CN109119624B - Preparation method of lithium titanium phosphate coated lithium-rich manganese-based positive electrode material - Google Patents

Preparation method of lithium titanium phosphate coated lithium-rich manganese-based positive electrode material Download PDF

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CN109119624B
CN109119624B CN201811135072.1A CN201811135072A CN109119624B CN 109119624 B CN109119624 B CN 109119624B CN 201811135072 A CN201811135072 A CN 201811135072A CN 109119624 B CN109119624 B CN 109119624B
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郑俊超
杨书棋
王鹏博
田业成
韦韩信
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Central South University
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Abstract

A preparation method of a lithium-rich manganese-based cathode material coated by lithium titanium phosphate comprises the following steps: (1) mixing and grinding the lithium-rich manganese-based precursor and a lithium source, calcining in an air atmosphere, and cooling; (2) dispersing the lithium-rich manganese-based positive electrode material in an anhydrous organic solvent I, and uniformly stirring; adding a titanium source, and uniformly stirring to obtain a black suspension a; (3) weighing a lithium source and a phosphorus source, adding the lithium source and the phosphorus source into an anhydrous organic solvent II, and uniformly stirring to obtain a mixed suspension b; (4) adding the mixed suspension b into the black suspension a for reaction, and evaporating to dryness in an oil bath to obtain dry gel powder; (5) and calcining the dry gel powder in a reducing atmosphere to obtain the high-strength high-. The lithium titanium phosphate is used as a surface coating layer, so that the cracking of secondary particles and the phase change of layered spinel can be relieved, the kinetics of an anode-electrolyte interface can be improved, and the lithium-rich manganese-based anode material composite material coated by the lithium titanium phosphate has excellent cycle stability.

Description

Preparation method of lithium titanium phosphate coated lithium-rich manganese-based positive electrode material
Technical Field
The invention relates to a preparation method of a positive electrode material, in particular to a preparation method of a lithium-rich manganese-based positive electrode material coated by lithium titanium phosphate.
Background
The lithium ion battery has the advantages of high specific energy density, long charging and discharging life, no memory effect, small environmental pollution, low self-discharging rate and the like, and occupies the high-end market of the portable battery all the time since the coming.
The lithium-rich manganese-based cathode material is the most concerned material in the current lithium ion battery research and can be used in a general formulaxLi2MnO3·(1-x)LiMO2(M＝Ni、Co、Mn，0<x<1) Represents; the composite material has the advantages of high capacity, high thermal stability, high energy density and the like, but has the problems of serious voltage attenuation, low conductivity and the like. This is because Mn ions migrate from octahedral to tetrahedral gaps during charge and discharge, resulting in Li2MnO3The phase is transformed from a monoclinic structure to a spinel structure, thereby showing severe voltage decay in electrochemical performance. The surface coating technique can suppress volume change of the base material and reduce parasitic reaction caused by contact between the material and the electrolyte. Therefore, the selection of suitable surface coating materials is to reduce Li2MnO3Effective means of phase transformation.
Fast ion conductor lithium titanium phosphate (LiTi)2(PO4)3) Spacing of (2) and Li+Most radius matched and it has a three-dimensional space framed crystal structure that contributes to Li+The method has the advantages of fast de-intercalation and good electrochemical performance.
CN107591529A discloses a synthesis method for coating lithium titanium phosphate on a nickel-cobalt-manganese ternary positive electrode material by using a hydrothermal method, however, the first discharge capacity of the obtained material is only 173.7 mAh/g at 0.1C, and the electrochemical performance needs to be improved; moreover, the hydrothermal method has certain uncontrollable property and low yield, and is not suitable for large-scale production.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a preparation method of a lithium-rich manganese-based cathode material coated by lithium titanium phosphate.
The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of a lithium-rich manganese-based cathode material coated by lithium titanium phosphate comprises the following steps:
(1) mixing and grinding the lithium-rich manganese-based precursor and a lithium source, calcining in an air atmosphere, and cooling to obtain a lithium-rich manganese-based positive electrode material;
(2) dispersing the lithium-rich manganese-based positive electrode material obtained in the step (1) in an anhydrous organic solvent I, and uniformly stirring; adding a titanium source, and uniformly stirring to obtain a black suspension a;
(3) calculating the amount of titanium in the titanium source in the step (2), weighing the lithium source and the phosphorus source according to the mass ratio of Li to Ti to P =1 to 2 to 3, adding the lithium source and the phosphorus source into the anhydrous organic solvent II, and uniformly stirring to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction,the oil bath is dried by distillation to dryness, obtaining dry gel powder;
(5) and (4) calcining the dry gel powder obtained in the step (4) in the atmosphere to obtain the dry gel powder.
Preferably, in step (1), the lithium-rich manganese-based precursor is Mn0.674Ni0.163Co0.163CO3、Mn0.674Ni0.163Co0.163(OH)2、Mn4/6Ni1/6Co1/6CO3、 Mn4/6Ni1/6Co1/6 (OH)2、Mn0.75Ni0.25 (OH)2、Mn0.75Ni0.25CO3At least one of (1).
Preferably, in the step (1), the lithium source is at least one of lithium carbonate, lithium nitrate, lithium acetate and lithium hydroxide. Lithium sources may also employ hydrates of lithium nitrate, lithium acetate and lithium hydroxide.
Preferably, in the step (1), the calcination is carried out in two steps, namely, the calcination is carried out at 400-550 ℃ for 4-8h, and then the calcination is carried out at 700-1100 ℃ for 8-20 h.
Preferably, in the step (1), the ratio of the amount of lithium contained in the lithium source to the total amount of Ni, Co and Mn in the lithium-rich manganese-based precursor is 1.5-1.6: 1.
Preferably, in the step (1), the grinding time is 0.5-4 h; too short a milling time, uneven mixing, too long a milling time, long exposure of the material to air, have an impact on the material properties.
Preferably, in the step (2), the titanium source is one or more of tetrabutyl titanate, titanium tetrachloride and titanium isopropoxide.
Preferably, in the step (2), the anhydrous organic solvent I is one or more of anhydrous methanol, anhydrous ethanol or anhydrous propanol.
Preferably, in the step (2), the molar ratio of the lithium-rich manganese-based positive electrode material to the titanium element in the titanium source is 337.8: 10-40.
Preferably, in the step (3), the lithium source is one or more of lithium acetate, lithium acetate dihydrate, lithium hydroxide, lithium carbonate or lithium nitrate.
Preferably, in the step (3), the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphoric acid.
Preferably, in the step (3), the anhydrous organic solvent II is one or more of anhydrous methanol, anhydrous ethanol or anhydrous propanol.
Preferably, in the step (4), the reaction temperature is 50-80 ℃, and the reaction time is 2-10 hours.
Preferably, in the step (4), the oil bath evaporation temperature is 50-80 ℃.
Preferably, in the step (4), the drying time is 10-40 h.
Preferably, in the step (5), the calcining temperature is 400-950 ℃.
Preferably, in the step (5), the calcination time is 6-30 h.
Preferably, in the step (5), the atmosphere is helium, nitrogen or argon, or a mixed atmosphere of argon and hydrogen.
In the obtained lithium-rich manganese-based cathode material coated by lithium titanium phosphate, the molar ratio of the lithium-rich manganese-based cathode material to the lithium titanium phosphate is 100: 0.5 to 10.
The invention first passes throughSol gel processAnd preparing the in-situ composite lithium titanium phosphate coated lithium-manganese-rich cathode material. Wherein the composite material comprises three parts: the core is made of lithium-rich manganese-based anode material, and the shell is three-dimensionalA lithium titanium phosphate material with a rice structure and a two-phase uniform transition gradient layer. The lithium titanium phosphate is used as a surface coating layer, so that the cracking of secondary particles and the phase change of layered spinel can be relieved, the kinetics of a positive electrode-electrolyte interface can be improved, and the lithium-rich manganese-based positive electrode material composite material coated by the lithium titanium phosphate has excellent cycling stability.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention synthesizes the lithium-rich manganese-based composite material with in-situ coated lithium titanium phosphate by a sol-gel method. Wherein the composite material comprises three parts: the core is a lithium-rich manganese-based anode material, the shell is a three-dimensional nano-structure lithium titanium phosphate material, and the two-phase uniform transition gradient layer.
(2) The lithium titanium phosphate is used as a surface coating layer, so that the cracking of secondary particles and the phase change of layered spinel can be relieved, the kinetics of a positive electrode-electrolyte interface can be improved, and the lithium-rich manganese-based positive electrode material composite material coated by the lithium titanium phosphate has excellent cycling stability.
(3) The lithium titanium phosphate has higher ionic conductivity and is beneficial to Li+The defects of poor electric conductivity, poor multiplying power performance and the like of the lithium-rich manganese-based material are effectively overcome.
Drawings
Fig. 1 is an SEM image of a lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate prepared in example 1 of the present invention;
fig. 2 is an SEM image of a lithium-rich manganese-based positive electrode material prepared in comparative example 1 of the present invention;
FIG. 3 is a TEM image of the lithium titanium phosphate coated lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention;
fig. 4 is a graph of the cycle performance at 0.2C discharge rate of a button cell assembled from the lithium titanium phosphate coated lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention and the lithium-rich manganese-based positive electrode material of comparative example 1;
FIG. 5 is a charge-discharge curve diagram of the lithium-rich manganese-based lithium titanium phosphate-coated cathode material prepared in example 1 after different cycles;
FIG. 6 is a schematic structural diagram of the lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained by the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the following examples which illustrate preferred embodiments of the invention, and are not intended to limit the scope of the invention, which is defined by the claims.
Example 1
The embodiment comprises the following steps:
(1) preparation of lithium-rich manganese-based positive electrode material
0.0840mol of lithium-rich manganese-based precursor Mn are weighed4/6Ni1/6Co1/6CO3Coupled with 0.1302 molLiOH-2Carrying out hand-milling mixing on O (the excessive lithium amount is 5%), and milling for 2 h; putting the raw materials into a crucible, placing the crucible in a muffle furnace, presintering for 6h at 500 ℃ in the air atmosphere, then sintering for 10h at 900 ℃, wherein the heating rate is 5 ℃/min, and obtaining the lithium-rich manganese-based positive electrode material 0.5Li after the furnace temperature is cooled to room temperature2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
(2) Dissolving 3.0000g of lithium-rich manganese-based positive electrode material (337.8 mmol) obtained in step (1) in 90mLCH3CH2OH, stirring evenly, adding 20.0000mmol C16H36O4Ti (density 0.9660 g/cm)3) Stirring uniformly to obtain black suspension a;
(3) 30.0000mmol H3PO4、10.0000mmol CH3COOLi·2H2O dissolved in 10mLCH3CH2In OH, uniformly stirring to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2), and carrying out sealed stirring reaction for 3 hours at the temperature of 55 ℃, so that uniform gel is precipitated; steaming the wet gel in an oil bath kettle at 75 ℃ for 20h to obtain dry gel powder;
(5) placing the dry gel powder obtained in the step (4) in an argon atmosphere, sintering at 700 ℃ for 5h to obtain the lithium-rich manganese-based positive electrode material 0.5Li coated by lithium titanium phosphate2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2@ 1%LiTi2(PO4)3。
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating the mixture on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
As shown in FIG. 4, the assembled battery has a capacity retention rate of 86.7% after 25 cycles at a charge-discharge rate of 0.2C within a voltage range of 2.0-4.8V.
Example 2
The embodiment comprises the following steps:
(1) preparation of lithium-rich manganese-based positive electrode material
0.1680mol of lithium-rich manganese-based precursor Mn are weighed4/6Ni1/6Co1/6CO3And 0.1310molLi2CO3Hand milling and mixing (6% of excessive lithium) for 3 h; putting the raw materials into a crucible, placing the crucible in a muffle furnace, presintering the raw materials for 6h at 500 ℃ in the air atmosphere, then sintering the raw materials for 15h at 950 ℃, wherein the heating rate is 5 ℃/min, and after the furnace temperature is cooled to room temperature, obtaining the lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
(2) Dissolving 1.5000g (168.9 mmol) of the lithium-rich manganese-based positive electrode material obtained in the step (1) in 90mLCH3CH2OH, stirring evenly, adding 20.0000mmol C16H36O4Ti (density 0.9660 g/cm)3) Stirring uniformly to obtain black suspension a;
(3) 30.0000mmol H3PO4、10.0000mmol CH3COOLi·2H2O dissolved in 10ml CH3CH2In OH, uniformly stirring to obtain a mixed suspension b;
(4) and (3) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction, hermetically stirring and reacting for 3 hours at 55 ℃, so that uniform gel is separated out, and evaporating wet gel for 24 hours in an oil bath kettle at 75 ℃ to obtain the dry gel powder.
(5) Placing the dry gel powder obtained in the step (4) in an argon atmosphere, sintering at 750 ℃ for 5h to obtain the lithium-rich manganese-based positive electrode material 0.5Li coated by lithium titanium phosphate2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2@ 2%LiTi2(PO4)3。
Assembling the battery: weighing 0.8000g of lithium manganese base-rich lithium phosphate coated titanium lithium phosphate anode material obtained in the embodiment of the invention, adding 0.1000g of conductive carbon black as a conductive agent and 0.1000g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating on an aluminum foil to prepare an anode plate, and taking a metal lithium plate as a cathode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the capacity retention rate is 86.1%.
Example 3
The embodiment comprises the following steps:
(1) preparation of lithium-rich manganese-based positive electrode material
0.1680mol of lithium-rich manganese-based precursor Mn are weighed4/6Ni1/6Co1/6CO3And 0.1302molLi2CO3Hand milling and mixing (5% of excessive lithium) for 2 h; putting the raw materials into a crucible, putting the crucible into a muffle furnace, presintering the raw materials for 5h at 500 ℃, then sintering the raw materials for 12h at 900 ℃, wherein the heating rate is 3 ℃/min, and after the furnace temperature is cooled to room temperature, obtaining the lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
(2) Dissolving 3.0000g of lithium-rich manganese-based positive electrode material (337.8 mmol) obtained in step (1) in 40mLCH3CH2OH, stirring evenly, adding 20.0000mmol C16H36O4Ti (density 0.9660 g/cm)3) Stirring uniformly to obtain black suspension a;
(3) 30.0000mmol H3PO4、10.0000mmol CH3COOLi·2H2O in 5ml CH3CH2In OH, uniformly stirring to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction, and carrying out sealed stirring reaction for 3 hours at 55 ℃ to precipitate uniform gel; steaming the wet gel in an oil bath pan at 85 ℃ for 25h to obtain dry gel powder;
(5) placing the dry gel powder obtained in the step (4) in an argon atmosphere, sintering at 700 ℃ for 7h to obtain the lithium-rich manganese-based positive electrode material 0.5Li coated by lithium titanium phosphate2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2@ 1%LiTi2(PO4)3。
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating the mixture on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the retention rate is 85.2%.
Example 4
The embodiment comprises the following steps:
(1) preparation of lithium-rich manganese-based positive electrode material
0.0840mol of lithium-rich manganese-based precursor Mn are weighed0.674Ni0.163Co0.163CO3With 0.1293molLi (NO)3) Hand milling and mixing (the lithium content is 4 percent), and milling time is 2 h; placing the raw materials into a crucible, placing the crucible into a muffle furnace, presintering the raw materials for 5h at 500 ℃, then sintering the raw materials for 12h at 900 ℃, wherein the heating rate is 5 ℃/min, and cooling the raw materials to room temperatureObtaining the lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
(2) Dissolving 1.0000g of lithium-rich manganese-based positive electrode material (337.8 mmol) obtained in step (1) in 40mLCH3CH2OH, stirring evenly, adding 20.0000 mmoleTiCl4Stirring uniformly to obtain black suspension a;
(3) 30.0000mmol (NH)4)2H(PO4)、10.0000mmolLiOH﹒H2O in 5ml CH3CH2In OH, uniformly stirring to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction, and carrying out sealed stirring reaction for 3 hours at 55 ℃ to precipitate uniform gel; steaming the wet gel in an oil bath pan at 85 ℃ for 22h to obtain dry gel powder;
(5) placing the dry gel powder obtained in the step (4) in a mixed atmosphere of argon and hydrogen (the volume ratio of argon to hydrogen is 1: 1), and sintering at 700 ℃ for 8h to obtain the lithium-rich manganese-based positive electrode material 0.5Li coated by lithium titanium phosphate2MnO3·0.5Li(Ni1/3Co1/ 3Mn1/3)O2@ 3%LiTi2(PO4)3。
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating the mixture on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the retention rate is 84.8%.
Example 5
The embodiment comprises the following steps:
(1) preparation of lithium-rich manganese-based positive electrode material
0.0840mol of lithium-rich manganese-based precursor Mn are weighed0.674Ni0.163Co0.163(OH)2And 0.1285molCH3Mixing COOLi by hand milling (the lithium content is 3%), and milling for 2 h; putting the raw materials into a crucible, putting the crucible into a muffle furnace, presintering the raw materials for 5h at 500 ℃, then sintering the raw materials for 10h at 900 ℃, wherein the heating rate is 5 ℃/min, and after the furnace temperature is cooled to room temperature, obtaining the lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
(2) Dissolving 3.0000g of lithium-rich manganese-based positive electrode material (337.8 mmol) obtained in the step (1) in 40mLCHCOCH3Stirring uniformly, adding 20.0000mmolTi { OCH (CH3)2}4, and stirring uniformly to obtain a black suspension a;
(3) 30.0000mmol (NH)4)2H(PO4)、5.0000mmol Li2CO3Dissolved in 5ml of CHCOCH3Stirring uniformly to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction, and carrying out sealed stirring reaction for 3 hours at 55 ℃ to precipitate uniform gel; steaming the wet gel in an oil bath kettle at 85 ℃ for 20h to obtain dry gel powder;
(5) placing the dry gel powder obtained in the step (4) in helium atmosphere, sintering at 750 ℃ for 5h to obtain lithium titanium phosphate coated lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2@ 1%LiTi2(PO4)3。
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating the mixture on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the retention rate is 85.9%.
Example 6
The embodiment comprises the following steps:
(1) preparation of lithium-rich manganese-based positive electrode material
0.0840mol of lithium-rich manganese-based precursor Mn are weighed0.75Ni0.25 (OH)2With 0.0659mol Li2CO3Hand milling and mixing (the lithium content is 7 percent), and milling time is 3 h; putting the raw materials into a crucible, putting the crucible into a muffle furnace, presintering the raw materials for 5h at 500 ℃, then sintering the raw materials for 12h at 900 ℃, wherein the heating rate is 5 ℃/min, and after the furnace temperature is cooled to room temperature, obtaining the lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
(2) Dissolving 1.0000g of lithium-rich manganese-based positive electrode material (337.8 mmol) obtained in step (1) in 40mLCH3CH2OH, stirring uniformly, adding 20.0000mmol of Ti { OCH (CH)3)2}4Stirring uniformly to obtain black suspension a;
(3) 30.0000mmol (NH)4)H2(PO4)、10.0000mmol LiNO3Dissolve in 5mlCH3CH2In OH, uniformly stirring to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction, and carrying out sealed stirring reaction for 3 hours at 55 ℃ to precipitate uniform gel; steaming the wet gel in an oil bath pan at 85 ℃ for 25h to obtain dry gel powder;
(5) placing the dry gel powder obtained in the step (4) in a nitrogen atmosphere, sintering at 700 ℃ for 10h to obtain the lithium-rich manganese-based positive electrode material 0.5Li coated by lithium titanium phosphate2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2@ 3%LiTi2(PO4)3。
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black serving as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) serving as bondingUniformly mixing the components, coating the mixture on aluminum foil to prepare a positive plate, taking a metal lithium plate as a negative electrode and Celgard2300 as a diaphragm in a vacuum glove box, and taking 1mol/L LiPF6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the retention rate is 86.7%.
Comparative example 1
(1) Preparation of lithium-rich manganese-based positive electrode material
0.0840mol of lithium-rich manganese-based precursor Mn are weighed4/6Ni1/6Co1/6CO3Coupled with 0.1302 molLiOH-2Carrying out hand-milling mixing on O (the excessive lithium amount is 5%), and milling for 2 h; putting the raw materials into a crucible, placing the crucible in a muffle furnace, presintering for 6h at 500 ℃ in the air atmosphere, then sintering for 10h at 900 ℃, wherein the heating rate is 5 ℃/min, and obtaining the lithium-rich manganese-based positive electrode material 0.5Li after the furnace temperature is cooled to room temperature2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating the mixture on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the capacity retention rate is 66.7%.
Comparative example 2
(1) Preparation of lithium-rich manganese-based positive electrode material
0.1680mol of lithium-rich manganese-based precursor Mn are weighed4/6Ni1/6Co1/6CO3And 0.1310molLi2CO3Hand milling and mixing (6% of excessive lithium) for 3 h; placing the raw materials into a crucible, placing the crucible into a muffle furnace, and pre-heating the crucible at 500 ℃ in air atmosphereSintering for 6h, then sintering for 15h at 950 ℃, wherein the heating rate is 5 ℃/min, and obtaining the lithium-rich manganese-based positive electrode material 0.5Li after cooling to room temperature in the furnace2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
Assembling the battery: weighing 0.4000g of lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate obtained in the embodiment of the invention, adding 0.0500g of conductive carbon black as a conductive agent and 0.0500g of PVDF (polyvinylidene fluoride) as a binder, uniformly mixing, coating the mixture on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the capacity retention rate is 61.9%.
Comparative example 3
(1) Preparation of lithium-rich manganese-based positive electrode material
0.1680mol of lithium-rich manganese-based precursor Mn are weighed4/6Ni1/6Co1/6CO3And 0.1302molLi2CO3Hand milling and mixing (5% of excessive lithium) for 2 h; putting the raw materials into a crucible, putting the crucible into a muffle furnace, presintering the raw materials for 5h at 500 ℃, then sintering the raw materials for 12h at 900 ℃, wherein the heating rate is 3 ℃/min, and after the furnace temperature is cooled to room temperature, obtaining the lithium-rich manganese-based positive electrode material 0.5Li2MnO3·0.5Li(Ni1/3Co1/3Mn1/3)O2；
Assembling the battery: weighing 0.8000g of the lithium titanium phosphate coated nickel-cobalt-manganese ternary positive electrode material obtained in the embodiment of the invention, adding 0.1000g of conductive carbon black serving as a conductive agent and 0.1000g of PVDF (polyvinylidene fluoride) serving as a binder, uniformly mixing, coating on an aluminum foil to prepare a positive electrode plate, and taking a metal lithium plate as a negative electrode, Celgard2300 as a diaphragm and 1mol/L LiPF (lithium iron phosphate/polyvinylidene fluoride) in a vacuum glove box6DMC (volume ratio 1: 1) as electrolyte, and assembling into a CR2025 button cell.
The assembled battery is cycled for 25 circles under the charge-discharge rate of 0.2C within the voltage range of 2.0-4.8V, and the retention rate is 65.7%.

Claims (7)

1. The preparation method of the lithium-rich manganese-based positive electrode material coated by the lithium titanium phosphate is characterized in that the chemical formula of the lithium titanium phosphate is LiTi2(PO4)3The method comprises the following steps:
(1) mixing and grinding the lithium-rich manganese-based precursor and a lithium source, calcining in an air atmosphere, and cooling to obtain a lithium-rich manganese-based positive electrode material;
(2) dispersing the lithium-rich manganese-based positive electrode material obtained in the step (1) in an anhydrous organic solvent I, and uniformly stirring; adding a titanium source, and uniformly stirring to obtain a black suspension a;
(3) calculating the amount of titanium in the titanium source in the step (2), weighing the lithium source and the phosphorus source according to the mass ratio of Li to Ti to P =1 to 2 to 3, adding the lithium source and the phosphorus source into the anhydrous organic solvent II, and uniformly stirring to obtain a mixed suspension b;
(4) adding the mixed suspension b obtained in the step (3) into the black suspension a obtained in the step (2) for reaction, and evaporating in an oil bath to dryness to obtain dry gel powder;
(5) calcining the dry gel powder obtained in the step (4) in the atmosphere, wherein the calcining temperature is 400-950 ℃, and the calcining time is 6-30 hours; the atmosphere is helium, nitrogen or argon, or the mixed atmosphere of argon and hydrogen.
2. The method for preparing the lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate according to claim 1, wherein in the step (1), the lithium-rich manganese-based precursor is Mn0.674Ni0.163Co0.163CO3、Mn0.674Ni0.163Co0.163(OH)2、Mn4/6Ni1/6Co1/ 6CO3、 Mn4/6Ni1/6Co1/6 (OH)2、Mn0.75Ni0.25 (OH)2、Mn0.75Ni0.25CO3At least one of; the lithium source is lithium carbonate, lithium nitrate hydrate, lithium acetate and lithium acetate waterAt least one of a compound, lithium hydroxide or lithium hydroxide hydrate.
3. The preparation method of the lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate according to claim 1 or 2, wherein in the step (1), the calcination is carried out in two steps, namely, the calcination is carried out at 400-550 ℃ for 4-8h, and then the calcination is carried out at 700-1100 ℃ for 8-20 h; the ratio of the amount of lithium contained in the lithium source to the total amount of Ni, Co and Mn in the lithium-rich manganese-based precursor is 1.5-1.6: 1; the grinding time is 0.5-4 h.
4. The method for preparing the lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate according to claim 1 or 2, wherein in the step (2), the titanium source is one or more of tetrabutyl titanate, titanium tetrachloride and titanium isopropoxide; the anhydrous organic solvent I is one or more of anhydrous methanol, anhydrous ethanol or anhydrous propanol; the molar ratio of the lithium-rich manganese-based positive electrode material to the titanium element in the titanium source is 337.8: 10-40.
5. The method for preparing the lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate according to claim 1 or 2, wherein in the step (3), the lithium source is one or more of lithium acetate, lithium hydroxide, lithium carbonate or lithium nitrate; the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate or phosphoric acid; the anhydrous organic solvent II is one or more of anhydrous methanol, anhydrous ethanol or anhydrous propanol.
6. The method for preparing the lithium titanium phosphate coated lithium-rich manganese-based cathode material according to claim 5, wherein in the step (3), the lithium source is one or more of lithium acetate dihydrate, lithium hydroxide, lithium carbonate or lithium nitrate.
7. The preparation method of the lithium-rich manganese-based positive electrode material coated with lithium titanium phosphate according to claim 1 or 2, wherein in the step (4), the reaction temperature is 50-80 ℃, and the reaction time is 2-10 hours; evaporating the mixture to dryness in an oil bath at the temperature of 50-80 ℃; the drying time is 10-40 h.
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