1. The preparation method of the hollow tubular manganese cobaltate is characterized by comprising the following steps of:

s1, solution preparation: dissolving PVP in a certain amount of CH₃CH₂OH solution is mixed to prepare mixed solution, and cobalt salt and manganese salt are added into CH₃Mixing and stirring the two mixed solutions in a diluted solution of COOH and water to form a salt solution;

s2, electrostatic spinning: spinning the salt solution in the S1 on conductive glass, and forming a film on the conductive glass by interlacing the overlapped fibers;

s3: pre-fixing a binding point: spraying a solution containing sulfur particles on the surface of the film in the S2;

s4, sintering and forming: drying the film at 60-80 ℃, putting the film into a muffle furnace for sintering, and hollowing the film to form hollow tubular manganese cobaltate nanofibers connected in a flaky manner;

s5, grinding, adsorbing and testing electrochemical performance: the hollow tubular manganese cobaltate and sulfur particles obtained in S3 were mixed in a ratio of 3: solid phase grinding at a ratio of 6-7, heating at 160 ℃ in a reaction kettle at 130-.

2. The method for preparing the hollow tubular manganese cobaltate according to claim 1, wherein the method comprises the following steps: in S1, the cobalt salt and the manganese salt are respectively Co (AC)₂·4H₂O and Mn (AC)₂·4H₂O, and Co (AC)₂·4H₂O and Mn (AC)₂·4H₂The molar ratio of O is 2-2.5: 1.

3. the method for preparing the hollow tubular manganese cobaltate according to claim 1, wherein the method comprises the following steps: in S4, the sulfur particles previously fixed to the nanofiber surface of the thin film are gradually removed during the sintering process.

4. The method for preparing the hollow tubular manganese cobaltate according to claim 1, wherein the method comprises the following steps: in the S5, solid phase grinding can break the flaky connected hollow tubular manganese cobaltate and break the fibrous hollow tubular manganese cobaltate into segment-shaped structures.

5. The method for preparing the hollow tubular manganese cobaltate as claimed in claim 4, wherein the method comprises the following steps: the manganese cobaltate with the segment structure loads sulfur particles and forms active substances.

6. The method for preparing the hollow tubular manganese cobaltate according to claim 1, wherein the method comprises the following steps: in S3, the ratio of the sulfur particles to the cobalt salt, manganese salt 4: 3 in a ratio of 3.

7. The method for preparing the hollow tubular manganese cobaltate according to claim 1, wherein the method comprises the following steps: in the S1, CH₃The dilution ratio of COOH and water was 1: 10.

8. the method for preparing the hollow tubular manganese cobaltate according to claim 1, wherein the method comprises the following steps: in the S1, the two mixed solutions are respectively stirred for at least 3 hours and then mixed, and the mixture is stirred for at least 12 hours.

9. The method for preparing the hollow tubular manganese cobaltate as claimed in claim 8, wherein the method comprises the following steps: and in the S4, after the film is dried, heating the film to 600 ℃ from the normal temperature in a muffle furnace at a speed of 4-6 ℃/min for 5-6 h.

10. The hollow tubular manganese cobaltate prepared by the preparation method according to claim 1 is used for a lithium-sulfur battery cathode material.

Background

With the ever-decreasing fossil energy and the increasing pressure of environmental protection, the development and utilization of renewable clean energy are imminent. Safe, low cost electrochemical energy storage devices are key to the development of new energy sources. Secondary batteries represented by lead-acid batteries, nickel-metal hydride batteries, and lithium ion batteries have been widely used in mobile phones, notebook computers, electric bicycles, and the like, as a convenient and recyclable energy storage device. Under the condition of increasingly serious energy crisis, countries around the world strive for the development of new energy electric vehicles, and the development of electric vehicles urgently needs the support of a high-energy-density secondary battery system. New secondary batteries have received wide attention as a new generation of energy storage devices. Wherein, the lithium-sulfur battery system has rich natural resources, low cost and extremely high theoretical capacity density (1675 mAh.g)^-1) Energy density (2600 Wh. kg)^-1) Becoming one of the hot spots of industry research.

However, in the process of charging and discharging the lithium sulfur battery, the elemental sulfur and the product lithium sulfide are repeatedly transformed, so that large volume change can occur, the elemental sulfur is not conductive, and the shuttle effect and the like can be generated after the intermediate product soluble lithium polysulfide is dissolved, so that the performance and the cycle service life of the battery are seriously influenced, and the development of the battery is limited.

In recent years, self-healing transition metal oxides (containing two or more types of cations) have received increasing attention since their introduction into the human eye. The added metal cations can improve the electrical property of the spinel structure, maintain the advantages of the spinel structure, have excellent characteristics in the aspects of light, electricity, magnetism, catalysis and the like, and are widely applied to scientific and engineering production. Transition metal oxide M of spinel structure₃O₄The divalent M ion in the catalyst is replaced by other transition metal ions, and due to the enhanced stability of the active phase and the synergistic effect between different metal oxides, the catalyst has certain degree of activityThe stability of the oxide and the performance of the oxide in the aspects of electricity, light and magnetism are improved. In the composite transition metal oxide, cobaltate has received much attention due to its larger specific capacity and more excellent cycle performance, and the cobaltate has a formula of MCo₂O₄(M ═ Mn, Fe, Zn, Ni, etc.). MCo₂O₄Spinel-type composite transition metal oxides are receiving more extensive attention due to their superior electrochemical properties. In the spinel structure, the oxygen ions are packed in a body centered cubic (F-C) stack, where M²⁺Occupying 1/8 tetrahedral spaces, Co³⁺Occupies 1/2 octahedral space, M²⁺The ion structure of the original transition metal oxide is not changed after the original metal ions are replaced, but different transition metal elements have different electrode potentials and different chemical activities, and the synergistic effect between the different metal elements can improve the lithium storage capacity and the activity of the metal ions, so that the discharge platform is more stable, and the specific capacity is improved.

Therefore, it is necessary to design and prepare a composite transition metal oxide, and the composite transition metal oxide is used as a sulfur carrier to solve the problems of volume change caused during the charging and discharging processes of a lithium sulfur battery, shuttle effect caused by polysulfide dissolution, and the like.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a preparation method and application of hollow tubular manganese cobaltate.

In order to achieve the purpose, the invention adopts the technical scheme that: a preparation method of hollow tubular manganese cobaltate comprises the following steps:

s1, solution preparation: dissolving PVP in a certain amount of CH₃CH₂OH solution is mixed to prepare mixed solution, and cobalt salt and manganese salt are added into CH₃Mixing and stirring the two mixed solutions in a diluted solution of COOH and water to form a salt solution;

s2, electrostatic spinning: spinning the salt solution in the S1 on conductive glass, and forming a film on the conductive glass by interlacing the overlapped fibers;

s3: pre-fixing a binding point: spraying a solution containing sulfur particles on the surface of the film in the S2;

s4, sintering and forming: drying the film at 60-80 ℃, putting the film into a muffle furnace for sintering, and hollowing the film to form hollow tubular manganese cobaltate nanofibers connected in a flaky manner;

s5, grinding, adsorbing and testing electrochemical performance: the hollow tubular manganese cobaltate and sulfur particles obtained in S3 were mixed in a ratio of 3: solid phase grinding at a ratio of 6-7, heating at 160 ℃ in a reaction kettle at 130-.

In a preferred embodiment of the present invention, in S1, the cobalt salt and the manganese salt are respectively Co (AC)₂·4H₂O and Mn (AC)₂·4H₂O, and Co (AC)₂·4H₂O and Mn (AC)₂·4H₂The molar ratio of O is 2-2.5: 1.

in a preferred embodiment of the present invention, in S4, the sulfur particles previously fixed on the nanofiber surface of the thin film are gradually removed during the sintering process.

In a preferred embodiment of the present invention, in S5, the solid phase grinding can break the hollow manganese cobaltate connected in the form of pieces and break the hollow manganese cobaltate in the form of fiber hollow tubes into segment-shaped structures.

In a preferred embodiment of the invention, the manganese cobaltate with the segment-shaped structure is loaded with sulfur particles and forms an active substance.

In a preferred embodiment of the present invention, in S3, the ratio of the sulfur particles to the cobalt salt and manganese salt 4: 3 in a ratio of 3.

In a preferred embodiment of the present invention, in S1, CH₃The dilution ratio of COOH and water was 1: 10.

in a preferred embodiment of the present invention, in S1, the two mixed solutions are stirred for at least 3 hours and then mixed, and then stirred for at least 12 hours.

In a preferred embodiment of the present invention, in S4, after the film is dried, the temperature is raised from the normal temperature to 600 ℃ for 5-6 hours in a muffle furnace at a rate of 4-6 ℃/min.

The hollow tubular manganese cobaltate prepared by the preparation method is used for the positive electrode material of the lithium-sulfur battery.

The invention solves the defects in the background technology, and has the following beneficial effects:

(1) the invention prepares MnCo with a hollow tubular structure₂O₄Selecting a material for synthesizing the manganese cobaltate positive electrode framework, preparing a proper concentration ratio for electrostatic spinning, and obtaining the structure of the manganese cobaltate positive electrode framework by changing an electrostatic spinning receiver and carrying out heat treatment at different temperatures.

(2) The invention prepares MnCo₂O₄The pre-fixing of the binding points is carried out in the process, and after the high-temperature sulfur particles fall off, the identification points easy to bind are formed, so that the MnCo is improved₂O₄The amount of adsorption to sulfur particles and the loading rate.

(3) According to the invention, a solid-phase grinding means is adopted to break up the flaky manganese cobaltate, and the manganese cobaltate nano-fibers are broken into a plurality of sections, the specific surface area of the broken manganese cobaltate nano-fibers is enlarged by 3-5 times, one part of sulfur particles are adsorbed on the binding points on the surfaces of the manganese cobaltate fibers, and one part of sulfur particles are adsorbed in the manganese cobaltate fibers, so that the loading rate of the manganese cobaltate and the sulfur particles is further improved.

(4) Heating to 155 ℃ in a reaction kettle, keeping the temperature for 24 hours, loading sulfur particles on manganese cobaltate with a segment structure, and forming an active substance to obtain the active substance; 155 ℃ is used as the temperature value with the maximum adsorption rate of the manganese cobaltate-loaded sulfur particles, and the temperature is kept at the temperature, so that the loading rate of the manganese cobaltate and the sulfur particles is further improved.

(5) The hollow tubular MnCo prepared by the invention₂O₄The nano-fiber is used as an adsorbent of polysulfide ions, can be directly used as a sulfur carrier and is loaded to form MnCo₂O₄(S) obtaining the metal oxide manganese cobaltate MnCo₂O₄the/S composite material is used as the positive electrode of the lithium-sulfur battery, so that the volume change caused in the charging and discharging processes of the lithium-sulfur battery can be relieved, the problems of shuttle effect and the like caused by polysulfide dissolution can be inhibited, and the electrochemical performance and the cycling stability of the lithium-sulfur battery are improved.

(6) The transition metal oxide manganese cobaltate MnCo of the invention₂O₄Formation of MnCo on sulfur-loaded particles₂O₄After the specific capacity is increased after the charge and the discharge are carried out for many times, the coulomb efficiency is still stabilized at a large value after a large cycle number.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts;

FIG. 1 is a MnCo of hollow tubular structure of a preferred embodiment of the present invention₂O₄SEM topography of;

FIG. 2 is a MnCo of hollow tubular structure of the preferred embodiment of the present invention₂O₄TGA profile of the/S composite;

FIG. 3 is a MnCo of hollow tubular structure of the preferred embodiment of the present invention₂O₄the/S is taken as a constant-current charge-discharge curve diagram of the positive electrode of the lithium-sulfur battery under the multiplying power of 0.1C;

FIG. 4 is a MnCo of hollow tubular structure of the preferred embodiment of the present invention₂O₄the/S is used as a plot of coulombic efficiency and cycling stability at 0.1C and 0.2C rate for the positive electrode of the lithium sulfur battery.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.

In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner, and are not to be considered limiting of the scope of the present application. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the invention, the meaning of "a plurality" is two or more unless otherwise specified.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art through specific situations.

The invention provides a hollow tubular manganese cobaltate MnCo₂O₄The preparation method comprises the following steps:

s1, solution preparation: dissolving PVP in a certain amount of CH₃CH₂And (3) adding the OH solution to prepare a mixed solution, stirring for at least 3 hours, and mixing the mixed solution with the molar ratio of 2-2.5: 1 Co (AC)₂·4H₂O、Mn(AC)₂·4H₂O

Adding the mixture to a dilution ratio of 1: 10 CH₃Stirring the diluted solution of COOH and water for at least 3h, and mixing and stirring the two mixed solutions for at least 12h to form a salt solution;

s2, electrostatic spinning: spinning the salt solution in the S1 on conductive glass, and forming a film on the conductive glass by interlacing the overlapped fibers;

s3: pre-fixing a binding point: and (4) spraying an aqueous solution containing sulfur particles on the surface of the film in the step S2, wherein the ratio of the sulfur particles to cobalt salt and manganese salt is 4: 3 is added in proportion;

s4, sintering and forming: drying the film at 60-80 ℃, putting the film into a muffle furnace, heating the film to 600 ℃ from normal temperature at a speed of 4-6 ℃/min, sintering the film for 5-6 h, gradually dropping sulfur particles pre-fixed on the surface of the nanofiber of the film in the sintering process, and hollowing the film to form hollow tubular manganese cobaltate nanofibers connected in a flaky manner;

s5, grinding, adsorbing and testing electrochemical performance: the hollow tubular manganese cobaltate and sulfur particles obtained in S3 were mixed in a ratio of 3: solid phase grinding is carried out according to the proportion of 6-7, hollow tubular manganese cobaltate connected in a slicing mode is broken, fiber hollow tubular manganese cobaltate is smashed into a segment structure, the segment structure is placed into a reaction kettle to be heated at the temperature of 130-160 ℃, sulfur particles are loaded on the manganese cobaltate with the segment structure, active substances are formed to obtain the active substances, the obtained active substances, carbon black and PVDF are coated according to the proportion of 8:1:1, and the battery is formed through drying, slicing, tabletting assembly and electrochemical performance testing.

The hollow tubular manganese cobaltate prepared by the preparation method is used for the positive electrode material of the lithium-sulfur battery.

It should be noted that in S4, after sintering, the sulfur particles loaded on the film are subjected to a high temperature of 600 ℃, the sulfur particles gradually fall off from the surface of the manganese cobaltate, and the bonding points on the surface of the manganese cobaltate fibers after falling off still exist, and can be used as the recognition points of the sulfur particles, so as to facilitate re-bonding. Therefore, the flaky connected hollow tubular manganese cobaltate nanofibers prepared in S4 in the present invention are only used as intermediates.

Examples

The embodiment discloses a hollow tubular manganese cobaltate MnCo₂O₄The preparation method comprises the following steps: s1, solution preparation: 1g PVP was dissolved in 10ml CH₃CH₂OH solution is added to prepare mixed solution, the mixed solution is stirred for 3.5 hours, and 2.491g of Co (AC)₂·4H₂O and 1.225gMn (AC)₂·4H₂O two salts to 1ml CH₃Stirring the COOH and 10ml of water in the diluted solution for 3.5 hours, and mixing and stirring the two mixed solutions for at least 12 hours to form a salt solution;

s2, electrostatic spinning: spinning the salt solution in the S1 on conductive glass, and forming a film on the conductive glass by interlacing the overlapped fibers;

s3: pre-fixing a binding point: spraying an aqueous solution containing sulfur particles on the surface of the film in S2, wherein the aqueous solution contains 4.954g of sulfur particles;

s4, sintering and forming: drying the film at 60 ℃, putting the film into a muffle furnace, heating the film to 600 ℃ from normal temperature at a speed of 5 ℃/min, sintering the film for 5h, gradually dropping sulfur particles pre-fixed on the surface of the nanofiber of the film in the sintering process, and hollowing the film to form hollow tubular manganese cobaltate nanofibers connected in a sheet form;

s5, grinding, adsorbing and testing electrochemical performance: the hollow tubular manganese cobaltate and sulfur particles obtained in S3 were mixed in a ratio of 3: 7, performing solid phase grinding for 30min, breaking the hollow tubular manganese cobaltate connected in a sheet form, crushing the hollow tubular manganese cobaltate into a segment structure, putting the segment structure manganese cobaltate into a reaction kettle, heating the reaction kettle at 155 ℃ for 24h, loading sulfur particles on the segment structure manganese cobaltate, forming an active substance to obtain the active substance, coating the obtained active substance, carbon black and PVDF according to the ratio of 8:1:1, drying, slicing, tabletting, assembling to form the battery, and performing electrochemical performance testing.

As shown in FIG. 1, MnCo of hollow tubular structure in S4 of the embodiment is shown₂O₄SEM topography of (a). The manganese cobaltate is of a fiber structure, and the interior of the fiber is in a hollow tubular shape. The film formed by interlacing a plurality of manganese cobaltates is connected in a piece and is discontinuous.

As shown in FIG. 2, Mn of hollow tubular structure in the present embodiment S4 is shownCo₂O₄TGA profile of the/S composite. The efficiency of loading hollow tubular manganese cobaltate with sulfur particles in a muffle furnace after fragmentation is as follows: in the stage from normal temperature to 155 ℃, the adsorption rate of manganese cobaltate and sulfur particles is high, the loading capacity of the manganese cobaltate and the sulfur particles is maximum, and the binding point is strengthened in the stage; in the stage of 150-250 ℃, the dropping rate of manganese cobaltate and sulfur particles is linear, and the dropping amount of manganese cobaltate fibers and sulfur particles is increased continuously; in the stage of 250-600 ℃, the shedding rate of manganese cobaltate and sulfur particles is reduced, and the loading capacity of manganese cobaltate fibers and sulfur particles is basically 0. And the bonding points on the surfaces of the manganese cobaltate fibers after the fibers are stripped still exist and can be used as identification points of sulfur particles.

In this example, the intermediate manganese cobaltate nanofibers prepared in S4 were broken up by grinding in S5, and since the intermediate manganese cobaltate in this example is in the nanometer level, the manganese cobaltate nanofibers can be broken into several pieces by only breaking up the pieces of manganese cobaltate by conventional grinding means. The specific surface area of the broken manganese cobaltate nano fiber is enlarged by 3-5 times, a part of sulfur particles are adsorbed on the binding points on the surface of the manganese cobaltate fiber, and a part of sulfur particles are adsorbed inside the manganese cobaltate fiber, so that the loading rate of manganese cobaltate and sulfur particles is further improved.

In the embodiment S5, manganese cobaltate with a segment structure is heated to 155 ℃ in a reaction kettle and is kept warm for 24 hours, sulfur particles are loaded on the manganese cobaltate, and an active substance is formed to obtain an active substance; 155 ℃ is used as the temperature value with the maximum adsorption rate of the manganese cobaltate-loaded sulfur particles, and the temperature is kept at the temperature, so that the loading rate of the manganese cobaltate and the sulfur particles is further improved.

FIG. 3 shows MnCo of the hollow tubular structure of the embodiment₂O₄and/S is taken as a constant current charge-discharge curve diagram of the positive electrode of the lithium-sulfur battery under the multiplying power of 0.1C. This example was conducted by detecting MnCo at 1 st, 2 nd, 10 th and 200 th times, respectively₂O₄and/S is used as the constant-current charging and discharging capacity of the positive electrode of the lithium-sulfur battery at the rate of 0.1C. The four curves in fig. 3, which go from 2.4V to 3.0V, are the charging curves at times 1, 2, 10 and 200, respectively; wherein the 1 st and 2 nd charging curves substantially coincide, and the 10 th and 200 th times reachThe required specific capacity of 3.0V increases in turn, but the increase is not great. The four curves from 2.4V to 1.5V are discharge curves at times 1, 2, 10 and 200, respectively; wherein the charging curves of the 1 st time and the 2 nd time are basically overlapped, and the specific capacities required for reaching 3.0V of the 10 th time and the 200 th time are sequentially increased but not greatly increased.

FIG. 4 shows MnCo of the hollow tubular structure of the embodiment₂O₄the/S is used as a plot of coulombic efficiency and cycling stability at 0.1C and 0.2C rate for the positive electrode of the lithium sulfur battery. MnCo at 0.1C and 0.2C magnifications₂O₄The specific capacity of the/S serving as the positive electrode of the lithium-sulfur battery is basically unchanged and basically coincided with the increase of the cycle number. And MnCo at 0.1C and 0.2C magnification₂O₄the/S is used as the positive electrode of the lithium-sulfur battery, and the coulombic efficiency is still stabilized between 92% and 98% along with the increase of the cycle number.

In conclusion, the MnCo prepared by the invention₂O₄The composite transition metal oxide has a hollow tubular shape, the discharge potential of the transition metal oxide is generally higher, and the generation of lithium dendrite can be avoided to a certain extent, so that the safety of the battery is improved. Most importantly, the hollow tubular MnCo prepared by the invention₂O₄The nano-fiber is used as an adsorbent of polysulfide ions, can be directly used as a sulfur carrier and is loaded to form MnCo₂O₄(S) obtaining the metal oxide manganese cobaltate MnCo₂O₄the/S composite material is used as the positive electrode of the lithium-sulfur battery, so that the volume change caused in the charging and discharging processes of the lithium-sulfur battery can be relieved, the problems of shuttle effect and the like caused by polysulfide dissolution can be inhibited, and the electrochemical performance and the cycling stability of the lithium-sulfur battery are improved.

MnCo prepared in this example₂O₄When the/S is used as the anode of the lithium-sulfur battery to carry out electrochemical performance test, constant current charging and discharging under 0.1C multiplying power and coulombic efficiency and circulation stability tests under 0.1C multiplying power and 0.2C multiplying power are carried out, and the following results are obtained: transition metal oxide manganese cobaltate MnCo of the present example₂O₄Formation of MnCo on sulfur-loaded particles₂O₄after/S, after a number of passesThe specific capacity is still larger after charging and discharging, and the coulombic efficiency is still stabilized at a larger value after a larger cycle number.

In light of the foregoing description of the preferred embodiment of the present invention, it is to be understood that various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.