CN115332518B - Quantum dot tin oxide loaded multiwall carbon nanotube composite material and preparation method and application thereof - Google Patents

Quantum dot tin oxide loaded multiwall carbon nanotube composite material and preparation method and application thereof Download PDF

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CN115332518B
CN115332518B CN202211053712.0A CN202211053712A CN115332518B CN 115332518 B CN115332518 B CN 115332518B CN 202211053712 A CN202211053712 A CN 202211053712A CN 115332518 B CN115332518 B CN 115332518B
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tin oxide
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tin
carbon nanotube
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袁斌
刘玉
李少波
黄佳艺
胡仁宗
朱敏
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South China University of Technology SCUT
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Abstract

The invention belongs to the technical field of lithium ion secondary batteries, and discloses a quantum dot tin oxide loaded multiwall carbon nanotube composite material, and a preparation method and application thereof. The method comprises the following steps: 1) Dissolving tin salt in water to obtain a tin salt solution; 2) Uniformly mixing the multiwall carbon nanotube with a tin salt solution to obtain a suspension A; 3) Placing the suspension A in a gas-liquid discharge plasma reaction device, and performing discharge reaction in an argon plasma atmosphere to obtain a suspension B; carrying out subsequent treatment to obtain a quantum dot tin oxide loaded multi-wall carbon nano tube composite material; the dosage of the multi-wall carbon nano tube is as follows: the mass ratio of the tin ions to the multiwall carbon nanotubes is (0.04-0.8): 1. the method provided by the invention is efficient, simple to operate and low in cost, and can realize the large-scale production of the quantum dot tin oxide carbon composite material. The material provided by the invention is used for a lithium ion battery, can obviously improve the cycle stability of an electrode material, and has excellent electrochemical performance.

Description

Quantum dot tin oxide loaded multiwall carbon nanotube composite material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of nano functional materials and lithium ion secondary batteries, and particularly relates to a quantum dot tin oxide loaded multiwall carbon nanotube material prepared by a gas-liquid phase plasma discharge reduction technology, and a preparation method and application thereof.
Background
Lithium Ion Batteries (LIBs) are composed of negative (also called anode) and positive (cathode) materials, and are made of a material that is modified by the action of Li ions (Li + ) A chargeable energy storage device for storing electric energy by reciprocating embedding and separating movement between positive and negative electrodes. During discharge, li ions will be transported from the anode to the cathode through the nonaqueous electrolyte and separator; while during charging, the process proceeds in the opposite direction.
LIBs have the advantages of high energy density (high specific capacity), light weight, long service life, no memory effect, etc. The specific capacity of a lithium ion battery is mainly determined by the materials of the positive electrode and the negative electrode. However, the theoretical capacity of the negative electrode material graphite used in the commercial lithium ion battery at present (-372 mAh g) -1 ) And discharge potential (-0.1V vs. Li) + Li, which is susceptible to overcharging, particularly lithium dendrite deposition at low temperatures, shorting through the separator, and safety accidents), is relatively low, and therefore, does not meet the needs of people for next generation lithium ion batteries (higher capacity, longer life, and safety over a wide temperature range). Therefore, development of an alternative anode material having a high specific capacity, a moderate discharge potential, and good cycle performance is required. Among various anode materials, tin oxide has a high theoretical specific capacity (1490 mAh g -1 Nearly 4 times that of graphite), moderate discharge potential (-0.6V vs. Li) + Li), easy preparation, low cost, environmental friendliness and the like. However, compared with a graphite anode with low capacity and very stable circulation, the tin oxide anode has a plurality of challenges which cannot be ignored, firstly, when the transformation reaction and the alloying reaction completely occur, the anode volume is caused to be greatly expanded (about 300 percent), and the anode material is easily pulverized and falls off due to the large volume change in the charge and discharge process; secondly, in the charge/discharge process, lithium oxide with poor conductivity is formed on the surface of tin to prevent internal alloy reaction from proceeding, so that the reaction reversibility is reduced, and the cycle performance is unstable; in addition, since tin has a low recrystallization temperature (-71 ℃), tin particles formed by dealloying are easily aggregated and grown at normal temperature, resulting in a decrease in electrochemical reaction kinetics and further a decrease in cycle reversibility.
In order to solve the above problems, some studies have been conducted. For example, chinese patent application CN201811493527.7 provides a method for preparing a quantum dot tin oxide/fluorinated graphene composite material, which comprises dissolving a tin-containing salt in deionized water, adding a surfactant, stirring at 20-70deg.C for 1-5 hr to obtain a tin-containing solution, and mixing the solution with an ultrasonic single-layer fluorinated graphene dispersionAnd carrying out solvothermal reaction for 5-30 hours at 150-210 ℃, and centrifugally drying to obtain the tin oxide quantum dot/fluorinated graphene composite anode material. The quantum dot tin oxide prepared by the method is uniformly dispersed between the layers of the fluorinated graphene, and can show better performance when being applied to sodium ion batteries. However, the method has the disadvantages of long time consumption, more energy consumption, complex preparation process and short process for large-scale production. Chinese patent No. CN201610048028.1 uses SnCl 2 ·2H 2 The hydrolytic character of O, introducing thiourea as catalyst and stabilizer, stirring at normal temperature for 12-24 hr to obtain yellow clear transparent SnO 2 And mixing the quantum dot solution with the carbon nano tube, stirring for a period of time, and filtering and drying to obtain the quantum dot tin oxide/carbon nano tube composite material. The preparation process of the method does not need high-temperature reaction, has low energy consumption and simple experimental operation, and can show good electrochemical performance when being applied to the cathode of the lithium ion battery. However, the quantum dot tin oxide prepared by the method has over high proportion and very dense particle distribution, so that the quantum dot particles are easy to aggregate and become large, and the cycle stability is not facilitated. In the prior art, most methods for preparing the quantum dot tin oxide composite material cannot realize controllable preparation of uniform nano small-size tin oxide on the premise of simple, efficient and clean production, and greatly limit mass production and application popularization of the quantum dot tin oxide composite material cathode in practice.
Disclosure of Invention
In order to overcome the defects of the existing preparation of the quantum dot tin oxide carbon composite material, the invention aims to provide the quantum dot tin oxide loaded multiwall carbon nanotube composite material and the high-efficiency preparation method thereof. The invention uses solvated electrons with strong reducibility in gas-liquid plasmas, can induce quantum dot tin oxide particles (about 5 nm) with uniform size to be loaded on multi-wall carbon nanotubes (MWCNTs) in a short time (5-30 minutes), has the characteristics of simple operation, low preparation cost, high efficiency and reliability, and the like, and is easy to realize mass production. In lithium ion batteries, the extremely small size (about 5 nm) of tin oxide can significantly increase the reaction area to effectively shorten Li + Is matched with the diffusion distance of the compositeThe stable structure of the carbon material can not only prevent the agglomeration of nano particles, but also obviously relieve the volume change brought by the charge and discharge process of the material, thereby improving the dynamics and the cycle performance of the electrode.
The invention further aims to provide application of the quantum dot tin oxide loaded multiwall carbon nanotube composite material in a lithium ion battery cathode. Compared with a common tin oxide negative electrode, the quantum dot tin oxide loaded multi-wall carbon nano tube composite material has higher cycling stability, can reach higher specific capacity and coulomb efficiency compared with a multi-wall carbon nano tube, and better meets the requirement of the composite material serving as a negative electrode material of a lithium ion battery.
The invention aims at realizing the following technical scheme:
the preparation method of the quantum dot tin oxide loaded multiwall carbon nanotube composite material comprises the following steps:
(1) Dissolving tin salt in water to obtain a tin salt solution;
(2) Uniformly mixing the multiwall carbon nanotube with a tin salt solution to obtain a suspension A;
(3) Placing the suspension A obtained in the step (2) into a gas-liquid discharge plasma reaction device, and performing discharge reaction in an argon plasma atmosphere to obtain a suspension B; and (5) carrying out subsequent treatment to obtain the quantum dot tin oxide loaded multiwall carbon nanotube composite material.
The tin salt in the step (1) comprises more than one of tin chloride (analytical pure AR, more than or equal to 98%), stannous chloride (AR, more than or equal to 98%), tin sulfate (AR, more than or equal to 98%) and stannous sulfate (AR, more than or equal to 98%) containing or not containing crystal water.
The mass ratio of the tin salt to the water is (10-200 mg): 30ml.
The adding amount of the multi-wall carbon nano tube in the step (2) satisfies the mass ratio of tin ions in the tin salt to the multi-wall carbon nano tube as follows (0.04-0.8): 1.
the uniformly mixing means uniformly stirring; the stirring speed is 100-400 rpm, and the stirring time is 1-6 h.
Conditions of the discharge reaction in step (3): the input voltage is controlled to be 20-80V, the output high voltage is 1-10 kilovolts, the discharge frequency is 10-100 kilohertz, and the discharge treatment time is 5-30 minutes.
The gas-liquid discharge plasma reaction device comprises a needle-shaped hollow electrode, a reactor main body and a disc electrode. The reactor main body is a cavity with two open ends, the bottom of the reactor main body is closed by a disc electrode, and the needle-shaped hollow electrode is arranged in the cavity of the reactor main body through the opening at the upper end of the reactor main body. The needle-shaped hollow electrode is provided with an air inlet. One end of the needle-shaped hollow electrode, which is provided with an air inlet, is connected with the negative electrode output end of the rectifier, and one end of the air outlet is arranged in the reactor main body; the disc electrode is connected with the positive electrode output end of the rectifier; the air outlet of the needle-shaped hollow electrode is connected with the air storage device; the rectifier is connected with a power supply.
The reactor main body is a cylindrical reactor, and is made of polytetrafluoroethylene; the needle-shaped hollow electrode is made of stainless steel, and the disc electrode is a graphite electrode; the depth of the reactor main body is 50 mm, and the diameter of the inner wall is 60 mm. After the suspension A is added, the depth of the suspension A is 25-35 mm, and the distance between the liquid surface of the suspension A and the lower end of the needle-shaped hollow electrode is 2-5 mm.
In the step (3), the flow rate of argon in the needle-shaped hollow electrode is 5-20 mL/min, and the purity is 99.999%.
The plasma discharge of the present invention is a pulsed dc discharge.
The subsequent treatment refers to filtration and drying. The drying is vacuum drying, the vacuum degree is 5000-10000 Pa, the drying temperature is 60-80 ℃ and the time is 8-12 hours.
The quantum dot tin oxide loaded multi-wall carbon nano tube composite material realizes that nano-scale tin oxide particles are uniformly loaded on the multi-wall carbon nano tube, wherein the loading amount is 15-30%, the size of the loaded particles is about 5nm, and metal particle agglomeration caused by over reduction does not occur.
The quantum dot tin oxide loaded multiwall carbon nanotube composite material prepared by the plasma reduction is applied to a lithium ion battery.
The principle of the invention is as follows: firstly, tin salt is dissolved in water to obtain tin ion solution, and then the tin ion solution is added into the multiwall carbon nanotube and continuously stirred to enable the tin ion to be uniformly dispersed around the multiwall carbon nanotube. The solvated electrons with strong reducibility generated by plasma discharge reduce tin ions adsorbed on the multi-wall carbon nano-tube into tin metal simple substance particles, and the tin metal simple substance particles are easily oxidized into tin oxide particles by oxygen in water due to extremely small particle size and are adsorbed on the multi-wall carbon nano-tube.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) The invention adopts a liquid phase discharge plasma system, generates a large amount of solvated electrons with strong reducibility under the action of plasma and liquid phase, and can quickly and efficiently reduce and adsorb most tin ions in the solution on the surface of the multiwall carbon nanotube material.
(2) The invention can reduce metallic tin by a simple one-step liquid phase discharge plasma treatment method and rapidly oxidize the metallic tin into tin oxide to be loaded on the surface of the multiwall carbon nanotube material, the discharge reaction time can be controlled within 30 minutes, the operation is simple and convenient, the process flow is short, the efficiency and the reliability are high, the preparation cost is low, and the mass production is easy to realize.
(3) The quantum dot tin oxide loaded multiwall carbon nanotube composite material prepared by the invention is applied to a lithium ion battery cathode, has excellent electrochemical performance, can have higher cycling stability compared with a commercial tin oxide material cathode, and can reach higher specific capacity and coulombic efficiency compared with a multiwall carbon nanotube.
Drawings
FIG. 1 is a schematic diagram of a gas-liquid discharge plasma reaction apparatus;
FIG. 2 is an XRD diffraction pattern of a quantum dot tin oxide loaded multiwall carbon nanotube of example 1, comprising a standard PDF card of multiwall carbon nanotubes and tin oxide;
FIG. 3 is a TEM image of a quantum dot tin oxide loaded multiwall carbon nanotube of example 1;
FIG. 4 is a thermal weight graph of a quantum dot tin oxide loaded multiwall carbon nanotube of example 1;
fig. 5 shows the quantum dot tin oxide loaded multiwall carbon nanotubes of example 1 as electrodes applied to half batteries of lithium ion batteries at low current densities (0.1A g -1 ) The lower circulation performance is compared with the circulation performance of the multiwall carbon nanotube;
FIG. 6 shows the application of the quantum dot tin oxide loaded multiwall carbon nanotubes as electrodes in a half cell of a lithium ion battery in example 1 at low current density (0.1A g -1 ) A coulombic efficiency plot for the lower cycle, compared to the coulombic efficiency of the multiwall carbon nanotubes;
FIG. 7 is a TEM image of a quantum dot tin oxide loaded multiwall carbon nanotube of example 2;
fig. 8 is a TEM image of a quantum dot tin oxide loaded multiwall carbon nanotube of example 3.
Detailed Description
For a better understanding of the present invention, reference will now be made to the following examples and accompanying drawings, but embodiments of the invention are not limited thereto.
As shown in fig. 1, the gas-liquid discharge plasma reaction device used in the present invention comprises a voltage device, a reaction device and a gas transmission device, wherein the voltage device comprises a common power supply 1 and a rectifier 2, and the reaction device comprises a needle-shaped hollow electrode 3, a reactor main body 4 and a disc electrode 5. The reactor main body is a cavity with two open ends, the bottom of the reactor main body is closed by a disc electrode, and the needle-shaped hollow electrode is arranged in the cavity of the reactor main body through the opening at the upper end of the reactor main body. The needle-shaped hollow electrode is provided with an air inlet. One end of the needle-shaped hollow electrode, which is provided with an air inlet, is connected with the negative electrode output end of the rectifier, and one end of the air outlet is arranged in the reactor main body; the disc electrode is connected with the positive electrode output end of the rectifier; the air outlet of the needle-shaped hollow electrode is connected with an air conveying device; the rectifier is connected with a power supply. The needle-shaped hollow electrode 3 and the disc electrode 5 are respectively made of stainless steel and graphite; the reactor main body is made of polytetrafluoroethylene, the depth of the main body is 50 mm, and the diameter of the inner wall is 60 mm; the gas delivery device comprises an argon bottle 6 and a gas pipe 7 connected with the argon bottle and the needle-shaped hollow electrode.
When the reaction occurs, the depth of the suspension A added into the reactor main body for reaction is 5-30 mm, and the distance between the liquid surface of the suspension and the lower end of the needle-shaped hollow electrode is 2-5 mm, namely the discharge interval or the discharge gap. The flow rate of argon in the needle-shaped hollow electrode is 5-20 ml/min, and the purity is over 99.999 percent.
The plasma power supply used by the invention is prepared by Nanjing Su Man plasma technology Co., ltd, and the model is CTP-2000K; meanwhile, in order to utilize the characteristic of direct current discharge as much as possible, a rectifier is utilized to change the output signal of the plasma power supply into a pulse direct current signal.
Example 1
(1) 98% analytically pure SnCl 2 ·2H 2 O (48 mg) was dissolved in deionized water (30 mL) and stirred under magnetic stirring at 300 rpm for 10 minutes to give solution A;
(2) Adding 150mg of high-purity multi-wall carbon nano tube (purchased from Kana carbon new materials Co., ltd., purity > 97%, pipe diameter of 3-15 μm, pipe length of 15-30 μm) into the solution A obtained in the step (1), and continuing stirring for 1h to obtain black suspension B;
(3) Transferring the black suspension B obtained in the step (2) into a gas-liquid discharge plasma cylinder reactor main body, controlling the distance between the liquid level of the suspension and the lower end of the needle-shaped hollow electrode to be 3 millimeters, controlling high-purity argon (10 milliliters/min, purity 99.999%) to directly blow the liquid level through the needle-shaped hollow electrode, switching on a plasma power supply, and continuously and stably reacting for 10 minutes under the conditions of 40 volts of input voltage, 5 kilovolts of output high voltage and 34.5 kilohertz of discharge frequency to obtain black suspension C;
(4) Filtering the black suspension C in the step (3) to wash impurities and separate solid from liquid, and then vacuum drying the solid black product after washing and separation for 12 hours at 70 ℃ under 10000Pa vacuum degree to obtain a quantum dot tin oxide metal-loaded multiwall carbon nanotube composite material with the size of about 5nm, which is marked as 1-QDSnO 2 /MWCNTs。
The XRD diffractogram of the quantum dot tin oxide metal loaded multiwall carbon nanotube composite of this example is shown in figure 2. Compared with the XRD of the original multi-wall carbon nano tube, the XRD of the quantum dot tin oxide metal loaded multi-wall carbon nano tube composite material has the advantages that except for a carbon peak, a peak of tin oxide with higher intensity appears at 26.5 degrees, so that an amorphous carbon peak at 26.2 degrees is covered, and an amorphous peak at 33.5 degrees and a significant peak at 52 degrees correspond to the peak of tin oxide, which indicates that the tin oxide loaded multi-wall carbon nano tube composite material is successfully prepared by plasma discharge.
The TEM image of the quantum dot tin oxide metal supported multiwall carbon nanotube composite of this embodiment is shown in fig. 3, and it can be clearly seen that particles with a size of about 5nm are supported on a single multiwall carbon nanotube, wherein the apparent lattice fringes of the nano-sized particles are measured as 0.34nm corresponding to the (1 1) plane of tin oxide, which proves to be tin oxide quantum dots, and in addition, the clear lattice fringes of the multiwall carbon nanotube edge correspond to the (0) plane of the multiwall carbon nanotube. This result further illustrates the successful synthesis of quantum dot tin oxide metal loaded multiwall carbon nanotubes. In addition, under the air atmosphere test condition of 25-650 ℃,1-QDSnO 2 The thermal weight curve of MWCNTs is shown in FIG. 4, and the tin oxide loading is calculated to be 22%.
In glove box (H) 2 O＜0.1％，O 2 Less than 0.1%) of the quantum dot tin oxide loaded multi-wall carbon nanotube composite material is used as an anode, calgard 2025 is used as a diaphragm, a metal lithium sheet is used as a cathode, lithium hexafluorophosphate is used as electrolyte salt (a solvent is EC: dec=2: 1) Pressing into a pole piece with the diameter of 12mm, and assembling with a CR2016 button battery shell into a half battery. The prepared half battery is subjected to charge and discharge performance test in a LAND battery test system, and specific parameters are as follows: as shown in fig. 5, when the current density is 0.1. 0.1A g -1 When the charge-discharge voltage is in the range of 0.01V-3V, the negative electrode prepared from micron-sized tin oxide synthesized by hydrothermal synthesis and commercial tin oxide has rapid capacity attenuation, compared with 1-QDSnO 2 Although the capacity of MWCNTs is not as high as that of the former two, the MWCNTs show the same excellent cycle stability as the MWCNTs, and the capacity is higher than that of the micron-sized tin oxide synthesized by hydrothermal method and commercial tin oxide after 30 times of cycles, and 1-QDSnO after 50 times of cycles 2 The specific capacities of the MWCNTs and the MWCNTs are 525mA h g respectively -1 And 365mA g -1 Micron-sized oxygen for hydrothermal synthesisTin oxide and commercial SnO 2 Then respectively decay to 403mA hg -1 And 411mA h g -1 . In addition, it is noted that in the comparison of coulomb efficiency under the low current density of fig. 6, the coulomb efficiency of the multi-wall carbon nanotube after the quantum dot tin oxide is loaded is greatly improved, which indicates that the material SEI film after the quantum dot tin oxide is loaded is more stable compared with the unstable SEI film generation caused by the large specific surface area of the original multi-wall carbon nanotube.
Fig. 5 shows the quantum dot tin oxide loaded multiwall carbon nanotubes of example 1 as electrodes applied to half batteries of lithium ion batteries at low current densities (0.1A g -1 ) The lower circulation performance is compared with the circulation performance of the multiwall carbon nanotube;
FIG. 6 shows the application of the quantum dot tin oxide loaded multiwall carbon nanotubes as electrodes in a half cell of a lithium ion battery in example 1 at low current density (0.1A g -1 ) The coulombic efficiency plot for the lower cycle compares to the coulombic efficiency of the multiwall carbon nanotubes.
Example 2
(1) 98% analytically pure SnCl 4 ·5H 2 O (75 mg) was dissolved in deionized water (30 mL) and stirred under magnetic stirring at 100 rpm for 8 minutes to give solution A;
(2) Adding 150mg of high-purity multi-wall carbon nano tube (purchased from Kana carbon new materials Co., ltd., purity > 97%, pipe diameter of 3-15 μm, pipe length of 15-30 μm) into the solution A obtained in the step (1), and continuing stirring for 3h to obtain black suspension B;
(3) Transferring the black suspension B obtained in the step (2) into a gas-liquid discharge plasma cylinder reactor main body, controlling the distance between the liquid level of the suspension and the lower end of the needle-shaped hollow electrode to be 2 millimeters, controlling high-purity argon (20 milliliters/min, purity 99.999%) to directly blow the liquid level through the needle-shaped hollow electrode, switching on a plasma power supply, and continuously and stably reacting for 30 minutes under the conditions of 80 volts of input voltage, 10 kilovolts of output high voltage and 65 kilohertz of discharge frequency to obtain black suspension C;
(4) Filtering the black suspension C in the step (3) to wash impurities and separate solid from liquid, and then subjecting the solid black product obtained by washing and separation to a vacuum degree of 5000PaVacuum drying at 80deg.C for 8 hr to obtain quantum dot tin oxide metal loaded multiwall carbon nanotube composite material with size of about 5nm, denoted as 2-QDSnO 2 /MWCNTs。
The reaction product was also quantum dot tin oxide particles of about 5nm in size supported on multi-walled carbon nanotubes (shown in fig. 7). Fig. 7 is a TEM image of a quantum dot tin oxide loaded multiwall carbon nanotube of example 2.
The 2-QDSnO prepared in this example 2 The MWCNTs material is used as the negative electrode of the lithium ion battery, so that the cycling stability of the tin oxide composite negative electrode can be effectively improved, the capacity of the original multi-wall carbon nano tube can be greatly improved and a more stable SEI film can be formed by adding the tin oxide, and the test result is similar to that of the embodiment 1.
Example 3
(1) 98% analytically pure SnSO 4 (48 mg) was dissolved in deionized water (30 mL) and stirred under magnetic stirring at 400 rpm for 5 minutes to give solution A;
(2) Adding 150mg of high-purity multi-wall carbon nano tube (purchased from Kana carbon new materials Co., ltd., purity > 97%, pipe diameter of 3-15 μm, pipe length of 15-30 μm) into the solution A obtained in the step (1), and continuing stirring for 2h to obtain a suspension B;
(3) Transferring the black suspension B obtained in the step (2) into a gas-liquid discharge plasma cylinder reactor, controlling the distance between the liquid level of the suspension and the lower end of the needle-shaped hollow electrode to be 3 mm, controlling high-purity argon (15 ml/min, purity 99.999%) to directly blow the liquid level through the needle-shaped hollow electrode, switching on a plasma power supply, and continuously and stably reacting for 20 minutes under the conditions of 20V input voltage, 1 kilovolt output high voltage and 30 kilohertz discharge frequency to obtain black suspension C;
(4) Filtering the black suspension C in the step (3) to wash impurities and separate solid from liquid, and then vacuum drying the solid black product D obtained by the washing and separation at the vacuum degree of 8000Pa and the temperature of 60 ℃ for 12 hours to obtain a quantum dot tin oxide metal-loaded multiwall carbon nano tube composite material with the size of about 5nm, which is marked as 3-QDSnO 2 /MWCNTs。
The reaction product was also quantum dot tin oxide particles of about 5nm in size supported on multi-walled carbon nanotubes (shown in fig. 8).
Fig. 8 is a TEM image of a quantum dot tin oxide loaded multiwall carbon nanotube of example 3.
The 3-QDSnO prepared in this example 2 The MWCNTs material is used as the negative electrode of the lithium ion battery, so that the cycling stability of the tin oxide composite negative electrode can be effectively improved, the capacity of the original multi-wall carbon nano tube can be greatly improved due to the existence of the tin oxide, a more stable SEI film is formed, and the test result is similar to that of the embodiment 1.
Example 4
(1) 98% analytically pure Sn (SO 4 ) 2 ·2H 2 O (100 mg) was dissolved in deionized water (30 mL) and stirred under magnetic stirring at 300 rpm for 5 minutes to give solution A;
(2) Adding 150mg of high-purity multi-wall carbon nano tube (purchased from Kana carbon new materials Co., ltd., purity > 97%, pipe diameter of 3-15 μm, pipe length of 15-30 μm) into the solution A obtained in the step (1), and continuing stirring for 2h to obtain a suspension B;
(3) Transferring the black suspension B obtained in the step (2) into a gas-liquid discharge plasma cylinder reactor main body, controlling the distance between the liquid level of the suspension and the lower end of the needle-shaped hollow electrode to be 4 millimeters, controlling high-purity argon (15 milliliters/min, purity is 99.999%) to directly blow the liquid level through the needle-shaped hollow electrode, switching on a plasma power supply, and continuously and stably reacting for 25 minutes under the conditions of 30 volts of input voltage, 4 kilovolts of output high voltage and 34.5 kilohertz of discharge frequency to obtain black suspension C;
(4) Filtering the black suspension C in the step (3) to wash impurities and separate solid from liquid, and then vacuum drying the solid black product D after washing and separation at the vacuum degree of 6000Pa and the temperature of 60 ℃ for 12 hours to obtain a quantum dot tin oxide metal-loaded multiwall carbon nanotube composite material, which is marked as 4-QDSnO 2 /MWCNTs。
The 4-QDSnO prepared in this example 2 As the anode of the lithium ion battery, the MWCNTs material can effectively improve the cycling stability of the tin oxide composite anode, the existence of the tin oxide can greatly improve the capacity of the original multi-wall carbon nano tube and form a more stable SEI film, and the test result is the same as that of the embodiment 1Like this.
Example 5
(1) 98% analytically pure Sn (SO 4 )·2H 2 O (200 mg) was dissolved in deionized water (30 mL) and stirred under magnetic stirring at 400 rpm for 5 minutes to give solution A;
(2) Adding 150mg of high-purity multi-wall carbon nano tube (purchased from Kana carbon new materials Co., ltd., purity > 97%, pipe diameter of 3-15 μm, pipe length of 15-30 μm) into the solution A obtained in the step (1), and continuing stirring for 2h to obtain a suspension B;
(3) Transferring the black suspension B obtained in the step (2) into a gas-liquid discharge plasma cylinder reactor main body, controlling the distance between the liquid level of the suspension and the lower end of the needle-shaped hollow electrode to be 5 mm, controlling high-purity argon (15 ml/min, purity 99.999%) to directly blow the liquid level through the needle-shaped hollow electrode, switching on a plasma power supply, and continuously and stably reacting for 30 minutes under the conditions of 60V input voltage, 8 KV output voltage and 60 KHz discharge frequency to obtain black suspension C;
(4) Washing impurities by suction filtration, separating solid from liquid in the black suspension C in the step (3), and then vacuum drying the solid black product D obtained by washing and separating at the vacuum degree of 8000Pa and the temperature of 60 ℃ for 12 hours to obtain a quantum dot tin oxide metal-loaded multiwall carbon nano tube composite material which is marked as 5-QDSnO 2 /MWCNTs。
The 5-QDSnO prepared in this example 2 The MWCNTs material is used as the negative electrode of the lithium ion battery, so that the cycling stability of the tin oxide composite negative electrode can be effectively improved, the capacity of the original multi-wall carbon nano tube can be greatly improved due to the existence of the tin oxide, a more stable SEI film is formed, and the test result is similar to that of the embodiment 1.

Claims (7)

1. A preparation method of a quantum dot tin oxide loaded multi-wall carbon nano tube composite material is characterized by comprising the following steps: the method comprises the following steps:
(1) Dissolving tin salt in water to obtain a tin salt solution;
(2) Uniformly mixing the multiwall carbon nanotube with a tin salt solution to obtain a suspension A;
(3) Placing the suspension A obtained in the step (2) into a gas-liquid discharge plasma reaction device, wherein the distance between the liquid surface of the suspension A and the lower end of a needle-shaped hollow electrode in the gas-liquid discharge plasma reaction device is 2-5 mm, and performing discharge reaction in an argon plasma atmosphere to obtain a suspension B; carrying out subsequent treatment to obtain a quantum dot tin oxide loaded multi-wall carbon nano tube composite material;
the dosage of the multi-wall carbon nano tube is as follows: the mass ratio of the tin ions to the multiwall carbon nanotubes is (0.04-0.8): 1;
conditions of the discharge reaction: controlling the input voltage to be 20-80V, the output high voltage to be 1-10 kilovolts, the discharge frequency to be 10-100 kilohertz, and the treatment duration to be 5-30 minutes;
the subsequent treatment refers to filtration and drying; the drying is vacuum drying, the vacuum degree is 5000-10000 Pa, the drying temperature is 60-80 ℃, and the time is 8-12 hours.
2. The method for preparing the quantum dot tin oxide supported multi-wall carbon nanotube composite material according to claim 1, which is characterized in that: the tin salt in the step (1) comprises more than one of tin chloride, stannous chloride, tin sulfate and stannous sulfate containing or not containing crystal water;
argon enters a discharge plasma reaction device through the needle-shaped hollow electrode in the step (3);
the flow rate of argon in the needle-shaped hollow electrode is 5-20 mL/min, and the purity is 99.999%;
the plasma discharge is a pulsed dc discharge.
3. The method for preparing the quantum dot tin oxide supported multi-wall carbon nanotube composite material according to claim 1, which is characterized in that: the mass volume ratio of the tin salt to the water is (10-200 mg) 30ml;
the step (2) of evenly mixing is evenly stirring; the stirring speed is 100-400 rpm, and the stirring time is 1-6 h.
4. The method for preparing the quantum dot tin oxide supported multi-wall carbon nanotube composite material according to claim 1, which is characterized in that: the gas-liquid discharge plasma reaction device comprises a needle-shaped hollow electrode, a reactor main body and a disc electrode; the reactor main body is a cavity with two open ends, the bottom of the reactor main body is closed by a disc electrode, and the needle-shaped hollow electrode is arranged in the cavity of the reactor main body through an opening at the upper end of the reactor main body; the needle-shaped hollow electrode is provided with an air inlet, one end of the needle-shaped hollow electrode, which is provided with the air inlet, is connected with the negative electrode output end of the rectifier, and one end of the air outlet is arranged in the reactor main body; the disc electrode is connected with the positive electrode output end of the rectifier; the air outlet of the needle-shaped hollow electrode is connected with the air storage device; the rectifier is connected with a power supply.
5. The method for preparing the quantum dot tin oxide supported multi-wall carbon nano tube composite material, which is characterized in that: the reactor main body is a cylindrical reactor, and is made of polytetrafluoroethylene; the needle-shaped hollow electrode is made of stainless steel, and the disc electrode is a graphite electrode; the depth of the reactor main body is 50 mm, and the diameter of the inner wall is 60 mm; and after the suspension A is added, the depth of the suspension A is 25-35 mm.
6. A quantum dot tin oxide supported multiwall carbon nanotube composite obtained by the method of any one of claims 1 to 5, characterized in that: the quantum dot tin oxide is loaded on the multiwall carbon nanotube composite material, nano-sized tin oxide particles are uniformly loaded on the multiwall carbon nanotube, the tin oxide loading is 15% -30% of the total mass of the quantum dot tin oxide loaded on the multiwall carbon nanotube composite material, and the size of the tin oxide particles is 4-6 nm.
7. The application of the quantum dot tin oxide loaded on the multi-wall carbon nano tube composite material according to claim 6, which is characterized in that: the quantum dot tin oxide is loaded on the multiwall carbon nanotube composite material and is used for a lithium ion battery as a negative electrode.
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