CN116247292A - Porous composite gel electrolyte, preparation method thereof and semisolid lithium ion battery - Google Patents

Porous composite gel electrolyte, preparation method thereof and semisolid lithium ion battery Download PDF

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CN116247292A
CN116247292A CN202310450134.2A CN202310450134A CN116247292A CN 116247292 A CN116247292 A CN 116247292A CN 202310450134 A CN202310450134 A CN 202310450134A CN 116247292 A CN116247292 A CN 116247292A
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gel electrolyte
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porous composite
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周天易
王晓龙
徐若晨
刘明义
黄茹玲
孙周婷
张江涛
王佳运
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Huaneng Clean Energy Research Institute
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a porous composite gel electrolyte, a preparation method thereof and a semisolid lithium ion battery. The porous composite gel electrolyte provided by the invention comprises poly (vinylidene fluoride-hexafluoropropylene), poly (methyl methacrylate) and basalt fiber. The porous composite gel electrolyte combines the poly (vinylidene fluoride-hexafluoropropylene) and the poly (methyl methacrylate) to reduce the crystallinity of a polymer matrix, simultaneously improves the interface problem of the poly (vinylidene fluoride-hexafluoropropylene) and an electrode, further introduces basalt fibers, effectively improves the mechanical strength and the thermal stability of the gel electrolyte, reduces the crystallinity of the polymer matrix and improves the conductivity of the electrolyte.

Description

Porous composite gel electrolyte, preparation method thereof and semisolid lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a porous composite gel electrolyte, a preparation method thereof and a semisolid lithium ion battery.
Background
With the vigorous development of the energy storage industry in recent years, the requirement on the safety of lithium ion batteries is also increasingly promoted. The polymer gel electrolyte has higher ionic conductivity close to that of the liquid electrolyte, so that electrolyte leakage is effectively reduced, the safety of the lithium ion battery is greatly ensured, and the polymer gel electrolyte has excellent application prospect.
Poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and poly (methyl methacrylate) (PMMA) are of great interest for their good performance in the selection of polymer matrix materials. PVDF-HFP is used as an excellent material, has the advantages of corrosion resistance, temperature resistance, easy film formation, high dielectric constant and the like, the crystallinity of the PVDF-HFP is far lower than that of similar PVDF, and the gel polymer electrolyte prepared by PVDF-HFP can show higher room temperature conductivity. The carbonyl group of PMMA has good compatibility with electrolyte, so that the wettability of the blend diaphragm to the electrolyte can be improved, and the PMMA has good interface stability to a lithium electrode, but the gel has poor mechanical strength and poor thermal stability after activation.
Therefore, there is a need to study new polymer gel electrolytes to meet the needs of the energy storage industry development.
Disclosure of Invention
The present invention has been made based on the findings and knowledge of the inventors regarding the following facts and problems:
CN110943258A provides a PVDF-HFP composite lignocellulose gel polymer electrolyte membrane, which combines excellent electrochemical properties of lignocellulose and PVDF-HFP, and at the same time, the mechanical strength of the composite membrane is improved; however, PVDF-HFP has poor contact with electrode materials and has interface problems.
CN110010829B provides a PVDF-HFP/PMMA/CMC composite membrane, which comprises a PVDF-HFP/PMMA film and a CMC film laminated, prepared by direct coating and drying, and has an ionic conductivity of 4.388mS/cm. However, the film lacks the introduction of high-strength inorganic filler, so that its mechanical properties are slightly insufficient, and it is prepared by a direct coating and drying method, which is disadvantageous for forming a porous structure.
The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, the embodiment of the invention provides the porous composite gel electrolyte, which combines the poly (vinylidene fluoride-hexafluoropropylene) and the poly (methyl methacrylate) to reduce the crystallinity of a polymer matrix, simultaneously improves the interface problem of the poly (vinylidene fluoride-hexafluoropropylene) and an electrode, further introduces basalt fibers, effectively improves the mechanical strength and the thermal stability of the gel electrolyte, reduces the crystallinity of the polymer matrix and improves the conductivity of the electrolyte.
The porous composite gel electrolyte of the embodiment of the invention comprises: poly (vinylidene fluoride-hexafluoropropylene), poly (methyl methacrylate), and basalt fiber.
The porous composite gel electrolyte provided by the embodiment of the invention has the advantages and technical effects that 1, in the embodiment of the invention, poly (vinylidene fluoride-hexafluoropropylene) and poly (methyl methacrylate) are simultaneously introduced, and the two are used in a composite manner, so that the problems of poor interface contact between the poly (vinylidene fluoride-hexafluoropropylene) and an electrode, poor mechanical strength and poor thermal stability of the activated poly (methyl methacrylate) gel can be solved, the crystallinity of a polymer film is effectively improved, and the electrochemical performance of the gel electrolyte and the interface stability of the electrode are enhanced; 2. in the embodiment of the invention, the mechanical strength of the gel electrolyte is further enhanced by introducing basalt fibers, the crystallinity of the polymer matrix is reduced, the conductivity of the gel electrolyte is improved, and the thermal stability of the gel electrolyte is also improved; 3. in the embodiment of the invention, the gel electrolyte with the porous structure can absorb more electrolyte, and the gel electrolyte with the porous structure is used forShould have more free Li + The quantity of the electrolyte can lead the composite gel electrolyte to have larger ionic conductivity.
In some embodiments, the mass ratio of poly (vinylidene fluoride-hexafluoropropylene) to poly (methyl methacrylate) is 20:1 to 1:20.
In some embodiments, the basalt fiber has a mass of 10 to 100% of the sum of the mass of poly (vinylidene fluoride-hexafluoropropylene) and poly (methyl methacrylate).
In some embodiments, the basalt fibers comprise at least one of chopped basalt fiber filaments, ground basalt fiber powders, and fine basalt fiber powders; preferably, the length of the basalt fiber chopped filaments is more than 1mm, the grain size of the basalt fiber coarse powder is 100-1 mm, and the grain size of the basalt fiber fine powder is 20-100 μm.
In some embodiments, lithium ion battery electrolyte is also included in the porous composite gel electrolyte.
The embodiment of the invention also provides a preparation method of the porous composite gel electrolyte, which comprises the following steps:
(1) Dissolving poly (vinylidene fluoride-hexafluoropropylene), poly (methyl methacrylate), basalt fiber and a pore-forming agent in a solvent to obtain a coating liquid;
(2) Coating the coating liquid obtained in the step (1) on a substrate, and then soaking the substrate coated with the coating liquid in deionized water for phase separation and film formation to obtain a polymer film;
(3) And (3) drying the polymer film obtained in the step (2), and soaking the polymer film in electrolyte to obtain the porous composite gel electrolyte.
The preparation method of the porous gel electrolyte provided by the embodiment of the invention has the advantages and technical effects that 1, according to the method provided by the embodiment of the invention, basalt fibers, poly (vinylidene fluoride-hexafluoropropylene) and poly (methyl methacrylate) are dissolved in a solvent, so that the basalt fibers are uniformly dispersed in a polymer matrix, and the interface problem is effectively improved; 2. according to the method provided by the embodiment of the invention, the pore-forming agent is added in the preparation process, so that the porosity of the polymer film can be increased, the liquid absorption rate of the gel electrolyte is further improved, and the ionic conductivity of the gel electrolyte is improved; 3. the method provided by the embodiment of the invention has the advantages of simple preparation process, easiness in operation and convenience in popularization and application in industrial production.
In some embodiments, in step (1), the solvent comprises at least one of DMF, NMP, DMSO, the solvent having a mass that is 2 to 10 times the sum of the masses of poly (vinylidene fluoride-hexafluoropropylene) and poly (methyl methacrylate); and/or the pore-forming agent is polyethylene oxide, and the mass of the pore-forming agent is 2-10% of the sum of the mass of poly (vinylidene fluoride-hexafluoropropylene) and the mass of poly (methyl methacrylate).
In some embodiments, in the step (2), the soaking time in the deionized water is 2 to 12 hours.
In some embodiments, in the step (3), the time of immersing in the electrolyte is 0.1 to 10 hours.
The embodiment of the invention also provides a semi-solid lithium ion battery, which comprises the porous composite gel electrolyte or the porous composite gel electrolyte prepared by the method.
The semi-solid lithium ion battery provided by the embodiment of the invention has all technical characteristics of the porous composite gel electrolyte provided by the embodiment of the invention, so that the semi-solid lithium ion battery provided by the embodiment of the invention has all advantages and technical effects provided by the porous composite gel electrolyte provided by the embodiment of the invention, and the description is omitted herein.
Drawings
FIG. 1 is a graph showing the cycle performance of a lithium ion battery assembled from the electrolyte prepared in example 1, a graphite negative electrode, and a lithium iron phosphate positive electrode;
fig. 2 is a cycle performance chart of a lithium ion battery assembled with a graphite negative electrode and a lithium iron phosphate positive electrode of the electrolyte prepared in comparative example 1.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
The porous composite gel electrolyte of the embodiment of the invention comprises: poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), poly (methyl methacrylate) (PMMA), and basalt fiber.
According to the porous composite gel electrolyte provided by the embodiment of the invention, PVDF-HFP and PMMA are introduced simultaneously, and the problems of poor contact between PVDF-HFP and an electrode interface, poor mechanical strength and poor thermal stability of the PMMA gel after activation can be solved by the composite use of the PVDF-HFP and the PMMA, so that the crystallinity of a polymer film is effectively improved, and the electrochemical performance of the gel electrolyte and the interface stability of an electrode are enhanced; the mechanical strength of the gel electrolyte is further enhanced by introducing basalt fibers, the crystallinity of the polymer matrix is reduced, the conductivity of the gel electrolyte is improved, and the thermal stability of the gel electrolyte is improved; gel electrolytes with porous structures are able to absorb more electrolyte and correspondingly have more free Li + The quantity of the electrolyte can lead the composite gel electrolyte to have larger ionic conductivity.
In some embodiments, preferably, the PVDF-HFP and PMMA are present in a mass ratio of 20:1 to 1:20. Further preferably, the mass ratio of the PVDF-HFP to the PMMA is 12:1-4:1.
In the implementation of the invention, the dosage ratio of PVDF-HFP and PMMA is optimized, so that the porous structure formed by PVDF-HFP and the electrolyte wettability of PMMA are enabled to have good synergistic effect, and the comprehensive performance of gel electrolyte is improved; if the PVDF-HFP is used too much, the improvement of the interface contact performance of the electrolyte and the electrode is not facilitated, and if the PVDF-HFP is used too much, the improvement of the mechanical strength of the electrolyte is not facilitated.
In some embodiments, preferably, the mass of the basalt fiber is 10 to 100% of the sum of the PVDF-HFP and PMMA masses. Further preferably, the mass of the basalt fiber is 30 to 50% of the sum of the mass of the PVDF-HFP and PMMA.
In the embodiment of the invention, the dosage of basalt fiber is optimized, so that the mechanical property and the thermal stability of the gel electrolyte can be effectively improved; if the dosage of basalt fiber is too small, the improvement of the mechanical property and the thermal stability of the gel electrolyte is limited, and if the dosage of basalt fiber is too large, the phenomenon of agglomeration in a polymer matrix can occur, but the improvement of the mechanical property is unfavorable.
In some embodiments, preferably, the basalt fibers comprise at least one of chopped basalt fiber filaments, chopped basalt fiber powder, and fine basalt fiber powder; preferably, the length of the basalt fiber chopped filaments is more than 1mm, the grain size of the basalt fiber coarse powder is 100-1 mm, and the grain size of the basalt fiber fine powder is 20-100 μm. Further preferably, the basalt fiber is a basalt fiber coarse powder.
In some embodiments, preferably, lithium ion battery electrolyte is also included in the porous composite gel electrolyte.
The embodiment of the invention also provides a preparation method of the porous composite gel electrolyte, which comprises the following steps:
(1) Dissolving PVDF-HFP, PMMA, basalt fiber and a pore-forming agent in a solvent to obtain a coating liquid;
(2) Coating the coating liquid obtained in the step (1) on a substrate, and then soaking the substrate coated with the coating liquid in deionized water for phase separation and film formation to obtain a polymer film;
(3) And (3) drying the polymer film obtained in the step (2), and soaking the polymer film in electrolyte to obtain the porous composite gel electrolyte.
According to the preparation method of the porous gel electrolyte, basalt fibers, PVDF-HFP and PMMA are dissolved in a solvent, so that the basalt fibers are uniformly dispersed in a polymer matrix, and the interface problem is effectively improved; the pore-forming agent is added in the preparation process, so that the porosity of the polymer film can be increased, the liquid absorption rate of the gel electrolyte is further improved, and the ionic conductivity of the gel electrolyte is improved; the preparation process is simple, easy to operate and convenient to popularize and apply in industrial production.
In some embodiments, preferably, in the step (1), the solvent comprises at least one of DMF, NMP, DMSO, and the mass of the solvent is 2 to 10 times of the sum of the mass of PVDF-HFP and PMMA; and/or the pore-forming agent is polyethylene oxide (PEO), and the mass of the pore-forming agent is 2-10% of the sum of PVDF-HFP and PMMA.
In the embodiment of the invention, the solvent is preferably used in an amount which can promote the dissolution of PVDF-HFP, PMMA and basalt fibers to form a uniform solution; PEO is preferably used as a pore-forming agent, and is different from other liquid pore-forming agents such as n-butanol, the PEO is slowly dissolved in the process of soaking in deionized water for phase separation and film forming, so that the formed pore structure is more uniform, and the problem of penetrating macropores or collapse of the pore structure caused by a large amount of rapid dissolution of the pore-forming agent is avoided; the PEO dosage is further optimized, so that a porous electrolyte is formed, the liquid absorption rate of the polymer film is further improved, and the ion conductivity of the gel electrolyte is improved.
In some embodiments, preferably, the step (1) further includes stirring to obtain a coating solution, and performing ultrasonic oscillation or vacuum assisted bubble removal on the coating solution. Further preferably, the stirring treatment is performed for a period of 1 to 10 hours. Still preferably, the stirring treatment is carried out for a period of 4 to 6 hours.
In the embodiment of the invention, the uniform coating liquid can be formed by stirring treatment, and the bubble content in the polymer film can be reduced by bubble removal treatment, so that the defects are reduced, and the quality of the prepared gel electrolyte is further ensured.
In some embodiments, preferably, in the step (2), the soaking time in the deionized water is 2 to 12 hours. Further preferably, the soaking time in the deionized water is 5 to 8 hours.
In the embodiment of the invention, the polymer film is separated from the glass plate by soaking in deionized water, preferably, the soaking time in the deionized water can ensure that the organic solvent and the PEO pore-forming agent are completely dissolved out, and the impurity content in the gel electrolyte is reduced.
In some embodiments, preferably, in the step (3), the drying treatment includes drying the surface of the polymer film by wiping off water, and then drying the polymer film in an oven at 40-60 ℃ for 2-24 hours. Further preferably, the drying time is 10 to 24 hours.
In some embodiments, preferably, in the step (3), the time of soaking in the electrolyte is 0.1 to 10 hours. Further preferably, the soaking time in the electrolyte is 0.5 to 2 hours.
The embodiment of the invention also provides a semi-solid lithium ion battery, which comprises the porous composite gel electrolyte or the porous composite gel electrolyte prepared by the method.
The semisolid lithium ion battery provided by the embodiment of the invention has all the technical characteristics of the porous composite gel electrolyte provided by the embodiment of the invention, so that all the advantages and technical effects brought by the porous composite gel electrolyte provided by the embodiment of the invention are not repeated here.
In some embodiments, preferably, the semi-solid lithium ion battery further comprises a positive electrode and a negative electrode. Further preferably, the positive electrode includes at least one of lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, and lithium cobalt oxide; the negative electrode comprises at least one of graphite, biomass carbon, silicon carbon composite material and metallic lithium.
The technical scheme of the present invention is described in detail below with reference to specific embodiments and drawings.
Example 1
(1) Dissolving PVDF-HFP and PMMA in DMF solvent according to the mass ratio of 9:1, wherein the mass of the DMF solvent is 5 times of the total amount of PVDF-HFP and PMMA; adding 40% basalt fiber fine powder (based on the total mass of PVDF-HFP and PMMA); thereafter, 5% PEO (based on the total mass of PVDF-HFP and PMMA) was added as a pore former;
(2) Stirring the mixed solution obtained in the step (1) for 5 hours;
(3) Then carrying out ultrasonic oscillation to remove bubbles, and obtaining coating liquid;
(4) Coating the coating liquid obtained in the step (3) on a glass plate smoothly and uniformly; immersing the glass plate with the surface coated with the coating liquid into deionized water horizontally at a constant speed for phase separation and film formation, and immersing to enable the organic solvent and the PEO pore-forming agent to be completely dissolved out, wherein the immersing time is 6 hours;
(5) Taking out the polymer film in deionized water, lightly wiping off surface moisture, and putting the polymer film into a 50 ℃ oven for drying to completely remove the moisture, wherein the drying time is 12 hours;
(6) And (3) soaking the polymer film obtained in the step (5) in the electrolyte for 1h to enable the polymer film to fully absorb the electrolyte to form gel, wherein the soaking time is 1h. Finally obtaining the PVDF-HFP/PMMA/basalt fiber porous composite gel electrolyte.
Examples 2 to 6
The preparation methods of examples 2 to 6 are the same as in example 1, except that: the PVDF-HFP to PMMA ratio in step (1) was adjusted to 18:1, 12:1, 6:1, 4:1, 1:1, respectively.
Examples 7 to 10
Examples 7 to 10 were prepared in the same manner as in example 1, except that: and (3) adjusting the addition amount of the basalt fiber in the step (1) to 10%, 30%, 50% and 100% respectively.
Examples 11 to 13
The preparation methods of examples 11 to 13 are the same as in example 1, except that: the PEO addition amounts in step (1) were adjusted to 1%, 2% and 10%, respectively.
Examples 14 to 17
The preparation methods of examples 14 to 17 were the same as in example 1, except that: and (3) respectively adjusting the soaking time in deionized water after the phase separation film forming in the step (4) to be 1h, 5h, 8h and 15h.
Examples 18 to 20
The preparation methods of examples 18 to 20 were the same as in example 1, except that: and (3) respectively adjusting the drying time of the polymer film in the step (5) to 10h, 24h and 30h.
Examples 21 to 24
The preparation methods of examples 21 to 24 were the same as in example 1, except that: and (3) respectively adjusting the soaking time of the polymer film in the electrolyte in the step (5) to 0.1h, 0.5h, 2h and 10h.
Comparative example 1
The preparation method of this comparative example is the same as in example 1, except that: the amount of PEO added in step (1) was adjusted to 20%.
Comparative example 2
The preparation method of this comparative example is the same as in example 1, except that: replacing basalt fibers in the step (1) with nano silicon dioxide.
Comparative example 3
The preparation method of this comparative example is the same as in example 1, except that: and (3) replacing the PEO pore-forming agent in the step (1) with n-butanol.
The electrolyte prepared in example 1 and comparative example 1 was assembled with an ink negative electrode and a lithium iron phosphate positive electrode to form a lithium ion battery, and the cycle performance was tested under the following conditions: performing a cyclic charge and discharge test under a current multiplying power of 0.5 ℃; the test results are shown in fig. 1 and 2.
The gel electrolytes prepared in examples 1 to 24 and comparative examples 1 to 3 were tested for their properties under the following mechanical properties: room temperature tensile testing; the test results are shown in the following tables, respectively:
table 1 PVDF-HFP in different proportions: effect of PMMA on gel electrolyte properties
Figure BDA0004197204750000071
According to examples 1 to 6, it can be seen that as the ratio of PMMA relative to PVDF-HFP increases, the gel electrolyte shows a tendency to increase and decrease in the liquid absorption, and the ionic conductivity shows the same change with the liquid absorption, which is the result of the synergistic effect of the porous structure formed by PVDF-HFP and the excellent electrolyte wettability of PMMA. In addition, if the PMMA content is too high, the tensile strain of the gel electrolyte is reduced, that is, toughness is lost to some extent.
TABLE 2 Effect of different basalt fiber contents on gel electrolyte Performance
Figure BDA0004197204750000072
According to the data of the table, as the content of basalt fibers increases, the liquid absorption rate of the gel electrolyte gradually decreases, which is caused by the fact that basalt fibers block part of pore structures, and the change rule of the ion conductivity is basically consistent with the change of the liquid absorption rate; the reason why the ion conductivity of example 9 is relatively higher than that of example 8 is that: the addition of basalt fiber can reduce the crystallinity of the polymer to a certain extent so as to improve the ion conductivity, and the influence of the crystallinity reduction on the ion conductivity is reflected under the condition of similar liquid absorption. In addition, the content of basalt fiber is too low, and the mechanical strength of the gel electrolyte is improved to a limited extent; the high basalt fiber content can cause a certain loss of toughness of the gel electrolyte.
TABLE 3 Effect of varying PEO pore former content on gel electrolyte performance
Figure BDA0004197204750000081
As can be seen from the data in table 3, too little amount of pore-forming agent results in lower porosity of the prepared gel electrolyte, and thus lower ionic conductivity; as the content of PEO pore-forming agent increases, the prepared gel electrolyte increases the liquid absorption rate and the ion conductivity due to the increase of the porosity; however, when the amount of PEO pore former is too large, the pore structure of the gel electrolyte becomes too large, which reduces the mechanical properties of the gel electrolyte.
TABLE 4 influence of different phase separation soak times on gel electrolyte performance
Figure BDA0004197204750000082
Figure BDA0004197204750000091
As can be seen from the data in table 4, the phase separation soak time was too short, the solvent and PEO pore-forming agent did not completely dissolve, the undissolved PEO filled the pores, and the imbibition rate was somewhat reduced, however, the residual solvent and pore-forming agent also somewhat reduced the crystallinity of the gel electrolyte, and thus the ionic conductivity of example 14 was slightly higher than that of the gel electrolyte at a similar imbibition rate. The soaking time for phase separation is too long and does not have a significant effect on the gel electrolyte performance, as the solvent and PEO pore-forming agent have completely dissolved out.
TABLE 5 influence of different drying times on gel electrolyte properties
Figure BDA0004197204750000092
As can be seen from the data in table 5, the drying time is too long, and the water is completely removed, so that the production efficiency is reduced and the time cost of industrial production is increased although the gel electrolyte performance is not significantly affected.
TABLE 6 influence of different electrolyte soaking times on gel electrolyte performance
Figure BDA0004197204750000093
Figure BDA0004197204750000101
As can be seen from the data of table 6, the soaking time in the electrolyte is shorter, so that the liquid absorption of the gel electrolyte is reduced, and the ionic conductivity is reduced; the soaking time in the electrolyte is too long, and the gel electrolyte performance is not obviously affected, because the electrolyte is completely soaked, the liquid absorption rate cannot be increased after the time is prolonged, but the production efficiency is reduced, and the time cost of industrial production is increased.
TABLE 7
Figure BDA0004197204750000102
As can be seen from the data of table 7, in comparative example 2, the basalt fiber was replaced with the nano silica material having a smaller size, which was easily agglomerated, thus resulting in inferior mechanical strength as compared with the gel electrolyte to which the basalt fiber was added, and the smaller size was filled into the pore structure, thus resulting in a decrease in the liquid absorption and thus in the ion conductivity. In comparative example 3, after the pore-forming agent was changed from PEO to liquid n-butanol, the dissolution rate of n-butanol was increased during the phase separation, so that the uniformity of the pore structure was deteriorated, and collapse and shrinkage of part of the pore channels were easily occurred, thus lowering the liquid absorption rate and the mechanical strength of the electrolyte membrane.
For purposes of this disclosure, the terms "one embodiment," "some embodiments," "example," "a particular example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While the above embodiments have been shown and described, it should be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations of the above embodiments may be made by those of ordinary skill in the art without departing from the scope of the invention.

Claims (10)

1. A porous composite gel electrolyte comprising: poly (vinylidene fluoride-hexafluoropropylene), poly (methyl methacrylate), and basalt fiber.
2. The porous composite gel electrolyte of claim 1, wherein the mass ratio of poly (vinylidene fluoride-hexafluoropropylene) to poly (methyl methacrylate) is 20:1 to 1:20.
3. The porous composite gel electrolyte according to claim 1 or 2, wherein the mass of the basalt fiber is 10 to 100% of the sum of the mass of the poly (vinylidene fluoride-hexafluoropropylene) and the poly (methyl methacrylate).
4. The porous composite gel electrolyte of claim 3 wherein the basalt fibers comprise at least one of chopped basalt fiber filaments, and fine basalt fiber powder; preferably, the length of the basalt fiber chopped filaments is more than 1mm, the grain size of the basalt fiber coarse powder is 100-1 mm, and the grain size of the basalt fiber fine powder is 20-100 μm.
5. The porous composite gel electrolyte of claim 1, further comprising a lithium ion battery electrolyte.
6. The method for producing a porous composite gel electrolyte according to any one of claims 1 to 5, comprising the steps of:
(1) Dissolving poly (vinylidene fluoride-hexafluoropropylene), poly (methyl methacrylate), basalt fiber and a pore-forming agent in a solvent to obtain a coating liquid;
(2) Coating the coating liquid obtained in the step (1) on a substrate, and then soaking the substrate coated with the coating liquid in deionized water for phase separation and film formation to obtain a polymer film;
(3) And (3) drying the polymer film obtained in the step (2), and soaking the polymer film in electrolyte to obtain the porous composite gel electrolyte.
7. The method for producing a porous composite gel electrolyte according to claim 6, wherein in the step (1), the solvent includes at least one of DMF, NMP, DMSO, and the mass of the solvent is 2 to 10 times of the sum of the mass of poly (vinylidene fluoride-hexafluoropropylene) and the mass of poly (methyl methacrylate); and/or the pore-forming agent is polyethylene oxide, and the mass of the pore-forming agent is 2-10% of the sum of the mass of poly (vinylidene fluoride-hexafluoropropylene) and the mass of poly (methyl methacrylate).
8. The method of preparing a porous composite gel electrolyte according to claim 6, wherein in the step (2), the time of immersing in the deionized water is 2 to 12 hours.
9. The method of preparing a porous composite gel electrolyte according to claim 6, wherein in the step (3), the time of immersing in the electrolyte is 0.1 to 10 hours.
10. A semi-solid lithium ion battery comprising the porous composite gel electrolyte of any one of claims 1 to 5 or the porous composite gel electrolyte produced by the method of any one of claims 6 to 9.
CN202310450134.2A 2023-04-24 2023-04-24 Porous composite gel electrolyte, preparation method thereof and semisolid lithium ion battery Pending CN116247292A (en)

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