A dry electrode for hybrid capacitor and preparation method thereof

Abstract

The present invention relates to the technical field of lithium-ion battery membranes, specifically a dry-process electrode for hybrid capacitors and a preparation method thereof. The method comprises the following steps: Step 1: Mixing a modified active material, a conductive agent, and a composite binder, stirring, and fibrillating to obtain a dry mixture; Step 2: Granulating the dry mixture, classifying, and roller-pressing to obtain a dry self-supporting membrane; Step 3: Roll-compounding the dry self-supporting membrane with a current collector; thereby obtaining a dry-process electrode for hybrid capacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery membranes, in particular to a dry-process electrode for a hybrid capacitor and a preparation method thereof. Background Art

[0002] With the rapid development of the lithium battery industry, people's pursuit of battery performance is gradually increasing. Currently, most wet preparation processes are used, which have the following problems: First, organic solvents such as NMP are often used, which are highly toxic, difficult to recycle, and have slow volatilization. Second, the drying process suffers from high energy consumption, low efficiency, and uneven coating. Third, during the preparation process, the slurry suffers from poor stability and dispersibility, which limits the conductive performance.

[0003] Therefore, dry electrode preparation technology has become a hot research topic at this stage. In dry electrode preparation, fibrillation is a key process. It mainly uses mechanical shear force to stretch the PVDF molecular chains to form a continuous fiber network. This network is interspersed between the active material and the conductive agent particles, forming a three-dimensional interwoven structure, thereby achieving a self-supporting film of the electrode material under solvent-free conditions. The fibrillation efficiency directly affects the electrode's porosity, mechanical strength, and the formation of ion transport channels.

[0004] At present, the preparation of dry electrodes has the following problems: First, traditional PVDF is not compatible with the polarity of the active material, and the fibrillation process is prone to large pores and poor compactness, low fiber formation efficiency, and poor network continuity; second, traditional PVDF has insufficient chemical compatibility with active materials and lacks a dynamic repair mechanism, resulting in a greatly reduced cycle life; third, the traditional fiber network only serves as a physical support and has not been chemically modified for lithium ion transmission, resulting in poor conductivity; fourth, the active material has the problems of high strength and easy agglomeration, resulting in large voids, decreased compactness, mechanical properties, adhesion, and battery performance.

[0005] In summary, it is of great significance to solve the above problems and prepare a dry electrode for hybrid capacitors. Summary of the Invention

[0006] The object of the present invention is to provide a dry electrode for a hybrid capacitor and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for preparing a dry electrode for a hybrid capacitor comprises the following steps:

[0009] Step 1: Mixing the modified active material, the conductive agent, and the composite binder, stirring, and fibrillating to obtain a dry mixture;

[0010] Step 2: Granulate the dry mixture, grade and roll-press to obtain a dry self-supporting film;

[0011] Step 3: Roll-compound the dry self-supporting film and the current collector (aluminum foil) to obtain a dry electrode.

[0012] More optimally, among the raw materials in the dry mix, the mass ratio of the modified active material, the conductive agent, and the composite binder is 90~95:0.5~1:3~6.

[0013] More optimally, the preparation process of the composite adhesive is:

[0014] S1-1: Add dimethyldichlorosilane, trifluoropropylmethyldichlorosilane, and methylhydrogendichlorosilane to toluene-deionized water, stir at -2-0°C for 1-3 hours under a nitrogen atmosphere, then add trifluoromethanesulfonic acid, react at 40-50°C for 2-6 hours under a nitrogen atmosphere, neutralize, purify, wash, and dry to obtain a fluorinated linear polysiloxane;

[0015] S1-2: Under a nitrogen atmosphere, a fluorinated linear polysiloxane, an allyl-modified cyclodextrin, allyl glycidyl ether, bisallyloxymethyl 18-crown-6, and a Karstedt catalyst were added to tetrahydrofuran, reacted at 40-60°C for 3-5 hours, filtered, and dried to obtain an epoxy-terminated modified polymer;

[0016] S1-3: adding epoxy-terminated modified polymer, ethylenediamine, and triethylamine to N,N-dimethylformamide, reacting at 60-80°C for 6-9 hours, adding α-lipoic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 4-dimethylaminopyridine under nitrogen atmosphere, reacting at 30-40°C for 12-24 hours, washing, and drying to obtain a modified binder;

[0017] S1-4: Compounding the modified binder, PVDF, and fluorinated acrylate copolymer to obtain a composite binder.

[0018] In a further embodiment, in the toluene-deionized water, the mass ratio of toluene to deionized water is 19-20:1.

[0019] More optimally, the raw materials of the composite adhesive include a modified adhesive, PVDF, and a fluorinated acrylate copolymer in a mass ratio of 1:5-8:0.05-0.2.

[0020] More optimally, the raw materials of the modified binder include the following components: 8 to 12 parts by mass of epoxy-terminated modified polymer, 1.5 to 2 parts of ethylenediamine, 0.1 to 0.2 parts of triethylamine, 1.5 to 2.5 parts of α-lipoic acid, 1.5 to 2 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 0.2 to 0.4 parts of 4-dimethylaminopyridine;

[0021] The raw materials of the epoxy-terminated modified polymer include the following components, calculated by mass: 5-7 parts of dimethyldichlorosilane, 4-6 parts of trifluoropropylmethyldichlorosilane, 3-5 parts of methylhydrogendichlorosilane, 0.5-1 part of trifluoromethanesulfonic acid, 9-10.5 parts of allyl-modified cyclodextrin, 2-3 parts of allyl glycidyl ether, 2.5-3.5 parts of bisallyloxymethyl 18-crown-6, and 0.2-0.4 parts of Karstedt catalyst.

[0022] In a further scheme, the preparation process of the allyl-modified cyclodextrin is as follows: under a nitrogen atmosphere, β-cyclodextrin, sodium hydroxide, and 3-bromopropylene are added to dimethyl sulfoxide, stirred at 30-60°C for 10-14 hours, filtered, and then sodium hydride, dimethyl sulfoxide, and iodomethane are added, reacted at 30-60°C for 2-4 hours, purified and washed to obtain the allyl-modified cyclodextrin.

[0023] In a further embodiment, the raw materials containing allyl-modified cyclodextrin include the following components: 4 to 5 parts of β-cyclodextrin, 0.2 to 0.26 parts of sodium hydroxide, 1 to 3 parts of 3-bromopropylene, 0.2 to 0.5 parts of sodium hydride, and 0.8 to 1.5 parts of iodomethane, calculated by mass.

[0024] More optimally, the preparation process of the modified active material is as follows: S2-1: adding lithium iron phosphate powder and aluminum isopropoxide to ethanol, stirring at 65-75°C until dry, calcining at 450-550°C under argon atmosphere for 0.5-1.5h, and cooling to obtain alumina-coated lithium iron phosphate;

[0025] S2-2: Add alumina-coated lithium iron phosphate and fluoride to methanol-ethanol, ultrasonically disperse, dry, and calcine at 250-350°C for 0.5-1.5h under argon atmosphere to obtain a modified active material.

[0026] In a further embodiment, the mass ratio of methanol to ethanol in the methanol-ethanol is 1:1-1.2.

[0027] More optimally, in the raw materials of the modified active material, fluoride accounts for 0.5-1.5 wt % of the alumina-coated lithium iron phosphate; in the raw materials of the alumina-coated lithium iron phosphate, aluminum isopropoxide accounts for 1-3 wt % of the lithium iron phosphate powder.

[0028] In a further embodiment, the fluoride includes one or more of lithium fluoride, aluminum fluoride, magnesium fluoride, and calcium fluoride.

[0029] More optimally, the thickness of the dry-process self-supporting film is 40 μm to 200 μm.

[0030] More optimally, the stirring speed is 15~30m / s, and the time is 3~5min; the fibrillation temperature is 10~19°C; the granulation speed is 2.5~4.5m / s, and the time is 3~5min; the temperature of the graded roller pressing is 100~135°C, and the differential speed ratio of each roller is 1.2~1.5; the temperature of the roller pressing compounding is 100~135°C, and the speed is 20~40r / min.

[0031] In a further embodiment, the conductive agent includes one or more of graphene, carbon nanotubes, and conductive carbon black.

[0032] In a further solution, the graded rolling adopts a four-stage rolling and secondary circulation process; the roller gaps of each level in the first rolling are 1200μm, 800μm, 400μm, and 300μm respectively, and the roller gap in the secondary circulation is increased by 280μm.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This solution combines composite binders with modified active materials to synergistically promote fibrillation efficiency, reduce porosity, and obtain dry-process electrodes with dense structure, strong adhesion, and high mechanical strength. The cycle life and conductivity of the prepared batteries are also improved.

[0035] The composite binder is created by mixing the modified binder with traditional PVDF and a fluorinated acrylate copolymer in a specific mass ratio. The fluorinated acrylate acts as a compatibilizer to reduce interfacial tension, allowing the binder to be evenly distributed on the surface of the active material. The three factors work together to further improve fibrillation efficiency.

[0036] In the preparation of the modified binder, fluorinated linear polysiloxane is used as the base. Compared with traditional spherical polysiloxane, linear fluorinated linear polysiloxane has higher viscosity and strength. Its fluorinated groups form intermolecular hydrogen bonds with the fluorine atoms of PVDF, increasing its compatibility with traditional PVDF. At the same time, the introduction of fluorinated silicone as a flexible chain segment can alleviate the volume expansion stress during the electrode cycle and improve the cycle life.

[0037] However, there is still a polarity difference between linear fluorinated linear polysiloxane and traditional PVDF, which leads to gaps and reduced electrode compactness. To solve this problem, the scheme uses hydrosilylation to graft cyclodextrin onto the silicon-oxygen chain segment to further reduce the polarity difference. At the same time, the hydrophobic cavity of cyclodextrin encompasses the organic groups on the surface of lithium iron phosphate, further reducing the gap and improving the compactness.

[0038] However, despite improving the tightness of the electrode, the binder still has problems with ion transport efficiency, resulting in reduced battery conductivity. To address this issue, the solution simultaneously grafted crown ether groups. On the one hand, its macrocyclic structure can complex with lithium ions, providing more ion transport channels and improving conductivity. On the other hand, crown ethers can form van der Waals forces with traditional PVDF, further improving adhesion.

[0039] However, during the battery's charge and discharge cycles, the pole pieces generate periodic stress due to the volume expansion of the active material. Traditional linear binder segments lack reversible crosslinking points. As the use time increases, the stress accumulates to a certain level, causing molecular chain breakage and film cracking. This can cause the active material to fall off, significantly reducing conductive properties such as cycle life. To address this issue, the proposed solution introduces α-lipoic acid into the binder backbone through epoxyamino ring opening and amidation reactions, forming a dynamic disulfide bond network. On the one hand, the disulfide bonds achieve reversible breakage through the dynamic network, avoiding stress concentration segment breakage, greatly improving adhesion and cycle life. On the other hand, during the fibrillation process, the disulfide bonds promote entanglement of the fiber network, allowing for re-crosslinking, fixing the fibrillated structure, and improving fibrillation efficiency.

[0040] To reduce the strength of the active material, improve its dispersibility, and address the agglomeration problem, the proposed method uses aluminum oxide to coat lithium iron phosphate and dope it with fluorine. This approach offers the following advantages: First, aluminum oxide has high chemical stability and excellent mechanical properties. When coated on the surface of lithium iron phosphate, it effectively inhibits particle agglomeration, alleviates volume change stress during charge and discharge, and reduces particle breakage. Second, aluminum oxide forms hydrogen or chemical bonds with the hydroxyl groups on the lithium iron phosphate surface, increasing interfacial forces with PVDF, improving compatibility, and ensuring uniform dispersion of the lithium iron phosphate during fibrillation, thereby increasing electrode density. Second, fluorine-doped aluminum oxide exhibits enhanced durability and charge retention, further improving cycle stability. It is important to note that the amount of aluminum oxide formed needs to be controlled. When aluminum isopropoxide accounts for less than 1wt% of the lithium iron phosphate powder, the aluminum oxide layer fails to fully cover the lithium iron phosphate particles, resulting in increased agglomeration. When aluminum isopropoxide accounts for more than 3wt% of the lithium iron phosphate powder, the aluminum oxide layer becomes too thick, reducing ion transport. DETAILED DESCRIPTION

[0041] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] It should be noted that the following parts are by mass, and all raw materials involved in the present invention are purchased from manufacturers without any special restrictions. Examples include: In the following examples, bisallyloxymethyl 18-crown-6 was purchased from Shanghai Yichen Chemical Raw Materials Co., Ltd.; the CAS number of dimethyldichlorosilane is 75-78-5; the CAS number of trifluoropropylmethyldichlorosilane is 870-56-4; the CAS number of methylhydrodichlorosilane is 75-54-7; the CAS number of allyl glycidyl ether is 106-92-3; the CAS number of Karstedt catalyst is 81032-58-8; the CAS number of α-lipoic acid is 107 7-28-7; 1-ethyl-(3-dimethylaminopropyl)carbodiimide has a CAS number of 25952-53-8; 4-dimethylaminopyridine has a CAS number of 1122-58-3; PVDF; the mass content of fluorinated acrylate in the fluorinated acrylate copolymer is 22%; β-cyclodextrin has a CAS number of 7585-39-9; 3-bromopropylene has a CAS number of 106-95-6; sodium hydride has a CAS number of 7646-69-7; iodomethane has a CAS number of 74-88-4; the particle size of the lithium iron phosphate powder is 10 μm; the D50 value of the conductive carbon black is 150 nm, and the specific surface area is 60 m 2 / g; the product number of spherical polysiloxane is BT-9100.

[0043] The following plans, special instructions:

[0044] The preparation process of cyclodextrin modified with allyl groups is as follows: under a nitrogen atmosphere, 4.5 parts of β-cyclodextrin, 0.23 parts of sodium hydroxide, and 2 parts of 3-bromopropylene are added to dimethyl sulfoxide, stirred at 45°C for 12 hours, filtered, and then 0.35 parts of sodium hydride, dimethyl sulfoxide, and 1.2 parts of iodomethane are added, reacted at 45°C for 3 hours, purified and washed to obtain cyclodextrin modified with allyl groups;

[0045] Toluene-deionized water includes toluene and deionized water in a mass ratio of 19.5:1;

[0046] Methanol-ethanol includes methanol and ethanol in a mass ratio of 1:1.1.

[0047] Example 1: A method for preparing a dry electrode for a hybrid capacitor, comprising the following steps:

[0048] Step 1: Preparation process of composite binder: S1-1: 6 parts of dimethyldichlorosilane, 5 parts of trifluoropropylmethyldichlorosilane, and 4 parts of methylhydrogendichlorosilane were added to toluene-deionized water, stirred at -1°C for 2h under nitrogen atmosphere, and then 0.8 parts of trifluoromethanesulfonic acid were added. The mixture was reacted at 45°C for 4h under nitrogen atmosphere, neutralized, purified, washed, and dried to obtain fluorinated linear polysiloxane; S1-2: Under nitrogen atmosphere, fluorinated linear polysiloxane, 9.8 parts of allyl-modified cyclodextrin, 2.5 parts of allyl glycidyl ether, 3 parts of bisallyloxymethyl 18-crown-6, and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran, stirred at 5 The mixture was reacted at 0°C for 4 hours, filtered and dried to obtain an epoxy-terminated modified polymer; S1-3: 10 parts of epoxy-terminated modified polymer, 1.8 parts of ethylenediamine and 0.15 parts of triethylamine were added to N,N-dimethylformamide, and the mixture was reacted at 70°C for 7.5 hours. Under a nitrogen atmosphere, 2 parts of α-lipoic acid, 1.8 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.3 parts of 4-dimethylaminopyridine were added, and the mixture was reacted at 35°C for 18 hours. The mixture was washed and dried to obtain a modified adhesive; S1-4: the modified adhesive, PVDF and fluorinated acrylate copolymer were compounded in a mass ratio of 1:6.5:0.12 to obtain a composite adhesive;

[0049] Step 2: S2-1: Add lithium iron phosphate powder and aluminum isopropoxide to ethanol, stir at 70°C until dry, calcine at 500°C for 1 hour under argon atmosphere, and cool. The aluminum isopropoxide accounts for 2wt% of the lithium iron phosphate powder to obtain alumina-coated lithium iron phosphate; S2-2: Add alumina-coated lithium iron phosphate and lithium fluoride to methanol-ethanol, ultrasonically disperse, dry, and calcine at 300°C for 1 hour under argon atmosphere. The fluoride accounts for 1wt% of the alumina-coated lithium iron phosphate to obtain a modified active material;

[0050] Step 3: The modified active material, conductive carbon black, and composite binder were mixed in a mass ratio of 92:0.8:4.5, stirred at a stirring speed of 22 m / s for 4 minutes, and fibrillated at 19° C. for 12 minutes to obtain a dry mixture;

[0051] Step 4: The dry mixture was granulated at a speed of 3.5 m / s for 4 minutes, and then a four-stage roller pressing and secondary circulation process was adopted. The roller gaps of each stage of the first rolling were set to 1200 μm, 800 μm, 400 μm, and 300 μm, respectively. The roller gap of the secondary circulation was increased by 280 μm. At 125°C, the rollers were graded and pressed with a differential speed ratio of 1.3 at each stage to obtain a dry self-supporting film with a thickness of 120 μm.

[0052] Step 5: The dry-process self-supporting film and the aluminum foil were rolled together at 125°C and 30 r / min for 3 minutes to obtain a dry-process electrode.

[0053] Example 2: A method for preparing a dry electrode for a hybrid capacitor, comprising the following steps:

[0054] Step 1: Preparation process of composite binder: S1-1: 6 parts of dimethyldichlorosilane, 5 parts of trifluoropropylmethyldichlorosilane, and 4 parts of methylhydrogendichlorosilane were added to toluene-deionized water, stirred at -1°C for 2h under nitrogen atmosphere, then 0.8 parts of trifluoromethanesulfonic acid were added, reacted at 45°C for 4h under nitrogen atmosphere, neutralized, purified, washed, and dried to obtain fluorinated linear polysiloxane; S1-2: Under nitrogen atmosphere, fluorinated linear polysiloxane, 9.8 parts of allyl-modified cyclodextrin, 2.5 parts of allyl glycidyl ether, 3 parts of bisallyloxymethyl 18-crown-6, and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran, and The mixture was reacted at 50°C for 4 hours, filtered and dried to obtain an epoxy-terminated modified polymer; S1-3: 10 parts of epoxy-terminated modified polymer, 1.8 parts of ethylenediamine and 0.15 parts of triethylamine were added to N,N-dimethylformamide, and the mixture was reacted at 70°C for 7.5 hours. Under a nitrogen atmosphere, 2 parts of α-lipoic acid, 1.8 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.3 parts of 4-dimethylaminopyridine were added, and the mixture was reacted at 35°C for 18 hours. The mixture was washed and dried to obtain a modified adhesive; S1-4: the modified adhesive, PVDF and fluorinated acrylate copolymer were compounded in a mass ratio of 1:5:0.05 to obtain a composite adhesive;

[0055] Step 2: S2-1: Add lithium iron phosphate powder and aluminum isopropoxide to ethanol, stir at 70°C until dry, calcine at 500°C for 1 hour under argon atmosphere, and cool. The aluminum isopropoxide accounts for 1wt% of the lithium iron phosphate powder to obtain alumina-coated lithium iron phosphate; S2-2: Add alumina-coated lithium iron phosphate and lithium fluoride to methanol-ethanol, ultrasonically disperse, dry, and calcine at 300°C for 1 hour under argon atmosphere. The fluoride accounts for 0.5wt% of the alumina-coated lithium iron phosphate to obtain a modified active material;

[0056] Step 3: The modified active material, conductive carbon black, and composite binder were mixed in a mass ratio of 90:0.5:3, stirred at a stirring speed of 22 m / s for 4 minutes, and fibrillated at 19° C. for 12 minutes to obtain a dry mixture;

[0057] Step 4: The dry mixture was granulated at a speed of 3.5 m / s for 4 minutes, and then a four-stage roller pressing and secondary circulation process was adopted. The roller gaps of each stage of the first rolling were set to 1200 μm, 800 μm, 400 μm, and 300 μm, respectively. The roller gap of the secondary circulation was increased by 280 μm. At 125°C, the rollers were graded and pressed with a differential speed ratio of 1.3 at each stage to obtain a dry self-supporting film with a thickness of 40 μm.

[0058] Step 5: The dry-process self-supporting film and the aluminum foil were rolled together at 125°C and 30 r / min for 3 minutes to obtain a dry-process electrode.

[0059] Example 3: A method for preparing a dry electrode for a hybrid capacitor, comprising the following steps:

[0060] Step 1: Preparation process of composite binder: S1-1: 6 parts of dimethyldichlorosilane, 5 parts of trifluoropropylmethyldichlorosilane, and 4 parts of methylhydrogendichlorosilane were added to toluene-deionized water, stirred at -1°C for 2h under nitrogen atmosphere, then 0.8 parts of trifluoromethanesulfonic acid were added, reacted at 45°C for 4h under nitrogen atmosphere, neutralized, purified, washed, and dried to obtain fluorinated linear polysiloxane; S1-2: Under nitrogen atmosphere, fluorinated linear polysiloxane, 9.8 parts of allyl-modified cyclodextrin, 2.5 parts of allyl glycidyl ether, 3 parts of bisallyloxymethyl 18-crown-6, and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran, and The mixture was reacted at 50°C for 4 hours, filtered and dried to obtain an epoxy-terminated modified polymer; S1-3: 10 parts of epoxy-terminated modified polymer, 1.8 parts of ethylenediamine and 0.15 parts of triethylamine were added to N,N-dimethylformamide, and the mixture was reacted at 70°C for 7.5 hours. Under a nitrogen atmosphere, 2 parts of α-lipoic acid, 1.8 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.3 parts of 4-dimethylaminopyridine were added, and the mixture was reacted at 35°C for 18 hours. The mixture was washed and dried to obtain a modified adhesive; S1-4: the modified adhesive, PVDF and fluorinated acrylate copolymer were compounded in a mass ratio of 1:8:0.2 to obtain a composite adhesive;

[0061] Step 2: S2-1: Add lithium iron phosphate powder and aluminum isopropoxide to ethanol, stir at 70°C until dry, calcine at 500°C for 1 hour under argon atmosphere, and cool. The aluminum isopropoxide accounts for 3wt% of the lithium iron phosphate powder to obtain alumina-coated lithium iron phosphate; S2-2: Add alumina-coated lithium iron phosphate and lithium fluoride to methanol-ethanol, ultrasonically disperse, dry, and calcine at 300°C for 1 hour under argon atmosphere. The fluoride accounts for 1.5wt% of the alumina-coated lithium iron phosphate to obtain a modified active material;

[0062] Step 3: The modified active material, conductive carbon black, and composite binder were mixed in a mass ratio of 95:1:6, stirred at a stirring speed of 22 m / s for 4 minutes, and fibrillated at 19° C. for 12 minutes to obtain a dry mixture;

[0063] Step 4: The dry mixture was granulated at a speed of 3.5 m / s for 4 minutes, and then a four-stage roller pressing and secondary circulation process was adopted. The roller gaps of each stage of the first rolling were set to 1200 μm, 800 μm, 400 μm, and 300 μm, respectively. The roller gap of the secondary circulation was increased by 280 μm. At 125°C, the rollers were graded and pressed with a differential speed ratio of 1.3 at each stage to obtain a dry self-supporting film with a thickness of 200 μm.

[0064] Step 5: The dry-process self-supporting film and the aluminum foil were rolled together at 125°C and 30 r / min for 3 minutes to obtain a dry-process electrode.

[0065] Comparative Example 1: Based on Example 1, α-lipoic acid was not added to the modified additive for modification, and the remaining processes remained unchanged, and were adjusted as follows:

[0066] Step 1: Preparation process of composite binder: S1-1: 6 parts of dimethyldichlorosilane, 5 parts of trifluoropropylmethyldichlorosilane, and 4 parts of methylhydrogendichlorosilane were added to toluene-deionized water, stirred at -1 ° C for 2 hours under nitrogen atmosphere, and then 0.8 parts of trifluoromethanesulfonic acid were added. The mixture was reacted at 45 ° C for 4 hours under nitrogen atmosphere, neutralized, purified, washed, and dried to obtain fluorinated linear polysiloxane; S1-2: Under nitrogen atmosphere, fluorinated linear polysiloxane, 9.8 parts of allyl-modified cyclodextrin, 2.5 parts of allyl glycidyl ether, and 3 parts of bisallyloxymethyl 18-crown-6 and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran, reacted at 50°C for 4 hours, filtered and dried to obtain an epoxy-terminated modified polymer; S1-3: 10 parts of epoxy-terminated modified polymer, 1.8 parts of ethylenediamine and 0.15 parts of triethylamine were added to N,N-dimethylformamide, reacted at 70°C for 7.5 hours, washed and dried to obtain a modified adhesive; S1-4: The modified adhesive, PVDF and fluorinated acrylate copolymer were compounded in a mass ratio of 1:6.5:0.12 to obtain a composite adhesive.

[0067] Comparative Example 2: Based on Example 1, lithium fluoride was not added to the modified active material for modification, and the remaining processes remained unchanged, and were adjusted as follows:

[0068] Step 2: Add lithium iron phosphate powder and aluminum isopropoxide to ethanol, stir at 70°C until dry, calcine at 500°C for 1 hour under argon atmosphere, and cool. The aluminum isopropoxide accounts for 2wt% of the lithium iron phosphate powder to obtain a modified active material.

[0069] Comparative Example 3: Based on Example 1, the bisallyloxymethyl 18-crown-6 grafting agent was not added to the modified additive, and the other processes remained unchanged, and were adjusted as follows:

[0070] Step 1: Preparation process of composite binder: S1-1: 6 parts of dimethyldichlorosilane, 5 parts of trifluoropropylmethyldichlorosilane, and 4 parts of methylhydrogendichlorosilane were added to toluene-deionized water, stirred at -1°C for 2 hours under a nitrogen atmosphere, and then 0.8 parts of trifluoromethanesulfonic acid were added. The mixture was reacted at 45°C for 4 hours under a nitrogen atmosphere, neutralized, purified, washed, and dried to obtain fluorinated linear polysiloxane; S1-2: Under a nitrogen atmosphere, fluorinated linear polysiloxane, 9.8 parts of allyl-modified cyclodextrin, 2.5 parts of allyl glycidyl ether, and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran and reacted at 50°C for 4 hours. , filtered and dried to obtain an epoxy-terminated modified polymer; S1-3: 9 parts of epoxy-terminated modified polymer, 1.8 parts of ethylenediamine, and 0.15 parts of triethylamine were added to N,N-dimethylformamide, and the mixture was reacted at 70°C for 7.5 hours. Under a nitrogen atmosphere, 2 parts of α-lipoic acid, 1.8 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 0.3 parts of 4-dimethylaminopyridine were added, and the mixture was reacted at 35°C for 18 hours. The mixture was washed and dried to obtain a modified adhesive; S1-4: The modified adhesive, PVDF, and fluorinated acrylate copolymer were compounded in a mass ratio of 1:6.5:0.12 to obtain a composite adhesive.

[0071] Comparative Example 4: Based on Example 1, conventional spherical polysiloxane was used, and the remaining processes remained unchanged, and the process was adjusted to:

[0072] Step 1: Preparation process of composite binder: S1-1: Under nitrogen atmosphere, 5 parts of spherical polysiloxane, 9.8 parts of allyl modified cyclodextrin, 2.5 parts of allyl glycidyl ether, 3 parts of bisallyloxymethyl 18-crown-6, and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran, reacted at 50°C for 4 hours, filtered and dried to obtain epoxy end-capped modified polymer; S1-2: 10 parts of epoxy end-capped modified polymer, 1.8 parts of ethylenediamine, 0.15 1.5 parts of triethylamine are added to N,N-dimethylformamide, and the mixture is reacted at 70°C for 7.5 hours. Under a nitrogen atmosphere, 2 parts of α-lipoic acid, 1.8 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 0.3 parts of 4-dimethylaminopyridine are added, and the mixture is reacted at 35°C for 18 hours. The mixture is washed and dried to obtain a modified binder. S1-3: The modified binder, PVDF, and a fluorinated acrylate copolymer are compounded in a mass ratio of 1:6.5:0.12 to obtain a composite binder.

[0073] Comparative Example 5: Based on Example 1, the content of aluminum isopropoxide in the modified active material was reduced, and the other processes remained unchanged, and were adjusted as follows:

[0074] Step 2: S2-1: Add lithium iron phosphate powder and aluminum isopropoxide to ethanol, stir at 70°C until dry, calcine at 500°C for 1 hour under argon atmosphere, cool, and aluminum isopropoxide accounts for 0.5wt% of the lithium iron phosphate powder to obtain alumina-coated lithium iron phosphate; S2-2: Add alumina-coated lithium iron phosphate and lithium fluoride to methanol-ethanol, ultrasonically disperse, dry, and calcine at 300°C for 1 hour under argon atmosphere. Fluoride accounts for 1wt% of the alumina-coated lithium iron phosphate; obtain modified active material.

[0075] Comparative Example 6: Based on Example 1, no allyl-modified cyclodextrin was added to the modified additive, and the remaining processes remained unchanged, and were adjusted as follows:

[0076] Step 1: Preparation process of composite binder: S1-1: 6 parts of dimethyldichlorosilane, 5 parts of trifluoropropylmethyldichlorosilane, and 4 parts of methylhydrogendichlorosilane were added to toluene-deionized water, stirred at -1°C for 2 hours under a nitrogen atmosphere, and then 0.8 parts of trifluoromethanesulfonic acid were added. The mixture was reacted at 45°C for 4 hours under a nitrogen atmosphere, neutralized, purified, washed, and dried to obtain fluorinated linear polysiloxane; S1-2: Under a nitrogen atmosphere, fluorinated linear polysiloxane, 2.5 parts of allyl glycidyl ether, 3 parts of bisallyloxymethyl 18-crown-6, and 0.3 parts of Karstedt catalyst were added to tetrahydrofuran and reacted at 50°C for 4 hours. Filter and dry to obtain an epoxy-terminated modified polymer; S1-3: add 8 parts of epoxy-terminated modified polymer, 1.8 parts of ethylenediamine, and 0.15 parts of triethylamine to N,N-dimethylformamide, and react at 70°C for 7.5 hours. Under a nitrogen atmosphere, add 1.8 parts of α-lipoic acid, 1.5 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 0.3 parts of 4-dimethylaminopyridine, and react at 35°C for 18 hours. Wash and dry to obtain a modified adhesive; S1-4: compound the modified adhesive, PVDF, and fluorine-containing acrylate copolymer in a mass ratio of 1:6.5:0.12 to obtain a composite adhesive.

[0077] Test experiment 1: The dry electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were subjected to performance tests on their compaction density and peel strength: (1) Compaction density: The dry electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were tested for pole piece mass and pole piece volume, and the results were calculated according to the formula: compaction density = pole piece mass / pole piece volume. The results are shown in Table 1; (2) Peel strength: The dry electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were tested with reference to the ASTM D3330 standard. The results are shown in Table 1.

[0078] Table 1

[0079]

[0080] Test Experiment 2: The dry-process electrodes prepared in Examples 1-3 and Comparative Examples 1-6 were used as positive electrodes and laminated with the negative electrodes, followed by hot pressing and cold pressing to produce soft-pack batteries. The resistance performance and cycle life of the batteries were tested in turn; the results are shown in Table 2.

[0081] Table 2

[0082]

[0083] Result analysis: According to the data analysis of Tables 1 and 2, it can be seen that the present application and the present scheme, through the synergistic effect of the composite binder and the modified active material, use fluorinated linear polysiloxane as the base to graft cyclodextrin and crown ether and introduce a dynamic disulfide bond network, and at the same time use alumina doped with fluorine to wrap the active material, thereby solving the problems of large interface gap, poor ion transport and insufficient mechanical strength of traditional dry-process electrodes, significantly improving the compactness of the electrode, and achieving synergistic enhancement of structural stability and electrochemical performance through dynamic crosslinking and interface optimization.

[0084] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a dry electrode for a hybrid capacitor, characterized by: The following steps are involved: Step 1: Mixing the modified active material, the conductive agent, and the composite binder, stirring, and fibrillating to obtain a dry mixture; Step 2: Granulate the dry mixture, grade and roll-press to obtain a dry self-supporting film; Step 3: Roll-pressing the dry-process self-supporting film and the current collector to obtain a dry-process electrode; Among the raw materials in the dry mix, the mass ratio of the modified active material, the conductive agent, and the composite binder is 90-95:0.5-1:3-6; Wherein, the preparation process of the composite adhesive is: S1-1: Add dimethyldichlorosilane, trifluoropropylmethyldichlorosilane, and methylhydrogendichlorosilane to toluene-deionized water, stir at -2-0°C for 1-3 hours under a nitrogen atmosphere, then add trifluoromethanesulfonic acid, react at 40-50°C for 2-6 hours under a nitrogen atmosphere, neutralize, purify, wash, and dry to obtain a fluorinated linear polysiloxane; S1-2: Under a nitrogen atmosphere, a fluorinated linear polysiloxane, an allyl-modified cyclodextrin, allyl glycidyl ether, bisallyloxymethyl 18-crown-6, and a Karstedt catalyst were added to tetrahydrofuran, reacted at 40-60°C for 3-5 hours, filtered, and dried to obtain an epoxy-terminated modified polymer; S1-3: adding epoxy-terminated modified polymer, ethylenediamine, and triethylamine to N,N-dimethylformamide, reacting at 60-80°C for 6-9 hours, adding α-lipoic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 4-dimethylaminopyridine under nitrogen atmosphere, reacting at 30-40°C for 12-24 hours, washing, and drying to obtain a modified binder; S1-4: compounding the modified binder, PVDF, and fluorinated acrylate copolymer to obtain a composite binder; The raw materials of the composite adhesive include a modified adhesive, PVDF, and a fluorinated acrylate copolymer in a mass ratio of 1:5-8:0.05-0.2; The raw materials of the modified binder include the following components: 8 to 12 parts by mass of an epoxy-terminated modified polymer, 1.5 to 2 parts of ethylenediamine, 0.1 to 0.2 parts of triethylamine, 1.5 to 2.5 parts of α-lipoic acid, 1.5 to 2 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 0.2 to 0.4 parts of 4-dimethylaminopyridine; The raw materials of the epoxy-terminated modified polymer include the following components: 55-7 parts by mass of dimethyldichlorosilane, 4-6 parts of trifluoropropylmethyldichlorosilane, 3-5 parts of methylhydrogendichlorosilane, 0.5-1 part of trifluoromethanesulfonic acid, 9-10.5 parts of allyl-modified cyclodextrin, 2-3 parts of allyl glycidyl ether, 2.5-3.5 parts of bisallyloxymethyl 18-crown-6, and 0.2-0.4 parts of Karstedt catalyst; The preparation process of the modified active material is as follows: S2-1: adding lithium iron phosphate powder and aluminum isopropoxide to ethanol, stirring at 65-75°C until dry, calcining at 450-550°C under argon atmosphere for 0.5-1.5h, and cooling to obtain alumina-coated lithium iron phosphate; S2-2: Add alumina-coated lithium iron phosphate and fluoride to methanol-ethanol, ultrasonically disperse, dry, and calcine at 250-350°C for 0.5-1.5h under argon atmosphere to obtain a modified active material.

2. The method for preparing a dry electrode for a hybrid capacitor according to claim 1, wherein: In the raw materials of the modified active material, fluoride accounts for 0.5-1.5 wt % of the alumina-coated lithium iron phosphate; in the raw materials of the alumina-coated lithium iron phosphate, aluminum isopropoxide accounts for 1-3 wt % of the lithium iron phosphate powder.

3. The method for preparing a dry electrode for a hybrid capacitor according to claim 1, characterized in that: The thickness of the dry-process self-supporting film is 40 μm to 200 μm.

4. The method for preparing a dry electrode for a hybrid capacitor according to claim 1, wherein: The stirring speed is 15~30m / s, and the time is 3~5min; the fibrillation temperature is 10~19°C; the granulation speed is 2.5~4.5m / s, and the time is 3~5min; the temperature of the graded roller pressing is 100~135°C, and the differential speed ratio of each roller is 1.2~1.5; the temperature of the roller pressing compounding is 100~135°C, and the speed is 20~40r / min.

5. A dry electrode prepared according to the method for preparing a dry electrode for a hybrid capacitor according to any one of claims 1 to 4.

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