JP2833626B2 - Polymer solid electrolyte - Google Patents

Abstract

PURPOSE:To obtain a solid polyelectrolyte excellent in heat resistance, low- temperature properties and mechanical properties by mixing a specified polymeric compound with an alkali (alkaline earth) metal salt. CONSTITUTION:A solid polyelectrolyte is formed by mixing a specified polymeric compound with an alkali metal salt or an alkaline earth metal salt, wherein the polymeric compound is a polyparabanic acid or its imino precursor having segments (I) comprising repeating unit of formula I or comprising segments (I) and segments (II) comprising repeating units of formula II. In the formulas, Ar and Ar' are different bivalent aromatic groups; and X is NH or O. Examples of the desired alkali metal salts and alkaline earth metal salts include LiClO4, LiBF4, LiAsF6, Li[CF3SO3], LiI, LiBr, and LiPF6.

Description

Description: TECHNICAL FIELD The present invention relates to a solid polymer electrolyte used for electrochemical devices such as batteries, electrochromic devices, and capacitors.

(Prior Art) Conventionally, as a polymer solid electrolyte of this type, a polymer compound having polyethylene oxide, polypropylene oxide, or a copolymer of ethylene oxide and polypropylene oxide in the main chain or side chain and an alkali metal salt or alkali A complex of an earth metal salt is mainly known.

The polyether of the polymer material constituting these conventional polymer solid electrolytes generally has a low glass transition temperature (for example, -67 ° C. in the case of polyethylene oxide), and softens as the temperature increases, resulting in a decrease in mechanical strength. The problem of lowering occurs. Further, for example, when the temperature is lowered to -100 ° C. or lower, not only the brittleness is exhibited but also the stability to various solvents and chemicals is lowered.

However, in recent years, there has been an increasing demand for using electrochemical devices such as batteries at higher or lower temperatures than the above-mentioned exemplary temperatures in accordance with the progress of electrical equipment, and overcoming the above-mentioned problems to cover a wider temperature range. Development of a solid polymer electrolyte that can be used is desired.

(Problems to be Solved by the Invention) The present invention overcomes the above-mentioned problems of the conventional polymer solid electrolyte and provides a new polymer solid electrolyte having excellent heat resistance and cold resistance and high mechanical strength. It is the purpose.

(Means for Solving the Problems) A first embodiment of the present invention for achieving the above object is characterized by a solid polymer electrolyte comprising a polyparabanic acid-based polymer compound segment containing an alkali metal salt. Is what you do. Further, the second embodiment of the present invention is characterized by a polymer solid electrolyte further comprising a polar solvent in the first embodiment.

(Action) The polyparabanic acid-based polymer compound, which is a main component of the polymer solid electrolyte of the present invention, has the following chemical formula (5) Or a polymer compound comprising the segment (I) of the unit compound 1 represented by the following formula (1), or the segment (I) and the following chemical formula (6) And a polymer compound obtained by bonding to the segment (II) of the unit compound 2 represented by Here, the segment refers to a unit composed of an arbitrary number of continuous bonding chains of each of the unit compounds 1 and 2.

Ar and Ar ′ in the above chemical formulas (5) and (6) each represent a different aromatic group, and X represents O or NH. Hereinafter, those in which X is O are referred to as polyparabanic acid, and those in which X is NH (imino group) are referred to as a polyparabanic acid imino precursor.
These polymer compound segments are collectively referred to as polyparabanic acid-based polymer compounds.

The different divalent aromatic groups Ar and Ar ′ contained in the unit compounds 1 and 2 constituting the polyparabanic acid-based polymer compound segment (I) and the segment (II) used in the present invention are preferably Selected from divalent aromatic groups represented by the following chemical formulas (7) to (13).

(However, R, R ¹ , R ² and R ³ in the chemical formulas (7) to (13) are
Each independently represents an H atom or an alkyl group having 1 to 4 carbon atoms. In addition, particularly preferred aromatic groups are those represented by the following chemical formulas (14) to (14).
It is a group represented by (18).

The polyparabanic acid-based polymer compound constituting the polymer solid electrolyte of the present invention has an extremely high glass transition point. That is, for example, the polymer compound (M-type PPA) of the segment (I) comprising a unit compound having an aromatic group represented by the chemical formula (14) where X is O and Ar has a glass transition point of about 290 ° C. The polymer compound (TM-type PPA) in which the segment (I) is bonded to the segment (II) in which X is O and Ar ′ is represented by the chemical formula (16) has a glass transition point of about 350 ° C. . In addition, the thermal decomposition temperature is 400 ° C or more, which has sufficient heat resistance, and the long-term heat resistance shows a UL temperature index of 180 ° C, and it is confirmed that it can sufficiently withstand the solder bath test at 260 ° C. ing.

Further, these polyparabanic acid-based polymer compounds have high chemical resistance and chemical stability, and also have excellent mechanical strength. On the other hand, these high molecular compounds have the feature that their mechanical strength does not decrease even at extremely low temperatures, for example, they can maintain a sufficiently high mechanical strength even in liquid nitrogen. It has been confirmed that polyparabanic acid-based polymer compounds also have similar properties.

The present invention relates to a polyparabanic acid-based polymer compound segment having high chemical stability and mechanical strength under a wide temperature environment as described above, and forming a complex by containing an alkali metal salt to form a stable solid electrolyte. It has been successfully used as a product. Further, since the solid electrolyte of the present invention can be dissolved in an organic polar solvent such as N, N-dimethylformamide (DMF), the dissolved solution is cast or applied on an arbitrary substrate, and then the solvent is applied. It is very convenient in use because it can be volatilized and removed by performing vacuum drying at an appropriate temperature and used as a film-like solid electrolyte. In this case, the polyparabanic acid-based polymer compound of the present invention is DMF
Since it has a certain affinity for organic polar solvents such as, a certain amount remains when making the film,
Since the organic polar solvent has a high dielectric constant, it interacts with the polyparabanic acid-based polymer compound or the alkali metal salt, so that even if it remains, it will have a high effect on the performance of the solid electrolyte and will not hinder the performance. .

The polyparabanic acid-based polymer compound used in the present invention can be easily obtained, for example, by the method disclosed in JP-B-49-20960. Further, as the alkali metal salt used in the present invention, a lithium salt is preferable. As lithium salts, lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiB
F ₄ ), lithium trifluoromethylsulfonate (Li
[CF ₃ SO ₃ ]), lithium arsenide hexafluoride (LiAsF ₆ ), lithium iodide (LiI), lithium bromide (LiBr), and lithium phosphorus hexafluoride (LiPF ₆ ).

(Examples) Some examples for showing the excellent effects of the present invention will be described below.

Example 1: 154 mg of TM-type PPA (intrinsic viscosity in N, N-dimethylformamide at 30 ° C. of about 1.0 dl / g) and 104 mg of lithium trifluoromethylsulfonate (Li [CF ₃ SO ₃ ]) 2.
DMF was uniformly dissolved in 5 mg of DMF, cast on a plastic substrate, and vacuum-dried at room temperature for 9 hours to volatilize DMF to obtain a polymer solid electrolyte film (sample 1) having a thickness of 220 μm.

This film was punched into a 15 mmφ, sandwiched between 13 mmφ platinum electrodes, and the ionic conductivity was determined by a complex impedance method. The resulting film is pale yellow and transparent, indicating that the lithium salt compound is uniformly dispersed in the polymer film, and that lithium ions have a chemical interaction with the polymer compound, such as complex formation. Is shown. The ionic conductivity determined by the complex impedance method is 6.8 × 10 ⁻⁷ Scm ⁻¹ at 25 ° C., and 1.3 × 10 ⁻⁴ S at 78.6 ° C.
cm ^-1 . In addition, in the film of this example,
The weight ratio of the lithium salt to the total amount of the polymer compound and the lithium salt was 40.3%.

Example 2: The same procedure as in Example 1 was repeated except that the same TM-type PPA and lithium trifluoromethyl sulfonate as in Example 1 were used and the weight ratio of the lithium salt to the total amount was variously changed.
Various kinds of polymer solid electrolyte films (samples 2 to 6) were prepared, and the ionic conductivity at 25 ° C. was measured. Table 1 shows the measurement results of the ionic conductivity corresponding to the weight ratio of the lithium salt.

Usually, the polyparabanic acid-based polymer compound used in the present invention has an affinity for DMF. Therefore, each film sample that had been vacuum-dried at room temperature for 9 hours was further heated and heated, and the effect of heating was examined by thermogravimetric analysis. As a result, when the temperature was raised to 300 ° C., a weight loss of about 5% to 20% was observed. However, in the case of vacuum drying at 160 ° C. for 9 hours, no weight loss was observed, and no decrease in film transparency or shape loss was observed. This means
The solid electrolyte film of the present invention has good heat resistance up to at least around 200 ° C., indicating that it can be stably used as a solid electrolyte. The volatile content generated when the sample 4 in Table 1 was heated to 445 ° C. by high-frequency heating for 3 seconds was analyzed by gas chromatography to find that the sample 4 contained 6.5% DMF by weight. Do you get it.

Example 3: As in Example 1, 205 mg of TM-type PPA and 77.6 mg of lithium perchlorate (LiClO ₄ ) were uniformly dissolved in 2.5 mg of DMF, cast on a plastic substrate, and dried at room temperature. DMF was removed by vacuum drying at 80 ° C. for 9 hours to obtain a light yellow transparent film having a thickness of 187 μm. Gold was vapor-deposited on both sides of the film thus obtained in a square shape of 1 cm × 1 cm, and the ionic conductivity was determined by a complex impedance method using a platinum electrode in the same manner as in Example 1. , 4.8 × 10 ^-7 Scm
It was ^-1 .

Example 4: Performed except that TM-type PPA (intrinsic viscosity in DMF at 30 ° C .: 0.8 dl / g) and lithium trifluoromethylsulfonate were used and the weight ratio of lithium salt to the total amount was changed to two. Films (Sample Nos. 7 and 8) were prepared in the same manner as in Example 1, and the ionic conductivity at 25 ° C. was measured in the same manner as in Example 1. Table 2 shows the measurement results of the ionic conductivity corresponding to the weight ratio of the lithium salt.

Further, a film having the same lithium weight ratio as that described above was prepared in the same procedure as in Example 1 except that the film was vacuum-dried at 70 to 80 ° C, and the ionic conductivity at 25 ° C was measured in the same procedure as in Example 1. However, the values were 2.9 × 10 ⁻⁸ Scm ⁻¹ and 1.4 × 10 ⁻⁷ Scm ⁻¹ , respectively.

Example 5: Lithium tetrafluoroborate (LiBF
_A film was prepared in the same manner as in Example 3 except that ₄ ) was used, and vacuum drying was performed at 160 ° C. for 9 hours after drying at room temperature. No change was observed. In the film
The weight ratio of LiBF ₄ relative to the total amount of TM type PPA and LiBF ₄ was 40%. The film was measured for ionic conductivity by a complex impedance method in the same procedure as in Example 3,
Table 3 shows the results of determining the temperature dependence of the ionic conductivity from 35 ° C to around 174 ° C.

Note that the film maintained a stable state without shape collapse even when the temperature was raised to 173.7 ° C. For comparison, when a similar ionic conductivity temperature dependence test was conducted using a conventional solid polymer electrolyte based on polyethylene oxide and polyvinyl alcohol, the film was already deformed at a temperature of 90 ° C. Measurement of the conductivity became impossible.

Example 6: A polymer solid electrolyte film was prepared in the same procedure as in Example 5, except that lithium trifluoromethylsulfonate (Li [CF ₃ SO ₂ ]) was used as the lithium salt. Li based on the total amount of TM-type PPA and Li [CF ₃ SO ₃ ] in the film
The weight ratio of [CF ₃ SO ₃ ] was 50.6%. The ionic conductivity of this film was measured by the complex impedance method in the same procedure as in Example 5, and the temperature dependence of ionic conductivity from 35 ° C. to around 173 ° C. was determined, and the results are shown in Table 4.

The film maintained its stable state in terms of strength without causing shape collapse even when the temperature was raised to 173 ° C.

(Effect of the Invention) As described above, according to the present invention, a polymer solid electrolyte having excellent mechanical strength, heat resistance, cold resistance and shape stability can be provided under a wide range of temperature environments. Its industrial value is extremely large.

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01M 10/40 H01G 9/02 331

Claims (2)

(57) [Claims] 1. A unit compound 1 represented by the following chemical formula (1)
Or a segment (I) consisting of
And a segment (II) consisting of a unit compound 2 represented by the following chemical formula (2): A solid polymer electrolyte comprising a polyparabanic acid-based polymer compound containing an alkali metal salt. (However, Ar and Ar ′ in the chemical formulas (1) and (2) are different divalent aromatic groups, and X represents NH or O.) 2. A polyparabanic acid-based segment obtained by bonding a segment (I) having the following chemical formula (3) as a unit compound, or a segment (II) having the segment (I) and a unit compound having the following chemical formula (4). A solid polymer electrolyte comprising a polymer compound containing an alkali metal salt and a polar solvent. (However, Ar and Ar ′ in the chemical formulas (3) and (4) are different divalent aromatic groups, and X represents NH or O.)