Polymer solid electrolyte and method for producing the same

Abstract

The present invention relates to a polymer solid electrolyte and a method for producing the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0067066 filed May 31, 2022 and Korean Patent Application No. 10-2023-0070099 filed May 31, 2023, and incorporates all contents disclosed in the documents of said Korean patent applications as part of this specification.

[0002] The present invention relates to a polymer solid electrolyte and a method for producing the same. [Background technology]

[0003] Lithium secondary batteries that use liquid electrolytes have a structure in which the negative and positive electrodes are separated by a separator, and if the separator is damaged by deformation or external impact, a short circuit can occur, which can lead to risks such as overheating and explosion. Therefore, the development of a solid electrolyte that can ensure safety in the field of lithium secondary batteries is a very important issue.

[0004] Lithium secondary batteries using solid electrolytes have the advantages of improved battery safety, preventing electrolyte leakage, improving battery reliability, and facilitating the production of thin batteries. Furthermore, because lithium metal can be used as the anode, it is possible to improve energy density, and solid electrolyte batteries are expected to be used in compact secondary batteries as well as high-capacity secondary batteries for electric vehicles, drawing attention as next-generation batteries.

[0005] Among solid electrolytes, polymer solid electrolytes may be made from ion-conductive polymer materials, or hybrid materials that combine polymer materials with inorganic materials have also been proposed. The inorganic material may be an inorganic material such as an oxide or sulfide.

[0006] Such conventional polymer solid electrolytes are manufactured through a process of forming a coating film and then drying it at high temperatures. However, conventional polymer solid electrolyte manufacturing techniques have a limitation: it is difficult to manufacture polymer solid electrolytes with improved ionic conductivity due to the high crystallinity of crystalline or semi-crystalline polymers. In other words, the higher the crystallinity of the polymer, the lower the chain mobility of the polymer. This restricts the movement of lithium ions within the polymer solid electrolyte, making it difficult to improve the ionic conductivity of the polymer solid electrolyte.

[0007] For example, conventional polymer solid electrolytes can be manufactured by forming a coating film using polyvinyl alcohol (PVA) containing a hydroxyl group, a cross-linking functional group, as a polymer, followed by a high-temperature drying process. Specifically, the PVA is dissolved in water to prepare a PVA aqueous solution, which is then solution-cast onto a substrate to form a coating film, followed by drying at room temperature or a high temperature to produce a PVA film-like polymer solid electrolyte. Here, high temperature may refer to temperatures above 80°C, the glass transition temperature (Tg) of PVA. After the water evaporates during the drying process, hydrogen bonds are formed between the cross-linking functional groups contained in the PVA. These hydrogen bonds cause chain folding of the polymer chains, resulting in an increase in the crystallinity of the polymer film. The higher the crystallinity, the more brittle the polymer film becomes. In a polymer film with high crystallinity and brittleness, the chain mobility of the polymer chains is reduced, and if dissociated ions exist within the polymer film, the mobility of the ions is significantly reduced. For this reason, a typical PVA film produced by forming a coating film and then drying it at a high temperature as described above exhibits physical properties that are unsuitable for use as a polymer solid electrolyte for lithium secondary batteries.

[0008] To overcome these limitations of conventional polymer solid electrolytes, a technology has been developed that adds a plasticizer to a crystalline or semi-crystalline polymer to improve the mobility of polymer chains and thereby enhance the ionic conductivity of the polymer solid electrolyte. However, when using a plasticizer, it can be difficult to set process conditions because appropriate dispersion and solubility between the polymer and plasticizer must be ensured. Furthermore, when a liquid plasticizer is used, its compatibility with the polymer decreases, making the polymer solid electrolyte manufacturing process difficult.

[0009] Therefore, there is a need to develop a technology that can improve the ionic conductivity of polymer solid electrolytes without the need for additional additives such as plasticizers. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] China Patent Publication No. 112259788 Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a polymer solid electrolyte with improved ionic conductivity and a method for producing the same.

[0012] Another object of the present invention is to provide an all-solid-state battery including the polymer solid electrolyte having improved ionic conductivity. [Means for solving the problem]

[0013] In order to achieve the above object, the present invention provides a polymer solid electrolyte comprising: a polymer containing a cross-linkable functional group; a lithium salt; and a solvent containing a first solvent and a second solvent; the polymer solid electrolyte comprises a cross-linked structure; and an amorphous polymer chain comprising the cross-linkable functional group; the cross-linked structure includes: (a) a cross-link between the cross-linking functional groups; (b) a cross-link between the cross-linking functional groups and the first solvent; and (c) a bond between the cross-linking functional groups and the lithium salt; The polymer solid electrolyte has a liquid phase evaporation rate (M(t)), which means the amount of evaporation of the solvent contained in the polymer solid electrolyte over time, defined by the following Equation 1:

[0014]

number

[0015] M∞ is the maximum value or saturation value of the liquid phase that can be contained in the polymer solid electrolyte, and is 0.2 to 0.6; D is the diffusion coefficient of the liquid phase inside the polymer solid electrolyte, and is 10 -9 cm 2 / s~10 -6 cm 2 / s, L is the thickness of the polymer solid electrolyte, which is 5 μm to 500 μm; The t is the time at which the liquid phase evaporation rate is measured.

[0016] In one embodiment of the present invention, the content of the first solvent may be 1 to 1000 ppm.

[0017] In one embodiment of the present invention, the first solvent may include one or more selected from the group consisting of water, ethanol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, NMP, a co-solvent made by mixing water and alcohol, and a co-solvent made by mixing water and dimethyl sulfoxide.

[0018] In one embodiment of the present invention, the second solvent may include one or more selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), diethyl carbonate (DEC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), dioxolane (DOX), dimethoxyethane (DME), diethoxyethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane.

[0019] In one embodiment of the present invention, the crosslinkable functional group may include one or more groups selected from the group consisting of a hydroxyl group, a carboxyl group, and an amide group.

[0020] In one embodiment of the present invention, the polymer containing a crosslinkable functional group may include one or more selected from the group consisting of polyvinyl alcohol (PVA), gelatin, methylcellulose, agar, dextrin, poly(vinyl pyrrolidone), poly(acrylic amide), starch-carboxymethyl cellulose, hyaluronic acid-methylcellulose, chitosan, poly(N-isopropylacrylamide), and amino-terminated polyethylene glycol (amino-terminated PEG).

[0021] In one embodiment of the present invention, the molar ratio ([Li] / [G]) of the lithium ([Li]) of the lithium salt to the cross-linkable functional group ([G]) of the polymer may be greater than 0.1 and less than 0.5.

[0022] In one embodiment of the present invention, the lithium salt is selected from the group consisting of LiTFSI (Lithium bis(trifluoromethanesulphonyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, and LiC(CF3SO2)3.

[0023] The present invention also provides a method for producing a polymer solid electrolyte-forming solution by adding a lithium salt to a solution containing a polymer having a cross-linkable functional group and a first solvent; (S2) applying the polymer solid electrolyte-forming solution onto a substrate to form a coating film; (S3) freezing and thawing the coating film to form a cross-linked polymer structure containing the cross-linkable functional group, the cross-linked polymer structure containing the lithium salt and the first solvent, to produce a first polymer solid electrolyte; and (S4) exchanging the first solvent in the first polymer solid electrolyte with a second solvent to produce a second polymer solid electrolyte.

[0024] The freezing may be carried out at -30°C to -10°C.

[0025] The thawing may be carried out at a temperature of 15°C to 35°C.

[0026] The solvent exchange may be performed by drying the first solvent contained in the first polymer solid electrolyte at a high temperature, and then immersing the first solvent in the second solvent to exchange the first solvent for the second solvent.

[0027] The present invention also provides an all-solid-state battery comprising the solid polymer electrolyte. [Effects of the Invention]

[0028] The polymer solid electrolyte according to the present invention has a high content of a solvent, which is a liquid phase contained therein, while the diffusion coefficient of the solvent is low, thereby exhibiting the effect of confining a large amount of liquid phase within the polymer solid electrolyte for a long period of time, thereby improving ionic conductivity.

[0029] The polymer solid electrolyte according to the present invention has a three-dimensional network structure formed by branched functional groups contained in the polymer and a structure including amorphous polymer chains, which reduces the crystallinity of the polymer, thereby improving ionic conductivity.

[0030] Furthermore, the polymer solid electrolyte exhibits physical properties such as reduced brittleness and increased ductility and viscosity due to the structural characteristics.

[0031] Furthermore, the ionic conductivity of the polymer solid electrolyte can be improved by solvent exchange. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will now be described in more detail to aid in understanding the invention.

[0033] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that an inventor can appropriately define the concepts of terms in order to best explain his or her invention.

[0034] As used herein, the term "crosslinked structure" refers to a structure including a three-dimensional frame formed by polymer chains and an internal space of the frame. The polymer chains may be formed by crosslinking involving crosslinking functional groups contained in the polymer. The crosslinked structure has a three-dimensional shape and is formed by polymer chains intertwined with each other, so it can also be referred to as a three-dimensional network structure.

[0035] Polymer solid electrolyte The present invention relates to a polymer solid electrolyte.

[0036] The polymer solid electrolyte of the present invention is a polymer solid electrolyte comprising: a polymer having a cross-linkable functional group; a lithium salt; and a solvent comprising a first solvent and a second solvent; wherein the polymer solid electrolyte comprises a cross-linked structure; and an amorphous polymer chain having the cross-linkable functional group, and the cross-linked structure may comprise (a) a cross-link between the cross-linkable functional groups, (b) a cross-link between the cross-linkable functional group and the first solvent, and (c) a bond between the cross-linkable functional group and the lithium salt.

[0037] The cross-linked polymer solid electrolyte according to the present invention may have improved ionic conductivity. The degree of improvement in ionic conductivity is related to the amount of liquid phase absorbed or adsorbed within the polymer solid electrolyte and the duration of time the absorbed or adsorbed liquid phase is present. In other words, the ionic conductivity of the polymer solid electrolyte improves as the amount of liquid phase absorbed or adsorbed within the polymer solid electrolyte and the duration of time the liquid phase is present increases. Here, the liquid phase refers to the solvent remaining after being used as a raw material during the preparation of the polymer solid electrolyte.

[0038] In relation to the amount of liquid phase absorbed or adsorbed within the polymer solid electrolyte, when the polymer solid electrolyte has a cross-linked structure, the free volume increases compared to a bulky polymer solid electrolyte having a non-cross-linked structure. As a result, the amount of liquid phase that can be absorbed or adsorbed in the increased free volume increases, which can be confirmed to improve the ionic conductivity of the polymer solid electrolyte.

[0039] Furthermore, in relation to the time during which the liquid phase is contained within the polymer solid electrolyte, if the polymer solid electrolyte has a cross-linked structure, the cross-linked structure formed by cross-linking may complicate the liquid phase migration path, making it difficult for the liquid phase contained within to diffuse, resulting in a low diffusion coefficient, which may delay the time for the liquid phase to diffuse or evaporate from the inside to the outside of the polymer solid electrolyte. The delay in the diffusion or evaporation of the liquid phase increases the time during which the solvent is contained within the polymer solid electrolyte, enhancing the entrapment effect of confining the liquid phase within the polymer solid electrolyte, thereby improving the ionic conductivity of the polymer solid electrolyte.

[0040] As described above, the ionic conductivity of the polymer solid electrolyte having a cross-linked structure according to the present invention is related to the content of the liquid phase contained in the polymer solid electrolyte and the time during which the liquid phase is present. Specifically, the time during which the liquid phase is present is related to the diffusion coefficient and evaporation rate of the liquid phase.

[0041] In other words, the ionic conductivity of the cross-linked polymer solid electrolyte according to the present invention improves as the amount of liquid phase absorbed or adsorbed in the polymer solid electrolyte and the time during which the liquid phase is present increase. Specifically, the increase in the time during which the liquid phase is present means that the diffusion coefficient of the liquid phase decreases and the evaporation rate also slows.

[0042] In the present invention, the improved ionic conductivity of the polymer solid electrolyte having the crosslinked structure is quantitatively defined based on the correlation between the content of the liquid phase that can be absorbed or adsorbed into the polymer solid electrolyte, the diffusion coefficient of the liquid phase, and the evaporation rate, so that the polymer solid electrolyte that satisfies these correlations can always maintain a certain level of ionic conductivity or higher.

[0043] In the present invention, the liquid phase evaporation rate (M(t)), which means the amount of the solvent contained in the polymer solid electrolyte that evaporates over time, is defined by the following formula 1:

[0044]

number

[0045] M∞ is the maximum value or saturation value of the liquid phase that can be contained in the polymer solid electrolyte, and is 0.2 to 0.6; D is the diffusion coefficient of the liquid phase inside the polymer solid electrolyte, and is 10 -9 cm 2 / s~10 -6 cm 2 / s, L is the thickness of the polymer solid electrolyte, and is 5 μm to 500 μm. The t refers to the time at which the liquid phase evaporation rate is measured.

[0046] The liquid phase may contain a second solvent, or may further contain a first solvent.

[0047] In the present invention, the liquid phase evaporation rate (M(t)), which represents the amount of solvent evaporated over time in Equation 1, can be experimentally measured. The measured liquid phase evaporation rate (M(t)) is applied to Equation 1 to derive M∞ and D, which are used as fitting parameters, to predict whether or not a crosslinked structure is formed in the polymer solid electrolyte and to determine the degree of improvement in ionic conductivity based on the results. In other words, by applying the experimentally measured M(t) to Equation 1 and varying M∞ and D to obtain a fitting graph, optimal M∞ and D that match the graph of Equation 1 can be obtained.

[0048] In this case, M(t) can be measured by monitoring the weight of the liquid phase evaporating over time while heating a sample of the polymer solid electrolyte using a balance. For example, M(t) can be measured by monitoring the weight of the liquid phase evaporating over time while heating the sample at a temperature of 55 to 70°C or at a temperature of 60°C using a heated electronic balance (AND MS-70).

[0049] Furthermore, M∞ is the maximum or saturated value of the liquid phase that can be contained in the polymer solid electrolyte. If M∞ is less than 0.2, it is difficult to sufficiently impregnate the polymer solid electrolyte with the desired amount of liquid phase, which may result in a decrease in ionic conductivity. If M∞ is more than 0.6, the mechanical properties of the polymer solid electrolyte are reduced due to the impregnation of the liquid phase, resulting in the polymer solid electrolyte exhibiting properties closer to a gel than a polymer solid electrolyte membrane or film. M∞ is used as a fitting parameter when fitting an experimentally measured M(t) value with Equation 1.

[0050] Furthermore, the D is the diffusion coefficient of the liquid phase contained in the polymer solid electrolyte, and is a general diffusion coefficient of the liquid phase, 10 -9 cm 2 / s~10 -6 cm 2 / s.-9 cm 2 If the temperature is less than 10 / s, it may be difficult to include a liquid phase inside the polymer solid electrolyte. -6 cm 2 If the D exceeds / s, the diffusion and evaporation rates of the liquid phase present inside the polymer solid electrolyte become so fast that it may be difficult to describe the effect of improving the ionic conductivity of the polymer solid electrolyte by including a liquid phase. The D is used as a fitting parameter when fitting the experimentally measured value of M(t) with Equation 1.

[0051] Furthermore, L is the thickness of the polymer solid electrolyte and may be 5 μm to 500 μm, and can be measured using a common micrometer or by analyzing a cross section of the polymer solid electrolyte with a scanning electron microscope (SEM). If L is less than 5 μm, swelling due to the liquid phase may reduce the mechanical strength of the polymer solid electrolyte, making it difficult to handle or causing damage. If L exceeds 500 μm, battery performance may be reduced.

[0052] Furthermore, the n is an arbitrary integer. The n is not limited to a specific numerical range, but may be an integer between 5 and 1000, and the greater the value of n, the higher the accuracy of the calculation.

[0053] Furthermore, the t refers to the time at which the liquid phase evaporation rate (M(t)) is measured. The t is not particularly limited, and may be, for example, 1 minute to 6 hours.

[0054] In the present invention, the polymer solid electrolyte having the cross-linked structure is in the form of a porous polymer matrix, and the diffusion coefficient (D P ) and the diffusion coefficient of the non-porous polymer matrix (D NP ) is the ratio of D P / D NPWhen such a diffusion coefficient ratio is satisfied, the liquid component contained in the internal pores of the porous polymer matrix having a cross-linked structure can be retained for a long time because desorption and evaporation to the outside of the polymer matrix are delayed.

[0055] In the present invention, the (a) cross-linking bond between the cross-linking functional groups may include a hydrogen bond between the cross-linking functional groups, and for example, the hydrogen bond may be a hydrogen bond between OH-.

[0056] If the cross-linked structure is composed only of cross-links between the (a) cross-linkable functional groups, the polymer solid electrolyte may become crystalline, possibly resulting in a decrease in ionic conductivity.

[0057] However, since the cross-linked structure includes not only (a) cross-links between the cross-linkable functional groups but also (b) cross-links between the cross-linkable functional groups and the first solvent, and (c) bonds between the cross-linkable functional groups and the lithium salt, the occurrence of crystallinity in the polymer solid electrolyte can be prevented.

[0058] In the present invention, the cross-linking between the (b) cross-linkable functional group and the first solvent may include a hydrogen bond, for example, the hydrogen bond may be a hydrogen bond between OH and H. In this case, H may be derived from the aqueous solvent.

[0059] The (b) cross-linking between the cross-linkable functional group and the first solvent may refer to hydrogen bonding between the cross-linkable functional group and a portion of the solvent remaining after the freezing and thawing process.

[0060] Furthermore, the crosslinking between the (b) crosslinkable functional group and the first solvent prevents crosslinking between the (a) crosslinkable functional groups, and prevents the crosslinked structure from consisting solely of crosslinks between the (a) crosslinkable functional groups, thereby preventing an increase in the crystallinity of the polymer solid electrolyte.

[0061] In the present invention, the bond between the (c) cross-linkable functional group and the lithium salt may include a bond due to a Lewis acid-base interaction, and for example, the bond may be a bond between OH and Li.

[0062] The bond between the (c) cross-linkable functional group and the lithium salt is a bond due to Lewis acid-base interaction, and may be a bond of the same type as a metal-ligand bond.

[0063] In addition, the bond between the (c) cross-linking functional group and the lithium salt prevents cross-linking between the (a) cross-linking functional groups and between the (b) cross-linking functional group and the first solvent, preventing the cross-linked structure from being composed solely of cross-links between the (a) cross-linking functional groups. This prevents the occurrence of crystallinity in the polymer solid electrolyte and promotes the formation of amorphous polymer chains. The more amorphous polymer chains are formed, the more the mobility of the polymer chains improves, thereby increasing the hopping effect of the lithium ions and improving the ionic conductivity of the polymer solid electrolyte.

[0064] In the present invention, the amorphous polymer chains can also be formed by a freezing process as described below, and refer to polymer chains that do not form crystals due to regular folding of the polymer chains but exist in a free state. That is, the amorphous polymer chains may include polymers containing cross-linkable functional groups that do not form bonds, such as (a), (b), and (c).

[0065] Due to the cross-linked structure, the polymer solid electrolyte is not easily broken or destroyed, and can therefore function as an electrolyte support that stably contains lithium ions.

[0066] In addition, the amorphous polymer chains provide elasticity to the polymer solid electrolyte, minimizing its brittleness. Furthermore, the polymer chain mobility is excellent, improving the mobility of lithium ions within the electrolyte, thereby providing a polymer solid electrolyte with improved ionic conductivity.

[0067] In the present invention, the cross-linkable functional group contained in the polymer containing the cross-linkable functional group may have the property of forming a cross-linked structure by forming bonds such as those described in (a), (b), and (c).

[0068] For example, the cross-linkable functional group may include one or more selected from the group consisting of a hydroxyl group, a carboxyl group, and an amide group.

[0069] The weight-average molecular weight (Mw) of the polymer containing cross-linkable functional groups may be 80,000 g / mol to 130,000 g / mol, specifically, 80,000 g / mol or more, 83,000 g / mol or more, or 85,000 g / mol or more, or 90,000 g / mol or less, 110,000 g / mol or less, or 130,000 g / mol or less. If the weight-average molecular weight (Mw) of the polymer containing cross-linkable functional groups is less than 80,000 g / mol, the bonds formed by the cross-linkable functional groups may not be sufficiently formed to obtain a cross-linked structure. If the weight-average molecular weight (Mw) of the polymer containing cross-linkable functional groups exceeds 130,000 g / mol, the entanglement of polymer chains increases in the polymer solution used in the manufacturing process, reducing the solvent penetration rate into the interior of the polymer chains. This may accelerate gelation of the polymer, reducing the solubility of the polymer, and inhibit smooth bonding via cross-linking functional groups, making it difficult to form a cross-linked structure.

[0070] Furthermore, the polymer containing the cross-linkable functional group may be characterized in that phase separation between the polymer and the solvent occurs smoothly in the polymer solution used in the manufacturing process, and the bonds (a), (b), and (c) are successfully formed by the cross-linkable functional group contained in the phase-separated polymer upon freezing.

[0071] For example, the polymer containing a crosslinkable functional group may include one or more selected from the group consisting of polyvinyl alcohol (PVA), gelatin, methylcellulose, agar, dextrin, poly(vinyl pyrrolidone), poly(acrylic amide), poly(acrylic acid) (PAA), starch-carboxymethyl cellulose, hyaluronic acid-methylcellulose, chitosan, poly(N-isopropylacrylamide), and amino-terminated polyethylene glycol (amino-terminated PEG). Preferably, the polymer having a cross-linkable functional group may be PVA, which may be advantageous in that phase separation between the PVA and a solvent is efficiently carried out upon freezing in the process of producing a polymer solid electrolyte, and that the PVA may form a cross-linked structure through the bonds (a), (b), and (c) derived from the cross-linkable functional group of the PVA that has phase-separated from the solvent.

[0072] In the present invention, the lithium salt is contained in a dissociated state in the internal space of the cross-linked structure, thereby improving the ionic conductivity of the polymer solid electrolyte.

[0073] In addition, the lithium salt forms a bond with the (c) cross-linking functional group, thereby preventing the occurrence of crystallinity in the polymer solid electrolyte and promoting the formation of amorphous polymer chains.

[0074] The lithium salts include (CF3SO2)2NLi (Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, and LiC(CF3SO2)3.

[0075] In the present invention, the molar ratio ([Li] / [G]) of the crosslinkable functional group ([G]) of the polymer containing the crosslinkable functional group to the lithium ([Li]) of the lithium salt contained in the polymer solid electrolyte may be greater than 0.1 and less than 0.5, specifically greater than 0.1, 0.2 or greater, or 0.3 or greater, or 0.4 or less, or less than 0.5. If the molar ratio ([Li] / [G]) is less than 0.1, the content of the lithium salt may be reduced, potentially reducing the ionic conductivity of the polymer solid electrolyte. If the molar ratio is greater than 0.5, the content of the polymer containing the crosslinkable functional group may be reduced, potentially preventing sufficient formation of the bonds (a), (b), and (c), resulting in increased crystallinity and reduced ionic conductivity. If the crosslinkable functional group is a hydroxyl group (OH-), the [G] may be expressed as [OH] or [O].

[0076] In one embodiment of the present invention, the solvent is contained within a cross-linked structure formed by physical cross-linking of the polymer solid electrolyte, facilitating a solvent exchange process and improving the ionic conductivity of the polymer solid electrolyte.

[0077] The solvent may include a first solvent and a second solvent.

[0078] The first solvent and the second solvent may be solvents distinct from each other and may have different solubilities for the polymer having the cross-linkable functional group.

[0079] The first solvent has high solubility for the polymer containing the cross-linkable functional group and can form a cross-linked structure with the polymer containing the cross-linkable functional group, while the second solvent has low solubility for the polymer containing the cross-linkable functional group and makes it difficult to form a cross-linked structure with the polymer containing the cross-linkable functional group.

[0080] The first solvent and the second solvent may be solvents that are classified as aqueous electrolyte solutions or non-aqueous electrolyte solutions depending on the battery structure.

[0081] The first solvent and the second solvent may be solvents distinguished from each other by a flame-retardant electrolyte.

[0082] The first solvent may be any one selected from the group consisting of water, ethanol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, NMP, a co-solvent made by mixing water and alcohols, and a co-solvent made by mixing water and dimethyl sulfoxide.

[0083] The boiling point of the first solvent may be 150° C. or less. The boiling point of the first solvent may be lower than the boiling point of the second solvent. If the boiling point of the first solvent exceeds 150° C., hydrogen bonds and Lewis acid-base interactions formed within the polymer may be broken during the removal of the first solvent, which may significantly reduce the mechanical properties of the polymer solid electrolyte.

[0084] The first solvent can dissolve the polymer containing cross-linkable functional groups and then form a cross-linked structure through a freezing / thawing process. For example, when the first solvent is water, significant phase separation with the polymer containing cross-linkable functional groups can occur during the freezing process, resulting in the formation of an ice phase and a rich phase of the polymer containing cross-linkable functional groups.

[0085] The reason for replacing the first solvent with the second solvent is that the polymer solid electrolyte of the present invention can be used in battery chemistries that are sensitive to water. For example, using water as the first solvent is not problematic in battery chemistries where performance degradation due to aqueous electrolytes does not occur, but in battery chemistries that are sensitive to water, battery performance may be degraded or the battery may not operate. To solve this problem, the first solvent can be removed and replaced with a second solvent that can be used inside the battery without losing ionic conductivity, thereby providing a polymer solid electrolyte that enables stable battery operation.

[0086] Furthermore, although the use of the first solvent does not pose a problem in the production of a solid electrolyte, the solvent is vulnerable to combustion in the event of a battery fire or explosion, causing greater damage. To solve this problem, the first solvent is removed and replaced with a flame-retardant second solvent, thereby providing a polymer solid electrolyte that enables stable battery operation.

[0087] Furthermore, although the use of a first solvent does not pose a problem in the production of a solid electrolyte, when the first solvent is used as an electrolyte inside a battery, problems may arise that shorten the lifespan of the product due to unexpected side reactions and decomposition of the solvent during battery operation. To solve this problem, the first solvent is removed and replaced with a second solvent that is stable against side reactions with the solvent, thereby providing a polymer solid electrolyte that enables stable battery operation.

[0088] The second solvent may include one or more selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), diethyl carbonate (DEC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), dioxolane (DOX), dimethoxyethane (DME), diethoxyethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane, or may include a combination thereof. For example, the second solvent may include, but is not limited to, EC:EMC (1:3), EC:EMC (1:1), EC:DMC:EMC:FEC (3:3:3:3:1), etc.

[0089] The content of the first solvent in the polymer solid electrolyte may be 1 to 1000 ppm. If the content of the first solvent exceeds 1000 ppm, absorption of the second solvent is hindered, resulting in problems such as a decrease in properties expected from the second solvent, such as ionic conductivity, and a decrease in battery stability.

[0090] In the present invention, the polymer solid electrolyte may be in the form of a free-standing film or a coating layer. The free-standing film refers to a film that can maintain its film form by itself at room temperature and pressure without a separate support. The coating layer refers to a layer obtained by coating on a substrate.

[0091] The free-standing film or coating layer exhibits elasticity, minimizes brittleness, and has properties as a support that stably contains lithium ions, making it a suitable form for a polymer solid electrolyte.

[0092] Method for producing polymer solid electrolyte A method for producing a solid polymer electrolyte according to one embodiment of the present invention may include the following steps: (S1) adding a lithium salt to a solution containing a polymer having a cross-linkable functional group and a first solvent to prepare a polymer solid electrolyte-forming solution; (S2) applying the polymer solid electrolyte-forming solution onto a substrate to form a coating film; (S3) freezing and thawing the coating film to form a cross-linked polymer structure containing the cross-linkable functional group, the cross-linked polymer structure containing the lithium salt and the first solvent, to produce a first polymer solid electrolyte; and (S4) A step of exchanging the first solvent in the first polymer solid electrolyte with a second solvent to produce a second polymer solid electrolyte.

[0093] In the method for preparing the polymer solid electrolyte, without adding a plasticizer, which is used to reduce the crystallinity of the polymer, the cross-linking functional groups contained in the polymer undergo a freezing process to induce (a) cross-linking between the cross-linking functional groups, (b) cross-linking between the cross-linking functional groups and the first solvent, and (c) bonding between the cross-linking functional groups and the lithium salt, thereby preventing crystallization of the polymer and producing a polymer solid electrolyte with improved ionic conductivity. Each step of the method for preparing the polymer solid electrolyte according to the present invention will now be described in more detail.

[0094] In one embodiment of the present invention, in the step (S1), a polymer solid electrolyte-forming solution can be formed by adding a lithium salt to a solution containing a polymer having a cross-linkable functional group and a first solvent.

[0095] The polymer, the first solvent, and the lithium salt are as described above.

[0096] The concentration of the polymer solution containing cross-linkable functional groups can be appropriately adjusted taking into consideration the degree to which the coating process of the polymer solid electrolyte-forming solution can proceed smoothly when applied to a substrate. For example, the concentration of the polymer solution containing cross-linkable functional groups may be 5% to 20%, specifically, 5% or more, 7% or more, or 9% or more, or 13%, 17%, or less, or 20% or less. If the concentration of the polymer solution containing cross-linkable functional groups is less than 5%, the concentration is too dilute and may run off when applied to a substrate. If the concentration is more than 20%, it may be difficult to dissolve the lithium salt at the desired concentration in the polymer solution, and the viscosity may be high, making it difficult to apply the solution in a uniform thin film.

[0097] In one embodiment of the present invention, in the step (S2), the polymer solid electrolyte-forming solution may be applied onto a substrate to form a coating film.

[0098] The substrate is not particularly limited as long as it can serve as a support on which the polymer solid electrolyte-forming solution is applied, and may be, for example, stainless steel (SS), polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0099] The coating method is not particularly limited as long as it can coat the polymer solid electrolyte-forming solution on the substrate in the form of a film, and may be, for example, bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, or solution casting.

[0100] In one embodiment of the present invention, in the step (S3), the coating film is frozen and thawed to form a crosslinked polymer structure containing the crosslinkable functional group, and the crosslinked polymer structure can produce a first polymer solid electrolyte containing the lithium salt and the first solvent.

[0101] The freezing process can cause phase separation between the polymer and water contained in the aqueous polymer solution containing cross-linking functional groups used to form the coating film. This phase separation can be induced by the stronger hydrogen bonds between water molecules than between the cross-linking functional groups and water molecules. The water molecules aggregated by the hydrogen bonds between water molecules exist in an ice phase during the freezing process. As a result, the number of cross-linking functional groups that form hydrogen bonds through their interaction with water molecules is significantly reduced.

[0102] Due to the phase separation, the inside of the coating film is divided into (i) a polymer-poor phase and (ii) a polymer-rich phase.

[0103] The (i) polymer-poor phase is a portion containing water molecules aggregated by hydrogen bonding between water molecules, and exists in an ice phase, which can also be called a free water state.

[0104] The (ii) polymer-rich phase is a portion containing polymers that have phase-separated from water. The phase-separated polymers are polymers containing cross-linking functional groups that have been freed from interactions with water molecules. After phase separation, they are in a free state, do not form crystals through regular folding, and exist in a relatively free, amorphous state, which is called an amorphous polymer chain.

[0105] In addition, some of the cross-linkable functional groups contained in the phase-separated polymer form localized crystallites, which act as cross-linkable junction points to form a cross-linked structure including the bonds (a), (b), and (c).

[0106] In addition, in the thawing process after the freezing process, the ice contained in the (i) polymer-poor phase melts and evaporates, thereby producing a polymer solid electrolyte with an increased free volume.

[0107] The freezing may be performed under appropriately selected conditions sufficient to freeze the coating film. For example, the freezing temperature may be between −30°C and −10°C. Specifically, the freezing temperature may be −30°C or higher, −25°C or higher, or −23°C or higher, or −18°C or lower, −15°C or lower, or −10°C or lower. If the freezing temperature is lower than −30°C, cracks may occur in the coating film. If the temperature exceeds −10°C, phase separation between the polymer and water may not occur sufficiently, making it difficult to form an amorphous polymer chain region. The freezing may be performed for a period of time within a range of 20 to 30 hours, taking into account sufficient freezing.

[0108] The thawing may be performed under appropriately selected conditions that allow the frozen coating film to be thawed to an extent that it can be used as a polymer solid electrolyte. For example, the thawing temperature may be 15°C to 35°C, or may be room temperature (25°C). If the thawing temperature is lower than 15°C, the efficiency of drying water after thawing (ice melting) may decrease, and if it exceeds 35°C, the coating film may shrink, causing wrinkles or warping.

[0109] In one embodiment of the present invention, in the step (S4), the first solvent in the first polymer solid electrolyte may be exchanged with a second solvent to produce a second polymer solid electrolyte.

[0110] The first solvent and the second solvent are as described above.

[0111] The solvent exchange means removing the first solvent in the first polymer solid electrolyte and replacing it so that the second solvent is mostly present, and by the solvent exchange, a second polymer solid electrolyte containing the second solvent can be produced.

[0112] The solvent exchange can be performed by drying the first solvent contained in the first polymer solid electrolyte at a high temperature, followed by immersion in the second solvent to exchange the first solvent for the second solvent. More specifically, the first polymer solid electrolyte containing the first solvent is placed in a vacuum oven, dried at a low temperature (50°C) for 6 hours, then dried at a high temperature (100°C) for 12 hours, and then immersed in the second solvent at room temperature for 24 hours in a dry room environment, thereby exchanging the first solvent for the second solvent.

[0113] In the present invention, after the step (S4), a step (S5) of measuring the liquid phase evaporation rate (M(t)) of the polymer solid electrolyte and applying it to Equation 1 to fit M∞ and D may be further carried out to prepare a polymer solid electrolyte having ionic conductivity above a certain level.

[0114] all solid state battery The present invention also relates to an all-solid-state battery including the polymer solid electrolyte, the all-solid-state battery including a negative electrode, a positive electrode, and a polymer solid electrolyte interposed between the negative electrode and the positive electrode, and the solid electrolyte has the above-mentioned characteristics.

[0115] Specifically, the polymer solid electrolyte is suitable as an electrolyte for an all-solid-state battery because the crystallinity is reduced by forming physical crosslinks through a freezing and thawing process, and the ionic conductivity is improved through a solvent exchange process.

[0116] In the present invention, the positive electrode included in the all-solid-state battery may include a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of a positive electrode current collector.

[0117] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0118] The positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions. For example, lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), Li[Ni x Co y Mn z M v ]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, and x+y+z+v=1), Li (Li a M b-a-b’ M' b’ )O 2-c A c (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2, M comprises Mn and one or more elements selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more elements selected from the group consisting of Al, Mg, and B; and A is one or more elements selected from the group consisting of P, F, S, and N), or compounds substituted with one or more transition metals; 1+y Mn 2-y Lithium manganese oxides such as LiMnO4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-y Ni-site lithium nickel oxide represented by MyO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 to 0.3); chemical formula: LiMn 2-y M y Examples of lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0119] The positive electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40 wt % or more, or 50 wt % or more, or 70 wt % or less, or 80 wt % or less. If the content of the positive electrode active material is less than 40 wt %, the connectivity between the wet positive electrode active material layer and the dry positive electrode active material layer may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be increased.

[0120] The binder may be a component that assists in binding the positive electrode active material to the conductive material and the like and binding to the current collector, and may be selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylic The binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl cellulose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0121] The binder may be included in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1 wt % or more or 3 wt % or more, and 15 wt % or less or 30 wt % or less. If the binder content is less than 1 wt %, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced. If the binder content exceeds 30 wt %, the adhesive strength may be improved, but the content of the positive electrode active material may be reduced accordingly, which may reduce the battery capacity.

[0122] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not induce chemical changes in the battery, and has excellent electrical conductivity. Representative examples include graphite or conductive carbon, and include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based substances having a graphene or graphite crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more.

[0123] The conductive material may typically be included in an amount of 0.5 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the conductive material content may be 0.5 wt % or more, or 1 wt % or more, or 20 wt % or less, or 30 wt % or less. If the conductive material content is too low, such as less than 0.5 wt %, it may be difficult to expect an improvement in electrical conductivity or the electrochemical characteristics of the battery may be degraded. If the conductive material content is too high, such as more than 30 wt %, the amount of positive electrode active material may be relatively small, which may result in a decrease in capacity and energy density. The method for incorporating the conductive material into the positive electrode is not particularly limited, and a conventional method known in the art, such as coating the positive electrode active material, may be used.

[0124] The positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between an external conductor and the positive electrode active material layer.

[0125] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the all-solid-state battery and has high electronic conductivity. For example, the positive electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, palladium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, silver, or the like, or an aluminum-cadmium alloy.

[0126] The positive electrode current collector may have a micro-irregular structure or a three-dimensional porous structure on its surface to strengthen the bonding strength with the positive electrode active material layer, and may have various forms such as a film, sheet, foil, mesh, net, porous body, foam, or nonwoven fabric.

[0127] The positive electrode can be manufactured by a conventional method. Specifically, the positive electrode active material, conductive material, and binder are mixed in an organic solvent to form a composition for forming a positive electrode active material layer. The composition is then coated on a positive electrode current collector, dried, and optionally, compression-molded into a current collector to improve electrode density. Preferably, the organic solvent is one that can uniformly disperse the positive electrode active material, binder, and conductive material and is easily evaporated. Specific examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, and isopropyl alcohol.

[0128] In the present invention, the negative electrode included in the all-solid-state battery may include a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0129] The negative electrode active material is lithium (Li + The lithium ion-containing compound may include a material capable of reversible intercalation or deintercalation of lithium ions, a material capable of reversibly reacting with lithium ions to form a lithium-containing compound, lithium metal, or a lithium alloy.

[0130] The lithium ion (Li +The material capable of reversibly inserting or de-inserting lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The material capable of reacting with lithium (Li) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0131] Preferably, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0132] The negative electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt % or more, or 50 wt % or more, or 70 wt % or less, or 80 wt % or less. If the content of the negative electrode active material is less than 40 wt %, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be increased.

[0133] The binder is the same as that described above in the positive electrode active material layer.

[0134] The conductive material is the same as that described above in the positive electrode active material layer.

[0135] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, an aluminum-cadmium alloy, etc. Similarly to the positive electrode current collector, the negative electrode current collector may be in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric having fine irregularities formed on the surface.

[0136] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode may be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the art, such as compression bonding, coating, or vapor deposition. The negative electrode of the present invention also includes a battery in which a thin lithium film is formed on the metal plate by initial charging after assembling the battery without a thin lithium film on the negative electrode current collector.

[0137] The present invention also provides a battery module including the all-solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

[0138] Specific examples of the device include, but are not limited to, power tools powered by a battery-powered motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems. Preferred embodiments of the present invention will be described below to aid in understanding the present invention. However, the following embodiments are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical spirit of the present invention. Such changes and modifications are also intended to fall within the scope of the appended claims.

[0139] In the following Examples and Comparative Examples, polymer solid electrolytes containing a polymer having a crosslinkable functional group, a lithium salt, and a solvent as shown in Table 1 below were prepared.

[0140] [Table 1]

[0141] Example Example 1: Preparation of polymer solid electrolyte PVA (MW: 89,000 g / mol; degree of hydrolysis: >99%) was mixed with water to prepare a 10% PVA aqueous solution. LiTFSI was added to the PVA aqueous solution and stirred to prepare a solution containing PVA, a polymer having cross-linkable functional groups, and LiTFSI, a lithium salt. The molar ratio ([Li] / [O]) of the cross-linkable functional group "O" of the PVA to the "Li" contained in the lithium salt was set to 0.4.

[0142] The solution was applied to a substrate, SS foil, by bar coating to form a coating film, which was then frozen at -20°C for 24 hours and thawed at 25°C to prepare a polymer solid electrolyte.

[0143] After removing the first solvent, water (H2O), from the prepared polymer solid electrolyte, a second solvent, ethyl methyl carbonate (EMC), was added to prepare a polymer solid electrolyte.

[0144] Comparative Example Comparative Example 1 A polymer solid electrolyte was prepared in the same manner as in Example 1, except that a solution containing PVA, a polymer having a cross-linkable functional group, and LiTFSI, a lithium salt, was coated on an SS foil substrate and then dried at 80°C without a freezing and thawing process.

[0145] Comparative Example 2 A polymer solid electrolyte was prepared in the same manner as in Example 1, except that a solution containing PVA, a polymer having a cross-linkable functional group, and LiTFSI, a lithium salt, was coated on an SS foil substrate and then dried at 25°C without a freezing and thawing process.

[0146] Experimental Example Experimental Example 1 In order to measure the ionic conductivity of the film-shaped polymer solid electrolytes prepared in the examples and comparative examples, a test was carried out using a 1.7671 cm 2 The solid polymer electrolyte was punched out into a circle of the same size, and the punched solid polymer electrolyte was placed between two pieces of stainless steel (SS) to prepare a coin cell.

[0147] (1) Ionic conductivity Resistance was measured using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) at 25°C with an amplitude of 10 mV and a scan range of 500 KHz to 20 MHz, and then the ionic conductivity of the polymer solid electrolyte was calculated using the following Equation 2.

[0148]

number

[0149] In the above formula 2, σ i is the ionic conductivity (S / cm) of the polymer solid electrolyte, R is the resistance (Ω) of the polymer solid electrolyte measured by the electrochemical impedance spectrometer, L is the thickness (μm) of the polymer solid electrolyte, and A is the area (cm 2 ) means

[0150] (2) Observation of the appearance of the polymer solid electrolyte - whether or not a free-standing film is formed and the state of the sample after the freezing / thawing process The ionic conductivity of the polymer solid electrolyte calculated using Equation 2, whether a freestanding film could be formed, and the results of observing the appearance of the polymer solid electrolyte are shown in Table 2. Whether a freestanding film could be formed (formed: ◯, not formed: ×) and the appearance of the polymer solid electrolyte were observed with the naked eye.

[0151] (3) Liquid phase evaporation rate (M(t)) The weights of the liquid phase (solvent) contained in the polymer solid electrolyte were measured before and after evaporation during the manufacturing process of the Examples and Comparative Examples, and the liquid phase evaporation rate (M(t)) was measured using the weight change rate.

[0152] (4) M∞ and D The calculated liquid phase evaporation rate (M(t)) was applied to the following equation 1 to derive the values ​​of fitting parameters M∞ and D.

[0153]

number

[0154] M∞ is the maximum value or saturation value of the liquid phase that can be contained in the polymer solid electrolyte, and is 0.2 to 0.6; D is the diffusion coefficient of the liquid phase inside the polymer solid electrolyte, and is 10 -9 cm 2 / s~10 -6 cm 2 / s, L is the thickness of the polymer solid electrolyte, which is 5 μm to 500 μm; The t refers to the time at which the liquid phase evaporation rate is measured.

[0155] [Table 2]

[0156] As shown in Table 2, Example 1 is M ∞ It was confirmed that the material satisfied all the characteristics of a large ionic conductivity (Ic) and a small diffusion coefficient (D), and that it had high ionic conductivity.

[0157] Although the present invention has been described above using limited examples and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims set forth below.

Claims

1. A polymer solid electrolyte comprising: a polymer comprising a cross-linkable functional group; a lithium salt; and a solvent comprising a first solvent and a second solvent; The content of the first solvent is 1 ppm to 1000 ppm; the polymer solid electrolyte comprises a cross-linked structure; and an amorphous polymer chain comprising the cross-linkable functional group; the cross-linked structure includes: (a) a cross-link between the cross-linking functional groups; (b) a cross-link between the cross-linking functional groups and the first solvent; and (c) a bond between the cross-linking functional groups and the lithium salt; The liquid phase evaporation rate (M(t)), which means the amount of evaporation of the solvent contained in the polymer solid electrolyte over time, is defined by the following formula 1: [Equation 1] M∞ is the maximum value or saturation value of the liquid phase that can be contained in the polymer solid electrolyte, and is 0.2 to 0.6; The D is the diffusion coefficient of the liquid phase in the polymer solid electrolyte, and is 10 －９ cm ２ / s~10 －６ cm ２ / s, L is the thickness of the polymer solid electrolyte, which is 5 μm to 500 μm; The t is the time at which the liquid phase evaporation rate is measured.

2. 2. The polymer solid electrolyte according to claim 1, wherein the first solvent comprises at least one selected from the group consisting of water, ethanol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, NMP, a co-solvent made by mixing water and alcohol, and a co-solvent made by mixing water and dimethyl sulfoxide.

3. 2. The polymer solid electrolyte according to claim 1, wherein the second solvent comprises one or more selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), diethyl carbonate (DEC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), dioxolane (DOX), dimethoxyethane (DME), diethoxyethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane.

4. 2. The polymer solid electrolyte according to claim 1, wherein the crosslinkable functional group comprises at least one selected from the group consisting of a hydroxyl group, a carboxyl group, and an amide group.

5. The polymer containing the cross-linking functional group may be polyvinyl alcohol (PVA), gelatin, methylcellulose, agar, dextrin, poly(vinyl pyrrolidone), poly(acrylamide), starch-carboxymethyl cellulose, hyaluronic acid-methyl cellulose, or the like.

2. The polymer solid electrolyte according to claim 1, comprising at least one selected from the group consisting of N-isopropylacrylamide, ...

6. 2. The polymer solid electrolyte according to claim 1, wherein the molar ratio ([Li] / [G]) of the lithium ([Li]) of the lithium salt to the cross-linking functional group ([G]) of the polymer is greater than 0.1 and less than 0.

5.

7. The lithium salts include LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), and LiNO ３ , LiOH, LiCl, LiBr, LiI, LiClO ４ , LiBF ４ , LiB １０ Cl １０ , LiPF ６ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiAlCl ４ , C.H. ３ SO ３ Li, CF ３ SO ３ Li, LiSCN, and LiC(CF ３ SO ２ ) ３ The polymer solid electrolyte according to claim 1 , comprising one or more selected from the group consisting of:

8. (S1) adding a lithium salt to a solution containing a polymer having a cross-linkable functional group and a first solvent to prepare a polymer solid electrolyte-forming solution; (S2) applying the polymer solid electrolyte-forming solution onto a substrate to form a coating film; (S3) freezing and thawing the coating film to form a cross-linked polymer structure containing the cross-linkable functional group, and the cross-linked polymer structure contains the lithium salt and the first solvent, thereby producing a first polymer solid electrolyte; and (S4) exchanging the first solvent in the first polymer solid electrolyte with a second solvent to produce a second polymer solid electrolyte; The method for producing a polymer solid electrolyte, wherein the polymer solid electrolyte comprises: the polymer containing the cross-linkable functional group; the lithium salt; and a solvent containing the first solvent and the second solvent.

9. The method for producing a polymer solid electrolyte according to claim 8, wherein the freezing is carried out at a temperature of −30° C. to −10° C.

10. The method for producing a polymer solid electrolyte according to claim 8, wherein the thawing is carried out at 15°C to 35°C.

11. 11. The method for producing a polymer solid electrolyte according to claim 8, wherein the solvent exchange comprises drying a first solvent contained in a first polymer solid electrolyte at a high temperature, followed by immersing the first polymer solid electrolyte in the second solvent, thereby exchanging the first solvent for the second solvent.

12. An all-solid-state battery comprising the polymer solid electrolyte according to any one of claims 1 to 7.

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