WO2024040858A1 - 负极极片、二次电池及用电设备 - Google Patents

负极极片、二次电池及用电设备 Download PDF

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WO2024040858A1
WO2024040858A1 PCT/CN2023/071003 CN2023071003W WO2024040858A1 WO 2024040858 A1 WO2024040858 A1 WO 2024040858A1 CN 2023071003 W CN2023071003 W CN 2023071003W WO 2024040858 A1 WO2024040858 A1 WO 2024040858A1
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negative electrode
active material
active layer
negative
electrode sheet
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French (fr)
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居小康
胡梦
张耀
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Sunwoda Mobility Energy Technology Co Ltd
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Sunwoda Mobility Energy 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/626—Metals
    • 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 invention relates to the field of energy storage technology, and in particular, to a negative electrode plate, a secondary battery and electrical equipment.
  • the present invention aims to solve at least one of the technical problems existing in the prior art.
  • the first aspect of the present invention proposes a negative electrode plate that can effectively improve the first-cycle Coulombic efficiency and capacity.
  • a second aspect of the invention also provides a secondary battery.
  • a third aspect of the present invention also provides an electrical device.
  • a first embodiment of the present invention provides a negative electrode sheet.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector.
  • the negative electrode active layer includes a first active layer. and a second active layer; the first active layer is located between the second active layer and the negative electrode current collector;
  • the first active layer includes a first negative active material, and the second active layer includes a second negative active material;
  • the (002) crystal plane layer spacing d1 of the first negative electrode active material is greater than the (002) crystal plane layer spacing d2 of the second negative electrode active material.
  • the present invention enables the negative electrode sheet to improve the Coulombic efficiency of the first cycle of the sodium ion battery. and maintain high battery capacity. This is because the function of the first active layer is to provide more sodium storage capacity and increase the capacity; the function of the second active layer is to reduce side reactions with the electrolyte, thereby improving the first-cycle Coulombic efficiency.
  • the (002) crystal plane layer spacing d1 of the first negative electrode active material and the (002) crystal plane layer spacing d2 of the second negative electrode active material satisfy: d1/d2 ⁇ 1.2.
  • the first active layer and the second active layer have better compatibility. If the difference between the layer spacing is too large, the stress change will be greatly different during the charge and discharge process (the layer spacing will affect the volume expansion when sodium ions are embedded, and the layer spacing will affect the volume expansion when sodium ions are embedded. If the spacing difference is too large, the volume expansion gap will be very large), resulting in poor compatibility between the two, and the second active layer will easily peel off.
  • the (002) crystal plane layer spacing d1 of the first negative active material satisfies According to some embodiments of the present invention, the (002) crystal plane layer spacing d1 of the first negative active material is Or within the range consisting of any two of the above values.
  • the (002) crystal plane spacing d2 of the second negative active material satisfies According to some embodiments of the present invention, the (002) crystal plane layer spacing d2 of the second negative active material is Or within the range consisting of any two of the above values.
  • the interlayer spacing is characterized by transmission electron microscopy.
  • the first negative active material and the second negative active material each independently include heteroatoms, and the heteroatoms include at least two of nitrogen, oxygen, sulfur, or boron.
  • the heteroatom content in the first negative active material is greater than the heteroatom content in the second negative active material.
  • the content of the heteroatoms is tested by inductively coupled plasma atomic emission spectrometer (ICP-OES) or scanning electron microscope-energy spectrometer (SEM-EDS).
  • ICP-OES inductively coupled plasma atomic emission spectrometer
  • SEM-EDS scanning electron microscope-energy spectrometer
  • the compacted density of the negative electrode piece is 1.1 mg/cm 3 to 1.7 mg/cm 3 . According to some embodiments of the present invention, the compacted density of the negative electrode piece is 1.3 mg/cm 3 to 1.5 mg/cm 3 . According to some embodiments of the present invention, the compacted density of the negative electrode sheet is 1.1 mg/cm 3 , 1.3 mg/cm 3 , 1.5 mg/cm 3 , 1.7 mg/cm 3 or any two of the above values. within the composition range. As a result, it has better first-turn Coulomb efficiency and dynamic performance.
  • the first active layer further includes a first conductive agent, a first binder and a first dispersant
  • the second active layer further includes a second conductive agent, a second binder and a second dispersant
  • the first active layer calculated based on the total mass of the first active layer, includes the following mass percentage components:
  • the second active layer calculated based on the total mass of the second active layer, includes the following mass percentage components:
  • the first negative active material and the second negative active material each include at least one of hard carbon, soft carbon, and mesocarbon microspheres.
  • the first binder and the second binder independently include polyvinylidene fluoride, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, poly(vinylidene fluoride), At least one of vinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, sulfonated EPDM, styrene-butadiene rubber and fluorine rubber.
  • the first conductive agent and the second conductive agent are independently selected from conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder or carbon fiber at least one of them.
  • the first dispersant and the second dispersant are independently selected from at least one of sodium carboxymethylcellulose (CMC-Na) or lithium carboxymethylcellulose.
  • the negative electrode current collector includes copper foil, aluminum foil, copper mesh, aluminum mesh, aluminum foil coated with a conductive carbon layer, copper foil coated with a conductive carbon layer, polymer coated with aluminum At least one of a polymer film, a copper-coated polymer film, a conductive polymer film, or a conductive film having corrosion stability when used in an electrolyte system.
  • the preparation method of the negative electrode sheet includes the following steps:
  • a second embodiment of the present application provides a secondary battery, which includes a positive electrode sheet, an electrolyte, a separator, and a negative electrode sheet as described above, and the separator is between the positive electrode sheet and the negative electrode sheet. Between the sheets, the electrolyte is filled between the positive electrode sheet and the negative electrode sheet and infiltrates the separator.
  • the secondary battery of the present application includes the negative electrode plate of the first possible embodiment of the application, because the negative electrode plate of the first aspect of the application can effectively improve the capacity and first-cycle Coulombic efficiency of the sodium-ion battery. Therefore, the secondary battery provided by this application has higher battery capacity and first-cycle Coulombic efficiency.
  • the positive electrode sheet includes a positive current collector and a positive active material layer formed on the surface of the positive current collector.
  • the positive active material layer includes a positive active material, and the positive active material includes At least one of a sodium transition metal oxide, a polyanionic compound, or a Prussian blue compound.
  • the transition metal in the sodium transition metal oxide, may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the sodium transition metal oxide is, for example, Na x MO 2 , where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 ⁇ x ⁇ 1.
  • the polyanionic compound may be a type of compound having sodium ions, transition metal ions, and tetrahedral (YO 4 ) n- anion units.
  • the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y can be at least one of P, S and Si;
  • n represents (YO 4 ) n -valency.
  • Polyanionic compounds may also be compounds having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions.
  • the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y can be at least one of P, S and Si, n represents (YO 4 )
  • the valence state of n- ; the halogen can be at least one of F, Cl and Br.
  • Polyanionic compounds may also be a class of compounds having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ , and optionally halogen anions.
  • Y can be at least one of P, S and Si
  • n represents the valence state of (YO 4 ) n-
  • Z represents a transition metal, which can be Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V , Zr and Ce
  • m represents the valence state of (ZO y ) m+
  • the halogen can be at least one of F, Cl and Br.
  • Polyanionic compounds are, for example, NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na 3 (VO y ) 2 ( At least one of PO 4 ) 2 F 3-2y (0 ⁇ y ⁇ 1).
  • Prussian blue compounds can be compounds containing sodium ions, transition metal ions and cyanide ions (CN-).
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the cathode active material layer may further include a conductive agent to improve the conductive performance of the cathode.
  • a conductive agent to improve the conductive performance of the cathode.
  • the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene or carbon nanofibers.
  • the positive active material layer may further include a binder to firmly bond the positive active material and the optional conductive agent to the positive current collector.
  • a binder may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene At least one of rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA) or carboxymethyl chitosan (CMCS).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAA polyacrylic acid
  • PVA polyvinyl alcohol
  • EVA ethylene-vinyl acetate copolymer
  • SBR carboxymethyl cellulose
  • SA sodium alginate
  • PMA polymethacrylic acid
  • CMCS carboxymethyl
  • the positive electrode current collector adopts conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate or composite current collector, wherein the conductive carbon material of the conductive carbon sheet can be superconducting carbon, acetylene black, One or more of carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene or carbon nanofibers.
  • the metal materials of metal foil, carbon-coated metal foil and porous metal plate can be selected independently. From at least one of copper, aluminum, nickel and stainless steel.
  • the composite current collector may be a composite current collector formed by a combination of a metal foil material and a polymer base film.
  • the separator can be made of various materials suitable for secondary battery separators in the art, including but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, and polyterephthalene. At least one of ethylene glycol formate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the electrolyte solution includes an organic solvent and an electrolyte sodium salt.
  • organic solvents include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, One or more of diglyme, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and methyl tert-butyl ether;
  • electrolyte sodium salts include sodium hexafluorophosphate, bisfluorosulfonyl One or more of sodium imide, sodium bistrifluoromethanesulfonimide, sodium triflate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.
  • a third embodiment of the present application provides an electrical device, which includes the above-mentioned secondary battery.
  • Figure 1 is a schematic diagram of the negative electrode piece of Embodiment 1;
  • the reagents, methods and equipment used in the present invention are all conventional reagents, methods and equipment in this technical field unless otherwise specified.
  • the first negative active material A hard carbon (gram capacity 450mAh/g, proportion of each heteroatom N: 5%, S: 2.5%, P: 1%, B: 0.5%, total proportion 9%); d1 is
  • the first negative active material B hard carbon (gram capacity 400mAh/g, the proportion of each heteroatom is N: 2.5%, S: 1.5%, P: 0.5%, B: 0.5%, the total proportion is 5%); d1 for
  • the first negative active material C hard carbon (gram capacity 420mAh/g, the proportion of each heteroatom is N: 3.5%, S: 2%, P: 1%, B: 0.5%, the total proportion is 7%); d1 for
  • the first negative active material D hard carbon (gram capacity 500mAh/g, the proportion of each heteroatom is N: 6%, S: 2.5%, P: 1.5%, B: 1%, the total proportion is 11%); d1 for
  • Second negative electrode active material A hard carbon (gram capacity 360mAh/g, the proportion of each heteroatom is N: 3%, S: 1%, P: 0.5%, B: 0.5%, the total proportion is 5%), d2 for
  • Second negative active material B hard carbon (gram capacity 220mAh/g, the proportion of each heteroatom is N: 0.75%, S: 0.25%, P: 0%, B: 0%, the total proportion is 1%); d2 for
  • Second negative electrode active material C hard carbon (gram capacity 350mAh/g, the proportion of each heteroatom is N: 3%, S: 1%, P: 0.5%, B: 0%, the total proportion is 4.5%); d2 for
  • Second negative electrode active material D hard carbon (gram capacity 345mAh/g, the proportion of each heteroatom is N: 3%, S: 1%, P: 0%, B: 0.5%, the total proportion is 4.5%); d2 for
  • Second negative electrode active material E hard carbon (gram capacity 343mAh/g, the proportion of each heteroatom is N: 3%, S: 0.5%, P: 0.5%, B: 0.5%, the total proportion is 4.5%); d2 for
  • Second negative active material F hard carbon (gram capacity 342mAh/g, the proportion of each heteroatom is N: 2.5%, S: 1%, P: 0.5%, B: 0.5%, the total proportion is 4.5%); d2 for
  • Embodiment 1 provides a negative electrode sheet.
  • Figure 1 is a schematic structural diagram of the negative electrode sheet in Embodiment 1; wherein, 1 is the first active layer; 2 is the second active layer; and 3 is the negative electrode current collector. Its preparation method is as follows:
  • Examples 2 to 9 provide a series of negative electrode sheets, the preparation method and component content of which are the same as those in Example 1. The difference lies in that the first negative electrode active material and the second negative electrode active material are different. See Table 1 for details.
  • Embodiment 10 provides a negative electrode piece, and its preparation method is as follows:
  • Embodiment 11 provides a negative electrode piece, and its preparation method is as follows:
  • Embodiment 12 provides a negative electrode piece, and its preparation method is as follows:
  • Embodiment 13 provides a negative electrode piece, and its preparation method is as follows:
  • Embodiment 14 provides a negative electrode piece, and its preparation method is as follows:
  • Embodiment 15 provides a negative electrode piece, and its preparation method is as follows:
  • Comparative Example 1 provides a negative electrode piece, and its preparation method is as follows:
  • the surface density is 20 mg/cm 2.
  • the upper and lower dies use the first active layer slurry. Dry, roll, and cut to obtain the negative electrode.
  • the pole piece has a compacted density of 1.5g/cm 3 .
  • Comparative Example 2 provides a negative electrode piece, and its preparation method is as follows:
  • Comparative Example 3 provides a negative electrode piece, and its preparation method is as follows:
  • cathode material Na 3 V 2 (PO 4 ) 2 F 3 , accounting for 96%), conductive agent (SP, accounting for 3%), binder (PVDF, accounting for 3%) 1%) evenly mixed in N-methylpyrrolidone to obtain a positive electrode sheet slurry.
  • the positive electrode sheet slurry is applied to the positive electrode current collector, and the positive electrode sheet is obtained by drying, rolling, and cutting.
  • the Xinwei power battery testing system was used to conduct a 0.5A current charge and discharge test on the obtained sodium ion battery, and the battery capacity was obtained. The data were recorded in Table 2.
  • 80% capacity retention rate Charge and discharge with a current of 0.5C, and record the number of cycles when cycling to 80% capacity retention rate (80% SOH) at room temperature.
  • Comparative Example 1 has the highest capacity, but its Coulombic efficiency and cycle life are not up to standard. It can be seen that the single use of hard carbon with a large amount of element doping cannot achieve ideal performance. In Comparative Example 2, although its doping amount of impurity elements is smaller and its cycle performance and first effect are higher, its capacity is not up to standard.
  • the first active layer remains unchanged, and the width of the (002) crystal plane is adjusted by adjusting the heteroatom content of the second active layer.
  • Battery capacity and first efficiency are all up to standard.
  • the effects of various miscellaneous elements are further compared.
  • the doping amounts of boron, phosphorus, sulfur, and nitrogen were each reduced by 0.5% to determine the impact of each element on battery performance. Because the capacity difference between the groups of Examples 3 to 6 is basically not large ( ⁇ 0.05), it is obvious that the reduction of nitrogen and sulfur elements is more conducive to improving the first effect and cycle stability.
  • Example 9 the second active layer remained unchanged and the first active layer was changed.
  • the design parameters of the three embodiments 2, 7, and 8 are all within the specification range protected by the claims, and their performance is relatively excellent.
  • the first active layer of Example 9 uses hard carbon with a higher (002) crystal plane width. It has reached the limit of hard carbon materials, so its layered structure is easy to collapse and the cycle accelerates attenuation.
  • Example 14 increased the proportion of active material in the first active layer, the capacity was improved to a certain extent, and there was no significant difference in Coulombic efficiency and cycle stability. It can be seen that reducing the proportion of inactive substances is a feasible idea.
  • Example 15 reduces the proportion of active material in the first active layer, and the capacity is significantly reduced. From the perspective of increasing capacity, reducing the proportion of active materials has no obvious advantage.
  • Comparative Example 3 and Example 7 exchanged the positions of the active materials, resulting in Comparative Example 3 having d1/d2 ⁇ 1. Obviously, the capacity, cycle stability and first effect of Comparative Example 3 are not ideal.

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Abstract

本发明公开了一种负极极片、二次电池及用电设备，其负极极片包括负极集流体和设置在负极集流体至少一侧的负极活性层，负极活性层包括第一活性层和第二活性层；第一活性层位于第二活性层和负极集流体之间；第一活性层包括第一负极活性材料，第二活性层包括第二负极活性材料；第一负极活性材料的（002）晶面层间距d1大于第二负极活性材料的（002）晶面层间距d2。本发明通过限定第一负极活性材料的（002）晶面层间距d1大于所述第二负极活性材料的（002）晶面层间距d2，使得其负极极片能够提高二次电池的首圈库伦效率并保持较高的电池容量。

Description

负极极片、二次电池及用电设备
相关申请的交叉引用
本申请要求于2022年08月26日提交中国专利局、申请号为202211033942.0、发明名称为“负极极片、二次电池及用电设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及储能技术领域，尤其是涉及一种负极极片、二次电池及用电设备。
背景技术
目前在钠离子电池领域，更多的是使用硬碳作为负极活性材料。但是，硬碳电极的首圈库伦效率(ICE)普遍不足，这严重损害了钠离子电池的循环稳定性。为了进一步提升硬碳负极在钠离子电池领域的应用潜力，其首圈的库伦效率必须得到优化。
因此，有必要提供一种负极极片，使得钠离子电池具有较高的容量和较高的首圈库伦效率。
发明内容
本发明旨在至少解决现有技术中存在的技术问题之一。为此，本发明第一方面提出一种负极极片，能够有效提高首圈库伦效率和容量。
本发明第二方面还提供一种二次电池。
本发明第三方面还提供一种用电设备。
本发明的第一方面实施例提供一种负极极片，所述负极极片包括负极集流体和设置在所述负极集流体至少一侧的负极活性层，所述负极活性层包括第一活性层和第二活性层；所述第一活性层位于第二活性层和负极集流体之间；
所述第一活性层包括第一负极活性材料，所述第二活性层包括第二负极活性材料；
所述第一负极活性材料的(002)晶面层间距d1大于所述第二负极活性材料的(002)晶面层间距d2。
根据本发明实施例的负极极片，至少具有如下有益效果：
本发明通过限定第一负极活性材料的(002)晶面层间距d1大于所述第二负极活性材料的(002)晶面层间距d2，使得其负极极片能够提高钠离子电池首圈库伦效率和保持较高的电池容量。这是因为第一活性层的作用是提供更多的储钠能力，提高容量；第二活性层的作用是降低与电解液的副反应，从而提高首圈库伦效率。
根据本发明的一些实施例，所述第一负极活性材料的(002)晶面层间距d1和所述第二负极活性材料的(002)晶面层间距d2，满足：d1/d2≤1.2。由此，第一活性层和第二活性层的相容性更好，若层间距相差太大，在充放电过程应力变化的差异很大(层间距会影响钠离子嵌入时的体积膨胀，层间距差异过大，体积膨胀差距就会很大)，导致两者之间的相容性变差，第二活性层容易剥落。
根据本发明的一些实施例，所述第一负极活性材料的(002)晶面层间距d1满足
Figure PCTCN2023071003-appb-000001
Figure PCTCN2023071003-appb-000002
根据本发明的一些实施例，所述第一负极活性材料的(002)晶面层间距d1为
Figure PCTCN2023071003-appb-000003
或在由上述任意两个数值所组成的范围内。
根据本发明的一些实施例，所述第二负极活性材料的(002)晶面层间距d2满足
Figure PCTCN2023071003-appb-000004
Figure PCTCN2023071003-appb-000005
根据本发明的一些实施例，所述第二负极活性材料的(002)晶面层间距d2为
Figure PCTCN2023071003-appb-000006
或在由上述任意两个数值所组成的范围内。
根据本发明的一些实施例，所述层间距通过透射电镜来表征。
根据本发明的一些实施例，所述第一负极活性材料和所述第二负极活性材料中各自独立地包含杂原子，所述杂原子包括氮、氧、硫或硼中的至少两种。
根据本发明的一些实施例，所述第一负极活性材料中的杂原子含量大于所述第二负极活性材料中的杂原子含量。
根据本发明的一些实施例，所述杂原子的含量通过电感耦合等离子体原子发射光谱仪(ICP-OES)或者扫描电镜－能谱仪(SEM-EDS)来测试。
根据本发明的一些实施例，所述负极极片的压实密度为1.1mg/cm 3～1.7mg/cm 3。根据本发明的一些实施例，所述负极极片的压实密度为1.3mg/cm 3～1.5mg/cm 3。根据本发明的一些实施例，所述负极极片的压实密度为1.1mg/cm 3、1.3mg/cm 3、1.5mg/cm 3、1.7mg/cm 3或在由上述任意两个数值所组成的范围内。由此，具有较好的首圈库伦效率和动力学性能。
根据本发明的一些实施例，所述第一活性层还包括第一导电剂、第一粘结剂和第一分散剂，所述第二活性层还包括第二导电剂、第二粘结剂和第二分散剂。
根据本发明的一些实施例，以第一活性层的总质量计算，所述第一活性层包括如下质量百分比的组分：
Figure PCTCN2023071003-appb-000007
Figure PCTCN2023071003-appb-000008
根据本发明的一些实施例，以第二活性层的总质量计算，所述第二活性层包括如下质量百分比的组分：
Figure PCTCN2023071003-appb-000009
根据本发明的一些实施例，所述第一负极活性材料和所述第二负极活性材料均包括硬碳、软碳、中间相碳微球中的至少一种。
根据本发明的一些实施例，所述第一粘结剂和所述第二粘结剂彼此独立地包括聚偏二氟乙烯、聚乙烯醇、淀粉、羟丙基纤维素、再生纤维素、聚乙烯吡咯烷酮、四氟乙烯、聚乙烯、聚丙烯、乙烯－丙烯－二烯三元共聚物、磺化EPDM、丁苯橡胶和氟橡胶中的至少一种。
根据本发明的一些实施例，所述第一导电剂和所述第二导电剂独立地选自导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉或碳纤维中的至少一种。
根据本发明的一些实施例，所述第一分散剂和第二分散剂独立地选自羧甲基纤维素钠(CMC-Na)或羧甲基纤维素锂中的至少一种。
根据本发明的一些实施例，所述负极集流体包括铜箔、铝箔、铜网、铝网、涂覆有导电碳层的铝箔、涂覆有导电碳层的铜箔、涂覆有铝的聚合物薄膜、涂覆有铜的聚合物薄膜、导电的聚合物薄膜或在用于电解质系统时具有腐蚀稳定性的导电薄膜中的至少一种。
根据本申请的一些实施例，所述负极极片的制备方法，包括如下步骤：
S1、将第一负极活性材料、第一导电剂、第一粘结剂和第一分散剂搅拌得到第一活性层；将第二负极活性材料、第二导电剂、第二粘结剂和第二分散剂搅拌得到第二活性层；
S2、采用双层涂布法在集流体的上下表面涂布，烘干、辊压即得负极极片。
本申请的第二方面实施例提供一种二次电池，其包括正极极片、电解液、隔膜以及如上述所述的负极极片，所述隔膜介于所述正极极片和所述负极极片之间，所述电解液填充于所述正极极片和所述负极极片之间且浸润所述隔膜。
其中，本申请的二次电池包括本申请第一方面可能实施方式的负极极片，由于本申请第一方面的负极极片具有有效提高钠离子电池容量和首圈库伦效率。因此，本申请提供的二次电池具有较高的电池容量和首圈库伦效率。
根据本申请的一些实施例，所述正极极片包括正极集流体及形成于所述正极集流体表面 上的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括钠过渡金属氧化物、聚阴离子型化合物或普鲁士蓝类化合物中的至少一种。
根据本申请的一些实施例，钠过渡金属氧化物中，过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。钠过渡金属氧化物例如为Na xMO 2，其中M为Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0<x≤1。
根据本申请的一些实施例，聚阴离子型化合物可以是具有钠离子、过渡金属离子及四面体型(YO 4) n-阴离子单元的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种；n表示(YO 4) n-的价态。
聚阴离子型化合物还可以是具有钠离子、过渡金属离子、四面体型(YO 4) n-阴离子单元及卤素阴离子的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种，n表示(YO 4) n-的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物还可以是具有钠离子、四面体型(YO 4) n-阴离子单元、多面体单元(ZO y) m+及可选的卤素阴离子的一类化合物。Y可以是P、S及Si中的至少一种，n表示(YO 4) n-的价态；Z表示过渡金属，可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种，m表示(ZO y) m+的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物例如是NaFePO 4、Na 3V 2(PO 4) 3、NaM’PO4F(M’为V、Fe、Mn及Ni中的一种或几种)及Na 3(VO y) 2(PO 4) 2F 3-2y(0≤y≤1)中的至少一种。
普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN-)的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为Na aMe bMe’ c(CN) 6，其中Me及Me’各自独立地为Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0<a≤2，0<b<1，0<c<1。
根据本申请的一些实施例，正极活性物质层还可以包括导电剂，以改善正极的导电性能。本申请对导电剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯或碳纳米纤维中的一种或几种。
根据本申请的一些实施例，正极活性物质层还可以包括粘结剂，以将正极活性物质和可选的导电剂牢固地粘结在正极集流体上。本申请对粘结剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，粘结剂可以为聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚乙烯醇(PVA)、乙烯－醋酸乙烯酯共聚物(EVA)、丁苯橡胶(SBR)、羧甲基纤维素 (CMC)、海藻酸钠(SA)、聚甲基丙烯酸(PMA)或羧甲基壳聚糖(CMCS)中的至少一种。
根据本申请的一些实施例，正极集流体采用导电碳片、金属箔材、涂炭金属箔材、多孔金属板或复合集流体，其中导电碳片的导电碳材质可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯或碳纳米纤维中的一种或几种，金属箔材、涂炭金属箔材和多孔金属板的金属材质各自独立地可以选自铜、铝、镍及不锈钢中的至少一种。复合集流体可以为金属箔材与高分子基膜复合形成的复合集流体。
根据本申请的一些实施例，所述隔膜可以是本领域各种适用于二次电池隔膜的材料，例如，包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维中的至少一种。
根据本申请的一些实施例，所述电解液包括有机溶剂和电解质钠盐。例如，有机溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、碳酸亚丙酯、醋酸甲酯、丙酸乙酯、氟代乙烯碳酸脂、乙醚、二甘醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、甲基叔丁基醚中的一种或几种；电解质钠盐包括六氟磷酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠、四氟硼酸钠、二氟磷酸钠、高氯酸钠、氯化钠中的一种或几种。
本申请的第三方面实施例提供一种用电设备，所述用电设备包括上述所述的二次电池。
本发明的其它特征和优点将在随后的说明书中阐述，并且，部分地从说明书中变得显而易见，或者通过实施本发明而了解。
附图说明
本发明的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：
图1是实施例1的负极极片示意图；
其中，1为第一活性层；2为第二活性层，3为负极集流体。
具体实施方式
以下是本发明的具体实施例，并结合实施例对本发明的技术方案作进一步的描述，但本发明并不限于这些实施例。
本发明所采用的试剂、方法和设备，如无特殊说明，均为本技术领域常规试剂、方法和设备。
实施例和对比例用到的原料如下：
第一负极活性材料A：硬碳(克容量450mAh/g，各杂原子占比N:5％，S：2.5％，P:1％，B：0.5％，总占比9％)；d1为
Figure PCTCN2023071003-appb-000010
第一负极活性材料B：硬碳(克容量400mAh/g，其中各杂原子占比N:2.5％,S：1.5％，P:0.5％，B：0.5％，总占比5％)；d1为
Figure PCTCN2023071003-appb-000011
第一负极活性材料C：硬碳(克容量420mAh/g，其中各杂原子占比N:3.5％,S：2％，P:1％，B：0.5％，总占比7％)；d1为
Figure PCTCN2023071003-appb-000012
第一负极活性材料D：硬碳(克容量500mAh/g，其中各杂原子占比N:6％,S：2.5％，P:1.5％，B：1％，总占比11％)；d1为
Figure PCTCN2023071003-appb-000013
第二负极活性材料A：硬碳(克容量360mAh/g，其中各杂原子占比N:3％，S：1％，P:0.5％，B：0.5％，总占比5％)，d2为
Figure PCTCN2023071003-appb-000014
第二负极活性材料B：硬碳(克容量220mAh/g，其中各杂原子占比N:0.75％，S：0.25％，P:0％，B：0％，总占比1％)；d2为
Figure PCTCN2023071003-appb-000015
第二负极活性材料C：硬碳(克容量350mAh/g，其中各杂原子占比N:3％，S：1％，P:0.5％，B：0％，总占比4.5％)；d2为
Figure PCTCN2023071003-appb-000016
第二负极活性材料D：硬碳(克容量345mAh/g，其中各杂原子占比N:3％，S：1％，P:0％，B：0.5％，总占比4.5％)；d2为
Figure PCTCN2023071003-appb-000017
第二负极活性材料E：硬碳(克容量343mAh/g，其中各杂原子占比N:3％，S：0.5％，P:0.5％，B：0.5％，总占比4.5％)；d2为
Figure PCTCN2023071003-appb-000018
第二负极活性材料F：硬碳(克容量342mAh/g，其中各杂原子占比N:2.5％,S：1％，P:0.5％，B：0.5％，总占比4.5％)；d2为
Figure PCTCN2023071003-appb-000019
实施例1
实施例1提供一种负极极片，图1是实施例1的负极极片的结构示意图；其中，1为第一活性层；2为第二活性层，3为负极集流体。其制备方法如下：
S1、将94％的第一负极活性材料A、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将94％的第二负极活性材料A、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在负极集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.5g/cm 3。
实施例2～9
实施例2～9提供一系列负极极片，其制备方法和组分含量与实施例1相同，其区别在于，第一负极活性材料和第二负极活性材料不同，具体见表1。
表1实施例1～9的组分
Figure PCTCN2023071003-appb-000020
实施例10
实施例10提供一种负极极片，其制备方法如下：
S1、将94％的第一负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将94％的第二负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.0g/cm 3。
实施例11
实施例11提供一种负极极片，其制备方法如下：
S1、将94％的第一负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将94％的第二负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.1g/cm 3。
实施例12
实施例12提供一种负极极片，其制备方法如下：
S1、将94％的第一负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将94％的第二负极活性材料B、3％ 的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.7g/cm 3。
实施例13
实施例13提供一种负极极片，其制备方法如下：
S1、将94％的第一负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将94％的第二负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.9g/cm 3。
实施例14
实施例14提供一种负极极片，其制备方法如下：
S1、将99.85％的第一负极活性材料A、0.05％的导电炭黑、0.05％的丁苯橡胶和0.05％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将65％的第二负极活性材料A、15％的导电炭黑、15％的丁苯橡胶和5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在负极集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.5g/cm 3。
实施例15
实施例15提供一种负极极片，其制备方法如下：
S1、将65％的第一负极活性材料A、15％的导电炭黑、15％的丁苯橡胶和5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将99.85％的第二负极活性材料A、0.05％的导电炭黑、0.05％的丁苯橡胶和0.05％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在负极集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.5g/cm 3。
对比例1
对比例1提供一种负极极片，其制备方法如下：
S1、将94％的第一负极活性材料A、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，面密度均为20mg/cm 2，上下模头均采用第一活性层浆料，烘干、辊压、分切，即得负极极片，压实密度为1.5g/cm 3。
对比例2
对比例2提供一种负极极片，其制备方法如下：
S1、将94％第二负极活性材料A、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，面密度均为20mg/cm 2，上下模头均采用活性层浆料，烘干、辊压、分切，即得负极极片，压实密度为1.5g/cm 3；
对比例3
对比例3提供一种负极极片，其制备方法如下：
S1、将94％的第二负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第一活性层浆料；将94％的第一负极活性材料B、3％的导电炭黑、1.5％的丁苯橡胶和1.5％的羧甲基纤维素钠，溶剂为去离子水，搅拌得到第二活性层浆料；
S2、采用双层涂布法在集流体的上下表面涂布，第一活性层和第二活性层面密度相同，均为20mg/cm 2，烘干、辊压、分切，即得负极极片，压实密度为1.5g/cm 3。
性能测试
钠离子电池的制备：
(1)电解液：1M NaPF 6溶解在碳酸乙烯酯(EC)：碳酸二乙酯(DEC)＝3：7
(2)隔膜：PP膜；
(3)正极极片的组分：正极材料(Na 3V 2(PO 4) 2F 3，占比96％)，导电剂(SP，占比3％)，粘结剂(PVDF，占比1％)均匀混合于N－甲基吡咯烷酮中，得到正极极片浆料。将正极极片浆料涂敷于正极集流体，经烘干、辊压、分切得到正极极片。
(4)钠离子电池的组装
将实施例1～15和对比例1～3制备的负极极片、正极极片、隔膜和结构件等组装起来，卷绕相同层数后，经注液、化成、老化、密封等工序后得到钠离子电池。
采用新威动力电池测试系统对所得钠离子电池进行0.5A电流充放电测试，得电池容量，记录数据于表2。
首圈库伦效率：首圈库伦效率＝首次充电容量/首次放电容量*100％；记录数据于表2。
80％容量保持率：以0.5C电流充放电，记录室温下，循环至80％容量保持率(80％SOH)时的循环圈数。
表2实施例和对比例的数据
Figure PCTCN2023071003-appb-000021
从表1的测试结果可知，对比例1的容量最高，但是其库伦效率与循环寿命均不达标。可见，单一使用元素掺杂量较多的硬碳，并不能得到理想的性能。对比例2，其杂元素掺杂量虽然较少，循环性能和首效均较高，但是其容量并不合格。
如实施例1～6，保持第一活性层不变，通过调节第二活性层的杂原子含量来调节(002)晶面的宽度。在第二活性层的极限范围内
Figure PCTCN2023071003-appb-000022
电池容量，首效均能达标。此外，如实施例1，3～6进一步对比各杂元素的作用。实施例3～6分别在实施例1的基础上， 各降低0.5％的硼、磷、硫、氮掺杂量，从而判断各元素对电池性能的影响。因为实施例3～6各组容量差异基本不大(＜0.05)，但显然，氮、硫元素的降低更有助于提高首效以及循环稳定性。
实施例2，7～9保持第二活性层不变，改变了第一活性层。其中2，7，8三个实施例的设计参数均在权利要求书保护的规格范围内，其性能均较为优异。但是实施例9的第一活性层采用更高(002)晶面宽度的硬碳。其已经达到硬碳材料的极限，故其层状结构容易坍塌，循环加速衰减。
压实密度(压密)对电池性能的影响对比见实施例7，10～13。在合理的压实密度下，电池性能较好。但是，压实密度太低，孔隙较大，副反应较多，不利于库伦效率。因此，实施例10的首效偏低。而压密太高，材料被破坏的风险就越大。当达到1.9的压实密度，电池性能下降。
实施例14与实施例1相比，增加了第一活性层内活性物质占比，容量得到一定的提升，且库伦效率与循环稳定性无明显差异。可见，降低非活性物质占比是一种可行的思路。实施例15与实施例1相比，降低了第一活性层内活性物质占比，容量降低明显。从提高容量角度看，降低活性物质占比没有明显优势。
对比例3与实施例7互换了活性材料的位置，导致对比例3的其d1/d2＜1。很显然，对比例3的容量、循环稳定性以及首效均不理想。
上面结合本发明实施例作了详细说明，但本发明不限于上述实施例，在所属技术领域普通技术人员所具备的知识范围内，还可以在不脱离本发明宗旨的前提下作出各种变化。

Claims (10)

  1. 一种负极极片，其特征在于，所述负极极片包括负极集流体和设置在所述负极集流体至少一侧的负极活性层，所述负极活性层包括第一活性层和第二活性层；所述第一活性层位于第二活性层和负极集流体之间；
    所述第一活性层包括第一负极活性材料，所述第二活性层包括第二负极活性材料；
    所述第一负极活性材料的(002)晶面层间距d1大于所述第二负极活性材料的(002)晶面层间距d2。
  2. 根据权利要求1所述的负极极片，其特征在于，所述第一负极活性材料的(002)晶面层间距d1和所述第二负极活性材料的(002)晶面层间距d2满足如下条件中至少一者：
    (i)d1/d2≤1.2；
    (ii)
    Figure PCTCN2023071003-appb-100001
    (iii)
    Figure PCTCN2023071003-appb-100002
  3. 根据权利要求1或2所述的负极极片，其特征在于，所述第一负极活性材料和所述第二负极活性材料中各自独立地包含杂原子，所述杂原子包括氮、氧、硫或硼中的至少两种。
  4. 根据权利要求3所述的负极极片，其特征在于，所述第一负极活性材料中的杂原子含量大于所述第一负极活性材料中的杂原子含量。
  5. 根据权利要求1所述的负极极片，其特征在于，所述负极极片的压实密度为1.1mg/cm 3～1.7mg/cm 3。
  6. 根据权利要求1所述的负极极片，其特征在于，所述第一活性层还包括第一导电剂、第一粘结剂和第一分散剂，所述第二活性层还包括第二导电剂、第二粘结剂和第二分散剂。
  7. 根据权利要求6所述的负极极片，其特征在于，所述第一导电剂和所述第二导电剂各自独立地包括导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉或碳纤维中的至少一种；
    和/或，所述第一粘结剂和所述第二粘结剂各自独立地包括聚偏二氟乙烯、聚乙烯醇、淀粉、羟丙基纤维素、再生纤维素、聚乙烯吡咯烷酮、四氟乙烯、聚乙烯、聚丙烯、乙烯－丙烯－二烯三元共聚物、磺化EPDM、丁苯橡胶和氟橡胶中的至少一种；
    和/或，所述第一分散剂和所述第二分散剂各自独立地包括羧甲基纤维素钠、羧甲基纤维素锂中的至少一种。
  8. 根据权利要求1所述的负极极片，其特征在于，所述第一负极活性材料和所述第二负极活性材料均包括硬碳、软碳、中间相碳微球中的至少一种。
  9. 一种二次电池，其特征在于，包括正极极片、电解液、隔膜以及如权利要求1～8任一项所述的负极极片。
  10. 一种用电设备，其特征在于，包括权利要求9所述的二次电池。
PCT/CN2023/071003 2022-08-26 2023-01-06 负极极片、二次电池及用电设备 Ceased WO2024040858A1 (zh)

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