WO2022267012A1 - 电化学装置及电子装置 - Google Patents

电化学装置及电子装置 Download PDF

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WO2022267012A1
WO2022267012A1 PCT/CN2021/102397 CN2021102397W WO2022267012A1 WO 2022267012 A1 WO2022267012 A1 WO 2022267012A1 CN 2021102397 W CN2021102397 W CN 2021102397W WO 2022267012 A1 WO2022267012 A1 WO 2022267012A1
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conductive layer
auxiliary agent
electrochemical device
conductive
cellulose
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PCT/CN2021/102397
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English (en)
French (fr)
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应豆
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宁德新能源科技有限公司
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Priority to EP21946506.9A priority Critical patent/EP4362122A1/en
Priority to PCT/CN2021/102397 priority patent/WO2022267012A1/zh
Priority to CN202180025116.9A priority patent/CN115803902A/zh
Publication of WO2022267012A1 publication Critical patent/WO2022267012A1/zh
Priority to US18/394,374 priority patent/US20240170651A1/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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/028—Positive 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 field of energy storage, in particular to an electrochemical device and an electronic device.
  • Lithium-ion batteries have the advantages of high energy density, long cycle life, and small self-discharge, and have been widely used; with the continuous advancement of technology, people have higher and higher requirements for the energy density of lithium-ion batteries. How to improve lithium-ion batteries The energy density of ion batteries has become a research hotspot.
  • a primer layer is applied between the active material layer and the current collector to increase the adhesion between the active material layer and the current collector and reduce the sheet resistance of the electrode sheet.
  • the commonly used primer active material is generally conductive carbon, and the single particle of conductive carbon is about 70nm to 110nm. The force between nano-sized particles is relatively large, and it is difficult to disperse.
  • the particle size of the prepared slurry is generally at the micron level. The particle size of the slurry limits the thickness of the coating film, which to a certain extent reduces the compaction density and energy density of the battery, increases additional costs, and reduces product competitiveness.
  • the present application provides an electrochemical device with high energy density and good cycle performance.
  • the present application provides an electrochemical device, the electrochemical device includes a positive electrode, the positive electrode includes a current collector, a conductive layer and an active material layer, and the conductive layer is arranged between the current collector and the active material layer, wherein the conductive
  • the layer includes secondary particles formed of primary particles of the conductive agent, and D50 of the secondary particles satisfies: 0.1 ⁇ m ⁇ D50 ⁇ 0.4 ⁇ m.
  • the thickness of the conductive layer can be reduced to less than 1 ⁇ m, and the energy density of the electrochemical device can be increased while ensuring the adhesion between the active material layer and the current collector.
  • the D90 of the secondary particles satisfies: 0.2 ⁇ m ⁇ D90 ⁇ 0.6 ⁇ m.
  • An excessively high thickness of the conductive layer will reduce the compaction density and energy density of the electrochemical device and reduce product competitiveness.
  • the conductive layer further includes a first auxiliary agent and a second auxiliary agent, wherein the first auxiliary agent includes at least one of polyether polyol or cellulose ether, and the second auxiliary agent includes polycarboxylic acid At least one of salt, polycarboxylate or polycarboxylic acid.
  • first auxiliary agent and the second auxiliary agent will bond with the conductive agent, and there is also an intermolecular force between the first auxiliary agent and the second auxiliary agent.
  • the two additives act synergistically to form a network bonding structure with different conductive agents. Under the action of shearing force, the network bonding structure can effectively disperse the conductive agent, so that the particle size of the secondary particles of the conductive agent in the final conductive layer can be kept at a small level.
  • the electrochemical device satisfies at least one of the following conditions (a) to (c): (a) the weight average molecular weight of the first additive is 400,000 to 800,000, (a) the second The weight average molecular weight of the auxiliary agent is 300,000 to 600,000, and (c) the molecular weight distribution index of the first auxiliary agent and the second auxiliary agent is 1 to 2. If the molecular weight of the auxiliary agent is too low, the dispersion effect of the conductive agent will be poor, and the particle size of the secondary particles will be too large, thereby increasing the thickness of the conductive layer.
  • the thickness of the conductive layer is too large, the energy density of the electrochemical device will be reduced, and the internal resistance of the electrochemical device will be increased, which is not conducive to the improvement of the kinetic performance of the electrochemical device. If the molecular weight of the additive is too high, the viscosity of the additive will be too high, the stirring energy will be large and the stirring effect will be poor.
  • the polyether polyol includes at least one of trihydroxy polyether, phenol polyoxyethylene ether, polyethylene glycol dimethyl ether, or polyether-modified glycerol.
  • the cellulose ethers include methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, ethyl cellulose, benzyl cellulose, hydroxyethyl cellulose, At least one of cellulose, hydroxypropyl cellulose, cyanoethyl cellulose, benzyl cyanoethyl cellulose, carboxymethyl hydroxyethyl cellulose or phenyl cellulose.
  • polycarboxylate comprises structural unit A
  • polycarboxylic acid comprises structural unit B
  • polycarboxylate comprises structural unit C or D
  • R 1 to R 3 are the same or different, each independently selected from hydrogen or C 1 -C 6 alkyl
  • R 4 and R 5 are the same or different, each selected from C 1 -C 6 alkyl or hydroxy-substituted C 1 -C 6 alkyl
  • M is selected from alkali metals.
  • the polycarboxylate includes at least one of sodium polyacrylate or sodium polymethacrylate
  • the polycarboxylic acid includes at least one of polyacrylic acid or polymethacrylic acid
  • the polycarboxylate includes At least one of polyvinyl acetate, poly-2-hydroxyethyl methacrylate or polyisobutyl methacrylate.
  • the electrochemical device satisfies at least one of the following conditions (d) to (e):
  • the conductive agent includes conductive carbon black, acetylene black, carbon fiber, carbon nanotube or ketjen black
  • the specific surface area of the conductive agent is 50m 2 /g to 100m 2 /g.
  • the specific surface area of the conductive agent is too small, that is, the particles of the conductive agent are large, and the conductivity will be damaged. If the specific surface area of the conductive agent is too large, the intermolecular force between the conductive agents is large, which is not conducive to the dispersion of the conductive agent.
  • the mass content of the conductive agent is 40% to 75%
  • the mass content of the first auxiliary agent is 1% to 5%
  • the mass content of the second auxiliary agent is 20%. % to 55%. If the content of the first auxiliary agent and the second auxiliary agent is too low, the dispersion effect of the conductive agent is not good, the secondary particles of the conductive layer are large, the thickness of the conductive layer is large, and the volumetric energy density of the electrochemical device is low.
  • the rigidity of the auxiliary agent will be large, which will affect the compaction density of the electrochemical device. If the content of the first auxiliary agent and the second auxiliary agent is too high, the content of the conductive agent will decrease correspondingly, the conductivity of the conductive layer will deteriorate, and the internal resistance of the electrochemical device will increase.
  • the mass ratio of the first auxiliary agent to the second auxiliary agent is 1:4 to 1:50.
  • the second auxiliary agent has lower rigidity and greater cohesive force, so a higher content of the second auxiliary agent can further increase the energy density of the electrochemical device.
  • the preparation of the conductive layer includes the following steps:
  • Step A mixing the conductive agent, the first auxiliary agent, the second auxiliary agent and the solvent under the first solid content condition to obtain the conductive layer slurry
  • Step B after diluting the conductive layer slurry obtained in step A to the second solid content, coating it on the current collector,
  • the first solid content is 13% to 30%, and the second solid content is greater than or equal to 3%.
  • the shear force will not be enough to effectively disperse the conductive agent; if the first solid content is too high, the load current of the mixer will be too large, which will damage the mixer .
  • the conductive layer satisfies at least one of the following conditions (f) to (h): (f) the thickness T of the conductive layer is 0.3 ⁇ m to 1.0 ⁇ m; (g) the thickness T of the conductive layer is equal to The secondary particle D90 satisfies: T ⁇ 1.5 ⁇ D90; (h) The particle size distribution curve of the conductive layer is a monomodal distribution. In some embodiments, the thickness T of the conductive layer is 0.3 ⁇ m to 1.0 ⁇ m. If the thickness of the conductive layer is too high, the energy density of the electrochemical device will decrease.
  • the positive electrode satisfies at least one of the following conditions (i) to (l): (i) the coverage of the conductive layer is 60% to 100%; (j) the coating weight of the conductive layer is 0.01mg /cm 2 to 0.04mg/cm 2 ; (k) the sheet resistance of the positive electrode is 0.05 ⁇ to 5 ⁇ ; (l) the bonding force between the conductive layer and the active material layer is 10N/m to 50N/m.
  • the coverage of the conductive layer in the positive electrode is 60% to 100%. If the coverage of the conductive layer is too small, the content of the conductive agent and the adhesive force in the conductive layer will be too low, which will lead to an increase in the electronic impedance of the electrochemical device, a decrease in the rate performance, and a dive after demoulding at the end of the cycle.
  • the present application provides an electronic device, which includes the electrochemical device of the first aspect.
  • This application improves the dispersion of the conductive agent particles by adding specific additives in the conductive layer and utilizing the interaction between the additives and the conductive agent, so that the secondary particles of the conductive agent in the conductive layer are maintained at the nanometer level and conduct electricity.
  • the layer thickness is less than 1 ⁇ m, effectively increasing the compaction density and energy density of the electrochemical device of the present application.
  • FIG. 1 is a graph showing the particle size distribution of the conductive layer in the positive electrode of the electrochemical device of Examples 4-5 of the present application.
  • FIG. 2 is a graph showing the particle size distribution of the conductive layer in the positive electrode of the electrochemical device of Comparative Example 4-1 of the present application.
  • the term "about” is used to describe and account for small variations.
  • the terms can refer to instances in which the event or circumstance occurred exactly as well as instances in which the event or circumstance occurred with close approximation.
  • the term may refer to a range of variation of less than or equal to ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 10%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • a list of items linked by the term "at least one of” can mean any combination of the listed items. For example, if the items A and B are listed, the phrase "at least one of A and B" means A only; only B; or A and B. In another example, if the items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • references to “embodiment”, “partial embodiment”, “an embodiment”, “another example”, “example”, “specific example” or “partial example” in the entire specification mean that At least one embodiment or example in the present application includes a specific feature, structure, material or characteristic described in the embodiment or example.
  • descriptions that appear throughout the specification such as: “in some embodiments”, “in an embodiment”, “in one embodiment”, “in another example”, “in an example In”, “in a particular example” or “example”, they are not necessarily referring to the same embodiment or example in this application.
  • the particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.
  • the present application provides an electrochemical device, which includes a positive electrode, the positive electrode includes a current collector, a conductive layer and an active material layer, and the conductive layer is arranged between the current collector and the active material layer, wherein the conductive layer includes
  • the D50 of the secondary particles satisfies: 0.1 ⁇ m ⁇ D50 ⁇ 0.4 ⁇ m.
  • the D90 of the secondary particles satisfies: 0.2 ⁇ m ⁇ D90 ⁇ 0.6 ⁇ m.
  • the larger the D50 and D90 of the secondary particles the higher the thickness of the conductive layer will be. Excessive conductive layer thickness will reduce the compaction density and energy density of the electrochemical device, increase additional costs, and reduce product competitiveness.
  • the D50 of the secondary particle is 0.12 ⁇ m, 0.14 ⁇ m, 0.16 ⁇ m, 0.18 ⁇ m, 0.20 ⁇ m, 0.22 ⁇ m, 0.24 ⁇ m, 0.26 ⁇ m, 0.28 ⁇ m, 0.30 ⁇ m, 0.31 ⁇ m, 0.33 ⁇ m, 0.35 ⁇ m, 0.37 ⁇ m, 0.39 ⁇ m, or a range consisting of any two of these values.
  • the secondary particles have a D50 of 0.15 ⁇ m to 0.30 ⁇ m.
  • the D90 of the secondary particle is 0.22 ⁇ m, 0.25 ⁇ m, 0.27 ⁇ m, 0.30 ⁇ m, 0.33 ⁇ m, 0.35 ⁇ m, 0.38 ⁇ m, 0.40 ⁇ m, 0.42 ⁇ m, 0.45 ⁇ m, 0.47 ⁇ m, 0.50 ⁇ m, 0.53 ⁇ m , 0.55 ⁇ m, 0.57 ⁇ m or any two of these values.
  • the secondary particles have a D90 of 0.25 ⁇ m to 0.40 ⁇ m.
  • secondary particle refers to a particle formed by agglomerating primary particles of a conductive agent.
  • the conductive layer further includes a first auxiliary agent and a second auxiliary agent.
  • the first auxiliary agent includes at least one of polyether polyol or cellulose ether.
  • the second adjuvant includes at least one of polycarboxylates, polycarboxylates, or polycarboxylic acids.
  • the first auxiliary agent and the second auxiliary agent are added to the conductive layer at the same time. Both the first auxiliary agent and the second auxiliary agent will bond with the conductive agent, and there are molecules between the first auxiliary agent and the second auxiliary agent. Interaction force, such as the force between the hydroxyl group of the first auxiliary agent and the carboxyl group of the second auxiliary agent.
  • the two additives act synergistically to form a network bonding structure with different conductive agents.
  • the network bonding structure can effectively disperse the conductive agent, so that the particle size of the secondary particles of the conductive agent in the final conductive layer is maintained at a small level, thereby reducing the thickness of the conductive layer and improving the conductivity including the conductive layer.
  • Layer compaction density and energy density of the electrochemical device are the two additives act synergistically to form a network bonding structure with different conductive agents.
  • the weight average molecular weight of the first auxiliary agent is 400,000 to 800,000.
  • the weight average molecular weight of the first additive is 410,000, 430,000, 450,000, 470,000, 490,000, 500,000, 520,000, 540,000, 550,000, 570,000, 590,000, 600,000 , 620,000, 650,000, 670,000, 700,000, 720,000, 740,000, 760,000, 780,000, or any two of these values.
  • the weight average molecular weight of the second additive is 300,000 to 600,000.
  • the weight average molecular weight of the first additive is 310,000, 330,000, 350,000, 370,000, 390,000, 400,000, 420,000, 440,000, 450,000, 470,000, 490,000, 500,000 , 520,000, 550,000, 570,000, 590,000, or any two of these values.
  • the molecular chain segments of additives will bond with different conductive agents. Molecular segments bonded to different conductive agent aggregates will separate the conductive agent aggregates after being pulled by the shear force, thereby achieving effective dispersion of the conductive agent.
  • the molecular weight of the auxiliary agent is too low, that is, the molecular chain segment is short, and the number of molecular chain segments bonded to the conductive agent is small, the dispersion effect of the conductive agent will be poor, and the particle size of the secondary particles will be too large, thereby increasing the conductivity of the conductive layer. thickness. If the thickness of the conductive layer is too large, the energy density of the electrochemical device will be reduced and the internal resistance of the electrochemical device will be increased, which is not conducive to the improvement of the kinetic performance of the electrochemical device. If the molecular weight of the additive is too high, the viscosity of the additive will be too high, the stirring energy will be large and the stirring effect will be poor.
  • the first auxiliary agent includes polyether polyol
  • polyether polyol includes trihydroxy polyether, phenol polyoxyethylene ether, polyethylene glycol dimethyl ether or polyether modified glycerol. at least one of .
  • the first auxiliary agent includes cellulose ether
  • cellulose ether includes methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, ethyl cellulose cellulose, benzyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, cyanoethyl cellulose, benzyl cyanoethyl cellulose, carboxymethyl hydroxyethyl cellulose or phenyl cellulose at least one.
  • the first auxiliary agent includes trihydroxy polyether, phenol polyoxyethylene ether, polyethylene glycol dimethyl ether, polyether modified glycerin, sodium carboxymethyl cellulose, hydroxypropyl At least one of base cellulose and ethyl cellulose.
  • the hydroxyl group in the first auxiliary agent can increase the wettability, and on the other hand, it can form a bond with the carboxyl group in the second auxiliary agent, which contributes to the formation of a cross-linked network between the auxiliary agent and the conductive agent.
  • the second auxiliary agent includes polycarboxylate
  • the polycarboxylate includes the following structural unit A:
  • R 1 to R 3 are the same or different, each independently selected from hydrogen or C 1 -C 6 alkyl, and M is selected from alkali metals.
  • R to R are the same or different, each independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl , M is sodium or potassium.
  • the polycarboxylate includes at least one of sodium polyacrylate or sodium polymethacrylate.
  • the second auxiliary agent includes polycarboxylic acid
  • the polycarboxylic acid includes the following structural unit B:
  • R 1 to R 3 are the same or different, each independently selected from hydrogen or C 1 -C 6 alkyl. In some embodiments, R to R are the same or different, each independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl . In some embodiments, the polycarboxylic acid includes at least one of polyacrylic acid or polymethacrylic acid.
  • the second auxiliary agent includes polycarboxylate
  • the polycarboxylate includes the following structural unit C:
  • R 1 to R 3 are the same or different, each independently selected from hydrogen or C 1 -C 6 alkyl
  • R 4 is selected from C 1 -C 6 alkyl or C 1 -C 6 alkyl substituted by hydroxy.
  • R to R are the same or different, each independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec Butyl or tert-butyl.
  • R is selected from methyl, ethyl, n - propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hydroxy-substituted methyl, hydroxy-substituted ethyl or hydroxy-substituted propyl base.
  • the polycarboxylate includes at least one of poly-2-hydroxyethyl methacrylate or polyisobutyl methacrylate.
  • the second auxiliary agent includes polycarboxylate
  • polycarboxylate includes the following structural unit D:
  • R 1 to R 3 are the same or different, each independently selected from hydrogen or C 1 -C 6 alkyl
  • R 5 is selected from C 1 -C 6 alkyl or C 1 -C 6 alkyl substituted by hydroxy.
  • R to R are the same or different, each independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec Butyl or tert-butyl.
  • R is selected from methyl, ethyl, n - propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hydroxy-substituted methyl, hydroxy-substituted ethyl or hydroxy-substituted propyl base.
  • the polycarboxylate includes polyvinyl acetate.
  • the second additive includes sodium polyacrylate, sodium polymethacrylate, polyacrylic acid, polymethacrylic acid, polyvinyl acetate, polymethacrylate-2-hydroxyethyl or polymethyl at least one of isobutyl acrylate.
  • the carboxyl group in the second auxiliary agent can bond with the residual oxygen-containing functional groups on the conductive agent, and on the other hand, it can bond with the hydroxyl group in the first auxiliary agent, which contributes to the connection between the auxiliary agent and the conductive agent. Formation of cross-linked network.
  • the conductive agent includes at least one of conductive carbon black, acetylene black, carbon fiber, carbon nanotube, or Ketjen Black.
  • the conductive agent has a specific surface area of 50 m 2 /g to 100 m 2 /g.
  • the specific surface area of the conductive agent is 55m 2 /g, 60m 2 /g, 65m 2 /g, 70m 2 /g, 75m 2 /g, 80m 2 /g, 85m 2 /g, 90m 2 /g g, 95m 2 /g or a range consisting of any two of these values.
  • the specific surface area of the conductive agent is too small, that is, the particles of the conductive agent are large, and the conductivity will be damaged. If the specific surface area of the conductive agent is too large, the intermolecular force between the conductive agents is large, which is not conducive to the dispersion of the conductive agent.
  • the mass content of the conductive agent is 40% to 75%.
  • the mass content of the conductive agent is 42%, 45%, 47%, 50%, 53%, 55%, 57%, 59%, 62%, 65%, 67%, 69%, 71% , 73%, or a range consisting of any two of these values. If the content of the conductive agent is too low, the conductivity of the conductive layer will deteriorate, and the electronic impedance of the electrochemical device will increase. If the content of the conductive agent is too much, the adhesive force of the conductive layer is insufficient, and the safety performance of the electrochemical device is low.
  • the mass content of the first auxiliary agent is 1% to 5%.
  • the mass content of the first additive is 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.5%, 4.5%, or a range consisting of any two of these values.
  • the mass content of the second auxiliary agent is 20% to 55%.
  • the mass content of the second auxiliary agent is 25%, 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of these values. If the content of the first auxiliary agent and the second auxiliary agent is too low, the dispersion effect of the conductive agent is not good, the secondary particles of the conductive layer are large, the thickness of the conductive layer is large, and the volumetric energy density of the electrochemical device is low. In addition, when the content is too low, the rigidity of the auxiliary agent will be large, which will affect the compaction density of the electrochemical device. If the content of the first auxiliary agent and the second auxiliary agent is too high, the content of the conductive agent will decrease correspondingly, the conductivity of the conductive layer will deteriorate, and the internal resistance of the electrochemical device will increase.
  • the mass ratio of the first auxiliary agent to the second auxiliary agent is 1:4 to 1:50. In some embodiments, the mass ratio of the first auxiliary agent to the second auxiliary agent is 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or a range of any two of these values.
  • the second auxiliary agent has lower rigidity and greater cohesive force, so a higher content of the second auxiliary agent can further increase the energy density of the electrochemical device.
  • the preparation of the conductive layer includes the following steps:
  • Step A mixing the conductive agent, the first auxiliary agent, the second auxiliary agent and the solvent under the first solid content condition to obtain the conductive layer slurry
  • Step B after diluting the conductive layer slurry obtained in step A to the second solid content, coating it on the current collector,
  • the first solid content is 13% to 30%, and the second solid content is greater than or equal to 3%.
  • the first solids content is 15%, 17%, 19%, 20%, 21%, 23%, 25%, or a range consisting of any two of these values.
  • the second solid content is greater than or equal to 3%, less than the first solid content, such as 3% to 10%.
  • the solvent is water.
  • the thickness T of the conductive layer is 0.3 ⁇ m to 1.0 ⁇ m, such as 0.4 ⁇ m, 0.5 ⁇ m, 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m or any combination of these values.
  • An excessively high thickness of the conductive layer may result in a reduction in the energy density of the electrochemical device.
  • the thickness T of the conductive layer and the D90 of the secondary particles satisfy: T ⁇ 1.5 ⁇ D90.
  • the particle size distribution curve of the conductive layer is a monomodal distribution.
  • the coverage of the conductive layer of the positive electrode is 60% to 100%, such as 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any two of these values range of composition. If the coverage of the conductive layer is too small, the content of the conductive agent and the adhesive force in the conductive layer will be too low, so the electronic impedance of the electrochemical device will increase, the rate performance will decrease, and the mold will dive in the late stage of the cycle.
  • the degree of coverage of the conductive layer in this application represents the degree of coverage of the conductive layer on the current collector.
  • the coating weight of the conductive layer of the positive electrode is 0.01 mg/cm 2 to 0.04 mg/cm 2 , such as 0.015 mg/cm 2 , 0.02 mg/cm 2 , 0.025 mg/cm 2 , 0.03 mg /cm 2 , 0.035 mg/cm 2 , or a range consisting of any two of these values. If the coating weight of the conductive layer is too small, the coverage will be small, which will increase the electronic impedance of the electrochemical device and reduce the rate performance. The coating weight of the conductive layer is too large, the thickness of the conductive layer is too high, and the energy density of the electrochemical device is low.
  • the sheet resistance of the positive electrode is 0.05 ⁇ to 5 ⁇ , such as 0.5 ⁇ , 1.0 ⁇ , 1.5 ⁇ , 2.0 ⁇ , 2.5 ⁇ , 3.0 ⁇ , 3.5 ⁇ , 4.0 ⁇ , 4.5 ⁇ or among these values Any range consisting of the two.
  • the bonding force between the conductive layer of the positive electrode and the active material layer is 10N/m to 50N/m, such as 15N/m, 20N/m, 25N/m, 30N/m, 35N/m m, 40N/m, 45N/m, or a range consisting of any two of these values.
  • the active material layer includes a positive electrode active material.
  • the positive electrode active material of the present application may include lithium nickel cobalt manganate (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobaltate, lithium manganate, ferromanganese phosphate At least one of lithium or lithium titanate.
  • the current collector may use a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used.
  • the composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate.
  • the electrochemical device of the present application also includes a negative electrode.
  • the material, composition, and manufacturing method of the negative electrode used in the electrochemical device of the present application may include any technology disclosed in the prior art.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode active material layer includes a negative electrode active material
  • the negative electrode active material may include materials that reversibly intercalate/deintercalate lithium ions, lithium metal, lithium metal alloys, materials capable of doping/dedoping lithium Or transition metal oxides, such as Si, SiOx (0 ⁇ x ⁇ 2) and other materials.
  • the material that reversibly intercalates/deintercalates lithium ions may be a carbon material.
  • the carbon material can be any carbon-based negative active material commonly used in lithium-ion rechargeable electrochemical devices. Examples of carbon materials include crystalline carbon, amorphous carbon, and combinations thereof.
  • the crystalline carbon may be amorphous or plate-shaped, platelet-shaped, spherical or fibrous natural or artificial graphite.
  • the amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization product, fired coke, or the like. Both low-crystalline carbon and high-crystalline carbon can be used as the carbon material.
  • soft carbon and hard carbon may be generally included.
  • highly crystalline carbon materials natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesocarbon microbeads, mesophase pitch, and high-temperature calcined carbons (such as petroleum or coke derived from coal tar pitch) may generally be included. ).
  • the negative electrode active material layer contains a binder
  • the binder may include various binder polymers, such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP) , polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, containing Polymers of ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester)ized styrene-butadiene rubber, epoxy resin, nylon, etc., but not limited thereto Wait.
  • PVDF-co-HFP vinylidene fluoride-hexafluoropropylene copolymer
  • the negative electrode active material layer further includes a conductive material to improve electrode conductivity.
  • a conductive material can be used as the conductive material as long as it does not cause a chemical change.
  • conductive materials include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, etc.; metal-based materials such as metal powder or metal fibers including copper, nickel, aluminum, silver, etc. ; Conductive polymers, such as polyphenylene derivatives, etc.; or their mixtures.
  • the current collector can be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, or a combination thereof.
  • the electrochemical device of the present application also includes an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2.
  • LiPF 6 may be selected as a lithium salt because it can give high ion conductivity and improve cycle characteristics.
  • the non-aqueous solvent can be carbonate compound, carboxylate compound, ether compound, other organic solvent or their combination.
  • the above-mentioned carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or a combination thereof.
  • Examples of the aforementioned chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), carbonic acid Methyl ethyl ester (MEC) and combinations thereof.
  • Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof.
  • fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate Fluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Ethyl carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-dicarbonate Fluoro-1-methylethylene carbonate
  • Examples of the above carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone , decanolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.
  • ether compounds examples include dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • Examples of the aforementioned other organic solvents are dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, Formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters, and combinations thereof.
  • the electrochemical device of the present application further includes a separator.
  • the present application has no particular limitation on the material and shape of the isolation membrane, which can be any technology disclosed in the prior art.
  • the separator includes a polymer or an inorganic material formed of a material stable to the electrolyte of the present application.
  • a release film may include a substrate layer and a surface treatment layer.
  • the substrate layer is non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials.
  • the inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, At least one of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl alkoxy , polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene at least one.
  • Polymer is contained in the polymer layer, and the material of polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl alkoxide, polyvinylidene fluoride, At least one of poly(vinylidene fluoride-hexafluoropropylene).
  • the present application provides an electronic device, which includes the electrochemical device of the first aspect.
  • electronic devices of the present application include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets , VCR, LCD TV, Portable Cleaner, Portable CD Player, Mini Disc, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, Motorcycle, Assisted Bicycle, Bicycle , Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • Conductive layer particle size test Disassemble the cell to obtain the electrode pole piece, wash and dry it with NMP or stick the active layer with tape, then dissolve the conductive layer with deionized water to obtain the slurry to be tested .
  • the slurry to be tested was tested with a Malvern laser particle size analyzer. Specifically, select the Hydro SM Starter Sample (SOP) mode, use deionized water as the solvent, set the rotation speed to 2800 ⁇ 400rpm, and set the refractive index to 1.52. Measure the pure solution (deionized water), after deducting the background, take the slurry to be tested with a dropper, slowly add it to the target amount (it will turn green), and then click to test.
  • SOP Hydro SM Starter Sample
  • Conductive layer coverage test Disassemble the cell to obtain the electrode pole piece, wash and dry it with NMP or tape to remove the active layer, and then test it with a CCD detector. Specifically, focus first, turn the fine-tuning nut to adjust it clearly, take an optical image, and then choose to automatically measure the area. The specific parameters are set to dark area, threshold 60, lightness -20, and multiplier ⁇ 50. The coverage report can be obtained after the test is completed.
  • Diaphragm resistance measurement Disassemble the cell to obtain the electrode pole piece, wash off the electrolyte with DMC solution, and use a wiped and cleaned diaphragm resistance meter to test. Specifically, the pole piece is flattened, and the resistance value of the coated film area is measured at the middle position 25mm away from the edge and the uncoated film area, and the average value is obtained after 15 measurements.
  • the test conditions are single point mode, pressure 0.4T, test time 5s/point.
  • Adhesion test Disassemble the battery cell to obtain the electrode sheet, wash off the electrolyte with DMC solution, and then prepare the sample. First cut the pole piece into a pole piece sample with a width of 30mm and a length of 100mm to 160mm, and paste the special double-sided adhesive tape on the steel plate with a width of 20mm and a length of 90mm to 150mm. up, test side down. Then insert a paper tape with the same width as the pole piece sample and 80mm to 200mm longer than the sample length under the pole piece, and fix it with crepe glue.
  • Test the prepared sample with a high-speed rail tensile machine fix the steel plate, clamp the paper tape with the tensile machine, pull the paper tape at a speed of 50mm/min, record the force and displacement parameters, and then get the value of the bonding force, and take 5 samples for each group average value.
  • Preparation of the positive pole piece Add the conductive agent, the first auxiliary agent, the second auxiliary agent and solvent water into the double planetary mixer, stir and disperse at the first solid content to obtain the conductive layer slurry. After the conductive layer slurry is diluted with water to the second solid content, it is coated on the current collector (aluminum foil) by a gravure machine to obtain a current collector coated with the conductive layer.
  • the active material slurry is composed of lithium cobaltate, acetylene black and polyvinylidene fluoride in an appropriate amount of N-methyl Pyrrolidone solvent is fully stirred and mixed
  • the conductive agent is conductive carbon
  • the first auxiliary agent is sodium carboxymethyl cellulose
  • the second auxiliary agent is sodium polyacrylate.
  • negative electrode sheet Fully stir and mix graphite, polymethacrylic acid and styrene-butadiene rubber in an appropriate amount of deionized water solvent in a weight ratio of 98:1:1 to form a uniform negative electrode slurry.
  • the prepared negative electrode slurry is coated on the above-mentioned copper foil current collector, dried, and cold pressed to obtain a negative electrode sheet.
  • Lithium-ion batteries are obtained through processes such as formation, degassing, and trimming. Among them, 7 ⁇ m PE is used as the isolation film.
  • the electrolyte includes a solvent mixed with propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (about 1:1:1 by weight) and LiPF 6 .
  • the concentration of LiPF 6 is about 1.15mol/L.
  • Table 1 shows the weight average molecular weight of the first auxiliary agent (sodium carboxymethyl cellulose), the weight average molecular weight of the second auxiliary agent (sodium polyacrylate), and the specific surface area of the conductive agent (conductive carbon) to the prepared The performance of the positive pole piece and the lithium-ion battery containing the positive pole piece.
  • the first solid content is 15%, and the second solid content is greater than or equal to 3%.
  • the molecular weight distribution index of the first auxiliary agent is 1-2, and the molecular weight distribution index of the second auxiliary agent is 1-2.
  • the mass content of the first auxiliary agent in Examples 1-1 to 1-6 and Comparative Example 1-1 to Comparative Example 1-3 is 2.5%, and the mass content of the second auxiliary agent is 47.5%.
  • the mass content of the conductive agent is 50%.
  • the mass content of the first auxiliary agent in Comparative Examples 1-4 is 50%.
  • the mass content of the second auxiliary agent in Comparative Examples 1-5 was 50%.
  • Example 1-1 Comparative Examples 1-4 and Comparative Examples 1-5, it can be seen that when the first auxiliary agent and the second auxiliary agent are added to the conductive layer at the same time, the particle size of the secondary particles in the conductive layer is small , the thickness of the conductive layer is low, and the volumetric energy density of the lithium-ion battery is large.
  • both the first auxiliary agent and the second auxiliary agent will bond with the conductive agent aggregates, and there is also an intermolecular force between the first auxiliary agent and the second auxiliary agent.
  • the two additives act synergistically to form a network bonding structure with different conductive agent aggregates. Under the action of shearing force, the network bonding structure can effectively disperse the conductive agent, so that the particle size of the secondary particles of the conductive agent in the final conductive layer can be kept at a small level.
  • Example 1-1, Example 1-4 and Comparative Example 1-2 it can be seen that when the molecular weight of the first additive is in the range of 400,000 to 800,000, the lithium-ion battery has a higher volumetric energy density.
  • Example 1-1, Example 1-5 and Comparative Example 1-3 it can be seen that when the molecular weight of the second additive is in the range of 300,000 to 600,000, the lithium-ion battery has a higher volumetric energy density.
  • the molecular chain segments of additives will bond with different conductive agent aggregates. Molecular segments bonded to different conductive agent aggregates will separate the conductive agent aggregates after being pulled by the shear force, thereby achieving effective dispersion of the conductive agent.
  • the molecular weight of the additive is too low, that is, the molecular chain segment is short, and the number of molecular chain segments bonded to the agglomerates is small, the dispersion effect of the conductive agent will be poor, and the particle size of the secondary particles will be too large, thereby increasing the conductivity of the conductive layer. thickness. If the thickness of the conductive layer is too large, the energy density of the battery will be reduced and the internal resistance of the battery will be increased, which is not conducive to the improvement of the kinetic performance of the battery. If the molecular weight of the additive is too high, the viscosity of the additive will be too high, the stirring energy will be large and the stirring effect will be poor.
  • Example 1-7 According to the data of Example 1-1, Example 1-7 and Comparative Example 1-1, it can be seen that when the specific surface area of the conductive agent is in the range of 50m 2 /g to 100m 2 /g, the energy density of the lithium-ion battery High, low internal resistance.
  • the specific surface area of the conductive agent is too small, that is, the particles of the conductive agent are large, and the conductivity will be damaged. If the specific surface area of the conductive agent is too large, the intermolecular force between the conductive agents is large, which is not conducive to the dispersion of the conductive agent.
  • the mass content of the first auxiliary agent (sodium carboxymethyl cellulose), the second auxiliary agent (sodium polyacrylate) and the conductive agent (conductive carbon) is shown in table 2. Pole pieces affect the performance of lithium-ion batteries.
  • the weight average molecular weight of the first additive is 650,000
  • the weight average molecular weight of the second additive is 450,000
  • the specific surface area of the conductive agent is 65 m 2 /g.
  • the first solid content is 15%
  • the second solid content is greater than or equal to 3%.
  • the molecular weight distribution index of the first additive is 1.32
  • the molecular weight distribution index of the second additive is 1.57.
  • Table 3 shows the influence of the first solid content of the conductive layer slurry on the performance of the prepared positive electrode sheet and the lithium ion battery comprising the positive electrode sheet.
  • the second solid content is 7%
  • the weight average molecular weight of the first auxiliary agent is 650,000
  • the weight average molecular weight of the second auxiliary agent is 450,000
  • the specific surface area of the conductive agent is 65m 2 /g.
  • the molecular weight distribution index of the first additive is 1.47
  • the molecular weight distribution index of the second additive is 1.52.
  • the mass content of the first auxiliary agent is 2.5%
  • the mass content of the second auxiliary agent is 47.5%
  • the mass content of the conductive agent is 50%.
  • the performance of the battery is better when the first solid content is in the range of 13% to 25%.
  • the first solid content is too low and the shearing force is not enough to effectively disperse the conductive agent. If the solid content is too high, the load current of the mixer is too large, which will damage the mixer.
  • Table 4 shows the D50, D90 of the secondary particles of the conductive layer, and the influence of the thickness of the conductive layer on the performance of the prepared positive electrode sheet and the lithium ion battery comprising the positive electrode sheet.
  • the D50 and D90 of the secondary particles of the conductive layer and the thickness of the conductive layer are controlled by simultaneously controlling the content of each component of the conductive layer, the first solid content, and the stirring time.
  • the molecular weight of the first additive is 650,000
  • the molecular weight of the second additive is 450,000.
  • the molecular weight distribution index of the first additive is 1.32
  • the molecular weight distribution index of the second additive is 1.57.
  • the mass content of the first auxiliary agent is in the range of 1% to 5%
  • the mass content of the second auxiliary agent is in the range of 20% to 55%
  • the mass content of the conductive agent is in the range of 40% to 75%. within range.
  • the first solid content is greater than or equal to 13%
  • the second solid content is greater than or equal to 3%.

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Abstract

一种电化学装置及包括电化学装置的电子装置。电化学装置包括正极，正极包括集流体、导电层和活性物质层，导电层设置在集流体和活性物质层之间，其中导电层包括由导电剂一次颗粒形成的二次颗粒，二次颗粒的D50满足：0.1μm≤D50≤0.4μm。电化学装置正极的导电层厚度小于1μm，有效地增加了电化学装置的压实密度和能量密度。

Description

电化学装置及电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置及电子装置。
背景技术
锂离子电池具有能量密度高，循环寿命长、自放电小等优势，得到了非常广泛的应用；随着技术的不断进步，人们对锂离子电池的能量密度的要求越来越高，如何提升锂离子电池的能量密度成为了人们研究的热点。
目前制备锂离子电池时，会在活性物质层与集流体之间涂覆一层底涂层，用来增加活性物质层与集流体之间的粘接力，降低极片膜片电阻。常用底涂活性物质一般为导电碳，导电碳单个颗粒约70nm至110nm，纳米级颗粒间作用力较大，分散困难，所制成的浆料粒径一般都在微米级别。浆料颗粒度限制了涂膜厚度，一定程度上损耗了电池的压实密度和能量密度，增加了额外成本，降低了产品竞争力。
发明内容
针对现有技术存在的问题，本申请提供一种电化学装置，该电化学装置具有高的能量密度和好的循环性能。
在第一方面，本申请提供了一种电化学装置，该电化学装置包括正极，正极包括集流体、导电层和活性物质层，导电层设置在集流体和活性物质层之间，其中，导电层包括由导电剂一次颗粒形成的二次颗粒，二次颗粒的D50满足：0.1μm≤D50≤0.4μm。满足上述条件的电化学装置，导电层厚 度可以降至1μm以下，在保证活性物质层与集流体粘结力的同时，提升电化学装置的能量密度。
根据本申请的一些实施方式，二次颗粒的D90满足：0.2μm≤D90≤0.6μm。二次颗粒的D50和D90越大，导电层的厚度会越高。过高的导电层厚度会降低电化学装置的压实密度和能量密度，降低产品竞争力。
根据本申请的一些实施方式，导电层还包括第一助剂和第二助剂，其中第一助剂包括聚醚多元醇或纤维素醚中的至少一种，第二助剂包括聚羧酸盐、聚羧酸酯或聚羧酸中的至少一种。本申请中，第一助剂与第二助剂均会与导电剂进行键合，同时第一助剂与第二助剂之间也有分子间作用力。两个助剂协同作用与不同导电剂形成网络键合结构。该网络状键合结构在剪切力作用下，可将导电剂进行有效分散，使得最终导电层的导电剂二次颗粒的粒度维持在较小水平。
根据本申请的一些实施方式，电化学装置满足如下条件(a)至(c)中的至少一者：(a)第一助剂的重均分子量为40万至80万，(a)第二助剂的重均分子量为30万至60万，(c)第一助剂和第二助剂的分子量分布指数为1至2。如果助剂的分子量过低，会使得导电剂的分散效果不佳，二次颗粒的粒径过大，进而增加导电层的厚度。导电层的厚度过大，会降低电化学装置的能量密度、增加电化学装置的内阻，不利于电化学装置动力学性能的改善。如果助剂的分子量过高，助剂的粘度会过大，搅拌能耗大且搅拌效果差。
根据本申请的一些实施方式，聚醚多元醇包括三羟基聚醚、苯酚聚氧乙烯醚、聚乙二醇二甲醚或聚醚改性丙三醇中的至少一种。
根据本申请的一些实施方式，纤维素醚包括甲基纤维素、羟乙基甲基纤维素、羧甲基纤维素、羧甲基纤维素钠、乙基纤维素、苄基纤维素、羟乙基纤维素、羟丙基纤维素、氰乙基纤维素、苄基氰乙基纤维素、羧甲基羟乙基纤维素或苯基纤维素中的至少一种。
根据本申请的一些实施方式，聚羧酸盐包括结构单元A，聚羧酸包括结构单元B，聚羧酸酯包括结构单元C或D，
Figure PCTCN2021102397-appb-000001
其中，R 1至R 3相同或不同，各自独立选自氢或C 1-C 6烷基，R 4和R 5相同或不同，各自选自C 1-C 6烷基或羟基取代的C 1-C 6烷基，M选自碱金属。
根据本申请的一些实施方式，聚羧酸盐包括聚丙烯酸钠或聚甲基丙烯酸钠中的至少一种，聚羧酸包括聚丙烯酸或聚甲基丙烯酸中的至少一种，聚羧酸酯包括聚乙酸乙烯酯、聚甲基丙烯酸-2-羟乙酯或聚甲基丙烯酸异丁酯中的至少一种。
根据本申请的一些实施方式，电化学装置满足如下条件(d)至(e)中的至少一者：(d)导电剂包括导电炭黑、乙炔黑、碳纤维、碳纳米管或科琴黑中的至少一种；(e)导电剂的比表面积为50m 2/g至100m 2/g。 导电剂的比表面积过小，即导电剂颗粒大，导电性会有所损伤。导电剂的比表面积过大，导电剂之间的分子间作用力大，不利于导电剂的分散。
根据本申请的一些实施方式，以导电层总质量计，导电剂的质量含量为40％至75％，第一助剂的质量含量为1％至5％，第二助剂的质量含量为20％至55％。第一助剂和第二助剂的含量过低，导电剂的分散效果不好，导电层二次颗粒较大，导电层的厚度大，电化学装置的体积能量密度低。此外，含量过低时，助剂刚性大，会影响电化学装置的压实密度。第一助剂和第二助剂的含量过高，导电剂的含量会相应降低少，导电层的导电性会变差，电化学装置的内阻增加。
根据本申请的一些实施方式，第一助剂和第二助剂的质量比为1:4至1:50。相比于第一助剂，第二助剂的刚性低，粘结力大，因而较高的第二助剂含量，可进一步提高电化学装置的能量密度。
根据本申请的一些实施方式，导电层的制备包括以下步骤：
步骤A，将导电剂、第一助剂、第二助剂以及溶剂在第一固含量条件下混合得到导电层浆料，
步骤B，将步骤A得到的导电层浆料稀释至第二固含量后，涂布于集流体上，
其中，第一固含量为13％至30％，第二固含量大于或等于3％。
在导电层的制备中，混合时第一固含量过低，会导致剪切力不够，无法对导电剂进行有效分散；第一固含量过高，搅拌机负载电流过大，会对搅拌机有所损伤。
根据本申请的一些实施方式，导电层满足以下条件(f)至(h)中的 至少一者：(f)导电层的厚度T为0.3μm至1.0μm；(g)导电层的厚度T与二次颗粒D90满足：T≥1.5×D90；(h)导电层的颗粒度分布曲线为单峰分布。在一些实施例中，导电层的厚度T为0.3μm至1.0μm。导电层的厚度过高，会导致电化学装置的能量密度降低。
根据本申请的一些实施方式，正极满足以下条件(i)至(l)中的至少一者：(i)导电层覆盖度为60％至100％；(j)导电层涂覆重量为0.01mg/cm 2至0.04mg/cm 2；(k)正极的膜片电阻为0.05Ω至5Ω；(l)导电层与活性物质层之间的粘结力为10N/m至50N/m。
根据本申请的一些实施方式，正极中导电层覆盖度为60％至100％。导电层的覆盖度过小，会导致导电层中导电剂含量以及粘结力过低，进而引起电化学装置的电子阻抗增加，倍率性能下降，循环后期脱模跳水。
在第二方面，本申请提供了一种电子装置，其包括第一方面的电化学装置。
本申请通过在导电层中添加特定的助剂，利用助剂与导电剂之间的相互作用，提高了导电剂颗粒的分散性，使得导电层中的导电剂二次颗粒维持在纳米级别，导电层厚度小于1μm，有效地增加了本申请的电化学装置的压实密度和能量密度。
附图说明
图1为本申请的实施例4-5的电化学装置的正极中导电层的颗粒度分布曲线图。
图2为本申请的对比例4-1的电化学装置的正极中导电层的颗粒度分布曲线图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
如本文中所使用，术语“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
由术语“中的至少一种”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一种”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一种”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、 “在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
在第一方面，本申请提供了一种电化学装置，其包括正极，正极包括集流体、导电层和活性物质层，导电层设置在集流体和活性物质层之间，其中，导电层包括含导电剂的二次颗粒，二次颗粒的D50满足：0.1μm≤D50≤0.4μm。根据本申请的一些实施方式，二次颗粒的D90满足：0.2μm≤D90≤0.6μm。二次颗粒的D50和D90越大，导电层的厚度会越高。过高的导电层厚度会降低电化学装置的压实密度和能量密度，增加额外成本，降低产品竞争力。
根据本申请的一些实施方式，二次颗粒的D50为0.12μm、0.14μm、0.16μm、0.18μm、0.20μm、0.22μm、0.24μm、0.26μm、0.28μm、0.30μm、0.31μm、0.33μm、0.35μm、0.37μm、0.39μm或这些值中任意两者组成的范围。在一些实施例中，二次颗粒的D50为0.15μm至0.30μm。
在一些实施例中，二次颗粒的D90为0.22μm、0.25μm、0.27μm、0.30μm、0.33μm、0.35μm、0.38μm、0.40μm、0.42μm、0.45μm、0.47μm、0.50μm、0.53μm、0.55μm、0.57μm或这些值中任意两者组成的范围。在一些实施例中，二次颗粒的D90为0.25μm至0.40μm。
本申请中，术语“二次颗粒”指导电剂的一次颗粒团聚在一起形成的颗粒。
根据本申请的一些实施方式，导电层还包括第一助剂和第二助剂。在一些实施方式中，第一助剂包括聚醚多元醇或纤维素醚中的至少一种。在一些实施方式中，第二助剂包括聚羧酸盐、聚羧酸酯或聚羧酸中的至少一种。本申请在导电层中同时添加第一助剂和第二助剂，第一助剂与第二助剂均会与导电剂进行键合，同时第一助剂与第二助剂之间也有分子间作用力，例如第一助剂的羟基与第二助剂的羧基之间的作用力。两个助剂协同作用与不同导电剂形成网络键合结构。该网络状键合结构在剪切力作用下，可将导电剂进行有效分散，使得最终导电层的导电剂二次颗粒的粒度维持在较小水平，进而降低导电层的厚度，提升包括该导电层的电化学装置的压实密度和能量密度。
根据本申请的一些实施方式，第一助剂的重均分子量为40万至80万。在一些实施例中，第一助剂的重均分子量为41万、43万、45万、47万、49万、50万、52万、54万、55万、57万、59万、60万、62万、65万、67万、70万、72万、74万、76万、78万或这些值中任意两者组成的范围。
根据本申请的一些实施方式，第二助剂的重均分子量为30万至60万。在一些实施例中，第一助剂的重均分子量为31万、33万、35万、37万、39万、40万、42万、44万、45万、47万、49万、50万、52万、55万、57万、59万或这些值中任意两者组成的范围。导电层浆料中，助剂的分子链段会和不同的导电剂发生键合作用。键合在不同导电剂团聚体的分子链段在受到剪切力的拉扯作用后，会将导电剂团聚体分开，进而实现导电剂的有效分散。如果助剂的分子量过低，即分子链段短，分子链段与导电剂键合的数量少，会使得导电剂的分散效果不佳，二次颗粒的粒径过大，进而增加导电层的厚度。导电层的厚度过大，会降低电化学装置的 能量密度、增加电化学装置的内阻，不利于电化学装置动力学性能的改善。如果助剂的分子量过高，助剂的粘度会过大，搅拌能耗大且搅拌效果差。
根据本申请的一些实施方式，第一助剂包括聚醚多元醇，聚醚多元醇包括三羟基聚醚、苯酚聚氧乙烯醚、聚乙二醇二甲醚或聚醚改性丙三醇中的至少一种。
根据本申请的一些实施方式，第一助剂包括纤维素醚，纤维素醚包括甲基纤维素、羟乙基甲基纤维素、羧甲基纤维素、羧甲基纤维素钠、乙基纤维素、苄基纤维素、羟乙基纤维素、羟丙基甲基纤维素、氰乙基纤维素、苄基氰乙基纤维素、羧甲基羟乙基纤维素或苯基纤维素中的至少一种。
在本申请的一些实施方式中，第一助剂包括三羟基聚醚、苯酚聚氧乙烯醚、聚乙二醇二甲醚、聚醚改性丙三醇、羧甲基纤维素钠、羟丙基纤维素、乙基纤维素中的至少一种。第一助剂中的羟基一方面可以增加润湿性，另一方面可以与第二助剂中的羧基产生键合作用，有助于助剂与导电剂之间交联网络的形成。
根据本申请的一些实施方式，第二助剂包括聚羧酸盐，聚羧酸盐包括以下结构单元A：
Figure PCTCN2021102397-appb-000002
其中，R 1至R 3相同或不同，各自独立选自氢或C 1-C 6烷基，M选自碱金属。在一些实施例中，R 1至R 3相同或不同，各自独立选自氢、甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基或叔丁基，M为 钠或钾。在一些实施例中，聚羧酸盐包括聚丙烯酸钠或聚甲基丙烯酸钠中的至少一种。
根据本申请的一些实施方式，第二助剂包括聚羧酸，聚羧酸包括以下结构单元B：
Figure PCTCN2021102397-appb-000003
其中，R 1至R 3相同或不同，各自独立选自氢或C 1-C 6烷基。在一些实施例中，R 1至R 3相同或不同，各自独立选自氢、甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基或叔丁基。在一些实施例中，聚羧酸包括聚丙烯酸或聚甲基丙烯酸中的至少一种。
根据本申请的一些实施方式，第二助剂包括聚羧酸酯，聚羧酸酯包括以下结构单元C：
Figure PCTCN2021102397-appb-000004
其中，R 1至R 3相同或不同，各自独立选自氢或C 1-C 6烷基，R 4选自C 1-C 6烷基或羟基取代的C 1-C 6烷基。在一些实施例中，在一些实施例中，R 1至R 3相同或不同，各自独立选自氢、甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基或叔丁基。R 4选自甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、羟基取代的甲基、羟基取代的乙基或羟基取代的丙基。在一些实施例中，聚羧酸酯包括聚甲基丙烯酸-2-羟乙酯或聚甲基丙烯酸异丁酯中的至少一种。
根据本申请的一些实施方式，第二助剂包括聚羧酸酯，聚羧酸酯包括以下结构单元D：
Figure PCTCN2021102397-appb-000005
其中，R 1至R 3相同或不同，各自独立选自氢或C 1-C 6烷基，R 5选自C 1-C 6烷基或羟基取代的C 1-C 6烷基。在一些实施例中，在一些实施例中，R 1至R 3相同或不同，各自独立选自氢、甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基或叔丁基。R 5选自甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、叔丁基、羟基取代的甲基、羟基取代的乙基或羟基取代的丙基。在一些实施例中，聚羧酸酯包括聚乙酸乙烯酯。
根据本申请的一些实施方式，第二助剂包括聚丙烯酸钠、聚甲基丙烯酸钠、聚丙烯酸、聚甲基丙烯酸、聚乙酸乙烯酯、聚甲基丙烯酸-2-羟乙酯或聚甲基丙烯酸异丁酯中的至少一种。第二助剂中的羧基一方面能够与导电剂上的残留含氧官能团进行键合，另一方面可以与第一助剂中的羟基产生键合作用，有助于助剂与导电剂之间交联网络的形成。
根据本申请的一些实施方式，导电剂包括导电炭黑、乙炔黑、碳纤维、碳纳米管或科琴黑中的至少一种。
根据本申请的一些实施方式，导电剂的比表面积为50m 2/g至100m 2/g。在一些实施例中，导电剂的比表面积为55m 2/g、60m 2/g、65m 2/g、70m 2/g、75m 2/g、80m 2/g、85m 2/g、90m 2/g、95m 2/g或这些值中任意两者组成的范围。导电剂的比表面积过小，即导电剂颗粒大，导电性会有所损伤。导电剂的比表面积过大，导电剂之间的分子间作用力大，不利于导电剂的 分散。
根据本申请的一些实施方式，以导电层总质量计，导电剂的质量含量为40％至75％。在一些实施例中，导电剂的质量含量为42％、45％、47％、50％、53％、55％、57％、59％、62％、65％、67％、69％、71％、73％或这些值中任意两者组成的范围。导电剂的含量过低，导电层的导电性会变差，电化学装置的电子阻抗增加。导电剂含量过多，导电层粘接力不足，电化学装置的安全性能低。
根据本申请的一些实施方式，第一助剂的质量含量为1％至5％。在一些实施例中，第一助剂的质量含量为1.5％、2.0％、2.5％、3.0％、3.5％、4.5％、4.5％或这些值中任意两者组成的范围。
根据本申请的一些实施方式，第二助剂的质量含量为20％至55％。第二助剂的质量含量为25％、30％、35％、40％、45％、50％、或这些值中任意两者组成的范围。第一助剂和第二助剂的含量过低，导电剂的分散效果不好，导电层二次颗粒较大，导电层的厚度大，电化学装置的体积能量密度低。此外，含量过低时，助剂刚性大，会影响电化学装置的压实密度。第一助剂和第二助剂的含量过高，导电剂的含量会相应降低少，导电层的导电性会变差，电化学装置的内阻增加。
根据本申请的一些实施方式，第一助剂和第二助剂的质量比为1:4至1:50。在一些实施例中，第一助剂和第二助剂的质量比1:5、1:10、1:15、1:20、1:25、1:30、1:35、1:40、1:45或这些值中任意两者组成的范围。相比于第一助剂，第二助剂的刚性低，粘结力大，因而较高的第二助剂含量，可进一步提高电化学装置的能量密度。
根据本申请的一些实施方式，导电层的制备包括以下步骤：
步骤A，将导电剂、第一助剂、第二助剂以及溶剂在第一固含量条件下混合得到导电层浆料，
步骤B，将步骤A得到的导电层浆料稀释至第二固含量后，涂布于集流体上，
其中，第一固含量为13％至30％，第二固含量大于或等于3％。在一些实施例中，第一固含量为15％、17％、19％、20％、21％、23％、25％或这些值中任意两者组成的范围。在一些实施例中，第二固含量大于或等于3％，小于第一固含量，例如为3％至10％。在导电层的制备中，混合时第一固含量过低，会导致剪切力不够，无法对导电剂进行有效分散；第一固含量过高，搅拌机负载电流过大，会对搅拌机有所损伤。在一些实施例中，溶剂为水。
根据本申请的一些实施方式，导电层的厚度T为0.3μm至1.0μm，例如为0.4μm、0.5μm、0.6μm、0.7μm、0.8μm、0.9μm或这些值中任意两者组成的范围。导电层的厚度过高，可导致电化学装置的能量密度降低。
根据本申请的一些实施方式，导电层的厚度T与二次颗粒的D90满足：T≥1.5×D90。根据本申请的一些实施方式，导电层的颗粒度分布曲线为单峰分布。
根据本申请的一些实施方式，正极的导电层覆盖度为60％至100％，例如为65％、70％、75％、80％、85％、90％、95％或这些值中任意两者组成的范围。导电层的覆盖度过小，会导致导电层中导电剂含量以及粘接力过低，因而电化学装置的电子阻抗增加，倍率性能下降，循环后期脱模跳 水。本申请中导电层覆盖度代表的为导电层在集流体上的覆盖程度。
根据本申请的一些实施方式，正极的导电层涂覆重量为0.01mg/cm 2至0.04mg/cm 2，例如为0.015mg/cm 2、0.02mg/cm 2、0.025mg/cm 2、0.03mg/cm 2、0.035mg/cm 2或这些值中任意两者组成的范围。导电层涂覆重量过小会导致覆盖度小，致使电化学装置的电子阻抗增加，倍率性能下降。导电层涂覆重量过大，导电层厚度过高，电化学装置的能量密度低。
根据本申请的一些实施方式，正极的膜片电阻为0.05Ω至5Ω，例如0.5Ω、1.0Ω、1.5Ω、2.0Ω、2.5Ω、3.0Ω、3.5Ω、4.0Ω、4.5Ω或这些值中任意两者组成的范围。根据本申请的一些实施方式，正极的导电层与活性物质层之间的粘结力为10N/m至50N/m，例如15N/m、20N/m、25N/m、30N/m、35N/m、40N/m、45N/m或这些值中任意两者组成的范围。
根据本申请的一些实施方式，活性物质层包括正极活性物质。本申请的正极活性物质可以包括镍钴锰酸锂(811、622、523、111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。
根据本申请的一些实施方式，集流体可以采用金属箔片或复合集流体。例如，可以使用铝箔。复合集流体可以通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子基材上而形成。
本申请的电化学装置还包括负极。本申请的电化学装置中使用的负极的材料、构成和其制造方法可包括任何现有技术中公开的技术。
根据本申请的一些实施方式，负极包括负极集流体和负极活性材料层。
根据本申请的一些实施方式，负极活性材料层包括负极活性材料，负极活性材料可以包括可逆地嵌入/脱嵌锂离子的材料、锂金属、锂金属合金、能够掺杂/脱掺杂锂的材料或过渡金属氧化物，例如Si、SiOx(0<x<2)等材料。可逆地嵌入/脱嵌锂离子的材料可以是碳材料。碳材料可以是在锂离子可再充电电化学装置中通常使用的任何碳基负极活性物质。碳材料的示例包括结晶碳、非晶碳和它们的组合。结晶碳可以是无定形的或板形的、小片形的、球形的或纤维形的天然石墨或人造石墨。非晶碳可以是软碳、硬碳、中间相沥青碳化产物、烧制焦炭等。低结晶碳和高结晶碳均可以用作碳材料。作为低结晶碳材料，可通常包括软碳和硬碳。作为高结晶碳材料，可通常包括天然石墨、结晶石墨、热解碳、中间相沥青基碳纤维、中间相碳微珠、中间相沥青和高温锻烧炭(如石油或衍生自煤焦油沥青的焦炭)。
根据本申请的一些实施方式，负极活性材料层包含有粘合剂，且该粘合剂可以包括各种粘合剂聚合物，如二氟乙烯一六氟丙烯共聚物(PVDF-co-HFP)，聚偏二氟乙烯、聚丙烯睛、聚甲基丙烯酸甲醋、聚乙烯醇、羧甲基纤维素、羟丙基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等，但不限于此等。
根据本申请的一些实施方式，负极活性材料层还包括导电材料来改善电极导电率。可以使用任何导电的材料作为该导电材料，只要它不引起化学变化即可。导电材料的示例包括：碳基材料，例如天然石墨、人造石墨、炭黑、乙炔黑、科琴黑、碳纤维等；金属基材料，例如包括铜、镍、铝、银等的金属粉或金属纤维；导电聚合物，例如聚亚苯基衍生物等；或它们的 混合物。集流体可以为铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、包覆有导电金属的聚合物基板或它们的组合。
本申请的电化学装置还包括电解液，电解液包括锂盐和非水溶剂。
在本申请一些实施方案中，锂盐选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB和二氟硼酸锂中的一种或多种。举例来说，锂盐可以选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。
上述链状碳酸酯化合物的实例为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)及其组合。氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及其组合。
上述羧酸酯化合物的实例为甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊 内酯、甲瓦龙酸内酯、己内酯及其组合。
上述醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及其组合。
上述其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及其组合。
本申请的电化学装置还包括隔离膜。本申请对隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的至少一种。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的至少一种。
聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
在第二方面，本申请提供了一种电子装置，其包括第一方面的电化学装置。
本申请的电子设备或装置没有特别限定。在一些实施例中，本申请的电子设备包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
测试方法
1、导电层颗粒度测试：将电芯拆解得到电极极片，洗涤、晾干后用NMP洗除或用胶带粘除活性层，然后将导电层用去离子水溶解，得到待测浆料。用马尔文激光粒度仪对待测浆料进行测试。具体地，选择Hydro SM Starter  Sample(SOP)模式，以去离子水为溶剂，转速设置为2800±400rpm，折射率设定为1.52。测量纯溶液(去离子水)，扣除背景后，用滴管取待测浆料，将其缓慢滴加到目标滴加量(会变绿)，然后点击测试即可。
2、导电层厚度测试：将电芯拆解得到电极极片，洗涤、晾干后用NMP洗除或用胶带粘除活性层，然后用万分尺测试集流体和底涂导电层的总厚度，采用单点测试，取15个点的平均值。集流体和底涂导电层的总厚度减去集流体厚度即得导电层厚度。采用下式计算导电层的厚度T＝(T1+T2+T3+……+T15)/15-T(集流体)。
3、导电层覆盖度测试：将电芯拆解得到电极极片，洗涤、晾干后用NMP洗除或用胶带粘除活性层，然后用CCD检测仪进行测试。具体地，首先进行对焦，扭动微调螺母调清晰之后，拍摄光学图像，然后选择自动测量面积，具体参数设置为暗区、阈值60，明度-20，倍数×50。测试结束后即可得到覆盖度报告。
4、导电层重量计算：电芯拆解得到电极极片，洗涤、晾干后用NMP洗除或用胶带粘除活性层，然后用专用模具将极片裁成面积S为86×85.2mm 2的小方片，称重，计为M 集流体+导电层，单位为mg。然后再将导电层擦去，称集流体重量，计为m 集流体，单位为mg。导电层重量＝(M 集流体+导电层-m 集流体)×100/(86×85.2)
5、膜片电阻测量：将电芯拆解得到电极极片，用DMC溶液清洗掉电解液后，使用已擦拭清洁的膜片电阻仪进行测试。具体地，将极片展平，在距离边缘及未涂膜区25mm的中间位置测量涂膜区域的电阻值，测15次取平均值。测试条件为单点模式、压强0.4T，测试时间5s/点。
6、粘结力测试：将电芯拆解得到电极极片，用DMC溶液清洗掉电解液后进行制样。首先将极片裁剪成宽30mm、长100mm至160mm的极片试样，将专用双面胶贴于钢板上，胶带宽20mm、长90mm至150mm，将裁剪的极片试样贴在双面胶上，测试面朝下。然后将宽度与极片试样等宽，长度大于试样长度80mm至200mm的纸带插入极片下方，并且用皱纹胶固定。将制好的样品用高铁拉力机测试，固定钢板，拉力机夹住纸带，以50mm/min速度拉动纸带，记录力与位移参数，即可得到粘结力数值，每组测5个取平均值。
7、锂离子电池的电芯内阻(IMP)的测试：取被测电芯，分别连接电芯的两极耳，通过检测经过电芯的电流I以及施加的电压V，得到电芯内阻R＝V/I。
8、锂离子电池的体积能量密度(ED)的测试：取被测电芯，在常温条件下，以1.5C的电流充电至4.48V，再以4.48V的恒压充电至0.05C；静置5min，再以0.025C的电流恒流放电至3.0V，静止5min，记此时的容量为D，单位是mAh，然后将电芯以1.0C充电至4.0V，测量此时电芯的长宽厚，计算得到电芯的体积V，单位是mm 3，体积能量密度计算：ED＝(D×3.89×1000)/V，单位为Wh/L。
实施例及对比例
1、正极极片的制备：将导电剂、第一助剂、第二助剂以及溶剂水加入到双行星搅拌器中，在第一固含量下进行搅拌分散得到导电层浆料。用水将导电层浆料稀释至第二固含量后，通过凹版机将其涂布在集流体(铝箔) 上，得到涂覆有导电层的集流体。然后在带有导电层的集流体上继续涂覆活性材料浆料(活性材料浆料由钴酸锂、乙炔黑和聚偏二氟乙烯按重量比96∶2∶2在适量的N-甲基吡咯烷酮溶剂中充分搅拌混合得到)，形成活性物质层，烘干、冷压，得到正极极片。其中导电剂为导电碳。第一助剂为羧甲基纤维素钠，第二助剂为聚丙烯酸钠。各实施例与对比例中具体的导电剂、第一助剂及第二助剂的组成详见下表1至表4。
2、负极极片的制备：将石墨、聚甲基丙烯酸和丁苯橡胶按照98:1:1的重量比在适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料。将制得的负极浆料涂布在上述铜箔集流体上，烘干，冷压，得到负极极片。
3、锂离子电池的制备：将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极和负极中间以起到隔离的作用。卷绕得到裸电芯。将裸电芯置于外包装中，经真空干燥后，注入电解液，封装。经过化成、脱气、切边等工艺流程得到锂离子电池。其中以7μm的PE作为隔离膜。电解液包括由碳酸丙烯酯(PC)，碳酸乙烯酯(EC)，碳酸二乙酯(DEC)(重量比约1:1:1)混合而成的溶剂和LiPF 6，LiPF 6的浓度为约1.15mol/L。
表1中示出了第一助剂(羧甲基纤维素钠)的重均分子量、第二助剂(聚丙烯酸钠)的重均分子量、导电剂(导电碳)的比表面积对所制备得到的正极极片以及包含正极极片的锂离子电池的性能影响。
其中，各实施例和对比例中，第一固含量为15％，第二固含量大于等于3％。第一助剂的分子量分布指数为1至2，第二助剂的分子量分布指数为1至2。
以导电层的质量计，实施例1-1至1-6、对比例1-1至对比例1-3的第 一助剂的质量含量为2.5％，第二助剂的质量含量为47.5％，导电剂的质量含量为50％。对比例1-4的第一助剂的质量含量为50％。对比例1-5的第二助剂的质量含量为50％。
表1
Figure PCTCN2021102397-appb-000006
根据实施例1-1、对比例1-4和对比例1-5的数据可以看出，导电层中同时添加第一助剂和第二助剂时，导电层中二次颗粒的粒径小，导电层的厚度低，锂离子电池的体积能量密度大。这主要是因为第一助剂与第二助剂均会与导电剂团聚体进行键合，同时第一助剂与第二助剂之间也有分子间作用力。两个助剂协同作用与不同导电剂团聚体形成网络键合结构。该网络状键合结构在剪切力作用下，可将导电剂进行有效分散，使得最终导电层的导电剂二次颗粒的粒度维持在较小水平。
根据实施例1-1、实施例1-4和对比例1-2的数据可以看出，第一助剂 的分子量在40万至80万的范围内时，锂离子电池具有较高的体积能量密度。根据实施例1-1、实施例1-5和对比例1-3的数据可以看出，第二助剂的分子量在30万至60万的范围内时，锂离子电池具有较高的体积能量密度。导电层浆料中，助剂的分子链段会和不同的导电剂团聚体发生键合作用。键合在不同导电剂团聚体的分子链段在受到剪切力的拉扯作用后，会将导电剂团聚体分开，进而实现导电剂的有效分散。如果助剂的分子量过低，即分子链段短，分子链段与团聚体键合的数量少，会使得导电剂的分散效果不佳，二次颗粒的粒径过大，进而增加导电层的厚度。导电层的厚度过大，会降低电池的能量密度、增加电池的内阻，不利于电池动力学性能的改善。如果助剂的分子量过高，助剂的粘度会过大，搅拌能耗大且搅拌效果差。
根据实施例1-1、实施例1-7和对比例1-1的数据可以看出，导电剂的比表面积在50m 2/g至100m 2/g的范围内时，锂离子电池的能量密度高，内阻低。导电剂的比表面积过小，即导电剂颗粒大，导电性会有所损伤。导电剂的比表面积过大，导电剂之间的分子间作用力大，不利于导电剂的分散。
表2中示出了第一助剂(羧甲基纤维素钠)、第二助剂(聚丙烯酸钠)以及的导电剂(导电碳)的质量含量对所制备得到的正极极片以及包含正极极片的锂离子电池的性能影响。
其中，各实施例中，第一助剂的重均分子量为65万，第二助剂的重均分子量为45万，导电剂的比表面积为65m 2/g。第一固含量为15％，第二固含量大于或等于3％。第一助剂的分子量分布指数为1.32，第二助剂的分子量分布指数为1.57。
表2
Figure PCTCN2021102397-appb-000007
表3中示出了导电层浆料的第一固含量对所制备得到的正极极片以及包含正极极片的锂离子电池的性能影响。
其中，各实施例中，第二固含量为7％，第一助剂的重均分子量为65万，第二助剂的重均分子量为45万，导电剂的比表面积为65m 2/g。第一助剂的分子量分布指数为1.47，第二助剂的分子量分布指数为1.52。
以导电层的质量计，第一助剂的质量含量为2.5％，第二助剂的质量含量为47.5％，导电剂的质量含量为50％。
表3
Figure PCTCN2021102397-appb-000008
根据表3中的数据可以看出，第一固含量在13％至25％范围内，电池的性能较优。导电剂以及助剂搅拌混合时，第一固含量的过低，剪切力不够，无法对导电剂进行有效分散。固含量过高，搅拌机负载电流过大，会对搅拌机有所损伤。
表4中示出了导电层二次颗粒的D50、D90，以及导电层的厚度对所制备得到的正极极片以及包含正极极片的锂离子电池的性能影响。其中，通过同时控制导电层的各组分的含量以及第一固含量、搅拌时间等，来控制导电层二次颗粒的D50、D90以及导电层的厚度。
表4的实施例中，第一助剂的分子量为65万，第二助剂的分子量为45万。第一助剂的分子量分布指数为1.32，第二助剂的分子量分布指数为1.57。
以导电层的质量计，第一助剂的质量含量在1％至5％范围内，第二助剂的质量含量在20％至55％范围内，导电剂的质量含量在40％至75％范围内。第一固含量大于或等于13％，第二固含量大于或等于3％。
表4
Figure PCTCN2021102397-appb-000009
根据表4中的实施例数据可以看出，导电层二次颗粒的D50以及D90越大，导电层的厚度一般就越厚。导电层的厚度增加，膜片电阻和膜片粘接力会增大，但是电池的能量密度会有损耗。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (13)

  1. 一种电化学装置，包括正极，所述正极包括集流体、导电层和活性物质层，所述导电层设置在所述集流体和所述活性物质层之间，其中，所述导电层包括由导电剂一次颗粒形成的二次颗粒，所述二次颗粒的D50满足：0.1μm≤D50≤0.4μm。
  2. 根据权利要求1所述的电化学装置，其中，所述二次颗粒的D90满足：0.2μm≤D90≤0.6μm。
  3. 根据权利要求1所述的电化学装置，其中，所述导电层还包括第一助剂和第二助剂，所述第一助剂包括聚醚多元醇或纤维素醚中的至少一种，所述第二助剂包括聚羧酸盐、聚羧酸酯或聚羧酸中的至少一种。
  4. 根据权利要求3所述的电化学装置，其中，所述电化学装置满足如下条件(a)至(c)中的至少一者：
    (a)所述第一助剂的重均分子量为40万至80万，
    (b)所述第二助剂的重均分子量为30万至60万，
    (c)所述第一助剂和所述第二助剂的分子量分布指数为1至2。
  5. 根据权利要求3所述的电化学装置，其中，所述聚醚多元醇包括三羟基聚醚、苯酚聚氧乙烯醚、聚乙二醇二甲醚或聚醚改性丙三醇中的至少一种；
    所述纤维素醚包括甲基纤维素、羟乙基甲基纤维素、羧甲基纤维素、羧甲基纤维素钠、乙基纤维素、苄基纤维素、羟乙基纤维素、羟丙基纤维素、氰乙基纤维素、苄基氰乙基纤维素、羧甲基羟乙基纤维素或苯基纤维素中的至少一种；
    所述聚羧酸盐包括结构单元A，所述聚羧酸包括结构单元B，所述聚羧酸酯包括结构单元C或D，
    Figure PCTCN2021102397-appb-100001
    其中，R 1至R 3相同或不同，各自独立选自氢或C 1-C 6烷基，R 4和R 5相同或不同，各自选自C 1-C 6烷基或羟基取代的C 1-C 6烷基，M选自碱金属。
  6. 根据权利要求3所述的电化学装置，其中，所述聚羧酸盐包括聚丙烯酸钠或聚甲基丙烯酸钠中的至少一种，所述聚羧酸包括聚丙烯酸或聚甲基丙烯酸的中至少一种，所述聚羧酸酯包括聚乙酸乙烯酯、聚甲基丙烯酸-2-羟乙酯或聚甲基丙烯酸异丁酯中的至少一种。
  7. 根据权利要求3所述的电化学装置，其中，所述电化学装置满足如下条件(d)至(e)中的至少一者：
    (d)所述导电剂包括导电炭黑、乙炔黑、碳纤维、碳纳米管或科琴黑中的至少一种；
    (e)所述导电剂的比表面积为50m 2/g至100m 2/g。
  8. 根据权利要求3所述的电化学装置，其中，以所述导电层总质量 计，所述导电剂的质量含量为40％至75％，所述第一助剂的质量含量为1％至5％，所述第二助剂的质量含量为20％至55％。
  9. 根据权利要求3所述的电化学装置，其中，所述第一助剂和所述第二助剂的质量比为1:4至1:50。
  10. 根据权利要求3所述的电化学装置，其中，所述导电层的制备包括以下步骤：
    步骤A，将导电剂、第一助剂、第二助剂以及溶剂在第一固含量条件下混合得到导电层浆料，
    步骤B，将步骤A得到的导电层浆料稀释至第二固含量后，涂布于集流体上，
    其中，第一固含量为13％至30％，第二固含量大于或等于3％。
  11. 根据权利要求1所述的电化学装置，其中，所述导电层满足以下条件(f)至(h)中的至少一者：
    (f)所述导电层的厚度T为0.3μm至1.0μm；
    (g)所述导电层的厚度T与所述二次颗粒D90满足：T≥1.5×D90；
    (h)所述导电层的颗粒度分布曲线为单峰分布。
  12. 根据权利要求1所述的电化学装置，其中，所述正极满足以下条件(i)至(l)中的至少一者：
    (i)所述导电层覆盖度为60％至100％；
    (j)所述导电层涂覆重量为0.01mg/cm 2至0.04mg/cm 2；
    (k)所述正极的膜片电阻为0.05Ω至5Ω；
    (l)所述导电层与所述活性物质层之间的粘结力为10N/m至50N/m。
  13. 一种电子装置，其包括权利要求1至12中任一项所述的电化学装置。
PCT/CN2021/102397 2021-06-25 2021-06-25 电化学装置及电子装置 WO2022267012A1 (zh)

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