Two-element lithium supplementing additive, preparation method and application thereof

Abstract

The application discloses a two-element lithium supplementing additive, a preparation method thereof and application thereof. The two-element lithium supplementing additive comprises a carbon matrix and two-element lithium supplementing material dispersed in the carbon matrix, at least a carbon layer of a surface layer of the carbon matrix is a dense carbon layer, and a molecular formula of the two-element lithium supplementing material is Li a X b ; wherein, 1<=a<=3, 1<=b<=3, and X is selected from any one of F, S, N, B, P, O and Se. The two-element lithium supplementing additive contains two-element lithium supplementing material rich in lithium, maintains abundance of lithium ions in a battery system, improves first efficiency of the battery and overall electrochemical performance. The carbon matrix disperses the two-element lithium supplementing material in the carbon matrix, guarantees stability of the two-element lithium supplementing material, and realizes stable lithium supplementing effect. The preparation method can guarantee stability of structure and electrochemical performance of the prepared two-element lithium supplementing additive, and saves production cost. The two-element lithium supplementing additive is applied to a positive electrode lithium supplementing additive, a positive electrode material, a positive electrode and a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium batteries, and particularly relates to a two-element lithium supplementing additive and a preparation method and application thereof. BACKGROUND

[0002] The oil energy crisis in the 1960s and 1970s forced people to find new alternative energy sources. Lithium ion batteries are considered to be one of the most promising energy sources due to their high working voltage and energy density, relatively small self-discharge level, no memory effect, no pollution of heavy metal elements such as lead and cadmium, and super-long cycle life.

[0003] During the first charging process of a lithium ion battery, the formation of a solid electrolyte interface (SEI) film on the surface of the negative electrode is usually accompanied by the consumption of a large amount of Li + , which means that part of the Li + stripped from the positive electrode material is irreversibly consumed, resulting in a decrease in the reversible capacity of the battery. The negative electrode material, especially the silicon-oxygen negative electrode material, further consumes Li + , causing a low first-cycle coulombic efficiency.

[0004] To improve the low coulombic efficiency problem caused by the irreversible loss of the negative electrode, in addition to pre-lithiation of the negative electrode material and electrode sheet, supplementing lithium to the positive electrode can also achieve the requirement of high energy density. The theoretical capacity of the lithium supplementing additive is as high as 867 mAh / g, the working voltage window is consistent with that of conventional lithium ion batteries, and the lithium supplementing additive basically does not participate in the electrochemical process in the later stage, so it is a lithium supplementing additive with broad prospects.

[0005] Although the currently commonly used lithium supplementing materials have high lithium content and some of the lithium supplementing materials have certain stability in air, the electronic conductivity and ionic conductivity of the lithium supplementing materials are generally low, and the electrochemical decomposition potential of pure lithium supplementing components such as LiF is as high as 6.1 V, which is much higher than the cutoff voltage (4.4 V) of existing positive electrode materials. This makes it difficult for lithium to be stripped during charging of the positive electrode, and the decomposition of LiF produces toxic gas F2. Therefore, overcoming these defects of the lithium supplementing components is challenging.

[0006] There are currently reports of positive electrode lithium supplementing materials. In one reported positive electrode lithium supplementing material, the lithium supplementing component is loaded in a porous carbon material. However, it is found in actual application and research that for the lithium supplementing material of the porous carbon, it is difficult for the molten lithium metal to be uniformly loaded into the pores of the porous carbon, especially the internal pores and micropores. After the lithium in the larger pores reacts with the reaction gas, the obtained lithium supplementing material particles are large, the lithium ion migration distance is too long, and the polarization is large; and the lithium and the porous carbon skeleton are difficult to achieve close contact.

[0007] In another positive electrode lithium supplement material disclosed, elemental metal particles are dispersed in the lithium supplement material structure, but it is found through research that lithium and CoF3 have high viscosity under melting, and it is difficult to achieve uniform mixing through ordinary stirring, and the uniformity and consistency of the obtained material are difficult to guarantee.

[0008] In another positive electrode lithium supplement material disclosed, it is a lithium supplement material containing Co-doped or Co-doped high-iron lithium and carbon material, and a sol-gel preparation method. However, during the in-situ coating process of the carbon source at high temperature in the conventional sol-gel, part of the lithium source is easily reacted to form non-electrochemical active lithium carbonate, affecting the proportion of the active main body.

[0009] Therefore, through research on the disclosed related positive electrode lithium supplement material, it is found that although the current disclosed positive electrode lithium supplement material can play a lithium supplement role and help improve the electronic conductivity of LiF particles, the existing disclosed positive electrode lithium supplement material still has deficiencies, specifically, the lithium is difficult to be removed during the charging process of the positive electrode, the ionic conductivity is low, the electronic conductivity is not ideal, the purity is not high, and a large amount of residual alkali remains on the surface. The material interface lacks a passivation layer protection, and is easily reacted with moisture in the environment to form LiOH again. Due to the low purity and unstable interface, a large amount of residual alkali remains on the surface, resulting in that the storage stability and processing stability of the existing positive electrode lithium supplement material are not ideal, the lithium supplement effect is not ideal, the capacity needs to be improved, and large-scale production is not easy. SUMMARY

[0010] The purpose of the present application is to overcome the above-mentioned deficiencies of the prior art, and to provide a two-component lithium supplement additive and its preparation method and application, in order to solve the technical problems of the existing positive electrode lithium supplement additive, such as poor storage stability and processing stability, low purity, etc.

[0011] In order to achieve the above-mentioned purpose of the application, one aspect of the present application provides a two-component lithium supplement additive. The two-component lithium supplement additive of the present application comprises a carbon matrix and a two-component lithium supplement material dispersed in the carbon matrix, and at least the carbon layer of the surface layer of the carbon matrix is a dense carbon layer, and the molecular formula of the two-component lithium supplement material is Li a X b ; wherein 1≤a≤3, 1≤b≤3, and X is selected from any one of F, S, N, B, P, O and Se.

[0012] Another aspect of the present application provides a preparation method of the two-component lithium supplement additive. The preparation method of the two-component lithium supplement additive of the present application comprises the following steps:

[0013] The lithium source, the first X element source and the first carbon source are mixed and treated to prepare a first precursor; wherein the lithium source and the first X element source are respectively according to the molecular formula Li a X bThe lithium source and the first element source X were measured by elemental stoichiometry, and the Li... a X b In the given information, 1≤a≤3, 1≤b≤3, and X is selected from any one of F, S, N, B, P, O, and Se.

[0014] In a protective atmosphere, the first precursor is subjected to a first heat treatment, causing the lithium source and the first X element source to react and generate Li. a X b The first carbon source is cracked to generate carbon, resulting in a binary lithium supplement additive.

[0015] This invention also provides another method for preparing a binary lithium supplementary additive. The method for preparing the binary lithium supplementary additive of this invention includes the following steps:

[0016] Preparation of Li a X b A binary lithium supplementary material; wherein, the Li a X b In the given information, 1≤a≤3, 1≤b≤3, and X is selected from any one of F, S, N, B, P, O, and Se.

[0017] The binary lithium supplement material is mixed with a second carbon source to form a second precursor;

[0018] The second precursor is carbonized in a protective atmosphere to obtain a binary lithium supplementary additive.

[0019] In another aspect, the present invention provides a cathode lithium replenishment additive. The cathode lithium replenishment additive of the present invention includes the binary lithium replenishment additive of the present invention or a binary lithium replenishment additive prepared by the preparation method of the binary lithium replenishment additive of the present invention.

[0020] In another aspect, the present invention provides a cathode material. The cathode material of the present invention includes the binary lithium supplement additive of the present invention, or a binary lithium supplement additive prepared by the method for preparing the binary lithium supplement additive of the present invention, or the cathode lithium supplement additive of the present invention.

[0021] In another aspect, the present invention provides a positive electrode. The positive electrode of the present invention includes a current collector and a positive electrode active layer bonded to the surface of the current collector, wherein the positive electrode active layer includes a positive electrode active material, a lithium supplementation additive, a binder, and a conductive agent; wherein the lithium supplementation additive is a binary lithium supplementation additive of the present invention, or a binary lithium supplementation additive prepared by the binary lithium supplementation additive preparation method of the present invention, or a positive electrode lithium supplementation additive of the present invention.

[0022] In another aspect, the present invention provides a lithium-ion battery. The lithium-ion battery of the present invention includes a positive electrode, wherein the positive electrode is the positive electrode of the present invention.

[0023] Compared with the prior art, the present application has the following technical effects:

[0024] The two-element lithium supplementing additive contains two-element lithium supplementing material rich in lithium, which can provide abundant lithium, so that in the first charging process, as a "sacrificial agent", all lithium ions are released at one time to supplement the irreversible lithium ions consumed by the formation of SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the initial efficiency and overall electrochemical performance of the battery. The at least surface carbon layer of the carbon matrix as a dense carbon layer increases the electronic contact between the lithium supplementing material and the carbon matrix. The dispersion of the two-element lithium supplementing material in the characteristic carbon matrix ensures the stability of the two-element lithium supplementing material, realizes stable lithium supplementing effect, and also improves the electronic conductive environment of the lithium supplementing material, which is beneficial to reducing polarization and promoting the release of lithium ions.

[0025] The preparation method of the two-element lithium supplementing additive can uniformly disperse the two-element lithium supplementing material in the above-mentioned characteristic carbon matrix, endow the prepared two-element lithium supplementing additive with the above-mentioned effects, and effectively ensure that the prepared two-element lithium supplementing additive is rich in lithium and has high purity, endowing the prepared two-element lithium supplementing additive with high capacity and lithium supplementing effect, as well as good storage stability and processing stability. In addition, the preparation method of the two-element lithium supplementing additive can ensure that the prepared two-element lithium supplementing additive has stable structure and electrochemical performance, and has high efficiency and saves production cost.

[0026] The positive electrode lithium supplementing additive and the positive electrode material contain the two-element lithium supplementing additive of the present application, so in the charging and discharging process, the positive electrode lithium supplementing additive and the positive electrode material can act as a lithium source in the first charging process as a "sacrificial agent" to supplement the irreversible lithium ions consumed by the formation of SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the initial efficiency and overall electrochemical performance of the battery.

[0027] The lithium ion battery contains the two-element lithium supplementing additive of the present application, so the positive electrode has good cycle performance and low internal resistance, thereby endowing the lithium ion battery of the present application with excellent initial coulomb efficiency and battery capacity, cycle performance, long service life and stable electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0029] Figure 1Transmission electron microscope (TEM) image of the two-element lithium supplement additive in Example 1 of the present application;

[0030] Figure 2 Preparation method flowchart of the two-element lithium supplement additive in Example 2 of the present application;

[0031] Figure 3 Preparation method flowchart of the two-element lithium supplement additive in Example 2 of the present application;

[0032] Figure 4 XRD image of Example 3 of the present application. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved in the present application more clear and explicit, the present application will be further described in detail in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0034] 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 mean that 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.

[0035] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or similar expressions mean any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean 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.

[0036] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and part or all steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0037] 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", "said" 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.

[0038] The weight of the related components mentioned in the embodiment specification of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the related components in the embodiment specification of the present application is proportionally enlarged or reduced, it is within the scope disclosed in the embodiment specification of the present application. Specifically, the mass mentioned in the embodiment specification of the present application can be μg, mg, g, kg, etc. mass units commonly known in the chemical industry.

[0039] The terms "first", "second" are only for descriptive purposes and are used 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 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 defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0040] In one aspect, the present application provides a two-element lithium supplement additive. The two-element lithium supplement additive of the present application comprises a carbon matrix and a two-element lithium supplement material dispersed in the carbon matrix.

[0041] In the two-element lithium supplement additive of the present application, the two-element lithium supplement material contained therein can provide abundant lithium, so that it can be released as a "sacrificial agent" during the first charging process, and the irreversible lithium ions consumed by the formation of SEI film in the negative electrode can be released at one time, so as to maintain the abundance of lithium ions in the battery system and improve the first efficiency and overall electrochemical performance of the battery. The carbon layer of the carbon matrix at least on the surface layer is a dense carbon layer, which increases the electronic contact between the two-element lithium supplement material and the carbon matrix, and improves the electronic conductivity of the two-element lithium supplement additive. The overall electronic conductivity of the two-element lithium supplement additive is measured to be 10 -5 -10 -2 S cm -1 , further 10 -3 -10 -2 S cm -1 . To simultaneously play the role of isolating the two-element lithium supplement material from air and improving the stability of the two-element lithium supplement material. Dispersing the two-element lithium supplement material in the characteristic carbon matrix ensures uniform dispersion and stability of the two-element lithium supplement material, and achieves stable lithium supplement effect. Moreover, it can also improve the electronic conductivity environment of the lithium supplement material, which is beneficial to reduce polarization and promote the release of lithium ions.

[0042] The dense carbon layer refers to a carbon matrix with low porosity and relatively large density. In the embodiments, the porosity of the dense carbon matrix is measured to be 0.1%-1%, and the typical but non-limiting porosity can be 0.1%, 0.3%, 0.5%, 0.7%, 1%, etc. The density of the carbon matrix of which at least the surface layer carbon is the dense carbon layer is 1.6-2.2 g cm -3 , and the typical but non-limiting density can be 1.6 g cm -3 , 1.7 g cm -3 , 1.8 g cm -3 , 1.9 g cm -3 , 2.0 g cm -3 , 2.1 g cm -3 , 2.2 g cm -3 , etc. Therefore, the carbon matrix with low porosity and large density can improve the stability of the two-element lithium supplement material and the stability of the lithium supplement effect. Since at least the surface layer carbon of the carbon matrix is the dense carbon layer, the entire carbon matrix can also be the dense carbon, i.e., the entire carbon matrix is the dense carbon matrix.

[0043] In the embodiments, the material of the carbon matrix includes at least one of hard carbon and soft carbon. The carbon matrix formed by the material has excellent electrical conductivity, high porosity, and high density, which can effectively fix the two-element lithium supplement additive dispersed in the carbon matrix, and improve the stability of the two-element lithium supplement additive and the stability of the lithium supplement.

[0044] In further embodiments, the material of the carbon matrix is doped with a conductive agent. In the embodiments, the mass content of the conductive agent in the two-element lithium supplement additive is 10%-30%, and the typical but non-limiting mass content can be 10%, 15%, 20%, 25%, 30%, etc. In specific embodiments, the conductive agent includes at least one of carbon nanotubes, graphene, and carbon nanofibers. Doping the carbon matrix with a conductive agent such as carbon nanotubes can effectively form a conductive network structure in the carbon matrix, improve the electrical conductivity of the carbon matrix, and improve the electrical conductivity and chemical properties of the two-element lithium supplement additive. Carbon nanotubes are beneficial to the uniform dispersion of the two-element lithium supplement material and help to obtain highly dispersed two-element lithium supplement material particles.

[0045] The molecular formula of the two-element lithium supplement material contained in the two-element lithium supplement additive of the embodiments is Li a X b ; wherein 1≤a≤3, 1≤b≤3, and X is selected from any one of F, S, N, B, P, O, and Se. The molecular formula is Li a X bThe two-element lithium supplement material is rich in lithium, thereby endowing the two-element lithium supplement additive of the embodiment of the application with the capability of providing abundant lithium so as to serve as a "sacrificial agent" during the first charging process. The molecular formula of the two-element lithium supplement material is Li a X b In an embodiment, the two-element lithium supplement material comprises at least one of LiF, Li2S, Li3N, Li3B, Li3P, and Li2Se. The two-element lithium supplement material has high lithium content and good stability.

[0046] In an embodiment, the two-element lithium supplement material has a granular morphology, that is, the two-element lithium supplement material is embedded into the above-mentioned characteristic carbon matrix in a granular morphology, and the two-element lithium supplement material and the carbon matrix form a Figure 1 pomegranate-like structure as shown in the figure, at which time the morphology of the two-element lithium supplement additive is a pomegranate-like structure morphology. The two-element lithium supplement material and the carbon matrix form a pomegranate-like structure, which endows the two-element lithium supplement additive of the embodiment of the application. The two-element lithium supplement material particles in the pomegranate structure are small and are embedded in the carbon matrix, and the particles are separated by carbon, thereby avoiding agglomeration and reducing the migration distance of the Li + material when it is released.

[0047] In a specific embodiment, when the two-element lithium supplement additive is a pomegranate-like structure, the particle size of the two-element lithium supplement material of this morphology is 20-100 nm, and the particle size can be 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 65 nm, 70 nm, 75 nm, 80 nm, 90 nm, or 100 nm, which are typical but non-limiting particle sizes.

[0048] In the above-mentioned embodiments, the mass content of the two-element lithium supplement material in the two-element lithium supplement additive is 40%-80%. By controlling and optimizing the content of the two-element lithium supplement material, the role of the two-element lithium supplement material in supplementing lithium can be fully improved, thereby maintaining the abundance of lithium ions in the battery system and improving the first efficiency and overall electrochemical performance of the battery.

[0049] In the above embodiments, the morphology of the binary lithium supplementary additive can be controlled as needed, such as particles or other morphologies. In the embodiments of the present invention, a particle morphology is relatively preferred. Furthermore, when the binary lithium supplementary additive is in particle morphology, it can be primary or secondary particles. When the binary lithium supplementary additive is in particle morphology, regardless of whether it is a primary or secondary particle, in the embodiments, the particle size of the binary lithium supplementary additive is 0.1-5 μm, specifically 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, typical but not limiting particle sizes; wherein, the particle size is D10 / D5≥0.1, D90 / D50≤3. The inventors found in their research that when the D50 of the binary lithium supplementary additive is <0.1 μm, the specific surface area of ​​the binary lithium supplementary additive increases with decreasing particle size, its activity increases, leading to a stable decrease in the performance of the binary lithium supplementary additive. The D50 of binary lithium supplementary additives is greater than 5 μm. As the particle size of the binary lithium supplementary additive increases, the lithium-ion migration path lengthens accordingly, thereby increasing the probability of kinetic polarization and reducing the capacity utilization effect. Therefore, binary lithium supplementary additives in this particle size range can fully exert their aforementioned functions such as lithium supplementation and high capacity, while improving their dispersibility.

[0050] Testing revealed that Raman spectroscopy analysis of the binary lithium supplementation additives in the above embodiments showed that the Raman spectra of the binary lithium supplementation additives at a wavelength of 1330 cm⁻¹... -1 With 1580cm -1 It has a scattering peak at a wavelength of 1330 cm⁻¹ -1 With 1580cm -1 The intensities of the scattering peaks at each location are denoted as I. D I G In the embodiment, when I D I G Satisfy: I D / I G At a conductivity <5.0, the binary lithium supplement additive exhibits excellent conductivity. The binary lithium supplement additive has few surface channels, low porosity, and high density, making it less prone to water absorption during storage, thus contributing to its stable performance. The inventors further discovered that I D / I G When the concentration increases, such as above 5.0, the binary lithium additive exhibits decreased conductivity, more surface pores, difficulty in material preservation, and a tendency to absorb moisture in normal environments, leading to performance degradation.

[0051] Accordingly, embodiments of the present invention also provide a method for preparing the binary lithium supplementation additive described above. In the embodiments, the process flow for preparing the binary lithium supplementation additive is as follows: Figure 2 As shown, its preparation method includes the following steps:

[0052] S01: mixing and processing a lithium source, a first X element source, and a first carbon source to prepare a first precursor;

[0053] S02: performing a first heat treatment on the first precursor in a protective atmosphere to cause the lithium source and the first X element source to react to generate Li a X b , and the first carbon source to crack to generate carbon, thereby obtaining a two-element lithium supplement additive.

[0054] In step S01, the lithium source and the first X element source are taken in stoichiometric amounts of Li a X b , respectively. In particular, Li a X b is a two-element lithium supplement material contained in the two-element lithium supplement additive. Therefore, 1≤a≤3 and 1≤b≤3 in Li a X b , and X is selected from any one of F, S, N, B, P, O, and Se. Therefore, the stoichiometric ratio in step S01 can be a molar ratio or a mass ratio converted from the molar ratio. In an embodiment, the lithium source includes at least one of LiOH and Li2SO4. The first X element source includes at least one of LiOH and Li2SO4. When Li a X b is Li2O and Li2S, etc., the lithium source and the first X element source can be the same, such as when Li a X b is Li2O, the lithium source and the first X element source are combined into LiOH. After mixing the lithium source and the first X element source in a certain proportion, they can be effectively mixed uniformly, and the raw materials have low cost, thereby effectively reducing the cost of the two-element lithium supplement material.

[0055] In an embodiment, the mixing ratio of the first carbon source to the lithium source and the first X element source satisfies that the mass content of the two-element lithium supplement material in the two-element lithium supplement additive is 40%-80% after the two-element lithium supplement additive is generated in step S02. In a specific embodiment, the first carbon source includes at least one of resorcinol, polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN), and polystyrene (PS).

[0056] Further, a conductive agent is added in the mixing process of the first carbon source with the lithium source and the first X element source. In an embodiment, the amount of the conductive agent is ensured to have a mass content of 10%-30% in the prepared two-element lithium supplement additive, and can be a typical but non-limiting mass content of 10%, 15%, 20%, 25%, 30%, etc. In a specific embodiment, the conductive agent includes at least one of carbon nanotubes, graphene, and carbon nanofibers.

[0057] The inventors found in the research that the particle size of each component and the mixing uniformity of each component in the first precursor have an influence on the carbon density and porosity generated in the first heat treatment in step S02, the smaller the particle size of each component and the more uniform the mixing of each component, the higher the carbon density and the lower the porosity generated in the first heat treatment in step S02. Therefore, the smaller the particle size of the lithium source and the first X element source, such as in the nanometer range, is more ideal, and it is ideal to select a soluble raw material so that each component can be dissolved to prepare a mixed solution, so that each component can be fully mixed and uniform, to increase the carbon density generated in the first heat treatment in S02 and reduce the porosity.

[0058] In the embodiment, the method of preparing the precursor in step S01 includes the following steps:

[0059] The lithium source, the first X element source, the carbon source, and the solvent are mixed and processed to prepare a mixed solution, and the mixed solution is granulated and dried to obtain a granular precursor.

[0060] When the conductive agent is mixed in the precursor, the conductive agent in the above-mentioned proportion is also added during the mixing process. In addition, the granulation and drying of the mixed solution can be but not limited to spray drying. The solution method preferably uses spray drying granulation to improve the uniformity of the dispersion of the components in the first precursor, thereby increasing the density of the carbon generated in the first heat treatment in step S02, i.e., the carbon matrix, and reducing the porosity.

[0061] The mixing process in step S01 is to mix each source material uniformly, so the mixing process can be a conventional mixing process, and it is ideal to use a grinding process to refine the particle size of each source compound under the premise of achieving uniform mixing of each source material, thereby further improving the uniformity of the mixing of each source material, thereby increasing the density of the carbon generated in the first heat treatment in step S02, i.e., the carbon matrix, and reducing the porosity, to improve the stability of the structure and electrochemical performance of the two-element lithium supplement additive.

[0062] In step S02, the first precursor in step S01 reacts with the first X element source to generate Li a X b The two-element lithium supplement material shown in the formula, i.e., the two-element lithium supplement material contained in the above-mentioned two-element lithium supplement additive. Specifically, when the lithium source and the first X element source are both LiOH and Li2SO4, LiOH decomposes to generate Li2O, and Li2SO4 decomposes to generate Li2S and O2 in the first heat treatment.

[0063] In the first heat treatment, the lithium source reacts with the first X element source to generate Li a X bThe first carbon source is cracked to form the carbon matrix contained in the above-mentioned two-element lithium supplement additive, specifically, the carbon matrix with at least the surface carbon layer being a dense carbon layer, thereby forming the above-mentioned two-element lithium supplement additive.

[0064] In the embodiment, the first heat treatment is performed at a temperature of 650-900°C, specifically, for example, but not only, at a typical but non-limiting temperature of 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, etc. The first heat treatment should be sufficient at this temperature, for example, for 2-4h.

[0065] The two-element lithium supplement additive generated after the above-mentioned first heat treatment can be a primary particle or a secondary particle.

[0066] In addition, the protective atmosphere of the first heat treatment in step S02 should be an environment that ensures the cracking of the carbon source, such as a non-oxygen environment. In a specific embodiment, the protective atmosphere is an argon protective atmosphere.

[0067] In order to make the carbon matrix contained in the prepared two-element lithium supplement additive have at least the surface carbon of the carbon matrix being a dense carbon layer, in the embodiment, after the treatment in step S02, a carbon layer can be further deposited on the surface of the two-element lithium supplement additive. Alternatively, the two-element lithium supplement additive is immersed in a molten carbon source or a carbon source solution for impregnation treatment, and then carbonized treatment is performed to at least improve the density of the carbon of the surface layer of the carbon matrix contained in the two-element lithium supplement additive, that is, to at least reduce the porosity of the carbon of the surface layer of the carbon matrix, such as to control the porosity to be 0.1%-1% as mentioned above.

[0068] Therefore, the above-mentioned method for preparing the two-element lithium supplement additive of the embodiment of the present application can effectively ensure that the prepared two-element lithium supplement additive is rich in lithium and has high purity, and the prepared two-element lithium supplement additive has high capacity and lithium supplement effect, as well as good storage stability and processing stability. a X b The raw materials of the elements contained in the two-element lithium supplement material are integrally mixed with the carbon source, and the two-element lithium supplement additive is generated after heat treatment, which gives the prepared two-element lithium supplement additive the excellent lithium supplement effect and electrochemical performance as mentioned above. Moreover, the prepared two-element lithium supplement additive can be effectively ensured to be rich in lithium and have high purity, which gives the prepared two-element lithium supplement additive high capacity and lithium supplement effect, as well as good storage stability and processing stability. In addition, the method for preparing the two-element lithium supplement additive can ensure that the prepared two-element lithium supplement additive has stable structure and electrochemical performance, and has high efficiency and saves production cost.

[0069] In the embodiment, the process flow of the method for preparing the two-element lithium supplement additive is as shown in the figure. Figure 3 The method for preparing the two-element lithium supplement additive includes the following steps:

[0070] S03: preparing a two-element lithium supplement material with a molecular formula of Li a X b ;

[0071] S04: mixing the two-element lithium supplement material with the second carbon source to form a second precursor;

[0072] S05: carbonizing the second precursor in a protective atmosphere to obtain the two-element lithium supplement additive.

[0073] In the formula of step S03, Li a X b The two-element lithium supplement material is the two-element lithium supplement material described above, Li a X b Therefore, in the formula of Li a X b 1≤a≤3, 1≤b≤3, and X is selected from any one of F, S, N, B, P, O, and Se.

[0074] In the embodiment, the method for preparing the two-element lithium supplement material with the formula of Li a X b includes the following steps:

[0075] Step S031: mixing a second X element source with the formula of Li a X b with elemental lithium to form a two-element lithium supplement material precursor;

[0076] Step S032: performing a second heat treatment on the two-element lithium supplement material precursor to generate a displacement reaction, thereby generating the two-element lithium supplement material with the formula of Li a X b .

[0077] In step S031, the second X element source includes at least one of Fe3O4, NiO, Mn3O4, CoS2, and CoF3. The second X element source provides the X element and can generate a displacement reaction with elemental lithium during the second heat treatment, thereby generating Li a X b . For example, when the second X element source is Fe3O4, NiO, Mn3O4, or the like, the Fe3O4, NiO, Mn3O4, or the like generates Li2O through a displacement reaction with lithium. When the second X element source is CoS2, the CoS2 generates Li2S through a displacement reaction with lithium. When the second X element source is CoF3, the CoF3 generates LiF through a displacement reaction with lithium.

[0078] CoS2+4Li→Co+2Li2S; CoF3+3Li→Co+3LiF

[0079] In embodiments, the second heat treatment is at a temperature of 190-250 °C, which can be a typical but non-limiting temperature of 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, etc., which ensures that the second X element source and lithium element can effectively undergo a displacement reaction, thereby improving the efficiency of the displacement reaction. At this temperature, the displacement reaction should be sufficient, such as 2-4 h.

[0080] In addition, the second heat treatment should be carried out in a protective atmosphere, such as a non-oxygen environment or a vacuum environment. In specific embodiments, the protective atmosphere is an argon protective atmosphere. The two-element lithium supplement material generated after the second heat treatment can be a primary particle or a secondary particle.

[0081] In addition, in order to improve the density of the carbon generated by the carbonization treatment in step S05, i.e., the carbon matrix, and reduce the porosity, the particle size of the two-element lithium supplement material prepared in step S01 should be controlled to the maximum extent, such as in the nanometer range, specifically 20-100 nm.

[0082] In step S04, the mixing ratio of the second carbon source and the two-element lithium supplement material prepared in step S01 satisfies that in the carbonization treatment in step S05 to generate the two-element lithium supplement additive, the mass content of the two-element lithium supplement material in the two-element lithium supplement additive is 40%-80%, which can be a typical but non-limiting mass content of 40%, 50%, 60%, 70%, 80%, etc. In specific embodiments, the second carbon source includes at least one of phenolic resin, polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN), and polystyrene (PS).

[0083] Further, in the mixing process of the two-element lithium supplement material and the second carbon source, a conductive agent is also added. In embodiments, the amount of the conductive agent added ensures that the mass content of the two-element lithium supplement additive prepared in step S05 is 10%-30%. In specific embodiments, the conductive agent includes at least one of carbon nanotubes, graphene, and carbon nanofibers. Ideally, the particle size of the conductive agent can also be in the nanometer range, specifically 20-100 nm, which can be a typical but non-limiting particle size of 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc., to improve the density of the carbon generated by the carbonization treatment in step S05, i.e., the carbon matrix, and reduce the porosity.

[0084] The mixing treatment in step S04 is to mix the two-element lithium supplement material and the second carbon source uniformly. Therefore, the mixing treatment can be a conventional mixing treatment, and desirably a grinding treatment. In the premise of achieving uniform mixing of the source materials, the particle size of each source compound is refined, and the uniformity of mixing of the source materials is further improved, so as to improve the density of the carbon generated in the carbonization treatment in step S05, i.e., the carbon matrix, and reduce the porosity, so as to improve the stability of the structure and electrochemical performance of the two-element lithium supplement additive.

[0085] In step S05, the second precursor in step S04 is subjected to carbonization treatment, and the second carbon source is cracked to generate the carbon matrix contained in the two-element lithium supplement additive described above, specifically a dense carbon matrix, so as to form the two-element lithium supplement additive described above.

[0086] In the embodiments, the carbonization treatment is performed at a temperature of 500-900°C, specifically a typical but non-limiting temperature of 500°C, 600°C, 700°C, 800°C, 900°C, etc. At the temperature, the carbonization treatment should be sufficient, for example, 3-5h.

[0087] In order to make the carbon matrix contained in the prepared two-element lithium supplement additive have at least a dense carbon layer on the surface, in the embodiments, after the treatment in step S04, the second precursor can be subjected to an impregnation treatment in a molten carbon source or a carbon source solution, and then subjected to the carbonization treatment in step S05.

[0088] The two-element lithium supplement additive after the carbonization treatment in step S05 can also be subjected to an impregnation treatment in a molten carbon source or a carbon source solution, and then subjected to a secondary carbonization treatment, so as to at least improve the density of the carbon on the surface layer of the carbon matrix contained in the two-element lithium supplement additive, i.e., at least reduce the porosity of the carbon on the surface layer of the carbon matrix, for example, to control the porosity to be 0.1%-1% as described above.

[0089] The two-element lithium supplement additive generated after the above carbonization treatment can be a primary particle or a secondary particle.

[0090] In addition, the protective atmosphere for the carbonization treatment in step S05 should be an environment in which the carbon source can be cracked, for example, a non-oxygen environment. In specific embodiments, the protective atmosphere is an argon protective atmosphere.

[0091] Therefore, the above-mentioned method for preparing the two-element lithium supplement additive of the embodiments of the present application can prepare the Li a X bThe elements contained in the two-element lithium supplementing material are directly mixed with the carbon source for treatment, and the two-element lithium supplementing additive is generated by carbonization treatment, which gives the prepared two-element lithium supplementing additive the excellent lithium supplementing effect and electrochemical performance described above. Moreover, it can effectively ensure that the prepared two-element lithium supplementing additive is rich in lithium and has high purity, giving the prepared two-element lithium supplementing additive high capacity and lithium supplementing effect, as well as good storage stability and processing stability. In addition, the preparation method of the two-element lithium supplementing additive can ensure that the prepared two-element lithium supplementing additive has stable structure and electrochemical performance, and has high efficiency and saves production cost.

[0092] In another aspect, the embodiments of the present application provide a positive electrode lithium supplementing additive. The positive electrode lithium supplementing additive of the embodiments of the present application comprises the two-element lithium supplementing additive of the above embodiments of the present application. The positive electrode lithium supplementing additive can be the two-element lithium supplementing additive of the above embodiments of the present application, and of course can further comprise other additives suitable for the positive electrode or auxiliary additives that are beneficial to fully exert the lithium supplementing effect of the two-element lithium supplementing additive of the above embodiments of the present application. When containing other additives, the ratio between the two-element lithium supplementing additive and the additives can be adjusted according to the actual application needs. Since the positive electrode lithium supplementing additive contains the two-element lithium supplementing additive of the above embodiments of the present application, the positive electrode lithium supplementing additive can act as a lithium source in the first charging process as a "sacrificial agent" to supplement the irreversible lithium ions consumed by the formation of SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the initial efficiency and overall electrochemical performance of the battery.

[0093] In still another aspect, the embodiments of the present application provide a positive electrode material. The positive electrode material of the embodiments of the present application comprises a lithium supplementing additive. The lithium supplementing additive is the two-element lithium supplementing additive of the above embodiments of the present application or the positive electrode lithium supplementing additive of the above embodiments of the present application. Of course, the positive electrode material can also comprise the positive electrode materials in the field of lithium ion batteries. Since the positive electrode material of the embodiments of the present application contains the two-element lithium supplementing additive of the above embodiments of the present application, the two-element lithium supplementing additive contained in the positive electrode material can act as a lithium source in the first charging process as a "sacrificial agent" to supplement the irreversible lithium ions consumed by the formation of SEI film on the negative electrode, thereby maintaining the abundance of lithium ions in the battery system and improving the initial efficiency and overall electrochemical performance of the battery.

[0094] In the embodiments, the content of the two-element lithium supplementing additive of the above embodiments of the present application in the positive electrode material is 0.1wt%-10wt%, and can be a typical but non-limiting content of 0.1wt%, 1wt%, 2wt%, 3wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% and the like. By controlling and optimizing the content of the two-element lithium supplementing additive in the positive electrode material, the two-element lithium supplementing additive can fully exert its above effects.

[0095] Meanwhile, based on the positive electrode material of the embodiment of the present application, the embodiment of the present application further provides a positive electrode and a lithium battery containing the positive electrode of the embodiment of the present application.

[0096] The active material contained in the positive electrode is the positive electrode material of the embodiment of the present application described above. The positive electrode can be a conventional positive electrode of a lithium battery, such as one comprising a current collector and a positive electrode active layer bonded to the surface of the current collector.

[0097] The positive electrode current collector comprises, but is not limited to, any one of a copper foil and an aluminum foil.

[0098] The positive electrode active layer contains the positive electrode material of the embodiment of the present application described above, i.e. contains the lithium supplement additive, specifically contains the binary lithium supplement additive of the embodiment of the present application described above or the positive electrode lithium supplement additive of the embodiment of the present application described above. In the embodiment, the mass content of the lithium supplement additive, i.e. the binary lithium supplement additive of the embodiment of the present application described above or the positive electrode lithium supplement additive of the embodiment of the present application described above, in the positive electrode active layer is 0.1wt%-10wt%; specifically, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% and the like typical but non-limiting contents, and preferably 2wt%-3wt%.

[0099] The positive electrode active layer comprises, in addition to the lithium supplement additive, a positive electrode active material, a binder and a conductive agent.

[0100] In the embodiment, the positive electrode active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, lithium nickel cobalt manganate and lithium nickel manganate.

[0101] In the embodiment, the content of the binder in the positive electrode active layer is 3wt%-5wt%, specifically, it can be 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% and the like typical but non-limiting contents. In the specific embodiment, the binder comprises one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, butadiene styrene rubber, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives.

[0102] In the embodiment, the content of the conductive agent in the positive electrode active layer is 2wt%-4wt%, specifically, it can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt% and the like typical but non-limiting contents. In the specific embodiment, the conductive agent comprises one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotube.

[0103] In the embodiment, the preparation process of the positive electrode is as follows: the positive electrode active material, the lithium supplementing additive, the conductive agent, and the binder are mixed to obtain an electrode slurry, the electrode slurry is coated on a current collector, and the positive electrode sheet is prepared through steps such as drying, rolling, and die cutting.

[0104] At this time, the lithium battery of the embodiment contains the positive electrode. Of course, the lithium battery of the embodiment also has the necessary components of the lithium battery, such as a negative electrode, a separator, and an electrolyte.

[0105] In addition, the lithium battery of the embodiment can be a lithium ion battery or a lithium metal battery.

[0106] Since the positive electrode contains the two-element lithium supplementing additive or the positive electrode lithium supplementing additive, in the first charging process of the lithium battery of the embodiment, the positive electrode contains the lithium supplementing additive of the embodiment as a "sacrificial agent" to release all lithium ions at one time as much as possible, so as to supplement the irreversible lithium ions consumed by the formation of the SEI film of the negative electrode, thereby keeping the lithium in the lithium battery system of the embodiment sufficient and improving the overall electrochemical performance of the lithium battery of the embodiment, such as the first efficiency, the capacity, and the cycle performance.

[0107] The two-element lithium supplementing additive of the embodiment, the preparation method and application thereof are illustrated by a plurality of specific embodiments.

[0108] 1. Two-element lithium supplementing additive and preparation method thereof

[0109] Embodiment A1

[0110] The embodiment provides a two-element lithium supplementing additive and a preparation method thereof. The two-element lithium supplementing additive comprises a dense carbon matrix and Li2O distributed and embedded in the dense carbon matrix, and the Li2O and the dense carbon matrix form a garnet structure.

[0111] The preparation method of the two-element lithium supplementing additive of the embodiment comprises the following steps:

[0112] S1. Preparation of Li2O: under the protection of Ar atmosphere, a proper amount of Co3O4 is mixed with metal Li, heated to 190-250°C, the reaction time is 2-4h, and continuous mechanical stirring is performed during the reaction to ensure the uniformity of the mixture. Li can displace Co element to obtain Li2O nanoparticles embedded in the Co matrix. The reaction equation is: 8Li+Co3O4→3Co+4Li2O;

[0113] S2. Preparation of the two-element lithium supplementing additive with a garnet structure:

[0114] The Li2O / Co and the carbon source are uniformly mixed in solid phase, and carbonization treatment is performed at 500-700°C for 2-4 hours.

[0115] The two-element lithium supplement additive of the present example was subjected to transmission electron microscopy (TEM) analysis, and the TEM image thereof is shown in Figure 1 As can be seen from the TEM image, the Li2O is dispersed in the form of particles and embedded in the dense carbon matrix (as the black spots in the image, i.e. the Li2O particles), and forms a stone-like structure. Figure 1 Figure 1 The two-element lithium supplement additive of the present example was subjected to transmission electron microscopy (TEM) analysis, and the TEM image thereof is shown in

[0116] The carbon matrix contained in the two-element lithium supplement additive of the present example was detected to have a density of 1.7-1.9 g cm -3 , a porosity of 0.3%-0.5%, a Li2O content of 50%-70%, a Li2O particle size of 30-60 nm, and a D50 of 0.9 μm.

[0117] Example A2

[0118] The present example provides a two-element lithium supplement additive and a preparation method thereof. The two-element lithium supplement additive comprises a dense carbon matrix and Li2O distributed and embedded in the dense carbon matrix, and the Li2O and the dense carbon matrix form a stone structure.

[0119] The preparation method of the two-element lithium supplement additive of the present example comprises the following steps:

[0120] S1: LiOH, resorcinol, ammonia water, formaldehyde solution, and carbon nanotube dispersion liquid are added into water in a mass ratio of 1:2:1 for LiOH, resorcinol, and carbon nanotube, and a volume ratio of 1:1.5:100 for ammonia water, formaldehyde solution, and water, and the mixture is stirred for several hours, and then spray dried to obtain spherical two-element lithium supplement additive precursor particles in a microstructure;

[0121] S2: The spherical two-element lithium supplement additive precursor particles are placed in a tube furnace and reacted at about 1000°C for 2-4 h in an argon atmosphere. The LiOH is decomposed into Li2O, and the resorcinol resin is carbonized at high temperature to obtain a two-element lithium supplement additive in a stone structure.

[0122] The two-element lithium supplement additive of the present example was subjected to TEM analysis, and the TEM image thereof is similar to that of Figure 1 The Li2O is dispersed in the form of particles and embedded in the dense carbon matrix, and forms a stone-like structure.

[0123] The carbon matrix contained in the two-element lithium supplement additive of the present example was detected to have a density of 1.9 g cm -3 , a porosity of 0.2%-0.4%, a Li2O content of 40-60%, a Li2O particle size of 10-40 nm, and a D50 of 0.4 μm.

[0124] Example A3​

[0125] This embodiment provides a binary lithium supplement additive and its preparation method. The binary lithium supplement additive includes a dense carbon matrix and Li2S distributed and embedded in the dense carbon matrix, wherein the Li2S and the dense carbon matrix form a garnet structure.

[0126] The preparation method of the binary lithium supplementary additive in this embodiment includes the following steps:

[0127] Preparation of Li₂S: Under an Ar atmosphere, an appropriate amount of CoS₂ was mixed with metallic Li and heated to 185-220℃ for 1-4 hours. Continuous mechanical stirring was performed during the reaction to ensure uniform mixing of the reactants. Li displaced elemental Co, resulting in Li₂S nanoparticles embedded in a Co matrix. The reaction equation is: 4Li + CoS₂ → Co + 2Li₂S;

[0128] Preparation of S2 pomegranate-structured binary lithium supplementary additive:

[0129] Mix Li2S / Co and carbon source evenly and perform carbonization treatment (500-700℃, 2-4 hours).

[0130] The binary lithium-supplementing additive of this embodiment was analyzed by transmission electron microscopy (TEM), and the TEM image is shown below. Figure 1 As shown. By Figure 1 It can be seen that Li2S is dispersed in particulate form and embedded in a dense carbon matrix (such as...). Figure 1 The black dots in the sample are Li2S particles, which form the pomegranate-like morphological structure.

[0131] The binary lithium supplementation additive prepared in this embodiment was analyzed by X-ray diffraction (XRD), and its XRD pattern is shown below. Figure 4 As shown. By Figure 4 It can be seen that the binary lithium supplement additive in this embodiment contains Li2S@C related characteristic peaks.

[0132] Testing revealed that the density of the carbon matrix in the binary lithium supplement additive of this embodiment is 1.7-1.9 g / cm³. -3 The porosity is 0.2%-1%, the Li2S content is 50-70%, the Li2S particle size is 5-30nm, and the D50 of the binary lithium supplement additive is 1μm.

[0133] Comparative Example A1

[0134] We provide Li2O binary lithium supplementation materials.

[0135] Comparative Example A2

[0136] The comparative example provides a two-element lithium supplementing additive, which is different from example A2 in that the carbon matrix is a porous carbon matrix.

[0137] The preparation method of the two-element lithium supplementing additive of the comparative example comprises the following steps:

[0138] The lithium metal is melted under vacuum, mixed with the porous carbon material, and the molten lithium is allowed to penetrate into the pores of the porous carbon material at 180-500°C; after the penetration of the molten lithium is complete, O2 is introduced at a rate of 0.5-1.5 m 3 / min for reaction for 5-60 min, and after the reaction is complete, the product is cooled under a protective atmosphere to obtain the positive electrode lithium supplementing additive.

[0139] 2. Lithium ion battery examples:

[0140] The two-element lithium supplementing additives provided in examples A1-A3 and the two-element lithium supplementing additives provided in comparative examples A1-A2 are respectively prepared into positive electrodes and assembled into lithium ion batteries according to the following methods:

[0141] Positive electrode: the lithium supplementing additive is mixed with lithium cobaltate at a mass ratio of 5:95 to obtain a mixture, the mixture is mixed with polyvinylidene fluoride and SP-Li at a mass ratio of 93:3:4 to obtain a positive electrode slurry, and the positive electrode slurry is coated on the surface of an aluminum foil, rolled, and vacuum dried at 110°C overnight to obtain a positive electrode sheet;

[0142] Negative electrode: lithium metal sheet;

[0143] Electrolyte: ethylene carbonate and methyl ethyl carbonate are mixed at a volume ratio of 3:7, and LiPF6 is added to form an electrolyte, and the concentration of LiPF6 is 1 mol / L;

[0144] Separator: polypropylene microporous separator.

[0145] Lithium ion battery assembly: lithium ion batteries are assembled in an inert atmosphere glove box according to the assembly sequence of lithium metal sheet-separator-electrolyte-positive electrode sheet.

[0146] Related property tests

[0147] Lithium ion battery electrochemical performance:

[0148] The electrochemical performance of lithium secondary batteries containing the two-element lithium supplementing additives of examples A1-A3 and the two-element lithium supplementing additives of comparative examples A1-A2 is tested, and the test conditions are: the voltage range is 4.2-3.0 V vs. Li + / Li, and the current density is 0.1C.

[0149] The results of the related electrochemical performance tests of the lithium secondary batteries are shown in Table 1 below:

[0150] Table 1

[0151]

[0152] As can be seen from Table 1, the specific capacity of the first charge of Examples A1-A3 is greatly improved compared to Comparative Examples A1 and A2, and the corresponding first coulombic efficiency is also lower, which shows that the lithium supplementing agent in the examples can release more lithium ions during the first charge, thereby supplementing the irreversible capacity loss of the negative electrode during the first cycle and consuming as few lithium ions of the positive electrode material itself as possible. The excellent performance of the examples comes from the unique structural design of the corresponding lithium supplementing material. The dense carbon matrix in the pomegranate-like structure can inhibit particle agglomeration and growth, and has good electronic contact with the lithium supplementing particles, thereby reducing polarization and facilitating the release of lithium ions.

[0153] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A two-component lithium supplementing additive, characterized in that: The lithium supplement material comprises a carbon base and a two-element lithium supplement material dispersed in the carbon base, and at least a carbon layer of a surface layer of the carbon base is a dense carbon layer, and a molecular formula of the two-element lithium supplement material is Li a X b ; wherein, 1<=a<=3, 1<=b<=3, and X is selected from any one of F, S, N, B, P, O and Se. The porosity of the dense carbon layer is 0.1%-1%; The two-element lithium supplement material is in a granular morphology, and the two-element lithium supplement material and the carbon matrix form a pomegranate-shaped structure, and the particle size of the two-element lithium supplement material is 20-100 nm.

2. The bi-lithium supplement additive according to claim 1, characterized in that: The material of the carbon matrix includes at least one of hard carbon and soft carbon; and / or The mass content of the two-element lithium supplement material in the two-element lithium supplement additive is 40%-80%; and / or The two-element lithium supplement material includes at least one of LiF, Li2S, Li3N, Li3B, Li2O, Li3P and Li2Se; and / or The particle size of the two-element lithium supplement additive is 0.1-5 μm; and / or The particle size of the two-element lithium supplement additive is D10 / D5≥0.1, and D90 / D50≤3.

3. The two-component lithium supplementing additive according to any one of claims 1-2, characterized in that: The material of the carbon matrix is further doped with at least one conductive agent of carbon nanotubes, graphene and carbon nanofibers.

4. The bi-lithium supplement additive according to any one of claims 1-2, characterized in that: The two-element lithium supplementing additive has scattering peaks at wavelengths of 1330 cm -1 and 1580 cm -1 , and the intensity of the scattering peaks at wavelengths of 1330 cm -1 and 1580 cm -1 is respectively denoted as I D and I G , and I D and I G satisfy: I D / I G < 5.0; and / or The overall electronic conductivity of the two-component lithium supplementing additive is 10 -5 -10 -2 S cm -1 .

5. The preparation method of the two-element lithium supplement additive according to any one of claims 1-4, comprising the following steps: The first precursor is prepared by mixing a lithium source, a first X element source and a first carbon source. The lithium source and the first X element source are respectively taken in stoichiometric amounts according to the molecular formula Li aX b a X b The lithium source and the first X element source are respectively taken in stoichiometric amounts according to the molecular formula Li aX b a X b 1≤a≤3, 1≤b≤3, and X is selected from any one of F, S, N, B, P, O, and Se. In a protective atmosphere, the first precursor is subjected to a first heat treatment, so that the lithium source and the first X element source react to generate Li a X b , and the first carbon source is cracked to generate carbon, to obtain a two-element lithium supplement additive.

6. The method of claim 5, wherein: The lithium source includes at least one of LiOH and Li2SO4; and / or The first X element source includes at least one of LiOH and Li2SO4; and / or The first carbon source includes at least one of resorcinol, polyvinylpyrrolidone, polyacrylonitrile and polystyrene; and / or In the step of mixing the lithium source, the first X element source and the first carbon source, a conductive agent is further added to participate in the mixing process; and / or The temperature of the first heat treatment is 650-900 ℃; and / or The method for preparing the first precursor comprises the following steps: The lithium source, the first X element source and the carbon source and a solvent are mixed to prepare a mixture solution, and the mixture solution is granulated and dried to obtain the granular first precursor.

7. The method of claim 6, wherein: The Li a X b When X is Li2O, Li2S, the source of lithium and / or X element comprises at least one of LiOH, Li2SO4.

8. The preparation method of the two-element lithium supplement additive according to any one of claims 1-4, comprising the following steps: A two-element lithium supplement material with a molecular formula of Li a X b ; wherein, The Li a X b 1≤a≤3, 1≤b≤3, X is selected from any one of F, S, N, B, P, O, Se; The two-element lithium supplement material is mixed with a second carbon source to form a second precursor; The second precursor is carbonized in a protective atmosphere to obtain the two-element lithium supplement additive.

9. The method of claim 8, wherein: The temperature of the carbonization treatment is 500-900 ℃; and / or The second carbon source includes at least one of phenolic resin, polyvinylpyrrolidone, polyacrylonitrile and polystyrene; and / or The preparation method of the binary lithium supplement material of the molecular formula Li a X b The preparation method of the binary lithium supplement material of the molecular formula Li The molecular formula is Li a X b The second X element source is mixed with lithium element to form a two-element lithium supplement material precursor. In a protective atmosphere, the two-element lithium supplementing material precursor is subjected to a second heat treatment to generate the two-element lithium supplementing material with a molecular formula of Li a X b ​ 10. The method of claim 9, wherein: The second X element source includes at least one of Fe3O4, NiO, Mn3O4 and Co3O4; and / or The temperature of the second heat treatment is 190-250 ℃.

11. A positive electrode lithium supplementing additive, characterized by: The two-element lithium supplement additive according to any one of claims 1-4 or prepared by the preparation method according to any one of claims 6-8 or the preparation method according to any one of claims 8-10.

12. A positive electrode material, characterized by: The two-element lithium supplement additive according to any one of claims 1-4 or prepared by the preparation method according to any one of claims 5-7 or the preparation method according to any one of claims 8-10 or the positive electrode lithium supplement additive according to claim 11.

13. A positive electrode, characterized by comprising: The positive electrode active layer comprises a positive electrode active material, a lithium supplementing additive, a binder and a conductive agent; wherein the lithium supplementing additive is the binary lithium supplementing additive according to any one of claims 1-4 or prepared by the preparation method according to any one of claims 5-7 or 8-10 or the positive electrode lithium supplementing additive according to claim 11.

14. The positive electrode according to claim 13, characterized by: The content of the lithium supplementing additive in the positive electrode active layer is 0.1 wt%-10 wt%; and / or The content of the conductive agent in the positive electrode active layer is 2 wt%-4 wt%; and / or The content of the binder in the positive electrode active layer is 3 wt%-5 wt%.

15. A lithium battery comprising a positive electrode, characterized in that: The positive electrode is the positive electrode according to any one of claims 13-14.

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