JP5261906B2 - Ion conductive electrolyte and secondary battery using the ion conductive electrolyte - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion-conducting electrolyte capable of achieving high ionic conductivity and high voltage-resistance and to provide a secondary battery using the same. <P>SOLUTION: The lithium ion conducting electrolyte contains a polymer formed by synthesizing salt monomers comprising onium cations having a polymerizable functional group and an organic anions, a lithium salt, and a normal temperature molten salt, and the polymer is synthesized by using a polymerization initiator represented by formula (1) X-O-O-Y. In the formula (1), X and Y show a group represented by substituted or non-substituted -R, -CO-R, -CO-OR, -R-O-O-R, or -R-O-R, and in these groups, the main chain of the group as X is composed of 5-10 atoms, the main chain of the group as Y is composed of 2-10 atoms, R is a 1 or more C alkyl group, and may be a ring system, or may contain a hetero atom, but R contains no double bond or no triple bond. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an ion conductive electrolyte and a secondary battery using the ion conductive electrolyte.

As electronic devices become smaller and lighter and more portable, research and development of lithium secondary batteries having characteristics such as high voltage and high energy density are being actively conducted. Particularly in recent portable electronic devices, power consumption is also rapidly increasing with rapid performance improvement. In such a background, a lithium secondary battery capable of realizing higher voltage and higher energy density is required.
In order to cope with such a secondary battery, an ion conductive electrolyte that exhibits high ion conductivity, is electrochemically stable in a wide potential range, and has a high withstand voltage has been required.
In order to achieve excellent ionic conductivity, attempts have been made to use room temperature molten salts (see, for example, Patent Document 1). However, the room temperature molten salt itself is liquid at a temperature near room temperature, and when used in a secondary battery, the degree of freedom of the shape of the battery is narrow, and in particular, it has been difficult to apply to a large lithium secondary battery. .
As a method for improving this, a salt monomer composed of an onium cation having a polymerizable functional group and an organic anion having a polymerizable functional group was used in an ion conductive electrolyte containing a polymer, a lithium salt, and a room temperature molten salt. A method using a polymer as a support (for example, see Patent Document 2) has been considered. However, the electrolyte proposed here does not sufficiently exhibit the withstand voltage of room temperature molten salt, and the capacity maintenance is insufficient for use in the next generation high capacity secondary battery.
From such a background, there is a demand for an ion conductive electrolyte that can realize good ionic conductivity, is electrochemically stable in a wider potential range, and has a high withstand voltage.
JP-A-11-307121 JP-A-10-265673

  The present invention provides a lithium ion conductive electrolyte capable of realizing excellent ion conductivity and having a high withstand voltage, and a secondary battery using the same.

The present invention is achieved by the following items (1) to (4).
(1) Lithium ion conduction comprising a polymer synthesized including a salt monomer composed of an onium cation having a polymerizable functional group and an organic anion having a polymerizable functional group, a lithium salt and a room temperature molten salt A lithium ion conductive electrolyte, wherein the polymer is synthesized using a polymerization initiator represented by the following formula (1).
X-O-O-Y (1)
(In the formula (1), X and Y are represented by substituted or unsubstituted —R, —CO—R, —CO—OR, —R—O—O—R, or —R—O—R. In which the main chain of the group as X is composed of 5 to 10 atoms, and the main chain of the group as Y is composed of 2 to 10 atoms R is an alkyl group having 1 or more carbon atoms, and each R may be the same or different, and R may be a ring structure, and these may be heteroatoms. (However, R does not include a double bond or a triple bond.)
(2) The lithium ion conductive electrolyte according to item (1), wherein the polymerization initiator has different structures as X and Y in the formula (1).
(3) The polymerization initiator according to (1) or (2), wherein the main chain of the group is composed of 8 to 10 atoms as X in the formula (1). Lithium ion conductive electrolyte.
(4) A secondary battery comprising the lithium ion conductive electrolyte according to any one of (1) to (3) as a constituent element.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion conductive electrolyte which exhibits the outstanding ion conductivity and high withstand voltage can be provided, and the secondary battery using this expresses a favorable charging / discharging characteristic.

  The present invention relates to a polymer synthesized containing a salt monomer composed of an onium cation having a polymerizable functional group and an organic anion having a polymerizable functional group, a lithium ion comprising a lithium salt and a room temperature molten salt In the conductive electrolyte, by using the polymer synthesized by using the polymerization initiator represented by the formula (1), lithium ion having a high withstand voltage while realizing good ionic conductivity. It has been found that a conductive electrolyte can be obtained, and further studies have been made to complete the present invention.

According to the present invention, by synthesizing a polymer using the salt monomer, an ionic bond site is formed in the skeleton of the polymer, and ions in the polymer in the electrolyte can be obtained by using a room temperature molten salt together. Since the bond concentration can be further increased, the dissociation of the lithium salt in the lithium ion conductive electrolyte can be promoted, and the compatibility of each component can be achieved by adding an appropriate length alkyl chain to the polymer terminal. Since the distance between the polymers can be controlled so as to prevent the movement of lithium ions while maintaining the above, it is considered that excellent lithium ion conductivity is exhibited.
Further, in the above room temperature molten salt, lithium ion is used in a wide potential range by using a material having excellent voltage resistance and using a polymerization initiator comprising an alkyl group that does not contain a double bond in the carbon-carbon bond. It is possible to use a conductive electrolyte. The polymer obtained by including the salt monomer can solidify the lithium ion conductive electrolyte, and can improve the degree of freedom of the shape of the battery during battery production. Furthermore, the polymer containing the salt monomer and obtained using the polymerization initiator has a high affinity with a room temperature molten salt, and a homogeneous solid is obtained.

First, a salt monomer composed of an onium cation having a polymerizable functional group and an organic anion having a polymerizable functional group, which is used for obtaining a polymer used in the present invention, will be described.
Examples of the onium cation having a polymerizable functional group constituting the salt monomer used in the present invention include fluoronium (F ⁺ ), oxonium (O ⁺ ), sulfonium (S ⁺ ), ammonium (N ⁺ ), and phosphonium (P ⁺ ). Etc. are mentioned as cationic species. From the viewpoint of versatility and workability, a phosphonium cation, a sulfonium cation and an ammonium cation are more preferable, and among them, an ammonium cation is most preferable.

Specific examples of the sulfonium cation include a cation in which a sulfur atom is substituted with three substituents R. At least one of the three substituents R is a group containing a polymerizable functional group. The substituent R is a substituted or unsubstituted alkyl group: C _n H _{2n + 1} , aryl group: (R ′) _n —C ₆ H _5-n —, aralkyl group: (R ′) _m —C ₆ H _{5-m -C n H 2n -} , alkenyl group: R'-CH = CH-R'- , aralkenyl _{group: (R ') n -C 6} H 5-n -CH = CH-R'-, alkoxyalkyl Group: R′—O—C _n H _2n —, acyloxyalkyl group: R′—COO—C _n H _2n — and the like can be exemplified. The substituent R may contain a hetero atom or a halogen atom. The three Rs may be different or the same. In the substituent R in the sulfonium cation, R ′ is hydrogen or a substituted or unsubstituted alkyl group having 20 or less carbon atoms, and when there are a plurality thereof, they may be different from each other, and m is an integer of 1 or more and 5 or less. Yes, n is an integer of 1-20. Examples of the substituent when R and R ′ are substituted include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and n-pentyl. Group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and other linear or branched alkyl groups, cyclohexyl group and 4-methylcyclohexyl group Linear or branched alkoxy such as alkyl group, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group and n-hexyloxy group Group, cyclic alkoxy group such as cyclohexyloxy group, methoxymethoxy group, methoxyethoxy group, ethoxyethoxy Group, alkoxyalkoxy group such as methoxypropoxy group, ethoxypropoxy group, propoxypropoxy group, phenyl group, p-tolyl group, m-tolyl group, o-tolyl group, p-chlorophenyl group, m-chlorophenyl group and o-chlorophenyl Aryl groups such as phenoxy groups, m-methylphenoxy groups, o-methylphenoxy groups, p-chlorophenoxy groups, m-chlorophenoxy groups, o-chlorophenoxy groups and pn-butylphenoxy groups Group, phenylthio group, p-methylphenylthio group, m-methylphenylthio group, o-methylphenylthio group, o-ethylphenylthio group, p-propylphenylthio group and 2,4,6-trimethylphenylthio group Arylthio group such as methylcarbonylamino group, ethylcarbonyl Mino group, alkylcarbonylamino group such as n-propylcarbonylamino group, isopropylcarbonylamino group and n-butylcarbonylamino group, methoxycarbonylamino group, ethoxycarbonylamino group, n-propoxycarbonylamino group, isopropoxycarbonylamino group And an alkoxycarbonylamino group such as an n-butoxycarbonylamino group, an alkylcarbonyl group such as a methylcarbonyl group, an ethylcarbonyl group, an n-propylcarbonyl group, an isopropylcarbonyl group and an n-butylcarbonyl group, a methylcarboxy group, an ethylcarboxy group Alkylcarboxy groups such as n-propylcarboxy group, isopropylcarboxy group and n-butylcarboxy group, methoxycarboxy group, ethoxycarboxy group, n-propoxy group Alkoxycarboxy groups such as carboxy group, isopropoxycarboxy group and n-butoxycarboxy group, methoxycarbonylmethoxy group, ethoxycarbonylethoxy group, ethoxycarbonylmethoxy group, n-propoxycarbonylmethoxy group, isopropoxycarbonylmethoxy group and n-butoxy Examples thereof include an alkoxycarbonylalkoxy group such as a carbonylmethoxy group, and these substituents may contain a halogen atom or a heteroatom. Furthermore, examples of the substituent include a cyano group and halogen atoms such as fluorine, chlorine and bromine.

Specific examples of the phosphonium cation include cations in which a phosphorus atom is substituted with four substituents R. At least one of the four substituents R is a group containing a polymerizable functional group. The substituent R is a substituted or unsubstituted alkyl group: C _n H _{2n + 1} , aryl group: (R ′) _n —C ₆ H _5-n —, aralkyl group: (R ′) _m —C ₆ H _{5-m -C n H 2n -} , alkenyl group: R'-CH = CH-R'- , aralkenyl _{group: (R ') n -C 6} H 5-n -CH = CH-R'-, alkoxyalkyl Group: R′—O—C _n H _2n —, acyloxyalkyl group: R′—COO—C _n H _2n — and the like can be exemplified. The substituent R may contain a hetero atom or a halogen atom. The four Rs may be different or the same. In the substituent R in the phosphonium cation, R ′ is hydrogen or a substituted or unsubstituted alkyl group having 20 or less carbon atoms, and when there are a plurality thereof, they may be different from each other, and m is an integer of 1 or more and 5 or less. Yes, n is an integer of 1-20. Examples of the substituent when substituted in R and R ′ include the same as those in the sulfonium cation.

The ammonium cation is a cation that can be generated from an amine compound, and it goes without saying that the amine compound includes all amine compounds such as aliphatic amine compounds, aromatic amine compounds, and nitrogen-containing heterocyclic amine compounds. If it has the positive charge resulting from an amine, it will not specifically limit. Specific examples include cations in which a nitrogen atom is substituted with four substituents R. At least one of the four substituents R is a group containing a polymerizable functional group. The substituent R is a substituted or unsubstituted alkyl group: C _n H _{2n + 1} , aryl group: (R ′) _n —C ₆ H _5-n —, aralkyl group: (R ′) _m —C ₆ H _{5-m -C n H 2n -} , alkenyl group: R'-CH = CH-R'- , aralkenyl _{group: (R ') n -C 6} H 5-n -CH = CH-R'-, alkoxyalkyl Group: R′—O—C _n H _2n —, acyloxyalkyl group: R′—COO—C _n H _2n — and the like can be exemplified. The substituent R may contain a hetero atom or a halogen atom. The four Rs may be different or the same. In the substituent R in the ammonium cation, R ′ is hydrogen or a substituted or unsubstituted alkyl group having 20 or less carbon atoms, and when there are a plurality thereof, they may be different from each other, and m is an integer of 1 to 5. Yes, n is an integer of 1-20. Examples of the substituent when substituted in R and R ′ include the same as those in the sulfonium cation.

  Examples of the ammonium cation other than the ammonium cation include aromatic ammonium cations such as pyridinium cation, pyraridinium cation and quinolinium cation, and aliphatic heterocyclic ammonium such as pyrrolidinium cation, piperidinium cation and piperazinium cation. Mention may also be made of ammonium cations such as cations, heterocyclic ammonium cations containing heteroatoms other than nitrogen such as morpholine cations, and unsaturated nitrogen-containing heterocyclic cations such as imidazolium cations. Further, the cyclic ammonium cation may be a cation having a different nitrogen position, a cation having a substituent on the ring, or a cation having a substituent containing a hetero atom.

  The polymerizable functional group in the onium cation is not particularly limited as long as it is a functional group that can be polymerized by radical polymerization, ionic polymerization, coordination polymerization, redox polymerization, or the like, but a group having a carbon-carbon double bond is available. A radical polymerizable functional group is preferable. The radical polymerizable functional group is more preferably capable of radical polymerization by active energy rays or heat. Examples of such a functional group include (meth) acryloyl group, (meth) acryloyloxy group, (meth) acrylamide group, allyl group, vinyl group, and styryl group. Among these, (meth) acryloyl group Oxy group, (meth) acrylamide group, styryl group, allyl group and vinyl group are preferred.

  Specific examples of the onium cation having a polymerizable functional group constituting the salt monomer include (meth) acryloyloxyethyltrimethylammonium cation, (meth) acryloyloxyethyltriethylammonium cation, (meth) acryloyloxyethyltri-n-propyl. Ammonium cation, (meth) acryloyloxyethyl tri-iso-propylammonium cation, (meth) acryloyloxyethyl tri-n-butylammonium cation, (meth) acryloyloxyethyl tri-iso-butylammonium cation, (meth) acryloyloxy Ethyltri-tert-butylammonium cation, (meth) acryloyloxyethyltriethylammonium cation, (meth) acryloyloxyethyl Diethyl-n-hexylammonium cation, (meth) acryloyloxyethyltridecylammonium cation, (meth) acryloyloxyethyltrioctylammonium cation, (meth) acryloyloxyethyldodecyldimethylammonium cation, (meth) acryloyloxydimethylbenzylammonium cation (Meth) acryloyloxyethyldodecylhexylmethylammonium cation, diallyldimethylammonium cation, bisstyrylmethyldimethylammonium cation, bisstyrylethyldimethylammonium cation, (meth) acrylamidoethyltrimethylammonium cation, (meth) acrylamidopropyltrimethylammonium cation, (Meth) acrylamide Rutriethylammonium cation, (meth) acrylamide ethyltri-n-propylammonium cation, (meth) acrylamideethyltri-iso-propylammonium cation, (meth) acrylamideethyltri-n-butylammonium cation, (meth) acrylamideethyltri -Iso-butylammonium cation, (meth) acrylamidoethyltri-tert-butylammonium cation, (meth) acrylamidoethyltriethylammonium cation, (meth) acrylamidoethyldiethyl-n-hexylammonium cation, (meth) acrylamidoethyltridecylammonium cation Cation, (meth) acrylamide ethyl trioctyl ammonium cation, (meth) acrylamide ethyl Various ammonium cations such as decyldimethylammonium cation and (meth) acrylamidoethyldodecylhexylmethylammonium cation, styrylmethylmethylpyrrolidinium cation, bisstyrylmethylpiperidinium cation, N, N ′-((meth) acryloyloxyethylmethyl ) Piperazinium cation, (meth) acrylamidoethylmethylmorpholinium cation, (meth) acryloyloxyethylmethylimidazolium cation, and the like.

Further, the organic anion constituting the salt monomer used in the present invention is not particularly limited as long as it is an anion having a polymerizable functional group. For example, an anion from which a proton of a hydroxyl group-containing organic compound such as alcoholate and phenolate is eliminated. : RO ^- anion, thiolate and anionic proton desorbed such thiophenolate: RS ^- anions, sulfonate anions: RSO ₃ ^-, carboxylate anions: RCOO ^-, is part of the hydroxyl groups of phosphoric acid and phosphorous acid Phosphorus-containing derivative anion substituted with an organic group: R _x (OR) _y (O) _z P ⁻ , where x, y and z are integers of 0 or more and x + y + 2z = 3 or x + y + 2z = 5 , substituted borate _{anion: R x (oR) y B} -, ( provided that, x, y is 0 or an integer, and, x + y = 4), substituted aluminum _{Anions: R x (OR) y Al} -, ( provided that, x, y is 0 or an integer, and, x + y = 4), carbanions (EA) ₃ C ^-, nitrogen anion (EA) ₂ N ^- and Can be mentioned. EA represents a hydrogen atom or an electron withdrawing group.

As the organic anion, RSO ₃ ⁻ , RCOO ⁻ , RPO ₃ ²⁻ and (RO ₂ S) ₂ N ^{− which} are anions derived from a sulfoxyl group, a carboxyl group, a phosphoxyl group and a sulfonimide group are particularly preferable. Here, R in the organic anion is hydrogen, substituted or unsubstituted alkyl group C _n H _{2n + 1} , aryl group (R ′) _n —C ₆ H _5-n —, aralkyl group (R ′) _{m. -C 6 H 5-m -C n} H 2n -, R'-CH = CH-R'- alkenyl, aralkenyl group _{(R ') n -C 6 H} 5-n -CH = CH-R'-, Examples thereof include an alkoxyalkyl group R′—O—C _n H _2n —, an acyloxyalkyl group R′—COO—C _n H _2n — and the like, which may have a ring structure, It may contain atoms. When there are two or more Rs in the molecule, they may be the same or different from each other. However, in the case of an anion having one substituent R, when R has a plurality of substituents R, at least one is a group containing a polymerizable functional group, and similarly one substituent EA In the case of an anion having EA, when the EA has a plurality of substituents EA, at least one is a group containing a polymerizable functional group. R ′ in R in the organic anion is hydrogen or a substituted or unsubstituted alkyl group having 20 or less carbon atoms, and when there are a plurality thereof, they may be different from each other, m is an integer of 1 or more and 5 or less, n is an integer of 1-20. Also included are those in which some or all of the hydrogen atoms on the carbon of R are replaced by halogen atoms. Examples of the substituent when substituted in R and R ′ include the same as those in the sulfonium cation.

  Examples of the polymerizable functional group in the organic anion include the same ones as those of the onium cation having the polymerizable functional group. The salt monomer has at least two polymerizable functional groups, and these polymerizable functional groups may be the same or different from each other.

  Specific examples of the organic anion having a polymerizable functional group constituting the salt monomer include 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-[(2-propenyloxy) methoxy] ethenesulfonic acid, 3- (2-propenyloxy) -1-propene-1-sulfonic acid, vinylsulfonic acid, 2-vinylbenzenesulfonic acid, 3-vinylbenzenesulfonic acid, 4-vinylbenzenesulfonic acid, 4-vinylbenzylsulfonic acid, 2-methyl -1-pentene-1-sulfonic acid, 1-octene-1-sulfonic acid, 4-vinylbenzenemethanesulfonic acid, acrylic acid, methacrylic acid, 2-acrylamido-2-methyl-1-propanephosphoric acid and 2- ( Examples include various anions derived from (meth) acryloyloxy-1-ethanephosphoric acid and the like.

  Examples of the salt monomer composed of an onium cation having a polymerizable functional group and an organic anion having a polymerizable functional group used in the present invention include, for example, metal salts such as silver salts of the organic anion having the polymerizable functional group, and These can be synthesized by reacting with a halide of an onium cation having a polymerizable functional group, but the synthesis method is not limited as long as the target salt monomer can be obtained.

As a polymerization initiator used in order to obtain the polymer used for this invention, it has a structure represented by Formula (1).
X-O-O-Y
(In the formula (1), X and Y are represented by substituted or unsubstituted —R, —CO—R, —CO—OR, —R—O—O—R, or —R—O—R. In these groups, the main chain of the group as X is composed of 5 to 10 atoms, and the main chain of the group as Y is composed of 2 to 10 atoms. However, the main chain of the group as X may be composed of 8 to 10 atoms, wherein R is an alkyl group having 1 or more carbon atoms, and each R is the same or different. R may also be a ring structure, and these may contain heteroatoms, provided that R does not contain a double or triple bond.)

In the groups X and Y bonded to the peroxide group constituting the polymerization initiator, the number of main chain atoms as the X is 4 or less in the number of main chain atoms bonded to the peroxide group. If the number of atoms in the main chain is 1 as Y, the polymer chain alkyl chain structure is small, the distance between the polymers is shortened, and the movement of lithium ions is structurally inhibited. Moreover, when it is 11 or more as X and Y, the compatibility of a polymer, normal temperature molten salt, and Li salt will fall, a component will isolate | separate, and the function of electrolyte will fall remarkably.
In addition, if a carbon-carbon double bond or triple bond is present in the structure of the polymerization initiator, it is electrochemically unstable, and this may cause a film to form on the electrode interface, and the electric resistance of the electrolyte is reduced. descend.
Specific examples of the alkyl group having 1 or more carbon atoms as R include 1 to 10 carbon atoms such as methyl group, ethyl group, isopropyl group, t-butyl group, heptyl group, octyl group, nonyl group, and decyl group. And a cyclic alkyl group having 3 to 10 carbon atoms such as a chain alkyl group, a cyclohexyl group and a cyclopentoxy group.

  Specific examples of the polymerization initiator include 1,1-di (t-hexylperoxy) -2-methylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (t-butylperoxy). ) Peroxyketals such as butane and n-butyl 4,4-di- (t-butylperoxy) valerate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and di-t-hexylper Diacyl peroxides such as oxide, diacyl peroxides such as di (3,3,5-trimethylhexanoyl) peroxide, di-n-octanoyl peroxide and disuccinic acid peroxide, di-n-propyl peroxydicarbonate, Diisopropyl peroxydicarbonate, di (t-butylcyclohexyl) peroxydica Peroxydicarbonates such as bonate, di (2-ethoxyethyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di (3-methoxybutyl) peroxydicarbonate and di-sec-butylperoxydicarbonate, 1 1,1,3,3-tetramethylbutyl peroxyneodecanate, t-hexylperoxyneodecanate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethyl Hexanate, t-hexylperoxy-isopropyl monocarbonate, t-butylperoxyneodecanate, 1-cyclohexyl-1-methylethylperoxyneodecanate, t-butylperoxy-2-ethylhexanoate, t-butylpero Shi 3,3,5-trimethylhexamethylene diisocyanate, t- butyl peroxy - peroxy esters such as isopropyl monocarbonate and t-butyl peroxy-2-ethylhexyl monocarbonate and the like.

  As a method of synthesizing a polymer by polymerizing the salt monomer, the salt monomer is dissolved in an organic solvent such as methanol and acetonitrile, the polymerization initiator is added, and the polymerization is performed by heating at 30 to 150 ° C., for example. Thus, a desired polymer can be synthesized.

  In the lithium ion conductive electrolyte of the present invention, a polymer may be synthesized in advance and mixed with other components, or the salt monomer, the polymerization initiator, and other components constituting the polymer may be mixed. Then, it may be a polymer.

  As the addition amount of the polymerization initiator in the synthesis of the polymer, the total number of moles of the polymerizable functional group contained in the salt monomer, and when the synthesis is performed after mixing with the components constituting the electrolyte, The amount is preferably about 0.01 to 30 mol%, more preferably 0.1 to 20 mol%, based on the number of moles of the polymerizable functional group that the component has. In the synthesis, polymerization may be performed in a solvent in consideration of workability.

  In the polymer used in the present invention, other monomers can be used in combination with the salt monomer. Examples of such monomers include polymerizable functionalities such as methylene bisacrylamide, ethylene glycol di (meth) acrylate, divinylbenzene, diallylmethylamine, diallylethylamine, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate and diallyl phthalate. Monomers having a plurality of groups, N, N-dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, stearyl acrylate, diacetone acrylamide, 1-adamantyl (meth) acrylate and 2-ethyl (meth) acrylate And monomers having one polymerizable functional group such as adamantyl.

  In the lithium ion conductive electrolyte of the present invention, the preferred content of the polymer synthesized containing the salt monomer is preferably a lower limit of 0.1 wt%, a preferred upper limit of 99.8 wt%, and a more preferred lower limit. The value is 1 wt%, and a more preferable upper limit value is 98 wt%. The polymer content here is the amount of polymer added when it is added. When the salt monomer is polymerized in a state mixed with other components constituting the electrolyte, the salt monomer and optional It is content of the said other monomer used together.

Examples of the lithium salt used in the present invention include LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiBF ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ and LiC ( CF ₃ SO ₂ ) ₃ and Li ion-containing ionic liquids (ionic liquids for electrolytes disclosed in Japanese Patent Application Laid-Open No. 2004-307481, etc.) are included, and these are used alone or in combination of two or more. May be used. The addition amount of the lithium salt used is preferably 0.1 wt%, a preferred upper limit is 99.8 wt%, more preferred lower limit is 1 wt%, and a more preferred upper limit is 98 wt% in the lithium ion conductive electrolyte. It is.

The room temperature molten salt used in the present invention is composed of a cation component and an anion component. Examples of the cation component constituting the room temperature molten salt include nitrogen, sulfur, phosphorus, oxygen, selenium, tin, iodine and antimony. There is no particular limitation as long as it is a cation having at least one group formed by coordination of a cation-type atomic group to a compound containing an element having a lone pair of electrons, so-called onium cation. An onium cation having a lone pair of sulfur or phosphorus is preferable, and a quaternary ammonium cation represented by the formula (1) is more preferable because the withstand voltage is increased.
N ⁺ R ₁ R ₂ R ₃ R ₄ (1)
(Wherein R ₁ , R ₂ , R ₃ and R ₄ each represents an alkyl group, an alkoxyalkyl group, an aralkyl group, an aryl group, an alkenyl group or an aralkenyl group, and may be the same or different. Any one or more of these may form a ring structure and may contain a hetero atom.)

Here, the groups R ₁ , R ₂ , R ₃ and R ₄ contained in the quaternary ammonium cation are groups selected from alkyl groups, alkoxyalkyl groups, aralkyl groups, aryl groups, alkenyl groups and aralkenyl groups. Some cases are preferred. Furthermore, an alkyl group, an alkoxyalkyl group, and an aralkyl group are more preferable, and an alkyl group and an alkoxyalkyl group are most preferable. Furthermore, specific examples of these groups include alkyl groups such as methyl group, ethyl group and propyl group, alkoxyalkyl groups such as methoxymethyl group, methoxyethyl group, (methoxyethoxy) ethyl group and (hydroxyethoxy) ethyl group. Group, an aryl group such as phenyl group and naphthyl group, an aralkyl group such as benzyl group, an alkenyl group represented by R′—CH═CH—R′—, (R ′) _m —C ₆ H _5−m —CH═ An aralkenyl group represented by CH—R′— (R ′ is hydrogen or a substituted or unsubstituted alkyl group having 20 or less carbon atoms, etc., and when there are a plurality thereof, they may be different from each other, and m is from 1 to 5; In addition, (hydroxyethyl) methylamino group, methoxy (carbonylethyl) group, hydroxyethyl group, oxazolyl group and morpholinyl group. And the like.

The anionic component constituting the ionic liquid used in the present invention, proton desorbed RO hydroxyl group-containing organic compounds such as alcoholates and phenolates ^- anion; proton such as thiolate and thiophenolate is eliminated RS ^- anion Sulfonic acid anion RSO ₃ ⁻ , carboxylate anion RCOO ⁻ ;, phosphorus-containing derivative anion R _x (OR) _y (O) _z P in which a part of hydroxyl groups of phosphoric acid and phosphorous acid are substituted with organic groups ^- , (Where x, y, z are integers of 0 or more and x + y + 2z = 3 or x + y + 2z = 5) ;, substituted borate R _x (OR) _y B ⁻ , where x and y are 0 or more an integer, and, x + y = 4) ;, substituted aluminum anions ^{_{R x (oR) y Al -}} , ( provided that, x, y is 0 or an integer, and, x + y = 4) ;, nitrogen anion ( A) ₂ N ^-, carbanions (EA) ₃ C ^- and organic anions, such as the inorganic anions such as halogen ions, and the like. Wherein, R represents hydrogen, substituted or unsubstituted, alkyl group C _n H _2n-1 -, an aryl group _{(Rc) m -C 6 H 5} -m -, an aralkyl group (Rc) _m -C ₆ H _{5 -m} -C _n H _2n -, alkenyl group Rc-CH = CH-Rc-, aralkenyl _{(Rc) m -C 6 H 5} -m -CH = CH-Rc-, alkoxyalkyl group Rc-O-C _n A group selected from H _2n — and an acyloxyalkyl group Rc—COO—C _n H _2n — (in the R, Rc is a substituted or unsubstituted alkyl group having 20 or less carbon atoms, or hydrogen; And m is an integer of 1 to 5, and n is an integer of 1 to 20, and these may have a ring structure. Moreover, a hetero atom may be included. When there are two or more Rs in the molecule, they may be the same or different from each other. EA represents a hydrogen atom or an electron withdrawing group. In addition, some of the above-mentioned hydrogen atoms on the carbon of R are substituted with halogen atoms, and those substituted with fluorine atoms are particularly preferred cases.
In particular, the organic anion is preferably RSO ₃ ⁻ , RCOO ⁻ , (RO ₂ S) ₂ N ⁻ as a nitrogen anion, and (RO ₂ S) ₃ C ⁻ as a carbanion, and ClO which is a halogen-containing ion as an inorganic anion. Preferred examples include ₄ ⁻ , BF ₄ ⁻ , AsF ₆ ⁻ , PF ₆ ⁻ and halogen ions F ⁻ , Cl ⁻ , Br ⁻ and I ⁻ .

Furthermore, when the anion component constituting the room temperature molten salt is an anion component selected from the anions represented by the formula (2), the withstand voltage of the lithium ion conductive electrolyte is increased, which is more preferable.
N (R ₁ SO ₂ ) (R ₂ SO ₂ ) ⁻ , N (R ₃ SO ₃ ) ⁻ , C (R ₄ SO ₂ ) (R ₅ SO ₂ ) (R ₆ SO ₂ ) ⁻ (2)
(In the formula, R _{1 to} R ₆ are each a substituted or unsubstituted group selected from an alkyl group, an alkoxyalkyl group, an aralkyl group, an aryl group, an alkenyl group, and an aralkenyl group. They may be different, they may have a ring structure, and they may contain heteroatoms.)

Here, the groups R _{1 to} R ₆ contained in the anion represented by the formula (2) are groups selected from alkyl groups, alkoxyalkyl groups, aralkyl groups, aryl groups, alkenyl groups, and aralkenyl groups. In addition, the lithium ion conductive electrolyte preferably has a high withstand voltage, but an alkyl group, an alkoxyalkyl group, and an aralkyl group are more preferable. Furthermore, specific examples of these groups include the same groups as those groups in the ammonium cation constituting the room temperature molten salt. In addition, when these groups are substituted, the substituents are methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group. Linear or branched alkyl groups such as neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group and n-decyl group, cyclic groups such as cyclohexyl group and 4-methylcyclohexyl group Linear or branched alkoxy groups such as alkyl groups, methoxy groups, ethoxy groups, n-propoxy groups, isopropoxy groups, n-butoxy groups, isobutoxy groups, sec-butoxy groups, tert-butoxy groups and n-hexyloxy groups Cyclic alkoxy groups such as cyclohexyloxy group, dimethoxy group, methoxyethoxy group, diethoxy group, methoxypro Alkoxyalkoxy groups such as xy group, ethoxypropoxy group, dipropoxy group, aryl such as phenyl group, p-tolyl group, m-tolyl group, o-tolyl group, p-chlorophenyl group, m-chlorophenyl group and o-chlorophenyl group Group, phenoxy group, m-methylphenoxy group, o-methylphenoxy group, p-chlorophenoxy group, m-chlorophenoxy group, o-chlorophenoxy group and pn-butylphenoxy group, aryloxy groups, phenylthio group Arylthio groups such as p-methylphenylthio group, m-methylphenylthio group, o-methylphenylthio group, o-ethylphenylthio group, p-propylphenylthio group and 2,4,6-trimethylphenylthio group Methylcarbonylamino group, ethylcarbonylamino group, n-propyl group Alkylcarbonylamino groups such as bonylamino group, isopropylcarbonylamino group and n-butylcarbonylamino group, methoxycarbonylamino group, ethoxycarbonylamino group, n-propoxycarbonylamino group, isopropoxycarbonylamino group and n-butoxycarbonylamino group Alkylcarbonyl groups such as alkoxycarbonylamino group, methylcarbonyl group, ethylcarbonyl group, n-propylcarbonyl group, isopropylcarbonyl group and n-butylcarbonyl group, methylcarboxy group, ethylcarboxy group, n-propylcarboxy group, etc. Alkylcarboxy groups such as isopropylcarboxy group and n-butylcarboxy group, methoxycarboxy group, ethoxycarboxy group, n-propoxycarboxy group, isopropoxy Alkoxycarboxy groups such as xycarboxy group and n-butoxycarboxy group, methoxycarbonylmethoxy group, ethoxycarbonylethoxy group, ethoxycarbonylmethoxy group, n-propoxycarbonylmethoxy group, isopropoxycarbonylmethoxy group and n-butoxycarbonylmethoxy group These substituents may contain a halogen atom or a heteroatom, and all of them may be substituted with a halogen.
The addition amount of the room temperature molten salt used is preferably a lower limit of 0.1 wt% and a preferred upper limit of 99.8 wt% in the lithium ion conductive electrolyte, a more preferred lower limit of 1 wt%, and a more preferred upper limit of 98 wt. %.

  In addition to the above components, a plasticizer, a polymerization initiator, a flame retardant electrolyte dissolving agent, and other additives can be used for the lithium ion conductive electrolyte of the present invention.

As a method for producing the lithium ion conductive electrolyte of the present invention, first, a salt monomer, a polymerization initiator, a lithium salt, a room temperature molten salt, and if necessary, a mixture of other monomers, a plasticizer and other additives are prepared. Then, a polymer is synthesized by polymerizing the salt monomer in the mixture, and optionally other monomers, to obtain a lithium ion conductive electrolyte. Here, the other components optionally mixed with the salt monomer are added so that the content of the polymer synthesized thereby becomes the above ratio. The lithium ion conductive electrolyte can also be obtained by mixing a polymer obtained by containing the salt monomer, a lithium salt, and a room temperature molten salt. Also in this case, other monomers, plasticizers, polymerization initiators and other additives may be used as necessary.
The mixing method may be a known mixing method such as solution mixing, powder mixing and melt kneading. In the other additive, when a plasticizer is used, a solution in which a lithium salt is previously dissolved in a plasticizer may be mixed with a monomer such as a salt monomer.
In addition, when a monomer such as a salt monomer, a polymerization initiator, a lithium salt, a room temperature molten salt, and a flame retardant electrolyte solubilizer, a plasticizer, and other additives are mixed as necessary to prepare a liquid or paste-like mixture Alternatively, a solution obtained by dissolving a lithium salt in a room temperature molten salt or a flame retardant electrolyte dissolving agent and a monomer such as a salt monomer may be mixed.

Examples of the plasticizer include cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as ethyl methyl carbonate and diethyl carbonate. These can be used alone or in combination of two or more. .
Examples of the flame retardant electrolyte salt solubilizer include compounds that exhibit self-extinguishing properties and contribute to dissolving the electrolyte salt in the presence of the electrolyte salt, and are generally added to the electrolyte for non-aqueous electrolyte batteries. Flame retardant solvents, such as phosphate esters, halogen compounds and phosphazenes.

Furthermore, a method for producing a lithium ion conductive electrolyte in the method for producing a secondary battery will be described with reference to specific examples, but the method for producing the electrolyte is not limited to these.
First, a salt monomer, a polymerization initiator, a lithium salt, a room temperature molten salt, and if necessary, other monomers, a plasticizer, and other additives are mixed to prepare a mixture. This mixture is liquid or pasty. Those in a homogeneous form are preferred. However, in actuality, when the lithium ion conductive electrolyte is manufactured, from the preparation of the above mixture until the curing by the polymerization of the salt monomer is completed, the above mixture may be an emulsion, an emulsion, a colloid, a coacervate, or the like. If the solution state can be maintained, the mixture can be used even if the turbidity of the mixture is high.
The mixture prepared above is poured into a predetermined cell or formwork provided with electrodes, and the salt monomer is polymerized by a method such as heating or energy ray irradiation to obtain an ion conductive electrolyte. .
If the mixture prepared above has a high viscosity and is difficult to work with, the salt monomer is polymerized and cured using a mixture prepared by diluting with a low-boiling diluent solvent such as tetrahydrofuran, methanol, and acetonitrile. Later, a known method for manufacturing a cell, such as a method for removing the diluted solvent or a method for replacing the diluted solvent with an electrolytic solution used for a battery, may be used.
Depending on the cell configuration, a lithium ion conductive electrolyte can be obtained by a known method such as a casting method or a solid phase polymerization method in addition to the liquid injection.

The secondary battery of the present invention comprises the lithium ion conductive electrolyte obtained above as a constituent element, and can be manufactured by combining a positive electrode and a negative electrode in addition to the ion conductive electrolyte.
The active material used for the positive electrode used in the battery of the present invention is preferably a transition metal oxide containing lithium having a high energy density and excellent reversible lithium ion insertion / extraction, such as LiCoO ₂ . Examples include lithium cobalt oxide, lithium manganese oxide such as LiMn ₂ O ₄ , lithium nickel oxide such as LiNiO ₂ , a mixture of these oxides, and a part of nickel in LiNiO ₂ substituted with cobalt or manganese. . The negative electrode active material is not limited as long as it is a material that can insert and desorb lithium ions, and examples thereof include metallic lithium and carbon-based materials. Examples of the carbon material include natural graphite, artificial graphite, mesocarbon microbeads, and graphite.

Examples of a method for producing a secondary battery using the polymer solid electrolyte of the present invention include a positive electrode active material such as LiCoO ₂ , a conductive agent such as graphite, and a binder such as poly (vinylidene fluoride). Are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in N-methyl-2-pyrrolidone to obtain a slurry-like positive electrode mixture. This positive electrode mixture is uniformly applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm, etc., dried, and then compression molded with a roll press to obtain a positive electrode.
Next, a negative electrode active material such as graphite powder and a binder such as poly (vinylidene fluoride) are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in N-methyl-2-pyrrolidone. To obtain a slurry-like negative electrode mixture. This negative electrode mixture is uniformly applied to both surfaces of a negative electrode current collector made of a copper foil having a thickness of 15 μm, etc., dried, and then compression molded with a roll press to obtain a negative electrode.
The positive electrode, the ion conductive electrolyte, and the negative electrode obtained as described above are bonded to form a single-layer cell, and this cell is inserted into an outer package made of a laminate film having a three-layer structure of polyester film-aluminum film-modified polyolefin film. The secondary battery is obtained by sealing.

  Although a specific example is shown about the method of manufacturing the lithium ion conductive electrolyte sheet of this invention, this invention is not limited to these.

(Synthesis example)
[Synthesis of salt monomer]
10.36 g (50 mmol) of 2-acrylamido-2-methyl-1-propanesulfonic acid was dissolved in 500 ml of methanol / 4 ml of distilled water, and 27.6 g (100 mmol) of silver carbonate was added thereto. After stirring gently for 4 hours and filtering, a clear and colorless solution was obtained. To this filtrate, 101 mmol of a solution prepared by dissolving methacrylamidopropyltrimethylammonium chloride in 100 ml of methanol was dropped. The reaction proceeded quantitatively. The reaction product silver chloride was removed by filtration, and a colorless and transparent methanol solution was recovered. The filtrate was concentrated under reduced pressure using an evaporator, and allowed to stand all day in a cool and dark place to recrystallize the target product, and colorless and transparent plate crystals (hereinafter referred to as salt monomers) were collected.

[Example 1]
In an argon atmosphere (dew point temperature: −60 ° C. or lower), 10.00 g of the salt monomer obtained in the above synthesis example was added to 30 ml of methanol and completely dissolved. After sufficiently degassing, add 0.12 g of thermal polymerization initiator di (t-butylcyclohexyl) peroxydicarbonate (X: 10, -CO-R type Y: 10; -CO-R type) and stir well And dissolved uniformly. Then, it heated and polymerized at 60 degreeC for 40 minutes. The obtained polymer solution was reprecipitated with acetone, and then the white polymer was collected by filtration. The obtained solid was dried in a vacuum dryer at 60 ° C. for 3 hours.
1 g of the obtained polymer, 8 g of room temperature molten salt (diethylmethyl (methoxyethyl) ammonium bis (trifluoromethanesulfone) imide), 1 g of lithium bis (trifluoromethanesulfone) imide and 2 ml of methanol as a diluent solvent are mixed and dissolved. A prepared composition was prepared. After the prepared composition is impregnated into a microporous sheet made of polysulfone resin under reduced pressure, methanol is removed at room temperature under reduced pressure, and the impregnated sheet is further vacuum dried at 80 ° C. for 2 hours. A lithium ion conductive electrolyte sheet was obtained.

A secondary battery using the lithium ion conductive electrolyte sheet obtained above was prepared and its cycle characteristics were evaluated as follows.
A positive electrode mixture was prepared by mixing 85% by weight of LiCoO ₂ as a positive electrode active material, 5% by weight of graphite as a conductive agent, and 10% by weight of poly (vinylidene fluoride) as a binder. The positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to obtain a slurry-like positive electrode mixture. This positive electrode mixture was uniformly applied to both surfaces of a 20 μm thick aluminum foil used as a positive electrode current collector, dried, and then compression molded with a roll press to obtain a positive electrode.
A negative electrode mixture was prepared by mixing 90% by weight of pulverized graphite powder as a negative electrode active material and 10% by weight of poly (vinylidene fluoride) as a binder, and this negative electrode mixture was mixed with N-methyl. A slurry-like negative electrode mixture was prepared by dispersing in 2-pyrrolidone. This negative electrode mixture was uniformly applied to both surfaces of a 15 μm thick copper foil used as a negative electrode current collector, dried, and then compression molded with a roll press to obtain a negative electrode.
The positive electrode, lithium ion conductive electrolyte sheet, and negative electrode obtained as described above were bonded to form a single layer cell. This cell is inserted into an outer package made of a laminate film having a three-layer structure of polyester film-aluminum film-modified polyolefin film, the outer peripheral edge of the outer film is sealed, and the positive electrode terminal and the negative electrode terminal are opened in the outer film. The single-layer cell was sealed in an exterior film under reduced pressure to obtain a secondary battery using a lithium ion conductive electrolyte.
Using the obtained secondary battery, a 500 mA constant current voltage charge was performed to an upper limit of 4.2 V for 2 hours in an atmosphere at 25 ° C., and then a discharge at 500 mA (1 hour rate discharge) was performed at a final voltage of 2 It went to 5V. This was charged and discharged as one cycle, and the capacity retention rate at the 100th cycle when the discharge capacity at the first cycle was taken as 100% was 90%.

[Example 2]
Prepared in the same manner as in Example 1 except that the thermal polymerization initiator was changed to 0.12 g of t-butylperoxyneodecanate (X: 8, -CO-R type Y: 2, -R type). A secondary battery was created. As a result of measuring the capacity retention rate of the obtained secondary battery in the same manner as in Example 1, it was 93%.

[Comparative Example 1]
A secondary battery was prepared in the same manner as in Example 1 except that the thermal polymerization initiator was changed to 0.12 g of t-butyl peroxypivalate. The capacity retention rate of the obtained secondary battery was measured in the same manner as in Example 1. As a result, it was 77%.

[Comparative Example 2]
It was prepared in the same manner as in Example 1 except that the thermal polymerization initiator was changed to 0.12 g of lauroyl peroxide. However, the thermal polymerization initiator was not dissolved in the ionic liquid, and the polymer was prepared in a non-uniform state. A secondary battery was created. As a result of measuring the capacity retention rate of the obtained secondary battery in the same manner as in Example 1, it was 25%.

Claims (4)

Polymers synthesized comprise comprised salt monomer and an organic anion having a polymerizable functional group and onium cation having a polymerizable functional group, the lithium ion conductive electrolyte configured to include a lithium salt and ambient temperature molten salt A lithium ion conductive electrolyte sheet obtained by impregnating a porous sheet , wherein the polymer is synthesized using a polymerization initiator represented by the following formula (1): Electrolyte sheet .
X-O-O-Y (1)
(In the formula (1), X and Y are represented by substituted or unsubstituted —R, —CO—R, —CO—OR, —R—O—O—R, or —R—O—R. In which the main chain of the group as X is composed of 5 to 10 atoms, and the main chain of the group as Y is composed of 2 to 10 atoms R is an alkyl group having 1 or more carbon atoms, and each R may be the same or different, and R may be a ring structure, and these may be heteroatoms. (However, R does not include a double bond or a triple bond.) The lithium ion conductive electrolyte sheet according to claim 1, wherein the polymerization initiator has different structures as X and Y in the formula (1). 3. The lithium ion conductive electrolyte sheet according to claim 1, wherein the polymerization initiator is a group having a main chain composed of 8 to 10 atoms as X in the formula (1). 4. A secondary battery comprising the lithium ion conductive electrolyte sheet according to any one of claims 1 to 3 as a constituent element.