WO2023078043A1 - 用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池 - Google Patents

用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池 Download PDF

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WO2023078043A1
WO2023078043A1 PCT/CN2022/124720 CN2022124720W WO2023078043A1 WO 2023078043 A1 WO2023078043 A1 WO 2023078043A1 CN 2022124720 W CN2022124720 W CN 2022124720W WO 2023078043 A1 WO2023078043 A1 WO 2023078043A1
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Prior art keywords
electrode
reference electrode
copper wire
battery
pole piece
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French (fr)
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贾文杰
陈亭枫
魏奕民
王少飞
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co 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
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/75—Wires, rods or strips
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium batteries, in particular to a method for preparing a reference electrode, a reference electrode, a method for preparing a three-electrode battery, and a three-electrode battery.
  • lithium-ion batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as power tools, military equipment, aerospace and other fields.
  • energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as power tools, military equipment, aerospace and other fields.
  • the capacity of lithium-ion batteries will decline.
  • Introducing a reference electrode into the full battery can measure the potential and impedance of the positive and negative electrodes in the battery relative to the reference electrode, thereby realizing the monitoring of the performance of the positive and negative electrodes during the charge and discharge process.
  • the existing reference electrode has the problems of unstable potential and short life, and cannot monitor the long-term cycle performance of the battery. Therefore, the existing reference electrodes still need to be improved.
  • the present application was made in view of the above-mentioned problems, and an object thereof is to provide a reference electrode having a stable potential and a long life, so as to monitor the long-term cycle performance of a battery.
  • the present application provides a method for preparing a reference electrode, a reference electrode, a method for preparing a three-electrode battery, and a three-electrode battery.
  • the first aspect of the present application provides a method for preparing a reference electrode, comprising: providing a copper wire whose surface insulation layer has been removed in advance, and the copper wire is fixed to a support; providing a slurry containing lithium titanate; The material is coated on the surface of the copper wire; wherein, the diameter of the copper wire is 40 ⁇ m to 60 ⁇ m, optionally 44 ⁇ m to 50 ⁇ m; the coating speed is 0.5 mm/s to 10 mm/s, optionally 1 mm/s to 5 mm /s; the coating thickness is 5 ⁇ m ⁇ 50 ⁇ m, optionally 7 ⁇ m ⁇ 20 ⁇ m, further optionally 8 ⁇ m ⁇ 15 ⁇ m.
  • the present application controls the diameter of the copper wire, the thickness of the coating and the speed within an appropriate range, thereby making the slurry containing lithium titanate evenly coated on the surface of the copper wire, and making the lithium titanate coating layer If the thickness is within an appropriate range, then a reference electrode with an appropriate diameter and thickness of the lithium titanate coating layer can be obtained.
  • the reference electrode prepared according to the method of the present application has the advantages of stable potential and long life. It is applied to a three-electrode lithium-ion battery and can monitor the cycle performance of the battery for a long time.
  • providing the copper wire with the surface insulation layer removed in advance includes: fixing the two ends of the copper wire on a support with a hollowed out part, so that the copper wire part is in the hollowed out part; soaking the support part In concentrated sulfuric acid to expose a predetermined length of copper wire to concentrated sulfuric acid; clean the copper wire.
  • the surface of the copper wire is treated with concentrated sulfuric acid to more fully remove the insulating layer on the surface of the copper wire, so that the copper wire has good electrical conductivity and bonding force with the slurry.
  • the support can effectively support the micron-sized copper wire, and the hollow part prevents the concentrated sulfuric acid from climbing along the gap between the copper wire and the support, thereby ensuring the consistency of the copper wire soaking height.
  • cleaning the copper wire includes: treating the copper wire with a plasma cleaning method. Treating the copper wire with plasma cleaning can reduce the surface tension of the copper wire, which is more conducive to the coating of the slurry.
  • the preset length is 10 mm to 30 mm.
  • the length of the part of the copper wire in which the insulating layer is removed is within an appropriate range, which is more convenient for the processing of the reference electrode and the assembly of the three-electrode battery.
  • the coating length is 10 mm to 30 mm.
  • the coating speed and thickness can be better controlled, so that the thickness of the lithium titanate coating layer is more uniform.
  • providing the slurry containing lithium titanate includes: uniformly mixing lithium titanate, a binder, a conductive agent, and an organic solvent to obtain the slurry.
  • the slurry contains a binder and a conductive agent, which can improve the bonding performance of lithium titanate and copper wire and the conductivity of the reference electrode, so that the reference electrode has a long life without affecting the cycle performance of the battery.
  • the mass fraction of lithium titanate is 85wt%-93wt%
  • the mass fraction of the binder is 3wt%-7wt%
  • the mass fraction of the conductive agent is 4wt%- 8wt%.
  • the mass ratio of lithium titanate to binder and conductive agent is 90:5:5. Controlling the mass ratio of binder and conductive agent to lithium titanate in an appropriate range can make the lithium titanate coating layer not easy to fall off and have good conductivity, and at the same time contain enough lithium titanate, so that the reference electrode has Long-term stable potential and longer life.
  • the solid content of the slurry is 20wt%-50wt%, optionally 30wt%-40wt%.
  • the solid content of the slurry is controlled within the above appropriate range, which can ensure that the slurry is evenly and tightly coated on the surface of the copper wire, thereby further ensuring that the reference electrode has a long life and a stable potential.
  • the supporting member is copper foil, and the thickness of the copper foil is 20 ⁇ m ⁇ 30 ⁇ m.
  • the hollowed-out part is N rectangles, the length of the rectangle is 20mm-25mm, the width of the rectangle is 30mm-45mm, and the distance between the N rectangles is 10mm-15mm, where N is an integer ⁇ 2.
  • the copper foil with multiple hollowed out rectangles can effectively support the micron-sized copper wires and prevent the copper wires from being loose, entangled, and knotted.
  • the copper foil with multiple hollow rectangles can increase the tension of the copper wire, and can also coat the front and back of the copper wire at the same time, which is beneficial to improve the uniformity of coating.
  • the supporting member is made of polytetrafluoroethylene, and the thickness of the supporting member is 2mm ⁇ 5mm.
  • the hollowed-out parts are M rectangles, the length of the rectangle is 20mm-25mm, the width of the rectangle is 30mm-45mm, and the distance between the M rectangles is 10mm-15mm, wherein M is an integer ⁇ 1.
  • the support made of polytetrafluoroethylene can effectively support the micron-sized copper wire, and prevent the copper wire from being loose, entangled, and knotted.
  • the support made of PTFE can increase the tension of the copper wire, and can also coat the front and back of the copper wire at the same time, which is beneficial to improve the uniformity of coating.
  • fixing the two ends of the copper wires on the support with a hollowed out part includes: fixing a plurality of copper wires on the support with an interval of 3 mm to 5 mm, so that the copper wires are partly in the Hollow parts. Controlling the distance between the copper wires within an appropriate range can prevent the copper wires from sticking to each other, thereby ensuring that the slurry can be evenly coated on the surface of the copper wires.
  • the second aspect of the present application also provides a reference electrode, including a copper wire and a lithium titanate layer coated on the surface of the copper wire, the diameter of the copper wire is 40 ⁇ m to 60 ⁇ m, optionally 44 ⁇ m to 50 ⁇ m; lithium titanate The thickness of the layer is 5 ⁇ m to 50 ⁇ m, optionally 7 ⁇ m to 20 ⁇ m, further optionally 8 ⁇ m to 15 ⁇ m.
  • the copper wire has a suitable diameter and the thickness of the lithium titanate layer is suitable, which can give full play to the good conductivity of the copper wire and the advantages of stable lithium titanate potential and high lithium ion diffusion coefficient, and can Make the reference electrode have a suitable volume.
  • the reference electrode of the present application has the advantages of stable potential and long life, and it is applied to a three-electrode battery, which can monitor the cycle performance of the battery for a long time.
  • the diameter of the reference electrode is 50 ⁇ m-150 ⁇ m, optionally 50 ⁇ m-80 ⁇ m, further optionally 65 ⁇ m-80 ⁇ m. Controlling the diameter of the reference electrode prepared by lithium titanate-coated copper wire within the above-mentioned appropriate range can avoid the influence of the reference electrode on the transmission of active lithium, and will not cause severe indentation of the positive and negative electrodes, which will lead to The problem of local lithium analysis.
  • the third aspect of the application provides a three-electrode battery, including an electrode assembly, the electrode assembly includes a reference electrode prepared according to the method of the first aspect of the application, or a reference electrode according to the second aspect of the application, and a first positive electrode
  • the first positive pole piece, the second positive pole piece, the negative pole piece, the first positive pole piece, the reference electrode, the negative pole piece and the second positive pole piece are arranged at intervals in sequence, between the first positive pole piece and the reference electrode, between the negative pole piece and the reference electrode Separators are arranged between the specific electrodes and between the negative pole piece and the second positive pole piece.
  • the three-electrode battery of the present application includes the reference electrode prepared according to the method of the first aspect of the present application provided by the present application, or the reference electrode according to the second aspect of the present application, thus having at least the same advantages as the reference electrode.
  • the fourth aspect of the present application provides a method for preparing the three-electrode battery according to the third aspect of the present application, including: assembling the three-electrode battery, including packaging the electrode assembly, vacuum liquid injection, etc., so as to obtain the assembled three-electrode battery Electrode battery; activating the reference electrode, including charging the reference electrode to the preset cut-off voltage with a current of 5 ⁇ A to 10 ⁇ A through the positive electrode after the assembled three-electrode battery is left and formed, and then charging the reference electrode with a current of 5 ⁇ A to 10 ⁇ A.
  • the reference electrode discharges 40-50% of the lithium intercalation capacity to activate the reference electrode.
  • the reference electrode can be charged to the preset cut-off voltage through the positive electrode with a current of 5 ⁇ A to 10 ⁇ A, and then discharged to the reference electrode with a current of 5 ⁇ A to 10 ⁇ A, thereby activating the reference electrode and ensuring Stability of the reference electrode. In this way, the time for activating the reference electrode can be greatly reduced, thereby improving the preparation efficiency of the three-electrode battery.
  • the cut-off voltage is determined by the voltage plateau of the positive electrode material relative to the reference electrode. In this way, lithium can be inserted into the reference electrode more efficiently, thereby ensuring the stability of the reference electrode.
  • FIG. 1 is a schematic diagram of an electrode assembly according to an embodiment of the present application.
  • Fig. 2 is a schematic diagram of a copper wire and a supporting member according to an embodiment of the present application.
  • FIG. 3 is a time-voltage curve diagram of a battery charging and discharging test at a small rate corresponding to Example 1 of the present application.
  • Fig. 4 is the time-(negative electrode-reference voltage) curve diagram of the battery low-rate charge-discharge test corresponding to Comparative Example 8 of the present application.
  • Fig. 5 is a curve graph of cycle number-(negative electrode-reference voltage) of the reference electrode life test corresponding to Example 1 of the present application.
  • FIG. 6 is a graph showing the number of cycles-voltage curve of the life test of the reference electrode corresponding to Comparative Example 8 of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • reference electrodes are mainly made of copper wire or copper sheet electrochemically plated with lithium, or made of a strip-shaped copper substrate coated with lithium titanate.
  • the depletion of Li metal on the reference electrode surface not only leads to a shorter lifetime of the reference electrode, but also leads to potential instability. Therefore, the reference electrode made of traditional copper wire or copper plated with lithium can only realize short-term monitoring of battery performance.
  • the reference electrode made of traditional copper wire or copper sheet lithium plating needs to go through a long charging and lithium plating process to activate the reference electrode before use, which also causes a waste of time and cost.
  • the inventor found that the lithium titanate material has a stable potential, and the discharge point potential is very flat, which can meet the requirements for the reference electrode. Moreover, lithium titanate hardly reacts with the electrolyte, and will not be consumed during battery cycling to cause failure of the reference electrode. In addition, lithium titanate has a high diffusion coefficient of lithium ions, which can reach 2*10 -8 cm 2 /s, and lithium ions have good mobility. Lithium titanate also has "zero strain". When the crystal inserts or extracts lithium ions, the lattice constant and volume change are very small (less than 1%), which can avoid the destruction of the structure due to the back and forth expansion and contraction of the electrode material, thereby improving the electrode quality. cycle performance and service life.
  • the reference electrodes coated with lithium titanate currently use a traditional coating method to coat lithium titanate slurry on copper foil to form a lithium titanate coating layer.
  • This coating method is not only difficult to control the thickness of the lithium titanate coating layer, but also difficult to coat the copper foil with a small width, resulting in the shape of the reference electrode being too wide, thereby hindering the transmission of lithium ions in the electrolyte, which is harmful to the irreversible damage to the battery interface.
  • the lithium titanate coating layer coated by the traditional coating method has weak bonding force with the copper foil, and it is easy to fall off during use.
  • the shape of the reference electrode made of a strip-shaped copper substrate coated with lithium titanate not only has a short life, but also affects the cycle performance of the battery.
  • the inventor provided a method for preparing a reference electrode, a reference electrode, a method for preparing a three-electrode battery, and a three-electrode battery through extensive experimental research.
  • the reference electrode provided in the present application can be applied to the scene of short-term or long-term cycle performance monitoring of lithium-ion batteries, especially the scene of long-term cycle performance monitoring of positive and negative electrode state changes. Based on the above scenario, the reference electrode provided by the present application can be used as a component of a battery assembly to prepare a three-electrode or multi-electrode battery.
  • the battery can be a three-electrode single-layer laminate battery, a three-electrode multilayer laminate battery, a multi-electrode single-layer laminate battery with four electrodes or more, a multi-electrode multilayer laminate battery with four electrodes or more, three Electrode pouch battery, multi-electrode pouch battery with four electrodes or more
  • the present application proposes a method for preparing a reference electrode, comprising: providing a copper wire whose surface insulation layer has been removed in advance, and the copper wire is fixed to a support; providing a slurry containing lithium titanate material; the slurry is coated on the surface of the copper wire.
  • the diameter of the copper wire is 40 ⁇ m ⁇ 60 ⁇ m, optionally 44 ⁇ m ⁇ 50 ⁇ m;
  • the coating speed is 0.5mm/s ⁇ 10mm/s, optionally 1mm/s ⁇ 5mm/s, 1mm/s ⁇ 4mm/s s, 1.5mm/s ⁇ 4mm/s, 2mm/s ⁇ 3mm/s;
  • coating thickness is 5 ⁇ m ⁇ 50 ⁇ m, optionally 7 ⁇ m ⁇ 20 ⁇ m, 7 ⁇ m ⁇ 18 ⁇ m, 8 ⁇ m ⁇ 18 ⁇ m, further optionally 8 ⁇ m ⁇ 15 ⁇ m.
  • the surface of the untreated copper wire is covered with a layer of polymer insulating layer.
  • the polymer insulating layer needs to be removed.
  • sandpaper grinding or soaking in concentrated sulfuric acid can be used, and then cleaning is performed, which is not limited here.
  • the copper wire can be fixed on the support, and the support can be fixed on the coating stand, and the copper wire can be coated from top to bottom at the above-mentioned coating speed with a hand-held nip roller.
  • the reference electrode made of a smaller copper wire and lithium titanate can not only take advantage of the stable potential of lithium titanate and the high diffusion coefficient of lithium ions, but also It can improve the conductivity of the reference electrode and make up for the shortcoming of poor conductivity of lithium titanate.
  • the inventors have found that the volume of the reference electrode is too large to cause obvious indentation on the positive and negative pole pieces, and the part of the positive and negative pole pieces covered by the reference electrode cannot intercalate lithium, resulting in the removal of active lithium. Failure to intercalate in time results in lithium precipitation, which affects the cycle performance and cycle life of the battery. Controlling the diameter of the reference electrode prepared by lithium titanate-coated copper wire within the above-mentioned appropriate range can avoid the influence of the reference electrode on the transmission of active lithium, and will not cause the problem of indentation of the positive and negative electrodes.
  • the inventors have found through a large number of experiments that the thickness of the lithium titanate coating layer is also an important factor affecting the performance of the reference electrode.
  • the separator may be partially pierced, causing the risk of short circuit between the positive and negative electrodes and the reference; when the lithium titanate coating layer is too thin, the lithium intercalation amount of lithium titanate is too low , will lead to short life of the reference electrode.
  • the inventor repeatedly tested and found that the coating speed is too fast, it is easy to stretch the flexible copper wire, so that it loses tension and becomes loose, and the slurry is easy to form droplets on the loose and bent copper wire, and it is easy to puncture after solidification
  • the diaphragm becomes a short circuit point; if the coating speed is too slow, the slurry on the copper wire will easily dry out, which is not conducive to coating.
  • the coating thickness will directly affect the thickness of the finally formed lithium titanate coating layer. Coating copper wires of 5 ⁇ m to 50 ⁇ m at the coating speed and coating thickness in the method of the present application can obtain a reference electrode with uniform coating and appropriate thickness of the coating layer.
  • the copper wire is coated with the coating speed and coating thickness of the present application, and after drying, reference electrodes with diameters of 50 ⁇ m-150 ⁇ m, 50 ⁇ m-80 ⁇ m, and 65 ⁇ m-80 ⁇ m can be obtained.
  • the reference electrode prepared according to the method of the present application uses the copper wire whose surface insulation layer has been removed in advance, so that the slurry containing lithium titanate can be more tightly coated on the surface of the copper wire.
  • the method of the present application controls the diameter of the copper wire, the speed of coating and the thickness in an appropriate range, so that the slurry containing lithium titanate is evenly coated on the surface of the copper wire, and the thickness of the lithium titanate coating layer is between Within an appropriate range, a reference electrode with an appropriate diameter and an appropriate thickness of the lithium titanate coating layer can be obtained.
  • the reference electrode prepared according to the method of the present application has the advantages of stable potential and long life. It is applied to a three-electrode battery and can monitor the cycle performance of the battery for a long time.
  • providing the copper wire with the surface insulation layer removed in advance may include: fixing the two ends of the copper wire on a support with a hollowed out part, so that the copper wire part is in the hollowed out part; soaking the support part in Concentrated sulfuric acid to expose a predetermined length of copper wire to concentrated sulfuric acid; clean the copper wire.
  • the copper wire may be fixed to the support with an adhesive or the copper wire may be fixed to the support with a limiting member, which is not particularly limited here.
  • double-sided tape can be used to fix both ends of the copper wire on the support.
  • the supporting member can be made of a material with certain strength, which does not react with the copper wire, and will not be corroded by concentrated sulfuric acid to destroy its mechanical properties.
  • the supporting member can be copper foil, polytetrafluoroethylene PTFE and the like.
  • the preset length can be adjusted according to the specification of the prepared reference electrode or the specification of the battery to be prepared, which is not limited here.
  • the time for the support part to be soaked in concentrated sulfuric acid may be determined according to the removal of the insulating layer on the surface of the copper wire. In one example, the soaking time may be 40 minutes to 60 minutes.
  • the copper wire there are many ways to clean the copper wire, for example, it can be rinsed with deionized water, and then ultrasonically cleaned with absolute ethanol.
  • the copper wire is fixed on the support, and the surface of the copper wire is treated with concentrated sulfuric acid, which can more fully remove the insulating layer on the surface of the copper wire, so that the copper wire has good electrical conductivity and a combination with the slurry. force.
  • the support can effectively support the micron-sized copper wire, and the hollow part prevents the concentrated sulfuric acid from climbing along the gap between the copper wire and the support, thereby ensuring the consistency of the copper wire soaking height.
  • cleaning the copper wire may include: treating the copper wire with a plasma cleaning method.
  • the copper wire may be rinsed with deionized water, ultrasonically cleaned with absolute ethanol, and then treated with a plasma cleaning method.
  • Treating the copper wire with plasma cleaning can reduce the surface tension of the copper wire, which is more conducive to the spreading of the slurry on the surface of the copper wire.
  • the preset length may be 10mm-30mm, 10mm-20mm, 10mm-18mm, 12mm-18mm, 15mm-18mm.
  • the length of the part of the copper wire in which the insulating layer is removed is within an appropriate range, which is more convenient for the processing of the reference electrode and the assembly of the three-electrode battery.
  • the length of coating can also be controlled.
  • the coating length can be adjusted according to the specifications of the prepared reference electrode or the specifications of the battery to be prepared, which is not limited herein. Specifically, the coating length may be less than or equal to the aforementioned predetermined length.
  • the coating length may be 10mm-30mm, 10mm-20mm, 10mm-18mm, 12mm-18mm, 15mm-18mm.
  • the length of the coating is consistent with the length of the part where the insulating layer is removed, which can ensure that lithium ions are fully intercalated into lithium titanate when the reference electrode is activated, thereby avoiding the formation of metallic lithium. Moreover, if the coating length is within an appropriate range, the coating speed and thickness can be better controlled, so that the thickness of the lithium titanate coating layer is more uniform.
  • providing the slurry containing lithium titanate may include: uniformly mixing lithium titanate, a binder, a conductive agent, and an organic solvent to obtain a slurry.
  • Binders may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer , at least one of tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the aforementioned organic solvent may be N-methylpyrrolidone (NMP).
  • the slurry prepared in this embodiment contains a binder and a conductive agent, which can improve the bonding performance of lithium titanate and copper wire and the conductivity of the reference electrode, so that the reference electrode has a long life without affecting the performance of the battery. cycle performance.
  • the mass fraction of lithium titanate is 85wt% to 93wt%
  • the mass fraction of the binder is 3wt% to 7wt%
  • the mass fraction of the conductive agent is 4wt% to 8wt%.
  • the mass ratio of lithium titanate to binder and conductive agent is 90:5:5.
  • the lithium titanate content in the slurry is too low, which means that there is less active lithium that can be inserted, and the life of the reference electrode is shorter; the lithium titanate content is too high, and the content of the binder and the conductive agent is relatively low, so that As a result, the viscosity of the slurry is not enough, it cannot be tightly combined with the copper wire, and the conductivity of the coating layer is poor, which increases the difficulty of lithium intercalation. Controlling the mass ratio of binder and conductive agent to lithium titanate in an appropriate range can make the lithium titanate coating layer not easy to fall off and have good conductivity, and at the same time contain enough lithium titanate, so that the reference electrode has Long-term stable potential and longer life.
  • the solid content of the slurry can be 20wt%-50wt%, 20wt%-45wt%, 25wt%-45wt%, 30wt%-45wt%, 30wt%-40wt%, 30wt%-35wt%.
  • the solid content of the slurry is controlled within the above appropriate range, which can ensure that the slurry is evenly and tightly coated on the surface of the copper wire, thereby further ensuring that the reference electrode has a long life and a stable potential.
  • the support member may be copper foil, and the thickness of the copper foil may be 20 ⁇ m ⁇ 30 ⁇ m.
  • the hollowed-out part can be N rectangles, the length of the rectangle can be 20mm-25mm, the width of the rectangle can be 30mm-45mm, and the distance between the N rectangles can be 10mm-15mm, where N can be an integer ⁇ 2.
  • Copper foil with multiple hollow rectangles can effectively support micron-sized copper wires.
  • the support When the support is partially immersed in concentrated sulfuric acid, it can avoid concentrated sulfuric acid climbing along the gap between copper wires and copper foils, ensuring that the copper wires are soaked at a consistent height sex.
  • the blank area between the N rectangles plays a load-bearing role and supports the central part of the copper foil, which can prevent the copper wire from loosening, winding, and knotting.
  • the copper foil with multiple hollow rectangles can increase the tension of the copper wire, and can also coat the front and back of the copper wire at the same time, which is beneficial to improve the uniformity of coating.
  • the support is made of polytetrafluoroethylene, and the thickness of the support may be 2mm ⁇ 5mm.
  • the hollowed-out part can be M rectangles, the length of the rectangles can be 20mm-25mm, the width of the rectangles can be 30mm-45mm, and the distance between the M rectangles can be 10mm-15mm, where M can be an integer ⁇ 1.
  • the strength of polytetrafluoroethylene is relatively high, and the supporting piece made of polytetrafluoroethylene may only have a hollowed-out rectangle.
  • the concentrated sulfuric acid can be prevented from climbing along the gap between the copper wire and the copper foil, so as to ensure the consistency of the soaking height of the copper wire.
  • the blank area between the rectangles plays a load-bearing role, supporting the central part of the copper foil, which can prevent the copper wire from loosening, entanglement, and knotting.
  • the support made of PTFE can increase the tension of the copper wire, and can also coat the front and back of the copper wire at the same time, which is beneficial to improve the uniformity of coating.
  • fixing the two ends of the copper wires on the support with the hollow part may include: fixing a plurality of copper wires on the support with an interval of 3 mm to 5 mm, so that the copper wire part is in the hollow parts.
  • Controlling the distance between the copper wires within an appropriate range can prevent the copper wires from sticking to each other, thereby ensuring that the slurry can be evenly coated on the surface of the copper wires.
  • a reference electrode including a copper wire and a lithium titanate layer coated on the surface of the copper wire.
  • the diameter of the copper wire is 40 ⁇ m ⁇ 60 ⁇ m, optionally 44 ⁇ m ⁇ 50 ⁇ m.
  • the thickness of the lithium titanate layer is 5 ⁇ m ⁇ 50 ⁇ m, optionally, the thickness of the lithium titanate layer is 7 ⁇ m ⁇ 20 ⁇ m, 7 ⁇ m ⁇ 18 ⁇ m, 8 ⁇ m ⁇ 18 ⁇ m, 8 ⁇ m ⁇ 15 ⁇ m.
  • the copper wire has a suitable diameter and the thickness of the lithium titanate layer is suitable, which can give full play to the good conductivity of the copper wire and the advantages of stable lithium titanate potential and high lithium ion diffusion coefficient, and can Make the reference electrode have a suitable volume.
  • the reference electrode of the present application has the advantages of stable potential and long life, and it is applied to a three-electrode battery, which can monitor the cycle performance of the battery for a long time.
  • the diameter of the reference electrode can be 50 ⁇ m-150 ⁇ m, 50 ⁇ m-140 ⁇ m, 50 ⁇ m-120 ⁇ m, 50 ⁇ m-80 ⁇ m, 65 ⁇ m-80 ⁇ m.
  • the volume of the reference electrode is too large to cause obvious indentation on the positive and negative pole pieces, and the part of the positive and negative pole pieces covered by the reference electrode cannot intercalate lithium, resulting in the prolapsed active lithium cannot be intercalated in time, resulting in lithium precipitation. Thus affecting the cycle performance and cycle life of the battery. Controlling the diameter of the reference electrode prepared by lithium titanate-coated copper wire within the above-mentioned appropriate range can avoid the influence of the reference electrode on the transmission of active lithium, and will not cause the problem of indentation of the positive and negative electrodes.
  • reference electrode of any embodiment of the second aspect of the present application can be prepared by the method of any embodiment of the first aspect of the present application.
  • a three-electrode battery is further provided, including an electrode assembly.
  • an electrode assembly includes a positive pole piece, a negative pole piece, a reference electrode, an electrolyte, and a separator.
  • the first positive pole piece 11, the reference electrode 12 negative pole piece 13 and the second positive pole piece 14 are arranged at intervals in sequence, between the first positive pole piece 11 and the reference electrode 12, the negative pole piece 13 Separators 15 are provided between the reference electrode 12 and between the negative pole piece 13 and the second positive pole piece 14 , thereby constituting the electrode assembly 10 .
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the reference electrode monitors the performance of the positive and negative electrodes during the charge and discharge process.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the reference electrode, and the negative pole piece and the reference electrode, mainly to prevent the short circuit of the positive and negative poles, and at the same time allow ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector, and the positive electrode film layer includes the positive electrode active material according to the first aspect of the present application.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode film layer can be disposed on any one of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material known in the art for batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn At least one of 0.1 O 2 (also abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al
  • lithium-containing phosphates with olivine structure may include but not limited to lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite material of lithium manganese phosphate and carbon, manganese phosphate At least one of the composite materials of iron lithium, lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • manganese phosphate At least one of the composite materials of iron lithium, lithium iron manganese phosphate and carbon.
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • CMC-Na sodium carboxymethylcellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the reference electrode includes a reference electrode prepared according to the method of any embodiment of the first aspect of the present application, or a reference electrode according to the second aspect of the present application.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte can be liquid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is also included in the three-electrode cell.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly by a lamination or winding process.
  • a three-electrode battery can include an outer packaging.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer package of the three-electrode battery can be a soft bag, such as a pouch-type soft bag.
  • the material of the soft bag can be an aluminum-plastic composite film, which is formed by pressing the outer nylon layer, the middle aluminum layer, and the inner heat-sealing layer polypropylene layer.
  • the three-electrode battery of the present application includes the reference electrode prepared by the method provided by the application according to any embodiment of the first aspect of the application, or the reference electrode according to any embodiment of the second aspect of the application, thus at least having the same Same advantages over electrodes.
  • the fourth aspect of the present application provides a method for preparing the three-electrode battery according to the third aspect of the present application, including: assembling the three-electrode battery, including packaging the electrode assembly, vacuumizing the electrode assembly after hot pressing, and injecting the electrolyte, thereby Get the assembled three-electrode battery; activate the reference electrode, including charging the reference electrode to the preset cut-off voltage with a current of 5 ⁇ A to 10 ⁇ A through the positive electrode after the assembled three-electrode battery is left and formed, and then charging the reference electrode with a current of 5 ⁇ A A current of ⁇ 10 ⁇ A releases 40% ⁇ 50% of the lithium intercalation capacity to the reference electrode, so as to activate the reference electrode and make the reference electrode in a stable state.
  • the reference electrode can be charged to the preset cut-off voltage through the positive electrode with a current of 5 ⁇ A to 10 ⁇ A, and then discharged to the reference electrode with a current of 5 ⁇ A to 10 ⁇ A, thereby activating the reference electrode and ensuring Stability of the reference electrode. In this way, the time for activating the reference electrode can be greatly reduced, thereby improving the preparation efficiency of the three-electrode battery.
  • the cut-off voltage can be determined by the voltage plateau of the positive electrode material relative to the reference electrode. In this way, lithium can be inserted into the reference electrode more efficiently, thereby ensuring the stability of the reference electrode.
  • the cut-off voltage can be a voltage close to the voltage plateau of the positive electrode material relative to the reference electrode. For example, for a ternary material NCM-graphite battery, at a state of half charge of 3.8V, the NCM to the reference electrode If the voltage platform is around 2.3V, the cut-off voltage can be 2.6V.
  • Lithium titanate, PVDF, and conductive carbon were weighed in a mass ratio of 90:5:5 for later use. Add PVDF to NMP, stir until dissolved, and add NMP according to the total solid content of 30wt% of the slurry; then add conductive carbon, stir at a rate of 1000rpm for 30min; finally add lithium titanate, and stir at a rate of 1000rpm for 3h.
  • a plurality of copper wires with a diameter of 44 ⁇ m to 50 ⁇ m were fixed on the copper foil at a distance of 3 mm with double-sided adhesive tape.
  • the size of the copper foil is 12cm*12cm, and the thickness is 8 ⁇ m ⁇ 15 ⁇ m.
  • the coating length is 15mm-20mm, and the coating thickness is 8 ⁇ m-15 ⁇ m.
  • Negative active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), thickener carboxymethylcellulose sodium (CMC-Na) are dissolved in the solvent according to the mass ratio of 95:2:2:1
  • Negative electrode slurry is prepared by fully stirring and mixing in deionized water; the negative electrode slurry is evenly coated on the two opposite surfaces of the copper foil of the negative electrode current collector in the thickness direction, and then dried, cold pressed, and cut to obtain Negative pole piece.
  • the positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black in the solvent N-methylpyrrolidone (NMP) according to the mass ratio of 97:2:1, and stir and mix evenly
  • NMP N-methylpyrrolidone
  • the electrode assembly is obtained through the lamination process; the electrode assembly is placed in the outer package, and the electrolyte is injected after drying; and other processes to obtain a three-electrode battery.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the solid content of the slurry is 20 wt%.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the solid content of the slurry is 50 wt%.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the solid content of the slurry is 40wt%.
  • the preparation of the reference electrode, the preparation of the negative electrode sheet, the preparation of the positive electrode sheet and the preparation of the three-electrode battery are the same as in Example 1, the difference is that the mass ratio of lithium titanate, PVDF, and conductive carbon in the slurry is 93: 3:4.
  • the preparation of the reference electrode, the preparation of the negative electrode sheet, the preparation of the positive electrode sheet and the preparation of the three-electrode battery are the same as in Example 1, the difference is that the mass ratio of lithium titanate, PVDF, and conductive carbon in the slurry is 85: 7:8.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, the difference is that there is only one hollowed out rectangle in the copper foil, the length of the matrix is constant, and the width is the same as in Example 1. The sum of the widths of the two rectangles in Example 1.
  • Example 7 part of the copper wires were broken after coating, and the copper wires with good shape were used to prepare the three-electrode battery.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the thickness of the coating is 15 ⁇ m-20 ⁇ m.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the coating speed is 0.5 mm/s.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the coating speed is 10 mm/s.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the thickness of the coating is 2 ⁇ m-5 ⁇ m.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the thickness of the coating is 55 ⁇ m-75 ⁇ m.
  • the preparation of the reference electrode, the preparation of the negative pole piece, the preparation of the positive pole piece and the preparation of the three-electrode battery are the same as in Example 1, except that the coating speed is 0.1 mm/s.
  • the difference in the preparation of the reference electrode is that the coating speed is 20mm/s.
  • the copper wire loses its tension and becomes slack, and the slurry gathers into droplets on the surface of the copper wire, making the reference electrode almost unusable.
  • the preparation of the reference electrode is the same as that of Example 1, except that the copper foil has no hollow rectangle.
  • the contact part between the copper wire and the copper foil in Comparative Example 5 could not be coated, so the prepared reference electrode could hardly be used.
  • the preparation of the reference electrode is the same as in Example 1, except that the solid content of the slurry is 5 wt%. Because the solid content of the slurry is too low and the viscosity is too small, it cannot be coated.
  • the preparation of the reference electrode is the same as in Example 1, except that the solid content of the slurry is 70wt%. Because the solid content of the slurry is too high and the viscosity is too high, the slurry is agglomerated on the surface of the copper wire during coating, and the prepared reference electrode cannot be used.
  • the preparation of the negative pole piece, the preparation of the positive pole piece, and the preparation of the three-electrode battery are the same as in Example 1, the difference is that the reference electrode is made of lithium-plated copper wire with a diameter of 40 ⁇ m to 60 ⁇ m, and the specific lithium plating process is: positive electrode Charge the copper wire with reference 10 ⁇ A for 2h, and then charge the negative electrode with reference 10 ⁇ A for 2h.
  • the number of reference electrodes prepared in an example or comparative example is denoted as n, wherein, the number of reference electrodes that can be used to prepare a three-electrode battery and the prepared three-electrode battery can be tested for performance is denoted as m, then the reference The efficiency of the electrode is defined as: (m/n)*100%.
  • the battery charge and discharge test process is as follows: use an electrochemical workstation or a Xinwei machine with auxiliary channels, and place the battery and equipment channel test lines in a Harding high and low temperature box. At 25°C, the three-electrode battery was charged to 4.2V at a constant current rate of 0.05C, left for 5min, and then discharged to 2.8V at 0.05C. Taking the positive electrode, negative electrode, and full battery electrode voltage as the ordinate, and time or capacity as the abscissa, the time-voltage curve and capacity-voltage curve can be obtained.
  • FIG. 3 is a time-voltage curve diagram corresponding to Example 1
  • FIG. 4 is a time-voltage curve diagram corresponding to Comparative Example 8.
  • the life test method of the reference electrode is to use a 5V 1A Xinwei machine with an auxiliary channel to conduct a cycle charge and discharge test on the battery, and place the Xinwei machine channel test line and the three-electrode battery in the Harding high and low temperature box to control the test temperature , the auxiliary channel test line is clamped on the tabs of the negative electrode and the reference electrode, and the voltage between the negative electrode and the reference electrode is monitored. If the curve suddenly rises or falls, it proves that the reference electrode is invalid and the test is terminated.
  • the battery cycle charge and discharge test process is as follows: at 25°C, charge the three-electrode battery with a constant current of 1C rate to 4.2V, and then charge it with a constant voltage of 4.2V until the current is 0.05C. Discharge to 2.8V, then wait for 15 minutes to charge, and cycle charge and discharge according to this process.
  • Fig. 5 is the graph that the voltage between the negative electrode and the reference electrode corresponding to Example 1 changes with the number of cycles
  • Fig. 6 is the curve of the voltage between the negative electrode and the reference electrode corresponding to Comparative Example 8 as the number of cycles changes picture.
  • the copper wire diameter, coating speed, and coating thickness of Examples 1-10 are within the scope of the method of the present application, and the prepared reference electrodes not only have a higher yield rate, but also have a longer service life.
  • the mass ratio and solid content of lithium titanate, binder, and conductive agent are controlled in an appropriate range, and the prepared reference electrode can exhibit higher yield and longer life.
  • the method for preparing the reference electrode, the reference electrode, the method for preparing the three-electrode battery, and the three-electrode battery provided by the present application can realize the monitoring of the long-term cycle performance of the battery.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池。其中，方法包括：提供预先去除表面绝缘层的铜丝；提供包含钛酸锂的浆料；将浆料涂布于铜丝的表面；其中，铜丝的直径为40μm～60μm，可选地为44μm～50μm；涂布厚度为5μm～50μm，可选地为7μm～20μm，进一步可选地为8μm～15μm。

Description

用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池
相关申请的交叉引用
本申请要求享有于2021年11月02日提交的名称为“用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池”的中国专利申请202111290697.7的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及锂电池技术领域，尤其涉及一种用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、军事装备、航空航天等多个领域。随着工作时间的增长，锂离子电池的容量会有所衰减。在电池设计和研究的过程中，需要独立地分析正极和负极对电池容量变化产生的影响。在全电池中引入参比电极，能够分别测量电池中正极和负极相对于参比电极的电位和阻抗，从而实现在充放电过程中对正负极性能的监测。
但是，现有的参比电极存在电位不稳定、寿命短的问题，无法监测电池的长期循环性能。因此，现有的参比电极仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种具有稳定电位、长寿命的参比电极，以实现对电池的长期循环性能的监测。
为了达到上述目的，本申请提供了用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池。
本申请的第一方面提供了一种用于制备参比电极的方法，包括：提供预先去除表面绝缘层的铜丝，该铜丝固定于支撑件；提供包含钛酸锂的浆料；将浆料涂布于铜丝的表面；其中，铜丝的直径为40μm～60μm，可选地为44μm～50μm；涂布速度为0.5mm/s～10mm/s，可选地为1mm/s～5mm/s；涂布厚度为5μm～50μm，可选地为7μm～20μm，进一步可选地为8μm～15μm。
由此，本申请通过控制铜丝直径、涂布的厚度和速度在合适的范围 内，从而使得包含钛酸锂的浆料均匀地包覆于铜丝表面，并且使钛酸锂包覆层的厚度在合适的范围内，进而得到直径、钛酸锂包覆层厚度适当的参比电极。根据本申请的方法制备的参比电极，具有电位稳定、寿命长的优点，将其应用于三电极锂离子电池，能够长期监测电池的循环性能。
在本申请任意实施方式中，提供预先去除表面绝缘层的铜丝，包括：将铜丝的两端固定于具有镂空部位的支撑件上，以使铜丝部分处于镂空部位；将支撑件部分浸泡于浓硫酸中，以使预设长度的铜丝暴露于浓硫酸；清洗铜丝。
该实施方式中，用浓硫酸对铜丝表面进行处理，能够更充分地去除铜丝表面的绝缘层，从而使铜丝具有良好的导电性以及与浆料的结合力。并且，支撑件可以有效地支撑起为微米级的铜丝，镂空部分避免了浓硫酸沿着铜丝与支撑件间隙爬坡，从而能够确保铜丝浸泡高度的一致性。
在本申请任意实施方式中，清洗铜丝包括：用等离子清洗法处理铜丝。用等离子清洗法处理铜丝，能够减小铜丝的表面张力，从而更利于浆料的涂布。
在本申请任意实施方式中，预设长度为10mm～30mm。铜丝中去除绝缘层部分的长度在合适的范围内，更便于参比电极的加工和三电极电池的组装。
在本申请任意实施方式中，涂布的长度为10mm～30mm。涂布的长度在合适的范围内，能够更好地控制涂布的速度和厚度，从而使钛酸锂包覆层的厚度更均匀。
在本申请任意实施方式中，上述提供包含钛酸锂的浆料，包括：将钛酸锂、粘结剂、导电剂与有机溶剂混合均匀，从而得到浆料。浆料中包含粘结剂、导电剂，能够提高钛酸锂与铜丝的结合性能以及参比电极的导电性能，从而使参比电极具备长寿命，且不会影响电池的循环性能。
在本申请任意实施方式中，基于浆料的总质量，钛酸锂的质量分数为85wt％～93wt％，粘结剂的质量分数为3wt％～7wt％，导电剂的质量分数为4wt％～8wt％。可选地，钛酸锂与粘结剂、导电剂的质量比为90:5:5。控制粘结剂和导电剂与钛酸锂的质量比在合适的范围内，能使钛酸锂包覆层不易脱落、导电性良好的同时，含有足够的钛酸锂，从而使参比电极具有长期稳定的电位以及更长的寿命。
在本申请任意实施方式中，浆料的固含量为20wt％～50wt％，可选地为30wt％～40wt％。浆料的固含量控制在上述合适的范围内，能够保证浆料均匀、紧密地包覆在铜丝表面，从而进一步保证参比电极具有长寿命和稳定的电位。
在本申请任意实施方式中，支撑件为铜箔，铜箔的厚度为20μm～30μm。
镂空部位为N个矩形，矩形的长为20mm～25mm，矩形的宽为30mm～45mm，N个矩形之间的距离为10mm～15mm，其中，N为≥2的整 数。
具有多个镂空矩形的铜箔可以有效支撑微米级的铜丝，避免铜丝松垮、缠绕、打结。此外，在后续涂布工序，具有多个镂空矩形的铜箔可增大铜丝张力，还可将铜丝的正面与背面同时涂覆，有利于提高涂布的均匀性。
在本申请任意实施方式中，支撑件由聚四氟乙烯制成，支撑件的厚度为2mm～5mm。
镂空部位为M个矩形，矩形的长为20mm～25mm，矩形的宽为30mm～45mm，M个矩形之间的距离为10mm～15mm，其中，M为≥1的整数。
由聚四氟乙烯制成的支撑件可以有效支撑微米级的铜丝，避免铜丝松垮、缠绕、打结。此外，在后续涂布工序，由聚四氟乙烯制成的支撑件可增大铜丝张力，还可将铜丝的正面与背面同时涂覆，有利于提高涂布的均匀性。
在本申请任意实施方式中，将铜丝的两端固定于具有镂空部位的支撑件上，包括：将多根铜丝以3mm～5mm的间隔距离固定于支撑件上，以使铜丝部分处于镂空部位。铜丝之间的间距控制在合适的范围内，可以防止铜丝之间相互粘连，从而保证浆料能够均匀地涂覆于铜丝表面。
本申请的第二方面还提供一种参比电极，包括铜丝以及包覆于铜丝表面的钛酸锂层，铜丝的直径为40μm～60μm，可选地为44μm～50μm；钛酸锂层的厚度为5μm～50μm，可选地为7μm～20μm，进一步可选地为8μm～15μm。
根据本申请的参比电极中，铜丝具有合适的直径、钛酸锂层的厚度合适，能够充分发挥铜丝良好的导电性和钛酸锂电位稳定、锂离子扩散系数高的优点，并且能够使参比电极具有合适的体积。本申请的参比电极具有电位稳定、寿命长的优点，将其应用于三电极电池，能够长期监测电池的循环性能。
在本申请任意实施方式中，参比电极的直径为50μm～150μm，可选地为50μm～80μm，进一步可选地为65μm～80μm。控制钛酸锂包覆铜丝制备的参比电极的直径在上述合适的范围内，既能够避免参比电极对活性锂传输的影响，也不会导致正负极极片出现严重压痕而导致局部析锂的问题。
本申请的第三方面提供一种三电极电池，包括电极组件，电极组件包括根据本申请第一方面的方法制备的参比电极，或者根据申请第二方面的参比电极，以及第一正极极片、第二正极极片负极极片，第一正极极片、参比电极、负极极片第二正极极片依次间隔排列，第一正极极片与参比电极之间、负极极片与参比电极之间、负极极片与第二正极极片之间分别设置有隔离膜。
本申请的三电极电池包括本申请提供据本申请第一方面的方法制备的参比电极，或者根据本申请第二方面的参比电极，因而至少具有与参比电极相同的优势。
本申请的第四方面提供一种用于制备根据本申请第三方面的三电极电池的方法，包括：组装三电极电池，包括将电极组件封装、真空注液化成等，从而得到组装后的三电极电池；激活参比电极，包括在对组装后的三电极电池搁置、化成后，通过正极以5μA～10μA的电流对参比电极充电至预设的截止电压，再以5μA～10μA的电流对参比电极放电40～50％的嵌锂容量，以激活参比电极。
由于钛酸锂具有稳定电位，可以通过正极以5μA～10μA的电流对参比电极充电至预设的截止电压，再以5μA～10μA的电流对参比电极放电，从而将参比电极激活并保证参比电极的稳定性。这样，能够大幅减小激活参比电极的时间，从而提高三电极电池的制备效率。
在本申请任意实施方式中，截止电压通过正极材料相对于参比电极的电压平台确定。如此，能够更高效地对参比电极嵌锂，从而保证参比电极稳定性。
附图说明
图1是本申请一实施方式的电极组件的示意图。
图2是本申请一实施方式的铜丝及支撑件的示意图。
图3是本申请实施例1对应的电池小倍率充放电测试的时间-电压曲线图。
图4是本申请对比例8对应的电池小倍率充放电测试的时间-(负极-参比电压)曲线图。
图5是本申请实施例1对应的参比电极寿命测试的循环圈数-(负极-参比电压)曲线图。
图6是本申请对比例8对应的参比电极寿命测试的循环圈数-电压曲线图。
附图标记说明：
10电极组件；11第一正极极片；12参比电极；13负极极片；14第二正极极片；15隔离膜。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围 的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在电池设计和研究的过程中，需要独立地分析正极和负极对电池容量变化产生的影响。在全电池中引入参比电极，能够分别测量全电池中正极和负极相对于参比电极的电位和阻抗，从而实现在充放电过程中对正负极性能的监测。
目前较多的参比电极主要由铜丝或者铜片用电化学方法镀锂制成，或者由条状的铜基材涂覆钛酸锂制成。
发明人研究发现，传统的铜丝或者铜片镀锂制得的参比电极，其表面的锂金属会与电解液发生反应，从而导致金属锂包覆层的消耗。参比电极表面锂金属的消耗不仅会导致参比电极的寿命较短，还会导致电位不稳定。由此，传统的铜丝或者铜片镀锂制得的参比电极只能实现对电池性能的短期监测。此外，传统的铜丝或者铜片镀锂制得的参比电极在使用前需要经过时间较长的充电镀锂过程，以激活参比电极，这也造成了时间成本的浪费。
发明人经大量的实验和研究，发现钛酸锂材料具有稳定的电位，且放点电位非常平坦，可以满足对参比电极的要求。并且，钛酸锂几乎不与电解液反应，不会在电池循环过程中被消耗而导致参比电极失效。此外，钛酸锂具有高的锂离子扩散系数，可达2*10 -8cm 2/s，锂离子具有很好的迁移性。钛酸锂还具有“零应变性”，晶体在嵌入或脱出锂离子时晶格常数和体积变化都很小(小于1％)能够避免由于电极材料的来回伸缩而导致结构的破坏，从而提高电极的循环性能和使用寿命。
但是，目前钛酸锂包覆的参比电极多是使用传统涂布法将钛酸锂浆料涂布于铜箔上，从而形成钛酸锂包覆层。这种涂布方法不仅难以控制钛酸锂包覆层的厚度，而且难以对宽度较小的铜箔进行涂布，导致参比电极的形状过宽，从而阻碍电解液中锂离子的传输，对电池界面造成不可逆损伤。另外，传统涂布法涂布而得的钛酸锂包覆层与铜箔的结合力不强，容易在使用过程中脱落。由条状的铜基材涂覆钛酸锂制成的参比电极形状不仅自身寿命短，还会影响电池的循环性能。
基于此，发明人经过大量实验研究，提供了一种用于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池。
本申请提供的参比电极可适用于对锂离子电池进行短期或长期循环性能监测的场景，尤其是对长期循环性能正负极状态变化监测的场景。基于上述场景，本申请提供的参比电极可作为电池组件的部件，用于制备三电极或多电极电池。具体地，该电池可以为三电极单层叠片电池，三电极多层叠片电池，四电极或四电极以上的多电极单层叠片电池，四电极或四电极以上的多电极多层叠片电池，三电极软包电池，四电极或四电极以上的多电极软包电池
用于制备参比电极的方法
本申请的一个实施方式中，本申请提出了一种用于制备参比电极的方法，包括：提供预先去除表面绝缘层的铜丝，该铜丝固定于支撑件；提供包含钛酸锂的浆料；将浆料涂布于铜丝的表面。
其中，铜丝的直径为40μm～60μm，可选地为44μm～50μm；涂布速度为0.5mm/s～10mm/s，可选地为1mm/s～5mm/s，1mm/s～4mm/s，1.5mm/s～4mm/s，2mm/s～3mm/s；涂布厚度为5μm～50μm，可选地为7μm～20μm，7μm～18μm，8μm～18μm，进一步可选地为8μm～15μm。
未经处理的铜丝表面包覆了一层聚合物绝缘层，为了发挥铜丝的导电性，需要将聚合物绝缘层去除。去除聚合物绝缘层的方法有多种，例如可以使用砂纸打磨或浓硫酸浸泡，再进行清洗，在此不作限制。
在一个示例中，可以将铜丝固定于支撑件上，并将支撑件固定于涂布立架上，用手持夹辊自上而下地以上述涂布速度对铜丝进行涂布。具体地，可以通过控制涂布速度、浆料的用量和固含量、涂布的次数来控制涂布的厚度在本申请方法的范围内。容易理解的，由铜丝制备参比电极的方式可以有多种，本示例是由铜丝制备参比电极的一种实现方式，仅是为了解释本申 请，而不是为了限制本申请。
并非意在受限于任何理论或解释，发明人发现，将体积较小的铜丝与钛酸锂复合制成参比电极，既能够发挥钛酸锂电位稳定、锂离子扩散系数高等优势，又能够改善参比电极的导电性，弥补钛酸锂导电性差的缺点。
进一步地，经发明人研究发现，参比电极的体积过大会使得正负极极片出现明显的压痕，并且正负极极片被参比电极遮挡的部分无法嵌锂，导致脱出的活性锂无法及时嵌入而产生析锂现象，从而影响电池的循环性能和循环寿命。控制钛酸锂包覆铜丝制备的参比电极的直径在上述合适的范围内，既能够避免参比电极对活性锂传输的影响，也不会导致正负极极片出现压痕的问题。
更进一步地，发明人经大量实验发现，钛酸锂包覆层的厚度也是影响参比电极性能的重要因素。钛酸锂包覆层过厚时，有可能会局部刺穿隔膜，造成正负极与参比之间短路的风险；钛酸锂包覆层过薄时，钛酸锂的嵌锂量过低，会导致参比电极寿命短。
鉴于此，发明人反复试验，发现涂布速度过快，容易拉伸柔韧的铜丝，使其失去张力变的松弛，浆料容易在松弛弯曲的铜丝上形成液滴，凝固后容易扎破隔膜成为短路点；涂布速度过慢则容易使得铜丝上的浆料变干，不利于涂布。涂布厚度则会直接影响最后形成的钛酸锂包覆层的厚度。对5μm～50μm的铜丝以本申请方法中的涂布速度及涂布厚度进行涂布，能够得到包覆均匀且包覆层厚度合适的参比电极。具体地，以本申请的涂布速度以及涂布厚度对铜丝进行涂布，干燥后可以得到直径为50μm～150μm、50μm～80μm、65μm～80μm的参比电极。
根据本申请的方法制备的参比电极，使用预先去除表面绝缘层的铜丝，能够使包含钛酸锂的浆料更紧密地包覆在铜丝表面。本申请的方法控制铜丝直径、涂布的速度和厚度在合适的范围内，从而使得包含钛酸锂的浆料均匀地包覆于铜丝表面，并且使钛酸锂包覆层的厚度在合适的范围内，进而得到直径、钛酸锂包覆层厚度适当的参比电极。根据本申请的方法制备的参比电极，具有电位稳定、寿命长的优点，将其应用于三电极电池，能够长期监测电池的循环性能。
在一些实施方式中，提供预先去除表面绝缘层的铜丝，可以包括：将铜丝的两端固定于具有镂空部位的支撑件上，以使铜丝部分处于镂空部位；将支撑件部分浸泡于浓硫酸中，以使预设长度的铜丝暴露于浓硫酸；清洗铜丝。
该实施方式中，固定铜丝的方法可以有多种，例如可以用粘接剂将铜丝固定于支撑件或者用限位构件将铜丝固定于支撑件，在此不作特别限定。在一个示例中，可以用双面胶将铜丝的两端固定于支撑件上。支撑件可以由具有一定强度的、不与铜丝反应、不会被浓硫酸腐蚀而破坏力学性能的材料制成，例如，支撑件可以为铜箔、聚四氟乙烯PTFE等。
预设长度可以根据制备的参比电极的规格或者所要制备的电池的规格 进行调整，在此不作限定。支撑件部分浸泡于浓硫酸中的时间可以根据铜丝表面的绝缘层的去除情况确定，在一个示例中，浸泡时间可以为40min～60min。
清洗铜丝的方法可以有多种，例如，可以用去离子水冲洗，再用无水乙醇超声清洗。
该实施方式中，将铜丝固定于支撑件，用浓硫酸对铜丝表面进行处理，能够更充分地去除铜丝表面的绝缘层，从而使铜丝具有良好的导电性以及与浆料的结合力。并且，支撑件可以有效地支撑起为微米级的铜丝，镂空部分避免了浓硫酸沿着铜丝与支撑件间隙爬坡，从而能够确保铜丝浸泡高度的一致性。
在一些实施方式中，清洗铜丝可以包括：用等离子清洗法处理铜丝。具体地，可以用去离子水冲洗铜丝后，用无水乙醇超声清洗，再用等离子清洗法处理铜丝。
用等离子清洗法处理铜丝，能够减小铜丝的表面张力，从而更利于浆料在铜丝表面的铺展。
在一些实施方式中，上述预设长度可为10mm～30mm，10mm～20mm，10mm～18mm，12mm～18mm，15mm～18mm。
铜丝中去除绝缘层部分的长度在合适的范围内，更便于参比电极的加工和三电极电池的组装。
本申请的方法中，还可以控制涂布的长度。涂布的长度可以根据制备的参比电极的规格或者所要制备的电池的规格进行调整，在此不作限定。具体地，涂布的长度可以小于或等于上述预设的长度。
在一些实施方式中，涂布的长度可为10mm～30mm，10mm～20mm，10mm～18mm，12mm～18mm，15mm～18mm。
涂布的长度与去除绝缘层部分的长度保持一致，能够在激活参比电极时，保证锂离子充分地嵌入钛酸锂，从而避免形成金属锂。并且，涂布的长度在合适的范围内，能够更好地控制涂布的速度和厚度，从而使钛酸锂包覆层的厚度更均匀。
在一些实施方式中，上述提供包含钛酸锂的浆料可以包括：将钛酸锂、粘结剂、导电剂与有机溶剂混合均匀，从而得到浆料。
粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。上述有机溶剂可以为N-甲基吡咯烷酮(NMP)。
该实施方式制备的浆料中包含粘结剂、导电剂，能够提高钛酸锂与铜丝的结合性能以及参比电极的导电性能，从而使参比电极具备长寿命，且不会影响电池的循环性能。
在一些实施方式中，基于浆料的总质量，钛酸锂的质量分数为 85wt％～93wt％，粘结剂的质量分数为3wt％～7wt％，导电剂的质量分数为4wt％～8wt％。可选地，钛酸锂与粘结剂、导电剂的质量比为90:5:5。
浆料中的钛酸锂含量过低，意味着可嵌入的活性锂较少，参比电极的寿命较短；钛酸锂含量过高，则粘结剂与导电剂的含量相对较低，从而导致浆料粘度不够，无法与铜丝紧密结合，以及包覆层导电性差，增大嵌锂难度。控制粘结剂和导电剂与钛酸锂的质量比在合适的范围内，能使钛酸锂包覆层不易脱落、导电性良好的同时，含有足够的钛酸锂，从而使参比电极具有长期稳定的电位以及更长的寿命。
在一些实施方式中，浆料的固含量可为20wt％～50wt％，20wt％～45wt％，25wt％～45wt％，30wt％～45wt％，30wt％～40wt％，30wt％～35wt％。
浆料的固含量过低，会导致浆料的粘度不足，从而无法涂覆于铜丝表面。浆料的固含量过高，会导致浆料的粘度过大，很容易团聚形成液滴，从而无法将铜丝均匀覆盖，进而形成局部不良，甚至会造成局部短路。浆料的固含量控制在上述合适的范围内，能够保证浆料均匀、紧密地包覆在铜丝表面，从而进一步保证参比电极具有长寿命和稳定的电位。
在一些实施方式中，支撑件可以为铜箔，铜箔的厚度可为20μm～30μm。
镂空部位可为N个矩形，矩形的长可为20mm～25mm，矩形的宽可为30mm～45mm，N个矩形之间的距离可为10mm～15mm，其中，N可为≥2的整数。
具有多个镂空矩形的铜箔可以有效支撑微米级的铜丝，将支撑件部分浸泡于浓硫酸中时，能够避免浓硫酸沿着铜丝与铜箔间隙爬坡，确保铜丝浸泡高度的一致性。N个矩形之间的留白区起到承重作用，支撑铜箔的中央部位，可以避免铜丝松垮、缠绕、打结。此外，在后续涂布工序，具有多个镂空矩形的铜箔可增大铜丝张力，还可将铜丝的正面与背面同时涂覆，有利于提高涂布的均匀性。
在一些实施方式中，支撑件由聚四氟乙烯制成，支撑件的厚度为可2mm～5mm。
镂空部位可为M个矩形，矩形的长可为20mm～25mm，矩形的宽可为30mm～45mm，M个矩形之间的距离可为10mm～15mm，其中，M可为≥1的整数。
聚四氟乙烯的强度较高，由聚四氟乙烯制成的支撑件可以只具有一个镂空矩形。将支撑件部分浸泡于浓硫酸中时，能够避免浓硫酸沿着铜丝与铜箔间隙爬坡，确保铜丝浸泡高度的一致性。当支撑件上具有数量大于1的矩形时，矩形之间的留白区起到承重作用，支撑铜箔的中央部位，可以避免铜丝松垮、缠绕、打结。此外，在后续涂布工序，由聚四氟乙烯制成的支撑件可增大铜丝张力，还可将铜丝的正面与背面同时涂覆，有利于提高涂布的均匀性。
在一些实施方式中，将铜丝的两端固定于具有镂空部位的支撑件上，可以包括：将多根铜丝以3mm～5mm的间隔距离固定于支撑件上，以使铜丝部分处于镂空部位。
铜丝之间的间距控制在合适的范围内，可以防止铜丝之间相互粘连，从而保证浆料能够均匀地涂覆于铜丝表面。
参比电极
本申请第二方面的一个实施方式中，还提供了一种参比电极，包括铜丝以及包覆于铜丝表面的钛酸锂层。铜丝的直径为40μm～60μm，可选地为44μm～50μm。钛酸锂层的厚度为5μm～50μm，可选地，钛酸锂层的厚度为7μm～20μm、7μm～18μm、8μm～18μm，8μm～15μm。
根据本申请的参比电极中，铜丝具有合适的直径、钛酸锂层的厚度合适，能够充分发挥铜丝良好的导电性和钛酸锂电位稳定、锂离子扩散系数高的优点，并且能够使参比电极具有合适的体积。本申请的参比电极具有电位稳定、寿命长的优点，将其应用于三电极电池，能够长期监测电池的循环性能。
在一些实施方式中，参比电极的直径可为50μm～150μm，50μm～140μm，50μm～120μm，50μm～80μm，65μm～80μm。
参比电极的体积过大会使得正负极极片出现明显的压痕，并且正负极极片被参比电极遮挡的部分无法嵌锂，导致脱出的活性锂无法及时嵌入而产生析锂现象，从而影响电池的循环性能和循环寿命。控制钛酸锂包覆铜丝制备的参比电极的直径在上述合适的范围内，既能够避免参比电极对活性锂传输的影响，也不会导致正负极极片出现压痕的问题。
容易理解的，本申请第二方面任一实施方式的参比电极可通过本申请第一方面任一实施方式的方法制备得到。
三电极电池
本申请的第三方面的一个实施方式中，还提供一种三电极电池，包括电极组件。通常情况下，电极组件包括正极极片、负极极片、参比电极、电解质和隔离膜。如图1所示，第一正极极片11、参比电极12负极极片13以及第二正极极片14依次间隔排列，第一正极极片11与参比电极12之间、负极极片13与参比电极12之间、负极极片13与第二正极极片14之间分别设置有隔离膜15，从而构成电极组件10。
在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。参比电极在充放电过程中对正负极性能进行监测。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和参比电极、负极极片和参比电极之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。在一些实施方式中，正极膜层可设置在正极集流体相对的两个表面的其中任意一者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[参比电极]
参比电极包括根据本申请第一方面任一实施方式的方法制备的参比电极，或者根据本申请第二方面的参比电极。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，三电极电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过叠片或卷绕工艺制成电极组件。
在一些实施方式中，三电极电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，三电极电池的外包装可以是软包，例如袋式软包。软包的材质可以是铝塑复合膜，由外层尼龙层，中间铝层，内层热封层聚丙烯层压制而成。
本申请的三电极电池包括本申请提供据本申请第一方面任一实施方式的方法制备的参比电极，或者根据本申请第二方面的任一实施方式的参比电极，因而至少具有与参比电极相同的优势。
用于制备三电极电池的方法
本申请的第四方面提供一种用于制备根据本申请第三方面的三电极电池的方法，包括：组装三电极电池，包括将电极组件封装、热压后进行抽真空、注入电解液，从而得到组装后的三电极电池；激活参比电极，包括在对组装后的三电极电池搁置、化成后，通过正极以5μA～10μA的电流对参比电极充电至预设的截止电压，再以5μA～10μA的电流对参比电极放出 40％～50％嵌锂容量，以激活参比电极且使得参比电极处于一个稳定的状态。
由于钛酸锂具有稳定电位，可以通过正极以5μA～10μA的电流对参比电极充电至预设的截止电压，再以5μA～10μA的电流对参比电极放电，从而将参比电极激活并保证参比电极的稳定性。这样，能够大幅减小激活参比电极的时间，从而提高三电极电池的制备效率。
在本申请任意实施方式中，截止电压可以通过正极材料相对于参比电极的电压平台确定。如此，能够更高效地对参比电极嵌锂，从而保证参比电极稳定性。
在一个示例中，截止电压可以为与正极材料相对于参比电极的电压平台大小相近的电压，例如，对于三元材料NCM-石墨电池，在半电3.8V的状态下，NCM对参比电极的电压平台在2.3V左右，则截止电压可以为2.6V。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
参比电极的制备
【钛酸锂浆料的制备】
将钛酸锂、PVDF、导电碳以90:5:5的质量比称取物料备用。将PVDF加入NMP中，搅拌至溶解，NMP添加量按照总浆料固含量30wt％加入；再加入导电碳，以1000rpm的速率搅拌30min；最后加入钛酸锂，以1000rpm的速率搅拌3h。
【铜丝前处理】
如图2所示，用双面胶将多根直径为44μm～50μm的铜丝以3mm的间距固定于铜箔上。铜箔尺寸为12cm*12cm，厚度8μm～15μm。铜箔上具有两个镂空的矩形，每个矩形的长为20mm～25mm，宽为30mm～45mm，两矩形之间的距离为10mm。
将铜箔卷成筒状浸泡至盛有40mL浓硫酸的50mL烧杯中，以使15mm～20mm的铜丝暴露于浓硫酸。浸泡40min～60min后，用去离子水冲洗3min～5min，用无水乙醇超声清洗2～3次，自然晾干备用。待浆料制备好后，再使用等离子体清洗1min～2min。
【涂布浆料】
将浆料导入料盒，调节刮刀位置，转动钢辊使其均匀涂上一层浆料，再使用手持夹辊转动涂抹钢辊上的浆料；
将固定有铜丝的铜箔固定在涂布立架上，用夹子夹紧；
使用手持夹辊以1mm/s的速度自上而下，均匀地将浆料涂在铜丝 上，使形成的小珠滴处于铜丝根部，便于使用时剪掉不良处。
涂布的长度为15mm～20mm，涂层厚度为8μm～15μm。
【负极极片的制备】
将负极活性材料人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为95:2:2:1溶于溶剂去离子水中，充分搅拌混合均匀后制备成负极浆料；将负极浆料均匀涂覆在负极集流体铜箔自身厚度方向上相对的两个表面，之后经过烘干、冷压、分切，得到负极极片。
【正极极片的制备】
将正极活性材料磷酸铁锂、粘结剂聚偏氟乙烯(PVDF)、导电剂乙炔黑按照质量比为97:2:1溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后制备成正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，之后经过烘干、冷压、分切，得到正极极片。
【三电极电池的制备】
将单面涂正极极片I、隔离膜、参比电极、隔离膜、双面涂负极极片、隔离膜、单面涂正极极片II、按顺序叠好，使隔离膜处于正极极片和参比电极之间、负极极片和参比电极之间起到隔离的作用，然后经叠片工艺得到电极组件；将电极组件置于外包装中，干燥后注入电解液；之后经过化成、静置等工艺，得到三电极电池。
利用高精度设备如电化学工作站，使用5μA～10μA的电流将正极对参比充电至2.6V，将钛酸锂激活。再使用5μA～10μA的电流放出40％～50％的嵌锂容量，保证参比电极的镀锂状态在放电平台中间位置以使得参比电极处于一个稳定的状态。
实施例2
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：浆料的固含量为20wt％。
实施例3
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：浆料的固含量为50wt％。
实施例4
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：浆料的固含量为40wt％。
实施例5
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：浆料中钛酸锂、PVDF、导电碳的质量比为93:3:4。
实施例6
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：浆料中钛酸锂、PVDF、导电碳的质 量比为85:7:8。
实施例7
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：铜箔中只有一个镂空矩形，矩阵的长度不变，宽度为实施例1中两个矩形的宽度之和。
实施例7中涂布后部分铜丝断裂，选用形态良好的铜丝用于制备三电极电池。
实施例8
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：涂层厚度为15μm～20μm。
实施例9
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：涂布速度为0.5mm/s。
实施例10
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：涂布速度为10mm/s。
对比例1
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：涂层厚度为2μm～5μm。
对比例2
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：涂层厚度为55μm～75μm。
对比例3
参比电极的制备、负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：涂布速度为0.1mm/s。
由于涂布速度过慢，覆盖于铜丝表面的浆料明显不均匀。
对比例4
参比电极的制备，区别在于：涂布速度为20mm/s。
由于涂布速度过快，铜丝失去张力变得松弛，浆料在铜丝表面聚成液滴，制得的参比电极几乎无法使用。
对比例5
参比电极的制备与实施例1相同，区别在于：铜箔无镂空矩形。
对比例5中的铜丝与铜箔接触部分无法涂布，因此制得的参比电极几乎无法使用。
对比例6
参比电极的制备与实施例1相同，区别在于：浆料的固含量为5wt％。由于浆料固含量过低，粘度过小，无法进行涂布。
对比例7
参比电极的制备与实施例1相同，区别在于：浆料的固含量为 70wt％。由于浆料固含量过高，粘度过大，涂布时浆料团聚于铜丝表面，制得的参比电极无法使用。
对比例8
负极极片的制备、正极极片的制备与、三电极电池的制备与实施例1相同，区别在于：参比电极为直径40μm～60μm的铜丝镀锂制成，具体镀锂过程为：正极对铜丝参比10μA充电2h，再将负极对铜丝参比10μA充电2h。
将上述实施例1～10和对比例1～5、8中得到的三电极电池进行性能测试。
测试部分
(1)参比电极的优率
将一个实施例或对比例中制备得到的参比电极数量记为n，其中，可用于制备三电极电池且制备得到的三电极电池可进行性能测试的参比电极数量记为m，则参比电极的优率定义为：(m/n)*100％。
(2)电池小倍率充放电测试
电池充放电测试过程如下：使用电化学工作站或者有辅助通道的新威机，电池与设备通道测试线置于哈丁高低温箱中。在25℃下，将三电极电池以0.05C倍率恒流充电至4.2V，搁置5min，再以0.05C放电至2.8V。以正极、负极、全电池三个电极电压为纵坐标，时间或者容量为横坐标，可获得时间-电压曲线图和容量-电压曲线图。
图3为实施例1对应的时间-电压曲线图，图4为对比例8对应的时间-电压曲线图。
(3)参比电极寿命测试
参比电极的寿命测试方法是，使用有辅助通道的5V 1A新威机对电池进行循环充放电测试，将新威机通道测试线和三电极电池放在哈丁高低温箱里面来调控测试温度，辅助通道测试线夹在负极与参比电极的极耳上，监控负极与参比电极之间的电压，若出现曲线突然升高或降低的情况则证明参比电极失效，终止测试。
电池循环充放电测试过程如下：在25℃下，将三电极电池以1C倍率恒流充电至4.2V，再以4.2V恒定电压充电，至电流为0.05C截止，搁置15min后，以1C恒流放电至2.8V，再搁置15min进行充电，按照此过程循环充放电。
图5为实施例1对应的负极与参比电极之间的电压随循环圈数变化的曲线图，图6为对比例8对应的负极与参比电极之间的电压随循环圈数变化的曲线图。
具体制备参数及测试结果见表1。
表1：实施例1～10及对比例1～8的制备参数及测试结果
Figure PCTCN2022124720-appb-000001
根据上述结果可知，实施例1～10的铜丝直径、涂布速度、涂布厚度在本申请方法的范围内，制备得到的参比电极不仅良率较高，寿命也更长。尤其是，钛酸锂、粘结剂、导电剂的质量比以及固含量控制在合适范围 内的实施例，制备的参比电极能够表现出更高的良率、更长的寿命。
而相对于此，对比例1～8制备得到的参比电极寿命短，优率低，不能有效地监控充放电过程中正负极电压变化，其性能未取得有效提高。
此外，由图3和图4也可以看出，与对比例8的参比电极相比，实施例1的参比电极表现出了更稳定的电极电位。
可见，本申请提供的由于制备参比电极的方法、参比电极、用于制备三电极电池的方法、三电极电池能够以实现对电池的长期循环性能的监测。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (11)

  1. 一种用于制备参比电极的方法，包括：
    提供预先去除表面绝缘层的铜丝，
    提供包含钛酸锂的浆料；
    将所述浆料涂布于所述铜丝的表面；
    其中，所述铜丝的直径为40μm～60μm，可选地为44μm～50μm；涂布厚度为5μm～50μm，可选地为7μm～20μm，进一步可选地为8μm～15μm。
  2. 根据权利要求1所述的方法，其中，所述提供预先去除表面绝缘层的铜丝，包括：
    将所述铜丝的两端固定于具有镂空部位的支撑件上，以使所述铜丝部分处于所述镂空部位；
    将所述支撑件部分浸泡于浓硫酸中，以使预设长度的所述铜丝暴露于所述浓硫酸；
    清洗所述铜丝。
  3. 根据权利要求2所述的方法，其中，所述清洗所述铜丝包括：用等离子清洗法处理固定于所述支撑件的所述铜丝。
  4. 根据权利要求2或3所述的方法，其中，所述预设长度为10mm～30mm。
  5. 根据权利要求1-4任一项所述的方法，其中，所述涂布的长度为10mm～30mm。
  6. 根据权利要求1-5任一项所述的方法，其中，所述涂布的速度为0.5mm/s～10mm/s，可选地为1mm/s～5mm/s。
  7. 根据权利要求2-6任一项所述的方法，其中，所述支撑件满足如下至少一者：
    (1)所述支撑件为铜箔，所述铜箔的厚度为20μm～30μm；所述镂空部位为N个矩形，所述矩形的长为20mm～25mm，所述矩形的宽为30mm～45mm，所述N个矩形之间的距离为10mm～15mm，其中，N为≥2的整数；
    (2)所述支撑件由聚四氟乙烯制成，所述支撑件的厚度为2mm～5mm；所述镂空部位为M个矩形，所述矩形的长为20mm～25mm，所述矩形的宽为30mm～45mm，所述M个矩形之间的距离为10mm～15mm，其中，M为≥1的整数。
  8. 根据权利要求2-7任一项所述的方法，其中，所述将所述铜丝的两端固定于具有镂空部位的所述支撑件上，包括：
    将多根所述铜丝以3mm～5mm的间隔距离固定于所述支撑件上，以使所述铜丝部分处于所述镂空部位。
  9. 一种参比电极，包括铜丝以及包覆于所述铜丝表面的钛酸锂层，所述铜丝的直径为40μm～60μm，可选地为44μm～50μm；
    所述钛酸锂层的厚度为5μm～50μm，可选地为7μm～20μm，进一步可选地为8μm～15μm。
  10. 一种三电极电池，包括电极组件，所述电极组件包括根据权利要求1-8任一项的方法制备的参比电极，或者根据权利要求9的参比电极，以及第一正极极片、第二正极极片、负极极片，所述第一正极极片、所述参比电极、所述负极极片以及所述第二正极极片依次间隔排列，所述第一正极极片与所述参比电极之间、所述负极极片与所述参比电极之间、所述负极极片与所述第二正极极片之间分别设置有隔离膜。
  11. 一种用于制备根据权利要求10所述三电极电池的方法，包括：
    组装所述三电极电池，包括将所述电极组件封装、热压后进行抽真空、注入电解液，从而得到组装后的三电极电池；
    激活所述参比电极，包括在对所述组装后的三电极电池搁置、化成后，通过正极以5μA～10μA的电流对所述参比电极充电至预设的截止电压，再以5μA～10μA的电流对所述参比电极放出40％～50％嵌锂容量，以激活所述参比电极。
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