阅读说明：本技术 隔膜和电池 (Separator and battery ) 是由 彭冲 李俊义 徐延铭 于 2021-08-30 设计创作，主要内容包括：本发明提供一种隔膜和电池,其中,所述隔膜包括基材膜和第一涂层,所述第一涂层位于所述基材膜的第一侧,所述第一涂层包括导电剂、金属有机骨架化合物材料和粘结剂。本发明解决了隔膜中所吸附的多硫化物的重复利用率较低的问题。(The invention provides a diaphragm and a battery, wherein the diaphragm comprises a substrate film and a first coating, the first coating is positioned on the first side of the substrate film, and the first coating comprises a conductive agent, a metal organic framework compound material and a binder. The invention solves the problem of low recycling rate of polysulfide adsorbed in the diaphragm.)

1. A separator comprising a substrate film and a first coating layer on a first side of the substrate film, the first coating layer comprising a conductive agent, a metal organic framework compound material, and a binder.

2. A separator as claimed in claim 1, further comprising a second coating on the side of the first coating remote from the substrate film, the second coating being a high molecular polymer coating.

3. The separator of claim 2, wherein the second coating layer has a thickness in the range of 1nm to 200 nm.

4. The membrane of claim 1, further comprising a third coating on a second side of the substrate film, wherein the first and second sides are opposite sides of the substrate film, and wherein the third coating is a high molecular polymer coating.

5. The separator according to claim 4, wherein the thickness of the high molecular polymer coating layer is in the range of 1nm to 200 nm.

6. The membrane according to claim 1, characterized in that said MOFs materials have a specific surface area in the range of 100m²/g～6000m²/g。

7. The membrane according to claim 1, wherein the MOFs material has a pore size in the range of 0.1nm to 50 nm.

8. The separator of claim 1, wherein the first coating has a thickness in the range of 49nm to 300 nm.

9. A battery comprising a positive electrode sheet, a negative electrode sheet, and the separator according to any one of claims 1 to 8, said separator being located between said positive electrode sheet and said negative electrode sheet, said first coating layer being disposed adjacent to said positive electrode sheet, and said substrate film being disposed adjacent to said negative electrode sheet.

10. The battery of claim 9, wherein the battery is a lithium sulfur battery.

Technical Field

The invention relates to the technical field of lithium batteries, in particular to a diaphragm and a battery.

Background

During the charging and discharging processes of the lithium sulfur battery, the shuttling effect of polysulfide can cause the attenuation of battery capacity, and the service life of the battery is influenced. In the prior art, a Metal Organic Framework (MOFs) material is generally coated on a substrate film of a separator, and a polysulfide is adsorbed on the MOFs material to suppress a shuttling effect of the polysulfide.

However, since the conductivity of the MOFs material is poor, the polysulfide adsorbed in the MOFs material is difficult to undergo redox reaction, so that the recycling rate of the polysulfide adsorbed in the separator is low, resulting in much attenuation of the battery capacity, which affects the service life of the battery.

Disclosure of Invention

The embodiment of the invention provides a diaphragm and a battery, and aims to solve the problem that the recycling rate of polysulfide adsorbed in the diaphragm is low.

The embodiment of the invention provides a diaphragm which comprises a substrate film and a first coating, wherein the first coating is positioned on the first side of the substrate film, and the first coating comprises a conductive agent, a metal organic framework compound MOFs material and a binder.

Optionally, the separator further comprises a second coating layer, the second coating layer is positioned on the side of the first coating layer far away from the substrate film, and the second coating layer is a high molecular polymer coating layer.

Optionally, the second coating has a thickness in the range of 1nm to 200 nm.

Optionally, the separator further comprises a third coating layer on the second side of the substrate film, wherein the first side and the second side are opposite sides of the substrate film, and the third coating layer is a high molecular polymer coating layer.

Optionally, the thickness of the high molecular polymer coating ranges from 1nm to 200 nm.

Optionally, the specific surface area of the MOFs material is in the range of 100m²/g～6000m²/g。

Optionally, the pore size of the MOFs material ranges from 0.1nm to 50 nm.

Optionally, the first coating has a thickness in the range of 49nm to 300 nm.

The embodiment of the invention also provides a battery, which comprises a positive plate, a negative plate and the diaphragm, wherein the diaphragm is positioned between the positive plate and the negative plate, the first coating is arranged close to the positive plate, and the substrate film is arranged close to the negative plate.

Optionally, the battery is a lithium sulfur battery.

In this embodiment, the first coating includes a conductive agent and a MOFs material. MOFs materials can adsorb polysulfides and the conductive agent increases the conductivity of the MOFs material, i.e. the conductivity of the first coating. Therefore, the ratio of the active elements participating in the oxidation-reduction reaction in the polysulfides adsorbed on the MOFs is increased, and the active elements participating in the oxidation-reduction reaction can be reused. Therefore, through the arrangement of the first coating, the repeated utilization rate of polysulfide adsorbed in the diaphragm is improved, the internal resistance of the battery is reduced, and the service life of the battery is prolonged.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a schematic diagram of a diaphragm provided in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a diaphragm provided in accordance with another embodiment of the present invention;

fig. 3 is a structural schematic diagram of a first coating under a scanning electron microscope according to an embodiment of the present invention.

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 some, not all, embodiments of the present invention. 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.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.

As shown in fig. 1 to 3, an embodiment of the present invention provides a separator, including a substrate film 10 and a first coating layer 11, where the first coating layer 11 is located on a first side of the substrate film 10, and the first coating layer 11 includes a conductive agent, a metal organic framework compound MOFs material, and a binder.

It should be understood that the specific structure of the MOFs materials is not limited herein. For example, in some embodiments, the MOFs material is prepared from N, N-dimethylformamide, absolute ethanol and deionized water, a metal salt, and 1,3, 5-benzenetricarboxylic acid.

In this embodiment, the structure of the conductive agent is not limited herein. For example, in some embodiments, the conductive agent is at least one of ketjen black, Super-p, acetylene black, fullerene, nanoporous carbon, carbon nanotubes, graphene.

In the present embodiment, the first coating layer 11 includes a conductive agent and a MOFs material. The MOFs material can adsorb polysulfides and the conductive agent increases the conductive capacity of the MOFs material, i.e. the conductive capacity of the first coating 11. Therefore, the ratio of the active elements participating in the oxidation-reduction reaction in the polysulfides adsorbed on the MOFs is increased, and the active elements participating in the oxidation-reduction reaction can be reused. Therefore, through the arrangement of the first coating layer 11, the recycling rate of polysulfide adsorbed in the diaphragm is improved, the internal resistance of the battery is reduced, and the service life of the battery is prolonged.

Optionally, the separator further comprises a second coating layer 12, the second coating layer 12 is located on the side of the first coating layer 11 away from the substrate film 10, and the second coating layer 12 is a high molecular polymer coating layer.

It is to be understood that the separator is generally applied to a battery of a lithium sulfur battery, disposed between a positive electrode tab and a negative electrode tab. The lithium sulfur battery has large volume expansion in the circulation process, and a gap exists between the diaphragm and the positive plate or the negative plate.

Under the condition that the diaphragm is provided with the second coating 12 and the second coating 12 is arranged close to the positive plate, the connection strength between the second coating 12 and the positive plate can be improved due to the fact that the high polymer coating is high in viscosity. On one hand, the influence of cell deformation caused by volume expansion on the performance of the battery can be reduced. On the other hand, by improving the connection stability between the positive plate and the separator, the conduction between the positive plate and the first coating layer 11 can be stabilized, so that polysulfide adsorbed in the first coating layer 11 can smoothly participate in redox reaction.

In this embodiment, the separator further comprises a second coating 12. Through the setting of the second coating 12, the viscosity of the diaphragm is improved, so that the connection stability of the diaphragm and the positive plate or the negative plate is improved, and the probability of gaps between the diaphragm and the positive plate or the negative plate is avoided. Thus, the probability that polysulfides in the first coating layer 11 cannot participate in redox reactions due to the absence of a conductive loop is reduced.

Optionally, in some embodiments, the second coating 12 has a thickness in the range of 1nm to 200 nm.

Optionally, the separator further includes a third coating layer 13, the third coating layer 13 is located on a second side of the substrate film 10, wherein the first side and the second side are two opposite sides of the substrate film 10, and the third coating layer 13 is a high molecular polymer coating layer.

It is to be understood that the second coating layer 12 is a high molecular polymer coating layer and the third coating layer 13 is a high molecular polymer coating layer. The specific structure of the high molecular polymer coating is not limited herein. The second coating layer 12 and the third coating layer 13 may be the same or different high molecular polymer coating layers. As shown in fig. 2, the separator generally includes a second coating layer 12 and a third coating layer 13, and in a specific implementation, the second coating layer 12 and the third coating layer 13 generally have the same structure for ease of fabrication.

The diaphragm is equipped with third coating 13, just third coating 13 is close to under the condition that the negative pole piece set up, because the viscidity of high molecular polymer coating is stronger, can improve third coating 13 with the connection stability of negative pole piece to avoid diaphragm and negative pole interface break away from and the lithium dendrite growth that the extension of lithium ion migration route that leads to arouses, promote the security performance of battery.

In this embodiment, the separator further comprises a third coating layer 13. Through the arrangement of the third coating layer 13, the connection stability of the diaphragm and the positive plate or the negative plate is improved, the probability of growth of lithium dendrites caused by prolonging of a lithium ion migration path due to a gap between the diaphragm and the negative plate is reduced, and the stability of the battery is improved.

Optionally, in some embodiments, the thickness of the high molecular polymer coating ranges from 1nm to 200 nm.

Optionally, in some embodiments, the MOFs materials have a specific surface area in the range of 100m²/g～6000m²/g。

In specific implementation, the specific surface area of the MOFs material may be adjusted by adjusting the type and proportion of the raw materials for preparing the MOFs material, or may be adjusted by adjusting the reaction conditions for preparing the MOFs material.

In the embodiment, the specific surface area of the MOFs material is in the range of 100m²/g～6000m²The specific surface area of the MOFs material in the embodiment is high, so that the adsorption effect of the MOFs material on polysulfide is improved, the loss of polysulfide adsorbed in the diaphragm is further reduced, and the service life of the battery is prolonged.

Optionally, in some embodiments, the pore size of the MOFs material ranges from 0.1nm to 50 nm.

In specific implementation, the pore size of the MOFs material may be adjusted by adjusting the type and proportion of the raw materials for preparing the MOFs material, or may be adjusted by adjusting the reaction conditions for preparing the MOFs material.

In this embodiment, the pore size range of the MOFs material is 0.1nm to 50nm, and since the pore size of the MOFs material in this embodiment is small, ions with different particle sizes can be screened, so that the adsorption effect of the MOFs material on polysulfides is improved, the shuttle inhibition effect on polysulfides is improved, the loss of the polysulfides adsorbed in the separator is further reduced, and the service life of the battery is improved.

Optionally, in some embodiments, the thickness of the first coating layer 11 ranges from 49nm to 300 nm.

The embodiment of the invention also provides a battery, which comprises a positive plate, a negative plate and the diaphragm, wherein the diaphragm is positioned between the positive plate and the negative plate, the first coating layer 11 is arranged close to the positive plate, and the base material film 10 is arranged close to the negative plate.

It will be appreciated that in particular implementations, the battery also includes an electrolyte. The electrolyte is filled between the diaphragm and the positive plate and between the diaphragm and the negative plate.

Optionally, in some embodiments, the battery is a lithium sulfur battery.

In this embodiment, the diaphragm is the diaphragm in the above embodiment, and the specific structure may refer to the description in the above embodiment, which is not described herein again. Since the separator in the above embodiment is employed in the present embodiment, the present embodiment provides a battery having all the advantageous effects of the separator in the above embodiment.

The preparation methods of the separator and the battery provided in this example were as follows:

and preparing the MOFs material.

MOFs are crystalline porous materials with periodic network structures formed by connecting inorganic metal centers (metal ions or metal clusters) and bridged organic ligands with each other through self-assembly. MOFs are an organic-inorganic hybrid material, which in some embodiments may also be referred to as coordination polymers. The specific structure of the MOFs is not limited herein. The structure of the MOFs materials is different according to the raw materials used, the preparation conditions, and the like. In specific implementation, the specific surface area and the pore size of the MOFs are adjusted by adjusting the raw materials and the preparation conditions.

In some embodiments, fabricating the MOFs material may include the steps of: mixing N, N-dimethylformamide, absolute ethyl alcohol and deionized water to obtain a corresponding mixture. Adding a metal salt and 1,3, 5-benzenetricarboxylic acid to the mixture to obtain a mixed solution. And putting the mixed solution into a reaction kettle, reacting at a preset temperature for a first preset time to obtain a suspension, and collecting the suspension after the processes of centrifuging, washing, drying and the like to obtain the MOFs material.

Optionally, in some embodiments, the metal salt is at least one of a soluble salt of cobalt, a soluble salt of copper, a soluble salt of zinc, a soluble salt of aluminum, a soluble salt of manganese, a soluble salt of iron, and a soluble salt of titanium.

Optionally, the preset temperature and the first preset time length may be set according to a time requirement. For example, in one embodiment, the predetermined temperature ranges from 50 ℃ to 400 ℃, and the first predetermined time period ranges from 0.1h to 24 h.

And mixing the MOFs material, the conductive agent and the binder to obtain a mixture.

And mixing the conductive agent, the binder and the MOFs material prepared in the step 101 to obtain a mixture.

Optionally, in some embodiments, the conductive agent is at least one of ketjen black, Super-p, acetylene black, fullerene, nanoporous carbon, carbon nanotube, graphene.

A solvent is added to the mixture to form a slurry.

In particular implementations, the mixture is typically a powdered material, and thus, coating is facilitated by adding a solvent to the mixture to form a slurry. Wherein different solvents may be selected according to the nature of the mixture. For example, the solvent is water or an organic solvent.

The slurry is applied to a first side of a substrate film 10 to form a first coating layer 11.

The slurry is applied to a first side of the substrate film 10, and the substrate film 10 is dried to form a coating of the slurry on the first side of the substrate film 10. For convenience, in the following description, the separator prepared in the above-described step is referred to as a base separator.

Optionally, in some embodiments, after the step of applying the slurry to the first side of the substrate film 10 to form the first coating layer 11, the method further includes:

a high molecular polymer coating layer is formed on at least one of the second side of the substrate film 10 and the side of the first coating layer 11 away from the substrate film 10.

Adding TRIS (hydroxymethyl) aminomethane into a hydrochloric acid solution to obtain a buffer solution, wherein the buffer solution is TRIS (hydroxymethyl) aminomethane hydrochloride (Tris-HCl) solution. Wherein, the amount of the tris can be adjusted according to actual requirements. Furthermore, the amount of the hydrochloric acid solution can be adjusted according to actual requirements, and the hydrogen ion concentration index of the buffer solution, that is, the PH value of the buffer solution can be adjusted by adjusting the amount of the hydrochloric acid solution. Preferably, the pH is in the range of 7 to 12.

And adding a dopamine monomer into the buffer solution, and stirring and dissolving to obtain a target solution. And placing the basic diaphragm in the target solution, keeping the basic diaphragm in the target solution for a second preset time length, and performing drying treatment to enable the target solution to form a high polymer coating on the second side of the base material film 10 and the side of the first coating 11 far away from the base material film 10. The second preset time length is not limited herein, and can be adjusted according to time requirements. In some embodiments, the second predetermined time period ranges from 1min to 10 h.

In particular implementations, the degree to which the base membrane is immersed in the target solution may be adjusted. For example, in the first case, the base membranes are all located in the target solution, and after the base membranes are kept for the second preset time period, the base membranes are dried. At this time, the polymer coating layer is formed on both sides of the base separator. In the second case, the second side of the substrate film 10 is immersed in the target solution, the side of the first coating layer 11 away from the substrate film 10 is located outside the target solution, and after the second preset time period, the substrate film is dried. At this time, the second side of the substrate film 10 is formed with the high molecular polymer coating layer. In a third case, the side of the first coating layer 11 away from the substrate film 10 is located in the target solution, and after the second preset time period is kept, the drying treatment is performed. At this time, the first coating layer 11 is formed with the high molecular polymer coating layer on the side away from the substrate film 10.

For better understanding of the present invention, the following description will be made of the effects of the preparation process of the separator and the application of the separator according to the present application by way of concrete implementation.

Comparative example

A lithium sulfur battery is manufactured using the substrate film 10. The electrochemical performance of the lithium-sulfur battery prepared in the comparative example was tested.

The test results are shown in the following table:

number of cycles	0	100	200	300
					Capacity retention rate	100％	70％	60％	55％

Example one

The structure of the separator provided in this embodiment is shown in fig. 2, and the separator provided in this embodiment includes a substrate film 10, a first coating layer 11, a second coating layer 12, and a third coating layer 13. The sum of the thicknesses of the first coating layer 11 and the second coating layer 12 is 2 μm, and the thickness of the third coating layer 13 is 100 nm. Wherein the first coating layer 11 is composed of Co-MOFs, KB and polyvinylidene fluoride (poly (vinylidene fluoride), PVDF), and the structure of the surface of the first coating layer 11 under a Scanning Electron Microscope (SEM) is shown in fig. 3.

The preparation method of the separator in this embodiment includes: mixing N, N-dimethylformamide, absolute ethyl alcohol and deionized water according to a volume ratio of 15: 1: 1, mixing, adding cobalt nitrate and 1,3, 5-benzenetricarboxylic acid to obtain a mixed solution, then putting the mixed solution into a reaction kettle, reacting for 5 hours at 120 ℃ to obtain a suspension, and collecting to obtain Co-MOFs material powder through the working procedures of centrifugation, washing, drying and the like; wherein the mass ratio of the cobalt nitrate to the 1,3, 5-benzenetricarboxylic acid is 4: 3.

mixing Co-MOFs material, KB and PVDF powder according to the weight ratio of 97.5: 1: 1.5, adding N-methylpyrrolidone (NMP), stirring and dispersing into slurry, coating the slurry on the first side of the base material film 10, and drying to obtain a basic diaphragm; wherein the viscosity of the slurry is 1500 mPas.

Tris-HCl buffer solution with concentration of 10mmol/L was prepared by adding Tris-hydroxymethyl aminomethane to hydrochloric acid solution, and pH was adjusted to 8.5.

And adding dopamine monomer with the concentration of 5g/L into the buffer solution, and stirring and dissolving to obtain a mixed solution.

And (3) placing the basic diaphragm obtained in the step into the mixed solution, standing for 30 minutes, and then taking out and drying to obtain the diaphragm.

A lithium sulfur battery was prepared using the separator provided in example one. The electrochemical performance of the lithium-sulfur battery prepared in example one was tested:

the test results are shown in the following table:

number of cycles	0	100	200	300
					Capacity retention rate	100％	95％	92％	90％

As a result of comparing the test results of the first embodiment with the test results of the comparative example, it was found that the capacity retention rate of the lithium-sulfur battery was high during the cycle after the first coating layer 11 was coated on the substrate film 10. Therefore, the first coating layer 11 is coated on the substrate film 10, so that the capacity loss of the lithium-sulfur battery in the cycle process can be reduced, and the service life of the lithium-sulfur battery can be prolonged.

Example two

The structure of the separator provided in this embodiment is shown in fig. 2, and the separator provided in this embodiment includes a substrate film 10, a first coating layer 11, a second coating layer 12, and a third coating layer 13. The sum of the thicknesses of the first coating layer 11 and the second coating layer 12 is 2 μm, and the thickness of the third coating layer 13 is 100 nm. Wherein the first coating 11 consists of Zn-MOFs, graphene and PVDF.

The preparation method of the separator in this embodiment includes: mixing N, N-dimethylformamide, absolute ethyl alcohol and deionized water according to a volume ratio of 13: 2: 2, mixing, adding cobalt nitrate and 1,3, 5-benzenetricarboxylic acid to obtain a mixed solution, then putting the mixed solution into a reaction kettle, reacting for 5 hours at 120 ℃ to obtain a suspension, and collecting Zn-MOFs material powder after the processes of centrifuging, washing, drying and the like; wherein the mass ratio of the zinc nitrate to the 1,3, 5-benzenetricarboxylic acid is 4: 3.

mixing Zn-MOFs material, graphene and PVDF powder according to the weight ratio of 97: 1: 2, adding NMP, stirring and dispersing into slurry, coating the slurry on the first side of the base material film 10, and drying to obtain the base diaphragm, wherein the viscosity of the slurry is 1300mPa & s.

Tris-HCl buffer solution with concentration of 10mmol/L was prepared by adding Tris-hydroxymethyl aminomethane to hydrochloric acid solution, and pH was adjusted to 9.5.

And adding dopamine monomer with the concentration of 10g/L into the buffer solution, and stirring and dissolving to obtain a mixed solution.

And (3) placing the basic diaphragm obtained in the step into the mixed solution, standing for 10 minutes, and then taking out and drying to obtain the diaphragm.

A lithium sulfur battery was prepared using the separator provided in example two. As can be seen from the test of the electrochemical performance of the lithium sulfur battery prepared in example two, the electrochemical performance of the lithium sulfur battery prepared in example two is similar to that of the lithium sulfur battery prepared in example one.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.