KR20230090763A - Gel electrolyte for lithium secondary battery and producing method thereof - Google Patents

Abstract

The present invention relates to a gel electrolyte for a lithium secondary battery obtained by gelating a liquid electrolyte using only inorganic particles without additional components such as a crosslinking agent and a polymer, and a method for preparing the same.

Description

Gel electrolyte for lithium secondary battery and its manufacturing method

The present invention relates to a gel electrolyte for a lithium secondary battery obtained by gelating a liquid electrolyte using only inorganic particles without additional components such as a crosslinking agent and a polymer, and a method for preparing the same.

In general, a gel polymer electrolyte used in a lithium secondary battery includes a linear polymer having a long main chain having a molecular weight of about 200,000 mol / g to 450,000 mol / g or more, such as PVdF, PVdF-HFP, PMMA, PAN, PEO. In order to improve the physical properties and ionic conductivity of the gel polymer electrolyte, a crosslinking agent is additionally added to chemically crosslink or a small amount of inorganic materials are added. However, the polymer as described above is electrochemically unstable during operation of the lithium secondary battery, which causes electrolyte depletion and cell deterioration.

Accordingly, Korean Patent Publication No. 10-2020-0137398 (Prior Art 1) proposed a gel electrolyte using only inorganic materials excluding polymers. The above prior art 1 is characterized by gelling the liquid electrolyte of a lithium-air battery by utilizing nano-sized silica having a large specific surface area. According to the prior art 1, deterioration of the electrolyte and the cell can be suppressed by removing oxygen radicals and polymers decomposed by high voltage. However, as in the prior art 1, when the liquid electrolyte is gelled using silica, stable operation is possible in an electrolyte that does not contain elemental fluorine. There is a problem that the cell is formed and the cell deteriorates.

Korean Patent Publication No. 10-2020-0137398

An object of the present invention is to provide a gel electrolyte for a lithium secondary battery that does not generate hydrogen fluoride and does not affect the performance of the electrolyte and the cell, and a manufacturing method thereof.

The object of the present invention is not limited to the object mentioned above. The objects of the present invention will become more apparent from the following description, and will be realized by means and combinations thereof set forth in the claims.

A gel electrolyte for a lithium secondary battery according to an embodiment of the present invention includes a liquid electrolyte; and a polymer provided in the liquid electrolyte and obtained by polymerizing inorganic particles including alumina and a reactive group bonded to the alumina.

The polymer has a three-dimensional network structure, the alumina is provided at the intersection of the network structure, and the liquid electrolyte can be gelated by the network structure.

The reactor may include a vinyl group.

The reactor may include at least one selected from the group consisting of methacrylate, styrene, acrylonitrile, and combinations thereof.

The specific surface area of the inorganic particles may be 50 m ² /g to 500 m ² /g.

The inorganic particle may have a particle size (D50) of 15 nm to 25 nm.

The liquid electrolyte may include an organic solvent; and a lithium salt containing elemental fluorine.

The lithium salt is a group consisting of LiPF ₆ , LiFSI (LiN(SO ₂ F) ₂ ), LiTFSI (LiN(SO ₂ CF ₃ ) ₂ ) and LiBETI (LiN(SO ₂ C ₂ F ₅ ) ₂ ) and combinations thereof. It may include at least one selected from.

A method of manufacturing a gel electrolyte for a lithium secondary battery according to an embodiment of the present invention includes preparing a starting solution including inorganic particles including alumina and a reactive group coupled to the alumina, and a liquid electrolyte; Injecting an initiator into the starting solution; and UV-treating or heat-treating the starting solution to prepare a polymer in which the inorganic particles are polymerized by the initiator.

The starting solution contains 80% to 90% by weight of a liquid electrolyte; and 10% to 20% by weight of the inorganic particles.

The initiator may include at least one UV initiator selected from the group consisting of α-hydroxyalkylphenone, α-aminoketone, camphorquinone, and combinations thereof.

The initiator may include at least one thermal initiator selected from the group consisting of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), and combinations thereof.

The initiator may be added in an amount of 1 to 2 parts by weight based on 100 parts by weight of the starting solution.

According to the present invention, it is possible to obtain a gel electrolyte for a lithium secondary battery that does not affect the performance of the electrolyte and the cell because hydrogen fluoride is not generated.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 schematically depicts a polymer according to the present invention.
2a is a transmission electron microscope (TEM) analysis result of the gel composition according to Example 1.
Figure 2b is a transmission electron microscope (TEM) analysis result for the gel composition according to Comparative Example 1.
Figure 3a is the result of evaluating the lifespan of the lithium metal battery according to Example 3.
Figure 3b is the result of evaluating the lifespan of the lithium metal battery according to Comparative Example 3.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

Like reference numerals have been used for like elements throughout the description of each figure. In the accompanying drawings, the dimensions of the structures are shown enlarged than actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where another part is present in the middle. Conversely, when a part such as a layer, film, region, plate, etc. is said to be "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is in the middle.

Unless otherwise specified, all numbers, values and/or expressions expressing quantities of components, reaction conditions, polymer compositions and formulations used herein refer to the number of factors that such numbers arise, among other things, to obtain such values. Since these are approximations that reflect the various uncertainties of the measurement, they should be understood to be qualified by the term "about" in all cases. Also, when numerical ranges are disclosed herein, such ranges are contiguous and include all values from the minimum value of such range to the maximum value inclusive, unless otherwise indicated. Furthermore, where such ranges refer to integers, all integers from the minimum value to the maximum value inclusive are included unless otherwise indicated.

In the present specification, "lithium secondary battery" means a battery capable of reversible charging and discharging to which a gel electrolyte can be applied, and may include, for example, a lithium ion battery, a lithium metal battery, a lithium air battery, and the like.

The gel electrolyte for a lithium secondary battery according to the present invention may include a liquid electrolyte and a polymer obtained by polymerizing inorganic particles provided in the liquid electrolyte and including alumina and a reactive group bonded to the alumina.

Figure 1 schematically depicts the polymer. Referring to this, the polymer may have a three-dimensional network structure. The alumina 10 may be provided at the intersection of the network structure, and the reactor 20 may be provided between each intersection. The liquid electrolyte may be gelated by the network structure.

The inorganic particle may be one in which a reactive group is bonded to the surface of a nano-sized alumina particle. The reactor may be chemically and/or physically bonded to the alumina, preferably chemically bonded.

The inorganic particles may be represented by Chemical Formula 1 below.

[Formula 1]

In Formula 1, R ₁ to R ₄ each mean a reactive group bonded to the alumina (Al ₂ O ₃ ). Each reactor may include a vinyl group having a double bond, and specifically, at least one selected from the group consisting of methacrylate, styrene, acrylonitrile, and combinations thereof. It may include any one.

Since the reactor has a double bond, the inorganic particles may be polymerized alone to form a polymer. Therefore, according to the present invention, the liquid electrolyte can be gelated only with the inorganic particles without additional components such as a crosslinking agent and a polymer.

The inorganic particles may have a specific surface area of 50 m ² /g to 500 m ² /g and a particle size (D50) of 15 nm to 25 nm. The specific surface area and particle size (D50) of the inorganic particles are main characteristics that determine whether the inorganic particles can be polymerized alone. That is, when the specific surface area and particle size (D50) of the inorganic particles fall within the above ranges, a reactive group may be sufficiently formed on the surface of alumina to form a polymer.

The liquid electrolyte may include an organic solvent and a lithium salt.

The organic solvent is not particularly limited, and examples thereof include dimethyl ether (DME), tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol diethyl ether (DEGDEE), dimethylacetamide (DMAc), and combinations thereof. It may include at least one selected from.

The lithium salt may contain elemental fluorine. Specifically, the lithium salt is LiPF ₆ , LiFSI (LiN(SO ₂ F) ₂ ), LiTFSI (LiN(SO ₂ CF ₃ ) ₂ ) and LiBETI (LiN(SO ₂ C ₂ F ₅ ) ₂ ) and combinations thereof. It may include at least one selected from the group consisting of.

A method for manufacturing a gel electrolyte for a lithium secondary battery according to the present invention includes preparing a starting solution containing the inorganic particles and a liquid electrolyte, injecting an initiator into the starting solution, and UV-treating or heat-treating the starting solution to obtain the initiator It may include preparing a polymer in which the inorganic particles are polymerized by.

The starting solution may include 80% to 90% by weight of the liquid electrolyte and 10% to 20% by weight of the inorganic particles. If the content of the inorganic particles is less than 10% by weight, the gelation of the liquid electrolyte may not proceed properly due to slow formation of polymers. Fairness may be compromised.

The initiator may include a UV initiator or a thermal initiator.

When the polymerization of the inorganic particles proceeds through UV treatment, the initiator is at least one UV initiator selected from the group consisting of α-hydroxyalkylphenone, α-aminoketone, camphorquinone, and combinations thereof can include

In addition, when the polymerization of the inorganic particles proceeds through heat treatment, the initiator includes at least one thermal initiator selected from the group consisting of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), and combinations thereof can do.

The initiator may be added in an amount of 1 to 2 parts by weight based on 100 parts by weight of the starting solution. If the amount of the initiator is less than 1 part by weight, polymerization may not be performed properly, and gelation of the liquid electrolyte may be difficult.

Conditions and methods of UV treatment of the starting solution are not particularly limited, and for example, the starting solution into which the initiator is added may be irradiated with ultraviolet light having a wavelength of about 365 nm for about 10 minutes to 1 hour.

In addition, conditions and methods of heat treatment of the starting solution are not particularly limited, and, for example, the starting solution into which the initiator is added may be heated at about 80° C. for about 30 minutes or longer.

The UV treatment or heat treatment decomposes the reactive double bonds included in the inorganic particles and generates radicals, thereby polymerizing the inorganic particles to form a polymer. As the polymerization of the inorganic particles progresses, the liquid electrolyte is gelled and finally a gel electrolyte can be obtained.

The UV treatment or heat treatment may be performed after impregnating the starting solution into a cathode structure, a separator, or the like. That is, gelation may be performed after the starting solution in a liquid state is injected into the cell. Accordingly, the energy density may be increased by maximizing the utilization rate of the electrolyte while minimizing the injection amount of the electrolyte.

Hereinafter, the present invention will be described in more detail through specific examples. However, these examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1, Example 2, Comparative Example 1 and Comparative Example 2

A starting solution was prepared by mixing the inorganic particles and the liquid electrolyte in the contents shown in Table 1, and an initiator was added thereto.

As the inorganic particles, alumina and methacrylate were used, and the inorganic particles had a specific surface area of about 130 m ² /g and a particle size (D50) of about 15 nm to 25 nm. As the liquid electrolyte, one containing dimethyl ether (DME) as an organic solvent and 1M LiFSI as a lithium salt was used. As the initiator, 2-Hydroxy-2-methylpropiophenon was used.

A gel electrolyte was prepared by irradiating the starting solution containing the initiator with ultraviolet rays having a wavelength of about 365 nm for about 10 minutes. The lithium ion conductivity and gelation of the gel electrolyte are shown in Table 1 below.

division Furtherance Properties starting solution initiator lithium ion
conductivity
[mS/cm] Gelation or not inorganic particles liquid electrolyte Sum Example 1 0.3g 2.7g 3.0g 0.03g 1.9 possible Example 2 0.35g 2.65g 3.0g 0.035g 1.8 solidity Comparative Example 1 0.3g 2.7g 3.0g 0.01g 4 impossible Comparative Example 2 0.1g 2.9g 3.0g 0.01g 4.5 impossible

In addition, transmission electron microscope (TEM) analysis results of the gel compositions according to Example 1 and Comparative Example 1 are shown in FIGS. 2A and 2B, respectively.

Referring to the results of Example 1 and Comparative Example 2 in Table 1, it can be seen that gelation of the liquid electrolyte is sufficiently achieved when the content of the inorganic particles is about 10% by weight or more.

Referring to the results of Example 1 and Comparative Example 1 in Table 1, it can be seen that gelation of the liquid electrolyte is sufficiently achieved only when the initiator is added in an amount of 1 part by weight or more of the starting solution. 2a and 2b, it can be seen that the gel composition of Example 1 sufficiently formed a network structure polymer and sufficiently progressed gelation, whereas the gel composition of Comparative Example 1 did not sufficiently aggregate.

Referring to the results of Example 1 and Example 2 in Table 1, it can be seen that the physical properties of the gel electrolyte increase as the content of the inorganic particles increases.

Example 3 and Comparative Example 3

(Example 3) After injecting the starting solution containing the initiator of Example 1 into a cell including an anode, separator, and lithium metal (cathode), ultraviolet rays of a wavelength of about 365 nm were irradiated for about 10 minutes to form a gel electrolyte. A lithium metal battery comprising a was prepared.

(Comparative Example 3) After injecting the starting solution containing the initiator of Comparative Example 1 into a cell including an anode, separator, and lithium metal (cathode), ultraviolet rays having a wavelength of about 365 nm were irradiated for about 10 minutes to form a gel electrolyte. A lithium metal battery comprising a was prepared.

The lifespan of the lithium metal battery according to Example 3 and Comparative Example 3 was evaluated. The results are shown in Figs. 3a and 3b, respectively. Referring to this, it can be seen that the lithium metal battery according to Example 3 operates very stably for more than 2,200 hours, whereas the lithium metal battery according to Comparative Example 3 has significantly deteriorated lifespan performance compared to Example 3.

As above, the experimental examples and examples of the present invention have been described in detail, the scope of the present invention is not limited to the above-described experimental examples and examples, and the basic concept of the present invention defined in the following claims Various modifications and improvements made by those skilled in the art are also included in the scope of the present invention.

10: alumina 20: reactor

Claims (13)

liquid electrolyte; and
A gel electrolyte for a lithium secondary battery comprising: a polymer provided in the liquid electrolyte and obtained by polymerizing inorganic particles including alumina and a reactive group bonded to the alumina. According to claim 1,
The polymer has a three-dimensional network structure,
The alumina is provided at the intersection of the network structure,
A gel electrolyte for a lithium secondary battery in which the liquid electrolyte is gelated by the network structure. According to claim 1,
The reactor is a gel electrolyte for a lithium secondary battery comprising a vinyl group. According to claim 1,
The reactor gel electrolyte for a lithium secondary battery comprising at least one selected from the group consisting of methacrylate, styrene, acrylonitrile, and combinations thereof. According to claim 1,
The inorganic particles have a specific surface area of 50 m ² /g to 500 m ² /g of a gel electrolyte for a lithium secondary battery. According to claim 1,
The particle size (D50) of the inorganic particles is a gel electrolyte for a lithium secondary battery of 15 nm to 25 nm. According to claim 1,
The liquid electrolyte may include an organic solvent; and
A gel electrolyte for a lithium secondary battery comprising a lithium salt containing elemental fluorine. According to claim 7,
The lithium salt is a group consisting of LiPF ₆ , LiFSI (LiN(SO ₂ F) ₂ ), LiTFSI (LiN(SO ₂ CF ₃ ) ₂ ) and LiBETI (LiN(SO ₂ C ₂ F ₅ ) ₂ ) and combinations thereof. A gel electrolyte for a lithium secondary battery comprising at least one selected from A method for producing the gel electrolyte for a lithium secondary battery according to any one of claims 1 to 8,
Preparing a starting solution containing inorganic particles including alumina and a reactive group bound to the alumina, and a liquid electrolyte;
Injecting an initiator into the starting solution;
Method for producing a gel electrolyte for a lithium secondary battery comprising: preparing a polymer in which the inorganic particles are polymerized by the initiator by UV treatment or heat treatment of the starting solution. According to claim 9,
The starting solution contains 80% to 90% by weight of a liquid electrolyte; and
Method for producing a gel electrolyte for a lithium secondary battery comprising 10% to 20% by weight of the inorganic particles. According to claim 9,
The initiator is a method for producing a gel electrolyte for a lithium secondary battery comprising at least one UV initiator selected from the group consisting of α-hydroxyalkylphenone, α-aminoketone, camphorquinone, and combinations thereof. According to claim 9,
The initiator is a method for producing a gel electrolyte for a lithium secondary battery comprising at least one thermal initiator selected from the group consisting of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), and combinations thereof. According to claim 9,
The initiator is a method for producing a gel electrolyte for a lithium secondary battery, which is added in an amount of 1 part by weight to 2 parts by weight based on 100 parts by weight of the starting solution.

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