Preparation method of battery diaphragm, battery diaphragm and application of battery diaphragm

Abstract

The invention discloses a preparation method of a battery composite diaphragm, the composite diaphragm and application of the composite diaphragm, and the preparation method of the composite diaphragm comprises the following steps: mixing 4, 40-difluorobenzophenone, sulfonated 4, 40-difluorobenzophenone sodium, 2, 20-bis (4-hydroxyphenyl) hexafluoropropane, 4, 40-methylenebis [2-(1H-benzimidazole-2-yl)] phenol and anhydrous potassium carbonate, and stirring uniformly to obtain a mixture A of 4, 40-difluorobenzophenone, sulfonated 4, 40-difluorobenzophenone sodium, 2, 20-bis (4-hydroxyphenyl) hexafluoropropane, 4, 40-methylenebis [2-(1H-benzimidazole-2-yl) phenol and anhydrous potassium carbonate; adding a reaction medium solvent and an entrainer to form a first mixed solution; carrying out reflux reaction on the first mixed solution in the presence of inert gas, carrying out heat preservation reaction after removing the entrainer, cooling, and precipitating and purifying to prepare the novel sulfonated polyaryletherketone; the preparation method comprises the following steps: dissolving novel sulfonated polyaryletherketone and polyethylene glycol in a reaction medium solvent to prepare a membrane casting solution; and coating the membrane casting solution on the surface of the membrane, immersing in an ethanol coagulating bath for curing, and drying to obtain the composite membrane. The composite diaphragm can reduce the contact angle, improve the infiltration rate and solve the problems of liquid injection and overflow of the battery.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a preparation method of a battery separator, a battery separator and applications thereof. Background Art

[0002] In today's energy field, lithium batteries have become key energy storage components for many electronic devices and new energy industries due to their advantages such as high energy density and long cycle life. With the continuous increase in market demand for energy storage, such as the improvement of electric vehicle range and the expansion of the scale of power storage systems, batteries are developing towards large capacity and high energy density. For example, in the mass production of high-capacity batteries such as 314Ah, 500Ah, and 688Ah, the high-pressure compaction design of the positive and negative electrodes has increased the energy density, but it has led to a reduction in the porosity of the pole pieces, a decrease in the infiltration rate, and an increasingly prominent problem of liquid injection and overflow. At present, the industry's short-term solution to battery cell overflow is to reduce the amount of electrolyte injection. However, the electrolyte retention volume is closely related to the battery cycle life and is a necessary guarantee for achieving 7,000 or even 10,000 cycles. Reducing the amount of injection will seriously affect the battery's service life and performance.

[0003] As a key component of lithium batteries, the separator plays a key role in battery performance. Although the traditional polyolefin separator has low cost and good mechanical properties, it has low surface energy and poor hydrophilicity, resulting in poor electrolyte wettability. Therefore, it is urgent to improve the performance of the separator to reduce the problem of battery cell liquid overflow. Summary of the invention

[0004] In order to overcome the defects in the prior art, the first object of the present invention is to provide a method for preparing a battery composite diaphragm, the second object of the present invention is to provide a composite diaphragm prepared by the above preparation method, the third object of the present invention is to provide a lithium battery including the above composite diaphragm, and the fourth object of the present invention is to provide an electrical device including the above lithium battery.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, a method for preparing a battery composite separator comprises the following steps: mixing a benzophenone derivative, a sulfonated aromatic compound, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, a bisphenol compound and a potassium-based alkaline catalyst, and adding a reaction medium solvent and an azeotropic agent to form a first mixed solution;

[0007] The first mixed solution is subjected to reflux reaction under an inert gas, and after removing the azeotropic agent, the solution is kept warm for reaction, and after cooling, the solution is precipitated and purified to obtain a novel sulfonated polyaryletherketone;

[0008] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in a reaction medium solvent to prepare a film casting solution;

[0009] The casting liquid is coated on the surface of the diaphragm, immersed in a coagulation bath of an alcohol solvent for solidification, and dried to obtain a composite diaphragm.

[0010] The present invention improves the infiltration rate and enhances the absorption and retention capacity by optimizing the design of the polar coating of the composite diaphragm and the pore structure, thereby reducing electrolyte retention and solving the problem of liquid overflow during injection.

[0011] Preferably, the benzophenone derivative is selected from one or more of 4,40-dichlorobenzophenone and 4,40-dibromobenzophenone;

[0012] The sulfonated aromatic compound is selected from one or more of sulfonated 4,40-dichlorobenzophenone sodium and sulfonated 4,40-dibromobenzophenone sodium;

[0013] The bisphenol compound is a bisphenol compound containing a benzimidazole structure, and preferably, the bisphenol compound is 4,40-methylenebis[2-(1H-benzotriazole-1-yl)]phenol;

[0014] The potassium-based alkaline catalyst is selected from one or more of anhydrous potassium carbonate, sodium carbonate and potassium hydroxide.

[0015] The reaction medium solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone. Preferably, the reaction medium solvent is N,N-dimethylformamide. N,N-dimethylacetamide has good solubility and can dissolve various reaction raw materials.

[0016] The entrainer is selected from one or more of toluene, cyclohexane, n-pentane, and ethyl acetate. Preferably, the entrainer is toluene. Toluene as an entrainer can take away moisture during the reaction and promote the polycondensation reaction.

[0017] The alcohol solvent is selected from one or more of ethanol, isopropanol, tert-butanol and n-propanol.

[0018] Further preferably, the method comprises the following steps:

[0019] Mixing 4,40-difluorobenzophenone, sulfonated 4,40-difluorobenzophenone sodium, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate, and adding N,N-dimethylformamide and toluene to form a first mixed solution;

[0020] The first mixed solution is subjected to reflux reaction under an inert gas, and after removing toluene, the solution is subjected to heat preservation reaction, and after cooling, the solution is subjected to precipitation and purification to obtain a novel sulfonated polyaryletherketone;

[0021] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylformamide to prepare a casting solution;

[0022] The casting liquid is coated on the surface of the diaphragm, immersed in an ethanol coagulation bath for solidification, and dried to obtain a composite diaphragm.

[0023] The coating of the prepared composite membrane contains a new type of sulfonated polyaryletherketone. The new type of sulfonated polyaryletherketone achieves a comprehensive improvement in membrane performance through side chain functionalization design and multiple polar groups synergy. First, the sulfonic acid group (-SO 3 - ), carbonyl (C=O), ether bond (COC) and strong electron withdrawing group (-CF 3 ) greatly enhances the polarity of the material, significantly improving the affinity between the membrane surface and the electrolyte, and reducing the contact angle to 3°, which is much lower than the 48° of ordinary PE membranes, thereby achieving instantaneous infiltration of the electrolyte and avoiding retention and overflow caused by interfacial tension during injection. 3 ) Enhance the interaction between polymer chains, and the tensile strength reaches 17-19MPa, ensuring that the diaphragm is not easily damaged during the winding / stacking process. Second, the polyethylene glycol-assisted pore formation and ethanol coagulation bath process are combined to form a high-porosity network structure, and the electrolyte absorption rate is increased to 140-150% / h, taking into account both rapid injection and long-term liquid retention capabilities.

[0024] When preparing the new sulfonated polyaryletherketone, 4,40-difluorobenzophenone, sulfonated 4,40-difluorobenzophenone sodium, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and other raw materials are used for reaction. These raw materials are commercially available chemical raw materials and can be purchased directly from Shanghai MacLean Biochemical Technology Co., Ltd. The structure and reaction mode of these raw materials determine the type of side chain groups of the final polymer. Among them, the sources of each group are mainly as follows:

[0025] Sulfonic acid group (-SO 3 - ) is provided by the monomer sulfonated 4,40-difluorobenzophenone sodium, which is grafted onto the polymer backbone in the form of a sodium salt through a sulfonation reaction. 3 - ) as a side chain polar group, which significantly enhances the lyophilicity of the membrane surface and reduces the electrolyte contact angle.

[0026] Hexafluoropropane group (-CF 3 ) comes from the monomer 2,20-bis(4-hydroxyphenyl)hexafluoropropane, which is connected to the main chain through an ether bond during the polymerization process to form a side chain branch. 3The strong electronegativity polarizes the surrounding chemical bonds, further reducing the surface energy of the separator and promoting the spreading of the electrolyte. 3 The hydrophobicity of the sulfonic acid group and the hydrophilicity of the sulfonic acid group form a microphase separation structure, balancing the liquid absorption and liquid retention capabilities.

[0027] The benzimidazole group is introduced from the monomer 4,40-methylenebis[2-(1H-benzimidazole-2-yl)]phenol and bridged to the main chain through the methylene group. The rigid structure of the benzimidazole ring enhances the interaction between polymer chains and improves the mechanical strength.

[0028] The hydroxyl groups (-OH) and ether bonds (COC) from the monomer 2,20-bis(4-hydroxyphenyl)hexafluoropropane participate in the polycondensation reaction to form ether bonds. The hydroxyl groups form the main chain ether bonds (COC) through the condensation reaction, and some unreacted hydroxyl groups can remain as side chain terminal groups. The residual hydroxyl groups enhance the surface polarity of the diaphragm, form hydrogen bonds with the carbonate solvent in the electrolyte, and increase the wetting rate.

[0029] The carbonyl group (C=O) is retained in the polymer main chain by the carbonyl group in the monomer 4,40-difluorobenzophenone, or forms a side chain branch through reaction. The carbonyl group mainly serves as a rigid unit of the main chain to improve thermal stability and ensure battery safety and service life.

[0030] Preferably, the method comprises mixing 4,40-difluorobenzophenone, sulfonated sodium 4,40-difluorobenzophenone, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate, and adding N,N-dimethylformamide and toluene to form a first mixed solution, comprising:

[0031] 4,40-difluorobenzophenone, sulfonated sodium 4,40-difluorobenzophenone, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate are mixed in a molar ratio of (3-5):(5-7):(8-10):1:(11-13), and N,N-dimethylformamide and toluene are added to form a first mixed solution. The volume ratio of N,N-dimethylformamide and toluene is (6-8):(2-3). Preferably, the volume ratio of the reaction medium solvent and the entrainer is 13:5. The ratio of the reaction medium solvent and the entrainer will affect the uniformity of the reaction. If the ratio is unbalanced, the casting solution will have poor fluidity and uneven coating.

[0032] Preferably, the molar ratio of 4,40-difluorobenzophenone, sodium sulfonated 4,40-difluorobenzophenone, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate is 4:6:9:1:12.

[0033] The molar ratio of each component can affect the molecular structure and performance of the new sulfonated polyaryletherketone. The present invention optimizes the distribution ratio of each component in the raw material. In the present invention, the molar ratio of the sulfonated monomer sulfonated 4,40-difluorobenzophenone sodium is controlled to be 6%, ensuring that the sulfonic acid group (-SO 3 - ) and rigid groups (-CF 3 , benzimidazole) is reasonably distributed so that the sulfonation degree of the new sulfonated polyaryletherketone is between 5% and 10%.

[0034] Sulfonation is a high-cost process. Compared with the existing sulfonated polyaryletherketone, the sulfonation degree of the present invention is controlled at 5% to 10%, which can reduce production costs. The low sulfonation degree of 5% to 10% can ensure the function of the polar group while avoiding water absorption and expansion caused by excessive sulfonic acid groups, mechanical strength reduction and side reactions (such as LiPF 6 Hydrolysis), so that the capacity retention rate after 500 cycles is stabilized at 0.98%, which is suitable for the mass production demand of large-capacity battery cells.

[0035] Preferably, the first mixed solution is subjected to reflux reaction under an inert gas, and after removing the entrainer, the mixture is subjected to heat preservation reaction, and after cooling, precipitation and purification are performed to obtain the novel sulfonated polyaryletherketone, comprising:

[0036] The first mixed solution is refluxed under an inert gas for 4 to 6 hours, and after dehydration and removal of the entrainer, the temperature is raised to 170 to 190°C, and the reaction is kept warm for 20 to 25 hours. The reflux time is controlled to 4 to 6 hours, preferably, reflux for 4 hours. Insufficient reflux reaction time will result in too low molecular weight and decreased tensile strength, while too long will increase energy consumption. Keep warm at 170 to 190°C for 20 to 25 hours. High temperature can promote crosslinking of polymer chains to form a stable structure. If the temperature is too low, insufficient crosslinking will result and low mechanical strength. If the temperature is too high, polymer decomposition will occur.

[0037] After the reaction is kept warm, the mixture is cooled to room temperature, a precipitant is used to precipitate the polymer, and the obtained polymer is purified and dried through a redissolution-precipitation cycle to obtain a novel sulfonated polyaryletherketone. The redissolution-precipitation cycle refers to dissolving first and then precipitating, and the operation is repeated multiple times.

[0038] Preferably, the inert gas is selected from one or more of nitrogen, helium or argon. Reflux under an inert gas can prevent oxidation side reactions and ensure efficient polycondensation reaction.

[0039] Preferably, the precipitant is selected from one or more of ethanol, isopropanol, tert-butanol, and n-propanol. Precipitation with the precipitant can remove reaction monomers and small molecular byproducts.

[0040] Preferably, the purification includes at least 3 redissolution-precipitation cycles. Further preferably, the purification includes 3 to 5 redissolution-precipitation cycles. If the precipitation is not thorough, impurities will remain, reducing the uniformity of the coating and increasing the contact angle.

[0041] Preferably, the drying temperature is 80-85° C. Residual solvent is removed by drying to prevent bubbles from being generated during the subsequent film forming process. If the drying temperature is too high, the polymer may be thermally degraded and the tensile strength may decrease.

[0042] Preferably, the step of dissolving the novel sulfonated polyaryletherketone and polyethylene glycol in a reaction medium solvent to obtain a casting solution comprises:

[0043] The novel sulfonated polyaryletherketone, polyethylene glycol and reaction medium solvent are mixed in a mass ratio of (4-20):1:(20-40) to prepare a casting solution at 60-65 DEG C.

[0044] Preferably, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and reaction medium solvent is 5:1:20.

[0045] Polyethylene glycol is used as a porogen to be blended with the prepared novel sulfonated polyaryletherketone polymer to form a casting solution. In the ratio of the two, if the proportion of polyethylene glycol is too high, the coating will be too brittle and have low tensile strength.

[0046] The method comprises coating the casting liquid on the surface of the diaphragm, immersing the diaphragm in a coagulation bath of an alcohol solvent for solidification, and drying to obtain a composite diaphragm, comprising:

[0047] The casting liquid is applied on the surface of the PE diaphragm by a wire rod coating process to obtain a pre-processed film;

[0048] The pre-processed membrane is immersed in an ethanol coagulation bath for solidification and drying to obtain a composite membrane. The ethanol coagulation bath treatment can induce phase separation to form a porous structure.

[0049] Preferably, the wire rod diameter is 10 μm. Deviation of the wire rod diameter will lead to uneven coating thickness. The present invention controls the coating thickness and ensures pore uniformity by selecting a wire rod diameter of 10 μm.

[0050] In a second aspect, a composite diaphragm is prepared by the above-mentioned method for preparing the battery composite diaphragm.

[0051] Preferably, the surface of the composite membrane contains sulfonic acid groups, carbonyl groups, ether bonds, hexafluoropropane groups, benzimidazole groups and hydroxyl groups, the contact angle of the composite membrane is ≤10°, and the electrolyte infiltration rate of the composite membrane is ≥140% / hour.

[0052] A third aspect provides a lithium battery, comprising the composite separator.

[0053] A fourth aspect provides an electrical device, comprising the lithium battery described above.

[0054] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0055] 1. By preparing a new type of sulfonated polyaryletherketone, sulfonic acid groups, carboxyl groups, ether bonds and strong electron-withdrawing groups are introduced into the molecular structure of the new polyaryletherketone to form a multi-polar synergistic effect, reducing the electrolyte contact angle to 3°, achieving instantaneous infiltration of the electrolyte on the surface of the diaphragm, and avoiding liquid accumulation due to interfacial tension.

[0056] 2. The polyethylene glycol-assisted pore formation and ethanol coagulation bath process constructs a highly porous interconnected network, which increases the electrolyte absorption rate to 140-150% / h (80% / h for ordinary PE diaphragms), quickly adsorbs and evenly distributes the electrolyte, and reduces the risk of overflow during the static stage after injection.

[0057] The low sulfonation degree design of 3.5% to 10% inhibits excessive water absorption or side reactions of the sulfonic acid groups while ensuring polarity. Combined with the high mechanical strength of 17 to 19 MPa, it ensures the stability of the diaphragm during battery assembly and use, ultimately achieving a nearly 1-fold increase in the wetting rate, an 80% reduction in overflow losses, and a long-life performance with a capacity retention rate of 0.98% after 500 cycles, perfectly adapting to the industrial needs of large-capacity batteries such as 314Ah / 500Ah.

[0058] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 It is the infrared spectra of the diaphragms in Example 1, Example 2 and Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Embodiment 1:

[0063] A method for preparing a battery composite diaphragm comprises the following steps:

[0064] 0.8730 g (4 mmoles) of 4,40-difluorobenzophenone, 2.5337 g (6 mmoles) of sulfonated sodium 4,40-difluorobenzophenone, 3.0261 g (9 mmoles) of 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 0.4325 g (1 mmole) of 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and 1.6585 g (12 mmoles) of anhydrous potassium carbonate were added to a three-necked flask and mixed. Subsequently, 60 ml of N,N-dimethylacetamide and 25 ml of toluene were added as a solvent and an azeotropic agent to form a first mixed solution.

[0065] The first mixed solution was refluxed for 4 hours under a nitrogen atmosphere, and after dehydration and removal of toluene, the temperature was raised to 170°C and maintained for 20 hours. After the reaction was incubated, the solution was cooled to room temperature, the polymer was precipitated using an ethanol precipitant, and the obtained polymer was purified by three redissolution-precipitation cycles. The solution was vacuum dried at 80°C overnight to obtain a light yellow solid novel sulfonated polyaryletherketone.

[0066] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylacetamide, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and N,N-dimethylacetamide is 5:1:20, and a casting solution is formed at 60°C.

[0067] The degassed casting solution was scraped onto the surface of the microporous PE diaphragm by an automatic film coater through a 10 μm wire rod, and then immediately placed in an ethanol coagulation bath for several hours and dried to obtain a composite diaphragm.

[0068] This embodiment also discloses a composite diaphragm, which is prepared by the above-mentioned composite diaphragm preparation method.

[0069] The surface of the composite membrane contains sulfonic acid groups, carbonyl groups, ether bonds and -CF 3 The contact angle of the composite membrane is 6°, and the electrolyte infiltration rate of the composite membrane is 140% / H.

[0070] This embodiment also discloses a lithium battery, which includes the composite diaphragm.

[0071] Embodiment 2:

[0072] A method for preparing a battery composite diaphragm comprises the following steps:

[0073] 0.8730 g (4 mmoles) of 4,40-difluorobenzophenone, 2.5337 g (6 mmoles) of sodium sulfonated 4,40-difluorobenzophenone, 3.0261 g (9 mmoles) of 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 0.4325 g (1 mmole) of 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and 1.65858 g (12 mmoles) of anhydrous potassium carbonate were added to a three-necked flask and mixed. Subsequently, 60 ml of N,N-dimethylacetamide and 25 ml of toluene were added as a solvent and an azeotropic agent to form a first mixed solution.

[0074] The first mixed solution was refluxed for 4 hours under a nitrogen atmosphere, and after dehydration and removal of toluene, the temperature was raised to 170°C and maintained for 20 hours. After the reaction was incubated, the solution was cooled to room temperature, the polymer was precipitated using an ethanol precipitant, and the obtained polymer was purified by five redissolution-precipitation cycles. The solution was vacuum dried at 80°C overnight to obtain a light yellow solid novel sulfonated polyaryletherketone.

[0075] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylacetamide, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and N,N-dimethylacetamide is 5:1:20, and a casting solution is formed at 60°C.

[0076] The degassed casting solution was scraped onto the surface of the microporous PE diaphragm by an automatic film coater through a 10 μm wire rod, and then immediately placed in an ethanol coagulation bath for several hours and dried to obtain a composite diaphragm.

[0077] This embodiment also discloses a composite diaphragm, which is prepared by the above-mentioned composite diaphragm preparation method.

[0078] The surface of the composite membrane contains sulfonic acid groups, carbonyl groups, ether bonds and -CF 3 The contact angle of the composite membrane is 3°, and the electrolyte infiltration rate of the composite membrane is 150% / H.

[0079] This embodiment also discloses a lithium battery, which includes the composite diaphragm.

[0080] Comparative Example 1:

[0081] A method for preparing a battery composite diaphragm comprises the following steps:

[0082] 1.310 g (6 mmoles) of 4,40-difluorobenzophenone, 2.5337 g (6 mmoles) of sulfonated sodium 4,40-difluorobenzophenone, 3.0261 g (9 mmoles) of 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 0.4325 g (1 mmole) of 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and 1.6585 g (12 mmoles) of anhydrous potassium carbonate were added to a three-necked flask and mixed. Subsequently, 60 ml of N,N-dimethylacetamide and 25 ml of toluene were added as a solvent and an azeotropic agent to form a first mixed solution.

[0083] The first mixed solution was refluxed for 4 hours under a nitrogen atmosphere, and after dehydration and removal of toluene, the temperature was raised to 170°C and maintained for 20 hours. After the reaction was incubated, the solution was cooled to room temperature, the polymer was precipitated using an ethanol precipitant, and the obtained polymer was purified by five redissolution-precipitation cycles. The solution was vacuum dried at 80°C overnight to obtain a light yellow solid novel sulfonated polyaryletherketone.

[0084] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylacetamide, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and N,N-dimethylacetamide is 5:1:20, and a casting solution is formed at 60°C.

[0085] The degassed casting solution was scraped onto the surface of the microporous PE diaphragm by an automatic film coater through a 10 μm wire rod, and then immediately placed in an ethanol coagulation bath for several hours and dried to obtain a composite diaphragm.

[0086] This comparative example also discloses a composite diaphragm, which is prepared by the above-mentioned composite diaphragm preparation method.

[0087] This comparative example also discloses a lithium battery, which includes the composite diaphragm.

[0088] Comparative Example 2:

[0089] A method for preparing a battery composite diaphragm comprises the following steps:

[0090] 0.8730 g (4 mmoles) of 4,40-difluorobenzophenone, 2.5337 g (6 mmoles) of sulfonated sodium 4,40-difluorobenzophenone, 3.0261 g (9 mmoles) of 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 0.4325 g (1 mmole) of 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and 1.6585 g (12 mmoles) of anhydrous potassium carbonate were added to a three-necked flask and mixed. Subsequently, 60 ml of N,N-dimethylacetamide and 25 ml of toluene were added as a solvent and an azeotropic agent to form a first mixed solution.

[0091] The first mixed solution was refluxed for 4 hours under a nitrogen atmosphere, and after dehydration and removal of toluene, the temperature was raised to 170°C and maintained for 20 hours. After the reaction was incubated, the solution was cooled to room temperature, the polymer was precipitated using an ethanol precipitant, and the obtained polymer was purified by five redissolution-precipitation cycles. The solution was vacuum dried at 80°C overnight to obtain a light yellow solid novel sulfonated polyaryletherketone.

[0092] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylacetamide, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and N,N-dimethylacetamide is 5:5:20, and a casting solution is formed at 60°C.

[0093] The degassed casting solution was scraped onto the surface of the microporous PE diaphragm by an automatic film coater through a 10 μm wire rod, and then immediately placed in an ethanol coagulation bath for several hours and dried to obtain a composite diaphragm.

[0094] This comparative example also discloses a composite diaphragm, which is prepared by the above-mentioned composite diaphragm preparation method.

[0095] This comparative example also discloses a lithium battery, which includes the composite diaphragm.

[0096] Comparative Example 3:

[0097] A method for preparing a battery composite diaphragm comprises the following steps:

[0098] 0.8730 g (4 mmoles) of 4,40-difluorobenzophenone, 2.5337 g (6 mmoles) of sulfonated sodium 4,40-difluorobenzophenone, 3.0261 g (9 mmoles) of 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 0.4325 g (1 mmole) of 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and 1.6585 g (12 mmoles) of anhydrous potassium carbonate were added to a three-necked flask and mixed. Subsequently, 60 ml of N,N-dimethylacetamide and 25 ml of toluene were added as a solvent and an azeotropic agent to form a first mixed solution.

[0099] The first mixed solution was refluxed for 4 hours under a nitrogen atmosphere, and after dehydration and removal of toluene, the temperature was raised to 170°C and maintained for 20 hours. After the reaction was incubated, the solution was cooled to room temperature, the polymer was precipitated using an ethanol precipitant, and the obtained polymer was purified by five redissolution-precipitation cycles. The solution was vacuum dried at 80°C overnight to obtain a light yellow solid novel sulfonated polyaryletherketone.

[0100] The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylacetamide, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and N,N-dimethylacetamide is 5:1:10, and a casting solution is formed at 60°C.

[0101] The degassed casting solution was scraped onto the surface of the microporous PE diaphragm by an automatic film coater through a 10 μm wire rod, and then immediately placed in an ethanol coagulation bath for several hours and dried to obtain a composite diaphragm.

[0102] This comparative example also discloses a composite diaphragm, which is prepared by the above-mentioned composite diaphragm preparation method.

[0103] This comparative example also discloses a lithium battery, which includes the composite diaphragm.

[0104] Comparative Example 4:

[0105] A commercially available PE separator was used. The PE separator was purchased from Ningbo Shanshan Co., Ltd. and a lithium battery was made from the PE separator.

[0106] The formula of the above battery is:

[0107] Positive electrode (16.0 mg / cm on each side 2 ) is composed of LFP, Super P, PVDF 5130 and CNT in a weight ratio of 96:1.8:1.7:0.5. Negative electrode (10.1 mg / cm on each side 2 ) is composed of graphite, LA136D, Super P, CNT and CMC in a weight ratio of 96:2.3:0.9:0.4:0.4. The N / P value is close to 1.13. The electrolyte contains 1M L iPF6 / EC:EMC (volume ratio is 3:7). The diaphragm adopts the diaphragm prepared corresponding to the above embodiment or comparative example. All batteries use copper foil with a thickness of 6.0μm as the negative electrode current collector. The charge and discharge range is 2.5-3.6V.

[0108] The following tests were performed on the separators and lithium batteries in Examples 1, 2 and Comparative Examples 1 to 4:

[0109] Chemical composition test: The chemical composition of the separator was measured by attenuated total reflectance infrared spectroscopy (ATR-FTIR, Nicol et 6700, USA).

[0110] Tensile strength test: A universal tensile testing machine (C41.103, S insanse) was used to test the tensile strength of the separator.

[0111] Contact angle test: The contact angle of the membrane was measured by a contact angle meter (XG-CAMB3).

[0112] Membrane wetting rate test: The membrane was immersed in electrolyte at room temperature for 2 hours, and then the excess electrolyte on the membrane surface was removed with lens paper to measure the membrane weight. The electrolyte solution is composed of ethylene carbonate / diethyl carbonate / dimethyl carbonate (the volume ratio of EC / DEC / DMC is 1:1:1). Electrolyte absorption rate per hour (%) = ((mm 0 ) / m 0 )×100%, where m 0 and m are the weights of the separator before and after being immersed in the electrolyte, respectively.

[0113] Electrochemical performance test: The test was carried out at 2.5V-3.65V at a rate of 0.5C / 0.5C on a BlueDian electrochemical workstation.

[0114]

[0115] At 1472cm -1 and 720cm -1 The peaks at 2 -group bending and rocking vibration. For the PE separator with sulfonated polyaryletherketone coating, some new characteristic peaks appeared along with some other peaks originating from the initial PE separator. -1 The stretching vibration bands of C–O, C–O–C, Ar-O-Ar and Ar–CO–Ar groups were observed at 1085 cm -1 and 1029cm -1 The absorption band at 100° confirmed the sulfonic acid group of the sulfonated polyaryletherketone polymer. The above shows that Example 1 and Example 2 successfully implemented sulfonation and were evenly coated on the PE diaphragm, while Comparative Example 1 could not achieve sulfonation due to the ratio, and Comparative Example 2 and Comparative Example 3 could not achieve slurry with good fluidity and coating on PE due to the ratio, so they could not achieve even coating on PE.

[0116] The contact angle test shows that the contact angle of Example 2 is the smallest, which is mainly because the purity is higher and the performance is better as the number of cycles increases.

[0117] The wetting rate test shows that the wetting rates of Examples 1 and 2 are nearly 1 times higher than those of commercial PE diaphragms, and the battery cells can quickly absorb the electrolyte.

[0118] Electrochemical performance tests show that implementations 1 and 2 have excellent cycling performance compared to commercial PE, and this advantage will be more obvious in the later stages of the cycle.

[0119] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a battery composite diaphragm, characterized in that: The following steps are involved: Mixing a benzophenone derivative, a sulfonated aromatic compound, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, a bisphenol compound and a potassium-based alkaline catalyst, and adding a reaction medium solvent and an azeotropic agent to form a first mixed solution; The first mixed solution is subjected to reflux reaction under an inert gas, and after removing the azeotropic agent, the solution is kept warm for reaction, and after cooling, the solution is precipitated and purified to obtain a novel sulfonated polyaryletherketone; The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in a reaction medium solvent to prepare a film casting solution; The casting liquid is coated on the surface of the diaphragm, immersed in a coagulation bath of an alcohol solvent for solidification, and dried to obtain a composite diaphragm.

2. The method for preparing the composite diaphragm according to claim 1, characterized in that: The benzophenone derivative is selected from one or more of 4,40-dichlorobenzophenone and 4,40-dibromobenzophenone; The sulfonated aromatic compound is selected from one or more of sulfonated 4,40-dichlorobenzophenone sodium and sulfonated 4,40-dibromobenzophenone sodium; The bisphenol compound is a bisphenol compound containing a benzimidazole structure, and preferably, the bisphenol compound is 4,40-methylenebis[2-(1H-benzotriazole-1-yl)]phenol; The potassium-based alkaline catalyst is selected from one or more of anhydrous potassium carbonate, sodium carbonate, and potassium hydroxide; The reaction medium solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone; The azeotropic agent is selected from one or more of toluene, cyclohexane, n-pentane and ethyl acetate; The alcohol solvent is selected from one or more of ethanol, isopropanol, tert-butanol and n-propanol.

3. The method for preparing a composite diaphragm according to claim 1, characterized in that: The following steps are involved: Mixing 4,40-difluorobenzophenone, sulfonated 4,40-difluorobenzophenone sodium, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate, and adding N,N-dimethylformamide and toluene to form a first mixed solution; The first mixed solution is subjected to reflux reaction under an inert gas, and after removing toluene, the solution is subjected to heat preservation reaction, and after cooling, the solution is subjected to precipitation and purification to obtain a novel sulfonated polyaryletherketone; The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in N,N-dimethylformamide to prepare a casting solution; The casting liquid is coated on the surface of the diaphragm, immersed in an ethanol coagulation bath for solidification, and dried to obtain a composite diaphragm.

4. The method for preparing a battery composite separator according to claim 3, characterized in that: The method comprises mixing 4,40-difluorobenzophenone, sulfonated 4,40-difluorobenzophenone sodium, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate, and adding N,N-dimethylformamide and toluene to form a first mixed solution; comprising: Mix 4,40-difluorobenzophenone, sulfonated 4,40-difluorobenzophenone sodium, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate in a molar ratio of (3-5):(5-7):(8-10):1:(11-13), and add N,N-dimethylformamide and toluene to form a first mixed solution; The volume ratio of N,N-dimethylformamide and toluene is (6-8):(2-3); Preferably, the molar ratio of 4,40-difluorobenzophenone, sodium sulfonated 4,40-difluorobenzophenone, 2,20-bis(4-hydroxyphenyl)hexafluoropropane, 4,40-methylenebis[2-(1H-benzimidazol-2-yl)]phenol and anhydrous potassium carbonate is 4:6:9:1:

12.

5. The method for preparing a battery composite separator according to claim 1, characterized in that: The first mixed solution is subjected to reflux reaction under an inert gas, and after removing the entrainer, the solution is subjected to heat preservation reaction, and after cooling, the solution is precipitated and purified to obtain a novel sulfonated polyaryletherketone, comprising: The first mixed solution is refluxed under an inert gas for 4 to 6 hours, and after dehydration and removal of the entrainer, the temperature is raised to 170 to 190° C., and the reaction is carried out by heat preservation for 20 to 25 hours; After the reaction is kept at room temperature, the polymer is cooled to room temperature, a precipitant is used to precipitate the polymer, and the obtained polymer is purified and dried through a redissolution-precipitation cycle to obtain a novel sulfonated polyaryletherketone; The inert gas is selected from one or more of nitrogen, helium or argon; The precipitant is selected from one or more of ethanol, isopropanol, tert-butanol, and n-propanol; The purification comprises at least 3 redissolution-precipitation cycles; The drying temperature is 80-85°C.

6. The method for preparing a battery composite separator according to claim 1, characterized in that: The novel sulfonated polyaryletherketone and polyethylene glycol are dissolved in a reaction medium solvent to prepare a casting solution, comprising: The novel sulfonated polyaryletherketone, polyethylene glycol and a reaction medium solvent are mixed in a mass ratio of (4-20):1:(20-40) to prepare a casting solution at 60-65°C; Preferably, the mass ratio of the novel sulfonated polyaryletherketone, polyethylene glycol and reaction medium solvent is 5:1:

20.

7. The method for preparing a battery composite separator according to claim 1, characterized in that: The method comprises coating the casting liquid on the surface of the diaphragm, immersing the diaphragm in a coagulation bath of an alcohol solvent for solidification, and drying to obtain a composite diaphragm, comprising: The casting liquid is applied on the surface of the PE diaphragm by a wire rod coating process to obtain a pre-processed film; The pre-processed membrane is immersed in an ethanol coagulation bath for solidification and drying to obtain a composite membrane; Preferably, the diameter of the wire rod is 10 μm.

8. A composite diaphragm, characterized in that: The composite diaphragm is prepared by the preparation method of the battery composite diaphragm according to any one of claims 1 to 7; The surface of the composite membrane contains sulfonic acid groups, carbonyl groups, ether bonds, hexafluoropropane groups, benzimidazole groups and hydroxyl groups. The contact angle of the composite membrane is ≤10°, and the electrolyte infiltration rate of the composite membrane is ≥140% / hour.

9. A lithium battery, characterized in that: The lithium battery comprises the composite separator according to claim 8.

10. An electrical device, characterized in that: The electrical device comprises the lithium battery according to claim 9.

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