CN113066964A

CN113066964A - Double-metal phosphide-inlaid carbon hollow nano cage and preparation method and application thereof

Info

Publication number: CN113066964A
Application number: CN202110277541.9A
Authority: CN
Inventors: 吴泽亮; 王珺
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2021-03-15
Filing date: 2021-03-15
Publication date: 2021-07-02
Anticipated expiration: 2041-03-15
Also published as: CN113066964B

Abstract

The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a double-metal phosphide-inlaid carbon hollow nano cage as well as a preparation method and an application thereof, wherein the double-metal phosphide-inlaid carbon hollow nano cage comprises the following steps: dispersing the nickel cobalt prussian blue derivative in a liquid medium to prepare a dispersion liquid, and adding dopamine hydrochloride into the dispersion liquid to prepare polydopamine-coated nickel cobalt prussian blue; calcining the polydopamine-coated nickel-cobalt Prussian blue derivative to prepare a carbon hollow nanocage with embedded nickel-cobalt double-metal particles; phosphine is used as a phosphating agent, and the carbon hollow nano cage inlaid with the bimetallic particles is phosphated in one step to prepare the carbon hollow nano cage inlaid with the bimetallic phosphide; preparing dispersion liquid from the double-metal phosphide-inlaid carbon hollow nano cage, carbon black and polyvinylidene fluoride, coating the dispersion liquid on a polypropylene diaphragm, and drying to obtain the multifunctional diaphragm; the invention obviously improves the comprehensive performance of the lithium-sulfur battery.

Description

Double-metal phosphide-inlaid carbon hollow nano cage and preparation method and application thereof

Technical Field

The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a double-metal phosphide-inlaid carbon hollow nano cage and a preparation method and application thereof.

Background

The lithium-sulfur battery generally comprises four parts, namely a metal lithium cathode, a sulfur anode, an electrolyte and a diaphragm, is a high-energy-density battery system which realizes mutual conversion of electric energy and chemical energy by the fracture generation of a sulfur-sulfur bond, has the advantages of low cost, environmental friendliness and the like, and has theoretical specific capacity and energy density of 1675mAh h respectively^-1And 2600Wh kg^-1And is more than five times of the theoretical energy density of the lithium ion battery which is commercialized at present.

However, there are still some problems with lithium sulfur batteries:

(1) s and Li₂S₂/Li₂S is an electronic insulating material, so that greater internal resistance can be generated in the charge-discharge cycle process of the battery, and the activity of the reaction is reduced; the method for solving the problem at present mainly compounds S and various carbon materials with good conductivity, which can greatly reduce the loading capacity of S to a certain extent; in addition, due to Li₂Poor conductivity of S, and difficult complete conversion of S to Li on the electrode₂S, and thus it is often difficult to obtain a theoretical specific capacity;

(2) due to S (2.03g cm)^-3) And Li₂S(1.66g cm^-3) There is a density difference between them, and thus in a fully discharged state, sulfur will undergo a volume expansion of up to 80%, and severe volume expansion will cause exfoliation and failure of the electrode material, thereby causing a drastic deterioration in battery performance, while also limiting further applications of sulfur positive electrodes having a high loading;

(3) the working mechanism of the lithium-sulfur battery is a 'solid-liquid-solid' process, and polysulfide intermediates generally have good solubility in an organic solvent, so that a positive electrode material is continuously dissolved out into an electrolyte in a circulating process to cause irreversible capacity; in addition, S is superior to Li in solubility in organic solvent₂S, resulting in a faster conversion of S to polysulfide than polysulfide to Li₂Conversion of S, which further allows electricity to be generatedIncreasing the polysulfide content in the electrolyte; at the same time, polysulfide dissolved in the electrolyte is reduced to Li₂S usually covers the surface of the positive electrode, which reduces the conductivity of the positive electrode;

(4) shuttle effect: since polysulfide can be well dissolved in the organic ether electrolyte, it can easily diffuse to the surface of the negative electrode, and thus directly react with the metal lithium sheet of the negative electrode, resulting in capacity loss, and Li generated by the reaction₂S has poor conductivity and can also affect the cycling stability of the cathode to a certain degree; major research efforts are currently conducted to improve the conductivity of the positive electrode and inhibit the shuttle effect of the polar material, such as adding a large amount of conductive carbon material, polar metal compound, etc., while the energy density of the positive electrode is more or less reduced by the added sulfur host material of the positive electrode.

Therefore, in view of the above problems, further research is still needed on how to further improve the performance of the lithium sulfur battery.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a double-metal phosphide-inlaid carbon hollow nano cage and a preparation method and application thereof, the invention coats a polydopamine layer on the outer layer of a nickel-cobalt Prussian blue derivative, generates the hollow nickel-cobalt double-metal particle-inlaid carbon hollow nano cage at high temperature, prepares the nickel-cobalt double-metal phosphide-inlaid carbon hollow nano cage by a one-step phosphorization method, and coats the nickel-cobalt double-metal phosphide-inlaid carbon hollow nano cage on a polypropylene diaphragm (Celgard2500) for the first time to obtain a multifunctional diaphragm which is applied to a lithium-sulfur battery system so as to enhance the comprehensive performance of the lithium-sulfur battery system.

The present invention is thus achieved.

The first purpose of the invention is to provide a preparation method of a double-metal phosphide inlaid carbon hollow nano cage, which comprises the following steps:

s1 preparation of polydopamine-coated nickel cobalt Prussian blue compound (Ni-Co-PBA @ PDA)

Dispersing the nickel cobalt prussian blue derivative and dopamine hydrochloride in a liquid medium containing an initiator, and under the action of the initiator, carrying out self-polymerization on the dopamine on the surface of the nickel cobalt prussian blue derivative to generate poly-dopamine so as to prepare Ni-Co-PBA @ PDA;

s2 preparation of hollow carbon nanocage (Ni-Co @ C) embedded with nickel-cobalt double-metal particles

Calcining the Ni-Co-PBA @ PDA prepared in S1 at 400-700 ℃ in a protective gas atmosphere to obtain Ni-Co @ C;

s3 preparation of double-metal phosphide inlaid carbon hollow nanocage (Ni-Co-P @ C)

And (2) taking phosphine as a phosphating agent, and preparing the Ni-Co @ C prepared by S2 at 350-450 ℃ by adopting a one-step phosphating method.

Preferably, in S1, the initiator is a tris (hydroxymethyl) aminomethane buffer solution, the liquid medium is a mixed solution prepared from water and ethanol at a volume ratio of 0.5-2: 1, and the concentration of the initiator in the liquid medium is 5-15 mmol/L.

Preferably, in S2, the heating rate is 2-10 ℃/min, and the calcination time is 1-4 h.

Preferably, in S3, the heating rate is 2-10 ℃/min^-1And the phosphating time is 1-4 h.

Preferably, in S3, in the process of the one-step phosphating method, the phosphating agent is obtained by directly introducing phosphine gas or decomposing sodium hypophosphite by heating at high temperature to generate phosphine gas, and the mass ratio of the sodium hypophosphite to Ni-Co @ C is 5-10: 1.

The second object of the present invention is to provide Ni-Co-P @ C prepared by the above-mentioned preparation method.

It is a third object of the present invention to provide a multifunctional separator (Ni-Co-P @ C/PP) obtained by coating the above Ni-Co-P @ C on a commercial polypropylene separator.

Preferably, the coating process specifically comprises: preparing a dispersion solution from the Ni-Co-P @ C, the carbon black and the polyvinylidene fluoride, coating the dispersion solution on a commercial polypropylene diaphragm, and drying to obtain the multifunctional diaphragm.

Preferably, the dispersing agent of the dispersion liquid is N-methyl pyrrolidone, Ni-Co-P @ C, and the mass ratio of carbon black to polyvinylidene fluoride is 7-8: 2-1: 1.

The fourth purpose of the invention is to provide the application of the Ni-Co-P @ C/PP in the lithium-sulfur battery.

Compared with the prior art, the invention has the advantages that:

(1) the poly dopamine layer is coated on the outer layer of the nickel cobalt Prussian blue derivative, the hollow carbon nanocage inlaid with nickel cobalt bimetallic particles is generated in situ at high temperature, and the hollow carbon nanocage inlaid with phosphide of the nickel cobalt bimetallic with a regular structure is prepared for the first time by a one-step phosphating method, and the structure of the hollow carbon nanocage is as follows: the nickel-cobalt double-metal phosphide hollow nanocage is of a cubic structure, the interior of the cube is of a hollow structure, the outer side of the hollow nanocage is wrapped by a polydopamine-derived carbon layer, and the inner side of the hollow nanocage is attached with embedded nickel-cobalt phosphide (capable of providing Ni-Co-P active sites);

(2) the nickel-cobalt double-metal phosphide hollow nanometer cage is coated on a polypropylene diaphragm for the first time to prepare a multifunctional diaphragm, and after the multifunctional diaphragm is used for preparing a lithium-sulfur battery, the performance of the lithium-sulfur battery can be improved, and the mechanism is as follows:

through the construction of the hollow structure, the volume expansion of the active substance in the charging and discharging process can be effectively relieved, and the stability of the battery structure is ensured; the attached Ni-Co-P active sites can effectively adsorb polysulfide, limit the polysulfide in the reaction process on the positive electrode side, simultaneously effectively promote catalytic conversion among the polysulfide, promote the conversion of long-chain liquid polysulfide to solid short-chain lithium sulfide, and inhibit the shuttle effect in the battery reaction, thereby improving the discharge specific capacity, the rate capability and the cycle performance of the battery; in addition, the bimetal phosphide has excellent conductivity, and is matched with the carbon layer on the outer side and the hollow structure in the inner part, so that the bimetal phosphide is more favorable for the rapid conduction of electrons and ions;

(3) the multifunctional diaphragm is used for the lithium-sulfur battery, the positive electrode and the negative electrode can be separated by the diaphragm, the short circuit phenomenon is avoided, the pore channel in the diaphragm is mainly responsible for transferring ions, the battery reaction circulation is promoted to continue, the electrochemical performance of the battery is obviously improved, and when the sulfur surface loading is 1.8mg cm^-2Can be used at high current 5C (1C: 1672mA g)^-1) Strip for packaging articlesThe discharge specific capacity is improved by 2.67 times compared with that of the common polypropylene diaphragm, the cyclic charge-discharge test can be carried out for 1000 circles under the current density of 0.5C, the average attenuation rate per circle is only 0.056 percent and is far less than 0.112 percent (731 circles) of the common polypropylene diaphragm battery, and the cyclic charge-discharge test is carried out under the conditions of different high-surface loading capacity (2.4-4.5 mg cm)^-2) The high cycle stability is still maintained;

(4) the method for preparing the multifunctional diaphragm is simple, the raw materials are easy to obtain, and the multifunctional diaphragm is suitable for improving the performance of the lithium-sulfur battery.

Drawings

Figures 1, 2 and 3 are XRD, SEM and TEM, respectively, of nickel cobalt prussian blue prepared in example 1;

FIG. 4, FIG. 5 and FIG. 6 are XRD, SEM and TEM images, respectively, of Ni-Co @ C prepared in example 1;

FIG. 7, FIG. 8 and FIG. 9 are SEM and TEM images of Ni-Co-P @ C prepared in example 1, respectively;

fig. 10 is a cross-sectional SEM image of the multifunctional separator prepared in example 1;

fig. 11 is a mechanical folding test digital photograph of the multifunctional separator prepared in example 1;

FIG. 12 is a charge-discharge capacity-voltage curve at a rate of 0.1 to 5C for a lithium-sulfur battery assembled using the multifunctional separator prepared in example 1;

fig. 13 is a charge and discharge capacity-voltage curve at a rate of 5C for a lithium-sulfur battery assembled using the multifunctional separator prepared in example 1 and a general polypropylene separator;

FIG. 14 is a lithium sulfur battery assembled using the multifunctional separator prepared in example 1 and a general polypropylene separator (sulfur loading of 1.8mg cm)^-2) A charge-discharge long cycle test chart under 0.5C multiplying power;

FIG. 15 shows lithium sulfur cells assembled using the multifunctional separator of example 1 at various sulfur loadings ranging from 2.4 to 3.5mg cm^-2A long cycle test chart with the multiplying power of 0.5C;

FIG. 16 shows sulfur loading of 4.5mg cm for a lithium sulfur battery assembled using the multifunctional separator prepared in example 1^-2Double, doubleLong cycle test plot with a rate of 0.2C.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The following test methods and detection methods, unless otherwise specified, are conventional methods; the starting materials and reagents are not specifically indicated and are commercially available.

Example 1

A preparation method of a multifunctional diaphragm of a lithium-sulfur battery comprises the following steps:

(1) preparation of nickel cobalt prussian blue derivative (Ni-Co-PBA): 1.75 g (20 mmol) of nickel nitrate hexahydrate and 2.65 g (75 mmol) of trisodium citrate are dissolved in 200 ml of deionized water to form solution A; dissolving 1.33 g of potassium cobalt cyanide in 200 ml of deionized water to form a solution B; then mixing the solution A and the solution B, and finishing the whole process in the stirring process; stirring for half an hour at room temperature, standing for 18 hours, then washing by centrifugation, collecting light blue precipitate, and drying in vacuum to obtain the nickel cobalt Prussian blue derivative.

(2) Dopamine hydrochloride-coated nickel cobalt prussian blue derivative (Ni-Co-PBA @ PDA): dispersing 200 mg of the prepared Ni-Co-PBA powder in 60 ml of a mixed solution of ethanol and deionized water containing 10 mmol per liter of tris (hydroxymethyl) aminomethane buffer solution, wherein the volume ratio of water to ethanol is 1: 1; after ultrasonic dispersion, 200 mg of dopamine hydrochloride is added into the mixed solution, stirred for 12 hours, filtered, washed and dried to obtain solid powder.

(3) Preparation of carbon layer-wrapped bimetallic hollow nanocages (Ni-Co @ C): 0.5 g of Ni-Co-PBA @ PDA powder is put into a quartz boat and calcined in a tube furnace in argon atmosphere, the calcination temperature is 600 ℃, and the heating rate is 5 ℃/min^-1The calcination time is 2 h.

(4) Preparation of bimetallic hollow phosphide nanocages (Ni-Co-P @ C): 0.1 g of Ni-Co @ C and 1 g of phosphorous monohydrateSodium acid is respectively placed in two quartz boats, the boat carrying sodium hypophosphite is placed at the upstream of a heating pipe, argon is used as carrier gas to ensure that phosphine gas generated by decomposition in the high-temperature process can flow through the surface of Ni-Co @ C, the phosphating temperature is 400 ℃, the phosphating time is 2h, and the heating rate is 5 ℃/min^-1And cooling, washing and drying to obtain Ni-Co-P @ C powder.

(5) Preparation of multifunctional separator (Ni-Co-P @ C/PP): the prepared bimetallic hollow nano cage (Ni-Co-P @ C), carbon black and polyvinylidene fluoride are ground and mixed according to the mass ratio of 8:1:1, then are dispersed in an N-methyl pyrrolidone solution, and after stirring for 8 hours, a coating machine is used for coating the slurry on a commercial polypropylene diaphragm (Celgard2500), and then after drying, the disc with the diameter of 19 mm is cut.

Example 2

(1) preparation of nickel cobalt prussian blue derivative (Ni-Co-PBA): dissolving 0.35 g of nickel nitrate hexahydrate and 0.53 g of trisodium citrate in 200 ml of deionized water to form solution A; 0.266 g of potassium cobalt cyanide was dissolved in 200 ml of deionized water to form solution B; then mixing the solution A and the solution B, and finishing the whole process in the stirring process; stirring for half an hour at room temperature, standing for 18 hours, then washing by centrifugation, collecting light blue precipitate, and drying in vacuum to obtain the nickel cobalt Prussian blue derivative.

(2) Dopamine hydrochloride-coated nickel cobalt prussian blue derivative (Ni-Co-PBA @ PDA): dispersing 200 mg of the prepared Ni-Co-PBA powder in 60 ml of a mixed solution of ethanol and deionized water containing 15mmol/l of tris (hydroxymethyl) aminomethane buffer, wherein the volume ratio of water to ethanol is 2: 1; after ultrasonic dispersion, 200 mg of dopamine hydrochloride is added into the mixed solution, stirred for 12 hours, filtered, washed and dried to obtain solid powder.

(3) Preparation of carbon layer-wrapped bimetallic hollow nanocages (Ni-Co @ C): 0.5 g of Ni-Co-PBA @ PDA powder is put into a quartz boat and calcined in a tube furnace in argon atmosphere, the calcination temperature is 400 ℃, and the heating speed is increasedThe rate is 2 ℃/min^-1The calcination time is 4 h.

(4) Preparation of bimetallic hollow phosphide nanocages (Ni-Co-P @ C): respectively placing 0.1 g of Ni-Co @ C and 1 g of sodium hypophosphite monohydrate in two quartz boats, placing the boats carrying the sodium hypophosphite at the upstream of a heating pipe, taking argon as carrier gas to ensure that phosphine gas generated by decomposition in the high-temperature process can flow through the surface of the Ni-Co @ C, the phosphating temperature is 350 ℃, the phosphating time is 4h, and the heating rate is 2 ℃/min^-1And cooling, washing and drying to obtain Ni-Co-P @ C powder.

(5) Preparation of multifunctional separator (Ni-Co-P @ C/PP): the prepared bimetallic hollow nano cage (Ni-Co-P @ C), carbon black and polyvinylidene fluoride are ground and mixed according to the mass ratio of 7:2:1, then are dispersed in an N-methyl pyrrolidone solution, and after stirring for 8 hours, a coating machine is used for coating the slurry on a commercial polypropylene diaphragm (Celgard2500), and then after drying, the disc with the diameter of 19 mm is cut.

Example 3

(1) preparation of nickel cobalt prussian blue derivative (Ni-Co-PBA): dissolving 1.75 g of nickel nitrate hexahydrate and 2.65 g of trisodium citrate in 200 ml of deionized water to form solution A; dissolving 1.33 g of potassium cobalt cyanide in 200 ml of deionized water to form a solution B; then mixing the solution A and the solution B, and finishing the whole process in the stirring process; stirring for half an hour at room temperature, standing for 18 hours, then washing by centrifugation, collecting light blue precipitate, and drying in vacuum to obtain the nickel cobalt Prussian blue derivative.

(2) Dopamine hydrochloride-coated nickel cobalt prussian blue derivative (Ni-Co-PBA @ PDA): dispersing 200 mg of the prepared Ni-Co-PBA powder in 60 ml of a mixed solution of ethanol and deionized water containing 5mmol per liter of tris (hydroxymethyl) aminomethane buffer solution, wherein the volume ratio of water to ethanol is 1: 2; after ultrasonic dispersion, 200 mg of dopamine hydrochloride is added into the mixed solution, stirred for 12 hours, filtered, washed and dried to obtain solid powder.

(3)Preparation of carbon layer-wrapped bimetallic hollow nanocages (Ni-Co @ C): 0.5 g of Ni-Co-PBA @ PDA powder is put into a quartz boat and calcined in a tube furnace in argon atmosphere, the calcination temperature is 700 ℃, the heating rate is 10 ℃/min^-1The calcination time is 1 h.

(4) Preparation of bimetallic hollow phosphide nanocages (Ni-Co-P @ C): respectively placing 0.1 g of Ni-Co @ C and 1 g of sodium hypophosphite monohydrate in two quartz boats, placing the boats carrying the sodium hypophosphite at the upstream of a heating pipe, taking argon as carrier gas to ensure that phosphine gas generated by decomposition in the high-temperature process can flow through the surface of the Ni-Co @ C, the phosphating temperature is 450 ℃, the phosphating time is 1h, and the heating rate is 10 ℃/min^-1And cooling, washing and drying to obtain Ni-Co-P @ C powder.

The properties of the materials prepared in the above examples 1 to 3 are similar, and the structure of the materials is characterized by taking the example 1 as an example, and the specific characteristics can be seen in fig. 1 to 11.

Fig. 1, 2 and 3 are XRD, SEM and TEM analyses of Ni-Co-PBA, respectively, and through peak type comparison, a nickel cobalt prussian blue derivative was successfully synthesized, and the shape was cubic, the inside was solid, and the particle size was uniform.

Fig. 4, 5 and 6 are XRD, SEM and TEM analyses of Ni — Co @ C, respectively, from which it is clear that after calcination, a nickel-cobalt alloy is formed, and from fig. 5, after calcination, the cubic structure is maintained, and from TEM, after calcination, the interior is hollow and the exterior is coated with a carbon layer of about 15 nm.

Fig. 7, 8 and 9 show XRD, SEM and TEM images of Ni-Co-P @ C, respectively. Compared with a PDF card, the diffraction peak of Ni-Co-P is successfully obtained, and the appearance before and after phosphorization is not changed as can be seen from SEM and TEM results.

From the SEM image of Ni-Co-P @ C/PP in FIG. 10, it can be seen that the multifunctional phosphide layer had a thickness of about 3.2 microns and a unit area loading of about 0.4mg cm^-2. FIG. 11 is a mechanical folding test digital photo of Ni-Co-P @ C/PP, and it can be seen from the digital photo of FIG. 11 that when the diaphragm is subjected to a mechanical test, Ni-Co-P @ C is better adhered to the diaphragm, and after being folded, the Ni-Co-P @ C does not fall off and has a uniform surface.

The performances of the materials prepared in the above examples 1-3 are similar, and the following materials are used for preparing a lithium-sulfur battery and detecting the battery performance by taking the example 1 as an example, and the specific preparation method is as follows:

the exterior of the lithium-sulfur battery button battery (CR2032) consists of stainless steel positive and negative motor shells. The electrolyte is DME/DOL solution of 1M lithium bis (trifluoromethane) sulfonimide containing 2 wt% of lithium nitrate, and is prepared by tabletting in a glove box in an argon atmosphere.

The results are shown in fig. 12-16, in which fig. 12 is a charge and discharge capacity-voltage curve of the lithium-sulfur battery assembled by using the multifunctional separator at a rate of 0.1-5C, and the prepared battery is subjected to standing stabilization, and then to rate and cycle charge and discharge tests, and shows 1412.6,1093.9,961.3,906.1,821.5 and 654.5mAh g at current densities of 0.1, 0.2, 0.5, 1, 2, 5C^-1The specific discharge capacity (fig. 12) of the lithium sulfur battery is improved by 2.67 times compared with that of the common polypropylene diaphragm (fig. 13 is a charge-discharge capacity-voltage curve of the lithium sulfur battery assembled by the multifunctional diaphragm and the common polypropylene diaphragm under the multiplying power of 5C), and 414.8mAh g can be still maintained after repeated charge-discharge circulation reaches 1000 circles under the current density of 0.5C^-1The specific discharge capacity of (a) was 0.056%, which is much lower than 0.112% (731 cycles) of a battery using a general polypropylene separator (fig. 14 is a lithium sulfur battery assembled using a multifunctional separator and a general polypropylene separator (sulfur loading is 1.8mg cm)^-2) Charge-discharge long cycle test pattern at 0.5C rate); at the same time, the method is also researched under the condition of high sulfur loading capacity, and the sulfur loading is between 2.4 and 4.5mg cm^-2A cycle test was performed within the range of (1) (FIGS. 15 to 16); the high cycling stability is still maintained at different high areal loadings.

In conclusion, when the multifunctional diaphragm prepared by the invention is used for the lithium-sulfur battery, the diaphragm can separate the anode and the cathode, so that the short circuit phenomenon is avoided, the pore channel in the diaphragm is mainly responsible for transferring ions, the circulation of the battery reaction is promoted to continue, the electrochemical performance of the battery is obviously improved, and when the loading capacity on the sulfur surface is 1.8mg cm^-2Can be used at high current 5C (1C: 1672mA g)^-1) The battery can be stably charged and discharged under the condition, compared with the common polypropylene diaphragm, the discharge specific capacity is improved by 2.67 times, the battery can be circularly charged and discharged under the current density of 0.5C for 1000 circles, the average attenuation rate per circle is only 0.056 percent and is far less than 0.112 percent (731 circles) of the common polypropylene diaphragm battery, and under the conditions of different high surface loading capacity (2.4-4.5 mg cm)^-2) The high cycle stability is still maintained, and the mechanism is as follows: the hollow nano-cage of the nickel-cobalt double-metal phosphide prepared by the method is of a cubic structure, the interior of the cube is of a hollow structure, the outer side of the hollow nano-cage is wrapped by a layer of carbon layer derived from polydopamine, and the inner side of the hollow nano-cage is attached with the inlaid nickel-cobalt phosphide (capable of providing Ni-Co-P active sites), so that the volume expansion of an active substance in the charging and discharging process can be effectively relieved through the construction of the hollow structure, and the stability of the battery structure is ensured; the attached Ni-Co-P active sites can effectively adsorb polysulfide, limit the polysulfide in the reaction process on the positive electrode side, simultaneously effectively promote catalytic conversion among the polysulfide, promote the conversion of long-chain liquid polysulfide to solid short-chain lithium sulfide, and inhibit the shuttle effect in the battery reaction, thereby improving the discharge specific capacity, the rate capability and the cycle performance of the battery; in addition, the bimetal phosphide has excellent conductivity, and is matched with the carbon layer on the outer side and the hollow structure in the inner side, so that the bimetal phosphide is more favorable for quick conduction of electrons and ions.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A preparation method of a double-metal phosphide-inlaid carbon hollow nano cage is characterized by comprising the following steps:

s1 preparation of polydopamine-coated nickel cobalt Prussian blue compound

Dispersing the nickel cobalt prussian blue derivative and dopamine hydrochloride in a liquid medium containing an initiator, and under the action of the initiator, carrying out self-polymerization on the dopamine on the surface of the nickel cobalt prussian blue derivative to generate polydopamine so as to prepare a polydopamine-coated nickel cobalt prussian blue compound;

s2 preparation of hollow carbon nanocage embedded with nickel-cobalt double-metal particles

Calcining the polydopamine-coated nickel-cobalt Prussian blue compound prepared in S1 at 400-700 ℃ in a protective gas atmosphere to prepare a carbon hollow nano cage with embedded nickel-cobalt double metal particles;

s3 preparation of double-metal phosphide inlaid carbon hollow nanocage

And (2) taking phosphine as a phosphating agent, and preparing the hollow carbon nanocage inlaid with the nickel-cobalt double-metal particles prepared by S2 at 350-450 ℃ by adopting a one-step phosphating method.

2. The method for preparing a double metal phosphide-inlaid carbon hollow nanocage as claimed in claim 1, wherein in S1, the initiator is tris (hydroxymethyl) aminomethane buffer solution, the liquid medium is a mixed solution prepared from water and ethanol in a volume ratio of 0.5-2: 1, and the concentration of the initiator in the liquid medium is 5-15 mmol/L.

3. The method for preparing a hollow carbon nanocage with a dual metal phosphide mosaic as claimed in claim 1, wherein in S2, the temperature rise rate is 2-10 ℃/min and the calcination time is 1-4 h.

4. The dual metal phosphide damascene of claim 1The preparation method of the carbon hollow nano cage is characterized in that in S3, the heating rate is 2-10 ℃/min^-1And the phosphating time is 1-4 h.

5. The method for preparing the hollow carbon nanocage with the dual metal phosphide inlaid structure as recited in claim 1, wherein in the step of the one-step phosphating process in S3, the phosphating agent is obtained by directly introducing phosphine gas or decomposing sodium hypophosphite by high-temperature heating to generate phosphine gas, and the mass ratio of the sodium hypophosphite to the nickel-cobalt dual metal particle inlaid carbon hollow nanocage is 5-10: 1.

6. The double metal phosphide-inlaid carbon hollow nanocage prepared by the preparation method according to any one of claims 1 to 5.

7. A multifunctional membrane prepared by coating the double metal phosphide-inlaid carbon hollow nanocage of claim 6 on a commercial polypropylene membrane.

8. The multifunctional membrane according to claim 7, characterized in that the process of coating is in particular: preparing a dispersion of the dual metal phosphide-inlaid carbon hollow nanocage of claim 6, carbon black and polyvinylidene fluoride, and then coating the dispersion on a commercial polypropylene separator, and drying to obtain a multifunctional separator.

9. The multifunctional membrane as claimed in claim 8, wherein the dispersant of the dispersion is N-methylpyrrolidone, and the mass ratio of the double metal phosphide-inlaid carbon hollow nanocages to the carbon black to the polyvinylidene fluoride is 7-8: 2-1: 1.

10. Use of the multifunctional separator according to any one of claims 7 to 9 in a lithium-sulfur battery.