Composite lithium supplementing material and preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a composite lithium supplementing material and a preparation method and application thereof. The composite lithium supplement material comprises an inner core containing a lithium supplement material and a functional layer coating the outer surface of the inner core, wherein the functional layer contains a metal oxide and a fluorinated aromatic compound. The composite lithium supplementing material has an excellent lithium supplementing effect, can effectively supplement loss of lithium ions in the charging and discharging process of the battery, and improves the capacity stability of the battery. Through the coated functional layer structure and material design, the composite lithium supplement material can reduce residual alkali residues, can timely adsorb and capture oxygen molecules / oxygen free radicals generated in the battery, effectively generates structures and substances beneficial to a battery system, and optimizes the construction of an SEI film. The oxygen generated by lithium removal after battery charging and discharging is greatly reduced, the oxygen yield after a high-temperature storage stage is also greatly reduced, the cycling stability of the battery is effectively improved, and the service life of the battery is effectively prolonged.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a composite lithium supplement material and a preparation method and application thereof. Background Art

[0002] During the first cycle of charging of lithium-ion batteries, the solid electrolyte interface formed on the negative electrode surface will irreversibly consume the active lithium in the battery system, resulting in a decrease in battery energy density and a shortened cycle life. Pre-lithiation technology is considered to be an effective way to solve the problem of active lithium loss in batteries.

[0003] Lithium-rich cobalt oxide and other lithium supplements have a high theoretical capacity, but their large residual alkali, poor air stability and obvious gas production during high-temperature storage affect their application. After the first cycle of charge and discharge, the lithium supplement material will produce a large amount of oxygen molecules or oxygen free radicals, which diffuse into the electrolyte and undergo oxidation and decomposition reactions with some components in the electrolyte to form a large amount of carbon dioxide, hydrogen and other gases. The increase in gas production will cause the battery to swell and induce safety problems.

[0004] Therefore, there is an urgent need to provide a lithium-supplementing material with high stability in the air storage environment and low gas production during use. Summary of the invention

[0005] The purpose of the present application is to provide a composite lithium supplement material and a preparation method and application thereof, aiming to solve the problem of large gas production and poor stability during the use of existing lithium supplement materials to a certain extent.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present application provides a composite lithium supplement material, comprising a core containing a lithium supplement material and a functional layer coated on the outer surface of the core, wherein the functional layer contains a metal oxide and a fluorinated aromatic compound.

[0008] In some possible implementations, the metal oxide is disposed in contact with the lithium supplementing material and the fluorinated aromatic compound.

[0009] In some possible implementations, the fluorinated aromatic compound, under the catalytic action of the metal oxide, reacts with oxygen atoms to generate an oxygen capture functional material.

[0010] In some possible implementations, the metal oxide and the fluorinated aromatic compound are in close contact with each other on the outer surface of the inner core to form the fully encapsulated functional layer; wherein the metal oxide is located between the inner core and the fluorinated aromatic compound.

[0011] In some possible implementations, the metal oxide includes at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide, and nano palladium oxide.

[0012] In some possible implementations, the fluorinated aromatic compound includes at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine.

[0013] In some possible implementations, the lithium supplement material includes at least one of lithium-rich lithium cobalt oxide, lithium-rich lithium nickel oxide, lithium-rich lithium iron oxide, and lithium-rich lithium manganese oxide.

[0014] In some possible implementations, the oxygen capture functional material includes 4-fluoro-1,2-benzoquinone.

[0015] In some possible implementations, in the functional layer, the mass ratio of the metal oxide to the fluorinated aromatic compound is (1-3):10.

[0016] In some possible implementations, in the composite lithium-supplementing material, the mass ratio of the core to the functional layer is 10:(0.3-1).

[0017] In some possible implementations, the particle size D50 of the metal oxide is 100 nm to 300 nm.

[0018] In some possible implementations, the thickness of the functional layer is 50 nm to 300 nm.

[0019] In some possible implementations, the particle size D50 of the inner core is 5 μm to 45 μm.

[0020] In some possible implementations, the water absorption rate of the composite lithium-replenishing material is no higher than 5.0 ppm / s in an environment with a humidity of 40%.

[0021] In a second aspect, the present application provides a method for preparing a composite lithium supplement material, comprising the following steps:

[0022] Obtain lithium supplement materials;

[0023] A functional layer including metal oxide and fluorinated aromatic compound is prepared on the surface of the lithium supplement material to obtain a composite lithium supplement material.

[0024] In some possible implementations, the step of preparing the functional layer includes: under an inert atmosphere, mixing the lithium supplement material with the metal oxide, adding the powder of the fluorinated aromatic compound for mixing, heating to 150°C to 200°C at a heating rate of 1°C / min to 3°C / min, keeping warm for 3 to 6 hours, grinding and sieving to obtain the composite lithium supplement material.

[0025] In some possible implementations, the mass ratio of the metal oxide to the fluorinated aromatic compound is (1-3):10.

[0026] In some possible implementations, the ratio of the mass of the lithium supplementing material to the total mass of the metal oxide and the fluorinated aromatic compound is 10:(0.3-1).

[0027] In some possible implementations, the metal oxide includes at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide, and nano palladium oxide.

[0028] In some possible implementations, the fluorinated aromatic compound includes at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine.

[0029] In some possible implementations, the lithium supplement material includes at least one of lithium-rich lithium cobalt oxide, lithium-rich lithium nickel oxide, lithium-rich lithium iron oxide, and lithium-rich lithium manganese oxide.

[0030] In a third aspect, the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet contains the above-mentioned composite lithium supplement material or the composite lithium supplement material prepared by the above-mentioned method.

[0031] In some possible implementations, in the positive electrode material layer of the positive electrode sheet, the mass percentage of the composite lithium supplementing material is 2% to 5%.

[0032] The composite lithium supplement material provided in the first aspect of the present application comprises a core containing a lithium supplement material and a functional layer coated on its outer surface, wherein the functional layer comprises a metal oxide and a fluorinated aromatic compound. On the one hand, by coating the functional layer, the residual alkali residue of the lithium supplement material can be effectively reduced, and the environmental stability of the lithium supplement material can be improved. On the other hand, the metal oxide in the functional layer not only has a high conductivity, which is beneficial to improve the efficiency of electron migration and transfer, but also has a good catalytic effect. Under the catalytic action of the metal oxide, the fluorinated aromatic compound can react with the oxygen molecules / oxygen free radicals generated by the lithium removal during the first cycle of charging and discharging of the battery and the oxygen molecules / oxygen free radicals generated by the lithium removal product initiation reaction to generate fluorobenzoquinone. Fluorobenzoquinone has an excellent oxygen capture function, and can be dissolved in the electrolyte to continuously absorb and capture the oxygen molecules / oxygen free radicals generated by the battery during the charging and discharging stage and high temperature storage or lithium removal product reaction, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the energy efficiency and cycle life when compounded with the positive electrode material. In addition, the F element in the fluorinated aromatic compound has high electronegativity, high ion potential and low polarizability, and can also participate in the construction of the SEI solid electrolyte interface film through synergistic transformation, which can help lithium ions to deposit more evenly at the negative electrode, so as to construct a uniform and stable LiF-rich interface film, which can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery. Therefore, the composite lithium supplement material of the present application has an excellent lithium supplement effect, can effectively supplement the loss of lithium ions during the battery charging and discharging process, and improve the battery capacity stability. In addition, through the coated functional layer structure and material design, the composite lithium supplement material can timely adsorb and capture the oxygen molecules / oxygen free radicals generated by the lithium removal and the oxygen molecules / oxygen free radicals generated by the lithium removal product initiation reaction, effectively generate structures and substances that are beneficial to the battery system, and optimize the construction of the SEI film. The oxygen generated by the lithium removal after the battery charging and discharging is greatly reduced, and the oxygen production after the high temperature storage stage is also greatly reduced, which effectively improves the cycle stability and service life of the battery.

[0033] The preparation method of the composite lithium supplement material provided in the second aspect of the present application, a functional layer including metal oxide and fluorinated aromatic compound is prepared on the surface of the lithium supplement material, and the residual alkali residue of the lithium supplement material can be effectively reduced by coating the functional layer, and the environmental stability of the lithium supplement material can be improved. Among them, the metal oxide has a high conductivity, and can catalyze the fluorinated aromatic compound and the oxygen molecules / oxygen free radicals generated by the de-lithiation process of the first cycle of the battery charge and discharge, and the oxygen molecules / oxygen free radicals generated by the de-lithiation product initiation reaction to generate fluorobenzoquinone and other oxygen capture functions. It can continuously absorb and capture the oxygen molecules / oxygen free radicals generated by the battery during the charge and discharge stage and high temperature storage or de-lithiation product reaction, reduce gas enrichment and achieve less lithium loss and inhibit the decomposition of the electrolyte, and improve the energy efficiency and cycle life when compounded with the positive electrode material. It can also participate in the construction of the SEI solid electrolyte interface film through synergistic transformation, and can help lithium ions to deposit more evenly at the negative electrode to construct a uniform and stable LiF-rich interface film, which can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery.

[0034] In the secondary battery of the present application, the positive electrode sheet contains the above-mentioned composite lithium supplement material, which has good lithium supplement effect, small amount of residual alkali, small amount of gas production, high environmental stability, long cycle life, and improves the electrochemical properties of the secondary battery such as energy density, conductivity, and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 It is a schematic diagram of the three-dimensional model structure of the composite lithium supplement material provided in the embodiment of the present application;

[0037] Figure 2 Schematic diagram of the process for preparing the composite lithium supplement material provided in the embodiment of the present application;

[0038] Figure 3 This is a transmission electron microscope image of the composite lithium supplement material provided in Example 1 of the present application. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the 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.

[0040] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0041] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0042] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0043] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0044] The weight of the relevant components mentioned in the embodiments of the present specification can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components in the embodiments of the present specification is proportionally enlarged or reduced, it is within the scope disclosed in the embodiments of the present specification. Specifically, the mass in the embodiments of the present specification can be μg, mg, g, kg and other mass units known in the chemical industry.

[0045] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0046] The first aspect of the present application provides a composite lithium supplement material, Figure 1As shown, it includes a core containing a lithium supplement material and a functional layer coated on the outer surface of the core, wherein the functional layer contains a metal oxide and a fluorinated aromatic compound.

[0047] The composite lithium supplement material provided in the first aspect of the embodiment of the present application includes a core containing a lithium supplement material and a functional layer coated on its outer surface, and the functional layer contains metal oxides and fluorinated aromatic compounds. On the one hand, through the coating of the functional layer, the residual alkali residue of the lithium supplement material can be effectively reduced, and the environmental stability of the lithium supplement material can be improved. On the other hand, the metal oxide in the functional layer not only has a high conductivity, which is conducive to improving the efficiency of electron migration and transfer, but also has a good catalytic effect. Under the catalytic action of the metal oxide, the fluorinated aromatic compound can react with the oxygen molecules / oxygen free radicals generated by the lithium removal during the first cycle of charging and discharging of the battery and the oxygen molecules / oxygen free radicals generated by the lithium removal product initiation reaction to generate compounds such as fluorobenzoquinone. Fluorobenzoquinone and other compounds have excellent oxygen capture function, and can be dissolved in the electrolyte to continuously absorb and capture the oxygen molecules / oxygen free radicals generated by the battery during the charging and discharging stage and high temperature storage or lithium removal product reaction, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the energy efficiency and cycle life when compounded with the positive electrode material. In addition, the F element in the fluorinated aromatic compound has high electronegativity, high ion potential and low polarizability, and can also participate in the construction of the SEI solid electrolyte interface film through synergistic transformation, which can help lithium ions to deposit more evenly at the negative electrode to construct a uniform and stable LiF-rich interface film, which can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery. Therefore, the composite lithium supplement material of the embodiment of the present application has an excellent lithium supplement effect, can effectively supplement the loss of lithium ions during the battery charging and discharging process, and improve the battery capacity stability. In addition, through the coated functional layer structure and material design, the composite lithium supplement material can timely adsorb and capture the oxygen molecules / oxygen free radicals generated by the lithium removal and the oxygen molecules / oxygen free radicals generated by the lithium removal product initiation reaction, effectively generate structures and substances that are beneficial to the battery system, and optimize the construction of the SEI film. The oxygen generated by lithium removal after the battery charging and discharging is greatly reduced, and the oxygen production after the high temperature storage stage (for example, the battery is charged to a certain voltage and aged at 60°C for 12 hours to observe the gas production) is also greatly reduced, which effectively improves the cycle stability and service life of the battery.

[0048] In some possible implementations, the metal oxide is arranged in contact with the lithium supplement material and the fluorinated aromatic compound. In some possible implementations, the metal oxide and the fluorinated aromatic compound are in close contact with each other on the outer surface of the inner core to form a fully encapsulated functional layer; wherein the metal oxide is located between the inner core and the fluorinated aromatic compound. In this case, the portion of the metal oxide in contact with the lithium supplement material can better improve the efficiency of electron migration and improve the conductivity, and the portion of the metal oxide in contact with the fluorinated aromatic compound can better catalyze the reaction between the fluorinated aromatic compound and the oxygen atom.

[0049] In some possible implementations, fluorinated aromatic compounds react with oxygen atoms under the catalytic action of metal oxides to generate oxygen capture functional materials. Under the catalytic action of metal oxides, fluorinated aromatic compounds can react with oxygen molecules / oxygen free radicals generated by the lithium-supplementing material during the first cycle of charge and discharge of the battery, as well as oxygen molecules / oxygen free radicals generated by the delithiation product and the side reaction caused by the electrolyte to generate products such as fluorobenzoquinone. The generated products such as fluorobenzoquinone have excellent oxygen capture function. Fluorobenzoquinone and other products with oxygen capture function dissolved in the electrolyte can continuously absorb and capture oxygen molecules / oxygen free radicals generated by the battery during the charge and discharge stage, high temperature storage or delithiation product reaction, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the energy efficiency and cycle life when compounded with positive active materials such as lithium iron phosphate.

[0050] In some possible implementations, the metal oxide includes at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide, and nano palladium oxide. In this case, these metal oxides not only have high conductivity, which is beneficial to improving the efficiency of electron transfer, but also have no side effects on the battery system, and have good catalytic effects. They can catalyze the reaction of fluorinated aromatic compounds with oxygen to generate oxygen capture materials such as fluorobenzoquinone.

[0051] In some possible implementations, the particle size D50 of the metal oxide is 100 nm to 300 nm. Exemplarily, the particle size D50 of the metal oxide can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any typical but non-limiting point value or an interval value between any two point values. In this case, the metal oxide with a nanoparticle size has a larger specific surface area and more abundant active reaction sites, and can better catalyze the reaction of fluorinated aromatic compounds with oxygen to form fluorobenzoquinone.

[0052] In some possible implementations, the fluorinated aromatic compound includes at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine. These fluorinated aromatic compounds are easily combined with oxygen and oxidized to fluorobenzoquinone under the action of metal oxides such as silver oxide as catalysts.

[0053] In some possible implementations, the fluorinated aromatic compound includes at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine. Exemplarily, after the first cycle of charge and discharge of the lithium supplement material, the silver oxide-containing 4-fluorocatechol on its outer layer preferentially adsorbs a large amount of oxygen molecules or oxygen free radicals, thereby generating an oxidation reaction to generate a functional 4-fluoro-1,2-benzoquinone product, which is dissolved in the electrolyte as a good additive. Subsequently, the functional 4-fluoro-1,2-benzoquinone product dissolved in the electrolyte will continue to capture the oxygen molecules / oxygen free radicals generated by the first cycle of charge and discharge, high temperature storage or lithium removal product reaction, and then synergistically transform and participate in the construction of the SEI film to construct a uniform and stable LiF-rich interface film, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the energy efficiency and cycle life when compounded with lithium iron phosphate.

[0054] In some possible implementations, the oxygen capture functional material includes 4-fluoro-1,2-benzoquinone. In this case, with metal oxides such as silver oxide as a catalyst, 4-fluorocatechol combines with oxygen and oxidizes to form 4-fluoro-1,2-benzoquinone. 4-Fluoro-1,2-benzoquinone has excellent oxygen capture function. When dissolved in the electrolyte, it can continuously absorb and capture oxygen molecules / oxygen free radicals generated by the battery during the charge and discharge stage and high-temperature storage or delithiation product reaction, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the energy efficiency and cycle life when compounded with lithium iron phosphate. It can also participate in the construction of SEI solid electrolyte interface film through synergistic transformation, help lithium ions to deposit more evenly at the negative electrode, so as to construct a uniform and stable LiF-rich interface film, which can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery.

[0055] In some possible implementations, the lithium supplement material includes at least one of lithium cobalt-rich lithium, lithium nickel-rich lithium, lithium iron-rich lithium, and lithium manganese-rich lithium. These lithium supplement materials have relatively high capacity, but have large residual alkali and relatively poor stability. The coating of the functional layer containing metal oxides and fluorinated aromatic compounds in the embodiment of the present application can significantly reduce the residual alkali of the lithium supplement material, reduce gas production, and improve the stability of the lithium supplement material.

[0056] In some possible implementations, in the functional layer, the mass ratio of the metal oxide to the fluorinated aromatic compound is (1-3):10, which can be any typical but non-limiting point value such as 1:10, 2:10, 3:10, or an interval value between any two points. In this case, the content of the metal oxide ensures both the improvement of the electrical conductivity and the catalytic effect on the fluorinated aromatic compound, and fully catalyzes the reaction of the fluorinated aromatic compound with oxygen to generate fluorobenzoquinone.

[0057] In some possible implementations, in the composite lithium supplement material, the mass ratio of the core to the functional layer is 10:(0.3-1), specifically, it can be 10:0.3, 10:0.4, 10:0.5, 10:0.6, 10:0.7, 10:0.8, 10:0.9, 10:1, etc., typical but non-restrictive arbitrary point values ​​or interval values ​​between any two point values. In this case, the content of the core ensures the lithium supplement effect of the composite lithium supplement material.

[0058] In some possible implementations, the particle size D50 of the core is 5 μm to 45 μm, and can be any typical but non-limiting point value or interval value between any two point values ​​such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, etc. In this case, the core lithium supplement material has a larger active specific surface area, which is conducive to improving the lithium supplement effect.

[0059] In some possible implementations, the thickness of the functional layer is 50nm to 300nm. Exemplarily, the thickness of the functional layer can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, or any other typical but non-limiting point value or an interval value between any two point values. In this case, the functional layer coated on the outer surface of the lithium supplement material can effectively reduce the residual alkali residue, reduce the gas production, and improve the stability and service life of the material.

[0060] In some possible implementations, the composite lithium supplement material has a water absorption rate of no more than 5.0 ppm / s in an environment with a humidity of 40%, specifically no more than 4.5 ppm / s, further no more than 4 ppm / s, further no more than 3 ppm / s, further no more than 2 ppm / s, further no more than 1 ppm / s, etc. The lithium supplement material coated with the functional layer of the embodiment of the present application has good environmental stability, low water absorption, and good storage performance.

[0061] In a second aspect, the present invention provides a method for preparing a composite lithium supplement material. Figure 2 As shown, the following steps are included:

[0062] S10. Obtaining lithium supplement materials;

[0063] S20. Preparing a functional layer including metal oxides and fluorinated aromatic compounds on the surface of the lithium supplement material to obtain a composite lithium supplement material.

[0064] The preparation method of the composite lithium supplement material provided in the second aspect of the embodiment of the present application, a functional layer including metal oxide and fluorinated aromatic compound is prepared on the surface of the lithium supplement material, and the residual alkali residue of the lithium supplement material can be effectively reduced by coating the functional layer, and the environmental stability of the lithium supplement material can be improved. Among them, the metal oxide has a high conductivity, and can catalyze the fluorinated aromatic compound and the oxygen molecules / oxygen free radicals generated by the de-lithiation process of the first cycle of the battery charge and discharge, and the oxygen molecules / oxygen free radicals generated by the de-lithiation product initiation reaction to generate fluorobenzoquinone and other oxygen capture functions. It can continuously absorb and capture the oxygen molecules / oxygen free radicals generated by the battery during the charge and discharge stage and high temperature storage or de-lithiation product reaction, reduce gas enrichment and achieve less lithium loss and inhibit the decomposition of the electrolyte, and improve the energy efficiency and cycle life when compounded with the positive electrode material. It can also participate in the construction of the SEI solid electrolyte interface film through synergistic transformation, and can help lithium ions to deposit more evenly at the negative electrode to construct a uniform and stable LiF-rich interface film, which can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery.

[0065] In the above step S10, in some possible implementations, the lithium supplement material includes at least one of lithium cobalt-rich lithium, lithium nickel-rich lithium, lithium iron-rich lithium, and lithium manganese-rich lithium. These lithium supplement materials have relatively high capacity, but have large residual alkali and relatively poor stability. Through the coating of the functional layer containing metal oxides and fluorinated aromatic compounds in the embodiment of the present application, the residual alkali of the lithium supplement material can be significantly reduced, the gas production can be reduced, and the stability of the lithium supplement material can be improved.

[0066] In some possible implementations, the lithium supplement material includes lithium-rich cobalt oxide Li6CoO4, and the synthesis steps include: weighing an appropriate amount of lithium oxide and cobalt tetraoxide, wherein the molar ratio of lithium to cobalt is 5 to 7:1, and then mixing them evenly through a degassing machine, and then transferring them to a nickel metal ark in an argon-protected glove box, and then quickly transferring them to an atmosphere tube furnace. Under an argon / argon protective atmosphere, the temperature is raised to 600°C to 800°C at a heating rate of 2°C / min, kept warm for 6 to 10 hours, and then programmed to cool at a rate of 2 to 5°C / min. After cooling, the product is quickly transferred to an atmosphere glove box for crushing and sieving to obtain a dark blue powder, namely the Li6CoO4 lithium supplement material.

[0067] In the above step S20:

[0068] In some possible implementations, the step of preparing the functional layer includes: mixing the lithium supplement material with the metal oxide under an inert atmosphere, adding the powder of the fluorinated aromatic compound for mixing, heating to 150°C to 200°C at a heating rate of 1°C / min to 3°C / min, keeping warm for 3 to 6 hours, grinding and sieving, and obtaining a composite lithium supplement material. In this case, a functional layer containing metal oxides and fluorinated aromatic compounds is formed in situ on the surface of the lithium supplement material by a high-temperature molten liquid phase method, so that the metal oxides and fluorinated aromatic compounds are stably coated on the outer surface of the lithium supplement material to form a coating structure, which reduces the residual alkali residue of the material while further improving the environmental stability of the lithium supplement material.

[0069] Exemplarily, the heating rate for preparing the functional layer can be 1°C / min, 2°C / min, 3°C / min, or other typical but non-limiting arbitrary point values, or an interval value between any two point values; the insulation temperature can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or other typical but non-limiting arbitrary point values, or an interval value between any two point values; the insulation time can be 3 hours, 4 hours, 5 hours, 6 hours, or other typical but non-limiting arbitrary point values, or an interval value between any two point values.

[0070] In some possible implementations, the mass ratio of the metal oxide to the fluorinated aromatic compound is (1-3): 10. In this case, the content of the metal oxide ensures both the improvement of the electrical conductivity and the catalytic effect on the fluorinated aromatic compound, fully catalyzing the reaction of the fluorinated aromatic compound with oxygen to generate fluorobenzoquinone.

[0071] In some possible implementations, the ratio of the mass of the lithium supplementing material to the total mass of the metal oxide and the fluorinated aromatic compound is 10:(0.3-1). In this case, the content of the lithium supplementing material ensures the lithium supplementing effect of the composite lithium supplementing material.

[0072] In some possible implementations, the metal oxide includes at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide, and nano palladium oxide; these metal oxides not only have high conductivity, which is beneficial to improving the efficiency of electron transfer, but also have no side effects on the battery system, and have good catalytic effects. They can catalyze the reaction of fluorinated aromatic compounds with oxygen to generate oxygen capture materials such as fluorobenzoquinone.

[0073] In some possible implementations, the fluorinated aromatic compounds include at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine; these fluorinated aromatic compounds are easily combined with oxygen and oxidized into fluorobenzoquinone under the action of metal oxides such as silver oxide as catalysts.

[0074] In some embodiments, the step of preparing the functional layer includes: weighing the powder of the above-mentioned lithium supplement material and an appropriate amount of metal oxide powder such as silver oxide in an argon-protected glove box, and uniformly mixing them in a degassing machine. Pulverizing fluorinated aromatic compounds such as 4-fluorocatechol, and weighing a certain mass of the pulverized fluorinated aromatic compound powder and adding it to the mixed powder, and then uniformly mixing it in a degassing machine, and then transferring it to a metal nickel boat and placing it in an atmosphere tube furnace, heating it to 150°C to 200°C at a rate of 2°C / min in an argon atmosphere, and keeping it warm for 3 to 6 hours. After the reaction is completed, the product is ground and sieved to obtain a composite lithium supplement material with a functional layer coated with a lithium supplement material.

[0075] In a third aspect, an embodiment of the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet contains the above composite lithium supplement material or the composite lithium supplement material prepared by the above method.

[0076] In the secondary battery of the embodiment of the present application, the positive electrode sheet contains the above-mentioned composite lithium supplement material. The composite lithium supplement material has good lithium supplement effect, small amount of residual alkali, small amount of gas production, high environmental stability, and long cycle life, thereby improving the electrochemical properties of the secondary battery such as energy density, conductivity, and cycle life.

[0077] The present application does not specifically limit the positive electrode sheet, negative electrode sheet, electrolyte, separator, etc. in the secondary battery of the embodiment, and can be applied to any battery system.

[0078] In some possible implementations, the positive electrode sheet includes a current collector and a positive electrode material layer formed on the surface of the current collector, and the positive electrode material layer includes the above-mentioned composite lithium supplement material or the composite lithium supplement material prepared by the above-mentioned method. The composite lithium supplement material has the characteristics of good structural stability, excellent lithium supplement effect, high conductivity, good rate performance, good cycle stability, etc., thereby improving the electrochemical properties of the positive electrode sheet, such as stability, capacity, rate performance, cycle performance, etc.

[0079] In some possible implementations, the mass percentage of the composite lithium supplement material in the positive electrode material layer of the positive electrode sheet is 2% to 5%, which can be 2%, 3%, 4%, 5% or any other typical but non-restrictive point value or an interval value between any two point values. In this case, the amount of the composite lithium supplement material added to the material layer of the positive electrode sheet fully ensures the lithium supplement effect on the positive electrode sheet, can effectively supplement the loss of lithium ions during the charging and discharging process, and can participate in the construction of the SEI film to construct a uniform and stable LiF-rich interface film, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the cycle life of the battery and other performance.

[0080] In some possible implementations, the preparation of the positive electrode material layer includes the steps of: mixing the above-mentioned composite lithium supplement material, conductive agent and binder to form an electrode slurry, coating the electrode slurry on the current collector, and preparing a positive electrode sheet through steps such as drying, rolling and die cutting.

[0081] In some possible implementations, the current collector of the positive electrode sheet includes but is not limited to any one of copper foil and aluminum foil.

[0082] In some possible implementations, the content of the binder in the active material layer of the positive electrode sheet is 2 wt% to 5 wt%. In specific embodiments, the content of the binder can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc., which are typical but not limiting contents.

[0083] In some possible implementations, the binder includes one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0084] In some possible implementations, the content of the conductive agent in the active material layer of the positive electrode sheet is 1 wt% to 5 wt%. In specific embodiments, the content of the conductive agent can be 3 wt%, 4 wt%, 5 wt%, etc., which are typical but not limiting contents.

[0085] In some possible implementations, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes.

[0086] In some possible implementations, the negative electrode active material of the secondary battery includes, but is not limited to, carbon materials such as graphite, soft carbon (such as coke), hard carbon, or nitrides, tin-based oxides, tin-based oxides, tin alloys, and nano-negative electrode materials, etc. The current collector includes, but is not limited to, any one of copper foil and aluminum foil.

[0087] In some possible embodiments, the steps of making a negative electrode sheet include: mixing a negative electrode active material with a conductive agent such as conductive carbon black, a binder such as carboxymethyl cellulose and styrene-butadiene rubber, and a solvent such as water in a mass ratio of (80-99):(1-5):(2-10):100 to make a negative electrode mixed slurry, vacuum degassing, discharging, coating on a coating machine, and obtaining a negative electrode sheet after rolling, slitting, and die-cutting.

[0088] In some possible implementations, the separator can block the passage of electrons and allow the passage of ions. Exemplarily, the separator includes, but is not limited to, at least one material selected from polypropylene fiber, polyacrylonitrile fiber, polyvinyl formal fiber, poly(ethylene terephthalate), polyethylene terephthalate, polyamide fiber, and poly(p-phenylene terephthalamide).

[0089] In some possible implementations, the electrolyte includes at least one soluble metal salt. In some specific embodiments, the metal salt includes LiClO4, LiBF4, LiPF6, LiAsF6, LiCF3SO3, LiTDI, Li[(CF3SO2)2N], Li[(FSO2)2N], Li[(C m F 2m+1 SO2)(C n F 2n+1 SO2)N], wherein m and n are natural numbers. These electrolytic salts can ensure high ionic conductivity of the electrolyte, and do not cause harmful side reactions with electrode materials, electrolytes, diaphragms, etc., and have good chemical stability.

[0090] In some possible implementations, the secondary battery includes at least one of a battery cell, a battery module, and a battery pack.

[0091] In some possible implementations, the battery cell types include lithium-ion batteries and the like.

[0092] In some possible implementations, the battery cells of the present application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Further, the battery module can also include a housing with a storage space, and multiple battery cells are stored in the storage space.

[0093] In a possible implementation, the battery cells and / or battery modules may also be assembled into a battery pack, and the number of battery cells or battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0094] In order to enable the above implementation details and operations of the present application to be clearly understood by those skilled in the art, and to demonstrate the significant performance improvements of the composite lithium supplement material and its preparation method and application in the embodiments of the present application, the above technical solution is illustrated by multiple embodiments below.

[0095] Example 1

[0096] A composite lithium supplement material comprises a core of a Li6CoO4 lithium supplement material and a functional layer coated on its outer surface, wherein the functional layer comprises silver oxide and 4-fluorocatechol; wherein the mass ratio of nano silver oxide powder to 4-fluorocatechol is 2:10, and the mass ratio of the coating functional layer material to the core material is 0.5:10.

[0097] Its preparation comprises the following steps:

[0098] 1. Synthesis of Li6CoO4, a lithium supplement for the inner core: Weigh an appropriate amount of lithium oxide and cobalt tetraoxide, where the molar ratio of lithium to cobalt is 5 to 7:1, and then mix them evenly through a degassing machine, and then transfer them to a nickel metal ark in an argon-protected glove box, and then quickly transfer them to an atmosphere tube furnace. In an argon / argon protective atmosphere, heat the mixture to 600°C at a heating rate of 2°C / min, keep the temperature for 6 hours, and then perform a programmed cooling at a rate of 2°C / min. After cooling, quickly transfer the product to an atmosphere glove box for crushing and sieving to obtain a dark blue powder, namely, the Li6CoO4 lithium supplement material.

[0099] 2. Preparation of composite lithium supplement material containing nano silver oxide and 4-fluorocatechol functional layer:

[0100] ① In an argon-protected glove box, weigh the above blue powder and an appropriate amount of nano silver oxide powder, and mix them evenly in a degassing machine. ② Crush 4-fluorocatechol, weigh a certain amount of crushed 4-fluorocatechol powder and add it to the mixed powder in step 1, then mix evenly in a degassing machine, then transfer it to a metal nickel boat and place it in an atmosphere tube furnace, heat it to 200°C at a rate of 2°C / min in an argon atmosphere, and keep it warm for 3 hours. After the reaction is completed, the product is ground and sieved to obtain a Li6CoO4 material coated with a functional layer, that is, a composite lithium supplement material.

[0101] Example 2

[0102] The embodiment of the present application uses LFO as the core. The difference between it and Example 1 lies in the preparation of the inner core lithium supplement in step 1: weigh appropriate amounts of lithium oxide and iron oxide, where the molar ratio of lithium to cobalt is 5:1, and then mix them evenly through a degasser, and then transfer them to a nickel metal ark in an argon-protected glove box, and then quickly transfer them to an atmosphere tube furnace. Under an argon / argon protective atmosphere, heat the temperature to 700°C at a heating rate of 2°C / min, keep warm for 6 hours, and then perform program cooling at a rate of 2°C / min. After cooling, the product is quickly transferred to an atmosphere glove box for crushing and sieving to obtain a brown powder, namely the Li5FeO4 lithium supplement material.

[0103] Example 3

[0104] The difference between the embodiment of the present application and embodiment 1 is that in step 2, nano silver oxide is replaced by nano platinum dioxide, and the other steps and proportions remain unchanged.

[0105] Example 4

[0106] The difference between the embodiment of the present application and embodiment 1 is that in step 2, 4-fluorocatechol is replaced by 4-fluoro-o-phenylenediamine, and the other steps and proportions remain unchanged.

[0107] Example 5

[0108] The difference between the embodiment of the present application and embodiment 1 is that in step 2, the mass ratio of nano silver oxide to 4-fluorocatechol is adjusted to 1:10, and the mass ratio of the coating layer to the core material remains unchanged.

[0109] Example 6

[0110] The difference between the embodiment of the present application and embodiment 1 is that in step 2, the mass ratio of nano silver oxide to 4-fluorocatechol is adjusted to 4:10, and the mass ratio of the coating layer to the core material remains unchanged.

[0111] Example 7

[0112] The difference between the embodiment of the present application and embodiment 1 is that in step 2, the mass ratio of the coating layer to the core material is adjusted to 0.3:10, and the other steps and ratios remain unchanged.

[0113] Example 8

[0114] The difference between the embodiment of the present application and embodiment 1 is that in step 2, the mass ratio of the coating layer to the core material is adjusted to 1:10, and the other steps and ratios remain unchanged.

[0115] Comparative Example 1

[0116] A battery made of pure LFP (lithium iron phosphate LiFePO4) material is used as comparative example 1, that is, no additional lithium supplement is added to the positive electrode of the battery.

[0117] Comparative Example 2

[0118] A Li6CoO4 lithium supplement material, the preparation steps of which include: synthesis of a core lithium supplement agent Li6CoO4: weighing an appropriate amount of lithium oxide and cobalt tetraoxide, wherein the molar ratio of lithium to cobalt is 5 to 7:1, and then mixing them evenly through a degassing machine, and then transferring them to a nickel metal ark in an argon-protected glove box, and then quickly transferring them to an atmosphere tube furnace. In an argon / argon protective atmosphere, the temperature is raised to 600°C at a heating rate of 2°C / min, kept warm for 6 hours, and then programmed to cool at a rate of 2°C / min. After cooling, the product is quickly transferred to an atmosphere glove box for crushing and sieving to obtain a dark blue powder, namely the Li6CoO4 lithium supplement material.

[0119] Comparative Example 3

[0120] This comparative example is Li5FeO4 without any coating. Weigh appropriate amounts of lithium oxide and ferric oxide, where the molar ratio of lithium to iron is 5:1, and then mix them evenly through a degasser. Then transfer them to a nickel metal ark in an argon-protected glove box, and then quickly transfer them to an atmosphere tube furnace. In an argon / argon protective atmosphere, heat the mixture to 700°C at a rate of 2°C / min, keep the temperature for 6 hours, and then perform a programmed cooling at a rate of 2°C / min. After cooling, quickly transfer the product to an atmosphere glove box for crushing and sieving to obtain a brown powder, namely the Li5FeO4 lithium supplement material.

[0121] Comparative Example 4

[0122] In this comparative example, Li6CoO4 is only coated with nano-silver oxide. The above blue powder and an appropriate amount of nano-silver oxide powder are weighed in an argon-protected glove box and uniformly mixed in a degassing machine.

[0123] Comparative Example 5

[0124] In this comparative example, Li6CoO4 is only coated with 4-fluorocatechol. The 4-fluorocatechol is crushed, and a certain mass of the crushed 4-fluorocatechol powder is weighed and added to the mixed powder in step 1, and then evenly mixed in a degassing machine, and then transferred to a metal nickel boat and placed in an atmosphere tube furnace, and heated to 200°C at a rate of 2°C / min in an argon atmosphere, and kept warm for 3 hours. After the reaction is completed, the product is ground and sieved to obtain a Li6CoO4 material coated with a functional layer.

[0125] In order to verify the progress of the embodiments of the present application, the following performance tests were performed on the above embodiments and comparative examples respectively:

[0126] 1. Transmission electron microscopy image of the composite lithium supplement material prepared in Example 1, as shown in Figure 3 As shown, it can be seen that the metal oxide and the fluorinated aromatic compound form a coating functional layer structure on the surface of the core lithium supplement material.

[0127] 2. The composite lithium supplement material provided in each embodiment and comparative example was applied to a secondary battery for electrochemical performance test, and a control group without adding the lithium supplement material was set up:

[0128] The present embodiments 1 to 8 and comparative examples 1 to 5 provide a lithium ion battery respectively. Each lithium ion battery is assembled into a lithium ion battery according to the following method:

[0129] 1) Positive electrode:

[0130] The materials obtained in Examples 1 to 8 and Comparative Examples 1-5 were mixed in an appropriate amount of NMP at a mass ratio of 95:3:1:1 for the positive electrode active material (LiFeO4, LFP): composite lithium supplement material: Su-P conductive agent: PVDF binder under the same conditions to prepare a positive electrode slurry; after homogenization-coating-drying-cutting operations, a positive electrode sheet was prepared, and the positive electrode sheet was baked in a vacuum oven at 100°C to remove trace water.

[0131] 2) Negative electrode sheet: The negative electrode active material graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the mass ratio of graphite: Super P: CMC: SBR is 95:2:0.5:2.5. The negative electrode slurry is coated on the current collector copper foil, and after drying-rolling-secondary drying process, the negative electrode sheet is made.

[0132] 3) Diaphragm: Use polyethylene (PE) diaphragm.

[0133] 4) 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.

[0134] 5) Assembly of secondary battery: Assemble the above positive electrode sheet, negative electrode sheet, electrolyte and separator into a lithium-ion soft-pack battery according to the requirements of lithium-ion battery assembly.

[0135] The lithium-ion soft-pack batteries assembled in the above embodiments were subjected to electrochemical performance tests, wherein the formation test conditions were: charging to 2.6V at a low current constant current of 0.05C, then charging to 3.2V at 0.1C, and then standing for 5 minutes. The aging test conditions were: placing the sealed soft-pack battery in a blast oven at 60°C for more than 12 hours, and checking the gas production. The test conditions for gas production were: clamping the soft-pack battery with a clamp to slowly squeeze the gas into the air bag, and then connecting the air bag to a differential electrochemical mass spectrometer for testing.

[0136] The relevant test results are shown in Table 1 below:

[0137] Table 1

[0138]

[0139] From the above test results, it can be seen that when the composite lithium supplement material of the embodiment of the present application is compounded with the positive electrode material, the overall capacity and capacity retention rate of the battery are significantly improved, and the overall gas production of the modified lithium supplement material is significantly reduced. It shows that the nano silver oxide and 4-fluorocatechol introduced in the composite lithium supplement material of the embodiment of the present application as coating materials can timely adsorb and capture the oxygen molecules / oxygen free radicals produced by the de-lithiation oxygen molecules / oxygen free radicals and the de-lithiation product initiation reaction, and generate functional 4-fluoro-1,2-benzoquinone products in situ, which are dissolved in the electrolyte and continue to capture the oxygen molecules / oxygen free radicals produced in the first cycle of charge and discharge and high temperature storage or de-lithiation product reactions, and then synergistically transform and participate in the construction of the SEI film, so as to construct a uniform and stable LiF-rich interface film, reduce gas enrichment, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby leading to the improvement of the overall energy efficiency and cycle life of the battery.

[0140] By comparing Examples 3 and 4, it can be seen that the use of specific conductive metal oxides and organic precursors can generate the functional material 4-fluoro-1,2-benzoquinone in this battery system, thereby improving the cycle life and gas production of the battery.

[0141] By comparing Examples 1, 5, and 6, it can be seen that different ratios of metal oxide to organic precursor may affect the conductivity and coating effect of the material, affect its adsorption effect on oxygen gas / oxygen free radicals, and further affect the production of functional materials.

[0142] By comparing Examples 7 and 8, it can be seen that the quality of the coating layer and the core material determines the lithium replenishment capacity and gas production effect of the material. The thinner the coating layer, the higher the overall capacity, but the poor coating effect, the lower the functional material generated, the capacity retention rate also decreases significantly, and the overall gas production is also high.

[0143] By comparing Example 2 with Comparative Examples 1 and 3, it can be seen that the technical solution is universal in maintaining battery capacity and controlling gas production, and can be applied to different lithium supplement materials.

[0144] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A composite lithium supplement material, characterized in that: The invention comprises a core containing a lithium supplement material and a functional layer coated on the outer surface of the core, wherein the functional layer contains metal oxides and fluorinated aromatic compounds.

2. The composite lithium supplement material according to claim 1, characterized in that: The metal oxide is disposed in contact with the lithium supplement material and the fluorinated aromatic compound; And / or, the fluorinated aromatic compound, under the catalytic action of the metal oxide, reacts with oxygen atoms to generate an oxygen capture functional material.

3. The composite lithium supplement material according to claim 2, characterized in that: The metal oxide and the fluorinated aromatic compound are in close contact with each other on the outer surface of the inner core to form the fully covered functional layer; wherein the metal oxide is located between the inner core and the fluorinated aromatic compound.

4. The composite lithium supplement material according to claim 2 or 3, characterized in that: The metal oxide comprises at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide, and nano palladium oxide; And / or, the fluorinated aromatic compound includes at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine; And / or, the lithium supplement material includes at least one of lithium-rich lithium cobalt oxide, lithium-rich lithium nickel oxide, lithium-rich lithium iron oxide, and lithium-rich lithium manganese oxide; And / or; the oxygen capture functional material includes 4-fluoro-1,2-benzoquinone.

5. The composite lithium supplement material according to claim 4, characterized in that: In the functional layer, the mass ratio of the metal oxide to the fluorinated aromatic compound is (1-3):10; And / or, in the composite lithium supplement material, the mass ratio of the core to the functional layer is 10:(0.3-1); And / or, the particle size D50 of the metal oxide is 100nm to 300nm; And / or, the thickness of the functional layer is 50nm to 300nm; And / or, the particle size D50 of the inner core is 5 μm to 45 μm.

6. The composite lithium supplement material according to any one of claims 1 to 3, characterized in that: The composite lithium-supplementing material has a water absorption rate of no more than 5.0 ppm / s in an environment with a humidity of 40%.

7. A method for preparing a composite lithium supplement material, characterized in that: The following steps are involved: Obtain lithium supplement materials; A functional layer including metal oxide and fluorinated aromatic compound is prepared on the surface of the lithium supplement material to obtain a composite lithium supplement material.

8. The method for preparing the composite lithium supplement material according to claim 7, characterized in that: The steps of preparing the functional layer include: mixing the lithium supplement material with the metal oxide under an inert atmosphere, adding the powder of the fluorinated aromatic compound for mixing, heating to 150°C to 200°C at a heating rate of 1°C / min to 3°C / min, keeping the temperature for 3 to 6 hours, grinding and sieving to obtain the composite lithium supplement material; and / or, the mass ratio of the metal oxide to the fluorinated aromatic compound is (1-3):10; and / or, the ratio of the mass of the lithium supplementing material to the total mass of the metal oxide and the fluorinated aromatic compound is 10:(0.3-1); And / or, the metal oxide includes at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide, and nano palladium oxide; And / or, the fluorinated aromatic compound includes at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine; And / or, the lithium supplement material includes at least one of lithium-rich lithium cobalt oxide, lithium-rich lithium nickel oxide, lithium-rich lithium iron oxide, and lithium-rich lithium manganese oxide.

9. A secondary battery, characterized in that: The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet contains the composite lithium supplement material as claimed in any one of claims 1 to 6 or the composite lithium supplement material prepared by the method as claimed in any one of claims 7 to 8.

10. The secondary battery according to claim 9, characterized in that In the positive electrode material layer of the positive electrode sheet, the mass percentage of the composite lithium supplement material is 2% to 5%.

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