CN1452794A - Microporous solid electrolytes and methods for preparing them - Google Patents

Abstract

The present invention is directed to an elecrolyte film and/or a solid electrolyte, having a microporous structure, for a rechargeable cell. According to the present invention, when preparing the electrolyte film and/or the solid electrolyte, an inorganic absorbent is added in the amount of more than 70% by weight in a polymer matrix to prevent the porous structure from being destructed at the cell-assembling process such as lamination or pressing, whereby the absorbing power of a liquid electrolyte to the solid electrolyte film and the ionic conductivity can be maintained. The inorganic absorbent contained over the specific amount, together with the microporous structure, improves the capacity of absorbing the liquid electrolyte and, in particular, works as a structure element of increasing the mechanical strength of electrolyte film and/or solid electrolyte.

Description

Microporous inorganic solid electrolyte and preparation method thereof

technical field

The present invention relates to solid electrolyte films that can be used in rechargeable batteries. More specifically, the present invention relates to providing a path for ions to move between a cathode and an anode during repeated charging and discharging of a rechargeable battery by providing a solid electrolyte membrane having a microporous structure and containing more than a specified amount of absorbent This is achieved by introducing a liquid component and a lithium salt (hereinafter, both are referred to as "liquid electrolyte").

The rechargeable battery of the present invention includes three essential components, namely, a cathode, an anode and an electrolyte. Batteries are made by laminating cathodes, anodes, and sheet electrolytes. The substance used for the anode is carbon or a polymer material that can add/remove metallic lithium or lithium ions. The substance used for the cathode is a transition metal oxide or a polymer material that can add/remove metallic lithium or lithium ions. As a substance for the electrolyte, one of the electrolytes described in the present invention can be used, and the liquid electrolyte is introduced into the battery after the battery is assembled.

Background technique

The electrolyte in batteries, such as rechargeable batteries or electrochemical reaction systems, is placed between the conductive surfaces of the cathode and anode. The electrolyte is an insulator that is not electronically conductive but ionically conductive. So far, general electrolytes consist only of liquid components; however, recently, more attention has been paid to solid electrolytes, which have many advantages. Among them, attempts have been made to use polymers as electrolytes.

Because pure polymer electrolytes containing polar heteroatoms have an extremely low ionic conductivity of ^10-8 S/cm, they are difficult to use at room temperature, therefore, research on polymer electrolytes has mainly focused on improving their conductivity, As a representative example, it has been proposed to introduce a liquid electrolyte component into the structure of the polymer.

A gel-type electrolyte containing a liquid electrolyte in a polymer backbone disclosed in U.S. Patent No. 5,219,679 has appropriate conductivity while exhibiting polymer characteristics, however, a large amount of liquid electrolyte has been included during the manufacture of the polymer electrolyte, The problem with said patent is therefore that evaporation/loss of liquid components can occur, resulting in a change in composition and a decrease in conductivity. In addition, because lithium salts in liquid electrolytes are sensitive to moisture, stringent dehumidification conditions are required for the fabrication of gel electrolytes.

The hybrid polymer electrolyte system proposed in US Pat. Nos. 5,296,318 and 5,418,091, while having the advantages of gel-type polymer electrolytes, can minimize the impact of moisture on the battery manufacturing process by adding liquid electrolytes after battery packaging. Since the liquid electrolyte is added after the electrolyte film is prepared, it is necessary for the inside of the electrolyte film to have a place capable of absorbing the liquid component therein. For this purpose, plasticizers/processing aids are added during the step of preparing the electrolyte film, and they are extracted with organic solvents after completion of battery assembly. However, due to the need for such a process, the fatal disadvantages of the above method are low reproducibility, low manufacturing yield, and difficulty in automating large-scale production.

In order to solve these problems, attempts have been made to form small pores therein so that a liquid electrolyte can be easily absorbed when preparing a polymer film. More specifically, it has been proposed to cast a polymer dissolved in a solvent in the form of a thin film, and then contact the polymer film with a non-solvent. In addition to this approach, it has also been proposed to introduce porosity into polymer membranes by vulcanization, curing or stretching. When liquid electrolytes are absorbed in the polymer membranes prepared by the above method, their ionic conductivity at room temperature exceeds 10 ⁻³ S/cm, a value suitable for industrial applications. However, there is also a problem that the process of introducing porosity into the polymer is complicated, or that the microporous structure formed in the polymer film is easily destroyed during the lamination or pressing steps of assembling the battery. The ionic conductivity drops rapidly. In other words, the polymer electrolyte itself shows excellent characteristics, but it is difficult to apply it to the practice of manufacturing batteries.

To address the issue of porosity disruption, attempts have been made to directly attach polymer membranes to the cathode and/or anode and expose the resulting structure to a non-solvent. However, using the electrode surface as a method of preparing an electrolyte thin film substrate complicates the production process, and water used as a non-solvent has a bad influence on the cathode and/or anode. Therefore, it is also difficult to apply to the practice of manufacturing batteries.

US Patent No. 5,631,103 discloses electrolyte systems in which inorganic fillers are added. However, in order to reach the industrial production level, it is necessary to increase the amount of inorganic filler added, so the mechanical strength of the polymer film will become weak. Therefore, this method is also not suitable for the actual process. In addition, said patent uses the method of casting a polymer film by adding a processing aid thereto and then removing it to introduce porosity into the film, which also leads to 5,418,091 questions.

Meanwhile, Japanese Laid-Open Patent Publication No. 99-16561 discloses a polymer electrolyte system in which an inorganic filler is added to a microporous structure made of a polyvinylidene fluoride-based resin. This system can provide excellent ionic conductivity at room temperature and mechanical strength that can be cast into a film shape; however, the content of inorganic materials is only 1.9-66% by weight of the total electrolyte film (equivalent to every 100 parts by weight poly Difluorovinyl resin 2-200 parts by weight), preferably 4.8-33.3 parts by weight (equivalent to 5-50 parts by weight), it is not enough to support the microporous structure, thereby causing the destruction of the microporous structure of the polymer electrolyte and the battery Short circuit of battery during assembly. Also, since the ionic conductivity of the electrolyte cannot be maintained at a constant level in practice, a battery with excellent characteristics cannot be manufactured.

The problems of the above-mentioned prior art can be summarized as follows:

(1) Electrolytes made of pure polymers have poor ionic conductivity, making them difficult to apply to practical battery fabrication processes.

(2) The gel-type polymer electrolyte prepared under the condition of containing liquid electrolyte has excellent ionic conductivity at room temperature because of the ionic conductivity of the liquid electrolyte, but the process operating conditions are limited and it is difficult to maintain a constant capacity.

(3) Hybrid polymer electrolytes made by adding plasticizers/processing aids to create thin film shapes and then removing them to allow liquid electrolytes to absorb inside, the advantage of this method is that the method is less affected by manufacturing conditions influence and have sufficient ion conductivity; however, complicated multiple steps and additional substances are required, and thus operation costs increase, and it is difficult to automate the process.

(4) The problem with introducing porous polymer electrolytes into it by various methods such as solvent/non-solvent exchange, vulcanization, curing, stretching, etc. is that the microporous structure will be destroyed during lamination or pressing, This results in insufficient absorption of the liquid electrolyte.

(5) The method of forming a thin film with a microporous structure on the electrode surface has the advantage of increasing the adhesive strength of the electrode surface, but the process conditions are not simple, so it is not preferable.

(6) There have been attempts to increase the mechanical strength by adding inorganic materials, but it cannot completely solve the problem of the destruction of the microporous structure during battery assembly, nor can it maintain the ionic conductivity.

Meanwhile, the present inventors provided a system in PCT 99/KR99/00798 in which the conductivity of lithium ions can be increased by introducing microporosity into the matrix of the electrolyte film containing absorbents to facilitate the absorption of liquid electrolytes sex. In the system, the moisture-sensitive liquid electrolyte is added after cell assembly, whereby the absorbent does not have to be removed after cell assembly. In addition, plasticizers or processing aids such as in US Patents 5,296,318, 5,418,091 and 5,631,103 are not required, so the process is simple and the process cost is low. However, as described above, the present inventors have found that there is such a problem that the microporous structure of the solid electrolyte membrane is destroyed and the absorbing capacity decreases in the step of combining the cathode and/or anode with the membrane. Therefore, the present inventors found that more than a certain amount of absorbent is required in order to solve the above-mentioned problems, and thus completed the present invention.

invention disclosure

Therefore, the present invention provides adding more than a specific amount of inorganic materials with structural filler and absorbent functions to prevent the destruction of the microporous structure, and maintain the absorption capacity of the solid electrolyte film, and in the battery assembly process, such as lamination or pressing Lithium ion conductivity. Inclusion of absorbent particles in a specific amount or more improves the ability to absorb liquid electrolytes together with the microporous structure, specifically, serves as a structural member for improving the mechanical strength of the electrolyte film and/or the solid electrolyte. Therefore, the excellent conductivity of lithium ions can be maintained even after battery assembly. Furthermore, no separation operation is required for the absorption of the liquid electrolyte, and it appears that the liquid electrolyte is such an important feature to introduce after battery assembly.

The solid electrolyte of the present invention includes an inorganic absorbent, and also includes an electrolyte film having a microporous structure and an ion-conductive liquid electrolyte. In other words, solid electrolytes for rechargeable batteries can be prepared through an activation process that absorbs ionically conductive liquid electrolytes into a microporous electrolyte film made only of inorganic absorbents and polymer binders. The term "electrolyte film" used in this specification refers to an electrolyte film which is in a dry state and does not contain any liquid electrolyte. The term "solid electrolyte" used in this specification means the electrolyte film having ion conductivity by introducing a liquid electrolyte therein. Although solid electrolytes are not completely solid because they contain liquid electrolytes, they are called "solid electrolytes" to distinguish them from liquid electrolytes because the basic skeleton of solid electrolytes begins with a solid electrolyte film.

The electrolyte thin film can preferably be prepared by a phase inversion method. Examples of such methods include wet and dry methods. The wet method refers to a method used to prepare an electrolyte film, which includes the steps of dissolving a mixture of an absorbent and a polymer binder in a solvent for the polymer binder, and forming the resulting solution into a film , exchanging the solvent with a non-solvent for the polymer binder, and then drying the resulting material to form an electrolyte film. On the contrary, the dry method refers to another method used to prepare the electrolyte film, which includes the steps of: binding the mixture of absorbent and polymer binder with solvent for polymer binder, insoluble polymer The non-solvent of the agent, the pore former (pore former) and the wetting agent are mixed, the resulting mixture is formed into a film, and then the obtained film is completely dried.

Due to the high affinity for liquid electrolytes, the inorganic absorbent used in the present invention will absorb liquid electrolytes or increase the absorption capacity of liquid electrolytes, and should not have electronic conductivity. Likewise, they should also have excellent mechanical, thermal, chemical and electrochemical properties. As such an inorganic absorbent, one kind or two or more kinds of particles selected from mineral particles, synthetic oxide compound particles and mesoporous molecular sieves can be used. Examples of the mineral particles include mineral particles having a phyllosilicate structure such as clay, sodium mica, montmorillonite, and mica. Examples of the synthetic oxide compound particles include zeolite, porous silica, porous alumina and magnesia. Examples of mesoporous molecular sieves include mesoporous molecular sieves made of oxides such as silica with a pore diameter of 2-30 nm. The mineral particles, synthetic oxide compound particles and mesoporous molecular sieves may be used in a mixture in which two or more absorbents selected from the above absorbents are combined.

The particle size of the inorganic absorbent is preferably not more than 40um, more preferably not more than 20um, so as not to reduce the mechanical strength and uniformity of the electrolyte film. However, when the particle size is too small, the absorbing capacity decreases or the resulting electrolyte film tends to have a dense structure, so it is not preferable. Existing techniques, such as Japanese Laid-Open Patent Publication 1999-16561, use inorganic materials with very small particle sizes (e.g., below 20 nm); however, in this case, the inorganic materials cannot be used as absorbers and may hinder filling crystallinity of the agent or polymer film. That is, in order to show the characteristics of the absorbent together with the structural elements in the present invention, the inorganic absorbent should have a particle diameter of 50 nm or more or an aggregated form in units of several micrometers. There is no particular limitation on the form of the inorganic absorbent, which may be in the form of fibers, needles, plates or spheres, but an asymmetric form is preferred in order to increase the mechanical strength of the electrolyte membrane.

A first object of the present invention is to prepare a solid electrolyte that maintains liquid electrolyte absorption capacity and ionic conductivity, resulting from the fact that the microporous structure is not destroyed and has mechanical strength even after battery assembly. The present inventors found that the amount of inorganic absorbent is a key condition to achieve the above object. The amount of the inorganic absorbent is preferably at least 70% by weight or more, more preferably 70%-95% by weight, of the amount of the electrolyte film composed of the inorganic absorbent and the polymer binder. When it is more than 95% by weight, the ionic conductivity does not increase as the amount increases, but instead, the mechanical strength of the formed electrolyte film and the surface adhesion between electrodes may deteriorate. On the contrary, 70% by weight is the starting point where there is a problem.

First, when the amount of inorganic matter is not more than 70% by weight, since the microporous structure of the solid electrolyte film tends to be broken during the lamination or pressing step of battery assembly, the absorption capacity and ion conductivity of the liquid electrolyte are greatly reduced. reduce. The present inventors prepared solid electrolyte thin films containing different amounts of inorganic absorbents, and then observed changes in thickness and ion conductivity with external pressure applied during battery production. From such tests, it was found that the thickness and ionic conductivity of the solid electrolyte thin film abruptly changed from 70% by weight. Nothing like this is suggested or taught in the prior art, and this is the first discovery by the inventors. Based on experimental facts, only more than 70% by weight can guarantee good performance of batteries, in which the microporous structure of the solid electrolyte is not damaged by the external pressure imposed by the production process, and this content does not reduce the ability to absorb liquid electrolyte , thus maintaining the ionic conductivity.

Secondly, when the amount of the inorganic matter is not more than 70% by weight, since the volume fraction of the polymer is large with respect to the total weight of the solid electrolyte, the deformation of the shape becomes large. That is, since shrinkage/swelling occurs at the step of drying the electrolyte or the step of impregnating the liquid electrolyte after battery assembly, the dimensional stability of the electrolyte film/solid electrolyte decreases.

Third, when the amount of inorganic matter is not more than 70% by weight, it is difficult to completely solve the problems of electrolytes mainly containing polymers even if many absorbents are included. For example, as in existing polymer electrolytes, deterioration occurs at low or high temperatures. In general, the effect of temperature on ionic conductivity becomes extremely significant because the movement of polymer chains directly affects ionic conductivity in polymer electrolytes. In particular, the movement of polymer chains is restricted at low temperatures, which significantly reduces ionic conductivity and thus leads to severe degradation of battery performance. On the other hand, the use of inorganic absorbers increases the ionic conductivity as in the present invention. In addition, the use of an inorganic absorber that is not temperature sensitive beyond a specified amount minimizes temperature effects contrary to the properties of the polymer electrolyte present. Also, because the electrolyte contains a large amount of inorganic absorbent, the electrolyte of the present invention has the advantage that its resistance to ignition or explosion is improved compared to electrolytes containing a large amount of organic materials such as polymers.

Considering that the amount of inorganic substances added in the prior art or other related art is usually about 50% by weight or less, the finding that the above-mentioned problem can be solved only when the organic absorbent is included in more than a specific amount is of great significance to the present invention. There are general concepts that are very exceptional, and it has been done through many experiments and analyzes based on large additions of inorganic substances.

As polymer binders, most common polymers can be used. Among them, it is preferable to use one or a mixture of two or more polymers selected from the following list, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a mixture of vinylidene fluoride and maleic anhydride Copolymer, polyvinyl chloride, polyvinyl alcohol, polyvinyl formal, polymethyl methacrylate, polymethacrylate, cellulose triacetate, polyurethane, polyimide, polycarbonate, polysulfone, poly Ether, polyethylene oxide, polyolefins such as polyethylene or polypropylene, polyisobutylene, polybutadiene, polyacrylonitrile, acrylonitrile butadiene rubber, ethylene-propylene-diene-monomer, tetra(ethylenediene Alcohol) diacrylates, dimethicone and polysilicon, or copolymers or polymer blends thereof.

Polymer binders whose properties change on a large scale or undergo crosslinking reactions, curing reactions, etc. under heat and pressure are not preferred. Likewise, polymer binders that induce polymerization, copolymerization, crosslinking, and curing reactions in the monomeric state by adding at least one substance are also not preferred. This is because unreacted monomers can become impregnated in the inorganic absorber, which can subsequently react with electrolyte compounds to degrade the performance of the battery, requiring a separation process to remove them. Therefore, it is preferable to avoid a situation where the above-mentioned problems may occur during the manufacturing process of the electrolyte thin film or the assembling process of the battery.

As a solvent for the polymer binder, which has solubility for the polymer binder, a mixture of one, two or more solvents selected from the group consisting of N-methylpyrrolidone, dimethylformaldehyde, Amides, Dimethylacetamide, Tetrahydrofuran, Acetonitrile, Cyclohexanone, Chloroform, Dichloromethane, Hexamethylphosphoramide, Dimethylsulfoxide, Acetone, and Dioxane.

As a non-solvent for polymer binders, it has little or no solubility in polymer binders, it is miscible with solvents, and one or two or more selected from Mixture of the following: water, ethanol, ethylene glycol, glycerin, acetone, methylene chloride, ethyl acetate, butanol, pentanol, hexanol and ether.

Hereinafter, a method of preparing the solid electrolyte having a porous structure will be explained in more detail.

wet method

The solid electrolyte with microporous structure of the present invention can be prepared by a wet method consisting of five steps, namely, dissolving polymer binder, mixing inorganic absorbent, casting film, preparing porous polymer matrix and drying, and activation.

First, the polymer binder is dissolved in a solvent, and then the inorganic absorbent is added to the solution, mixed well to make it evenly dispersed. The solid content of the mixed solution is preferably 5-60% by weight of the total weight of the solution. If the content is not more than 5% by weight, the mechanical strength of the electrolyte film decreases, and if the content is more than 60% by weight, the inorganic absorbent cannot be sufficiently dispersed or the viscosity of the mixed solution becomes very high, which causes problems.

In order to facilitate the dispersion of the inorganic absorbent, a magnetic stirrer, a mechanical stirrer, a planetary stirrer or a high-speed disperser can be used to agitate the mixed solution. While stirring, an ultrasonic stirrer may be used to prevent the absorbent from agglomerating or foaming during mixing. In addition, the mixed solution may be subjected to defoaming and filtering steps, if necessary.

After uniformly mixing the polymer binder and the inorganic absorbent, the resulting mixture is made into a film form. For example, the mixed solution can be poured onto a flat plate and then cast. Alternatively, fixed gaps can be used to extract the mixed solution from the die and apply it to the substrate. As substrates, substances that are chemically, thermally and mechanically stable and can be separated from the electrolyte film during the lamination process can be used, for example, polymer films such as polyester, polytetrafluoroethylene, paper, etc. can be used. Various other coating methods can be chosen.

After casting, the film is contacted with a non-solvent to exchange the solvent for the polymer binder. For example, the solvent can be extracted by dipping the film in a non-solvent bath. Therefore, it is preferred to choose a combination of miscible solvents and non-solvents. Depending on the type of solvent and non-solvent, soaking times in the non-solvent pool vary from one minute to one hour. When the time is short, it is difficult to obtain sufficient porosity. On the contrary, when the time exceeds the limited time, the productivity becomes low, which is not preferable. The temperature in the cell is preferably from 10°C to 90°C, more preferably from 20°C to 80°C. If the temperature is lower than the above-mentioned temperature, it is difficult to obtain sufficient porosity, and if the temperature is too high, the mechanical strength of the electrolyte film decreases, which is also not preferable. After extracting the solvent and completely drying the resulting film, an electrolyte film is produced.

dry method

The solid electrolyte with microporous structure of the present invention can be prepared by a dry method consisting of five steps, that is, dissolving the polymer binder, mixing the inorganic absorbent, adding additives (non-solvent, pore-forming agent, wetting agent), cast film and drying, and activation.

Dissolve the polymer binder in the solvent, then add the inorganic absorbent to the solution, mix well to make it evenly dispersed. The dispersing or mixing procedure is the same as the wet method. After uniformly mixing the polymer binder and absorbent, a non-solvent is added in an amount that does not cause precipitation of the polymer binder. In order to facilitate the formation of a microporous structure, it is preferred to add a pore forming agent or a wetting agent. The film casting procedure is the same as the wet method. After the film preparation is completed, the obtained electrolyte film is completely dried at 20° C. to 200° C. to produce an electrolyte film.

Compared with the wet method, the dry method has the following disadvantages, so the wet method is more preferably used.

(1) In the case of dry process, it is more difficult to completely disperse or mix absorbent, polymer binder and additives. When dispersion or mixing is incomplete, (i) it is difficult to achieve uniform dispersion of the pore former or absorbent, (ii) it is difficult to cast in the form of an electrolyte film and (iii) mechanical strength and reproducibility become low. That is, in the case of non-uniform dispersion of pore formers or absorbents, it has been confirmed that (a) when the electrolyte film is used as the electrolyte of an electrochemical cell, the reaction in the cell proceeds in a non-uniform localized state; (b) in the Casting in thin film form becomes difficult; and (c) mechanical strength is reduced, which poses serious limitations to the dry process.

(2) In order to form pores, the dry method needs to add a non-solvent. Considering the principle of the dry method, the solvent should evaporate before the non-solvent so that pores can be formed. If the non-solvent evaporates before the solvent, pores cannot form. In this regard, it is essential that the non-solvent should be non-volatile or have a higher boiling point than the solvent. For this reason, the dry method is likely to have the problem of residual non-solvent. In other words, the non-solvent, which has a higher boiling point than the solvent or is non-volatile, is difficult to completely remove from the electrolyte thin film in the drying step. Therefore, another step should be taken in order to completely remove the non-solvent (for example, extraction with alcohol or ether or sufficiently increasing the drying temperature). In addition, since the non-solvent is chemically and electrochemically unstable, if the non-solvent remains in the electrolyte film, it may cause side reactions or be oxidized or reduced by repeated charge and discharge of the battery, and therefore, may Deterioration of battery performance, such as reduction in battery capacity or gas evolution, may occur. The same issue applies to other additives than solvents. It is considered that a method of preparing an electrolyte thin film consisting only of an absorbent and a polymer binder by completely removing additives and the like may be complicated, which makes it difficult to repeat the method.

Preferably, the thickness of the film of the present invention is controlled within the range of 20-200um. If the film thickness is not more than 20 µm, the mechanical strength is lowered, so it is not preferable. On the contrary, if the film thickness exceeds 200 µm, ion conductivity decreases, so it is also not preferable. Preferably, the pore size of the electrolyte membrane of the present invention is less than 20um, more preferably less than 10um, and more preferably 0.01-5um. Preferably, the electrolyte membrane of the present invention has a porosity of 5-95%, more preferably 20-90%, and still more preferably 40-85%.

A liquid electrolyte absorbed into the microporous film prepared above can be prepared by dissolving lithium salt into an organic solvent.

It is preferable that the organic solvent has high polarity and does not react with metallic lithium in order to increase the degree of dissociation of ions by increasing the polarity of the electrolyte and to promote ion conductivity by reducing local viscosity around ions. Examples of such organic solvents include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate Ester (EMC), r-butyrolactone (GBL), dimethylsulfoxide (DMSO), 1,3-dioxane (DO), tetrahydrofuran (THF), 2-methyltetrahydrofuran, sulfolane, N, N - Dimethylformamide (DMF), diglyme (DME), triglyme and tetraglyme. In particular, the organic solvent is preferably used in the form of a mixed solution of two or more solvents, consisting of a high-viscosity solvent and a low-viscosity solvent.

The lithium salt preferably has low lattice energy and a high degree of dissociation. Examples of such lithium salts include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSCN, LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ and LiC(CF ₃ SO ₂ ) ₃ . Optional mixtures thereof may also be used. The concentration of the lithium salt is preferably 0.5M-2M.

The liquid electrolyte may be added in an amount of 20-90% by weight, preferably 40-85% by weight, of the total amount of electrolyte containing the liquid electrolyte. In this case, lithium ions in a solid electrolyte have a conductivity of 1–3 mS/cm at room temperature.

It is an object of the present invention to provide rechargeable batteries, in particular rechargeable lithium batteries, wherein said microporous solid electrolyte is used as electrolyte.

A method of producing a rechargeable battery containing a solid electrolyte of the present invention is described below.

The assembly of the battery is achieved by combining the cathode and anode with the interposed electrolyte film prepared through the above steps by lamination, pressing, or the like. The cathode and anode are prepared separately and the cathode is electrically connected to the cathode current collector and the anode is electrically connected to the anode current collector. Thus, the assembled device is activated to allow it to absorb a liquid electrolyte, thereby resulting in a ready-to-operate electrochemical cell.

It is preferable to prepare the electrolyte membrane and the electrodes (cathode and anode) separately, since then quality control, process design and equipment are simpler. If necessary, in order to increase the binding ability between the electrode and the electrolyte film and make the thickness of the electrolyte film thinner, a solid electrolyte slurry composed of absorbent, polymer binder, solvent, etc. can be directly coated on the electrode to form an electrolyte film. However, the above-mentioned method is not preferable because it will be difficult to adopt when the electrodes and the electrolyte membrane do not match each other, or when the electrodes or the electrolyte membrane are easily contaminated or lose their properties during the manufacturing process.

Considering the performance of the battery or the operating conditions of the process, the method of placing the electrolyte film between the electrodes and then assembling or laminating it on the battery by lamination or pressing can be improved. (i) First, the electrolyte film is laminated on one electrode of the cathode and the anode, and then the other electrode is laminated on the other side of the electrolyte film. (ii) An electrolyte thin film is laminated on the surfaces of the cathode and the anode, respectively, and then the cathode and the anode are laminated in a state where the electrolytes face each other. (iii) Cathode, electrolyte and anode are stacked sequentially at the same time.

In the lamination process, it is preferable to set the lamination conditions so as to minimize the decrease of the electrolyte film so that it does not exceed 50% by volume. The volume reduction of the electrolyte film means the destruction of the porous structure, but for lamination by heating or pressing, a little volume reduction is inevitable. Therefore, it is beneficial to find stacking conditions that minimize volume reduction. As stated above, it has been shown that the addition of inorganic absorbents in excess of at least 70% by weight, which is one of the most important features of the present invention, minimizes this volume reduction.

If desired, in order to limit the volume loss of the electrolyte, means can be used to set the temperature and pressure as low as possible and to allow the bonding between the electrodes and the electrolyte membrane to take place through the adhesive layer. For example, PE solution/dispersion, ethylene/ethyl acrylate-based or ethylene/vinyl acetate-based adhesives, etc. can be used. However, these adhesive components should be thermally, chemically and electrochemically stable, and the bonding layer made from them should not destroy the porous structure of the surface and not increase the damping of the surface. Therefore, it is preferable to use an adhesive layer in consideration of battery manufacture and performance control.

The method for preparing the cathode or anode is as follows. The cathode or anode consists of a current collector and an active material layer. The active material layer includes an active material, a conductive material, a binder, and the like. Besides, various additives can be introduced in order to improve the performance of the battery. The current collectors, conductive substances, binders and additives contained in the cathode or anode may be the same or different depending on the desired purpose. A mixture of the respective cathode or anode materials is kneaded together to obtain a slurry. The resulting slurry is made into a thin film by casting, coating and screen printing, and then the resulting thin film is combined with a current collector by pressing or lamination to form a cathode and/or an anode. Alternatively, the slurry can be coated directly on the current collector to form the cathode and/or anode.

The current collector provides a path for movement of electrons generated in oxidation/reduction reactions occurring at the cathode or anode. As a current collector, grids, foils, punched foils, and etched foils, etc. are generally used depending on the performance of the battery and the manufacturing process. Using a grid can increase the active material loading, but it may complicate the manufacturing process. Using foil can improve battery performance and simplify the manufacturing process, but it can degrade the compaction of the active material. Copper, aluminum, nickel, titanium, stainless steel, carbon, etc. can be used as current collectors. Typically, aluminum is used for the cathode and copper for the anode. If desired, the current collector may be pretreated, such as washing, surface treatment or tie coat coating.

In view of the fact that the charging and discharging reactions (or oxidation/reduction reactions) of the battery take place on the active material, it is considered that the active material is the most decisive component of the electrochemical cell, since it determines the performance of the battery. Furthermore, the active material occupies the largest content in the active material layer. As the cathode active material, transition metal oxides/sulfides, organic compounds, polymers, etc. can be used, preferably metal oxides or polymers can be used, such as lithium cobalt oxide (Li _x CoO ₂ ), lithium nickel oxide (Li _x NiO ₂ ), lithium nickel cobalt oxide (Li _x Ni _y Co _1-y O ₂ ), spinel lithium manganese oxide (Li _x Mn ₂ O ₄ ), manganese dioxide (MnO ₂ ), etc. As the anode active material, alkali metals, alkaline earth metals, carbon, oxide or sulfide compounds of transition metals, organic compounds and polymers can be used, preferably carbon or polymers can be used. It is important that the active material should be selected according to the desired battery performance or use.

The conductive substance refers to the substance added to the cathode or anode to improve electronic conductivity, usually carbon. Among them, the conductive substance is preferably graphite, coke, activated carbon and carbon black, more preferably graphite and carbon black. One or two or more conductive substances selected from the above may be used, regardless of whether they are artificial or natural substances. The added amount of the conductive substance is 3-15% by weight of the total weight of the electrode material. If the amount of the conductive substance added is not more than 3% by weight, the electrical conductivity decreases, thereby causing a problem of overvoltage. If the amount exceeds 15% by weight, the energy density per unit volume decreases, and side reactions caused by conductive substances become severe.

Binders refer to components, usually polymers, added to increase the binding capacity of active substances. Polymers used to prepare solid electrolyte thin films can be used as binders. A binder that is the same as or has miscibility with the polymer of the electrolyte membrane is preferably used. The binder is added in an amount of 15% by weight or less of the total weight of the electrode material. If the amount of binder is lower than required, the binding ability of the electrode may be reduced. If the amount of the binder exceeds 15% by weight, the processability and porosity of the electrode decrease.

Additives refer to substances added to improve battery or electrode performance, and can be selected in a wide range according to desired performance or use. The purpose of adding additives is to improve the binding ability with the inside of the composite electrode or the current collector, to make the composite electrode porous or non-crystalline, to improve the dispersion of the material constituting the composite electrode or the efficiency of the method used to manufacture the electrode, and to prevent the active material from dissipating. Overcharging/overdischarging, recombining or removing side reactants, or increasing the absorption capacity of liquid electrolytes. In general, salts, organic/inorganic compounds, minerals, and polymers can be used as additives, and the choice of absorbents added to the electrolyte membrane can be selected.

In a word, compared with the prior art, the solid electrolyte of the present invention and the rechargeable battery using the solid electrolyte have the following advantages:

(1) The manufacturing process and material requirements are simple. The formation of the film is simple, and excellent porosity can be obtained by simple methods such as wet methods; therefore, compared with the prior art, that is, vulcanization, curing stretching methods, especially methods using plasticizers/processing aids, It's very simple. In addition, the electrolyte film of the present invention has a simple composition, which contains a large amount of inorganic absorber and a small amount of polymer binder, and does not separately require plasticizers/processing aids, cured polymers, cross-linked polymers, or fibrous structures Material.

(2) The performance and stability of the electrolyte are excellent. Since the conduction of ions is performed through the liquid phase impregnated in the porous structure, the ionic conductivity is high. Low polymer content and high inorganic absorber content, whereby (i) ionic conductivity is not affected by temperature, (ii) mechanical, thermal and electrochemical stability are excellent, and (iii) form stable due to small volume change Good sex. In addition, the electrolyte of the present invention has a wide electrochemical potential window, and resistance to ignition and explosion. In particular, the inclusion of an inorganic absorbent in a certain amount or more is used as a structural member, which improves damping during lamination or pressing, so that there is little decrease in electrolyte performance even after battery assembly.

(3) The assembly of the battery is simple. No specific dehumidifying atmosphere is required during the preparation of the electrolyte film and the assembly of the battery; thus, the fabrication process is simple and easy to automate for mass production.

Brief description of the drawings

Fig. 1 shows a graph showing test results of linear sweep voltammetry for measuring the electrochemical stability of the solid electrolyte of the present invention.

Figures 2, 4 and 5 show changes in the discharge capacity of batteries using the inorganic absorbent of the present invention.

Figure 3 shows the changes in thickness and ionic conductivity of films prepared with different amounts of inorganic absorber, where the changes are expressed relative to the initial values.

Best Mode for Carrying Out the Invention

In the present invention, the solid electrolyte of the present invention and a method of manufacturing a battery by using the solid electrolyte are described in detail. The preparation and performance tests of solid electrolyte were carried out. In addition, the solid electrolyte is assembled with the anode and cathode to form a battery, and then the procedure for testing the performance of the battery is described. However, the present invention is not limited to those examples, and various changes can be made thereto within the scope of the present invention. Embodiment 1 (wet method: experiment carried out according to the type and amount of inorganic absorbent and the type of liquid electrolyte)

A polymer binder solution was prepared by dissolving 14 g of PVdF (polyvinylidene fluoride) in 86 g of NMP (N-methylpyrrolidone). The inorganic absorbent is added to the solution and stirring is continued until the inorganic absorbent is completely dispersed. In order to prevent the absorbent particles from agglomerating with each other, the solution was ultrasonically stirred for 30 minutes while stirring. The mixed solution thus prepared was applied to a glass plate having a thickness of 100 um. The coated film was immersed in the non-solvent bath for approximately 10 minutes, then removed from the bath and dried at 70°C for 1 hour. The porous electrolyte film thus prepared was immersed in a liquid electrolyte solution for about 10 minutes. After the liquid electrolyte has been completely absorbed, the weight change is measured. Ionic conductivity was also measured by using an alternating current impedance method.

Table 1 summarizes the types of inorganic absorbers and binders, and the properties of the porous solid electrolyte in terms of content and conductivity. To compare the ability of porous electrolyte films to absorb liquid electrolytes, the absorption capacity (Δ _ab ) is defined as follows:

Δ _ab = [amount of absorbed liquid electrolyte (mg)]/[weight of electrolyte film (mg)]

In addition, the case where the volume of the solvent containing the liquid electrolyte is not indicated means that the solvents are mixed in the same volume.

Table 1 Example absorbent PVdF Absorbed dose (%) non-solvent liquid electrolyte _Δab Ionic conductivity (mS/cm) Mechanical strength type g g a Sodium mica 0.18 0.60 23.1 H ₂ O EC/DMC1MLiPF ₆ 7.2 1.8 good b Sodium mica 0.17 0.31 35.4 H ₂ O EC/DMC1MLiPF ₆ 6.9 2.1 good c Sodium mica 0.31 0.28 52.5 H ₂ O EC/PC1MLiPF ₆ 6.7 1.9 good d Sodium mica 0.72 0.24 75.0 H ₂ O EC/PC1MLiPF ₆ 6.9 1.9 good e Sodium mica 1.06 0.26 80.3 H ₂ O EC/PC1MLiPF ₆ 7.5 1.8 good f Sodium mica 0.85 0.26 76.6 H ₂ O EC/DMC1MLiPF ₆ 7.9 2.1 good g Sodium mica 1.51 0.26 85.3 H ₂ O EC/DMC1MLiPF ₆ 8.0 2.4 good h Sodium mica 2.00 0.26 88.5 H ₂ O EC/DMC1MLiPF ₆ 8.5 2.5 good i Sodium mica 1.98 0.25 88.8 ethanol EC/DMC1MLiPF ₆ 5.1 1.0 good j Zeolite 1.37 0.60 69.5 H ₂ O EC/DMC1MLiPF ₆ 7.2 1.9 good k Zeolite 1.50 0.38 79.8 H ₂ O EC/DMC1MLiPF ₆ 8.2 2.0 good l Zeolite 1.65 0.29 85.1 H ₂ O EC/DMC1MLiPF ₆ 8.0 2.4 good m Montmorillonite 1.34 0.58 69.8 H ₂ O EC/DMC1MLiPF ₆ 8.0 2.8 good no Montmorillonite 1.50 0.38 79.8 H ₂ O EC/DMC1MLiPF ₆ 8.2 2.9 good o porous silica 1.35 0.59 69.6 H ₂ O EC/DMC1MLiPF ₆ 8.5 2.4 good

In the above Table 1 and the following Table 2, the item "mechanical strength" is measured when the electrolyte film is formed or in a state where the liquid electrolyte is impregnated, so it is the same as the electrolyte film showing resistance to lamination or pressing at the time of battery assembly The meaning is different. That is, the one with good mechanical strength in the table may show different properties at the time of battery assembly depending on the content of the inorganic absorbent. Example 2 (wet method: experiment according to adhesive type)

The experiment was conducted by changing the adhesive type in the same manner as in Example 1, and the results are summarized in Table 2.

Table 2 Example Absorbent (sodium mica) Adhesive Absorbed dose (%) liquid electrolyte _Δab Ionic conductivity (mS/cm) Mechanical strength g substance g p 1.98 PVdF 0.24 89.2 EC/DMC1MLiPF ₆ 8.1 2.4 good q 2.00 P(VdF-HFP) 0.26 88.5 EC/DMC1MLiPF ₆ 8.0 2.6 good r 1.95 PAN 0.25 88.6 EC/DMC1MLiPF ₆ 7.8 2.2 good the s 2.00 PU 0.26 88.5 EC/DMC1MLiPF ₆ 8.9 2.9 good t 1.98 pvc 0.25 88.8 EC/DMC1MLiPF ₆ 7.4 2.0 good Embodiment 3 (dry method)

0.5 g of P(VdF-HFP) (poly(vinylidene fluoride-hexafluoropropylene)) was dissolved in 8 g of acetone in a 20 ml vial to prepare a polymer binder solution. To the resulting mixture was added 1.17 g of sodium mica, followed by continuous stirring until the particles were completely dispersed. In order to prevent the absorbent particles from agglomerating with each other, the resulting solution was additionally subjected to ultrasonic stirring for 30 minutes while stirring. 0.9 g of ethylene glycol, 0.1 g of Triton X-100 (wetting agent) and 1.8 g of isopropanol (pore forming agent) were added to the resulting mixed solution, and the resulting mixture was ultrasonically stirred for about 10 minutes until the added mixture was Mix well. The mixed solution thus prepared was applied to a glass plate having a thickness of 100 um. The coating film was dried at 40°C for about 2 hours, and dried for an additional about 6 hours in a vacuum dryer set at 50°C. The electrolyte film thus prepared was immersed in an EC/DEC 1M LiPF ₆ solution for about 10 minutes. After the liquid electrolyte has been completely absorbed, the weight change is measured. The Δ _ab value determined by weight change was 7.5. The conductivity measured by alternating current impedance method at room temperature was 2.0 mS/cm. Example 4 (comparative example: experiment of preparing a solid electrolyte with a non-porous structure)

14 g of PVdF was dissolved in 86 g of NMP to prepare a polymer binder solution. 2 g of sodium mica powder was added to 1.85 g of the polymer binder solution and stirring continued until the particles were completely mixed. In order to prevent the absorbent particles from agglomerating with each other, the resulting solution was additionally subjected to ultrasonic stirring for 30 minutes while stirring. The mixed solution thus prepared was applied to a glass plate having a thickness of 100 um. The coating film was dried at room temperature for about 2 hours, and then dried for another about 6 hours in a vacuum drier controlled at a temperature of about 50°C. The electrolyte film thus prepared was immersed in an EC/DEC 1M LiPF ₆ solution for about 10 minutes. After the liquid electrolyte was completely absorbed, the weight change was measured, and the conductivity was measured by the AC impedance method. The measured conduction of lithium ions at room temperature is 0.72 mS/cm. This example differs from Examples 1-3 in that the method of forming a porous structure was not implemented. From the results of this example, it can be confirmed that the method of introducing porosity in the wet or dry process is necessary to improve the performance of the battery. Embodiment 5 (electrochemical stability experiment)

In order to determine the electrochemical stability of the microporous solid electrolyte, it was determined by linear sweep voltammetry using stainless steel (#304) as the working electrode, metallic lithium as the counter electrode and reference electrode. The electrochemical voltage applied in linear sweep voltammetry ranged from open circuit voltage to 5.5 V, and the scan rate of linear sweep voltammetry was 10 mV/sec. In Fig. 1, the linear sweep voltammetry result measured on the microporous solid electrolyte prepared by the method of embodiment 1-(h), 1-(1), 1-(n) and 2-(s) respectively Denoted by A, B, C and D, it can be seen from Figure 1 that the solid electrolyte according to the present invention is electrochemically stable up to 4.8V. Likewise, it can also be seen that synthetic oxide absorbents are more stable than natural mineral absorbents. Embodiment 6 (battery performance experiment)

In order to measure the performance of the battery using the solid electrolyte, the battery was prepared as follows. By mixing the oxide active material, conductive carbon powder, polymer binder and additives in a slurry phase at a weight ratio of 82:7:8:3, and coating the slurry on an aluminum grid, and then drying it. Prepare the cathode. An anode was prepared by mixing artificial graphite, conductive carbon powder, polymer binder and additives in a slurry phase at a weight ratio of 85:3:10:2, and coating the slurry on a copper grid, followed by drying it. Three (3) layers of cathode, electrolyte membrane, and anode are simultaneously laminated to make a battery, which is then allowed to absorb a liquid electrolyte. Seal the cell with wrapping film, except for the electrode ends that are exposed. Charge and discharge tests were carried out on the batteries thus fabricated. A constant current is applied at a rate that charges to reversible capacity within 2 hours (C/2 rate) until the battery voltage becomes 4.2V, and then a constant voltage of 4.2V is applied again until the current drops to C/10mA. Subsequently, a discharge current was applied at a rate (C/2 rate) to discharge to a voltage of 2.5 V or 2.75 V within 2 hours. Repeat the charge and discharge test to measure the change in discharge capacity with charge and discharge. The cell composition and test results are summarized in Table 3 below and shown in FIG. 2 . As listed in Table 3, the solid electrolyte refers to a case in which a liquid electrolyte is absorbed into an electrolyte film. In addition, no battery test was performed on the solid electrolyte obtained in Example 4.

table 3 Example cathode anode solid electrolyte picture active substance conductive substance Adhesive additive active substance conductive substance Adhesive additive u _LiCoO2 carbon black PVdF Sodium mica graphite carbon black PVdF Sodium mica Example 1-(g) Figure 2-E v _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Embodiment 1-(1) Figure 2-F w _LiCoO2 carbon black P(VdF-HFP) Zeolite graphite carbon black P(VdF-HFP) Zeolite Example 3 Figure 2-G x LiMn ₂ O ₄ carbon black P(VdF-HFP) Sodium mica graphite carbon black P(VdF-HFP) Sodium mica Embodiment 2-(q) Figure 2-H

Fig. 2 shows the comparison of the discharge capacity of the battery obtained by the corresponding embodiment when it is repeatedly charged and discharged and the discharge capacity for the first time. It was confirmed from the test results that using the solid electrolyte obtained by the wet method (Examples 1 and 2) (Example 6 -u, v, x) show much better battery performance, i.e., solid electrolytes containing inorganic absorbers and prepared by wet method have a much better impact on the overall performance of the battery (charging and discharging performance, etc.), although The properties (ionic conductivity, mechanical strength, etc.) of the electrolyte film or the solid electrolyte itself did not show any significant difference. Embodiment 7 (property experiment carried out according to the variation of the amount of sodium mica used as inorganic absorbent)

A 10 ^cm porous solid electrolyte film was prepared by changing the amount of sodium mica powder as the inorganic absorbent as in Example 1, and then pressing with a pressure of 1 ton by an experimental press at 130 °C within 15 seconds. The change in thickness before and after pressing was measured, and the change in ionic conductivity before and after pressing was also measured by AC impedance method. The results are summarized in Table 4. Figure 3 shows the film thickness and ionic conductivity after pressing expressed as a percentage based on the film thickness and ionic conductivity before pressing. The liquid electrolyte used in the determination of ionic conductivity was EC/DMC/DEC 1M LiPF ₆ .

Table 4 Example absorbent PVdF Absorbed dose (%) Before suppression After pressing type g g Film thickness (μm) Ionic conductivity (mS/cm) Film thickness (μm) Ionic conductivity (mS/cm) the y Sodium mica 0.18 0.60 23.1 100 1.7 30 0.10 z Sodium mica 0.17 0.31 35.4 100 2.0 35 0.15 aa Sodium mica 0.31 0.28 52.5 100 1.8 40 0.25 bb Sodium mica 0.46 0.27 63.0 100 1.9 45 0.35 cc Sodium mica 0.57 0.24 70.4 100 2.0 50 0.50 dd Sodium mica 0.73 0.25 74.5 100 2.0 60 0.8 ee Sodium mica 1.06 0.26 80.3 100 2.1 80 1.2 ff Sodium mica 1.98 0.26 88.4 100 2.5 85 1.8 gg Sodium mica 3.65 0.20 94.5 100 2.6 90 2.0 hh Sodium mica 5.02 0.15 97.1 100 2.7 90 2.1

As confirmed by the above results, when the content of the inorganic absorbent is greater than 70% by weight (Example 7-cc and its next example), there is little difference between the film thickness and ion conductivity after pressing and before pressing, That is, it can be seen that although the difference in ion conductivity of the electrolyte film or solid electrolyte itself does not mainly depend on the content of the inorganic absorbent, its influence becomes greater when the electrolyte film or solid electrolyte is subjected to the pressing process. Example 8 (property experiment carried out according to the variation of the amount of zeolite used as inorganic absorbent)

An experiment using zeolite as an inorganic absorbent was carried out in the same manner as in Example 7. The changes in electrolyte film and ionic conductivity before and after pressing are summarized in Table 5.

table 5 Example absorbent PVdF Absorbed dose (%) Before suppression After pressing type g g Film thickness (μm) Ionic conductivity (mS/cm) Film thickness (μm) Ionic conductivity (mS/cm) i Zeolite 0.30 1.0 20.5 100 1.8 30 0.10 jj Zeolite 0.44 0.80 35.6 100 2.0 35 0.17 kk Zeolite 0.88 0.80 55.1 100 2.0 40 0.26 ll Zeolite 1.42 0.60 70.3 100 1.9 50 0.50 mm Zeolite 1.50 0.55 73.2 100 2.0 60 0.75 n Zeolite 1.50 0.38 79.8 100 2.0 75 1.2 oo Zeolite 2.00 0.27 88.1 100 2.2 85 1.8 pp Zeolite 3.99 0.21 95.0 100 2.3 90 2.0 qq Zeolite 4.20 0.13 97.0 100 2.4 90 2.1

As confirmed by the results of Example 7, when the content of the inorganic absorbent was greater than 80% by weight (Examples 8-11 and its next example), there was little difference between the film thickness and ion conductivity after pressing and before pressing. difference. Summarizing the results of Example 7 and this example, it can be seen that the above-mentioned characteristic phenomena have little correlation with the type of inorganic substance. It is also expected that when cells containing those electrolytes are fabricated by lamination or pressing and then the performance of the cells is measured, they will show significant differences depending on the content of the inorganic absorber. Embodiment 9 (battery performance experiment carried out according to the variation of inorganic absorbent type and content)

A battery was constructed in the same manner as in Example 6, and the effect of changing the type and content of the inorganic absorbent on the battery was studied. The composition and test results of the cells are summarized in Table 6 and shown in FIGS. 4 and 5 . It can be seen from Table 6 that each solid electrolyte is in a state where the liquid electrolyte is absorbed into the electrolyte film.

Table 6 Example cathode anode solid electrolyte picture active substance conductive substance Adhesive additive active substance conductive substance Adhesive additive rr _LiCoO2 carbon black PVdF Sodium mica graphite carbon black PVdF Sodium mica Embodiment 7-(y) Figure 4-I ss _LiCoO2 carbon black PVdF Sodium mica graphite carbon black PVdF Sodium mica Example 7-(aa) Figure 4-J tt _LiCoO2 carbon black PVdF Sodium mica graphite carbon black PVdF Sodium mica Embodiment 7-(dd) Figure 4-K u u _LiCoO2 carbon black PVdF Sodium mica graphite carbon black PVdF Sodium mica Embodiment 7-(ff) Figure 4-L vv _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Embodiment 8-(ii) Figure 5-M ww _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Embodiment 8-(kk) Figure 5-N xxx _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Example 8-(mm) Figure 5-O yy _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Example 8-(oo) Figure 5-P

As can be seen from the above test results, when the inorganic absorbent content in the solid electrolyte is greater than 70% by weight (Example 9-tt, uu or Example 9-xx, yy) will show a better performance than other contents. performance. Summarizing the results of Examples 7, 8 and this example, it can be seen that although only for the electrolyte film or solid electrolyte itself, its properties such as ionic conductivity and mechanical strength have almost no difference with the content of inorganic absorbents. However, the effect of the absorber content is greatly shown when they are laminated or pressed when fabricated into batteries. In other words, it can be said that when the content of the inorganic absorbent exceeds 70% by weight, the ability to absorb liquid electrolyte is not lost even after battery assembly, and has an excellent influence on battery performance. It was also confirmed that this phenomenon was exhibited regardless of the kind of the inorganic absorbent.

Industrial Applicability

The present invention provides a solid electrolyte having excellent ion conductivity, which is formed by allowing a liquid electrolyte to be easily absorbed into an electrolyte film to which an inorganic absorbent is added and porosity is introduced. The present invention also provides a method of preparing those solid electrolytes; and a rechargeable lithium battery using the solid electrolyte as an electrolyte. The solid electrolyte of the present invention has the advantages of simple manufacturing process and material requirements, excellent capacity and stability of the electrolyte, and easy assembly of batteries using the solid electrolyte. In particular, since the inorganic absorbent is added in excess of a specific amount, the porosity of the electrolyte film and the ability to absorb liquid electrolyte can be maintained during lamination or pressing, thereby maintaining the same solid electrolyte even after battery assembly. Excellent nature as good as itself.

Claims (8)

1. A solid electrolyte for a rechargeable battery, comprising: An electrolyte membrane with a thickness of 20-200 μm and a microporous structure, wherein the electrolyte membrane contains an inorganic absorbent with a particle size of not more than 40 μm in an amount of at least 70% by weight of the total weight of the electrolyte membrane under dry conditions without liquid electrolyte; and An ion-conductive liquid electrolyte in an amount of 20-90% by weight of the total weight of the electrolyte comprising the liquid electrolyte. 2. The solid electrolyte for rechargeable batteries according to claim 1, wherein the content of the inorganic absorbent is 70-95% by weight. 3. The solid electrolyte for rechargeable batteries according to claim 1, wherein The inorganic absorbent is a mixture of one or two or more selected from the following groups: Mineral particles with phyllosilicate structure, such as clay, sodium mica, montmorillonite and mica; synthetic oxide compound particles, such as zeolite, porous silica and porous alumina, magnesium oxide; pore size of 2-30um, made of oxide Mesoporous molecular sieves made of polymers or polymers; and other commercially available absorbents; The polymer binder is a mixture of one or two or more selected from the following groups: Polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, copolymer of vinylidene fluoride and maleic anhydride, polyvinyl chloride, polymethyl methacrylate, polymethacrylate, triacetate fiber Polyurethane, polysulfone, polyether, polyethylene, polypropylene, polyethylene oxide, polyisobutylene, polybutadiene, polyvinyl alcohol, polyacrylonitrile, polyimide, polyvinyl formal, acrylic Nitrile butadiene rubber, ethylene-propylene-diene-monomer, tetra(ethylene glycol) diacrylate, polydimethylsiloxane, polycarbonate and silicon polymers, or their copolymers or mixtures. 4. The solid electrolyte of a rechargeable battery according to claim 1, wherein said electrolyte thin film is prepared by a wet method comprising: dispersing an inorganic absorbent in a solution consisting of a polymer binder and a solvent thereof, A step in which the resulting mixture is prepared into a film, the solvent is exchanged with a non-solvent for the polymer binder, and the resulting substance is dried. 5. The solid electrolyte for a rechargeable battery according to claim 4, wherein The solvent used for the polymer binder is a mixture of two or more solvents selected from the group consisting of: N-methylpyrrolidone, dimethylformamide, dimethylacetamide, tetrahydrofuran, acetonitrile, cyclohexanone, chloroform, methylene chloride, hexamethylphosphoramide, dimethylsulfoxide, acetone and dioxane; The non-solvent for the polymer binder is a mixture of one or two or more solvents selected from the following groups: Water, Ethanol, Ethylene Glycol, Glycerin, Acetone, Methylene Chloride, Ethyl Acetate, Butanol, Pentanol, Hexanol and Diethyl Ether. 6. The solid electrolyte for a rechargeable battery according to any one of claims 1-4, wherein the solid electrolyte is prepared by an activation process in which an ionically conductive liquid electrolyte is absorbed into the electrolyte film, and The ion-conductive liquid electrolyte is obtained by adding a material selected from LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSCN, LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ and LiC(CF ₃ SO ₂ ) ₃ One or two or more lithium salts are dissolved into a concentration of 0.5M-2M in a mixture of one or two or more organic solvents selected from the following group to obtain: Ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, r-butyrolactone, 1,3-dioxane, tetrahydrofuran, 2-methyl carbonate tetrahydrofuran, dimethylsulfoxide, sulfolane, N,N-dimethylformamide, diglyme, triglyme and tetraglyme. 7. A rechargeable lithium battery obtained through the following steps: Disperse the inorganic absorbent with a particle size not exceeding 40um in a weight ratio based on the polymer binder of 70/30-95/5 into a solution composed of the polymer binder and its solvent, The resulting mixture was formed into a thin film, exchanging the solvent with a non-solvent for the polymer binder, and drying it to form a microporous electrolyte film with a thickness of 20-200um, wherein the diameter of the micropores does not exceed 20um, and the porosity is 5-95%, placing the resulting electrolyte membrane between the cathode and the anode, The resulting structure is laminated and bonded by lamination or pressing to assemble it into a battery form, and then The resulting battery is allowed to absorb an ionically conductive liquid electrolyte. 8. The rechargeable lithium battery according to claim 7, wherein said cathode and said anode are prepared separately from the electrolyte membrane, the polymer binder for the cathode and/or anode is the same as or compatible with the polymer binder of the electrolyte membrane, The additives for the cathode and/or anode are one or a mixture of two or more selected from absorbents for electrolyte films.

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