A composite lithium supplementing material, a preparation method and application thereof

Abstract

This application provides a composite lithium supplement material, its preparation method, and its application. The composite lithium supplement material comprises a main phase and a secondary phase, wherein the main phase includes Li₂. x A y The secondary phase comprises a compound containing lithium and element M; wherein element M includes at least one of C, H, and O, and element A includes at least one of N, P, S, F, B, O, and Se, 0 < x ≤ 5, y > 0; the secondary phase is doped into the main phase, and / or the secondary phase coats the surface of the main phase. The above-mentioned composite lithium replenishment material exhibits both high structural stability and high lithium replenishment activity, and is less prone to side reactions with organic solvents used in battery manufacturing, achieving efficient lithium replenishment. Therefore, it can be used to provide secondary batteries with high initial charge-discharge efficiency, energy density, and large battery capacity.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a composite lithium replenishment material, its preparation method, and its application. Background Technology

[0002] In recent years, with the widespread application of rechargeable batteries, the market has placed higher demands on their energy density and capacity. However, lithium-ion rechargeable batteries generally experience irreversible Li-ion degradation during the first charge and discharge process. + Lithium loss affects battery capacity and energy density. Generally, the industry uses either positive or negative electrode lithium replenishment to address this issue, with positive electrode lithium replenishment being safer than negative electrode lithium replenishment. However, some common positive electrode lithium replenishment materials, such as Li3N, Li3P, and Li2S, readily react with organic solvents (e.g., N-methylpyrrolidone) commonly used in electrode preparation to form gels, thus failing to effectively replenish lithium. Summary of the Invention

[0003] Therefore, this application provides a composite lithium replenishment material, its preparation method, and its application. This composite lithium replenishment material exhibits both high structural stability and high lithium replenishment activity, and is less prone to side reactions with organic solvents used in battery manufacturing, thus achieving efficient lithium replenishment.

[0004] A first aspect of this application provides a composite lithium replenishment material, comprising a main phase and a secondary phase, wherein the main phase comprises Li₂. x A y The aforementioned secondary phase includes compounds containing lithium and element M; wherein the aforementioned element M includes at least one of C, H and O, the aforementioned element A includes at least one of N, P, S, F, B, O and Se, 0 < x ≤ 5, y > 0; the aforementioned secondary phase is doped in the aforementioned main phase, and / or the aforementioned secondary phase is coated on the surface of the aforementioned main phase.

[0005] The presence of the secondary phase is beneficial to improving the structural stability of the composite lithium replenishment material and allows lithium vacancies to form in the main phase, thereby improving the lithium replenishment efficiency. Furthermore, the aforementioned secondary phase exhibits good chemical stability, enhancing the chemical stability of the composite lithium replenishment material and enabling the main phase to fully utilize its lithium replenishment performance, thus successfully providing a large amount of active Li to the battery. + This enables efficient lithium replenishment of the battery, thereby improving the battery's first charge / discharge efficiency, battery capacity, and energy density.

[0006] The second aspect of this application provides a method for preparing a composite lithium supplement material, comprising the following steps:

[0007] (1) Provide the main phase material;

[0008] (2) Mix the main phase material with the secondary phase raw material to obtain a mixture;

[0009] (3) The above mixture is sintered under an inert atmosphere to obtain a composite lithium replenishing material; wherein the composite lithium replenishing material includes a main phase and a secondary phase, and the main phase includes Li x A y The aforementioned secondary phase includes compounds containing lithium and element M; wherein the aforementioned element M includes at least one of C, H and O, the aforementioned element A includes at least one of N, P, S, F, B, O and Se, 0 < x ≤ 5, y > 0; the aforementioned secondary phase is doped in the aforementioned main phase, and / or the aforementioned secondary phase is coated on the surface of the aforementioned main phase.

[0010] This preparation method is simple, highly controllable, and has low production costs, making it suitable for large-scale industrial production.

[0011] The third aspect of this application provides a positive electrode sheet having the composite lithium replenishing material provided in the first aspect of this application or containing the composite lithium replenishing material prepared according to the preparation method provided in the second aspect of this application.

[0012] This positive electrode can be used to provide secondary batteries with high initial charge-discharge efficiency, large battery capacity, and high battery energy density.

[0013] The fourth aspect of this application provides a secondary battery having a positive electrode provided in the third aspect of this application.

[0014] This secondary battery has high initial charge / discharge efficiency, large battery capacity, and high energy density. Attached Figure Description

[0015] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the composite lithium supplement material prepared in Example 6 of this application. Detailed Implementation

[0016] Specifically, this application provides a composite lithium replenishment material. This composite lithium replenishment material includes a main phase and a secondary phase, wherein the main phase includes Li. x A y The aforementioned secondary phase includes compounds containing lithium and element M; wherein the aforementioned element M includes at least one of C, H and O, the aforementioned element A includes at least one of N, P, S, F, B, O and Se, 0 < x ≤ 5, y > 0; the aforementioned secondary phase is doped in the aforementioned main phase, and / or the aforementioned secondary phase is coated on the surface of the aforementioned main phase.

[0017] The secondary phase is less prone to ion migration during charge and discharge, which helps improve the structural stability of the composite lithium replenishment material. Furthermore, the presence of the secondary phase can partially capture or attract lithium elements from the main phase lattice, creating lithium vacancies in the main phase and thus accelerating the activation of Li. + Diffusion and extraction within the main phase promotes the uniform distribution of lithium elements, thereby improving the lithium replenishment efficiency of the composite lithium replenishment material. Furthermore, the aforementioned secondary phase exhibits good chemical stability, reducing the risk of chemical reactions between materials such as Li3N, Li3P, and Li2S and substances like NMP, allowing the main phase to fully utilize its lithium replenishment performance. Moreover, the secondary phase also possesses a certain degree of lithium replenishment effect. In summary, the aforementioned composite lithium replenishment material can be used to provide secondary batteries with high initial charge-discharge efficiency, high battery capacity, and high energy density.

[0018] In some embodiments of this application, the aforementioned secondary phase further contains element X. Element X includes, but is not limited to, at least one of N, P, S, F, B, O, and Se. The presence of element X can synergistically increase the difficulty of ion migration in the secondary phase during charge and discharge, thereby further improving the structural stability of the composite lithium replenishment material during charge and discharge. Furthermore, the introduction of element X can further improve the chemical stability and lithium replenishment capability of the secondary phase.

[0019] In this application, the A element in the main phase and the X element in the secondary phase can be the same or different. Those skilled in the art can choose according to actual production needs. In some embodiments of this application, the A element in the main phase and the X element in the secondary phase of the composite lithium supplement material are the same.

[0020] In some embodiments of this application, the aforementioned secondary phase includes, but is not limited to, Li. a C b X c H d O e Wherein, 1≤a≤15, 0≤b≤4, 0≤c≤5, 0≤d≤5, 0≤e≤10, and at least one of b, d, and e is not 0. For example, the above-mentioned secondary phases can be Li2NH, Li4C2NH, Li6C3NHO3, Li4C3N2, etc.

[0021] In some embodiments of this application, element A is N, element M includes O, and element X is N. In this case, the composite lithium supplement material provides active Li... + At the same time, other elements can be released as gases (e.g., O2, CO2, N2, etc.). After lithium replenishment, the composite lithium replenishment material leaves almost no residue, thus effectively preventing side reactions between the composite lithium replenishment material and other substances in the battery that could affect battery performance.

[0022] In some embodiments of this application, chemical bonds exist between the main phase and the secondary phase. In this case, while the main phase and the secondary phase are connected by physical forces (e.g., friction between main phase particles and secondary phase particles, extrusion force between multiple main phase particles and secondary phase particles, etc.), the presence of the chemical bonds can further improve the structural stability of the composite lithium supplementation material.

[0023] In this application, the chemical bonds between the secondary phase and the primary phase are formed by thermal diffusion between the primary phase and the secondary phase (secondary phase raw material) during the sintering process.

[0024] In some embodiments of this application, all of the aforementioned secondary phases exist as dopants in the main phase.

[0025] In other embodiments of this application, at least some secondary phases coat the surface of the main phase, which may be partial coating or complete coating of the main phase. In some embodiments, the thickness of the coating layer formed by the secondary phase is in the range of 1 nm to 200 nm. Exemplarily, the thickness of the coating layer can be 1 nm, 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, etc. In some specific embodiments, the thickness of the coating layer formed by the secondary phase is in the range of 2 nm to 60 nm. Controlling the thickness of the coating layer within the above range is beneficial for controlling the activity of Li. + The transmission path is relatively short, which is conducive to achieving efficient lithium replenishment.

[0026] In some cases, all the secondary phases can coat the surface of the main phase. In other cases, some of the secondary phases can be incorporated into the main phase as a core material, while other secondary phases coat the surface of the core material to form a coating layer.

[0027] The incorporation of secondary phases into the main phase can improve the overall interfacial conductivity of the composite lithium replenishment material, further enhancing its cycle stability. The secondary phase coating the surface of the core material (main phase and the main phase doped with secondary phases) can more effectively prevent gelation reactions between the main phase and the organic solvents or electrolytes required during battery fabrication, thus facilitating battery fabrication and performance, while also improving battery safety and stability. Furthermore, the secondary phase coating on the outside of the core material acts as a "sacrificial" physical barrier, protecting the core material from corrosion by moisture, O2, CO2, and other substances in the air. When the secondary phase is simultaneously incorporating the main phase and coating the surface of the core material, the composite lithium replenishment material possesses both of these characteristics, resulting in superior overall performance.

[0028] In some embodiments of this application, the surface of the composite lithium replenishment material is coated with a carbon material. This carbon material coats the surface of the primary particles of the composite lithium replenishment material. In some cases, there are secondary particles formed by the aggregation of multiple primary composite lithium replenishment material particles coated with a carbon layer. In this case, carbon material is distributed on the outer surface and / or in the gaps between the secondary particles (specifically, the gaps between multiple primary particles within the secondary particles). In this application, the carbon material includes, but is not limited to, hydrophobic carbon materials. Exemplarily, the carbon material can be amorphous carbon, carbon black, graphite, graphene, carbon nanotubes, etc. The presence of the carbon layer can effectively isolate water vapor, oxygen, and CO2 in the air, improving the storage stability and environmental stability of the composite lithium replenishment material, and can significantly improve the conductivity of the composite lithium replenishment material.

[0029] In some embodiments of this application, the carbon material and the composite lithium replenishment material have chemical bonds (chemical bonds can exist between the carbon material and the main phase, and between the carbon material and the secondary phase). These chemical bonds are formed during high-temperature processing. The presence of these chemical bonds further enhances the bonding force between the carbon material and the composite lithium replenishment material particles, allowing the carbon layer to more tightly and stably coat the outer surface of the composite lithium replenishment material particles. This enables the carbon layer to fully exert its protective function during subsequent battery fabrication, thus facilitating successful battery fabrication and maximizing the lithium replenishment performance of the composite lithium replenishment material.

[0030] In some embodiments, the mass percentage of the carbon material in the composite lithium-supplementing material is in the range of 0.1%-5%. For example, the mass percentage of the carbon material in the composite lithium-supplementing material can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc. Controlling the carbon material content within the above range can, on the one hand, control the content of lithium-supplementing materials (main phase and secondary phase) in the composite lithium-supplementing material to be relatively high. On the other hand, this can improve the uniformity of the carbon material coating on the surface of the composite lithium-supplementing material, reduce the risk of the composite lithium-supplementing material being exposed, and also help ensure that the carbon layer has a suitable thickness, so that the carbon layer can better isolate the external environment while avoiding an excessively thick carbon layer that hinders the activity of Li. + Desorption occurs. The thickness of the carbon layer formed by the aforementioned carbon material is controlled within the range of 2nm-200nm, preferably within the range of 2nm-50nm. For example, the thickness of the carbon layer can be 2nm, 5nm, 10nm, 15nm, 20nm, 30nm, 50nm, 100nm, 150nm, 200nm, etc. In summary, controlling the quality of the carbon material and the thickness of the carbon layer within the aforementioned ranges is beneficial for improving the environmental and storage stability of the composite lithium replenishment material while also ensuring the activity of Li. + The transmission is relatively fast, ultimately enabling efficient lithium replenishment.

[0031] In this application, the surface of the composite lithium replenishment material can be coated with at least one of conductive oxides and conductive organic materials. Exemplarily, these can be polyaniline, polypyrrole, polyethylene oxide, poly3,4-ethyldioxothiophene, In₂O₃, ZnO, and SnO₂, etc. These materials have good conductivity, which can improve the lithium replenishment effect and stability of the composite lithium replenishment material. They also act as a barrier against moisture, oxygen, and CO₂ in the air, which is beneficial for improving the storage stability of the composite lithium replenishment material. The thickness of the coating layer formed on the surface of the composite lithium replenishment material can be in the range of 2 nm to 200 nm. In some specific embodiments, it can be in the range of 2 nm to 50 nm.

[0032] In some embodiments of this application, the D50 particle size (average particle size, measured by dynamic light scattering) of the main phase is in the range of 0.01 μm to 15 μm. The D50 particle size (average particle size, measured by dynamic light scattering) of the secondary phase is in the range of 0.01 μm to 20 μm. In some specific embodiments, the D50 particle size of the main phase is in the range of 0.01 μm to 6 μm. The D50 particle size of the secondary phase is in the range of 0.01 μm to 4 μm. Exemplarily, the D50 particle size of the main phase can be 0.01 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc. For example, the D50 particle size of the above-mentioned subphase can be 0.01μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc.

[0033] In other embodiments of this application, the D50 particle size of the main phase is in the range of 10 nm to 1000 nm. Exemplarily, the D50 particle size of the main phase can be 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, etc. The D50 particle size of the secondary phase is in the range of 10 nm to 1000 nm. The D50 particle size of the aforementioned subphase can be 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, etc. In this case, the composite lithium supplement material can achieve nanoscale doping, which is beneficial for further improving the structural and chemical stability of the composite lithium supplement material.

[0034] In some embodiments of this application, the size of the composite lithium replenishing material is in the range of 0.01 μm-50 μm, and more specifically, the size of the composite lithium replenishing material is in the range of 0.1 μm-50 μm. Even further, in some specific embodiments, the size of the composite lithium replenishing material is in the range of 0.1 μm-20 μm. Exemplarily, the size of the composite lithium replenishing material can be 0.01 μm, 0.1 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc. When the secondary phase is completely doped in the main phase, the size of the composite lithium replenishing material is in the range of 0.01 μm-35 μm, and more preferably 0.1 μm-35 μm. When the composite lithium replenishing material has a coating layer, the size of the composite lithium replenishing material is in the range of 0.01μm-30μm, and more preferably 0.1μm-30μm.

[0035] In some embodiments of this application, the mass percentage of the aforementioned secondary phase in the composite lithium replenishment material is in the range of 1%-30%. In some specific embodiments, the mass percentage of the aforementioned secondary phase in the composite lithium replenishment material is in the range of 1%-10%. Exemplarily, the mass percentage of the aforementioned secondary phase in the composite lithium replenishment material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, etc. Controlling the mass percentage of the secondary phase within the above range means controlling the composite lithium replenishment material to have appropriate amounts of primary and secondary phases, so that the composite lithium replenishment material can have both strong lithium replenishment capacity and excellent environmental stability, chemical stability, and structural stability.

[0036] In some embodiments of this application, the specific surface area (referring to the BET specific surface area) of the above-mentioned composite lithium replenishment material is 0.1 m². 2 / g-40m 2 Within the range of / g. Controlling the specific surface area of ​​the composite lithium supplementation material within the above range is beneficial to the activity of Li. + This allows for efficient lithium replenishment through the transmission of lithium.

[0037] Accordingly, this application also provides a method for preparing a composite lithium supplementation material. The method includes the following steps:

[0038] (1) Provide the main phase material;

[0039] (2) Mix the main phase material with the secondary phase raw material to obtain a mixture;

[0040] (3) The above mixture is sintered under an inert atmosphere to obtain a composite lithium replenishing material; wherein the composite lithium replenishing material includes a main phase and a secondary phase, and the main phase includes Li x A y The aforementioned secondary phase includes compounds containing lithium and element M; wherein the aforementioned element M includes at least one of C, H and O, the aforementioned element A includes at least one of N, P, S, F, B, O and Se, 0 < x ≤ 5, y > 0; the aforementioned secondary phase is doped in the aforementioned main phase, and / or the aforementioned secondary phase is coated on the surface of the aforementioned main phase.

[0041] This preparation method is simple, highly controllable, and has low production costs, making it suitable for large-scale industrial production. Furthermore, the composite lithium-supplementing material prepared by this method exhibits good structural and chemical stability, which facilitates the successful fabrication of batteries and can improve the initial charging efficiency and overall electrochemical performance of the batteries.

[0042] In this application, the mixing method in step (2) can be mechanical stirring, high-energy grinding, mechanical fusion, etc. The main phase material and secondary phase raw material mentioned above can be powders, which are easier to disperse evenly during the mixing process.

[0043] In some embodiments of this application, the aforementioned secondary phase raw material may be the secondary phase compound itself, or it may be a compound selected from those required for the synthesis of the secondary phase.

[0044] In some specific embodiments, the aforementioned secondary phase raw material may be Li₂C₂, Li₂NH, Li₂NCN, LiPON, LiH₂PO₄, etc. In other specific embodiments, the aforementioned secondary phase raw material may also include lithium oxides. For example, it may be Li₂CO₃, Li₂O, etc. In this case, the aforementioned element M includes element O.

[0045] In some embodiments of this application, the above preparation method further includes step (4): adding carbon material to the obtained composite lithium replenishing material, mixing thoroughly, and performing high-temperature treatment under an inert atmosphere to obtain a composite lithium replenishing material coated with carbon material. The mixing method can be mechanical stirring, high-energy grinding, mechanical fusion, etc. The high-temperature treatment temperature is controlled between 450℃ and 700℃.

[0046] This application also provides a positive electrode sheet, which has the composite lithium replenishing material provided in this application embodiment or has the composite lithium replenishing material prepared by the preparation method provided in this application embodiment.

[0047] This positive electrode can be used to provide secondary batteries with high initial charge-discharge efficiency, large battery capacity, and high battery energy density.

[0048] In some embodiments of this application, the positive electrode sheet includes a current collector and a positive electrode active material layer disposed on at least one surface of the current collector. The positive electrode active material contains the aforementioned composite lithium-supplementing material, the positive electrode active material, a binder, and optionally a conductive agent. In some specific embodiments, the composite lithium-supplementing material accounts for 1%-10% of the mass percentage of the positive electrode active material layer.

[0049] In some embodiments of this application, the positive electrode sheet includes a current collector, and a positive active material layer and a lithium replenishment layer are sequentially disposed on at least one surface of the current collector. The positive active material layer is disposed close to the current collector, and the lithium replenishment layer contains the composite lithium replenishment material and a binder.

[0050] In this application, the aforementioned positive electrode active material is a positive electrode active material well known to those skilled in the art. For example, the aforementioned positive electrode active material may be lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium fluorinated vanadium phosphate, lithium titanate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc.

[0051] This application also provides a secondary battery with a positive electrode provided in this application.

[0052] This secondary battery has high initial charge / discharge efficiency, large battery capacity, and high energy density.

[0053] In this application, the aforementioned secondary battery can be either a pouch battery or a hard-case battery. The battery cells in the aforementioned secondary battery can be stacked cells or wound cells.

[0054] The technical solution of this application will be described in detail below with reference to specific embodiments.

[0055] Example 1

[0056] (1) Preparation of the main phase: The lithium block was placed in a tube furnace filled with nitrogen and heated to 750°C at a heating rate of 5°C / min. After holding at the temperature for 8 hours, it was cooled to room temperature and the product was crushed to obtain Li3N powder.

[0057] (2) Preparation of composite lithium supplementation material: 0.05g of secondary phase raw material, Li2NH, was added to 5g of Li3N powder and mixed evenly in a ball mill. The mixture was then sintered at 550℃ for 4h under a nitrogen atmosphere to obtain a composite material with Li3N as the main phase and Li2NH as the secondary phase.

[0058] This composite lithium supplement material is a particulate material with a particle size of 0.70 μm and a BET specific surface area of ​​0.79 m². 2 / g. Among them, the secondary phase is doped in the main phase, the D50 particle size of the secondary phase is 0.05μm, and the D50 particle size of the main phase is 0.62μm.

[0059] Example 2

[0060] The difference from Example 1 is as follows: (2) Preparation of composite lithium supplement material: Add secondary phase raw materials: 0.07g of Li2C2 and 0.08g of Li2NH to 5g of Li3N powder, mix evenly in a ball mill, and sinter at 520℃ for 4h under nitrogen atmosphere to obtain composite lithium supplement material with Li3N as the main phase and Li4C2NH as the secondary phase.

[0061] This composite lithium supplement material is a particulate material with a particle size of 0.81 μm and a BET specific surface area of ​​0.8 m². 2 / g. Among them, a portion of the secondary phase is coated on the outer layer of the composite lithium replenishment material in the form of coating, with a thickness of 15nm. The D50 particle size of the secondary phase is 0.01μm, and the D50 particle size of the main phase is 0.67μm.

[0062] Example 3

[0063] The difference from Example 1 is as follows: (2) Preparation of composite lithium supplementation material: Add secondary phase raw materials: 1.0g of Li2C2 and 0.5g of Li2NH to 5g of Li3N powder, mix evenly in a ball mill, and sinter at 510°C for 4h under nitrogen atmosphere to obtain a composite material with Li3N doped with Li4C2NH as the main phase and Li4C2NH as the secondary phase.

[0064] This composite lithium supplement material is a particulate material with a particle size of 0.73 μm and a BET specific surface area of ​​0.76 m². 2 / g. The secondary phase is coated on the outer layer of the composite lithium replenishment material in the form of a coating layer with a thickness of 30nm. The D50 particle size of the secondary phase is 0.02μm, and the D50 particle size of the main phase is 0.65μm.

[0065] Example 4

[0066] The difference from Example 1 is as follows: (2) Preparation of composite lithium supplementation material: 0.03g of secondary phase raw materials Li2C2 and 0.02g of Li2NCN were added to 5g of Li3N powder, and after being mixed evenly in a ball mill, the mixture was sintered at 550°C for 3h under a nitrogen atmosphere to obtain a composite material with Li3N as the main phase and Li4C3N2 as the secondary phase.

[0067] This composite lithium supplement material is a particulate material with a particle size of 0.73 μm and a BET specific surface area of ​​0.79 m². 2 / g. Among them, the secondary phase is doped in the main phase, the D50 particle size of the secondary phase is 0.03μm, and the D50 particle size of the main phase is 0.65μm.

[0068] Example 5

[0069] (1) Preparation of the main phase: A certain mass of metallic lithium and red phosphorus were heated to 750°C at a heating rate of 2°C / min, held for 7 hours and then cooled to room temperature. The product was then crushed to obtain Li3P powder.

[0070] (2) Preparation of composite lithium supplement material: 0.07g of Li2C2 and 0.08g of LiPON secondary phase raw materials were added to 5g of Li3P powder and mixed evenly in a ball mill. The mixture was then sintered at 560℃ for 5h under an argon atmosphere to obtain a composite lithium supplement material with Li3P as the main phase and Li3C2PON as the secondary phase.

[0071] This composite lithium supplement material is a particulate material with a particle size of 0.67 μm and a BET specific surface area of ​​0.82 m². 2 / g. Among them, the secondary phase is doped in the main phase, the D50 particle size of the secondary phase is 0.09μm, and the D50 particle size of the main phase is 0.56μm.

[0072] Example 6

[0073] The difference from Example 1 is as follows: (2) Preparation of composite lithium supplement material: Add secondary phase raw materials: 0.06g of Li2CNC, 0.07g of Li2NH and 0.02g of Li2O to 5g of Li3N powder, mix evenly in a ball mill, and sinter at 600°C for 4h under nitrogen atmosphere to obtain a composite lithium supplement material with Li3N as the main phase and Li6C2N2HO as the secondary phase.

[0074] This composite lithium supplement material is a particulate material with a particle size of 0.68 μm and a BET specific surface area of ​​0.84 m². 2 / g. Among them, the secondary phase is doped in the main phase, the D50 particle size of the secondary phase is 0.05μm, and the D50 particle size of the main phase is 0.59μm.

[0075] Example 7

[0076] The difference from Example 1 is that the parameters for preparing the main phase and the sintering mixture of the main and secondary phases were finely adjusted, resulting in a composite lithium-supplementing material with a particulate form, a particle size of 520 nm, and a BET specific surface area of ​​1.84 m². 2 / g. Among them, the secondary phase is doped in the main phase, the D50 particle size of the secondary phase is 20nm, and the D50 particle size of the main phase is 490nm.

[0077] Example 8

[0078] The difference from Example 1 is that 3 wt% graphene was added to the composite lithium supplement material prepared in Example 1, and sintered at 500°C for 3 hours to obtain a composite material with a carbon layer on the surface, the main phase being Li3N and the secondary phase being Li2NH.

[0079] This composite lithium supplement material is a particulate material with a particle size of 0.79 μm and a BET specific surface area of ​​0.82 m². 2 / g. The thickness of the carbon layer is 14nm.

[0080] To highlight the beneficial effects of the embodiments of this application, the following comparative examples are provided.

[0081] Comparative Example 1

[0082] Commercially available Li3N powder was used directly as the lithium supplement.

[0083] Comparative Example 2

[0084] Commercially available Li3P powder was used directly as the lithium supplement.

[0085] 1. The composite lithium replenishment material prepared in the above embodiments was subjected to XRD testing.

[0086] 2. The composite lithium replenishing materials and comparative lithium replenishing agents prepared in the above embodiments are added to the positive electrode active material to prepare the positive electrode sheet and the secondary battery.

[0087] (1) Preparation of positive electrode sheet: The positive electrode slurry is prepared by mixing the solvent N-methylpyrrolidone (NMP), positive electrode active material - lithium iron phosphate, composite lithium supplement material (or comparative lithium supplement agent), conductive agent - Super P, and binder - polyvinylidene fluoride PVDF in a mass ratio of 100:93:2:2:3. The positive electrode slurry is coated on the positive electrode current collector - aluminum foil, and the positive electrode sheet is prepared by drying, rolling, die cutting and other steps.

[0088] (2) Preparation of negative electrode sheet: The negative electrode active material - graphite, conductive agent - Super P, thickener - carboxymethyl cellulose (CMC) and binder - styrene-butadiene rubber (SBR) are mixed evenly in deionized water to obtain a negative electrode slurry; the above negative electrode slurry is coated on the negative electrode current collector - copper foil, and the negative electrode sheet is prepared by drying, rolling and die cutting.

[0089] (3) The positive and negative electrode sheets obtained in the above steps are alternately stacked with the separator to prepare a battery by stacking. The positive and negative electrode sheets are arranged alternately and are separated by the separator to obtain a dry cell. The dry cell is placed in an aluminum-plastic film outer packaging, electrolyte is injected, and then it is vacuum sealed. After being placed at 60°C for 48 hours, a pressure layer is applied at 60°C, followed by secondary encapsulation, degassing, and capacity testing to obtain a full cell.

[0090] Among them, the batteries with positive electrode sheets containing the composite lithium replenishing materials provided in Examples 1-8 are respectively designated as S1-S8, and the batteries with positive electrode sheets containing the lithium replenishing agents of Comparative Examples 1 and 2 are designated as DS1 and DS2.

[0091] Electrochemical performance tests were performed on the above batteries: 1) Charging: 0.05C constant current and constant voltage charging to 4.0V / Cell, cut-off current 0.02C, rest for 10min; 2) Discharging: 0.05C constant current to 2.5V / Cell, rest for 10min.

[0092] 3) Cycle 3 times, and record the discharge capacity of the third discharge as the actual capacity C0 of the battery; 4) Charge: Charge the battery to 4.0V with constant current and constant voltage at 1C with the actual capacity C0 as 1C, and cut off the current at 0.02C; 5) Let it rest for 10 minutes; 6) Discharge: Discharge the battery to 2.5V with constant current at 1C with the actual capacity C0 as 1C; 7) Let it rest for 10 minutes; 8) Cycle 4) to 7) a total of 200 times.

[0093] The specific capacity of the battery during the first charge and the cycle capacity retention rate after 200 cycles were tested, and the specific capacity improvement of each material was calculated. The results are summarized in Table 1.

[0094] Table 1. Electrochemical performance test results of batteries in each embodiment and comparative example.

[0095]

[0096]

[0097] Figure 1 The XRD patterns of the composite lithium supplement material prepared in Example 6 and the XRD pattern of Li3N are shown. The XRD patterns of Example 6 clearly show the sharp characteristic peaks of the main phase Li3N (the peak positions of the XRD pattern of the main phase Li3N match the standard peak positions of Li3N material with crystal structure space group P6 / mmm

[191] in the crystal structure database) and the secondary phase Li6C2N2HO, and the composite lithium supplement material has a high degree of crystallinity.

[0098] As can be seen from Table 1, the secondary batteries containing Examples S1-S8 of this application have a significantly higher initial charge specific capacity than the comparative examples DS1-DS2 batteries. Furthermore, after 200 cycles at 1C, the capacity retention of batteries S1-S8 is greater than 89%. Battery S8, due to the presence of a carbon layer, exhibits a higher initial charge specific capacity and capacity retention than battery S1. This demonstrates that the composite lithium-replenishing additive of this application possesses excellent lithium-replenishing effects, imparting good cycle stability to lithium-ion batteries. In particular, the composite lithium-replenishing material obtained in Example 2 has a more ideal content of secondary phases, therefore, battery S2 exhibits superior electrochemical performance compared to the batteries of other examples.

[0099] In summary, the composite lithium replenishment material provided in this application has good structural stability and can achieve efficient lithium replenishment, thereby improving the first charge-discharge efficiency and energy density of the secondary battery.

[0100] The above description is an exemplary embodiment of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A composite lithium supplementation material, characterized in that, The composite lithium supplement material comprises a main phase and a secondary phase, wherein the main phase includes Li. x A y The element A includes at least one of N, P, S, F, B, O, and Se, where 0 < x ≤ 5 and y > 0; the secondary phase includes Li. a C b X c H d O e The element X includes N, 1≤a≤15, 0≤b≤4, 0<c≤5, 0≤d≤5, 0≤e≤10, and at least one of b, d, and e is not 0; the secondary phase is doped in the main phase.

2. The composite lithium replenishment material according to claim 1, characterized in that, Part of the secondary phase is coated on the surface of the primary phase.

3. The composite lithium replenishment material according to claim 1, characterized in that, The X element also includes at least one of P, S, F, B, O, and Se.

4. The composite lithium replenishment material according to claim 2, characterized in that, The X element is the same as the A element.

5. The composite lithium replenishment material according to claim 1, characterized in that, At least some of the secondary phases are coated on the surface of the main phase, and the thickness of the coating layer is in the range of 1 nm to 500 nm.

6. The composite lithium replenishment material according to claim 1, characterized in that, The composite lithium replenishing material is further coated with carbon material; the mass percentage of carbon material in the composite lithium replenishing material is 0.1%-5%; the thickness of the carbon layer formed by the carbon material is in the range of 2nm-200nm.

7. The composite lithium replenishment material according to claim 1, characterized in that, The D50 particle size of the main phase is in the range of 0.01 μm to 15 μm; the D50 particle size of the secondary phase is in the range of 0.01 μm to 20 μm.

8. The composite lithium replenishment material according to claim 1, characterized in that, The particle size of the composite lithium replenishment material is in the range of 0.01 μm to 50 μm.

9. The composite lithium replenishment material according to claim 1, characterized in that, The mass percentage of the secondary phase in the composite lithium supplement material is in the range of 1%-30%.

10. The composite lithium supplementation material according to claim 1, characterized in that, The specific surface area of ​​the composite lithium replenishment material is 0.1 m². 2 / g-40m 2 Within the range of / g.

11. A method for preparing a composite lithium supplement material, characterized in that, Includes the following steps: (1) Provide the main phase material; (2) Mix the main phase material with the secondary phase material to obtain a mixture; (3) The mixture is sintered under an inert atmosphere to obtain a composite lithium replenishing material; wherein the composite lithium replenishing material comprises a main phase and a secondary phase, and the main phase comprises Li x A y The element A includes at least one of N, P, S, F, B, O, and Se, where 0 < x ≤ 5 and y > 0; the secondary phase includes Li. a C b X c H d O e The element X includes N, where 1≤a≤15, 0≤b≤4, 0<c≤5, 0≤d≤5, 0≤e≤10, and at least one of b, d, and e is not 0; the secondary phase is doped in the main phase.

12. A positive electrode plate, characterized in that, The positive electrode sheet has a composite lithium replenishing material as described in any one of claims 1-10 or has a composite lithium replenishing material prepared by the preparation method described in claim 11.

13. A secondary battery, characterized in that, The secondary battery has a positive electrode as described in claim 12.

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