A positive electrode side composite separator and a method for manufacturing the same

Abstract

This invention relates to the field of battery separator technology, specifically to a composite separator attached to the positive electrode side and its preparation method. The Ti3C2T separator obtained by this invention via a hydrothermal method... x The material is safer to react, takes less time, and reduces the Ti3C2T content. x The material size increases the interplanar spacing. (Ti3C2T) x It has excellent hydrophilicity, and when loaded onto a nonwoven membrane, part of Ti3C2T... x It penetrates into the fibers of the nonwoven membrane wall. The negatively charged functional groups have an electrostatic attraction with lithium ions, giving the membrane excellent electrolyte affinity. Furthermore, Ti3C2T x The coating does not completely cover the pores of the nonwoven membrane, does not change the structure of the nonwoven membrane, and results in a low increase in air permeability of the composite membrane. The composite separator prepared by this invention does not use binders or other additives; the coating is loaded onto the surface of the separator, resulting in excellent air permeability. When used on the positive electrode side, the composite separator prepared by this invention can store lithium ions, thereby increasing battery capacity.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a composite separator attached to the positive electrode side and its preparation method. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries that primarily function by the movement of lithium ions between the positive and negative electrodes. A lithium-ion battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrodes are immersed in the electrolyte, and lithium ions move between them using the electrolyte as a medium, thus enabling the battery to charge and discharge. To prevent short circuits between the positive and negative electrodes through the electrolyte, a separator is used to separate them. The main functions of the separator are: to prevent internal short circuits and to provide a channel for lithium ion movement as an electrolyte carrier. The separator has a crucial impact on the operating environment, specific capacity, safety performance, and lifespan of lithium-ion batteries. Therefore, researching and developing polymer separators with excellent performance, simple manufacturing processes, and suitability for industrial production is an important direction for improving the application of lithium-ion batteries.

[0003] As the safety requirements for batteries in new energy vehicles continue to increase, higher demands are also placed on the performance of separators. Currently, the main method is to coat the separator surface with an inorganic powder coating. However, inorganic powders have poor wettability to electrolytes, and the channels on the coated separator surface are small, which will cause the battery's internal resistance to increase and its capacity to decrease.

[0004] Patent CN202110758147.7 describes the filtration of Ti3C2T on the surface of a PBC. x Aqueous dispersion, SnS2 uniformly deposited on Ti3C2T by magnetron sputtering x -PBC membrane surface, to obtain Ti3C2T x / SnS2-PBC composite separator. Ti3C2T was prepared by etching method. x Materials, utilizing polar Ti3C2T x The -OH and -F groups in the PBC membrane form strong hydrogen bonds with the hydroxyl groups, which improves the ionic conductivity of the membrane. However, the etching method requires in-situ synthesis of HF, which is dangerous.

[0005] To address the aforementioned issues and improve the wettability of powder on the membrane surface, this invention provides a composite membrane attached to the positive electrode side and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a composite separator attached to the positive electrode side and its preparation method, so as to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A Ti3C2T xPowder, the Ti3C2T x The preparation method of the powder is as follows: NaBF4 is added to HCl solution and stirred to obtain a mixed solution; Ti3AlC2 powder is added to the mixed solution and stirred for 30-40 min, followed by hydrothermal treatment. The resulting reactants are then centrifuged, washed, and then filtered with deionized water, dried, and ground. After grinding, the powder is transferred to a tube furnace, heated to 250℃, held for 2-2.5 h, and cooled to obtain Ti3C2T. x Powder.

[0009] Ideally, the mass ratio of Ti3AlC2 powder to NaBF4 is 1:(1-1.35); and the concentration of the HCl solution is 6-7 mol / L.

[0010] Ideally, the hydrothermal treatment temperature is 120-125℃ and the hydrothermal time is 3-3.5h.

[0011] A Ti3C2T x Dispersion, Ti3C2T x The method for preparing the dispersion is as follows: Take Ti3C2T x Powder, Ti3C2T x The powder was added to deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4-4.5 hours. After centrifugation, Ti3C2T was obtained. x Dispersion.

[0012] In a more optimized manner, the Ti3C2T x The concentration of the dispersion is 0.02-0.03 g / mL.

[0013] A composite separator attached to the positive electrode side, the composite separator comprising a base film and Ti3C2T x The dispersion liquid layer, the Ti3C2T x The dispersion liquid layer is composed of Ti3C2T x Obtained by coating or impregnation with dispersion; or by alumina-modified Ti3C2T x Obtained by coating or impregnation with a dispersion.

[0014] In a more optimized manner, the base film is placed in Ti3C2T x The membrane is immersed in the dispersion for 5-15 minutes, then removed and dried at 40-45℃ to obtain the composite membrane.

[0015] Ideally, the base membrane is any one or more of nonwoven membrane, PE membrane, PP membrane, and PI membrane.

[0016] In a more optimized manner, the Ti3C2T x The dispersion is alumina-modified Ti3C2T xDispersion; the alumina-modified Ti3C2T x The method for preparing the dispersion includes the following steps:

[0017] Step 1: Take Ti3C2T x The dispersion was filtered and dried to obtain Ti3C2T. x Take Ti3C2T x Sodium hydroxide aqueous solution was stirred at 25-30℃ for 2-3 hours, centrifuged, washed until the pH value was approximately 7-8, the precipitate was collected, deionized water was added, ultrasonically dispersed, centrifuged, and dried to obtain the exfoliated Ti3C2T. x ;

[0018] Step 2: Take aluminum nitrate nonahydrate and anhydrous ethanol, stir well, add deionized water and the stripped Ti3C2T x Stir for 30-40 minutes, add ammonia, stir for another 30-40 minutes, ultrasonically disperse for 1-2 hours, add methyldiethoxysilane, continue stirring for 1-2 hours, let stand, wash, filter, and activate to obtain alumina-modified Ti3C2T. x ;

[0019] Step 3: Take alumina-modified Ti3C2T x Deionized water was mixed thoroughly to obtain alumina-modified Ti3C2T. x Dispersion.

[0020] More preferably, the base membrane is a modified separator, and the preparation method of the modified separator is as follows:

[0021] S1: Take methanol and methyl acrylate, mix them evenly, and add them to the mixture; take diethylenetriamine, add it dropwise to the mixture, let it stand for 10-12 hours, raise the temperature to 140-145℃, and react for 3-5 hours to obtain the amino branched compound.

[0022] S2: Take amino-branched compound and deionized water, stir evenly, add sodium alginate, heat to 55-60℃, react for 4-5 hours to obtain a mixture of amino-branched sodium alginate; immerse the diaphragm in a beaker containing the mixture of amino-branched sodium alginate for 5-15 minutes, remove, dry to obtain the modified diaphragm.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0024] (1) The Ti3C2T obtained by the hydrothermal method in this invention x The material is safer to react, takes less time, and reduces the Ti3C2T content. x Material size increased for Ti3C2T x The interplanar spacing of the material gives it a high surface area (specific surface area of ​​8-12 μm). 2The lithium-ion transport pathway was further expanded (between / g); for Ti3C2T x Annealing the material increases the number of -O functional groups on the surface, which can accelerate lithium-ion transport, improve the conductivity of the separator, and enhance the wettability between the separator and the electrolyte.

[0025] (2)Ti3C2T x It possesses excellent hydrophilicity, and is loaded onto a nonwoven membrane using van der Waals forces and electrostatic forces, partially forming Ti3C2T. x It penetrates into the fibers of the nonwoven membrane wall. The negatively charged functional groups have an electrostatic attraction with lithium ions, giving the membrane excellent electrolyte affinity. Furthermore, Ti3C2T x It does not completely cover the pores of the nonwoven membrane, does not change the structure of the nonwoven membrane, and the composite membrane has a low increase in air permeability.

[0026] (3) The composite separator prepared by this invention does not use binders or other additives. The coating is loaded onto the surface of the separator, resulting in excellent air permeability. When used on the positive electrode side, the composite separator prepared by this invention can store lithium ions, thereby increasing battery capacity. The coating of the composite separator prepared by this invention has a high specific surface area and hydrophilic functional groups, which can improve the wettability of the separator and the electrolyte, allowing for sufficient contact with the electrolyte.

[0027] (4) The present invention also employs an exfoliation method to prepare Ti3C2T x Increased the Ti3C2T x The increased surface area exposes more hydroxyl functional groups, thus increasing the surface area of ​​Ti3C2T. x It possesses hydrophilicity and surface activity. However, due to Ti3C2T x Difficult to disperse, this invention is based on Ti3C2T x Loaded alumina particles effectively solve the Ti3C2T problem. x The problem of easy agglomeration. Furthermore, the loading of alumina particles increases Ti3C2T. x The increased surface area enhances the hydrophilicity of the membrane and improves the wettability between the membrane and the electrolyte. Further modification with methyldiethoxysilane allows for the modification of alumina-modified Ti3C2T. x It is loaded with silanol groups.

[0028] (5) Sodium alginate is a natural polysaccharide. Its molecular structure contains a large number of carboxylic acid groups and hydroxyl groups. These functional groups give it high hydrophilicity in water. Aminoation modification of sodium alginate allows the amino groups in the aminated sodium alginate to react with alumina-modified Ti3C2T. x The reaction of silanol groups on the surface enhances the alumina-modified Ti3C2T. xThe adhesion of the dispersion to the membrane further enhances its hydrophilicity. Then, an aminated sodium alginate solution is coated onto the surface of the nonwoven fabric. Sodium alginate can form a microporous structure on the surface of the nonwoven membrane, increasing its specific surface area and improving the surface hydrophilicity of the nonwoven membrane. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] There are no special restrictions on the suppliers of the raw materials involved in this invention, and exemplary suppliers include:

[0031] The dispersant is an aliphatic amide dispersant: vinyl bis-stearamide 110-30-5, provided by Wuhan Jixin Yibang Biotechnology Co., Ltd.; the binder is polyacrylic acid: ETERSO 1730, provided by Changxing Materials; the wetting agent is polyethylene glycol: provided by Shandong Ruifeng New Materials Co., Ltd.; the alumina powder: model: 199974, provided by Merck; CMC: sodium carboxymethyl cellulose, provided by Sichuan Lanyang Daily Chemical Co., Ltd.

[0032] Example 1: A method for preparing a composite separator attached to the positive electrode side, comprising the following steps:

[0033] Step 1: Ti3C2T x Preparation of dispersion:

[0034] 4g of NaBF4 was added to 20mL of 6mol / L HCl solution and stirred at 27℃. 3g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120℃ for 3h. The resulting reactants were centrifuged, washed, and the process was repeated multiple times. Then, deionized water was added for filtration, drying, and grinding to obtain Ti3C2T. x Powder; weigh 2g Ti3C2T x The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0035] Step 2: Preparation of the composite membrane:

[0036] A 20μm thick nonwoven membrane was cut to a size of 4cm×4cm and placed inside a container containing Ti3C2T. x The dispersion was immersed in a beaker for 5 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0037] Example 2: A method for preparing a composite separator attached to the positive electrode side, comprising the following steps:

[0038] Step 1: Ti3C2T x Preparation of dispersion:

[0039] 4g of NaBF4 was added to 20mL of 6mol / L HCl solution and stirred at 27℃. 4g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30min, the mixture was poured into a reaction vessel for hydrothermal treatment at 110℃ for 3h. The resulting reactants were centrifuged, washed, and the process was repeated multiple times. Then, deionized water was added for filtration, drying, and grinding to obtain Ti3C2T. x Powder; weigh 3g Ti3C2T x The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 2g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0040] Step 2: Preparation of the composite membrane:

[0041] A 20μm thick nonwoven membrane was cut to a size of 4cm×4cm and placed inside a container containing Ti3C2T. x The dispersion was immersed in a beaker for 5 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0042] Example 3: A method for preparing a composite separator attached to the positive electrode side, comprising the following steps:

[0043] Step 1: Ti3C2T x Preparation of dispersion:

[0044] 4 g of NaBF4 was added to 20 mL of 6 mol / L HCl solution and stirred at 27 °C. 3.6 g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30 min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120 °C for 3 h. The resulting reactants were centrifuged, washed, and the process was repeated several times. Then, deionized water was added, and the mixture was filtered, dried, and ground to obtain Ti3C2T. x Powder; weigh 3g Ti3C2Tx The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1.5 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0045] Step 2: Preparation of the composite membrane:

[0046] A 20μm thick nonwoven membrane was cut to a size of 4cm×4cm, sprayed evenly onto the nonwoven membrane using a spray gun, and dried at 40℃ to obtain a composite membrane.

[0047] Example 4: A method for preparing a composite separator attached to the positive electrode side, comprising the following steps:

[0048] Step 1: Ti3C2T x Preparation of dispersion:

[0049] 4 g of NaBF4 was added to 20 mL of 6 mol / L HCl solution and stirred at 27 °C. 3.6 g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30 min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120 °C for 3 h. The resulting reactants were centrifuged, washed, and the process was repeated several times. Then, deionized water was added, and the mixture was filtered, dried, and ground to obtain Ti3C2T. x Powder; weigh 3g Ti3C2T x The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1.5 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 20g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0050] Step 2: Preparation of the composite membrane:

[0051] A 20μm thick nonwoven membrane was cut to a size of 4cm×4cm and placed inside a container containing Ti3C2T. x The dispersion was immersed in a beaker for 2 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0052] Comparative Example 1: A method for preparing a composite separator attached to the positive electrode side, comprising the following steps:

[0053] Step 1: Preparation of alumina slurry:

[0054] 0.5 wt% of dispersant was added to 59.3 wt% deionized water and stirred for 30 min. Then, 30 wt% of alumina powder was added and stirred for 30 min. Next, 6 wt% of a 4% CMC aqueous solution was added, and the slurry system was uniformly dispersed using a planetary ball mill with the parameters set to 400 rpm / min and a stirring time of 1 h. Then, 4 wt% of binder was added to the above solution system, and the ball milling continued for 30 min. Finally, 0.2 wt% of wetting agent was added, and the ball milling continued for 30 min to obtain the alumina slurry.

[0055] Step 2: Cut a PE film with a thickness of 20μm to a size of 4cm×4cm, immerse it in a beaker containing alumina slurry for 2 minutes, remove it, and dry it at 40℃ to obtain a composite membrane.

[0056] Comparative Example 2: A method for preparing a composite separator attached to the positive electrode side, Ti3C2T x The method for preparing the dispersion differs, but the remaining steps are the same as in Example 1:

[0057] Step 1: Ti3C2T x Preparation of dispersion:

[0058] HCl, HF, and H₂O were mixed in a volume ratio of 7:2:1 to obtain solution A. 4g of Ti₃AlC₂ powder was slowly added to 100mL of solution A. The reaction temperature was 60℃, and the reaction time was 48h. The resulting reactants were centrifuged, washed, and the process was repeated several times. Then, deionized water was added and the mixture was filtered. The filtered product was poured into 50mL of LiCl solution and stirred for 24h. After centrifugation, washing, drying, and grinding, Ti₃C₂T₂ was obtained. x Powder; Ti3C2T x The powder and deionized water were added to a single-necked flask at a mass ratio of 1:200, an inert protective gas was introduced, and the mixture was sonicated in an ice bath for 5 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion; Ti3C2T x The dispersion was transferred into a reactor and subjected to hydrothermal treatment in a vacuum oven at a temperature of 130°C for 6 hours.

[0059] Example 5: A method for preparing a composite separator attached to the positive electrode side, comprising the following steps:

[0060] Step 1: Ti3C2T x Preparation of dispersion:

[0061] 4g of NaBF4 was added to 20mL of 6mol / L HCl solution and stirred at 27℃. 3g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120℃ for 3h. The resulting reactants were centrifuged, washed, and the process was repeated multiple times. Then, deionized water was added for filtration, drying, and grinding to obtain Ti3C2T. x Powder; weigh 2g Ti3C2T x The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0062] Step 2: Alumina-modified Ti3C2T x Preparation of dispersion:

[0063] S1: Take Ti3C2T x The dispersion was filtered and dried to obtain Ti3C2T. x Take 1g of Ti3C2T x 40 mL of 1 mol / L sodium hydroxide aqueous solution was stirred at 27 °C for 2.5 h, centrifuged, and washed until the pH was approximately 7. The precipitate was collected, 50 mL of deionized water was added, and the mixture was ultrasonically dispersed, centrifuged, and dried to obtain the exfoliated Ti3C2T. x ;

[0064] S2: Take 0.5g of aluminum nitrate nonahydrate and 30mL of anhydrous ethanol, stir well, add 120mL of deionized water and 1g of stripped Ti3C2T x Stir for 35 min, add 40 mL of ammonia water, stir for another 35 min, ultrasonically disperse for 1.5 h, add 0.5 mL of methyldiethoxysilane, continue stirring for 1.5 h, let stand, wash, filter, and activate to obtain alumina-modified Ti3C2T. x Take 1g of alumina-modified Ti3C2T x 50g of deionized water was stirred until homogeneous to obtain alumina-modified Ti3C2T. x Dispersion;

[0065] Step 3: Preparation of modified nonwoven membrane:

[0066] S1: Take 100 mL of methanol and 40 g of methyl acrylate, mix them evenly, and pour them into the mixture; take 55 mL of diethylenetriamine, add it dropwise to the mixture, let it stand for 11 h, raise the temperature to 143 °C, and react for 4 h to obtain the amino branched compound.

[0067] S2: Take 3g of amino-branched compound and 100mL of deionized water, stir well, add 2g of sodium alginate, heat to 57℃, react for 4.5h to obtain a mixture of amino-branched sodium alginate.

[0068] S3: Cut a 20μm thick nonwoven membrane to a size of 4cm×4cm, immerse it in a beaker containing a mixture of amino-modified sodium alginate for 5 minutes, remove it, dry it, and obtain the modified nonwoven membrane.

[0069] Step 4: Preparation of the composite membrane:

[0070] The modified nonwoven membrane was placed into a container filled with alumina-modified Ti3C2T. x The dispersion was immersed in a beaker for 5 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0071] Comparative Example 3: Incorrect Ti3C2T x Peeling, the remaining steps are the same as in Example 5:

[0072] Step 1: Ti3C2T x Preparation of dispersion:

[0073] 4g of NaBF4 was added to 20mL of 6mol / L HCl solution and stirred at 27℃. 3g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120℃ for 3h. The resulting reactants were centrifuged, washed, and the process was repeated multiple times. Then, deionized water was added for filtration, drying, and grinding to obtain Ti3C2T. x Powder; weigh 2g Ti3C2T x The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0074] Step 2: Alumina-modified Ti3C2T x Preparation:

[0075] S1: Take Ti3C2T x The dispersion was filtered and dried to obtain Ti3C2T. x ;

[0076] S2: Take 0.5g aluminum nitrate nonahydrate and 30mL anhydrous ethanol, stir well, add 120mL deionized water and 1g Ti3C2T xStir for 35 min, add 40 mL of ammonia water, stir for another 35 min, ultrasonically disperse for 1.5 h, add 0.5 mL of methyldiethoxysilane, continue stirring for 1.5 h, let stand, wash, filter, and activate to obtain alumina-modified Ti3C2T. x Take 1g of alumina-modified Ti3C2T x 50g of deionized water was stirred until homogeneous to obtain alumina-modified Ti3C2T. x Dispersion;

[0077] Step 3: Preparation of modified nonwoven membrane:

[0078] S1: Take 100 mL of methanol and 40 g of methyl acrylate, mix them evenly, and pour them into the mixture; take 55 mL of diethylenetriamine, add it dropwise to the mixture, let it stand for 11 h, raise the temperature to 143 °C, and react for 4 h to obtain the amino branched compound.

[0079] S2: Take 3g of amino-branched compound and 100mL of deionized water, stir well, add 2g of sodium alginate, heat to 57℃, react for 4.5h to obtain a mixture of amino-branched sodium alginate.

[0080] S3: Cut a 20μm thick nonwoven membrane to a size of 4cm×4cm, immerse it in a beaker containing a mixture of amino-modified sodium alginate for 5 minutes, remove it, dry it, and obtain the modified nonwoven membrane.

[0081] Step 4: Preparation of the composite membrane:

[0082] The modified nonwoven membrane was placed into a container filled with alumina-modified Ti3C2T. x The dispersion was immersed in a beaker for 5 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0083] Comparative Example 4: Incorrect Ti3C2T x Alumina loading was performed, and the remaining steps were the same as in Example 5:

[0084] Step 1: Ti3C2T x Preparation of dispersion:

[0085] 4g of NaBF4 was added to 20mL of 6mol / L HCl solution and stirred at 27℃. 3g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120℃ for 3h. The resulting reactants were centrifuged, washed, and the process was repeated multiple times. Then, deionized water was added for filtration, drying, and grinding to obtain Ti3C2T. x Powder; weigh 2g Ti3C2T xThe powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0086] Step 2: Ti3C2T after peeling x Preparation of dispersion:

[0087] S1: Take Ti3C2T x The dispersion was filtered and dried to obtain Ti3C2T. x Take 1g of Ti3C2T x 40 mL of 1 mol / L sodium hydroxide aqueous solution was stirred at 27 °C for 2.5 h, centrifuged, and washed until the pH was approximately 7. The precipitate was collected, 50 mL of deionized water was added, and the mixture was ultrasonically dispersed, centrifuged, and dried to obtain the exfoliated Ti3C2T. x ;

[0088] Take 1g of the exfoliated Ti3C2T x 50g of deionized water, stirred evenly, to obtain the exfoliated Ti3C2T x Dispersion;

[0089] Step 3: Preparation of modified nonwoven membrane:

[0090] S1: Take 100 mL of methanol and 40 g of methyl acrylate, mix them evenly, and pour them into the mixture; take 55 mL of diethylenetriamine, add it dropwise to the mixture, let it stand for 11 h, raise the temperature to 143 °C, and react for 4 h to obtain the amino branched compound.

[0091] S2: Take 3g of amino-branched compound and 100mL of deionized water, stir well, add 2g of sodium alginate, heat to 57℃, react for 4.5h to obtain a mixture of amino-branched sodium alginate.

[0092] S3: Cut a 20μm thick nonwoven membrane to a size of 4cm×4cm, immerse it in a beaker containing a mixture of amino-modified sodium alginate for 5 minutes, remove it, dry it, and obtain the modified nonwoven membrane.

[0093] Step 4: Preparation of the composite membrane:

[0094] The modified nonwoven membrane was placed into a container filled with alumina-modified Ti3C2T. x The dispersion was immersed in a beaker for 5 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0095] Comparative Example 5: Sodium alginate was not aminated; the remaining steps were the same as in Example 5.

[0096] Step 1: Ti3C2T x Preparation of dispersion:

[0097] 4g of NaBF4 was added to 20mL of 6mol / L HCl solution and stirred at 27℃. 3g of Ti3AlC2 powder was then added to the mixture, and after stirring for 30min, the mixture was poured into a reaction vessel for hydrothermal treatment at 120℃ for 3h. The resulting reactants were centrifuged, washed, and the process was repeated multiple times. Then, deionized water was added for filtration, drying, and grinding to obtain Ti3C2T. x Powder; weigh 2g Ti3C2T x The powder was placed in a corundum crucible and transferred to a tube furnace. The temperature was raised to 250°C and held for 2 hours. After natural cooling, 1 g of Ti3C2T was weighed out. x The powder was added to a single-necked flask with 50g of deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4 hours. The mixture was then poured into centrifuge tubes and centrifuged to obtain Ti3C2T. x Dispersion;

[0098] Step 2: Alumina-modified Ti3C2T x Preparation of dispersion:

[0099] S1: Take Ti3C2T x The dispersion was filtered and dried to obtain Ti3C2T. x Take 1g of Ti3C2T x 40 mL of 1 mol / L sodium hydroxide aqueous solution was stirred at 27 °C for 2.5 h, centrifuged, and washed until the pH was approximately 7. The precipitate was collected, 50 mL of deionized water was added, and the mixture was ultrasonically dispersed, centrifuged, and dried to obtain the exfoliated Ti3C2T. x ;

[0100] S2: Take 0.5g of aluminum nitrate nonahydrate and 30mL of anhydrous ethanol, stir well, add 120mL of deionized water and 1g of stripped Ti3C2T x Stir for 35 min, add 40 mL of ammonia water, stir for another 35 min, ultrasonically disperse for 1.5 h, add 0.5 mL of methyldiethoxysilane, continue stirring for 1.5 h, let stand, wash, filter, and activate to obtain alumina-modified Ti3C2T. x Take 1g of alumina-modified Ti3C2T x 50g of deionized water was stirred until homogeneous to obtain alumina-modified Ti3C2T. x Dispersion;

[0101] Step 3: Preparation of modified nonwoven membrane:

[0102] S2: Take 2g of sodium alginate and 100mL of deionized water, stir evenly to obtain sodium alginate dispersion;

[0103] S3: Cut a 20μm thick nonwoven membrane to a size of 4cm×4cm, immerse it in a beaker containing sodium alginate dispersion for 5 minutes, remove it, dry it, and obtain the modified nonwoven membrane.

[0104] Step 4: Preparation of the composite membrane:

[0105] The modified nonwoven membrane was placed into a container filled with alumina-modified Ti3C2T. x The dispersion was immersed in a beaker for 5 minutes, then removed and dried at 40°C to obtain a composite diaphragm.

[0106] experiment:

[0107] The composite separators prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests. The air permeability of lithium battery separators was tested according to GB / T36363-2018, and the contact angle of the composite separators was measured using a contact angle measuring instrument. The data obtained are shown in the table below:

[0108]

[0109] Conclusion: The data comparison in the table shows that the composite membrane prepared by this invention, without the use of binders or other additives, loads the coating onto the membrane surface, resulting in excellent air permeability. The composite membranes prepared in Examples 1 to 4 exhibit Ti3C2T... x Compared with Comparative Example 1, the dispersion layer has a higher specific surface area and hydrophilic functional groups, which can improve the wettability of the membrane and electrolyte, has a smaller contact angle, and results in a lower gas permeability increase in the composite membrane. Example 5: In Ti3C2T... x By loading alumina particles onto the nonwoven fabric membrane and modifying it with aminoated sodium alginate, the performance of the prepared composite membrane was further improved. (Comparative Example 3 is not related to Ti3C2T) x Peeling, Ti3C2T x The smaller surface area and fewer loaded alumina particles negatively impact the performance of the composite membrane. Comparative Example 4 does not use Ti3C2T. x Alumina loading reduced the hydrophilicity of the membrane. Comparative Example 5 did not involve amination modification with sodium alginate; instead, alumina-modified Ti3C2T... x The adhesion of the dispersion to the diaphragm becomes worse, and the hydrophilicity of the diaphragm decreases.

[0110] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 composite separator attached to the positive electrode side, characterized in that: The composite membrane is prepared by placing the base membrane into Ti3C2T x The membrane is immersed in the dispersion for 5-15 minutes, then removed and dried at 40-45℃ to obtain the composite membrane. The Ti3C2T x The dispersion is alumina-modified Ti3C2T x The dispersion is prepared by the following steps: Step 1: Take Ti3C2T x The dispersion was filtered and dried to obtain Ti3C2T. x Take Ti3C2T x Sodium hydroxide aqueous solution was stirred at 25-30℃ for 2-3 hours, centrifuged, washed until the pH was 7-8, the precipitate was collected, deionized water was added, ultrasonically dispersed, centrifuged, and dried to obtain the exfoliated Ti3C2T. x ; Step 2: Take aluminum nitrate nonahydrate and anhydrous ethanol, stir well, add deionized water and the stripped Ti3C2T x Stir for 30-40 minutes, add ammonia, stir for another 30-40 minutes, ultrasonically disperse for 1-2 hours, add methyldiethoxysilane, continue stirring for 1-2 hours, let stand, wash, filter, and activate to obtain alumina-modified Ti3C2T. x ; Step 3: Take alumina-modified Ti3C2T x Deionized water was mixed thoroughly to obtain alumina-modified Ti3C2T. x Dispersion; The base membrane is a modified separator, and the preparation method of the modified separator is as follows: S1: Take methanol and methyl acrylate, mix them evenly, and add them to the mixture; take diethylenetriamine, add it dropwise to the mixture, let it stand for 10-12 hours, raise the temperature to 140-145℃, and react for 3-5 hours to obtain the amino branched compound. S2: Take amino-branched compound and deionized water, stir evenly, add sodium alginate, heat to 55-60℃, react for 4-5 hours to obtain a mixture of amino-branched sodium alginate; immerse the diaphragm in a beaker containing the mixture of amino-branched sodium alginate for 5-15 minutes, remove, dry to obtain the modified diaphragm.

2. The composite separator attached to the positive electrode side according to claim 1, characterized in that: The base membrane is any one or more of the following: non-woven membrane, PE membrane, PP membrane, and PI membrane.

3. The composite separator attached to the positive electrode side according to claim 1, characterized in that: The Ti3C2T x The method for preparing the dispersion is as follows: Ti3C2T x The powder was added to deionized water, nitrogen gas was introduced, and the mixture was sonicated in an ice bath for 4-4.5 hours. After centrifugation, Ti3C2T was obtained. x Dispersion.

4. The composite separator attached to the positive electrode side according to claim 3, characterized in that: The Ti3C2T x The concentration of the dispersion is 0.02-0.03 g / mL.

5. The composite separator attached to the positive electrode side according to claim 3, characterized in that: The Ti3C2T x The powder preparation method is as follows: NaBF4 is added to HCl solution and stirred to obtain a mixed solution; Ti3AlC2 powder is added to the mixed solution and stirred for 30-40 min, followed by hydrothermal treatment. The resulting reactants are then centrifuged, washed, and then filtered with deionized water, dried, and ground. After grinding, the powder is transferred to a tube furnace, heated to 250℃, held for 2-2.5 h, and cooled to obtain Ti3C2T. x Powder.

6. The composite separator attached to the positive electrode side according to claim 5, characterized in that: The mass ratio of Ti3AlC2 powder to NaBF4 is 1:(1-1.35); the concentration of the HCl solution is 6-7 mol / L.

7. A composite separator attached to the positive electrode side according to claim 5, characterized in that: The hydrothermal treatment temperature is 120-125℃, and the hydrothermal time is 3-3.5h.

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