WO2024077507A1 - 粘结组合物、电极浆料、电极极片、二次电池及用电装置 - Google Patents

粘结组合物、电极浆料、电极极片、二次电池及用电装置 Download PDF

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WO2024077507A1
WO2024077507A1 PCT/CN2022/124776 CN2022124776W WO2024077507A1 WO 2024077507 A1 WO2024077507 A1 WO 2024077507A1 CN 2022124776 W CN2022124776 W CN 2022124776W WO 2024077507 A1 WO2024077507 A1 WO 2024077507A1
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group
cross
linking agent
bonding composition
main polymer
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PCT/CN2022/124776
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English (en)
French (fr)
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徐军
张铜贤
张明
庄再裕
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/124776 priority Critical patent/WO2024077507A1/zh
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    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

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  • the present application relates to the field of batteries, and in particular to an adhesive composition, an electrode slurry, an electrode plate, a secondary battery and an electrical device.
  • the cycle life of secondary batteries is often improved by increasing the loading amount of active materials on the pole piece.
  • the specific preparation process is: coating the electrode slurry containing active materials on the current collector, and then drying to obtain the pole piece. Increasing the coating thickness can increase the loading amount of active materials on the obtained pole piece.
  • the volatilization of the solvent will cause stress inside the pole piece.
  • the cohesive force provided by the binder component in the electrode slurry is not enough to withstand the stress, which will cause the pole piece to crack.
  • the pole piece is prone to cracking, which has a negative impact on the cycle stability of the secondary battery.
  • the repeated charge and discharge of the battery will cause the volume of the active material to change, which will cause the pole piece structure to be destroyed, thereby reducing the cycle stability of the secondary battery.
  • the present application provides a bonding composition, an electrode slurry, an electrode plate, a secondary battery and an electrical device, aiming to improve the stability and anti-cracking ability of the electrode plate, thereby improving the cycle stability of the secondary battery.
  • a bonding composition comprising a main polymer and a cross-linking agent, the main polymer comprising structural units represented by formulas (1) to (3):
  • X1 represents a structural group containing a first active group, and each occurrence of X2 is independently selected from H or an alkyl group having 1 to 10 carbon atoms;
  • the first active group can chemically react with the functional group contained in the cross-linking agent, and the functionality of the cross-linking agent is ⁇ 2.
  • the components of the above-mentioned binder include a main polymer containing specific structural units.
  • a main polymer containing specific structural units When preparing an electrode plate, the presence of a cyano group and a first active group can increase the solid content and adhesion of the electrode slurry.
  • the hydrocarbon segment in the structure shown in formula (3) is beneficial to improving the flexibility of the electrode plate and can prevent the film layer from cracking.
  • the first active group in the main polymer can react chemically with the functional group in the cross-linking agent, and the formed cross-linked network structure has a small swelling degree in solvents such as electrolytes.
  • the swelling degree of the electrode active layer in the electrolyte can be suppressed, thereby suppressing the swelling of the electrode plate, thereby reducing the volume expansion of the battery, maintaining good conductivity of the electrode plate, and improving the cycle performance of the battery.
  • the structural unit of formula (1) satisfies at least one of the conditions (a) to (b):
  • X1 is selected from the first reactive group or an alkyl group having 1 to 10 carbon atoms substituted by the first reactive group;
  • the first reactive group includes at least one of a carboxyl group, an amine group, a hydroxyl group, an epoxy group and an amidoxime group.
  • the chemical reaction includes at least one of a condensation reaction and a ring-opening reaction.
  • the functional group contained in the cross-linking agent includes at least one of an amine group, a hydroxyl group, a carbodiimide group, an aziridine group and an isocyanate group.
  • the mass proportion of the structural unit represented by formula (3) is 55% to 75%
  • the mass proportion of the structural unit represented by formula (2) is 10% to 38%
  • the mass proportion of the structural unit represented by formula (1) is 0.1% to 25%.
  • the weight average molecular weight of the main polymer is 300,000 to 700,000; optionally, the weight average molecular weight of the main polymer is 400,000 to 700,000.
  • the mass ratio of the main polymer to the cross-linking agent is (0.5-5):(0.01-0.4); optionally, the mass ratio of the main polymer to the cross-linking agent is (0.5-5):(0.1-0.3).
  • each occurrence of X2 is independently selected from any one of H, methyl, ethyl or isopropyl.
  • an electrode slurry comprising an electrode active material and the bonding composition of the first aspect.
  • the mass proportion of the main polymer is 0.5% to 5%.
  • the mass proportion of the cross-linking agent is 0.01% to 0.4%;
  • the mass proportion of the cross-linking agent is 0.1% to 0.3%.
  • the electrode active material satisfies at least one of the following conditions (c) to (d):
  • the electrode active material comprises a positive electrode active material
  • the electrode active material accounts for 74.60% to 99.49%.
  • the solid content of the electrode slurry is 50% to 80%.
  • an electrode plate comprising a current collector and an active layer located on the surface of the current collector, wherein the raw material for preparing the active layer comprises the bonding composition of the first aspect; or
  • the active layer is prepared by using the electrode slurry of the second aspect; or
  • the active layer has a cross-linked network structure in which the main polymer in the bonding composition of the first aspect and the cross-linking agent are connected by cross-linking groups, and the cross-linking groups include groups formed by chemical reactions between the first active groups in the main polymer and the functional groups contained in the cross-linking agent.
  • a secondary battery comprising the electrode plate according to the third aspect.
  • an electrical device wherein the electrical device comprises the secondary battery according to the fourth aspect.
  • FIG. 1 is a schematic diagram of one embodiment of a secondary battery.
  • FIG. 2 is an exploded view of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 4 is an exploded view of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of an electric device using a secondary battery as a power source.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • multiple refers to more than two (including two).
  • multiple groups refers to more than two groups (including two groups), and “multiple pieces” refers to more than two pieces (including two pieces).
  • alkyl refers to a group formed when an alkane loses a hydrogen, such as methane losing a hydrogen to form a methyl group.
  • chain alkane refers to an alkane in which the carbon atoms are all connected by carbon-carbon single bonds and do not form a ring, and the remaining valence bonds are all bonded to hydrogen, including straight-chain alkanes and branched-chain alkanes.
  • linking site when a linking site is not specified in a group, it means that an optional linking site in the group can be used as a linking site.
  • structural unit means: the basic unit of a monomer molecule entering a macromolecular chain through a polymerization reaction, also called a "monomer unit".
  • the elemental composition of a structural unit may be the same as or different from the elemental composition of a monomer unit.
  • the structural unit in a polymer molecule may be one or more.
  • the "structural unit” is a repeating unit.
  • polyvinyl chloride (CH 2 —CHCl)n its repeating unit is the same as the structural unit, both of which are —CH 2 CHCl—, while nylon-66 has two structural units.
  • the volatilization of the solvent will cause stress inside the pole piece.
  • the cohesive force provided by the binder component in the electrode slurry is not enough to withstand the stress, which will cause the pole piece to crack.
  • the pole piece is prone to cracking, which has a negative impact on the cycle stability of the battery.
  • linear binders such as PVDF or SBR are often used, and their cohesive force is not enough to withstand drying stress.
  • the technical personnel of this application have conducted a lot of experimental research on the structure of the binder and the performance of the pole piece, and found that the cross-linked structure of the three-dimensional network structure of the binder is only one of the factors that improve the cohesion of the binder.
  • the selection of groups on the macromolecular chain in the binder also plays an important role in the bonding strength and stability of the binder.
  • the technical personnel of this application have obtained the bonding composition in this application that can improve the stability and crack resistance of the pole piece, and thus improve the cycle stability of the battery.
  • One embodiment of the present application provides a bonding composition, which includes a main polymer and a cross-linking agent, wherein the main polymer includes structural units represented by formulas (1) to (3):
  • X1 represents a structural group containing a first active group, and each occurrence of X2 is independently selected from H or an alkyl group having 1 to 10 carbon atoms.
  • the first active group can chemically react with the functional group contained in the cross-linking agent, and the functionality of the cross-linking agent is ⁇ 2.
  • the components of the above-mentioned binder include a main polymer containing specific structural units.
  • the presence of the cyano group and the first active group can increase the solid content and adhesion of the electrode slurry.
  • the hydrocarbon segment in the structure shown in formula (3) is beneficial to improving the flexibility of the electrode plate and preventing the film layer from cracking.
  • the first active group in the main polymer can react chemically with the functional group in the cross-linking agent to form a cross-linked network structure with a small swelling degree in solvents such as electrolytes.
  • the swelling degree of the electrode active layer in the electrolyte can be suppressed, thereby suppressing the swelling of the electrode plate, thereby reducing the volume expansion of the battery, maintaining good conductivity of the electrode plate, and improving the cycle performance of the battery.
  • the functionality of the crosslinking agent refers to the number of functional groups contained in one molecule of the crosslinking agent.
  • the functionality of the crosslinking agent can be measured by a commonly used functionality test method in the art, for example, a small molecule crosslinking agent can be determined based on the molecular structure of the compound, and a polymer can be calculated by the molecular weight after the crosslinking and the characteristic peak area ratio obtained by NMR testing to obtain an average functionality.
  • the functionality can be found based on the product model information.
  • X1 or X2 may be the same or different each time it appears.
  • the * in the structure is the connection site between the structure and the chain-forming atoms of the main chain in the host polymer.
  • the polymerization form of the structural units represented by formulas (1) to (3) can be random copolymerization, regular copolymerization, or block copolymerization.
  • the main polymer is composed of structural units represented by formulas (1) to (3).
  • the first reactive group includes at least one of a carboxyl group, an amine group, a hydroxyl group, an epoxy group, and an amidoxime group.
  • X1 is selected from the first reactive group or an alkyl group having 1 to 10 carbon atoms substituted by the first reactive group.
  • X1 can be a single first reactive group, such as a carboxyl group, an amine group, a hydroxyl group, an epoxy group, and an amidoxime group, or an alkyl group having 1 to 10 carbon atoms substituted by at least one first reactive group, such as a methyl group substituted by a hydroxyl group, or a methyl group substituted by an amine group.
  • X1 is selected from the first reactive group or a chain alkyl group having 1 to 10 carbon atoms substituted by the first reactive group.
  • X1 is selected from the first reactive group or a chain alkyl group having 1 to 5 carbon atoms substituted by the first reactive group.
  • X1 is selected from the first reactive group or a linear alkyl group having 1 to 5 carbon atoms substituted by the first reactive group.
  • the functional group contained in the cross-linking agent includes at least one of an amine group, a hydroxyl group, a carbodiimide group, an aziridine group and an isocyanate group.
  • the chemical reaction includes at least one of a condensation reaction and a ring-opening reaction.
  • Condensation reaction refers to the reaction in which two organic substances interact with each other to form a new molecule. Some condensation reactions are accompanied by the release of small molecules, such as water, while some do not release small molecules.
  • the specific pathways of condensation reactions include, but are not limited to, substitution, addition, and elimination. For example, carboxylic acid and hydroxyl, carboxylic acid and amine are condensed through substitution, which can also be called esterification or amidation, while hydroxyl and hydroxyl can be condensed through dehydration elimination.
  • the amine group can undergo condensation reaction or ring-opening reaction with functional groups such as carboxyl group and epoxy group
  • the hydroxyl group can undergo condensation reaction or ring-opening reaction with functional groups such as carboxyl group, epoxy group, hydroxyl group, etc.
  • the carbodiimide group can react with carboxyl group or epoxy group
  • the aziridine group can react with functional groups such as carboxyl group, amine group, hydroxyl group, epoxy group and amidoxime group
  • the isocyanate group can react with functional groups such as carboxyl group, amine group, hydroxyl group, etc.
  • hydroxyl groups can also undergo dehydration condensation reaction.
  • the cross-linking agent is at least one of aziridine, polycarbodiimide, isocyanate cross-linking agent or isocyanate-modified aziridine cross-linking agent.
  • the cross-linking agent is an aziridine cross-linking agent.
  • the crosslinking agent is polyethylenimine crosslinking agent SaC-100, and further, its average functionality is 2.8.
  • the mass proportion of the structural unit represented by formula (3) is 55% to 75%
  • the mass proportion of the structural unit represented by formula (2) is 10% to 38%
  • the mass proportion of the structural unit represented by formula (1) is 0.1% to 25%.
  • the adhesion and toughness can be further improved.
  • the mass percentage of the structural unit represented by formula (3) is 65% to 75%.
  • the mass percentage of the structural unit represented by formula (2) is 18% to 28%.
  • the mass percentage of the structural unit represented by formula (1) is 1% to 25%.
  • the value can be the two end points or any value between the two end points.
  • Non-limiting examples include but are not limited to: 55%, 60%, 65%, 70%, 75%.
  • the value can be the two end points and any value between the two end points.
  • Non-limiting examples include but are not limited to: 10%, 15%, 18%, 20.0%, 25.0%, 28.0%, 30.0%, 34.0%, 34.9%, 35%, 36%, 37%, 38%.
  • the value can be the two end points and any value between the two end points.
  • Non-limiting examples include but are not limited to: 0.1%, 0.5%, 1%, 2%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%.
  • the weight average molecular weight of the main polymer is 300,000 to 700,000.
  • the adhesion and stability of the adhesive composition can be further optimized.
  • the molecular weight of the main polymer is too low, the generated bonding force is insufficient to meet the requirements, the bonding effect is poor, and the pole piece is prone to cracking and demolding; when the molecular weight of the main polymer is too high, it is easy to have problems such as difficulty in dissolving and slurry gelling.
  • the weight average molecular weight of the main polymer is 400,000 to 700,000.
  • the weight average molecular weight of the main polymer is 500,000 to 700,000.
  • the mass ratio of the main polymer to the cross-linking agent is (0.5-5):(0.01-0.4).
  • the mass ratio of the main polymer to the cross-linking agent is (0.5-5):(0.1-0.3).
  • the degree of cross-linking between the two can be regulated, and the perfection of the formed cross-linked network structure can be further optimized.
  • the anti-swelling performance can be improved while ensuring good toughness and adhesion, thereby improving the anti-cracking performance of the electrode plates.
  • each occurrence of X2 is independently selected from any one of H or a chain alkyl group having 1 to 10 chain carbon atoms.
  • each occurrence of X2 is independently selected from any one of H or a linear alkyl group having 1 to 5 chain carbon atoms.
  • each occurrence of X2 is independently selected from any one of H, methyl, ethyl or isopropyl.
  • the bonding composition further comprises a functional additive
  • the functional additive includes but is not limited to at least one of an antioxidant and an antioxidant.
  • the mass proportions of the structural units shown in formulas (1) to (3) in the main polymer can be controlled by controlling the feed ratio of each type of monomer.
  • the feed ratio of each type of monomer can be regarded as the mass proportion of the structural units shown in formulas (1) to (3) in the main polymer; the mass proportion of the structural units shown in formulas (1) to (3) can also be calculated and analyzed by measuring the content of each active functional group in the prepared main polymer.
  • an electrode slurry is provided.
  • the electrode slurry includes an electrode active material and the bonding composition of the first aspect.
  • the mass proportion of the main polymer in the bonding composition is 0.5% to 5%.
  • the mass proportion of the cross-linking agent is 0.01% to 0.4%.
  • the mass proportion of the cross-linking agent is 0.1% to 0.3%.
  • the electrode active material may be a positive electrode active material or a negative electrode active material.
  • the electrode active material includes a positive electrode active material.
  • the positive electrode active material may be a commonly used positive electrode active material in the present application, such as a lithium ion positive electrode active material or a sodium ion positive electrode active material.
  • the lithium ion active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • an olivine-structured lithium-containing phosphate a lithium transition metal oxide
  • their respective modified compounds their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide , lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Mn0 .
  • lithium-containing phosphates with olivine structure may include but are not limited to at least one of lithium iron phosphate (such as LiFePO 4 , referred to as LFP) lithium manganese phosphate (such as LiMnPO 4 ), and lithium manganese iron phosphate.
  • lithium iron phosphate such as LiFePO 4 , referred to as LFP
  • lithium manganese phosphate such as LiMnPO 4
  • lithium manganese iron phosphate lithium manganese iron phosphate
  • the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO 4 , where x is any number from 0 to 1.
  • LiFe x Mn (1-x) PO 4 is LiMnPO 4 lithium manganese phosphate
  • LiFePO 4 is LiFePO 4 lithium iron phosphate (LFP).
  • the sodium ion active material may include at least one of the following materials: at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound.
  • a sodium transition metal oxide at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.
  • the positive electrode active material includes at least one of a sodium transition metal oxide, a polyanionic compound and a Prussian blue compound;
  • the transition metal in the sodium transition metal oxide, includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the sodium transition metal oxide is, for example, Na x MO 2 , wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 ⁇ x ⁇ 1.
  • the polyanionic compound can be a class of compounds having sodium ions, transition metal ions and tetrahedral (YO 4 ) n- anion units.
  • the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y includes at least one of P, S and Si;
  • n represents the valence state of (YO 4 ) n- .
  • the polyanionic compound may also be a compound having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions.
  • the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y includes at least one of P, S and Si, and
  • n represents the valence state of (YO 4 ) n- ;
  • the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ and optional halogen anions.
  • Y includes at least one of P, S and Si, and n represents the valence state of (YO 4 ) n- ;
  • Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents the valence state of (ZO y ) m+ ;
  • the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound is, for example, at least one of NaFePO4 , Na3V2 ( PO4 ) 3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3 ( PO4 ) 2 ( P2O7 ), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3 ( VOy ) 2 ( PO4 )2F3-2y ( 0 ⁇ y ⁇ 1 ).
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - ).
  • the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the proportion of the electrode active material is 74.60% to 99.49%.
  • the electrode slurry further includes a conductive agent.
  • the conductive agent may be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs and graphene and composite conductive agents thereof.
  • the weight ratio of the conductive agent is 0 to 20 wt % based on the total weight of the components in the electrode slurry except the solvent.
  • the solid content of the electrode slurry is 50% to 80%.
  • an electrode plate comprises a current collector and an active layer located on the surface of the current collector, and the raw material for preparing the active layer comprises the above-mentioned bonding composition; or
  • the active layer is prepared by using the above-mentioned electrode slurry; or
  • the active layer has a cross-linked network structure in which the main polymer in the bonding composition and the cross-linking agent are connected by cross-linking groups.
  • the cross-linking groups include groups formed by chemical reactions between the first active groups in the main polymer and the functional groups contained in the cross-linking agent.
  • the electrode plate has excellent toughness and swelling resistance.
  • the electrode plate when the electrode active material in the above active layer is a positive electrode active material, the electrode plate is a positive electrode plate, and when the electrode active material in the above active layer is a negative electrode active material, the electrode plate is a negative electrode plate.
  • the electrode sheet is a positive electrode sheet.
  • the current collector in the positive electrode sheet has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the current collector in the positive electrode sheet may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • the solid content of the positive electrode slurry is 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa ⁇ s to 25000mPa ⁇ s.
  • the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet; the unit surface density of the positive electrode powder coating is 150 to 350mg/ m2 , and the compaction density of the positive electrode sheet is 3.0 to 3.6g/ cm3 , and can be optionally 3.3 to 3.5g/ cm3 .
  • the calculation formula of the compaction density is:
  • Compacted density coating surface density/(thickness of the electrode after extrusion - thickness of the current collector).
  • a secondary battery includes the electrode plate as described above.
  • the electrode plate is a positive electrode plate, which will not be described in detail here.
  • the negative electrode plate and the isolation membrane are briefly described as follows.
  • the negative electrode plate includes a current collector and a negative electrode active layer arranged on the surface of the current collector.
  • the components of the negative electrode active layer include a negative electrode active material, a negative electrode conductive agent and a negative electrode binder.
  • the negative electrode active material adopts the commonly used negative electrode active material in this application; further, as an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate, etc.
  • the silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys.
  • the tin-based material can be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.
  • the weight ratio of the negative electrode active material in the negative electrode active layer is 70 wt % to 100 wt % based on the total weight of the negative electrode active layer.
  • the negative electrode conductive agent can be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it can be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs and graphene and composite conductive agents thereof.
  • the weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.
  • the above-mentioned negative electrode binder can be a commonly used binder in the art, and can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.
  • the negative electrode active layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of other additives in the negative electrode active layer is 0-15 wt%.
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as carbon material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000mPa ⁇ s to 10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained.
  • the negative electrode powder coating unit area density is 75mg/ m2 to 220mg/ m2
  • the negative electrode sheet compaction density is 1.2g/ m3 to 2.0g/ m3 .
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet.
  • the present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the secondary battery further comprises an electrolyte.
  • the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly by a winding process or a lamination process.
  • the electrolyte plays a role of conducting ions between the positive electrode and the negative electrode.
  • the electrolyte may include an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiPF
  • the above-mentioned solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl
  • the electrolyte further includes additives, such as additives that may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance.
  • additives such as additives that may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance.
  • the secondary battery further comprises a shell for packaging the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte.
  • the shell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. It may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • the secondary battery of the present application is a lithium-ion secondary battery.
  • FIG1 is a secondary battery 4 of a square structure as an example.
  • the housing may include a shell 41 and a cover plate 43.
  • the shell 41 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
  • the shell 41 has an opening connected to the receiving cavity, and the cover plate 43 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly 42.
  • the electrode assembly 42 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 42.
  • the number of electrode assemblies 42 included in the battery 4 can be one or more, which can be adjusted according to needs.
  • the present application also provides an electrical device, which includes the secondary battery mentioned above.
  • the secondary battery may exist in the form of a battery cell, or may be further assembled into a battery pack.
  • the battery pack 1 includes a battery box and one or more secondary batteries 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and form a closed space for the secondary batteries 4.
  • the plurality of secondary batteries 4 may be arranged in the battery box in any manner.
  • the secondary battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.
  • the above-mentioned electrical devices may be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • mobile devices such as mobile phones, laptops, etc.
  • electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.
  • electric trains ships and satellites, energy storage systems, etc.
  • Fig. 5 is an example of an electric device 5.
  • the electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack may be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a battery may be used as a power source.
  • 400g of water, 90g of acrylonitrile, 20g of methacrylic acid and the prepared appropriate amount of emulsifier, regulator, activator, etc. are accurately measured and added into a 10L polymerization kettle, evacuated and replaced with nitrogen for 3 times, 200g of butadiene is added, the temperature in the kettle is adjusted to the reaction temperature, and 0.5wt% of initiator potassium persulfate is added to initiate polymerization. After the reaction starts, the total solid content of the latex is measured at regular intervals and the conversion rate is calculated. When the conversion rate reaches the control index, 0.05wt% of terminator dimethyl dithiocarbamate is added, and the temperature is lowered and discharged to obtain the main polymer latex.
  • the prepared polymer latex was transferred to a coagulation kettle, and 700 g of sodium chloride aqueous solution was added during stirring for coagulation.
  • the coagulated rubber blocks were washed with soft water for several times and then placed in a blast drying oven for drying to obtain the main polymer raw rubber.
  • the weight average molecular weight of the synthesized substance was confirmed by nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography.
  • the nitrile content was measured by nitrogen determination method and the carboxyl content was measured by non-aqueous titration method.
  • the mass proportion of each monomer structure was analyzed and calculated. The specific results are shown in Table 1.
  • the positive electrode slurry was evenly coated on one surface of an aluminum foil with a thickness of 12 ⁇ m to obtain a single-sided film sheet with a weight of 400 mg/1540.25 mm 2 (excluding substrate), dried at 105° C., cold pressed, and subjected to tab forming, slitting and other processes to obtain a positive electrode sheet.
  • the negative electrode slurry was evenly coated on one surface of an aluminum foil or copper foil with a thickness of 8 ⁇ m, dried at 110°C, and cold pressed to obtain a prefabricated electrode sheet with a negative electrode active material layer thickness of 110 ⁇ m, and then subjected to processes such as tab forming and slitting to obtain a negative electrode sheet.
  • non-aqueous organic solvents ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent, and then the lithium salt LiPF6 was dissolved in the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol/L.
  • Isolation film Polypropylene film is used as the isolation film.
  • Preparation of lithium-ion batteries stack the positive electrode sheet, separator, and negative electrode sheet in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, and then wind them to obtain an electrode assembly; place the electrode assembly in an outer packaging shell, inject electrolyte after drying, and obtain a lithium-ion battery through vacuum packaging, standing, forming, shaping and other processes.
  • Test tool Rolling needle (diameter: 1mm, 1.2mm, 1.5mm, 2mm, 3mm)
  • Needle winding Take the cold-pressed electrode, start with the largest needle (3mm), and wind the electrode around the needle in sequence, aligning the part around the needle with force;
  • Microscope observation Aim the objective lens at the bent tip, magnify it 100 times, and observe whether there are cracks. Record the diameter of the winding needle that the positive electrode can withstand. The smaller the diameter of the winding needle that can be tolerated, the better the flexibility.
  • Sample preparation Glue the cold-pressed double-sided positive electrode sheet to the substrate with double-sided tape.
  • Test Place the prepared sample on a tensile testing machine and use a 90° peel test method. Record the value when the tensile testing machine reading is stable, which is the bonding force of the electrode.
  • An optical microscope was used to observe the number of cracks on the surface of the pole piece before cold pressing, and the number of cracks within a range of 50 mm ⁇ 50 mm was recorded.
  • Positive electrode sheet immersion electrolyte peeling test Dry the positive electrode sheet, then soak it in the electrolyte for 24 hours, take it out and place it in a 60°C oven to dry, and observe whether it peels off.
  • lithium-ion batteries 7. The performance of lithium-ion batteries is tested, including the following:
  • the lithium-ion battery was charged at a constant current of 1/3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left to stand for 5 minutes, and then discharged at 1/3C to 2.5V to record the discharge capacity C0.
  • the lithium-ion battery was then charged to 3.65V at a constant current of 1.0C, left to stand for 5 minutes, and then discharged to 2.5V at 1/3C to record the discharge capacity C1.
  • Discharge gram capacity test The battery was charged to 3.65V at a constant current of 1/3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left to stand for 5 minutes, and then discharged to 2.5V at 1/3C, and the discharge capacity C0 was recorded.
  • the discharge gram capacity was calculated based on the weight ratio of C0 to the active material.
  • the lithium-ion battery made of the positive electrode sheet is cycled at 45°C for 800 cycles according to the above-mentioned cycle charging conditions, and then discharged at a constant current of 1/3C to 2.5V.
  • the lithium-ion battery is disassembled and the thickness of the positive electrode sheet is tested and recorded as K1.
  • the thickness expansion rate of the positive electrode plate K (%) (K1/K0-1) ⁇ 100%.
  • the thickness of the pole piece is tested using a micrometer.
  • the volume expansion of the positive electrode sheet and the secondary battery can be characterized by the thickness growth rate of the positive electrode sheet, wherein the smaller the thickness growth rate of the positive electrode sheet, the smaller the volume expansion of the positive electrode sheet and the secondary battery.
  • Examples 2 to 7 are basically the same as Example 1, except that in step (1), the mass ratio of acrylonitrile, methacrylic acid, and butadiene is controlled, as shown in Table 1.
  • Examples 8 to 11 are substantially the same as Example 1, except that in step (1), the degree of polymerization is controlled to obtain main polymers with different molecular weights.
  • Examples 12 to 15 are substantially the same as Example 1. The only difference is that in step (2), the addition amounts of the positive electrode active material and the main polymer are regulated so that the proportion of the main polymer in the solid component of the positive electrode slurry is different from that in Example 1.
  • Examples 16 to 19 are substantially the same as Example 1. The only difference is that in step (2), the amount of the positive electrode active material and the crosslinking agent added is adjusted so that the proportion of the crosslinking agent in the solid component of the positive electrode slurry is different from that in Example 1.
  • Example 20 is substantially the same as Example 1, except that in step (1), acrylonitrile is replaced by methacrylonitrile.
  • Example 21 is substantially the same as Example 1, except that in step (1), acrylic acid is replaced by allyl alcohol.
  • Example 22 is substantially the same as Example 1, except that in step (1), acrylic acid is replaced by allylamine.
  • Comparative Example 1 is substantially the same as Example 2, except that in step (3), the main polymer is replaced with an equal mass of nitrile rubber.
  • Comparative Example 2 is substantially the same as Example 1, except that in step (2), the main polymer is replaced with an equal mass of nitrile rubber and no cross-linking agent is added.
  • Comparative Example 3 is basically the same as Example 1, except that: in step (2), polyvinylidene fluoride (HSV900) is directly used as a binder, and the preparation process is as follows:
  • the lithium iron phosphate positive electrode active material, the conductive agent carbon black, and polyvinylidene fluoride (HSV900) were mixed evenly in a mass ratio of 97.0:1.0:2.0, and then NMP was added as a solvent. The mixture was stirred under a vacuum mixer until the system was uniform to obtain a positive electrode slurry with a solid content of 55wt%.
  • the positive electrode slurry was evenly coated on one surface of an aluminum foil with a thickness of 12 ⁇ m to obtain a single-sided film sheet with a weight of 400 mg/1540.25 mm 2 (excluding substrate), dried at 105° C., cold pressed, and subjected to tab forming, slitting and other processes to obtain a positive electrode sheet.
  • A represents the mass fraction of the structural monomer part generated by butadiene through polymerization reaction
  • B represents the mass fraction of the structural monomer part generated by acrylonitrile or methacrylonitrile through polymerization reaction
  • C represents the mass fraction of the structural unit containing the first active group in the main polymer
  • D represents the weight average molecular weight of the synthesized main polymer
  • E represents the mass fraction of the main polymer in the solid component of the slurry
  • F1 represents the mass fraction of the cross-linking agent in the solid component of the slurry
  • F2 represents the average functionality of the cross-linking agent
  • N represents the diameter of the winding needle that can be tolerated during the flexibility test of the positive electrode
  • T represents the bonding force
  • G represents the number of cracks in the electrode
  • H represents the swelling degree
  • J represents the demolding test result of immersion in electrolyte (whether demolding)
  • K represents the thickness expansion rate of the positive electrode
  • W represents the discharge capacity in grams of the lithium-

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Abstract

本申请涉及一种粘结组合物、电极浆料、电极极片、二次电池及用电装置。该粘结组合物包括主体聚合物及交联剂，所述主体聚合物包括式(1)～(3)所示的结构单元，其中，X1表示含有第一活性基团的结构基团，X2每次出现，分别独立地选自H或碳原子数为1～10的烷基；所述第一活性基团能与所述交联剂含有的官能团发生化学反应，且所述交联剂的官能度≥2。该粘结组合物用于制备电极极片时，能提高极片的稳定性及防开裂能力，进而能提高二次电池的循环稳定性。

Description

粘结组合物、电极浆料、电极极片、二次电池及用电装置 技术领域
本申请涉及电池领域，具体涉及一种粘结组合物、电极浆料、电极极片、二次电池及用电装置。
背景技术
二次电池具有出色的循环性能、优异的安全性能、较低的成本及环境友好等特点，是新能源领域的关注热点。随着科技的发展，为满足各种电器的小型化、轻薄化的发展趋势以及提升电动汽车的续航里程，人们对锂电池的循环使用寿命提出越来越高的要求。
传统技术中，常通过提高极片上的活性物质的负载量来提高二次电池的循环使用寿命，具体制备过程为：将含活性物质的电极浆料涂布在集流体上，然后干燥制得极片，提高涂布的厚度就可以提高制得的极片上活性物质的负载量。然而，在干燥过程中，溶剂的挥发会使极片内部产生应力，电极浆料中的粘结剂组分提供的内聚力不足以承受应力，就会导致极片开裂，特别是厚涂布时，极片容易出现开裂的问题，反而对二次电池的循环稳定性产生负面影响，同时，电池的反复充放电会使活性材料的体积发生变化，会导致极片结构被破坏，从而降低二次电池的循环稳定性。
发明内容
鉴于上述问题，本申请提供一种粘结组合物、电极浆料、电极极片、二次电池及用电装置，旨在提高极片的稳定性及防开裂能力，进而能提高二次电池的循环稳定性。
本申请第一方面，提供了一种粘结组合物，所述粘结组合物包括主体聚合物及交联剂，所述主体聚合物包括式(1)～(3)所示的结构单元：
Figure PCTCN2022124776-appb-000001
其中，X 1表示含有第一活性基团的结构基团，X 2每次出现，分别独立地 选自H或碳原子数为1～10的烷基；
所述第一活性基团能与所述交联剂含有的官能团发生化学反应，且所述交联剂的官能度≥2。
上述粘结剂的组分包括含有特定结构单元的主体聚合物，制备电极极片时，其中氰基和第一活性基团的存在可提高电极浆料的固含量及粘结性，式(3)所示结构中的烃链段有利于提高电极极片的柔韧性，能防止膜层开裂，与此同时，主体聚合物中的第一活性基团能与交联剂中的官能团可以发生化学反应，形成的交联网状结构在电解液等溶剂中的溶胀度小，由此，在保持优异的粘结性能的同时，能抑制电极活性层在电解液中的溶胀度，从而抑制电极极片的溶胀，进而降低电池的体积膨胀，保持电极极片良好的导电性，提高电池的循环性能。
在本申请任意实施例中，所述式(1)结构单元满足(a)～(b)中至少一个条件：
(a)X 1选自第一活性基团或被所述第一活性基团取代的碳原子数为1～10的烷基；
(b)所述第一活性基团包括羧基、胺基、羟基、环氧基团及偕胺肟基中的至少一种。
在本申请任意实施例中，所述化学反应包括缩合反应和开环反应中的至少一种。
在本申请任意实施例中，所述交联剂含有的官能团包括胺基、羟基、碳化二亚胺基团、氮丙啶基团和异氰酸酯基中的至少一种。
在本申请任意实施例中，在所述主体聚合物中，所述式(3)所示的结构单元的质量占比为55％～75％，所述式(2)所示的结构单元的质量占比为10％～38％，所述式(1)所示的结构单元的质量占比为0.1％～25％。
在本申请任意实施例中，所述主体聚合物的重均分子量为30万～70万；可选地，所述主体聚合物的重均分子量为40万～70万。
在本申请任意实施例中，所述主体聚合物与所述交联剂的质量之比为(0.5～5):(0.01～0.4)；可选地，所述主体聚合物与所述交联剂的质量之比为(0.5～5):(0.1～0.3)。
在本申请任意实施例中，X 2每次出现，分别独立地选自H、甲基、乙基 或异丙基中的任意一种。
本申请第二方面，提供一种电极浆料，所述电极浆料包括电极活性材料及第一方面的粘结组合物。
在本申请任意实施例中，以所述电极浆料中除溶剂之外的组分的总质量为基准，所述主体聚合物的质量占比为0.5％～5％。
在本申请任意实施例中，以所述电极浆料中除溶剂之外的组分的总质量为基准，所述交联剂的质量占比为0.01％～0.4％；
可选地，所述交联剂的质量占比为0.1％～0.3％。
在本申请任意实施例中，所述电极活性材料满足如下条件(c)～(d)中的至少一个：
(c)所述电极活性材料包括正极活性材料；
(d)以所述电极浆料中除溶剂之外的组分的总质量为基准，所述电极活性材料的占比为74.60％～99.49％。
在本申请任意实施例中，所述电极浆料的固含量为50％～80％。
本申请第三方面，提供一种电极极片，所述电极极片包括集流体及位于所述集流体表面的活性层，所述活性层的制备原料包括第一方面的粘结组合物；或
所述活性层采用第二方面的电极浆料制得；或
所述活性层具有第一方面的粘结组合物中的所述主体聚合物与所述交联剂通过交联基团连接的交联网状结构，所述交联基团包括所述主体聚合物中的所述第一活性基团与所述交联剂含有的官能团经化学反应形成的基团。
本申请第四方面，提供一种二次电池，所述二次电池包括第三方面的电极极片。
本申请第五方面，提供一种用电装置，所述用电装置包括第四方面的二次电池。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是二次电池的一实施方式的示意图。
图2是图1的分解图。
图3是电池包的一实施方式的示意图。
图4是图3的分解图。
图5是二次电池用作电源的用电装置的一实施方式的示意图。
附图标记说明：
1、电池包；2、上箱体；3、下箱体；4、二次电池；41、壳体；42、电极组件；43、盖板；5、用电装置。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的 或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
在本申请实施例的描述中，技术术语“中心”“纵向”“横向”“长度”“宽度”“厚度”“上”“下”“前”“后”“左”“右”“竖直”“水平”“顶”“底”“内”“外”“顺时针”“逆时针”“轴向”“径向”“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请实施例的限制。
在本申请实施例的描述中，除非另有明确的规定和限定，技术术语“安装”“相连”“连接”“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；也可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请实施例中的具体含义。
在本申请中，术语“烷基”指的是烷烃失去一个氢后形成的基团，例如甲烷失去一个氢后形成甲基。术语“链烷烃”是指碳原子都以碳碳单键相连且不成环，其余的价键都与氢结合而成的烷烃，包括直链烷烃和支链烷烃。
本申请中，基团中未指明连接位点时，表示基团中任选可连接位点作为连接位点。
本申请中，术语“结构单元”表示：单体分子通过聚合反应进入大分子链的基本单元，也称为“单体单元”，结构单元的元素组成可以与单体单元的元素组成相同，也可以不同。聚合物分子中的结构单元可以是一种或多种，当聚合物分子中的结构单元只有一种时，“结构单元”即为重复单元，例如 聚氯乙烯(CH 2—CHCl)n，其重复单元与结构单元是相同的，都是—CH 2CHCl—，而尼龙-66则有两种结构单元。
如背景技术所述，制备极片时，溶剂的挥发会使极片内部产生应力，电极浆料中的粘结剂组分提供的内聚力不足以承受应力，就会导致极片开裂，特别是厚涂布时，极片容易出现开裂的问题，反而对电池的循环稳定性产生负面影响。传统技术中，常采用PVDF或SBR的等线性粘结剂，其内聚力不足以承受干燥应力，一些技术尝试采用可交联聚合物作为粘结剂，然而，但对极片的防开裂及稳定性的提升仍有限。
本申请的技术人员对粘结剂的结构与极片性能做了大量实验探究，研究发现：粘结剂的三维网状结构的交联结构只是提升粘结剂内聚力的其中一个因素，粘结剂中的大分子链上的基团的选择对粘结剂的粘结力及稳定性也起到重要作用。本申请技术人员通过大量创造性实验，获得本申请中能提高极片的稳定性及防开裂能力，进而能提高电池的循环稳定性的粘结组合物。
本申请一实施方式提供了一种粘结组合物，该粘结组合物包括主体聚合物及交联剂，主体聚合物包括式(1)～(3)所示的结构单元：
Figure PCTCN2022124776-appb-000002
其中，X 1表示含有第一活性基团的结构基团，X 2每次出现，分别独立地选自H或碳原子数为1～10的烷基。
第一活性基团能与交联剂含有的官能团发生化学反应，且交联剂的官能度≥2。
上述粘结剂的组分包括含有特定结构单元的主体聚合物，制备电极极片时，其中氰基和第一活性基团的存在可提高电极浆料的固含量及粘结性，式(3)所示结构中的烃链段有利于提高电极极片的柔韧性，能防止膜层开裂，与此同时，主体聚合物中的第一活性基团能与交联剂中的官能团可以发生化学反应，形成的交联网状结构在电解液等溶剂中的溶胀度小，由此，在保持优异的粘结性能的同时，能抑制电极活性层在电解液中的溶胀度， 从而抑制电极极片的溶胀，进而降低电池的体积膨胀，保持电极极片良好的导电性，提高电池的循环性能。
可理解，上述交联剂的官能度是指一分子交联剂中含有的官能团的数量。交联剂的官能度可采用本领域常用的官能度测试方法测得，例如小分子类交联剂根据化合物分子结构就可以确定，聚合物可通过节后分子量及核磁测试获得的特征峰面积比进行计算获得平均官能度。
具体地，若直接采用商品化的交联剂，根据商品型号信息可查询到官能度。
需要说明的是，上述式(1)～(3)所示的结构单元中的“[]”代表其中的结构是位于聚合物的主链上。也可表示为如下形式：
Figure PCTCN2022124776-appb-000003
*为连接位点。
且，式(1)～(2)作为结构单元在主体聚合物分子中重复出现时，X 1或X 2每次出现可相同或不同。
可理解，该结构中的*为该结构与主体聚合物中主链的成链原子的连接位点。
在本申请任意实施例中，在上述主体聚合物中，式(1)～(3)所示的结构单元的聚合形式可以是无规共聚、也可以是有规共聚，也可以是嵌段共聚。
在本申请任意实施例中，上述主体聚合物由式(1)～(3)所示的结构单元组成。
在本申请任意实施例中，第一活性基团包括羧基、胺基、羟基、环氧基团及偕胺肟基中的至少一种。
在本申请任意实施例中，X 1选自第一活性基团或被第一活性基团取代的碳原子数为1～10的烷基。
可理解，X 1可以是单独的第一活性基团，例如羧基、胺基、羟基、环氧基团及偕胺肟基，也可以是被至少一种第一活性基团取代的碳原子数为1～10的烷基，例如被羟基取代的甲基、被胺基取代的甲基。
在本申请任意实施例中，X 1选自第一活性基团或被第一活性基团取代 的碳原子数为1～10的链烷基。
在本申请任意实施例中，X 1选自第一活性基团或被第一活性基团取代的碳原子数为1～5的链烷基。
在本申请任意实施例中，X 1选自第一活性基团或被第一活性基团取代的碳原子数为1～5的直链烷基。
在本申请任意实施例中，交联剂含有的官能团包括胺基、羟基、碳化二亚胺基团、氮丙啶基团和异氰酸酯基中的至少一种。
在本申请任意实施例中，化学反应包括缩合反应和开环反应中的至少一种。
缩合反应是指两种有机物互相作用形成一个新分子的反应，有的缩合反应伴随着小分子物质的释放。例如水等，有的并未释放小分子，缩合反应的具体途径包括但不限于：取代、加成及消除等。例如，羧酸和羟基、羧酸和胺基均是通过取代的途径缩合，也可称为酯化或酰胺化，而羟基和羟基可以通过脱水消除途径进行缩合。
上述交联剂含有的官能团中，胺基能与羧基、环氧基团等官能基团进行缩合反应或开环反应，羟基能与羧基、环氧基团、羟基等官能基团进行缩合反应或开环反应，碳化二亚胺基团能与羧基或环氧基反应，氮丙啶基团能与羧基、胺基、羟基、环氧基团及偕胺肟基等官能基团反应，异氰酸酯基能与羧基、胺基、羟基等官能基团反应，羟基与羟基之间还可通过脱水缩合反应。
在本申请任意实施例中，上述交联剂为氮丙啶类、聚碳化二亚胺及异氰酸酯类交联剂或异氰酸酯改性氮丙啶类交联剂中的至少一种。
在其中一些实施例中，上述交联剂为氮丙啶类交联剂。
在一具体示例中，上述交联剂为聚氮丙啶交联剂SaC-100，进一步地，其平均官能度为2.8。
在本申请任意实施例中，在主体聚合物中，式(3)所示的结构单元的质量占比为55％～75％，式(2)所示的结构单元的质量占比为10％～38％，式(1)所示的结构单元的质量占比为0.1％～25％。
通过调控各结构单元的质量占比，以进一步提高粘结力与韧性。
可选地，式(3)所示的结构单元的质量占比为65％～75％。
可选地，式(2)所示的结构单元的质量占比为18％～28％。
可选地，式(1)所示的结构单元的质量占比为1％～25％。
上述“55％～75％”中，取值可以是两端点及位于两端点之间的任意数值，非限制示例包括但不限于：55％、60％、65％、70％、75％。
上述“10％～38％”中，取值可以是两端点及位于两端点之间的任意数值，非限制示例包括但不限于：10％、15％、18％、20.0％、25.0％、28.0％、30.0％、34.0％、34.9％、35％、36％、37％、38％。
上述“0.1％～25％”中，取值可以是两端点及位于两端点之间的任意数值，非限制示例包括但不限于：0.1％、0.5％、1％、2％、5％、6％、7％、8％、9％、10％、11％、12％、13％、14％、15％、16％、17％、18％、19％、20％、21％、22％、23％、24％、25％。
在本申请任意实施例中，主体聚合物的重均分子量为30万～70万。
通过调控主体聚合物的重均分子量，可进一步优化粘结组合物的粘结性及稳定性，当主体聚合物的分子量过低时，产生的粘结力不足以满足要求，粘结效果较差，极片容易开裂、脱模；当主体聚合物的分子量过高时，容易出现溶解困难，浆料凝胶等问题。
在本申请任意实施例中，主体聚合物的重均分子量为40万～70万。
在本申请任意实施例中，主体聚合物的重均分子量为50万～70万。
在本申请任意实施例中，主体聚合物与交联剂的质量之比为(0.5～5):(0.01～0.4)。
可选地，主体聚合物与交联剂的质量之比为(0.5～5):(0.1～0.3)。
通过调控主体聚合物与交联剂的质量之比，可以调控两者的交联程度，进一步优化形成的交联网络结构的完善性，应用于制备电极极片时，在保证良好的韧性和粘结性的前提下，提高抗溶胀性能，从而提高电极极片防脱裂性能。
在本申请任意实施例中，X 2每次出现，分别独立地选自H、或链碳原子数为1～10的链烷基中的任意一种。
在本申请任意实施例中，X 2每次出现，分别独立地选自H、或链碳原子数为1～5的直链烷基中的任意一种。
在本申请任意实施例中，X 2每次出现，分别独立地选自H、甲基、乙基 或异丙基中的任意一种。
在本申请任意实施例中，上述粘结组合物还包括功能助剂，功能助剂包括但不限于：防老剂、抗氧化剂中的至少一种。
上述主体聚合物的制备过程中，通过采用式(1)～(3)所示的结构单元所对应的单体进行聚合，可通过控制各类单体的投料比，以控制主体聚合物中式(1)～(3)所示的结构单元分别对应的质量占比。
可理解，可将各类单体的投料比视为主体聚合物中式(1)～(3)所示的结构单元分别对应的质量占比；也可以通过对制得的主体聚合物中的各活性官能团进行含量测定，进而计算分析出式(1)～(3)所示的结构单元分别对应的质量占比。
本申请一实施方式，提供一种电极浆料，该电极浆料包括电极活性材料及第一方面的粘结组合物。
在本申请任意实施例中，以电极浆料中除溶剂之外的组分的总质量为基准，粘结组合物中的主体聚合物的质量占比为0.5％～5％。
在本申请任意实施例中，以电极浆料中除溶剂之外的组分的总质量为基准，交联剂的质量占比为0.01％～0.4％。
可选地，交联剂的质量占比为0.1％～0.3％。
上述电极活性材料可以是正极活性材料，也可以是负极活性材料。
在本申请任意实施例中，电极活性材料包括正极活性材料。
上述正极活性材料可采用本申请中的常用的正极活性材料，例如锂离子正极活性材料或钠离子正极活性材料。
进一步地，作为示例，锂离子活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可 以简称为NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4、简称为LFP))磷酸锰锂(如LiMnPO 4)、磷酸锰铁锂中的至少一种。
在本申请任意实施方式中，锂离子活性材料的分子式为：LiFe xMn (1-x)PO 4，x取0～1任一数。
可理解，当x取0时，LiFe xMn (1-x)PO 4即为LiMnPO 4磷酸锰锂，当x取1时，LiFePO 4即为LiFePO 4磷酸铁锂(LFP)。
作为示例，钠离子活性材料可包括以下材料中的至少一种：钠过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作钠离子电池正极活性材料的传统公知的材料。
在本申请任意实施方式中，正极活性材料包括钠过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种；
作为本申请可选的技术方案，钠过渡金属氧化物中，过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。钠过渡金属氧化物例如为Na xMO 2，其中M至少包括Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。
作为本申请可选的技术方案，聚阴离子型化合物可以是具有钠离子、过渡金属离子及四面体型(YO 4) n-阴离子单元的一类化合物。过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y至少包括P、S及Si中的至少一种；n表示(YO 4) n-的价态。
聚阴离子型化合物还可以是具有钠离子、过渡金属离子、四面体型(YO 4) n-阴离子单元及卤素阴离子的一类化合物。过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y至少包括P、S及Si中的至少一种，n表示(YO 4) n-的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物还可以是具有钠离子、四面体型(YO 4) n-阴离子单元、多面体单元(ZO y) m+及可选的卤素阴离子的一类化合物。Y至少包括P、S及Si中的至少一种，n表示(YO 4) n-的价态；Z表示过渡金属，至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种，m表示(ZO y) m+的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物例如是NaFePO 4、Na 3V 2(PO 4) 3(磷酸钒钠，简称NVP)、Na 4Fe 3(PO 4) 2(P 2O 7)、NaM’PO 4F(M’为V、Fe、Mn及Ni中的一种或几种)及Na 3(VO y) 2(PO 4) 2F 3-2y(0≤y≤1)中的至少一种。
普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN -)的一类化合物。过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为Na aMe bMe’ c(CN) 6，其中Me及Me’各自独立地至少包括Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。
在本申请任意实施例中，以电极浆料中除溶剂之外的组分的总质量为基准，电极活性材料的占比为74.60％～99.49％。
在其中一些实施例中，上述电极浆料还包括导电剂。导电剂可以采用本领域常用的导电材料，包括但不限于：石墨、碳纳米管、纳米纤维、炭黑和石墨烯中的至少一种。具体地，可选自SP、KS-6，乙炔黑、有支链结构的科琴黑ECP，SFG-6，气相生长碳纤维VGCF，碳纳米管CNTs和石墨烯及其复合导电剂中的至少一种。
以电极浆料中除溶剂之外的组分的总质量为基准，导电剂的重量比为0～20wt％。
在本申请任意实施例中，电极浆料的固含量为50％～80％。
本申请一实施方式，提供一种电极极片，电极极片包括集流体及位于集流体表面的活性层，活性层的制备原料包括上述的粘结组合物；或
活性层采用上述的电极浆料制得；或
活性层具有上述的粘结组合物中的主体聚合物与交联剂通过交联基团连接的交联网状结构，交联基团包括主体聚合物中的第一活性基团与交联剂含有的官能团经化学反应形成的基团。
该电极极片的韧性及抗溶胀性优异。
可理解，上述活性层中的电极活性材料为正极活性材料时，电极极片即为正极极片，上述活性层中的电极活性材料为负极活性材料时，电极极片即为负极极片，
在一具体示例中，上述极片为正极极片。作为示例，正极极片中的集流体具有在其自身厚度方向相对的两个表面，正极活性材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极片中的集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极片的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在集流体上，经烘干、冷压等工序后，即可得到正极片。正极浆料固含量为40wt％～80wt％，室温下的粘度调整到5000mPa·s～25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极极片；正极粉末涂布单位面密度为150～350mg/m 2，正极极片压实密度为3.0～3.6g/cm 3，可选为3.3～3.5g/cm 3。所述压实密度的计算公式为：
压实密度＝涂布面密度/(挤压后极片厚度-集流体厚度)。
本发明一实施方式，提供一种二次电池，二次电池包括如上述所述的电极极片。
在一具体示例中，上述电极极片为正极极片，在此不再赘述，如下对负极极片及隔离膜作简述。
【负极极片】
负极极片包括集流体及设于集流体表面的负极活性层。
负极活性层的组分包括负极活性物质、负极导电剂及负极粘结剂。
上述负极活性材料采用本申请中的常用的负极活性材料；进一步地，作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
基于负极活性层的总重量计，负极活性材料在负极活性层中的重量比为70wt％～100wt％。
在其中一些实施例中，上述负极导电剂可以采用本领域常用的导电材料，包括但不限于：石墨、碳纳米管、纳米纤维、炭黑和石墨烯中的至少一种。具体地，可选自SP、KS-6，乙炔黑、有支链结构的科琴黑ECP，SFG-6，气相生长碳纤维VGCF，碳纳米管CNTs和石墨烯及其复合导电剂中的至少一种。
基于负极活性层的总重量计，负极导电剂在负极活性层中的重量比为0～20wt％。
上述负极粘结剂可采用本领域常用的粘结剂，可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
基于负极活性层的总重量计，负极粘结剂在负极活性层中的重量比为0～30wt％。
在一些实施方式中，负极活性层还可选地包括其他助剂，例如增稠剂，如羧甲基纤维素钠(CMC-Na)等。基于负极活性层的总重量计，其他助剂在负极活性层中的重量比为0～15wt％。
在一些实施方式中，可以通过以下方式制备负极片：将上述用于制备负极片的组分，例如碳材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极片。
其中负极浆料固含量为30wt％～70wt％，室温下的粘度调整到2000mPa·s～10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极片。负极粉末涂布单位面密度为75mg/m 2～220mg/m 2，负极片压实密度1.2g/m 3～2.0g/m 3。
[隔离膜]
隔离膜设于正极片和负极片之间。
本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在其中一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在本申请任意实施方式中，上述二次电池还包电解液。
正极片、负极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。电解液在正极和负极之间起到传导离子的作用。
上述电解液可以包括电解质盐和溶剂。作为示例，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
作为示例，上述溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、 氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，电解液中还包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
上述二次电池还包括外壳，用于包装正极片、负极片、隔离膜及电解液。
在其中一些实施方式中，上述外壳的可以是硬壳，例如硬塑料壳、铝壳、钢壳等。也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
在一具体示例中，本申请的二次电池是锂离子二次电池。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池4。
在一些实施例中，参照图2，外壳可包括壳体41和盖板43。其中，壳体41可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体41具有与容纳腔连通的开口，盖板43能够盖设于所述开口，以封闭所述容纳腔。
正极片、负极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件42。电极组件42封装于容纳腔。电解液浸润于电极组件42中。电池4所含电极组件42的数量可以为一个或多个，可根据需求来调节。
本申请还提供一种用电装置，该用电装置包括上述的二次电池。
进一步地，在上述用电装置中，二次电池可以电池单体的形式存在，也可以进一步组装成电池包的形式存在。
图3和图4是作为一个示例的电池包1。在电池包1中包括电池箱和 设置于电池箱中的一个或多个二次电池4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于二次电池4的封闭空间。
多个二次电池4可以按照任意的方式排布于电池箱中。
上述二次电池或其组装成的电池包可以用作用电装置的电源，也可以作为用电装置的能量存储单元。
上述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
图5是作为一个示例的用电装置5。该用电装置5为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置5对二次电池的高功率和高能量密度的需求，可以采用电池包形式。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池作为电源。
下面将结合具体的实施例对本发明进行了说明，但本发明并不局限于下述实施例，应当理解，所附权利要求概括了本发明的范围，在本发明构思的引导下本领域的技术人员应意识到，对本发明的各实施例所进行的一定的改变，都将被本发明的权利要求书的精神和范围所覆盖。
以下为具体实施例。
具体实施例
实施例1
(1)制备主体聚合物，具体步骤如下：
将水400g、丙烯腈90g、甲基丙烯酸20g及配置好的合适用量的乳化剂、调节剂、活化剂等准确计量后加入到10L聚合釜中，抽真空后用氮气置换3次，加入丁二烯200g，调节釜内温度至反应温度，加入0.5wt％引发剂过硫酸钾引发聚合。反应开始后每隔一段时间取样测定胶乳的总固物含量并计算转化率，当转化率达到控制指标后加入0.05wt％终止剂二甲基二硫代氨基甲酸盐，降温出料，得到主体聚合物乳胶。
将制备的聚合物乳胶转至凝聚釜中，在搅拌过程中加入700g氯化钠水溶液进行凝聚，将凝聚好的胶块用软水洗涤数次后放入鼓风干燥箱中烘干制得主体聚合物生胶。
对制得的主体聚合物生胶进行红外光谱测测试：红外光谱谱图显示1558cm -1附近有羧酸盐特征峰，2250cm -1附近-CN特征峰，2940cm -1为-CH 2-不对称伸缩振动、2900cm- 1处为-CH 2-对称伸缩振动、1640cm -1处为C＝C伸缩振动峰。
采用核磁共振氢谱及凝胶渗透色谱测试确认合成物质的重均分子量，定氮法测量腈基含量，非水滴定法测量羧基含量，从而分析计算得到各单体结构的质量占比，具体结果请见表1。
(2)正极极片的制备：将正极活性材料磷酸铁锂、导电剂炭黑、上述主体聚合物生胶、交联剂(聚氮丙啶SaC-100、平均官能度为2.8)按照质量比为97.7:1.0:1.0:0.3混合均匀，然后加入NMP作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为65wt％的正极浆料。
将正极浆料均匀涂覆在厚度为12μm的铝箔的一个表面上，得到单面膜片重量400mg/1540.25mm 2(不含基材)的极片，105℃条件下烘干，冷压后经过极耳成型、分切等工序得到正极极片。
(3)负极极片的制备：将负极活性材料人造石墨、导电剂导电炭黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素(CMC)按照质量比96:0.9:1.6:1.5混合，加入去离子水作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为54wt％的负极浆料。将负极浆料均匀涂覆在厚度为8μm的铝箔铜箔的一个表面上，110℃条件下烘干，冷压后得到负极活性材料层厚度为110μm的预制极片，然后经过极耳成型、分切等工序得到负极极片。
(4)电解液的制备
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将非水有机溶剂碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯按照体积比1:1:1进行混合得到电解液溶剂，随后将锂盐LiPF 6溶解于混合后的溶剂中，配置成锂盐浓度为1mol/L的电解液。
(5)隔离膜：以聚丙烯膜作为隔离膜。
(6)锂离子电池的制备：将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离作用，然后卷绕得到电极组件；将电极组件置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到锂离子电池。
(7)性能测试，具体如下：
1、正极片柔韧性判断：采用卷针法
测试工具：卷针(直径：1mm、1.2mm、1.5mm、2mm、3mm)
测试条件：T＝25±1℃、相对湿度RH＝65±5％；
测试步骤：
卷针卷绕：取冷压后的极片，从最大号卷针开始(3mm)，依次将极片绕过卷针，绕过卷针部分用力对齐；
显微镜观察：物镜对准弯折的尖头部位，放大倍数100倍，观察是否有裂纹。记录正极极片可承受的卷针直径，能承受的卷针直径越小，说明柔韧性越好。
2、正极片粘结力测试：拉力机90°剥离测试
制样：将冷压好的双面正极片用双面胶粘在基底上，
测试：将制好的样品放在拉力机上，采用90°剥离测试方法，记录拉力机读数平稳时的数值，即为极片的粘结力。
3、正极片外观：观察极片烘干后是否有裂纹：
采用光学显微镜(CCD)观察为冷压前极片表面裂纹数量，记50mm×50mm范围内存在的裂纹数量。
4、正极片溶胀测试：通过测试正极活性层的吸液量，测试前，将正极活性层需烘干(85℃)，原始重量记为H0，然后将正极活性层置于电解液中，60℃浸泡温度10天，每24h测试一次取出正极活性层测试重量，称重前用无尘纸擦干正极活性层表面，持续测试10天，10天后正极活性层质量为H1，则溶胀度H(％)＝(H1/H0-1)×100％。
5、正极片浸泡电解液脱膜测试：烘干的正极片，然后将其浸泡在电解液中24h，取出并将其放置于60℃烘箱中烘干，观察其是否有脱落情况。
6、将正极浆料于24℃下静置6h，观察浆料状态，是否出现凝胶。
7、锂离子电池的性能进行测试，包括如下：
容量保持率测试：
在45℃下，将锂离子电池分别以1/3C恒流充电至3,65V，再3.65V恒压充电至电流为0.05C，静置5min，再以1/3C放电至2.5V记录放电容量C0。
再将锂离子电池以1.0C恒流充电至3.65V，静置5min，再以1/3C放电至2.5V记录放电容量C1。
重复上述步骤800次，记录循环第800次后锂离子电池的放电容量C800，容量保持率P800＝C800/C0×100％。
放电克容量测试：将电池分别以1/3C恒流充电至3.65V，再以3.65V恒压充电至电流为0.05C，静置5min，再以1/3C放电至2.5V记录放电容量C0，根据C0与活性物质重量比值计算放电克容量。
对正极极片的膨胀率进行测试：
(1)在25℃下，测试正极极片的初始厚度记为K0。
(2)将采用该正极极片制得的锂离子电池按照上述循环充方面条件，在45℃循环800cycle后，以1/3C恒流放电至2.5V，将锂离子电池拆解后测试此时正极极片厚度并记为K1。
正极极片的厚度膨胀率K(％)＝(K1/K0-1)×100％。
极片的厚度采用螺旋测微器测试。
通过正极极片的厚度增长率可以表征正极极片以及二次电池的体积膨胀，其中正极极片的厚度增长率越小，正极极片以及二次电池的体积膨胀越小。
实施例2～7
实施例2～7与实施例1基本相同，不同之处仅在于：步骤(1)中，控制丙烯腈、甲基丙烯羧酸、丁二烯的加入质量比，具体见表1
其他步骤和条件与实施例1相同。
实施例8～11
实施例8～11与实施例1基本相同，不同之处仅在于：步骤(1)中，控制聚合程度得到不同分子量主体聚合物。
其他步骤和条件与实施例1相同。
实施例12～15
实施例12～15与实施例1基本相同。不同之处仅在于：步骤(2)中，调控正极活性材料与主体聚合物的添加量，以使主体聚合物在正极浆料的固体组分中的占比与实施例1不同。
其他步骤和条件与实施例1相同。
实施例16～19
实施例16～19与实施例1基本相同。不同之处仅在于：步骤(2)中，调控正极活性材料与交联剂的添加量，以使交联剂在正极浆料的固体组分中的占比与实施例1不同。
其他步骤和条件与实施例1相同。
实施例20
实施例20与实施例1基本相同。不同之处仅在于：步骤(1)中，将丙烯腈替换成甲基丙烯腈。
其他步骤和条件与实施例1相同。
实施例21
实施例21与实施例1基本相同。不同之处仅在于：步骤(1)中，将丙烯酸替换成烯丙醇。
其他步骤和条件与实施例1相同。
实施例22
实施例22与实施例1基本相同。不同之处仅在于：步骤(1)中，将丙烯酸替换成烯丙胺。
其他步骤和条件与实施例1相同。
对比例1
对比例1与实施例2基本相同，不同之处仅在于：步骤(3)中，将主体聚合物替换成等质量的丁腈橡胶。
其他步骤和条件与实施例1相同。
对比例2
对比例2与实施例1基本相同，不同之处仅在于：步骤(2)中，将将主体聚合物替换成等质量的丁腈橡胶且不加入交联剂。
其他步骤和条件与实施例1相同。
对比例3
对比例3与实施例1基本相同，不同之处仅在于：步骤(2)直接以聚偏二氟乙烯(HSV900)为粘结剂，制备过程如下：
将磷酸铁锂正极活性材料、导电剂碳黑、聚偏二氟乙烯(HSV900)按质量比为97.0:1.0:2.0混合均匀，然后加入NMP作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为55wt％的正极浆料。
将正极浆料均匀涂覆在厚度为12μm的铝箔的一个表面上，得到单面膜片重量400mg/1540.25mm 2(不含基材)的极片，105℃条件下烘干，冷压后经过极耳成型、分切等工序得到正极极片。
其他步骤和条件与实施例1相同。
各实施例及对比例中的正极浆料静置6h后均未出现凝胶，各实施例及对比例中相关的物理参数及测试结果请见表1。
其中，A表示由丁二烯通过聚合后反应生成的结构单体部分占主体聚合物的质量分数，B表示由丙烯腈或甲基丙烯腈通过聚合后反应生成的结构单体部分占主体聚合物的质量分数，C表示含第一活性基团的结构单元占主体聚合物的质量分数，D表示合成的主体聚合物的重均分子量，E表示主体聚合物占浆料固体组分的质量分数，F1表示交联剂占浆料固体组分的质量分数，F2表示交联剂的平均官能度，N代表正极片柔韧性测试时，可承受的卷针直径，T代表粘结力，G代表极片裂纹数量，H代表溶胀度，J代表浸泡电 解液脱膜测试结果(是否脱模)，K代表正极片厚度膨胀率，W代表锂离子电池的放电克容量。
表1
Figure PCTCN2022124776-appb-000004
“/”表示测试过程中锂离子电池无法顺利完成测试。
由表1中实验结果分析可知：本申请中具有特定结构的粘结组合物制备极片时，能保持与极片上的活性材料及集流体的具有良好的粘接性，粘接稳定性高，同时兼具优异的内聚力，能提高极片的防裂性能，且能够有效抑制活性材料在循环充放电过程中的体积变化，进而提高电池的循环稳定性。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种粘结组合物，其特征在于，所述粘结组合物包括主体聚合物及交联剂，所述主体聚合物包括式(1)～(3)所示的结构单元：
    Figure PCTCN2022124776-appb-100001
    其中，X 1表示含有第一活性基团的结构基团，X 2每次出现，分别独立地选自H或碳原子数为1～10的烷基；
    所述第一活性基团能与所述交联剂含有的官能团发生化学反应，且所述交联剂的官能度≥2。
  2. 如权利要求1所述的粘结组合物，其特征在于，所述式(1)结构单元满足(a)～(b)中至少一个条件：
    (a)X 1选自第一活性基团或被所述第一活性基团取代的碳原子数为1～10的烷基；
    (b)所述第一活性基团包括羧基、胺基、羟基、环氧基团及偕胺肟基中的至少一种。
  3. 如权利要求1～2任一项所述的粘结组合物，其特征在于，所述化学反应包括缩合反应和开环反应中的至少一种。
  4. 如权利要求1～3任一项所述的粘结组合物，其特征在于，所述交联剂含有的官能团包括胺基、羟基、碳化二亚胺基团、氮丙啶基团和异氰酸酯基中的至少一种。
  5. 如权利要求1～4任一项所述的粘结组合物，其特征在于，在所述主体聚合物中，所述式(3)所示的结构单元的质量占比为55％～75％，所述式(2)所示的结构单元的质量占比为10％～38％，所述式(1)所示的结构单元的质量占比为0.1％～25％。
  6. 如权利要求1～5任一项所述的粘结组合物，其特征在于，所述主体聚合物的重均分子量为30万～70万；可选地，所述主体聚合物的重均分子量为40万～70万。
  7. 如权利要求1～6任一项所述的粘结组合物，其特征在于，所述主体聚合物与所述交联剂的质量之比为(0.5～5):(0.01～0.4)；可选地，所述主 体聚合物与所述交联剂的质量之比为(0.5～5):(0.1～0.3)。
  8. 如权利要求1～7任一项所述的粘结组合物，其特征在于，X 2每次出现，分别独立地选自H、甲基、乙基或异丙基中的任意一种。
  9. 一种电极浆料，其特征在于，所述电极浆料包括电极活性材料及如权利要求1～8任一项所述的粘结组合物。
  10. 如权利要求9所述的电极浆料，其特征在于，以所述电极浆料中除溶剂之外的组分的总质量为基准，所述主体聚合物的质量占比为0.5％～5％。
  11. 如权利要求9～10任一项所述的电极浆料，其特征在于，以所述电极浆料中除溶剂之外的组分的总质量为基准，所述交联剂的质量占比为0.01％～0.4％；
    可选地，所述交联剂的质量占比为0.1％～0.3％。
  12. 如权利要求9～11任一项所述的电极浆料，其特征在于，所述电极活性材料满足如下条件(c)～(d)中的至少一个：
    (c)所述电极活性材料包括正极活性材料；
    (d)以所述电极浆料中除溶剂之外的组分的总质量为基准，所述电极活性材料的占比为74.60％～99.49％。
  13. 如权利要求9～12任一项所述的电极浆料，其特征在于，所述电极浆料的固含量为50％～80％。
  14. 一种电极极片，其特征在于，所述电极极片包括集流体及位于所述集流体表面的活性层，所述活性层的制备原料包括如权利要求1～8任一项所述的粘结组合物；或
    所述活性层采用如权利要求9～13任一项所述的电极浆料制得；或
    所述活性层具有权利要求1～8任一项所述的粘结组合物中的所述主体聚合物与所述交联剂通过交联基团连接的交联网状结构，所述交联基团包括所述主体聚合物中的所述第一活性基团与所述交联剂含有的官能团经化学反应形成的基团。
  15. 一种二次电池，其特征在于，所述二次电池包括如权利要求14所述的电极极片。
  16. 一种用电装置，其特征在于，所述用电装置包括如权利要求15所述的二次电池。
PCT/CN2022/124776 2022-10-12 2022-10-12 粘结组合物、电极浆料、电极极片、二次电池及用电装置 WO2024077507A1 (zh)

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