JP2002110245A - Polymer solid electrolyte lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery using a polymer solid electrolyte, eliminating leakage of an electrolytic solution with improved current load characteristic, in particular, current load characteristic at a low temperature. SOLUTION: The lithium ion secondary battery comprises (1) an oxcetane ring containing polymer, (2) a cation polymerization initiator, (3) an electrolytic solvent and (4) a lithium electrolyte salt. The oxcetane ring containing polymer (1) allows a solid electrolyte crosslinking composition in a liquid form of a 5 wt.% or less in a total amount to be gelled into the polymer solid electrolyte in use for the lithium ion secondary battery by crosslinking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer solid electrolyte lithium ion secondary battery, and more particularly, to a rechargeable secondary battery having a cylindrical, square, sheet or other shape. The liquid is solidified using a polymer from the conventional liquid, eliminating leakage of the electrolyte and
The present invention relates to a lithium ion secondary battery using a polymer solid electrolyte having improved current load characteristics, particularly current load characteristics at low temperatures, a method for producing the same, and a liquid crosslinkable composition for the solid electrolyte.

[0002]

2. Description of the Related Art A lithium ion secondary battery is a small and lightweight rechargeable battery having a large storage capacity per unit volume or unit weight, and a portable electronic device such as a cellular phone or a notebook personal computer. It is widely used in portable personal computers, personal digital assistants (PDAs), MD decks, video cameras, digital cameras, and the like, and is indispensable for various portable devices that are small and light and have relatively large power consumption. . By the way, most of current lithium ion secondary batteries use a liquid electrolyte in which a lithium electrolyte salt is dissolved in an electrolyte solvent mainly composed of propylene carbonate, ethylene carbonate or the like, that is, an electrolyte, as an electrolyte. It is. However, batteries using such an electrolytic solution may cause liquid leakage or temperature rise (in case of self-heating during use or charging / discharging; misuse: short-circuit; use of a plurality of batteries; When inserted and used; when exposed to high temperatures in the operating environment; or when soldering during device installation, etc.), the internal pressure rises (low boiling point due to the vapor pressure of the solvent in the electrolyte) (The internal pressure rises as much as the internal pressure increases.) There is a safety problem such as leakage, rupture, and danger of ignition, and solidification of the electrolyte, that is, development of a solid electrolyte is being actively conducted.

As the solid electrolyte, a polymer material is generally used, and various materials including a material having a polyoxyethylene chain have been conventionally studied, but these materials have the most basic characteristics. Certain ionic conductivity is significantly inferior to liquid electrolytes, and has not yet reached a practical level. Therefore, recently, the development of polymer gel type solid electrolytes in which the liquid electrolyte is made of a polymer material in a gel state has been activated, and at present, ionic conductivity close to the liquid electrolyte is being obtained. It is being put to practical use.

[0004] In a sheet-shaped thin battery, at present, (1) after forming a positive electrode and a negative electrode, a polyvinylidene fluoride-based material is formed on the electrode surface or a separator or nonwoven fabric inserted between the positive electrode and the negative electrode. A polyacrylonitrile-based polymer is made into a solution, emulsion, or dispersion using a solvent or a dispersion medium, or is heated and melted to be liquefied and applied. In the case of an emulsion or dispersion, the polymer particles are not merely dried, but are dried. (2) a method of forming a gel by swelling by immersing in an electrolytic solution composed of an electrolyte salt and an electrolytic solution solvent to form a gel; (2) an electrolytic solution containing a crosslinkable monomer, oligomer, etc. Apply it to the electrode surface or a separator or non-woven fabric inserted between the positive and negative electrodes, and apply the polymer by heating or radiation such as ultraviolet rays. Various methods are adopted, such as a method of cross-linking and forming a gel and bonding both positive and negative electrodes with a separator or non-woven fabric sandwiched, or a method of cross-linking a polymer by heating after bonding. However, any method requires dedicated equipment corresponding to each process such as coating, drying (including film formation), bonding, and swelling.

[0005] The polymer used in the method (1) must not be dissolved in the electrolytic solution (it is necessary to swell), but, on the other hand, in order to apply the polymer, it must be dissolved in some way (using a solvent or a dispersion medium). It is necessary to be a liquid in a solution, emulsion, dispersion, etc., so it must be a non-crosslinked polymer (a crosslinked polymer cannot be made into a solution, and a film cannot be formed even as an emulsion or dispersion). Currently, the polymers that can be used are limited to polyvinylidene fluoride, polyacrylonitrile, etc., and because they form a gel by natural swelling, the swelling tends to be uneven and insufficient, and the amount of polymer forming the gel is large. Become. Furthermore, it is convenient to swell after winding or laminating the electrode, separator or nonwoven fabric, but in that case, the electrolyte solution is difficult to spread sufficiently, swelling is likely to be incomplete, and it takes a long time to swell. There is a problem that it costs.

[0006] In the method (2), when applying, it is necessary to take a measure such as spontaneous swelling by a method of forming a gel at once by crosslinking using an electrolytic solution containing low molecular monomers and oligomers. No, at first glance it looks ideal,
Since the application is performed in a state that the electrolyte solvent is contained, there is a problem that the electrolyte solvent is easily volatilized at the time of application and crosslinking, and a low-boiling electrolyte solvent cannot be used. Solvents with low boiling point are important for obtaining good ionic conductivity (especially ionic conductivity at low temperature). Good characteristics for conventional batteries such as cylindrical type and square type using liquid electrolyte. To obtain good properties, especially at low temperatures, low boiling electrolyte solvents such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate,
Dimethoxyethane, methyl propionate, ethyl propionate and the like are appropriately used), and the sheet type manufactured by the method (2) cannot use these low-boiling-point electrolyte solvents, which makes it difficult to obtain good characteristics. Having. Therefore, although high-boiling ethylene carbonate and propylene carbonate which can be used must be the center, ethylene carbonate has a high boiling point (36 ° C.) and cannot be used alone, and propylene carbonate (melting point:- 49 ° C.) alone or as a mixture with ethylene carbonate. Further, propylene carbonate cannot use a graphite-based carbon material for the negative electrode (the propylene carbonate is decomposed), and the usable carbon material is limited to an amorphous material such as hard carbon. This graphite-based carbon material has an excellent property that the voltage at the time of discharge is easily maintained at a constant value, but also has a disadvantage that it cannot be used unfortunately in the battery according to the method (2). .

[0007] In addition, although the above-mentioned polymer gel type solid electrolytes are getting ionic conductivity close to liquid electrolytes, they are still inferior to liquid electrolytes and relatively large discharge currents. It cannot be used for applications that require high performance, and can only exhibit insufficient performance as a substitute for batteries using conventional liquid electrolytes (practical for small discharge current applications that can be used even if the internal resistance is slightly high) And the conventional sheet type battery is a typical example).
The biggest factor is that a gel cannot be formed unless a relatively large amount of a component which is harmful to ionic conductivity such as a polymer is contained in order to obtain a solid property called a gel. In order to improve the ionic conductivity of the polymer gel type solid electrolyte, studies have been made on both the polymer content and the polymer structure, such as reducing the amount of the polymer component in the gel and using a high dielectric constant polymer.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve these problems, and found that an oxetane ring-containing polymer was prepared in a solution of an electrolyte solvent and a lithium electrolyte salt (electrolyte solution) by a cationic method. By cross-linking in the presence of a polymerization initiator, even in an extremely small amount of 5% or less (wt%, the same applies hereinafter), the electrolytic solution does not separate (bleed) from the gel, so that a good gel can be formed. Was found. In addition, if a specific lithium electrolyte salt is used, the cationic polymerization initiator can be omitted, and the ionic conductivity can be significantly improved by using a specific combination as an electrolyte solvent, particularly low-molecular carboxylic acid esters. Also found. Based on these findings, the present inventors have used a liquid cross-linkable composition for a solid electrolyte containing the above-mentioned components, and cross-linked this for an existing lithium ion secondary battery similar to a conventional liquid electrolyte. For example, the gelation of the system occurs due to the formation of a polymer solid, which solves the above-mentioned problems at once, and has a polymer gel type having excellent characteristics not inferior to lithium ion secondary batteries using a liquid electrolyte. It has been found that a solid electrolyte lithium ion secondary battery can be obtained, and the present invention has been completed.

A polymer electrolyte utilizing cationic polymerization has already been disclosed in Japanese Patent No. 2925231 (Heisei 1).
Issued on July 28, 2001), “Polymer compounds formed by cationic ring-opening polymerization of epoxies of compounds having epoxy groups are compatible with ionic salts (including lithium electrolyte salts) and ionic salts. A solid polymer electrolyte comprising a compound (including an electrolyte solvent) that can be used. Here, the compound having an epoxy group is defined as “a polymer compound having a network structure by polymerization”. Specifically, the compound having the formula:

Embedded imageAlicyclic epoxy compounds and bisphenol epoxy
Only two of the compounds are illustrated, and
Oxetane ring-containing radical copolymer clearly clarified
Different. In addition, the polymer in the polymer solid electrolyte of
The limmer content is determined, for example, from the formulation of Example 2.
When calculated, it reached about 47% and the ionic conductivity was 5 × 1
0 ^-FourS / cm (25 ° C), not a practical level
No. In contrast, in the present invention, the polymer content is 5% or less.
It is characterized by its ion conductivity (ion conductivity).
As shown in the figure, the value is 10 to 20 times that of the former
It is recognized that.

That is, the present invention relates to the above oxetane ring-containing polymer (1) comprising (1) an oxetane ring-containing polymer, (2) a cationic polymerization initiator, (3) an electrolyte solvent, and (4) a lithium electrolyte salt. The liquid cross-linkable composition having a content of 5% or less in the total amount (hereinafter referred to as a liquid composition) is formed into a polymer solid electrolyte by gelling by cross-linking for a lithium ion secondary battery. An object of the present invention is to provide a polymer solid electrolyte lithium ion secondary battery.

The oxetane ring-containing polymer (1) in the present invention is a polymer having a plurality of oxetane rings in the polymer structure, and does not matter the skeleton structure of the polymer, but can be easily obtained by simple radical polymerization. Can be. That is, a radical polymerizable monomer having an oxetane ring (hereinafter, referred to as an oxetane polymerizable monomer) and, if necessary, a radical polymerizable monomer having an epoxy group (hereinafter, referred to as an epoxy polymerizable monomer), and other radical polymerizable monomers. Is produced by radical polymerization, and the molecular weight is usually set to 10,000 or more. If the molecular weight is less than 10,000, the amount of polymer required to form a gel tends to be large. The upper limit of the molecular weight is not particularly limited, but the upper limit is 1 in maintaining the liquid composition (solution state) of the liquid composition described below.
It is appropriate to suppress it to about 100,000, preferably about 500,000.

In the above radical polymerization, a radical polymerization initiator [for example, N, N'-azobisisobutyronitrile,
Dimethyl N, N'-azobis (2-methylpropionate), benzoyl peroxide, lauroyl peroxide and the like, and if necessary, a molecular weight modifier such as mercaptans. Due to the relatively large molecular weight of the polymer, 60-80
Solution polymerization carried out at a temperature of the order of ° C. is preferred. As the solvent, use of a cyclic carbonate, a chain carbonate, or a low-molecular carboxylic acid ester exemplified by the electrolyte solution solvent (3) described below is preferable.

The oxetane polymerizable monomer is, for example, a compound represented by the formula:

Embedded image (Wherein R ₁ is H or CH ₃ ; and R ₂ is H or alkyl having 1 to 6 carbon atoms), specifically (3-oxetanyl) methyl (meth) acrylate , (3-methyl-3-oxetanyl)
Methyl (meth) acrylate, (3-ethyl-3-oxetanyl) methyl (meth) acrylate, (3-butyl-3-oxetanyl) methyl (meth) acrylate,
(3-hexyl-3-oxetanyl) methyl (meth) acrylate and the like are used, and at least one of these is used. When the above-mentioned epoxy polymerized monomer is not used, the amount is usually 5 to 50%, preferably 1 to 50% of the total amount of the monomer.
Select within the range of 0 to 30%. If it is less than 5%, the amount of the polymer required for gelation will increase, and if it exceeds 50%, the electrolyte will tend to separate (bleed) from the gel. In this specification, “(meth) acryl” means acryl and methacryl, and “(meth) acrylate” means acrylate and methacrylate.

Examples of the epoxy polymerizable monomer used as required include, for example,

Embedded image Wherein R ₅ is H or CH ₃ ; and R ₆ is

Embedded image ), Specifically, 3,4
-Epoxycyclohexylmethyl (meth) acrylate, glycidyl (meth) acrylate, and at least one of these is used. The amount used is usually such that the proportion of the epoxy polymerizable monomer in the total amount with the oxetane polymerizable monomer is 90% or less, and the total amount of both monomers is 5 to 50%, preferably 10 to 10% in the total amount of the monomer.
What is necessary is just to select so that it may be set to 30%.

The other radically polymerizable monomer has the formula:

Embedded image Wherein R ₃ is H or CH ₃ ; and R ₄ is —COOC
_{H 3, -COOC 2 H 5,} -COOC 3 H 7, -COOC 4 H
_{9, -COO (CH 2 CH 2} O) 1 ~ 3 CH 3, -COO (CH 2
_{CH 2 O) 1 ~ 3 C} 2 H 5, -COO (CH 2 CH (CH 3) O) 1
_{~ 3 CH 3, -COO (CH} 2 CH (CH 3) O) 1 ~ 3 C 2 H 5,
—OCOCH ₃ , or —OCOC ₂ H ₅ ) are preferred. In addition, other than these can be used, but if the affinity with the used electrolyte solvent (3) is low, the electrolyte may be separated (bleed) from the gel. The oxetane ring-containing polymer (1) thus produced is used alone, or a part of the oxetane ring-containing polymer (1) contains a radical polymerizable monomer having the epoxy group and another radical polymerizable monomer. Has a molecular weight of 10 obtained by radical copolymerization under the same conditions as described above.
000 or more epoxy group-containing polymers may be used in combination.

The cationic polymerization initiator (2) in the present invention
As various onium salts (for example, ammonium,
Phosphonium, arsonium, stibonium, sulfoni
-BF of cations such as uranium and iodonium_Four, -P
F₆, -SbF₆, -CF_ThreeSO _Three, -CLO_FourSuch as ani
Onium salts) can be used.
Can be used without using the lithium electrolyte salt (4)
Lithium fluorophosphate and / or tetrafluoro
If lithium borate is used, the original lithium electrolyte salt
Acts as the cationic polymerization initiator in addition to the action of
It is convenient. Use of cationic polymerization initiator
Is an extra component for the electrolyte,
This leads to a decrease in conductivity, complicates the manufacturing process,
It is accompanied by a rise in strike. Naturally, one of the cationic polymerization initiators
As part, onium salt is lithium hexafluorophosphate
Or lithium tetrafluoroborate can be used together
It is.

Examples of the electrolyte solvent (3) in the present invention include cyclic carbonates (ethylene carbonate, propylene carbonate, butylene carbonate, etc.); and chain carbonates (dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate,
Cyclic esters (lactones) (γ-butyrolactone, γ-valerolactone, etc.); cyclic ethers (tetrahydrofuran, methyltetrahydrofuran, etc.); low molecular carboxylic acids Esters (ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, butyl butyrate, etc.); chain ethers (dimethoxyethane, methoxyethoxyethane, etc.); cyanoethyl group-containing compounds (Methyl 2-cyanoethyl ether, ethyl 2-
Cyanoethyl ether, bis 2-cyanoethyl ether, methyl 2-cyanoethyl carbonate, propionic acid 2-
Cyanoethyl), and at least one selected from these groups is used. In particular, cyclic carbonates, it is preferable to use a mixture of chain carbonates and low molecular weight carboxylic esters in a solvent having a high dielectric constant of cyclic esters, and furthermore, cyclic carbonates such as ethylene carbonate and carbonic acid Propylene and chain carbonates such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and low molecular weight carboxylic acid esters, and among the low molecular weight carboxylic acid esters, ethyl acetate which is a chain ester having a total number of carbon atoms constituting 4 to 6; It is preferable to use a mixture of propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and methyl butyrate, and among them, propyl acetate and ethyl propionate, which are chain esters having 5 carbon atoms. The use of methyl butyrate is preferred. The mixing ratio of the cyclic carbonates / chain carbonates / low-molecular carboxylic esters = 10 to 50: 0 to 50: 5
It is preferable to set the ratio to 0 to 90 (weight ratio) and to set the low molecular carboxylic acid esters to 50% or more of the whole solvent. In the low-molecular carboxylic acid esters, when the total number of carbons constituting the molecule is less than 4, the boiling point of the solvent is too low, and when the battery is used, a problem that the internal pressure of the battery increases at a high temperature tends to occur. When the total number of carbon atoms is 7 or more, the ionic conductivity tends to decrease and the characteristics of the battery tend to decrease. In these electrolyte solvents (3), the type and mixing ratio greatly affect the ionic conductivity, and as a result, the battery charge such as the internal resistance of the battery, the current load characteristics, and the current load characteristics at low temperatures. It is carefully determined because it has a significant effect on the battery life due to the effects of the discharge characteristics and the electrochemical stability due to the chemical structure of the solvent.

The lithium electrolyte salt according to the present invention (4)
Is preferably composed of an anion (acid group) having excellent solubility in the electrolytic solution solvent (3), high ionic conductivity and high resistance to oxidation to reduction potential, and is not particularly limited. Examples thereof include lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and the like, and at least one of these is used. In particular, lithium tetrafluoroborate and lithium hexafluorophosphate are preferable because good ionic conductivity is obtained and the oxetane ring-containing polymer (1) has an action of crosslinking. The concentration of the lithium electrolyte salt (4) is usually about 1 mol / dm ^3, but is not particularly limited.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer solid electrolyte lithium ion secondary battery according to the present invention comprises the above-mentioned oxetane ring-containing polymer (1) or a combination thereof with an epoxy group-containing polymer, a cationic polymerization initiator (2), An electrolyte solution solvent (3) and a lithium electrolyte salt (4) are used as components, and a low-viscosity liquid composition obtained by mixing and dissolving them is used as a crosslinkable composition for a solid electrolyte,
It can be manufactured according to the following procedure.

First, the proportion of the oxetane ring-containing polymer (1) and, if necessary, the epoxy group-containing polymer (together, referred to as a crosslinkable polymer) in the total amount of the liquid composition is set to 5% or less. That is, the polymer content in the formed solid electrolyte is set to a value as low as possible to stably maintain ionic conductivity. next,
Within the time limit of the pot life of the liquid composition (the time during which the liquid composition can be handled such as injection by maintaining the liquid state),
For a lithium ion secondary battery, the mixture is poured into a sealed container incorporating a unit such as an electrode or a separator, and is allowed to penetrate into a gap between the electrode and the separator. Alternatively, the polymer is easily gelled by heat crosslinking, and the intended polymer solid electrolyte lithium ion secondary battery is obtained by forming the polymer solid electrolyte.

In this way, a polymer solid electrolyte lithium ion secondary battery excellent in characteristics and stability can be obtained in the same process as the conventional battery production without requiring new equipment. In conventional polymer gel-type polymer solid electrolytes, it is important to reduce polymer components that are harmless to ionic conductivity.However, even if the crosslink density is increased unnecessarily, the The electrolyte solution is easily separated due to the decrease, and the structure of the polymer constituting the gel is also very important. However, it can be said that the present invention has solved these problems by using a crosslinkable polymer. Incidentally, the liquid composition used in the present invention, by changing the electrolyte solvent and lithium electrolyte salt, in addition to lithium ion secondary batteries, lithium batteries, lithium secondary batteries,
It can also be used as a polymer gel type polymer solid electrolyte such as an electric double layer capacitor, a chemical capacitor, and an electrochromic device.

[0022]

EXAMPLES Next, Production Examples, Examples and Comparative Examples will be given.
The present invention will be described more specifically. Production Example 1 (Production of oxetane ring-containing polymer) 108 g of methyl methacrylate previously dehydrated with a molecular sieve in a 1000 ml three-necked corben which has been sufficiently dried with dry nitrogen gas, and previously dehydrated with a molecular sieve (3-ethyl-3- 0.225 g of dimethyl N, N'-azobis (2-methylpropionate) was added to a mixed liquid of 36 g of oxetanyl) methyl acrylate, 432 g of heated normal ethylene carbonate which had been previously dehydrated with a molecular sieve and distilled under reduced pressure, and dried. The mixture is stirred at 70 ° C. while introducing nitrogen gas, and is further heated and stirred for 12 hours to perform radical polymerization. Next, the temperature is lowered to 40 to 50 ° C., and 378 g of ethyl propionate, which has been dried in advance with molecular sieve and distilled under reduced pressure, is stirred and dissolved until the whole becomes uniform to obtain a 15% solution of the oxetane ring-containing polymer. This polymer solution was a colorless and transparent viscous liquid, and as a result of infrared absorption spectrum measurement, the wave number was 980 / c.
It was confirmed that m had a distinctive oxetane ring characteristic absorption.

Example 1 (Preparation of Liquid Composition A) In a glove box filled with dry nitrogen gas, 10 g of the solution of the oxetane ring-containing polymer obtained in Production Example 1 and lithium hexafluorophosphate were adjusted to 1 molar concentration. Dissolved ethylene carbonate / diethyl carbonate / dimethyl carbonate (10/10
The liquid composition A is prepared by mixing and dissolving 40 g of a mixed solvent solution (/ 40, weight ratio). The polymer concentration in the liquid composition A is 3.0%. This liquid composition A is heated to 70 ° C.
And crosslinked by heating to evaluate the gelling property, gel state and ionic conductivity (10 ⁻³ S / cm). The gelation property and the gel state are visually observed; the ionic conductivity is measured by injecting the liquid composition into a closed cell in which a gold-plated electrode is incorporated, heating at 70 ° C. for 5 hours in a closed state, and then cooling it. Body and
The measurement was performed using an LCZ meter at a frequency of 1 KHz and a measurement temperature of 20 ° C. or −20 ° C. The results are shown in Table 1 below.

Example 2 (Preparation of Liquid Composition B) In the same manner as in Example 1, 10 g of the solution of the oxetane ring-containing polymer obtained in Production Example 1 and 1.3 mol of lithium hexafluorophosphate were dissolved. 40 g of a mixed solvent solution of ethylene carbonate / dimethyl carbonate / ethyl propionate (15/15/70, weight ratio) is mixed and dissolved to prepare a liquid composition B (polymer concentration: 3.0%). In the same manner as in Example 1, the gelling property, gel state, and ionic conductivity of this liquid composition B were evaluated, and the results are shown in Table 1 below.

[Table 1] In Table 1, ○ indicates gelation.

Comparative Example 1 Formula:

Embedded image Low molecular weight alicyclic epoxy compounds (Daicel Industries, Ltd.)
2.5 g of “Celloxide 2021P”, ethylene carbonate / dimethyl carbonate / ethyl propionate (15 moles) prepared by dissolving lithium hexafluorophosphate in a 1.0 molar concentration.
(15/70, weight ratio) in 47.5 g of a mixed solvent solution to prepare a liquid composition C (low-molecular alicyclic epoxy compound concentration: 5%). In the same manner as in Example 1, this liquid composition C was polymerized by heating at 70 ° C., and the gelling property, the gel state, and the ionic conductivity were evaluated. The results are shown in Table 2 below.

Comparative Examples 2 and 3 In Comparative Example 1, the concentration of the low molecular weight alicyclic epoxy compound was 6% (Comparative Example 2) or 8% (Comparative Example 3).
Except that the liquid compositions D and E are prepared in the same manner,
Table 2 below shows the evaluation results of the gelling property, the gel state, and the ionic conductivity.

Comparative Example 4 Formula:

Embedded image Low molecular weight oxetane ring-containing compound (Ube Industries, Ltd.,
3 g of “XDO”) was dissolved in 47 g of a mixed solvent solution of ethylene carbonate / dimethyl carbonate / ethyl propionate (15/15/70, by weight) in which lithium hexafluorophosphate was dissolved at a 1.0 molar concentration, A liquid composition F (low-molecular-weight oxetane ring-containing compound concentration: 6%) is prepared. In the same manner as in Example 1, this liquid composition F was polymerized by heating at 70 ° C., and the gelling property, the gel state, and the ionic conductivity were evaluated.
The results are shown in Table 2 below.

Comparative Examples 5 and 6 The liquid compositions were prepared in the same manner as in Comparative Example 4, except that the concentration of the low-molecular weight oxetane ring-containing compound was changed to 8% (Comparative Example 5) or 10% (Comparative Example 6). G and H were prepared, and the evaluation results of gelling property, gel state and ionic conductivity are shown in Table 2 below.

[0029]

[Table 2] In Table 2, × indicates a liquid state without gelation ○ indicates gelation From the results in Table 2, the low molecular alicyclic epoxy compound or the low molecular oxetane ring-containing compound [monomer] is simply polymerized and gelled. When the polymer content was about 5% (assuming that the monomer was converted to 100% polymer, and the monomer content was used as the polymer content), gelation did not occur (Comparative Examples 1 and 4), and 6% Although gelation occurs above this level, liquid components bleed and good gel formation was not possible.
It is recognized that good results are not obtained for the ionic conductivity.

Example 3 (Preparation of Lithium-Ion Secondary Battery A) An aluminum-laminated film bag-like container incorporating a unit made of a nonwoven fabric and electrodes for a lithium-ion battery prepared in advance was used. Liquid composition A
1.85 g was injected, vacuum impregnated and sealed,
Heating at 19 ° C. for 19 hours causes gelation by cross-linking, thereby producing a thin polymer solid electrolyte lithium ion secondary battery A. The unit of the thin lithium ion secondary battery used above has a structure in which a positive electrode and a negative electrode are wound via a nonwoven fabric, and the positive electrode has an aluminum foil coated on both surfaces with an active material mainly composed of lithium cobaltate. The size is 50 × 80 mm, the negative electrode is a copper foil coated with a carbon-based material, the size is 52 × 110 mm, and the non-woven fabric is a 20 μm thick polyester fine fiber product. It is incorporated in a bag-shaped aluminum laminate film (inner surface: polyethylene, outer surface: polypropylene) whose periphery is heat-sealed. The battery capacity is 180
Six identical batteries (No. 1 to 6) of the mAH type were prepared.

Example 4 (Preparation of Lithium Ion Secondary Battery B) In the same manner as in Example 3, using the liquid composition B of Example 2,
Thin polymer solid electrolyte lithium ion secondary battery B
(6) Thin polymer solid electrolyte lithium ion secondary batteries A and B prepared in Examples 3 and 4
Tables 3 and 4 show the results of the charge / discharge repetition test, load characteristics at normal temperature, and load characteristics at low temperature, respectively. The conditions of the charge / discharge repetition test were as follows.
The charge / discharge cycle is repeated at C (180 mA), and the capacity at the initial one cycle, the capacity after ten cycles, and the retention are shown. The load characteristics at room temperature are as follows.
mA), discharge is 0.2C, 1C, 2C (360mA),
The retention rates for the respective discharge capacities and 0.2 C discharge capacities are shown. The load characteristics at a low temperature are obtained by measuring the capacity retention at 0.5 C (90 mA) discharge capacity at -20 ° C for both charge and discharge and 0.5 C (90 mA) discharge capacity at normal temperature. All charging was performed until a constant current of 4.2 V was reached, and all discharging was performed at a constant current of 2.2 V.
It is assumed that the voltage reaches 75V.

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

From the results shown in Tables 3 and 4, the polymer solid electrolyte lithium ion secondary battery according to the present invention is excellent in load characteristics, particularly in large current (expressed by 2C characteristics) load characteristics and low temperature load characteristics. This shows that the practical significance of the lithium ion secondary battery using the polymer solid electrolyte is very large.

Continued on the front page (72) Inventor Yuji Yamamichi 5-88 Fukushima, Yao-cho, Neguro-gun, Toyama Prefecture Inside Maxell Hokuriku Seiki Co., Ltd. (72) Izumi Morii 5-88 Fukushima, Yao-cho, Meguri-gun, Toyama Ma Inside Xell Hokuriku Seiki Co., Ltd. (72) Inventor Toshiharu Takahata 5-88, Fukushima, Yao-cho, Negashi-gun, Toyama Prefecture Inside Maxell Hokuriku Seiki Co., Ltd. (72) Inventor Shun Nishikawa 7-1 Akitacho, Takatsuki-shi, Osaka Sunstar Giken Co., Ltd. (72) Inventor Shinji Bessho 7-1, Akitacho, Takatsuki-shi, Osaka Sunstar Giken Co., Ltd. (72) Inventor Katsumi Tanino 150, Futamicho, Takaoka-shi, Toyama Pref. Toyama Prefectural Industrial Technology Center (72) Inventor Toshifuji Fujishiro 150, Fukamicho, Takaoka City, Toyama Prefecture Inside the Toyama Prefectural Industrial Technology Center (72) Inventor Masahiro Kadozaki 150, Futamicho, Takaoka City, Toyama Pref. F-Turner in Toyama Prefectural Industrial Technology Center (Reference) 4J002 BG071 DD007 EB006 EN136 EV257 EV296 EW047 EW176 EY017 EY026 FD146 GQ02 5H029 AJ02 AK03 AL06 AM00 AM03 AM04 AM07 AM16 BJ04 DJ09 EJ12

Claims (23)

[Claims] 1. An oxetane ring-containing polymer comprising: (1) an oxetane ring-containing polymer; (2) a cationic polymerization initiator; (3) an electrolyte solvent; and (4) a lithium electrolyte salt, wherein the oxetane ring-containing polymer (1) is contained in an amount of 5% or less. A polymer solid electrolyte lithium ion secondary battery, characterized in that a liquid crosslinkable composition for a solid electrolyte of not more than weight% is gelled by crosslinking for a lithium ion secondary battery to form a polymer solid electrolyte. 2. The polymer according to claim 1, wherein the oxetane ring-containing polymer (1) is a polymer having a molecular weight of 10,000 or more obtained by radical copolymerization of a radical polymerizable monomer having an oxetane ring with another radical polymerizable monomer. Polymer solid electrolyte lithium ion secondary battery. 3. The polymer solid electrolyte lithium ion secondary battery according to claim 2, wherein the amount of the radical polymerizable monomer having an oxetane ring is 5 to 50% by weight based on the total amount of the monomer. 4. The oxetane ring-containing polymer (1) has a molecular weight of 1 obtained by radical copolymerization of a radical polymerizable monomer having an oxetane ring, a radical polymerizable monomer having an epoxy group, and another radical polymerizable monomer.
The polymer solid electrolyte lithium ion secondary battery according to claim 1, wherein the polymer is a polymer having a molecular weight of 0000 or more. 5. The proportion of the radical polymerizable monomer having an epoxy group in the total amount of the radical polymerizable monomer having an oxetane ring is 90% by weight or less, and the total amount of both monomers is 5 to 50% by weight in the total amount of the monomer. %.
3. The polymer solid electrolyte lithium ion secondary battery according to 1. 6. An epoxy group-containing polymer having a molecular weight of 10,000 or more obtained by radical copolymerization of a radical polymerizable monomer having an epoxy group and another radical polymerizable monomer, as a part of the oxetane ring-containing polymer (1). The polymer solid electrolyte lithium ion secondary battery according to claim 1. 7. The radical polymerizable monomer having an oxetane ring has the formula: (In the formula, R ₁ is H or CH _3; and R ₂ is H or alkyl of 1 to 6 carbon atoms) polymer according to any one of claims 2 to 5 which is (meth) acrylic monomer Solid electrolyte lithium ion secondary battery. 8. The other radically polymerizable monomer has the formula: Wherein R ₃ is H or CH ₃ ; and R ₄ is —COOC
_{H 3, -COOC 2 H 5,} -COOC 3 H 7, -COOC 4 H
_{9, -COO (CH 2 CH 2} O) 1 ~ 3 CH 3, -COO (CH 2
_{CH 2 O) 1 ~ 3 C} 2 H 5, -COO (CH 2 CH (CH 3) O) 1
_{~ 3 CH 3, -COO (CH} 2 CH (CH 3) O) 1 ~ 3 C 2 H 5,
-OCOCH ₃ or -OCOC ₂ H is ₅₎ vinyl or (meth) polymer solid electrolyte lithium ion secondary battery according to any one of claims 2 to 7 is an acrylic monomer. 9. The radical polymerizable monomer having an epoxy group has the formula: Wherein R ₅ is H or CH ₃ ; and R ₆ is 9) is a (meth) acrylate.
The polymer solid electrolyte lithium ion secondary battery according to any one of the above. 10. The polymer solid electrolyte lithium ion secondary battery according to claim 1, wherein the cationic polymerization initiator (2) is an onium salt. 11. An electrolytic solution solvent (3) comprising a cyclic carbonate, a chain carbonate, a cyclic carboxylate, a cyclic ether, a low molecular chain carboxylic ester, a low molecular chain ether, The polymer solid electrolyte lithium ion secondary battery according to any one of claims 1 to 10, wherein the lithium ion secondary battery is at least one selected from the group consisting of cyanoethyl group-containing compounds. 12. The polymer solid electrolyte lithium according to claim 1, wherein the electrolyte solvent (3) is at least one selected from the group consisting of cyclic carbonates and chain carbonates. Ion secondary battery. 13. A low molecular chain carboxylic ester is added to at least one selected from the group consisting of cyclic carbonates, chain carbonates and cyclic carboxylate esters as the electrolyte solvent (3). Claims 1 to 1
0. The polymer solid electrolyte lithium ion secondary battery according to any one of 0 to 0. 14. The lithium electrolyte salt (4) is at least one selected from the group consisting of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate and lithium trifluoromethanesulfonate. The polymer solid electrolyte lithium ion secondary battery according to any one of the above. 15. The method according to claim 1, wherein lithium hexafluorophosphate and / or lithium tetrafluoroborate used as the lithium electrolyte salt (4) is used as part or all of the cationic polymerization initiator (2). The polymer solid electrolyte lithium ion secondary battery according to any one of the preceding claims. 16. A liquid crosslinkable composition for a solid electrolyte comprising: an oxetane ring-containing polymer (1), an electrolyte solvent (3), and lithium hexafluorophosphate and / or tetrafluoroborane as a lithium electrolyte salt (4). 16. The polymer solid electrolyte lithium ion secondary battery according to claim 15, comprising lithium oxide. 17. An oxetane ring-containing polymer comprising: (1) an oxetane ring-containing polymer; (2) a cationic polymerization initiator; (3) an electrolyte solvent; and (4) a lithium electrolyte salt. A liquid cross-linkable composition for a solid electrolyte, characterized in that the content is not more than% by weight. 18. An oxetane ring-containing polymer, an electrolytic solution solvent, and lithium hexafluorophosphate and / or lithium tetrafluoroborate as a lithium electrolyte salt, wherein the oxetane ring-containing polymer accounts for 5% by weight or less of the total amount. A liquid crosslinkable composition for a solid electrolyte, comprising: 19. An oxetane ring-containing polymer comprising (1) an oxetane ring-containing polymer, (2) a cationic polymerization initiator, (3) an electrolyte solution solvent, and (4) a lithium electrolyte salt, wherein the oxetane ring-containing polymer (1) is contained in an amount of 5% or less. % By weight of a liquid crosslinkable composition for a solid electrolyte is injected into a sealable container or case for lithium ion secondary batteries incorporating units such as electrodes and separators, and gelled by crosslinking. A method for producing a polymer solid electrolyte lithium ion secondary battery, which is converted into a solid electrolyte. 20. An oxetane ring-containing polymer (1)
20. The production method according to claim 19, wherein the polymer is a polymer having a molecular weight of 10,000 or more obtained by radical copolymerization of a radical polymerizable monomer having an oxetane ring with another radical polymerizable monomer. 21. The method according to claim 20, wherein the amount of the radically polymerizable monomer having an oxetane ring is 5 to 50% by weight based on the total amount of the monomer. 22. An oxetane ring-containing polymer (1)
20. The production method according to claim 19, wherein the polymer is a polymer having a molecular weight of 10,000 or more obtained by radical copolymerization of a radical polymerizable monomer having an oxetane ring, a radical polymerizable monomer having an epoxy group, and another radical polymerizable monomer. 23. An epoxy group-containing polymer having a molecular weight of 10,000 or more obtained by radical copolymerization of a radical polymerizable monomer having an epoxy group with another radical polymerizable monomer, as a part of the oxetane ring-containing polymer (1). The method according to any one of claims 19 to 22, which is used in combination.