Solid-state polymer electrolyte and preparation method thereof, positive pole piece, solid-state lithium battery and preparation method thereof, and electric equipment

Abstract

The invention relates to the technical field of solid-state lithium batteries, in particular to a solid-state polymer electrolyte, a preparation method of the solid-state polymer electrolyte, a positive pole piece, a solid-state lithium battery, a preparation method of the solid-state lithium battery and electric equipment. The solid polymer electrolyte is mainly prepared from a lithium salt, an ionic liquid monomer containing a carbon-carbon double bond and a monomer having an anchoring effect on anions of the lithium salt. The solid polymer electrolyte provided by the invention has a high electrochemical window and high ionic conductivity.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium battery technology, and more specifically, to solid polymer electrolytes and their preparation methods, positive electrode sheets, solid-state lithium batteries and their preparation methods, and electrical devices. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronics, electric vehicles, and aerospace, but their development is limited by the leakage, volatility, and flammability of liquid electrolytes. Therefore, solid-state electrolytes are key materials for achieving high safety and cycle stability in all-solid-state batteries. Compared to inorganic solid-state electrolytes, solid polymer electrolytes offer advantages such as high air stability, ease of processing, low cost, and light weight. Furthermore, theoretically, solid polymer electrolytes have low porosity, weak grain boundary effects, and low surface roughness, which are beneficial for internal series connection and simplifying battery pack structure, thereby increasing energy density. Therefore, they are considered an ideal choice for electrolytes in future lithium batteries.

[0003] Currently, lithium iron phosphate batteries based on polyethylene oxide (PEO)-based solid-state electrolytes have been successfully commercialized by Bollore in France, demonstrating significant technological advantages. However, their oxidation decomposition potential is low. When used with higher-voltage cathode materials (such as lithium cobalt oxide and high-nickel ternary cathode materials), their polyether chains undergo oxidative decomposition, generating significant interfacial impedance and causing a sharp decline in battery capacity. Current construction strategies for high-voltage solid-state polymer electrolytes mainly include molecular modification and component control. Molecular modification primarily involves introducing electron-withdrawing groups, but direct introduction can affect lithium-ion coordination, leading to impaired ion transport. Component control includes adding inorganic components to reduce physical contact at the electrode / electrolyte interface and suppress electronic interaction between the electrode and electrolyte. However, agglomeration or sedimentation problems can easily lead to uneven distribution of inorganic fillers in the polymer, affecting local differences in ion conduction and the uniformity of electrode reactions.

[0004] CN114188595A discloses a comb-shaped solid polymer electrolyte and a lithium-ion battery including the solid polymer electrolyte. Compared with polyethylene oxide (PEO) polymer electrolyte, the solid polymer electrolyte has higher conductivity and a higher electrochemical window, but its inherent ether functional groups limit the cathode materials that can be adapted to higher voltages.

[0005] CN110048158A discloses a method for preparing a solid polymer electrolyte lithium-ion battery, the cell of which includes a negative electrode, a polymer electrolyte layer, and a positive electrode. The polymerization method can improve the tight contact of the materials. However, it has low room temperature ionic conductivity and poor cycle stability.

[0006] It is evident that the solid-state batteries prepared above still suffer from problems such as low room temperature ionic conductivity, low oxidation decomposition potential, low energy density, and poor cycle stability.

[0007] Therefore, it is essential to develop solid-state polymer electrolytes with high voltage windows and lithium metal batteries that include such electrolytes.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] The primary objective of this invention is to provide a solid polymer electrolyte in which the abundant cations and anions in the ionic liquid monomer can effectively dissociate lithium salts. At the same time, the molecular anchoring effect increases the restriction of lithium salt anions, thereby increasing the lithium ion migration number and broadening the electrochemical window of the solid polymer electrolyte.

[0010] The second objective of this invention is to provide a method for preparing a solid polymer electrolyte. This method uses in-situ thermal polymerization to completely solidify the liquid electrolyte. This fundamentally solves the problems of easy leakage, volatility, and flammability of liquid electrolytes. At the same time, it ensures that the electrolyte is uniformly dispersed in the electrode material and tightly bonded to it, reducing mutual interference between internal battery components and reducing the contact between the solution and solid interfaces during the process. This reduces internal battery heat and reaction risks, and improves battery safety performance and cycle life.

[0011] The third objective of this invention is to provide a positive electrode sheet.

[0012] The fourth objective of this invention is to provide a solid-state lithium battery.

[0013] The fifth objective of this invention is to provide a method for preparing a solid-state lithium battery.

[0014] The sixth objective of this invention is to provide an electrical device.

[0015] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0016] The present invention first provides a solid polymer electrolyte, which is mainly composed of lithium salt, ionic liquid monomer containing carbon-carbon double bonds, and monomer that has an anchoring effect on the anions of said lithium salt.

[0017] The present invention further provides a method for preparing the solid polymer electrolyte, comprising the following steps:

[0018] The raw materials are mixed and then thermally polymerized in situ.

[0019] Preferably, the temperature of the in-situ thermal polymerization is 50–70°C;

[0020] Preferably, the preparation method of the solid polymer electrolyte specifically includes: in-situ thermal polymerization of a mixture of a lithium salt, an ionic liquid monomer containing a carbon-carbon double bond, a monomer that anchors the anion of the lithium salt, a crosslinking agent, and an initiator to obtain the solid polymer electrolyte.

[0021] The present invention further provides a positive electrode sheet, comprising the solid polymer electrolyte;

[0022] Preferably, the mass of the solid polymer electrolyte accounts for less than 10% of the total mass of the raw materials other than the current collector in the positive electrode sheet.

[0023] The present invention also provides a solid-state lithium battery, including the solid polymer electrolyte;

[0024] Preferably, the thickness of the solid polymer electrolyte is 50–300 μm.

[0025] Preferably, the room temperature ionic conductivity of the solid-state lithium battery is >0.6 mS·cm. -1 .

[0026] The present invention further provides a method for preparing the solid-state lithium battery, comprising the following steps:

[0027] After stacking the positive electrode, separator, and negative electrode, the raw materials for preparing the solid polymer electrolyte are added, and in-situ thermal polymerization is carried out, followed by encapsulation and formation.

[0028] The present invention also provides an electrical device including the solid-state lithium battery.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) The solid polymer electrolyte provided by the present invention has abundant anions and cations in the ionic liquid monomer that can effectively dissociate lithium salts. At the same time, the restriction on lithium salt anions is increased through molecular anchoring, which can increase the migration number of lithium ions and improve the electrochemical window of the solid polymer electrolyte.

[0031] (2) This invention constructs a novel high-voltage resistance mechanism for polymer electrolytes. Based on polymer molecular engineering and theoretical calculations, this invention avoids the structural groups that are easily oxidized in traditional lithium-ion solid polymer electrolytes from the perspective of molecular structure design. Through the synergistic regulation strategy of high-fluorine monomer structure and ionic liquid and molecular anchoring effect, the restriction on lithium salt anions is increased, the highest occupied molecular orbital (HOMO) energy level of the overall polymer electrolyte is reduced, and the electrochemical stability window is broadened.

[0032] (3) This invention optimizes the polymer electrolyte / lithium metal interface and the polymer electrolyte / cathode interface by regulating the monomer and lithium salt structure of the polymer electrolyte, adding high-fluorine monomers (fluorinated olefin compounds), and introducing boron-containing lithium salts (boron-containing lithium salts are beneficial to further improve the electrochemical window and the stability of the cathode), and precisely regulates the interface passivation layer, thereby generating an ideal interface with high ionic and low electronic conductivity, regulating the interaction between local molecules, dynamically suppressing electrochemical decomposition, and helping the battery to operate stably under high voltage.

[0033] (4) This invention has made targeted designs on some key parameters for forming solid polymer electrolytes. For example, by screening the side chain length of fluorinated olefin compounds, comparing the structure of ionic liquid monomers containing carbon-carbon double bonds, and optimizing the molar ratio of each raw material, a single-ion polymer electrolyte system film with excellent mechanical properties, higher ionic conductivity and lithium ion transference number can be obtained. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 Linear cyclic voltammogram of a solid-state lithium battery prepared in Example 1 of this invention;

[0036] Figure 2 Charge-discharge curves of the solid-state lithium battery prepared in Example 1 of this invention;

[0037] Figure 3 Charge-discharge curves of the solid-state lithium battery prepared in Example 2 of this invention;

[0038] Figure 4 Rate performance test chart of the solid-state lithium battery prepared in Example 2 of the present invention;

[0039] Figure 5 Cycle performance curve of the solid-state lithium battery prepared in Example 1 of this invention. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0041] Unless otherwise specified, in this invention, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0042] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0043] Unless otherwise specified, in this invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. "Several" refers to any two or more.

[0044] In a first aspect, the present invention provides a solid polymer electrolyte, which is mainly composed of a lithium salt, an ionic liquid monomer containing polymerizable carbon-carbon double bonds, and a monomer that has an anchoring effect on the anions of the lithium salt.

[0045] Based on polymer molecular engineering and theoretical calculations, this invention avoids the easily oxidized structural groups of traditional lithium-ion solid polymer electrolytes from the perspective of molecular structure design. It adopts a synergistic regulation strategy of the structure with the anchoring effect on lithium salt anions and ionic liquid, which increases the restriction on lithium salt anions, reduces the highest occupied molecular orbital (HOMO) energy level of the overall polymer electrolyte, and broadens the electrochemical stability window.

[0046] In polyionic liquid-based polymer electrolyte systems, in addition to the lithium salt anions, there are also additional anions that attract the polycations. Therefore, the number of anions is much higher than in traditional polymer systems, resulting in a very low lithium-ion transference number. This invention, by introducing monomers that anchor the anions, significantly restricts anion movement, thereby increasing the lithium-ion transference number.

[0047] In some specific embodiments, the structural formula of the ionic liquid monomer containing carbon-carbon double bonds is shown in formula (Ⅰ):

[0048]

[0049] In formula (Ⅰ), R1, R2, and R3 are each independently selected from hydrogen, halogen, nitro, cyano, substituted or unsubstituted C. 1～ C 12 Alkyl, substituted or unsubstituted C 1～ C 12 The alkoxy group, and any one of the substituted or unsubstituted amino groups; M is an ionic liquid structural group including inorganic anions and organic cations.

[0050] In some specific embodiments, M includes at least one of the groups having structures as shown in formulas (II) to (X):

[0051]

[0052]

[0053] In equations (II) to (X), X θ It is an inorganic anion, X θ Including (FSO2)2N θ (CF3SO2)2N θ -COO θ -PO3 θ -SO3 θ BF4 θ PF6 θ Cl θ and Br θ At least one of the following; n is a natural number from 0 to 12.

[0054] In equations (II) to (X), n includes, but is not limited to, any one of the point values ​​of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, or any range of values ​​between any two.

[0055] The wavy lines in equations (II) to (X) represent the connection points with M in equation (I), and each of the wavy line connections in equations (II) to (X) contains a carbon atom, for example, equation (II) with the following structural formula: The junction of the wavy lines (inside the circle) contains one carbon atom.

[0056] The ionic liquid monomer with the above-described structure has abundant cations and anions, which can effectively dissociate lithium salts, thereby increasing ionic conductivity. Furthermore, by using the ionic liquid monomer with the above-described structure, solid polymer electrolyte films with excellent mechanical properties, higher ionic conductivity, and higher lithium-ion transference numbers can be obtained.

[0057] In some specific embodiments, the anchoring effect is achieved through at least one of the following forces: hydrogen bonding, anion-π interaction, ionic dipole force, and dipole-dipole force.

[0058] Molecular anchoring can increase the confinement of lithium salt anions, improve the lithium ion migration number, and increase the electrochemical window.

[0059] In some specific embodiments, the monomer that anchors the anion of the lithium salt includes a fluorinated olefin compound.

[0060] The introduction of fluorinated olefin compounds can greatly restrict the movement of anions in lithium salts, thereby increasing the lithium-ion transference number.

[0061] In some specific embodiments, the fluorinated olefin compound includes at least one of fluoroolefin esters, fluoroolefin carbonates, and fluoroolefin ethers.

[0062] In some specific embodiments, the fluoroolefin ester compound has the structural formula as shown in formula (1).

[0063] As shown:

[0064] In equation (1), n ​​is a natural number from 1 to 10.

[0065] In equation (1), n ​​includes, but is not limited to, any one of the point values ​​of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or any range of values ​​between any two.

[0066] In some specific embodiments, the structural formula of the fluoroolefin carbonate compound is shown in formula (2):

[0067] In equation (2), n is a natural number from 1 to 10.

[0068] In equation (2), n includes, but is not limited to, any one of the point values ​​of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or any range of values ​​between any two.

[0069] In some specific embodiments, the structural formula of the fluoroolefin ether compound is shown in formula (3):

[0070] In equation (3), n is a natural number from 1 to 10.

[0071] In equation (3), n includes, but is not limited to, any one of the point values ​​of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or any range of values ​​between any two.

[0072] By using fluorinated olefin compounds with the above-mentioned structural formula, solid polymer electrolyte films with excellent mechanical properties, higher ionic conductivity, and lithium-ion transference number can be obtained.

[0073] In some specific embodiments, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium oxalateborate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, and lithium hexafluorophosphate.

[0074] Preferably, the lithium salt is selected from at least one of lithium difluorooxalate borate, lithium oxalate borate, and lithium tetrafluoroborate. By adding boron-containing lithium salts, the polymer electrolyte / lithium metal interface and the polymer electrolyte / cathode interface can be optimized, thereby obtaining an interface with high ionic and low electronic conductivity, and improving the cycle stability of high-voltage solid-state batteries.

[0075] In some specific embodiments, the molar ratio of the lithium salt to the ionic liquid monomer containing carbon-carbon double bonds is 1:1 to 10; including but not limited to any one of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any range between the two.

[0076] In some specific embodiments, the molar ratio of the ionic liquid monomer containing carbon-carbon double bonds to the monomer that anchors the anion of the lithium salt is 1 to 20:1, including but not limited to any one of 1:1, 2:1, 3:1, 5:1, 7:1, 8:1, 10:1, 12:1, 13:1, 15:1, 18:1, 20:1 or any range between the two.

[0077] This invention optimizes the molar ratio of each raw material to comprehensively improve the mechanical properties, ionic conductivity, and lithium-ion transference number of solid polymer electrolytes.

[0078] In some specific embodiments, the raw materials for preparing the solid polymer electrolyte further include a crosslinking agent. The crosslinking agent can be any crosslinking agent commonly used in the art.

[0079] In some specific embodiments, the crosslinking agent includes at least one of N,N-methylenebisacrylamide, divinylbenzene, polyethylene glycol dimethacrylate, and polyethylene glycol diacrylate.

[0080] In some specific embodiments, the molar ratio of the crosslinking agent to the ionic liquid monomer containing carbon-carbon double bonds is 1:30 to 100; including but not limited to any one of 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, 1:100 or any range between two of them.

[0081] In some specific embodiments, the raw materials for preparing the solid polymer electrolyte further include an initiator. The initiator can be any initiator commonly used in the art.

[0082] In some specific embodiments, the initiator includes at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, ethyl 4-(N,N-dimethylamino)benzoate, and methyl o-benzoylbenzoate.

[0083] In some specific embodiments, the molar ratio of the initiator to the ionic liquid monomer containing carbon-carbon double bonds is 1:300 to 1000, a point value of any one of 1:300, 1:350, 1:400, 1:450, 1:500, 1:550, 1:600, 1:650, 1:700, 1:750, 1:800, 1:850, 1:900, 1:950, and 1:1000, or a range between any two.

[0084] In some specific embodiments, the ionic conductivity of the battery containing the above-mentioned solid polymer electrolyte is greater than 1 mS cm⁻¹. -1 ; including but not limited to 1.1mS cm -1 1.2mS cm -1 1.3mS cm -1 1.4mS cm -1 The point value of any one of them or the range value between any two.

[0085] Batteries fabricated using the solid polymer electrolyte provided by this invention exhibit high room temperature ionic conductivity. In some specific embodiments, the room temperature ionic conductivity of solid-state lithium batteries containing the solid polymer electrolyte is >0.6 mS·cm. -1 including but not limited to 0.65 mS·cm -1 0.67mS·cm -1 0.7 mS·cm-1 0.8 mS·cm -1 0.9 mS·cm -1 1mS·cm -1 1.1 mS·cm -1 1.2 mS·cm -1 1.3 mS·cm -1 1.4 mS·cm -1 1.5mS·cm -1 The point value of any one of them or the range value between any two.

[0086] Secondly, the present invention provides a method for preparing the above-mentioned solid polymer electrolyte, comprising the following steps:

[0087] The raw materials are mixed and then thermally polymerized in situ.

[0088] This invention employs an in-situ thermal polymerization method to completely solidify the liquid electrolyte. This fundamentally solves the problems of easy leakage, volatility, and flammability of liquid electrolytes, while also ensuring that the electrolyte is uniformly dispersed in the electrode material and tightly bonded to it. This reduces mutual interference between internal battery components and minimizes contact between the solution and solid interfaces during the process, thereby reducing internal battery heat and reaction risks, and improving battery safety performance and cycle life.

[0089] In some specific embodiments, the temperature of the in-situ thermal polymerization is 50 to 70°C; including but not limited to any one of 50°C, 53°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, and 70°C, or any range between two of them.

[0090] In some specific implementations, the in-situ thermal polymerization time can be any conventional polymerization time. For example, the in-situ thermal polymerization time is 2 to 10 hours, including but not limited to any one of 2 hours, 4 hours, 5 hours, 6 hours, 8 hours, and 10 hours, or any range between two of them.

[0091] In some specific embodiments, the preparation method of the solid polymer electrolyte specifically includes: in-situ thermal polymerization of a mixture of a lithium salt, an ionic liquid monomer containing a carbon-carbon double bond, a monomer that anchors the anion of the lithium salt, a crosslinking agent, and an initiator to obtain the solid polymer electrolyte.

[0092] Preferably, the preparation method of the solid polymer electrolyte specifically includes: mixing and stirring a lithium salt, an ionic liquid monomer containing a carbon-carbon double bond, and a monomer that anchors the anion of the lithium salt to form a homogeneous solution; then mixing a crosslinking agent with the lithium salt and dissolving it in the above homogeneous solution; then adding an initiator to the solution, stirring evenly, and heating to carry out in-situ polymerization; and finally obtaining the solid polymer electrolyte after cooling.

[0093] Thirdly, the present invention provides a positive electrode sheet comprising the above-mentioned solid polymer electrolyte.

[0094] Adding the above-mentioned solid polymer electrolyte to the positive electrode sheet can effectively bind the positive electrode material and the conductive agent, and promote the conduction of lithium ions in the positive electrode sheet.

[0095] In some specific embodiments, the positive electrode includes a current collector, a positive electrode material, a binder, a conductive agent, and the aforementioned solid polymer electrolyte.

[0096] In some specific embodiments, the mass of the solid polymer electrolyte accounts for less than 10% of the total mass of the raw materials other than the current collector in the positive electrode sheet, including but not limited to any one of 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, and 1%, or any range between two of them.

[0097] In some specific implementations, the positive electrode sheet is prepared using a wet process.

[0098] In some specific embodiments, the preparation method of the positive electrode sheet includes: uniformly mixing a positive electrode material, a binder, a conductive agent, a precursor for forming the solid polymer electrolyte, and a solvent, coating the mixture onto a current collector, and drying it to form a positive electrode sheet. The precursor for forming the solid polymer electrolyte is a mixture of a lithium salt, an ionic liquid monomer containing carbon-carbon double bonds, a monomer that anchors the anions of the lithium salt, a crosslinking agent, and an initiator.

[0099] In some specific embodiments, the adhesive includes any commonly used adhesive materials in the art, such as polytetrafluoroethylene, styrene-butadiene rubber, polyacrylonitrile, carboxymethyl cellulose salt, polyvinylidene fluoride, polyacrylic acid, polyacrylamide, chitosan, etc., but is not limited thereto.

[0100] In some specific embodiments, the binder accounts for 0.1% to 10% of the total mass of the mixture containing the positive electrode material, binder, conductive agent, precursor for forming the solid polymer electrolyte, and solvent.

[0101] In some specific embodiments, the conductive agent includes any conductive material commonly used in the art, such as carbon nanotubes, carbon black, vapor-deposited carbon fibers, graphene, etc., but is not limited thereto.

[0102] In some specific embodiments, the conductive agent accounts for 0.1% to 10% of the total mass of the mixture containing the positive electrode material, binder, conductive agent, precursor for forming the solid polymer electrolyte, and solvent.

[0103] In some specific embodiments, the solvent may be any solvent commonly used in the art, such as N-methylpyrrolidone, but is not limited thereto.

[0104] In some specific embodiments, the cathode material includes any cathode material commonly used in the art, such as lithium cobalt oxide, high-nickel ternary cathode, lithium nickel manganese oxide, and lithium-rich cathode materials, but is not limited thereto.

[0105] Fourthly, the present invention provides a high-voltage solid-state lithium battery, comprising the above-mentioned solid polymer electrolyte.

[0106] This invention uses polyionic liquid units and units that anchor lithium salt anions as the main framework to prepare a solid polymer electrolyte, which can produce a solid-state battery with high specific energy and high cycle stability.

[0107] In some specific embodiments, a solid-state lithium battery includes a cell, which includes a negative electrode, a solid polymer electrolyte, and a positive electrode.

[0108] In some specific embodiments, the thickness of the solid polymer electrolyte is 50 to 300 μm, including but not limited to any one of 50 μm, 60 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, and 300 μm, or any range between two of them. This can effectively reduce the interface impedance and improve the battery performance.

[0109] In some specific embodiments, the room temperature ionic conductivity of the solid-state lithium battery is >0.6 mS·cm -1 including but not limited to 0.65 mS·cm -1 0.67mS·cm -1 0.7 mS·cm -1 0.8 mS·cm -1 0.9 mS·cm -1 1mS·cm -1 1.1 mS·cm -1 1.2 mS·cm -1 1.3 mS·cm -1 1.4 mS·cm -1 1.5mS·cm -1 The point value of any one of them or the range value between any two.

[0110] Fifthly, the present invention provides a method for preparing the above-mentioned solid-state lithium battery, comprising the following steps:

[0111] After stacking the positive electrode, separator, and negative electrode, the raw materials for preparing the solid polymer electrolyte are added, and in-situ thermal polymerization is carried out, followed by encapsulation and formation.

[0112] The solid-state lithium battery prepared by the above method has high capacity, high rate performance and excellent cycle stability at high voltage.

[0113] The raw materials for preparing the solid polymer electrolyte include lithium salt, ionic liquid monomer containing carbon-carbon double bonds, monomer that anchors the anions of the lithium salt, crosslinking agent, and initiator.

[0114] In some specific embodiments, lithium salt, ionic liquid monomer containing carbon-carbon double bonds, monomer that anchors the anion of the lithium salt, crosslinking agent and initiator are injected into the battery cell. After complete wetting, monomer polymerization is initiated under certain conditions to form an in-situ solid-state battery. Alternatively, liquid electrolyte is first injected into the battery cell, and after aging and formation, lithium salt, ionic liquid monomer containing carbon-carbon double bonds, monomer that anchors the anion of the lithium salt, crosslinking agent and initiator are injected, and in-situ polymerization and gelation are carried out under certain conditions.

[0115] In a sixth aspect, the present invention provides an electrical device including the aforementioned solid-state lithium battery.

[0116] The aforementioned electrical equipment includes any device, equipment, or system that includes the aforementioned solid-state lithium battery.

[0117] The solid-state lithium battery provided by this invention can be widely used in various fields, such as transportation, electronics, aerospace, medical and energy storage, but is not limited thereto.

[0118] As an example, the aforementioned electrical equipment includes, but is not limited to, electric vehicles, electric motorcycles, electric bicycles, power tools, starting power supplies, energy storage systems, electronic products, household appliances, and office equipment.

[0119] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0120] Example 1

[0121] The method for preparing the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment includes the following steps:

[0122] (1) Preparation of precursor solutions for forming solid polymer electrolytes:

[0123] Under an inert atmosphere, 0.1 mol of hexafluorobutyl acrylate (a monomer that anchors the anion of lithium salts) and 0.9 mol of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer (an ionic liquid monomer containing carbon-carbon double bonds) were mixed thoroughly. Then, 0.5 mol of lithium bis(trifluoromethanesulfonyl)imide was added, and the mixture was heated and stirred at 50°C until the solution became clear and transparent, forming the first solution. The chemical structural formula of hexafluorobutyl acrylate is as follows: Hexafluorobutyl acrylate exhibits ion-dipole and dipole-dipole interactions with the anion in lithium bis(trifluoromethanesulfonyl)imide. The chemical structural formula of the 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide monomer is as follows:

[0124]

[0125] 0.01 mol N,N-methylenebisacrylamide (MBA) and 0.001 mol azobisisobutyronitrile (AIBN) were added to the first solution above, and the mixture was stirred at room temperature at a speed of 500 r / min until the solution became clear and transparent, thus obtaining the precursor solution.

[0126] (2) Preparation of positive and negative electrode sheets: 8g of nickel-cobalt-manganese ternary material (Li[Ni 0.8 Co 0.1 Mn 0.1 After uniformly mixing 1g of conductive carbon black, 0.5g of precursor solution prepared in step (1), and 0.5g of polyvinylidene fluoride (dissolved in 10g NMP), the mixture was stirred at room temperature for 10h at a speed of 600r / min. Then it was coated on the surface of carbon-coated aluminum foil current collector. After drying, rolling and cutting, the positive electrode sheet was obtained.

[0127] Battery-grade lithium sheets (99.9%, 16mm × 0.6mm) are slit to obtain negative electrode sheets.

[0128] (3) Preparation of solid-state lithium battery: The positive electrode, separator (glass fiber: GF / A-GF / D) and negative electrode obtained in step (2) are stacked to form a battery cell. Then, the precursor solution obtained in step (1) is added, and the mixture is heated at 70°C for 10 h to initiate monomer polymerization. After in-situ thermal polymerization, a solid polymer electrolyte is formed. Then, the mixture is sequentially encapsulated, formed, shaped and degassed to obtain a solid-state lithium battery. The thickness of the solid polymer electrolyte is 160 μm.

[0129] Example 2

[0130] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment are basically the same as those in Example 1, except that the nickel-cobalt-manganese ternary material Li[Ni] in step (2) is used instead of the original method. 0.8 Co 0.1 Mn 0.1 Replace O2) with an equal mass of Li[Ni 0.9 Co 0.05 Mn 0.05 O2, meaning all stoichiometric ratios are consistent with those in Example 1.

[0131] Example 3

[0132] The method for preparing the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment includes the following steps:

[0133] (1) Preparation of precursor solutions for forming solid polymer electrolytes:

[0134] Under an inert atmosphere, 0.3 mol of dodecafluoroheptyl acrylate (i.e., a monomer that anchors the anion of lithium salts) and 0.7 mol of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer (i.e., an ionic liquid monomer containing carbon-carbon double bonds) were mixed evenly, and then 0.5 mol of lithium bis(trifluoromethanesulfonyl)imide was added. The mixture was heated and stirred at 50°C until the solution became clear and transparent, forming the first solution.

[0135] The chemical structural formula of dodecafluoroheptyl acrylate is as follows: Dodecyl fluoroheptyl acrylate exhibits ion-dipole and dipole-dipole interactions with the anion in lithium bis(trifluoromethanesulfonyl)imide.

[0136] 0.01 mol N,N-methylenebisacrylamide (MBA) and 0.001 mol azobisisobutyronitrile (AIBN) were added to the first solution above, and the mixture was stirred at room temperature at a speed of 500 r / min until the solution became clear and transparent, thus obtaining the precursor solution.

[0137] (2) Preparation of positive electrode sheet: 8g of nickel-cobalt-manganese ternary material (Li[Ni 0.8 Co 0.1 Mn 0.1 After uniformly mixing 1g of conductive carbon black, 0.8g of the precursor solution prepared in step (1), and 0.2g of polyvinylidene fluoride (dissolved in 10g NMP), the mixture was stirred at room temperature for 10h at a speed of 600r / min. The mixture was then coated onto the surface of the carbon-coated aluminum foil current collector. After drying, rolling and slitting, the positive electrode sheet was obtained.

[0138] The negative electrode sheet is the same as in Example 1.

[0139] (3) Preparation of solid-state lithium battery: The positive electrode, separator (same as in Example 1), and negative electrode obtained in step (2) are stacked to form a battery cell. Then, the precursor solution obtained in step (1) is added, and the mixture is heated at 50°C for 10 hours to initiate monomer polymerization. After in-situ thermal polymerization, a solid polymer electrolyte is formed. Then, the mixture is sequentially encapsulated, formed, shaped, and degassed to obtain a solid-state lithium battery. The thickness of the solid polymer electrolyte is 250 μm.

[0140] Example 4

[0141] The preparation methods of the solid polymer electrolyte, positive electrode and solid lithium battery provided in this embodiment are basically the same as those in Example 3. The only difference is that when the precursor solution is prepared in step (1), 0.3 mol dodecafluoroheptyl acrylate is replaced with 0.1 mol allyl hexafluorobutyl carbonate and the molar amount of 1-allyl 3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer is replaced with 0.9 mol.

[0142] The structural formula of allyl hexafluorobutyl carbonate is: Allyl hexafluorobutyl carbonate exhibits ion-dipole and dipole-dipole interactions with the anion in lithium bis(trifluoromethanesulfonylimide).

[0143] Example 5

[0144] The preparation methods of the solid polymer electrolyte, positive electrode and solid lithium battery provided in this embodiment are basically the same as those in Example 3. The only difference is that when the precursor solution is prepared in step (1), 0.3 mol dodecyl fluoroheptyl acrylate is replaced with 0.1 mol allyl pentafluoropropyl ether, and the molar amount of 1-allyl 3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer is replaced with 0.9 mol.

[0145] The structural formula of allyl pentafluoropropyl ether is as follows: Allyl pentafluoropropyl ether exhibits ion-dipole and dipole-dipole interactions with the anion in lithium bis(trifluoromethanesulfonylimide).

[0146] Example 6

[0147] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment are basically the same as those in Example 3. The only difference is that when preparing the precursor solution in step (1), 0.3 mol dodecafluoroheptyl acrylate is replaced with 0.1 mol hexafluorobutyl acrylate, and 0.7 mol 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonate)imide salt monomer is replaced with 0.9 mol 1-allyl-1-methylpyrrole bis(trifluoromethanesulfonate)imide salt monomer.

[0148] The structural formula of the 1-allyl-1-methylpyrrole bis(trifluoromethanesulfonate)imide salt monomer is as follows:

[0149]

[0150] Example 7

[0151] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment are basically the same as those in Example 1, except that in step (1), when preparing the precursor solution, the 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer is replaced with an equimolar amount of 1-allyl-1-methylpiperidine hexafluorophosphate monomer, the structural formula of which is:

[0152]

[0153] Example 8

[0154] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment are basically the same as those in Example 1, except that in step (1), when preparing the precursor solution, the 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer is replaced with an equimolar amount of 1-allyl-3-methylpyrazole tetrafluoroborate, the structural formula of which is:

[0155]

[0156] Example 9

[0157] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this embodiment are basically the same as those in Example 1, except that in step (1), when preparing the precursor solution, the 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer is replaced with an equimolar amount of the 1-allyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide salt monomer, the structural formula of which is:

[0158]

[0159] Example 10

[0160] The preparation methods of the solid polymer electrolyte, positive electrode and solid lithium battery provided in this embodiment are basically the same as those in Example 1. The only difference is that in step (1), lithium bis(trifluoromethanesulfonyl)imide is replaced with an equimolar amount of lithium difluorooxalateborate.

[0161] Example 11

[0162] The preparation methods of the solid polymer electrolyte, positive electrode sheet and solid lithium battery provided in this embodiment are basically the same as those in Example 1. The only difference is that in step (1), N,N-methylenebisacrylamide is replaced with an equimolar amount of divinylbenzene and azobisisobutyronitrile is replaced with an equimolar amount of benzoyl peroxide.

[0163] Comparative Example 1

[0164] The method for preparing the lithium battery provided in this comparative example includes:

[0165] (1) Preparation of liquid electrolyte: Weigh the following components according to the following mass ratio: ethylene carbonate: diethyl carbonate: vinylene carbonate = 40:30:30, and then add LiPF6 to obtain a liquid electrolyte with a LiPF6 concentration of 1 mol / L.

[0166] (2) Preparation of the electrolyte cell to be injected: using lithium metal and nickel-cobalt-manganese ternary materials (Li[Ni 0.8 Co 0.1 Mn 0.1 O2) is used as the active material for both the cathode and anode. Then, acetylene black, a conductive agent, and PVDF, a binder, are added. The mass ratio of active material to conductive agent to binder is 8:1:1. After stirring, coating, cold pressing, slitting, welding and other processes, the electrode sheet to be wound is obtained. Then, it is wound together with the separator to obtain the bare cell. The top and side are sealed with aluminum-plastic film as the packaging bag, and then baked.

[0167] (3) Liquid injection and cell forming: The liquid electrolyte obtained in step (1) is injected into the baked cell obtained in step (2), and left to stand until the electrolyte fully wets the entire membrane. Then, the forming, shaping, degassing and other processes are carried out to finally obtain the formed battery.

[0168] Comparative Example 2

[0169] The preparation methods of the solid polymer electrolyte, positive electrode and solid lithium battery provided in this comparative example are basically the same as those in Example 1. The only difference is that in step (1), hexafluorobutyl acrylate is replaced with an equimolar amount of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt monomer, that is, hexafluorobutyl acrylate is not added.

[0170] Comparative Example 3

[0171] The preparation methods of the solid polymer electrolyte, positive electrode sheet and solid lithium battery provided in this comparative example are basically the same as those in Example 2, except that N,N-methylenebisacrylamide was not added in step (1).

[0172] Comparative Example 4

[0173] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this comparative example are basically the same as those in Example 1, except that in step (1), hexafluorobutyl acrylate is replaced with an equimolar amount of butyl acrylate (whose structural formula is...). ).

[0174] Comparative Example 5

[0175] The preparation methods of the solid polymer electrolyte, positive electrode, and solid lithium battery provided in this comparative example are basically the same as those in Example 3, except that in step (1), dodecafluoroheptyl acrylate is replaced with an equimolar amount of heptyl acrylate, the structural formula of which is:

[0176]

[0177] Experimental Example

[0178] The electrochemical performance of the batteries prepared in each embodiment and each comparative example was tested, and the results are shown in Table 1.

[0179] The testing methods for electrochemical performance are as follows:

[0180] Room temperature ionic conductivity test method: After cutting the solid polymer electrolyte film, it is assembled with a stainless steel gasket to form a stainless steel / solid electrolyte / stainless steel button cell. The thickness of the solid polymer electrolyte is measured using a screw micrometer. Impedance test is performed using an electrochemical workstation at 25°C. The test frequency range is 7MHz to 0.1Hz.

[0181] Electrochemical window testing method: Coin cells assembled with stainless steel / solid electrolyte / lithium metal were tested using an electrochemical workstation at 25℃. The test voltage range was 0V~8V, and the scan rate was 2mV / s.

[0182] The linear sweep voltammetry curve of the solid-state lithium battery prepared in Example 1 is shown in [reference needed]. Figure 1 As shown. The charge-discharge curves of the solid-state lithium battery prepared in Example 1 are shown in [reference]. Figure 2 As shown. The charge-discharge curves of the solid-state lithium battery prepared in Example 2 are shown in [reference needed]. Figure 3 As shown. The rate performance test results of the solid-state lithium battery prepared in Example 2 are shown in [reference needed]. Figure 4 As shown. The cycle performance curves of the solid-state lithium battery prepared in Example 1 are shown in [reference needed]. Figure 5 As shown.

[0183] Table 1. Test results of electrochemical performance

[0184]

[0185]

[0186] As can be seen from Table 1, the solid lithium batteries prepared in each embodiment have better electrochemical performance.

[0187] In contrast, Comparative Example 1, being a liquid electrolyte, has a high ionic conductivity but a low electrochemical window. During cycling, the electrolyte is prone to decomposition, resulting in suboptimal cycling stability.

[0188] Comparative Example 2 lacks high-fluorine monomers, resulting in a lower electrochemical window and ionic conductivity compared to Example 1, leading to poor cycling stability.

[0189] Due to the lack of crosslinking agent, the overall polymer network structure of Comparative Example 3 is relatively loose, and its electrochemical window and ionic conductivity are lower than those of Example 1, resulting in poor cycling stability.

[0190] In Comparative Example 4, the electron cloud density was reduced by replacing all the fluorine atoms in hexafluorobutyl acrylate with hydrogen atoms, which suppressed further dissociation of lithium salt, resulting in a significant reduction in the electrochemical window and a decrease in ionic conductivity.

[0191] In Comparative Example 5, the electron cloud density of the polymer backbone was reduced by replacing all the fluorine atoms in dodecafluoroheptyl acrylate with hydrogen atoms, which suppressed further dissociation of lithium salt, resulting in a significant reduction in the electrochemical window and ionic conductivity, as well as poor cycling stability.

[0192] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A solid polymer electrolyte, characterized in that, It is mainly composed of lithium salt, ionic liquid monomer containing carbon-carbon double bonds, and monomer that anchors the anion of the lithium salt.

2. The solid polymer electrolyte according to claim 1, characterized in that, The structural formula of the ionic liquid monomer containing carbon-carbon double bonds is shown in formula (Ⅰ): In formula (Ⅰ), R1, R2, and R3 are each independently selected from hydrogen, halogen, nitro, cyano, substituted or unsubstituted C. 1～ C 12 Alkyl, substituted or unsubstituted C 1～ C 12 M is any one of alkoxy, substituted or unsubstituted amino groups; M is an ionic liquid structural group including inorganic anions and organic cations; Preferably, M comprises at least one of the groups having the structures shown in formulas (II) to (X): In equations (II) to (X), X θ It is an inorganic anion, X θ Including (FSO2)2N θ (CF3SO2)2N θ -COO θ -PO3 θ -SO3 θ BF4 θ PF6 θ Cl θ and Br θ At least one of the following; n is a natural number from 0 to 12.

3. The solid polymer electrolyte according to claim 1, characterized in that, The anchoring effect is achieved through at least one of the following forces: hydrogen bonding, anion-π interaction, ionic dipole force, and dipole-dipole force. Preferably, the monomer that anchors the anion of the lithium salt includes a fluorinated olefin compound; Preferably, the fluorinated olefin compound includes at least one selected from fluoroolefin esters, fluoroolefin carbonates, and fluoroolefin ethers. More preferably, the structural formula of the fluoroolefin ester compound is shown in formula (1): In equation (1), n ​​is a natural number from 1 to 10; More preferably, the structural formula of the fluoroolefin carbonate compound is shown in formula (2): In equation (2), n is a natural number from 1 to 10; More preferably, the structural formula of the fluoroolefin ether compound is shown in formula (3): In equation (3), n is a natural number from 1 to 10.

4. The solid polymer electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium oxalateborate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, and lithium hexafluorophosphate. And / or, the molar ratio of the lithium salt to the ionic liquid monomer containing carbon-carbon double bonds is 1:1 to 10; And / or, the molar ratio of the ionic liquid monomer containing carbon-carbon double bonds to the monomer that anchors the anion of the lithium salt is 1 to 20:

1.

5. The solid polymer electrolyte according to claim 1, characterized in that, The raw materials for preparing the solid polymer electrolyte also include a crosslinking agent; Preferably, the crosslinking agent includes at least one of N,N-methylenebisacrylamide, divinylbenzene, polyethylene glycol dimethacrylate, and polyethylene glycol diacrylate; Preferably, the molar ratio of the crosslinking agent to the ionic liquid monomer containing carbon-carbon double bonds is 1:30 to 100; Preferably, the raw materials for preparing the solid polymer electrolyte further include an initiator; Preferably, the initiator comprises at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, ethyl 4-(N,N-dimethylamino)benzoate, and methyl o-benzoylbenzoate. Preferably, the molar ratio of the initiator to the ionic liquid monomer containing carbon-carbon double bonds is 1:300 to 1000.

6. A method for preparing a solid polymer electrolyte as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The raw materials are mixed and then thermally polymerized in situ. Preferably, the temperature of the in-situ thermal polymerization is 50–70°C; Preferably, the preparation method of the solid polymer electrolyte specifically includes: in-situ thermal polymerization of a mixture of a lithium salt, an ionic liquid monomer containing a carbon-carbon double bond, a monomer that anchors the anion of the lithium salt, a crosslinking agent, and an initiator to obtain the solid polymer electrolyte.

7. A positive electrode sheet, characterized in that, Includes the solid polymer electrolyte as described in any one of claims 1 to 5; Preferably, the mass of the solid polymer electrolyte accounts for less than 10% of the total mass of the raw materials other than the current collector in the positive electrode sheet.

8. A solid-state lithium battery, characterized in that, Includes the solid polymer electrolyte as described in any one of claims 1 to 5; Preferably, the thickness of the solid polymer electrolyte is 50–300 μm; Preferably, the room temperature ionic conductivity of the solid-state lithium battery is >0.6 mS·cm. -1 .

9. A method for preparing a solid-state lithium battery as described in claim 8, characterized in that, Includes the following steps: After stacking the positive electrode, separator, and negative electrode, the raw materials for preparing the solid polymer electrolyte are added, and in-situ thermal polymerization is carried out, followed by encapsulation and formation.

10. An electrical appliance, characterized in that, Including the solid-state lithium battery as described in claim 8.

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