Lithium supplement agent and preparation method and application thereof

Abstract

The invention provides a lithium supplement agent and a preparation method and application thereof, and belongs to the field of lithium ion batteries, the preparation method of the lithium supplement agent comprises the following steps: adding an aluminum source, a lithium source and a surfactant into a mixed solvent containing deionized water, ethanol and ammonia water to obtain a premixed rubber material; carrying out drying and heat preservation treatment on the premixed rubber material to obtain precursor sol; sintering the precursor sol for the first time to obtain an amorphous precursor material; mixing the amorphous precursor material with a carbon source and deionized water to obtain mixed slurry; dispersing and drying the mixed slurry to obtain an intermediate product; and sintering the intermediate product for the second time to obtain the lithium supplement agent, wherein the lithium supplement agent is an amorphous Li5AlO4 / C material. The amorphous Li5AlO4 / C material prepared by the invention has a relatively high specific surface area and a disordered atomic structure, so that lithium ions are relatively easy to embed and deintercalate, and a relatively high lithium supplementing capacity is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a lithium supplementing agent and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of the new energy vehicle industry, the demand for efficient energy storage systems is increasing. As the key power source of new energy vehicles, the performance of lithium ion batteries is directly related to the endurance, safety and service life of the vehicle. Lithium ion batteries are widely used in energy storage batteries, power batteries and other industries due to their high energy density, long cycle life, high coulomb efficiency, low self-discharge rate, low operation and maintenance cost, wide working temperature range and excellent reliability. However, during the first charge and discharge process of lithium ion batteries, a solid electrolyte interface film (SEI) is formed at the interface between the electrode material and the electrolyte. This process consumes a large amount of active lithium ions, resulting in a decrease in the energy density of the battery.

[0003] Adding a lithium supplementing agent to the electrode material can achieve the purpose of supplementing lithium ions. Conventional lithium supplementing agents are of a crystal type and are a one-time consumable. In the positive electrode material, they only play a role in filling the lithium ions consumed by the SEI film. The structure limits the transmission rate of lithium ions, and lithium ions cannot be completely released, resulting in low utilization and affecting the charge and discharge performance of the battery. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a lithium supplementing agent and a preparation method and application thereof, aiming to solve the technical problems of limited lithium ion transmission rate and low utilization in existing lithium supplementing agents of a crystal type.

[0005] In a first aspect, the embodiments of the present application provide a preparation method of a lithium supplementing agent, comprising the following steps:

[0006] An aluminum source, a lithium source and a surfactant are added to a mixed solvent comprising deionized water, ethanol and ammonia water to obtain a premixed rubber;

[0007] The premixed rubber is subjected to solid-liquid separation, drying and heat preservation treatment to obtain a precursor sol;

[0008] The precursor sol is subjected to first sintering to obtain an amorphous precursor material;

[0009] The amorphous precursor material is mixed with a carbon source and deionized water to obtain a mixed slurry;

[0010] The mixed slurry is subjected to dispersion and drying treatment to obtain an intermediate product;

[0011] The intermediate product is subjected to second sintering to obtain a lithium supplementing agent;

[0012] wherein the lithium supplement agent is an amorphous Li5AlO4 / C material.

[0013] In the technical scheme of the embodiments of the present application, the raw materials are mixed, ground and dispersed, spray dried, and sintered to obtain a carbon-coated amorphous Li5AlO4 material with small particle size, providing the possibility of using amorphous materials as lithium supplement agents. The prepared amorphous Li5AlO4 / C material has a high specific surface area and a disordered atomic structure, making it easier for lithium ions to be inserted and extracted, thereby providing a higher lithium supplement capacity. The amorphous structure enables the lithium ions in the lithium supplement agent to be released more quickly and completely, improving the utilization rate of lithium ions and reducing the consumption of lithium ions due to the formation of SEI films. The amorphous lithium supplement agent has the advantages of high lithium supplement capacity, good compatibility, and simple preparation process, and can effectively improve the energy density, cycle performance, and service life of the battery, providing strong support for the development of high-performance lithium-ion batteries.

[0014] In some embodiments, the molar ratio of the aluminum source, the lithium source, and the surfactant is 1:(5-6.5):(1-2); and / or the volume ratio of deionized water, ethanol, and ammonia in the mixed solvent is (4-5):(3-4):1.

[0015] In this embodiment, by accurately controlling the molar ratio of the aluminum source, the lithium source, and the surfactant, the content of lithium ions in the lithium supplement agent can be ensured to reach the optimal level, thereby more effectively supplementing the consumed lithium ions during the first charge and discharge process of the battery, improving the first coulomb efficiency of the battery. The volume ratio of deionized water, ethanol, and ammonia provides a suitable solvent environment, which helps the dissolution and dispersion of the aluminum source, the lithium source, and the surfactant, controls the progress of the reaction, and promotes the formation of an amorphous structure.

[0016] In some embodiments, the aluminum source is one or more of Al2O3, AlCl3, Al(NO3)3, Al2(SO4)3, and Al(OH)3; and / or the lithium source is one or more of Li2O2, Li2O, LiOH, Li2SO4, LiNO3, and Li2CO3; and / or the surfactant is one or more of sodium dodecyl benzene sulfonate, sodium polystyrene sulfonate, and PEG.

[0017] In this embodiment, by selecting appropriate aluminum sources, lithium sources, and surfactants, the preparation process of the lithium supplement agent can be optimized, and the performance of the lithium supplement agent can be improved. Suitable aluminum sources and lithium sources can ensure that the content of lithium ions in the lithium supplement agent reaches the optimal level, improving the first coulomb efficiency of the battery; suitable surfactants can promote the uniform formation of the precursor sol, improving the specific surface area of the lithium supplement agent and the lithium ion transmission rate. By selecting appropriate aluminum sources, lithium sources, and surfactants, the stability of the lithium supplement agent can be enhanced, and the service life of the lithium supplement agent can be prolonged.

[0018] In some embodiments, the drying and heat preservation treatment is performed at a temperature of 60-100°C for 5-8h.

[0019] In this embodiment, the drying and heat preservation treatment promotes the evaporation of the mixed solvent, and solidifies the premixed glue to form a precursor sol. A suitable temperature can ensure rapid evaporation of the solvent, while avoiding rapid agglomeration or structural damage to the sol due to excessively high temperature. The heat preservation time is controlled within 5-8h, which can ensure the formation of a uniform and stable precursor sol.

[0020] In some embodiments, the first sintering is performed at a temperature increasing rate of 1-10°C / min, a heat preservation temperature of 400-900°C, and a heat preservation time of 8-10h; and / or the first sintering is performed in air or oxygen.

[0021] In this embodiment, a slow temperature increasing rate helps to uniformly release the internal stress of the material, ensuring the integrity of the material structure. The control of the heat preservation temperature helps to initiate the reaction between the aluminum source, the lithium source and the surfactant, forming an amorphous precursor material. The heat preservation time can ensure that the reaction has sufficient time to proceed, so that the reaction between the aluminum source, the lithium source and the surfactant can be fully completed, forming a uniform and stable precursor material. The selection of air or oxygen as the sintering atmosphere can promote the oxidation reaction of the material, helping to form a stable oxide structure.

[0022] In some embodiments, the carbon source is one or more of glucose, sucrose, starch, acetylene, ethylene, epoxy resin, and cellulose; and / or the addition amount of the carbon source is 4-6% of the mass of the amorphous precursor material; and / or the solid content of the mixed slurry is 25-35%.

[0023] In this embodiment, the carbon source can be converted into carbon material during the sintering process, which combines with the amorphous precursor material to form a composite material. An appropriate amount of carbon source can improve the electrical conductivity of the lithium supplement and increase the conduction rate of lithium ions, thereby improving the charge and discharge performance of the battery. The solid content range of the mixed slurry can ensure that the mixed slurry has good flowability and uniformity during the dispersion and drying processes, and an appropriate solid content can help the mixed slurry to form a uniform intermediate product in the subsequent processing process.

[0024] In some embodiments, the dispersion treatment is performed for 2-5h at a ball milling speed of 500-1500rpm and a ball-to-material ratio of (10-20):1, and the particle size D50 of the material after the dispersion treatment is 0.250-0.350μm; and / or the drying treatment is performed at an inlet air temperature of 100-200°C and an outlet air temperature of 85-100°C; and / or the particle size D50 of the intermediate product is 10-25μm.

[0025] In this embodiment, the selection of the dispersion processing time, the ball mill rotation speed and the ball-to-material ratio helps to achieve uniform dispersion of the material in the mixed slurry. The selection of the inlet air temperature and the outlet air temperature of the drying process can ensure uniform heating of the material during the drying process, avoiding local overheating that can cause damage to the material structure. The particle size control of the intermediate product can ensure good sintering performance of the material during the subsequent sintering process.

[0026] In some embodiments, the heating rate of the second sintering is 1-10℃ / min, the holding temperature is 300-500℃, the holding time is 3-10h, and the furnace pressure is 20-100pa; and / or the atmosphere of the second sintering is inert gas; and / or the inert gas is one or more of nitrogen, argon, and helium.

[0027] In this embodiment, the slow heating rate can ensure uniform distribution of the internal temperature of the material, reducing the influence of thermal stress. Controlling the holding temperature in the range of 300-500℃ can promote the reaction between the carbon source and the amorphous precursor material, forming a stable Li5AlO4 / C composite material. Controlling the holding time in the range of 3-10h can ensure that the reaction proceeds sufficiently, allowing the carbon source and the amorphous precursor material to fully combine and form a uniform composite material structure. Controlling the furnace pressure can create a low-oxygen environment to prevent the material from being oxidized during the sintering process. Using an inert gas atmosphere as the sintering atmosphere can further prevent the material from reacting with oxygen during the sintering process, ensuring the chemical stability of the material.

[0028] In a second aspect, the embodiments of the present application provide a lithium supplement prepared by the preparation method of the lithium supplement of the first aspect, wherein the lithium supplement has a particle size D50 of 0.5-2.0μm and a specific surface area of 8-38m 2 / g.

[0029] In the technical solutions of the embodiments of the present application, the appropriate particle size helps to increase the contact area between the lithium supplement and the electrode material, thereby improving the transmission efficiency of lithium ions. The high specific surface area helps to improve the reactivity of the lithium supplement, promoting the release and transmission of lithium ions, thereby improving the energy density and charge-discharge performance of the battery.

[0030] In a third aspect, the embodiments of the present application provide a positive electrode material comprising the lithium supplement of the second aspect, wherein the addition amount of the lithium supplement is 1-6% of the mass of the positive electrode material.

[0031] In this embodiment, the positive electrode material contains the above-mentioned lithium supplement, thereby having the advantage of high specific capacity.

[0032] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application more clearly understood and can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0034] Figure 1 Process flow chart for the preparation method of the lithium supplement agent in the embodiments of the present application;

[0035] Figure 2 XRD pattern of the lithium supplement agent prepared in Example 2 and Comparative Example 1 of the present application;

[0036] Figure 3 SEM pattern of the lithium supplement agent prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0037] The embodiments of the technical solutions of the present application will be described in detail below in conjunction with the drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0039] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0040] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with one another.

[0041] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing together, and B existing alone. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0042] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0043] Although lithium ion batteries have advantages such as high energy density and long service life, the SEI film formed by the first charge and discharge consumes lithium ions and reduces the energy density. In order to supplement lithium ions, a lithium supplement is often added to the electrode material. However, the traditional lithium supplement is mostly of a crystal type, which is only used to compensate for the lithium ions consumed by the SEI film, and has low utilization.

[0044] In order to solve the technical problem of low lithium supplement capacity of the traditional crystal type lithium supplement, the present application provides a lithium supplement, a preparation method and application thereof, wherein the lithium supplement with amorphous structure has a high specific surface area and disordered atomic structure, so that lithium ions are more easily inserted and extracted, thereby providing higher lithium supplement capacity, and further improving the electrochemical performance of the positive electrode material.

[0045] Please refer to Figure 1 , in a first aspect, the embodiment of the present application provides a preparation method of a lithium supplement, comprising the following steps:

[0046] S1. An aluminum source, a lithium source and a surfactant are added to a mixed solvent comprising deionized water, ethanol and ammonia water to obtain a premixed rubber;

[0047] S2. The premixed rubber is subjected to solid-liquid separation, drying and heat preservation treatment to obtain a precursor sol;

[0048] S3. The precursor sol is subjected to first sintering to obtain an amorphous precursor material;

[0049] S4. The amorphous precursor material is mixed with a carbon source and deionized water to obtain a mixed slurry;

[0050] S5. The mixed slurry is subjected to dispersion and drying treatment to obtain an intermediate product;

[0051] S6. The intermediate product is subjected to a second sintering to obtain a lithium supplement agent; wherein the lithium supplement agent is an amorphous Li5AlO4 / C material.

[0052] In the technical scheme of the embodiments of the present application, the aluminum source and the lithium source are uniformly dispersed in the solvent, which provides a good reaction environment for the subsequent reaction. The solid-liquid separation, drying and heat preservation treatment help to remove the water and organic matter in the solvent, so that the premixed sizing material gradually forms a sol state. The precursor sol is subjected to a first sintering to promote the reaction of the aluminum source and the lithium source, forming an amorphous Li5AlO4 precursor material. The addition of the carbon source helps to improve the electrical conductivity and stability of the material, and the deionized water is used to adjust the viscosity of the slurry. The mixed slurry is subjected to dispersion and drying treatment to ensure that the carbon source is uniformly distributed in the amorphous precursor material and the water in the slurry is removed. The second sintering can further promote the reaction, so that the amorphous precursor material is closely combined with the carbon source to form an amorphous Li5AlO4 / C material. The material has excellent lithium ion conduction performance and lithium ion release efficiency, can effectively supplement the lithium ions consumed due to the formation of the SEI film, and improve the energy density and charge-discharge performance of the battery.

[0053] Further, in some embodiments, the molar ratio of the aluminum source, the lithium source and the surfactant is 1:(5-6.5):(1-2); and / or the volume ratio of the deionized water, the ethanol and the ammonia water in the mixed solvent is (4-5):(3-4):1.

[0054] In the technical scheme of the embodiments of the present application, during the reaction process, the ratio of the aluminum source and the lithium source helps to ensure that the subsequent reaction is completely carried out to generate the target product Li5AlO4. At the same time, the excess lithium source also helps to compensate for the possible loss of lithium in the subsequent sintering process. The surfactant plays a role of a template and a stabilizer during the reaction process, which helps to control the morphology and size of the precursor sol. The appropriate ratio of the surfactant can promote the formation of an amorphous structure, thereby improving the performance of the lithium supplement agent. The deionized water and the ethanol together as a solvent provide a suitable polar and non-polar environment, which helps to dissolve and disperse the aluminum source, the lithium source and the surfactant. The addition of the ethanol also helps to adjust the evaporation rate of the solvent, thereby affecting the drying process of the precursor sol. The ammonia water plays a role of a mineralizer in the reaction, which helps to promote the hydrolysis and polycondensation reaction of the aluminum source and the lithium source, thereby forming the precursor sol. The appropriate amount of ammonia water can also adjust the pH value of the solution, promoting the formation of an amorphous structure.

[0055] Specifically, the molar ratio of the aluminum source, the lithium source and the surfactant can be 1:5:1, 1:5.1:1.25, 1:6:1.5, 1:6.5:2, or any value within the range of 1:(5-6.5):(1-2). The volume ratio of deionized water, ethanol and ammonia in the mixed solvent can be 4:3:1, 5:4:1, or any value within the range of (4-5):(3-4):1.

[0056] Further, in some embodiments, the aluminum source is one or more of Al2O3, AlCl3, Al(NO3)3, Al2(SO4)3, Al(OH)3; and / or the lithium source is one or more of Li2O2, Li2O, LiOH, Li2SO4, LiNO3, Li2CO3; and / or the surfactant is one or more of sodium dodecyl benzene sulfonate, sodium polystyrene sulfonate, PEG (polyethylene glycol).

[0057] In the technical solution of the embodiments of the present application, the aluminum source provides stable aluminum ions, the lithium source provides high-concentration lithium ions, and the surfactant improves the dispersibility and processing performance of the premix, and the three work together to optimize the preparation process of the lithium supplement and improve the performance of the lithium supplement.

[0058] Further, in some embodiments, the temperature of the drying and heat preservation treatment is 60-100℃, and the time is 5-8h.

[0059] In the technical solution of the embodiments of the present application, by controlling the temperature and time of the drying and heat preservation treatment, the uniformity of the precursor sol can be ensured, and material non-uniformity caused by local overheating or insufficient reaction can be avoided. Uniform precursor sol helps to form uniform lithium supplement material in the subsequent sintering process. In addition, the drying and heat preservation treatment can enhance the stability of the precursor sol, preventing it from agglomerating or being structurally damaged in subsequent processing.

[0060] Further, in some embodiments, the temperature rising speed of the first sintering is 1-10℃ / min, the heat preservation temperature is 400-900℃, and the heat preservation time is 8-10h; and / or the atmosphere of the first sintering is air or oxygen.

[0061] In the technical scheme of the embodiment of the present application, the temperature rising speed is controlled at 1-10℃ / min, which can avoid excessive thermal stress of the material caused by too fast temperature rising, thereby preventing cracks or structure damage of the material in the sintering process. The holding temperature is set at 400-900℃, which is helpful for solid phase reaction between the aluminum source, the lithium source and the surfactant to form the required compound, and avoids excessive sintering or structure collapse of the material caused by too high temperature. The holding time is 8-10h, which is helpful for full reaction and formation of the amorphous precursor material. Proper time control can avoid unstable performance of the material caused by insufficient reaction, and is helpful for eliminating internal stress of the material and improving the density and mechanical properties. The sintering atmosphere is selected as air or oxygen, which can inhibit possible reduction reaction of the material in the sintering process and ensure the chemical stability of the material.

[0062] Further, in some embodiments, the carbon source is one or more of glucose, sucrose, starch, acetylene, ethylene, epoxy resin, cellulose; and / or the addition amount of the carbon source is 4-6% of the mass of the amorphous precursor material; and / or the solid content of the mixed slurry is 25-35%.

[0063] In the technical scheme of the embodiment of the present application, the carbon material has good electrical conductivity, which can improve the electronic conductivity of the lithium supplement agent and thereby improve the rate performance of the battery. Different carbon sources have different carbonization characteristics and reactivity, and a suitable carbon source can be selected according to specific requirements to optimize the performance of the lithium supplement agent. The addition amount of the carbon source can ensure uniform distribution of the carbon material in the lithium supplement agent, while too much carbon source will not affect the overall performance of the lithium supplement agent. The solid content of the mixed slurry is controlled at 25-35%, which can avoid too thick slurry caused by too high solid content or too thin slurry caused by too low solid content. By selecting a suitable carbon source, controlling the addition amount of the carbon source and the solid content of the mixed slurry, the preparation process of the lithium supplement agent can be optimized, and the electrical conductivity, lithium ion conductivity and structural stability of the lithium supplement agent can be improved.

[0064] Further, in some embodiments, the dispersion treatment time is 2-5h, the ball milling rotation speed is 500-1500rpm, the ball-to-material ratio is (10-20):1, and the particle size D50 of the material after the dispersion treatment is 0.250-0.350μm; and / or the inlet air temperature of the drying treatment is 100-200℃, the outlet air temperature is 85-100℃; and / or the particle size D50 of the intermediate product is 10-25μm.

[0065] In the technical solutions of the embodiments of the present application, through dispersion treatment and drying treatment, the uniform distribution of the components of the lithium supplement agent and the stable structure are ensured. The appropriate dispersion time can make the material mixing more uniform and reduce the agglomeration phenomenon. The ball milling speed affects the collision energy and frequency in the ball milling process. Higher speed can increase the collision energy and help to refine the material, but too high speed can cause excessive wear and temperature rise, affecting the stability of the material. Higher ball-to-material ratio can provide more collision opportunities and help to refine the material. Higher air inlet temperature can speed up the drying rate, but too high temperature can cause thermal decomposition or structural damage to the material. The appropriate air outlet temperature can ensure uniform drying of the material and avoid local overheating or insufficient drying. Controlling the particle size of the intermediate product can ensure good flowability and processability of the material in the subsequent processing process, while also helping to improve the uniformity and performance of the lithium supplement agent.

[0066] Further, in some embodiments, the heating rate of the second sintering is 1-10℃ / min, the holding temperature is 300-500℃, the holding time is 3-10h, and the furnace pressure is 20-100pa; and / or the atmosphere of the second sintering is inert gas; and / or the inert gas is one or more of nitrogen, argon, and helium.

[0067] In the technical solutions of the embodiments of the present application, the heating rate affects the temperature gradient and thermal stress of the material during heating. A slower heating rate helps to evenly distribute the internal temperature of the material, reduces thermal stress, and avoids cracks and deformation. A faster heating rate can cause uneven temperature distribution, increase thermal stress, and increase porosity. The holding temperature is the main stage of densification and grain growth of the material during sintering. An appropriate temperature can avoid excessive sintering and grain coarsening, and an appropriate holding time can help the material to fully densify, reduce porosity, and promote grain growth. Controlling the furnace pressure and sintering atmosphere can reduce uneven stress distribution in the material, avoid the generation of cracks and defects, and improve the uniformity and stability of the product.

[0068] Further, after the second sintering, the sintered amorphous Li5AlO4 / C material can be further refined by air jet milling to optimize its particle size distribution and meet the requirements of subsequent applications for material particle size. Specifically, the frequency of the classification wheel of the air jet mill is 30-80Hz, and the milling gas is nitrogen.

[0069] In a second aspect, the embodiments of the present application provide a lithium supplement agent prepared by the preparation method of the lithium supplement agent of the first aspect, wherein the particle size D50 of the lithium supplement agent is 0.5-2.0μm, and the specific surface area is 8-38m 2 / g.

[0070] In the technical scheme of the embodiment of the present application, by optimizing the particle size D50 and the specific surface area, the contact area of the lithium supplementing agent and the positive electrode material can be significantly increased, the lithium supplementing capacity can be increased, and the lithium supplementing efficiency can be enhanced.

[0071] In a third aspect, the embodiment of the present application provides a positive electrode material, which comprises the lithium supplementing agent according to the second aspect, and the addition amount of the lithium supplementing agent is 1-6% of the mass of the positive electrode material.

[0072] In the technical scheme of the embodiment of the present application, the positive electrode material comprises the lithium supplementing agent described above, and thus has the advantage of high specific capacity.

[0073] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation on the present application. If a specific technology or condition is not specified in the embodiments, the technology or condition is performed according to the technology or condition described in the literature in the field or according to the product instruction. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained from the market.

[0074] I. Preparation method

[0075] Embodiment 1

[0076] The embodiment provides a preparation method of a lithium supplementing agent, which comprises the following steps:

[0077] S1. 2 mmol of aluminum nitrate, 10.2 mmol of lithium hydroxide and 0.0025 mol of a surfactant PEG are added into a mixed solvent comprising 100 mL of deionized water, 75 mL of ethanol and 25 mL of ammonia water to obtain a premixed rubber;

[0078] S2. The premixed rubber is separated by centrifugal dehydration, and is aged at 80℃ for 6 h to obtain a precursor sol;

[0079] S3. The precursor sol is sent into a sintering furnace for first sintering, the furnace temperature is increased from room temperature to 450℃ at a speed of 3℃ / min, and after reaching 450℃, the temperature is kept for 8 h to obtain an amorphous precursor material;

[0080] S4. 500 g of the amorphous precursor material is mixed with 5 wt% of glucose and deionized water to obtain a mixed slurry, and the solid content is 30%;

[0081] S5. The mixed slurry is placed in a sand mill, and the slurry is cooled by condensate water while being ground, the ball milling speed is 1000 rpm, the time is 2.5 h, and the ball-to-material ratio is 10:1; the ground slurry is pumped into a spray drying device for spray drying, the inlet air temperature of the spray drying device is 170℃, and the outlet air temperature is 95℃, to obtain an intermediate product;

[0082] S6. The intermediate product is sintered for the second time, high-purity nitrogen is introduced in advance, the amount of introduction is 150 L / min, the oxygen content is less than 1 ppm, then the furnace temperature is raised from room temperature to 450℃ at a rate of 3℃ / min, after reaching 450℃, the temperature is kept for 4h, the furnace pressure is 60pa, the sintered material is air-pulverized, the classification wheel frequency is controlled at 65Hz, and the lithium supplement agent is obtained.

[0083] Example 2

[0084] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the first sintering is 550℃.

[0085] Example 3

[0086] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the first sintering is 650℃.

[0087] Example 4

[0088] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the first sintering is 750℃.

[0089] Example 5

[0090] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the first sintering is 400℃.

[0091] Example 6

[0092] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the first sintering is 900℃.

[0093] Example 7

[0094] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 2 in that the amount of lithium hydroxide added is 12.6mmol.

[0095] Example 8

[0096] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the second sintering is 300℃.

[0097] Example 9

[0098] The embodiment provides a preparation method of a lithium supplement agent, and only differs from example 1 in that the temperature of the second sintering is 500℃.

[0099] Comparative Example 1

[0100] The comparative example provides a preparation method of a lithium supplement agent, and the only difference from example 1 is that the temperature of the first sintering is 950°C, and the obtained lithium supplement agent is a crystal Li5AlO4 / C material.

[0101] Comparative example 2

[0102] The comparative example provides a preparation method of a lithium supplement agent, and the only difference from example 1 is that the temperature of the first sintering is 350°C.

[0103] Comparative example 3

[0104] The comparative example provides a preparation method of a lithium supplement agent, and the only difference from example 1 is that the temperature of the second sintering is 250°C.

[0105] Comparative example 4

[0106] The comparative example provides a preparation method of a lithium supplement agent, and the only difference from example 1 is that the temperature of the second sintering is 550°C.

[0107] II. Test method

[0108] 1. SEM test

[0109] The MERLIN Compact field emission scanning electron microscope (model: Quanta200FEG) produced by Zeiss Company was used to detect the lithium supplement agent prepared in example 2.

[0110] 2. XRD test

[0111] The XRD-6100 produced by Japan Shimadzu was used to detect the lithium supplement agent prepared in example 2 and comparative example 1.

[0112] 3. Particle size test

[0113] The laser particle size analyzer was used to test the particle size of the lithium supplement agent prepared in the examples and comparative examples.

[0114] 4. BET test

[0115] The nitrogen adsorption BET test method was used to test the specific surface area of the lithium supplement agent prepared in the examples and comparative examples.

[0116] 5. Capacity test

[0117] The positive active material LiFePO4, lithium supplement agent (3%), conductive agent Super-P, binder PVDF and NMP were stirred and slurried, the slurry was uniformly coated on an aluminum box to make an electrode sheet, a metal lithium sheet was used as a negative electrode sheet, 1 mol / L LiPF6 / (EC+DEC) with a mass ratio of 1:1 was used as an electrolyte, a simulation battery was assembled, 0.33C was used for charging test, 1C was used for discharging test, and the voltage range was 2.0-4.3V. Comparative Example 5 was a simulation battery without adding the lithium supplement agent prepared in the application.

[0118] The test results are shown in Tables 1 and 2.

[0119] Table 1: Test results of lithium supplement agents provided by examples and comparative examples

[0120] Item Particle size (pm) BET(m 2 / g) Example 1 1.213 28.35 Example 2 1.103 37.62 Example 3 1.368 22.44 Example 4 1.612 12.65 Example 5 0.965 36.12 Example 6 1.752 8.73 Example 7 1.011 34.23 Example 8 1.272 35.45 Example 9 1.253 29.42 Comparative Example 1 1.516 8.52 Comparative Example 2 1.423 8.56 Comparative Example 3 0.686 22.13 Comparative Example 4 0.879 19.60

[0121] Table 2: Test results of battery performance

[0122]

[0123]

[0124] III. Analysis of test results of examples and comparative examples

[0125] As can be seen from Table 1, in the examples, as the first sintering temperature increases, the sample gradually changes from amorphous to crystalline, and the specific surface area gradually decreases. The specific surface area of Example 2 reaches 37.62 m 2 / g, which meets the specific surface area characteristics of amorphous materials. Moderate particle size and high specific surface area may be beneficial to the diffusion of lithium ions and the contact between the electrode and the electrolyte, thereby improving the desorption efficiency of lithium ions and the reaction activity during the charging process.

[0126] As can be seen from Table 2, in the examples, the specific capacity of the battery is 352-951 mAh / g, with a large span, indicating that the performance of the lithium supplement agent is significantly different under different test conditions. Examples 2 (951 mAh / g), 7 (902 mAh / g) and 1 (878 mAh / g) all exceed 850 mAh / g, showing that some formulations can significantly improve the lithium supplement efficiency. The examples are superior to the comparative examples in 0.33C charging capacity, 1C discharging capacity and initial efficiency. Example 2 has the best comprehensive performance, indicating that the irregular and porous structure of the material significantly improves the desorption efficiency of lithium ions.

[0127] From Figure 2It can be seen that the lithium supplementing agent prepared in Comparative Example 1 is a crystalline Li5AlO4 / C material, which shows obvious sharp diffraction peaks, indicating that the sample has a high degree of crystallinity, and the position and intensity of the diffraction peaks are consistent with the standard data in PDF card 27-1209, confirming the crystal structure thereof. The lithium supplementing agent prepared in Example 2 is an amorphous Li5AlO4 / C material, which shows a broad diffraction peak without obvious sharp peaks, indicating that the sample is amorphous.

[0128] From Figure 3 It can be seen that the lithium supplementing agent particles prepared in Example 2 exhibit irregular shapes, rough edges and porosity, which are consistent with the characteristics of amorphous materials. The particle surface has many small protrusions and recesses, indicating that it has a high surface area and porosity.

[0129] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, other modes constructed by combining part of the elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a lithium supplement, characterized in that: The following steps are involved: adding an aluminum source, a lithium source and a surfactant into a mixed solvent comprising deionized water, ethanol and ammonia water to obtain a premixed rubber material; The premixed rubber material is subjected to solid-liquid separation, drying and heat preservation treatment to obtain a precursor sol; sintering the precursor sol for the first time to obtain an amorphous precursor material; Mixing the amorphous precursor material with a carbon source and deionized water to obtain a mixed slurry; Dispersing and drying the mixed slurry to obtain an intermediate product; sintering the intermediate product for a second time to obtain a lithium supplement; Wherein, the lithium supplement agent is an amorphous Li5AlO4 / C material.

2. The method for preparing a lithium supplement according to claim 1, wherein: The molar ratio of the aluminum source, the lithium source and the surfactant is 1:(5-6.5):(1-2); and / or The volume ratio of deionized water, ethanol and ammonia water in the mixed solvent is (4-5):(3-4):

1.

3. The method for preparing a lithium supplement according to claim 1, wherein: The aluminum source is one or more of Al2O3, AlCl3, Al(NO3)3, Al2(SO4)3, and Al(OH)3; and / or The lithium source is one or more of Li2O2, Li2O, LiOH, Li2SO4, LiNO3, and Li2CO3; and / or The surfactant is one or more of sodium dodecylbenzene sulfonate, sodium polystyrene sulfonate and PEG.

4. The method for preparing a lithium supplement according to claim 1, wherein: The temperature of the drying and heat preservation treatment is 60-100° C., and the time is 5-8 hours.

5. The method for preparing a lithium supplement according to claim 1, wherein: The first sintering has a heating rate of 1 to 10°C / min, a holding temperature of 400 to 900°C, and a holding time of 8 to 10 hours; and / or The atmosphere of the first sintering is air or oxygen.

6. The method for preparing a lithium supplement according to claim 1, wherein: The carbon source is one or more of glucose, sucrose, starch, acetylene, ethylene, epoxy resin, and cellulose; and / or The amount of the carbon source added is 4-6% of the mass of the amorphous precursor material; and / or The solid content of the mixed slurry is 25-35%.

7. The method for preparing a lithium supplement according to claim 6, wherein: The dispersion treatment time is 2 to 5 hours, the ball mill speed is 500 to 1500 rpm, the ball-to-material ratio is (10 to 20):1, and the particle size D50 of the material after dispersion treatment is 0.250 to 0.350 μm; and / or The inlet air temperature of the drying process is 100-200°C, and the outlet air temperature is 85-100°C; and / or The particle size D50 of the intermediate product is 10 to 25 μm.

8. The method for preparing a lithium supplement according to claim 1, wherein: The second sintering has a heating rate of 1-10°C / min, a holding temperature of 300-500°C, a holding time of 3-10h, and a furnace pressure of 20-100Pa; and / or The atmosphere of the second sintering is an inert gas; and / or The inert gas is one or more of nitrogen, argon and helium.

9. A lithium supplement, characterized in that: The lithium supplement is prepared by the preparation method of any one of claims 1 to 8, wherein the particle size D50 of the lithium supplement is 0.5 to 2.0 μm and the specific surface area is 8 to 38 m 2 / g.

10. A positive electrode material, characterized in that The lithium supplement agent according to claim 9 is included, wherein the amount of the lithium supplement agent added is 1 to 6% of the mass of the positive electrode material.

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