WO2023061136A1 - 一种极片及其制备方法 - Google Patents

一种极片及其制备方法 Download PDF

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Publication number
WO2023061136A1
WO2023061136A1 PCT/CN2022/118742 CN2022118742W WO2023061136A1 WO 2023061136 A1 WO2023061136 A1 WO 2023061136A1 CN 2022118742 W CN2022118742 W CN 2022118742W WO 2023061136 A1 WO2023061136 A1 WO 2023061136A1
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Prior art keywords
pole piece
weight
optionally
group
carbon atoms
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PCT/CN2022/118742
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English (en)
French (fr)
Inventor
林江辉
赵延杰
李星
金海族
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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 EP22880078.5A priority Critical patent/EP4239729A1/en
Publication of WO2023061136A1 publication Critical patent/WO2023061136A1/zh
Priority to US18/330,093 priority patent/US20230317948A1/en

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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
    • 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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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 batteries, in particular to a pole piece and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries are widely used in many fields due to their long cycle life and environmental friendliness. Obtaining better performing Li-ion batteries is a common quest.
  • the existing pole piece has small porosity and uneven distribution of pores, which is not conducive to the infiltration of electrolyte and insufficient electrolyte retention, which increases the polarization of the pole piece and further leads to unsatisfactory battery performance.
  • the present application was made in view of the above-mentioned problems, and an object thereof is to provide a pole piece having a high porosity and uniform pore distribution.
  • the present application provides a pole piece, which includes a current collector and a pole piece material layer disposed on at least one surface of the current collector, and the pole piece material layer includes an active material and a conductive agent, wherein,
  • the pole piece material layer also includes a compound of formula (I):
  • R1 and R2 are each independently selected from hydrogen, an alkyl group with 1-6 carbon atoms, an alkoxyl group with 1-6 carbon atoms, and an alkenyl group with 2-6 carbon atoms , an aryl group, a hydroxyl group or an amino group with a carbon number of 6-20; wherein the alkyl group, alkoxy group, alkenyl group and aryl group are each independently optionally selected from at least one of the following groups One kind of substitution: alkyl group with 1-3 carbon atoms, alkyl group with 1-6 carbon atoms, hydroxyl group, hydroxyl group, amino group, amido group, cyano group, carboxyl group, halogen group; and n is an integer of 50-10000 .
  • the present application provides a pole piece with higher porosity and more uniform distribution of pores. Moreover, the pole piece of the present application has better initial wetting effect of electrolyte, good liquid retention capacity for electrolyte, reduced initial polarization, and reduced DC resistance (DCR).
  • DCR DC resistance
  • R 1 and R 2 are each independently selected from hydrogen, an alkyl group with 1-6 carbon atoms, an alkenyl group with 2-6 carbon atoms, or a phenyl group ; wherein the alkanyl, alkenyl and phenyl are each independently optionally substituted by at least one of the following groups: alkyl, hydroxyl or amino with 1-3 carbon atoms;
  • R is selected from an alkyl group with 1-6 carbon atoms, an unsubstituted alkenyl group with 1-6 carbon atoms or a phenyl group, and the alkyl group and phenyl group are each independently any is optionally substituted by an alkyl or hydroxyl group with 1-3 carbon atoms; more optionally, R is selected from ethyl, isopropyl, allyl, hydroxymethyl or p-hydroxyphenyl; and R is hydrogen.
  • n is an integer of 75-5000; optionally, n is an integer of 100-2000.
  • the pore structure characteristics (such as porosity and distribution uniformity) of the pole piece can be further improved, and the resistance of the pole piece to the electrolyte can be further improved. "Grab" and liquid retention capabilities, reduced initial polarization, reduced DCR, etc.
  • the pole piece material layer comprises 0.1-20 wt%, optionally 0.2-10 wt% of the compound of formula (I), based on the total weight of the pole piece material layer.
  • the pole piece containing the compound of formula (I) in the above content has better electrolyte wetting effect.
  • the pole piece is a negative pole piece.
  • the active material is at least one selected from the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate.
  • the performance of the negative electrode sheet is further improved.
  • a second aspect of the present application provides a method for preparing a pole piece, comprising:
  • R 1 , R 2 and n are as defined above,
  • the preparation method of the pole piece of the present application is provided.
  • the compound of formula (I) is used as a pore-forming agent, which improves the porosity, uniformity and consistency of the pole piece, and improves the performance of the pole piece being infiltrated by the electrolyte and the liquid retention performance of the electrolyte, Therefore, the cycle performance of the pole piece and the battery containing the pole piece is improved.
  • the solid content of the pole piece material slurry is 40% by weight to 70% by weight, optionally 40% by weight to 65% by weight, more preferably 45% by weight to 60% by weight, Based on the total weight of the pole piece material slurry.
  • the pore-forming effect can be controlled and improved by controlling the solid content of the slurry.
  • the pore-forming effect can be controlled and improved by controlling the added amount of the compound of the pore-forming agent formula (I).
  • the first temperature is 20-30°C, optionally 22-28°C, more preferably 25°C.
  • a first temperature is selected so that the compound of formula (I) can be dissolved in a solvent (such as water) during slurry preparation to achieve a more desirable pore-forming effect.
  • the drying is performed at a temperature above 45°C, optionally at 90°C-150°C, more preferably at 115°C-145°C, most preferably at 125-135°C.
  • the ideal drying rate can be obtained, while taking into account the production efficiency, the desired pore-forming process can be realized; the obtained pole piece structure is more stable, and the pores are more uniform, so that the performance of the pole piece is better. good.
  • the water is deionized water. Further selection of deionized water can reduce the residue of impurities in the pole piece and avoid its adverse effect on the electrochemical performance of the pole piece.
  • the pole piece is a negative pole piece.
  • the active material is at least one selected from the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. Further selection of the negative electrode active material can further improve the performance of the negative electrode sheet.
  • the third aspect of the present application provides the use of the compound of formula (I) as a pore-forming agent
  • R 1 , R 2 and n are as defined above.
  • the present application provides a use of the compound of formula (I) as a pore-forming agent.
  • the compound is used for pore-forming purposes, the operation is simple, the process is environmentally friendly, and the obtained porosity is high and the pores are evenly distributed.
  • the pore forming agent is used to create pores for the pole piece material layer of the pole piece.
  • the pole piece is a negative pole piece.
  • the compound of formula (I) when used as a pore-forming agent to make holes in the battery pole piece, in addition to increasing the porosity and improving the uniformity of the pore distribution, it can also improve the electrolysis of the pole piece due to its retention in the pole piece.
  • the wetting performance of the liquid improves the liquid retention performance of the electrolyte of the pole piece, thereby improving the cycle performance of the pole piece and the battery.
  • a fourth aspect of the present application provides a secondary battery, which includes the pole piece of the first aspect of the present application or the pole piece obtained by the preparation method of the second aspect.
  • a fifth aspect of the present application provides a battery module including the secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, which includes the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides an electric device, which includes at least one selected from the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, or the battery pack of the sixth aspect of the present application.
  • the pole piece provided by this application has at least one of the following effects: high porosity, uniform distribution of pores, good electrolyte infiltration effect, strong ability to retain electrolyte, small initial polarization, small internal resistance, and good cycle performance .
  • secondary batteries, battery modules, battery packs and electrical devices comprising the pole piece of the present application all have improved cycle performance.
  • Fig. 1 is the schematic diagram of the pore-forming principle of the compound of formula (I) of the present application
  • Fig. 2 is the schematic diagram that the compound of formula (I) of the present application is retained in the pole plate pores and absorbs the swelling of the electrolyte;
  • Fig. 3 is the scanning electron micrograph of the pole piece cross-sectional morphology of the present application.
  • FIG. 4 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Fig. 5 is an exploded view of the secondary battery according to one embodiment of the present application shown in Fig. 4;
  • FIG. 6 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 7 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • Fig. 8 is an exploded view of the battery pack according to an embodiment of the present application shown in Fig. 7;
  • FIG. 9 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • Embodiments of the pole piece of the present application, its preparation method, a secondary battery, a battery module, a battery pack, and an electrical device will be described in detail below. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known items and repeated descriptions of substantially the same configurations may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art.
  • the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • holes are usually formed by converting the pore-forming agent in the pole piece into gas to escape through high temperature or electrochemical process, but this method consumes a lot of energy and costs high; moreover, the escape of gas is uncontrollable, Pore uniformity cannot thus be guaranteed. Additionally, these gases can be corrosive and detrimental to equipment life and personnel health.
  • the pore-forming agent in the pole piece is dissolved in the electrolyte to remove the pore-forming agent to achieve pore-forming, although some of the above-mentioned problems can be avoided and it is easy to operate, the dissolution of the pore-forming agent will change the composition of the electrolyte. , which may impair battery performance.
  • the inventors used the compound of formula (I) as a pore forming agent.
  • the compound has a hydrophobic group (eg, R 1 and/or R 2 ) and a hydrophilic amide group in its molecule.
  • the compound has "temperature-sensitive" properties - when the temperature is low, it can form hydrogen bonds with solvents (such as water) and dissolve in it, showing hydrophilicity; however, when the temperature rises to a certain extent, the hydrogen bonds fracture, which in turn assumes hydrophobic properties.
  • the molecular chain of the pore-forming agent is still soluble in water, and presents a stretched state, absorbs water and swells, and has a large volume, each occupying a certain volume in the pole piece material layer.
  • the temperature of the pole piece material layer rises, the hydrogen bond between the pore-forming agent molecules and the solvent water breaks, the hydrophobic interaction between the molecular chains takes the dominant position, and the molecular chains gradually shrink and gather from the stretched state during dissolution. Eventually form a compact colloidal particle.
  • Such a transformation reduces the molecular volume of the compound by several times or even dozens of times, so pores are formed in the dry pole piece, and the porosity is significantly increased.
  • the compound of the formula (I) can be uniformly distributed in the slurry and the pole piece material layer formed therefrom due to being soluble in water, the resulting pores are evenly distributed. Moreover, there is no need for additional energy-consuming steps, no gas generation, and no change in the composition of the electrolyte during the pore-forming process, thus overcoming many shortcomings of the prior art.
  • the compound of the pore-forming agent formula (I) is not removed, but remains in the pores of the pole piece of the present application. It will not decompose or volatilize at the following temperature.
  • the mechanism is not completely clear, the inventors have unexpectedly found that when the newly made pole piece of the application is infiltrated by the electrolyte, there is a gap between the compound of formula (I) present in the pores of the pole piece and the electrolyte. Affinity, so it can "grab" the electrolyte, further improve the wetting effect of the electrolyte, and reduce the initial polarization of the pole piece.
  • the pole piece of this application has increased porosity, improved electrolyte infiltration, and improved cycle performance, thereby prolonging the service life.
  • the first aspect of the present application provides a pole piece, which includes a current collector and a pole piece material layer disposed on at least one surface of the current collector, the pole piece material layer includes an active material and a conductive agent, wherein the Pole sheet material layer comprises the compound of formula (I):
  • R1 and R2 are each independently selected from hydrogen, an alkyl group with 1-6 carbon atoms, an alkoxyl group with 1-6 carbon atoms, and an alkenyl group with 2-6 carbon atoms , an aryl group, a hydroxyl group or an amino group with a carbon number of 6-20; wherein the alkyl group, alkoxy group, alkenyl group and aryl group are each independently optionally selected from at least one of the following groups One kind of substitution: alkyl group with 1-3 carbon atoms, alkyl group with 1-6 carbon atoms, hydroxyl group, hydroxyl group, amino group, amido group, cyano group, carboxyl group, halogen group; and n is an integer of 50-10000 .
  • the present application provides a pole piece with higher porosity and more uniform distribution of pores.
  • the electrode sheet electrolyte of the present application has a better initial wetting effect, a good liquid retention capacity for the electrolyte, and has reduced initial polarization and reduced DC resistance (DCR).
  • the battery comprising the pole piece will have improved performance, for example, cycle performance, power performance.
  • the term "power performance” refers to a high proportion of useful work to the total work performed by the battery when it is discharged. In other words, during the process of discharging the battery, the electric power loss (for example, due to resistance heat generation, etc.) is less, and the useful work output is more, that is, the power output is more. Therefore, it can be understood that in this application, since the DCR of the pole piece is relatively small, the power performance is correspondingly better.
  • R 1 and R 2 are each independently selected from hydrogen, an alkyl group with 1-6 carbon atoms, an alkenyl group with 2-6 carbon atoms, or a phenyl group ; wherein the alkanyl, alkenyl and phenyl are each independently optionally substituted by at least one of the following groups: alkyl, hydroxyl or amino with 1-3 carbon atoms; And, R 2 is hydrogen.
  • R is selected from an alkenyl group with 1-6 carbon atoms, an unsubstituted alkenyl group or a phenyl group with 2-6 carbon atoms, and the alkyl group and Each of the phenyl groups is independently optionally substituted by an alkyl group or a hydroxyl group with 1-3 carbon atoms, more optionally, R is selected from ethyl, isopropyl, allyl, hydroxymethyl or p-hydroxybenzene and, R 2 is hydrogen.
  • n is an integer of 75-5000; alternatively, n is an integer of 100-2000.
  • the pore structure characteristics (such as porosity and distribution uniformity) of the pole piece can be further improved, and the resistance of the pole piece to the electrolyte can be further improved. "Grab" ability and liquid retention ability, reduce initial polarization, reduce DCR, etc.
  • the molecular weight of the compound of formula (I) can be moderate, so that while having good solubility, there is an appropriate dissolved volume (so that pores of the desired size can be produced), when the temperature rises Appropriate volume change rate, so that pores with better uniformity and consistency of pore size and distribution can be obtained in the pole piece.
  • the pole piece material layer includes 0.1-20 wt%, alternatively 0.2-10 wt% of the compound of formula (I), based on the total weight of the pole piece material layer.
  • the pole piece material layer contains the compound of formula (I).
  • the pole piece material layer contains the compound of formula (I).
  • the pole piece sample containing the compound of formula (I)
  • the pole piece is a negative pole piece.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode sheet material layer arranged on at least one surface of the negative electrode current collector, and the electrode sheet material layer includes an active material and a conductive agent; wherein, the negative electrode sheet material layer includes the application No. A compound of formula (I) according to one aspect.
  • the pole piece material layer includes 0.1-20 wt%, optionally 0.2-10 wt% of the compound of formula (I), based on the total weight of the pole piece material layer.
  • total weight of the pole piece material layer refers to the total weight of all substances contained in the dried pole piece material layer.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode sheet material layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon (or soft carbon), hard carbon (or hard carbon), silicon-based materials, tin-based materials, lithium titanate, etc. .
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys. But the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials may be used alone or in combination of two or more. By selecting the negative electrode active material, the performance of the negative electrode sheet is further improved.
  • the negative electrode sheet material layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode sheet material layer includes a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode sheet material layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active 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 current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the pole piece of the present application may be a positive pole piece.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode sheet material layer disposed on at least one surface of the positive electrode current collector, and the positive electrode sheet material layer includes the compound of formula (I) in the first aspect of the application.
  • the positive electrode sheet may contain the compound of formula (I) in any amount suitable for creating pores in the sheet.
  • the pole piece material layer of the positive pole piece comprises 0.1-20% by weight, optionally 0.2-10% by weight of the compound of formula (I), based on the total weight of the pole piece material layer weighing scale.
  • the positive current collector has two opposing surfaces in its own thickness direction, and the positive electrode sheet material layer is disposed on any one or both of the two opposing surfaces of the positive current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can 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 can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode sheet material layer includes a positive electrode active material.
  • a positive electrode active material positive active materials known in the art for batteries can be used.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and 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 of batteries can 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 oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also may be abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode sheet material layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode sheet material layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • a second aspect of the present application provides a method for preparing a pole piece, comprising:
  • R 1 , R 2 and n are as defined above,
  • dry blend mixture refers to a mixture obtained by mixing materials used to prepare the mixture without a solvent.
  • the preparation method of the pole piece of the present application is provided.
  • the compound of formula (I) is used as a pore-forming agent, which improves the porosity, uniformity and consistency of the pole piece, and improves the performance of the pole piece being infiltrated by the electrolyte and the effect on the electrolyte.
  • the liquid retention performance thereby improving the cycle performance and power performance of the pole piece and the battery containing the pole piece.
  • the electrode sheet material slurry can be applied on at least one surface of the current collector by any conventional means in the art, including, but not limited to, coating.
  • the solid content of the pole piece material slurry is 40% by weight to 70% by weight, optionally 40% by weight to 65% by weight, more preferably 45% by weight to 60% by weight, Based on the total weight of the pole piece material slurry.
  • the pore-forming effect of the compound of formula (I) as a pore-forming agent can be controlled and improved by controlling the solid content of the slurry.
  • the drying time of the pole piece can be made within the desired range; and the water content allows the compound of formula (I) to form an appropriate amount of hydrogen bonds with it, which makes the volume change rate of the compound appropriate during the drying process. , and produce pores of suitable size and stable structure in the pole piece.
  • the pole piece material slurry comprises 0.1% by weight to 20% by weight, alternatively 0.15% by weight to 15% by weight, more alternatively 0.2% by weight to 10% by weight of the formula (I) compound, based on the dry weight of the pole piece material slurry composition.
  • dry weight refers to the total weight of all matter (or, all dry matter) remaining after removal of the solvent (eg, water) from the pole piece material slurry.
  • the pore-forming effect can be controlled and improved by controlling the added amount of the compound of the pore-forming agent formula (I). Specifically, controlling the content of the compound of formula (I) in the slurry within the above-mentioned range can obtain a good pore-forming effect: the amount of pores in the obtained pole piece material layer is appropriate, and the pore structure is stable (that is, these The pores are not easy to be destroyed in the subsequent cold pressing, resulting in another decrease in porosity). In addition, the above content range of the compound of formula (I) allows the loading amount of the active material in the pole piece to be within a reasonable range, thereby making the energy density of the battery meet expectations.
  • the first temperature is room temperature. In some embodiments, the first temperature is 20-30°C, optionally 22-28°C, more optionally 25°C. Such a first temperature is selected so that the compound of formula (I) can exhibit higher hydrophilicity and dissolve in water during the preparation of the slurry, so as to be evenly distributed in the slurry and the pole piece material layer formed thereby to achieve a uniform The purpose of making holes.
  • drying is performed at any temperature. In some embodiments, drying is performed at a temperature above 45°C. In some embodiments, drying is optionally performed at 90°C-150°C, more preferably at 115°C-145°C, most preferably at 125-135°C.
  • the water is deionized water. In this way, the residue of impurities in the pole piece can be reduced, and the adverse effect on the electrochemical performance of the pole piece can be avoided.
  • the prepared pole piece is a negative pole piece.
  • the active material is at least one selected from the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Further selection of the negative electrode active material can further improve the performance of the negative electrode sheet.
  • the third aspect of the present application provides the use of the compound of formula (I) as a pore-forming agent
  • R 1 , R 2 and n are as defined above.
  • the present application provides a use of a compound of formula (I) as a pore-forming agent.
  • the compound is used for pore-forming purposes, the operation is simple, the process is environmentally friendly, and the obtained porosity is high and the pores are evenly distributed.
  • the compound of formula (I) of the present application can be used to create pores for positive and negative electrodes, and can also be used for creating pores for separator materials.
  • the pore forming agent is used to create pores for the pole piece material layer of the pole piece.
  • the pole piece is a negative pole piece.
  • a compound of formula (I) is added as a pore-forming agent in the slurry of the pole piece (especially the negative pole piece), and the compound can be dissolved in a solvent (such as water) and shrink in volume when heated during the coating process To create holes, so as to form uniform pores in the final pole piece, thereby increasing the porosity of the pole piece.
  • a solvent such as water
  • the compound since the compound will remain in the pole piece material layer after the hole is made, its hydrophobic property will make it have affinity with the electrolyte, thereby improving the wettability of the pole piece to the electrolyte; and, because it is Swelling will occur after the electrolyte is infiltrated, which further improves the retention capacity of the pole piece to the electrolyte, thereby improving the cycle performance of the lithium-ion battery.
  • the fourth aspect of the present application provides a secondary battery, which includes the pole piece of the first aspect of the present application or the pole piece obtained by the preparation method of the second aspect of the present application.
  • a fifth aspect of the present application provides a battery module including the secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, which includes the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides an electric device, which includes at least one selected from the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect, or the battery pack of the sixth aspect.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 4 shows a secondary battery 5 having a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 6 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 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 cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 9 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • Graphite, conductive agent carbon black, and the compound of formula (I) (as shown in the following table 1) as pore-forming agent are dry-mixed at a weight ratio of 96:1:2, and deionized water is added to adjust the solid content to 55% by weight , then add 1% by weight of the binder styrene-butadiene rubber (SBR), stir evenly to obtain the negative electrode sheet material slurry, and then apply the negative electrode sheet material slurry on the current collector with a loading capacity of 12 mg/cm On the copper foil, dry at a temperature of 130°C ⁇ 5°C, and then cold-press and cut to make negative pole pieces.
  • SBR binder styrene-butadiene rubber
  • Example Compounds of formula (I) source 1 Poly(N-isopropylacrylamide) Hubei Shixing Chemical Co., Ltd. 2 poly(N-ethylacrylamide) Shanghai Aladdin Biochemical Technology Co., Ltd. 3 Poly(N-allyl acrylamide) Shanghai Yihe Biotechnology Co., Ltd. 4 Poly(N-methylolacrylamide) Shanghai Yuanye Biotechnology Co., Ltd. 5 Poly(N-p-hydroxyphenylacrylamide) Shenzhen Aituo Chemical Co., Ltd.
  • NMP solvent N- Methylpyrrolidone
  • Electrolyte preparation mix ethylene carbonate (EC)/ethyl methyl carbonate (EMC) according to the volume ratio of 3/7, and then add LiPF 6 to it so that the final concentration of LiPF 6 is 12.5% by weight, and stir evenly , to obtain the electrolyte.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • Battery preparation wind the above-mentioned negative and positive pole pieces and 12 ⁇ m thick PP diaphragm into a battery cell, and package it with aluminum-plastic film to form a dry battery cell. After liquid injection, chemical formation, aging and other processes, the secondary secondary battery.
  • Examples 6-14 used the poly(N-isopropylacrylamide) of Example 1 as a pore-forming agent, and prepared pole pieces and secondary batteries according to Example 1. The difference from Example 1 is the number n of polymerized units of poly(N-isopropylacrylamide), see Table 3 below for details.
  • Examples 15-22 use the poly(N-isopropylacrylamide) of Example 1 as a pore-forming agent, and prepare pole pieces and secondary batteries according to Example 1, wherein the graphite, carbon black, and pore-forming agent The quality ratios are shown in Table 2 below.
  • Example Graphite carbon black: pore former (mass ratio) 15 97.95:1:0.05 16 97.9:1:0.1 17 97.8:1:0.2 18 91:1:7 19 88:1:10 20 83:1:15 twenty one 68:1:20 twenty two 63:1:25
  • Example 22-29 The poly(N-isopropylacrylamide) of Example 1 was used as a pore-forming agent, and the pole pieces and secondary batteries were prepared according to Example 1. The difference from Example 1 is the solid content of the negative electrode material slurry, see Table 3 below for details.
  • the negative electrode slurry was coated on the current collector copper foil with a load of 12mg/cm 2 , dried at 130°C ⁇ 5°C, and then cold-pressed and cut into negative electrode sheets.
  • the positive electrode sheet and the secondary battery were prepared according to the relevant steps of Example 1.
  • the negative electrode sheet was prepared according to the preparation steps of Example 1, wherein the pore-forming agent was ammonium carbonate.
  • the positive electrode sheet and the secondary battery were prepared according to the relevant steps of Example 1.
  • the volume V2 is in cm 3
  • the capillary that has absorbed the electrolyte is clamped above the pole piece in a manner perpendicular to the pole piece, so that the lower end of the capillary is facing the material layer of the pole piece.
  • Test n (n ⁇ 3) parallel samples in the above manner, and then calculate the average value.
  • the secondary batteries prepared in each example and comparative example were charged at a constant current rate of 1C to a charge cut-off voltage of 4.35V, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 10 minutes, and then constant current at a rate of 4C Discharge to the discharge cut-off voltage of 2.8V, and record the discharge capacity C 4C .
  • the above-mentioned secondary battery was charged at a constant current rate of 1C to a cut-off voltage of 4.35V, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 10 minutes, and then discharged at a constant current rate of 1C to a cut-off voltage of 2.8V. Record the discharge capacity C 1C .
  • the secondary batteries prepared in each example and comparative example were charged at a constant current rate of 1C to a charge cut-off voltage of 4.30V, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 10 minutes, and then constant current at a rate of 1C Discharge to the discharge cut-off voltage of 3.3V, and stand still for 10 minutes.
  • This is a charge-discharge cycle (ie, 1 cycle), and record the discharge capacity C 1 .
  • FIG. 1 shows a side-by-side comparison of the cross-sectional morphology of the negative electrode sheets of Example 1 and Comparative Example C1.
  • the pores in the pole piece material layer of Example 1 are more uniform and have better consistency.
  • the pole piece of Example 1 has relatively uniform distribution of pores in the direction perpendicular to the current collector (located at the bottom of the picture), and the upper and lower porosity and pore size are basically the same; while in the pole piece of Comparative Example C1, the pores Small and uneven.
  • Table 3 has shown the test result of embodiment 1-30 and the pole piece of comparative example and battery.
  • the pole piece of the present application has a reduced direct current resistance (DCR) of the fresh cell compared to the prior art.
  • DCR direct current resistance
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了一种极片及其制备方法。本申请的极片包括集流体和设置于所述集流体至少一个表面上的极片材料层，所述极片材料层包括活性物质和任选地导电剂，其中所述极片材料层包括式(I)的化合物。本申请的极片孔隙率较高、孔隙分布更均匀、电解液初始浸润效果更好、对电解液的保液能力好，并且具有降低的初始极化、减小的直流阻抗(DCR)，进而能够改善包含该极片的电池的性能。

Description

一种极片及其制备方法 技术领域
本申请涉及锂电池技术领域，尤其涉及一种极片及其制备方法、二次电池、电池模块、电池包和用电装置。
背景技术
锂离子电池作为一种高性能二次电池，因其循环寿命长和环境友好等特点，被广泛应用于诸多领域。获得性能更好的锂离子电池是普遍的追求。
现有的极片中孔隙率小，孔隙分布不均匀，不利于电解液的浸润，对电解液的保有量不足，这使极片极化增大，进一步导致电池性能不理想。
为解决上述问题，现有技术中采用多种方式对极片造孔，但所得极片的孔隙率、孔隙分布等均不够理想，并且造孔过程还伴随有污染、腐蚀、成本高等问题。
因此，本领域急需开发一种孔隙率提高、孔隙分布均匀的极片。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种孔隙率高、孔隙分布均匀的极片。
为了达到上述目的，本申请提供了一种极片，其包括集流体和设置于所述集流体至少一个表面上的极片材料层，所述极片材料层包括活性物质和导电剂，其中，所述极片材料层还包括式(I)的化合物：
Figure PCTCN2022118742-appb-000001
其中，R 1与R 2各自独立地选自氢、碳原子数为1-6的链烷基、碳原子数为1-6的链烷氧基、碳原子数为2-6的链烯基、碳原子数为6-20的芳基、羟基或氨基；其中所述链烷基、链烷氧基、链烯基和芳基各自独立地任选地被选自以下的基团中的至少一种所取代：碳原子数为1-3的烷基、碳原子数为1-6的烷基羟基、羟基、氨基、酰胺基、氰基、羧基、卤素；并且n为50-10000的整数。
由此，本申请提供了一种极片，其孔隙率较高、孔隙分布更均匀。并且，本申请的极片电解液初始浸润效果更好、对电解液的保液能力好、具有降低的初始极化、减小的直流阻抗(DCR)。
在任意实施方式中，式(I)中，R 1与R 2各自独立地选自氢、碳原子数为1-6的链烷基、碳原子数为2-6的链烯基或苯基；其中所述链烷基、链烯基和苯基各自独立地任选地被选自以下的基团中的至少一种所取代：碳原子数为1-3的烷基、羟基或氨基；可选地，R 1选自碳原子数为1-6的链烷基、未取代的碳原子数为1-6的链烯基或苯基，所述链烷基和苯基各自独立地任选地被碳原子数为1-3的烷基或羟基取代；更可选地，R 1选自乙基、异丙基、烯丙基、羟甲基或对羟基苯基；并且R 2为氢。
在任意实施方式中，式(I)中，n为75-5000的整数；可选地，n为100-2000的整数。
以上，通过进一步选择式(I)中的各个基团和聚合单元数n，能够进一步改善极片的孔隙结构特性(如，孔隙率和分布均匀性)，并且能够进一步提高极片对电解液的“抓取”和保液能力，降低初始极化，减小DCR等。
在任意实施方式中，所述极片材料层包括0.1-20重量％，可选地0.2-10重量％的式(I)的化合物，基于所述极片材料层的总重量计。 以上述含量包含式(I)的化合物的极片，其具有更好的电解液浸润效果。
在任意实施方式中，所述极片为负极极片。
在任意实施方式中，所述活性物质选自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。
通过选择负极活性物质，进一步提升负极极片的性能。
本申请的第二方面提供一种极片的制备方法，包括：
(1)将活性物质、导电剂和式(I)的化合物的干混混合物、水、粘结剂在低于35℃的第一温度下混合，得到极片材料浆料，
Figure PCTCN2022118742-appb-000002
其中，R 1、R 2和n如上文所定义，
(2)将所述极片材料浆料施加在集流体的至少一个表面上，干燥，得到极片。
以上，提供了本申请的极片的制备方法。其中，采用式(I)的化合物作为造孔剂，实现了对极片孔隙率、均匀性和一致性的改善，并改善了极片被电解液浸润的性能和对电解液的保液性能，从而改善了极片和包含该极片的电池的循环性能。
在任意实施方式中，所述极片材料浆料的固含量为40重量％-70重量％，可选地为40重量％-65重量％，更可选地为45重量％-60重量％，基于所述极片材料浆料的总重量计。
在本申请的极片制备方法中，通过控制浆料的固含量可以控制并改善造孔效果。
通过控制造孔剂式(I)的化合物的加入量可以控制和改善造孔效果。
在任意实施方式中，所述第一温度为20-30℃，可选地为22-28℃，更可选地为25℃。选择这样的第一温度使式(I)的化合物在浆料制 备期间能够溶于溶剂(如，水)中，以实现更理想的造孔效果。
在任意实施方式中，所述干燥在高于45℃的温度下，可选地在90℃-150℃，更可选在115℃-145℃，最可选在125-135℃下进行。通过将干燥温度选择在上述范围内，可以获得理想的烘干速率，兼顾生产效率的同时，实现期望的造孔过程；所得到的极片结构更稳定，孔道更均匀，从而使极片性能更好。
在任意实施方式中，所述水为去离子水。进一步选择去离子水，能够减少杂质在极片内的残留，避免其对极片的电化学性能造成不良影响。
在任意实施方式中，所述极片是负极极片。
在任意实施方式中，所述活性物质选自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。进一步选择负极活性物质，能够进一步改善负极极片性能。
本申请的第三方面提供式(I)的化合物作为造孔剂的用途，
Figure PCTCN2022118742-appb-000003
其中，R 1、R 2和n如上文所定义。
以上，本申请提供了一种式(I)的化合物作为造孔剂的用途。该化合物用于造孔用途，操作简单、过程环保，所得到的孔隙率高、孔隙分布均匀。
在任意实施方式中，所述造孔剂用于对极片的极片材料层造孔。
在任意实施方式中，所述极片为负极极片。
当式(I)的化合物作为造孔剂用于对电池极片造孔时，除了能够提高孔隙率，改善孔隙分布均匀度之外，由于其保留在极片中，还能够改善极片被电解液的浸润性能、提高极片的电解液的保液性能，进而提高极片和电池的循环性能。
本申请的第四方面提供一种二次电池，其包括本申请第一方面的 极片或通过第二方面的制备方法得到的极片。
本申请的第五方面提供一种电池模块，其包括本申请第四方面的二次电池。
本申请的第六方面提供一种电池包，其包括本申请第五方面的电池模块。
本申请的第七方面提供一种用电装置，其包括选自本申请第四方面的二次电池、本申请第五方面的电池模块或本申请第六方面的电池包中的至少一种。
本申请所提供的极片具有以下效果中的至少一种：孔隙率高、孔隙分布均匀、电解液浸润效果好、对电解液保液能力强、初始极化小、内阻小、循环性能好。相应地，包含本申请的极片的二次电池、电池模块、电池包和用电装置均具有改善的循环性能。
附图说明
图1为本申请式(I)的化合物的造孔原理示意图；
图2为本申请式(I)的化合物保留在极片孔隙中，吸收电解液溶胀的示意图；
图3为本申请的极片截面形貌的扫描电镜图；
图4是本申请一实施方式的二次电池的示意图；
图5是图4所示的本申请一实施方式的二次电池的分解图；
图6是本申请一实施方式的电池模块的示意图；
图7是本申请一实施方式的电池包的示意图；
图8是图7所示的本申请一实施方式的电池包的分解图；
图9是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，详细说明本申请的极片及其制备方法、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、 (b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
现有技术的极片由于孔隙率较小且孔隙分布不均，不利于电解液浸润，因此极片远端(即，更接近集流体的一侧)的活性物质难以充分发挥其容量作用。此外，锂离子二次电池随着循环次数增加，电芯膨胀后，极片孔隙率进一步下降，极片内的电解液被消耗、挤出，使极片极化增大，从而导致电池的循环性能并不理想。
为解决上述问题，现有技术中采用多种方式对极片造孔，但其基本思路是使用造孔剂在极片制备时占据一定体积，而在造孔完毕后将其除去，从而得到孔隙。造孔剂的除去通常是通过例如高温或电化学过程使其分解或挥发为气体逸出，或者通过使其溶于电解液。现有造孔方法虽然在一定程度上实现了孔隙率的提升，但同时也带来诸多问题。例如，本领域通常通过高温还是电化学过程使极片中的造孔剂转化为气体逸出这种方式造孔，但这种方式能耗大、成本高；并且，气体的逸出不可控，因而无法保证孔隙均匀性。此外，这些气体还可能具有腐蚀性而不利于设备寿命和人员健康。再例如，如果采用将极片中的造孔剂溶解于电解液的方式除去造孔剂而实现造孔，虽然能够避免上述某些问题且易于操作，但是造孔剂的溶解会改变电解液组成，从而可能损害电池性能。
因此，本领域急需开发一种具备具有提高的孔隙率且不存在上述 问题的极片。
为提高极片孔隙率，发明人采用式(I)的化合物作为造孔剂。该化合物的分子中具有疏水性基团(如，R 1和/或R 2)和亲水性基团酰胺基。该化合物具有“温敏”性质——在温度较低时，能够与溶剂(如，水)形成氢键而溶解于其中，呈现亲水性；然而，在温度升高到一定程度时，氢键断裂，其转而呈现疏水性质。
Figure PCTCN2022118742-appb-000004
尽管机理尚未完全明确，但该化合物的造孔过程大体上可参考图1来理解。如图1所示，在制备浆料时，温度较低，该化合物的分子链中的酰胺基与周围水分子存在强烈的氢键作用，使该分子溶于水而均匀分布在浆料中。随后，浆料被涂布在集流体上形成湿润的(也即，尚未被干燥的)极片材料层。此时，由于极片尚未干燥，造孔剂分子链由于仍溶于水中，而呈现伸展状态，吸水溶胀，体积较大，在极片材料层中各自占据一定的体积。随着干燥进行，极片材料层的温度上升，造孔剂分子与溶剂水之间的氢键断裂，分子链间的疏水作用占据主导地位，分子链逐渐由溶解时的伸展状态逐渐收缩聚集，最终形成紧密的胶粒状。这样的转变使化合物分子体积减少数倍甚至几十倍，因此在干燥的极片中形成孔隙，孔隙率明显提高。
由于式(I)的化合物能够由于溶于水而均匀地分布于浆料及由此形成的极片材料层中，其产生的孔隙分布均匀。并且，在造孔过程中无需额外的耗能步骤、不产生气体，也不会改变电解液的成分，因此克服了现有技术的诸多缺点。
此外，值得注意的是，在造孔完成后，造孔剂式(I)的化合物而并未被除去，而是保留在本申请极片的孔隙中——发明人发现，该化合物在200℃以下的温度下不会分解或挥发。尽管机理尚不完全明确，发明人却出乎预料地发现，当新制的本申请的极片在被电解液浸 润时，存在于极片孔隙中的式(I)的化合物与电解液之间存在亲和力，因此能够“抓取”电解液，进一步提高了电解液的浸润效果，降低极片的初始极化。同时，由于该化合物在被电解液浸润后，会吸收电解液而溶胀(如图2所示)，这又能够进一步改善极片在多次循环后对电解液的保有量，从而能够减少极片在循环后期的极化，从而进一步改善了电池的循环性能。
得益于本申请所采用的造孔剂——式(I)的化合物，本申请的极片具有提高的孔隙率，改善的电解液浸润，改善的循环性能，从而延长了使用寿命。
以下详细说明本申请。
本申请的第一方面提供一种极片，其包括集流体和设置于所述集流体至少一个表面上的极片材料层，所述极片材料层包括活性物质和导电剂，其中，所述极片材料层包括式(I)的化合物：
Figure PCTCN2022118742-appb-000005
其中，R 1与R 2各自独立地选自氢、碳原子数为1-6的链烷基、碳原子数为1-6的链烷氧基、碳原子数为2-6的链烯基、碳原子数为6-20的芳基、羟基或氨基；其中所述链烷基、链烷氧基、链烯基和芳基各自独立地任选地被选自以下的基团中的至少一种所取代：碳原子数为1-3的烷基、碳原子数为1-6的烷基羟基、羟基、氨基、酰胺基、氰基、羧基、卤素；并且n为50-10000的整数。
由此，本申请提供了一种极片，其孔隙率较高，孔隙分布更均匀。同时，本申请的极片电解液初始浸润效果更好，对电解液的保液能力好，具有降低的初始极化、减小的直流阻抗(DCR)。进一步地，包含该极片的电池将会具有改善的性能，例如，循环性能、功率性能。
如本文所使用的，术语“功率性能”是指，电池在放电做功时，有用功在总功中的占比高。换言之，电池在放电做功过程中，电功损 失(如，由于电阻产热等)较少，对外输出的有用功较多，也即功率输出多。因此，能够理解，在本申请中，由于极片的DCR较小，相应地，功率性能较好。
在一些实施方式中，式(I)中，R 1与R 2各自独立地选自氢、碳原子数为1-6的链烷基、碳原子数为2-6的链烯基或苯基；其中所述链烷基、链烯基和苯基各自独立地任选地被选自以下的基团中的至少一种所取代：碳原子数为1-3的烷基、羟基或氨基；并且，R 2为氢。
在一些实施方式中，可选地，R 1选自碳原子数为1-6的链烷基、未取代的碳原子数为2-6的链烯基或苯基，所述链烷基和苯基各自独立地任选地被碳原子数为1-3的烷基或羟基取代，更可选地，R 1选自乙基、异丙基、烯丙基、羟甲基或对羟基苯基；并且，R 2为氢。
在一些实施方式中，式(I)中，n为75-5000的整数；可选地，n为100-2000的整数。
以上，通过进一步选择式(I)中的各个基团和聚合单元数n，能够进一步改善极片的孔隙结构特性(如，孔隙率和分布均匀性)，并且能够进一步提高极片对电解液的“抓取”能力和保液能力，降低初始极化，减小DCR等。
发明人发现，式(I)的化合物的聚合单元数n会影响极片的孔隙率和孔隙分布均匀性。根据上文，式(I)的化合物是利用其在升温前后的体积变化来实现造孔；而式(I)的化合物的聚合单元数n会影响其在升温前后的体积变化率。通过将聚合单元数n控制在上述范围内，能够使式(I)的化合物的分子量适中，从而能在具有良好溶解度的同时，具有适当的溶解体积(这样才能产生期望大小的孔隙)，升温时适当的体积变化率，从而在极片中得到孔隙尺寸和分布的均匀性和一致性更好的孔隙。
在一些实施方案中，所述极片材料层包括0.1-20重量％，可选地0.2-10重量％的式(I)的化合物，基于所述极片材料层的总重量计。
可以通过红外光谱测试来证明极片材料层包含式(I)的化合物。检测时，从待测极片的极片材料层直接刮下粉末，依据 GB/T6040-2002红外光谱分析方法测试。包含有式(I)化合物的极片样品在其红外谱图中，能够看到式(I)化合物的特征峰，如，1600-1700cm -1处的酰胺C＝O伸缩振动峰。
负极极片
在一些实施方式中，所述极片为负极极片。
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极极片材料层，所述极片材料层包括活性物质和导电剂；其中，所述负极极片材料层包括本申请第一方面的式(I)的化合物。
在一些实施方式中，所述极片材料层包括0.1-20重量％，可选地0.2-10重量％的式(I)的化合物，基于所述极片材料层的总重量计。
如本文中所使用的，术语“极片材料层的总重量”是指经干燥的极片材料层中所包含的所有物质的总重量。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极极片材料层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。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材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、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，负极活性物质可采用本领域公知的用于电池的负极活性物质。作为示例，负极活性物质可包括以下材料中的至少一种：人造石墨、天然石墨、软炭(或软碳)、硬炭(或硬碳)、硅基材料、锡基材料和钛酸锂等。所述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。所述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物质的传 统材料。这些负极活性物质可以仅单独使用一种，也可以将两种以上组合使用。通过选择负极活性物质，进一步提升负极极片的性能。
在一些实施方式中，负极极片材料层还可选地包括粘结剂。所述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。
在一些实施方式中，负极极片材料层包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极极片材料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。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性物质、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，即可得到负极极片。
正极极片
在一些实施方式中，本申请的极片可以是正极极片。正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极极片材料层，所述正极极片材料层包括本申请第一方面的式(I)的化合物。
在一些实施方式中，正极极片可以以任何适合于在极片内造孔的量包含式(I)的化合物。在一些实施方式中，可选地，正极极片的极片材料层包括0.1-20重量％，可选地0.2-10重量％的式(I)的化合物，基于所述极片材料层的总重量计。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极极片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，所述正极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，正极极片材料层包括正极活性物质。正极活性物质可采用本领域公知的用于电池的正极活性物质。作为示例，正极活性物质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物质的传统材料。这些正极活性物质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NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、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(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极极片材料层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极极片材料层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
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极片的组分，例如正极活性物质、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
本申请的第二方面提供一种极片的制备方法，包括：
(1)将活性物质、导电剂和式(I)的化合物的干混混合物、水、粘结剂在低于35℃的第一温度下混合，得到极片材料浆料，
Figure PCTCN2022118742-appb-000006
其中，R 1、R 2和n如上文所定义，
(2)将所述极片材料浆料施加在集流体的至少一个表面上，干燥，得到极片。
如本文所使用的，术语“干混混合物”是指将用于制备混合物的材料在无溶剂的情况下进行混合得到的混合物。
以上，提供了本申请的极片的制备方法。在本申请的方法中，采用式(I)的化合物作为造孔剂，实现了对极片孔隙率、均匀性和一致性的改善，并改善了极片被电解液浸润的性能和对电解液的保液性能，从而改善了极片和包含该极片的电池的循环性能、功率性能等。
在一些实施方式中，可以采用本领域任何常规方式将所述极片材料浆料施加在集流体的至少一个表面上，包括，但不限于，涂布。
在一些实施方式中，所述极片材料浆料的固含量为40重量％-70重量％，可选地为40重量％-65重量％，更可选地为45重量％-60重量％，基于所述极片材料浆料的总重量计。
在本申请的极片制备方法中，通过控制浆料的固含量可以控制并改善式(I)的化合物作为造孔剂的造孔效果。固含量在上述范围内时，能够使极片的干燥时间处于期望范围内；并且，水含量允许式(I) 的化合物与之形成适量氢键，这使得在干燥过程中该化合物体积变化率适当，并在极片中产生尺寸合适且结构稳定的孔隙。
在一些实施方式中，所述极片材料浆料包括0.1重量％-20重量％，可选地0.15重量％-15重量％，更可选地0.2重量％-10重量％的式(I)的化合物，基于所述极片材料浆料组合物的干重计。
如本文所使用的，术语“干重”是指，从极片材料浆料中除去溶剂(如，水)后，剩余的全部物质(或，全部干物质)的总重量。
通过控制造孔剂式(I)的化合物的加入量可以控制和改善造孔效果。具体来说，将浆料中式(I)的化合物的含量控制在上述范围内，能够获得良好的造孔效果：所得到的极片材料层中孔隙量适当，且孔隙结构稳定(也即，这些孔隙不易在随后的冷压中被破坏，而导致孔隙率再次下降)。另外，式(I)的化合物的上述含量范围允许极片中活性物质的负载量处于合理范围内，进而能够使电芯的能量密度合乎期望。
在一些实施方式中，第一温度为室温。在一些实施方式中，所述第一温度为20-30℃，可选地为22-28℃，更可选地为25℃。选择这样的第一温度使式(I)的化合物在浆料制备期间能够呈现较高亲水性而溶于水中，从而均匀分布在浆料及由此形成的极片材料层中，以实现均匀造孔的目的。
在一些实施方式中，干燥在任何温度下进行。在一些实施方式中，干燥在高于45℃的温度下进行的。在一些实施方式中，可选地，干燥在90℃-150℃，更可选在115℃-145℃，最可选在125-135℃下进行。通过将干燥温度选择在上述范围内，可以获得理想的干燥速率，兼顾生产效率的同时，实现期望的造孔过程；所得到的极片结构更稳定，孔道更均匀，从而使极片性能更好。
在一些实施方式中，可选地，所述水为去离子水。如此能够减少杂质在极片内的残留，避免其对极片的电化学性能造成不良影响。
在一些实施方式中，所制备的极片是负极极片。
在一些实施方式中，所述活性物质选自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。进一步选择负极活性物质，能够进一步改善负极极片性能。
本申请的第三方面提供式(I)的化合物作为造孔剂的用途，
Figure PCTCN2022118742-appb-000007
其中，R 1、R 2和n如上文所定义。
由此，本申请提供了一种式(I)的化合物作为造孔剂的用途。该化合物用于造孔用途，操作简单、过程环保，所得到的孔隙率高、孔隙分布均匀。
在一些实施方式中，本申请的式(I)的化合物可用于对正极、负极极片造孔，也可用于对隔膜材料造孔。
在一些实施方式中，所述造孔剂用于对极片的极片材料层造孔。
在一些实施方式中，所述极片为负极极片。
在极片(特别是负极极片)的浆料中加入式(I)的化合物作为造孔剂，利用该化合物能够溶解于溶剂(如，水)中，并在涂布过程中受热发生体积收缩来造孔，从而在最终得到的极片中形成均匀的孔隙，从而提高极片孔隙率。并且，由于在造孔后，该化合物会保留在极片材料层中，其疏水性质会使其与电解液之间具有亲和力，从而改善极片对电解液的浸润性能；并且，由于其在被电解质浸润之后会发生溶胀，又进一步提高了极片对电解液的保留能力，进而改善锂离子电池的循环性能。
本申请的第四方面提供一种二次电池，其包括本申请第一方面的极片或通过本申请第二方面的制备方法得到的极片。
本申请的第五方面提供一种电池模块，其包括本申请第四方面的二次电池。
本申请的第六方面提供一种电池包，其包括本申请第五方面的电池模块。
本申请的第七方面提供一种用电装置，其包括选自本申请第四方面的二次电池、第五方面的电池模块或第六方面的电池包中的至少一种。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1，4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、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、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。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。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，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。
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4是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图5，外包装可包括壳体51和盖板53。其中，壳体51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51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图6是作为一个示例的电池模块4。参照图6，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图7和图8是作为一个示例的电池包1。参照图7和图8，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块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，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(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，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图9是作为一个示例的用电装置。该用电装置为纯电动车、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，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1-5
负极极片制备
将石墨、导电剂炭黑以及作为造孔剂的式(I)的化合物(如下表1所示)按重量比96∶1∶2干混后，加入去离子水，调节固含量至55重量％，再加入1重量％的粘结剂丁苯橡胶(SBR)，搅拌均匀后得到负极极片材料浆料，而后将该负极极片材料浆料以12mg/cm 2的负载量涂布在集流体铜箔上，在130℃±5℃的温度下干燥，再经冷压、分切制成负极极片。
表1 实施例1-5中作为造孔剂的式(I)的化合物
实施例 式(I)的化合物 来源
1 聚(N-异丙基丙烯酰胺) 湖北实兴化工有限公司
2 聚(N-乙基丙烯酰胺) 上海阿拉丁生化科技股份有限公司
3 聚(N-烯丙基丙烯酰胺) 上海依赫生物科技有限公司
4 聚(N-羟甲基丙烯酰胺) 上海源叶生物科技有限公司
5 聚(N-对羟苯基丙烯酰胺) 深圳爱拓化学有限公司
正极极片制备
将正极镍钴锰三元材料LiNi 0.5Co 0.2Mn 0.3O 2、导电剂炭黑和粘接剂聚偏氟乙烯(PVDF)按重量比96∶2.5∶1.5的加入混合均匀后，添加溶剂N-甲基吡咯烷酮(NMP)，调节固含量至70重量％-80重量％，搅拌均匀后得到正极浆料，而后将该正极浆料以20mg/cm 2的负载量涂布在集流体铝箔上，经干燥、冷压、分切制成正极极片；
二次电池制备
1.电解液制备：将碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，再向其中加入LiPF 6，使LiPF 6的终浓度为12.5 重量％，搅拌均匀，得到电解液。
2.电池制备：将上述制得的负极和正极极片与12μm厚的PP隔膜卷绕成电芯，并用铝塑膜封装成干电芯，经注液、化成、老化等工序，制备得到二次电池。
实施例6-14
实施例6-14采用实施例1的聚(N-异丙基丙烯酰胺)作为造孔剂，按照实施例1进行极片及二次电池的制备。与实施例1不同的是聚(N-异丙基丙烯酰胺)的聚合单元数n，详见下表3。
实施例15-22
实施例15-22采用实施例1的聚(N-异丙基丙烯酰胺)作为造孔剂，按照实施例1进行极片及二次电池的制备，其中，石墨、炭黑和造孔剂的质量比如下表2所示。
表2 实施例中石墨、炭黑和造孔剂的质量比
实施例 石墨∶炭黑∶造孔剂(质量比)
15 97.95∶1∶0.05
16 97.9∶1∶0.1
17 97.8∶1∶0.2
18 91∶1∶7
19 88∶1∶10
20 83∶1∶15
21 68∶1∶20
22 63∶1∶25
实施例23-30
实施例22-29采用实施例1的聚(N-异丙基丙烯酰胺)作为造孔剂，按照实施例1进行极片及二次电池的制备。与实施例1不同的是负极材料浆料的固含量，详见下表3。
对比例C1
负极极片制备
将活性物质石墨、导电剂炭黑以重量比98∶1干混后，加入去离 子水，调节固含量至55重量％，然后加入1重量％粘结剂丁苯橡胶，搅拌均匀后得到负极浆料，而后将负极浆料以12mg/cm 2的负载量涂布在集流体铜箔上，在130℃±5℃干燥后，再经冷压、分切制成负极极片。
正极极片和二次电池依照实施例1相关步骤制备。
对比例C2
负极极片制备
按照实施例1的制备步骤制备负极极片，其中，造孔剂为碳酸铵。
正极极片和二次电池依照实施例1相关步骤制备。
将上述实施例1-30和对比例C1和C2中得到的负极极片及二次电池，进行性能测试。测试方法如下：
【极片相关测试】
1.孔隙率测试：
将待测极片裁剪成一定长宽尺寸的方形样品，先测得样品的表观体积V1，V1＝S×d，S为极片面积可用长×宽测得，单位cm 2，d为极片厚度可直接测得，单位cm。采用AccuPyc II 1340真密度仪，参考GB/T 24586-2009中孔隙率测试方法，利用氦气置换法，结合阿基米德原理和玻尔定律(PV＝nRT)，精确测量被测材料的真实体积V2，单位cm 3，通过公式计算得到待测样品的孔隙率p＝(V1-V2)/V1*100％。
2.吸液速率测试：
将待测极片在100℃干燥30min，然后裁剪成5cm×5cm的正方形，固定在样品台上，采用内径d＝200μm的毛细管吸取如实施例1中所制备的电解液(密度ρ为1.6g/cm 3)，管中吸入的电解液液面高度h＝3mm。测试开始前，将吸取了电解液的毛细管以与极片垂直的方式夹持于极片上方，使毛细管下端正对极片材料层。测试开始后将毛细管保持垂直并逐渐下移至与极片材料层刚好接触时，停止移动毛细管并开始用秒表计时。用Dino-Lite Edge Digital Microscope(型号：AM7115MZT)观察毛细管内液面下降，当液面下降至毛细管下端管口时，读取时间t。根据公式计算单个极片的吸液速率v，v＝π×(d/2) 2 ×h×ρ/t(π为圆周率)。
以上述方式测试n(n≥3)个平行样，然后计算平均值。
3.极片断面形貌表征：
采用蔡司sigma300扫描电子显微镜，用剪刀剪取5mm*5mm大小的极片样品并粘贴在粘有导电胶的样品台上，拍取截面形貌，设备参数为——模式：In-lens，电压：10KV，光阑：30μm，工作距离：4.5mm。测试流程：100倍左右移动样品，确认样品整体无明显异常后采用所需放大倍数随机选取两个视野拍照。
4.极片材料层成分检测
取根据实施例的方法制备的负极极片，将极片材料层刮下，依据GB/T6040-2002采用红外光谱法对极片材料进行检测，以确认其中含有式(I)化合物。
【二次电池性能测试】
1.大倍率放电测试：
(1)4C放电容量：
在25℃，将各实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压4.35V，之后恒压充电至电流≤0.05C，静置10min，再以4C倍率恒流放电至放电截止电压2.8V，记录放电容量C 4C。
(2)1C放电容量：
在25℃，将上述二次电池以1C倍率恒流充电至充电截止电压4.35V，之后恒压充电至电流≤0.05C，静置10min，再以1C倍率恒流放电至放电截止电压2.8V，记录放电容量C 1C。
(3)计算电芯大倍率放电容量保持率＝C 4C/C 1C*100％。
2.循环性能测试：
在25℃，将各实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压4.30V，之后恒压充电至电流≤0.05C，静置10min，再以1C倍率恒流放电至放电截止电压3.3V，静置10min，此为一个充放电循环(即，1圈)，记录放电容量C 1。按照此方法对 电池进行1000圈(cls)充放电循环测试，记录相应的放电容量C 1000，计算放电容量保持率＝C 1000/C 1*100％。
3.电池直流阻抗(DCR)测试：
在25℃下，将待测电池以1/3C恒流充电至4.3V，再以4.3V恒定电压充电至电流为0.05C，搁置5min后，记录电压V1。然后再以1/3C放电30s，记录电压V2，则电池的内阻DCR＝(V2-V1)/(1/3C)。
测试结果如下：
1.极片断面形貌：
图1示出了实施例1和对比例C1的负极极片的断面形貌的并排比较。
首先，通过比较两者可见，实施例1的负极极片的极片材料层中孔隙明显大于对比例C1。
其次，由图1还可以看到，相比于对比例C1的极片，实施例1的极片材料层中孔隙较均匀，一致性较好。具体来说，实施例1的极片在垂直于集流体(位于图片最下方)的方向上，孔隙分布较为均匀，上下的孔隙率及孔隙大小基本一致；而对比例C1的极片中，孔隙较小且不均匀。
这说明通过加入本申请的式(I)的化合物作为造孔剂实现了理想的造孔效果——提高了极片的孔隙率，使极片内孔隙较大且分布较均匀。
2.极片成分
通过红外光谱法，确认了根据实施例1的方法制备的极片的极片材料层中含有式(I)化合物的特征峰——1600-1700cm -1处有酰胺C＝O伸缩振动峰。
3.极片及二级电池的性能测试结果
表3 示出了实施例1-30与对比例的极片及电池的测试结果。
Figure PCTCN2022118742-appb-000008
Figure PCTCN2022118742-appb-000009
Figure PCTCN2022118742-appb-000010
由表3可见，相比于对比例C1，本发明各个实施例的负极极片的孔隙率有所提高，这说明加入本申请的造孔剂可提高极片孔隙率。相较于对比例C1，大倍率下电池的放电容量保持率(参见，表3中“4C放电容量保持率”一栏)有所提高，说明经本申请的造孔剂造孔后，极片的孔隙率增大，孔隙均匀，更有利于电解液在其中进行离子传导，进而改善了电池的倍率性能。而从循环1000圈后的容量保持率来看，加入造孔剂后，电池的循环性能相较于对比例C1也有明显改善。
相较于对比例C2，在孔隙率基本相同的情况下，本申请实施例极片的吸液速率有所提升。可见，由于本申请的造孔剂——式(I)的化合物在造孔后仍保留在极片的极片材料层中，其具有“抓取”电解液的能力，从而能够进一步改善新制极片的电解液浸润效果。
此外，相较于现有技术，本申请的极片具有降低的新制电池的直流阻抗(DCR)。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (21)

  1. 一种极片，其包括集流体和设置于所述集流体至少一个表面上的极片材料层，所述极片材料层包括活性物质和导电剂，其中，所述极片材料层还包括式(I)的化合物：
    Figure PCTCN2022118742-appb-100001
    其中，
    R 1与R 2各自独立地选自氢、碳原子数为1-6的链烷基、碳原子数为1-6的链烷氧基、碳原子数为2-6的链烯基、碳原子数为6-20的芳基、羟基或氨基；其中所述链烷基、链烷氧基、链烯基和芳基各自独立地任选地被选自以下的基团中的至少一种所取代：碳原子数为1-3的烷基、碳原子数为1-6的烷基羟基、羟基、氨基、酰胺基、氰基、羧基、卤素；并且
    n为50-10000的整数。
  2. 根据权利要求1所述的极片，其中，R 1与R 2各自独立地选自氢、碳原子数为1-6的链烷基、碳原子数为2-6的链烯基或苯基；其中所述链烷基、链烯基和苯基各自独立地任选地被选自以下的基团中的至少一种所取代：碳原子数为1-3的烷基、羟基或氨基；可选地，R 1选自碳原子数为1-6的链烷基、碳原子数为2-6的链烯基或苯基，所述链烷基和苯基各自独立地任选地被碳原子数为1-3的烷基或羟基取代；更可选地，R 1选自乙基、异丙基、烯丙基、羟甲基或对羟基苯基；并且
    R 2为氢。
  3. 根据权利要求1或2所述的极片，其中，n为75-5000的整数；可选地，n为100-2000的整数。
  4. 根据权利要求1至3中任一项所述的极片，其中所述极片材料层包括0.1-20重量％，可选地0.2-10重量％的式(I)的化合物，基于所述极片材料层的总重量计。
  5. 根据权利要求1至4中任一项所述的极片，其中所述极片为负极极片。
  6. 根据权利要求5所述的极片，其中所述活性物质选自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。
  7. 一种极片的制备方法，包括：
    (1)将活性物质、导电剂和式(I)的化合物的干混混合物、水、粘结剂在低于35℃的第一温度下混合，得到极片材料浆料，
    Figure PCTCN2022118742-appb-100002
    其中，R 1、R 2和n如权利要求1所定义，
    (2)将所述极片材料浆料施加在集流体的至少一个表面上，干燥，得到极片。
  8. 根据权利要求7所述的制备方法，其中所述极片材料浆料的固含量为40重量％-70重量％，可选地为40重量％-65重量％，更可选地为45重量％-60重量％，基于所述极片材料浆料的总重量计。
  9. 根据权利要求7或8所述的制备方法，其中所述极片材料浆料包括0.1重量％-20重量％，可选地0.15重量％-15重量％，更可选地0.2重量％-10重量％的式(I)的化合物，基于所述极片材料浆料的干重计。
  10. 根据权利要求7-9中任一项所述的制备方法，其中，所述第一温度为20-30℃，可选地为22-28℃，更可选地为25℃。
  11. 根据权利要求7-10中任一项所述的制备方法，其中所述干燥在高于45℃的温度下，可选地在90℃-150℃，更可选在115℃-145℃， 最可选在125-135℃下进行。
  12. 根据权利要求7-11中任一项所述的制备方法，其中所述水为去离子水。
  13. 根据权利要求7-12任一项所述的制备方法，其中所述极片是负极极片。
  14. 根据权利要求13所述的制备方法，其中所述活性物质选自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。
  15. 式(I)的化合物作为造孔剂的用途，
    Figure PCTCN2022118742-appb-100003
    其中，R 1、R 2和n如权利要求1所定义。
  16. 根据权利要求15所述的用途，其中，所述造孔剂用于对极片的极片材料层造孔。
  17. 根据权利要求16所述的用途，其中，所述极片为负极极片。
  18. 一种二次电池，其包括权利要求1-6中任一项所述的极片或通过权利要求7-14中任一项所述的制备方法得到的极片。
  19. 一种电池模块，其包括权利要求18所述的二次电池。
  20. 一种电池包，其包括权利要求19所述的电池模块。
  21. 一种用电装置，其包括选自权利要求18所述的二次电池、权利要求19所述的电池模块或权利要求20所述的电池包中的至少一种。
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CN115832295B (zh) 2023-10-20
US20230317948A1 (en) 2023-10-05
EP4239729A1 (en) 2023-09-06

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