WO2025102765A1 - 正极极片、钠离子二次电池、用电装置 - Google Patents

正极极片、钠离子二次电池、用电装置 Download PDF

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WO2025102765A1
WO2025102765A1 PCT/CN2024/103550 CN2024103550W WO2025102765A1 WO 2025102765 A1 WO2025102765 A1 WO 2025102765A1 CN 2024103550 W CN2024103550 W CN 2024103550W WO 2025102765 A1 WO2025102765 A1 WO 2025102765A1
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sodium
positive electrode
active material
electrode active
battery
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French (fr)
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吴凯
许宝云
唐正
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—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 battery technology, and in particular to a positive electrode sheet, a sodium ion secondary battery, and an electrical device.
  • the purpose of the embodiments of the present application is to provide a positive electrode plate, a sodium ion secondary battery, and an electrical device, aiming to solve the problem of poor cycle performance of sodium ion batteries.
  • an embodiment of the present application provides a positive electrode plate, comprising a sodium supplement and a positive electrode active material, wherein the sodium supplement comprises NaqMnxMyO2 , 1 ⁇ q ⁇ 1.2 , 0.15 ⁇ x ⁇ 0.45, y>0, 0.9 ⁇ x+y ⁇ 1, and M comprises a transition metal element; and Dv50 of the sodium supplement is less than Dv50 of the positive electrode active material.
  • Mn-based sodium-supplementing oxide NaqMnxMyO2 is added to the positive electrode plate as a sodium-supplementing agent.
  • the Mn in NaqMnxMyO2 includes unstable Mn3 + , so that the structure of NaqMnxMyO2 has greater instability and is easy to release sodium (Mn3 + can be converted into stable Mn4 + in this process) .
  • NaqMnxMyO2 can be used as an active sodium source consumed in forming a solid electrolyte interface film ( SEI film), thereby reducing the consumption of active sodium contained in the positive electrode active material in the early charge and discharge process of the battery, improving the structural damage of the positive electrode active material, and being beneficial to improving the cycle performance of the battery.
  • SEI film solid electrolyte interface film
  • the sodium supplement agent can have a higher reactivity than the positive electrode active material, and has faster kinetics during the early charge and discharge process of the battery, so it can preferentially release sodium ions than the positive electrode active material to provide for the formation of the SEI film, thereby further reducing the consumption of active sodium in the positive electrode active material and improving the cycle performance of the battery.
  • q can reflect the Na content in NaqMnxMyO2 . Setting q within these ranges can not only enable NaqMnxMyO2 to provide sodium ions, reduce the consumption of active sodium contained in the positive electrode active material during the first cycle of charging, and help improve the capacity of the positive electrode sheet and improve the battery cycle performance; but also enable the sodium supplement to have good structural stability after sodium removal.
  • x can reflect the Mn content in NaqMnxMyO2 .
  • the Mn in NaqMnxMyO2 includes unstable Mn3 + .
  • Setting x in the above range can make NaqMnxMyO2 contain sufficient Mn3 + , so that the structure of NaqMnxMyO2 has greater instability and is easy to release sodium, which is beneficial to achieve the effect of sodium supplementation .
  • Mn has different valence states in different structures and can adapt to different Na contents.
  • y reflects the content of transition metal M in NaqMnxMyO2 . Adding an appropriate amount of M to NaqMnxMyO2 helps to improve the structural stability of NaqMnxMyO2 after sodium removal, so that NaqMnxMyO2 does not suffer from serious structural collapse during the sodium removal process.
  • the M includes one or more of Fe, Ni, Co, Cu, Al , Ti, and V. These transition metals are helpful to improve the structural stability of NaqMnxMyO2 after desodiumization .
  • the M includes Fe and Ni
  • the sodium supplement includes NaqMnxNiy1Fey2O2 , 1 ⁇ q ⁇ 1.2 , 0.15 ⁇ x ⁇ 0.45, y1>0, y2>0, 0.9 ⁇ x+y1+y2 ⁇ 1.
  • the transition metal is a combination of Ni and Fe, which can form a stable metal layer structure with Mn; and studies have shown that the combination of Ni and Fe is beneficial to improving the energy density of the material.
  • the phase structure of the sodium supplement includes an O3 phase.
  • Na + has different coordination environments and contents.
  • the sodium supplement of the present application embodiment includes an O3 phase, which is a phase structure with a high sodium content, and thus is conducive to the sodium supplement providing a large amount of sodium.
  • the Dv50 of the sodium supplement is 6% to 75% of the Dv50 of the positive electrode active material, and optionally 6% to 25%. Setting the particle size of the sodium supplement to be smaller than the particle size of the positive electrode active material can make the sodium supplement have a higher reaction activity than the positive electrode active material, and have faster kinetics during the first cycle of charging and the early cycle of the battery. Therefore, it can preferentially release sodium ions than the positive electrode active material to provide for the formation of the SEI film, thereby reducing the consumption of active sodium in the positive electrode active material and improving the cycle performance of the battery. At the same time, when there is a certain difference between the Dv50 of the sodium supplement and the Dv50 of the positive electrode active material, the battery can exhibit better cycle performance.
  • the Dv50 of the sodium supplement is 0.5 ⁇ m to 6 ⁇ m, optionally 1 ⁇ m to 3 ⁇ m.
  • the sodium supplement has a high specific surface area, high specific surface energy, and a short sodium transmission path, which is beneficial to improving its reaction activity and promoting sodium removal.
  • the Dv50 of the positive electrode active material is 6 ⁇ m to 20 ⁇ m, optionally 6 ⁇ m to 10 ⁇ m.
  • the reaction activity of the positive electrode active material is lower than that of the sodium supplement, and it can slowly release sodium ions during the early charge and discharge process of the battery without preferentially releasing sodium ions, which can slow down the consumption of active sodium in the positive electrode active material.
  • the positive electrode active material and the sodium supplement are compounded with large and small particle sizes, and the small particle size sodium supplement can be filled between the large particle size positive electrode active materials, which is beneficial to increase the compaction density of the positive electrode sheet, thereby increasing the energy density of the positive electrode sheet.
  • the mass ratio of the sodium supplement to the positive electrode active material is 1:(14-95), optionally 1:(18-46.5).
  • the mass ratio of the sodium supplement to the positive electrode active material has an effect on the cycle performance of the sodium ion battery. At the above mass ratio, the sodium ion battery can exhibit excellent cycle performance.
  • the mass content of the sodium supplement in the active layer of the positive electrode is 1% to 6%, and optionally 2% to 5%. Adding a small amount of the sodium supplement of the present application embodiment to the active layer of the positive electrode can effectively achieve the sodium supplement effect and improve the battery cycle performance.
  • the positive electrode active material includes one or more of layered oxides, polyanion compounds, and Prussian blue compounds; optionally, the layered oxide includes Na m M 1 z O 2 , 0.4 ⁇ m ⁇ 0.9, 0.9 ⁇ z ⁇ 1, and M 1 includes a transition metal element.
  • the positive electrode sheet of the embodiment of the present application is suitable for various positive electrode active materials, and can improve the structural damage of these positive electrode active materials during the battery cycle process and improve the cycle performance of the battery.
  • the present application provides a sodium ion secondary battery, wherein the sodium ion secondary battery comprises the positive electrode plate described in the first aspect.
  • the above-mentioned positive electrode plate contains a sodium supplement with a special structure, and the sodium supplement is combined with the positive electrode active material according to a specific particle size. After the positive electrode plate is applied to a sodium ion secondary battery, it is beneficial to improve the cycle performance of the sodium ion secondary battery.
  • the present application provides an electrical device, which includes the sodium ion secondary battery described in the second aspect.
  • the sodium ion secondary battery disclosed in the embodiment of the present application can be used in electrical devices that use secondary batteries as power sources, or various energy storage systems that use batteries as energy storage elements, to provide electrical energy.
  • the above-mentioned sodium ion secondary battery has good cycle performance. Therefore, the use of the above-mentioned sodium ion secondary battery can stably provide electrical energy for various electrical devices, thereby improving the user experience of various electrical devices.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG1 ;
  • FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;
  • FIG. 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that there may be three relationships.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and A exists alone. Only the three cases B exist.
  • the character "/" in this article generally indicates that the objects before and after are in an "or" relationship.
  • the term "at least one” refers to one or more, and “plurality” refers to two or more. "At least one of the following” or similar expressions refers to any combination of these items, including any combination of single items or plural items.
  • “at least one of a, b, or c”, or “at least one of a, b, and c” can all represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple, respectively.
  • the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
  • the mass of the relevant components mentioned in the specification of the examples of this application can not only refer to the specific content of each component, but also represent the proportional relationship between the masses of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the examples of this application, it is within the scope disclosed in the specification of the examples of this application.
  • the mass described in the specification of the examples of this application can be mass units known in the chemical industry such as ⁇ g, mg, g, and kg.
  • sodium-ion batteries have received extensive attention and research because their raw materials are abundant and widely distributed in nature. Similar to lithium-ion batteries, sodium-ion batteries mainly achieve the conversion of chemical energy into electrical energy through the intercalation and deintercalation of sodium ions between the positive and negative electrodes. That is, during the charging process, the active material of the positive electrode releases sodium ions, which are then embedded in the active material of the negative electrode after being transported by the electrolyte; during the discharging process, the sodium ions are released from the negative electrode active material and returned to the positive electrode active material.
  • the pre-sodiumization method includes adding sodium powder or sodium foil to the positive or negative electrode by roller pressing or adsorption; or adding a pre-sodiumization reagent (sodium supplement) to the positive or negative electrode and the electrolyte to compensate for the lost sodium.
  • sodium powder or sodium foil has a strong reaction activity, has high requirements for the operating environment, and has potential safety issues.
  • Most sodium supplements have limited sodium supplementation effects during the battery charging and discharging process. It is difficult to release sodium ions before the positive electrode active material during the charging and discharging process. Therefore, the positive electrode active material needs to provide sodium ions during the early charging and discharging process of the battery, which will also cause irreversible sodium loss in the positive electrode active material.
  • the embodiment of the present application adds a specific Mn-based sodium supplement oxide as a sodium supplement NaqMnxMyO2 to the positive electrode plate .
  • the sodium supplement contains unstable Mn3 + , which makes the structure of NaqMnxMyO2 more unstable and easy to release sodium; and the particle size of the sodium supplement is smaller than that of the positive electrode active material, so it has a higher reaction activity than the positive electrode active material, and can release sodium ions preferentially than the positive electrode active material to participate in the electrochemical reaction. Therefore, under the action of this sodium supplement, the consumption of active sodium contained in the positive electrode active material during the early charge and discharge process of the battery can be reduced, the structural damage of the positive electrode active material can be improved, and the cycle performance of the battery can be improved.
  • the positive electrode plate containing the sodium supplement agent in the embodiment of the present application can be used to make a secondary battery, and can be further applied to various electrical devices.
  • the present application provides a positive electrode plate, comprising a sodium supplement and a positive electrode active material, wherein the sodium supplement comprises NaqMnxMyO2 , 1 ⁇ q ⁇ 1.2 , 0.15 ⁇ x ⁇ 0.45, y>0, 0.9 ⁇ x+y ⁇ 1, and M comprises a transition metal element; and Dv50 of the sodium supplement is less than Dv50 of the positive electrode active material.
  • the positive electrode active material is an important substance in the positive electrode plate that participates in the electrochemical reaction of the battery and can serve as a medium for the transmission of ions in the electrochemical reaction.
  • the positive electrode active material refers to the positive electrode active material of the sodium ion battery.
  • the sodium supplement contains NaqMnxMyO2 , and the crystal morphology of the NaqMnxMyO2 can be determined by X-ray diffraction, and the type of each element and the content and proportion of each element can be obtained by combining with an element analyzer, and then the subscripts q, x, and y of each element in the chemical formula can be obtained by conversion.
  • Dv50 is a way of expressing the particle size of a material. For the particle size distribution of a material, it is usually expressed as the percentage of particles in different particle size ranges to the total amount. There are many benchmarks for determining particle size distribution, such as number distribution, length distribution, area distribution, volume distribution, weight distribution, etc.
  • Dv50 is a specific particle size distribution based on volume distribution, also known as the median particle size, which refers to the particle size at which the cumulative distribution of particle volume is 50%, indicating that 50% of the particles have a diameter exceeding this value and 50% of the particles have a diameter below this value.
  • the Dv50 of the particles can be obtained by referring to GB/T 19077-2016/ISO 13320:2009 "Laser Diffraction Method for Particle Size Distribution".
  • the particle morphology of the sodium supplement and the positive electrode active material can be independently regular spherical, ellipsoidal, polygonal, or other irregular shapes.
  • spherical particles their particle size is their diameter; for non-spherical or other irregularly shaped particles, their particle size is their equivalent diameter.
  • Mn-based sodium-supplementing oxide NaqMnxMyO2 is added to the positive electrode plate as a sodium-supplementing agent.
  • the Mn in NaqMnxMyO2 includes unstable Mn3 + , so that the structure of NaqMnxMyO2 has greater instability and is easy to release sodium (Mn3 + can be converted into stable Mn4 + in this process) .
  • NaqMnxMyO2 can be used as an active sodium source consumed in forming a solid electrolyte interface film ( SEI film), thereby reducing the consumption of active sodium contained in the positive electrode active material in the early charge and discharge process of the battery, improving the structural damage of the positive electrode active material, and being beneficial to improving the cycle performance of the battery.
  • SEI film solid electrolyte interface film
  • the sodium supplement agent can have a higher reactivity than the positive electrode active material, and has faster kinetics during the early charge and discharge process of the battery, so it can preferentially release sodium ions than the positive electrode active material to provide for the formation of the SEI film, thereby further reducing the consumption of active sodium in the positive electrode active material and improving the cycle performance of the battery.
  • 1 ⁇ q ⁇ 1.2 optionally, 1 ⁇ q ⁇ 1.1.
  • q can be selected as any point value of 1.0, 1.1, 1.2 or a range value between any two of them.
  • q can reflect the Na content in NaqMnxMyO2 . Setting q within these ranges can not only enable NaqMnxMyO2 to provide sodium ions, reduce the consumption of active sodium contained in the positive electrode active material during the initial charge and discharge process of the battery, and help to increase the capacity of the positive electrode sheet and improve the battery cycle performance; but also enable the sodium supplement to have good structural stability after sodium removal.
  • x can be selected from any one of 0.15, 0.2, 0.25, 0.3 , 0.35, 0.4, 0.44 or a range of values between any two of them .
  • x can reflect the Mn content in NaqMnxMyO2 .
  • the Mn in NaqMnxMyO2 includes unstable Mn3 + . Setting x in the above range can make NaqMnxMyO2 contain enough Mn3 + , so that the structure of NaqMnxMyO2 has greater instability and is easy to remove sodium , which is conducive to achieving the effect of sodium supplementation.
  • Mn has different valence states in different structures, which can be suitable for In response to different Na contents, that is, more Na can be allowed to be added to NaqMnxMyO2 by changing its own valence state, which is beneficial to increase the Na content in NaqMnxMyO2 , and further beneficial to increase the capacity of the positive electrode sheet and improve the battery cycle performance.
  • y can be selected from any one of 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8 or a range of values between any two of them.
  • y reflects the content of transition metal M in NaqMnxMyO2. Adding an appropriate amount of M to NaqMnxMyO2 helps to improve the structural stability of NaqMnxMyO2 , so that NaqMnxMyO2 does not suffer from severe structural collapse during the sodium removal process.
  • M includes one or more of Fe, Ni, Co, Cu, Al, Ti, and V.
  • M includes at least one of Fe and Ni. These transition metals help to improve the structural stability of NaqMnxMyO2 .
  • M includes Fe and Ni
  • the sodium supplement includes NaqMnxNiy1Fey2O2 , 1 ⁇ q ⁇ 1.2 , 0.15 ⁇ x ⁇ 0.45, y1>0, y2>0, 0.9 ⁇ x+y1+y2 ⁇ 1.
  • the transition metal is a combination of Ni and Fe, which can form a stable metal layer structure with Mn; and studies have shown that the combination of Ni and Fe is beneficial to improving the energy density of the material.
  • y1>0 optionally, 0.3 ⁇ y1 ⁇ 0.44, for example, y1 can be any point value of 0.3, 0.35, 0.4, 0.44 or a range value between any two of them.
  • y2>0 optionally, 0.24 ⁇ y2 ⁇ 0.34, for example, y2 can be any point value of 0.24, 0.25, 0.3, 0.34 or a range value between any two of them.
  • Combining Ni and Fe in a certain ratio is conducive to better structural stability and energy density improvement.
  • the phase structure of the sodium supplement includes an O3 phase.
  • the Mn-based sodium supplement oxide NaqMnxMyO2 belongs to a layered oxide, which is formed by stacking TO6 (in the embodiment of the present application, T includes Mn and transition metal element M ) layered structures, and Na + is embedded and extracted between the layers of the TO6 stack.
  • the phase structure of the layered oxide can be divided into O phase and P phase.
  • O means that Na + is octahedral coordinated (Octahedral), and Na + occupies octahedral sites;
  • P means that Na + is triangular prism coordinated (Prismatic), and Na + occupies triangular prism sites.
  • Na + and the TO6 structure are connected in an edge-sharing manner in the O phase, and in a face-sharing and edge-sharing manner in the P phase.
  • the layered oxides can be further divided into P2 phase, O2 phase, P3 phase and O3 phase, where the stacking method of P2 is ABBA, the stacking method of O2 is ABAC (or ABCB), the stacking method of P3 is ABBCCA, and the stacking method of O3 is ABCABC.
  • the numbers "2" and "3" represent the number of transition metal layers of different types of O stacking in each unit.
  • the phase structure can be obtained by X-ray diffraction analysis.
  • an X-ray powder diffractometer is used to test the sample to obtain the X-ray diffraction spectrum of the sample.
  • the phase structure of the sample can be confirmed by comparing the XRD diffraction peaks in the X-ray diffraction spectrum with the standard card of the XRD analysis software.
  • phase structure of the sodium supplement in the embodiment of the present application includes an O3 phase, which is a phase structure with a high sodium content, and thus is conducive to the sodium supplement providing a large amount of sodium.
  • the Dv50 of the sodium supplement is 6% to 75% of the Dv50 of the positive electrode active material, and optionally 6% to 25%.
  • the Dv50 of the sodium supplement is 6%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% of the Dv50 of the positive electrode active material, or any range between two of them.
  • the particle size of the sodium supplement to be smaller than the particle size of the positive electrode active material can make the sodium supplement have a higher reaction activity than the positive electrode active material, and have faster kinetics during the first cycle of charging and the early cycle of the battery, so that it can preferentially release sodium ions than the positive electrode active material to provide for the formation of the SEI film, thereby reducing the consumption of active sodium in the positive electrode active material and improving the cycle performance of the battery.
  • the battery when there is a certain difference between the sodium supplement Dv50 and the positive electrode active material Dv50, the battery can exhibit better cycle performance.
  • the Dv50 of the sodium supplement is 0.5 ⁇ m to 6 ⁇ m, optionally 1 ⁇ m to 3 ⁇ m, for example Any point value among 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, 5.5 ⁇ m, 6 ⁇ m or any range value between two of them.
  • the sodium supplement has a high specific surface area, a high specific surface energy, and a short sodium transmission path, which is beneficial to improve its reaction activity and promote sodium removal.
  • the mass ratio of the sodium supplement to the positive electrode active material is 1: (14-95), optionally 1: (18-46.5), for example, the mass ratio of the two can be 1: 14, 1: 20, 1: 25, 1: 30, 1: 35, 1: 40, 1: 45, 1: 50, 1: 55, 1: 60, 1: 65, 1: 70, 1: 75, 1: 80, 1: 85, 1: 90, 1: 95, any one point value or any range value between the two.
  • the mass ratio of the sodium supplement to the positive electrode active material has an effect on the cycle performance of the sodium ion battery. At the above mass ratio, the sodium ion battery exhibits excellent cycle performance.
  • the mass content of the sodium supplement in the active layer contained in the positive electrode plate is 1% to 6%, optionally 2% to 5%, for example, it can be any one of 1%, 2%, 3%, 4%, 5%, 6% or a range between any two. Adding a small amount of the sodium supplement of the embodiment of the present application to the active layer contained in the positive electrode plate can effectively achieve the sodium supplement effect and improve the battery cycle performance.
  • the Dv50 of the positive electrode active material is 6 ⁇ m to 20 ⁇ m, optionally 6 ⁇ m to 10 ⁇ m, for example, it can be any point value of 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 12 ⁇ m, 14 ⁇ m, 16 ⁇ m, 18 ⁇ m, 20 ⁇ m or any range value between two of them.
  • the reaction activity of the positive electrode active material is lower than that of the sodium supplement, and it can slowly release sodium ions during the early charge and discharge process of the battery without preferentially releasing sodium ions, thereby slowing down the consumption of active sodium in the positive electrode active material.
  • the positive electrode active material and the sodium supplement are compounded with large and small particle sizes, and the small particle size sodium supplement can be filled between the large particle size positive electrode active materials, which is beneficial to increase the compaction density of the positive electrode sheet, thereby increasing the energy density of the positive electrode sheet.
  • the positive electrode active material may include one or more of a layered oxide, a polyanion compound, and a Prussian blue compound.
  • the layered oxide may include Na m M 1 z O 2 , 0.4 ⁇ m ⁇ 0.9, optionally 0.8 ⁇ m ⁇ 0.9; 0.9 ⁇ z ⁇ 1, and M 1 includes a transition metal element.
  • the layered oxide may include Na m1 Mn z1 M z2 O 2 , 0.8 ⁇ m1 ⁇ 0.9, 0.09 ⁇ z1 ⁇ 0.45, and 0.9 ⁇ z1+z2 ⁇ 1.
  • the layered oxide may include Na 0.7 CoO 2 , Na 0.6 MnO 2 , Na 0.44 MnO 2 , Na 0.65 Mn 0.75 Ni 0.25 O 2 , Na 0.78 Ni 0.23 Mn 0.69 O 2 , Na 0.67 Mn 0.67 Ni 0.33 O 2 , Na 0.82 Mn 0.33 Ni 0.33 Fe 0.33 O 2 , and the like.
  • the polyanion compound may be a compound having sodium ions, transition metal ions and tetrahedral (YO 4 ) n- anion units; or, the polyanion compound may be a compound having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions, wherein the halogen includes one or more of F, Cl and Br; or, the polyanion compound may be a compound having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) n1+ and optional halogen anions.
  • the transition metal and Z may independently include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce
  • Y includes one or more of P, S and Si
  • n represents the valence of (YO 4 ) n-
  • n1 represents the valence of (ZO y ) n1+
  • the polyanion compound may include one or more of phosphate, pyrophosphate, sulfate, and anion-doped compounds, such as one or more of olivine-type NaFePO 4 , Na 2 FeP 2 O 7 , NaFePO 4 F, Na 3 V 2 (PO 4 ) 3 , and NaFeSO 4 .
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN-), wherein the transition metal includes one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.
  • the Prussian blue compound may include Na a M 2 b [M 3 c (CN) 6 ] d , 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0.8 ⁇ d ⁇ 1, M 2 , M 3 independently includes transition metal elements.
  • a can be any point value of 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2 or a range between any two of them; b can be any point value of 0.2, 0.4, 0.6, 0.8, 1 or a range between any two of them; c can be any point value of 0.2, 0.4, 0.6, 0.8, 1 or a range between any two of them; d can be any point value of 0.8, 0.85, 0.9, 0.95, 1 or a range between any two of them; M 2 and M 3 can independently include one or more of Ni, Cu, Fe, Mn, Co, and Zn.
  • the Prussian blue compound may include one or more of Na 0.61 Fe[Fe(CN) 6 ] 0.94 , BR-FeHCF, Na 1.48 Ni[Fe(CN) 6 ] 0.89 , and NaNi 0.05 Mn 0.95 [Fe(CN) 6 ].
  • the positive electrode sheet of the embodiment of the present application is suitable for various positive electrode active materials, and can improve the structural damage of these positive electrode active materials during the battery cycle process, thereby improving the cycle performance of the battery.
  • the mass content of the positive electrode active material in the active layer contained in the positive electrode sheet is 80% to 98%, for example, it can be any point value of 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98% or any range value between two of them.
  • the positive electrode active material is the main substance participating in the electrochemical reaction in the positive electrode sheet and provides capacity. It can be understood that the high mass content of the positive electrode active material in the positive electrode active layer will be beneficial to improve the energy density of the positive electrode sheet.
  • the compaction density of the positive electrode sheet is 2.5 g/cm 3 to 4 g/cm 3 , and optionally 2.6 g/cm 3 to 3.3 g/cm 3 , for example, it can be any point value of 2.5 g/cm 3 , 2.6 g/cm 3 , 2.8 g/cm 3 , 3 g/cm 3 , 3.2 g/cm 3 , 3.4 g/cm 3 , 3.5 g/cm 3 , 3.6 g/cm 3 , 3.8 g/cm 3 , 4 g/cm 3 or a range value between any two of them.
  • the compaction density is the density of the product under a certain pressure.
  • the compaction density can refer to relevant standards, such as Appendix L "Test Method for Powder Compaction Density" in GB/T 24533-2019, and is obtained by testing with a compaction density meter.
  • the compaction density has an impact on the energy density, electrolyte wetting performance, sodium ion transmission rate, etc. of the positive electrode plate.
  • the greater the compaction density the higher the mass of the positive electrode active material and the sodium supplement per unit volume, which is beneficial to improving the energy density of the positive electrode plate.
  • the compaction density also reflects the porosity of the plate.
  • the plate has good electrolyte wetting performance, which facilitates the transmission of sodium ions.
  • the positive electrode plate of the embodiment of the present application has a suitable compaction density, which is not only beneficial to improving the energy density of the plate, but also beneficial to improving the electrolyte wetting performance of the plate and accelerating the transmission of sodium ions.
  • the positive electrode plate usually also includes a conductive agent, a binder, and a positive current collector.
  • the conductive agent, the binder, the above-mentioned sodium supplement, and the positive active material form the active layer of the positive electrode plate, and the active layer is arranged on at least one surface of the positive current collector.
  • the conductive agent is used to collect microcurrents between the active materials and between the active materials and the positive current collector to improve the electronic conductivity. At the same time, the conductive agent can also promote the infiltration of the electrolyte into the positive electrode plate.
  • the binder can increase the bonding strength between the substances in the active layer and between the active layer and the positive current collector.
  • the positive current collector is used to transmit electrons.
  • the mass content of the conductive agent in the active layer contained in the positive electrode plate is 0.5% to 5%, optionally 1% to 5%, for example, any point value among 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range value between any two of them, and can also be set to other contents as needed.
  • the conductive agent may include, but is not limited to, one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.
  • SP acetylene black
  • super-P conductive carbon black
  • Ketjen black Ketjen black
  • carbon fiber carbon fiber
  • graphene graphene
  • the mass content of the binder in the active layer contained in the positive electrode plate is 0.5% to 5%, optionally 1% to 7%, for example, any point value among 0.5%, 1%, 2%, 3%, 4%, 5% or a range value between any two of them, and can also be set to other contents as needed.
  • the binder may include but is not limited to polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, One or more of olefins, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.
  • the positive electrode current collector may include but is not limited to a metal current collector, a carbon current collector, a conductive resin current collector, a composite current collector of metal and resin, etc., more specifically, aluminum, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotube (CNT), graphite, etc.
  • the positive electrode current collector includes aluminum.
  • the positive electrode sheet of the embodiment of the present application can be prepared by the following preparation method, including:
  • the sodium supplement comprises NaqMnxMyO2 , 1 ⁇ q ⁇ 1.2 , 0.15 ⁇ x ⁇ 0.45, y>0, 0.9 ⁇ x+y ⁇ 1, and M comprises a transition metal element; and Dv50 of the sodium supplement is less than Dv50 of the positive electrode active material.
  • the structural instability of NaqMnxMyO2 can be utilized to use it as an active sodium source consumed in forming a solid electrolyte interface film, thereby reducing the consumption of active sodium contained in the positive electrode active material during the first cycle of charging, improving the structural damage of the positive electrode active material, and being beneficial to improving the cycle performance of the battery;
  • the small-particle-size sodium supplement has a higher reaction activity than the large-particle-size positive electrode active material, and has faster kinetics during the first cycle of charging and the early cycle of the battery. Therefore, it can release sodium ions preferentially compared with the positive electrode active material to provide for the formation of the SEI film, further reducing the consumption of active sodium in the positive electrode active material and improving the cycle performance of the battery.
  • the positive electrode sheet can be made as follows:
  • the positive electrode slurry is coated on at least one surface of the current collector, and after drying and compacting, a positive electrode sheet is obtained.
  • the solvent may include but is not limited to N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the compaction method may include one or more of hot pressing and cold pressing. The pressure used in the compaction step may be determined according to the target compaction density.
  • the sodium supplement in the embodiment of the present application can be prepared by a solid phase method or other methods.
  • the sodium supplement can be prepared by referring to the following method:
  • the Na source, Mn source and M source are calcined together.
  • the temperature of calcination treatment is 600 °C ⁇ 1200 °C, for example, it may include but not limited to any one of 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C, 1200 °C or any range between two values.
  • the holding time at the temperature of calcination treatment is 5h ⁇ 24h, for example, it may include but not limited to any one of 5h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h or any range between two values.
  • the temperature of calcination treatment and the holding time at this temperature can be directly set and controlled on the calcination equipment, such as muffle furnace. At the appropriate calcination temperature and time, each raw material can be fully melted, mixed and reacted to form a composite metal oxide of Na, Mn and M.
  • the above calcination treatment step can be carried out in air or oxygen atmosphere.
  • the step of mixing the Na source, the Mn source and the M source may be included.
  • the mixing method includes but is not limited to one or more of mechanical stirring, grinding and ball milling to fully mix the raw materials and reduce the Small material particle size.
  • a crushing step may be further included to allow the sodium supplementer to have a desired particle size.
  • the Na source, the Mn source and the M source can be selected independently from their respective soluble compounds or insoluble compounds.
  • the specific types of each raw material can be selected from the following compounds:
  • the Na source includes, but is not limited to, one or more of Na 2 CO 3 , NaHCO 3 , NaOH, Na 2 O 2 and other sodium salts;
  • the Mn source includes, but is not limited to, one or more of Mn 2 O 3 , Mn 3 O 4 , MnO, and MnO 2 ;
  • the M source includes, but is not limited to, one or more of an oxide containing M, a hydroxide containing M, a carbonate containing M, and a bicarbonate containing M.
  • the positive electrode sheet containing the specific sodium supplement can be used to make a sodium ion secondary battery (hereinafter referred to as a secondary battery).
  • a second aspect of an embodiment of the present application provides a secondary battery, which includes the positive electrode plate of the first aspect.
  • secondary batteries are divided into battery cells, battery modules, and battery packs.
  • the secondary battery of the embodiment of the present application may include one or more of the battery cells, battery modules, and battery packs.
  • the positive electrode plate contains a sodium supplement with a special structure, and the sodium supplement is combined with the positive electrode active material according to a specific particle size. After the positive electrode plate is applied to a secondary battery, it is beneficial to improve the cycle performance of the secondary battery.
  • a secondary battery also includes a negative electrode plate, an electrolyte, a separator, an outer package or other components.
  • the components of a secondary battery are described below.
  • the negative electrode plate is usually isolated from the positive electrode plate (usually by a separator).
  • the negative electrode plate includes a negative electrode current collector and optionally a negative electrode active layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active layer contains a negative electrode active material.
  • the negative electrode current collector may include but is not limited to a metal or a composite current collector.
  • a metal sodium, sodium alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. may be used.
  • sodium or sodium alloy as the negative electrode current collector, since sodium or sodium alloy itself can also be used as a negative electrode active material, the negative electrode plate may not contain a negative electrode active layer, and sodium or sodium alloy is both a current collector and a negative electrode active material.
  • the composite current collector may include a composite material of a polymer material and a metal, wherein the polymer material may include but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc., and the metal may include but is not limited to sodium, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy.
  • the composite current collector may be obtained by mixing a polymer material and a metal, or may be coated on at least one side of the polymer material by electroplating, coating or other methods.
  • the negative electrode active material in the negative electrode active layer may include but is not limited to a mixture or composite material formed by any one or more of carbon-based materials, alloy materials, titanium-based materials, and sodium metal.
  • carbon-based materials include but are not limited to one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers
  • alloy materials include but are not limited to one or more of sodium-tin alloy, sodium-germanium alloy, and sodium-antimony alloy
  • titanium-based materials include but are not limited to one or more of titanium dioxide, titanate, and titanium phosphate.
  • the mass content of the negative electrode active material in the negative electrode active layer can be set to 85% to 98%, such as 95% to 98%, for example, any one of 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or a range between any two of them.
  • the negative electrode active layer may also include one or more of a conductive agent and a binder.
  • the conductive agent is used to collect microcurrents between active materials and between active materials and current collectors to improve electronic conductivity. It promotes the infiltration of electrolyte into the negative electrode.
  • the binder can improve the bonding strength between the substances in the active layer and between the active layer and the current collector.
  • the mass content of the conductive agent in the negative electrode active layer can be set to 0.5% to 10%, for example, any one of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range between any two of them, and can also be set to other contents as needed.
  • the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.
  • SP acetylene black
  • super-P conductive carbon black
  • Ketjen black Ketjen black
  • carbon fiber carbon fiber
  • graphene graphene
  • the mass content of the binder in the negative electrode active layer is 0.5% to 10%, for example, any one of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range between any two of them, and can also be set to other contents as needed.
  • the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.
  • the negative electrode active layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC).
  • CMC carboxymethyl cellulose
  • the mass content of the thickener in the positive electrode active layer may be set to 0.5% to 5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any range between two of them.
  • the current collector When the current collector is the negative electrode active material, the current collector can be cut into pieces to form a negative electrode sheet.
  • the secondary battery also includes an electrolyte solution, and the positive electrode plate and the negative electrode plate are in contact with the electrolyte independently.
  • the electrolyte plays the role of conducting ions between the positive electrode plate and the negative electrode plate.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte may be an electrolyte solution including an electrolyte sodium salt and a solvent.
  • the electrolyte sodium salt includes one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium sulfide, sodium chloride, sodium fluoride, sodium sulfate, sodium carbonate, sodium phosphate, sodium nitrate, sodium difluorooxalatoborate, sodium pyrophosphate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, trisodium citrate, sodium metaborate, sodium borate, sodium molybdate, sodium tungstate, sodium bromide, sodium nitrite, sodium iodate, sodium iodide, sodium silicate, sodium ligninsulfonate, sodium oxalate, sodium aluminate, sodium methanesulfonate, sodium acetate, sodium dichromate, sodium hexafluoroarsenate, sodium tetrafluorobo
  • Solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl ether (DME), diethylene glycol dimethyl ether, diethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, 2,2,2,2-trifluoroethyl ether, ethylene glycol diethyl ether, triethylene glycol dimethyl ether, methyl trifluoroethyl carbonate (FEMC), dioxolane (DOL), acetonitrile (AN), fluorobenzene, One or more of triethyl phosphate (TEP), sulfolane, 2-methyltetrahydrofuran, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylacetamide.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DME dimethyl ether
  • FEMC methyl trifluoroethyl carbonate
  • FEMC dio
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high or low temperature performance of the secondary battery, and the like.
  • the secondary battery also includes a separator, which is arranged between the positive electrode and the negative electrode to separate the positive and negative electrodes.
  • the separator prevents electrons in the secondary battery from passing freely, preventing short circuits between the electrodes, but allows ions in the electrolyte to pass freely between the positive electrode and the negative electrode.
  • the isolation membrane can be a porous structure isolation membrane with electrochemical stability and mechanical stability, such as a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).
  • PE polyethylene
  • PP polypropylene
  • PVDF polyvinylidene fluoride
  • the secondary battery may include an outer package that can be used to package an electrode assembly including a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.
  • the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.; or a soft package, such as a bag-type soft package.
  • the material of the soft package can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • the outer package of the secondary battery may be cylindrical, square or any other shape.
  • FIG1 is a secondary battery with a square outer package as an example.
  • the outer package may include a shell 01 and a cover plate 02.
  • the shell 01 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 01 has an opening connected to the receiving cavity, and the cover plate 02 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 03 through a winding process or a lamination process.
  • One or more electrode assemblies 03 are encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 03.
  • the secondary battery of the embodiment of the present application includes one or more of a battery cell, a battery module, and a battery pack.
  • secondary batteries can be divided into battery cells, battery modules, and battery packs.
  • the battery cell is the most basic unit of the secondary battery, including an electrode assembly and an electrolyte.
  • the electrode assembly usually includes a positive electrode sheet, a negative electrode sheet, a lithium supplement electrode, and a separator.
  • the positive electrode sheets and the negative electrode sheets are alternately stacked, and a separator is set between the positive electrode sheets and the negative electrode sheets to play an isolation role, to obtain a bare cell, or a bare cell after winding.
  • the bare cell is placed in an outer package, injected with electrolyte, and packaged to obtain a battery cell.
  • One or more battery cells are integrated to form a battery module, which can provide higher voltage and capacity, and have output with specific functions.
  • One or more battery modules are installed in the battery box, and a battery management system is usually added to form a battery pack.
  • the battery pack is usually a product provided to users.
  • one or more battery cells can be directly installed in the box to form a battery pack.
  • a plurality of battery cells 04 may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 04 may be fixed by fasteners.
  • the battery module may further include a housing having a housing space in which a plurality of battery cells 04 are housed. Accommodate space.
  • the battery pack may include a battery box and a plurality of battery modules 05 disposed in the battery box.
  • the battery box includes an upper box body 06 and a lower box body 07, and the upper box body 06 can be covered on the lower box body 07 to form a closed space for accommodating the battery modules 05.
  • the plurality of battery modules 05 can be arranged in the battery box in any manner.
  • An embodiment of the present application further provides an electrical device, which includes the secondary battery mentioned above.
  • the secondary battery disclosed in the embodiment of the present application can be used in electrical devices that use the secondary battery as a power source, or various energy storage systems that use the secondary battery as an energy storage element, to provide electrical energy.
  • the secondary battery has good cycle performance, so the use of the secondary battery can stably provide electrical energy to various electrical devices, improving the user experience of various electrical devices.
  • the electric device may include but is not limited to mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc.
  • the electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc.
  • the spacecraft may include airplanes, rockets, space shuttles and spacecraft, etc.
  • a battery cell, a battery module or a battery pack in a secondary battery may be selected according to its use requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • This embodiment provides a positive electrode sheet, wherein the active layer thereof comprises a sodium supplement Na 1.1 Mn 0.44 Ni 0.3 Fe 0.24 O 2 and a positive electrode active material Na 0.82 Mn 0.33 Ni 0.33 Fe 0.33 O 2 .
  • the method for preparing the positive electrode sheet comprises the following steps:
  • the positive electrode active material, sodium supplement, binder (polyvinylidene fluoride, PVDF) and conductive agent (conductive carbon) were fully stirred and mixed in a solvent (N-methylpyrrolidone, NMP) to obtain a positive electrode slurry.
  • the mass ratio of the positive electrode active material, sodium supplement, binder and conductive agent is 92:3:2:3.
  • the positive electrode slurry was coated on the current collector (aluminum foil), dried and cold pressed to obtain a positive electrode sheet with a compaction density of 3g/ cm3 .
  • the positive electrode sheet is applied to assemble a sodium ion battery.
  • the sodium ion battery comprises the positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and the like.
  • the negative electrode active material hard carbon
  • conductive agent conductive carbon
  • binder carboxymethyl cellulose, CMC
  • the mass ratio of the negative electrode active material, conductive agent, and binder is 95:2:3.
  • the negative electrode slurry is coated on the current collector (copper foil), dried, and cold pressed to obtain a negative electrode sheet.
  • Glass fiber film is used as the isolation membrane.
  • the positive electrode sheet, the separator and the negative electrode sheet are stacked in order, and the electrode assembly is formed after winding.
  • the electrode assembly is placed in a packaging shell, and after adding electrolyte, it is sealed, formed and left to stand.
  • Example 1 The difference between this comparative example and Example 1 is that the positive electrode plate does not contain a sodium supplement.
  • Example 1 The difference between this comparative example and Example 1 is that the sodium supplement Na 1.1 Mn 0.44 Ni 0.3 Fe 0.24 O 2 is replaced by Na 0.7 Mn 0.09 Ni 0.6 Fe 0.24 O 2 .
  • Example 1 The difference between this comparative example and Example 1 is that the sodium supplement Na 1.1 Mn 0.44 Ni 0.3 Fe 0.24 O 2 is replaced by Na 1.1 Mn 0.5 Ni 0.3 Fe 0.19 O 2 .
  • the test data shows that adding a suitable sodium supplement to the positive electrode plate can well realize the sodium supplement function, reduce the sodium loss of the positive electrode active material during the first cycle of charge and discharge (shown as high first efficiency), and is conducive to improving the battery cycle performance. Moreover, it can be seen from the comparison that after adding appropriate sodium supplements to the positive electrode plates in Examples 1 to 3, the discharge capacity and first efficiency of the sodium ion battery are similar to those without adding the sodium supplement, or even improved, reflecting that these sodium supplements will not cause a decrease in the capacity and first efficiency of the sodium ion battery.
  • Example 1, Example 4, Example 5 and Comparative Example 4 use sodium supplements with different Dv50 in the positive electrode plate, so that the sodium ion battery exhibits different cycle performance.
  • the Dv50 of the positive active material it can be seen that when the Dv50 of the sodium supplement is less than the Dv50 of the positive active material (Example 1, Example 4, Example 5), the capacity retention rate of the sodium ion battery after 300 cycles is high; and when the Dv50 of the sodium supplement is greater than the Dv50 of the positive active material (Comparative Example 4), the capacity retention rate of the sodium ion battery after 300 cycles is reduced.
  • the sodium supplement with a small particle size has a higher reaction activity during the charge and discharge process, and the sodium ions it provides preferentially participate in the formation of the SEI film and other electrochemical reactions that will consume active sodium, thereby reducing the loss of active sodium in the positive active material, so that the sodium ion battery exhibits excellent cycle performance.
  • the sodium supplement Dv50 when there is a certain difference between the sodium supplement Dv50 and the positive electrode active material Dv50, for example, when the sodium supplement Dv50 is 6.25% to 75% of the positive electrode active material Dv50, the capacity retention rate of the sodium ion battery after 300 cycles is above 82.7%; and when the sodium supplement Dv50 is 25% of the positive electrode active material Dv50, the capacity retention rate of the sodium ion battery is higher than other cases.
  • test results show that under different sodium supplements Dv50, sodium ion batteries have higher discharge capacity and first efficiency, reflecting that these sodium supplements will not cause a decrease in the capacity and first efficiency of sodium ion batteries.
  • the test results show that the amount of sodium supplement has an impact on the cycle performance of sodium ion batteries.
  • the mass ratio of sodium supplement to positive electrode active material is in the range of 1:(14.8-94)
  • the capacity retention rate of sodium ion batteries after 300 cycles increases first and then decreases; among them, when the mass ratio of sodium supplement to positive electrode active material is 1:(18-46.5), the capacity retention rate after 300 cycles is higher than other cases. Therefore, sodium ion batteries can exhibit better cycle performance by adjusting the mass ratio of sodium supplement to positive electrode active material.
  • Dv50 was obtained by using a laser particle size analyzer.
  • the sodium ion battery was left to stand for 30 minutes; then charged to 4.0V at a constant current rate of 0.33C, then charged to a current of 0.05C at a constant voltage of 4.0V; then left to stand for 30 minutes; discharged to 2V at a constant current rate of 0.33C, and then left to stand for 30 minutes.
  • This is a cycle of charge and discharge.
  • the sodium ion battery was cycled for 300 cycles according to the above steps, and the discharge capacity C 21 at this time was recorded.

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Abstract

本申请涉及电池技术领域，尤其涉及正极极片、钠离子二次电池、用电装置。所述正极极片包含补钠剂和正极活性材料，补钠剂包含NaqMnxMyO2，1≤q≤1.2，0.15≤x＜0.45，y＞0，0.9≤x+y≤1，M包括过渡金属元素；补钠剂的Dv50小于正极活性材料的Dv50。本申请的补钠剂NaqMnxMyO2具有较大的结构不稳定性，容易脱出钠；且该补钠剂的粒径小于正极活性材料的粒径，从而具有较正极活性材料更高的反应活性，能够较正极活性材料优先脱出钠离子参与电化学反应，有利于减少电池前期充放电过程中对正极活性材料所含活性钠的消耗，从而改善正极活性材料的结构破坏情况，改善电池的循环性能。

Description

正极极片、钠离子二次电池、用电装置
本申请要求于2023年11月16日在中国专利局提交的、申请号为202311531803.5、发明名称为“正极极片、钠离子二次电池、用电装置”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
本申请涉及电池技术领域，具体涉及一种正极极片、钠离子二次电池、用电装置。
背景技术
钠离子电池具有与锂离子电池类似的工作机理，主要通过钠离子在正极与负极之间的脱嵌来实现化学能与电能的转换。即，在充电过程中，正极的活性材料脱出钠离子，钠离子经过电解质的传输作用后嵌入负极的活性材料中；在放电过程中，钠离子再从负极活性材料中脱出，回到正极活性材料中。
在实践中发现，在钠离子电池充放电过程中容易发生容量衰减，循环性能不佳的问题，制约了钠离子电池的发展。
申请内容
本申请实施例的目的在于：提供一种正极极片、钠离子二次电池、用电装置，旨在解决钠离子电池循环性能不佳的问题。
技术解决方案
本申请实施例采用的技术方案是：
第一方面，本申请实施例提供一种正极极片，所述正极极片包含补钠剂和正极活性材料，所述补钠剂包含NaqMnxMyO2，1≤q≤1.2，0.15≤x＜0.45，y＞0，0.9≤x+y≤1，所述M包括过渡金属元素；所述补钠剂的Dv50小于所述正极活性材料的Dv50。
本申请实施例通过在正极极片中加入Mn基补钠氧化物NaqMnxMyO2作为补钠剂，NaqMnxMyO2中的Mn包括不稳定的Mn3+，使得NaqMnxMyO2的结构具有较大的不稳定性，容易脱出钠(Mn3+在该过程中可转换为稳定的Mn4+)。因此，电池前期充放电过程中，可利用NaqMnxMyO2作为形成固体电解质界面膜(SEI膜)消耗的活性钠源，从而减少电池前期充放电过程中对正极活性材料所含活性钠的消耗，改善正极活性材料的结构破坏情况，有利于改善电池的循环性能。
同时，通常地，小粒径材料相较大粒径材料具有更高的反应活性。本申请实施例通过将补钠剂的粒径设置为小于正极活性材料的粒径，可以使补钠剂具有较正极活性材料更高的反应活性，在电池前期充放电过程中具有更快的动力学，因此可以较正极活性材料优先脱出钠离子，以供SEI膜的形成，从而进一步减少对正极活性材料中活性钠的消耗，改善电池的循环性能。
在一些实施例中，1≤q≤1.1。q可以反映NaqMnxMyO2中的Na含量，将q设置在这些范围中，不仅可以使NaqMnxMyO2提供钠离子，减少首圈充电过程中对正极活性材料所含活性钠的消耗，有利于提高正极极片的容量和改善电池循环性能；而且可以使补钠剂在脱钠后具有很好的结构稳定性。
在一些实施例中，0.2≤x≤0.44。x可以反映NaqMnxMyO2中的Mn含量，NaqMnxMyO2中的Mn包括不稳定的Mn3+，将x设置在上述范围中，能使NaqMnxMyO2含有足够的Mn3+，使得NaqMnxMyO2的结构具有较大的不稳定性，容易脱出钠，从而有利于实现补钠效果。 而且，Mn在不同结构中具有不同的价态，能够适应不同Na含量的情况，也就是可以通过改变自身价态允许NaqMnxMyO2中加入更多的Na，从而有利于提高NaqMnxMyO2中的Na含量，进而有利于提高正极极片的容量和改善电池循环性能。
在一些实施例中，0.5≤y≤0.8。y反映NaqMnxMyO2中的过渡金属M含量。在NaqMnxMyO2加入适当含量的M，有助于提高NaqMnxMyO2脱钠后的结构稳定性，使NaqMnxMyO2在脱钠过程中不发生严重的结构坍塌。
在一些实施例中，所述M包括Fe、Ni、Co、Cu、Al、Ti、V中的一种或多种。这些过渡金属有助于提高NaqMnxMyO2脱钠后的结构稳定性。
在一些实施例中，所述M包括Fe和Ni，所述补钠剂包括NaqMnxNiy1Fey2O2，1≤q≤1.2，0.15≤x＜0.45，y1＞0，y2＞0，0.9≤x+y1+y2≤1。过渡金属采用Ni、Fe的组合，可以与Mn形成稳定的金属层结构；且研究表明，Ni、Fe组合有利于提高材料的能量密度。
在一些实施例中，所述补钠剂的相结构包括O3相。在不同的相结构中，Na+具有不同的配位环境和含量。本申请实施例的补钠剂包括O3相，O3相是一种具有高钠含量的相结构，因此有利于补钠剂提供大量的钠。
在一些实施例中，所述补钠剂的Dv50为所述正极活性材料的Dv50的6％～75％，可选地为6％～25％。将补钠剂的粒径设置为小于正极活性材料的粒径，可以使补钠剂具有较正极活性材料更高的反应活性，在首圈充电以及电池的前期循环过程中具有更快的动力学，因此可以较正极活性材料优先脱出钠离子，以供SEI膜的形成，从而减少对正极活性材料中活性钠的消耗，改善电池的循环性能。同时，在补钠剂Dv50与正极活性材料Dv50之间具有一定差值的情况下，能够使电池表现出更优的循环性能。
在一些实施例中，所述补钠剂的Dv50为0.5μm～6μm，可选地为1μm～3μm。在该粒径下，补钠剂具有高比表面积，比表面能高，而且钠的传输路径短，有利于提高其反应活性，促进脱钠。
在一些实施例中，所述正极活性材料的Dv50为6μm～20μm，可选地为6μm～10μm。在该粒径下，正极活性材料的反应活性较补钠剂低，能够在电池前期充放电过程中缓慢脱出钠离子，而不优先脱出钠离子，能够减慢正极活性材料中活性钠的消耗。而且，将正极活性材料与补钠剂进行大小粒径复配，小粒径的补钠剂可以填充到大粒径的正极活性材料之间，有利于提高正极极片的压实密度，进而提高正极极片的能量密度。
在一些实施例中，所述补钠剂与所述正极活性材料的质量比为1：(14～95)，可选地为1：(18～46.5)。补钠剂与正极活性材料的质量比对钠离子电池的循环性能具有影响。在上述质量比下，可以使钠离子电池表现出优异的循环性能。
在一些实施例中，所述补钠剂在所述正极极片所含活性层中的质量含量为1％～6％，可选地为2％～5％。在正极极片所含活性层中加入少量本申请实施例的补钠剂，即可有效实现补钠效果，改善电池循环性能。
在一些实施例中，所述正极活性材料包括层状氧化物、聚阴离子类化合物、普鲁士蓝类化合物中的一种或多种；可选地，所述层状氧化物包括NamM1 zO2，0.4≤m≤0.9，0.9≤z≤1，所述M1包括过渡金属元素。本申请实施例的正极极片适用于各种正极活性材料，可以对改善这些正极活性材料在电池循环过程中的结构破坏情况，改善电池的循环性能。
第二方面，本申请提供一种钠离子二次电池，所述钠离子二次电池包括第一方面所述正极极片。
上述正极极片含有特殊结构的补钠剂，且补钠剂与正极活性材料按照特定的粒径进行组合，将该正极极片应用于钠离子二次电池后，有利于改善钠离子二次电池的循环性能。
第三方面，本申请提供一种用电装置，所述用电装置包括第二方面所述钠离子二次电池。
本申请实施例公开的钠离子二次电池可以用于以二次电池作为电源的用电装置，或者以电池作为储能元件的各种储能系统，用于提供电能。上述钠离子二次电池具有良好的循环性能，因此，采用上述钠离子二次电池能够稳定地为各种用电装置提供电能，改善各种用电装置的使用体验。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或示范性技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的附图。
图1为本申请一实施方式的二次电池的示意图；
图2为图1所示的本申请一实施方式的二次电池的分解图；
图3为本申请一实施方式的电池模块的示意图；
图4为本申请一实施方式的电池包的示意图；
图5为图4所示的本申请一实施方式的电池包的分解图；
图6为本申请一实施方式的二次电池用作电源的用电装置的示意图。
具体实施方式中的附图标号如下：
壳体01，盖板02，电极组件03，电池单体04，电池模块05，上箱体06，下箱体07。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，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、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，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，可以表示：单独存在A，同时存在A和B，单 独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，“a,b,或c中的至少一项(个)”，或，“a,b,和c中的至少一项(个)”，均可以表示：a,b,c,a-b(即a和b),a-c,b-c,或a-b-c，其中a,b,c分别可以是单个，也可以是多个。
应理解，在本申请的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，部分或全部步骤可以并行执行或先后执行，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
本申请实施例说明书中所提到的相关成分的质量不仅仅可以指代各组分的具体含量，也可以表示各组分间质量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。具体地，本申请实施例说明书中所述的质量可以是μg、mg、g、kg等化工领域公知的质量单位。
钠离子电池由于原材料在自然界蕴藏丰富，分布广泛，受到了广泛关注和研究。与锂离子电池类似地，钠离子电池主要通过钠离子在正极与负极之间的脱嵌来实现化学能与电能的转换。即，在充电过程中，正极的活性材料脱出钠离子，钠离子经过电解质的传输作用后嵌入负极的活性材料中；在放电过程中，钠离子再从负极活性材料中脱出，回到正极活性材料中。
然而，实际上，并非所有正极活性材料在充电过程中脱出的钠离子都可以重新回到正极活性材料中。例如，在充电过程中，正极活性材料脱出的钠离子达到负极活性材料后，会有部分钠离子在负极活性材料表面形成固体电解质界面膜(SEI膜)，无法继续参与后续的循环；也有部分钠离子嵌入负极活性材料后无法在后续放电过程中从负极活性材料的晶格中脱出。这些现象造成了钠的不可逆损失，从而使得电池容量发生衰减，劣化钠离子电池的循环性能。
研究人员开发了对正极或负极进行预钠化的技术手段来解决上述问题。预钠化的方法包括通过辊压或吸附的方式将钠粉或钠箔加入正极或负极中；或者在正极或负极、电解液中加入预钠化试剂(补钠剂)，利用补钠剂来对损失的钠进行补偿。
不过在实践中发现，钠粉或钠箔反应活性极强，对操作环境要求较高，且存在潜在的安全问题。而多数补钠剂在电池充放电过程中的补钠效果有限，在充放电过程中难以较正极活性材料优先脱出钠离子，因此在电池前期充放电过程中需要正极活性材料提供钠离子，也会造成正极活性材料的不可逆钠损失。
针对上述问题，本申请实施例在正极极片添加一种特定的Mn基补钠氧化物作为补钠剂NaqMnxMyO2，该补钠剂包含不稳定的Mn3+，使得NaqMnxMyO2的结构具有较大的不稳定性，容易脱出钠；且该补钠剂的粒径小于正极活性材料的粒径，从而具有较正极活性材料更高的反应活性，能够较正极活性材料优先脱出钠离子参与电化学反应。因此，在这种补钠剂的作用下，能够减少电池前期充放电过程中对正极活性材料所含活性钠的消耗，改善正极活性材料的结构破坏情况，有利于改善电池的循环性能。
本申请实施例的包含该补钠剂的正极极片，可以应用于制作二次电池，从而可以进一步应用于各种用电装置。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
【正极极片】
第一方面，本申请提供一种正极极片，该正极极片包含补钠剂和正极活性材料，补钠剂包含NaqMnxMyO2，1≤q≤1.2，0.15≤x＜0.45，y＞0，0.9≤x+y≤1，M包括过渡金属元素；补钠剂的Dv50小于正极活性材料的Dv50。
正极活性材料是正极极片中参与电池电化学反应的重要物质，可以作为电化学反应离子传送的媒介。在本文的正极极片中，正极活性材料指的是钠离子电池正极活性材料。补钠剂包含NaqMnxMyO2，该NaqMnxMyO2可以通过X射线衍射法确定其晶体形态，并可以结合元素分析仪获得各元素种类以及各元素的含量、比例，再经换算得到该化学式中各元素的下标q、x、y。
Dv50是材料粒径的一种表示方式。对于材料的粒径分布，通常采用不同粒径区间内的颗粒占总量的百分数来表示。粒径分布的测定方法有多种基准，如数量分布、长度分布、面积分布、体积分布、重量分布等。Dv50是基于体积分布得到的特定粒径分布，也称中值粒径，指的是颗粒体积累积分布为50％的粒径，表示有50％的颗粒的直径超过此值，有50％的颗粒的直径低于此值。颗粒的Dv50可以参照GB/T 19077-2016/ISO 13320:2009《粒度分布激光衍射法》测试得到。本申请实施例中，补钠剂和正极活性材料的颗粒形貌可以分别独立是规则的球形，也可以是椭球形、多边形，或者是其他不规则的形状，对于球形颗粒，其粒径即其直径；对于非球形，或者其他不规则形状的颗粒，其粒径为其等效直径。
本申请实施例通过在正极极片中加入Mn基补钠氧化物NaqMnxMyO2作为补钠剂，NaqMnxMyO2中的Mn包括不稳定的Mn3+，使得NaqMnxMyO2的结构具有较大的不稳定性，容易脱出钠(Mn3+在该过程中可转换为稳定的Mn4+)。因此，电池前期充放电过程中，可利用NaqMnxMyO2作为形成固体电解质界面膜(SEI膜)消耗的活性钠源，从而减少电池前期充放电过程中对正极活性材料所含活性钠的消耗，改善正极活性材料的结构破坏情况，有利于改善电池的循环性能。
同时，通常地，小粒径材料相较大粒径材料具有更高的反应活性。本申请实施例通过将补钠剂的粒径设置为小于正极活性材料的粒径，可以使补钠剂具有较正极活性材料更高的反应活性，在电池前期充放电过程中具有更快的动力学，因此可以较正极活性材料优先脱出钠离子，以供SEI膜的形成，从而进一步减少对正极活性材料中活性钠的消耗，改善电池的循环性能。
在一些实施方式中，1≤q≤1.2，可选地，1≤q≤1.1。例如，q可以选择1.0、1.1、1.2中的任意一者点值或者任意两者之间的范围值。q可以反映NaqMnxMyO2中的Na含量，将q设置在这些范围中，不仅可以使NaqMnxMyO2提供钠离子，减少电池前期充放电过程中对正极活性材料所含活性钠的消耗，有利于提高正极极片的容量和改善电池循环性能；而且可以使补钠剂在脱钠后具有很好的结构稳定性。
在一些实施方式中，0.15≤x＜0.45，可选地，0.2≤x≤0.44。例如x可以选择0.15、0.2、0.25、0.3、0.35、0.4、0.44中的任意一者点值或者任意两者之间的范围值。x可以反映NaqMnxMyO2中的Mn含量，NaqMnxMyO2中的Mn包括不稳定的Mn3+，将x设置在上述范围中，能使NaqMnxMyO2含有足够的Mn3+，使得NaqMnxMyO2的结构具有较大的不稳定性，容易脱出钠，从而有利于实现补钠效果。而且，Mn在不同结构中具有不同的价态，能够适 应不同Na含量的情况，也就是可以通过改变自身价态允许NaqMnxMyO2中加入更多的Na，从而有利于提高NaqMnxMyO2中的Na含量，进而有利于提高正极极片的容量和改善电池循环性能。
在一些实施方式中，y＞0，可选地，0.5≤y≤0.8。例如，y可以选择0.5、0.55、0.6、0.65、0.7、0.75、0.8中的任意一者点值或者任意两者之间的范围值。y反映NaqMnxMyO2中的过渡金属M含量。在NaqMnxMyO2加入适当含量的M，有助于提高NaqMnxMyO2的结构稳定性，使NaqMnxMyO2在脱钠过程中不发生严重的结构坍塌。
在一些实施方式中，M包括Fe、Ni、Co、Cu、Al、Ti、V中的一种或多种，可选地，M包括Fe和Ni中的至少一种。这些过渡金属有助于提高NaqMnxMyO2的结构稳定性。
在一些实施方式中，M包括Fe和Ni，补钠剂包括NaqMnxNiy1Fey2O2，1≤q≤1.2，0.15≤x＜0.45，y1＞0，y2＞0，0.9≤x+y1+y2≤1。过渡金属采用Ni、Fe的组合，可以与Mn形成稳定的金属层结构；且研究表明，Ni、Fe组合有利于提高材料的能量密度。
在一些实施方式中，y1＞0，可选地，0.3≤y1≤0.44，例如y1可以是0.3、0.35、0.4、0.44中的任意一者点值或者任意两者之间的范围值。y2＞0，可选地，0.24≤y2≤0.34，例如y2可以是0.24、0.25、0.3、0.34中的任意一者点值或者任意两者之间的范围值。将Ni、Fe按照一定的比例进行组合，有利于发挥更好的结构稳定作用以及能量密度提升作用。
在一些实施方式中，补钠剂的相结构包括O3相。Mn基补钠氧化物NaqMnxMyO2属于层状氧化物，由TO6(在本申请实施例中，T包括Mn、过渡金属元素M)层状结构堆叠而成，Na+在TO6堆叠的层间嵌入和脱出。根据Na+配位环境的不同，层状氧化物的相结构可以分为O相和P相。O表示Na+是八面体配位(Octahedral)，Na+占据八面体点位；P表示Na+是三棱柱配位(Prismatic)，Na+占据三角形棱柱点位。晶体结构中，Na+与TO6结构在O相中以棱共享方式连接，在P相中以面共享和棱共享方式连接。
根据氧层的堆积顺序，可将层状氧化物进一步分为P2相、O2相、P3相和O3相，其中P2的堆积方式为ABBA，O2的堆积方式为ABAC(或ABCB)，P3的堆积方式为ABBCCA，O3的堆积方式为ABCABC。数字“2”和“3”表示每个单元中不同种类的O堆叠的过渡金属层数。
相结构可以通过X射线衍射分析得到。例如，采用X射线粉末衍射仪对样品进行测试，获得样品的X射线衍射谱，通过将X射线衍射谱中的XRD衍射峰与XRD分析软件的标准卡片对比，可确认样品的相结构。
在不同的相结构中，Na+具有不同的配位环境和含量。本申请实施例的补钠剂的相结构包括O3相，O3相是一种具有高钠含量的相结构，因此有利于补钠剂提供大量的钠。
在一些实施方式中，补钠剂的Dv50为正极活性材料Dv50的6％～75％，可选地为6％～25％。例如，补钠剂的Dv50为正极活性材料Dv50的6％、10％、15％、20％、25％、30％、35％、40％、45％、50％、55％、60％、65％、70％、75％中的任意一者点值或者任意两者之间的范围值。将补钠剂的粒径设置为小于正极活性材料的粒径，可以使补钠剂具有较正极活性材料更高的反应活性，在首圈充电以及电池的前期循环过程中具有更快的动力学，因此可以较正极活性材料优先脱出钠离子，以供SEI膜的形成，从而减少对正极活性材料中活性钠的消耗，改善电池的循环性能。同时，在补钠剂Dv50与正极活性材料Dv50之间具有一定差值的情况下，能够使电池表现出更优的循环性能。
在一些实施方式中，补钠剂的Dv50为0.5μm～6μm，可选地为1μm～3μm，例如可以是 0.5μm、1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm中的任意一者点值或者任意两者之间的范围值。在该粒径下，补钠剂具有高比表面积，比表面能高，而且钠的传输路径短，有利于提高其反应活性，促进脱钠。
在一些实施方式中，补钠剂与正极活性材料的质量比为1：(14～95)，可选地为1：(18～46.5)，例如二者的质量比可以是1：14，1：20，1：25，1：30，1：35，1：40，1：45，1：50，1：55，1：60，1：65，1：70，1：75，1：80，1：85，1：90，1：95中的任意一者点值或者任意两者之间的范围值。补钠剂与正极活性材料的质量比对钠离子电池的循环性能具有影响。在上述质量比下，钠离子电池表现出优异的循环性能。
在一些实施方式中，补钠剂在正极极片所含活性层中的质量含量为1％～6％，可选地为2％～5％，例如可以是1％、2％、3％、4％、5％、6％中的任意一者点值或者任意两者之间的范围值。在正极极片所含活性层中加入少量本申请实施例的补钠剂，即可有效实现补钠效果，改善电池循环性能。
在一些实施方式中，正极活性材料的Dv50为6μm～20μm，可选地为6μm～10μm，例如可以是6μm、7μm、8μm、9μm、10μm、12μm、14μm、16μm、18μm、20μm中的任意一者点值或者任意两者之间的范围值。在该粒径下，正极活性材料的反应活性较补钠剂低，能够在电池前期充放电过程中缓慢脱出钠离子，而不优先脱出钠离子，从而减慢正极活性材料中活性钠的消耗。而且，将正极活性材料与补钠剂进行大小粒径复配，小粒径的补钠剂可以填充到大粒径的正极活性材料之间，有利于提高正极极片的压实密度，进而提高正极极片的能量密度。
在一些实施方式中，正极活性材料可以包括层状氧化物、聚阴离子类化合物、普鲁士蓝类化合物中的一种或多种。例如，层状氧化物可以包括NamM1 zO2，0.4≤m≤0.9，可选地0.8≤m≤0.9；0.9≤z≤1，M1包括过渡金属元素。例如m可以是0.4、0.5、0.6、0.7、0.8、0.9中的任意一者点值或者任意两者之间的范围值；z可以是0.9、0.92、0.94、0.96、0.98、1中的任意一者点值或者任意两者之间的范围值；M1包括Fe、Mn、Ni、Co、Cr、Sc、Ti、V、Cr、Cu、Zn中的一种或多种。可选地，层状氧化物可以包括Nam1Mnz1Mz2O2，0.8≤m1≤0.9，0.09＜z1＜0.45，0.9≤z1+z2≤1。例如层状氧化物可以包括Na0.7CoO2、Na0.6MnO2、Na0.44MnO2、Na0.65Mn0.75Ni0.25O2、Na0.78Ni0.23Mn0.69O2、Na0.67Mn0.67Ni0.33O2、Na0.82Mn0.33Ni0.33Fe0.33O2等。
聚阴离子类化合物可以是具有钠离子、过渡金属离子及四面体型(YO4)n-阴离子单元的一类化合物；或者，聚阴离子类化合物可以是具有钠离子、过渡金属离子、四面体型(YO4)n-阴离子单元及卤素阴离子的一类化合物，卤素包括F、Cl、Br中的一种或多种；或者，聚阴离子类化合物可以是具有钠离子、四面体型(YO4)n-阴离子单元、多面体单元(ZOy)n1+及可选的卤素阴离子的一类化合物。其中过渡金属、Z可以分别独立地包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr、Ce中一种或多种，Y包括P、S、Si中的一种或多种，n表示(YO4)n-的价态，n1表示(ZOy)n1+的价态。例如，聚阴离子类化合物可以包括磷酸盐、焦磷酸盐、硫酸根型、阴离子掺杂型中的一种或多种，例如橄榄石型NaFePO4、Na2FeP2O7、NaFePO4F、Na3V2(PO4)3、NaFeSO4中的一种或多种。
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，其中过渡金属包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr、Ce中一种或多种。例如普鲁士蓝类化合物可以包括NaaM2 b[M3 c(CN)6]d，0＜a≤2，0＜b≤1，0＜c≤1，0.8≤d≤1，M2、 M3分别独立地包括过渡金属元素。例如a可以是0.4、0.6、0.8、1、1.2、1.4、1.6、1.8、2中的任意一者点值或者任意两者之间的范围值；b可以是0.2、0.4、0.6、0.8、1中的任意一者点值或者任意两者之间的范围值；c可以是0.2、0.4、0.6、0.8、1中的任意一者点值或者任意两者之间的范围值；d可以是0.8、0.85、0.9、0.95、1中的任意一者点值或者任意两者之间的范围值；M2、M3可以分别独立地包括Ni、Cu、Fe、Mn、Co、Zn中的一种或多种。例如普鲁士蓝类化合物可以包括Na0.61Fe[Fe(CN)6]0.94、BR-FeHCF、Na1.48Ni[Fe(CN)6]0.89、NaNi0.05Mn0.95[Fe(CN)6]中的一种或多种。
本申请实施例的正极片适用于各种正极活性材料，可以对改善这些正极活性材料在电池循环过程中的结构破坏情况，改善电池的循环性能。
在一些实施方式中，正极活性材料在正极极片所含活性层中的质量含量为80％～98％，例如可以是80％、82％、84％、86％、88％、90％、92％、94％、96％、98％中的任意一者点值或者任意两者之间的范围值。正极活性材料作为正极极片中参与电化学反应的主要物质，提供容量，可以理解地，其在正极活性层中的质量含量高，将有利于改善正极极片的能量密度。
在一些实施方式中，正极极片的压实密度为2.5g/cm3～4g/cm3，可选地为2.6g/cm3～3.3g/cm3，例如可以是2.5g/cm3、2.6g/cm3、2.8g/cm3、3g/cm3、3.2g/cm3、3.4g/cm3、3.5g/cm3、3.6g/cm3、3.8g/cm3、4g/cm3中的任意一者点值或者任意两者之间的范围值。压实密度是产品在一定的压力下的密度，对于正极极片，其压实密度＝面密度/(正极极片压实后的厚度-集流体厚度)。压实密度可以参照相关标准，如GB/T 24533-2019中的附录L《粉末压实密度的测试方法》，采用压实密度仪测试得到。压实密度对正极极片的能量密度、电解液浸润性能、钠离子传输速率等具有影响。压实密度越大，则单位体积中正极活性材料、补钠剂的质量越高，有利于提高正极极片的能量密度。同时，压实密度也反映极片的孔隙率，在合适的孔隙率下，极片具有很好的电解液浸润性能，方便钠离子的传输。本申请实施例的正极极片具有合适的压实密度，不仅有利于提高极片的能量密度，也有利于提高极片的电解液浸润性能，加快钠离子的传输。
另外，正极极片通常还包含导电剂、粘结剂、正极集流体。导电剂、粘结剂与上述补钠剂、正极活性材料形成正极极片的活性层，活性层设置于正极集流体的至少一个表面上。导电剂用于在活性材料之间，以及活性材料与正极集流体之间收集微电流，提高电子电导率，同时导电剂还可以促进电解液对正极极片的浸润。粘结剂则能够提高活性层中各物质之间，以及活性层与正极集流体之间的结合强度。正极集流体用于传输电子。
可选地，导电剂在正极极片所含活性层的质量含量为0.5％～5％，可选地为1％～5％，例如0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％中的任意一者点值或者任意两者之间的范围值，也可以根据需要设置为其他的含量。
导电剂可以包括但不限于乙炔黑(SP)、碳纳米管、导电炭黑(super-P)、科琴黑、碳纤维、石墨烯中的一种或多种。
可选地，粘结剂在正极极片所含活性层中的质量含量为0.5％～5％，可选地为1％～7％，例如0.5％、1％、2％、3％、4％、5％中的任意一者点值或者任意两者之间的范围值，也可以根据需要设置为其他的含量。
粘结剂可以包括但不限于聚偏二氟乙烯、聚偏氟乙烯-六氟丙烯共聚物、聚氧化乙 烯、聚酰亚胺、聚四氟乙烯、聚丙烯酸丁酯、聚丙烯腈、羧甲基纤维素、羧甲基纤维素盐、聚丙烯酸、聚丙烯酸盐、聚乙烯醇、海藻酸钠、环糊精、丁苯橡胶、醋酸乙烯树脂、丙烯酸树脂、氯化橡胶中的一种或多种。
本申请实施例中，正极集流体可以包括但不限于金属集流体、碳集流体、导电树脂集流体、金属与树脂的复合集流体等，更具体例如铝、铜、镍、钛、铁及它们各自的合金，不锈钢、碳纤维、碳纳米管(CNT)、石墨等。可选地，正极集流体包括铝。
【正极极片的制备方法】
本申请实施例的正极极片可以通过如下制备方法制备得到，包括：
制备包含补钠剂和正极活性材料的正极浆料，将正极浆料涂布在集流体的至少一个表面上，经干燥、压实，得到正极极片；
补钠剂包含NaqMnxMyO2，1≤q≤1.2，0.15≤x＜0.45，y＞0，0.9≤x+y≤1，M包括过渡金属元素；补钠剂的Dv50小于正极活性材料的Dv50。
通过在正极极片的制备过程中加入包含NaqMnxMyO2，且Dv50小于正极活性材料的补钠剂，一方面可以利用NaqMnxMyO2的结构不稳定性，将其作为形成固体电解质界面膜消耗的活性钠源，从而减少首圈充电过程中对正极活性材料所含活性钠的消耗，改善正极活性材料的结构破坏情况，有利于改善电池的循环性能；另一方面，小粒径的补钠剂具有较大粒径正极活性材料更高的反应活性，在首圈充电以及电池的前期循环过程中具有更快的动力学，因此可以较正极活性材料优先脱出钠离子，以供SEI膜的形成，进一步减少对正极活性材料中活性钠的消耗，改善电池的循环性能。
更具体地，可以按照如下方法制作正极极片：
将补钠剂和正极活性材料、导电剂、粘结剂(可选地还可以根据需要加入增稠剂或其他添加剂)与溶剂混合，得到正极浆料；
将正极浆料涂布在集流体的至少一个表面上，经干燥、压实，得到正极极片。
其中的溶剂可以包括但不限于N-甲基吡咯烷酮(NMP)。压实的方法可以包括热压、冷压中的一种或多种，压实步骤中可以根据目标压实密度来确定所采用的压力大小。
另外，本申请实施例的补钠剂可以通过固相法或其他方法制备得到，例如，可以参考如下方法制备补钠剂：
按照NaqMnxMyO2的原子比例，将Na源、Mn源和M源进行共同煅烧处理。
通过采用固相法，对各种原料进行共同煅烧处理，即可得到NaqMnxMyO2，制备方法简单，适合于大规模生产。
其中，煅烧处理的温度为600℃～1200℃，例如可以包括但不限于600℃、650℃、700℃、750℃、800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃、1150℃、1200℃中的任意一者点值或者任意两者之间的范围值。在煅烧处理的温度下的保温时间为5h～24h，例如可以包括但不限于5h、10h、12h、14h、16h、18h、20h、22h、24h中的任意一者点值或者任意两者之间的范围值。煅烧处理的温度以及在该温度下的保温时间可以通过在煅烧设备，例如马弗炉上直接设置并进行控制。在合适的煅烧温度和时间下，各原料能够充分熔融混合并发生反应，形成Na、Mn和M的复合金属氧化物。
上述的煅烧处理步骤可以在空气或氧气气氛中进行。
煅烧处理步骤前，可以包括将Na源、Mn源和M源进行混合处理的步骤。混合处理的方法包括但不限于机械搅拌、研磨、球磨中的一种或多种，以使各原料充分混合，并减 小材料粒径。
在煅烧处理步骤后，还可以包括破碎处理的步骤，以使补钠剂具有所需粒径。
补钠剂的制备方法中，Na源、Mn源和M源可以分别独立地可以选择其各自的溶解性化合物或非溶解性化合物。例如，各原料的具体种类可选择如下化合物：
Na源包括但不限于Na2CO3、NaHCO3、NaOH、Na2O2以及其他钠盐中的一种或多种；
Mn源包括但不限于Mn2O3、Mn3O4、MnO、MnO2中的一种或多种；
M源包括但不限于含M的氧化物、含M的氢氧化物、含M的碳酸盐、含M的碳酸氢盐中的一种或多种。
【钠离子二次电池】
上述含有特定补钠剂的正极极片可应用于制作钠离子二次电池(以下称二次电池)。
本申请实施例第二方面提供一种二次电池，该二次电池包括上述第一方面的正极极片。
按照包装形式不同，二次电池分为电池单体、电池模组、电池包。本申请实施例的二次电池可以包括电池单体、电池模组、电池包中的一种或多种。
上述正极极片含有特殊结构的补钠剂，且补钠剂与正极活性材料按照特定的粒径进行组合，将该正极极片应用于二次电池后，有利于改善二次电池的循环性能。
通常地，二次电池还包括负极极片、电解质、隔离膜、外包装或其他组成部分。以下对二次电池各组成部分进行说明。
1.负极极片
在二次电池中，负极极片通常与正极极片相互隔离(通常通过隔离膜进行隔离)。负极极片包括负极集流体，还可选地包括设置在负极集流体至少一侧的负极活性层，负极活性层包含负极活性材料。
其中，负极集流体可以包括但不限于金属或复合集流体。例如，作为金属，可以采用钠、钠合金、铜、铜合金、镍、镍合金、钛、钛合金、银、银合金等。在采用钠或钠合金作为负极集流体的情况下，由于钠或钠合金自身也可以作为负极活性材料，因此负极极片可以不含负极活性层，钠或钠合金既是集流体也是负极活性材料。
复合集流体可以包括高分子材料与金属的复合材料，其中的高分子材料可以包括但不限于聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等，金属可以包括但不限于钠、铜、铜合金、镍、镍合金、钛、钛合金、银、银合金。复合集流体可以由高分子材料与金属相互掺混而得，也可以通过电镀、涂布或其他方式使覆于高分子材料的至少一侧。
对于负极极片包括负极活性层的情况，负极活性层中的负极活性材料可以包括但不限于碳基材料、合金材料、钛基材料、钠金属中的任意一种或多种形成的混合或复合材料。其中碳基材料包括但不限于石墨、软碳、硬碳、碳微球、碳纤维中的一种或多种；合金材料包括但不限于钠锡合金、钠锗合金、钠锑合金中的一种或多种；钛基材料包括但不限于二氧化钛、钛酸盐、钛磷酸盐中的一种或多种。
负极活性材料在负极活性层中的质量含量可以设置为85％～98％，再如95％～98％，例如85％、90％、91％、92％、93％、94％、95％、96％、97％、98％中的任意一者点值或者任意两者之间的范围值。
负极活性层还可以包括导电剂、粘结剂中的一种或多种。导电剂用于在活性材料之间，以及活性材料与集流体之间收集微电流，提高电子电导率，同时导电剂还可以 促进电解液对负极极片的浸润。粘结剂则能够提高活性层中各物质之间，以及活性层与集流体之间的结合强度。
导电剂在负极活性层的质量含量可以设置为0.5％～10％，例如0.5％、1％、2％、3％、4％、5％、6％、7％、8％、9％、10％中的任意一者点值或者任意两者之间的范围值，也可以根据需要设置为其他的含量。
导电剂包括乙炔黑(SP)、碳纳米管、导电炭黑(super-P)、科琴黑、碳纤维、石墨烯中的一种或多种。
粘结剂在负极活性层中的质量含量为0.5％～10％，例0.5％、1％、2％、3％、4％、5％、6％、7％、8％、9％、10％中的任意一者点值或者任意两者之间的范围值，也可以根据需要设置为其他的含量。
粘结剂包括但不限于聚偏二氟乙烯、聚偏氟乙烯-六氟丙烯共聚物、聚氧化乙烯、聚酰亚胺、聚四氟乙烯、聚丙烯酸丁酯、聚丙烯腈、羧甲基纤维素、羧甲基纤维素盐、聚丙烯酸、聚丙烯酸盐、聚乙烯醇、海藻酸钠、环糊精、丁苯橡胶、醋酸乙烯树脂、丙烯酸树脂、氯化橡胶中的一种或多种。
负极活性层还可选地包括增稠剂，例如羧甲基纤维素(CMC)。增稠剂在正极活性层中的质量含量可以设置为0.5％～5％，例如0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％中的任意一者点值或者任意两者之间的范围值。
在集流体即为负极活性材料的情况下，通过对该集流体进行分切即可作为负极极片。
对于负极极片包括负极活性层的情况，可以通过物理气相沉积、化学气相沉积、电镀等方式将负极活性材料覆于集流体的至少一侧上。或者，可以通过制浆、涂布、干燥、压实等工序制作形成负极极片。例如，将负极活性材料、导电剂、粘结剂(可选地还可以根据需要加入其他添加剂)与溶剂混合，得到负极浆料；将负极浆料涂布在集流体上，经干燥、压实，得到负极极片。其中的溶剂可以包括但不限于N-甲基吡咯烷酮(NMP)。压实的方法可以包括热压、冷压中的一种或多种，压实步骤中可以根据目标压实密度来确定所采用的压力大小。
2.电解质
二次电池还包括电解质液，正极极片和负极极片分别独立地与电解质接触。电解质在正极极片和负极极片之间起到传导离子的作用。电解质可以是液态的、凝胶态的或全固态的。
例如，电解质可以采用电解液，电解液包括电解质钠盐和溶剂。
电解质钠盐包括六氟磷酸钠、双氟磺酰亚胺钠、三氟甲基磺酸钠、硫化钠、氯化钠、氟化钠、硫酸钠、碳酸钠、磷酸钠、硝酸钠、二氟草酸硼酸钠、焦磷酸钠、十二烷基苯磺酸钠、十二烷基硫酸钠、柠檬酸三钠、偏硼酸钠、硼酸钠、钼酸钠、钨酸钠、溴化钠、亚硝酸钠、碘酸钠、碘化钠、硅酸钠、木质素磺酸钠、草酸钠、铝酸钠、甲基磺酸钠、醋酸钠、重铬酸钠、六氟砷酸钠、四氟硼酸钠、高氯酸钠、三氟甲烷磺酰亚胺钠中的一种或多种。
溶剂包括碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、二甲醚(DME)、二乙二醇二甲醚、二乙二醇二乙醚、四乙二醇二甲醚、2,2,2,2-三氟乙醚、乙二醇二乙醚、三乙二醇二甲醚、甲基三氟乙基碳酸酯(FEMC)、二氧戊环(DOL)、乙腈(AN)、氟苯、 磷酸三乙酯(TEP)、环丁砜、2-甲基四氢呋喃、四氢呋喃、二甲基亚砜、N,N二甲基乙酰胺中的一种或多种。
电解液还可以包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善二次电池某些性能的添加剂，例如改善二次电池过充性能的添加剂、改善二次电池高温或低温性能的添加剂等。
3.隔离膜
二次电池还包括隔离膜，隔离膜设置在正极极片和负极极片之间，可以将正负极分隔开。隔离膜可以让二次电池内的电子不能自由通过，防止电极之间接触短路，但是能够让电解质中的离子在正极极片与负极极片之间自由通过。
隔离膜可以选用具有电化学稳定性和机械稳定性的多孔结构隔离膜，例如玻璃纤维、无纺布、聚乙烯(PE)、聚丙烯(PP)及聚偏二氟乙烯(PVDF)中的一种或多种的单层或多层薄膜。
4.外包装
二次电池可包括外包装。该外包装可用于封装包含正极极片、负极极片、隔离膜的电极组件，及电解质。
二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等；也可以是软包，例如袋式软包。软包的材质可以是塑料，例如聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
二次电池的外包装形状可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的外包装形状为方形结构的二次电池。
参照图2，外包装可包括壳体01和盖板02。其中，壳体01可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体01具有与容纳腔连通的开口，盖板02能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件03。一个或多种电极组件03封装于容纳腔内。电解液浸润于电极组件03中。
5.电池单体、电池模组、电池包
本申请实施例的二次电池包括电池单体、电池模组、电池包中的一种或多种。
按照包装形式不同，二次电池可以分为电池单体、电池模组、电池包。其中电池单体是二次电池最基本的单元，包括电极组件和电解质，电极组件通常包括正极极片、负极极片、补锂电极和隔离膜。将正极极片和负极极片交替层叠设置，并在正极极片和负极极片之间设置隔离膜以起到隔离的作用，得到裸电芯，也可以是经卷绕后得到裸电芯。将裸电芯置于外包装中，注入电解液，经封装得到电池单体。
将一个或多个电池单体整合后则形成电池模组，电池模组能够提供更高的电压和容量，有特定功能的输出。将一个或多个电池模组安装于电池的箱体中，通常还会加入电池管理系统等，形成电池包。该电池包通常是提供给用户的产品。或者，也可直接将一个或多个电池单体安装设置于箱体中形成电池包。
参考图3，其是一个示例的电池模块。在电池模块中，多个电池单体04可以沿电池模块的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体04进行固定。
可选地，电池模块还可以包括具有容纳空间的外壳，多个电池单体04容纳于该容 纳空间。
参考图4和图5，其作为一个示例的电池包。在电池包中可以包括电池箱和设置于电池箱中的多个电池模块05。电池箱包括上箱体06和下箱体07，上箱体06能够盖设于下箱体07，并形成用于容纳电池模块05的封闭空间。多个电池模块05可以按照任意的方式排布于电池箱中。
【用电装置】
本申请实施例还提供一种用电装置，该用电装置包括上述二次电池。
本申请实施例公开的二次电池可以用于以二次电池作为电源的用电装置，或者以二次电池作为储能元件的各种储能系统，用于提供电能。上述二次电池具有良好的循环性能，因此，采用上述二次电池能够稳定地为各种用电装置提供电能，改善各种用电装置的使用体验。
用电装置可以包括但不限于手机、平板、笔记本电脑、电动玩具、电动工具、电瓶车、电动汽车、轮船、航天器等等。其中，电动玩具可以包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等，航天器可以包括飞机、火箭、航天飞机和宇宙飞船等等。作为所述用电装置，可以根据其使用需求来选择二次电池中的电池单体、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
以下详细说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
【正极极片】
本实施例提供一种正极极片，其活性层中包含补钠剂Na1.1Mn0.44Ni0.3Fe0.24O2和正极活性材料Na0.82Mn0.33Ni0.33Fe0.33O2。其中，补钠剂的Dv50为2μm，补钠剂在活性层中的质量含量为3％；正极活性材料的Dv50为8μm，正极活性材料在活性层中的质量含量为92％(补钠剂与正极活性材料的质量比＝3：92＝1：30.7)。
该正极极片的制备方法包括如下步骤：
将正极活性材料、补钠剂、粘结剂(聚偏二氟乙烯，PVDF)和导电剂(导电碳)在溶剂(N-甲基吡咯烷酮，NMP)中充分搅拌混合均匀后，得到正极浆料。其中正极活性材料、补钠剂、粘结剂和导电剂的质量比为92：3：2：3。将正极浆料涂覆于集流体(铝箔)上，烘干、冷压，得到压实密度为3g/cm3的正极极片。
【钠离子电池】
本实施例将上述正极极片应用于组装钠离子电池。该钠离子电池包含上述正极极片，以及负极极片、隔离膜、电解液等。
(1)电解液
以1mol/L NaPF6溶液作为电解液，溶剂包括：碳酸乙烯酯EC：碳酸丙烯酯PC：氟代碳酸乙烯酯FEC＝47.5：47.5：5(体积比)。
(2)负极极片
将负极活性材料(硬碳)、导电剂(导电碳)、粘结剂(羧甲基纤维素，CMC)在去离子水中充分搅拌混合均匀后，得到负极浆料。其中负极活性材料、导电剂、粘结剂的质量比为95：2：3。将负极浆料涂覆于集流体(铜箔)上，烘干、冷压，得到负极极片。
(3)隔离膜
以玻璃纤维薄膜作为隔离膜。
(4)钠离子电池
将上述正极极片、隔离膜以及负极极片按顺序叠放，经卷绕后形成电极组件，将电极组件装入包装外壳中，加入电解液后封口、化成、静置。
实施例2
本实施例与实施例1的区别在于：将补钠剂Na1.1Mn0.44Ni0.3Fe0.24O2替换为Na1.2Mn0.2Ni0.44Fe0.34O2。
实施例3
本实施例与实施例1的区别在于：将补钠剂Na1.1Mn0.44Ni0.3Fe0.24O2替换为NaMn0.44Ni0.3Fe0.24O2。
实施例4
本实施例与实施例1的区别在于：补钠剂的Dv50为0.5μm。
实施例5
本实施例与实施例1的区别在于：补钠剂的Dv50为6μm。
实施例6
本实施例与实施例1的区别在于：正极极片中，保持补钠剂与正极活性材料在活性层中的总质量含量不变，将补钠剂在活性层中的质量含量设置为1％(补钠剂与正极活性材料的质量比＝1：94)。
实施例7
本实施例与实施例1的区别在于：正极极片中，保持补钠剂与正极活性材料在活性层中的总质量含量不变，将补钠剂在活性层中的质量含量设置为2％(补钠剂与正极活性材料的质量比＝2：93＝1：46.5)。
实施例8
本实施例与实施例1的区别在于：正极极片中，保持补钠剂与正极活性材料在活性层中的总质量含量不变，将补钠剂在活性层中的质量含量设置为5％(补钠剂与正极活性材料的质量比＝5：90＝1：18)。
实施例9
本实施例与实施例1的区别在于：正极极片中，保持补钠剂与正极活性材料在活性层中的总质量含量不变，将补钠剂在活性层中的质量含量设置为6％(补钠剂与正极活性材料的质量比＝6：89＝1：14.8)。
对比例1
本对比例与实施例1的区别在于，正极极片中不含补钠剂。
对比例2
本对比例与实施例1的区别在于：将补钠剂Na1.1Mn0.44Ni0.3Fe0.24O2替换为Na0.7Mn0.09Ni0.6Fe0.24O2。
对比例3
本对比例与实施例1的区别在于：将补钠剂Na1.1Mn0.44Ni0.3Fe0.24O2替换为Na1.1Mn0.5Ni0.3Fe0.19O2。
对比例4
本实施例与实施例1的区别在于：补钠剂的Dv50为10μm。
对各实施例和对比例的钠离子电池的容量、首效，以及循环性能进行测试，结果如下表1～表3所示。
表1.采用不同补钠剂下的电化学性能测试结果(补钠剂Dv50＝2μm，正极活性材料Dv50＝8μm，补钠剂与正极活性材料的质量比＝1：30.7)
表1反映，相较未在正极极片中添加补钠剂的情况(对比例1)，实施例1～实施例3在正极极片的活性层中添加3％(补钠剂与正极活性材料的质量比＝1：30.7)、Dv50＝2μm的Na1.1Mn0.44Ni0.3Fe0.24O2、Na1.2Mn0.2Ni0.44Fe0.34O2、NaMn0.44Ni0.3Fe0.24O2作为补钠剂，可以使钠离子电池表现出很好的循环性能，经过300圈循环后容量保持率高达86.8％～89.2％；同时，钠离子电池还表现出高首效。测试数据反映出采用在正极极片中加入合适的补钠剂能够很好地实现补钠功能，能够减少正极活性材料在首圈充放电过程中的钠损耗(表现为高首效)，并有利于改善电池循环性能。而且，比较可见，实施例1～实施例3在正极极片中加入合适的补钠剂后，钠离子电池的放电容量、首效与未添加补钠剂的情况相近，甚至有所提高，反映了这些补钠剂不会造成钠离子电池容量、首效的降低。
相比之下，当所采用的补钠剂中元素具有不恰当的比例时，例如对比例2中q和x过小，即Na与Mn的比例过小，而对比例3中x过大，即Mn的比例过大，其在钠离子电池充放电过程中不能很好地达到补钠的效果，钠离子电池的循环性能较实施例1～实施例3发生了较大的劣化。
表2.不同补钠剂粒径下的电化学性能测试结果(补钠剂化学式为Na1.1Mn0.44Ni0.3Fe0.24O2，补钠剂与正极活性材料的质量比＝1：30.7)
实施例1、实施例4、实施例5以及对比例4在正极极片中采用了不同Dv50的补钠剂，使得钠离子电池表现出不同的循环性能。结合正极活性材料的Dv50进行分析可见，在补钠剂Dv50小于正极活性材料Dv50的情况下(实施例1、实施例4、实施例5)，钠离子电池循环300圈后的容量保持率较高；而在补钠剂Dv50大于正极活性材料Dv50的情况下(对比例4)，钠离子电池循环300圈后的容量保持率降低。这可能是因为在补钠剂Dv50小于正极活性材料Dv50的情况下，在充放电过程中小粒径的补钠剂具有更高的反应活性，其提供的钠离子优先参与SEI膜的形成以及其他会损耗活性钠的电化学反应，从而减少正极活性材料的活性钠损失，使钠离子电池表现出优异的循环性能。
同时，在补钠剂Dv50与正极活性材料Dv50之间具有一定差值的情况下，例如补钠剂Dv50为正极活性材料Dv50的6.25％～75％的情况下，钠离子电池循环300圈后的容量保持率均在82.7％以上；且在补钠剂Dv50为正极活性材料Dv50的25％的情况下，钠离子电池的容量保持率较其他情况更高。
另外，测试结果显示，在不同补钠剂Dv50下，钠离子电池均具有较高的放电容量和首效，反映出这些补钠剂不会造成钠离子电池容量、首效的降低。
表3.不同补钠剂用量下的电化学性能测试结果(补钠剂化学式为Na1.1Mn0.44Ni0.3Fe0.24O2，Dv50＝2μm；正极活性材料Dv50＝8μm)
测试结果显示，补钠剂的用量对钠离子电池的循环性能具有影响。补钠剂与正极活性材料的质量比在1：(14.8～94)范围内，随着补钠剂质量比例的增大，钠离子电池循环300圈后的容量保持率发生了先增加后降低的现象；其中，补钠剂与正极活性材料的质量比为1：(18～46.5)时，循环300圈后的容量保持率高于其他情况。因此，可以通过调整补钠剂与正极活性材料的质量比来使钠离子电池表现出更好的循环性能。
附：上述各种性能的具体测试方法如下：
(1)Dv50
参照GB/T 19077-2016/ISO 13320:2009《粒度分布激光衍射法》，采用激光粒度仪测试得到Dv50。
(2)压实密度
参考GB/T 24533-2019中的附录L《粉末压实密度的测试方法》，采用压实密度仪测试得到。
(3)容量、首效、容量保持率
在25℃下，将钠离子电池静置30min；然后以0.33C倍率恒流充电至4.0V，之后以4.0V恒压充电至电流为0.05C；之后静置30min；以0.33C倍率恒流放电至2V，再静置30min，此为一个循环充放电过程。记录第一圈循环充放电过程中的充电容量C10和放电容量C20，采用公式计算得到首效：首效＝C20/C10×100％。
将钠离子电池按照上述步骤继续进行循环300圈，记录此时的放电容量C21，经计算得 到循环300圈后的容量保持率(容量保持率＝C21/C20×100％)。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (15)

  1. 一种正极极片，其特征在于，所述正极极片包含补钠剂和正极活性材料，所述补钠剂包含NaqMnxMyO2，1≤q≤1.2，0.15≤x＜0.45，y＞0，0.9≤x+y≤1，所述M包括过渡金属元素；所述补钠剂的Dv50小于所述正极活性材料的Dv50。
  2. 根据权利要求1所述正极极片，其特征在于，1≤q≤1.1。
  3. 根据权利要求1或2所述正极极片，其特征在于，0.2≤x≤0.44。
  4. 根据权利要求1至3中任一项所述正极极片，其特征在于，0.5≤y≤0.8。
  5. 根据权利要求1至4中任一项所述正极极片，其特征在于，所述M包括Fe、Ni、Co、Cu、Al、Ti、V中的一种或多种。
  6. 根据权利要求1至5中任一项所述正极极片，其特征在于，所述M包括Fe和Ni，所述补钠剂包括NaqMnxNiy1Fey2O2；1≤q≤1.2，0.15≤x＜0.45，y1＞0，y2＞0，0.9≤x+y1+y2≤1。
  7. 根据权利要求1至6中任一项所述正极极片，其特征在于，所述补钠剂的相结构包括O3相。
  8. 根据权利要求1至7中任一项所述正极极片，其特征在于，所述补钠剂的Dv50为所述正极活性材料的Dv50的6％～75％，可选地为6％～25％。
  9. 根据权利要求1至8中任一项所述正极极片，其特征在于，所述补钠剂的Dv50为0.5～6μm，可选地为1～3μm。
  10. 根据权利要求1至9中任一项所述正极极片，其特征在于，所述正极活性材料的Dv50为6～20μm，可选地为6～10μm。
  11. 根据权利要求1至10中任一项所述正极极片，其特征在于，所述补钠剂与所述正极活性材料的质量比为1：(14～94)，可选地为1：(18～46.5)。
  12. 根据权利要求1至11中任一项所述正极极片，其特征在于，所述补钠剂在所述正极极片所含活性层中的质量含量为1％～6％，可选地为2％～5％。
  13. 根据权利要求1至12中任一项所述正极极片，其特征在于，所述正极活性材料包括层状氧化物、聚阴离子类化合物、普鲁士蓝类化合物中的一种或多种；可选地，所述层状氧化物包括NamM1 zO2，0.4≤m≤0.9，0.9≤z≤1，所述M1包括过渡金属元素。
  14. 一种钠离子二次电池，其特征在于，所述电池包括权利要求1至13中任一项所述正极极片。
  15. 一种用电装置，其特征在于，所述用电装置包括权利要求14所述的钠离子二次电池。
PCT/CN2024/103550 2023-11-16 2024-07-04 正极极片、钠离子二次电池、用电装置 Pending WO2025102765A1 (zh)

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