A manganese-based cathode material slow-release pre-lithiation agent, its preparation method and application

Abstract

This invention discloses a manganese-based cathode material slow-release pre-lithiation agent, its preparation method, and its application, belonging to the field of battery material technology. The slow-release pre-lithiation agent has a mixed structure, comprising a lithium-rich manganese-based phase with a layered structure and a lithium iron phosphate phase with an olivine structure. The slow-release pre-lithiation agent is characterized by the slow release of lithium ions during cycling, resulting in batteries made from this material exhibiting a trend of first increasing and then decreasing cycle retention, thus improving battery cycle performance. Furthermore, the industrial preparation method involved in this invention is mature and has good prospects for large-scale application.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a manganese-based cathode material slow-release pre-lithiation agent, its preparation method, and its application. Background Technology

[0002] With the rapid development of global technology and profound changes in the energy landscape, lithium-ion batteries have been widely used in various electronic devices, new energy vehicles, and energy storage systems due to their high energy density, long cycle life, and clean and environmentally friendly characteristics. However, in practical applications, mainstream cathode materials such as LMO (LiMn2O4), LCO (LiCoO2), and NCM (nickel-cobalt-manganese ternary materials) all face the prominent problem of poor cycle performance, which seriously restricts the battery's lifespan and energy density stability.

[0003] Specifically, LMO, affected by Jahn-Teller distortion, transforms from a cubic to a tetragonal crystal system during charge-discharge cycles. This volume expansion leads to particle cracking, resulting in rapid capacity decay with increasing cycle count. Simultaneously, HF generated from the decomposition of LiPF6 in the electrolyte reacts with LMO, causing Mn dissolution and further exacerbating cycle performance degradation. In LCO, repeated charge-discharge cycles cause repeated contraction and expansion of the LCO lattice due to lithium-ion insertion and extraction. Long-term cycling can lead to structural collapse, increasing internal resistance and causing a continuous decrease in capacity, especially under high-temperature or deep charge-discharge conditions. In NCM, with increasing cycle count, transition metal ions easily dissolve and migrate to the negative electrode, catalyzing abnormal SEI film growth. Simultaneously, the release of lattice oxygen under high voltage leads to surface structural degradation, hindering lithium-ion diffusion and causing rapid capacity decay. The higher the nickel content, the more pronounced the cycle stability issues.

[0004] To improve the cycling performance of the aforementioned materials, conventional modification methods are mostly designed for single materials. For example, patent CN106450217B proposes a method to obtain carbon-coated modified lithium nickel cobalt manganese oxide (NCO) material by performing vapor deposition under carbon source gas and protective gas conditions. This method solves the problem of lithium nickel oxide reduction during the carbon coating process of traditional ternary materials, while improving the initial charge-discharge efficiency, lithium-ion diffusion coefficient, and electronic conductivity, and reducing strong side reactions between the organic electrolyte and electrode materials and impedance during charge-discharge. After 50 cycles at 2.75-4.50V and 1C rate, the material still retains 96.2% of its capacity, but this method is only applicable to NCM systems. Patent CN114267834A employs an in-situ hydrolysis method to uniformly coat the surface of lithium cobalt oxide powder with an aminosilane coupling agent-modified oxide NQ-SiO2, forming a nanoscale coating layer. This overcomes the defects of inert coating layers, such as poor lithium-ion transport capability and excessive coating thickness, reducing side reactions between the cathode material and the electrolyte, and meeting the requirements of cathode material for capacity, cycle performance, and safety under high voltage. The material retains over 95% of its original strength after 50 cycles at 3.0-4.48V and 0.2C rate, but this is only applicable to LCO systems. Patent CN115528239B mentions doping lithium manganese oxide with aluminum and fluorine, modifying the lithium manganese oxide by partially replacing oxygen with fluorine, thus improving the strength of chemical bonds. 3+ and F - Binary ions stabilize the main structure of lithium manganese oxide, Al 3+ It enters the modified lithium manganese oxide lattice and partially replaces Mn. 3+ The above methods improve the high-temperature performance of modified lithium manganese oxide, reduce the Jahn-Teller effect, and effectively stabilize the spinel structure of lithium manganese oxide, but they are only applicable to LMO systems. Therefore, these methods are designed for specific materials and have poor universality.

[0005] Slow-release pre-lithiation technology utilizes pre-lithiation additives to gradually release lithium ions during battery cycling, continuously replenishing the active lithium consumed by processes such as SEI film repair and cathode structure degradation. This significantly improves battery cycle stability without sacrificing initial capacity. However, existing pre-lithiation agents still have shortcomings in terms of release rate control, structural stability, and compatibility with various cathode materials. Therefore, developing a slow-release pre-lithiation agent with controllable release characteristics, structural stability, and broad applicability is of great value for improving the overall performance of lithium-ion batteries. Summary of the Invention

[0006] The purpose of this invention is to provide a slow-release pre-lithiation agent for manganese-based cathode materials, its preparation method, and its application. This slow-release pre-lithiation agent can slowly release lithium ions during cycling to continuously replenish the active lithium consumed by the formation of the SEI film, significantly improving the poor cycle performance of existing cathode materials and significantly improving the overall performance of the battery. Moreover, the preparation method is simple and applicable to cathode materials of different systems, showing good application prospects.

[0007] To achieve the above objectives, the present invention provides a manganese-based cathode material slow-release pre-lithiation agent, wherein the slow-release pre-lithiation agent comprises a lithium-rich manganese-based phase with a layered structure and a lithium manganese iron phosphate phase with an olivine structure;

[0008] The ratio of lithium-rich manganese-based phase to lithium manganese iron phosphate ranges from 1:3 to 3:1.

[0009] The chemical formula of the lithium-rich manganese-based phase is xLi2MnO3·1-xLiTMO2, where 0<x≤0.14, TM represents Ni and Mn, and the molar ratio of Ni:Mn in the chemical formula is a:1-a, 0.42≤a≤0.48;

[0010] The chemical formula of lithium manganese iron phosphate phase is LiMn. y Fe 1-y PO4, where 0.6≤y≤0.8, and particle size distribution D50≤300nm.

[0011] This invention also provides a method for preparing the above-mentioned manganese-based cathode material slow-release pre-lithiation agent, specifically including the following steps:

[0012] S1, Preparation of lithium-rich manganese matrix phase:

[0013] S1-1. A metal salt solution is prepared by adding soluble nickel salt and soluble manganese salt to deionized water, a precipitant solution is prepared by adding precipitant to deionized water, and a complexing agent solution is prepared by diluting with deionized water.

[0014] S1-2. The metal salt solution, precipitant solution and complexing agent solution are heated to 50-70℃ and then injected into the reaction vessel. A protective gas is introduced, and the mixture is kept at the temperature and stirred to carry out a co-precipitation reaction. After filtration, the precipitate is successively aged, washed and vacuum dried to obtain the nickel-manganese precursor.

[0015] S1-3. Lithium salt and nickel-manganese precursor are mixed and subjected to gradient sintering in air atmosphere. After sintering, the mixture is cooled, crushed and sieved to obtain a uniform lithium-rich manganese matrix phase.

[0016] S2, Preparation of lithium manganese iron phosphate phase:

[0017] S2-1. Add lithium source, iron source, manganese source and phosphorus source to dry mixer and mix evenly to obtain pre-milled material;

[0018] S2-2. Add the pre-milled material and solvent to the sand mill for initial sand milling. Add the material after initial sand milling to the spray dryer for drying. Then add it to the atmosphere furnace for gradient sintering. After sintering, cool down.

[0019] S2-3. The cooled material is added to a sand mill for secondary dry sand milling. The material after secondary dry milling is sieved to obtain nano-sized lithium manganese iron phosphate phase.

[0020] S3. Preparation of slow-release pre-lithiation agent for manganese-based cathode materials:

[0021] The lithium-rich manganese-based phase obtained in step S1 and the lithium manganese iron phosphate phase obtained in step S2 are mixed evenly. The mixed material and solvent are added to a ball mill for ball milling. After ball milling, the mixture is vacuum dried, crushed and sieved to obtain a manganese-based cathode material slow-release pre-lithiation agent.

[0022] Preferably, in step S1-1, the soluble nickel salt is one or more of nickel sulfate, nickel acetate, nickel nitrate, nickel chloride, and nickel bromide; the soluble manganese salt is one or more of manganese sulfate, manganese nitrate, and manganese chloride; and the total cation concentration of the metal salt solution is 2-5 mol / L.

[0023] The precipitant is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate; the total anion concentration of the precipitant solution is 2-5 mol / L.

[0024] The complexing agent is ammonia water, and the concentration of the complexing agent solution is 1.5-2 mol / L.

[0025] Preferably, in steps S1-2, the protective gas is one or more of nitrogen or argon; the stirring speed is 500-1000 rpm; the aging time is 15-20 h; and the vacuum drying temperature is 150-180℃.

[0026] Preferably, in steps S1-3, the lithium salt is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium chloride;

[0027] The specific operation of gradient sintering is as follows: in the first stage, the temperature is raised to 480-520℃ at a heating rate of 2-5℃ and sintered for 4-6 hours; in the second stage, the temperature is raised to 850-950℃ at a heating rate of 2-5℃ and sintered for 10-20 hours; the cooling rate is 2-10℃.

[0028] Preferably, in step S2-1, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium chloride; the iron source is one or more of ferrous oxalate, ferrous acetate, ferrous oxide, and ferric phosphate; the manganese source is one or more of manganese sulfate, manganese nitrate, and manganese chloride; and the phosphorus source is ammonium dihydrogen phosphate.

[0029] Preferably, in step S2-2, the solid content of the slurry in the initial sand mill is 30-40%; the solvent is one or more of deionized water and ethanol; the sand milling speed is 1500-2500 rpm; the sand milling time is 2-4 hours; and the atmosphere in the atmosphere furnace is one or more of nitrogen and argon.

[0030] The specific parameters for gradient sintering are as follows: in the first stage, the temperature is increased to 300-450℃ at a heating rate of 2-5℃ / min and sintered for 2-3 hours; in the second stage, the temperature is increased to 650-800℃ at a heating rate of 3-5℃ / min and sintered for 8-12 hours; the cooling rate is 2-10℃ / min.

[0031] Preferably, in steps S2-3, the rotation speed of the secondary dry sand mill is 1500-2000 rpm; the sand milling time is 0.5-1 h.

[0032] Preferably, in step S3, the solvent is ethanol; the ball milling speed is 200-300 rpm; the ball milling time is 2-4 h; and the vacuum drying temperature is 120-180℃.

[0033] The present invention also provides the application of the above-mentioned manganese-based cathode material slow-release pre-lithiation agent in the assembly and preparation of lithium-ion batteries.

[0034] Therefore, the manganese-based cathode material slow-release pre-lithiation agent, its preparation method, and its application provided by the present invention have the following beneficial effects:

[0035] (1) The manganese-based cathode material slow-release pre-lithiation agent with layered structure and olivine structure prepared by the present invention achieves controlled slow release of lithium ions and effectively compensates for the loss of active lithium during the cycle.

[0036] (2) The slow-release agent material prepared by the present invention does not depend on the crystal structure or chemical composition of a specific cathode material. It can play a role in mainstream cathode materials such as LMO, LCO, and NCM, and can solve the cycle performance problem of cathode materials of different systems in a unified manner.

[0037] (3) The co-precipitation, gradient sintering, sand milling, ball milling and other processes involved in this invention are all mature industrial processes with high equipment compatibility, controllable production costs, and good prospects for large-scale application.

[0038] (4) The battery assembled from the slow-release material of the present invention shows a trend of first increasing and then decreasing in cycle retention rate, which significantly improves the cycle performance of the battery.

[0039] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0040] Figure 1 This is a process flow diagram for preparing the manganese-based cathode material slow-release pre-lithiation agent of the present invention;

[0041] Figure 2 This is the XRD pattern of the manganese-based cathode material slow-release pre-lithiation agent prepared in Example 1 of this invention;

[0042] Figure 3 This is a SEM image of the manganese-rich cathode material slow-release pre-lithiation agent prepared in Example 1 of this invention;

[0043] Figure 4 This is a characteristic graph of the specific capacity cycling performance of the manganese-based cathode material slow-release pre-lithiation agent in the voltage range of 2.75-4.30V according to Embodiment 1 of the present invention.

[0044] Figure 5 This is a comparison chart of the cycle performance of batteries made in Example 1 and Comparative Example 1 of the present invention at a 1C rate within a voltage range of 2.75-4.30V.

[0045] Figure 6 This is a comparison chart of the cycle performance of batteries made in Example 2 and Comparative Example 2 of the present invention at a 1C rate within a voltage range of 2.75-4.50V.

[0046] Figure 7 This is a comparison chart of the cycle performance of batteries made in Example 3 and Comparative Example 3 of the present invention at a 1C rate within a voltage range of 2.75-4.55V. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0048] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0049] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0050] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art, and the testing standards all use national or international standards commonly used in the field, without further explanation.

[0051] Example 1

[0052] like Figure 1 As shown, this embodiment provides a method for preparing a manganese-based cathode material slow-release pre-lithiation agent, specifically including the following steps:

[0053] S1, Preparation of lithium-rich manganese matrix phase:

[0054] S1-1. Prepare a mixed metal salt solution containing nickel sulfate and manganese sulfate, with a molar ratio of nickel ions to manganese ions of 45:55 and a total cation concentration of 2 mol / L. Prepare a sodium hydroxide solution by adding sodium hydroxide to deionized water, with an anion concentration of 4 mol / L. Then dilute the solution with ammonia water to obtain an ammonia solution with a concentration of 2 mol / L.

[0055] S1-2. Ammonia and sodium hydroxide solution were added to a 300L reactor, maintaining the reactor temperature at 60℃. Simultaneously, a mixed metal salt solution was added, stirred, and nitrogen gas was continuously introduced, maintaining the pH of the reaction system at 11.5-12. The reaction time was 24 hours, and the stirring speed was 500 rpm. The mixed metal salt solution was added at a rate of 4L / h, and the nitrogen gas flow rate was 10L / h. After the reaction, the mixture was filtered, and the precipitate was aged for 15 hours, washed, and then vacuum dried at 150℃ for 8 hours to obtain the chemical formula [Ni]. 0.45 Mn 0.55 Nickel-manganese precursor of (OH)2.

[0056] S1-3. Lithium hydroxide and nickel-manganese precursor are mixed uniformly at a molar ratio of 1.27:1 and added to a muffle furnace for gradient sintering in air atmosphere. After sintering, the mixture is cooled at a rate of 5°C, crushed, and sieved to obtain a lithium-rich manganese-based phase with the chemical formula 0.1Li₂MnO₃·0.9LiNi. 0.5 Mn 0.5 O2. During the sintering process, the heating rate in the first stage is 3℃, the sintering temperature is 520℃, and the sintering time is 4h. The heating rate in the second stage is 3℃, the sintering temperature is 870℃, and the sintering time is 18h.

[0057] S2, Preparation of lithium manganese iron phosphate phase:

[0058] S2-1. Lithium hydroxide, ferrous oxide, manganese sulfate and ammonium dihydrogen phosphate are added to a dry mixer and mixed evenly to obtain a pre-ground abrasive material, wherein the molar ratio of lithium hydroxide, ferrous oxide, manganese sulfate and ammonium dihydrogen phosphate is 1.05:0.6:0.4:1.1.

[0059] S2-2. Add 1000 mL of deionized water and 500 g of pre-ground sand material to a horizontal sand mill for initial sand milling. The milling media are 0.5 mm zirconia beads, and the rotation speed is 2000 rpm for 3 hours. Spray dry the initially milled material with an inlet air temperature of 200℃ and an outlet air temperature of 100℃. The feed rate is 25 mL / min. Add the dried material to a muffle furnace for gradient sintering. After sintering, cool it down at a rate of 5℃. The sintering process is conducted under a nitrogen atmosphere. The first stage has a heating rate of 3℃, a sintering temperature of 400℃, and a sintering time of 3 hours. The second stage has a heating rate of 3℃, a sintering temperature of 750℃, and a sintering time of 8 hours.

[0060] S2-3. The cooled material is crushed and then fed into a sand mill for secondary dry sand milling. The milling media are 0.3mm zirconium oxide beads, the rotation speed is 2000rpm, and the milling time is 1 hour. Nano-sized lithium manganese iron phosphate phase is obtained, with a particle size distribution D50 ≤ 300nm, and its chemical formula is LiMn. 0.6 Fe 0.4 PO4.

[0061] S3. Preparation of slow-release pre-lithiation agent for manganese-based cathode materials:

[0062] The lithium-rich manganese-based phase (LLOs) obtained in step S1 and the lithium manganese iron phosphate phase (LMFP) obtained in step S2 were mixed evenly at a molar ratio of 1:3. 100g of the mixture and 200g of anhydrous ethanol were added to a planetary ball mill for ball milling at 300rpm. The ball milling beads were made of zirconia balls with a diameter of 5mm, the ball-to-material ratio was 10:1, and the milling time was 2 hours. After ball milling, the mixture was vacuum dried at 170℃ for 4 hours, crushed, and sieved to obtain the manganese-based cathode material slow-release pre-lithiation agent.

[0063] Depend on Figure 2 It is known that the slow-release pre-lithiation agent includes a lithium-rich manganese-based phase and a manganese iron phosphate phase.

[0064] Depend on Figure 3 It can be seen that the slow-release pre-lithiation agent is a homogeneous mixture of a lithium-rich manganese-based phase with uniform particle distribution and a lithium manganese iron phosphate phase.

[0065] Depend on Figure 4 It can be seen that the battery prepared by the slow-release pre-lithiating agent has a significant slow-release effect and improved performance after electrical performance cycling test.

[0066] The slow-release pre-lithiation agent material was mixed uniformly with lithium manganese oxide (LMO) at a mass ratio of 1:4. The mixture, conductive carbon black, PVDF, and NMP were then uniformly ground and mixed at a mass ratio of 8:1:1:24 to obtain a positive electrode slurry, which was then uniformly coated onto the surface of aluminum foil. After vacuum drying, the slurry was cut into 10mm electrode sheets and assembled into coin cells for electrical performance cycling tests. The discharge specific capacity, first-cycle efficiency, 1C discharge specific capacity, slow-release peak retention rate, and number of slow-release peak cycles were recorded within the voltage range of 2.75-4.30V at 0.1C rate. The results are shown in Table 1.

[0067] Example 2

[0068] This embodiment provides a method for preparing a manganese-based cathode material slow-release pre-lithiation agent, specifically including the following steps:

[0069] S1, Preparation of lithium-rich manganese matrix phase:

[0070] S1-1. Prepare a mixed metal salt solution containing nickel sulfate and manganese sulfate, with a molar ratio of nickel ions to manganese ions of 48:52 and a total cation concentration of 2 mol / L. Prepare a sodium hydroxide solution by adding sodium hydroxide to deionized water, with an anion concentration of 5 mol / L. Then dilute the solution with ammonia water to obtain an ammonia solution with a concentration of 2 mol / L.

[0071] S1-2. Ammonia and sodium hydroxide solution were added to a 300L reactor, maintaining the reactor temperature at 60℃. Simultaneously, a mixed metal salt solution was added, stirred, and nitrogen gas was continuously introduced, maintaining the pH of the reaction system at 11.3-12. The reaction time was 24 hours, and the stirring speed was 500 rpm. The mixed metal salt solution was added at a rate of 4L / h, and the nitrogen gas flow rate was 10L / h. After the reaction, the mixture was filtered, and the precipitate was aged for 18 hours, washed, and then vacuum dried at 150℃ for 8 hours to obtain the chemical formula [Ni]. 0.48 Mn 0.52 Nickel-manganese precursor of (OH)2.

[0072] S1-3. Lithium carbonate and nickel-manganese precursor are mixed uniformly at a molar ratio of 1.21:1 and added to a muffle furnace for gradient sintering in air atmosphere. After sintering, the mixture is cooled at a rate of 10°C, crushed, and sieved to obtain a lithium-rich manganese matrix phase with the chemical formula 0.04Li₂MnO₃·0.96LiNi. 0.5 Mn 0.5 O2. During the sintering process, the heating rate in the first stage is 5℃, the sintering temperature is 520℃, and the sintering time is 4h. The heating rate in the second stage is 5℃, the sintering temperature is 870℃, and the sintering time is 18h.

[0073] S2, Preparation of lithium manganese iron phosphate phase:

[0074] S2-1. Lithium carbonate, ferrous oxalate, manganese nitrate and ammonium dihydrogen phosphate are added to a dry mixer and mixed evenly to obtain a pre-ground material, wherein the molar ratio of lithium carbonate, ferrous oxalate, manganese nitrate and ammonium dihydrogen phosphate is 1.05:0.7:0.3:1.1.

[0075] S2-2. Add 1000 mL of deionized water and 500 g of pre-ground sand material to a horizontal sand mill for initial sand milling. The milling media are 0.5 mm zirconia beads, and the rotation speed is 2000 rpm for 3 hours. Spray dry the initially milled material with an inlet air temperature of 200℃ and an outlet air temperature of 100℃. The feed rate is 25 mL / min. Add the dried material to a muffle furnace for gradient sintering. After sintering, cool it down at a rate of 10℃. The sintering process is conducted under a nitrogen atmosphere. The first stage has a heating rate of 5℃, a sintering temperature of 400℃, and a sintering time of 3 hours. The second stage has a heating rate of 5℃, a sintering temperature of 750℃, and a sintering time of 8 hours.

[0076] S2-3. The cooled material is crushed and then fed into a sand mill for secondary dry sand milling. The milling media are 0.3mm zirconium oxide beads, the rotation speed is 2000rpm, and the milling time is 1 hour. Nano-sized lithium manganese iron phosphate phase is obtained, with a particle size distribution D50 ≤ 300nm, and its chemical formula is LiMn. 0.7 Fe 0.3 PO4.

[0077] S3. Preparation of slow-release pre-lithiation agent for manganese-based cathode materials:

[0078] The lithium-rich manganese-based phase obtained in step S1 and the lithium manganese iron phosphate phase obtained in step S2 were mixed evenly at a molar ratio of 3:1. 100g of the mixture and 200g of anhydrous ethanol were added to a planetary ball mill for ball milling at 300 rpm. The ball milling beads were made of zirconia balls with a diameter of 5mm, the ball-to-material ratio was 8:1, and the milling time was 2.5 hours. After ball milling, the mixture was vacuum dried at 170℃ for 4 hours, crushed, and sieved to obtain the manganese-based cathode material slow-release pre-lithiation agent.

[0079] The slow-release pre-lithiation agent material was mixed uniformly with lithium cobalt oxide (LCO) at a mass ratio of 1:4. The mixture, conductive carbon black, PVDF, and NMP were then uniformly ground and mixed at a mass ratio of 8:1:1:24 to obtain a positive electrode slurry, which was then uniformly coated onto the surface of aluminum foil. After vacuum drying, the slurry was cut into 10mm electrode sheets and assembled into coin cells for electrical performance cycling tests. The discharge specific capacity, first-cycle efficiency, 1C discharge specific capacity, slow-release peak retention rate, and number of slow-release peak cycles were recorded within the voltage range of 2.75-4.50V at 0.1C. The results are shown in Table 1.

[0080] Example 3

[0081] This embodiment provides a method for preparing a manganese-based cathode material slow-release pre-lithiation agent, specifically including the following steps:

[0082] S1, Preparation of lithium-rich manganese matrix phase:

[0083] S1-1. Prepare a mixed metal salt solution containing nickel sulfate and manganese sulfate, with a molar ratio of nickel ions to manganese ions of 43:57 and a total cation concentration of 2 mol / L. Prepare a sodium hydroxide solution by adding sodium hydroxide to deionized water, with an anion concentration of 4 mol / L. Then dilute the solution with ammonia water to obtain an ammonia solution with a concentration of 1.5 mol / L.

[0084] S1-2. Ammonia and sodium hydroxide solution were added to a 300L reactor, maintaining the reactor temperature at 60℃. Simultaneously, a mixed metal salt solution was added, stirred, and nitrogen gas was continuously introduced, maintaining the pH of the reaction system at 11.3-12. The reaction time was 24 hours, and the stirring speed was 500 rpm. The mixed metal salt solution was added at a rate of 4L / h, and the nitrogen gas flow rate was 10L / h. After the reaction, the precipitate was aged for 16 hours, washed, and then vacuum dried at 150℃ for 8 hours to obtain the chemical formula [Ni]. 0.43 Mn 0.57 Nickel-manganese precursor of (OH)2.

[0085] S1-3. Lithium chloride and nickel-manganese precursor are mixed uniformly at a molar ratio of 1.33:1 and added to a muffle furnace for gradient sintering. After sintering, the mixture is cooled at a rate of 8°C, crushed, and sieved to obtain a lithium-rich manganese-based phase with the chemical formula 0.14Li₂MnO₃·0.86LiNi. 0.5 Mn 0.5 O2. During the sintering process, the heating rate in the first stage is 3℃, the sintering temperature is 520℃, and the sintering time is 4h. The heating rate in the second stage is 3℃, the sintering temperature is 870℃, and the sintering time is 18h.

[0086] S2, Preparation of lithium manganese iron phosphate phase:

[0087] S2-1. Lithium chloride, ferrous acetate, manganese chloride and ammonium dihydrogen phosphate are added to a dry mixer and mixed evenly to obtain a pre-ground material, wherein the molar ratio of lithium chloride, ferrous acetate, manganese chloride and ammonium dihydrogen phosphate is 1.05:0.75:0.25:1.1.

[0088] S2-2. Add 1000 mL of deionized water and 500 g of pre-ground sand material to a horizontal sand mill for initial sand milling. The milling media are 0.5 mm zirconia beads, and the rotation speed is 2000 rpm for 3 hours. Spray dry the initially milled material with an inlet temperature of 200℃ and an outlet temperature of 100℃. The feed rate is 25 mL / min. Add the dried material to a muffle furnace for gradient sintering. After sintering, cool at a rate of 8℃. The sintering process is conducted under a nitrogen atmosphere. The first stage has a heating rate of 3℃, a sintering temperature of 400℃, and a sintering time of 3 hours. The second stage has a heating rate of 3℃, a sintering temperature of 750℃, and a sintering time of 8 hours.

[0089] S2-3. The cooled material is crushed and then fed into a sand mill for secondary dry sand milling. The milling media are 0.3mm zirconium oxide beads, the rotation speed is 2000rpm, and the milling time is 1 hour. Nano-sized lithium manganese iron phosphate phase is obtained, with a particle size distribution D50 ≤ 300nm, and its chemical formula is LiMn. 0.75 Fe 0.25 PO4.

[0090] S3. Preparation of slow-release pre-lithiation agent for manganese-based cathode materials:

[0091] The lithium-rich manganese-based phase obtained in step S1 and the lithium manganese iron phosphate phase obtained in step S2 were mixed evenly at a molar ratio of 3:1. 100g of the mixture and 200g of anhydrous ethanol were added to a planetary ball mill for ball milling at 300 rpm. The ball milling beads were made of zirconia balls with a diameter of 5mm, the ball-to-material ratio was 10:1, and the milling time was 2 hours. After ball milling, the mixture was vacuum dried at 170℃ for 4 hours, crushed, and sieved to obtain the manganese-based cathode material slow-release pre-lithiation agent.

[0092] The slow-release pre-lithiation agent material was uniformly mixed with lithium nickel cobalt manganese oxide (NCM) at a mass ratio of 1:4. The mixture, conductive carbon black, PVDF, and NMP were uniformly ground and mixed at a mass ratio of 8:1:1:24 to obtain a positive electrode slurry, which was then uniformly coated onto the surface of aluminum foil. After vacuum drying, the slurry was cut into 10mm electrode sheets and assembled into coin cells for electrical performance cycling tests. The discharge specific capacity, first-cycle efficiency, 1C discharge specific capacity, slow-release peak retention rate, and number of slow-release peak cycles were recorded within the voltage range of 2.75-4.55V at 0.1C. The results are shown in Table 1.

[0093] Comparative Example 1

[0094] This comparative example provides a method for preparing LMO cathode material: Lithium carbonate and manganese dioxide are mixed uniformly at a molar ratio of 1:2, and then ball-milled in a planetary ball mill for 60 minutes at a speed of 15-20 r / min. The resulting mixture is then calcined in a muffle furnace with air introduced, heated to 160℃, and maintained at this temperature for 1 hour. The temperature is then increased to 600℃ and calcined at this temperature for 5 hours, followed by cooling. The cooled material is then subjected to airflow crushing, electromagnetic iron removal 3-4 times, and sieved through a 200-250 mesh sieve to obtain LiMn2O4.

[0095] LMO, conductive carbon black, PVDF, and NMP were uniformly ground and mixed in a mass ratio of 8:1:1:24 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the surface of aluminum foil. After vacuum drying, the slurry was cut into 10mm electrode sheets and assembled into coin cells for electrical performance cycling tests. The discharge specific capacity, first-cycle efficiency, and discharge specific capacity at 1C rate were recorded within a voltage range of 2.75-4.55V. The results are shown in Table 1.

[0096] Comparative Example 2

[0097] This comparative example provides a method for preparing LCO cathode material: Cobalt chloride is added to deionized water to prepare a salt solution with a concentration of 60 g / L, and then a sodium hydroxide solution with a concentration of 100 g / L is prepared as a precipitant. Under a nitrogen atmosphere, the cobalt salt solution and the precipitant are mixed and reacted at a reaction temperature of 80℃ for 30 min. The mixture is then filtered, washed, and dried to obtain cobalt salt. The cobalt salt is added to a muffle furnace and calcined at 800℃ for 5 hours under a nitrogen atmosphere. The cobalt salt is then pulverized to obtain cobalt tetroxide. Subsequently, lithium carbonate and cobalt tetroxide are mixed at a molar ratio of 1.04:1 and calcined at 900℃ for 15 hours under an air atmosphere. The mixture is then crushed and sieved to obtain LiCoO2.

[0098] LCO, conductive carbon black, PVDF, and NMP were uniformly ground and mixed in a mass ratio of 8:1:1:24 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the surface of aluminum foil. After vacuum drying, the slurry was cut into 10mm electrode sheets and assembled into coin cells for electrical performance cycle testing. The discharge specific capacity, first-cycle efficiency, and discharge specific capacity at 1C rate were recorded within a voltage range of 2.75-4.55V. The results are shown in Table 1.

[0099] Comparative Example 3

[0100] This comparative example provides a method for preparing NCM cathode material: a mixed salt solution of nickel, cobalt, manganese, and zirconium with a total metal ion concentration of 1.5 mol / L was prepared according to a Ni:Co:Mn molar ratio of 0.65:0.15:0.20; a NaOH aqueous solution with a concentration of 6 mol / L and an ammonia aqueous solution with a concentration of 8 mol / L were prepared. 120 L of the NaOH and ammonia aqueous solutions were added to a 300 L reactor, and the pH was adjusted to 11.0. Nitrogen gas was continuously introduced into the reactor at a flow rate of 12 L / min. The flow rates of the mixed salt solution, NaOH aqueous solution, and ammonia aqueous solution were 65 mL / min, and the pH and temperature in the reactor were controlled at 60 °C to carry out a co-precipitation reaction. After the reaction was completed, the precursor Ni was washed and dried to obtain Ni. 0.65 Co 0.15 Mn 0.20 (OH)₂. The precursor and LiOH·H₂O were mixed evenly in a mixer at a molar ratio of 1.0:1.05. The mixture was then added to a muffle furnace. The furnace was first heated to 400°C, and air (removed from carbon dioxide and water) was introduced. The furnace was then calcined for 3 hours. The temperature was then increased to 750°C and calcined for 8 hours, with air continuously introduced. The mixture was cooled, crushed, and sieved to obtain lithium nickel cobalt manganese oxide.

[0101] NCM, conductive carbon black, PVDF, and NMP were uniformly ground and mixed in a mass ratio of 8:1:1:24 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the surface of aluminum foil. After vacuum drying, the slurry was cut into 10mm electrode sheets and assembled into coin cells for electrical performance cycle testing. The discharge specific capacity, first-cycle efficiency, and discharge specific capacity at 1C rate were recorded within a voltage range of 2.75-4.55V. The results are shown in Table 1.

[0102] Table 1: Comparison of electrical properties of materials prepared in the examples and comparative examples

[0103] ;

[0104] As shown in Table 1, the batteries prepared by adding slow-release pre-lithiation agent have a certain degree of improved discharge specific capacity at different rates and have stable cycle performance, showing a good improvement effect.

[0105] Depend on Figure 5 It can be seen that adding a slow-release pre-lithiation agent can improve the cycling stability of LMO within a certain range, and the discharge specific capacity at 0.1C rate is increased by 10.4% to reach 102.4mAh / g.

[0106] Depend on Figure 6It can be seen that after adding the slow-release pre-lithiation agent, the discharge specific capacity of LCO showed a trend of first increasing and then decreasing, and the cycle stability was significantly improved within a certain range. The discharge specific capacity at 0.1C rate increased by 22.8% to reach 207.1mAh / g.

[0107] Depend on Figure 7 It can be seen that after adding the slow-release pre-lithiation agent, the discharge specific capacity of NCM showed a trend of first increasing and then decreasing. At the same time, the addition of the slow-release pre-lithiation agent significantly improved the cycle stability of NCM within a certain range, with the discharge specific capacity increasing by 30.6% to 212.7 mAh / g at 0.1C rate.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. Use of a manganese-based cathode material slow-release prelithium agent, characterized in that: The slow-release pre-lithium agent is mixed with the positive electrode material and applied in the assembly and preparation of a lithium ion battery. The preparation method of the slow-release pre-lithium agent specifically comprises the following steps: S1, preparation of a lithium-rich manganese-based phase: S1-1, a soluble nickel salt and a soluble manganese salt are added to deionized water to prepare a metal salt solution, a precipitant is added to deionized water to prepare a precipitant solution, and a complexing agent is added to deionized water to prepare a complexing agent solution; S1-2, the metal salt solution, the precipitant solution and the complexing agent solution are heated to 50-70 DEG C respectively, then injected into a reaction kettle and passed through a protective gas, and then a co-precipitation reaction is carried out under the condition of heat preservation and stirring, followed by filtration, aging, washing and vacuum drying of the precipitate in sequence to obtain a nickel-manganese precursor; S1-3, a lithium salt and the nickel-manganese precursor are mixed and gradient sintering is carried out in an air atmosphere, and then the sintered product is cooled, crushed and sieved to obtain a uniform lithium-rich manganese-based phase; S2, preparation of a lithium iron manganese phosphate phase: S2-1, a lithium source, an iron source, a manganese source and a phosphorus source are uniformly mixed in a dry blender to obtain a pre-sand grinding material; S2-2, the pre-sand grinding material and a solvent are added to a sand mill for primary sand grinding, the primary sand grinding material is dried in a spray dryer, and then gradient sintering is carried out in an atmosphere furnace, and then the sintered product is cooled; S2-3, the cooled material is added to a sand mill for secondary dry sand grinding, and then the secondary dry sand grinding material is sieved to obtain a nano-sized lithium iron manganese phosphate phase; S3, preparation of a manganese-based positive electrode material slow-release pre-lithium agent: The lithium-rich manganese-based phase prepared in step S1 and the lithium iron manganese phosphate phase prepared in step S2 are uniformly mixed, the mixed material and a solvent are added to a ball mill for ball milling, and then the ball-milled product is vacuum dried, crushed and sieved to obtain a manganese-based positive electrode material slow-release pre-lithium agent; The slow-release pre-lithium agent comprises a lithium-rich manganese-based phase with a layered structure and a lithium iron manganese phosphate phase with an olivine structure; The ratio of the lithium-rich manganese-based phase to the lithium iron manganese phosphate phase ranges from 1:3 to 3:1; The chemical formula of the lithium-rich manganese-based phase is xLi2MnO3·1-xLiTMO2, wherein 0 The chemical formula of the lithium iron manganese phosphate phase is LiMn y Fe 1-y PO4, wherein 0.6≤y≤0.8, the particle size distribution D50≤300 nm.

2. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S1-1, the soluble nickel salt is one or more of nickel sulfate, nickel acetate, nickel nitrate, nickel chloride and nickel bromide; the soluble manganese salt is one or more of manganese sulfate, manganese nitrate and manganese chloride; and the total cation concentration of the metal salt solution is 2-5 mol / L; The precipitant is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate; and the total anion concentration of the precipitant solution is 2-5 mol / L; The complexing agent is ammonia water, and the concentration of the complexing agent solution is 1.5-2 mol / L.

3. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S1-2, the protective gas is one or more of nitrogen or argon; the stirring speed is 500-1000 rpm; the aging time is 15-20 h; and the vacuum drying temperature is 150-180 DEG C.

4. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S1-3, the lithium salt is one or more of lithium carbonate, lithium acetate, lithium nitrate and lithium chloride. The specific operation of gradient sintering is: the first stage is sintered at 480-520℃ for 4-6h with a temperature rising rate of 2-5℃, and the second stage is sintered at 850-950℃ for 10-20h with a temperature rising rate of 2-5℃; the cooling rate is 2-10℃.

5. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S2-1, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate and lithium chloride; the iron source is one or more of ferrous oxalate, ferrous acetate, ferrous oxide and iron phosphate; the manganese source is one or more of manganese sulfate, manganese nitrate and manganese chloride; and the phosphorus source is ammonium dihydrogen phosphate.

6. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S2-2, the solid content of the slurry for the first sanding is 30-40%; the solvent is one or more of deionized water and ethanol; the sanding speed is 1500-2500rpm, and the sanding time is 2-4h; the atmosphere in the atmosphere furnace is one or more of nitrogen and argon; The specific parameters of gradient sintering are: the first stage is sintered at 300-450℃ for 2-3h with a temperature rising rate of 2-5℃ / min; the second stage is sintered at 650-800℃ for 8-12h with a temperature rising rate of 3-5℃ / min; and the cooling rate is 2-10℃ / min.

7. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S2-3, the speed of the second dry sanding is 1500-2000rpm; and the sanding time is 0.5-1h.

8. The use of a manganese-based cathode material slow-release prelithium agent according to claim 1, characterized in that: In step S3, the solvent is ethanol; the ball milling speed is 200-300rpm, and the ball milling time is 2-4h; and the vacuum drying temperature is 120-180℃.

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