CN109279658B - Method for preparing nickel manganese spinel cathode material through magnetic field texturing - Google Patents

Method for preparing nickel manganese spinel cathode material through magnetic field texturing Download PDF

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CN109279658B
CN109279658B CN201810862650.5A CN201810862650A CN109279658B CN 109279658 B CN109279658 B CN 109279658B CN 201810862650 A CN201810862650 A CN 201810862650A CN 109279658 B CN109279658 B CN 109279658B
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nickel
magnetic field
manganese
preparing
manganese spinel
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CN109279658A (en
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汪乾
阮丁山
刘婧婧
唐盛贺
李长东
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/54—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [Mn2O4]-, e.g. Li(NixMn2-x)O4, Li(MyNixMn2-x-y)O4
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a method for preparing a nickel-manganese spinel anode material by magnetic field texturing. The preparation method comprises the following steps: 1) preparing a nickel-manganese precursor by a coprecipitation method by using nickel salt and manganese salt; 2) uniformly mixing a nickel-manganese precursor with a lithium source, and calcining to obtain a nickel-manganese spinel material; 3) the nickel manganese spinel material is crushed and sieved, is stirred and mixed with the auxiliary agent in a stirrer, and an external magnetic field is applied to the slurry in the stirring process. The invention utilizes Mn3+The positive electrode slurry is coated on the aluminum foil to the maximum extent by facing the (111) crystal face to the direction contacting with the electrolyte through the interaction with the magnetic field and texturing treatment is realized through the magnetic field, so that the purposes of improving capacity attenuation and poor high-temperature cycle performance in the charging and discharging processes of the nickel-manganese spinel are achieved. The positive pole piece prepared by the method has excellent cycle and rate performance after being assembled into a battery, has high energy density, and has wide application prospects in the fields of power automobiles, large-scale power equipment and the like.

Description

Method for preparing nickel manganese spinel cathode material through magnetic field texturing
Technical Field
The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a method for preparing a nickel manganese spinel anode material by magnetic field texturing.
Background
The lithium ion battery has the advantages of high working voltage, no memory effect, environmental protection and the like, and is widely applied to the 3C field of notebook computers, mobile phones and the like. The development of electric vehicles, hybrid electric vehicles and other large power equipment puts higher demands on the performance of the electric vehicles, hybrid electric vehicles and other large power equipment, and particularly, the energy density and the power density of lithium ion batteries are further increased if necessary and urgent. The high energy density can give better security to the battery system, and simultaneously will further reduce battery volume, weight, realize the lightweight to a certain extent.
LiNi of spinel structure0.5Mn1.5O4Has 4.7V (vs. Li/Li)+) The theoretical capacity of the high-voltage discharge platform is 147mAh/g, the energy density can reach 650Wh/kg, and the high-voltage discharge platform is expected to become a next-generation advanced lithium ion battery anode material. However, the positive electrode material has problems of capacity fading, poor high-temperature cycle performance and the like in the charging and discharging processes, and the reasons for the phenomena are mainly as follows: the first, Jahn-Teller effect, i.e. repeated deintercalation of lithium ions, causes distortion of lattice structure, reduction of symmetry, and irreversible change of crystal structure from cubic phase to tetragonal phase, resulting in reduction of material performance. II, Mn3+Spontaneous disproportionation reaction. Mn3+Mn at the end of discharge, which is thermodynamically unstable3+At a high concentration, it will spontaneously turn to Mn2+And Mn4+The transformation, during which the following reaction takes place: 2Mn3+(s)→Mn2+(l)+Mn4+(s), and Mn2+Easily dissolved in the electrolyte, resulting in loss of active material. And thirdly, oxidizing and decomposing the salt in the electrolyte by the positive electrode material. In the charged state of the nickel-manganese spinel cathode material, Ni with high concentration and strong oxidizing property exists in the material in a highly delithiated state4+The ions will continue to oxidatively decompose the electrolyte at the electrode surface, producing very corrosive HF. And fourthly, corroding the anode material by HF and dissolving metal ions. The corrosion of the electrode material by HF causes nickel and manganese ions to dissolve from the positive electrode material into the electrolyte, thereby causing the destruction of the material structure and the decay of the discharge capacity.
At present, the process means of bulk phase doping, surface coating and the like are generally adopted to solve the technical barrier problems of the industries such as capacity attenuation, poor high-temperature cycle performance and the like of the nickel-manganese spinel. Lee et al calculated the surface energy of the low-index crystallographic planes in nickel manganese spinel using the first principles of linearity and indicated that the (111) planes had the tightest atomic arrangement, the lowest surface energy, and increased the diffusion coefficient of lithium ions, thereby improving the rate capability of the cathode material (Nanotechnology,2013,24(42): 424007). Nano Mn in cubic porous structure Lin2O3The particles are used as a template agent,the nickel manganese spinel anode material mainly oriented to the (111) crystal face is prepared. Electrochemical performance tests show that the cathode material mainly oriented to the (111) crystal face has excellent cycle and rate performance, and the capacity retention rate of the cathode material after 3000 cycles at the rate of 10 ℃ at room temperature is 78.1%; the capacity retention rate is 83.2 percent (J.Mater.chem.A.2014,2:11987-11995) after 5C multiplying power circulation for 500 times under the high-temperature environment of 55 ℃. The study further indicates that the (111) crystal plane helps promote the formation of a protective SEI (solid electrolyte) film, thereby imparting excellent cycling stability to the nickel manganese spinel cathode material. Therefore, the nickel manganese spinel cathode material with the (111) crystal face orientation has obvious advantages in the aspects of improving cycle and rate capability.
In addition, it is noted that the nickel manganese spinel has two space group structures, namely, ordered P43A type 32 original simple cubic structure and a disordered type Fd3m type face-centered cubic structure. Wherein, because partial oxygen vacancy exists in the disordered Fd3m structure, in order to maintain the principle of electric neutrality, partial manganese ions are represented by Mn3+Exist in the form of (1). The ordered and disordered structures are generally coexisting in the nickel manganese spinel material, i.e. Mn is inevitably present in the material3+And the presence of a certain amount of disordered structure is extremely beneficial to the electrochemical performance of the nickel manganese spinel cathode material. Coulomb potential calculation of a lithium ion diffusion path shows that the disordered Fd3m space group structure is more beneficial to the diffusion of lithium ions, and the diffusion rate of the lithium ions is closely related to the rate capability of the cathode material. In terms of electron conductivity, due to the presence of high conductivity Mn in the amorphous spinel3+Conductivity of disordered spinel (10)-4.5S·cm-1) Relatively ordered spinel conductivity (10)-7S·cm-1) Higher by 2.5 orders of magnitude. Therefore, the amorphous spinel is more suitable for charging and discharging at a large rate than the ordered spinel. In-situ XRD analysis of lithium ion extraction depth of nickel manganese spinel with different space group structures in charge-discharge process shows that ordered P4332 need to undergo two phase transitions between the three cubic structures, while the disordered form Fd3m undergoes only one phase transition between the two cubic structures. This indicates that both of Fd3m type and Fd3m type are charged and discharged at a small currentP4332 type, all have enough time to carry out lithium ion extraction and intercalation, all show better performance. While charging and discharging at high rate, P43When there is not enough time to complete the two-phase transformation, the 32-type crystal is likely to have poor electrochemical performance due to phase lag phenomenon during the charge and discharge process caused by poor structural reversibility. Therefore, the nickel manganese spinel with the disordered Fd3m structure has better electrochemical performance.
Mantiram A et al used Mn using NMR (nuclear magnetic resonance) techniques3+The interaction with the magnetic field characterizes the order of the cations in the nickel manganese spinel (J.Mater.chem.A.2013,1: 10745-10752). This means that Mn in the nickel manganese spinel3+And an interaction force exists between the magnetic field and the crystal grains, and the crystal grains can be directionally distributed in a specific direction under the action of the magnetic field. In fact, texturing of materials by means of an applied magnetic field to improve the properties of the materials has been used in many fields. Wang et al adopts an external magnetic field method to make alumina grains present directional distribution, and the linear transmittance of the finally prepared transparent ceramic in the wavelength range of 400-. CN103130508A discloses a method for preparing boride ultra-high temperature ceramic by magnetic field texturing, which improves the defect that single-phase boride ceramic is difficult to densify, the relative density of the prepared ceramic is more than 98%, the orientation factor f (001) is as high as 0.95, and each performance in a specific direction is greatly improved compared with the performance without texturing.
It should be noted that, although the prior art methods such as bulk phase doping and surface coating can improve the problems of capacity fading and poor high temperature cycle performance of nickel-manganese spinel to some extent, they inevitably cause a reduction in the specific capacity of the cathode material because the introduction of non-electrochemically active material is mostly required. And the mode of preparing a core-shell structure, a gradient distribution structure and the like by coating nickel manganese spinel with other electrochemical active anode materials cannot reduce specific capacity, but the process flow is complex and is not beneficial to industrial production.
Disclosure of Invention
The invention aims to utilize Mn by introducing an external magnetic field3+The method has the advantages that the method interacts with a magnetic field, texturing treatment is carried out on anode material slurry to be coated, the advantage of (111) crystal face orientation in the nickel-manganese spinel is fully exerted, and the nickel-manganese spinel is enabled to face the direction contacting with an electrolyte to the maximum extent, so that the problems of capacity attenuation, poor cycle performance and the like of the nickel-manganese spinel are solved, and the method for preparing the nickel-manganese spinel anode material through magnetic field texturing is further provided.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
a method for preparing a nickel manganese spinel cathode material by magnetic field texturing comprises the following steps:
1) preparing a nickel-manganese precursor by a coprecipitation method by using nickel salt and manganese salt;
2) uniformly mixing a nickel-manganese precursor with a lithium source, and calcining to obtain a nickel-manganese spinel material;
3) and crushing and sieving the nickel-manganese spinel material, mixing and stirring the crushed nickel-manganese spinel material and the auxiliary agent in a stirrer, and applying an external magnetic field to the slurry in the stirring process to obtain the nickel-manganese spinel anode material with the textured magnetic field.
In the step 1), the preparation of the nickel-manganese precursor by a coprecipitation method comprises the following steps:
s1: mixing nickel salt and manganese salt in water to prepare a metal salt solution with the total metal ion concentration of 0.35-0.8 mol/L;
s2: preparing a precipitator solution with the same volume and concentration as the metal salt solution;
s3: preparing ammonia water solution with the concentration of 0.3-0.6 mol/L;
s4: introducing a metal salt solution, a precipitator solution and an ammonia water solution into a reaction kettle, mixing and stirring for reaction to obtain a precipitate;
s5: and washing and drying the precipitate to obtain the nickel-manganese precursor.
In the step 1), the molar ratio of the nickel ions to the manganese ions is 1: 3.
In the step 1), the precipitator is at least one of sodium carbonate, sodium hydroxide, oxalic acid and ammonium oxalate.
In the step 2), the molar ratio of Li to Me is controlled to be (0.9-1.2): 1, wherein Me is transition metal Ni and Mn.
In the step 2), the calcining temperature is 700-1050 ℃, and the calcining time is 8-18 h.
In the step 3), the included angle between the magnetic field and the stirring shaft of the stirrer is 0-90 degrees.
In the step 3), the intensity of the magnetic field is 6T-20T.
In the step 3), the auxiliary agent is at least one of a conductive agent, a binder, a solvent, a dispersing agent, a defoaming agent and a plasticizer.
The lithium ion battery anode material comprises the material obtained by the magnetic field texturing preparation method.
The invention has the beneficial effects that:
the invention utilizes Mn3+The positive electrode slurry is coated on the aluminum foil to the maximum extent by facing the (111) crystal face to the direction contacting with the electrolyte through the interaction with the magnetic field and texturing treatment is realized through the magnetic field, so that the purposes of improving capacity attenuation and poor high-temperature cycle performance in the charging and discharging processes of the nickel-manganese spinel are achieved. The positive pole piece prepared by the method has excellent cycle and rate performance after being assembled into a battery, has high energy density, and has wide application prospects in the fields of power automobiles, large-scale power equipment and the like.
The method comprises the following specific steps:
firstly, the process flow of preparing the cathode material by the existing coprecipitation method is not changed, only a magnetic field with certain strength is added in the stirring process of the cathode slurry, the texturing process and the preparation process of the slurry to be coated are synchronously carried out, and new working procedures are not added, and the production period is not prolonged. Secondly, the characteristics of the material composition are fully utilized, the advantages of the material structure are exerted to the maximum extent, and non-electrochemical active substances for reducing the specific capacity of the cathode material are not introduced in the process.
Drawings
FIG. 1 is a schematic view of the orientation of an included angle between an applied magnetic field and a stirring shaft of positive electrode slurry;
FIG. 2 is a scanning electron microscope image of the octahedral nickel manganese spinel material with the (111) crystal plane orientation structure prepared by the invention.
Detailed Description
A method for preparing a nickel manganese spinel cathode material by magnetic field texturing comprises the following steps:
1) preparing a nickel-manganese precursor by a coprecipitation method by using nickel salt and manganese salt;
2) uniformly mixing a nickel-manganese precursor with a lithium source, and calcining to obtain a nickel-manganese spinel material;
3) and crushing and sieving the nickel-manganese spinel material, mixing and stirring the crushed nickel-manganese spinel material and the auxiliary agent in a stirrer, and applying an external magnetic field to the slurry in the stirring process to obtain the nickel-manganese spinel anode material with the textured magnetic field.
Further, in the step 1), the preparation of the nickel-manganese precursor by a coprecipitation method comprises the following steps:
s1: mixing nickel salt and manganese salt in water to prepare a metal salt solution with the total metal ion concentration of 0.35-0.8 mol/L;
s2: preparing a precipitator solution with the same volume and concentration as the metal salt solution;
s3: preparing ammonia water solution with the concentration of 0.3-0.6 mol/L;
s4: introducing a metal salt solution, a precipitator solution and an ammonia water solution into a reaction kettle, mixing and stirring for reaction to obtain a precipitate;
s5: and washing and drying the precipitate to obtain the nickel-manganese precursor.
Preferably, in step 1), the molar ratio of nickel ions to manganese ions is 1: 3.
Preferably, in the step 1), the nickel salt is at least one of sulfate, acetate, nitrate, oxalate and chloride of nickel; further, the nickel salt is at least one of nickel sulfate, nickel acetate, nickel nitrate, nickel chloride and nickel oxalate.
Preferably, in the step 1), the manganese salt is at least one of sulfate, acetate, nitrate, oxalate and chloride of manganese; further, the manganese salt is at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese oxalate.
Preferably, in step 1), the precipitant is at least one of sodium carbonate, sodium hydroxide, oxalic acid and ammonium oxalate.
Preferably, in S4 of step 1), the metal salt solution, the precipitant solution, and the aqueous ammonia solution are introduced into the reaction tank by a peristaltic pump.
Preferably, in the step 1) of S4, the reaction temperature is 40-70 ℃, the reaction time is 7-16 h, the stirring speed is 800-1200 r/min, and the reaction pH is controlled to be 9.5-11; the pH is controlled by an on-line pH meter.
Preferably, in step 1) S5, the washing is at least three times with deionized water, and the drying is performed at 115-125 ℃ for 20-30 h under a protective atmosphere; the protective atmosphere is nitrogen or inert gas.
Preferably, in the step 2), the molar ratio of Li to Me is controlled to be (0.9-1.2): 1, wherein Me is transition metal Ni and Mn.
Preferably, in the step 2), the calcining temperature is 700-1050 ℃, and the calcining time is 8-18 h.
Further, the nickel manganese spinel material obtained in the step 2) has octahedrons with the main (111) crystal face orientation.
Preferably, in the step 3), the crushing and sieving is carried out by a 400-mesh vibrating sieve, and the particle size D of the particles is controlled50Is 3-12 μm.
Preferably, in the step 3), an included angle (theta) between the magnetic field and a stirring shaft of the stirrer is 0-90 degrees. In the stirring process, an external magnetic field is applied to the anode slurry, and the purpose of changing the (111) crystal face orientation arrangement is achieved by changing the included angle theta between the direction of the magnetic field and the stirring shaft. In specific situations, the coating process of the positive pole piece needs to be referred to, and the (111) crystal face is ensured to face the direction contacting with the electrolyte to the maximum extent.
The schematic view of the included angle between the applied external magnetic field and the anode slurry stirring shaft in the invention can be seen in the attached figure 1. The stirring shaft of the stirrer is vertical to the horizontal plane.
Preferably, in step 3), the strength of the magnetic field is 6T to 20T.
Preferably, in step 3), the auxiliary agent is at least one of a conductive agent, a binder, a solvent, a dispersant, a defoaming agent and a plasticizer. The conductive agent, the binder, the solvent, the dispersant, the defoamer, the plasticizer and other auxiliary agents are common raw materials in the field, and the specific types are common knowledge in the field. For example, KS-6/SP is selected as the conductive agent, PVDF is selected as the binder, and NMP is selected as the solvent.
The lithium ion battery anode material comprises the material obtained by the magnetic field texturing preparation method.
Further, coating the positive electrode material with the magnetic field texturing on an aluminum foil to prepare the positive electrode of the lithium ion battery.
Preferably, the coating method is a doctor blade method or a roll method.
The present invention will be described in further detail with reference to specific examples. The starting materials used in the examples are, unless otherwise specified, commercially available from conventional sources.
Example 1:
dissolving nickel nitrate and manganese nitrate in deionized water according to a molar ratio of 1:3 to prepare a salt solution with metal ion concentration of 0.35mol/L, simultaneously preparing sodium carbonate with the same volume and concentration as a precipitator and 0.4mol/L ammonia water as a complexing agent, introducing the three components into a reaction kettle in equal volume by using a peristaltic pump, controlling the reaction temperature to be 55 +/-0.5 ℃, controlling the pH value to be 10 +/-0.2, and stirring at the speed of 1000 r/min. After 12h of reaction, the obtained precipitate was washed with deionized water for 3 times and dried at 120 ℃ for 24h under a nitrogen atmosphere. The obtained precursor and lithium carbonate are uniformly mixed according to the mol ratio Li/Me of 1.2, and are calcined for 8 hours at 1050 ℃ in a high-temperature furnace. The obtained blocky split bodies are crushed, sieved and mixed with a binder and a conductive agent to prepare positive slurry, an external magnetic field with the strength of 10T is applied in the stirring process, the included angle between the direction of the magnetic field and a slurry stirring shaft is 0 degree, and the magnetic field textured nickel manganese spinel positive material of the embodiment 1 is prepared and obtained through the process, and the scanning electron microscope picture of the material can be seen in an attached figure 2. As can be seen from fig. 2, the nickel manganese spinel cathode material has a regular octahedral structure, and after the magnetic field texturing treatment, the particles exhibit a distinct orientation distribution, and the (111) crystal planes of the particles are oriented substantially uniformly.
The textured positive electrode slurry of example 1 was coated on an aluminum foil by a doctor blade method to fabricate a positive electrode sheet. In a half-cell test, the primary efficiency is 89.5%, the specific capacity is 131.6mAh/g, and the capacity retention rate is 97.1% after 200 times of circulation at 2C multiplying power at room temperature.
Example 2:
dissolving nickel sulfate and manganese sulfate in deionized water according to a molar ratio of 1:3 to prepare a salt solution with metal ion concentration of 0.8mol/L, preparing sodium hydroxide with the same volume and concentration as a precipitator and 0.6mol/L ammonia water as a complexing agent, introducing the three components into a reaction kettle in equal volume by using a peristaltic pump, controlling the reaction temperature to be 70 +/-0.5 ℃, the pH value to be 9.7 +/-0.2, and stirring at a speed of 800 r/min. After 7h of reaction, the obtained precipitate was washed with deionized water for 3 times and dried at 120 ℃ for 24h under the protection of argon. The obtained precursor and lithium carbonate are uniformly mixed according to the mol ratio Li/Me of 1.02, and are calcined for 13 hours in a high-temperature furnace at 900 ℃. The obtained blocky split bodies are crushed, sieved and mixed with a binder and a conductive agent to prepare positive electrode slurry, an external magnetic field with the strength of 20T is applied in the stirring process, the included angle between the direction of the magnetic field and a slurry stirring shaft is 45 degrees, and the magnetic field textured nickel manganese spinel positive electrode material of the embodiment 2 is prepared.
The textured positive electrode slurry obtained in example 2 was coated on an aluminum foil by a doctor blade method to prepare a positive electrode sheet. In a half-cell test, the first efficiency is 91.3%, the specific capacity is 134.2mAh/g, and the capacity retention rate is 98.4% after 200 times of circulation at 2C multiplying power at room temperature.
Example 3:
dissolving nickel acetate and manganese acetate in deionized water according to a molar ratio of 1:3 to prepare a salt solution with metal ion concentration of 0.6mol/L, preparing ammonium oxalate with the same volume and concentration as a precipitator and 0.3mol/L ammonia water as a complexing agent, introducing the three components into a reaction kettle in equal volumes by using a peristaltic pump, controlling the reaction temperature to be 40 +/-0.5 ℃, the pH value to be 10.8 +/-0.2, and stirring at a speed of 1200 r/min. After 16h of reaction, the obtained precipitate was washed with deionized water for 3 times and dried at 120 ℃ for 24h under a nitrogen atmosphere. The obtained precursor and lithium carbonate are uniformly mixed according to the mol ratio Li/Me of 0.9, and are calcined for 18 hours in a high-temperature furnace at 700 ℃. The obtained blocky split bodies are crushed, sieved and mixed with a binder and a conductive agent to prepare positive electrode slurry, an external magnetic field with the strength of 6T is applied in the stirring process, the included angle between the direction of the magnetic field and a slurry stirring shaft is 90 degrees, and the magnetic field textured nickel manganese spinel positive electrode material of the embodiment 3 is prepared.
The textured positive electrode slurry obtained in example 3 was coated on an aluminum foil by a doctor blade method to prepare a positive electrode sheet. In a half-cell test, the first efficiency is 90.2%, the specific capacity is 132.6mAh/g, and the capacity retention rate is 97.7% after 200 times of circulation at 2C multiplying power at room temperature.
Example 4:
dissolving nickel nitrate and manganese acetate in deionized water according to a molar ratio of 1:3 to prepare a salt solution with metal ion concentration of 0.5mol/L, simultaneously preparing oxalic acid with the same volume and concentration as a precipitator and 0.5mol/L ammonia water as a complexing agent, introducing the three components into a reaction kettle in equal volume by using a peristaltic pump, controlling the reaction temperature to be 60 +/-0.5 ℃, controlling the pH value to be 10.5 +/-0.2, and stirring at a speed of 950 r/min. After reacting for 10h, the obtained precipitate is washed by deionized water for 3 times and then dried for 24h at 120 ℃ under the protection of argon. The obtained precursor and lithium carbonate are uniformly mixed according to the mol ratio Li/Me of 1.1, and are calcined for 15h at 850 ℃ in a high-temperature furnace. The obtained blocky split bodies are crushed, sieved and mixed with a binder and a conductive agent to prepare positive electrode slurry, an external magnetic field with the strength of 14T is applied in the stirring process, the included angle between the direction of the magnetic field and a stirring shaft of the slurry is 30 degrees, and the magnetic field textured nickel manganese spinel positive electrode material of the embodiment 4 is prepared.
The textured positive electrode slurry obtained in example 4 was coated on an aluminum foil by a doctor blade method to prepare a positive electrode sheet. In a half-cell test, the first efficiency is 89.9%, the specific capacity is 132.2mAh/g, and the capacity retention rate is 97.4% after 200 times of circulation at 2C multiplying power at room temperature.
Comparative example 1:
dissolving nickel nitrate and manganese acetate in deionized water according to a molar ratio of 1:3 to prepare a salt solution with metal ion concentration of 0.5mol/L, simultaneously preparing oxalic acid with the same volume and concentration as a precipitator and 0.6mol/L ammonia water as a complexing agent, introducing the three components into a reaction kettle in equal volume by using a peristaltic pump, controlling the reaction temperature to be 55 +/-0.5 ℃, controlling the pH value to be 9.9 +/-0.2, and stirring at a speed of 1000 r/min. After the reaction for 11 hours, the obtained precipitate is washed by deionized water for 3 times and then dried for 24 hours at 120 ℃ under the protection of argon. The obtained precursor and lithium carbonate are uniformly mixed according to the mol ratio Li/Me of 1.05, and are calcined for 14 hours at 870 ℃ in a high-temperature furnace. The obtained blocky split bodies are crushed and sieved and then mixed with the binder and the conductive agent to prepare positive pole slurry, no external magnetic field is applied in the stirring process, and the positive pole slurry is coated on the aluminum foil by adopting a scraper method to prepare a positive pole piece.
Comparative example 1 since no external magnetic field was applied, the nickel manganese spinel particles were randomly distributed rather than directionally arranged, and in a half-cell test, the first efficiency was only 88.17%, the specific capacity was 129.6mAh/g, and the capacity retention rate was 93.4% after 200 cycles at 2C rate at room temperature.
Comparative example 2:
dissolving nickel nitrate and manganese acetate in deionized water according to a molar ratio of 1:3 to prepare a salt solution with metal ion concentration of 0.6mol/L, simultaneously preparing oxalic acid with the same volume and concentration as a precipitator and 0.4mol/L ammonia water as a complexing agent, introducing the three components into a reaction kettle in equal volume by using a peristaltic pump, controlling the reaction temperature to be 45 +/-0.5 ℃, controlling the pH value to be 9.6 +/-0.2, and stirring at a speed of 950 r/min. After reacting for 10h, the obtained precipitate is washed by deionized water for 3 times and then dried for 24h at 120 ℃ under the protection of argon. The obtained precursor and lithium carbonate are uniformly mixed according to the mol ratio Li/Me of 1.05, and are calcined for 12 hours in a high-temperature furnace at 1000 ℃. The obtained blocky split bodies are crushed and sieved and then mixed with the binder and the conductive agent to prepare anode slurry, and the anode slurry is coated on the aluminum foil by adopting a scraper method to prepare the anode piece.
The prepared positive pole piece of comparative example 2 was treated in an applied magnetic field of 10T strength for a period of time. Because the particles are difficult to directionally move in a solid state, in a half-cell test, the initial efficiency is only 88.34%, the specific capacity is 129.9mAh/g, and the capacity retention rate is 93.7% after 200 times of circulation at 2C multiplying power at room temperature.
While embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, which are intended to be illustrative rather than limiting, and many modifications may be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (9)

1. A method for preparing a nickel manganese spinel cathode material by magnetic field texturing is characterized by comprising the following steps: the method comprises the following steps:
1) preparing a nickel-manganese precursor by a coprecipitation method by using nickel salt and manganese salt;
2) uniformly mixing a nickel-manganese precursor with a lithium source, and calcining to obtain a nickel-manganese spinel material;
3) crushing and sieving the nickel-manganese spinel material, mixing and stirring the nickel-manganese spinel material and an auxiliary agent in a stirrer, and applying an external magnetic field to the slurry in the stirring process to obtain a magnetic field textured nickel-manganese spinel anode material;
in the step 3), the strength of the magnetic field is 6T-20T.
2. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 1, characterized in that: in the step 1), the preparation of the nickel-manganese precursor by a coprecipitation method comprises the following steps:
s1: mixing nickel salt and manganese salt in water to prepare a metal salt solution with the total metal ion concentration of 0.35-0.8 mol/L;
s2: preparing a precipitator solution with the same volume and concentration as the metal salt solution;
s3: preparing ammonia water solution with the concentration of 0.3-0.6 mol/L;
s4: introducing a metal salt solution, a precipitator solution and an ammonia water solution into a reaction kettle, mixing and stirring for reaction to obtain a precipitate;
s5: and washing and drying the precipitate to obtain the nickel-manganese precursor.
3. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 1 or 2, characterized by comprising the following steps: in the step 1), the molar ratio of the nickel ions to the manganese ions is 1: 3.
4. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 2, characterized in that: in the step 1), the precipitator is at least one of sodium carbonate, sodium hydroxide, oxalic acid and ammonium oxalate.
5. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 1, characterized in that: in the step 2), the molar ratio of Li to Me is controlled to be (0.9-1.2): 1, wherein Me is transition metal Ni and Mn.
6. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 1, characterized in that: in the step 2), the calcining temperature is 700-1050 ℃, and the calcining time is 8-18 h.
7. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 1, characterized in that: in the step 3), the included angle between the magnetic field and the stirring shaft of the stirrer is 0-90 degrees.
8. The method for preparing the nickel manganese spinel cathode material through magnetic field texturing according to claim 1, characterized in that: in the step 3), the auxiliary agent is at least one of a conductive agent, a binder, a solvent, a dispersing agent, a defoaming agent and a plasticizer.
9. A lithium ion battery positive electrode material, which comprises the material obtained by the preparation method of any one of claims 1 to 8.
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