Solid electrolyte

Abstract

Regarding a solution for forming a solid electrolyte (5), the solution is a plurality of silicon oxide particles (1) dissolved in a liquid medium, which are non-hydrogen atoms of at least 4, one of which is a non-hydrogen atom covalently bonded to the silicon atom of the silicon oxide particle, and a linkable functional group (21) capable of reacting with another identical linkable functional group (21) to form a covalent bond after activation by a radical species, and the solution contains silicon oxide particles (1) functionalized with an organic moiety (2) containing the linkable functional group (21). The organic moiety (2) contains at least 2 atoms that are not part of the linkable functional group (21), and these atoms are bonded to each other by a π bond. The ratio of the number of organic moieties (2) to the number of silicon atoms contained in the plurality of silicon oxide particles (1) is at least 0.3. Furthermore, the solution contains an electrolyte compound (52).

Description

Technical Field

[0001] The present invention relates to the field of solid electrolytes. More specifically, the present invention relates to a solution for forming a solid electrolyte and a method for forming a solid electrolyte using the same.

Background Art

[0002] In a lithium-ion battery (LIB), by using a solid electrolyte instead of a liquid electrolyte, when combined with state-of-the-art electrode materials, there is a possibility of increasing the energy density to a value exceeding 800 Wh / L. Since the electrolyte usually does not contribute to the energy density of the battery, it should be made as thin as possible. The solid electrolyte can be made very thin, thereby increasing the amount of active material in the battery. The solid electrolyte is desirably in good contact with the electrode and is therefore desirably somewhat flexible. Furthermore, its ionic conductivity is desirably high enough not to limit the charging and discharging rates of the battery.

[0003] The solid electrolyte can contain a liquid electrolyte compound such as an ionic liquid (IL). An ionic liquid is a salt with a melting point below 100°C. Incorporating IL into the solid electrolyte is an effective approach for realizing a safe lithium-ion battery because IL has beneficial properties such as high ionic conductivity, a wide electrochemical stability window, and non-flammability. IL can be confined within a solid material, which is called an "ion gel". This ion gel electrolyte generally shares the excellent properties of IL and also has the advantage of reducing the risk of leakage. This type of solid electrolyte can contain many different solid matrices, which are generally divided into two categories. That is, polymer materials and inorganic materials.

[0004] In polymer - type ion gel electrolytes, ILs (e.g., dissolved lithium salts, ionic liquid electrolytes (ILEs), etc.) are incorporated into the polymer matrix, and the ILs may act as plasticizers. Their functional properties (e.g., lithium - ion conductivity) are often not more beneficial than those of pure ILEs.

[0005] In inorganic - type ion gel electrolytes, various inorganic materials such as metal oxides (e.g., TiO2) and non - metal oxides (e.g., SiO2) are used as solid matrices for incorporating ILs. However, the latter is a much more common option. Porous silicon oxide provides a large surface area and has high thermal and mechanical stability. Furthermore, the interfacial layer that may form on the pore walls of porous silicon oxide can be formed by strongly adsorbed highly ordered IL cations and anions, which may lead to good ion conduction. This effect can exceed the reduction in ion conductivity due to the confinement of ILs and may result in an ion conductivity several times that of the incorporated ILE. Under appropriate synthesis conditions, these materials can form a mutually connected oxide matrix. That is, there is a continuous surface, and a path for lithium - ion conduction is formed without interruption from one end to the other end of the porous silicon oxide matrix of the ion gel electrolyte.

[0006] For use in a commercially viable production process, ion gel electrolytes desirably need to meet the following three conditions. First, the ion gel electrolyte desirably needs to have excellent functional properties. The role of the ion gel electrolyte is to transport (lithium) ions from one electrode to the other electrode. This rate can be expressed as ion conductivity. Desirably, the ion gel electrolyte of the battery has good ion conductivity. If the ion conductivity of the ion gel electrolyte is low, ions are not easily transported between the electrodes, polarization increases, and the occurrence of redox reactions within the electrodes may be limited. This can ultimately reduce the energy density and power density of the battery.

[0007] Second, it is desirable that the ion gel electrolyte has good manufacturability. Good battery performance may depend on the successful integration of the electrolyte and the porous electrode. In order to fully utilize its functional characteristics, the ion gel electrolyte needs to be in close contact with the porous battery electrode. This can be achieved by a liquid treatment in which the ion gel electrolyte is impregnated into the electrode as a solution, for example a liquid precursor, and then changed to a solid. In this approach, a certain priority is placed on the manufacturability of the ion gel electrolyte. More specifically, by developing a large-scale continuous impregnation process, preferably, the chemistry and process involved in the solidification reaction can be accurately controlled, and preferably, this process can be made to occur within a very short and controllable time frame.

[0008] Third, the ion gel electrolyte preferably has good compatibility with other components of the battery. Regarding the impregnation of the solution for forming the ion gel electrolyte in the porous electrode, preferably, both components are compatible with each other. For example, the presence of an acid or a base in the solution may damage the crystal structure of the electrode particles. Also, due to contact with the solid surface, the properties of the solution (e.g., pH value) change, and as a result, the chemical reaction changes, and solidification may be hindered, delayed, or its functional properties may be lost. Ideally, the solution does not contain any components that may damage the electrode and has no effect on the solidification process by being present in the electrode.

[0009] State-of-the-art ion gel electrolytes do not meet each of the three basic requirements described above. Ion gel electrolytes can be classified into three classes, each of which usually meets at most two of the three requirements.

[0010] The first type of ionic gel electrolyte is a polymer-based ionic gel electrolyte. When an electrolyte compound, such as ILE, is incorporated into a polymer matrix, lithium ions interact with the polymer chains (depending on the functional groups). ILE often interacts with the polymer, resulting in good miscibility and a decrease in ionic conductivity. Polymer-based ionic gel electrolytes are generally easy to manufacture by a high-speed polymerization process. For example, in the microwave-assisted thermal polymerization of a liquid solution containing acrylate-type monomers, a polymer-based ionic gel electrolyte can be formed in just a few seconds. Polymer-based ionic gel electrolytes are generally excellent in compatibility with electrodes. The target ionic gel electrolyte can be prepared simply by dropping the solution for forming the ionic gel electrolyte onto the electrode. In this method, the adhesion is high and the structure is not damaged. These ionic gel electrolytes have both flexibility and mechanical resistance. However, polymer-based ionic gel electrolytes generally have low ionic conductivity and are often lower than the ionic conductivity of the incorporated ionic liquid. SiO2 nanoparticles are used as fillers in polymer-based ionic gel electrolytes, but these do not significantly increase the ionic conductivity. The dispersion of these filler nanoparticles in polymer-based ionic gel electrolytes does not lead to the formation of a continuous interface such as silicon oxide, and a path for lithium ions to conduct without interruption is not formed, so the transport of lithium ions is still limited by movement throughout the polymer matrix.

[0011] The second type of ion gel electrolyte is a silicon oxide-based ion gel electrolyte formed by non-hydrolytic solidification. In a silicon oxide-based ion gel electrolyte, an electrolyte compound (e.g., ILE) can be incorporated into a porous silicon oxide matrix. In a classical sol-gel non-hydrolytic synthesis method for an ion gel electrolyte based on a porous silicon oxide matrix with a large surface area and interconnected pores, a homogeneous liquid mixture containing an electrolyte compound and a silane that can form a porous silicon oxide matrix after hydrolysis and condensation is prepared. The electrolyte compound and the silicon oxide matrix form a complex in situ, and a silicon oxide matrix precursor (e.g., tetraethyl orthosilicate) reacts to form a matrix that encapsulates the electrolyte compound. The electrolyte compound is selected to function as a template for the formation of the porous silicon oxide matrix.

[0012] This type of ion gel electrolyte can potentially be composed of a continuous silicon oxide surface, which means that lithium ions can be transported from one end of the matrix to the other through a conduction path without interruption. This enables high ion conductivity values to be achieved. That is, these materials have excellent functional properties. Since the process of forming the porous silicon oxide matrix from a solution (also containing ILE) is promoted by catalysis, it can be formed in a short time (usually several hours) and is easy to manufacture. In state-of-the-art synthesis protocols, acids such as formic acid (FA), hydrochloric acid (HCl), or HPF6 are usually added to form the porous silicon oxide matrix in a short time. This type of synthesis protocol can also be used for organic modification of the matrix. The integration of these ion gel electrolytes with battery electrodes is usually carried out by impregnating a solution into a porous electrode structure. Unfortunately, the addition of an acid to the solution may not be compatible with the electrode, and the acid may damage the active material particles. Therefore, the aforementioned advantages brought about by this type of ion gel electrolyte cannot be realized in all-solid-state batteries.

[0013] The third ion gel electrolyte is a standard nano-solid composite electrolyte (nano-SCE). The standard nano-SCE is composed of a porous silicon oxide matrix and an ILE filler (e.g., CHEN, Xubin et al., Silica gel solid nano-composite electrolyte with enhanced interfacial conductivity exceeding the bulk Li-ion conductivity of ionic liquid electrolyte fillers, Science advances, 2020, 6.2: eaav3400). In contrast to the second type of ion gel electrolyte, nano-SCE is not synthesized via a non-hydrolytic route. Instead, an aqueous solution mixture with a pH of about 5, containing ILE and TEOS / organic silicon compounds and in a large excess of water and alcohol solvents, is used as the solution for forming the ion gel electrolyte. At this pH, the hydrolysis of alkoxy groups is usually slower compared to the condensation reaction. After gelation, the gel is dried to remove all free water and solvents. Since a continuous surface of silicon oxide may be formed, the nano-scale solid electrolyte may have high ionic conductivity. A chemically adsorbed water layer may also exist on the silicon oxide surface, which may improve the molecular order of the IL. This ultimately improves the dissociation of Li + ions and enables fast diffusion of lithium ions along the interfacial layer. In this synthesis procedure, a porous silicon oxide matrix composed of densely packed silicon oxide nanoparticles is generated, with relatively small pores (10 - 30 nm) formed around relatively large pores (100 - 150 nm). This structure has a very high specific surface area and may be advantageous for obtaining high ionic conductivity. As a result, bulk ion conductivity values several times that of the incorporated ILE may be obtained. That is, the standard nano-SCE has excellent functional properties. No acid is added to the solution, meaning the solution has high compatibility with battery electrodes.

[0014] The standard manufacturing process of nano-SCE is to mix all the reagents and start the gelation process immediately after mixing. This is a time-dependent process and usually takes several days until the solution is completely solidified. The exact gelation time depends on many factors, such as temperature, the specific ILE incorporated, and the silane used to form the porous silicon matrix. Therefore, the main drawback of the standard nano-SCE is manufacturability. It requires a long time for solidification, has variations, and significantly slows down the battery manufacturing process, thus limiting the scalability of this technology. As mentioned above, the gelation process of the electrolyte highly depends on the pH of the solution. When the solution for forming the ion gel electrolyte is injected into the pores, the pH of the solution may change significantly due to the surface chemistry of the active material. Therefore, depending on the type of active material, the electrochemical properties of the ion gel electrolyte may vary, or the electrolyte may not solidify at all. When solidification occurs, it is necessary to perform the casting process at an appropriate timing. That is, the precursor solution has a viscosity compatible with the coating technology (usually blade coating or slot die coating) and is at the timing before gelation. This is possible by controlling the timing of the casting process. Since the appropriate coating time is greatly affected by slight differences in temperature, humidity, and convection, this method is not very reliable. As another method of measuring the process timing, a method of measuring the turbidity of the precursor solution over time and identifying the optimal time for casting the solution is known. However, this process itself takes too much time to be compatible with the continuous processing of battery production. Lithium-ion batteries are usually manufactured in a roll-to-roll manner at a maximum speed of 1 ms -1 . It is not possible to stop the roll to wait for the appropriate timing.

[0015] Therefore, in this technical field, there is still a need for devices and methods to address at least some of the above problems. Summary of the Invention

[0016] An object of the present invention is to provide an excellent solution that can be used for forming a solid electrolyte. Another object of the present invention is to provide a solid electrolyte formed thereby. Further, an object of the present invention is to provide an excellent method for forming a solid electrolyte.

[0017] The above object is achieved by the method and apparatus according to the present invention.

[0018] An advantage of an embodiment of the present invention is that the solution can have good long-term stability, so that the solution can be prepared, for example, for at least one month before applying the solution to an electrode to form an electrolyte.

[0019] A further advantage of an embodiment of the present invention is that the formation of the solid electrolyte from the solution can occur in a short time frame, for example within a few minutes, after adding a radical initiator and applying a trigger (UV light and / or temperature). Further, the formation of the solid electrolyte is not caused by electricity and does not require a current-conducting substrate, so the applicability of the solution is generalized. Therefore, an advantage of an embodiment of the present invention is that the manufacturing is easy. For example, this solution can be stored without an initiator for a period exceeding one month, and the initiator can be added to the precursor solution when loading a container supplied with a blade coater or a slot die coater. Immediately after blade coating or slot die coating, it can be installed so as to irradiate / heat the coating with a UV lamp and / or a heating device.

[0020] Since the formation may not require the presence of a base or an acid, it is an advantage of an embodiment of the present invention that the compatibility with other components of the battery, such as the electrode, may be good. A further advantage of an embodiment of the present invention is that the formed solid electrolyte can have good ionic conductivity.

[0021] Therefore, an advantage of an embodiment of the present invention is that it can provide a combination of easy manufacturing, compatibility with other battery components, and good ionic conductivity.

[0022] In a first aspect, the present invention relates to a solution for forming a solid electrolyte. This solution contains a plurality of silicon oxide particles dissolved in a liquid medium, and the silicon oxide particles are functionalized with an organic moiety containing at least four non-hydrogen atoms (one of which is covalently bonded to the silicon atom of the silicon oxide particle) and a bondable functional group capable of forming a covalent bond by reaction with another identical bondable functional group after activation by radical species. The organic moiety contains at least two atoms that are not part of the bondable functional groups bonded to each other by π bonds, and the ratio of the number of the organic moieties to the number of silicon atoms contained in the plurality of silicon oxide particles is at least 0.3. This solution further contains an electrolyte compound.

[0023] In a second aspect, the present invention relates to a method for forming a solid electrolyte, the method including the following steps: a) obtaining a solution according to an embodiment of the first aspect of the present invention, b) adding to the solution a radical initiator suitable for forming radical species for inducing activation, and c) converting the radical initiator into radical species.

[0024] In a third aspect, the present invention relates to a solid electrolyte including a porous silicon oxide matrix and an electrolyte compound covering the pore walls of the porous silicon oxide matrix, wherein at least 30% of the silicon atoms constituting the silicon oxide matrix are separated from another silicon atom in the silicon oxide matrix by at least four atoms constituting an organic linking chain.

[0025] In a fourth aspect, the present invention relates to a battery including the solid electrolyte according to an embodiment of the third aspect.

[0026] Specific preferred embodiments of the present invention are described in the appended independent and dependent patent claims. The features described in the dependent patent claims may be appropriately combined with the features of the independent patent claims and the features of other dependent patent claims, and are not limited to those explicitly described in the patent claims.

[0027] Improvements, changes, and evolutions of devices in this field have been continuously carried out. However, this concept is considered to present substantial new and innovative improvements that make this type of device more efficient, stable, and reliable, including deviations from conventional practices.

[0028] The above and other characteristics, features, and advantages of the present invention will become apparent by referring to the following detailed description in conjunction with the accompanying drawings. This description explains the principles of the present invention in an exemplary manner and is for illustrative purposes only and does not limit the scope of the present invention. The reference figures cited below refer to the accompanying drawings.

Brief Description of the Drawings

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[0030] In different figures, the same reference numerals indicate the same or similar elements.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention is described with reference to specific drawings with respect to specific embodiments, but the present invention is not limited thereto and is limited only by the claims. The drawings described are schematic and non-limiting. In the drawings, for the purpose of explanation, the sizes of some elements may be exaggerated and not drawn to scale. Dimensions and relative dimensions do not correspond to the scale in the actual implementation of the invention.

[0032] Furthermore, terms such as "first", "second", "third", etc. in the specification and claims are used to distinguish similar elements and do not necessarily describe an order in a temporal, spatial, sequential, or other manner. Such terms are interchangeable under appropriate circumstances, and it should be understood that the embodiments of the invention described herein can operate in an order other than that described or illustrated herein.

[0033] Furthermore, terms such as "above", "below", "upper", "lower", etc. in the description and claims are used for explanatory purposes and do not necessarily describe a relative position. Under appropriate circumstances, such terms used in this way are interchangeable, and it should be understood that the embodiments of the invention described herein can operate in other directions other than those described or illustrated herein.

[0034] It should be noted that the term "comprising" used in the claims should not be construed as being limited to the means recited thereafter. This term does not exclude other elements or steps. Accordingly, it should be construed as identifying the presence of the recited features, integers, steps, or components and not excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Accordingly, the term "comprising" covers both the case where only the recited features are present and the case where these features and one or more other features are present. Accordingly, the term "comprising" in this invention includes, as one embodiment, the case where no additional components are present. Accordingly, the scope of the expression "an apparatus comprising means A and B" should not be construed as being limited to an apparatus consisting only of components A and B. This only means, with respect to this invention, that the relevant components of the apparatus are A and B.

[0035] The expressions "one embodiment" or "an embodiment" throughout this specification mean that a particular function, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Accordingly, the expressions "in one embodiment" or "in an embodiment" described in various places in this specification do not necessarily all refer to the same embodiment, although they may do so. Furthermore, the particular functions, structures, or characteristics can be combined in any suitable manner in one or more embodiments, as will be apparent to those skilled in the art from this disclosure.

[0036] Likewise, in the description of exemplary embodiments herein, for the sake of simplifying the disclosure and making it easier to understand one or more various aspects of the invention, it should be understood that various features of the invention herein may sometimes be described together in one embodiment, figure, or description thereof. However, such a disclosure method should not be construed as reflecting an intention that the invention recited in the claims requires more features than are explicitly recited in each claim. Rather, as reflected in the following claims, aspects of the invention are less than all the features of a single prior disclosed embodiment. Accordingly, the claims following the detailed description are hereby expressly incorporated herein, and each claim stands on its own as a separate embodiment of the present specification.

[0037] Furthermore, some embodiments described herein include some functions included in other embodiments but do not include other functions. Combinations of functions of different embodiments are within the scope of the present invention and form different embodiments, as can be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0038] Furthermore, some embodiments are described herein as a method or a combination of method elements that can be implemented by a processor of a computer system or other means for performing functions. Accordingly, a processor having the necessary instructions for implementing such a method or method element forms means for implementing the method or method element. Furthermore, the elements of the apparatus embodiments described herein are examples of means for performing the functions performed by those elements for the purpose of implementing the present invention.

[0039] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention can be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of the present specification.

[0040] In a first aspect, the present invention relates to a solution for forming a solid electrolyte. This solution contains a plurality of silicon oxide particles dissolved in a liquid medium, and the silicon oxide particles are functionalized with an organic moiety containing at least four non-hydrogen atoms (one of which is covalently bonded to the silicon atom of the silicon oxide particle) and a bondable functional group capable of forming a covalent bond by reaction with another identical bondable functional group after activation by radical species. The organic moiety contains at least two atoms bonded to each other by a π bond that are not part of the bondable functional group, and the ratio of the number of the organic moieties to the number of silicon atoms contained in the plurality of silicon oxide particles is at least 0.3. This solution further contains an electrolyte compound.

[0041] In an embodiment, the solid electrolyte may be an ion gel electrolyte.

[0042] The organic moiety is bonded to the silicon oxide particle by an Si-C bond.

[0043] In an embodiment, the ratio is from 0.3 to 1.0, preferably from 0.4 to 0.9, more preferably from 0.4 to 0.6. This ratio results from the compounds used in the production of the solution and can be determined therefrom if the protocol used in the production of the solution is available. This ratio is preferably determined from NMR spectroscopy, for example, 29Si NMR spectroscopy, performed on the solution. The chemical structure of the organic moiety can be determined by techniques well known to those skilled in the art, such as NMR spectroscopy.

[0044] The functional groups activated by radical species can bond different silicon oxide particles to each other. Since this reaction is induced by radicals, it proceeds at a high rate. Therefore, the solidification in the solution of the embodiment of the present invention, and thus the formation of the solid electrolyte, may proceed at a high rate. At the same time, although the concentration of the functional groups is relatively high, the organic moieties can react with each other only when activated, so the stability of the solution is good.

[0045] The non-hydrogen atoms that form linkable functional groups are included in at least four non-hydrogen atoms contained in each organic moiety.

[0046] In embodiments, the organic moiety is bonded to the silicon atom via a silicon-carbon bond. The possibility that the silicon-carbon bond may be stable is an advantage of these embodiments. In embodiments, at least four non-hydrogen atoms are selected from carbon, oxygen, nitrogen, sulfur, preferably selected from carbon, oxygen, nitrogen. In embodiments, the organic moiety is composed of atoms selected from carbon, oxygen, nitrogen, sulfur, and hydrogen, preferably atoms selected from carbon, oxygen, nitrogen, and hydrogen. In embodiments, each silicon oxide particle consists of a silicon oxide network. The organic moiety is located around the silicon oxide particle.

[0047] In embodiments, at least two atoms bonded to each other by a π bond are part of a π-conjugated system. The π-conjugated system consists of at least four atoms different from hydrogen. The fact that the organic moiety can have high rigidity is an advantage of these embodiments. In embodiments, the at least two atoms may be selected from carbon, oxygen, nitrogen, sulfur, preferably may be selected from carbon, oxygen, nitrogen, and more preferably may be selected from carbon and oxygen. Preferably, the at least two atoms are only the two atoms that form a carbonyl group conjugated to the double bond of the linkable functional group. Preferably, the linkable functional group is part of an acrylate group or a methacrylate group, preferably a methacrylate group. The at least two atoms are not part of the linkable functional group, but the linkable functional group may be part of the π-conjugated system. The advantage of the π-conjugated system is that high rigidity can be achieved within the organic moiety. This rigidity may result in steric hindrance that can limit the condensation reaction rate achievable by the silicon oxide particles constituting the linkable functional group.

[0048] In an embodiment, the organic moiety consists of a linear organic chain composed of at least four atoms. In an embodiment, a linkable functional group and an organic connector chain that binds the linkable functional group to a silicon atom form a linear organic chain having at least four atoms. In an embodiment, the organic moiety may be branched or may include at least one substituent, such as a side chain or an aromatic group, in addition to the linear organic chain. Since the organic moiety may induce steric hindrance and reduce the condensation rate of the silicon oxide particles, there is an advantage that the stability of the solution is improved.

[0049] In an embodiment, the silicon oxide particles (e.g., silicon dioxide particles) are adapted to form a continuous silicon oxide matrix. In an embodiment, each of the silicon oxide particles consists of a plurality of groups independently selected from alkoxy groups and hydroxy groups bonded to the silicon atoms constituting the silicon oxide particles. Due to the presence of these alkoxy groups and / or hydroxy groups, a condensation reaction may occur between different silicon oxide particles. Without being bound by theory, due to the activation, different silicon oxide particles may bind to each other by covalent bonds formed by reactions between bondable functional groups on different silicon oxide particles. As a result, the alkoxy groups and / or hydroxy groups on different silicon oxide particles may be located close to each other. Thereby, the condensation reaction may proceed rapidly. By the condensation reaction, a continuous silicon oxide matrix may be formed by a plurality of silicon oxide particles.

[0050] In an embodiment, the connectable functional group is separated from the silicon atom to which the organic moiety is attached by an organic connector chain of up to 100 atoms, preferably up to 40 atoms, more preferably up to 20 atoms, and even more preferably up to 10 atoms. Preferably, the organic connector chain has at least 2 atoms. In an embodiment, the connectable functional group is separated from the silicon atom to which the organic moiety is attached by a chain of at least 2 atoms. In an embodiment, these atoms may be selected from carbon, oxygen, nitrogen, sulfur, preferably may be selected from carbon, oxygen, nitrogen, and even more preferably may be selected from carbon and oxygen. Preferably, all atoms other than carbon forming the chain are linked to two carbon atoms belonging to the chain. In these embodiments, after activation which may connect different silicon oxide particles, the silicon atoms of different silicon oxide particles may be located close to each other.

[0051] In an embodiment, the connectable functional group may be selected from an epoxide group, a vinyl group, and a vinylidene group.

[0052] In a preferred embodiment, the connectable functional group is a vinyl group or a vinylidene group. These are preferred because they have high stability in solution. The vinyl group and the vinylidene group can readily react with the vinyl group and the vinylidene group after activation by radical species. Preferably, the connectable functional group belongs to an acrylate functional group or a methacrylate functional group (a double bond). The fact that the reaction between different connectable functional groups can proceed very rapidly after activation by radical species is an advantage of these embodiments.

[0053] In an embodiment, at least one of the organic moieties has the formula CH2=C(Y)COOL - and has.

[0054] In an embodiment, at least 50 mol%, preferably at least 60 mol%, more preferably at least 70 mol%, still more preferably at least 80 mol%, still more preferably at least 90 mol%, and most preferably all of the organic moiety has the formula CH2=C(Y)COOL - wherein:

[0055] L is an alkylene group having from 1 to 7 carbon atoms, preferably from 1 to 5 carbon atoms, more preferably from 2 to 4 carbon atoms. Preferably, L is (CH2) n where n is from 1 to 5, preferably from 2 to 4, more preferably 3.

[0056] Y is CH3 or H, preferably CH3.

[0057] In a preferred embodiment, L is (CH2) n where n is from 1 to 5 and Y is CH3.

[0058] In a more preferred embodiment, L is (CH2) n where n is from 2 to 4 and Y is CH3.

[0059] In the most preferred embodiment, L is (CH2) nwhere n is 3 and Y is CH3. In embodiments, the functionalized silicon oxide particles can be obtained by aging a precursor solution consisting of an organosilane containing a silicon atom bonded to four groups consisting of an organic group and at least two alkoxy groups, preferably an organic group and three alkoxy groups. In these embodiments, the organosilane may include triethoxy(1-phenylethenyl)silane or 3-trimethoxysilylpropyl methacrylate, preferably 3-trimethoxysilylpropyl methacrylate. In embodiments, the precursor solution may further include a trialkoxysilane or a tetraalkoxysilane, preferably a tetraalkoxysilane. The tetraalkoxysilane may include tetramethyl orthosilicate or tetraethyl orthosilicate, preferably tetraethyl orthosilicate. The advantage of these embodiments is that the tetraalkoxysilane can form an extensive silicon oxide network by hydrolysis and condensation. This is due to the fact that each tetraalkoxysilane can bond to four different silicon atoms via four silicon-oxygen-silicon bonds.

[0060] In embodiments, the aging can be carried out for 0 days to 70 days, such as 2 hours to 50 days, or 30 days to 40 days. The structure of the particles can vary depending on whether aging is carried out and for what period. In embodiments where aging is not carried out or is carried out for a short time, such as up to 1 day, the solution of the embodiments of the present invention may have the same composition as the precursor solution, whereby the particles may include an organosilane and optionally a tetraalkoxysilane. These embodiments are not preferred because they may not result in the formation of a solid electrolyte having an extensive silicon oxide matrix. In embodiments where aging is carried out, such as when carried out for at least 1 day, hydrolysis and condensation of the organosilane molecules form particles such as clusters or oligomers, and other silanes such as tetraalkoxysilane are also formed if present.

[0061] In an embodiment, the liquid medium contains water and may hydrolyze any (functionalized or non-functionalized) alkoxysilane in the solution. In an embodiment, the liquid medium contains an alcohol such as methanol or ethanol. The alcohol can be a good solvent for the silicon oxide particles. In a preferred embodiment, the liquid medium contains both water and an alcohol. Preferably, the liquid medium contains more alcohol than water. More preferably, the volume ratio of alcohol to water is 1.5 to 2.5. The silicon oxide particles are dissolved in the liquid medium. Thus, the solution of the present invention is distinguished from a sol, i.e., a colloidal solution, which is often used in the prior art to form a solid electrolyte.

[0062] In an embodiment, the solution has a pH of 5 to 7 as measured by a Hanna® HI-11310 pH Edge electrode. The solution has the advantage of being compatible with various materials such as, for example, battery electrodes. However, other materials may be more suitable in different pH ranges. The pH of the solution can be adjusted so that the solution is compatible with a particular material. An advantage of the embodiments of the present invention is that the pH of the solution does not affect the solidification rate because activation may be caused by radicals rather than protons.

[0063] In an embodiment, the first concentration of the organosilane and the second concentration of the trialkoxysilane and / or tetraalkoxysilane in the precursor solution are adapted such that the solution of the present invention is formed after the aging. In a preferred embodiment where each organosilane consists of a single organic moiety, the ratio of the first concentration to the sum of the first and second concentrations in the precursor solution is approximately equal to the ratio of the number of organic moieties contained in the plurality of silicon oxide particles in the solution to the number of silicon atoms contained in the plurality of silicon oxide particles.

[0064] In an embodiment, the concentration of the organosilane in the precursor solution is from 0.1 M to 1.3 M, preferably from 0.2 M to 0.7 M. In an embodiment, the total concentration of the trialkoxysilane and tetraalkoxysilane in the precursor solution is from 0.2 M to 1.3 M, preferably from 0.4 M to 0.7 M.

[0065] In embodiments, each silicon atom of the plurality of silicon oxide particles is bonded to at most one organic moiety. It is an advantage of these embodiments that the linkable functional groups of the organic moieties on the silicon oxide particles are unlikely to react with the same linkable functional groups of another organic moiety on the same silicon oxide particle.

[0066] In some embodiments, the solution contains a radical initiator capable of generating radical species, which are generated, for example, after application of a trigger such as irradiation or heating of the solution. The lifetime of the radical initiator may be limited, so radical species may be generated from the radical initiator even in the absence of a trigger. Accordingly, the radical species are preferably added only immediately before the solution is used to form the solid electrolyte.

[0067] In an embodiment, the electrolyte compound is configured to act as a template for forming a porous silicon oxide matrix. In an embodiment, the electrolyte compound comprises an ionic liquid electrolyte, a polymer electrolyte, or a mixture thereof. Preferably, the electrolyte compound comprises an ionic liquid electrolyte. In an embodiment, the ionic liquid electrolyte is composed of an ionic liquid and a metal salt. In an embodiment, the polymer electrolyte consists of a polymer and a metal salt. In these embodiments, the silicon oxide matrix formed from the solution may include a plurality of interconnected pores. The plurality of interconnected pores may be the result of the presence of the electrolyte compound in the solution (e.g., CHEN, Nan et al., Ionic Gel Electrolytes for High-Performance Lithium Batteries: A Review. Advanced Energy Materials, 2018, 8.12:1702675; and CHEN, Xubin et al., Silica Gel Solid Nanocomposite Electrolytes with Interfacial Conductivity Promotion Exceeding the Bulk Lithium Ion Conductivity of Ionic Liquid Electrolyte Fillers. Science Advances, 2020, 6.2:eaav3400). Without being bound by theory, the solution is thought to consist of regions of the electrolyte compound. The silicon oxide matrix is formed around the regions of the electrolyte compound. Thereby, the regions of the electrolyte compound form a plurality of interconnected pores within the porous silicon oxide matrix. The electrolyte compound can cover the inner surface of the porous silicon oxide matrix. Here, a first layer made of an ionic liquid or a polymer may cover the inner surface of the porous silicon oxide matrix, and a second layer made of a metal salt may cover the first layer. Due to a specific combination of interactions between the porous silicon oxide matrix, the first layer, and the second layer, ions of the metal salt, such as lithium, can move relatively freely within the pores.

[0068] In an embodiment, the ionic liquid may contain a cation selected from 1-pentyl-1-methylpyrrolidinium, 1-butyl-1-methylpyrrolidinium, 1-propyl-1-methylpyrrolidinium, 1-ethyl-1-methylpyrrolidinium, 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1,2-diethyl-3,5-dimethylimidazolium, trimethyl-n-hexylammonium, N-butyl-N-methylpyrrolidinium, N-methyl-N-propylpiperidinium, and N-ethyl-N-methylmorpholinium. In an embodiment, the ionic liquid is ClO4 - , BF4 - , PF6 - , BH4 - , PO4 3- , Cl - , Br - , I - , NO3 - , dicyanamide, thiocyanate, bistriflimide, bis(fluorosulfonyl)imide, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, bis-(perfluoroethylsulfonyl)imide, N-(trifluoromethylsulfonyl)acetamide, triflate (trifluoromethylsulfonate), DFOB (difluoro(oxalato)borate), PDI (dicyano-pentafluoroethyl-imidazole), TDI (dicyano-trifluoromethyl-imidazole), DMSI (cyclo-difluoromethyl-1,1-bis(sulfonyl)imide), HPSI (cyclo-hexafluoropropyl-1,1-bis(sulfonyl)imide), DFOD (difluoro(oxalato)borate), BFMB (bis(fluoromalonate)borate), BISON (tetracyano-borate), N-(trifluoromethylsulfonyl)acetamide, DCTA (dicyanotriazolate), and bis(oxalato)borate.

[0069] In an embodiment, the polymer may include a PEO-PPO block copolymer, such as a poloxamer like Pluronic® F127, P123, or F107, where PEO is polyethylene oxide and PPO is polypropylene oxide. In an embodiment, the polymer may include an amphiphilic block copolymer such as oligomerized alkyl poly(ethylene oxide) (Brij®, Tergitol®), alkylphenol poly(ethylene oxide) (Triton®), or sorbitan ester (Tween®, Span®).

[0070] In an embodiment, the metal salt may include Li + , Na + , K + , Ca 2+ , Mg 2+ , and Al 3+ selected from metal cations, preferably Li + . In an embodiment, the metal salt may include Cl - (chloride), Br - (bromide), I - (iodide), ClO4 - (perchlorate), BF4 - (tetrafluoroborate), NO3 - (nitrate), BH4 - (borohydride), PF6 - (hexafluorophosphate), dicyanamide, thiocyanate, bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, bis-(perfluoroethylsulfonyl)imide, BOB (bis(oxalato)borate), PO4 3-(Phosphate), triflate (trifluoromethanesulfonic acid), BETI (bis(pentafluoroethanesulfonyl)imide), DFOB (difluoro(oxalato)borate), PDI (dicyanopentafluoroethylimidazole), TDI (dicyanotrifluoromethylimidazole), DMSI (cyclodifluoromethane-1,1-bis(sulfonyl)imide), HPSI (cyclohexafluoropropane-1,1-bis(sulfonyl)imide), DFOD (difluoro(oxalato)borate), BFMB (bis(fluoromalonato)borate), BISON (tetracyano borate), N-(trifluoromethylsulfonyl)acetamide, and an anion selected from DCTA (dicyanotriazole) may be included.

[0071] In an embodiment, the concentration of the electrolyte compound in the solution is 0.1 to 1.2 g / ml, preferably 0.5 to 0.9 g / ml.

[0072] In an embodiment where the electrolyte compound contains an ionic liquid electrolyte, the concentration of the ionic liquid in the solution is 0.08 to 1.2 g / ml, and the concentration of the metal salt is 0 to 0.24 g / ml, for example, 0.01 to 0.24 g / ml.

[0073] In an embodiment where the electrolyte compound contains a polymer electrolyte, the concentration of the polymer in the solution is 0.08 to 1.2 g / ml, and the concentration of the metal salt is 0 to 0.24 g / ml, for example, 0.01 to 0.24 g / ml.

[0074] Preferably, the ratio of the molar concentration of the electrolyte compound to the molar concentration of the silicon atoms contained in the silicon oxide particles is 0.1 to 5, preferably 0.5 to 4.

[0075] The features of any embodiment of the first aspect can be described independently so as to correspond to any embodiment of any other aspect of the present invention.

[0076] In a second aspect, the present invention relates to a method of forming a solid electrolyte, the method comprising the following steps: a) obtaining a solution according to an embodiment of the first aspect of the present invention, b) adding to the solution a radical initiator adapted to form radical species for inducing said activation, and c) converting the radical initiator into radical species.

[0077] Preferably, step c) is carried out within 1 day, preferably within 1 hour, after the execution of step b). In an embodiment, step c) is carried out while the solution has a pH of 5 to 7 as measured with a glass electrode. The fact that the solution can be in contact with the electrode without damaging the electrode, as usually occurs when the solution is basic or acidic, is an advantage of these embodiments.

[0078] In an embodiment, said conversion consists of irradiating or heating the solution. In an embodiment, said irradiation consists of UV radiation. In an embodiment, the radical initiator comprises dimethoxy-2-phenylacetophenone, dibenzoyl peroxide, or azobisisobutyronitrile. The advantage of these embodiments is that it may be possible to efficiently activate the reaction between linkable functional groups, particularly when the linkable functional groups are vinyl or vinylidene groups. In an embodiment, the concentration of the radical initiator in the solution after adding the radical initiator in step b) is from 1 g / l to 10 g / l.

[0079] In an embodiment, the method further comprises a step d) of drying the solid electrolyte after step c). Said drying may be for removing a liquid medium, such as water and / or alcohol. For this purpose, the solid electrolyte may be placed in a drying chamber, i.e. a chamber with a very low humidity, capable of evaporating a liquid medium, such as water and / or alcohol. Alternatively, the solid electrolyte may be dried by heating to a temperature of preferably up to 70°C.

[0080] Any feature of any embodiment of the second aspect can be described independently so as to correspond to any embodiment of any other aspect of the present invention.

[0081] In a third aspect, the present invention relates to a solid electrolyte comprising a porous silicon oxide matrix and an electrolyte compound covering the pore walls of the porous silicon oxide matrix, wherein at least 30% of the silicon atoms constituting the silicon oxide matrix are separated from another silicon atom in the silicon oxide matrix by at least 4 atoms constituting an organic linking chain.

[0082] The organic linking chain has the advantage that it can bring about an improvement in the mechanical properties of the solid electrolyte, such as elasticity and structural integrity.

[0083] In an embodiment, the porous silicon oxide matrix comprises an oxide matrix containing pores. These pores have a diameter of 5 to 500 nm, preferably 10 to 150 nm. Preferably, the pores are interconnected such that the porous silicon oxide matrix constitutes a path through the interconnected pores from one side of the solid electrolyte to the other side. Thereby, the electrolyte compound covering the pore walls can form an ion conduction path from one side of the solid electrolyte to the other side. In an embodiment, the porous silicon oxide matrix has a porosity of 60 to 90%.

[0084] In an embodiment, the solid electrolyte can be formed by reacting a solution according to an embodiment of the first aspect of the present invention in a method according to an embodiment of the second aspect of the present invention.

[0085] In an embodiment, the organic linking chain is a reaction product of two different organic moieties after two linkable functional groups of the two different organic moieties have reacted after being activated by radical species. Usually, the organic linking chain contains two organic groups excluding at least the linkable functional groups, and further contains the reaction product after the radical reaction between the linkable functional groups. For example, when the linkable functional group contains vinyl, the organic linking chain contains at least a linear saturated chain of 4 carbon atoms and further contains an organic group excluding the linkable functional group.

[0086] In an embodiment, 30% to 100%, preferably 40% to 90%, more preferably 40% to 60% of the silicon atoms are separated from each other by at least 4 atoms constituting the organic linking chain.

[0087] Preferably, the ratio of the molar concentration of the electrolyte compound to the molar concentration of the silicon atoms constituting the solid electrolyte is 0.1 to 5, preferably 0.5 to 4. Since the mechanical properties of the solid electrolyte are good, a large amount of the electrolyte compound can be present in the solid electrolyte.

[0088] Any embodiment of the third aspect can independently describe, in a corresponding manner, any embodiment of any other aspect of the present invention.

[0089] In a fourth aspect, the present invention relates to a battery including a solid electrolyte according to an embodiment of the third aspect.

[0090] In an embodiment, the battery includes an anode and a cathode separated from each other by a solid electrolyte. The solid electrolyte may have a thickness of, for example, 25 μm to 1 mm, preferably 25 μm to 100 μm.

[0091] The solid electrolyte has, for example, at least 10 -5 S / cm, preferably at least 10 -4 S / cm, for example 10 -2 to 10 -4 S / cm of ionic conductivity at 25°C. The solid electrolyte may have a low electrical conductivity of, for example, at most 10 -6 S / cm, preferably at most 10 -14 / cm at 25°C.

[0092] In an embodiment, the anode includes a conductive substrate containing copper, nickel, aluminum, or stainless steel, preferably copper. Since copper does not intercalate lithium at low voltage, that is, copper does not alloy with lithium, it is often used as the anode substrate of a solid-state battery composed of lithium for ion conduction. In an embodiment, the cathode includes a conductive substrate containing aluminum, nickel, or stainless steel.

[0093] In an embodiment, the solid electrolyte may be impregnated into a porous active electrode material present on the above-mentioned conductive substrate, thereby forming a composite electrode (i.e., a composite positive electrode or a composite negative electrode).

[0094] The porous active electrode material typically includes an active composite material, a polymer binder, and a conductive additive. The active composite material typically includes electrode particles that are in electrical contact with each other. In these embodiments, the active composite material is combined with the polymer binder, that is, combined to physically stabilize the porous active electrode material. Examples of the conductive additive include carbon black, graphite, carbon-based fibers or beads, or stainless steel fibers. These are incorporated into the porous active material electrode material and are usually present within its pores. For example, the conductive additive is 0 to 15% by weight, preferably 0.1 to 12% by weight, more preferably 4 to 11% by weight of the porous active material electrode material.

[0095] In embodiments, the composite electrode is suitable for incorporation into a solid-state battery and is used as the positive electrode. In these embodiments, the active composite material may comprise at least one material selected from lithium manganese nickel oxide (LMNO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium manganese phosphate (LMP), lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide (NMC), and lithium nickel cobalt aluminum oxide (NCA). In different embodiments, the composite electrode is suitable for incorporation into a solid-state battery, in which case it is used as the negative electrode. In these embodiments, the active composite material may comprise at least one material selected from lithium, graphite, silicon, tin, graphene, and lithium titanate (LTO). In embodiments, the porous active electrode material comprises, for example, a composite material comprising silicon and graphite; or silicon and graphene.

[0096] The active composite material is typically present in an amount of 70 to 91 wt% of the weight of the porous active electrode material.

[0097] A typical example of the polymer binder is poly(vinylidene fluoride). The polymer binder is typically present in an amount of 5 to 15% of the weight of the porous active electrode material.

[0098] In embodiments, infiltrating the porous active electrode material comprises filling the pores of the porous active electrode material with a solution according to any embodiment of the first aspect.

[0099] Any feature of any embodiment of the fourth aspect can be implemented independently according to the corresponding description for any embodiment of any other aspect of the present invention.

[0100] The present invention will now be described by way of a detailed description of some embodiments of the present invention. It will be apparent to those skilled in the art that other embodiments of the present invention can be configured without departing from the technical teachings of the present invention.

[0101] Example 1: Preparation of Solution In this example, a solution according to an embodiment of the present invention is prepared. First, a precursor solution containing an electrolyte compound, such as an ionic liquid electrolyte or a polymer electrolyte, and an organosilane, such as a trialkoxysilane and / or a dialkoxysilane, is prepared. Here, the organic moiety is covalently bonded to the silicon atom of the organosilane. In this example, the organic moiety contains a linkable functional group that is a vinyl group. The organic moiety further contains at least four non-hydrogen atoms, one of which is covalently bonded to the silicon atom of the silicon oxide particles. Furthermore, the organic moiety contains at least two atoms that are not part of the linkable functional groups and are bonded to each other by a π bond.

[0102] Furthermore, the precursor solution contains a liquid medium, which in this example contains water and an alcohol, such as ethanol. In this example, the precursor solution further contains a tetraalkoxysilane, such as tetraethyl orthosilicate. In this example, the organosilane contains a single organic moiety. The ratio of the number of organosilane molecules in the precursor solution to the combined number of organosilane molecules and tetraalkoxysilane molecules is at least 0.3. Therefore, the ratio of the number of organic groups to the number of silicon atoms in the precursor solution is at least 0.3.

[0103] The precursor solution is aged for 0 to 70 days. During this aging, the organosilane and the tetraalkoxysilane undergo hydrolysis, and the alkoxy groups of the organosilane and the tetraalkoxysilane are replaced by hydroxy groups. TIFF2025518530000002.tif31163

[0104] For simplicity, for the organic moiety R’, only the linkable functional group, which is a vinyl group in this example, is shown. The hydroxy group enables condensation reactions between the hydrolyzed organosilane and the hydrolyzed tetraalkoxysilane, and between themselves. TIFF2025518530000003.tif28130

[0105] Tetraalkoxysilane contains four alkoxy groups, which are hydrolyzed. Therefore, the hydrolyzed tetraalkoxysilane can subsequently condense with four other hydrolyzed silane molecules. Thus, each tetraalkoxysilane molecule can form four bonds with other silane molecules (e.g., organosilane and / or tetraalkoxysilane). The advantage of embodiments containing tetraalkoxysilane is that a large continuous silicon oxide network may be formed. However, although the presence of tetraalkoxysilane is preferred, it is not essential. Instead, the precursor solution may contain organic silane or may not contain tetraalkoxysilane.

[0106] Referring to FIG. 1. The condensation reaction may result in the formation of a plurality of silicon oxide particles 1 functionalized with organic moieties 2. Without being bound by theory, the silicon oxide particles 1 are considered to constitute a silicon oxide network. The silicon oxide particles 1 are functionalized with organic groups 2 located around the silicon oxide particles 1. Here, each organic group 2 is covalently bonded to a silicon atom of this silicon oxide network. For simplicity, only the bondable functional groups of the organic group 2 in FIG. 1 are shown, which is a vinyl group in this example. The ratio of the number of organic groups to the number of silicon atoms in the precursor solution is at least 0.3 before the hydrolysis and condensation reactions. As a result, after the hydrolysis and condensation reactions, the ratio of the number of organic groups contained in the plurality of silicon oxide particles to the number of silicon atoms contained in the plurality of silicon oxide particles is at least 0.3. Thus, in this example, by aging the precursor solution, a solution according to an embodiment of the present invention is formed.

[0107] Example 2: Obtaining a stable solution In this example, it is evaluated which features can provide a solution according to an embodiment of the present invention having long-term stability. In the prior art, solutions for forming solid electrolytes tend to be chemically unstable, and as a result, solid electrolytes may be formed before being applied to electrodes.

[0108] In this example, the stability of various solutions composed of various organosilanes and optionally tetraethyl orthosilicate was evaluated. Here, the concentrations of the organosilane and tetraethyl orthosilicate were varied. The stability (at room temperature) of the solutions containing the following organosilanes was evaluated. TIFF2025518530000004.tif71127

[0109] Each of these organosilanes contains an organic moiety having a bondable functional group that is a vinyl group or a vinylidene group. For example, TMSPMA contains an organic moiety having 9 non-hydrogen atoms (7 carbon atoms and 2 oxygen atoms), that is, at least 4 non-hydrogen atoms. Also, the organic moiety of TMSPMA contains 2 atoms (the carbon atom and the oxygen atom forming a carbonyl group). That is, it contains at least 2 atoms that are not hydrogen atoms and are not part of the bondable functional group, and are bonded to each other by a π bond. In the case of TMSPMA, these 2 atoms constitute a π-conjugated system. The π-conjugated system further contains a bondable functional group, that is, a vinylidene group. The bondable functional group in TMSPMA is separated from the silicon atom to which the organic moiety is bonded by an organic linking chain consisting of 5 atoms. These atoms from the silicon atom to the bondable functional group are C, C, C, O, and C. The organic linking chain separating the bondable functional group from the silicon atom and the bondable functional group together form a linear organic chain consisting of at least 4 atoms, that is, 7 atoms including 6 carbon atoms and 1 oxygen atom. The linear organic chain is branched, that is, branched by the oxygen atom of the carbonyl group and the methyl group.

[0110] In addition to adding organic silane and TEOS to make a total of 0.7 M, each solution was further added with an ionic liquid electrolyte (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) at 0.5 g / ml, and water and ethanol in a volume ratio of 1:2. For each organic silane, various solutions were prepared. Here, the different solutions were composed of different amounts of organosilane and tetraethyl orthosilicate. The molar concentrations of organosilane and tetraethyl orthosilicate were constant among the different solutions.

[0111] If no visible gelation, precipitation, or other visual changes were observed in the solution 5 weeks after preparing the solution, the solution was considered stable. In these stable solutions, no Tyndall scattering was observed, further confirming that no sol, i.e., colloidal suspension, was formed. If gelation, precipitation, or other visual changes were observed within 5 weeks after preparing the solution, the solution was considered unstable. In these unstable solutions, Tyndall scattering was observed.

[0112] Table I summarizes the experiments and results. Here, [TEOS]:[organosilane] indicates the relative molar concentrations of TEOS and organosilane in the solution.

[0113] Table I: Summary of experiments to determine the stability of solutions TIFF2025518530000005.tif63167

[0114] As is clear from Table I, for the three types of organosilanes under investigation, namely vinyltriethoxysilane (VTEOS), allyltriethoxysilane (ATEOS), and trimethoxy(7-octen-1-yl)silane (TMOYS), stable solutions could not be obtained. In the case of VTEOS and ATEOS, since the size of the organic part is limited, the steric hindrance is also limited, and the condensation reaction can proceed without being hindered in the solution, and solidification may occur. In the case of TMOYS, the bondable functional groups are bonded to the silicon atom via an organic linking chain having a length of six carbon atoms. However, in the organic part, at least two atoms (not part of the bondable functional groups) are not bonded to each other by a π bond. Therefore, the steric hindrance is limited. As a result, in a solution containing TMOYS, the condensation reaction may proceed without being hindered.

[0115] For the other two organosilanes, namely dimethoxydimethylvinylsilane (DMMVS) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), solutions with long-term stability could be obtained. For DMMVS, a stable solution could be obtained when the ratio of the amount of DMMVS to the total amount of DMMVS and TEOS was at least 0.6. For TMSPMA, a stable solution could be obtained when the ratio of the amount of TMSPMA to the total amount of TMSPMA and TEOS was at least 0.5.

[0116] Since DMMVS is a dialkoxysilane, it can form only two bonds. Therefore, condensation is possible only in the formation of linear chains, preventing the formation of a large interconnected network. Some solutions containing DMMVS maintain stability even after aging for two months.

[0117] TMSPMA is composed of at least two atoms that are not part of linkable functional groups bonded to each other by π bonds. Therefore, the organic portion of TMSPMA induces more steric hindrance compared to a linear organic chain of the same length, i.e., the organic portion of TMOYS having the same seven atoms as TMSPMA. Due to the large steric hindrance of the organic portion of TMSPMA, the condensation rate of TMSPMA is limited, and there is a possibility that a silicon oxide matrix is not formed in solution. The presence of the ester group may increase the polarity of the organic portion of TMSPMA and may affect the condensation rate. Some solutions containing TMSPMA maintained stability even after 18 months of aging.

[0118] For all the organic silane compounds investigated, solutions with varying amounts of TEOS were prepared. Increasing the amount of TEOS increases the likelihood of a solidification reaction because TEOS can form four bonds with other silane molecules (organic silane and / or TEOS). Stable solutions could not be formed with VTEOS, ATEOS, or TMOYS. As described above, for DMMVS, a stable solution can be obtained when the ratio of the amount of DMMVS to the total amount of the amount of DMMVS and TEOS is at least 0.6. For TMSPMA, a stable solution can be obtained when the ratio of the amount of TMSPMA to the total amount of the amount of TMSPMA and TEOS is at least 0.5. Further addition of TEOS resulted in an unstable solution that solidified to form a solid electrolyte.

[0119] Therefore, the following features of the organic moiety are thought to enhance the stability of the solution. The organic moiety contains at least four non-hydrogen atoms, which causes steric hindrance. Further, in the organic moiety, at least two atoms that are not part of the connectable functional groups are bonded to each other by π bonds, which increases the rigidity of the organic moiety and may further cause steric hindrance. To further increase the steric hindrance, the organic moiety may include a linear organic chain consisting of at least four atoms. Further, the linear organic chain may be branched, for example, it may include at least one side chain. The steric hindrance introduced by the organic moiety has the advantage of potentially limiting the rate of the condensation reaction between the silicon oxide particles formed in the solution. Thereby, the lifetime of the solution, i.e., the time until spontaneous solidification occurs in the solution, may be extended.

[0120] Preferably, the kinetics of hydrolysis and condensation of the organosilane compound are faster than those of TEOS.

[0121] The stable solution composed of TMSPMA in this example will contain, after aging, a plurality of silicon oxide particles functionalized with connectable functional groups, i.e., vinyl groups or vinylidene groups (see Figure 1). Aging may require several days, for example 14 days, or even longer periods, but this does not impair the manufacturability of the solution according to the embodiments of the present invention. In fact, the aging can be carried out separately from the production line, for example, separately from the electrode on which the solution is applied to form a solid electrolyte.

[0122] Example 3: Activation of Solidification Refer to FIG. 2A. In this example, the method according to this embodiment is implemented. A small amount of a radical initiator (for example, dimethoxy-2-phenylacetophenone) is dissolved in the aging solution according to this embodiment. For example, the aging solution may be the one formed in Example 1 above, or a stable solution composed of TMSPMA formed in Example 2. Thus, the aging solution contains a plurality of silicon oxide particles 1 constituting the organic group 2, and among them, the connectable functional groups constitute vinyl groups or vinylidene groups. The aging solution further contains an electrolyte compound, for example, an ionic liquid electrolyte or a polymer electrolyte. Nitrogen gas may be bubbled into the solution to remove the oxygen gas dissolved in the solution from the solution.

[0123] The solution may be used, for example, to form a free-standing film by applying the solution onto a silicon wafer, or may be used, for example, to form a part of a battery by impregnating the solution into an electrode.

[0124] The solution is subjected to a trigger, for example, by being placed under a UV lamp or being heated. Thereby, the radical initiator may be induced to form radical species. For example, when the radical initiator is dimethoxy-2-phenylacetophenone, the formed radical species contain benzoyl radicals.

[0125] The radical species can activate the connectable functional group 2 of the silicon oxide particle 1, that is, the vinyl group, to form a covalent bond with another connectable functional group 21 on another silicon oxide particle 1. In this way, the silicon oxide particles 1 in the solution are connected to each other by the organic linking chain 4. The organic linking chain 4 is formed by the organic part on another silicon oxide particle 1 after the reaction of the connectable functional group 21 on a separate silicon oxide particle 1. After the bonding of the silicon oxide particles 1 to each other, a precursor matrix 3 is formed from the silicon oxide particles bonded by the connectable functional group 21. Thus, the precursor matrix 3 is a porous silicon oxide matrix, but contains an intermittent silicon oxide network.

[0126] When exposed to a trigger, the solution can solidify within a few minutes to form the precursor matrix 3. This is a short enough time frame for large-scale manufacturing applications. Here, the electrolyte compound induces the formation such that a continuous network of pores is formed in the precursor matrix 3. After the solidification step, water and the solvent are removed, for example, by heat treatment or application of a vacuum.

[0127] Over time, the presence of hydroxy groups in the precursor matrix 3 can cause further condensation reactions. Thus, a solid electrolyte 5 comprising a porous silicon oxide matrix 50 consisting of a continuous silicon oxide network and comprising organic linking chains may be formed over time. Here, at least 30% of the silicon atoms contained in the silicon oxide matrix 50 are separated from another silicon atom within the silicon oxide matrix 50 by at least 4 atoms contained in the organic linking chains. Here, the electrolyte compound of the solid electrolyte 5 is present on the walls of the pores 51 of the porous silicon oxide matrix 50. These pores 51 communicate with each other and form a continuous network of pores through the porous silicon oxide matrix 50.

[0128] Referring to FIG. 2B, this is an enlarged view of the solid electrolyte showing the network of pores 51 of the porous silicon oxide matrix 50. The electrolyte compound 52 used to induce the formation of the porous silicon oxide matrix 50 such that the pores 51 are formed therein is located on the walls of the pores 51. When the electrolyte compound 52 comprises an ionic liquid 521 and a metal salt 522, for example a lithium salt, the ionic liquid 521 may form a first layer covering the inner walls of the pores of the porous silicon oxide matrix 50, and the metal salt 522 may form a second layer covering the first layer, i.e., the ionic liquid 521. Since the walls of the pores 51 of the silicon oxide matrix 50 may be continuous, i.e., non-discontinuous, between opposing aspects of the solid electrolyte, the electrolyte compound 52 is continuous throughout the solid electrolyte. Metal salts, e.g., Li +The ions of, the ion mobility may be very fast through the electrolyte compound 52 of the wall. Therefore, the ionic conductivity of the solid electrolyte may be fast.

[0129] This procedure was carried out on a solution consisting of organosilanes summarized in Table I. This procedure does not work very well for a solution consisting of DMMVS. This is because DMMVS contains only two alkoxy groups and may be hydrolyzed and involved in the condensation reaction. Therefore, in DMMVS, the formation of large clusters after applying a trigger (e.g., UV or heating) may be hindered.

[0130] The presence of organic moieties in the porous silicon oxide matrix can result in high mass and volume. This can reduce the volume content of the electrolyte compound in the solid electrolyte, and as a result, may reduce its ionic conductivity. However, this potential drawback may be solved by optimizing the ratio of the electrolyte compound to the porous silicon oxide matrix. The organic linking chains can impart favorable mechanical properties to the solid electrolyte, such as improved elasticity and structural integrity. This structural integrity enables the synthesis of solid electrolytes with a very high ratio of liquid electrolyte to porous silicon oxide matrix (e.g., up to [electrolyte compound] / [SiO2]=4, molar ratio), which can further improve the ionic conductivity of the solid electrolyte.

[0131] Example 4: Formation of Solid Electrolyte In this example, the following were mixed to prepare a series of precursor solutions. · 1.65 g of ionic liquid electrolyte, a 1 M solution of a metal salt of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) (lithium salt) in an ionic liquid of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) · 0.5 mL of water (as a reagent) · 1 mL of ethanol (as a solvent) · 2.26 mmol of silane, with various ratios: o Organosilane 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) o Tetraethyl orthosilicate (TEOS)

[0132] In this series, the first sample contains only TMSPMA (i.e., no TEOS). The second sample contains equimolar amounts of TMSPMA and TEOS. The third sample contains equimolar amounts of TMSPMA and TEOS, and further, the amount of ILE (g) is made to be more than the amount of TMSPMA (g) and more than the amount of TEOS (g) up to 4.4 g.

[0133] The Lewis structures of LiTFSI, EMITFSI, TMSPMA, and TEOS are as follows. TIFF2025518530000006.tif7294

[0134] When the metal salt LiTFSI is dissolved in the ionic liquid EMITFSI, an ionic liquid electrolyte (ILE) is formed. The reagents TMSPMA and TEOS are added as precursors for the formation of the silicon oxide matrix. TMSPMA and TEOS may form functionalized silicon oxide particles by hydrolysis (reaction with water) of the alkoxy groups and subsequent condensation. Since TEOS has four alkoxy groups, it can form bonds with four other silane (i.e., TEOS and / or TMSPMA) molecules. Since TMSPMA has three alkoxy groups, it can form only three such bonds. TMSPMA also contains an organic moiety bonded to silicon, and this organic moiety contains a bondable functional group that is vinyl.

[0135] As shown in Example 2, depending on the molar ratio of TMSPMA to TEOS, the precursor may solidify naturally (when the ratio of the amount of TMSPMA to the total amount of TMSPMA and TEOS is at most 0.4) or may remain liquid for a longer time (when the ratio of the amount of TMSPMA to the total amount of TMSPMA and TEOS is at least 0.5). As described above, this may be due to the fact that (i) TMSPMA can form only three bonds at this stage, and (ii) the organic part of TMSPMA may induce steric hindrance.

[0136] This series of three precursor solutions was aged for at least 5 weeks so that the silanes hydrolyzed and condensed to form multiple silicon oxide particles, thereby forming a series of three solutions according to an embodiment of the present invention.

[0137] Thereafter, a radical initiator, namely the photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA), was dissolved in each of the series of solutions at a concentration of 5 mg / mL. Next, nitrogen gas was bubbled through the solution to remove the dissolved oxygen. The aging solution containing the photoinitiator was poured into a mold and subjected to UV irradiation for 1 hour. This caused the photoinitiator to form radical species and initiated the reaction between the vinylidene groups of the organic parts of different silicon oxide particles. As a result, solidification occurred within a time frame of about 1 minute, forming a solid electrolyte (see FIG. 3 for a photograph of the formed solid electrolyte and FIG. 7 for a transmission electron microscope image of the formed solid electrolyte).

[0138] The solid electrolytes were dried, and their ionic conductivities were measured at various temperatures using electrochemical impedance spectroscopy. The electrochemical cell was placed in a binder oven, and the temperature was precisely controlled. The samples were placed in a thermostatic bath, and the conductivity of the incorporated ILE was measured using a conductivity meter. Figure 16 is an Arrhenius plot showing the conductivities of the solid electrolytes and the ILE incorporated in them as a function of temperature. The temperature dependencies of the three solid electrolytes are very similar, but the conductivity of the ILE varies more with temperature. This means that the solid electrolyte obtained from Sample 3 has a temperature range (i.e., below 25 °C) where it exhibits a higher conductivity than the incorporated ILE. Table II summarizes the measured ionic conductivities at 20 °C of each solid electrolyte formed from the first, second, and third samples. When only trialkoxysilane TMSPMA was used as the precursor to form the porous silicon oxide matrix (Sample 1), the ionic conductivity of the solid electrolyte (at 20 °C) was 1.01 mS / cm. When TEOS was also included in the solution, the ionic conductivity of the solid electrolyte (at 20 °C) reached 1.37 mS / cm (Sample 2). By increasing the amount of ILE in the solution and raising the concentration of ILE in the porous silicon oxide matrix, the ionic conductivity was further improved, reaching 2.70 mS / cm (Sample 3). For comparison, the ionic conductivity of pure ILE is 2.51 mS / cm.

[0139] Table II: Ionic conductivity values (at 20 °C) of the solid electrolytes formed from the first, second, and third samples TIFF2025518530000007.tif30150

[0140] Refer to Figure 4. This is a plot of linear sweep voltammetry performed for each of the three solid electrolytes. Here, linear sweep voltammetry was carried out at room temperature with a sweep rate of 10 mVs -1This was carried out using a stainless steel / lithium coin cell. Linear sweep voltammetry may provide information regarding the anodic stability limit. From the linear sweep voltammetry, it was found that the solid electrolyte formed from Sample 1 had the lowest electrochemical stability. The solid electrolyte formed from Sample 2 in the presence of TEOS increased the stability limit. Finally, increasing the concentration of ILE had no significant effect on the stability.

[0141] Figure 5A is a plot of three cyclic voltammetry steps performed on the solid electrolyte formed from Sample 3, and Figure 5B is a plot of current versus time during a 30-minute constant voltage period following a 20-minute constant voltage period preceding the cyclic voltammetry of Figure 5A. The dissolution of lithium into the solid electrolyte formed from Sample 3 was investigated. The solid electrolyte formed from Sample 3 was sandwiched between electrodes to construct a symmetric lithium / lithium coin cell. Three cyclic voltammetry steps were performed (-2 to 2 V, at a rate of 20 mV s -1 . The current at 2 V in the third cycle was 1.07 mA / cm 2 . After 20 minutes at open circuit voltage, a potential of 1 V was applied, and a steady-state current of 0.0596 mA / cm 2 was measured after 1800 s (see Figure 5B). These values are similar to those of a state-of-the-art reference solid electrolyte formed from a reference solution having a similar ILE concentration to Solution 3, but the silane was composed of TEOS (1.42 mA / cm 2 and 0.23 mA / cm 2 , respectively). This indicates that the lithium ion dissolution in the solid electrolyte formed from Sample 3 is similar to that in the state-of-the-art reference solid electrolyte.

[0142] Referring to Figure 6, this is a plot of thermogravimetric analysis of the solid electrolyte formed from Sample 1 in an N2 atmosphere at a rate of 10 °C / min. The thermal decomposition profile shows that the solid electrolyte is stable up to a temperature of ~300 °C.

[0143] Referring to Fig. 7, this is a transmission electron microscope (TEM) image of the formed solid electrolyte of Sample 1 after washing with acetonitrile and subsequent drying to remove all ILE in the solid electrolyte. Thus, Fig. 7 shows a (pure) porous silicon oxide matrix. The TEM image shows that the solid porous silicon oxide matrix of the solid electrolyte is composed of particles of about 50 nm, and these particles are interconnected to form an interconnected porous network. ILE will be contained in the interconnected porous network of the solid electrolyte.

[0144] Referring to Fig. 8. This is the measured viscosity of Sample 1 with respect to the passage of time after the formation of the (unaged, precursor) solution. Here, the viscosity is measured at a temperature of 20 °C and a shear rate of 100 s -1 . The viscosity increases significantly during the first two weeks of aging, indicating that hydrolysis and condensation reactions are occurring within this time frame. After two weeks of aging, the viscosity stagnates, indicating that the condensation reaction has ended after two weeks.

[0145] Refer to Figs. 9A and 9B, Fig. 10, and Fig. 11. These are spectra obtained by different types of NMR spectroscopy performed on Sample 2, shown as a function of time (0 to 5 weeks from the preparation of the unaged solution). Refer to Figs. 9A and 9B. These show the 29Si NMR spectra of Sample 2. It may be observed that the TMSPMA peak decreases much faster than the TEOS peak. Therefore, it can be concluded that the hydrolysis and condensation rate of TMSPMA is considerably faster than that of TEOS. Furthermore, the T1, T2, T3 structures (corresponding to TMSPMA molecules that have undergone hydrolysis and condensation reactions with 1, 2, and 3 different silane molecules respectively) are formed more rapidly than the Q1, Q2, Q3, Q4 structures (corresponding to TEOS molecules that have undergone hydrolysis and condensation reactions with 1, 2, 3, and 4 different silane molecules respectively). The formation of these condensed species suggests that large silicon oxide particles are being formed during the investigation period.

[0146] For Sample 21 1H NMR spectrum (Figure 10) and 13 In the 13C NMR spectrum (Figure 11), it is observed that the signals of the atoms of the alkoxy groups of the silane gradually disappear. This occurs faster for TMSPMA than for TEOS, which 29 supports the observations in the Si spectrum. The signals related to ILE's EMITFSI do not change over the 5 weeks observed, indicating that ILE is stable during this period. The signals from the organic part of TMSPMA broaden over time. This indicates that the structure becomes more rigid and suggests that the TMSPMA molecules are incorporated into larger silicon oxide particles that form over time. This 29 supports the observations in the Si spectrum.

[0147] Three weeks and five weeks after the formation of the solution 29 Si, 1 H, 13 The changes in the 13C NMR spectra are limited. Therefore, it can be inferred that hydrolysis and condensation reactions are almost complete after 5 weeks, and silicon oxide reaches its final composition after this period.

[0148] Example 5: Fabrication of a battery The electrode slurry was prepared using 80 wt% active composite material, 10 wt% carbon black (Super C65, Imerys), and 10 wt% polyvinylidene fluoride (PVDF, Alfa Aesar). These components were ball milled (LiFePO4 (LFP), Retsch Emax, 500 rpm, 30 minutes, zirconia balls with a diameter of 1 cm) or planetary vacuum mixed (LiNi 0.6 Mn 0.2 Co 0.2 (NMC622, Thinky ARV 310 LED, 2000 rpm, 10 minutes) in N-methyl-2-pyrrolidone (NMP, Alfa Aesar, 99.0% or more). The slurry was coated on an aluminum foil with a thickness of 15 μm (blade height: 150 μm). The coated slurry was dried at 110 °C (2 hours). The mass loading of the electrode was 1.9 mg·cm -2(LFP) and 2.17 mg·cm -2 (NMC622).

[0149] Sample 3 was impregnated into a laminate of an electrode and a thin glass fiber (EL-CELL, diameter 19 mm, thickness 0.26 mm) and irradiated with UV for 1 hour. The obtained impregnated laminate was dried in a drying chamber for at least 2 weeks before cell assembly. LFP / Li and NMC622 / Li coin cells (CR2025 type) were assembled in an argon-filled glove box (MBraun, H2O < 0.1 ppm, O2 < 0.1 ppm) and subjected to constant current cycling (BCS-805, Bio-Logic) after an open circuit voltage (OCV) period (16 hours). The LFP / Li cells were cycled in a voltage range of 2 - 4.5 V (theoretical capacity 170 mAh.g -1 ), and the NMC622 / Li cells were cycled in a voltage range of 3 - 4.3 V (theoretical capacity 175 mAh.g -1 ). All charge-discharge cycles were performed with an open circuit voltage period of 30 minutes in between.

[0150] The constant current charge-discharge curve of the LFP / Li cell (Figure 12) shows a voltage plateau centered around approximately 3.5 V characteristic of LFP. This indicates that (i) the solidification of Sample 3 after impregnation, irradiation, and drying into the electrode and separator was successful, (ii) the bulk active material was not decomposed during each step of impregnation / irradiation / drying, and (iii) the solidified material actually has the functional characteristics required for a solid electrolyte. This cell showed discharge capacities of 136, 130, 122, 97, 39 mAh.g -1 at 0.05C, 0.1C, 0.2C, 0.5C, 1C, respectively, at room temperature (Figure 13). These discharge capacities are slightly higher than the results by CHEN, Xubin, et al. using an LFP electrode combined with a standard nanoSCE electrolyte (obtained without solidification induction) and a similar loading. This, together with the reproducibility and stability of the obtained results (see the standard deviation shown in the shaded area of Figure 13), demonstrates the functionality, manufacturability, and electrode compatibility of the electrolyte described herein.

[0151] The stability of the solid electrolyte obtained from Sample 3 was investigated by cycling an LFP / Li battery containing the electrolyte at 0.1 C at room temperature for a long time (Figure 14, current density 32 μA cm-2). This battery did not lose any capacity during 50 cycles (about 35 days of continuous battery operation). This demonstrates that the solid electrolyte has high bulk stability during the electrochemical operation in combination with the LFP cathode.

[0152] An NMC622 / Li battery containing the solid electrolyte obtained from Sample 3 was assembled and its compatibility with a high-energy density cathode material was tested. The constant current charge-discharge curves of such a battery were obtained by continuous cycling at 0.1 C at room temperature (Figure 15, current density 38 μA.cm -2 ) and show the sloping curves commonly observed for NMC622. As in the case of the LFP / Li cell, this indicates (i) the success of the solidification of the electrolyte during the impregnation, irradiation, and drying processes, (ii) the bulk stability of NMC622 during the impregnation / irradiation / drying processes, and (iii) the functional characteristics of the solid electrolyte.

[0153] Preferred embodiments, specific structures and configurations, and materials are described herein with respect to the devices according to the present invention, but it should be understood that various changes or modifications in form and detail may be made without departing from the scope of the present invention. Steps may be added or removed from the methods described within the scope of this specification.

Claims

1. A solution for forming a solid electrolyte (5), A plurality of silicon oxide particles (1) dissolved in a liquid medium, comprising: at least four non-hydrogen atoms, one of which is covalently bonded to a silicon atom of the silicon oxide particle; and a linkable functional group (21) that, after activation by a radical species, is capable of reacting with another identical linkable functional group (21) to form a covalent bond; silicon oxide particles (1) functionalized with an organic moiety (2) comprising the organic moiety (2) comprises at least two atoms that are not part of the linkable functional group (21), and the atoms are bonded to each other by a π bond; the ratio of the number of organic moieties (2) to the number of silicon atoms contained in the plurality of silicon oxide particles (1) is at least 0.3; moreover, ・Electrolyte compound (52), A solution containing

2. 2. The solution according to claim 1, wherein said ratio is between 0.4 and 0.9, preferably between 0.4 and 0.

6.

3. 3. The solution of claim 1, wherein at least two atoms bonded to each other by a π bond are part of a π-conjugated system.

4. 3. The solution according to claim 1 or 2, wherein the organic moiety (2) comprises a linear organic chain containing at least four atoms.

5. 3. The solution of claim 1 or 2, wherein the linkable functional group (21) is separated from the silicon atom to which the organic moiety (2) is attached by an organic linking chain of up to 20 atoms.

6. 3. The solution according to claim 1 or 2, wherein the linkable functional group (21) is a vinyl group or a vinylidene group.

7. 3. The solution according to claim 1 or 2, wherein the functionalized silicon oxide particles (1) are obtained by ageing a precursor solution comprising an organic moiety (21) and an organosilane comprising a silicon atom bonded to four groups, including at least two alkoxy groups.

8. 8. The solution of claim 7, wherein the organosilane comprises 3-trimethoxysilylpropyl methacrylate.

9. The solution of claim 7 , wherein the precursor solution further comprises a tetraalkoxysilane.

10. A method for forming a solid electrolyte (5), comprising the steps of: a) obtaining a solution according to claim 1 or 2, b) adding to the solution a radical initiator suitable for forming radical species for inducing activation; and c) converting the radical initiator into a radical species; A method comprising:

11. 11. The method of claim 10, wherein step c) is carried out while the solution has a pH between 5 and 7.

12. 11. The method of claim 10, wherein the converting step comprises irradiating or heating the solution.

13. The method of claim 10, wherein the radical initiator comprises dimethoxy-2-phenylacetophenone, dibenzoyl peroxide, or azobisisobutyronitrile.

14. A solid electrolyte (5) comprising a porous silicon oxide matrix (50) and an electrolyte compound (52) coating the walls of the pores (51) of the porous silicon oxide matrix (50), wherein at least 30% of the silicon atoms contained in the silicon oxide matrix (50) are separated from other silicon atoms in the silicon oxide matrix (50) by at least four atoms contained in organic connecting chains (4).

15. A battery comprising a solid electrolyte (5) according to claim 14.

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