An in-situ self-supporting gel polymer electrolyte, a preparation method and application thereof

Abstract

The present application relates to an in-situ self-supporting gel polymer electrolyte, a preparation method and application thereof. The in-situ self-supporting gel polymer electrolyte comprises a polymer gel framework and a liquid electrolyte swelled in the polymer gel framework; wherein the polymer gel framework is obtained by ring-opening polymerization of a hydrogen-containing epoxy silane polymer monomer through a chain initiator.

Description

Technical Field

[0001] This invention relates to an in-situ self-supporting gel polymer electrolyte, its preparation method, and its application, belonging to the field of battery technology. Background Technology

[0002] With the continuous development of mobile phones, computers, wearable electronic devices, and electric vehicles, society's demand for lithium-ion batteries is increasing, and higher performance requirements are being placed on them. However, currently commercially available lithium-ion battery electrolytes suffer from uneven lithium deposition, leading to lithium dendrite growth and potentially causing battery short circuits or even explosions under abnormal conditions. Furthermore, lithium metal has an extremely low redox potential, making it highly reactive with liquid electrolytes and causing electrolyte consumption. These are all critical issues that urgently need to be addressed.

[0003] Using gel polymer electrolytes can effectively solve the above problems. Compared with liquid electrolytes, gel polymer electrolytes not only promote uniform lithium deposition and prevent lithium dendrite formation, but also stabilize the active metal anode, effectively improving the battery's power density and energy density. Furthermore, gel polymer electrolytes have a larger electrochemical window, preventing electrolyte decomposition caused by excessively high charging potentials.

[0004] Currently, in-situ gel polymer electrolytes require methods such as ultraviolet irradiation and heating to promote monomer polymerization. Even with external energy assistance, the gelation time still takes several days, which is too long. Therefore, in order to realize the practical application of gel polymer electrolytes in the battery field, it is necessary to shorten the gelation time and simplify the process. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art (long polymerization time, requiring external energy assistance), the present invention provides a novel gel polymer electrolyte system, its preparation method and application.

[0006] In a first aspect, the present invention provides an in-situ self-supporting gel polymer electrolyte, comprising: a polymer gel skeleton and a liquid electrolyte swollen in the polymer gel skeleton; wherein the polymer gel skeleton is obtained by ring-opening polymerization of a hydrogen-containing epoxy silane polymer monomer through a chain initiator.

[0007] Preferably, the hydrogen-containing epoxysilane is an epoxysilane with Si-H bonds, and is preferably selected from at least one of 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8,10-pentamethylcyclopentasiloxane, heptamethylcyclotetrasiloxane, and tetraethylcyclotetrasiloxane. For example, hexamethyldisilazine lithium is an organic base that can form LiHMDS H+ in solution, and the base can cause the hydrogen-containing epoxysilane to undergo ring-opening polymerization.

[0008] Preferably, the chain initiator is at least one selected from butyllithium, phenyllithium, diisopropylaminolithium (LDA), and hexamethyldisilazine-lithium (LiHMDS).

[0009] Preferably, the liquid electrolyte is at least one of carbonate-based electrolyte, ether-based electrolyte, ionic liquid-based electrolyte, and amide-based electrolyte.

[0010] Preferably, the electrolyte in the liquid electrolyte is selected from at least one of LiTFSI, LiPF6, LiBF4, LiN(SO2F)2, LiClO4, LiB(C2O4)2 and LiBF2(C2O4), and the concentration is 0.1 to 3 mol / L.

[0011] Preferably, the ratio of the chain initiator to the liquid electrolyte is (1-20) mmol / L: 1L. Adding a specific amount of chain initiator transforms the electrolyte into a gel polymer electrolyte while simultaneously forming a Si-containing protective layer in situ on the negative electrode surface. This technology promotes uniform lithium deposition / stripping. It can also be applied in metal-air batteries to prevent damage to the active metal negative electrode from a semi-open environment and to prevent electrolyte evaporation and leakage. Without the chain initiator, a liquid electrolyte is formed, which easily leads to lithium dendrite formation, creating safety hazards; it also fails to protect the positive electrode, and the Si-containing protective layer on the negative electrode will not form.

[0012] Preferably, the volume ratio of the hydrogen-containing epoxy silane polymer monomer to the liquid electrolyte is 10:3 to 5.

[0013] On the other hand, the present invention provides a method for preparing an in-situ self-supporting gel polymer electrolyte, comprising:

[0014] (1) Mix the chain initiator and the electrolyte to obtain an electrolyte containing the chain initiator;

[0015] (2) After coating the substrate surface with hydrogen-containing epoxy silane, an electrolyte containing a chain initiator is coated again. After standing treatment, an in-situ self-supporting gel polymer electrolyte is formed. This invention introduces a chain initiator (such as LiHMDS) into the electrolyte, which promotes the in-situ formation of a self-supporting gel polymer electrolyte by hydrogen-containing epoxy silane monomers (such as tetramethylcyclotetrasiloxane monomers). This saves the use of a separator and can form a Si-containing protective layer on the negative electrode surface, promoting uniform lithium deposition and protecting the negative electrode from being powdered by water in the air environment.

[0016] Preferably, the coating method is drop application or scraping; the substrate is a horizontal substrate; the horizontal substrate is stainless steel or glass plate; and the settling time does not exceed 80 minutes.

[0017] Furthermore, this invention provides a lithium battery comprising: a positive electrode, an in-situ self-supporting gel polymer electrolyte, and a negative electrode; preferably, the positive electrode is at least one selected from multi-walled carbon nanotube positive electrode, lithium cobalt oxide, lithium nickel cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, ternary lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium manganese iron phosphate, lithium iron phosphate, sulfur, and lithium sulfide; preferably, the negative electrode is at least one selected from lithium metal, lithium metal alloy, graphite, hard carbon, molybdenum disulfide, lithium titanate, graphene, silicon, silicon-carbon, silicon-oxygen, and silicon-oxygen-carbon negative electrode. When the positive electrode is a multi-walled carbon nanotube, the lithium battery is a lithium-air battery.

[0018] Beneficial effects:

[0019] The in-situ self-supporting gel polymer electrolyte of this invention has the following functions: First, it serves as both a component of the electrolyte and can replace the separator in the battery, forming an in-situ self-supporting gel polymer electrolyte. Second, it can form a Si-containing protective layer on the surface of the battery negative electrode in a short time, promoting uniform deposition and stripping of the negative electrode. Third, if applied in the field of metal-air batteries, it can effectively protect the active metal negative electrode from damage by complex components in the air. The preparation process of the gel polymer electrolyte disclosed in this invention is simple, requires no external energy assistance, and is suitable for mass production. Attached Figure Description

[0020] Figure 1 Scanning electron microscope images of gel polymer electrolytes formed with different initiator concentrations: (a) 2.5 mM LiHMDS; (a) 4.9 mM LiHMDS; (a) 9.8 mM LiHMDS; (a) 19.6 mM LiHMDS;

[0021] Figure 2 A comparison of the cycle performance of lithium-air batteries assembled with liquid electrolyte and gel polymer electrolyte;

[0022] Figure 3 This is a comparison of the cycle performance of lithium symmetric batteries assembled from liquid electrolyte and gel polymer electrolyte. Detailed Implementation

[0023] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0024] In this disclosure, an organic base is used as a chain initiator to initiate the ring-opening polymerization of hydrogen-containing epoxy silanes, which crosslinks to form a gel polymer electrolyte. This gel polymer electrolyte can replace the membrane and act as a self-supporting body, thereby forming a self-supporting gel polymer electrolyte.

[0025] In one embodiment of the present invention, the self-supporting gel polymer electrolyte formed in situ is mainly obtained by the interaction of an organic base as a chain initiator, a polymer monomer, and a liquid electrolyte.

[0026] The chain initiator is at least one selected from butyllithium, phenyllithium, diisopropylaminolithium (LDA), and hexamethyldisilazine-lithium (LiHMDS). According to the present invention, the chain initiator is an organic base capable of promoting the ring-opening polymerization of hydrogen-containing epoxy silanes. Furthermore, the time for forming the gel polymer electrolyte can be controlled by adjusting the concentration of the initiator without any external assistance. The gel polymer electrolyte proposed in this invention can also serve as a membrane component, replacing traditional membranes and forming a self-supporting gel polymer electrolyte in situ.

[0027] The hydrogen-containing epoxy silane is at least one of 2,4,6,8-tetramethylcyclotetrasiloxane and 2,4,6,8,10-pentamethylcyclopentasiloxane. The liquid electrolyte is at least one of carbonate-based, ether-based, ionic liquid-based, and amide-based electrolytes. As an example of the preparation of an in-situ self-supporting gel polymer electrolyte, it includes: using LiHMDS as a chain initiator, dissolving it in the electrolyte and mixing thoroughly, and then using 2,4,6,8-tetramethylcyclotetrasiloxane (D4... H As a polymer monomer, the above-mentioned electrolyte is added to achieve the preparation of in-situ self-supporting gel polymer electrolyte material within a short period of standing time.

[0028] At least one of the chain initiators is mixed uniformly with at least one of the liquid electrolytes to form an electrolyte containing the chain initiator. The molar content of the chain initiator in the electrolyte containing the chain initiator is 1-20 mM. If the chain initiator content is too low, the gelation time will be too long, which is not conducive to commercial production; if the content is too high, the interaction between the chain initiator and the hydrogen-containing epoxy silane will be stronger, removing the H from the hydrogen-containing epoxy silane, resulting in an uneven and dense gel polymer electrolyte with many large bubbles, affecting the performance of the electrolyte.

[0029] At least one of the hydrogen-containing epoxy silanes is dropped onto a horizontal substrate (the horizontal substrate can be a stainless steel sheet or a glass plate; if lithium batteries are to be prepared directly, it can be prepared directly on the positive electrode surface or the negative electrode surface).

[0030] An electrolyte containing a chain initiator is dropped onto the substrate and left to stand for 3-70 minutes to form a self-supporting gel polymer electrolyte in situ.

[0031] This self-supporting gel polymer electrolyte replaces the separator, reducing its usage and preventing battery short circuits. Furthermore, it forms a Si-containing protective layer in situ on the negative electrode surface, promoting uniform lithium-ion deposition. In addition, its application in metal-air batteries effectively prevents damage to the active metal negative electrode from water in the external environment. The preparation method provided by this invention is simple, requires no additional energy to promote monomer polymerization, saves on separator usage, and is easy to industrialize.

[0032] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. In the following examples and comparative examples, unless otherwise specified, the reagents, materials, and instruments used are all conventional reagents, conventional materials, and conventional instruments, all commercially available. The reagents involved can also be synthesized using conventional synthetic methods.

[0033] Example 1

[0034] Example 1 provides a method for preparing a self-supporting gel polymer: LiHMDS is selected as the chain initiator; 2,4,6,8-tetramethylcyclotetrasiloxane is selected as the polymerization monomer; and 1M LiTFSI / TEGDME is selected as the organic electrolyte. The specific preparation method includes:

[0035] (1) LiHMDS (concentration 2.5mM) was introduced into LiTFSI / TEGDME electrolyte to obtain an electrolyte containing chain initiator.

[0036] (2) Place the lithium metal anode on a horizontal table and drop 100 μL of polymer monomer onto the surface of the anode;

[0037] (3) Continue to add 30 μL of electrolyte containing LiHMDS chain initiator to the above negative electrode surface and let it stand for 60-70 minutes to form an in-situ self-supporting gel polymer electrolyte.

[0038] The process of assembling a lithium metal air button battery using the above-mentioned negative electrode with electrolyte includes: a 2032 type battery casing with the negative electrode casing opening facing upwards, placed flat on a panel; placing a spring sheet into the negative electrode casing; placing a pad on the spring sheet, and then clamping the above-mentioned negative electrode with electrolyte; clamping the positive electrode sheet and placing it in the center of the separator; using tweezers to clamp the porous positive electrode casing to cover it; and pressing it with a button battery packaging machine to complete the process.

[0039] Example 2

[0040] The preparation process of the in-situ self-supporting gel polymer electrolyte in Example 2 is the same as in the example, except that in step (1), LiHMDS (concentration 4.9 mM) is introduced into the LiTFSI / TEGDME electrolyte to obtain an electrolyte containing a chain initiator. Due to the increased concentration of the chain initiator, it only needs to stand for 35-50 minutes to form the in-situ self-supporting gel polymer electrolyte.

[0041] Example 3

[0042] The preparation process of the in-situ self-supporting gel polymer electrolyte in Example 3 is the same as in the Example, except that in step (1), LiHMDS initiator (concentration 9.8 mM) is introduced into the LiTFSI / TEGDME electrolyte to obtain an electrolyte containing chain initiator. Due to the increased concentration of chain initiator, it only needs to stand for 10-20 minutes to form the in-situ self-supporting gel polymer electrolyte.

[0043] Example 4

[0044] The preparation process of the in-situ self-supporting gel polymer electrolyte in Example 4 is the same as in the example, except that in step (1), LiHMDS initiator (concentration 19.6 mM) is introduced into the LiTFSI / TEGDME electrolyte to obtain an electrolyte containing chain initiator. Due to the increased concentration of chain initiator, it only needs to stand for 3-5 minutes to form the in-situ self-supporting gel polymer electrolyte.

[0045] Example 5

[0046] The preparation process of the in-situ self-supporting gel polymer electrolyte in Example 5 is the same as that in Example 5, except that in step (2), the lithium metal negative electrode is placed on a horizontal table and 50 μL of polymer monomer is dropped onto the surface of the negative electrode.

[0047] Example 6

[0048] The preparation process of the in-situ self-supporting gel polymer electrolyte in Example 6 is the same as in the example, except that in step (2), the lithium metal anode is placed on a horizontal table and 150 μL of polymer monomer is dropped onto the surface of the anode.

[0049] Example 7

[0050] Example 7 provides a method for preparing a self-supporting gel polymer: LiHMDS is selected as the chain initiator; 2,4,6,8-tetramethylcyclotetrasiloxane is selected as the polymerization monomer; and 1M LiTFSI / TEGDME is selected as the organic electrolyte. The specific preparation method includes:

[0051] (1) 2.5 mM LiHMDS was introduced into LiTFSI / TEGDME electrolyte to obtain an electrolyte containing chain initiator.

[0052] (2) Place the lithium metal anode on a horizontal table and drop 100 μL of polymer monomer onto the anode surface.

[0053] (3) Continue to drop 30 μL of electrolyte with chain initiator onto the above negative electrode surface and let it stand for 60-70 minutes to form an in-situ self-supporting gel polymer electrolyte.

[0054] The process of assembling a lithium symmetrical button cell using the aforementioned electrolyte-containing negative electrode includes: a 2025 type battery casing with the negative electrode casing opening facing upwards, placed flat on a panel; inserting a spring sheet into the negative electrode casing; placing a clamping pad on the spring sheet, and then clamping the aforementioned electrolyte-containing negative electrode; clamping the lithium metal negative electrode and placing it in the center; using tweezers to clamp the positive electrode casing to cover it; and pressing it with a button cell packaging machine to complete the process.

[0055] Comparative Example 1

[0056] As a comparison with Example 7, a liquid electrolyte was selected to assemble a lithium symmetric battery: the battery case was a 2025 type, with the negative electrode case opening facing upwards, and it was placed flat on the panel; a spring sheet was placed into the negative electrode case; a pad was clamped and placed on the spring sheet, and then a lithium sheet was clamped and placed in the center of the pad; the separator was clamped and covered with the lithium sheet, and 1M LiTFSI / TEGDME electrolyte (at this time, Comparative Example 1 and Example 1 have two differences: (1) it does not contain a chain initiator; (2) it does not contain epoxy silane) was added to the separator; the lithium metal negative electrode was clamped and placed in the center of the separator, the positive electrode case was clamped and covered with tweezers, and the battery was pressed with a button cell packaging machine to obtain a button lithium symmetric battery. The amount of electrolyte added in the button cell was 50μL.

[0057] Comparative Example 2

[0058] As a comparison with Example 7, a liquid electrolyte was selected to assemble a lithium symmetric battery: the battery case was a 2025 type, with the negative electrode case opening facing upwards, and it was placed flat on the panel; a spring sheet was placed into the negative electrode case; a spacer was placed on the spring sheet, and then a lithium sheet was placed in the center of the spacer; the separator was clamped to cover the lithium sheet, and the polymer monomer 2,4,6,8-tetramethylcyclotetrasiloxane and 1MLiTFSI / TEGDME electrolyte were added to the lithium negative electrode using a pipette; the lithium metal negative electrode was clamped to the center of the separator, and the positive electrode case was clamped to cover it with tweezers. The battery was then pressed using a button cell packaging machine to obtain a coin cell lithium-air battery. The amount of electrolyte added to the coin cell was 30 μL, and the volume of the polymer monomer was 100 μL.

[0059] Table 1 shows the composition and performance parameters of the metal-air battery prepared in this invention:

[0060] Battery types Polymer monomer Initiator / mM Loop count / time Example 1 Lithium-air batteries 100μL 2.5 180 times Example 2 Lithium-air batteries 100μL 4.9 115 times Example 3 Lithium-air batteries 100μL 9.8 98 times Example 4 Lithium-air batteries 100μL 19.6 67 times Example 5 Lithium-air batteries 50μL 2.5 83 times Example 6 Lithium-air batteries 150μL 2.5 149 times Example 7 Lithium symmetric battery 100μL 2.5 670h Comparative Example 1 Lithium symmetric battery - - 240h Comparative Example 2 Lithium symmetric battery 30μL - 380h .

Claims

1. An in-situ self-supporting gel polymer electrolyte, characterized by, The application relates to a self-supporting in-situ gel polymer electrolyte, which comprises: a polymer gel framework and a liquid electrolyte swelled in the polymer gel framework; wherein the polymer gel framework is obtained by ring-opening polymerization of hydrogen-containing epoxy silane polymer monomers through a chain initiator, the hydrogen-containing epoxy silane is an epoxy silane with a Si-H bond, the ratio of the chain initiator and the liquid electrolyte is (1-20) mmol: 1 L, and the volume ratio of the hydrogen-containing epoxy silane polymer monomers and the liquid electrolyte is 10:3-5. The hydrogen-containing epoxy silane is at least one selected from 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8,10-pentamethylcyclopentasiloxane, heptamethylcyclotetrasiloxane and tetraethylcyclotetrasiloxane.

2. The in-situ self-supporting gel polymer electrolyte according to claim 1, wherein, The chain initiator is at least one selected from butyllithium, phenyllithium, diisopropylaminolithium (LDA) and hexamethyldisilazanide lithium (LiHMDS).

3. The in-situ self-supporting gel polymer electrolyte according to claim 1, wherein, The liquid electrolyte is at least one selected from carbonate-based electrolyte, ether-based electrolyte, ionic liquid-based electrolyte and amide-based electrolyte.

4. The in-situ self-supporting gel polymer electrolyte according to claim 1, wherein, The electrolyte in the liquid electrolyte is at least one selected from LiTFSI, LiPF6, LiBF4, LiN(SO2F)2, LiClO4, LiB(C2O4)2 and LiBF2(C2O4), and the concentration is 0.1-3 moL / L.

5. The in situ self-supporting gel polymer electrolyte according to any one of claims 1-4, characterized in that, The application further discloses a preparation method of the self-supporting in-situ gel polymer electrolyte.

6. A method of producing the in-situ self-supporting gel polymer electrolyte according to any one of claims 1 to 5, characterized by, (1) mixing the chain initiator and the electrolyte to obtain electrolyte containing the chain initiator; (2) coating the hydrogen-containing epoxy silane on the surface of a substrate, then coating the electrolyte containing the chain initiator again, and in-situ forming the self-supporting in-situ gel polymer electrolyte through standing treatment. The coating mode is drop coating or blade coating; 7. The production method according to claim 6, wherein The substrate is a horizontal substrate, and the horizontal substrate is stainless steel or a glass plate. The standing treatment time is not more than 80 minutes. The application further discloses a lithium battery.

8. A lithium battery, characterized by The positive electrode is at least one selected from a multi-walled carbon nanotube positive electrode, lithium cobaltate, lithium nickel cobaltate, lithium manganate, lithium nickel manganate, ternary lithium nickel cobalt manganate, lithium nickel cobalt aluminum manganate, lithium manganese iron phosphate, lithium iron phosphate, sulfur, lithium sulfide. The negative electrode is at least one selected from metal lithium, metal lithium alloy, graphite, hard carbon, molybdenum disulfide, lithium titanate, graphene, silicon, silicon carbon, silicon oxygen and silicon oxygen carbon. ​ ​

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