Composite lithium supplementing material, preparation method and application thereof

Abstract

The application 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 supplementing material comprises an inner core containing a lithium supplementing material and a functional layer coated on the outer surface of the inner core, and the functional layer contains a metal oxide and a fluorinated aromatic compound. The composite lithium supplementing material has excellent lithium supplementing effect, can effectively supplement the loss of lithium ions in the charging and discharging process of the battery, and improves the capacity stability of the battery. Through the structure and material design of the coated functional layer, the composite lithium supplementing material can reduce residual alkali residues, can timely adsorb and capture oxygen molecules / oxygen free radicals generated in the battery, effectively generate structures and substances beneficial to the battery system, and optimize the construction of the SEI film. The oxygen generated by lithium extraction after the charging and discharging of the battery is greatly reduced, and the oxygen generation amount after the high-temperature storage stage is also greatly reduced, effectively improving the cycle stability and service life of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a composite lithium supplementing material and a preparation method and application thereof. BACKGROUND

[0002] During the first cycle charging process of a lithium ion battery, the solid-state electrolyte interface formed on the surface of the negative electrode irreversibly consumes active lithium in the battery system, resulting in a decrease in the energy density of the battery and a shortening of the cycle life. The pre-lithiation technology is considered to be an effective method to solve the problem of active lithium loss in the battery.

[0003] As a lithium supplementing agent, lithium-rich lithium cobalt oxide has a high theoretical capacity, but the residual alkali residue is large, the air stability is poor, and the phenomenon of obvious gas production during high-temperature storage affects its application. After the first cycle charging and discharging of the lithium supplementing material, a large amount of oxygen molecules or oxygen radicals are generated, the oxygen molecules or oxygen radicals diffuse into the electrolyte, and an oxidation decomposition reaction occurs with part of the components in the electrolyte, forming a large amount of carbon dioxide and hydrogen gas, etc. The increase in the amount of gas produced will cause the battery to swell, etc., and induce safety problems.

[0004] Therefore, it is urgent to provide a lithium supplementing material with high air storage environment stability and less gas production during use. SUMMARY

[0005] The application aims to provide a composite lithium supplementing material and a preparation method and application thereof, and aims to solve the problems of large gas production and poor stability of the existing lithium supplementing material to some extent.

[0006] To achieve the above application purposes, the technical solutions adopted by the application are as follows:

[0007] In a first aspect, the application provides a composite lithium supplementing material, which comprises an inner core containing a lithium supplementing material and a functional layer coated on the outer surface of the inner core, and the functional layer contains a metal oxide and a fluorinated aromatic compound.

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

[0009] In some possible implementation manners, the fluorinated aromatic compound reacts with oxygen atoms to generate an oxygen capturing functional material under the catalysis of the metal oxide.

[0010] In some possible implementation manners, the metal oxide and the fluorinated aromatic compound are in close contact on the outer surface of the inner core to constitute the fully-coated functional layer; and 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, nano palladium monoxide.

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

[0013] In some possible implementations, the lithium supplement material includes at least one of lithium-rich lithium cobaltate, lithium-rich lithium nickelate, lithium-rich lithium ferrate and lithium-rich lithium manganate.

[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 and the fluorinated aromatic compound is (1-3):10.

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

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

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

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

[0020] In some possible implementations, the composite lithium supplement material has a water absorption rate of the lithium supplement material of not higher than 5.0 ppm / s in an environment with a humidity of 40%.

[0021] In a second aspect, the application provides a preparation method of a composite lithium supplement material, including the following steps:

[0022] Obtaining a lithium supplement material;

[0023] Preparing a functional layer including a metal oxide and a fluorinated aromatic compound 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: mixing the lithium supplement material with the metal oxide under an inert atmosphere, adding a powder of the fluorinated aromatic compound for mixing treatment, heating to 150-200 ℃ at a heating rate of 1-3 ℃ / min, keeping warm for 3-6 hours, grinding and sieving to obtain the composite lithium supplement material.

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

[0026] In some possible implementations, a ratio of a mass of the lithium supplement material to a 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, nano palladium monoxide.

[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 cobalt oxide, lithium nickel oxide, lithium iron oxide and lithium manganese oxide.

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

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

[0032] The composite lithium supplementing material provided in the first aspect of the application comprises an inner core containing a lithium supplementing material and a functional layer coated on the outer surface of the inner core, and the functional layer contains a metal oxide and a fluorinated aromatic compound. On the one hand, the coating of the functional layer can effectively reduce the residual alkali residue of the lithium supplementing material and improve the environmental stability of the lithium supplementing material. On the other hand, the metal oxide in the functional layer not only has high conductivity, which is conducive to improving the transfer efficiency of electrons, but also has good catalytic effect. Under the catalysis of the metal oxide, the fluorinated aromatic compound can react with oxygen molecules / oxygen radicals generated in the first circle of battery charging and discharging and oxygen molecules / oxygen radicals generated in the reaction of the lithium stripping product to generate fluorinated benzoquinone. Fluorinated benzoquinone has excellent oxygen capture function and can continuously absorb and capture oxygen molecules / oxygen radicals generated in the charging and discharging stage of the battery and the high-temperature storage or lithium stripping product reaction, reduce the enrichment of gas, achieve less lithium loss and inhibit the decomposition of electrolyte, thereby improving the energy efficiency and cycle life when compounded with the positive material. In addition, the F element in the fluorinated aromatic compound has high electronegativity, high ionic potential and low polarizability, and can also participate in the construction of SEI solid electrolyte interface film through synergistic transformation, which can help lithium ions to be more uniformly deposited on the negative electrode to construct a uniform and stable LiF-rich interface film, and can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery. Therefore, the composite lithium supplementing material has excellent lithium supplementing effect, can effectively supplement the loss of lithium ions in the charging and discharging process of the battery, and improve the capacity stability of the battery. Moreover, through the functional layer structure and material design of the coating, the composite lithium supplementing material can timely adsorb and capture oxygen molecules / oxygen radicals generated in the lithium stripping and oxygen molecules / oxygen radicals generated in the reaction of the lithium stripping product, effectively generate structures and substances beneficial to the battery system, and optimize the construction of SEI film. After the charging and discharging of the battery is completed, the oxygen generated in the lithium stripping is greatly reduced, and the oxygen generation amount after the high-temperature storage stage is also greatly reduced, effectively improving the cycle stability and service life of the battery.

[0033] The preparation method of the composite lithium supplementing material provided in the second aspect of the present application is to prepare a functional layer comprising a metal oxide and a fluorinated aromatic compound on the surface of the lithium supplementing material. Through the coating of the functional layer, the residual alkali residue of the lithium supplementing material can be effectively reduced, and the environmental stability of the lithium supplementing material can be improved. The metal oxide has high conductivity and can catalyze the reaction of the fluorinated aromatic compound with the oxygen molecules / oxygen radicals generated during the delithiation of the first circle of the battery and the oxygen molecules / oxygen radicals generated by the reaction of the delithiation products to generate oxygen capture functions such as fluorinated benzoquinone. Oxygen molecules / oxygen radicals generated during the charging and discharging stage and high-temperature storage or delithiation of the battery can be continuously absorbed and captured, the enrichment of gas can be reduced, less lithium loss can be achieved, and the decomposition of the electrolyte can be inhibited, thereby improving the energy efficiency and cycle life when the lithium supplementing material is compounded with the positive electrode material. The lithium supplementing material can also participate in the construction of the SEI solid electrolyte interface film and help lithium ions to be more uniformly deposited on the negative electrode, so as to construct a uniform and stable LiF-rich interface film and 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 supplementing material. The composite lithium supplementing material has good lithium supplementing effect, less residual alkali residue, less gas production, high environmental stability, and long cycle life, thereby improving the energy density, electrical conductivity, cycle life, and other electrochemical properties of the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 is a three-dimensional model structure schematic diagram of the composite lithium supplementing material provided by the embodiments of the present application;

[0037] Figure 2 is a flowchart schematic diagram of the preparation method of the composite lithium supplementing material provided by the embodiments of the present application;

[0038] Figure 3 is a transmission electron microscope image of the composite lithium supplementing material provided by Embodiment 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 will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0040] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, 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 it.

[0041] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or the like means any combination of the items, including any combination of single or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0042] It should be understood that the size of the sequence number of the above-mentioned processes in various embodiments of the present application does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence. The execution order of each process should be determined according to 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" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0044] The weight of the related components mentioned in the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component. Therefore, as long as the content of the related components in the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiments of the present application. Specifically, the mass in the embodiments of the present application can be μg, mg, g, kg, etc. mass units commonly known in the chemical field.

[0045] The terms "first", "second" are only used for description purposes, to distinguish objects such as substances from each other, and cannot 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 can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more of the features.

[0046] The first aspect of the embodiments of the present application provides a composite lithium supplementing material, and the composite lithium supplementing material comprises Figure 1The composite lithium supplement material includes an inner core containing a lithium supplement material and a functional layer coated on the outer surface of the inner core, and 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 includes an inner core containing a lithium supplement material and a functional layer coated on the outer surface of the inner core, and the functional layer contains a metal oxide and a fluorinated aromatic compound. On the one hand, the coating of the functional layer can effectively reduce the residual alkali residue of the lithium supplement material and improve the environmental stability of the lithium supplement material. On the other hand, the metal oxide in the functional layer not only has high conductivity, which is conducive to improving the transfer efficiency of electrons, but also has good catalytic effect. Under the catalysis of the metal oxide, the fluorinated aromatic compound can react with oxygen molecules / oxygen radicals generated in the first circle of battery charging and discharging and oxygen molecules / oxygen radicals generated by the reaction of the lithium product to generate fluorinated benzoquinone and other compounds. Fluorinated benzoquinone and other compounds have excellent oxygen capture function, and can continuously absorb and capture oxygen molecules / oxygen radicals generated in the charging and discharging stage of the battery and the high-temperature storage or lithium product reaction in the electrolyte, reduce the accumulation of gas, achieve less lithium loss and inhibit the decomposition of the electrolyte, and thus improve the energy efficiency and cycle life when compounded with the positive material. In addition, the F element in the fluorinated aromatic compound has high electronegativity, high ionic potential and low polarizability, and can also participate in the construction of the SEI solid electrolyte interface film, which can help lithium ions to be more uniformly deposited in the negative electrode, to construct a uniform and stable LiF-rich interface film, and can significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery. Therefore, the composite lithium supplement material has excellent lithium supplement effect, can effectively supplement the loss of lithium ions in the charging and discharging process of the battery, and improve the capacity stability of the battery. Moreover, through the functional layer structure and material design of the coating, the composite lithium supplement material can timely adsorb and capture oxygen molecules / oxygen radicals generated by the reaction of the lithium product and oxygen molecules / oxygen radicals generated by the reaction of the lithium product, effectively generate structures and substances beneficial to the battery system, and optimize the construction of the SEI film. After the battery charging and discharging, the oxygen generated by the lithium product is greatly reduced, and the oxygen production after the high-temperature storage stage (for example, the battery is charged to a certain voltage and then aged at 60°C for 12 hours to observe the oxygen production) is also greatly reduced, effectively improving the cycle stability and service life of the battery.

[0048] In some possible implementations, the metal oxide is 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 to form a full-coated functional layer on the outer surface of the core; and the metal oxide is located between the core and the fluorinated aromatic compound. In this case, the part of the metal oxide in contact with the lithium supplement material can better improve the transfer efficiency of electrons and the conductivity, and the part of the metal oxide in contact with the fluorinated aromatic compound can better catalyze the reaction between the fluorinated aromatic compound and oxygen atoms.

[0049] In some possible implementations, the fluorinated aromatic compound reacts with oxygen atoms to generate an oxygen capture functional material under the catalysis of the metal oxide. Under the catalysis of the metal oxide, the fluorinated aromatic compound can react with oxygen molecules / oxygen radicals generated by the lithium supplement material during the first cycle of charging and discharging of the battery, and oxygen molecules / oxygen radicals generated by the side reaction of the lithium supplement product and the electrolyte to generate fluorinated benzoquinone and other products. The generated fluorinated benzoquinone and other products have excellent oxygen capture function. The fluorinated benzoquinone and other products with oxygen capture function dissolved in the electrolyte can continuously absorb and capture oxygen molecules / oxygen radicals generated by the battery during the charging and discharging stage, high-temperature storage or the reaction of the lithium supplement product, reduce the accumulation of gas, achieve less lithium loss, and inhibit the decomposition of the electrolyte, thereby improving the energy efficiency and cycle life when the lithium iron phosphate and other positive active materials are compounded.

[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 monoxide. In this case, these metal oxides not only have high conductivity, which is conducive to improving the transfer efficiency of electrons, but also have no side effects on the battery system, and have good catalytic effect. They can catalyze the reaction of the fluorinated aromatic compound with oxygen to generate fluorinated benzoquinone and other oxygen capture materials.

[0051] In some possible implementations, the particle size D50 of the metal oxide is 100 nm to 300 nm. For example, the particle size D50 of the metal oxide can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, and the like, which are typical but not limited to any point value or interval value between any two point values. In this case, the nano-sized metal oxide has a larger specific surface area and more active reaction sites, which can better catalyze the reaction of the fluorinated aromatic compound with oxygen to generate fluorinated benzoquinone.

[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 easy to combine with oxygen and oxidize into fluorinated benzoquinone under the catalysis of metal oxides such as silver oxide.

[0053] In some possible implementations, the fluorinated aromatic compound includes at least one of 4-fluororesorcinol and 4-fluoro-ortho-phenylenediamine. Exemplarily, after the first cycle of charging and discharging of the lithium supplementing material, the outer layer of the lithium supplementing material containing 4-fluororesorcinol and silver oxide preferentially adsorbs a large amount of oxygen molecules or oxygen radicals, and then generates 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 continues to capture oxygen molecules / oxygen radicals generated in the first cycle of charging and discharging and in the high-temperature storage or delithiation product reaction, and cooperatively transforms to participate in the construction of the SEI film, to construct a uniform and stable LiF-rich interface film, reduce the enrichment of gas, achieve less lithium loss and inhibit the decomposition of the electrolyte, and thus improve the energy efficiency and cycle life when compounded with lithium iron phosphate.

[0054] In some possible implementations, the oxygen capturing functional material includes 4-fluoro-1,2-benzoquinone. In this case, under the catalysis of metal oxides such as silver oxide, 4-fluororesorcinol combines with oxygen to generate 4-fluoro-1,2-benzoquinone through oxidation. The 4-fluoro-1,2-benzoquinone has excellent oxygen capturing function, and can continuously absorb and capture oxygen molecules / oxygen radicals generated in the charging and discharging stage and in the high-temperature storage or delithiation product reaction of the battery when dissolved in the electrolyte, reduce the enrichment of gas, achieve less lithium loss and inhibit the decomposition of the electrolyte, and thus improve the energy efficiency and cycle life when compounded with lithium iron phosphate. It can also cooperatively transform to participate in the construction of the SEI solid electrolyte interface film, help the more uniform deposition of lithium ions on the negative electrode, construct a uniform and stable LiF-rich interface film, and significantly inhibit the growth of lithium dendrites, thereby improving the safety and cycle stability of the battery.

[0055] In some possible implementations, the lithium supplementing 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. The capacity of these lithium supplementing materials is relatively high, but there is a problem of large residual alkali residue and relatively poor stability. The coating of the functional layer containing the metal oxide and the fluorinated aromatic compound can significantly reduce the residual alkali residue of the lithium supplementing material, reduce gas production and improve the stability of the lithium supplementing material.

[0056] In some possible implementations, the mass ratio of the metal oxide and the fluorinated aromatic compound in the functional layer is (1-3):10, and can be 1:10, 2:10, 3:10 or other typical but non-limiting arbitrary point values or interval values between any two point values. In this case, the content of the metal oxide not only ensures the improvement of the electrical conductivity, but also ensures the catalysis of the fluorinated aromatic compound, and fully catalyzes the reaction of the fluorinated aromatic compound with oxygen to generate fluorinated benzoquinone.

[0057] In some possible implementation manners, the mass ratio of the core to the functional layer in the composite lithium supplementing material is 10:(0.3-1), and 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, or an interval value between any two point values of the foregoing typical but non-limiting point values. In this case, the content of the core ensures the lithium supplementing effect of the composite lithium supplementing material.

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

[0059] In some possible implementation manners, the thickness of the functional layer is 50-300 nm. For example, the thickness of the functional layer can be 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or an interval value between any two point values of the foregoing typical but non-limiting point values. In this case, the functional layer coated on the outer surface of the lithium supplementing material can effectively reduce residual alkali residues and reduce the gas production rate, thereby improving the stability and service life of the material.

[0060] In some possible implementation manners, the composite lithium supplementing material has a water absorption rate of not higher than 5.0 ppm / s in an environment with a humidity of 40%, and can be not higher than 4.5 ppm / s, not higher than 4 ppm / s, not higher than 3 ppm / s, not higher than 2 ppm / s, or not higher than 1 ppm / s. The lithium supplementing material coated with the functional layer has good environmental stability, low water absorption rate, and good storage performance.

[0061] In a second aspect, the embodiment of the present application provides a preparation method of a composite lithium supplementing material. Figure 2 As shown in the figure, the method comprises the following steps:

[0062] S10. Obtaining a lithium supplementing material.

[0063] S20. Preparing a functional layer comprising a metal oxide and a fluorinated aromatic compound on the surface of the lithium supplementing material to obtain a composite lithium supplementing material.

[0064] The preparation method of the composite lithium supplementing material provided in the second aspect of the embodiments of the present application prepares a functional layer including a metal oxide and a fluorinated aromatic compound on the surface of the lithium supplementing material. Through the coating of the functional layer, the residual alkali residue of the lithium supplementing material can be effectively reduced, and the environmental stability of the lithium supplementing material can be improved. The metal oxide has high conductivity and can catalyze the reaction of the fluorinated aromatic compound with oxygen molecules / oxygen radicals generated during the first cycle charging and discharging of the battery and oxygen molecules / oxygen radicals generated by the reaction of the lithium supplementing material to generate oxygen capture functions such as fluorinated benzoquinone. Oxygen molecules / oxygen radicals generated during the charging and discharging stage of the battery and high-temperature storage or the reaction of the lithium supplementing material can be continuously absorbed and captured, the enrichment of gas can be reduced, less lithium loss can be achieved, and the decomposition of the electrolyte can be inhibited, thereby improving the energy efficiency and cycle life when the lithium supplementing material is compounded with the positive electrode material. The lithium supplementing material can also participate in the construction of the SEI solid electrolyte interface film, which can help lithium ions to be more uniformly deposited on the negative electrode, thereby constructing a uniform and stable LiF-rich interface film, and the growth of lithium dendrites can be significantly inhibited, thereby improving the safety and cycle stability of the battery.

[0065] In some possible implementation manners, the lithium supplementing 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. These lithium supplementing materials have relatively high capacity, but have the problems of large residual alkali residue and relatively poor stability. Through the coating of the functional layer including the metal oxide and the fluorinated aromatic compound, the residual alkali residue of the lithium supplementing material can be significantly reduced, gas production can be reduced, and the stability of the lithium supplementing material can be improved.

[0066] In some possible implementation manners, the lithium supplementing material includes lithium-rich lithium cobalt oxide Li6CoO4, and the synthesis steps include: weighing appropriate amounts of lithium oxide and copper tetroxide, wherein the molar ratio of lithium to cobalt is 5 to 7:1, then uniformly mixing by a degassing machine, then transferring to a nickel metal canister in a glove box under argon protection, and then quickly transferring to an atmosphere tube furnace. Under the protective atmosphere of argon / argon, the temperature is raised to 600 DEG C to 800 DEG C at a temperature raising rate of 2 DEG C / min, and then the temperature is kept for 6 to 10 hours, and then the temperature is lowered at a rate of 2 to 5 DEG C / min. After the temperature is lowered, the product is quickly transferred to an atmosphere glove box for crushing and sieving, and a dark blue powder, i.e., the Li6CoO4 lithium supplementing material, is obtained.

[0067] In the above step S20:

[0068] In some possible implementation manners, the step of preparing the functional layer comprises: after mixing the lithium supplementing material with the metal oxide under an inert atmosphere, adding a powder of the fluorinated aromatic compound for mixing treatment, heating at a heating rate of 1-3 ℃ / min to 150-200 ℃, keeping the temperature for 3-6 hours, grinding and sieving to obtain the composite lithium supplementing material. In this case, a functional layer containing the metal oxide and the fluorinated aromatic compound is formed in situ on the surface of the lithium supplementing material by a high-temperature melting liquid phase method, the metal oxide and the fluorinated aromatic compound are stably coated on the outer surface of the lithium supplementing material to form a coating structure, and the residual alkali residue of the material is reduced, and the environmental stability of the lithium supplementing material is further improved.

[0069] For example, the heating rate for preparing the functional layer can be 1 ℃ / min, 2 ℃ / min, 3 ℃ / min, or any point value or interval value between any two point values, the holding temperature can be 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, or any point value or interval value between any two point values, and the holding time can be 3 hours, 4 hours, 5 hours, 6 hours, or any point value or interval value between any two point values.

[0070] In some possible implementation manners, 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 not only ensures the improvement of the electrical conductivity, but also ensures the catalytic effect on the fluorinated aromatic compound, and the fluorinated aromatic compound is fully catalyzed to react with oxygen to generate fluorinated benzoquinone.

[0071] In some possible implementation manners, the mass ratio 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 implementation manners, the metal oxide comprises at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide and nano palladium monoxide. These metal oxides not only have high electrical conductivity, which is beneficial to improving the transfer efficiency of electrons, but also have no side effects on the battery system, and have good catalytic effect. The fluorinated aromatic compound can be catalyzed to react with oxygen to generate fluorinated benzoquinone and other oxygen capturing materials.

[0073] In some possible implementation manners, the fluorinated aromatic compound comprises at least one of 4-fluorocatechol and 4-fluoro-o-phenylenediamine. Under the catalytic effect of the metal oxide such as silver oxide, the fluorinated aromatic compound is easy to combine with oxygen and oxidize into fluorinated benzoquinone.

[0074] In some embodiments, the step of preparing the functional layer comprises: weighing the powder of the above-mentioned lithium supplementing material and an appropriate amount of metal oxide powder such as silver oxide in an argon-protected glove box, and uniformly mixing in a debubbling machine. The fluorinated aromatic compound such as 4-fluorocatechol is crushed, and a certain mass of the crushed fluorinated aromatic compound powder is weighed and added to the mixed powder, and then uniformly mixed in the debubbling machine, and then transferred to a metal nickel boat and placed in an atmosphere tube furnace, heated to 150-200°C at a rate of 2°C / min in an argon atmosphere, and kept for 3-6 hours. After the reaction is completed, the product is ground and sieved to obtain a composite lithium supplementing material in which the functional layer coats the lithium supplementing material.

[0075] In a third aspect, the embodiments of the present application provide a secondary battery, which comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet contains the above-mentioned composite lithium supplementing material or the composite lithium supplementing material prepared by the above-mentioned method.

[0076] In the secondary battery of the embodiments of the present application, the positive electrode sheet contains the above-mentioned composite lithium supplementing material, which has good lithium supplementing effect, small residual alkali residue, small gas production, high environmental stability, long cycle life, and improves the energy density, electrical conductivity, cycle life and other electrochemical properties of the secondary battery.

[0077] The positive electrode sheet, the negative electrode sheet, the electrolyte, the separator and the like in the secondary battery of the embodiments of the present application are not specifically limited and can be applied to any battery system.

[0078] In some possible implementations, the positive electrode sheet comprises a current collector and a positive electrode material layer formed on the surface of the current collector, and the positive electrode material layer contains the above-mentioned composite lithium supplementing material or the composite lithium supplementing material prepared by the above-mentioned method. The composite lithium supplementing material has good structural stability, excellent lithium supplementing effect, high electrical conductivity, good rate performance and good cycle stability, and thus improves the stability, capacity, rate performance, cycle performance and other electrochemical properties of the positive electrode sheet.

[0079] In some possible implementations, the mass percentage content of the composite lithium supplementing material in the positive electrode material layer of the positive electrode sheet is 2%-5%, and can be 2%, 3%, 4%, 5% and the like, or an interval value between any two point values. In this case, the addition amount of the composite lithium supplementing material in the material layer of the positive electrode sheet sufficiently ensures the lithium supplementing effect on the positive electrode sheet, can effectively supplement the loss of lithium ions in the charging and discharging process, can participate in the construction of the SEI film, can construct a uniform and stable LiF-rich interface film, can reduce the enrichment of gas and achieve less lithium loss and inhibit the decomposition of the electrolyte, and thus improves the cycle life and other properties of the battery.

[0080] In some possible implementations, the preparation of the positive electrode material layer includes the steps of mixing the composite lithium supplementing material, the conductive agent, and the binder to form an electrode slurry, coating the electrode slurry on a current collector, and performing drying, rolling, die cutting, and the like to obtain a positive electrode sheet.

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

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

[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%, and the like.

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

[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), and hard carbon, or nitrides, tin-based oxides, tin-based oxides, tin alloys, and nano negative electrode materials. The current collector includes, but is not limited to, any one of a copper foil and an aluminum foil.

[0087] In some possible implementations, the step of preparing the negative electrode sheet includes the steps of mixing the negative electrode active material, a conductive agent such as conductive carbon black, a binder such as carboxymethyl cellulose and styrene butadiene rubber, and a solvent such as water to form a negative electrode mixed slurry at a mass ratio of (80-99):(1-5):(2-10):100, vacuum degassing, discharging, coating on a coating machine, and performing rolling, slitting, and die cutting to obtain the negative electrode sheet.

[0088] In some possible implementations, the separator can block electrons and allow ions to pass. For example, the separator includes, but is not limited to, at least one material including polypropylene fiber, polyacrylonitrile fiber, polyvinyl formal fiber, poly(ethylene terephthalate), polyethylene terephthalate, polyamide fiber, and poly(p-phenyleneterephthalamide).

[0089] In some possible implementations, the electrolyte includes at least one soluble metal salt. In some specific embodiments, the metal salt includes at least one of LiCIO4, 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 electrolyte salts can ensure high ionic conductivity of the electrolyte, and do not have harmful side reactions with electrode materials, electrolytes, separators, 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 type includes a lithium ion battery, etc.

[0092] In some possible implementations, the battery cell of the present application can be assembled into a battery module, and the number of battery cells included 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 further include a housing having an accommodation space, and a plurality of battery cells are accommodated in the accommodation space.

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

[0094] In order to enable the above-mentioned implementation details and operations of the present application to be clearly understood by those skilled in the art, and the significant performance of the composite lithium supplement material, the preparation method and application thereof are embodied, the following multiple embodiments are used to illustrate the above technical solutions.

[0095] Embodiment 1

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

[0097] The preparation thereof includes the following steps:

[0098] 1. Synthesis of the kernel lithium supplementing agent Li6CoO4: Take an appropriate amount of lithium oxide and one cobalt tetroxide, wherein the molar ratio of lithium to cobalt is 5 to 7:1, then mix uniformly through a deaerator, then transfer to a nickel metal canister in a glove box under argon protection, and then quickly transfer to a tube furnace in an atmosphere. Under the protective atmosphere of argon / argon, heat to 600℃ at a heating rate of 2℃ / min, and keep for 6 hours, and then perform programmed cooling at a rate of 2℃ / min. After cooling, quickly transfer the product to an atmospheric glove box for crushing, sieving, and obtain a dark blue powder, which is the Li6CoO4 lithium supplementing material.

[0099] 2. Preparation of a composite lithium supplementing material containing nano silver oxide and a 4-fluoro-o-phenol functional layer coating:

[0100] ① In an argon-protected glove box, take the above blue powder and an appropriate amount of nano silver oxide powder, and mix uniformly in a deaerator. ② Crush 4-fluoro-o-phenol, and take a certain amount of crushed 4-fluoro-o-phenol powder and add it to the mixed powder in step 1, then mix uniformly in a deaerator, and then transfer to a metal nickel canister and place it in a tube furnace in an atmosphere. Heat to 200℃ at a rate of 2℃ / min in an argon atmosphere, and keep for 3 hours. After the reaction is complete, the product is ground and sieved to obtain a Li6CoO4 material with a functional layer coating, which is a composite lithium supplementing material.

[0101] Example 2

[0102] The LFO is used as the kernel in the embodiments of the present application, and the difference from Example 1 is the preparation of the kernel lithium supplementing agent in step 1: take an appropriate amount of lithium oxide and one iron monoxide, wherein the molar ratio of lithium to cobalt is 5:1, then mix uniformly through a deaerator, then transfer to a nickel metal canister in a glove box under argon protection, and then quickly transfer to a tube furnace in an atmosphere. Under the protective atmosphere of argon / argon, heat to 700℃ at a heating rate of 2℃ / min, and keep for 6 hours, and then perform programmed cooling at a rate of 2℃ / min. After cooling, quickly transfer the product to an atmospheric glove box for crushing, sieving, and obtain a brown powder, which is the Li5FeO4 lithium supplementing material.

[0103] Example 3

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

[0105] Example 4

[0106] The difference between the embodiments of the present application and Example 1 is that in step 2, 4-fluoro-o-phenylenediamine is used instead of 4-fluoro-o-phenol, and the other steps and proportions remain unchanged.

[0107] Example 5

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

[0109] Example 6

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

[0111] Example 7

[0112] The difference between the example of the present application and Example 1 is that the mass ratio of the coating layer to the core material in Step 2 is adjusted to 0.3:10, and other steps and proportions are unchanged.

[0113] Example 8

[0114] The difference between the example of the present application and Example 1 is that the mass ratio of the coating layer to the core material in Step 2 is adjusted to 1:10, and other steps and proportions are unchanged.

[0115] Comparative Example 1

[0116] A battery with 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 the core lithium supplement Li6CoO4: an appropriate amount of lithium oxide and one cobalt tetroxide are weighed, wherein the molar ratio of lithium to cobalt is 5 to 7:1, then mixed uniformly by a debubbler, then transferred to a nickel metal canister in a glove box under argon protection, and then quickly transferred to an atmosphere tube furnace. Under the protection of argon / argon atmosphere, the temperature is raised to 600°C at a rate of 2°C / min, and then held 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, sieving, and obtaining a deep blue powder, i.e., the Li6CoO4 lithium supplement material.

[0119] Comparative Example 3

[0120] The comparative example is Li5FeO4 without any coating. An appropriate amount of lithium oxide and iron monoxide are weighed, wherein the molar ratio of lithium to iron is 5:1, and then uniformly mixed by a deaerator. Then, the mixture is transferred into a nickel metal boat in a glove box under argon protection, and then quickly transferred into a tube furnace under an argon atmosphere. The temperature is raised to 700°C at a rate of 2°C / min under an argon / argon protective atmosphere, and then held for 6 hours. Then, the temperature is lowered at a rate of 2°C / min. After the temperature is lowered, the product is quickly transferred into an atmosphere glove box for crushing and sieving to obtain a brown powder, which is Li5FeO4 lithium supplement material.

[0121] Comparative Example 4

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

[0123] Comparative Example 5

[0124] The comparative example Li6CoO4 is only coated with 4-fluoro-o-dihydroxybenzene. The 4-fluoro-o-dihydroxybenzene is crushed, and a certain amount of crushed 4-fluoro-o-dihydroxybenzene powder is added to the mixed powder in step one, and then uniformly mixed in a deaerator. Then, the mixture is transferred into a metal nickel boat and placed in a tube furnace under an argon atmosphere. The temperature is raised to 200°C at a rate of 2°C / min, and then held for 3 hours. After the reaction is completed, the product is ground and sieved to obtain Li6CoO4 material with a functional layer coating.

[0125] In order to verify the progressiveness of the embodiments of the present application, the above-mentioned embodiments and comparative examples are subjected to the following performance tests:

[0126] 1. The transmission electron microscope image of the composite lithium supplement material prepared in Example 1 is shown in FIG. 1. As shown in FIG. 1, the metal oxide and the fluorinated aromatic compound form a functional layer structure on the surface of the core lithium supplement material. Figure 3

[0127] 2. The composite lithium supplement materials provided by the embodiments and comparative examples are applied to secondary batteries for electrochemical performance tests, and a control group without the addition of lithium supplement materials is set:

[0128] Examples 1 to 8 and Comparative Examples 1 to 5 each provide a lithium ion battery. Each lithium ion battery is assembled into a lithium ion battery according to the following method:

[0129] 1) Positive electrode sheet:

[0130] ​The materials obtained in Examples 1 to 8 and Comparative Examples 1-5 were mixed in the same conditions according to the ratio of 95:3:1:1 of positive active material (LiFe04, LFP): composite lithium supplement material: Su-P conductive agent: PVDF binder to prepare a positive electrode slurry in an appropriate amount of NMP; and a positive electrode sheet was prepared through homogenizing-coating-drying-cutting operations, 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, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were mixed uniformly in deionized water to prepare a negative electrode slurry, wherein the mass ratio of graphite: Super P: CMC: SBR was 95:2:0.5:2.5. The negative electrode slurry was coated on a current collector copper foil, and after the drying-rolling-second drying process, a negative electrode sheet was prepared.

[0132] 3) Separator: a polyethylene (PE) separator was used.

[0133] 4) Electrolyte: the electrolyte was a 1 mol / L LiPF6 solution, and the solvent was composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1.

[0134] 5) Assembly of secondary battery: the above-mentioned positive electrode sheet, negative electrode sheet, electrolyte, and separator were assembled 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-mentioned examples were subjected to electrochemical performance tests, wherein the formation test conditions were: small current constant current 0.05C charging to 2.6V, then 0.1C charging to 3.2V, 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 of gas production were: the soft pack battery was clamped with a clamp to slowly extrude the gas into a gas bag, and then the gas bag was connected 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 test results, it can be seen that, compared with Comparative Examples 1, 2, 4 and 5, the overall capacity and capacity retention of the battery are significantly improved when the composite lithium supplement material of the application is compounded with the positive electrode material, and the gas production of the modified lithium supplement material is significantly reduced. It is shown that the nano-silver oxide and 4-fluorocatechol introduced in the composite lithium supplement material of the application as a coating material can timely adsorb and capture the oxygen molecules / oxygen radicals produced by the lithium extraction reaction and the oxygen molecules / oxygen radicals produced by the reaction of the lithium extraction product, and in-situ generate functional 4-fluoro-1,2-benzoquinone products, which are dissolved in the electrolyte to continue to capture the oxygen molecules / oxygen radicals produced by the lithium extraction product in the first circle of charging and discharging and high-temperature storage, and then participate in the construction of the SEI film to construct a uniform and stable LiF-rich interface film, reduce the enrichment of gas, achieve less lithium loss and inhibit the decomposition of the electrolyte, thereby improving the overall energy efficiency and cycle life of the battery.

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

[0141] As can be seen from Comparative Examples 1, 5 and 6, different ratios of metal oxides and organic precursors can affect the conductivity and coating effect of the material, affect the adsorption effect of oxygen gas / oxygen radicals, and then affect the generation of functional materials.

[0142] As can be seen from Comparative Examples 7 and 8, the mass of the coating layer and the core material determines the lithium supplement capacity and gas production effect of the material. The thinner the coating layer, the higher the overall capacity, but the coating effect is poor, the generated functional material is low, the capacity retention is also significantly decreased, and the overall gas production is also high.

[0143] As can be seen from Comparative Example 2 and Comparative Examples 1 and 3, the technical solution has universality in battery capacity retention and gas control, and can be applied to different lithium supplement materials.

[0144] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A composite lithium supplementing material, characterized in that, The composite lithium supplementing material comprises an inner core containing a lithium supplementing material and a functional layer coated on the outer surface of the inner core, the functional layer containing a metal oxide and a fluorinated aromatic compound; the metal oxide comprises at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide and nano palladium monoxide; the fluorinated aromatic compound comprises at least one of 4-fluoro-o-benzosemiquinone and 4-fluoro-o-phenylenediamine; the fluorinated aromatic compound reacts with oxygen atoms to generate an oxygen capturing functional material under the catalysis of the metal oxide; the mass ratio of the metal oxide to the fluorinated aromatic compound in the functional layer is (2-3):10; and the mass ratio of the inner core to the functional layer in the composite lithium supplementing material is 10:(0.4-1).

2. The lithium-lithiating composite material of claim 1, wherein, The metal oxide is in contact with the lithium supplementing material and the fluorinated aromatic compound.

3. The lithium supplement composite material of claim 2, wherein, The metal oxide and the fluorinated aromatic compound are in close contact to form a full-coated functional layer on the outer surface of the inner core; wherein the metal oxide is located between the inner core and the fluorinated aromatic compound.

4. The lithium supplement material composite according to claim 2 or 3, wherein, The lithium supplementing material comprises 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 capturing functional material comprises 4-fluoro-1,2-benzoquinone.

5. The lithium-lithiating composite material of claim 4, wherein, The particle size D50 of the metal oxide is 100-300 nm; And / or, the thickness of the functional layer is 50-300 nm; And / or, the particle size D50 of the inner core is 5-45 μm.

6. The lithium supplement composite material according to any one of claims 1 to 3, wherein, The composite lithium supplementing material has a water absorption rate of the lithium supplementing material of not higher 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 method comprises the following steps: Obtaining a lithium supplementing material; Preparation of a functional layer containing a metal oxide and a fluorinated aromatic compound on the surface of the lithium supplementing material to obtain a composite lithium supplementing material; wherein the mass ratio of the metal oxide to the fluorinated aromatic compound is (2-3):10; the mass ratio of the lithium supplementing material to the total mass of the metal oxide and the fluorinated aromatic compound is 10:(0.4-1); the metal oxide comprises at least one of nano silver oxide, nano gold trioxide, nano platinum dioxide and nano palladium monoxide; the fluorinated aromatic compound comprises at least one of 4-fluoro-o-benzosemiquinone and 4-fluoro-o-phenylenediamine; the fluorinated aromatic compound reacts with oxygen atoms to generate an oxygen capturing functional material under the catalysis of the metal oxide.

8. The method for preparing the composite lithium-supplementing material as described in claim 7, characterized in that, The step of preparing the functional layer comprises: mixing the lithium supplementing material with the metal oxide under an inert atmosphere, adding a powder of the fluorinated aromatic compound for mixing treatment, heating to 150-200℃ at a heating rate of 1-3℃ / min, holding for 3-6 hours, grinding and sieving to obtain the composite lithium supplementing material. And / or, the lithium supplementing material comprises 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 by comprising: The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet comprises the composite lithium supplementing material according to any one of claims 1-6 or the composite lithium supplementing material prepared by the method according to any one of claims 7-8.

10. The secondary battery according to claim 9, wherein The mass percentage of the composite lithium supplementing material in the positive electrode material layer of the positive electrode sheet is 2%-5%.

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