Disclosure of Invention
The invention aims to solve the technical problem of providing a negative electrode material ZnCo of a lithium ion battery2O4Preparation method of nano rod, namely preparation of ZnCo with one-dimensional porous structure by reflux recrystallization2O4The nano-rod has a one-dimensional structure which can shorten a lithium ion diffusion path, and a porous structure which can inhibit volume strain in the charge and discharge process so as to improve ZnCo2O4Electrochemical properties of the negative electrode material.
The technical scheme of the invention is as follows:
negative electrode material ZnCo of lithium ion battery2O4The preparation method of the nano rod specifically comprises the following steps:
(1) dissolving zinc salt and cobalt salt in an organic solvent according to a molar ratio of 1:2, and then dissolving a surfactant in the organic solvent;
(2) putting the solution obtained in the step (1) into a reaction container, performing reflux reaction for 3-10h under the condition of magnetic stirring at the temperature of 60-150 ℃ to obtain white precipitate, and cleaning the white precipitate to obtain ZnCo2O4A precursor;
(3) ZnCo obtained in the step (2)2O4Calcining the precursor in air atmosphere to obtain ZnCo2O4The nano-rod, wherein the calcining temperature is 300-600 ℃, and the calcining time is 2-10 h.
The zinc salt in the step (1) is at least one of zinc acetate, zinc nitrate, zinc sulfate and zinc chloride.
The cobalt salt in the step (1) is at least one of cobalt acetate, cobalt nitrate, cobalt sulfate and cobalt chloride.
The organic solvent in the step (1) is at least one of ethanol, ethylene glycol, isooctane, n-hexane, xylene and n-pentanol.
The surfactant in the step (1) is at least one of polyvinyl pyrrolidone, cetyl trimethyl ammonium bromide, sodium diisooctyl sulfosuccinate, sodium dodecyl sulfate and octyl phenyl polyvinyl ether.
In the step (2), the white precipitate is alternately cleaned for multiple times by adopting ethanol and distilled water, and is dried after being cleaned to obtain ZnCo2O4And (3) precursor.
The invention has the advantages that:
(1) the method has the advantages of simple preparation process, relatively mild reaction conditions and easy operation.
(2) The invention adopts surfactant as the carrier for nanorod production and adopts a reflux recrystallization method to prepare ZnCo with a one-dimensional porous structure2O4The nano-rod has a one-dimensional structure which can shorten a lithium ion diffusion path, and a porous structure which can inhibit volume strain in the charge and discharge process so as to improve ZnCo2O4Electrochemical properties of the negative electrode material.
(3) The ZnCo2O4 nano-rod prepared by the invention has loose surface and larger specific surface of porous structure, can increase the contact area with electrolyte so as to provide more active sites and be beneficial to improving the electrochemical performance, and the first discharge specific capacity of the ZnCo2O4 nano-rod is as high as 1121.1 mAh/g.
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
Negative electrode material ZnCo of lithium ion battery2O4The preparation method of the nano rod specifically comprises the following steps:
(1) dissolving 1 mmol of zinc acetate and 2 mmol of cobalt acetate in ethanol, and then dissolving polyvinyl pyrrolidone (PVP) in the ethanol to obtain colorless transparent solution;
(2) placing the colorless transparent solution into a three-neck round-bottom flask, carrying out reflux reaction for 5 hours under the condition of magnetic stirring at the temperature of 90 ℃ to obtain white precipitate, washing the white precipitate with hot ethanol and water for a plurality of times, and drying to obtain ZnCo with a one-dimensional structure2O4A precursor;
(3) ZnCo to be obtained2O4Calcining the precursor in air atmosphere to obtain ZnCo2O4The nano-rods are prepared, wherein the calcining temperature is 300 ℃, and the calcining time is 10 h.
See FIG. 1, FESEM photograph of ZnCo2O4 precursor, ZnCo obtained in step (2)2O4The precursor is composed of nano rods with the length of 3-5 mu m and the diameter of 200-250 nm.
Referring to FIG. 2, the XRD pattern of the prepared ZnCo2O4 nanorod is not clear, and the obvious impurity peak is not seen from the XRD pattern, which indicates that the prepared ZnCo2O4 nanorod is2O4The nano-rod is high-purity ZnCo2O 4.
Referring to FIG. 3, the obtained ZnCo2O4 nanorod has a FESEM image, in which the ZnCo2O4 nanorod has a nanorod structure with a length of about 2-4 μm and a diameter of 150-200 nm, and the surface of the nanorod has a loose porous structure.
Referring to fig. 4, the electrochemical performance of the prepared ZnCo2O4 nanorod is shown, the first specific discharge capacity of the ZnCo2O4 nanorod negative electrode material at a current density of 0.1C (1C =1000 mAh/g) reaches 1121.2 mAh/g, and the specific discharge capacities at current densities of 0.1C, 0.2C, 0.5C, 1C and 2C are 823.5 mAh/g, 783.5 mAh/g, 745.2 mAh/g, 615.2 mAh/g and 508.6 mAh/g, respectively.
Example 2
Negative electrode material ZnCo of lithium ion battery2O4The preparation method of the nano rod specifically comprises the following steps:
(1) dissolving 2 mmol of zinc nitrate and 4 mmol of cobalt nitrate in ethanol, and then dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) in the ethanol to obtain colorless transparent solution;
(2) placing the colorless transparent solution into a three-neck round-bottom flask, performing reflux reaction for 6h under the condition of magnetic stirring at the temperature of 80 ℃ to obtain white precipitate, and performing reflux reaction on the white precipitate by using hot ethanol and waterWashing for several times and drying to obtain ZnCo with one-dimensional structure2O4A precursor;
(3) ZnCo to be obtained2O4Calcining the precursor in air atmosphere to obtain ZnCo2O4The nano-rods are prepared, wherein the calcining temperature is 600 ℃, and the calcining time is 2 hours.
Referring to fig. 5, a FESEM image of the prepared ZnCo2O4 material shows that the morphology of ZnCo2O4 is nanorod.
Referring to fig. 6, an electrochemical performance diagram of the ZnCo2O4 material shows that the first specific discharge capacity of the ZnCo2O4 negative electrode material at a current density of 0.1C (1C =1000 mAh/g) is 1042.1 mAh/g. Specific discharge capacities at current densities of 0.1C, 0.2C, 0.5C, 1C and 2C were 741.6 mAh/g, 713.4 mAh/g, 605.4 mAh/g, 507.4 mAh/g and 440.3 mAh/g, respectively.
Example 3
Negative electrode material ZnCo of lithium ion battery2O4The preparation method of the nano rod specifically comprises the following steps:
(1) dissolving 5 mmol of zinc sulfate and 10 mmol of cobalt sulfate in ethanol, and then dissolving diisooctyl succinate sodium sulfonate (NaAOT) in isooctane to obtain colorless transparent solution;
(2) placing the colorless transparent solution into a three-neck round-bottom flask, carrying out reflux reaction for 3 hours under the condition of magnetic stirring at the temperature of 100 ℃ to obtain white precipitate, washing the white precipitate with hot ethanol and water for a plurality of times, and drying to obtain ZnCo with a one-dimensional structure2O4A precursor;
(3) ZnCo to be obtained2O4Calcining the precursor in air atmosphere to obtain ZnCo2O4The nano-rods are prepared, wherein the calcining temperature is 500 ℃, and the calcining time is 3 h.
Referring to fig. 7, the FESEM of the prepared ZnCo2O4 material shows that the morphology of ZnCo2O4 is nanorod.
Referring to fig. 8, an electrochemical performance diagram of the ZnCo2O4 material shows that the first specific discharge capacity of the ZnCo2O4 negative electrode material at a current density of 0.1C (1C =1000 mAh/g) is 1070.7 mAh/g. Specific discharge capacities at current densities of 0.1C, 0.2C, 0.5C, 1C and 2C were 801.5 mAh/g, 762.3 mAh/g, 717.4 mAh/g, 588.1 mAh/g and 468.7 mAh/g, respectively.
Comparative example 1
Negative electrode material ZnCo of lithium ion battery2O4The preparation method specifically comprises the following steps:
(1) dissolving 1 mmol of zinc acetate and 2 mmol of cobalt acetate in ethanol;
(2) putting the solution obtained in the step (1) into a three-mouth round-bottom flask, carrying out reflux reaction for 5 hours under the condition of magnetic stirring at 90 ℃ to obtain white precipitate, washing the obtained white precipitate with hot ethanol and water for several times, and drying to obtain ZnCo2O4A precursor;
(3) ZnCo2O4Calcining the precursor in air atmosphere at 300 ℃ for 10h to obtain ZnCo2O4A material.
Referring to fig. 9, a FESEM of the prepared ZnCo2O4 material shows that the morphology of ZnCo2O4 has rod-like and block-like compositions with different sizes, i.e., a ZnCo2O4 nanorod structure cannot be formed without adding a surfactant.
Referring to fig. 10, an electrochemical performance diagram of the ZnCo2O4 material shows that the first specific discharge capacity of the ZnCo2O4 negative electrode material at a current density of 0.1C (1C =1000 mAh/g) is 995.2 mAh/g. Specific discharge capacities at current densities of 0.1C, 0.2C, 0.5C, 1C and 2C were 654.3 mAh/g, 632.2 mAh/g, 518.3 mAh/g, 443.9 mAh/g and 389.4 mAh/g, respectively.
Comparative example 2
Negative electrode material ZnCo of lithium ion battery2O4The preparation method specifically comprises the following steps:
(1) dissolving 1 mmol of zinc acetate and 2 mmol of cobalt acetate in ethanol, and then dissolving polyvinyl pyrrolidone (PVP) in the ethanol to obtain colorless transparent solution;
s2, placing the colorless transparent solution into a three-neck round-bottom flask, magnetically stirring at 90 ℃ until the solvent is completely evaporated to obtain a white precipitate, and washing the obtained white precipitate with hot ethanol and waterObtaining ZnCo after several times of drying2O4A precursor;
s3, mixing ZnCo2O4Calcining the precursor in air atmosphere at 300 ℃ for 10h to obtain ZnCo2O4A material.
Referring to fig. 11, a FESEM image of ZnCo2O4, it can be seen that ZnCo2O4 is composed of some particles and has no rod-like morphology, which indicates that ZnCo2O4 nanorods cannot be formed without using a reflux reaction, i.e., without using a reflux recrystallization method.
Referring to fig. 12, an electrochemical performance diagram of the ZnCo2O4 material, a first specific discharge capacity of the ZnCo2O4 material at a current density of 0.1C (1C =1000 mAh/g) is 935.2 mAh/g, and specific discharge capacities at current densities of 0.1C, 0.2C, 0.5C, 1C and 2C are 632.4 mAh/g, 573.4 mAh/g, 461.2 mAh/g, 257.4 mAh/g and 211.7 mAh/g, respectively.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.