A polyionic liquid-based material, and a preparation method and application thereof

Abstract

The application provides a polyionic liquid-based material, a preparation method and application thereof. The polyionic liquid-based material comprises a copolymer and a metal salt, the copolymer comprises an ionic liquid structural unit and an electron-deficient structural unit, and the electron-deficient structural unit comprises at least one of an amide group, an ester group or a heteroatom. The polyionic liquid-based material has strong bonding capacity, high ion transference number, high oxidation resistance and non-flammability, so as to improve the technical problems of poor solid-solid interface physical contact and poor electrochemical stability, and can be applied to the electrode inside of a solid-state battery, replaces the solid-state electrolyte and the binder component, and thus excellent electrochemical performance is obtained.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a polyionic liquid-based material, its preparation method, and its application. Background Technology

[0002] To improve battery energy density and safety, combining lithium metal anodes and high-voltage cathodes with solid-state electrolytes is considered one of the most effective approaches. Solid-state electrolytes offer higher safety and stability compared to traditional liquid electrolytes and can effectively suppress lithium dendrite growth, thereby reducing the risk of battery short circuits and thermal runaway. Among these, polymer electrolytes, in addition to their excellent flexibility, high thermal stability, and ease of processing, also possess the characteristic of suppressing leakage and explosion risks.

[0003] However, the application of polymer electrolytes in solid-state lithium metal batteries faces the challenge of a narrow electrochemical stability window, especially under high voltage (≥4.3V) conditions, where their polar groups are prone to oxidative decomposition, leading to a decline in battery performance. This problem limits the widespread application of polymer electrolytes in high-energy-density batteries. To address these issues, researchers have proposed numerous polymer design strategies to broaden their electrochemical stability window, including adjusting intermolecular interactions or constructing high-voltage resistant structures. In recent years, polyionic liquid materials have attracted considerable attention due to their wide electrochemical window, non-flammability, high chemical stability, and good ionic conductivity. However, the high polarizability of polyionic liquids makes their electrochemical performance at interfaces unstable, and solid-solid contact separation still exists between the polymer and the interface, leading to problems such as high interfacial impedance and insufficient kinetics during battery charging and discharging.

[0004] Based on the above, existing technologies for solving solid-state battery interface problems mainly include constructing artificial interface films, introducing functional lithium salts, or designing fluorinated electrolytes. However, polyionic liquid materials still face interface problems in practical applications, thus necessitating the simultaneous resolution of both solid-solid interface mechanics and interfacial electrochemistry issues.

[0005] Therefore, there is an urgent need in this field to develop a polyionic liquid-based material with a simple synthesis route, while ensuring that it has good interfacial contact performance and electrochemical stability when applied to solid-state batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polyionic liquid-based material, its preparation method, and its applications. This invention provides a polyionic liquid-based material that combines strong adhesion, high ion mobility number, high oxidation resistance, and non-flammability, thereby improving the technical problems of poor physical contact and poor electrochemical stability at the solid-solid interface. Furthermore, it can be applied to the internal electrodes of solid-state batteries, replacing solid electrolyte and binder components to achieve excellent electrochemical performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a polyionic liquid-based material, the polyionic liquid-based material comprising a copolymer and a metal salt, wherein the copolymer comprises ionic liquid structural units and electron-deficient structural units;

[0009] The electron-deficient structural unit contains at least one of an amide group, an ester group, or a heteroatom.

[0010] To address the technical problems of high viscosity and low metal ion transport number in existing polyionic liquid materials, this invention introduces anion acceptor structural units with specific types of groups into the polyionic liquid system. This regulates the distribution and state of anions to increase the metal ion transport number. At the same time, strong interaction forces between electron-deficient structural units provide viscosity, thereby preparing a polyionic liquid-based viscous electrolyte material with strong adhesion, high ion transport number, high oxidation resistance, and non-flammability.

[0011] Specifically, firstly, due to the polymeric properties of polyionic liquids and the strong interactions between electron-deficient structural units, the copolymer material provided by this invention can firmly bond to the surface of the electrode material, alleviating stress and strain on the electrode material during cycling, thereby improving the interfacial stability of the solid-state battery. Secondly, by controlling the distribution and state of anions, this invention reduces anion migration and increases conductivity, thereby increasing the ion transference number of the polyionic liquid-based viscous electrolyte and obtaining anion-rich interface. In addition, the polyionic liquid material itself has high chemical stability and electrochemical window, and can remain stable at high potentials, thus making it suitable for high-voltage battery systems. Finally, compared with traditional organic electrolytes, the polyionic liquid-based viscous electrolyte provided by this invention has non-flammable properties, thereby significantly improving battery safety.

[0012] Furthermore, this polyionic liquid-based viscous electrolyte exhibits excellent ionic conductivity and high viscosity, thus enabling it to simultaneously replace conventional solid electrolytes and binder components in the positive or negative electrodes of solid-state batteries, simplifying the electrode fabrication process. Moreover, it can construct continuous and stable ion transport channels within the solid electrode, thereby addressing the technical problems of insufficient physical contact separation and ion transport kinetics at the solid-solid interface. Compared to traditional polyionic liquid electrolytes, the polyionic liquid-based viscous electrolyte provided by this invention is advantageous for obtaining solid-state batteries with high specific energy and high interfacial stability.

[0013] Preferably, the electron-deficient structural unit is derived from the first monomer.

[0014] Preferably, the first monomer comprises a compound having at least one carbon-carbon double bond and at least one electron-deficient group.

[0015] Preferably, the electron-deficient group includes at least one of an amide group, an ester group, or a heteroatom.

[0016] Preferably, the first monomer is selected from any one or a combination of at least two of the following: organic ester monomers containing at least one carbon-carbon double bond, amide monomers containing at least one carbon-carbon double bond, heteroatom-containing compound monomers containing at least one carbon-carbon double bond, or amphoteric compound monomers containing at least one carbon-carbon double bond, and preferably organic ester monomers containing at least one carbon-carbon double bond.

[0017] The aforementioned first monomers not only possess electron-deficient centers, which facilitate the attraction of anions to increase the migration number of metal cations, but also exhibit interactions such as hydrogen bonds, covalent bonds, or ionic bonds between them. After polymerization, these monomers provide strong adhesion, thereby further improving poor physical contact at the solid-solid interface. Thus, this invention, by optimizing the type of the first monomer, achieves precise control over the distribution of anions, thereby preparing polyionic liquid-based materials with high ionic conductivity, high migration number, and excellent interfacial stability.

[0018] Preferably, the first monomer is selected from any one or a combination of at least two of mono-2-(methacryloyloxy)ethyl phthalate, 3-acrylamidophenylboronic acid pinacol ester, or 3-[(3-acrylamidopropyl)dimethylamino]propane-1-sulfonate, and is more preferably mono-2-(methacryloyloxy)ethyl phthalate, because organic ester monomers can not only anchor anions, but also have strong hydrogen bond interactions between chain segments.

[0019] Preferably, the ionic liquid structural unit is derived from the second monomer.

[0020] Preferably, the second monomer comprises a polycationic ionic liquid monomer and / or a polyanionic ionic liquid monomer, and more preferably a polycationic ionic liquid monomer.

[0021] Preferably, the polycationic ionic liquid monomer is selected from at least one of imidazolium ionic liquid, pyridinium ionic liquid, or pyrrolidineium ionic liquid.

[0022] Preferably, the polyanionic ionic liquid monomer is selected from polyphosphate ionic liquids.

[0023] Preferably, the copolymer further includes other structural units.

[0024] Preferably, the other structural units are derived from the third monomer.

[0025] Preferably, the third monomer is selected from nitrile monomers and / or halogenated olefin monomers. The present invention selects the above-mentioned types of third monomers to achieve the technical effect of both reducing the viscosity of the polymerization system and improving ionic conductivity through coordination with or electron-withdrawing interactions with metal ions.

[0026] Preferably, the metal salt includes lithium salt and / or sodium salt.

[0027] It should be noted that the specific selection of metal salts in this invention can be designed according to specific actual usage requirements. For example, if the polyionic liquid-based material is used in a lithium-ion battery, then lithium salt is selected as the metal salt; if the polyionic liquid-based material is used in a sodium-ion battery, then sodium salt is selected as the metal salt.

[0028] It should also be noted that the present invention does not impose any special restrictions on the specific selection of lithium salts, and commonly used lithium salts in the art are applicable, including but not limited to lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), or lithium bis(oxalateborate)borate (LiBOB), etc.; the present invention also does not impose any special restrictions on the specific selection of sodium salts, and commonly used sodium salts in the art are also applicable.

[0029] Preferably, based on the molar amount of all structural units in the copolymer being 100%, the molar percentage of the electron-deficient structural units is 5%-60%, more preferably 10%-20%, for example, it can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, etc.

[0030] This invention significantly improves the ionic conductivity and interfacial contact performance of the prepared polyionic liquid-based material by controlling the molar percentage of electron-deficient structural units. Using electron-deficient structural units with a low molar percentage results in ineffective anion anchoring; while using electron-deficient structural units with a high molar percentage leads to excessively strong interactions within the system, resulting in poor electrochemical performance of the solid-state battery.

[0031] Preferably, based on the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the ionic liquid structural unit is 20%-80%, more preferably 20%-60%, and can be, for example, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, etc.

[0032] This invention achieves lower viscosity and higher ionic conductivity in polyionic liquid-based materials by controlling the molar percentage of ionic liquid structural units. Using a lower molar percentage of ionic liquid structural units results in lower ionic conductivity and consequently poorer electrochemical performance; conversely, using a higher molar percentage results in higher viscosity.

[0033] Preferably, with the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the other structural units is 0%-50%, more preferably 20%-50%, for example, it can be 0%, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, etc.

[0034] This invention further modulates the molar percentage of other structural units, thereby further improving the ionic conductivity of polyionic liquid-based materials. If other structural units with a lower molar percentage are used, the improvement in ionic conductivity of the polyionic liquid-based material is not significant; if other structural units with a higher molar percentage are used, other electrochemical properties will be affected.

[0035] This invention achieves degree of polymerization control by optimizing the appropriate monomer ratio and polymerization time, so that the prepared polyionic liquid-based material has both high viscosity and excellent electrochemical performance.

[0036] Preferably, the metal salt has a mass percentage content of 20%-60%, more preferably 35%-45%, based on the total mass of the first monomer, the second monomer and the third monomer as 100%, and can be, for example, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, etc.

[0037] This invention ensures that the prepared polyionic liquid-based material exhibits high ionic conductivity and high ion transport number by controlling the mass percentage content of the metal salt. A low mass percentage of the metal salt results in fewer charge carriers, slower metal ion migration, and increased battery polarization; conversely, a high mass percentage of the metal salt leads to a significant increase in the viscosity of the polyionic liquid-based material, thereby hindering ion migration.

[0038] In a second aspect, the present invention provides a method for preparing the polyionic liquid-based material according to the first aspect, the method comprising the following steps:

[0039] A precursor solution is obtained by mixing a first monomer that forms an electron-deficient structural unit, a second monomer that forms an ionic liquid structural unit, a metal salt, and an initiator, and then reacting to obtain the polyionic liquid-based material.

[0040] Preferably, the initiator is a photoinitiator. Exemplary photoinitiators include at least one of free radical photoinitiators (such as benzoin, acetophenone compounds, or acylphosphine oxides), cationic photoinitiators (such as ononium salts), or visible light initiators (such as camphorquinone or eosin), but the present invention is not limited thereto.

[0041] Preferably, the reaction is carried out under ultraviolet light.

[0042] In this invention, the reaction is carried out under an inert atmosphere, which may include, but is not limited to, a nitrogen atmosphere or an argon atmosphere, etc., to avoid the metal salt from coming into contact with water and oxygen components, causing it to undergo a water-absorbing reaction.

[0043] Preferably, the reaction temperature is 20℃-30℃, for example, 20℃, 22℃, 25℃, 28℃, 30℃, etc. A lower reaction temperature will slow down the polymerization rate, while a higher reaction temperature will increase the occurrence of side reactions.

[0044] Preferably, the reaction time is 10s-30s, for example, 10s, 12s, 15s, 18s, 20s, 22s, 25s, 28s, 30s, etc. If the polymerization reaction time is too short, the monomers are difficult to polymerize completely, while if the polymerization reaction time is too long, the copolymer will have a high degree of polymerization, which will affect the ionic conductivity of the obtained polyionic liquid-based material.

[0045] This invention introduces electron-deficient structural units and other preferred structural units to prepare a polyionic liquid-based material with both viscosity and high lithium-ion transference number using an in-situ copolymerization method. This improves the physical contact and electrochemical stability of the solid-solid interface and can also be applied inside the electrodes of solid-state batteries, thereby enhancing the electrochemical performance of solid-state batteries.

[0046] Thirdly, the present invention provides a solid electrode comprising an electrode active material, a polymer electrolyte, and a conductive agent, wherein the polymer electrolyte comprises the polyionic liquid-based material according to the first aspect.

[0047] Preferably, the mass ratio of the electrode active material, polymer electrolyte, and conductive agent is (80-90):(5-10):(3-15), for example, it can be 80:5:15, 82:6:12, 85:8:7, 88:7:5, 90:5:5, etc.

[0048] Fourthly, the present invention provides a solid-state battery comprising electrodes and a solid electrolyte, wherein the electrodes comprise the solid-state electrodes according to the third aspect.

[0049] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] This invention provides a polyionic liquid-based material. By introducing anion acceptor structural units with specific types of groups into the polyionic liquid system, the distribution and state of anions are regulated to increase the migration number of metal ions. At the same time, strong interaction forces between electron-deficient structural units provide viscosity, thereby preparing a polyionic liquid-based viscous electrolyte material with strong adhesion, high ion migration number, high oxidation resistance and non-flammability.

[0052] Specifically, firstly, due to the polymeric properties of polyionic liquids and the strong interactions between electron-deficient structural units, the copolymer material provided by this invention can firmly bond to the surface of the electrode material, alleviating stress and strain on the electrode material during cycling, thereby improving the interfacial stability of the solid-state battery. Secondly, by controlling the distribution and state of anions, this invention reduces anion migration and increases conductivity, thereby increasing the ion transference number of the polyionic liquid-based viscous electrolyte and obtaining anion-rich interface. In addition, the polyionic liquid material itself has high chemical stability and electrochemical window, and can remain stable at high potentials, thus making it suitable for high-voltage battery systems. Finally, compared with traditional organic electrolytes, the polyionic liquid-based viscous electrolyte provided by this invention has non-flammable properties, thereby significantly improving battery safety.

[0053] Furthermore, this polyionic liquid-based viscous electrolyte exhibits excellent ionic conductivity and high viscosity, thus enabling it to simultaneously replace conventional solid electrolytes and binder components in the positive or negative electrodes of solid-state batteries, simplifying the electrode fabrication process. Moreover, it can construct continuous and stable ion transport channels within the solid electrode, thereby addressing the technical problems of insufficient physical contact separation and ion transport kinetics at the solid-solid interface. Compared to traditional polyionic liquid electrolytes, the polyionic liquid-based viscous electrolyte provided by this invention is advantageous for obtaining solid-state batteries with high specific energy and high interfacial stability.

[0054] The preparation method of polyionic liquid-based materials provided by this invention is simple, efficient, and highly operable. Attached Figure Description

[0055] Figure 1 This is a test diagram of the adhesive force of the polyionic liquid-based material provided in Example 1 of this invention.

[0056] Figure 2 This is a lithium-ion transference number test chart of the polyionic liquid-based material provided in Example 1 of this invention.

[0057] Figure 3 This is an electrochemical window test diagram of the polyionic liquid-based material provided in Example 1 of this invention.

[0058] Figure 4 This is a flammability test diagram of the polyionic liquid-based material provided in Example 1 of this invention.

[0059] Figure 5 This is a cycle performance diagram of a solid-state lithium-ion battery assembled from the polyionic liquid-based material provided in Example 1 of this invention. Detailed Implementation

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0061] Example 1

[0062] This embodiment provides a polyionic liquid-based material, which includes a copolymer and a lithium LiTFSI salt. The copolymer includes a 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit, a phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit, and an acrylonitrile structural unit.

[0063] Specifically, based on the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit is 40%, the molar percentage of the phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit is 15%, and the molar percentage of the acrylonitrile structural unit is 45%; based on the total mass of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid, phthalic acid mono-2-(methacryloyloxy)ethyl ester, and acrylonitrile being 100%, the mass percentage of the LiTFSI lithium salt is 40%.

[0064] This embodiment also provides a method for preparing the above-mentioned polyionic liquid-based material, the preparation method comprising the following steps:

[0065] In a glove box, the above-described amounts of 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid monomer, mono-2-(methacryloyloxy)ethyl phthalate, and acrylonitrile were mixed, and lithium LiTFSI salt and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide photoinitiator (based on the total mass of the copolymer, the mass percentage of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide photoinitiator was 0.5%) were added and stirred until a transparent solution was obtained, thus obtaining a precursor solution. A volume of 30 μL of the above precursor solution was dropped onto the surface of the positive electrode in the positive electrode shell, and a polymerization reaction was initiated by ultraviolet light for 15 s to obtain the polyionic liquid-based material.

[0066] Example 2

[0067] This embodiment provides a polyionic liquid-based material, which includes a copolymer and a lithium LiTFSI salt. The copolymer includes a 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit, a phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit, and an acrylonitrile structural unit.

[0068] Specifically, based on the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit is 30%, the molar percentage of the phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit is 20%, and the molar percentage of the acrylonitrile structural unit is 50%; based on the total mass of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid, phthalic acid mono-2-(methacryloyloxy)ethyl ester, and acrylonitrile being 100%, the mass percentage of the LiTFSI lithium salt is 35%.

[0069] This embodiment also provides a method for preparing the above-mentioned polyionic liquid-based material, the preparation method comprising the following steps:

[0070] In a glove box, the above-described amounts of 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid monomer, mono-2-(methacryloyloxy)ethyl phthalate, and acrylonitrile were mixed, and lithium LiTFSI salt and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide photoinitiator (based on the total mass of the copolymer, the mass percentage of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide photoinitiator was 0.5%) were added and stirred until a transparent solution was obtained, thus obtaining a precursor solution. A volume of 30 μL of the above precursor solution was dropped onto the surface of the positive electrode in the positive electrode shell, and a polymerization reaction was initiated by ultraviolet light for 15 s to obtain the polyionic liquid-based material.

[0071] Example 3

[0072] This embodiment provides a polyionic liquid-based material, which includes a copolymer and a lithium LiTFSI salt. The copolymer includes a 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit, a phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit, and an acrylonitrile structural unit.

[0073] Specifically, based on the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit is 60%, the molar percentage of the phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit is 10%, and the molar percentage of the acrylonitrile structural unit is 30%; based on the total mass of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid, phthalic acid mono-2-(methacryloyloxy)ethyl ester, and acrylonitrile being 100%, the mass percentage of the LiTFSI lithium salt is 45%.

[0074] This embodiment also provides a method for preparing the above-mentioned polyionic liquid-based material, the preparation method comprising the following steps:

[0075] In a glove box, the above-described amounts of 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid monomer, mono-2-(methacryloyloxy)ethyl phthalate, and acrylonitrile were mixed, and lithium LiTFSI salt and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide photoinitiator (based on the total mass of the copolymer, the mass percentage of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide photoinitiator was 0.5%) were added and stirred until a transparent solution was obtained, thus obtaining a precursor solution. A volume of 30 μL of the above precursor solution was dropped onto the surface of the positive electrode in the positive electrode shell, and a polymerization reaction was initiated by ultraviolet light for 15 s to obtain the polyionic liquid-based material.

[0076] Example 4

[0077] The difference between this embodiment and Example 1 is that the phthalic acid mono-2-(methacryloyloxy)ethyl ester monomer is replaced with an equal amount of 3-[(3-acrylamidopropyl)dimethylamino]propane-1-sulfonate lithium monomer, while all other aspects are the same as in Example 1.

[0078] Example 5

[0079] The difference between this embodiment and Example 1 is that the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine monomer is replaced with an equal amount of 1-vinyl-3-ethylimidazolium hexafluorophosphate lithium monomer, while all other aspects are the same as in Example 1.

[0080] Example 6

[0081] The difference between this embodiment and Example 1 is that no acrylonitrile structural unit is introduced into the copolymer structure. Based on the molar amount of all structural units in the copolymer being 100%, the molar percentage of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imide ionic liquid structural unit is 50%, and the molar percentage of the phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit is 50%. All other aspects are the same as in Example 1.

[0082] Example 7

[0083] The difference between this embodiment and Example 1 is that, based on the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit is 78%, the molar percentage of the phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit is 2%, and the molar percentage of the acrylonitrile structural unit is 20%. All other aspects are the same as in Example 1.

[0084] Example 8

[0085] The difference between this embodiment and Example 1 is that, based on the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural unit is 10%, the molar percentage of the phthalic acid mono-2-(methacryloyloxy)ethyl ester structural unit is 70%, and the molar percentage of the acrylonitrile structural unit is 20%. All other aspects are the same as in Example 1.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is that the copolymer does not introduce phthalic acid mono-2-(methacryloyloxy)ethyl ester structural units. Based on the molar amount of all structural units in the copolymer being 100%, the molar percentage of 1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imine ionic liquid structural units is 60%, and the molar percentage of acrylonitrile structural units is 40%. All other aspects are the same as in Example 1.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 1 is that phthalic acid mono-2-(methacryloyloxy)ethyl ester is replaced with an equal amount of ethylene oxide monomer, while all other aspects are the same as in Example 1.

[0090] Comparative Example 3

[0091] This comparative example provides a polyionic liquid-based composite material, which includes a polymer composite material and a LiTFSI lithium salt. The polymer composite material is prepared by mixing poly(1-allyl-1-methylpyrrolidone bis(trifluoromethanesulfonyl)imide ionic liquid, poly(2-(methacryloyloxy)ethyl phthalate) and polyacrylonitrile in a mass ratio of 6:2:2. The LiTFSI lithium salt has a mass percentage content of 40% based on the total mass of the polymer composite material as 100%.

[0092] Application Examples 1-8 and Comparative Application Examples 1-3

[0093] Solid-state cathodes were prepared using the polyionic liquid-based materials provided in Examples 1 to 8 and Comparative Examples 1 to 3, and further assembled into solid-state lithium-ion batteries. The preparation methods are as follows:

[0094] Preparation of solid positive electrode sheet: Lithium iron phosphate positive electrode active material, the polyionic liquid-based material and conductive material (AB) provided in the above examples or comparative examples were weighed and mixed in a mass ratio of 90:5:5. N-methylpyrrolidone solvent (NMP) was added, and the mixture was stirred until uniformly dispersed. The prepared positive electrode slurry was coated onto an aluminum foil current collector and dried in a vacuum drying oven. After rolling, it was cut into solid positive electrode discs with a diameter of 12 mm and stored in a glove box for later use.

[0095] The positive electrode shell, the aforementioned solid positive electrode sheet, cellulose membrane, lithium sheet, steel sheet, spring sheet, and negative electrode shell are assembled in sequence. A 30 μL volume of the aforementioned precursor solution is dropped onto the surface of the solid positive electrode sheet in the positive electrode shell. A polymerization reaction is initiated using ultraviolet light to assemble a solid lithium-ion battery. The battery is then left to stand for 12 hours before electrochemical performance testing.

[0096] Test conditions

[0097] The solid-state lithium-ion batteries provided in Application Examples 1 to 8 and Comparative Application Examples 1 to 3 were subjected to performance tests under the following conditions:

[0098] (1) Lithium-ion transference number: Explanation of the test and calculation formula for lithium-ion transference number in solid electrolytes: The battery system used in the test was "lithium sheet / solid electrolyte membrane / lithium sheet". The assembled battery was tested on an electrochemical workstation with a polarization potential of 10mV. The impedance of the battery before and after polarization was measured by electrochemical impedance spectroscopy. The initial current and steady-state current were obtained by steady-state current spectroscopy. The data were then substituted into t Li+ =Is(△VR) o ·I o ) / I o (△VR s ·I s The lithium-ion transport number t was calculated. Li+ , where I o For the initial current, I s For steady-state current, R o Let R be the initial resistance. s Here, ΔV is the steady-state resistance, and ΔV is the polarization voltage.

[0099] (2) Electrochemical window: Linear scanning voltammetry was performed at a potential scan rate of 0.1 mV / s.

[0100] (3) Cyclic performance test: The Li|polymer electrolyte|LFP solid lithium-ion battery was subjected to constant current charge and discharge test using the Xinwei Battery Test Cabinet.

[0101] The test results are shown in Table 1:

[0102] Table 1

[0103]

[0104]

[0105] From Table 1 and Figures 1-5 It can be seen that the polyionic liquid-based material provided in Example 1 has high adhesion properties, such as Figure 1 As shown, the corresponding lithium-ion transference numbers are... Figure 2 The corresponding electrochemical windows are shown below. Figure 3 The corresponding flammability test can be found in [link to relevant test]. Figure 4 This indicates that a polyionic liquid-based viscous electrolyte with high adhesion, high lithium-ion transport number, good oxidation resistance, and non-flammability was prepared. Furthermore, the electrochemical cycling performance of the assembled solid-state lithium-ion battery is shown in [reference needed]. Figure 5 This indicates that the cycle stability of solid-state batteries has been significantly improved.

[0106] Comparing Example 1 and Example 6, it can be seen that by selecting the third monomer that forms other structural units and further controlling its content, the ion conduction performance of the polyionic liquid-based material is greatly improved, and the cycle performance of the solid lithium-ion battery assembled from it is also improved.

[0107] Comparing Examples 1 and 7-8, it can be seen that the present invention can significantly improve the ionic conductivity and interfacial contact performance of the prepared polyionic liquid-based material by adjusting the molar percentage content of electron-deficient structural units and further optimizing the distribution of anions and interfacial stability.

[0108] Comparing Example 1 and Comparative Examples 1-2, it can be seen that the prior art cannot achieve all the technical effects of the present invention if it does not introduce a first monomer to form a specific type of electron-deficient structural unit or introduces other types of monomers.

[0109] Comparing Example 1 with Comparative Example 3, it can be seen that polymers obtained by polymerization of different monomers cannot increase the migration number of metal ions after simple physical mixing, resulting in poor cycling performance and ion conduction performance.

[0110] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A polyionic liquid-based material, characterized in that, The polyionic liquid-based material comprises a copolymer and a metal salt, wherein the copolymer comprises ionic liquid structural units and electron-deficient structural units; The electron-deficient structural unit contains at least one of an amide group, an ester group, or a heteroatom.

2. The polyionic liquid-based material according to claim 1, characterized in that, The electron-deficient structural unit is derived from the first monomer; Preferably, the first monomer comprises a compound having at least one carbon-carbon double bond and at least one electron-deficient group; Preferably, the electron-deficient group includes at least one of an amide group, an ester group, or a heteroatom; Preferably, the first monomer is selected from any one or a combination of at least two of the following: an organic ester monomer containing at least one carbon-carbon double bond, an amide monomer containing at least one carbon-carbon double bond, a heteroatom-containing compound monomer containing at least one carbon-carbon double bond, or an amphoteric compound monomer containing at least one carbon-carbon double bond; and preferably an organic ester monomer containing at least one carbon-carbon double bond. Preferably, the first monomer is selected from any one or a combination of at least two of mono-2-(methacryloyloxy)ethyl phthalate, 3-acrylamidophenylboronic acid pinacol ester or 3-[(3-acrylamidopropyl)dimethylamino]propane-1-sulfonate, and is preferably mono-2-(methacryloyloxy)ethyl phthalate.

3. The polyionic liquid-based material according to claim 1 or 2, characterized in that, The ionic liquid structural unit is derived from the second monomer; Preferably, the second monomer comprises a polycationic ionic liquid monomer and / or a polyanionic ionic liquid monomer, and more preferably a polycationic ionic liquid monomer; Preferably, the polycationic ionic liquid monomer is selected from at least one of imidazolium ionic liquid, pyridinium ionic liquid, or pyrrolidineium ionic liquid; Preferably, the polyanionic ionic liquid monomer is selected from polyphosphate ionic liquids.

4. The polyionic liquid-based material according to any one of claims 1-3, characterized in that, The copolymer also includes other structural units; Preferably, the other structural units are derived from the third monomer; Preferably, the third monomer is selected from nitrile monomers and / or halogenated olefin monomers; Preferably, the metal salt includes lithium salt and / or sodium salt.

5. The polyionic liquid-based material according to claim 4, characterized in that, With the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the electron-deficient structural units is 5%-60%, preferably 10%-20%. Preferably, based on the molar amount of all structural units in the copolymer being 100%, the molar percentage of the ionic liquid structural unit is 20%-80%, more preferably 20%-60%. Preferably, with the total molar amount of all structural units in the copolymer being 100%, the molar percentage of the other structural units is 0%-50%, more preferably 20%-50%; Preferably, the metal salt has a mass percentage content of 20%-60%, more preferably 35%-45%, based on the total mass of the first monomer, the second monomer and the third monomer as 100%.

6. A method for preparing a polyionic liquid-based material according to any one of claims 1-5, characterized in that, The method includes the following steps: A precursor solution is obtained by mixing a first monomer that forms an electron-deficient structural unit, a second monomer that forms an ionic liquid structural unit, a metal salt, and an initiator, and then reacting to obtain the polyionic liquid-based material.

7. The method according to claim 6, characterized in that, The initiator is a photoinitiator; Preferably, the reaction is carried out under ultraviolet light; Preferably, the reaction temperature is 20℃-30℃; Preferably, the reaction time is 10s-30s.

8. A solid-state electrode, characterized in that, The solid electrode comprises an electrode active material, a polymer electrolyte, and a conductive agent, wherein the polymer electrolyte comprises a polyionic liquid-based material according to any one of claims 1-5.

9. The solid-state electrode according to claim 8, characterized in that, The mass ratio of the electrode active material, polymer electrolyte, and conductive agent is (80-90):(5-10):(3-15).

10. A solid-state battery, characterized in that, The solid-state battery includes electrodes and a solid electrolyte, wherein the electrodes include the solid-state electrodes according to claim 8 or 9.

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