CN111048754A

CN111048754A - Tin-doped rutile TiO2Preparation method and application of composite material

Info

Publication number: CN111048754A
Application number: CN201911207974.6A
Authority: CN
Inventors: 卢锋奇; 戎超; 夏颖
Original assignee: Guilin University of Technology
Current assignee: Guilin Qi Hong Technology Co ltd
Priority date: 2019-11-30
Filing date: 2019-11-30
Publication date: 2020-04-21
Anticipated expiration: 2039-11-30
Also published as: CN111048754B

Abstract

The invention provides a tin-doped rutile TiO₂A preparation method and application of the composite material. Sn-TiO can be obtained by combining ion exchange and substitution and post-calcination in a tubular furnace₂Then coating with polydopamine, carbonizing, compounding with graphene oxide, and reducing graphite oxide to obtain tin-doped rutile TiO₂A composite material. The tin-doped rutile TiO₂Composite materialThe method is applied to the cathode material of the lithium ion battery. The invention obtains the tin-doped rutile TiO by utilizing simple ion exchange and adsorption and carbon material modification₂A composite material. When the material is used as an energy storage electrode material, the material shows high capacity and good cycle stability. The method provides a synthesis strategy of inorganic metal doped titanate, and provides reference significance for obtaining materials with high capacity, high multiplying power and cycling stability.

Description

Tin-doped rutile TiO2Preparation method and application of composite material

Technical Field

The invention belongs to the technical field of nano materials and electrochemical devices, and particularly relates to tin-doped rutile TiO₂Composite material (Sn-TiO)₂@ C/RGO composite) and its application. The method prepares the tin-doped rutile TiO by means of ion adsorption and doping at room temperature₂And then carrying out carbon coating and composite reduced graphene oxide modification on the graphene oxide. The composite material is applied to a lithium ion battery cathode material and has certain popularization.

Background

For these years, TiO has₂As a transition metal oxide, it is widely used in the field of energy storage because of its small volume change during charge and discharge. The electrode has good cycling stability, and compared with a graphite electrode, the electrode has a higher working platform, lithium dendrite is not easy to generate, but as a rutile structure with the highest thermal stability, because the lag between the deintercalated lithium is lower, the diffusion of lithium ions in the structure is anisotropic, the capacity of the rutile structure is lower, the application of the rutile structure is greatly inhibited, and the performance of the rutile structure can be improved by nanocrystallization and doping. The tin-based material has high capacity, but the volume expansion rate of the Sn-based electrode reaches 250 percent in the alloying/dealloying process, so that the capacity is reduced rapidly due to the serious electrode pulverization, and the characteristics of the two materials are combined, so that the tin is used for treating the TiO₂And (6) doping. Due to Sn⁴⁺Has an ionic radius (0.71 Å) to Ti⁴⁺Has a large ionic radius (0.68 Å), and Sn doping replaces Ti to enlarge TiO₆Octahedral volume, is Li⁺The intercalation of (2) provides more space and channels, reducing the resistance of lithium ions to diffusion within. Meanwhile, after tin doping heat treatment, a porous structure can be formed, the nano porous structure provides an effective channel for lithium ion diffusion, the transmission path of lithium ions is shortened, the specific capacity during large-current density charging and discharging can be improved, and a safe electrode material with high capacity and good cycling stability can be obtained.

Nano-particle TiO₂The graphene oxide is easy to agglomerate in the charging and discharging processes, the poly-dopamine coating is carried out on the graphene oxide, a carbon layer obtained through carbonization can slow down the agglomeration of the material in the charging and discharging processes, and the graphene oxide is high in specific surface and high in conductivity and is favored by researchers. Carbon-coated tin-doped titanium dioxide and reduced graphite oxideThe graphene is compounded, the unique composite material can provide a rapid channel for the transmission of electrons, so that the electronic and ionic conductivity of the electrode material is improved, meanwhile, the contact area of the electrode material and electrolyte is increased due to the two-dimensional graphene structure, the internal resistance can be effectively reduced, and the cathode material with excellent electrochemical performance can be obtained.

Disclosure of Invention

The invention aims to provide tin-doped rutile TiO with simple preparation process₂A preparation method and application of the composite material. The prepared composite material has excellent electrochemical performance so as to overcome the defects of the conventional cathode material.

Preparation of tin-doped rutile TiO₂The composite material comprises the following specific steps:

(1) 0.5 g of TiN was weighed and ultrasonically dispersed in 120 mL of deionized water, and then 16 mL of 30 wt% H was added₂O₂Then adding 16 mL of 25 wt% ammonia water, stirring the obtained mixed solution continuously, slowly changing the color from black to a transparent yellow solution, then adding 76 mL of absolute ethyl alcohol, stirring for 10 minutes, placing the mixture into an oil bath kettle at 80 ℃ for reaction for 12 hours to obtain a white precipitate, washing the white precipitate to be neutral by using deionized water and ethanol, and drying to obtain the amorphous TiO₂Nanospheres.

(2) Weighing 0.2 g of the amorphous TiO obtained in step (1)₂The nanospheres were ultrasonically dispersed in 100 mL absolute ethanol, the resulting solution was placed in a glove box and magnetically stirred, followed by the addition of 0.3 g SnCl₂·2H₂O, the solution is quickly changed into light yellow, the mixture is continuously stirred and reacts for 4 hours, the mixture is washed twice by alcohol and then by deionized water until the washing liquid is neutral, the obtained product is put into a vacuum drying oven to be dried and then put into a tubular furnace, the temperature is raised to 450 ℃ at the heating rate of 2 ℃/min and is kept for 4 hours, and the product is cooled to room temperature along with the furnace to prepare Sn-doped rutile Sn-TiO₂A nanoporous ball.

(3) Weighing 0.2 g of Sn doped rutile Sn-TiO prepared in the step (2)₂Ultrasonically dispersing the nano porous ball in 50 mL of deionized water, then adding 0.1 g of dopamine hydrochloride with the purity of 99 percent, stirring for 10 minutes, and then adding 0.061 g of pure dopamineTrihydroxyaminomethane with the degree of 99.9 percent is stirred for 12 hours, then is centrifugally cleaned by deionized water to be neutral, the obtained product is dried for 6 hours at the temperature of 60 ℃, is put into argon atmosphere to be heated to 450 ℃ at the heating rate of 2 ℃/min and is kept warm for 2 hours, and Sn-TiO is prepared₂Sample @ C.

(4) Taking 40 mg of graphene oxide, ultrasonically dispersing in deionized water, and then adding 0.18 g of Sn-TiO prepared in the step (3)₂The sample of @ C is stirred for 2 hours, dispersed evenly and then freeze-dried and collected, and the obtained product is thermally treated for 2 hours at 450 ℃ under the atmosphere of argon, thus obtaining the tin-doped rutile TiO₂Composite material (Sn-TiO)₂@ C/RGO composite).

The TiN is nano TiN with the purity of more than or equal to 99 percent and is black.

The graphene oxide is prepared according to a traditional Hummers method.

The tin-doped rutile TiO of the invention₂The composite material is applied to a lithium ion battery cathode material.

Sn-TiO obtained by the invention₂The @ C/RGO composite material has a higher specific surface area, the contact between electrolyte and an electrode material can be increased by the composite reduced graphene oxide, the transmission path of electrons and ions in electrochemical reaction can be shortened, the volume effect of doped tin in the alloying and dealloying process can be relieved by the carbon-coated carbon layer, the nano-particle agglomeration in the charging and discharging process can be inhibited by the reduced graphene oxide and the carbon layer, and meanwhile, the Sn is added⁴⁺Has an ionic radius (0.71 Å) greater than Ti⁴ ⁺Ionic radius of (0.68 Å), enlargement of TiO by Sn doping and substitution of Ti₆The octahedron volume provides larger space and more convenient channels for Li intercalation, and reduces the resistance of lithium ions to diffusion in the interior. Meanwhile, after tin doping heat treatment, a porous structure can be formed, and the nano porous structure provides an effective channel for lithium ion diffusion and also shortens a lithium ion transmission path. It is believed that the carbon material modification allows the electrode material doped with tin to have a synergistic effect with titanium dioxide so as to achieve superior electrochemical performance.

The invention has the beneficial effects that:

the Sn-TiO is obtained by utilizing a simple ion exchange principle and modifying a carbon material₂@ C/RGO composite. When the material is used as an energy storage electrode material, the material has the advantages of high capacity and good cycle stability. The invention adds SnCl₂·2H₂O and amorphous TiO₂Putting into alcohol together, performing ion exchange at room temperature, washing, drying, and heat treating to obtain Sn-TiO with porous rutile structure₂Then polydopamine coating is carried out, the polydopamine coating is compounded with graphene oxide after carbonization, and Sn-TiO is obtained after heat treatment₂@ C/RGO composite.

The invention has the advantages of simple process, environmental protection and the like. Using a lithium plate as a positive electrode, the Sn-TiO₂The @ C/RGO composite material is used as a negative electrode to assemble the half cell. At 0.1 Ag^-1After the current density is cycled for 200 circles, the specific discharge capacity is kept at 489.7mAh g^-1Far higher than rutile TiO₂The theoretical capacity of (a). At 1A g^-1After circulating for 400 circles under high current density, 160 mAh g is still kept^-1The reversible specific capacity of (a). At 0.05, 0.1, 0.2, 0.4, 0.8, 1, 2A g^-1The discharge capacities of the materials are 548.4, 408, 308.1, 270.1, 169, 144.6 and 76 mAh g respectively when the rate test is carried out under different current densities^-1When the current is from 2 Ag^-1Back to 0.05 Ag^-1The discharge capacity was 481.9 mAh g^-1And the electrochemical performance is excellent. The method provides a synthesis strategy of inorganic metal doped titanate, and provides reference significance for obtaining materials with high capacity, high multiplying power and cycling stability.

The method has important significance in the field of energy storage, can effectively solve the agglomeration of the nano material, can solve the problems that the carbon material relieves the volume effect of the nano material, the nano material has poor conductivity, the nano material has poor circulation stability, the nano material has stable structure and the like, can be conveniently popularized in the doping of other nano materials and the modification of the carbon material, and has strong universality.

Drawings

FIG. 1 shows Sn-TiO of the present invention₂Preparation process of @ C/RGO composite materialIntention is.

FIG. 2 shows Sn-TiO in an example of the present invention₂SEM and TEM images of @ C/RGO composite and amorphous TiO₂SEM image of (d).

FIG. 3 shows Sn-TiO in an example of the present invention₂XRD data for @ C/RGO composites.

FIG. 4 shows Sn-TiO in an example of the present invention₂The BET plot of the @ C/RGO composite.

FIG. 5 shows Sn-TiO in an example of the present invention₂The sweep rate of a circulating voltammogram of the @ C/RGO composite material is 0.1 mV/s, and the voltage range is 0.01-3.0V.

FIG. 6 shows Sn-TiO in an example of the present invention₂@ C/RGO composite material at 0.1A g^-1Voltage-capacity curve at current density.

FIG. 7 shows Sn-TiO in an example of the present invention₂@ C/RGO composite material at 1A g^-1Four hundred cycles of charge and discharge data under current.

FIG. 8 shows Sn-TiO in an example of the present invention₂@ C/RGO composite material at 0.1A g^-1The charge-discharge curve is cycled for two hundred cycles under current.

FIG. 9 shows Sn-TiO in an example of the present invention₂@ C/RGO composite material in 0.05-2A g^-1The magnification test chart of (1).

Detailed Description

Example (b):

the following is a detailed description by way of specific examples, which are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the following examples.

Sn-TiO₂The preparation flow diagram of the @ C/RGO composite material is shown in figure 1. Sn-TiO can be obtained by ion exchange and substitution combined with heat treatment in a tube furnace₂Then coating with polydopamine, carbonizing, compounding with graphene oxide, and reducing graphite oxide to obtain Sn-TiO₂@ C/RGO composite. The method comprises the following specific steps:

(1) 0.5 g of TiN was weighed and dispersed in 120 mL by ultrasonicIonic water, then 16 mL of 30 wt% H₂O₂Then adding 16 mL of 25 wt% ammonia water, stirring the obtained mixed solution continuously, slowly changing the color from black to a transparent yellow solution, then adding 76 mL of absolute ethyl alcohol, stirring for 10 minutes, placing the mixture into an oil bath kettle at 80 ℃ for reaction for 12 hours to obtain a white precipitate, washing the white precipitate to be neutral by using deionized water and ethanol, and drying to obtain the amorphous TiO₂Nanospheres.

(3) Weighing 0.2 g of Sn doped rutile Sn-TiO prepared in the step (2)₂Ultrasonically dispersing nano porous balls in 50 mL of deionized water, then adding 0.1 g of dopamine hydrochloride with the purity of 99%, stirring for 10 minutes, then adding 0.061 g of trihydroxyaminomethane with the purity of 99.9%, stirring for 12 hours, then centrifugally cleaning with deionized water to be neutral, drying the obtained product at 60 ℃ for 6 hours, then putting the dried product into an argon atmosphere, raising the temperature to 450 ℃ at the heating rate of 2 ℃/min, and preserving the heat for 2 hours to obtain Sn-TiO₂Sample @ C.

(4) Taking 40 mg of Graphene Oxide (GO) to be ultrasonically dispersed in deionized water, and then adding 0.18 g of Sn-TiO prepared in the step (3)₂The sample of @ C is stirred for 2 hours, dispersed evenly and then freeze-dried and collected, and the obtained product is thermally treated for 2 hours at 450 ℃ under the atmosphere of argon, thus obtaining Sn-TiO₂@ C/RGO composite.

The TiN is nano TiN with the purity of 99 percent and is black.

The graphene oxide is prepared according to a traditional Hummers method.

As shown in FIG. 2, SEM images of each stage of the preparation process can verify Sn-TiO₂@ C/RGO formation Process, FIG. 2 (a) is amorphous TiO₂Are uniform in size, mainly 50-80 nm nanospheres. FIG. 2 (b) is a tin-doped rutile TiO₂The SEM appearance shows that the appearance of the sample is not changed after tin doping, and the appearance is also nanospheres. FIG. 2 (c) is Sn-TiO₂The SEM shape of @ C/RGO shows that the composite effect of reduced graphene oxide and nanospheres is good, and the tin-doped rutile TiO₂The nanospheres are uniformly attached to the reduced graphene oxide. FIG. 2 (d-e) shows a tin-doped rutile TiO₂The TEM appearance of the nanospheres shows that the nanospheres have porous characteristics and uniform particle sizes.

FIG. 2 (f) is a tin-doped rutile TiO₂The HRTEM image shows that the obvious two interplanar distances are respectively 0.329 nm and 0.253 nm and respectively correspond to the tin-doped TiO₂The (101) and (110) crystal planes of the crystal are slightly larger than rutile TiO₂The corresponding large interplanar spacing, which results from the Sn doping and Ti site substitution expands the TiO₆Octahedral volume, leading to increased interplanar spacing.

For the Sn-TiO of this example₂The structure of the @ C/RGO composite material is characterized: as shown in FIG. 3, it can be seen from XRD that it is in the rutile phase, in combination with pure rutile TiO₂Compared with the structure, the position of the peak is slightly shifted to the left due to Sn⁴⁺Radius greater than Ti⁴⁺Sn doping and Ti site substitution broaden TiO₆Octahedral volume, resulting in lattice enlargement and left shift, while carbon can be obtained as amorphous carbon,

as shown in FIG. 4, Sn-TiO can be seen₂Specific surface area of @ C/RGO 95.2 m²The pore size distribution is around 3.8 nm, which is mainly due to H3 type adsorption, which reflects Sn-TiO₂The holes of @ C/RGO are mainly generated by micropores in slit holes, and the function of reducing graphene oxide in a sheet shape is also existed.

Sn-TiO obtained in this example₂When the @ C/RGO composite material is used as the negative electrode material of the lithium ion battery, the material is prepared according to the active substancesThe mass ratio of acetylene black to PVDF (binder) is 7:2: 1. Firstly putting PVDF into a glass beaker, adding N-methyl pyrrolidone, magnetically stirring until the PVDF is clear, grinding an active substance acetylene black in a mortar for 40 minutes, taking out the PVDF and putting the PVDF into the glass beaker, stirring for 8 hours, finally uniformly coating the PVDF on a current collector, putting the PVDF into a vacuum drying oven for drying for 12 hours at the temperature of 100 ℃, taking out a slice, wherein the area of the slice is 1.13 cm²The coating weight of each wafer is about 1.1 mg, the pressed active material is used as a working electrode, a metal lithium sheet is used as a reference electrode, a microporous organic membrane (Celgard 2400) is used as a diaphragm, and the battery shell is CR 2032. The electrolyte is prepared from 1mol/L LiPF₆And Ethylene Carbonate (EC)/dimethyl carbonate (DMC) were mixed in an equal volume ratio. The half cell of CR2032 was assembled and sealed in an argon filled glove box with an oxygen content and a water content of less than 0.1 ppm, wherein the charge-discharge capacity was calculated on the mass of the active material.

FIG. 5 is a cyclic voltammogram of the first three times of the composite material as an electrode material at a voltage range of 0.01 to 3V and a scanning rate of 0.1 mV/s. As can be seen from the CV chart, the curves of the second and third circles almost coincide, indicating that the electrode material has good reversibility.

FIG. 6 shows the electrode material at a current density of 0.1A g^-1The voltage-capacity curve of the first three corresponding circles. It can be seen that the first discharge plateau is around 1V and disappears after the second cycle, which corresponds to irreversible tin oxide conversion and Li₂The formation of O and the production of a solid electrolyte membrane. The discharge platform after the second circle is about 1.7V corresponding to rutile TiO₂The operating voltage platform of (1).

FIG. 7 shows the electrode material at high current 1A g^-1After the circulation is carried out for 400 circles, 160 mAh g still remains^-1Reversible specific capacity. Exhibits extremely high capacity and electrochemical cycling stability.

FIG. 8 shows the electrode material at 0.1 Ag^-1The data graph after 200 cycles of circulation under the current density shows that the first discharge specific capacity is 1049 mAh g^-1The first charging specific capacity is 605 mAh g^-1Corresponding to a coulombic efficiency of 57.7%,the reason why the coulombic efficiency is not very high is mainly due to the formation of SEI film and irreversible reaction of Sn, and after 200 cycles, the reversible specific capacity is 489.7mAh g which is extremely high^-1。

FIG. 9 shows the current density of the electrode material at 0.05 to 2A g^-1The corresponding charge-discharge curve, Sn-TiO₂@ C/RGO samples at 0.05, 0.1, 0.2, 0.4, 0.8, 1, 2A g^-1The discharge capacities of the materials are 548.4, 408, 308.1, 270.1, 169, 144.6 and 76 mAh g respectively^-1When the current is from 2 Ag^-1Back to 0.05 Ag^-1The discharge capacity was 481.9 mAh g^-1And excellent rate capability is embodied.

The excellent electrochemical performance of the composite material is closely related to the structure of the composite material, and is mainly attributed to the following points:

(1) the doped tin provides a large amount of capacity in the alloying dealloying process; (2) the coated carbon layer can increase the conductivity of the electrode material, relieve the agglomeration of the electrode material in the charging and discharging process and simultaneously protect TiO caused by the volume effect of the doped tin in the alloying process₂Structural damage; (3) the modified carbon material is compounded with the reduced graphene oxide, so that the specific surface area of the electrode material can be greatly increased, the agglomeration effect can be effectively reduced, meanwhile, the reduced graphene oxide has extremely high conductivity, the conductivity of electrons and ions is increased, and the transmission path of the ions and the electrons is also shortened, so that the carbon material modification can be considered to enable the doped tin of the electrode material to have a synergistic effect with titanium dioxide; (4) sn (tin)⁴⁺Has an ionic radius (0.71 Å) greater than Ti⁴⁺Ion radius of (0.68 Å), Sn doping and Ti site substitution broaden TiO₆The octahedral volume provides a larger space and more convenient channels for Li ion intercalation. The resistance to diffusion of lithium ions inside is reduced. After the simultaneous tin doping heat treatment, a porous structure is formed. The nano porous structure provides an effective channel for lithium ion diffusion and can provide a rapid channel for electron transmission.

Claims

1. Tin-doped rutile TiO₂The preparation method of the composite material is characterized by comprising the following specific steps:

(1) 0.5 g of TiN was weighed and ultrasonically dispersed in 120 mL of deionized water, and then 16 mL of 30 wt% H was added₂O₂Then adding 16 mL of 25 wt% ammonia water, stirring the obtained mixed solution continuously, slowly changing the color from black to a transparent yellow solution, then adding 76 mL of absolute ethyl alcohol, stirring for 10 minutes, placing the mixture into an oil bath kettle at 80 ℃ for reaction for 12 hours to obtain a white precipitate, washing the white precipitate to be neutral by using deionized water and ethanol, and drying to obtain the amorphous TiO₂Nanospheres;

(2) weighing 0.2 g of the amorphous TiO obtained in step (1)₂The nanospheres were ultrasonically dispersed in 100 mL absolute ethanol, the resulting solution was placed in a glove box and magnetically stirred, followed by the addition of 0.3 g SnCl₂·2H₂O, the solution is quickly changed into light yellow, the mixture is continuously stirred and reacts for 4 hours, the mixture is washed twice by alcohol and then by deionized water until the washing liquid is neutral, the obtained product is put into a vacuum drying oven to be dried and then put into a tubular furnace, the temperature is raised to 450 ℃ at the heating rate of 2 ℃/min and is kept for 4 hours, and the product is cooled to room temperature along with the furnace to prepare Sn-doped rutile Sn-TiO₂A nanoporous ball;

(3) weighing 0.2 g of Sn doped rutile Sn-TiO prepared in the step (2)₂Ultrasonically dispersing nano porous balls in 50 mL of deionized water, then adding 0.1 g of dopamine hydrochloride with the purity of 99%, stirring for 10 minutes, then adding 0.061 g of trihydroxyaminomethane with the purity of 99.9%, stirring for 12 hours, then centrifugally cleaning with deionized water to be neutral, drying the obtained product at 60 ℃ for 6 hours, then putting the dried product into an argon atmosphere, raising the temperature to 450 ℃ at the heating rate of 2 ℃/min, and preserving the heat for 2 hours to obtain Sn-TiO₂The @ C sample;

(4) taking 40 mg of graphene oxide, ultrasonically dispersing in deionized water, and then adding 0.18 g of Sn-TiO prepared in the step (3)₂The sample of @ C is stirred for 2 hours, dispersed evenly and then freeze-dried and collected, and the obtained product is thermally treated for 2 hours at 450 ℃ under the atmosphere of argon, thus obtaining the tin-doped rutile TiO₂A composite material;

the TiN is nano TiN with the purity of more than or equal to 99 percent and is black;

the graphene oxide is prepared according to a traditional Hummers method.

2. The method of claim 1, wherein the rutile-doped TiO is prepared by the method₂The application of the composite material is characterized in that: the tin-doped rutile TiO₂The composite material is applied to a lithium ion battery cathode material.