CN108598405B

CN108598405B - Preparation method of three-dimensional graphene tin oxide carbon composite negative electrode material

Info

Publication number: CN108598405B
Application number: CN201810341294.2A
Authority: CN
Inventors: 武大鹏; 任好雨; 杨东晓; 王红菊; 徐芳; 高志永; 蒋凯
Original assignee: Henan Normal University
Current assignee: Henan Normal University
Priority date: 2018-04-17
Filing date: 2018-04-17
Publication date: 2021-02-02
Anticipated expiration: 2038-04-17
Also published as: CN108598405A

Abstract

The invention discloses a preparation method of a three-dimensional graphene tin oxide carbon composite negative electrode material, and belongs to the technical field of synthesis of inorganic functional materials. The technical scheme provided by the invention has the key points that: the three-dimensional graphene tin oxide carbon composite negative electrode material is prepared by uniformly loading tin oxide nanocrystals with uniform sizes in a three-dimensional graphene net structure, and performing one-step nitrogen doping and carbon coating by using dopamine hydrochloride as a nitrogen source and a carbon source. The invention effectively relieves the volume expansion of the tin oxide in the alloying and dealloying process and enhances the stability of the lithium ion battery cathode material.

Description

Preparation method of three-dimensional graphene tin oxide carbon composite negative electrode material

Technical Field

The invention belongs to the technical field of synthesis of inorganic functional materials, and particularly relates to a preparation method of a three-dimensional graphene tin oxide carbon composite negative electrode material.

Background

Lithium ion batteries with high energy density and good cycle performance are widely used in portable electronic devices and energy storage devices, and although carbon-based negative electrode materials have been put into practice on a large scale, the industrialization of lithium ion batteries is severely limited by the lower theoretical specific capacity. Graphene has been used as a lithium ion battery cathode material for 20 years, and the theoretical capacity of graphene is 372mAh^-1And poor performance in the case of high-rate charge and discharge. SnO due to its own low cost, environmental protection and higher theoretical specific capacity₂Become a ratioAnd (3) a promising alternative material. More importantly, SnO is compared to other transition metal oxides₂Has a lower working voltage (the platform discharge voltage is between 0.3 and 0.5V), thereby leading to SnO₂The lithium ion battery cathode material has higher energy density in the aspect of application. Therefore, it is an urgent task to find an electrode material with high capacity and good cycle performance. In addition, the tin oxide also has the advantages of abundant product, environmental protection, no toxicity and the like. Therefore, tin oxide has become a hot spot of research in recent years as an anode material for lithium ion batteries. SnO₂The discharge process can be illustrated by the following equation:

SnO₂+4Li⁺+4e^-→Sn+2Li₂O (1)

for pure SnO₂The first reaction process is irreversible, and the theoretical capacity is only 780mAh g^-1. And for nano-sized SnO₂The first reaction process is reversible or partially reversible, and the theoretical capacity reaches 1494mAh g^-1This capacity is up to 3 times the capacity of commercial graphite. The second reaction is a reaction that is widely regarded as reversible, i.e., alloying and dealloying reactions can occur repeatedly during charging and discharging. SnO in improving cycle stability of lithium ion battery negative electrode material₂Severe volume expansion during charging and discharging (>300%) has been a difficult obstacle to overcome. In order to improve the cycle stability of the lithium ion battery, a large number of researchers research the influence of different morphologies of tin oxide on the performance of the battery, such as nanowires, nanotubes, nanosheets, solid and hollow nanospheres and the like. Besides the method of improving the performance, element doping is a very common way, such as graphene and tin oxide compounding, tin oxide and titanium oxide compounding, except that the method can be controlled by morphology, but the problem is not well solved in the previous research work. Thus, improveThe stability of tin oxide anode materials is still a problem to be solved.

Patent publication No. CN 105742635A discloses synthesis of carbon-coated graphene-tin oxide composite with glucose as carbon source at 100mA g^-1The discharge capacity after 100 charge-discharge cycles at the current density of (1) was maintained at 750mAh g^-1. The patent with publication number CN 106159245A uses hydrazine hydrate or sodium borohydride as a reducing agent to reduce graphene-tin oxide compound to obtain graphene-tin oxide compound, and the graphene-tin oxide compound is reduced at 100mA g^-1The discharge capacity after 100 charge-discharge cycles at the current density of (1) is kept at 820mAh g^-1. Patent publication No. CN 105355891A discloses that graphene and polystyrene are compounded to obtain a composite particle film, then the composite particle film and a tin oxide precursor are subjected to high-temperature calcination in a calcination mode to obtain a tin oxide-based composite material, and the discharge capacity is kept at 850mAh g after 100 charge-discharge cycles under the current density of 0.3C^-1. Therefore, the application of tin oxide in energy storage materials is to be further improved.

Disclosure of Invention

The composite negative electrode material prepared by the method takes graphene as a structural unit, graphene nanocrystals are successfully compounded on a graphene network structure in situ, so that the good conductivity of the graphene and the high specific capacity of tin oxide are organically combined, lone-pair electrons are introduced to increase active sites through nitrogen doping, and carbon coating further reduces the volume change of the tin oxide in the charging and discharging processes, effectively relieves the volume expansion of the tin oxide in the alloying and dealloying processes, and enhances the stability of the negative electrode material of the lithium ion battery.

The invention adopts the following technical scheme for solving the technical problems, and the preparation method of the three-dimensional graphene tin oxide carbon composite anode material is characterized by comprising the following specific steps of: 6.4mL of a gel containing 0.128g of graphene oxide was added to a beaker, and n-butanol was added to the beaker to make the solutionThe total volume is 32mL, then 0.6mL concentrated hydrochloric acid is added, the mixture is stirred for 10min, and 0.6mmol SnCl is added under the stirring condition₂·2H₂Adding O into a beaker, carrying out ultrasonic treatment for 40min until the graphene solution is completely dispersed, transferring the prepared suspension into a hydrothermal reaction kettle, carrying out hydrothermal reaction for 2h at 180 ℃, cooling the hydrothermal reaction kettle to the normal temperature, washing the obtained precipitate with alcohol and water for 3 times to obtain a graphene tin oxide compound, adding the graphene tin oxide compound into a 10mM Tris solution, stirring for 10min, adding 0.15g of dopamine hydrochloride, stirring for 6h at the normal temperature, centrifuging the solution, washing with deionized water and ethanol for 3 times, pre-freezing the product at-80 ℃ for 10h, transferring the product into a freeze-drying machine, freeze-drying for 48h, heating the product to 550 ℃ at the heating rate of 5 ℃/min in a nitrogen atmosphere, and calcining for 3h to carbonize the coated dopamine hydrochloride, thereby finally obtaining the nitrogen-doped graphene tin oxide composite negative electrode material.

Preferably, the three-dimensional graphene tin oxide carbon composite negative electrode material is prepared by uniformly loading tin oxide nanocrystals with uniform size in a three-dimensional graphene network structure, and performing one-step nitrogen doping and carbon coating by using dopamine hydrochloride as a nitrogen source and a carbon source, wherein the size of the tin oxide nanocrystals is 8-18 nm.

Compared with the prior art, the invention has the following beneficial effects: according to the invention, the reversible capacity of the negative electrode material is adjusted by adjusting the ratio of graphene to tin oxide in an acidic environment of concentrated hydrochloric acid. Meanwhile, the performance of undoped heteroatoms and doped nitrogen elements is compared by utilizing the difference of carbon sources, so that the graphene tin oxide carbon composite negative electrode material with high specific capacity and good cycling stability is obtained. The preparation method is simple, the repetition rate is high, and the prepared three-dimensional graphene tin oxide carbon composite negative electrode material has high rate performance and cycling stability.

Drawings

FIG. 1 is pure SnO₂SEM images of (a, b) and graphene oxide (c, d);

FIG. 2 is sample 3DG @ SnO₂SEM (a-b and e), TEM (C-d) and Mapping (f-i) profiles of @ N-C-2;

FIG. 3 shows a sample3DG@SnO₂XRD analysis pattern of @ N-C-2;

FIG. 4 is sample 3DG @ SnO₂@ N-C-2 at 100mA g^-1A charge-discharge cycle test chart at the current density of (a);

FIG. 5 is sample 3DG @ SnO₂@ N-C-2 at 200mA g^-1A cycle performance test chart under current density;

FIG. 6 is sample 3DG @ SnO₂The multiplying power performance test chart of @ N-C-2 under different current densities.

Detailed Description

The present invention is described in further detail below with reference to examples, but it should not be construed that the scope of the above subject matter of the present invention is limited to the following examples, and that all the technologies realized based on the above subject matter of the present invention belong to the scope of the present invention.

Examples

Graphene oxide (20mg mL) was prepared by modifying the classical Hummer's method^-1). Graphene oxide was prepared by modifying the classical Hummer's method: a250 mL round bottom flask was weighed 46mL concentrated sulfuric acid and added to 0.1g KNO₃In the process, NO is introduced₃ ^-The ions enhance the strong oxidizing property of the concentrated acid to a certain extent. After stirring for 10min to completely dissolve, 2g of graphite was weighed and slowly added to the flask with stirring for about 1h, and stirring was continued for 10min after completion to ensure more complete exfoliation of the graphite in concentrated sulfuric acid. 6g of potassium permanganate is weighed, slowly added into the flask under the condition of ice bath stirring, used for about 1 hour, and released heat in the process of adding the potassium permanganate, and the slow addition and the ice water bath are both used for preventing explosion. Stirring was continued for 2h under ice-water bath conditions so that the graphite was more completely exfoliated and oxidized in the strong acid solution. In the process, the color of the mixture solution of concentrated sulfuric acid, graphite and potassium permanganate gradually changes from black to dark green, which indicates that the graphite undergoes an oxidation reaction in the process. The flask was transferred to a 35 ℃ oil bath and stirred for 1h, then again to an ice-water bath, 92mL of deionized water was added dropwise, the rate of addition was controlled to avoid explosion due to intense heat evolution, during which the color of the mixed solution was determined by the inkThe green color changed to reddish brown. And transferring the flask into an oil bath at the temperature of 80 ℃, keeping the temperature for 15min, then transferring into the oil bath at the temperature of 60 ℃, dropwise adding 80mL of hydrogen peroxide with the mass fraction of 3% under the stirring condition, and changing the color of the solution from reddish brown to bright yellow. After stirring for 10min, the flask was allowed to stand for 2 h. The supernatant was decanted off and the yellow precipitate was washed 3 times with 5% dilute hydrochloric acid and then 3 times with deionized water. The solvent used in this experiment was n-butanol, so after three washes with water, the alcohol wash was continued with n-butanol. The precipitate was transferred to a buchner funnel and filtered with suction and washed again three times with n-butanol. Finally, a highly dispersed graphene solution with n-butanol as a dispersant was obtained. After the graphene colloidal solution is subjected to ultrasonic treatment for 1 hour, weighing and measuring the volume density of the graphene solution: weighing empty surface vessels₁Placing a certain volume v of graphene solution in a watch glass, and weighing the graphene solution with a mass m₂The petri dish was transferred to a forced air drying oven and dried overnight before weighing it to mass m₃By rho ═ m₃-m₁) Volume density of graphene (20mg mL) was measured by volume/v^-1)。

32mL of n-butanol was added to a beaker, 0.6mL of concentrated hydrochloric acid was added, and then 0.6mmol of SnCl was weighed₂·2H₂Adding O into a beaker, stirring for 10min, continuing to perform ultrasonic treatment for 40min, transferring the obtained mixed dispersion liquid into a high-temperature hydrothermal reaction kettle, and performing hydrothermal reaction at 180 ℃ for 2h to obtain pure SnO₂。

3.2mL (0.064g), 6.4mL (0.128g), 9.6mL (0.192g), 17mL (0.256g) of graphene oxide gel were weighed into a beaker, different volumes of n-butanol were added to the beaker to make the total volume of the solution 32mL, then 0.6mL of concentrated hydrochloric acid was added, stirring was carried out for 10min, and 0.6mmol of SnCl was added under stirring₂·2H₂Adding O into a beaker, carrying out ultrasonic treatment for 40min, transferring the prepared turbid liquid into a hydrothermal reaction kettle for hydrothermal reaction for 2h at 180 ℃ after the graphene solution is completely dispersed, and carrying out alcohol washing and water washing on the obtained precipitate for 3 times after the hydrothermal reaction kettle is cooled to normal temperature to obtain a graphene tin oxide composite 3DG @ SnO₂-1、3DG@SnO₂-2、3DG@SnO₂-3 and 3DG @ SnO₂-4, complexing graphene tin oxideAdding the compound into 10mM Tris solution, stirring for 10min, adding 0.15g dopamine hydrochloride, stirring for 6h at normal temperature, centrifuging the solution, washing for 3 times by using deionized water and ethanol, pre-freezing the product at-80 ℃ for 10h, transferring the product to a freeze dryer for freeze-drying for 48h, heating the product to 550 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, calcining for 3h to carbonize the coated dopamine hydrochloride, and finally obtaining the nitrogen-doped carbon-coated graphene tin oxide composite negative electrode material 3DG @ SnO₂@N-C-1、3DG@SnO₂@N-C-2、3DG@SnO₂@ N-C-3 and 3DG @ SnO₂@N-C-4。

Optimized analysis of graphene and SnO₂The influence of different proportions on the rate capability and the cycle performance of the electrode material, the optimal proportion of the product is 100mA g^-1The current density of the battery can be increased to 1349.5mAh g after 100 charge-discharge cycles^-1The reversible capacity of (a). After passing through the higher current density and returning to 200mA g^-1When charging and discharging, 726mAh g is still maintained^-1Higher reversible capacity. The obtained 3DG @ SnO₂The @ N-C-2, PVDF and conductive carbon black are coated on a copper foil according to the mass ratio of 8:1:1, the thickness of the copper foil is about 60 mu m, the copper foil is cut into pole pieces with the diameter of 14mm by a sheet punching machine, the pole pieces are assembled into a 2025 button battery, and an electrical property test is carried out.

Fig. 1 is an SEM image and a TEM image of pure graphene oxide and tin oxide prepared in this example, and it can be seen from (a) and (b) that pure tin oxide nanoparticles are synthesized during the experiment, and it can be seen from (c) and (d) that pure three-dimensional graphene oxide is synthesized during the experiment.

FIG. 2 is an SEM image and a TEM image of the material prepared in this example, wherein the network structure of three-dimensional graphene can be seen from (a), (b), and (e) in FIG. 2, and highly uniformly dispersed SnO can be seen from (c) in FIG. 2₂Nanoparticles, approximately 18nm in size. In FIG. 2 (d), the black marked region has a thin layer of carbon with a thickness of about 2.3nm, and the white dotted marked region shows SnO₂The lattice fringes of (2) are 0.265 nm. In FIG. 2, (e) is 3DG @ SnO₂Low magnification SEM image of @ N-C-2, (f), (g), (h), (i) are corresponding to those in FIG. 2(e)3DG@SnO₂The Mapping graph of @ N-C-2 shows C, O, Sn and the uniform distribution of N element, and at the same time, the realization of N element doping in the carbon coating process is proved again.

FIG. 3 shows sample 3DG @ SnO prepared in this example₂XRD analysis pattern of @ N-C-2. From FIG. 3, it can be seen that SnO synthesized during the experiment₂And SnO₂Diffraction peaks of the standard card (Cassieterite, JCPDS No.41-1445) were completely identical, and this result indicates that SnO having high purity was synthesized₂. In graphene oxide and SnO₂After recombination, the diffraction peak of graphene disappeared, indicating that graphene oxide was reduced to reduced graphene oxide in the process of high temperature.

FIG. 4 is an electrochemical test chart of the sample prepared in this example. FIG. 4 is sample 3DG @ SnO₂@ N-C-2 at 100mA g^-1The first charge and discharge specific capacities of the proportional samples are 1977.7mAh g respectively^-1And 1316.1mAh g^-1The coulombic efficiency reaches 66.5 percent, and 1279.2mAh g can still be obtained after 50 times of charge-discharge cycles^-1Higher specific capacity. The charging and discharging images of the 50 th cycle and the 100 th charging and discharging cycle are almost completely overlapped, the sample with the proportion has better cycle performance, in the process of compounding graphene and tin oxide, a better three-dimensional structure of the graphene and a higher specific capacity provided by the conversion reaction of the tin oxide are perfectly combined together, and the structural integrity of the sample is maintained in the process of cycling.

FIG. 6 shows 3DG @ SnO₂The multiplying power performance test chart of @ N-C-2 under different current densities. As is clear from the figure, sample 3DG @ SnO₂@ N-C-2 at 200mA g^-1、400mA g^-1、600mA g^-1、800mA g^-1And 1A g^-1Respectively maintain 857.1mA g^-1、722.7mA g^-1、651.3mA g^-1、578.1mA g^-1And 540.5mAh g^-1And 200mA g again after high current density charging and discharging^-1Current density charging and dischargingThe reversible capacity can still reach 726mAh g^-1。

The foregoing embodiments illustrate the principles, principal features and advantages of the invention, and it will be understood by those skilled in the art that the invention is not limited to the foregoing embodiments, which are merely illustrative of the principles of the invention, and that various changes and modifications may be made therein without departing from the scope of the principles of the invention.

Claims

1. A preparation method of a three-dimensional graphene tin oxide carbon composite negative electrode material is characterized by comprising the following specific steps: adding 6.4mL of gel containing 0.128g of graphene oxide into a beaker, adding n-butanol into the beaker to make the total volume of the solution be 32mL, adding 0.6mL of concentrated hydrochloric acid, stirring for 10min, and adding 0.6mmol of SnCl under stirring₂·2 H₂Adding O into a beaker, carrying out ultrasonic treatment for 40min until the graphene solution is completely dispersed, transferring the prepared suspension into a hydrothermal reaction kettle, carrying out hydrothermal reaction for 2h at 180 ℃, cooling the hydrothermal reaction kettle to the normal temperature, washing the obtained precipitate with alcohol and water for 3 times to obtain a graphene tin oxide compound, adding the graphene tin oxide compound into 10mM Tris solution, stirring for 10min, adding 0.15g of dopamine hydrochloride, stirring for 6h at the normal temperature, centrifuging the solution, washing with deionized water and ethanol for 3 times, pre-freezing the product for 10h at-80 ℃, and then transferring the product to a freeze dryer for freeze drying for 48h, and then heating the product to 550 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere for calcining for 3h so as to carbonize the coated dopamine hydrochloride, thereby finally obtaining the nitrogen-doped carbon-coated graphene tin oxide composite negative electrode material.

2. The preparation method of the three-dimensional graphene tin oxide carbon composite anode material according to claim 1, characterized by comprising the following steps: the three-dimensional graphene tin oxide carbon composite negative electrode material is prepared by uniformly loading tin oxide nanocrystals with uniform sizes in a three-dimensional graphene net structure, and performing one-step nitrogen doping and carbon coating by using dopamine hydrochloride as a nitrogen source and a carbon source, wherein the size of the tin oxide nanocrystals is 8-18 nm.