Lithium supplements and methods for manufacturing the same, positive electrode plates and secondary batteries

Abstract

The present application provides a lithium supplement belonging to the field of energy storage technology, wherein the lithium supplement comprises lithium phosphite (Li2HPO3) and a coating layer covering the surface of the lithium phosphite, and the material of the coating layer comprises iron boride. The present application can solve problems in related technology such as poor safety and stability of lithium supplement materials, high costs, and the generation of residues during the lithium supplementation process.

Description

Technology Field

[0001] The present invention relates to the field of energy storage technology, and specifically to a lithium supplement, a method for manufacturing the same, a positive electrode plate, and a secondary battery. Background Technology

[0002] Lithium-ion batteries are widely applied in energy storage fields, such as new energy vehicle batteries. Due to their advantages, including high theoretical capacity, stable operating voltage, high energy density, long cycle life, and excellent chemical stability, lithium-ion batteries have become one of the rechargeable batteries with the widest range of current applications (e.g., new energy vehicles).

[0003] During the first charging process of lithium-ion batteries, a Solid Electrolyte Interphase (SEI) film forms on the surface of the negative electrode. This consumes a large amount of active lithium, leading to irreversible lithium loss. Consequently, the energy density and cycle performance of lithium-ion batteries are degraded, thereby limiting their applications. To address this issue and compensate for the loss of active lithium, methods such as prelithification or lithium replenishment are generally used to improve the energy density and cycle stability of lithium-ion batteries.

[0004] Compared to cathode lithium replenishment, anode lithium replenishment is receiving significant attention for its simpler operation and superior safety. However, most current high-capacity lithium replenishment materials are prone to gas generation during the initial charging process, which can easily cause the battery volume to expand, potentially leading to safety and stability issues.

[0005] Considering the technical problems existing in the background technology, the present application provides a lithium supplement, a method for manufacturing the same, a positive electrode plate, and a secondary battery to solve the problems of poor safety and stability and high cost of lithium supplement materials in the related technology.

[0006] In a first aspect, the lithium supplement provided by an embodiment of the present application comprises lithium phosphite (Li2HPO3) and a coating layer covering the surface of the lithium phosphite, wherein

[0007] The material of the above coating layer includes iron boride.

[0008] In the technical means according to the embodiment of the present application, the lithium supplement adopts a coating layer having iron boride to coat the surface of lithium phosphate, thereby obtaining two lithium atoms and metaphosphoric acid after the lithium phosphate is delithiated and preventing the generation of waste gas, which is advantageous for improving safety performance; furthermore, since the lithium phosphate is coated with a coating layer, it becomes difficult for the lithium phosphate to come into contact with the external environment, which is advantageous for preventing the oxidation of phosphite ions into phosphate ions, thereby reducing the formation of "dead lithium" and improving the lithium supplementation effect; and even if a small amount of metaphosphoric acid leaks out, it reacts due to the residual alkali on the surface of the lithium supplement to form a salt, thereby avoiding erosion of the lithium supplement and improving the stability of the lithium supplement; In addition, since the metaphosphoric acid produced after the delithiation of lithium phosphate has strong moisture absorption properties, the product after the delithiation of lithium phosphate can absorb a small amount of moisture present in the lithium supplement, thereby preventing moisture from entering the electrolyte and causing electrolyte decomposition, and thereby further improving the performance stability of the lithium supplement and the battery; finally, a coating layer having iron boride is adopted to coat the lithium phosphate, and since the material of the coating layer has relatively strong stability and good conductivity, the stability of the lithium supplement is improved while the conductivity of the lithium supplement is improved. In addition, compared to lithium supplement materials with high lithium capacity, such as lithium-rich lithium ferrite used in related technologies, the lithium supplement has a low raw material cost and a low cost.

[0009] In some embodiments, the thickness of the coating layer is 0.6 μm to 2 μm, and / or the coverage rate of the coating layer is 93% or more.

[0010] In this embodiment, by controlling the thickness and coverage rate of the coating layer within the above range, the coating layer is advantageous for more completely covering the lithium phosphate and reducing leakage of the lithium phosphate, while at the same time avoiding adverse effects on the lithium ion conductivity of the lithium phosphate caused by the coating layer.

[0011] In some embodiments, the lithium phosphite has a quasi-spherical shape, and the sphericity of the quasi-spherical shape is 0.81 to 0.87; and / or the particle size distribution of the lithium supplement is such that the D50 particle size is 0.3 μm to 3.8 μm, the D10 particle size is 0.1 μm to 1.9 μm, and the D90 particle size is 1.3 μm to 6.4 μm.

[0012] In this embodiment, by controlling the sphericity of the lithium supplement to within the above range, it is advantageous to adjust the sphericity of lithium phosphite, thereby allowing the coating layer to more easily and completely coat the lithium phosphite; additionally, the particle size distribution of the lithium supplement is such that the D50 particle size is 0.3μm to 3.8μm, the D10 particle size is 0.1μm to 1.9μm, and the D90 particle size is 1.3μm to 6.4μm, and since the lithium supplement has a concentrated particle size distribution and small particle size, it can effectively reduce the particle sensation during the coating process when applied to the positive electrode plate, thereby improving the flatness of the positive electrode plate.

[0013] In some embodiments, the tap density of the lithium supplement is 1.43 g / mL to 1.59 g / mL; and / or the compaction density of the lithium supplement is 2.48 g / mL to 2.76 g / mL; and / or the specific surface area of ​​the lithium supplement is 3.47 m² 2 / g~4.79 m 2 / g is.

[0014] In this embodiment, by controlling the tap density and compaction density of the lithium supplement to within the above range, the energy density of the lithium supplement can be effectively improved; and by controlling the specific surface area of ​​the lithium supplement to within the above range, when the lithium supplement is applied to a secondary battery, it can have an appropriate contact area with the electrolyte, etc., thereby fully exhibiting the lithium supplementation effect.

[0015] In a second aspect, the method for manufacturing a lithium supplement provided by an embodiment of the present application is,

[0016] A step of preparing a first slurry containing lithium phosphite;

[0017] A step of mixing the above first slurry with sodium borohydride and ferrous chloride and obtaining a crude product through a first reaction treatment;

[0018] The method includes the step of obtaining the lithium supplement by filtering, washing, and drying the above crude product;

[0019] The above lithium supplement comprises lithium phosphate (Li2HPO3) and a coating layer covering the surface of the lithium phosphate, and the material of the coating layer comprises iron boride.

[0020] In the technical means according to the embodiment of the present application, after preparing a lithium phosphate slurry, the lithium phosphate slurry is mixed with sodium borohydride and ferrous chloride, and iron boride is obtained by reacting sodium borohydride and ferrous chloride, thereby obtaining a lithium supplement having a coating layer of iron boride formed on the surface of lithium phosphate; in this lithium supplement, after the lithium phosphate is delithiated, two lithium atoms and metaphosphoric acid are obtained, and since no waste gas is generated, it is advantageous for improving safety performance; furthermore, since the lithium phosphate is coated with a coating layer, it becomes difficult for the lithium phosphate to come into contact with the external environment, which is advantageous for preventing the oxidation of phosphate ions into phosphate ions, thereby reducing the formation of "dead lithium" and improving the lithium supplementation effect; and even if a small amount of metaphosphoric acid leaks out, it reacts due to the alkalinity of the residual alkali on the surface of the lithium supplement to form a salt, thereby avoiding erosion of the lithium supplement and improving the stability of the lithium supplement; In addition, since the metaphosphoric acid produced after the delithiation of lithium phosphate has strong moisture absorption, the product after the delithiation of lithium phosphate can absorb a small amount of moisture present in the lithium supplement, thereby preventing the inflow of such moisture into the electrolyte and causing the decomposition of the electrolyte, and thereby further improving the performance stability of the lithium supplement and the battery; finally, a coating layer having iron boride is adopted to coat the lithium phosphate, and since the material of the coating layer has relatively strong stability and good conductivity, the stability of the lithium supplement is improved while the conductivity of the lithium supplement is improved. In addition, compared to lithium supplement materials with high lithium capacity, such as lithium-rich lithium ferrite used in related technologies, the lithium supplement has a low raw material cost and a low manufacturing cost.

[0021] In some embodiments, the step of preparing a first slurry containing lithium phosphite is,

[0022] A step of obtaining a first solution of phosphoric acid—the solvent of the first solution comprises at least one of methanol, ethanol, glycerol, propanol, and propylene glycol—;

[0023] A step of adding a lithium salt to a first solution of phosphoric acid and obtaining a first reaction slurry through a second reaction treatment;

[0024] The method includes the step of grinding the first reaction slurry until the lithium phosphate in the first reaction slurry reaches a preset particle size to obtain the first slurry.

[0025] In this embodiment, a lithium salt is added to a first solution of phosphoric acid, and through a second reaction treatment, a first reaction slurry is obtained by utilizing the characteristic that lithium phosphate has low solubility in the solvent to cause lithium phosphate to crystallize and precipitate from the first solution, and then the first reaction slurry is ground to obtain a first slurry in which the lithium phosphate in the first reaction slurry has a preset particle size. Here, since using phosphoric acid as a raw material is advantageous for maintaining the first slurry as acidic, the first reaction treatment is performed under acidic conditions when the subsequent first reaction treatment is carried out, which is advantageous for the formation of iron boride, and the iron boride is chemically coated on the surface of the lithium phosphate to form a coating layer.

[0026] In some embodiments, the ratio of the amount of substance of the phosphoric acid, sodium borohydride, and ferrous chloride is 1:(0.05–0.1):(0.025–0.05); and / or

[0027] The temperature of the second reaction treatment is 35℃~55℃, and the time of the second reaction treatment is 0.5h~1h; and / or

[0028] The lithium salt comprises at least one of lithium carbonate, lithium sulfite, and lithium bicarbonate; and / or

[0029] The ratio of the amount of lithium element to phosphoric acid in the lithium salt is (1.8–1.9):1; and / or

[0030] The preset particle size is 0.3μm to 3μm.

[0031] In this embodiment, by adjusting the material amount ratio of phosphoric acid, sodium borohydride, and ferrous chloride to within the above range, the first reaction treatment is performed under acidic conditions and an excess amount of sodium borohydride, which is advantageous for the reaction between sodium borohydride and ferrous chloride, and a coating layer of appropriate thickness is formed on the surface of lithium phosphate. By adjusting the temperature and time of the second reaction treatment to within the above range, the reaction in which the lithium salt reacts with phosphoric acid to produce lithium phosphate is sufficiently carried out. By adopting lithium carbonate, lithium sulfite, and / or lithium bicarbonate, these lithium salts react with phosphoric acid to produce lithium phosphate and gas, thereby reducing the influx of impurities while manufacturing lithium phosphate. By adjusting the material amount ratio of the lithium element in the lithium salt to phosphoric acid to (1.8~1.9):1, an appropriate excess amount of phosphoric acid is secured to maintain acidic conditions, and the first reaction treatment is performed smoothly under acidic conditions. By controlling the preset particle size to 0.3μm to 3μm, it is advantageous to obtain lithium phosphate with a concentrated particle size distribution and small particle size, which is advantageous for obtaining lithium supplements with a concentrated particle size distribution and small particle size.

[0032] In some embodiments, the step of mixing the first slurry with sodium borohydride and ferrous chloride and obtaining a crude product through a first reaction treatment is,

[0033] The method includes the step of mixing a solution containing sodium borohydride, a solution containing ferrous chloride, and a first slurry, and then obtaining a crude product after a first predetermined time at a first reaction temperature.

[0034] In this embodiment, a solution containing sodium borohydride, a solution containing ferrous chloride, and a first slurry are mixed, and then the sodium borohydride and ferrous chloride are sufficiently reacted at a first reaction temperature for a first predetermined time, and the reaction product is used to uniformly coat lithium phosphite, thereby improving the coating uniformity of the coating layer in the crude product.

[0035] In some embodiments, the mixing time is 60 min to 120 min, and the mixing temperature is 25°C to 45°C; and / or

[0036] The temperature of the first reaction treatment above is 25℃ to 45℃; and / or

[0037] The first setting time is 30 min to 60 min.

[0038] In this embodiment, by controlling the mixing time and temperature, the uniformity of mixing of the first slurry, sodium borohydride, and ferrous chloride can be improved, which is advantageous for sufficient coating of lithium phosphate. When the first reaction temperature is controlled to 25 to 45°C and / or the first preset time to 30 min to 60 min, sufficient iron boride is generated and is advantageous for coating the surface of lithium phosphate, and thus a coating layer having an appropriate thickness and coating rate can be formed on the surface of lithium phosphate. Additionally, by controlling the mixing temperature and the temperature of the first reaction treatment to be the same, iron boride can be generated during the mixing process, and sufficient iron boride is generated, which is advantageous for improving the uniformity of coating of the coating layer and increasing the coating rate.

[0039] In some embodiments, the temperature of the drying treatment is 80°C to 100°C, and the vacuum level of the drying treatment is -0.09 MPa to -0.07 MPa.

[0040] In this embodiment, by controlling the temperature and vacuum level of the drying process, the inflow of oxygen and water vapor from the air is reduced, which is advantageous for improving the material stability of the lithium supplement and reducing the generation of by-products such as lithium phosphate.

[0041] In a third aspect, the positive electrode plate provided by an embodiment of the present application comprises a current collector and a positive material disposed on at least one side along the self-thickness direction of the current collector, wherein the positive material comprises a lithium supplement according to a first aspect or a lithium supplement manufactured by a method for manufacturing a lithium supplement according to a second aspect.

[0042] In this embodiment, the positive electrode plate includes the aforementioned lithium supplement, and the lithium supplement adopts a coating layer having iron boride to coat the surface of lithium phosphite, thereby having improved safety, stability, conductivity, and lithium supplementation effects, and is inexpensive, so the safety, stability, conductivity, and lithium supplementation effects of the positive electrode plate are improved, the cost of the positive electrode plate is reduced, and it is advantageous to improve the capacity of the battery when applied to a battery.

[0043] In a fourth aspect, a secondary battery provided by an embodiment of the present application comprises a positive electrode plate, a negative electrode plate, and a separator, wherein the positive electrode plate is selected from the positive electrode plates according to the third aspect.

[0044] In this embodiment, the secondary battery has the advantages of the positive electrode plate by including the positive electrode plate.

[0045] The above description is merely an overview of the technical solution of the present application. To understand the technical means of the present application more thoroughly, it may be implemented in accordance with the contents of the specification. Furthermore, to enable a clearer understanding of the purpose, features, and advantages of the present application, specific embodiments of the present application are described below. Brief explanation of the drawing

[0046] Hereinafter, to more clearly explain the technical means of the present application, the drawings used in the description of the present application are briefly introduced. The drawings described below are merely some embodiments of the present application, and it is obvious to those skilled in the art that other drawings can be obtained based on these drawings without creative work. FIG. 1 is a flowchart illustrating a method for manufacturing a lithium supplement according to an embodiment of the present application. Figure 2 is a scanning electron microscope image of the lithium supplement provided in Example 1 of the present application. Figure 3 is a diagram showing the particle size distribution results of the lithium supplement provided in Example 1 of the present application. Specific details for implementing the invention

[0047] Hereinafter, embodiments of the technical means of the present application will be described in detail with reference to the attached drawings. The following embodiments are used merely to more clearly explain the technical means of the present application and are therefore illustrative; the scope of protection of the present application is not to be limited thereto.

[0048] All technical and scientific terms used in this specification have the same meaning as generally understood by those skilled in the art to which the present invention pertains, unless otherwise defined; terms used in this specification are intended to specifically describe embodiments and are not to be interpreted as limiting the scope of this application; and terms "comprising," "having," and all variations thereof as used in the description of the invention, claims, and drawings in this application are interpreted to cover non-exclusive inclusions.

[0049] In the embodiments of this application, terms such as "first," "second," etc. are used merely to distinguish different objects and should not be interpreted as indicating or implying relative importance, or as implicitly indicating the number of technical features being modified, a specific order, or a subject-object relationship. In the embodiments of this application, "plural" means two or more unless specifically defined otherwise.

[0050] In this specification, "Examples" means that specific features, structures, or characteristics described in combination with the Examples may be included in at least one Example of this application. As stated in various places in this specification, this phrase does not necessarily refer to the same Example, nor are they independent or alternative Examples mutually exclusive from other Examples. Those skilled in the art will understand clearly and implicitly that the Examples described in this specification may be combined with other Examples.

[0051] In the embodiments of this application, the term "and / or" merely describes the association between related objects and indicates that three relationships may exist; for example, “A and / or B” may represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, in this specification, the symbol " / " generally indicates that the related objects before and after it have an "or" relationship.

[0052] In the embodiments of the present application, the term “plural” means two or more (including two), likewise, “plural group” means two or more groups (including two groups), and “plural part” means two or more parts (including two parts).

[0053] In the description of the embodiments of the present application, the directional or positional relationships indicated by technical terms such as “center,” “longitudinal,” “transverse,” “length,” “width,” “thickness,” “top,” “bottom,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inside,” “outside,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circular” are based on the directional or positional relationships illustrated in the attached drawings and are merely intended to easily and briefly explain the embodiments of the present application. They do not indicate or imply that the mentioned devices or components must have a specific direction or be configured and operated in a specific direction, and therefore should not be interpreted as limiting the present application.

[0054] Unless otherwise specifically stated in the description of the embodiments of this application, technical terms such as “mounting,” “connecting to each other,” “connecting,” and “fixing” should be interpreted in a broad sense, for example, they may be fixedly connected, detachably connected, or integrally formed; or they may be mechanically connected or electrically connected; or they may be directly connected or indirectly connected through an intermediate element; or the interiors of two components may be in communication or there may be an interaction relationship between two components. A person skilled in the art to which this application pertains will be able to readily understand the specific meaning that the said terms have in the embodiments of this application depending on the specific circumstances.

[0055] Currently, commonly used high-capacity cathode lithium replenishment materials mainly include lithium-rich compounds (e.g., lithium-rich lithium ferrite (Li5FeO4), lithium-rich lithium nickelate (Li2NiO2), etc.) and binary lithium compounds (e.g., Li3N, Li2O2, etc.). Among these, lithium-rich compounds have problems such as poor air stability, easy moisture absorption and hydrolysis, and the generation of gases (oxygen, etc.). Furthermore, lithium-rich compounds themselves are sensitive to water vapor and carbon dioxide in the air, easily causing reactions to generate residual surface alkali, which makes homogenization difficult and hinders the extraction of lithium ions. Additionally, lithium-rich compounds have problems such as poor air stability and high cost. Moreover, lithium-rich compounds require the use of lithium oxide as a raw material, have relatively high alkalinity, and are difficult to process. Additionally, they release a large amount of oxygen during the lithium replenishment process, resulting in residual LiFeO2, which has a certain effect on battery cell performance. Bilithium compounds have a high-voltage platform, and during the first charging process, oxygen is released and reacts with the electrolyte, destroying the stable SEI film between the anode and the electrolyte; this can worsen battery stability and even cause safety issues.

[0056] Therefore, providing lithium supplements with higher safety and stability and lower costs is emerging as an urgent task.

[0057] To solve the above technical problem, the embodiments of the present application provide a lithium supplement, a method for manufacturing the same, a positive electrode plate, and a secondary battery. The lithium supplement provided in the embodiments of the present application has the advantages of excellent stability, high safety, low cost, and excellent lithium supplementation effect. When applied to the positive electrode plate of a battery, it effectively improves the Coulomb efficiency of the positive electrode material and compensates for the lithium loss of the negative electrode due to the formation of an SEI film. Therefore, it is advantageous for improving the capacity and cycle performance of a secondary battery having the lithium supplement, and furthermore, the electrochemical performance of the positive electrode plate and the secondary battery is also improved.

[0058] The electric devices provided in the embodiments of the present application may be, but are not limited to, mobile phones, tablets, laptop computers, electric toys, electric tools, electric cart vehicles, electric automobiles, ships, spacecraft, etc. Here, electric toys may include stationary or mobile electric toys, and may include, for example, game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, and spacecraft may include airplanes, rockets, space shuttles, spacecraft, etc.

[0059] In a first aspect, the lithium supplement provided by an embodiment of the present application comprises lithium phosphite (Li2HPO3) and a coating layer covering the surface of the lithium phosphite, wherein the material of the coating layer comprises iron boride.

[0060] In this lithium supplement, two lithium atoms and metaphosphoric acid are obtained after lithium phosphite is delithiated during the lithium supplementation process, and the safety of the lithium supplement is enhanced because no waste gas is generated. In addition, since the lithium phosphite is coated with a coating layer, it becomes difficult for the lithium phosphite to come into contact with the external environment, thereby reducing the oxidation of phosphite ions into phosphate ions, which reduces the formation of "dead lithium" and improves the lithium supplementation effect. Even if a small amount of metaphosphoric acid leaks out, it reacts with residual alkali (e.g., Li2O, etc.) on the surface of the lithium supplement to form a salt, thus preventing the lithium supplement from being corroded and improving the stability of the lithium supplement. Furthermore, since the metaphosphoric acid generated after the delithiation of lithium phosphite has strong water absorption properties, the product after the delithiation of lithium phosphite can absorb a small amount of moisture present in the lithium supplement, preventing moisture from entering the electrolyte and causing electrolyte decomposition, thereby further improving the performance stability of the lithium supplement and the battery.

[0061] In addition, a coating layer having iron boride is adopted to coat lithium phosphite, and since the material of the coating layer has relatively strong stability and good conductivity, it improves the stability of the lithium supplement while simultaneously improving the conductivity of the lithium supplement. Furthermore, iron boride has strong stability and good conductivity, so it can act as a conductive agent in the positive electrode plate.

[0062] In addition, compared to high-capacity lithium supplement materials such as lithium-rich lithium ferrite used in related technologies, the lithium supplement has a lower raw material cost, effectively reducing the manufacturing cost of the lithium supplement.

[0063] Specifically, when the above lithium supplement is applied to the cathode material, the lithium phosphite within the lithium supplement is used for lithium replenishment, and after delithiation, two lithium atoms and metaphosphoric acid are obtained (the reaction equation is as shown in Equation (1) below), and no waste gas is generated, which is advantageous for improving safety performance. In addition, by coating the lithium phosphite as a coating layer, the metaphosphoric acid generated from the lithium delithiation of the lithium phosphite does not leak easily, and even if a small amount of metaphosphoric acid leaks out, it reacts due to the alkalinity of the residual alkali on the surface of the lithium supplement to form a salt (the reaction equation is as shown in Equations (2) and (3) below), thereby preventing the lithium supplement from being corroded and improving the stability of the lithium supplement. Furthermore, since metaphosphoric acid has strong water absorption properties, it can absorb a small amount of moisture present in the lithium supplement (the reaction equation is as shown in Equation (2) below), which is advantageous for preventing moisture from entering the electrolyte and causing the decomposition of the electrolyte. In addition, since lithium phosphite is coated with a coating layer, it is advantageous for preventing phosphite ions from oxidizing into phosphate ions. Furthermore, because the material of the coating layer possesses relatively strong stability and good conductivity, it improves the stability of the lithium supplement while simultaneously enhancing its conductivity.

[0064] Formula (1): Li2HPO3→2Li+2HPO3

[0065] Equation (2): HPO3+H2O→H3PO4

[0066] Equation (3): Li2O + 2H3PO4 → 2LiH2PO4 + H2O

[0067] In some embodiments, the thickness of the aforementioned coating layer may be 0.6 μm to 2 μm. Preferably, the thickness of the coating layer may be 1 μm to 2 μm. For example, the thickness of the coating layer may be 0.63 μm, 0.67 μm, 1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or 2 μm.

[0068] In this embodiment, by controlling the thickness of the coating layer to within the above range, the coating layer is advantageous for more completely coating the lithium phosphite and reducing the leakage of metaphosphoric acid generated by the lithium extraction of lithium phosphite, while at the same time avoiding adverse effects on the lithium ion conductivity of the lithium phosphite by the coating layer.

[0069] In some embodiments, the material of the coating layer is iron boride.

[0070] In some embodiments, the coverage rate of the coating layer is 93% or higher. The coverage rate refers to the percentage of the area where the coating layer covers the surface of lithium phosphate relative to the total surface area of ​​lithium phosphate. Preferably, the coverage rate of the coating layer is 93% to 99%. More preferably, the coverage rate of the coating layer is 94% to 99%. For example, the coverage rate of the coating layer may be 95%, 96%, 97%, 98%, 99%, or 100%, etc. Such a coating layer can completely cover the lithium phosphate, thereby reducing leakage of metaphosphoric acid generated by lithium extraction from the lithium phosphate and reducing contact between the lithium phosphate and the external environment, which is advantageous for improving the lithium replenishment effect.

[0071] In some embodiments, the surface of the lithium phosphate is relatively smooth, which is advantageous for the coating layer to more completely coat the lithium phosphate.

[0072] In some embodiments, the lithium supplement has a quasi-spherical shape, and the sphericity of the lithium supplement is greater than 0.8. For example, the sphericity of the lithium supplement may be 0.81, 0.82, 0.83, 0.84, 0.85, 0.9, 0.92, 0.94, 0.95, or 0.99.

[0073] In some embodiments, the sphericity of the lithium supplement is 0.81 to 0.87. For example, the sphericity of the semi-spherical may be 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, or 0.87, etc.

[0074] In some embodiments, the span value of the lithium supplement particle size (i.e., the value of (D90 particle size - D10 particle size) / D50 particle size) is 0.7 to 4, and the particle size distribution of the lithium supplement is concentrated, which is advantageous for reducing the particle size of the lithium supplement when applied to the positive electrode plate, thereby improving the flatness of the positive electrode plate.

[0075] In some embodiments, the particle size distribution of the lithium supplement is such that the D50 particle size is 0.3μm to 3.8μm, the D10 particle size is 0.1μm to 1.9μm, and the D90 particle size is 1.3μm to 6.4μm. Here, the D50 particle size, D10 particle size, and D90 particle size were measured using a laser particle size distribution analyzer, where the D50 particle size refers to the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 50%, the D10 particle size refers to the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 10%, and the D90 particle size refers to the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 90%.

[0076] For example, the D50 particle size may be 0.3μm, 0.5μm, 0.7μm, 0.8μm, 1.0μm, 1.5μm, 1.7μm, 1.9μm, 2.0μm, 2.2μm, 2.4μm, 2.5μm, 2.7μm, 2.9μm, 3.0μm, 3.1μm, 3.5μm, or 3.9μm, etc.; the D10 particle size may be 0.1μm, 0.2μm, 0.3μm, 0.5μm, 0.8μm, 0.9μm, 1.0μm, 1.3μm, 1.6μm, 1.7μm, or 1.9μm, etc.; The D90 particle size may be 1.3μm, 1.4μm, 1.5μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.5μm, 2.9μm, 3.0μm, 3.2μm, 3.5μm, 3.6μm, 3.8μm, 4.0μm, 4.2μm, 4.8μm, 4.9μm, 5.0μm, 5.2μm, 5.5μm, 5.8μm, 6.0μm, 6.3μm, or 6.4μm, etc.

[0077] Since the lithium supplement has D50 particle sizes of 0.3μm to 3.8μm, D10 particle sizes of 0.1μm to 1.9μm, and D90 particle sizes of 1.3μm to 6.4μm, the lithium supplement has a concentrated particle size distribution and small particle size, which is advantageous for effectively reducing particle texture during the coating process when applied to the positive electrode plate, thereby improving the flatness of the positive electrode plate.

[0078] In some embodiments, the tap density of the lithium supplement is 1.43 g / mL to 1.59 g / mL; and / or the compaction density of the lithium supplement is 2.48 g / mL to 2.76 g / mL; and / or the specific surface area of ​​the lithium supplement is 3.47 m² 2 / g~4.79 m 2 / g is.

[0079] For example, the tap density of the lithium supplement may be 1.43 g / mL, 1.45 g / mL, 1.46 g / mL, 1.48 g / mL, 1.5 g / mL, 1.52 g / mL, 1.53 g / mL, 1.55 g / mL, 1.56 g / mL, 1.57 g / mL, or 1.59 g / mL, etc.

[0080] The compaction density of the lithium supplement may be 2.48 g / mL, 2.50 g / mL, 2.52 g / mL, 2.55 g / mL, 2.58 g / mL, 2.60 g / mL, 2.62 g / mL, 2.64 g / mL, 2.65 g / mL, 2.67 g / mL, 2.68 g / mL, 2.70 g / mL, 2.71 g / mL, 2.73 g / mL, 2.74 g / mL, 2.75 g / mL, or 2.76 g / mL, etc.

[0081] The specific surface area of ​​the lithium supplement is 3.47 m² 2 / g, 3.48m 2 / g, 3.49m 2 / g, 3.50 m 2 / g, 3.52 m 2 / g, 3.54 m 2 / g, 3.57 m 2 / g, 3.58 m 2 / g, 3.59 m 2 / g, 3.60 m2 / g, 3.63 m 2 / g, 3.65 m 2 / g, 3.68 m 2 / g, 3.67 m 2 / g, 3.68 m 2 / g, 3.71 m 2 / g, 3.72 m 2 / g, 3.73 m 2 / g, 3.75 m 2 / g, 3.78 m 2 / g, 3.82 m 2 / g, 3.85 m 2 / g, 3.88 m 2 / g, 3.89 m 2 / g, 3.92 m 2 / g, 3.94 m 2 / g, 3.96 m 2 / g, 3.97 m 2 / g, 4.01 m 2 / g, 4.02 m 2 / g, 4.05 m 2 / g, 4.08 m 2 / g, 4.09 m 2 / g, 4.13 m 2 / g, 4.15 m 2 / g, 4.18 m 2 / g, 4.19 m 2 / g, 4.25 m 2 / g, 4.26 m 2 / g, 4.28 m 2 / g, 4.30 m 2 / g, 4.33 m 2 / g, 4.35 m 2 / g, 4.38 m 2 / g, 4.40 m 2 / g, 4.45 m 2 / g, 4.49 m 2 / g, 4.52 m 2 / g, 4.57 m 2 / g, 4.59 m 2 / g, 4.63 m 2 / g, 4.65 m 2 / g, 4.69 m 2 / g, 4.72 m 2 / g, 4.75 m 2 / g, 4.78 m 2 / g or 4.79 m 2 / g can be etc.

[0082] By controlling the tap density and compaction density of the lithium supplement to within the aforementioned tap density and compaction density, the energy density of the lithium supplement can be effectively improved; and by controlling the specific surface area of ​​the lithium supplement to within the above range, when the lithium supplement is applied to a secondary battery, it can have an appropriate contact area with the electrolyte, etc., thereby fully exhibiting the lithium supplement effect.

[0083] In some embodiments, the mass ratio of iron element in the lithium supplement is 3.47% to 5.49%, the mass ratio of boron element is 0.46% to 1.26%, the mass ratio of lithium element in the lithium supplement is 12.78% to 13.99%, and the mass ratio of phosphorus element in the lithium supplement is 30.98% to 31.98%. For example, the mass percentage of iron elements in the lithium supplement is 3.47%, 3.49%, 3.52%, 3.54%, 3.55%, 3.62%, 3.67%, 3.70%, 3.72%, 3.75%, 3.79%, 3.81%, 3.83%, 3.85%, 3.89%, 3.92%, 3.94%, 3.96%, 3.98%, 4.0%, 4.05%, 4.08%, 4.1%, 4.15%, 4.18%, 4.2%, 4.25%, 4.3%, 4.36%, 4.38%, 4.4%, 4.42%, 4.45%, 4.47%, 4.49%, 4.5%, 4.53%, 4.55%, 4.58%, 4.59%, 4.6%, 4.63%, 4.67%, 4.69%, 4.71%, 4.73%, 4.75%, 4.78%, 4.8%, 4.83%, 4.85%, 4.89%, 4.91%, 4.95%, 4.97%, 4.99%, 5.02%, 5.06%, 5.08%, 5.09%, 5.12%, 5.14%, 5.18%, 5.19%, 5.23%, 5.25%, 5.28%, 5.29%, 5.33%, It may be 5.36%, 5.38%, 5.39%, 5.4%, 5.42%, 5.43%, 5.45%, 5.47%, or 5.49%, etc.; The mass ratio of boron element may be 0.46%, 0.5%, 0.51%, 0.53%, 0.55%, 0.58%, 0.6%, 0.61%, 0.63%, 0.64%, 0.67%, 0.69%, 0.7%, 0.75%, 0.79%, 0.82%, 0.86%, 0.89%, 0.93%, 0.95%, 0.96%, 0.98%, 1%, 1.1%, 1.15%, 1.16%, 1.19%, 1.22%, 1.25%, or 1.26%, etc.

[0084] The coating layer of these lithium supplements has relatively high conductivity, which is advantageous for improving the conductivity of the lithium supplements.

[0085] In some embodiments, the moisture content in the lithium supplement is less than 205 ppm; and / or the chloride ion content in the lithium supplement is less than 90 ppm; and / or the metaborate ion content in the lithium supplement is less than 70 ppm; and / or the residual amount of carbonate ions in the lithium supplement is less than 680 ppm. Additionally, the moisture content in the lithium supplement is 101 ppm to 204 ppm; the chloride ion content in the lithium supplement is 17 ppm to 87 ppm; the metaborate ion content in the lithium supplement is 35 ppm to 69 ppm; and the residual amount of carbonate ions in the lithium supplement is 512 ppm to 678 ppm. For example, the moisture content in the lithium supplement may be 200 ppm, 190 ppm, 189 ppm, 185 ppm, 182 ppm, 180 ppm, 175 ppm, 172 ppm, 170 ppm, 168 ppm, 165 ppm, 160 ppm, 158 ppm, 155 ppm, 152 ppm, 149 ppm, 147 ppm, 145 ppm, 140 ppm, 135 ppm, 130 ppm, 128 ppm, 125 ppm, 123 ppm, 120 ppm, 115 ppm, 110 ppm, 108 ppm, 105 ppm, or 101 ppm, etc.; The chloride ion content in the lithium supplement may be 80 ppm, 78 ppm, 75 ppm, 70 ppm, 60 ppm, 56 ppm, 52 ppm, 50 ppm, 45 ppm, 42 ppm, 40 ppm, 35 ppm, or 30 ppm, etc.; the metaborate ion content in the lithium supplement may be 69 ppm, 65 ppm, 60 ppm, 50 ppm, 40 ppm, 32 ppm, 30 ppm, 29 ppm, 25 ppm, or 20 ppm, etc.; The residual amount of carbonate ions in the lithium supplement may be 678 ppm, 675 ppm, 670 ppm, 663 ppm, 660 ppm, 658 ppm, 655 ppm, 650 ppm, 648 ppm, 643 ppm, 641 ppm, 639 ppm, 620 ppm, 610 ppm, 590 ppm, 569 ppm, 557 ppm, 520 ppm, 503 ppm, or 512 ppm, etc.

[0086] By controlling the content of the aforementioned moisture, chloride ions, metaborate ions, and / or carbonate ions to within their respective ranges, the effect of moisture, chloride ions, metaborate ions, and / or carbonate ions on the lithium supplement can be reduced, thereby improving the stability of the lithium supplement and reducing the generation of byproducts, which is advantageous for enhancing the lithium supplementation effect, and further improving the capacity, safety, and stability of a secondary battery containing such a lithium supplement.

[0087] In some embodiments, the powder resistivity of the lithium supplement is less than 1.0 Ω·m. Additionally, the powder resistivity of the lithium supplement may be 0.3 Ω·m to 0.9 Ω·m. For example, the powder resistivity of the lithium supplement may be 0.9 Ω·m, 0.7 Ω·m, 0.67 Ω·m, 0.5 Ω·m, 0.4 Ω·m, or 0.3 Ω·m.

[0088] These lithium supplements have excellent conductivity, so when applied to the positive electrode plate, they can act as both a lithium supplement and a conductive agent, thereby improving the performance of the secondary battery.

[0089] In some embodiments, under conditions of 25°C and 8% humidity, the lithium supplement has a first charge specific capacity at a 0.05C ratio of 512mAh / g to 518mAh / g, preferably 514mAh / g to 518mAh / g; and under conditions of 25°C and 8% humidity, the lithium supplement has a first discharge specific capacity at a 0.05C ratio of 86.1mAh / g to 89.5mAh / g.

[0090] For example, under conditions of 25°C and 8% humidity, the lithium supplement may have a first charge capacity of 513 mAh / g, 514 mAh / g, 516 mAh / g, or 518 mAh / g, etc. at a 0.05 C multiplier, and the lithium supplement may have a first discharge capacity of 87 mAh / g, 89 mAh / g, or 89.5 mAh / g, etc. at a 0.05 C multiplier.

[0091] These lithium supplements have relatively high initial charge and initial discharge capacities and possess a distinct lithium replenishment effect.

[0092] In some embodiments, the lithium supplement has excellent stability when applied to the positive electrode plate of a secondary battery. Specifically, after being left in air at a temperature of 25°C and a humidity of 70% for 1 hour, the lithium supplement has a first charge specific capacity at a 0.05C ratio of 507 mAh / g to 510.1 mAh / g, preferably 509 mAh / g to 510.1 mAh / g; and a first discharge specific capacity of 82.6 mAh / g to 86.7 mAh / g.

[0093] After being left in air at a temperature of 25℃ and a humidity of 70% for 4 hours, the lithium supplement has a first charge capacity of 504mAh / g to 505mAh / g at a 0.05C ratio and a first discharge capacity of 80mAh / g to 83.2mAh / g.

[0094] After being left in air at a temperature of 25℃ and a humidity of 70% for 24 hours, the lithium supplement has a first charge capacity of 500mAh / g to 502mAh / g at a 0.05C ratio and a first discharge capacity of 77mAh / g to 81.5mAh / g.

[0095] After being left in air at a temperature of 25℃ and a humidity of 70% for 48 hours, the lithium supplement has a first charge capacity of 488mAh / g to 501.2mAh / g at a 0.05C ratio and a first discharge capacity of 75mAh / g to 81.3mAh / g.

[0096] For example, after being left in air at a temperature of 25°C and a humidity of 70% for 1 hour, the lithium supplement may have a first charge capacity at a 0.05C ratio of 508mAh / g, 509mAh / g, or 510.1mAh / g, etc.; and after being left in air at a temperature of 25°C and a humidity of 70% for 1 hour, the lithium supplement may have a first discharge capacity at a 0.05C ratio of 83mAh / g, 84mAh / g, 85mAh / g, 86mAh / g, etc.

[0097] For example, after being left in air at a temperature of 25°C and a humidity of 70% for 4 hours, the lithium supplement may have a first charge specific capacity at a 0.05C ratio of 504.5mAh / g, 504.8mAh / g, etc.; and after being left in air at a temperature of 25°C and a humidity of 70% for 4 hours, the lithium supplement may have a first discharge specific capacity at a 0.05C ratio of 81mAh / g, 82mAh / g, 82.5mAh / g, or 83.2mAh / g, etc.

[0098] For example, after being left in air at a temperature of 25°C and a humidity of 70% for 24 hours, the lithium supplement may have a first charge specific capacity at a 0.05C ratio of 500.5mAh / g, 501mAh / g, 501.5mAh / g, or 502mAh / g, etc.; and after being left in air at a temperature of 25°C and a humidity of 70% for 24 hours, the lithium supplement may have a first discharge specific capacity at a 0.05C ratio of 77.5mAh / g, 79mAh / g, or 81mAh / g, etc.

[0099] For example, after being left in air at a temperature of 25°C and a humidity of 70% for 48 hours, the lithium supplement may have a first charge specific capacity at a 0.05C ratio of 490mAh / g, 491mAh / g, 492mAh / g, 493mAh / g, 494mAh / g, 495mAh / g, 498mAh / g, or 501.2mAh / g, etc.; and after being left in air at a temperature of 25°C and a humidity of 70% for 48 hours, the lithium supplement may have a first discharge specific capacity at a 0.05C ratio of 75.1mAh / g, 76mAh / g, 77mAh / g, 79mAh / g, 80.7mAh / g, or 81mAh / g, etc.

[0100] In some embodiments, the first charge specific capacity and first discharge specific capacity of the lithium supplement are obtained by manufacturing a positive electrode plate containing the lithium supplement and then testing a button battery assembled with the positive electrode plate.

[0101] In some embodiments, the positive electrode plate comprises a positive active material, a binder, and a conductive agent. The positive active material is the lithium supplement mentioned above. The binder is preferably PVDF (polyvinylidene fluoride), but other binder materials suitable for the positive electrode plate may also be used. The conductive agent is preferably a carbon conductive material such as, for example, conductive carbon black (SP). The positive active material, binder, and conductive agent are mixed in an appropriate mass ratio, and an aluminum sheet is used as a current collector to manufacture the positive electrode plate, and the mass ratio of the positive active material, binder, and conductive agent may be 85:8:7.

[0102] In a second aspect, as illustrated in FIG. 1, the method for manufacturing a lithium supplement provided in an embodiment of the present application comprises the following steps.

[0103] Step S11: Prepare a first slurry containing lithium phosphite.

[0104] S12 Step: The first slurry is mixed with sodium borohydride and ferrous chloride, and subjected to the first reaction treatment to obtain a crude product.

[0105] Step S13: The crude product is filtered, washed, and dried to obtain the lithium supplement.

[0106] Here, the lithium supplement comprises lithium phosphate (Li2HPO3) and a coating layer covering the surface of the lithium phosphate, and the material of the coating layer comprises iron boride.

[0107] The method for manufacturing a lithium supplement provided in the embodiments of the present application can be used to manufacture a lithium supplement as described above.

[0108] In some embodiments, lithium phosphite may be obtained through commercial channels or in-house production, and is not particularly limited thereto.

[0109] After preparing the first slurry, the first slurry is mixed with sodium borohydride and ferrous chloride, and the sodium borohydride and ferrous chloride are reacted to form iron boride, and the specific reaction formula is as shown in the following formula (4), thereby obtaining a coating layer that covers the surface of lithium phosphite, and the material of this coating layer is iron boride. The above manufacturing method is simple and the raw materials are easy to obtain, and the above lithium supplement has a lower raw material cost and lower manufacturing cost compared to the lithium supplement material with a high lithium capacity of the related technology.

[0110] Equation (4): NaBH4+FeCl2→ FeB+NaCl+H2+HCl

[0111] In some embodiments, the step S11 of preparing a first slurry containing lithium phosphite is,

[0112] Step of obtaining a first solution of phosphoric acid -the solvent of the first solution comprises at least one of methanol, ethanol, glycerol, propanol, and propylene glycol-;

[0113] A step of adding a lithium salt to a first solution of phosphoric acid and obtaining a first reaction slurry through a second reaction treatment;

[0114] The method includes the step of grinding the first reaction slurry until the lithium phosphate in the first reaction slurry reaches a preset particle size to obtain the first slurry.

[0115] A lithium salt is added to a first solution of phosphoric acid, and through a second reaction treatment, a first reaction slurry is obtained by utilizing the characteristic that lithium phosphate has low solubility in the solvent to cause the lithium phosphate to crystallize and precipitate from the first solution, and then the first reaction slurry is ground to obtain a first slurry in which the lithium phosphate in the first reaction slurry has a predetermined particle size. Here, since using phosphoric acid as a raw material is advantageous for maintaining the first slurry as acidic, the first reaction treatment is performed under acidic conditions when the subsequent first reaction treatment is carried out, which is advantageous for the formation of iron boride, and the iron boride is chemically coated on the surface of the lithium phosphate to form a coating layer.

[0116] In some embodiments, the ratio of the amount of phosphoric acid, sodium borohydride, and ferrous chloride is 1:(0.05~0.1):(0.025~0.05). By adjusting the ratio of the amount of phosphoric acid, sodium borohydride, and ferrous chloride to within the above range, the first reaction treatment is performed under acidic conditions and an excess amount of sodium borohydride, which is advantageous for the reaction between sodium borohydride and ferrous chloride, and a coating layer of appropriate thickness is formed on the surface of lithium phosphorate.

[0117] For example, the ratio of the amount of substance of phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.05:0.025, 1:0.07:0.025, 1:0.08:0.025, 1:0.08:0.025, 1:0.09:0.025, 1:0.1:0.025, 1:0.05:0.03, 1:0.05:0.04, 1:0.05:0.05, 1:0.06:0.03, 1:0.07:0.03, 1:0.08:0.03, 1:0.1:0.03, 1:0.06:0.04, 1:0.06:0.05, 1:0.07:0.04, It may be 1:0.07:0.05, 1:0.08:0.04, 1:0.08:0.05, 1:0.09:0.04, 1:0.09:0.05, 1:0.1:0.04 or 1:0.1:0.05, etc.

[0118] In some embodiments, the temperature of the second reaction treatment is 35°C to 55°C, and the time of the second reaction treatment is 0.5h to 1h. By controlling the temperature and time of the second reaction treatment within the above ranges, the reaction in which the lithium salt reacts with phosphoric acid to produce lithium phosphorate is sufficiently carried out.

[0119] For example, the temperature of the second reaction treatment may be 35℃, 38℃, 39℃, 40℃, 42℃, 45℃, 46℃, 48℃, 50℃, 52℃, 53℃, or 55℃, etc., and the time of the second reaction treatment may be 0.5h, 0.7h, 0.8h, 0.9h, or 1h.

[0120] In some embodiments, the lithium salt comprises at least one of lithium carbonate, lithium sulfite, and lithium bicarbonate. Since the above-described lithium salt reacts with phosphoric acid to produce lithium phosphate and gas, the introduction of impurities is reduced while manufacturing lithium phosphate.

[0121] Here, lithium carbonate and lithium sulfite can be added in solid form, and lithium hydrogen carbonate can be added in solution form.

[0122] In some embodiments, the preset particle size is 0.3 μm to 3 μm. The preset particle size may be the D50 particle size of lithium phosphate, and setting the range to 0.3 μm to 3 μm is advantageous for obtaining lithium phosphate with a concentrated particle size distribution and small particle size, which is advantageous for obtaining a lithium supplement with a coated layer and a concentrated particle size distribution and small particle size.

[0123] For example, the preset particle size may be 0.5μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.1μm, 2.2μm, 2.5μm, 2.8μm, etc.

[0124] In some embodiments, the lithium salt is selected from lithium carbonate. When the lithium salt is selected from lithium carbonate, the gas produced by the reaction of lithium carbonate with phosphoric acid is carbon dioxide, and the production of irritating gas is reduced compared to when the gas is sulfur dioxide.

[0125] In some embodiments, by setting the ratio of the amount of lithium element to phosphoric acid in the lithium salt to (1.8 to 1.9):1, an appropriate excess amount of phosphoric acid is secured to maintain acidic conditions, and the first reaction treatment is performed smoothly under acidic conditions to obtain iron boride.

[0126] For example, the ratio of the amount of lithium element to phosphoric acid in the lithium salt may be 1.8:1, 1.82:1, 1.84:1, 1.86:1, 1.88:1, or 1.9:1.

[0127] When the lithium salt is selected from at least one of lithium carbonate or lithium sulfite, the ratio of the amount of lithium salt to phosphoric acid is (0.9 to 0.95):1.

[0128] In some embodiments, when the solvent of the first solution is selected from methanol, the first solution of phosphoric acid may be a methanol solution of phosphoric acid.

[0129] In some embodiments, the step of obtaining a first reaction slurry is,

[0130] A lithium salt may be added to a first solution of phosphoric acid under stirring, and the reaction may be completed by reacting at a temperature of 35°C to 55°C for 0.5h to 1h until no bubbles are generated, thereby obtaining a first reaction slurry. The reaction equation is as shown in the following equation (5).

[0131] Equation (5): H3PO3+Li2CO3→Li2HPO3+H2O+CO2↑

[0132] In some embodiments, the mass fraction of phosphoric acid in the first solution of phosphoric acid may be 5% to 10%. For example, the concentration of the first solution of phosphoric acid may be 5%, 6%, 7%, 8%, 9%, or 10%, etc.

[0133] In some embodiments, the first reaction slurry can be ground by ball milling to obtain a first slurry containing lithium phosphite having a preset particle size.

[0134] In some embodiments, when grinding the first reaction slurry by ball milling, ceramic balls may be added for grinding. The diameter of the ceramic balls may be 0.3 mm to 0.8 mm.

[0135] In some embodiments, step S12, which involves mixing the first slurry with sodium borohydride and ferrous chloride and undergoing a first reaction treatment to obtain a crude product,

[0136] The method includes the step of mixing a solution containing sodium borohydride, a solution containing ferrous chloride, and a first slurry, and then obtaining a crude product after a first predetermined time at a first reaction temperature.

[0137] In these embodiments, by mixing a solution containing sodium borohydride, a solution containing ferrous chloride, and a first slurry, the product generated by the reaction of sodium borohydride and ferrous chloride is made to uniformly coat lithium phosphite, which is advantageous for improving the uniformity of the coating layer.

[0138] In some embodiments, the mixing may be performed under first stirring, and the speed of the first stirring may be 100 r / min to 300 r / min, thereby improving the degree of uniformity of mixing of the first slurry, the solution containing sodium borohydride, and the solution containing ferrous chloride.

[0139] In some embodiments, the temperature of the mixture may be 25°C to 45°C, for example, 26°C, 30°C, 35°C, 40°C, etc.

[0140] In some embodiments, the mixing time is 60 min to 120 min, thereby enabling sufficient mixing of the first slurry, the solution containing sodium borohydride, and the solution containing ferrous chloride.

[0141] In some embodiments, mixing a solution containing sodium borohydride, a solution containing ferrous chloride, and a first slurry may involve first mixing the solution containing sodium borohydride and the solution containing ferrous chloride, and then transferring them together to the first slurry to mix with the first slurry; or the solution containing sodium borohydride and the solution containing ferrous chloride may be transferred to the first slurry and mixed together with the first slurry. For reference, when the solution containing sodium borohydride and the solution containing ferrous chloride are first mixed and then transferred together to the first slurry to mix with the first slurry, the mixing time, the temperature at the time of mixing, and the first stirring speed at the time of mixing described above are the mixing time and the stirring speed at the time of mixing when the solution containing sodium borohydride and the solution containing ferrous chloride are mixed and then mixed with the first slurry.

[0142] In some embodiments, the mass fraction of sodium borohydride in the solution containing sodium borohydride may be 3% to 8%, and the mass fraction of ferrous chloride in the solution containing ferrous chloride may be 5% to 10%. For example, the mass fraction of sodium borohydride in the solution containing sodium borohydride may be 3%, 4%, 5%, 6%, 7%, or 8%, etc., and the mass fraction of ferrous chloride in the solution containing ferrous chloride may be 5%, 6%, 7%, 8%, 9%, or 10%, etc.

[0143] In some embodiments, the first reaction temperature is 25°C to 45°C, and may be, for example, 26°C, 30°C, 35°C, 40°C, etc.

[0144] In this embodiment, by controlling the first reaction temperature to 25°C to 45°C, sufficient iron boride is produced, which is advantageous for forming a coating layer with an appropriate thickness and coverage rate on the surface of lithium phosphite.

[0145] In some embodiments, the temperature at the time of mixing may be the same as the first reaction temperature.

[0146] In some embodiments, the first preset time is 30 min to 60 min, and may be, for example, 35 min, 40 min, 45 min, 50 min, 55 min, etc., which is advantageous for sufficiently generating iron boride to improve the coating rate of the coating layer on the surface of lithium phosphite.

[0147] In addition, the solvent used in the solution containing sodium borohydride and the solvent used in the solution containing ferrous chloride are each independently at least one selected from the group consisting of methanol, ethanol, glycerol, propanol, and propylene glycol. That is, they may be the same as the solvent used in the first solution.

[0148] For example, if the first solution of phosphoric acid is a methanol solution of phosphoric acid, the solution containing sodium borohydride may be a methanol solution of sodium borohydride, and the solution containing ferrous chloride may be a methanol solution of ferrous chloride.

[0149] In some embodiments, a solution containing sodium borohydride and a solution containing ferrous chloride are mixed with a first slurry, and then a second stirring is performed for a first preset time at a first reaction temperature, which is advantageous for a sufficient reaction between sodium borohydride and ferrous chloride.

[0150] In some embodiments, the speed of the second stirring may be 100 r / min to 300 r / min.

[0151] In some embodiments, the speed of the first stirring is the same as the speed of the second stirring.

[0152] In some embodiments, in step S13, the lithium phosphite with the coating layer formed can be washed using the same solvent as the first solution, and the mother liquor after washing and the mother liquor collected after filtration can be reused by distilling and recovering them.

[0153] For example, if the solvent used in the first solution is methanol, the lithium phosphate with the coating layer formed can be washed using methanol, which is advantageous for reducing residual moisture within the lithium phosphate with the coating layer formed during the washing process, thereby minimizing the ingress of moisture into the lithium supplement.

[0154] In some embodiments, the drying may be performed under vacuum. That is, the drying treatment may be vacuum drying. The vacuum level of the drying treatment may be -0.09 MPa to -0.07 MPa, and the temperature of the drying treatment may be 80°C to 100°C, which is advantageous for more effective moisture removal and reduces moisture residue. For example, the vacuum level of the drying treatment may be -0.09 MPa, -0.08 MPa, or -0.07 MPa, etc., and the temperature of the drying treatment may be 80°C, 85°C, 90°C, 95°C, or 100°C, etc.

[0155] In some embodiments, when the drying treatment is performed under vacuum, the gas in the vacuum chamber may be replaced using a protective gas until the oxygen content in the vacuum chamber becomes less than 500 ppm, and then vacuum evacuation may be performed until the vacuum level becomes -0.09 MPa to -0.07 MPa. This is advantageous for further reducing the oxygen content during drying, thereby further improving the material stability of the lithium supplement and reducing the generation of by-products such as lithium phosphate.

[0156] For example, the above-mentioned protective gas may include nitrogen, argon and / or helium, etc.

[0157] In some embodiments, during the drying process, if the moisture content is less than 0.1% based on mass fraction, the drying is terminated, which can reduce the moisture in the lithium supplement and improve the stability of the lithium supplement.

[0158] In some embodiments, the manufacturing method may further include steps such as sieving, electromagnetic iron removal, and packaging of the material after drying, thereby obtaining a lithium supplement that meets requirements such as particle size and impurity content, and realizing effective lithium supplementation.

[0159] In a third aspect, the positive electrode plate provided in an embodiment of the present application comprises a current collector and a positive material disposed on at least one side along the self-thickness direction of the current collector, wherein the positive material comprises a lithium supplement according to the first aspect.

[0160] The positive electrode plate provided in the embodiment of the present application includes the aforementioned lithium supplement, and the lithium supplement adopts a coating layer having iron boride to coat the surface of lithium phosphite, thereby having improved safety, stability, conductivity, and lithium supplementation effects, and is inexpensive, so the safety, stability, conductivity, and lithium supplementation effects of the positive electrode plate are improved, the cost of the positive electrode plate is reduced, and it is advantageous to improve the capacity of the battery when applied to a battery.

[0161] In a fourth aspect, the secondary battery provided in the embodiment of the present application comprises a positive electrode plate, a negative electrode plate, and a separator, wherein

[0162] Here, the positive electrode plate is a positive electrode plate according to the third aspect.

[0163] The secondary battery provided in the embodiment of the present application includes the aforementioned positive electrode plate, thereby having improved safety, stability, and capacity, and reducing manufacturing costs.

[0164] In a fifth aspect, the electric device provided in an embodiment of the present application comprises a plurality of batteries connected in series and / or parallel, wherein at least one battery is a secondary battery according to the fourth aspect.

[0165] In the electric device provided in the embodiment of the present application, the secondary battery has excellent stability and safety performance, is inexpensive, allows for effective lithium replenishment, and has a relatively high capacity; thus, the electric device has excellent stability and safety performance and reduced manufacturing costs.

[0166] The electric devices provided in the embodiments of the present application may be, but are not limited to, mobile phones, tablets, laptop computers, electric toys, electric tools, electric cart vehicles, electric automobiles, ships, spacecraft, etc. Here, electric toys may include stationary or mobile electric toys, and may include, for example, game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, and spacecraft may include airplanes, rockets, space shuttles, spacecraft, etc.

[0167] Some specific embodiments are listed below. It should be noted that the embodiments described below are illustrative and used merely to explain the present application, and should not be construed as limiting the application. Where specific techniques or conditions are not specified in the embodiments, the invention shall be performed in accordance with the techniques or conditions described in literature of the art to which the invention pertains or in product descriptions. Unless the manufacturer is specified, all reagents or equipment used are ordinary products available on the market.

[0168] [Example 1]

[0169] The method for manufacturing the lithium supplement provided in Example 1 is as follows.

[0170] Phosphorous acid is added to methanol to obtain a transparent methanol solution with a phosphorous acid concentration (based on mass fraction) of 8% (i.e., the first solution), then lithium carbonate (lithium salt) is added under stirring conditions, and the reaction is carried out at 45°C for 1 hour until no bubbles are generated, with a material ratio of lithium salt to phosphorous acid being 0.93:1, to obtain a first reaction slurry, and the first reaction slurry is placed in a ball mill and ground, wherein ceramic balls with a diameter of 0.6 mm are introduced and ground until the particle size of lithium phosphate becomes 2.12 μm (pre-set particle size) to obtain a first slurry; A solution containing sodium borohydride and a solution containing ferrous chloride are prepared using methanol as a solvent, the mass fraction of sodium borohydride in the solution containing sodium borohydride is 6%, and the mass fraction of ferrous chloride in the solution containing ferrous chloride is 8%, the solution containing sodium borohydride and the solution containing ferrous chloride are transferred via a peristaltic pump and mixed with a first slurry, the mass ratio of the mixed phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.08:0.038, the mixing is completed with a stirring speed of 200 r / min, a mixing time of 90 min, and a mixing temperature of 35℃, and then the reaction is continued at a speed of 200 r / min at 35℃ for 50 min to obtain a crude product; After filtering, washing, and drying the crude product, the obtained material is sieved, electromagnetically deiring, and vacuum-packaged to obtain iron-boride-coated lithium phosphate (lithium supplement). Here, washing is performed with methanol, and the methanol recovered by distilling the methanol after washing and the filtered mother liquor is recycled. When drying the washed material, nitrogen is first filled into a vacuum drying oven so that the oxygen content inside the oven is less than 500 ppm, and then vacuum evacuation is performed. The drying temperature is set to 90°C and the vacuum level to -0.085 MPa, so that the moisture content (based on mass fraction) of the material is 0.After drying until the content is less than 1%, the material is cooled until the temperature reaches 40℃, then removed and subjected to sieving, electromagnetic iron removal, and vacuum packaging.

[0171] The final test data for the lithium supplement is shown in Table 1.

[0172] characteristic Li P Fe B BET Tap density data 13.42% 31.21% 4.59% 0.92% 3.73m 2 / g 1.55g / mL Compaction density moisture Na K Ca Mg Ni 2.73g / mL 125ppm 65.3ppm 12.4ppm 16.8ppm 19.4ppm 2.5ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.2ppm 0.1ppm 0.3ppm 17ppm 37ppm 0.5Ω·m 569ppm Spherical shape 0.87

[0173] [Example 2]

[0174] The method for manufacturing the lithium supplement provided in Example 2 is as follows.

[0175] Phosphorous acid is added to methanol to obtain a transparent methanol solution with a phosphorous acid concentration (based on mass fraction) of 5% (i.e., the first solution), then lithium carbonate (lithium salt) is added under stirring conditions, and the reaction is carried out at 35°C for 0.8 hours until no bubbles are generated, with a material ratio of lithium salt to phosphorous acid of 0.90:1, to obtain a first reaction slurry, and the first reaction slurry is placed in a ball mill and ground, wherein ceramic balls with a diameter of 0.3 mm are introduced and ground until the particle size of lithium phosphate becomes 3 μm (pre-set particle size) to obtain a first slurry; A solution containing sodium borohydride and a solution containing ferrous chloride are prepared using methanol as a solvent, the mass fraction of sodium borohydride in the solution containing sodium borohydride is 8%, and the mass fraction of ferrous chloride in the solution containing ferrous chloride is 3%, the solution containing sodium borohydride and the solution containing ferrous chloride are transferred via a peristaltic pump and mixed with a first slurry, the mass ratio of the mixed phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.1:0.025, the mixing is completed with a stirring speed of 300 r / min, a mixing time of 60 min, and a mixing temperature of 25℃, and then the reaction is continued by stirring at a speed of 300 r / min at 25℃ for 30 min to obtain a crude product; After filtering, washing, and drying the crude product, the obtained material is sieved, electromagnetically de-ironed, and vacuum-packed to obtain lithium phosphate coated with iron boride (lithium supplement). Here, washing is performed with methanol, and the methanol recovered by distilling the methanol after washing and the filtered mother liquor is recycled. When drying the washed material, nitrogen is first filled into a vacuum drying oven so that the oxygen content inside the vacuum drying oven is less than 500 ppm, then vacuum evacuated, and the drying temperature is set to 80°C and the vacuum level to -0.07 MPa. The material is dried until the moisture content (based on mass fraction) is less than 0.1%, then cooled until the temperature of the material reaches 40°C, then removed and subjected to sieving, electromagnetic de-ironing, and vacuum-packing.

[0176] The final test data for the lithium supplement is shown in Table 2.

[0177] characteristic Li P Fe B BET Tap density data 12.78% 31.98% 4.01% 1.26% 3.58m 2 / g 1.59g / mL Compaction density moisture Na K Ca Mg Ni 2.71g / mL 168ppm 69.7ppm 10.2ppm 12.9ppm 21.6ppm 2.1ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.5ppm 0.1ppm 0.9ppm 28ppm 68ppm 0.9Ω·m 512ppm Spherical shape 0.82

[0178] [Example 3]

[0179] The method for manufacturing the lithium supplement provided in Example 3 is as follows.

[0180] Phosphorous acid is added to methanol to obtain a transparent methanol solution with a phosphorous acid concentration (based on mass fraction) of 10% (i.e., the first solution), then lithium carbonate (lithium salt) is added under stirring conditions, and the reaction is carried out at 55°C for 0.5 hours until no bubbles are generated, with a material ratio of lithium salt to phosphorous acid being 0.95:1, to obtain a first reaction slurry, and the first reaction slurry is placed in a ball mill and ground, wherein ceramic balls with a diameter of 0.8 mm are introduced and ground until the particle size of lithium phosphate becomes 0.3 μm (pre-set particle size) to obtain a first slurry; A solution containing sodium borohydride and a solution containing ferrous chloride are prepared using methanol as a solvent, the mass fraction of sodium borohydride in the solution containing sodium borohydride is 3%, and the mass fraction of ferrous chloride in the solution containing ferrous chloride is 5%, the solution containing sodium borohydride and the solution containing ferrous chloride are transferred via a peristaltic pump and mixed with a first slurry, the mass ratio of the mixed phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.05:0.05, the mixing is completed with a stirring speed of 100 r / min, a mixing time of 120 min, and a mixing temperature of 45℃, and then the reaction is continued at a speed of 200 r / min at 45℃ for 60 min to obtain a crude product; After filtering, washing, and drying the crude product, the obtained material is sieved, electromagnetically de-ironed, and vacuum-packed to obtain lithium phosphate coated with iron boride (lithium supplement). Washing is performed with methanol, and the methanol recovered by distilling the methanol after washing and the filtered mother liquor is recycled. When drying the washed material, nitrogen is first filled into a vacuum drying oven so that the oxygen content inside the vacuum drying oven is less than 500 ppm, then vacuum evacuated, and the drying temperature is set to 100°C and the vacuum level to -0.09 MPa. The material is dried until the moisture content (based on mass fraction) is less than 0.1%, then cooled until the temperature of the material reaches 40°C, then removed and subjected to sieving, electromagnetic de-ironing, and vacuum-packing.

[0181] The final test data for the lithium supplement is shown in Table 3.

[0182] characteristic Li P Fe B BET Tap density data 13.99% 30.98% 5.03% 0.84% 3.98m 2 / g 1.51g / mL Compaction density moisture Na K Ca Mg Ni 2.61g / mL 111ppm 60.5ppm 14.6ppm 19.5ppm 21.5ppm 2.9ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.2ppm 0.2ppm 0.3ppm 38ppm 58ppm 0.6Ω·m 513ppm Spherical shape 0.84

[0183] [Example 4]

[0184] The method for manufacturing the lithium supplement provided in Example 4 is basically the same as the method for manufacturing the lithium supplement provided in Example 1, and

[0185] The only difference is that the lithium phosphate was ground until its particle size became 0.1 μm (pre-set particle size).

[0186] The final test data for the lithium supplement is shown in Table 4.

[0187] characteristic Li P Fe B BET Tap density data 13.44% 31.17% 4.58% 0.91% 4.79m 2 / g 1.43g / mL Compaction density moisture Na K Ca Mg Ni 2.48g / mL 204ppm 67.9ppm 12.9ppm 17.4ppm 21.1ppm 2.9ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.2ppm 0.2ppm 0.6ppm 87ppm 35ppm 0.67Ω·m 557ppm Spherical shape 0.81

[0188] [Example 5]

[0189] The method for manufacturing the lithium supplement provided in Example 5 is basically the same as the method for manufacturing the lithium supplement provided in Example 1, and

[0190] The only difference is that the lithium phosphate was ground until its particle size became 3.5 μm (pre-set particle size).

[0191] The final test data for the lithium supplement is shown in Table 5.

[0192] characteristic Li P Fe B BET Tap density data 13.41% 31.18% 4.61% 0.91% 3.69m 2 / g 1.58g / mL Compaction density moisture Na K Ca Mg Ni 2.75g / mL 101ppm 63.6ppm 16.3ppm 16.1ppm 19.1ppm 2.1ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.2ppm 0.2ppm 0.4ppm 21ppm 41ppm 0.4Ω·m 523ppm Spherical shape 0.86

[0193] [Example 6]

[0194] The method for manufacturing the lithium supplement provided in Example 6 is basically the same as the method for manufacturing the lithium supplement provided in Example 1, and

[0195] The only difference is that the solution containing sodium borohydride and the solution containing ferrous chloride are transferred via a peristaltic pump and mixed with the first slurry, and the ratio of the amount of the mixed phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.03:0.025.

[0196] The final test data for the lithium supplement is shown in Table 6.

[0197] characteristic Li P Fe B BET Tap density data 13.69% 31.49% 3.87% 0.49% 3.70m 2 / g 1.52g / mL Compaction density moisture Na K Ca Mg Ni 2.70g / mL 169ppm 67.8ppm 18.6ppm 15.2ppm 17.9ppm 2.1ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.1ppm 0.2ppm 0.2ppm 25ppm 41ppm 0.7Ω·m 613ppm Spherical shape 0.85

[0198] [Example 7]

[0199] The method for manufacturing the lithium supplement provided in Example 7 is basically the same as the method for manufacturing the lithium supplement provided in Example 1, and

[0200] The only difference is that the solution containing sodium borohydride and the solution containing ferrous chloride are transferred via a peristaltic pump and mixed with the first slurry, and the ratio of the amount of the mixed phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.1:0.06.

[0201] The final test data for the lithium supplement is shown in Table 7.

[0202] characteristic Li P Fe B BET Tap density data 13.21% 31.11% 5.49% 1.18% 3.47m 2 / g 1.59g / mL Compaction density moisture Na K Ca Mg Ni 2.76g / mL 116ppm 69.6ppm 13.8ppm 15.4ppm 18.4ppm 2.2ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.2ppm 0.2ppm 0.4ppm 27ppm 69ppm 0.3Ω·m 603ppm Spherical shape 0.84

[0203] [Example 8]

[0204] The method for manufacturing the lithium supplement provided in Example 8 is basically the same as the method for manufacturing the lithium supplement provided in Example 1, and

[0205] The only difference is that the solution containing sodium borohydride and the solution containing ferrous chloride are transferred via a peristaltic pump and mixed with the first slurry, and the ratio of the amount of the mixed phosphoric acid, sodium borohydride, and ferrous chloride is 1:0.03:0.06.

[0206] The final test data for the lithium supplement is shown in Table 8.

[0207] characteristic Li P Fe B BET Tap density data 13.61% 31.44% 5.45% 0.46% 3.65m 2 / g 1.51g / mL Compaction density moisture Na K Ca Mg Ni 2.71g / mL 127ppm 67.1ppm 18.1ppm 15.9ppm 17.1ppm 2.2ppm Cr Cu Zn chloride ions metaborate ions Powder resistivity CO3 2- 0.1ppm 0.2ppm 0.4ppm 31ppm 48ppm 0.4Ω·m 678ppm Spherical shape 0.83

[0208] [Comparative Example 1]

[0209] The method for manufacturing the lithium-rich lithium ferrite lithium supplement provided in Comparative Example 1 is as follows.

[0210] Ferric oxide and lithium oxide are mixed so that the ratio of the amount of iron to lithium in the mixture is 1:5.25, then the mixture is calcined at a temperature of 750°C for 6 hours under nitrogen protection, then cooled until the material temperature reaches 135°C and discharged, then nitrogen with 5% humidity is supplied into a grinder under positive pressure, and the mixture is ground using nitrogen with a temperature of 120°C and 2% humidity, with the dew point of nitrogen being -20°C and the particle size being 2.7 μm to obtain a lithium-rich lithium ferrite lithium supplement.

[0211] The final test data for the lithium supplement is shown in Table 9.

[0212] characteristic Li Fe BET Tap density pH Compaction density data 23.14% 35.45% 7.56m 2 / g 1.86g / mL 11.78 3.2g / mL Thickness of the coating layer Coverage rate No covering layer /

[0213] [Comparative Example 2]

[0214] The method for manufacturing the lithium supplement provided in Comparative Example 2 is as follows.

[0215] Phosphorous acid is added to methanol to obtain a transparent methanol solution with a phosphorous acid concentration (based on mass fraction) of 8% (i.e., the first solution), then lithium carbonate (lithium salt) is added under stirring conditions, and the reaction is carried out at 45°C for 1 hour until no bubbles are generated, with a material ratio of lithium salt to phosphorous acid being 0.93:1, to obtain a first reaction slurry, and the first reaction slurry is placed in a ball mill and ground, wherein ceramic balls with a diameter of 0.6 mm are introduced and ground until the particle size of lithium phosphate becomes 2.12 μm (pre-set particle size) to obtain a first slurry; Wash with methanol and dry the washed material. First, fill a vacuum drying oven with nitrogen so that the internal oxygen content is less than 500 ppm, then vacuum evacuate, set the drying temperature to 90°C and the vacuum level to -0.085 MPa, and dry the material until the moisture content (based on mass fraction) is less than 0.1%, then cool the material until the temperature reaches 40°C, then remove it and perform sieving, electromagnetic iron removal, and vacuum packaging to obtain uncoated lithium phosphate (lithium supplement).

[0216] [Test Method and Test Results]

[0217] 1. The lithium supplement provided in Example 1 was morphologically characterized using a scanning electron microscope, and the results are shown in FIG. 2. As can be seen in FIG. 2, the particle size distribution of the lithium supplement is relatively uniform, and the particles have a semi-spherical shape.

[0218] 2. Testing of Chemical and Physicochemical Indicators of Lithium Supplements

[0219] The test results of the chemical component indicators and physicochemical indicators for the lithium supplements provided in Examples 1 to 8 and Comparative Example 1 are shown in Tables 1 to 9, respectively.

[0220] In the chemical composition indicator test, the amount of Fe is measured using potentiometric titration, the phosphorus content is measured using the quinoline phosphate molybdate weighing method, the content of lithium, sodium, potassium, calcium, magnesium, chromium, copper, and zinc is measured using inductively coupled plasma atomic emission spectroscopy, chloride ions are measured using potentiometric titration, metaborate ions are measured using titration, and carbonate ions are measured using potentiometric titration.

[0221] In physicochemical indicator tests, the moisture content in the lithium supplement is measured using the KF (Karl Fischer) method; the specific surface area of ​​the lithium supplement is measured using a BET specific surface area measurement method such as the nitrogen adsorption multi-point BET method; the powder resistivity is measured using a 4-probe method at a pressure of 10 MPa; sphericity has a direct effect on fluidity and stacking performance, and the sphericity of the lithium supplement can be measured using a method that combines microscopic measurement methods and image processing techniques, and after obtaining information on the particle size and shape of each particle by processing and analyzing particle images through image analysis software, and then statistically processing the information on the particle size and shape of each particle, results such as particle size (D50) and particle size distribution, average length-diameter and aspect ratio distribution, average roundness and roundness distribution can be obtained, where the average roundness represents the sphericity of the lithium supplement.

[0222] In addition, the tap density was measured using a tap density meter, and the number of vibrations was set to 5,000.

[0223] The method for measuring compaction density is to use a compaction density meter and measure with a test pressure of 3T and a compression time of 30S.

[0224] As can be seen from Tables 1 to 9, the lithium supplements according to Examples 1 to 8 provided in this application all contain iron and boron elements, and the mass ratio of the iron element can reach 3.47% to 5.49% and the mass ratio of the boron element can reach 0.46% to 1.26%, indicating that the lithium supplements according to Examples 1 to 8 have a coating layer of iron boride material formed on the surface of lithium phosphite.

[0225] 3. A particle size distribution test is performed on the lithium supplements provided in Examples 1 to 8 and Comparative Examples 1 to 2 using a laser particle size analyzer. The particle size distribution curve of Example 1 is shown in FIG. 3, and the particle size distribution results of the lithium supplements of Examples 1 to 8 and Comparative Examples 1 to 2 are shown in Table 10 below.

[0226] The thickness of the coating layer is measured using a transmission electron microscope, and the coverage rate is defined as the percentage of the surface area covered by the coating layer relative to the total surface area of ​​the particle (i.e., lithium phosphate). The amount of the coating layer is measured using diffuse reflection infrared Fourier transform spectroscopy, and the coverage rate can be calculated using the amount of coating and the cross-sectional area of ​​the coating layer (also referred to as the cross-sectional area). The calculation formula is , where n is the coverage ratio, M is the coverage amount, q is the molecular weight of the coverage layer material, and NA is a constant (6.023×10⁻⁶ 23 ), a0 is the cross-sectional area of ​​the coating layer, S w represents the specific surface area of ​​the particle. The thickness and coverage rate of the coating layer of Examples 1 to 8 are shown in Table 10.

[0227]

[0228] In Table 10 above, D50 particle size refers to the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 50%, D10 particle size refers to the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 10%, and D90 particle size refers to the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 90%.

[0229] As can be seen from Table 10 above, compared to the lithium supplements provided in Comparative Examples 1 and 2, the lithium supplements provided in Examples 1 to 8 of the present application have a concentrated particle size distribution and smaller particle size, which is advantageous for effectively preventing particle texture during the coating process of the anode material, thereby improving the flatness of the electrode plate.

[0230] 4. Testing of Electrical Performance Indicators of Lithium Supplements

[0231] (1) The lithium supplements provided in Examples 1 to 8 and Comparative Examples 1 to 2 were each used as the positive active material and mixed with conductive carbon black (SP) and PVDF in a mass ratio of 85:7:8. Then, NMP was added to perform slurry homogenization, and the mixture was coated onto an aluminum foil, dried, and rolled. The compaction density was 2.1 g / mL, the electrolyte was 1 mol / L lithium hexafluorophosphate, the organic solvents of the electrolyte were ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and the negative electrode was a lithium sheet. A button battery was assembled and tested.

[0232] Button batteries manufactured using the lithium supplements provided in Examples 1 to 8 were tested for the first charge specific capacity and first discharge specific capacity at a 0.05C magnification under conditions of 25°C, 8% humidity, and a voltage of 2.0V to 4.0V; button batteries manufactured using the lithium supplement provided in Comparative Example 1 were tested for the first charge specific capacity and first discharge specific capacity at a 0.05C magnification under conditions of 2.0V to 4.5V and 2.0V to 4.0V, respectively; and button batteries manufactured using the lithium supplement provided in Comparative Example 2 were tested for the first charge specific capacity and first discharge specific capacity at a 0.05C magnification under conditions of 2.0V to 4.0V, and the results are shown in Table 11.

[0233]

[0234] As can be seen in Table 11, compared to the button batteries manufactured using the lithium supplements provided in Comparative Examples 1 and 2, the button batteries manufactured using the lithium supplements provided in Examples 1 to 8 have a higher first charge capacity under voltage conditions of 2.0V to 4.0V. Specifically, the button batteries manufactured using the lithium supplements provided in Examples 1 to 8 have a first charge capacity at a 0.05C multiplier within the range of 501mAh / g to 520mAh / g under voltage conditions of 2.0V to 4.0V, and a first discharge capacity at a 0.05C multiplier is maintained within the range of 81mAh / g to 90mAh / g.

[0235] As can be seen from the first charge capacity and first discharge capacity of the button battery manufactured using the lithium supplement provided in Examples 1 to 8 and the button battery manufactured using the lithium supplement provided in Comparative Example 1, the button battery manufactured using the lithium supplement of the present application has a higher charge capacity and discharge capacity in the same charge-discharge range (2.0V to 4.0V), which indicates that the lithium supplement provided in the examples of the present application has a lower operating voltage than lithium-rich lithium ferrite and is more suitable for application to the positive electrode plate of a secondary battery.

[0236] As can be seen by comparing the first charge capacity and first discharge capacity of the button battery manufactured using the lithium supplement provided in Examples 1 to 8 with that of the button battery manufactured using the lithium supplement provided in Comparative Example 2, the first charge capacity of the button battery manufactured using the lithium supplement provided in Examples 1 to 8 under a 0.05C magnification condition is significantly higher than the first charge capacity of the button battery manufactured using the lithium supplement provided in Comparative Example 2 under a 0.05C magnification condition. This means that the lithium supplement provided in Examples 1 to 8 of the present application is advantageous in preventing the oxidation of phosphite ions into phosphate ions by making it difficult for the lithium phosphite to come into contact with the external environment through the formation of a coating layer on the surface of the lithium phosphite, thereby reducing the formation of "inert lithium" and improving the lithium replenishment effect. Furthermore, since the material of the coating layer has relatively strong stability and good conductivity, it means that the conductivity and material stability of the lithium supplement are further improved and the lithium replenishment effect is further enhanced.

[0237] (2) The lithium supplements provided in Examples 1 to 8 and Comparative Examples 1 to 2 were left in air (temperature 25°C, humidity 70%) for 1 hour, 4 hours, 24 hours, and 48 hours, respectively, and then assembled into button batteries according to part (1) above and tested, and the test results are shown in Table 12.

[0238]

[0239] As can be seen in Table 12, the button batteries manufactured using the lithium supplements provided in Examples 1 to 8 show a significantly smaller change in the first charge capacity and first discharge capacity as the storage time increases under conditions of a temperature of 25°C and a humidity of 70% compared to the button batteries manufactured using the lithium supplements provided in Comparative Examples 1 and 2. This means that the lithium supplements provided in Examples 1 to 8 can better satisfy actual application demands by effectively improving the capacity and stability of the lithium supplements through the formation of a coating layer having iron boride on the surface of lithium phosphite.

[0240] It should be noted that the present application is not limited to the embodiments described above. The embodiments described above are merely examples, and any embodiment having substantially the same configuration as the technical concept and achieving the same functional effect within the scope of the technical solution of the present application is included within the technical scope of the present application. Furthermore, any various modifications that a person skilled in the art may make to the embodiments without departing from the essence of the present application, or any other forms formed by combining some components of the embodiments, are all included within the scope of the present application.

Claims

Claim 1 A lithium supplement comprising lithium phosphite (Li2HPO3) and a coating layer covering the surface of the lithium phosphite, wherein the material of the coating layer comprises iron boride. Claim 2 A lithium supplement according to claim 1, characterized by satisfying at least one of the following conditions: a condition in which the thickness of the coating layer is 0.6 μm to 2 μm; and a condition in which the coating rate of the coating layer is 93% or more. Claim 3 A lithium supplement according to claim 1, characterized by satisfying at least one of the following conditions: the lithium supplement having a quasi-spherical shape, wherein the sphericity of the lithium supplement is 0.81 to 0.87; and the particle size distribution of the lithium supplement having a D50 particle size of 0.3μm to 3.8μm, a D10 particle size of 0.1μm to 1.9μm, and a D90 particle size of 1.3μm to 6.4μm. Claim 4 A lithium supplement according to claim 1, characterized by satisfying at least one of the following conditions: a condition in which the tap density of the lithium supplement is 1.43 g / mL to 1.59 g / mL; a condition in which the compaction density of the lithium supplement is 2.48 g / mL to 2.76 g / mL; and a specific surface area of ​​the lithium supplement is 3.47 m² 2 / g~4.79 m 2 Condition for / g. Claim 5 A method for manufacturing a lithium supplement comprising: a step of preparing a first slurry containing lithium phosphate; a step of mixing the first slurry with sodium borohydride and ferrous chloride and obtaining a crude product through a first reaction treatment; and a step of obtaining the lithium supplement by filtering, washing, and drying the crude product; wherein the lithium supplement comprises lithium phosphate (Li2HPO3) and a coating layer covering the surface of the lithium phosphate, and the material of the coating layer comprises iron boride. Claim 6 In claim 5, the step of preparing a first slurry containing lithium phosphate comprises: a step of obtaining a first solution of phosphoric acid—the solvent of the first solution comprises at least one of methanol, ethanol, glycerol, propanol, and propylene glycol—; a step of adding a lithium salt to the first solution of phosphoric acid and obtaining a first reaction slurry through a second reaction treatment; and a step of grinding the first reaction slurry until the lithium phosphate in the first reaction slurry reaches a preset particle size of 0.3 μm to 3 μm to obtain the first slurry; and is characterized by satisfying at least one of the following conditions: a condition in which the ratio of the amount of substance of the phosphoric acid, the sodium borohydride, and the ferrous chloride is 1:(0.05~0.1):(0.025~0.05); the temperature of the second reaction treatment is 35℃~55℃, and the time of the second reaction treatment Condition of 0.5h to 1h; condition in which the lithium salt comprises at least one of lithium carbonate, lithium sulfite, and lithium bicarbonate; and condition in which the ratio of the amount of lithium element in the lithium salt to the amount of phosphoric acid is (1.8 to 1.9):

1. Claim 7 A method for manufacturing a lithium supplement according to claim 6, wherein the step of mixing the first slurry with sodium borohydride and ferrous chloride and obtaining a crude product through a first reaction treatment comprises the step of mixing the solution containing the sodium borohydride, the solution containing the ferrous chloride, and the first slurry, and then obtaining the crude product through a first predetermined time at a first reaction temperature, and satisfying at least one of the following conditions: a condition in which the mixing time is 60 min to 120 min and the mixing temperature is 25℃ to 45℃; a condition in which the first reaction temperature is 25℃ to 45℃; and a condition in which the first predetermined time is 30 min to 60 min. Claim 8 A method for manufacturing a lithium supplement according to claim 5, characterized in that the temperature of the drying treatment is 80℃ to 100℃ and the vacuum degree of the drying treatment is -0.09Mpa to -0.07MPa. Claim 9 A positive electrode plate comprising: a current collector; and a positive electrode material disposed on at least one side along the self-thickness direction of the current collector, wherein the positive electrode material comprises a lithium supplement according to any one of claims 1 to 4, or a lithium supplement manufactured by a method for manufacturing a lithium supplement according to any one of claims 5 to 8. Claim 10 A secondary battery characterized by comprising a positive electrode plate, a negative electrode plate, and a separator selected from the group consisting of positive electrode plates according to claim 9.

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