CN113140789B

CN113140789B - Recyclable self-repairing gel-state electrolyte and preparation method and application thereof

Info

Publication number: CN113140789B
Application number: CN202110435815.2A
Authority: CN
Inventors: 兰金叻; 孙卓凡; 杨小平; 于运花
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-04-22
Filing date: 2021-04-22
Publication date: 2022-09-09
Anticipated expiration: 2041-04-22
Also published as: CN113140789A

Abstract

The invention relates to a recoverable self-repairing gel-state electrolyte, a preparation method and application thereof, which solve the technical problems that the preparation method of the existing electrolyte requires harsh environment, single performance or higher use environment requirement, and the electrolyte contains epoxy resin and a cross-linking agent, wherein the epoxy resin is one or the combination of more of DGEBA, PEGDGE, DGEBF, DGEBS, EPS25 and EPS 70; the cross-linking agent is one or more of 4-AFD, 2-AFD, DTDA, MPD, DETA, DDM and IPD. The invention also provides a preparation method and application thereof. The invention can be used in the field of battery material preparation.

Description

Recyclable self-repairing gel-state electrolyte and preparation method and application thereof

Technical Field

The invention relates to a battery material, a preparation method and application thereof, in particular to a recyclable self-repairing gel-state electrolyte, a preparation method and application thereof.

Background

With the development of society, the market has higher requirements on the energy density of energy storage devices. Since lithium metal has a high specific capacity, a low electrode potential, and a low density, the lithium metal battery is considered as an ideal choice for the next-generation battery. However, the uncontrolled growth of lithium dendrites may cause a short circuit of the battery, thereby causing a safety accident that the liquid electrolyte burns and the battery explodes. Compared with liquid electrolytes, quasi-solid electrolytes can inhibit the growth of lithium dendrites, and play an important role in improving the safety of batteries.

In recent years, the research on self-healing materials is receiving more and more attention. Ordinary materials are gradually degraded and damaged in use. Compared with the prior art, the self-healing material has the self-healing capacity and the capacity of utilizing the external environment for healing, and has longer service life. Therefore, in order to improve safety and extend life, a self-healing material is used in the battery. When the battery is damaged by external collision, the self-repairing gel electrolyte can heal internal damage, so that the safety of the lithium battery is improved, and the service life of the lithium battery is prolonged.

The green sustainable development is always the goal of social development. However, gel-state electrolytes are difficult to dissolve in solvents as polymers, and an effective means for recycling has been lacking. Therefore, the current research on the recovery of the electrolyte is relatively rare, and it is necessary to develop a recyclable electrolyte.

The Chinese patent application with publication number CN112652814A discloses a self-repairing solid electrolyte, a preparation method and application thereof, wherein the preparation method comprises the following specific steps: s1, mixing the dissociated lithium salt compound with a solvent, and carrying out ultrasonic treatment to obtain a dissociation solution; s2, adding a self-repairing polymer, a cross-linking agent and lithium salt into the dissociation solution, uniformly mixing, and heating to react to obtain a self-repairing precursor solution; s3, placing the self-repairing precursor solution on a polytetrafluoroethylene plate to prepare a membrane, and drying in vacuum to obtain the self-repairing solid electrolyte. The preparation method adopted by the method has high requirements on the external environment, the electrolyte is sensitive to air, the reaction process needs to be carried out under the vacuum and oxygen-free condition, if the vacuum environment cannot be ensured during preparation, lithium salt in the electrolyte is oxidized and loses efficacy, and the electrolyte cannot play a role in promoting ion transmission in the battery. Meanwhile, the electrolyte prepared in the patent has low mechanical strength, can not effectively inhibit the growth of lithium dendrites, and improves the performance of the battery.

The Chinese patent with publication number CN112646209A discloses a double-network physical crosslinking ionic gel electrolyte system based on polyvinyl alcohol-poloxamer and a preparation method thereof, polyvinyl alcohol (PVA) is mixed with distilled water, sealed and then placed in a water bath at 80-100 ℃ for heating and stirring for 1-3h until the polyvinyl alcohol (PVA) is completely dissolved, thus obtaining a polyvinyl alcohol (PVA) solution; adding borax into deionized water under stirring to obtain borax solution; mixing Pluronic and sodium chloride (NaCl), adding polyvinyl alcohol (PVA) solution into the mixture, sealing, heating in water bath at 50-70 deg.C, and stirring for 1-3 hr to obtain sol system; adding a borax solution into the sol system, placing the sol system in a water bath at 50-70 ℃, heating and stirring for 1-3h, and standing for 20-30h to obtain a polyvinyl alcohol-poloxamer-based double-network physical cross-linking ionic gel electrolyte system (PVA-Pluronic P123-NaCl). The electrolyte prepared by the method is a reversible system constructed by dynamic borate ester bonds and hydrogen bonds, and the electrolyte constructed based on the method can show self-repairability only in specific environmentThe exchange reaction of, for example, a borate bond is very sensitive to the external pH, and only when the environment is acidic, there is H ₂ When O and the like exist, the material can generate reversible reaction, and self-repairing performance is embodied.

Chinese patent application publication No. CN111584945A discloses an all-solid battery. The all-solid battery comprises an electrode laminate having a positive electrode including a positive electrode layer, a negative electrode including a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a resin layer including a polymer having a structure crosslinked by bonding of a host molecule and a guest molecule and having a self-repairing function is disposed on at least a part of an end portion in a surface direction of the electrode laminate, a first region of the resin layer covering at least a part of an end portion in a surface direction of the positive electrode and a second region of the resin layer covering at least a part of an end portion in a surface direction of the solid electrolyte layer are bonded to each other before and after a predetermined confining pressure in a lamination direction is applied to the electrode laminate, and a third region of the resin layer covering at least a part of an end portion in a surface direction of the negative electrode and the second region are bonded to each other.

The resin prepared by the method only has self-repairing performance and no ion transmission function, can only be used as an intermediate layer between a battery and an electrolyte for bonding the battery and the electrolyte, improves the interface compatibility, and cannot be directly used as the electrolyte.

Disclosure of Invention

The invention aims to solve the technical problems of harsh preparation method requirement, single performance or higher use environment requirement of the existing material and method, and provides a recyclable self-repairing gel electrolyte with simple method and better performance, a preparation method and application thereof.

To this end, the invention provides a recoverable self-repairing gel state electrolyte, which contains epoxy resin and cross-linking agent, wherein the epoxy resin is one or more of DGEBA, PEGDGE, DGEBF, DGEBS, EPS25 and EPS 70; the cross-linking agent is one or more of 4-AFD, 2-AFD, DTDA, MPD, DETA, DDM and IPD.

The invention also provides a preparation method of the recyclable self-repairing gel electrolyte, which is characterized by comprising the following steps: (1) stirring and mixing the epoxy resin A and the epoxy resin B to obtain mixed solutions with different molar ratios; (2) adding a cross-linking agent and a pore-forming agent into the substance obtained in the step (1), and stirring and mixing to obtain a solution; (3) preparing the solution obtained in the step (2) into a film, soaking the film in a solvent, removing a pore-forming agent, and drying to obtain a dry electrolyte; (4) and (4) transferring the film prepared in the step (3) to a glove box to soak electrolyte, thus obtaining the gel-state electrolyte.

Preferably, the molar ratio of the epoxy resin A to the epoxy resin B in the step (1) is 1: (1-9), wherein the epoxy resin A and the epoxy resin B are respectively one or a combination of more of DGEBA, PEGDGE, DGEBF, DGEBS, EPS25 and EPS 70.

Preferably, in the step (2), the pore-forming agent is one or more of PEG200, PEG400, PEG600 and ESO.

Preferably, in the step (2), the mass ratio of the cross-linking agent to the epoxy resin is (0.5-2): 1, the mass ratio of the pore-forming agent to the epoxy resin is 1: (0.5-2).

Preferably, in the step (3), the mixed solution is cast on a polytetrafluoroethylene plate by using a casting method, a gasket is placed on the periphery of the mixed solution, another polytetrafluoroethylene plate is placed on the gasket to form a sandwich structure, and the sandwich structure is placed in a blast oven and is subjected to heat treatment at the temperature of 120 ℃ and 150 ℃ for 2 to 5 hours to obtain the film.

Preferably, in the step (3), the solvent is one or more of deionized water, absolute ethyl alcohol and acetone.

Preferably, in the step (4), the electrolyte contains an electrolyte lithium salt, an electrolyte solvent, and ethers.

Preferably, the electrolyte lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium bis (fluoroamide) imide and lithium bis (trifluoromethanesulfonamide) imide; the electrolyte solvent is one or a combination of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate; the ethers are one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

The invention also provides application of the recyclable self-repairing gel-state electrolyte as a battery material.

The invention has the following beneficial effects:

(1) the electrolyte with excellent self-repairing performance is obtained by using a plurality of epoxy resins with different performances and blending the epoxy resins in proportion; for an electrolyte system, the epoxy resin can be used for effectively improving the mechanical property of the electrolyte and simply and quickly constructing various dynamic networks, so that the electrolyte has excellent self-repairing performance. For example, using epoxy resin DGEBA, reversible chemical bonds can be introduced at the crosslinking points. When the molecular chain is broken due to the damage of the material, the chemical bonds at the cross-linking points generate reversible reaction to reconnect the broken molecular chain and repair the damage of the material. When EPS25 is used, reversible chemical bonds in a cross-linked network exist in a main chain of a molecular chain, the movement capability of the molecular chain is enhanced under certain pressure or temperature, reversible reaction occurs between the molecular chains, and the damage of the material is repaired. Therefore, the invention introduces dynamic chemical bonds into the electrolyte system through the epoxy resin, and utilizes a dynamic network system which is not influenced by external environment and can be continuously carried out by reversible reaction to endow the electrolyte with self-repairability and recyclability, thereby improving the safety and the service life of the battery in the using process and providing a green recyclable electrolyte system.

(2) The invention utilizes the characteristic of reversible chemical bonds to convert epoxy resin which is difficult to dissolve in a solvent into a soluble substance, thereby obtaining the recyclable electrolyte.

Drawings

FIG. 1 is a graph of the infrared spectrum of the electrolyte in example 1 of the present invention;

FIG. 2 is a photograph showing the healing process of the electrolyte in example 2 of the present invention;

FIG. 3 is a graph showing the bulk impedance of the electrolyte prepared in examples 3 and 4 of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

(1) Mixing the components in a molar ratio of 1: DGEBA and PEGDGE of 1 were mixed with stirring.

(2) Adding the epoxy resin into the solution obtained in the step (1) in a mass ratio of 1: PEG200 of 2 and 1: 2-AFD, at 90 ℃ with stirring.

(3) And (2) casting the solution obtained in the step (1) on a polytetrafluoroethylene plate, placing a gasket on the periphery of the polytetrafluoroethylene plate, placing the other polytetrafluoroethylene plate on the gasket to form a sandwich structure, placing the sandwich structure in a blast oven, heating at 130 ℃ for 2 hours and at 150 ℃ for 2 hours to prepare a film, placing the film in deionized water, soaking for three days, and drying to obtain the unactivated electrolyte.

(4) The film was transferred to a glove box and immersed in an electrolyte (a mixed solution of lithium hexafluorophosphate doped dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate in a mass ratio of dimethyl carbonate to ethyl methyl carbonate to ethylene carbonate of 1:1:1, concentration 1M) for 24 hours. Finally obtaining the gel-state polymer electrolyte.

Example 2

(1) Mixing the components in a molar ratio of 1: 9 DGEBA and PEGDGE were mixed with stirring.

(2) Adding the epoxy resin into the solution obtained in the step (1) in a mass ratio of 1: PEG200 of 2 and 2: 1, 2-AFD, at 90 ℃ with stirring.

(4) The film was transferred to a glove box, and immersed in an electrolyte (a mixed solution of dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate doped with lithium hexafluorophosphate in a mass ratio of dimethyl carbonate to ethyl methyl carbonate to ethylene carbonate of 1:1:1, concentration 1M) for 24 hours. Finally obtaining the gel-state polymer electrolyte.

Example 3

(2) Adding an epoxy resin into the solution obtained in the step (1) in a mass ratio of 2: PEG200 and 2 of 1:1, 2-AFD, at 90 ℃ with stirring.

Example 4

(3) And (2) casting the solution obtained in the step (1) on a polytetrafluoroethylene plate, placing a gasket on the periphery of the polytetrafluoroethylene plate, placing the other polytetrafluoroethylene plate on the gasket to form a sandwich structure, placing the sandwich structure in a blast oven, heating at 120 ℃ for 2.5 hours and at 150 ℃ for 2 hours to prepare a film, placing the film in deionized water, soaking for three days, and drying to obtain the unactivated electrolyte.

Example 5

(2) Adding an epoxy resin into the solution obtained in the step (1) in a mass ratio of 2: ESO of 1 and 2: 1, 2-AFD, at 90 ℃ with stirring.

(3) And (2) casting the solution obtained in the step (1) on a polytetrafluoroethylene plate, placing a gasket on the periphery of the polytetrafluoroethylene plate, placing the other polytetrafluoroethylene plate on the gasket to form a sandwich structure, placing the sandwich structure in a blast oven, heating at 120 ℃ for 2.5 hours and at 150 ℃ for 2 hours to prepare a film, placing the film in absolute ethyl alcohol, soaking for three days, and drying to obtain the unactivated electrolyte.

Table 1 examples 1-5 varying experimental conditions and effects on electrolyte generation

As can be seen from table 1 above:

1. example 1 and example 2: compared with the electrolyte in the example 1, the electrolyte in the example 2 has lower external temperature and better self-repairing performance, but the mechanical performance is inferior to that in the example 1.

2. Example 2 and example 3: compared with the example 2, the electrolyte has the advantages that the quantity of the pore-forming agent is large, the ionic conductivity is larger, the electrochemical performance is better, but the number of pores in the electrolyte is increased, and the tensile strength is reduced.

3. Example 3 and example 4, two different reaction temperatures and times: the two methods can prepare the electrolyte, and the electrolyte performance is not obviously different.

4. Example 4 and example 5: compared with the embodiment 4, the pore-forming agent used in the embodiment 5 can generate pores with larger pore diameters, is beneficial to the electrolyte to adsorb the electrolyte, and has larger ionic conductivity, but the mechanical property is inferior to that of the embodiment 4.

Example 6

(1) The electrolyte in the embodiment 1 is subjected to electrochemical performance test, and the ionic conductivity of the electrolyte at room temperature can reach 10 ^-3 Meanwhile, the interface impedance is small, and the contact with the electrode interface is good.

(2) The electrolyte in example 1 was cut, healed, and mechanical properties and ionic conductivity tests were performed after 3 cycles, and the mechanical properties and ionic conductivity of the electrolyte were almost unchanged before and after the repair, indicating that the electrolyte was completely repaired and still able to be used in a battery.

(3) The electrolyte in example 1 is subjected to a battery cycle performance test, and compared with the change of performance before and after healing, the electrolyte can still stably circulate in the battery after being repaired, and after 50 cycles of circulation, the coulomb efficiency is as high as 98.9%.

(4) The electrolyte of example 1 was placed in an aqueous solution of TCEP/DMF and the electrolyte was completely dissolved at room temperature for 24 h.

The test result shows that the recyclable self-repairing gel-state electrolyte has excellent self-repairing performance, can improve the cycle performance of the battery, and has recyclability. The electrolyte can be used as a battery material in the fields of lithium ion batteries, lithium metal batteries and the like, and can be used in flexible batteries and green batteries.

Comparative example 1

The patent with publication number CN112652814A prepares a self-repairing solid electrolyte, and the specific preparation process is as follows: and mixing the dissociated lithium salt compound with a solvent, and performing ultrasonic treatment to obtain a dissociation solution. Adding a self-repairing polymer, a cross-linking agent and lithium salt into the dissociation liquid, uniformly mixing, heating to react to obtain a self-repairing precursor solution, placing the self-repairing precursor solution on a polytetrafluoroethylene plate for film making, and drying in vacuum to obtain the self-repairing solid electrolyte.

In terms of preparation technology, the preparation method adopted in patent CN112652814A requires a vacuum environment, while the preparation process of the electrolyte in the present invention can be performed in air, and the requirements on the external environment are not high. In the aspect of electrolyte performance, the tensile strength of the electrolyte in CN112652814A is only 0.24MPa, while the tensile strength of the electrolyte in the invention is as high as 13MPa, so that the uniform deposition of ions can be effectively promoted, and the safety of the battery is improved. Meanwhile, the electrolyte has more excellent self-repairing performance, and can be completely repaired within 2 hours. In addition, the electrolyte prepared by the method has recoverability, can be dissolved in a solvent for recovery, and is green and recyclable in the whole production, use and recovery process.

However, the above description is only exemplary of the present invention, and the scope of the present invention should not be limited thereby, and the replacement of the equivalent components or the equivalent changes and modifications made according to the protection scope of the present invention should be covered by the claims of the present invention.

Claims

1. A preparation method of a recyclable self-repairing gel state electrolyte comprises an epoxy resin and a cross-linking agent, wherein the epoxy resin is one or more of DGEBA and PEGDGE; the cross-linking agent is 2-AFD; the method is characterized by comprising the following steps: (1) stirring and mixing the epoxy resin A and the epoxy resin B to obtain mixed solutions with different molar ratios; the molar ratio of the epoxy resin A to the epoxy resin B is 1: (1-9), wherein the epoxy resin A and the epoxy resin B are respectively one or more of DGEBA and PEGDGE; (2) adding a cross-linking agent and a pore-forming agent into the substance obtained in the step (1), and stirring and mixing to obtain a solution; the pore-forming agent is one or a combination of more of PEG200 and ESO; the mass ratio of the cross-linking agent to the epoxy resin is (0.5-2): 1, the mass ratio of the pore-forming agent to the epoxy resin is 1: (0.5 to 2); (3) casting the mixed solution obtained in the step (2) on a polytetrafluoroethylene plate by using a casting method, placing gaskets on the periphery of the mixed solution, placing the other polytetrafluoroethylene plate on the gaskets to form a sandwich structure, placing the sandwich structure in a blast oven, and carrying out heat treatment for 2-5 hours at 120-150 ℃ to obtain a film; soaking the prepared film in a solvent, removing a pore-forming agent, and drying to obtain a dry electrolyte; the solvent is one or a combination of more of deionized water, absolute ethyl alcohol and acetone; (4) and (4) transferring the film prepared in the step (3) to a glove box to soak electrolyte, so as to obtain the gel-state electrolyte.

2. The method for preparing the recyclable self-repairing gel state electrolyte as claimed in claim 1, wherein in the step (4), the electrolyte contains an electrolyte lithium salt, an electrolyte solvent and ethers.

3. The method for preparing the recyclable self-repairing gel-state electrolyte according to claim 2, wherein the electrolyte lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate, lithium bis (fluoroamide) imide and lithium bis (trifluoromethanesulfonamide) imide; the electrolyte solvent is one or a combination of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate; the ethers are one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.