Multiple defect transition metal hydroxides, their preparation and use

Abstract

The application relates to the field of electrode materials, in particular to a multiple-defect transition metal hydroxide, a preparation method and application thereof. A transition metal salt is dissolved in a mixed solvent, the obtained mixed solution is transferred into a stainless steel hydrothermal kettle, after high-temperature solvothermal reaction, the product is subjected to centrifugal, washing and vacuum drying treatment to obtain a transition metal hydroxide; the transition metal hydroxide is dispersed in deionized water, and is uniformly dispersed through ultrasonic treatment; an etching agent solution is added dropwise, stirring and reaction are carried out at room temperature, and the multiple-defect transition metal hydroxide is obtained through centrifugal, washing and vacuum drying treatment. On the basis of the multiple metal hydroxide, the construction of a defect structure can be realized in the prepared transition metal hydroxide through the high-efficiency room-temperature etching reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrode materials, in particular to a multi-defect transition metal hydroxide, its preparation and application. BACKGROUND

[0002] Due to the advantages of rich resources, adjustable valence state / component, controllable morphology, high redox activity and easy preparation, transition metal hydroxide is considered as an electrode material with great development potential in the field of electrochemical energy storage and catalysis. However, due to the semiconductor nature of transition metal hydroxide itself, the electron transfer rate is relatively slow in the subsequent electrochemical reaction process, resulting in high electron transfer impedance of the electrode material and slow reaction kinetics. Secondly, the traditional transition metal hydroxide has less active site and low utilization rate of active site, which is difficult to realize high-efficiency electrochemical reaction at the interface between electrode material and electrolyte ions. Therefore, how to effectively improve the conductivity, expose more active sites and improve the reaction sites of the traditional transition metal hydroxide has become one of the hot research directions in the field of electrochemical energy storage and catalysis. SUMMARY

[0003] In order to solve the problems of high electron transfer impedance and slow reaction kinetics of transition metal hydroxide in the electrochemical reaction process, the present application provides a multi-defect transition metal hydroxide, its preparation and application.

[0004] The present application is realized by the following technical solutions:

[0005] In the first aspect, the present application provides a preparation method of a multi-defect transition metal hydroxide, comprising the following steps:

[0006] ①Dissolve transition metal salt in mixed solvent to obtain a mixed solution, transfer the mixed solution to a stainless steel hydrothermal kettle, and after high-temperature solvothermal reaction, the product is treated by centrifugation, washing and vacuum drying to obtain transition metal hydroxide;

[0007] ②Disperse the transition metal hydroxide prepared in step ① in deionized water, uniformly disperse by ultrasonic treatment; add etching agent solution dropwise, stir and react at room temperature, and then treat by centrifugation, washing and vacuum drying to obtain multi-defect transition metal hydroxide.

[0008] As a further improvement of the technical solutions of the present application, the transition metal salt is selected from a mixture of one or more salts of nickel, cobalt, iron, manganese, zinc and copper.

[0009] As a further improvement of the technical solutions of the present application, the transition metal salt is nitrate, acetate, chloride or sulfate.

[0010] As a further improvement of the technical scheme of the present application, the mixed solvent is a mixed solvent of an organic solvent and water.

[0011] As a further improvement of the technical scheme of the present application, the reaction temperature of the high-temperature solvothermal reaction is 100-220 DEG C, and the reaction time is 1-12 h.

[0012] As a further improvement of the technical scheme of the present application, the etchant solution is a mixture of one or more of hydrogen peroxide, sodium peroxodisulfate, potassium permanganate and sodium hypochlorite.

[0013] As a further improvement of the technical scheme of the present application, the concentration of the etchant solution is 0.01-4 mol / L, and the reaction time at room temperature is 0.5-12 h.

[0014] In a second aspect, the present application provides a preparation method of a multi-defect transition metal hydroxide.

[0015] Preferably, the multi-defect transition metal hydroxide comprises transition metal cation vacancies, anion vacancies and amorphous phases.

[0016] In a third aspect, the present application provides an application of the multi-defect transition metal hydroxide prepared by the preparation method of the multi-defect transition metal hydroxide as an electrode material in an electrochemical energy storage device.

[0017] The multi-defect transition metal hydroxide, its preparation and application provided by the present application have the following advantages compared with the prior art:

[0018] 1. The present application can realize the preparation of single transition metal, double transition metal and multi-element transition metal hydroxides by simply regulating the amount of transition metal ions. In particular, compared with single transition metal and double transition metal hydroxides, the electronic interaction between metal ions in multi-element transition metal hydroxides can significantly improve the intrinsic conductivity of the hydroxide and increase the electrochemical reaction active sites;

[0019] 2. On the basis of multi-element transition metal hydroxides, the present application can realize the construction of defect structures, such as metal ion vacancies, anion vacancies and amorphous phases, in the prepared transition metal hydroxides by means of efficient room-temperature etching reaction, further optimize the electronic structure, and be beneficial to the electronic transfer in the electrochemical reaction process; and the constructed defect structures can act as active sites in the electrochemical reaction process, further enrich the electrochemical reaction at the interface between the electrode material and the electrolyte ions, and thus greatly improve the electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the application and, together with the description, further serve to explain the principles of the application.

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, simple introductions to the drawings needed to be used in the embodiments or the prior art description will be given below. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0022] Figure 1 Scanning electron microscope (SEM) image of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7.

[0023] Figure 2 Transmission electron microscope (TEM) image of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7.

[0024] Figure 3 X-ray diffraction (XRD) spectrum of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7.

[0025] Figure 4 Raman spectrum of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7.

[0026] Figure 5 Electron paramagnetic resonance (EPR) spectrum of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7.

[0027] Figure 6 Cyclic voltammetry (CV) test result of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7 as an electrode material.

[0028] Figure 7 Galvanostatic charge-discharge (GCD) test result of the multiple-defect nickel-cobalt-iron hydroxide prepared in Example 7 as an electrode material.

[0029] Figure 8 Rate curve of the hydroxides prepared in different examples as an electrode material.

[0030] Figure 9 Electrochemical impedance (EIS) spectrum of the hydroxides prepared in different examples as an electrode material. DETAILED DESCRIPTION

[0031] In order to enable the above-mentioned objects, features and advantages of the present application to be more clearly understood, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0033] This invention provides a specific embodiment of a method for preparing multi-defect transition metal hydroxides, comprising the following steps:

[0034] ① The transition metal salt is dissolved in a mixed solvent, and the resulting mixed solution is transferred to a stainless steel hydrothermal reactor. After a high-temperature solvothermal reaction, the product is centrifuged, washed and vacuum dried to obtain the transition metal hydroxide.

[0035] ② The transition metal hydroxide prepared in step ① is dispersed in deionized water and ultrasonically treated to ensure uniform dispersion; an etchant solution is added dropwise, stirred and reacted at room temperature, and then centrifuged, washed and vacuum dried to obtain a multi-defect transition metal hydroxide.

[0036] In one example provided by the present invention, the transition metal salt is selected from one or more salts of nickel, cobalt, iron, manganese, zinc, and copper. Further, the transition metal salt is a nitrate, acetate, chloride, or sulfate. Preferably, nickel nitrate hexahydrate (Ni(NO3)2·6H2O), cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and ferric nitrate nonahydrate (Fe(NO3)3·9H2O) can be used, wherein Fe... 3+ :Co 2+ :Ni 2+ The molar ratio is 0~1:0~1:1. In this molar ratio, when Fe... 3+ Co 2+ When the value is 0, it indicates that the corresponding transition metal salt is 0. In this invention, Fe 3+ Co 2+ It can be 0 at the same time, or it can be Fe. 3+ For 0, Co 2+ A non-zero number between 0 and 1; it can also be Fe. 3+ Non-zero numbers between 0 and 1, Co 2+ It is 0.

[0037] In another example provided by the present invention, the mixed solvent is a mixture of an organic solvent and water.

[0038] The organic solvent can be any one of N,N-dimethylformamide, N-methylpyrrolidone, acetone, and ethylene glycol. Preferably, the organic solvent is N-methylpyrrolidone, and the volume ratio of N-methylpyrrolidone to water is 1:10 to 20:1.

[0039] In one example of the present application, the reaction temperature of the high-temperature solvothermal reaction is 100-220℃, and the reaction time is 1-12h. Preferably, the reaction temperature is 160-200℃, and the reaction time is 6-10h.

[0040] In step ①, when the product is subjected to centrifugation, washing and vacuum drying treatment, the preferred drying temperature is 60-90℃, and the preferred drying time is 4-6h.

[0041] In step ②, the concentration of the transition metal hydroxide in deionized water is 1.5-15mg / mL.

[0042] In another example of the present application, the etchant solution is a mixture of one or more of hydrogen peroxide, sodium peroxodisulfate, potassium permanganate and sodium hypochlorite. Preferably, the etchant solution is hydrogen peroxide or sodium peroxodisulfate; more preferably, the etchant solution is hydrogen peroxide.

[0043] In one example of the present application, the concentration of the etchant solution is 0.01-4mol / L, and the reaction time at room temperature is 0.5-12h. The volume ratio of the aqueous solution of transition metal hydroxide to the etchant solution is 1:1-20:1.

[0044] The present application further provides a preparation method of a multi-defect transition metal hydroxide.

[0045] Specifically, the multi-defect transition metal hydroxide comprises transition metal cation vacancies, anion vacancies and amorphous phases.

[0046] The present application also provides an application of the multi-defect transition metal hydroxide prepared by the preparation method of a multi-defect transition metal hydroxide as an electrode material in an electrochemical energy storage device.

[0047] The specific embodiments of the present application are described in detail below.

[0048] Example 1

[0049] 291.3mg of Ni(NO3)2·6H2O was dissolved in a mixed solvent of N-methylpyrrolidone / water (volume ratio of 5:1), and subjected to magnetic stirring at room temperature for 30min to obtain a clear and transparent mixed solution; the mixed solution was transferred to a stainless steel hydrothermal kettle, and subjected to reaction at 160℃ for 8h to obtain a product, which was subjected to centrifugation, washing and vacuum drying treatment (drying temperature of 80℃ and drying time of 6h) to obtain Ni(OH)2.

[0050] Example 2

[0051] Dissolve 145.1 mg of Ni(NO3)2·6H2O and 291.3 mg of Co(NO3)2·6H2O in a mixed solvent of N-methyl pyrrolidone / water (volume ratio of 5:1), and magnetically stir at room temperature for 30 min to obtain a clear and transparent mixed solution; transfer the mixed solution to a stainless steel hydrothermal kettle, and react at 160°C for 8 h to obtain a product; and centrifuge, wash, and vacuum dry (drying temperature of 80°C and drying time of 6 h) to obtain a nickel-cobalt hydroxide.

[0052] Example 3

[0053] Dissolve 145.1 mg of Ni(NO3)2·6H2O, 145.1 mg of Co(NO3)2·6H2O, and 50 mg of Fe(NO3)3·9H2O in a mixed solvent of N-methyl pyrrolidone / water (volume ratio of 11:1), and magnetically stir at room temperature for 30 min to obtain a clear and transparent mixed solution; transfer the mixed solution to a stainless steel hydrothermal kettle, and react at 180°C for 6 h to obtain a product; and centrifuge, wash, and vacuum dry (drying temperature of 80°C and drying time of 6 h) to obtain a nickel-cobalt-iron hydroxide.

[0054] Example 4

[0055] Dissolve 291.1 mg of Ni(NO3)2·6H2O, 291.3 mg of Co(NO3)2·6H2O, and 100 mg of Fe(NO3)3·9H2O in a mixed solvent of N-methyl pyrrolidone / water (volume ratio of 11:1), and magnetically stir at room temperature for 30 min to obtain a clear and transparent mixed solution; transfer the mixed solution to a stainless steel hydrothermal kettle, and react at 180°C for 6 h to obtain a product; and centrifuge, wash, and vacuum dry (drying temperature of 80°C and drying time of 6 h) to obtain a nickel-cobalt-iron hydroxide.

[0056] Ultrasonically disperse 100 mg of the nickel-cobalt-nickel hydroxide into 19 mL of deionized water for 5 min, drop 1 mL of hydrogen peroxide with a concentration of 0.45 mol / L, and stir and react at room temperature for 4 h; obtain a product, and centrifuge, wash, and vacuum dry (drying temperature of 80°C and drying time of 6 h) to obtain a multiple-defect nickel-cobalt-iron hydroxide.

[0057] Example 5

[0058] Dissolve 291.1 mg of Ni(NO3)2·6H2O, 291.3 mg of Co(NO3)2·6H2O and 50 mg of Fe(NO3)3·9H2O in a mixed solvent of N-methyl pyrrolidone / water (volume ratio of 11:1), and stir magnetically at room temperature for 30 min to obtain a clear and transparent mixed solution; transfer the mixed solution to a stainless steel hydrothermal kettle, and react at 180 °C for 6 h to obtain a product; and perform centrifugation, washing and vacuum drying treatment (drying temperature of 80 °C and drying time of 6 h) to obtain nickel-cobalt-iron hydroxide.

[0059] Ultrasonically disperse 100 mg of nickel-cobalt-nickel hydroxide into 19 mL of deionized water for 5 min, drop 1 mL of sodium hypochlorite with a concentration of 0.45 mol / L, and stir and react at room temperature for 4 h; obtain a product, and perform centrifugation, washing and vacuum drying treatment (drying temperature of 80 °C and drying time of 6 h) to obtain multiple-defect nickel-cobalt-iron hydroxide.

[0060] Example 6

[0061] Dissolve 291.1 mg of Ni(NO3)2·6H2O, 291.3 mg of Co(NO3)2·6H2O and 50 mg of Fe(NO3)3·9H2O in a mixed solvent of N-methyl pyrrolidone / water (volume ratio of 11:1), and stir magnetically at room temperature for 30 min to obtain a clear and transparent mixed solution; transfer the mixed solution to a stainless steel hydrothermal kettle, and react at 180 °C for 6 h to obtain a product; and perform centrifugation, washing and vacuum drying treatment (drying temperature of 80 °C and drying time of 6 h) to obtain nickel-cobalt-iron hydroxide.

[0062] Ultrasonically disperse 100 mg of nickel-cobalt-nickel hydroxide into 19 mL of deionized water for 5 min, drop 1 mL of sodium hypochlorite with a concentration of 0.45 mol / L, and stir and react at room temperature for 4 h; obtain a product, and perform centrifugation, washing and vacuum drying treatment (drying temperature of 80 °C and drying time of 6 h) to obtain multiple-defect nickel-cobalt-iron hydroxide.

[0063] Example 7

[0064] Dissolve 291.1 mg of Ni(NO3)2·6H2O, 291.3 mg of Co(NO3)2·6H2O and 50 mg of Fe(NO3)3·9H2O in a mixed solvent of N-methyl pyrrolidone / water (volume ratio of 11:1), and stir magnetically at room temperature for 30 min to obtain a clear and transparent mixed solution; transfer the mixed solution to a stainless steel hydrothermal kettle, and react at 180 °C for 6 h to obtain a product; and perform centrifugation, washing and vacuum drying treatment (drying temperature of 80 °C and drying time of 6 h) to obtain nickel-cobalt-iron hydroxide.

[0065] 100 mg of nickel-cobalt-nickel hydroxide was ultrasonically dispersed in 15 mL of deionized water for 5 min, 5 mL of hydrogen peroxide with a concentration of 2.24 mol / L was added dropwise, and stirring and reaction were carried out at room temperature for 4 h; the product was obtained, and was treated by centrifugation, washing and vacuum drying (drying temperature was 80℃, and drying time was 6 h) to obtain the multiple-defect nickel-cobalt-iron hydroxide.

[0066] Table 1. Transition metal ion content in the hydroxide prepared in Examples 2 and 7

[0067]

[0068] The hydroxides of Examples 2, 3, 5, 6 and 7 were placed in a maroon mortar with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, a small amount of N-methyl pyrrolidone was added dropwise, and the mixture was ground to obtain a slurry electrode material, which was uniformly coated on the surface of clean nickel foam with a coating area of 1×1 cm 2 After vacuum drying treatment, the coated nickel foam was flattened under a pressure of 10 MPa (working electrode), the mass before and after coating was weighed, and the corresponding active material loading was calculated to be about 2-3 mg; a three-electrode system was constructed with the prepared working electrode, Hg / HgO and platinum sheet, 3M KOH solution was used as the electrolyte, and the electrochemical performance of the corresponding hydroxide as an electrode material was tested to obtain the cyclic voltammogram and constant current charge / discharge curve of Example 7, as well as the rate curve and electrochemical impedance spectrum of Examples 2, 3, 5, 6 and 7.

[0069] From Figure 1 It can be seen that the multiple-defect nickel-cobalt-iron hydroxide obtained in Example 7 has a flower-like morphology constructed by nanosheets, which is beneficial to the contact of reaction sites with electrolyte ions and promotes the adsorption / diffusion behavior of electrolyte ions, thereby strengthening the redox reaction process.

[0070] From Figure 2 It can be seen that the multiple-defect nickel-cobalt-iron hydroxide obtained in Example 7 does not exhibit a clear crystal lattice microregion, thereby confirming that it is a typical amorphous phase.

[0071] From Figure 3 It can be seen that the diffraction peak intensity of the multiple-defect nickel-cobalt-iron hydroxide obtained in Example 7 is weak and tends to disappear, showing the characteristics of an amorphous phase.

[0072] From Figure 4 It can be seen that the bonding structure of the multiple-defect nickel-cobalt-iron hydroxide obtained in Example 7 is a transition metal hydroxide, and the characteristic peaks of the transition metal hydroxide are at 420 cm -1 , 512 cm -1 , 650 cm-1 and 730 cm -1 The Raman signal peaks at 650, 730, 850 and 950 cm

[0073] It can be seen from Figure 5 that the multiple defect nickel-cobalt-iron hydroxide obtained in Example 7 has obvious oxygen vacancy defect signal peaks, which can confirm the existence of oxygen vacancy defect structure in the final material.

[0074] It can be seen from Figure 6 that the multiple defect nickel-cobalt-iron hydroxide obtained in Example 7 as an electrode material shows obvious redox peaks at different scanning rates, indicating that the electrode material is a typical “battery” type material; secondly, with the increase of scanning rate, the CV curve does not deform obviously, which confirms that the obtained electrode material has high rate performance.

[0075] It can be seen from Figure 7 that the multiple defect nickel-cobalt-iron hydroxide obtained in Example 7 as an electrode material shows obvious charge and discharge platforms at different current densities, and with the increase of current density, the GCD curve does not deform basically, which further confirms that the electrode material has high rate performance.

[0076] It can be seen from Figure 8 that at a current density of 1 A g -1 , the specific capacity of Examples 2, 3, 5, 6 and 7 is 423.1 C g -1 , 483.6 C g -1 , 723.8 C g -1 , 568.9 C g -1 and 912.9 C g -1 , respectively; when the current density increases to 30 A g -1 , the specific capacity retention rate of Examples 2, 3, 5, 6 and 7 is 39.1%, 62.4%, 64.2%, 65.4% and 69.7%, respectively, which further confirms that the multiple defect nickel-cobalt-iron hydroxide obtained in Example 7 as an electrode material has high specific capacity and rate performance.

[0077] It can be seen from Figure 9 that compared with Examples 2, 3, 5 and 6, the multiple defect nickel-cobalt-iron hydroxide obtained in Example 7 as an electrode material has lower equivalent impedance (the intersection point of the curve and the horizontal axis), charge transfer impedance (the diameter of the semicircle arc) and ion diffusion impedance (the slope of the terminal line).

[0078] The above description is merely one specific implementation of the application, and thus the technical solutions recorded in the foregoing embodiments can be modified or some or all of the technical features can be substituted equivalently by those skilled in the art, without departing from the scope of the technical solutions of the embodiments, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the embodiments, and should be included in the protection scope of the claims.

Claims

1. A method for preparing a multi-defect transition metal hydroxide, characterized by, The method comprises the following steps: ① 291.1 mg of Ni(NO3)2·6H2O, 291.3 mg of Co(NO3)2·6H2O and 50 mg of Fe(NO3)3·9H2O are dissolved in an N-methylpyrrolidone / water mixed solvent, and the solution is stirred magnetically at room temperature for 30 min to obtain a clear and transparent mixed solution; The mixed solution is transferred to a stainless steel hydrothermal kettle, and the reaction is carried out at 180℃ for 6 h to obtain a product, which is subjected to centrifugal separation, washing and vacuum drying to obtain a nickel-cobalt-iron hydroxide; the volume ratio of N-methylpyrrolidone to water in the mixed solvent is 11:1; ② 100 mg of the nickel-cobalt-iron hydroxide is ultrasonically dispersed in 15 mL of deionized water for 5 min, 5 mL of hydrogen peroxide with a concentration of 2.24 mol / L is added dropwise, and the mixture is stirred and reacted at room temperature for 4 h; the product is obtained, which is subjected to centrifugal separation, washing and vacuum drying to obtain a multiple-defect nickel-cobalt-iron hydroxide; the multiple-defect transition metal hydroxide comprises transition metal cation vacancies, anion vacancies and amorphous phases.

2. The multiple-defect transition metal hydroxide prepared by the method of claim 1.

3. The multiple-defect transition metal hydroxide prepared by the method of claim 1 is used as an electrode material in an electrochemical energy storage device.

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