WO2023246796A1 - 负极片、二次电池和用电设备 - Google Patents

负极片、二次电池和用电设备 Download PDF

Info

Publication number
WO2023246796A1
WO2023246796A1 PCT/CN2023/101456 CN2023101456W WO2023246796A1 WO 2023246796 A1 WO2023246796 A1 WO 2023246796A1 CN 2023101456 W CN2023101456 W CN 2023101456W WO 2023246796 A1 WO2023246796 A1 WO 2023246796A1
Authority
WO
WIPO (PCT)
Prior art keywords
negative electrode
electrode sheet
active material
negative
material layer
Prior art date
Application number
PCT/CN2023/101456
Other languages
English (en)
French (fr)
Inventor
郭姿珠
韩晓燕
马永军
潘仪
孙华军
Original Assignee
比亚迪股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 比亚迪股份有限公司 filed Critical 比亚迪股份有限公司
Publication of WO2023246796A1 publication Critical patent/WO2023246796A1/zh

Links

Classifications

    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 disclosure belongs to the field of batteries, and specifically relates to a negative electrode sheet, a secondary battery and electrical equipment.
  • High energy density batteries are inseparable from the development of high energy density anodes.
  • the current method to increase the storage capacity of negative electrode sheets is to add a certain proportion of silicon negative electrode material to the graphite negative electrode, or even use lithium metal negative electrodes. Regardless of whether it is a silicon anode or a lithium metal anode, there is a problem of large volume expansion during cycling. Because most battery usage scenarios require the battery to work in a fixed space, excessive volume expansion will, on the one hand, bring bottleneck problems to the battery PACK process. On the other hand, unguided volume expansion will affect the battery cycle performance. Rapid decay.
  • the battery package volume is fixed, with the charging and discharging process, the battery cell volume expands, causing the battery to bear pressure from the package body. It shows a periodic increase and then decrease.
  • the uneven changes in pressure that the battery core undergoes are not conducive to the good cycle performance of the battery, resulting in rapid cycle decay of the high-capacity negative electrode.
  • the large volume change of high-capacity negative electrodes during the cycle process that is, the volume of the negative electrode sheet expands from a large volume during charging to a large volume shrinkage during discharge.
  • the physical contact between the active particles of the negative electrode sheet will gradually change. Poor, leading to material deactivation.
  • the large volume change of the pole piece also poses a great challenge to the ductility and fatigue resistance of the separator, which will lead to the deterioration of battery performance.
  • the present disclosure aims to solve one of the technical problems in the related art, at least to a certain extent.
  • a The purpose is to propose a negative electrode sheet and its application, which have a low volume change rate during the battery cycle, and at the same time can make good physical contact between the negative electrode active material particles in the negative electrode sheet, thereby ensuring that the negative electrode sheet has a low volume change rate during a single battery cycle.
  • the battery cell size is stable while improving the battery cycle performance.
  • the present disclosure provides a negative electrode sheet.
  • the negative electrode sheet includes:
  • a negative active material layer is provided on the surface of the negative current collector, and the negative active material layer includes a negative active material and a piezoelastic additive;
  • the rebound rate of the negative electrode sheet is 2%-40%, and the compression rate of the negative electrode sheet is 2%-40%; the pressure X satisfies 0.3Mpa ⁇ X ⁇ 5Mpa.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is provided on the surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material and a pressure elastic additive, wherein
  • the piezoelastic additive in the negative active material layer has resilience and compressibility, so that the negative active material layer exhibits piezoelastic properties.
  • the pressure elastic additive in the negative active material layer shrinks in volume under the action of pressure, releasing part of the space for the active material, thus buffering the active material during the lithium insertion process.
  • a large volume expansion is generated, which slows down the large volume expansion rate of the negative active material layer when lithium is intercalated.
  • the volume of the pressure elastic additive rebounds and gradually returns to the initial volume, occupying the volume of the active material. The released space then buffers the volume shrinkage in the negative active material layer caused by delithiation of the active material.
  • the negative active material layer with piezoelastic properties can buffer the large volume changes of the negative electrode sheet during the charge and discharge process.
  • the pressure elastic additive in the negative active material layer can ensure good physical contact between the negative active material particles in the negative active material layer and avoid material deactivation.
  • the negative electrode sheet has volume elastic change and self-recovery functions, so that the negative electrode sheet has a lower volume change rate during the battery cycle, and at the same time, good physical contact between the negative electrode active material particles in the negative electrode sheet can be ensured, thereby ensuring Stability of cell volume during a single battery cycle, while improving battery cycle performance.
  • the negative electrode sheet according to the above embodiments of the present disclosure may also have the following additional technical features:
  • the thickness of a single side of the negative active material layer is 10 ⁇ m-150 ⁇ m. As a result, the cycle stability performance of the battery can be improved.
  • the mass ratio of the negative active material and the pressure elastic additive is 100:3-50. As a result, the volume change rate of the negative electrode sheet during a single electrical cycle can be reduced.
  • the mass ratio of the negative active material and the pressure elastic additive is 100:3-30. As a result, the volume change rate of the negative electrode sheet during a single electrical cycle can be reduced.
  • the negative active material includes graphite, hard carbon, Si, SiOx , silicon carbon material Si/C, Sn, Sb, silicon-based alloy, lithium silicon oxide and silicon magnesium oxide. At least one of, wherein, in addition to Si, the silicon-based alloy also includes at least one of Li, Al, Mg, B, Ni, Fe, Cu and Co, where the value of x is 0 ⁇ x ⁇ 2 .
  • the negative active material layer further includes a binder, the binder includes at least one of polyacrylic acid, sodium alginate, and polyimide; the negative active material and the The mass ratio of the binder is 100:0.05-15.
  • the piezoelastic additive is three-dimensional graphene.
  • the negative electrode sheet can have volume elastic change and self-recovery functions, and the volume change rate of the negative electrode sheet during a single electrical cycle can be reduced.
  • the three-dimensional graphene meets at least one of the following conditions (1)-(5): (1) the particle size of the three-dimensional graphene is 500 nm-20 ⁇ m; (2) the three-dimensional graphene The pore volume of graphene is 1cm 3 /g-10cm 3 /g; (3) the three-dimensional graphene includes overlapping graphene sheets, and the breaking strength between the graphene sheets is 20N/m-50N/m ; (4) The three-dimensional graphene includes overlapping graphene sheets, and the lateral size of the graphene sheets is 10nm-100nm; (5) The average pore size of the three-dimensional graphene is not greater than 250nm.
  • the graphene sheets have a lateral size of 10 nm-20 nm.
  • the negative active material layer further includes a conductive agent.
  • the mass ratio of the negative active material to the conductive agent is 100:0-2.5.
  • the conductive agent includes at least one of single-walled carbon nanotubes and carbon black.
  • the present disclosure provides a secondary battery.
  • the secondary battery includes the above-mentioned negative electrode sheet. Therefore, the secondary battery has excellent cycle stability performance.
  • the present disclosure provides an electrical device having the above-mentioned lithium battery.
  • Figure 1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present disclosure
  • Figure 2 is a diagram of battery cycle performance test results obtained using the lithium-rich negative electrode sheets of Example 2 and Comparative Example 2.
  • the present disclosure provides a negative electrode sheet.
  • the negative electrode sheet The pole piece includes a negative current collector 100 and a negative active material layer 200 .
  • the negative active material layer 200 is provided on the surface of the negative current collector 100, and the negative active material layer 200 includes a negative active material and a piezoelectric additive.
  • the rebound rate of the negative electrode sheet is 2%-40%, and the compression rate of the negative electrode sheet is 2%-40%; the pressure X meets 0.3Mpa ⁇ X ⁇ 5Mpa.
  • the rebound rate of the negative electrode sheet is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.
  • the compression rate of the negative electrode sheet is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 32% , 35%, 38%, 40%, etc.
  • the pressure is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 32% , 35%, 38%, 40%, etc.
  • the pressure is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 32% , 35%, 38%, 40%, etc.
  • the piezoelastic additive in the negative active material layer 200 has resilience and compressibility, so that the negative active material layer 200 exhibits piezoelastic properties.
  • the volume of the negative active material gradually increases, and the thickness of the negative electrode sheet increases.
  • the battery core is subjected to external sources (such as the package body, case, etc.)
  • the pressure of the body increases.
  • the pressure elastic additive in the negative active material layer 200 shrinks in volume under the action of pressure, releasing part of the space for the active material, thereby buffering the active material during the lithium intercalation process. Larger volume expansion.
  • the volume of the negative active material decreases.
  • the external pressure endured by the battery core decreases or even disappears.
  • the volume of the pressure elastic additive rebounds, occupying the space released by the volume contraction of the active material, thereby buffering Volume shrinkage in the negative active material layer 20 due to delithiation of the active material.
  • the volume of the piezoelastic additive in the negative active material layer 200 rebounds during the discharge process, which can ensure good physical contact between the negative active material particles in the negative active material layer and avoid material deactivation.
  • the single-sided thickness of the negative active material layer 200 is 10 ⁇ m-150 ⁇ m, such as 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m, 65 ⁇ m, 70 ⁇ m, 75 ⁇ m. , 80 ⁇ m, 85 ⁇ m, 90 ⁇ m, 95 ⁇ m, 100 ⁇ m, 105 ⁇ m, 110 ⁇ m, 115 ⁇ m, 120 ⁇ m, 125 ⁇ m, 130 ⁇ m, 135 ⁇ m, 140 ⁇ m, 145 ⁇ m, 150 ⁇ m.
  • the coating layer in the negative electrode sheet can be coated on one side of the current collector, or it can be coated on both sides of the current collector, when the coating layer is coated on one side of the current collector, the present disclosure
  • the mass ratio of the negative active material and the pressure elastic additive is 100:3-50, such as 100:5-45, 100:10-40, 100:15-35, 100:20-30 , 100: 25-30.
  • the inventor found that if the amount of binder added is too high, in addition to increasing the cost and reducing the energy density of the battery cell, it will also increase the polarization of the battery and increase the internal resistance of the battery. If the amount of binder added is too low, during the battery cycle, the high-capacity negative active material will pulverize during repeated expansion and contraction, resulting in a sharp decline in cycle performance; if the amount of pressure elastic additive added is too high, the In addition to cost, the energy density of the battery will be reduced.
  • the mass ratio of the negative active material and the pressure elastic additive is 100:3-30.
  • the negative active material includes at least one of graphite, hard carbon, Si, SiOx , silicon carbon material Si/C, Sn, Sb, silicon-based alloy, lithium silicon oxide, and silicon magnesium oxide.
  • the silicon-based alloy also includes at least one of Li, Al, Mg, B, Ni, Fe, Cu and Co, where the value of x is 0 ⁇ x ⁇ 2.
  • the pressure elastic additive is three-dimensional graphene.
  • Three-dimensional graphene has good piezoelastic properties and conductive properties, and can assume part of the role of conductive agent.
  • the three-dimensional graphene is lithiophilic. In highly lithium-rich negative electrode sheets, it guides lithium to be deposited in the pores of the electrode sheet, avoiding the risk of lithium Deposited on the surface of the electrode piece, it reduces the volume expansion of the negative electrode piece caused by lithium deposition.
  • the three-dimensional graphene meets at least one of the following conditions (1)-(5):
  • the particle size of the three-dimensional graphene is 500nm-20 ⁇ m, such as 1 ⁇ m-20 ⁇ m, 3 ⁇ m-18 ⁇ m, 5 ⁇ m-15 ⁇ m, 7 ⁇ m-13 ⁇ m, 10 ⁇ m-12 ⁇ m, etc.;
  • the pore volume of the three-dimensional graphene is 1cm 3 /g-10cm 3 /g, such as 3cm 3 /g-8cm 3 /g, 5cm 3 /g-7cm 3 /g, etc.;
  • the three-dimensional graphene includes overlapping graphene sheets, and the breaking strength between the graphene sheets is 20N/m-50N/m, such as 25N/m-45N/m, 30N/m-45N/m. m, 35N/m-45N/m, 40N/m-45N/m, etc.;
  • the three-dimensional graphene includes overlapping graphene sheets, and the lateral size of the graphene sheets is 10nm-100nm, such as 10nm-20nm, 20nm-100nm, 30nm-90nm, 40nm-80nm, 50nm-70nm ;
  • the average pore diameter of the three-dimensional graphene does not exceed 250nm, such as 10nm, 30nm, 50nm, 80nm, 100nm, 120nm, 150nm, 170nm, 200nm, 220nm, 250nm, etc.
  • the maximum pore diameter of the three-dimensional graphene is 300 nm.
  • the pore volume of the above three-dimensional graphene can be measured by using the nitrogen adsorption method on the three-dimensional graphene.
  • the fracture strength between the above-mentioned graphene sheets can be obtained by using an atomic force microscope (AFM) to conduct nanoindentation testing on the overlap of three-dimensional graphene: fix the three-dimensional graphene on a silicon wafer with small holes on the surface , use a probe to apply pressure to the graphene sheet on the small hole.
  • the position of the pressure should be near the overlap position of two adjacent graphene sheets, and record the force that can cause the overlap of the two graphene sheets to break.
  • the critical pressure is the breaking strength of the overlap between graphene sheets.
  • the above-mentioned lateral size of the graphene sheet refers to the length or width of the graphene sheet, and can be known from an electron microscope photograph of three-dimensional graphene.
  • the above three-dimensional graphene can be grown using plasma chemical vapor deposition (PECVD).
  • PECVD plasma chemical vapor deposition
  • An exemplary preparation method includes the following steps: passing a mixed gas of carbon source (such as C 2 H 2 ) and H 2 into a deposition chamber heated to a certain temperature in the plasma deposition equipment, and turning on the plasma generator to deposit the The three-dimensional graphene material is deposited and grown by the PECVD method on the substrate (such as Cu) placed in the chamber.
  • the auxiliary gas such as Ar, He, etc.
  • the resulting sample is then taken out of the deposition chamber, and the three-dimensional graphene material is peeled off from the substrate and broken into the desired particle size.
  • the particle size of the three-dimensional graphene is 500nm-20 ⁇ m;
  • the pore volume of the three-dimensional graphene is 1cm 3 /g-10cm 3 /g;
  • the three-dimensional graphene includes overlapping graphene sheets, and the breaking strength between the graphene sheets is 20N/m-50N/m;
  • the three-dimensional graphene includes overlapping graphene sheets, and the lateral size of the graphene sheets is 10nm-100nm;
  • the average pore diameter of the three-dimensional graphene does not exceed 250nm.
  • An exemplary preparation method includes the following steps: passing a mixed gas of carbon source (such as C 2 H 2 ) and H 2 into a deposition chamber heated to a certain temperature in the plasma deposition equipment, and turning on the plasma generator to deposit the The three-dimensional graphene material is deposited and grown by the PECVD method on the substrate (such as Cu) placed in the chamber. After the growth of the three-dimensional graphene is completed, the auxiliary gas (such as Ar, He, etc.) is introduced to cool the deposition chamber to At room temperature, the resulting sample is then taken out of the deposition chamber, and the three-dimensional graphene material is peeled off from the substrate and broken into the desired particle size.
  • the PECVD process can generate high energy density and large volume plasma, which can decompose the carbon source C 2 H 2 into more carbon-containing reaction free radicals, thereby achieving the growth of three-dimensional graphene.
  • the inflow flow of C 2 H 2 is 20mL/min
  • the inflow flow of H 2 is 250mL/min
  • the temperature of deposition growth can be 950°C
  • the inflow flow of auxiliary gas Ar is 200mL/min
  • the plasma generator The operating power is 300W.
  • the above-mentioned negative active material layer 200 further includes a conductive agent, and the mass ratio of the negative active material to the conductive agent is 100:0-2.5, such as 100:0.05-2.2, 100:0.1-2, 100: 0.3-1.8, 100:0.5-1.5, 100:0.7-1.2, 100:1-1.2, etc.
  • the conductive agent includes but is not limited to at least one of single-walled carbon nanotubes and carbon black, preferably single-walled carbon nanotubes.
  • the above-mentioned negative active material layer 200 further includes a binder, and the mass ratio of the negative active material and the binder is 100:0.05-15, such as 100:0.1-15, 100:0.2- 15, 100: 0.5-15, 100: 1-15, 100: 3-15, 100: 5-15, 100: 7-15, 100: 10-15, 100: 12-15, etc.
  • the energy density of the cell can be increased while reducing the polarization of the pole pieces.
  • the binder includes but is not limited to at least one of polyacrylic acid, sodium alginate and polyimide.
  • the binder includes polyacrylic acid.
  • r 1 and p may be the same or different, and X 1 and X 2 may be the same or
  • the negative electrode sheet of the present application has volume elastic change and self-recovery functions, so that the negative electrode sheet has a lower volume expansion rate during the battery cycle, and at the same time, good physical contact between the negative electrode active material particles in the negative electrode sheet can be achieved. This ensures the stability of the cell volume during a single battery cycle while improving the battery's cycle performance.
  • the method includes applying a negative electrode slurry including a negative active material and a pressure elastic additive on the negative current collector to form a negative active material layer on the negative current collector to obtain a negative electrode sheet.
  • the above-mentioned negative electrode slurry further includes a conductive agent.
  • the electrical conductivity of the negative electrode sheet can be improved.
  • this method can be used to prepare the above-mentioned negative electrode sheet with volume elastic change and self-recovery function, thereby reducing the volume expansion rate of a single cycle of the battery during the charge and discharge process and improving the battery cycle stability. It should be noted that the features and advantages described above for the negative electrode sheet are also applicable to the method of preparing the negative electrode sheet, and will not be described again here.
  • the present disclosure provides a secondary battery.
  • a secondary battery includes the above-mentioned negative electrode sheet. Therefore, by using the above-mentioned negative electrode sheet with high cycle stability, the secondary battery exhibits high and excellent cycle stability. It should be noted that the features and advantages described above for the negative electrode sheet and its preparation method are also applicable to the secondary battery, and will not be described again here.
  • the present disclosure provides an electrical device.
  • the electrical equipment can be vehicles such as cars and boats, or laptop computers, mobile terminals, etc.
  • the electrical device has the above-mentioned secondary battery. Therefore, by loading the electrical equipment with the above-mentioned secondary battery with excellent cycle stability, the electrical equipment has excellent cruising range and safety performance. It should be noted that the features and advantages described above for the secondary battery are also applicable to the electrical equipment and will not be described again here.
  • Methods for preparing negative electrode sheets include:
  • the silicon carbon negative electrode Si/C with a specific capacity of 1250 mAh/g, polyacrylic acid and three-dimensional graphene at a mass of 100:5:8 to prepare the negative electrode slurry, and then coat the negative electrode slurry on both sides of the copper with a thickness of 8 ⁇ m. on the foil surface (the density of both sides is the same, the density of one side is 45g/m 2 ), and then cured and rolled to form a negative active material layer with a thickness of 32 ⁇ m on both sides of the copper foil to obtain a negative electrode sheet .
  • the three-dimensional graphene used in Example 1 includes overlapping graphene sheets and the three-dimensional graphene has a porous structure.
  • the three-dimensional graphene has an average particle size of 0.6 ⁇ m and a pore volume of 3 cm 3 /g.
  • the three-dimensional graphene is porous.
  • the average pore diameter of the structure is 150nm; through AFM nanoindentation testing, the fracture strength of the joints of overlapping graphene sheets in three-dimensional graphene was measured to be 35N/m, and the overlapping graphene sheets were The lateral size is 10nm-100nm.
  • the method for preparing the negative electrode sheet includes:
  • Example 2 The difference from Example 1 is that SiO Coated on copper foil with a thickness of 8 ⁇ m on the surface (both sides are coated with the same surface density, and the single-sided density is 47.5g/m 2 ), and then cured and rolled to form a negative active material layer with a single-sided thickness of 33 ⁇ m on both sides of the copper foil to obtain a negative electrode sheet .
  • Example 5 The difference from Example 1 is that the three-dimensional graphene used in Example 5 includes overlapping graphene sheets and the three-dimensional graphene has a porous structure.
  • the three-dimensional graphene has an average particle size of 1.5 ⁇ m and a pore volume of 5 cm 3 / g, the average pore diameter of the porous structure in the three-dimensional graphene is 200nm; the nanoindentation test was conducted by AFM, and the fracture strength of the joints of the overlapping graphene sheets in the three-dimensional graphene was measured to be 30N/m, and The lateral size of the overlapping graphene sheets is 10nm-100nm.
  • Example 1 The difference from Example 1 is that the silicon carbon negative electrode Si/C with a specific capacity of 1250 mAh/g, polyacrylic acid and three-dimensional graphene are mixed with a mass of 100:10:47 to prepare a negative electrode slurry, and the negative electrode slurry is coated on one side
  • the areal density was 62.5 g/m 2 and the same areal capacity as in Example 1 was maintained.
  • Example 2 The difference from Example 1 is that the average particle size of the three-dimensional graphene is 12 ⁇ m, the pore volume is 11 cm 3 /g, and the average pore size of the porous structure in the three-dimensional graphene is 150 nm; the nanoindentation test was performed by AFM, and the three-dimensional The breaking strength of the joints between overlapping graphene sheets in graphene is 20N/m.
  • Methods for preparing negative electrode sheets include:
  • the silicon carbon negative electrode Si/C and polyacrylic acid with a gram specific capacity of 1250mAh at a mass of 100:5 to prepare the negative electrode slurry, and then coat the negative electrode slurry on both sides of the copper foil surface with a thickness of 8 ⁇ m (double-sided surface density The same, the single-sided density is 41.5g/m 2 , keeping the same surface capacity as Example 1), and then cured and rolled to form a negative active material layer with a single-sided thickness of 30 ⁇ m on both sides of the copper foil. , get the negative electrode piece.
  • Methods for preparing negative electrode sheets include:
  • Methods for preparing negative electrode sheets include:
  • Example 1 Mix the silicon carbon Si/C negative electrode sheet with a gram specific capacity of 1250mAh, polyacrylic acid and three-dimensional graphene at a mass of 100:5:2.5 to prepare the negative electrode slurry, and then coat the negative electrode slurry on both sides of the copper foil with a thickness of 8 ⁇ m. on the surface (the density of both sides is the same, the density of one side is 42g/m 2 , and the surface capacity is kept the same as in Example 1), and then cured and rolled to form a single-side thickness of 30 ⁇ m on both sides of the copper foil. negative active material layer to obtain a negative electrode sheet.
  • the three-dimensional graphene of Comparative Example 3 is the same as that of Example 1.
  • Preparation of battery for specific capacity test Take the negative electrode sheet, PE separator and 100 micron thick lithium foil prepared in each example and comparative example, use 1 mol/L LiPF 6 as the electrolyte, and the volume ratio of EC to EMC is 1:1, and assemble For the battery, charge and discharge the battery between 0.005-1.5V.
  • Preparation of test cells for recycling NCM811, binder PVDF and conductive agent Sup-P are mixed into a slurry at a mass ratio of 100:3:1, and then coated on the surface of the aluminum foil with a single surface density of 225g/ m2 .
  • Make a positive electrode sheet Then, take the prepared positive electrode sheet, the negative electrode sheet or the lithium-rich negative electrode sheet, and the PE separator obtained in each example and comparative example.
  • the electrolyte uses 1 mol/L LiPF6, and the EC to EMC volume ratio is 1:1, and is assembled into a battery. Test the cycle performance of the corresponding battery.
  • the first charge-discharge specific capacity test of the negative electrode After the battery is discharged to 0.005V at a constant current of 0.1C, then discharged to 0.005V at a constant current of 0.05C, and then charged to 1.5V at a constant current of 0.1C.
  • the test results are shown in Table 1 and Figure 2.
  • Example 1 It can be seen from Table 1 and Figure 2 that the battery cycle performance of Example 1 is significantly better than Comparative Example 1 and Comparative Example 3. The cycle stability of the battery using Example 2 is significantly better than that of Comparative Example 2. Comparing Example 2 with Comparative Example 4, it can be seen that adding too much pressure elastic additive can not improve the specific capacity of the pole piece while reducing it. Battery cycle performance.
  • Table 1 shows that the use of the negative electrode sheet with a small volume expansion rate of the present application can reduce the pressure inside the battery core, thereby significantly improving the battery cycle stability performance.
  • Pole piece rebound performance test method Apply a pressure of X 1 Mpa to the pole piece, measure the thickness H 1 of the pole piece under the pressure of 2 , then the rebound rate of the pole piece is:
  • Pole piece rebound rate r (H 2 -H 1 )/H 1
  • Pole piece compression performance test method Apply a pressure X 2 Mpa to the pole piece with an initial thickness of H 3 , and record the thickness H 4 of the pole piece under the pressure of
  • Pole piece compression ratio p (H 3 -H 4 )/H 3

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

本申请公开了一种负极片、二次电池和用电设备，其中负极片包括负极集流体和负极活性材料层，负极活性材料层设在负极集流体的表面上，负极活性材料层包括负极活性材料和压弹添加剂，在沿所述负极片厚度方向被施加压力X后，所述负极片的回弹率为2％-40％，所述负极片的压缩率为2％-40％；所述压力X满足0.3Mpa≤X≤5Mpa。

Description

负极片、二次电池和用电设备
优先权信息
本公开请求于2022年06月21日向中国国家知识产权局提交的、专利申请号为202210708415.9、公开名称为“负极片及其应用”的中国专利公开的优先权，并且其全部内容通过引用结合在本公开中。
技术领域
本公开属于电池领域，具体涉及一种负极片、二次电池和用电设备。
背景技术
随着市场对更长续航里程电动汽车的需求逐步增加，进一步提高动力电池能量密度的需求也越来越迫切。高能量密度电池离不开高能量密度负极开发。目前提高负极片可储存容量的方法主要是石墨负极中添加一定比例的硅负极材料，甚至采用锂金属负极。不管是硅负极还是锂金属负极，均存在循环过程中较大的体积膨胀的问题。因为大多数电池使用场景均要求电池在固定空间内工作，因此过大的体积膨胀，一方面给电池PACK工艺带来了瓶颈问题，另一方面，不加引导的体积膨胀，会导致电池循环性能快速衰减。高容量负极制作的电池随着电池充电，锂离子进入负极，电池体积膨胀，而在电池放电过程中，随着锂离子从负极迁出，嵌入正极，电池体积逐渐减小。由此可见，在每一次电池充放电循环过程中，电池厚度均会经历一次体积逐渐增大再体积逐渐减小的过程，这个过程对锂金属电池和硅负极电池尤其显著，我们称这个体积周期变化的过程为“电池呼吸作用”。
采用高容量负极制备的电池，在循环过程中，显著的“呼吸作用”，在电池固定包体体积的情况下，随着充电、放电过程，因电芯体积膨胀导致电池承受来自包体的压力呈现周期性的增大再减小。电芯承受压力的不均匀变化，不利于电池良好的循环性能，导致高容量负极循环衰减快。另外，高容量负极在循环过程中较大的体积变化，即负极片体积从充电时较大的体积膨胀，到放电时较大的体积收缩，一方面会导致负极片活性颗粒间物理接触逐渐变差，导致材料失活，另一方面，极片较大的体积变化也是对隔膜的延展性能以及抗疲劳性能提出了极大的挑战，这些都会导致电池性能恶化。
因此，现有的负极片有待改进。
公开内容
本公开旨在至少在一定程度上解决相关技术中的技术问题之一。为此，本公开的一个 目的在于提出一种负极片及其应用，该负极片在电池循环过程中具有较低的体积变化率，同时可以使负极片中负极活性材料颗粒间物理接触良好，进而保证在单次电池循环过程中电芯体积大小的稳定性的同时提高电池的循环性能。
本公开的一个方面，本公开提出了一种负极片，根据本公开的实施例，该负极片包括：
负极集流体；和
负极活性材料层，所述负极活性材料层设在所述负极集流体的表面上，并且所述负极活性材料层包括负极活性材料和压弹添加剂；
其中，在沿所述负极片厚度方向被施加压力X后，所述负极片的回弹率为2％-40％，所述负极片的压缩率为2％-40％；所述压力X满足0.3Mpa≤X≤5Mpa。
根据本公开实施例的负极片，该负极片包括负极集流体和负极活性材料层，负极活性材料层设在负极集流体的表面上，并且负极活性材料层包括负极活性材料和压弹添加剂，其中负极活性材料层中的压弹添加剂具有回弹性和压缩性，从而使得负极活性材料层表现出压弹特性。在充电过程中，随着负极嵌锂，负极活性材料体积逐渐增大，负极活性材料层厚度增大，在固定电池包或电池壳体体积的工况下，电芯承受来自外部(如包体、壳体)的压力增大，此时在压力作用下，负极活性材料层中的压弹添加剂在压力的作用下体积收缩，释放一部分空间给活性材料，从而缓冲了活性材料在嵌锂过程中产生较大的体积膨胀，减缓了负极活性材料层在嵌锂时的较大的体积膨胀率。在放电时，随着锂离子的脱出，负极片中的活性材料体积减小，电芯承受的压力减小甚至消除，该压弹添加剂体积回弹，逐渐恢复至初始体积，占据活性材料体积收缩释放的空间，进而缓冲负极活性材料层中因活性材料脱锂导致的体积收缩，因此具有压弹特性的负极活性材料层可以缓冲负极片在充放电过程中较大体积变化。同时负极活性材料层中的压弹添加剂可以保证负极活性材料层中的负极活性材料颗粒间良好的物理接触，避免材料失活。由此，该负极片具有体积弹性变化和自恢复功能，从而使得该负极片在电池循环过程中具有较低的体积变化率，同时可以使负极片中负极活性材料颗粒间物理接触良好，进而保证在单次电池循环过程中电芯体积大小的稳定性，同时提高电池的循环性能。
另外，根据本公开上述实施例的负极片还可以具有如下附加技术特征：
在本公开的一些实施例中，所述负极活性材料层的单面厚度为10μm-150μm。由此，可以提高电池的循环稳定性能。
在本公开的一些实施例中，所述负极活性材料和压弹添加剂的质量比为100：3-50。由此，可以降低负极片在单次电循环过程中体积变化率。
在本公开的一些实施例中，所述负极活性材料和压弹添加剂的质量比为100：3-30。由此，可以降低负极片在单次电循环过程中体积变化率。
在本公开的一些实施例中，所述负极活性材料包括石墨、硬碳、Si、SiOx、硅碳材料Si/C、Sn、Sb、硅基合金、锂硅氧化物和硅镁氧化物中的至少之一，其中，所述硅基合金除含Si外，还包括Li、Al、Mg、B、Ni、Fe、Cu和Co中的至少一种，其中x取值为0<x<2。根据本公开的实施例，所述负极活性材料层还包括粘结剂，所述粘结剂包括聚丙烯酸、海藻酸钠和聚酰亚胺中的至少之一；所述负极活性材料与所述粘结剂的质量比为100：0.05-15。
在本公开的一些实施例中，所述压弹添加剂为三维石墨烯。由此，可以使负极片具有体积弹性变化和自恢复功能，降低单次电循环过程中使负极片体积变化率。
在本公开的一些实施例中，所述三维石墨烯满足下列(1)-(5)至少之一条件：(1)所述三维石墨烯的粒径为500nm-20μm；(2)所述三维石墨烯的孔体积为1cm3/g-10cm3/g；(3)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片间的断裂强度为20N/m-50N/m；(4)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片的横向尺寸为10nm-100nm；(5)所述三维石墨烯的平均孔径不大于250nm。
在本公开的一些实施例中，所述石墨烯片的横向尺寸为10nm-20nm。
在本公开的一些实施例中，所述负极活性材料层进一步包括导电剂。
在本公开的一些实施例中，所述负极活性材料与所述导电剂的质量比为100:0-2.5。
在本公开的一些实施例中，所述导电剂包括单壁碳纳米管和炭黑中的至少之一。
本公开的第二个方面，本公开提供了一种二次电池。所述二次电池包括上述负极片。由此，该二次电池具有优异的循环稳定性能。
本公开的第三个方面，本公开提供了一种用电设备，所述用电设备具有上述所述的锂电池。
本公开实施例的优点将会在下面的说明书中部分阐明，一部分根据说明书是显而易见的，或者可以通过本公开实施例的实施而获知。
附图说明
附图是用来提供对本公开的进一步理解，并且构成说明书的一部分，与下面的具体实施方式一起用于解释本公开，但并不构成对本公开的限制。在附图中：
图1是根据本公开一个实施例的负极片的结构示意图；
图2是采用实施例2与对比例2的富锂负极片得到的电池循环性能测试结果图。
具体实施方式
下面详细描述本公开的实施例，旨在用于解释本公开，而不能理解为对本公开的限制。
本公开的一个方面，本公开提出了一种负极片，根据本公开的实施例，参考图1，该负 极片包括负极集流体100和负极活性材料层200。
需要说明的是，本领域技术人员可以根据实际需要对负极集流体100的材质进行选择，例如采用铜箔。
根据本公开的实施例，负极活性材料层200设在负极集流体100的表面上，并且负极活性材料层200包括负极活性材料和压弹添加剂。在沿所述负极片厚度方向被施加压力X后，所述负极片的回弹率为2％-40％，所述负极片的压缩率为2％-40％；所述压力X满足0.3Mpa≤X≤5Mpa。例如，所述负极片的回弹率为5％，8％，10％，12％，15％，18％，20％，23％，25％，28％，30％，32％，35％，38％，40％等；所述负极片的压缩率为5％，8％，10％，12％，15％，18％，20％，23％，25％，28％，30％，32％，35％，38％，40％等；所述压力X满足0.3Mpa，0.5Mpa，0.8Mpa，1Mpa，1.5Mpa，2Mpa，2.5Mpa，3Mpa，3.5Mpa，4Mpa，4.5Mpa，5Mpa等。
发明人发现，负极活性材料层200中的压弹添加剂具有回弹性和压缩性，从而使得负极活性材料层200表现出压弹特性。在充电过程中，随着负极嵌锂，负极活性材料体积逐渐增大，负极片厚度增大，在固定电池包或电池壳体体积的工况下，电芯承受来自外部(如包体、壳体)的压力增大，此时在压力作用下，负极活性材料层200中的压弹添加剂在压力的作用下体积收缩，释放一部分空间给活性材料，从而缓冲了活性材料在嵌锂过程中产生较大的体积膨胀。在放电时，随着锂离子的脱出，负极活性材料体积减小，此时电芯承受的外部压力减小甚至消失，该压弹添加剂体积回弹，占据活性材料体积收缩释放的空间，进而缓冲负极活性材料层20中因活性材料脱锂导致的体积收缩。同时负极活性材料层200中的压弹添加剂在放电过程中体积回弹，可以保证负极活性材料层中的负极活性材料颗粒间良好的物理接触，避免材料失活。
本公开一些实施方式中，上述负极活性材料层200的单面厚度为10μm-150μm，例如10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、55μm、60μm、65μm、70μm、75μm、80μm、85μm、90μm、95μm、100μm、105μm、110μm、115μm、120μm、125μm、130μm、135μm、140μm、145μm、150μm。
由于负极片中的涂覆层可以是涂覆在集流体中的单面，也可以是涂覆在集流体的两面，因此，当涂覆层涂覆在集流体中的单面时，本公开中的“单面厚度”是指涂覆面的负极活性材料层200的厚度；当涂覆层涂覆在集流体中的两面时，本公开中的“单面厚度”是指两侧中任意一侧涂覆层中的负极活性材料层200的厚度。
在本公开的一些实施方式中，负极活性材料和压弹添加剂的质量比为100：3-50，例如100：5-45，100：10-40，100：15-35，100：20-30，100：25-30。发明人发现；若粘结剂添加量过高，则除了增加成本，降低电芯能量密度外，还会增大电池极化，增大电池内阻， 若粘结剂添加量过低，则在电池循环过程中，高容量负极活性材料在反复膨胀收缩过程中，极片粉化，导致循环性能急剧下降；若压弹添加剂添加量过高，则增加成本外，会降低电池能量密度，若压弹添加剂添加量过低，则无法实现极片良好的压缩回弹性能。由此，在负极活性材料层200中加入上述比例的压弹添加剂，可以在降低成本的同时提高电池循环稳定性。在本公开的一些实施方式中，负极活性材料和压弹添加剂的质量比为100：3～30。
在本公开的一些实施方式中，负极活性材料包括石墨、硬碳、Si、SiOx、硅碳材料Si/C、Sn、Sb、硅基合金、锂硅氧化物和硅镁氧化物中的至少之一，其中，所述硅基合金除含Si外，还包括Li、Al、Mg、B、Ni、Fe、Cu和Co中的至少一种，其中x取值为0<x<2。
本公开一些实施方式中，压弹添加剂为三维石墨烯。三维石墨烯具有较好的压弹性能和导电性能，可以承担部分导电剂作用，同时该三维石墨烯具有亲锂性，在高富锂负极片中，引导锂沉积在极片孔隙中，避免了锂沉积在极片表面，减小了锂沉积时带来的负极片体积膨胀。
本公开一些实施方式中，该三维石墨烯满足下列(1)-(5)至少之一条件：
(1)所述三维石墨烯的粒径为500nm-20μm，例如1μm-20μm，3μm-18μm，5μm-15μm，7μm-13μm，10μm-12μm等；
(2)所述三维石墨烯的孔体积为1cm3/g-10cm3/g，例如3cm3/g-8cm3/g，5cm3/g-7cm3/g等；
(3)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片间的断裂强度为20N/m-50N/m，例如25N/m-45N/m，30N/m-45N/m，35N/m-45N/m，40N/m-45N/m等；
(4)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片的横向尺寸为10nm-100nm，例如10nm-20nm，20nm-100nm，30nm-90nm，40nm-80nm，50nm-70nm；
(5)所述三维石墨烯的平均孔径不超过250nm，例如10nm，30nm，50nm，80nm，100nm，120nm，150nm，170nm，200nm，220nm，250nm等。
本公开一些实施方式中，所述三维石墨烯最大孔径为300nm。
上述三维石墨烯的孔体积可以通过对三维石墨烯采用氮吸附法测得。上述石墨烯片间的断裂强度可通过对三维石墨烯采用原子力显微镜(Atomic Force Microscope，AFM)对搭接处进行纳米压痕测试得到：将三维石墨烯固定在表面开设有小孔的硅片上，用探针对小孔上的石墨烯片施加一个压力，施加压力的位置应在相邻两石墨烯片材的搭接位置附近，记录能使两个石墨烯片材的搭接处断裂的临界压力，即获得石墨烯片间搭接处的断裂强度。上述石墨烯片的横向尺寸是指石墨烯片材的长度或宽度等，可通过三维石墨烯的电子显微镜照片获知。
具体的，足量的孔体积，可以保证三维石墨烯具有优良的压缩性能，适宜的孔径大小 以及石墨烯片间的断裂强度，则保证三维石墨烯在压缩后具有良好的回弹性能，不会因压力导致结构坍塌，失去回弹性能。同时在电池循环过程中，稳定保持其压缩-回弹性能。具备以上特性的三维石墨烯，具有优异的压缩-回弹性能，从而使得制备得到的负极活性材料层200表现出较高的压弹特性，进而可以缓冲负极片在充放电过程中较大体积膨胀。
本公开一些实施方式中，上述三维石墨烯可以采用等离子体化学气相沉积法(PECVD)生长得到。示例性的制备方法包括以下步骤：将碳源(如C2H2)和H2的混合气体通入到等离子沉积设备中加热至一定温度的沉积室中，开启等离子体发生器，以在沉积室中放置的基底(如Cu)上通过PECVD法沉积生长三维石墨烯材料，待三维石墨烯的生长结束后，通入辅助气体(如Ar、He等)以在惰性气氛下使沉积室冷却至室温，之后将所得样品从沉积室取出，并从基底上将三维石墨烯材料剥离下来，并将其破碎至所需的粒径。通过调整生长条件，可以获得满足以下(1)-(5)至少之一条件的石墨烯：
(1)所述三维石墨烯的粒径为500nm-20μm；
(2)所述三维石墨烯的孔体积为1cm3/g-10cm3/g；
(3)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片间的断裂强度为20N/m-50N/m；
(4)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片的横向尺寸为10nm-100nm；
(5)所述三维石墨烯的平均孔径不超过250nm。
示例性的制备方法包括以下步骤：将碳源(如C2H2)和H2的混合气体通入到等离子沉积设备中加热至一定温度的沉积室中，开启等离子体发生器，以在沉积室中放置的基底(如Cu)上通过PECVD法沉积生长三维石墨烯材料，待三维石墨烯的生长结束后，通入辅助气体(如Ar、He等)以在惰性气氛下使沉积室冷却至室温，之后将所得样品从沉积室取出，并从基底上将三维石墨烯材料剥离下来，并将其破碎至所需的粒径。PECVD过程中可产生高能量密度和较大体积的等离子体，可将碳源C2H2分解成较多的含碳反应自由基，进而实现三维石墨烯的生长。其中，C2H2的通入流量为20mL/min，H2的通入流量为250mL/min，沉积生长的温度可以是950℃，辅助气体Ar的通入流量为200mL/min，等离子发生器的工作功率为300W。
根据本公开的实施例，上述负极活性材料层200还包括导电剂，并且负极活性材料与导电剂的质量比为100:0-2.5，例如100:0.05-2.2，100:0.1-2，100:0.3-1.8，100:0.5-1.5，100:0.7-1.2，100:1-1.2等。由此，可以提高负极片的导电性能。需要说明的是，本领域技术人员可以根据实际需要对导电剂的具体类型进行选择，例如导电剂包括但不限于单壁碳纳米管和炭黑中的至少之一，优选单壁碳纳米管。
在本公开的一些实施方式中，上述负极活性材料层200还包括粘结剂，并且负极活性材料和粘结剂的质量比为100：0.05-15，例如100：0.1-15，100：0.2-15，100：0.5-15，100：1-15，100：3-15，100：5-15，100：7-15，100：10-15，100：12-15等。由此，可以在降低极片极化的同时提高电芯能量密度。
需要说明的是，本领域技术人员可以根据实际需要对粘结剂的具体类型进行选择，例如粘结剂包括但不限于聚丙烯酸、海藻酸钠和聚酰亚胺中的至少之一。在本公开的一些实施方式中，粘结剂包括聚丙烯酸。
本公开中，负极片的回弹性能和压缩性能的测试方法如下：沿负极片的厚度方向对负极片施加一个值为X1Mpa的压力，测定负极片在X1Mpa压力下的厚度为H1；然后撤掉该压力，待负极片的厚度稳定后，再测定负极片的厚度，记作H2，则该负极片的厚度回弹率r1＝(H2-H1)/H1。沿负极片的厚度方向对初始厚度为H3的负极片施加一个值为X2Mpa的压力，测定负极片在X2Mpa压力下的厚度，记作H4，则该负极片的厚度压缩率p＝(H3-H4)/H3。因此，上述“在沿所述负极片厚度方向被施加压力X后，所述负极片的回弹率为2％-40％，所述负极片的压缩率为2％-40％；所述压力X满足0.3Mpa≤X≤5Mpa”可以理解为：沿负极片的厚度方向对负极片施加0.3Mpa≤X1≤5Mpa的压力X1，测定负极片在该压力X1下的厚度为H1；然后撤掉该压力，待负极片的厚度稳定后，再测定负极片的厚度，记作H2，则负极片的厚度回弹率r1＝(H2-H1)/H1，r1在2％-40％的范围内；沿负极片的厚度方向对初始厚度为H3的负极片施加0.3≤X2≤5Mpa的压力X2，测定负极片在该压力X2下的厚度，记作H4，则该负极片的厚度压缩率p＝(H3-H4)/H3，p在2％-40％的范围内。r1和p可以相同也可以不同，X1和X2可以相同也可以不同。
由此，本申请的负极片具有体积弹性变化和自恢复功能，从而使得该负极片在电池循环过程中具有较低的体积膨胀率，同时可以使负极片中负极活性材料颗粒间物理接触良好，进而保证在单次电池循环过程中电芯体积大小的稳定性的同时提高电池的循环性能。
为了方便理解，下面对制备上述负极片的方法进行描述。根据本公开的实施例，该方法包括：在负极集流体上施加包括负极活性材料和压弹添加剂的负极浆料，以便在所述负极集流体上形成负极活性物质层，得到负极片。
根据本公开的实施例，上述负极浆料中还包括导电剂。由此，可以提高负极片的导电性能。
由此，采用该方法可以制备得到上述具有体积弹性变化和自恢复功能的负极片，从而可以减小电池在充放电过程中单次循环产生的体积膨胀率，提高电池循环稳定性。需要说明的是，上述针对负极片所描述的特征和优点同样适用于该制备负极片的方法，此处不再赘述。
本公开的第二个方面，本公开提供了一种二次电池。根据本公开的实施例，二次电池包括上述负极片。由此，由此，该二次电池通过采用上述具有高循环稳定性的负极片，使得该二次电池表现出较高优异的循环稳定性。需要说明的是，上述针对负极片及其制备方法所描述的特征和优点同样适用于该二次电池，此处不再赘述。
本公开的第三个方面，本公开提供了一种用电设备。该用电设备可以是车、船等交通工具，也可以是笔记本电脑、移动终端等。根据本公开的实施例，所述用电设备具有上述所述的二次电池。由此，该用电设备通过装载上述具有优异循环稳定性的二次电池，使得用电设备具有优异的续航里程和安全性能。需要说明的是，上述针对二次电池所描述的特征和优点同样适用于该用电设备，此处不再赘述。
下面参考具体实施例，对本公开进行描述，需要说明的是，这些实施例仅仅是描述性的，而不以任何方式限制本公开。
实施例1
制备负极片的方法包括：
将克比容量1250mAh/g的硅碳负极Si/C、聚丙烯酸与三维石墨烯按照质量为100：5：8混合配置负极浆料，然后将负极浆料双面涂布在厚度为8μm的铜箔表面上(双面面密度相同，单面面密度为45g/m2)，然后经固化后辊压，以便在铜箔两面上分别形成单面厚度为32μm的负极活性材料层，得到负极片。
实施例1所用三维石墨烯包括相互搭接的石墨烯片材且三维石墨烯具有多孔结构，该三维石墨烯的平均粒径为0.6μm，孔体积为3cm3/g，该三维石墨烯中多孔结构的平均孔径为150nm；经AFM进行纳米压痕测试，测得三维石墨烯中相互搭接在一起的石墨烯片材连接处的断裂强度为35N/m，并且相互搭接的石墨烯片的横向尺寸为10nm-100nm。
实施例2
与实施例1不同的是，制备负极片的方法包括：
将SiOx(x＝1.02)、聚丙烯酸、单壁碳纳米管与三维石墨烯按照质量为100：14：0.5：15混合配置负极浆料，然后将负极浆料双面涂布在厚度为8μm的铜箔表面上(两面涂布面密度相同，单面密度为40g/m2)，然后经固化后辊压，以便在铜箔两面上分别形成单面厚度为28μm的负极活性材料层，得到负极片，最后在惰性气氛中，将10微米厚的锂薄膜与所得负极片热压，获得富锂负极片。
实施例3
与实施例1不同的是：将SiOx(x＝1.02)、聚丙烯酸、单壁碳纳米管与三维石墨烯按照质量为100：14：0.5：15混合配置负极浆料，然后将负极浆料涂布在厚度为8μm的铜箔 表面上(两面涂布面密度相同，单面密度为47.5g/m2)，然后经固化后辊压，以便在铜箔两面上分别形成单面厚度为33μm的负极活性材料层，得到负极片。
实施例4
与实施例1不同的是：将石墨、SiOx(x＝1.02)、聚丙烯酸、单壁碳纳米管与三维石墨烯按照质量为70：30：7：0.2：5混合配置负极浆料，然后将负极浆料涂布在厚度为8μm的铜箔表面上(两面涂布面密度相同，单面面密度为87g/m2)，然后经固化后辊压，以便在铜箔两面上分别形成单面厚度为54μm的负极活性材料层，得到负极片。
实施例5
与实施例1不同的是：实施例5所用三维石墨烯包括相互搭接的石墨烯片材且三维石墨烯具有多孔结构，该三维石墨烯的平均粒径为1.5μm，孔体积为5cm3/g，该三维石墨烯中多孔结构的平均孔径为200nm；经AFM进行纳米压痕测试，测得三维石墨烯中相互搭接在一起的石墨烯片材连接处的断裂强度为30N/m，并且相互搭接的石墨烯片的横向尺寸为10nm-100nm。
实施例6
与实施例1不同的是：将克比容量1250mAh/g的硅碳负极Si/C、聚丙烯酸与三维石墨烯按照质量为100：10：47混合配置负极浆料，负极浆料涂布单面面密度为62.5g/m2，保持与实施例1相同的面容量。
实施例7
与实施例1的区别在于，三维石墨烯的平均粒径为12μm，孔体积为11cm3/g，该三维石墨烯中多孔结构的平均孔径为150nm；经AFM进行纳米压痕测试，测得三维石墨烯中相互搭接在一起的石墨烯片材连接处的断裂强度为20N/m。
对比例1
制备负极片的方法包括：
将克比容量1250mAh的硅碳负极Si/C、聚丙烯酸按照质量为100：5混合配置负极浆料，然后将负极浆料双面涂布在厚度为8μm的铜箔表面上(双面面密度相同，单面面密度为41.5g/m2，保持与实施例1的面容量相同)，然后经固化后辊压，以便在铜箔双面上分别形成单面厚度为30μm的负极活性材料层，得到负极片。
对比例2
制备负极片的方法包括：
将SiOx(x＝1.02)、聚丙烯酸、单壁碳纳米管按照质量为100：14：0.5混合配置负极浆料，然后将负极浆料双面涂布在厚度为8μm的铜箔表面上(双面面密度相同，单面面密度为35.4g/m2，保持与实施例2的面容量相同)，然后经固化后辊压，以便在铜箔双面上分 别形成单面厚度为25μm的负极活性材料层，得到负极片，最后在惰性气氛中，将10微米厚的锂薄膜与所得负极片热压，获得富锂负极片。
对比例3
制备负极片的方法包括：
将克比容量1250mAh的硅碳Si/C负极片、聚丙烯酸和三维石墨烯按照质量为100：5:2.5混合配置负极浆料，然后将负极浆料双面涂布在厚度为8μm的铜箔表面上(双面面密度相同，单面面密度为42g/m2，保持面容量与实施例1相同)，然后经固化后辊压，以便在铜箔两面上分别形成单面厚度为30μm的负极活性材料层，得到负极片。对比例3的三维石墨烯与实施例1相同。
对比例4
对比例4与实施例2不同的是，将SiOx(x＝1.02)、聚丙烯酸、单壁碳纳米管与三维石墨烯按照质量为100：14：0.5：55混合配置负极浆料。
比容量测试用电池制备：取各实施例和对比例制备的负极片、PE隔膜与100微米厚的锂箔，电解液采用1mol/L的LiPF6，EC与EMC体积比为1:1，组装为电池，将电池在0.005-1.5V之间充放电。
循环用测试电池制备：将NCM811与粘结剂PVDF和导电剂Sup-P按照100:3:1质量比混合制浆，按照在铝箔表面按照单面面密度为225g/m2的进行涂布，制成正极片。然后取制备的正极片分别与各实施例和对比例得到的负极片或富锂负极片、PE隔膜，电解液采用1mol/L的LiPF6，EC与EMC体积比为1:1，组装为电池，测试对应电池的循环性能。
负极首次充放电比容量测试：将电池在0.1C恒流放电至0.005V后，再以0.05C恒流放电至0.005V，然后以0.1C充电至1.5V。负极首次放电比容量＝放电容量/负极活性材料层总质量；负极首次充电比容量＝充电容量/负极活性材料层总质量；
容量保持率测试：在0.5C下首先恒定电流充电至4.25V，然后在4.25V下恒定电压充电至截止电流为0.1C，然后1C放电至2.5V，如此循环300次，记录首次放电容量和循环300次后的放电容量，容量保持率＝循环300次后的放电容量/首次放电容量。测试结果如表1和图2所示。
表1

由表1和图2可以看出，实施例1的电池循环性能性能显著优于对比例1和对比例3。采用实施例2的电池循环稳定性明显优于对比例2，实施例2与对比例4相比，可以看出，加入过多的压弹添加剂，在降低极片比容量的同时，并不能提升电池的循环性能。表1数据表明采用本申请的具有体积膨胀率小的负极片，可以减缓电芯内部所承受的压力，从而显著改善电池循环稳定性能。
将上述经过首次充放电比容量测试后的全电池拆解，取各实施例或对比例对应的全电池拆解获得的负极片分别进行极片回弹性能和压缩性能的测试，结果汇总在下表2-3中。
极片回弹性能测试方法：对极片施加X1Mpa的压力，测定在X1Mpa压力下极片厚度H1，然后撤掉压力，待极片厚度稳定后，再测定极片的厚度H2，则极片的回弹率为：
极片回弹率r＝(H2-H1)/H1
极片压缩性能测试方法：对初始厚度为H3的极片施加一个压力X2Mpa，记录X2Mpa压力下极片的厚度H4，则极片的压缩率为：
极片压缩率p＝(H3-H4)/H3
表2回弹性能和压缩性能测试结果(X1＝0.5Mpa，X2＝0.3Mpa)

表3回弹性能和压缩性能测试结果(X1＝5Mpa，X2＝5Mpa)
结合表1-表3可以看出，实施例1-6的负极片，具有较高的回弹性能和压缩性能，同时通过实施例2与对比例2的数据可以看出，加入等量的三维石墨烯和常规导电剂后，加入常规导电剂的对比例2的极片压缩回弹性能较差，与常规极片性能一样，其组装的电池循环300次后容量保持率明显低于实施例1-6。通过对比例4可知，虽然加入一定量的三维石墨烯然而极片回弹率和压缩率不在2％-40％范围内时，其循环性能相比于实施例也会一定程度上降低。
以上所述实施例仅表达了本公开的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本公开专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本公开构思的前提下，还可以做出若干变形和改进，这些都属于本公开的保护范围。因此，本公开专利的保护范围应以所附权利要求为准。

Claims (12)

  1. 一种负极片，其中，包括：
    负极集流体；
    负极活性材料层，所述负极活性材料层设在所述负极集流体的表面上，所述负极活性材料层包括负极活性材料和压弹添加剂；
    其中，在沿所述负极片厚度方向被施加压力X后，所述负极片的回弹率为2％-40％，所述负极片的压缩率为2％-40％；所述压力X满足0.3Mpa≤X≤5Mpa。
  2. 根据权利要求1所述的负极片，其中，所述负极活性材料层单面的厚度为10μm-150μm。
  3. 根据权利要求1或2所述的负极片，其中，所述负极活性材料和所述压弹添加剂的质量比为100：3-50。
  4. 根据权利要求1-3中任意一项所述的负极片，其中，所述负极活性材料和压弹添加剂的质量比为100：3-30。
  5. 根据权利要求1-4中任意一项所述的负极片，其中，所述负极活性材料包括石墨、硬碳、Si、SiOx、硅碳材料、Sn、Sb、硅基合金、锂硅氧化物和硅镁氧化物中的至少之一；其中，所述硅基合金除含Si外，还包括Li、Al、Mg、B、Ni、Fe、Cu和Co中的至少一种，其中x取值为0<x<2。
  6. 根据权利要求1-5中任意一项所述的负极片，其中，所述负极活性材料层还包括粘结剂，所述粘结剂包括聚丙烯酸、海藻酸钠和聚酰亚胺中的至少之一；所述负极活性材料与所述粘结剂的质量比为100：0.05-15。
  7. 根据权利要求1-6中任意一项所述的负极片，其中，所述压弹添加剂为三维石墨烯。
  8. 根据权利要求1-7中任意一项所述的负极片，其中，所述三维石墨烯满足下列(1)-(5)至少之一条件：
    (1)所述三维石墨烯的粒径为500nm-20μm；
    (2)所述三维石墨烯的孔体积为1cm3/g-10cm3/g；
    (3)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片间的断裂强度为20N/m-50N/m；
    (4)所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片的横向尺寸为10nm-100nm，优选为10nm-20nm；
    (5)所述三维石墨烯的平均孔径不大于250nm。
  9. 根据权利要求1-8中任意一项所述的负极片，其中，所述三维石墨烯包括相互搭接的石墨烯片，所述石墨烯片的横向尺寸为10nm-20nm。
  10. 根据权利要求1-9中任意一项所述的负极片，其中，所述负极活性材料层进一步包括导电剂，所述导电剂包括单壁碳纳米管和炭黑中的至少之一；所述负极活性材料与所述导电剂的质量比为100:0-2.5。
  11. 一种二次电池，其中，所述二次电池包括权利要求1-10中任一项所述的负极片。
  12. 一种用电设备，其中，所述用电设备具有权利要求11所述的二次电池。
PCT/CN2023/101456 2022-06-21 2023-06-20 负极片、二次电池和用电设备 WO2023246796A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202210708415.9A CN117317225A (zh) 2022-06-21 2022-06-21 负极片及其应用
CN202210708415.9 2022-06-21

Publications (1)

Publication Number Publication Date
WO2023246796A1 true WO2023246796A1 (zh) 2023-12-28

Family

ID=89279908

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2023/101456 WO2023246796A1 (zh) 2022-06-21 2023-06-20 负极片、二次电池和用电设备

Country Status (2)

Country Link
CN (1) CN117317225A (zh)
WO (1) WO2023246796A1 (zh)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170283265A1 (en) * 2014-08-29 2017-10-05 Nec Corporation Carbon material, anode material and spacer additive for lithium ion battery
CN109065850A (zh) * 2018-06-29 2018-12-21 南京工业大学 一种三维石墨烯硅碳负极复合材料及其制备方法
CN111710874A (zh) * 2020-08-19 2020-09-25 广州纳诺新材料科技有限公司 一种固态锂电池、复合负极及其制备方法
CN112103469A (zh) * 2020-09-22 2020-12-18 傲普(上海)新能源有限公司 一种硅碳负极极片及其制备方法和锂离子电池
CN114628652A (zh) * 2021-12-07 2022-06-14 万向一二三股份公司 一种长循环快充SiO石墨复合负极材料及其制备方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170283265A1 (en) * 2014-08-29 2017-10-05 Nec Corporation Carbon material, anode material and spacer additive for lithium ion battery
CN109065850A (zh) * 2018-06-29 2018-12-21 南京工业大学 一种三维石墨烯硅碳负极复合材料及其制备方法
CN111710874A (zh) * 2020-08-19 2020-09-25 广州纳诺新材料科技有限公司 一种固态锂电池、复合负极及其制备方法
CN112103469A (zh) * 2020-09-22 2020-12-18 傲普(上海)新能源有限公司 一种硅碳负极极片及其制备方法和锂离子电池
CN114628652A (zh) * 2021-12-07 2022-06-14 万向一二三股份公司 一种长循环快充SiO石墨复合负极材料及其制备方法

Also Published As

Publication number Publication date
CN117317225A (zh) 2023-12-29

Similar Documents

Publication Publication Date Title
WO2022012477A1 (zh) 一种掺硅负极极片及包括该负极极片的锂离子电池
WO2021223655A1 (zh) 一种正极片、制备方法及包含其的锂离子电池
US10038182B2 (en) Graphene coating modified electrode plate for lithium secondary battery and method for producing the same
Uchida et al. Electrochemical properties of non-nano-silicon negative electrodes prepared with a polyimide binder
CN111916668B (zh) 一种负极片及其制备方法和包含该负极片的锂离子电池
CN111969214A (zh) 一种异型结构的正极片及包括该正极片的锂离子电池
WO2020098769A1 (zh) 一种正极极片及电化学装置
WO2022037092A1 (zh) 一种集流体、极片和电池
WO2022267534A1 (zh) 锂金属负极极片、电化学装置及电子设备
WO2022100661A1 (zh) 一种负极片及其应用
WO2014032406A1 (zh) 一种硅碳复合负极材料及其制备方法和锂离子电池
WO2021223654A1 (zh) 一种正极片、制备方法及包含其的锂离子电池
WO2021233387A1 (zh) 一种高负载电极、制备方法及其锂离子电池
CN112002883A (zh) 一种负极活性物质用硅基复合材料及负极片和锂离子电池
WO2021258900A1 (zh) 正极片及电池
JP7313362B2 (ja) バインダ分布が最適化した二次電池用負極及びこれを含む二次電池
WO2022199505A1 (zh) 一种负极及其制备方法和应用
WO2023083147A1 (zh) 一种负极活性材料及含有该负极活性材料的负极片和锂离子电池
CN113193161B (zh) 一种电极组件及电化学装置
WO2023108963A1 (zh) 一种锂离子电池
WO2022257728A1 (zh) 一种隔膜以及包括该隔膜的锂离子电池
CN115885418A (zh) 具有含碳涂层的电化学电池和电极及其制造方法
CN109428051A (zh) 锂离子电池及其正极片
CN114068857A (zh) 一种电极片的制备方法及其应用
WO2024087842A1 (zh) 二次电池及用电设备

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23826443

Country of ref document: EP

Kind code of ref document: A1