A lithium metal battery eutectic gel electrolyte and its preparation method and application

Abstract

The present application discloses a eutectic gel electrolyte for lithium metal batteries and its preparation method and application, which belongs to the field of solid electrolytes. The eutectic gel electrolyte of the present invention is prepared by photocuring a photocurable precursor solution containing a photoinitiator, wherein the photocurable precursor solution contains a two-component liquid compound and a deep eutectic solvent; the two-component liquid compound contains 4-acryloylmorpholine and a photocurable polyethylene glycol derivative; the deep eutectic solvent is formed by a liquid mixture containing succinonitrile, lithium bis(trifluoromethylsulfonyl)imide and fluoroethylene carbonate. The eutectic gel electrolyte of the present invention is composed of a deep eutectic solvent having functional groups such as cyano and sulfonyloxy and a polymer electrolyte having functional groups such as etheroxy and a unique skeleton structure. It can give advantages such as high ionic conductivity, wide electrochemical window and high interface stability based on the interaction between functional groups and the spatial confinement of the polymer electrolyte skeleton structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolytes, and in particular relates to a eutectic gel electrolyte for lithium metal batteries, a preparation method thereof, and applications thereof. Background Art

[0002] With the widespread adoption of lithium-ion batteries in fields such as electric vehicles and portable electronics, higher demands are being placed on their energy density, cycle life, and safety. However, conventional commercial lithium-ion batteries generally use organic liquid electrolytes, which are inherently flammable and can easily cause battery fires and explosions, hindering the practical application of lithium metal batteries. Therefore, designing new electrolyte systems for lithium metal batteries with excellent safety and cycle stability has become a key issue.

[0003] Deep eutectic gel polymer electrolytes, formed by introducing deep eutectic solvents as plasticizers into gel polymer electrolytes, have become a promising new electrolyte system due to their advantages such as high ionic conductivity, good interfacial compatibility, and high safety. However, due to the limited matching selectivity between the polymer matrix and the deep eutectic solvent, there are relatively few deep eutectic gel polymer electrolytes that can simultaneously meet the requirements of high ionic conductivity, a wide electrochemical window, and good interfacial stability.

[0004] Therefore, it is urgent to develop and design a deep eutectic gel polymer electrolyte with high ionic conductivity, wide electrochemical window and interface stability. Summary of the Invention

[0005] The present application discloses a eutectic gel electrolyte for lithium metal batteries, its preparation method and application. By optimizing the design of the polymer matrix and introducing a specifically matched deep eutectic solvent, the efficient preparation and universal application of eutectic gel electrolyte for lithium metal batteries with high ionic conductivity, wide electrochemical window and interface stability are effectively achieved.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] In a first aspect, the present application provides a lithium metal battery eutectic gel electrolyte, which is prepared by photocuring a photocurable precursor solution containing a photoinitiator; wherein,

[0008] The photocurable precursor solution comprises a two-component liquid compound and a deep eutectic solvent;

[0009] The two-component liquid compound comprises 4-acryloylmorpholine and a photocurable polyethylene glycol derivative;

[0010] The deep eutectic solvent is formed from a liquid mixture comprising succinonitrile, lithium bis(trifluoromethylsulfonyl)imide and fluoroethylene carbonate.

[0011] According to the lithium metal battery eutectic gel electrolyte disclosed herein, the photocurable polyethylene glycol derivative comprises at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polyethylene glycol methyl ether acrylate.

[0012] According to the lithium metal battery eutectic gel electrolyte disclosed herein, the molar ratio of the photocurable polyethylene glycol derivative to the 4-acryloylmorpholine is 0.005-0.01.

[0013] According to the lithium metal battery eutectic gel electrolyte disclosed herein, the mass ratio of the lithium bis(trifluoromethylsulfonyl)imide to the succinonitrile is 1:1-2.

[0014] According to the lithium metal battery eutectic gel electrolyte disclosed herein, the mass content of the fluoroethylene carbonate is 1 to 10 wt % of the sum of the mass of the succinonitrile and the lithium bis(trifluoromethylsulfonyl)imide.

[0015] According to the lithium metal battery eutectic gel electrolyte disclosed herein, the volume ratio of the two-component liquid compound and the deep eutectic solvent contained in the photocurable precursor solution is 50-85: 50-15.

[0016] According to the preparation method disclosed in the present application, the photoinitiator is any one of benzophenone, ethyl 2,4,6-trimethylbenzoylphosphonate, ethyl 4-dimethylaminobenzoate, and 2-hydroxy-2-methylpropiophenone.

[0017] The second aspect of the present application further provides a method for preparing the eutectic gel electrolyte for lithium metal batteries according to the present invention, which comprises the following steps:

[0018] Fluoroethylene carbonate is added to a liquid mixture of succinonitrile and lithium bis(trifluoromethylsulfonyl)imide to prepare a deep eutectic solvent;

[0019] adding the deep eutectic solvent to a two-component liquid compound of 4-acryloylmorpholine and a photocurable polyethylene glycol derivative, and mixing them uniformly to obtain a photocurable precursor solution;

[0020] A photoinitiator is added to the photocurable precursor solution and an ultraviolet curing reaction is carried out to obtain the lithium metal battery eutectic gel electrolyte.

[0021] The third aspect of the present application also provides a lithium metal solid-state battery, which comprises a positive electrode, a negative electrode and a solid electrolyte, wherein the solid electrolyte comprises the lithium metal battery eutectic gel electrolyte described in the present invention.

[0022] The fourth aspect of the present application further provides an electrical device, which at least includes the lithium metal solid-state battery described in the present invention.

[0023] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application include at least:

[0024] The present invention introduces a photocurable polyethylene glycol derivative into 4-acryloylmorpholine for cross-linking optimization to form a polymer electrolyte with a rigid-flexible skeleton structure and functional groups such as ether oxygen, and specifically matches it with a deep eutectic solvent with functional groups such as cyano and sulfonyl oxygen formed by succinonitrile, lithium bis(trifluoromethylsulfonyl)imide and fluoroethylene carbonate. On the one hand, the ratio of solvent molecules to free molecules can be synergistically controlled through the interaction of the specifically matching functional groups between the deep eutectic solvent and the polymer electrolyte and the spatial confinement of the polymer electrolyte skeleton structure, thereby effectively enhancing the Li + transmission capacity and improve the window voltage; on the other hand, the rigid-flexible skeleton structure of the polymer electrolyte can effectively improve stress adaptability and inhibit lithium dendrite puncture, thereby improving interface stability. Therefore, the present invention sets a polymer electrolyte with a rigid-flexible skeleton structure and introduces a deep eutectic solvent that specifically matches its functional groups for synergistic optimization. Not only does the prepared eutectic gel electrolyte have the advantages of high ionic conductivity, wide electrochemical window and high interface stability, but the eutectic gel electrolyte can be prepared and formed by ultraviolet light-induced polymerization, with the advantages of short reaction time, low energy consumption, strong controllability, high efficiency, etc. It is expected to meet the needs of high-performance and high-safety lithium metal batteries, and has broad commercial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some of the embodiments described in this application. Those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0026] Figure 1 This is a conductivity impedance diagram of the eutectic gel electrolyte film obtained in Example 1 of the present application;

[0027] Figure 2 This is an electrochemical window test diagram of the eutectic gel electrolyte film obtained in Example 1 of the present application;

[0028] Figure 3 This is the rate performance curve of the eutectic gel electrolyte film obtained in Example 1 of the present application;

[0029] Figure 4 This is the cycle performance curve of the eutectic gel electrolyte film obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] In the relevant descriptions of this application, the term "and / or" is used to describe the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural.

[0032] In the relevant description of this application, the term "at least one" refers to one or more, wherein "plurality" refers to two or more. "At least one of the following" or similar descriptions thereof refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of A, B or C", or "at least one of A, B and C" means one of A, B, C, or A+B, or A+C, or B+C, or A+B+C, wherein A, B, C can be single or multiple.

[0033] In the relevant description of this application, the order of serial numbers does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined based on its function and internal logic, and should not constitute a limitation on the implementation process of the present invention.

[0034] In the relevant description of this application, numerical ranges are also understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any intermediate value within a stated value or stated range and any other intermediate value within the stated range is also disclosed in this application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0035] Unless otherwise indicated, the technical / scientific terms used in this application have meanings and / or interpretations that are generally familiar to those of ordinary skill in the art. Although this application only describes possible materials and / or methods of the present invention, any materials and / or methods similar or equivalent to the present invention may also be used in the implementation or experiments disclosed in this application. In addition, all documents mentioned in this application are incorporated by reference to disclose and describe the materials and / or methods related to the documents. In the event of any conflict with any incorporated document, the technical content of the present invention shall prevail.

[0036] In a first aspect, the present application provides, by way of example, a eutectic gel electrolyte for a lithium metal battery. The eutectic gel electrolyte for a lithium metal battery according to an embodiment of the present invention is prepared by photocuring a photocurable precursor solution containing a photoinitiator. The photocurable precursor solution comprises a two-component liquid compound and a deep eutectic solvent; the two-component liquid compound comprises 4-acryloylmorpholine and a photocurable polyethylene glycol derivative; and the deep eutectic solvent is formed from a liquid mixture comprising succinonitrile, lithium bis(trifluoromethylsulfonyl)imide, and fluoroethylene carbonate.

[0037] The lithium metal battery eutectic gel electrolyte provided by the embodiment of the present invention is compounded by a deep eutectic solvent having functional groups such as cyano and sulfonyloxy and a polymer electrolyte having functional groups such as etheroxy. The cyano group contained in the deep eutectic solvent molecule can form a dipole-dipole interaction with the etheroxy group on the polymer electrolyte structure, effectively enhancing the interfacial compatibility and reducing the interfacial impedance. At the same time, the sulfonyloxy contained in the deep eutectic solvent and the Li + The strong coordination effect of the eutectic solvent effectively promotes the dissociation of lithium salts and interfacial charge transfer, and a continuous Li + transmission channel, effectively enhancing Li + transport capacity and impart a wide electrochemical window. At the same time, the rigid segment of 4-acryloylmorpholine and the flexible segment of photocurable polyethylene glycol derivatives can be cross-linked to form a polymer electrolyte with a rigid-flexible skeleton structure, which can not only effectively adapt to the infiltration and swelling of the deep eutectic solvent, but also trigger the contraction of the cross-linked network under overcharge / high temperature, physically blocking side reactions and effectively inhibiting the formation and puncture of lithium dendrites. Based on the above specific matching design of deep eutectic solvent and polymer electrolyte, and combining it with the dynamic adaptive interface of the rigid-flexible skeleton structure of the polymer electrolyte, the preparation of eutectic gel electrolyte with the performance requirements of high ionic conductivity, wide electrochemical window and high interface stability is effectively achieved, which is expected to meet the development needs of high-efficiency and high-safety lithium metal batteries and has broad commercial prospects.

[0038] In some specific embodiments, the photocurable polyethylene glycol derivative is preferably at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polyethylene glycol methyl ether acrylate. These polyethylene glycol derivatives not only possess a large number of polar sites, such as ether oxygen and possible residual acrylate groups, which facilitate interaction with highly polar eutectic solvents to enhance ion conduction, but also possess photosensitivity that allows them to form a rigid-flexible framework structure via photoinitiation, making their preparation simple and capable of optimizing the electrochemical performance of eutectic gel electrolytes.

[0039] In some specific embodiments, the molar ratio of the photocurable polyethylene glycol derivative to the 4-acryloylmorpholine is 0.005 to 0.01, and the optional molar ratio includes but is not limited to 0.005 and 0.01. Among them, the present invention can effectively optimize the skeleton structure of the formed polymer electrolyte by controlling the above molar ratio, thereby ensuring that the prepared eutectic gel electrolyte has excellent Li + transport capability and a wide electrochemical window.

[0040] In some specific embodiments, the mass ratio of the lithium bis(trifluoromethylsulfonyl)imide to the succinonitrile is 1:1-2, and the optional mass ratio includes but is not limited to 1:1.32, 1:1.5, 1:1.67, etc.

[0041] In some specific embodiments, the mass content of the fluoroethylene carbonate is preferably 1-10 wt % of the sum of the mass of succinonitrile and lithium bis(trifluoromethylsulfonyl)imide, and the optional mass content includes but is not limited to 1 wt %, 2 wt %, 5 wt %, 8 wt % and 10 wt %.

[0042] In some specific embodiments, the volume ratio of the two-component liquid compound and the deep eutectic solvent contained in the photocurable precursor solution is 50~85:50~15, and the optional volume ratio includes but is not limited to 50:50, 75:25 and 85:15.

[0043] In some specific embodiments, the photoinitiator is preferably any one of benzophenone, ethyl 2,4,6-trimethylbenzoylphosphonate, ethyl 4-dimethylaminobenzoate, and 2-hydroxy-2-methylpropiophenone. The present invention does not limit the amount of the photoinitiator and can be reasonably selected based on actual conditions. For example, in the embodiments of the present application, the mass ratio of the photoinitiator to 4-acryloylmorpholine is 1:78.6.

[0044] In a second aspect, the present application further provides a method for preparing a eutectic gel electrolyte for a lithium metal battery according to the present invention, the method comprising the steps of:

[0045] Fluoroethylene carbonate is added to a liquid mixture of succinonitrile and lithium bis(trifluoromethylsulfonyl)imide to prepare a deep eutectic solvent;

[0046] adding the deep eutectic solvent to a two-component liquid compound of 4-acryloylmorpholine and a photocurable polyethylene glycol derivative, and mixing them uniformly to obtain a photocurable precursor solution;

[0047] A photoinitiator is added to the photocurable precursor solution and an ultraviolet curing reaction is carried out to obtain the lithium metal battery eutectic gel electrolyte.

[0048] In a third aspect, the present application also provides a lithium metal solid-state battery using the lithium metal battery eutectic gel electrolyte of the present invention as an electrolyte, wherein the lithium metal solid-state battery comprises at least a positive electrode, a negative electrode, and the lithium metal battery eutectic gel electrolyte of the present invention. In particular, since the lithium metal battery eutectic gel electrolyte of the present invention has high ionic conductivity, a wide electrochemical window, and high interfacial stability, the lithium metal solid-state battery has high specific capacity, long cycle life, and extremely high safety.

[0049] Fourthly, this application also provides electrical devices using the lithium metal solid-state battery of the present invention. Specific electrical devices include, but are not limited to, electric vehicles, portable electronic products, and smart wearable devices. Portable electronic products include, but are not limited to, mobile audio terminals, tablet computers, and smartphones; smart wearable devices include, but are not limited to, Bluetooth headsets, AR / VR / MR smart glasses, wearable speakers, smart watches, smart bracelets, and smart detectors.

[0050] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0051] Example 1

[0052] This example provides a method for preparing a eutectic gel electrolyte for lithium metal batteries, the specific steps comprising:

[0053] S1-Preparation of deep eutectic solvent (1.32DES)

[0054] Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and succinonitrile (SN) in a mass ratio of 1:1.32 were added to a stirring flask, heated and stirred until a transparent liquid was formed, and then 5 wt% of fluoroethylene carbonate (FEC) equivalent to the total mass of the two was added and mixed thoroughly to obtain a deep eutectic solvent (1.32DES);

[0055] S2-Preparation of eutectic gel electrolyte

[0056] 0.039 g polyethylene glycol diacrylate (PEGDA, M w =1000g / mol) was added to 1.1g 4-acryloylmorpholine (ACMO, M w =141 g / mol) and heated and stirred to melt into a fully mixed two-component liquid compound, 1.32DES was first added at a volume ratio of the two-component liquid compound to the deep eutectic solvent of 75:25, and then 0.014 g of benzophenone was added and fully stirred and mixed. The resulting mixed solution was then evenly injected into a PET solid electrolyte mold and placed in a UV curing machine (wavelength 365 nm, power 400 W) for reaction for 20 minutes to obtain a eutectic gel electrolyte (1.32DES-ACMO 1.1 / PEGDA 0.039).

[0057] Example 2

[0058] This example provides a method for preparing a eutectic gel electrolyte for lithium metal batteries, the specific steps comprising:

[0059] S1-Preparation of deep eutectic solvent (1.67DES)

[0060] Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and succinonitrile (SN) in a mass ratio of 1:1.67 were added to a stirring flask, heated and stirred until a transparent liquid was formed, and then fluoroethylene carbonate (FEC) equivalent to 5 wt% of the mass of the FEC was added and mixed thoroughly to obtain a deep eutectic solvent (1.67DES);

[0061] S2-Preparation of eutectic gel electrolyte

[0062] 0.039 g polyethylene glycol diacrylate (PEGDA, M w =1000g / mol) was added to 1.1g 4-acryloylmorpholine (ACMO, M w =141 g / mol) and heated and stirred to melt into a fully mixed two-component liquid compound, 1.67DES was first added at a volume ratio of the two-component liquid compound to the deep eutectic solvent of 75:25, and then 0.014 g of benzophenone was added and fully stirred and mixed. The resulting mixed solution was then evenly injected into a PET solid electrolyte mold and placed in a UV curing machine (wavelength 365 nm, power 400 W) for reaction for 20 minutes to obtain a eutectic gel electrolyte (1.67DES-ACMO 1.1 / PEGDA 0.039 ).

[0063] Example 3

[0064] This example provides a method for preparing a eutectic gel electrolyte for lithium metal batteries, the specific steps comprising:

[0065] S1-Preparation of deep eutectic solvent (1.5DES)

[0066] Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and succinonitrile (SN) in a mass ratio of 1:1.5 were added to a stirring flask, heated and stirred until a transparent liquid was formed, and then fluoroethylene carbonate (FEC) equivalent to 5 wt% of the mass of the FEC was added and mixed thoroughly to obtain a deep eutectic solvent (1.5DES);

[0067] S2-Preparation of eutectic gel electrolyte

[0068] 0.039 g polyethylene glycol diacrylate (PEGDA, M w=1000g / mol) was added to 1.1g 4-acryloylmorpholine (ACMO, M w =141 g / mol) and heated and stirred to melt into a fully mixed two-component liquid compound, 1.5DES was first added at a volume ratio of the two-component liquid compound to the deep eutectic solvent of 75:25, and then 0.014 g of benzophenone was added and fully stirred and mixed. The resulting mixed solution was then evenly injected into a PET solid electrolyte mold and placed in a UV curing machine (wavelength 365 nm, power 400 W) for reaction for 20 minutes to obtain a eutectic gel electrolyte (1.5DES-ACMO 1.1 / PEGDA 0.039 ).

[0069] Example 4

[0070] This example provides a method for preparing a eutectic gel electrolyte for lithium metal batteries, the specific steps comprising:

[0071] S1-Preparation of deep eutectic solvent (1.5DES)

[0072] Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and succinonitrile (SN) in a mass ratio of 1:1.5 were added to a stirring flask, heated and stirred until a transparent liquid was formed, and then fluoroethylene carbonate (FEC) equivalent to 5 wt% of the mass of the FEC was added and mixed thoroughly to obtain a deep eutectic solvent (1.5DES);

[0073] S2-Preparation of eutectic gel electrolyte

[0074] 0.078 g polyethylene glycol diacrylate (PEGDA, M w =1000g / mol) was added to 1.1g 4-acryloylmorpholine (ACMO, M w =141 g / mol) and heated and stirred to melt into a fully mixed two-component liquid compound, 1.5DES was first added at a volume ratio of the two-component liquid compound to the deep eutectic solvent of 75:25, and then 0.014 g of benzophenone was added and fully stirred and mixed. The resulting mixed solution was then evenly injected into a PET solid electrolyte mold and placed in a UV curing machine (wavelength 365 nm, power 400 W) for reaction for 20 minutes to obtain a eutectic gel electrolyte (1.5DES-ACMO 1.1 / PEGDA 0.078 ).

[0075] Example 5

[0076] This example provides a method for preparing a eutectic gel electrolyte for lithium metal batteries, the specific steps comprising:

[0077] S1-Preparation of deep eutectic solvent (1.32DES)

[0078] Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and succinonitrile (SN) in a mass ratio of 1:1.32 were added to a stirring flask, heated and stirred until a transparent liquid was formed, and then 5 wt% of fluoroethylene carbonate (FEC) equivalent to the total mass of the two was added and mixed thoroughly to obtain a deep eutectic solvent (1.32DES);

[0079] S2-Preparation of eutectic gel electrolyte

[0080] 0.078 g polyethylene glycol dimethacrylate (PEGDMA, M w =2000g / mol) was added to 1.1g 4-acryloylmorpholine (ACMO, M w =141 g / mol) and heated and stirred to melt into a fully mixed two-component liquid compound, 1.32DES was added at a volume ratio of 75:25 between the two-component liquid compound and the deep eutectic solvent, and then 0.014 g of benzophenone was added and fully stirred and mixed. The resulting mixed solution was then evenly injected into a PET solid electrolyte mold and placed in a UV curing machine (wavelength 365 nm, power 400 W) for reaction for 20 minutes to obtain a eutectic gel electrolyte (1.32DES-ACMO 1.1 / PEGDMA 0.078 ).

[0081] In order to illustrate the performance effects of the eutectic gel electrolyte prepared in the examples of the present invention, the present application also provides comparative examples 1 to 3.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is:

[0084] In the step of preparing the eutectic gel electrolyte, 0.039 g of polyethylene glycol diacrylate (PEGDA, M w =1000g / mol) was replaced with 0.39g, and the rest was exactly the same as in Example 1.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is:

[0087] In the step of preparing the eutectic gel electrolyte, 0.039 g of polyethylene glycol diacrylate (PEGDA, M w =1000g / mol) is replaced by 0, and the rest is exactly the same as in Example 1.

[0088] Comparative Example 3

[0089] The difference between this comparative example and Example 1 is:

[0090] In the step of preparing the eutectic gel electrolyte, polyethylene glycol diacrylate was replaced with 1,6-hexanediol diacrylate (HDDA), wherein the molar ratio of 1,6-hexanediol diacrylate (HDDA) to 4-acryloylmorpholine was 1:2, and the rest was exactly the same as in Example 1.

[0091] Test Example 1: Ionic Conductivity

[0092] The eutectic gel electrolyte prepared in Example 1 was assembled into a stainless steel|electrolyte film|stainless steel button cell, and its electrochemical impedance spectroscopy was tested. The results were Figure 1 As shown. Among them, Figure 1 This is the electrochemical impedance spectroscopy of the eutectic gel electrolyte prepared in Example 1.

[0093] according to Figure 1 It can be seen that the eutectic gel electrolyte prepared in Example 1 has a relatively small electrochemical impedance in the temperature range of 30-80°C.

[0094] According to the above method, the electrochemical impedance spectra of the eutectic gel electrolytes prepared in Examples 2 and 5 and the molded products prepared in Comparative Examples 1 to 3 were tested respectively, and then the ionic conductivities were calculated and recorded in Table 1.

[0095] Table 1 - Ionic conductivity test results

[0096]

[0097] According to Table 1, the eutectic gel electrolytes prepared in Examples 1, 2, and 5 have the same order of magnitude of ionic conductivity and are significantly better than those in Comparative Examples 1 to 3, indicating that the present invention effectively improves the ionic conductivity by introducing 0.5 to 1 mol% of PEGDMA or PEGDA into 4-acryloylmorpholine for cross-linking optimization. The reason may be that 0.5 to 1 mol% of PEGDA / PEGDMA cross-links with ACMO to form a Li-ion-promoting barrier. + The continuous ether oxygen bond functional groups of the migrated polymer network can effectively enhance the Li + transport, making the eutectic gel electrolyte have the best ionic conductivity; when the molar amount of PEGDA is greater than 1 mol%, PEGDA and ACMO are excessively cross-linked to form a dense polymer network, making Li +The transmission path is blocked, resulting in a significant decrease in the ionic conductivity of the eutectic gel electrolyte. Therefore, the present invention preferably uses a molar ratio of photocurable polyethylene glycol derivatives to 4-acryloylmorpholine of 0.005 to 0.01 to ensure that the eutectic gel electrolyte has high ionic conductivity. At the same time, comparing Example 1 with Comparative Example 3, it can be seen that the introduction of polyethylene glycol diacrylate (PEGDA) cross-linking into 4-acryloylmorpholine also produces an order of magnitude difference in ionic conductivity compared to 1,6-hexanediol diacrylate (HDDA). The reason may be that the alkane chain of HDDA has no coordination ability and is highly dependent on the eutectic solvent to provide Li + ion transport channels, but the HDDA structure lacks ether oxygen bond groups that are well compatible with deep eutectic solvents, resulting in fragmentation of the ion transport channels and decomposition of the deep eutectic solvent with the precipitation of SN, resulting in low ionic conductivity. Therefore, the present invention effectively improves the ionic conductivity of the prepared eutectic gel electrolysis by selectively introducing 0.5-1 mol% of a photocurable polyethylene glycol derivative such as PEGDA or PEGDMA into 4-acryloylmorpholine.

[0098] Test Example 2: Electrochemical Performance

[0099] 2.1 Electrochemical Window

[0100] The eutectic gel electrolyte sample prepared in Example 1 was assembled into a Li|electrolyte film|stainless steel button cell and its electrochemical window was tested. The results were Figure 2 As shown. Among them, Figure 2 This is the electrochemical window test diagram of the eutectic gel electrolyte prepared in Example 1.

[0101] according to Figure 2 It can be seen that the electrochemical window of the eutectic gel electrolyte film prepared in Example 1 is 4.8V.

[0102] According to the above method, the electrochemical windows of the eutectic gel electrolytes prepared in Examples 2 to 5 and the molded products prepared in Comparative Examples 1 to 3 were tested and recorded in Table 2.

[0103] Table 2: Electrochemical window test results

[0104] Sample name electrochemical window 0.1C initial specific capacity Example 1 4.9V 151.5mAh / g Example 2 4.8V 149.2mAh / g Example 3 4.8V 150.5mAh / g Example 4 4.8V 149.6mAh / g Example 5 4.8V 150.1mAh / g Comparative Example 1 4.7V 134.3mAh / g Comparative Example 2 4.2V 141.8mAh / g Comparative Example 3 4.6V 135.6mAh / g

[0105] According to Table 2, the eutectic gel electrolytes prepared in Examples 1 to 5 have relatively similar electrochemical windows and initial specific capacities and are significantly better than those in Comparative Examples 1 to 3, indicating that the present invention effectively achieves a simultaneous improvement in electrochemical window and specific capacity by cross-linking optimization by introducing 0.5-1 mol% PEGDMA / PEGDA into 4-acryloylmorpholine. The reason may be that the polymer network formed by cross-linking 0.5-1 mol% PEGDA / PEGDMA with ACMO can effectively balance the intermolecular forces, improve the antioxidant capacity, and effectively enhance the Li + The transport of PEGDA and the widening of the electrochemical window make the eutectic gel electrolyte have a wide electrochemical window and high specific capacity. When the molar amount of PEGDA is greater than 1 mol%, the polymer network formed by cross-linking PEGDA and ACMO may reduce the regulation of the ratio of solvent molecules and free molecules, resulting in a slight decrease in the electrochemical window of the eutectic gel electrolyte, but more seriously hindering the Li + The migration of PEGDA increases the interface impedance, resulting in a significant decrease in specific capacity. When the molar amount of PEGDA is 0, ACMO forms a loose network structure by photopolymerization, which cannot effectively regulate the ratio of solvent molecules and free molecules, resulting in a significant decrease in the electrochemical window of the eutectic gel electrolyte. However, the loose network structure helps Li + The migration and transmission of 4-acryloylmorpholine can be reduced, thereby reducing the specific capacity of the eutectic gel electrolyte. Therefore, the present invention preferably uses a molar ratio of photocurable polyethylene glycol derivatives to 4-acryloylmorpholine of 0.005 to 0.01, so that the eutectic gel electrolyte has a wide electrical window and high specific capacity. At the same time, comparing Example 1 with Comparative Example 3, it can be seen that the electrochemical window and specific capacity of 4-acryloylmorpholine after cross-linking with polyethylene glycol diacrylate (PEGDA) are significantly reduced compared to 1,6-hexanediol diacrylate (HDDA). The reason may be that the alkane chain of HDDA has no coordination ability and is highly dependent on the eutectic solvent to provide Li + ion transport channel, but the HDDA structure lacks ether oxygen bond groups that are well compatible with deep eutectic solvents, resulting in Li + The fragmentation of ion transport channels significantly reduces the specific capacity of the eutectic gel electrolyte. However, the polymer network formed by crosslinking HDDA and ACMO still regulates the ratio of solvent molecules to free molecules, resulting in a relatively low reduction in the electrochemical window of the eutectic gel electrolyte. Therefore, the present invention effectively improves the specific capacity and electrochemical window of the prepared eutectic gel electrolyte by introducing a photocurable polyethylene glycol derivative at a molar ratio of 0.005 to 0.01 to 4-acryloylmorpholine.

[0106] 2.2 Rate performance and cycle performance

[0107] The eutectic gel electrolyte prepared in Example 1 was assembled into a Li|electrolyte film|LiFePO4 asymmetric button cell, and its rate performance and cycle performance were tested. The results were as follows: Figures 3 and 4 As shown. Among them, Figure 3 : is the rate performance curve of the eutectic gel electrolyte film obtained in Example 1; Figure 4 This is the cycle performance curve of the eutectic gel electrolyte film obtained in Example 1.

[0108] according to Figure 3 It can be seen that the discharge specific capacities of the eutectic gel electrolyte prepared in Example 1 at 0.1C, 0.2C, 0.5C, 1C and 2C are 151.5mAh / g, 145.2mAh / g, 143.4mAh / g, 122.1mAh / g and 82.5mAh / g, respectively, indicating that the eutectic gel electrolyte has relatively good rate performance; at the same time, when the discharge rate is restored to 0.1C, the specific capacity rebounds, indicating that the eutectic gel electrolyte has good reversibility.

[0109] according to Figure 4 It can be seen that the eutectic gel electrolyte prepared in Example 1 can maintain a capacity of 142.6 mAh / g after 100 cycles at a discharge rate of 0.5 C, and the battery capacity retention rate can reach 97.2%.

[0110] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0111] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A lithium metal battery eutectic gel electrolyte, characterized in that: Prepared by performing a photocuring reaction on a photocurable precursor solution containing a photoinitiator; Wherein, the photocurable precursor solution comprises a two-component liquid compound and a deep eutectic solvent; The two-component liquid compound comprises 4-acryloylmorpholine and polyethylene glycol methyl ether acrylate; The deep eutectic solvent is formed from a liquid mixture comprising succinonitrile, lithium bis(trifluoromethylsulfonyl)imide and fluoroethylene carbonate; The molar ratio of the polyethylene glycol methyl ether acrylate to the 4-acryloylmorpholine is 0.005 to 0.01; The mass ratio of the lithium bis(trifluoromethanesulfonyl)imide to the succinonitrile is 1:1-2; The mass content of the fluoroethylene carbonate is 1 to 10 wt % of the sum of the mass of the succinonitrile and the lithium bis(trifluoromethylsulfonyl)imide; The volume ratio of the two-component liquid compound and the deep eutectic solvent contained in the photocurable precursor solution is 50-85:50-15.

2. The lithium metal battery eutectic gel electrolyte according to claim 1, characterized in that: The photoinitiator is any one of benzophenone, 2,4,6-trimethylbenzoyl ethyl phosphonate, 4-dimethylamino-ethyl benzoate, and 2-hydroxy-2-methylpropiophenone.

3. A method for preparing the eutectic gel electrolyte for lithium metal batteries according to claim 1 or 2, characterized in that: The following steps are included: Fluoroethylene carbonate is added to a liquid mixture of succinonitrile and lithium bis(trifluoromethylsulfonyl)imide to prepare a deep eutectic solvent; adding the deep eutectic solvent to a two-component liquid compound of 4-acryloylmorpholine and polyethylene glycol methyl ether acrylate, and mixing them uniformly to obtain a photocurable precursor solution; A photoinitiator is added to the photocurable precursor solution and an ultraviolet curing reaction is carried out to obtain the lithium metal battery eutectic gel electrolyte.

4. A lithium metal solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte, characterized in that: The solid-state electrolyte comprises the lithium metal battery eutectic gel electrolyte according to claim 1 or 2.

5. An electrical equipment, characterized in that: Comprising the lithium metal solid-state battery according to claim 4.

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