Electrolyte prepolymer solution, solid-state electrolyte, and use

Abstract

The present application provides an electrolyte prepolymer solution, a solid-state electrolyte, and a use. The electrolyte prepolymer solution comprises the following components in percentage by weight: 0.2％-0.6％ of LiNO3, 5％-10％ of LiPF6, 0.5％-1.5％ of LiDFOB, 2%-22% of a monomer, 0.03%-1% of an initiator, and 72%-92.27% of a solvent, and can be used for preparing a solid-state electrolyte of a solid-state battery.

Description

Electrolyte prepolymer, solid electrolyte and its application Technical Field

[0001] The present application relates to the field of solid electrolyte technology, and in particular to an electrolyte prepolymer solution, a solid electrolyte and applications. Background Art

[0002] Currently, the vast majority of commercial lithium-ion batteries use organic liquid materials as electrolytes, which have drawbacks such as flammability, leakage, and toxicity, thus limiting their large-scale application in the power battery field. Therefore, there is an urgent need to develop next-generation battery systems that combine high specific energy with high safety. Solid-state electrolytes are a key and popular technology for realizing this next-generation lithium-ion battery. Technical issues

[0003] Solid-state batteries replace traditional liquid electrolytes and separator systems with solid-state electrolytes. Organic electrolytes are not present in the battery structure. Solid-state electrolytes are primarily classified into three categories: inorganic solid electrolytes, polymer electrolytes, and composite solid electrolytes. Polymer electrolytes offer the advantages of high flexibility and ease of large-scale production. However, the application of existing polymer electrolytes in lithium metal batteries suffers from low solid-solid interface compatibility between the solid electrolyte layer and the negative electrode after long cycles, resulting in reduced capacity retention over long cycles. Technical Solutions

[0004] In view of this, the present application provides an electrolyte prepolymer liquid, a solid electrolyte and applications.

[0005] In a first aspect, the present application provides an electrolyte prepolymer solution, which comprises, calculated by weight percentage:

[0006] 0.2% to 0.6% LiNO3;

[0007] 5% to 10% LiPF6;

[0008] 0.5% to 1.5% LiDFOB;

[0009] 2% to 22% monomer;

[0010] 0.03% to 1% initiator; and

[0011] 72% to 92.27% solvent.

[0012] In a second aspect, the present application provides a solid electrolyte prepared by in-situ self-polymerization of an electrolyte prepolymer solution, wherein the electrolyte prepolymer solution comprises, calculated by weight percentage:

[0013] 0.2% to 0.6% LiNO3;

[0014] 5% to 10% LiPF6;

[0015] 0.5% to 1.5% LiDFOB;

[0016] 2% to 22% monomer;

[0017] 0.03% to 1% initiator; and

[0018] 72% to 92.27% solvent.

[0019] In a third aspect, the present application provides an application of an electrolyte prepolymer solution or a solid electrolyte in the preparation of a solid-state battery, wherein the electrolyte prepolymer solution comprises, calculated by weight percentage:

[0020] 0.2% to 0.6% LiNO3;

[0021] 5% to 10% LiPF6;

[0022] 0.5% to 1.5% LiDFOB;

[0023] 2% to 22% monomer;

[0024] 0.03% to 1% initiator; and

[0025] 72% to 92.27% solvent;

[0026] The solid electrolyte is prepared by in-situ self-polymerization of the electrolyte prepolymer solution. Beneficial effects

[0027] The electrolyte prepolymer of the present application can be used to prepare a solid electrolyte for a solid-state battery. The electrolyte prepolymer compounds LiNO3, LiPF6, LiDFOB, monomers, initiators and solvents in a specific proportion, which can reduce the growth ability of lithium dendrites, so that the lithium deposition after a long cycle of the solid-state battery is relatively uniform and the surface is relatively smooth, thereby improving the solid / solid interface compatibility between the solid electrolyte layer and the negative electrode, which is beneficial to improving the long-cycle stability and life of the solid-state battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0029] FIG1 is a schematic flow chart of a method for preparing an electrolyte prepolymer solution provided in an embodiment of the present application.

[0030] FIG2 is a SEI microscopic morphology image of the first lithium-copper half-cell provided in an embodiment of the present application after electrochemical testing.

[0031] FIG3 is a SEI microscopic morphology image of the seventh lithium-copper half-cell provided in an embodiment of the present application after electrochemical testing.

[0032] FIG4 is a SEI microscopic morphology image of the twelfth lithium-copper half-cell provided in an embodiment of the present application after electrochemical testing. Modes for Carrying Out the Invention

[0033] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0034] The embodiments of the present application provide an electrolyte prepolymer, a solid electrolyte, and applications. Detailed descriptions are provided below. It should be noted that the order in which the following embodiments are described does not limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to." The terms first, second, third, etc. are used merely as labels and do not impose numerical requirements or establish an order. The various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is intended to include any cited number (fractional or integer) within the indicated range.

[0035] In this application, the term "including" means "including but not limited to".

[0036] The term "and / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can represent three situations: the first situation is that A exists alone; the second situation is that A and B exist at the same time; the third situation is that B exists alone, where A and B can be singular or plural respectively.

[0037] The term "at least one" means one or more, and "a plurality of" means two or more. The terms "at least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can be expressed as: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or plural, respectively.

[0038] An embodiment of the present application provides an electrolyte prepolymer solution, which includes, by weight percentage, 0.2% to 0.6% of LiNO3 (lithium nitrate), 5% to 10% of LiPF6 (lithium hexafluorophosphate), 0.5% to 1.5% of LiDFOB (lithium difluorooxalatoborate), 2% to 22% of a monomer, 0.03% to 1% of an initiator, and 72% to 92.27% of a solvent.

[0039] The electrolyte prepolymer of the present application can be used to prepare a solid electrolyte for a solid-state battery. The electrolyte prepolymer compounds LiNO3, LiPF6, LiDFOB, monomers, initiators and solvents in a specific proportion, which can reduce the growth ability of lithium dendrites, so that the lithium deposition after a long cycle of the solid-state battery is relatively uniform and the surface is relatively smooth, thereby improving the solid / solid interface compatibility between the solid electrolyte layer and the negative electrode, which is beneficial to improving the long-cycle stability and life of the solid-state battery.

[0040] In the electrolyte prepolymer solution, the weight percentage of LiNO3 can be, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% or a value between any two of the foregoing values. LiNO3 plays a key role in the formation of the negative electrode SEI film. The weight percentage of LiNO3 in the electrolyte prepolymer solution in the range of 0.2% to 0.6% can improve the film formation sufficiency of the lithium metal negative electrode solid electrolyte interface (SEI), thereby facilitating the improvement of the life of the solid-state battery, and can control the viscosity and system impedance of the electrolyte prepolymer solution within an appropriate range, which is beneficial to improving the cycle effect of the solid-state battery.

[0041] In the electrolyte prepolymer solution, the weight percentage of LiPF6 can be, for example, 5%, 6%, 7%, 8%, 9%, 10% or a value between any two of the aforementioned values. The weight percentage of LiDFOB can be, for example, 0.5%, 0.8%, 1%, 1.2%, 1.5% or a value between any two of the aforementioned values. The weight percentage of the monomer can be, for example, 2%, 5%, 10%, 13%, 15%, 17%, 20%, 22% or a value between any two of the aforementioned values. The weight percentage of the initiator can be, for example, 0.03%, 0.05%, 0.07%, 0.1%, 0.3%, 0.5%, 0.8%, 1% or a value between any two of the aforementioned values. It should be noted that the applicant has found that for the electrolyte prepolymer solution, if the LiDFOB therein is replaced with other lithium salts (such as lithium difluorobis(oxalophosphate) (LiDFTOP)) and the weight percentage remains consistent, the discharge specific capacity of the solid-state battery will decrease.

[0042] In order to further improve the problem of low solid / solid interface compatibility between the solid electrolyte layer and the negative electrode after long cycles, thereby further improving the capacity retention rate of long cycles, in some embodiments of the present application, the solvent is a mixture of a first compound, a second compound and diethyl carbonate, wherein the first compound is selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, butylene carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate , methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, diethyl sulfite, 1,3-propane sultone, δ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, 1,3 dioxolane, cyclopentane and dimethyl sulfoxide; the second compound is selected from one or more of fluoroethylene carbonate, 1-butyl-1-methylpyrrolidine hexafluorophosphate and N-propyl-N-methylpyrrolidine hexafluorophosphate.

[0043] In some embodiments of the present application, in the electrolyte prepolymer, the mass ratio of LiDFOB to the second compound is LiDFOB: the second compound is 1: (5-15), for example, it can be 1: 5, 1: 8, 1: 10, 1: 12, 1: 15 or a value between any two of the aforementioned ratios, which can not only produce a dense and uniform SEI layer to stabilize the negative electrode, but also reduce the loss of LiPF6 during the cycle. Excessive addition of LiDFOB will lead to a high proportion of lithium salt in the electrolyte prepolymer, thereby increasing the viscosity of the electrolyte prepolymer and increasing the difficulty of curing, thereby reducing the cycle performance of the solid-state battery; too little addition of LiDFOB will reduce the circulation effect of the electrolyte and accelerate the drying of the electrolyte. In addition, excessive addition of the second compound will cause the solid-state battery to expand and increase during the early charge and discharge process, and too little addition of the second compound will affect the cycle performance of the electrolyte.

[0044] As an example, the second compound is selected from fluoroethylene carbonate. Fluoroethylene carbonate can not only serve as a solvent but also as a film-forming aid. Fluoroethylene carbonate can participate in the construction of SEI, reduce the side reaction between the electrolyte and the lithium negative electrode, and thus improve the cycle life of the solid-state battery.

[0045] Based on considerations of multiple factors such as solvent properties, solubility of lithium salts, and compatibility with metallic lithium negative electrodes, in some embodiments of the present application, the first compound is selected from ethylene carbonate; and / or the weight of the first compound accounts for 29% to 50% of the total weight of the electrolyte prepolymer solution, for example, it can be 29%, 32%, 35%, 40%, 42%, 45%, 50% or a value between any two of the foregoing values.

[0046] In some embodiments of the present application, the monomer is selected from one or more of vinylene carbonate, butyl acrylate, and N,N'-methylenebisacrylamide.

[0047] In at least one embodiment of the present application, the monomer is N,N'-methylenebisacrylamide, and the weight of the monomer accounts for 2% to 5% of the total weight of the electrolyte prepolymer. It should be noted that N,N'-methylenebisacrylamide also acts as a crosslinking agent. Using N,N'-methylenebisacrylamide as a monomer eliminates the need for an additional crosslinking agent, which not only simplifies the composition of the electrolyte prepolymer and reduces preparation costs, but also improves the compatibility of the electrolyte prepolymer system itself and its affinity for the lithium metal anode.

[0048] In at least one embodiment of the present application, the monomer is a mixture of N,N'-methylenebisacrylamide and vinylene carbonate. The weight of the N,N'-methylenebisacrylamide accounts for 3% to 6% of the total weight of the electrolyte prepolymer solution, for example, 3%, 4%, 5%, 6%, or a value between any two of the aforementioned values; and the weight of the vinylene carbonate accounts for 9% to 16% of the total weight of the electrolyte prepolymer solution, for example, 9%, 11%, 14%, 16%, or a value between any two of the aforementioned values.

[0049] In at least one embodiment of the present application, the monomer is a mixture of N,N'-methylenebisacrylamide and butyl acrylate. The weight of the N,N'-methylenebisacrylamide accounts for 2% to 3% of the total weight of the electrolyte prepolymer solution, for example, 2%, 2.5%, 3%, or a value between the aforementioned two values; and the weight of the butyl acrylate accounts for 4% to 6% of the total weight of the electrolyte prepolymer solution, for example, 4%, 5%, 6%, or a value between the aforementioned two values.

[0050] In some embodiments of the present application, the initiator is selected from azo initiators, for example, one or more selected from azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

[0051] In some embodiments of the present application, calculated by weight percentage, the electrolyte prepolymer solution consists of 0.2% to 0.6% LiNO3, 5% to 10% LiPF6, 0.5% to 1.5% LiDFOB, 2% to 5% N,N'-methylenebisacrylamide, 0.03% to 1% azobisisobutyronitrile, 40% to 50% ethylene carbonate, 10% to 15% fluoroethylene carbonate and 28% to 38% diethyl carbonate.

[0052] The present application also provides a method for preparing an electrolyte prepolymer solution, which can be used to prepare any of the electrolyte prepolymer solutions described above, as shown in FIG1 , comprising the following steps:

[0053] S1, providing a first solution system comprising LiNO3, LiPF6, LiDFOB and a solvent;

[0054] S2. Mixing the first solution system, monomers and initiator to obtain an electrolyte prepolymer solution.

[0055] In the above-mentioned method for preparing the electrolyte prepolymer, a first solution system comprising a lithium salt and a solvent is first provided, and then the first solution system, a monomer and an initiator are mixed. On the one hand, the dispersion performance of the lithium salt in the electrolyte prepolymer can be improved, thereby improving the distribution uniformity of the product electrolyte. When actually applied to solid-state batteries, dendrites are not easily grown, which is beneficial to improving the cycle performance of the solid-state battery. On the other hand, if the lithium salt, monomer, initiator and solvent are mixed simultaneously, the problem of dissolution heat promoting rapid polymerization of some monomers may occur, which reduces the quality of the solid-state electrolyte and may even make it impossible to generate the target solid-state electrolyte.

[0056] In some embodiments of the present application, step S1 includes: first mixing LiNO3 with the first compound to obtain a second solution system; then mixing the second solution system, LiPF6, LiDFOB, diethyl carbonate, and the second compound to obtain a first solution system. The applicant has found that preferentially dissolving LiNO3 in the first compound can improve the cycle stability of the solid-state battery, while simultaneously mixing LiNO3, the first compound, LiPF6, LiDFOB, diethyl carbonate, and the second compound will result in overcharging and unstable charge and discharge. In addition, preferentially dissolving LiNO3 in the first compound can improve the solubility and dispersibility of LiNO3 in the electrolyte prepolymer solution, which is conducive to the formation of a more uniform LiN layer on the SEI.

[0057] The present application also provides a solid electrolyte, which is prepared by in-situ self-polymerization of any of the electrolyte prepolymer solutions described above. The in-situ self-polymerization can be performed under heat treatment conditions, such as a temperature of 60° C. and a time of 2 hours.

[0058] The embodiments of the present application also provide an electrolyte prepolymer solution as described in any one of the foregoing, or a method for preparing an electrolyte prepolymer solution as described in any one of the foregoing, or the use of a solid electrolyte as described in any one of the foregoing in preparing a solid-state battery.

[0059] The present application also provides a solid-state battery comprising a solid electrolyte layer, a positive electrode, and a negative electrode, wherein the material of the solid electrolyte layer comprises any of the solid electrolytes described above. It should be noted that the solid electrolyte layer can be sandwiched between the positive electrode and the negative electrode, and external terminals can be connected to the positive and negative electrodes to electrically connect to the outside, thereby forming a solid-state battery; alternatively, the solid electrolyte layer can be filled in the pores of the battery body composed of the positive and negative electrodes.

[0060] In this application, a solid-state battery can be a laminated structure formed by stacking a positive electrode, a negative electrode, and a solid electrolyte layer, or a wound body formed by winding the laminated structure. According to the form, the solid-state battery can be a laminated battery, a soft-pack battery, a square battery, a cylindrical battery, a coin battery, or a button battery; according to the material, the solid-state battery can be a lithium metal battery, a lithium-ion battery, a lithium-sulfur battery, or a lithium-air battery.

[0061] In some embodiments of the present application, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector, and the materials of the positive electrode active material layer include a positive electrode active substance, a positive electrode binder, and a positive electrode conductive agent. The materials of the positive electrode current collector, the positive electrode active substance, the positive electrode binder, and the positive electrode conductive agent can be conventional materials in the art, for example: the materials of the positive electrode current collector include but are not limited to aluminum foil, platinum foil, or palladium foil; the positive electrode active substance includes but is not limited to one or more of lithium cobalt oxide, lithium manganese oxide, lithium permanganate, lithium iron phosphate, lithium nickel oxide, lithium manganese phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. It is understood that for the compounds listed above as the positive electrode active material, their surfaces may have a coating layer, and the materials of the coating layer include but are not limited to carbon materials; the positive electrode binder includes but is not limited to one or more of vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and polytetrafluoroethylene; the positive electrode conductive agent includes but is not limited to one or more of carbon black, graphite, and graphene.

[0062] The positive electrode preparation method may include the steps of: mixing a positive electrode active material, a conductive agent, a binder, and a first solvent to obtain a first mixture; then, coating the first mixture on a positive electrode current collector, followed by a drying process and a roll pressing process to obtain a positive electrode plate. It should be noted that the first mixture may also be cast onto a separate carrier to form a film layer, which is then separated from the carrier and laminated onto one side of the positive electrode current collector. The first solvent includes, but is not limited to, N-methylpyrrolidone, acetone, and water.

[0063] In some embodiments of the present application, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The material of the negative electrode active material layer includes a negative electrode active substance, a negative electrode binder, and a negative electrode conductive agent. The materials of the negative electrode current collector, the negative electrode active substance, the negative electrode binder, and the negative electrode conductive agent can be conventional materials in the art. For example, the material of the negative electrode current collector includes, but is not limited to, aluminum foil, platinum foil, or palladium foil; the negative electrode active substance includes, but is not limited to, one or more of lithium单质, a metal that can be alloyed with lithium, a semi-metal, a transition metal oxide, a non-transition metal oxide, and a carbon material. The metal or semi-metal that can be alloyed with lithium includes, but is not limited to, Si, Sn, Al, Ge, Pb, Bi, Sb, a Si-Y1 alloy (Y1 is an alkali metal, an alkaline earth metal, an element of Group 13-16, a transition metal, a rare earth element, or a combination thereof, excluding Si), and a Sn-Y2 alloy (Y2 is an alkali metal, an alkaline earth metal, an element of Group 13-16, a transition metal, a rare earth element, or a combination thereof, excluding Sn). The transition metal oxide includes, but is not limited to, one or more of a lithium titanium oxide, a vanadium oxide, a lithium vanadium oxide, and a titanium niobium oxide. The non-transition metal oxide includes, but is not limited to, SnO2 and SiO x (0 < x < 2), and the carbon material includes, but is not limited to, one or more of crystalline carbon (such as graphite) and amorphous carbon. The negative electrode binder can be the same as the positive electrode binder, and the negative electrode conductive agent can be the same as the positive electrode conductive agent. The preparation method of the negative electrode can be carried out by referring to the preparation method of the positive electrode.

[0064] It should be noted that the solid-state battery of the embodiments of the present application may further include other conventional structures. For example, the solid-state battery of the embodiments of the present application further includes a separator disposed between the positive electrode and the negative electrode. The material of the separator includes, but is not limited to, one or more of glass fiber, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene.

[0065] The preparation method of the solid-state battery in the embodiments of the present application, for example, includes the steps of: first assembling the positive electrode, the negative electrode, and the separator to form a battery body, then injecting a prepolymerized electrolyte solution into the battery body for infiltration, and then heating to initiate in-situ polymerization to obtain a solid electrolyte. Among them, the infiltration, for example, includes the steps of: encapsulating the battery body injected with the prepolymerized electrolyte solution, and then standing at room temperature. The standing time can be, for example, 4h to 10h. It should be noted that the applicant has found that adding a room temperature standing process before the in-situ polymerization process can improve the uniformity of polymerization, thereby further improving the performance of the solid-state battery.

[0066] The technical solutions and technical effects of the present application will be described in detail below through specific examples, comparative examples, and experimental examples. The following examples are only partial examples of the present application and do not specifically limit the present application.

[0067] Example 1

[0068] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Calculated by weight percentage, the electrolyte prepolymer includes: 0.4% LiNO3, 9% LiPF6, 1% LiDFOB, 3% N,N'-methylenebisacrylamide, 0.03% azobisisobutyronitrile, 15% fluoroethylene carbonate, 41.57% ethylene carbonate, and 30% diethyl carbonate.

[0069] The preparation method of the electrolyte prepolymer solution in this embodiment includes the following steps:

[0070] S1.1. First, add LiNO3 to ethylene carbonate according to the formula ratio, heat and stir until completely dissolved to obtain a second solution system, then gradually add diethyl carbonate, fluoroethylene carbonate, LiPF6 and LiDFOB, stir at room temperature until completely dissolved, to obtain a first solution system;

[0071] S1.2. Add N,N'-methylenebisacrylamide and azobisisobutyronitrile to the first solution system, and stir at room temperature until they are completely dissolved to obtain an electrolyte prepolymer solution.

[0072] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0073] In a glove box filled with argon, NCM811 was used as the positive electrode material (the positive electrode loading was 3.2 mAh, and the material of the positive electrode current collector was aluminum foil), lithium metal was used as the negative electrode material (the thickness of the lithium metal layer was 20 μm, and the material of the negative electrode current collector was copper foil), and polyethylene was used as the diaphragm material. Under the condition of an injection volume of 1.6 g / Ah, a 6.2 Ah soft-pack battery was made, and then the electrolyte prepolymer was injected into the interior of the battery for infiltration. After packaging, it was allowed to stand at room temperature for 8 hours, and then heated at 60°C for 2 hours to induce in-situ self-polymerization of the electrolyte prepolymer to form a solid electrolyte to obtain the lithium metal battery of this embodiment.

[0074] Example 2

[0075] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that the weight percentage of LiNO3 is 0.2%, and the weight percentage of ethylene carbonate is 41.77%.

[0076] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0077] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0078] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0079] Example 3

[0080] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that the weight percentage of LiNO3 is 0.6%, and the weight percentage of ethylene carbonate is 41.37%.

[0081] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0082] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0083] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0084] Example 4

[0085] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the electrolyte prepolymer in this embodiment differs in that the weight percentage of N,N'-methylenebisacrylamide is 5%, and the weight percentage of ethylene carbonate is 39.57%.

[0086] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0087] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0088] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0089] Example 5

[0090] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that the weight percentage of fluoroethylene carbonate is 5%, and the weight percentage of ethylene carbonate is 51.57%.

[0091] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0092] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0093] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0094] Example 6

[0095] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that the weight percentage of fluoroethylene carbonate is 10%, and the weight percentage of ethylene carbonate is 46.57%.

[0096] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0097] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0098] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0099] Example 7

[0100] This embodiment provides an electrolyte prepolymer solution, a solid electrolyte, and a lithium metal battery. The components of the electrolyte prepolymer solution in this embodiment are the same as those in Example 1.

[0101] Compared with the preparation method of the electrolyte prepolymer solution in Example 1, the difference of the preparation method of the electrolyte prepolymer solution in this embodiment is that: step S1.1 is replaced by "take each component according to the formula ratio, add LiNO3, LiPF6, LiDFOB, diethyl carbonate and fluoroethylene carbonate to ethylene carbonate, heat and stir until completely dissolved, and obtain a first solution system."

[0102] Example 8

[0103] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that, calculated by weight percentage, the electrolyte prepolymer includes: 0.4% LiNO3, 9% LiPF6, 1% LiDFOB, 3% N,N'-methylenebisacrylamide, 12% vinylene carbonate, 0.03% azobisisobutyronitrile, 15% fluoroethylene carbonate, 29.57% ethylene carbonate, and 30% diethyl carbonate.

[0104] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0105] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0106] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0107] Example 9

[0108] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that, calculated by weight percentage, the electrolyte prepolymer includes: 0.4% LiNO3, 9% LiPF6, 1% LiDFOB, 3% N,N'-methylenebisacrylamide, 5% butyl acrylate, 0.03% azobisisobutyronitrile, 15% fluoroethylene carbonate, 36.57% ethylene carbonate, and 30% diethyl carbonate.

[0109] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0110] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0111] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0112] Example 10

[0113] This embodiment provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that ethylene carbonate is replaced by "propylene carbonate".

[0114] The preparation method of the electrolyte prepolymer solution in this embodiment is carried out with reference to Example 1.

[0115] The solid electrolyte in this embodiment is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0116] Compared with the lithium metal battery in Example 1, the lithium metal battery in this embodiment is different in that the electrolyte is a solid electrolyte in this embodiment.

[0117] Comparative Example 1

[0118] This comparative example provides an electrolyte prepolymer, a solid electrolyte and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that the weight percentage of LiNO3 is 1%, and the weight percentage of ethylene carbonate is 40.97%.

[0119] The preparation method of the electrolyte prepolymer solution in this comparative example is carried out with reference to Example 7.

[0120] The solid electrolyte in this comparative example is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0121] Compared with the lithium metal battery in Example 1, the lithium metal battery in this comparative example is different in that the electrolyte is the solid electrolyte of this example.

[0122] Comparative Example 2

[0123] This comparative example provides an electrolyte prepolymer, a solid electrolyte, and a lithium metal battery. Compared with the electrolyte prepolymer in Example 1, the difference of the electrolyte prepolymer in this embodiment is that the weight percentage of fluoroethylene carbonate is 20%, and the weight percentage of ethylene carbonate is 36.57%.

[0124] The preparation method of the electrolyte prepolymer solution in this comparative example is carried out with reference to Example 7.

[0125] The solid electrolyte in this comparative example is prepared by in-situ self-polymerization of the electrolyte prepolymer solution in this embodiment.

[0126] Compared with the lithium metal battery in Example 1, the lithium metal battery in this comparative example is different in that the electrolyte is the solid electrolyte of this example.

[0127] Experimental Example 1

[0128] Performance tests were performed on the lithium metal batteries in Examples 1 to 10, Comparative Examples 1, and 2. Specifically, each formed lithium metal battery was subjected to a cycle test. Each lithium metal battery was charged at 25°C at a constant current rate of 0.33C to a voltage of 4.2V, and then discharged at a constant current rate of 0.5C until the voltage reached 3V. The above charge and discharge cycles were repeated 300 times, with a time interval of 10 minutes between adjacent cycles. The capacity retention rate after 100 cycles at 25°C was obtained, and each lithium metal battery that completed the above cycle test was subjected to the national standard needle penetration test.

[0129] The test results are shown in Table 1 below:

[0130] Table 1

[0131] As can be seen from Table 1, compared with the lithium metal batteries in Comparative Examples 1 and 2, the cycle performance of the lithium metal batteries in Examples 1 to 10 is superior, and the capacity retention rate of the lithium metal batteries in Examples 1 to 10 after 100 cycles at 25°C is significantly higher than that of the lithium metal batteries in Comparative Examples 1 and 2. For example, the capacity retention rate of the lithium metal battery in Example 1 after 100 cycles at 25°C is 31.51% higher than that of the lithium metal battery in Comparative Example 2. This shows that the electrolyte prepolymer solution of the embodiment of the present application is used to prepare a solid electrolyte for a solid-state battery, which is beneficial to improving the long-cycle stability and life of the solid-state battery.

[0132] Continuing to refer to Table 1, the solid-state batteries in Example 7, Comparative Example 1 and Comparative Example 2 failed the needle penetration test. The reason is that LiNO3 was not preferentially dissolved during the preparation of the electrolyte prepolymer solution in Example 7, Comparative Example 1 and Comparative Example 2, resulting in limited solubility and dispersibility of LiNO3 in the electrolyte prepolymer solution. The corresponding solid-state batteries will experience overcharging and unstable charging and discharging, and the formed LiN layer has low uniformity, resulting in an increased risk of thermal runaway when the solid-state battery is punctured.

[0133] In addition, each lithium metal battery after formation (without the aforementioned cycle test) was charged at a constant current of 0.33C at 25°C to a voltage of 4.2V, and then discharged at a constant current of 0.5C until the voltage reached 3V to obtain the first-cycle discharge specific capacity. The difference in the first-cycle discharge specific capacity of the lithium metal batteries in Examples 1 to 10, Comparative Examples 1 and 2 is small. This shows that compared with the lithium metal batteries in Comparative Examples 1 and 2, the comprehensive performance of the lithium metal batteries in Examples 1 to 10 is better.

[0134] Experimental Example 2

[0135] The electrolyte prepolymer solutions of Examples 1 to 10, Comparative Examples 1, and 2 were used to prepare lithium-copper half-cells for electrochemical testing of the Li-Cu half-cells. The electrochemical testing conditions were as follows: (A) discharging at a constant current of 0.72 mA for 10 h, followed by charging at a constant current of 0.72 mA for 10 h to a voltage of 1 V; (B) discharging at a constant current of 0.72 mA for 2 h, followed by charging at a constant current of 0.72 mA for 2 h; and repeating step (B) 300 times to observe the SEI film formation.

[0136] The lithium-copper half-cells subjected to electrochemical testing are the first to twelfth lithium-copper half-cells. The solid electrolyte in Example 1 is applied to the first lithium-copper half-cell, the solid electrolyte in Example 2 is applied to the second lithium-copper half-cell, and so on. The solid electrolyte in Comparative Example 1 is applied to the eleventh lithium-copper half-cell, and the solid electrolyte in Comparative Example 2 is applied to the twelfth lithium-copper half-cell.

[0137] Electrochemical testing of the Li-Cu half-cells revealed that, compared with the eleventh and twelfth lithium-copper half-cells, a more uniform LiN layer was formed on the SEI in the first to tenth lithium-copper half-cells and a lithium-dendrite-free state was observed, as shown in FIG2 . This shows that the electrolyte prepolymer system of the embodiment of the present application has a low ability to grow lithium dendrites. The reason is that: LiN converted from LiNO3 on SEI provides sufficient mechanical strength to resist dendrites; LiDFOB and the second compound are additives. Under a reasonable ratio, they can produce a dense and uniform SEI layer to stabilize the negative electrode and reduce the loss of LiPF6 during the cycle; the polymer network formed after the thermal polymerization of N,N'-methylenebisacrylamide and the LiN converted from LiNO3 on SEI provide sufficient mechanical strength to resist dendrites, so that the lithium deposition is relatively uniform after long cycles and the surface is relatively smooth, which improves the solid / solid interface compatibility between the solid electrolyte layer and the negative electrode. When N,N'-methylenebisacrylamide is used as both a monomer and a cross-linking agent, it can further improve the compatibility of the electrolyte prepolymer system and its affinity for the lithium metal negative electrode.

[0138] In addition, from the electrochemical test results of the first lithium-copper half-cell to the eleventh lithium-copper half-cell, it can be seen that in the preparation process of the electrolyte prepolymer, LiNO3 is preferentially dissolved, which can make the dispersion performance of LiNO3 in the electrolyte prepolymer better, which is beneficial to further reduce the growth ability of lithium dendrites, thereby improving the charging and discharging stability of the solid-state battery and reducing the risk of internal short circuit after long cycles.

[0139] The above is a detailed introduction to the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An electrolyte prepolymer solution, wherein Calculated by weight percentage, the electrolyte prepolymer solution includes: 0.2% to 0.6% LiNO3; 5% to 10% LiPF6; 0.5% to 1.5% LiDFOB; 2% to 22% monomer; 0.03% to 1% initiator; and 72% to 92.27% solvent.

2. The electrolyte prepolymer solution according to claim 1, wherein The solvent is a mixture consisting of the first compound, the second compound and diethyl carbonate; Wherein, the first compound is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, butylene carbonate, methylpropyl carbonate, ethylpropyl carbonate, dipropyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, diethyl sulfite, 1,3-propane sultone, δ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, 1,3 dioxolane, sulfolane and dimethyl sulfoxide; The second compound is selected from one or more of fluoroethylene carbonate, 1-butyl-1-methylpyrrolidino hexafluorophosphate, and N-propyl-N-methylpyrrolidino hexafluorophosphate.

3. The electrolyte prepolymer solution according to claim 2, wherein The first compound is selected from ethylene carbonate.

4. The electrolyte prepolymer solution according to claim 2 or 3, wherein The mass ratio of the LiDFOB to the second compound is LiDFOB:second compound is 1:(5-15).

5. The electrolyte prepolymer solution according to any one of claims 2 to 4, wherein The weight of the first compound accounts for 29% to 50% of the total weight of the electrolyte prepolymer solution.

6. The electrolyte prepolymer solution according to any one of claims 1 to 5, wherein The monomer is selected from one or more of vinylene carbonate, butyl acrylate and N,N'-methylenebisacrylamide; And / or, the initiator is selected from azo initiators; optionally, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

7. The electrolyte prepolymer solution according to claim 6, wherein The monomer is N,N'-methylenebisacrylamide, and the weight of the monomer accounts for 2% to 5% of the total weight of the electrolyte prepolymer solution; Alternatively, the monomer is a mixture of N,N'-methylenebisacrylamide and vinylene carbonate, wherein the weight of the N,N'-methylenebisacrylamide accounts for 3% to 6% of the total weight of the electrolyte prepolymer solution, and the weight of the vinylene carbonate accounts for 9% to 16% of the total weight of the electrolyte prepolymer solution; Alternatively, the monomer is a mixture of N,N'-methylenebisacrylamide and butyl acrylate, wherein the weight of the N,N'-methylenebisacrylamide accounts for 2% to 3% of the total weight of the electrolyte prepolymer solution, and the weight of the butyl acrylate accounts for 4% to 6% of the total weight of the electrolyte prepolymer solution.

8. The electrolyte prepolymer solution according to any one of claims 1 to 7, wherein Calculated by weight percentage, the electrolyte prepolymer solution consists of 0.2% to 0.6% LiNO3, 5% to 10% LiPF6, 0.5% to 1.5% LiDFOB, 2% to 5% N,N'-methylenebisacrylamide, 0.03% to 1% azobisisobutyronitrile, 40% to 50% ethylene carbonate, 10% to 15% fluoroethylene carbonate and 28% to 38% diethyl carbonate.

9. The electrolyte prepolymer solution according to any one of claims 1 to 8, wherein The preparation method of the electrolyte prepolymer solution comprises the following steps: Providing a first solution system comprising LiNO3, LiPF6, LiDFOB, and a solvent; and The first solution system, monomers and initiator are mixed to obtain the electrolyte prepolymer solution.

10. The electrolyte prepolymer solution according to claim 9, wherein The step of providing a first solution system comprising LiNO3, LiPF6, LiDFOB and a solvent comprises: first mixing LiNO3 with the first compound as described in claim 2 to obtain a second solution system; then, mixing the second solution system, LiPF6, LiDFOB, diethyl carbonate and the second compound as described in claim 2 to obtain the first solution system.

11. A solid electrolyte, wherein: The electrolyte prepolymer is prepared by in-situ self-polymerization, and the electrolyte prepolymer comprises, calculated by weight percentage: 0.2% to 0.6% LiNO3; 5% to 10% LiPF6; 0.5% to 1.5% LiDFOB; 2% to 22% monomer; 0.03% to 1% initiator; and 72% to 92.27% solvent.

12. The solid electrolyte according to claim 11, wherein The solvent is a mixture of a first compound, a second compound and diethyl carbonate; wherein the first compound is selected from ethylene carbonate, propylene carbonate, One or more of dimethyl carbonate, ethyl methyl carbonate, butylene carbonate, methylpropyl carbonate, ethylpropyl carbonate, dipropyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, diethyl sulfite, 1,3-propane sultone, δ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, 1,3-dioxolane, sulfolane and dimethyl sulfoxide; the second compound is selected from one or more of fluoroethylene carbonate, 1-butyl-1-methylpyrrolidino hexafluorophosphate and N-propyl-N-methylpyrrolidino hexafluorophosphate; and / or, the mass ratio of LiDFOB to the second compound is LiDFOB:second compound is 1:(5-15); and / or, the monomer is selected from one or more of vinylene carbonate, butyl acrylate and N,N'-methylenebisacrylamide; And / or, the initiator is selected from azo initiators; optionally, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

13. The solid electrolyte according to claim 11 or 12, wherein The in-situ self-polymerization is carried out under heat treatment conditions, the heat treatment temperature is 50° C. to 80° C., and the heat treatment time is 1 hour to 5 hours.

14. Use of an electrolyte prepolymer or solid electrolyte in the preparation of a solid-state battery, wherein: Calculated by weight percentage, the electrolyte prepolymer solution includes: 0.2% to 0.6% LiNO3; 5% to 10% LiPF6; 0.5% to 1.5% LiDFOB; 2% to 22% monomer; 0.03% to 1% initiator; and 72% to 92.27% solvent; The solid electrolyte is prepared by in-situ self-polymerization of the electrolyte prepolymer solution.

15. The use according to claim 14, wherein: The solvent is a mixture of a first compound, a second compound and diethyl carbonate; wherein the first compound is selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, butylene carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, diethyl sulfite, 1,3-propane sultone, δ-valerolactone, One or more of tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, 1,3-dioxolane, sulfolane and dimethyl sulfoxide; the second compound is selected from one or more of fluoroethylene carbonate, 1-butyl-1-methylpyrrolidino hexafluorophosphate and N-propyl-N-methylpyrrolidino hexafluorophosphate; and / or, the mass ratio of LiDFOB to the second compound is LiDFOB:second compound is 1:(5-15); and / or, the monomer is selected from one or more of vinylene carbonate, butyl acrylate and N,N'-methylenebisacrylamide; And / or, the initiator is selected from azo initiators; optionally, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

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