CN114050262A - Phosphate gradient modified lithium manganate material and preparation method thereof - Google Patents

Phosphate gradient modified lithium manganate material and preparation method thereof Download PDF

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CN114050262A
CN114050262A CN202111317138.0A CN202111317138A CN114050262A CN 114050262 A CN114050262 A CN 114050262A CN 202111317138 A CN202111317138 A CN 202111317138A CN 114050262 A CN114050262 A CN 114050262A
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phosphate
lithium
lithium manganate
manganese
manganate material
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蔡碧博
马岩华
贺兆书
赵春阳
王剑锋
陈静波
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Anhui Boshi Hi Hi Tech New Material Co ltd
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    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
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    • H01M4/366—Composites as layered products
    • 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
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract

The invention discloses a phosphate gradient modified lithium manganate material and a preparation method thereof, belonging to the field of lithium ion battery anode materials; the surface coating layer of the composite modified lithium manganate material is a multi-metal phosphate gradient coating layer, the surface close to the main material is mainly rich in lithium manganese-based phosphate, and the outermost layer is mainly little lithium or no lithium manganese-based phosphate; the synthesis method of the composite modified lithium manganate material specifically comprises the following steps: (1) firstly, calcining manganese oxide and a lithium source to synthesize a lithium manganate material, dispersing the prepared lithium manganate material in an aqueous solution, adding manganese salt, lithium salt, a phosphate precipitator and an organic complexing agent, reacting for a period of time, continuing to add manganese salt and phosphate in a certain proportion, and carrying out precipitation reaction again; (2) and washing and drying the obtained mixture by water and alcohol, and further calcining to finally obtain the phosphate composite modified lithium manganate material. The modification method is simple and easy to operate, and the product has controllable appearance, uniform coating and good stability.

Description

Phosphate gradient modified lithium manganate material and preparation method thereof
Technical Field
The invention relates to a synthesis method of a lithium ion battery anode material, in particular to a phosphate gradient modified lithium manganate material and a preparation method thereof.
Background
Spinel lithium manganate (LiMn)2O4) The lithium ion battery has become a key electrode material of the three current power lithium ion batteries because of having a proper high charging and discharging voltage platform, good thermal stability, low cost, simple synthesis process and the like, which are widely researched and discussed. However, during the cycling process of the battery, Jahn-Teller effect is easy to occur in the material, and the induced lattice distortion causes the structural phase transformation to occur: mn3+Disproportionation reaction to produce Mn2+Further resulting in dissolution of manganese under corrosion of the electrolyte, leading to a drastic deterioration in the cycle performance of the material. In order to solve this problem, modification treatment is usually performed on the lithium manganate material, and coating modification has been widely studied as the most extensive, most simple and effective modification method. However, a single coating layer has a limited improvement on the material performance and cannot maintain the structural stability of the material in a long-cycle process. The concentration gradient material serving as the coating layer can effectively improve the structural stability and the capacity retention rate of the surface of the material, so that the lithium manganate material is subjected to composite coating to synthesize the coating layer with the concentration gradient, and the specific capacity and the structural stability of the material can be effectively improved.
CN112993229B discloses a preparation method of a multi-metal MOF gradient coated modified ternary precursor. The method synthesizes the ternary cathode material with high stability through one-step surface growth. CN108767216A discloses a lithium ion battery anode material with a variable slope and full concentration gradient and a synthesis method thereof. The method synthesizes the lithium ion battery anode material with full concentration gradient, long service life and high safety performance by controlling the feeding rate. Aiming at the advantages of high electrochemical performance and high structural stability of the concentration gradient material, a concentration gradient coated spinel lithium manganate positive electrode material with good structural stability is required to be found so as to solve the technical problems of the lithium manganate material and obtain a lithium manganate material synthesis method with excellent performance and low cost.
Disclosure of Invention
The invention also aims to provide a phosphate gradient modified lithium manganate material and a preparation method thereof, aiming at synthesizing a phosphate gradient coated lithium manganate material, wherein the obtained product has uniform particles, and the synthesis process is simple and easy to operate. And simultaneously shows excellent electrochemical performance.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention also provides a phosphate gradient modified lithium manganate material and a preparation method thereof, which are characterized by comprising the following steps:
(1) manganese oxide and lithium source are mixed and calcined to synthesize lithium manganate LiMn2O4Dispersing the prepared lithium manganate material in an aqueous solution, adding manganese salt, lithium salt, phosphate precipitator and organic complexing agent, reacting for a period of time to obtain a primary precipitate, and continuing to add manganese salt and phosphate in a certain proportion for precipitation reaction again; and washing with water, washing with alcohol and drying to obtain a solid mixture.
(2) And further calcining the obtained mixture to finally obtain the phosphate composite modified lithium manganate material.
Preferably, the manganese oxide is one or more of manganese dioxide and trimanganese tetroxide.
Preferably, the lithium source is one or more of lithium carbonate and lithium hydroxide.
Preferably, the synthesized lithium manganate LiMn2O4The calcination temperature is 750-950 ℃, and the calcination time is 6-20 h.
Preferably, the molar ratio of the lithium source to the manganese oxide, n (Li) to n (Mn), is (1.05-1.1) to 2.
Preferably, the manganese salt in the primary precipitation process in the step (1) is one or more of manganese nitrate, manganese acetate and manganese sulfate.
Preferably, the lithium salt in the primary precipitation process in the step (1) is one or more of lithium nitrate, lithium acetate and lithium sulfate.
Preferably, the phosphate in the primary precipitation process in the step (1) is one or more of ammonium dihydrogen phosphate and sodium dihydrogen phosphate.
Preferably, the organic complexing agent in the primary precipitation process in the step (1) is one or more of citric acid, PVP and SDS.
Preferably, the molar ratio of the lithium salt, the manganese salt, the phosphate and the organic additive in the primary precipitation process in the step (1) is (1-1.04) to 1:1 (0.05-0.1), and the molar ratio of the manganese salt to the LiMn is2O4In a molar ratio of 0.01:1 to 0.05: 1.
Preferably, the molar ratio of manganese salt to phosphate in the secondary precipitation process in the step (1) is 1: 1-1: 2, the manganese salt with LiMn2O4The molar ratio of (A) to (B) is 0.01:1-0.03: 1.
Preferably, the calcination temperature in the step (2) is 300-600 ℃, and the calcination time is 3-10 h.
Preferably, the calcining atmosphere in the step (2) is one of air or oxygen atmosphere.
The invention has the beneficial effects that: the method comprises the step of coating a phosphate material with a concentration gradient on the surface of the lithium manganate material in situ. And respectively precipitating a lithium manganese phosphate material and a lithium manganese oxide material on the surface of the lithium manganese oxide material from inside to outside through a secondary precipitation process, and further calcining at high temperature to synthesize a phosphate coating layer with a concentration gradient. The synthesis process is simple and easy to operate, and the synthesized particles are uniform in size distribution. The lithium manganate material after composite modification shows better electrical property and structural stability.
Drawings
FIG. 1 is a graph of cycle performance for example 1 of the present invention.
FIG. 2 is an SEM image of example 2 of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples and the accompanying drawings.
Example 1
(1) Adding 0.1mol of MnO2With 0.0525mol LiOH is fully and uniformly ground in a mortar, the mixed powder is placed in a muffle furnace to be calcined and reacted for 8 hours at 800 ℃, and lithium manganate LiMn is synthesized2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.5mmol Mn (NO) in turn3)2、0.5mmol LiNO3、0.5mmol NH4H2PO40.01g SDS, and obtaining LiMnPO after 5 hours of reaction4@LiMn2O4Continuously adding 0.3mmol Mn (NO) into the solution3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; as shown in FIG. 1, the specific discharge capacity after 200 cycles is 108.9 mA hr g-1Capacity retention ratioThe content was 89.3%.
Comparative example 1
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.5mmol Mn (NO) in turn3)2、0.5mmol LiNO3、0.5mmol NH4H2PO40.01g SDS, and obtaining LiMnPO after 5 hours of reaction4@LiMn2O4And the dried powder is obtained after one time of water washing, one time of alcohol washing and 12 hours of drying at 60 ℃.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a phosphate modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 95.4 mA h g-1The capacity retention rate was 76.6%.
Comparative example 2
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.3mmol Mn (NO) in turn3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2@LiMn2O4And the dried powder is obtained after one time of water washing, one time of alcohol washing and 12 hours of drying at 60 ℃.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a manganese phosphate modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 88.7 mA h g-1The capacity retention rate was 73.6%.
Example 2
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize the lithium manganateLiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.3mmol Mn (NO) in turn3)2、0.3mmol LiNO3、0.3mmol NH4H2PO40.006g SDS, and obtaining LiMnPO after 5 hours of reaction4@LiMn2O4Continuously adding 0.3mmol Mn (NO) into the solution3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
As shown in FIG. 2, the material is polyhedral with a particle size of about 15 μm. After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 115.8 mA h g-1The capacity retention rate was 94.3%.
Example 3
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.3mmol Mn (NO) in turn3)2、0.3mmol LiNO3、0.3mmol NH4H2PO40.006g SDS, and obtaining LiMnPO after 5 hours of reaction4@LiMn2O4Continuously adding 0.5mmol Mn (NO) into the solution3)2And 0.34mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; discharge after 200 cyclesThe specific capacity is 102.7 mA h g-1The capacity retention rate was 85.6%.
Example 4
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.5mmol Mn (NO) in turn3)2、0.5mmol LiNO3、0.5mmol NH4H2PO40.01g SDS, and obtaining LiMnPO after 5 hours of reaction4@LiMn2O4Continuously adding 0.3mmol Mn (NO) into the solution3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 400 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, charging at different potentials is carried outDischarging, activating the sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 105.9 mA h g-1The capacity retention rate was 87.4%.
Example 5
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.5mmol Mn (NO) in turn3)2、0.5mmol LiNO3、0.5mmol NH4H2PO40.01g SDS, and obtaining LiMnPO after 5 hours of reaction4@LiMn2O4Continuously adding 0.3mmol Mn (NO) into the solution3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at the temperature of 600 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 96.2 mA h g-1The capacity retention rate was 83.5%.
Example 6
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.5mmol Mn (NO) in turn3)2、0.5mmol LiNO3、0.5mmol NH4H2PO40.01g of PVP, and reacting for 5 hours to obtain LiMnPO4@LiMn2O4Continuously adding 0.3mmol Mn (NO) into the solution3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 100.8 mA h g-1The capacity retention rate was 86.0%.
Example 7
(1) Adding 0.1mol of MnO2Fully and uniformly grinding the mixture and 0.0525mol of LiOH in a mortar, putting the mixed powder into a muffle furnace, and calcining and reacting for 8 hours at 800 ℃ to synthesize lithium manganate LiMn2O4A material; taking 0.02mol of prepared LiMn2O4Dispersing in 30ml of water solution, adding 0.5mmol Mn (NO) in turn3)2、0.5mmol LiNO3、0.5mmol NH4H2PO40.01g of citric acid, and reacting for 5 hours to obtain LiMnPO4@LiMn2O4Continuously adding 0.3mmol Mn (NO) into the solution3)2And 0.2mmol NH4H2PO4After further reaction for 4 hours, Mn is obtained3(PO4)2-LiMnPO4@LiMn2O4(ii) a And carrying out water washing once, alcohol washing once and drying at 60 ℃ for 12h to obtain dried powder.
(2) And placing the obtained powder in a muffle furnace to calcine for 6 hours at 500 ℃ to obtain a phosphate composite modified lithium manganate product.
The synthesized modified lithium manganate is used as an active substance of a positive electrode material, is mixed with Acetylene Black (AB) serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 8:1:1, is placed in a small beaker with N-methylpyrrolidone (NMP) serving as a solvent, and is stirred and mixed for 2 hours at a rotating speed of 800r/min, so that slurry is obtained. Coating the slurry on a current collector aluminum foil by using an automatic coating machine, flatly placing the current collector aluminum foil on toughened glass, transferring the current collector aluminum foil to a vacuum drying oven at 85 ℃ for drying for 4h, preparing a pole piece with the diameter of 14mm by punching, drying for 4h at 105 ℃ in the vacuum drying oven, placing the pole piece in a glove box with the water content and the oxygen content both lower than 0.1ppm and filled with argon atmosphere for 4h to reduce the water absorbed by the pole piece in the transferring process, and then assembling the pole piece into a CR2032 type button cell in the glove box. The battery uses a pure metal lithium sheet with the diameter of 16mm and the thickness of 0.5mm as a negative electrode, and a porous polyethylene film with the diameter of 18mm and the model of Celgard2300 as a diaphragm.
After the battery is assembled and aged for 12 hours, performing charge and discharge tests of different potentials, activating a sample for 3 circles at 0.1C under the voltage of 4.3V, and then circulating for 200 circles at the multiplying power of 1C; the specific discharge capacity after 200 cycles is 107.2 mA h g-1The capacity retention rate was 91.5%.
The above description is only a basic description of the present invention, and any equivalent changes made according to the technical solution of the present invention should fall within the protection scope of the present invention.

Claims (10)

1. A phosphate gradient modified lithium manganate material and a preparation method thereof are characterized by comprising the following steps:
step (1) mixing and calcining manganese oxide and a lithium source to synthesize lithium manganate LiMn2O4Dispersing the prepared lithium manganate material in an aqueous solution, adding manganese salt, lithium salt, phosphate precipitator and organic complexing agent, reacting for a period of time to obtain a primary precipitate, and continuing to add manganese salt and phosphate in a certain proportion for precipitation reaction again; washing with water, washing with alcohol, and drying to obtain a solid mixture;
further calcining the obtained mixture to finally obtain a phosphate composite modified lithium manganate material;
in the synthesis of the lithium manganate main body material, the manganese oxide is one or more of manganese dioxide and mangano-manganic oxide, and the lithium source is one or more of lithium carbonate and lithium hydroxide.
2. The phosphate gradient modified lithium manganate material as set forth in claim 1, wherein the calcination temperature of said lithium manganate is 750-950 ℃ and the calcination time is 6-20 h.
3. The phosphate gradient modified lithium manganate material as set forth in claim 1, wherein the molar ratio of lithium source to manganese oxide, n (Li) to n (Mn), is 1.05-1.1: 2.
4. The phosphate gradient modified lithium manganate material and the preparation method thereof as claimed in claim 1, characterized in that, in said primary precipitation process of step (1), manganese salt is one or more of manganese nitrate, manganese acetate and manganese sulfate.
5. The phosphate gradient modified lithium manganate material and the preparation method thereof of claim 1, characterized in that, in said primary precipitation process of step (1), the lithium salt is one or more of lithium nitrate, lithium acetate and lithium sulfate.
6. The phosphate gradient modified lithium manganate material and the preparation method thereof of claim 1, characterized in that, in the primary precipitation process of step (1), the phosphate is one or more of ammonium dihydrogen phosphate and sodium dihydrogen phosphate.
7. The phosphate gradient modified lithium manganate material and the preparation method thereof of claim 1, characterized in that, the organic complexing agent in the primary precipitation process of step (1) is one or more of citric acid, PVP, and SDS.
8. The phosphate gradient modified lithium manganate material as claimed in claim 1, characterized in that, in step (1), the molar ratio of lithium salt, manganese salt, phosphate and organic additive in the primary precipitation process is (1-1.04):1:1 (0.05-0.1), and the molar ratio of manganese salt to LiMn is 1:1 (0.05-0.1)2O4In a molar ratio of 0.01:1 to 0.05: 1.
9. The phosphate gradient modified lithium manganate material as claimed in claim 1, wherein said manganese salt and phosphate during said secondary precipitation in step (1) are selected from the group consisting of manganese saltThe molar ratio is 1: 1-1: 2, the manganese salt with LiMn2O4The molar ratio of (A) to (B) is 0.01:1-0.03: 1.
10. The phosphate gradient modified lithium manganate material and the preparation method thereof as claimed in claim 1, wherein said calcination temperature in step (2) is 300-600 ℃ and the calcination time is 3-10 h.
CN202111317138.0A 2021-11-09 2021-11-09 Phosphate gradient modified lithium manganate material and preparation method thereof Withdrawn CN114050262A (en)

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