Lithium supplement additive, its preparation method and application

Abstract

The present application discloses a lithium supplement additive, a preparation method thereof and an application. The lithium supplement additive of the present application includes granular lithium supplement material, and also includes lithium fluoride, and the lithium fluoride is at least combined on the surface of the lithium supplement material, and the lithium fluoride is generated by the reaction of an organic fluorine source with residual alkali contained in the lithium supplement material. The lithium supplement additive of the present application has high purity, and the lithium fluoride coating layer at least in-situ combined on the surface of the lithium supplement material effectively plays a role of isolation and protection, ensuring that the lithium supplement material has high lithium supplement effect, storage performance and processing performance; moreover, the lithium fluoride improves the lithium ion insertion and extraction properties and lithium ion conductivity. In addition, the preparation method of the lithium supplement additive can ensure the stability of the structure and electrochemical performance of the prepared lithium supplement additive, and has high efficiency and saves production costs.

Description

Technical Field

[0001] This application belongs to the field of secondary batteries, and particularly relates to a lithium supplement additive, a preparation method thereof, and an application thereof. Background Art

[0002] The oil energy crisis problems in the 1960s and 1970s forced people to search for new alternative energy sources. With the enhancement of people's awareness of environmental protection and energy crisis, lithium-ion batteries are considered to be one of the most promising energy sources because of their advantages such as high working voltage, high energy density, relatively low self-discharge level, no memory effect, no heavy metal element pollution such as lead and cadmium, and extremely long cycle life. Lithium-ion batteries are widely used in many aspects such as electric vehicles, power tools, portable electronic consumer products, and energy storage.

[0003] Currently, the most commonly used cathode materials for lithium-ion batteries mainly include lithium iron phosphate, lithium nickel cobalt manganese (aluminum) oxide ternary materials (commonly known as ternary materials), lithium cobalt oxide, lithium manganate, etc. The most widely used anode materials are carbon-based graphite materials and silicon-based anode materials, etc. Although lithium-ion batteries have many advantages, during the first charging process of lithium-ion batteries, a solid electrolyte interface (SEI) film is usually formed on the surface of the anode, and this process will consume a large amount of Li + , which means that part of the Li + released from the cathode material is irreversibly consumed, corresponding to a decrease in the reversible specific capacity of the battery cell. Anode materials, especially silicon-based anode materials, will further consume Li + , resulting in lithium loss in the cathode material and reducing the first Coulombic efficiency and battery capacity of the battery. For example, in a lithium-ion battery system using a graphite anode, about 10% of the lithium source will be consumed during the first charging. When using high specific capacity anode materials, such as alloy-based (silicon, tin, etc.), oxide-based (silicon oxide, tin oxide) and amorphous carbon anodes, the consumption of the cathode lithium source will be further aggravated.

[0004] To improve the low Coulombic efficiency problem caused by irreversible anode loss, researchers have developed related lithium-rich compounds, such as Li3N, Li2S, Li2NiO2, Li5FeO4, Li2MnO2, etc., as additives to solve the problem of irreversible lithium-ion loss during the first charge and discharge.

[0005] Among these existing lithium-rich compounds, most of the lithium supplement materials are lithium salts of transition metals as lithium supplement materials. However, due to the preparation process and its own property defects, this material often leads to incomplete reaction of raw materials, low purity, poor performance, and also makes the material sensitive to water and oxygen. Especially when encountering water, it will react and deteriorate seriously. The water control requirements in the processing process are extremely strict, and it is difficult to be widely applied on the existing battery production lines. Although there are currently disclosures of using, for example, carbon-coated lithium-rich compounds to isolate adverse factors such as water and oxygen in the environment, the existing coating layers cannot effectively remove the raw material residues contained in the lithium-rich compounds, and the coating density is not ideal. Moreover, it additionally increases the path of ion insertion and extraction and affects the ionic conductivity. Summary of the Invention

[0006] The purpose of this application is to overcome the above deficiencies of the existing technology and provide a lithium supplement additive and its preparation method to solve the technical problems that the existing lithium supplement additives have low purity, resulting in unsatisfactory lithium supplement effect, storage performance and processability.

[0007] Another purpose of this application is to provide a positive electrode sheet and a secondary battery containing this electrode sheet to solve the technical problems that the electrochemical performance such as the first Coulomb efficiency of the existing secondary batteries is not ideal.

[0008] To achieve the above application purposes, in the first aspect of this application, a lithium supplement additive is provided. The lithium supplement additive of this application includes granular lithium supplement material, and also includes lithium fluoride, and lithium fluoride is at least combined on the surface of the lithium supplement material, and lithium fluoride is generated by the reaction of an organic fluorine source and the residual alkali contained in the lithium supplement material.

[0009] Further, the lithium fluoride combined on the surface of the lithium supplement material forms a lithium fluoride coating layer that completely or partially coats the lithium supplement material.

[0010] Further, lithium fluoride is generated by the thermal cracking treatment of an organic fluorine source and the lithium supplement material in a protective atmosphere and the reaction with the residual alkali contained in the lithium supplement material.

[0011] Further, the particle surface layer of the lithium supplement material also contains lithium fluoride, and the content of lithium fluoride combined on the particle surface is higher than that contained in the particle surface layer.

[0012] Further, in the lithium supplement additive, the mass percentage content of lithium fluoride is 0.1 - 5%.

[0013] Further, the lithium supplement additive also includes a hydrophobic encapsulation layer, and the hydrophobic encapsulation layer coats the lithium supplement material and the lithium fluoride distributed on the surface of the lithium supplement material.

[0014] Further, the lithium supplement material includes L x M y O z 、Liw At least one of A, wherein L in the molecular formula is Li or / and a mixed alkali metal element of Li and at least one of K and Na not exceeding 30%; M includes at least one of Fe, Co, Ni, Mn, V, Fe-Co, Cu, Mo, Al, Ti, Mg; O is oxygen element; A includes at least one element of C, N, O, P, S, F, B, Se, 0 < x ≤ 6, 0 < y ≤ 3, 0 < z ≤ 5, 0 < w ≤ 5.

[0015] Furthermore, the residual alkali contained in the lithium supplement material includes lithium oxide and / or lithium carbonate, the residual amount of lithium oxide is less than 0.15%, and the residual amount of lithium carbonate is less than 0.45%.

[0016] Furthermore, the lithium supplement additive is a positive electrode lithium supplement additive, and the capacity decay rate of the positive electrode sheet prepared from the positive electrode lithium supplement additive, conductive agent and binder after storing for 20 hours at an ambient humidity of 25% relative to the capacity after storing for 0.5 hours is not more than 30%; or the capacity decay rate of the positive electrode sheet prepared from the positive electrode lithium supplement additive, conductive agent and binder after storing for 20 hours at an ambient humidity of 10% relative to the capacity after storing for 0.5 hours is not more than 20%.

[0017] Even further, the hydrophobic encapsulation layer includes at least one of an ion conductor encapsulation layer and an electron conductor encapsulation layer.

[0018] In the second aspect of the present application, a preparation method of the lithium supplement additive of the present application is provided. The preparation method of the lithium supplement additive of the present application includes the following steps:

[0019] In a protective atmosphere, an organic fluorine source is mixed with the raw material particles of the lithium supplement material and subjected to a reaction treatment to generate lithium fluoride on the surface of the lithium supplement material with a particle morphology at least.

[0020] Furthermore, the raw material particles of the lithium supplement material and the fluorine source are mixed in a mass ratio of 100:(1 - 15).

[0021] Furthermore, the temperature of the mixing treatment is 80 - 400 °C.

[0022] Furthermore, the temperature of the reaction treatment is 300 - 600 °C.

[0023] Furthermore, the generated lithium fluoride forms a lithium fluoride coating layer, which completely or partially coats the lithium supplement material.

[0024] Furthermore, the protective atmosphere is formed by continuously introducing a chemically inert gas, and the chemically inert gas is introduced into the raw material particles of the lithium supplement material for bubbling treatment to achieve the mixing treatment.

[0025] Specifically, the organofluorine source is mixed with the raw material of the lithium supplementing material in a flowing manner and reacted simultaneously.

[0026] Specifically, the organofluorine source includes an organofluoride that decomposes below 600 °C and does not contain hydroxyl groups.

[0027] In the third aspect of the present application, an electrode sheet is provided. The electrode sheet of the present application includes a current collector and an electrode active layer combined on the surface of the current collector. The electrode active layer contains the lithium supplementing additive of the present application or the lithium supplementing additive prepared by the preparation method of the lithium supplementing additive of the present application.

[0028] In the fourth aspect of the present application, a secondary battery is provided. The present application includes a positive electrode sheet and a negative electrode sheet; the positive electrode sheet is the electrode sheet of the present application, and the lithium supplementing additive contained in the electrode sheet of the present application is a positive electrode lithium supplementing additive;

[0029] And / or, the negative electrode sheet is the electrode sheet of the present application, and the lithium supplementing additive contained in the electrode sheet of the present application is a negative electrode lithium supplementing additive.

[0030] Compared with the prior art, the present application has the following technical effects:

[0031] The lithium supplementing additive of the present application reacts with the residual alkali contained in the lithium supplementing material through the fluorine source to in-situ generate lithium fluoride at least on the surface of the lithium supplementing material. On the one hand, it effectively reduces or removes the residual alkali such as the residual raw material of the lithium supplementing material, improves the purity of the lithium supplementing material, and thus endows the lithium supplementing additive of the present application with a good lithium supplementing effect; on the other hand, due to the high purity of the lithium supplementing material and the generated lithium fluoride being at least in-situ combined on the surface of the lithium supplementing material, it effectively plays an insulating and protective role, isolates the lithium supplementing material from the outside, avoids the contact between the outside such as moisture and carbon dioxide and the lithium supplementing material, ensures the stability of the lithium supplementing material, and thus ensures the lithium supplementing effect and the stability of lithium supplementation of the lithium supplementing additive, and improves the storage performance and processing performance; on the third hand, the good ionic conductivity of lithium fluoride also endows the lithium supplementing additive of the present application with high lithium ion intercalation / deintercalation ability and lithium ion conductivity, thereby improving the lithium supplementing effect of the lithium supplementing additive.

[0032] The preparation method of the lithium supplementing additive of the present application can effectively react the fluorine source with the residual alkali contained in the lithium supplementing material to directly generate lithium fluoride, so that the prepared lithium supplementing additive has lithium fluoride in-situ combined at least on the surface of the lithium supplementing material in terms of particle morphology, and the prepared lithium supplementing additive contains low residual alkali and other impurities, has high purity, and has the characteristic of isolating the environment, and has good lithium supplementing effect, storage performance and processing performance. In addition, the preparation method of the lithium supplementing additive can ensure the stable structure and electrochemical performance of the prepared positive electrode lithium supplementing additive, and has high efficiency and saves production costs.

[0033] Since the electrode sheet of the present application contains the lithium supplement additive of the present application, the lithium supplement additive contained in the electrode sheet of the present application can serve as a "sacrificial agent" during the first-cycle charging process to supplement the irreversible lithium ions consumed by the formation of the SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the first efficiency and overall electrochemical performance of the battery. Moreover, the contained lithium supplement additive has good processability, and the electrode active layer of the electrode sheet of the present application has high quality and stability.

[0034] Since the secondary battery of the present application contains the electrode sheet of the present application, the lithium-ion battery of the present application has excellent first Coulomb efficiency, battery capacity, and cycle performance, a long service life, and stable electrochemical performance. Description of the Drawings

[0035] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a schematic structural diagram of a lithium supplement additive according to an embodiment of the present application;

[0037] Figure 2 It is another schematic structural diagram of a lithium supplement additive according to an embodiment of the present application. Detailed Embodiments

[0038] In order to make the technical problems to be solved, technical solutions, and beneficial effects of the present application clearer and more understandable, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0039] In the present application, the term "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0040] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or a similar expression means any combination of these items, including any combination of single item(s) or plural item(s). For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0041] It should be understood that in various embodiments of this application, the magnitudes of the serial numbers of the above - mentioned processes do not mean the order of execution. Some or all of the steps can be executed in parallel or successively. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0042] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms of "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0043] The weights of the relevant components mentioned in the specification of the embodiments of this application not only can refer to the specific contents of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the specification of the embodiments of this application are scaled up or down proportionally, they are within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass mentioned in the specification of the embodiments of this application can be mass units well - known in the chemical industry such as μg, mg, g, kg, etc.

[0044] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of this application, the first XX can also be called the second XX. Similarly, the second XX can also be called the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0045] In a first aspect, an embodiment of this application provides a lithium - supplementing additive. The lithium - supplementing additive in the embodiment of this application includes a lithium - supplementing material and lithium fluoride.

[0046] Among them, the lithium supplementing material contained in the lithium supplementing additive of the embodiment of the present application is granular, that is, the lithium supplementing material has a granular morphology. The lithium supplementing material is rich in lithium, so as to ensure that the lithium supplementing additive of the embodiment of the present application can provide abundant lithium. After being added to the electrode as a lithium supplementing additive, it acts as a "sacrificial agent" during the first cycle charging process, and releases all the lithium ions contained in the lithium supplementing additive as much as possible at one time, so as to supplement the irreversible lithium ions consumed by the formation of the SEI film on the negative electrode.

[0047] In addition, the particle size of the granular lithium supplementing material can be controlled and adjusted according to production conditions or application needs. For example, in the embodiment, the particle size of the granular lithium supplementing material is 3-20 μm. By controlling and adjusting the particle size of the granular lithium supplementing material, the overall particle size of the lithium supplementing additive of the embodiment of the present application can be controlled and adjusted. Thus, the lithium supplementing effect of the lithium supplementing material can be fully exerted.

[0048] In the embodiment, the above-mentioned lithium supplementing material may include L x M y O z 、Li w A or at least one of them. Among them, L x M y O z In the molecular formula, L is Li or / and a mixed alkali metal element of Li and at least one of K and Na not exceeding 30%; M includes at least one of Fe, Co, Ni, Mn, V, Fe-Co, Cu, Mo, Al, Ti, Mg; 0 < x ≤ 6, 0 < y ≤ 3, 0 < z ≤ 5. Therefore, according to the types of elements shown by M, the lithium supplementing material can be at least one of iron-based lithium supplementing materials, manganese-based lithium supplementing materials, nickel-based lithium materials, etc. In a specific embodiment, when M in L x M y O z is Fe and Al, the lithium-rich lithium supplementing material shown by L x M y O z can be Li5Fe 0.98 Al 0.02 O4. It can also be but not limited to Li2NiO2, Li5FeO4, LiCoO2, Li2MnO2, LiMn2O4, LiFePO4, etc., and can also be lithium iron phosphate manganese. These lithium supplementing materials are rich in lithium and can release lithium ions during the first cycle charging process to play an effective lithium supplementing role. When the lithium supplementing material has an anti-fluorite structure, it can also improve the unidirectional capacity characteristics of the lithium supplementing material, thereby ensuring the lithium supplementing effect of the lithium supplementing additive of the present application. When the lithium supplementing material contains aluminum element doping, the Al atoms exist in the form of substituting the iron atom lattice, and the Al atoms existing in this form can broaden the lithium ion transmission channels and improve the lithium ion extraction rate.

[0049] In Li w A, A includes at least one element among C, N, O, P, S, F, B, and Se, and 0 < w ≤ 5. This Li w The lithium supplement material precursor shown in A is a binary lithium supplement material precursor, and specifically may be but not limited to Li3N, Li2S, Li2O, Li2O2, etc.

[0050] In addition, according to the type of the lithium supplement material, such as being a cathode lithium supplement material or an anode lithium supplement material, it determines the type of the lithium supplement additive in the embodiments of the present application, such as being a cathode lithium supplement additive or an anode lithium supplement additive. When it is an anode lithium supplement additive, the anode lithium supplement additive is formed by using lithium salts such as lithium, lithium oxide, and lithium hydroxide as raw materials through high-temperature sintering.

[0051] According to the characteristics of the existing lithium supplement materials, the residual alkali contained therein is at least or mainly distributed on the surface of the lithium supplement materials. Among them, the residual alkali includes, for example, the residual raw materials of the lithium supplement material precursor, and also includes other by-products generated during the preparation process, such as residual alkali impurities such as lithium carbonate and lithium oxide. Through detection, taking the contents of lithium carbonate and lithium oxide as an example, the residual content of lithium oxide in the existing lithium supplement materials is approximately 0.5 wt% - 3 wt%, and the residual content of lithium carbonate is approximately 0.02 wt% - 9 wt%.

[0052] The lithium fluoride contained in the lithium supplement additive in the embodiments of the present application is at least combined on the surface of the lithium supplement material with the above-mentioned particle morphology, and this lithium fluoride is generated by the reaction of an organic fluorine source with the residual alkali contained in the lithium supplement material. In this way, the lithium supplement additive in the embodiments of the present application in-situ generates lithium fluoride at least on the surface of the lithium supplement material through the reaction of the organic fluorine source with the residual alkali contained in the lithium supplement material. First, it effectively reduces or removes the residual of the residual alkali contained in the lithium supplement material, improves the purity of the lithium supplement material, and thus endows the lithium supplement additive in the embodiments of the present application with a good lithium supplement effect. Through detection, further, the residual amount of the residual alkali contained in the lithium supplement additive in the embodiments of the present application is significantly reduced, such as being able to remove about 95% - 98% of the residual alkali. Taking the residual alkali lithium oxide and lithium carbonate contained in the lithium supplement additive in the embodiments of the present application as an example, the residual amount of the residual lithium oxide is less than 0.15%, and the residual amount of the residual lithium carbonate is less than 0.45%. Second, due to the high purity of the lithium supplement material and the fact that the generated lithium fluoride is at least in-situ combined on the surface of the lithium supplement material, it effectively plays a role of isolation and protection, enables the lithium supplement material to be effectively isolated from the outside world, avoids the contact of the outside world such as moisture and carbon dioxide with the lithium supplement material, ensures the stability of the lithium supplement material, and thus ensures the lithium supplement effect and the stability of lithium supplementation of the lithium supplement additive, and improves the storage performance and processing performance. Thirdly, the good ionic conductivity of lithium fluoride also endows the lithium supplement additive in the embodiments of the present application with high lithium ion insertion / extraction property and lithium ion conductivity, thereby improving the electrochemical performance of the lithium supplement additive.

[0053] In the embodiments, the lithium fluoride contained in the lithium supplement additive of the present application is at least combined on the surface of the above-mentioned lithium supplement material. Moreover, due to the distribution of the residual alkali contained in the lithium supplement material, in the embodiments, the lithium fluoride combined on the surface of the above-mentioned lithium supplement material can form a lithium fluoride coating layer that completely or partially coats the lithium supplement material. At this time, the lithium supplement additive of the embodiments of the present application constitutes a core-shell structure, specifically as Figure 1 shown. The above-mentioned lithium supplement material with the particle morphology constitutes the core body 10, and the lithium fluoride coating layer 21 constitutes the shell layer 20, at least a part of the shell layer 20. Among them, the lithium fluoride coating layer 21 can completely or partially coat the lithium supplement material, which is also the core body 10. Ideally, it is a complete coating, which can effectively reduce or remove residues such as raw materials and residual alkali, improve the purity of the lithium supplement material, and improve the protective effect of the lithium fluoride coating layer 21 on the lithium supplement material, as well as the storage performance, processability and lithium supplement stability of the lithium supplement additive of the embodiments of the present application.

[0054] In the embodiments, when the organic fluorine source reacts with the residual alkali contained in the lithium supplement material, the lithium fluoride contained in the lithium supplement additive of the embodiments of the present application is generated by thermally cracking the organic fluorine source and the lithium supplement material in a protective atmosphere and reacting with the precursor raw material of the lithium supplement material. Specifically, as described in the preparation method of the lithium supplement additive below. Using the organic fluorine source as the fluorine source, in the thermal cracking process, the C-F bond is broken and reacts with the residual precursor raw material of the lithium supplement material contained in the lithium supplement material to generate lithium fluoride, which is then at least in-situ combined on the surface of the lithium supplement material, such as forming the lithium fluoride coating layer 21. Moreover, the organic fluorine source has basically no corrosion on the lithium supplement material, effectively ensuring the stability of the electrochemical performance of the lithium supplement material. At the same time, the organic fluorine source can effectively reduce the reaction conditions, improve the electrochemical performance and economic cost of the lithium supplement additive.

[0055] In addition, although the residual alkali contained in the lithium supplement material is mainly distributed on its surface, it may also be further distributed in the surface layer of the lithium supplement material. Therefore, in the embodiments, the lithium fluoride contained in the lithium supplement additive of the embodiments of the present application can also be further distributed in the surface layer of the above-mentioned lithium supplement material with the particle morphology, that is, in addition to the surface of the above-mentioned lithium supplement material particles being combined with lithium fluoride, the surface layer of the particles also contains lithium fluoride. At this time, the content of lithium fluoride combined on the surface of the above-mentioned lithium supplement material particles is higher than that contained in the surface layer of the particles. By forming lithium fluoride in the surface layer of the above-mentioned lithium supplement material with the particle morphology, the residual alkali contained in the lithium supplement material can be reduced or removed as much as possible, thereby improving the purity of the above-mentioned lithium supplement material with the particle morphology, improving its lithium supplement effect, storage performance and processing performance, and further improving the ion extraction efficiency of the lithium supplement additive of the embodiments of the present application.

[0056] In the examples, the mass percentage content of the total lithium fluoride contained in the lithium supplement additive of the embodiments of the present application is 0.1-5%, further 1-5%, and specifically can be typical but non-limiting contents such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc. By controlling the content of lithium fluoride, the purity and ion extraction efficiency of the lithium supplement material with the above particle morphology can be improved, and it is also possible to make the lithium fluoride combined on the surface of the lithium supplement material with the above particle morphology form a lithium fluoride coating layer as much as possible to achieve full coating of the lithium supplement material, thereby improving the lithium supplement effect, storage performance and processing performance of the lithium supplement additive of the embodiments of the present application.

[0057] On the basis of the above embodiments, as in the embodiments of the present application, the lithium supplement additive of the embodiments of the present application further includes a hydrophobic encapsulation layer. The hydrophobic encapsulation layer encapsulates the above lithium supplement material. At this time, it is natural that the hydrophobic encapsulation layer should encapsulate the lithium fluoride distributed on the surface of the lithium supplement material.

[0058] For example, when the lithium fluoride combined on the surface of the lithium supplement material forms a full coating, the hydrophobic encapsulation layer is coated on the outer surface of the fully coated lithium fluoride coating layer. When the lithium fluoride combined on the surface of the lithium supplement material forms a partial coating, the hydrophobic encapsulation layer is coated on the outer surface of the partially coated lithium fluoride coating layer. By adding the hydrophobic encapsulation layer to the lithium supplement additive of the embodiments of the present application, the hydrophobic encapsulation layer can effectively encapsulate the above lithium supplement material and the lithium fluoride combined on its surface, specifically such as the fully coated or partially coated lithium fluoride coating layer. Through the hydrophobic encapsulation layer or further hydrophobic encapsulation layer and the lithium fluoride distributed on the surface of the lithium supplement material, a good dense hydrophobic coating layer is formed to encapsulate the above lithium supplement material, thereby improving the isolation effect between the above lithium supplement material and the outside world, avoiding the contact between the outside world such as moisture and carbon dioxide and the above lithium supplement material, ensuring the stability of the above lithium supplement material and thus ensuring the lithium supplement effect and lithium supplement stability of the lithium supplement additive of the present application. At the same time, the lithium fluoride also plays a role in improving the lithium ion conductivity.

[0059] For example, in the examples, the structure of the lithium supplement additive of the embodiments of the present application is as Figure 2 shown, combined with Figure 1 , the hydrophobic encapsulation layer 22 encapsulates the above lithium supplement material core 10, and the hydrophobic encapsulation layer 22 encapsulates the lithium fluoride distributed on the surface of the lithium supplement material core 10, specifically such as the lithium fluoride coating layer 21 distributed on the surface of the lithium supplement material core 10.

[0060] In the examples, the above particulate lithium supplement material such as Figure 1 and Figure 2 The particulate lithium supplement material contained in can be at least one of primary particles and secondary particles. Similarly, Figure 2The lithium supplementing material in the form of particles coated with the hydrophobic encapsulation layer 22 can also be at least one of primary particles and secondary particles. The particle size of the particulate lithium supplementing material or the primary or secondary particles of the particulate lithium supplementing material with lithium fluoride bound to the surface can be controlled and adjusted according to actual needs.

[0061] When the lithium supplementing additive in the embodiment of the present application contains the above-mentioned hydrophobic encapsulation layer, the hydrophobic encapsulation layer can be a layer structure that can effectively isolate adverse factors such as water vapor or carbon dioxide in the environment. Then, the material thereof can be a material that can form a dense hydrophobic coating layer to effectively ensure the stability of the particulate lithium supplementing material. On this basis, the material of the hydrophobic encapsulation layer can also be an ion conductor encapsulation layer that is conducive to ion conduction, or an electron conductor encapsulation layer that is conducive to improving conductivity. Of course, it can also be a composite layer structure of an ion conductor encapsulation layer and an electron conductor encapsulation layer. When the hydrophobic encapsulation layer is a composite layer structure of an ion conductor encapsulation layer and an electron conductor encapsulation layer, any one of the ion conductor encapsulation layer or the electron conductor encapsulation layer can be directly coated on the surface of the particulate lithium supplementing material with lithium fluoride bound to the surface as described above. Among them, the ion conductor encapsulation layer can improve the intercalation and deintercalation effect of lithium ions and the ionic conductivity of lithium ions in the lithium supplementing material. The electron conductor encapsulation layer can improve the electronic conductivity of the lithium supplementing material, improve its conductive performance, stimulate the specific capacity of the lithium supplementing additive to play, and achieve efficient lithium supplementing in the true sense.

[0062] When the hydrophobic encapsulation layer includes an ion conductor encapsulation layer, the ion conductor encapsulation layer or further combines with lithium fluoride bound to the surface of the particulate lithium supplementing material, and Figure 1 and Figure 2 the lithium fluoride coating layer 21 shown in plays a role in improving the lithium ion conductivity. Therefore, the material of the ion conductor encapsulation layer can be a material that is conducive to improving the ion conductivity, such as but not limited to including at least one of perovskite type, NASICON type, and garnet type. In a specific embodiment, the perovskite type includes Li 3x La 2 / 3- x TiO3 (LLTO), specifically such as Li 0.5 La 0.5 TiO3, Li 0.33 La 0.57 TiO3, Li 0.29 La 0.57 TiO3, Li 0.33 Ba 0.25 La 0.39 TiO3, (Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.01 O3, Li 0.5 La 0.5Ti 0.95 Zr 0.05 At least one of O3, etc., NASICON type such as but not limited to Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (LATP), garnet type includes Li7La3Zr2O 12 (LLZO), Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li 6.5 La3Zr 1.5 Ta 0.5 O 12 At least one of them. By selecting the material of the ion conductor encapsulation layer, the ionic conductivity of the ion conductor encapsulation layer can be further improved.

[0063] When the hydrophobic encapsulation layer includes an electronic conductor encapsulation layer, the electronic conductor encapsulation layer can enhance the electronic conductivity of the hydrophobic encapsulation layer, thereby enhancing the electronic conductivity of the lithium supplement additive, which is beneficial to reducing the impedance inside the electrode. At the same time, during and after the release process of the above-mentioned granular lithium supplement material as a "sacrificial" release, the electronic conductor encapsulation layer can also be reused for a second time to play an auxiliary role as a conductive agent inside the electrode. Moreover, the electronic conductor encapsulation layer or further plays a synergistic role with the ion conductor encapsulation layer to improve the densification of the hydrophobic encapsulation layer, thereby improving the lithium supplement stability and lithium supplement effect of the lithium supplement additive. Based on the role of the electronic conductor encapsulation layer, it can be fully encapsulated or partially encapsulated by the electronic conductor encapsulation layer. In the embodiment, the material of the electronic conductor encapsulation layer includes at least one of carbon materials, conductive oxides, and conductive organic substances. In a specific embodiment, when the material of the electronic conductor encapsulation layer is a carbon material, the carbon material includes at least one of amorphous carbon, carbon nanotubes, graphite, carbon black, graphene, etc. In some other specific embodiments, when the material of the electronic conductor encapsulation layer is a conductive oxide, the conductive oxide may include at least one of In2O3, ZnO, and SnO2. The conductive organic substance can be a conductive polymer, etc. By adjusting the content and material of the electronic conductor encapsulation layer, its electronic conductivity can be further improved.

[0064] In a further embodiment, the hydrophobic encapsulation layer, such as Figure 2 As shown, the thickness of the hydrophobic encapsulation layer 22 can be 5 - 100 nm. For example, it can be adjusted by controlling the thickness of the ion conductor encapsulation layer and the electronic conductor encapsulation layer contained in the above-mentioned hydrophobic encapsulation layer. Controlling the thickness of the hydrophobic encapsulation layer within this range can improve the densification of the hydrophobic encapsulation layer, further improve the storage stability and processing stability of the lithium supplement additive, and at the same time improve the ionic and / or electronic conductivity of the lithium supplement additive.

[0065] In addition, the hydrophobic encapsulation layer may further include other functional layers as needed, and the types of other functional layers can be flexibly selected as needed.

[0066] Based on the structure and properties of the lithium supplement additive in the embodiments of the present application, especially when the hydrophobic encapsulation layer 22 is included, the lithium supplement additive in the embodiments of the present application is given excellent storage properties, processability, and stable electrochemical properties. As detected, when the lithium supplement additive in the embodiments of the present application is used as the cathode lithium supplement additive, for the directly prepared cathode sheet, such as the cathode sheet prepared from the cathode lithium supplement additive, the binder, and the conductive agent (excluding the cathode active material), the capacity attenuation rate after storing for 20 hours at an environmental humidity of 25% relative to the capacity after storing for 0.5 hours is not more than 30%, further not more than 15%. The capacity attenuation rate after storing for 20 hours at an environmental humidity of 20% relative to the capacity after storing for 0.5 hours is not more than 20%, further not more than 8.5%. The capacity attenuation rate after storing for 20 hours at an environmental humidity of 10% relative to the capacity after storing for 0.5 hours is not more than 10%, further not more than 3%. This reflects the excellent storage properties, high lithium supplement effect, and lithium supplement stability of the lithium supplement additive in the embodiments of the present application. Ideally, the lithium supplement additive in the present application is stored in a favorable environment of dryness and oxygen-free, such as a vacuum environment, to maximize the electrochemical performance of the lithium supplement additive in the present application. (Note: The attenuation rate = (1 - specific capacity after standing for 20 h / specific capacity after standing for 0.5 h) * 100%).

[0067] In a second aspect, the embodiments of the present application also provide a preparation method for the above-mentioned lithium supplement additive. The preparation method for the lithium supplement additive in the embodiments of the present application includes the following steps:

[0068] In a protective atmosphere, the organic fluorine source and the lithium supplement material particle raw material are mixed and reacted, and lithium fluoride is formed at least on the surface of the lithium supplement material with a particle morphology.

[0069] Among them, the lithium supplement material particle raw material is the raw material for forming the lithium supplement material with a particle morphology contained in the lithium supplement additive in the embodiments of the present application. Therefore, like the conventional lithium supplement material, the lithium supplement material particle raw material generally contains at least residual lithium supplement material precursor raw material on its surface. Then the types and particle sizes of the lithium supplement material particle raw material are the same as those of the lithium supplement material with a particle morphology contained in the lithium supplement additive in the embodiments of the present application. For the sake of brevity, the lithium supplement material particle raw material will not be described in detail here.

[0070] In the process of mixing the organic fluorine source and the raw material of lithium supplement material particles, the addition amount of the organic fluorine source is ideally relatively excessive, so that the residual alkali contained in the raw material of lithium supplement material particles can react with the organic fluorine source as much as possible to generate lithium fluoride. For example, by controlling the amount of organic fluorine source added, the content of the generated lithium fluoride is as described above, and the mass percentage of lithium fluoride in the lithium supplement additive is 0.1-5%, thereby reducing the content of impurities in the raw material of lithium supplement material particles to the greatest extent and improving the purity of the lithium supplement material generated after the reaction treatment. The inventor found in the study that when the addition amount of the organic fluorine source is too much, during the reaction treatment process, a certain corrosion phenomenon is caused to the lithium supplement material after the reaction treatment, which will cause a certain adverse effect on the lithium supplement effect of the lithium supplement material, and will also cause a waste of the organic fluorine source, increasing the production cost of the lithium supplement additive. Therefore, in the embodiment, the raw material of lithium supplement material particles and the organic fluorine source can be mixed according to a mass ratio of 100: (0.1-15). The mixing ratio within this range can make the residual alkali contained in the raw material of the lithium supplement material particles fully react with the organic fluorine source to generate lithium fluoride, improve the purity of the lithium supplement material generated after the reaction treatment, thereby improving the lithium supplement effect and processing performance of the lithium supplement material, and at the same time, make the lithium fluoride form a lithium fluoride coating layer on the surface of the lithium supplement material as much as possible, and ideally, the lithium fluoride coating layer fully covers the lithium supplement material. In addition, the corrosion of the lithium supplement material due to excessive organic fluorine source is avoided as much as possible, thereby improving the lithium supplement effect of preparing the lithium supplement additive.

[0071] The mixing treatment of the organic fluorine source and the raw material of the lithium-replenishing material particles should be sufficient, so that lithium fluoride can be fully generated during the reaction treatment process, and the uniformity of the distribution of lithium fluoride, especially the lithium fluoride on the surface of the lithium-replenishing material, can be improved. In the embodiment, the fluorine source is mixed with the raw material of the lithium-replenishing material particles in a flowing manner, and at the same time, the above-mentioned reaction treatment is carried out while the mixing treatment is carried out. Mixing the fluorine source with the raw material of the lithium-replenishing material particles in a flowing manner can effectively improve the contact between the fluorine source and the raw material of the lithium-replenishing material particles, and improve the reaction treatment efficiency of the organic fluorine source, so that the lithium-replenishing material precursor raw material or other residual alkali contained in the raw material of the lithium-replenishing material particles is reacted, the purity of the lithium-replenishing material is improved, and the uniformity of the distribution of lithium fluoride, especially on the surface of the lithium-replenishing material, is improved, so that the lithium fluoride can give full play to the role of the protective layer and the improvement of ion conductivity.

[0072] In the embodiment, the temperature of the fluorine source lithium supplement material particle raw material for mixing treatment is controlled at 80-400° C. By controlling the temperature in this range during the mixing treatment stage, the efficiency of the reaction treatment can be improved, lithium fluoride can be fully generated, and the dispersion uniformity of lithium fluoride can be improved.

[0073] In the embodiment, the protective atmosphere is formed by continuously introducing a chemically inert gas, and the chemically inert gas is introduced into the raw material of the lithium supplementing material particles for bubbling treatment to achieve the above-mentioned mixing treatment. By bubbling the raw material of the lithium supplementing material particles with the chemically inert gas, the raw material of the lithium supplementing material particles and the fluorine source can be kept in dynamic mixing treatment during the reaction treatment, so that the two are fully mixed and contacted. Further, the bubbling treatment can be maintained during the reaction treatment, thereby effectively improving the reaction treatment efficiency of the fluorine source and increasing the contact between the two, so that the lithium supplementing material precursor raw material or other residual alkalis and other components contained in the raw material of the lithium supplementing material particles are reacted, and the uniformity of the distribution of lithium fluoride, especially on the surface of the lithium supplementing material, is improved, so as to give full play to the role of lithium fluoride as a protective layer and improving the ionic conductivity. In a specific embodiment, the chemically inert gas can be a conventional chemically inert gas, such as at least one of Ar, N2, He, etc.

[0074] Based on the above embodiment of bubbling and introducing a chemically inert gas, the introduced chemically inert gas can be used as a carrier gas to load the organic fluorine source and mix it with the raw material of the lithium supplementing material particles, and the above-mentioned organic fluorine source can be mixed with the raw material of the lithium supplementing material particles in a flowing manner.

[0075] The above reaction treatment should be such that the organic fluorine source reacts with the residual alkali contained in the raw material of the lithium supplementing material particles, so that the fluorine element reacts with the residual alkali contained in the raw material of the lithium supplementing material particles to generate lithium fluoride. Then, after the raw material of the lithium supplementing material particles has also undergone the reaction treatment, it becomes the lithium supplementing material with the particle morphology contained in the above-mentioned lithium supplementing additive. Among them, the temperature of the reaction treatment should be at least the temperature at which the organic fluorine source decomposes.

[0076] The temperature of the reaction treatment can be specifically determined according to the type of the organic fluorine source. In the embodiment, the organic fluorine source can be a hydroxy-free organic fluoride that can decompose below 600 °C, such as at least one of fluorobenzene, pentafluorobenzene, 1,3-difluorobenzene, trifluorotoluene, 3-fluorotrifluorotoluene, 4-fluorotrifluorotoluene, 2,3,5,6-tetrafluorotrifluorotoluene, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether. These organic fluorine sources are rich in fluorine, can provide fluorine during the reaction treatment and react with impurities such as residual alkalis contained in the raw material of the lithium supplementing material particles to generate lithium fluoride, and will not produce corrosive or gaseous side products during the reaction treatment, such as will not corrode the generated lithium supplementing material, ensuring the stable electrochemical performance of the lithium supplementing material. At the same time, the organic fluoride is easy to decompose, which can reduce the reaction treatment conditions, such as reducing the reaction temperature and increasing the formation of lithium fluoride components.

[0077] At the same time, the inventors found in the research that when the temperature of the reaction treatment increases, although the efficiency of the reaction treatment can be improved, the temperature is not the higher the better. If the temperature is too high, the reaction rate of the organic fluorine source will be too fast, resulting in uneven reaction between the organic fluorine source and lithium, and thus uneven distribution of the generated lithium fluoride. In this way, the effect of lithium fluoride in exerting ionic conductivity is not ideal. At the same time, too high a temperature will also make the distribution of lithium fluoride bound to at least the surface of the lithium supplement additive uneven, and it is difficult to form a uniformly distributed lithium fluoride coating layer, such as a fully coated lithium fluoride coating layer. In addition, when the reaction treatment is carried out at too high a temperature, the organic fluorine source decomposes itself or reacts with the raw materials of the lithium supplement material particles to produce by-products, thereby affecting the lithium supplement effect or capacity of the lithium supplement material and reducing the electrochemical performance of the lithium supplement additive. By controlling the reaction treatment conditions such as temperature, the components of the organic fluorine source can be effectively reacted to generate lithium fluoride, and at the same time, the electrochemical performance of the generated lithium supplement material can be improved. Especially when the lithium supplement material contains silicon, the carbon generated by the cracking of the organic fluorine source will react with silicon to generate silicon carbide without electrochemical activity, thereby reducing the capacity of the lithium supplement material. Therefore, in the embodiment, the temperature of the above reaction treatment is 300-600°C. On the one hand, this reaction treatment temperature can effectively make the fluorine source react with the remaining raw materials of the lithium supplement material particles to generate lithium fluoride, and at the same time can effectively reduce or avoid the generation of by-products to improve the excellent lithium supplement effect or capacity of the lithium supplement material, that is, the lithium supplement additive. In addition, the reaction treatment time should be sufficient, such as 1-4 h at the above reaction treatment temperature.

[0078] In a further embodiment, after the step of generating lithium fluoride on at least the surface of the lithium supplement material with a particle morphology after the above reaction treatment, there is also a step of forming a hydrophobic encapsulation layer on the surface of the lithium supplement material. Among them, the hydrophobic encapsulation layer should be a coating layer that covers and distributes on the surface of the lithium supplement material. Such as forming the ionic conductor coating layer or the electronic conductor coating layer or the composite layer of the ionic conductor coating layer and the electronic conductor coating layer contained in the above lithium supplement additive. In addition, the method of forming the hydrophobic encapsulation layer can be selected according to the film layer structure and materials to form the corresponding or suitable method.

[0079] In the embodiment, when the hydrophobic encapsulation layer is a carbon coating layer, the carbon coating layer can be formed by thermal cracking encapsulation using a solid carbon source. If solid carbon source encapsulation is adopted, first, the material obtained by crushing the lithium supplement additive after the above reaction treatment is mixed with the solid-phase carbon source. The mixing methods include at least one of ball mill solid-phase mixing, soybean milk machine mixing, three-dimensional mixer mixing, high-efficiency mixer mixing, and fusion machine mixing. After mixing, sintering is carried out under inert conditions. The carbon source can be at least one of glucose, sucrose, starch, citric acid, cellulose, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), asphalt, etc. The inert atmosphere can be at least one of Ar, N2, and He. The sintering temperature can be 400 - 800 °C, and the time can be 1 - 10 h. This sintering treatment can make the carbon coating layer uniform and dense. If the temperature is too low, the carbon source is difficult to crack, and the carbon coating effect cannot be achieved. If the temperature is too high, the carbon source may crack too fast, resulting in uneven carbon coating. Moreover, when the lithium supplement material contains silicon, carbon and silicon may react at high temperatures to form silicon carbide that does not have electrochemical activity, thereby reducing the material capacity. Finally, the mass ratio of carbon to the lithium supplement material is controlled to be (2 - 20):100. If the final carbon content is too low in this mixing ratio, carbon cannot completely coat the lithium supplement material, and there will be defective positions in the surface conductivity of the material.

[0080] Therefore, the preparation method of the above lithium supplement additive can effectively react the fluorine source directly with the residual alkali contained in the lithium supplement material to generate lithium fluoride, so that the prepared lithium supplement additive has the structural characteristics and corresponding electrochemical properties of the lithium supplement additive in this application, such as at least having a lithium fluoride coating layer in-situ combined on the surface of the lithium supplement material particles, and making the prepared lithium supplement additive have low residual alkali and other impurities, high purity, and the characteristics of isolating the environment, good lithium supplement effect, storage performance, and processing performance. In addition, the preparation method of the lithium supplement additive can ensure the stability of the structure and electrochemical performance of the prepared cathode lithium supplement additive, with high efficiency and cost savings in production.

[0081] In the third aspect, the embodiments of this application also provide an electrode sheet. The electrode sheet in the embodiments of this application includes an electrode current collector and an electrode active layer combined on the surface of the electrode current collector. The electrode active layer contains the electrode lithium supplement additive in the embodiments of this application. Since the electrode sheet in the embodiments of this application contains the above electrode lithium supplement additive in the embodiments of this application, during the charge and discharge process, the lithium supplement additive contained in the electrode sheet plays the above role, and can be consumed first as a "sacrificial agent" during the first-cycle charging process as a lithium source to supplement the irreversible lithium ions consumed for forming the SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the first efficiency and overall electrochemical performance of the battery. Moreover, the quality of the electrode sheet is stable and the yield is high.

[0082] In one embodiment, the mass content of the electrode lithium supplement additive contained in the electrode active layer of the present application can be 1-20 wt%, further 2-10 wt%. The electrode active layer includes, in addition to the electrode lithium supplement additive, an electrode active material, a binder, and a conductive agent. Among them, the binder can be a common electrode binder, such as one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives. In the embodiments of the present application, the conductive agent can be a common conductive agent, such as one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes. The electrode active material can be a positive electrode active material or a negative electrode active material. In specific embodiments, the positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorovanadate, lithium titanate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

[0083] When the electrode sheet of the embodiment of the present application is a positive electrode sheet, the electrode active material contained in the electrode active layer thereof is a positive electrode active material, and the lithium supplement additive of the above embodiment of the present application contained therein is a positive electrode lithium supplement additive. When the electrode sheet of the embodiment of the present application is a negative electrode sheet, the electrode active material contained in the electrode active layer thereof is a negative electrode active material, and the lithium supplement additive of the above embodiment of the present application contained therein is a negative electrode lithium supplement additive.

[0084] In the embodiment, the process of preparing the electrode sheet can be: mixing the electrode active material, the electrode lithium supplement additive, the conductive agent, and the binder to obtain an electrode paste, coating the electrode paste on an electrode current collector, and preparing the electrode sheet through steps such as drying, rolling, and die-cutting.

[0085] Fourthly, the embodiment of the present application also provides a secondary battery. The secondary battery of the embodiment of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, and of course also includes other necessary or auxiliary components. Among them, the positive electrode sheet and / or the negative electrode sheet is the electrode sheet of the above embodiment of the present application. Specifically, when the above electrode sheet is a positive electrode sheet and contains the lithium supplement additive of the above embodiment of the present application, and this lithium supplement additive is a positive electrode lithium supplement additive, then the positive electrode sheet contained in the secondary battery is the electrode sheet (positive electrode sheet) of the above embodiment of the present application. When the above electrode sheet is a negative electrode sheet and contains the lithium supplement additive of the above embodiment of the present application, and this lithium supplement additive is a negative electrode lithium supplement additive, then the negative electrode sheet contained in the secondary battery is the electrode sheet (negative electrode sheet) of the above embodiment of the present application. Or both the positive electrode sheet and the negative electrode sheet contain the lithium supplement additive of the above embodiment of the present application.

[0086] Since the secondary battery in the embodiment of the present application contains the lithium supplement additive in the above-mentioned embodiment of the present application, based on the excellent lithium supplement performance of the lithium supplement additive in the above-mentioned embodiment of the present application, or further having ionic conductivity and / or electronic conductivity and processing performance, the secondary battery in the embodiment of the present application is given excellent initial Coulomb efficiency, battery capacity and cycle performance, long life and stable electrochemical performance.

[0087] The following uses multiple specific examples to illustrate the lithium supplement additive in the embodiment of the present application, its preparation method, application, etc.

[0088] 1. Embodiment of the lithium supplement additive and its particle size control method:

[0089] Example 1

[0090] This embodiment provides a lithium supplement additive and a preparation method. The lithium supplement additive is a granular Li2NiO2 lithium supplement material, and at least a lithium fluoride coating layer is coated on the surface of the lithium supplement material, and a carbon coating layer is further included on the outer surface of the lithium fluoride coating layer. The lithium fluoride coating layer and the carbon coating layer form a hermetic encapsulation layer.

[0091] The control method of the lithium supplement additive in this embodiment includes the following steps:

[0092] S1. Preparation of the Li2NiO2 lithium supplement material particle raw material:

[0093] Li2NiO2 is prepared from lithium hydroxide and nickel hydroxide;

[0094] S2. In-situ formation of lithium fluoride on at least the surface of the Li2NiO2 lithium supplement material particles:

[0095] Under anhydrous conditions, Li2NiO2 is placed in a tube furnace and heated in a nitrogen atmosphere. After the internal temperature of the tube furnace rises to 200°C, according to the weight ratio of the anhydrous organic fluorine source to Li2NiO2 of 8:100, pentafluorobenzene is added to the heatable device, and the reaction is kept at 500°C for 4 h to obtain a fluoride-coated Li2NiO2 material; among them, the method of adding the anhydrous organic fluorine source to the heatable device is: injecting liquid pentafluorobenzene into a container, and the container contains a pipeline connected to the heatable device; continuously introducing an inert gas into the pentafluorobenzene, and making the inert gas bubble in the anhydrous organic fluorine source, and volatilize the pentafluorobenzene through bubbling and enter the heatable device through the pipeline;

[0096] S3. In-situ formation of a carbon coating layer on the surface of the lithium supplement material containing lithium fluoride:

[0097] After the fluoride-coated Li2NiO2 material is first crushed and sieved, carbon coating treatment is carried out. Among them, the method of carbon coating treatment is as follows: After mixing the fluoride-coated Li2NiO2 and pitch at a mass ratio of 3:100, heat treatment is carried out under an argon atmosphere, sintered at 700 °C for 6 h, and taken out after natural cooling; after the carbon coating treatment is completed, it is crushed and sieved for the second time to obtain the final product.

[0098] After testing, the mass content of lithium fluoride in the lithium supplement additive is 3.8%, the average thickness of the carbon coating layer is about 20 nm, and the particle size D50 of the lithium supplement additive is about 3.8 μm.

[0099] Example 2

[0100] This example provides a lithium supplement additive and a preparation method. The lithium supplement additive is a granular Li5FeO4 lithium supplement material, at least a lithium fluoride coating layer is coated on the surface of the lithium supplement material, and a carbon coating layer is further included on the outer surface of the lithium fluoride coating layer. The lithium fluoride coating layer and the carbon coating layer form a hermetic encapsulation layer.

[0101] The control method of the lithium supplement additive in this example includes the following steps:

[0102] S1. Preparation of Li5FeO4 lithium supplement material particle raw materials:

[0103] Prepare Li5FeO4 lithium supplement material particles according to the existing method;

[0104] S2. In-situ formation of lithium fluoride on the surface of at least Li5FeO4 lithium supplement material particles:

[0105] Under anhydrous conditions, place the prepared Li5FeO4 in a tubular furnace and heat it under an argon atmosphere. After the internal temperature of the tubular furnace rises to 350 °C, add benzotrifluoride to the heatable device according to the weight ratio of anhydrous organic fluorine source to Li5FeO4 of 8:100, and keep the temperature at 580 °C for 6 h to obtain Li5FeO4 material with a fluoride layer on the surface;

[0106] S3. In-situ formation of a carbon coating layer on the surface of the lithium supplement material containing lithium fluoride:

[0107] After the Li5FeO4 with a fluoride layer on the surface is first crushed and sieved, carbon coating treatment is carried out. Among them, the method of carbon coating treatment is as follows: After mixing the silicon oxide treated with organic fluorine and glucose at a mass ratio of 5:100, heat treatment is carried out under an argon atmosphere, sintered at 650 °C for 4 h, and taken out after natural cooling; after the carbon coating treatment is completed, it is crushed and sieved for the second time to obtain the final product.

[0108] After detection, the lithium fluoride has a mass content of 4.5% in the lithium supplement additive, the carbon coating layer has a thickness of 50 nm in the lithium supplement additive, and the particle size D50 of the lithium supplement additive is 9.7 μm.

[0109] Example 3

[0110] This comparative example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive in this comparative example is the raw material of the lithium supplement material particles prepared in step S1 of Example 1. Compared with Example 1, the lithium supplement additive in this comparative example does not contain a carbon layer, and the lithium fluoride coating layer is the same as that in Example 1.

[0111] Example 4

[0112] This comparative example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive in this comparative example is the raw material of the lithium supplement material particles prepared in step S1 of Example 2. Compared with Example 2, the lithium supplement additive in this comparative example does not contain a carbon layer, and the lithium fluoride coating layer is the same as that in Example 2.

[0113] Comparative Example 1

[0114] This comparative example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive in this comparative example is the raw material of the lithium supplement material particles prepared in step S1 of Example 1. Compared with Example 1, the lithium supplement additive in this comparative example does not contain a lithium fluoride layer, and the carbon coating layer is the same as that in Example 1.

[0115] Comparative Example 2

[0116] This comparative example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive in this comparative example is the raw material of the lithium supplement material particles prepared in step S1 of Example 2. Compared with Example 2, the lithium supplement additive in this comparative example does not contain a lithium fluoride coating layer, and the carbon coating layer is the same as that in Example 2.

[0117] 2. Lithium-ion battery examples:

[0118] The lithium supplement additives provided in the above Examples 1 to 3 and Comparative Examples 1 to 2 and the lithium supplement additives provided in the comparative examples are assembled into a positive electrode and a lithium-ion battery respectively according to the following method:

[0119] Positive electrode: Under the same conditions, mix according to the mass ratio of lithium supplement additive: Super P-Li: PVDF of 90:5:5. The solvent is NMP, and the mixing method is ball mill mixing or defoaming mixer mixing. If using a ball mill, the ball milling time is 30 min, and the rotation frequency is set to 20 HZ. If using a homogenizing and defoaming machine for mixing, first mix at 600 rpm for 30 seconds, and then mix at 2000 rpm for 15 min. After homogenization - coating - drying - cutting operations, a positive electrode sheet is prepared, and the positive electrode sheet is baked in a vacuum oven at 100 °C to remove trace water. Among them, the lithium supplement additives are the lithium supplement additives provided in the above Examples 1 to 3 and Comparative Examples 1 to 2;

[0120] Negative electrode: Lithium metal sheet;

[0121] Electrolyte: The electrolyte is a 1 mol / L LiPF6 solution, and the solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1;

[0122] Separator: PE separator;

[0123] Battery case: (including negative electrode case, stainless steel gasket, and positive electrode case) Model CR2032

[0124] Lithium-ion battery assembly: Assemble in the order of negative electrode case - stainless steel gasket - lithium metal sheet - separator - electrolyte - positive electrode sheet - positive electrode case in a glove box filled with argon and with water and oxygen contents both lower than 10 ppm to form a button lithium-ion battery.

[0125] 3. Performance tests related to lithium-ion batteries

[0126] Test the relevant electrochemical performances of each lithium-ion battery assembled in the above lithium-ion battery examples. The test conditions are as follows:

[0127] In a 25 °C constant temperature box, place the assembled battery horizontally and let it stand for 6 h before starting the test steps. Charge at a constant current of 0.03C to 4.3V, let it stand for 5 min, and then charge at a constant voltage until the current reaches 0.01C and cut off. Record the capacities in the constant current and constant voltage charging stages and the constant voltage ratio, where the constant voltage ratio is the ratio of the charging capacity in the constant voltage stage to the sum of the charging capacities in the constant current and constant voltage charging stages. The results obtained are shown in Table 1 below.

[0128] Table 1

[0129]

[0130] It can be seen from the embodiments and comparative examples in the above table that when the lithium supplement material lacks a lithium fluoride coating, the constant current stage charging capacity is significantly reduced, and the constant voltage ratio of the constant material internal resistance is significantly increased. This is because there is residual alkali on the surface of the lithium supplement material before it is treated with fluoride, and a small amount of water exists in the environment or battery system during processing, causing the material internal resistance to become significantly larger, but compared to the lithium supplement material with a lithium fluoride coating, due to the presence of a conductive carbon coating, the material conductivity is improved, so the internal resistance will also be reduced accordingly, so the constant voltage ratio is also relatively low. After being treated with lithium fluoride and carbon coating, it is insensitive to trace amounts of water, exerts a very high capacity, and the constant voltage ratio is also very low. Can play an excellent lithium supplement effect.

[0131] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A lithium supplement additive, comprising a particulate lithium supplement material, characterized in that, It also includes lithium fluoride, and the lithium fluoride is at least combined on the surface of the lithium supplement material, and the lithium fluoride is generated by thermal cracking treatment of an organic fluorine source and the lithium supplement material in a protective atmosphere and reaction with the residual alkali contained in the lithium supplement material; wherein, lithium fluoride is also contained in the particle surface layer of the lithium supplement material, and the content of the lithium fluoride combined on the surface of the lithium supplement material is higher than that of the lithium fluoride contained in the particle surface layer; in the lithium supplement additive, the mass percentage content of the lithium fluoride is 0.1-5%; The lithium supplement additive also includes a hydrophobic encapsulation layer, the hydrophobic encapsulation layer covers the lithium supplement material, and covers the lithium fluoride distributed on the surface of the lithium supplement material, and the hydrophobic encapsulation layer includes an electronic conductor encapsulation layer.

2. The lithium supplement additive according to claim 1, characterized in that: The lithium fluoride combined on the surface of the lithium supplement material forms a lithium fluoride coating layer that completely covers or partially covers the lithium supplement material.

3. The lithium supplement additive according to claim 1 or 2, characterized in that: The lithium supplement material includes L x M y O z , Li w at least one of A, wherein L in the molecular formula is Li or / and a mixed alkali metal element of Li and at least one of K and Na not exceeding 30%; M includes at least one of Fe, Co, Ni, Mn, V, Fe-Co, Cu, Mo, Al, Ti, Mg; A includes at least one element of C, N, O, P, S, F, B, Se, 0 < x ≤ 6, 0 < y ≤ 3, 0 < z ≤ 5, 0 < w ≤ 5; and / or The residual alkali contained in the lithium supplement material includes lithium oxide and / or lithium carbonate, the residual amount of lithium oxide is less than 0.15%, and the residual amount of lithium carbonate is less than 0.45%; and / or The lithium supplement additive is a positive electrode lithium supplement additive, and the capacity attenuation rate of the positive electrode sheet prepared from the positive electrode lithium supplement additive, a conductive agent and a binder after being stored for 20 hours at an ambient humidity of 25% relative to the capacity after being stored for 0.5 hours is not more than 30%; or the capacity attenuation rate of the positive electrode sheet prepared from the positive electrode lithium supplement additive, a conductive agent and a binder after being stored for 20 hours at an ambient humidity of 10% relative to the capacity after being stored for 0.5 hours is not more than 20%.

4. The lithium supplement additive according to claim 3, characterized in that: The hydrophobic encapsulation layer includes an ion conductor encapsulation layer.

5. A preparation method of the lithium supplement additive according to any one of claims 1-4, characterized in that, It includes the following steps: In a protective atmosphere, an organic fluorine source and a lithium supplement material particle raw material are mixed and reacted to generate lithium fluoride at least on the surface of the lithium supplement material with a particle morphology.

6. The preparation method according to claim 5, characterized in that, The lithium supplement material particle raw material and the fluorine source are subjected to the mixing treatment according to a mass ratio of 100:(1-15); and / or The temperature of the mixing treatment is 80-400 °C; and / or The temperature of the reaction treatment is 300-600 °C; and / or The generated lithium fluoride forms a lithium fluoride coating layer that completely covers or partially covers the lithium supplement material.

7. The preparation method according to claim 5 or 6, characterized in that, The protective atmosphere is formed by continuously introducing a chemically inert gas, and the chemically inert gas is introduced into the lithium supplement material particle raw material for bubbling treatment to achieve the mixing treatment.

8. The preparation method according to claim 7, characterized in that, The organic fluorine source is mixed with the lithium supplement material particle raw material in a flowing manner and the reaction treatment is carried out simultaneously; and / or The organic fluorine source includes an organic fluoride that decomposes below 600 °C and does not contain hydroxyl groups.

9. An electrode sheet, comprising a current collector and an electrode active layer bonded to the surface of the current collector, characterized in that: The electrode active layer contains the lithium supplement additive according to any one of claims 1-4 or the lithium supplement additive prepared by the preparation method according to any one of claims 5-8.

10. A secondary battery, comprising a positive electrode sheet and a negative electrode sheet, characterized in that: The positive electrode sheet is the electrode sheet according to claim 9, and the lithium supplement additive contained in the electrode sheet is a positive electrode lithium supplement additive; and / or The negative electrode sheet is the electrode sheet according to claim 9, and the lithium supplement additive contained in the electrode sheet is a negative electrode lithium supplement additive.

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