A solid electrolyte, an electrode comprising the solid electrolyte, and a solid-state lithium battery

Abstract

The present invention relates to a solid electrolyte, an electrode comprising the solid electrolyte, and a solid-state lithium battery. The solid electrolyte includes a polymer, the polymer contains a flexible main chain and a rigid segment, the flexible main chain contains an ether group unit and an acrylate unit; the rigid segment contains an olefin compound unit with a urea group. The solid electrolyte has the comprehensive properties of a flexible polymer and a rigid polymer. By introducing a dimeric urea group unit with a substituted or unsubstituted functional group into the main chain, the rigidity of the flexible polymer is increased, thereby enhancing the strength of the polymer electrolyte; by adjusting the dimeric content, the mechanical properties of the polymer electrolyte can be regulated. This solid electrolyte is beneficial to further improving the safety performance of lithium-ion batteries, especially excellent in anti-dendrite performance, and has excellent market application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of modifying the mechanical properties of solid electrolytes, and particularly to a solid electrolyte, an electrode comprising the solid electrolyte, and a solid-state lithium battery. Background Art

[0002] Since the industrialization of lithium-ion batteries by Sony in the 1990s of the 20th century, they have played an important role in fields such as 3C products, large-scale storage, and current new energy power batteries. With the progress of technology, society has put forward higher requirements for lithium-ion batteries, including high specific energy, high safety, and long cycle life, etc. Therefore, it is extremely urgent to develop lithium-ion batteries that meet the above requirements to meet people's needs.

[0003] Traditional lithium-ion batteries mostly use liquid organic electrolytes such as ethers and carbonates as electrolytes, but liquid electrolytes have problems such as easy leakage, easy volatilization, flammability, and explosiveness. In addition, during the cycling of the battery, unevenly deposited lithium dendrites will pierce the separator, triggering battery short circuits and even safety accidents. To solve the above problems, people have turned their attention to solid electrolytes. Generally speaking, solid electrolytes have advantages such as thermal stability, chemical stability, electrochemical stability, and good mechanical strength. Therefore, the use of solid electrolytes can fundamentally eliminate potential safety hazards. At the same time, solid electrolytes have a relatively high electrochemical stability window (>4.7V), so they can be used for high-voltage cathode materials, thereby improving the specific energy of lithium batteries. In addition, solid electrolytes can also achieve high lithium-ion transport and promote the uniform deposition of lithium metal.

[0004] At the present stage, solid electrolytes include inorganic solid electrolytes, gel polymer electrolytes, and solid polymer electrolytes. Among them, solid polymer electrolytes have relatively high lithium-ion conductivity and electrode / electrolyte contact interfaces. At the same time, their excellent flexibility and ductility make them the most promising for commercialization. However, the crystallinity of polymers makes it difficult to decouple mechanical properties and ionic conductivity. Traditional solid electrolytes based on linear poly(ethylene oxide) (PEO) have a high crystallinity at room temperature, resulting in a low room-temperature lithium-ion conductivity and poor mechanical properties. By adding inorganic fillers or organic plasticizers, the ionic conductivity of polymer solid electrolytes can be improved, but it will lead to a decrease in crystallinity and affect the mechanical properties of solid polymer electrolytes; chemical crosslinking can effectively improve the mechanical strength of polymers, but usually forms rigid polymers with high crystallinity and low lithium-ion conductivity. The segmental movement of flexible segments in polymer molecules can effectively conduct lithium ions. Increasing the proportion of flexible segments in polymer electrolyte molecules can effectively promote the ion transport process. According to the design concept of "combining rigidity with flexibility", combining rigid segments with flexible main chains can effectively alleviate the contradiction that it is difficult to simultaneously have high mechanical properties and high room-temperature ionic conductivity in solid polymer electrolytes.

[0005] The polyethylene glycol unit is a common processable PEO-based polymer, which has the advantages of easy processing, low cost, high biocompatibility and no pollution, and can be used as a flexible main chain. However, its mechanical properties are poor, it cannot inhibit the formation of lithium dendrites, resulting in a short battery cycle life. At present, solid polymer electrolytes based on PEO still have difficulty meeting the actual use requirements of lithium metal batteries. The main problem is that it is difficult to have both high room temperature ionic conductivity and excellent mechanical properties. The above problems greatly limit the practical application of solid electrolytes and the development of solid-state lithium metal batteries. Summary of the Invention

[0006] In order to solve the above problems, this patent invents a polymer with multifunctional segments and a polymer electrolyte prepared therefrom. By introducing rigid segments, the mechanical properties of the polymer electrolyte can be effectively regulated, and controllable mechanical properties can be achieved while maintaining high ionic conductivity.

[0007] The specific solutions are as follows:

[0008] A solid electrolyte, the solid electrolyte includes a polymer, the polymer contains a flexible main chain and a rigid segment, the flexible main chain contains an ether group unit and an acrylate unit, and the flexible main chain includes a segment with a structural formula as shown in formula (1):

[0009]

[0010] Wherein, R1 is independently selected from H, halogen, nitro, ester group, cyano, nitro, carboxyl group, trifluoromethyl group, hydrocarbonthio group, carbonyl group, substituted or unsubstituted C1-C 15 alkyl, substituted or unsubstituted C1-C 15 alkoxy, substituted or unsubstituted amino, substituted or unsubstituted (hetero)aryl, substituted or unsubstituted C1-C 12 alkylene; n is a positive integer from 10 to 1000;

[0011] At least one of R2 and R3 is a rigid segment, the rigid segment contains an olefin compound unit with a ureido group, and the rigid segment includes a segment with a structural formula as shown in formula (2):

[0012]

[0013] Wherein, R1’, R4’ and R5’ are independently selected from H, carbonyl group, hydroxyl group, cyano group, unsaturated carbon-carbon double bond, halogen, amino group, nitro group, acyl group, carboxyl group, ester group, trifluoromethyl group, hydrocarbonthio group, substituted or unsubstituted C1-C 20 alkyl, substituted or unsubstituted C1-C 20Alkoxy, substituted or unsubstituted C4-60 (hetero)aryl, substituted or unsubstituted C2-C containing a heterocyclic atom 15 cycloalkyl; R2' and R3' are each independently selected from H, ester group, carboxyl group, carbonyl group, substituted or unsubstituted C1-C 10 alkyl, substituted or unsubstituted C1-C 15 alkoxy, substituted or unsubstituted amino, substituted or unsubstituted (hetero)aryl;

[0014] The rigid segment is connected to the sites shown by R2 and / or R3 on the flexible main chain through R1'.

[0015] Furthermore, the rigid segment is formed from the polymerization reaction of monomer 1, and the monomer 1 is prepared by adding 2-amino-4-hydroxy-6-methylpyrimidine and isocyanatoethyl methacrylate and reacting at 100-150 °C for 10-20 minutes;

[0016] In a specific embodiment, the structural formula of monomer 1 is shown in the following formula (3):

[0017]

[0018] Alternatively, the structural formula of monomer 1 is shown in the following formula (4):

[0019]

[0020] Preferably, the rigid segment is formed from the polymerization reaction of monomer 1 and monomer 4, and the monomer 4 is pentaerythritol tetrakis(mercaptoacetate) and / or bis(mercapto) polyethylene glycol.

[0021] Furthermore, the flexible main chain is formed from the polymerization reaction of monomer 2, and the monomer 2 is polyethylene glycol diacrylate;

[0022] Preferably, the flexible main chain is formed from the polymerization reaction of monomer 2 and monomer 3, and the monomer 3 is at least one of acrylonitrile, pentaerythritol tetraacrylate, polyethylene glycol acrylate, polyethylene glycol monomethyl ether acrylate, ethylene glycol methyl ether acrylate or diethyl allyl phosphate.

[0023] Furthermore, the mass ratio of the flexible main chain in the polymer is 80-99.8%, and the mass ratio of the rigid segment is 0.2-20%; preferably, the mass ratio of the flexible main chain is 80-90%, and the mass ratio of the rigid segment is 10-20%;

[0024] Optionally, when R2 and R3 are non-rigid chain segments, R2 and R3 are independently selected from H, halogen, nitro, ester group, cyano group, nitro group, carboxyl group, trifluoromethyl group, hydrocarbonthio group, carbonyl group, substituted or unsubstituted C1-C15 alkyl group, substituted or unsubstituted C1-C15 alkoxy group, substituted or unsubstituted amino group, substituted or unsubstituted (hetero)aryl group, substituted or unsubstituted C1-C12 alkylene group;

[0025] Optionally, the number average molecular weight of the polymer is 2000-1000000, preferably, the number average molecular weight of the polymer is 10000-600000.

[0026] Furthermore, the solid electrolyte further comprises a lithium salt, an auxiliary agent and an initiator, and by mass percentage, they are respectively: 30% - 93% of the polymer, 5% - 45% of the lithium salt, 0% - 25% of the auxiliary agent, and 0 - 2% of the initiator;

[0027] Preferably, by mass percentage, they are respectively: 28.9% - 93% of the polymer, 5% - 45% of the lithium salt, 1% - 25% of the auxiliary agent, and 0.1 - 2% of the initiator.

[0028] Furthermore, the lithium salt is at least one of LiTFSI, LiFSI, LiBOB, LiFOB, LiClO4;

[0029] Optionally, the auxiliary agent is at least one of oxide electrolytes, nano-fillers, carbonates, ethers or amides;

[0030] Optionally, the initiator is at least one of dicumyl peroxide, bis(tert-butylperoxy)diisopropylbenzene, benzoyl peroxide or azodiisobutyronitrile.

[0031] Furthermore, the morphology of the solid electrolyte is a thin film or a bulk, the stress is 4.5 MPa - 1000 MPa, the strain is 1.5% - 1000%, and the Young's modulus is 3 GPa - 20 GPa; the conductivity is 1×10 -6 ~1×10 - 3 S cm -1 .

[0032] The present invention also provides a preparation method of the solid electrolyte, which includes heating the monomers, the lithium salt, the auxiliary agent and the initiator that form the polymer to a temperature of 50 - 160 °C under the protection of an inert gas for a reaction time of 0.2 - 24 hours to obtain the solid electrolyte.

[0033] The present invention also protects an electrode, which includes an active material and an electrolyte, the electrolyte is the solid electrolyte described above, and the solid electrolyte is present inside and / or on the surface of the active material.

[0034] The present invention also protects a solid-state lithium battery, which includes the solid electrolyte or includes the electrode.

[0035] Advantageous effects:

[0036] In the present invention, in the solid electrolyte, a chain segment containing an ether group unit and an acrylate unit is used as a flexible main chain. By introducing a rigid chain segment onto the main chain, the mechanical properties of the solid electrolyte are improved, and at the same time, it has good electrical conductivity.

[0037] Furthermore, for the solid electrolyte, a flexible main chain polymer precursor liquid is prepared from monomer 2 and monomer 3, and the polymer formed by its polymerization with monomer 1 realizes excellent contact between the electrode and the electrolyte. The macroscopic ductility of the flexible chain segment is beneficial to the fitting of the interface. At the same time, the low crystallinity and high degree of amorphousness promote the conduction of ions inside the polymer. The excellent contact at the interface and the integrated structure of the electrode / electrolyte are beneficial to the migration of ions between the interfaces.

[0038] Further, for the solid electrolyte, a rigid chain segment is formed by the polymerization reaction of monomer 1 and monomer 4. After combining with the flexible main chain, the dendrite resistance of the polymer is realized. Even under a large current, on the one hand, the rigid chain segment can promote the uniform deposition of lithium, and on the other hand, even if dendrites are formed, it can effectively avoid puncture and cause short circuit, thereby greatly improving the safety performance of the solid electrolyte. Description of the drawings

[0039] In order to more clearly illustrate the technical solutions of the present invention, the drawings will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0040] Figure 1 It is the nuclear magnetic H spectrum of the rigid chain segment prepared in Example 1 of the present invention. Corresponding to the structural formula (2), R1’ is an unsaturated alkane substituent, and R2’, R3’, R4’, and R5’ are H.

[0041] Figure 2 It is the nuclear magnetic H spectrum of the comparative sample rigid chain segment prepared in Example 1 of the present invention. Corresponding to the structural formula (2), R1’ is an acrylonitrile substituent functional group, R2’, R3’, and R5’ are H, and R4’ is a propionitrile functional group.

[0042] Figure 3 It is the nuclear magnetic H spectrum of the polymer prepared in Example 4 of the present invention. Corresponding to the structural formula (1), R1 is H, R2 and R3 are rigid chain segments. In the corresponding structural formula (2) of the rigid chain segment, R1’ is an unsaturated alkane substituent, and R2’, R3’, R4’, and R5’ are H.

[0043] Figure 4 1H NMR spectrum of the comparative polymer prepared in Comparative Example 4-1 of the present invention. Corresponding to the structural formula (1), R1 is H, R2 and R3 are rigid chain segments. In the structural formula (2) corresponding to the rigid chain segment, R1' is an acrylonitrile substituent functional group, R2', R3', and R5' are H, and R4' is a propionitrile functional group. Detailed implementation manners

[0044] The following gives the definitions of some terms used in the present invention. Other terms not mentioned have the definitions and meanings well known in the art:

[0045] The solid electrolyte in the present invention includes a polymer. The polymer contains a flexible main chain and a rigid chain segment. The flexible main chain contains ether units and acrylate units, but is not limited to these two units. The flexible main chain contains a chain segment as shown in the structural formula (1):

[0046]

[0047] In the above structural formula, R1 is independently selected from H, halogen, nitro, ester group, cyano, nitro, carboxyl group, trifluoromethyl group, hydrocarbonthio group, carbonyl group, substituted or unsubstituted C1-C 15 alkyl, substituted or unsubstituted C1-C 15 alkoxy, substituted or unsubstituted amino group, substituted or unsubstituted (hetero)aryl group, substituted or unsubstituted C1-C 12 alkylene.

[0048] Preferably, R1 is independently selected from H, cyano, substituted or unsubstituted C1-C15 alkyl, and substituted or unsubstituted C1-C12 alkylene.

[0049] n is a positive integer from 10 to 1000; preferably, n is 8, 50, 240, or 600.

[0050] In the formula (1), the positions shown by R2 and R3 can be respectively used as the connection sites with the rigid chain segment, or can be individually connected to the rigid chain segment. For example, R2 is independently selected from H, halogen, nitro, ester group, cyano, nitro, carboxyl group, trifluoromethyl group, hydrocarbonthio group, carbonyl group, substituted or unsubstituted C1-C 15 alkyl, substituted or unsubstituted C1-C 15 alkoxy, substituted or unsubstituted amino group, substituted or unsubstituted (hetero)aryl group, substituted or unsubstituted C1-C 12An alkylene group; R3 is a rigid segment. Alternatively, R3 is independently selected from H, halogen, nitro, ester group, cyano group, nitro group, carboxyl group, trifluoromethyl group, hydrocarbonthio group, carbonyl group, substituted or unsubstituted C1-C15 alkyl group, substituted or unsubstituted C1-C15 alkoxy group, substituted or unsubstituted amino group, substituted or unsubstituted (hetero)aryl group, substituted or unsubstituted C1-C12 alkylene group; R2 is a rigid segment. Alternatively, both R2 and R3 are rigid segments.

[0051] In the present invention, the rigid segment contains an olefin compound unit with a ureido group, and the rigid segment includes a segment with a structural formula as shown in Formula (2):

[0052]

[0053] Wherein, R1', R4' and R5' are each independently selected from H, carbonyl group, hydroxyl group, cyano group, unsaturated carbon-carbon double bond, propionitrile-substituted functional group, halogen, amino group, nitro group, acyl group, carboxyl group, ester group, trifluoromethyl group, hydrocarbonthio group, substituted or unsubstituted C1-C 20 alkyl group, substituted or unsubstituted C1-C 20 alkoxy group, substituted or unsubstituted C4-60 (hetero)aryl group, substituted or unsubstituted C2-C containing a heterocyclic atom 15 cycloalkyl group; R2' and R3' are each independently selected from H, ester group, carboxyl group, carbonyl group, substituted or unsubstituted C1-C 10 alkyl group, substituted or unsubstituted C1-C 15 alkoxy group, substituted or unsubstituted amino group, substituted or unsubstituted (hetero)aryl group.

[0054] Preferably, when R2', R3' and R5' are H, R4' is a propionitrile-substituted functional group, and R1' is an unsaturated carbon-carbon double bond, under the condition of the same proportion of rigid segments, the modification effect on the mechanical properties of the polymer electrolyte is the best.

[0055] The rigid segment is connected to the sites represented by R2 and / or R3 on the flexible main chain through R1'. For example, in a specific embodiment, the structural formula of the polymer is as follows:

[0056] Or

[0057] For the solid electrolyte as described above, wherein the number-average molecular weight of the polymer is 2000-1000000, preferably, the number-average molecular weight of the polymer is 10000-600000.

[0058] Among them, the mass fraction of the flexible main chain in the polymer is 80-99.8%, and the mass fraction of the rigid chain segment in the polymer is 0.2-20%. Preferably, the mass fraction of the flexible main chain is 80-90%, and the mass fraction of the rigid chain segment is 10-20%.

[0059] The solid electrolyte of the present invention, in addition to including the above polymer, further includes a lithium salt and an additive.

[0060] The present invention does not particularly limit the lithium salt in the solid electrolyte, and any lithium salt commonly used in the art can be used, such as at least one of compounds composed of lithium metal cations and organic or inorganic anion groups such as LiTFSI, LiFSI, LiBOB, LiFOB, LiClO4, etc.

[0061] In addition, the additive is selected from at least one of small organic molecules such as oxide electrolytes, nano-fillers, carbonates, ethers, or amides.

[0062] In one embodiment, the solid electrolyte includes, by mass percentage: 30% to 93% of the polymer, 5% to 45% of the lithium salt, 0% to 25% of the additive, and 0 to 2% of the initiator. Preferably, by mass percentage, they are respectively: 28.9% to 93% of the polymer, 5% to 45% of the lithium salt, 1% to 25% of the additive, and 0.1 to 2% of the initiator.

[0063] Furthermore, in the solid polymer electrolyte of the present invention, in addition to including a flexible main chain and a rigid chain segment, it may further include other structural units that do not contain a ureido group and are not from a cross-linking agent. Such structural units are referred to as auxiliary structural units in the present invention. It should be noted that the polymer may contain multiple different auxiliary structural units. For example, the auxiliary structural unit may be from at least one of acrylic, siloxane, and acrylonitrile materials.

[0064] Furthermore, the number average molecular weight of the polymer is 2000-1000000. Among them, when the polymer only includes a flexible main chain and a rigid chain segment, the mass fraction of the flexible main chain in the polymer is 80-99.8%, and the mass fraction of the rigid chain segment in the polymer is 0.2-20%. When the polymer further includes an auxiliary structural unit, the mass fraction of the flexible main chain in the polymer is 10%-95%, the mass fraction of the rigid chain segment in the polymer is 0.5%-85%, and the mass fraction of the auxiliary structural unit in the polymer is 0.1-20%.

[0065] The preparation method of the polymer of the present invention is not particularly different from the polymer preparation methods in the art. For example, a solvent system including monomers and initiators is heated to a certain temperature under the protection of an inert gas to initiate a polymerization reaction. During the reaction process, the degree of polymerization of the reaction system can be monitored in real time to judge the progress of the reaction, which is conducive to obtaining a polymer that meets the target molecular weight.

[0066] Specifically, the addition amount of the initiator is 0.1-2% of the total mass of the polymer monomers. The initiator can be the commonly used initiators in the art, including but not limited to at least one of diisopropylbenzene peroxide, diisopropylbenzene bis(tert-butyl peroxide), benzoyl peroxide, and azobisisobutyronitrile.

[0067] The present invention does not limit the preparation method of the solid electrolyte. In a specific embodiment, the preparation method of the solid electrolyte includes heating a monomer, a lithium salt, an additive, and an initiator for forming the polymer to a temperature of 50-160 °C for a reaction time of 0.2-24 hours under the protection of an inert gas to obtain the solid electrolyte. In a specific embodiment, the polymer, the lithium salt, and the additive can be mixed evenly to form a precursor liquid, and then the slurry is coated on a substrate. After initiation and curing, the solid electrolyte of the present invention is obtained. Alternatively, a precursor liquid formed by mixing a monomer, a lithium salt, and an additive for preparing the polymer is in-situ initiated on or between the positive and negative electrodes to form a polymer to obtain the solid electrolyte of the present invention.

[0068] The stress of the solid polymer electrolyte prepared by the present invention is 4.5 MPa to 1000 MPa, the strain is 1.5% to 1000%, and the Young's modulus is 3 GPa to 20 GPa. The conductivity is 1×10 -6 ~1×10 -3 S cm -1 .

[0069] The present invention also provides an electrode, which can be a positive electrode or a negative electrode, and can be in the form of a sheet or a block. Taking the positive electrode sheet as an example, the positive electrode sheet includes the solid electrolyte described above; the positive electrode sheet includes a positive electrode active layer, and the solid electrolyte is present inside and / or on the surface of the positive electrode active layer.

[0070] The present invention does not limit the preparation method of the positive electrode sheet. In a specific embodiment, the positive electrode active material, polymer electrolyte or polymer precursor liquid, conductive agent, binder, etc. can be mixed in a solvent to form a positive electrode slurry. Subsequently, the positive electrode slurry is coated on the surface of the current collector, and after drying and rolling, a positive electrode sheet including a polymer electrolyte inside is obtained according to the present invention. Further, a precursor liquid including a solid polymer electrolyte can also be prepared, and the precursor liquid is coated on the surface of the above positive electrode sheet to obtain a positive electrode sheet with solid polymer electrolyte on both the surface and inside the positive electrode. Alternatively, the positive electrode active material, binder, conductive agent, etc. are mixed evenly in a solvent to prepare a positive electrode slurry, and a precursor liquid including a solid polymer electrolyte is prepared at the same time. Subsequently, the positive electrode slurry is first coated on the functional surface of the positive electrode current collector, and after drying, the precursor liquid is coated on the dried positive electrode surface. After curing is initiated and dried again, a positive electrode sheet with solid polymer electrolyte on the surface is obtained according to the present invention.

[0071] The drying in the above preparation process includes treating at 70-125 °C for 6-72 hours.

[0072] The present invention does not make special limitations on the positive electrode active material, conductive agent, and binder.

[0073] In the traditional positive electrode matrix, the polymer electrolyte decomposes under high potential, easily generating a large amount of gas and causing an explosion. At the same time, there is a problem of large interfacial impedance / polarization, resulting in poor battery rate performance and inducing concentration polarization. By introducing an inert rigid segment into the flexible main chain in the present invention, a stable polymer coating layer is formed inside the positive electrode, preventing the oxidation decomposition of the flexible main chain under high potential. The polymer electrolyte is formed on the surface, promoting the transport of lithium ions between interfaces. The polymer electrolyte formed in situ inside / on the surface of the positive electrode forms an integrated structure, reducing the interfacial impedance and reducing the concentration polarization.

[0074] Of course, the solid electrolyte can also be used for the preparation of the negative electrode, such as a negative electrode sheet. The negative electrode sheet includes a negative electrode matrix, and the polymer electrolyte is present inside and / or on the surface of the negative electrode matrix. In the traditional negative electrode matrix, there are problems of dendrites, which easily cause battery short circuits. At the same time, there is a problem of large interfacial impedance / polarization, resulting in poor battery rate performance and inducing concentration polarization. By forming the polymer electrolyte on the surface in the present invention, the uniform deposition of lithium ions is promoted, solving the dendrite problem. The polymer electrolyte formed in situ inside / on the surface of the negative electrode forms an integrated structure, reducing the interfacial impedance and reducing the concentration polarization.

[0075] The present invention also provides a solid-state lithium-ion battery, including the above-mentioned solid electrolyte, wherein the polymer in the solid electrolyte is obtained by copolymerization of a flexible main chain and a rigid segment. The mechanical properties of traditional polymers are poor, making the battery prone to short circuits; the oxidation potential is low, making the polymer electrolyte easily oxidized and decomposed, generating a large amount of gas. This polymer has more excellent mechanical strength, and the rigid segment has a higher oxidation potential, which can effectively reduce the decomposition of the polymer electrolyte. Therefore, it has excellent performance in improving the safety performance of lithium-ion batteries. This polymer electrolyte can not only achieve the conduction of lithium ions, but also significantly improve the interfacial stability of lithium-ion batteries.

[0076] In a specific embodiment, the solid-state lithium-ion battery can use the above-mentioned solid electrolyte as the electrolyte. At this time, there are no special requirements for the positive and negative electrode sheets in the battery compared with the existing positive and negative electrode sheets in the art.

[0077] It is also possible to use an electrode containing the above-mentioned solid electrolyte, such as a positive electrode sheet. This solid electrolyte can significantly improve the interfacial stability of the positive electrode sheet and still maintain a normal working state under long-term cycling. Or a negative electrode sheet, which includes the above-mentioned solid electrolyte, and this solid electrolyte can significantly improve the interfacial stability of the negative electrode sheet and still maintain a normal working state under long-term cycling.

[0078] The present invention does not limit the preparation method of the solid-state lithium-ion battery. For example, it can be obtained by stacking a positive electrode sheet, a solid electrolyte, and a negative electrode sheet in sequence and then encapsulating. It is also possible to stack a positive electrode sheet, a separator, and a negative electrode sheet in sequence to form a basic battery cell, and then inject a uniformly mixed polymer precursor solution into it. After sufficient infiltration and heating and curing, the solid-state lithium-ion battery of the present invention is obtained. Among them, the precursor solution includes polymer monomers, lithium salts, additives, and initiators.

[0079] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. For those where specific techniques or conditions are not indicated in the examples, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase. In the following examples, unless otherwise specified, "%" all refers to weight percentage.

[0080] The following test methods are used:

[0081] (1) Detection of the number-average molecular weight of the polymer: The polymer is dissolved in a solvent to form a uniform liquid system, filtered through an organic membrane by suction filtration, and a sample is taken and detected by a Shimadzu GPC-20A gel permeation chromatograph in Japan to collect molecular weight information.

[0082] (2) The test method for the ionic conductivity of the solid electrolyte is as follows: The ionic conductivity of the solid electrolyte is tested by the alternating current impedance method, and the instrument used is the CHI660E electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. In the argon glove box, a button cell is assembled in the order of the positive electrode shell, stainless steel gasket, solid polymer electrolyte, stainless steel gasket, shrapnel, and negative electrode shell. The alternating current impedance test frequency is 100 mHz to 1000 KHz, the amplitude voltage is 5 mV, and the test temperature is room temperature.

[0083] The calculation formula for the ionic conductivity of the solid electrolyte:

[0084] ρ = L / (R·S)

[0085] Wherein, R is the bulk impedance (Ω) of the solid polymer electrolyte; L is the thickness (cm) of the solid electrolyte; S is the effective contact area (cm 2 ) of the button cell.

[0086] (3) The test method for the cycle performance of the solid polymer lithium-ion battery is as follows: The lithium-ion battery is placed on a battery charge and discharge test cabinet for charge and discharge cycle testing. The test conditions are room temperature °C, activation at 0.1C / 0.1C, charge and discharge at 0.5C / 0.5C, and the charge and discharge start and stop voltages are 3.0 - 4.5 V for LCO and 2.6 - 4.1 V for LFP. Record the number of cycles experienced when the capacity decays to 80% of the first discharge capacity.

[0087] (4) The mechanical properties refer to the macroscopic mechanical strength of the polymer, which is the result obtained by testing with a tensile machine. The strain test refers to the GB / T 1040.5 - 2008 standard.

[0088] The main reagents used hereinafter include:

[0089] The meanings represented by the abbreviations used are as follows: FEC fluoroethylene carbonate; EMC ethyl methyl carbonate; EC ethylene carbonate; LLZTO lithium lanthanum zirconium tantalum oxide; LLZO lithium lanthanum zirconium oxide. Other terms not mentioned have the definitions and meanings well-known in the art.

[0090] Examples 1 - 10

[0091] The preparation method of Polymer 1 includes the following steps:

[0092] S1: Under an inert atmosphere, 4.2 g of 2-amino-4-hydroxy-6-methylpyrimidine was added to 100 ml of dimethyl sulfoxide, and the mixture was stirred at 100 - 150 °C for 10 - 20 minutes. Then, 2.6 g of isocyanatoethyl methacrylate was added to the flask. When the solution cooled to room temperature, a white solid precipitated. The precipitate was collected and washed multiple times with methanol and acetone. After stirring at 50 °C at a speed of 500 r / min for 1 h, it was dried under vacuum at 30 °C for 5 hours to remove the solvent, obtaining monomer 1.

[0093] Monomer 1 is an olefin compound containing a urea group, that is, a rigid segment monomer. Its 1H NMR spectrum is as Figure 1 shown. According to the structural formula of the rigid segment, that is, in structural formula (2), R1’ is an unsaturated alkane substituent, and R2’, R3’, R4’, and R5’ are H.

[0094] S2: Using polyethylene glycol diacrylate as the flexible main chain, that is, monomer 2. Under an inert atmosphere, monomer 1 or monomer 1-1, monomer 2, initiator, additive, and lithium salt obtained in S1 were added to a sealed container. After stirring at a speed of 600 r / min for 6 h, the mixture was uniformly mixed and reacted at 70 °C for 60 min to obtain polymer 1. The amounts of each substance are shown in Table 1.

[0095] To test the influence of different rigid segments on the material properties, step S1 was changed, and monomer 1-1 was prepared by the following method:

[0096] Under an inert atmosphere, 3.0 g of 2-amino-4-hydroxy-6-propionitrile pyrimidine was added to 85 ml of dimethyl sulfoxide, and the mixture was stirred at 100 - 150 °C for 10 - 20 minutes. Then, 2.2 g of isocyanatoethyl cyanoacrylate was added to the flask. When the solution cooled to -20 °C, a pale yellow solid precipitated. The precipitate was collected and washed multiple times with methanol and acetone. After stirring at 50 °C at a speed of 500 r / min for 1 h, it was dried under vacuum at 30 °C for 5 hours to remove the solvent, obtaining monomer 1-1.

[0097] The prepared monomer 1-1 has a 1H NMR spectrum as Figure 2 shown. According to the structural formula of the rigid segment, that is, in structural formula (2), R1’ is an acrylonitrile substituent functional group, R2’, R3’, and R5’ are H, and R4’ is a propionitrile functional group.

[0098] Using monomer 1-1 to replace monomer 1, step S2 was respectively carried out with reference to Example 4, Example 5, and Example 8, and were respectively denoted as Comparative Example 4-1, Comparative Example 5-1, and Comparative Example 8-1. The amounts of each substance are shown in Table 1.

[0099] The 1H NMR spectrum of the polymer 1 formed by the polymerization of monomer 1 and monomer 2 is as Figure 3As shown, the 1H NMR spectrum of Polymer 1 formed by polymerizing Monomer 1-1 and Monomer 2 is as follows Figure 4 as shown.

[0100] Note: The content unit of the monomers in Table 1 is parts by mass. The total mass of Monomer 1 (or Monomer 1-1) and Monomer 2 is 100 g.

[0101] The unit of the lithium salt is g. For example, LiTFSI / 5 means the mass of LiTFSI is 5 g; LiTFSI:LiFSI = 2:8 / 5 means the mass ratio of LiTFSI to LiFSI is 2:8, and the total mass of the two is 5 g, and so on for the rest.

[0102] The unit of the initiator is %, which refers to the mass fraction of the initiator in the total amount of raw materials in Step S2. For example, AIBN / 0.2 means the amount of AIBN used is 0.2% of the total mass of the raw materials in Step S2. BPO:AIBN = 1:1 / 0.1 means the mass ratio of BPO to AIBN is 1:1, and the two together account for 0.1% of the total mass of the raw materials in Step S2.

[0103] The addition amount of the additives is 3 g for all.

[0104] Table 1 Proportion of raw materials and performance table of Polymer 1

[0105]

[0106]

[0107]

[0108]

[0109] As can be seen from Table 1, adjusting the proportion of the rigid chain segment (Monomer 1) can effectively adjust the mechanical properties of the polymer, and adding inorganic particles can effectively adjust the mechanical properties of the polymer electrolyte. Preferably, when the proportion of the rigid chain segment is 10-20% and the additive is an inorganic particle, the mechanical properties of the polymer are the best. For example, when the proportion of the rigid chain segment is 10-17.5% and the inorganic nanoparticle is used as the additive, its mechanical properties can reach 100-200 MPa, the mechanical strength can reach 8-20 GPa, the strain is 5-300%, and the comprehensive mechanical properties of the polymer electrolyte are the best.

[0110] By comparing the comparative examples with the corresponding examples, it can be concluded that Monomer 1-1 is superior to Monomer 1 in improving the mechanical properties.

[0111] Examples 11-16

[0112] The preparation method of Polymer 2 includes the following steps:

[0113] S1: Under an inert atmosphere, equal masses of monomer 2 (polyethylene glycol diacrylate) and monomer 3 (see Table 2), and 0.01 g of initiator are added to a sealed container. After stirring at a speed of 600 r / min for 6 h, the mixture is uniformly mixed to obtain a flexible main-chain polymer precursor liquid.

[0114] Table 2 Parameters of the flexible main-chain polymer precursor liquid

[0115] Monomer 3 Initiator Mixing Temperature / °C Product Number Acrylonitrile AIBN 50 Precursor 1A Pentaerythritol tetraacrylate AIBN 45 Precursor 2A Polyethylene glycol acrylate BPO 20 Precursor 3A Methoxypolyethylene glycol acrylate DCP 30 Precursor 4A 2-Methoxyethyl acrylate BIPB 50 Precursor 5A Diethyl allylphosphonate BPO 15 Precursor 6A

[0116] S2: Under an inert atmosphere, 1.5 g of the flexible main-chain polymer precursor liquid, 0.18 g of monomer 1 (the olefin compound containing a ureido group prepared in Example 1), 0.02 g of initiator, and a lithium salt (LiTFSI, with a mass content of 20% of the total weight of the raw materials) are added to a sealed container. After stirring at a speed of 600 r / min for 4 h, the mixture is uniformly mixed and reacted at 80 °C for 2 h to obtain Polymer 2. The specific reaction conditions and product properties are shown in Table 3.

[0117] Table 3 Reaction conditions and performance test table of Polymer 2

[0118]

[0119] As can be seen from Table 3, it is difficult to decouple the mechanical properties and ionic conductivity. A high mechanical property means a large proportion of rigid chain segments, resulting in the dominant position of the crystalline region of the polymer segments and a decrease in ionic conductivity. However, through our reasonable design of the molecular structure, the best balance can be achieved.

[0120] From Example 11, it can be concluded that by increasing the molar molecular weight of the polymer, even if the number of rigid chain segments is increased, a high room-temperature ionic conductivity can still be achieved on the premise of maintaining high mechanical properties.

[0121] Examples 17 - 24

[0122] The preparation method of Polymer 3 includes the following steps:

[0123] S1: Under an inert atmosphere, 1.5 g of monomer 1 (the olefin compound containing a ureido group prepared in Example 1), monomer 4 (specific information is shown in Table 4), and 0.01 g of thiol curing agent are added to a sealed container. After stirring at a speed of 600 r / min for 4 h, the mixture is uniformly mixed and reacted at 150 °C for 10 min, and then cooled to room temperature to precipitate a solid. Vacuum drying gives the rigid chain segment B.

[0124] Table 4 Preparation conditions table of the rigid chain segment B

[0125]

[0126] S2: Under an inert atmosphere, 1.0 g of monomer 2 (polyethylene glycol diacrylate), 0.3 g of rigid segment B, and 0.02 g of initiator were added to a sealed container. After stirring at a speed of 600 r / min for 4 h, the mixture was uniformly mixed and reacted at 80 °C for 2 h to obtain polymer 3. The specific reaction conditions and product properties are shown in Table 5.

[0127] Table 5 Reaction Conditions and Performance Test Table of Polymer 3

[0128]

[0129]

[0130] It can be seen from Table 5 that the initiator has limited influence on the overall physical and chemical properties of the polymer. In the polymer with polyethylene glycol diacrylate as the main body, the better the mechanical properties, the lower the ionic conductivity. The above results indicate that the composition of the rigid segment has a significant impact on the crystallization of the polymer.

[0131] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0132] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any suitable way. To avoid unnecessary repetition, the present invention does not separately describe various possible combination methods.

[0133] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A solid electrolyte, characterized in that: The solid electrolyte includes a polymer, the polymer contains a flexible main chain and a rigid segment, the flexible main chain contains an ether group unit and an acrylate unit, and the flexible main chain includes a segment represented by the structural formula as shown in formula (1): （1） Wherein, R1 is independently selected from H, halogen, ester group, cyano group, nitro group, carboxyl group, trifluoromethyl group, hydrocarbonthio group, carbonyl group, substituted or unsubstituted C1-C 15 alkyl group, substituted or unsubstituted C1-C 15 alkoxy group, substituted or unsubstituted amino group, substituted or unsubstituted heteroaryl group, substituted or unsubstituted C1-C 12 alkylene group; n is a positive integer of 10-1000; At least one of R2 and R3 is a rigid segment, the rigid segment contains an olefin compound unit with a ureido group, and the rigid segment includes a segment represented by the structural formula as shown in formula (2): （2） Among them, R1 ， , R4 ， and R5 ， are each independently selected from H, carbonyl, hydroxyl, cyano, unsaturated carbon-carbon double bond, propionitrile-substituted functional group, halogen, amino, nitro, acyl, carboxyl, ester group, trifluoromethyl, hydrocarbonthio group, substituted or unsubstituted C1-C 20 alkyl group, substituted or unsubstituted C1-C 20 alkoxy group, substituted or unsubstituted C4-60 heteroaryl group, substituted or unsubstituted C2-C containing a heteroatom 15 cycloalkyl group; R2 ， , R3 ， are each independently selected from H, ester group, carboxyl, carbonyl, substituted or unsubstituted C1-C 10 alkyl group, substituted or unsubstituted C1-C 15 alkoxy group, substituted or unsubstituted amino group, substituted or unsubstituted heteroaryl group; The flexible main chain is formed from the polymerization reaction of monomer 2, and monomer 2 is polyethylene glycol diacrylate; The rigid segment is connected through R1 ， to the sites shown by R2 and / or R3 on the flexible main chain; the rigid segment is formed by the polymerization reaction of monomer 1 and monomer 4. Monomer 1 is prepared by reacting 2-amino-4-hydroxy-6-methylpyrimidine and isocyanatoethyl methacrylate at 100-150 °C for 10-20 minutes. Monomer 4 is pentaerythritol tetrakis(mercaptoacetate) and / or bis(mercapto polyethylene glycol); In the polymer, the mass ratio of the flexible main chain is 80-99.8%, and the mass ratio of the rigid segment is 0.2-20%; The stress of the solid electrolyte is 98 MPa to 1000 MPa.

2. The solid electrolyte according to claim 1, wherein: The flexible main chain is formed from the polymerization reaction of monomer 2 and monomer 3, and monomer 3 is at least one of acrylonitrile, pentaerythritol tetraacrylate, polyethylene glycol acrylate, polyethylene glycol monomethyl ether acrylate, ethylene glycol methyl ether acrylate or diethyl allyl phosphate.

3. The solid electrolyte according to claim 1, wherein: The mass ratio of the flexible main chain is 80-90%, and the mass ratio of the rigid segment is 10-20%; When R2 and R3 are non-rigid segments, R2 and R3 are independently selected from H, halogen, ester group, cyano group, nitro group, carboxyl group, trifluoromethyl group, hydrocarbon thio group, carbonyl group, substituted or unsubstituted C1-C15 alkyl group, substituted or unsubstituted C1-C15 alkoxy group, substituted or unsubstituted amino group, substituted or unsubstituted heteroaryl group, substituted or unsubstituted C1-C12 alkylene group; The number average molecular weight of the polymer is 2000-1000000.

4. The solid electrolyte according to claim 3, wherein: The number average molecular weight of the polymer is 10000-600000.

5. The solid electrolyte according to any one of claims 1-4, characterized in that: The solid electrolyte further includes a lithium salt, an additive and an initiator, and by mass percentage are respectively: polymer 30% - 93%, lithium salt 5% - 45%, additive 0% - 25%, initiator 0 - 2%.

6. The solid electrolyte according to any one of claims 1-4, characterized in that: The solid electrolyte by mass percentage are respectively: polymer 28.9% - 93%, lithium salt 5% - 45%, additive 1% - 25%, initiator 0.1 - 2%.

7. The solid electrolyte according to claim 5, characterized in that: The lithium salt is at least one of LiTFSI, LiFSI, LiBOB, LiFOB, LiClO4; The additive is at least one of an oxide electrolyte, a nano filler, a carbonate, an ether or an amide; The initiator is at least one of dicumyl peroxide, bis(tert-butylperoxy)diisopropylbenzene, benzoyl peroxide or azobisisobutyronitrile.

8. The solid electrolyte according to any one of claims 1-4, characterized in that: The morphology of the solid electrolyte is a thin film or a bulk, with a strain of 1.5% to 1000% and a Young's modulus of 3 GPa to 20 GPa; the conductivity is 1×10 -6 ~ 1×10 -3 S·cm -1 .

9. A method for preparing the solid electrolyte according to any one of claims 1-8, characterized in that: It includes heating the monomers, lithium salt, additive and initiator for forming the polymer to a temperature of 50-160 °C under the protection of an inert gas, and the reaction time is 0.2-24 hours to obtain the solid electrolyte.

10. An electrode comprising an active material and an electrolyte, characterized in that, The electrolyte is the solid electrolyte according to any one of claims 1-8, and the interior and / or surface of the active material has the solid electrolyte.

11. A solid-state lithium battery, comprising the solid electrolyte according to any one of claims 1-8, or comprising the electrode according to claim 10.

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