CN114085325B - Ion-conducting semi-interpenetrating network polymer and preparation method and application thereof - Google Patents
Ion-conducting semi-interpenetrating network polymer and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to an ion-conducting semi-interpenetrating network polymer and a preparation method and application thereof. Polyvinylidene fluoride-polyhexafluoropropylene has excellent mechanical property and film forming property, and a polymer containing ethylene oxide units has excellent lithium ion conduction performance, so that a semi-interpenetrating cross-linked network polymer consisting of the polyvinylidene fluoride-polyhexafluoropropylene and polymerizable monomer groups containing the ethylene oxide units can provide enough mechanical support and lithium ion conduction performance, and can be used for preparing an electrode coating of a lithium metal battery. And a solid electrolyte protective layer of lithium salt is added on the basis of the artificial protective layer of the ion-conducting semi-interpenetrating network polymer, the lithium salt provides a continuous channel for lithium ion transmission and restrains electrolyte solvent molecules entering the protective layer, so that corrosion and consumption of the lithium negative electrode by the electrolyte solvent molecules are avoided, and the lithium ion battery can also be used for preparing an electrode coating of a lithium metal battery.
Description
Technical Field
The invention relates to the field of polymers and lithium batteries, in particular to an ion-conducting semi-interpenetrating network polymer and a preparation method and application thereof.
Background
In the lithium metal negative electrode protection strategy, constructing an artificial polymer protective layer is an effective method. The requirements for polymers are mainly two of the following: first, good mechanical properties. The polymer with good mechanical property can adapt to the volume change of the lithium metal negative electrode in the circulating process; second, high lithium ion conductivity. The stronger the ionic conductivity of the polymer, the more pronounced the effect of a uniform lithium ion stream.
The polymer realizes the conduction of lithium ions through the chain segment movement, wherein the movement capacity of a polymer chain, the movement capacity of a chain segment and the arrangement of ethylene oxide units are main factors influencing the lithium ion conductivity. The traditional linear polyethylene oxide (PEO) has high crystallinity, compact molecular chain arrangement, difficult lithium ion transmission among chains and ion conductivity of only 10 at room temperature -8 ～10 -7 S/cm, which is far from meeting the requirement of lithium ion conductivity in the practical use of lithium batteries. In addition, the use of the above-mentioned polymer as a lithium negative electrode protective layer reduces the coulombic efficiency of a lithium metal battery.
Disclosure of Invention
The invention aims to provide an ion-conducting semi-interpenetrating network polymer, a preparation method and application thereof, aiming at the defects of low ionic conductivity of the polymer and low coulombic efficiency of a lithium metal battery.
The invention is realized by the following technical scheme:
an ion-conducting semi-interpenetrating network polymer, the structural formula of which is shown as follows:
wherein m is the mass percent of hexafluoropropylene in polyvinylidene fluoride-polyhexafluoropropylene, n = 2-10, R = H or OCH 3 。
The preparation method of the ion-conducting semi-interpenetrating network polymer comprises the steps of adding polyvinylidene fluoride-polyhexafluoropropylene, polymerizable monomer containing ethylene oxide units, cross-linking agent and initiator into a solvent, uniformly dispersing, and carrying out polymerization reaction under a heating condition to obtain the ion-conducting semi-interpenetrating network polymer.
Preferably, the polymerizable monomer containing ethylene oxide units is polyethylene glycol diacrylate or polyethylene glycol dimethacrylate, and the crosslinking agent is pentaerythritol tetraacrylate or pentaerythritol tetrakis (3-mercaptopropionate).
Preferably, the mass of polyvinylidene fluoride-polyhexafluoropropylene accounts for 20-80% of the mass of the ion-conducting semi-interpenetrating network polymer, the mass of the initiator accounts for 0.2-2% of the total mass of the polymerizable monomer containing ethylene oxide units and the cross-linking agent, and the molar ratio of the polymerizable monomer containing ethylene oxide units to the cross-linking agent is (2-8): (8-2).
Preferably, the solvent is N, N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone, and the initiator is azobisisobutyronitrile.
Preferably, the polymerization reaction temperature is 60-80 ℃, and the polymerization reaction time is 5-80 min.
A preparation method of a solid electrolyte type ion-conducting semi-interpenetrating network polymer is characterized in that polyvinylidene fluoride-polyhexafluoropropylene, a polymerizable monomer containing ethylene oxide units, a cross-linking agent, lithium salt and an initiator are added into a solvent, uniformly dispersed, and subjected to polymerization reaction under a heating condition to obtain the solid electrolyte type ion-conducting semi-interpenetrating network polymer containing the lithium salt.
Preferably, the lithium salt is bis (trifluoromethyl) sulfonamide lithium salt, trifluoromethyl sulfonamide lithium salt, lithium hexafluorophosphate or lithium tetrafluoroborate, and the mass of the lithium salt accounts for 50-150% of the total mass of the polyvinylidene fluoride-polyhexafluoropropene, the polymerizable monomer containing ethylene oxide units and the crosslinking agent.
The quasi-solid electrolyte obtained by the preparation method is adopted.
The ion-conducting semi-interpenetrating network polymer or the solid electrolyte-like ion-conducting semi-interpenetrating network polymer is applied to a lithium metal battery as an electrode coating.
Compared with the prior art, the invention has the following beneficial technical effects:
the ion-conducting semi-interpenetrating network polymer comprises polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) and a polymer containing ethylene oxide units, wherein the polyvinylidene fluoride-polyhexafluoropropylene has excellent mechanical property and film-forming property, the polymer containing the ethylene oxide units has good lithium ion conductivity, more importantly, the polyvinylidene fluoride-polyhexafluoropropylene and the polymer containing the ethylene oxide units form an interpenetrating network, so that the crystallinity of a polymer chain containing the ethylene oxide units is greatly reduced, and the lithium ion conductivity of the polymer is improved.
According to the lithium metal battery, the lithium salt is added into the semi-interpenetrating network polymer, on one hand, the lithium salt participates in the formation of a continuous lithium ion transmission channel, on the other hand, the lithium salt can restrict electrolyte solvent molecules entering the interior of a protective layer through forming a solvation structure, so that the lithium negative electrode is prevented from being corroded by the lithium salt, the coulomb efficiency of the lithium metal battery is obviously improved, the cycle life of the battery is prolonged, and the robustness in the battery cycle process is enhanced.
Drawings
FIG. 1 is PVDF-HFP- (PAE) room temperature ionic conductivity;
FIG. 2 is a PVDF-HFP- (PAE) room temperature stress-strain curve;
FIG. 3 is the Coulomb efficiencies of PVDF-HFP- (PAE) @ Li-PVDF-HFP- (PAE) @ Cu (a), PVDF-HFP- (PAE) -LTFS @ Li-PVDF-HFP- (PAE) @ Cu (b), and comparative samples of lithium copper batteries;
FIG. 4 shows the UV spectrum of PVDF-HFP- (PAE) -LTFS soaked in solvent DME.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The invention provides an ion-conducting semi-interpenetrating network polymer, a preparation method thereof and application thereof in a lithium metal battery. The semi-interpenetrating network polymer is prepared from polyvinylidene fluoride-polyhexafluoropropylene and polymerizable monomers containing ethylene oxide units, wherein the polyvinylidene fluoride-polyhexafluoropropylene provides mechanical strength and structural integrity, the polymerizable monomers containing the ethylene oxide units provide a lithium ion conduction channel, and the coulombic efficiency of the lithium metal battery is improved to 95% of the average coulombic efficiency within 250 circles. In addition, lithium salt is added into the semi-interpenetrating network polymer to prepare a solid electrolyte artificial protection layer, so that the coulombic efficiency of the lithium metal battery is further improved to 99% of the average coulombic efficiency in 250 circles.
The ion-conducting semi-interpenetrating network polymer has the following molecular structure:
wherein m is the mass percent of hexafluoropropylene in polyvinylidene fluoride-polyhexafluoropropylene, m =10% -90%, n = 2-10, R = H or OCH 3 。
The preparation method of the ion-conducting semi-interpenetrating network polymer comprises the following steps:
uniformly dispersing polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP), a polymerizable monomer containing an ethylene oxide unit, a cross-linking agent and an initiator in a solvent, and carrying out polymerization reaction under heating conditions.
In the above preparation method, the polymerizable monomer containing an oxyethylene unit is polyethylene glycol diacrylate (PEGDA, n =2 to 9) or polyethylene glycol dimethacrylate (PEGDMA, n =2 to 9), and the crosslinking agent is pentaerythritol tetraacrylate (PET 4A) or pentaerythritol tetrakis (3-mercaptopropionate) (4-SH). The molecular weight of the polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) is 15 w-60 w.
In the above production method, the molar ratio of the polymerizable monomer having an oxyethylene unit to the crosslinking agent is (2 to 8): (8-2), the mass fraction of the polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) in the ion-conducting semi-interpenetrating network polymer is 20-80%.
In the above preparation method, the solvent is N, N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone, and the initiator is Azobisisobutyronitrile (AIBN).
In the above preparation method, the initiator accounts for 0.2-2%, preferably 0.6-1.5% of the sum of the mass of the polymerizable monomer containing ethylene oxide units and the cross-linking agent.
In the above preparation method, the polymerization reaction temperature is 60 ℃ to 80 ℃, preferably 65 ℃ to 75 ℃, and the polymerization reaction time is 5min to 80min, preferably 10min to 40min.
In the preparation method, lithium salt can be added to prepare a solid electrolyte type ion-conducting semi-interpenetrating network polymer serving as an artificial protective layer, wherein the lithium salt is bis (trifluoromethyl) sulfamide lithium salt (LiTFSI), trifluoromethyl sulfamide lithium salt (LiFSI) or lithium hexafluorophosphate (LiPF) 6 ) Or lithium tetrafluoroborate (LiBF) 4 ) The mass of the lithium salt accounts for 50-150% of the total mass of the polyvinylidene fluoride-polyhexafluoropropylene, the polymerizable monomer containing ethylene oxide units and the cross-linking agent.
The application of the ion-conducting semi-interpenetrating network polymer or the similar solid electrolyte type ion-conducting semi-interpenetrating network polymer in the lithium metal battery is as follows:
and respectively coating the solution of the semi-interpenetrating network polymer or the quasi-solid electrolyte type ion-conducting semi-interpenetrating network polymer on a lithium belt and a copper foil, and drying cut pieces, wherein the specification is that a lithium cathode is a phi 16mm wafer, and a copper counter electrode is a phi 19mm wafer.
In use, the solution concentration is preferably 0.1wt% to 0.3wt%. The solvent is any one of N, N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP).
In application, the drying temperature of the lithium negative electrode is 80-120 ℃, and preferably 85-105 ℃.
In application, the drying time of the lithium negative electrode is 2 to 6 hours, and preferably 3 to 4 hours.
In application, the drying temperature of the copper counter electrode is 80-120 ℃, preferably 85-105 ℃.
In application, the drying time of the copper counter electrode is 12-30 h, preferably 20-24 h.
And assembling the lithium cathode and the copper counter electrode into a battery, wherein the electrolyte is any one of 1M LiFSI DME, 2M LiFSI DME and 1M LiTFSI DME. Preferably 2M LiFSI DME in an amount of 80. Mu.L, and the membrane used is a Celgard membrane.
The cells were tested on the Xinwei system under a current density of 1mA cm -2 The deposition amount is 1mAh cm -2 Current density 1mA cm -2 The deposition amount was 2mAh cm -2 Current density 2mA cm -2 The deposition amount was 1mAh cm -2 Current density 2mA cm -2 The deposition amount was 2mAh cm -2 Any one of them. The test conditions used are preferably a current density of 2mA cm -2 The deposition amount is 1mAh cm -2 。
1. Preparation of polyethylene glycol diacrylate (PEGDA, n = 9) monomer and pentaerythritol tetraacrylate (PET 4A) Cross-Linked copolymer (PAE)
Example 1 PAE31
300mg of polyethylene glycol diacrylate (N = 9) monomer, 71mg of pentaerythritol tetraacrylate (PET 4A), 3.7mg of Azobisisobutyronitrile (AIBN), dissolved oxygen removed by bubbling, 3.34g of N, N-Dimethylformamide (DMF) solvent, and the reaction was stirred at 65 ℃ for 28min.
Example 2 PAE11
100mg of polyethylene glycol diacrylate (N = 9) monomer, 70.5mg of pentaerythritol tetraacrylate (PET 4A), 1.7mg of Azobisisobutyronitrile (AIBN), dissolved oxygen removed by bubbling, 1.53g of N, N-Dimethylformamide (DMF) solvent, and the reaction was stirred at 65 ℃ for 15min.
Example 3 PAE13
50mg of polyethylene glycol diacrylate (N = 9) monomer, 105mg of pentaerythritol tetraacrylate (PET 4A), 1.6mg of Azobisisobutyronitrile (AIBN), dissolved oxygen removed by bubbling, 1.39g of N, N-Dimethylformamide (DMF) solvent, and the reaction was stirred at 65 ℃ for 7min.
2. Preparation of semi-interpenetrating network polymer of polyethylene glycol diacrylate (n = 9) monomer, pentaerythritol tetraacrylate (PET 4A) and polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP)
The structural general formula of the semi-interpenetrating network polymer can be expressed as PVDF-HFP x -PAE 1-x ，x＝0.1～0.9。
Example 4 PVDF-HFP 0.2 -(PAE31) 0.8
93mg of polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) and 3g of N, N-Dimethylformamide (DMF) solvent are heated to 50 ℃ to be completely dissolved, 300mg of polyethylene glycol diacrylate (N = 9) monomer, 71mg of pentaerythritol tetraacrylate (PET 4A), 3.7mg of Azobisisobutyronitrile (AIBN), 1.17g of N, N-Dimethylformamide (DMF) solvent are added after the temperature of the reaction bottle is reduced to the room temperature, dissolved oxygen is removed by bubbling, and the reaction is stirred at 65 ℃ for 28min, wherein the molecular weight of the polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) is preferably 40w.
Example 5 PVDF-HFP 0.4 -(PAE31) 0.6
370mg of polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) and 6g of N, N-Dimethylformamide (DMF) solvent are heated to 50 ℃ to be completely dissolved, 450mg of polyethylene glycol diacrylate (N = 9) monomer, 106mg of pentaerythritol tetraacrylate (PET 4A), 5.6mg of Azobisisobutyronitrile (AIBN), 2.3g of N, N-Dimethylformamide (DMF) solvent are added when the temperature of the reaction bottle is reduced to the room temperature, dissolved oxygen is removed by bubbling, the reaction is stirred at 65 ℃ for 25min, and the molecular weight of the polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) is preferably 40w.
Example 6 PVDF-HFP 0.6 -(PAE31) 0.4
278mg of polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) and 3g of N, N-Dimethylformamide (DMF) solvent are heated to 50 ℃ to be completely dissolved, 150mg of polyethylene glycol diacrylate (N = 9) monomer, 35mg of pentaerythritol tetraacrylate (PET 4A), 1.9mg of Azobisisobutyronitrile (AIBN), 1.17g of N, N-Dimethylformamide (DMF) solvent are added after the temperature of the reaction bottle is reduced to the room temperature, dissolved oxygen is removed by bubbling, and the reaction is stirred at 65 ℃ for 20min, wherein the molecular weight of the polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) is preferably 40w.
Example 7 PVDF-HFP 0.8 -(PAE31) 0.2
740mg of polyvinylidene fluoride-polyhexafluoropropene (PVDF-HFP) and 7g of N, N-Dimethylformamide (DMF) solvent were heated to 50 ℃ to be completely dissolved, 150mg of polyethylene glycol diacrylate (N = 9) monomer, 35mg of pentaerythritol tetraacrylate (PET 4A), 1.9mg of Azobisisobutyronitrile (AIBN), 2.3g of N, N-Dimethylformamide (DMF) solvent were added after the temperature of the reaction flask was lowered to room temperature, dissolved oxygen was removed by bubbling, and the reaction was stirred at 65 ℃ for 30 minutes, wherein the molecular weight of polyvinylidene fluoride-polyhexafluoropropene (PVDF-HFP) was preferably 40w.
The solutions of examples 4 to 7 were each formed into a film by a solution casting method, and the room temperature ionic conductivity of the resulting film was measured as shown in FIG. 1. It can be seen that as the content of the polymerizable monomer chain segment containing ethylene oxide unit is reduced, the unit for conducting lithium ions in the material is reduced, and the overall lithium ion conductivity of the semi-interpenetrating network is reduced, and can reach 8.9 multiplied by 10 at most -5 S/cm. Table 1 lists the room temperature ionic conductivities of the four materials.
The solutions of examples 5-7 were all formed into films by solution casting, and the stress-strain curves of the resulting films were measured and are shown in FIG. 2. It can be seen that the elastic modulus of the material increases with increasing content of polyvinylidene fluoride-polyhexafluoropropene, wherein the elastic modulus of example 7 can reach 91MPa. The modulus of elasticity of the three materials is listed in table 2.
TABLE 1 Room temperature Ionic conductivity of the materials
| Serial number | Ion conductivity at room temperature (S/cm) |
| Example 4 | 8.9×10 -5 |
| Example 5 | 1.6×10 -5 |
| Example 6 | 1.1×10 -5 |
| Example 7 | 8×10 -6 |
TABLE 2 modulus of elasticity of the materials
| Serial number | Modulus of elasticity (MPa) |
| Example 5 | 3.08 |
| Example 6 | 60 |
| Example 7 | 91 |
3. Preparation of polyethylene glycol diacrylate (n = 9) monomer, pentaerythritol tetraacrylate (PET 4A), polyvinylidene fluoride-polyhexafluoropropylene (PVDF-HFP) and lithium bistrifluoromethylsulfonamide (LiTFSI) composite layer
Example 8 PVDF-HFP 0.2 -(PAE31) 0.8 -LTFS1
93mg of vinylidene fluoride-polyhexafluoropropylene (PVDF-HFP), 3g of N, N-Dimethylformamide (DMF) solvent and 464mg of bis (trifluoromethyl) sulfonamide lithium salt (LTFS) were heated to 50 ℃ to be completely dissolved, and after the temperature of the reaction flask was lowered to room temperature, 300mg of polyethylene glycol diacrylate (N = 9) monomer, 71mg of pentaerythritol tetraacrylate (PET 4A), 3.7mg of Azobisisobutyronitrile (AIBN), 1.17g of N, N-Dimethylformamide (DMF) solvent were added, and dissolved oxygen was bubbled and removed, followed by stirring at 65 ℃ for reaction for 26 minutes.
Example 9 PVDF-HFP 0.4 -(PAE31) 0.6 -LTFS1
370mg of vinylidene fluoride-polyhexafluoropropylene (PVDF-HFP), 6g of N, N-Dimethylformamide (DMF) solvent and 1.026g of lithium bistrifluoromethylsulfonamide (LTFS) are heated to 50 ℃ to be completely dissolved, 450mg of polyethylene glycol diacrylate (N = 9) monomer, 106mg of pentaerythritol tetraacrylate (PET 4A), 5.6mg of Azobisisobutyronitrile (AIBN), 2.3g of N, N-Dimethylformamide (DMF) solvent are added after the temperature of the reaction flask is reduced to room temperature, dissolved oxygen is removed by bubbling, and the mixture is stirred and reacted at 65 ℃ for 23min.
Example 10 PVDF-HFP 0.6 -(PAE31) 0.4 -LTFS1
278mg of vinylidene fluoride-polyhexafluoropropylene (PVDF-HFP), 3g of N, N-Dimethylformamide (DMF) solvent and 463mg of lithium bistrifluoromethylsulfonamide (LTFS) salt are heated to 50 ℃ to be completely dissolved, 150mg of polyethylene glycol diacrylate (N = 9) monomer, 35mg of pentaerythritol tetraacrylate (PET 4A), 1.9mg of Azobisisobutyronitrile (AIBN), 1.17g of N, N-Dimethylformamide (DMF) solvent are added after the temperature of the reaction bottle is reduced to room temperature, dissolved oxygen is bubbled to remove, and the reaction is stirred at 65 ℃ for 18min.
Example 11 PVDF-HFP 0.8 -(PAE31) 0.2 -LTFS1
740mg of vinylidene fluoride-polyhexafluoropropylene (PVDF-HFP), 7g of N, N-Dimethylformamide (DMF) solvent and 925mg of lithium bistrifluoromethylsulfonamide (LTFS) were heated to 50 ℃ to be completely dissolved, 150mg of polyethylene glycol diacrylate (N = 9) monomer, 35mg of pentaerythritol tetraacrylate (PET 4A), 1.9mg of Azobisisobutyronitrile (AIBN), 2.3g of N, N-Dimethylformamide (DMF) solvent were added after the temperature of the reaction flask was lowered to room temperature, dissolved oxygen was bubbled and reacted for 28 minutes with stirring at 65 ℃.
4. Lithium copper half cell preparation and testing
Example 12 PVDF-HFP 0.4 -(PAE31) 0.6 @Li/PVDF-HFP 0.4 -(PAE31) 0.6 @Cu
0.1wt% of a solution containing PVDF-HFP 0.4 -(PAE31) 0.6 Was coated on a 3cm x 7cm lithium tape and dried in a vacuum oven at 85 ℃ for 3h. 0.1wt% of a mixture containing PVDF-HFP 0.4 -(PAE31) 0.6 70 μ L of DMF solution was coated on a copper foil of 4cm x 7cm and dried in a vacuum oven at 85 ℃ for 24h. Cutting the lithium belt and the copper foil into wafers with the diameter of 16mm and the diameter of 19mm respectively, and assembling a CR2032 battery in a glove box with the water value and the oxygen value of less than 0.1ppm, wherein the electrolyte is 2M LiFSI DME, the dosage is 80 mu L, and the diaphragm is a Celgard diaphragm. Standing the assembled battery for 4h in a test environment, and testing on a Xinwei system under the test condition that the current density is 2mA cm -2 The deposition amount is 1mAh cm -2 。
Example 13 PVDF-HFP 0.4 -(PAE31) 0.6 -LTFS1@Li/PVDF-HFP 0.4 -(PAE31) 0.6 -LTFS1@Cu
0.1wt% of a solution containing PVDF-HFP 0.4 -(PAE31) 0.6 -LTFS1 in DMF 15. Mu.L was coated on 3cm x 7cm lithium tape and dried in a vacuum oven at 85 ℃ for 3h. 0.1wt% of a solution containing PVDF-HFP 0.4 -(PAE31) 0.6 70. Mu.L of a DMF solution of-LTFS 1 was coated on a copper foil of 4cm x 7cm and dried in a vacuum oven at 85 ℃ for 24h. Cutting the lithium belt and the copper foil into wafers with the diameter of 16mm and the diameter of 19mm respectively, and assembling a CR2032 battery in a glove box with the water value and the oxygen value of less than 0.1ppm, wherein the electrolyte is 2M LiFSI DME, the dosage is 80 mu L, and the diaphragm is a Celgard diaphragm. Standing the assembled battery for 4h in a test environment, and testing on a Xinwei system under the test condition that the current density is 2mA cm -2 The deposition amount is 1mAh cm -2 。
Comparative example 1 Li/Cu
Cutting the lithium belt and the copper foil into wafers with the diameter of 16mm and the diameter of 19mm respectively, and assembling a CR2032 battery in a glove box with the water value and the oxygen value of less than 0.1ppm, wherein the electrolyte is 2M LiFSI DME, the dosage is 80 mu L, and the diaphragm is a Celgard diaphragm. Standing the assembled battery for 4h in a test environment, and testing on a Xinwei system under the test condition that the current density is 2mA cm -2 The deposition amount is 1mAh cm -2 。
In the ion-conducting semi-interpenetrating network, polyvinylidene fluoride-polyhexafluoropropylene provides excellent mechanical property, relieves the volume change of a lithium cathode in the circulating process, and a polymerizable monomer chain segment containing an ethylene oxide unit provides good lithium ion conductivity, and promotes the uniform deposition of lithium ions. Referring to fig. 3a, it can be seen that the cycle life and the coulombic efficiency of the lithium copper battery with the applied ion-conducting semi-interpenetrating network polymer artificial protection layer are respectively improved to 300 cycles and 95% compared to the comparative example. The lithium salt is added to provide a continuous channel for lithium ion transmission, and electrolyte solvent molecules entering the protective layer are restrained at the same time, so that corrosion and consumption of the lithium negative electrode by the electrolyte solvent molecules are avoided. Referring to fig. 3b, it can be seen that the cycle life and the coulombic efficiency of the lithium copper battery with the solid electrolyte protective layer made of the added lithium salt on the basis of the applied ion-conducting semi-interpenetrating network polymer artificial protective layer are respectively improved to 300 circles and 99 percent compared with the comparative example. Table 3 shows the coulombic efficiencies obtained for the test cells.
TABLE 3 coulombic efficiency of the cells
| Serial number | Coulombic efficiency |
| Example 12 | 95％ |
| Example 13 | 99％ |
| Comparative example 1 | 89％ |
In addition, the lithium salt added to the solid-state electrolyte-like layer is required to be always contained in the layer and not to migrate into the bulk electrolyte, and for this problem, a film made of the solid-state electrolyte-like layer is soaked in an electrolyte solvent DME, and after standing, whether a signal of the lithium salt appears in the solvent is tested by an ultraviolet spectrophotometer. Referring to FIG. 4, after example 13 was soaked in DME for 70 days, the liquid was sampled and tested for UV absorption. The standard peak position of LiTFSI in DME was determined with LiTFSI/DME, which salt showed a strong absorption peak at 249nm in DME, which was not detected in DME soaked in example 13, indicating that the lithium salt was always contained in the solid electrolyte-like layer and no migration occurred.
Claims (9)
1. The ion-conducting semi-interpenetrating network polymer is characterized in that the structural formula is as follows:
2. The preparation method of the ion-conducting semi-interpenetrating network polymer of claim 1, wherein polyvinylidene fluoride-polyhexafluoropropene, polymerizable monomer containing ethylene oxide unit, cross-linking agent and initiator are added into solvent, uniformly dispersed, and subjected to polymerization reaction under heating condition to obtain ion-conducting semi-interpenetrating network polymer;
the polymerizable monomer containing ethylene oxide units is polyethylene glycol diacrylate, and the cross-linking agent is pentaerythritol tetraacrylate.
3. The method for preparing the ion-conducting semi-interpenetrating network polymer according to claim 2, wherein the mass of polyvinylidene fluoride-polyhexafluoropropylene accounts for 20-80% of the mass of the ion-conducting semi-interpenetrating network polymer, the mass of the initiator accounts for 0.2-2% of the total mass of the polymerizable monomer containing ethylene oxide units and the cross-linking agent, and the molar ratio of the polymerizable monomer containing ethylene oxide units to the cross-linking agent is (2~8): (8~2).
4. The method of claim 2, wherein the solvent is N, N-dimethylformamide, dimethylsulfoxide, or N-methylpyrrolidinone, and the initiator is azobisisobutyronitrile.
5. The method for preparing the ion conducting semi-interpenetrating network polymer of claim 2, wherein the polymerization temperature is 60 ℃ to 80 ℃, and the polymerization time is 5min to 80min.
6. The preparation method of the quasi solid electrolyte type ion-conducting semi-interpenetrating network polymer is characterized by further comprising the step of adding lithium salt into a solvent on the basis of the preparation method of the ion-conducting semi-interpenetrating network polymer in claim 2, so as to obtain the quasi solid electrolyte type ion-conducting semi-interpenetrating network polymer containing the lithium salt.
7. The preparation method of the solid electrolyte type ion-conducting semi-interpenetrating network polymer according to claim 6, wherein the lithium salt is bis-trifluoromethyl sulfonamide lithium salt, lithium hexafluorophosphate or lithium tetrafluoroborate, and the mass of the lithium salt accounts for 50-150% of the total mass of polyvinylidene fluoride-polyhexafluoropropene, polymerizable monomer containing ethylene oxide units and crosslinking agent.
8. The solid electrolyte-like ion conducting semi-interpenetrating network polymer obtained by the preparation method of claim 6 or 7.
9. Use of the ion conducting semi-interpenetrating network polymer of claim 1 or the solid electrolyte like ion conducting semi-interpenetrating network polymer of claim 8 as an electrode coating in a lithium metal battery.
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