阅读说明：本技术 一种改性隔膜材料、改性隔膜和锂硫扣式电池 (Modified diaphragm material, modified diaphragm and lithium-sulfur button cell ) 是由 罗沈 林韶文 苏立 林洪栋 李飞 王建明 陈光后 于 2021-07-27 设计创作，主要内容包括：本发明涉及电池技术领域,尤其涉及一种改性隔膜材料、改性隔膜和锂硫扣式电池。本发明公开了一种一种改性隔膜材料,该改性隔膜材料由2D有机分子和碳材料复合而成。该改性隔膜材料中的碳材料有利于电子、离子电导,还可以起到物理限域减缓硫在充放电过程中的流失；改性隔膜材料中的2D有机分子在能够吸附聚硫化物防止其穿梭,同时能够催化多硫化物转化成不溶性的Li-2S增加反应动力学。本发明改性隔膜材料中的碳材料和2D有机分子协同作用,使得电池具有优异的电化学性能。(The invention relates to the technical field of batteries, in particular to a modified diaphragm material, a modified diaphragm and a lithium-sulfur button battery. The invention discloses a modified diaphragm material which is formed by compounding 2D organic molecules and a carbon material. The carbon material in the modified diaphragm material is beneficial to electronic and ionic conductivity, and can play a role in slowing down the loss of sulfur in the charge-discharge process in a physical confinement manner; the 2D organic molecules in the modified membrane material are capable of adsorbing polysulfides to prevent shuttling thereof, while at the same time being capable of catalyzing the conversion of polysulfides to insoluble Li 2 S increases the reaction kinetics. Book (I)The carbon material and the 2D organic molecules in the modified diaphragm material provided by the invention act synergistically, so that the battery has excellent electrochemical performance.)

1. A modified membrane material is characterized by comprising a carbon material and 2D organic molecules compounded with the carbon material.

2. The modified membrane material according to claim 1, wherein the mass ratio of the carbon material to the 2D organic molecules in the modified membrane material is (50-80): (0.2-3.5).

3. The modified separator material according to claim 1, wherein the carbon material is cobalt nitrogen porous carbon, conductive carbon black, Super P and/or CNT.

4. The modified membrane material of claim 1, wherein the 2D organic molecule is one or more of chenodeoxycholic acid, meso-tetra (4-carboxyphenyl) porphin, berberine chloride hydrate, and poly (diallyldimethylammonium chloride).

5. A modified membrane, comprising a membrane and the modified membrane material of any one of claims 1 to 4 adhered to the surface of the membrane.

6. A preparation method of a modified diaphragm is characterized by comprising the following steps:

step 1: mixing a binder, a solvent, 2D organic molecules and a carbon material to obtain a mixture;

step 2: and (3) carrying out vacuum filtration on the mixture on a diaphragm under the ultrasonic condition, and drying to obtain the modified diaphragm.

7. The preparation method according to claim 6, wherein the binder is polyvinylidene fluoride, La133 type binder or sodium alginate;

the solvent is selected from absolute ethyl alcohol, N-methyl pyrrolidone or nitrogen-nitrogen dimethyl formamide;

the 2D organic molecule is one or more than two of chenodeoxycholic acid, meso-tetra (4-carboxyphenyl) porphin, berberine chloride hydrate and polydiallyldimethyl ammonium chloride;

the carbon material is one or more than two of cobalt nitrogen porous carbon, conductive carbon black, Super P and CNT.

8. The method for preparing according to claim 6, wherein the binder: solvent: 2D organic molecule: the mass-volume ratio of the carbon material is (10-40) mg: (60-90) mL: (0.2-3.5) mg: (50-80) mg.

9. Use of the modified separator of claim 5 in a lithium sulfur battery.

10. A lithium sulfur button cell comprising the modified separator of claim 5.

Technical Field

The invention relates to the technical field of batteries, in particular to a modified diaphragm material, a modified diaphragm and a lithium-sulfur button battery.

Background

With the continuous development of human society, portable electronic devices, hybrid vehicles, and the like are widely used, and thus, higher requirements are placed on advanced energy storage devices. The traditional lithium ion battery has lower specific capacity, the use of the traditional lithium ion battery in advanced energy storage devices is severely limited, and the development of a secondary battery with high specific energy density is an urgent task in the field of new energy. The lithium-sulfur battery has higher theoretical specific capacity and energy density and has wide application prospect.

In the lithium-sulfur battery, sulfur has the advantages of abundant earth reserves, low toxicity, low price and the like, and can generate 1675mAh g^-1Specific capacity of 2600Whk g^-1These all make sulfur a high capacity electrode material with great application potential and commercial value. However, in practical application, the lithium-sulfur battery has problems of shuttle effect of polysulfide, pulverization of active substances, and the like. Currently, researchers mainly load sulfur on various carbon substrates or add a carbon-based barrier layer to inhibit the shuttling effect of polysulfide, thereby prolonging the cycle life of the battery.

However, the method of loading sulfur on a carbon matrix only physically plays a certain limiting role on sulfur and polysulfide, which is inevitably dissolved in the electrolyte, and finally causes most of sulfur loss, so that the cycle performance and rate performance of the battery are deteriorated.

Disclosure of Invention

In view of the above, the invention provides a modified diaphragm material, a modified diaphragm and a lithium sulfur buttonThe modified diaphragm material can quickly convert easily soluble high-valence polysulfide into final product Li₂And S, so that the loss of polysulfide and active sulfur is effectively reduced, the reaction kinetics of the lithium-sulfur battery is increased, and the cycle performance and the rate capability of the battery are improved.

The specific technical scheme is as follows:

the invention provides a modified diaphragm material which comprises a carbon material and 2D organic molecules compounded with the carbon material.

In the modified diaphragm material, the mass ratio of the carbon material to the 2D organic molecules is (50-80): (0.2-3.5).

In the invention, the carbon material is cobalt nitrogen porous carbon (HC), conductive carbon black, Super P and/or CNT;

the 2D organic molecule is one or more than two of Chenodeoxycholic Acid (CA), meso-tetra (4-carboxyphenyl) porphin (TTBA), Berberine Chloride Hydrate (BCH) and poly (diallyl dimethyl ammonium chloride) (PDDA). In the present invention, the PDDA is in the form of liquid.

The invention also provides a modified diaphragm which comprises a diaphragm and the modified diaphragm material adhered to the surface of the diaphragm.

The invention also provides a preparation method of the modified diaphragm, which comprises the following steps:

step 1: mixing a binder, a solvent, 2D organic molecules and a carbon material to obtain a mixture;

step 2: and (4) carrying out vacuum filtration on the mixture on a diaphragm, and drying to obtain the modified diaphragm.

In the invention, the 2D organic molecules in the modified diaphragm material on the surface of the modified diaphragm are physically mixed with the carbon material, so that the 2D organic molecules are distributed around the carbon material.

In step 1 of the present invention, the solvent is one or more selected from anhydrous ethanol, N-methylpyrrolidone and nitrogen-nitrogen dimethylformamide, and preferably, anhydrous ethanol and N-methylpyrrolidone;

the step 1 of the invention specifically comprises the following steps: dispersing the binder in N-methyl pyrrolidone to completely dissolve the binder, and then adding absolute ethyl alcohol, 2D organic molecules and a carbon material to disperse the 2D organic molecules and the carbon material;

the binder is polyvinylidene fluoride, La133 type binder or sodium alginate;

the 2D organic molecule is one or more than two of chenodeoxycholic acid, meso-tetra (4-carboxyphenyl) porphin, berberine chloride hydrate and polydiallyldimethyl ammonium chloride;

the carbon material is one or more than two of cobalt nitrogen porous carbon (HC), conductive carbon black, Super P and CNT;

the adhesive is as follows: solvent: 2D organic molecule: the mass-volume ratio of the carbon material is (10-40) mg: (60-90) mL: (0.2-3.5) mg: (50-80) mg, preferably 30 mg: 85 mL: (0.3-1.5) mg: 60 mg.

The step 1 of the invention specifically comprises the following steps: dispersing a binder in N-methyl pyrrolidone to obtain a uniform solution, adding absolute ethyl alcohol, 2D organic molecules and a carbon material, adding the mixture, preferably mixing under an ultrasonic condition, to obtain a mixture; the ultrasonic time is 0.5-3 h.

In step 2 of the invention, the diaphragm is a commercial diaphragm PP;

the vacuum filtration time is 5-10 min; the drying is air blast drying, and the drying temperature is 50-80 ℃.

The invention also provides application of the modified diaphragm or the modified diaphragm prepared by the preparation method in a lithium-sulfur battery.

The invention also provides a lithium-sulfur button cell, which comprises the modified diaphragm or the modified diaphragm prepared by the preparation method.

The lithium-sulfur button cell provided by the invention has excellent cycle performance and rate capability.

The lithium-sulfur button cell also specifically comprises the electrode plate, a lithium metal sheet, electrolyte, a modified diaphragm, foamed nickel, a positive electrode shell and a negative electrode shell. The structure of the lithium-sulfur button cell is the prior art, and the structure of the lithium-sulfur button cell is not particularly limited by the invention.

According to the technical scheme, the invention has the following advantages:

the invention provides a modified diaphragm material which is formed by compounding 2D organic molecules and a carbon material. The carbon material in the modified diaphragm material is beneficial to electronic and ionic conductivity, and can play a role in slowing down the loss of sulfur in the charge-discharge process in a physical confinement manner; the 2D organic molecules in the modified membrane material are capable of adsorbing polysulfides to prevent shuttling thereof, while at the same time being capable of catalyzing the conversion of polysulfides to insoluble Li₂S increases the reaction kinetics. The carbon material and the 2D organic molecules in the modified diaphragm material have synergistic effect, so that the battery has excellent electrochemical performance.

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 described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a flow chart illustrating the preparation of a modified separator according to example 1 of the present invention;

FIG. 2 is an SEM image of a modified membrane prepared in example 1 of the present invention;

FIG. 3 is a CV comparison graph of lithium sulfur button cells made from different separators of example 5 of the present invention;

FIG. 4 is a graph of mass capacity versus cycle number for lithium sulfur button cells made with different separators according to example 5 of the present invention at different rates;

FIG. 5 is a graph comparing the cycling performance at 2C current density for lithium sulfur button cells made with different separators of example 5 of the present invention;

FIG. 6 shows the high sulfur loading of 2.3mg/cm for Li-S button cell made of different separators according to example 5 of the present invention at 1C current density²A cycle performance map of (a); (ii) a

FIG. 7 shows that the lithium-sulfur button cell prepared from the modified membrane of example 1 has a high sulfur load of 5.3mg/cm at a current density of 0.1C²A cycle performance map of (a);

FIG. 8 shows that the lithium-sulfur button cell prepared from the modified membrane of example 1 has a high sulfur load of 6.2mg/cm at a current density of 0.1C²、7.6mg/cm²And 8.9mg/cm²Cycle performance map of (c).

Detailed Description

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it should be apparent that the embodiments described below are only a part of the embodiments of the present invention, and not all 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.

Example 1

The embodiment is a preparation method of an organic matter PDDA composite carbon material modified diaphragm, and the preparation method specifically comprises the following steps:

dispersing 30mg of polyvinylidene fluoride in 5ml of N-methyl pyrrolidone, and stirring for 30 minutes to obtain a uniform solution; then adding 80 ml of absolute ethyl alcohol, 1.5 ml of poly (diallyldimethylammonium chloride) (PDDA) and 60mg of cobalt-nitrogen porous carbon (HC) material into the solution, carrying out ultrasonic treatment for 2 hours (the ultrasonic power is 80W) to obtain a uniform solution, carrying out vacuum filtration on 1.5 ml of the mixture solution, carrying out suction filtration on a commercial diaphragm PP (diameter: 19mm), and then carrying out forced air drying at 60 ℃ for 24 hours to obtain an organic matter PDDA composite carbon material modified diaphragm;

fig. 1 is a flow chart of the preparation of the modified separator of this example. It can be seen from fig. 1 that the organic PDDA composite carbon material exhibits black carbon material characteristics on one side of the commercial separator, and the other side is the color of the commercial separator itself.

Fig. 2 is an SEM image of the modified membrane prepared in this example, and the top right corner of fig. 2 is a folded physical image of the organic PDDA composite carbon material. As can be seen from fig. 2, the organic PDDA composite carbon material is attached to the separator, and the separator has good toughness in the folded state from the upper right corner. In addition, the cross-sectional SEM images revealed that the material attached to the membrane was about 15 microns thick.

Example 2

The embodiment is a preparation method of a chenodeoxycholic acid CA composite carbon material modified diaphragm, which comprises the following steps:

dispersing 30mg of polyvinylidene fluoride in 5ml of N-methyl pyrrolidone, and stirring for 30 minutes to obtain a uniform solution; and then adding 80 ml of absolute ethyl alcohol, 0.3mg of chenodeoxycholic acid and 60mg of cobalt-nitrogen porous carbon material into the solution, carrying out ultrasonic treatment for 2 hours (the ultrasonic power is 80W) to obtain a uniform solution, carrying out vacuum filtration on 1.5 ml of the solution by a commercial diaphragm PP (diameter: 19mm), and then carrying out forced air drying at 60 ℃ for 24 hours to obtain the organic CA composite carbon material modified diaphragm.

Example 3

Preparing a TTBA modified diaphragm of a meso-tetra (4-carboxyphenyl) porphin composite carbon material:

dispersing 30mg of polyvinylidene fluoride in 5ml of N-methyl pyrrolidone, and stirring for 30 minutes to obtain a uniform solution; and then adding 80 ml of absolute ethyl alcohol, 0.3mg of meso-tetra (4-carboxyphenyl) porphine and 60mg of cobalt-nitrogen porous carbon material into the solution, carrying out ultrasonic treatment for 2 hours (the ultrasonic power is 80W) to obtain a uniform solution, carrying out vacuum filtration on 1.5 ml of the solution, carrying out suction filtration on a commercial diaphragm PP (diameter: 19mm), and then carrying out forced air drying at the temperature of 60 ℃ for 24 hours to obtain the diaphragm modified by the organic TTBA composite carbon material.

Example 4

Preparing a modified diaphragm of a BCH composite carbon material of berberine chloride hydrate:

dispersing 30mg of polyvinylidene fluoride in 5ml of N-methyl pyrrolidone, and stirring for 30 minutes to obtain a uniform solution; and then adding 80 ml of absolute ethyl alcohol, 0.3mg of berberine chloride hydrate and 60mg of cobalt-nitrogen porous carbon material into the solution, performing ultrasonic treatment for 2 hours (the ultrasonic power is 80W) to obtain a uniform solution, performing vacuum filtration on 1.5 ml of the solution by using a commercial diaphragm PP (diameter: 19mm), and performing forced air drying at 60 ℃ for 24 hours to obtain the organic matter composite carbon material modified diaphragm.

Comparative example 1

The comparative example is the preparation of the carbon material modified diaphragm, and the specific preparation steps are as follows:

dispersing 30mg of polyvinylidene fluoride in 5ml of N-methyl pyrrolidone, and stirring for 30 minutes to obtain a uniform solution; subsequently, 80 ml of anhydrous ethanol and 60mg of cobalt nitrogen porous carbon material were added to the above solution, and subjected to ultrasonication for 2 hours (ultrasonic power: 80W) to obtain a uniform solution, and 1.5 ml of the solution was suction-filtered under vacuum filtration onto a commercial separator PP (diameter: 19mm), followed by forced air drying at 60 ℃ for 24 hours to obtain a separator modified with a carbon material.

Example 5

This example is a preparation of a lithium-sulfur button cell, which includes the following specific steps:

in the waterless and anaerobic glove box, the opening of the positive electrode shell of the button cell is upward, the button cell is horizontally placed on a base plate, and a positive plate is placed in the center of the positive electrode shell; then 10 microliter of electrolyte (1.0M lithium bis (trifluoromethanesulfonimide) dissolved in DME/DOL at a volume ratio of 1:1 and containing 0.2 MLiNO) is added dropwise by using a pipette gun₃) Infiltrating the surface of the positive plate; clamping a diaphragm and covering the positive plate; dripping 10 microliter of electrolyte again to wet the surface of the diaphragm; clamping a metal lithium sheet in the center of the diaphragm; padding foam nickel; and covering the negative electrode shell and sealing to obtain the lithium-sulfur button cell.

The membranes described in this example are commercial membranes PP, modified membranes prepared in examples 1-5 and comparative example 1.

The CV and mass capacity-cycle number test results of the lithium-sulfur button cell prepared in this embodiment at different multiplying powers are shown in fig. 3 to 4.

FIG. 3 is a CV comparison chart of lithium-sulfur button cells prepared from different separators of this example (test conditions: 25 ℃, charging/discharging interval: 1.8-2.7V, sweep rate: 0.1mV s)^-1) Wherein plot a includes plots of the polarization values for peak B and peak C from CV. As can be seen from fig. 3, in example 1, as the polarization value of the battery after the modification of the separator is decreased, particularly, the polarization of the separator modified by the carbon material of BCH and PDDA composite is minimized, the conversion capability of polysulfide is increased, which may be related to the positively charged amino group of the organic matter.

Fig. 4 is a graph of mass capacity versus cycle number of lithium-sulfur button cells prepared from different separators of the present example under different multiplying factors (test conditions: 25 ℃, charging and discharging intervals: 1.8-2.7V, under 0.2, 0.4, 1, 2, 3, 5, and 10C conditions, wherein 1C is 1675 mAh/g). As can be seen from fig. 4, the separator modified with the carbon material of PDDA composite in particular had the best rate performance after modification of the separator.

Fig. 5 is a graph showing the comparison of the cycling performance of the lithium-sulfur button cell prepared by different separators of the embodiment at a current density of 2C, wherein the graph includes a graph of capacity versus cycle number and a graph of coulombic efficiency versus cycle number (under the test condition: 25 ℃, the charging and discharging interval: 1.8-2.7V, wherein 1C is 1675 mAh/g). As can be seen in fig. 5, the PDDA composite carbon material modified separator produced a lithium sulfur button cell that exhibited the best cycling performance at 2C current density compared to the pure commercial separator and the carbon material modified separator of comparative example 1 for example 1.

FIG. 6 shows the high sulfur loading of 2.3mg/cm for lithium sulfur button cell made with modified separator of example 1 at 1C current density²The cycle performance diagram of (1) comprises a capacity-cycle number diagram and coulombic efficiency-cycle number (test conditions: 25 ℃, charge-discharge interval: 1.8-2.7V, wherein 1C is 1675 mAh/g). As can be seen from FIG. 6, the PDDA composite carbon material modified separator is used to prepare the lithium-sulfur button cell with high sulfur load of 2.3mg/cm²The cycling of the cell at 1C current density was relatively stable.

FIG. 7 shows the high sulfur loading of 5.3mg/cm for lithium sulfur button cell made with modified separator of example 1 at 0.1C current density²The cycle performance diagram of (1) comprises an area capacity-cycle frequency diagram and coulombic efficiency-cycle frequency (test conditions: 25 ℃, charge-discharge interval: 1.8-2.7V, wherein 1C is 1675 mAh/g). As can be seen from FIG. 7, the high sulfur loading of 5.3mg/cm for the lithium-sulfur button cell prepared from the PDDA composite carbon material modified separator is high at the current density of 0.1C²The cell exhibited a relatively high area capacity over 200 cycles.

FIG. 8 shows high sulfur loadings of 6.2, 7.6, and 8.9mg/cm at 0.1C current density for lithium sulfur button cells made with modified separator of example 1²The cycle performance diagram of (1) comprises an area capacity-cycle frequency diagram and coulombic efficiency-cycle frequency (test conditions: 25 ℃, charge-discharge interval: 1.8-2.7V, wherein 1C is 1675 mAh/g). As can be seen from FIG. 8, the high sulfur loading of 6.2mg/cm for the lithium-sulfur button cell prepared from the PDDA composite carbon material modified separator is 6.2mg/cm at the current density of 0.1C²、7.6mg/cm²And 8.9mg/cm²The cell exhibited a relatively high area capacity after 80 cycles.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.