JP3418437B2 - Oligo (β-propiolactone) macromer, electrolyte and battery using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates is related aprotic electrochemical cell using aprotic electrolytes and this has been prepared as a main component a high-dielectric-macromers over with novel polymerizable vinyl group.

[0002]

2. Description of the Related Art Conventionally, electrolytes for electrochemical batteries such as primary batteries, secondary batteries, and electrochromic display devices have been used as a protic liquid such as dilute sulfuric acid, ammonium chloride water, KOH water, and propylene carbonate and dimethoxy. Aprotic liquids such as ethane have been used.

However, since the liquid electrolyte is liable to leak to the outside of the component and the electrode material is likely to be eluted, there is a problem of long-term reliability. Furthermore, in the case of a proton-based electrolyte, the unit cell voltage is up to 2 V, and it is 3 to 4 like a non-proton-based electrolyte.
There are problems such as the inability to output a high voltage of V and the generation of hydrogen gas, which may cause a rupture due to an increase in internal pressure when a closed structure is used.

On the other hand, since the aprotic solid electrolyte does not have the above-mentioned problems and a battery having a high energy density can be manufactured, the structure of the device can be simplified, and further, the weight can be reduced by thinning the film. It has advantages such as miniaturization. These characteristics meet the demands for various electronic parts with smaller size and lighter weight, more flexibility in shape, and higher reliability with the progress of electronics.
As a solid electrolyte material, Tetsuichi Kudo, Kazuo Fueki, "Solid State Ionics" (Kodansha Scientific, 1986)
Inorganic substances such as those described in, for example, stabilized zirconia, silver iodide, silver rubidium iodide, β-alumina and the like are well known. Some of these inorganic solid electrolytes have an ionic conductivity similar to that of liquid electrolytes, but they have the fatal drawback of low decomposition voltage and must be molded and formed into an arbitrary shape. Is often difficult, and the properties as a material are extremely insufficient.

On the other hand, organic polymers are lighter in weight, more viscoelastic and flexible than inorganic substances, and have excellent moldability and processability. Naoya, "Conductive polymer" 95-150
Polyesters such as poly (ethylene oxide) and poly (propylene oxide), polyesters such as poly (ethylene succinate) and poly (β-propiolactone), as described on page (Kodansha Scientific, 1990). Matrix polymers such as polyimines such as poly (ethyleneimine) and poly (N-methylethyleneimine) have been reported. Further, these matrix polymers and solid electrolyte compositions comprising a combination of lithium, an inorganic ion salt such as sodium, and those compositions are used, for example, JP-A Nos. 1-169873 and 2-2950.
Batteries such as those described in No. 70 and No. 3-129603 have been reported. However, these polymer solid electrolytes have only obtained ion conductivity considerably lower than that of conventionally used organic liquid electrolytes using, for example, a mixed liquid of propylene carbonate and dimethoxyethane.

On the other hand, as an attempt to obtain a polymer solid electrolyte having a high ionic conductivity, a polymer solid electrolyte using poly (phosphazene) having a low molecular weight poly (ethylene oxide) introduced into its side chain is disclosed in Japanese Patent Laid-Open No. 61- Poly (phosphazene) in which an organic group containing an amide bond is introduced into the side chain of 254626
Japanese Patent Laid-Open No. 186766/1988 discloses a solid polymer electrolyte using poly (phosphazene) having a branched low molecular weight poly (alkylene oxide) introduced into its side chain. No. 252762. However, although these polymer solid electrolytes have good film-forming properties, they have not yet reached a level comparable to the ionic conductivity of the above-mentioned organic liquid electrolytes.

From the viewpoint of polymer design for improving ionic conductivity, factors that can be improved are the permittivity ε and the glass transition point Tg, and in order to improve ionic conductivity, ε must be made large and Tg must be made low. I won't. However, large ε and low T
g has a contradictory relationship, and so far, polymer synthesis has been carried out focusing only on low Tg.

The inventors of the present invention have developed this argument and, as a result of earnest research to make conflicting properties compatible with each other, as a result, it is thought that ε increase can be improved by introducing a dissociation promoting group and low Tg can be improved by introducing a flexible segment. It arrived. Specifically, it has been found that by introducing an oligomer having a large ε in the form of a side chain into the main chain having good moldability, a polymer having a low Tg can be obtained while maintaining the state where the ε is large.

[0009]

The object of the present invention is novel .
Oligo a (beta-propiolactone) group is to provide a polymer solid electrolyte containing a polymer having in the side chain. Another object of the present invention is to provide an electrochemical cell using the above polymer solid electrolyte.

[0010]

Means for Solving the Problems The present invention has the general formula (1) oligo represented by (beta-propiolactone) macromers over the <br/> polymerized to a polymer solid electrolyte containing a polymer obtained,
It also relates to an electrochemical cell using this polymer solid electrolyte.

[0011]

[Chemical 2]

However, in the formula, X represents Li, Na, K, a methyl group, an ethyl group, or an allyl group, and n is the average number of repeating β-propiolactone units in the range of 1≤n≤25. is there. R represents H or a methyl group.

Oligo (β-propiolactone) of the present invention
The macromer can be synthesized, for example, by the Michaelae addition reaction of acrylic acid in the light-shielded state. For the synthesis, for example, triphenylphosphine or an alkali metal salt of acrylic acid is used as an initiator, a radical polymerization inhibitor is added, and
It can be carried out by reacting at 120 ° C. for 5 to 200 hours. For the esterification of the terminal, for example, the corresponding sulfate can be converted into an alkali metal salt by an alcoholate by a conventional method. The obtained oligo (β-propiolactone) macromers varied from a white solid to a liquid depending on the number of repetitions of the addition reaction and the difference in the terminal X.

The solid electrolyte is prepared, for example, by adding ionic dissociative supporting salt and about 0.5 to 2 mol% of benzoin to a predetermined amount of macromer and dehydrating and distilling dimethylformamide (D).
After being dissolved in MF), the mixture is cast on a Teflon dish, the DMF is removed under reduced pressure, and a 100 W high-pressure mercury lamp is irradiated from a distance of about 30 cm for 30 minutes for polymerization. Since the polymer is a colorless and transparent tough film and has no organic soluble portion due to solvent extraction, it is considered that all macromers participated in the polymerization.

This solid electrolyte membrane was sandwiched between stainless steel electrodes, and AC conductivity was measured by a complex impedance method at a predetermined temperature. In addition, from the preparation of the solid electrolyte, all the operations were performed in a dry inert atmosphere. Conductivity is 25 ℃
It ^exceeded 10 ^-4 S / cm and was good.

A feature of the present invention is that by arranging an oligo (β-propiolactone) side chain having a high ionic affinity and ε, the dissociation of the electrolyte salt is promoted and the number of mobile ions is increased. The purpose is to obtain a polymer solid electrolyte having excellent properties.

Among the organic solid electrolytes of the present invention, a solid electrolyte composed of an oligo (β-propiolactone) macromer having an allyl group, or a mixture thereof, and an electrolyte salt is used to form a mechanical electrolyte membrane by cross-linking. It is possible to increase the strength. The cross-linking can be carried out by a usual method, that is, a method by heating, a method by irradiating with ultraviolet rays or the like. Furthermore, it is also possible to add a solvent and produce a solid electrolyte membrane. Examples of the solvent include dimethoxyethane, ethoxymethoxyethane, diethoxyethane, dimethoxypropane, alkoxy polyalkylene ether,
Dioxane, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, linear or cyclic ethers such as methoxytetrahydrofuran, ethyl acetate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, diethyl carbonate, ethylene carbonate,
Linear or cyclic esters such as propylene carbonate and butylene carbonate, nitriles such as acetonitrile and methoxypropionitrile, cyclic amides such as methylpyrrolidone and cyclohexylpyrrolidone, sulfolanes, or phosphoric acid esters, or a mixture thereof. Can be used.

Oligo (β-propiolactone) of the present invention
The ionic dissociative supporting salt used in the electrolyte prepared from the macromer is not particularly limited, but the cation contains at least one of Li ⁺ , Na ⁺ , K ⁺ , Cs ⁺ , and Ag ⁺ , and the anion is BF. _{^{4 -, AlCl 4 -, PF}} 6 -, AsF 6 -, ClO
One or more electrolyte salts selected from the group of ₄ ⁻ , CF ₃ SO ₃ ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , for example LiBF ₄ , Li.
AlCl ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , CF ₃ SO
₃ Li, LiF, LiCl, LiBr, LiI, LiSCN, Na
Br, NaI, NaSCN, KI, KSCN, AgNO _{3 and the} like can be preferably used. Above all, LiClO ₄ ,
CF ₃ SO ₃ Li, LiBF _{4 and the} like are particularly preferable.

Examples of electrochemical cells using the present electrolyte include non-aqueous primary cells, secondary cells, and electrochromic display elements. Taking the Li secondary battery as an example, the positive electrode active material includes transition metals, chalcogens, metal oxides and a small amount of alkali metal ions doped with alkali metals and ionization potentials which are significantly different from each other. Is preferred. Transition metals include Ni and S
n, Co, Fe and the like can be mentioned, but Sn is most preferable. The chalcogens include CuS, FeS ₂ , FeSe ₂ , Ti.
Such as _{S 2, TiSe 2, VS 2} , VSe 2, MoS 2, MoSe 2 is preferred. Further, as the metal oxide, MnO ₂ , Co
O ₂ , V ₂ O ₅ , MoO ₃ , WO _{3 and the} like are suitable. on the other hand,
Examples of the negative electrode active material include alkali metals such as lithium, sodium, and potassium, as well as Al, Pb, Sn alloys, graphite, and polyacetylene-containing alkali metal doping materials. The solid electrolyte battery of the present invention can be constructed by forming the positive electrode and the negative electrode of these materials into, for example, a thin plate shape, and bonding the both with the above-described polymer solid electrolyte.

[0020]

The present invention will be described in detail below with reference to examples, but the invention is not limited to the examples.

Example 1 [Synthesis of oligo (β-propiolactone) macromer sodium salt] 2 mmol of p was added to 40 mmol of acrylic acid.
-Hydroquinone and 1 mmol triphenylphosphine were added, and after reacting at 100 ° C for 150 hours in the dark, diluted with chloroform, poured into a large amount of ether for reprecipitation purification, and a white solid substance was obtained. Obtained. This polymer was dissolved in ether, a methanol solution of sodium methoxide was added under cooling with dry ice, and the formed precipitate was collected to obtain the corresponding sodium salt almost quantitatively.

The results of various analyzes are as follows. In the IR spectrum, the CH expansion and contraction of methylene at 2960 cm ^-1 is 1730.
The absorption of the carbonyl group of the oligoester was observed at cm ⁻¹ , and in ¹ H-NMR, α-methylene triplet was detected at 2.7 ppm, β-methylene triplet was detected at 4.4 ppm, and
Absorption of 3 acrylic protons was observed in the multiplet at 5.8 to 6.5 ppm. Further, from the attribution of ¹³ C-NMR spectrum in FIG. 1, it was confirmed that the substance was a substance having a structure of X = Na and R = H in the general formula (1). The polymerization degree n of this compound was about 20 in terms of polystyrene by GPC, and the molecular weight dispersion Mw / Mn was 1.08. Similarly, the macromer was synthesized by changing the ratio of acrylic acid and triphenylphosphine, and the polymerization degree of the product was measured. The results are shown in Table 1.

[0023]

[Table 1]

Example 2 [Synthesis of oligo (β-propiolactone) macromer methyl ester] Using sodium acrylate as an initiator
The reaction mixture synthesized in the same manner as in Example 1 was dissolved in N-methylpyrrolidone, and equimolar dimethyl sulfate and 1.
A 5-fold molar amount of potassium carbonate was added, and the reaction was stirred at room temperature for 72 hours. After the reaction, the mixture was poured into ice water and extracted with ether to obtain a macromer ester. The results are shown in Table 2.

[0025]

[Table 2]

Example 3 To the macromer obtained in Example 1 No. 8 was added 2 mol% benzoin and 5 wt% LiClO ₄ , and THF / CHCl was added.
_A material uniformly dissolved in an equal amount mixture of ₃ was cast on a Teflon dish, dried under reduced pressure at 60 ° C. for 2 days, and then irradiated with a 100 W high pressure mercury lamp from a distance of 30 cm for 10 minutes to polymerize the mixture. The electrolyte membrane was sandwiched between stainless electrodes, and the AC conductivity was measured by the complex impedance method at a predetermined temperature. The sample preparation etc. after the drying under reduced pressure were performed in a dry inert gas.
AC conductivity value by complex impedance method is 1 × 10 ^-5
It showed S / cm (30 ° C).

Example 4 To the macromer obtained in Example 2 No. 8 was added 2 mol% benzoin and 5 wt% LiClO ₄ , and THF / CHCl was added.
_A material uniformly dissolved in an equal amount mixture of ₃ was cast on a Teflon dish, dried under reduced pressure at 60 ° C. for 2 days, and then irradiated with a 100 W high pressure mercury lamp from a distance of 30 cm for 10 minutes to polymerize the mixture. The electrolyte membrane was sandwiched between stainless electrodes, and the AC conductivity was measured by the complex impedance method at a predetermined temperature. The sample preparation etc. after the drying under reduced pressure were performed in a dry inert gas.
AC conductivity value by complex impedance method is 3 × 10 ^-4
It showed S / cm (30 ° C).

Example 5 The macromer obtained in No. 8 of Example 1 was dissolved in acetone, 0.8 mol of dimethylsulfate, 0.2 mol of diallyl sulfate and 1.5 times mol of potassium carbonate were added under ice-cooling, and the mixture was cooled to room temperature. At 72
The reaction was stirred for an hour. After the reaction, the mixture was poured into ice water and extracted with ether to obtain a macromer ester. 40 parts of this macromer ester to 60 parts of propylene carbonate,
Irganox 184 (1 part) and lithium perchlorate 1
0 part was added and ultrasonic treatment was performed at 40 ° C. or lower to obtain an electrolyte. Insert this electrolyte between transparent ITO electrodes and
By irradiating light of a high-pressure mercury lamp of 0 W, the cross-linking reaction of the polymerized groups was performed to form an electrolyte membrane having a cross-linked structure. AC conductivity value by complex impedance method is 3.0 × 10 ^-3 S / c
It showed m (30 ° C.) and had an ionic conductivity an order of magnitude higher than that of an electrolyte containing no propylene carbonate.

Example 6 In order to know the upper limit of the oxidation potential of the electrolyte obtained in Example 4, cyclic voltammetry on the oxidation side was carried out using a platinum electrode, and it was found to be 1.9 V with respect to the saturated sweet potato electrode. A peak of oxidation current was observed. A similar test was conducted using an electrolyte prepared by adding 10 wt% of LiClO ₄ to polyethylene glycol having an average molecular weight of about 700.
A peak of oxidation current was observed at 7V. From this,
It can be seen that this electrolyte is superior in oxidation resistance to the polyether-based electrolyte. For this reason, there is no concern that the electrolyte will be oxidized even with respect to the metal oxide positive electrode active material that generates a high voltage, and it can be suitably used for a 4V class lithium secondary battery.

Example 7 As a specific example of the battery according to the present invention, a sheet type thin film battery as shown in FIG. 2 was produced. The external dimensions are adapted to a business card size of 5.5 cm x 9 cm, and the thickness is about 0.1 mm. First, 2% of amorphous V ₂ O ₅ obtained by the ultra-quenching method was used.
As an aqueous solution, 6.66 g is evenly applied to 36 cm ² of the central portion of a stainless steel plate having a size of 5.5 cm × 9 cm and a thickness of 20 μm. This one 8
After drying at 0-100 ℃ for about 1 hour to form a film, 200 ℃
The positive electrode member is heat-treated for 2 hours. On this member, oligo (β-propiolactone) was prepared in the same manner as in Example 4.
A polymer solid electrolyte film based on macromer methyl ester is formed.

On the other hand, in an argon atmosphere, 5.5 cm × 9 cm, thickness 20 with a polyolefin sealing material attached on the periphery.
A 30 μm-thick lithium foil is pressure-bonded to the central portion 36 cm ² of a μm-thick stainless steel plate to separately prepare a negative electrode member. The bipolar member was thermocompression bonded under vacuum to produce a sheet battery. The open circuit electromotive voltage of this battery is 4.10V, 1.0mA at 30 ℃.
The result of the constant current discharge was as shown in FIG. 3, and the discharge capacity density until the voltage dropped to 2 V was 170 Ah / kg with respect to the positive electrode active material. Further, FIG. 4 shows the situation of the second cycle when the charging / discharging repeated test of this battery was performed. Curve portions a and a'represent a rest period after charging, b a discharging state, c a rest period after discharging, and d a charging state. The charge / discharge efficiency of the battery was 99% or more, and it was confirmed that the battery system including the electrolyte was a secondary battery having good charge / discharge characteristics.

Comparative Example 1 [Linear poly (β-propiolactone) electrolyte] Method of Watanabe et al. [Macromolecules, Vol. 17, 2908-2912 (19)
84)], using a diethylzinc / water-based catalyst, 20 g of β-propiolactone was subjected to ring-opening polymerization at -25 ° C for 72 hours, followed by reprecipitation purification with chloroform / ethanol to give a direct molecular weight average molecular weight of about 20,000. Chain poly (β-propiolactone)
Got To this polymer was added 10 wt% LiClO ₄ ,
The electrolyte was prepared by uniformly dissolving it at 00 ° C, sandwiched between stainless electrodes, and the AC conductivity was measured by the complex impedance method at 30 ° C as in Example 4. Its value is 3.0 x 1
It was 0 ⁻⁶ S / cm, which was 1/100 of that of Example 4.

[0033]

INDUSTRIAL APPLICABILITY The acrylic polymer having a novel oligo (β-propiolactone) group of the present invention has a dramatically improved ionic conductivity as compared with the conventional one by dissolving a salt, and can be put to practical use. It is a polymer solid electrolyte having oxidation resistance capable of passing an electric current. Therefore, the acrylic polymer having an oligo (β-propiolactone) group and a mixture thereof according to the present invention can be used as a solid polymer electrolyte for all solid-state primary and secondary batteries, solid-state display devices, sensors and electrochemical devices such as capacitors. Electricity, etc.
It can be applied to a wide range of fields such as electronic industry, chemical industry and medical field.

[Brief description of drawings]

FIG. 1 ¹³ C-NM of oligo (β-propiolactone) macromer sodium salt obtained in No. 1 of Example 1.
It is an R spectrum.

FIG. 2 is a schematic cross-sectional view of a sheet type thin film battery which is a specific example of the battery of the present invention.

FIG. 3 is the sheet battery obtained in Example 7 of the present invention at 30 ° C.
It is a figure which shows the result of the constant current discharge in 1 mA in FIG.

FIG. 4 is the sheet battery obtained in Example 7 of the present invention at 30 ° C.
It is a figure which shows the result of having performed the constant current charge / discharge test in 1 mA in FIG.

[Explanation of symbols]

1 V ₂ O ₅ membrane 2 metallic lithium 3 organic polymer solid electrolyte membrane 4 stainless steel foil 5 sealant

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Tada 463 Kagasuno, Kawauchi Town, Tokushima City, Tokushima Prefecture, Tokushima Laboratory, Otsuka Chemical Co., Ltd. (56) Reference JP-A-3-178949 (JP, A) JP-A-2 -232287 (JP, A) JP-A-6-56933 (JP, A) JP-A-61-112161 (JP, A) JP-A-58-47066 (JP, A) JP-A-2-295070 (JP, A) ) JP-A-6-329589 (JP, A) JP-A-63-91659 (JP, A) JP-B-47-47010 (JP, B1) Bulletin of the Chemical Society of Japan, 1972, Vol. 45, No. 12,3604-7 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 6/00 C07C 69/00 H01M 10/00 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. An oligo (β-
Propiolactone) one or a mixture of two or more of the macromer of the polymer, or one of this substance or 2
An aprotic electrolyte containing a polymer of a mixture of at least one species as a main component and an ion-dissociative supporting salt coexisting therein. [Chemical 1] However, X in the formula is Li, Na, K, a methyl group, an ethyl group,
Or an allyl group, n is a β-propiolactone unit
The average number of repetitions is in the range of 1 ≦ n ≦ 25. Also, R is
H or a methyl group is shown. 2. An aprotic electrochemical cell using the electrolyte of claim 1 .