A solid polymer electrolyte based on an interlocking network and its preparation method and application

Abstract

The present invention provides a solid polymer electrolyte based on an interlocking network, and its preparation method and application. The solid polymer electrolyte of the present invention comprises an interlocking polyethylene oxide and a lithium salt electrolyte, wherein the interlocking polyethylene oxide is composed of a cross-linked polyethylene oxide containing a reversible imine bond and a cross-linked polyethylene oxide containing a reversible disulfide bond; the weight-average molecular weight of the polyethylene oxide segments of the cross-linked polyethylene oxide containing a reversible imine bond and the cross-linked polyethylene oxide containing a reversible disulfide bond is independently 1,000 to 10,000 g / mol. The present invention introduces two dynamic cross-linking networks, reversible imine bonds and reversible disulfide bonds, into the polyethylene oxide to achieve topological interlocking, while specifically selecting the polyethylene oxide molecular weight and the ratio of the two single networks in the interlocking polyethylene oxide, which can significantly improve the mechanical properties and ionic conductivity of the solid polymer electrolyte.

Description

Technical Field

[0001] The present invention relates to the field of all-solid-state lithium battery energy technology, in particular to a solid polymer electrolyte based on an interlocking network and a preparation method and application thereof. Background Art

[0002] Rechargeable lithium-ion batteries (LIBs) are widely used in everyday life, including electronic and communication products (e.g., mobile phones), electric vehicles, and wearable flexible smart devices. Among them, lithium metal batteries (LMBs, with metallic lithium as the anode and intercalation cathodes (lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, etc.) and sulfur cathodes) have become a candidate for high-energy-density energy storage devices due to their ultra-high theoretical specific capacity (3860 mAh / g), low electrochemical potential (-3.042 V vs. standard hydrogen electrode), and low density.

[0003] However, the liquid electrolyte in LMBs may evaporate and leak during storage, transportation, and use. At the same time, uncontrollable side reactions often occur between lithium metal and the liquid electrolyte, forming a chemically unstable solid electrolyte interface (SEI), which is easily broken during repeated lithium deposition / stripping, leading to lithium dendrite growth, dead lithium generation, and ultimately irreversible capacity loss. Furthermore, the continued growth of lithium dendrites may pierce the separator, causing battery short circuits and combustion.

[0004] In order to solve the problems of safety and cycle life, solid electrolytes have gradually emerged in recent decades, hoping to overcome the shortcomings of liquid electrolytes. Among them, inorganic solid electrolytes have excellent room temperature ionic conductivity (>10 -4 S / cm), high modulus and wide chemical window, but still have disadvantages such as high interfacial impedance, large brittleness and difficulty in large-scale preparation. As an alternative, solid polymer electrolyte (SPE) has the advantages of good elasticity, light weight, high chemical stability and easy processing, but its narrow electrochemical window and low ionic conductivity (10 -8 ~10 -4 S / cm) greatly limits their practical applications.

[0005] Polyethylene oxide (PEO) is one of the commonly used polymer matrices in SPE. In PEO, the long-range migration of lithium ions is achieved through the continuous complexation / dissociation between the oxygen atoms of the PEO skeleton and ions in the amorphous region, and with the help of the local movement of the PEO segments. However, the crystallinity of PEO is not conducive to its ionic conductivity. Therefore, a large number of studies have been conducted to reduce the crystallinity and glass transition temperature (Tg) of PEO through physical (such as blending) and chemical (such as grafting, cross-linking and copolymerization) methods. g ) in order to improve ionic conductivity. Since the proportion of PEO in blending, grafting and copolymerization is reduced, even if the crystallinity or Tg The ionic conductivity of the modified PEO material is still far from meeting the requirements of use. At the same time, although high cross-linking can eliminate crystallization without reducing the PEO content, the movement of the molecular chain is restricted, so heating conditions are required to maintain the mobility of the molecular chain.

[0006] Reversibly interlocking polymer networks (RILNs) technology achieves molecular-level interpenetration by utilizing the topological reorganization between cross-linked polymer networks containing reversible covalent bonds. It has many advantages that traditional technologies do not have (Materials Today 2019, 16, 1394-1398; Materials Chemistry Frontiers, 2022, 10.1039 / D2QM00090C), and provides a new approach to solving the above contradictions: First, the interlocking network formed by two cross-linked PEO single networks can maintain a high content of PEO; at the same time, previous studies have shown that the interlocking network can effectively inhibit the crystallinity of the crystalline component (Macromolecules, 2020, 53, 584-593), thereby increasing the content of amorphous regions; in addition, in the interlocking network, the two single networks are not bound by covalent bonds, thus giving the single network appropriate mobility, and its interlocking network chains can slide relative to each other during battery operation.

[0007] Although the introduction of reversible bonds can restore the structural integrity and ion conduction path of the solid polymer electrolyte in time after damage, thereby extending the service life of the battery, the solid polymer electrolytes based on reversible bonds reported so far generally have poor mechanical properties (tensile strength of approximately 0.1 MPa). It is well known that ultra-thin solid polymer electrolyte layers are prone to cracks and damage during assembly and use, posing a safety hazard.

[0008] Therefore, it is necessary to develop a solid polymer electrolyte with high room-temperature ionic conductivity, excellent mechanical strength and self-healing ability to promote room-temperature solid-state lithium metal batteries (including lithium metal batteries with lithium insertion / delithiation mechanism and lithium-sulfur batteries with redox mechanism). Summary of the Invention

[0009] Based on this, the purpose of the present invention is to overcome the defects of poor mechanical properties of existing reversible solid electrolytes and provide a solid polymer electrolyte based on an interlocking network.

[0010] Another object of the present invention is to provide a method for preparing the interlocking network-based solid polymer electrolyte.

[0011] Another object of the present invention is to provide an application of the interlocking network-based solid polymer electrolyte in the preparation of lithium metal batteries.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] A solid polymer electrolyte based on an interlocking network, comprising an interlocking polyethylene oxide and a lithium salt electrolyte;

[0014] The interlocking polyethylene oxide is composed of cross-linked polyethylene oxide containing a reversible imine bond and cross-linked polyethylene oxide containing a reversible disulfide bond, and the weight percentage of the cross-linked polyethylene oxide containing a reversible imine bond in the interlocking polyethylene oxide is 25 to 75%;

[0015] The weight average molecular weights of the polyethylene oxide segments of the cross-linked polyethylene oxide containing a reversible imine bond and the cross-linked polyethylene oxide containing a reversible disulfide bond are independently 1000 to 10000 g / mol;

[0016] In the solid polymer electrolyte, the weight percentage of the lithium salt electrolyte is 20-40%.

[0017] The formation process of solid polymer electrolytes based on interlocking networks involves rapid dynamic exchange reactions and reversible dissociation / association reactions of two reversible covalent bonds, as well as hydrogen bonding and molecular chain entanglement between the two components. How to choose a suitable combination of reversible covalent bonds to avoid cross-reactions of reversible bonds between different polymer networks, and at the same time use the interlocking structure to effectively inhibit PEO crystallization, present excellent room-temperature lithium ion transmission capacity, while maintaining high mechanical strength and room-temperature self-healing ability, will become the key to the preparation of solid polymer electrolytes based on interlocking networks.

[0018] The inventors discovered in their small molecule model research that the dynamic exchange reaction of polyethylene oxide containing imine bonds and the dynamic exchange reaction of polyethylene oxide containing disulfide bonds can proceed smoothly at room temperature without interfering with each other (the reaction mechanisms of the two reversible bonds are different, and the reactants or products will not react with each other). This means that the two single networks will not be covalently connected during the interlocking process and have the basis for room temperature self-repair.

[0019] Through further research, the present invention has found that by selecting polyethylene oxide (PEO) of an appropriate molecular weight and making a specific selection for the ratio of the two single networks (referring to the network containing disulfide bonds and the network containing imine bonds) in the interlocking polyethylene oxide, the mechanical strength of the solid polymer electrolyte can be significantly improved. At the same time, the conductivity of lithium ions in the lithium salt electrolyte can be further improved, thereby improving the ionic conductivity of the solid polymer electrolyte.

[0020] If the molecular weight of polyethylene oxide is too low, although it basically does not crystallize, the molecular weight between the cross-linking points is reduced, the mobility of the molecular chain segments is poor, and the resulting solid polymer electrolyte has insufficient toughness; if the molecular weight of polyethylene oxide is too high, on the one hand, it reduces the proportion of amorphous regions and reduces the probability of lithium ions in the lithium salt electrolyte to move and transport through complexation / decomplexation with the polyethylene oxide molecular segments; on the other hand, if the molecular weight is too high, the crystallization rate increases, and the interlocking network structure cannot effectively inhibit crystallization, thereby reducing the ionic conductivity of the solid polymer electrolyte.

[0021] Preferably, the weight-average molecular weights of the cross-linked polyethylene oxide segments containing reversible imine bonds and the cross-linked polyethylene oxide segments containing reversible disulfide bonds are independently 3000 to 5000 g / mol. At these molecular weights, the resulting solid polymer electrolyte has superior mechanical strength and higher ionic conductivity.

[0022] Reversible imine bonds have a faster exchange reaction rate and can act as sacrificial bonds to break and reconnect under external forces, effectively dissipating energy and improving the material's toughness. Reversible disulfide bonds have a relatively slow exchange reaction rate, maintaining the material's strength and stability. A reasonable combination of these two reversible bonds can improve the mechanical properties of solid polymer electrolytes while also ensuring high ionic conductivity. If the content of cross-linked polyethylene oxide containing reversible imine bonds is too high, the mechanical strength of the solid polymer electrolyte will decrease. If the content of cross-linked polyethylene oxide containing reversible imine bonds is too low, the solid polymer electrolyte, while having high mechanical strength, will lack toughness, making chain segment movement difficult, and also reducing the ionic conductivity of the solid polymer electrolyte.

[0023] Preferably, the weight percentage of cross-linked polyethylene oxide containing reversible imine bonds in the interlocking polyethylene oxide body is 50%.

[0024] Preferably, the weight percentage of the lithium salt electrolyte in the solid polymer electrolyte is 25-30%. If too little lithium salt electrolyte is added, the resulting electrolyte's ionic conductivity is low and cannot meet the required conductivity. If too much lithium salt electrolyte is added, it cannot completely dissociate, resulting in agglomeration, which affects the interaction between lithium ions and polyethylene oxide structural units. Furthermore, the agglomerated lithium salt particles will hinder the movement of PEO chain segments, reducing the material's ionic conductivity. Furthermore, since lithium salt electrolyte is an inorganic filler with poor compatibility with the polymer matrix, adding too much will also reduce the mechanical strength of the resulting solid polymer electrolyte.

[0025] Preferably, the cross-linked polyethylene oxide containing a reversible imine bond comprises the following monomers in parts by weight:

[0026] 25-75 parts of amino-terminated polyethylene glycol;

[0027] 0.3-9.9 parts of polyaldehyde monomer;

[0028] The amino-terminated polyethylene glycol is a 2- to 6-arm amino-terminated polyethylene glycol; the polyaldehyde monomer is an aromatic aldehyde compound. Selecting multi-arm (2- to 6-arm) amino-terminated polyethylene glycol and polyaldehyde monomers can increase the crosslinking density within a single network as the functionality increases, further improving the mechanical strength of the resulting solid polymer electrolyte. However, this can lead to a decrease in elongation at break and hinder lithium ion transport, resulting in a decrease in conductivity. Selecting an appropriate functionality (e.g., 2- to 6-arm) can simultaneously ensure that the solid polymer electrolyte has good mechanical properties and ionic conductivity.

[0029] Preferably, the amino-terminated polyethylene glycol is At least one of;

[0030] The polyaldehyde monomer is

[0031] At least one of .

[0032] It should be noted that the cross-linked polyethylene oxide containing a reversible imine bond is prepared by conventional polymerization reaction in the art, specifically by polymerizing the above components at 60-80° C. in a polar solvent and then removing the solvent by vacuum.

[0033] Preferably, the cross-linked polyethylene oxide containing reversible disulfide bonds comprises the following monomers in parts by weight:

[0034] 30-90 parts of epoxy-terminated polyethylene glycol;

[0035] 0.5-4.8 parts of diaminodiphenyl disulfide;

[0036] The epoxy-terminated polyethylene glycol is 2-6 arm epoxy-terminated polyethylene glycol.

[0037] Preferably, the epoxy-terminated polyethylene glycol is

[0038] At least one of;

[0039] The diaminodiphenyl disulfide is At least one of;

[0040] It should be noted that the cross-linked polyethylene oxide containing reversible disulfide bonds is prepared by conventional polymerization reaction in the art, specifically by polymerizing the above components at 90-140° C. in a polar solvent and then removing the solvent by vacuum.

[0041] Conventional lithium salt electrolytes can be used in the present invention, and the lithium salt electrolytes include but are not limited to at least one of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl imide), lithium difluorooxalatoborate, and lithium bis(trifluoromethylsulfonyl imide).

[0042] The method for preparing the interlocking network-based solid polymer electrolyte comprises the following steps:

[0043] S1. The cross-linked polyethylene oxide containing a reversible imine bond and the cross-linked polyethylene oxide containing a reversible disulfide bond are mixed and dissolved in a co-solvent at 100 to 140 ° C under an inert atmosphere;

[0044] S2. After cooling to 60-90° C., a lithium salt electrolyte is added, stirred evenly, and the co-solvent is removed to obtain the interlocking network-based solid polymer electrolyte.

[0045] Preferably, the inert atmosphere is an atmosphere formed by a combination of at least one of helium, argon or nitrogen.

[0046] Preferably, the dissolution time in step S1. is 0.5 to 24 hours.

[0047] Preferably, the co-solvent is a polar solvent, and the polar solvent is at least one of dimethylformamide or dimethyl sulfoxide.

[0048] Preferably, the specific operation of removing the co-solvent is: drying at 70-90° C. to constant weight.

[0049] The application of the above-mentioned interlocking network-based solid polymer electrolyte in the preparation of lithium metal batteries is also within the protection scope of the present invention.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention uses an exchange reaction of two non-interfering room-temperature reversible bonds (reversible imine bonds and reversible disulfide bonds) and a dynamic reversible bond cross-linked single network as raw material to prepare a solid polymer electrolyte based on an interlocking network. The interlocking nested topological structure inhibits PEO crystallization, and the transfer of neighboring groups and the synergistic strain under force significantly improve the ionic conductivity and mechanical properties compared to a single polymer network. In addition, the dynamic bond exchange reaction is conducive to maintaining the mobility of the cross-linked network, and the molecular chains of the interlocking network can move relative to each other, which is conducive to the interfacial compatibility between the electrolyte and the lithium metal electrode, forming a stable lithium deposition-stripping process.

[0052] As a solid-state electrolyte, it also has the ability to inhibit the shuttling effect of polysulfides. At the same time, by utilizing the room-temperature reversibility of reversible covalent bonds, it can not only change its shape through network topology reorganization, thereby better matching the lithium metal anode and improving interfacial bonding and stability; it can also give the solid electrolyte room-temperature self-repairing ability. When the solid electrolyte is damaged, its structural integrity and ion transport pathways are restored, ultimately improving the cycle stability and life of the lithium metal battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 FTIR spectra of solid polymer electrolytes RILNs-3 / 1-LiPF6-1 (Example 1), RILNs-1 / 1-LiPF6-2 (Example 2), RILNs-1 / 3-LiPF6-3 (Example 3) and the corresponding single network component polyethylene oxide (SN-CN-1, SN-SS-1);

[0054] Figure 2 DSC spectra of solid polymer electrolytes RILNs-3 / 1-LiPF6-1 (Example 1), RILNs-1 / 1-LiPF6-2 (Example 2), RILNs-1 / 3-LiPF6-3 (Example 3), and solid polymer electrolytes prepared from corresponding single networks (SN-CN-LiPF6 of Comparative Example 1, SN-SS-LiPF6 of Comparative Example 2);

[0055] Figure 3 XRD spectra of solid polymer electrolytes RILNs-3 / 1-LiPF6-1 (Example 1), RILNs-1 / 1-LiPF6-2 (Example 2), RILNs-1 / 3-LiPF6-3 (Example 3), and solid polymer electrolytes prepared from corresponding single networks (SN-CN-LiPF6 of Comparative Example 1, SN-SS-LiPF6 of Comparative Example 2);

[0056] Figure 4 Battery cycling stability diagrams of solid polymer electrolytes RILNs-3 / 1-LiPF6-1 (Example 1), RILNs-1 / 1-LiPF6-2 (Example 2), RILNs-1 / 3-LiPF6-3 (Example 3), and solid polymer electrolytes prepared from corresponding single networks (SN-CN-LiPF6 of Comparative Example 1, SN-SS-LiPF6 of Comparative Example 2);

[0057] Figure 5 This is a comparison chart of the battery cycle stability of the solid polymer electrolyte RILNs-3 / 1-LiPF6-1 before and after thermal repair in the embodiment. DETAILED DESCRIPTION

[0058] For better explanation of the purpose, technical scheme and advantage of the present invention, the present invention will be further described below in conjunction with specific embodiment and accompanying drawing, but embodiment does not limit the present invention in any form.Unless otherwise stated, the reagent, method and equipment adopted in the present invention are conventional reagents, methods and equipment in the art.Unless otherwise stated, reagents and materials used in the present invention are commercially available.

[0059] Example 1

[0060] This embodiment provides a solid polymer electrolyte, the preparation method of which includes the following steps:

[0061] S1. 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond, 25 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond, and 400 parts by weight of dimethylformamide were added to a round-bottomed three-necked flask with an argon protection device and mechanical stirring, and stirred at 120 ° C for 12h;

[0062] S2. After the mixture obtained by dissolving in step S1 was cooled to 70°C, 35 parts of lithium hexafluorophosphate (i.e., the weight proportion of lithium salt electrolyte in the solid polymer electrolyte was 25.93%) was added and stirred for 15 minutes. The mixture was then poured into a silicone mold and vacuum dried at 70°C for 24 hours to obtain a solid polymer electrolyte based on an interlocking network (RILNs-3 / 1-LiPF6-1). The FTIR, DSC, XRD, EIS, and tensile curves were as follows: Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 shown.

[0063] Among them, cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond was prepared by the following method: 50 parts of two-arm amino-terminated polyethylene glycol 2Arm-PEO-NH2 (weight average molecular weight 5000 g / mol), 1.1 parts of trimesaldehyde and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with an argon protection device and mechanical stirring, and stirred at 70°C for 0.5h. The reaction mixture obtained after stirring was then cast on a silica gel mold and vacuum dried at 70°C for 48h to obtain cross-linked polyethylene oxide 1 containing a reversible imine bond (denoted as SN-CN-1). The FTIR spectrum is as follows: Figure 1 shown.

[0064] Cross-linked polyethylene oxide SN-SS-1 containing reversible disulfide bonds was prepared by the following method: 60 parts of two-arm epoxy-terminated polyethylene glycol 2Arm-PEO-epoxy (weight average molecular weight 3400g / mol and 5000g / mol mass ratio of 1:5), 1.6 parts of 4,4'-diaminodiphenyl disulfide and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with argon protection and mechanical stirring, and stirred at 90°C for 12 hours. Then, the reaction mixture was cast on a silica gel mold and vacuum dried at 70°C for 48 hours to obtain cross-linked polyethylene oxide 1 (SN-SS-1) containing reversible imine bonds. The FTIR spectrum is as follows: Figure 1 shown.

[0065] Example 2

[0066] This embodiment provides a solid polymer electrolyte, which differs from Example 1 in that: in step S1., the composition of polyethylene oxide is 50 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond and 50 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond; the electrolyte obtained in step S2. is recorded as RILNs-1 / 1-LiPF6-2.

[0067] Example 3

[0068] This embodiment provides a solid polymer electrolyte, which differs from Example 1 in that: in step S1., the composition of polyethylene oxide is 25 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond and 75 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond; the electrolyte obtained in step S2. is recorded as RILNs-1 / 3-LiPF6-3.

[0069] Example 4

[0070] This embodiment provides a solid polymer electrolyte, which differs from Example 1 in that the amount of lithium hexafluorophosphate added in step S2 is 28 parts by weight (i.e., the weight proportion of the lithium salt electrolyte in the solid polymer electrolyte is 21.8%), and the obtained electrolyte is recorded as RILNs-3 / 1-LiPF6-4.

[0071] Example 5

[0072] This embodiment provides a solid polymer electrolyte, which differs from Example 1 in that: in step S2, the amount of lithium hexafluorophosphate added is 42 parts by weight (i.e., the weight proportion of the lithium salt electrolyte in the solid polymer electrolyte is 29.58%), and the obtained electrolyte is recorded as RILNs-3 / 1-LiPF6-5.

[0073] Example 6

[0074] This embodiment provides a solid polymer electrolyte, which differs from Example 1 in that the amount of lithium hexafluorophosphate added in step S2 is 66 parts by weight (i.e., the weight proportion of the lithium salt electrolyte in the solid polymer electrolyte is 39.76%), and the obtained electrolyte is recorded as RILNs-3 / 1-LiPF6-6.

[0075] Example 7

[0076] This embodiment provides a solid polymer electrolyte, which is different from Example 1 in that: in step S2, 35 parts by weight of lithium hexafluorophosphate is replaced with 35 parts by weight of lithium difluorooxalatoborate, and the obtained electrolyte is recorded as RILNs-3 / 1-C2BF2LiO4-7.

[0077] Example 8

[0078] This embodiment provides a solid polymer electrolyte, which is different from Example 1 in that: in step S2, 35 parts by weight of lithium hexafluorophosphate is replaced with 35 parts by weight of lithium bis(fluorosulfonyl)imide, and the obtained electrolyte is recorded as RILNs-3 / 1-F2LiNO4S2-8.

[0079] Example 9

[0080] This embodiment provides a solid polymer electrolyte, which differs from Example 1 in that: in step S2, 35 parts by weight of lithium hexafluorophosphate are replaced with 35 parts by weight of lithium perchlorate, and the obtained electrolyte is recorded as RILNs-3 / 1-LiClO4-9.

[0081] Example 10

[0082] This embodiment provides a solid polymer electrolyte, which is different from Example 1 in that: in step S2, 35 parts by weight of lithium hexafluorophosphate is replaced with 35 parts by weight of lithium dioxalatoborate, and the obtained electrolyte is recorded as RILNs-3 / 1-C4BLiO8-10.

[0083] Example 11

[0084] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced with 75 parts by weight of cross-linked polyethylene oxide SN-CN-2 containing a reversible imine bond;

[0085] SN-CN-2 was prepared as follows: 50 parts of a three-arm amino-terminated polyethylene glycol (3Ar-PEO-NH2) (weight-average molecular weight 5000 g / mol), 1.6 parts of trimesaldehyde, and 250 parts of dimethylformamide were added to a round-bottom three-necked flask equipped with an argon shield and mechanical stirring at 70°C for 0.5 h. The reaction mixture was then cast onto a silica gel mold and dried under vacuum at 70°C for 48 h to obtain cross-linked polyethylene oxide 2 (SN-CN-2) containing reversible imine bonds.

[0086] Example 12

[0087] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced with 75 parts by weight of cross-linked polyethylene oxide SN-CN-3 containing a reversible imine bond;

[0088] SN-CN-3 was prepared as follows: 50 parts of four-arm amino-terminated polyethylene glycol (4Ar-PEO-NH2) (weight-average molecular weight 5000 g / mol), 2.2 parts of trimesaldehyde, and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with argon protection and mechanical stirring at 70°C for 0.5 h. The reaction mixture was then cast onto a silica gel mold and dried under vacuum at 70°C for 48 h to obtain cross-linked polyethylene oxide 3 (SN-CN-3) containing reversible imine bonds.

[0089] Example 13

[0090] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced with 75 parts by weight of cross-linked polyethylene oxide SN-CN-4 containing a reversible imine bond;

[0091] SN-CN-4 was prepared as follows: 50 parts of 6Ar-PEO-NH2 (weight-average molecular weight 5000 g / mol), 3.3 parts of trimesaldehyde, and 250 parts of dimethylformamide were added to a three-necked round-bottom flask with argon protection and mechanical stirring at 70°C for 0.5 h. The reaction mixture was then cast onto a silica gel mold and dried under vacuum at 70°C for 48 h to obtain cross-linked polyethylene oxide 4 (SN-CN-4) containing reversible imine bonds.

[0092] Example 14

[0093] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced with 75 parts by weight of cross-linked polyethylene oxide SN-CN-5 containing a reversible imine bond;

[0094] SN-CN-5 was prepared as follows: 50 parts of 2Ar-PEO-NH2 (weight-average molecular weight 5000 g / mol), 0.97 parts of 1,2,4,5-pyromellitic acid, and 250 parts of dimethylformamide were added to a three-necked round-bottom flask with argon protection and mechanical stirring at 70°C for 0.5 h. The reaction mixture was then cast onto a silica gel mold and dried under vacuum at 70°C for 48 h to obtain cross-linked polyethylene oxide 5 (SN-CN-5) containing reversible imine bonds.

[0095] Example 15

[0096] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced with 75 parts by weight of cross-linked polyethylene oxide SN-CN-6 containing a reversible imine bond;

[0097] SN-CN-6 was prepared as follows: 50 parts of 2Arm-PEO-NH2 (weight-average molecular weight 5000 g / mol), 2.2 parts of tetrakis(4-formylphenyl)methane, and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with argon protection and mechanical stirring at 70°C for 0.5 h. The reaction mixture was then cast on a silica gel mold and vacuum-dried at 70°C for 48 h to obtain cross-linked polyethylene oxide 6 (SN-CN-6) containing reversible imine bonds.

[0098] Example 16

[0099] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 75 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced with 75 parts by weight of cross-linked polyethylene oxide SN-CN-7 containing a reversible imine bond;

[0100] SN-CN-7 was prepared as follows: 50 parts of 2Arm-PEO-NH2 (weight-average molecular weight 5000 g / mol), 3.0 parts of N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine, and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with argon protection and mechanical stirring at 70°C for 0.5 h. The reaction mixture was then cast on a silica gel mold and vacuum-dried at 70°C for 48 h to obtain cross-linked polyethylene oxide 7 (SN-CN-7) containing reversible imine bonds.

[0101] Example 17

[0102] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 25 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing reversible disulfide bonds is replaced with 25 parts by weight of cross-linked polyethylene oxide SN-SS-2 containing reversible disulfide bonds;

[0103] SN-SS-2 was prepared as follows: 60 parts of 2Arm-PEO-epoxy (weight-average molecular weight 3400 g / mol and 5000 g / mol, mass ratio 1:5), 1.6 parts of 2,2'-diaminodiphenyl disulfide, and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with argon protection and mechanical stirring at 90°C for 12 hours. The reaction mixture was then cast on a silica gel mold and vacuum-dried at 70°C for 48 hours to obtain cross-linked polyethylene oxide 2 (SN-SS-2) containing reversible imine bonds.

[0104] Example 18

[0105] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 25 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing reversible disulfide bonds is replaced with 25 parts by weight of cross-linked polyethylene oxide SN-SS-3 containing reversible disulfide bonds;

[0106] SN-SS-3 was prepared as follows: 50 parts of 3Arm-PEO-epoxy (weight-average molecular weight 5000 g / mol), 1.8 parts of 4,4'-diaminodiphenyl disulfide, and 250 parts of dimethylformamide were added to a round-bottomed three-necked flask with argon protection and mechanical stirring at 90°C for 12 hours. The reaction mixture was then cast onto a silica gel mold and vacuum-dried at 70°C for 48 hours to obtain cross-linked polyethylene oxide 3 (SN-SS-3) containing reversible imine bonds.

[0107] Example 19

[0108] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., 25 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing reversible disulfide bonds is replaced with 25 parts by weight of cross-linked polyethylene oxide SN-SS-4 containing reversible disulfide bonds;

[0109] SN-SS-4 was prepared as follows: 50 parts of four-arm epoxy-terminated polyethylene glycol (4Arm-PEO-epoxy) (weight-average molecular weight 5000 g / mol), 2.4 parts of 4,4'-diaminodiphenyl disulfide, and 250 parts of dimethylformamide were added to a round-bottom three-necked flask with argon protection and mechanical stirring at 90°C for 12 hours. The reaction mixture was then cast onto a silica gel mold and vacuum-dried at 70°C for 48 hours to obtain cross-linked polyethylene oxide 4 (SN-SS-4) containing reversible imine bonds.

[0110] Example 20

[0111] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., the composition of the polyethylene oxide is 25 parts by weight of cross-linked polyethylene oxide SN-CN-8 containing a reversible imine bond and 75 parts by weight of cross-linked polyethylene oxide SN-SS-5 containing a reversible disulfide bond;

[0112] The preparation method of SN-CN-8 is different from that of SN-CN-1, except that the weight-average molecular weight of the two-arm amino-terminated polyethylene glycol 2Arm-PEO-NH2 is 1000 g / mol;

[0113] The preparation method of SN-SS-5 is different from that of SN-SS-1, except that the weight average molecular weight of the 2Arm-PEO-epoxy is 1000 g / mol.

[0114] Example 21

[0115] This embodiment provides a solid polymer electrolyte, which differs from embodiment 1 in that: in step S1., the composition of the polyethylene oxide is 25 parts by weight of cross-linked polyethylene oxide SN-CN-9 containing a reversible imine bond and 75 parts by weight of cross-linked polyethylene oxide SN-SS-6 containing a reversible disulfide bond;

[0116] The preparation method of SN-CN-9 is different from that of SN-CN-1, except that the weight-average molecular weight of the two-arm amino-terminated polyethylene glycol 2Arm-PEO-NH2 is 10,000 g / mol;

[0117] The preparation method of SN-SS-6 is different from that of SN-SS-1, except that the weight average molecular weight of the 2Arm-PEO-epoxy is 10,000 g / mol.

[0118] Comparative Example 1

[0119] This comparative example provides a solid polymer electrolyte, the preparation method of which is different from that of Example 1 in that the cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond is replaced by a cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond, that is, the interlocked polyethylene oxide body contains only cross-linked polyethylene oxide containing a reversible imine bond, which is recorded as SN-CN-LiPF6.

[0120] Comparative Example 2

[0121] This comparative example provides a solid polymer electrolyte, the preparation method of which is different from that of Example 1 in that the cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond is replaced by a cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond, that is, the interlocked polyethylene oxide body contains only cross-linked polyethylene oxide containing a reversible disulfide bond, which is recorded as SN-SS-LiPF6.

[0122] Comparative Example 3

[0123] This comparative example provides a solid polymer electrolyte, the preparation method of which is different from that of Example 1 in that: in step S1., the composition of the polyethylene oxide is 10 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond and 90 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond.

[0124] Comparative Example 4

[0125] This comparative example provides a solid polymer electrolyte, the preparation method of which is different from that of Example 1 in that: in step S1., the composition of the polyethylene oxide is 90 parts by weight of cross-linked polyethylene oxide SN-CN-1 containing a reversible imine bond and 10 parts by weight of cross-linked polyethylene oxide SN-SS-1 containing a reversible disulfide bond.

[0126] Comparative Example 5

[0127] This comparative example provides a solid polymer electrolyte, the preparation method of which differs from that of Example 1 in that: in step S1., the composition of the polyethylene oxide is 25 parts by weight of cross-linked polyethylene oxide SN-CN-10 containing a reversible imine bond and 75 parts by weight of cross-linked polyethylene oxide SN-SS-7 containing a reversible disulfide bond;

[0128] The preparation method of SN-CN-10 is different from that of SN-CN-1, except that the weight-average molecular weight of the two-arm amino-terminated polyethylene glycol 2Arm-PEO-NH2 is 500 g / mol;

[0129] The preparation method of SN-SS-7 is different from that of SN-SS-1, except that the weight average molecular weight of the 2Arm-PEO-epoxy is 500 g / mol.

[0130] Comparative Example 6

[0131] This comparative example provides a solid polymer electrolyte, the preparation method of which differs from that of Example 1 in that: in step S1., the composition of the polyethylene oxide is 25 parts by weight of cross-linked polyethylene oxide SN-CN-11 containing a reversible imine bond and 75 parts by weight of cross-linked polyethylene oxide SN-SS-8 containing a reversible disulfide bond;

[0132] The preparation method of SN-CN-11 is different from that of SN-CN-1, except that the weight-average molecular weight of the two-arm amino-terminated polyethylene glycol 2Arm-PEO-NH2 is 15000 g / mol;

[0133] The preparation method of SN-SS-8 is different from that of SN-SS-1, except that the weight average molecular weight of the 2Arm-PEO-epoxy is 15,000 g / mol.

[0134] Performance Testing

[0135] The mechanical properties and conductive properties of the solid polymer electrolytes obtained in the above examples and comparative examples were characterized. The specific test items, test methods, and results are as follows:

[0136] 1. Mechanical properties:

[0137] The solid polymer electrolytes obtained in the examples and comparative examples were prepared into dumbbell-shaped tensile specimens. Tensile tests were performed using a tensile testing machine at room temperature (25°C) at a speed of 50 mm / min. The test results of the tensile strength (MPa) and elongation at break (%) are shown in Table 1.

[0138] 2. Ionic conductivity:

[0139] The ionic conductivity of the solid polymer electrolyte at 25 °C was measured by AC impedance spectroscopy (×10 -4 Scm -1 ), the test results are shown in Table 1.

[0140] 3. The solid polymer electrolytes of Example 1 and Comparative Examples 1 and 2 were assembled into lithium / lithium iron phosphate button batteries, and the cycle performance of the batteries was tested at room temperature (25°C). The results showed that the solid polymer electrolyte based on the interlocking network can greatly improve the cycle stability (see Figure 4 ), the cycle performance of the solid polymer electrolytes of other embodiments is similar to that of Example 1;

[0141] 4. Self-repair performance: The solid polymer electrolyte of Example 1 was divided into two parts, one of which was heated to 70°C and then cooled to room temperature (25°C). The heated and cooled solid polymer electrolyte and the original solid polymer electrolyte that was not heated and cooled were then assembled into lithium / lithium iron phosphate button batteries, and their cycle performance at room temperature (25°C) was tested. Figure 5 As shown, the two have similar cycling performance, indicating that the interlocking network-based solid polymer electrolyte of the present invention has good self-healing performance.

[0142] Table 1 Test results of solid polymer electrolytes obtained in Examples and Comparative Examples

[0143]

[0144] The results in Table 1 show that:

[0145] The results of Examples 1-3 and Comparative Examples 3-4 show that as the weight percentage of cross-linked polyethylene oxide containing reversible imine bonds in the interlocking polyethylene oxide matrix increases, the mechanical properties of the solid polymer electrolyte first increase and then decrease. This is because when the cross-linked polyethylene oxide component containing reversible imine bonds is too low, the solid electrolyte cannot quickly exchange and dissipate energy through the aromatic imine bonds under external tensile force, and the toughening effect is weakened. Conversely, when the cross-linked polyethylene oxide component containing reversible imine bonds is too high, the cross-linked polyethylene oxide component containing reversible disulfide bonds to maintain structural stability is too low, resulting in a decrease in the strength of the solid electrolyte. At the same time, as the weight percentage of cross-linked polyethylene oxide containing reversible imine bonds in the interlocking polyethylene oxide matrix increases, the ionic conductivity of the solid polymer electrolyte gradually increases. This is mainly because the highly dynamic imine bonds increase the mobility of the chain segments and improve the transport capacity of lithium ions.

[0146] The interlocked polyethylene oxide bodies of Comparative Examples 1 and 2 contain only one reversible cross-linked network structure. It can be seen that the mechanical properties and ionic conductivity of the solid polymer electrolytes prepared therefrom are significantly reduced, proving that in the absence of an interlocked nested structure, the mechanical properties of a single network are very poor, and due to PEO crystallization, the ionic conductivity is also very low.

[0147] The results of Example 1 and Examples 4 to 6 show that as the amount of lithium salt electrolyte added increases, the tensile strength gradually decreases, while the material becomes softer and the elongation increases slightly; the ionic conductivity shows a trend of first increasing and then decreasing, which is because if the amount added is too little, the number of lithium ions that can migrate is small and the conductivity is low; if the amount of lithium salt electrolyte added is too much, it cannot be completely dissociated, resulting in agglomeration, which affects the interaction between lithium ions and polyethylene oxide structural units; at the same time, the agglomerated lithium salt particles will also hinder the chain segment movement of PEO, causing the ionic conductivity to decrease.

[0148] The results of Example 1 and Examples 6 to 10 show that the easier it is for the added lithium salt to dissociate, the higher the conductivity of the solid electrolyte.

[0149] The results of Example 1, Examples 11 to 13, and Examples 18 to 19 show that as the functionality in polyethylene oxide increases, the single network crosslinking density increases, which can improve the tensile strength of the final interlocking network-based solid electrolyte, but also lead to a decrease in elongation and is not conducive to lithium ion transport, so the conductivity will decrease.

[0150] The results of Example 1, Examples 20-21, and Comparative Examples 5-6 show that when the molecular weight of polyethylene oxide is too low (such as Comparative Example 5), although it is basically non-crystallized and the conductivity is increased, the molecular weight between the cross-linking points is reduced, the mobility of the molecular chain segments is poor, and the toughness of the obtained solid polymer electrolyte is poor; when the molecular weight of polyethylene oxide is too high (such as Comparative Example 6), on the one hand, the proportion of amorphous regions is reduced, and the probability of lithium ions in the lithium salt electrolyte moving and transporting through complexation / decomplexation with the polyethylene oxide molecular segments is reduced; on the other hand, the molecular weight is too high, the crystallization rate is increased, and the interlocking network structure cannot effectively inhibit crystallization, thereby significantly reducing the ionic conductivity of the solid polymer electrolyte.

[0151] Figure 1 Solid polymer electrolytes based on interlocking networks (Examples 1 to 3) and the corresponding single network component polyethylene oxide (SN-CN-1, SN-SS-1) FTIR spectra are given, which prove that Examples 1 to 3 have characteristic peaks of two single network components (SN-CN-1 and SN-SS-1) and lithium hexafluorophosphate, indicating that solid polymer electrolytes based on interlocking networks have been successfully prepared.

[0152] Figure 2 and Figure 3 The DSC and XRD of solid polymer electrolytes based on interlocking networks (Examples 1 to 3) and solid polymer electrolytes prepared from corresponding single networks (Comparative Examples 1 and 2) are given. The results show that the two single networks have obvious crystalline melting peaks and crystalline diffraction peaks, while the corresponding interlocking networks do not, indicating that the interlocking structure can effectively inhibit crystallization.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A solid polymer electrolyte based on an interlocking network, characterized in that including an interlocking polyethylene oxide and a lithium salt electrolyte; The interlocked polyethylene oxide is composed of cross-linked polyethylene oxide containing a reversible imine bond and cross-linked polyethylene oxide containing a reversible disulfide bond, and the weight percentage of the cross-linked polyethylene oxide containing a reversible imine bond in the interlocked polyethylene oxide is 25 to 75%; The cross-linked polyethylene oxide containing a reversible imine bond comprises the following monomers in parts by weight: 25-75 parts of amino-terminated polyethylene glycol; 0.3-9.9 parts of polyaldehyde monomer; The amino-terminated polyethylene glycol is a 2-6-arm amino-terminated polyethylene glycol; the multi-aldehyde monomer is an aromatic aldehyde compound; The cross-linked polyethylene oxide containing reversible disulfide bonds comprises the following monomers in parts by weight: 30-90 parts of epoxy-terminated polyethylene glycol; 0.5-4.8 parts of diaminodiphenyl disulfide; The epoxy-terminated polyethylene glycol is a 2-6 arm epoxy-terminated polyethylene glycol; The weight average molecular weights of the polyethylene oxide segments of the cross-linked polyethylene oxide containing a reversible imine bond and the cross-linked polyethylene oxide containing a reversible disulfide bond are independently 1000 to 10000 g / mol; In the solid polymer electrolyte, the weight percentage of the lithium salt electrolyte is 20-40%.

2. The interlocking network-based solid polymer electrolyte according to claim 1, wherein The weight percentage of the cross-linked polyethylene oxide containing a reversible imine bond in the interlocking polyethylene oxide body is 50%.

3. The interlocking network-based solid polymer electrolyte according to claim 1, wherein The weight average molecular weights of the polyethylene oxide segments of the cross-linked polyethylene oxide containing reversible imine bonds and the cross-linked polyethylene oxide containing reversible disulfide bonds are independently 3000-5000 g / mol.

4. The interlocking network-based solid polymer electrolyte according to claim 1, wherein The amino-terminated polyethylene glycol is 、 、 、 or At least one of; The polyaldehyde monomer is 、 、 、 、 、 、 、 、 、 、 、 、 、 or At least one of .

5. The interlocking network-based solid polymer electrolyte according to claim 1, wherein The epoxy-terminated polyethylene glycol is 、 、 、 、 or At least one of; The diaminodiphenyl disulfide is or At least one of .

6. The interlocking network-based solid polymer electrolyte according to claim 1, wherein The lithium salt electrolyte is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl imide), lithium difluorooxalatoborate, and lithium bis(trifluoromethylsulfonyl imide).

7. The method for preparing the interlocking network-based solid polymer electrolyte according to any one of claims 1 to 6, characterized in that: The steps include: S1. Mixing a cross-linked polyethylene oxide containing a reversible imine bond and a cross-linked polyethylene oxide containing a reversible disulfide bond, and dissolving the mixture in a co-solvent at 100-140°C under an inert atmosphere; S2. After cooling to 60-90°C, a lithium salt electrolyte is added, stirred evenly, and the co-solvent is removed to obtain the interlocking network-based solid polymer electrolyte.

8. Use of the interlocking network-based solid polymer electrolyte according to any one of claims 1 to 6 in the preparation of a lithium metal battery.

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