Surface site and interlayer structure coupled pinning layered manganese oxide electrode material as well as preparation method and application thereof

Abstract

The invention discloses a surface site and interlayer structure coupled pinning layered manganese oxide electrode material as well as a preparation method and application thereof, and belongs to the technical field of energy storage materials. The preparation method comprises the following steps: firstly, preparing a metal ion Mo pinning layered manganese oxide precursor by utilizing a hydrothermal method, and then treating the precursor by utilizing a plasmon effect of laser to obtain the metal ion Mo pinning layered manganese oxide rich in oxygen defects. And finally, processing the metal ion Mo pinning layered manganese oxide rich in oxygen defects by using the plasmon effect of the laser again in an anion environment to obtain the surface site and interlayer structure coupled pinning layered manganese oxide electrode material. According to the preparation method disclosed by the invention, the distribution environment of charges around atoms in a MnO2 bulk phase is changed, and the Haendean band gap width of the MnO2 bulk phase is regulated and controlled, so that the MnO2 bulk phase has a proper work function. When the MnO2 is used as a water-based zinc ion battery positive electrode material, the reaction activity of MnO2 and the stability of a circulating structure can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage materials, and in particular to a layered manganese oxide electrode material with surface sites and interlayer structure coupled pinned thereto, and a preparation method and application thereof. Background Art

[0002] At present, the most widely used energy storage systems are lithium-ion and sodium-ion batteries. However, the defects of this system, such as flammability, explosion, insufficient storage capacity of lithium / sodium metal negative electrodes and high cost, limit its application and development. Therefore, it is urgent to find alternative products. Aqueous zinc-ion batteries (AZIBs) are favored by researchers at home and abroad for their abundant reserves, low price, relatively stable zinc as working ions, water as electrolyte solvent, easy raw material availability, low cost, easy recycling, good cycle performance and high energy density / power density. It has become one of the most promising alternatives to organic battery systems such as lithium-ion / sodium-ion. As an important carrier for energy storage, the selection of electrode materials has become an important scientific issue currently faced.

[0003] Manganese dioxide (MnO2) has become one of the most promising positive electrode materials for aqueous zinc-ion batteries due to its comprehensive advantages such as low cost, high theoretical capacity (single electron capacity 380 mAh / g), good environmental compatibility and high discharge platform (1.35V). Among the many types of MnO2 crystals, δ-MnO2 is considered to be the most ideal manganese-based aqueous zinc-ion battery material with its two-dimensional layered crystal structure and sufficient ion (~7Å) transmission channels. However, it still faces side reactions such as insufficient ion storage capacity caused by the Jahn-Teller effect and interlayer structural slippage during ion reversible storage, as well as phase changes caused by unknown structural stability. At present, in order to solve the above scientific problems, the commonly used modification methods are defect construction and ion doping (anions, cations). Among them, cations such as metal ions Cu / Ni / K / Na can effectively serve as interlayer pillar structures of δ-MnO2 to inhibit interlayer slippage. Defect engineering mainly improves the activity and diffusion kinetics of energy storage sites of MnO2-based electrode materials, such as oxygen defects and cation defect engineering. The above-mentioned control methods are relatively single and cannot simultaneously solve the problems faced by layered MnO2-based electrode materials, such as low capacity storage capacity and poor structural stability. If the metal ion interlayer construction and defect engineering are simultaneously introduced into the layered MnO2 bulk phase, and the synergistic effect of the two modification methods is combined to improve the layered MnO2 ion storage capacity and achieve a fast kinetic process, the intrinsic conductivity and charge / mass transfer efficiency of MnO2 can be improved. At the same time, the structural stability of MnO2 can be improved with the help of metal cation pillaring, and it has excellent electrochemical performance when used as a positive electrode material for aqueous zinc ion batteries. However, the presence of oxygen defects will change the bond energy of the Mn-O bond in MnO2, and the bond energy of some Mn-O bonds will be weakened. In the water molecule environment, H +It will combine with the oxygen atoms in MnO2 to form hydroxyl (-OH) and other groups, thereby promoting the breaking of the Mn-O bond and making Mn 2+ Manganese ions are more easily dissolved from the MnO2 crystal structure, causing the structure of MnO2 to be gradually eroded and the stability to be reduced. As manganese ions continue to dissolve, the crystal structure of MnO2 will be continuously destroyed, which may eventually lead to the collapse of the entire structure. In addition, defect engineering construction methods usually adopt high-temperature calcination, electrochemical treatment, mechanical ball milling and hydrothermal methods. The above-mentioned methods for regulating oxygen defects either use high temperature conditions or use explosive reducing gases. The process is complex, there are disadvantages such as high energy consumption and high risk, and impurities and by-products are inevitably introduced, which is not conducive to the pure and high-performance regulation of oxygen defects in manganese dioxide nanomaterials. The patent with application number CN202210550295.4 discloses a manganese oxide ultrafine nanopowder containing high-index crystal plane oxygen defects and its preparation method and application. The patent with application number CN202210267245.5 discloses a method for preparing an oxygen-rich defect ε-MnO2 / carbon quantum dot composite film. The above patents obtain manganese oxide films or particles with oxygen defects by hydrothermal method or electrochemical treatment, but there is no report on the induction of oxygen defects in layered manganese oxide. Therefore, a simple, green and safe method for regulating the micro-nano composite structure with reasonable oxygen defect components of the cation pinned MnO2 interlayer structure is needed. Summary of the invention

[0004] In view of the above-mentioned prior art, the purpose of the present invention is to provide a layered manganese oxide electrode material coupled with surface sites and interlayer structure pinning, and its preparation method and application. The present invention uses the laser plasmon effect to construct a micro-nano composite structure of anion pinning oxygen defects coupled with metal ions pinning layered MnO2 interlayers, and uses two modification methods to regulate the charge distribution environment around atoms in the MnO2 bulk phase and its Hubbard band gap width, so that it has a suitable work function. The MnO2 charge / mass transfer efficiency is improved while its structural stability and electrochemical stability are improved, and when it is used as a positive electrode material for aqueous zinc ion batteries, the reaction activity and cyclic structural stability of MnO2 can be significantly improved.

[0005] To achieve the above object, the present invention adopts the following technical solution: In a first aspect of the present invention, a method for preparing a layered manganese oxide electrode material having surface sites coupled with an interlayer structure and pinned thereto is provided, comprising the following steps: (1) dissolving a manganese salt and a molybdenum salt in deionized water in sequence and performing a hydrothermal reaction to obtain a metal ion Mo-pinned layered manganese oxide precursor; (2) Under a protective atmosphere, a plasmon laser is used to irradiate a metal ion Mo-pinned layered manganese oxide precursor to obtain oxygen-rich defect metal ion Mo-pinned MnO2; (3) In an anion source, a plasmon laser is used to irradiate MnO2 pinned with oxygen-rich defect metal ions Mo to obtain a layered manganese oxide electrode material with surface sites and interlayer structure coupled pinning.

[0006] Preferably, in step (1), the manganese salt includes KMnO4 and MnSO4·H2O; the molybdenum salt is H 24 Mo7N6O 24 ·4H2O; the KMnO4, MnSO4·H2O and H 24 Mo7N6O 24 The molar ratio of 4H2O is 1:0.15:0.003~0.01.

[0007] Preferably, in step (1), the temperature of the hydrothermal reaction is 120-160° C., and the time of the hydrothermal reaction is 10-16 hours.

[0008] Preferably, in step (1), after the hydrothermal reaction is completed, the precipitate is filtered and washed, and the precipitate is vacuum freeze-dried to obtain a metal ion Mo pinned layered manganese oxide precursor.

[0009] The washing is performed by washing with deionized water for 3-8 times, and then washing with ethanol for 2-5 times. The freeze drying temperature is -80 to -40°C, and the freeze drying time is 12 hours.

[0010] Preferably, in step (2) and step (3), the parameters of the plasmon laser are: line spacing of 0.001-0.004 mm, laser scanning speed of 200-500 mm / s, and laser power of 30%-40%.

[0011] Preferably, in step (3), the anion source is ammonia gas or sulfur powder; when the anion source is ammonia gas, the reaction environment is filled with ammonia gas; when the anion source is sulfur powder, the reaction environment is filled with protective gas.

[0012] Preferably, the mass ratio of MnO2 pinned by the oxygen-rich defect metal ion Mo and sulfur powder is 10:1; the mass ratio of MnO2 pinned by the oxygen-rich defect metal ion Mo and ammonia is 1:3~6.

[0013] Preferably, the protective gas is argon.

[0014] The second aspect of the present invention provides a layered manganese oxide electrode material obtained by the above-mentioned preparation method and coupled with surface sites and interlayer structure pinning, wherein the layered manganese oxide electrode material is a layered MnO2 in which anion pinning oxygen defects are coupled with metal ion Mo pinning.

[0015] Specifically, the structure of the layered manganese oxide electrode material coupled with the surface site and the interlayer structure is as follows: Mo is located in the middle layer of the layered MnO2, the layered MnO2 contains some oxygen defects and some of the oxygen defects are filled with anions.

[0016] Preferably, the doping amount of Mo is 3 wt %; the doping amount of the anion is 6 wt %; the anion is S 2- or N 3- .

[0017] The third aspect of the present invention provides the application of surface site and interlayer structure coupled pinned layered manganese oxide electrode material in specific capacity and cycle stability.

[0018] Beneficial effects of the present invention: (1) The surface sites and interlayer structure coupled pinning layered manganese oxide electrode materials constructed by the present invention utilize anion pinning oxygen defects to couple metal ions to pin layered MnO2, regulate the atomic charge distribution in the MnO2 bulk phase, reduce the Hubbard band gap, and make it have a suitable work function, thereby improving the charge / mass transfer efficiency of MnO2. At the same time, by means of anion pinning oxygen defects, the migration and aggregation of oxygen defects are inhibited, the lattice structure of MnO2 is stabilized, and the weakening of Mn-O bonds caused by oxygen defects is effectively prevented, reducing the Mn 2 + The dissolution of the layered manganese oxide can be achieved by coupling the pinning and pillaring of the metal cation MnO2 layers to prevent interlayer slippage, thereby improving the overall structural stability of MnO2. Therefore, when it is used as a positive electrode material for aqueous zinc-ion batteries, it can achieve fast and reversible zinc ion storage, giving the layered manganese oxide electrode material a fast kinetic process, high reversible charge and discharge cycle capacity, and long cycle life.

[0019] (2) The preparation method adopted by the present invention is simple, the reaction process is non-toxic and pollution-free, the preparation cost is low, the raw material source is abundant, and it can be used for industrial production. Laser treatment constructs oxygen vacancies or laser treatment constructs anion pinning oxygen vacancies. This preparation method can effectively avoid the traditional calcination method to construct oxygen defects in the layered manganese oxide structure and cause phase change. The preparation method has universality and potential for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : (a) SEM image of layered MnO2; (b) SEM image of Mo-MnO2 prepared in step (1) of Example 1; (c) SEM image of Ov-Mo-MnO2 prepared in step (2) of Example 1; (d) SEM image of N / Ov-Mo-MnO2 prepared in Example 1; (e) SEM image of S / Ov-Mo-MnO2 prepared in Example 2; Figure 2: (a) TEM image of layered MnO2; (b) TEM image of Mo-MnO2 prepared in step (1) of Example 1; (c) TEM image of Ov-Mo-MnO2 prepared in step (2) of Example 1; (d) TEM image of N / Ov-Mo-MnO2 prepared in Example 1; (e) TEM image of S / Ov-Mo-MnO2 prepared in Example 2; Figure 3 : (a) SEM image of Comparative Example 1; (b) SEM image of Comparative Example 2; (c) SEM image of Comparative Example 3; (d) SEM image of Comparative Example 4; (e) SEM image of Comparative Example 5; Figure 4 : (a) XPS spectrum of N element distribution at different etching depths; (b) XPS spectrum of oxygen defects distribution at different etching depths; (c) EPR spectra of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2. Figure 5 : XRD patterns of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2; Figure 6 : Band gap width and Fermi level position of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2; Figure 7 : Work function values ​​of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2; Figure 8 : MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2 versus Zn 2+ / H + The adsorption energy of Fig. 9 :(a)MnO2’s adsorption energy for water;(b)Mo-MnO2’s adsorption energy for water;(c)Ov-Mo-MnO2’s adsorption energy for water;(d)N / Ov-Mo-MnO2’s adsorption energy for water;(e)S / Ov-Mo-MnO2’s adsorption energy for water; Fig.10:(a)CV curves of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2;(b)Charge and discharge curves of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2;(c)CV curves of comparative examples 1~5;(d)Charge and discharge curves of comparative examples 1~5; Fig.11 :MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2 at a current density of 1A g -1 Long cycle performance under Fig.12 :MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2 under different cycle numbers 2+ Dissolution conditions; Fig.13 :(a)Galvanostatic intermittent titration images (GITT) of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2; (b)Mn in MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2 2+ The migration barrier Fig.14 :Schematic diagram of the working principle of surface site and interlayer structure coupling pinning layered manganese oxide electrode materials in aqueous zinc ion batteries. DETAILED DESCRIPTION

[0021] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0022] As introduced in the background technology section, the layered manganese oxide has insufficient capacity output and low structural stability for energy storage active sites, thus limiting its application in charge / mass transport performance. + and Zn 2+ Phase changes are prone to occur during the insertion / extraction process, which can affect the capacity output capability of the electrode material and reduce its cycle life.

[0023] Based on this, the purpose of the present invention is to provide a layered manganese oxide electrode material coupled with a surface site and an interlayer structure, and a preparation method and application thereof. The present invention firstly adopts a hydrothermal synthesis method to prepare a metal Mo-pinned layered MnO2 precursor. Then, the metal Mo-pinned layered MnO2 precursor is treated with a laser to obtain a metal Mo-pinned layered MnO2 rich in oxygen defects. Finally, the metal Mo-pinned layered MnO2 is spread flat on the bottom of a porcelain boat, and in a specific atmosphere / anion source environment, a plasmon laser is used to irradiate and collect the sputtered powder to obtain a layered manganese oxide electrode material coupled with a surface site and an interlayer structure, and the material is an anion-pinned oxygen defect coupled metal ion-pinned layered MnO2 micro-nano composite structure. It is mixed with carbon powder and a binder, N-methylpyrrolidone is added, and it is ground evenly to obtain a viscous electrode slurry. The viscous electrode slurry is evenly coated on a base titanium foil, and dried in a vacuum drying oven to obtain a layered MnO2 electrode sheet loaded with anions pinned oxygen defects coupled with metal ions pinned.

[0024] The present invention uses the laser plasmon effect to obtain layered MnO2 pinned by metal Mo rich in oxygen defects and layered MnO2 partially pinned (filled) by anions rich in oxygen defects. In an aqueous environment, oxygen defects can adjust the electronic structure and increase conductivity. Oxygen defects can increase ion storage sites and improve the specific capacity of the positive electrode. However, if there are too many oxygen defects, water molecules will attack the oxygen defects, making Mn 4+ Dissolution affects the performance of aqueous batteries; so the amount of oxygen defects needs to be controlled. Therefore, it is necessary to fill some oxygen defects with anions, and use anions to control the amount of oxygen defects, so the filling amount of anions has a great influence on the performance of the final material. If the amount of anions added is too large, the MnO2 material will undergo a phase change, for example, to MnS2; if the amount of anions added is too small, the anions cannot fill the oxygen defects. In addition, the laser processing parameters of the laser plasmon effect also affect the performance of the material: if the power is too large, the MnO2 material will undergo a phase change and the valence state of the anions will change; if the power is too small, the anions cannot fill the oxygen defects.

[0025] like Fig.14 As shown, the oxygen defects and backfilled anions generated by the layered MnO2 composite material prepared by the present invention under the action of laser are evenly distributed in the bulk phase of manganese oxide. The anion pinning oxygen defects is coupled with the metal ion pinning layered MnO2 to regulate the charge distribution around the atoms in the bulk phase of MnO2, reduce the Hubbard band gap, and make it have a suitable work function, thereby improving the charge / mass transfer efficiency of MnO2. At the same time, the migration and aggregation of oxygen defects are suppressed by pinning oxygen defects with anions, the lattice structure of MnO2 is stabilized, and the weakening of Mn-O bonds caused by oxygen defects is effectively prevented, reducing the MnO2 2+The dissolution of the layered manganese oxide can be achieved by coupling the pinning and pillaring of the metal cation MnO2 layers to prevent interlayer slippage, thereby improving the overall structural stability of MnO2. When used as a positive electrode material for aqueous zinc-ion batteries, it can achieve fast and reversible zinc ion storage, giving the layered manganese oxide electrode material a fast kinetic process, high reversible charge and discharge cycle capacity, and long cycle life.

[0026] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0027] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0028] Example 1: Preparation of N / Ov-Mo-MnO2 (1) Using the hydrothermal synthesis method, 200 mg KMnO4 and 39.2 mg MnSO4·H2O were added to the inner lining of the hydrothermal reactor, and 30 ml deionized water was added and stirred until dissolved to form a solution ①. Then 10 mg H 24 Mo7N6O 24 ·4H2O was placed in solution ① and stirred until dissolved to obtain solution ②. The reactor containing solution ② was placed in an oven and kept warm at 160℃ for 16h. After the reactor was cooled, the sample was collected, washed three times with deionized water and ethanol, and then freeze-dried at -60℃ for 24h to obtain metal ion Mo pinned layered MnO2 powder, recorded as Mo-MnO2.

[0029] (2) Take 100 mg of Mo-MnO2 and place it at the bottom of a 2 cm×2 cm corundum boat. Place the boat in a glass reactor (the reactor cover is a quartz plate with a thickness of 4 mm). Let argon gas flow for 10 min to expel the air in the reactor. Use an HTF50M laser marker (set the scanning speed to 500 mm / s, the power to 35%, the line spacing to 0.002 mm, and the number of scanning circles to 3) to scan the powder. After the scanning, collect the sputtered powder to obtain manganese dioxide powder pinned by oxygen-rich defect metal ions Mo; record it as Ov-Mo-MnO2.

[0030] (3) Take 100 mg of Ov-Mo-MnO2 and place it at the bottom of a 2 cm × 2 cm corundum boat. Place ammonia gas into the boat in a glass reactor (the reactor cover is a quartz sheet with a thickness of 4 mm, the reactor has a diameter of 8 cm and a height of 5.6 cm) for 10 min to expel the air in the reactor. The flow rate is controlled at 1 cm 3 / s, use HTF50M laser marking machine (set scanning speed to 500 mm / s, power to 35%, line spacing to 0.002 mm, scanning number to 3) to scan the powder, collect the sputtered powder after scanning, and obtain anion N pinning oxygen vacancy coupling metal ion Mo pinning layered manganese dioxide powder. Recorded as N / Ov-Mo-MnO2.

[0031] Example 2: Preparation of S / Ov-Mo-MnO2 (1) Using the hydrothermal synthesis method, 200 mg KMnO4 and 39.2 mg MnSO4·H2O were added to the inner lining of the hydrothermal reactor, and 30 ml deionized water was added and stirred until dissolved to form a solution ①. Then 15 mg H 24 Mo7N6O 24 ·4H2O was placed in solution ① and stirred until dissolved to obtain solution ②. The reactor containing solution ② was placed in an oven and kept warm at 160℃ for 16h. After the reactor was cooled, the sample was collected, washed three times with deionized water and ethanol, and then freeze-dried at -60℃ for 24h to obtain metal ion Mo pinned layered MnO2 powder, recorded as Mo-MnO2.

[0032] (2) Take 100 mg of Mo-MnO2 and place it at the bottom of a 2 cm×2 cm corundum boat. Place the boat in a glass reactor (the reactor cover is a quartz plate with a thickness of 4 mm). Let argon gas flow for 10 min to expel the air in the reactor. Use an HTF50M laser marker (set the scanning speed to 500 mm / s, the power to 35%, the line spacing to 0.002 mm, and the number of scanning circles to 3) to scan the powder. After the scanning, collect the sputtered powder to obtain manganese dioxide powder pinned by oxygen-rich defect metal ions Mo; record it as Ov-Mo-MnO2.

[0033] (3) Take 100 mg of Ov-Mo-MnO2 and put it in a mortar. Add 10 mg of sulfur powder to it and grind the two together to obtain a mixed powder. Put the mixed powder at the bottom of a 2 cm×2 cm corundum boat. Put the boat in a glass reactor (the reactor cover is a quartz sheet with a thickness of 4 mm) and pass argon gas for 10 min to exhaust the air in the reactor. Use an HTF50M laser marker (set the scanning speed to 500 mm / s, the power to 35%, the line spacing to 0.002 mm, and the number of scanning circles to 3) to scan the powder. After the scanning is completed, collect the sputtered powder to obtain anion S pinning oxygen-rich defects coupled with metal ion Mo pinning layered manganese dioxide powder. It is recorded as S / Ov-Mo-MnO2.

[0034] Comparative Example 1 The difference from Example 1 is that in step (3), the power of the HTF50M laser marking machine is 20%, and finally anion N pinning oxygen vacancies coupled metal ion Mo pinning layered manganese dioxide powder is prepared, which is recorded as N-Mo-MnO2-20%.

[0035] Comparative Example 2 The difference from Example 1 is that in step (3), the power of the HTF50M laser marking machine is 50%, and finally anion N pinning oxygen vacancies coupled metal ion Mo pinning layered manganese dioxide powder is prepared, which is recorded as N-Mo-MnO2-50%.

[0036] Comparative Example 3 The difference from Example 1 is that in step (3), the scanning number of the HTF50M laser marking machine is 6, and finally anion N pinning oxygen vacancies coupled metal ion Mo pinning layered manganese dioxide powder is prepared, which is recorded as N-Mo-MnO2-6.

[0037] Comparative Example 4 The difference from Example 2 is that in step (3), the mass ratio of Mo-MnO2 to sulfur powder is 5:1, and finally anion S pinning oxygen vacancies coupled with metal ion Mo pinning layered manganese dioxide powder is prepared, namely S-Mo-MnO2-5.

[0038] Comparative Example 5 The difference from Example 2 is that in step (3), the mass ratio of Mo-MnO2 to sulfur powder is 15:1, and finally anion S pinning oxygen vacancies coupled with metal ion Mo pinning layered manganese dioxide powder is prepared, namely S-Mo-MnO2-15.

[0039] Test Example 1: Characterization MnO2, Mo-MnO2 prepared in step (1) of Example 1, Ov-Mo-MnO2 prepared in step (2) of Example 1, N / Ov-Mo-MnO2 prepared in Example 1, S / Ov-Mo-MnO2 prepared in Example 2, N-Mo-MnO2-20% prepared in Comparative Example 1, N-Mo-MnO2-50% prepared in Comparative Example 2, N-Mo-MnO2-6 prepared in Comparative Example 3, S-Mo-MnO2-5 prepared in Comparative Example 4 and S-Mo-MnO2-15 prepared in Comparative Example 5 were characterized.

[0040] like Figure 1~2As shown, the anion-pinned oxygen-rich defect-coupled metal ion Mo-pinned layered manganese dioxide prepared in Examples 1 and 2 is in the form of nanosheet microspheres. Compared with the original MnO2, the Mo-MnO2 prepared in step (1) of Example 1 does not substantially change the morphology of MnO2. The Ov-Mo-MnO2 nanosheet microstructure prepared in step (2) of Example 1 is slightly damaged, and the transmission electron microscope scanning image shows that the nano-microspheres composed of nanosheets are agglomerated. This is because too many oxygen defects cause vacancies or interstitial atoms in the lattice, causing lattice distortion and internal stress, which in turn affects the stability of the nanosheet structure, resulting in local deformation and dislocation of the microstructure, and causing structural loss.

[0041] Compared with Ov-Mo-MnO2, the N / Ov-Mo-MnO2 nanosheet microstructure prepared in Example 1 has no obvious damage, and the transmission electron microscope scanning image shows that the nanosphere structure is intact. Although the S / Ov-Mo-MnO2 prepared in Example 2 has a relatively complete nanosheet microstructure, the transmission electron microscope scanning image shows slight agglomeration. Anions can pin oxygen defects by bonding with atoms around oxygen defects. The electronegativity of N is greater than that of S. In the coupled metal ion Mo pinned layered MnO2 structure, N can more effectively regulate the distribution of electron clouds, making the electron cloud distribution around oxygen defects and the overall structure of MnO2 more uniform, and the charge balance is better, reducing structural damage caused by electronic disorder, and improving microstructural stability. However, S is weak in regulating electron clouds and maintaining charge balance, which can easily induce structural stress and reduce microstructural stability.

[0042] Figure 3 The scanning electron microscope images of the composite materials of Comparative Examples 1 to 5 are shown. Comparative Example 1 changes the laser parameters and reduces the laser power to 20%, but the nanosheet microspheres are relatively intact, and the morphology changes slightly compared with the N / Ov-Mo-MnO2 of Example 1. Comparative Example 2 increases the laser power to 50%, and the nanosheets on the surface of the material have been destroyed and are needle-shaped. Comparative Example 3 is determined by the laser power, but the number of laser scanning circles is changed to 6 circles. It will be found that the nanosheet structure of the obtained sample is a microsphere structure formed by the aggregation of nanospheres connected by bead curtain-like nanosheets, forming a nitride and coating the surface of the nanospheres. Used as an electrode, it will affect the embedding of zinc ions. Comparative Example 4 is determined by the laser parameters, increasing the proportion of S powder, and the surface of the obtained sample is destroyed to form microspheres of nanoparticle agglomeration. Comparative Example 5 is determined by the laser parameters, reducing the proportion of S powder, and its surface structure is close to S / Ov-Mo-MnO2, but there are still some damages in the structure. In summary, it can be seen that the morphological changes of Comparative Examples 1 and 5 are relatively small, while Comparative Examples 2 to 4 all undergo certain morphological changes.

[0043] from Figure 4 (a) and Figure 4As can be seen in (b), the XPS test of the content of nitrogen and oxygen defects in N / Ov-Mo-MnO2 shows that as the etching depth increases, the intensity of the characteristic peaks corresponding to the N element and oxygen defects in the XPS spectrum does not change, indicating that the content of N element and oxygen defects is uniformly distributed in MnO2.

[0044] Figure 4 (c) shows the EPR images of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2. Compared with MnO2, the oxygen defect content in Mo-MnO2 slightly increased after Mo atoms pinned layered MnO2; however, the oxygen defect content in Ov-Mo-MnO2 increased significantly after oxygen-rich defects coupled with metal ions Mo pinned layered MnO2, indicating that laser treatment can effectively increase the defect content in the material. Compared with Ov-Mo-MnO2, the defect content of N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 decreased significantly after anions N or S pinned oxygen defects coupled with metal ions Mo pinned layered MnO2, indicating the successful pinning of anions.

[0045] Figure 5 The XRD patterns of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2 are shown in Figure 2. Compared with MnO2, the physical phases of Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2 have not changed, but the corresponding characteristic peaks have shifted, proving that the lattice spacing has changed. After the metal ion Mo pinned the layered MnO2, the XRD spectrum of Mo-MnO2 showed that the characteristic peaks shifted to small angles, indicating that the interlayer spacing of MnO2 became larger. After the anion N or S pinned the oxygen defect and coupled the metal ion Mo pinned the layered MnO2, the interlayer spacing of N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 will also increase, which is conducive to the construction of fast ion transport channels.

[0046] Figure 6The band gap widths and Fermi level positions of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2 are shown in Figure 2. MnO2 has a wide band gap (1.64 eV). When Mo atoms are used as interlayer pillars, the band gap of Mo-MnO2 becomes narrower (0.87 eV). After oxygen defects are created by laser irradiation, the band gap width of Ov-Mo-MnO2 is 0.62 eV. Although the band system is significantly narrowed after laser treatment, it still has a large bandwidth. However, after the anion N or S pins the oxygen defect, the band gaps of N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 are almost completely filled, and the bandwidths are significantly reduced to 0.0006 eV (N pinning) and 0.0019 eV (S pinning), respectively, which significantly enhances the conductivity of the material. In addition, the Fermi level gradually moves up, the carrier concentration increases, the conductivity improves, and the electrochemical activity increases. This increases the density of energy storage active sites. At the same time, it can enhance the Zn 2+ The adsorption force of the electrode can be improved, the diffusion path within the material can be optimized, the electrode reaction kinetics can be accelerated, and the storage capacity, charge and discharge efficiency and rate performance can be improved.

[0047] Test Example 2: Performance Test (1) MnO2, Mo-MnO2 prepared in step (1) of Example 1, Ov-Mo-MnO2 prepared in step (2) of Example 1, N / Ov-Mo-MnO2 prepared in Example 1, S / Ov-Mo-MnO2 prepared in Example 2, N-Mo-MnO2-20% prepared in Comparative Example 1, N-Mo-MnO2-50% prepared in Comparative Example 2, N-Mo-MnO2-6 prepared in Comparative Example 3, S-Mo-MnO2-5 prepared in Comparative Example 4 and S-Mo-MnO2-15 prepared in Comparative Example 5 were mixed with carbon powder and a binder (mass ratio of 7:2:1), N-methylpyrrolidone was added, and the mixture was ground evenly to obtain a viscous electrode slurry. The viscous electrode slurry was evenly coated on a base titanium foil (0.02 mm) and the loading amount was controlled to be 1 mg cm 2 The obtained product was dried in a vacuum drying oven and cut into discs with a radius of 6 mm using a cutting machine to obtain manganese dioxide electrode sheets.

[0048] (2) The above-mentioned manganese dioxide electrode sheet is used as the positive electrode, the zinc sheet with a thickness of 0.1 mm is used as the negative electrode, the separator is a glass fiber of model 1825-150, and the electrolyte is 2 mol·L -1 ZnSO4+0.1 mol·L -1 MnSO4 solution, assembled button cells, battery model CR2025. Battery performance was measured by Blue Battery Test System and CHI Electrochemical Workstation.

[0049] Figure 7 The work function values ​​of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2 are shown in Table 1. After the Mo atom is pinned to the layered MnO2, the work function of Mo-MnO2 decreases. This is because the electronic orbit of Mo hybridizes with the electronic orbit of layered MnO2, which changes the distribution of the electronic state density of the entire system, increases the electronic state density near the Fermi level, and makes it easier for electrons to escape from the material surface, thereby reducing the work function. After the introduction of oxygen defects, the work function of Ov-Mo-MnO2 is further reduced. The local electric field formed by the charge around the oxygen defect and the distortion of the electron cloud, and the interaction between the electron cloud near the oxygen defect and the electron cloud around Mo strengthens the regulation of electrons, thereby further reducing the work function of the material. After the anion N or S pins the oxygen defect and the metal ion Mo pins the layered MnO2, the N or S in N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 gather near the oxygen defect. The electronegativity of N or S is different from that of O. This pinning effect changes the distribution of the electron cloud around the oxygen defect, enhances the binding ability of the electrons at the oxygen defect, and makes the electron cloud more concentrated in the defect area. This change in the distribution of the electron cloud causes the coupling metal Mo to hybridize with the electron orbit of the layered MnO2 in the interlayer electron orbit, forming an additional electric field, thereby changing the distribution of the electronic state density of the entire system, making it easier for electrons to escape from the inside of the material to the surface, reducing the work function of the material. In addition, the electronegativity of N (3.04) is greater than that of S (2.58). When pinning oxygen defects, N has a stronger ability to attract electrons, which makes it easier to distort the distribution of the electron cloud around the oxygen defect and form a stronger local electric field. Therefore, the work function of N / Ov-Mo-MnO2 is the lowest. For materials with low work function, electrons are more likely to overflow, which enhances the electrochemical activity of MnO2 and accelerates the Zn 2+ The redox reaction rate during the embedding and extraction process. It can be concluded that N / Ov-Mo-MnO2 has a higher charge / mass transfer efficiency and reaction kinetics.

[0050] Figure 8 For MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2 for Zn 2+ and H +The adsorption energy of Ov-Mo-MnO2 is significantly reduced, among which the pinning of Mo reduces the adsorption energy to a certain extent. The construction of oxygen defects affects the energy of the adsorption sites, which makes the adsorption energy of Ov-Mo-MnO2 significantly reduced. However, after the anion pinning, the adsorption energy of N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 increases (N / Ov-Mo-MnO2: -1.82 eV, S / Ov-Mo-MnO2: -1.74 eV). The adsorption energy represents the interaction strength between the adsorbate and the substrate. The more negative the adsorption energy, the more stable the adsorption process and the more difficult the desorption will be. Therefore, the moderate adsorption energy of the layered MnO2 composite material pinned by anions N or S and coupled with oxygen defects of metal ions Mo is more conducive to Zn 2+ / H + The embedding / ejection process.

[0051] Fig. 9 The adsorption energy of water by MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2. In the aqueous electrolyte system, active water easily attacks oxygen defects, causing structural collapse. Therefore, the higher the adsorption energy of water by the material, the less favorable it is for the stability of the material. Fig. 9 It can be seen that N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 have the smallest adsorption energy for water and higher stability.

[0052] Fig.10 (a) and Fig.10 (b) shows the CV curves and charge-discharge cycle curves of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2; Fig.10 In (c) and Fig.10 (d) is the CV curve and charge-discharge curve of comparative examples 1 to 5. It can be concluded from the CV curve that each curve has two pairs of redox peaks, indicating that the electrochemical process of the material is a dual ion insertion / extraction process, but N / Ov-Mo-MnO2 has the highest peak current, indicating that N / Ov-Mo-MnO2 has the highest electrode activity and the best electrode reaction kinetics. The information obtained from the discharge curve is the same as the CV curve. Each curve has two discharge platforms, indicating that the electrochemical process of the material is a dual ion insertion / extraction process, and N / Ov-Mo-MnO2 has the highest capacity.

[0053] The laser power of Comparative Example 1 is insufficient, N cannot effectively pin oxygen defects, it is difficult to adjust the electronic structure, and the battery capacity is reduced compared to N / Ov-Mo-MnO2. The laser power of Comparative Example 2 is too high, which destroys the surface structure of MnO2 and reduces the ion storage sites, greatly affecting the cycle stability of the material and the battery capacity. The number of scanning circles in Comparative Example 3 is too many, and nitrides are easily formed on the surface, attached to the surface of the active material, affecting the embedding of ions and reducing the material capacity. The excessive doping of S in Comparative Example 4 leads to the formation of a layer of sulfide on the surface of the material. During charging and discharging, it is difficult for ions to embed, reducing the material capacity. The S doping amount in Comparative Example 5 is too little, S cannot effectively pin oxygen defects, and cannot achieve the effect of adjusting the electronic structure and stabilizing the structure. The battery capacity is reduced compared to S / Ov-Mo-MnO2.

[0054] Fig.11 For MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2 at a current density of 1Ag -1 It can be seen from the figure that the anion N pinning oxygen defect coupled with the metal ion Mo pinning layered MnO2 composite material has the largest number of cycles and the highest capacity.

[0055] Fig.12 The Mn dissolution of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, and S / Ov-Mo-MnO2 during charge and discharge. 2+ The concentration is the Mn in the electrolyte after charge and discharge. 2+ When the number of cycles is the same, relative to MnO2, after the Mo atoms are pinned to the layered MnO2, the Mn 2+ The solution was inhibited to a certain extent, but in the Ov-Mo-MnO2 electrolyte, Mn 2+ The content of Mn in the electrolyte of N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 increased, indicating that too much oxygen defect is not conducive to the stability of the material. After the anion pinning of oxygen-rich defects coupled with metal ion Mo pinning of layered MnO2, the Mn 2+ The content of MnO2 decreased significantly, indicating that the anion N or S pinned oxygen defect coupled with the metal ion Mo pinned layered MnO2 composite material has good stability.

[0056] Fig.13 The images of constant current intermittent titration (GITT) of MnO2, Mo-MnO2, Ov-Mo-MnO2, N / Ov-Mo-MnO2, S / Ov-Mo-MnO2 and Mn 2+Migration energy. The pinning of Mo atoms in Mo-MnO2 increases the interlayer spacing of layered MnO2, reduces the ion diffusion energy, and accelerates the ion migration rate. In Ov-Mo-MnO2, the presence of oxygen defects weakens the electrostatic force between ions and layers during ion diffusion, so the ion diffusion rate is further accelerated and the diffusion energy is reduced. In N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2, a built-in electric field is formed between anions and cations, and the migration of ions is accelerated again under the support of the electric field, making the diffusion rate of ions in N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 faster and the migration energy lower.

[0057] Fig.14 Schematic diagram of the principle of coupling surface sites and interlayer structure to pin layered manganese oxide electrode materials in aqueous zinc ion batteries. The interlayer spacing of MnO2 is small, which is not conducive to Zn 2+ After Mo pins the interlayer structure, the interlayer spacing of Mo-MnO2 expands, which is beneficial to the insertion and extraction of Zn 2+ The Mo atoms can be embedded and extracted, and they can serve as interlayer pillars to prevent the layered structure from sliding during charge and discharge, which would lead to structural collapse. After the oxygen defects are introduced by laser, the traps in Ov-Mo-MnO2 can adjust the electronic structure and increase the conductivity. At the same time, the oxygen defects can increase the ion storage sites and improve the specific capacity of the positive electrode. However, there are too many oxygen defects, and the adsorption effect on water molecules in the aqueous solution is strong. Water molecules can easily attack oxygen defects, causing Jahn-Taylor distortion and leading to Mn dissolution, affecting the cyclic stability and specific capacity of the material. After the anions N or S pin the oxygen defects, the adsorption of water by N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 is weakened, the Jahn-Taylor distortion is suppressed, and the cyclic stability and specific capacity of N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2 are improved. In addition, the anions N or S will form a built-in electric field with Mo, accelerating the diffusion rate of ions in N / Ov-Mo-MnO2 and S / Ov-Mo-MnO2.

[0058] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a layered manganese oxide electrode material with surface sites coupled with an interlayer structure, characterized in that: The following steps are involved: (1) dissolving a manganese salt and a molybdenum salt in deionized water in sequence and performing a hydrothermal reaction to obtain a metal ion Mo-pinned layered manganese oxide precursor; (2) Under a protective atmosphere, a plasmon laser is used to irradiate a metal ion Mo-pinned layered manganese oxide precursor to obtain oxygen-rich defect metal ion Mo-pinned MnO2; (3) In an anion source, a plasmon laser is used to irradiate MnO2 pinned by oxygen-rich defect metal ions Mo to obtain a layered manganese oxide electrode material with surface sites and interlayer structure coupled pinning.

2. The preparation method according to claim 1, characterized in that: In step (1), the manganese salt includes KMnO4 and MnSO4·H2O; the molybdenum salt is H 24 Mo7N6O 24 ·4H2O; the KMnO4, MnSO4·H2O and H 24 Mo7N6O 24 The molar ratio of 4H2O is 1:0.15:0.003~0.

01.

3. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the hydrothermal reaction is 120-160° C., and the time of the hydrothermal reaction is 10-16 hours.

4. The preparation method according to claim 1, characterized in that: In step (1), after the hydrothermal reaction is completed, the precipitate is filtered and washed, and the precipitate is vacuum freeze-dried to obtain a metal ion Mo pinned layered manganese oxide precursor.

5. The preparation method according to claim 1, characterized in that: In step (2) and step (3), the parameters of the plasmon laser are: line spacing of 0.001-0.004 mm, laser scanning speed of 200-500 mm / s, and laser power of 30%-40%.

6. The preparation method according to claim 1, characterized in that: In step (3), the anion source is ammonia gas or sulfur powder; when the anion source is ammonia gas, the reaction environment is filled with ammonia gas; when the anion source is sulfur powder, the reaction environment is filled with protective gas.

7. The preparation method according to claim 6, characterized in that: The mass ratio of MnO2 pinned by the oxygen-rich defect metal ion Mo and sulfur powder is 10:1; the mass ratio of MnO2 pinned by the oxygen-rich defect metal ion Mo and ammonia is 1:3~6.

8. The surface site and interlayer structure coupled pinned layered manganese oxide electrode material obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The surface site and interlayer structure coupled pinned layered manganese oxide electrode material is layered MnO2 in which anion pinning oxygen defects are coupled with metal ion Mo pinning.

9. The surface site and interlayer structure coupled pinned layered manganese oxide electrode material according to claim 8, characterized in that: The doping amount of Mo is 3 wt %; the doping amount of the anion is 6 wt %; the anion is S 2- or N 3- .

10. Use of the surface site and interlayer structure coupled pinned layered manganese oxide electrode material according to claim 8 or 9 in improving the specific capacity and cycle stability of aqueous zinc ions.

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