A cross-linked polymer, a method for synthesizing the cross-linked polymer, and a solid-state polymer electrolyte

Abstract

The present application provides a kind of crosslinking polymer, synthesis method and solid-state polymer electrolyte, wherein the crosslinking polymer contains the crosslinking structure generated by crosslinking agent reaction and the polymer chain connected with crosslinking structure, and the polymer chain includes first structural unit and second structural unit, wherein, the polymer chain is connected with crosslinking structure by first structural unit.Crosslinking agent contains at least two crosslinking groups for crosslinking, so that each crosslinking structure is connected with at least two first structural units respectively, and the crosslinking group is selected from one or several of the following: amino, hydroxyl or mercapto.The crosslinking polymer of the present application has excellent mechanical properties and ionic conductivity, and has good application prospect in solid-state polymer electrolyte.

Description

Technical Field

[0001] This invention relates to the field of polymers, and particularly to a crosslinked polymer, a method for synthesizing the crosslinked polymer, and a solid polymer electrolyte. Background Technology

[0002] Electrochemical energy storage technology, characterized by high energy density and high safety performance, holds immense promise for large-scale energy storage systems. Developing efficient electrochemical energy storage technologies offers significant social and economic benefits for improving existing power generation systems, ensuring the large-scale development of renewable energy, and guaranteeing the safe and economical operation of the power grid. Lithium-ion batteries have attracted widespread attention from researchers due to their high energy density, light weight, high operating voltage, and lack of memory effect. Lithium metal anodes, in particular, have become the most promising high-energy lithium battery anode materials due to their high theoretical specific capacity, lowest electrochemical potential, and low density. The electrolyte, as a crucial component of the battery, directly affects the energy density, cycle life, and safety performance of lithium-ion batteries. While liquid electrolytes have achieved commercial application, they suffer from drawbacks such as volatility, leakage, and the potential for side reactions with lithium metal anodes. Lithium metal batteries based on liquid electrolytes are susceptible to lithium dendrite punctures, causing internal micro-short circuits, which can lead to thermal runaway, fire, or even explosion in severe cases.

[0003] Replacing liquid electrolytes with solid-state electrolytes holds promise for improving battery energy density while addressing potential safety issues in current batteries, aligning with the requirements and expectations of future large-scale energy storage technologies. All-solid-state electrolytes are generally classified into two main categories: solid-state inorganic electrolytes and solid-state polymer electrolytes. While solid-state inorganic electrolytes offer advantages in ionic conductivity and lithium-ion transference number, they often suffer from poor interfacial compatibility and complex manufacturing processes, hindering their widespread application. In contrast, solid-state polymer electrolytes offer advantages such as flexibility, processability, and good interfacial adhesion, making them promising candidates for applications in solid-state batteries and flexible electronics. However, solid-state polymer electrolytes typically suffer from low room-temperature ionic conductivity, low lithium-ion transference number, and insufficient mechanical modulus, issues that urgently need to be addressed. Summary of the Invention

[0004] The purpose of this invention is to provide a crosslinked polymer and a method for synthesizing the crosslinked polymer, in order to solve the above-mentioned problems.

[0005] The present invention provides a crosslinked polymer containing a crosslinked structure generated by a crosslinking agent and a polymer chain connected to the crosslinked structure. The polymer chain includes a first structural unit and a second structural unit. The first structural unit is the structure shown in formula (1-1) and / or formula (1-2), and the second structural unit is the structure shown in formula (2). The polymer chain is connected to the crosslinked structure through the first structural unit. In formulas (1-1) and (1-2), * represents the connection point connected to the crosslinked structure.

[0006] Equation (1-1): Equation (1-2): Equation (2):

[0007] The crosslinking agent contains at least two crosslinking groups for crosslinking, such that each crosslinked structure is connected to at least two first structural units respectively, wherein the crosslinking groups are selected from one or more of the following: amino, hydroxy, or mercapto; wherein R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene; and R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkyl.

[0008] The crosslinked polymer of this invention can form films, has good mechanical properties and structural advantages, and has broad application prospects.

[0009] Optionally, the crosslinked polymer is formed by crosslinking a polyether homopolymer with cyclic carbonate side groups to the crosslinking agent, wherein the polyether homopolymer is shown in formula (3):

[0010] Equation (3):

[0011] Wherein, n represents the degree of polymerization, which ranges from 5 to 10000; a portion of the repeating units in the polyether homopolymer have their cyclic carbonate side groups crosslinked with the crosslinking agent to form the first structural unit, while another portion of the repeating units do not undergo crosslinking to form the second structural unit; R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkyl.

[0012] Optionally, the crosslinking agent is composed of formula (4):

[0013] Equation (4): A-(B) b

[0014] Wherein, B is the crosslinking group arbitrarily substituted on A, with the structural formula —NH2, —OH or —SH, b represents the number of crosslinking groups, which is 2 or more; A is a linking group having two or more linking sites, the linking group being selected from the following substituted or unsubstituted groups: alkyl, heteroalkyl, alkylcarbonyl, heteroalkylcarbonyl, heterocycloalkyl, heterocycloalkylcarbonyl, alkylester, aryl, aralkyl, heteroaryl, heteroarylalkyl, aralkylcarbonyl, aralkyl-hexaalkylcarbonyl, heteroaryl-hexaalkylcarbonyl, cycloalkyl, cyclohexaalkyl, cycloalkylcarbonyl, cycloalkyl-hexaalkylcarbonyl, cage-type polysilsesquioxanealkyl.

[0015] Optionally, A is selected from the following groups: alkyl, aryl, aralkyl, alkoxy, heteroaralkyl, aralkylcarbonyl, amide, amidealkyl, amidealkoxy.

[0016] Optionally, A is selected from the following structural formulas:

[0017]

[0018]

[0019] Where * represents the connection point with the crosslinking group B; n ranges from 2 to 10000; x1, x2, x3, and x4 each range from 1 to 1000.

[0020] Optionally, R1 can be selected from the following structure:

[0021]

[0022] Where n ranges from 1 to 100; * represents a connection point.

[0023] Alternatively, R2 can be selected from the following structure:

[0024]

[0025] Where X is selected from halogen atoms; * indicates a connection point.

[0026] Optionally, the first structural unit in the crosslinked polymer accounts for 10% to 80% of the total number of the first structural unit and the second structural unit.

[0027] The present invention also provides a method for synthesizing a crosslinked polymer, wherein the method comprises reacting a polyether homopolymer represented by formula (3) with the crosslinking agent to obtain the crosslinked polymer;

[0028] Equation (3):

[0029] Wherein, n represents the degree of polymerization, which ranges from 5 to 10000; in the polyether homopolymer, a portion of the repeating units have their cyclic carbonate side groups crosslinked with the crosslinking agent to form the first structural unit, while another portion of the repeating units do not undergo crosslinking to form the second structural unit.

[0030] Optionally, the polyether homopolymer is subjected to a crosslinking reaction with the crosslinking agent. The reaction temperature of the crosslinking reaction is 25–180 degrees Celsius, the reaction time is 0.5–72 hours, and the reaction solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, tetrahydrofuran, acetonitrile, dimethyl carbonate, diethyl carbonate, 1,3-dioxane, and acetone.

[0031] Optionally, the reaction temperature is 25–120 degrees Celsius, the reaction time is 1–48 hours, and the reaction solvent is one or more of N,N-dimethylformamide, tetrahydrofuran, acetonitrile, dimethyl carbonate, and acetone.

[0032] Optionally, the molar ratio of the crosslinking groups in the selected crosslinking agent to the cyclic carbonate groups on the side groups of the polyether homopolymer is 0.1-0.8.

[0033] Optionally, the method further includes the synthesis of the polyether homopolymer: using epoxy monomers as raw materials to carry out ring-opening polymerization to form the polyether homopolymer, wherein the epoxy monomers are composed of formula (5):

[0034] Equation (5):

[0035] R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkylene.

[0036] Optionally, in the ring-opening polymerization reaction, the initiator is an onium salt, the catalyst is an aluminum complex and / or a boron complex, and the terminator is an alcohol, ammonia, water, organic or inorganic acid containing an active proton hydrogen.

[0037] Optionally, the initiator is one or more of tetraoctylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetraoctylammonium azide, and bis(triphenyl)phosphine-ammonium chloride; the catalyst is one or more of triethylboron, triisobutylaluminum, triethylaluminum, triphenylboron, and tripentafluorophenylboron; and the terminator is one or more of water, methanol, ethanol, formic acid, and acetic acid.

[0038] Optionally, in the ring-opening polymerization reaction, the reaction temperature is -30 to 60 degrees Celsius, and the reaction solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, tetrahydrofuran, acetonitrile, toluene, benzene, cyclohexane, and chlorobenzene.

[0039] The present invention also provides a solid polymer electrolyte comprising the above-described crosslinked polymer.

[0040] Optionally, the solid polymer electrolyte further includes a lithium salt, wherein the crosslinked polymer has a mass fraction of 10%-95% in the solid polymer electrolyte, and the lithium salt has a mass fraction of 5%-90% in the solid polymer electrolyte.

[0041] Optionally, the room temperature ionic conductivity of the solid polymer electrolyte is in the range of 10. -5 The S / cm ratio is above 0.2 and the lithium-ion transference number is above 0.2.

[0042] The present invention also provides an electrochemical device comprising the above-described solid polymer electrolyte.

[0043] The present invention also provides the application of the solid polymer electrolyte as described above in electrochemical devices or flexible devices, particularly in lithium-ion or lithium metal batteries, and more particularly in improving the ionic conductivity and / or lithium-ion transference number of the solid electrolyte of lithium-ion batteries and / or the electrochemical stability window of lithium-ion batteries and / or the rate performance and cycle performance of lithium metal batteries. Attached Figure Description

[0044] Figure 1 A structural model diagram of a polyether homopolymer containing cyclic carbonate side groups is shown.

[0045] Figure 2 A structural model diagram illustrating a specific embodiment of a crosslinked polymer formed by the crosslinking reaction of a polyether homopolymer containing cyclic carbonate side groups and an amino crosslinking agent;

[0046] Figure 3 Infrared absorption spectra of polyether homopolymers containing cyclic carbonate side groups and cross-linked polymers formed after cross-linking with an amino cross-linking agent;

[0047] Figure 4 Temperature-dependent ionic conductivity diagram of the solid polymer electrolyte prepared in a specific embodiment;

[0048] Figure 5 The graph shows the lithium-ion transference number of a solid polymer electrolyte.

[0049] Figure 6 Cycle curves of a lithium-lithium symmetric battery at different current densities are shown in specific embodiments using a solid polymer electrolyte.

[0050] Figure 7 Cycle curves of a lithium-lithium symmetric battery with a solid polymer electrolyte as an example;

[0051] Figure 8 The graph shows the cycling results of a lithium iron phosphate-lithium full battery with a specific embodiment using a solid polymer electrolyte.

[0052] Figure 9 The image shows the wide-angle X-ray diffraction pattern of PEOEC-1 and lithium salt LiTFSI in Example 3.

[0053] Figure 10 The graph shows the ionic conductivity obtained from the solid polymer electrolyte test in Comparative Example 2. Detailed Implementation

[0054] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0055] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0056] definition:

[0057] Adding the prefix "alkylene" before a group indicates that the group is a divalent part. For example, alkylene is the divalent part of an alkyl group, alkeneoxy is the divalent part of an alkoxy group, and heteroalkylene is the divalent part of a heteroalkyl group.

[0058] The term "alkyl" refers to all possible variations for various numbers of carbon atoms in an alkyl group, namely methyl, ethyl; for 3 carbon atoms: n-propyl and isopropyl; for 4 carbon atoms: n-butyl, isobutyl, and tert-butyl; for 5 carbon atoms: n-pentyl, 1,1-dimethyl-propyl, 2,2-dimethylpropyl, and 2-methyl-butyl, etc.; for 8 carbon atoms: and so on. The hydrogen atoms on the alkyl group defined herein can be replaced by one or more substituents (e.g., phenyl, halogen, etc.). The alkyl groups of the present invention may, for example, contain 1-20 carbon atoms, preferably 1-12 carbon atoms, and particularly saturated straight-chain or branched-chain hydrocarbon groups containing 1-6 (e.g., 1, 2, 3, or 4) carbon atoms.

[0059] The term "heteroalkyl" refers to an alkyl group in which one or more (preferably 1, 2, or 3) carbon atoms have been replaced by oxygen, nitrogen, phosphorus, boron, selenium, silicon, or sulfur atoms. That is, the main chain contains both carbon atoms and heteroatoms. Ether bonds and heteroether groups (ether groups containing heteroatoms such as N, S, etc.) are all classified as heteroalkyl groups.

[0060] The term "alkane carbonyl" refers to a group whose main chain contains both alkyl and carbonyl groups.

[0061] The term "heteroalkyl carbonyl" refers to a group that simultaneously contains heteroatoms, alkyl groups, and carbonyl groups on its main chain.

[0062] The term "heterocyclic alkyl" refers to a main chain containing both heterocyclic and alkyl groups, which are linked together to form a chain-like group.

[0063] The term "heterocyclic alkyl carbonyl" can be understood with reference to "heterocyclic alkyl" above. It refers to a main chain containing heterocycles, alkyl groups and carbonyl groups, with the heterocycles, alkyl groups and carbonyl groups linked together to form the linking group.

[0064] The term "alkyl ester group" can be understood with reference to "alkyl carbonyl group" mentioned above, referring to a main chain that contains both alkyl and ester groups.

[0065] The term "aryl" refers to an organic group derived from aromatic compounds, including both monocyclic and polycyclic groups. Examples of aryl groups include phenyl, biphenyl, and naphthyl groups. For example, aryl groups can have 6-18 carbon atoms. Divalent aryl groups represent aromatic organic groups derived by removing two hydrogen atoms, and similarly, trivalent and tetravalent aryl groups represent aromatic organic groups derived by removing three and four hydrogen atoms, respectively.

[0066] The term "aralkyl" refers to an aryl-alkyl complex group, where alkyl and aryl are defined as described above. Examples of aralkyl groups include benzyl, phenethyl, etc.

[0067] The term "aromatic group" refers to both aryl groups (such as benzene, naphthalene, and biphenyl) and heteroaryl groups.

[0068] The term "heteroaryl" refers to a monocyclic or polycyclic aromatic ring containing a carbon atom and one or more heteroatoms (e.g., nitrogen, oxygen, sulfur) in its ring structure. Heteroaryl groups include, but are not limited to, pyridyl, pyrroloyl, pyridazinyl, furanyl, pyrazinyl, pyrimidinyl, pyrimidinyl, piperazinyl, triazinyl, pyrazolyl, imidazolyl, tetrazolyl, thiophenyl, isoxazolyl, thiazolyl, isoxazolyl, and oxazolyl. Heteroaryl groups may be unsubstituted or substituted with one, two, or more suitable substituents. Heteroaryl groups can be monocyclic, wherein the ring may contain 1-5 carbon atoms and 1-4 heteroatoms.

[0069] The term "heteroaryl" can be understood with reference to "heterocyclic alkyl" above. It refers to a main chain containing heteroaryl and alkyl groups, where the heteroaryl and alkyl groups form the main chain of the linking group.

[0070] The term "aromatic carbonyl" can be understood with reference to "heterocyclic carbonyl" mentioned above. It refers to a main chain containing aryl, alkyl, and carbonyl groups, with the aryl, alkyl, and carbonyl groups forming the main chain of the linking group.

[0071] The term "aromatic carbonyl" refers to a main chain containing aryl, heteroalkyl, and carbonyl groups, with the aryl, heteroalkyl, and carbonyl groups forming the main chain of the linking group.

[0072] The term "heteroarylene carbonyl" refers to a main chain containing heteroaryl, heteroalkyl, and carbonyl groups, with the heteroaryl, heteroalkyl, and carbonyl groups forming the main chain of the linking group.

[0073] The term "cycloalkyl" refers to a saturated cyclic group containing one or more rings (preferably 1 or 2) and a plurality of cyclic carbon atoms (e.g., 3 to 14), preferably 3 to 10 (especially 3, 4, 5, 6 or 7) cyclic carbon atoms. The hydrogen atoms on the cycloalkyl group defined herein can be substituted by one or more substituents, such as methyl, fluorine, chlorine, bromine or iodine atoms.

[0074] The term "cyclohexaalkyl" is a non-aromatic cycloalkyl group that contains at least one heteroatom, such as oxygen, sulfur, nitrogen, or phosphorus, on the ring. For example: The asterisk (*) represents a connection point with other groups.

[0075] The term "cycloalkane carbonyl" refers to a ring composed of alkyl and carbonyl groups linked together.

[0076] The term "cyclohexaalkyl carbonyl" can be understood with reference to "cyclohexaalkyl" above. It refers to a group that simultaneously contains heteroatoms, alkyl groups, and carbonyl groups on a ring, which together form a ring.

[0077] The term "halogen" includes, for example, fluorine, chlorine, bromine, and iodine.

[0078] Cage-type polysilsesquioxane is also known as POSS, with the general formula (RSiO). 3 / 2 ) n In this context, R represents the group to which the eight vertices of Si atoms are attached. The cage-like polysilsesquioxane is a group formed by replacing the hydrogen atoms on the R group in the aforementioned cage-like polysilsesquioxane, where there can be multiple substitution sites.

[0079] The term "amide group" refers to a group whose main chain has an amide structure.

[0080] The term "alkoxy" refers to an alkyl group in which one or more (preferably 1, 2 or 3) carbon atoms have been replaced by oxygen atoms.

[0081] The term "amide alkyl" refers to a main chain containing an amide group and an alkyl group, with the amide group and alkyl group forming the main chain of the linking group.

[0082] The term "amide alkoxy" refers to a main chain containing an amide group and an alkoxy group, with the amide group and alkoxy group forming the linking group.

[0083] The aforementioned alkyl, cycloalkyl, heteroalkyl, alkane carbonyl, heteroalkyl carbonyl, heterocycloalkyl, heterocycloalkyl carbonyl, alkyl ester, aryl, aralkyl, heteroaryl, heteroaryl, arane carbonyl, arane carbonyl, heteroarylene carbonyl, cycloalkyl, cycloalkyl carbonyl, and cage-like polysilsesquioxane can be linking groups with multiple linking sites. The linking sites of the aforementioned chain-like groups are located on their main chain, and their specific positions on the main chain are arbitrary. The linking sites of the aforementioned cyclic groups are located on the atoms forming the ring. For example, there can be 2, 3, 4, or 8 linking sites, which are correspondingly connected to the rest of the molecule through 2, 3, 4, or 8 covalent bonds. For example, formula (4): A-(B) b In this system, B is any substituent group on A, and A is a linking group. B is connected to A as a substituent group, and the value of b can be 2 or more. For example, when b is 2, the corresponding A is a linking group with two linking sites; when b is 3, the corresponding A is a linking group with three linking sites; when b is 4, the corresponding A is a linking group with four linking sites. When b is n, the corresponding A has a linking group with n linking sites.

[0084] In this invention, "substituted" in "substituted or unsubstituted" refers to the substitution of a hydrogen atom in a functional group by another atom or group (i.e., a substituent). For example, the substituent can be replaced by one or more substituents selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, aryl, alicyclic, heterocyclic, heteroaryl, ester, ether, halogen, heteroatom, etc. Preferably, the "substituted" group is an inert group that does not participate in the monomer polymerization reaction or the crosslinking reaction between the polymer and the crosslinking agent.

[0085] The meaning of active proton hydrogen is known in this field. For example, hydrogen atoms in carboxyl, hydroxyl, amino, and mercapto groups are all considered active proton hydrogens.

[0086] The inventors discovered that oxygen atoms in polyether polymers can complex with lithium ions, giving polyether polymers a high dielectric constant, good lithium ion solubility and transport capabilities, making them promising organic lithium-ion conductors. However, polyether polymers also suffer from problems such as crystallinity, low lithium-ion transference number, poor room-temperature ion conductivity, and a narrow electrochemical stability window.

[0087] The inventors also considered that cyclic carbonate groups can act as crosslinking points to undergo crosslinking reactions, thereby obtaining crosslinked network polymers. If such crosslinked polymers possess good film-forming properties, they are expected to be used as self-supporting electrolyte films in solid-state batteries. However, polymer electrolytes containing cyclic carbonate groups often suffer from problems such as high glass transition temperatures, poor ion conductivity, and brittle films due to the rigidity of the cyclic carbonate groups. The design, synthesis, and structural optimization of polymers containing cyclic carbonate groups are urgent problems to be solved.

[0088] To address this, the inventors attempted to construct and synthesize a polymer that fully utilizes the advantages of the aforementioned ether groups and cyclic carbonate groups, while simultaneously solving the problems present in their respective homopolymers. The inventors discovered that by designing and synthesizing epoxy monomers containing cyclic carbonate groups, under suitable initiation and catalytic conditions, polyether homopolymers with cyclic carbonate side groups can be obtained. Further, by partially crosslinking the polymer with the cyclic carbonate side groups using a suitable crosslinking agent, a crosslinked polymer is obtained, achieving the desired effect.

[0089] Specifically, the present invention provides a crosslinked polymer containing a crosslinked structure generated by a crosslinking agent and polymer chains connected to the crosslinked structure. In the crosslinked polymer of the present invention, two structural units are directly connected to the polyether backbone. The first structural unit is a structure formed after a crosslinking reaction with the crosslinking agent, containing hydroxyl and linear ester groups, and is the structure shown in formula (1-1) and / or formula (1-2). Cyclic carbonate side groups in the polymer that have not undergone a crosslinking reaction are retained as the second structural unit, as shown in formula (2). The first and second structural units are randomly distributed on the backbone. The polymer chains are connected to the crosslinked structure through the first structural unit, and * in formulas (1-1) and (1-2) represents the connection point connected to the crosslinked structure.

[0090] Equation (1-1): Equation (1-2): Equation (2):

[0091] The crosslinking agent contains at least two crosslinking groups for crosslinking, such that each crosslinked structure is connected to at least two first structural units. For clarity, the following specific embodiments of the crosslinked polymer are illustrated using a crosslinking agent with two crosslinking groups, with formula (1-1) as the first structural unit. The first structural unit and the crosslinked structure provided by the crosslinking agent form the following structure, denoted as formula (6). Using a crosslinking agent with two crosslinking groups, with formula (1-2) as the first structural unit, the first structural unit and the crosslinked structure provided by the crosslinking agent form the following structure, denoted as formula (7). Using a crosslinking agent with two crosslinking groups, with formulas (1-1) and (1-2) as the first structural units, the two first structural units are connected to the crosslinked structure provided by the crosslinking agent, respectively, forming the following structure, denoted as formula (8).

[0092]

[0093] The crosslinking groups are selected from one or more of the following: amino, hydroxy, or mercapto. R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkyl. When R2 is a substituted alkyl, it can be, for example, a haloalkyl. R3 is a crosslinked structure generated by a crosslinking agent, connecting two first structural units. The crosslinking group that crosslinks R3 with the first structural unit is amino, hydroxy, or mercapto. It can be two identical crosslinking groups, such as two amino groups, or two different crosslinking groups as crosslinking points, for example, the groups crosslinking the two first structural units are amino and hydroxyl, or hydroxyl and mercapto.

[0094] The first and second structural units described above form a crosslinked polymer as two structural units. The main chain of the crosslinked polymer of this invention is a polyether structure, and the side chains contain two different components: one is a component containing hydroxyl and linear ester groups, i.e., the first structural unit. The first structural unit is the structure formed after crosslinking with a crosslinking agent. The other is a component containing cyclic carbonate groups, i.e., the second structural unit. The arrangement of the first and second structural units on the main chain is random. This random arrangement is actually due to random crosslinking with the crosslinking agent. The cyclic carbonate on the polymer side chain reacts with the crosslinking groups on the crosslinking agent to form the first structural unit. The crosslinking groups are amino, hydroxyl, or thiol. The cyclic carbonate undergoes a ring-opening reaction with the above three crosslinking groups. A hydroxyl group forms at one end of the ring-opening point, and a linear ester group is connected to the crosslinking group at the other end. The remaining part of the polymer does not undergo crosslinking, thus remaining as the second structural unit. The ring-opening reaction of amino, hydroxyl, or thiol groups with the cyclic carbonate can form two structures, i.e., formula (1-1) or formula (1-2) described above. These two structural formulas arise only from the different ring-opening positions, as shown in reaction formulas (1) and (2) below, which respectively represent the two ring-opening positions of the cyclic carbonate side groups. Although crosslinking can produce two different first structural units, they do not affect the properties of the crosslinked polymer. That is, regardless of the proportions of formulas (1-1) and (1-2) in the first structural unit of the crosslinked polymer, the crosslinked polymer exhibits the same performance in terms of mechanical properties, electrochemical properties, etc. This invention does not limit the structural ratio of formulas (1-1) and (1-2) in the first structural unit. The resulting crosslinked polymer can be entirely of the formula (1-1) structure, entirely of the formula (1-2) structure, or contain both the formula (1-1) and formula (1-2) structures. As long as hydroxyl and linear ester groups are formed through the ring-opening reaction of the cyclic carbonate, the purpose of this invention is achieved.

[0095]

[0096]

[0097] The crosslinked polymer designed in this invention possesses two structural units: a first structural unit and a second structural unit. The first structural unit generates a crosslinked network, enhancing the mechanical strength of the system and its ability to suppress lithium dendrite formation. This polymer electrolyte can form a self-supporting electrolyte film. The second structural unit imparts a high dielectric constant to the polymer, promoting the dissolution and dissociation of lithium salts, increasing the ionic conductivity and lithium-ion transference number of the system, and enhancing the antioxidant capacity of the polymer electrolyte. The two structural units complement each other, jointly exerting their respective advantages.

[0098] The crosslinked polymer of the present invention contains various structures such as hydroxyl groups, linear urethanes, cyclic carbonates, and etheroxy groups, which can form various hydrogen bonding interactions. These hydrogen bonding interactions can further enhance the mechanical properties of the crosslinked polymer, enhance its ability to suppress lithium dendrites, and alleviate the volume effect during lithium ion deposition.

[0099] The films formed by the aforementioned cross-linked polymers have good mechanical properties. Dynamic mechanical analysis tests have shown that the tensile strength of the cross-linked polymer films can reach more than 0.1 MPa, and the elongation at break can be greater than 10%.

[0100] In addition, the cross-linked polymer formed by the present invention is an amorphous polymer, which is beneficial to improving ionic conductivity.

[0101] We discovered that combining the polyether backbone with cyclic carbonate side groups can increase the polymer's thermal decomposition temperature and enhance its thermal stability. The thermal decomposition temperatures of both the polyether and cyclic carbonate groups are below 200 degrees Celsius, while the cross-linked polymer formed by their combination maintains good thermal stability below 300 degrees Celsius. Higher thermal stability implies greater safety when this cross-linked polymer is used as a solid-state electrolyte in batteries.

[0102] It can also be observed that the cross-linked polymer obtained through molecular design in this invention can leverage the advantages of both polyether and cyclic carbonate structures while simultaneously addressing the problems inherent in their respective homopolymers. The polyether backbone in the cross-linked polymer imparts flexibility, enhances chain segment movement, and improves its lithium-ion conductivity. Meanwhile, the cyclic carbonate functional groups can dissolve large amounts of lithium salts, such as 80 wt% lithium salts, which is a significant advantage of this cross-linked polymer as a solid polymer electrolyte. High salt solubility is beneficial for improving ionic conductivity and lithium-ion transference number, as well as forming a stable solid electrolyte interphase (SEI) membrane. The cross-linked polymer of this invention can form films and possesses excellent mechanical properties and ionic conductivity, particularly suitable as a solid polymer electrolyte for electrochemical devices (e.g., lithium batteries, sodium batteries), showing promising application prospects in the electrochemical field.

[0103] The components containing hydroxyl and linear ester groups essentially serve as crosslinking points between the crosslinked polymer molecular chains, thereby connecting different molecular chains to form a crosslinked network. This crosslinked network, through chemical crosslinking, enables the polymer electrolyte to become a self-supporting electrolyte film, enhancing its mechanical strength and ability to suppress lithium dendrite formation. Furthermore, the crosslinking process generates new hydroxyl and linear ester groups, yielding the aforementioned first structural unit. The hydroxyl and linear ester groups in the first structural unit can undergo physical crosslinking through intermolecular hydrogen bonds, further enhancing the mechanical properties of the electrolyte film.

[0104] Furthermore, the crosslinked polymer is formed by crosslinking a polyether homopolymer with cyclic carbonate side groups with the crosslinking agent, wherein the polyether homopolymer is as shown in formula (3):

[0105] Equation (3):

[0106] Wherein, n represents the degree of polymerization, ranging from 5 to 10000; in the polyether homopolymer, a portion of the repeating units' cyclic carbonate side groups are crosslinked with a crosslinking agent to form the first structural unit, while another portion of the repeating units are not crosslinked to form the second structural unit; R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene groups; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkyl groups. The crosslinked polymer of the present invention is formed by crosslinking the above-mentioned polyether homopolymer, therefore R1 and R2 in the polyether homopolymer are the same as those in the crosslinked polymer.

[0107] Compared to the design of this invention, for polymers with cyclic carbonates in the main chain, such as Polymers are rigid and lack molecular flexibility. They also have a high glass transition temperature. As solid polymer electrolytes, they have disadvantages such as low ionic conductivity and brittle and fragile electrolyte membranes.

[0108] Compared to the design of this invention, for polymers with cyclic carbonates as side chains but CC chains as the main chain, such as... While the carbon-carbon backbone of polyolefins imparts a certain degree of flexibility to the polymer, the direct connection of cyclic carbonate groups to the backbone and steric hindrance effects result in a high glass transition temperature and low ionic conductivity when used as an electrolyte. Furthermore, the inability of the polyolefin component to conduct lithium ions reduces lithium ion transport in the electrolyte to some extent. Additionally, these polymers are only soluble in highly polar, high-boiling-point solvents such as DMF, DMAc, DMSO, and NMP, which present challenges in removal and severe side reactions with lithium metal. In contrast, the design of this invention is soluble in solvents such as THF and DOL, which are lithium-metal-compatible and have low boiling points for easy removal, enabling direct in-situ crosslinking on the lithium metal surface to form a solid polymer electrolyte membrane. The chemical structure of the polyether homopolymer containing cyclic carbonate side groups and the chemical structure of the crosslinked polymer formed after the reaction of this polyether homopolymer with a crosslinking agent containing two amino groups are described below using a graphical model.

[0109] In the attached diagram Figure 1 This diagram illustrates the structural model of a polyether homopolymer containing cyclic carbonate side groups. Figure 2 This diagram illustrates a structural model of one embodiment of a crosslinked polymer formed by the crosslinking reaction of a polyether homopolymer containing cyclic carbonate side groups and an amino crosslinking agent. Figure 1The linear structure is a polyether backbone, and the structure circled at position C in the figure represents a side group containing a cyclic carbonate structure. Figure 2 Taking a crosslinking agent with two amino groups as an example, it crosslinks with a polyether homopolymer. The amino groups at both ends of the crosslinking agent react with a cyclic carbonate side group, causing the cyclic carbonate to open its ring and connect with the amino group to form a crosslinking point. The position of the side groups connected to the crosslinking agent is arbitrary; it can connect to two side groups on the same chain or to side groups on different chains. Through the crosslinking reaction between the crosslinking agent and the polyether homopolymer containing cyclic carbonate side groups, a network-like crosslinked polymer is formed. Figure 2 The structure circled at position D can be one of the above equations (6) to (8).

[0110] Taking a crosslinking agent with two crosslinking groups as an example, the following simplified structural formula is used, namely formula (9), which is only used to schematically represent the structural composition and connection relationship of the formed crosslinked polymer, and does not fully show all the connection structures of the crosslinked polymer.

[0111] Equation (9):

[0112] Taking the crosslinking reaction of a crosslinking agent with a polyether homopolymer containing cyclic carbonate side groups to generate formula (1-1) as an example, a schematic connection structure of formula (9) is formed. The main chain of the first structural unit is connected to the main chain of the second structural unit to form a polymer chain in the crosslinked polymer, i.e. Figure 2 The E position in the cross-linked network structure represents the linear structure.

[0113] In formula (9), R3 is a cross-linked structure, and the two ends of R3 are cross-linked groups, which are connected to the carbonyl groups on the side groups respectively.

[0114] R3 is provided by a crosslinking agent, which in this invention is composed of formula (4):

[0115] Equation (4): A-(B) b

[0116] Wherein, B is a crosslinking group arbitrarily substituted on A, with the structural formula —NH2, —OH, or —SH; b represents the number of crosslinking groups, which can be 2 or more, further up to 2 to 1000, and even further up to 2 to 8. A is a linking group having multiple linking sites, the number of linking sites corresponding to the number of B groups. The linking group is selected from the following substituted or unsubstituted groups: alkyl, cycloalkyl, heteroalkyl, alkylcarbonyl, heteroalkylcarbonyl, heterocycloalkyl, heterocycloalkylcarbonyl, alkylester, aryl, aralkyl, heteroaryl, heteroaryl, aralkylcarbonyl, aralkylcarbonyl, heteroarylalkylcarbonyl, heteroarylalkylcarbonyl, cycloalkyl, cycloalkyl, cycloalkylcarbonyl, cycloalkylcarbonyl.

[0117] When b is chosen as 2, the corresponding A is a linking group with two linking sites, and the two substituents B are linked to A. Similarly, when b is chosen as 3, the corresponding A is a linking group with three links. And so on, the linking group is specifically an organic group. The following shows the connection between the crosslinking agent and the polyether polymer when b is 4, that is, when the crosslinking agent has four crosslinking groups, as shown in the following reaction formula (3). This reaction formula is only used to schematically represent the structural composition and connection relationship of the formed crosslinked polymer, and does not completely show all the connection structures of the crosslinked polymer.

[0118]

[0119] In the above reaction formula, the crosslinking agent has four amino groups, each connected to one of the four side groups in the polyether polymer containing cyclic carbonate side groups. Specifically, A is selected from the following structural formulas:

[0120]

[0121]

[0122] Where * represents the connection point with the crosslinking group B; n ranges from 2 to 10000, and can further be from 2 to 5000; x1, x2, x3, and x4 each range from 1 to 1000.

[0123] Preferably, A is selected from, such as The alkyl chain structure is beneficial for improving the mobility of local segments in crosslinked polymers.

[0124] Preferably, A is selected from, such as Alkoxy chain structure: Alkoxy chains can improve the mobility of local chain segments in cross-linked polymers, and at the same time facilitate the dissolution and transport of lithium ions.

[0125] Preferably, A is selected from, such as The presence of amide groups in the structure facilitates the construction of multiple hydrogen bond structures in cross-linked polymers, enhancing the mechanical strength and self-healing ability of the system, improving its adaptability to volume changes during battery cycling, and aiding in the suppression of lithium dendrites.

[0126] Preferably, when A is selected as a structure containing one or more benzene rings, the introduction of the benzene ring structure is beneficial to enhance the rigidity of the crosslinked polymer and improve the mechanical properties of the crosslinked polymer.

[0127] Preferably, A is selected from nanoparticles such as POSS, the introduction of which can enhance the mechanical properties of the polymer and facilitate the dissociation of lithium salt and the conduction of lithium ions.

[0128] Furthermore, R1 in the crosslinked polymer is selected from the following structures:

[0129]

[0130] Where n ranges from 1 to 100; * represents a join point. The join points mentioned above can connect to the main chain and the side chain, respectively.

[0131] Preferably, when R1 is selected from an alkyl chain structure, the introduction of the alkyl chain can enhance molecular flexibility, reduce the glass transition temperature of the polymer, and decouple the polyether backbone and the cyclic carbonate side groups, thereby enhancing the mobility of the cyclic carbonate side groups, improving its solubility in solvents and its ion conduction ability as a solid electrolyte.

[0132] Preferably, when R1 is selected from an alkoxy structure, in addition to having the advantages of similar alkyl chains mentioned above, it can also provide lithium ion solvation sites, which is beneficial to lithium ion conduction.

[0133] Furthermore, R2 in the crosslinked polymer is selected from the following structures:

[0134]

[0135] Where X is selected from halogen atoms; * indicates a connection point. X3 and X2 represent 3 or 2 X atoms bonded to C.

[0136] Preferably, when R2 is selected from hydrogen atoms, it can reduce the steric hindrance of the cyclic carbonate groups, which is beneficial to the crosslinking reaction between them and the crosslinking agent.

[0137] Preferably, when R2 is selected from halogen atoms such as fluorine atoms, it is beneficial to improve the electrochemical stability window of the cross-linked polymer, enhance the antioxidant capacity of the electrolyte, adapt to higher voltage cathode materials, and also facilitate the formation of a more stable SEI film.

[0138] Furthermore, the proportion of the first structural unit in the crosslinked polymer relative to the sum of the first and second structural units can be 5% to 99%, that is, the molar proportion is 0.05 to 0.99. Taking the above formula (9) as an example, that is, (n1+n3) / (n1+n2+n3+n4)=0.05~0.99.

[0139] Preferably, the proportion of the first structural unit in the crosslinked polymer relative to the total number of the first and second structural units is 10% to 80%, that is, the molar proportion is 0.1 to 0.8, and the proportion of the first structure in the entire crosslinked polymer is 10% to 80%, which can maintain high ionic conductivity while having high mechanical strength. More specifically, the proportion of the first structural unit relative to the total number of the first and second structural units is 10% to 60%.

[0140] The crosslinked polymers of the above embodiments have a tensile strength ≥ 0.1 MPa and an elongation at break ≥ 10%. The tensile strength and elongation at break of the present invention were obtained by testing using the tensile mode of a dynamic thermomechanical analysis (DMA) instrument.

[0141] The present invention also provides a method for synthesizing a crosslinked polymer, wherein the method comprises mixing a polyether copolymer containing cyclic carbonate side groups represented by formula (3) with the crosslinking agent to undergo a crosslinking reaction to obtain the crosslinked polymer;

[0142] Equation (3):

[0143] Wherein, n represents the degree of polymerization, which ranges from 5 to 10000; in the polyether homopolymer, a portion of the repeating units have their cyclic carbonate side groups crosslinked with the crosslinking agent to form the first structural unit, while another portion of the repeating units do not undergo crosslinking to form the second structural unit.

[0144] Furthermore, crosslinking agents containing amino, hydroxyl, or thiol groups undergo a ring-opening reaction with cyclic carbonates to generate crosslinked polymers. Compared to other crosslinking methods, the crosslinking synthesis method provided by this invention requires no additional chemical additives, produces a clean reaction system without generating impurities, and features mild reaction conditions and a short reaction time. This is of great significance for the rapid molding of polymer electrolyte membranes and the improvement of battery performance. For example, traditional crosslinked polymer electrolytes often require the addition of a certain amount of photo- and heat-initiating free radicals. The small amount of impurities generated after the reaction may have an immeasurable impact on the final battery performance, which is detrimental to improving battery performance.

[0145] The method for synthesizing crosslinked polymers provided by this invention maintains 100% atom utilization from a chemical reaction perspective, demonstrating atom economy and conforming to the concept of green chemistry. Furthermore, the crosslinking reaction can be achieved at room temperature, with mild reaction conditions and short reaction time. From an electrolyte perspective, this method avoids the unpredictable effects of introducing impurities, optimizes the chemical environment of the electrolyte, and is beneficial to the development of high-performance lithium batteries.

[0146] The following explanation of this type of reaction is illustrated by the following reaction formula (4).

[0147] Reaction (4):

[0148]

[0149] In the above formula, a polyether homopolymer containing cyclic carbonate side groups and a butanediamine crosslinking agent are selected as raw materials for crosslinking reaction. Through the reaction of active amino groups with cyclic carbonate groups, some cyclic carbonate groups are converted into another component containing hydroxyl and linear ester groups in a quantity of (n1+n3), while the remaining cyclic carbonate units in the crosslinked polymer are (n2+n4) unreacted. It can also be seen that a butanediamine molecule has two amino active groups and can react with two cyclic carbonate groups at the same time, thus forming a solid polymer film with a crosslinked structure. The first structural unit is not limited to the structure in the above reaction formula (4), and may also include the structure shown in formula (1-2) of the present invention. Reaction formula (4) is only shown as an example.

[0150] In the crosslinking reaction of this invention, a polyether homopolymer containing carbonate side groups and a crosslinking agent are dissolved in a solvent, and the reaction between the active amino groups and the cyclic carbonate groups occurs efficiently at room temperature. If the reaction temperature is increased to 50 degrees Celsius, the reaction rate will be further increased. The active amino groups and the cyclic carbonate groups can undergo a quantitative chemical reaction. Therefore, by changing the molar ratio of the active amino groups to the cyclic carbonate groups, the ratio of the two components in the crosslinked polymer can be controlled, thereby controlling the crosslinking density in the crosslinked polymer. Generally, the higher the crosslinking density, the greater the mechanical strength. The cyclic carbonate groups can not only dissolve and dissociate lithium salts and conduct lithium ions, but also participate in the crosslinking reaction as crosslinking points, allowing the polymer electrolyte to simultaneously possess both ionic conductivity and mechanical properties.

[0151] This type of reaction can be used to synthesize cross-linked polymers with different (n1+n3) and (n2+n4) ratios, allowing for extensive adjustment of the cross-linked polymer composition. For example, the values ​​of (n1+n3) can range from 1 to 10000, and the values ​​of (n2+n4) can also range from 1 to 10000. That is, the value of the first structural unit in the cross-linked structure can range from 1 to 10000, and the value of the second structural unit in the cross-linked structure can also range from 1 to 10000.

[0152] This type of reaction can utilize different crosslinking agents to produce different interchain crosslinked structures. The active group in the crosslinking agent can be amino, hydroxyl, or thiol. Furthermore, in this reaction, the active nucleophilic group attacks the carbonyl group of the cyclic carbonate group, undergoing a nucleophilic substitution reaction, and the cyclic carbonate undergoes ring-opening to generate hydroxyl and linear ester groups.

[0153] This invention provides a method for synthesizing the aforementioned crosslinked polymer, which benefits from the quantitative reaction of cyclic carbonate groups with active groups such as amino, hydroxyl, or thiol groups. Cyclic carbonates and the active groups of the crosslinking agent can undergo an equimolar reaction. Therefore, by controlling the amount of crosslinking agent added in the reaction, the ring-opening reaction ratio of cyclic carbonate groups in the polyether homopolymer containing cyclic carbonate side groups can be precisely quantified, thereby accurately quantifying the composition of the first and second structural units in the crosslinked polymer. Simultaneously, the atom utilization rate of the above-mentioned crosslinked polymer synthesis method can reach 100%. Compared with other types of crosslinking reactions, such as double bond polymerization crosslinking, thiol-double bond click reaction crosslinking, or azide-alkynyl reaction crosslinking, the crosslinked polymer synthesis method provided by this invention has the advantages of mild reaction conditions, high efficiency, and a clean system.

[0154] In the above method for synthesizing crosslinked polymers, the polyether homopolymer and the crosslinking agent are dissolved in a reaction solvent to form a homogeneous solution for crosslinking reaction. The reaction temperature of the crosslinking reaction can be in the range of 25 to 180 degrees Celsius, and the reaction time is 0.5 to 72 hours. The reaction solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, tetrahydrofuran, acetonitrile, dimethyl carbonate, diethyl carbonate, 1,3-dioxane, and acetone.

[0155] Furthermore, the molar ratio of the crosslinking groups to the cyclic carbonate groups on the side groups of the polyether homopolymer in the selected crosslinking agent is 0.1-0.8, that is, the proportion of the first structural unit in the crosslinked polymer relative to the sum of the first and second structural units is 10%-80%.

[0156] The above synthesis method also includes the synthesis of polyether homopolymers containing cyclic carbonate side groups: using epoxy monomers as raw materials for ring-opening polymerization to form the polyether homopolymers, wherein the epoxy monomers are composed of formula (5):

[0157] Equation (5):

[0158] R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene groups; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkyl groups. Polyether homopolymers containing cyclic carbonate side groups are synthesized using the above monomers, followed by a crosslinking reaction.

[0159] In the above-mentioned ring-opening polymerization reaction, the initiator is an onium salt, the catalyst is an aluminum complex and / or a boron complex, and the terminator is an alcohol, ammonia, water, organic or inorganic acid containing an active proton hydrogen. The polymerization reaction using epoxy monomers in this invention belongs to anionic ring-opening polymerization. Furthermore, under the action of the initiator and catalyst, the epoxy monomer is activated, initiated, and propagated, and the reaction is terminated by the terminator. Specifically, the initiator is tetraoctylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetraoctylammonium azide, or bis(triphenyl)phosphine-ammonium chloride; the catalyst is triethylboron, triisobutylaluminum, triethylaluminum, triphenylboron, or tripentafluorophenylboron; and the terminator is an alcohol, ammonia, water, organic or inorganic acid containing an active proton hydrogen.

[0160] Furthermore, in the ring-opening polymerization reaction, preferably, the initiator is tetraoctylammonium bromide, tetrabutylammonium chloride, or tetrabutylammonium bromide; the catalyst is triethylboron or triisobutylaluminum; and the terminator is water, methanol, ethanol, formic acid, or acetic acid.

[0161] Further, in the ring-opening polymerization reaction, the reaction solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, tetrahydrofuran, acetonitrile, toluene, benzene, cyclohexane, or chlorobenzene; the reaction temperature is -30 to 60 degrees Celsius. Preferably, the reaction solvent is dichloromethane, tetrahydrofuran, or toluene; the reaction temperature is -10 to 25 degrees Celsius.

[0162] The polymerization method provided by this invention is anionic ring-opening polymerization with monomer activation. Notably, this type of monomer possesses two types of active groups suitable for ring-opening polymerization: a three-membered epoxy ring and a five-membered carbonate ring. This invention provides a method for selectively performing ring-opening polymerization of the three-membered epoxy ring. This initiator-catalyst binary system can regulate the activity of the monomer and terminal oxygen anions during polymerization, suppressing side reactions such as chain transfer. Under these polymerization conditions, the five-membered carbonate ring remains stable, resulting in a polymer with well-defined end groups and narrow dispersion.

[0163] This invention also proposes a solid polymer electrolyte, using the crosslinked polymer from the above embodiments as the effective component. Additionally, the solid electrolyte also includes salts. For lithium batteries, the solid polymer electrolyte further includes lithium salts. The lithium salts can be, for example, one or more of lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluorosilicate, and lithium dioxalate borate; the mass fraction of the lithium salt in the solid polymer electrolyte is 5%-90%. The mass fraction of the crosslinked polymer in the solid polymer electrolyte is 10%-95%.

[0164] Preferably, the crosslinked polymer has a mass fraction of 20%-75% in the solid polymer electrolyte; the lithium salt is lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, or lithium dioxalateborate; preferably, the lithium salt has a mass fraction of 25%-80% in the solid polymer electrolyte.

[0165] The solid polymer electrolyte provided by this invention significantly improves room-temperature ionic conductivity and lithium-ion transference number compared to traditional polyether solid electrolytes and polycyclic carbonate solid electrolytes. Applying this solid polymer electrolyte to lithium metal batteries enables stable cycling of all-solid-state lithium metal batteries at room temperature, exhibiting excellent rate performance, cycle performance, and coulombic efficiency.

[0166] The solid polymer electrolyte obtained by this invention can achieve an ionic conductivity of 10 at room temperature. -5 The S / cm ratio is above 0.2, and the lithium-ion transference number is above 0.2. Furthermore, the ionic conductivity is above 1.0 × 10⁻⁶. -5 ~7.6×10 -5 S / cm, lithium-ion transference number above 0.5. Further, lithium-ion transference number above 0.7.

[0167] The present invention also provides an electrochemical device comprising the above-mentioned solid polymer electrolyte. The electrochemical device may be, for example, a lithium metal battery, a sodium metal battery, etc.

[0168] This invention also provides the application of crosslinked polymers in electrochemical or flexible devices, particularly in solid polymer electrolytes for lithium-ion or lithium metal batteries, and more particularly in improving the ionic conductivity and / or lithium-ion transference number of solid electrolytes for lithium batteries and / or the electrochemical stability window of lithium-ion batteries and / or the rate performance and cycle performance of lithium metal batteries. Flexible devices include, for example, wearable electronic devices, electronic skin, flexible sensors, etc.

[0169] The present invention will now be described with reference to specific embodiments. These examples do not constitute a limitation of the present invention.

[0170] Example 1

[0171] 1.0 g of epoxy monomer (5.75 mmol) was added to a 25 mL high-vacuum reactor and dried under vacuum at 50 °C for 12 hours. The monomer was then dissolved in 4 mL of dry dichloromethane solvent under vacuum. Under a nitrogen atmosphere, 0.157 g of NOct4Br (0.287 mmol) and 0.171 g of Al(i-Bu)3 (0.863 mmol) were added to the reactor sequentially. The 25 mL reactor was placed in an ice bath at 0 °C for 24 hours. Finally, a trace amount of methanol was added to the reactor through a vacuum line to terminate the reaction. The reaction route is shown in reaction formula (5).

[0172] Reaction (5):

[0173]

[0174] The following are the 1H NMR spectra of the polymer obtained from the polymerization reaction initiated by Example 1: 1 ¹H NMR (DMSO-d6) δ (ppm): 4.92 (s, 1H), 4.52 (m, 1H), 4.26 (m, 1H), 3.76–3.42 (m, 7H). The number-average molecular weight (Mn) obtained by gel permeation chromatography characterization was... n ): 3.5 kg / mol, molecular weight dispersion The Tg of the polymer was obtained by thermogravimetric analysis. d,5％ The temperature at which 5% weight loss occurs is 298℃.

[0175] By adjusting the ratio of initiator NOct4Br and catalyst Al(i-Bu)3 to monomer, homopolymers containing cyclic carbonate groups with different number-average molecular weights can be obtained (e.g., M...). n =7.8 kg / mol, M n =12.2 kg / mol, )

[0176] Example 2

[0177] 1.0 g of epoxy monomer (5.75 mmol) was added to a 25 mL high-vacuum reactor, and the reactor was heated under vacuum at 50 °C for 12 hours to remove trace amounts of moisture. 4 mL of dichloromethane solvent, dried with calcium hydride, was transferred via a vacuum line. Under nitrogen gas protection, 0.0320 g of NBu4Cl (0.115 mmol) and 0.0686 g of Al(i-Bu)3 (0.345 mmol) were added to the reactor via syringe. The reactor was then placed in an ice bath at 0 °C for 48 hours. Finally, a trace amount of methanol was added via vacuum distillation to terminate the polymerization reaction. The reaction route is shown in the following reaction formula (6).

[0178] Reaction (6):

[0179]

[0180] The following are the 1H NMR spectra of the polymer obtained based on the reaction initiated in Example 2: 1¹H NMR (DMSO-d6) δ (ppm): 4.92 (s, 1H), 4.52 (m, 1H), 4.26 (m, 1H), 3.76–3.42 (m, 7H). Number-average molecular weight obtained by gel permeation chromatography: 8.7 kg / mol; molecular weight dispersion: 1.57.

[0181] Example 3

[0182] Weigh 20 mg of polyether homopolymer with cyclic carbonate groups on the side group, 66 mg of LiTFSI (EC / Li = 1:2), and 3 mg of the diamine crosslinking agent shown in reaction formula (7) and add them to the mixture. Dissolve the mixture in 100 μL of ultra-dry tetrahydrofuran, and shake to ensure thorough mixing and dissolution, resulting in a uniform and transparent solution. Spread the mixture evenly onto a lithium sheet or stainless steel sheet. Let it stand at room temperature for two hours to obtain a polymer film with certain mechanical strength, named PEOEC-1. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. In infrared testing, as shown in the attached figure... Figure 3 As shown, the characteristic peak of the stretching vibration of the carbonyl C=O group in the raw material, attributed to the cyclic carbonate, is located at 1789 cm⁻¹. -1 The newly appearing region in the infrared absorption spectrum of the product is located at 1697 cm⁻¹. -1 and 3350cm -1 The characteristic peaks are attributed to the stretching vibrations of the urethane group and the hydroxyl group, respectively, which proves the formation of the crosslinking product. The reaction route is shown in the following reaction formula (7).

[0183] Reaction formula (7):

[0184]

[0185] By adjusting the content of lithium salt LiTFSI and diamine crosslinking agent in the crosslinked polymer, crosslinked polymers with different lithium salt contents and different ratios of the first and second structural units were obtained. For example, in PEOEC-2, EC / Li = 1:1 and the ratio of the first and second structural units is 1:1; in PEOEC-3, EC / Li = 1:0.5 and the ratio of the first and second structural units is 1:2.

[0186] Example 4

[0187] Weigh 20 mg of polyether homopolymer containing cyclic carbonate side groups, 16.5 mg of LiTFSI (EC / Li = 1:0.5), and 2.2 mg of 1,4-cyclohexanediamine crosslinking agent into a 2 mL glass bottle, add 100 μL of tetrahydrofuran solvent, and slowly shake until the lithium salt, polymer, and crosslinking agent are completely dissolved and the system is uniform and transparent. Apply the mixed solution evenly to the surface of a lithium sheet or stainless steel sheet using a pipette. Heat at 60°C for six hours to obtain a polymer film with a certain mechanical strength. In this example, the ratio of the first structural unit and the second structural unit in the crosslinked polymer is 1:2. The reaction route is shown in the following reaction formula (8). In the infrared spectrum, the groups belonging to linear urethane groups and hydroxyl groups are observed at 1697 cm⁻¹. -1 and 3350cm -1 The characteristic peaks of stretching vibrations confirm the successful synthesis of this crosslinked polymer.

[0188] Reaction (8):

[0189]

[0190] Example 5

[0191] Weigh 20 mg of polyether homopolymer containing cyclic carbonate groups, 6.6 mg of LiTFSI (EC / Li = 1:0.2), and 3.5 mg of diamine crosslinking agent as shown in reaction (9) and add them to a glass bottle. Pipette 100 μL of ultra-dry tetrahydrofuran solvent into the bottle and shake to mix and dissolve the mixture thoroughly until it is uniform and transparent. Spread the mixture evenly onto a lithium sheet or stainless steel sheet. Let it stand at 60°C for two hours to obtain a polymer film with certain mechanical strength. In the infrared spectrum, the linear urethane group and hydroxyl group are observed to be located at 1697 cm⁻¹. -1 and 3350cm -1 The characteristic peaks of stretching vibrations confirm the successful synthesis of the crosslinked polymer. In this embodiment, the ratio of the first structural unit and the second structural unit in the crosslinked polymer is 1:3. The reaction route is shown in the following reaction formula (9).

[0192] Reaction formula (9):

[0193]

[0194] Example 6

[0195] Add 20 mg of weighed polyether homopolymer with cyclic carbonate groups on the side group, 6.6 mg of lithium salt LiTFSI (EC / Li = 1:0.2), and 3.1 mg of diol crosslinking agent as shown in reaction formula (10) to a 2 mL glass bottle. Dissolve the mixture in 100 μL of ultra-dry tetrahydrofuran solvent and shake continuously to ensure thorough mixing. The final system presents a uniform and transparent solution. Apply the mixed solution evenly to a lithium sheet or stainless steel sheet using a pipette. Heat at 80 degrees Celsius for twelve hours to obtain a polymer film with a certain mechanical strength. Observing stretching vibration characteristic peaks belonging to linear carbonate groups and hydroxyl groups respectively in the infrared spectrum proves the successful synthesis of the crosslinked polymer. The crosslinked polymer obtained in this example has a ratio of 1:3 between the first structural unit and the second structural unit. The reaction route is shown in reaction formula (10) below.

[0196] Reaction formula (10):

[0197]

[0198] Example 7

[0199] Weigh 20 mg of a polyether homopolymer containing cyclic carbonate groups, 16.5 mg of LiTFSI (EC / Li = 1:0.5), and 7.6 mg of the polyether diol (M) as in reaction (11). w =400) was added to the mixing system as a crosslinking agent for the crosslinking reaction. 200 μL of tetrahydrofuran solvent was measured with a pipette and the system was continuously shaken to ensure thorough mixing and dissolution. The mixed solution was uniformly coated onto a lithium sheet or a stainless steel sheet. The mixture was heated at 80 degrees Celsius for twelve hours to obtain a polymer film with a certain mechanical strength. In infrared testing, the formation of linear carbonate groups and hydroxyl groups could be observed. In this example, the ratio of the first structural unit and the second structural unit in the crosslinked polymer was 1:2. The reaction route is shown in the following reaction formula (11).

[0200] Reaction formula (11):

[0201]

[0202] Example 8

[0203] Weigh 20 mg of the polyether homopolymer with cyclic carbonate groups on the side group as shown in reaction formula (12), 26.6 mg of lithium LiTFSI (EC / Li = 1:1), and 2.4 mg of the diol crosslinking agent as shown in reaction formula (12) and add them to the reaction flask. Measure 100 μL of ultra-dry tetrahydrofuran solvent to dissolve it, and shake to ensure the system is fully mixed and dissolved, resulting in a uniform and transparent state. Spread the mixed solution evenly on a lithium sheet or stainless steel sheet. Heat at 60 degrees Celsius for six hours to obtain a polymer film with certain mechanical strength. In infrared testing, the formation of linear urethane and hydroxyl structures can be observed. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. The reaction route is shown in reaction formula (12) below.

[0204] Reaction formula (12):

[0205]

[0206] Example 9

[0207] Weigh 20 mg of the polyether homopolymer with methyl-substituted cyclic carbonate groups as shown in reaction formula (13), 30.5 mg of LiTFSI salt (EC / Li = 1:1), and 2.8 mg of diamino crosslinking agent and add them to the mixture. Dissolve the homopolymer in 100 μL of ultra-dry tetrahydrofuran solvent and shake continuously to ensure thorough mixing. Pipette the mixture evenly onto a lithium sheet or stainless steel sheet. Let it stand at 50°C for two hours to obtain a polymer film with a certain mechanical strength. In infrared spectroscopy, the formation of linear urethane groups and hydroxyl groups can be observed. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. The reaction route is shown in reaction formula (13).

[0208] Reaction formula (13):

[0209]

[0210] Example 10

[0211] Weigh 20 mg of the polyether homopolymer with fluorine-substituted cyclic carbonate groups on the side groups as shown in reaction formula (14), 15.0 mg of LiTFSI (EC / Li = 1:0.5), and 3.6 mg of dimercapto crosslinking agent and add them to the mixture. Dissolve the mixture in 100 μL of ultra-dry tetrahydrofuran, and shake to ensure thorough mixing and dissolution until the mixture is uniform and transparent. Use a pipette to evenly drop the mixed solution onto a lithium sheet or stainless steel sheet. Let it stand at 60 degrees Celsius for two hours to obtain a polymer film with a certain mechanical strength. In infrared testing, the formation of thiocarbonate groups and hydroxyl groups can be observed. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. The reaction route is shown in reaction formula (14) below.

[0212] Reaction formula (14):

[0213]

[0214] Example 11

[0215] Weigh 20 mg of polyether homopolymer containing cyclic carbonate groups, 6.6 mg of LiTFSI (EC / Li = 1:0.2), and 3.5 mg of dithiol crosslinking agent as shown in reaction formula (15) and add them to a 2 mL glass reaction flask. Dissolve the mixture in 200 μL of ultra-dry tetrahydrofuran solvent, and shake continuously to ensure thorough mixing and dissolution. Apply the mixed solution evenly to the surface of a lithium sheet or stainless steel sheet using a pipette. Heat at 100 degrees Celsius for six hours to obtain a polymer film with a certain mechanical strength. In infrared spectroscopy, the formation of linear thiocarbonate and hydroxyl groups can be observed. In the crosslinked polymer obtained in this example, the ratio of the first structural unit and the second structural unit is 1:3. The reaction route is shown in reaction formula (15) below.

[0216] Reaction formula (15)

[0217]

[0218] Example 12

[0219] Weigh 20 mg of a polyether homopolymer with cyclic carbonate groups on the side groups, 6.6 mg of LiTFSI (EC / Li = 1:0.2), and 4.7 mg of a tetrathiol crosslinking agent as shown in reaction formula (16) and add them to the mixture. Dissolve the mixture in 300 μL of ultra-dry tetrahydrofuran solvent and shake continuously to ensure thorough mixing. Use a pipette to evenly drop the mixture onto a lithium sheet or stainless steel sheet. Let it stand at 80 degrees Celsius for six hours to obtain a polymer film with a certain mechanical strength. In infrared testing, the formation of linear thiocarbonate and hydroxyl structures can be observed. In the crosslinked polymer obtained in this example, the ratio of the first structural unit and the second structural unit is 1:2. The reaction route is shown in reaction formula (16) below.

[0220] Reaction formula (16):

[0221]

[0222] Example 13

[0223] Weigh 20 mg of a polyether homopolymer with cyclic carbonate groups on the side groups, 6.6 mg of LiTFSI (EC / Li = 1:0.2), and 2.8 mg of the triamino crosslinking agent as shown in reaction formula (17) and add them to a reaction flask. Dissolve the mixture in 100 μL of ultra-dry tetrahydrofuran solvent, and shake to ensure thorough mixing and dissolution until the mixture is uniform and transparent. Spread the mixed solution evenly onto a lithium sheet or a stainless steel sheet. Allow it to stand at room temperature for six hours to obtain a polymer film with a certain mechanical strength. In infrared spectroscopy, the formation of linear urethane and hydroxyl structures can be observed. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. The reaction route is shown in reaction formula (17) below.

[0224] Reaction formula (17)

[0225]

[0226] Example 14

[0227] Weigh 20 mg of polyether homopolymer with cyclic carbonate groups on the side groups, 6.6 mg of lithium LiTFSI (EC / Li = 1:0.2), and 11.5 mg of polyether triol crosslinking agent (Mw: 600) and add them to the mixture. Add 300 μL of tetrahydrofuran to dissolve the mixture, and shake to ensure thorough mixing and dissolution. Evenly drop the mixture onto the surface of a lithium sheet or stainless steel sheet. Heat at 80°C for twelve hours to obtain a polymer film with a certain mechanical strength. In infrared spectroscopy, the formation of linear carbonate groups and hydroxyl structures can be observed. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. The reaction route is shown in reaction formula (18).

[0228] Reaction formula (18):

[0229]

[0230] Example 15

[0231] Weigh 20 mg of polyether homopolymer containing cyclic carbonate groups, 6.6 mg of LiTFSI (EC / Li = 1:0.2), and 5.5 mg of octaaminoPOSS crosslinking agent and add them to the mixture. Dissolve the mixture in 100 μL of ultra-dry tetrahydrofuran, and shake to ensure thorough mixing and dissolution until the mixture is homogeneous and transparent. Spread the mixture evenly onto a lithium sheet or stainless steel sheet. Let it stand at 60°C for 12 hours to obtain a polymer film with certain mechanical strength. In infrared spectroscopy, the formation of linear urethane and hydroxyl structures can be observed. In this example, the crosslinked polymer has a 1:1 ratio of the first structural unit and the second structural unit. The reaction route is shown in the following reaction formula (19).

[0232] Reaction formula (19):

[0233]

[0234] Example 16:

[0235] Infrared absorption spectroscopy characterization: Fourier transform infrared (FT-IR) spectrometry was used to characterize the homopolymers and crosslinked polymers containing cyclic carbonate side groups at room temperature. The spectral range was 4000-650 cm⁻¹. -1 . Figure 3 Infrared absorption spectra of the PEOEC homopolymer containing cyclic carbonate side groups (the homopolymer in Example 1) and the crosslinked polymer formed by reacting the homopolymer with a 2,2'-diaminodiethyl ether crosslinking agent containing two amino groups are shown. The infrared spectrum of the PEOEC homopolymer is located at 1789 cm⁻¹. -1 The characteristic peaks are attributed to the stretching vibrations of the carbonyl C=O groups in the side groups of the cyclic carbonate; compared to the homopolymer, the infrared absorption spectra of the crosslinked polymer show new characteristic peaks, such as those at 1697 cm⁻¹. -1 The characteristic peak is the carbonyl stretching vibration peak of the linear urethane structure formed after crosslinking, located at 3350 cm⁻¹. -1 The broad peaks around 1534 cm⁻¹ are characteristic peaks of the stretching vibration of the generated hydroxyl group and the stretching vibration peak of NH in the urethane structure. -1 and 1255cm -1 The characteristic peaks are attributed to the bending and stretching vibrations of the carbon and nitrogen groups in the linear urethane structure, respectively. In the cross-linked polymer, the peaks located at 1050 cm⁻¹ are... -1The characteristic peaks on the left and right are attributed to the stretching vibrations of the carbonyl groups in the ether oxygen chain segment.

[0236] Example 17:

[0237] Ion conductivity testing: In an argon glove box (H2O < 0.01 ppm, O2 < 0.01 ppm), the crosslinked polymer from Example 3 was assembled into a stainless steel-stainless steel button cell. The temperature-dependent ion conductivity was further tested on the autoLab electrochemical platform. The conductivity results for PEOEC-1, PEOEC-2, and PEOEC-3 are as follows: Figure 4 As shown in the figure, among the tested samples, PEOEC-1 exhibited the highest room temperature conductivity, reaching 7.6 × 10⁻⁶. -5 S / cm. The conductivity of PEOEC-2 and PEOEC-3 are 4.1 × 10⁻⁶ S / cm. -5 S / cm and 2.1×10 -5 S / cm. The solid polymer electrolyte prepared in this invention has a room temperature conductivity of 2.1 × 10⁻⁶ S / cm. -5 S / cm up to 7.6×10 -5 Between S / cm.

[0238] Example 18:

[0239] Ion transport number testing: The cross-linked polymer was assembled into lithium-lithium coin cells in an argon glove box (H₂O < 0.01 ppm, O₂ < 0.01 ppm). The lithium-ion transport number was further tested on the autoLab electrochemical platform. The lithium-ion transport number measurement results for the PEOEC-1 solid polymer electrolyte are shown below. Figure 5 As shown in the figure, the lithium-ion transference number of the prepared solid polymer electrolyte is 0.71, which is much higher than that of traditional polyether electrolytes (0.1-0.2) and small molecule liquid electrolytes (0.3-0.4).

[0240] Example 19:

[0241] Symmetrical battery constant current cycling test: Lithium-lithium symmetric batteries were assembled using the PEOEC-1 solid polymer electrolyte from Example 3 in an argon glove box (H2O < 0.01 ppm, O2 < 0.01 ppm). Critical current density tests were performed on a LAND-CT3002A testing system. Test conditions were 30 degrees Celsius, with a one-hour charge-one-hour discharge cycle at different current densities (0.05-0.5 mA cm⁻¹). -2 The polarization voltage was recorded as a function of cycling time. The experimental results are shown in Figure 6. The results indicate that the lithium-to-lithium battery assembled in PEOEC-1 exhibits a polarization voltage of 0.05–0.5 mA cm⁻¹. -2Stable cycling is possible at all current densities, and the polarization voltage increases almost linearly with increasing current density, indicating that the concentration polarization is small and the lithium-ion flow deposition / stripping is relatively uniform in this system.

[0242] Example 20:

[0243] Symmetrical battery constant current cycling test: Lithium-lithium symmetric batteries were assembled using PEOEC-1 solid polymer electrolyte in an argon glove box (H2O < 0.01 ppm, O2 < 0.01 ppm), and constant current cycling performance was tested on a LAND-CT3002A testing system. The test conditions were 30 degrees Celsius, one hour of charging and one hour of discharging, with a current density of 0.2 mA cm⁻¹. -2 The polarization voltage was recorded as a function of cycle time. The experimental results are as follows: Figure 7 As shown, the results indicate that the lithium-to-lithium battery assembled in PEOEC-1 can cycle stably for more than 660 hours.

[0244] Example 21:

[0245] Lithium iron phosphate-lithium metal battery cycle testing: Lithium iron phosphate-lithium metal full cells were assembled using the PEOEC-1 solid polymer electrolyte from Example 3 within an argon-filled glove box and tested on a LAND-CT3002A testing system. Test conditions were set as follows: charge / discharge current 0.5C, test temperature 30 degrees Celsius. The charge / discharge test results of the all-solid-state battery are as follows... Figure 8 As shown, the average coulombic efficiency is 99.96%, and the capacity retention rate can reach over 90% after 500 stable cycles, exhibiting high capacity, high coulombic efficiency, and long-term cycle stability.

[0246] The PEOEC-1 crosslinked polymer described in Example 3, as a solid polymer electrolyte, exhibits high room temperature ionic conductivity (7.6 × 10⁻⁶). -5 The lithium-ion transfer number (S / cm) of this solid polymer electrolyte is one to two orders of magnitude higher than that of common PEO-type electrolytes. Simultaneously, the lithium-ion transference number (LTL) of this solid polymer electrolyte is as high as 0.71, significantly higher than that of PEO-type polymer electrolytes (typically 0.1–0.2) and small-molecule liquid electrolytes (typically 0.3–0.4). Therefore, this solid polymer electrolyte can simultaneously achieve high ionic conductivity and high LTL, while also possessing certain mechanical strength, making it suitable as a self-supporting polymer electrolyte membrane. Furthermore, the PEOEC-1 solid polymer electrolyte described in Example 3 contains a large amount of dissolved lithium salt (23 wt% crosslinked polymer matrix and 77 wt% LiTFSI).

[0247] The sample from Example 3 was characterized by wide-angle X-ray diffraction and compared with pure lithium salt LiTFSI. Figure 9The images show the wide-angle X-ray diffraction patterns of PEOEC-1 and pure lithium salt LiTFSI. Wide-angle X-ray diffraction experiments revealed no macroscopic phase separation between the polymer and lithium salt, confirming its amorphous structure. Thanks to its unique cross-linked polymer structure, this polymer electrolyte possesses a remarkably high dielectric constant, capable of dissolving large amounts of lithium salt without phase separation. Combined with excellent in-situ cross-linking techniques, it becomes a solid polymer electrolyte exhibiting both lithium-ion conductivity and superior mechanical properties.

[0248] Lithium salts are crystalline structures, exhibiting sharp peaks in wide-angle X-ray diffraction, while amorphous structures show enveloping peaks. The PEOEC-1 electrolyte in Example 3 shows enveloping peaks, lacking the sharp crystalline peaks characteristic of lithium salts, demonstrating that the lithium salt is completely dissolved in the polymer matrix. The precipitation of lithium salts hinders lithium ion conduction in the polymer electrolyte, resulting in a decrease in ionic conductivity.

[0249] Compared to PEOEC-1, PEOEC-2 reduced the lithium salt content in the solid polymer electrolyte (38 wt% polymer and 62 wt% LiTFSI) while still achieving relatively good ionic conductivity (4.1 × 10⁻⁶). -5 With a high S / cm ratio and a high lithium-ion transference number (0.48), its electrochemical performance is also superior to traditional PEO polymer electrolytes and polymer electrolytes with cyclic carbonate groups in the main chain. In addition, although PEOEC-2 has slightly worse electrochemical performance than PEOEC-1, it has slightly better mechanical properties due to its relatively low lithium salt content.

[0250] Comparative Example 1

[0251] 1.0 g of ethylene ethylene carbonate monomer (VEC) was weighed into a vacuum reaction flask, and 0.1 wt% of AIBN initiator was added under a nitrogen atmosphere. The mixture was heated to 70 degrees Celsius under an inert atmosphere and reacted for 48 hours. The resulting polymer was named PVEC. The PVEC polymer obtained in this comparative example contained ~40 mol% of VEC monomer and low molecular weight oligomers. The crude product was purified by dissolution-precipitation to obtain pure PVEC polymer. Its synthesis process is shown in reaction formula (20).

[0252] Reaction formula (20):

[0253]

[0254] The 1H NMR spectrum data of the PVEC polymer obtained from Comparative Example 1 are as follows: 1¹H NMR (DMSO-d6) δ (ppm): 5.04–4.01 (m, 3H), 2.31–1.04 (m, 3H). Number-average molecular weight obtained by gel permeation chromatography: 10.2 kg / mol, molecular weight dispersion: 2.14. Thermogravimetric analysis yielded the Tg of this polymer. d,5％ The temperature is 195℃.

[0255] Comparative Example 2

[0256] Weigh 10 mg of the polymer PVEC from Comparative Example 1 and 25.2 mg of LiTFSI (VEC / Li = 1:1), and dissolve them in 100 μL of ultradry N,N-dimethylformamide solution (DMF). Shake the solution to ensure thorough mixing until a homogeneous and transparent mixture is formed. Distribute the mixed solvent evenly onto a stainless steel sheet. Dry under vacuum at 80°C for 12 hours to remove the solvent, yielding a PVEC-based polymer electrolyte, named PVEC-1.

[0257] Figure 10 The diagram shows the ionic conductivity of PVEC-1 in Comparative Example 2. Due to its high rigidity and high glass transition temperature, the solid polymer electrolyte PVEC-1 in Comparative Example 2 has a relatively low room-temperature ionic conductivity of 8.1 × 10⁻⁶. - 7 Its S / cm concentration results in poor performance as a solid polymer electrolyte. Furthermore, its poor solubility, only dissolving in highly polar, high-boiling-point solvents, makes solvent removal difficult and prone to leaving residues in the electrolyte. Additionally, the solid electrolyte membrane formed based on PVEC is brittle and easily damaged, severely hindering its application in polymer electrolytes.

[0258] Comparative Example 3

[0259] Weigh 20 mg of a polyether homopolymer containing cyclic carbonate groups and 66 mg of LiTFSI (EC / Li = 1:2), dissolve in 100 μL of ultra-dry tetrahydrofuran, shake to thoroughly mix and dissolve the mixture until it becomes homogeneous and transparent, and then vacuum dry to remove the solvent to obtain a polymer electrolyte based on PEOEC that has not undergone crosslinking. However, the uncrosslinked polymer electrolyte is a gel-like electrolyte lacking mechanical strength and exhibiting a certain degree of fluidity, which is not conducive to its application in electrochemical devices such as solid-state batteries.

[0260] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A crosslinked polymer, characterized in that, The crosslinked polymer contains a crosslinked structure formed by a crosslinking agent and polymer chains connected to the crosslinked structure. The polymer chains comprise a first structural unit and a second structural unit. The first structural unit is the structure shown in formula (1-1) and / or formula (1-2), and the second structural unit is the structure shown in formula (2). The polymer chains are connected to the crosslinked structure through the first structural unit. In formulas (1-1) and (1-2)... Represents the connection point that is connected to the cross-linked structure; Equation (1-1): Equation (1-2): Equation (2): The crosslinking agent contains at least two crosslinking groups for crosslinking, such that each crosslinked structure is connected to at least two first structural units, wherein the crosslinking groups are selected from one or more of the following: amino, hydroxy, or thiol; Wherein, R1 is selected from substituted or unsubstituted alkylene, alkoxy or heteroalkylene; R2 is selected from hydrogen or halogen, or from substituted or unsubstituted alkyl or heteroalkyl. The crosslinked polymer is formed by crosslinking a polyether homopolymer with cyclic carbonate side groups with the crosslinking agent, and the polyether homopolymer is shown in formula (3): Equation (3): Wherein, n represents the degree of polymerization, which ranges from 5 to 10000; a portion of the repeating units in the polyether homopolymer have their cyclic carbonate side groups crosslinked with the crosslinking agent to form the first structural unit, while another portion of the repeating units do not undergo crosslinking to form the second structural unit; R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkyl.

2. The crosslinked polymer according to claim 1, characterized in that, The crosslinking agent is composed of formula (4): Equation (4): A - (B) b Wherein, B is the crosslinking group arbitrarily substituted on A, with the structural formula —NH2, —OH or —SH, b represents the number of crosslinking groups, which is 2 or more; A is a linking group having two or more linking sites, the linking group being selected from the following substituted or unsubstituted groups: alkyl, heteroalkyl, alkylcarbonyl, heteroalkylcarbonyl, heterocycloalkyl, heterocycloalkylcarbonyl, alkylester, aryl, aralkyl, heteroaryl, heteroarylalkyl, aralkylcarbonyl, aralkyl-hexaalkylcarbonyl, heteroaryl-hexaalkylcarbonyl, cycloalkyl, cyclohexaalkyl, cycloalkylcarbonyl, cycloalkyl-hexaalkylcarbonyl, cage-type polysilsesquioxanealkyl.

3. The crosslinked polymer as described in claim 2, characterized in that, A is selected from the following groups: alkyl, aryl, aralkyl, alkoxy, heteroaralkyl, aralkyl carbonyl, amide, amide alkyl, amide alkoxy.

4. The crosslinked polymer according to claim 2, characterized in that, A is selected from the following structural formula: in, Represents the connection point with the crosslinking group B; n ranges from 2 to 10000; x1, x2, x3, and x4 each range from 1 to 1000.

5. The crosslinked polymer as claimed in claim 1, characterized in that, R1 is selected from the following structure: Where n ranges from 1 to 100; * represents a connection point.

6. The crosslinked polymer according to claim 1, characterized in that, R2 is selected from the following structure: Wherein, X is selected from halogen atoms; Indicates the connection point.

7. The crosslinked polymer according to claim 1, characterized in that, The first structural unit in the crosslinked polymer accounts for 10% to 80% of the total number of the first structural unit and the second structural unit.

8. A method for synthesizing a cross-linked polymer, characterized in that, The method for synthesizing the crosslinked polymer as described in any one of claims 1-7 comprises reacting a polyether homopolymer represented by formula (3) with the crosslinking agent to obtain the crosslinked polymer; Equation (3): Wherein, n represents the degree of polymerization, which ranges from 5 to 10000; in the polyether homopolymer, a portion of the repeating units have their cyclic carbonate side groups crosslinked with the crosslinking agent to form the first structural unit, while another portion of the repeating units do not undergo crosslinking to form the second structural unit.

9. The synthesis method as described in claim 8, characterized in that, The polyether homopolymer is subjected to a crosslinking reaction with the crosslinking agent. The reaction temperature of the crosslinking reaction is 25-180 degrees Celsius, the reaction time is 0.5-72 hours, and the reaction solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, tetrahydrofuran, acetonitrile, dimethyl carbonate, diethyl carbonate, 1,3-dioxane, and acetone.

10. The synthesis method according to claim 9, characterized in that, The reaction temperature is 25-120 degrees Celsius, the reaction time is 1-48 hours, and the reaction solvent is one or more of N,N-dimethylformamide, tetrahydrofuran, acetonitrile, dimethyl carbonate, and acetone.

11. The synthesis method as described in claim 8, characterized in that, The molar ratio of the crosslinking group to the cyclic carbonate group on the side group of the polyether homopolymer in the selected crosslinking agent is 0.1-0.

8.

12. The synthesis method according to any one of claims 9-11, characterized in that, It also includes the synthesis of the polyether homopolymer: using epoxy monomers as raw materials to carry out ring-opening polymerization to form the polyether homopolymer, wherein the epoxy monomers are composed of formula (5): Equation (5): R1 is selected from substituted or unsubstituted alkylene, alkoxy, or heteroalkylene; R2 is selected from hydrogen, halogen, or substituted or unsubstituted alkyl or heteroalkylene.

13. The synthesis method according to claim 12, characterized in that, In the ring-opening polymerization reaction, the initiator is an onium salt, the catalyst is an aluminum complex and / or a boron complex, and the terminator is an alcohol, ammonia, water, organic or inorganic acid containing an active proton hydrogen.

14. The synthesis method according to claim 13, characterized in that, The initiator is one or more of tetraoctylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetraoctylammonium azide, and bis(triphenyl)phosphine-ammonium chloride; the catalyst is one or more of triethylboron, triisobutylaluminum, triethylaluminum, triphenylboron, and tripentafluorophenylboron; and the terminator is one or more of water, methanol, ethanol, formic acid, and acetic acid.

15. The synthesis method according to claim 14, characterized in that, In the ring-opening polymerization reaction, the reaction temperature is -30 to 60 degrees Celsius, and the reaction solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, tetrahydrofuran, acetonitrile, toluene, benzene, cyclohexane, and chlorobenzene.

16. A solid polymer electrolyte, characterized in that, It includes the crosslinked polymer as described in any one of claims 1-7.

17. The solid polymer electrolyte as described in claim 16, characterized in that, The solid polymer electrolyte further includes a lithium salt, wherein the crosslinked polymer has a mass fraction of 10%-95% in the solid polymer electrolyte, and the lithium salt has a mass fraction of 5%-90% in the solid polymer electrolyte.

18. The solid polymer electrolyte as described in claim 16 or 17, characterized in that, The room temperature ionic conductivity of the solid polymer electrolyte is 10. -5 The S / cm ratio is above 0.2 and the lithium-ion transference number is above 0.

2.

19. An electrochemical device, characterized in that, It includes the solid polymer electrolyte as described in any one of claims 16-18.

20. The use of the solid polymer electrolyte as described in any one of claims 16-18 in electrochemical devices or flexible devices.

21. The application as described in claim 20, characterized in that, The solid polymer electrolyte is used in lithium-ion or lithium metal batteries.

22. The application as described in claim 21, characterized in that, The solid polymer electrolyte is used to improve the ionic conductivity and / or lithium-ion transference number of solid electrolytes for lithium batteries and / or the electrochemical stability window of lithium-ion batteries and / or the rate performance and cycle performance of lithium metal batteries.

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