JP6526970B2 - Polycarbonate-based solid electrolyte and magnesium ion secondary battery - Google Patents

Description

  The present invention relates to a polycarbonate-based solid electrolyte and a magnesium ion secondary battery. More specifically, the present invention relates to a polycarbonate-based solid electrolyte for a magnesium ion secondary battery having high conductivity, and a magnesium ion secondary battery using the same.

At present, lithium ion secondary batteries are used in various applications. However, since lithium can only be collected in a limited area, secondary batteries using other metals are required. Among these, since magnesium generates divalent ions, there is a possibility that the charge and discharge capacity can be increased, and research on secondary batteries (magnesium ion secondary batteries) using magnesium ions has been conducted in recent years.
By the way, many lithium ion secondary batteries use an electrolyte composed of a lithium salt and an organic solvent as an electrolyte. Therefore, there was a problem that ignition may occur due to leakage of the organic solvent in an emergency. In order to solve this problem, a polymer solid electrolyte in which a lithium salt and an organic solvent are held in a polymer matrix has been proposed.
The magnesium ion secondary battery also has this problem. For example, Solid State Ionics 149 (2002) 115-123 (Non-patent Document 1) proposes a solid electrolyte using polyethylene oxide as a matrix.

Solid State Ionics 149 (2002) 115-123

  Since the improvement of the conductivity of the polymer solid electrolyte has a very large effect on the improvement of the performance of the magnesium secondary battery, the improvement is desired.

  The inventors of the present invention have found that the conductivity can be improved by using polyethylene carbonate instead of polyethylene oxide as a result of earnestly examining the components of the solid electrolyte in order to further improve the conductivity. It reached.

Thus, according to the present invention, it is seen containing an organic salt 40 to 100 parts by weight of magnesium as an electrolyte salt and polyethylene carbonate 100 parts by weight,
The organic salt of magnesium is magnesium bis trifluoromethane sulfonylamide, magnesium bis (fluoro sulfonyl) imide, magnesium trifluoro methane sulfonic acid, magnesium bis penta fluoro ethane sulfonyl amide, magnesium bis oxalato boric acid and magnesium difluoro [trifluoro -2- trifluoro [trifluoro -2-] There is provided a polyethylene carbonate-based solid electrolyte for a magnesium ion secondary battery selected from oxide-2-trifluoro-methylpropionato (2-)-0,0] boric acid .
Furthermore, according to the present invention, a positive electrode and a negative electrode as a pair of electrodes, and a solid electrolyte positioned between the pair of electrodes, wherein the solid electrolyte is the above-mentioned polyethylene carbonate-based solid electrolyte A magnesium ion secondary battery is provided.

According to the present invention, it is possible to provide a solid electrolyte containing an organic salt of magnesium, which has high conductivity, and a magnesium ion secondary battery containing this solid charge material.
Further, according to the present invention, a solid electrolyte having higher conductivity can be provided when any of the following is provided.
(1) The organic salt of magnesium is magnesium bis trifluoromethane sulfonylamide, magnesium bis (fluoro sulfonyl) imide, magnesium trifluoro methane sulfonic acid, magnesium bis penta fluoro ethane sulfonyl amide, magnesium bis oxalato boric acid and magnesium difluoro [trifluoro [trifluoro- It is selected from 2-oxide-2-trifluoro-methylpropionato (2-)-0,0] boric acid.
(2) Polyethylene carbonate has a number average molecular weight of 5,000 to 1,000,000.
(3) The organic salt of magnesium is magnesium bis trifluoromethane sulfonylamide, and it is contained 40 to 100 parts by weight with respect to 100 parts by weight of polyethylene carbonate.

3 is a DSC curve of the solid electrolyte of Example 1. 3 is a Raman spectrum of the solid electrolyte of Example 1. 3 is an impedance plot of the solid electrolyte of Example 1; 5 is a graph showing the temperature dependency of the conductivity of the solid electrolyte of Example 1. FIG. 5 is a graph showing the relationship between the conductivity and activation energy of the solid electrolyte of Example 1 and the content of Mg (TFSA) ₂ ; 7 is an XRD pattern of the solid electrolyte of Example 2. 7 is an impedance plot of the solid electrolyte of Example 2. 5 is a graph showing the temperature dependency of the solid electrolyte of Example 2. FIG.

  The inventors of the present invention have intensively studied the effect of an organic salt of magnesium as an electrolyte salt on a polymer species constituting a matrix of a solid electrolyte in a magnesium ion secondary battery. As a result, when polyethylene carbonate is used, the conductivity increases once and then decreases and the glass transition temperature (Tg) does not change significantly according to the decrease of the content, and the present inventors surprisingly It found and came to this invention. The present inventors believe that polyethylene carbonate having a carbonate bond that interacts with magnesium ion with a weaker force than polyethylene oxide effectively works for ion conduction.

(Solid electrolyte)
The solid electrolyte contains 100 parts by weight of polyethylene carbonate and 10 to 900 parts by weight of an organic salt of magnesium. If the content of the organic salt of magnesium is less than 10 parts by weight, it may be insulating. If it is more than 900 parts by weight, the flexibility may be lost. The content of the organic salt of magnesium is preferably 20 to 500 parts by weight, and more preferably 40 to 100 parts by weight.
(1) Polyethylene carbonate The polyethylene carbonate is not particularly limited, and examples thereof include those obtained by polymerizing ethylene oxide and carbon dioxide in the presence of a metal catalyst. As a metal catalyst, an aluminum catalyst, a zinc catalyst, etc. are mentioned, for example. Among these, in the polymerization reaction of ethylene oxide and carbon dioxide, a zinc catalyst is preferably used because it has high polymerization activity, and among zinc catalysts, an organic zinc catalyst is preferably used.

Examples of organozinc catalysts include: organozinc catalysts such as zinc acetate, diethylzinc and dibutylzinc; primary amines, divalent phenols, divalent aromatic carboxylic acids, aromatic hydroxy acids, aliphatic dicarboxylic acids, aliphatic The organic zinc catalyst etc. which are obtained by making compounds, such as a monocarboxylic acid, and a zinc compound react are mentioned. Among these organic zinc catalysts, organic zinc catalysts obtained by reacting a zinc compound, an aliphatic dicarboxylic acid, and an aliphatic monocarboxylic acid are preferable because they have higher polymerization activity.
The amount of the metal catalyst used for the polymerization reaction is preferably 0.001 to 20 parts by weight with respect to 100 parts by weight of ethylene oxide. When the amount of the metal catalyst used is less than 0.001 parts by weight, the polymerization reaction may be difficult to proceed. In addition, when the amount of metal catalyst used exceeds 20 parts by weight, the effect may not be met and the amount may not be economical. The amount used is more preferably 0.01 to 10 parts by weight.

The method of reacting ethylene oxide and carbon dioxide in the presence of a metal catalyst in the polymerization reaction is not particularly limited. For example, the ethylene oxide, the metal catalyst and, if necessary, the reaction solvent may be charged into an autoclave, mixed, and then carbon dioxide may be injected to cause a reaction.
It does not specifically limit as a reaction solvent used as needed in a polymerization reaction, Various organic solvents can be used. Specific examples of the organic solvent include aliphatic hydrocarbon solvents such as pentane, hexane, octane, decane and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene and xylene; chloromethane, methylene dichloride, Chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, ethyl chloride, trichloroethane, 1-chloropropane, 2-chloropropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, chlorobenzene, Halogenated hydrocarbon solvents such as bromobenzene; carbonate solvents such as dimethyl carbonate, diethyl carbonate, propylene carbonate and the like can be mentioned.

The amount of the reaction solvent used is preferably 300 to 10,000 parts by weight with respect to 100 parts by weight of ethylene oxide from the viewpoint of facilitating the reaction.
Although the working pressure of carbon dioxide used in the polymerization reaction is not particularly limited, it is preferably 20 MPa or less. When the working pressure of carbon dioxide exceeds 20 MPa, the working pressure may not be effective and it may not be economical. The working pressure is more preferably 0.1 to 10 MPa, and still more preferably 0.1 to 5 MPa.
The polymerization reaction temperature in the polymerization reaction is not particularly limited, but is preferably 30 to 100 ° C. When the polymerization reaction temperature is less than 30 ° C., the polymerization reaction may take a long time. When the polymerization reaction temperature exceeds 100 ° C., side reactions may occur and the yield may be reduced. The polymerization reaction temperature is more preferably 40 to 80 ° C. The polymerization reaction time can not generally be mentioned because it varies depending on the polymerization reaction temperature, but usually, it is preferably 2 to 40 hours.
In the polymerization reaction, the reaction can be carried out in the presence of a compound having an active proton, for the purpose of controlling the molecular weight as necessary. Examples of compounds having active protons include alcohols such as water, methanol, ethanol, benzyl alcohol and ethylene glycol; carboxylic acids such as acetic acid, propionic acid, benzoic acid, oxalic acid, malonic acid, succinic acid and terephthalic acid; Phenols such as phenol, p-cresol, hydroquinone and the like can be mentioned.
The compounds having these active protons can be reacted either in the absence or in the presence of one or more compounds.
The amount of the compound having an active proton is preferably 20 parts by weight or less and more preferably 10 parts by weight or less with respect to 100 parts by weight of ethylene oxide. When the amount of the compound having an active proton exceeds 20 parts by weight, the polymerization reaction may be difficult to proceed.
After completion of the polymerization reaction, the resultant is separated by filtration or the like, and if necessary, after washing with a solvent or the like, polyethylene carbonate can be obtained by drying.

The number average molecular weight (in terms of polystyrene) of polyethylene carbonate is preferably 50,000 to 1,000,000. If the number average molecular weight of polyethylene carbonate is less than 5,000, the viscosity of the solid electrolyte may be low, and shape retention may be difficult. If it exceeds 1,000,000, the compatibility with the organic salt of magnesium may be darkened. A more preferable number average molecular weight is 10,000 to 500,000. The number average molecular weight is small by increasing the amount of the compound having an active proton contained in the reaction system under the above-mentioned production conditions, and reduces the amount of the compound having an active proton contained in the reaction system. And / or can be largely adjusted by reducing the amount of catalyst used. The measurement method of number average molecular weight is described below.
By preparing a chloroform solution with a polyethylene carbonate concentration of 0.5% by weight, and comparing the measured values obtained using high performance liquid chromatograph with the data of polystyrene with known number average molecular weight measured under the same conditions, Calculate number average molecular weight. The measurement conditions are as follows.
Model: HLC-8020
Column: GPC column (manufactured by Tosoh Corp., TSK GEL Multipore H _XL- M)
Column temperature: 40 ° C
Eluent: chloroform flow rate: 1 mL / min

(2) Organic Salt of Magnesium The organic salt of magnesium is not particularly limited, and any salts known as electrolyte salts for secondary batteries can be used. As an organic salt of magnesium, for example, magnesium bis trifluoromethane sulfonylamide, magnesium bis (fluoro sulfonyl) imide, magnesium trifluoro methane sulfonic acid, magnesium bis penta fluoro ethane sulfonyl amide, magnesium bis oxalato boric acid, magnesium difluoro [trifluoro- 2-oxide -2- trifluoro- methyl propionato (2-)-0, 0] boric acid etc. are mentioned.
Among the above organic salts of magnesium, magnesium bistrifluoromethanesulfonylamide is preferred. When magnesium bis trifluoromethane sulfonylamide is used, it is preferable that magnesium bis trifluoro methane sulfonylamide is contained 40 to 100 parts by weight with respect to 100 parts by weight of polyethylene carbonate from the viewpoint of further improving the conductivity.

(3) Other Components The solid electrolyte may contain other components such as an inorganic salt of magnesium, a solvent, and a conductive material as long as the effects of the present invention are not impaired.
As an inorganic salt of magnesium, Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ , MgBr ₂ , MgCl ₂ , MgI ₂ , Mg (SCN) ₂ , Mg (BF ₄ ) ₂ , Mg (AsF ₄ ) ₂ , _{mg (ClO 4) 2, mg} (PF 6) 2, MgS-P 2 S 5 , and the like.
As the solvent, acetone, methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, dimethyl carbonate, diethyl carbonate, propylene carbonate, acetonitrile, toluene, tetrahydrofuran, nitrotoluene, cyclohexanone, triglyme, tetraglyme, ethyl isopropyl sulfone etc. It can be mentioned.
Examples of the conductive material include carbon black such as acetylene black, denka black and ketjen black, carbon nanotubes, natural graphite, artificial graphite, vapor grown carbon fiber (VGCF) and the like.

(4) Method of Producing Solid Electrolyte As a method of producing a solid electrolyte, for example, (i) polyethylene carbonate and an organic salt of magnesium are mixed in a solvent to obtain a liquid mixture, and the liquid mixture is coated on a substrate, Method for drying the obtained coating film, (ii) Method for flowing the mixed solution into a mold and then drying, (iii) Organic salt of magnesium is added to the melted polyethylene carbonate and mixed, and the obtained mixture is obtained The method of extruding a smelt to a film form etc. are mentioned. In the methods (i) and (ii), the polyethylene carbonate and the organic salt of magnesium may be dissolved in the solvent or may be dispersed without being dissolved.

(Magnesium um ion secondary battery)
A magnesium- um ion secondary battery includes a positive electrode and a negative electrode as a pair of electrodes, and a solid electrolyte located between the pair of electrodes. The above-mentioned polyethylene carbonate type solid electrolyte is used for the solid electrolyte which constitutes a battery.
(1) Positive Electrode The positive electrode is not particularly limited as long as it contains a positive electrode active material. The positive electrode active material may be any material as long as it can reversibly insert and remove magnesium ions, for example, manganese oxides such as fluorinated graphite ((CF) _n ) and manganese dioxide (MnO ₂ ), Vanadium oxides such as vanadium pentoxide (V ₂ O ₅ ), sulfur and sulfur compounds, magnesium copper oxide (Mg _x Cu _y O _z ), magnesium iron oxide (Mg _x Fe _y O _z ), chevrel compounds, etc. Can be mentioned.

The positive electrode may contain a conductive material. The conductive material is not particularly limited, and the field of secondary batteries such as carbon black such as acetylene black (AB), denka black, ketjen black, carbon nanotubes, natural graphite, artificial graphite, vapor grown carbon fiber (VGCF), etc. Carbon materials used as conductive materials in the In addition, a binder such as polyvinylidene fluoride may be included.
The positive electrode may include a current collector. Examples of the current collector include an aluminum plate, a gold plate, and a platinum plate.

(2) Negative Electrode The negative electrode is not particularly limited as long as it contains a negative electrode active material. As a negative electrode active material, it is sufficient if magnesium ions can be supplied, and metal magnesium, various magnesium alloys and the like can be mentioned.
Similar to the positive electrode, the negative electrode may contain a conductive material and a binder. In addition, the negative electrode may be provided with a current collector as in the case of the positive electrode. Metal magnesium or a magnesium alloy can also be used for the current collector, in which case the negative electrode active material will also serve as the current collector.

(3) Method of Manufacturing Secondary Battery The method of manufacturing the secondary battery is not particularly limited, and the method of placing the solid electrolyte on the positive electrode or the negative electrode and placing the remaining negative electrode or the positive electrode on the solid electrolyte is It can be mentioned. In addition, it is also possible to improve the capacity and voltage of the secondary battery by stacking a plurality of units of the positive electrode, the solid electrolyte, and the negative electrode as one unit and laminating the plurality of units.
The unit consisting of the positive electrode, the solid electrolyte and the negative electrode may be sealed by a metal can or may be sealed by a resin bag in order to improve the handleability of the secondary battery.

Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited thereto.
Example 1
(Production of polyethylene carbonate)
In a 300 mL four-necked flask equipped with a stirrer, nitrogen gas inlet tube, thermometer, and reflux condenser, 8.1 g (100 mmol) of zinc oxide, 12.7 g (96 mmol) of glutaric acid, 0.1 g of acetic acid 2 mmol) and 130 g (150 mL) of toluene were charged. Next, the inside of the reaction system was replaced with a nitrogen atmosphere, the temperature was raised to 55 ° C., and the mixture was reacted by stirring at the same temperature for 4 hours. Thereafter, the temperature was raised to 110 ° C., and stirring was carried out at the same temperature for 4 hours to carry out azeotropic dehydration to remove only water, followed by cooling to room temperature to obtain a reaction liquid containing an organozinc catalyst.
As a result of measuring IR (Thermo Nicolet Japan company make, brand name: AVATAR 360) about the organic zinc catalyst obtained by fractionating a part of this reaction liquid and filtering, the peak based on a carboxylic acid group was not recognized .

The inside of a 1 L autoclave equipped with a stirrer, a gas inlet tube and a thermometer is previously replaced with a nitrogen atmosphere, and then 8.0 mL of the reaction liquid containing the above organozinc catalyst (containing 1.0 g of the organozinc catalyst), hexane 131 g (200 mL) and 35.2 g (0.80 mol) of ethylene oxide were charged. Next, while stirring, carbon dioxide was charged until the inside of the reaction system reached 1.5 MPa. Thereafter, the temperature was raised to 60 ° C., and the polymerization reaction was carried out for 6 hours while supplying carbon dioxide consumed by the reaction.
After completion of the reaction, the autoclave was cooled, depressurized, filtered and dried under reduced pressure to obtain 68.4 g of polyethylene carbonate.

The obtained polyethylene carbonate could be identified by having the following physical properties.
IR (KBr): 1740, 1447, 1386, 1217, 1029, 785 (all in cm ^-1 )
Moreover, the number average molecular weight of the obtained polyethylene carbonate was 67,700.

(Manufacture of solid electrolyte)
Seven PEC solutions were prepared by dissolving 100 parts by weight of the above polyethylene carbonate (PEC) in 1000 parts by weight of acetonitrile. In each of the seven PEC solutions obtained, 10 parts by weight, 30 parts by weight, 50 parts by weight, 70 parts by weight, 80 parts by weight, 100 parts by weight of magnesium bistrifluoromethanesulfonylamide (Mg (TFSA) ₂ ) 120 parts by weight was dissolved to obtain a solution for forming a solid electrolyte. Seven solid electrolytes were obtained by pouring the solution for solid electrolyte formation into the container which has a circular-shaped bottom with a depth of 18 mm, and a diameter of 41 mm, and removing acetonitrile at 60 degreeC under a normal pressure. The obtained solid electrolyte was a transparent free standing film regardless of the content of Mg (TFSA) ₂ .

Among the obtained solid electrolytes, the DSC curves of those with a content of 10 parts by weight, 50 parts by weight, 80 parts by weight and 80 parts by weight of Mg (TFSA) ₂ are shown in FIG. The Raman spectra of 50 parts by weight, 80 parts by weight and 100 parts by weight are shown in FIG. 2 (the Raman spectra of PEC only and Mg (TFSA) ₂ alone are also shown together), and the impedance plot of 80 parts by weight is shown in FIG. Figure 4 shows the temperature dependence of the conductivity of 50 parts by weight, 80 parts by weight and 100 parts by weight between a pair of SUSs), conductivity and activation energy at 60 ° C, and Mg (TFSA) ₂ The relationship with the content of is shown in FIG.

In FIG. 1, it is understood that the Tg of the solid electrolyte does not rise sharply, since the change of the DSC curve due to the increase of the content of Mg (TFSA) ₂ is not observed.
FIG. 2 shows that the peak of TFSA (around 741 cm ⁻¹ ) in the solid electrolyte is shifted to a shorter wavelength side than the peak of Mg (TFSA) ₂ alone. From this, it is estimated that Mg (TFSA) ₂ is dissociated into Mg ²⁺ ion and TFSA ⁻ ion in the solid electrolyte. It is believed that this Mg ²⁺ ion contributes to the improvement of the conductivity.

In FIG. 3, the spike derived from the ion blocking behavior is shown on the low frequency side, and it can be seen that the solid electrolyte is an ion conductor.
In FIG. 4, it is shown that the solid electrolyte having a content of Mg (TFSA) ₂ of 80 parts by weight has higher conductivity in any temperature range than those of 50 parts by weight and 100 parts by weight.
It is shown in FIG. 5 that there is a range of Mg (TFSA) ₂ content at which the conductivity and activation energy show peaks.

Example 2
In the same manner as in Example 1, a solution for forming a solid electrolyte containing 80 parts by weight of Mg (TFSA) ₂ was obtained. A mixed solution was obtained by mixing the obtained solution with an inorganic salt of magnesium represented by Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ which is an inorganic solid electrolyte material (PEC: inorganic salt = 60 : 40 (volume ratio)). A solid electrolyte was obtained by removing acetonitrile from the obtained mixture in the same manner as in Example 1.

Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ was produced by the following procedure. That is, the molar ratio of MgHPO _4. 3 H ₂ O, ZrO (NH ₃ ) _{2. 2} H ₂ O, Nb ₂ O ₅ and NH ₄ H ₂ PO ₄ is 0.7: 3.4: 0.3: 5.3. And then heat treated in air at 300 ° C. for 5 hours. After heat treatment, it was pressure-formed into pellets. The obtained pellet was heat treated in air at 1200 ° C. for 12 hours to obtain Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ . It was confirmed by measuring the XRD pattern that it was Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ .
The preparation of Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ was carried out with reference to the contents described in N. Imanaka et al., Electrochem. Solid-State Lett., 3 (2000) 327. The

The XRD pattern of the obtained solid electrolyte is shown in FIG. 6 by using Mg (TFSA) ₂ containing 80 (Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ only and Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ The impedance plot is shown in FIG. 7 (measured at 80 ° C. between a pair of SUSs) and the temperature dependence of the conductivity is shown in FIG.

In FIG. 6, the pattern of the solid electrolyte of Example 2 is the pattern of Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ only, and Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ not containing Mg (TFSA) ) ₂ only solid electrolyte comprising 80 parts by weight corresponds to a combination of the pattern, since the movement of the peak was not _{observed, Mg 0.7 (Zr 0.85 Nb 0.15} ) 4 P 6 O 24 has been changed I understand that there is not.
In FIG. 7, the spike derived from the ion blocking behavior is shown on the low frequency side, and it can be seen that the solid electrolyte is an ion conductor.
In FIG. 8, although the conductivity is lowered by containing Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ compared to the non-containing solid electrolyte, Mg _0.7 (Zr _0.85 Nb _0.15 ) ₄ P ₆ O ₂₄ sintering It can be seen that the conductivity is about four orders of magnitude higher than the body.

Claims (4)

100 parts by weight of polyethylene carbonate and the organic salt 40 to 100 parts by weight of magnesium as an electrolyte salt seen including,
The organic salt of magnesium is magnesium bis trifluoromethane sulfonylamide, magnesium bis (fluoro sulfonyl) imide, magnesium trifluoro methane sulfonic acid, magnesium bis penta fluoro ethane sulfonyl amide, magnesium bis oxalato boric acid and magnesium difluoro [trifluoro -2- trifluoro [trifluoro -2-] Polyethylene carbonate-based solid electrolyte for magnesium ion secondary battery selected from oxide-2-trifluoro-methyl propionato (2-)-0,0] boric acid . The polyethylene carbonate-based solid electrolyte according to claim 1 , wherein the polyethylene carbonate has a number average molecular weight of 5,000 to 1,000,000. The polyethylene carbonate-based solid electrolyte according to claim 1 or 2 , wherein the organic salt of magnesium is magnesium bistrifluoromethanesulfonylamide, and is contained in an amount of 40 to 100 parts by weight with respect to 100 parts by weight of the polyethylene carbonate. A positive electrode and a negative electrode as a pair of electrodes, and a solid electrolyte positioned between the pair of electrodes, wherein the solid electrolyte is the polyethylene carbonate-based solid electrolyte according to any one of claims 1 to 3. Magnesium ion secondary battery characterized by