阅读说明：本技术 一种CuCo-BDC超薄纳米片及其制备方法和用途 (CuCo-BDC ultrathin nanosheet and preparation method and application thereof ) 是由 崔接武 张会龙 吴玉程 余东波 王岩 张勇 于 2021-08-25 设计创作，主要内容包括：本发明公开了一种CuCo-BDC超薄纳米片及其制备方法和用途,所述制备方法包括以下步骤：将二水合氯化铜、六水合氯化钴、对苯二甲酸超声溶于N,N-二甲基甲酰胺、乙醇、去离子水的混合溶液；将上述步骤所得溶液进行搅拌,在搅拌状态下加入三乙胺,随后置于超声机内超声,然后进行离心,将离心后所得产物用乙醇清洗数次,烘干后得到Cu/Co-BDC粉末,即为所述CuCo-BDC超薄纳米片。本发明通过调控金属元素的比例来获得最优性能的Cu/Co-BDC超薄纳米片,然后直接用作锂离子电池负极材料。Cu～(2+)离子的掺杂提高材料的放电平均电位,并且与Co～(2+)形成双金属有机框架,通过双金属离子的协调作用进一步改善材料的电化学储锂性能。(The invention discloses a CuCo-BDC ultrathin nanosheet and a preparation method and application thereof, wherein the preparation method comprises the following steps: ultrasonically dissolving copper chloride dihydrate, cobalt chloride hexahydrate and terephthalic acid into a mixed solution of N, N-dimethylformamide, ethanol and deionized water; stirring the solution obtained in the step, adding triethylamine under a stirring state, then placing the solution into an ultrasonic machine for ultrasonic treatment, then centrifuging, washing a product obtained after centrifuging for a plurality of times by using ethanol, and drying to obtain Cu/Co-BDC powder, namely the CuCo-BDC ultrathin nanosheet. According to the invention, the Cu/Co-BDC ultrathin nanosheet with the optimal performance is obtained by regulating the proportion of metal elements, and then the Cu/Co-BDC ultrathin nanosheet is directly used as a lithium ion battery cathode material. Cu 2+ The doping of ions increases the discharge average potential of the material and with Co 2+ Form a pairAnd the metal organic framework further improves the electrochemical lithium storage performance of the material through the coordination of the bimetallic ions.)

1. A preparation method of CuCo-BDC ultrathin nanosheets is characterized by comprising the following steps:

(1) ultrasonically dissolving copper chloride dihydrate, cobalt chloride hexahydrate and terephthalic acid into a mixed solution of N, N-dimethylformamide, ethanol and deionized water;

(2) stirring the solution obtained in the step (1), adding triethylamine under a stirring state, then placing the solution in an ultrasonic machine for ultrasonic treatment, then centrifuging, washing a product obtained after centrifuging for a plurality of times by using ethanol, and drying to obtain Cu/Co-BDC powder, namely the CuCo-BDC ultrathin nanosheet.

2. The preparation method of CuCo-BDC ultrathin nanosheets as recited in claim 1, wherein the preparation method comprises the following steps: in the step (1), the volume ratio of the N, N-dimethylformamide to the ethanol to the deionized water is 16: 1.

3. The preparation method of CuCo-BDC ultrathin nanosheets as recited in claim 1, wherein the preparation method comprises the following steps: in the step (1), the concentration of copper chloride dihydrate is 0.001-0.005 mmol/L, the concentration of cobalt chloride hexahydrate is 0.009-0.045 mmol/L, and the concentration of terephthalic acid is 20-25 mmol/L.

4. The preparation method of CuCo-BDC ultrathin nanosheets as recited in claim 1, wherein the preparation method comprises the following steps: in the step (1), the concentration of copper chloride dihydrate is 0.006mmol/L, the concentration of cobalt chloride hexahydrate is 0.014mmol/L, and the concentration of terephthalic acid is 20.83 mmol/L.

5. The preparation method of CuCo-BDC ultrathin nanosheets as recited in claim 1, wherein the preparation method comprises the following steps: the dropwise adding speed of triethylamine in the step (2) is 40-100 ml/h, the stirring time is 5-10 min, and the ultrasonic reaction time is 8 hours.

6. The preparation method of CuCo-BDC ultrathin nanosheets as recited in claim 1, wherein the preparation method comprises the following steps: in the step (2), the washing times of the ethanol are 3-5 times, the centrifugal rotating speed is 2000-3000 r/min, the centrifugal time is 3-5 min, and the temperature of the oven is 50-100 ℃.

7. A CuCo-BDC ultrathin nanosheet is characterized in that: prepared by the method of any one of claims 1 to 6.

8. Use of CuCo-BDC ultrathin nanoplates according to claim 7, characterised in that: the CuCo-BDC ultrathin nanosheet is applied to preparation of a lithium ion battery cathode material.

Technical Field

The invention relates to the technical field of preparation of nano functional materials, in particular to a CuCo-BDC ultrathin nanosheet and a preparation method and application thereof.

Background

The Metal Organic Frameworks (MOFs) are composed of metal ions and organic ligands, have the advantages of variety and structural diversity, large specific surface area, adjustable pore channel structure and the like, have the specific functions of host metal ions and guest organic ligands, and show unique advantages and application prospects in energy conversion and storage. For example, MOFs can realize the controllability of porosity by keeping metal ions unchanged and introducing ligands with different carbon chain lengths; the metal ions can be regulated and controlled by keeping the organic ligand unchanged, so that MOFs with similar or completely different structures can be obtained. As an electrode material, the large specific surface area and controllable pore channel structure are important for storing active substances, improving charge transfer kinetics and relieving volume expansion, so that two-dimensional MOFs are not the second choice for preparing the electrode material. In the existing method for synthesizing the two-dimensional MOFs ultrathin nanosheets, the commonly used solvothermal method is complex in operation, long in time consumption, high in cost, low in yield, toxic and harmful. Therefore, a production method which is environment-friendly, simple to operate and capable of preparing MOFs in large quantities is urgently needed.

Disclosure of Invention

The CuCo-BDC ultrathin nanosheet prepared by the method effectively shortens the diffusion distance of lithium ions, and exposes more active sites, so that the storage performance of the lithium ions can be remarkably improved.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of CuCo-BDC ultrathin nanosheets comprises the following steps:

(1) ultrasonically dissolving copper chloride dihydrate, cobalt chloride hexahydrate and terephthalic acid into a mixed solution of N, N-dimethylformamide, ethanol and deionized water;

(2) stirring the solution obtained in the step (1), adding triethylamine under a stirring state, then placing the solution in an ultrasonic machine for ultrasonic treatment, then centrifuging, washing a product obtained after centrifuging for a plurality of times by using ethanol, and drying to obtain Cu/Co-BDC powder, namely the CuCo-BDC ultrathin nanosheet.

Preferably, the volume ratio of the N, N-dimethylformamide to the ethanol to the deionized water in the step (1) is 16: 1: 1.

preferably, in the step (1), the concentration of copper chloride dihydrate is 0.001-0.005 mmol/L, the concentration of cobalt chloride hexahydrate is 0.009-0.045 mmol/L, and the concentration of terephthalic acid is 20-25 mmol/L.

Preferably, in the step (1), the concentration of the copper chloride dihydrate is 0.006mmol/L, the concentration of the cobalt chloride hexahydrate is 0.014mmol/L, and the concentration of the terephthalic acid is 20.83 mmol/L.

Preferably, the dropwise adding rate of triethylamine in the step (2) is 40-100 ml/h, the stirring time is 5-10 min, and the ultrasonic reaction time is 8 hours.

Preferably, the ethanol washing time in the step (2) is 3-5 times, the centrifugal rotating speed is 2000-3000 r/min, the centrifugal time is 3-5 min, and the oven temperature is 50-100 ℃.

A CuCo-BDC ultrathin nanosheet is prepared by the method.

The application of the CuCo-BDC ultrathin nanosheet in preparing a lithium ion battery cathode material is provided.

Compared with the prior art, the invention has the beneficial effects that:

1) according to the invention, an organic ligand is completely dissolved in an organic solvent, copper salt and cobalt salt are added for complete dissolution through ultrasound, triethylamine is added into the mixed solution dropwise for deprotonation, and finally the ultrathin nanosheet of the bimetallic organic framework Cu/Co-BDC is prepared through a liquid-phase ultrasound-assisted method. The ligand terephthalic acid adopted by the invention is a bridging group with a symmetrical carboxylic acid structure, and the existence of the bridging group is helpful for controlling the growth of MOF crystals to a specific direction and maintaining the consistency and stability of the structure;

2) the transition metal salt adopted by the invention not only has higher theoretical capacityAmount, and also higher conductivity, Cu²⁺The doping of ions increases the discharge average potential of the material and with Co²⁺Forming a bimetallic organic framework, and further improving the electrochemical lithium storage performance of the material through the coordination of bimetallic ions;

3) the method does not need to add a surfactant, and is simple to operate;

4) the ultrathin nanosheet of Cu/Co-BDC prepared by the method effectively shortens the diffusion distance of lithium ions, and exposes more active sites, so that the storage performance of the lithium ions can be remarkably improved. The ultrathin nanosheet synthesized by the method can be directly used as a lithium ion battery cathode, does not need annealing, is green and environment-friendly, has low cost and high yield, and is suitable for large-scale production. And secondly, the method is simple, universal and controllable, and has a greater practical application value in the field of energy storage.

Drawings

FIG. 1 is a low magnification (a) and high magnification (b) FESEM photographs of a bimetallic organic framework 10Cu90Co-BDC prepared in example 1 of the present invention;

FIG. 2 is a low magnification (a) and high magnification (b) FESEM photographs of a bimetallic organic frame 30Cu70Co-BDC prepared in example 2 of the present invention;

FIG. 3 is a low magnification (a) and high magnification (b) FESEM photographs of a metal organic framework Cu-BDC prepared in example 3 of the present invention;

FIG. 4 is a low magnification (a) and high magnification (b) FESEM photographs of a two-dimensional metal organic framework Co-BDC prepared in example 4 of the present invention;

FIG. 5 is the XRD diffraction patterns of two-dimensional metal-organic framework 10Cu90Co-BDC prepared in example 1, 30Cu70Co-BDC prepared in example 2, metal-organic framework Cu-BDC prepared in example 3, and metal-organic framework Co-BDC nanosheets prepared in example 4 of the present invention;

fig. 6 is a graph of electrochemical performance of two-dimensional metal-organic framework 10Cu90Co-BDC prepared in example 1, 30Cu70Co-BDC prepared in example 2, metal-organic framework Cu-BDC prepared in example 3, and metal-organic framework Co-BDC nanosheets prepared in example 4 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

the preparation method of the 10Cu/90Co-BDC ultrathin nanosheet specifically comprises the following steps:

firstly, 125.86mg of terephthalic acid is dissolved in a mixed solution of 12ml of N, N-dimethylformamide, 2ml of absolute ethyl alcohol and 2ml of deionized water, then 12.91mg of copper chloride dihydrate dissolved in 10ml of N, N-dimethylformamide solution and 162mg of cobalt chloride hexahydrate dissolved in 10ml of N, N-dimethylformamide solution are sequentially added into the solution, triethylamine is dropwise added at the rate of 48ml/h while the solution is stirred uniformly by ultrasound, after stirring for five minutes, the dropwise addition is stopped, the solution is ultrasonically treated for 8 hours, ethanol is used for centrifugally washing for 3 times at the rotating speed of 2500r/min, and then the solution is placed in an oven at the temperature of 80 ℃ for drying to obtain the pink powdery ultrathin 10Cu/90Co-BDC nanosheet.

Fig. 1 shows FESEM photographs of a bimetallic organic framework 10Cu90Co-BDC prepared by the present example, which are low-power (a) and high-power (b), the thickness of the nanosheet is thin, the whole nanosheet has a distinct spatial stereoscopic impression, and the nanosheet has pores with different sizes.

Example 2:

the preparation method of the 30Cu/70Co-BDC ultrathin nanosheet is similar to that in example 1, and is different from the method in that the mass of copper chloride dihydrate is 38.75mg, and the mass of cobalt chloride hexahydrate is 126.17 mg.

Fig. 2 shows FESEM photographs of the bi-metal organic frame 30Cu70Co-BDC prepared in this example at low magnification (a) and high magnification (b), which have a reduced spatial stereoscopic effect and increased thickness compared to 10Cu90 Co-BDC.

Example 3:

the preparation method of the Cu-BDC ultrathin nanosheet specifically comprises the following steps:

firstly, 125.86mg of terephthalic acid is dissolved in a mixed solution of 12ml of N, N-dimethylformamide, 2ml of absolute ethyl alcohol and 2ml of deionized water, then 129.15mg of copper chloride dihydrate dissolved in 20ml of N, N-dimethylformamide solution is added into the mixed solution, triethylamine is dropwise added into the mixed solution at the speed of 48ml/h after uniform ultrasonic treatment, after five minutes of stirring, ultrasonic treatment is carried out for 8 hours, ethanol is used for centrifugal washing for 3 times at the rotating speed of 2500r/min, and then the mixed solution is placed in an oven at 80 ℃ for drying to obtain the powdery Cu-BDC ultrathin nanosheet.

Fig. 3 is a low power (a) and high power (b) FESEM photographs of the metal organic framework Cu-BDC prepared in this example, which are uniform band-shaped in morphology.

Example 4:

the preparation method of the Co-BDC ultrathin nanosheet is similar to that in example 3, except that 129.15mg of copper chloride dihydrate is changed into 180.25mg of cobalt chloride hexahydrate.

Fig. 4 is FESEM photographs of the metal organic framework Co-BDC prepared in this example at low magnification (a) and high magnification (b), which are relatively broad nanosheets in morphology, exhibiting a three-dimensional network structure. Fig. 5 can see that the bimetallic organic framework 10Cu90Co-BDC nanoplates and the metallo-organic framework Co-BDC nanoplates have the same phase, with a tendency to shift like the Cu-BDC peak with increasing Cu content.

Example 5:

the ultrathin nanosheets of the 4 examples are subjected to battery assembly and performance test

The prepared sample, conductive carbon black and polyvinylidene fluoride are mixed according to the mass ratio of 8: 1: 1, fully grinding and uniformly mixing in a mortar, then adding a proper amount of 1-methyl-2 pyrrolidone reagent, continuously grinding for a period of time to prepare slurry with proper viscosity, uniformly coating the slurry on a copper foil, and drying in a vacuum drying oven. After a working electrode is manufactured by a press, the button cell is assembled by using an ester-based electrolyte with 1.0mol/LLIPF6 as a diaphragm and a lithium electrode as a counter electrode in a glove box of high-purity argon gas.

Fig. 6 is a graph of electrochemical performance of the two-dimensional metal-organic framework 10Cu90Co-BDC prepared in example 1, the 30Cu70Co-BDC prepared in example 2, the metal-organic framework Cu-BDC prepared in example 3, and the metal-organic framework Co-BDC nanosheet prepared in example 4. It can be seen that the lithium storage performance for Co-BDC is significantly improved when Cu is doped at 10%, but if Cu is doped excessively, the performance is degraded. Therefore, 10Cu90Co-BDC is the best choice as the negative electrode material of the lithium ion battery.

The foregoing is merely exemplary and illustrative of the present invention and various modifications, additions and substitutions may be made by those skilled in the art to the specific embodiments described without departing from the scope of the present invention as defined in the accompanying claims.