CN113651356B - Preparation method and application of titanium dioxide graphene complex with core-shell cavity structure - Google Patents

Preparation method and application of titanium dioxide graphene complex with core-shell cavity structure Download PDF

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CN113651356B
CN113651356B CN202110941341.9A CN202110941341A CN113651356B CN 113651356 B CN113651356 B CN 113651356B CN 202110941341 A CN202110941341 A CN 202110941341A CN 113651356 B CN113651356 B CN 113651356B
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赵睿
冉柯
宋金铃
薛卫东
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University of Electronic Science and Technology of China
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Abstract

The invention relates to a preparation method and application of a titanium dioxide graphene complex with a core-shell cavity structure, and belongs to the technical field of nano materials. The aim is to improve the electrochemical cycling stability and the cycling ratio capacity of the material. The main scheme comprises the steps of firstly preparing a mixture of graphene and potassium chloride salt by an ionothermal method by taking potassium chloride as a salt template and metal-free phthalocyanine as a carbon source and a nitrogen source, then hydrolyzing isopropyl titanate in ethanol, enabling a layer of titanium dioxide to uniformly grow on the surface of the graphene under the action of a hexadecylamine surfactant, and finally centrifuging, washing and drying to obtain the titanium dioxide graphene complex with the core-shell cavity structure. And the lithium ion battery can be successfully applied to the lithium ion battery, and has the advantages of good long cycle stability, high cycle specific capacity and excellent electrochemical performance.

Description

Preparation method and application of titanium dioxide graphene complex with core-shell cavity structure
Technical Field
The invention relates to a preparation method of a titanium dioxide graphene complex with a core-shell cavity structure and application of the titanium dioxide graphene complex as an anode material of a lithium ion battery, and belongs to the technical field of nano materials.
Background
Global petroleum resources and other conventional energy sources are becoming more and more scarce, and development and utilization of novel renewable energy sources, such as solar energy, wind energy, tidal power and the like, are urgently required at present. But the power system requires a stable and continuous power supply, but wind and solar energy are intermittent and unstable in nature, which has prompted the development and research of rechargeable secondary batteries. Conventional lead-acid batteries, nickel-cadmium batteries and nickel hydride batteries have some disadvantages, such as short service life, environmental pollution and low energy density, which greatly limit their large-scale commercial applications. At present, the main task of the battery industry is to find rechargeable secondary batteries to replace the traditional lead-acid batteries and nickel-cadmium storage batteries, and to develop non-toxic and non-polluting electrode materials and battery separators, and non-polluting batteries are urgent. Compared with the traditional secondary chemical battery, the Lithium Ion Battery (LIBS) has a dominant position in electronic products, and with the technological progress, various electric automobiles and electronic products are rapidly applied and developed, so that people have higher pursuit on the lithium ion battery, and the development of materials with high safety, good cycle stability and high specific capacity has become the object of people for pursuing excellent electrochemical performance of the lithium ion battery.
The traditional carbon material as the lithium battery anode has many potential safety hazards, for example, the insertion and extraction processes of lithium ions can cause the volume change of the electrode surface and the formation of lithium dendrites, thereby easily causing the short circuit or explosion of the battery, so that the graphene is generally used as the anode material of the lithium ion battery, and is generally compounded with other transition metal oxides, and the graphene compound is used as the lithium ion battery anode. Transition metal oxides such as titanium dioxide, manganese dioxide, etc. are the hot spots of research.
The Ti-based material has high reversible lithium ion storage capacity, long cycle life and high safety, and the low-cost electrode material can effectively avoid the deposition of lithium metal. In addition, the Ti-based material has a certain oxygen absorption function at high temperature and has obvious safety, so that the Ti-based material is considered as an ideal anode material. Wherein, TiO2The lithium ion battery has the advantages of high safety, proper lithium storage voltage platform, stable structure, low power consumption, low raw material price, simple preparation method and high theoretical electrochemical performance index. In addition, TiO as anode material for Lithium Ion Batteries (LIBS)2Has a high operating voltage of about 1.75V, which can suppress the generation of lithium dendrites and improve safety. However, TiO2Still have some disadvantages in practical applications. Since it is a semiconductor material (band gap 3.2 eV),both the electron conductivity and the ion conductivity are low, which results in a reduction in lithium ion diffusion and deintercalation properties; in addition, are present in TiO2Especially nano-TiO2The hydroxyl groups on the surface of the material will react with the electrolyte during charging and discharging. These affect their electrochemical performance, resulting in reduced cycling performance and rate performance. Therefore, the advantages of two materials can be fully exerted by coating the graphene with the titanium dioxide, and the improvement of TiO is mainly focused on2The material has the advantages of long cycle life, high safety, good electronic conductivity and good ionic conductivity, and can complement the mutual defects of the electronic conductivity and the ionic conductivity to synthesize the titanium dioxide graphene complex lithium battery anode material with the core-shell cavity structure.
Disclosure of Invention
The invention provides a preparation method of a titanium dioxide graphene complex with a core-shell cavity structure and application of the titanium dioxide graphene complex as an anode material of a lithium ion battery, and aims to improve the electrochemical cycling stability and the cycling specific capacity of the material.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the invention discloses a preparation method of a titanium dioxide graphene complex with a core-shell cavity structure and application of the titanium dioxide graphene complex as an anode material of a lithium ion battery.
The invention provides a preparation method of a titanium dioxide graphene complex with a core-shell cavity structure, which comprises the following specific steps:
step (1): weighing 200-220 ml of ethanol and 40-50 ml of cyclohexane, mixing and stirring, then adding 0.10-0.20 g of metal-free phthalocyanine, mixing and stirring until the metal-free phthalocyanine is fully dissolved, simultaneously soaking the reaction container in an ice-water bath environment (-1 to 1 ℃), continuously dropwise adding 50-60 ml of saturated potassium chloride solution, continuously stirring, aging in an ice-water bath environment after dropwise adding, cleaning with ethanol (washing all cyclohexane away) after aging, filtering with a microporous filtering membrane (organic system), collecting the product, vacuum drying for 8 hours at 60-80 ℃, and finally obtaining a composite precursor of phthalocyanine particles and potassium chloride salt, which is marked as Pc/KCl;
step (2): transferring the composite precursor of the phthalocyanine particles and the potassium chloride salt prepared in the step (1) into a quartz tube for drying, placing the quartz tube into a tube furnace for high-temperature sintering, calcining the quartz tube in the tube furnace in an inert gas atmosphere at 700 ℃ for 8h, and naturally cooling the quartz tube to room temperature to carbonize the composite precursor into a two-dimensional thin graphene sheet layer with a regular cubic structure;
and (3): taking 1-2 g of the two-dimensional thin-layer graphene sheet layer with the regular cubic structure in the step (2), adding the two-dimensional thin-layer graphene sheet layer into 150-170 ml of ethanol solution for ultrasonic treatment, then adding 0.1-0.3 g of hexadecylamine, continuously stirring, then dropwise adding 10 mu l of deionized water every 10 min, and continuously stirring for 24 hours to obtain a uniform dispersion solution of the titanium dioxide graphene complex; finally, centrifuging and drying to finally obtain a titanium dioxide graphene complex with a core-shell cavity structure, which is marked as 24-G @ TiO2。
In the technical scheme, the metal-free phthalocyanine is used as a carbon source and a nitrogen source, potassium chloride (the melting point is 750 ℃) is used as a salt template, and a mixture of graphene and potassium chloride salt is prepared by an anti-solvent method.
In the above technical scheme, in the step (2), the inert gas atmosphere is Ar gas or nitrogen gas; the temperature rising procedure of sintering in the tube furnace is as follows: introducing argon at room temperature for 1 h, and then introducing argon at 5 ℃ for min-1The temperature is raised to 300 ℃ at the temperature raising rate, then the temperature is kept for 1 h, and then the temperature is raised to 2 ℃ for min-1The temperature is raised to 700 ℃, the temperature is kept for 8 hours, and then the temperature is naturally cooled to the room temperature.
In the technical scheme, in the step (3), hexadecylamine is used as a surfactant, and the hydrolysis time of titanium dioxide is 24 hours.
The invention also discloses an application of the titanium dioxide graphene complex with the core-shell cavity structure, which is prepared by the preparation method, namely the titanium dioxide graphene complex is used as an anode material of a lithium ion battery.
Compared with the prior art, the invention has the beneficial effects that:
1. the titanium dioxide graphene complex with the core-shell cavity structure is prepared by adopting conventional medicines through salt template, calcination and hydrolysis, the preparation method and the equipment of the product are simple, the used raw materials are easy to obtain, the titanium dioxide graphene complex is actually applied to a lithium ion battery and shows excellent long-cycle stability, and the capacity of 180 mAh g can be kept after stable cycle lasts 4000 circles-1The long cycle capacity and the final high capacity are better than the materials reported at present.
2. The invention researches the influence of different titanium dioxide hydrolysis time on the electrochemical performance, and obtains the optimal hydrolysis time of 24h according to the specific capacity of the battery by adding the cycle diagrams of the composite materials with different hydrolysis time.
3. The invention uses high-concentration ethanol with the concentration of 99.7 percent, aims to wash away cyclohexane, simultaneously does not wash away potassium chloride salt particles coated inside, and can cause explosion danger when sintering at high temperature in a tube furnace subsequently if cyclohexane cannot be completely washed away. If washed with water, the salt will be washed away; or other organic solvent, and even after washing away cyclohexane, the organic solvent itself remains, and therefore has a great influence on the product.
Drawings
Fig. 1 is SEM photographs of two-dimensional thin-layer graphene sheets sintered at different temperatures of 500 ℃, 700 ℃ and 900 ℃ obtained in example 1 of the present invention, which correspond to fig. 1 (a), fig. 1 (b) and fig. 1 (c), respectively;
FIG. 2 is the core-shell cavity structure titanium dioxide graphene composite 18-G @ TiO obtained in this example 12SEM image with magnification of × 2000;
FIG. 3 is the titanium dioxide graphene composite 24-G @ TiO with core-shell cavity structure obtained in this example 12SEM image with magnification of × 2000;
FIG. 4 shows a core-shell cavity structure titanium dioxide graphene composite 30-G @ TiO obtained in this example 12SEM image with magnification of × 2000;
FIG. 5 shows a core-shell cavity structure titanium dioxide graphene complex 18-G @ TiO2 with different time gradients obtained in example 1 of the present invention2、24-G@TiO2And 30-G @ TiO2At 1 A.g-1At a current density of (2), the voltage range tested was 0.01V
Figure 549954DEST_PATH_IMAGE002
2.5V (vs Li/Li) +) The long cycle performance diagram of the lithium ion battery of (1);
FIG. 6 shows the core-shell G @ TiO obtained in example 1 of the present invention2Thermogravimetric analysis of C in composite (TG-DTG).
FIG. 7 shows the 24-G @ TiO obtained in example 1 of the present invention2Impedance plots of lithium ion batteries at initial state, cycle 2, cycle 3, and cycle 4.
FIG. 8 shows the 24-G @ TiO obtained in example 1 of the present invention2And (3) a multiplying power cycle performance diagram of the lithium ion battery under different current densities.
FIG. 9 shows the 24-G @ TiO obtained in example 1 of the present invention2CV curve diagram of the lithium ion battery of the first circle and the second circle under the sweeping speed of 0.1 mv/s.
FIG. 10 shows 24-G @ TiO obtained in example 1 of the present invention2At different sweep speeds of 0.1mv s-1、0.4 mv·s-1、0.6 mv·s-1、0.8 mv·s-1And 1mv s-1CV curve of lithium ion battery.
Detailed Description
The following detailed description of the embodiments of the present invention is provided with reference to the drawings and specific embodiments, which are implemented on the premise of the technical solution of the present invention, and the detailed embodiments and specific operation procedures are provided, but the scope of the present invention is not limited to the following embodiments.
The experimental methods used in the following examples are all conventional methods unless otherwise specified.
Reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
The titanium dioxide graphene complex with the core-shell cavity structure is used as a battery anode, and the experimental part for specifically manufacturing the battery electrode is as follows:
a working electrode was manufactured by mixing 80% of an active material, 10% of a conductive agent (Super P), and 10% of a binder, namely, polyvinylidene-dipropyleneboron difluoride (PVDF), using N-methyl-2-pyrrolidone (NMP) as a solvent, and the resulting slurry was pasted on a Cu foil and dried in a vacuum oven at 70 ℃ for 12 hours. To perform electrochemical measurements of lithium ion batteries, 1M LiPF6 was prepared in a 1:1 (v/v) mixed solution containing ethylene carbonate and diethyl carbonate (EC/DEC) using a Celgard 2500 membrane as a separator and used as an electrolyte to assemble CR2032 coin cells in an argon filled glove box. The battery test system was tested at 1.0-3.0V (vs. Li/Li) using LAND-CT2001A+) The voltage electrostatic discharge charge curve is measured over a voltage range of (1).
Example 1
Step (1): measuring 200
Figure 201515DEST_PATH_IMAGE002
220 ml of ethanol and 40
Figure 715673DEST_PATH_IMAGE002
50 ml of cyclohexane are mixed and stirred and then 0.10 ml of cyclohexane is added
Figure 845303DEST_PATH_IMAGE002
0.20 g of metal-free phthalocyanine is mixed and stirred until the metal-free phthalocyanine is fully dissolved, meanwhile, the reaction container is soaked in an ice-water bath environment (-1 to 1 ℃), 50 to 60 ml of saturated potassium chloride solution is continuously dripped, the mixture is continuously stirred, after the dripping is finished, the mixture is aged in the ice-water bath environment, after the aging is finished, the mixture is cleaned by ethanol (cyclohexane is completely cleaned), filtered by a microporous filtering membrane (organic system), and then the product is collected to 60 to 80 ℃ for vacuum drying for 8 hours, and finally, the composite precursor of phthalocyanine particles and potassium chloride salt is recorded as Pc/KCl;
step (2): transferring the composite precursor of the phthalocyanine particles and the potassium chloride salt prepared in the step (1) into a quartz tube for drying, placing the quartz tube into a tube furnace for high-temperature sintering, calcining the quartz tube in the tube furnace in an inert gas atmosphere at 700 ℃ for 8h, and naturally cooling the quartz tube to room temperature to carbonize the composite precursor into a two-dimensional thin graphene sheet layer with a regular cubic structure;
and (3): taking the two-dimensional thin-layer graphene sheet layer 1 with the regular cubic structure in the step (2)
Figure 518730DEST_PATH_IMAGE002
2 g, adding the mixture into 150-170 ml of ethanol solution, performing ultrasonic treatment, adding 0.1-0.3 g of hexadecylamine, continuously stirring, dropwise adding 10 mu l of deionized water every 10 min, controlling different hydrolysis time to ensure that the thicknesses of titanium dioxide on the surface of graphene are different, setting 3 groups of comparison experiments with different hydrolysis time, wherein the hydrolysis time is 18h, 24h and 30h respectively, and obtaining uniform dispersion solution of a titanium dioxide graphene complex; and finally, centrifuging and drying to obtain a titanium dioxide graphene complex with a core-shell cavity structure, wherein the complex is marked as 18-G @ TiO2, 24-G @ TiO2 and 30-G @ TiO 2. By researching the difference of electrochemical properties, the optimal hydrolysis coating time is 24 h.
Fig. 1 is SEM photographs of two-dimensional thin-layer graphene sheets sintered at different temperatures of 500 ℃, 700 ℃ and 900 ℃ obtained in example 1 of the present invention, which correspond to fig. 1 (a), fig. 1 (b) and fig. 1 (c), respectively. As can be clearly seen from fig. 1 (b), cubic potassium chloride salt particles sintered at 700 ℃ are very uniform, regularly stacked in morphology, and a layer of layered graphene is uniformly coated on the surfaces of the cubic salt particles.
A comparison sample of 500 ℃ and 900 ℃ is also made in a tube furnace in inert gas atmosphere, the SEM picture 1 (a) shows that the crystal face of the cubic salt crystal of potassium chloride sintered at 500 ℃ is smooth, no metal carbon source molecules have adsorption and spreading behaviors on the crystal face, the SEM picture 1 (c) shows that at 900 ℃, no metal phthalocyanine is cracked to obtain a two-dimensional carbon material structure after roasting, and at the temperature, the cubic crystal presented by molten salt is not perfect after the molten salt chlorination is carried out in a sodium solid-liquid-solid stage. So the sample at this sintering temperature for the optimum 700 ℃ was finally selected for further study.
FIG. 2 shows 18-G @ TiO obtained in example 12The scanning photograph of (2) is magnified × 2000. In the process of synthesizing the titanium dioxide graphene composite material with the core-shell cavity structure by using the two-dimensional thin graphene sheets with the cubic structure, after 18 hours of hydrolysis of isopropyl titanate, uniformly coating a layer of thin titanium dioxide on the surfaces of the two-dimensional thin graphene sheets with the cubic structure, and performing operations such as centrifugation, washing and the like to obtain the structure shown in fig. 2. As can be seen from the figure, the synthesized 18-G @ TiO2The surface-coated titanium dioxide of the composite material is very uniform but thin.
FIG. 3 shows the 24-G @ TiO obtained in example 12The scanning photograph of (2) is magnified × 2000. In the process of synthesizing the titanium dioxide graphene composite material with the core-shell cavity structure by using the two-dimensional thin-layer graphene sheet with the cubic structure, after 24 hours of hydrolysis of isopropyl titanate, uniformly coating a layer of titanium dioxide on the surface of the two-dimensional thin-layer graphene sheet with the cubic structure, and performing operations such as centrifugation, washing and the like to obtain the structure shown in fig. 2. As can be seen from the figure, the synthesized 24-G @ TiO2The titanium dioxide coated on the surface of the composite material is very uniform, and after washing, some core-shell cavity structures still keep cubic structures, and some core-shell cavity structures have opened a window.
FIG. 4 shows 30-G @ TiO obtained in example 12The scanning photograph of (2) is magnified × 2000. As can be seen from the figure, the synthesized 30-G @ TiO2The titanium dioxide coated on the surface of the composite material is uneven, rod-shaped titanium dioxide appears, and the hydrolysis time of isopropyl titanate is too long, so that the titanium dioxide is excessively attached to the surface of the cubic graphene, and the structure is slightly collapsed.
FIG. 5 shows 18-G @ TiO obtained in example 12 、24-G@TiO2 、30-G@TiO2The cycle performance after assembly into a CR2032 cell is shown in (1A · g)-1At a current density of (2), the test voltage range is 0.01
Figure 341192DEST_PATH_IMAGE002
2.5V (vs Li/Li)+)). The comparison found that 18-G @ TiO2Can stably circulate 4000 circles, and the first discharge specific capacity of the battery is 325 mAh g-1The cycle curve shows that the first 100 circles are decreased and then start to continuously and stably increase to 3500 circles and then keep stable, and finally the capacity can be kept at 139 mAh g-1The capacity retention rate is 42.1%; 24-G @ TiO2Can also stably circulate 4000 circles, and the first discharge specific capacity of the battery is 380 mAh g-1The circulation curve shows that the first 100 circles of the circulation curve firstly decline and then continuously and stably rise to 3000 circles of the circulation curve, and finally the capacity can be kept at 180 mAh g-1The capacity retention rate is 46.6%;
30-G@TiO2can also stably circulate about 4000 circles, and the first discharge specific capacity of the battery is 300 mAh.g-1The cycle curve shows that the first 100 circles are decreased and then start to continuously and stably increase to 3500 circles and then keep stable, and finally the capacity can be kept at 130.3 mAh g-1The capacity retention rate is 43.3%; by contrast of 18-G @ TiO2 、24-G@TiO2 、30-G@TiO2After the respective long cycle performance, we can obtain 24-G @ TiO2Has optimal electrochemical performance and capacity, and can maintain the capacity of 180 mAh g after long circulation of 4000 circles-1The long cycle capacity and the final high capacity are better than the materials reported at present. Therefore, the following other characterization tests mainly focused on 24-G @ TiO2。
FIG. 6 shows the synthesis of 24-G @ TiO for the purpose of exploring2The content of C in example 1 was thermogravimetric analysis (TG-DTG) performed in an air atmosphere at a temperature ranging from 30 deg.C
Figure 342646DEST_PATH_IMAGE002
The temperature rise rate is 10 ℃ min at 700 DEG C-1. Core-shell TiO can be observed2The mass percentage of the @ G composite material is obviously reduced within the temperature range of 30-700 ℃, and two platforms appear, which show that 24-G @ TiO in the temperature rising process2Water molecule head ofEvaporation first, resulting in a decrease in mass percent; then the carbon in the composite material reacts with air to generate carbon dioxide gas, and the oxidation of the composite material is considered, so that the carbon dioxide gas with the concentration of 24-G @ TiO can be obtained2The content of C in the product is 8.12%.
Fig. 7 is an Electrochemical Impedance Spectroscopy (EIS) of the titanium dioxide graphene composite material with the core-shell cavity structure obtained in example 1, and it can be clearly seen from the EIS that the first circle of black impedance curve has a significant large semicircular arc in the high-frequency region, which is the impedance generated by typical charge transfer; the impedance curves of turns 2, 3, 4 and 3500 form two small half-arcs in the front large arc region, the radius of the half-arc gradually decreasing during the cycle, which means that the charge transfer impedance (Rct) gradually decreases. This apparent change indicates graphene and TiO 2The contact and the electric contact among the particles of the nano sheets are enhanced, which is related to the special core-shell cavity structure of the composite material, and as can be seen from the figure, 3 lines of the front small semicircle are almost overlapped, which shows that the charge transfer resistance is generated by the intercalation of lithium ions on the surface of an active material; the three lines of the rear semicircle are not overlapped, which shows that the SEI film changes under different charging and discharging turns; finally, the oblique lines in the low-frequency region are parallel and gradually stable after 2-4 cycles, and the structural stability is good. The cubic structure of the titanium dioxide graphene composite material with the core-shell cavity structure always keeps a stable structure beneficial to Li + diffusion in the charge-discharge cycle process. In short, the EIS results reveal 24-G @ TiO2The material has excellent Li + storage capacity.
FIG. 8 shows the 24-G @ TiO obtained in this example2The rate profiles were used as lithium ion batteries at different current densities. The 24-G @ TiO can be clearly seen from the figure2At a low current density of 0.2 A.g-1The specific capacity of the battery can reach 225 mAh.g-1The specific capacity of the battery is reduced in a step-like manner along with the increase of the current density, and when the current density is 5 A.g-1The capacity was maintained at 100 mAh g-1Left and right, average discharge capacityThe amount of the catalyst can still reach 0.2 A.g-145% of (a), indicating 24-G @ TiO2The special cubic structure of the core-shell cavity has excellent adaptability to charge and discharge current; the capacity gradually increased with the decrease of the current density, and it can be seen from the figure that the current density was again 0.2A · g-1In the process, the capacity can be recovered quickly, and almost no attenuation exists, which shows that the battery has good capacity retention rate, good cycle stability, high reversibility and good rate performance.
FIG. 9 shows 24-G @ TiO prepared in this example2At a sweep rate of 0.1 A.g-1The following CV curve graph, which is obvious to us from the figure, is the CV curve graph of titanium dioxide, and also has a typical carbon oxidation reduction peak, and also proves that the composite material of the titanium dioxide and graphene of the material has a reduced CV curve area at the second circle, which proves that an SEI film is formed.
FIG. 10 is a graph showing 24-G @ TiO at different sweeps2From the graph we can see that the curve is very reproducible and has distinct oxidation and reduction peaks and that the area of the curve increases with increasing sweep number, and that after the first four cycles the CV curve shows two corresponding peaks at different scan rates, indicating typical Ti4+/Ti 3+A redox couple. In contrast, voltage hysteresis becomes severe at higher scan rates; this phenomenon is common in titanium dioxide graphene composites and is due to a sharp increase in the polarization reaction.
In conclusion, by controlling different hydrolysis times, the difference of electrochemical properties is explored, and the optimal hydrolysis coating time is 24 h. The performance and the performance characteristics of the core-shell composite material 24-G @ TiO2 prepared by the invention when applied to a lithium ion anode material are also explored: can stably circulate 4000 circles and the capacity can be kept at 180 mAh g-1The capacity retention rate is 46.6%, the rate capability is good, the electrochemical performance is very excellent, and the electrochemical performance is superior to the related electrochemical performance of the titanium dioxide carbon material reported at present.

Claims (5)

1. A preparation method of a titanium dioxide graphene complex with a core-shell cavity structure is characterized by comprising the following steps: firstly, preparing a mixture of graphene and potassium chloride salt by an ionothermal method by taking potassium chloride as a salt template and metal-free phthalocyanine as a carbon source and a nitrogen source, then hydrolyzing isopropyl titanate in ethanol, enabling a layer of titanium dioxide to uniformly grow on the surface of the graphene under the action of a hexadecylamine surfactant, and finally centrifuging, washing and drying to obtain a titanium dioxide graphene complex with a core-shell cavity structure;
the method specifically comprises the following steps:
step (1): weighing 200-220 ml of ethanol and 40-50 ml of cyclohexane, mixing and stirring, then adding 0.10-0.20 g of metal-free phthalocyanine, mixing and stirring until the metal-free phthalocyanine is fully dissolved, simultaneously soaking the reaction container in an ice-water bath environment at-1 to 1 ℃, continuously dropwise adding 50-60 ml of saturated potassium chloride solution, continuously stirring, after dropwise adding, aging in an ice-water bath environment, cleaning with ethanol after aging, completely cleaning cyclohexane, filtering with a microporous filtering membrane, collecting the product, vacuum drying for 8 hours at 60-80 ℃, and finally obtaining a composite precursor of phthalocyanine particles and potassium chloride salt, wherein the Pc/KCl is recorded;
step (2): transferring the Pc/KCl prepared in the step (1) into a quartz tube for drying, placing the quartz tube into a tube furnace for high-temperature sintering, respectively calcining the quartz tube in the tube furnace in an inert gas atmosphere at 700 ℃ for 8h, and naturally cooling the quartz tube to room temperature to carbonize a composite precursor into a two-dimensional thin graphene sheet layer with a regular cubic structure, which is marked as G/KCl;
and (3): taking 1-2 g of the two-dimensional thin-layer graphene sheet layer with the regular cubic structure in the step (2), adding the two-dimensional thin-layer graphene sheet layer into 150-170 ml of ethanol solution for ultrasonic treatment, then adding 0.1-0.3 g of hexadecylamine, continuously stirring, then dropwise adding 10 mu l of deionized water every 10 min, and continuously stirring for 24 hours to obtain a uniform dispersion solution of the titanium dioxide graphene complex; finally, centrifuging and drying to finally obtain a titanium dioxide graphene complex with a core-shell cavity structure, which is marked as G @ TiO2；
The method comprises the steps of preparing a mixture of graphene and potassium chloride salt by an ionothermal method by using metal-free phthalocyanine as a carbon source and a nitrogen source and potassium chloride as a salt template, and marking the mixture as G/KCl.
2. The preparation method of the titanium dioxide graphene complex with the core-shell cavity structure according to claim 1, which is characterized in that: in the step (2), the inert gas atmosphere is Ar gas or nitrogen gas; the temperature rising procedure of sintering in the tube furnace is as follows: introducing argon at room temperature for 1 h, and then introducing argon at 5 ℃ for min-1The temperature is raised to 300 ℃ at the temperature raising rate, then the temperature is kept for 1 h, and then the temperature is raised to 2 ℃ for min-1The temperature is raised to 700 ℃, the temperature is kept for 8 hours, and then the temperature is naturally cooled to the room temperature.
3. The preparation method of the titanium dioxide graphene complex with the core-shell cavity structure according to claim 2, which is characterized in that: in the step (3), hexadecylamine is used as a surfactant, and the hydrolysis time of titanium dioxide is 24 hours.
4. The titanium dioxide graphene complex with the core-shell cavity structure prepared by the preparation method of any one of claims 1 to 3.
5. The application of the titanium dioxide graphene composite with the core-shell cavity structure, which is disclosed by claim 4, is characterized in that: the material is used as the anode material of the lithium ion battery.
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