CN111900375B - Preparation method of long-life negative electrode material for power energy storage and application of long-life negative electrode material in lithium ion battery - Google Patents

Preparation method of long-life negative electrode material for power energy storage and application of long-life negative electrode material in lithium ion battery Download PDF

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CN111900375B
CN111900375B CN202010619670.7A CN202010619670A CN111900375B CN 111900375 B CN111900375 B CN 111900375B CN 202010619670 A CN202010619670 A CN 202010619670A CN 111900375 B CN111900375 B CN 111900375B
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negative electrode
electrode material
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CN111900375A (en
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吴凯
胡钱巍
杨斌
蒋建杰
王德康
李健
钱卫良
满敬彬
方亮
郭旺
吴锦领
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HUZHOU ELECTRIC POWER DESIGN INSTITUTE CO LTD
Huazhong University of Science and Technology
Huzhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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HUZHOU ELECTRIC POWER DESIGN INSTITUTE CO LTD
Huazhong University of Science and Technology
Huzhou Power Supply Co of State Grid Zhejiang Electric Power 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
    • H01M4/36—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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/003—Titanates
    • C01G23/005—Alkali titanates
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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
    • H01M2004/027—Negative 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a preparation method of a long-life negative electrode material for power energy storage and application of the long-life negative electrode material in a lithium ion battery, relating to the technical field of lithium ion battery material preparation and comprising the following preparation steps: (1) mixing and grinding a titanium source, a lithium source, a main metal doping source and an auxiliary metal doping source to prepare a double-doped lithium titanate precursor; (2) placing the double-doped lithium titanate precursor in a tube furnace, roasting in a protective gas atmosphere, then cooling to room temperature, and grinding to prepare the long-life negative electrode material for power energy storage; the chemical formula of the cathode material is Li4−(x+y)MxNyTi5O12X + y =0.05-0.3, x =0.05-0.3, y =0-0.04 and y ≠ 0; after the bimetallic element is doped in the lithium titanate material, the conductivity of the lithium titanate can be obviously improved, the polarization of a battery is reduced, and the reversible capacity, the cycle performance and the rate capability of the material are improved.

Description

Preparation method of long-life negative electrode material for power energy storage and application of long-life negative electrode material in lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion battery material preparation, in particular to a preparation method of a long-life negative electrode material for power energy storage and a lithium ion battery.
Background
Currently, most of commercial lithium ion battery cathode materials are carbon cathode materials. Although the specific capacity of the carbon material is up to 372mAh/g, the carbon material still has a plurality of disadvantages: (1) the SEI film is formed by first charge and discharge, and the charge and discharge efficiency is low; (2) the potential of the carbon material is only about 0.1V, the potential is very close to the precipitation potential of metallic lithium, and Li is generated during the overcharge of the battery+Ions are easy to precipitate on the surface of negative electrode carbon to form lithium dendrite, so that a diaphragm is pierced to cause short circuit, and potential safety hazard exists. Spinel Li in comparison with carbon material4Ti5O12The volume of the negative electrode material can hardly change in the charging and discharging process, the negative electrode material is called as a zero-strain material, the cycle life is long, the charging and discharging platform is stable, other side reactions with electrolyte can not occur, the safety is high, the theoretical specific capacity is 175mAh/g, the cost is low, the preparation is easy, the environment is not polluted, and the negative electrode material is a novel environment-friendly energy material. Li4Ti5O12Despite the many advantages mentioned above, the electrons are in Li4Ti5O12The energy gap of the medium transition is more than 2eV, and the electronic conductivity is lower and is only 10－9S/cm, therefore, has been restricting Li4Ti5O12Large-scale industrial application.
For example, the publication No. CN103904332B discloses a lithium titanate negative electrode material, which includes lithium titanate particles coated with hydrophobic groups on the surface, and the bonding manner between the hydrophobic groups and the lithium titanate particles is covalent bond connection. The lithium titanate with the hydrophobic surface reduces the catalytic activity of the lithium titanate, thereby remarkably improving the problem of flatulence of the lithium titanate battery and improving the high-temperature performance of the lithium titanate battery. However, although the invention solves the problem of improving the flatulence of the lithium titanate battery, the electronic conductivity of the lithium titanate battery is still low.
Disclosure of Invention
The invention aims to overcome the defects of the prior Li4Ti5O12Negative electrode material with electrons in Li4Ti5O12The energy gap of the medium transition is more than 2eV, and the electronic conductivity is lower and is only 10－9S/cm and the like, and provides a preparation method of a long-life negative electrode material for power energy storage.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) mixing and grinding a titanium source, a lithium source, a main metal doping source and an auxiliary metal doping source to prepare a double-doped lithium titanate precursor;
(2) placing the double-doped lithium titanate precursor in a tube furnace, roasting in a protective gas atmosphere, then cooling to room temperature, and grinding to prepare the long-life negative electrode material for power energy storage;
the chemical formula of the anode material is Li4-(x+y)MxNyTi5O12X + y is 0.05-0.3, x is 0.05-0.3, y is 0-0.04 and y is not equal to 0; wherein M is a main metal element selected from one of Ca, Mg, Al, Zn and Fe, N is an auxiliary metal element selected from one of Mg, Al, Zn, Fe, Ni and Cr, and the activity of the main metal element is higher than that of the auxiliary metal element.
According to the invention, the lithium titanate is doped by adopting the main metal element and the auxiliary metal element simultaneously, wherein the activity of the main metal element is higher than that of the auxiliary metal element, because the metal with stronger metal activity is easier to be added into the lithium titanate structure as the main metal element during the preparation of the cathode material, the structure is more stable, and after the auxiliary metal element is doped, the auxiliary metal element and the main metal element are cooperated with each other to occupy the lattice position of the lithium titanate together, so that the electron conduction effect is increased, the conductivity of the lithium titanate can be obviously improved, the electrochemical performance is further influenced, and the cycle performance is effectively improved. This is because the conductivity of the original lithium carbonate is relatively poor; the single metal element is added, so that the conductivity of the lithium titanate can be improved, but the single element has the same radius, so that the appropriate occupation of lithium titanate unit cells cannot be ensured, and the conductivity of the material cannot be improved to the utmost extent; the radii of the double elements can be mutually complemented and coordinated, so that the metal elements can occupy lithium titanate unit cells to the maximum extent under the condition of ensuring the stable structure of lithium titanate, the electronic conduction distance is reduced, and the conductivity of the material is improved. Therefore, after the bimetallic element is doped in the lithium titanate material, the charge transfer impedance of the lithium titanate material in the charge-discharge process is obviously reduced, the kinetic limitation of the charge-discharge process is effectively overcome, the polarization of the battery is reduced, and the reversible capacity, the cycle performance and the rate capability of the material are improved.
Also, the chemical formula of the anode material of the present invention is defined as Li4-(x+y)MxNyTi5O12Wherein x + y is 0.05-0.3, x is 0.05-0.3, y is 0-0.04 and y is not equal to 0. When x + y is more than 0.3, or x is more than 0.3, and y is more than 0.04, the structure of the lithium titanate is unstable, which is not beneficial to long cycle, especially, the atomic radius of the auxiliary metal element is generally larger, and the excessive amount can play an opposite role, which affects the structural position of the main element in the lithium titanate.
Preferably, the titanium source is nano TiO2(ii) a The lithium source is Li2CO3。
Preferably, in the step (1), when the mixture is ground, n (Li) and n (Ti) are 0.84-0.86.
When mixed and milled, the lithium source is in a suitable excess because of partial volatilization of lithium at high temperatures.
Preferably, the main metal doping source comprises CaO, MgO and Al2O3、ZnO、Fe3O4The auxiliary metal doping source comprises MgO and Al2O3、ZnO、Fe3O4、NiO、Cr2O3One kind of (1).
Preferably, the roasting conditions are as follows: raising the temperature to 750 ℃ and 850 ℃ at the temperature raising rate of 1-3 ℃/min, and preserving the temperature for 10-14 h.
In the invention, because the bimetal is adopted for doping, and the reactivity of the two metal elements is different, the rate of the temperature rise process is reduced to 1-3 ℃/min in the roasting process, so that the temperature rise difference of the two metal element oxides is small, and the reaction is more thorough in the subsequent product crystal generation process; secondly, in the present invention, the holding time for calcination needs to be longer, 10 to 14 hours, and when the activities of the main metal element and the auxiliary metal element are lower than that of Fe, the holding time needs to be further limited to 13 to 14 hours, since the time needed for the reaction to form crystals and grow is longer when the metal elements having lower activities are contained.
Preferably, the grinding time in step (2) is 30-90 min.
In the invention, the time for grinding the calcined product in the pot body needs to be more than 30min, otherwise, the compaction and rate capability of the pole piece can be influenced when the negative electrode material is used for preparing the electrode.
Preferably, the protective gas comprises one of nitrogen or an inert gas.
An application of a long-life negative electrode material for power energy storage in a lithium ion battery.
Therefore, the invention has the following beneficial effects: after the bimetallic element is doped in the lithium titanate material, the conductivity of the lithium titanate can be obviously improved, the charge transfer impedance of the lithium titanate material in the charge-discharge process is obviously reduced, the kinetic limitation of the charge-discharge process is effectively overcome, the polarization of a battery is reduced, and the reversible capacity, the cycle performance and the rate capability of the material are improved.
Drawings
FIG. 1 shows Ca and Mg co-doped negative electrode material and L in example 1 of the present invention4Ti5O12(LTO) XRD pattern.
FIG. 2 shows Ca and Mg co-doped anode material and L in example 1 of the present invention4Ti5O12(111) peak of (LTO) enlarged XRD pattern locally.
FIG. 3 shows that Ca and Mg co-doped negative electrode material and L in embodiment 1 of the invention4Ti5O12(LTO) assembled coin cell cyclic voltammetry test spectra.
FIG. 4 shows Ca and Mg co-doped anode material and L in example 1 of the present invention4Ti5O12(LTO) rate capability at different rates.
FIG. 5 shows Ca and Mg co-doped anode material and L in example 1 of the present invention4Ti5O12(LTO) 2C-rate charge/discharge stability diagram.
FIG. 6 shows Ca and Mg co-doped anode material and L in example 1 of the present invention4Ti5O12(LTO) first charge/discharge performance at 2C rate.
FIG. 7 shows Ca and Mg co-doped anode material and L in example 1 of the present invention4Ti5O12(LTO) alternating current impedance test pattern.
Detailed Description
The invention is further described with reference to specific embodiments.
General example: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3Mixing and grinding the main metal doping source and the auxiliary metal doping source to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84-0.86; the main metal doping source comprises CaO, MgO and Al2O3、ZnO、Fe3O4The auxiliary metal doping source comprises MgO and Al2O3、ZnO、Fe3O4、NiO、Cr2O3One of (1);
(2) placing the double-doped lithium titanate precursor in a tube furnace, heating to 750-850 ℃ at the heating rate of 1-3 ℃/min under the atmosphere of nitrogen or inert gas, preserving heat for 10-14h for roasting, then cooling to room temperature, grinding for 30-60min, and preparing the long-life negative electrode material for power energy storage;
the chemical formula of the cathode material is Li4-(x+y)MxNyTi5O12X + y is 0.05-0.3, x is 0.05-0.3, y is 0-0.04 and y is not equal to 0; wherein M is a main metal element selected from one of Ca, Mg, Al, Zn and Fe, N is an auxiliary metal element selected from one of Mg, Al, Zn, Fe, Ni and Cr, and the activity of the main metal element is higher than that of the auxiliary metal element.
Example 1: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3CaO as main metal doping source and MgO as auxiliary metal doping source3.9Ca0.09Mg0.01Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tube furnace, heating to 750 ℃ at the heating rate of 3 ℃/min under the nitrogen atmosphere, keeping the temperature for 12 hours for roasting, then cooling to room temperature, and grinding for 30 minutes to prepare the long-life negative electrode material for power energy storage.
Example 2: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3CaO as main metal doping source and MgO as auxiliary metal doping source3.7Ca0.26Mg0.04Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tube furnace, heating to 750 ℃ at the heating rate of 2 ℃/min under the argon atmosphere, keeping the temperature for 13h for roasting, then cooling to room temperature, and grinding for 90min to obtain the long-life negative electrode material for power energy storage.
Example 3: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3A main metal doping source MgO and an auxiliary metal doping source NiOLi3.9Mg0.08Ni0.02Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) and n (Ti) are 0.84;
(2) the double-doped lithium titanate precursor is placed in a tube furnace, the temperature is raised to 800 ℃ at the heating rate of 2 ℃/min under the nitrogen atmosphere, the temperature is kept for 13 hours for roasting, then the temperature is reduced to room temperature, and the long-life negative electrode material for power energy storage is prepared after grinding for 90 minutes.
Example 4: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3MgO as main metal doping source and Al as auxiliary metal doping source2O3According to Li3.9Mg0.09Al0.01Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tube furnace, heating to 750 ℃ at the heating rate of 3 ℃/min under the argon atmosphere, keeping the temperature for 14h for roasting, then cooling to room temperature, and grinding for 60min to obtain the long-life negative electrode material for power energy storage.
Example 5: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3ZnO as main metal doping source and Fe as auxiliary metal doping source3O4According to Li3.9Zn0.08Fe0.02Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tubular furnace, heating to 850 ℃ at the heating rate of 2 ℃/min under the nitrogen atmosphere, keeping the temperature for 14h for roasting, then cooling to room temperature, and grinding for 90min to obtain the long-life negative electrode material for power energy storage.
Example 6: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3MgO as main metal doping source and Cr as auxiliary metal doping source2O3According to Li3.9Mg0.09Cr0.01Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) the double-doped lithium titanate precursor is placed in a tube furnace, the temperature is raised to 800 ℃ at the heating rate of 2 ℃/min under the nitrogen atmosphere, the temperature is kept for 13 hours for roasting, then the temperature is reduced to room temperature, and the long-life negative electrode material for power energy storage is prepared after grinding for 90 minutes.
Example 7: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3CaO as main metal doping source and NiO as auxiliary metal doping source3.9Ca0.09Ni0.01Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) the double-doped lithium titanate precursor is placed in a tube furnace, the temperature is raised to 800 ℃ at the heating rate of 2 ℃/min under the nitrogen atmosphere, the temperature is kept for 13 hours for roasting, then the temperature is reduced to room temperature, and the long-life negative electrode material for power energy storage is prepared after grinding for 60 minutes.
Example 8: a preparation method of a long-life negative electrode material for power energy storage comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3A main metal doping source CaO and an auxiliary metal doping source Co3O4According to Li3.9Ca0.09Co0.01Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tubular furnace, heating to 800 ℃ at a heating rate of 1 ℃/min in a nitrogen atmosphere, keeping the temperature for 13 hours for roasting, then cooling to room temperature, and grinding for 90 minutes to prepare the long-life negative electrode material for power energy storage.
Comparative example 1: a preparation method of the anode material comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3Metallic doping source CaO is Li3.9Ca0.1Ti5O12Mixing and grinding the components according to the proportion to prepare a doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tube furnace, heating to 750 ℃ at the heating rate of 3 ℃/min under the nitrogen atmosphere, keeping the temperature for 12 hours for roasting, then cooling to room temperature, and grinding for 30 minutes to obtain the cathode material.
Comparative example 2: a preparation method of the anode material comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3CaO as main metal doping source and NiO as auxiliary metal doping source3.5Ca0.4Ni0.1Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) the double-doped lithium titanate precursor is placed in a tube furnace, the temperature is raised to 800 ℃ at the heating rate of 1 ℃/min under the nitrogen atmosphere, the temperature is kept for 13 hours for roasting, then the temperature is reduced to room temperature, and the long-life negative electrode material for power energy storage is prepared after grinding for 60 minutes.
Comparative example 3: a preparation method of the anode material comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3CaO as main metal doping source and ZnO as auxiliary metal doping source3.5Ca0.4Zn0.1Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) the double-doped lithium titanate precursor is placed in a tube furnace, the temperature is raised to 800 ℃ at the heating rate of 1 ℃/min under the nitrogen atmosphere, the temperature is kept for 13 hours for roasting, then the temperature is reduced to room temperature, and the long-life negative electrode material for power energy storage is prepared after grinding for 60 minutes.
Comparative example 4: a preparation method of the anode material comprises the following preparation steps:
(1) adding TiO into the mixture2、Li2CO3CaO as main metal doping source and NiO as auxiliary metal doping source3.9Ca0.09Ni0.01Ti5O12Mixing and grinding the components according to the proportion to prepare a double-doped lithium titanate precursor; wherein n (Li) n (Ti) is 0.84;
(2) and (3) placing the double-doped lithium titanate precursor in a tubular furnace, heating to 600 ℃ at the heating rate of 2 ℃/min in the air atmosphere, keeping the temperature for 8 hours for roasting, then cooling to room temperature, and grinding for 15 minutes to obtain the long-life negative electrode material for power energy storage.
The anode material prepared in example 1 and the undoped modified anode material L4Ti5O12The results are shown in FIGS. 1-2.
FIG. 1 shows Ca and Mg co-doped anode material and L in example 14Ti5O12(LTO) XRD pattern, it can be seen that characteristic peak of the negative electrode material prepared in example 1 and spinel type L4Ti5O12The result is that the anode material synthesized in example 1 is L4Ti5O12A spinel structure. It can also be seen from the figure that the diffraction peaks after doping are all sharper, indicating better crystallinity.
FIG. 2 shows Ca and Mg co-doped anode material and L in example 14Ti5O12The (111) peak of (LTO) was partially enlarged in XRD pattern, and it was found that the peak pattern after doping in example 1 was shifted to a low angle, and the peak intensity was slightly reduced and broadened because of Ca2+、Mg2+The incorporation of (2) causes a small distortion of the lithium titanate lattice. It is obvious that Ca is doped2+Later, the lattice constant slightly increases, mainly due to the high valence of Ca2+(0.1nm) and a small amount of Mg2+(0.078nm) substituted for Li at position 8a+(0.076nm), Ti was generated to maintain charge balance4+/Ti3+The mixed valence state of the LTO, thereby improving the conductivity of the LTO, reducing the polarization phenomenon in the charging and discharging process of the LTO and improving the high-rate charging and discharging performance of the LTO.
Preparing a battery: mixing acetylene black and PVDF according to the mass ratio of 8:1:1, dispersing in NMP, uniformly coating the uniformly stirred slurry on a copper foil, drying in a vacuum drying oven at 110 ℃ for 16h, punching into sheets with the diameter of 16mm after drying, and drying in the vacuum drying oven at 80 ℃ for 8h to obtain the electrode plate. The electrode plate, lithium metal plate, Celgard2400 diaphragm, 1mol/L LiPF were then placed in an argon-filled glove box6the/EC + DEC (volume ratio 1: 1) solution was assembled into button cell type CR 2025. And standing for 24h, and then carrying out electrochemical performance test.
FIG. 3 shows Ca and Mg co-doped anode material and L in example 14Ti5O12(LTO) assembled button cell cyclic voltammetry test profile, test conditions were: 0.8-2.8V, 0.5 mV/s. A pair of redox peaks can be obviously observed from the graph, which shows that the high coulombic efficiency is achieved, the peak current of the cathode material in example 1 is obviously enhanced at the same scanning speed, the peak area is obviously increased, which means that the doped cathode material has higher capacity, and the cathode material in example 1 is relatively higher than Li4Ti5O12The oxidation reduction peak is sharper, the highest peak current reaches 7mA and 1.9mA respectively, which indicates that doping causes Li4Ti5O12The material has better conductivity. Meanwhile, in the embodiment 1, the peak distance of the Ca and Mg co-doped cathode material is reduced, namely the potential difference is reduced, which shows that the reversibility is better, the conductivity is increased, and the polarization phenomenon is obviously reduced. The charge-discharge performance is better under the condition of high-magnification working.
FIG. 4 shows Ca and Mg co-doped anode material and L in example 14Ti5O12(LTO) rate capability at different rates. It is understood from the graph that the discharge capacity decreases with the increase of the discharge rate, and Li increases with the increase of the charge/discharge current4Ti5O12The attenuation amplitude is larger than that of the Ca and Mg co-doped negative electrode material in the embodiment 1. To 5C, Li4Ti5O12And the Ca and Mg co-doped negative electrode material of the embodiment 1 has the specific discharge capacity of 68.7mA/g and 106.1 mA/g. The retention rates of the lithium secondary batteries were 44.12% and 6%, respectively, relative to the respective first discharge capacities8.01 percent. Therefore, the Ca and Mg co-doped negative electrode material in the embodiment 1 has better performance than that of the undoped Li under the same multiplying power4Ti5O12. The Ca and Mg co-doped negative electrode material in the embodiment 1 can effectively reduce the contact resistance between crystal grains and particles in the material and reduce the polarization degree in the charge and discharge process, thereby improving the high-rate charge and discharge performance of the lithium titanate material.
FIG. 5 shows Ca and Mg co-doped anode material and L in example 14Ti5O12(LTO) charge-discharge stability diagram at 2C magnification; it can be seen from the graph that, in example 1, after 100 charge and discharge cycles, the Ca and Mg co-doped negative electrode material still has a discharge specific capacity of 115.1mAh/g, and the attenuation amplitude is only 5.42% compared with the first discharge specific capacity of 121.7 mAh/g. After LTO is charged and discharged for 100 times in a circulating mode, the specific capacity is 80.1mAh/g, and compared with the first discharge specific capacity of 93mAh/g, the attenuation amplitude is 13.87%. From the data, the cycle stability of the Ca and Mg co-doped negative electrode material in example 1 is greatly enhanced and the capacity retention rate is higher compared with the undoped pure-phase LTO.
FIG. 6 shows Ca and Mg co-doped anode material and L in example 14Ti5O12(LTO) first charge and discharge performance diagram under 2C multiplying power, it can be known in the diagram that the first charge and discharge specific capacity of the Ca and Mg co-doped negative electrode material in example 1 is higher than that of undoped LTO under 2C multiplying power, and the charge and discharge platforms are all around 1.55, but it is obvious that the charge and discharge platform of the Ca and Mg co-doped negative electrode material in example 1 is long, and the distance between the charge and discharge platforms is smaller than that of pure-phase LTO, which shows that the polarization phenomenon is greatly reduced after doping.
FIG. 7 shows Ca and Mg co-doped anode material and L in example 14Ti5O12(LTO) alternating current impedance test pattern, which is alternating current impedance test result after charging and discharging 20 circles, frequency range is 0.01 Hz-100kHz, and amplitude is 5 mV/s. As can be seen, the impedance map consists of two parts, namely the capacitive reactance arc of a high-frequency region and the Warburg impedance of a middle-frequency region and a low-frequency region. By calculation, Li4Ti5O12In example 1, the charge transfer resistances of the Ca and Mg co-doped negative electrode material in the charging and discharging processes are 156.7 omega and 219.3 omega respectively, and in example 1, Ca and Mg are co-dopedThe conductive performance of the negative electrode material is improved, the charge transfer resistance of the material is reduced in the process of lithium intercalation, and the electrode polarization is reduced, so that the electrochemical performance of the negative electrode material is improved.
The capacity and cycle performance tests of the examples and comparative examples are shown in the following table:
Figure GDA0003398190110000081
according to the data, the co-doped negative electrode material prepared by the method has high capacity and excellent cycle performance; as can be seen from comparative example 1, the cycle performance was poor when only Ca was used for doping; from comparative examples 2 to 3, it is understood that when the doping ratio exceeds the defined range, both the capacity and the cycle performance are degraded; as can be seen from comparative example 4, when the preparation conditions were outside the defined ranges, the prepared anode material was inferior in both capacity and cycle performance.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.

Claims (7)

1. A preparation method of a long-life negative electrode material for power energy storage is characterized by comprising the following preparation steps:
(1) mixing and grinding a titanium source, a lithium source, a main metal doping source and an auxiliary metal doping source to prepare a double-doped lithium titanate precursor;
(2) placing the double-doped lithium titanate precursor in a tube furnace, and roasting in a protective gas atmosphere, wherein the roasting conditions are as follows: heating to 750-850 ℃ at the heating rate of 1-3 ℃/min, preserving the heat for 10-14h, then cooling to room temperature, and grinding to prepare the long-life negative electrode material for power energy storage;
the chemical formula of the anode material is Li4-(x+y)MxNyTi5O12X + y is 0.05-0.3, x is 0.05-0.3, y is 0-0.04 and y is not equal to 0; wherein M is a main metal element selected from one of Ca, Mg, Al, Zn and Fe, N is an auxiliary metal element selected from one of Mg, Al, Zn, Fe, Ni and Cr, and the activity of the main metal element is higher than that of the auxiliary metal element.
2. The method for preparing the long-life negative electrode material for electric power energy storage according to claim 1, wherein the titanium source is nano TiO2(ii) a The lithium source is Li2CO3。
3. The method for preparing a long-life anode material for electric power energy storage according to claim 1 or 2, wherein n (Li) n (Ti) is 0.84-0.86 when the mixing and grinding are performed in the step (1).
4. The method for preparing long-life anode material for electric power energy storage according to claim 1 or 2, wherein the main metal doping source comprises CaO, MgO and Al2O3、ZnO、Fe3O4The auxiliary metal doping source comprises MgO and Al2O3、ZnO、Fe3O4、NiO、Cr2O3One kind of (1).
5. The method for preparing a long-life anode material for electric power energy storage according to claim 1 or 2, wherein the grinding time in the step (2) is 30-90 min.
6. The method for preparing a long-life anode material for electric power energy storage according to claim 1 or 2, wherein the protective gas comprises one of nitrogen or inert gas.
7. Use of the long-life negative electrode material for power energy storage obtained by the preparation method according to any one of claims 1 to 6 in a lithium ion battery.
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