WO2023169365A1 - 一种补锂添加剂及其制备方法和应用 - Google Patents

一种补锂添加剂及其制备方法和应用 Download PDF

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WO2023169365A1
WO2023169365A1 PCT/CN2023/079868 CN2023079868W WO2023169365A1 WO 2023169365 A1 WO2023169365 A1 WO 2023169365A1 CN 2023079868 W CN2023079868 W CN 2023079868W WO 2023169365 A1 WO2023169365 A1 WO 2023169365A1
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Prior art keywords
lithium
nitride
crystal phase
supplement additive
lithium nitride
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English (en)
French (fr)
Inventor
赖佳宇
万远鑫
孔令涌
谭旗清
张莉
赵中可
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Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
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Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
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Priority to EP23765943.8A priority Critical patent/EP4492502A4/en
Priority to US18/839,221 priority patent/US20250158074A1/en
Publication of WO2023169365A1 publication Critical patent/WO2023169365A1/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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/0607—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with alkali metals
    • C01B21/061—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with alkali metals with lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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 belongs to the technical field of lithium-ion battery additives, and particularly relates to a lithium supplement additive and its preparation method and application.
  • High specific capacity lithium supplement additives can form an SEI film when the lithium-ion battery is first charged and discharged, reducing the loss of active lithium in the cathode material, thus improving the first Coulombic efficiency and battery capacity of the battery.
  • the main methods of lithium supplementation include positive electrode lithium supplementation and negative electrode lithium supplementation.
  • the processes of lithium powder spraying, early formation, and adding electrodes to the negative electrode are demanding on equipment and process technology, and are difficult to be widely used at the current technical level.
  • the lithium replenishment method of positive electrode lithium-rich materials introduces non-metallic lithium compounds into the positive electrode, which can achieve prelithiation of the negative electrode during the first charge.
  • lithium nitride prepared by traditional methods has an uncontrollable crystal phase ratio and poor stability.
  • lithium replenishing additive When it is used as a lithium replenishing additive and combined with the lithium battery preparation process, there will be an unstable gram specific capacity, thus Affects the consistency of battery capacity. Therefore, these non-metallic lithium compounds can only be used in an inert environment, limiting large-scale applications.
  • One of the purposes of the embodiments of the present application is to provide a lithium supplement additive and its preparation method and application, aiming to solve the technical problem of poor stability of existing lithium supplement additives.
  • the present application provides a lithium supplement additive, which includes lithium nitride, and the lithium nitride includes ⁇ crystal phase lithium nitride and/or ⁇ crystal phase lithium nitride.
  • this application provides a method for preparing a lithium supplement additive, which includes the following steps:
  • the metal lithium is calcined in a nitrogen atmosphere and then ground to obtain lithium nitride.
  • this application provides a positive electrode material, which contains the electrode lithium supplement additive provided by this application or the lithium supplement additive prepared by the preparation method provided by this application.
  • the present application provides a secondary battery, which contains the cathode material provided by the present application.
  • the lithium supplement additive contains lithium nitride, which is pure ⁇ crystal phase lithium nitride or pure ⁇ crystal phase lithium nitride or is composed of ⁇ crystal phase and ⁇ crystal phase.
  • the phase composition of mixed crystal phase lithium nitride, pure ⁇ crystal phase lithium nitride has high lithium ion conductivity, which is conducive to the extraction of lithium ions, and pure ⁇ crystal phase lithium nitride has a high lithium ion migration energy barrier and high decomposition voltage.
  • the beneficial effect of the preparation method of the lithium supplement additive provided by the embodiments of the present application is that: the preparation method of the lithium supplement additive is to place the provided metal lithium in a nitrogen atmosphere, perform a calcination treatment, and then grind it to obtain Lithium nitride can be used as a lithium supplement additive.
  • the preparation process is simple, easy to implement, and the production cost is low.
  • the lithium nitride prepared by this preparation method has good material stability and electrochemical properties, which is beneficial to improving the first charging efficiency and overall electrochemical performance of the battery.
  • the beneficial effect of the positive electrode material provided by the embodiments of the present application is that the positive electrode material contains the electrode lithium supplement additive provided by the present application or the lithium supplement additive prepared by the preparation method provided by the present application. Therefore, the positive electrode material has material stability and electrochemical performance. Good, it can ensure that the voltage of the battery changes smoothly during the charging process.
  • the beneficial effect of the secondary battery provided by the embodiment of the present application is that the secondary battery contains the cathode material provided by the present application. Therefore, during the first charging process, the lithium supplement additive contained in the secondary battery of the present application can be used as a lithium source. Lithium ions are released during the first charging process to achieve lithium replenishment, thereby maintaining sufficient lithium ions in the battery system and improving the battery's first charging efficiency and overall charge and discharge performance.
  • Figure 1 is a preparation flow chart of the lithium supplement additive provided by the embodiment of the present application.
  • Figure 2 is an XRD pattern of the lithium nitride core provided by the embodiment of the present application.
  • Figure 3 is a capacity-voltage diagram of the lithium-replenishing additive-assembled button battery provided in Example 5 and Comparative Example 2 of the present application;
  • Figure 4 is a capacity-voltage diagram of a button cell without adding a lithium supplement additive and adding a lithium supplement additive provided in Example 3 of the present application to the lithium iron phosphate positive electrode.
  • a and/or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. Condition. Where A and B can be singular or plural.
  • the character "/" generally indicates that the related objects are in an "or" relationship.
  • At least one refers to one or more
  • plural refers to two or more.
  • At least one of the following” or similar expressions thereof refers to any combination of these items, including any combination of a single item (items) or a plurality of items (items).
  • at least one of a, b, or c or “at least one of a, b, and c” can mean: a, b, c, a-b ( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple respectively.
  • the size of the sequence numbers of the above-mentioned processes does not mean the order of execution. Some or all steps can be executed in parallel or one after another. The execution order of each process should be based on its function and order. The internal logic is determined and should not constitute any limitation on the implementation process of the embodiments of the present application.
  • weights of relevant components mentioned in the description of the embodiments of the present application may not only refer to the specific content of each component, but also represent the proportional relationship of weight between the components. Therefore, as long as the relevant components are combined according to the description of the embodiments of the present application, Any scaling up or down of the content is within the scope disclosed in the examples of this application.
  • the mass described in the description of the embodiments of this application may be mass units well known in the chemical industry such as ⁇ g, mg, g, kg, etc.
  • first and second are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features.
  • first XX may also be called the second XX
  • second XX may also be called the first XX. Therefore, features defined as “first” and “second” may explicitly or implicitly include one or more of these features.
  • the first aspect of the embodiments of the present application provides a lithium supplement additive.
  • the lithium supplement additive includes lithium nitride, and the lithium nitride includes ⁇ crystal phase lithium nitride and/or ⁇ crystal phase lithium nitride.
  • the lithium supplement additive provided in the embodiment of the present application includes lithium nitride, which is pure ⁇ crystal phase lithium nitride or pure ⁇ crystal phase lithium nitride or mixed crystal phase nitrogen composed of ⁇ crystal phase and ⁇ crystal phase.
  • Lithium oxide, pure alpha crystalline phase lithium nitride has high lithium ion conductivity, which is conducive to the extraction of lithium ions.
  • Pure beta crystalline phase lithium nitride has a high lithium ion migration energy barrier and high decomposition voltage, making lithium ions in the battery system.
  • the migration is more stable, the activity of mixed crystalline lithium nitride is reduced, and it can avoid reaction with the widely used N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) in the homogenization process, and it has good stability during use.
  • NMP N-methylpyrrolidone
  • PVDF polyvinylidene fluoride
  • lithium nitride includes ⁇ crystal phase lithium nitride and/or ⁇ crystal phase lithium nitride, that is, it may include ⁇ crystal phase lithium nitride, ⁇ crystal phase lithium nitride, composed of ⁇ crystal phase and ⁇ crystal phase Composed of mixed crystalline phases of lithium nitride in either case.
  • the lithium nitride core may be ⁇ crystal phase lithium nitride, ⁇ crystal phase lithium nitride, or mixed crystal phase lithium nitride composed of ⁇ crystal phase and ⁇ crystal phase.
  • lithium nitride includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride, and the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is (2-10): (90-98 ) or (70-98): (2-30). Within the range of the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride provided in this embodiment, the ⁇ crystal phase and ⁇ crystal phase are mixed.
  • the stability of crystalline lithium nitride is optimal, and the maximum number of lithium ions released from lithium nitride during the first cycle of charging can optimize the first charging efficiency and overall electrochemical performance of the battery.
  • the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride can be but is not limited to 2:90, 2:92, 2:94, 2:96, 2:98, 6: 91, 6:93, 6:95, 6:97, 6:98, 10:90, 10:92, 10:94, 2:96, 2:98, 70:2, 70:10, 70:20, 70:30, 85:2, 85:10, 85:20, 85:30, 98:2, 98:10, 98:20, 98:30.
  • lithium nitride may be primary particles of lithium nitride or secondary particles formed by agglomeration of primary particles.
  • the particle size of lithium nitride is 0.1-50 ⁇ m.
  • the particle size of lithium nitride is 1-5 ⁇ m.
  • the specific particle size of the lithium nitride core may be, but is not limited to, 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m.
  • the conductivity and stability of the lithium supplement additive can be optimized.
  • the lithium supplement additive further includes a two-dimensional conductive material bonded to the surface of lithium nitride.
  • the two-dimensional conductive materials included in the embodiments of the present application are at least combined on the surface of lithium nitride. Since the two-dimensional conductive materials have good chemical stability and conductivity, combining on the surface of lithium nitride can improve the stability of the lithium nitride material. And increase the overall conductivity of the lithium supplement additive, which is beneficial to the voltage stability of the charging process.
  • the two-dimensional conductive material combined on the surface of lithium nitride forms a two-dimensional conductive material coating layer that fully or partially covers lithium nitride.
  • the lithium-replenishing additive in the embodiment of the present application forms a core-shell structure
  • the lithium-replenishing material with the above particle shape forms the core body
  • the two-dimensional conductive material coating layer forms the shell layer, at least a part of the shell layer.
  • the two-dimensional conductive material coating layer may be fully covered or partially covered with a lithium-supplementing material and also a lithium nitride core.
  • the ideal is full coverage, which can improve the protective effect of the two-dimensional conductive material coating layer on the lithium supplement material, can isolate the lithium nitride core from contact with the air, and prevent water, oxygen and carbon dioxide in the air from damaging the lithium nitride core. Corrosion can improve the stability of lithium nitride materials.
  • two-dimensional The layered two-dimensional conductive material has the ability to adsorb and desorb various atoms or molecules, which facilitates adsorption on the surface of lithium nitride to form a uniform and tight coating layer, thereby facilitating the extraction of lithium ions during the charging process of lithium nitride.
  • the two-dimensional conductive material includes at least one of graphene, graphyne, transition metal dichalcogenides, and MXenes materials; wherein, the general formula of the MXenes material is M n+1 X n T x , and M includes Ti , Cr, Mo, V, Nb, Hf, Ta, Sc; X includes at least one of C and N; T x includes OH - , F - , O 2- , NH 4 + , NH 3 At least one of them; n is 1-4.
  • Specific M n + 1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Transition metal dichalcogenides include at least one of MoS 2 , WS 2 , SnS 2 , and TiS 2 .
  • the mass ratio of lithium nitride to the two-dimensional conductive material coating layer is (9-99):1.
  • the stability, moisture resistance and conductivity of lithium nitride are optimal, and the two-dimensional conductive material coats lithium nitride.
  • a lithium supplement additive it has the best gram specific capacity and low raw material cost.
  • the thickness of the two-dimensional conductive material coating layer is 5-100 nm.
  • the thickness of the two-dimensional conductive material coating layer is 10-30 nm.
  • the thickness of the specific two-dimensional conductive material coating layer can be, but is not limited to, 5nm, 7nm, 9nm, 10nm, 15nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm.
  • the particle size of the lithium supplement additive is 5-60 ⁇ m.
  • the particle size of the lithium supplement additive is 5-10 ⁇ m.
  • the specific particle size of the lithium supplement additive can be, but is not limited to, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, and 60 ⁇ m.
  • the conductivity and stability of the lithium supplement additive can be optimized.
  • the lithium supplement additive is placed in the air with a relative humidity of 30% for 24 hours, and the lithium hydroxide content is below 45%.
  • the second aspect of the embodiments of the present application provides a method for preparing a lithium supplement additive, as shown in Figure 1, including Includes the following steps:
  • the preparation method of the lithium-replenishing additive provided by the embodiment of the present application is to place the provided metallic lithium in a nitrogen atmosphere for calcination treatment and then grind it to obtain lithium nitride, which can be used as a lithium-replenishing additive.
  • the preparation process is simple and easy to implement. And the production cost is lower.
  • the lithium nitride prepared by this preparation method has good material stability and electrochemical properties, which is beneficial to improving the first charging efficiency and overall electrochemical performance of the battery.
  • step S20 the preparation method of lithium nitride includes the following steps: placing metal lithium in a nitrogen atmosphere for calcination treatment, and then grinding to obtain lithium nitride.
  • the calcination treatment is carried out in an inert gas, and the calcination treatment includes the following steps: passing in nitrogen and inert gas according to a flow ratio of (1-9):1, and raising the temperature to 180-900°C, keep the temperature for 5-24h, then only add nitrogen, and cool down to 25°C at a rate of 1-50°C/min.
  • the flow ratio of nitrogen and inert gas is (1-9):1.
  • the flow ratio of nitrogen and inert gas can be but is not limited to 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 , 7:3.
  • the temperature rise rate of the calcination treatment is 1-10°C/min.
  • the heating rate can be adjusted specifically according to the heating capacity of the equipment used. Within the range of the heating rate of the calcination process provided in the embodiment of the present application, the temperature in the furnace cavity is uniform, the time consumption is moderate, and the negative impact on the equipment can be reduced. Specifically, the heating rate can be, but is not limited to, 1°C/min, 2°C/min, 3°C/min, 4°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min, 9°C/min, 10°C/min.
  • the holding temperature of the calcination treatment is 180-900°C, and the holding time is 5-24 hours.
  • the heat preservation temperature of the calcination treatment can be, but is not limited to, 180°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C
  • the heat preservation time of the calcination treatment can be, but is not limited to, 5h, 7h, 9h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h.
  • the pressure of the calcination treatment is 0.1-100 MPa.
  • the pressure during the calcination process can be, but is not limited to, 0.1MPa, 0.5MPa, 1MPa, 10MPa, 30MPa, 50MPa, 70MPa, 90MPa, and 100MPa.
  • the temperature reduction rate of the calcination process is 1-50°C/min. Since ⁇ crystal phase lithium nitride is a high-temperature stable crystal phase, the temperature above 500K is conducive to the transformation of ⁇ crystal phase lithium nitride into ⁇ crystal phase lithium nitride; ⁇ crystal phase lithium nitride is a low-temperature stable crystal phase, and the temperature is below 300K. It is beneficial to the stable existence of ⁇ crystal phase lithium nitride. Therefore, after high-temperature and high-pressure gas-liquid reaction nitriding, as the temperature decreases, ⁇ -crystalline lithium nitride transforms into ⁇ -crystalline lithium nitride.
  • ⁇ -crystalline phase lithium nitride can be suppressed by controlling the cooling rate under high pressure. Transformed into ⁇ crystal phase lithium nitride, thereby achieving the control of the mass ratio of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • mixed phase lithium nitride of ⁇ crystal phase and ⁇ crystal phase within the mass ratio range provided by the embodiments of the present application can be prepared, so that the prepared ⁇
  • the mixed phase lithium nitride of the crystalline phase and the ⁇ crystalline phase has the best stability and lithium release ability, so the first charging efficiency and overall electrochemical performance of the battery are optimal.
  • the cooling rate can be but not limited to 1°C/min, 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min, 30°C/min, 35°C/min, 40°C/min, 45°C/min, 50°C/min.
  • the preparation method of lithium supplement additive further includes the following steps:
  • S30 Disperse lithium nitride and two-dimensional conductive material in a solvent to obtain a mixed solution, and dry the mixed solution to form a lithium supplement additive coated with two-dimensional conductive material.
  • the solvent includes at least one of N,N-dimethylformamide, tetrahydrofuran, n-hexane, and benzene.
  • the solvent can be N,N-dimethylformamide, tetrahydrofuran, or n-hexane.
  • the drying treatment conditions include: drying temperature is 30-100°C, and drying time is 6-10 hours.
  • the solvent evaporation rate can be moderate, and lithium nitride can be prevented from being enriched on the surface, which is conducive to the formation of a uniform coating layer on the surface of lithium nitride by the two-dimensional conductive material.
  • the drying temperature can be, but is not limited to, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C. Drying time can be but not limited to 6h, 7h, 8h, 9h, 10h.
  • the third aspect of the embodiments of this application provides a cathode material.
  • the cathode material contains the electrode lithium supplement additive provided by this application or the lithium supplement additive prepared by the preparation method provided by this application.
  • the positive electrode material provided in the embodiments of the present application contains the electrode lithium supplement additive provided by the present application or the lithium supplement additive prepared by the preparation method provided by the present application. Therefore, the positive electrode material has good material stability and electrochemical performance. It can ensure that the voltage of the battery changes smoothly during the charging process.
  • the fourth aspect of the embodiments of the present application provides a secondary battery, which contains the cathode material provided by the present application.
  • the secondary battery provided by the embodiment of the present application contains the cathode material provided by the present application. Therefore, during the first charging process, the lithium replenishing additive contained in the electrode sheet of the present application can be used as a lithium source to release lithium ions during the first charging process to achieve the lithium replenishing effect, thereby maintaining sufficient lithium ions in the battery system and improving the battery's first charging process. Charging efficiency and overall charge and discharge performance.
  • a constant current and constant voltage charging method is adopted.
  • the charging voltage is 2.5-4.3V
  • the charging current is 0.1C
  • the cut-off current is 0.01C
  • the secondary battery is nitrided during the first cycle of charging. lithium
  • the number of lithium ions extracted is 1.2-2.8.
  • Lithium supplement additive and preparation method thereof Lithium supplement additive and preparation method thereof:
  • the lithium supplement additive includes pure alpha crystalline phase lithium nitride and a graphene coating layer combined on the surface of the alpha crystalline phase lithium nitride core.
  • S20 Place the metal lithium in the corundum boat and put it into the high-temperature and high-pressure reactor. According to the flow rate of 300mL/min, argon gas is introduced for 30 minutes to exhaust; then, according to the flow rate of 70:30mL/min, argon gas is introduced. and nitrogen, and raise the temperature to 800°C at a rate of 10°C/min. After holding for 10 hours, increase the pressure in the furnace to 5MPa, and cool down to 25°C at a rate of 40°C/min to obtain ⁇ crystal phase lithium nitride; finally, ⁇ Crystalline phase lithium nitride is ground to obtain pure alpha crystalline phase lithium nitride particles.
  • the particle size of the alpha crystal phase lithium nitride particles is 1-8 ⁇ m
  • the thickness of the graphene coating layer is 10-30 nm
  • the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m.
  • the lithium supplement additive includes pure beta crystalline phase lithium nitride and a graphene coating layer combined on the surface of the beta crystalline phase lithium nitride core.
  • step S20 of the example the temperature is lowered to 25°C at a rate of 1°C/min to obtain a lithium supplement additive in which graphene is coated on the surface of ⁇ crystal phase lithium nitride particles.
  • the particle size of the ⁇ crystal phase lithium nitride particles is 1-8 ⁇ m
  • the thickness of the graphene coating layer is 10-30 nm
  • the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m.
  • the lithium supplement additive includes alpha crystalline phase lithium nitride and beta crystalline phase lithium nitride.
  • step S20 of this embodiment the temperature is cooled to 25°C at a rate of 32°C/min to obtain the ⁇ crystal phase and the ⁇ crystal phase.
  • Mixed crystal phase lithium nitride is obtained in step S20 of this embodiment.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m; in the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase, the ⁇ crystal phase lithium nitride and the ⁇ crystal phase nitrogen
  • the mass ratio of lithium is 90:10.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of the ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride core.
  • step S20 of this embodiment the temperature is cooled to 25°C at a rate of 35°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In mixed crystal phase lithium nitride with ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 98:2.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S20 of this embodiment the temperature is cooled to 25°C at a speed of 32°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In mixed crystal phase lithium nitride with ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 90:10.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S20 of this embodiment the temperature is cooled to 25°C at a rate of 28°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In the mixed crystal phase lithium nitride with the ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 80:20.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S20 of this embodiment the temperature is cooled to 25°C at a rate of 25°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In mixed crystal phase lithium nitride with ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 70:30.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S20 of this embodiment the temperature is cooled to 25°C at a rate of 18°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In mixed crystal phase lithium nitride with ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 10:90.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S20 of this embodiment the temperature is cooled to 25°C at a speed of 13°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In the mixed crystal phase lithium nitride with the ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 8:92.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S20 of this embodiment the temperature is lowered to 25°C at a rate of 8°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In mixed crystal phase lithium nitride with ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 5:95.
  • the lithium supplement additive includes ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride and a graphene coating layer combined on the surface of ⁇ crystal phase lithium nitride and ⁇ crystal phase lithium nitride.
  • step S10 of this embodiment the temperature is lowered to 25°C at a rate of 5°C/min to obtain graphene coated in ⁇ crystal.
  • the particle size of the mixed crystal phase lithium nitride of the ⁇ crystal phase and the ⁇ crystal phase is 1-8 ⁇ m, the thickness of the graphene coating layer is 30 nm, and the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m;
  • the ⁇ crystal phase In mixed crystal phase lithium nitride with ⁇ crystal phase the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 2:98.
  • This comparative example provides a lithium supplement additive and a preparation method thereof.
  • the lithium supplement additive includes lithium nitride particles.
  • the preparation method of the lithium supplement additive of this comparative example includes the following steps:
  • the particle size of lithium nitride particles is 1-8 ⁇ m.
  • the mass ratio of ⁇ crystal phase lithium nitride to ⁇ crystal phase lithium nitride is 65:35.
  • This comparative example provides a lithium supplement additive and a preparation method thereof.
  • the lithium supplement additive includes lithium nitride particles and a graphene coating layer combined on the surface of the lithium nitride.
  • the particle size of lithium nitride particles is 1-8 ⁇ m
  • the thickness of the graphene coating layer is 30 nm
  • the particle size of the lithium supplement additive is 1.01-8.05 ⁇ m
  • the mass ratio to ⁇ crystal phase lithium nitride is 65:35.
  • the lithium nitride core provided in the above-mentioned Example 1, Example 2, Example 4, Example 6, and Example 8 was subjected to X-ray diffraction analysis, and its XRD pattern is shown in Figure 2. It can be seen from Figure 2 that as the mass proportion of ⁇ crystal phase lithium nitride decreases and the mass proportion of ⁇ crystal phase lithium nitride increases, the intensity of the diffraction peak of the ⁇ crystal phase of lithium nitride weakens accordingly. The intensity of the diffraction peak of the ⁇ crystal phase of lithium nitride is correspondingly enhanced.
  • Example 3 The lithium supplement additive provided in Example 3 and Comparative Example 1 was added to the LFP positive electrode, and N,N-dimethylformamide solvent was used to prepare the positive electrode slurry.
  • the lithium supplement additives provided in Examples 1-11 are released under 30% air humidity.
  • the lithium hydroxide content after being placed for 24 hours was significantly lower than the lithium hydroxide content of the lithium supplement additive provided in Comparative Example 1-2 after being placed under 30% air humidity for 24 hours, and the lithium supplement additive provided by Example 1-11 corresponded to
  • the capacity of the battery and the number of lithium nitride delithiation in the first cycle are significantly higher than the capacity of the battery corresponding to the lithium supplement additive provided in Comparative Example 1-2 and the number of lithium nitride delithiation in the first cycle, indicating that the ⁇ crystal and ⁇ crystal of the present application
  • the mixed-phase lithium nitride, alpha crystalline phase lithium nitride and beta crystalline phase lithium nitride have better stability than traditional lithium nitride and can give the battery better electrochemical performance.
  • Figure 3 is a capacity-voltage diagram of the lithium additive-assembled button battery provided in Example 5 and Comparative Example 2. It can be seen from Figure 3 that in the graphene-coated mixed-phase lithium nitride provided in Example 5, ⁇ crystal The mass ratio of phase lithium nitride to ⁇ crystal phase lithium nitride is 90:10. It is used as a lithium supplement additive and has more lithium coming out during the charging process, making the voltage change during the charging process relatively smooth. This is due to the ⁇ crystal phase nitrogen. The stability is best when the mass ratio of lithium oxide to ⁇ crystal phase lithium nitride is 90:10. However, the lithium nitride provided in Comparative Example 2 was used as a lithium supplement additive.
  • FIG 4 is a capacity-voltage diagram of a button battery without adding the lithium supplement additive and adding the lithium supplement additive provided in Example 3 to the lithium iron phosphate positive electrode.
  • adding the lithium supplement additive provided in Example 3 of the present application The cathode capacity performance has been significantly improved. This is because the lithium nitride ions contained in the lithium supplement additive transfer from the positive electrode to the negative electrode during the first cycle of charging, participating in the formation of the SEI film of the negative electrode to avoid the loss of active lithium ions in the LFP material. Therefore, lithium supplementation additives can improve the capacity performance of LFP batteries.

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Abstract

本申请涉及锂离子电池添加剂技术领域，提供了一种补锂添加剂，其包括α晶相氮化锂和/或β晶相氮化锂。本申请提供的补锂添加剂，所含的纯α晶相氮化锂的锂离子导电率高，有利于锂离子的脱出，所含的纯β晶相氮化锂的锂离子迁移能垒高，分解电压高，使锂离子在电池体系的迁移更加稳定，所含的混合晶相氮化锂活泼性降低，可以避免在匀浆工艺中与广泛使用的N-甲基吡咯烷酮(NMP)、聚偏氟乙烯(PVDF)反应，稳定性好。因此，本申请提供的氮化锂用作补锂添加剂时，电池在首圈充电过程中，氮化锂可以补充负极形成SEI膜而消耗的锂离子，使电池体系内的锂离子保持充裕，提高电池首次充电效率和整体电化学性能，在充电过程中电压变化平稳。

Description

一种补锂添加剂及其制备方法和应用
本申请要求于2022年03月10日在中国专利局提交的、申请号为202210254247.0、申请名称为“一种补锂添加剂及其制备方法和应用”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
本申请属于锂离子电池添加剂技术领域，尤其涉及一种补锂添加剂及其制备方法和应用。
背景技术
高比容量的补锂添加剂可以在锂离子电池首次充放电时形成SEI膜，降低正极材料活性锂的损失，从而提高电池首次库伦效率和电池容量。目前，补锂的方法主要有正极补锂和负极补锂。但是，负极补锂技术中锂粉喷涂、提前化成和负极增加电极的工艺都对设备和工艺技术要求苛刻，难以在当前技术水平上广泛应用。正极富锂材料补锂法通过在正极引入非金属锂化合物，可以在首次充电时实现对负极预锂化，然而这些非金属锂化合物在空气中不稳定，极易与空气中的水汽和氧气等发生反应而变质，例如采用传统方法制备的氮化锂，其晶相比例不可控，稳定性差，当其作为补锂添加剂与锂电池制备工艺结合时会存在克比容量不稳定的问题，从而影响电芯容量的一致性。因此，这些非金属锂化合物只能在惰性环境下使用，限制了大规模应用。
技术问题
本申请实施例的目的之一在于：提供一种补锂添加剂及其制备方法和应用，旨在解决现有的补锂添加剂存在稳定性差的技术问题。
技术解决方案
为解决上述技术问题，本申请实施例采用的技术方案是：
第一方面，本申请提供一种补锂添加剂，该补锂添加剂包括氮化锂，所述氮化锂包括α晶相氮化锂和/或β晶相氮化锂。
第二方面，本申请提供一种补锂添加剂的制备方法，包括以下步骤：
提供金属锂；
将所述金属锂置于氮气气氛中进行煅烧处理，然后研磨，得到氮化锂。
第三方面，本申请提供一种正极材料，正极材料含有本申请提供的电极补锂添加剂或本申请提供的制备方法制得的补锂添加剂。
第四方面，本申请提供一种二次电池，该二次电池含有本申请提供的正极材料。
有益效果
本申请实施例提供的补锂添加剂的有益效果在于：补锂添加剂含有氮化锂，该氮化锂为纯α晶相氮化锂或纯β晶相氮化锂或由α晶相和β晶相构成的混合晶相氮化锂，纯α晶相氮化锂的锂离子导电率高，有利于锂离子的脱出，纯β晶相氮化锂的锂离子迁移能垒高，分解电压高，使锂离子在电池体系的迁移更加稳定，混合晶相氮化锂活泼性降低，可以避免在匀浆工艺中与广泛使用的N-甲基吡咯烷酮(NMP)、聚偏氟乙烯(PVDF)反应，其在使用时稳定性好，因此，本申请提供的氮化锂用作补锂添加剂时，电池在首圈充电过程中，氮化锂可以补充负极形成SEI膜而消耗的锂离子，使电池体系内的锂离子保持充裕，从而提高电池首次充电效率和整体电化学性能。因此能确保在充电过程中电压变化相对平稳。
本申请实施例提供的补锂添加剂的制备方法的有益效果在于：补锂添加剂的制备方法通过将提供的金属锂置于氮气气氛中进行煅烧处理，然后研磨，得 到氮化锂，可作为补锂添加剂，该制备工艺简单，容易实现，且生产成本较低。另外，通过该制备方法制备得到的氮化锂具有材料稳定性和电化学性能好，利于提高电池首次充电效率和整体电化学性能。
本申请实施例提供的正极材料的有益效果在于：正极材料含有本申请提供的电极补锂添加剂或本申请提供的制备方法制得的补锂添加剂，因此该正极材料具有材料稳定性和电化学性能好，能确保电池在充电过程电压变化平稳。
本申请实施例提供的二次电池的有益效果在于：二次电池含有本申请提供的正极材料，因此，在首次充电过程中，本申请二次电池所含的补锂添加剂能够作为锂源，在首次充电过程中释放锂离子实现补锂作用，从而保持电池体系内锂离子的充裕，提高电池首次充电效率和整体充放电性能。
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是本申请实施例提供的补锂添加剂的制备流程图；
图2是本申请实施例提供的氮化锂内核的XRD图谱；
图3是本申请实施例5和对比例2提供的补锂添加剂组装扣电池的容量-电压图；
图4是未添加补锂添加剂和添加本申请实施例3提供的补锂添加剂到磷酸铁锂正极后的扣电池容量-电压图。
本发明的实施方式
为了使本申请要解决的技术问题、技术方案及有益效果更加清楚明白，以 下结合实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
本申请中，术语“和/或”，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的情况。其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
本申请中，“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。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其他含义。
本申请实施例说明书中所提到的相关成分的重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重量的比例关系，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。
术语“第一”、“第二”仅用于描述目的，用来将目的如物质彼此区分开，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。例如，在不脱离本申请实施例范围的情况下，第一XX也可以被称为第二XX，类似地，第二XX也可以被称为第一XX。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。
本申请实施例第一方面提供一种补锂添加剂，该补锂添加剂包括氮化锂，该氮化锂包括α晶相氮化锂和/或β晶相氮化锂。
本申请实施例提供的补锂添加剂，包括氮化锂，该氮化锂为纯α晶相氮化锂或纯β晶相氮化锂或由α晶相和β晶相构成的混合晶相氮化锂，纯α晶相氮化锂的锂离子导电率高，有利于锂离子的脱出，纯β晶相氮化锂的锂离子迁移能垒高，分解电压高，使锂离子在电池体系的迁移更加稳定，混合晶相氮化锂活泼性降低，可以避免在匀浆工艺中与广泛使用的N-甲基吡咯烷酮(NMP)、聚偏氟乙烯(PVDF)反应，其在使用时稳定性好，因此，本申请提供的氮化锂用作补锂添加剂时，电池在首圈充电过程中，氮化锂可以补充负极形成SEI膜而消耗的锂离子，使电池体系内的锂离子保持充裕，从而提高电池首次充电效率和整体电化学性能。因此能确保在充电过程中电压变化相对平稳。
在实施例中，氮化锂包括α晶相氮化锂和/或β晶相氮化锂，即可以包括α晶相氮化锂、β晶相氮化锂、由α晶相和β晶相组成的混合晶相氮化锂中的任一种情形。在具体的实施例中，氮化锂内核可以为α晶相氮化锂，还可以为β晶相氮化锂，还可以为由α晶相和β晶相组成的混合晶相氮化锂。
在实施例中，氮化锂包括α晶相氮化锂和β晶相氮化锂，α晶相氮化锂与β晶相氮化锂的质量比为(2-10)：(90-98)或(70-98)：(2-30)。在本实施例提供的α晶相氮化锂与β晶相氮化锂的质量比的范围内，α晶相和β晶相混合 晶相氮化锂的稳定性达到最优，并且首圈充电过程氮化锂的锂离子脱出数量达到最多，能使电池首次充电效率和整体电化学性能达到最优。在具体的实施例中，α晶相氮化锂与β晶相氮化锂的质量比可以为但不限于2：90，2：92，2：94，2：96，2：98，6：91，6：93，6：95，6：97，6：98，10：90，10：92，10：94，2：96，2：98，70：2，70：10，70：20，70：30，85：2，85：10，85：20，85：30，98：2，98：10，98：20，98：30。
在实施例中，氮化锂可以是氮化锂一次颗粒，也可以是由一次颗粒团聚形成的二次颗粒。当氮化锂为一次颗粒或二次颗粒时，氮化锂的粒径为0.1-50μm。优选地，氮化锂的粒径为1-5μm。具体氮化锂内核的粒径可以为但不限于0.1μm，0.5μm，1μm，2μm，3μm，4μm，5μm，10μm，20μm，30μm，40μm，50μm。在本申请实施例提供的氮化锂的粒径范围内，能使补锂添加剂的导电性和稳定性能达到最优。
在实施例中，补锂添加剂还包括结合在氮化锂表面的二维导电材料。本申请实施例所含的二维导电材料是至少结合在氮化锂表面，由于二维导电材料具有良好的化学稳定性和导电性，结合在氮化锂表面可以提高氮化锂材料的稳定性和增加补锂添加剂整体的导电性，有利于充电过程的电压平稳。
在实施例中，结合在氮化锂表面的二维导电材料形成全包覆或部分包覆氮化锂的二维导电材料包覆层。此时，本申请实施例补锂添加剂构成了核壳结构，上文颗粒形貌补锂材料构成核体，该二维导电材料包覆层构成了壳层，至少是壳层的一部分。其中，该二维导电材料包覆层可以是全包覆或部分包覆补锂材料也是氮化锂核体。理想的是全包覆，能够提高二维导电材料包覆层对补锂材料的保护作用，可以隔绝氮化锂内核与空气接触，避免空气中的水、氧气和二氧化碳等对氮化锂内核进行腐蚀，能够提高氮化锂材料的稳定性。另外，二维 层状的二维导电材料，具有吸附和脱附各种原子或分子的能力，便于在氮化锂表面吸附形成均匀紧密包覆层，从而有利于氮化锂充电过程锂离子的脱出。
在实施例中，二维导电材料包括石墨烯、石墨炔、过渡金属二硫化物、MXenes材料中的至少一种；其中，MXenes材料的通式为Mn+1XnTx，M包括Ti、Cr、Mo、V、Nb、Hf、Ta、Sc中的至少一种；X包括C、N中的至少一种；Tx包括OH-、F-、O2-、NH4 +、NH3中的至少一种；n为1-4。具体Mn+1XnTx可以包括但不限于Ti2CO，Ti3C2O，Ti2NO，Ti3N2O，Ti2COH，Ti3C2OH中的至少一种。过渡金属二硫化物包括MoS2、WS2、SnS2、TiS2中的至少一种。
在实施例中，在补锂添加剂中，氮化锂与二维导电材料包覆层的质量比为(9-99)：1。在本实施例提供的氮化锂与二维导电材料包覆层的质量比的范围内，氮化锂的稳定性、耐湿性和导电性达到最佳，同时二维导电材料包覆氮化锂作为补锂添加剂具有最优的克比容量，且原材料成本低。
二维导电材料包覆层的厚度为5-100nm，优选地，二维导电材料包覆层的厚度为10-30nm。具体二维导电材料包覆层的厚度可以为但不限于5nm，7nm，9nm，10nm，15nm，20nm，25nm，30nm，40nm，50nm，60nm，70nm，80nm，90nm，100nm。补锂添加剂的粒径为5-60μm，优选地，补锂添加剂的粒径为5-10μm。具体补锂添加剂的粒径可以为但不限于5μm，6μm，7μm，8μm，9μm，10μm，20μm，30μm，40μm，50μm，60μm。在本申请实施例提供的二维导电材料包覆层的厚度和补锂添加剂的粒径范围内，能使补锂添加剂的导电性和稳定性能达到最优。
在实施例中，补锂添加剂放置在相对湿度为30％的空气中24h，氢氧化锂的含量在45％以下。
本申请实施例第二方面提供一种补锂添加剂的制备方法，如图1所示，包 括以下步骤：
S10：提供金属锂；
S20：将金属锂置于氮气气氛中进行煅烧处理，然后研磨，得到氮化锂。
本申请实施例提供的补锂添加剂的制备方法，通过将提供的金属锂置于氮气气氛中进行煅烧处理，然后研磨，得到氮化锂，可作为补锂添加剂，该制备工艺简单，容易实现，且生产成本较低。另外，通过该制备方法制备得到的氮化锂具有材料稳定性和电化学性能好，利于提高电池首次充电效率和整体电化学性能。
在S20步骤中，氮化锂的制备方法包括如下步骤：将金属锂置于氮气气氛中进行煅烧处理，然后研磨，得到氮化锂。
在实施例中，煅烧处理在惰性气体中进行，煅烧处理包括如下步骤：按照流量比为(1-9)：1，通入氮气和惰性气体，并按照1-10℃/min的速度升温至180-900℃，保温5-24h，然后只通入氮气，并按照1-50℃/min的速度降温至25℃。
在一些实施例中，氮气和惰性气体的流量比为(1-9)：1。在本实施例提供的氮气和惰性气体的流量比的范围内，有利于煅烧处理过程中提高渗碳反应的稳定性和实验安全性。具体的，氮气和惰性气体的流量比可以为但不限于1：1，2：1，3：1，4：1，5：1，6：1，7：1，8：1，9：1，7：3。
在一些实施例中，煅烧处理的升温速度为1-10℃/min。升温速度具体可以根据所用设备的升温能力进行调整，在本申请实施例提供的煅烧处理的升温速度的范围内，利于炉腔内的温度均匀，耗时适中，能减少对设备的负面影响。具体的，升温速度可以为但不限于1℃/min，2℃/min，3℃/min，4℃/min，5℃/min，6℃/min，7℃/min，8℃/min，9℃/min，10℃/min。
在一些实施例中，煅烧处理的保温温度为180-900℃，保温时间为5-24h。在本申请实施例提供的煅烧处理的保温温度和保温时间范围内，有利于节省能耗，降低材料成本。具体的，煅烧处理的保温温度可以为但不限于180℃，200℃，300℃，400℃，500℃，600℃，700℃，800℃，900℃，煅烧处理的保温时间可以为但不限于5h，7h，9h，10h，12h，14h，16h，18h，20h，22h，24h。
在一些实施例中，煅烧处理的压力为0.1-100MPa，在本申请实施例提供的煅烧处理的保温温度和压力范围内，有利于降低对设备的要求，降低生产成本。具体的，煅烧过程的压力可以但不限于0.1MPa，0.5MPa，1MPa，10MPa，30MPa，50MPa，70MPa，90MPa，100MPa。
在一些实施例中，煅烧处理的降温速度为1-50℃/min。由于α晶相氮化锂为高温稳定晶相，温度高于500K有利于β晶相氮化锂转化为α晶相氮化锂；β晶相氮化锂为低温稳定晶相，温度低于300K有利于β晶相氮化锂稳定存在。因此，在高温高压气-液反应渗氮之后，随着温度降低，α晶相氮化锂转变为β晶相氮化锂，由此通过控制高压下的降温速度可以抑制α晶相氮化锂转变为β晶相氮化锂，从而实现调控β晶相氮化锂和α晶相氮化锂的质量比。在本申请实施例提供的高压环境和降温速度的范围内进行降温，可以制备出本申请实施例提供的质量比范围内的α晶相和β晶相混合相氮化锂，使制备得到的α晶相和β晶相混合相氮化锂的稳定性和释锂能力达到最好，因此电池首次充电效率和整体电化学性能达到最优。具体的，降温速度可以为但不限于1℃/min，5℃/min，10℃/min，15℃/min，20℃/min，25℃/min，30℃/min，35℃/min，40℃/min，45℃/min，50℃/min。
在实施例中，补锂添加剂的制备方法，还包括以下步骤：
S30：将氮化锂和二维导电材料分散在溶剂中，得到混合溶液，将混合溶液进行干燥处理，形成二维导电材料包覆的补锂添加剂。
在步骤S30中，溶剂包括N,N-二甲基甲酰胺、四氢呋喃、正己烷、苯的至少一种。在具体的实施例中，溶剂可以为N,N-二甲基甲酰胺，还可以为四氢呋喃，还可以为正己烷。
在实施例中，干燥处理的条件包括：干燥温度为30-100℃，干燥时间为6-10h。在本申请提供的干燥温度和干燥时间的范围内，能使溶剂挥发速度适中，能避免氮化锂富集到表面，有利于二维导电材料在氮化锂表面形成均匀的包覆层。具体的，干燥温度可以为但不限于30℃，40℃，50℃，60℃，70℃，80℃，90℃，100℃。干燥时间可以为但不限于6h，7h，8h，9h，10h。
本申请实施例第三方面提供一种正极材料，正极材料含有本申请提供的电极补锂添加剂或本申请提供的制备方法制得的补锂添加剂。
本申请实施例提供的正极材料，由于该正极材料含有本申请提供的电极补锂添加剂或本申请提供的制备方法制得的补锂添加剂，因此该正极材料具有材料稳定性和电化学性能好，能确保电池在充电过程电压变化平稳。
本申请实施例第四方面提供一种二次电池，该二次电池含有本申请提供的正极材料。
本申请实施例提供的二次电池，由于该二次电池含有本申请提供的正极材料。因此，在首次充电过程中，本申请电极片所含的补锂添加剂的能够作为锂源，在首次充电过程中释放锂离子实现补锂作用，从而保持电池体系内锂离子的充裕，提高电池首次充电效率和整体充放电性能。
在实施例中，采用恒流恒压的充电方式，在充电电压为2.5-4.3V，充电电流为0.1C，截止电流为0.01C的情况下，二次电池在首圈充电过程中，氮化锂 的锂离子脱出数量为1.2-2.8个。
下面结合具体实施例进行说明。
1.补锂添加剂及其制备方法：
实施例1
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括纯α晶相氮化锂和结合在α晶相氮化锂内核表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，包括以下步骤：
S10：提供金属锂；
S20：将金属锂置于刚玉舟中并放入高温高压反应炉中，按照流速为300mL/min，通入氩气30min进行排气；然后按照流量比为70：30mL/min，通入氩气和氮气，并按照10℃/min的速度升温至800℃，保温10h之后，升高炉内压力到5MPa，按照40℃/min的速度降温至25℃，得到α晶相氮化锂；最后将α晶相氮化锂研磨，得到纯α晶相氮化锂颗粒。
S30：按照α晶相氮化锂颗粒与石墨烯的质量比为30：1，将α晶相氮化锂颗粒和石墨烯加入N,N-二甲基甲酰胺中进行高速搅拌60min，得到混合溶液，然后将混合溶液在50℃的温度下干燥8h，得到石墨烯包覆在α晶相氮化锂颗粒表面的补锂添加剂。
经检测，α晶相氮化锂颗粒的粒径为1-8μm，石墨烯包覆层的厚度为10-30nm，该补锂添加剂的粒径为1.01-8.05μm。
实施例2
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括纯β晶相氮化锂和结合在β晶相氮化锂内核表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实 施例的步骤S20中，按照1℃/min的速度降温至25℃，得到石墨烯包覆在β晶相氮化锂颗粒表面的补锂添加剂。
经检测，β晶相氮化锂颗粒的粒径为1-8μm，石墨烯包覆层的厚度为10-30nm，该补锂添加剂的粒径为1.01-8.05μm。
实施例3
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照32℃/min的速度降温至25℃，得到α晶相和β晶相混合晶相氮化锂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为90：10。
实施例4
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂内核表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照35℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为98：2。
实施例5
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例4的不同之处在于，在本实施例的步骤S20中，按照32℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为90：10。
实施例6
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照28℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为80：20。
实施例7
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照25℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为70：30。
实施例8
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照18℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为10：90。
实施例9
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照13℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为8：92。
实施例10
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S20中，按照8℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为5：95。
实施例11
本实施例提供一种补锂添加剂及其制备方法。该补锂添加剂包括α晶相氮化锂和β晶相氮化锂和结合在α晶相氮化锂和β晶相氮化锂表面的石墨烯包覆层。
本实施例的补锂添加剂的制备方法，与实施例1的不同之处在于，在本实施例的步骤S10中，按照5℃/min的速度降温至25℃，得到石墨烯包覆在α晶相氮化锂和β晶相氮化锂内核表面的补锂添加剂。
经检测，α晶相和β晶相混合晶相氮化锂的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm；α晶相和β晶相混合晶相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为2：98。
对比例1
本对比例提供一种补锂添加剂及其制备方法。该补锂添加剂包括氮化锂颗粒。
本对比例的补锂添加剂的制备方法，包括以下步骤：
S10：将金属锂置于刚玉舟中并放入高温高压反应炉中，按照流速为300mL/min，通入氩气30min进行排气；然后按照流量比为70：30mL/min，通入氩气和氮气，并按照10℃/min的速度升温至800℃，保温10h之后，自然降温至25℃，得到氮化锂；最后将氮化锂研磨，得到氮化锂颗粒。
经检测，氮化锂颗粒的粒径为1-8μm，氮化锂颗粒中，α晶相氮化锂与β晶相氮化锂的质量比为65：35。
对比例2
本对比例提供一种补锂添加剂及其制备方法。该补锂添加剂包括氮化锂颗粒和结合在氮化锂表面的石墨烯包覆层。
本对比例的补锂添加剂的制备方法，与对比例1的不同之处在于，本对比例还包括以下步骤：
S20：按照氮化锂颗粒与石墨烯的质量比为30：1，将氮化锂颗粒和石墨烯加入N,N-二甲基甲酰胺中进行高速搅拌60min，得到混合溶液，然后将混合溶液在50℃的温度下干燥8h，得到石墨烯包覆在氮化锂颗粒表面的补锂添加剂。
经检测，氮化锂颗粒的粒径为1-8μm，石墨烯包覆层的厚度为30nm，该补锂添加剂的粒径为1.01-8.05μm，氮化锂颗粒中，α晶相氮化锂与β晶相氮化锂的质量比为65：35。
2.相关特性测试分析。
1.补锂添加剂包含的氮化锂内核的结构表征：
将上述实施例1、实施例2、实施例4、实施例6、实施例8提供的氮化锂内核进行X射线衍射分析，其XRD图谱如图2所示。从图2可以看出，随着α晶相氮化锂的质量占比减小，β晶相氮化锂的质量占比增大，氮化锂的α晶相的衍射峰的强度相应减弱，氮化锂的β晶相的衍射峰的强度相应增强。
2.锂离子电池电化学性能测试分析：
将实施例3和对比例1提供的补锂添加剂加入到LFP正极中，采用N,N-二甲基甲酰胺溶剂制备正极浆料。采用0.1C恒流恒压方式充电，电压区间为2.0-3.7V，截止电流为0.01C，测试电池的充放电性能。测试结果如表1所示。
表1
从表1可以看出，实施例1-11提供的补锂添加剂在30％的空气湿度下放 置24h后的氢氧化锂含量均明显低于对比例1-2提供的补锂添加剂在30％的空气湿度下放置24h后的氢氧化锂含量，并且实施例1-11提供的补锂添加剂对应电池的容量和首圈氮化锂脱锂个数均明显高于对比例1-2提供的补锂添加剂对应电池的容量和首圈氮化锂脱锂个数，说明本申请α晶和β晶的混相氮化锂、α晶相氮化锂以及β晶相氮化锂相比于传统的氮化锂具有更好的稳定性，能赋予电池更好的电化学性能。
图3为实施例5和对比例2提供的补锂添加剂组装扣电池的容量-电压图，从图3可以看出，实施例5提供的由石墨烯包覆的混相氮化锂中，α晶相氮化锂与β晶相氮化锂的质量比为90：10，其用作补锂添加剂在充电过程具有更多的锂脱出，使得充电过程电压变化相对平稳，这是由于α晶相氮化锂与β晶相氮化锂的质量比为90：10时，其稳定性最好。而对比例2提供的氮化锂用作补锂添加剂，在充电过程一开始出现严重极化，这是由于氮化锂自身稳定性差造成。因此，在本申请实施例提供的α晶相氮化锂与β晶相氮化锂的质量比的范围内，α晶相和β晶相混合晶相氮化锂的稳定性达到最优，并且首圈充电过程氮化锂的锂离子脱出数量达到最多，能维持电池充电过程电压平稳。
图4为未添加补锂添加剂和添加实施例3提供的补锂添加剂到磷酸铁锂正极后的扣电池容量-电压图，从图4可以看出，添加本申请实施例3提供的补锂添加剂的正极容量性能得到明显提升。这是由于首圈充电过程补锂添加剂所含的氮化锂的锂离子从正极转移到负极，参与负极SEI膜的形成，避免LFP材料中活性锂离子的损耗。因此，补锂添加剂可以提高LFP电池容量性能。
以上仅为本申请的可选实施例而已，并不用于限制本申请。对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的权利要求范围之内。

Claims (19)

  1. 一种补锂添加剂，其特征在于，所述补锂添加剂包括氮化锂，所述氮化锂包括α晶相氮化锂和/或β晶相氮化锂。
  2. 如权利要求1所述的补锂添加剂，其特征在于，所述氮化锂包括α晶相氮化锂和β晶相氮化锂，所述α晶相氮化锂与所述β晶相氮化锂的质量比为(2-10)：(90-98)或(70-98)：(2-30)。
  3. 如权利要求1或2所述的补锂添加剂，其特征在于，所述补锂添加剂还包括结合在所述氮化锂表面的二维导电材料。
  4. 如权利要求3所述的补锂添加剂，其特征在于，结合在所述氮化锂表面的所述二维导电材料形成全包覆或部分包覆所述氮化锂的二维导电材料包覆层。
  5. 如权利要求4所述的补锂添加剂，其特征在于，所述二维导电材料包括石墨烯、石墨炔、过渡金属二硫化物、MXenes材料中的至少一种；
    其中，所述MXenes材料的通式为Mn+1XnTx，M包括Ti、Cr、Mo、V、Nb、Hf、Ta、Sc中的至少一种；X包括C、N中的至少一种；Tx包括OH-、F-、O2-、NH4 +、NH3中的至少一种；n为1-4。
  6. 如权利要求5所述的补锂添加剂，其特征在于，所述过渡金属二硫化物包括MoS2、WS2、SnS2、TiS2中的至少一种。
  7. 如权利要求4-6任一项所述的补锂添加剂，其特征在于，在所述补锂添加剂中，所述氮化锂与所述二维导电材料包覆层的质量比为(9-99)：1。
  8. 如权利要求4-6任一项所述的补锂添加剂，其特征在于，所述二维导电材料包覆层的厚度为5-100nm。
  9. 如权利要求4-6任一项所述的补锂添加剂，其特征在于，所述氮化锂的粒径为0.1-50μm。
  10. 如权利要求4-6任一项所述的补锂添加剂，其特征在于，包覆后的所述补锂添加剂的粒径为5-60μm。
  11. 如权利要求4-6任一项所述的补锂添加剂，其特征在于，所述补锂添加剂放置在湿度为30％RH的空气中24h，氢氧化锂的含量在45％以下。
  12. 一种补锂添加剂的制备方法，其特征在于，包括以下步骤：
    提供金属锂；
    将所述金属锂置于氮气气氛中进行煅烧处理，然后研磨，得到氮化锂。
  13. 如权利要求12所述的制备方法，其特征在于，所述煅烧处理包括如下步骤：
    按照流量比为(1-9)：1，通入所述氮气和惰性气体，并按照1-10℃/min的速度升温至180-900℃，保温5-24h，然后只通入氮气，并按照1-50℃/min的速度降温至25℃。
  14. 如权利要求12或13所述的制备方法，其特征在于，所述制备方法还包括：
    将所述氮化锂和二维导电材料分散在溶剂中，得到混合溶液，将所述混合溶液进行干燥处理，形成二维导电材料包覆的补锂添加剂。
  15. 如权利要求14所述的制备方法，其特征在于，所述干燥处理的条件包括：干燥温度为30-100℃，干燥时间为6-10h。
  16. 如权利要求14所述的制备方法，其特征在于，所述溶剂包括N,N-二甲基甲酰胺、四氢呋喃、正己烷、苯的至少一种。
  17. 一种正极材料，其特征在于，所述正极材料含有权利要求1-11任一项所述的补锂添加剂和/或权利要求12-16任一项所述的补锂添加剂的制备方法制得的补锂添加剂。
  18. 一种二次电池，其特征在于，所述二次电池含有如权利要求17所述的正极材料。
  19. 如权利要求18所述的二次电池，其特征在于，采用恒流恒压的充电方 式，在充电电压为2.5-4.3V，充电电流为0.1C，截止电流为0.01C的情况下，所述二次电池在首圈充电过程中，所述氮化锂的锂离子脱出数量为1.2-2.8个。
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