WO2023082245A1 - 电极及其制作方法、电化学装置和电子装置 - Google Patents

电极及其制作方法、电化学装置和电子装置 Download PDF

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WO2023082245A1
WO2023082245A1 PCT/CN2021/130625 CN2021130625W WO2023082245A1 WO 2023082245 A1 WO2023082245 A1 WO 2023082245A1 CN 2021130625 W CN2021130625 W CN 2021130625W WO 2023082245 A1 WO2023082245 A1 WO 2023082245A1
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active material
material layer
electrode
positive electrode
current collector
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PCT/CN2021/130625
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English (en)
French (fr)
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刘明举
李娅洁
张青文
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东莞新能源科技有限公司
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Priority to CN202180026308.1A priority Critical patent/CN115380398A/zh
Priority to PCT/CN2021/130625 priority patent/WO2023082245A1/zh
Publication of WO2023082245A1 publication Critical patent/WO2023082245A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of 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

Definitions

  • the present application relates to the field of electrochemical energy storage, in particular to an electrode and a manufacturing method thereof, an electrochemical device and an electronic device.
  • Electrochemical devices such as lithium-ion batteries, have the advantages of high energy density, high power, and long cycle life, and are widely used in various fields. With the development of technology, the requirements for the energy density of electrochemical devices are getting higher and higher. In order to increase the energy density of electrochemical devices, some technologies increase the capacity or voltage of active materials, while others increase the content of active materials per unit volume and reduce the content of inactive materials. By reducing the thickness of the current collector or separator, reducing the proportion of inactive materials in the formulation, and preparing thicker electrodes, the proportion of inactive materials can be reduced.
  • the thickness of the current collector and separator Both have been reduced to close to the limit, so the thickness of the electrode can only be increased, but too much increase in the thickness of the electrode may affect the performance of the electrochemical device, so the thickness of the electrode cannot be greatly increased. Therefore, how to improve the energy density of the electrochemical device while ensuring the performance of the electrochemical device is still an urgent problem to be solved.
  • Some embodiments of the present application provide an electrode and its preparation method, an electrochemical device, and an electronic device, wherein the active material layer of the electrode is subjected to thermogravimetric analysis at a heating rate of 10°C/min under an inert atmosphere.
  • thermogravimetric analysis at a heating rate of 10°C/min under an inert atmosphere.
  • the results of reanalysis show that the mass change of the active material layer is 0% to 0.2% at 200°C to 800°C, which can improve the conductivity of the active material layer, which is beneficial to increase the energy density of the electrochemical device.
  • an electrode in some embodiments of the present application, is proposed; the electrode includes a current collector and an active material layer located on one or both sides of the current collector; the active material layer is subjected to thermogravimetric analysis at a heating rate of 10°C/min under an inert atmosphere , the results of thermogravimetric analysis showed that the mass change of the active material layer at 200°C to 800°C was 0% to 0.2%.
  • the active material layer has good electrical conductivity, which is beneficial to the performance of the electrochemical device and to the improvement of energy density.
  • the results of thermogravimetric analysis show that the number of weight loss peaks of the active material layer at 200°C to 800°C is zero. This shows that the polymer compound content in the active material layer in the present application is zero or very low, which is beneficial to improve ion and electron conduction in the active material layer.
  • the electrode is positive or negative.
  • the electrode is a negative electrode
  • the active material layer is a negative electrode active material layer
  • the current collector is a negative electrode current collector
  • the compaction density ⁇ 1 of the negative electrode active material layer is ⁇ 0.6g/cm 3 , and a higher compaction density is beneficial to Increase the energy that can be stored in electrochemical devices per unit volume.
  • the thickness h 1 of the negative electrode active material layer on one side of the negative electrode current collector is greater than or equal to 10 ⁇ m, and a thicker thickness is conducive to improving the energy density of the electrochemical device.
  • the porosity n 1 of the negative electrode active material layer satisfies: 35% ⁇ n 1 ⁇ 25%. By setting an appropriate porosity, the infiltration of the electrolyte and the electrical conductivity can be ensured while ensuring the energy density.
  • the resistivity of the negative electrode active material layer is 0.01 ⁇ *cm to 50 ⁇ *cm, which indicates that the negative electrode active material layer of the present application has good conductivity, which is beneficial to the charge and discharge performance of the electrochemical device.
  • the negative electrode active material layer includes a negative electrode material, and the negative electrode material includes at least one of lithium titanate, silicon-based material, tin-based material, lithium metal material or carbon material.
  • the electrode is a negative electrode
  • the active material layer is a negative electrode active material layer
  • the current collector is a negative electrode current collector
  • the compacted density ⁇ 1 of the negative electrode active material layer satisfies: 1.85g/cm 3 ⁇ ⁇ 1 ⁇ 0.65g/cm 3 , which is conducive to improving the energy density of the electrochemical device.
  • the thickness h 1 of the negative electrode active material layer on one side of the negative electrode current collector satisfies: 1500 ⁇ m ⁇ h 1 ⁇ 15 ⁇ m, which is beneficial to prevent the active material layer from falling off while increasing the energy density of the electrochemical device.
  • the compacted density ⁇ 1 of the negative electrode active material layer satisfies: 1.83g/cm 3 ⁇ 1 ⁇ 1.0g/cm 3 .
  • the thickness h 1 of the negative electrode active material layer on one side of the negative electrode current collector satisfies: 150 ⁇ m ⁇ h 1 ⁇ 30 ⁇ m.
  • the electrode is a positive electrode
  • the active material layer is a positive electrode active material layer
  • the current collector is a positive electrode current collector.
  • Energy density of chemical devices In some embodiments, the thickness h 2 of the positive electrode active material layer on one side of the positive electrode current collector is greater than or equal to 20 ⁇ m, which is beneficial to increase the energy density of the electrochemical device.
  • the porosity n 2 of the positive electrode active material layer satisfies: 20% ⁇ n 2 ⁇ 15%, so as to ensure the infiltration and conductivity of the electrolyte while not significantly affecting the energy density.
  • the positive electrode active material layer has a resistivity of 0.1 ⁇ *cm to 500 ⁇ *cm, so as to have better conductivity.
  • the positive electrode active material layer includes a positive electrode material, and the positive electrode material includes at least one of lithium iron phosphate, lithium nickel cobalt manganate, lithium manganate, lithium cobaltate, and lithium nickel cobalt aluminate.
  • the electrode is a positive electrode
  • the active material layer is a positive electrode active material layer
  • the current collector is a positive electrode current collector
  • the compacted density ⁇ 2 of the positive electrode active material layer satisfies: 4.25g/cm 3 ⁇ ⁇ 2 ⁇ 2.3 g/cm 3 , thereby preventing the positive electrode active material layer from falling off or breaking while increasing the energy density.
  • the thickness h 2 of the positive electrode active material layer on one side of the positive electrode current collector satisfies: 1500 ⁇ m ⁇ h 2 ⁇ 25 ⁇ m, so as to increase the energy density of the electrochemical device while avoiding increasing the thickness of the positive electrode active material layer and the positive electrode collector.
  • the compacted density ⁇ 2 of the positive electrode active material layer satisfies: 4.23g/cm 3 ⁇ 2 ⁇ 4.0g/cm 3 .
  • the thickness h 2 of the positive electrode active material layer on one side of the positive electrode current collector satisfies: 130 ⁇ m ⁇ h 2 ⁇ 26 ⁇ m.
  • the active material layer includes a first conductive agent and a second conductive agent; the first conductive agent includes carbon nanotubes, and the second conductive agent includes carbon fiber, acetylene black, graphene, Ketjen black or conductive carbon At least one of black.
  • the long-range conductivity of carbon nanotubes is beneficial to improve the conductivity of the active material layer, and it is beneficial to maintain the structural stability of the active material layer.
  • the active material layer includes active materials, and the active material layer includes the following components in mass: 0 to 2 parts of the first conductive agent and 0 parts, 0 to 1 part of the second conductive agent, 97 parts of the active material Parts to 100 parts, so that the energy density can be guaranteed while ensuring the electrical conductivity.
  • the carbon nanotubes have a diameter of 0.5 nm to 10 nm and a length of 1 ⁇ m to 100 ⁇ m. Every 2 to 1000 carbon nanotubes form an aggregate, the diameter of the aggregate is 1 nm to 500 nm, and the length of the aggregate is 1 ⁇ m to 100 nm. 100 ⁇ m, which is conducive to stabilizing the structural stability of the active material layer.
  • an electrode preparation method which can be used to manufacture any electrode of the present application, including: coating the slurry of the active material layer on at least one surface of the current collector, drying, and cold pressing , to obtain the initial electrode; the initial electrode is processed to obtain the electrode; wherein, the processing of the initial electrode includes: plasma treatment of the initial electrode in a vacuum environment, the plasma power is 0.5kW to 5kW, and the gas source includes nitrogen, argon At least one of gas or carbon tetrafluoride, the gas flow rate is 3000sccm to 5000sccm, the temperature is 20°C to 60°C, and the treatment time is 1min to 60min; or, the initial electrode is heat treated in a vacuum or inert gas environment, heat treatment The temperature is greater than 200°C, and the heat treatment time is not less than 5 minutes; or, laser bombards the initial electrode in a vacuum or inert gas environment, the laser intensity is 30W to 100W, the treatment time is 1s to 600s,
  • the present application proposes an electrochemical device, including an electrode: the electrode is any one of the electrodes in the present application, or the electrode is an electrode prepared by using the electrode preparation method proposed in the present application.
  • the present application proposes an electronic device, including the electrochemical device provided in the present application.
  • the electrode includes a current collector and an active material layer located on one or both sides of the current collector; the active material layer is subjected to thermogravimetry at a heating rate of 10°C/min under an inert atmosphere Analysis, the results of thermogravimetric analysis show that the mass change of the active material layer at 200 ° C to 800 ° C is 0% to 0.2%, which shows that in the electrode proposed in the examples of the application, the active material layer has good conductivity, which is beneficial to The thickness of the active material layer is increased without deteriorating the performance, thereby facilitating the improvement of the energy density of the electrochemical device using the electrode.
  • FIG. 1 is a schematic diagram of an electrode according to an embodiment of the present disclosure.
  • some technologies increase the energy density of the electrochemical device by increasing the thickness of the active material layer in the electrode, and increasing the thickness of the active material layer in the electrode may deteriorate the activity because the active material layer is too thick
  • the conductivity of the material layer in order to improve the conductivity of the active material layer, in some technologies, the structure of the multi-layer active material layer is adopted, but the composite cold pressing process of multiple single-layer structures is complicated, and it is unavoidable that each The original compaction density and porosity of the single layer change, and the joint between the layers is prone to release due to weak bonding, which affects the conduction of electrons and ions and deteriorates cycle performance.
  • the efficiency of laser drilling is low, the cost is high, and the energy density is easily lost during the drilling process.
  • the pore-forming agent solution is coated on the electrode surface, but this cannot avoid the dissolution of the electrode surface, and the depth of the pores formed by the pore-forming agent is limited, and the improvement on the side near the current collector is limited.
  • the above technologies have solved the ion transport from the electrolyte to the surface of the active material through different methods, but the ion transport from the surface of the active material to the interior of the active material layer has not changed, and the obstacles to ion transport and long-range electron transport still exist, and the improvement effect is not good.
  • the electrode can be an electrode sheet; the electrode includes a current collector and an active material layer located on one or both sides of the current collector; the active material layer is subjected to thermogravimetric analysis at a heating rate of 10°C/min under an inert atmosphere , the results of thermogravimetric analysis showed that the mass change of the active material layer at 200°C to 800°C was 0% to 0.2%.
  • the detection accuracy of the thermogravimetric analysis equipment is 0.2%, and the mass change of the active material layer in this embodiment is not greater than the detection accuracy, which indicates that the content of high molecular compounds in the active material layer in this application is zero or extremely low , which is beneficial to improve the conduction of ions and electrons in the active material layer, thereby helping to improve the electrical performance of the electrochemical device.
  • the results of thermogravimetric analysis show that the number of weight loss peaks of the active material layer at 200°C to 800°C is zero.
  • the active material layer contains a polymer compound, such as a polymer binder
  • thermogravimetric analysis in the range of 200°C to 800°C, a weight loss peak will be generated due to thermal decomposition, and in this application There is no weight loss peak in the active material layer from 200°C to 800°C, which shows that the active material layer in the embodiment of the present application does not contain polymer compounds, which can avoid the organic matter in the active material layer from affecting the electron conduction and ion conduction of the active material layer.
  • the electrodes proposed in the embodiments of the present application are conducive to improving the performance of electrochemical devices using the electrodes and improving energy density.
  • the electrode is a positive electrode or a negative electrode, for example, it may be a positive electrode of an electrochemical device or a negative electrode of an electrochemical device.
  • the electrode is a negative electrode
  • the active material layer is a negative electrode active material layer
  • the current collector is a negative electrode current collector.
  • the negative electrode current collector can be copper foil, aluminum foil, steel foil, etc., which is not limited.
  • the negative electrode The compaction density of the active material layer ⁇ 1 ⁇ 0.6g/cm 3 , a higher compaction density indicates that the mass of the active material layer carried by the unit volume of the electrode is more, and the mass of the active material layer is more conducive to improving the unit Bulk electrochemical devices are capable of storing energy, thereby increasing energy density.
  • the compacted density ⁇ 1 of the negative electrode active material layer satisfies: 1.85g/cm 3 ⁇ 1 ⁇ 0.65g/cm 3 , optionally, 1.83g/cm 3 ⁇ 1 ⁇ 1.0g/cm 3. This is conducive to improving the energy density of the electrochemical device.
  • the energy density of the electrochemical device can be further ensured by limiting the compacted density of the negative electrode active material layer to not less than 1.0 g/cm 3 , while limiting the negative electrode active material
  • the compacted density of the layer is not greater than 1.83g/cm 3 , which can prevent the particles in the active material layer from being broken due to excessive compacted density, which will increase the consumption of electrolyte and deteriorate the cycle performance.
  • the thickness h 1 of the negative electrode active material layer on one side of the negative electrode current collector is ⁇ 10 ⁇ m. In some embodiments, the thicker thickness of the negative electrode active material layer is conducive to increasing the proportion of the active material layer in the electrochemical device. , thereby increasing the energy density of the electrochemical device.
  • the thickness h 1 of the negative electrode active material layer on one side of the negative electrode current collector satisfies: 1500 ⁇ m ⁇ h 1 ⁇ 15 ⁇ m, optionally, 150 ⁇ m ⁇ h 1 ⁇ 30 ⁇ m, by limiting the thickness of the negative electrode active material layer
  • the thickness of the negative electrode active material layer is not less than 30 ⁇ m, which can ensure that the thickness of the negative electrode active material layer is relatively thick, thereby increasing the energy density of the electrochemical device as a whole.
  • the material layer is too thick, there may be a problem of detachment between the negative electrode active material layer and the current collector.
  • the porosity n1 of the negative electrode active material layer satisfies: 35% ⁇ n1 ⁇ 25 %. In some embodiments, the porosity of the negative electrode active material layer is not less than 25%, so as to ensure that the negative electrode active material layer and The electrolyte can be fully infiltrated and can provide sufficient transmission channels for the transmission of ions and electrons. The porosity of the negative electrode active material layer is not greater than 35%, which can prevent the energy density from being affected by excessive porosity. By setting an appropriate porosity It can ensure the infiltration and electrical conductivity of the electrolyte, and at the same time ensure the energy density.
  • the resistivity of the negative electrode active material layer is 0.01 ⁇ *cm to 50 ⁇ *cm, which indicates that the negative electrode active material layer of the present application has good electrical conductivity, which is beneficial to the electrical performance of the electrochemical device.
  • the negative electrode active material layer includes a negative electrode material, and the negative electrode material includes at least one of lithium titanate, silicon oxide, silicon, graphite, and hard carbon, for example, a combination of at least two of the above materials.
  • the electrode is a positive electrode
  • the active material layer is a positive electrode active material layer
  • the current collector is a positive electrode current collector
  • the compaction density of the positive electrode active material layer ⁇ 2 ⁇ 2g/cm 3 Density is beneficial to increase the energy density of electrochemical devices.
  • the compacted density ⁇ 2 of the positive electrode active material layer satisfies: 4.25g/cm 3 ⁇ 2 ⁇ 2.3g/cm 3 , optionally, 4.23g/cm 3 ⁇ 2 ⁇ 4.0g /cm 3 , thereby preventing the positive electrode active material layer from falling off from the positive electrode current collector and particle breakage while increasing the energy density.
  • the thickness h 2 of the positive electrode active material layer on one side of the positive electrode current collector is ⁇ 20 ⁇ m, and a thicker positive electrode active material layer can store more energy, which is conducive to improving the energy density of the electrochemical device.
  • the thickness h 2 of the positive electrode active material layer on one side of the positive electrode current collector satisfies: 1500 ⁇ m ⁇ h 2 ⁇ 25 ⁇ m, optionally, 130 ⁇ m ⁇ h 2 ⁇ 26 ⁇ m, so as to increase the energy density of the electrochemical device while , to avoid falling off between the positive electrode active material layer and the positive electrode current collector because the positive electrode active material layer is too thick.
  • the porosity n 2 of the positive electrode active material layer satisfies: 20% ⁇ n 2 ⁇ 15%, so as to ensure the infiltration and conductivity of the electrolyte without significantly affecting the energy density.
  • the resistivity of the positive electrode active material layer is 0.1 ⁇ *cm to 500 ⁇ *cm, which indicates that the positive electrode active material layer has good electrical conductivity, which is beneficial to improve the electrical performance of the electrochemical device.
  • the positive electrode active material layer includes a positive electrode material, and the positive electrode material includes at least one of lithium iron phosphate, lithium nickel cobalt manganate, lithium manganate, lithium cobaltate, and lithium nickel cobalt aluminate.
  • the active material layer includes a first conductive agent and a second conductive agent; the first conductive agent includes carbon nanotubes, and the carbon nanotubes may include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.
  • the second conductive agent includes at least one of carbon fiber, acetylene black, graphene, Ketjen black or conductive carbon black. The long-range conductivity of carbon nanotubes is beneficial to improve the conductivity of the active material layer, and it is beneficial to maintain the structural stability of the active material layer.
  • the active material layer includes active materials, and the active material layer includes the following components in mass: 0 to 2 parts of the first conductive agent and 0 parts, 0 to 1 part of the second conductive agent, 97 parts of the active material Parts to 100 parts, so that the energy density can be guaranteed while ensuring the electrical conductivity.
  • the second conductive agent can be 0 parts, but the first conductive agent cannot be 0 parts, that is, the active material layer must contain carbon nanotubes, because the active material layer in the embodiment of the present application It does not contain a polymer compound, and therefore does not contain a polymer binder, so carbon nanotubes can be used to stabilize the structure of the active material layer while improving conductivity.
  • the carbon nanotubes have a diameter of 0.5 nm to 10 nm and a length of 1 ⁇ m to 100 ⁇ m, and every 2 to 1000 carbon nanotubes form an aggregate, and the diameter of the aggregate is 1 nm to 500 nm.
  • the length is 1 ⁇ m to 100 ⁇ m, which is conducive to stabilizing the structural stability of the active material layer.
  • the composition of an electrode in one embodiment including a current collector 10 and an active material layer, wherein the active material layer includes an active material 20 and a conductive agent 30, and the conductive agent Can include zero-dimensional conductive agent, one-dimensional conductive agent and two-dimensional conductive agent, zero-dimensional conductive agent can include conductive carbon black and other granular conductive agents, one-dimensional conductive agent can include carbon nanotubes, and two-dimensional conductive agent can include graphite
  • the structural stability of the active material layer can be further enhanced by the aggregate, and the gap between the active materials 20 can be better filled by the zero-dimensional to two-dimensional multi-dimensional conductive agent, further improving the active material layer conductivity.
  • a preparation method of an electrode is proposed, which can be used to manufacture the electrode of any electrochemical device of the present application, including: coating the slurry of the active material layer on at least one surface of the current collector, drying and cold pressing to obtain an initial electrode; and processing the initial electrode to obtain an electrode.
  • processing the initial electrode includes: performing plasma treatment on the initial electrode in a vacuum environment, the plasma power is 0.5kW to 5kW, the gas source includes at least one of nitrogen, argon or carbon tetrafluoride, and the gas flow rate is 3000sccm to 5000sccm, the temperature is 20°C to 60°C, and the treatment time is 1min to 60min; or, the initial electrode is heat treated in a vacuum or an inert gas environment, the heat treatment temperature is greater than 200°C, and the heat treatment time is not less than 5min.
  • the heat treatment temperature can be 200°C to 800°C, and the heat treatment time can be 5min to 600min; or, the initial electrode is subjected to laser bombardment in a vacuum or inert gas environment, the laser intensity is 30W to 100W, and the treatment time is 1s to 600s , when performing laser bombardment, the distance between the laser and the initial electrode can be 3cm to 10cm.
  • the preparation method of the electrode proposed in the embodiment of the present application can remove the high molecular compound in the active material layer by treating the electrode, which is beneficial to improve the conductivity of the electrochemical device and further improve the energy density.
  • the active material layer of the electrode includes active materials and conductive agents, and does not contain polymer compounds (such as polymer binders and thickeners), which avoids the impact of polymer compounds on the transmission of electrons and ions. hinder.
  • the electrochemical device includes an electrode, and the electrode may be the electrode in any embodiment of the present application, or an electrode prepared by using the electrode preparation method proposed in the present application.
  • an electrochemical device includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.
  • the positive electrode or the negative electrode can be any one of the above-mentioned electrodes.
  • Al foil may be used as the current collector of the positive electrode, and of course, other current collectors commonly used in the field may also be used.
  • 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 can be wound or stacked.
  • the positive electrode and/or negative electrode of the electrochemical device can be a wound or stacked multilayer structure, or a single-layer structure in which a single-layer positive electrode, a separator, and a single-layer negative electrode are stacked.
  • 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, Encapsulated, that is, made into a lithium-ion battery. Then, performance tests were performed on the prepared lithium-ion batteries.
  • the present application proposes an electronic device, including an electrochemical device; the electrochemical device is any one of the electrochemical devices of the present application.
  • 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, Drones, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, or large batteries for household use, etc.
  • Preparation of the positive electrode sheet mix the positive electrode materials lithium cobaltate, polyvinylidene fluoride, carbon nanotubes as the first conductive agent, and conductive carbon black (Super P) as the second conductive agent according to the mass ratio of 97.5:1.0:1.0:0.5, N-methylpyrrolidone (NMP) was used as a solvent to prepare a slurry, and the slurry was stirred uniformly to form a positive electrode active material layer. The slurry was evenly coated on the positive electrode current collector aluminum foil, and dried at 90°C to obtain the positive electrode sheet.
  • NMP N-methylpyrrolidone
  • Negative electrode material graphite, conductive agent (carbon nanotubes and conductive carbon black (Super P), the mass ratio is 2:1), and carboxymethyl cellulose lithium are mixed according to the mass ratio of 97.5:1.5:1.0 , using deionized water as a solvent to form a negative electrode active material layer slurry, using copper foil as a negative electrode current collector, coating the negative electrode active material layer slurry on the negative electrode current collector, drying at 90 ° C, and drying
  • the final pole piece is subjected to heat treatment, the heat treatment temperature is 350° C., and the heat treatment time can be 10 minutes. After the heat treatment, the negative pole piece is obtained.
  • the isolation membrane is polyethylene (PE) with a thickness of 8 ⁇ m.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP propyl propionate
  • VC vinylene carbonate
  • Preparation of lithium-ion battery stack the positive pole piece, separator, and negative pole piece in order, so that the separator is in the middle of the positive pole piece and the negative pole piece 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.
  • the negative electrode material is graphite
  • the negative electrode material mass percentage composition is 98.5% in the negative electrode active material layer
  • the conductive agent of the negative electrode active material layer is carbon nanotube (CNT) and conductive carbon black, carbon nanotube and The mass ratio of conductive carbon black is 2:1
  • the mass percentage composition of conductive agent in the negative electrode active material layer is 1.5%
  • the thermogravimetric mass change of negative electrode active material layer is 0% at 200 °C to 800 °C
  • the weight loss peak quantity is 0,
  • the resistivity of the negative electrode active material layer is 0.1 ⁇ *cm
  • the single layer thickness of the negative electrode active material layer is 75 ⁇ m
  • the compacted density of the negative electrode active material layer is 1.78 g/cm 3 .
  • Embodiments 2 to 6, 13 to 22, and 34 to 43 change parameters based on the steps in embodiment 1, and the specific parameters to be changed are shown in the table below.
  • the positive electrode material lithium cobaltate, polyvinylidene fluoride, conductive agent (carbon nanotubes and conductive carbon black (Super P), the mass ratio is 2:1) are mixed according to the mass ratio of 97.5:1:1.5 , using N-methylpyrrolidone (NMP) as a solvent, preparing a slurry, and stirring to uniformly form the slurry of the positive electrode active material layer.
  • NMP N-methylpyrrolidone
  • the slurry is evenly coated on the positive electrode current collector aluminum foil, dried at 90°C and then heat treated.
  • the heat treatment temperature is 500°C, and the heat treatment time can be 10 minutes. After the heat treatment, the positive electrode sheet is obtained.
  • Preparation of negative electrode sheet Mix negative electrode materials graphite, styrene acrylate, and carboxymethyl cellulose lithium in a mass ratio of 98:1:1, use deionized water as a solvent to form a negative electrode active material layer slurry, and use copper
  • the foil is used as the negative electrode current collector, and the slurry of the negative electrode active material layer is coated on the negative electrode current collector, and the negative electrode sheet is obtained after drying at 90°C.
  • Example 7 The remaining preparation steps of Example 7 are the same as Example 1.
  • Embodiments 8 to 11, and 23 to 33 change parameters based on the steps in embodiment 7, and the specific parameters to be changed are shown in the table below.
  • the positive electrode material lithium cobaltate, polyvinylidene fluoride, conductive agent (carbon nanotubes and conductive carbon black (Super P), the mass ratio is 2:1) are mixed according to the mass ratio of 97.5:1:1.5 , using N-methylpyrrolidone (NMP) as a solvent, preparing a slurry, and stirring to uniformly form the slurry of the positive electrode active material layer.
  • NMP N-methylpyrrolidone
  • the slurry is uniformly coated on the aluminum foil of the positive electrode current collector, and the dried pole piece is subjected to heat treatment.
  • the heat treatment temperature is 500 ° C, and the heat treatment time can be 10 minutes. After the heat treatment, the positive pole piece is obtained.
  • Preparation of negative electrode sheet Mix negative electrode material graphite, conductive agent carbon nanotubes, and sodium carboxymethyl cellulose according to a mass ratio of 97.5:1.5:1.0, and use deionized water as a solvent to form a negative electrode active material layer slurry. Copper foil is used as the negative electrode current collector, and the slurry of the negative electrode active material layer is coated on the negative electrode current collector, and dried at 90°C, and the dried pole piece is heat treated, the heat treatment temperature is 350°C, and the heat treatment time can be After 10 minutes, the negative electrode sheet was obtained after heat treatment.
  • Example 12 The remaining preparation steps of Example 12 are the same as in Example 1.
  • Embodiments 13 to 43 change parameters on the basis of the steps in Embodiment 1, and the specific parameters to be changed are shown in the table below.
  • Negative electrode material graphite, binder (styrene acrylate and sodium carboxymethyl cellulose, mass ratio is 2:1.5) are mixed according to mass ratio 96.5:3.5, with deionized water as solvent, A negative electrode active material layer slurry was formed, using copper foil as a negative electrode current collector, coating the negative electrode active material layer slurry on the negative electrode current collector, and drying at 90° C. to obtain a negative electrode sheet.
  • Comparative Example 1 The remaining preparation steps of Comparative Example 1 are the same as that of Example 1, and the differences between the parameters of Comparative Example 1 and Example 1 are shown in the table below.
  • the positive electrode material lithium cobaltate, polyvinylidene fluoride, and conductive carbon black (Super P) are mixed according to the mass ratio of 95:3.5:1.5, and N-methylpyrrolidone (NMP) is used as the solvent.
  • NMP N-methylpyrrolidone
  • Comparative Example 4 The remaining preparation steps of Comparative Example 4 are the same as in Example 7, and the specific parameter changes are shown in the table below.
  • test method of the present application is described below.
  • Thermogravimetric analysis is used to measure the positive electrode active material layer and negative electrode active material layer of the prepared lithium-ion battery for thermogravimetric analysis, and to test the mass change and the number of weight loss peaks during the thermogravimetric analysis.
  • the test range is 200°C to 800°C, and the temperature rises
  • the rate is 10°C/min
  • the test atmosphere is an inert atmosphere.
  • a small AC current of 1Khz is applied to the positive and negative electrodes of the battery, and the AC resistance value of the battery is obtained by measuring the voltage response.
  • 3C discharge capacity retention rate (3C discharge capacity/0.2C discharge capacity) ⁇ 100%
  • Example 1 The preparation parameters and performance test results of Examples 1 to 6, 12 and Comparative Examples 1 to 3 are shown in Table 1, wherein the difference of Examples 1 to 6 and Comparative Examples 1 to 3 is only in the parameters shown in Table 1, and the implementation In Examples 1 to 6, heat treatment was performed on the negative electrode. In Example 12, heat treatment was performed on both the negative electrode and the positive electrode. In Comparative Examples 1 to 3, heat treatment was not performed on the positive electrode and the negative electrode.
  • thermogravimetric mass change of the negative active material layer in Examples 1 to 6 and 12 at 200°C to 800°C is less than 0.2%, and the number of weight loss peaks is 0.
  • the thermogravimetric mass change to 800°C is greater than 0.2%, and the number of weight loss peaks is not 0.
  • the AC resistance and DC resistance of lithium-ion batteries in Examples 1 to 6 and 12 are significantly smaller than those of Comparative Examples 1 to 12. 3. This also matches the resistivity data.
  • the capacity retention rate after 3C rate discharge in Examples 1 to 6 and 12 is significantly higher than that in Comparative Examples 1 to 3.
  • Example 7 to 12 The preparation parameters and performance test results of Examples 7 to 12 and Comparative Examples 4 to 6 are shown in Table 2, wherein the differences of Examples 7 to 11 and Comparative Examples 4 to 6 are only the parameters shown in Table 2, and Example 7 In 11 to 11, heat treatment was performed on the positive electrode. In Example 12, heat treatment was performed on both the negative electrode and the positive electrode. In Comparative Examples 4 to 6, no heat treatment was performed on the positive electrode and the negative electrode.
  • thermogravimetric mass change of the positive electrode active material layer at 200°C to 800°C in Examples 7 to 12 is less than 0.2%, and the number of weight loss peaks is 0.
  • the thermogravimetric mass change of °C is greater than 0.2%, and the number of weight loss peaks is not 0.
  • the AC resistance and DC resistance of lithium-ion batteries in Examples 7 to 12 are significantly smaller than Comparative Examples 4 to 6, which also Matching the resistivity data, the capacity retention rate after 3C rate discharge in Examples 7 to 12 is obviously higher than that in Comparative Examples 4 to 6.
  • Table 3 shows the preparation parameters and performance test results of Examples 2, 13 to 22. The difference between the above Examples 13 to 22 and Example 2 lies in the parameters shown in Table 3, and the other parameters are the same.
  • the thickness of the negative electrode active material layer on one side of the negative electrode current collector increases, the AC resistance and DC resistance of the lithium-ion battery increase, and the 3C discharge capacity retention rate decreases, which may be because
  • the increase in the thickness of the negative electrode active material layer leads to an increase in the path of ion and electron transport, which is not conducive to conductivity, but if the thickness of the negative electrode active material layer is too small, it will lead to a decrease in the storage capacity of the negative electrode, which is not conducive to energy density. Therefore, it is necessary to Balancing Li-ion battery performance and capacity density.
  • the negative electrode materials are silicon oxide, lithium titanate, graphite, silicon, and hard carbon, they all have better overall performance, but different The negative electrode material will affect the resistivity, compaction density, etc. In general, when the negative electrode material is graphite, the overall performance is better.
  • Table 4 shows the preparation parameters and performance test results of Examples 8, 23 to 33.
  • the difference between the above Examples 23 to 33 and Example 8 lies in the parameters shown in Table 4, and the other parameters are the same.
  • the thickness of the positive electrode active material layer on one side of the positive electrode current collector increases, the AC resistance and DC resistance of the lithium-ion battery increase, and the 3C discharge capacity retention rate decreases, which may be because
  • the increase in the thickness of the positive electrode active material layer leads to an increase in the path of ion and electron transport, which is not conducive to conductivity, but if the thickness of the positive electrode active material layer is too small, it will lead to a decrease in the storage capacity of the negative electrode, which is not conducive to energy density. Therefore, it is necessary to Balancing Li-ion battery performance and capacity density.
  • Example 34 to 43 The only difference between the parameters of Examples 34 to 43 and Example 2 lies in the data shown in Table 5, and the other parameters not shown are the same as those of Example 2.
  • CNTs in Table 5 are carbon nanotubes in the positive and negative electrodes.
  • the aggregate diameter is limited to 1nm in some embodiments To 500nm, in order to avoid the impact on the performance of the lithium-ion battery when the diameter of the aggregate is too large, if the diameter of the aggregate is too small, the structure of the active material layer may not be well stabilized.

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Abstract

本申请提出一种电极及其制作方法、电化学装置和电子装置。其中，电极包括集流体和位于集流体一侧或两侧的活性物质层；在惰性气氛下以10℃/min的升温速度对活性物质层进行热重分析，热重分析的结果显示活性物质层在200℃至800℃的质量变化为0％至0.2％，这表明本申请实施例中提出的电极中，活性物质层具有良好的导电性，有利于在不恶化性能的同时增加活性物质层的厚度，从而有利于提高电化学装置的能量密度。

Description

电极及其制作方法、电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及电极及其制作方法、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，具有能量密度大、功率高、循环寿命长等优点，在各个领域被广泛使用，随着技术的发展，对电化学装置的能量密度的要求越来越高。为了提高电化学装置的能量密度，一些技术中提高活性材料的容量或电压，另一些技术中提高单位体积内活性材料的含量，降低非活性材料的含量。通过降低集流体或隔离膜的厚度，降低配方内非活性材料占比，制备较厚的电极等均可以降低非活性物质的占比，但是，在实际应用过程中，集流体、隔离膜的厚度均已降低到接近极限，因此只能增加电极厚度，但电极的厚度增加过多可能会影响电化学装置的性能，所以无法大幅增加电极的厚度。因此，如何在确保电化学装置的性能的同时，提高电化学装置的能量密度，仍是亟待解决的问题。
发明内容
本申请的一些实施例提供了一种电极及其制备方法、电化学装置和电子设备，其中，在惰性气氛下以10℃/min的升温速度对电极的活性物质层进行热重分析，其热重分析的结果显示活性物质层在200℃至800℃的质量变化为0％至0.2％，从而能够改善活性物质层的导电性，进而有利于提高电化学装置的能量密度。
本申请一些实施例中提出一种电极；电极包括集流体和位于集流体上一侧或两侧的活性物质层；在惰性气氛下以10℃/min的升温速度对活性物质层进行热重分析，热重分析的结果显示活性物质层在200℃至800℃的质量变化 为0％至0.2％。本申请中活性物质层具有良好的导电性，从而有利于电化学装置的性能，并有利于提高能量密度。
在本申请的一些实施例中，热重分析的结果显示活性物质层在200℃至800℃的失重峰数量为0。这表明本申请中活性物质层中的高分子化合物含量为零或极低，这有利于提高活性物质层中离子和电子传导。
在本申请的一些实施例中，电极为正极或负极。一些实施例中，电极为负极，活性物质层为负极活性物质层，集流体为负极集流体，负极活性物质层的压实密度ρ 1≥0.6g/cm 3，较高的压实密度有利于提高单位体积电化学装置能够存储的能量。一些实施例中，负极集流体单侧的负极活性物质层的厚度h 1≥10μm，较厚的厚度有利于提高电化学装置能量密度。一些实施例中，负极活性物质层的孔隙率n 1满足：35％≥n 1≥25％，通过设置适当的孔隙率能够保证电解液的浸润以及电导性能的同时，保证能量密度。一些实施例中，负极活性物质层的电阻率为0.01Ω*cm至50Ω*cm，这表明本申请的负极活性物质层具有良好的导电性，有利于电化学装置的充放电性能。一些实施例中，负极活性物质层包括负极材料，负极材料包括钛酸锂、硅基材料、锡基材料、锂金属材料或碳材料中的至少一种。
在本申请的一些实施例中，电极为负极，活性物质层为负极活性物质层，集流体为负极集流体，负极活性物质层的压实密度ρ 1满足：1.85g/cm 3≥ρ 1≥0.65g/cm 3，这样有利于提高电化学装置的能量密度。一些实施例中，负极集流体单侧的负极活性物质层的厚度h 1满足：1500μm≥h 1≥15μm，这样有利于在提高电化学装置的能量密度的同时，防止活性物质层脱落。
在本申请的一些实施例中，负极活性物质层的压实密度ρ 1满足：1.83g/cm 3≥ρ 1≥1.0g/cm 3。在本申请的一些实施例中，负极集流体单侧的负极活性物质层的厚度h 1满足：150μm≥h 1≥30μm。
在本申请的一些实施例中，电极为正极，活性物质层为正极活性物质层，集流体为正极集流体，正极活性物质层的压实密度ρ 2≥2g/cm 3，从而有利于提高电化学装置的能量密度。一些实施例中，正极集流体单侧的正极活性物质层的厚度h 2≥20μm，从而有利于提高电化学装置的能量密度。一些实施例中，正极活性物质层的孔隙率n 2满足：20％≥n 2≥15％，从而在保证电解液浸润和 导电性的同时，不对能量密度造成明显影响。一些实施例中，正极活性物质层的电阻率为0.1Ω*cm至500Ω*cm，从而能够具有较好的导电性。一些实施例中，正极活性物质层包括正极材料，正极材料包括磷酸铁锂、镍钴锰酸锂、锰酸锂、钴酸锂、镍钴铝酸锂中的至少一种。
在本申请一些实施例中，电极为正极，活性物质层为正极活性物质层，集流体为正极集流体，正极活性物质层的压实密度ρ 2满足：4.25g/cm 3≥ρ 2≥2.3g/cm 3，从而在提高能量密度的同时防止正极活性物质层脱落或破碎。一些实施例中，正极集流体单侧的正极活性物质层的厚度h 2满足：1500μm≥h 2≥25μm，从而在提高电化学装置的能量密度的同时，避免提高对于正极活性物质层与正极集流体之间粘结力的要求。在本申请的一些实施例中，正极活性物质层的压实密度ρ 2满足：4.23g/cm 3≥ρ 2≥4.0g/cm 3。一些实施例中，正极集流体单侧的正极活性物质层的厚度h 2满足：130μm≥h 2≥26μm。
在本申请一些实施例中，活性物质层包括第一导电剂和第二导电剂；第一导电剂包括碳纳米管，第二导电剂包括碳纤维、乙炔黑、石墨烯、科琴黑或导电炭黑中的至少一种。碳纳米管的长程导电性有利于提高活性物质层的导电性，并且其有利于维持活性物质层的结构稳定性。一些实施例中，活性物质层包括活性材料，活性物质层包括如下质量的组分：第一导电剂0份至2份且不含0份、第二导电剂0份至1份、活性材料97份至100份，从而可以在保证导电性的同时，保证能量密度。一些实施例中，碳纳米管的直径为0.5nm至10nm，长度为1μm至100μm，每2根至1000根碳纳米管形成一个聚集体，聚集体直径为1nm至500nm，聚集体长度为1μm至100μm，从而有利于稳定活性物质层的结构稳定性。
在本申请的一些实施例中提出一种电极的制备方法，可以用于制造本申请任一的电极，包括：将活性物质层的浆料涂布于集流体的至少一个表面，干燥，冷压，得到初始电极；对初始电极进行处理，得到电极；其中，对初始电极进行处理包括：在真空环境下对初始电极进行等离子体处理，等离子体功率为0.5kW至5kW，气源包括氮气、氩气或四氟化碳中的至少一种，气体流量为3000sccm至5000sccm，温度为20℃至60℃，处理时间为1min至60min；或，在真空或惰性气体环境下对初始电极进行热处理，热处理温度大于200℃，热处理时间不少于5min；或，在真空或惰性气体环境下对初始电 极进行激光轰击，激光强度为30W至100W，处理时间为1s至600s，激光与初始电极的间距为3cm至10cm。
本申请提出一种电化学装置，包括电极：电极为本申请中任一项的电极，或者，电极为采用本申请提出的电极制备方法制备的电极。
本申请提出一种电子装置，包括本申请提出的电化学装置。
本申请实施例中的提出的一种电极；电极包括集流体和位于集流体上一侧或两侧的活性物质层；在惰性气氛下以10℃/min的升温速度对活性物质层进行热重分析，热重分析的结果显示活性物质层在200℃至800℃的质量变化为0％至0.2％，这表明本申请实施例中提出的电极中，活性物质层具有良好的导电性，有利于在不恶化性能的同时增加活性物质层的厚度，从而有利于提高采用该电极的电化学装置的能量密度。
附图说明
结合附图并参考以下具体实施方式，本公开各实施例的上述和其他特征、优点及方面将变得更加明显。贯穿附图中，相同或相似的附图标记表示相同或相似的元素。应当理解附图是示意性的，元件和元素不一定按照比例绘制。
图1是本公开实施例的一种电极的示意图。
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。
为了提高电化学装置的能量密度，一些技术中通过增加电极中活性物质层的厚度来提高电化学装置的能量密度，而提高电极中活性物质层的厚度可能会因为活性物质层过厚而恶化活性物质层的导电性，为了提高活性物层的导电性，一些技术中，采用多层活性物质层的结构，但是多个单层结构的复合冷压工艺复杂，无法避免再次冷压过程中每个单层原有压实密度及孔隙率的改变，且层与层之间结合处容易因为结合不牢出现脱膜，影响电子、离子的传导，恶化循环性能，另一些技术中，采用激光对活性物质层进行打孔，然而激光打孔的效率低，成本高，且打孔过程中容易损失能量密度。另一些技术中，将造孔剂溶液涂布于电极表面，但是这样无法避免电极表面溶解， 且造孔剂形成的孔深度有限，对近集流体侧改善有限。以上技术通过不同方法解决了电解液到活性物质表面的离子传输，但活性物质表面到活性物质层内部的离子传输仍未改变，离子传输和长程电子传输的阻碍依然存在，改善效果不佳。
本申请的一些实施例提供了一种电极，能够改善电极的活性物质层的导电性，减弱离子传输阻碍，从而有利于提高采用该电极的电化学装置的能量密度。一些实施例中，电极可以是电极片；电极包括集流体和位于集流体上一侧或两侧的活性物质层；在惰性气氛下以10℃/min的升温速度对活性物质层进行热重分析，热重分析的结果显示活性物质层在200℃至800℃的质量变化为0％至0.2％。一些实施例中，热重分析的设备的检测精度为0.2％，本实施例中活性物质层的质量变化不大于检测精度，这表明本申请中活性物质层中高分子化合物的含量为零或极低，这有利于提高活性物质层中离子和电子传导，从而有利于提高电化学装置的电性能。
在本申请的一些实施例中，热重分析的结果显示活性物质层在200℃至800℃的失重峰数量为0。一些实施例中，如果活性物质层中含有高分子化合物，例如高分子类粘结剂，在200℃至800℃范围内进行热重分析时，会因为受热分解而产生失重峰，而本申请中活性物质层在200℃到800℃中不存在失重峰，这表明本申请实施例中活性物质层不包含高分子化合物，这样可以避免活性物质层中有机物对于活性物质层的电子传导和离子传导的影响，从而提高活性物质层对于离子和电子的传导性能，这样当增加活性物质层的厚度从而提高电化学装置的能量密度时，由于活性物质层具有较好的导电性，因此不会因为活性物质层的厚度增加而恶化电化学装置的电性能。由此可知，在本申请的实施例中提出的电极，由于活性物质层具有良好的导电性，从而有利于提高采用该电极的电化学装置的性能，并有利于提高能量密度。
高分子化合物在本申请的一些实施例中，电极为正极或负极，例如可以为电化学装置的正极或电化学装置的负极。一些实施例中，电极为负极，活性物质层为负极活性物质层，集流体为负极集流体，负极集流体可以是铜箔、铝箔、钢箔等，对此不作限定，一些实施例中，负极活性物质层的压实密度ρ 1≥0.6g/cm 3，较高的压实密度表明，电极单位体积所承载的活性物质层的质量较多，活性物质层的质量越多能够有利于提高单位体积电化学装置能够存 储的能量，从而提高能量密度。在一些实施例中，负极活性物质层的压实密度ρ 1满足：1.85g/cm 3≥ρ 1≥0.65g/cm 3，可选的，1.83g/cm 3≥ρ 1≥1.0g/cm 3，这样有利于提高电化学装置的能量密度，一些实施例中，通过限定负极活性物质层的压实密度不小于1.0g/cm 3能够进一步保证电化学装置的能量密度，而限定负极活性物质层的压实密度不大于1.83g/cm 3能够防止因为压实密度过大，导致活性物质层中颗粒破碎而增加电解液的消耗以及恶化循环性能。
在一些实施例中，负极集流体单侧的负极活性物质层的厚度h 1≥10μm，一些实施例中，负极活性物质层较厚的厚度有利于提高电化学装置中活性物质层所占的比例，从而提高电化学装置的能量密度。在本申请的一些实施例中，负极集流体单侧的负极活性物质层的厚度h 1满足：1500μm≥h 1≥15μm，可选的，150μm≥h 1≥30μm，通过限定负极活性物质层的厚度不小于30μm，可以保证负极活性物质层的厚度较厚，从而提高电化学装置整体的能量密度，通过限定负极活性物质层的厚度不大于150μm，从而防止负极活性物质层过厚，当负极活性物质层过厚时，可能会出现负极活性物质层与集流体之间脱离的问题。
在一些实施例中，负极活性物质层的孔隙率n 1满足：35％≥n 1≥25％，一些实施例中，负极活性物质层的孔隙率不小于25％从而可以保证负极活性物质层与电解液能够充分浸润，并且可以为离子和电子的传输提供足够的传输通道，负极活性物质层的孔隙率不大于35％，这样可以防止因为孔隙率过大影响能量密度，通过设置适当的孔隙率能够保证电解液的浸润以及电导性能的同时，保证能量密度。
在一些实施例中，负极活性物质层的电阻率为0.01Ω*cm至50Ω*cm，这表明本申请的负极活性物质层具有良好的导电性，有利于电化学装置的电性能。在一些实施例中，负极活性物质层包括负极材料，负极材料包括钛酸锂、氧化亚硅、硅、石墨、硬碳中的至少一种，例如可以为上述材料中至少两种的组合。
在本申请的一些实施例中，电极为正极，活性物质层为正极活性物质层，集流体为正极集流体，正极活性物质层的压实密度ρ 2≥2g/cm 3，较高的压实密度有利于提高电化学装置的能量密度。在本申请一些实施例中，正极活性物 质层的压实密度ρ 2满足：4.25g/cm 3≥ρ 2≥2.3g/cm 3，可选的，4.23g/cm 3≥ρ 2≥4.0g/cm 3，从而在提高能量密度的同时防止正极活性物质层从正极集流体上脱落以及颗粒破碎。
在本申请一些实施例中，正极集流体单侧的正极活性物质层的厚度h 2≥20μm，较厚的正极活性物质层能够存储较多的能量，有利于提高电化学装置的能量密度。一些实施例中，正极集流体单侧的正极活性物质层的厚度h 2满足：1500μm≥h 2≥25μm，可选的，130μm≥h 2≥26μm，从而在提高电化学装置的能量密度的同时，避免因为正极活性物质层过厚，导致正极活性物质层与正极集流体之间脱落。
在本申请的一些实施例中，正极活性物质层的孔隙率n 2满足：20％≥n 2≥15％，从而在保证电解液浸润和导电性的同时，不对能量密度造成明显影响。
在本申请的一些实施例中，正极活性物质层的电阻率为0.1Ω*cm至500Ω*cm，这说明正极活性物质层具有较好的导电性，有利于提高电化学装置的电性能。一些实施例中，正极活性物质层包括正极材料，正极材料包括磷酸铁锂、镍钴锰酸锂、锰酸锂、钴酸锂、镍钴铝酸锂中的至少一种。
在本申请一些实施例中，活性物质层包括第一导电剂和第二导电剂；第一导电剂包括碳纳米管，碳纳米管可以包括单壁碳纳米管和多壁碳纳米管中的至少一种，第二导电剂包括碳纤维、乙炔黑、石墨烯、科琴黑或导电炭黑中的至少一种。碳纳米管的长程导电性有利于提高活性物质层的导电性，并且其有利于维持活性物质层的结构稳定性。
一些实施例中，活性物质层包括活性材料，活性物质层包括如下质量的组分：第一导电剂0份至2份且不含0份、第二导电剂0份至1份、活性材料97份至100份，从而可以在保证导电性的同时，保证能量密度。一些实施例中，按照质量进行计算，第二导电剂可以为0份，但第一导电剂不能为0份，即活性物质层必定含有碳纳米管，这是因为本申请实施例中活性物质层不包含高分子化合物，也就不包含高分子类粘结剂，因此可以利用碳纳米管在提高导电性的同时稳定活性物质层的结构。
在本公开的一些实施例中，碳纳米管的直径为0.5nm至10nm，长度为1μm至100μm，每2根至1000根碳纳米管形成一个聚集体，聚集体直径为1nm 至500nm，聚集体长度为1μm至100μm，从而有利于稳定活性物质层的结构稳定性。一些实施例中，请参考图1，图1示意性的显示了一个实施例中的电极的组成，包括集流体10和活性物质层，其中活性物质层包括活性材料20和导电剂30，导电剂可以包括零维导电剂、一维导电剂和二维导电剂，零维导电剂可以包括导电炭黑等颗粒状的导电剂，一维导电剂可以包括碳纳米管，二维导电剂可以包括石墨烯，本实施例中，通过聚集体可以进一步增强活性物质层的结构稳定性，并且通过零维到二维的多维度导电剂可以更好的填充活性材料20之间的间隙，进一步提高活性物质层的导电性能。
在本申请的一些实施例中提出一种电极的制备方法，可以用于制造本申请任一的电化学装置的电极，包括：将活性物质层的浆料涂布于集流体的至少一个表面，干燥，冷压，得到初始电极；对初始电极进行处理，得到电极。
其中，对初始电极进行处理包括：在真空环境下对初始电极进行等离子体处理，等离子体功率为0.5kW至5kW，气源包括氮气、氩气或四氟化碳中的至少一种，气体流量为3000sccm至5000sccm，温度为20℃至60℃，处理时间为1min至60min；或，在真空或惰性气体环境下对初始电极进行热处理，热处理温度大于200℃，热处理时间不少于5min，一些实施例中，热处理温度可以为200℃至800℃，热处理时间可以为5min至600min；或，在真空或惰性气体环境下对初始电极进行激光轰击，激光强度为30W至100W，处理时间为1s至600s，进行激光轰击时，激光与初始电极的间距可以为3cm至10cm。
本申请实施例中提出的电极的制备方法，通过对电极进行处理，从而可以去除活性物质层中的高分子化合物，从而有利于提高电化学装置的导电性，进而有利于提高能量密度。本公开一些实施例中，电极的活性物质层包括活性材料和导电剂，不包含高分子化合物(例如高分子类粘结剂和增稠剂)，避免了高分子化合物对电子和离子的传输的阻碍。
本申请一些实施例中电化学装置，包括电极，电极可以是本申请中任一实施例中的电极，也可以是采用本申请提出的电极的制备方法所制备的电极。一些实施例中，电化学装置包括正极、负极、设置在正极和负极之间的隔离膜。在一些实施例中，正极或负极可以为上述任一种电极。在一些实施例中， 正极的集流体可以采用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，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。
在本申请的一些实施例中，电化学装置的可以为卷绕式或堆叠式。在一些实施例中，电化学装置的正极和/或负极可以是卷绕或堆叠式形成的多层结构，也可以是单层正极、隔离膜、单层负极叠加的单层结构。
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。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请提出一种电子装置，包括电化学装置；电化学装置为本申请任一项的电化学装置。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、无人机、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机或家庭用大型蓄电池等。
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：将正极材料钴酸锂、聚偏氟乙烯、第一导电剂碳纳米管、第二导电剂导电炭黑(Super P)按照质量比97.5：1.0：1.0：0.5进行混合，以N-甲基吡咯烷酮(NMP)作为溶剂，调配成为浆料，并搅拌均匀形成正极活性物质层的浆料。将浆料均匀涂覆在正极集流体铝箔上，90℃条件下烘干以后得到正极极片。
负极极片的制备：将负极材料石墨、导电剂(碳纳米管与导电炭黑(Super P)，质量比为2:1)、羧甲基纤维素锂按照质量比97.5：1.5：1.0进行混合，以去离子水为溶剂，形成负极活性物质层浆料，采用铜箔作为负极集流体，将负极活性物质层的浆料涂覆于负极集流体上，90℃条件下烘干，对烘干后的极片进行热处理，热处理温度为350℃，热处理时间可以为10min，热处理以后得到负极极片。
隔离膜的制备：隔离膜为8μm厚的聚乙烯(PE)。
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)：碳酸二乙酯(DEC)：碳酸亚丙酯(PC)：丙酸丙酯(PP)：碳酸亚乙烯酯(VC)＝20：30：20：28：2，重量比)按重量比8：92配制以形成电解液。
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，使隔离膜处于正极极片和负极极片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。
实施例1的相关参数如下：负极材料为石墨、负极活性物质层中负极材料质量百分含量为98.5％，负极活性物质层导电剂为碳纳米管(CNT)和导电炭黑，碳纳米管和导电炭黑的质量比为2:1，负极活性物质层中导电剂的质量百分含量为1.5％，负极活性物质层在200℃至800℃的热重质量变化为0％，失重峰数量为0，负极活性物质层的电阻率为0.1Ω*cm，负极活性物质层单层厚度为75μm，负极活性物质层的压实密度为1.78g/cm 3。
实施例2到6、13至22、34至43是在实施例1的步骤的基础上进行参数变更，具体变更的参数如下面的表格所示。
实施例7
正极极片的制备：将正极材料钴酸锂、聚偏氟乙烯、导电剂(碳纳米管和导电炭黑(Super P)，质量比为2:1)按照质量比97.5：1：1.5进行混合，以N-甲基吡咯烷酮(NMP)作为溶剂，调配成为浆料，并搅拌均匀形成正极活性物质层的浆料。将浆料均匀涂覆在正极集流体铝箔上，90℃下烘干后进行热处理，热处理温度为500℃，热处理时间可以为10min，热处理以后得到正极极片。
负极极片的制备：将负极材料石墨、苯乙烯丙烯酸酯、羧甲基纤维素锂按照质量比98：1：1进行混合，以去离子水为溶剂，形成负极活性物质层浆料，采用铜箔作为负极集流体，将负极活性物质层的浆料涂覆于负极集流体上，90℃条件下烘干以后得到负极极片。
实施例7的其余制备步骤与实施例1相同。
实施例8到11、23至33是在实施例7的步骤的基础上进行参数变更，具体变更的参数如下面的表格所示。
实施例12
正极极片的制备：将正极材料钴酸锂、聚偏氟乙烯、导电剂(碳纳米管和导电炭黑(Super P)，质量比为2:1)按照质量比97.5：1：1.5进行混合，以N-甲基吡咯烷酮(NMP)作为溶剂，调配成为浆料，并搅拌均匀形成正极活性物质层的浆料。将浆料均匀涂覆在正极集流体铝箔上，对烘干后的极片 进行热处理，热处理温度为500℃，热处理时间可以为10min，热处理以后得到正极极片。
负极极片的制备：将负极材料石墨、导电剂碳纳米管、羧甲基纤维素钠按照质量比97.5：1.5：1.0进行混合，以去离子水为溶剂，形成负极活性物质层浆料，采用铜箔作为负极集流体，将负极活性物质层的浆料涂覆于负极集流体上，90℃条件下烘干，对烘干后的极片进行热处理，热处理温度为350℃，热处理时间可以为10min，热处理以后得到负极极片。
实施例12的其余制备步骤与实施例1相同。
实施例13到43是在实施例1的步骤的基础上进行参数变更，具体变更的参数如下面的表格所示。
对比例1
负极极片的制备：将负极材料石墨、粘结剂(苯乙烯丙烯酸酯与羧甲基纤维素钠，质量比为2:1.5)按照质量比96.5：3.5进行混合，以去离子水为溶剂，形成负极活性物质层浆料，采用铜箔作为负极集流体，将负极活性物质层的浆料涂覆于负极集流体上，90℃条件下烘干，得到负极极片。
对比例1的其余制备步骤与实施例1相同，对比例1与实施例1的参数区别见下表。
对比例2和3的是在对比例1的步骤的基础上进行参数变更，具体变更的参数如下面表格所示。
对比例4
正极极片的制备：将正极材料钴酸锂、聚偏氟乙烯、导电剂导电炭黑(Super P)按照质量比95：3.5：1.5进行混合，以N-甲基吡咯烷酮(NMP)作为溶剂，调配成为浆料，并搅拌均匀形成正极活性物质层的浆料。将浆料均匀涂覆在正极集流体铝箔上，90℃下烘干得到正极极片。
对比例4的其余制备步骤与实施例7相同，具体参数变更见下面表格。
对比例5和6是在对比例4的步骤的基础上进行参数变更，具体变更的参数如下面表格所示。
下面描述本申请的测试方法。
1、热重测试
采用热重分析法测定制备的锂离子电池的正极活性物质层和负极活性物质层进行热重分析，测试热重分析过程中的质量变化以及失重峰数量，测试范围为200℃至800℃，升温速率为10℃/min，测试气氛为惰性气氛。
2、电阻率测试
采用电阻测试仪对正极活性物质层和负极活性物质层的电阻率进行测试，采用上下平面可控压探头直接测量极片，向测试正极极片或负极极片加载交流电流，同时对测试活性物质层施加一定压力(0.35T)，获得极片厚度方向的整体电阻，同时收集被测试极片的面积(A)和厚度(l)，根据电阻率计算公式(ρ＝R*A/l)推导出被测试极片的电阻率。
3、交流电阻测试
采用1Khz的交流小电流加于电池正负极，通过测量其电压的响应得出电池的交流电阻值。
4、25℃直流电阻DCR测试
在25℃下，以0.5C将锂离子电池恒流充电至3.95V，再恒压充电至0.05C；静置30min；以0.1C放电10s(0.1s取点一次，记录对应电压值U 1)，以1C放电360s(0.1s取点一次，记录对应电压值U 2)。重复充放电步骤5次。其中，“1C”是在1小时内将电池容量完全放完的电流值。按如下公式计算得出电池的DCR：DCR＝(U 2-U 1)/(1C-0.1C)。
5、倍率性能的测试
在25℃的环境中，将电池恒流放电至3V，进行第一次充电和放电，在0.7C的充电电流下进行恒流充电，直到上限电压为4.48V，再恒压充电至0.05C，然后在0.2C的放电电流下进行恒流放电，直到最终电压为3V，此时记录0.2C的放电容量，然后重复对电池进行0.7C的充电电流下充电，直到上限电压为4.48V，再恒压充电至0.05C，然后设置放电倍率为3C恒流放电，直到最终电压为3V，此时记录3C的放电容量。
3C放电容量保持率＝(3C放电容量/0.2C时的放电容量)×100％
表1
Figure PCTCN2021130625-appb-000001
表1中示出了实施例1至6、12和对比例1至3的制备参数和性能测试结果，其中实施例1至6以及对比例1至3的差异仅在于表1所示参数，实施例1至6中对负极进行了热处理，实施例12既对负极进行了热处理，也对正极进行了热处理，对比例1至3没有对正极和负极进行热处理。
请参考表1，实施例1至6以及12中负极活性物质层在200℃至800℃的热重质量变化小于0.2％，失重峰数量为0，对比例1至3中负极活性层在200℃至800℃的热重质量变化大于0.2％，失重峰数量不为0，从表1可以看出，实施例1至6以及12中锂离子电池的交流电阻和直流电阻均明显小于对比例1至3，这也和电阻率数据相匹配，实施例1至6以及12中3C倍率放电后的容量保持率明显高于对比例1至3。由上述数据可以看出，当负极活性物质层在200℃至800℃进行热重分析后，失重峰的质量变化小于0.2％时，能够提高负极活性物质层的导电性，进而减小电化学装置的电阻，有利于提高倍率性能。
表2
Figure PCTCN2021130625-appb-000002
Figure PCTCN2021130625-appb-000003
表2中示出了实施例7至12和对比例4至6的制备参数和性能测试结果，其中实施例7至11以及对比例4至6的差异仅在于表2所示参数，实施例7至11中对正极进行了热处理，实施例12既对负极进行了热处理，也对正极进行了热处理，对比例4至6没有对正极和负极进行热处理。
请参考表2，实施例7至12中正极活性物质层在200℃至800℃的热重质量变化小于0.2％，失重峰数量为0，对比例4至6中正极活性层在200℃至800℃的热重质量变化大于0.2％，失重峰数量不为0，从表2可以看出，实施例7至12中锂离子电池的交流电阻和直流电阻均明显小于对比例4至6，这也和电阻率数据相匹配，实施例7至12中3C倍率放电后的容量保持率明显高于对比例4至6。由上述数据可以看出，当正极活性物质层在200℃至800℃进行热重分析后，失重峰的质量变化小于0.2％时，能够提高正极活性物质层的导电性，进而减小电化学装置的电阻，有利于提高倍率性能。
从表1和表2中还可以看出实施例12中锂离子电池的直流电阻和交流电阻最小，3C放电容量保持率最高，综合性能最优，这是因为实施例12中不仅对负极进行了热处理，还对正极进行了热处理，正极活性物质和负极活性物质层在200℃至800℃的热重质量变化均小于0.2％，正极和负极中均不含有高分子化合物，从而获得了最佳的动力学性能。
表3
Figure PCTCN2021130625-appb-000004
Figure PCTCN2021130625-appb-000005
表3中示出了实施例2、13至22的制备参数和性能测试结果，上述实施例13至22与实施例2的差异仅在于表3所示参数，其余参数相同。
如实施例2、13至15所示，随着负极活性物质层压实密度的增加，负极活性物质层的孔隙率降低、负极活性物质层的电阻率降低、锂离子电池的交流电阻逐渐减小，直流电阻也逐渐减小，3C放电容量保持率逐渐降低，由此可知，当负极活性物质层的压实密度过低时，不利于交流电阻和直流电阻，即不利于动力学性能，并且体积能量密度低，适当增加负极活性物质层的压实密度，可以减小锂离子电池的电阻，但压实密度过大不利于倍率性能，这可能是因为压实密度过大时不利于电解液的浸润。
如实施例2、16至18所示，随着负极集流体单侧负极活性物质层厚度的增加，锂离子电池的交流电阻和直流电阻升高，且3C放电容量保持率下降，这可能是因为负极活性物质层的厚度增加导致离子和电子传输的路径增加，因此不利于导电性，但如果负极活性物质层的厚度过小，将导致负极能够存储的容量降低，不利于能量密度，因此，需要平衡锂离子电池的性能和容量密度。
如实施例2、19至22所示，其显示了不同的负极材料的影响，当负极材料为氧化硅、钛酸锂、石墨、硅、硬碳时均具有较好的综合性能，但不同的负极材料会影响电阻率、压实密度等，综合来看当负极材料为石墨时综合性能较好。
表4
Figure PCTCN2021130625-appb-000006
Figure PCTCN2021130625-appb-000007
表4中示出了实施例8、23至33的制备参数和性能测试结果，上述实施例23至33与实施例8的差异仅在于表4所示参数，其余参数相同。
如实施例8、23至25所示，随着正极活性物质层压实密度的增加，正极活性物质层的孔隙率降低、正极活性物质层的电阻率降低、锂离子电池的交流电阻逐渐减小，直流电阻也逐渐减小，3C放电容量保持率先降低后升高，由此可知，当正极活性物质层的压实密度过低时，不利于交流电阻和直流电阻，即不利于动力学性能，并且会影响体积能量密度，适当增加负极活性物质层的压实密度，可以减小锂离子电池的电阻，但压实密度过大不利于倍率性能。
如实施例8、26至29所示，随着正极集流体单侧正极活性物质层厚度的增加，锂离子电池的交流电阻和直流电阻升高，且3C放电容量保持率下降，这可能是因为正极活性物质层的厚度增加导致离子和电子传输的路径增加，因此不利于导电性，但如果正极活性物质层的厚度过小，将导致负极能够存储的容量降低，不利于能量密度，因此，需要平衡锂离子电池的性能和容量密度。
如实施例8、30至33所示，其显示了不同的正极材料的影响，当正极材料为磷酸铁锂、镍钴锰酸锂、钴酸锂、锰酸锂、镍钴铝酸锂时均具有较好的综合性能，但不同的正极材料会影响电阻率、压实密度等，综合来看当正极材料为钴酸锂时综合性能较好。
表5
Figure PCTCN2021130625-appb-000008
实施例34至43与实施例2的参数区别仅在于表5所示的数据，其余未示出的参数与实施例2相同。表5中CNT为正极和负极中的碳纳米管。
如实施例2、34至35所示，当碳纳米管的管径(直径)为0.5nm至10nm范围内时，锂离子电池的综合性能较好，碳纳米管的管径过长时，可能不利于导电性和倍率性能。
如实施例2、36至37所示，随着CNT长度的增加，降低了直流电阻和交流电阻，并提高了3C放电容量保持率，这是因为碳纳米管长度的增加提高了长程导电性，并有利于稳定活性物质层的结构。
如实施例2、38至29所示，随着聚集体中包含的碳纳米管的数量的增加，锂离子电池的导电性和3C放电容量保持率略有下降，在聚集体包括的碳纳米管的数量为2至1000范围内，锂离子电池整体性能较好。
如实施例2、40至41所示，随着聚集体的直径的增加，锂离子电池的交流电阻和直流电阻增加，且3C放电容量保持率下降，因此一些实施例中限定 聚集体直径为1nm至500nm，以避免聚集体的直径过大时对于锂离子电池性能影响，如果聚集体的直径过小，可能无法很好的稳定活性物质层的结构。
如实施例2、42至43所示，随着聚集体长度的增加，锂离子电池的交流电阻和直流电阻下降，3C放电容量保持率升高，这可能是因为聚集体较长时提高了活性物质层整体结构的稳定性，并且提高了长程导电性。
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 (14)

  1. 一种电极，其特征在于，所述电极包括集流体和位于所述集流体一侧或两侧的活性物质层；在惰性气氛下以10℃/min的升温速度对所述活性物质层进行热重分析，所述热重分析的结果显示所述活性物质层在200℃至800℃的质量变化为0％至0.2％。
  2. 根据权利要求1所述的电极，其特征在于，
    所述热重分析的结果显示所述活性物质层在200℃至800℃的失重峰数量为0。
  3. 根据权利要求1所述的电极，其特征在于，
    所述电极为负极，所述活性物质层为负极活性物质层，所述集流体为负极集流体。
  4. 根据权利要求3所述的电极，其特征在于，所述电极满足如下条件中的至少一项：
    (a)所述负极活性物质层的压实密度ρ 1≥0.6g/cm 3；
    (b)所述负极集流体单侧的所述负极活性物质层的厚度h 1≥10μm；
    (c)所述负极活性物质层的孔隙率n 1满足：35％≥n 1≥25％；
    (d)所述负极活性物质层的电阻率为0.01Ω*cm至50Ω*cm；
    (e)所述负极活性物质层包括负极材料，所述负极材料包括钛酸锂、氧化亚硅、石墨、硅、硬碳中的至少一种。
  5. 根据权利要求3所述的电极，其特征在于，所述电极满足如下条件中的至少一项：
    (f)所述负极活性物质层的压实密度ρ 1满足：1.85g/cm 3≥ρ 1≥0.65g/cm 3；
    (g)所述负极集流体单侧的所述负极活性物质层的厚度h 1满足：1500μm≥h 1≥15μm。
  6. 根据权利要求3所述的电极，其特征在于，所述电极满足如下条件中的至少一项：
    (h)所述负极活性物质层的压实密度ρ 1满足：1.83g/cm 3≥ρ 1≥1.0g/cm 3；
    (i)所述负极集流体单侧的所述负极活性物质层的厚度h 1满足：150μm≥h 1≥30μm。
  7. 根据权利要求1所述的电极，其特征在于，所述电极为正极，所述活性物质层为正极活性物质层，所述集流体为正极集流体，所述电极满足如下条件中的至少一项：
    (j)所述正极活性物质层的压实密度ρ 2≥2g/cm 3；
    (k)所述正极集流体单侧的所述正极活性物质层的厚度h 2≥20μm；
    (l)所述正极活性物质层的孔隙率n 2满足：20％≥n 2≥15％；
    (m)所述正极活性物质层的电阻率为0.1Ω*cm至500Ω*cm；
    (n)所述正极活性物质层包括正极材料，所述正极材料包括磷酸铁锂、镍钴锰酸锂、锰酸锂、钴酸锂、镍钴铝酸锂中的至少一种。
  8. 根据权利要求1所述的电极，其特征在于，所述电极为正极，所述活性物质层为正极活性物质层，所述集流体为正极集流体，所述电极满足如下条件中的至少一项：
    (o)所述正极活性物质层的压实密度ρ 2满足：4.25g/cm 3≥ρ 2≥2.3g/cm 3；
    (p)所述正极集流体单侧的所述正极活性物质层的厚度h 2满足：1500μm≥h 2≥25μm。
  9. 根据权利要求1所述的电极，其特征在于，所述电极为正极，所述活性物质层为正极活性物质层，所述集流体为正极集流体，所述电极满足如下条件中的至少一项：
    (q)所述正极活性物质层的压实密度ρ 2满足：4.23g/cm 3≥ρ 2≥4.0g/cm 3；
    (r)所述正极集流体单侧的所述正极活性物质层的厚度h 2满足：130μm≥h 2≥26μm。
  10. 根据权利要求1所述的电极，其特征在于，
    所述活性物质层包括第一导电剂和第二导电剂；
    所述第一导电剂包括碳纳米管，所述第二导电剂包括碳纤维、乙炔黑、石墨烯、科琴黑或导电炭黑中的至少一种。
  11. 根据权利要求10所述的电极，其特征在于，满足如下条件中的至少一项：
    (s)所述活性物质层包括活性材料，所述活性物质层包括如下质量的组分：所述第一导电剂0份至2份且不含0份、所述第二导电剂0份至1份、所述活性材料97份至100份；
    (t)所述碳纳米管的直径为0.5nm至10nm，长度为1μm至100μm，每2根至1000根碳纳米管形成一个聚集体，所述聚集体直径为1nm至500nm，所述聚集体长度为1μm至100μm。
  12. 一种用于制备如权利要求1至11任一项所述电极的制备方法，其特征在于，包括：
    将活性物质层的浆料涂布于集流体的至少一个表面，干燥，冷压，得到初始电极；
    对所述初始电极进行处理，得到所述电极；
    其中，对所述初始电极进行处理包括：
    在真空环境下对所述初始电极进行等离子体处理，等离子体功率为0.5kW至5kW，气源包括氮气、氩气或四氟化碳中的至少一种，气体流量为3000sccm至5000sccm，温度为20℃至60℃，处理时间为1min至60min；
    或，
    在真空或惰性气体环境下对所述初始电极进行热处理，热处理温度大于200℃，热处理时间不少于5min；
    或，
    在真空或惰性气体环境下对所述初始电极进行激光轰击，激光强度为30W至100W，处理时间为1s至600s。
  13. 一种电化学装置，其特征在于，包括电极：
    所述电极为权利要求1至11中任一项所述的电极，或者，
    所述电极为采用权利要求12所述制备方法制备的电极。
  14. 一种电子装置，其特征在于，包括权利要求13所述的电化学装置。
PCT/CN2021/130625 2021-11-15 2021-11-15 电极及其制作方法、电化学装置和电子装置 WO2023082245A1 (zh)

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