CN109346682B - Preparation method of lithium ion battery cathode composite material - Google Patents

Preparation method of lithium ion battery cathode composite material Download PDF

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CN109346682B
CN109346682B CN201810955999.3A CN201810955999A CN109346682B CN 109346682 B CN109346682 B CN 109346682B CN 201810955999 A CN201810955999 A CN 201810955999A CN 109346682 B CN109346682 B CN 109346682B
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lithium ion
ion battery
composite material
geo
washing
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CN109346682A (en
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郑俊超
宋生超
安长胜
左定川
汤林波
贺振江
童汇
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Central South University
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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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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

A preparation method of a lithium ion battery cathode composite material comprises the following steps: (1) taking Ti3AlC2Adding into hydrofluoric acid water solution; (2) centrifuging the mixed solution I, carrying out first washing until the pH value of the solution is neutral, carrying out ultrasonic treatment, centrifuging again, carrying out second washing, and drying; (3) mixing Ti3C2TxAdding the material into deionized water, adding ammonia water and GeO2Powder; (4) reacting NaBH4Adding into water, dissolving in ice bath to obtain NaBH4An aqueous solution; dripping NaBH into the mixed solution II4And (5) obtaining the lithium ion battery cathode composite material in the aqueous solution. In the invention, T with good appearance is etched by HF acid3iC2TxBy reacting GeOxUniformly grows between MXene layers and on MXene surface, effectively limits GeOxThe volume expansion problem in the charging and discharging process is solved, thereby greatly improving GeOxThe material has stable cycling performance in the charging and discharging processes.

Description

Preparation method of lithium ion battery cathode composite material
Technical Field
The invention relates to a preparation method of a lithium ion battery cathode material, in particular to a lithium ion battery cathode composite material GeOxPreparation method of MXene.
Background
In recent years, with the rapid development of the industry fields of electronic equipment, electric automobiles and the like, the research on energy storage materials with high energy efficiency, environmental friendliness and rich resources becomes a must path for realizing sustainable development of the human society. In order to meet the huge market demand, the performance of the battery material, such as energy density, charge and discharge rate, is far from sufficient by only depending on the performance. The manufacturing cost and energy consumption of the battery, whether the battery pollutes the environment or not and the recycling rate of resources also become important indexes for evaluating battery materials. Therefore, a negative electrode material with more prominent important indexes of battery materials has become a popular subject in the field of lithium ion battery research.
The improvement of the performance of the lithium ion battery is a very critical technology for the development and progress of the times. Currently, researchers have conducted a great deal of research and development work on the search and development of negative electrode materials.
For the negative electrode of lithium ion battery, elemental germanium and its oxide GeO2The material can be used as a lithium ion battery cathode material, the theoretical specific capacity of the material is respectively as high as 1600 mAh/g and 1125 mAh/g, and the material is far higher than that of a common carbon material by 3-4 times. Compared with the silicon element with the same period, the electronic conductivity of the silicon element is 100 times that of silicon, and the ionic conductivity of the silicon element is 400 times that of silicon. However, germanium materials also have defects, and volume expansion can occur in the charging and discharging processes, so that the material structure is cracked and pulverized, and the electrochemical performance is poor.
The two-dimensional layered material can provide excellent environment for lithium ion intercalation, deintercalation and storage, and is a novel material with great development prospect. Currently, the hottest novel two-dimensional material MXene is researched, and by compounding MXene and a metal negative electrode material, the problem of volume expansion of the metal material is limited by using the advantages of an MXene layered structure, the intercalation and deintercalation of lithium ions are promoted, and the advantages are complemented. Provides a certain reference for developing novel electrode materials of lithium ion secondary batteries.
CN107579210A discloses a lithium ion battery cathode material GeOxPreparation method of/CNTs, self-assembled carbon network structure GeOxAlthough the capacity of the/CNTs negative electrode material is greatly improved, the cycle performance is attenuated quickly.
CN107633954A discloses a preparation method of a graphene/MXene composite electrode material, wherein MXene particle materials enter between graphene sheet layers, the agglomeration effect between the graphene sheet layers is overcome, and the usable specific surface area of the graphene/MXene composite electrode material is increased. However, the problems of re-stacking and loss of active regions of the MXene nanosheets are not well solved.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a preparation method of a lithium ion battery cathode composite material with simple operation, and the obtained lithium ion battery cathode composite material has high capacity and good cycle stability.
The technical scheme adopted by the invention for solving the technical problem is that the preparation method of the lithium ion battery cathode composite material comprises the following steps:
(1) taking Ti3AlC2Adding (titanium aluminum carbide) into hydrofluoric acid aqueous solution, heating and stirring, etching, and removing an Al layer to obtain a mixed solution I;
(2) centrifuging the mixed solution I obtained in the step (1), carrying out first washing until the pH value of the solution is neutral, carrying out ultrasonic treatment, centrifuging again, carrying out second washing, and drying to obtain Ti3C2TxMaterial (an MXene material);
(3) ti obtained in the step (2)3C2TxAdding the material into deionized water, ultrasonically dispersing, adding ammonia water and GeO2Stirring and dissolving the powder to obtain a mixed solution II;
(4) reacting NaBH4Adding into water, dissolving in ice bath to obtain NaBH4An aqueous solution; dripping NaBH into the mixed solution II obtained in the step (3)4Stirring, centrifuging, washing and drying in the aqueous solution to obtain the lithium ion battery negative electrode composite GeOx/MXene。
Preferably, in the step (1), the mass fraction of the hydrofluoric acid aqueous solution is 30-50%. Ti3AlC2The mass ratio of the hydrofluoric acid to hydrofluoric acid in the hydrofluoric acid aqueous solution is 1: 6-20. If the concentration of hydrofluoric acid is too low or too high, Ti having a stable structure is hardly formed3C2Tx. The addition of the hydrofluoric acid is too little,the aluminum layer is not fully etched, and the effect is poor; the carbon-aluminum-titanium frame is easy to be etched and damaged due to excessive addition of hydrofluoric acid and over-etching, and an ideal structure cannot be ensured.
Preferably, in the step (1), the heating temperature is 50-120 ℃. Too low or too high a temperature may result in Ti3AlC2Underetching or overetching.
Preferably, in the step (1), the heating time is 5-12 h. Even Ti etching cannot be obtained when the heating time is too short or too long3C2TxA material.
Preferably, in the step (1), the stirring speed is 400-1000 r/min.
Preferably, in the step (2), the ultrasonic time is 0.5-4 h. If the ultrasonic time is too short, Ti can not be treated3C2TxRemoving an Al layer in the two-dimensional nano material; if the ultrasonic time is too long, the sheet material may be broken and the efficiency may be deteriorated.
Preferably, in the step (2), the power of the ultrasonic treatment is 200-400W.
Preferably, in the step (2), the centrifugal rate is 3000-10000 r/min.
Preferably, in the step (2), the first washing is to remove hydrofluoric acid and other impurities in the mixed solution, and the first washing is carried out until the solution is neutral; the first washing can adopt deionized water, and also can adopt the cross washing of deionized water and ethanol. Impurities exist after the ultrasonic treatment, the second washing is to remove the impurities, and the second washing is performed by using deionized water and ethanol in a cross mode; the total number of washing times is more than or equal to 4 times (one time of washing with deionized water and one time of washing with ethanol).
Preferably, in the step (2), the drying temperature is 45-90 ℃ and the drying time is 12-48 h.
Preferably, in step (3), Ti3C2TxAnd GeO2The mass ratio of (A) to (B) is 0.1-1: 1 (more preferably 0.2-0.8: 1).
Preferably, in the step (3), the ammonia content and GeO in the ammonia water2The ratio of the amount of the powder material is 5 to 15: 1. AmmoniaIf the water quantity is insufficient, GeO cannot be generated2And (4) completely reacting.
Preferably, in the step (3), the ultrasonic treatment time is 5-60 min (more preferably 10-30 min). Too short ultrasonic time to make Ti3C2TxThe material forms a homogeneous aqueous suspension.
Preferably, in the step (3), the power of the ultrasound is 200-400W.
Preferably, NaBH added in step (4)4Amount of substance(s) and GeO added in step (3)2The amount ratio of the substance(s) is 3 to 10: 1.
Preferably, in step (4), NaBH4The ice-bath dissolution time is 5-60 min.
Preferably, in the step (4), the mixed solution II obtained in the step (3) is dropped into NaBH4After the aqueous solution is added, the stirring time is 12 to 48 hours (more preferably 18 to 32 hours).
Preferably, in the step (4), washing refers to cross washing with deionized water and ethanol, and the total number of washing is more than or equal to 5 times (one time by using deionized water and one time by using ethanol).
Preferably, in the step (4), the rotation speed of the centrifugation is 3000-10000 r/min (more preferably 4000-7000 r/min).
Preferably, in the step (4), the drying temperature is 45-90 ℃, and the drying time is 12-48 h.
The invention has simple and safe operation and is suitable for Ti3C2TxModification of nano-micro materials with GeOxThe materials are successfully compounded to prepare the high-capacity and good-cycling stability lithium ion battery cathode composite GeOx/MXene。
The invention has the following advantages and positive effects:
(1) in the invention, T with good appearance is etched by HF acid3iC2TxBy reacting GeOxUniformly grows between MXene layers and on MXene surface, effectively limits GeOxThe volume expansion problem in the charging and discharging process is solved, thereby greatly improving GeOxCycling stability of materials during charging and dischargingCan be used.
(2) The lithium ion battery cathode composite material GeO of the inventionxThe lithium ion battery assembled by the MXene has the first discharge capacity of 2340.2 mAh/g within the voltage range of 0.01-3.0V and the current density of 0.1A/g; under the multiplying power of 0.2A/g, 0.5A/g, 1A/g and 2A/g, the first discharge specific capacity is 560.3 mAh/g, 418.0 mAh/g, 317.4 mAh/g and 182.7 mAh/g respectively; description of the composite GeOxThe lithium ion battery assembled by the MXene has high specific capacity and stable cycle performance.
Drawings
FIG. 1 shows GeO, a lithium ion battery negative electrode composite material obtained in example 1 of the present inventionxXRD pattern of/MXene;
FIG. 2, FIG. 3, and FIG. 4 show GeO, which is a negative electrode composite material for lithium ion battery obtained in example 1 of the present inventionxSEM image of/MXene (wherein FIG. 2 is 5000 times magnification, FIG. 3 is 30000 times magnification, and FIG. 4 is 50000 times magnification);
FIG. 5 shows GeO, a lithium ion battery negative electrode composite material obtained in example 1 of the present inventionxthe/MXene is applied to a charge-discharge rate performance curve chart of the lithium ion battery;
FIG. 6 shows GeO, a lithium ion battery negative electrode composite material, obtained in example 1 of the present inventionxthe/MXene is applied to a charge-discharge cycle performance diagram of the lithium ion battery.
Detailed Description
The invention is further illustrated by the following examples and figures.
Examples of the invention the chemicals used in the examples of the invention are, unless otherwise specified, commercially available in a conventional manner.
Example 1
The embodiment comprises the following steps:
(1) adding 30.0 g hydrofluoric acid aqueous solution (mass fraction: 40%) into a polytetrafluoroethylene tank, and adding 1.0 g Ti3AlC2Heating and stirring for 7 h at the constant temperature of 90 ℃ at 600 revolutions per minute, etching, and removing an Al layer to obtain a mixed solution I;
（2）centrifuging the mixed solution I obtained in the step (1) at 10000 r/min, washing the mixed solution I with deionized water until the pH value of a washing solution is neutral, and then performing ultrasonic treatment for 2 hours at 350W; centrifuging again at 5000 r/min, alternately washing with deionized water and anhydrous ethanol for 4 times, vacuum drying at 80 deg.C for 24 hr to obtain MXene powder-Ti3C2TxA material;
(3) taking Ti obtained in the step (2)3C2TxAdding 0.05g of the material into 40 ml of deionized water, performing ultrasonic treatment at 200W for 10 min to obtain a uniform water suspension, adding 2ml of ammonia water with the concentration of 13.38mol/L, stirring at 600 revolutions/min for 1 h, and adding 2.39 mmol of GeO2Continuously stirring the powder (0.25 g) for 1 h at 600 revolutions per minute to obtain a mixed solution II;
(4) 11.84 mmol of NaBH was taken4Adding into 8 ml deionized water, dissolving in ice bath, stirring at 600 r/min for 0.5 h to obtain NaBH4An aqueous solution; then dripping NaBH into the mixed solution II obtained in the step (3)4Continuously stirring the mixture in the aqueous solution for 24 hours at the normal temperature at 600 revolutions per minute; centrifuging at 5000 r/min, alternately washing with deionized water and anhydrous ethanol for 6 times, and drying at 60 deg.C for 24 hr to obtain lithium ion battery negative electrode composite material-GeOxthe/MXene composite material.
FIG. 1 shows GeO, a lithium ion battery negative electrode composite material obtained in example 1 of the present inventionxXRD pattern of/MXene;
FIG. 2, FIG. 3, and FIG. 4 show GeO, which is a negative electrode composite material for lithium ion battery obtained in example 1 of the present inventionxSEM image of/MXene (wherein FIG. 2 is 5000 times magnification, FIG. 3 is 30000 times magnification, and FIG. 4 is 50000 times magnification);
FIG. 5 shows GeO, a lithium ion battery negative electrode composite material obtained in example 1 of the present inventionxthe/MXene is applied to a charge-discharge rate performance curve chart of the lithium ion battery;
FIG. 6 shows GeO, a lithium ion battery negative electrode composite material, obtained in example 1 of the present inventionxthe/MXene is applied to a charge-discharge cycle performance diagram of the lithium ion battery.
As shown in FIG. 1, the lithium ion battery negative electrode composite GeO obtained in the examplexThe peak value on XRD of/MXene is basically consistent with the peak value of the standard substance, and it can be determined that GeO is obtained in the embodiment of the inventionx/MXene, no other impurities were produced.
As shown in FIGS. 2 to 4, the lithium ion battery negative electrode composite GeO obtained in the embodiment of the inventionxin/MXene, GeOxUniformly grow on the MXene surface and between layers, GeOxThe agglomeration problem is well suppressed.
Assembling the battery: 0.08 g of GeO serving as the negative electrode composite material of the lithium ion battery obtained in the embodiment is weighed respectivelyxThe preparation method comprises the following steps of taking MXene as a negative electrode material, adding 0.05g of acetylene black (SP) as a conductive agent and 0.05g of PVDF (HSV-900) as a binder, fully grinding, adding 2mL of NMP for dispersing and mixing, uniformly mixing, then carrying out slurry drawing on a copper foil with the thickness of 16 mu m to prepare a negative electrode plate, taking a metal lithium plate as a positive electrode in an anaerobic glove box, and taking 1mol/L LiPF6A 2025 button cell is assembled by using a mixed solution of ethylene carbonate, dimethyl carbonate and dimethyl carbonate (volume ratio =1:1: 1) as an electrolyte; and testing the constant current charge and discharge performance of the assembled lithium ion battery under the voltage range of 0.01-3.0V.
As shown in FIG. 5, the first discharge capacity of the negative electrode of the assembled lithium ion battery can reach 2340.2 mAh/g under the current density of 0.1A/g; under the multiplying power of 0.2A/g, 0.5A/g, 1A/g and 2A/g, the first discharge specific capacity is 560.3 mAh/g, 418.0 mAh/g, 317.4 mAh/g and 182.7 mAh/g respectively; then, under the multiplying power of 0.1A/g, the specific discharge capacity can still reach 617.2 mAh/g, which indicates that the prepared GeOxthe/MXene composite material has excellent capacity reversibility.
As shown in FIG. 6, under the current density of 0.1A/g, the first reversible specific capacity of the assembled lithium ion battery can reach 1675.6 mAh/g, and after 155 cycles, 601.3 mAh/g still exists.
From the above, the lithium ion battery negative electrode composite material GeO obtained in the embodiment of the inventionxThe lithium ion battery assembled by the MXene has higher specific capacity and good cycling stability.
Example 2
The embodiment comprises the following steps:
(1) adding 30.0 g hydrofluoric acid aqueous solution (mass fraction: 40%) into a polytetrafluoroethylene tank, and adding 1.0 g Ti3AlC2Stirring for 12 hours at the constant temperature of 120 ℃ at 1000 revolutions per minute; etching is carried out, and the Al layer is removed, so as to obtain a mixed solution I;
(2) centrifuging the mixed solution I obtained in the step (1) at 10000 r/min, washing with deionized water until the pH value of the solution is neutral, then performing ultrasonic treatment at 400W for 4 h, alternately washing the precipitate with deionized water and absolute ethyl alcohol at 10000 r/min for 4 times, and performing vacuum drying at 90 ℃ for 12 h to obtain Ti3C2TxMaterial (an MXene material);
(3) ti obtained in the step (2)3C2TxMixing 0.25 g of the material with 40 ml of deionized water, performing ultrasonic treatment at 400W for 60 min to obtain a uniform water suspension, adding 2.5 ml of 13.38mol/L ammonia water, stirring at 1000 rpm for 1 h, and collecting 2.39 mmol of GeO2Adding powder (0.25 g) into the solution, and continuously stirring for 1 h at 1000 r/min to obtain a mixed solution II;
(4) 23.9 mmol of NaBH was taken4Adding into 8 ml deionized water, dissolving in ice bath to obtain NaBH4An aqueous solution; stirring for 0.5 h at 1000 r/min, and then dripping NaBH into the mixed solution II obtained in the step (3)4Continuously stirring the mixture in the water solution for 48 hours at the normal temperature at 1000 rpm; centrifuging at 10000 r/min, alternately washing with deionized water and anhydrous ethanol for 6 times, drying at 90 deg.C for 12 hr to obtain GeO as negative electrode of lithium ion batteryxthe/MXene composite material.
Through detection, the lithium ion battery cathode composite material GeO obtained in the embodiment of the inventionxThe peak value on XRD of/MXene is basically consistent with the peak value of the standard substance, and it can be determined that GeO is obtained in the embodiment of the inventionx/MXene, no other impurities were produced.
Through detection, the lithium ion battery cathode composite material GeO obtained in the embodiment of the inventionxin/MXene, GeOxThe growth is basically on the MXene surface, but the distribution is not particularly uniform.
Assembling the battery: the same as example 1; and testing the constant current charge and discharge performance of the assembled lithium ion battery under the voltage range of 0.01-3.0V.
Through detection, the first discharge capacity of the cathode of the assembled lithium ion battery can reach 1760.2 mAh/g under the current density of 0.1A/g; under the multiplying power of 0.2A/g, 0.5A/g, 1A/g and 2A/g, the first discharge specific capacity is 493.3 mAh/g, 351.4 mAh/g, 212.1 mAh/g and 121.8 mAh/g respectively; then under the multiplying power of 0.1A/g, the specific discharge capacity can still reach 457.2 mAh/g, which shows that the prepared GeOxthe/MXene composite material has good capacity reversibility.
Through detection, under the current density of 0.1A/g, the first reversible specific capacity of the assembled lithium ion battery can reach 1564.7 mAh/g, and after 100 cycles, the first reversible specific capacity is 432.7 mAh/g.
From the above, the lithium ion battery negative electrode composite material GeO obtained in the embodiment of the inventionxThe lithium ion battery assembled by the MXene has higher specific capacity and good cycling stability.
Example 3
The embodiment comprises the following steps:
(1) adding 30.0 g hydrofluoric acid aqueous solution (mass fraction: 40%) into a polytetrafluoroethylene tank, and adding 1.0 g Ti3AlC2Stirring for 5 hours at the constant temperature of 50 ℃ at the speed of 400 r/min, etching, and removing an Al layer to obtain a mixed solution I;
(2) centrifuging the mixed solution I obtained in the step (1) at 3000 r/min, washing with deionized water until the pH value of the solution is neutral, then performing ultrasonic treatment at 200W for 0.5 h, performing cross washing on the precipitate with deionized water and absolute ethyl alcohol at 3000 r/min for 4 times, and performing vacuum drying at 45 ℃ for 48 h to obtain Ti3C2TxMaterial (an MXene material);
(3) ti obtained in the step (2)3C2TxMixing 0.025 g of material with 40 ml of deionized water, performing ultrasonic treatment at 200W for 5 min to obtain uniform water suspension, adding 1 ml of 13.38mol/L ammonia water, stirring at 400 rpm for 1 h, and collecting 2.39 mmol GeO2Adding powder (0.25 g) into the solution, and continuously stirring for 1 h at 400 r/min to obtain a mixed solution II;
(4) taking 7 mmol NaBH4Adding into 8 ml deionized water, dissolving in ice bath, and stirring at 400 r/min for 0.5 h. Then dripping NaBH into the mixed solution II obtained in the step (3)4Stirring the aqueous solution at the normal temperature at 400 r/min for 12 h. Centrifuging at 5000 r/min, alternately washing with deionized water and anhydrous ethanol for 6 times, drying at 45 deg.C for 48 hr to obtain GeO as negative electrode of lithium ion batteryxthe/MXene composite material.
Through detection, the lithium ion battery cathode composite material GeO obtained in the embodiment of the inventionxThe peak value on XRD of/MXene is basically consistent with the peak value of the standard substance, and it can be determined that GeO is obtained in the embodiment of the inventionx/MXene, no impurities were produced.
Through detection, the lithium ion battery cathode composite material GeO obtained in the embodiment of the inventionxin/MXene, GeOxGrows on MXene surface more uniformly but because of GeOxWhen the amount is too large, a partial agglomeration phenomenon occurs.
Assembling the battery: the same as example 1; and testing the constant current charge and discharge performance of the assembled lithium ion battery under the voltage range of 0.01-3.0V.
Through detection, the first discharge capacity of the cathode of the assembled lithium ion battery can reach 1915.2 mAh/g under the current density of 0.1A/g; under the multiplying power of 0.2A/g, 0.5A/g, 1A/g and 2A/g, the first discharge specific capacity is 483.5.2 mAh/g, 359.7 mAh/g, 278.2 mAh/g and 148.7 mAh/g respectively; then, under the multiplying power of 0.1A/g, the specific discharge capacity can still reach 361.1 mAh/g, which indicates that the prepared GeOxthe/MXene composite material has a high initial discharge capacity but a slightly poor capacity reversibility.
Through detection, under the current density of 0.1A/g, the first reversible specific capacity of the assembled lithium ion battery can reach 1705.2 mAh/g, and is 353.8 mAh/g after 100 cycles.
From the above, the lithium ion battery negative electrode composite material GeO obtained in the embodiment of the inventionxLithium ion assembled by MXeneThe battery has higher initial specific capacity and good cycling stability.
Example 4
The embodiment comprises the following steps:
(1) adding 30.0 g hydrofluoric acid aqueous solution (mass fraction: 40%) into a polytetrafluoroethylene tank, and adding 1.0 g Ti3AlC2Stirring for 7 hours at the constant temperature of 90 ℃ at the speed of 600 r/min, etching, and removing an Al layer to obtain a mixed solution I;
(2) centrifuging the mixed solution I obtained in the step (1) at 10000 r/min, washing with deionized water until the pH value of the solution is neutral, then performing ultrasonic treatment for 2 h at 350W, then centrifuging at 5000 r/min, then performing cross washing for 4 times by using deionized water and absolute ethyl alcohol, and performing vacuum drying for 24 h at 60 ℃ to obtain Ti3C2TxMaterial (an MXene material);
(3) ti obtained in the step (2)3C2TxMixing 0.1 g of the material with 40 ml of deionized water, performing ultrasonic treatment at 350W for 10 min to obtain a uniform water suspension, adding 1.5 ml of 13.38mol/L ammonia water, stirring at 600 rpm for 1 h, and collecting 2.39 mmol of GeO2Adding powder (0.25 g) into the solution, and continuously stirring for 1 h at 600 revolutions per minute to obtain a mixed solution II;
(4) 11.84 mmol of NaBH was taken4Adding into 8 ml deionized water, dissolving in ice bath, and stirring at 600 r/min for 0.5 h. Then dripping NaBH into the mixed solution II obtained in the step (3)4Stirring the mixture in the water solution at the normal temperature for 24 hours at 600 revolutions per minute; centrifuging at 6000 r/min, alternately washing with deionized water and anhydrous ethanol for 6 times, drying at 60 deg.C for 24 hr to obtain GeO as cathode of lithium ion batteryxthe/MXene composite material.
Through detection, the lithium ion battery cathode composite material GeO obtained in the embodiment of the inventionxThe peak value on XRD of/MXene is basically consistent with the peak value of the standard substance, and it can be determined that GeO is obtained in the embodiment of the inventionx/MXene, no impurities were produced.
Through detection, the lithium ion battery cathode composite material GeO obtained in the embodiment of the inventionxIn the case of/MXene,GeOxthe MXene grows on the surface and between layers more uniformly.
Assembling the battery: the same as example 1; and testing the constant current charge and discharge performance of the assembled lithium ion battery under the voltage range of 0.01-3.0V.
Through detection, the first discharge capacity of the cathode of the assembled lithium ion battery can reach 2110.7 mAh/g under the current density of 0.1A/g; under the multiplying power of 0.2A/g, 0.5A/g, 1A/g and 2A/g, the first discharge specific capacity is 537.2 mAh/g, 386.2 mAh/g, 281.4 mAh/g and 183.2 mAh/g respectively; then under the multiplying power of 0.1A/g, the specific discharge capacity can still reach 524.8 mAh/g, which shows that the prepared GeOxthe/MXene composite material has excellent capacity reversibility.
Through detection, under the current density of 0.1A/g, the first reversible specific capacity of the assembled lithium ion battery can reach 1854.7 mAh/g, and after 100 cycles, the first reversible specific capacity is 513.6 mAh/g.
From the above, the lithium ion battery negative electrode composite material GeO obtained in the embodiment of the inventionxThe lithium ion battery assembled by the MXene has higher specific capacity and good cycling stability.
Comparative example 1
(1) 2.39 mmol of GeO are taken2Adding 40 ml of deionized water into the powder, stirring for 0.5 h, adding 2ml of 13.38mol/L ammonia water, and continuously stirring for 1 h to obtain a mixed solution;
(2) 11.84 mmol of NaBH was taken4Adding into 8 ml deionized water, dissolving in ice bath, stirring at 600 r/min for 0.5 h to obtain NaBH4An aqueous solution;
(3) dripping the mixed solution obtained in the step (1) into NaBH obtained in the step (2)4Stirring the aqueous solution at 600 rpm for 24 h at normal temperature. Centrifuging at 6000 r/min, alternately washing the precipitate with deionized water and anhydrous ethanol for 6 times, drying at 60 deg.C for 24 hr to obtain GeO as negative electrode of lithium ion batteryxA material.
Through detection, the lithium ion battery cathode material GeO obtained in the embodiment of the inventionxThe peak value on XRD is basically consistent with that of the standard product, and it can be confirmed that GeO is obtained in the embodiment of the inventionx。
Through detection, the lithium ion battery cathode material GeO obtained in the embodiment of the inventionx，GeOxThe particle size is more uniform, and is 80-150 nm, but the agglomeration phenomenon is very serious.
Assembling the battery: the same as example 1; and testing the constant-current charge and discharge performance of the assembled lithium ion battery under the voltage range of 0.. 01-3.0V.
Through detection, the first discharge capacity of the cathode of the assembled lithium ion battery can reach 2221.5 mAh/g under the current density of 0.1A/g; under the multiplying power of 0.2A/g, 0.5A/g, 1A/g and 2A/g, the first discharge specific capacity is 671.3 mAh/g, 426.5 mAh/g, 388.4 mAh/g and 184.4 mAh/g respectively; GeO illustrating the preparationxThe capacity of the material decays rapidly.
Through detection, under the current density of 0.1A/g, the first reversible specific capacity of the assembled lithium ion battery can reach 2040 mAh/g, and the capacity is attenuated to 577.6 mAh/g after 50 times of circulation.
From the above, the lithium ion battery negative electrode material GeO obtained in the embodiment of the inventionxThe assembled lithium ion battery has higher initial specific capacity, but the capacity is quickly attenuated, and the capacity reversibility is poor.
In summary, the lithium ion battery negative electrode composite material GeO obtained in the embodiments 1-4 of the inventionxCompared with the lithium ion battery cathode composite material GeO obtained in the comparative example, the lithium ion battery assembled by MXenexThe assembled lithium ion battery has more excellent electrochemical performance and higher capacity retention rate, and the lithium ion battery cathode composite material GeO obtained in the embodiments 1-4 of the invention is shownxThe lithium ion battery assembled by the/MXene is more stable in the long-range charge and discharge process. This is due to inhibition of GeO by MXenexThe volume change of the material in the charging and discharging process improves the rate capability and the cycle stability of the material. Meanwhile, the 3D frame constructed by MXene is beneficial to the transmission of electrons, provides a channel for lithium ion diffusion and improves the electrochemical performance of the material.

Claims (10)

1. The preparation method of the lithium ion battery cathode composite material is characterized by comprising the following steps of:
(1) taking Ti3AlC2Adding the mixed solution into hydrofluoric acid aqueous solution, heating and stirring, etching, and removing an Al layer to obtain a mixed solution I;
(2) centrifuging the mixed solution I obtained in the step (1), carrying out first washing until the pH value of the solution is neutral, carrying out ultrasonic treatment, centrifuging again, carrying out second washing, and drying to obtain Ti3C2TxA material;
(3) ti obtained in the step (2)3C2TxAdding the material into deionized water, ultrasonically dispersing, adding ammonia water and GeO2Stirring and dissolving the powder to obtain a mixed solution II;
(4) reacting NaBH4Adding the mixture into water, and dissolving the mixture in ice bath to obtain NaBH4 aqueous solution; dripping NaBH into the mixed solution II obtained in the step (3)4Stirring, centrifuging, washing and drying in the aqueous solution to obtain a lithium ion battery negative electrode composite material-GeOx/MXene; added NaBH4Amount of substance(s) and GeO added in step (3)2The amount ratio of the substance(s) is 3 to 10: 1.
2. The preparation method of the lithium ion battery cathode composite material according to claim 1, wherein in the step (1), the mass fraction of the hydrofluoric acid aqueous solution is 30% -50%; ti3AlC2The mass ratio of the hydrofluoric acid to hydrofluoric acid in the hydrofluoric acid aqueous solution is 1: 6-20.
3. The preparation method of the lithium ion battery negative electrode composite material according to claim 1 or 2, wherein in the step (1), the heating temperature is 50-120 ℃, and the heating time is 5-12 h; the stirring speed is 400-1000 r/min.
4. The preparation method of the lithium ion battery negative electrode composite material according to claim 1 or 2, wherein in the step (2), the ultrasonic time is 0.5-4 h; the power of ultrasonic treatment is 200-400W.
5. The preparation method of the lithium ion battery negative electrode composite material according to claim 1 or 2, wherein in the step (2), the centrifugation rate is 3000-10000 r/min.
6. The method for preparing the lithium ion battery anode composite material according to claim 1 or 2, wherein in the step (2), the second washing is performed by cross washing with deionized water and ethanol; the total washing times are more than or equal to 4 times; the drying temperature is 45-90 ℃, and the drying time is 12-48 h.
7. The method for preparing the negative electrode composite material for the lithium ion battery according to claim 1 or 2, wherein in the step (3), Ti3C2TxAnd GeO2The mass ratio of (A) to (B) is 0.1-1: 1; amount of ammonia-containing substance in aqueous ammonia and GeO2The ratio of the amount of the powder material is 5 to 15: 1.
8. The preparation method of the lithium ion battery cathode composite material according to claim 1 or 2, wherein in the step (3), the ultrasonic time is 5-60 min; the power of the ultrasonic wave is 200-400W.
9. The preparation method of the lithium ion battery anode composite material according to claim 1 or 2, wherein in the step (4), NaBH is added4The ice-bath dissolution time is 5-60 min; dripping NaBH into the mixed solution II obtained in the step (3)4And after the water solution is added, stirring for 12-48 h.
10. The preparation method of the lithium ion battery cathode composite material according to claim 1 or 2, wherein in the step (4), the washing refers to cross washing with deionized water and ethanol, and the total washing times are more than or equal to 5 times; the centrifugal rotating speed is 3000-10000 r/min; the drying temperature is 45-90 ℃, and the drying time is 12-48 h.
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