CN110783552B

CN110783552B - Carbon-coated titanium-doped tin dioxide material and preparation method and application thereof

Info

Publication number: CN110783552B
Application number: CN201911164919.3A
Authority: CN
Inventors: 袁斌; 梁紫微; 闫钰; 胡仁宗; 杨黎春; 刘军; 朱敏
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2019-11-25
Filing date: 2019-11-25
Publication date: 2022-02-15
Anticipated expiration: 2039-11-25
Also published as: CN110783552A

Abstract

The invention discloses a carbon-coated titanium-doped tin dioxide material and preparation and application thereof. The preparation method comprises the following steps: firstly SnSO₄Aqueous solution with H₂SO₄Uniformly mixing; adding 60-120nm spherical or nearly spherical nickel-titanium alloy powder into the aqueous solution, continuously adding a glucose organic matter, uniformly mixing, transferring the solution into a tetrafluoroethylene lining high-pressure reaction kettle, and reacting for 18-30 hours at 150-200 ℃; and after the reaction is finished and the temperature is cooled to room temperature, centrifugally collecting reaction products, respectively washing the reaction products for a plurality of times by using water and ethanol, then drying the products in vacuum, and then putting the products into a tubular furnace protected by argon for calcination to obtain the carbon-coated titanium-doped tin dioxide material. The improved preparation method has strong controllability and simple operation, can be used for large-scale production of the electrode material of the lithium ion secondary battery, and can obviously improve the cycle and rate performance of the electrode material.

Description

Carbon-coated titanium-doped tin dioxide material and preparation method and application thereof

Technical Field

The invention belongs to the field of nano functional materials and lithium ion secondary batteries, and particularly relates to a carbon-coated titanium-doped tin dioxide material as well as a preparation method and application thereof.

Background

Lithium Ion Batteries (LIBs) mainly comprise four parts, namely an anode, a cathode, a diaphragm and electrolyte, and realize the mutual conversion of electric energy and chemical energy by repeatedly embedding and extracting Li ions between the anode and the cathode. In the charging process, the lithium ion battery does work by an external power supply, and lithium ions are separated from the anode material and separated from crystal lattices of the anode material. The electrolyte is transported to the vicinity of the negative electrode material through the separator and inserted into the gap of the negative electrode material, and electrons are transported to the negative electrode from an external circuit in the process. When the battery does work externally, lithium ions are extracted from the negative electrode material and are transported to the vicinity of the positive electrode material through the electrolyte and are inserted into the crystal lattice of the positive electrode material, and electrons move from the negative electrode to the positive electrode in an external circuit. In general, the nature of the reversible cycle process of a lithium ion battery is the process of repeated intercalation and deintercalation of lithium ions with two electrodes.

LIBs have the advantages of high energy density (high specific capacity), light weight, long 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 (372 mAh g) of the negative electrode material graphite used in the commercial lithium ion battery at present^-1) And discharge potential (. about.0.1V vs. Li/Li)⁺Easy overcharge, resulting in deposition of lithium dendrites, forming short circuits) are relatively low, so that it cannot meet the demands (higher capacity, longer life, and higher safety) of the next generation of lithium ion batteries. Therefore, there is a need to develop alternative anode materials with high specific capacity, moderate discharge potential, and good cycling performance. Among the various alternative anode materials, the transition metal oxide SnO₂Due to high theoretical specific capacity (1494mAh g)^-1) Easy preparation, low cost and environmental protection, etc. and is widely concerned. However, currently SnO₂The negative electrode material is also difficult to replace graphite, mainly because there are some key problems to be solved, including poor conductivity; first coulombic efficiencyLow; during the charge/discharge process, especially at high discharge/charge rates, drastic volume changes occur, eventually causing pulverization and shedding of the negative electrode material; in addition, the reversibility of the conversion reaction process is poor, resulting in rapid decrease of reversible capacity and cycle performance. The existing method for solving the problems mainly comprises the steps of designing nano electrodes with different shapes and structures, compounding the nano electrodes with high-conductivity materials and the like. The purpose of various improvements is to be able to give Li⁺And electron rapid transmission provides effective channel to and alleviate the huge volume change and increase conductivity that the charge-discharge process produced through designing electrode material structure, thereby avoid causing destruction to the cathode material structure, provide cycle stability.

The nano electrode is to refine the anode material to nano level, and aims to reduce the absolute volume change of powder particles in the charge and discharge process and shorten Li⁺Thereby improving the cycle stability and rate capability. However, a single nano anode material is easy to agglomerate and has a large specific surface area, and each nano particle reacts with an electrolyte to generate an sei (solid electrolyte interface) film, so that a lithium source is consumed, and the capacity is reduced. In addition, no matter how fine the nano material is, the semiconductor characteristics of the bulk material of the nano material are not changed, and the conductivity and the reversibility of the conversion reaction process are not improved fundamentally.

The high-conductivity material composite refers to a composite negative electrode material formed by combining a matrix material and a conductive substance (such as carbon, amorphous oxide, transition metal and the like) in a certain mode. The introduction of the conductive substance can enhance the conductivity of the cathode particles, and the conductive substance coated cathode material can play a role in limiting the agglomeration of the nanoparticles, relieving the volume expansion in the charge-discharge process and preventing the agglomeration and growth of Sn particles, thereby increasing the reversibility of the conversion reaction process and improving the cycle performance thereof, which is the most common method used at present. However, this method also does not improve the intrinsic conductivity of the anode material, and the added transition metal is partially non-uniform, resulting in rapid decay of rate performance and cycle stability after long cycles.

In summary, separate miningSnO is not satisfactorily solved by any of the above methods₂The intrinsic conductivity of the cathode material is poor, and the reversibility and rate property of the conversion reaction process are poor. The reason for this is that SnO is not changed at the atomic level₂The electronic structure and the electrical conductivity of the composite material, and the problem of agglomeration and growth of nano Sn particles generated after the conversion reaction on the atomic level are solved, which can not meet the requirement of SnO₂The reversibility of conversion reaction and rate capability required by the anode material in the long-term circulation process.

CN2016103788472 discloses a C-SnO₂/Ti₃C₂Two-dimensional nano lithium ion battery cathode material and preparation method thereof, and Ti is used₃C₂As a matrix, with SnCl₄·nH₂O is used as a tin source, polyvinyl alcohol (PVA) is used as a carbon source, and SnO is generated by annealing at high temperature through a solid-phase sintering method₂Supported on Ti₃C₂And is coated with amorphous carbon on the surface thereof, thereby providing a carbon-coated granular tin dioxide/two-dimensional nano titanium carbide (C-SnO)₂/Ti₃C₂) A method for preparing the composite material; mixing Ti₃AlC₂Chemical etching is carried out in HF acid to ensure that Al is selectively etched away to form a two-dimensional layered material Ti₃C₂Then in a two-dimensional layered material Ti₃C₂Loaded SnO₂Make Ti be₃C₂The specific surface is larger, and SnO is considered₂Has the advantages of good heat conductivity and electric conductivity. In this technique, although a C-SnO was successfully prepared₂/Ti₃C₂Two-dimensional nano lithium ion battery cathode material, however, the material is 1Ag^-1Can only keep less than 200mAh g under the current density^-1The capacity and the cycling stability of the catalyst are poor, and the main problem of poor reversibility of the conversion reaction of the tin dioxide is not solved.

Disclosure of Invention

In order to overcome the existing SnO₂The invention provides a carbon-coated titanium-doped tin dioxide material, and a preparation method and application thereof.

The invention uses SnSO₄As a source of tin, inGlucose is used as a carbon source, nickel titanium (NiTi) alloy powder is added into a reaction system, and the carbon-coated titanium-doped SnO is prepared₂Nano material with good intrinsic conductivity and Ti uniformly distributed in SnO₂On the nano-matrix. The material is used as a lithium ion battery cathode material and can reinforce Li⁺And the transmission of electrons, relieve the volume change produced in the charge-discharge process, achieve the goal of improving the capacity, cycle performance and rate performance of the lithium ion battery.

According to the invention, the NiTi alloy powder and the glucose organic matter which are added into the reaction system at the same time can introduce metal into the reaction system at the same time, realize carbon coating and enhance SnO₂Intrinsic conductivity of the electrode material and structural stability. SnO after introduction of NiTi alloy powder and organic matter of grape₂Is basically unchanged and mainly presents as a nano-sized spherical structure which is beneficial to Li⁺Rapid insertion and extraction of Li and shortening of Li⁺And the transmission distance of the electrons; simultaneously, the introduction of NiTi alloy and the coating of carbon can effectively buffer SnO₂The volume expansion generated in the charging and discharging process enhances the structural stability of the material, thereby improving the cycle stability of the material. The spherical SnO prepared by the invention₂The material can better meet the requirement of being used as the lithium ion battery cathode material, and the preparation process is simple and easy to realize large-scale production.

The purpose of the invention is realized by at least one of the following technical solutions.

The invention provides a preparation method of a carbon-coated titanium-doped tin dioxide material, which comprises the following steps:

(1) SnSO₄Adding the mixture into deionized water, and uniformly stirring to obtain a solution A;

(2) dropwise adding H into the solution A obtained in the step (1) under stirring₂SO₄Obtaining a solution B;

(3) adding nano NiTi alloy powder into the solution B obtained in the step (2) under a stirring state to obtain a solution C;

(4) adding glucose (organic matter) into the solution C obtained in the step (3) under the stirring state to obtain a solution D;

(5) transferring the solution D obtained in the step (4) into a reaction kettle, heating for heating treatment, and cooling to room temperature to obtain a heated product;

(6) and (4) centrifuging the heated product obtained in the step (5), taking the precipitate, washing and drying to obtain powder, and putting the powder into a tubular furnace under a protective atmosphere to heat and calcine to obtain the carbon-coated titanium-doped tin dioxide material.

Further, in the solution A in the step (1), SnSO₄The concentration of (b) is 0.047mol/L-0.093 mol/L.

Preferably, the SnSO of step (1)₄For analyzing pure SnSO₄。

Further, step (2) said H₂SO₄The mass percentage concentration of the solution is 3-8 wt%; h in the step (2)₂SO₄The volume of the solution is 9-15% of the volume of the water in the step (1).

Further, the nano NiTi alloy powder in the step (3) is spherical or nearly spherical particles, and the particle size of the nano NiTi alloy powder is 60-120 nm; in the nano NiTi alloy powder, the weight percentage of Ni is 54-56%; the mass of the nano NiTi alloy powder is the SnSO in the step (1)₄10-30% of the mass.

Further, the glucose in the step (4) is analytically pure grade glucose; the glucose in the step (3) and the SnSO in the step (1)₄The mass ratio of (1.5-2.5): 1.

further, the reaction kettle in the step (5) is a polytetrafluoroethylene lining high-pressure reaction kettle; the temperature of the heating treatment is 150-; the washing comprises the following steps: washing with water and ethanol respectively; the number of washing times is 3-5.

Further, the drying manner in the step (6) comprises vacuum drying; the drying temperature is 60-80 ℃, the drying time is 12-30h, and the vacuum degree of drying is 1000-4000 Pa.

Further, the protective atmosphere in the step (6) is argon atmosphere; the rate of temperature rise is 3-5 ℃/min; the temperature of the calcination treatment is 400-600 ℃, and the time of the calcination treatment is 2-8 hours.

Preferably, the stirring manner in the step (1), the step (2), the step (3) and the step (4) includes magnetic stirring, the rotation speed of the stirring in the step (1), the step (2), the step (3) and the step (4) is 100-400 rpm, and the stirring time is 2-60 minutes.

The invention provides a carbon-coated titanium-doped tin dioxide material prepared by the preparation method, the shape of the carbon-coated titanium-doped tin dioxide material is spherical nano particles, the particle size is 200-1000nm, and the titanium doping amount in the carbon-coated titanium-doped tin dioxide material is 0.8-4%.

The carbon-coated titanium-doped tin dioxide material provided by the invention can be applied to preparation of electrode materials of secondary lithium batteries.

The preparation method provided by the invention is characterized in that H is added into a reaction system₂SO₄By means of H₂SO₄Dealloying of Ni and Ti elements in NiTi alloy powder, H₂SO₄Can dissolve Ni and Ti elements into Ni²⁺And Ti⁴⁺However, the binding energy of Ti-O was 662KJ/mol, that of Ni-O was 391.6KJ/mol and that of Sn-O was 548KJ/mol, so that only Ti ions could be adsorbed on SnO₂And is uniformly doped into SnO at atomic level in the reaction₂In the nanoparticles, SnO is changed due to Ti doping₂Thereby changing SnO₂The intrinsic conductivity and the catalytic activity of the composite material, and the growth of nano Sn particles generated by conversion reaction is limited at an atomic level. However, Ni has a weak bonding force with O and does not participate in SnO₂The growth process of (1). Finally, the coated glucose is carbonized by calcining in a high-temperature tube furnace, and SnO is doped in Ti₂The surface of the titanium dioxide layer is coated with a carbon layer, so that the carbon-coated Ti-doped spherical tin dioxide material is prepared.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the preparation method provided by the invention can realize uniform doping of Ti and coating of external carbon by simultaneously adding the glucose organic matter and the nano NiTi alloy powder, and has the advantages of simple process, high efficiency and batch production;

(2) according to the invention, the nano-scale high-conductivity composite anode material can be obtained by a simple one-step hydrothermal method, and the operation is simple and convenient;

(3) the carbon-coated titanium-doped SnO prepared by the invention₂The material is used as the lithium ion battery cathode, can effectively improve the volume expansion caused by long-term circulation, and improves the overall capacity, rate capability and cycle life of the lithium ion battery.

Drawings

FIG. 1 is a graph showing that the original SnO prepared without adding glucose and NiTi alloy powder in example 1₂Sample and SnO prepared by only adding NiTi alloy powder₂Sample and SnO prepared by simultaneously adding glucose and NiTi alloy powder₂The XRD diffraction pattern of the sample also includes the addition of NiTi alloy powder and standard SnO in figure 1₂A diffraction spectrum;

FIG. 2 is a view showing that SnO prepared by adding glucose and NiTi alloy powders simultaneously in example 1₂Sample, SnO prepared by only adding NiTi alloy powder₂Samples and original SnO prepared without adding glucose and NiTi alloy powder₂23-31 ° partial magnification of XRD diffractogram of the sample;

FIG. 3 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂SEM images of the samples at 10k magnification;

FIG. 4 is SnO prepared by adding only NiTi alloy powder in example 1₂SEM images of the samples at 10k magnification;

FIG. 5 shows the raw SnO prepared without adding glucose and NiTi alloy powder in example 1₂SEM images of the samples at 10k magnification;

FIG. 6 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂The element distribution diagram of the EDX energy spectrum of the sample under the 2k magnification;

FIG. 7 is SnO prepared by adding only NiTi alloy powder in example 1₂The element distribution diagram of the EDX energy spectrum of the sample under the 2k magnification;

FIG. 8 shows SnO with a nano-spherical structure prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂Analyzing each element of the EDX energy spectrum of the sample;

FIG. 9 shows SnO with a nano-spherical structure prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂Thermogravimetric analysis curve of the sample;

FIG. 10 shows SnO with a nano-spherical structure prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂The sample is SnO prepared by only adding NiTi alloy powder in example 1₂Samples and original SnO prepared without adding glucose and NiTi alloy powder₂A cycle performance chart of the sample at the current density of 1A/g for 600 times;

FIG. 11 shows the raw SnO of example 1₂Sample, SnO prepared by adding NiTi alloy powder only₂Sample and SnO prepared by simultaneously adding glucose and NiTi alloy powder₂A comparison graph of rate performance of the sample;

FIG. 12 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂Sample, SnO prepared by only adding NiTi alloy powder₂Samples and original SnO prepared without adding glucose and NiTi alloy powder₂Nyquist plot for the sample.

FIG. 13 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 2₂SEM images of the samples at 10k magnification;

FIG. 14 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 2₂The EDX energy spectrum of the sample shows the result of each element analysis;

FIG. 15 shows SnO prepared by adding glucose and NiTi alloy powders in examples 1, 2 and 3₂Graph of the cycle performance of the sample at 1000 times at 2A/g current density;

FIG. 16 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 3₂SEM images of the samples at 10k magnification;

FIG. 17 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 3₂Results of analysis of each element of EDX spectrum of sampleFigure (a).

Detailed Description

The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.

Example 1

A preparation method of a carbon-coated titanium-doped tin dioxide material comprises the following steps:

(1) 1.07g of SnSO to be analytically pure₄Dissolving in 100mL of deionized water, magnetically stirring for 30 minutes at 200 revolutions per minute, and uniformly stirring to obtain a solution A;

(2) adding 9mL of H with the solubility of 5% dropwise into the solution A obtained in the step (1) under magnetic stirring₂SO₄Stirring for 2 minutes at 250 revolutions per minute, and uniformly stirring to obtain a solution B;

(3) adding 0.161g of 60nm spherical NiTi alloy (the mass percent of Ni in the alloy components is 55%) powder into the solution B obtained in the step (2) under magnetic stirring, stirring for 30 minutes at 250 revolutions per minute, and uniformly stirring to obtain a solution C;

(4) adding 2g of glucose into the solution C obtained in the step (3) under magnetic stirring, stirring for 60 minutes at 250 revolutions per minute, and uniformly stirring to obtain a solution D;

(5) transferring the solution D obtained in the step (4) into a tetrafluoroethylene-lined high-pressure reaction kettle, and reacting for 24 hours at 180 ℃.

(6) After the reaction is finished and the temperature is cooled to room temperature, centrifugally collecting the reaction product obtained in the step (5), washing the reaction product with water and ethanol for 3 times respectively, and then carrying out vacuum drying on the reaction product for 24 hours at the temperature of 60 ℃ under the vacuum degree of 1000Pa to obtain a powder sample E;

(7) calcining the powder sample E obtained in the step (6) in a tubular furnace protected by argon, reacting for 3 hours at 500 ℃ with the heating rate of 5 ℃/min to obtain the carbon-coated titanium-doped tin dioxide material, and using SnO in the figure 1₂and/NiTi @ C.

Removing the steps (2), (3), (4) and (7), and obtaining the original SnO without adding glucose and NiTi alloy powder without changing other steps₂Samples, using SnO in FIG. 1₂And (4) showing.

Removing the steps (4) and (7), and obtaining SnO only added with NiTi alloy powder without changing other steps₂Samples, using SnO in FIG. 1₂and/NiTi.

SnO mentioned above₂/NiTi@C、SnO₂NiTi and SnO₂The XRD diffraction patterns of the three-dimensional diffraction pattern are respectively shown as a, b and c in figure 1. In FIG. 1, no diffraction peak (d in FIG. 1) of the original added nano NiTi alloy powder appears, which indicates that the NiTi alloy participates in the reaction, no residue exists, and the generated SnO₂The material is of a tetragonal structure. In FIG. 1, e is standard SnO₂XRD diffraction spectrum of the material, and original SnO obtained without adding glucose and NiTi alloy powder₂The XRD results for the materials are consistent (as in c of fig. 1). In difference, SnO prepared by simultaneously adding glucose and NiTi alloy powder₂Sample and SnO prepared by only adding NiTi alloy powder₂The XRD diffraction spectrum of the sample is relative to the original SnO prepared by not adding glucose and NiTi alloy powder₂The XRD diffraction spectrum of the sample is enlarged (as shown in figure 2) and has the phenomenon of rightward shift, i.e. the interplanar spacing is reduced, which is mainly because of Ti⁴⁺Has a radius of 60.5pm, Sn⁴⁺Has a radius of 69pm, calculated according to the Bragg equation, with Ti having a smaller radius⁴⁺By substituting part of Sn⁴⁺The position of (2) causes the lattice constant to decrease and the interplanar spacing to become smaller.

FIG. 6 is a SnO prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂Performing surface scanning on a sample under a 2k magnification to obtain an EDX energy spectrum element distribution diagram; in fig. 6, (a) is a Sn element distribution diagram, (b) is an O element distribution diagram, (C) is a C element distribution diagram, (d) is a Ti element distribution diagram, and (e) is a Ni element distribution diagram, it can be confirmed from the energy spectrum element distribution diagram of fig. 6 that only Sn, O, C, and Ti exist in the sample and are uniformly distributed, and Ni is almost not.

FIG. 7 is SnO prepared by adding only NiTi alloy powder in example 1₂Performing surface scanning on a sample under a 2k magnification to obtain an EDX energy spectrum element distribution diagram; in fig. 7, (a) is a Sn element distribution diagram, (b) is an O element distribution diagram, (c) is a Ti element distribution diagram, and (d) is a Ni element distribution diagram, it can be confirmed from the energy spectrum element distribution diagram of fig. 7 that only Sn, O, and Ti exist in the sample and are uniformly distributed, and Ni is almost not.

Fig. 8 is a graph showing the distribution of elements in the EDX spectrum of the carbon-coated titanium-doped tin dioxide material prepared by adding glucose and NiTi alloy powder simultaneously in example 1, obtained by surface scanning at a magnification of 2 k. Table 1 below shows SnO with a nano spherical structure prepared by adding glucose and NiTi alloy powder simultaneously in example 1₂The data in table 1 correspond to the element distribution curves of fig. 8, and the relative content percentages of the elements of the EDX spectra of the samples obtained by surface scanning at 2k magnification. From the EDX spectroscopy elemental analysis results of fig. 8 and table 1, it can be seen that the mass percentage of Ti in the carbon-coated titanium-doped tin dioxide material prepared in example 1 was about 3.3%.

Fig. 9 is a thermogravimetric analysis curve obtained by testing the carbon-coated titanium-doped tin dioxide material prepared by simultaneously adding glucose and NiTi alloy powder in the temperature range of 40 ℃ to 600 ℃ and the temperature rise rate of 5 ℃/min to 10 ℃/min in example 1, and the carbon content of the carbon-coated titanium-doped tin dioxide material is about 16.4% as shown in the thermogravimetric analysis curve of fig. 9, so that the carbon-coated titanium-doped tin dioxide material prepared in example 1 can be obtained.

TABLE 1

The carbon-coated titanium-doped tin dioxide material prepared in example 1 has a nano-spherical structure as a basic unit, and compared with pure tin dioxide (as shown in fig. 5, the particle size is 200-1000nm, and a small amount of flaky particles are added in addition to spherical particles), all the carbon-coated titanium-doped tin dioxide material is prepared by only adding NiTi alloy powder, so that the nano-spherical particles are uniform in morphology, the particle size is obviously refined (as shown in fig. 4), and the particle size is 100-300 nm. For the sample prepared by adding glucose and NiTi alloy powder at the same time (i.e. the carbon-coated titanium-doped tin dioxide material, as shown in figure 3), part of the particles grow up due to high-temperature calcination, part of the spherical particles grow up to 1000nm, the small particles are still about 200nm, and the flaky particles disappear. However, due to the addition of glucose and NiTi alloy powder, the doping of titanium and the coating of carbon can be simultaneously realized, the volume expansion generated in the lithium deintercalation reaction process can be effectively buffered, and the structural stability of the material in the long-cycle process is enhanced.

The carbon-coated titanium-doped tin dioxide material prepared in example 1 was pressed into a button cell 12mm in diameter as a working electrode, PE as a separator, a metal lithium sheet as a counter electrode, and ethylene carbonate as an electrolyte in a glove box to form a half cell. The prepared half cell is subjected to charge and discharge performance test in a blue battery test system, and the specific parameters are as follows: the current density is 1A/g, and the charge-discharge voltage range is 0.01-3V. As can be seen from FIG. 10, the first discharge capacity of the sample prepared by adding glucose and the nano NiTi alloy powder reaches 1232.5mAh/g, and reaches 82.5% of the theoretical capacity (1494mAh/g) (if the conversion reaction is completely irreversible, the capacity should be 783mAh/g, which is 52.4% of the theoretical capacity), which indicates that the conversion reaction is good in reversibility; the specific capacity after 600 times of circulation can be kept at 844.2mAh/g (a in figure 10), the circulation performance is excellent, and the capacity is kept stable; the first discharge capacity of a sample prepared by only adding NiTi alloy powder reaches 1112.7mAh/g, and can reach 74.5% of theoretical capacity, which indicates that the conversion reaction reversibility is general; the specific capacity after 600 cycles can be kept at 678.9mAh/g (b in figure 10), and the capacity retention rate is about 61%. However, for the original SnO prepared without addition of NiTi alloy and glucose₂The first discharge capacity reaches 984mAh/g, and only reaches 65.9 percent of theoretical capacity, which indicates that the conversion reaction reversibility is poor; the specific capacity after 600 cycles is reduced to below 197.5mAh/g, and the capacity retention rate is only about 20% (c in figure 10); further, the test parameters become: the current density is 2A/g, and the charge-discharge voltage range is 0.01-3V. Samples made with simultaneous addition of glucose and NiTi alloy powder (i.e., carbon-coated titanium-doped tin dioxide)Material, denoted SnO in fig. 15₂/NiTi@C₂) The first discharge capacity reaches 1172.1mAh/g, the specific capacity after 1000 cycles can be kept at 801.4mAh/g (a in figure 15), and the capacity retention rate is about 68.4%. In addition, from the rate performance curve (fig. 11), it can be seen that, from the current density of 0.1A/g to 2A/g, the sample prepared by only adding NiTi alloy powder shows better rate performance than the original tin dioxide, and simultaneously, the titanium doped SnO coated with carbon is realized by adding glucose and NiTi alloy powder₂The material (the carbon-coated titanium-doped tin dioxide material) showed the best rate performance, so the carbon-coated titanium-doped SnO₂The material exhibits excellent cycling stability, rate capability and high capacity characteristics.

FIG. 12 shows SnO prepared by adding glucose and NiTi alloy powder simultaneously₂Sample (SnO in FIG. 12)₂/NiTi @ C), SnO prepared by only adding NiTi alloy powder₂Sample (SnO in FIG. 12)₂NiTi) and original SnO prepared from non-added glucose and NiTi alloy powder₂Sample (SnO in FIG. 12)₂) The radius of the circle in fig. 12 represents the interface impedance of the electrode material, and the smaller the diameter represents the smaller the interface impedance, the better the conductivity of the electrode material. As can be seen from FIG. 12, the addition of the NiTi alloy powder and glucose can indeed reduce the charge transfer resistance, which indicates that SnO prepared by adding glucose and NiTi alloy powder simultaneously₂The sample had better electronic conductivity.

Example 2

(1) 1g of analytically pure SnSO₄Dissolving in 100mL of deionized water, magnetically stirring for 30 minutes at 400 rpm, and uniformly stirring to obtain a solution A;

(2) under magnetic stirring, 12mL of H with the solubility of 8% is added dropwise to the solution A obtained in the step (1)₂SO₄Stirring for 3 minutes at the speed of 400 revolutions per minute, and uniformly stirring to obtain a solution B;

(3) adding 0.3g of powder of 120nm spherical NiTi alloy (the mass percent of Ni in the alloy components is 56%) into the solution B obtained in the step (2) under magnetic stirring, stirring at 420 r/min for 25 min, and uniformly stirring to obtain a solution C;

(4) adding 1.5g of glucose into the solution C obtained in the step (3) under magnetic stirring, stirring at 480 revolutions per minute for 50 minutes, and uniformly stirring to obtain a solution D;

(5) transferring the solution D obtained in the step (4) into a tetrafluoroethylene-lined high-pressure reaction kettle, and reacting for 30 hours at the temperature of 150 ℃.

(6) After the reaction is finished and the temperature is cooled to room temperature, centrifugally collecting the reaction product obtained in the step (4), washing the reaction product with water and ethanol for 5 times respectively, and then carrying out vacuum drying on the reaction product for 12 hours at 80 ℃ under 3000Pa vacuum degree to obtain a powder sample E;

(7) and (4) putting the powder sample E obtained in the step (6) into a tubular furnace protected by argon gas for calcining, and reacting for 8 hours at the temperature rise rate of 3 ℃/min400 ℃ to obtain the carbon-coated titanium-doped tin dioxide material.

The reaction product (the carbon-coated titanium-doped tin dioxide material prepared in example 2) is SnO with a tetragonal structure₂The basic unit of the reaction product is a nano spherical structure, and the particle diameter is 200-1000nm (as shown in figure 13). Meanwhile, according to the EDX element energy spectrum analysis result of FIG. 14 and the data of the following Table 2, it can be proved that only Sn, O, C and Ti exist in the sample, but Ni is almost not existed, and the doping amount of Ti is about 3.9% by mass. Due to the addition of the glucose and the NiTi alloy powder, the doping of titanium and the coating of carbon can be simultaneously realized, the volume expansion generated in the lithium desorption reaction process can be effectively buffered, and the structural stability of the material in the long-circulating process is enhanced.

TABLE 2

The carbon-coated titanium-doped tin dioxide material (sample prepared by adding 1.5g of glucose) prepared in the embodiment is used as a lithium ion battery cathode, and the prepared half battery is subjected to charge and discharge performance test in a blue battery test system, and the prepared half battery has the advantages ofThe body parameters were as follows: the current density is 2A/g, and the charge-discharge voltage range is 0.01-3V. As can be seen from c of FIG. 15, the sample (denoted SnO in FIG. 15) made with the addition of 1.5g of glucose₂/NiTi@C_1.5) The first discharge capacity reaches 1252.8mAh/g, the specific capacity after 1000 cycles can be kept at 145.6mAh/g (c in figure 15), and the capacity retention rate is about 11.6%.

Example 3

(1) 2g of analytically pure SnSO₄Dissolving in 100mL of deionized water, magnetically stirring for 30 minutes at 300 revolutions per minute, and uniformly stirring to obtain a solution A;

(2) adding 15mL of H with the solubility of 3% dropwise into the solution A obtained in the step (1) under magnetic stirring₂SO₄Stirring for 2 minutes at 300 revolutions per minute, and uniformly stirring to obtain a solution B;

(3) adding 0.2g of 80nm spherical NiTi alloy (the mass percentage of Ni in the alloy components is 54%) powder into the solution B obtained in the step (2) under magnetic stirring, stirring for 30 minutes at 360 revolutions per minute, and uniformly stirring to obtain a solution C;

(4) under magnetic stirring, adding 5g of glucose into the solution C obtained in the step (3), stirring at 390 rpm for 60 minutes, and uniformly stirring to obtain a solution D;

(5) transferring the solution D obtained in the step (4) into a tetrafluoroethylene-lined high-pressure reaction kettle, and reacting for 18 hours at the temperature of 200 ℃.

(6) After the reaction is finished and the temperature is cooled to room temperature, centrifugally collecting the reaction product obtained in the step (4), washing the reaction product with water and ethanol for 3 times respectively, and then carrying out vacuum drying on the reaction product for 30 hours at 70 ℃ under the vacuum degree of 2000Pa to obtain a powder sample E;

(7) and (4) putting the powder sample E obtained in the step (6) into a tubular furnace protected by argon gas for calcining, and reacting for 2 hours at the temperature rise rate of 5 ℃/min and the temperature of 600 ℃ to obtain the carbon-coated titanium-doped tin dioxide material.

SnO with reaction product also having tetragonal structure₂The basic unit of the reaction product is in the shape of a nanosphereThe structure has a particle diameter of 200-1000nm (as shown in FIG. 16). Meanwhile, the elemental analysis results of the EDX spectrum of FIG. 17 and the data of Table 3 below show that only Sn, O, C and Ti exist in the sample, but Ni is almost absent, and the doping amount of Ti is about 0.8% by mass. Due to the addition of the glucose and the NiTi alloy powder, the doping of titanium and the coating of carbon can be simultaneously realized, the volume expansion generated in the lithium desorption reaction process can be effectively buffered, and the structural stability of the material in the long-circulating process is enhanced.

TABLE 3

The carbon-coated titanium-doped tin dioxide material (sample prepared by adding 5g of glucose) prepared in this example was used as a negative electrode of a lithium ion battery, and the specific parameters were as follows: the current density is 2A/g, and the charge-discharge voltage range is 0.01-3V. As can be seen from b in FIG. 15, a sample (denoted as SnO in FIG. 15) was prepared by adding 5g of glucose₂/NiTi@C₅) The first discharge capacity reaches 1113.6mAh/g, the specific capacity after 1000 cycles can be kept at 572.9mAh/g (b in figure 15), and the capacity retention rate is about 51.4%; and the sample showed excellent cycle stability.

The above examples are only preferred embodiments of the present invention, which are intended to be illustrative and not limiting, and those skilled in the art should understand that they can make various changes, substitutions and alterations without departing from the spirit and scope of the invention.

Claims

1. A preparation method of a carbon-coated titanium-doped tin dioxide material is characterized by comprising the following steps:

(1) SnSO₄Adding the mixture into water, and uniformly stirring to obtain a solution A;

(2) dropwise adding H into the solution A in the step (1) under the stirring state₂SO₄Obtaining a solution B;

(4) adding glucose into the solution C obtained in the step (3) under the stirring state to obtain a solution D;

(6) and (4) centrifuging the heated product in the step (5) to obtain a precipitate, washing and drying to obtain powder, and heating the powder in a protective atmosphere to perform calcination treatment to obtain the carbon-coated titanium-doped tin dioxide material.

2. The method of claim 1, wherein the SnSO is in the solution A in the step (1)₄The concentration of (b) is 0.047mol/L-0.093 mol/L.

3. The method of claim 1, wherein the H in step (2) is₂SO₄The mass percentage concentration of the solution is 3-8 wt%; h in the step (2)₂SO₄The volume of the solution is 9-15% of the volume of the water in the step (1).

4. The method for preparing the carbon-coated titanium-doped tin dioxide material as claimed in claim 1, wherein the nano NiTi alloy powder in the step (3) is spherical or nearly spherical particles, and the particle diameter of the nano NiTi alloy powder is 60-120 nm; in the nano NiTi alloy powder, the weight percentage of Ni is 54-56%; the mass of the nano NiTi alloy powder is the SnSO in the step (1)₄10-30% of the mass.

5. The method of preparing a carbon-coated titanium-doped tin dioxide material according to claim 1, wherein the glucose in the step (4) is analytically pure glucose; the glucose in the step (4) and the SnSO in the step (1)₄The mass ratio of (1.5-2.5): 1.

6. the method for preparing the carbon-coated titanium-doped tin dioxide material according to claim 1, wherein the reaction kettle in the step (5) is a polytetrafluoroethylene-lined high-pressure reaction kettle; the temperature of the heating treatment is 150-; the washing of step (6) comprises: washing with water and ethanol respectively; the number of washing times is 3-5.

7. The method of claim 1, wherein the drying of step (6) comprises vacuum drying; the drying temperature is 60-80 ℃, the drying time is 12-30h, and the vacuum degree of drying is 1000-4000 Pa.

8. The method of preparing a carbon-coated titanium-doped tin dioxide material as claimed in claim 1, wherein the protective atmosphere in step (6) is an argon atmosphere; the rate of temperature rise is 3-5 ℃/min; the temperature of the calcination treatment is 400-600 ℃, and the time of the calcination treatment is 2-8 hours.

9. The carbon-coated titanium-doped tin dioxide material prepared by the preparation method of any one of claims 1 to 8 is characterized in that the morphology is spherical nanoparticles, the particle diameter is 200-1000nm, and the titanium-doped amount in the carbon-coated titanium-doped tin dioxide material is 0.8-3.9%.

10. Use of the carbon-coated titanium-doped tin dioxide material of claim 9 in the preparation of an electrode material for a secondary lithium battery.