Nano-catalyst, preparation method thereof and application of nano-catalyst in inhibition of side reaction of lithium-oxygen battery

Abstract

The invention discloses a nano-catalyst, a preparation method thereof and application of the nano-catalyst in inhibition of side reaction of a lithium-oxygen battery, and belongs to the technical field of novel energy storage materials. The nano-catalyst comprises a hollow carrier and monodisperse active metal, the hollow carrier comprises a porous shell layer and a spherical cavity enclosed by the porous shell layer; the porous shell layer is made of cobalt oxide; the monodisperse active metal is loaded on the surface of the porous shell layer. A large number of active sites exist on the surface of the nano-catalyst, and oxygen can be efficiently activated, so that the battery has high discharge capacity which can reach 12728mAh / g. More importantly, the catalyst can inhibit side reactions in the charge and discharge process, reduce the generation of lithium carbonate, significantly improve the reversibility of the battery in the operation process, and obtain excellent cycle stability.

Description

Technical Field

[0001] The present application relates to a nano catalyst, a preparation method thereof, and an application in suppressing side reactions of a lithium-oxygen battery, belonging to the technical field of new energy storage materials. Background Art

[0002] With the development of society, the transformation from fossil energy to renewable energy has become an important goal faced by mankind. However, the large-scale utilization of renewable energy (such as solar energy and wind energy) requires a large-capacity energy storage medium for matching energy storage and release. However, the capacity of current lithium-ion batteries is difficult to meet the corresponding requirements, and a higher-capacity battery system needs to be found. Lithium-oxygen batteries have received extensive attention due to their ultra-high theoretical energy density (comparable to gasoline).

[0003] However, lithium-oxygen batteries are currently difficult to be commercially applied as secondary batteries, mainly because the discharge product lithium peroxide is difficult to be efficiently decomposed and serious side reactions often occur during the charge and discharge processes. Lithium carbonate is one of the main by-products in lithium-oxygen batteries. Its chemical properties are more stable than those of lithium peroxide and are difficult to decompose in subsequent cycles, thus blocking the electrode pores, affecting the electrode diffusion process, and resulting in poor battery reversibility. In addition, lithium-oxygen batteries are prone to generate highly reactive superoxides and singlet oxygen at high charging potentials. These active substances will react with the electrode and electrolyte to cause irreversible side reactions, resulting in battery capacity attenuation and even cycle termination. Therefore, suppressing the side reactions during the charge and discharge process of the battery and avoiding the generation of lithium carbonate are of great help in reducing the battery overpotential, improving the reversibility, and extending the life. However, the current strategies for suppressing side reactions of lithium-oxygen batteries are very limited.

[0004] Therefore, developing a positive electrode catalyst to suppress side reactions in lithium-oxygen batteries, reducing or even avoiding the formation of by-products, and improving the actual discharge capacity and reversibility of lithium-oxygen batteries will contribute to promoting the commercial application of lithium-oxygen batteries. Summary of the Invention

[0005] In order to mitigate the side reaction problems during the charge and discharge processes in the existing technology of lithium-oxygen batteries and promote the reversible formation and decomposition of lithium peroxide as the discharge product, the present application provides a nano-catalyst. The nano-catalyst framework is a hollow sphere carrier of an active metal oxide, and the surface of the carrier is loaded with monodispersed metal active centers. The monodispersed metal active centers and the metal oxide produce a synergistic catalytic effect, which can improve the activation ability of oxygen, regulate the growth of lithium peroxide as the discharge product, reduce the battery overpotential and increase the battery discharge capacity. In addition, the synergistic catalysis of the monodispersed metal active centers and the metal oxide carrier can reduce the vacancy formation energy on the material surface, promote the rapid conversion of oxygen on the surface, avoid the accumulation of highly oxidizing lithium superoxide during the charge and discharge processes, reduce the corrosion of the electrolyte and electrode materials, inhibit the occurrence of side reactions, and avoid the formation of by-product lithium carbonate, thereby improving the battery reversibility and extending the battery life.

[0006] The present application adopts the following technical solutions:

[0007] According to one aspect of the present application, there is provided a nano-catalyst, the nano-catalyst comprising a hollow carrier and monodispersed active metal;

[0008] The hollow carrier comprises a porous shell layer and a spherical cavity surrounded by the porous shell layer;

[0009] The material of the porous shell layer is cobalt oxide;

[0010] The monodispersed active metal is loaded on the surface of the porous shell layer.

[0011] The active metal is in a monodispersed state. By controlling the selection of the annealing temperature, a metal oxide hollow structure with a surface containing monodispersed metal centers is formed from the precursor.

[0012] Optionally, the outer surface of the porous shell layer has a stacked structure formed by porous nanosheets.

[0013] Optionally, the size of the porous nanosheets in the length direction is 200 nm to 300 nm;

[0014] Optionally, the size of the holes on the porous nanosheets is 2 nm to 10 nm.

[0015] Optionally, the monodispersed active metal is selected from at least one of Ru, Rh, Ta, Nb, In, and Bi in a monodispersed state.

[0016] According to another aspect of the present application, there is provided a preparation method of the above-mentioned nano-catalyst. The preparation method has a simple process, mild conditions, is easy to achieve large-scale preparation, and at the same time has a high metal utilization rate in the catalyst, low cost, and good industrial application prospects.

[0017] Optionally, the method for preparing the nano-catalyst includes the following steps:

[0018] S1. Obtain cobalt oxide solid spheres as precursor A;

[0019] S2. Place the mixture containing precursor A and water in a sealed container, react to obtain precursor B; in this process, the cobalt oxide solid spheres are transformed into a hollow sphere solution with a surface stacked by porous flakes.

[0020] S3. Subject the mixture containing precursor B, alcohol, and active metal salt to ultrasonic treatment and drying in sequence to obtain precursor C;

[0021] S4. Anneal precursor C to obtain the nano-catalyst.

[0022] Optionally, in step S1, the method for preparing the cobalt oxide solid spheres includes the following steps:

[0023] Place the mixture containing soluble cobalt salt, isopropanol, and glycerol in a sealed container, after hydrothermal reaction, centrifuge to collect the precipitate, wash with isopropanol, and dry to obtain the cobalt oxide solid spheres.

[0024] Optionally, in step S1, cobalt nitrate is added to the mixture containing isopropanol and glycerol under stirring conditions, and stirred until the cobalt nitrate is completely dissolved to obtain a mixture containing soluble cobalt salt, water, isopropanol, and glycerol.

[0025] Optionally, in step S1, the weight ratio of isopropanol to glycerol is 2.3:1.

[0026] Optionally, in step S1, the regulation of stirring includes: the stirring time is 30 min to 50 min.

[0027] Optionally, in step S1, the conditions of the hydrothermal reaction include: the hydrothermal temperature is 150 °C to 200 °C, and the hydrothermal time is 3 h to 8 h.

[0028] Optionally, in step S2, the reaction conditions include: the temperature is 140 °C to 180 °C, and the reaction time is 1 h to 6 h.

[0029] Optionally, in step S3, the active metal salt is selected from at least one of phosphates, chlorides, nitrates, and sulfates of active metals, where the active metal is selected from at least one of Ru, Rh, Ta, Nb, In, and Bi.

[0030] Optionally, in step S3, the alcohol is selected from at least one of methanol and ethanol.

[0031] Optionally, in step S3, the concentration of the active metal salt in the mixture is 0.01 g / L to 0.1 g / L.

[0032] Optionally, in step S3, the concentration of the active metal salt in the mixed solution is selected from any value of 0.01 g / L, 0.02 g / L, 0.03 g / L, 0.04 g / L, 0.05 g / L, 0.06 g / L, 0.07 g / L, 0.08 g / L, 0.09 g / L, 0.1 g / L or the range value between any two of them.

[0033] Optionally, in step S3, the drying method is selected from at least one of rotary evaporation, air drying, vacuum drying, and freeze drying.

[0034] Optionally, in step S3, the time of ultrasonic treatment is 30 min to 60 min. After ultrasonic treatment, a uniformly mixed suspension is obtained.

[0035] Optionally, in step S3, the drying temperature is 40°C to 100°C.

[0036] Optionally, in step S3, the drying temperature is selected from any value of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or the range value between any two of them.

[0037] Optionally, in step S4, the annealing conditions include: the annealing temperature is 150°C to 300°C, and the annealing time is 1 h to 6 h.

[0038] Optionally, in the annealing conditions of step S4, the annealing temperature is selected from any value of 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C or the range value between any two of them.

[0039] Optionally, in the annealing conditions of step S4, the annealing time is selected from any value of 1 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, 6.0 h or the range value between any two of them.

[0040] Optionally, in step S4, the annealing atmosphere is air.

[0041] According to another aspect of the present application, there is also provided an application of the above-mentioned nano-catalyst or the nano-catalyst prepared according to the above preparation method as a positive electrode catalyst material in inhibiting side reactions of a lithium-oxygen battery.

[0042] The catalyst can significantly improve the activation ability of oxygen, increase the discharge capacity of the battery, and can significantly reduce the occurrence of side reactions in the lithium-oxygen battery, obtaining relatively excellent reversibility and cycle stability.

[0043] The beneficial effects that can be produced by this application include:

[0044] The nano-catalyst provided by this application has monodispersed metal active centers on its surface, which catalyze together with the active metal oxide. In the application of suppressing side reactions in lithium-oxygen batteries, it can improve the activation ability of oxygen, regulate the growth of discharge product lithium peroxide, reduce the battery overpotential and increase the battery discharge capacity. In addition, the co-catalysis of the monodispersed metal active centers and the metal oxide support can reduce the vacancy formation energy on the material surface, promote the rapid conversion of oxygen on the surface, avoid the accumulation of strongly oxidizing lithium superoxide during charge and discharge, reduce the corrosion of the electrolyte and electrode materials, significantly inhibit and reduce the occurrence of side reactions in lithium-oxygen batteries, avoid the formation of by-product lithium carbonate, thereby improving the battery reversibility and cycle stability and prolonging the battery life.

[0045] The preparation method of the nano-catalyst provided by this application has simple process, mild conditions, is easy to realize large-scale preparation. At the same time, the metal utilization rate in the catalyst is high and the cost is low, having good industrial application prospects. Brief Description of the Drawings

[0046] Figure 1 It is the transmission electron microscope image of the nano-catalyst prepared in Example 1 of this application.

[0047] Figure 2 It is the XPS spectra of the discharge products of the nano-catalysts prepared in Examples 1 and 11 of this application and the catalyst prepared in Comparative Example 1.

[0048] Figure 3 It is the first charge-discharge curves of the nano-catalysts prepared in Examples 1 and 11 of this application and the catalyst prepared in Comparative Example 1.

[0049] Figure 4 It is the cycle stability of the nano-catalysts prepared in Examples 1 and 11 of this application and the catalyst prepared in Comparative Example 1.

[0050] Figure 5 It is the spherical aberration corrected transmission electron microscope image of Comparative Example 1 of this application. Detailed Description of the Embodiments

[0051] The following describes this application in detail with reference to the embodiments, but this application is not limited to these embodiments.

[0052] Unless otherwise specified, the raw materials in the embodiments of this application are all purchased through commercial channels.

[0053] Unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all the settings recommended by the manufacturers.

[0054] In the embodiments of the present application, the analysis method includes: performing morphology analysis using a transmission electron microscope, analyzing battery side reactions using X-ray photoelectron spectroscopy, and performing electrochemical analysis using a constant current charge-discharge tester.

[0055] Example 1 Preparation of Nano-Catalyst

[0056] (a) Synthesis of Solid Alcohol Cobalt Oxide Spheres

[0057] Mix 30 mL of isopropanol and 8 mL of glycerol evenly. While stirring continuously, add 291 mg of cobalt nitrate to the above solution, and continue stirring until all the solid salts are dissolved to obtain a metal salt solution (precursor A). Subsequently, transfer it to a reaction kettle for hydrothermal reaction. React at a reaction temperature of 180 °C for 6 h. After cooling, centrifuge to separate the solid matter, wash it several times with ethanol, and dry it in vacuum at 60 °C to obtain solid alcohol cobalt oxide spheres;

[0058] (b) Synthesis of Hollow Sphere Precursors

[0059] Disperse 0.1 g of the above solid alcohol cobalt oxide spheres in 20 mL of deionized water, and ultrasonicate for 30 min to make the suspension evenly dispersed. Transfer the above suspension (precursor B) to a reaction kettle for hydrothermal reaction. React at a reaction temperature of 160 °C for 3 h. After cooling, centrifuge to separate the solid matter, wash it several times with ethanol, and dry it in vacuum at 60 °C to obtain hollow sphere precursors;

[0060] (c) Loading of Active Metal

[0061] Using ethanol as the rotary evaporation dispersion liquid, take 60 mg of the above hollow sphere precursors and disperse them in 50 mL of ethanol, denoted as dispersion liquid A. Continue ultrasonication for 1 h. Dissolve 1.5 mg of tantalum chloride (active metal salt) in 5 mL of ethanol, denoted as solution B. Under ultrasonic treatment, dropwise add solution B to dispersion liquid A to obtain a mixed solution. Evaporate the solvent by rotary evaporation at 50 °C, and collect the solid matter, which is the precursor after loading the active metal.

[0062] (d) Annealing Treatment of Materials

[0063] The precursor after loading the active metal is heated to 200 °C (annealing temperature) in an air atmosphere using a muffle furnace and maintained for 2 h (annealing time) for annealing treatment, and finally a nano-catalyst with a hollow structure having monodispersed metal centers on the surface is obtained. The microscopic morphology is as Figure 1 shown.

[0064] Example 2

[0065] In the preparation method of the nano-catalyst with a hollow structure provided in this example, except that the hydrothermal temperature of precursor A in step (a) is changed to 160 °C, other process steps and process parameters are the same as those in Example 1.

[0066] Example 3

[0067] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal temperature of precursor A in step (a) is changed to 200 °C, other process steps and process parameters are the same as those in Example 1.

[0068] Example 4

[0069] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal time of precursor A in step (a) is changed to 4 h, other process steps and process parameters are the same as those in Example 1.

[0070] Example 5

[0071] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal time of precursor A in step (a) is changed to 8 h, other process steps and process parameters are the same as those in Example 1.

[0072] Example 6

[0073] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal temperature of precursor B in step (b) is changed to 140 °C, other process steps and process parameters are the same as those in Example 1.

[0074] Example 7

[0075] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal temperature of precursor B in step (b) is changed to 180 °C, other process steps and process parameters are the same as those in Example 1.

[0076] Example 8

[0077] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal time of precursor B in step (b) is changed to 1 h, other process steps and process parameters are the same as those in Example 1.

[0078] Example 9

[0079] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that the hydrothermal time of precursor B in step (b) is changed to 5 h, other process steps and process parameters are the same as those in Example 1.

[0080] Example 10

[0081] For the preparation method of the hollow-structured nanocatalyst provided in this example, except that tantalum chloride is replaced by ruthenium chloride in step (c), other process steps and process parameters are the same as those in Example 1.

[0082] Example 11

[0083] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the amount of tantalum chloride in step (c) is changed to 7.5 mg.

[0084] Example 12

[0085] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that tantalum chloride in step (c) is replaced with bismuth nitrate.

[0086] Example 13

[0087] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that tantalum chloride in step (c) is replaced with indium nitrate.

[0088] Example 14

[0089] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that tantalum chloride in step (c) is replaced with rhodium chloride.

[0090] Example 15

[0091] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the rotary evaporation dispersion liquid in step (c) is changed from ethanol to methanol.

[0092] Example 16

[0093] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the way of drying the solvent in step (c) is changed from rotary evaporation to drying in a vacuum drying oven.

[0094] Example 17

[0095] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the way of drying the solvent in step (c) is changed from rotary evaporation to drying in a forced air drying oven.

[0096] Example 18

[0097] The preparation method of the hollow-structured nano-catalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the way of drying the solvent in step (c) is changed from rotary evaporation to freeze drying.

[0098] Example 19

[0099] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 150 °C in step (d).

[0100] Example 20

[0101] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 160 °C in step (d).

[0102] Example 21

[0103] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 170 °C in step (d).

[0104] Example 22

[0105] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 180 °C in step (d).

[0106] Example 23

[0107] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 190 °C in step (d).

[0108] Example 24

[0109] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 220 °C in step (d).

[0110] Example 24

[0111] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 240 °C in step (d).

[0112] Example 25

[0113] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that in Example 1 in terms of other process steps and process parameters, except that the annealing temperature is changed to 260 °C in step (d).

[0114] Example 26

[0115] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing temperature in step (d) is changed to 280 °C.

[0116] Example 27

[0117] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing temperature in step (d) is changed to 300 °C.

[0118] Example 28

[0119] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing time in step (d) is changed to 1 h.

[0120] Example 29

[0121] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing time in step (d) is changed to 3 h.

[0122] Example 30

[0123] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing time in step (d) is changed to 4 h.

[0124] Example 31

[0125] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing time in step (d) is changed to 5 h.

[0126] Example 32

[0127] The preparation method of the hollow-structured nanocatalyst provided in this embodiment is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing time in step (d) is changed to 6 h.

[0128] Example 33

[0129] The preparation method of the hollow-structured nanocatalyst provided in this embodiment has an active metal salt concentration of 0.5 g / L, and other process steps and process parameters are the same as those of Example 1.

[0130] Comparative Example 1

[0131] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that of Example 1 in terms of other process steps and process parameters, except that tantalum chloride is not added in step (c).

[0132] Comparative Example 2

[0133] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that of Example 1 in terms of other process steps and process parameters, except that the hydrothermal temperature in step (b) is changed to 100 °C.

[0134] Comparative Example 3

[0135] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that of Example 1 in terms of other process steps and process parameters, except that the hydrothermal temperature in step (b) is changed to 200 °C.

[0136] Comparative Example 4

[0137] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing temperature in step (d) is changed to 400 °C.

[0138] Comparative Example 5

[0139] The preparation method of the hollow-structured nanocatalyst provided in this example is the same as that of Example 1 in terms of other process steps and process parameters, except that the annealing temperature in step (d) is changed to 500 °C.

[0140] Test Example 1

[0141] The transmission electron microscope image of the hollow-structured nanocatalyst prepared in Example 1 is as Figure 1 shown. The diameter of the hollow sphere is approximately 1 μm, and the surface is composed of stacked thin sheets. The thin sheets exhibit a porous structure, and the active metal tantalum is in a monodispersed state. The morphologies of the hollow-structured nanocatalysts prepared in Examples 2 to 33 are similar to that of Example 1, with diameters ranging from approximately 500 nm to 1 μm. The thin sheets on the surface are porous, but there is slight agglomeration of the thin sheets on the surface of some of the hollow-structured catalysts. The catalyst prepared in Comparative Example 1 also exhibits a hollow sphere composed of stacked thin sheets, but the active metal tantalum therein is in an aggregated state. Its spherical aberration corrected transmission electron microscope image is as Figure 5 shown. For the catalyst prepared in Comparative Example 2, the hollow structure is partially hollow, with a part of the solid structure. For the catalysts prepared in Comparative Examples 3 to 5, the surface sheet agglomeration is serious, and the hollow structure is slightly collapsed.

[0142] The XPS spectra of the discharge products of the nanocatalysts prepared in Examples 1 and 11 and the catalyst prepared in Comparative Example 1 are as Figure 2As shown, the discharge products of the catalyst prepared in Comparative Example 1 are lithium peroxide and lithium carbonate, and lithium carbonate by-products can be clearly seen. The discharge products of the catalysts prepared in Examples 1 and 11 are mainly lithium peroxide, and no obvious lithium carbonate is seen, indicating that there is an obvious inhibitory effect on the by-products in the battery. Different contents of by-product lithium carbonate are detected in the hollow-structured nanocatalysts prepared in Examples 2-10 and 12-33, showing different degrees of inhibition of by-products, and the batteries show different degrees of overpotential reduction and cyclicity improvement. However, a certain amount of by-product lithium carbonate is detected in the discharge products of the catalyst prepared in Comparative Example 1, and the battery overpotential increases and the cyclicity decreases.

[0143] Test Example 2

[0144] Combined with the synthesis method of preparing the catalyst and the morphological changes of the catalyst, we selected several representative comparative samples for subsequent tests. The charge-discharge curves and cyclic stability of the nanocatalysts prepared in Examples 1 and 11 and the catalyst prepared in Comparative Example 1 were tested.

[0145] The specific detection method is as follows: The positive electrode of the battery is prepared by coating the material slurry on the carbon paper. The slurry consists of 45 wt% of the prepared catalyst, 45 wt% of carbon black (KB), and 10 wt% of polyvinylidene fluoride (PVDF), and is dispersed in NMP. The loading amount is about 0.7 mg. The CR2032 type battery is assembled in a glove box filled with an argon atmosphere, and consists of a negative lithium sheet, a glass fiber filter membrane, a positive electrode, and an electrolyte of 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in tetraethylene glycol dimethyl ether (TEGDME). The impedance spectrum (EIS) and cyclic voltammetry curve (CV) are tested on a Chen Hua electrochemical workstation.

[0146] The results are as follows. The first charge-discharge curve is as Figure 3 shown. The catalyst prepared in Example 1 shows the lowest overpotential, and the battery shows the best reversibility.

[0147] The cyclic stability is as Figure 4 shown. The battery equipped with the catalyst prepared in Example 1 can be stably cycled more than 240 times, showing the best cyclic stability. Example 11 is cycled more than 150 times, while Comparative Example 1 is only cycled less than 100 times.

[0148] As mentioned above, these are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the disclosed technical content is equivalent to equivalent implementation cases, and all belong to the scope of the technical solution.

Claims

1. A nano-catalyst, characterized in that, The nano-catalyst includes a hollow support and monodisperse active metal; The hollow support includes a porous shell layer and a spherical cavity surrounded by the porous shell layer; The material of the porous shell layer is cobalt oxide; The monodisperse active metal is loaded on the surface of the porous shell layer.

2. The nano-catalyst according to claim 1, wherein The outer surface of the porous shell layer has a stacked structure formed by porous nanosheets.

3. The nano-catalyst according to claim 2, wherein, The size of the porous nanosheets in the length direction is 200 nm to 300 nm; Preferably, the size of the voids on the porous nanosheets is 2 nm to 10 nm.

4. The nano-catalyst according to claim 1, characterized in that, The monodisperse active metal is selected from at least one of Ru, Rh, Ta, Nb, In, and Bi in monodisperse state.

5. The preparation method of the nano-catalyst according to any one of claims 1 to 4, characterized in that, It includes the following steps: S1. Obtain a cobalt oxide solid sphere as precursor A; S2. Place the mixed solution containing precursor A and water in a sealed container, react to obtain precursor B; S3. Ultrasonically treat and dry the mixed solution containing precursor B, alcohol, and active metal salt in sequence to obtain precursor C; S4. Anneal precursor C to obtain the nano-catalyst.

6. The preparation method according to claim 5, characterized in that, In step S1, the preparation method of the cobalt oxide solid sphere includes the following steps: Place the mixed solution containing soluble cobalt salt, isopropyl alcohol, and glycerol in a sealed container, perform hydrothermal reaction, centrifuge to collect the precipitate, wash with isopropyl alcohol, and dry to obtain the cobalt oxide solid sphere.

7. The preparation method according to claim 5, characterized in that, In step S2, the reaction conditions include: the temperature is 140 °C to 180 °C, and the reaction time is 1 h to 6 h.

8. The preparation method according to claim 5, characterized in that, In step S3, the active metal salt is selected from at least one of phosphates, chlorides, nitrates, and sulfates of active metals; Preferably, in step S3, the alcohol is selected from at least one of methanol and ethanol; Preferably, in step S3, the concentration of the active metal salt in the mixed solution is 0.01 g / L to 0.1 g / L; Preferably, in step S3, the drying method is selected from at least one of rotary evaporation, air drying, vacuum drying, and freeze drying; Preferably, in step S3, the drying temperature is 40 °C to 100 °C.

9. The preparation method according to claim 5, characterized in that, In step S4, the annealing conditions include: the annealing temperature is 150 °C to 300 °C, and the annealing time is 1 h to 6 h; Preferably, in step S4, the annealing atmosphere is air.

10. Application of the nano-catalyst according to any one of claims 1 to 4 or the nano-catalyst prepared by the preparation method according to any one of claims 5 to 9 as a positive electrode catalyst material in suppressing side reactions of lithium-oxygen batteries.

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