CN112803002A - Lithium-rich manganese-based positive electrode material with surface coated by mixed ion conductor and electronic conductor, and preparation method and application thereof - Google Patents
Lithium-rich manganese-based positive electrode material with surface coated by mixed ion conductor and electronic conductor, and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a lithium-rich manganese-based anode material with an ion conductor-electron conductor mixed coating structure on the surface, and a preparation method and application thereof, wherein the lithium-rich manganese-based anode material comprises a lithium-rich manganese-based anode material core and an ion conductor-electron conductor mixed coating layer; the ion conductor-electron conductor mixed coating layer is a surface modification layer formed by mixing and crosslinking an ion conductor and an electron conductor, wherein the ion conductor is a fluorine-based polyanion compound, and the electron conductor is cyclized polyacrylonitrile. The preparation method is simple in preparation process and easy to operate, the heterostructure with the lithium-embedded active substance is cooperatively constructed by coating, the interface between the lithium-rich material and the electrolyte can be stabilized under high voltage, the side reaction between the electrolyte and the lithium-rich material is inhibited, the cycling stability and the rate capability of the material are improved, and the electrochemical performance is obviously improved.
Description
Technical Field
The invention relates to the technical field of lithium ion battery materials, in particular to a lithium-rich manganese-based positive electrode material with an ion conductor-electronic conductor mixed coating structure on the surface, and a preparation method and application thereof.
Background
The environmental pollution and energy crisis problems are two hot problems in recent years, which attract people's extensive attention, and the storage of fossil energy and the pollution problem caused by use are urgent. In order to respond to the national carbon emission reduction call, new energy and storage technology thereof are urgently developed. The lithium ion battery is used as a representative of a new energy storage technology and has an important position in the fields of 3C, energy storage and power batteries, and the positive electrode material is used as a core part of the lithium ion battery and plays an important role in the performance of the lithium ion battery. Therefore, it is necessary to prepare a positive electrode material for a lithium ion battery having good properties.
The lithium ion battery cathode material currently used in commercialization is essentially LiCoO2(LCO)、 LiNixCoyMn1-x-yO2(NCM)、LiNixCoyAl1-x-yO2(NCA)、LiFePO4(LFP) and LiMn2O4(LMO), but LCO, NCM and NCA cost is high and the security performance is relatively poor, LFP and LMO's volume energy density is low, can't satisfy the development requirement of new energy industry. Therefore, there is a need to develop a positive electrode material with higher energy density, lower cost, and higher safety. Lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2(M＝Ni,Co,Mn0<x<1) Because of its ultra-high energy density (theoretical specific capacity)>250mAhg-1) High working voltage, low cost, high safety and low pollution, and is considered as an ideal choice for the next generation of lithium ion battery cathode material. Although the lithium-rich material has ultrahigh capacity, the lithium-rich material also has very serious problems, and the practical production and application of the lithium-rich material are limited by the problems of low first effect, serious capacity attenuation, poor rate performance, voltage drop and the like.
The high capacity of lithium-rich comes mainly from Li2MnO3In the phase, the oxidation and reduction of oxygen anions and the irreversible separation of the oxygen anions cause the migration of transition metal ions, destroy the crystal structure and generate the irreversible transformation from the lamellar phase to the spinel phase and the disordered rock salt phase. In addition, the interface between the lithium-rich electrolyte and the electrolyte is unstable under high voltage, side reaction is easy to occur, the electrolyte is deteriorated to generate HF and other substances, the surface structure of the lithium-rich electrolyte is damaged, and the transition metal is dissolved. Therefore, it is necessary to improve its structural stability and electrochemical properties and modify the material to have good cycle stability. The surface modification is the simplest and most effective means for improving the electrochemical performance of the lithium-rich manganese-based positive electrode material at present. Traditional surface coating substances, such as metal oxides, are electrochemically inert materials that only act as physical barriers, while losing lithium-rich partial capacity; phosphate or organic matter coating only can conduct ions or electrons singly, only plays a role on one hand, and certain organic coating substances are unstable under high voltage, so that the improvement effect is limited.
Disclosure of Invention
Aiming at the defects of the existing surface modification technology, the invention aims to provide a lithium-rich manganese-based positive electrode material with an ion conductor-electron conductor mixed coating structure on the surface and a preparation method thereof, wherein the lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based positive electrode material inner core and an ion conductor-electron conductor mixed coating layer; the ion conductor-electron conductor mixed coating layer is a surface modification layer formed by mixing and crosslinking an ion conductor and an electron conductor, wherein the ion conductor is a fluorine-based polyanion compound, and the electron conductor is cyclized polyacrylonitrile.
In order to achieve the above purpose, the invention provides the following technical scheme:
a lithium-rich manganese-based anode material with an ion conductor-electron conductor mixed coating structure on the surface comprises a lithium-rich manganese-based anode material inner core and an ion conductor-electron conductor mixed coating layer; the ion conductor-electron conductor mixed coating layer is a surface modification layer formed by mixing and crosslinking an ion conductor and an electron conductor, wherein the ion conductor is a fluorine-based polyanion compound, and the electron conductor is cyclized polyacrylonitrile.
In a preferred scheme, the chemical formula of the lithium-rich manganese-based cathode material core is xLi2MnO3·(1-x)LiTMO2Wherein x is more than or equal to 0.2 and less than or equal to 0.8, and TM is at least one of Ni, Co and Mn.
In the preferable scheme, in the lithium-rich manganese-based positive electrode material, the mass ratio of the lithium-rich manganese-based positive electrode material core to the ion conductor-electron conductor mixed coating layer is 1: 0.005 to 0.05; more preferably 1: 0.02-0.03.
In the preferable scheme, in the ion conductor-electron conductor mixed coating layer, the mass ratio of the ion conductor to the electron conductor is 0.5-2: 1.
the invention also provides a preparation method of the lithium-rich manganese-based anode material with the surface structure coated by the mixed ion conductor and the electronic conductor, which comprises the following steps:
1) adding polyacrylonitrile into a solvent, performing ultrasonic treatment for many times, heating and stirring to obtain a uniform solution; adding the fluorine-based polyanion compound into the uniform solution, and continuously stirring to obtain a uniform mixed solution;
2) then adding the lithium-rich manganese-based positive electrode material into the uniform mixed solution obtained in the step 1), stirring and evaporating to dryness, and grinding to obtain the lithium-rich manganese-based positive electrode material coated with polyacrylonitrile and a fluorine-based polyanion compound;
3) and (3) sintering the coated lithium-rich manganese-based positive electrode material obtained in the step 2) at a low temperature to obtain the lithium-rich manganese-based positive electrode material with the surface constructed with the ion conductor-electron conductor mixed coating.
Preferably, in the step 1), the solvent is one of N-methyl pyrrolidone, absolute ethyl alcohol, dimethylformamide and dimethyl sulfoxide; the concentration fraction of polyacrylonitrile is 0.00167-0.05 g/ml; the concentration fraction of the fluorine-based polyanionic compound is 0.00167-0.05 g/ml.
In the preferable scheme, in the step 1), the ultrasonic time is 10-30 min, the ultrasonic frequency is 1-3 times, and the temperature is 30-70 ℃.
Preferably, in step 1), the fluoro polyanion compound is sodium vanadium fluorophosphate (Na)3V2(PO4)2F3) Lithium vanadium fluorophosphate (LiVPO)4F) One or more of (a).
Preferably, in step 2), the evaporation temperature is 80-150 ℃.
In the preferable scheme, in the step 3), the low-temperature sintering temperature is 200-350 ℃, the sintering time is 0.5-5 h, and the sintering atmosphere is vacuum, nitrogen or argon. According to the invention, through low-temperature sintering, polyacrylonitrile is subjected to dehydrocyclization to obtain good electronic conductivity, and meanwhile, the fluorine-based polyanion active material and the lithium-rich manganese-based material form good interface contact to form the lithium-rich manganese-based positive electrode material with the surface constructed and coated by an ion conductor-electron conductor.
The invention also provides application of the lithium-rich manganese-based anode material with the surface coated by the ion conductor-electron conductor mixture, and the lithium-rich manganese-based anode material is used as an anode material of a lithium ion battery to prepare the lithium ion battery.
The fluorine-based polyanion compound has good ionic conductivity and a three-dimensional ion channel, can enable lithium ions to be transferred more quickly, effectively improves the multiplying power performance of rich lithium, has more stable structure, has certain resistance to harmful substances such as HF and the like generated in an electrolyte in the circulating process as a fluorine-based material, and can protect the surface of the lithium-rich material circulating under high voltage from being damaged; the cyclized polyacrylonitrile can be cooperatively coated to remarkably improve the electronic conductivity, and is crosslinked and coated on the lithium-rich surface with the fluorine-based polyanion compound after heated cyclization, so that the cyclized polyacrylonitrile has good tolerance under high charging voltage, the interface stability of the material and the electrolyte is improved, and the cycle performance is improved.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention constructs a heterostructure with lithium intercalation double-active substances by the cooperative coating of the fluorine-based polyanion compound and the cyclized polyacrylonitrile, can stabilize the interface between the lithium-rich material and the electrolyte under high voltage, inhibit the side reaction between the electrolyte and the lithium-rich material, improve the cycling stability and the rate capability of the material and obviously improve the electrochemical performance.
(2) The lithium-rich manganese-based positive electrode material with the surface structure coated by the ion conductor-electron conductor mixture is prepared by a simple liquid phase method assisted by low-temperature sintering, the preparation process is simple, the operation is easy, the electrochemical performance of the lithium-rich material after synergistic coating is obviously improved, and the lithium-rich manganese-based positive electrode material has a wide development prospect.
Drawings
FIG. 1 shows Li as a lithium-rich material in comparative example 11.2Ni0.13Co0.13Mn0.54O2SEM picture of (1);
FIG. 2 shows Li-rich material with a surface coated by an ion conductor-electron conductor mixture prepared in example 11.2Ni0.13Co0.13Mn0.54O2SEM picture of (1);
FIG. 3 is a 100 cycle-capacity plot at 1C rate for example 1 and comparative examples 1 and 3;
FIG. 4 is a graph of rate performance for example 1 and comparative examples 1 and 3;
FIG. 5 is a first-turn charge-discharge curve chart of example 1 and comparative example 1;
FIG. 6 is a 100 cycle-capacity plot at 1C rate for example 2 and comparative example 2;
Detailed Description
Example 1
Weighing 0.10g of polyacrylonitrile, dissolving in 15ml of dimethylformamide, ultrasonically stirring for 10min and 10min for three times alternately, then heating to 50 ℃ and continuously stirring until the polyacrylonitrile is completely dissolved to form a solution, and adding 0.10g of sodium vanadium fluorophosphate (Na) into the solution3V2(PO4)2F3) Stirring is continued for 20min, then 10g of Li-rich material1.2Ni0.13Co0.13Mn0.54O2Adding into the mixture, keeping stirring at 90 deg.C until the solvent is dried, vacuum drying at 120 deg.C to obtain mixture, grinding, processing at 250 deg.C under argon atmosphere for 1h to obtain Li-rich material with surface coated with ion conductor-electron conductor1.2Ni0.13Co0.13Mn0.54O2. The coating amount is 2.0 wt% in experimental design, and the mass ratio of the fluorine-based polyanion compound to the cyclized polyacrylonitrile is 1: 1. as shown in fig. 2, a mixed coating of an ion conductor and an electron conductor is attached to the surface thereof.
According to the following steps of 8: 1: weighing the modified lithium-rich material, acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 1, after uniformly grinding, dropwise adding a proper amount of NMP to prepare mixed slurry, then uniformly coating the slurry on an aluminum foil by using a scraper, then placing the aluminum foil in a vacuum drying box at 120 ℃ for heat preservation for 8 hours, then rolling and stamping the pole piece to obtain a 14mm pole piece, and finally assembling a 2025 button type half cell in a super-purification glove box, wherein 1C is 250mAg-1As a nominal specific capacity, a charge-discharge cycle test was performed within a voltage range of 2 to 4.8V, and as shown in fig. 3, the capacity retention ratio was found to be 82.58% after 100 cycles under the 1C condition.
Example 2
Weighing polyacrylonitrile 0.20g, dissolving in 20ml N-methyl pyrrolidone and 5ml anhydrous ethanol, performing ultrasonic stirring for 10min for three times alternately, heating to 60 deg.C, stirring continuously until completely dissolving to obtain solution, adding 0.10g vanadium lithium fluorophosphate (LiVPO)4F) Stirring is continued for 20min, then 10g of Li-rich material1.2Ni0.13Co0.13Mn0.54O2Adding into the mixture, keeping stirring at 100 deg.C until the solvent is dried, vacuum drying at 120 deg.C to obtain mixture, grinding, and treating at 290 deg.C for 1h in vacuum environment to obtain Li-rich material with surface coated with ion conductor-electron conductor1.2Ni0.13Co0.13Mn0.54O2. The coating amount is 3.0 wt% in experimental design, and the mass ratio of the fluorine-based polyanion compound to the cyclized polyacrylonitrile is 1: 2.
according to the following steps of 8: 1: weighing modified rich lithium, acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 1, after uniformly grinding, dropwise adding a proper amount of NMP to prepare mixed slurry, then uniformly coating the slurry on an aluminum foil by using a scraper, then placing the aluminum foil in a vacuum drying box at 120 ℃ for heat preservation for 8 hours, then rolling and stamping the pole piece to obtain a 14mm pole piece, and finally assembling a 2025 button type half cell in a super-purification glove box, wherein 1C is 250mAg-1As a nominal specific capacity, a charge-discharge cycle test was performed within a voltage range of 2 to 4.8V, and as shown in fig. 6, the capacity retention ratio was found to be 86.41% after 100 cycles under the 1C condition.
Example 3
Weighing polyacrylonitrile 0.20g, dissolving in mixed solvent of dimethyl sulfoxide 15ml and ethanol 5ml, ultrasonic stirring for 20min for 15min for three times alternately, heating to 50 deg.C, stirring to obtain uniform dispersion, adding vanadium sodium fluorophosphate (Na) 0.10g into the dispersion3V2(PO4)2F3) Stirring is continued for 30min, then 10g of Li-rich material is added1.2Ni0.13Co0.13Mn0.54O2Adding into the mixture, keeping stirring at 80 deg.C until the solvent is dried, vacuum drying at 120 deg.C to obtain mixture, grinding, and treating at 300 deg.C for 30min in vacuum environment to obtain Li-rich material with surface coated by ion conductor-electron conductor1.2Ni0.13Co0.13Mn0.54O2. The coating amount is 3.0 wt% in experimental design, and the mass ratio of the fluorine-based polyanion compound to the cyclized polyacrylonitrile is 2: 1.
according to the following steps of 8: 1: weighing modified rich lithium, acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 1, after uniformly grinding, dropwise adding a proper amount of NMP to prepare mixed slurry, then uniformly coating the slurry on an aluminum foil by using a scraper, then placing the aluminum foil in a vacuum drying oven at 120 ℃ for heat preservation for 8 hours, then rolling and stamping the pole piece to obtain a 14mm pole piece, and finally assembling a 2025 button type half cell in a super-purification glove box, wherein 1C is 2 ═ 250mAg-1And performing charge-discharge cycle test within a voltage range of 2-4.8V to obtain a nominal specific capacity, wherein the capacity retention rate is 83.62% after the battery is cycled for 100 circles under the condition of 1C.
Example 4
Weighing 0.10g of polyacrylonitrile, dissolving in 15ml of dimethyl amide, ultrasonically stirring for 20min and 15min for three times alternately, then heating to 50 ℃ and continuously stirring to obtain uniform dispersion liquid, adding 0.20g of sodium vanadium fluorophosphate (Na) into the solution3V2(PO4)2F3) Stirring is continued for 30min, then 10g of Li-rich material is added1.2Ni0.2Mn0.6O2Adding into the mixture, keeping stirring at 90 deg.C until the solvent is dried, vacuum drying at 120 deg.C to obtain mixture, grinding, and treating in muffle furnace at 250 deg.C for 2 hr to obtain Li-rich material with surface coated with ion conductor-electron conductor1.2Ni0.2Mn0.6O2. The coating amount is 3.0 wt% in experimental design, and the mass ratio of the fluorine-based polyanion compound to the cyclized polyacrylonitrile is 1: 2.
according to the following steps of 8: 1: weighing modified rich lithium, acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 1, after uniformly grinding, dropwise adding a proper amount of NMP to prepare mixed slurry, then uniformly coating the slurry on an aluminum foil by using a scraper, then placing the aluminum foil in a vacuum drying box at 120 ℃ for heat preservation for 8 hours, then rolling and stamping the pole piece to obtain a 14mm pole piece, and finally assembling a 2025 button type half cell in a super-purification glove box, wherein 1C is 250mAg-1And performing charge-discharge cycle test within a voltage range of 2-4.8V to obtain a nominal specific capacity, wherein the capacity retention rate is 85.19% after the battery is cycled for 100 circles under the condition of 1C.
Comparative example 1
In contrast to example 1, the difference is only that Li is not added to the lithium-rich bare material1.2Ni0.13Co0.13Mn0.54O2And (4) processing, and directly carrying out battery assembly and electrochemical performance test. As shown in fig. 1, the surface was smooth and free of adherent matter. It was determined that the capacity retention rate was only 65.68% after 100 cycles at 1C rate, as shown in fig. 3.
Comparative example 2
In contrast to example 2, the difference is only that lithium vanadium fluorophosphate alone is selected for the lithium-rich bare material Li1.2Ni0.13Co0.13Mn0.54O2And (3) performing coating treatment, wherein the coating amount is designed to be 3.0 wt%, the coating method is completely consistent with that of the example 2, and performing battery assembly and electrochemical performance test on the coated rich lithium. The capacity retention rate was found to be 80.26% after 100 cycles at 1C rate, as shown in fig. 6.
Comparative example 3
In contrast to example 1, the difference is only that only cyclized polyacrylonitrile is selected for the lithium-rich bare material Li1.2Ni0.13Co0.13Mn0.54O2And (3) performing coating treatment, wherein the coating amount is designed to be 2.0 wt%, the coating method is completely consistent with that of the example 1, and performing battery assembly and electrochemical performance test on the coated rich lithium. The capacity retention was found to be only 75.63% after 100 cycles at 1C rate.
Claims (10)
1. A lithium-rich manganese-based positive electrode material with an ion conductor-electron conductor mixed coating structure on the surface is characterized in that: comprises a lithium-rich manganese-based positive electrode material inner core and an ion conductor-electron conductor mixed coating layer; the ion conductor-electron conductor mixed coating layer is a surface modification layer formed by mixing and crosslinking an ion conductor and an electron conductor, wherein the ion conductor is a fluorine-based polyanion compound, and the electron conductor is cyclized polyacrylonitrile.
2. The surface-structured lithium-rich manganese-based positive electrode material coated with an ionic conductor-electronic conductor mixture as claimed in claim 1, wherein: the chemical formula of the lithium-rich manganese-based positive electrode material core is xLi2MnO3·(1-x)LiTMO2Wherein x is more than or equal to 0.2 and less than or equal to 0.8, and TM is at least one of Ni, Co and Mn.
3. The surface-structured lithium-rich manganese-based positive electrode material coated with an ionic conductor-electronic conductor mixture as claimed in claim 1, wherein: in the lithium-rich manganese-based positive electrode material, the mass ratio of the core of the lithium-rich manganese-based positive electrode material to the ion-electron mixed coating layer is 1: 0.005-0.05.
4. The surface-structured lithium-rich manganese-based positive electrode material coated with an ionic conductor-electronic conductor mixture as claimed in claim 1, wherein: in the ion conductor-electron conductor mixed coating layer, the mass ratio of the ion conductor to the electron conductor is 0.5-2: 1.
5. the method for preparing the lithium-rich manganese-based cathode material coated with the surface structure ionic conductor-electronic conductor mixture in any one of claims 1 to 4, is characterized by comprising the following steps:
1) adding polyacrylonitrile into a solvent, performing ultrasonic treatment for many times, heating and stirring to obtain a uniform solution; adding the fluorine-based polyanion compound into the uniform solution, and continuously stirring to obtain a uniform mixed solution;
2) then adding the lithium-rich manganese-based positive electrode material into the uniform mixed solution obtained in the step 1), stirring and evaporating to dryness, and grinding to obtain the lithium-rich manganese-based positive electrode material coated with polyacrylonitrile and a fluorine-based polyanion compound;
3) and (3) sintering the coated lithium-rich manganese-based positive electrode material obtained in the step 2) at a low temperature to obtain the lithium-rich manganese-based positive electrode material with the surface constructed with the ion conductor-electron conductor mixed coating.
6. The method of claim 5, wherein: in the step 1), the solvent is one of N-methyl pyrrolidone, absolute ethyl alcohol, dimethylformamide and dimethyl sulfoxide; the concentration fraction of polyacrylonitrile is 0.00167-0.05 g/ml; the concentration fraction of the fluorine-based polyanionic compound is 0.00167-0.05 g/ml.
7. The method of claim 5, wherein: in the step 1), the ultrasonic time is 10-30 min, the ultrasonic frequency is 1-3 times, and the temperature is 30-70 ℃;
the fluorine-based polyanion compound is one or more of sodium vanadium fluorophosphate and lithium vanadium fluorophosphate.
8. The method of claim 5, wherein: in the step 2), the drying temperature is 80-150 ℃.
9. The method of claim 5, wherein: in the step 3), the low-temperature sintering temperature is 200-350 ℃, the sintering time is 0.5-5 h, and the sintering atmosphere is vacuum, nitrogen or argon.
10. The use of the surface-structured lithium-rich manganese-based cathode material coated with a mixed ionic conductor and an electronic conductor according to any one of claims 1 to 4 or the lithium-rich manganese-based cathode material coated with a mixed ionic conductor and an electronic conductor prepared by the preparation method according to any one of claims 5 to 9, is characterized in that: the lithium ion battery anode material is used for preparing a lithium ion battery as a lithium ion battery anode material.
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|---|---|---|---|---|
| CN114388759A (en) * | 2022-01-13 | 2022-04-22 | 厦门大学 | Double-coated composite material and preparation method and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2024148453A1 (en) * | 2023-01-09 | 2024-07-18 | 宁德时代新能源科技股份有限公司 | Lithium-rich metal oxide and preparation method therefor, positive electrode sheet, battery cell, and battery |
| CN115863656A (en) * | 2023-03-01 | 2023-03-28 | 江门市科恒实业股份有限公司 | High-temperature-resistant ternary lithium ion battery cathode material and preparation method thereof |
| CN115863656B (en) * | 2023-03-01 | 2023-05-05 | 江门市科恒实业股份有限公司 | High-temperature-resistant ternary lithium ion battery positive electrode material and preparation method thereof |
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| CN112803002B (en) | 2022-06-21 |
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