Preparation method and application of natural graphite negative electrode material of alkaline manganese battery
By performing ultrasonic-assisted complexation and impurity removal, low-temperature plasma nitrogen-boron co-doping, and gradient temperature activation treatment on natural graphite, a nitrogen-boron co-doped modified layer and a multi-level porous structure are formed, which solves the problems of high cost and poor electrochemical performance of natural graphite anode materials, and realizes alkaline manganese batteries with high capacity, long life and high rate performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-05
- Publication Date
- 2026-03-10
AI Technical Summary
Existing natural graphite anode materials for alkaline manganese batteries suffer from high cost, poor electrochemical performance, and limitations in preparation processes, making it difficult to meet the demands for high capacity, long lifespan, and high rate capability.
Using natural graphite as the matrix, an innovative process is employed, including ultrasonic-assisted complexation and impurity removal, low-temperature plasma nitrogen-boron co-doping and pore control, gradient temperature activation and surface modification, to form a nitrogen-boron co-doped modified layer and a multi-level porous structure, which significantly improves the conductivity and electrochemical performance of the material.
It significantly improves the electrochemical performance of the material, reduces production energy consumption, and the material cost is only 1/3 to 1/2 of that of artificial graphite. The 1C rate discharge capacity of the battery is increased by 25% to 30%, the capacity retention rate after 500 cycles is ≥85%, and the low-temperature discharge performance is significantly improved.
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery materials technology, specifically to a method for preparing and applying a natural graphite anode material for alkaline manganese batteries. Background Technology
[0002] Alkaline manganese batteries are widely used in portable electronic devices, medical devices, and small household appliances due to their advantages such as stable discharge performance, relatively low cost, and wide range of applications. The negative electrode material, as one of the core components of an alkaline manganese battery, directly affects the battery's charge / discharge capacity, cycle stability, rate performance, and lifespan.
[0003] Currently, the commonly used negative electrode materials for alkaline manganese batteries are mostly artificial graphite or natural graphite that has undergone simple purification. Among them, although artificial graphite has good conductivity and structural stability, its preparation process requires high-temperature graphitization treatment, which consumes a lot of energy and has high production costs. Moreover, in the alkaline electrolyte environment of alkaline manganese batteries, problems such as surface oxidation and interlayer delamination are prone to occur, leading to a decline in battery cycle performance.
[0004] Traditional natural graphite anode materials, despite their wide availability and low cost, suffer from numerous impurities (such as ash and organic contaminants) on their surface, insufficient regularity in their layered structure, and unreasonable pore distribution. Direct application of natural graphite results in poor conductivity, poor electrolyte wettability, and high resistance to lithium-ion insertion / extraction. Current technologies for modifying natural graphite often employ common methods such as acid leaching purification, high-temperature calcination, or simple coating. These methods either fail to effectively remove deep impurities and optimize the pore structure or damage the integrity of the graphite's layered structure, making it difficult to balance conductivity, structural stability, and electrochemical performance. Consequently, they cannot meet the demands of alkaline manganese batteries for higher capacity, longer lifespan, and higher rate capability.
[0005] Therefore, developing a novel natural graphite anode material that is low in raw material cost, simple in preparation process, and has excellent performance, while avoiding existing publicly available patented technologies and general technologies, is of great significance for promoting the performance upgrade of alkaline manganese batteries. Summary of the Invention
[0006] The purpose of this invention is to solve the problems of high cost, poor electrochemical performance and limited preparation process of graphite anode materials for alkaline manganese batteries in the prior art, and to provide a method for preparing natural graphite anode materials for alkaline manganese batteries and their application.
[0007] This invention provides a natural graphite anode material for alkaline manganese batteries. Based on natural graphite, the material achieves efficient removal of impurities and precise structural control through innovative pretreatment, modification, and post-treatment processes, significantly improving the electrochemical performance of the material. The invention also provides a preparation method and application of the material, which is simple, energy-efficient, and can be mass-produced.
[0008] The natural graphite anode material for alkaline manganese batteries prepared by this invention uses natural flake graphite as a matrix. A doped modification layer is formed on the surface of the matrix, and a hierarchical porous structure is distributed within the matrix. The doped modification layer is formed by co-doping with nitrogen and boron, wherein the mass fraction of nitrogen is 0.8-1.5% and the mass fraction of boron is 0.3-0.8%. The hierarchical porous structure includes mesopores with a pore size of 2-5 nm and macropores with a pore size of 50-200 nm. The mesopore volume accounts for 40-60% of the total pore volume, and the macropore volume accounts for 25-45% of the total pore volume. The tap density of the anode material is 1.2-1.5 g / cm³. 3 Specific surface area is 35-60 m² 2 / g, initial charge / discharge efficiency ≥90%, capacity retention ≥85% after 500 cycles at 1C rate.
[0009] A method for preparing a natural graphite anode material for an alkaline manganese battery, characterized in that the preparation method is specifically carried out according to the following steps:
[0010] I. Raw material pretreatment:
[0011] Natural flake graphite was added to a complexing and impurity removal solution to obtain a mixed system. The mixed system was placed in an ultrasonic reactor and ultrasonically treated for a period of time. After filtration, the precipitate was collected, washed with water until neutral, and then placed in a vacuum drying oven for vacuum drying to obtain pretreated natural graphite.
[0012] II. Low-temperature plasma-assisted nitrogen-boron co-doping and porosity control:
[0013] ① Mix the pretreated natural graphite with the doped precursor, and then place it in a planetary ball mill for a period of time to obtain a mixed powder;
[0014] The doping precursor mentioned in step 2① is a mixture of urea and boric acid in a mass ratio of 5:1;
[0015] ② Place the mixed powder in a low-temperature plasma reaction chamber, introduce protective gas, control the pressure in the reaction chamber to 10~20Pa, and raise the temperature to 300~400℃;
[0016] ③ Turn on the plasma power supply, adjust the power to 150~250W, introduce the reaction gas, and react for a period of time at a temperature of 300~400℃ and a pressure of 10~20Pa; after the reaction is completed, stop the introduction of the reaction gas, and continue to introduce the protective gas until the reaction chamber cools down to room temperature to obtain nitrogen-boron co-doped graphite.
[0017] The reaction gas mentioned in step 2③ is a mixture of ammonia and borane in a volume ratio of 10:1;
[0018] III. Gradient Temperature Activation and Surface Modification:
[0019] ① Place nitrogen-boron co-doped graphite in a tube furnace, introduce inert gas, and use a gradient heating method: raise the temperature from room temperature to 200℃ and hold; raise the temperature to 400℃ and hold; finally raise the temperature to 600℃ and hold for 1 hour; after the holding period, allow it to cool naturally to room temperature to obtain the reaction product.
[0020] ② Add the reaction product to the modifier solution and react for a period of time under heating and stirring. After the reaction is complete, filter, collect the solid material, wash, and vacuum dry to obtain the natural graphite anode material for alkaline manganese batteries.
[0021] A natural graphite anode material for an alkaline manganese battery is used to prepare the anode sheet for the alkaline manganese battery; the anode sheet of the alkaline manganese battery is used to assemble the alkaline manganese battery; the alkaline manganese battery has a discharge capacity of 320-350 mAh / g at 1C rate, a capacity retention rate of ≥85% after 500 cycles at 1C rate, and a discharge capacity retention rate of ≥70% at -20℃.
[0022] The beneficial effects of this invention are:
[0023] I. The natural graphite anode material for alkaline manganese batteries prepared by this invention uses natural graphite as raw material, and its cost is only 1 / 3 to 1 / 2 of that of artificial graphite. Moreover, through innovative processes such as ultrasonic-assisted complexation and impurity removal, low-temperature plasma nitrogen-boron co-doping and pore control, gradient temperature activation and surface modification, impurities are effectively removed, forming a nitrogen-boron co-doped modified layer and a multi-level porous structure. The material's tap density, specific surface area, first charge-discharge efficiency and cycle stability are significantly improved, solving the problems of poor conductivity and poor electrolyte wettability of traditional natural graphite.
[0024] Second, the preparation method of the present invention does not require high-temperature graphitization, strong acid and strong alkali treatment and other common high-energy-consuming and high-polluting processes. The reaction temperature is low (maximum only 600℃), energy consumption is reduced by more than 40%, and there is no harmful wastewater or exhaust gas emission, which meets the requirements of green production. At the same time, the process steps are simple and easy to scale up production.
[0025] Third, the natural graphite anode material of the alkaline manganese battery prepared by this invention can be applied to alkaline manganese batteries. The 1C rate discharge capacity of the battery can reach 320~350mAh / g, which is 25%~30% higher than that of traditional natural graphite anode batteries. The capacity retention rate after 500 cycles is ≥85%, which is 15%~20% higher than that of artificial graphite anode batteries. Moreover, the rate performance and low temperature discharge performance (discharge capacity retention rate ≥70% at -20℃) of the battery are significantly improved, which can meet the performance requirements of high-end alkaline manganese batteries. Detailed Implementation
[0026] Specific Implementation Method 1: This implementation method is a method for preparing natural graphite anode material for alkaline manganese batteries, specifically completed according to the following steps:
[0027] I. Raw material pretreatment:
[0028] Natural flake graphite was added to a complexing and impurity removal solution to obtain a mixed system. The mixed system was placed in an ultrasonic reactor and ultrasonically treated for a period of time. After filtration, the precipitate was collected, washed with water until neutral, and then placed in a vacuum drying oven for vacuum drying to obtain pretreated natural graphite.
[0029] II. Low-temperature plasma-assisted nitrogen-boron co-doping and porosity control:
[0030] ① Mix the pretreated natural graphite with the doped precursor, and then place it in a planetary ball mill for a period of time to obtain a mixed powder;
[0031] The doping precursor mentioned in step 2① is a mixture of urea and boric acid in a mass ratio of 5:1;
[0032] ② Place the mixed powder in a low-temperature plasma reaction chamber, introduce protective gas, control the pressure in the reaction chamber to 10~20Pa, and raise the temperature to 300~400℃;
[0033] ③ Turn on the plasma power supply, adjust the power to 150~250W, introduce the reaction gas, and react for a period of time at a temperature of 300~400℃ and a pressure of 10~20Pa. After the reaction is completed, stop introducing the reaction gas and continue to introduce the protective gas until the reaction chamber cools down to room temperature to obtain nitrogen-boron co-doped graphite.
[0034] The reaction gas mentioned in step 2③ is a mixture of ammonia and borane in a volume ratio of 10:1;
[0035] III. Gradient Temperature Activation and Surface Modification:
[0036] ① Place nitrogen-boron co-doped graphite in a tube furnace, introduce inert gas, and use a gradient heating method: raise the temperature from room temperature to 200℃ and hold; raise the temperature to 400℃ and hold; finally raise the temperature to 600℃ and hold for 1 hour; after the holding period, allow it to cool naturally to room temperature to obtain the reaction product.
[0037] ② Add the reaction product to the modifier solution and react for a period of time under heating and stirring. After the reaction is complete, filter, collect the solid material, wash, and vacuum dry to obtain the natural graphite anode material for alkaline manganese batteries.
[0038] In step one of this embodiment, ultrasonic-assisted complexation can efficiently remove metallic impurities (such as Fe, Ca, Mg, etc.) and organic impurities from the surface and interlayer of natural graphite, while avoiding the damage to the graphite structure caused by traditional acid leaching.
[0039] Step two of this embodiment uses low-temperature plasma assistance to achieve uniform doping of nitrogen and boron elements at a lower temperature. At the same time, the etching effect of plasma is used to form a multi-level porous structure inside the graphite, avoiding the problems of high energy consumption and structural collapse caused by high-temperature processing, and significantly improving the doping efficiency and porosity control precision.
[0040] In step three of this embodiment, gradient temperature activation can further optimize the pore structure, remove residual doped precursor impurities, and improve the conductivity of the material; surface modification can improve the compatibility between the material and the electrolyte and reduce interfacial impedance.
[0041] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the particle size of the natural flake graphite mentioned in step one is 30~50μm; the complexing and impurity removal solution mentioned in step one is prepared by mixing citric acid solution, disodium ethylenediaminetetraacetate solution, and water in a volume ratio of 3:1:6; the concentration of the citric acid solution is 0.5~1mol / L; and the concentration of the disodium ethylenediaminetetraacetate solution is 0.2~0.4mol / L. Other steps are the same as in Specific Implementation Method One.
[0042] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in the following ways: the mass ratio of natural flake graphite to complexing and impurity removal solution in step one is 1:5; the ultrasonic treatment temperature in step one is 60~80℃, the ultrasonic treatment power is 300~500W, and the ultrasonic treatment time is 2h~4h; the vacuum drying temperature in step one is 100~120℃, the vacuum degree is -0.08~-0.1MPa, and the vacuum drying time is 6~8h. Other steps are the same as in Specific Implementation Method One or Two.
[0043] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the mass ratio of pretreated natural graphite to doped precursor in step two① is 10:(1~3); the ball-to-material ratio in the ball milling in step two① is 20:1, the ball milling speed is 200~300 r / min, and the ball milling time is 1~2 h. Other steps are the same as in Specific Implementation Methods One to Three.
[0044] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the heating rate in step two ② is 5~10℃ / min; the reaction time in step two ③ is 30~60min; and the protective gas in steps two ② and two ③ is a mixture of argon and hydrogen in a volume ratio of 9:1. Other steps are the same as in Specific Implementation Methods One to Four.
[0045] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the inert gas mentioned in step three ① is nitrogen; the heating rate mentioned in step three ① is 2~5℃ / min; and the holding time mentioned in step three ① is 1~2h. Other steps are the same as in Specific Implementation Methods One to Five.
[0046] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the modifier solution mentioned in step three ② is an ethanol solution of polyvinylpyrrolidone with a concentration of 5-10%; the volume ratio of the reaction product to the modifier solution in step three ② is (1.2-1.5):1; in step three ②, the reaction product is added to the modifier solution and reacted for 1-2 hours at a temperature of 40-60℃ and a speed of 150-200 r / min. After the reaction is completed, the mixture is filtered, the solid material is collected, washed with water 3-5 times, and finally vacuum dried for 4-6 hours at a temperature of 80-100℃ and a vacuum degree of -0.08--0.1 MPa to obtain the natural graphite anode material for alkaline manganese batteries. Other steps are the same as in Specific Implementation Methods One to Six.
[0047] Specific Implementation Method Eight: In this implementation method, the natural graphite negative electrode material of the alkaline manganese battery is used to prepare the negative electrode sheet of the alkaline manganese battery; the negative electrode sheet of the alkaline manganese battery is used to assemble the alkaline manganese battery.
[0048] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the natural graphite negative electrode material of the alkaline manganese battery is used to prepare the negative electrode sheet of the alkaline manganese battery, specifically by following these steps:
[0049] 1. Mix the natural graphite anode material, binder and conductive agent of alkaline manganese battery at a mass ratio of 90:5:5, add deionized water, and stir at 800~1000 r / min for 3~5 h to obtain anode slurry with a solid content of 40~50%.
[0050] The adhesive mentioned in step one is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:2;
[0051] The conductive agent mentioned in step one is carbon black;
[0052] II. Preparation of the negative electrode:
[0053] A negative electrode slurry with a solid content of 40-50% is uniformly coated onto a copper foil current collector to a thickness of 80-120 μm. It is then dried in an oven at 80-100°C for 2 hours, followed by vacuum drying in a vacuum drying oven at 120-140°C and a vacuum degree of -0.08 to -0.1 MPa for 8-10 hours. Finally, it is rolled and slit under a pressure of 10-15 MPa to obtain the negative electrode sheet for the alkaline manganese battery. Other steps are the same as in specific embodiments one through eight.
[0054] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the negative electrode sheet of the alkaline manganese battery is used to assemble the alkaline manganese battery, specifically by following these steps:
[0055] Using an alkaline manganese battery as the negative electrode, a manganese dioxide positive electrode as the positive electrode, a 6-8 mol / L potassium hydroxide aqueous solution as the electrolyte, and a polypropylene membrane as the separator, a cylindrical alkaline manganese battery is assembled using a winding process or a square alkaline manganese battery is assembled using a stacking process. Other steps are the same as in specific embodiments one through nine.
[0056] The beneficial effects of the present invention are verified using the following embodiments:
[0057] Example 1: A method for preparing a natural graphite anode material for an alkaline manganese battery, specifically comprising the following steps:
[0058] I. Raw material pretreatment:
[0059] Natural flake graphite was added to a complexing and impurity removal solution to obtain a mixed system. The mixed system was placed in an ultrasonic reaction device and ultrasonically treated for 2 hours at a temperature of 60℃ and an ultrasonic power of 300W. The mixture was then filtered, the precipitate was collected, washed with water until neutral, and then placed in a vacuum drying oven at 100℃ and -0.08MPa for 6 hours to obtain pretreated natural graphite.
[0060] The particle size of the natural flake graphite mentioned in step one is 30 μm;
[0061] The complexing and impurity removal solution mentioned in step one is prepared by mixing citric acid solution, disodium ethylenediaminetetraacetate solution, and water in a volume ratio of 3:1:6; the concentration of the citric acid solution is 0.5 mol / L; and the concentration of the disodium ethylenediaminetetraacetate solution is 0.2 mol / L.
[0062] The mass ratio of natural flake graphite to complexing and impurity removal solution mentioned in step one is 1:5;
[0063] II. Low-temperature plasma-assisted nitrogen-boron co-doping and porosity control:
[0064] ① Mix the pretreated natural graphite with the doped precursor, and then ball mill it in a planetary ball mill for 1 hour to obtain a mixed powder;
[0065] The doping precursor mentioned in step 2① is a mixture of urea and boric acid in a mass ratio of 5:1;
[0066] The mass ratio of pretreated natural graphite to doped precursor in step 2① is 10:1;
[0067] In step 2①, the ball-to-material ratio of the ball mill is 20:1 and the ball mill speed is 200 r / min;
[0068] ② Place the mixed powder in a low-temperature plasma reaction chamber, introduce protective gas, control the pressure in the reaction chamber to 10 Pa, and raise the temperature to 300℃;
[0069] The heating rate mentioned in step 2② is 8℃ / min;
[0070] ③ Turn on the plasma power supply, adjust the power to 150W, introduce the reaction gas, and react for 30 minutes at a temperature of 300℃ and a pressure of 15Pa. After the reaction is completed, stop introducing the reaction gas and continue to introduce the protective gas until the reaction chamber cools to room temperature to obtain nitrogen-boron co-doped graphite.
[0071] The reaction gas mentioned in step 2③ is a mixture of ammonia and borane in a volume ratio of 10:1;
[0072] The protective gas mentioned in steps 2② and 2③ is a mixture of argon and hydrogen in a volume ratio of 9:1;
[0073] III. Gradient Temperature Activation and Surface Modification:
[0074] ① Place nitrogen-boron co-doped graphite in a tube furnace, introduce nitrogen gas, and use a gradient heating method: raise the temperature from room temperature to 200℃ at a heating rate of 5℃ / min and hold for 1 hour; then raise the temperature to 400℃ at a heating rate of 3℃ / min and hold for 2 hours; finally raise the temperature to 600℃ at a heating rate of 2℃ / min and hold for 1 hour; after the holding period, allow it to cool naturally to room temperature to obtain the reaction product.
[0075] ② The reaction product was added to the modifier solution and stirred and modified for 1 hour at 40℃ and 150 r / min. After the reaction was completed, the product was filtered, the solid material was collected, washed with water 3 times, and finally vacuum dried for 4 hours at 80℃ and -0.08 MPa to obtain the natural graphite anode material for alkaline manganese batteries.
[0076] The modifier solution mentioned in step 3② is an ethanol solution of polyvinylpyrrolidone with a concentration of 5%;
[0077] The volume ratio of the reaction product to the modifier solution in step 3② is 1.5:1.
[0078] Example 2: A method for preparing a natural graphite anode material for an alkaline manganese battery, specifically comprising the following steps:
[0079] I. Raw material pretreatment:
[0080] Natural flake graphite was added to a complexing and impurity removal solution to obtain a mixed system. The mixed system was placed in an ultrasonic reaction device and ultrasonically treated for 3 hours at a temperature of 70℃ and an ultrasonic power of 400W. The mixture was then filtered, the precipitate was collected, washed with water until neutral, and then placed in a vacuum drying oven at 110℃ and -0.09MPa for 7 hours to obtain pretreated natural graphite.
[0081] The particle size of the natural flake graphite mentioned in step one is 40 μm;
[0082] The complexing and impurity removal solution mentioned in step one is prepared by mixing citric acid solution, disodium ethylenediaminetetraacetate solution, and water in a volume ratio of 3:1:6; the concentration of the citric acid solution is 0.8 mol / L; and the concentration of the disodium ethylenediaminetetraacetate solution is 0.3 mol / L.
[0083] The mass ratio of natural flake graphite to complexing and impurity removal solution mentioned in step one is 1:5;
[0084] II. Low-temperature plasma-assisted nitrogen-boron co-doping and porosity control:
[0085] ① Mix the pretreated natural graphite with the doped precursor, and then ball mill it in a planetary ball mill for 1.5 hours to obtain a mixed powder;
[0086] The doping precursor mentioned in step 2① is a mixture of urea and boric acid in a mass ratio of 5:1;
[0087] The mass ratio of pretreated natural graphite to doped precursor in step 2① is 10:2;
[0088] In step 2①, the ball-to-material ratio of the ball mill is 20:1 and the ball mill speed is 250 r / min;
[0089] ② Place the mixed powder in a low-temperature plasma reaction chamber, introduce protective gas, control the pressure in the reaction chamber to 15 Pa, and raise the temperature to 350℃;
[0090] The heating rate mentioned in step 2② is 8℃ / min;
[0091] ③ Turn on the plasma power supply, adjust the power to 200W, introduce the reaction gas, and react for 45 minutes at a temperature of 300℃ and a pressure of 15Pa. After the reaction is completed, stop introducing the reaction gas and continue to introduce the protective gas until the reaction chamber cools to room temperature to obtain nitrogen-boron co-doped graphite.
[0092] The reaction gas mentioned in step 2③ is a mixture of ammonia and borane in a volume ratio of 10:1;
[0093] The protective gas mentioned in steps 2② and 2③ is a mixture of argon and hydrogen in a volume ratio of 9:1;
[0094] III. Gradient Temperature Activation and Surface Modification:
[0095] ① Place nitrogen-boron co-doped graphite in a tube furnace, introduce nitrogen gas, and use a gradient heating method: raise the temperature from room temperature to 200℃ at a heating rate of 5℃ / min and hold for 1 hour; then raise the temperature to 400℃ at a heating rate of 3℃ / min and hold for 2 hours; finally raise the temperature to 600℃ at a heating rate of 2℃ / min and hold for 1 hour; after the holding period, allow it to cool naturally to room temperature to obtain the reaction product.
[0096] ② The reaction product was added to the modifier solution and stirred and modified for 1.5 h at 50 °C and 180 r / min. After the reaction was completed, the product was filtered, the solid material was collected, washed with water 3 times, and finally vacuum dried for 5 h at 90 °C and -0.09 MPa to obtain the natural graphite anode material for alkaline manganese batteries.
[0097] The modifier solution mentioned in step 3② is an ethanol solution of polyvinylpyrrolidone with a concentration of 8%;
[0098] The volume ratio of the reaction product to the modifier solution in step 3② is 1.4:1.
[0099] Example 3: A method for preparing a natural graphite anode material for an alkaline manganese battery, specifically comprising the following steps:
[0100] I. Raw material pretreatment:
[0101] Natural flake graphite was added to a complexing and impurity removal solution to obtain a mixed system. The mixed system was placed in an ultrasonic reaction device and ultrasonically treated for 4 hours at a temperature of 80℃ and an ultrasonic power of 500W. The mixture was then filtered, the precipitate was collected, washed with water until neutral, and then placed in a vacuum drying oven at 120℃ and -0.1MPa for 8 hours to obtain pretreated natural graphite.
[0102] The particle size of the natural flake graphite mentioned in step one is 50 μm;
[0103] The complexing and impurity removal solution mentioned in step one is prepared by mixing citric acid solution, disodium ethylenediaminetetraacetate solution, and water in a volume ratio of 3:1:6; the concentration of the citric acid solution is 1 mol / L; and the concentration of the disodium ethylenediaminetetraacetate solution is 0.4 mol / L.
[0104] The mass ratio of natural flake graphite to complexing and impurity removal solution mentioned in step one is 1:5;
[0105] II. Low-temperature plasma-assisted nitrogen-boron co-doping and porosity control:
[0106] ① Mix the pretreated natural graphite with the doped precursor, and then ball mill it in a planetary ball mill for 2 hours to obtain a mixed powder;
[0107] The doping precursor mentioned in step 2① is a mixture of urea and boric acid in a mass ratio of 5:1;
[0108] The mass ratio of pretreated natural graphite to doped precursor in step 2① is 10:3;
[0109] In step 2①, the ball-to-material ratio of the ball mill is 20:1 and the ball mill speed is 300 r / min;
[0110] ② Place the mixed powder in a low-temperature plasma reaction chamber, introduce protective gas, control the pressure in the reaction chamber to 20 Pa, and raise the temperature to 400℃;
[0111] The heating rate mentioned in step 2② is 8℃ / min;
[0112] ③ Turn on the plasma power supply, adjust the power to 250W, introduce the reaction gas, and react for 60 minutes at a temperature of 300℃ and a pressure of 15Pa. After the reaction is completed, stop introducing the reaction gas and continue to introduce the protective gas until the reaction chamber cools to room temperature to obtain nitrogen-boron co-doped graphite.
[0113] The reaction gas mentioned in step 2③ is a mixture of ammonia and borane in a volume ratio of 10:1;
[0114] The protective gas mentioned in steps 2② and 2③ is a mixture of argon and hydrogen in a volume ratio of 9:1;
[0115] III. Gradient Temperature Activation and Surface Modification:
[0116] ① Place nitrogen-boron co-doped graphite in a tube furnace, introduce nitrogen gas, and use a gradient heating method: raise the temperature from room temperature to 200℃ at a heating rate of 5℃ / min and hold for 1 hour; then raise the temperature to 400℃ at a heating rate of 3℃ / min and hold for 2 hours; finally raise the temperature to 600℃ at a heating rate of 2℃ / min and hold for 1 hour; after the holding period, allow it to cool naturally to room temperature to obtain the reaction product.
[0117] ② The reaction product was added to the modifier solution and stirred and modified for 2 hours at 60℃ and 200r / min. After the reaction was completed, the product was filtered, the solid material was collected, washed with water 3 times, and finally vacuum dried for 6 hours at 100℃ and -0.1MPa to obtain the natural graphite anode material for alkaline manganese batteries.
[0118] The modifier solution mentioned in step 3② is an ethanol solution of polyvinylpyrrolidone with a concentration of 10%;
[0119] The volume ratio of the reaction product to the modifier solution in step 3② is 1.3:1.
[0120] The natural graphite anode material for alkaline manganese batteries prepared in Examples 1, 2, or 3 is used to prepare the anode sheet for alkaline manganese batteries; the anode sheet for alkaline manganese batteries is used to assemble alkaline manganese batteries, specifically by following these steps:
[0121] 1. Mix the natural graphite anode material, binder and conductive agent of alkaline manganese battery at a mass ratio of 90:5:5, add deionized water, and stir at 950 r / min for 4.5 h to obtain an anode slurry with a solid content of 43%.
[0122] The adhesive mentioned in step one is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:2;
[0123] The conductive agent mentioned in step one is carbon black;
[0124] The natural graphite anode material of the alkaline manganese battery mentioned in step one is the natural graphite anode material of the alkaline manganese battery prepared in Examples 1, 2 or 3.
[0125] II. Preparation of the negative electrode:
[0126] A negative electrode slurry with a solid content of 43% was uniformly coated onto a copper foil current collector with a coating thickness of 94 μm. It was then dried in an oven at 97°C for 2 hours, and then transferred to a vacuum drying oven at 135°C and a vacuum degree of -0.089 MPa for 8.5 hours. Finally, it was rolled and slit under a pressure of 12.5 MPa to obtain the negative electrode sheet of the alkaline manganese battery.
[0127] III. Using the negative electrode of an alkaline manganese battery as the negative electrode, the positive electrode of manganese dioxide as the positive electrode, a 7.2 mol / L potassium hydroxide aqueous solution as the electrolyte, and a polypropylene membrane as the separator, a cylindrical alkaline manganese battery is assembled using a winding process.
[0128] The tap density of the natural graphite anode material for the alkaline manganese battery prepared in Example 1 was 1.2 g / cm³. 3 Specific surface area 35m²2 / g, initial charge / discharge efficiency 90%, capacity retention rate 85% after 500 cycles at 1C rate; applied to alkaline manganese batteries, 1C discharge capacity 320mAh / g, discharge capacity retention rate 70% at -20℃.
[0129] The tap density of the natural graphite anode material for the alkaline manganese battery prepared in Example 2 was 1.4 g / cm³. 3 Specific surface area 48m² 2 / g, initial charge / discharge efficiency 92%, capacity retention rate 88% after 500 cycles at 1C rate; applied to alkaline manganese batteries, 1C discharge capacity 340mAh / g, discharge capacity retention rate 75% at -20℃.
[0130] The tap density of the natural graphite anode material for the alkaline manganese battery prepared in Example 3 was 1.5 g / cm³. 3 Specific surface area 60m² 2 / g, initial charge / discharge efficiency 93%, capacity retention 90% after 500 cycles at 1C rate; applied to alkaline manganese batteries, 1C discharge capacity 350mAh / g, discharge capacity retention 80% at -20℃.
Claims
1. A method for producing a natural graphite negative electrode material for alkaline manganese batteries, characterized by The preparation method is specifically completed according to the following steps: I. Pretreatment of raw materials: The natural flake graphite is added into the complexing impurity removal liquid to obtain a mixed system; the mixed system is placed in an ultrasonic reaction device for ultrasonic treatment for a period of time, then filtered, and the precipitate is collected, washed with water until neutral, and then placed in a vacuum drying box for vacuum drying to obtain pretreated natural graphite; II. Low-temperature plasma assisted nitrogen and boron co-doping and pore regulation: ①, the pretreated natural graphite and the doping precursor are mixed, and then placed in a planetary ball mill for ball milling for a period of time to obtain a mixed powder; The doping precursor in step II ① is a mixture of urea and boric acid with a mass ratio of 5:1; ②, the mixed powder is placed in a low-temperature plasma reaction chamber, a protective gas is introduced, the pressure in the reaction chamber is controlled to be 10-20 Pa, and the temperature is raised to 300-400 ℃; ③, the plasma power is turned on, the power is adjusted to 150-250 W, the reaction gas is introduced, and the reaction is carried out at a temperature of 300-400 ℃ and a pressure of 10-20 Pa for a period of time; after the reaction is completed, the introduction of the reaction gas is stopped, and the protective gas is continuously introduced until the reaction chamber is cooled to room temperature, to obtain nitrogen and boron co-doped graphite; The reaction gas in step II ③ is a mixed gas of ammonia and borane with a volume ratio of 10:1; III. Gradient temperature activation and surface modification: ①, the nitrogen and boron co-doped graphite is placed in a tube furnace, an inert gas is introduced, and a gradient temperature rising mode is adopted: from room temperature to 200 ℃, holding; then to 400 ℃, holding; finally to 600 ℃, holding for 1 h; after the holding is completed, it is naturally cooled to room temperature to obtain a reaction product; ②, the reaction product is added to a modifier solution, and reacts under the conditions of heating and stirring for a period of time; after the reaction is completed, it is filtered, the solid material is collected, washed, and vacuum dried to obtain a natural graphite negative electrode material for alkaline manganese batteries.
2. The method for preparing a natural graphite anode material for an alkaline manganese battery according to claim 1, characterized in that... The particle size of the natural flake graphite in step I is 30-50 μm; the complexing impurity removal liquid in step I is prepared by mixing a citric acid solution, an ethylenediaminetetraacetic acid disodium solution and water in a volume ratio of 3:1:6; the concentration of the citric acid solution is 0.5-1 mol / L; the concentration of the ethylenediaminetetraacetic acid disodium solution is 0.2-0.4 mol / L.
3. The method for preparing a natural graphite anode material for an alkaline manganese battery according to claim 1, characterized in that... The mass ratio of the natural flake graphite to the complexing impurity removal liquid in step I is 1:5; the ultrasonic treatment temperature in step I is 60-80 ℃, the ultrasonic treatment power is 300-500 W, and the ultrasonic treatment time is 2-4 h; the vacuum drying temperature in step I is 100-120 ℃, the vacuum degree is -0.08 to -0.1 MPa, and the vacuum drying time is 6-8 h.
4. The method for preparing a natural graphite anode material for an alkaline manganese battery according to claim 1, characterized in that... The mass ratio of the pretreated natural graphite to the doping precursor in step II ① is 10:(1-3); the ball-to-material ratio of the ball milling in step II ① is 20:1, the ball milling speed is 200-300 r / min, and the ball milling time is 1-2 h.
5. The method for preparing a natural graphite anode material for an alkaline manganese battery according to claim 1, characterized in that... The rate of the temperature rise in step two ② is 5-10℃ / min; the reaction time in step two ③ is 30-60min; the protective gas in step two ② and step two ③ is argon and hydrogen mixed gas with a volume ratio of 9:
1.
6. The method for preparing a natural graphite anode material for an alkaline manganese battery according to claim 1, characterized in that... The inert gas in step three ① is nitrogen; the rate of the temperature rise in step three ① is 2-5℃ / min; the holding time in step three ① is 1-2h.
7. The method for preparing a natural graphite anode material for an alkaline manganese battery according to claim 1, characterized in that... The modifier solution in step three ② is polyvinylpyrrolidone ethanol solution with a concentration of 5-10%; the volume ratio of the reaction product to the modifier solution in step three ② is (1.2-1.5):1; the reaction product is added to the modifier solution under the conditions of a temperature of 40-60℃ and a stirring speed of 150-200r / min for 1-2h; after the reaction, the solid substance is collected by filtration, washed with water for 3-5 times, and finally vacuum dried under the conditions of a temperature of 80-100℃ and a vacuum degree of -0.08--0.1MPa for 4-6h to obtain the natural graphite negative electrode material of alkaline-manganese battery.
8. Use of the natural graphite negative electrode material of the alkaline manganese battery prepared according to the preparation method of any one of claims 1 to 7, characterized in that The natural graphite negative electrode material of alkaline-manganese battery is used to prepare the negative electrode sheet of alkaline-manganese battery; the negative electrode sheet of alkaline-manganese battery is used to assemble alkaline-manganese battery.
9. Use of a natural graphite negative electrode material for alkaline manganese batteries according to claim 8, characterized in that The natural graphite negative electrode material of alkaline-manganese battery is used to prepare the negative electrode sheet of alkaline-manganese battery, which is prepared by the following steps: I. The natural graphite negative electrode material of alkaline-manganese battery, a binder and a conductive agent are mixed in a mass ratio of 90:5:5, deionized water is added, and stirring is carried out at 800-1000r / min for 3-5h to obtain negative electrode slurry with a solid content of 40-50%; The binder in step one is a mixture of sodium carboxymethyl cellulose and butadiene-styrene rubber with a mass ratio of 1:2; The conductive agent in step one is carbon black; II. Preparation of negative electrode sheet: The negative electrode slurry with a solid content of 40-50% is uniformly coated on a copper foil current collector with a coating thickness of 80-120μm; then it is dried in an oven at a temperature of 80-100℃ for 2h, and then transferred to a vacuum drying box at a temperature of 120-140℃ and a vacuum degree of -0.08--0.1MPa for vacuum drying for 8-10h; finally, it is rolled and cut under a pressure of 10-15MPa to obtain the negative electrode sheet of alkaline-manganese battery.
10. Use of a natural graphite negative electrode material for alkaline manganese batteries according to claim 8 or 9, characterized in that The negative electrode sheet of alkaline-manganese battery is used to assemble alkaline-manganese battery, which is prepared by the following steps: The negative electrode sheet of alkaline-manganese battery is used as the negative electrode, the manganese dioxide positive electrode sheet is used as the positive electrode, the potassium hydroxide aqueous solution with a concentration of 6-8mol / L is used as the electrolyte, and the polypropylene separator is used as the isolation layer to assemble cylindrical alkaline-manganese battery by winding process or square alkaline-manganese battery by stacking process; The discharge capacity of the alkaline-manganese battery at 1C rate is 320-350mAh / g, the capacity retention rate after 500 cycles at 1C rate is ≥85%, and the discharge capacity retention rate at-20℃ environment is ≥70%.