 μm-... The ratio of inorganic solid electrolyte with particle size D100 of 2μm-3.5μm: acrylate multi-component copolymer: alkylbenzene sulfonate: aryl ether sulfonate: polysaccharide binder: polyhydroxy alcohol wetting agent is (20-30 parts): (10-40 parts): (0.3-0.8 parts): (0.5-1.2 parts): (3-4 parts): (0.3-0.9 parts), wherein R of the acrylate multi-component copolymer is a C2-C4 alkyl group having a pyridine ring.

[0085] We also investigated acrylate multi-component copolymers, in which the pyridine ring and ester group are linked. A greater distance between the pyridine ring and the ester group is beneficial for the structural stability of the acrylate multi-component copolymer. Furthermore, the longer branches of the acrylate multi-component copolymer contribute to the flexibility of the formed functional membrane. Through comparative verification using Examples 1-4, we found that the battery and separator performance of Example 1 were superior to those of Example 4. We further optimized the acrylate multi-component copolymer, where R is a C4 alkyl group with a pyridine ring.

[0086] Building upon this, we further investigated that when the inorganic solid electrolyte is the lithium lanthanum zirconium oxide compound from Example 1, it exhibits superior thermal stability compared to other inorganic solid electrolytes. Based on this, we recommend omitting sodium dodecylbenzenesulfonate from Example 1. Sodium dodecylbenzenesulfonate offers better flexibility, allowing for better adsorption onto the lithium lanthanum zirconium oxide compound. Its longer alkyl chain provides better steric hindrance, promoting uniform dispersion of the lithium lanthanum zirconium oxide compound. Furthermore, it reduces the influence of benzene rings and sulfonate groups on the alkyl group, thus enabling better coordination between the alkyl group and the hydroxyl groups in glycerol, thereby improving the dispersibility and wettability of the lithium lanthanum zirconium oxide compound. The three hydroxyl groups in glycerol reduce the probability of intermolecular hydrogen bonding due to excessive hydroxyl groups, ensuring the wettability of the lithium lanthanum zirconium oxide compound while also synergizing with sodium dodecylbenzenesulfonate. The addition of hydroxyl groups to polyethylene glycol alkyl aryl ether sulfonate further enhances the solubility of dispersant B in the slurry. Xanthan gum possesses unique rheological properties and exhibits good stability to heat and acids / alkalis, improving the texture of the slurry and thus enhancing coating uniformity. Furthermore, the multi-hydroxyl and multi-carboxyl structure of xanthan gum better binds particles in the slurry, increasing its adhesion and the bond strength between the separator and the positive and negative electrodes of the battery. In addition, we found that sodium polyethylene glycol alkyl aryl ether sulfonate, xanthan gum, and glycerol all possess multi-hydroxyl structures, exhibiting better compatibility, which improves the dispersibility and adhesion of the various components in the slurry, contributing to its stability. We verified through comparison between Example 1 and Examples 5-7 that Example 1 yielded the best battery electrical performance and the best battery separator performance. We further optimized the composition of lithium lanthanum zirconium oxide compound, acrylate multi-component copolymer, sodium dodecylbenzene sulfonate, sodium polyethylene glycol alkyl aryl ether sulfonate, xanthan gum, and glycerol, with a particle size of D50 of 0.2 μm-1.5 μm and a particle size of D100 of 2 μm-3.5 μm, by weight. The ratio of lithium lanthanum zirconium oxide compound with a particle size of 1.5 μm and a particle size of D100 of 2 μm-3.5 μm: acrylate multi-component copolymer: sodium dodecylbenzenesulfonate: sodium polyethylene glycol alkyl aryl ether sulfonate: xanthan gum: glycerol is (20-30 parts): (10-40 parts): (0.3-0.8 parts): (0.5-1.2 parts): (3-4 parts): (0.3-0.9 parts), wherein R in the acrylate multi-component copolymer is a C4 alkyl group having a pyridine ring.

[0087] Based on this, we further tested other properties of the battery separator obtained in Example 1. The measured increase in air permeability was 8 s / 100 mL, and the areal density was 0.88 g / m³. 2The needle penetration strength is 5.0 N, the longitudinal tensile strength is 200 MPa (MD direction), and the transverse tensile strength is 180 MPa (TD direction). After baking at 130℃ for 1 hour, the longitudinal thermal shrinkage rate is 0.5% (MD direction) and the transverse thermal shrinkage rate is 0.5% (TD direction). Therefore, the battery separator obtained by this invention has good thermal stability.

[0088] In summary, the battery separator of the present invention can not only improve the thermal stability of the separator, but also improve the electrical performance of the battery.

[0089] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery separator, characterized by, The diaphragm comprises a base film, at least one layer of the base film is coated with a functional coating, raw materials of the functional coating include inorganic solid-state electrolyte, acrylic ester multi-copolymer, the ratio of the inorganic solid-state electrolyte: acrylic ester multi-copolymer is (20 parts-30 parts):(10 parts-40 parts) by mass, the acrylic ester multi-copolymer has the structure of chemical formula (I): Wherein, n, m are selected from integers not less than 1; R is selected from one or more of C2-C4 alkyl groups with a pyridine ring.

2. The battery separator of claim 1, wherein, Raw materials of the functional coating further include dispersant A, dispersant B, binder, wetting agent, the ratio of the inorganic solid-state electrolyte: acrylic ester multi-copolymer: dispersant A: dispersant B: binder: wetting agent is (20 parts-30 parts):(10 parts-40 parts):(0.3 parts-0.8 parts):(0.5 parts-1.2 parts):(3 parts-4 parts):(0.3 parts-0.9 parts) by mass.

3. The battery separator of claim 1, wherein, Raw materials of the functional coating further include a solution, the mass fraction of the solution in raw materials is 47%-69%.

4. The battery separator of claim 1, wherein, The inorganic solid-state electrolyte includes one or more of lithium lanthanum zirconium oxide compound, lithium lanthanum zirconium tantalum oxide compound, lithium lanthanum titanium oxide compound, lithium aluminum titanium phosphate compound.

5. The battery separator of claim 4, wherein, The inorganic solid-state electrolyte particle D50 particle size is 0.2-1.8 μm, and the particle D100 particle size is 1.7-3.5 μm.

6. The battery separator of claim 2, wherein The dispersant A includes one or more of sodium phosphate salt, citrate salt, alkyl benzene sulfonate salt, ammonium salt; the dispersant B includes one or more of fatty acid ethylene oxide adduct, polyethylene glycol type polyol, polyethylene imine derivative, aryl ether sulfonate, polyoxyethylene type ether, modified polyether polymer, polyacrylate; the binder includes one or more of carboxymethylated derivative binder of cellulose, polyester binder, rubber binder, polysaccharide binder, polyalcohol binder, amino ester binder, nitrile binder; the wetting agent includes one or more of polyacid ester wetting agent, ether wetting agent, monohydroxy alcohol wetting agent, polyhydroxy alcohol wetting agent, alkyl sulfate salt wetting agent, sulfone base wetting agent, sulfonate wetting agent.

7. The battery separator of claim 6, wherein The sodium phosphate salt includes one or more of sodium hexametaphosphate, sodium tripolyphosphate; The citrate salt includes sodium citrate; The alkyl benzene sulfonate salt includes sodium dodecyl benzene sulfonate; The ammonium salt includes polyacrylammonium salt; The aryl ether sulfonate salt includes polyethylene glycol sodium alkyl aryl ether sulfonate; The polyoxyethylene type ether includes one or more of polyoxyethylene alkyl phenol ether, alkyl phenol polyoxyethylene ether; The polyacrylate includes sodium polyacrylate; The carboxymethylated derivative binder includes sodium carboxymethyl cellulose; The polyester binder includes one or more of polyacrylate, polymethyl acrylate; The rubber binder includes styrene butadiene rubber; The polyalcohol binder includes polyvinyl alcohol; The amino ester binder includes polyurethane; The polysaccharide binder includes one or more of xanthan gum, sodium alginate; The nitrile binder includes polyacrylonitrile; The polyacid ester wetting agent includes methyl acrylate; The ether wetting agent includes dodecyl phenol polyoxyethylene ether; The monohydric alcohol wetting agent includes ethanol; The polyhydric alcohol wetting agent includes one or more of propylene glycol and glycerol; The sulfone-based wetting agent includes dimethyl sulfoxide.

8. The battery separator of claim 1, wherein, The raw materials of the functional coating include inorganic solid-state electrolyte, acrylate multi-copolymer, alkyl benzene sulfonate, aryl ether sulfonate, polysaccharide binder, and polyhydric alcohol wetting agent, the particle D50 size of the inorganic solid-state electrolyte is 0.2 μm-1.5 μm, the particle D100 size is 2 μm-3.5 μm, the mass ratio of the inorganic solid-state electrolyte: acrylate multi-copolymer: alkyl benzene sulfonate: aryl ether sulfonate: polysaccharide binder: polyhydric alcohol wetting agent is (20 parts-30 parts):(10 parts-40 parts):(0.3 parts-0.8 parts):(0.5 parts-1.2 parts):(3 parts-4 parts):(0.3 parts-0.9 parts), and R of the acrylate multi-copolymer is C2-C4 alkyl having a pyridine ring.

9. The battery separator of claim 1, wherein, The raw materials of the functional coating include lithium lanthanum zirconium oxide, acrylate multi-copolymer, sodium dodecyl benzene sulfonate, sodium polyethylene glycol alkyl aryl ether sulfonate, xanthan gum, and glycerol, the particle D50 size of the lithium lanthanum zirconium oxide is 0.2 μm-1.5 μm, the particle D100 size is 2 μm-3.5 μm, the mass ratio of the lithium lanthanum zirconium oxide: acrylate multi-copolymer: sodium dodecyl benzene sulfonate: sodium polyethylene glycol alkyl aryl ether sulfonate: xanthan gum: glycerol is (20 parts-30 parts):(10 parts-40 parts):(0.3 parts-0.8 parts):(0.5 parts-1.2 parts):(3 parts-4 parts):(0.3 parts-0.9 parts), and R of the acrylate multi-copolymer is C4 alkyl having a pyridine ring.

10. The battery separator of claim 4, wherein The inorganic solid-state electrolyte has a particle D50 size of 0.2 μm-1.5 μm and a particle D100 size of 2 μm-3.5 μm.

11. Process for the production of the separator according to any one of claims 1 to 10, characterized in that, The preparation method includes: S1: inorganic solid-state electrolyte, dispersant A, wetting agent, and solution are weighed according to the mass ratio and stirred and dispersed; S2: acrylate multi-copolymer, dispersant B are added to S1 according to the mass ratio, and stirred and dispersed uniformly; S3: S1 and S2 are mixed uniformly, a binder is added, stirred uniformly, and a slurry of the functional coating is obtained; S4: the slurry is coated on at least one side of the base film, vacuum dried, and a separator is obtained.

12. The method of claim 11, wherein the membrane is prepared by a process comprising: The stirring and dispersing time in S1 is 30-40 minutes, the stirring and dispersing speed is 2000-3000 r / min; the stirring and dispersing time in S2 is 30-90 minutes, the stirring and dispersing speed is 500-2000 r / min; the stirring and uniformizing time in S3 is 20-30 minutes, the stirring and uniformizing speed is 500-800 r / min; the vacuum drying temperature in S4 is 60-130 ℃, the vacuum drying time is 5-40 minutes.

13. An electrochemical device, characterized by, The electrochemical device has the separator of any one of claims 1-10.

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