WO2024255258A1 - 正极极片及其制备方法、储能装置、用电设备 - Google Patents

正极极片及其制备方法、储能装置、用电设备 Download PDF

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Publication number
WO2024255258A1
WO2024255258A1 PCT/CN2024/074391 CN2024074391W WO2024255258A1 WO 2024255258 A1 WO2024255258 A1 WO 2024255258A1 CN 2024074391 W CN2024074391 W CN 2024074391W WO 2024255258 A1 WO2024255258 A1 WO 2024255258A1
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Prior art keywords
additive
positive electrode
active material
electrode active
material layer
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English (en)
French (fr)
Inventor
文佳琪
张国栋
柯梦晶
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Xiamen Hithium Energy Storage Technology Co Ltd
Shenzhen Hithium Energy Storage Technology Co Ltd
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Xiamen Hithium Energy Storage Technology Co Ltd
Shenzhen Hithium Energy Storage Technology Co Ltd
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Publication of WO2024255258A1 publication Critical patent/WO2024255258A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or 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
    • H01M4/13—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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage technology, and specifically to a positive electrode plate and a preparation method thereof, an energy storage device, and an electrical equipment.
  • the carbon negative electrode consumes the sodium element in the positive electrode active material to form a solid electrolyte interface (SEI) film.
  • SEI solid electrolyte interface
  • the irreversible consumption of sodium in the positive electrode active material greatly reduces the energy density of sodium-ion batteries. This problem has become one of the bottlenecks restricting the development of sodium-ion batteries.
  • Pre-sodiumization technology can effectively supplement the irreversible sodium loss of positive electrode active materials during the cycle process, so it plays an important role in the practical application of sodium-ion batteries.
  • the current sodium replenishment routes include the negative electrode sodium replenishment route and the positive electrode sodium replenishment route. Compared with the negative electrode sodium replenishment route, the positive electrode lithium replenishment route of adding sodium replenisher to the positive electrode is safer and more compatible with the existing battery production process.
  • the commonly used sodium supplements usually do not contain fluorine.
  • the fluorine in the sodium supplement containing fluorine is conducive to the formation of solid electrolyte interface (CEI) film.
  • the existing sodium supplement containing fluorine has strong toxicity, which is not conducive to commercial transformation and application.
  • the present application aims to solve one of the technical problems in the related art at least to some extent.
  • the first aspect of the present application provides a positive electrode plate for a sodium battery, comprising a current collector, a positive electrode active material layer and a first additive, wherein the positive electrode active material layer is arranged on at least one side of the current collector, and the first additive comprises sodium monofluorophosphate and/or sodium difluorophosphate.
  • the positive electrode plate of the present application includes at least the following beneficial effects: on the one hand, sodium monofluorophosphate and sodium difluorophosphate provide additional sodium ions, play the role of sodium supplement, and can effectively improve the first coulomb efficiency and the first discharge capacity of the positive electrode, thereby improving the energy density of the sodium battery; on the other hand, sodium monofluorophosphate and sodium difluorophosphate also play the role of positive electrode film-forming additives, and can form byproducts NaF and Na 3 PO 3 in the process of replenishing sodium ions. NaF and Na 3 PO 3 can form an interface layer on the surface of the positive electrode plate.
  • the formation of the interface layer can reduce side reactions and reduce the self-discharge of the battery during high-temperature storage, thereby improving the high-temperature cycle stability of the sodium battery; sodium monofluorophosphate and sodium difluorophosphate are non-toxic, Therefore, the preparation process of the positive electrode is more environmentally friendly; sodium monofluorophosphate and sodium difluorophosphate are stable in nature, simple to obtain and low in cost, and are suitable for mass production.
  • the second aspect of the present application provides a method for preparing the aforementioned positive electrode sheet, comprising: forming a positive electrode active material layer on at least one side of a current collector; wherein a first additive is dispersed in the positive electrode active material layer, and the first additive comprises sodium monofluorophosphate and/or sodium difluorophosphate.
  • the preparation method of the positive electrode sheet is not only simple in process and can better meet the requirements of green environmental protection, but also does not require upgrading the existing production equipment of the positive electrode sheet, and is suitable for mass production.
  • the first coulomb efficiency and first discharge capacity of the prepared positive electrode sheet are relatively high, and the energy density and cycle stability of the sodium battery can be improved.
  • the third aspect of the present application provides a method for preparing the above-mentioned positive electrode sheet, comprising: forming a positive electrode active material layer on at least one side of a current collector; forming a functional layer on a side of the positive electrode active material layer away from the current collector; wherein a first additive is dispersed in the positive electrode active material layer, and the first additive and/or a second additive are dispersed in the functional layer, and the second additive comprises at least one of Na 2 O, Na 2 O 2 , Na 2 CO 3 , Na 2 S, Na 3 P, NaN 3 , NaNiO 2 , NaCrO 2 , NaFeO 2 , Na 3 C 6 H 5 O 7 , Na 2 C 6 O 6 , NaF, and NaHF 2.
  • the preparation method of the positive electrode sheet is not only simple in process, but also can better meet the requirements of green environmental protection, and does not require upgrading the existing production equipment of the positive electrode sheet, and is suitable for mass production.
  • the first coulomb efficiency and first discharge capacity of the prepared positive electrode sheet are relatively high, and the energy density and cycle stability of the sodium battery can be improved.
  • the fourth aspect of the present application provides an energy storage device, comprising the aforementioned positive electrode sheet.
  • the energy storage device has all the features and advantages of the aforementioned positive electrode sheet, which will not be repeated here. In general, the energy storage device has a higher energy density and cycle performance.
  • the fifth aspect of the present application provides an electrical device, comprising the aforementioned energy storage device.
  • the electrical device has all the features and advantages of the aforementioned energy storage device, which will not be described in detail here.
  • FIG1 is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of the present application.
  • FIG2 is a schematic diagram of the structure of another positive electrode sheet provided in an embodiment of the present application.
  • FIG3 is a charge and discharge curve of the half-cells prepared in Example 1 and Comparative Example 1;
  • a first aspect of the present application provides a positive electrode plate for a sodium battery, referring to FIG1 , comprising: a current collector 1, a positive electrode active material layer 2 and a first additive, wherein the positive electrode active material layer 2 is disposed on at least one side of the current collector 1, and the first additive comprises sodium monofluorophosphate (Na 2 PO 3 F) and/or sodium difluorophosphate (NaPO 2 F 2 ).
  • sodium monofluorophosphate and sodium difluorophosphate provide additional sodium ions and play the role of sodium supplementers, which can effectively improve the first coulombic efficiency and first discharge capacity of the positive electrode, thereby improving the energy density of the sodium battery;
  • sodium monofluorophosphate and sodium difluorophosphate also play the role of positive electrode film-forming additives, and can form by-products NaF and Na 3 PO 3 in the process of replenishing sodium ions.
  • NaF and Na 3 PO 3 can form an interface layer on the surface of the positive electrode.
  • the main components of the interface layer include Na 2 O, Na 2 CO 3 , NaF, Na 3 PO 3 and other substances.
  • the formation of the interface layer can reduce side reactions and reduce the self-discharge of the battery during high-temperature storage, thereby improving the high-temperature cycle stability of the sodium battery; sodium monofluorophosphate and sodium difluorophosphate are non-toxic, so the preparation process of the positive electrode is more environmentally friendly; sodium monofluorophosphate and sodium difluorophosphate are stable in nature, simple to obtain and low in cost, and are suitable for mass production.
  • the first additive may preferably be sodium monofluorophosphate (Na 2 PO 3 F). Compared with sodium difluorophosphate, sodium monofluorophosphate has a higher sodium content, which is beneficial for further reducing the amount of the additive while satisfying the sodium supplementation effect.
  • the first additive may be dispersed in the positive electrode active material layer 2.
  • the dispersion of the first additive in the positive electrode active material layer is conducive to the first additive playing a role in sodium supplementation, thereby reducing the consumption of sodium in the positive electrode active material, and thus improving the first coulombic efficiency of the positive electrode;
  • the dispersion of the first additive in the positive electrode active material layer is conducive to the first additive forming an interface layer on the surface of the positive electrode sheet, thereby reducing side reactions, and thus improving the high temperature cycle stability of the sodium battery.
  • the positive electrode plate may further include a functional layer 3.
  • Layer 3 is located on the side of the positive electrode active material layer 2 away from the current collector 1, and at least one of the positive electrode active material layer 2 and the functional layer 3 is dispersed with the first additive.
  • the functional layer may be dispersed with the first additive, and at this time, the positive electrode active material layer may contain the first additive or may not contain the first additive; as some other specific embodiments, the functional layer may not contain the first additive, and at this time, the positive electrode active material layer may be dispersed with the first additive.
  • the functional layer can simply play the role of sodium supplementation.
  • the functional layer can not only fully contact with the electrolyte, so that the sodium element can migrate to the vicinity of the negative electrode plate at a faster speed for film formation consumption, but also help to reduce the consumption of sodium generated by the positive electrode active material and improve the first coulomb efficiency.
  • the mass percentage of the first additive is 4.7wt%-20wt%; if the mass percentage of the first additive is too large, on the one hand, the relative content of the positive electrode active material in the positive electrode sheet is too small, which will have a certain negative impact on the energy density of the sodium battery; on the other hand, if the mass percentage of the first additive in the functional layer is too large, its thickness is also relatively large, which is easy to cause a significant increase in the polarization of the electrode sheet, affecting the electrochemical performance of the battery; if the mass percentage of the first additive is too small, it is difficult to achieve a significant sodium supplement effect.
  • the present application can better balance the sodium supplement effect and the comprehensive performance of the sodium battery by controlling the mass percentage of the first additive within the above range.
  • the mass percentage of the first additive can be 4.7wt%, 5wt%, 7.5wt%, 9wt%, 10wt%, 11wt%, 12wt%, 12.5wt%, 13wt%, 14wt%, 15wt%, 17.5wt% or 20wt%, etc., preferably 9wt%-15wt%.
  • the total mass of the positive electrode active material, the conductive agent and the binder can be used as a benchmark to control the mass percentage of the first additive to 5wt%-20wt%, preferably 10wt%-15wt%, to meet the mass percentage requirement of the first additive in the positive electrode sheet.
  • the positive electrode plate may further include a second additive, and the second additive may include at least one of Na 2 O, Na 2 O 2 , Na 2 CO 3 , Na 2 S, Na 3 P, NaN 3 , NaNiO 2 , NaCrO 2 , NaFeO 2 , Na 3 C 6 H 5 O 7 , Na 2 C 6 O 6 , NaF, and NaHF 2.
  • the second additive only has the function of supplementing sodium, and the decomposition potential of the second additive is lower than that of the first additive, which enables the sodium element to migrate to the vicinity of the negative electrode plate at a faster speed for film formation consumption, thereby being beneficial to the first coulomb efficiency of the positive electrode.
  • the second additive may preferably be NaF and/or NaHF 2.
  • NaF and NaHF 2 have a higher sodium content, so a smaller amount can achieve a certain sodium supplementation effect, and the sodium supplementation effect is higher.
  • the second additive (not shown) may be dispersed in the positive electrode active material layer 2.
  • the mass ratio of the first additive to the second additive may be (1-3): (1-3), and further It is thought to be 1:(1-3). Therefore, it can not only better take into account the effect of graded sodium supplementation and the improvement of battery electrochemical performance, but also better meet the needs of green environmental protection.
  • the positive electrode plate may further include a functional layer 3, and the second additive may be dispersed in the positive electrode active material layer 2 and/or in the functional layer 3.
  • the second additive when the first additive is dispersed only in the positive electrode active material layer, the second additive may be dispersed in the positive electrode active material layer, may be dispersed only in the functional layer, or may be dispersed in both the positive electrode active material layer and the functional layer; when the first additive is dispersed only in the functional layer, the second additive may be dispersed in the positive electrode active material layer, may be dispersed in the functional layer, or may be dispersed in both the positive electrode active material layer and the functional layer; when the first additive is dispersed in both the positive electrode active material layer and the functional layer, the second additive may be dispersed in the positive electrode active material layer, may be dispersed in the functional layer, or may be dispersed in both the positive electrode active material layer and the functional layer.
  • the second additive may be dispersed in the functional layer, or the first additive and the second additive may be dispersed in the functional layer. It should be noted that when the functional layer does not contain the first additive and the second additive, the positive electrode plate may not be provided with a functional layer.
  • the positive electrode plate may contain the positive electrode active material layer 2 and the functional layer 3 at the same time, the first additive may be dispersed in the positive electrode active material layer 2, and the second additive may be dispersed in the functional layer.
  • the first additive is more stable, and the combination of the first additive and the second additive can not only achieve the effect of graded sodium supplementation, but also reduce the impact of the byproducts produced by the second additive on the battery performance.
  • the total mass percentage of the first additive and the second additive is 4.7wt%-20wt% based on the total mass of the positive active material layer; for example, the total mass percentage of the first additive and the second additive can be 4.7wt%, 5wt%, 7.5wt%, 9wt%, 10wt%, 11wt%, 12wt%, 12.5wt%, 13wt%, 14wt%, 15wt%, 17.5wt% or 20wt%, etc.
  • the total mass percentage of the first additive and the second additive can preferably be 9wt%-15wt%.
  • the total mass percentage of the first additive and the second additive can be controlled to be 5wt%-20wt%, preferably 10wt%-15wt%, based on the total mass of the positive active material, the conductive agent and the binder, so as to meet the total mass percentage content requirement of the first additive and the second additive in the positive electrode plate.
  • the mass ratio of the first additive to the second additive may be (1-3):(1-3), and may further be 1:(1-3).
  • the mass ratio of the first additive to the second additive can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.
  • the first additive is also conducive to the formation of a stable CEI film on the surface of the positive electrode, but it is more stable than the second additive.
  • the mass of the first additive is too small relative to the second additive, on the one hand, it is not conducive to the formation of the CEI film, affecting the effect of improving the side reactions on the surface of the electrode and improving the high-temperature cycle stability of the sodium battery. On the other hand, it is not conducive to significantly reducing the use of the second additive with strong toxicity or corrosiveness; and if the mass of the first additive is too much relative to the second additive, it is not conducive to rapid sodium supplementation during the formation process, and it is difficult to achieve a better graded sodium supplementation effect.
  • the mass ratio of the first additive to the second additive can be 1:(1-2), which is not only conducive to achieving a better graded sodium supplementation effect, but also conducive to improving the energy density and high-temperature cycle stability of the battery, and is also conducive to further reducing the use of the second additive that is toxic or corrosive.
  • the thickness range of the functional layer 3 can be 0.5 ⁇ m to 5 ⁇ m.
  • the functional layer can be dispersed with the first additive but not the second additive, or with the second additive but not the first additive, or with the first additive and the second additive at the same time.
  • Increasing the thickness of the functional layer is conducive to improving the sodium supplement effect, but if its thickness is too large, it is easy to cause the resistance of the functional layer to be higher than the positive electrode plate, so that the polarization of the electrode plate is too large, affecting the electrochemical performance of the battery.
  • the present application can better balance the sodium supplement effect and the comprehensive performance of the battery by controlling the thickness of the functional layer within the above range.
  • the thickness of the functional layer can be controlled to be 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, etc.
  • additive refers to the first additive and/or the second additive; specifically, when the positive electrode active material layer or the functional layer contains only the first additive, the “additive” refers specifically to the first additive; when the positive electrode active material layer or the functional layer contains only the second additive, the “additive” refers specifically to the second additive; when the positive electrode active material layer or the functional layer contains only the first additive and the second additive, the “additive” refers to the first additive and the second additive.
  • the additives in the positive electrode active material layer need to meet the sodium supplement dosage requirements; when only the functional layer contains additives, the additives in the functional layer need to meet the sodium supplement dosage requirements; when the positive electrode active material layer contains additives and the functional layer contains additives, the sum of the additives in the positive electrode active material layer and the functional layer needs to meet the sodium supplement dosage requirements.
  • the current collector may be aluminum foil.
  • the type of positive electrode active material is not particularly limited, and those skilled in the art may flexibly select it in the relevant field according to actual needs.
  • the positive electrode active material may be
  • the invention may include at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue compounds; as some specific examples, the layered transition metal oxides may include but are not limited to NaFeO2 and Na2 / 3MnO2 , the polyanionic compounds may include but are not limited to Na3V2 ( PO4 ) 3 and NaFePO4, and the Prussian blue compounds may include but are not limited to Na2MnFe (CN) 6 ⁇ nH2O .
  • the second aspect of the present application provides a method for preparing the aforementioned positive electrode plate, comprising: forming a positive electrode active material layer on at least one side of the current collector; wherein a first additive is dispersed in the positive electrode active material layer, and the first additive comprises sodium monofluorophosphate and/or sodium difluorophosphate.
  • a second additive may be dispersed in the positive electrode active material layer, and the second additive may include at least one of Na 2 O, Na 2 O 2 , Na 2 CO 3 , Na 2 S, Na 3 P, NaN 3 , NaNiO 2 , NaCrO 2 , NaFeO 2 , Na 3 C 6 H 5 O 7 , Na 2 C 6 O 6 , NaF, and NaHF 2. It should be noted that the optional materials and mass percentages of the first additive and the second additive in the positive electrode sheet have been described in detail in the previous section and will not be repeated here.
  • the step of forming the positive electrode active material layer in which the additive is dispersed on the surface of the current collector comprises:
  • Step S11 preparing a positive electrode slurry, in which the additives, positive electrode active material, conductive agent and binder are dispersed; specifically, the solvent of the positive electrode slurry includes but is not limited to at least one of NMP (N-methylpyrrolidone), DMF (N,N-dimethylformamide), acetone and tetrahydrofuran, and the types and relative amounts of the positive electrode active material, conductive agent and binder are not particularly limited, and those skilled in the art can flexibly select according to actual needs.
  • NMP N-methylpyrrolidone
  • DMF N,N-dimethylformamide
  • acetone and tetrahydrofuran the types and relative amounts of the positive electrode active material, conductive agent and binder are not particularly limited, and those skilled in the art can flexibly select according to actual needs.
  • Step S12 coating the positive electrode slurry on the surface of the current collector to obtain a positive electrode slurry layer; the coating process includes but is not limited to a slit coating process and a scraping process.
  • Step S13 performing a first drying on the positive electrode slurry layer to obtain a positive electrode active material layer.
  • the temperature and time of the first drying are not particularly limited, and those skilled in the art can flexibly select according to actual needs.
  • the third aspect of the present application provides another method for preparing the aforementioned positive electrode sheet, comprising: forming a positive electrode active material layer on at least one side of a current collector; forming a functional layer on the side of the positive electrode active material layer away from the current collector; wherein a first additive is dispersed in the positive electrode active material layer, and the first additive and/or a second additive are dispersed in the functional layer, the first additive comprises sodium monofluorophosphate and/or sodium difluorophosphate, and the second additive comprises at least one of Na 2 O, Na 2 O 2 , Na 2 CO 3 , Na 2 S, Na 3 P, NaN 3 , NaNiO 2 , NaCrO 2 , NaFeO 2 , Na 3 C 6 H 5 O 7 , Na 2 C 6 O 6 , NaF, and NaHF 2.
  • the optional materials and mass percentages of the first additive and the second additive in the positive electrode sheet have been described in detail in the aforementioned section and will
  • the step of forming the positive electrode active material layer dispersed with the additive on the surface of the current collector may refer to steps S11-S13; the step of forming a functional layer on the surface of the positive electrode active material layer away from the current collector includes:
  • Step S21 preparing a sodium-supplementing suspension, in which a first additive and/or a second additive is dispersed, and whether to add the first additive to the sodium-supplementing suspension can be selected based on the type of additive in the positive electrode slurry layer;
  • the solvent of the sodium-supplementing suspension can include but is not limited to at least one of NMP (N-methylpyrrolidone), DMF (N,N-dimethylformamide), acetone, and tetrahydrofuran, and the concentration of the additive in the sodium-supplementing suspension can be flexibly selected according to actual needs.
  • Step S22 coating the sodium-supplementing suspension on the surface of the positive electrode active material layer to obtain a sodium-supplementing slurry layer; the coating process includes but is not limited to a slit coating process and a scraping process.
  • the preparation method of the positive electrode sheet provided in the second and third aspects of the present application is based on the same application concept as the positive electrode sheet of the first aspect of the present application.
  • the characteristics and effects described for the positive electrode sheet are also applicable to the preparation method of the positive electrode sheet, which will not be described one by one here.
  • the preparation method of the positive electrode sheet is not only simple in process, but also can better meet the needs of green environmental protection, and does not require the existing production equipment of the positive electrode sheet to be upgraded, which is suitable for mass production.
  • the first coulomb efficiency and first discharge capacity of the prepared positive electrode sheet are high, which can improve the energy density and cycle stability of the sodium battery.
  • the fourth aspect of the present application provides an energy storage device, which includes the positive electrode plate described above.
  • the energy storage device can be a sodium battery, and the sodium battery includes a sodium metal battery and a sodium ion battery.
  • the type of sodium battery is not particularly limited, and those skilled in the art can flexibly choose according to actual needs.
  • it can be a square battery, a cylindrical battery or a button battery, etc.
  • the square battery can be a laminated battery or a wound battery.
  • it can be a liquid battery or a semi-solid battery.
  • the energy storage device has all the characteristics and advantages of the positive electrode plate described above, which will not be repeated here. In general, the energy storage device has high energy density and cycle performance.
  • the energy storage device further comprises a negative electrode sheet and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, and the separator comprises a body and an aluminum oxide layer disposed on at least one side of the body, wherein the aluminum oxide can neutralize byproducts (such as HF or F2 ) that may be generated by the fluorine-containing additive, reduce the deterioration of the battery system, and improve the battery life.
  • byproducts such as HF or F2
  • the aluminum oxide layer is located on the surface of at least one side of the body, that is, the aluminum oxide layer can be located on a partial area or the entire surface of one side of the body, or on a partial area or the entire surface of both sides of the body.
  • the aluminum oxide layer is formed by, but not limited to, a coating method, for example, the aluminum oxide layer can be formed by coating an aluminum oxide slurry on the surface of the body, and the prepared aluminum oxide layer includes, but is not limited to, aluminum oxide particles, and can also include a small amount of a binder, and the binder is used to fix the aluminum oxide particles on the surface of the body.
  • the aluminum oxide particles have a small particle size and a large specific surface area, and the fluorine-containing gas can be adsorbed onto the surface of the aluminum oxide particles by physical adsorption to generate a surface compound aluminum fluoride, which effectively neutralizes the byproducts (such as HF or F2 ) that may be generated by the fluorine-containing additive.
  • the fluorine-containing gas can be adsorbed onto the surface of the aluminum oxide particles by physical adsorption to generate a surface compound aluminum fluoride, which effectively neutralizes the byproducts (such as HF or F2 ) that may be generated by the fluorine-containing additive.
  • the main body of the diaphragm may be a diaphragm base film, such as a polyethylene film, a polypropylene film, and the like.
  • the diaphragm further includes a fiber mesh layer disposed on at least one side of the body, the alumina layer includes alumina particles, and at least a portion of the alumina particles are distributed in the gaps of the fiber mesh layer.
  • This structural arrangement can increase the contact area between the alumina particles and the electrolyte. When the electrolyte and the first additive accidentally react to generate fluorine-containing gas, the alumina particles can contact and neutralize the fluorine-containing gas more promptly, preventing the fluorine-containing gas from damaging the SEI film, thereby increasing the service life of the energy storage device.
  • the alumina layer may also include but is not limited to alumina particles.
  • the alumina layer may consist only of alumina particles, or may also include components such as a binder.
  • a binder is beneficial to improving the adhesion between the alumina particles and the fiber mesh layer.
  • the material, thickness and mesh aperture of the fiber mesh layer are not particularly limited, as long as they can meet the embedding or fixation requirements of the alumina particles.
  • the material of the fiber mesh layer may include but is not limited to aramid.
  • the material of the fiber mesh layer may be an insulator or a poor conductor of electricity.
  • the thickness of the fiber mesh layer may be no less than 0.5 times the particle size of the alumina particles, and may be selected from 0.5 to 3 times, 0.8 times, 1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, etc., of the particle size of the alumina particles, so that the thickness of the fiber mesh layer is The degree meets the requirements of the given range, which is beneficial to take into account the thickness of the diaphragm on the basis of increasing the exposed area of the alumina particles, and avoids the excessive thickness affecting the performance of the battery such as the energy density;
  • the mesh aperture of the fiber mesh layer can be no less than 0.5 times the particle size of the alumina particles, and can be selected as 0.5 to 5 times, 0.8 times, 1 times, 1.2 times, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, etc., of the particle size of the alumina particles, so that the mesh aperture of the fiber mesh layer meets the requirements of the given range, which is beneficial to the
  • the preparation of the above-mentioned diaphragm includes the following steps: preparing a coating slurry, the coating slurry contains alumina particles and a binder; attaching a fiber mesh cloth to at least one side of the body, applying the coating slurry to the surface of the fiber mesh cloth, and then drying, and obtaining an alumina layer in which the alumina particles are embedded in the gaps of the fiber mesh cloth after drying.
  • the alumina layer is formed on the two side surfaces of the diaphragm, after attaching the fiber mesh cloth to the two side surfaces of the body, it can be directly double-sided coated by the equipment machine, and then dried, or it can be first single-sided coated and dried, and then the other side surface is coated and dried.
  • the binder used in the coating slurry includes but is not limited to organic polymer materials
  • the organic polymer materials include but are not limited to one or more of polyimide, aramid (preferably aramid micro-nano fiber), polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, and polyvinylidene fluoride.
  • the form of providing the organic polymer material includes but is not limited to organic powder and suspension, and the fiber mesh cloth includes but is not limited to aramid mesh cloth.
  • the particle size Dv50 of the aluminum oxide particles satisfies: 2 ⁇ m ⁇ Dv50 ⁇ 12 ⁇ m, such as Dv50 can be 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m or 12 ⁇ m, etc.
  • the Dv50 of the alumina particles is not less than 2 ⁇ m, which can ensure that there is sufficient gap between the particles, so that on the one hand, the fluorine-containing gas can contact the alumina particles faster and more smoothly and undergo a neutralization reaction, and on the other hand, the active ions can smoothly pass through the alumina layer and the diaphragm body and shuttle between the positive and negative electrode sheets; while the Dv50 of the alumina particles is too large, which is not conducive to their firm embedding in the fiber mesh layer.
  • the alumina particles are easy to fall out of the fiber mesh layer, thereby scratching the surface of the positive electrode sheet or the negative electrode sheet, which is not conducive to the cycle life of the energy storage device; the present application stipulates that the Dv50 of the alumina particles is not greater than 12 ⁇ m, which is more conducive to improving the firmness of their embedding in the fiber mesh layer, thereby improving the cycle life of the energy storage device.
  • the thickness of the aluminum oxide layer may be 0.1 ⁇ m to 10 ⁇ m.
  • the thickness of the aluminum oxide layer may be 0.1 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m or 10 ⁇ m, etc.
  • the thickness of the aluminum oxide layer is greater than or equal to 0.1 ⁇ m, which can effectively improve the insulation of the diaphragm and neutralize more fluorine-containing gases; the thickness of the aluminum oxide layer is less than or equal to 10 ⁇ m, which can ensure the impregnation performance of the electrolyte.
  • the diaphragm may also satisfy at least one of the following conditions: the porosity of the diaphragm is ⁇ 30%, the average pore size of the diaphragm is ⁇ 25nm, the ionic conductivity of the diaphragm is ⁇ 1.1mS/cm, and the thickness of the body is 2 ⁇ m to 20 ⁇ m.
  • the diaphragm satisfies the given range of conditions, it is more conducive to the energy storage device to obtain better electrochemical performance.
  • the fifth aspect of the present application provides an electrical device, comprising the above energy storage device, wherein the energy storage device is used to provide electrical energy.
  • the energy storage device can be used as a power source for the electrical device, or as a power source for the electrical device.
  • the electrical device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop computer), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck), an electric train, a ship, a satellite, an energy storage module, an energy storage cabinet, or an energy storage container.
  • a positive electrode active material Na 0.67 Ni 0.33 Mn 0.67 O 2
  • a conductive agent conductive carbon black SP
  • a binder polyvinylidene fluoride PVDF
  • NMP N-methylpyrrolidone
  • a first additive Na 2 PO 3 F
  • the positive electrode slurry is coated on the surface of a current collector to obtain a positive electrode slurry layer, the positive electrode slurry layer is dried, and a positive electrode active material layer with a thickness of 90 ⁇ m is obtained after rolling, and the surface density of the positive electrode active material layer is 14 mg/cm 2 ;
  • the second additive (NaF) is dispersed in N-methylpyrrolidone (NMP) solvent to obtain a sodium supplement suspension; the sodium supplement suspension is coated on the surface of the positive electrode active material layer to obtain a sodium supplement slurry layer, and the sodium supplement slurry layer is dried to obtain a functional layer with a thickness of 2 ⁇ m, and the mass ratio of the additive in the functional layer to the additive in the positive electrode active material layer is 1:1.
  • NMP N-methylpyrrolidone
  • the prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the electrolyte is injected into the electrode assembly; then the sodium battery is obtained after vacuum packaging, standing, forming, and shaping processes.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector.
  • the negative electrode active material layer is formed by a negative electrode active material (hard carbon), a conductive agent (conductive carbon black SP), carboxymethyl cellulose CMC, and styrene butadiene rubber SBR in a mass ratio of 95.5:1:1:2.5.
  • the compacted density of the negative electrode active material layer is 0.95g/ cm3 and the thickness is 150 ⁇ m;
  • the separator is a ceramic separator with a single-sided Al2O3 coating (the ceramic separator is formed by attaching an aramid fiber mesh cloth to one side of the base film and A coating slurry including alumina particles and PVDF is coated on the mesh cloth and dried, the thickness of the Al2O3 coating is 2 ⁇ m, the base film is PP (polypropylene), and the thickness of the base film is 16 ⁇ m; the concentration of the electrolyte NaClO4 in the electrolyte is 1mol/L, and the solvent is a composite solvent of polypropylene carbonate PC+polyethylene carbonate EC+dimethyl carbonate DMC.
  • a metallic sodium sheet was selected as the negative electrode sheet, a porous glass fiber was selected as the separator, the concentration of NaPF6 in the electrolyte was 1 mol/L, the solvent of the electrolyte was a mixed solvent, the volume ratio of ethylene carbonate EC, propylene carbonate PC and dimethyl carbonate DMC in the mixed solvent was 1:1:1, the electrolyte also contained 5% by volume of fluoroethylene carbonate FEC, and the button cells were assembled in an argon glove box with a water oxygen value below 0.1 ppm.
  • the total amount of additives refers to the amount of the first additive; when the positive electrode sheet contains only the second additive, the total amount of additives refers to the amount of the second additive; when the positive electrode sheet contains the first additive and the second additive, the total amount of additives refers to the total amount of the first additive and the second additive; when the additive is only dispersed in the positive active material layer, the “total amount of additives” refers to the amount of additives in the positive active material layer; when the additive is dispersed in the positive active material layer and the functional layer at the same time, the “amount of additives” refers to the total amount of additives in the positive active material layer and the functional layer.
  • the difference between Examples 1-5 is that the amount of the second additive in the functional layer is different; the difference between Example 3, Examples 6-9, and Example 13 is that the thickness of the Al2O3 coating in the full battery separator is different; the difference between Example 10 and Example 3 is that the types of additives in the functional layer are different; the difference between Examples 11-12 and Example 3 is that the types of the first additive in the positive electrode active material layer are different; the difference between Examples 15, 16, 18, and 19 and Example 1 is that the types of additives in the functional layer are different; Example 14, Example 17, and Comparative Examples 1-2 do not contain a functional layer, and the difference between Example 14, Example 17, and Comparative Example 2 is that the types of additives in the positive electrode active material layer are different; Comparative Example 1 does not contain an additive.
  • the amounts of additives in the positive electrode active material layer of Examples 1-19 and Comparative Example 2 are the same; when the amount of additives in the positive electrode active material layer changes, the total mass of the additives and the positive electrode active material is kept unchanged by adjusting the amount of the positive electrode active material.
  • Example 1 The charge and discharge capacity of the half-cells prepared in Example 1 and Comparative Example 1 were tested under the same conditions.
  • the test method is as follows: The half-cell is mounted on a blue battery tester and placed in a test environment at 25 ⁇ 2°C. Setting procedure: Stand for 10 minutes ⁇ Charge to 4.2V at a constant current of 0.1C ⁇ let stand for 10min ⁇ discharge to 2.0V at a constant current of 0.1C, and repeat the above steps 3 times as a repetitive unit.
  • FIG3 shows a comparison of the charge and discharge curves of the half-cells prepared in Example 1 and Comparative Example 1.
  • the charge and discharge specific capacity of the half-cell prepared in Example 1 is higher than that of Comparative Example 1, indicating that adding additives to the positive electrode sheet can increase the initial charge and discharge specific capacity of the sodium battery, thereby increasing the energy density of the sodium battery.
  • the first discharge capacity test method clamp the whole battery with a fixture and install it on the test instrument. After the whole battery is formed and aged, place it in a 25 ⁇ 2°C test environment. Set the program: stand for 10 minutes ⁇ discharge to 2.0V at a constant current of 0.1C ⁇ stand for 10 minutes ⁇ charge to 4.0V at a constant current of 0.1C ⁇ stand for 10 minutes ⁇ discharge to 1.5V at a constant current of 0.1C, and then test the battery capacity.
  • the positive electrode active material layer and the functional layer in the positive electrode sheet contains sodium monofluorophosphate and/or sodium difluorophosphate, which can effectively improve the first coulombic efficiency and the first discharge capacity of the positive electrode, and improve the normal temperature and high temperature cycle stability of the sodium battery; further, compared with only the positive electrode active material layer dispersed with the first additive, the surface of the positive electrode active material layer has a functional layer, and the material of the functional layer includes the first additive and/or the second additive, which can further improve the first coulombic efficiency; further, the material of the functional layer includes the second additive, which can further improve the first coulombic efficiency; from the comparison between Example 3 and Example 10, it can be seen that compared with the first additive dispersed in the functional layer, the second additive dispersed in the functional layer can further improve the first coulombic efficiency; from the comparison between Examples 14 and 17 and Comparative Example 2, it can be seen that compared with conventional fluorine-containing additives, the first additive can
  • first and second are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as “first” or “second” may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of “plurality” is two or more, unless otherwise clearly and specifically defined.

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Abstract

正极极片及其制备方法、储能装置、用电设备。正极极片包括：集流体、正极活性物质层和第一添加剂，所述正极活性物质层设置在所述集流体的至少一侧，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠。

Description

正极极片及其制备方法、储能装置、用电设备 技术领域
本申请涉及储能技术领域，具体涉及正极极片及其制备方法、储能装置、用电设备。
背景技术
在钠离子电池循环过程中，碳负极会消耗正极活性材料中的钠元素以形成固态电解质界面(SEI)膜。正极活性材料中钠元素的不可逆消耗很大程度上降低了钠离子电池的能量密度，这一问题已成为制约钠离子电池发展的瓶颈之一。预钠化技术可有效补充正极活性材料在循环过程中的不可逆钠损耗，因此在钠离子电池的实际应用中具有重要地位。目前的补钠路线包括负极补钠路线和正极补钠路线，与负极补钠路线相比，在正极中添加补钠剂的正极补锂路线安全性更高，与现有电池生产工艺的兼容性更好。
目前常用的补钠剂中通常不含氟元素。与不含氟补钠剂相比，含氟补钠剂中的氟元素有利于形成固态电解质界面(CEI)膜。然而，现有含氟补钠剂具有较强的毒性，不利于商业转化应用。
公开内容
本申请旨在至少在一定程度上解决相关技术中的技术问题之一。
为了实现上述目的，本申请的第一方面提供了一种正极极片，用于钠电池，包括集流体、正极活性物质层和第一添加剂，所述正极活性物质层设置在所述集流体的至少一侧，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠。
相对于现有技术，本申请的正极极片至少包括如下所述的有益效果：一方面，单氟磷酸钠和二氟磷酸钠提供额外钠离子，发挥补钠剂的作用，能够有效提升正极的首次库伦效率和首次放电容量，从而提高钠电池的能量密度；另一方面，单氟磷酸钠和二氟磷酸钠还发挥正极成膜添加剂的作用，能够在补充钠离子过程中形成副产物NaF和Na3PO3，NaF和Na3PO3能够在正极极片表面形成界面层，界面层的形成能够减少副反应，减少了电池在高温存储时的自放电，从而提高了钠电池的高温循环稳定性；单氟磷酸钠和二氟磷酸钠无毒， 因此正极极片制备过程更加环保；单氟磷酸钠和二氟磷酸钠性质稳定、获取方法简单且成本低廉，适合大批量生产。
本申请的第二方面提供了一种制备前述正极极片的方法，包括：在集流体的至少一侧形成正极活性物质层；其中，所述正极活性物质层中分散有第一添加剂，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠。该正极极片的制备方法不仅工艺简单，能更好地满足绿色环保的需求，还不需要对现有正极极片的生产设备进行升级，适合大批量生产，制得的正极极片的首次库伦效率和首次放电容量较高，能够提高钠电池的能量密度和循环稳定性。
本申请的第三方面提供了一种制备前述正极极片的方法，包括：在集流体的至少一侧形成正极活性物质层；在所述正极活性物质层背离所述集流体的一侧形成功能层；其中，所述正极活性物质层中分散有第一添加剂，所述功能层中分散有所述第一添加剂和/或第二添加剂，所述第二添加剂包括Na2O、Na2O2、Na2CO3、Na2S、Na3P、NaN3、NaNiO2、NaCrO2、NaFeO2、Na3C6H5O7、Na2C6O6、NaF、NaHF2中的至少一种。该正极极片的制备方法不仅工艺简单，能更好地满足绿色环保的需求，还不需要对现有正极极片的生产设备进行升级，适合大批量生产，制得的正极极片的首次库伦效率和首次放电容量较高，能够提高钠电池的能量密度和循环稳定性。
本申请的第四方面提供了一种储能装置，包括前述正极极片。该储能装置具有前面所述的正极极片所具有的全部特征以及优点，在此不再赘述。总的来说，该储能装置具有较高的能量密度和循环性能。
本申请的第五方面提供了一种用电设备，包括前述储能装置。该用电设备具有前面所述的储能装置所具有的全部特征以及优点，在此不再赘述。
附图说明
本申请的上述和/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为本申请实施例提供的一种正极极片的结构示意图；
图2为本申请实施例提供的另一种正极极片的结构示意图；
图3为对实施例1和对比例1制备的半电池的充放电曲线；
附图标记：
1-集流体；2-正极活性物质层；3-功能层。
具体实施方式
下面对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。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。所用试剂未注明生产厂商者，均为可以通过市购获得的常规产品。
本申请的第一方面提供了一种正极极片，用于钠电池，参见图1，包括：集流体1、正极活性物质层2和第一添加剂，所述正极活性物质层2设置在所述集流体1至少一侧，所述第一添加剂包括单氟磷酸钠(Na2PO3F)和/或二氟磷酸钠(NaPO2F2)。一方面，单氟磷酸钠和二氟磷酸钠提供额外钠离子，发挥补钠剂的作用，能够有效提升正极的首次库伦效率和首次放电容量，从而提高钠电池的能量密度；另一方面，单氟磷酸钠和二氟磷酸钠还发挥正极成膜添加剂的作用，能够在补充钠离子过程中形成副产物NaF和Na3PO3，NaF和Na3PO3能够在正极极片表面形成界面层，界面层的主要成分包括Na2O、Na2CO3、NaF、Na3PO3等物质，界面层的形成能够减少副反应，减少了电池在高温存储时的自放电，从而提高了钠电池的高温循环稳定性；单氟磷酸钠和二氟磷酸钠无毒，因此正极极片制备过程更加环保；单氟磷酸钠和二氟磷酸钠性质稳定、获取方法简单且成本低廉，适合大批量生产。
在本申请的一些实施方式中，所述第一添加剂可以优选单氟磷酸钠(Na2PO3F)。与二氟磷酸钠相比，单氟磷酸钠具有更高的钠含量，有利于在满足补钠效果的同时进一步降低添加剂的用量。
在本申请的一些实施方式中，所述正极活性物质层2中可以分散有所述第一添加剂(未示出)。一方面，第一添加剂分散在正极活性物质层中有利于第一添加剂发挥补钠作用，从而有利于减少正极活性材料中的钠元素的消耗，进而有利于提高正极的首次库伦效率；另一方面，第一添加剂分散在正极活性物质层中有利于第一添加剂在正极极片表面形成界面层，从而有利于减少副反应，进而有利于提高钠电池的高温循环稳定性。
在本申请的一些实施方式中，参见图2，所述正极极片还可以包括功能层3，所述功能 层3位于所述正极活性物质层2背离所述集流体1的一侧，此时正极活性物质层2和功能层3中的至少之一分散有第一添加剂。例如，作为一些具体实施例，所述功能层中可以分散有所述第一添加剂，此时，所述正极活性物质层中可以含有第一添加剂，也可以不含第一添加剂；作为另一些具体实施例，所述功能层可以不含第一添加剂，此时所述正极活性物质层中可以分散有第一添加剂。功能层可以单纯的起到补钠作用，与在正极活性物质层中分散第一添加剂相比，功能层不仅能够与电解液充分接触，使得钠元素能够以更快的速度迁移至负极极片附近进行成膜消耗，还有利于减少正极活性物质产生的钠的消耗，提高首次库伦效率。
在本申请的一些实施例中，以所述正极活性物质层的总质量为基准，所述第一添加剂的质量百分比为4.7wt％-20wt％；第一添加剂的质量百分比过大，一方面，正极极片中正极活性物质的相对含量过小，会对钠电池的能量密度产生一定的负面影响；另一方面，若功能层中第一添加剂的质量百分比过大，其厚度也相对较大，易导致极片极化明显增加，影响电池的电化学性能；第一添加剂的质量百分比过小，难以起到明显的补钠效果。本申请通过将所述第一添加剂的质量百分比控制在上述范围内，可以更好地兼顾补钠效果和钠电池的综合性能。例如，所述第一添加剂的质量百分比可以为4.7wt％、5wt％、7.5wt％、9wt％、10wt％、11wt％、12wt％、12.5wt％、13wt％、14wt％、15wt％、17.5wt％或20wt％等，优选可以为9wt％-15wt％。作为一些具体示例，在制备正极活性物质层时，可以以所述正极活性物质、导电剂和粘结剂的总质量为基准，控制第一添加剂的质量百分比为5wt％-20wt％，优选为10wt％-15wt％，以满足正极极片中第一添加剂的质量百分比要求。
在本申请的一些实施方式中，所述正极极片还可以包括第二添加剂，所述第二添加剂可以包括Na2O、Na2O2、Na2CO3、Na2S、Na3P、NaN3、NaNiO2、NaCrO2、NaFeO2、Na3C6H5O7、Na2C6O6、NaF、NaHF2中的至少一种。第二添加剂仅具有补钠的作用，相对于第一添加剂，第二添加剂的分解电位较低，这使得钠元素能够以更快的速度迁移至负极极片附近进行成膜消耗，从而有利于正极的首次库伦效率。
在本申请的一些实施方式中，所述第二添加剂可以优选NaF和/或NaHF2。NaF和NaHF2具有更高的钠含量，因此使用更少的量就可以达到一定的补钠效果，补钠效果更高。
在本申请的一些实施方式中，正极活性物质层2中可以分散有所述第二添加剂(未示出)。在此基础上，第一添加剂与第二添加剂的质量比可以为(1-3):(1-3)，进一步可 以为1:(1-3)，由此，不仅可以更好地兼顾分级补钠效果和对电池电化学性能的提升效果，还更符合绿色环保的需求。
在本申请的一些实施方式中，正极极片还可以包括功能层3，所述第二添加剂可以分散在所述正极活性物质层2中和/或所述功能层3中。例如，当第一添加剂仅分散在正极活性物质层中时，所述第二添加剂可以分散在正极活性物质层中，也可以仅分散在功能层中，也可以同时分散在所述正极活性物质层中和所述功能层中；当第一添加剂仅分散在功能层中时，所述第二添加剂可以分散在正极活性物质层中，也可以分散在功能层中，也可以同时分散在所述正极活性物质层中和所述功能层中；当第一添加剂同时分散在所述正极活性物质层中和所述功能层中时，所述第二添加剂可以分散在正极活性物质层中，也可以分散在功能层中，也可以同时分散在所述正极活性物质层中和所述功能层中。即，当正极极片中同时含有第二添加剂和功能层3时，既可以使所述功能层中分散有所述第二添加剂，也可以使所述功能层中同时分散有所述第一添加剂和所述第二添加剂。需要说明的是，当功能层中不含有第一添加剂和第二添加剂时，所述正极极片可以不设置功能层。
作为一些优选的实施方式，所述正极极片可以同时含有所述正极活性物质层2和功能层3，所述第一添加剂可以分散于所述正极活性物质层2中，所述第二添加剂可以分散于所述功能层中。相对于第二添加剂，第一添加剂更为稳定，将第一添加剂和第二添加剂配合使用不仅能够起到分级补钠的效果，还能够减少第二添加剂产生的副产物对电池性能的影响。
在本申请的一些实施例中，当正极极片同时含有第一添加剂和第二添加剂时，以所述正极活性物质层的总质量为基准，所述第一添加剂和所述第二添加剂的总质量百分比为4.7wt％-20wt％；例如，所述第一添加剂和所述第二添加剂的总质量百分比可以为4.7wt％、5wt％、7.5wt％、9wt％、10wt％、11wt％、12wt％、12.5wt％、13wt％、14wt％、15wt％、17.5wt％或20wt％等。所述第一添加剂和所述第二添加剂的总质量百分比可以优选为9wt％-15wt％。作为一些具体示例，在制备正极活性物质层时，可以以所述正极活性物质、导电剂和粘结剂的总质量为基准，控制第一添加剂和第二添加剂的总质量百分比为5wt％-20wt％，优选为10wt％-15wt％，以满足正极极片中第一添加剂和第二添加剂的质量百分比总含量要求。
在本申请的一些实施例中，当正极极片中同时含有第一添加剂和第二添加剂时，所述第一添加剂与所述第二添加剂的质量比可以为(1-3):(1-3)，进一步可以为1:(1-3)， 示例性的，在满足补钠剂量要求的基础上，所述第一添加剂与所述第二添加剂的质量比可以为1:1、1:1.5、1:2、1:2.5、1:3等。第一添加剂除起到补钠作用外，还有利于在正极极片表面形成稳定的CEI膜，但其相对于第二添加剂更稳定，若第一添加剂相对于第二添加剂的质量过少，一方面不利于CEI膜的形成，影响改善极片表面副反应和提高钠电池高温循环稳定性的效果，另一方面还不利于显著降低具有毒性或腐蚀性较强的第二添加剂的使用；而若第一添加剂相对于第二添加剂的质量过多，又不利于化成过程中的快速补钠，难以实现较好的分级补钠效果。通过控制第一添加剂和第二添加剂的质量在所给范围内，不仅可以更好地兼顾分级补钠效果和对电池电化学性能的提升效果，还更符合绿色环保的需求。进一步地，所述第一添加剂与所述第二添加剂的质量比可以为1:(1-2)，由此不仅有利于达到更好的分级补钠效果，有利于提高电池的能量密度和高温循环稳定性，还有利于进一步降低具有毒性或腐蚀性的第二添加剂的使用。
在本申请的一些实施例中，所述功能层3的厚度范围值可以为0.5μm～5μm，此时，所述功能层中可以分散有所述第一添加剂而不含第二添加剂，也可以分散有第二添加剂而不含第一添加剂，也可以同时分散有第一添加剂和所述第二添加剂。增大功能层厚度有利于提高补钠效果，但若其厚度过大易导致功能层阻值高于正极极片，使极片极化过大，影响电池的电化学性能，本申请通过将功能层厚度控制在上述范围内，可以更好地兼顾补钠效果和电池的综合性能。示例性的，在满足补钠剂量要求的基础上，可以控制所述功能层的厚度为0.5μm、1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm等。
为了便于后续描述，本申请引入“添加剂”这一概念，“添加剂”指代第一添加剂和/或第二添加剂；具体的，当正极活性物质层或功能层中仅含有第一添加剂时，所述“添加剂”专指第一添加剂；当正极活性物质层或功能层中仅含有第二添加剂时，所述“添加剂”专指第二添加剂；当正极活性物质层或功能层中仅含有第一添加剂和第二添加剂时，所述“添加剂”指代第一添加剂和第二添加剂。需要说明的是，仅正极活性物质层中含有添加剂时，正极活性物质层中的添加剂需要满足补钠剂量要求；仅功能层中含有添加剂时，功能层中的添加剂需要满足补钠剂量要求；当正极活性物质层中含有添加剂且功能层中含有添加剂时，需要正极活性物质层和功能层中的添加剂总和满足补钠剂量要求。
在本申请的一些实施例中，所述集流体可以为铝箔。正极活性物质的种类并不受特别限制，本领域技术人员可以根据实际需要在所属领域内灵活选择，例如，正极活性物质可 以包括层状过渡金属氧化物、聚阴离子化合物、普鲁士蓝类化合物中至少一种；作为一些具体示例，层状过渡金属氧化物可以包括但不限于NaFeO2、Na2/3MnO2，聚阴离子化合物可以包括但不限于Na3V2(PO4)3、NaFePO4，普鲁士蓝类化合物可以包括但不限于Na2MnFe(CN)6·nH2O。
基于同样的申请构思，本申请的第二方面提供了一种制备前述的正极极片的方法，包括：在集流体的至少一侧形成正极活性物质层；其中，所述正极活性物质层中分散有第一添加剂，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠。
在一些实施方式中，所述正极活性物质层中还可以分散有第二添加剂，所述第二添加剂可以包括Na2O、Na2O2、Na2CO3、Na2S、Na3P、NaN3、NaNiO2、NaCrO2、NaFeO2、Na3C6H5O7、Na2C6O6、NaF、NaHF2中的至少一种。需要说明的是，正极极片中第一添加剂和第二添加剂的可选材料以及质量百分数已经在前述部分做了详细说明，此处不再赘述。
在本申请的一些实施方式中，在所述集流体的表面形成分散有所述添加剂的所述正极活性物质层的步骤包括：
步骤S11、配制正极浆料，所述正极浆料中分散有所述添加剂、正极活性物质、导电剂和粘结剂；具体的，正极浆料的溶剂包括但不限于NMP(N-甲基吡咯烷酮)、DMF(N,N-二甲基甲酰胺)、丙酮、四氢呋喃中的至少一种，正极活性物质、导电剂和粘结剂的种类和相对用量并不受特别限制，本领域技术人员可以根据实际需要灵活选择。
步骤S12、将所述正极浆料涂覆在集流体的表面，得到正极浆料层；涂覆工艺包括但不限于狭缝涂布工艺、刮涂工艺。
步骤S13、对所述正极浆料层进行第一干燥，得到正极活性物质层。需要说明的是，第一干燥的温度和时间并不受特别限制，本领域技术人员可以根据实际需要灵活选择。
基于同样的申请构思，本申请的第三方面提供了另一种制备前述的正极极片的方法，包括：在集流体的至少一侧形成正极活性物质层；在所述正极活性物质层背离所述集流体的一侧形成功能层；其中，所述正极活性物质层中分散有第一添加剂，所述功能层中分散有所述第一添加剂和/或第二添加剂，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠，所述第二添加剂包括Na2O、Na2O2、Na2CO3、Na2S、Na3P、NaN3、NaNiO2、NaCrO2、NaFeO2、Na3C6H5O7、Na2C6O6、NaF、NaHF2中的至少一种。需要说明的是，正极极片中第一添加剂和第二添加剂的可选材料以及质量百分数已经在前述部分做了详细说明，此处不再赘述。
在本申请的一些实施方式中，在所述集流体的表面形成分散有所述添加剂的所述正极活性物质层的步骤可以参见步骤S11-S13；在所述正极活性物质层背离所述集流体的一侧表面形成功能层的步骤包括：
步骤S21、配制补钠悬浊液，所述补钠悬浊液中分散有第一添加剂和/或第二添加剂，可以基于正极浆料层中的添加剂种类选择是否在补钠悬浊液中加入第一添加剂；补钠悬浊液的溶剂可以包括但不限于NMP(N-甲基吡咯烷酮)、DMF(N,N-二甲基甲酰胺)、丙酮、四氢呋喃中的至少一种，补钠悬浊液中添加剂的浓度可以根据实际需要灵活选择。
步骤S22、将所述补钠悬浊液涂覆在所述正极活性物质层的表面，得到补钠浆料层；涂覆工艺包括但不限于狭缝涂布工艺、刮涂工艺。
步骤S23、对所述补钠浆料层进行第二干燥，得到功能层。需要说明的是，第二干燥的温度和时间并不受特别限制，本领域技术人员可以根据实际需要灵活选择。
在一些实施例中，功能层还可以采用真空蒸镀等其他工艺形成。
需要说明的是，本申请第二方面和第三方面提供的正极极片的制备方法与本申请第一方面的正极极片是基于同样的申请构思提出的，针对所述正极极片所描述的特征及效果同样适用于该正极极片的制备方法，此处不再一一赘述。总的来说，该正极极片的制备方法不仅工艺简单，能更好的满足绿色环保的需求，还不需要对现有正极极片的生产设备进行升级，适合大批量生产，制得的正极极片的首次库伦效率和首次放电容量较高，能够提高钠电池的能量密度和循环稳定性。
本申请的第四方面提供了一种储能装置，储能装置包括前面所述的正极极片，储能装置可以为钠电池，钠电池包括钠金属电池、钠离子电池。需要说明的是，该钠电池的种类并不受特别限制，本领域技术人员可以根据实际需要灵活选择，例如，可以为方形电池、圆柱电池或扣式电池等，所述方形电池又可以为叠片电池或卷绕电池，再例如，可以为液态电池或半固态电池等。此外，还需要说明的是，该储能装置具有前面所述的正极极片所具有的全部特征以及优点，在此不再赘述。总的来说，该储能装置具有较高的能量密度和循环性能。
在本申请的一些实施例中，储能装置还包括负极极片和隔膜，所述正极极片和所述负极极片之间设有所述隔膜，所述隔膜包括本体和设在所述本体至少一侧上的氧化铝层，氧化铝能够中和含氟添加剂可能产生的副产物(如HF或F2)，减少电池体系恶化，改善电 池的稳定性。
作为一些具体示例，氧化铝层位于本体至少一侧的表面上，即，氧化铝层可以位本体一侧表面的部分区域或者整个表面，也可以位本体两侧表面的部分区域或者整个表面。进一步的，氧化铝层的形成方式包括但不限于涂布法，例如可以通过在本体表面涂覆氧化铝浆料形成氧化铝层，制备得到的氧化铝层中包括但不限于氧化铝颗粒，例如还可以包括少量粘结剂，粘结剂用以将氧化铝颗粒固定在本体表面。其中，氧化铝颗粒粒径较小，比表面积大，可以通过物理吸附作用将含氟气体吸附到氧化铝颗粒表面，生成表面化合物氟化铝，有效中和含氟添加剂可能产生的副产物(如HF或F2)。
作为一些具体示例，所述隔膜的本体可以为隔膜基膜，例如可以为聚乙烯膜、聚丙烯膜等。
在本申请的一些实施例中，所述隔膜还包括设在所述本体至少一侧的纤维网格层，所述氧化铝层包括氧化铝颗粒，所述氧化铝颗粒的至少一部分分布于所述纤维网格层的间隙中，该结构设置能够增大氧化铝颗粒与电解液的接触面积，当电解液与第一添加剂偶然性发生副反应生成含氟气体时，氧化铝颗粒能够更及时地接触并中和掉含氟气体，防止含氟气体破坏SEI膜，进而提升了储能装置的使用寿命。需要说明的是，该结构设置中，所述氧化铝层也可以包括但不限于氧化铝颗粒，例如，所述氧化铝层可以仅由氧化铝颗粒组成，也可以同时包括粘结剂等组分，利用粘结剂有利于提高氧化铝颗粒与纤维网格层间的附着力。另外，还需要说明的是，所述纤维网格层的材质、厚度及网格孔径并不受特别限制，只要能够满足氧化铝颗粒的嵌入或固定需求即可，例如，纤维网格层的材质可以包括但不限于芳纶，优选地，纤维网格层的材质可以为绝缘体或电的不良导体；再例如，纤维网格层的厚度可以不小于氧化铝颗粒粒径的0.5倍，可选为氧化铝颗粒粒径的0.5～3倍、0.8倍、1倍、1.2倍、1.5倍、2倍、2.5倍，等等，使纤维网格层的厚度满足所给范围需求，有利于在提高氧化铝颗粒裸露面积的基础上兼顾隔膜的厚度，避免其厚度过大影响电池能量密度等性能；又例如，所述纤维网格层的网格孔径可以不小于氧化铝颗粒粒径的0.5倍，可选为氧化铝颗粒粒径的0.5～5倍等、0.8倍、1倍、1.2倍、1.5倍、2倍、2.5倍、3倍、3.5倍、4倍、4.5倍，等等，使纤维网格层的网格孔径满足所给范围需求，有利于氧化铝颗粒的有效嵌入和分散分布。可以理解的是，每个氧化铝颗粒可以分别独立地完全嵌入纤维网格层的间隙中或部分嵌入纤维网格层的间隙中，每个纤维网格层的网格可以分别独立地分 布一个或多个氧化铝颗粒。
作为一些具体示例，上述隔膜的制备包括以下步骤：配制涂布浆料，涂布浆料中含有氧化铝颗粒和粘结剂；在本体的至少一侧表面贴附纤维网格布，将涂布浆料涂覆在纤维网格布的表面，随后进行干燥，干燥后得到氧化铝颗粒嵌入在纤维网格布的间隙中的氧化铝层。当在隔膜的两侧表面形成氧化铝层时，在本体的两侧表面贴附纤维网格布之后，既可以通过设备机台直接进行双面涂覆，随后进行干燥，也可以先进行单面涂覆和干燥，随后进行另一侧表面的涂覆和干燥。需要说明的是，涂布浆料中采用的粘结剂包括但不限于有机聚合物材料，所述有机聚合物材料包括但不限于聚酰亚胺、芳纶(优选芳纶微纳米纤维)、聚偏二氟乙烯、聚甲基丙烯酸甲酯、聚丙烯腈、聚偏氟乙烯中的一种或多种，有机聚合物材料的提供形式包括但不限于有机粉料、悬浮液，纤维网格布包括但不限于芳纶网格布。
进一步的，所述氧化铝颗粒的粒径Dv50满足：2μm≤Dv50≤12μm，如Dv50可以为2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm或12μm等。氧化铝颗粒的Dv50不小于2μm，能够保证颗粒之间有足够的间隙，从而一方面使得含氟气体可以更快、更顺畅地与氧化铝颗粒接触并发生中和反应，另一方面还使得活性离子能够顺畅的通过氧化铝层和隔膜本体在正负极极片之间穿梭；而氧化铝颗粒的Dv50过大，不利于其牢固地嵌入纤维网格层内，在隔膜与正极极片、负极极片一起卷绕形成电极组件的工序时，氧化铝颗粒易从纤维网格层中脱出，从而划伤正极极片或负极极片的表面，不利于储能装置的循环寿命；本申请中限定氧化铝颗粒的Dv50不大于12μm更有利于提高其嵌在纤维网格层中的牢固程度，从而提高储能装置的循环寿命。
进一步的，所述氧化铝层的厚度可以为0.1μm～10μm。示例性的，氧化铝层的厚度可以为0.1μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm等。氧化铝层的厚度大于或等于0.1μm能够有效提高隔膜的绝缘性，且能够中和掉较多的含氟气体；氧化铝层的厚度小于或等于10μm，能够保证电解液的浸渍性能。
进一步的，所述隔膜还可以满足以下条件中的至少之一：所述隔膜的孔隙率≥30％、所述隔膜的平均孔径≥25nm、所述隔膜的离子电导率≥1.1mS/cm、所述本体的厚度为2μm～20μm，使隔膜满足所给条件范围更有利于使储能装置获得较好的电化学性能。
本申请的第五方面提供了一种用电设备，包括上述储能装置，所述储能装置用于提供电能。具体的，所述储能装置可以作为所述用电设备的电源，也可以作为所述用电设备的 能量存储单元。所述用电设备可以但不限于是移动设备(例如手机、笔记本电脑)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车)、电气列车、船舶及卫星、储能模组、储能柜或储能集装箱。
为了使本申请实施例所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
实施例1
(1)制备正极极片
将正极活性物质(Na0.67Ni0.33Mn0.67O2)、导电剂(导电炭黑SP)和粘结剂(聚偏氟乙烯PVDF)按照质量比为95.5：2：2.5分散在N-甲基吡咯烷酮(NMP)溶剂中，并加入第一添加剂(Na2PO3F)，得到正极浆料，以正极活性物质、导电剂和粘结剂的总质量为基准，第一添加剂的用量为5％；将正极浆料涂覆在集流体的表面，得到正极浆料层，对正极浆料层进行干燥，辊压后得到厚度为90μm的正极活性物质层，正极活性物质层的面密度为14mg/cm2；
将第二添加剂(NaF)分散在N-甲基吡咯烷酮(NMP)溶剂中得到补钠悬浊液；将补钠悬浊液涂覆在正极活性物质层的表面，得到补钠浆料层，对补钠浆料层进行干燥，得到厚度为2μm的功能层，功能层中的添加剂与正极活性物质层中的添加剂的质量比为1：1。
(2)制备全电池
将制得的正极极片、隔膜、负极极片按顺序叠好，使隔膜处于正极极片与负极极片之间，然后卷绕得到电极组件；将电极组件置于外包装中，向电极组件中注入电解液；随后经过真空封装、静置、化成、整形工序，获得钠电池。其中，负极极片包括负极集流体和位于负极集流体表面的负极活性物质层，负极活性物质层由负极活性物质(硬碳)、导电剂(导电炭黑SP)、羧甲基纤维素CMC和丁苯橡胶SBR按照质量比为95.5:1:1:2.5形成，负极活性物质层的压实密度为0.95g/cm3，厚度为150μm；隔膜为具有单面Al2O3涂层的陶瓷隔膜(该陶瓷隔膜通过以下方式形成，在基膜一侧贴附芳纶纤维网格布，并在芳纶纤维 网格布上涂布包括氧化铝颗粒和PVDF的涂布浆料、干燥)，Al2O3涂层的厚度为2μm，基膜为PP(聚丙烯)，基膜的厚度为16μm；电解液中电解质NaClO4的浓度为1mol/L，溶剂为聚碳丙烯酯PC+聚碳乙烯酯EC+二甲基碳酸酯DMC的复合溶剂。
(3)制备半电池
选用金属钠片作为负极极片，选用多孔玻璃纤维作为隔膜，电解液中NaPF6的浓度为1mol/L，电解液的溶剂为混合溶剂，混合溶剂中碳酸乙烯酯EC、碳酸丙烯酯PC和碳酸二甲酯DMC的体积比为1：1：1，电解液中还含有体积比5％的氟代碳酸乙烯酯FEC，在水氧值低于0.1ppm的氩气手套箱组装扣式电池。
实施例2～19-对比例1-2
实施例2～19-对比例1-2与实施例1的区别详见表1。需要说明的是，表1中正极极片中添加剂的总用量是以正极活性物质、导电剂和粘结剂的总质量为基准限定的，即，添加剂的总用量＝添加剂的总质量/(正极活性物质的质量+导电剂的质量+粘结剂的质量)×100％。当正极极片中仅含有第一添加剂时，添加剂的总用量是指第一添加剂的用量；当正极极片中仅含有第二添加剂时，添加剂的总用量是指第二添加剂的用量；当正极极片中含有第一添加剂和第二添加剂时，添加剂的总用量是指第一添加剂和第二添加剂的总用量；当添加剂仅分散于正极活性物质层中时，“添加剂的总用量”指正极活性物质层中的添加剂用量；当添加剂同时分散于正极活性物质层中和功能层中时，“添加剂的用量”指正极活性物质层中和功能层中的添加剂的总用量。
其中，实施例1-5的区别在于功能层中第二添加剂的用量不同；实施例3、实施例6-9、实施例13的区别在于全电池隔膜中Al2O3涂层厚度不同；实施例10与实施例3的区别在于功能层中添加剂的种类不同；实施例11-12与实施例3的区别在于正极活性物质层中第一添加剂的种类不同；实施例15、16、18、19与实施例1的区别在于功能层中添加剂的种类不同；实施例14、实施例17、对比例1-2中均不含功能层，实施例14、实施例17、对比例2的区别在于正极活性物质层中添加剂的种类不同；对比例1中不含添加剂。
实施例1-19、以及对比例2的正极活性物质层中添加剂的用量相同；正极活性物质层中添加剂的用量发生变化时，通过调整正极活性物质的用量保持添加剂和正极活性物质的总质量不变。
表1实施例2～19和对比例1-2与实施例1的区别
性能测试：
(1)在相同条件下对实施例1和对比例1制备的半电池进行充放电容量测试。测试方法如下：将半电池安装在蓝电测试仪上，并置于25±2℃测试环境中。设置程序：静置10min→ 以0.1C的电流恒流充电至4.2V→静置10min→以0.1C的电流恒流放电至2.0V，以上述步骤作为重复单元，重复上述步骤3次。
图3示出了实施例1和对比例1中制得的半电池的充放电曲线对比图。由图3可知，实施例1中制得的半电池的充放电比容量均高于对比例1，说明在正极极片中添加添加剂能够提高钠电池首次充放电比容量，从而提高钠电池的能量密度。
(2)在相同条件下对实施例1-19和对比例1-2制备的全电池进行电化学性能测试，测试方法如下，结果参见表2。
首次放电容量测试方法：将全电池用夹具夹好，并安装在测试仪器上，全电池化成老化结束后，将其置于25±2℃测试环境中。设置程序：静置10min→以0.1C的电流恒流放电至2.0V→静置10min→以0.1C的电流恒流充电至4.0V→静置10min→以0.1C的电流恒流放电至1.5V，随后测试电池容量。
首次库伦效率测试方法：全电池化成结束后，静置30min→0.02C恒流充电至电压2.8V→0.05C恒流充电至电压3.4V→0.1C恒流充电至电压4.0V→静置20min，进行电池容量测试得到充电容量C1；随后，0.1C电流恒流放电至1.5V，进行电池容量测试得到放电容量D1；随后，0.1C电流恒流充电至4.0V，进行电池容量测试得到充电容量C2；随后，0.1C电流恒流放电至1.5V，进行电池容量测试得到放电容量D2；计算首次库伦效率，首次库伦效率＝D2/(C1+C2-D1)*100％。
循环性能测试方法：1)25℃电池循环性能测试：将全电池安装在测试仪器上，置于25±2℃环境中，静置60min→1.0C恒流放电至1.5V→静置10min→1.0C恒流充电至4.0V→静置10min→1.0C恒流放电至4.0V，上述步骤作为重复单元，重复上述步骤100次，进行电池容量测试以得到25℃循环100圈电池容量，25℃循环100圈容量保持率＝25℃循环100圈电池容量/25℃首次放电容量×100％；2)45℃电池循环性能测试：其与25℃电池循环性能测试方法的区别在于：电池置于45±2℃环境中，以得到45℃循环100圈电池容量和45℃首次放电容量，随后进行45℃循环100圈容量保持率的计算。
表2实施例1～19和对比例1-2中全电池的测试结果

结果与结论：
由表2可知，正极极片中的正极活性物质层与功能层中的至少之一含有单氟磷酸钠和/或二氟磷酸钠能够有效提升正极的首次库伦效率和首次放电容量，并提高了钠电池的常温、高温循环稳定性；进一步的，与仅正极活性物质层分散有第一添加剂相比，正极活性物质层表面具有功能层，功能层的材料包括第一添加剂和/或第二添加剂，能够进一步提高首次库伦效率；更进一步的，功能层的材料包括第二添加剂，能够进一步提高首次库伦效率；由实施例3和实施例10的对比可知，与功能层中分散有第一添加剂相比，功能层中分散有第二添加剂，能够进一步提高首次库伦效率；由实施例14、17与对比例2的对比可知，与常规含氟添加剂相比，第一添加剂能够提高钠电池的循环性能；由实施例13与实施例3、 6-9的对比可知，与不含有Al2O3涂层的常规隔膜相比，含有Al2O3涂层的陶瓷隔膜能够提高钠电池的循环性能。
在本申请的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B表示单独存在A、同时存在A和B、单独存在B这三种情况。
文中术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。在本申请的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
尽管上面已经示出和描述了本申请的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本申请的限制，本领域的普通技术人员在本申请的范围内可以对上述实施例进行变化、修改、替换和变型。在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。

Claims (21)

  1. 一种正极极片，用于钠电池，其中，包括：集流体、正极活性物质层和第一添加剂，所述正极活性物质层设置在所述集流体的至少一侧，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠。
  2. 根据权利要求1所述的正极极片，其中，所述正极活性物质层中分散有所述第一添加剂。
  3. 根据权利要求1或2所述的正极极片，其中，还包括功能层，所述功能层位于所述正极活性物质层背离所述集流体的一侧，所述功能层中分散有所述第一添加剂。
  4. 根据权利要求3所述的正极极片，其中，所述功能层的厚度范围值为0.5μm～5μm。
  5. 根据权利要求1或4所述的正极极片，其中，以所述正极活性物质层的总质量为基准，所述第一添加剂的质量百分比为4.7wt％-20wt％。
  6. 根据权利要求5所述的正极极片，其中，所述第一添加剂的质量百分比为9wt％-15wt％。
  7. 根据权利要求1或2所述的正极极片，其中，还包括第二添加剂，所述第二添加剂包括Na2O、Na2O2、Na2CO3、Na2S、Na3P、NaN3、NaNiO2、NaCrO2、NaFeO2、Na3C6H5O7、Na2C6O6、NaF、NaHF2中的至少一种。
  8. 根据权利要求7所述的正极极片，其中，所述正极活性物质层中分散有所述第二添加剂；和/或，
    所述第一添加剂与所述第二添加剂的质量比为(1-3):(1-3)。
  9. 根据权利要求7或8所述的正极极片，其中，所述第一添加剂与所述第二添加剂的质量比为1:(1-3)。
  10. 根据权利要求7所述的正极极片，其中，还包括：功能层，所述功能层位于所述正极活性物质层背离所述集流体一侧，所述功能层中分散有所述第二添加剂，或者所述功能层中分散有所述第一添加剂和所述第二添加剂。
  11. 根据权利要求10所述的正极极片，其中，所述第一添加剂分散于所述正极活性物质层中，所述第二添加剂分散于所述功能层中。
  12. 根据权利要求10或11所述的正极极片，其中，满足以下三个条件中的至少之一：
    所述功能层的厚度范围值为0.5μm～5μm；
    所述第一添加剂与所述第二添加剂的质量比为(1-3):(1-3)；
    以所述正极活性物质层的总质量为基准，所述第一添加剂和所述第二添加剂的总质量百分比为4.7wt％-20wt％。
  13. 根据权利要求12所述的正极极片，其中，所述第一添加剂和所述第二添加剂的总质量百分比为9wt％-15wt％；和/或，
    所述第一添加剂与所述第二添加剂的质量比为1:(1-3)。
  14. 一种制备权利要求1～13中任一项所述的正极极片的方法，其中，包括：
    在集流体的至少一侧形成正极活性物质层；
    其中，所述正极活性物质层中分散有第一添加剂，所述第一添加剂包括单氟磷酸钠和/或二氟磷酸钠。
  15. 一种制备权利要求1～13中任一项所述的正极极片的方法，其中，包括：
    在集流体的至少一侧形成正极活性物质层；
    在所述正极活性物质层背离所述集流体的一侧形成功能层；
    其中，所述正极活性物质层中分散有第一添加剂，所述功能层中分散有所述第一添加剂和/或第二添加剂，所述第二添加剂包括Na2O、Na2O2、Na2CO3、Na2S、Na3P、NaN3、NaNiO2、NaCrO2、NaFeO2、Na3C6H5O7、Na2C6O6、NaF、NaHF2中的至少一种。
  16. 一种储能装置，其中，包括权利要求1～13中任一项所述的正极极片。
  17. 根据权利要求16所述的储能装置，其中，还包括负极极片和隔膜，所述正极极片和所述负极极片之间设有所述隔膜，所述隔膜包括本体和设在所述本体至少一侧上的氧化铝层。
  18. 根据权利要求17所述的储能装置，其中，满足以下条件中的至少之一：
    所述隔膜还包括设在所述本体至少一侧的纤维网格层，所述氧化铝层包括氧化铝颗粒，所述氧化铝颗粒的至少一部分分布于所述纤维网格层的间隙中；
    所述隔膜的孔隙率≥30％；
    所述隔膜的平均孔径≥25nm；
    所述隔膜的离子电导率≥1.1mS/cm；
    所述本体的厚度为2μm～20μm。
  19. 根据权利要求18所述的储能装置，其中，所述氧化铝颗粒的粒径Dv50满足：2μm≤Dv50≤12μm。
  20. 根据权利要求17～19中任一项所述的储能装置，其中，所述氧化铝层的厚度为0.1μm～10μm。
  21. 一种用电设备，特征在于，包括权利要求16～20中任一项所述的储能装置。
PCT/CN2024/074391 2023-06-14 2024-01-29 正极极片及其制备方法、储能装置、用电设备 Ceased WO2024255258A1 (zh)

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