CN114284638A - Organic-inorganic hybrid diaphragm of lithium metal battery, preparation method of organic-inorganic hybrid diaphragm and lithium metal battery - Google Patents
Organic-inorganic hybrid diaphragm of lithium metal battery, preparation method of organic-inorganic hybrid diaphragm and lithium metal battery Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 7
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims abstract description 44
- 239000002121 nanofiber Substances 0.000 claims abstract description 43
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 39
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 39
- -1 mercaptopropyl Chemical group 0.000 claims abstract description 20
- 238000012650 click reaction Methods 0.000 claims abstract description 6
- 230000000977 initiatory effect Effects 0.000 claims abstract description 6
- 238000009987 spinning Methods 0.000 claims description 77
- 239000012528 membrane Substances 0.000 claims description 30
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- 239000002904 solvent Substances 0.000 claims description 13
- RWCCWEUUXYIKHB-UHFFFAOYSA-N benzophenone Chemical group C=1C=CC=CC=1C(=O)C1=CC=CC=C1 RWCCWEUUXYIKHB-UHFFFAOYSA-N 0.000 claims description 8
- 239000012965 benzophenone Substances 0.000 claims description 8
- 238000010041 electrostatic spinning Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 6
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- 125000003158 alcohol group Chemical group 0.000 claims description 4
- 238000004090 dissolution Methods 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 21
- 210000001787 dendrite Anatomy 0.000 abstract description 11
- 230000008901 benefit Effects 0.000 abstract description 5
- 230000002401 inhibitory effect Effects 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 27
- 210000004027 cell Anatomy 0.000 description 21
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- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 19
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 16
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- 238000003760 magnetic stirring Methods 0.000 description 10
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- 229910001416 lithium ion Inorganic materials 0.000 description 9
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- 239000000835 fiber Substances 0.000 description 7
- 239000011259 mixed solution Substances 0.000 description 7
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 6
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 6
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical group CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 6
- 238000005286 illumination Methods 0.000 description 6
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- 229910052782 aluminium Inorganic materials 0.000 description 5
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- 229910010710 LiFePO Inorganic materials 0.000 description 4
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 4
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Abstract
The invention discloses an organic-inorganic hybrid diaphragm of a lithium metal battery, which comprises two polyvinylidene fluoride-hexafluoropropylene-based nanofiber layers and a polyvinyl alcohol-based nanofiber layer positioned between the two polyvinylidene fluoride-hexafluoropropylene-based nanofiber layers; the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer is a three-dimensional network generated by carrying out click reaction on polyvinylidene fluoride-hexafluoropropylene, mercaptopropyl cage-type silsesquioxane and double-bond-terminated cage-type silsesquioxane under the initiation of a photoinitiator; the polyvinyl alcohol-based nanofiber layer is a three-dimensional network generated by click reaction of polyvinyl alcohol, mercaptopropyl cage-type silsesquioxane and double-bond-terminated cage-type silsesquioxane under the initiation of a photoinitiator. The invention also discloses a preparation method of the organic-inorganic hybrid diaphragm and a lithium metal battery comprising the diaphragm. The organic-inorganic hybrid diaphragm has the advantages of good lyophilic property, large porosity, excellent ionic conductivity and capability of obviously inhibiting the growth of lithium dendrites.
Description
Technical Field
The invention relates to the field of lithium metal batteries, in particular to an organic-inorganic hybrid diaphragm of a lithium metal battery, a preparation method of the organic-inorganic hybrid diaphragm and the lithium metal battery.
Background
As early as 1970 s, lithium metal batteries were proposed to be used in the field of high energy density batteries, but have been staying in the initial stage of development for decades because of their short safety and cycle life. In which lithium dendrites grow during lithium deposition, which may lead to capacity loss or even to short circuits. In recent years, lithium metal batteries have not been commercially used on a large scale, although safety and cycle efficiency have been remarkably improved. In contrast, "rocking chair" lithium ion batteries, which have graphite as the anode to facilitate the reaction of lithium ions in the electrode reaction, have been successfully commercialized in the 1990's for portable electronic devices, and more recently, for electric vehicle applications.
As the power and the endurance of electric vehicles and portable electronic devices increase, development of batteries having high energy density and stable cycle performance is urgently required. Metallic lithium is considered to be one of the most promising negative electrodes for next-generation batteries because it has 0.53g/cm3Low density, -low anode potential of 3.04V and high specific energy density of 3860mAh/g, which is a significant advantage over graphite anodes (372mAh/g) in current commercial lithium ion batteries. However, the use of lithium metal as a negative electrode in batteries remains challenging because of the Li in Li+Lithium dendrites formed during the plating/stripping process can lead to low coulombic efficiency, fast capacity fade, electrolyte consumption and safety issues. Accordingly, many efforts have been made to suppress the growth of dendrites in lithium metal batteries, including the construction of a 3D-structured lithium negative electrode, the introduction of a solid electrolyte, a functional separator, an electrolyte additive, and the like.
Among these studies, the introduction of a functional separator is one of the most effective methods because it can inhibit the formation of lithium dendrites or regulate the transport and deposition of lithium ions through a mechanical barrier without significantly increasing the weight or volume of the battery. However, the current commercialized polyolefin separator has poor thermal stability, and cannot effectively inhibit the uniform deposition of lithium metal and the growth of lithium dendrite, and once the lithium dendrite penetrates through the separator, the battery has internal short circuit, thermal runaway, and even combustion and explosion.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide an organic-inorganic hybrid diaphragm of a lithium metal battery, which has the advantages of good lyophilic property, large porosity, excellent ionic conductivity and capability of obviously inhibiting the growth of lithium dendrite.
The invention also aims to provide a preparation method of the organic-inorganic hybrid diaphragm of the lithium metal battery, which has the characteristics of simple synthesis method and easy realization of operation environment.
The invention further aims to provide a lithium metal battery, which is charged and discharged at 25 ℃ with the rate of 2C, and the capacity retention rate is up to 99.6% after 200 circles. At the same time, the assembled button cell shows excellent rate performance.
The purpose of the invention is realized by the following technical scheme:
an organic-inorganic hybrid diaphragm of a lithium metal battery comprises two polyvinylidene fluoride-hexafluoropropylene-based nanofiber layers and a polyvinyl alcohol-based nanofiber layer positioned between the two polyvinylidene fluoride-hexafluoropropylene-based nanofiber layers;
the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer is a three-dimensional network generated after a click reaction of polyvinylidene fluoride-hexafluoropropylene, mercaptopropyl cage-type silsesquioxane and double-bond-terminated cage-type silsesquioxane under initiation of a photoinitiator;
the polyvinyl alcohol-based nanofiber layer is a three-dimensional network generated after a click reaction is carried out on polyvinyl alcohol, mercaptopropyl cage-type silsesquioxane and double-bond-terminated cage-type silsesquioxane under the initiation of a photoinitiator.
Preferably, the double bond-terminated cage silsesquioxane is octavinyl cage silsesquioxane (VSQ) or octamethacrylate-based cage silsesquioxane (MASQ).
Preferably, the photoinitiator is Benzophenone (BP).
Preferably, in the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer, the mass ratio of the total mass of the mercaptopropyl cage-type silsesquioxane and the double-bond-terminated cage-type silsesquioxane to the mass of the polyvinylidene fluoride-hexafluoropropylene is 0.01-0.2: 1.
Preferably, in the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer, the molar ratio of the double-bond-terminated cage-type silsesquioxane to the mercaptopropyl cage-type silsesquioxane is 1: 0.2-1.
Preferably, in the polyvinyl alcohol-based nanofiber layer, the molar ratio of double-bond-terminated cage-type silsesquioxane to mercaptopropyl cage-type silsesquioxane is 1: 0.2-1; the mass ratio of the total mass of the double-bond-terminated cage-type silsesquioxane to the mass of the mercaptopropyl cage-type silsesquioxane to the polyvinyl alcohol is 0.1-5%.
Preferably, in the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer, the addition amount of the photoinitiator is 0.5-5% of the total mass of the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer;
in the polyvinyl alcohol group nano fiber layer, the addition amount of the photoinitiator is 0.5-5% of the total mass of the polyvinyl alcohol group nano fiber layer.
Preferably, the thickness of the organic-inorganic hybrid diaphragm is 50-100 mu m, wherein the thickness ratio of the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer to the polyvinyl alcohol-based nanofiber layer is 1: 0.6-2.
The preparation method of the organic-inorganic hybrid diaphragm of the lithium metal battery comprises the following steps:
preparing a polyvinylidene fluoride-hexafluoropropylene-based spinning solution: dissolving mercaptopropyl cage-type silsesquioxane, double-bond-terminated cage-type silsesquioxane and a photoinitiator in a first solvent, adding polyvinylidene fluoride-hexafluoropropylene after complete dissolution, and stirring until complete dissolution to obtain polyvinylidene fluoride-hexafluoropropylene-based spinning solution;
preparing a polyvinyl alcohol-based spinning solution: dissolving mercaptopropyl cage-type silsesquioxane, double-bond-terminated cage-type silsesquioxane and a photoinitiator in a second solvent, adding polyvinyl alcohol solid, and completely dissolving to obtain polyvinyl alcohol-based spinning solution;
preparing a nanofiber membrane: respectively adding the polyvinylidene fluoride-hexafluoropropylene-based spinning solution and the polyvinyl alcohol-based spinning solution into an injector, then alternately performing electrostatic spinning under the irradiation of ultraviolet light to prepare the nanofiber membrane with the sandwich structure, washing in ethanol and drying to obtain the organic-inorganic hybrid membrane.
A lithium metal battery comprises the organic-inorganic hybrid diaphragm of the lithium metal battery.
Preferably, the first solvent is a mixed solution of N, N '-dimethylacetamide (DMAc) and Acetone (ACE), wherein the volume ratio of the N, N' -dimethylacetamide to the acetone is (0.4-1): 1.
preferably, the second solvent is a mixed solvent of NMP and water, wherein the volume ratio of water to NMP is 8-9: 1.
Preferably, the molecular weight of PVDF-HFP is 200000 to 400000.
Preferably, the molecular weight of PVA is 100000-300000.
Preferably, the spinning parameters of the PVDF-HFP fiber layer are set as follows: spinning voltage is 17-19 kV, spinning speed is 2-3 ml/h, and the distance from the needle point to the receiver is set to be 10-15 cm; the spinning parameters of the PVA fiber layer were set as follows: the spinning voltage is 21-25 kV, the spinning speed is 0.5-0.6 ml/h, and the distance from the needle point to the receiver is set to be 10-15 cm; the illumination of an ultraviolet lamp at the receiver is 25mW/cm2。
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the organic-inorganic hybrid nanofiber membrane of the lithium metal battery has the advantages of good lyophilic property, large porosity, excellent ionic conductivity, capability of obviously inhibiting the growth of lithium dendrite and the like. The PVDF-HFP and lithium have good interface stability, and the interface resistance between the PVDF-HFP and the lithium metal surface is small, so that the transmission of lithium ions is facilitated; after PVA and lithium metal are contacted, OH functional groups on the surface react to form a C-O-Li bond; therefore, a large amount of lithium in the PVA phase is uniformly dispersed in polymer molecules, and the lithium-rich layer is beneficial to uniform transmission of lithium ions in the PVA phase. Meanwhile, due to the existence of a three-dimensional cross-linked network, the crystallinity of PVDF-HFP and PVA is further reduced, and the lithium ion migration is facilitated.
(2) The preparation method of the organic-inorganic hybrid diaphragm of the lithium metal battery has the characteristics of simple synthesis method and easy realization of operation environment.
(3) The lithium metal battery prepared by the organic-inorganic hybrid diaphragm of the lithium metal battery is charged and discharged at the rate of 2C at 25 ℃, and the capacity retention rate is up to 99.6% after 200 circles. At the same time, the assembled button cell shows excellent rate performance.
Drawings
Fig. 1 is a macro-photograph of an organic-inorganic hybrid separator prepared in example 1 of the present invention.
Fig. 2 is a microscopic cross-sectional photograph of the organic-inorganic hybrid separator prepared in example 1 of the present invention.
Fig. 3 is an interface impedance spectrum of the organic-inorganic hybrid separator prepared in example 2 of the present invention.
Fig. 4 is a Linear Sweep Voltammetry (LSV) curve of the organic-inorganic hybrid membrane prepared in example 2 of the present invention.
Fig. 5 is a graph of rate performance of a lithium iron phosphate full cell prepared in example 3 of the present invention.
Fig. 6 is a graph of cycle performance at 2C for a lithium iron phosphate full cell prepared in example 4 of the present invention.
Fig. 7 is a graph of cycle performance at 5C for a lithium iron phosphate full cell prepared in example 5 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1
1.7g of PVDF-HFP was weighed and added to a mixed solution of ACE and DMAc in which 0.085g of VSQ, 0.085g of TSQ and 0.5 wt% of BP were dissolved (V/V ═ 3:7), and dissolved completely under magnetic stirring to obtain a spinning dope 1; 0.9g of PVA was weighed out and added to H dissolved with 0.045g of VSQ, 0.045g of TSQ and 5 wt% of BP2Dissolving the mixture of O and NMP (V/V is 9:1) at 80 ℃ under magnetic stirring to obtain spinning solution 2;
adding the spinning solution 1 and the spinning solution 2 into a shading injector 1 and a shading injector 2 of 10ml respectively, then alternately performing electrostatic spinning under the irradiation of ultraviolet light to prepare the nanofiber membrane with the sandwich structure, washing in ethanol and drying the obtained fiber membrane. Wherein, the spinning parameters of the spinning solution 1 are set as follows: spinning voltage is 17-19 kV, spinning speed is 2-3 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the spinning parameters of dope 2 were set as follows: the spinning voltage is 21-25 kV, the spinning speed is 0.5-0.6 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the illumination of an ultraviolet lamp at the receiver is 25mW/cm2. The thickness of the three layers is controlled to be 3.5:3:3.5 by controlling the spinning time.
The obtained organic-inorganic hybrid diaphragm is cut into a plurality of circular diaphragm sheets with the diameter of 19mm, and the circular diaphragm sheets are used for assembling a button cell (CR 2032).
When the button cell positive plate is prepared, the active material in the positive slurry adopts lithium iron phosphate (LiFePO)4) The adhesive is polyvinylidene fluoride (PVDF), the conductive agent is Super-P (SP), the mass ratio of the Super-P (SP) to the conductive agent is 8:1:1, and the solvent is N-methylpyrrolidone. After the positive slurry is prepared, the positive slurry is coated on an aluminum foil current collector by a scraper and is dried in a vacuum oven at the temperature of 110 ℃. And then cutting the dried pole piece into small round pieces with the diameter of 14mm for later use.
When the button cell is prepared, a lithium sheet is adopted as a negative electrode, and the diameter of the lithium sheet is 15.6 mm.
When the button cell is prepared, 1mol/L lithium hexafluorophosphate (LiPF) is adopted as electrolyte6) The solvent is Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC) and Ethylene Carbonate (EC), and the volume ratio of the ethyl methyl carbonate to the dimethyl carbonate to the ethylene carbonate is 1:1: 1.
The button cell is assembled in a glove box filled with argon (Ar), and the oxygen index and the moisture index in the glove box are controlled to be below 0.1ppm and 0.1ppm respectively.
Fig. 1 is a macro-photograph of the organic-inorganic hybrid separator prepared in this example, and it can be seen that the added electrolyte can be completely absorbed by the separator, indicating that the affinity of the separator is good, and the separator has no obvious curling phenomenon after imbibing liquid, indicating that the separator has excellent dimensional stability in the electrolyte.
Fig. 2 is a microscopic cross-sectional photograph of the organic-inorganic hybrid membrane prepared in this example, and it can be seen from the figure that the membrane is composed of three layers of PVDF-HFP, PVA, and PVDF-HFP, and the thickness is about 100 μm, further verifying that we successfully prepared the membrane with the sandwich structure.
Example 2
1.7g of PVDF-HFP was weighed and added to a mixed solution of 0.085g of VSQ, 0.080g of TSQ, and 0.5 wt% of BP in ACE and DMAc (V/V ═ 3:7), and dissolved completely under magnetic stirring to obtain a spinning dope 1; 0.9g of PVA was weighed out and added to H dissolved with 0.0112g of VSQ, 0.0112g of TSQ and 0.5 wt% of BP2Dissolving the mixture of O and NMP (V/V is 9:1) at 80 ℃ under magnetic stirring to obtain spinning solution 2;
mixing the spinning solution1 and 2 are respectively added into a shading injector 1 and a shading injector 2 of 10ml, and then the sandwich structure nanofiber membrane is prepared by alternative electrostatic spinning under the irradiation of ultraviolet light, and the obtained fiber membrane is washed in ethanol and dried. Wherein, the spinning parameters of the spinning solution 1 are set as follows: spinning voltage is 17-19 kV, spinning speed is 2-3 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the spinning parameters of dope 2 were set as follows: the spinning voltage is 21-25 kV, the spinning speed is 0.5-0.6 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the illumination of an ultraviolet lamp at the receiver is 25mW/cm2. Controlling the thickness of the three layers to be 3.5:3:3.5 by controlling the spinning time;
the resulting polymer separator was cut into circular separator sheets of 19mm diameter for assembly of button cells (CR 2032).
When the button cell positive plate is prepared, the active material in the positive slurry adopts lithium cobaltate (LiCoO)2) The binder is polyvinylidene fluoride (PVDF), the conductive agent is Super-P (SP), the mass ratio of the Super-P (SP) to the conductive agent is 8:1:1, and the solvent is N-methylpyrrolidone. After the positive slurry is prepared, the positive slurry is coated on an aluminum foil current collector by a scraper and is dried in a vacuum oven at the temperature of 110 ℃. And then cutting the dried pole piece into small round pieces with the diameter of 14mm for later use.
Fig. 3 is an interface impedance spectrum of the organic-inorganic hybrid membrane prepared in this example, and it can be seen from the graph that the membrane has a small charge transfer resistance and interface resistance, and at the same time, the bulk resistance is small, and the membrane has a relatively excellent lithium ion transport ability.
Fig. 4 is a Linear Sweep Voltammetry (LSV) curve of the organic-inorganic hybrid membrane prepared in this example, and it can be seen that the battery has an oxidation potential as high as 5.21V, thereby providing a possibility for application in high-voltage charging and discharging.
Example 3
1.7g of PVDF-HFP was weighed and added to a mixed solution of ACE and DMAc (V/V ═ 3:7) in which 0.17g of VSQ and 0.5 wt% of BP were dissolved, and dissolved completely under magnetic stirring to obtain a spinning solution 1; 0.9g of PVA was weighed into H dissolved with 45mg of VSQ and 0.5 wt% of BP2Mixed solution of O and NMP (V/V ═ 9:1)Dissolving the mixture completely at 80 ℃ under magnetic stirring to obtain spinning solution 2;
adding the spinning solution 1 and the spinning solution 2 into a shading injector 1 and a shading injector 2 of 10ml respectively, then alternately performing electrostatic spinning under the irradiation of ultraviolet light to prepare the nanofiber membrane with the sandwich structure, washing in ethanol and drying the obtained fiber membrane. Wherein, the spinning parameters of the spinning solution 1 are set as follows: spinning voltage is 17-19 kV, spinning speed is 2-3 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the spinning parameters of dope 2 were set as follows: the spinning voltage is 21-25 kV, the spinning speed is 0.5-0.6 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the illumination of an ultraviolet lamp at the receiver is 25mW/cm2. Controlling the thickness of the three layers to be 1:1:1 by controlling the spinning time;
the resulting polymer separator was cut into circular separator sheets of 19mm diameter for assembly of button cells (CR 2032).
When the button cell positive plate is prepared, the active material in the positive slurry adopts lithium iron phosphate (LiFePO)4) The binder is polyvinylidene fluoride (PVDF), the conductive agent is Super-P (SP), the mass ratio of the Super-P (SP) to the conductive agent is 8:1:1, and the solvent is N-methylpyrrolidone. After the positive slurry is prepared, the positive slurry is coated on an aluminum foil current collector by a scraper and is dried in a vacuum oven at the temperature of 110 ℃. And then cutting the dried pole piece into small round pieces with the diameter of 14mm for later use.
Fig. 5 is a rate performance graph of the lithium iron phosphate full battery prepared in this example, and it can be seen that the specific capacity of 95mAh/g is still maintained when the rate of the battery is increased from 0.5C to 5C, and the specific capacity of 160mAh/g is still maintained when the rate is decreased to 0.5C.
Example 4
1.6g of PVDF-HFP was weighed and added to a mixed solution of ACE and DMAc in which 0.32g of VSQ, 0.30g of TSQ and 0.5 wt% of BP were dissolved (V/V ═ 3:7), and dissolved completely under magnetic stirring to obtain a spinning solution 1; 0.8g of PVA was weighed out and added to H dissolved with 0.022g of VSQ, 0.018g of TSQ and 1 wt% of BP2Dissolving the mixture of O and NMP (V/V is 9:1) at 80 ℃ under magnetic stirring to obtain spinning solution 2;
adding the spinning solution 1 and the spinning solution 2 into a shading injector 1 and a shading injector 2 of 10ml respectively, then alternately performing electrostatic spinning under the irradiation of ultraviolet light to prepare the nanofiber membrane with the sandwich structure, washing in ethanol and drying the obtained fiber membrane. Wherein, the spinning parameters of the spinning solution 1 are set as follows: spinning voltage is 17-19 kV, spinning speed is 2-3 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the spinning parameters of dope 2 were set as follows: the spinning voltage is 21-25 kV, the spinning speed is 0.5-0.6 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the illumination of an ultraviolet lamp at the receiver is 25mW/cm2. Controlling the thickness of the three layers to be 3.5:3:3.5 by controlling the spinning time;
the resulting polymer separator was cut into circular separator sheets of 19mm diameter for assembly of button cells (CR 2032).
When the button cell positive plate is prepared, the active material in the positive slurry adopts lithium iron phosphate (LiFePO)4) The adhesive is polyvinylidene fluoride (PVDF), the conductive agent is Super-P (SP), the mass ratio of the Super-P (SP) to the conductive agent is 9:0.5:0.5, and the solvent is N-methylpyrrolidone. After the positive slurry is prepared, the positive slurry is coated on an aluminum foil current collector by a scraper and is dried in a vacuum oven at the temperature of 110 ℃. And then cutting the dried pole piece into small round pieces with the diameter of 14mm for later use.
Fig. 6 is a cycle performance diagram of the lithium iron phosphate full battery prepared in this embodiment at 2C, and it can be known from the diagram that, when the charge-discharge rate is 2C, the battery can still maintain a specific capacity of 125mAh/g after 200 cycles, and the capacity retention rate is as high as 99.6%, indicating that the battery has excellent cycle performance, which further illustrates that, in use, the growth of lithium dendrite is greatly inhibited.
Example 5
1.7g of PVDF-HFP was weighed and added to a mixed solution of 0.090g of MASQ, 0.080g of TSQ, and 0.5 wt% of BP in ACE and DMAc (V/V ═ 3:7), and dissolved completely under magnetic stirring to obtain a spinning solution 1; 0.9g of PVA was weighed into H dissolved with 45mg of VSQ and 3 wt% of BP2Dissolving the mixture of O and NMP (V/V is 9:1) at 80 ℃ under magnetic stirring to obtain spinning solution 2;
adding the spinning solution 1 and the spinning solution 2 into a shading injector 1 and a shading injector 2 of 10ml respectively, then alternately performing electrostatic spinning under the irradiation of ultraviolet light to prepare the nanofiber membrane with the sandwich structure, washing in ethanol and drying the obtained fiber membrane. Wherein, the spinning parameters of the spinning solution 1 are set as follows: spinning voltage is 17-19 kV, spinning speed is 2-3 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the spinning parameters of dope 2 were set as follows: the spinning voltage is 21-25 kV, the spinning speed is 0.5-0.6 ml/h, and the distance from the needle point to the receiver is set to be 15 cm; the illumination of an ultraviolet lamp at the receiver is 25mW/cm2. The thickness of the three layers is controlled to be 3.5:3:3.5 by controlling the spinning time.
The obtained organic-inorganic hybrid diaphragm is cut into a plurality of circular diaphragm sheets with the diameter of 19mm, and the circular diaphragm sheets are used for assembling a button cell (CR 2032).
When the button cell positive plate is prepared, the active material in the positive slurry adopts lithium iron phosphate (LiFePO)4) The binder is polyvinylidene fluoride (PVDF), the conductive agent is Super-P (SP), the mass ratio of the Super-P (SP) to the conductive agent is 8:1:1, and the solvent is N-methylpyrrolidone. After the positive slurry is prepared, the positive slurry is coated on an aluminum foil current collector by a scraper and is dried in a vacuum oven at the temperature of 110 ℃. And then cutting the dried pole piece into small round pieces with the diameter of 14mm for later use.
When the button cell is prepared, a lithium sheet is adopted as a negative electrode, and the diameter of the lithium sheet is 15.6 mm.
When the button cell is prepared, 1mol/L lithium hexafluorophosphate (LiPF) is adopted as electrolyte6) The solvent is Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC) and Ethylene Carbonate (EC), and the volume ratio of the ethyl methyl carbonate to the dimethyl carbonate to the ethylene carbonate is 1:1: 1.
The button cell is assembled in a glove box filled with argon (Ar), and the oxygen index and the moisture index in the glove box are controlled to be below 0.1ppm and 0.1ppm respectively.
Fig. 7 is a graph of the cycle performance at 5C of the lithium iron phosphate full battery prepared in this example, and it can be seen from the graph that, at the charge and discharge rate of 5C, the battery has an average specific capacity of 80mAh/g during 200 cycles, and the coulomb efficiency is as high as 98%, indicating that the battery has excellent cycle performance, which further illustrates that, in use, the growth of lithium dendrites is greatly inhibited.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. An organic-inorganic hybrid diaphragm of a lithium metal battery is characterized by comprising two polyvinylidene fluoride-hexafluoropropylene-based nanofiber layers and a polyvinyl alcohol-based nanofiber layer positioned between the two polyvinylidene fluoride-hexafluoropropylene-based nanofiber layers;
the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer is a three-dimensional network generated after a click reaction of polyvinylidene fluoride-hexafluoropropylene, mercaptopropyl cage-type silsesquioxane and double-bond-terminated cage-type silsesquioxane under initiation of a photoinitiator;
the polyvinyl alcohol-based nanofiber layer is a three-dimensional network generated after a click reaction is carried out on polyvinyl alcohol, mercaptopropyl cage-type silsesquioxane and double-bond-terminated cage-type silsesquioxane under the initiation of a photoinitiator.
2. The organic-inorganic hybrid membrane of the lithium metal battery as claimed in claim 1, wherein the double-bond-terminated cage-type silsesquioxane is octavinyl cage-type silsesquioxane or octamethacrylate-based cage-type silsesquioxane.
3. The organic-inorganic hybrid separator for lithium metal batteries according to claim 1, wherein said photoinitiator is benzophenone.
4. The organic-inorganic hybrid membrane of the lithium metal battery as claimed in claim 1, wherein the mass ratio of the total mass of the mercaptopropyl cage-type silsesquioxane and the double-bond-terminated cage-type silsesquioxane to the mass of polyvinylidene fluoride-hexafluoropropylene in the polyvinylidene fluoride-hexafluoropropylene nanofiber layer is 0.01-0.2: 1.
5. The organic-inorganic hybrid membrane of the lithium metal battery as claimed in claim 1, wherein the molar ratio of the double-bond-terminated cage-type silsesquioxane to the mercaptopropyl cage-type silsesquioxane in the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer is 1: 0.2-1.
6. The organic-inorganic hybrid membrane of the lithium metal battery as claimed in claim 1, wherein in the polyvinyl alcohol-based nanofiber layer, the molar ratio of double-bond-terminated cage-type silsesquioxane to mercaptopropyl cage-type silsesquioxane is 1: 0.2-1; the mass ratio of the total mass of the double-bond-terminated cage-type silsesquioxane to the mass of the mercaptopropyl cage-type silsesquioxane to the polyvinyl alcohol is 0.1-5%.
7. The organic-inorganic hybrid membrane of the lithium metal battery as claimed in claim 1, wherein the amount of the photoinitiator added in the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer is 0.5-5% of the total mass of the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer;
in the polyvinyl alcohol group nano fiber layer, the addition amount of the photoinitiator is 0.5-5% of the total mass of the polyvinyl alcohol group nano fiber layer.
8. The organic-inorganic hybrid separator of a lithium metal battery according to claim 1, wherein the thickness of the organic-inorganic hybrid separator is 50 to 100 μm, and the thickness ratio of the polyvinylidene fluoride-hexafluoropropylene-based nanofiber layer to the polyvinyl alcohol-based nanofiber layer is 1:0.6 to 2.
9. A method for preparing an organic-inorganic hybrid separator for a lithium metal battery according to any one of claims 1 to 8, comprising the steps of:
preparing a polyvinylidene fluoride-hexafluoropropylene-based spinning solution: dissolving mercaptopropyl cage-type silsesquioxane, double-bond-terminated cage-type silsesquioxane and a photoinitiator in a first solvent, adding polyvinylidene fluoride-hexafluoropropylene after complete dissolution, and stirring until complete dissolution to obtain polyvinylidene fluoride-hexafluoropropylene-based spinning solution;
preparing a polyvinyl alcohol-based spinning solution: dissolving mercaptopropyl cage-type silsesquioxane, double-bond-terminated cage-type silsesquioxane and a photoinitiator in a second solvent, adding polyvinyl alcohol solid, and completely dissolving to obtain polyvinyl alcohol-based spinning solution;
preparing a nanofiber membrane: respectively adding the polyvinylidene fluoride-hexafluoropropylene-based spinning solution and the polyvinyl alcohol-based spinning solution into an injector, then alternately performing electrostatic spinning under the irradiation of ultraviolet light to prepare the nanofiber membrane with the sandwich structure, washing in ethanol and drying to obtain the organic-inorganic hybrid membrane.
10. A lithium metal battery comprising the organic-inorganic hybrid separator for a lithium metal battery according to any one of claims 1 to 8.
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