阅读说明：本技术 一种多孔碳负载氧化铕材料及其制备方法和应用 (Porous carbon loaded europium oxide material and preparation method and application thereof ) 是由 李爱菊 彭林 张明坤 于 2020-12-24 设计创作，主要内容包括：本发明属于新能源材料与器件领域,公开了一种多孔碳负载氧化铕材料及其制备方法和应用。本发明主要以多孔碳和硝酸铕为原料,室温下采用pH值控制沉积法制备,经过超声,搅拌,抽滤,烘干,可得碳的前驱体,再将该前驱体在管式炉中通氮气,在700-1000℃下煅烧,可得多孔碳负载氧化铕材料。该材料可用于锂硫电池隔膜修饰材料。在0.05C(1C＝1675mAh/g)的倍率下,首圈放电比容量可达1610mAh/g,在1C的倍率下,科琴黑负载的氧化铕材料用于隔膜修饰层组装的电池经过500圈循环后,每圈的容量衰减率仅为0.05％,与涂覆有科琴黑和未涂覆材料的空白隔膜相比,比容量显著提升,具有优异的循环稳定性。(The invention belongs to the field of new energy materials and devices, and discloses a porous carbon loaded europium oxide material and a preparation method and application thereof. The porous carbon europium nitrate material is prepared by mainly using porous carbon and europium nitrate as raw materials and adopting a pH value control deposition method at room temperature, a precursor of carbon can be obtained by ultrasonic treatment, stirring, suction filtration and drying, and then nitrogen is introduced into the precursor in a tube furnace, and the precursor is calcined at the temperature of 700 plus materials and 1000 ℃ to obtain the porous carbon loaded europium oxide material. The material can be used as a lithium-sulfur battery diaphragm modification material. Under the multiplying power of 0.05C (1C: 1675mAh/g), the first circle of specific discharge capacity can reach 1610mAh/g, under the multiplying power of 1C, after the europium oxide material loaded by the Ketjen black is used for a battery assembled by a diaphragm modification layer and is circulated for 500 circles, the capacity attenuation rate of each circle is only 0.05%, compared with a blank diaphragm coated with the Ketjen black and uncoated materials, the specific capacity is obviously improved, and the excellent cycle stability is achieved.)

1. A preparation method of a porous carbon loaded europium oxide material is characterized by comprising the following steps:

(1) uniformly dispersing porous carbon in absolute ethyl alcohol, and then adding Eu (NO)₃)₃Uniformly stirring and mixing the solution, adding alkali to adjust the pH value to 7.5-9, continuously stirring and reacting, separating the obtained reaction product, washing and drying the obtained solid to obtain a precursor;

(2) and heating and calcining the obtained precursor in nitrogen or inert atmosphere to obtain the porous carbon europium oxide-loaded composite material.

2. The method for preparing a porous carbon-supported europium oxide material according to claim 1, characterized in that:

the porous carbon in the step (1) is at least one of carbon nano tube, graphene, Ketjen black, Super-p and acetylene black.

3. The method for preparing a porous carbon-supported europium oxide material according to claim 1, characterized in that:

eu (NO) as defined in step (1)₃)₃The solution is Eu (NO) with concentration of 0.01-0.5mol/L₃)₃An aqueous solution;

the porous carbon and Eu (NO) in step (1)₃)₃The dosage of the solution satisfies the following conditions: the porous carbon accounts for 40-80% of the total mass of the porous carbon and the europium nitrate, and the europium nitrate accounts for 20-60% of the total mass of the porous carbon and the europium nitrate.

4. The method for preparing a porous carbon-supported europium oxide material according to claim 1, characterized in that:

the step (1) of uniformly mixing and stirring refers to stirring for 0.5-3 hours so as to uniformly mix;

the continuous stirring reaction in the step (1) is a continuous stirring reaction for 0.5 to 3 hours.

5. The method for preparing a porous carbon-supported europium oxide material according to claim 1, characterized in that:

the heating calcination in the step (2) refers to raising the temperature to 700-1000 ℃ at a temperature raising rate of 3-5 ℃ and keeping the temperature for 1-3 h.

6. A porous carbon-supported europium oxide material prepared according to the method of any one of claims 1 to 5.

7. Use of the porous carbon-supported europium oxide material of claim 6 as a lithium-sulfur battery separator modification material.

8. A modified lithium-sulfur battery diaphragm material is characterized by being prepared by the following method: mixing the porous carbon europium oxide-loaded composite material of claim 6 and a binder in a mass ratio of 6-8: 2-4, uniformly mixing the mixture into uniform slurry, and coating the uniform slurry on a commercial diaphragm to obtain the modified lithium-sulfur battery diaphragm material.

9. The modified lithium sulfur battery separator material of claim 8, wherein:

the binder is at least one of polyvinylidene fluoride, sodium carboxymethylcellulose, styrene butadiene rubber and sodium alginate;

the commercial diaphragm is a polypropylene or polyethylene film.

10. A lithium sulfur battery comprising the modified lithium sulfur battery separator material of any one of claims 8-9.

Technical Field

The invention belongs to the field of new energy materials and devices, and particularly relates to a porous carbon loaded europium oxide material and a preparation method and application thereof.

Background

With the environmental pollution and the increasing exhaustion of fossil fuels, a number of sustainable and environmentally friendly new energy devices have attracted strong attention. Among portable energy storage devices, lithium ion batteries dominate the emerging market today. The lithium ion battery is a secondary battery which has relatively higher theoretical specific capacity and energy density, longer cycle life and is more environment-friendly compared with nickel-chromium batteries, lead-acid batteries, silver-zinc batteries and the like. The theoretical energy density of the lithium ion battery is only 150Wh/kg, and the demand of high-energy density storage equipment on the market still cannot be met.

The lithium-sulfur battery is one of the most promising secondary batteries for the next generation, and has high theoretical specific energy (2500Wh/kg) and theoretical specific capacity (1675mAh/g), and the sulfur elementary substance used by the anode has abundant reserves on the earth, is environment-friendly, nontoxic and low in price, and attracts the strong attention of researchers.

However, the lithium-sulfur battery has many problems in the commercialization process, mainly in the following aspects: sulfur as active material of positive electrode and lithium sulfide (Li) as discharge product₂S) has stronger insulating property; with simultaneous generation of Li₂S can cause severe volume expansion of the anode; and which, during charging and discharging, intermediate products are lithium polysulphides (Li)₂Sn,4<n is less than or equal to 8) shuttles back and forth between the positive and negative electrodes, commonly referred to as the shuttle effect, when Li is present₂S_nIs reduced to Li₂S deposits on the negative electrode, which can severely corrode the lithium metal negative electrode, reducing the coulombic efficiency of the active material of the positive electrode sulfur and the battery, causing a rapid decay of the specific capacity of the battery.

In recent studies, sulfur is often coated with a carbon material as a positive electrode of a lithium sulfur battery, and since the carbon material has a non-polar surface, it is difficult to fix polysulfides having a polarity, and the "shuttling effect" of the polysulfides cannot be effectively suppressed. However, the manufacturing cost of the anode is high, and the problem that the solution is urgently needed exists, so that the anode is not beneficial to actual industrial production. In recent years, the research on the modification of the separator has attracted the attention of researchers as a new strategy. For example, chinese patent publication CN111293255A discloses that composite nanosheets of cobalt hydroxide and graphene are deposited on the surface of a polypropylene separator, and this modified separator effectively prevents lithium dendrites from penetrating the separator, and at the same time greatly obstructs the shuttle pathway of polysulfides, improving the electrochemical performance of the lithium-sulfur battery.

In the current work, the manufacturing of the positive electrode composite material in the lithium-sulfur battery is relatively complicated, the manufacturing cost of the material is high, and the industrial production is difficult to realize.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention mainly aims to provide a preparation method of a porous carbon loaded europium oxide material.

The invention also aims to provide the porous carbon loaded europium oxide material prepared by the method.

The invention further aims to provide application of the porous carbon loaded europium oxide material as a lithium-sulfur battery diaphragm modification material. Porous carbon loaded europium oxide (Eu) is adopted₂O₃) As a lithium-sulfur battery diaphragm modification material, the specific capacity and the cycling stability of the lithium-sulfur battery are improved, and the manufacturing process of the lithium-sulfur battery is simplified.

The purpose of the invention is realized by the following scheme:

a preparation method of a porous carbon loaded europium oxide material comprises the following steps:

(1) uniformly dispersing porous carbon in absolute ethyl alcohol, and then adding Eu (NO)₃)₃Uniformly stirring and mixing the solution, adding alkali to adjust the pH value to 7.5-9, continuously stirring and reacting, separating the obtained reaction product, washing and drying the obtained solid to obtain a precursor;

(2) and heating and calcining the obtained precursor in inert atmosphere such as nitrogen or argon to obtain the porous carbon-loaded europium oxide composite material.

The porous carbon in the step (1) is at least one of carbon nano tube, graphene, Ketjen black, Super-p and acetylene black; ketjen black is preferred.

The dosage of the porous carbon and the ethanol in the step (1) meets the requirement that 2-5mg of porous carbon is correspondingly added into each 1ml of ethanol.

The step (1) of uniformly dispersing the porous carbon in the absolute ethyl alcohol is preferably to uniformly disperse the porous carbon in the absolute ethyl alcohol by ultrasonic treatment at room temperature for 1-3h, and more preferably ultrasonic treatment for 1.5 h.

Eu (NO) as defined in step (1)₃)₃The solution is Eu (NO) with concentration of 0.01-0.5mol/L₃)₃An aqueous solution; preferably Eu (NO) at a concentration of 0.1mol/L₃)₃An aqueous solution.

The porous carbon and Eu (NO) in step (1)₃)₃The dosage of the solution satisfies the following conditions: the mass percentage of the porous carbon in the total raw materials (the porous carbon and the europium nitrate) is 40-80%, and the mass percentage of the europium nitrate in the total raw materials (the porous carbon and the europium nitrate) is 20-60%.

The step (1) of uniformly mixing and stirring refers to stirring for 0.5-3 hours so as to uniformly mix;

the alkali in the step (1) is preferably at least one of concentrated ammonia water, sodium hydroxide, potassium hydroxide and the like, and preferably 20-30 wt% of ammonia water.

The continuous stirring reaction in the step (1) is carried out for 0.5 to 3 hours;

the stirring in step (1) is performed for the purpose of bringing the raw materials into sufficient contact with each other, and therefore, the stirring speed is not limited.

The heating calcination in the step (2) refers to raising the temperature to 700-1000 ℃ at a temperature raising rate of 3-5 ℃ and keeping the temperature for 1-3h, preferably raising the temperature to 900 ℃ at a temperature raising rate of 5 ℃ for 2 h.

In the present invention, the temperature not specified is room temperature.

The porous carbon europium oxide-loaded composite material prepared by the method.

The porous carbon-loaded europium oxide composite material is applied as a lithium-sulfur battery diaphragm modification material.

A modified lithium-sulfur battery separator material is prepared by the following method: mixing a porous carbon-loaded europium oxide composite material and a binder in a mass ratio of 6-8: 2-4, uniformly mixing the mixture into uniform slurry, coating the uniform slurry on a commercial diaphragm, and drying to obtain the modified lithium-sulfur battery diaphragm material.

The binder is at least one of polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose, styrene butadiene rubber and sodium alginate, and preferably polyvinylidene fluoride (PVDF);

the commercial separator is preferably a polypropylene or polyethylene film.

A lithium-sulfur battery comprising the modified lithium-sulfur battery separator material described above;

the positive pole piece of the lithium-sulfur battery adopts sulfur powder: conductive carbon black: polyvinylidene fluoride ═ 6-8: 1-2: grinding and size mixing are carried out according to the mass ratio of 1-2, a scraper is used for coating on the aluminum foil, and drying is carried out to obtain the positive pole piece.

The conductive carbon black is preferably Super-P or acetylene black.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the material of the invention is simple to prepare and has a wide industrial production prospect. The material is applied to a lithium sulfur battery diaphragm modification material, can physically adsorb polysulfide and chemically adsorb the polysulfide, greatly hinders shuttle of the polysulfide on a transmission path of the polysulfide, and reduces the manufacturing cost of a sulfur anode. In addition, the europium oxide is doped to efficiently promote the conversion of polysulfide and accelerate the dynamic rate of redox reaction.

Loading Eu by porous carbon₂O₃The modified diaphragm is used for the lithium sulfur battery, can physically adsorb polysulfide and chemically adsorb the polysulfide, and simultaneously, the doping of europium oxide efficiently promotes the catalytic conversion of the polysulfide and accelerates the dynamic rate of the redox reaction. At a rate of 0.05C, the pore carbon is negativeEuropium oxide-loaded Eu₂O₃The first-turn capacity of the modified diaphragm used in the lithium-sulfur battery can reach 1610 mAh/g. At a magnification of 1C, the capacity fade rate was only 0.05% and was low through 500 cycles.

Drawings

Fig. 1 is an X-ray powder diffraction pattern of the porous carbon-supported europium oxide material prepared in example 1.

FIG. 2 is a TEM image of the porous carbon-supported europium oxide material of example 1.

Fig. 3 is a schematic diagram of the porous carbon-supported europium oxide material prepared in example 1 as a separator modification layer for a lithium-sulfur battery.

Fig. 4 is a cyclic voltammogram of the porous carbon-supported europium oxide material prepared in example 1 as a separator modification layer for a lithium-sulfur battery.

Fig. 5 is a first-turn charge and discharge curve of the porous carbon-supported europium oxide material prepared in example 1 as a separator modification layer for a lithium-sulfur battery at a current density of 0.05C (1C 1675 mAh/g).

Fig. 6 is a long cycle performance graph at 1C rate of the porous carbon-supported europium oxide material prepared in example 1 as a separator modification layer for a lithium sulfur battery.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The reagents used in the examples are commercially available without specific reference.

Example 1

A porous carbon loaded europium oxide material mainly comprises main raw materials of porous carbon and europium nitrate, wherein the mass percentage of the porous carbon (Keqin black) is 60%, and the mass percentage of the europium nitrate is 40%.

The porous carbon-loaded europium oxide material can be obtained through the following steps:

(1) 200mg of Ketjen black was weighed into a glass beaker, and 80ml of absolute ethanol was added thereto and sonicated for 2 hours.

(2) Adding 0.1mol/L Eu (NO)₃)₃The solution was magnetically stirred for 0.5 h.

(3) Adding strong ammonia water, adjusting the pH value to 8.5, and magnetically stirring for 1 h.

(3) And separating, washing and drying the obtained solution to obtain a precursor.

(4) Calcining the obtained precursor at 900 ℃ for 2h in the atmosphere of nitrogen at the high temperature of 5 ℃/min to obtain the porous carbon loaded europium oxide composite material Eu₂O₃@KB。

The porous carbon-supported europium oxide material Eu prepared in the embodiment 1₂O₃The X-ray powder diffraction pattern of @ KB is shown in FIG. 1, which illustrates the successful synthesis of the porous carbon-supported europium oxide material Eu₂O₃@KB。

The porous carbon-supported europium oxide material Eu prepared in the embodiment 1₂O₃As shown in FIG. 2, it can be seen from the transmission electron micrograph of @ KB that europium oxide is uniformly dispersed in the carbon material.

Application example 1

A porous carbon-supported vanadium nitride electrode material is used as a lithium-sulfur battery separator modification material, and the mass ratio of the porous carbon-supported vanadium nitride electrode material to polyvinylidene fluoride (PVDF) is 6: 4 mixing, grinding and size mixing, and coating on a commercial diaphragm (Celgard2400) to obtain the modified diaphragm material. Because the diaphragm material is the polypropylene diaphragm, we will refer to the blank diaphragm for short as PP diaphragm. Coating Ketjen black and Ketjen black loaded europium oxide material on PP diaphragm to obtain modified diaphragm material, which is abbreviated as KB/PP and Eu₂O₃@KB/PP。

The anode adopts the following steps: conductive carbon black: polyvinylidene fluoride ═ 7: 2: 1, diluting with N-methyl pyrrolidone to prepare uniform slurry, coating on an aluminum foil by using a scraper, drying at 60 ℃ for 24 hours, and cutting into a disc with the thickness of 10 mm.

The electrolyte is a 1, 3-Dioxolane (DOL)/glyme (DME) mixed solution (volume ratio is 1:1) with the concentration of 1mol/L lithium bistrifluoromethanesulfonylimide (LiTFSI), and the electrolyte simultaneously contains 1% of anhydrous lithium nitrate as an additive.

The lithium metal sheet serves as the negative electrode.

The CR2032 button cell was assembled in a glove box filled with argon by a conventional method and tested for electrochemical performance.

Fig. 3 is a schematic diagram of the porous carbon-supported europium oxide material prepared in example 1 as a separator modification layer for a lithium-sulfur battery.

FIG. 4 is a cyclic voltammogram of the porous carbon-supported europium oxide material prepared in example 1 as a separator modification layer for a lithium-sulfur battery, and it can be seen from the cyclic voltammogram that in the first scanning cycle, there are two reduction peaks at 2.28V and 2.03V, corresponding to the conversion of elemental sulfur to Li₂S₄Conversion of (2), Li₂S₄To Li₂And (4) converting S. Two oxidation peaks at 2.34V and 2.41V, corresponding to Li respectively₂S to Li₂S₄Conversion of (2), Li₂S₄Conversion to elemental sulphur. The better overlapping of the two circles can be seen in the scanning of the second circle and the third circle, which indicates that the europium oxide doped in the porous carbon has high-efficiency adsorption effect on polysulfide when being used as a lithium-sulfur diaphragm coating material, and also indicates that the material has good electrochemical stability and reversibility when being used in a lithium-sulfur battery.

FIG. 5 is a charge-discharge curve at a magnification of 0.05C, during the re-discharge process, the first plateau is around 2.3V and the second plateau is around 2.1V, corresponding to the elemental sulfur to Li, respectively₂S₄Conversion of (2), Li₂S₄To Li₂And (4) converting S.

Fig. 6 is a graph of long cycle performance at 1C rate, and the lower three lines shown in fig. 6 correspond to specific capacity curves of the lithium-sulfur battery composed of the ketjen black-loaded europium oxide material-modified separator material, the ketjen black-modified separator material, and the blank separator material, respectively, and the upper three lines are coulombic efficiency curves thereof. After 500 cycles, the capacity fading rate per cycle was only 0.05%. Meanwhile, compared with a blank diaphragm (PP) coated with Ketjen black (KB/PP) and uncoated material, the Ketjen black loaded europium oxide material has the advantages that the specific capacity is remarkably improved, and the cycle stability is excellent.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.