WO2021184531A1 - 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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WO2021184531A1
WO2021184531A1 PCT/CN2020/091577 CN2020091577W WO2021184531A1 WO 2021184531 A1 WO2021184531 A1 WO 2021184531A1 CN 2020091577 W CN2020091577 W CN 2020091577W WO 2021184531 A1 WO2021184531 A1 WO 2021184531A1
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active material
negative electrode
electrochemical device
material layer
electrode active
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English (en)
French (fr)
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冯鹏洋
董佳丽
唐佳
谢远森
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This application relates to the field of energy storage, in particular to an electrochemical device and an electronic device, especially a lithium ion battery.
  • Electrochemical devices for example, lithium-ion batteries
  • Small-sized lithium-ion batteries are generally used as power sources for driving portable electronic communication devices (for example, camcorders, mobile phones, or notebook computers, etc.), especially high-performance portable devices.
  • portable electronic communication devices for example, camcorders, mobile phones, or notebook computers, etc.
  • Examples of medium-sized and large-sized lithium batteries with high output characteristics have been developed for use in electric vehicles (EV) and large-scale energy storage systems (ESS). With the widespread application of lithium-ion batteries, their first-time efficiency and cycle performance have become key technical issues to be solved urgently.
  • this application attempts to solve at least one problem existing in the related field at least to some extent.
  • the present application provides an electrochemical device comprising a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material Containing graphite, wherein when the electrochemical device is in a 50% charged state, by X-ray diffraction, the interplanar spacing of the negative electrode active material is D1, and when the electrochemical device is in a 100% charged state, By X-ray diffraction method, the interplanar spacing of the negative active material is D2, and D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.55. In some embodiments, D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.50.
  • D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.45. In some embodiments, D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.30. In some embodiments, D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.40.
  • the D1 when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range. In some embodiments, when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range.
  • the D1 when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range. In some embodiments, when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range.
  • the D1 when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to Within the range, the 2 ⁇ value corresponding to the 002 peak of the negative active material is in the range of 25.2000 ° 2Th. to 25.3000 ° 2Th., and the peak area of the negative active material is in the range of 5000cts ⁇ °2Th. to 50000cts ⁇ °2Th.
  • the peak intensity of the 002 peak is in the range of 5000 cts to 200,000 cts
  • the FWHM of the 002 peak is in the range of 0.1200°2Th. to 0.2100°2Th.
  • the negative electrode active material layer is at least one of 280°C to 300°C or 320°C to 400°C There is a thermal weight loss peak on it.
  • the mass change of the negative electrode active material layer when the electrochemical device is in a 100% charged state, the mass change of the negative electrode active material layer is -2.0% to 2.3% by thermogravimetric analysis. In some embodiments, when the electrochemical device is in a 100% charged state, the mass change of the negative active material layer is -1.5% to 2.0% by thermogravimetric analysis. In some embodiments, when the electrochemical device is in a 100% charged state, the mass change of the negative electrode active material layer is -1.0% to 1.0% by thermogravimetric analysis. In some embodiments, when the electrochemical device is in a 100% charged state, the mass change of the negative electrode active material layer is -0.5% to 0.5% by thermogravimetric analysis.
  • the negative electrode active material layer has an infrared absorption peak at 1150cm -1 to 1250cm -1.
  • the negative electrode includes at least one of Ni, Mn, Cr, Fe, S, Si, or Zn.
  • the Ni content is 0.001 wt% to 0.004wt%
  • the Mn content is 0.001wt% to 0.005wt%
  • the Cr content is 0.001wt% to 0.003wt%
  • the Fe content is 0.005wt% to 0.010wt%
  • the S content is 0.002wt %
  • the Si content is not more than 0.0053 wt%
  • the Zn content is 0.003 wt% to 0.005 wt%.
  • the negative active material layer satisfies at least one of conditions (a) to (e):
  • the negative active material includes secondary particles
  • the thickness of the negative electrode active material layer is 0.13 mm to 0.16 mm;
  • the compaction density of the negative electrode active material layer is 1.40 g/cm 3 to 1.80 g/cm 3 ;
  • the porosity of the anode active material layer is 25% to 32%.
  • the thickness of the negative active material layer is 0.14 mm to 0.15 mm.
  • the compacted density of the negative active material layer is 1.50 g/cm 3 to 1.70 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is about 1.50 g/cm 3 , about 1.55 g/cm 3 , about 1.60 g/cm 3 , about 1.65 g/cm 3 , and about 1.70 g/cm 3. About 1.75g/cm 3 or about 1.80g/cm 3 .
  • the negative active material layer C004/C110 measured by X-ray diffraction method is 8 to 16.5. In some embodiments, the negative active material layer C004/C110 measured by X-ray diffraction method is 9-15. In some embodiments, the negative active material layer C004/C110 measured by X-ray diffraction method is 10-12.
  • the porosity of the negative active material layer is 28% to 30%. In some embodiments, the porosity of the negative active material layer is about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, or about 32%.
  • the grain size Lc of the graphite along the vertical direction is 29 nm to 32 nm
  • the grain size La of the graphite along the horizontal direction is 160 nm to 165 nm.
  • the median particle diameter Dv50 of the secondary particles of the negative active material is 7 ⁇ m to 30 ⁇ m. In some embodiments, the median diameter Dv50 of the secondary particles is 10 ⁇ m to 25 ⁇ m. In some embodiments, the median diameter Dv50 of the secondary particles is 15 ⁇ m to 20 ⁇ m. In some embodiments, the median diameter Dv50 of the secondary particles is about 7 ⁇ m, about 10 ⁇ m, about 12 ⁇ m, about 15 ⁇ m, about 18 ⁇ m, about 20 ⁇ m, about 22 ⁇ m, about 25 ⁇ m, about 28 ⁇ m, or about 30 ⁇ m.
  • the present application provides an electronic device, which includes the electrochemical device according to the present application.
  • FIG. 1 shows a scanning electron microscope (SEM) image of the negative active material used in Example 6 according to the present application.
  • FIG. 2 shows the X-ray diffraction pattern of the negative electrode active material used in Example 8 of the present application.
  • FIG. 3 shows the thermogravimetric curve of the negative electrode active material layer used in Example 16 according to the present application.
  • FIG. 4 shows the infrared spectrum of the negative active material layer used in Example 13 of the present application.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C” means only A; or only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • Electrochemical devices for example, lithium ion batteries
  • Electrochemical devices have been widely used in various electronic devices, especially in small, light and thin digital electronic products.
  • the use of a coating material to coat the surface of the negative electrode active material can inhibit the expansion between the negative electrode active material particles, reduce the generation of polarization and the accumulation of side reaction products, thereby improving the lithium-ion battery during the cycle. Thickness expansion problem.
  • the coating layer will seriously reduce the first-time efficiency of the lithium-ion battery, making the overall performance of the lithium-ion battery poor.
  • the present application provides an electrochemical device comprising a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising Graphite, wherein when the electrochemical device is in a 50% charged state, the interplanar spacing of the negative electrode active material is D1 by X-ray diffraction, and when the electrochemical device is in a 100% charged state, By X-ray diffraction method, the interplanar spacing of the negative active material is D2, and D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.55. In some embodiments, D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.50.
  • D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.45. In some embodiments, D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.30. In some embodiments, D1 and D2 satisfy (D2-D1)/D1 ⁇ 0.40.
  • the D1 when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to Within the range, the 2 ⁇ value corresponding to the 002 peak of the negative active material is in the range of 25.2000 ° 2Th. to 25.3000 ° 2Th., and the peak area of the negative active material is in the range of 5000cts ⁇ °2Th. to 50000cts ⁇ °2Th.
  • the peak intensity of the 002 peak is in the range of 5000 cts to 200,000 cts, and the FWHM of the 002 peak is in the range of 0.1200°2Th. to 0.1800°2Th.
  • the D1 when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range. In some embodiments, when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range. In some embodiments, when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range. In some embodiments, when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range. In some embodiments, when the electrochemical device is in a 50% charged state, by X-ray diffraction, the D1 is to In the range.
  • the D2 when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range. In some embodiments, when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range. In some embodiments, when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range. In some embodiments, when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range. In some embodiments, when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range.
  • the D2 when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range. In some embodiments, when the electrochemical device is in a 100% charged state, by X-ray diffraction, the D2 is to In the range.
  • lithium ion battery Take the lithium ion battery as an example.
  • the lithium ion battery is in different states of charge, lithium ions enter the negative electrode active material layer (ie, the graphite layer) to form different interlayer compounds Li x C 6 , which leads to the deterioration of the negative electrode active material.
  • the interplanar spacing changes.
  • This application uses highly isotropic graphite as the negative electrode material to control the interplanar spacing of the negative electrode active material, so that the graphite particles can influence each other during the lithium insertion process of the lithium ion battery, thereby suppressing interlayer expansion.
  • the features in the X-ray diffraction pattern are related to the inherent characteristics of the negative electrode active material, which can characterize the performance of the negative electrode active material.
  • the negative electrode active material When the negative electrode active material is in different lithium insertion states, its interplanar spacing and X-ray diffraction characteristics (for example, diffraction angle, etc.) will change.
  • the interplanar spacing and X-ray diffraction characteristics of the negative active material can be controlled by controlling the degree of particle recombination of the negative active material.
  • the primary particles of the negative electrode active material can be compounded to form secondary particles by using a high-viscosity binder or increasing the amount of the binder. Controlling the particle size of the secondary particles of the negative electrode active material and the ratio of the particle size of the secondary particles to the particle size of the primary particles can control the interplanar spacing and X-ray diffraction characteristics of the negative electrode active material.
  • the negative active material of the present application can be obtained by the following method: adding a high-viscosity additive to the primary particles of the negative active material to obtain a mixture, and sintering the mixture to obtain secondary particles of the negative active material, wherein
  • the high-viscosity additive includes at least one of oil-based high-temperature asphalt, coal-based high-temperature asphalt, or resin polymer materials. Based on the total weight of the negative electrode active material, the content of the high-viscosity additive is not more than 30 wt%.
  • the negative electrode active material layer when the electrochemical device is in a 100% charged state, by thermogravimetric analysis, the negative electrode active material layer is at least one of 280°C to 300°C or 320°C to 400°C There is a thermal weight loss peak on it.
  • the existence of the thermal weight loss peak indicates that there are substances involved in the reaction, which is related to the composition and content of the negative electrode active material layer and its surface characteristics. The higher the temperature corresponding to the thermal weight loss peak, the lower the thermal reactivity of the surface of the negative electrode active material layer, the better the thermal stability of the surface of the negative electrode active material layer, and the higher the safety of the electrochemical device.
  • the negative electrode active material layer has a thermal weight loss peak in the above temperature range, the negative electrode active material layer has good and balanced thermal stability and thermal reactivity.
  • the mass change of the negative electrode active material layer when the electrochemical device is in a 100% charged state, the mass change of the negative electrode active material layer is -2.0% to 2.3% by thermogravimetric analysis. In some embodiments, when the electrochemical device is in a 100% charged state, the mass change of the negative active material layer is -1.5% to 2.0% by thermogravimetric analysis. In some embodiments, when the electrochemical device is in a 100% charged state, the mass change of the negative electrode active material layer is -1.0% to 1.0% by thermogravimetric analysis. In some embodiments, when the electrochemical device is in a 100% charged state, the mass change of the negative electrode active material layer is -0.5% to 0.5% by thermogravimetric analysis.
  • the negative active material layer has an infrared absorption peak at 1150cm -1 to 1250cm -1.
  • Different functional groups in the negative active material will have different infrared absorption peaks.
  • the negative electrode active material layer has an infrared absorption peak within the above range, the primary efficiency of the electrochemical device can be effectively improved.
  • the negative electrode includes at least one of Ni, Mn, Cr, Fe, S, Si, or Zn.
  • the Ni content is 0.001 wt% to 0.004wt%
  • the Mn content is 0.001wt% to 0.005wt%
  • the Cr content is 0.001wt% to 0.003wt%
  • the Fe content is 0.005wt% to 0.010wt%
  • the S content is 0.002wt %
  • the Si content is not more than 0.0053 wt%
  • the Zn content is 0.003 wt% to 0.005 wt%.
  • the Ni content is 0.002 wt% to 0.003 wt%.
  • the Mn content is 0.002 wt% to 0.004 wt% based on the total weight of the negative active material layer.
  • the Cr content is 0.002 wt% to 0.003 wt% based on the total weight of the negative active material layer.
  • the Fe content is 0.007 wt% to 0.009 wt% based on the total weight of the negative active material layer.
  • the S content is 0.003 wt% to 0.005 wt% based on the total weight of the negative active material layer.
  • the Si content is not greater than 0.0050 wt% or not greater than 0.0030 wt%. In some embodiments, based on the total weight of the negative active material layer, the Zn content is 0.004 wt% to 0.005 wt%.
  • the anode active material in the anode active material layer includes secondary particles.
  • FIG. 1 shows a scanning electron microscope (SEM) image of the negative electrode active material according to Example 6 of the present application, in which the negative electrode active material is compounded to form secondary particles.
  • the negative active material further includes primary particles.
  • the median particle diameter Dv50 of the secondary particles of the negative active material is 7 ⁇ m to 30 ⁇ m. In some embodiments, the median diameter Dv50 of the secondary particles is 10 ⁇ m to 25 ⁇ m. In some embodiments, the median diameter Dv50 of the secondary particles is 15 ⁇ m to 20 ⁇ m. In some embodiments, the median particle diameter Dv50 of the secondary particles is 7 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 22 ⁇ m, 25 ⁇ m, 28 ⁇ m, or 30 ⁇ m.
  • the secondary particles in the negative active material are composited by primary particles with a median diameter D'v50 of 2.8 ⁇ m to 20 ⁇ m.
  • the median diameter of the primary particles and the median diameter of the secondary particles of the negative electrode active material can be obtained by statistics of the SEM spectrum. Specifically, at least 50 SEM images of negative electrode active material samples magnified 1000 times are taken, and the particle size of the secondary particles in the SEM image and the particle size of the primary particles composing the secondary particles are tested by software, and statistics are performed. The median particle diameter D'v50 of the primary particles of the negative electrode active material and the median particle diameter Dv50 of the secondary particles were obtained.
  • the secondary particles in the negative active material are composited by primary particles with a median diameter D'v50 of 3.5 ⁇ m to 15 ⁇ m. In some embodiments, the secondary particles in the negative active material are composited by primary particles with a median diameter D'v50 of 4 ⁇ m to 10 ⁇ m.
  • the ratio of the Dv50 of the secondary particles after the composite of the negative electrode active material to the D'v50 of the primary particles before the composite is 3:2 to 5:2. In some embodiments, the ratio of the Dv50 of the secondary particles after the composite of the negative active material to the D'v50 of the primary particles before the composite is 3:2 to 2:1. In some embodiments, the ratio of the Dv50 of the secondary particles after the composite of the negative active material to the D'v50 of the primary particles before the composite is 2:1 to 5:2.
  • the thickness of the negative active material layer when the electrochemical device is in a 50% charged state, is 0.13 mm to 0.18 mm. In some embodiments, when the electrochemical device is in a 50% charged state, the thickness of the negative active material layer is 0.14 mm to 0.16 mm.
  • the compacted density of the negative active material layer is 1.40 g/cm 3 to 1.80 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is 1.50 g/cm 3 to 1.70 g/cm 3 . In some embodiments, the compacted density of the negative active material layer is 1.40 g/cm 3 , 1.45 g/cm 3 , 1.50 g/cm 3 , 1.55 g/cm 3 , 1.60 g/cm 3 , 1.65 g/cm 3 cm 3 , 1.70g/cm 3 , 1.75g/cm 3 or 1.80g/cm 3 .
  • the compaction density of the negative active material layer is within the above range, it helps to improve the first-time efficiency and cycle thickness expansion rate of the lithium ion battery.
  • the ratio C004/C110 of the peak area C004 of the (004) plane and the peak area C110 of the (110) plane of the negative active material layer measured by X-ray diffraction method is 7.5 to 16.7.
  • the negative active material layer C004/C110 measured by X-ray diffraction method is 8 to 16.5.
  • the negative active material layer C004/C110 measured by X-ray diffraction method is 9-15.
  • the negative active material layer C004/C110 measured by X-ray diffraction method is 10-12.
  • the C004/C110 value of the negative electrode active material layer measured by the X-ray diffraction method can reflect the anisotropy of the negative electrode active material layer.
  • the small value of C004/C110 helps to improve the thickness expansion of ion batteries during cycling.
  • the porosity of the negative active material layer is 25% to 32%. In some embodiments, the porosity of the negative active material layer is 28% to 30%. In some embodiments, the porosity of the negative active material layer is 25%, 26%, 27%, 28%, 29%, 30%, 31%, or 32%. When the porosity of the negative active material layer is within the above range, it helps to improve the first-time efficiency and cycle thickness expansion rate of the lithium ion battery.
  • the grain size Lc of the graphite along the vertical direction is 29 nm to 32 nm
  • the grain size La of the graphite along the horizontal direction is 160 nm to 165 nm.
  • the negative electrode further includes a conductive layer.
  • the conductive material of the conductive layer may include any conductive material as long as it does not cause a chemical change.
  • conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, graphene, etc.), metal-based materials (e.g., metal Powder, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
  • the conductive layer is disposed between the negative active material layer and the negative current collector.
  • the negative electrode further includes a binder, and the binder is selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose , Polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, poly Propylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon, etc.
  • the binder is selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose , Polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone
  • the negative current collector includes at least one of copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, or a polymer substrate coated with conductive metal.
  • the negative electrode can be manufactured by any method known in the prior art.
  • the negative electrode can be made into a slurry by adding a binder and a solvent to the negative active material, and adding thickeners, conductive materials, fillers, etc. as needed, and coating the slurry on the current collector. It is formed by pressing after drying.
  • the positive electrode used in the electrochemical device of the present application includes a positive electrode current collector and a positive electrode active material provided on the positive electrode current collector.
  • the specific types of positive electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the positive active material includes a compound that reversibly intercalates and deintercalates lithium ions.
  • the positive active material may include a composite oxide containing lithium and at least one element selected from cobalt, manganese, and nickel.
  • the positive electrode active material is selected from lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material, lithium manganate (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ) , One or more of lithium iron phosphate (LiFePO 4 ).
  • the positive electrode active material layer may have a coating on the surface, or may be mixed with another compound having a coating.
  • the coating may include oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements ( At least one coating element compound selected from hydroxycarbonate).
  • the compound used for the coating may be amorphous or crystalline.
  • the coating element contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or a mixture thereof.
  • the coating can be applied by any method as long as the method does not adversely affect the performance of the positive electrode active material.
  • the method may include any coating method well-known to those of ordinary skill in the art, such as spraying, dipping, and the like.
  • the positive electrode active material layer further includes a binder, and optionally further includes a positive electrode conductive material.
  • the binder improves the bonding of the positive electrode active material particles to each other, and also improves the bonding of the positive electrode active material to the current collector.
  • binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl chloride Vinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin, nylon, etc.
  • the positive electrode active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode.
  • the positive electrode conductive material may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., Including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • the positive electrode current collector used in the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
  • a separator is provided between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation film that can be used in the embodiments of the present application are not particularly limited, and they can be any technology disclosed in the prior art.
  • the isolation membrane includes a polymer or an inorganic substance formed of a material that is stable to the electrolyte of the present application.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • the porous structure can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • a surface treatment layer is provided on at least one surface of the substrate layer.
  • the surface treatment layer may be a polymer layer or an inorganic substance layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles are selected from alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, One or a combination of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, One or a combination of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly At least one of (vinylidene fluoride-hexafluoropropylene).
  • the electrolyte that can be used in the embodiments of the present application may be an electrolyte known in the prior art.
  • the electrolyte that can be used in the electrolyte of the embodiments of the present application includes, but is not limited to: inorganic lithium salts, such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2, etc.; Fluorine-containing organic lithium salts, such as LiCF 3 SO 3 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,3- Lithium hexafluoropropane disulfonimide, lithium cyclic 1,2-tetrafluoroethane disulfonimide, LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2
  • Lithium salt containing dicarboxylic acid complex such as bis(oxalato) lithium borate, difluorooxalic acid Lithium borate, tris(oxalato)lithium, difluorobis(oxala
  • the electrolyte includes a combination of LiPF 6 and LiBF 4.
  • the electrolyte includes a combination of an inorganic lithium salt such as LiPF 6 or LiBF 4 and a fluorine-containing organic lithium salt such as LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , and LiN(C 2 F 5 SO 2 ) 2 .
  • the concentration of the electrolyte is in the range of 0.8 mol/L to 3 mol/L, for example, in the range of 0.8 mol/L to 2.5 mol/L, in the range of 0.8 mol/L to 2 mol/L, 1 mol/L Within the range of L to 2mol/L, for example, 1mol/L, 1.15mol/L, 1.2mol/L, 1.5mol/L, 2mol/L or 2.5mol/L.
  • Solvents that can be used in the electrolyte of the embodiments of the present application include, but are not limited to: carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof.
  • carbonate compounds include, but are not limited to, linear carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.
  • chain carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate ( EPC), ethyl methyl carbonate (MEC) and their combinations.
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • MEC methyl propyl carbonate
  • EPC ethylene propyl carbonate
  • MEC ethyl methyl carbonate
  • cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, carbonic acid 1,2 -Difluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, carbonic acid 1,2 -Difluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate,
  • ester-based compounds include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, ⁇ -butyrolactone, decanolide, Valerolactone, mevalonolactone, caprolactone, methyl formate, and combinations thereof.
  • ether-based compounds include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane Alkanes, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • ketone-based compounds include, but are not limited to, cyclohexanone.
  • alcohol-based compounds include, but are not limited to, ethanol and isopropanol.
  • aprotic solvents include, but are not limited to, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl- 2-pyrrolidone, formamide, dimethylformamide, acetonitrile, nitromethane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, 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 application also provides an electronic device, which includes the electrochemical device according to the 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 prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • Stereo headsets video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power assistance Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • Example 10 The coke was crushed to a particle size of 3-10 ⁇ m, and then oil-based pitch with a softening point temperature of 150°C-300°C was added (Examples 1-9 and 11-29 and Comparative Examples 1 and 2 were added with 15wt% pitch content , In Example 10, 20wt% asphalt content was added to 20wt%) and mixed. Put the mixture into a granulation equipment (such as a vertical kettle) for granulation. During the granulation process, stir at a rate of 20-100r/min (stirring rate is 20-100r/min) and at a rate of 50-200°C/min. The rate of h is heated to 500-1000°C, and then the graphitization process is performed. (The graphitization temperature is controlled at 2000-3500°C).
  • Graphite, styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are dispersed in deionized water at a weight ratio of 97.7:1.2:1.1, fully stirred and mixed uniformly to obtain negative electrode slurry.
  • the negative electrode slurry is coated on the negative electrode current collector, dried, and cold pressed to obtain the negative electrode active material layer, and the tabs are welded to obtain the negative electrode.
  • LiCoO 2 lithium cobaltate
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1, and LiPF 6 was added and mixed uniformly. Add 3% of fluoroethylene carbonate and mix uniformly to obtain an electrolyte, in which the concentration of LiPF 6 is 1.15 mol/L.
  • a 12 ⁇ m thick polyethylene (PE) porous polymer film is used as the separator.
  • the cyclic thickness expansion rate corresponding to the number of cyclic turns (H 1 -H 0 )/H 0 ⁇ 100%.
  • Table 1 shows the influence of the characteristics of the negative electrode active material on the first-time efficiency of lithium-ion batteries.
  • the negative electrodes of the lithium ion batteries of Examples 1-9 and Comparative Examples 1-2 contained 0.002% Ni, 0.003% Mn, 0.001% Cr, 0.007% Fe, 0.005% S, and 0.004% Zn.
  • the negative electrode of the lithium ion battery of Example 10 contains 0.003% Ni, 0.004% Mn, 0.003% Cr, 0.009% Fe, 0.009% S, and 0.006% Zn.
  • the interplanar spacing of the negative electrode active material can be controlled by controlling the particle size of the secondary particles of the negative electrode active material and the ratio of the particle size of the secondary particles to the primary particles.
  • the interplanar spacing of the negative active material is D1 and D2 satisfying (D2-D1)/D1 ⁇ 0.55
  • the first efficiency of the lithium-ion battery is significantly improved and the cycle expansion rate is significantly reduced, which can improve the energy density and cycle of the lithium-ion battery performance.
  • the interplanar spacing D1 of the negative electrode active material is in the to When it is within the range, it can ensure that the lithium-ion battery has a significantly increased first-time efficiency and a significantly reduced cycle expansion rate.
  • Table 2 shows the characteristics of the 002 peak in the X-ray diffraction pattern of the negative active material.
  • the results show that by controlling the particle size of the secondary particles of the negative electrode active material and the ratio of the particle size of the secondary particles to the primary particles, the X-ray diffraction pattern of the negative electrode active material will change.
  • the interplanar spacing D1 of the negative electrode active material is at to
  • the 2 ⁇ value corresponding to the 002 peak of the negative electrode active material is in the range of 25.2000°2Th. to 25.3000°2Th.
  • the peak area of the negative electrode active material is in the range of 5000cts ⁇ °2Th.
  • the peak intensity of the 002 peak is in the range of 5000 cts to 200,000 cts, and the FWHM of the 002 peak is in the range of 0.1200°2Th. to 0.2100°2Th.
  • the X-ray diffraction pattern of the negative electrode active material used in Example 8 is shown in FIG. 2.
  • Table 3 shows the influence of the characteristics of the negative active material layer on the first-time efficiency, direct current resistance (DCR) and cycle thickness expansion rate of the lithium-ion battery. Except for the parameters listed in Table 3, the conditions of Examples 11-29 are the same as those of Example 8.
  • the C004/C110 value of the negative electrode active material is constant, as the compaction density of the negative electrode active material layer decreases, the porosity and thickness of the negative electrode active material layer increase.
  • the lithium ion In the process of intercalation and deintercalation the formation of side-reaction products is reduced, the DC resistance of the lithium-ion battery is reduced, and the efficiency is increased for the first time.
  • the first efficiency of the lithium-ion battery can be significantly improved and the DC resistance of the lithium-ion battery can be significantly reduced, that is, the energy density and cycle performance of the lithium-ion battery can be significantly improved.
  • Table 4 shows the temperature corresponding to the thermal weight loss peak of the negative active material layer. Each example was tested 3 times.
  • FIG. 4 shows an infrared spectrum chart of the negative electrode active material layer used in Example 13. The results showed that the negative active material layer has an infrared absorption peak at 1150cm -1 to 1250cm -1.
  • references to “embodiments”, “parts of embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplary”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

一种电化学装置，其包含负极，所述负极包含负极集流体和负极活性材料层，所述负极活性材料层包含负极活性材料，所述负极活性材料包含石墨，所述电化学装置在50％荷电状态下具有特定的X射线衍射特征。该电化学装置具有改善的首次效率和循环性能。

Description

电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置和电子装置，尤其是锂离子电池。
背景技术
电化学装置(例如，锂离子电池)由于具有环境友好、工作电压高、比容量大和循环寿命长等优点而被广泛应用，已成为当今世界最具发展潜力的新型绿色化学电源。小尺寸锂离子电池通常用作驱动便携式电子通讯设备(例如，便携式摄像机、移动电话或者笔记本电脑等)的电源，特别是高性能便携式设备的电源。具有高输出特性的中等尺寸和大尺寸锂例子电池被发展应用于电动汽车(EV)和大规模储能系统(ESS)。随着锂离子电池的广泛应用，其首次效率和循环性能已成为亟待解决的关键技术问题。
有鉴于此，确有必要提供一种改进的电化学装置和电子装置。
发明内容
本申请通过提供一种电化学装置和电子装置以试图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。
根据本申请的一个方面，本申请提供了一种电化学装置，其包含负极，所述负极包含负极集流体和负极活性材料层，所述负极活性材料层包含负极活性材料，所述负极活性材料包含石墨，其中当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述负极活性材料的晶面间距为D1，当所述电化学装置在100％荷电状态下，通过X射线衍射法，所述的负极活性材料的晶面间距为D2，D1和D2满足(D2-D1)/D1≤0.55。在一些实施例中，D1和D2满足(D2-D1)/D1≤0.50。在一些实施例中，D1和D2满足(D2-D1)/D1≤0.45。在一些实施例中，D1和D2满足(D2-D1)/D1≥0.30。在一些实施例中，D1和D2满足(D2-D1)/D1≥0.40。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000001
至
Figure PCTCN2020091577-appb-000002
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000003
至
Figure PCTCN2020091577-appb-000004
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000005
至
Figure PCTCN2020091577-appb-000006
Figure PCTCN2020091577-appb-000007
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线 衍射法，所述D1在
Figure PCTCN2020091577-appb-000008
至
Figure PCTCN2020091577-appb-000009
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000010
至
Figure PCTCN2020091577-appb-000011
的范围内。
根据本申请的实施例，其中当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000012
至
Figure PCTCN2020091577-appb-000013
的范围内，所述负极活性材料的002峰对应的2θ值在25.2000°2Th.至25.3000°2Th.的范围内，所述负极活性材料的峰面积在5000cts·°2Th.至50000cts·°2Th.的范围内，所述002峰的峰强度在5000cts至200000cts的范围内，所述002峰的半高宽在0.1200°2Th.至0.2100°2Th.的范围内。
根据本申请的实施例，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层在280℃至300℃或320℃至400℃中的至少一者上存在热失重峰。
根据本申请的实施例，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-2.0％至2.3％。在一些实施例中，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-1.5％至2.0％。在一些实施例中，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-1.0％至1.0％。在一些实施例中，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-0.5％至0.5％。
根据本申请的实施例，通过红外光谱法，所述负极活性材料层在1150cm -1至1250cm -1处有红外吸收峰。
根据本申请的实施例，所述负极包含Ni、Mn、Cr、Fe、S、Si或Zn中的至少一种，基于所述负极活性材料层的总重量，所述Ni含量为0.001wt％至0.004wt％，所述Mn含量为0.001wt％至0.005wt％，所述Cr含量为0.001wt％至0.003wt％，所述Fe含量为0.005wt％至0.010wt％，所述S含量为0.002wt％至0.006wt％，所述Si含量不大于0.0053wt％，所述Zn含量为0.003wt％至0.005wt％。
根据本申请的实施例，所述负极活性材料层满足条件(a)至(e)中的至少一者：
(a)所述负极活性材料包含二次颗粒；
(b)当所述电化学装置在50％荷电状态下，所述负极活性材料层的厚度为0.13mm至0.16mm；
(c)所述负极活性材料层的压实密度为1.40g/cm 3至1.80g/cm 3；
(d)由X射线衍射法测定得到的所述负极活性材料层的(004)面的峰面积C004和(110)面的峰面积C110的比值C004/C110为7.5至16.7；
(e)所述负极活性材料层的孔隙率为25％至32％。
在一些实施例中，当所述电化学装置在50％荷电状态下，所述负极活性材料层的厚度为0.14mm至0.15mm。
在一些实施例中，所述负极活性材料层的压实密度为1.50g/cm 3至1.70g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为约1.50g/cm 3、约1.55g/cm 3、约1.60g/cm 3、约1.65g/cm 3、约1.70g/cm 3、约1.75g/cm 3或约1.80g/cm 3。
在一些实施例中，由X射线衍射法测定得到的所述负极活性材料层C004/C110为8至16.5。在一些实施例中，由X射线衍射法测定得到的所述负极活性材料层C004/C110为9至15。在一些实施例中，由X射线衍射法测定得到的所述负极活性材料层C004/C110为10至12。
在一些实施例中，所述负极活性材料层的孔隙率为28％至30％。在一些实施例中，所述负极活性材料层的孔隙率为约25％、约26％、约27％、约28％、约29％、约30％、约31％或约32％。
根据本申请的实施例，通过X射线衍射法，所述石墨沿垂直方向的晶粒尺寸Lc为29nm至32nm，所述石墨沿水平方向的晶粒尺寸La为160nm至165nm。
根据本申请的实施例，所述负极活性材料的二次颗粒的中值粒径Dv50为7μm至30μm。在一些实施例中，所述二次颗粒的中值粒径Dv50为10μm至25μm。在一些实施例中，所述二次颗粒的中值粒径Dv50为15μm至20μm。在一些实施例中，所述二次颗粒的中值粒径Dv50为约7μm、约10μm、约12μm、约15μm、约18μm、约20μm、约22μm、约25μm、约28μm或约30μm。
根据本申请的另一个方面，本申请提供了一种电子装置，其包括根据本申请所述的电化学装置。
本申请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 的结果来获得其他实施例的附图。
图1展示了根据本申请实施例6中使用的负极活性材料的扫描电子显微镜(SEM)图。
图2展示了根据本申请实施例8中使用的负极活性材料的X射线衍射图谱。
图3展示了根据本申请实施例16中使用的负极活性材料层的热重曲线。
图4展示了根据本申请实施例13中使用的负极活性材料层的红外光谱图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
在具体实施方式及权利要求书中，由术语“中的至少一种”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A或B中的至少一种”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B或C中的至少一种”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
电化学装置(例如，锂离子电池)已广泛应用于各种电子设备中，尤其是小型轻薄化数码类电子产品中。在此类应用中，提高锂离子电池的首次效率以及降低锂离子电池在循环过程中(尤其是高温条件下的循环过程中)的厚度膨胀尤为重要。使用包覆材料来包覆负极活性材料(例如，石墨)的表面可抑制负极活性材料颗粒之间的膨胀，减少极化的产生和副反应产物的堆积，从而改善锂离子电池在循环过程中的厚度膨胀问题。但该包覆层会严重降低锂离子电池的首次效率，使得锂离子电池的综合性能欠佳。
为了解决这一问题，本申请提供了一种电化学装置，其包含负极，所述负极包含负极集流体和负极活性材料层，所述负极活性材料层包含负极活性材料，所述负极活性材料包含石墨，其中当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述负极活性材料的晶面间距为D1，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述的负极活性材料的晶面间距为D2，D1和D2满足(D2-D1)/D1≤0.55。在一些实施例中，D1和D2满足(D2-D1)/D1≤0.50。在一些实施例中，D1和D2满足(D2-D1)/D1≤0.45。在一些实施例中，D1和D2满足(D2-D1)/D1≥0.30。在一些实施例中，D1和D2满足(D2-D1)/D1≥0.40。
根据本申请的实施例，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000014
至
Figure PCTCN2020091577-appb-000015
的范围内，所述负极活性材料的002峰对应的2θ值在25.2000°2Th.至25.3000°2Th.的范围内，所述负极活性材料的峰面积在5000cts·°2Th.至50000cts·°2Th.的范围内，所述002峰的峰强度在5000cts至200000cts的范围内，所述002峰的半高宽在0.1200°2Th.至0.1800°2Th.的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000016
Figure PCTCN2020091577-appb-000017
至
Figure PCTCN2020091577-appb-000018
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000019
至
Figure PCTCN2020091577-appb-000020
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000021
至
Figure PCTCN2020091577-appb-000022
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000023
至
Figure PCTCN2020091577-appb-000024
的范围内。在一些实施例中，当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
Figure PCTCN2020091577-appb-000025
至
Figure PCTCN2020091577-appb-000026
Figure PCTCN2020091577-appb-000027
的范围内。
根据本申请的实施例，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000028
至
Figure PCTCN2020091577-appb-000029
的范围内。在一些实施例中，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000030
至
Figure PCTCN2020091577-appb-000031
的范围内。在一些实施例中，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000032
至
Figure PCTCN2020091577-appb-000033
的范围内。在一些实施例中，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000034
至
Figure PCTCN2020091577-appb-000035
Figure PCTCN2020091577-appb-000036
的范围内。在一些实施例中，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000037
至
Figure PCTCN2020091577-appb-000038
的范围内。在一些实施例中，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000039
至
Figure PCTCN2020091577-appb-000040
Figure PCTCN2020091577-appb-000041
的范围内。在一些实施例中，当所述的电化学装置在100％荷电状态下，通过X射线衍射法，所述D2在
Figure PCTCN2020091577-appb-000042
至
Figure PCTCN2020091577-appb-000043
的范围内。
以锂离子电池为例，当锂离子电池处于不同的荷电状态时，锂离子进入负极活性材料层(即，石墨层)间形成不同的层间化合物Li xC 6，从而导致负极活性材料的晶面间距发生变化。本申请通过使用高度各向同性的石墨作为负极材料来控制负极活性材料的晶面间距，使得在锂离子电池的嵌锂过程中，石墨颗粒能够相互影响，从而抑制层间膨胀。X射线衍射图谱中的特征(例如，2θ值、峰强度、半高宽和峰面积等)与负极活性材料固有的特性相关，其可表征负极活性材料的性能。晶面间距是负极活性材料(例 如，石墨材料)的固有结构属性，其可通过X射线衍射数据中的衍射角计算得到。具体地，晶面间距D＝kλ/βcosθ，其中K为谢乐常数，通常为0.89；λ为X射线的波长；β为衍射峰的半高峰宽；θ为布拉格角。负极活性材料处于不同嵌锂状态时，其晶面间距和X射线衍射特征(例如，衍射角等)会发生变化。负极活性材料的晶面间距和X射线衍射特征可通过控制负极活性材料的颗粒复合程度来控制。具体来说，通过使用高粘性的粘结剂或提高粘结剂的用量可使负极活性材料的一次颗粒复合形成二次颗粒。控制负极活性材料的二次颗粒的粒径以及二次颗粒的粒径与一次颗粒的粒径比可控制负极活性材料的晶面间距以及X射线衍射特征。在一些实施例中，本申请的负极活性材料可通过以下方法得到：在负极活性材料的一次颗粒中添加高粘性添加剂，得到混合物，烧结所述混合物，得到负极活性材料的二次颗粒，其中所述高粘性添加剂包括油系高温沥青、煤系高温沥青或树脂高分子材料中的至少一种，基于所述负极活性材料的总重量，所述高粘性添加剂的含量为不大于30wt％。当电化学装置在50％荷电状态下具有如上所述的晶面间距和X射线衍射特征时，电化学装置可实现改善的首次效率和循环厚度膨胀率。
根据本申请的实施例，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层在280℃至300℃或320℃至400℃中的至少一者上存在热失重峰。热失重峰的存在表明有物质参与反应，其与负极活性材料层的成分及其含量以及其表面特性有关。热失重峰对应的温度越高，负极活性材料层表面的热反应性越低，负极活性材料层表面的热稳定性越好，电化学装置的安全性越高。当所述负极活性材料层在上述温度范围内存在热失重峰时，负极活性材料层具有良好的、平衡的热稳定性和热反应性。
根据本申请的实施例，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-2.0％至2.3％。在一些实施例中，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-1.5％至2.0％。在一些实施例中，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-1.0％至1.0％。在一些实施例中，当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层的质量变化为-0.5％至0.5％。
根据本申请的实施例，通过红外光谱法，所述负极活性材料层在1150cm -1至1250cm -1处有红外吸收峰。负极活性材料中不同官能团会具有不同的红外吸收峰。当负极活 性材料层在上述范围内具有红外吸收峰时，能够有效改善电化学装置的首次效率。
根据本申请的实施例，所述负极包含Ni、Mn、Cr、Fe、S、Si或Zn中的至少一种，基于所述负极活性材料层的总重量，所述Ni含量为0.001wt％至0.004wt％，所述Mn含量为0.001wt％至0.005wt％，所述Cr含量为0.001wt％至0.003wt％，所述Fe含量为0.005wt％至0.010wt％，所述S含量为0.002wt％至0.006wt％，所述Si含量不大于0.0053wt％，所述Zn含量为0.003wt％至0.005wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述Ni含量为0.002wt％至0.003wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述Mn含量为0.002wt％至0.004wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述Cr含量为0.002wt％至0.003wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述Fe含量为0.007wt％至0.009wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述S含量为0.003wt％至0.005wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述Si含量不大于0.0050wt％或不大于0.0030wt％。在一些实施例中，基于所述负极活性材料层的总重量，所述Zn含量为0.004wt％至0.005wt％。
根据本申请的实施例，所述负极活性材料层中的所述负极活性材料包含二次颗粒。图1展示了根据本申请实施例6的负极活性材料的扫描电子显微镜(SEM)图，其中负极活性材料复合形成二次颗粒。在一些实施例中，所述负极活性材料还包含一次颗粒。
根据本申请的实施例，所述负极活性材料的二次颗粒的中值粒径Dv50为7μm至30μm。在一些实施例中，所述二次颗粒的中值粒径Dv50为10μm至25μm。在一些实施例中，所述二次颗粒的中值粒径Dv50为15μm至20μm。在一些实施例中，所述二次颗粒的中值粒径Dv50为7μm、10μm、12μm、15μm、18μm、20μm、22μm、25μm、28μm或30μm。
根据本申请的实施例，所述负极活性材料中的二次颗粒由中值粒径D'v50为2.8μm至20μm的一次颗粒复合而成。
负极活性材料的一次颗粒的中值粒径和二次颗粒的中值粒径可以通过对SEM图谱进行统计得到。具体地，拍摄至少50张负极活性材料样品放大1000倍的SEM图，通过软件测试SEM图中二次颗粒的粒径以及组成该二次颗粒的一次颗粒的粒径，并进行统计，通过计算可得到负极活性材料的一次颗粒的中值粒径D'v50和二次颗粒的中值粒径Dv50。
在一些实施例中，所述负极活性材料中的二次颗粒由中值粒径D'v50为3.5μm至 15μm的一次颗粒复合而成。在一些实施例中，所述负极活性材料中的二次颗粒由中值粒径D'v50为4μm至10μm的一次颗粒复合而成。
根据本申请的实施例，所述负极活性材料复合后的二次颗粒的Dv50与复合前的一次颗粒的D'v50的比率为3:2至5:2。在一些实施例中，所述负极活性材料复合后的二次颗粒的Dv50与复合前的一次颗粒的D'v50的比率为3:2至2:1。在一些实施例中，所述负极活性材料复合后的二次颗粒的Dv50与复合前的一次颗粒的D'v50的比率为2:1至5:2。
根据本申请的实施例，当所述电化学装置在50％荷电状态下，所述负极活性材料层的厚度为0.13mm至0.18mm。在一些实施例中，当所述电化学装置在50％荷电状态下，所述负极活性材料层的厚度为0.14mm至0.16mm。
根据本申请的实施例，所述负极活性材料层的压实密度为1.40g/cm 3至1.80g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为1.50g/cm 3至1.70g/cm 3。在一些实施例中，所述负极活性材料层的压实密度为1.40g/cm 3、1.45g/cm 3、1.50g/cm 3、1.55g/cm 3、1.60g/cm 3、1.65g/cm 3、1.70g/cm 3、1.75g/cm 3或1.80g/cm 3。负极活性材料层的压实密度越小，负极活性材料层的孔隙率越大。当负极活性材料层的压实密度在上述范围内时，有助于改善锂离子电池的首次效率和循环厚度膨胀率。
根据本申请的实施例，由X射线衍射法测定得到的所述负极活性材料层的(004)面的峰面积C004和(110)面的峰面积C110的比值C004/C110为7.5至16.7。在一些实施例中，由X射线衍射法测定得到的所述负极活性材料层C004/C110为8至16.5。在一些实施例中，由X射线衍射法测定得到的所述负极活性材料层C004/C110为9至15。在一些实施例中，由X射线衍射法测定得到的所述负极活性材料层C004/C110为10至12。由X射线衍射法测定得到的所述负极活性材料层的C004/C110值可反映出负极活性材料层的各向异性。C004/C110值小，有助于改善离子电池的在循环过程中的厚度膨胀问题。
根据本申请的实施例，所述负极活性材料层的孔隙率为25％至32％。在一些实施例中，所述负极活性材料层的孔隙率为28％至30％。在一些实施例中，所述负极活性材料层的孔隙率为25％、26％、27％、28％、29％、30％、31％或32％。当负极活性材料层的孔隙率在上述范围内时，有助于改善锂离子电池的首次效率和循环厚度膨胀率。
根据本申请的实施例，通过X射线衍射法，所述石墨沿垂直方向的晶粒尺寸Lc为29nm至32nm，所述石墨沿水平方向的晶粒尺寸La为160nm至165nm。当石墨的晶 粒尺寸在上述范围内时，石墨具有合适数量的嵌锂位点，且在循环过程中发生较小的膨胀。
根据本申请的实施例，所述负极进一步包括导电层。在一些实施例中，所述导电层的导电材料可以包括任何导电材料，只要它不引起化学变化。导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、碳纳米管、石墨烯等)、基于金属的材料(例如，金属粉、金属纤维等，例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
根据本申请的实施例，所述导电层设置于负极活性材料层和负极集流体之间。
根据本申请的实施例，所述负极进一步包括粘结剂，所述粘结剂选自以下的至少一种：聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
根据本申请的实施例，所述负极集流体包括铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或覆有导电金属的聚合物基底中的至少一种。
根据本申请的实施例，负极可通过现有技术中已知的任何方法制造。在一些实施例中，负极可以通过在负极活性材料中加入粘合剂和溶剂并根据需要加入增稠剂、导电材料、填充材料等而制成浆料，将该浆料其涂布于集流体上，干燥后进行压制而形成。
本申请的电化学装置中所使用的正极包括正极集流体和设置在所述正极集流体上的正极活性材料。正极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。
根据本申请的实施例，正极活性材料包括可逆地嵌入和脱嵌锂离子的化合物。在一些实施例中，正极活性材料可以包括复合氧化物，所述复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。在又一些实施例中，正极活性材料选自钴酸锂(LiCoO 2)、锂镍锰钴三元材料、锰酸锂(LiMn 2O 4)、镍锰酸锂(LiNi 0.5Mn 1.5O 4)、磷酸铁锂(LiFePO 4)中的一种或几种。
根据本申请的实施例，正极活性材料层可以在表面上具有涂层，或者可以与具有涂层的另一化合物混合。所述涂层可以包括从涂覆元素的氧化物、涂覆元素的氢氧化物、涂覆元素的羟基氧化物、涂覆元素的碳酸氧盐(oxycarbonate)和涂覆元素的羟基碳酸盐(hydroxycarbonate)中选择的至少一种涂覆元素化合物。用于涂层的化合物可以是非晶的或结晶的。在涂层中含有的涂覆元素可以包括Mg、Al、Co、K、Na、Ca、Si、Ti、V、 Sn、Ge、Ga、B、As、Zr、F或它们的混合物。可以通过任何方法来施加涂层，只要所述方法不对正极活性材料的性能产生不利影响即可。例如，所述方法可以包括对本领域普通技术人员来说众所周知的任何涂覆方法，例如喷涂、浸渍等。
根据本申请的实施例，正极活性材料层还包含粘合剂，并且可选地还包括正极导电材料。
粘合剂提高正极活性材料颗粒彼此间的结合，并且还提高正极活性材料与集流体的结合。粘合剂的非限制性示例包括聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
正极活性材料层包括正极导电材料，从而赋予电极导电性。所述正极导电材料可以包括任何导电材料，只要它不引起化学变化。正极导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如，金属粉、金属纤维等，包括例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
用于根据本申请的电化学装置的正极集流体可以是铝(Al)，但不限于此。
在一些实施例中，正极与负极之间设有隔离膜以防止短路。可用于本申请的实施例中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。多孔结构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接性。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的一种或几种的组合。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯 酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。
聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
可用于本申请实施例的电解液可以为现有技术中已知的电解液。可用于本申请实施例的电解液中的电解质包括、但不限于：无机锂盐，例如LiClO 4、LiAsF 6、LiPF 6、LiBF 4、LiSbF 6、LiSO 3F、LiN(FSO 2) 2等；含氟有机锂盐，例如LiCF 3SO 3、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,3-六氟丙烷二磺酰亚胺锂、环状1,2-四氟乙烷二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)、LiC(CF 3SO 2) 3、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 2(CF 3) 2、LiBF2(C2F5)2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2；含二羧酸配合物锂盐，例如双(草酸根合)硼酸锂、二氟草酸根合硼酸锂、三(草酸根合)磷酸锂、二氟双(草酸根合)磷酸锂、四氟(草酸根合)磷酸锂等。另外，上述电解质可以单独使用一种，也可以同时使用两种或两种以上。例如，在一些实施例中，电解质包括LiPF 6和LiBF 4的组合。在一些实施例中，电解质包括LiPF 6或LiBF 4等无机锂盐与LiCF 3SO 3、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2等含氟有机锂盐的组合。
在一些实施例中，电解质的浓度在0.8mol/L至3mol/L的范围内，例如0.8mol/L至2.5mol/L的范围内、0.8mol/L至2mol/L的范围内、1mol/L至2mol/L的范围内、又例如为1mol/L、1.15mol/L、1.2mol/L、1.5mol/L、2mol/L或2.5mol/L。
可用于本申请实施例的电解液中的溶剂包括，但不限于：碳酸酯化合物、基于酯的化合物、基于醚的化合物、基于酮的化合物、基于醇的化合物、非质子溶剂或它们的组合。
碳酸酯化合物的实例包括，但不限于，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它们的组合。
链状碳酸酯化合物的实例包括，但不限于，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)及它们的组合。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)及它们的组合。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及它们的组合。
基于酯的化合物的实例包括，但不限于，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、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯及它们的组合。
基于醚的化合物的实例包括，但不限于，二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及它们的组合。
基于酮的化合物的实例包括，但不限于，环己酮。
基于醇的化合物的实例包括，但不限于，乙醇和异丙醇。
非质子溶剂的实例包括，但不限于，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、硝基甲烷、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及它们的组合。
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、太阳能电池或电容器。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。
本申请另提供了一种电子装置，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装置。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。
实施例
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。
一、锂离子电池的制备
1、负极的制备
将焦炭破碎至粒径为3-10μm，然后加入软化点温度为150℃-300℃的油系沥青(实施例1-9和11-29以及对比例1和2中加入15wt％的沥青的含量，实施例10中加入20wt％沥青含量为20wt％)，混合。将混合物置入造粒设备(如竖式釜)中进行造粒，造粒过程中加期间以20-100r/min的速率搅拌(搅拌速率为20-100r/min)并以50-200℃/h的速率加热至500-1000℃，然后进行石墨化工艺。(石墨化温度控制在2000-3500℃)。
将石墨、丁苯橡胶(SBR)和羧甲基纤维素钠(CMC)按照重量比97.7:1.2:1.1分散于去离子水中，充分搅拌混合均匀，得到负极浆料。将负极浆料涂覆在负极集流体上，烘干，冷压得到负极活性材料层，焊接极耳，得到负极。
2、正极的制备
将钴酸锂(LiCoO 2)、乙炔黑和聚偏二氟乙烯(PVDF)按重量比96:2:2在适量的N-甲基吡咯烷酮(NMP)中充分搅拌混合均匀后，涂覆于正极集流体铝箔上，烘干，冷压得到正极活性材料层，焊接极耳，得到正极。
3、电解液的制备
在干燥氩气环境下，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸二乙酯(DEC)以1:1:1的重量比混合，加入LiPF 6混合均匀。加入3％的氟代碳酸乙烯酯，混合均匀后得到电解液，其中LiPF 6的浓度为1.15mol/L。
4、隔离膜的制备
以12μm厚的聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将正极、隔离膜、负极按顺序叠好，使隔离膜处于正极和负极之间起到隔离的作用，然后卷绕，置于外包装箔铝塑膜中进行干燥，注入上述制备好的电解液，经过真空封装、静置、化成、整形、容量测试等工序，获得锂离子电池。
二、测试方法
1、负极活性材料的晶面间距的测试方法
在干燥环境下，从锂离子电池拆解负极活性材料，并用真空铝塑膜密封。然后将透明胶带贴在待测试样品上，通过X射线衍射法测试负极活性材料的晶面间距。
2、负极活性材料的粒径的测试方法
使用马尔文粒度测试仪测量负极活性材料的粒径：将负极活性材料样品分散在分散剂乙醇中，超声30分钟后，将样品加入到马尔文粒度测试仪内，测试负极活性材料的Dv50、Dv10和Dv90。
2、锂离子电池的循环厚度膨胀率的测试方法
在45℃下，用万分尺测试锂离子电池在初始半充电状态下的厚度，记为H 0。将锂离子电池以1.5C倍率充放电循环500圈，测量锂离子电池在满充状态下的厚度，记为H 1。通过下式计算锂离子电池的循环厚度膨胀率：
对应循环圈数的循环厚度膨胀率＝(H 1-H 0)/H 0×100％。
3、锂离子电池的首次效率的测试方法
将锂离子电池以0.5C充电至4.4V，记录首次充电容量C，然后以0.5C放电至3.0V，记录其放电容量D。通过下式计算锂离子电池的首次效率CE：
CE＝D/C。
4、锂离子电池的直流阻抗(DCR)的测试方法
以1.5C倍率的电流将锂离子电池恒流充电至4.2V，再以4.2V恒压充电至0.05C,静置30分钟。以0.1C倍率的电流放电10秒，测试电压值，记为U1。以1C放电360秒，测试电压值，记为U2。重复上述充放电步骤5次，使锂离子电池达到50％荷电状态(SOC)。“1C”指的是在1小时内使锂离子电池容量完全放完的电流值。按如下公式计算锂离子电池在50％荷电状态(SOC)下的直流阻抗R：
R＝(U2-U1)/(1C-0.1C)。
三、测试结果
表1展示了负极活性材料的特性对锂离子电池的首次效率的影响。实施例1-9和对比例1-2的锂离子电池的负极包含0.002％的Ni、0.003％的Mn、0.001％的Cr、0.007％的Fe、0.005％的S和0.004％的Zn。实施例10的锂离子电池负的极包含0.003％的Ni、0.004％的Mn、0.003％的Cr、0.009％的Fe、0.009％的S和0.006％的Zn。
表1
Figure PCTCN2020091577-appb-000044
Figure PCTCN2020091577-appb-000045
通过控制负极活性材料的二次颗粒的粒径以及二次颗粒与一次颗粒的粒径的比例可控制负极活性材料的晶面间距。当负极活性材料的晶面间距为D1和D2满足(D2-D1)/D1≤0.55时，锂离子电池的首次效率显著提升且循环膨胀率显著下降，从而可改善锂离子电池的能量密度和循环性能。当锂离子电池在50％荷电状态下的负极活性材料的晶面间距D1在
Figure PCTCN2020091577-appb-000046
至
Figure PCTCN2020091577-appb-000047
的范围内时，可保证锂离子电池具有显著升高的首次效率和显著降低的循环膨胀率。
表2展示了负极活性材料的X射线衍射图谱中002峰的特征。
表2
Figure PCTCN2020091577-appb-000048
结果表明，通过控制负极活性材料的二次颗粒的粒径以及二次颗粒与一次颗粒的粒径的比例，负极活性材料的X射线衍射图谱会发生变化。当上述实施例的锂离子电池在50％荷电状态下，负极活性材料的晶面间距D1在
Figure PCTCN2020091577-appb-000049
至
Figure PCTCN2020091577-appb-000050
的范围内，负极活性材料的002峰对应的2θ值在25.2000°2Th.至25.3000°2Th.的范围内，负极活性材料的峰面积在5000cts·°2Th.至50000cts·°2Th.的范围内，002峰的峰强度在5000cts至200000cts的范围内，所述002峰的半高宽在0.1200°2Th.至0.2100°2Th.的范围内。 实施例8中使用的负极活性材料的X射线衍射图谱如图2所示。
表3展示了负极活性材料层的特性对锂离子电池的首次效率、直流电阻(DCR)和循环厚度膨胀率的影响。除表3中所列参数以外，实施例11-29与实施例8的条件一致。
表3
Figure PCTCN2020091577-appb-000051
结果表明，在负极活性材料的压实密度一定的情况下，随着负极活性材料层的C004/C110值的降低，负极活性材料层的各向异性降低(即，C004/C110值增大)，锂离子电池的直流电阻和在循环过程中的厚度膨胀率逐渐降低。当负极活性材料层的C004/C110在7.5至16.7的范围内时，锂离子电池具有显著降低的直流电阻和循环厚度膨胀率。
在负极活性材料的C004/C110值一定的情况下，随着负极活性材料层的压实密度的降低，负极活性材料层的孔隙率和厚度增大，在锂离子电池的循环过程中，锂离子的嵌脱过程中形成副反应产物减少，锂离子电池的直流电阻降低，首次效率升高。在负极活 性材料层的C004/C110在大致相同的情况下，当负极活性材料层的压实密度在1.40g/cm 3至1.80g/cm 3的范围内和/或负极活性材料层的厚度在0.13mm至0.16mm的范围内时，可显著提升锂离子电池的首次效率并显著降低锂离子电池的直流电阻，即，可显著改善锂离子电池的能量密度和循环性能。
表4展示了负极活性材料层的热失重峰对应的温度。每个实施例测试3次。
表4
  测试1(℃) 测试2(℃) 测试3(℃)
实施例15 281.3 280.9 283.8
实施例16 290.1 290.6 292.9
实施例17 293.1 294.8 296.2
结果表明，通过热重分析法，实施例15-17的负极活性材料层在280℃至300℃存在热失重峰。实施例16中使用的负极活性材料层的热失重曲线如图3所示。
图4展示了实施例13中使用的负极活性材料层的红外光谱图。结果显示，负极活性材料层在1150cm -1至1250cm -1处有红外吸收峰。
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 (9)

  1. 一种电化学装置，其包含负极，所述负极包含负极集流体和负极活性材料层，所述负极活性材料层包含负极活性材料，所述负极活性材料包含石墨，其中：
    当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述负极活性材料的晶面间距为D1，
    当所述电化学装置在100％荷电状态下，通过X射线衍射法，所述的负极活性材料的晶面间距为D2，
    D1和D2满足(D2-D1)/D1≤0.55。
  2. 根据权利要求1所述的电化学装置，其中当所述电化学装置在50％荷电状态下，通过X射线衍射法，所述D1在
    Figure PCTCN2020091577-appb-100001
    至
    Figure PCTCN2020091577-appb-100002
    的范围内，所述负极活性材料的002峰对应的2θ值在25.2000°2Th.至25.3000°2Th.的范围内，所述负极活性材料的峰面积在5000cts·°2Th.至50000cts·°2Th.的范围内，所述002峰的峰强度在5000cts至200000cts的范围内，所述002峰的半高宽在0.1200°2Th.至0.2100°2Th.的范围内。
  3. 根据权利要求1所述的电化学装置，其中当所述电化学装置在100％荷电状态下，通过热重分析法，所述负极活性材料层在280℃至300℃或320℃至400℃中的至少一者上存在热失重峰。
  4. 根据权利要求3所述的电化学装置，其中所述负极活性材料层的质量变化为-2.0％至2.3％。
  5. 根据权利要求1所述的电化学装置，其中通过红外光谱法，所述负极活性材料层在1150cm -1至1250cm -1处有红外吸收峰。
  6. 根据权利要求1所述的电化学装置，其中所述负极包含Ni、Mn、Cr、Fe、S、Si或Zn中的至少一种，基于所述负极活性材料层的总重量，所述Ni含量为 0.001wt％至0.004wt％，所述Mn含量为0.001wt％至0.005wt％，所述Cr含量为0.001wt％至0.003wt％，所述Fe含量为0.005wt％至0.010wt％，所述S含量为0.002wt％至0.006wt％，所述Si含量不大于0.0053wt％，所述Zn含量为0.003wt％至0.005wt％。
  7. 根据权利要求1所述的电化学装置，其中所述负极活性材料层满足条件(a)至(e)中的至少一者：
    (a)所述负极活性材料包含二次颗粒；
    (b)当所述电化学装置在50％荷电状态下，所述负极活性材料层的厚度为0.13mm至0.16mm；
    (c)所述负极活性材料层的压实密度为1.40g/cm 3至1.80g/cm 3；
    (d)由X射线衍射法测定得到的所述负极活性材料层的(004)面的峰面积C004和(110)面的峰面积C110的比值C004/C110为7.5至16.7；
    (e)所述负极活性材料层的孔隙率为25％至32％。
  8. 根据权利要求1所述的电化学装置，其中通过X射线衍射法，所述石墨沿垂直方向的晶粒尺寸Lc为29nm至32nm，所述石墨沿水平方向的晶粒尺寸La为160nm至165nm。
  9. 一种电子装置，其包含权利要求1-8中任一项所述的电化学装置。
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