WO2023123480A1 - 一种粘结剂及其应用 - Google Patents

一种粘结剂及其应用 Download PDF

Info

Publication number
WO2023123480A1
WO2023123480A1 PCT/CN2021/143979 CN2021143979W WO2023123480A1 WO 2023123480 A1 WO2023123480 A1 WO 2023123480A1 CN 2021143979 W CN2021143979 W CN 2021143979W WO 2023123480 A1 WO2023123480 A1 WO 2023123480A1
Authority
WO
WIPO (PCT)
Prior art keywords
negative electrode
active material
binder
electrode active
material layer
Prior art date
Application number
PCT/CN2021/143979
Other languages
English (en)
French (fr)
Inventor
朱澍荞
程宝校
喻磊
李嘉文
Original Assignee
东莞新能源科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 东莞新能源科技有限公司 filed Critical 东莞新能源科技有限公司
Priority to PCT/CN2021/143979 priority Critical patent/WO2023123480A1/zh
Priority to CN202180032143.9A priority patent/CN115668548A/zh
Publication of WO2023123480A1 publication Critical patent/WO2023123480A1/zh

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium ion batteries, in particular to a binder and its application.
  • silicon materials have the advantages of high specific capacity, low cost, and abundant reserves in nature.
  • the volume expansion (about 300%) of silicon materials during charging, discharging and storage hinders its commercialization and wide application.
  • the huge volume expansion of silicon materials can easily cause the active material particles to break, causing the bridge to break in the power network, affecting the cycle life of the battery, increasing the internal resistance, and causing the battery to fail quickly.
  • a high-modulus binder is generally used.
  • the high-modulus binder is hard and brittle and lacks toughness. Once the active material particles expand beyond the binding limit, the binder will crack. , resulting in damage to the bonding interface.
  • the present application provides a new binder.
  • the first aspect of the present application provides a binder, which includes polyethyleneimine salt and carboxylate polymer.
  • the binder obtained by mixing the two has the advantages of high strength and high toughness, and the bonded particles ( For example, during the expansion process of silicon material), it can effectively release the stress, maintain the integrity of the molecular network, and provide sufficient toughness when the particle expansion exceeds the bound limit, so as to prevent the binder from cracking and causing the bond interface to be damaged.
  • the content of the polyethyleneimine salt is 0.2% to 38%, and the content of the carboxylate polymer is 62% to 99.8%. Controlling the content of polyethyleneimine and carboxylate polymers within the above range, the amino cation of polyethyleneimine and the carboxyl anion of carboxylate will associate with each other through electrostatic interaction to build a reversible cross-linked network to achieve Effective confinement of negative active materials.
  • the content of the polyethyleneimine salt is higher than 38%, the flexibility of the binder increases and the rigidity decreases, resulting in a decrease in the modulus of the binder, and the purpose of binding silicon particles cannot be achieved.
  • the content of polyethyleneimine salt is less than 0.2%, the number of amino cations decreases, and the electrostatic force between them and carboxyl anions decreases, which will lead to a decrease in the modulus of the binder.
  • the mass ratio of the carboxylate polymer to the polyethyleneimine salt is (1.7 ⁇ 2.3):1.
  • the mass ratio of polyethyleneimine salt and carboxylate polymer is outside the above range, the number of amino cations of polyethyleneimine salt and carboxyl anion of carboxylate polymer is unbalanced, and the intermolecular interaction force decreases , the modulus of the formed binder decreases.
  • the mass ratio of polyethyleneimine salt and carboxylate polymer within the above range, the number of amino cations and carboxyl anions is equivalent, and the crosslinking structure can be formed between each group to the greatest extent.
  • the formed binder has the advantages of better high strength and high toughness. During the expansion process of the bonded particles, it can release the stress more effectively and maintain the integrity of the molecular network. At the limit, it provides enough toughness to more effectively prevent the damage of the bonding interface caused by the cracking of the adhesive.
  • the polyethyleneimine salt includes at least one of a linear polyethyleneimine salt or a branched polyethyleneimine salt.
  • the carboxylate polymer comprises sodium polyacrylate, lithium polyacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium hydroxypropyl carboxymethyl cellulose or hydroxypropyl At least one of lithium carboxymethylcellulose.
  • the inventors have found that when the above-mentioned polyethyleneimine salts are used in combination with carboxylate polymers as a binder, it is beneficial to obtain a binder with higher modulus and toughness. Moreover, the above-mentioned polyethyleneimine salt and carboxylate polymers are easy to obtain, which is more conducive to commercialization.
  • the weight average molecular weight Mw 1 of the polyethyleneimine salt is from 700 g/mol to 1 ⁇ 10 5 g/mol; the weight average molecular weight Mw 2 of the carboxylate polymer is from 3000 g/mol to 8 ⁇ 10 6 g/mol.
  • the weight-average molecular weight of polyethyleneimine salt and carboxylate polymer directly affects the integrity and toughness of the crosslinked network.
  • the weight average molecular weight of the polymer-like polymer is adjusted within the above range, it is more conducive to obtaining a binder with higher modulus and toughness, so as to more effectively prevent the damage of the bonding interface caused by the cracking of the binder.
  • the adhesive has at least one of the following characteristics: a) the adhesive film storage modulus of the adhesive is 3GPa to 20GPa; b) the adhesive film of the adhesive The tensile strength at break is 40MPa to 140MPa; c) the elongation at break of the adhesive film is 5% to 40%.
  • the storage modulus of the adhesive film, the tensile breaking strength of the film, and the elongation at break of the film are regulated within the above ranges, indicating that there is an electrostatic cross-linking effect between the amine cation and the carboxyl anion to form a cross-linked molecular network. Therefore, the binder has the advantages of high strength and high toughness. During the expansion process of the bonded particles, it can effectively release the stress, maintain the integrity of the negative electrode sheet, and provide sufficient protection when the particle expansion exceeds the bound limit. Toughness to prevent the adhesive from cracking and causing damage to the bonded interface.
  • the second aspect of the present application provides a negative electrode sheet, including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes the negative electrode provided by the first aspect of the present application. binder.
  • the content of the binder is 1% to 10%. If the content of the binder is too low, the bonding effect cannot be achieved, and if the content of the binder is too high, the energy density of the electrochemical device will be reduced.
  • the negative active material in the negative active material layer includes at least one of silicon, silicon carbon, or silicon oxide.
  • the use of the negative electrode active material is conducive to improving the specific capacity of the negative electrode; further, when the negative electrode active material is used and bonded with the binder of the present application, the obtained negative electrode sheet can effectively reduce the viscosity while having a high capacity. When the binder is broken and the bonding interface is destroyed, the electrochemical device using the negative electrode sheet has a longer cycle life.
  • the content of silicon is 1% to 60%.
  • the content of silicon in the negative electrode active material is less than 1%, it is not conducive to improving the cycle life and capacity of the electrochemical device.
  • the silicon element content in the negative electrode active material is greater than 60%, the expansion of the negative electrode active material layer is too large during the cycle of the electrochemical device, which will exceed the binding limit of the binder to the negative electrode active material, affecting the cycle life and electrochemical performance such as capacity.
  • the negative electrode active material may also include at least one of graphite or hard carbon, which may be mixed with a silicon-containing negative electrode active material in a certain proportion to serve as a composite negative electrode material.
  • the D50 of the negative electrode active material is 5 ⁇ m to 40 ⁇ m.
  • the D50 regulation of the negative electrode active material is within the above range, and the binder has a good coating effect on the negative electrode active material.
  • the particle size of the negative electrode active material is larger than 40 ⁇ m, it is easy to cause the binder to cover the negative electrode active material with too small area, thereby affecting the binding force of the negative electrode sheet.
  • "D50" in this application refers to the particle size corresponding to when the cumulative particle size distribution percentage reaches 50%. Its physical meaning is that the volume of particles with a particle size larger than it accounts for 50%, and the volume of particles smaller than it also accounts for 50%. The particle size is measured with a laser particle size analyzer.
  • the negative electrode active material layer of the present application may also contain a conductive agent, and the application does not limit the type of the conductive agent in the negative pole sheet.
  • the conductive agent may include conductive carbon black, carbon nanotubes, conductive graphite, graphene, At least one of acetylene black or carbon nanofiber; through the addition of a conductive agent, the conductivity of the negative electrode sheet can be improved.
  • the present application has no special limitation on the content of the conductive agent in the negative electrode active material layer, as long as the purpose of the application can be achieved, for example, the conductive agent accounts for 0% to 1% of the total weight of the negative electrode active material layer.
  • the present application has no particular limitation on the negative electrode current collector, and negative electrode current collectors known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors.
  • the thickness of the negative electrode current collector and the negative electrode active material layer is not particularly limited, as long as the purpose of the present application can be achieved.
  • the thickness of the negative electrode current collector is 6 ⁇ m to 10 ⁇ m
  • the thickness of the negative electrode active material layer is 30 ⁇ m to 120 ⁇ m.
  • the negative electrode sheet has at least one of the following characteristics: d) the compacted density of the negative electrode active material layer is 1.45g/cm 3 to 1.85g/cm 3 ; e) the negative electrode The cohesive force of the active material layer is 20N/m to 200N/m; f) the binding force between the negative electrode active material layer and the negative electrode current collector is 10N/m to 850N/m.
  • the compaction density of the negative electrode active material layer is controlled within the above range, the risk of each negative electrode active material particle being broken is reduced, and the interface stability of the negative electrode active material layer can be improved.
  • the contact between each negative electrode active material particle is better, which is beneficial to Improve the conductivity of the conductive network and better regulate the interface stability of the negative electrode active material layer.
  • the cycle performance of the electrochemical device using the negative electrode sheet is improved.
  • the cohesion of the negative electrode active material layer is controlled within the above range, indicating that the negative electrode sheet has good cohesion, stabilizes the structure of the negative electrode sheet, and is more conducive to the improvement of the cycle performance of the electrochemical device using the negative electrode sheet.
  • the bonding force between the negative electrode active material layer and the negative electrode current collector is within the above range, indicating that there is good bonding force between the negative electrode active material layer and the negative electrode current collector, which is more conducive to the stability of the structure of the negative electrode sheet, and also makes it possible to use the negative electrode.
  • the cycle performance of the electrochemical device of the sheet is improved.
  • the third aspect of the present application provides an electrochemical device, which includes the negative electrode sheet provided in the second aspect of the present application.
  • the electrochemical device using the negative electrode sheet of the present application has better cycle performance.
  • the negative electrode sheet provided by this application is used as the negative electrode sheet, and other components, including the positive electrode sheet, separator and electrolyte, are not particularly limited.
  • a positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer.
  • the positive electrode current collector is not particularly limited, and may be a positive electrode current collector known in the art, such as copper foil, aluminum foil, aluminum alloy foil, and a composite current collector.
  • the positive electrode active material layer includes a positive electrode active material, the positive electrode active material is not particularly limited, and can be a positive electrode active material known in the art, for example, including nickel cobalt lithium manganate (811, 622, 523, 111), nickel cobalt lithium aluminate, At least one of lithium iron phosphate, lithium-rich manganese-based materials, lithium cobaltate, lithium manganate, lithium iron manganese phosphate or lithium titanate.
  • the thicknesses of the positive electrode current collector and the positive electrode active material layer are not particularly limited, as long as the purpose of the present application can be achieved.
  • the thickness of the positive electrode current collector is 8 ⁇ m to 12 ⁇ m
  • the thickness of the positive electrode active material layer is 25 ⁇ m to 100 ⁇ m.
  • the positive electrode sheet may further include a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode active material layer.
  • the composition of the conductive layer is not particularly limited, and may be a commonly used conductive layer in the field.
  • the conductive layer includes a conductive agent and a binder.
  • the conductive agent is not particularly limited, and may be any conductive agent known to those skilled in the art or a combination thereof, for example, at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent or a two-dimensional conductive agent may be used.
  • the conductive agent may include at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, vapor grown carbon fiber (VGCF) or graphene.
  • the amount of the conductive agent is not particularly limited, and can be selected according to common knowledge in the art.
  • One of the above-mentioned conductive agents may be used alone, or two or more of them may be used in combination in an arbitrary ratio.
  • the conductive layer binder in the conductive layer is not particularly limited, and may be any conductive layer binder known to those skilled in the art or a combination thereof, such as polyacrylate, polyimide, polyamide, polyamide At least one of imide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. These binders may be used alone or in combination of two or more in any ratio.
  • the separator in the electrochemical device of this application is used to separate the positive pole piece and the negative pole piece, prevent the internal short circuit of the electrochemical device, allow electrolyte ions to pass freely, and complete the electrochemical charge and discharge process.
  • the separator is not particularly limited, as long as the purpose of the present application can be achieved.
  • polyethylene PE
  • polypropylene PP
  • PO polyolefin
  • polyester film such as polyethylene terephthalate (PET) film
  • cellulose film polyamide Imine film (PI)
  • polyamide film PA
  • spandex film aramid film
  • woven film non-woven film (non-woven fabric)
  • microporous film composite film
  • separator paper laminated film or spun film at least one of these.
  • a separator may include a substrate layer and a surface treatment layer.
  • the substrate layer can be a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide, etc. kind.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.
  • at least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.
  • the inorganic layer includes inorganic particles and inorganic layer binder
  • the inorganic particles are not particularly limited, for example, can be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, At least one of nickel oxide, zinc oxide, calcium oxide, zirconia, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.
  • the inorganic layer binder is not particularly limited, for example, it can be selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyethylene At least one of pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the polymer layer comprises a polymer, and the polymer material includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( at least one of vinylidene fluoride-hexafluoropropylene) and the like.
  • the electrochemical device of the present application also includes an electrolyte, which may be at least one of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • an electrolyte which may be at least one of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), tetra Lithium phenylboron (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bistrifluoromethanesulfonylimide (LiN At least one of (SO 2 CF 3 ) 2 ), LiC(SO 2 CF 3 ) 3 , lithium hexafluorosilicate (LiSiF 6 ), lithium bisoxalate borate (LiBOB) or lithium difluoroborate (LiF 2 OB) .
  • LiPF 6 lithium hexafluorophosphate
  • the non-aqueous solvent may be at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.
  • the above-mentioned carbonate compound may be at least one of chain carbonate compound, cyclic carbonate compound or fluorocarbonate compound.
  • Examples of the above-mentioned chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylenepropyl carbonate (EPC) or carbonic acid At least one of ethyl methyl ester (EMC).
  • cyclic carbonate compound is at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylethylene carbonate (VEC).
  • fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate At least one of fluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate.
  • Examples of the above carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone , at least one of decanolactone, valerolactone, mevalonolactone or caprolactone.
  • Examples of the aforementioned ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl At least one of oxyethane, 2-methyltetrahydrofuran or tetrahydrofuran.
  • Examples of the aforementioned other organic solvents are propyl propionate, dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl - at least one of 2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphoric acid ester.
  • the total content of the above non-aqueous solvents is 5% to 90%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% , 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any range therebetween.
  • an electrochemical device can be manufactured through the following process: overlap the positive pole piece and the negative pole piece through the separator, and put it into the case after winding, folding, etc. as required, inject the electrolyte into the case and seal it.
  • anti-overcurrent elements, guide plates, etc. can also be placed in the casing as needed, so as to prevent pressure rise and overcharge and discharge inside the electrochemical device.
  • the fourth aspect of the present application provides an electronic device, which includes the electrochemical device provided in the third aspect of the present application.
  • the electronic device of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • the electronic device may include, but is not limited to, a notebook computer, a pen computer, a mobile computer, an e-book player, a cellular phone, a portable fax machine, a portable copier, a portable printer, a stereo headphone , VCR, LCD TV, Portable Cleaner, Portable CD Player, Mini Disc, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, Motorcycle, Assisted Bicycle, Bicycle , Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the binder of the present application through the electrostatic crosslinking network formed by the amino cation in the polyethyleneimine salt and the carboxyl anion in the carboxylate polymer, can effectively bind
  • the particles expand and release the stress to maintain the integrity of the molecular network, which has the advantages of high strength and high toughness, effectively reducing the damage of the bonding interface, and applying the negative electrode sheet including the binder of the present application to electrochemical devices.
  • the cycle performance of the electrochemical device is improved.
  • the use of the highly flexible binder of the present application also endows the processing advantages of the negative electrode sheet. During the rolling process, processing problems such as overpressure, decarburization, and edge drop are avoided, and the electrochemical device is improved. processing performance.
  • Fig. 1 is the adhesive film storage modulus test result of the negative pole sheet binder of embodiment 4 and comparative example 1;
  • Fig. 2 is the adhesive film tensile strength-elongation curve of the negative pole sheet binder of embodiment 4 and comparative example 1;
  • Fig. 3 is the cohesion test result of negative electrode active material layer and negative electrode current collector in the negative electrode sheet of embodiment 4 and comparative example 1;
  • Fig. 4 is the cohesion test result of the negative electrode active material layer in the negative electrode sheet of embodiment 4 and comparative example 1;
  • Fig. 5 is the capacity fading curve of the lithium ion battery of embodiment 4 and comparative example 1;
  • Fig. 6 is a schematic diagram of the intermolecular interaction of the binder of the present application.
  • Test steps Dry the adhesive at 120°C to prepare a film with a thickness of 120 ⁇ m, cut it into a sample with a width of 8 mm x a length of 40 mm, and fix the sample between the upper and lower fixtures of the dynamic thermomechanical analyzer along the length direction. The fixture does not move, and the lower fixture applies a sinusoidal strain to the sample to test the sinusoidal stress of the sample response.
  • Storage modulus (stress/strain) cos ⁇ . ⁇ : stress-strain phase difference.
  • Test steps Dry the adhesive at 120°C to prepare a film with a thickness of 300 ⁇ m, cut it into a sample with a width of 1.5 cm x a length of 4 cm, and fix the sample between the upper and lower clamps of the universal testing machine along the length direction.
  • the breaking strength Tensile force at break/cross-sectional area of the adhesive film, where the cross-sectional area of the adhesive film is the thickness of the adhesive film ⁇ width.
  • the negative electrode sheet was dried in an oven at 60°C for 15 hours, cut into strips of 1.5cm ⁇ 11cm, and subjected to a 180°peel test.
  • Test steps Use double-sided tape to paste the cut negative pole piece on a 3cm ⁇ 15cm steel plate, roll it with a small stick for 7 to 8 times, use a tensile machine to perform a peel test, and fix the steel plate in the lower fixture of the tensile machine , bend the negative pole piece by 180°, clamp the negative pole piece by the upper clamp, peel off 50mm at a constant rate of 50mm/min in the direction parallel to the negative pole piece, and obtain the stress and displacement data, the negative electrode active material layer and the negative electrode current collector.
  • Cohesion stress/displacement.
  • the negative electrode sheet was dried in an oven at 60°C for 15 hours, cut into strips of 1.5cm ⁇ 11cm, and subjected to a 180°peel test.
  • Test steps Use double-sided tape to paste the cut negative pole piece on the 3cm ⁇ 15cm steel plate, paste the high-viscosity green glue on the surface of the pole piece, roll the small stick 7 to 8 times, and fix the steel plate under tension
  • the upper fixture clamps the green glue, and peels off 50mm at a constant rate of 50mm/min in the direction parallel to the negative electrode sheet to obtain stress and displacement data.
  • Cohesion of the negative active material layer stress/displacement.
  • the lithium-ion battery is tested for cycle capacity retention: the test temperature is 25°C, charge to the rated voltage at a constant current of 0.5C, charge at a constant voltage to 0.025C, and discharge to 3.0V at 0.5C after standing for 5 minutes.
  • the capacity obtained in this step is taken as the initial capacity, and the 0.5C charge/0.5C discharge cycle test is carried out, and the capacity after each cycle is compared with the initial capacity to obtain the capacity decay curve.
  • the negative electrode slurry is coated on one surface of a copper foil current collector with a thickness of 10 ⁇ m, and the coating thickness is 50 ⁇ m to obtain a negative electrode sheet coated with a negative electrode active material layer on one side; after that, on the other side of the negative electrode sheet The above steps are repeated on the surface, and after cold pressing, a negative electrode sheet coated with a negative electrode active material layer on both sides is obtained.
  • the positive electrode sheet, separator, and negative electrode sheet are stacked in order, and the PE porous polymer film is used as the separator, so that the separator is placed in the middle of the positive and negative electrodes to play the role of isolation, and the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the outer packaging case, and after dehydration at 80°C, the above-mentioned electrolyte solution is injected and packaged, and a lithium-ion battery is obtained through processes such as chemical formation, degassing, and edge trimming.
  • lithium polyacrylate was replaced with carboxymethylcellulose sodium (CAS No. : 9004-32-4), and the rest are the same as in Example 3.
  • the film storage modulus test results and the tensile strength and elongation test results of the negative electrode sheet binders of Example 4 and Comparative Example 1 are shown in Figure 1 and Figure 2 respectively, as can be seen, the relative Compared with lithium polyacrylate as the binder, the storage modulus, breaking strength and elongation at break of the binder film of the present application are all significantly increased.
  • the capacity decay curves of the lithium-ion batteries of Example 4 and Comparative Example 1 are shown in FIG. 5 .
  • the results show that the lithium-ion battery using the binder of the present application has a higher cycle capacity retention rate.
  • the bonding force and cohesion of the negative electrode sheet are significantly improved, and the cycle capacity retention rate of the lithium-ion battery is significantly improved.
  • the inventors believe that there is an amino cation in the polyethyleneimine salt, and there is a carboxyl anion in the carboxylate polymer, so that there is an intermolecular electrostatic interaction between the two molecules (the interaction between the binder molecules).
  • the schematic diagram is shown in Figure 6), during the expansion of the negative active material particles, the binder can effectively release the stress, maintain the integrity of the molecular network, effectively reduce the damage of the bonding interface, and improve the cycle performance of the lithium-ion battery.
  • Example 6 and Example 7 it can be seen that the adhesives of different polyethyleneimine salts and carboxylate polymers of the present application can realize storage modulus, elongation at break, and strength at break. Correspondingly, the binding force and cohesion of the negative electrode active material layer of the negative electrode sheet using the binder and the cycle capacity retention rate of the lithium ion battery are also improved.
  • Example 3 From the comparison of Example 3 and Comparative Example 3, it can be seen that the use of the polyethyleneimine salt and carboxylate polymer binder of the present application, compared to the existing polyethyleneimine and polyacrylic acid Ester binder, the storage modulus, elongation at break, and breaking strength of the film are all significantly improved.
  • Example 8 to Example 11 From Example 8 to Example 11, it can be seen that with the increase of the binder content in the negative electrode active material layer, the adhesion and cohesion of the negative electrode sheet are improved, and the cycle capacity retention rate of the lithium-ion battery However, too high a binder content will reduce the energy density of the battery, so the preferred content of the binder in the negative electrode active material layer in the present application is 1wt% to 10wt%.
  • Example 12 to Example 15 it can be seen that as the content of silicon in the negative electrode active material increases, the adhesion and cohesion of the negative electrode sheet decrease, and the cycle performance of the lithium-ion battery also gradually decreases.
  • the inventors believe that the increase of the silicon element content leads to the expansion of the negative electrode active material, thereby reducing the adhesion and cohesion of the negative electrode sheet and the cycle performance of the lithium-ion battery. Therefore, in the present application, based on the total weight of the negative electrode active material, the silicon element content is 1% to 60%. It should also be noted that when the silicon element content in the present application reaches 60%, the cycle capacity retention rate of the lithium-ion battery can still reach 88.5%, which further shows that the binder of the present application can be applied to silicon-containing negative electrode active materials.
  • Example 16 to Example 19 it can be seen that with the increase of the particle size of the negative electrode active material, the binding force and cohesion of the negative electrode sheet decrease and the cycle performance also decreases thereupon, not limited to any theory, the invention It is believed that the increase of the particle size of the negative electrode active material will cause an increase in expansion, thereby reducing the adhesion and cohesion of the negative electrode sheet and the cycle performance of the lithium-ion battery.
  • the particle size D50 of the negative electrode active material is 10 ⁇ m
  • the thickness reaches 40 ⁇ m, the lithium-ion battery maintains a high cycle performance.
  • Example 20 to Example 23 it can be seen from Example 20 to Example 23 that when the compacted density of the negative electrode active material layer is in the range of 1.45 g/cm 3 to 1.85 g/cm 3 , the lithium-ion battery maintains a high cycle performance.

Abstract

本申请提供了一种粘结剂及应用其的负极极片、电化学装置和电子装置。其中，粘结剂包括聚乙烯亚胺盐和羧酸盐类聚合物。本申请的粘结剂能够在负极活性材料颗粒膨胀的过程中，有效释放应力，保持分子网络的完整性，兼具了高强度和高韧性的优势，有效降低粘结界面破坏，提高了电化学装置的循环性能。

Description

一种粘结剂及其应用 技术领域
本申请涉及锂离子电池技术领域，具体涉及一种粘结剂及其应用。
背景技术
硅材料作为下一代锂离子电池负极材料之一，具有高比容量，低成本，自然界储量丰富等优点。然而，硅材料在充放、存储过程中的体积膨胀(约300％)阻碍了其商业化及广泛应用。不同于传统碳材料，硅材料的巨大的体积膨胀容易造成活性材料颗粒破裂，引起电网络断桥，影响电池循环寿命，增加内阻，进而使电池快速失效。为了束缚硅的过度膨胀，一般会使用高模量粘结剂，然而，高模量粘结剂偏于硬脆、缺乏韧性，一旦活性材料颗粒膨胀超出束缚极限，将会出现粘结剂碎裂，造成粘结界面破坏。
发明内容
为解决硅材料的膨胀引起粘结剂碎裂、粘结界面破坏的问题，本申请提供了一种新的粘结剂。
本申请第一方面提供了一种粘结剂，其包括聚乙烯亚胺盐和羧酸盐类聚合物。
发明人发现，由于聚乙烯亚胺盐和羧酸盐类聚合物之间存在协同作用，使得两者混合获得的粘结剂兼具了高强度和高韧性的优势，在其粘结的颗粒(例如硅材料)发生膨胀的过程中，能够有效释放应力，保持分子网络的完整性，在颗粒膨胀超出束缚极限时，提供足够的韧性，以防止粘结剂碎裂，造成粘结界面破坏。
在一些实施方式中，基于所述粘结剂的总重量，所述聚乙烯亚胺盐的含量为0.2％至38％，所述羧酸盐类聚合物的含量为62％至99.8％。将聚乙烯亚盐和羧酸盐类聚合物的含量调控在上述范围内，聚乙烯亚胺的胺基阳离子及羧酸盐的羧基阴离子，通过静电作用相互缔合，构筑可逆交联网络，实现对负极活性材料的有效束缚。聚乙烯亚胺盐的含量高于38％时，粘结剂柔性提高，刚性降低，导致粘结剂模量下降，无法达到束缚硅颗粒的目的。聚乙烯亚胺盐的含量低于0.2％时，胺基阳离子数目下降，其与羧基阴离子间的静电作用力降低，将导致粘结剂的模量下降。
在一些实施方式中，所述羧酸盐类聚合物和所述聚乙烯亚胺盐的质量比例为(1.7～2.3):1。聚乙烯亚胺盐和羧酸盐类聚合物的质量比例在上述范围之外时，聚乙烯亚胺盐的胺基阳离子及羧酸盐类聚合物的羧基阴离子数量失衡，分子间相互作用力下降，形成 的粘结剂模量降低。通过将聚乙烯亚胺盐和羧酸盐类聚合物的质量比例调控在上述范围内，使胺基阳离子和羧基阴离子数量相当，各基团间能够最大程度形成交联结构。这样，形成的粘结剂具有更优的高强度和高韧性的优势，在其粘结的颗粒发生膨胀的过程中，能够更有效地释放应力，保持分子网络的完整性，在颗粒膨胀超出束缚极限时，提供足够的韧性，更有效地防止粘结剂碎裂所带来的粘结界面破坏。
在一些实施方式中，所述聚乙烯亚胺盐包括线性聚乙烯亚胺盐或支化聚乙烯亚胺盐中的至少一种。
在一些实施方式中，所述羧酸盐类聚合物包括聚丙烯酸钠、聚丙烯酸锂、羧甲基纤维素钠、羧甲基纤维素锂、羟丙基羧甲基纤维素钠或羟丙基羧甲基纤维素锂中的至少一种。
发明人发现，当采用上述种类的聚乙烯亚胺盐与羧酸盐类聚合物组合作为粘结剂时，有利于获得具有更高模量和韧性的粘结剂。并且，上述种类的聚乙烯亚胺盐和羧酸盐类聚合物易于取得，更利于实现商业化。
在一些实施方式中，所述聚乙烯亚胺盐的重均分子量Mw 1为700g/mol至1×10 5g/mol；所述羧酸盐类聚合物重均分子量Mw 2为3000g/mol至8×10 6g/mol。聚乙烯亚胺盐和羧酸盐类聚合物的重均分子量直接影响交联结构网络的完整性及韧性，在不影响粘结剂加工性能的前提下，将聚乙烯亚胺盐和羧酸盐类聚合物的重均分子量调控在上述范围内，更有利于获得具有更高模量和韧性的粘结剂，从而能更有效地防止粘结剂碎裂所带来的粘结界面破坏。
在一些实施方式中，所述的粘结剂具有以下特征中的至少一者：a)所述粘结剂的胶膜储能模量为3GPa至20GPa；b)所述粘结剂的胶膜拉伸断裂强度40MPa至140MPa；c)所述粘结剂的胶膜断裂伸长率为5％至40％。粘结剂的胶膜储能模量、胶膜拉伸断裂强度、胶膜断裂伸长率调控在上述范围内，表明胺基阳离子及羧基阴离子之间具有静电交联作用形成交联分子网络，从而使粘结剂兼具高强度和高韧性的优势，在其粘结的颗粒发生膨胀的过程中，能够有效释放应力，保持负极极片完整性，在颗粒膨胀超出束缚极限时，提供足够的韧性，以防止粘结剂碎裂，造成粘结界面破坏。
本申请第二方面提供了一种负极极片，包括负极集流体和设置于所述负极集流体至少一个表面的负极活性材料层，所述负极活性材料层中包含本申请第一方面所提供的粘结剂。
在一些实施方式中，基于所述负极活性材料层的总重量，所述粘结剂的含量为1％至 10％。粘结剂含量过低，起不到粘结作用，粘结剂含量过高，降低电化学装置的能量密度。
在一些实施方式中，所述负极活性材料层中的负极活性材料包括硅、硅碳或氧化亚硅中的至少一种。采用所述负极活性材料有利于提高负极比容量；进一步地，当采用所述负极活性材料，使用本申请的粘结剂粘结，获得的负极极片在具有高容量的同时，能够有效减少粘结剂碎裂、粘结界面破坏的情况发生，采用所述负极极片的电化学装置具有更长的循环寿命。
在一些实施方式中，基于所述负极活性材料的总重量，硅元素含量为1％至60％。负极活性材料中的硅元素含量小于1％时，不利于改善电化学装置的循环寿命和容量。负极活性材料中的硅元素含量大于60％时，电化学装置循环过程中，负极活性材料层的膨胀过大，将超出粘结剂对负极活性材料的束缚极限，影响电化学装置的循环寿命和容量等电化学性能。
在另一些实施方式中，所述负极活性材料还可以包括石墨或硬碳的至少一种，其可以与含硅的负极活性材料通过一定比例混合后作为复合负极材料。
在一些实施方式中，所述负极活性材料的D50为5μm至40μm。负极活性材料的D50调控在上述范围内，粘结剂对于负极活性材料具有良好的包覆作用。若负极活性材料粒径大于40μm，则容易造成粘结剂对于负极活性材料包覆面积过小，从而影响负极极片粘结力。本申请中的“D50”指累计粒度分布百分数达到50％时所对应的粒径。它的物理意义是粒径大于它的颗粒的体积占50％，小于它的颗粒的体积也占50％。所述粒径用激光粒度仪进行测定。
本申请的负极活性材料层中还可以包含导电剂，本申请对负极极片中导电剂的种类不做限定，例如所述导电剂可以包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种；通过导电剂的加入，能够提升负极极片的导电性能。本申请对负极活性材料层中导电剂的含量没有特别限制，只要能够实现本申请目的即可，例如导电剂占负极活性材料层总重量的0％至1％。
本申请对负极集流体没有特别限制，可以使用本领域公知的负极集流体，例如铜箔、铝箔、铝合金箔以及复合集流体等。在本申请中，负极集流体和负极活性材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，负极集流体的厚度为6μm至10μm，负极活性材料层的厚度为30μm至120μm。
在一些实施方式中，所述的负极极片具有以下特征中的至少一者：d)所述负极活性材 料层压实密度为1.45g/cm 3至1.85g/cm 3；e)所述负极活性材料层内聚力为20N/m至200N/m；f)所述负极活性材料层与所述负极集流体的粘结力为10N/m至850N/m。负极活性材料层的压实密度调控在上述范围内，各负极活性材料颗粒破碎的风险降低，能够提升负极活性材料层的界面稳定性，同时，各负极活性材料颗粒间的接触更好，有利于改善导电网络的导电性，更好的调控负极活性材料层的界面稳定性。由此，采用该负极极片的电化学装置的循环性能得以提升。负极活性材料层的内聚力调控在上述范围内，表明负极极片具有良好的内聚力，稳定了负极极片的结构，更利于采用该负极极片的电化学装置的循环性能的提升。负极活性材料层与负极集流体的粘结力在上述范围内，表明负极活性材料层与负极集流体之间具有良好的粘结力，更利于负极极片结构的稳定，也使得采用该负极极片的电化学装置的循环性能得以提升。
本申请第三方面提供了一种电化学装置，其包括本申请第二方面提供的负极极片。采用本申请的负极极片的电化学装置具有更好的循环性能。
本申请提供的电化学装置，其负极极片采用本申请提供的负极极片，而其它的组成部分，包括正极极片、隔离膜及电解液等，没有特别的限制。
例如，正极极片通常包含正极集流体和正极活性材料层。其中，正极集流体没有特别限制，可以为本领域公知的正极集流体，例如铜箔、铝箔、铝合金箔以及复合集流体等。正极活性材料层包括正极活性材料，正极活性材料没有特别限制，可以为本领域公知的正极活性材料，例如，包括镍钴锰酸锂(811、622、523、111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。在本申请中，正极集流体和正极活性材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，正极集流体的厚度为8μm至12μm，正极活性材料层的厚度为25μm至100μm。
任选地，正极极片还可以包含导电层，该导电层位于正极集流体和正极活性材料层之间。导电层的组成没有特别限制，可以是本领域常用的导电层。该导电层包括导电剂和粘结剂。所述导电剂没有特别限制，可以是本领域技术人员公知的任何导电剂或其组合，例如，可以采用零维导电剂、一维导电剂或二维导电剂中的至少一种。优选地，导电剂可以包括炭黑、导电石墨、碳纤维、碳纳米管、气相法生长碳纤维(VGCF)或石墨烯中的至少一种。导电剂的用量没有特别限制，可以根据本领域公知常识进行选择。上述导电剂可以单独使用一种，也可以将两种以上以任意比例组合使用。
所述导电层中的导电层粘结剂没有特别限制，可以是本领域技术人员公知的任何导电 层粘结剂或其组合，例如可以使用聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、羧甲基纤维素钠或羧甲基纤维素锂等的至少一种。这些粘结剂可以单独使用一种，也可以将两种以上以任意比例组合使用。
本申请电化学装置中的隔离膜，用以分隔正极极片和负极极片，防止电化学装置内部短路，允许电解质离子自由通过，完成电化学充放电过程的作用。在本申请中，隔离膜没有特别限制，只要能够实现本申请目的即可。例如，聚乙烯(PE)、聚丙烯(PP)为主的聚烯烃(PO)类隔离膜、聚酯膜(例如聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜(PI)、聚酰胺膜(PA)、氨纶膜、芳纶膜、织造膜、非织造膜(无纺布)、微孔膜、复合膜、隔膜纸、碾压膜或纺丝膜等中的至少一种。例如，隔离膜可以包括基材层和表面处理层。基材层可以为具有多孔结构的无纺布、膜或复合膜，基材层的材料可以包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺等中的至少一种。任选地，可以使用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。任选地，基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。例如，无机物层包括无机颗粒和无机物层粘结剂，该无机颗粒没有特别限制，例如可以选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡等中的至少一种。无机物层粘结剂没有特别限制，例如可以选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。聚合物层中包含聚合物，聚合物的材料包括聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)等中的至少一种。
本申请的电化学装置还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的至少一种，电解液包括锂盐和非水溶剂。
本申请对锂盐没有特别限制，例如，锂盐选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、六氟砷酸锂(LiAsF 6)、高氯酸锂(LiClO 4)、四苯硼锂(LiB(C 6H 5) 4)、甲基磺酸锂(LiCH 3SO 3)、三氟甲磺酸锂(LiCF 3SO 3)、双三氟甲烷磺酰亚胺锂(LiN(SO 2CF 3) 2)、LiC(SO 2CF 3) 3、六氟硅酸锂(LiSiF 6)、双草酸硼酸锂(LiBOB)或二氟硼酸锂(LiF 2OB)中的至少一种。举 例来说，锂盐可以选用LiPF 6，因为它具有高的离子电导率并改善循环特性。
本申请对非水溶剂没有特别限制，例如，非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物或其它有机溶剂中的至少一种。上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物或氟代碳酸酯化合物中的至少一种。上述链状碳酸酯化合物的实例为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)或碳酸甲乙酯(EMC)中的至少一种。环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)或碳酸乙烯基亚乙酯(VEC)中的至少一种。氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯或碳酸三氟甲基亚乙酯中的至少一种。上述羧酸酯化合物的实例为甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯或己内酯中的至少一种。上述醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃或四氢呋喃中的至少一种。上述其它有机溶剂的实例为丙酸丙酯、二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯或磷酸酯中的至少一种。基于电解液的质量，上述非水溶剂的总含量为5％至90％，例如5％、10％、15％、20％、25％、30％、35％、40％、45％、50％、55％、60％、65％、70％、75％、80％、85％、90％或其间的任何范围。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制。例如电化学装置可以通过以下过程制造：将正极极片和负极极片经由隔离膜重叠，并根据需要将其卷绕、折叠等操作后放入壳体内，将电解液注入壳体并封口。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止电化学装置内部的压力上升、过充放电。
本申请第四方面提供了一种电子装置，其包括本申请第三方面提供的电化学装置。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，所述电子装置可以包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子 记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
本申请的粘结剂，通过聚乙烯亚胺盐中的胺基阳离子和羧酸盐类聚合物中的羧基阴离子所形成的静电交联网络，在负极活性材料颗粒膨胀的过程中，能够有效束缚颗粒膨胀，并释放应力保持分子网络的完整性，兼具了高强度和高韧性的优势，有效降低粘结界面破坏，将包括本申请的粘结剂的负极极片应用于电化学装置中，提升了电化学装置的循环性能。进一步的，采用本申请具有高柔韧性的粘结剂也赋予了负极极片的加工优势，在辊压的过程中，避免过压、脱碳、边缘掉料等加工问题，提升了电化学装置的加工性能。
附图说明
为了更清楚地说明本申请实施例和现有技术的技术方案，下面对本申请实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1为实施例4与对比例1的负极极片粘结剂的胶膜储能模量测试结果；
图2为实施例4与对比例1的负极极片粘结剂的胶膜拉伸强度-伸长率曲线；
图3为实施例4与对比例1的负极极片中负极活性材料层与负极集流体的粘结力测试结果；
图4为实施例4与对比例1的负极极片中负极活性材料层内聚力测试结果；
图5为实施例4与对比例1的锂离子电池的容量衰减曲线；
图6为本申请粘结剂分子间作用示意图。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图并举实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员所获得的所有其他技术方案，都属于本申请保护的范围。
以下，基于实施例对本申请进行具体地说明，但本申请并不限于这些实施例。需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
在下述实施例、对比例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可 商购获得。
测试方法：
储能模量测试：
TA动态热机械分析仪DMA850；恒应变模式测试；
测试步骤：将粘结剂于120℃烘干，制备成厚120μm的胶膜，裁剪为8mm宽×40mm长的样品，将样品沿长度方向固定于动态热机械分析仪的上下夹具之间，上夹具不动，下夹具对样品施加正弦变化的应变，测试样品响应的正弦应力。储能模量＝(应力/应变)cosδ。δ：应力应变相位差。
伸长率测试：
万能试验机；拉伸模式测试。
测试步骤：将粘结剂于120℃烘干，制备成厚300μm的胶膜，裁剪为1.5cm宽×4cm长的样品，将样品沿长度方向固定于万能试验机的上下夹具之间，上下夹具初始间距L0，下夹具不动，上夹具以恒定速率50mm/min拉伸至样品断裂，此时上下夹具间距为L1，断裂伸长率＝(L1-L0)/L0×100％；断裂强度＝断裂拉力/胶膜截面积，其中胶膜截面积为胶膜厚度×宽度。
粘结力测试：
将负极极片在60℃烘箱中进行15h烘干，裁切成1.5cm×11cm的长条，进行180°剥离测试。
测试步骤：使用双面胶将裁切后的负极极片粘贴在3cm×15cm钢板上，小棍辊压7次至8次，使用拉力机进行剥离测试，将钢板固定在拉力机的下夹具中，将负极极片弯曲180°，上夹具夹住负极极片，在平行于负极极片的方向，以恒定速率50mm/min剥离50mm，得到应力与位移数据，负极活性材料层与负极集流体的粘结力＝应力/位移。
内聚力测试：
将负极极片在60℃烘箱中进行15h烘干，裁切成1.5cm×11cm的长条，进行180°剥离测试。
测试步骤：使用双面胶将裁切后的负极极片粘贴在3cm×15cm钢板上，将高粘绿胶黏贴在极片表面，小棍辊压7次至8次，将钢板固定在拉力机的下夹具中，上夹具夹住绿胶，在平行于负极极片的方向，以恒定速率50mm/min剥离50mm，得到应力与位移数据，负极活性材料层内聚力＝应力/位移。
循环容量保持率测试：
对锂离子电池进行循环容量保持率测试：测试温度为25℃，以0.5C恒流充电到额定电压，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。以此步骤得到的容量为初始容量，进行0.5C充电/0.5C放电进行循环测试，以每一次循环后的容量与初始容量做比值，得到容量衰减曲线。
实施例1
<正极极片的制备>
将正极活性材料钴酸锂、导电剂导电炭黑、粘结剂聚偏氟乙烯(PVDF)按质量比96.7:1.7:1.6的比例溶于N-甲基吡咯烷酮(NMP)溶液中，调配成固含量为75wt％的正极浆料；采用10μm厚的铝箔作为正极集流体，将正极浆料涂覆于正极集流体上，涂布厚度为50μm，经过干燥得到单面涂布的正极极片；之后，在该正极极片的另一个表面上重复以上步骤，冷压后即得到双面涂布正极活性材料的正极极片。
<负极极片的制备>
粘结剂制备：将支化聚乙烯亚胺盐(Mw 1＝1900g/mol)与聚丙烯酸锂(Mw 2＝5×10 5g/mol)以质量比0.2:99.8混合(即支化聚乙烯亚胺盐的质量含量为0.2％)，搅拌均匀，备用。
将负极活性材料(SiO/石墨＝10％，Si元素含量：6.3％)与粘结剂以质量比94:6在去离子水溶剂体系中充分搅拌混合均匀后，调配成固含量为50wt％的负极浆料，涂覆于厚度为10μm的铜箔集流体的一个表面上，涂布厚度为50μm，得到单面涂布负极活性材料层的负极极片；之后，在该负极极片的另一个表面上重复以上步骤，冷压后即得到双面涂布负极活性材料层的负极极片。
<电解液的制备>
在含水量小于10ppm的环境下，将LiPF 6与非水溶剂按照EC:PC:丙酸丙酯:DEC＝1:1:1:1的质量比配制成电解液，其中，LiPF 6的浓度为1.15mol/L。
<锂离子电池的制备>
将正极极片、隔离膜、负极极片按顺序叠好，以PE多孔聚合薄膜作为隔离膜，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装壳体中，在80℃下脱去水分后，注入上述电解液并封装，经过化成、脱气、切边等工艺流程得到锂离子电池。
实施例2至实施例5
除了按照表1调整负极极片的粘结剂中支化聚乙烯亚胺盐的质量含量，聚丙烯酸锂的质量含量随之变化以外，其余与实施例1相同。
实施例6
除了将负极极片的粘结剂中支化聚乙烯亚胺盐替换为线性聚乙烯亚胺盐(Mw 1＝2100g/mol)，将聚丙烯酸锂替换为与羧甲基纤维素钠(CAS号：9004-32-4)，其余与实施例3相同。
实施例7
除了将负极极片的粘结剂中支化聚乙烯亚胺盐替换为线性聚乙烯亚胺盐(Mw 1＝2100g/mol)，将聚丙烯酸锂替换为与羟丙基羧甲基纤维素钠(Mw 2＝5×10 5g/mol)，其余与实施例3相同。
实施例8至实施例11
除了按照表1调整粘结剂在负极活性材料层中的质量比，其余与实施例3相同。
实施例12至实施例15
除了调整负极活性材料中的硅元素含量，使负极活性材料中的硅元素含量如表1所示，其余与实施例3相同。
实施例16至实施例19
除了按照表1调整负极活性材料的粒径，其余与实施例3相同。
实施例20至实施例23
除了按照表1调整负极活性材料层的压实密度，其余与实施例3相同。
对比例1
除了负极极片中的粘结剂采用聚丙烯酸锂，其余与实施例1相同。
对比例2
除了负极极片中的粘结剂采用羧甲基纤维素锂，其余与实施例1相同。
对比例3
除了负极极片的粘结剂采用2-氰基丙烯酸乙酯10份，氰乙基乙二胺5份，柠檬酸3份，聚乙烯亚胺3份，聚丙烯酸酯17份，钛酸酯偶联剂2份，过硫酸铵引发剂0.8份，其余与实施例3相同。
其中，实施例4和对比例1的负极极片粘结剂的胶膜储能模量测试结果和拉伸强度及 伸长率测试结果分别如图1和图2所示，可以看出，相比于聚丙烯酸锂作为粘结剂，本申请的粘结剂胶膜储能模量、断裂强度和断裂伸长率均明显升高。
实施例4和对比例1的负极极片中，负极活性材料层与负极集流体的粘结力、负极活性材料层的内聚力结果分别如图3和图4所示。可以看出，相比于采用羧酸盐类聚合物聚丙烯酸锂作为粘结剂的负极极片，采用本申请的粘结剂的负极极片，其粘结力和内聚力均有所提高。
实施例4和对比例1的锂离子电池的容量衰减曲线如图5所示。结果表明，采用本申请的粘结剂的锂离子电池，具有更高的循环容量保持率。
此外，各实施例和对比例的制备参数以及性能测试结果分别如表1和表2所示。
Figure PCTCN2021143979-appb-000001
Figure PCTCN2021143979-appb-000002
表2
Figure PCTCN2021143979-appb-000003
从实施例1至实施例5、对比例1和对比例2的比较可以看出，采用本申请的粘结剂，将聚乙烯亚胺盐与羧酸盐类聚合物混合后，粘结剂胶膜的储能模量、断裂强度以及断裂伸长率均得到明显提高。不限于任何理论，发明人认为，处于本申请含量及比例范围内的羧酸盐类聚合物和聚乙烯亚胺盐之间存在某种协同作用，使得获得的粘结剂在韧性提高的同时，模量也有所提高，使本申请的粘结剂兼具了高强度和高韧性的优势。
此外，采用本申请的粘结剂，负极极片的粘结力和内聚力都得到明显提升，锂离子电池循环容量保持率得到明显提高。不限于任何理论，发明人认为，聚乙烯亚胺盐中存在胺基阳离子，羧酸盐类聚合物中存在羧基阴离子，从而使两种分子之间存在分子间静电作用(粘结剂分子间作用示意图如图6所示)，在负极活性材料颗粒膨胀的过程中，粘结剂能够有效释放应力，保持分子网络的完整性，有效降低粘结界面破坏，提高了锂离子电池的循环性能。
从实施例6和实施例7中可以看出，采用本申请的不同聚乙烯亚胺盐与羧酸盐类聚合物的粘结剂，均能够实现储能模量、断裂伸长率、断裂强度的提升，相应地，采用所述粘结剂的负极极片的负极活性材料层的粘结力、内聚力以及锂离子电池的循环容量保持率也得到了提升。
从实施例3与对比例3的比较中可以看出，采用本申请的聚乙烯亚胺盐与羧酸盐类聚合物的粘结剂，相比于现有的含有聚乙烯亚胺和聚丙烯酸酯的粘结剂，胶膜的储能模量、断裂伸长率、断裂强度均有明显提升。
从实施例8至实施例11中可以看出，随着负极活性材料层中粘结剂含量的升高，负极极片的粘结力和内聚力均有所提升，锂离子电池的循环容量保持率也得到提高，然而粘结剂含量过高会降低电池的能量密度，因此本申请优选粘结剂在负极活性材料层中的含量为1wt％至10wt％。
从实施例12至实施例15中可以看出，随着负极活性材料中硅元素含量的升高，负极极片的粘结力和内聚力随之下降，锂离子电池的循环性能也逐渐下降，不限于任何理论，发明人认为，硅元素含量的增加导致负极活性材料的膨胀加剧，进而降低了负极极片的粘结力、内聚力以及锂离子电池的循环性能。因此，本申请中，基于所述负极活性材料的总重量，硅元素含量为1％至60％。还需说明的是，本申请中硅元素含量达到60％时，锂离子电池的循环容量保持率仍能达到88.5％，进一步说明本申请的粘结剂能够适用于含硅负极活性材料。
从实施例16至实施例19中可以看出，随着负极活性材料粒径的增大，负极极片的粘结力、内聚力随之下降以及循环性能也随之下降，不限于任何理论，发明人认为，负极活性材料粒径的增大会引起膨胀的增加，从而降低了负极极片的粘结力、内聚力以及锂离子电池的循环性能，本申请中，当负极活性材料的粒径D50在10μm至40μm范围内时，锂离子电池均保持较高的循环性能。
从实施例20至实施例23中可以看出，当负极活性材料层的压实密度在1.45g/cm 3至1.85g/cm 3范围内时，锂离子电池均保持较高的循环性能。
以上所述仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (16)

  1. 一种粘结剂，其中，所述粘结剂包括聚乙烯亚胺盐和羧酸盐类聚合物。
  2. 根据权利要求1所述的粘结剂，其中，基于所述粘结剂的总重量，所述聚乙烯亚胺盐的含量为0.2％至38％，所述羧酸盐类聚合物的含量为62％至99.8％。
  3. 根据权利要求1所述的粘结剂，其中，所述聚乙烯亚胺盐和所述羧酸盐类聚合物的质量比例为(1.7～2.3):1。
  4. 根据权利要求1所述的粘结剂，其中，所述聚乙烯亚胺盐包括支化聚乙烯亚胺盐或线性聚乙烯亚胺盐中的至少一种。
  5. 根据权利要求1所述的粘结剂，其中，所述羧酸盐类聚合物包括聚丙烯酸钠、聚丙烯酸锂、羧甲基纤维素钠、羧甲基纤维素锂、羟丙基羧甲基纤维素钠或羟丙基羧甲基纤维素锂中的至少一种。
  6. 根据权利要求1所述的粘结剂，其中，所述聚乙烯亚胺盐的重均分子量Mw 1为700g/mol至1×10 5g/mol；所述羧酸盐类聚合物重均分子量Mw 2为3000g/mol至8×10 6g/mol。
  7. 根据权利要求1至6中任一项所述的粘结剂，其具有以下特征中的至少一者：
    a)所述粘结剂的胶膜储能模量为3GPa至20GPa；
    b)所述粘结剂的胶膜拉伸断裂强度40MPa至140MPa；
    c)所述粘结剂的胶膜断裂伸长率为5％至40％。
  8. 一种负极极片，包括负极集流体和设置于所述负极集流体至少一个表面的负极活性材料层，所述负极活性材料层中包含权利要求1至7中任一项所述的粘结剂。
  9. 根据权利要求8所述的负极极片，其中，基于所述负极活性材料层的总重量，所述粘结剂的含量为1％至10％。
  10. 根据权利要求8所述的负极极片，其中，所述负极活性材料层中的负极活性材料包括硅、硅碳或氧化亚硅中的至少一种。
  11. 根据权利要求10所述的负极极片，其中，基于所述负极活性材料的总重量，硅元素含量为1％至60％。
  12. 根据权利要求10所述的负极极片，其中，所述负极活性材料还包括石墨或硬碳的至少一种。
  13. 根据权利要求10所述的负极极片，其中，所述负极活性材料的D50为5μm至40μm。
  14. 根据权利要求8至13中任一项所述的负极极片，其具有以下特征中的至少一者：
    d)所述负极活性材料层压实密度为1.45g/cm 3至1.85g/cm 3；
    e)所述负极活性材料层内聚力为20N/m至200N/m；
    f)所述负极活性材料层与所述负极集流体的粘结力为10N/m至850N/m。
  15. 一种电化学装置，其包括权利要求8至14中任一项所述的负极极片。
  16. 一种电子装置，其包括权利要求15所述的电化学装置。
PCT/CN2021/143979 2021-12-31 2021-12-31 一种粘结剂及其应用 WO2023123480A1 (zh)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/CN2021/143979 WO2023123480A1 (zh) 2021-12-31 2021-12-31 一种粘结剂及其应用
CN202180032143.9A CN115668548A (zh) 2021-12-31 2021-12-31 一种粘结剂及其应用

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2021/143979 WO2023123480A1 (zh) 2021-12-31 2021-12-31 一种粘结剂及其应用

Publications (1)

Publication Number Publication Date
WO2023123480A1 true WO2023123480A1 (zh) 2023-07-06

Family

ID=85015028

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2021/143979 WO2023123480A1 (zh) 2021-12-31 2021-12-31 一种粘结剂及其应用

Country Status (2)

Country Link
CN (1) CN115668548A (zh)
WO (1) WO2023123480A1 (zh)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101447561A (zh) * 2007-11-28 2009-06-03 三星Sdi株式会社 可再充电锂电池用负极和包括该负极的可再充电锂电池
CN103155231A (zh) * 2010-11-08 2013-06-12 独立行政法人产业技术综合研究所 蓄电设备用负极材料及使用了它的蓄电设备用负极
CN103606648A (zh) * 2013-11-15 2014-02-26 江苏天鹏电源有限公司 一种比容量高且循环性良好的锂离子电池
JP2017143027A (ja) * 2016-02-12 2017-08-17 株式会社豊田自動織機 負極電極用スラリー及び負極電極の製造方法
CN111710852A (zh) * 2020-06-12 2020-09-25 嘉兴学院 一种硅负极材料及其制备方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101447561A (zh) * 2007-11-28 2009-06-03 三星Sdi株式会社 可再充电锂电池用负极和包括该负极的可再充电锂电池
CN103155231A (zh) * 2010-11-08 2013-06-12 独立行政法人产业技术综合研究所 蓄电设备用负极材料及使用了它的蓄电设备用负极
CN103606648A (zh) * 2013-11-15 2014-02-26 江苏天鹏电源有限公司 一种比容量高且循环性良好的锂离子电池
JP2017143027A (ja) * 2016-02-12 2017-08-17 株式会社豊田自動織機 負極電極用スラリー及び負極電極の製造方法
CN111710852A (zh) * 2020-06-12 2020-09-25 嘉兴学院 一种硅负极材料及其制备方法

Also Published As

Publication number Publication date
CN115668548A (zh) 2023-01-31

Similar Documents

Publication Publication Date Title
WO2022141473A1 (zh) 一种电化学装置、电子装置及电化学装置制备方法
WO2022141448A1 (zh) 电化学装置、电子装置及电化学装置的制备方法
WO2022110050A1 (zh) 一种电化学装置和电子装置
CN113273005B (zh) 二次电池、包括该二次电池的装置、二次电池的制备方法及粘结剂组合物
WO2022141508A1 (zh) 一种电化学装置和电子装置
KR102217766B1 (ko) 리튬 이차전지용 양극 활물질, 이의 제조방법, 이를 포함하는 리튬 이차전지용 양극 및 리튬 이차전지
CN113366673B (zh) 电化学装置和电子装置
CN113066961B (zh) 负极极片、电化学装置和电子装置
WO2022262287A1 (zh) 电化学装置和电子装置
WO2022120651A1 (zh) 一种卷绕式电极组件、电化学装置及电子装置
WO2022205165A1 (zh) 一种隔离膜及包含所述隔离膜的电化学装置和电子装置
WO2023039750A1 (zh) 一种负极复合材料及其应用
US20210151739A1 (en) Method for manufacturing electrode for lithium ion battery
US20230307649A1 (en) Electrochemical apparatus and electronic apparatus
WO2023178470A1 (zh) 电化学装置和电子装置
JP2014026946A (ja) 非水電解質電池用セパレータ及び非水電解質電池
WO2022204963A1 (zh) 一种电化学装置和电子装置
US20230231145A1 (en) Electrochemical apparatus and electronic apparatus
CN114128028A (zh) 用于电化学装置的复合隔板和包括该复合隔板的电化学装置
WO2023123480A1 (zh) 一种粘结剂及其应用
WO2023184208A1 (zh) 一种粘结剂、电化学装置和电子装置
WO2024077507A1 (zh) 粘结组合物、电极浆料、电极极片、二次电池及用电装置
WO2022141507A1 (zh) 极片、电化学装置和电子装置
JP7431040B2 (ja) シリコン材料、蓄電デバイス用電極、蓄電デバイス及びシリコン材料の製造方法
WO2022204962A1 (zh) 一种电化学装置和电子装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 21964973

Country of ref document: EP

Kind code of ref document: A1