CN115779938A - Ti 3 C 2 Preparation method of TX-loaded monatomic catalyst and application of TX-loaded monatomic catalyst in lithium-sulfur battery diaphragm - Google Patents
Ti 3 C 2 Preparation method of TX-loaded monatomic catalyst and application of TX-loaded monatomic catalyst in lithium-sulfur battery diaphragm Download PDFInfo
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Abstract
The invention relates to a Ti 3 C 2 T X A preparation method of a loaded monatomic catalyst and application thereof in a lithium-sulfur battery diaphragm belong to the fields of catalyst preparation and battery energy storage. The method adopts an improved minimum strength layering method to prepare single/few-layer Ti 3 C 2 T x Nanoflakes that create more titanium vacancies to anchor isolated metal atoms via vacancy anchorsAnd (3) doping and coordinating nitrogen atoms to synthesize a plurality of metal single-atom catalysts with unique carbon-nitrogen coordination structures. Ti prepared by the invention 3 C 2 T x The loaded monatomic catalyst can be used for modifying the diaphragm of the lithium-sulfur battery, the modified diaphragm does not have the phenomenon of powder falling after being bent and folded, the excellent mechanical property and the bonding stability are shown, and the Ti-supported monatomic catalyst is applied to the lithium-sulfur battery and shows the excellent rate performance and the stable cycle life, so that the Ti prepared by the method 3 C 2 T x The load of the carbon-nitrogen coordination monatomic catalyst and the modification of the performance of the diaphragm are promising approaches for constructing the high-performance lithium-sulfur battery.
Description
Technical Field
The invention relates to a Ti 3 C 2 T X A preparation method of a supported monatomic catalyst and application thereof in a lithium-sulfur battery diaphragm belong to the fields of catalyst preparation and battery energy storage.
Background
The progress of science and technology brings various intelligent products such as portable electronic equipment, electric automobiles and the like to human society. At the same time, excellent energy storage devices are needed to meet the long cycle charge and discharge and long life requirements of such products. Lithium-sulfur (Li-S) batteries are considered to be a promising electrochemical energy storage device, mainly because of the abundance of natural resources required to prepare lithium-sulfur batteries, the low cost of the sulfur component, and their excellent theoretical energy density (about 2600W h kg) -1 ) And high specific capacity (1675 mAh g) -1 ). However, the rate performance of the lithium-sulfur battery is poor, the cycle attenuation is serious, and the large-scale production and application of the lithium-sulfur battery are severely limited.
Various strategies have been developed to date to address the above problems. For example, a host material having high conductivity, polarity, and porosity is searched for to wrap the sulfur positive electrode, thereby improving the affinity, conversion rate, and the like between the sulfur positive electrode and polysulfide. However, these strategies do not hinder the shuttling effect of soluble polysulfides through the separator from the sulfur positive electrode to the lithium negative electrode. The diaphragm in the electrolyte can separate the anode and the cathode to a certain extent, and the shuttle effect of polysulfide is blocked. However, it is difficult for the conventional polypropylene separator (PP) to promote the adsorption and conversion of polysulfides. Therefore, ideal materials need to be explored to modify commercial membranes to achieve efficient adsorption and kinetic conversion of polysulfides.
Based on Ti 3 C 2 T x The hydrophilicity and polarity of the surface can achieve strong chemical interaction with polysulfides. However, pure Ti 3 C 2 T x It is difficult to obtain excellent lithium sulfur battery performance by the modified separator. In order to solve the above problems, ti is required 3 C 2 T x More active centers are reasonably constructed so as to improve the performance of the lithium-sulfur battery. The central metal atom utilization of the monatomic catalyst can reach nearly 100%, which can make full use of each active site. Supported on Ti 3 C 2 T x The above monatomic catalyst is theoretically achievable, which combines high atom utilization of the monatomic catalyst with the excellent performance of MXene.
In view of the above, it is necessary to design a Ti 3 C 2 T x A preparation method of a supported monatomic catalyst and application thereof in a lithium-sulfur battery diaphragm so as to solve the problems.
Disclosure of Invention
The purpose of the present invention is to provide a Ti 3 C 2 T X A preparation method of a loaded monatomic catalyst and application thereof in a lithium-sulfur battery diaphragm; ti produced by the method 3 C 2 T x The loaded monatomic catalyst can be used for modifying the diaphragm of the lithium-sulfur battery, the modified diaphragm does not have the phenomenon of powder falling after being bent and folded, the excellent mechanical property and the bonding stability are shown, and the Ti-supported monatomic catalyst is applied to the lithium-sulfur battery and shows the excellent rate performance and the stable cycle life, so that the Ti prepared by the method 3 C 2 T x Supported single-atom catalysts and for modifying separator performance are promising approaches to building high performance lithium sulfur batteries.
The purpose of the invention is realized by the following technical scheme;
the invention relates to a Ti 3 C 2 T x A method for preparing a supported monatomic catalyst, comprising the steps of:
the parent body Ti 3 AlC 2 MAX is immersed in LiF/HCl solution, etched for a period of time at constant temperature, and then stripped by ultrasound to separate stacked Ti 3 C 2 T x Obtaining single/few layer Ti 3 C 2 T x Nanosheets; followed by self-reduction process using Ti 3 C 2 T x Titanium vacancies in the nanoflakes to stabilize the monoatomic atoms and further openThe coordination of the nitrogen-peroxide doping is stable to obtain Ti 3 C 2 T x A supported monatomic catalyst.
The LiF/HCl solution is obtained by the following method: adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, then slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, and slowly stirring for 10min under the ice-water bath condition to dissolve and disperse the LiF in the concentrated hydrochloric acid.
The constant temperature is 35-45 ℃, and the etching time is 20-30h
The Ti 3 C 2 T x The preparation method of the supported monatomic catalyst specifically comprises the following steps:
s1, taking a single Ti layer and few Ti layers 3 C 2 T x Putting the powder into deionized water, performing ultrasonic treatment and stirring, adding metal chloride, stirring, adding melamine, and continuously stirring to fully and uniformly mix to obtain a precursor mixture;
and S2, transferring the precursor mixture into an ultrasonic machine for ultrasonic treatment, and performing ultrasonic treatment under the ice-water bath condition. Freezing the obtained sample, and then carrying out freeze drying treatment to obtain a powder sample;
and S3, drying the obtained powder sample, and annealing at a certain temperature in an inert atmosphere. The obtained sample was successively subjected to water washing and alcohol washing. Dried under vacuum at room temperature overnight. To obtain Ti 3 C 2 T x A supported monatomic catalyst.
Further, the ultrasonic time in the steps S1 and S2 is 20-40min, and the stirring time is 20-80min.
Further, the metal chloride described in step S1 includes MnCl 2 ·H 2 O，CoCl 2 ·H 2 O，NiCl 2 ·H 2 O，ZnCl 2 ·H 2 O，BiCl 2 ·H 2 O，CuCl 2 ·2H 2 O。
Further, the inert atmosphere in the step S3 comprises nitrogen, argon and helium, the annealing temperature is 400-600 ℃, and the annealing time is 1-3h.
Further, it is characterized byThe above Ti 3 C 2 T x The supported monatomic catalyst can be applied to a separator layer of a modified lithium-sulfur battery.
Further, the specific preparation method of the modified lithium-sulfur battery separator layer comprises the following steps: firstly, ti 3 C 2 T x The loaded monoatomic catalyst, the conductive carbon black and the polyvinylidene fluoride are mixed according to a certain mass ratio, and uniform pasty slurry is obtained in N-methyl pyrrolidone and is coated on one side of a commercial PP diaphragm. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x A supported monatomic catalyst modified membrane.
Further, said Ti 3 C 2 T x The mass ratio of the loaded monatomic catalyst to the conductive carbon black to the polyvinylidene fluoride is 1.
The invention prepares Ti 3 C 2 T x Supported monatomic catalyst and its use in modified lithium sulfur battery separator layers, ti 3 C 2 T x The loaded monatomic catalyst shows excellent rate performance and stable cycle life, and the diaphragm layer does not have the phenomenon of powder falling after being bent and folded, and shows excellent mechanical property and bonding stability.
Advantageous effects
1. Single or few-layer Ti is prepared by adopting improved minimum strength delamination method 3 C 2 T x Nanoflakes, which create more titanium vacancies to anchor isolated metal atoms. Tuning of immobilization to Ti using vacancy anchoring strategy and nitrogen doping strategy 3 C 2 T x Monatomic catalyst on nanosheets, ti 3 C 2 T x The loaded monatomic catalyst has effective adsorption on polysulfide and can promote the polysulfide to realize efficient kinetic conversion, which has important significance for inhibiting shuttle effect.
2、Ti 3 C 2 T x The supported monatomic catalyst exhibits excellent rate performance and stable cycle life. The catalyst is used for modifying a diaphragm and is used for assembling a lithium-sulfur battery, so that excellent battery performance is realized. At 3C, it is trueNow not less than 728mAh g -1 The high reversible specific capacity is still higher than 619mAh g after 1000 times of circulation -1 And the capacity attenuation rate of each circle is only 0.048% -0.084%. It was found that the introduction of unique metal monoatomic sites can suppress the shuttle effect by increasing the adsorption and kinetic transformation to polysulfides, thereby improving the performance of Li-S batteries.
Drawings
FIG. 1 shows Ti prepared in example 1 of the present invention 3 C 2 T x A flow diagram of a supported monatomic catalyst;
FIG. 2 shows Ti prepared in example 1 of the present invention 3 C 2 T x TEM images of the supported monatomic catalyst;
FIG. 3 shows Ti prepared in example 1 of the present invention 3 C 2 T x XRD pattern of supported monatomic catalyst;
FIG. 4 shows Ti prepared in example 1 of the present invention 3 C 2 T x Spherical aberration electron microscope images of the load monatomic catalyst;
FIG. 5 shows Ti prepared in example 1 of the present invention 3 C 2 T x A synchrotron radiation pattern of the supported monatomic catalyst;
FIG. 6 shows Ti prepared in example 1 of the present invention 3 C 2 T x Optical photographs and SEM pictures of the modified membrane supporting the monatomic catalyst;
FIG. 7 shows Ti prepared in example 1 of the present invention 3 C 2 T x Multiplying power diagram of the lithium-sulfur battery loaded with the monatomic catalyst modified diaphragm;
FIG. 8 shows Ti prepared in example 1 of the present invention 3 C 2 T x A long cycle chart of the lithium-sulfur battery loaded with the monatomic catalyst modified membrane;
FIG. 9 shows Ti prepared in example 1 of the present invention 3 C 2 T x And (3) a high-sulfur load cycle stability diagram of the lithium-sulfur battery loaded with the monatomic catalyst modified membrane.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the solution of the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.
In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The present invention provides a Ti 3 C 2 T x A method for preparing a supported monatomic catalyst, the method comprising: the matrix Ti 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for a certain time under the constant temperature condition, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x Obtaining single/few layer Ti 3 C 2 T X Nanosheets; preparation of Ti 3 C 2 T x Supported monatomic catalyst, by Ti 3 C 2 T x Titanium vacancies and nitrogen doping coordination on the nanoflakes stabilize the monoatomic atoms.
Wherein the LiF/HCl solution is obtained by the following method: adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, then slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, and slowly stirring for 10min under the ice-water bath condition to dissolve and disperse the LiF in the concentrated hydrochloric acid; the constant temperature is 35-45 deg.C, and the etching time is 20-30h.
Ti 3 C 2 T x The preparation method of the load monatomic catalyst specifically comprises the following steps:
s1, taking single few-layer Ti 3 C 2 T x Putting the powder into deionized water, performing ultrasonic treatment and stirring, adding metal chloride, stirring, adding melamine, and continuously stirring to fully and uniformly mix to obtain the productA precursor mixture;
wherein the ultrasonic treatment time is 20-40min, and the stirring time is 20-80min; the metal chloride comprises CuCl 2 ·2H 2 O，CoCl 2 ·6H 2 O，NiCl 2 ·6H 2 O，MnCl 2 ·4H 2 O，ZnCl 2 ，InCl 3 ·4H 2 O，SnCl 4 ·5H 2 O，PbCl 2 ，BiCl 3 。
And S2, transferring the precursor mixture into an ultrasonic machine for ultrasonic treatment, and performing ultrasonic treatment under the ice-water bath condition. Freezing the obtained sample, and then carrying out freeze drying treatment to obtain a powder sample;
wherein the ultrasonic treatment time is 20-40min, and the stirring time is 20-80min.
And S3, drying the obtained powder sample, and annealing at a certain temperature in an inert atmosphere. The obtained sample was successively subjected to water washing and alcohol washing. Dried under vacuum at room temperature overnight. To obtain Ti 3 C 2 T x A supported monatomic catalyst.
Wherein the inert atmosphere comprises nitrogen, argon and helium, the annealing temperature is 400-600 ℃, and the annealing time is 1-3h.
The specific preparation method of the modified lithium-sulfur battery diaphragm layer comprises the following steps: firstly, ti 3 C 2 T x The loaded monatomic catalyst, the conductive carbon black and the polyvinylidene fluoride are mixed according to a certain mass ratio, uniform pasty slurry is obtained in N-methyl pyrrolidone, and the slurry is coated on one side of a commercial PP diaphragm. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x A supported monatomic catalyst modified membrane.
Wherein, ti 3 C 2 T x The mass ratio of the loaded monatomic catalyst to the conductive carbon black to the polyvinylidene fluoride is 1.1-0.2.
Diaphragm assembly lithium sulfur battery: the electrolyte was measured by 1M LiTFSI and 1% LiNO3 in a 1:1V/V solution. Metallic lithium was used as the negative electrode. Button cells (CR 2032) were manufactured in a glove box in an Ar atmosphere. Electrochemical impedance spectra in the frequency range of 0.01-100 kHz were measured on the same bio-logical VMP3 electrochemical workstation. The charge and discharge test in the voltage range of 1.7-2.8V is carried out on a Newware battery test system.
Example 1
Adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, slowly stirring for 10min under the condition of ice-water bath to dissolve and disperse LiF in the concentrated hydrochloric acid to prepare LiF/HCl solution, and dissolving and dispersing Ti matrix in the concentrated hydrochloric acid to obtain Ti matrix 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for 26h under the constant temperature condition of 40 ℃, an Al layer is selectively removed, and then stacked Ti is separated by ultrasonic stripping 3 C 2 T X Obtaining single or few layers of Ti 3 C 2 T X And (3) nanosheets, namely single few-layer nanosheets with certain thicknesses are obtained.
Taking 50mg of single few-layer Ti 3 C 2 T x Putting the powder into 10mL deionized water, performing ultrasonic treatment for 40min, stirring for 20min, and adding 2mg CuCl 2 ·2H 2 And O, stirring for 1 hour, adding 100mg of melamine, and continuously stirring for 30min to fully and uniformly mix. Then, the precursor mixture is transferred to an ultrasonic machine for ultrasonic treatment for 20min, and ultrasonic treatment is carried out under the ice-water bath condition. The obtained sample was frozen, followed by freeze-drying treatment to obtain a powder sample. The obtained powder sample is dried and annealed for 2h at 500 ℃ in an Ar inert atmosphere. The obtained sample was successively subjected to water washing and alcohol washing. Dried under vacuum at room temperature overnight. The sample obtained was Ti 3 C 2 T x A supported Cu monatomic catalyst.
Mixing Ti 3 C 2 T x The supported Cu monatomic catalyst, conductive carbon black and polyvinylidene fluoride were mixed in a ratio of 1:0.13 mixing, resulting in a uniform paste slurry in N-methyl pyrrolidone and coated on the side of a commercial PP separator. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x A supported Cu monatomic catalyst modified membrane.
By using Ti 3 C 2 T x Modified diaphragm of loaded Cu monatomic catalystThe lithium-sulfur battery can realize 925mAh g at the time of 3C -1 The high reversible specific capacity is still higher than 619mAh g after 1000 times of circulation -1 And the capacity attenuation rate per turn is only 0.048%.
Example 2
Adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, slowly stirring for 10min under the condition of ice-water bath to dissolve and disperse LiF in the concentrated hydrochloric acid to prepare LiF/HCl solution, and dissolving and dispersing Ti matrix in the concentrated hydrochloric acid to obtain Ti matrix 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for 30 hours under the constant temperature condition of 35 ℃, an Al layer is selectively removed, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x Obtaining single or few layers of Ti 3 C 2 T x And (3) nanosheets, namely obtaining single few-layer nanosheets with certain thickness.
Taking 50mg of single few-layer Ti 3 C 2 T x Putting the powder into 10mL deionized water, performing ultrasonic treatment for 30min, stirring for 50min, and adding 2mg CoCl 2 ·2H 2 O, stirring for 1h, then adding 100mg of melamine, and continuously stirring for 50min to fully and uniformly mix. And then, transferring the precursor mixture into an ultrasonic machine for ultrasonic treatment for 30min, and carrying out ultrasonic treatment under the ice-water bath condition. The obtained sample was frozen, followed by freeze-drying treatment to obtain a powder sample. The powder samples obtained were subjected to a drying treatment in N 2 Annealing at 400 ℃ for 3h under an inert atmosphere. The obtained sample was successively subjected to water washing and alcohol washing. Dried under vacuum at room temperature overnight. The obtained sample was Ti 3 C 2 T x Supported Co monatomic catalyst.
Mixing Ti 3 C 2 T x The loaded Co monatomic catalyst, the conductive carbon black and the polyvinylidene fluoride are mixed according to the weight ratio of 1:0.1:0.1 mixing, resulting in a homogeneous paste slurry in N-methyl pyrrolidone and coated on the side of a commercial PP separator. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x The supported Co monatomic catalyst modified membrane.
By using Ti 3 C 2 T x Loaded Co monatomic catalystLithium-sulfur battery with oxidant modified diaphragm can realize 828mAh g at 3C -1 The high reversible specific capacity is still higher than 715mAh g after being cycled for 600 times -1 And the capacity attenuation rate per cycle is only 0.057%.
Example 3
Adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, slowly stirring for 10min under the condition of ice-water bath to dissolve and disperse LiF in the concentrated hydrochloric acid to prepare LiF/HCl solution, and dissolving and dispersing a matrix Ti in the concentrated hydrochloric acid to obtain the LiF/HCl solution 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for 20 hours under the constant temperature condition of 45 ℃, an Al layer is selectively removed, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x Obtaining single or few layers of Ti 3 C 2 T x And (3) nanosheets, namely single few-layer nanosheets with certain thicknesses are obtained.
Taking 50mg of single few-layer Ti 3 C 2 T x Putting the powder into 10mL deionized water, performing ultrasonic treatment for 20min, stirring for 80min, and adding 2mg ZnCl 2 ·2H 2 And O, stirring for 1 hour, adding 100mg of melamine, and continuously stirring for 30min to fully and uniformly mix. And then, transferring the precursor mixture into an ultrasonic machine for ultrasonic treatment for 30min, and performing ultrasonic treatment under the ice-water bath condition. The obtained sample was frozen, followed by freeze-drying treatment to obtain a powder sample. The powder samples obtained were subjected to a drying treatment in N 2 Annealing at 550 ℃ for 1h under an inert atmosphere. The obtained sample was successively subjected to water washing and alcohol washing. Dried under vacuum at room temperature overnight. The sample obtained was Ti 3 C 2 T x A supported Zn monatomic catalyst.
Mixing Ti 3 C 2 T x The loaded Zn monatomic catalyst, conductive carbon black and polyvinylidene fluoride are mixed in a ratio of 1:0.2 mixing, a homogeneous paste slurry in N-methylpyrrolidone and coating on the side of a commercial PP separator. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x The loaded Zn monatomic catalyst modified membrane.
By using Ti 3 C 2 T x Of a loadLithium-sulfur battery with Zn monatomic catalyst modified diaphragm can realize 782mAh g at the time of 3C -1 The high reversible specific capacity is still higher than 798mAh g after being circulated for 600 times -1 And the capacity fade rate per cycle is only 0.05%.
Example 4
Adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, slowly stirring for 10min under the condition of ice-water bath to dissolve and disperse LiF in the concentrated hydrochloric acid to prepare LiF/HCl solution, and dissolving and dispersing a matrix Ti in the concentrated hydrochloric acid to obtain the LiF/HCl solution 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for 30 hours under the constant temperature condition of 35 ℃, an Al layer is selectively removed, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x Obtaining single or few layers of Ti 3 C 2 T x And (3) nanosheets, namely single few-layer nanosheets with certain thicknesses are obtained.
Taking 50mg of single few-layer Ti 3 C 2 T x Putting the powder into 10mL deionized water, performing ultrasonic treatment for 30min, stirring for 50min, and adding 2mg MnCl 2 ·4H 2 And O, stirring for 1 hour, adding 100mg of melamine, and continuously stirring for 50min to fully and uniformly mix. And then, transferring the precursor mixture into an ultrasonic machine for ultrasonic treatment for 30min, and performing ultrasonic treatment under the ice-water bath condition. The obtained sample was frozen, followed by freeze-drying treatment to obtain a powder sample. The obtained powder sample is dried and annealed for 3h at 600 ℃ in Ar inert atmosphere. The obtained sample was successively subjected to water washing and alcohol washing. Dried under vacuum at room temperature overnight. The sample obtained was Ti 3 C 2 T x Supported Mn monatomic catalyst.
Mixing Ti 3 C 2 T x The supported Mn monatomic catalyst, the conductive carbon black and the polyvinylidene fluoride are mixed according to the weight ratio of 1:0.1:0.1 mixing, a homogeneous paste slurry in N-methylpyrrolidone and coating on the side of a commercial PP separator. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x The loaded Mn monatomic catalyst modifies the membrane.
By using Ti 3 C 2 T x Load(s)The Mn monatomic catalyst modified diaphragm lithium sulfur battery can realize 728mAh g at the time of 3C -1 The high reversible specific capacity is 730mAh g after being circulated for 600 times -1 And the capacity fade rate per cycle was only 0.066%.
Comparative example 1
Adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, slowly stirring for 10min under the condition of ice-water bath to dissolve and disperse LiF in the concentrated hydrochloric acid to prepare LiF/HCl solution, and dissolving and dispersing Ti matrix in the concentrated hydrochloric acid to obtain Ti matrix 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for 26h under the constant temperature condition of 40 ℃, an Al layer is selectively removed, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x Obtaining single or few layers of Ti 3 C 2 T x And (3) nanosheets, namely single few-layer nanosheets with certain thicknesses are obtained.
Taking 50mg of Ti 3 C 2 T x The mixture is placed in 15mL deionized water and is subjected to ultrasonic treatment for 20min and stirring for 10min, 100mg of melamine is added, stirring is carried out for 1h, and then ultrasonic treatment is carried out for 30min in an ice water bath. The obtained sample is subjected to freeze drying treatment for 48 hours to obtain a powder sample. And (3) putting the sample into a tube furnace for annealing, and annealing for 2h at 500 ℃ in Ar atmosphere. The obtained sample was washed with water three times and with alcohol three times. Dried under vacuum at room temperature overnight. The obtained sample was N-Ti 3 C 2 T x 。
Adding N-Ti 3 C 2 T x Conductive carbon black and polyvinylidene fluoride according to a weight ratio of 1:0.2:0.2 mixing, a homogeneous paste slurry in N-methylpyrrolidone and coating on the side of a commercial PP separator. Putting the modified diaphragm in a vacuum oven to obtain N-Ti 3 C 2 T x And (3) modifying the diaphragm.
Compared with examples 1,2,3,4, except that CuCl was not added 2 ·2H 2 O and the like, and the other steps are substantially the same as in example 1.
Using N-Ti 3 C 2 T x The lithium-sulfur battery with the modified diaphragm can only reach 547mAh g at 3C -1 The reversible specific capacity of the inorganic particles,can only be cycled for 400 times in long cycle of 1C, and the specific capacity after cycling is 712mAh g -1 . This proves that the metal elements such as copper, zinc and the like are loaded on the nitrogen-doped Ti in the form of isolated single atoms 3 C 2 T x On, can furthest exert the absorption of metal monoatomic pair polysulfide, avoid shuttle effect to promote lithium sulphur battery's performance greatly.
Comparative example 2
Adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, slowly adding lithium fluoride (LiF) into the concentrated hydrochloric acid, slowly stirring for 10min under the condition of ice-water bath to dissolve and disperse LiF in the concentrated hydrochloric acid to prepare LiF/HCl solution, and dissolving and dispersing a matrix Ti in the concentrated hydrochloric acid to obtain the LiF/HCl solution 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for 26h under the constant temperature condition of 40 ℃, an Al layer is selectively removed, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x Obtaining single or few layers of Ti 3 C 2 T x And (3) nanosheets, namely single few-layer nanosheets with certain thicknesses are obtained.
Mixing Ti 3 C 2 T x Conductive carbon black and polyvinylidene fluoride according to a weight ratio of 1:0.2:0.2 mixing, resulting in a uniform paste slurry in N-methyl pyrrolidone and coated on the side of a commercial PP separator. Putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x And (3) modifying the diaphragm.
Compared with examples 1,2,3,4, except that melamine and CuCl were not added 2 ·2H 2 O and other metal chloride salts, and the obtained nanosheets are directly applied to the modified diaphragm without carrying out a pyrolysis doping process.
By using Ti 3 C 2 T x Lithium-sulfur batteries with modified separators can only reach 410mAh g at 3C -1 The reversible specific capacity of the resin can be cycled for only 100 times in a long cycle of 1C, and the specific capacity after cycling is 498mAh g -1 . This proves that the metal elements such as copper, zinc and the like are loaded on the nitrogen-doped Ti in the form of isolated single atoms 3 C 2 T x In addition, the nitrogen doping mode can utilize carbon-nitrogen coordination to stabilize isolated metal single atoms, and can maximize the metal single atomsThe adsorption of metal monoatomic atoms to polysulfide is exerted to the utmost extent, and the shuttle effect is avoided, so that the performance of the lithium-sulfur battery is greatly improved. Without realizing the loading of metal single atoms and the doping of nitrogen atoms, pure Ti 3 C 2 T x It is difficult to achieve excellent performance when applied to a separator for a lithium sulfur battery.
In summary, the present invention provides a Ti 3 C 2 T x Preparation method of supported monatomic catalyst and application of supported monatomic catalyst in lithium-sulfur battery diaphragm, and single/few-layer Ti is prepared by adopting improved minimum strength layering method 3 C 2 T x Nanoflakes, which create more titanium vacancies to anchor isolated metal atoms. Tuning of immobilization to Ti using vacancy anchoring strategy and nitrogen doping strategy 3 C 2 T x Monatomic catalyst on nanosheets, ti 3 C 2 T X The loaded monoatomic catalyst modified diaphragm is applied to a lithium-sulfur battery, and shows excellent rate performance and stable cycle life. Ti produced by the method 3 C 2 T x The loaded monatomic catalyst can be used for modifying the diaphragm of the lithium-sulfur battery, the modified diaphragm does not have the powder shedding phenomenon after being bent and folded, the diaphragm shows excellent mechanical property and bonding stability, and the Ti-supported monatomic catalyst has excellent rate performance and stable cycle life when being applied to the lithium-sulfur battery, so that the Ti-prepared monatomic catalyst can be used for preparing Ti 3 C 2 T x The supported single-atom catalyst is a promising approach for constructing a high-performance lithium sulfur battery when being used for modifying the performance of a separation membrane.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.
Claims (6)
1.Ti 3 C 2 T X A method for preparing a supported monatomic catalyst, characterized in that: the parent body Ti 3 AlC 2 MAX is soaked in LiF/HCl solution inEtching for a period of time at constant temperature, and then separating the stacked Ti by ultrasonic stripping 3 C 2 T x To obtain single/few layer Ti 3 C 2 T x Nanosheets; followed by self-reduction process using Ti 3 C 2 T x Abundant titanium vacancy on the nano sheet is used for stabilizing single atom, and further coordination stabilization through nitrogen doping is carried out to obtain Ti 3 C 2 T x A supported monatomic catalyst.
2. The Ti of claim 1 3 C 2 T X A method for preparing a supported monatomic catalyst, characterized in that: the LiF/HCl solution is obtained by the following method: adding concentrated hydrochloric acid (HCl) into a polytetrafluoroethylene beaker, stirring, adding lithium fluoride (LiF), and stirring uniformly under the ice-water bath condition;
the constant temperature is 35-45 ℃, and the etching time is 20-30h.
3. The Ti of claim 1 3 C 2 T X A method for preparing a supported monatomic catalyst, characterized in that: the specific implementation method comprises the following steps:
s0: the parent body Ti 3 AlC 2 MAX is soaked in LiF/HCl solution, etching is carried out for a period of time under constant temperature condition, and then stacked Ti is separated through ultrasonic stripping 3 C 2 T x To obtain single/few layer Ti 3 C 2 T x Nanosheets;
s1, taking single/few-layer Ti 3 C 2 T x Putting the powder into deionized water, performing ultrasonic treatment and stirring, adding a metal chloride, stirring, adding melamine, and continuously stirring to fully and uniformly mix the mixture to obtain a precursor mixture;
s2, transferring the precursor mixture obtained in the S1 into an ultrasonic machine for ultrasonic treatment, and performing ultrasonic treatment under the ice-water bath condition; freezing the obtained sample, and then carrying out freeze drying treatment to obtain a powder sample;
s3, preparing the powder sample obtained in the step S2Drying, and annealing at a certain temperature in an inert atmosphere; continuously washing the obtained sample with water and alcohol; drying overnight at room temperature under vacuum; to obtain Ti 3 C 2 T x A supported monatomic catalyst.
4. The method of claim 3, wherein:
the ultrasonic time in the steps S1 and S2 is 20-40min, and the stirring time is 20-80min;
the metal chloride in step S1 comprises MnCl 2 ·H 2 O，CoCl 2 ·H 2 O，NiCl 2 ·H 2 O，ZnCl 2 ·H 2 O，BiCl 2 ·H 2 O，CuCl 2 ·2H 2 O；
The inert atmosphere in the step S3 comprises nitrogen, argon and helium, the annealing temperature is 400-600 ℃, and the annealing time is 1-3h.
5. Ti prepared by the method of any one of claims 1 to 4 3 C 2 T X The application of the loaded monatomic catalyst in the lithium-sulfur battery diaphragm is characterized in that: a separator layer for a modified lithium sulfur battery;
the specific preparation method of the modified lithium-sulfur battery diaphragm layer comprises the following steps: first, ti 3 C 2 T x Mixing the loaded monoatomic catalyst, the conductive carbon black and the polyvinylidene fluoride, obtaining uniform pasty slurry in N-methyl pyrrolidone, and coating the slurry on one side of a commercial PP diaphragm; putting the modified diaphragm in a vacuum oven to obtain Ti 3 C 2 T x A supported monatomic catalyst modified membrane;
the Ti 3 C 2 T x The mass ratio of the loaded monatomic catalyst to the conductive carbon black to the polyvinylidene fluoride is 1.1-0.2.
6. The use of claim 5, wherein: by using Ti 3 C 2 T x Lithium sulfur battery with loaded monatomic catalyst modified separator at 3CCan realize that the weight is not less than 728mAh g -1 The high reversible specific capacity is still higher than 619mAh g after 1000 times of circulation -1 And the capacity attenuation rate of each circle is only 0.048% -0.084%.
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