WO2022262612A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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Publication number
WO2022262612A1
WO2022262612A1 PCT/CN2022/097271 CN2022097271W WO2022262612A1 WO 2022262612 A1 WO2022262612 A1 WO 2022262612A1 CN 2022097271 W CN2022097271 W CN 2022097271W WO 2022262612 A1 WO2022262612 A1 WO 2022262612A1
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region
negative electrode
positive electrode
impedance
electrode coating
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PCT/CN2022/097271
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English (en)
French (fr)
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朱珊
关婷
吴飞
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宁德新能源科技有限公司
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Priority to EP22824092.5A priority Critical patent/EP4207351A1/en
Priority to JP2022554203A priority patent/JP2023534339A/ja
Publication of WO2022262612A1 publication Critical patent/WO2022262612A1/zh
Priority to US18/193,742 priority patent/US20230261200A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
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    • H01M4/623—Binders being polymers fluorinated polymers
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    • H01M10/052—Li-accumulators
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M4/04—Processes of manufacture in general
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    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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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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    • H01M4/139—Processes of manufacture
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/366—Composites as layered products
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
    • 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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    • H01M4/624—Electric conductive fillers
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    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemical energy storage, in particular to electrochemical devices and electronic devices.
  • An embodiment of the present application provides an electrochemical device, the electrochemical device includes a positive electrode sheet, and the positive electrode sheet includes a positive electrode current collector, a positive electrode active material layer, and a positive electrode coating.
  • the positive electrode current collector includes a first region, a second region and a third region located between the first region and the second region.
  • the positive electrode active material layer includes a first positive electrode active material, and the positive electrode active material layer includes a first part, a second part and a third part respectively arranged in the first area, the second area and the third area.
  • the positive electrode coating includes fourth and fifth portions disposed in the first region and the second region, respectively.
  • the fourth portion is located between the first portion and the first area, or the first portion is located between the fourth portion and the first area.
  • the fifth portion is located between the second portion and the second area, or the second portion is located between the fifth portion and the second area.
  • the combined impedance of the first part and the fourth part is greater than the impedance of the third part, and the combined impedance of the second part and the fifth part is greater than the impedance of the third part.
  • the ratio of the combined impedance of the fourth part and the first part to the impedance of the third part is 1.02 to 5, and the ratio of the combined impedance of the fifth part and the second part to the impedance of the third part is 1.02 to 5 .
  • the ratio of the width of the fourth portion to the width of the positive active material layer is 0.01 to 0.25, and the ratio of the width of the fifth portion to the width of the positive active material layer is 0.01 to 0.25.
  • the thickness of the fourth portion is greater than 0.5 ⁇ m and less than 8 ⁇ m.
  • the thickness of the fifth portion is greater than 0.5 ⁇ m and less than 8 ⁇ m.
  • the thickness of the third portion is greater than 20 ⁇ m and less than 200 ⁇ m.
  • the positive electrode coating includes at least one of conductive carbon, ceramic or lithium iron phosphate and a first binder. In some embodiments, the mass content of the first binder in the positive electrode coating is greater than 20%.
  • the first binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethylacrylate, polytetrafluoroethylene, carboxymethyl At least one of sodium cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber or polyvinyl alcohol.
  • the conductive carbon includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene, acetylene black, or carbon nanofibers.
  • the combined thickness of the first portion and the fourth portion is the same as the thickness of the third portion
  • the combined thickness of the second portion and the fifth portion is the same as the thickness of the third portion.
  • the electrochemical device includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer, and a negative electrode coating.
  • the negative electrode current collector includes a first region, a second region and a third region located between the first region and the second region.
  • the negative electrode active material layer includes a first negative electrode active material, and the negative electrode active material layer includes a first part, a second part and a third part respectively arranged in the first area, the second area and the third area.
  • the negative electrode coating is located between the third portion and the third area, or the third portion is located between the negative electrode coating and the third area.
  • the combined impedance of the negative electrode coating and the third portion is greater than the impedance of the first portion and greater than the impedance of the second portion.
  • the ratio of the impedance of the first portion to the combined impedance of the negative electrode coating and the third portion is 0.5 to 0.99
  • the ratio of the impedance of the second portion to the combined impedance of the negative electrode coating and the third portion is 0.5 to 0.99
  • the ratio of the width of the negative electrode coating layer to the width of the negative electrode active material layer is 0.75 to 0.99.
  • the thickness of the negative electrode coating is greater than 0.5 ⁇ m and less than 8 ⁇ m.
  • the negative electrode coating includes at least one of conductive carbon or ceramic and a first binder. In some embodiments, the thickness of both the first portion and the second portion is greater than 20 ⁇ m and less than 200 ⁇ m.
  • the mass content of the first binder in the negative electrode coating is greater than 20%.
  • the first binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethylacrylate, polytetrafluoroethylene, carboxymethyl At least one of sodium cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber or polyvinyl alcohol.
  • the conductive carbon includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene, acetylene black, or carbon nanofibers.
  • the combined thickness of the third portion and the negative electrode coating is the same as the thickness of the first portion, and the combined thickness of the third portion and the negative electrode coating is the same as the thickness of the second portion.
  • Some embodiments of the present application provide an electronic device, including any one of the above electrochemical devices.
  • the embodiment of the present application optimizes the lithium intercalation uniformity of the pole piece during the charging process and improves the edge analysis of the pole piece by providing the above-mentioned positive electrode coating in the positive pole piece, or setting the above-mentioned negative electrode coating in the negative pole piece.
  • the lithium problem broadens the lithium analysis window, which is conducive to the improvement of the rate performance of the electrochemical device.
  • FIG. 1 shows a cross-sectional view of a positive electrode tab 10 of an electrochemical device according to some embodiments of the present application, taken along a plane defined by its long width and thickness directions.
  • FIG. 2 shows a cross-sectional view of a positive electrode tab 10 of an electrochemical device according to another embodiment of the present application, taken along a plane defined in its width and thickness directions.
  • FIG. 3 shows a cross-sectional view of a negative electrode tab 12 of an electrochemical device according to some embodiments of the present application, taken along a plane defined in its width and thickness directions.
  • FIG. 4 shows a cross-sectional view of a negative electrode tab 12 of an electrochemical device according to another embodiment of the present application, taken along a plane defined in its width and thickness directions.
  • FIG. 1 and 2 illustrate cross-sectional views of a positive electrode tab 10 of an electrochemical device according to some embodiments of the present application, taken along a plane defined in its width and thickness directions.
  • the embodiment of the present application provides an electrochemical device, which includes a positive pole piece 10 as shown in FIG. .
  • FIG. 1 shows that the positive electrode active material layer 102 and the positive electrode coating 103 are located on both sides of the positive electrode current collector 101, this is only exemplary, and the positive electrode active material layer 102 and the positive electrode coating 103 may only be located on both sides of the positive electrode current collector 101. on one side of the current collector 101.
  • the positive electrode collector 101 includes a first region 1011, a second region 1012, and a first region 1011 between the second region 1012. Three area 1013.
  • the positive electrode active material layer 102 includes a first positive electrode active material, and the positive electrode active material layer 102 includes a first part 1021 and a second part 1022 respectively disposed in the first region 1011, the second region 1012 and the third region 1013. and third part 1023.
  • the positive electrode coating 103 may or may not include a second positive electrode active material, and the positive electrode coating 103 includes a fourth portion 1031 and a fifth portion 1032 respectively disposed in the first region 1011 and the second region 1012 .
  • the first portion 1021 is located between the fourth portion 1031 and the first region 1011 .
  • the fourth portion 1031 is located between the first portion 1021 and the first region 1011 .
  • the second portion 1022 is located between the fifth portion 1032 and the second region 1012 .
  • the fifth portion 1032 is located between the second portion 1022 and the second region 1012 . Therefore, the difference between FIG. 2 and FIG. 1 lies in the relative positions of the positive electrode active material layer 102 and the positive electrode coating 103 , and refer to FIG. 1 for other details.
  • the positive electrode current collector 101 may be continuous as a whole, and the positive electrode active material layer 102 may be continuous as a whole.
  • the combined impedance of the first portion 1021 and the fourth portion 1031 is greater than the impedance of the third portion 1023
  • the combined impedance of the second portion 1022 and the fifth portion 1032 is greater than the impedance of the third portion 1023 . That is, the impedance of the edge region of the positive electrode sheet 10 is greater than the impedance of the middle region of the positive electrode sheet 10 . In this way, the rate of lithium ions extracted from the edge region of the positive electrode sheet 10 (for example, the combination of the first part 1021 and the fourth part 1031 or the combination of the second part 1022 and the fifth part 1032) can be reduced, thereby reducing the charging rate. process the charging current density in the edge region.
  • the edge of the corresponding negative electrode sheet is relatively more prone to lithium deposition, and the reduction of the charging current density in the edge area can optimize the lithium intercalation uniformity of the corresponding negative electrode sheet during the charging process, improving the edge of the negative electrode sheet.
  • the lithium problem broadens the lithium analysis window, which is conducive to the improvement of the rate performance of the electrochemical device.
  • the impedance test method is as follows, which can be DC impedance or AC impedance. Regardless of the test method, the measured impedance is within the above impedance range.
  • the specific impedance test method is as follows. Test of DC impedance: Take out the corresponding area to be tested (take them out together for testing when measuring the combined impedance of the two parts) as the positive electrode and assemble it into a lithium-ion battery. Then install it on the Xinwei machine for charging and discharging, and monitor the voltage and current of the lithium-ion battery to obtain the DC impedance value of the lithium-ion battery.
  • the lithium-ion battery is charged at a constant current to a full charge voltage with a current of 0.5C, and then charged at a constant voltage to 0.05C. Then discharge with 1C current for 30min to make the lithium-ion battery in the state of 50% charge ratio, record the voltage V1, let it stand for 60min, and record the voltage V2. Discharge at a current of 0.1C for 10s, and record the voltage V3. Then discharge with a current of 1C for 1s, and record the voltage V4.
  • Calculate the DC resistance R T and DCR of the lithium-ion battery according to the following formula:
  • the test method of AC impedance Take out the corresponding area to make a symmetrical battery, that is, a battery composed of a positive pole piece to a positive pole piece, and a negative pole piece to a negative pole piece.
  • the EIS test was carried out on the symmetrical battery by using an electrochemical workstation, wherein the test temperature was 25°C, the test frequency range was 30mHz-500kHz, and the disturbance voltage was 5mV. After obtaining the EIS spectrum, read the AC impedance Rz of the symmetrical battery from the spectrum.
  • the ratio of the combined impedance of the fourth portion 1031 and the first portion 1011 to the impedance of the third portion 1023 is 1.02 to 5. In some embodiments, the ratio of the combined impedance of the fifth portion 1032 and the second portion 1022 to the impedance of the third portion 1023 is 1.02 to 5. That is, the ratio of the impedance of the edge region of the positive electrode tab 10 to the impedance of the middle region is 1.02 to 5. Because when the impedance difference between the edge region and the middle region is too large, the rate performance of the middle region (that is, the third part 1023 ) will be affected, which may affect the improvement of the overall rate performance of the electrochemical device.
  • the ratio of the width w1 of the fourth portion 1031 to the width W of the positive electrode active material layer 102 is 0.01 to 0.25. In some embodiments, the ratio of the width w2 of the fifth portion 1032 to the width W of the positive electrode active material layer 102 is 0.01 to 0.25. If the ratio is too small, the fourth part 1031 or the fifth part 1032 has a relatively limited effect on improving the lithium analysis; if the ratio is too large, the overall impedance of the positive electrode sheet 10 may be excessively increased, which is not conducive to electrochemical Improvement of the magnification performance of the device.
  • the width w1 of the fourth portion 1031 is the same as the width w2 of the fifth portion 1032 (as in the following specific embodiments), but the present application is not limited thereto, and the width w1 and the width w2 may also be different. It should be understood that, due to the existence of errors, the same here means that the difference within 5% can be considered the same.
  • the thickness h1 of the fourth portion 1031 is greater than 0.5 ⁇ m and less than 8 ⁇ m. In some embodiments, the thickness h2 of the fifth portion 1032 is greater than 0.5 ⁇ m and less than 8 ⁇ m. If the thickness h1 of the fourth part 1031 or the thickness h2 of the fifth part 1032 are too small, the improvement effect of the fourth part 1031 or the fifth part 1032 on the analysis of lithium is relatively limited; if the thickness h1 of the fourth part 1031 or the fifth part If the thickness h2 of 1032 is too large, the overall impedance of the positive pole piece 10 may be excessively increased, which is not conducive to the improvement of the rate performance of the electrochemical device.
  • the thickness h1 of the fourth part 1031 is the same as the thickness h2 of the fifth part 1032 (as in the following specific embodiments), but the present application is not limited thereto, and the thickness h1 and h2 may also be different. It should be understood that, due to the existence of errors, the same here means that the difference within 5% can be considered the same.
  • the third portion 1023 has a thickness greater than 20 ⁇ m and less than 200 ⁇ m. If the thickness of the third part 1023 is too small, it is not conducive to improving the energy density of the electrochemical device; if the thickness of the third part 1023 is too large, the lithium ion transmission path of the part of the positive electrode active material layer 102 close to the positive electrode current collector 101 is relatively weak. It is not conducive to the improvement of the rate performance of the electrochemical device.
  • the anode coating 103 includes at least one of conductive carbon, ceramic or lithium iron phosphate and a first binder.
  • the conductive carbon is beneficial to improve the conductivity of the positive electrode coating 103 .
  • Ceramics are beneficial to improve the structural strength of the positive electrode coating 103 .
  • Lithium iron phosphate is a positive electrode active material, which is conducive to improving the energy density of electrochemical devices.
  • the existence of the first binder in the positive electrode coating 103 is beneficial to bind various materials in the positive electrode coating 103 together.
  • the mass content of the first binder in the positive electrode coating 103 is greater than 20%. In this way, the structural stability of the positive electrode coating 103 can be improved, and the peeling of the positive electrode coating 103 is not easy to occur.
  • the first binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethylacrylate, polytetrafluoroethylene, carboxymethyl At least one of sodium cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber or polyvinyl alcohol.
  • the conductive carbon includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene, acetylene black, or carbon nanofibers.
  • the combined thickness of first portion 1021 and fourth portion 1031 is the same as the thickness of third portion 1023 .
  • the combined thickness of second portion 1022 and fifth portion 1032 is the same as the thickness of third portion 1023 . It should be understood that due to the existence of errors, the same here means that the difference within 5% can be considered the same. In this way, the overall combined thickness of the positive electrode active material layer 102 and the positive electrode coating layer can be relatively uniform, which facilitates subsequent processing of the electrochemical device, such as winding or stacking.
  • a positive electrode active material layer 102 of uniform thickness can be formed on the positive electrode current collector 101, and after forming the positive electrode coating 103, after cold pressing, the combined thickness of the positive electrode active material layer 102 and the positive electrode coating 103
  • the overall structure is uniform, but the compaction density in the partial area where the positive electrode active material layer 102 and the positive electrode coating layer 103 exists is greater than that in the area where only the positive electrode active material layer 102 exists.
  • the first positive electrode active material and the second positive electrode active material may each independently include at least one of lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium manganate.
  • the positive electrode active material layer 102 can also include a conductive agent and a binder, and the conductive agent in the positive electrode active material layer 102 can include conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotube or at least one of carbon fibers, the binder in the positive electrode active material layer 102 may include carboxymethylcellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide , polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene at least one.
  • CMC carboxymethylcellulose
  • the mass ratio of the positive electrode active material, the conductive agent and the first binder in the positive electrode active material layer 102 may be (80-99):(0.1-10):(0.1-10).
  • the positive electrode coating 103 may include a conductive agent (for example, conductive carbon) and a first binder, the mass content of the conductive agent in the positive electrode coating 103 is 30% to 80%, and the positive electrode coating 103 The mass content of the first binder may be 20% to 70%. It should be understood that the above description is only an example, and the positive electrode active material layer 102 may adopt any other suitable material, thickness and mass ratio.
  • Al foil may be used as the positive current collector, and of course, other current collectors commonly used in the art may also be used.
  • the positive electrode collector may have a thickness of 1 ⁇ m to 50 ⁇ m.
  • the electrochemical device includes a negative pole piece 12, the negative pole piece 12 includes a negative electrode current collector 121, a negative electrode active material layer 122 and a negative electrode coating 123 .
  • FIG. 1 shows that although the negative electrode active material layer 122 and the negative electrode coating 123 are located on both sides of the negative electrode current collector 121, this is only exemplary, and the negative electrode active material layer 122 and the negative electrode coating 123 may only be located on On one side of the negative electrode current collector 121.
  • the negative electrode collector 121 includes a first region 1211 , a second region 1212 and a third region 1213 located between the first region 1211 and the second region 1212 .
  • the negative electrode active material layer 122 includes a first negative electrode active material
  • the negative electrode active material layer 122 includes a first part 1221 and a second part 1222 respectively disposed in the first region 1211, the second region 1212 and the third region 1213. and third part 1223.
  • the negative electrode coating 123 may or may not include the second negative active material.
  • the third portion 1223 is located between the negative electrode coating 123 and the third region 1213 .
  • the negative electrode coating 123 is located between the third portion 1223 and the third region 1213 . Therefore, the difference between FIG. 4 and FIG. 3 lies in the relative positions of the negative electrode active material layer 122 and the negative electrode coating layer 123 . Refer to FIG. 3 for other details.
  • the first region 1211, the second region 1212 and the third region 1213 of the negative electrode current collector 121 are separated by a dotted line in FIG. 1222 and the third part 1223 are distinguished, but there may be no interface actually, the negative electrode current collector 121 may be continuous as a whole, and the negative electrode active material layer 122 may be continuous as a whole.
  • the combined impedance of negative electrode coating 123 and third portion 1223 is greater than the impedance of first portion 1221 and greater than the impedance of second portion 1222 . That is, the impedance of the edge region of the negative electrode sheet 12 is smaller than the impedance of the middle region of the negative electrode sheet 12 . In this way, with respect to the middle region of the negative pole piece 12 (for example, the combination of the third part 1223 and the negative electrode coating 123), the lithium concentration of the edge region (for example, the first part 1221 or the second part 1222) of the negative pole piece 12 can be enhanced. ion intercalation rate.
  • the edge region of the negative electrode sheet is relatively more prone to lithium precipitation, and by relatively improving the lithium ion intercalation rate in the edge region of the negative electrode sheet, it is beneficial to optimize the lithium insertion uniformity of the negative electrode sheet 12 in the charging process, and improve the negative electrode.
  • the problem of lithium precipitation at the edge of the pole piece widens the window of lithium precipitation, which is beneficial to the improvement of the rate performance of the electrochemical device.
  • the ratio of the impedance of the first portion 1221 to the combined impedance of the negative electrode coating 123 and the third portion 1223 is 0.5 to 0.99. In some embodiments, the ratio of the impedance of the second portion 1222 to the combined impedance of the negative electrode coating 123 and the third portion 1223 is 0.5 to 0.99. If the ratio is too small, the effect of improving lithium deposition in the edge region of the negative electrode sheet 12 is relatively limited.
  • the ratio of the width w of the negative electrode coating 123 to the width Y of the negative electrode active material layer 122 is 0.75 to 0.99. If the ratio is too small, the effect of the negative electrode coating 123 on improving the uniformity of lithium intercalation is relatively limited.
  • the thickness of the negative electrode coating 123 is greater than 0.5 ⁇ m and less than 8 ⁇ m. If the thickness of the negative electrode coating 123 is too small, the effect of the negative electrode coating 123 on improving the uniformity of lithium intercalation is relatively limited; if the thickness of the negative electrode coating 123 is too large, it will affect the overall impedance of the negative pole sheet 12 too much, This further affects the overall rate performance of the electrochemical device.
  • the negative electrode coating 123 includes at least one of conductive carbon or ceramic and a second binder.
  • the conductive carbon is beneficial to improve the conductivity of the negative electrode coating 123 .
  • Ceramics are beneficial to improve the structural strength of the negative electrode coating 123 .
  • the existence of the second binder in the negative electrode coating 123 is beneficial to bind various materials in the negative electrode coating 123 together.
  • the mass content of the second binder in the negative electrode coating 123 is greater than 20%. If the mass content of the second binder in the negative electrode coating 123 is too small, it is not conducive to the improvement of the binding force of the negative electrode coating 123 , and the stripping of the negative electrode coating 123 is easy to occur.
  • the second binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethylacrylate, polytetrafluoroethylene, carboxymethyl At least one of sodium cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber or polyvinyl alcohol.
  • the conductive carbon in the negative electrode coating 123 includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene, acetylene black, or carbon nanofibers.
  • the thicknesses of the first portion 1221 and the second portion 1222 are both greater than 20 ⁇ m and less than 200 ⁇ m. If the thickness of the first part 1221 or the second part 1222 is too small, that is, the thickness of the negative electrode active material layer 122 is too small, it is not conducive to improving the energy density of the electrochemical device; if the thickness of the negative electrode active material layer 12 is too large, then close to Part of the negative electrode active material layer 122 of the negative electrode current collector 121 has a long lithium ion transport path, which is not conducive to the improvement of the rate performance of the electrochemical device.
  • the combined thickness of the third portion 1223 and the negative electrode coating 123 is the same as the thickness of the first portion 1221 . In some embodiments, the combined thickness of third portion 1223 and negative electrode coating 123 is the same as the thickness of second portion 1222 . It should be understood that, due to the existence of errors, the same here means that the difference within 5% can be considered the same. In this way, the overall combined thickness of the negative electrode active material layer 122 and the negative electrode coating layer 123 can be relatively uniform, which facilitates subsequent processing of the electrochemical device, such as winding or stacking.
  • a negative electrode active material layer 122 of uniform thickness can be formed on the negative electrode current collector 121, and after forming the negative electrode coating 123, after cold pressing, the combined thickness of the negative electrode active material layer 122 and the negative electrode coating 123 The whole is uniform, but the compaction density in the part area where the negative electrode active material layer 122 and the negative electrode coating layer 123 exists is higher than that in the area where only the negative electrode active material layer 122 exists.
  • the first negative electrode active material and the second negative electrode active material may each independently include at least one of graphite, hard carbon, silicon, silicon oxide, or organic silicon.
  • the negative electrode active material layer 122 can also include a conductive agent and a binder, and the conductive agent in the negative electrode active material layer 122 can include conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotubes Or at least one of carbon fibers, the binder in the negative electrode active material layer 122 can include carboxymethylcellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide , polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene at least one.
  • CMC carboxymethylcellulose
  • the mass ratio of the positive active material, the conductive agent and the binder in the negative active material layer 122 may be (80 ⁇ 99):(0.1 ⁇ 10):(0.1 ⁇ 10). It should be understood that the above description is only an example, and the negative electrode active material layer 122 may adopt any other suitable material, thickness and mass ratio.
  • the negative electrode coating 123 may include a conductive agent (for example, conductive carbon) and a second binder, and the mass content of the conductive agent in the negative electrode coating 123 is 30% to 80%, and in the negative electrode coating 123 The mass content of the second binder is 20% to 70%.
  • the negative electrode current collector may use at least one of copper foil, nickel foil, or carbon-based current collector.
  • the thickness of the negative electrode collector may be 1 ⁇ m to 50 ⁇ m.
  • the electrochemical device may further include a separator disposed between the positive pole piece and the negative pole piece.
  • the isolation film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.
  • the thickness of the isolation film is in the range of about 5 ⁇ m to 50 ⁇ m.
  • the surface of the isolation membrane may also include a porous layer, the porous layer is arranged on at least one surface of the isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (Al 2 O 3 ), Silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium oxide (HfO 2 ), tin oxide (SnO 2 ), cerium oxide (CeO 2 ), nickel oxide (NiO), oxide Zinc (ZnO), calcium oxide (CaO), zirconia (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or sulfuric acid at least one of barium.
  • alumina Al 2 O 3
  • Silicon oxide SiO 2
  • magnesium oxide MgO
  • titanium oxide TiO 2
  • hafnium oxide HfO 2
  • the pores of the isolation membrane have a diameter in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the binder of the porous layer is selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, poly At least one of vinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
  • the electrochemical device includes a lithium-ion battery, although the present application is not limited thereto.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or one or more of lithium difluoroborate.
  • LiPF 6 is selected as a lithium salt because it has high ion conductivity and can improve cycle characteristics.
  • the non-aqueous solvent can be carbonate compound, carboxylate compound, ether compound, other organic solvent or their combination.
  • the carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or a combination thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl Ester (MEC) and combinations thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl Ester (MEC) and combinations thereof.
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or combinations thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, Fluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonic acid - Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonic acid - Difluoro-1-methylethylene carbonate, 1,1,2-trifluor
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decanolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or combinations thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy ethyl ethane, 2-methyltetrahydrofuran, tetrahydrofuran or a combination thereof.
  • organic solvents examples include dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl Amides, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
  • the positive electrode, separator, and negative electrode are sequentially wound or stacked into an electrode part, and then packed into an aluminum-plastic film for packaging, injected with an electrolyte, formed, Encapsulation, that is, made of lithium-ion batteries.
  • Embodiments of the present application also provide an electronic device including the above electrochemical device.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • Preparation of the positive pole piece Dissolve the positive active material lithium cobaltate, conductive agent, and binder polyvinylidene fluoride (PVDF) in the ratio of 97.6:1.1:1.3 by weight in N-methylpyrrolidone (NMP) solution, A cathode active material layer slurry is formed.
  • NMP N-methylpyrrolidone
  • a cathode active material layer slurry is formed.
  • Aluminum foil was used as the positive electrode current collector, and the positive electrode active material layer slurry was coated on the positive electrode current collector with a coating thickness of 50 ⁇ m and a pole piece width of 100 mm.
  • Dissolve the binder polyvinylidene fluoride (PVDF) and conductive carbon black in the ratio of 6:4 in N-methylpyrrolidone (NMP) solution to form the positive electrode coating slurry. Coating of the positive electrode coating was carried out on both edges of the pole piece, the coating width was 5 mm, and the thickness was 3
  • Negative active material artificial graphite, conductive carbon and binder styrene-butadiene rubber are dissolved in deionized water at a weight ratio of 97.5:0.5:2 to form a negative active material layer slurry.
  • Copper foil was used as the negative electrode current collector, and the negative electrode active material layer slurry was coated on the negative electrode current collector with a thickness of 60 ⁇ m and a width of 100 mm. After drying, cold pressing and slitting, the negative electrode sheet is obtained.
  • the base material of the isolation film is polyethylene (PE) with a thickness of 8 ⁇ m, and a 2 ⁇ m alumina ceramic layer is coated on both sides of the isolation film base material, and finally a 2.5 ⁇ m alumina ceramic layer is coated on both sides of the coated ceramic layer.
  • PE polyethylene
  • PVDF polyvinylidene fluoride
  • EC ethylene carbonate
  • PC propylene carbonate
  • PP polypropylene
  • DEC diethyl carbonate
  • Lithium-ion battery preparation stack the positive pole piece, separator, and negative pole piece in order, so that the separator is between the positive electrode and the negative pole to play the role of isolation, and wind up to obtain the electrode assembly.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium-ion battery is obtained through chemical formation, degassing, trimming and other processes.
  • parameters are changed on the basis of the steps in Example 1 or 12, and the parameters to be changed are as follows.
  • the impedance ratio R (1031+1021) /R 1023 is different from Embodiment 1.
  • the impedance ratio R (1031+1021) /R can be changed by adjusting the content of the binder 1023 .
  • the impedance ratio R (1031+1021) /R 1023 and the width of the positive electrode coating were different from Example 1.
  • the impedance ratio R (1031+1021) /R 1023 and the thickness of the positive electrode coating were different from Example 1.
  • Example 12 the positive electrode coating was not applied, and the preparation of the negative electrode sheet was different from Example 1:
  • Negative active material artificial graphite, conductive carbon and binder styrene-butadiene rubber are dissolved in deionized water at a weight ratio of 97.5:0.5:2 to form a negative active material layer slurry.
  • Copper foil was used as the negative electrode current collector, and the negative electrode active material layer slurry was coated on the negative electrode current collector with a coating thickness of 50 ⁇ m and a pole piece width of 100 mm.
  • the binder carboxymethyl cellulose sodium, styrene-butadiene rubber and conductive carbon black are dissolved in water at a ratio of 5:90:5 to form negative electrode coating slurry.
  • the negative electrode coating slurry was coated on the negative electrode active material layer with a coating width of 90 mm, and was coated in the middle of the pole piece, with the distance between the left and right sides being 5 mm and the coating thickness being 2 ⁇ m. After the coating is completed, the negative electrode sheet is obtained after drying and cold pressing.
  • the impedance ratio R 1221 /R (1223+123) is different from Embodiment 12, and other parameters are the same as Embodiment 12.
  • the width of the negative electrode coating was different from that of Example 12.
  • the negative electrode coating thickness was different from that of Example 12.
  • the lithium-ion battery to be tested at 25°C for 30 minutes, charge it with a constant current at a rate of 0.5C until the voltage reaches the rated voltage, and then charge it at a constant voltage until the charge-discharge rate reaches 0.05C.
  • the time between the time when charging starts and the time when charging stops is the full charge time.
  • Battery energy density Put the lithium-ion battery to be tested at 25°C for 30 minutes, charge it with a constant current at a rate of 0.5C until the voltage reaches the rated voltage, and then charge it at a constant voltage until the charge-discharge rate reaches 0.05C. And leave the electrochemical device to be tested for 30 minutes. Then discharge the battery to 3.0V at a rate of 0.2C, and place the lithium-ion battery to be tested for 30 minutes. Finally, take the discharge capacity as the actual battery capacity C of the battery.
  • Table 1 shows the respective parameters and evaluation results of the respective Examples 1 to 19 and Comparative Example 1.
  • Example 1 By comparing Example 1 and Comparative Example 1, it can be seen that after the formation of the positive electrode coating, it is beneficial to improve the charging capacity of the electrochemical device, while the full charge time and energy density of the electrochemical device remain basically unchanged. Similarly, by comparing Example 14 with Comparative Example 1, it can be seen that after the negative electrode coating is formed, it is beneficial to improve the charging capacity of the electrochemical device, while the full charge time and energy density of the electrochemical device remain basically unchanged.

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Abstract

本申请提供了电化学装置和电子装置。电化学装置包括正极极片，正极极片包括正极集流体、正极活性材料层和正极涂层。正极集流体包括第一区域、第二区域和第三区域。正极活性材料层包括分别设置在第一区域、第二区域和第三区域的第一部分、第二部分和第三部分。正极涂层包括分别设置在第一区域和第二区域的第四部分和第五部分。第一部分和第四部分的组合阻抗大于第三部分的阻抗，并且第二部分和第五部分的组合阻抗大于第三部分的阻抗。本申请优化了极片在充电过程中的嵌锂均匀性，改善了极片的边缘析锂问题，拓宽了析锂窗口，从而有利于电化学装置的倍率性能的提升。

Description

电化学装置和电子装置
相关申请的交叉引用
本申请基于申请号为202110662766.6、申请日为2021年06月15日，名称为“电化学装置和电子装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请涉及电化学储能领域，尤其涉及电化学装置和电子装置。
背景技术
电化学装置(例如，锂离子电池)在充放电过程中，特别是在快速充电过程中，极片的边缘区域和中间区域的动力学性能存在差异，导致边缘区域在大倍率快速充电过程中容易发生析锂，限制了电化学装置的快充性能的提升。
发明内容
本申请的实施例提供了一种电化学装置，电化学装置包括正极极片，正极极片包括正极集流体、正极活性材料层和正极涂层。沿正极极片的宽度方向，正极集流体包括第一区域、第二区域和位于第一区域和第二区域之间的第三区域。正极活性材料层包括第一正极活性材料，正极活性材料层包括分别设置在第一区域、第二区域和第三区域的第一部分、第二部分和第三部分。正极涂层包括分别设置在第一区域和第二区域的第四部分和第五部分。第四部分位于第一部分和第一区域之间，或者第一部分位于第四部分和第一区域之间。第五部分位于第二部分和第二区域之间，或者第二部分位于第五部分和第二区域之间。第一部分和第四部分的组合阻抗大于第三部分的阻抗，并且第二部分和第五部分的组合阻抗大于第三部分的阻抗。
在一些实施例中，第四部分与第一部分的组合阻抗和第三部分的阻抗的比值为1.02至5，第五部分与第二部分的组合阻抗和第三部分的阻抗的比值 为1.02至5。在一些实施例中，第四部分的宽度与正极活性材料层的宽度的比值为0.01至0.25，第五部分的宽度与正极活性材料层的宽度的比值为0.01至0.25。在一些实施例中，第四部分的厚度大于0.5μm并且小于8μm。在一些实施例中，第五部分的厚度大于0.5μm并且小于8μm。在一些实施例中，第三部分的厚度大于20μm并且小于200μm。在一些实施例中，正极涂层包括导电碳、陶瓷或磷酸铁锂中的至少一种以及第一粘结剂。在一些实施例中，正极涂层中的第一粘结剂的质量含量大于20％。在一些实施例中，第一粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种。在一些实施例中，导电碳包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种。在一些实施例中，第一部分和第四部分的组合厚度与第三部分的厚度相同，第二部分和第五部分的组合厚度与第三部分的厚度相同。
本申请的另一实施例提供了一种电化学装置，电化学装置包括负极极片，负极极片包括负极集流体、负极活性材料层和负极涂层。沿负极极片的宽度方向，负极集流体包括第一区域、第二区域和位于第一区域和第二区域之间的第三区域。负极活性材料层包括第一负极活性材料，负极活性材料层包括分别设置在第一区域、第二区域和第三区域的第一部分、第二部分和第三部分。负极涂层位于第三部分和第三区域之间，或者第三部分位于负极涂层和第三区域之间。负极涂层和第三部分的组合阻抗大于第一部分的阻抗，并且大于第二部分的阻抗。
在一些实施例中，第一部分的阻抗与负极涂层和第三部分的组合阻抗的比值为0.5至0.99，第二部分的阻抗与负极涂层和第三部分的组合阻抗的比值为0.5至0.99。在一些实施例中，负极涂层的宽度与负极活性材料层的宽度的比值为0.75至0.99。在一些实施例中，负极涂层的厚度大于0.5μm并且小于8μm。在一些实施例中，负极涂层包括导电碳或陶瓷中的至少一种以及第一粘结剂。在一些实施例中，第一部分和第二部分的厚度均大于20μm并且小于200μm。
在一些实施例中，负极涂层中的第一粘结剂的质量含量大于20％。在一些实施例中，第一粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、 聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种。在一些实施例中，导电碳包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种。在一些实施例中，第三部分和负极涂层的组合厚度与第一部分的厚度相同，第三部分和负极涂层的组合厚度与第二部分的厚度相同。
本申请的一些实施例提供了一种电子装置，包括上述任一电化学装置。
本申请的实施例通过在正极极片中设置上述正极涂层，或者在负极极片中设置上述负极涂层，优化了极片在充电过程中的嵌锂均匀性，改善了极片的边缘析锂问题，拓宽了析锂窗口，从而有利于电化学装置的倍率性能的提升。
附图说明
图1示出了根据本申请的一些实施例的电化学装置的正极极片10的沿着其长宽度和厚度方向限定的平面截取的截面图。
图2示出了根据本申请的另一实施例的电化学装置的正极极片10的沿着其宽度和厚度方向限定的平面截取的截面图。
图3示出了根据本申请的一些实施例的电化学装置的负极极片12的沿着其宽度和厚度方向限定的平面截取的截面图。
图4示出了根据本申请的另一实施例的电化学装置的负极极片12的沿着其宽度和厚度方向限定的平面截取的截面图。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
图1和图2示出了根据本申请的一些实施例的电化学装置的正极极片10的沿着其宽度和厚度方向限定的平面截取的截面图。本申请的实施例提供了一种电化学装置，该电化学装置包括如图1所示的正极极片10，该正极极片10包括正极集流体101、正极活性材料层102和正极涂层103。应该理解，虽然图1示出了正极活性材料层102和正极涂层103位于正极集流体101的 两侧上，但这仅是示例性的，正极活性材料层102和正极涂层103可以仅位于集流体101的一侧上。
在一些实施例中，如图1所示，沿正极极片10的宽度方向，正极集流体101包括第一区域1011、第二区域1012和位于第一区域1011和第二区域1012之间的第三区域1013。在一些实施例中，正极活性材料层102包括第一正极活性材料，正极活性材料层102包括分别设置在第一区域1011、第二区域1012和第三区域1013的第一部分1021、第二部分1022和第三部分1023。在一些实施例中，正极涂层103可以包括或可以不包括第二正极活性材料，正极涂层103包括分别设置在第一区域1011和第二区域1012的第四部分1031和第五部分1032。
在一些实施例中，如图1所示，第一部分1021位于第四部分1031和第一区域1011之间。在一些实施例中，如图2所示，第四部分1031位于第一部分1021和第一区域1011之间。在一些实施例中，如图1所示，第二部分1022位于第五部分1032和第二区域1012之间。在一些实施例中，如图2所示，第五部分1032位于第二部分1022和第二区域1012之间。因此，图2与图1的差别在于正极活性材料层102和正极涂层的103的相对位置不同，其他细节参考图1。另外，应该理解，虽然图1中通过虚线将正极集流体101的第一区域1011、第二区域1012和第三区域1013区分开，通过虚线将正极活性材料层102的第一部分1021、第二部分1022和第三部分1023区分开，但是实际上可能并不存在界面，正极集流体101整体可以是连续的，正极活性材料层102整体也可以是连续的。
在一些实施例中，第一部分1021和第四部分1031的组合阻抗大于第三部分1023的阻抗，并且第二部分1022和第五部分1032的组合阻抗大于第三部分1023的阻抗。即，正极极片10的边缘区域的阻抗大于正极极片10的中间区域的阻抗。如此，能够减小正极极片10的边缘区域(例如，第一部分1021和第四部分1031的组合或者第二部分1022和第五部分1032的组合)的脱出的锂离子速率，从而能够减小充电过程中的边缘区域的充电电流密度。而对应的负极极片的边缘是相对更容易发生析锂，边缘区域的充电电流密度的减小可以优化充电过程中的对应的负极极片的嵌锂均匀性，改善了负极极 片的边缘析锂问题，拓宽了析锂窗口，从而有利于电化学装置的倍率性能的提升。
阻抗测试方法如下，可以为直流阻抗也可以为交流阻抗，不管是哪种测试方法，测试出来的阻抗均处于上述阻抗范围内，具体阻抗测试方法如下。直流阻抗的测试：将待测的相应区域(在测量两个部分的组合阻抗时，将它们一起取出进行测试)取出作为正极组装成锂离子电池。然后安装于新威机上进行充放电，并监测锂离子电池的电压与电流，得到锂离子电池的直流阻抗值。具体地，以0.5C的电流将锂离子电池恒流充电至满充电压，再恒压充电至0.05C。再以1C电流放电30min使锂离子电池处于50％的荷电比状态，记录电压V1，静置60min，记录电压V2。以0.1C的电流放电10s，并记录电压V3。再以1C的电流放电1s，并记录电压V4。按如下公式计算得出锂离子电池的直流阻抗R T及DCR：
R T＝(V2-V1)/1C；DCR＝(V3-V4)/(1C-0.1C)
交流阻抗的测试方法：将相应的区域取出制作成对称电池，即正极极片对正极极片，负极极片对负极极片组成的电池。利用电化学工作站对对称电池进行EIS测试，其中测试温度为25℃，测试频率范围为30mHz～500kHz，扰动电压为5mV。得到EIS谱图后，由谱图读取对称电池的交流阻抗Rz。
在一些实施例中，第四部分1031与第一部分1011的组合阻抗和第三部分1023的阻抗的比值为1.02至5。在一些实施例中，第五部分1032与第二部分1022的组合阻抗和第三部分1023的阻抗的比值为1.02至5。即，正极极片10的边缘区域的阻抗与中间区域的阻抗的比值为1.02至5。因为在边缘区域与中间区域的阻抗差别太大时，对于中间区域(即第三部分1023)的倍率性能会有影响，从而可能影响电化学装置整体的倍率性能的提升。
在一些实施例中，第四部分1031的宽度w1与正极活性材料层102的宽度W的比值为0.01至0.25。在一些实施例中，第五部分1032的宽度w2与正极活性材料层102的宽度W的比值为0.01至0.25。如果该比值太小，则第四部分1031或第五部分1032对析锂的改善作用相对有限；如果该比值太大，则可能过分地增大正极极片10的整体阻抗，这不利于电化学装置的倍率性能的提升。在一些实施例中，第四部分1031的宽度w1和第五部分1032的宽度w2相同(如下面的具体实施例)，但是本申请不限于此，宽度w1与宽度 w2也可以不同。应该理解，由于误差的存在，此处的相同是指差异在5％以内均可以认为是相同。
在一些实施例中，第四部分1031的厚度h1大于0.5μm并且小于8μm。在一些实施例中，第五部分1032的厚度h2大于0.5μm并且小于8μm。如果第四部分1031的厚度h1或第五部分1032的厚度h2太小，则第四部分1031或第五部分1032对析锂的改善作用相对有限；如果第四部分1031的厚度h1或第五部分1032的厚度h2太大，则可能过分地增大正极极片10的整体阻抗，这不利于电化学装置的倍率性能的提升。在一些实施例中，第四部分1031厚度h1和第五部分1032的厚度h2相同(如下面的具体实施例)，但是本申请不限于此，厚度h1与厚度h2也可以不同。应该理解，由于误差的存在，此处的相同是指差异在5％以内均可以认为是相同。
在一些实施例中，第三部分1023的厚度大于20μm并且小于200μm。如果第三部分1023的厚度太小，则不利于提升电化学装置的能量密度；如果第三部分1023的厚度太大，则靠近正极集流体101的部分正极活性材料层102的锂离子传输路径较长，不利于电化学装置的倍率性能的提升。
在一些实施例中，正极涂层103包括导电碳、陶瓷或磷酸铁锂中的至少一种以及第一粘结剂。导电碳有利于提高正极涂层103的导电性。陶瓷有利于提升正极涂层103的结构强度。磷酸铁锂属于正极活性材料，有利于提升电化学装置的能量密度。正极涂层103中的第一粘结剂的存在有利于将正极涂层103中的各种材料粘结在一起。
在一些实施例中，正极涂层103中的第一粘结剂的质量含量大于20％。如此，可以提升正极涂层103的结构稳定性，不容易发生正极涂层103的脱膜。在一些实施例中，第一粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种。在一些实施例中，导电碳包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种。
在一些实施例中，第一部分1021和第四部分1031的组合厚度与第三部分1023的厚度相同。在一些实施例中，第二部分1022和第五部分1032的组合厚度与第三部分1023的厚度相同。应该理解，由于误差的存在，此处的相 同是指差异在5％以内均可以认为是相同。如此，可以使得正极活性材料层102和正极涂层的组合厚度整体较为均匀，方便电化学装置的后续加工，例如，卷绕或堆叠等。在一些实施例中，可以在正极集流体101上形成均匀厚度的正极活性材料层102，并且在形成正极涂层103之后，经过冷压，使正极活性材料层102和正极涂层103的组合厚度整体均匀，不过在存在正极活性材料层102和正极涂层103的部分区域比仅存在正极活性材料层102的区域的压实密度更大。
在一些实施例中，第一正极活性材料和第二正极活性材料可以各自独立地包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂或锰酸锂中的至少一种。在一些实施例中，正极活性材料层102还可以包括导电剂和粘结剂，正极活性材料层102中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种，正极活性材料层102中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，正极活性材料层102中的正极活性材料、导电剂和第一粘结剂的质量比可以为(80～99)：(0.1～10)：(0.1～10)。在一些实施例中，正极涂层103可以包括导电剂(例如，导电碳)和第一粘结剂，正极涂层103中的导电剂的质量含量为30％至80％，正极涂层103中的第一粘结剂的质量含量可以为20％至70％。应该理解，以上所述仅是示例，正极活性材料层102可以采用任何其他合适的材料、厚度和质量比。
在一些实施例中，正极集流体可以采用Al箔，当然，也可以采用本领域常用的其他集流体。在一些实施例中，正极集流体的厚度可以为1μm至50μm。
如图3所示，本申请的另一实施例提供了一种电化学装置，电化学装置包括负极极片12，负极极片12包括负极集流体121、负极活性材料层122和负极涂层123。应该理解，虽然图1示出了负极活性材料层122和负极涂层123位于负极集流体121的两侧上，但这仅是示例性的，负极活性材料层122和负极涂层123可以仅位于负极集流体121的一侧上。
在一些实施例中，沿负极极片12的宽度方向，负极集流体121包括第一区域1211、第二区域1212和位于第一区域1211和第二区域1212之间的第 三区域1213。在一些实施例中，负极活性材料层122包括第一负极活性材料，负极活性材料层122包括分别设置在第一区域1211、第二区域1212和第三区域1213的第一部分1221、第二部分1222和第三部分1223。在一些实施例中，负极涂层123可以包括或可以不包括第二负极活性材料。
在一些实施例中，如图3所示，第三部分1223位于负极涂层123和第三区域1213之间。在一些实施例中，如图4所示，负极涂层123位于第三部分1223和第三区域1213之间。因此，图4与图3的差别在于负极活性材料层122和负极涂层的123的相对位置不同，其他细节参考图3。另外，应该理解，虽然图3中通过虚线将负极集流体121的第一区域1211、第二区域1212和第三区域1213区分开，通过虚线将负极活性材料层122的第一部分1221、第二部分1222和第三部分1223区分开，但是实际上可能并不存在界面，负极集流体121整体可以是连续的，负极活性材料层122整体也可以是连续的。
在一些实施例中，负极涂层123和第三部分1223的组合阻抗大于第一部分1221的阻抗，并且大于第二部分1222的阻抗。即，负极极片12的边缘区域的阻抗小于负极极片12的中间区域的阻抗。如此，相对于负极极片12的中间区域(例如，第三部分1223和负极涂层123的组合)，能够增强负极极片12的边缘区域(例如，第一部分1221或者第二部分1222)的锂离子嵌入速率。而负极极片的边缘区域是相对更容易发生析锂，通过相对改善负极极片的边缘区域的锂离子嵌入速率，有利于优化充电过程中的负极极片12的嵌锂均匀性，改善了负极极片的边缘析锂问题，拓宽了析锂窗口，从而有利于电化学装置的倍率性能的提升。
在一些实施例中，第一部分1221的阻抗与负极涂层123和第三部分1223的组合阻抗的比值为0.5至0.99。在一些实施例中，第二部分1222的阻抗与负极涂层123和第三部分1223的组合阻抗的比值为0.5至0.99。如果该比值太小，则负极极片12的边缘区域的析锂的改善作用相对受限。
在一些实施例中，负极涂层123的宽度w与负极活性材料层122的宽度Y的比值为0.75至0.99。如果该比值太小，则负极涂层123改善嵌锂均匀性的作用相对受限。
在一些实施例中，负极涂层123的厚度大于0.5μm并且小于8μm。如果负极涂层123的厚度太小，则负极涂层123改善嵌锂均匀性的作用相对受限； 如果负极涂层123的厚度太大，则会过多地影响负极极片12的整体阻抗，进而影响电化学装置的整体倍率性能。
在一些实施例中，负极涂层123包括导电碳或陶瓷中的至少一种以及第二粘结剂。导电碳有利于提高负极涂层123的导电性。陶瓷有利于提升负极涂层123的结构强度。负极涂层123中的第二粘结剂的存在有利于将负极涂层123中的各种材料粘结在一起。在一些实施例中，负极涂层123中的第二粘结剂的质量含量大于20％。如果负极涂层123中的第二粘结剂的质量含量太小，则不利于负极涂层123的粘结力的提升，容易发生负极涂层123的脱膜。在一些实施例中，第二粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种。在一些实施例中，负极涂层123中的导电碳包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种。
在一些实施例中，第一部分1221和第二部分1222的厚度均大于20μm并且小于200μm。如果第一部分1221或第二部分1222的厚度太小，即，负极活性材料层122的厚度太小，则不利于提升电化学装置的能量密度；如果负极活性材料层12的厚度太大，则靠近负极集流体121的部分负极活性材料层122的锂离子传输路径较长，不利于电化学装置的倍率性能的提升。
在一些实施例中，第三部分1223和负极涂层123的组合厚度与第一部分1221的厚度相同。在一些实施例中，第三部分1223和负极涂层123的组合厚度与第二部分1222的厚度相同。应该理解，由于误差的存在，此处的相同是指差异在5％以内均可以认为是相同。如此，可以使得负极活性材料层122和负极涂层123的组合厚度整体较为均匀，方便电化学装置的后续加工，例如，卷绕或堆叠等。在一些实施例中，可以在负极集流体121上形成均匀厚度的负极活性材料层122，并且在形成负极涂层123之后，经过冷压，使负极活性材料层122和负极涂层123的组合厚度整体均匀，不过在存在负极活性材料层122和负极涂层123的部分区域比仅存在负极活性材料层122的区域的压实密度更大。
在一些实施例中，第一负极活性材料和第二负极活性材料可以各自独立地包括石墨、硬碳、硅、氧化亚硅或有机硅中的至少一种。在一些实施例中， 负极活性材料层122还可以包括导电剂和粘结剂，负极活性材料层122中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种，负极活性材料层122中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，负极活性材料层122中的正极活性材料、导电剂和粘结剂的质量比可以为(80～99)：(0.1～10)：(0.1～10)。应该理解，以上所述仅是示例，负极活性材料层122可以采用任何其他合适的材料、厚度和质量比。在一些实施例中，负极涂层123可以包括导电剂(例如，导电碳)和第二粘结剂，负极涂层123中的导电剂的质量含量为30％至80％，负极涂层123中的第二粘结剂的质量含量为20％至70％。
在一些实施例中，负极集流体可以采用铜箔、镍箔或碳基集流体中的至少一种。在一些实施例中，负极集流体的厚度可以为1μm至50μm。
在一些实施例中，电化学装置还可以包括设置于正极极片和负极极片之间的隔离膜。在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约5μm至50μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm至1μm的范围的直径。多孔层的粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或 聚六氟丙烯中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘结性。
在一些实施例中，电化学装置包括锂离子电池，但是本申请不限于此。在一些实施例中，电化学装置还可以包括电解质。电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，电解液包括锂盐和非水溶剂。锂盐选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或者二氟硼酸锂中的一种或多种。例如，锂盐选用LiPF 6，因为它具有高的离子导电率并可以改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。
链状碳酸酯化合物的实例为碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。所述环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)或者其组合。所述氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯或者其组合。
羧酸酯化合物的实例为乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯或者其组合。
醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃或者其组合。
其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁 砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯或者其组合。
在本申请的一些实施例中，以锂离子电池为例，将正极、隔离膜、负极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，即制成锂离子电池。本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
实施例1
正极极片的制备：将正极活性材料钴酸锂、导电剂、粘结剂聚偏氟乙烯(PVDF)按重量比97.6：1.1：1.3的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极活性材料层浆料。采用铝箔作为正极集流体，将正极活性材料层浆料涂覆于正极集流体上，涂布厚度为50μm，极片宽度为100mm。将粘结剂聚偏氟乙烯(PVDF)及导电碳黑按6：4的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极涂层浆料。在极片两个边缘进行正极涂层的涂布，涂布宽度均为5mm，厚度均为3μm。经过干燥、冷压、分切后得到正极极片。
负极极片的制备：将负极活性材料人造石墨、导电碳和粘结剂丁苯橡胶按重量比97.5：0.5：2的比例溶于去离子水中，形成负极活性材料层浆料。采用铜箔作为负极集流体，将负极活性材料层浆料涂布于负极集流体上，涂布厚度为60μm，极片宽度为100mm。经过干燥、冷压、分切后得到负极极片。
隔离膜的制备：隔离膜基材为8μm厚的聚乙烯(PE)，在隔离膜基材的两侧各涂覆2μm氧化铝陶瓷层，最后在涂布了陶瓷层的两侧各涂覆2.5mg/cm 2的粘结剂聚偏氟乙烯(PVDF)，烘干。
电解液的制备：在含水量小于10ppm的环境下，将六氟磷酸锂与非水有机溶剂(碳酸乙烯酯(EC)：碳酸丙烯酯(PC)：聚丙烯(PP)：二乙基碳酸酯(DEC)＝1：1：1：1，重量比)配制成基础电解液，其中，LiPF 6的浓度为1.15mol/L。
锂离子电池的制备：将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正极和负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
其他实施例和对比例是在实施例1或12的步骤的基础上进行参数变更，具体变更的参数如下所述。
在对比例1中，未涂覆正极涂层。在实施例2至5中，阻抗比值R (1031+1021)/R 1023与实施例1不同，在实施例中，可以通过调节粘结剂的含量来改变阻抗比值R (1031+1021)/R 1023。在实施例6至8中，阻抗比值R (1031+1021)/R 1023和正极涂层的宽度与实施例1不同。在实施例9至11中，阻抗比值R (1031+1021)/R 1023和正极涂层的厚度与实施例1不同。
在实施例12中，未涂覆正极涂层，并且负极极片的制备与实施例1不同：
负极极片的制备：将负极活性材料人造石墨、导电碳和粘结剂丁苯橡胶按重量比97.5：0.5：2的比例溶于去离子水中，形成负极活性材料层浆料。采用铜箔作为负极集流体，将负极活性材料层浆料涂布于负极集流体上，涂布厚度为50μm，极片宽度为100mm。将粘结剂羧甲基纤维素纳、丁苯橡胶及导电碳黑按5：90：5的比例溶于水中，形成负极涂层浆料。将负极涂层浆料涂覆于负极活性材料层上，涂布宽度为90mm，涂布于极片中间，左右两边的距离分别为5mm，涂布厚度为2μm。涂布完成后经过干燥、冷压后得到负极极片。
在实施例13至14中，阻抗比值R 1221/R (1223+123)与实施例12不同，其他参数与实施例12相同。在实施例15至16中，负极涂层的宽度与实施例12不同。在实施例17至19中，负极涂层厚度与实施例12不同。
下面描述本申请的各个参数的测试方法。
析锂窗口测试：
先把电化学装置放电至满放状态，然后设定特定温度(例如，25℃)，根据电化学装置设计以不同的倍率，如1C、1.1C、1.2C…进行常规充电(恒流+恒压)，即特定倍率下充电至电池截止电压，之后恒压充电至0.05C截止充电，充电后0.2C满放，对上述充放电流程循环10个周期。最后对电化学装置满充后进行拆解，观察负极极片是否析锂，在不析锂(负极极片表面不存在白斑)的情况下的最大电流定义为该电池的最大不析锂倍率，也就是析锂窗口。
满充时间测试：
将待测的锂离子电池在25℃环境中静置30分钟，以0.5C倍率恒流充电至电压至额定电压，随后以恒压充电直到充放电倍率达到0.05C时停止充电。计时开始充电的时刻到停止充电的时刻之间的时间为满充时间。
能量密度测试：
电池能量密度：将待测的锂离子电池在25℃环境中静置30分钟，以0.5C倍率恒流充电至电压至额定电压，随后以恒压充电直到充放电倍率达到0.05C时停止充电，并将待测的电化学装置放置30分钟。之后再以0.2C倍率将电池放电至3.0V，并将待测的锂离子电池放置30分钟。最后取放电容量作为电池的实际电池容量C。测试锂离子电池的长宽高分别为L，W，H，电池的放电平台电压为V，则电池的能量密度VED＝C×V/(L×W×H)。
表1示出了相应实施例1至19和对比例1的各个参数和评估结果。
表1
Figure PCTCN2022097271-appb-000001
Figure PCTCN2022097271-appb-000002
通过比较实施例1与对比例1可知，在形成正极涂层之后，有利于提升电化学装置的充电能力，而电化学装置的满充时间和能量密度基本保持不变。同样地，通过比较实施例14与对比例1可知，在形成负极涂层之后，有利于提升电化学装置的充电能力，而电化学装置的满充时间和能量密度基本保持不变。
通过比较实施例1至5可知，随着阻抗比值R (1031+1021)/R 1023的增大，电化学装置的充电能力先增强后保持不变，电化学装置的满充时间先保持不变后增加，电化学装置的能量密度先保持不变后减小。在阻抗比值R (1031+1021)/R 1023大于5时，充电能力不再提升，而满充时间增加，并且能量密度降低。
通过比较实施例6至8可知，随着正极涂层的宽度的增大，电化学装置的充电能力先增强后保持不变，电化学装置的满充时间有增加的趋势，电化学装置的能量密度有减小的趋势。在正极涂层的宽度与正极活性材料层的宽度的比值大于0.25时，电化学装置的充电能力基本保持不变，电化学装置的满充时间增加，电化学装置的能量密度减小。
通过比较实施例9至11可知，随着正极涂层的厚度的增大，电化学装置的充电能力先增强后保持不变，电化学装置的满充时间基本不变，电化学装置的能量密度有减小的趋势。在正极涂层的厚度大于8μm时，电化学装置的充电能力和满充时间基本保持不变，电化学装置的能量密度减小。
通过比较实施例12至14可知，随着阻抗比值R 1221/R (1223+123)的增大，电化学装置的充电能力有所减弱，电化学装置的满充时间有一定的缩短，电化学装置的能量密度有增大的趋势。
通过比较实施例15和16可知，随着负极涂层的宽度的增大，电化学装置的充电能力有所增强，电化学装置的满充时间稍微有所增加，电化学装置的能量密度基本保持不变。在负极涂层的宽度与负极活性材料层的宽度的比值小于0.75或大于0.99时，电化学装置的充电能力会相对减弱。
通过比较实施例17至19可知，随着负极涂层的厚度的增大，电化学装置的充电能力和满充时间基本不变，电化学装置的能量密度有减小的趋势。在正极涂层的厚度大于8μm时，电化学装置的充电能力和满充时间基本保持不变，电化学装置的能量密度减小。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖由上述技术特征或其等同 特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (10)

  1. 一种电化学装置，其包括正极极片，所述正极极片包括：
    正极集流体，沿所述正极极片的宽度方向，所述正极集流体包括第一区域、第二区域和位于所述第一区域和所述第二区域之间的第三区域；
    正极活性材料层，所述正极活性材料层包括分别设置在所述第一区域、所述第二区域和所述第三区域的第一部分、第二部分和第三部分；和
    正极涂层，所述正极涂层包括分别设置在所述第一区域和所述第二区域的第四部分和第五部分，
    其中，所述第四部分位于所述第一部分和所述第一区域之间，或者所述第一部分位于所述第四部分和所述第一区域之间；
    所述第五部分位于所述第二部分和所述第二区域之间，或者所述第二部分位于所述第五部分和所述第二区域之间；
    所述第一部分和所述第四部分的组合阻抗大于所述第三部分的阻抗，并且所述第二部分和所述第五部分的组合阻抗大于所述第三部分的阻抗。
  2. 根据权利要求1所述的电化学装置，其中，所述正极极片满足以下条件中的至少一个：
    所述第四部分与所述第一部分的组合阻抗和所述第三部分的阻抗的比值为1.02至5，所述第五部分与所述第二部分的组合阻抗和所述第三部分的阻抗的比值为1.02至5；
    所述第四部分的宽度与所述正极活性材料层的宽度的比值为0.01至0.25，所述第五部分的宽度与所述正极活性材料层的宽度的比值为0.01至0.25；
    所述第四部分的厚度大于0.5μm并且小于8μm；
    所述第五部分的厚度大于0.5μm并且小于8μm；
    所述第三部分的厚度大于20μm并且小于200μm。
  3. 根据权利要求1所述的电化学装置，其中，
    所述正极涂层包括导电碳或陶瓷中的至少一种以及第一粘结剂。
  4. 根据权利要求3所述的电化学装置，其中，所述正极极片满足以下条件中的至少一个：
    所述正极涂层中的所述第一粘结剂的质量含量大于20％；
    所述第一粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种；
    所述导电碳包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种。
  5. 根据权利要求1所述的电化学装置，其中，所述第一部分和所述第四部分的组合厚度与所述第三部分的厚度相同，所述第二部分和所述第五部分的组合厚度与所述第三部分的厚度相同。
  6. 一种电化学装置，其包括负极极片，所述负极极片包括：
    负极集流体，沿所述负极极片的宽度方向，所述负极集流体包括第一区域、第二区域和位于所述第一区域和所述第二区域之间的第三区域；
    负极活性材料层，所述负极活性材料层包括分别设置在所述第一区域、第二区域和第三区域的第一部分、第二部分和第三部分；和
    负极涂层；
    其中，所述负极涂层位于所述第三部分和所述第三区域之间，或者所述第三部分位于所述负极涂层和所述第三区域之间；
    所述负极涂层和所述第三部分的组合阻抗大于所述第一部分的阻抗，并且大于所述第二部分的阻抗。
  7. 根据权利要求6所述的电化学装置，其中，所述负极极片满足以下条件中的至少一个：
    所述第一部分的阻抗与所述负极涂层和所述第三部分的组合阻抗的比值为0.5至0.99，所述第二部分的阻抗与所述负极涂层和所述第三部分的组合阻抗的比值为0.5至0.99；
    所述负极涂层的宽度与所述负极活性材料层的宽度的比值为0.75至0.99；
    所述负极涂层的厚度大于0.5μm并且小于8μm；
    所述负极涂层包括导电碳或陶瓷中的至少一种以及第一粘结剂；
    所述第一部分和所述第二部分的厚度均大于20μm并且小于200μm。
  8. 根据权利要求7所述的电化学装置，其中，所述负极涂层包括导电碳或陶瓷中的至少一种以及第二粘结剂。
  9. 根据权利要求8所述的电化学装置，其中，所述负极极片满足以下条件中的至少一个：
    所述负极涂层中的所述第一粘结剂的质量含量大于20％；
    所述第一粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种；
    所述导电碳包括导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑或纳米碳纤维中的至少一种。
  10. 一种电子装置，包括根据权利要求1至9中任一项所述的电化学装置。
PCT/CN2022/097271 2021-06-15 2022-06-07 电化学装置和电子装置 WO2022262612A1 (zh)

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