Viscous polymer electrolyte and preparation method and application thereof

Abstract

The invention provides a viscous polymer electrolyte as well as a preparation method and application thereof. The viscous polymer electrolyte comprises a copolymer and a metal salt, wherein the copolymer comprises a hydrogen bond-containing structural unit and a conductive ion structural unit; the hydrogen bond-containing structural unit comprises at least one amide group, and the conductive ion structural unit comprises at least one of sulfuryl, sulfonyl, ether group, anhydride group or carbonate group. The viscous polymer electrolyte provided by the invention has excellent viscosity, so that the viscous polymer electrolyte not only can be used as an electrolyte to conduct metal ions, but also can replace a traditional positive electrode binder, thereby simplifying a manufacturing process of a solid secondary battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a viscous polymer electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium secondary batteries have been widely used in fields such as portable devices, power batteries, and energy storage devices. Currently, commercially available lithium secondary batteries mainly use liquid electrolytes, thus facing potential safety problems such as leakage of organic solvents and flammability. Compared with liquid electrolytes, the application of solid electrolytes in lithium secondary batteries can not only solve the safety problems of traditional liquid electrolytes, but also significantly improve the energy density and service life of the batteries. Among various types of solid electrolytes, polymer electrolytes have shown great potential in the preparation of large-scale electronic devices due to their advantages such as good flexibility, easy processing, moldability, and low density.

[0003] However, there are still the following problems in the application process of polymer electrolytes. For example, on the first hand, the interfacial contact performance between the all-solid polymer electrolyte and the electrode material is poor, mainly manifested as insufficient mechanical contact at the solid-solid interface, resulting in a large interfacial impedance, which in turn affects the charge-discharge efficiency and cycle life of the solid-state battery; on the second hand, the room-temperature ionic conductivity of polymer electrolytes is generally low, usually between 10 -6 to 10 -4 S / cm, which is much lower than that of liquid electrolytes; on the third hand, the lithium-ion transference number of most polymer electrolytes is low, which will cause concentration polarization during the charge-discharge process, thus affecting the cycle performance and rate performance of the solid-state battery; on the fourth hand, polymer electrolytes are easily oxidized at high voltages, especially when paired with high-voltage cathode materials (such as lithium cobaltate, lithium nickel cobalt manganese oxide, etc.), they are prone to violent electrochemical oxidative decomposition, resulting in a sharp decline in the electrochemical performance of the solid-state battery.

[0004] Therefore, in this field, there is an urgent need to develop a polymer electrolyte material to effectively improve its own ionic conduction performance and the interfacial performance between the electrode and the solid electrolyte. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a viscous polymer electrolyte, a preparation method thereof, and an application thereof. The viscous polymer electrolyte provided by the present invention has excellent viscosity, so it can not only conduct metal ions as an electrolyte, but also replace the traditional cathode binder, thereby simplifying the manufacturing process of solid-state secondary batteries.

[0006] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a viscous polymer electrolyte, which comprises a copolymer and a metal salt, and the copolymer comprises a hydrogen-bond-containing structural unit and an ion-conducting structural unit;

[0008] The hydrogen-bond-containing structural unit contains at least one amide group, and the ion-conducting structural unit contains at least one of a sulfone group, a sulfonyl group, an ether group, an anhydride group or a carbonate group.

[0009] By providing a viscous polymer electrolyte as a solid electrolyte material, the present invention significantly improves the interfacial performance between the electrode material and the solid electrolyte by utilizing its unique physical properties, and at the same time effectively increases the contact area between the two, thereby further reducing the interfacial resistance and increasing the ionic conductivity of the solid electrolyte at room temperature. In addition, due to its excellent adhesion performance, the viscous polymer electrolyte can also replace traditional cathode binders (such as polyvinylidene fluoride, abbreviated as PVDF) and be applied in the preparation process of cathode materials, and can effectively bond components such as cathode active materials and conductive agents, ensuring the integrity and stability of the cathode structure, and ultimately contributing to obtaining high-performance solid secondary batteries.

[0010] Specifically, by introducing a hydrogen-bond-containing structural unit and an ion-conducting structural unit, the present invention designs and obtains a viscous polymer electrolyte with both high ionic conductivity, excellent viscosity and high voltage resistance. On the one hand, since the hydrogen-bond-containing structural unit contains an amide group, it can not only effectively fix anions by forming hydrogen bonds with anions, thereby significantly increasing the transference number of metal ions (such as lithium ions) and reducing the adverse effects of anion migration on battery performance, but also form hydrogen bonds between polymer chains, enhancing the cohesion and viscosity of the copolymer, so that the prepared polymer electrolyte has excellent adhesion performance and is suitable for bonding electrode materials and solid electrolytes; on the other hand, at least one of the sulfone group, sulfonyl group, ether group, anhydride group or carbonate group contained in the ion-conducting structural unit provides a binding site for lithium ions, can effectively dissociate lithium salts and promote the dissociation and transport of lithium ions, thereby effectively improving the room-temperature ionic conductivity of the polymer electrolyte.

[0011] Preferably, the hydrogen-bond-containing structural unit is derived from a first monomer.

[0012] Preferably, the first monomer comprises a compound containing at least one carbon-carbon double bond and at least one amide group.

[0013] Preferably, the first monomer is selected from at least one of monofunctional acrylamide compounds, polyfunctional acrylamide compounds or propenylurea compounds.

[0014] Preferably, the monofunctional acrylamide compound is selected from any one or a combination of at least two of N-(2-amino-2-oxoethyl)acrylamide, N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(diethylamino)ethyl]acrylamide, N-(2-aminoethyl)methacrylamide, N-ethylacrylamide, or N-methyl-2-propenamide.

[0015] Preferably, the polyfunctional acrylamide compound is selected from any one or a combination of at least two of N,N′-vinylbisacrylamide, N,N′-bis(acryloyl)cystamine, or N,N′-methylenebisacrylamide.

[0016] Preferably, the allylurea compound is selected from allylurea.

[0017] By further optimizing the type of the first monomer, the present invention realizes the formation of hydrogen bond interactions and the anchoring of anions, thereby providing high viscosity and significantly improving the lithium ion transference number, such that the polymer electrolyte has both high ionic conductivity, excellent viscosity, and good mechanical properties.

[0018] Preferably, the ionic conductive structural unit is derived from a second monomer.

[0019] Preferably, the second monomer includes a compound containing at least one carbon-carbon double bond and at least one ionic conductive group.

[0020] Preferably, the ionic conductive group includes at least one of a sulfone group, a sulfonyl group, an ether group, an acid anhydride group, or a carbonate group, preferably a sulfone group and / or a sulfonyl group.

[0021] Preferably, the second monomer is selected from at least one of vinyl sulfone compounds, halogenated vinyl sulfonyl compounds, cyclic vinyl acid anhydride compounds, or cyclic vinyl carbonate compounds.

[0022] Preferably, the vinyl sulfone compounds include any one or a combination of at least two of methyl vinyl sulfone, (ethylsulfonyl)ethylene, or phenyl vinyl sulfone.

[0023] Preferably, the halogenated vinyl sulfonyl compound includes vinylsulfonyl fluoride.

[0024] Preferably, the cyclic vinyl acid anhydride compound includes maleic anhydride.

[0025] Preferably, the cyclic vinyl carbonate compound includes vinylene carbonate and / or ethylene vinylene carbonate.

[0026] By further optimizing the type of the second monomer, the present invention can effectively promote the dissociation of the metal salt and improve the ionic conductivity. These types of groups form stable complexes with the metal salt to lower the glass transition temperature of the polymer, thereby increasing the migration rate of metal ions.

[0027] Preferably, in the copolymer, the molar ratio of the hydrogen-bond-containing structural unit to the ion-conducting structural unit is 1:(2 - 10), preferably 1:5, and can be, for example, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, etc. By regulating the molar ratio of the hydrogen-bond-containing structural unit to the ion-conducting structural unit, the present invention enables the obtaining of a polymer electrolyte with high ionic conductivity, high transference number, and wide electrochemical window that has viscosity. If a lower molar content of the ion-conducting structural unit is used, the ionic conductivity of the polymer electrolyte will decrease accordingly; if a lower molar content of the hydrogen-bond-containing structural unit is used, the viscosity of the polymer electrolyte will decrease and the lithium ion transference number will decrease.

[0028] Preferably, the metal salt includes a lithium salt and / or a sodium salt.

[0029] It should be noted that in the present invention, the specific selection of the metal salt can be designed according to specific actual usage requirements. For example, if the viscous polymer electrolyte is used in a lithium-ion battery, the metal salt is selected as a lithium salt; if the viscous polymer electrolyte is used in a sodium-ion battery, the metal salt is selected as a sodium salt.

[0030] Meanwhile, it should be noted that the present invention has no special restrictions on the specific selection of the lithium salt, and commonly used lithium salts in the art are applicable, including but not limited to, for example, lithium difluorooxalate borate (LiDFOB), lithium difluorophosphate (LiPF2O2), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroborate (LiBF6), lithium trifluoromethanesulfonate (LiCF3SO3, LiTFA), lithium hexafluoroarsenate (LiAsF6), lithium bis(difluoromethanesulfonyl)imide (LiFSI), lithium bis(oxalato)borate (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or lithium malonate oxalate borate (LiMOB); the present invention also has no special restrictions on the specific selection of the sodium salt, and commonly used sodium salts in the art are also applicable.

[0031] Preferably, based on the total mass of the first monomer and the second monomer being 100%, the mass percentage of the metal salt is 10% - 25%, preferably 20%, and can be, for example, 10%, 12%, 15%, 18%, 20%, 22%, 25%, etc. By regulating the mass percentage of the metal salt in the present invention, the immiscible first monomer and second monomer are transformed into a miscible system without the presence of a solvent, and it is ensured that the prepared viscous polymer electrolyte has a high ionic conductivity. If a metal salt with a low mass percentage is used, the first monomer and the second monomer cannot be miscible; if a metal salt with a high mass percentage is used, the ionic conductivity of the viscous polymer electrolyte will decrease accordingly.

[0032] In a second aspect, the present invention provides a method for preparing the viscous polymer electrolyte according to the first aspect, and the method includes the following steps:

[0033] Mix the first monomer forming a hydrogen-bonding structural unit, the second monomer forming an ion-conducting structural unit, the metal salt, and the initiator to obtain a precursor solution, and obtain the viscous polymer electrolyte after a polymerization reaction.

[0034] Preferably, the polymerization reaction method includes photoinitiated polymerization or thermally initiated polymerization.

[0035] Preferably, the photoinitiated polymerization is carried out under ultraviolet light.

[0036] Preferably, the time of the photoinitiated polymerization is 10 s - 5 min, and can be, for example, 10 s, 20 s, 50 s, 1 min, 2 min, 3 min, 4 min, 5 min, etc.

[0037] Preferably, the temperature of the thermally initiated polymerization is 60°C - 80°C, and can be, for example, 60°C, 65°C, 70°C, 75°C, 80°C, etc.; the time is 0.5 h - 2 h, and can be, for example, 0.5 h, 1 h, 1.5 h, 2 h, etc.

[0038] By regulating the conditions of the polymerization reaction in the present invention, the polymerization degree of the copolymerization of the two monomers is adjusted, and then a viscous polymer electrolyte with high viscosity, high elasticity, and good electrochemical performance is obtained. If the polymerization degree is low, the reaction product is liquid; if the polymerization degree is high, the viscosity and ionic conductivity of the prepared polymer electrolyte are both poor.

[0039] In a third aspect, the present invention provides a solid-state positive electrode, and the solid-state positive electrode includes a positive electrode active material, a positive electrode binder, and a conductive agent, and the positive electrode binder includes the viscous polymer electrolyte according to the first aspect.

[0040] Preferably, the mass ratio of the positive electrode active material, the positive electrode binder, and the conductive agent is (80 - 90):(5 - 10):(3 - 15), and for example, it can be 80:5:15, 82:6:12, 85:8:7, 88:7:5, 90:5:5, etc.

[0041] Fourthly, the present invention provides a solid-state secondary battery, which includes a positive electrode, a negative electrode, and a solid electrolyte, and the positive electrode includes the solid positive electrode according to the third aspect.

[0042] The numerical ranges described in the present invention not only include the exemplified point values above, but also include any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention provides a viscous polymer electrolyte as a solid electrolyte material. Utilizing its unique physical properties, it significantly improves the interfacial performance between the electrode material and the solid electrolyte, and at the same time effectively increases the contact area between the two, thereby further reducing the interfacial resistance and increasing the ionic conductivity of the solid electrolyte at room temperature. In addition, due to its excellent adhesion properties, this viscous polymer electrolyte can also replace traditional positive electrode binders (such as polyvinylidene fluoride, abbreviated as PVDF) and be applied in the preparation process of positive electrode materials, and can effectively bond components such as positive electrode active materials and conductive agents, ensuring the integrity and stability of the positive electrode structure, and ultimately contributing to obtaining high-performance solid-state secondary batteries.

[0045] Specifically, by introducing a hydrogen-bond-containing structural unit and an ion-conducting structural unit, the present invention designs and obtains a viscous polymer electrolyte with both high ionic conductivity, excellent viscosity, and high voltage resistance. On the one hand, since the hydrogen-bond-containing structural unit contains an amide group, it can not only effectively fix anions by forming hydrogen bonds with anions, thereby significantly increasing the transference number of metal ions (such as lithium ions) and reducing the adverse effects of anion migration on battery performance, but also form hydrogen bonds between polymer chains, enhancing the cohesion and viscosity of the copolymer, so that the prepared polymer electrolyte has excellent adhesion properties and is suitable for bonding electrode materials and solid electrolytes; on the other hand, at least one group of sulfone group, sulfonyl group, ether group, anhydride group, or carbonate group contained in the ion-conducting structural unit provides a binding site for lithium ions, can effectively dissociate lithium salts and promote the dissociation and transmission of lithium ions, thereby effectively improving the room-temperature ionic conductivity of the polymer electrolyte. Description of the Drawings

[0046] Figure 1It is the test chart of the ionic conductivity of the viscous polymer electrolyte provided in Example 1 of the present invention.

[0047] Figure 2 It is the test chart of the lithium ion transference number of the viscous polymer electrolyte provided in Example 1 of the present invention.

[0048] Figure 3 It is the test chart of the electrochemical window of the viscous polymer electrolyte provided in Example 1 of the present invention;

[0049] Figure 4 It is the rate performance curve chart of the solid-state lithium ion battery prepared from the viscous polymer electrolyte and polyvinylidene fluoride binder respectively provided in Example 1 of the present invention. Detailed implementation manners

[0050] The technical solution of the present invention will be further described below by combining with the attached drawings and specific implementation manners. Those skilled in the art should understand that the said embodiments are only to help understand the present invention and should not be regarded as specific limitations to the present invention.

[0051] Example 1

[0052] This example provides a viscous polymer electrolyte. The viscous polymer electrolyte includes a copolymer and LiDFOB lithium salt. The copolymer includes N-(2-amino-2-oxoethyl)acrylamide structural unit and methyl vinyl sulfone structural unit.

[0053] Specifically, the molar ratio of N-(2-amino-2-oxoethyl)acrylamide structural unit to methyl vinyl sulfone structural unit in the copolymer is 1:5; based on the total mass of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone being 100%, the mass percentage content of LiDFOB lithium salt is 20%.

[0054] This example also provides a preparation method of the above viscous polymer electrolyte. The preparation method includes the following steps:

[0055] In a glove box filled with argon, mix the above-mentioned formulated amounts of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone at room temperature, add LiDFOB lithium salt and stir for 6 h to obtain a homogeneous and transparent solution. Then add BASF Irgacure 819 photoinitiator (based on the total mass of the copolymer being 100%, the mass percentage content of BASF Irgacure 819 photoinitiator is 5 wt.%), stir evenly to obtain a precursor solution; drop the above precursor solution on the surface of a polytetrafluoroethylene plate, and use ultraviolet light with a wavelength of 365 nm to initiate the polymerization reaction for 3 min to obtain the viscous polymer electrolyte.

[0056] Example 2

[0057] This embodiment provides a viscous polymer electrolyte, which includes a copolymer and a LiDFOB lithium salt. The copolymer includes N-(2-amino-2-oxoethyl)acrylamide structural units and methyl vinyl sulfone structural units.

[0058] Specifically, the molar ratio of N-(2-amino-2-oxoethyl)acrylamide structural units to methyl vinyl sulfone structural units in the copolymer is 1:6; based on the total mass of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone being 100%, the mass percentage content of the LiDFOB lithium salt is 20%.

[0059] This embodiment also provides a preparation method of the above-mentioned viscous polymer electrolyte. The preparation method includes the following steps:

[0060] In a glove box filled with argon, the above-mentioned formulated amounts of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone are mixed at room temperature, and the LiDFOB lithium salt is added and stirred for 6 h to obtain a homogeneous and transparent solution. Then, BASF Irgacure 819 photoinitiator is added (based on the total mass of the copolymer being 100%, the mass percentage content of BASF Irgacure 819 photoinitiator is 5 wt.%), and after stirring evenly, a precursor solution is obtained; the above-mentioned precursor solution is dropped onto the surface of a polytetrafluoroethylene plate, and a polymerization reaction is initiated with ultraviolet light having a wavelength of 365 nm for 3 min to obtain the viscous polymer electrolyte.

[0061] Example 3

[0062] This embodiment provides a viscous polymer electrolyte, which includes a copolymer and a LiTFSI lithium salt. The copolymer includes N-(2-amino-2-oxoethyl)acrylamide structural units and methyl vinyl sulfone structural units.

[0063] Specifically, the molar ratio of N-(2-amino-2-oxoethyl)acrylamide structural units to methyl vinyl sulfone structural units in the copolymer is 1:5; based on the total mass of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone being 100%, the mass percentage content of the LiTFSI lithium salt is 20%.

[0064] This embodiment also provides a preparation method of the above-mentioned viscous polymer electrolyte. The preparation method includes the following steps:

[0065] In a glove box filled with argon, the above-mentioned formulated amounts of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone were mixed at room temperature, and LiTFSI lithium salt was added and stirred for 6 h to obtain a homogeneous and transparent solution. Then, BASF Irgacure 819 photoinitiator (calculated based on the total mass of the copolymer being 100%, the mass percentage content of BASF Irgacure 819 photoinitiator is 5 wt.%) was added and stirred evenly to obtain a precursor solution; the above precursor solution was dropped onto the surface of a polytetrafluoroethylene plate, and a polymerization reaction was initiated with ultraviolet light having a wavelength of 365 nm for 3 min to obtain the viscous polymer electrolyte.

[0066] Example 4

[0067] The difference between this example and Example 1 is that the N-(2-amino-2-oxoethyl)acrylamide monomer was replaced with an equal content of N,N′-bis(acryloyl)cystamine monomer, and the others were the same as in Example 1.

[0068] Example 5

[0069] The difference between this example and Example 1 is that the methyl vinyl sulfone monomer was replaced with an equal content of (ethylsulfonyl)ethylene monomer, and the others were the same as in Example 1.

[0070] Example 6

[0071] The difference between this example and Example 1 is that the methyl vinyl sulfone monomer was replaced with an equal content of vinylene carbonate monomer, and the others were the same as in Example 1.

[0072] Example 7

[0073] The difference between this example and Example 1 is that the molar ratio of the N-(2-amino-2-oxoethyl)acrylamide structural unit to the methyl vinyl sulfone structural unit in the copolymer is 1:0.5, and the others are the same as in Example 1.

[0074] Example 8

[0075] The difference between this example and Example 1 is that the molar ratio of the N-(2-amino-2-oxoethyl)acrylamide structural unit to the methyl vinyl sulfone structural unit in the copolymer is 1:15, and the others are the same as in Example 1.

[0076] Example 9

[0077] The difference between this example and Example 1 is that calculated based on the total mass of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone being 100%, the mass percentage content of LiDFOB lithium salt is 5%, and the others are the same as in Example 1.

[0078] Example 10

[0079] The difference between this example and Example 1 is that, based on the total mass of N-(2-amino-2-oxoethyl)acrylamide and methyl vinyl sulfone being 100%, the mass percentage content of LiDFOB lithium salt is 30%, and the others are the same as in Example 1.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is that the N-(2-amino-2-oxoethyl)acrylamide monomer is replaced with an equal content of vinyl alcohol monomer, and the others are the same as in Example 1.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 1 is that the N-(2-amino-2-oxoethyl)acrylamide monomer is replaced with an equal content of methyl vinyl sulfone monomer, and the others are the same as in Example 1.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that the methyl vinyl sulfone monomer is replaced with an equal content of acrylonitrile monomer, and the others are the same as in Example 1.

[0086] Comparative Example 4

[0087] The difference between this comparative example and Example 1 is that the methyl vinyl sulfone monomer is replaced with an equal content of N-(2-amino-2-oxoethyl)acrylamide monomer, and the others are the same as in Example 1.

[0088] The viscous polymer electrolytes provided in Examples 1 to 10 and Comparative Examples 1 to 4 were used to prepare solid-state positive electrode sheets, and further assembled into solid-state lithium-ion batteries. The preparation method is as follows:

[0089] Preparation of solid-state positive electrode sheets: Weigh the viscous polymer electrolytes provided in Examples 1 to 10 and Comparative Examples 1 to 4 and N-methylpyrrolidone solvent in a mass ratio of 1:19, mix them, and stir for 2 h to obtain a homogeneous viscous polymer electrolyte solution. Then, weigh the positive electrode active material lithium cobaltate (abbreviated as LCO), conductive carbon Super P, and the obtained viscous polymer electrolyte solution in a mass ratio of 90:5:5, stir for more than 6 h to obtain a uniform positive electrode paste. The positive electrode paste is evenly coated on a carbon-coated aluminum foil current collector by a doctor blade method, placed in a vacuum drying oven at 80 °C for 12 h, cut into circular pieces with a 12 mm diameter punch, and roll-pressed to obtain positive electrode sheets.

[0090] The positive electrode case, the above-mentioned solid-state positive electrode sheet, the cellulose membrane, the lithium sheet, the steel sheet, the elastic sheet, the negative electrode case, etc. are assembled in sequence. After dropping the polymer precursor solution onto the surface of the cellulose membrane and fully wetting it, polymerization is carried out under an ultraviolet lamp with a wavelength of 365 nm for 1 min to assemble a solid-state lithium-ion battery. After standing at 30 °C for 12 h, electrochemical performance tests are carried out.

[0091] Comparative Example 5

[0092] This comparative example provides a method for preparing a solid-state positive electrode sheet using a polyvinylidene fluoride binder and assembling a solid-state lithium-ion battery, which includes the following steps:

[0093] Preparation of the solid-state positive electrode sheet: Weigh the polyvinylidene fluoride binder and N-methylpyrrolidone solvent in a mass ratio of 1:19 and mix them, and stir for 2 h to obtain a uniform polyvinylidene fluoride binder solution. Then, weigh the positive electrode active material lithium cobaltate (abbreviated as LCO), conductive carbon Super P, and the above-obtained polyvinylidene fluoride binder solution in a mass ratio of 90:5:5, stir for more than 6 h to obtain a uniform positive electrode paste, uniformly scrape the positive electrode paste onto the carbon-coated aluminum foil current collector by the doctor blade method, place it in a vacuum drying oven at 80 °C for 12 h, and then use a punching die with a diameter of 12 mm to cut it into circular pieces, and obtain the positive electrode sheet after rolling.

[0094] The positive electrode case, the above-mentioned solid-state positive electrode sheet, the polymer electrolyte, the lithium sheet, the steel sheet, the elastic sheet, the negative electrode case, etc. are assembled in sequence to obtain a solid-state lithium-ion battery. After standing at 30 °C for 12 h, electrochemical performance tests are carried out. Among them, the composition of the polymer electrolyte includes a polymer matrix obtained by polymerizing sulfolane, fluoroethylene carbonate, and dibutyl vinyl borate in a mass ratio of 4:1:0.05, and then an appropriate amount of LiTFSI lithium salt is added (calculated based on the total mass of the polymer matrix being 100%, the mass percentage content of LiTFSI lithium salt is 40%).

[0095] Test conditions

[0096] The solid-state lithium-ion batteries assembled in Examples 1 to 10 and Comparative Examples 1 to 5 are subjected to performance tests, and the test conditions are as follows:

[0097] (1) Ionic conductivity: Tested using an electrochemical workstation.

[0098] (2) Lithium ion transference number: Explanation of the test and calculation formula for the lithium ion transference number of the solid electrolyte: The system used for the tested battery is "lithium sheet / solid electrolyte membrane / lithium sheet". The assembled battery is tested on an electrochemical workstation with a polarization potential of 10 mV. The impedance of the battery before and after polarization is measured by electrochemical impedance spectroscopy. The initial current and steady-state current are obtained by the steady-state current method. The data is substituted into t Li+ = Is(△V - R o ·I o ) / I o (△V - R s ·I s ) to calculate the lithium ion transference number t Li+ , where I o is the initial current, I s is the steady-state current, R o is the initial resistance, R s is the steady-state resistance, and △V is the polarization voltage.

[0099] (3) Electrochemical window: Linear sweep voltammetry test is carried out at a potential sweep rate of 0.1 mV / s.

[0100] (4) Rate performance test: The Li|polymer electrolyte|LCO solid-state lithium ion battery is tested for constant current charge and discharge using a Neware battery test cabinet.

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

[0102] Table 1

[0103]

[0104] As can be seen from Table 1 and Figures 1-4 , the ionic conductivity of the viscous polymer electrolyte provided in Example 1 is as Figure 1 shown, the corresponding lithium ion transference number is shown in Figure 2 , the corresponding electrochemical window is shown in Figure 3 , and the rate performance curve of the solid-state lithium ion battery assembled with the commercial polyvinylidene fluoride binder provided in Comparative Example 5 is shown in Figure 4 , indicating that a viscous polymer electrolyte with high adhesion, high lithium ion transference number and good antioxidant properties is prepared, and the assembled solid-state lithium ion battery has good rate performance.

[0105] Comparing Example 1, Examples 7 - 8, it can be seen that by adjusting the molar ratio of the N-(2-amino-2-oxoethyl) acrylamide structural unit to the methyl vinyl sulfone structural unit in the copolymer to an appropriate range, the present invention can obtain a polymer electrolyte with high ionic conductivity, high transference number and wide electrochemical window having viscosity.

[0106] Comparing Example 1, Examples 9 - 10, it can be seen that by regulating the mass percentage content of LiDFOB lithium salt, the present invention enables the insoluble first monomer and second monomer to transform into a miscible system, without the need for the presence of a solvent, and ensures that the prepared viscous polymer electrolyte has a high ionic conductivity.

[0107] Comparing Example 1, Comparative Example 1 and Comparative Example 3, it can be seen that due to the large rigidity of the cyano group in acrylonitrile, it is not conducive to the movement and conduction of lithium ions, resulting in the ionic conductivity, lithium ion transference number and electrochemical window of the copolymerized electrolyte being inferior to those of the polymer electrolyte provided by the present invention, and it does not have the viscous property.

[0108] Comparing Example 1, Comparative Example 2 and Comparative Example 4, it can be seen that the polymer electrolyte obtained by using only one kind of monomer cannot achieve all the technical effects of the present invention. Among them, the methyl vinyl sulfone monomer in Comparative Example 2 is in a liquid state, and a gel polymer electrolyte is obtained after the polymerization reaction. Although its ionic conductivity is higher than that of the solid electrolyte, the lithium ion transference number is low, resulting in poor rate performance of the assembled solid lithium ion battery. And the N-(2-amino-2-oxoethyl)acrylamide monomer in Comparative Example 4 is in a solid state and cannot be miscible for reaction.

[0109] The applicant declares that the above are only specific embodiments 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 thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A viscous polymer electrolyte, characterized in that, The viscous polymer electrolyte includes a copolymer and a metal salt, and the copolymer includes a hydrogen-bond-containing structural unit and an ion-conducting structural unit; The hydrogen-bond-containing structural unit contains at least one amide group, and the ion-conducting structural unit contains at least one of a sulfone group, a sulfonyl group, an ether group, an acid anhydride group, or a carbonate group.

2. The sticky polymer electrolyte according to claim 1, wherein The hydrogen-bond-containing structural unit is derived from a first monomer; Preferably, the first monomer includes a compound containing at least one carbon-carbon double bond and at least one amide group; Preferably, the first monomer is selected from at least one of monofunctional acrylamide compounds, polyfunctional acrylamide compounds, or allylurea compounds; Preferably, the monofunctional acrylamide compound is selected from any one or a combination of at least two of N-(2-amino-2-oxoethyl)acrylamide, N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(diethylamino)ethyl]acrylamide, N-(2-aminoethyl)methacrylamide, N-ethylacrylamide, or N-methyl-2-acrylamide; Preferably, the polyfunctional acrylamide compound is selected from any one or a combination of at least two of N,N′-vinylbisacrylamide, N,N′-bis(acryloyl)cystamine, or N,N′-methylenebisacrylamide; Preferably, the allylurea compound is selected from allylurea.

3. The sticky polymer electrolyte according to claim 1 or 2, characterized in that, The ion-conducting structural unit is derived from a second monomer; Preferably, the second monomer includes a compound containing at least one carbon-carbon double bond and at least one ion-conducting group; Preferably, the ion-conducting group includes at least one of a sulfone group, a sulfonyl group, an ether group, an acid anhydride group, or a carbonate group, preferably a sulfone group and / or a sulfonyl group; Preferably, the second monomer is selected from at least one of vinyl sulfone compounds, halogenated vinyl sulfonyl compounds, cyclic vinyl acid anhydride compounds, or cyclic vinyl carbonate compounds; Preferably, the vinyl sulfone compound includes any one or a combination of at least two of methyl vinyl sulfone, (ethylsulfonyl)ethylene, or phenyl vinyl sulfone; Preferably, the halogenated vinyl sulfonyl compound includes vinyl sulfonyl fluoride; Preferably, the cyclic vinyl acid anhydride compound includes maleic anhydride; Preferably, the cyclic vinyl carbonate compound includes vinylene carbonate and / or ethylene vinylene carbonate.

4. The sticky polymer electrolyte according to any one of claims 1-3, characterized in that, In the copolymer, the molar ratio of the hydrogen-bond-containing structural unit to the ion-conducting structural unit is 1:(2 - 10), preferably 1:

5.

5. The sticky polymer electrolyte according to claim 3, characterized in that, The metal salt includes a lithium salt and / or a sodium salt; Preferably, based on the total mass of the first monomer and the second monomer being 100%, the mass percentage content of the metal salt is 10% - 25%, preferably 20%.

6. A method for preparing a viscous polymer electrolyte according to any one of claims 1-5, characterized in that, The method includes the following steps: Mixing a first monomer forming a hydrogen-bond-containing structural unit, a second monomer forming an ion-conducting structural unit, a metal salt, and an initiator to obtain a precursor solution, and obtaining the viscous polymer electrolyte after a polymerization reaction.

7. The method according to claim 6, characterized in that The manner of the polymerization reaction includes photoinitiated polymerization or thermally initiated polymerization; Preferably, the photoinitiated polymerization is carried out under ultraviolet light; Preferably, the time for photoinitiated polymerization is 10 s - 5 min; Preferably, the temperature for thermally initiated polymerization is 60 °C - 80 °C, and the time is 0.5 h - 2 h.

8. A solid-state positive electrode, characterized in that, The solid cathode includes a cathode active material, a cathode binder, and a conductive agent, and the cathode binder includes the viscous polymer electrolyte according to any one of claims 1 - 5.

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

10. A solid-state secondary battery, characterized in that, The solid secondary battery includes a cathode, an anode, and a solid electrolyte, and the cathode includes the solid cathode according to claim 8 or 9.

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