WO2022078340A1 - 极片及包含其的电化学装置和电子设备 - Google Patents

极片及包含其的电化学装置和电子设备 Download PDF

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Publication number
WO2022078340A1
WO2022078340A1 PCT/CN2021/123330 CN2021123330W WO2022078340A1 WO 2022078340 A1 WO2022078340 A1 WO 2022078340A1 CN 2021123330 W CN2021123330 W CN 2021123330W WO 2022078340 A1 WO2022078340 A1 WO 2022078340A1
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Prior art keywords
pole piece
active material
lithium
current collector
present application
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PCT/CN2021/123330
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English (en)
French (fr)
Inventor
江兵
王可飞
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宁德新能源科技有限公司
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Priority to EP21879384.2A priority Critical patent/EP4216299A4/en
Priority to JP2023522540A priority patent/JP2023546853A/ja
Publication of WO2022078340A1 publication Critical patent/WO2022078340A1/zh
Priority to US18/300,713 priority patent/US20230275323A1/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
    • H01M4/13—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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H01G11/28—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features arranged or disposed on a current collector; Layers or phases between electrodes and current collectors, e.g. adhesives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
    • H—ELECTRICITY
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    • 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
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    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
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    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • H—ELECTRICITY
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    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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    • 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
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
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    • H01M4/64—Carriers or collectors
    • H—ELECTRICITY
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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 energy storage, and in particular, to a pole piece and an electrochemical device and electronic device including the same, in particular to a lithium ion battery.
  • Lithium-ion batteries with high energy density and excellent life and cycle characteristics at the same time are one of the research directions.
  • the intercalation and deintercalation of lithium ions occur repeatedly in the positive and negative electrodes of the lithium ion battery, and the volume of the active material expands and contracts correspondingly with the intercalation and deintercalation of lithium ions.
  • the negative electrode active material (such as graphite, silicon-based material) has severe volume expansion and contraction.
  • the adhesive force of the active material part close to the surface of the negative electrode current collector is low, and the volume of the active material expands and contracts during the cycle. , it is easy to cause the separation of the negative electrode active material layer close to the surface of the current collector and the surface of the current collector, resulting in the peeling of the pole piece, which in turn leads to increased internal resistance and poor cyclability.
  • the purpose of the present application is to provide a pole piece and an electrochemical device and electronic equipment including the same, the pole piece is a pole piece with high adhesive force, which can at least to some extent solve at least one kind of existence in the related field.
  • the problem is to provide a pole piece and an electrochemical device and electronic equipment including the same, the pole piece is a pole piece with high adhesive force, which can at least to some extent solve at least one kind of existence in the related field.
  • a pole piece comprising: a current collector; and a diaphragm, the diaphragm including a primer layer disposed on the surface of the current collector and an active electrode disposed on the surface of the primer layer A substance layer, the primer layer includes a first binder and a first conductive agent; wherein, the adhesion between the membrane sheet and the current collector is ⁇ 20 N/m.
  • the adhesive force between the membrane sheet and the current collector is ⁇ 80 N/m; more preferably, according to some embodiments of the present application, the membrane sheet and the collector
  • the adhesive force of the fluid is ⁇ 100 N/m; more preferably, according to some embodiments of the present application, the adhesive force of the membrane sheet and the current collector is ⁇ 500 N/m.
  • the thickness of the undercoat layer is 100 nm to 2 ⁇ m; preferably, according to some embodiments of the present application, the thickness of the undercoat layer is 100 nm to 1000 nm; more preferably, according to the present application In some embodiments, the thickness of the primer layer is 100 nm to 800 nm.
  • the relationship between the average particle diameter of the first conductive agent or the average tube diameter D and the thickness H of the undercoat layer satisfies: the ratio D/H of D to H is 0.25-1.5; preferably is 0.5 to 1.25.
  • the compacted density of the membrane sheet is 1.30 g/cm 3 to 1.80 g/cm 3 .
  • the porosity of the membrane sheet is 20% to 50%.
  • the porosity of the membrane sheet is 25% to 40%.
  • the diaphragm resistance of the diaphragm is 3 m ⁇ to 50 m ⁇ .
  • the diaphragm resistance of the diaphragm is 3 m ⁇ to 30 m ⁇ .
  • the mass content of the first binder in the primer layer is 20% to 95%.
  • the mass content of the first conductive agent in the undercoat layer is 5% to 80%.
  • the first binder includes at least one of a carbon-carbon double bond, a carboxyl group, a carbonyl group, a carbon-nitrogen single bond, a hydroxyl group, an ester group, an acyl group or an aryl functional group.
  • the first binder includes at least one of a carboxyl group, a carbonyl group, a carbon-nitrogen single bond, a hydroxyl group or an ester group functional group.
  • the first binder includes at least one of SBR (styrene butadiene rubber), PAA (polyacrylic acid), PVP (polyvinylpyrrolidone) or PAM (polyacrylamide).
  • SBR styrene butadiene rubber
  • PAA polyacrylic acid
  • PVP polyvinylpyrrolidone
  • PAM polyacrylamide
  • the first conductive agent includes at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, or multi-walled carbon nanotubes.
  • the active material layer includes an active material and a second binder.
  • the active material includes at least one of a graphite-based material or a silicon-based material.
  • the silicon-based material includes at least one of silicon, silicon oxide, silicon carbon composite, or silicon alloy.
  • the silicon-based material includes at least one of pure silicon, SiO x (0 ⁇ x ⁇ 2) or silicon-carbon composite.
  • the active material layer further includes a second conductive agent.
  • the active material layer includes an active material content of 80 to 99% by mass, a second binder of 0.8 to 20%, and a second conductive agent of 0 to 5%.
  • the second binder includes PAA (polyacrylic acid), PVP (polyvinylpyrrolidone), PAM (polyacrylamide), SBR (styrene butadiene rubber) or CMC (carboxymethyl cellulose) ) at least one of them.
  • PAA polyacrylic acid
  • PVP polyvinylpyrrolidone
  • PAM polyacrylamide
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • the second conductive agent includes at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, or multi-walled carbon nanotubes.
  • an electrochemical device comprising: a positive pole piece; a negative pole piece; a separator disposed between the positive pole piece and the negative pole piece; wherein the negative pole piece
  • the pieces are pole pieces as described above.
  • the S ⁇ O double bond-containing compound includes at least one of the compounds represented by Formula 1,
  • W is selected from
  • L is selected from single bond or methylene
  • n is an integer from 1 to 4.
  • n is an integer from 0 to 2;
  • p is an integer from 0 to 6.
  • the compound represented by the formula 1 is selected from at least one of the following compounds:
  • n is an integer from 1 to 4.
  • n is an integer from 0 to 2;
  • p is an integer from 0 to 6.
  • an electronic device comprising the aforementioned electrochemical device.
  • the pole piece and the electrochemical device and electronic equipment including the pole piece provided by the present application by providing a primer layer on the membrane of the pole piece, the adhesion between the membrane and the current collector is improved, and the circulation of the pole piece is avoided. During the process, the film is removed due to expansion and contraction, and the cycle and shape stability of the electrochemical device are greatly improved, ensuring that the electrochemical device has excellent rate performance. Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part through the implementation of the embodiments of the present application in the subsequent description.
  • FIG. 1 is a schematic structural diagram of a pole piece provided by an exemplary embodiment of the present application.
  • FIG. 2 is a schematic cross-sectional view of a pole piece provided by an exemplary embodiment of the present application
  • FIG. 3 is a schematic diagram of the shape stability of the pole pieces provided in Examples 1-9 of the present application.
  • FIG. 4 is a schematic diagram of the shape stability of the pole piece provided in Comparative Examples 1-2 of the present application.
  • a list of items joined by the terms "at least one of,” “at least one of,” “at least one of,” or other similar terms may mean the listed items any combination of .
  • the phrase "at least one of A, B” means A only; B only; or A and B.
  • the phrase "at least one of A, B, C” means A only; or B only; C only; 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.
  • Electrodes (positive or negative electrodes) of electrochemical devices are typically prepared by mixing active materials, conductive agents, thickeners, binders, and solvents, and then coating the mixed slurry on the collector.
  • the theoretical capacity of an electrochemical device may vary with the kind of active material. Electrochemical devices typically experience a decrease in charge/discharge capacity as cycling progresses. This is because the electrode interface will change during the charging and/or discharging process of the electrochemical device, resulting in the inability of the electrode active material to perform its function.
  • the pole piece with specific adhesive force by using the pole piece with specific adhesive force, the stability of the electrode piece during the cycle process of the electrochemical device is ensured, and the film release due to the expansion and contraction of the negative electrode pole piece during the cycle process is avoided, thereby improving the cycle time of the electrochemical device. performance.
  • the pole piece of the specific adhesive force of the present application can be realized by controlling the structure of the pole piece and the functional group type of the binder.
  • an electrochemical device that includes a negative electrode, a positive electrode, and an electrolyte as described below.
  • the negative electrode sheet in some embodiments of the present application includes: a negative electrode current collector 10 and a membrane sheet 20 .
  • the adhesive force between the membrane 20 and the negative electrode current collector 10 is ⁇ 20 N/m.
  • the membrane 20 includes an undercoat layer 201 disposed on the surface of the negative electrode current collector 10 and an active material layer 202 disposed on the surface of the undercoat layer 201 .
  • the composition of the undercoat layer 201 includes a first binder and a first conductive agent.
  • the negative pole piece is provided with a primer layer including a first binder and a first conductive agent in the membrane piece, which improves the adhesion between the membrane piece and the negative electrode current collector.
  • a primer layer including a first binder and a first conductive agent in the membrane piece, which improves the adhesion between the membrane piece and the negative electrode current collector.
  • the circulation and shape of the negative pole piece Stability has also been greatly improved.
  • the existence of the primer layer can improve the surface defects of the negative electrode current collector, enhance the riveting effect between the active material layer and the pole piece, and increase the bond between the primer layer and the negative electrode current collector. Therefore, the bonding force between the whole diaphragm and the current collector is improved, and the risk of the diaphragm falling off is reduced.
  • the existence of the primer layer can play a good buffering role.
  • the primer layer avoids the expansion.
  • the active material directly exerts a force on the surface of the current collector.
  • the active material can only expand to the outer surface of the diaphragm as a whole, and when the lithium is released When the ions shrink, each part of the active material tends to shrink synchronously/or the inner side with better electronic conductivity may shrink faster, which will cause the active material that was in close contact with the surface of the current collector to separate from the current collector, resulting in membrane It falls off, which increases the internal resistance and deteriorates the cycle performance.
  • the pole pieces of the embodiments of the present application can significantly improve the adhesive force between the diaphragm and the current collector.
  • the use of a pole piece with a specific adhesive force ensures the pole piece stability of the electrochemical device during the cycle process, avoids the release of the pole piece due to expansion and contraction during the cycle process, and improves the cycle performance of the electrochemical device.
  • the adhesive force between the diaphragm and the current collector is ⁇ 80N/m; more preferably, in some embodiments, the adhesive force between the diaphragm and the current collector is ⁇ 100N/m; more preferably, In some embodiments, the adhesive force between the diaphragm and the current collector is ⁇ 500N/m, for example, the adhesive force between the diaphragm and the current collector is 20N/m, 60N/m, 80N/m, 100N/m, 120N /m, 130N/m, 160N/m, 180N/m, 220N/m, 300N/m, 400N/m, 500N/m, 540N/m, 600N/m, 630N/m, etc.
  • the thickness of the primer layer is 100 nm (nanometer) to 2 ⁇ m (micrometer); preferably, in some embodiments, the thickness of the primer layer is 100 nm to 1000 nm; more preferably, in some embodiments , the thickness of the primer layer is 100nm to 800nm.
  • the thickness of the primer layer is not easy to be too large, and the thickness of the primer layer is preferably in the nanometer level, which helps to obtain the required adhesion between the membrane and the current collector, and helps to make it have more excellent membrane resistance and circulation. stability.
  • the thickness of the primer layer is, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 800 nm, 900 nm, 950 nm, 999 nm, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, and any two of these point values.
  • the relationship between the average particle diameter of the first conductive agent or the average tube diameter D and the thickness H of the undercoat layer satisfies: D/H is 0.25-1.5; preferably 0.5-1.25.
  • the shape of the first conductive agent can be granular or tubular.
  • D /H the relationship between the average particle size D of the first conductive agent and the thickness H of the undercoat layer satisfies: D /H is 0.5-1.25; when the form of the first conductive agent is tubular, the relationship between the average tube diameter D of the first conductive agent and the thickness H of the primer layer satisfies: D/H is 0.5-1.25.
  • the average particle size or pipe diameter D/primer thickness H is, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.25 and any two of these point values The constituted range and any value within the range.
  • the pole piece can be made to have more excellent sheet resistance and cycle stability.
  • the average particle diameter of the particles or the average diameter of the tube D/the thickness H of the primer layer is less than 0.5, there will be too many small particles of the first conductive agent in the primer layer, and too many small particles of the first conductive agent will exist in the primer layer.
  • a stack of conductive agents will have excessive interface resistance, which will increase the resistance of the membrane and reduce the cycle stability.
  • the average particle diameter or tube average diameter D/the thickness H of the primer layer is greater than 1.25, it is easy to cause uneven distribution of the first conductive agent in the primer layer, which in turn leads to an increase in the resistance of the diaphragm and affects the cycle performance.
  • the diaphragm has a diaphragm resistance of 3 m ⁇ to 50 m ⁇ .
  • the diaphragm resistance of the diaphragm is 3m ⁇ to 30m ⁇ .
  • the diaphragm resistance of the diaphragm is, for example, 3m ⁇ , 5m ⁇ , 6m ⁇ , 9m ⁇ , 10m ⁇ , 15m ⁇ , 20m ⁇ , 22m ⁇ , 26m ⁇ , 30m ⁇ , 50m ⁇ and the range formed by any two of these point values. Any value in the range.
  • the compacted density of the membrane sheet is 1.30 g/cm 3 to 1.80 g/cm 3 .
  • the compacted density of the membrane sheet is, for example, 1.30 g/cm 3 , 1.40 g/cm 3 , 1.50 g/cm 3 , 1.55 g/cm 3 , 1.60 g/cm 3 , 1.70 g/cm 3 , 1.75 g/cm 3 , 1.80 g/cm 3 and any two of these point values, and any value in the range.
  • the primer layer can play a role of riveting and buffering, and then Helps to obtain more excellent cycle stability and rate performance.
  • the membrane sheet has a porosity of 20% to 50%.
  • the porosity of the membrane is 25% to 40%.
  • the porosity of the membrane is, for example, 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 35%, 37%, 40%, 45%, 50% and any two of these point values constitute a range and any value within the range.
  • the primer layer can play the role of riveting and buffering, and can be The electrolyte is fully contacted, which in turn helps to obtain more excellent cycle stability and rate performance.
  • the mass content of the first binder in the primer layer is 20% to 95%.
  • the mass content of the first binder in the primer layer is, for example, 20%, 30%, 40%, 50%, 60%, 65%, 70%, 72%, 80%, 83% %, 85%, 90%, 91%, 95%, and any two of these point values constitute a range and any value within the range.
  • the mass content of the first conductive agent in the undercoat layer is 5% to 80%.
  • the mass content of the first conductive agent in the primer layer is, for example, 5%, 10%, 20%, 30%, 40%, 50%, 55%, 60%, 70%, 80% and any two of these point values constitute a range and any value within the range.
  • the first binder includes at least one of a carbon-carbon double bond, a carboxyl group, a carbonyl group, a carbon-nitrogen single bond, a hydroxyl group, an ester group, an acyl group, or an aryl functional group.
  • the first binder includes at least one of a carboxyl group, a carbonyl group, a carbon-nitrogen single bond, a hydroxyl group, an ester group, and an acyl functional group.
  • a first binder containing one or more of the functional groups of carboxyl group, carbonyl group, carbon-nitrogen single bond, hydroxyl group, ester group, and acyl group can significantly improve the adhesion between the membrane and the current collector. This is due to the above
  • the functional group has strong polarity and has a strong attraction with the electron-rich metal current collector, which makes the shape stability of the membrane more stable. Even for high-expansion silicon-based active materials, it can also maintain excellent shape stability.
  • the first binder includes at least one of SBR (styrene butadiene rubber), PAA (polyacrylic acid), PVP (polyvinylpyrrolidone), or PAM (polyacrylamide).
  • SBR styrene butadiene rubber
  • PAA polyacrylic acid
  • PVP polyvinylpyrrolidone
  • PAM polyacrylamide
  • the first conductive agent includes, but is not limited to, at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, or multi-walled carbon nanotubes.
  • the composition of the active material layer includes an active material and a second binder.
  • the active material includes at least one of a graphite-based material or a silicon-based material.
  • the silicon-based material includes at least one of silicon, silicon oxide, silicon carbon composite, or silicon alloy.
  • the silicon-based material includes at least one of pure silicon, SiO x (0 ⁇ x ⁇ 2) or silicon-carbon composite, wherein, preferably, SiO x (1 ⁇ x ⁇ 2) .
  • the negative electrode active materials may be used alone or in combination.
  • the active material layer further includes a second conductive agent.
  • the first conductive agent may be contained in the primer layer, and the second conductive agent may or may not be contained in the active material layer.
  • the first binder in the primer layer and the second binder in the active material layer may use the same type of binder, or may use different types of binders.
  • the first conductive agent in the undercoat layer and the second conductive agent in the active material layer may use the same type of conductive agent, or may use different types of conductive agents.
  • the second binder in the active material layer can improve the bonding of the negative electrode active material particles to each other and the bonding of the negative electrode active material to the undercoat layer.
  • the types of the binder in the examples of the present application and the negative electrode active material layer are not particularly limited, as long as it is a material that is stable to the electrolyte or the solvent used in the production of the electrode.
  • the second binder includes a resin binder.
  • resin binders include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like.
  • the second binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) ) or its salts, polyvinyl alcohol, etc.
  • the second binder includes PAA (polyacrylic acid), PVP (polyvinylpyrrolidone), PAM (polyacrylamide), SBR (styrene butadiene rubber) or CMC (carboxymethyl cellulose) at least one of them.
  • the molecular weight of the first binder is < 1,500,000.
  • the molecular weight of the second binder is ⁇ 1,500,000.
  • the second conductive agent includes, but is not limited to, at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, or multi-walled carbon nanotubes.
  • the active material layer includes 80% to 99% by mass of the active material, 0.8% to 20% of the second binder, and 0 to 5% of the second conductive agent.
  • the mass content of the active material is, for example, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 99% and the range formed by any two of these point values and any value in the range;
  • the mass content of the second binder is, for example, 0.8%, 1%, 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20% and the range formed by any two of these point values and any value in the range;
  • the mass content of the second conductive agent is, for example, 0 , 1%, 2%, 3%, 4%, 5% and the range formed by any two of these point values and any value in the range.
  • the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • any known current collector can be used.
  • negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel-plated steel, and the like.
  • the anode current collector is copper.
  • the negative electrode current collector form may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a thin metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within a range composed of any two of the above-mentioned values.
  • the negative electrode can be prepared by the following method: first, coating a primer layer slurry containing a first binder and a first conductive agent on the negative electrode current collector, and then coating the primer layer with a negative electrode active material, a first conductive agent and a slurry after drying.
  • a negative electrode (negative electrode sheet) can be obtained by forming a negative electrode film sheet on the negative electrode current collector by rolling the slurry of the active material layer such as the two binders after drying.
  • a positive electrode sheet in some embodiments of the present application includes a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector.
  • the positive electrode active material layer contains a positive electrode active material.
  • the positive electrode active material layer may be one or more layers, and each layer of the multilayered positive electrode active material may contain the same or different positive electrode active materials.
  • the positive active material is any material that can reversibly intercalate and deintercalate metal ions such as lithium ions.
  • the discharge capacity of the positive active material is less than the rechargeable capacity of the negative active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • the positive electrode active material there is no particular limitation on the type of the positive electrode active material, as long as it can electrochemically occlude and release metal ions (eg, lithium ions).
  • the positive active material is a substance containing lithium and at least one transition metal.
  • the positive electrode active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
  • the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO 2 ; lithium nickel composite oxides such as LiNiO 2 ; lithium manganese composite oxides such as LiMnO 2 , LiMn 2 O 4 , and Li 2 MnO 4 ; LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 and other lithium-nickel-manganese-cobalt composite oxides, in which a part of the transition metal atoms serving as the host of these lithium transition metal composite oxides are Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements .
  • lithium transition metal composite oxide may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 and so on.
  • combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO 2 and LiMn 2 O 4 , wherein a portion of Mn in LiMn 2 O 4 may be replaced by transition metals (eg, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), a part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium-containing transition metal phosphate compounds include LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 and other iron phosphates, and LiCoPO 4 and other cobalt phosphates, wherein as these lithium transition metal phosphate compounds A part of the transition metal atoms of the host is replaced by Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and other elements.
  • a powdered material of lithium transition metal oxide Li a M b O 2 is used, wherein 0.9 ⁇ a ⁇ 1.1, 0.9 ⁇ b ⁇ 1.1, and M is primarily a transition metal selected from Mn, Co, and Ni , where the composition M varies with particle size.
  • A is selected from at least one of the elements Al, Mg, Ti, Cr, and A' At least one selected from elements F, Cl, S, Zr, Ba, Y, Ca, B, Be, Sn, Sb, Na, and Zn.
  • powders with a composition that is related to size ie one component with large particles (eg distributed centered at ⁇ 20 ⁇ m); the component is capable of rapid bulk diffusion.
  • Another component has small particles (eg distributed around 5 ⁇ m) and its composition ensures safety.
  • an electrode active material is provided that combines high cycle stability and high safety with high volumetric and high gravimetric energy density.
  • the positive electrode active material has a broad particle size distribution, which is defined as a particle size ratio of large particles to small particles greater than 3, and Dv90/Dv10>3, wherein Dv90 represents the particle size distribution on a volume basis, from small to small From the particle size side, the particle size reaches 90% of the cumulative volume.
  • Dv10 represents a particle size that reaches 10% of the cumulative volume from the small particle size side in the particle size distribution based on volume.
  • the particle size distribution of the powder can be determined by suitable methods known in the art. Suitable methods are eg laser diffraction or sieving by using sets of sieves with different mesh numbers.
  • the individual particles are substantially lithium transition metal oxides, and the individual particles have Co, whose content in the transition metal increases continuously with particle size.
  • the individual particles also contain Mn in the transition metal, and the Mn content decreases continuously with particle size.
  • the large particles have large particles close to the composition of LiCoO2 to achieve high Li diffusion constants, and thus to achieve adequate rate performance.
  • Large particles occupy only a small fraction of the total surface area of the positive electrode. Therefore, the heat released by the reaction with the electrolyte at the surface or at the outer part is limited; as a result, there are fewer large particles leading to poor safety.
  • Small particles have compositions containing less Co for increased safety. The lower lithium diffusion constant is acceptable in small particles without significant loss of rate performance due to the short length of the solid-state diffusion paths.
  • the preferred composition of the small particles contains smaller amounts of Co and larger amounts of stabilizing elements, such as Mn.
  • the slower Li bulk diffusion is acceptable, but the stability of the surface is high.
  • the preferred composition of large particles contains a larger amount of Co and a smaller amount of Mn due to the need for fast lithium body diffusion, while a slightly lower surface stability is acceptable.
  • preferably at least 80 w% of the M is cobalt or nickel in the interior of a single particle composed of LixMO2 .
  • the inner portion of the particle has a composition close to LiCoO 2 .
  • the outer part is lithium manganese nickel cobalt oxide.
  • the preparation of the electrode active material having a composition and size-dependent powdery form can be accomplished by depositing at least one transition metal-containing precipitate on seed particles, the seed particles having a transition metal composition different from that of the precipitate; A controlled amount of a lithium source is added; and at least one thermal treatment is performed wherein substantially all of the particles obtained contain a seed-derived inner core completely covered by a precipitate-derived layer.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent that dissolves the electrolyte.
  • the electrolyte used in the electrochemical devices of the present application further includes additives.
  • the electrolyte further comprises any non-aqueous solvent known in the art as a solvent for the electrolyte.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic ether, Chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing solvents.
  • examples of cyclic carbonates may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of chain carbonates may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-carbonate Chain carbonates such as propyl ester, ethyl-n-propyl carbonate, di-n-propyl carbonate, etc.
  • fluorine-substituted chain carbonates may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate base) carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of cyclic carboxylic acid esters may include, but are not limited to, one or more of the following: one or more of gamma-butyrolactone and gamma-valerolactone.
  • some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.
  • examples of chain carboxylates may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate , methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • some of the hydrogen atoms of the chain carboxylate may be replaced by fluorine.
  • examples of fluorine-substituted chain carboxylates may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2,2-trifluoroethyl ester, etc.
  • examples of cyclic ethers may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1 , 3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • examples of chain ethers may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethyl Oxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxy Ethoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of phosphorus-containing organic solvents may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate Ester, Ethylene Methyl Phosphate, Ethylene Ethyl Phosphate, Triphenyl Phosphate, Trimethyl Phosphite, Triethyl Phosphite, Triphenyl Phosphite, Tris(2,2,2-trifluorophosphate) ethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of sulfur-containing organic solvents may include, but are not limited to, one or more of the following: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, diethyl sulfolane Sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, sulfuric acid Diethyl ester and dibutyl sulfate.
  • some of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • aromatic fluorinated solvents include, but are not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluorobenzene Fluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, and combinations thereof.
  • the solvent used in the electrolyte of the present application includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, or ethyl acetate at least one of them.
  • the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone and combinations thereof .
  • the chain carboxylate and/or cyclic carboxylate can form a passivation film on the surface of the electrode, thereby improving the intermittent charging of the electrochemical device Capacity retention after cycling.
  • the electrolyte contains 1% to 60% of chain carboxylates, cyclic carboxylates, and combinations thereof.
  • the electrolyte contains ethyl propionate, propyl propionate, ⁇ -butyrolactone and combinations thereof, and the content of the combination is 1% to 60%, 10% to 10%, based on the total weight of the electrolyte solution. 60%, 10% to 50%, 20% to 50%.
  • the electrolyte contains 1% to 60%, 10% to 60%, 20% to 50%, 20% to 40%, or 30% propyl propionate based on the total weight of the electrolyte.
  • the electrolyte contains additives.
  • additives may include, but are not limited to, one or more of the following: fluorocarbonate, ethylene carbonate containing carbon-carbon double bonds, and sulfur-oxygen double bonds.
  • Compounds and acid anhydrides (containing S O double bonds).
  • the additive is present in an amount of 0.01% to 15%, 0.1% to 10%, or 1% to 5% based on the total weight of the electrolyte.
  • the content of the propionate is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times that of the additive based on the total weight of the electrolyte.
  • the additive comprises one or more fluorocarbonates.
  • fluorocarbonate can act together with propionate to form a stable protective film on the surface of the negative electrode, thereby inhibiting the decomposition reaction of the electrolyte.
  • examples of fluorocarbonates may include, but are not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4,4 -Difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methyl ethylene carbonate, 4-fluoro-5-methyl ethylene carbonate, trifluoromethyl methyl carbonate, carbonic acid Trifluoroethyl methyl ester and ethyl trifluoroethyl carbonate, etc.
  • the additive comprises one or more ethylene carbonates containing carbon-carbon double bonds.
  • carbon-carbon double bond-containing vinyl carbonates may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, carbonic acid-1,2 - Dimethyl vinylene, 1,2-diethyl vinylene carbonate, fluorovinylene carbonate, trifluoromethyl vinylene carbonate; vinyl ethylene carbonate, 1-methyl carbonate- 2-Vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate Ethyl carbonate, 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate, 1,1-dimethyl-2-methylene carbonate and carbonate- 1,1-Diethyl-2-methylene ethylene ester, etc.
  • the carbon-carbon double bond may include, but are not limited to
  • the additive comprises one or more sulfur-oxygen double bond-containing compounds.
  • compounds containing sulfur-oxygen double bonds may include, but are not limited to, one or more of the following: cyclic sulfates, chain sulfates, chain sulfonates, cyclic sulfonates, chain sulfites esters and cyclic sulfites, etc.
  • examples of cyclic sulfates may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propylene glycol sulfate, 1,3-propylene glycol sulfate, 1 ,2-Butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1 , 4-pentanediol sulfate and 1,5-pentanediol sulfate, etc.
  • chain sulfates may include, but are not limited to, one or more of the following: dimethyl sulfate, methyl ethyl sulfate, diethyl sulfate, and the like.
  • chain sulfonates may include, but are not limited to, one or more of the following: fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate , butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy) propionate and ethyl 2-(methanesulfonyloxy) propionate, etc.
  • fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate , butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy) propionate and ethyl 2-(methanesulfonyloxy) propionate, etc.
  • cyclic sulfonates may include, but are not limited to, one or more of the following: 1,3-propanesultone, 1-fluoro-1,3-propanesultone, 2-fluoro- 1,3-Propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sulfonate Acid lactone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1 -Propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro- 2-Propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone,
  • chain sulfites may include, but are not limited to, one or more of the following: dimethyl sulfite, methyl ethyl sulfite, diethyl sulfite, and the like.
  • cyclic sulfites may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propylene glycol sulfite, 1,3-propylene glycol sulfite , 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite Glycol sulfite, 1,4-pentanediol sulfite and 1,5-pentanediol sulfite, etc.
  • the additive comprises one or more acid anhydrides.
  • acid anhydrides may include, but are not limited to, one or more of cyclic phosphoric anhydrides, carboxylic acid anhydrides, disulfonic acid anhydrides, and carboxylic acid sulfonic acid anhydrides.
  • cyclic phosphoric anhydrides may include, but are not limited to, one or more of trimethylphosphoric acid cyclic anhydride, triethylphosphoric acid cyclic anhydride, and tripropylphosphoric acid cyclic anhydride.
  • carboxylic anhydrides may include, but are not limited to, one or more of succinic anhydride, glutaric anhydride, and maleic anhydride.
  • disulfonic anhydrides may include, but are not limited to, one or more of ethane disulfonic anhydride and propane disulfonic anhydride.
  • carboxylic acid sulfonic anhydride may include, but are not limited to, one or more of sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride.
  • the additive is a combination of a fluorocarbonate and a carbon-carbon double bond-containing ethylene carbonate. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of a fluorocarbonate and a cyclic carboxylate. In some embodiments, the additive is a combination of fluorocarbonate and cyclic phosphoric anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid anhydride. In some embodiments, the additive is a combination of fluorocarbonate and fluorine anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid anhydride.
  • the electrolyte is not particularly limited, and a known substance as an electrolyte may be arbitrarily used.
  • lithium salts are generally used.
  • electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 ; lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li and other carboxylate lithium salts; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3
  • (malonate) Lithium borate salts tris(malonate) lithium phosphate, difluorobis(malonate) lithium phosphate, tetrafluoro(malonate) lithium phosphate, etc.
  • the electrolyte is selected from LiPF 6 , LiSbF 6 , FSO 3 Li, CF 3 SO 3 Li, LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) ) 2 , LiN(C 2 F 5 SO 2 ) 2 , Lithium Cyclic 1,2-Perfluoroethane Bissulfonimide, Lithium Cyclic 1,3-Perfluoropropane Bissulfonimide, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F ) 5 ) 3.
  • Lithium difluorooxalate borate, lithium bis(oxalate)borate or lithium difluorobis(oxalato) phosphate which help to improve the output power characteristics, high rate charge and discharge characteristics, and high temperature storage characteristics of electrochemical devices and cycle characteristics, etc.
  • the content of the electrolyte is not particularly limited as long as the effects of the present application are not impaired.
  • the total molar concentration of lithium in the electrolyte is greater than 0.3 mol/L, greater than 0.4 mol/L, or greater than 0.5 mol/L.
  • the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L, or less than 2.0 mol/L.
  • the total molar concentration of lithium in the electrolyte is within a range consisting of any two of the above-mentioned values. When the electrolyte concentration is within the above-mentioned range, the amount of lithium as the charged particles is not too small, and the viscosity can be kept in an appropriate range, so that it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate.
  • the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate.
  • the electrolyte includes a lithium salt.
  • the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is present in an amount greater than 0.01% or greater than 0.1% based on the total weight of the electrolyte.
  • the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is present in an amount of less than 20% or less than 10% based on the total weight of the electrolyte. In some embodiments, the amount of salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is within a range consisting of any two of the foregoing values.
  • the electrolyte comprises one or more species selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more salts in addition thereto.
  • Other salts include the lithium salts exemplified above, and in some examples, LiPF 6 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN ( C 2 F 5 SO 2 ) 2 , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 .
  • the other salts include the lithium salt
  • the salts other than these are present in an amount greater than 0.01% or greater than 0.1% based on the total weight of the electrolyte. In some embodiments, the additional salt is present in an amount of less than 20%, less than 15%, or less than 10% based on the total weight of the electrolyte. In some embodiments, the content of other salts is within the range composed of any two of the above-mentioned values. The other salts having the above-mentioned contents help to balance the conductivity and viscosity of the electrolyte.
  • the electrolytic solution may contain additional additives such as a negative electrode coating film forming agent, a positive electrode protective agent, and an overcharge inhibitor as necessary.
  • additives generally used in non-aqueous electrolyte secondary batteries can be used, and examples thereof can include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluorobenzyl Ether, propane sultone, propene sultone, etc. These additives may be used alone or in any combination.
  • the content of these additives in the electrolytic solution is not particularly limited, and may be appropriately set according to the type and the like of the additives.
  • the additive is present in an amount of less than 5%, in the range of 0.01% to 5%, or in the range of 0.2% to 5%, based on the total weight of the electrolyte.
  • a separator is usually provided between the positive electrode and the negative electrode.
  • the electrolytic solution of the present application is usually used by permeating the separator.
  • the material and shape of the separator are not particularly limited as long as the effects of the present application are not significantly impaired.
  • the separator may be a resin, glass fiber, inorganic substance, or the like formed of a material that is stable to the electrolyte of the present application.
  • the separator includes a porous sheet or a non-woven fabric-like substance with excellent liquid retention properties.
  • materials for resin or fiberglass separators may include, but are not limited to, polyolefins, aramids, polytetrafluoroethylene, polyethersulfone, glass filters, and the like.
  • the material of the isolation membrane is a glass filter.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the separator can also be a material formed by laminating the above materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in the order.
  • inorganic materials may include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.).
  • inorganic forms may include, but are not limited to, particulate or fibrous.
  • the form of the separator may be in the form of a thin film, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, and the like.
  • the separator has a pore size of 0.01 ⁇ m to 1 ⁇ m and a thickness of 5 ⁇ m to 50 ⁇ m.
  • a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or the negative electrode using a resin-based binder can also be used,
  • a separator is formed by using a fluororesin as a binder to form a porous layer on both surfaces of a positive electrode with alumina particles having a particle size of less than 90% of 1 ⁇ m.
  • the thickness of the separator is arbitrary. In some embodiments, the thickness of the isolation membrane is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation membrane is less than 50 ⁇ m, less than 40 ⁇ m, or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within a range consisting of any two of the above-mentioned values. When the thickness of the separator is within the above range, insulating properties and mechanical strength can be secured, and the rate characteristics and energy density of the electrochemical device can be secured.
  • the porosity of the separator is arbitrary. In some embodiments, the porosity of the isolation membrane is greater than 20%, greater than 35%, or greater than 45%. In some embodiments, the isolation membrane has a porosity of less than 90%, less than 85%, or less than 75%. In some embodiments, the porosity of the isolation membrane is within a range consisting of any two of the above values. When the porosity of the separator is within the above range, insulating properties and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good rate characteristics.
  • the average pore diameter of the separator is also arbitrary. In some embodiments, the average pore size of the isolation membrane is less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the isolating membrane has an average pore size greater than 0.05 ⁇ m. In some embodiments, the average pore size of the isolation membrane is within a range consisting of any two of the above-mentioned values. When the average pore diameter of the separator exceeds the above-mentioned range, a short circuit is likely to occur. When the average pore diameter of the separator is within the above range, the membrane resistance can be suppressed while preventing short circuit, so that the electrochemical device has good rate characteristics.
  • the electrochemical device assembly includes an electrode group, a current collecting structure, an outer casing, and a protective element.
  • the electrode group may have any of a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, and a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator interposed therebetween.
  • the ratio of the mass of the electrode group to the internal volume of the battery is greater than 40% or greater than 50%.
  • the electrode set occupancy is less than 90% or less than 80%.
  • the occupancy rate of the electrode group is within a range composed of any two of the above-mentioned values.
  • the capacity of the electrochemical device can be ensured, and the reduction of characteristics such as repeated charge-discharge performance and high-temperature storage associated with an increase in internal pressure can be suppressed, and the operation of the gas release valve can be prevented.
  • the current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the bonding portion.
  • the electrode group has the above-described laminated structure, a structure in which the metal core portions of the respective electrode layers are bundled and welded to the terminals is suitably used.
  • the electrode area is increased, the internal resistance increases, so it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the internal resistance can be reduced by providing two or more lead structures for the positive electrode and the negative electrode, respectively, and bundling them on the terminals.
  • the material of the outer casing is not particularly limited as long as it is stable to the electrolyte solution used.
  • the outer casing can be used, but not limited to, nickel-plated steel sheet, stainless steel, metal such as aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil.
  • the outer casing is a metal or laminated film of aluminum or aluminum alloy.
  • Metal-based outer casings include, but are not limited to, a hermetically sealed structure formed by welding metals to each other by laser welding, resistance welding, or ultrasonic welding;
  • the outer casing using the above-mentioned laminated film includes, but is not limited to, a hermetically sealed structure formed by thermally adhering resin layers to each other, and the like.
  • a resin different from the resin used for the laminated film may be interposed between the above-mentioned resin layers.
  • a resin having a polar group or a modified resin into which a polar group is introduced can be used as a resin to be sandwiched due to the bonding of the metal and the resin.
  • the shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminated type, a button type, a large size, and the like, for example.
  • the protective element can use a positive temperature coefficient (PTC), a thermal fuse, a thermistor, whose resistance increases when abnormal heat is generated or an excessive current flows, and can be cut off by rapidly increasing the internal pressure or internal temperature of the battery when abnormal heat is generated A valve (current cutoff valve), etc. for the current flowing in the circuit.
  • PTC positive temperature coefficient
  • the above-mentioned protective element can be selected from a condition that does not work in normal use at high currents, and can also be designed in a form that does not cause abnormal heat release or thermal runaway even if the protective element is not present.
  • the electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the positive electrode piece, the separator, and the negative electrode piece are wound or stacked in sequence to form an electrode member, and then packed into, for example, an aluminum-plastic film for packaging, The electrolyte is injected, formed, and packaged to make a lithium-ion secondary battery. Then, performance test and cycle test were performed on the prepared lithium ion secondary battery.
  • electrochemical devices eg, lithium ion batteries
  • the present application further provides an electronic device comprising the electrochemical device according to the present application.
  • the use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the art.
  • the electrochemical devices of the present application may be used in, but not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power, motors, cars, motorcycles, power Bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • lithium-ion batteries The preparation of lithium-ion batteries is described below by taking lithium-ion batteries as an example and in conjunction with specific embodiments. Those skilled in the art will understand that the preparation methods described in this application are only examples, and any other suitable preparation methods are included in this application. within the range.
  • the first conductive agent and the first binder are mixed with deionized water in proportion by mass, and stirred evenly to obtain a primer slurry.
  • the primer slurry was coated on a 12 ⁇ m copper foil and baked at 50° C. for 5 min.
  • the active material, the second binder and the second conductive agent are mixed with deionized water in proportion by mass, and stirred evenly to obtain a negative electrode active material slurry.
  • This negative electrode active material slurry is coated on the undercoat layer. After drying, cold pressing, cutting and welding the tabs, the negative electrode is obtained.
  • the negative electrode was set according to the conditions of the following examples and comparative examples to have the corresponding composition and parameters.
  • the positive electrode material lithium cobaltate, conductive material (Super-P) and polyvinylidene fluoride (PVDF) are mixed with N-methylpyrrolidone (NMP) in a mass ratio of 95%: 2%: 3%, and stirred evenly to obtain a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry was coated on a 12 ⁇ m aluminum foil, dried, cold pressed, and then cut into pieces and welded with tabs to obtain a positive electrode.
  • the compound shown in the above formula 1 was added to the base electrolyte by mass percentage to study the influence of its content relationship on the performance of the lithium ion battery.
  • a polyethylene (PE) porous polymer film was used as the separator.
  • the obtained positive electrode, separator and negative electrode were wound in order and placed in an outer packaging foil, leaving a liquid injection port.
  • the electrolyte is poured from the liquid injection port, and the lithium ion battery is prepared through the processes of chemical formation and capacity.
  • Examples 2 to 6 the methods for the preparation of the positive electrode, the preparation of the electrolyte, the preparation of the separator, and the preparation of the lithium ion battery are the same as those in Example 1, and the differences between Examples 2 to 6 and Example 1 are only: The composition of the primer layer in the negative pole piece is different.
  • Comparative Example 1 the methods for the preparation of the positive electrode, the preparation of the electrolyte, the preparation of the separator, and the preparation of the lithium ion battery are the same as those in Examples 1 to 6.
  • the difference between Comparative Example 1 and Examples 1 to 6 is only:
  • the negative electrode in Comparative Example 1 did not contain an undercoat layer.
  • Example 7 to 9 the methods for the preparation of the positive electrode, the preparation of the electrolyte, the preparation of the separator and the preparation of the lithium ion battery are the same as those in Example 1, and the differences between Examples 2 to 6 and Example 1 are only:
  • the composition of the primer layer in the negative electrode pole piece is different, and the composition of the negative electrode active material layer is different.
  • Comparative Example 2 the methods for the preparation of the positive electrode, the preparation of the electrolyte, the preparation of the separator and the preparation of the lithium ion battery are the same as those in Examples 7-9, and the difference between Comparative Example 2 and Examples 7-9 is only: The negative electrode in Comparative Example 2 did not contain an undercoat layer.
  • the diaphragm resistance test adopts Yuanneng Technology equipment and diaphragm resistance tester.
  • test air pressure is set to "0".
  • the lithium-ion battery was charged to 4.45V at a constant current of 1C, then charged at a constant voltage of 4.45V to a current of 0.05C, and discharged at a constant current of 1C to 3.0V. This is the first cycle.
  • the lithium-ion battery was cycled according to the above conditions until the capacity retention rate after cycling was 80%, and the number of cycles was recorded.
  • “1C” refers to the current value at which the lithium-ion battery capacity is completely discharged within 1 hour.
  • the capacity retention rate after cycling of the lithium-ion battery is calculated by the following formula:
  • Capacity retention rate after cycling (discharge capacity corresponding to the number of cycles/discharge capacity at the first cycle) ⁇ 100%.
  • the lithium-ion battery was charged to 4.45V at a constant current of 1C, then charged at a constant voltage of 4.45V to a current of 0.05C, and discharged at a constant current of 1C to 3.0V. This is the first cycle.
  • the lithium-ion battery was subjected to 500 cycles under the above conditions.
  • “1C” refers to the current value at which the lithium-ion battery capacity is completely discharged within 1 hour.
  • the battery was disassembled, and the negative pole piece was taken out to observe whether the diaphragm was decarburized.
  • the samples were first baked in an oven for 2 hours to remove moisture. Weigh the sample before analysis
  • the dilatometer is taken out for cleaning, and the test is over.
  • Membrane porosity V pole porosity X ⁇ H/(H-h).
  • R 2 ⁇ (S/ ⁇ ) 1/2 ; wherein, S is the area of the granular conductive agent;
  • Table 1 lists the composition, adhesive force, sheet resistance and performance of the corresponding lithium ion batteries in the negative electrode plates of Examples 1 to 9 and Comparative Examples 1 to 2.
  • the compaction densities PD were all set to 1.30 g/cm 3 .
  • each part of the active material tends to shrink synchronously/or the inner side with better electronic conductivity may shrink faster, which will make the original close contact with the surface of the current collector
  • the active material is separated from the current collector, which leads to the detachment of the diaphragm, which increases the internal resistance and deteriorates the cycle performance.
  • Examples 2, 6-9 in which the primer layer binder has a polar functional group (carboxyl group) can significantly improve the adhesion between the membrane sheet and the current collector, thereby making the shape stability of the pole sheet more stable.
  • the use of Examples 7-9 with a carboxyl group in the primer layer binder can ensure the adhesion force of 500 N/m or more, and can maintain excellent shape stability even for high-expansion Si-based active materials.
  • Example 10 the only difference from Example 2 is that the compaction density (expressed as compaction) of the diaphragm of the negative pole piece and the porosity of the diaphragm are different.
  • Table 2 lists the corresponding porosity of the membrane and the cycle performance and rate performance of the corresponding lithium ion battery under the same negative electrode membrane composition and different compaction in Examples 2 and 10-14.
  • Examples 2, 10-13 with the compacted density of the membrane sheet ranging from 1.30 to 1.80 g/ cm3 , have a higher compaction than Example 14, which has a compaction density of 1.83 g/ cm3 . More excellent cycle stability and rate performance.
  • the embodiment with a compaction of 1.30 to 1.80 g/cm provides suitable porosity, which can buffer the volume expansion and contraction caused by the intercalation and deintercalation of lithium ions during cycling, reducing the demolition of the pole piece. risk.
  • Example 15-23 the only difference from Example 4 is that in the primer layer of the negative pole piece, the ratio relationship between the particle size of the first conductive agent (SP) and the thickness of the primer layer is different.
  • the only difference from Example 2 is that in the primer layer of the negative electrode sheet, the ratio relationship between the tube diameter of the first conductive agent (CNT) and the thickness of the primer layer is different.
  • Table 3 lists the relationship between the average particle diameter of the first conductive agent particles in the primer layer/the average diameter of the tube and the thickness of the primer layer in Examples 15 to 30, the compositions are the same as those in Example 4 (SP) and Example 2 (CNT), respectively. Effects on the adhesion of the corresponding pole pieces, the sheet resistance and the cycle stability of the corresponding lithium-ion batteries.
  • Examples 16-19, 21-23, and 25-31 with D/H in the range of 0.5 to 1.25 are compared to Examples 15, 20, 24, and 32, which are outside the above range.
  • the appropriate particle size (tube diameter)/primer thickness can avoid the stacking of too many small particles of conductive agents in the primer layer, and avoid the existence of excessive interface resistance, thereby reducing and improving the membrane resistance. Cycling stability; on the other hand, excessive particle size (tube diameter)/primer thickness will lead to uneven distribution of conductive agent in the primer layer, which in turn leads to increased membrane resistance.

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Abstract

本申请涉及储能技术领域，尤其涉及一种极片及包含其的电化学装置和电子设备。本申请的极片，包括：集流体；以及膜片，所述膜片包括设置于所述集流体表面的底涂层和设置于所述底涂层表面的活性物质层，所述底涂层包括第一粘结剂和第一导电剂；其中，所述膜片与所述集流体的粘结力为≥20N/m。本申请能够缓解现有技术中由于贴近集流体表面的活性材料部分粘接力偏低，导致极片容易脱膜等问题。

Description

极片及包含其的电化学装置和电子设备
本申请要求于2020年10月15日提交中国专利局，申请号为202011104624.X，申请名称为“极片及包含其的电化学装置和电子设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及储能技术领域，具体涉及一种极片及包含其的电化学装置和电子设备，特别是锂离子电池。
背景技术
随着技术的发展和对移动装置的需求的增加，人们对电化学装置(例如，锂离子电池)的需求显著增加。同时具有高能量密度以及优异的寿命和循环特性的锂离子电池是研究方向之一。
随着循环的进行，锂离子电池的正负极重复地发生锂离子的嵌入和脱出，伴随着锂离子的嵌入和脱出，活性材料的体积也相应地发生膨胀和收缩。其中，负极活性材料(如石墨、硅基材料)体积膨胀和收缩剧烈，现有技术中，贴近负极集流体表面的活性材料部分粘结力偏低，随着循环过程中活性材料体积的膨胀收缩，极易造成贴近集流体表层的负极活性材料层与集流体表面的分离，导致极片脱膜，进而带来内阻升高、循环性变差。
近年来，研究者们大力开发满足高能量密度需求的硅基负极材料，而硅基负极材料在锂离子的嵌入和脱出过程中，体积变化更加剧烈，在集流体表面部分由于上述体积变化导致的脱膜现象更加严重。
有鉴于此，确有必要提供一种改进的、具有优异的循环性能的电化学装置。
申请内容
本申请的目的在于提供一种极片及包含其的电化学装置和电子设备，该极片为具有高粘结力的极片，能够在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的第一方面，提供一种极片，包括：集流体；以及膜片，所述膜片包括设置于所述集流体表面的底涂层和设置于所述底涂层表面的活性物质层，所述底涂层包括第一粘结剂和第一导电剂；其中，所述膜片与所述集流体的粘结力为≥20N/m。
优选的，根据本申请的一些实施例，所述膜片与所述集流体的粘结力为≥80N/m； 更优选的，根据本申请的一些实施例，所述膜片与所述集流体的粘结力为≥100N/m；更优选的，根据本申请的一些实施例，所述膜片与所述集流体的粘结力为≥500N/m。
根据本申请的一些实施例，所述底涂层的厚度为100nm至2μm；优选的，根据本申请的一些实施例，所述底涂层的厚度为100nm至1000nm；更优选的，根据本申请的一些实施例，所述底涂层的厚度为100nm至800nm。
根据本申请的一些实施例，所述第一导电剂的颗粒平均粒径或管平均直径D与所述底涂层厚度H的关系满足：D与H的比值D/H为0.25～1.5；优选为0.5～1.25。
根据本申请的一些实施例，所述膜片的压实密度为1.30g/cm 3至1.80g/cm 3。
根据本申请的一些实施例，所述膜片的孔隙率为20％至50％。优选的，根据本申请的一些实施例，所述膜片的孔隙率为25％至40％。
根据本申请的一些实施例，所述膜片的膜片电阻为3mΩ至50mΩ。优选的，根据本申请的一些实施例，所述膜片的膜片电阻为3mΩ至30mΩ。
根据本申请的一些实施例，所述底涂层中的第一粘结剂的质量含量为20％至95％。
根据本申请的一些实施例，所述底涂层中的第一导电剂的质量含量为5％至80％。
根据本申请的一些实施例，所述第一粘结剂包括碳碳双键、羧基、羰基、碳氮单键、羟基、酯基、酰基或芳基官能团中的至少一种。优选的，根据本申请的一些实施例，所述第一粘结剂包括羧基、羰基、碳氮单键、羟基或酯基官能团中的至少一种。
根据本申请的一些实施例，所述第一粘结剂包括SBR(丁苯橡胶)、PAA(聚丙烯酸)、PVP(聚乙烯吡咯烷酮)或PAM(聚丙烯酰胺)中的至少一种。
根据本申请的一些实施例，所述第一导电剂包括导电炭黑、柯琴黑、单壁碳纳米管或多壁碳纳米管中的至少一种。
根据本申请的一些实施例，所述活性物质层包括活性物质和第二粘结剂。
根据本申请的一些实施例，所述活性物质包括石墨类材料或硅基材料中的至少一种。
根据本申请的一些实施例，所述硅基材料包括硅、硅氧化物、硅碳复合物或硅合金中的至少一种。优选的，根据本申请的一些实施例，所述硅基材料包括纯硅、SiO x(0＜x≤2)或硅碳复合物中的至少一种。
根据本申请的一些实施例，所述活性物质层还包括第二导电剂。
根据本申请的一些实施例，所述活性物质层包括质量含量为80％至99％的活性物质、0.8％至20％的第二粘结剂和0至5％的第二导电剂。
根据本申请的一些实施例，所述第二粘结剂包括PAA(聚丙烯酸)、PVP(聚乙 烯吡咯烷酮)、PAM(聚丙烯酰胺)、SBR(丁苯橡胶)或CMC(羧甲基纤维素)中的至少一种。
根据本申请的一些实施例，所述第二导电剂包括导电炭黑、柯琴黑、单壁碳纳米管或多壁碳纳米管中的至少一种。
根据本申请的第二方面，提供一种电化学装置，包括：正极极片；负极极片；隔离膜，设置于所述正极极片和所述负极极片之间；其中，所述负极极片为如上所述的极片。
根据本申请的一些实施例，所述电化学装置包括电解液，所述电解液包括含S＝O双键的化合物。
根据本申请的一些实施例，所述含S＝O双键的化合物包括环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯或环状亚硫酸酯中的至少一种。
根据本申请的一些实施例，所述含S＝O双键化合物包括式1所示化合物中的至少一种，
Figure PCTCN2021123330-appb-000001
其中：W选自
Figure PCTCN2021123330-appb-000002
L选自单键或亚甲基；
m为1至4的整数；
n为0至2的整数；且
p为0至6的整数。
根据本申请的一些实施例，所述式1所示化合物选自以下化合物中的至少一种：
Figure PCTCN2021123330-appb-000003
Figure PCTCN2021123330-appb-000004
其中，m为1至4的整数；
n为0至2的整数；且
p为0至6的整数。
根据本申请的一些实施例，所述含S＝O双键的化合物在所述电解液中的质量百分含量y与膜片孔隙率V的关系满足：0.01≤y/V≤0.07。
根据本申请的第三方面，提供一种电子设备，包括前述的电化学装置。
本申请的技术方案至少具有以下有益的效果：
本申请提供的极片以及包括该极片的电化学装置和电子设备，通过在所述极片的膜片设置底涂层，提高了膜片与集流体的粘结力，避免了极片循环过程中由于膨胀、收缩而脱膜，电化学装置的循环、形状稳定性大幅提升，保证了电化学装置具有优异的倍率性能。本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1为本申请示例性的一种实施方式提供的极片的结构示意图；
图2为本申请示例性的一种实施方式提供的极片的切面示意图；
图3为本申请实施例1-9提供的极片的形状稳定性的示意图片；
图4为本申请对比例1-2提供的极片的形状稳定性的示意图片。
其中，附图标记说明如下：
10-负极集流体；
20-膜片；
201-底涂层；
202-活性物质层。
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。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所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、B，那么短语“A、B中的至少一者”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、C，那么短语“A、B、C中的至少一者”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。
本文中使用的术语“和/或”或者“/”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。再者，为便于描述，本文中使用的“第一”“第二”以及类似的词语并不表示任何顺序、数量或者重要性，而只是用来区分不同的组成部分。
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。
电化学装置(例如，锂离子电池)的电极(正极或负极)通常通过以下方法制备：将活性材料、导电剂、增稠剂、粘结剂和溶剂混合，然后将混合后的浆料涂布于集流体上。此外，电化学装置的理论容量可随着活性物质的种类而变化。随着循环的进行， 电化学装置通常会产生充电/放电容量降低的现象。这是因为电化学装置在充电和/或放电过程中电极界面会发生变化，导致电极活性物质不能发挥其功能。
本申请通过使用特定粘结力的极片保证了电化学装置在循环过程中的极片稳定性，避免了负极极片循环过程中由于膨胀、收缩而脱膜，从而提高了电化学装置的循环性能。本申请特定粘结力的极片可通过控制极片的结构和粘结剂的官能团种类来实现。
在本申请的一些实施例中，提供了一种电化学装置，其包括如下所述的负极、正极和电解液。
[负极]
如图1-2所示，在本申请的一些实施例中的负极极片，其包括：负极集流体10和膜片20。其中，膜片20与负极集流体10的粘结力为≥20N/m。膜片20包括设置于负极集流体10表面的底涂层201和设置于底涂层201表面的活性物质层202，底涂层201的组成包括第一粘结剂和第一导电剂。
该负极极片通过在膜片中设置包括第一粘结剂和第一导电剂的底涂层，提高了膜片与负极集流体的粘结力，相应的，该负极极片的循环、形状稳定性也大幅提升。具体地讲，一方面，该底涂层的存在能提高负极集流体的表面缺陷，增强了活性物质层与极片之间的铆合作用，增加了底涂层与负极集流体之间的结合力，从而提高了膜片整体与集流体的粘结力，降低了膜片脱落的风险。另一方面，以该负极极片应用于锂离子电池中为例，底涂层的存在能够起到很好的缓冲作用，当负极活性物质在嵌入锂离子发生膨胀时，底涂层避免了膨胀的活性物质直接向集流体表面施加作用力，若直接向集流体表面施加作用力，由于该方向集流体固定并无法发生位移，则活性物质只能整体向膜片外表面膨胀，而当脱出锂离子收缩时，活性物质各部分倾向于同步收缩/或电子导电性更好的内侧可能收缩的更快，则会使得原来与集流体表面紧密接触的活性物质与集流体分离，从而导致膜片的脱落，使得内阻升高，循环性能变差。基于此，本申请的实施例的极片能够显著提高膜片与集流体的粘结力，在本申请的一些实施例中限定了膜片与集流体的粘结力为≥20N/m，通过使用特定粘结力的极片保证了电化学装置在循环过程中的极片稳定性，避免了极片循环过程中由于膨胀、收缩而脱膜，从而提高了电化学装置的循环性能。
在一些实施例中，膜片与集流体的粘结力为≥80N/m；更优选的，在一些实施例中，膜片与集流体的粘结力为≥100N/m；更优选的，在一些实施例中，膜片与集流体的粘结力为≥500N/m，例如，膜片与集流体的粘结力为20N/m、60N/m、80N/m、100N/m、 120N/m、130N/m、160N/m、180N/m、220N/m、300N/m、400N/m、500N/m、540N/m、600N/m、630N/m等。
在一些实施例中，底涂层的厚度为100nm(纳米)至2μm(微米)；优选的，在一些实施例中，底涂层的厚度为100nm至1000nm；更优选的，在一些实施例中，底涂层的厚度为100nm至800nm。底涂层的厚度不易过大，底涂层的厚度优选在纳米级，有助于获得所需的膜片与集流体的粘结力，有助于使其具有更加优异的膜片电阻以及循环稳定性。典型但非限制性的，底涂层的厚度例如为100nm、200nm、300nm、400nm、500nm、600nm、800nm、900nm、950nm、999nm、1μm、1.5μm、2μm以及这些点值中的任意两个所构成的范围及范围中的任意值。
在一些实施例中，第一导电剂的颗粒平均粒径或管平均直径D与底涂层厚度H的关系满足：D/H为0.25～1.5；优选为0.5～1.25。
应理解，该第一导电剂的形态可以为颗粒状或管状，当第一导电剂的形态为颗粒状时，第一导电剂的颗粒平均粒径D与底涂层厚度H的关系满足：D/H为0.5～1.25；当第一导电剂的形态为管状时，第一导电剂的管平均直径D与底涂层厚度H的关系满足：D/H为0.5～1.25。典型但非限制性的，颗粒平均粒径或管平均直径D/底涂层厚度H例如为0.5、0.6、0.7、0.8、0.9、1.0、1.1、1.2、1.25及这些点值中的任意两个所构成的范围及范围中的任意值。在上述颗粒平均粒径或管平均直径与底涂层厚度的比值范围内，能够使极片具有更加优异的膜片电阻及循环稳定性。在本申请的一些实施例中，当颗粒平均粒径或管平均直径D/底涂层厚度H小于0.5时，会使底涂层中存在过多小颗粒第一导电剂，过多小颗粒第一导电剂之间的堆叠会存在过多的界面电阻，进而使得膜片的电阻升高，降低了循环稳定性。当颗粒平均粒径或管平均直径D/底涂层厚度H大于1.25时，容易导致第一导电剂在底涂层中的分布不均匀，进而导致膜片的电阻升高，影响循环性能。
在一些实施例中，膜片的膜片电阻为3mΩ至50mΩ。优选的，在一些实施例中，膜片的膜片电阻为3mΩ至30mΩ。典型但非限制性的，膜片的膜片电阻例如为3mΩ、5mΩ、6mΩ、9mΩ、10mΩ、15mΩ、20mΩ、22mΩ、26mΩ、30mΩ、50mΩ及这些点值中的任意两个所构成的范围及范围中的任意值。
在一些实施例中，膜片的压实密度为1.30g/cm 3至1.80g/cm 3。典型但非限制性的，膜片的压实密度例如为1.30g/cm 3、1.40g/cm 3、1.50g/cm 3、1.55g/cm 3、1.60g/cm 3、1.70g/cm 3、1.75g/cm 3、1.80g/cm 3及这些点值中的任意两个所构成的范围及范围中的任意值。在合适的膜片压实密度范围内，有助于降低极片脱模的风险，保证了活性物质层与集流体 之间存在底涂层，底涂层能起到铆合和缓冲作用，进而有助于获得更加优异的循环稳定性和倍率性能。
在一些实施例中，膜片的孔隙率为20％至50％。优选的，在一些实施例中，膜片的孔隙率为25％至40％。典型但非限制性的，膜片的孔隙率例如为20％、22％、24％、25％、26％、28％、30％、32％、35％、37％、40％、45％、50％及这些点值中的任意两个所构成的范围及范围中的任意值。在合适的膜片孔隙率范围内，有助于降低极片脱模的风险，保证了活性物质层与集流体之间存在底涂层，底涂层能起到铆合和缓冲作用，能够与电解液充分接触，进而有助于获得更加优异的循环稳定性和倍率性能。
在一些实施例中，底涂层中的第一粘结剂的质量含量为20％至95％。典型但非限制性的，底涂层中的第一粘结剂的质量含量例如为20％、30％、40％、50％、60％、65％、70％、72％、80％、83％、85％、90％、91％、95％及这些点值中的任意两个所构成的范围及范围中的任意值。通过增加底涂层中第一粘结剂的含量，可以提高膜片与集流体的粘结力，获得更高粘结力的极片。
在一些实施例中，底涂层中的第一导电剂的质量含量为5％至80％。典型但非限制性的，底涂层中的第一导电剂的质量含量例如为5％、10％、20％、30％、40％、50％、55％、60％、70％、80％及这些点值中的任意两个所构成的范围及范围中的任意值。
在一些实施例中，第一粘结剂包括碳碳双键、羧基、羰基、碳氮单键、羟基、酯基、酰基或芳基官能团中的至少一种。优选的，在一些实施例中，第一粘结剂包括羧基、羰基、碳氮单键、羟基、酯基、酰基官能团中的至少一种。采用包含羧基、羰基、碳氮单键、羟基、酯基、酰基这些官能团中的一种或多种的第一粘结剂，能显著提高膜片与集流体的粘结力，这是由于上述官能团极性较强，与富含电子的金属集流体存在强烈的吸引作用，从而使得膜片的形状稳定性更加稳定，即使对于高膨胀的硅基活性物质，同样能够保持优异的形状稳定性。
在一些实施例中，第一粘结剂包括SBR(丁苯橡胶)、PAA(聚丙烯酸)、PVP(聚乙烯吡咯烷酮)或PAM(聚丙烯酰胺)中的至少一种。
在一些实施例中，第一导电剂包括但不限于导电炭黑、柯琴黑、单壁碳纳米管或多壁碳纳米管中的至少一种。
在一些实施例中，活性物质层的组成包括活性物质和第二粘结剂。
在一些实施例中，活性物质包括石墨类材料或硅基材料中的至少一种。
在一些实施例中，硅基材料包括硅、硅氧化物、硅碳复合物或硅合金中的至少一种。优选的，在一些实施例中，硅基材料包括纯硅、SiO x(0＜x≤2)或硅碳复合物中的至少一种，其中，优选的，SiO x(1＜x≤2)。负极活性材料可以单独使用或组合使用。
在一些实施例中，活性物质层还包括第二导电剂。该膜片中，在底涂层中包含第一导电剂，在活性物质层中可以包含第二导电剂，也可以不包含第二导电剂。
根据本申请的一些实施例，底涂层中的第一粘结剂和活性物质层中的第二粘结剂可以采用相同类型的粘结剂，也可以采用不同类型的粘结剂。底涂层中的第一导电剂和活性物质层中的第二导电剂可以采用相同类型的导电剂，也可以采用不同类型的导电剂。
活性物质层中的第二粘结剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与底涂层的结合。本申请的实施例与负极活性物质层中的粘结剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。示例性的，在一些实施例中，第二粘结剂包括树脂粘合剂。树脂粘合剂的实例包括但不限于，氟树脂、聚丙烯腈(PAN)、聚酰亚胺树脂、丙烯酸系树脂、聚烯烃树脂等。当使用水系溶剂制备负极活性物质层浆料时，第二粘结剂包括但不限于，羧甲基纤维素(CMC)或其盐、苯乙烯-丁二烯橡胶(SBR)、聚丙烯酸(PAA)或其盐、聚乙烯醇等。优选的，在一些实施例中，第二粘结剂包括PAA(聚丙烯酸)、PVP(聚乙烯吡咯烷酮)、PAM(聚丙烯酰胺)、SBR(丁苯橡胶)或CMC(羧甲基纤维素)中的至少一种。
在一些实施例中，第一粘结剂的分子量＜1,500,000。第二粘结剂的分子量＜1,500,000。
在一些实施例中，第二导电剂包括但不限于导电炭黑、柯琴黑、单壁碳纳米管或多壁碳纳米管中的至少一种。
在一些实施例中，活性物质层包括质量含量为80％至99％的活性物质、0.8％至20％的第二粘结剂和0至5％的第二导电剂。典型但非限制性的，该活性物质层中，活性物质的质量含量例如为80％、82％、84％、85％、86％、88％、90％、92％、94％、95％、96％、99％及这些点值中的任意两个所构成的范围及范围中的任意值；第二粘结剂的质量含量例如为0.8％、1％、2％、4％、5％、6％、8％、10％、12％、15％、18％、20％及这些点值中的任意两个所构成的范围及范围中的任意值；第二导电剂的质量含量例如为0、1％、2％、3％、4％、5％及这些点值中的任意两个所构成的范围及范围中的任意值。
在一些实施例中，负极活性物质的可充电容量大于正极活性物质的放电容量，以防止在充电期间锂金属无意地析出在负极上。
作为保持负极活性物质的负极集流体，可以任意使用公知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在上述任意两个数值所组成的范围内。
负极可以通过以下方法制备：首先，在负极集流体上涂布包含第一粘结剂、第一导电剂的底涂层浆料，干燥后再在底涂层上涂布包含负极活性物质、第二粘结剂等的活性物质层浆料，干燥后，进行压延而在负极集流体的形成负极膜片，由此可以得到负极(负极极片)。
[正极]
在本申请的一些实施例中的正极极片，其包括：正极集流体和设置在所述正极集流体的一个或两个表面上的正极活性物质层。
其中，正极活性物质层包含正极活性物质。正极活性物质层可以是一层或多层，多层正极活性物质中的每层可以包含相同或不同的正极活性物质。以电化学装置为锂离子电池为例，正极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，正极活性物质的放电容量小于负极活性物质的可充电容量，以防止在充电期间锂金属无意地析出在负极上。
根据本申请的一些实施例，对于正极活性材料的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。示例性的，在一些实施例中，正极活性材料为含有锂和至少一种过渡金属的物质。正极活性材料的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，锂过渡金属复合氧化物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，锂过渡金属复合氧化物包括LiCoO 2等锂钴复合氧 化物；LiNiO 2等锂镍复合氧化物；LiMnO 2、LiMn 2O 4、Li 2MnO 4等锂锰复合氧化物；LiNi 1/3Mn 1/3Co 1/3O 2、LiNi 0.5Mn 0.3Co 0.2O 2等锂镍锰钴复合氧化物，其中作为这些锂过渡金属复合氧化物的主体的过渡金属原子的一部分被Na、K、B、F、Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Si、Nb、Mo、Sn、W等其它元素所取代。锂过渡金属复合氧化物的实例可包括，但不限于，LiNi 0.5Mn 0.5O 2、LiNi 0.85Co 0.10Al 0.05O 2、LiNi 0.33Co 0.33Mn 0.33O 2、LiNi 0.45Co 0.10Al 0.45O 2、LiMn 1.8Al 0.2O 4和LiMn 1.5Ni 0.5O 4等。锂过渡金属复合氧化物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在一些实施例中，使用锂过渡金属氧化物Li aM bO 2的粉末状材料，其中0.9＜a＜1.1，0.9＜b＜1.1，且M主要是选自Mn、Co和Ni的过渡金属，其中，组成M随粒度改变。
在一些实施例中，在锂过渡金属氧化物Li aM bO 2的粉末状的电极活性材料中，其中M＝A ZA’ Z’M’ 1-Z-Z’，M’＝Mn xNi yCo 1-x-y，0≤y≤1，0≤x≤1，0≤Z+Z’＜0.1，Z’＜0.02，A选自元素Al、Mg、Ti、Cr中至少一种，且A’选自元素F、Cl、S、Zr、Ba、Y、Ca、B、Be、Sn、Sb、Na、Zn中的至少一种。
在一些实施例中，所述过渡金属平均组成是M＝Mn xNi yCo 1-x-y，其中0.03＜x＜0.35。
在一些实施例中，所述过渡金属平均组成是M＝Mn xNi yCo 1-x-y，其中0.03＜x，且x+y＜0.7。
在一些实施例中，在具有组成与尺寸相关的Li aM bO 2的粉末状的电极活性材料中，基本上所有颗粒的所有部分具有层状晶体结构，较大颗粒具有组成Li aM bO 2，其中M＝Mn xNi yCo 1-x-y，x+y＜0.35，小颗粒具有组成Li aM bO 2，其中M＝Mn x’Ni y’Co 1-x’-y’，其具有至少低10％的Co，(1-x’-y’)＜0.9×(1-x-y)，以及至少高5％的Mn，x’-x＞0.05。由此，可以获得具有组成与尺寸相关的粉末，也即一种成分具有大的颗粒(例如分布集中在≥20μm)；其成分能够快速体相扩散。另一种成分具有小的颗粒(例如分布于5μm周 围)且其成分能确保安全性。从而提供将高循环稳定性和高安全性与高体积能量密度和高重量能量密度结合起来的电极活性材料。
在一些实施例中，所述正极活性材料具有宽的粒度分布，其规定为大颗粒与小颗粒的粒度比大于3，Dv90/Dv10>3，其中，Dv90表示在体积基准的粒度分布中，从小粒径侧起、达到体积累积90％的粒径。Dv10表示在体积基准的粒度分布中，从小粒径侧起、达到体积累积10％的粒径。粉末的粒度分布可以通过现有技术中已知的适当方法测定。适当的方法例如激光衍射或通过使用具有不同目数的套筛进行筛分。
在一些实施例中，单个颗粒基本上是锂过渡金属氧化物，且单个颗粒具有Co，其在过渡金属中的含量随粒度连续提高。
在一些实施例中，单个颗粒在过渡金属中还含有Mn，且Mn含量随粒度连续降低。
在一些实施例中，大颗粒具有能获得高Li扩散常数的接近于LiCoO 2组成的大颗粒，因此能获得足够的速率性能。大颗粒仅占正极的总表面积的小部分。因此，由在表面或在外侧部分与电解质反应放出的热量得到限制；结果，大的颗粒较少导致差的安全性。小颗粒具有含有较少Co的组成以获得提高的安全性。较低的锂扩散常数在小颗粒中可以被接受而没有明显的速率性能的损失，这是由于固态扩散路径的长度短。
在一些实施例中，小颗粒的优选组成含有较少量的Co和较大量的稳定元素，如Mn。较缓慢的Li体扩散可以被接受，但表面的稳定性高。在本申请的阴极活性材料粉末中，大颗粒的优选组成含有较大量的Co和较少量的Mn，这是由于需要快速的锂体扩散，而表面稍低的稳定性可以被接受。
在一些实施例中，在组成为Li xMO 2的单个颗粒的内部中，优选至少80w％的M是钴或镍。在一些实施例中，颗粒的内侧部分具有接近于LiCoO 2的组成。外侧部分是锂锰镍钴氧化物。
制备具有组成与尺寸相关的粉末状的电极活性材料可以通过如下方法：将至少一种含有过渡金属的沉淀物沉积在晶种颗粒上，所述晶种颗粒具有与沉淀物不同的过渡金属组成；添加控制量的锂源；并进行至少一种热处理，其中基本上所有获得的颗粒含有得自晶种的内核，该内核完全被得自沉淀物的层覆盖。
[电解液]
本申请的电化学装置中的使用的电解液包括电解质和溶解该电解质的溶剂。在一些实施例中，本申请的电化学装置中的使用的电解液进一步包括添加剂。
在一些实施例中，电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，环状碳酸酯具有3-6个碳原子。
在一些实施例中，链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2,2-二氟乙基)碳酸酯、双(2,2,2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2,2-二氟乙基甲基碳酸酯和2,2,2-三氟乙基甲基碳酸酯等。
在一些实施例中，环状羧酸酯的实例可包括，但不限于，以下中的一种或多种：γ-丁内酯和γ-戊内酯中的一种或多种。在一些实施例中，环状羧酸酯的部分氢原子可被氟取代。
在一些实施例中，链状羧酸酯的实例可包括，但不限于，以下中的一种或多种：乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯、戊酸乙酯、特戊酸甲酯和特戊酸乙酯等。在一些实施例中，链状羧酸酯的部分氢原子可被氟取代。在一些实施例中，氟取代的链状羧酸酯的实例可包括，但不限于，三氟乙酸甲酯、三氟乙酸乙酯、三氟乙酸丙酯、三氟乙酸丁酯和三氟乙酸2,2,2-三氟乙酯等。
在一些实施例中，环状醚的实例可包括，但不限于，以下中的一种或多种：四氢呋喃、2-甲基四氢呋喃、1,3-二氧戊环、2-甲基1,3-二氧戊环、4-甲基1,3-二氧戊环、1,3-二氧六环、1,4-二氧六环和二甲氧基丙烷。
在一些实施例中，链状醚的实例可包括，但不限于，以下中的一种或多种：二甲氧基甲烷、1,1-二甲氧基乙烷、1,2-二甲氧基乙烷、二乙氧基甲烷、1,1-二乙氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基甲烷、1,1-乙氧基甲氧基乙烷和1,2-乙氧基甲氧基乙烷等。
在一些实施例中，含磷有机溶剂的实例可包括，但不限于，以下中的一种或多种：磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2,2,2-三氟乙基)酯和磷酸三(2,2,3,3,3-五氟丙基)酯等。
在一些实施例中，含硫有机溶剂的实例可包括，但不限于，以下中的一种或多种：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯、乙磺酸乙酯、硫酸二甲酯、硫酸二乙酯和硫酸二丁酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，芳香族含氟溶剂包括，但不限于，以下中的一种或多种：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
在一些实施例中，本申请的电解液中使用的溶剂包括环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包括碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、或乙酸乙酯中的至少一种。在一些实施例中，本申请的电解液中使用的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合。
在电解液中加入链状羧酸酯及/或环状羧酸酯后，链状羧酸酯及/或环状羧酸酯可在电极表面形成钝化膜，从而提高电化学装置的间歇充电循环后的容量保持率。在一些实施例中，电解液中含有1％至60％的链状羧酸酯、环状羧酸酯及其组合。在一些实施例中，电解液中含有丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合，基于电解液的总重量，该组合的含量为1％至60％、10％至60％、10％至50％、20％至50％。在一些实施例中，基于电解液的总重量，电解液中含有1％至60％、10％至60％、20％至50％、20％至40％或30％的丙酸丙酯。
在一些实施例中，电解液中包含添加剂，添加剂的实例可包括，但不限于，以下的一种或多种：氟代碳酸酯、含碳碳双键的碳酸乙烯酯、含硫氧双键(含S＝O双键)的化合物和酸酐。较佳的，添加剂包括含S＝O双键的化合物。
在一些实施例中，基于电解液的总重量，添加剂的含量为0.01％至15％、0.1％至10％或1％至5％。
根据本申请的实施例，基于电解液的总重量，丙酸酯的含量为添加剂的1.5至30倍、1.5至20倍、2至20倍或5-20倍。
在一些实施例中，添加剂包含一种或多种氟代碳酸酯。在锂离子电池充电/放电时，氟代碳酸酯可与丙酸酯共同作用以在负极的表面上形成稳定的保护膜，从而抑制电解液的分解反应。
在一些实施例中，氟代碳酸酯具有式C＝O(OR 1)(OR 2)，其中R 1和R 2各自选自具有1-6个碳原子的烷基或卤代烷基，其中R 1和R 2中的至少一者选自具有1-6个碳原子的氟代烷基，且R 1和R 2任选地连同其所连接的原子形成5元至7元环。
在一些实施例中，氟代碳酸酯的实例可包括，但不限于，以下的一种或多种：氟代碳酸乙烯酯、顺式4,4-二氟碳酸乙烯酯、反式4,4-二氟碳酸乙烯酯、4,5-二氟碳酸乙烯酯、4-氟-4-甲基碳酸乙烯酯、4-氟-5-甲基碳酸乙烯酯、碳酸三氟甲基甲酯、碳酸三氟乙基甲酯和碳酸乙基三氟乙酯等。
在一些实施例中，添加剂包含一种或多种含碳碳双键的碳酸乙烯酯。含碳碳双键的碳酸乙烯酯的实例可包括，但不限于，以下的一种或多种：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、碳酸-1,2-二甲基亚乙烯酯、碳酸-1,2-二乙基亚乙烯酯、碳酸氟亚乙烯酯、碳酸三氟甲基亚乙烯酯；碳酸乙烯基亚乙酯、碳酸-1-甲基-2-乙烯基亚乙酯、碳酸-1-乙基-2-乙烯基亚乙酯、碳酸-1-正丙基-2-乙烯基亚乙酯、碳酸1-甲基-2-乙烯基亚乙酯、碳酸-1,1-二乙烯基亚乙酯、碳酸-1,2-二乙烯基亚乙酯、碳酸-1,1-二甲基-2-亚甲基亚乙酯和碳酸-1,1-二乙基-2-亚甲基亚乙酯等。在一些实施例中，含碳碳双键的碳酸乙烯酯包括碳酸亚乙烯酯，其易于获得并可实现更为优异的效果。
在一些实施例中，添加剂包含一种或多种含硫氧双键的化合物。含硫氧双键的化合物的实例可包括，但不限于，以下的一种或多种：环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯和环状亚硫酸酯等。
其中，环状硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇硫酸酯、1,2-丙二醇硫酸酯、1,3-丙二醇硫酸酯、1,2-丁二醇硫酸酯、1,3-丁二醇硫酸酯、1,4-丁二醇硫酸酯、1,2-戊二醇硫酸酯、1,3-戊二醇硫酸酯、1,4-戊二醇硫酸酯和1,5-戊二醇硫酸酯等。
链状硫酸酯的实例可包括，但不限于，以下的一种或多种：硫酸二甲酯、硫酸甲乙酯和硫酸二乙酯等。
链状磺酸酯的实例可包括，但不限于，以下的一种或多种：氟磺酸甲酯和氟磺酸乙酯等氟磺酸酯、甲磺酸甲酯、甲磺酸乙酯、二甲磺酸丁酯、2-(甲磺酰氧基)丙酸甲酯和2-(甲磺酰氧基)丙酸乙酯等。
环状磺酸酯的实例可包括，但不限于，以下的一种或多种：1,3-丙磺酸内酯、1-氟-1,3-丙磺酸内酯、2-氟-1,3-丙磺酸内酯、3-氟-1,3-丙磺酸内酯、1-甲基-1,3-丙磺酸内酯、2-甲基-1,3-丙磺酸内酯、3-甲基-1,3-丙磺酸内酯、1-丙烯-1,3-磺酸内酯、2-丙烯-1,3-磺酸内酯、1-氟-1-丙烯-1,3-磺酸内酯、2-氟-1-丙烯-1,3-磺酸内酯、3-氟-1-丙烯-1,3-磺酸内酯、1-氟-2-丙烯-1,3-磺酸内酯、2-氟-2-丙烯-1,3-磺酸内酯、3-氟-2-丙烯-1,3-磺酸内酯、1-甲基-1-丙烯-1,3-磺酸内酯、2-甲基-1-丙烯-1,3-磺酸内酯、3-甲基-1-丙烯-1,3-磺酸内酯、1-甲基-2-丙烯-1,3-磺酸内酯、2-甲基-2-丙烯-1,3-磺酸内酯、3-甲基-2-丙烯-1,3-磺酸内酯、1,4-丁磺酸内酯、1,5-戊磺酸内酯、甲烷二磺酸亚甲酯和甲烷二磺酸亚乙酯等。
链状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：亚硫酸二甲酯、亚硫酸甲乙酯和亚硫酸二乙酯等。
环状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇亚硫酸酯、1,2-丙二醇亚硫酸酯、1,3-丙二醇亚硫酸酯、1,2-丁二醇亚硫酸酯、1,3-丁二醇亚硫酸酯、1,4-丁二醇亚硫酸酯、1,2-戊二醇亚硫酸酯、1,3-戊二醇亚硫酸酯、1,4-戊二醇亚硫酸酯和1,5-戊二醇亚硫酸酯等。
在一些实施例中，添加剂包含一种或多种酸酐。酸酐的实例可包括，但不限于，环状磷酸酐、羧酸酐、二磺酸酐和羧酸磺酸酐中的一种或多种。环状磷酸酐的实例可包括，但不限于，三甲基磷酸环酐、三乙基磷酸环酐和三丙基磷酸环酐中的一种或多种。羧酸酐的实例可包括，但不限于，琥珀酸酐、戊二酸酐和马来酸酐中的一种或多种。二磺酸酐的实例可包括，但不限于，乙烷二磺酸酐和丙烷二磺酸酐中的一种或多种。羧酸磺酸酐的实例可包括，但不限于，磺基苯甲酸酐、磺基丙酸酐和磺基丁酸酐中的一种或多种。
在一些实施例中，添加剂为氟代碳酸酯与含碳碳双键的碳酸乙烯酯的组合。在一些实施例中，添加剂为氟代碳酸酯与含硫氧双键的化合物的组合。在一些实施例中，添加剂为氟代碳酸酯与具有2-4个氰基的化合物的组合。在一些实施例中，添加剂为氟代碳酸酯与环状羧酸酯的组合。在一些实施例中，添加剂为氟代碳酸酯与环状磷酸酐的组合。在一些实施例中，添加剂为氟代碳酸酯与羧酸酐的组合。在一些实施例中，添加剂为氟代碳酸酯与璜酸酐的组合。在一些实施例中，添加剂为氟代碳酸酯与羧酸璜酸酐的组合。
根据本申请的一些实施例，电解质没有特别限制，可以任意地使用作为电解质公知的物质。在锂二次电池的情况下，通常使用锂盐。电解质的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiTaF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸 锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、CH 2FSO 3Li、CHF 2SO 3Li、CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，电解质选自LiPF 6、LiSbF 6、FSO 3Li、CF 3SO 3Li、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3、二氟草酸硼酸锂、双(草酸)硼酸锂或二氟双(草酸根合)磷酸锂，其有助于改善电化学装置的输出功率特性、高倍率充放电特性、高温保存特性和循环特性等。
电解质的含量没有特别限制，只要不损害本申请的效果即可。示例性的，在一些实施例中，电解液中的锂的总摩尔浓度为大于0.3mol/L以上、大于0.4mol/L或大于0.5mol/L。在一些实施例中，电解液中的锂的总摩尔浓度为小于3mol/L、小于2.5mol/L或小于2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由单氟磷酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的总重量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的总重量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为 小于20％或小于10％。在一些实施例中，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量在上述任意两个数值所组成的范围内。
在一些实施例中，电解质包含选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的一种以上物质和除此以外的一种以上的盐。作为除此以外的盐，可以举出在上文中例示的锂盐，在一些实施例中为LiPF 6、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3。在一些实施例中，除此以外的盐为LiPF 6。
在一些实施例中，基于电解质的总重量，除此以外的盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的总重量，除此以外的盐的含量为小于20％、小于15％或小于10％。在一些实施例中，除此以外的盐的含量在上述任意两个数值所组成的范围内。具有上述含量的除此以外的盐有助于平衡电解液的电导率和粘度。
在电解液中，除了含有上述溶剂、添加剂和电解质盐以外，可以根据需要含有负极被膜形成剂、正极保护剂、防过充电剂等额外添加剂。作为添加剂，可使用一般在非水电解质二次电池中使用的添加剂，其实例可包括，但不限于，碳酸亚乙烯酯、琥珀酸酐、联苯、环己基苯、2，4-二氟苯甲醚、丙烷磺内酯、丙烯磺内酯等。这些添加剂可以单独使用或任意组合使用。另外，电解液中的这些添加剂的含量没有特别限制，可以根据该添加剂的种类等适当地设定即可。在一些实施例中，基于电解液的总重量，添加剂的含量为小于5％、在0.01％至5％的范围内或在0.2％至5％的范围内。
[隔离膜]
为了防止短路，在正极与负极之间通常设置有隔离膜。这种情况下，本申请的电解液通常渗入该隔离膜而使用。
对隔离膜的材料及形状没有特别限制，只要不显著损害本申请的效果即可。隔离膜可为由对本申请的电解液稳定的材料所形成的树脂、玻璃纤维、无机物等。在一些实施例中，隔离膜包括保液性优异的多孔性片或无纺布状形态的物质等。树脂或玻璃纤维隔离膜的材料的实例可包括，但不限于，聚烯烃、芳香族聚酰胺、聚四氟乙烯、聚醚砜、玻璃过滤器等。在一些实施例中，隔离膜的材料为玻璃过滤器。在一些实施例中，聚烯烃为聚乙烯或聚丙烯。在一些实施例中，聚烯烃为聚丙烯。上述隔离膜的材料可以单独使用或任意组合使用。
隔离膜还可为上述材料层积而成的材料，其实例包括，但不限于，按照聚丙烯、聚乙烯、聚丙烯的顺序层积而成的三层隔离膜等。
无机物的材料的实例可包括，但不限于，氧化铝、二氧化硅等氧化物、氮化铝、氮化硅等氮化物、硫酸盐(例如，硫酸钡、硫酸钙等)。无机物的形式可包括，但不限于，颗粒状或纤维状。
隔离膜的形态可为薄膜形态，其实例包括，但不限于，无纺布、织布、微多孔性膜等。在薄膜形态中，隔离膜的孔径为0.01μm至1μm，厚度为5μm至50μm。除了上述独立的薄膜状隔离膜以外，还可以使用下述隔离膜：通过使用树脂类的粘合剂在正极和/或负极的表面形成含有上述无机物颗粒的复合多孔层而形成的隔离膜，例如，将氟树脂作为粘合剂使90％粒径小于1μm的氧化铝颗粒在正极的两面形成多孔层而形成的隔离膜。
隔离膜的厚度是任意的。在一些实施例中，隔离膜的厚度为大于1μm、大于5μm或大于8μm。在一些实施例中，隔离膜的厚度为小于50μm、小于40μm或小于30μm。在一些实施例中，隔离膜的厚度在上述任意两个数值所组成的范围内。当隔离膜的厚度在上述范围内时，则可以确保绝缘性和机械强度，并可以确保电化学装置的倍率特性和能量密度。
在使用多孔性片或无纺布等多孔质材料作为隔离膜时，隔离膜的孔隙率是任意的。在一些实施例中，隔离膜的孔隙率为大于20％、大于35％或大于45％。在一些实施例中，隔离膜的孔隙率为小于90％、小于85％或小于75％。在一些实施例中，隔离膜的孔隙率在上述任意两个数值所组成的范围内。当隔离膜的孔隙率在上述范围内时，可以确保绝缘性和机械强度，并可以抑制膜电阻，使电化学装置具有良好的倍率特性。
隔离膜的平均孔径也是任意的。在一些实施例中，隔离膜的平均孔径为小于0.5μm或小于0.2μm。在一些实施例中，隔离膜的平均孔径为大于0.05μm。在一些实施例中，隔离膜的平均孔径在上述任意两个数值所组成的范围内。若隔离膜的平均孔径超过上述范围，则容易发生短路。当隔离膜的平均孔径在上述范围内时，在防止短路的同时可抑制了膜电阻，使电化学装置具有良好的倍率特性。
[电化学装置组件]
电化学装置组件包括电极组、集电结构、外装壳体和保护元件。
电极组
电极组可以是由上述正极和负极隔着上述隔离膜层积而成的层积结构、以及上述正极和负极隔着上述隔离膜以漩涡状卷绕而成的结构中的任一种。在一些实施例中，电极组的质量在电池内容积中所占的比例(电极组占有率)为大于40％或大于50％。在一些实施例中，电极组占有率为小于90％或小于80％。在一些实施例中，电极组占有率在上述任意两个数值所组成的范围内。当电极组占有率在上述范围内时，可以确保电化学装置的容量，同时可以抑制与内部压力上升相伴的反复充放电性能及高温保存等特性的降低，进而可以防止气体释放阀的工作。
集电结构
集电结构没有特别限制。在一些实施例中，集电结构为降低配线部分及接合部分的电阻的结构。当电极组为上述层积结构时，适合使用将各电极层的金属芯部分捆成束而焊接至端子上所形成的结构。电极面积增大时，内部电阻增大，因而在电极内设置2个以上的端子而降低电阻也是适合使用的。当电极组为上述卷绕结构时，通过在正极和负极分别设置2个以上的引线结构，并在端子上捆成束，从而可以降低内部电阻。
外装壳体
外装壳体的材质没有特别限制，只要是对于所使用的电解液稳定的物质即可。外装壳体可使用，但不限于，镀镍钢板、不锈钢、铝或铝合金、镁合金等金属类、或者树脂与铝箔的层积膜。在一些实施例中，外装壳体为铝或铝合金的金属或层积膜。
金属类的外装壳体包括，但不限于，通过激光焊接、电阻焊接、超声波焊接将金属彼此熔敷而形成的封装密闭结构；或者隔着树脂制垫片使用上述金属类形成的铆接结构。使用上述层积膜的外装壳体包括，但不限于，通过将树脂层彼此热粘而形成的封装密闭结构等。为了提高密封性，还可以在上述树脂层之间夹入与层积膜中所用的树脂不同的树脂。在通过集电端子将树脂层热粘而形成密闭结构时，由于金属与树脂的接合，可使用具有极性基团的树脂或导入了极性基团的改性树脂作为夹入的树脂。另外，外装体的形状也是任意的，例如可以为圆筒形、方形、层积型、纽扣型、大型等中的任一种。
保护元件
保护元件可以使用在异常放热或过大电流流过时电阻增大的正温度系数(PTC)、温度熔断器、热敏电阻、在异常放热时通过使电池内部压力或内部温度急剧上升而切断在电路中流过的电流的阀(电流切断阀)等。上述保护元件可选择在高电流的常规 使用中不工作的条件的元件，亦可设计成即使不存在保护元件也不至于发生异常放热或热失控的形式。
[应用]
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
在本申请的一些实施例中，以锂离子二次电池为例，将正极极片、隔离膜、负极极片按顺序卷绕或堆叠成电极件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子二次电池。然后，对制备的锂离子二次电池进行性能测试及循环测试。本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请另提供了一种电子设备，其包括根据本申请的电化学装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子设备。在一些实施例中，本申请的电化学装置可用于，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。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
实施例1
一、锂离子电池的制备
1、负极的制备
将第一导电剂、第一粘结剂按质量比例与和去离子水混合，搅拌均匀，得到底涂浆料。将该底涂浆料涂布在12μm的铜箔上50℃烘烤5min。将活性物质、第二粘结剂 和第二导电剂按质量比例与和去离子水混合，搅拌均匀，得到负极活性物质浆料。将该负极活性物质浆料涂布在底涂层上。干燥，冷压，再经过裁片、焊接极耳，得到负极。根据以下实施例和对比例的条件设置负极，使其具有相应组成和参数。
2、正极的制备
将正极材料钴酸锂、导电材料(Super-P)和聚偏氟乙烯(PVDF)按照95％：2％：3％的质量比例与N-甲基吡咯烷酮(NMP)混合，搅拌均匀，得到正极浆料。将该正极浆料涂布在12μm的铝箔上，干燥，冷压，再经过裁片、焊接极耳，得到正极。
3、电解液的制备
在干燥氩气环境下，将EC、PC、PP和DEC(重量比1：1：1：1)混合，加入LiPF 6混合均匀，形成基础电解液，其中LiPF 6的浓度为1.15mol/L。
在基础电解液中按质量百分比添加如上式1所示化合物，以研究其含量关系对锂离子电池性能的影响。
4、隔离膜的制备
以聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将得到的正极、隔离膜和负极按次序卷绕，置于外包装箔中，留下注液口。从注液口灌注电解液，封装，再经过化成、容量等工序制得锂离子电池。
在实施例2～6中，正极的制备、电解液的制备、隔离膜的制备以及锂离子电池的制备的方法均与实施例1相同，实施例2～6与实施例1的区别仅在于：负极极片中底涂层的组成不同。
在对比例1中，正极的制备、电解液的制备、隔离膜的制备以及锂离子电池的制备的方法均与实施例1～6相同，对比例1与实施例1～6的区别仅在于：对比例1中的负极中不含有底涂层。
在实施例7～9中，正极的制备、电解液的制备、隔离膜的制备以及锂离子电池的制备的方法均与实施例1相同，实施例2～6与实施例1的区别仅在于：负极极片中底涂层的组成不同，以及负极活性物质层的组成不同。
在对比例2中，正极的制备、电解液的制备、隔离膜的制备以及锂离子电池的制备的方法均与实施例7～9相同，对比例2与实施例7～9的区别仅在于：对比例2中的负极中不含有底涂层。
实施例1～9以及对比例1～2的具体负极组成参见下表1所示。
实施例和对比例的各项性能参数的测定方法如下。
二、测试方法
1、粘结力测试方法
(1)取干燥后的极片，用刀片截取宽30mm×长度为100-160mm的试样。
(2)将专用双面胶贴于钢板上，胶带宽度20mm×长度90-150mm。
(3)将第(1)步截取的极片试样贴在双面胶上，测试面朝下。
(4)将宽度与极片等宽，长度大于试样长度80-200mm的纸带插入极片下方，并且用皱纹胶固定。
(5)打开三思拉力机电源，指示灯亮，调整限位块到合适位置。
2、膜片电阻测试方法
(1)膜片电阻测试采用元能科技设备，膜片电阻仪测试。
(2)设备电源保持220V，气压大于0.7MPa。
(3)将剪裁好的极片(60×80mm)平放置在载样台中。
(4)然后将载样台放置设备测试腔中，开始测试。
(5)整个测试过程中，测试气压设置为“0”。
3、循环稳定性的测试方法
在25℃下，将锂离子电池以1C恒流充电至4.45V，然后以4.45V恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行循环直至循环后容量保持率为80％，并记录循环次数。“1C”是指在1小时内将锂离子电池容量完全放完的电流值。
通过下式计算锂离子电池的循环后容量保持率：
循环后容量保持率＝(对应循环次数的放电容量/首次循环的放电容量)×100％。
4、变形测试方法
在25℃下，将锂离子电池以1C恒流充电至4.45V，然后以4.45V恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行500次循环。“1C”是指在1小时内将锂离子电池容量完全放完的电流值。
循环后将电池拆解，取出负极极片，观察膜片是否脱碳，脱碳则为变形，未脱碳则为未变形。
5、孔隙率的测试方法
极片孔隙率测试方法全部采用压汞仪，具体操作如下：
取一侧表面完全覆盖膜片的极片作为样品；
预计样品的密度和孔隙率，选择合适的膨胀计
样品先放烘箱烘烤2h，去除水分。分析前称量样品重量
样品装入膨胀计，密封好后称量重量，此为样品+膨胀计重量
将膨胀计装入低压站，编辑好低压文件开始低压分析
低压分析结束后，将膨胀计取出称量重量，此为样品+膨胀计+汞的重量
将膨胀计装入高压站，注意将膨胀计固定后再将高压仓头旋入，旋至底部并赶气泡
开始高压分析，按提示松开或旋紧排空阀
高压分析结束，将膨胀计取出清洗，测试结束。
此时测得的为极片孔隙率X；
将极片孔隙率X换算为膜片孔隙率V的方法如下：
在极片表面随机选择10处，测量极片的平均厚度为H；
利用有机溶剂将极片表面的膜片洗除，在集流体表面随机选择10处，测量集流体的平均厚度为h；
膜片孔隙率V＝极片孔隙率X×H/(H-h)。
6、倍率性能的测试方法
在25℃下，将锂离子电池以1C恒流充电到4.45V，然后以4.45V恒压充电至电流为0.05C，搁置5min后，以0.2C恒流放电至截至电压3V，此时将实际放电容量记为D0，然后以1C恒流充电到4.45V，再以恒压4.45V充电至电流为0.05C，最后以2C放电至截至电压3V，记录此时的实际放电容量为D1。锂离子电池的倍率性能＝[(D1-D0)/D0]×100％。
7、颗粒状导电剂平均粒径的测试方法
将样品铺展在测试样品台上，通过扫描电子显微镜(SEM)或透射电子显微镜(TEM)拍摄样品照片，然后，使用图像解析软件，从SEM或TEM照片中随机地选出10个颗粒状导电剂，求出这些颗粒状导电剂各自的面积，接着，假设颗粒状导电剂是球形，通过以下公式求出各自的粒径R(直径)：
R＝2×(S/π) 1/2；其中，S为颗粒状导电剂的面积；
对3张SEM或TEM图像进行求出上述颗粒状导电剂粒径R的处理，并将所得30(10×3)个颗粒状导电剂的粒径进行算数平均，从而求得所述颗粒状导电剂的平均粒径D。
8、管状导电剂平均直径的测试方法
将样品铺展在测试样品台上，通过扫描电子显微镜(SEM)或透射电子显微镜(TEM)拍摄样品照片，然后，使用图像解析软件，从SEM或TEM照片中随机地选出10个管状导电剂，从各个管状导电剂照片的两侧管壁上任选5个点，在各点沿垂直于所在管壁的延伸方向作垂线，至与另一侧管壁相交的平均距离为该管状导电剂的管径R；
对3张SEM或TEM图像进行求出上述管状导电剂管径R的处理，并将所得30(10×3)个管状导电剂的管径进行算数平均，从而求得所述管状导电剂的平均管径D。
三、测试结果
表1列出了实施例1～9以及对比例1～2中负极极片组成、粘结力、膜片电阻以及相应锂离子电池的性能。压实密度PD均设置为1.30g/cm 3。
表1
Figure PCTCN2021123330-appb-000005
从表1的数据中可以看出，具有底涂层的实施例1-9，相对于不含底涂层的对比例1-2，其粘结力大幅提高，相应的，其循环、形状稳定性也大幅提升，其原因在于，一 方面，底涂层的存在相当于提高铜箔的表面缺陷，增强了活性材料层与极片之间的铆合作用，增加了底涂层与铜箔之间的结合力，从而提高了膜片整体与集流体的粘结力，降低了膜片脱落的风险；另一方面，底涂层的存在能够起到很好的缓冲作用，当负极活性物质在嵌入锂离子发生膨胀时，底涂层避免了膨胀的活性物质直接向集流体表面施加作用力，若直接向集流体表面施加作用力，由于该方向集流体固定并无法发生位移，则活性物质只能整体向膜片外表面膨胀，而当脱出锂离子收缩时，活性物质各部分倾向于同步收缩/或电子导电性更好的内侧可能收缩的更快，则会使得原来与集流体表面紧密接触的活性物质与集流体分离，从而导致膜片的脱落，使得内阻升高，循环性能变差。进一步地，底涂层粘结剂具有极性官能团(羧基)的实施例2、6-9能够显著提高膜片与集流体的粘结力，从而使得极片的形状稳定性更加稳定。特别地，使用底涂层粘结剂具有羧基的实施例7-9能够保证粘结力500N/m以上，即使对于高膨胀的Si基活性物质，同样能够保持优异的形状稳定性。
另外，由图3和图4的对比也可以看出，本申请实施例1-提供的负极极片的形状稳定性相比于对比例1-2的负极极片的形状稳定性大幅提升。
在实施例10～14中，与实施例2的区别仅在于：负极极片的膜片的压实密度(以压密表示)和膜片的孔隙率不同。
表2列出了实施例2、10～14中，在相同负极膜片组成、不同压密下，膜片对应的孔隙率以及相应锂离子电池的循环性能、倍率性能。
表2
  压密g/cm 3 孔隙率 膨胀率 循环次数 倍率性能
实施例2 1.30 37.6％ 4.3％ 690 90％
实施例10 1.60 35.3％ 5％ 650 90％
实施例11 1.70 30.7％ 6％ 600 80％
实施例12 1.75 28.2％ 6.7％ 550 70％
实施例13 1.80 25.6％ 7％ 420 65％
实施例14 1.83 21.3％ 8％ 380 48％
从表2的数据中可以看出，膜片的压实密度为1.30至1.80g/cm 3的实施例2、10-13，相比于压密为1.83g/cm 3的实施例14，具有更加优异的循环稳定性和倍率性能。一方面，压密为1.30至1.80g/cm 3的实施例提供了合适的孔隙率，能够缓冲循环时由于锂离子的嵌入和脱出所带来的体积膨胀和收缩，降低了极片脱膜的风险。另一方面， 适当的压密也降低了对底涂层的压力，保证了活性物质层与集流体间存在底涂层，避免由于过高压力将底涂层挤压入活性物质层的缝隙中，从而起不到底涂层的铆合和缓冲作用。此外，较优的孔隙率，能够与电解液充分接触，保证了电池具有更优的倍率性能。
在实施例15～23中，与实施例4的区别仅在于：负极极片的底涂层中，第一导电剂(SP)的颗粒度与底涂层厚度的比例关系不同。在实施例24～32中，与实施例2的区别仅在于：负极极片的底涂层中，第一导电剂(CNT)的管直径与底涂层厚度的比例关系不同。
表3列出了实施例15～30中，组成分别同实施例4(SP)、实施例2(CNT)，底涂层中第一导电剂颗粒平均粒径/管平均直径与底涂厚度关系对相应极片的粘接力、膜片电阻以及相应锂离子电池循环稳定性的影响。
表3
Figure PCTCN2021123330-appb-000006
Figure PCTCN2021123330-appb-000007
从表3的数据中可以看出，D/H在0.5～1.25范围内的实施例16-19、21-23、25-31相比于在上述范围外的实施例15、20、24、32具有更加优异的膜片电阻以及循环稳定性。一方面，合适的颗粒度(管直径)/底涂厚度能够避免底涂层中过多小颗粒导电剂之间的堆叠，避免了存在过多的界面电阻，进而使得膜片电阻降低、提高了循环稳定性；另一方面，过大的颗粒度(管直径)/底涂厚度，会导致导电剂在底涂层中的分布不均，进而导致膜片电阻升高。
在实施例33～37中，与实施例2的区别仅在于：电解液中含有式1所示的含S＝O双键的化合物，且式1所示的含S＝O双键的化合物在电解液中的质量百分含量y与膜片孔隙率V满足一定的关系。
表4列出了实施例2、33～37中，式1所示的含S＝O双键的化合物在电解液中的质量百分含量y与膜片孔隙率V的关系对锂离子电池电化学性能的影响。
表4
  式1-1化合物含量y 孔隙率V y/V 循环次数 倍率性能
实施例2 0％ 37.6％ 0 690 90％
实施例33 0.5％ 37.6％ 0.013 720 92％
实施例34 1％ 37.6％ 0.026 730 93％
实施例35 2％ 37.6％ 0.053 750 95％
实施例36 2.5％ 37.6％ 0.066 750 93％
实施例37 3％ 37.6％ 0.080 700 91％
从表4的数据中可以看出，含S＝O双键的化合物含量与膜片孔隙率满足关系0.01≤y/V≤0.07，具有显著提高的循环稳定性和倍率性能。其原因在于，适量的式1所示的含S＝O双键的化合物能够在极片表面进一步形成完整、稳定的高离子导通性固体 电解质膜，从而进一步提高离子电导率、改善倍率性能。而当式1所示的含S＝O双键的化合物过量时，即y/V>0.07，形成的固体电解质膜过厚，反而不利于锂离子的传输。
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。
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 (11)

  1. 一种极片，其特征在于，包括：
    集流体；以及
    膜片，所述膜片包括设置于所述集流体表面的底涂层和设置于所述底涂层表面的活性物质层，所述底涂层包括第一粘结剂和第一导电剂；
    其中，所述膜片与所述集流体的粘结力为≥20N/m。
  2. 根据权利要求1所述的极片，其特征在于，所述底涂层的厚度为100nm至2μm；优选为100nm至1000nm。
  3. 根据权利要求1所述的极片，其特征在于，所述极片具有以下特征中的至少一个：
    a.所述膜片与所述集流体的粘结力为≥80N/m；
    b.所述膜片的压实密度为1.30g/cm 3至1.80g/cm 3；
    c.所述膜片的孔隙率为20％至50％；
    d.所述膜片的电阻为3mΩ至50mΩ。
  4. 根据权利要求1所述的极片，其特征在于，所述极片具有以下特征中的至少一个：
    e.所述底涂层中的第一粘结剂的质量含量为20％至95％；所述底涂层中的第一导电剂的质量含量为5％至80％；
    f.所述第一粘结剂包括碳碳双键、羧基、羰基、碳氮单键、羟基、酯基、酰基或芳基官能团中的至少一种；
    g.所述第一粘结剂包括丁苯橡胶、聚丙烯酸、聚乙烯吡咯烷酮或聚丙烯酰胺中的至少一种；
    h.所述第一导电剂包括导电炭黑、柯琴黑、单壁碳纳米管或多壁碳纳米管中的至少一种。
  5. 根据权利要求1所述的极片，其特征在于，所述第一导电剂的颗粒平均粒径或管平均直径D与所述底涂层厚度H的关系满足：
    D与H的比值D/H为0.25～1.5；优选为0.5～1.25。
  6. 根据权利要求1所述的极片，其特征在于，
    所述活性物质层包括活性物质和第二粘结剂；其具有以下特征中的至少一个：
    i.所述活性物质包括石墨类材料或硅基材料中的至少一种，所述硅基材料包括硅、硅氧化物、硅碳复合物或硅合金中的至少一种；
    j.所述活性物质层包括质量含量为80％至99％的活性物质、0.8％至20％的第二粘结剂和0至5％的第二导电剂。
  7. 一种电化学装置，包括：
    正极极片；
    负极极片；
    隔离膜，设置于所述正极极片和所述负极极片之间；
    其特征在于，所述负极极片为根据权利要求1-6任一项所述的极片。
  8. 根据权利要求7所述的电化学装置，其特征在于，所述电化学装置包括电解液，所述电解液包括含S＝O双键的化合物。
  9. 根据权利要求8所述的电化学装置，其特征在于，所述电化学装置具有以下特征中的至少一个：
    k.所述含S＝O双键的化合物包括环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯或环状亚硫酸酯中的至少一种；
    l.所述含S＝O双键化合物包括式1所示化合物中的至少一种，
    Figure PCTCN2021123330-appb-100001
    其中：W选自
    Figure PCTCN2021123330-appb-100002
    L选自单键或亚甲基；
    m为1至4的整数；
    n为0至2的整数；且
    p为0至6的整数。
  10. 根据权利要求9所述的电化学装置，所述含S＝O双键的化合物在所述电解液中的质量百分含量y与膜片孔隙率V的关系满足：0.01≤y/V≤0.07。
  11. 一种电子设备，其特征在于，包括权利要求7-10任一项所述的电化学装置。
PCT/CN2021/123330 2020-10-15 2021-10-12 极片及包含其的电化学装置和电子设备 WO2022078340A1 (zh)

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