Secondary battery

Abstract

Provided is a secondary battery with which excellent battery characteristics can be obtained. The secondary battery comprises: a positive electrode containing a sulfur-containing polymer compound; a negative electrode containing a magnesium-containing material; and an electrolytic solution containing an electrolyte salt. The sulfur-containing polymer compound contains carbon, nitrogen, and sulfur as constituent elements thereof and has a carbon-nitrogen bond and a carbon-sulfur bond. The electrolyte salt contains a magnesium ion and a lithium ion as cations and a halogen ion as an anion.

Description

secondary battery

[0001] The present technology relates to a secondary battery.

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as small, lightweight power sources that can provide high energy density. These secondary batteries include a positive electrode, a negative electrode, and an electrolyte, and various studies have been conducted on the configuration of these secondary batteries.

[0003] Specifically, the positive electrode contains sulfur, the negative electrode contains magnesium metal, and the electrolyte contains lithium chloride (see, for example, Patent Document 1), or the positive electrode contains a sulfur copolymer, and the negative electrode contains magnesium metal (see, for example, Patent Document 2).

[0004] Special table publication No. 2014-504423 Publication No. 2020-518536

[0005] Although various studies have been conducted on the configuration of secondary batteries, the battery characteristics of the secondary batteries are still insufficient and there is room for improvement.

[0006] There is a demand for a secondary battery that can provide excellent battery characteristics.

[0007] According to an embodiment of the present disclosure, there is provided a secondary battery including a positive electrode containing a sulfur-containing polymer compound, a negative electrode containing a magnesium-containing material, and an electrolyte solution containing an electrolyte salt. The sulfur-containing polymer compound contains carbon, nitrogen, and sulfur as constituent elements and has a carbon-nitrogen bond and a carbon-sulfur bond. The electrolyte salt contains magnesium ions and lithium ions as cations and a halogen ion as an anion.

[0008] Here, as described above, "sulfur-containing polymer compounds" is a general term for polymer compounds that contain carbon, nitrogen, and sulfur as constituent elements and have carbon-nitrogen bonds and carbon-sulfur bonds. Furthermore, "magnesium-containing materials" is a general term for materials that contain magnesium as a constituent element. The respective compositions of sulfur-containing polymer compounds and magnesium-containing materials will be described in detail below.

[0009] In a secondary battery according to an embodiment of the present technology, the positive electrode contains a sulfur-containing polymer compound, the negative electrode contains a magnesium-containing material, and the electrolyte solution contains an electrolyte salt. The sulfur-containing polymer compound contains carbon, nitrogen, and sulfur as constituent elements and has a carbon-nitrogen bond and a carbon-sulfur bond. The electrolyte salt contains magnesium ions and lithium ions as cations and halogen ions as anions, so that excellent battery characteristics can be obtained.

[0010] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0011] Fig. 1 is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present technology. Fig. 2 is an enlarged cross-sectional view illustrating the configuration of a battery element illustrated in Fig. 1. Fig. 3 is a cross-sectional view illustrating the configuration of a test secondary battery.

[0012] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing method 1-4. Actions and effects 2. Uses of secondary battery

[0013] 1. Secondary Battery First, a secondary battery according to an embodiment of the present technology will be described.

[0014] The secondary battery described here utilizes the deposition and dissolution of magnesium to cause charge and discharge reactions to proceed, and therefore is a secondary battery that utilizes the charge and discharge reactions to obtain battery capacity.

[0015] More specifically, the secondary battery is a so-called magnesium-sulfur secondary battery, since the positive electrode contains sulfur as a constituent element and the negative electrode contains magnesium as a constituent element.

[0016] In this magnesium-sulfur secondary battery, magnesium is precipitated and dissolved in the negative electrode, and magnesium is absorbed and released in an ionic state in the positive electrode. The configurations of the positive and negative electrodes will be described in detail later.

[0017] <1-1. Configuration> Fig. 1 shows a perspective view of the secondary battery, and Fig. 2 shows an enlarged cross-sectional configuration of the battery element 20 shown in Fig. 1. However, Fig. 1 shows a state in which the exterior film 10 and the battery element 20 are separated from each other, and the cross section of the battery element 20 along the XZ plane is shown by a dashed line. Fig. 2 shows only a portion of the battery element 20.

[0018] As shown in FIGS. 1 and 2, this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31, a negative electrode lead 32, and sealing films 41 and .

[0019] As described above, the secondary battery described here uses flexible or pliable exterior film 10 as an exterior member for housing battery element 20. Therefore, the secondary battery shown in Figures 1 and 2 is a so-called laminate film type secondary battery.

[0020] 1, the exterior film 10 has a bag-like structure that is sealed when the battery element 20 is housed therein. As a result, the exterior film 10 houses a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte solution (not shown), which will be described later.

[0021] Here, the exterior film 10 is a single film-like member that is folded in a folding direction F. The exterior film 10 is provided with a recessed portion 10U (a so-called deep drawn portion) for accommodating the battery element 20.

[0022] Specifically, the exterior film 10 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside out, and when the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers are fused to each other. The fusion layer contains a polymer compound such as polypropylene. The metal layer contains a metal material such as aluminum. The surface protection layer contains a polymer compound such as nylon.

[0023] However, the configuration (number of layers) of the exterior film 10 is not particularly limited, and may be one layer, two layers, or four or more layers.

[0024] [Battery Element] The battery element 20 is housed in an exterior film 10. This battery element 20 is a so-called power generation element, and as shown in Figures 1 and 2, includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown).

[0025] Here, battery element 20 is a so-called wound electrode body, and therefore positive electrode 21 and negative electrode 22 are wound around winding axis P while facing each other with separator 23 interposed therebetween. This winding axis P is a virtual axis extending in the Y-axis direction, as shown in FIG.

[0026] There are no particular limitations on the three-dimensional shape of battery element 20. Here, battery element 20 has a flat three-dimensional shape, and therefore the shape of a cross section (cross section along the XZ plane) of battery element 20 intersecting winding axis P is a flat shape defined by major axis J1 and minor axis J2.

[0027] The major axis J1 is an imaginary axis extending in the X-axis direction and has a length greater than that of the minor axis J2. The minor axis J2 is an imaginary axis extending in the Z-axis direction intersecting the X-axis direction and has a length less than that of the major axis J1. Here, the three-dimensional shape of the battery element 20 is a flattened cylinder, and therefore the cross-sectional shape of the battery element 20 is a flattened, approximately elliptical shape.

[0028] (Positive Electrode) The positive electrode 21 includes a positive electrode active material that absorbs and releases magnesium in an ionic state, and the positive electrode active material includes one or more sulfur-containing polymer compounds. This is because magnesium is more likely to be absorbed and released in an ionic state in the positive electrode 21. This makes it easier for a charge-discharge reaction that utilizes the deposition and dissolution of magnesium to proceed compared to when the positive electrode active material includes other materials such as elemental sulfur and sulfur compounds.

[0029] The sulfur-containing polymer compound contains sulfur as a constituent element. More specifically, the sulfur-containing polymer compound is a general term for polymer compounds that contain carbon, nitrogen, and sulfur as constituent elements and have carbon-nitrogen bonds and carbon-sulfur bonds, as described above.

[0030] The carbon-nitrogen bond is a so-called covalent bond between carbon and nitrogen, and the sulfur-containing polymer compound has a plurality of carbon-nitrogen bonds. Similarly, the carbon-sulfur bond is a so-called covalent bond between carbon and sulfur, and the sulfur-containing polymer compound has a plurality of carbon-sulfur bonds.

[0031] The structure of the sulfur-containing polymer compound is not particularly limited as long as it contains carbon, nitrogen, and sulfur as constituent elements and has a carbon-nitrogen bond and a carbon-sulfur bond.

[0032] The portion of the sulfur-containing polymer compound having a carbon-nitrogen bond may be linear or cyclic. Similarly, the portion of the sulfur-containing polymer compound having a carbon-sulfur bond may be linear or cyclic. The linear structure may be linear or branched.

[0033] Specifically, the sulfur-containing polymer compound includes a first cyclic portion, a second cyclic portion, and a linking portion. The configurations of the first cyclic portion and the second cyclic portion may be the same or different. Hereinafter, a sulfur-containing polymer compound including the first cyclic portion, the second cyclic portion, and the linking portion will be referred to as a "first sulfur-containing polymer compound."

[0034] The first annular portion and the second annular portion are spaced apart from each other. Each of the first annular portion and the second annular portion contains carbon and nitrogen as constituent elements. However, each of the first annular portion and the second annular portion may further contain one or more other elements, such as hydrogen, as constituent elements.

[0035] That is, each of the first cyclic moiety and the second cyclic moiety is a heterocyclic compound containing a nitrogen atom as a heteroatom (an atom other than carbon and hydrogen atoms). The heterocyclic compound may be a three-membered ring, a four-membered ring, a five-membered ring, a six-membered ring, or a seven- or higher-membered ring. The heterocyclic compound may also be a heterocyclic aromatic compound or a heterocyclic aliphatic compound.

[0036] Among these, the heterocyclic compound is preferably a heterocyclic aromatic compound, because a plurality of heterocyclic aromatic compounds are likely to undergo a polymerization reaction with each other, making it easier to synthesize a sulfur-containing compound having a sufficient molecular weight.

[0037] A specific example of a heterocyclic aromatic compound is pyridine, which is a six-membered ring containing one heteroatom (nitrogen atom).

[0038] The first sulfur-containing polymer compound may contain a plurality of first cyclic moieties, and the plurality of first cyclic moieties may be condensed with each other. Similarly, the first sulfur-containing polymer compound may contain a plurality of second cyclic moieties, and the plurality of second cyclic moieties may be condensed with each other. This is because a first sulfur-containing compound having a sufficient molecular weight can be easily synthesized.

[0039] The linking portion is a divalent group that is disposed between the first cyclic portion and the second cyclic portion and is linked to each of the first cyclic portion and the second cyclic portion. This allows the first cyclic portion and the second cyclic portion to be linked to each other via the linking portion. The linking portion contains sulfur as a constituent element. However, the linking portion may further contain one or more of other elements, such as hydrogen, carbon, and nitrogen, as constituent elements. Because the first cyclic portion and the second cyclic portion are spaced apart from each other as described above, the linking portion is interposed between the first cyclic portion and the second cyclic portion.

[0040] In particular, it is preferable that the linking portion contains only sulfur as a constituent element, because this allows magnesium to be easily and sufficiently absorbed and released in an ionic state in the first sulfur-containing polymer compound.

[0041] Specific examples of the linking moiety include -S n　 - (n is an integer of 1 or more), and more specifically, -S 2　 -(-S-S-) and -S 3　 -(-S-S-S-), etc.

[0042] As described above, when the first sulfur-containing polymer compound includes a plurality of first cyclic moieties and a plurality of second cyclic moieties, the first sulfur-containing polymer compound includes a plurality of linking moieties.

[0043] In this case, among the multiple sets of first annular portions and second annular portions, the first annular portions and second annular portions of all sets may be connected to each other via connecting portions, or only the first annular portions and second annular portions of some sets may be connected to each other via connecting portions.

[0044] The molecular weight of the first sulfur-containing polymer compound is not particularly limited and can be set arbitrarily. The molecular weight described here is the so-called weight average molecular weight.

[0045] Here, a specific example of the first sulfur-containing polymer compound is a polymer compound represented by formula (1), because magnesium can be easily absorbed and released in an ionic state in the positive electrode 21.

[0046] (n1 is an integer of 1 or more. An asterisk (*) represents a dangling bond.)

[0047] The polymer compound represented by formula (1) has the following structure. First, the first cyclic moiety (pyridine) and the second cyclic moiety (pyridine) are connected to a linking moiety (-S 3　 -). Second, a plurality of first annular portions are condensed with each other, and a plurality of second annular portions are condensed with each other, and a plurality of linking portions are present. Third, only some sets of first annular portions and second annular portions out of a plurality of sets of first annular portions and second annular portions are linked with each other via linking portions. Here, only two sets of first annular portions and second annular portions out of three sets of first annular portions and second annular portions are linked with each other via linking portions.

[0048] Alternatively, the sulfur-containing polymer compound includes a plurality of cyclic portions and linking portions. The configurations of the plurality of cyclic portions may be the same as or different from one another. Of course, the configurations of only some of the plurality of cyclic portions may be the same as one another. Hereinafter, a sulfur-containing polymer compound including a plurality of cyclic portions and linking portions is referred to as a "second sulfur-containing polymer compound."

[0049] The plurality of cyclic moieties are condensed with one another, and each of the plurality of bicyclic moieties contains carbon and nitrogen as constituent elements, but each of the plurality of cyclic moieties may further contain one or more other elements, such as hydrogen, as constituent elements.

[0050] That is, each of the plurality of cyclic moieties is a heterocyclic compound containing a nitrogen atom as a heteroatom, similar to each of the first and second cyclic moieties described above. Details regarding this heterocyclic compound are as described above.

[0051] The configuration of the connector is similar to the configuration of the connector described above, except as described below.

[0052] The linking portion is connected to any two of the plurality of ring portions and contains sulfur as a constituent element. As the plurality of ring portions are condensed with each other as described above, the linking portion extends from any one of the plurality of ring portions to another of the plurality of ring portions. The two ring portions connected by the linking portion may be two ring portions adjacent to each other, or may be two ring portions that are not adjacent to each other.

[0053] The number of linking moieties is not particularly limited, and the sulfur-containing polymer compound may include only one linking moiety or may include a plurality of linking moieties.

[0054] The molecular weight of the second sulfur-containing polymer compound is not particularly limited and can be set arbitrarily. The molecular weight described here is the so-called weight average molecular weight.

[0055] Here, a specific example of the second sulfur-containing polymer compound is a polymer compound represented by formula (2), because magnesium can be easily absorbed and released in an ionic state in the positive electrode 21.

[0056] (n2 is an integer of 1 or more. An asterisk (*) represents a dangling bond.)

[0057] The polymer compound represented by formula (2) has the following structure: First, a plurality of cyclic moieties (pyridine) are condensed with each other, and two of the cyclic moieties are linked to a linking moiety (-S-S-). Second, the two cyclic moieties linked to the linking moiety are adjacent to each other.

[0058] Of course, the first sulfur-containing polymer compound may be a polymer compound other than the polymer compound represented by formula (1). The second sulfur-containing polymer compound may be a polymer compound other than the polymer compound represented by formula (2). Furthermore, the sulfur-containing polymer compound may be a polymer compound other than the first sulfur-containing polymer compound and the second sulfur-containing polymer compound.

[0059] In order to confirm whether the positive electrode 21 contains a sulfur-containing polymer compound and to confirm the composition of the sulfur-containing polymer compound, the positive electrode 21 is analyzed using one or more of analytical methods such as infrared spectroscopy (IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure analysis (XAFS).

[0060] Although not specifically shown here, the positive electrode 21 may include a positive electrode current collector and a positive electrode active material layer.

[0061] The positive electrode current collector is a conductive support that supports the positive electrode active material layer and has a pair of surfaces on which the positive electrode active material layer is provided. This positive electrode current collector contains a conductive material such as a metal material, and a specific example of the conductive material is nickel.

[0062] The positive electrode active material layer is supported by the positive electrode current collector and contains one or more sulfur-containing polymer compounds as positive electrode active materials, but may further contain one or more other materials such as a positive electrode binder and a positive electrode conductive agent.

[0063] The positive electrode active material layer may be provided on both sides of the positive electrode current collector, or may be provided on only one side of the positive electrode current collector. The method for forming the positive electrode active material layer is not particularly limited, but specifically includes a coating method.

[0064] The positive electrode binder contains one or more resin materials such as a fluorine-based resin, a polyvinyl alcohol-based resin, and a styrene-butadiene copolymer rubber. Specific examples of the fluorine-based resin include polyvinylidene fluoride and polytetrafluoroethylene.

[0065] The positive electrode binder may contain a conductive polymer compound. Specific examples of the conductive polymer compound include polyaniline, polypyrrole, and polythiophene, and may also be copolymers of two or more of these. The conductive polymer compound may be unsubstituted or substituted with any one or more functional groups.

[0066] The positive electrode conductive agent contains one or more conductive materials such as a carbon material, a metal material, and a conductive polymer compound.

[0067] Specific examples of carbon materials include graphite, carbon fiber, carbon black, and carbon nanotubes. Graphite may be natural graphite or artificial graphite. Carbon fiber includes vapor-grown carbon fiber (VGCF). Carbon black includes acetylene black and ketjen black. Carbon nanotubes include single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT), and multi-walled carbon nanotubes include double-walled carbon nanotubes (DWCNT). Specific examples of metal materials include nickel.

[0068] (Negative Electrode) The negative electrode 22 contains one or more types of magnesium-containing materials, which are negative electrode active materials, because this facilitates the progress of charge / discharge reactions that utilize the deposition and dissolution of magnesium.

[0069] As described above, the magnesium-containing material is a general term for materials containing magnesium as a constituent element. That is, the magnesium-containing material may be magnesium alone (so-called magnesium metal), a magnesium alloy, a magnesium compound, or a mixture of two or more of these. Note that the purity of the magnesium metal is not particularly limited, and the magnesium metal may contain any amount of impurities.

[0070] The types of metal elements (except magnesium) contained as constituent elements in magnesium alloys are not particularly limited, as long as they are one or more of any metal elements, such as lithium, aluminum, and zinc.

[0071] The magnesium content in the magnesium alloy is not particularly limited, but specifically is 90 mol % or more, because this facilitates the progress of charge / discharge reactions that utilize the precipitation and dissolution of magnesium.

[0072] The lithium and aluminum contents in the magnesium alloy are not particularly limited, but are specifically 10 mol % or less. The zinc content in the magnesium alloy is also not particularly limited, but are specifically 2 mol % or less. This is because sufficient battery capacity can be obtained by ensuring the voltage during discharge.

[0073] Among these, the magnesium-containing material preferably contains magnesium metal, because this allows the charge-discharge reaction utilizing the precipitation and dissolution of magnesium to proceed sufficiently.

[0074] The thickness of the negative electrode 22 is not particularly limited, but specifically, it is 1 μm to 50 μm, because the energy density per volume is improved.

[0075] The negative electrode 22 may have a configuration similar to that of the positive electrode 21. That is, although not specifically illustrated here, the negative electrode 22 may include a negative electrode current collector and a negative electrode active material layer.

[0076] The negative electrode current collector is a conductive support that supports the negative electrode active material layer and has a pair of surfaces on which the negative electrode active material layer is provided. This negative electrode current collector contains a conductive material such as a metal material, and a specific example of the conductive material is nickel.

[0077] The negative electrode active material layer is supported by the negative electrode current collector and contains one or more magnesium-containing materials as negative electrode active materials, but may further contain one or more other materials such as a negative electrode binder and a negative electrode conductive agent.

[0078] The negative electrode active material layer may be provided on both sides of the negative electrode current collector, or may be provided on only one side of the negative electrode current collector. The method for forming the negative electrode active material layer is not particularly limited, but specifically includes a coating method.

[0079] The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductivity are the same as those regarding the positive electrode conductivity agent.

[0080] 2, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows magnesium to pass through in an ionic state while preventing short-circuiting between the positive electrode 21 and the negative electrode 22. The separator 23 contains one or more insulating polymer compounds, and a specific example of the insulating polymer compound is polyethylene.

[0081] (Electrolyte) The electrolyte is a liquid electrolyte, and is impregnated into each of the positive electrode 21 and the separator 23. However, the electrolyte may also be impregnated into the negative electrode 22.

[0082] The electrolytic solution contains an electrolyte salt, but may further contain a solvent that serves as a medium for dissolving and ionizing the electrolyte salt.

[0083] The electrolyte salt contains one or more metal salts containing cations and anions.

[0084] Specifically, the electrolyte salt contains magnesium ions and lithium ions as cations and halogen ions as anions, i.e., the electrolyte salt contains magnesium halide, which is a magnesium salt, and lithium halide, which is a lithium salt.

[0085] The electrolyte salt contains magnesium ions and lithium ions as cations because the voltage during discharge increases compared to when the electrolyte salt contains only magnesium ions as cations.

[0086] The electrolyte salt contains halogen ions as anions because the voltage during discharge increases compared to when the electrolyte salt does not contain halogen ions as anions.

[0087] For these reasons, when the electrolyte salt contains magnesium ions and lithium ions as cations and halogen ions as anions, the discharge voltage increases significantly, which facilitates the charging reaction by utilizing the deposition and dissolution of magnesium, resulting in a high battery capacity.

[0088] The type of halogen ion is not particularly limited, but specific examples include fluorine ions, chlorine ions, bromine ions, and iodine ions.

[0089] Among them, halogen ions contain chloride ions, so the electrolyte salt is magnesium chloride (MgCl 2　 It is preferable that the electrolyte contains lithium ion (LiCl) and lithium chloride (LiCl), because this sufficiently increases the voltage during discharge, thereby providing a sufficiently high battery capacity.

[0090] The electrolytic solution may further contain one or more of other electrolyte salts, except that the above-mentioned electrolyte salts containing magnesium ions and lithium ions as cations and halogen ions as anions are excluded from the other electrolyte salts described here.

[0091] The type of cation in the other electrolyte salt is not particularly limited as long as it is one or more of any positive ions (metal ions), and the type of anion in the other electrolyte salt is not particularly limited as long as it is one or more of any negative ions.

[0092] Specific examples of anions in other electrolyte salts include perchlorate ion, nitrate ion, sulfate ion, acetate ion, trifluoroacetate ion, tetrafluoroborate ion, tetraphenylborate ion, hexafluorophosphate ion, hexafluoroarsenate ion, bis(hexamethyldisilazide) ion, bis(trifluoromethanesulfonyl)imide ion, and bis[tetra(hexafluoroisopropyl)]borate ion. Examples of the halogen ion include fluorine ion, chloride ion, bromide ion, and iodide ion.

[0093] Specific examples of other electrolyte salts are as follows:

[0094] Specific examples of other electrolyte salts that are magnesium salts include magnesium perchlorate (Mg(ClO) 4　 ) 2　 ), magnesium nitrate (Mg(NO 3　 ) 2　 ), magnesium sulfate (MgSO 4　 ), magnesium acetate (Mg(CH 3　 COO) 2　 ), magnesium trifluoroacetate (Mg(CF 3　 COO) 2　 ), magnesium tetrafluoroborate (Mg(BF 4　 ) 2　 ), magnesium tetraphenylborate (Mg(B(C 6　 H 5　 ) 4　 ) 2　), magnesium hexafluorophosphate (Mg(PF 6　 ) 2　 ), magnesium hexafluoroarsenate (Mg(AsF 6　 ) 2　 ), bis(hexamethyldisilazide)magnesium (Mg[N(Si(CH 3　 ) 3　 ) 2　 ] 2　 ), bis(trifluoromethanesulfonyl)imide magnesium (Mg[N(CF 3　 SO 2　 ) 2　 ] 2　 and magnesium bis[tetra(hexafluoroisopropyl)]borate (Mg[B(OCH(CF 3　 ) 2　 ) 4　 ] 2　 ) etc.

[0095] Specific examples of other electrolyte salts that are lithium salts include lithium perchlorate (LiClO 4　 ), lithium nitrate (LiNO 3　 ), lithium sulfate (Li 2　 SO 4　 ), lithium acetate (LiCH 3　 COO), magnesium trifluoroacetate (LiCF 3　 COO), lithium tetrafluoroborate (LiBF 4　 ), magnesium tetraphenylborate (Li(B(C 6　 H 5　 ) 4　 ), lithium hexafluorophosphate (LiPF 6　 ), lithium hexafluoroarsenate (LiAsF 6　 ), bis(hexamethyldisilazide)magnesium (Li[N(Si(CH 3　 ) 3　 ) 2　 ]), bis(trifluoromethanesulfonyl)imide magnesium (Li[N(CF 3　 SO 2　 ) 2　 and lithium bis[tetra(hexafluoroisopropyl)]borate (Li[B(OCH(CF 3　 ) 2　 )4　 ) etc.

[0096] When the electrolyte salt contains other negative ions as well as chloride ions as anions, the content of chloride ions in the anions is not particularly limited. In particular, the content of chloride ions in the anions is preferably 20 mol % or more. This is because the voltage during discharge increases sufficiently, resulting in a sufficiently high battery capacity.

[0097] The content of electrolyte salt in the electrolyte solution (mol / l (= mol / dm 3　 However, the content of the electrolyte salt described here is the content of the electrolyte salt relative to the solvent.

[0098] The solvent contains one or more non-aqueous solvents (organic solvents). An electrolyte containing a non-aqueous solvent is a so-called non-aqueous electrolyte.

[0099] The type of non-aqueous solvent is not particularly limited. Among them, the non-aqueous solvent preferably contains an ether compound. This is because the electrolyte salt is easily dissolved in the ether compound, and the state of the electrolytic solution is stabilized.

[0100] The ether compound is a general term for compounds containing an ether bond (—O—). The ether compound may be chain-like or cyclic. The chain may be linear or branched. The number of ether bonds may be one or two or more.

[0101] Specific examples of the ether compound include dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and tetrahydrofuran.

[0102] [Positive Electrode Lead] As shown in FIGS. 1 and 2 , the positive electrode lead 31 is a positive electrode wiring connected to the positive electrode 21 and is led out of the exterior film 10. When the positive electrode 21 includes a positive electrode current collector, the positive electrode lead 31 is connected to the positive electrode current collector. The positive electrode lead 31 includes a conductive material such as a metal material, and a specific example of the conductive material is aluminum. The shape of the positive electrode lead 31 is either a thin plate shape or a mesh shape.

[0103] [Negative Electrode Lead] As shown in FIGS. 1 and 2 , the negative electrode lead 32 is a negative electrode wiring connected to the negative electrode 22 and is led out of the exterior film 10. If the negative electrode 22 includes a negative electrode current collector, the negative electrode lead 32 is connected to the negative electrode current collector. Here, the lead-out direction of the negative electrode lead 32 is the same as the lead-out direction of the positive electrode lead 31. The negative electrode lead 32 includes a conductive material such as a metal material, and a specific example of the conductive material is copper. The details regarding the shape of the negative electrode lead 32 are the same as the details regarding the shape of the positive electrode lead 31.

[0104] [Sealing Film] The sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and the sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. However, one or both of the sealing films 41 and 42 may be omitted.

[0105] The sealing film 41 is a sealing member that prevents outside air and the like from entering the inside of the exterior film 10. This sealing film 41 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 31, and a specific example of the polymer compound is polypropylene.

[0106] The configuration of the sealing film 42 is the same as the configuration of the sealing film 41, except that the sealing film 42 is a sealing member that has adhesiveness to the negative electrode lead 32. That is, the sealing film 42 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 32.

[0107] <1-2. Operation> The secondary battery operates in the battery element 20 as follows.

[0108] During discharge, the negative electrode active material (magnesium-containing material) dissolves in the negative electrode 22, causing magnesium to elute into the electrolyte, and the magnesium is absorbed in an ionic state in the positive electrode 21. On the other hand, during charge, magnesium is released in an ionic state from the positive electrode active material (sulfur-containing polymer compound) in the positive electrode 21 into the electrolyte, and the magnesium is precipitated at the negative electrode 22.

[0109] <1-3. Manufacturing Method> When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are each produced using the procedure of an example described below, and an electrolytic solution is prepared. Thereafter, the positive electrode 21, the negative electrode 22, and the electrolytic solution are used to assemble a secondary battery.

[0110] The following description will be given of the case where magnesium metal is used as the magnesium-containing material.

[0111] [Fabrication of Positive Electrode] First, a positive electrode active material (sulfur-containing polymer compound), a positive electrode binder, and a positive electrode conductive agent are mixed together to form a positive electrode mixture. Next, the positive electrode mixture is molded into a layer using a molding machine to form a positive electrode active material layer. Finally, the positive electrode active material layer is pressure-bonded to both sides of a positive electrode current collector using a compression device such as a molding machine and a roll press. This results in the fabrication of the positive electrode 21.

[0112] [Fabrication of Negative Electrode] Subsequently, a negative electrode active material (magnesium metal, which is a magnesium-containing material) is prepared as the negative electrode 22. In this case, magnesium foil is used as the magnesium-containing material.

[0113] [Preparation of Electrolyte Solution] An electrolyte solution is prepared by adding an electrolyte salt to a solvent.

[0114] [Assembly of Secondary Battery] First, the positive electrode lead 31 is connected to the positive electrode current collector of the positive electrode 21 using a joining method such as welding, and the negative electrode lead 32 is connected to the negative electrode 22 using a joining method such as welding.

[0115] Next, the positive electrode 21 and the negative electrode 22 are stacked one on top of the other with the separator 23 interposed therebetween, and then the positive electrode 21, the negative electrode 22, and the separator 23 are wound together to form a wound body (not shown). Next, the wound body is pressed using a compression device such as a press to form the wound body into a flat shape. The wound body after this formation has a configuration similar to that of the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with an electrolyte solution.

[0116] Next, after the roll is accommodated in the recess 10U, the exterior film 10 (adhesive layer / metal layer / surface protection layer) is folded to face each other. Next, the outer peripheral edges of two sides of the opposing adhesive layers are joined together using an adhesive method such as heat fusion, thereby accommodating the roll in the bag-shaped exterior film 10.

[0117] Finally, after injecting the electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining sides of the opposing fusion layers are joined together using an adhesive method such as heat fusion. In this case, a sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32.

[0118] As a result, the wound body is impregnated with the electrolyte, thereby producing the wound electrode body, which is the battery element 20. The battery element 20 is then sealed in the bag-shaped exterior film 10, thereby completing the secondary battery.

[0119] <1-4. Actions and Effects> In this secondary battery, the positive electrode 21 contains a sulfur-containing polymer compound, the negative electrode 22 contains a magnesium-containing material, and the electrolyte solution contains an electrolyte salt. The sulfur-containing polymer compound contains carbon, nitrogen, and sulfur as constituent elements and has a carbon-nitrogen bond and a carbon-sulfur bond. The electrolyte salt contains magnesium ions and lithium ions as cations and a halogen ion as an anion.

[0120] In this case, as described above, a series of actions described below are obtained.

[0121] First, because the positive electrode 21 contains a sulfur-containing polymer compound, magnesium is more likely to be absorbed and released in an ionic state in the positive electrode 21. This makes it easier for a charge-discharge reaction to proceed that utilizes the deposition and dissolution of magnesium compared to when the positive electrode 21 contains other materials such as elemental sulfur or a sulfur compound.

[0122] Specifically, when the positive electrode 21 contains elemental sulfur, sulfur is more likely to leach from the positive electrode 21 into the electrolyte. This causes a side reaction between the sulfur leachate in the electrolyte and the negative electrode 22, which tends to inhibit the charge-discharge reaction utilizing the deposition and dissolution of magnesium. In contrast, when the positive electrode 21 contains a sulfur-containing polymer compound, sulfur is less likely to leach from the positive electrode 21 into the electrolyte. This prevents the above-mentioned side reaction from occurring, which tends to stably facilitate the charge-discharge reaction utilizing the deposition and dissolution of magnesium.

[0123] Second, since the negative electrode 22 contains a magnesium-containing material, the charge-discharge reaction utilizing the deposition and dissolution of magnesium is more likely to proceed.

[0124] Third, since the electrolyte salt contains magnesium ions and lithium ions as cations, the voltage during discharge increases compared to when the electrolyte salt contains only magnesium ions as cations.

[0125] Fourth, since the electrolyte salt contains halogen ions as anions, the voltage during discharge increases more than when the electrolyte salt does not contain halogen ions as anions.

[0126] Therefore, when the electrolyte salt contains magnesium ions and lithium ions as cations and halogen ions as anions, the voltage during discharge increases significantly, and the charging reaction proceeds smoothly by utilizing the deposition and dissolution of magnesium, resulting in a high battery capacity.

[0127] These factors make it easier for the charge-discharge reaction utilizing the precipitation and dissolution of magnesium to proceed sufficiently and stably, thereby enabling excellent battery characteristics to be obtained.

[0128] In particular, if the sulfur-containing polymer compound includes a first annular portion, a second annular portion, and a connecting portion, each of the first annular portion and the second annular portion containing carbon and nitrogen as constituent elements, and the connecting portion containing sulfur as a constituent element (first sulfur-containing polymer compound), magnesium can be easily absorbed and released in an ionic state in the positive electrode 21, thereby achieving a greater effect.

[0129] In this case, if the sulfur-containing polymer compound contains a plurality of first cyclic portions, a plurality of second cyclic portions, and a plurality of linking portions, and the plurality of first cyclic portions are condensed with each other, and the plurality of second cyclic portions are condensed with each other, it becomes easier to synthesize a sulfur-containing compound having a sufficient molecular weight, and therefore, even greater effects can be obtained.

[0130] More specifically, if the sulfur-containing compound contains the polymer compound shown in formula (1), magnesium can be easily absorbed and released in an ionic state in the positive electrode 21, thereby achieving an even greater effect.

[0131] Furthermore, if the sulfur-containing polymer compound includes a plurality of ring portions and connecting portions, each of which contains carbon and nitrogen as constituent elements, and the connecting portions contain sulfur as a constituent element (second sulfur-containing polymer compound), magnesium can be easily absorbed and released in an ionic state in the positive electrode 21, thereby achieving a greater effect.

[0132] More specifically, if the sulfur-containing compound contains the polymer compound shown in formula (2), magnesium can be easily absorbed and released in an ionic state in the positive electrode 21, thereby achieving an even greater effect.

[0133] Furthermore, if the halogen ions contain chloride ions, the voltage during discharge increases sufficiently, and therefore a greater effect can be obtained.

[0134] Furthermore, if the solvent of the electrolyte solution contains an ether compound, the electrolyte salt is easily dissolved in the ether compound, and therefore the state of the electrolyte solution is stabilized, thereby achieving a greater effect.

[0135] Furthermore, if the magnesium-containing material contains magnesium metal, the charge-discharge reaction utilizing the deposition and dissolution of magnesium can proceed more easily, and therefore a greater effect can be obtained.

[0136] 2. Uses of Secondary Batteries There are no particular limitations on the uses (application examples) of secondary batteries. Secondary batteries used as power sources may be the main power source or auxiliary power source in electronic devices, electric vehicles, and the like. The main power source is a power source that is used preferentially regardless of the presence or absence of other power sources. The auxiliary power source may be a power source used in place of the main power source or a power source that can be switched from the main power source.

[0137] Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals; Storage devices such as backup power supplies and memory cards; Power tools such as power drills and power saws; Battery packs installed in electronic devices; Medical electronic devices such as pacemakers and hearing aids; Electric vehicles such as electric cars (including hybrid cars); Power storage systems such as home or industrial battery systems that store power in preparation for emergencies, etc. In these uses, only one secondary battery may be used, or two or more secondary batteries may be used.

[0138] The battery pack may use a single cell or a battery pack. The electric vehicle is a vehicle that runs on a secondary battery as a driving power source, and may be a hybrid vehicle that also has a driving source other than the secondary battery. In a home power storage system, power stored in a secondary battery, which is a power storage source, can be used to power home electrical appliances, etc.

[0139] An embodiment of the present technology will be described.

[0140] As will be described below, after the electrolyte solution and secondary battery were produced, the physical properties of the electrolyte solution and the battery characteristics of the secondary battery were evaluated.

[0141] Example 1 and Comparative Examples 1 to 3 Secondary batteries were manufactured according to the procedures described below, and then the battery characteristics of the secondary batteries were evaluated.

[0142] [Fabrication of Secondary Battery] A test secondary battery was fabricated to perform a simple evaluation of battery characteristics. Fig. 3 shows the cross-sectional structure of the test secondary battery, which was a coin-type magnesium-sulfur secondary battery.

[0143] In the following, the configuration of the test secondary battery will be described, and then the manufacturing procedure of the test secondary battery will be described.

[0144] (Configuration of Test Secondary Battery) As shown in FIG. 3, the test secondary battery includes a test electrode 51, a counter electrode 52, a separator 53, an outer cup 54, an outer can 55, a gasket 56, and an electrolyte (not shown).

[0145] The test electrode 51 is housed in an exterior cup 54, and the counter electrode 52 is housed in an exterior can 55. The test electrode 51 and the counter electrode 52 are stacked together with a separator 53 interposed therebetween, and the test electrode 51, the counter electrode 52, and the separator 53 are each impregnated with an electrolyte. The exterior cup 54 and the exterior can 55 are crimped together with a gasket 56, so that the test electrode 51, the counter electrode 52, and the separator 53 are sealed by the exterior cup 54 and the exterior can 55.

[0146] (Procedure for Manufacturing Test Secondary Battery) The procedure for manufacturing the test secondary battery is as follows.

[0147] First, 10 parts by mass of a positive electrode active material (sulfur-containing polymer compound), 30 parts by mass of a positive electrode binder (polytetrafluoroethylene, manufactured by AGC Inc.), and 60 parts by mass of a positive electrode conductive agent (ketjen black, ECP600JD, manufactured by Lion Corporation) were mixed together to prepare a positive electrode mixture.

[0148] As the sulfur-containing polymer compound, a compound represented by formula (1) (SIP, sulfurized polyacrylonitrile manufactured by Tokyo Chemical Industry Co., Ltd., sulfur content in the sulfur-containing polymer compound = 36 wt%) was used as the first sulfur-containing polymer compound.

[0149] Subsequently, the positive electrode mixture was molded into a layer using a roll press to form a positive electrode active material layer, and then the positive electrode active material layer was punched out into a disk shape (diameter = 15 mm).

[0150] Finally, a positive electrode active material layer was placed on one side of a disk-shaped positive electrode current collector (diameter = 15 mm), and then the positive electrode active material layer was pressure-bonded to the positive electrode current collector using a molding machine, thereby producing test electrode 51 (sulfur content in test electrode 51 = 10 wt %).

[0151] For comparison, sulfur element (S 8　 A test electrode 51 was fabricated in the same manner except that the test electrode 51 was fabricated using the same material.

[0152] Next, a magnesium foil (thickness = 200 μm) was prepared as a negative electrode active material (magnesium metal, which is a magnesium-containing material), and then the negative electrode active material was punched out into a disk shape (diameter = 16 mm), thereby producing a counter electrode 52.

[0153] Next, the electrolyte salt was added to the solvent, and the solvent was stirred to prepare an electrolyte solution.

[0154] The solvent used was tetrahydrofuran (TH), an ether compound (manufactured by Toyama Pharmaceutical Co., Ltd.).

[0155] The electrolyte salt is magnesium halide, magnesium chloride (MgCl 2　 , manufactured by Sigma-Aldrich Co.) and lithium halide, lithium chloride (LiCl, manufactured by Sigma-Aldrich Co.) were used.

[0156] Regarding the content of electrolyte salt in the electrolyte solution, the content of magnesium chloride was 1 mol / l (= 1 mol / dm 3　) and the content of lithium chloride in the solvent was 1 mol / l (= 1 mol / dm 3　 )

[0157] For comparison, an electrolyte solution was prepared in the same manner except that only magnesium chloride was used as the electrolyte salt without lithium chloride. The content of the electrolyte salt in the electrolyte solution was 2 mol / L (= 2 mol / dm 3　 )

[0158] For comparison, instead of the electrolyte salt lithium chloride, another electrolyte salt, bis(trifluoromethanesulfonyl)imide magnesium (MgTFSI 2　 The electrolyte solution was prepared in the same manner as above, except that the content of the electrolyte salt in the electrolyte solution was 0.4 mol / L (=0.4 mol / dm 3　 Regarding the content of other electrolyte salts in the electrolytic solution, the content of bis(trifluoromethanesulfonyl)imide magnesium was 0.4 mol / L (=0.4 mol / dm 3　 )

[0159] In this case, diethylene glycol dimethyl ether is used as the solvent instead of tetrahydrofuran because bis(trifluoromethanesulfonyl)imide magnesium does not dissolve unless diethylene glycol dimethyl ether is used.

[0160] Details regarding the combination of solvent and electrolyte salt are shown in Table 1.

[0161] After preparing the electrolyte solution, the electrolyte solution was analyzed using high-frequency inductively coupled plasma (ICP) atomic emission spectrometry, and the results confirmed that the contents of the electrolyte salt and the other electrolyte salt were as described above.

[0162] Next, the test electrode 51 was placed in the exterior cup 54, and the counter electrode 52 was placed in the exterior can 55. Next, the test electrode 51 placed in the exterior cup 54 and the counter electrode 52 placed in the exterior can 55 were stacked together with a separator 53 (glass fiber having a thickness of 200 μm, GC50 manufactured by Advantec Co., Ltd.) impregnated with an electrolyte interposed therebetween. In this case, the test electrode 51 was positioned so that the positive electrode active material layer faced the counter electrode 52 with the separator 53 interposed therebetween. Finally, with the test electrode 51 and the counter electrode 52 stacked together with the separator 53 interposed therebetween, the exterior cup 54 and the exterior can 55 were crimped together with a gasket 56. As a result, the test electrode 51 and the counter electrode 52 were sealed in the exterior cup 54 and the exterior can 55, completing a test secondary battery.

[0163] [Evaluation of Battery Characteristics] When the charge / discharge characteristics were evaluated as the battery characteristics, the results shown in Table 1 were obtained.

[0164] When evaluating the charge-discharge characteristics, the test secondary battery was repeatedly charged and discharged in a room temperature environment (temperature = 25°C) to measure the number of charge-discharge cycles (cycles), which is an index for evaluating the charge-discharge characteristics. This number of charge-discharge cycles is the number of times the test secondary battery could be charged and discharged while obtaining battery capacity.

[0165] During discharging, the battery was discharged at a constant current of 0.5 mA until the voltage reached 0.1 V, and during charging, the battery was charged at a constant current of 0.5 mA until the voltage reached 2.4 V.

[0166]

[0167] [Discussion] As shown in Table 1, the number of charge / discharge cycles when the counter electrode 52 contained a magnesium-containing material varied depending on the configuration of the test electrode 51 and the configuration of the electrolyte.

[0168] Specifically, when the electrolyte solution contained electrolyte salts (magnesium chloride and lithium chloride) but the test electrode 51 contained elemental sulfur (Comparative Example 1), the number of charge / discharge cycles was 0, and therefore charge / discharge was fundamentally impossible.

[0169] Similarly, in the case where the test electrode 51 contained a sulfur-containing polymer compound but the electrolyte solution contained an electrolyte salt (only magnesium chloride) (Comparative Example 2), the number of charge / discharge cycles was 0, so that charge / discharge was fundamentally impossible.

[0170] Similarly, in the case where the test electrode 51 contained a sulfur-containing polymer compound but the electrolyte solution contained an electrolyte salt (magnesium chloride) and another electrolyte salt (magnesium bis(trifluoromethanesulfonyl)imide) (Comparative Example 3), the number of charge / discharge cycles was 0, and thus charge / discharge was fundamentally impossible.

[0171] In contrast, when the test electrode 51 contained a sulfur-containing polymer compound and the electrolyte solution contained an electrolyte salt (magnesium chloride and lithium chloride (Example 1)), the number of charge / discharge cycles was 32, and charge / discharge was possible.

[0172] In this case, in particular, a series of trends described below were obtained. First, when the first sulfur-containing polymer compound was used as the sulfur-containing polymer compound, the number of charge / discharge cycles was sufficiently increased. In this case, a similar trend should be obtained even when the second sulfur-containing polymer compound was used as the sulfur-containing polymer compound. Second, when the electrolyte salt contained chloride ions as anions (halogen ions), the number of charge / discharge cycles was sufficiently increased. Third, when the solvent contained an ether compound, a sufficient number of charge / discharge cycles was obtained. Fourth, when the magnesium-containing material contained magnesium metal, a sufficient number of charge / discharge cycles was obtained.

[0173] [Summary] From the results shown in Table 1, when the positive electrode 21 contains a sulfur-containing polymer compound, the negative electrode contains a magnesium-containing material, and the electrolyte salt of the electrolyte solution contains magnesium ions and lithium ions as cations and halogen ions as anions, the number of charge / discharge cycles increased. Therefore, the charge / discharge characteristics were improved, and excellent battery characteristics were obtained.

[0174] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0175] Specifically, the battery structure of the secondary battery has been described as being of a laminate film type and a coin type. However, the battery structure of the secondary battery is not particularly limited, and may be of a cylindrical type, a square type, a button type, or the like.

[0176] The battery element has been described as having a wound structure. However, the structure of the battery element is not particularly limited, and may be a stacked structure or a zigzag structure. In the stacked structure, the positive and negative electrodes are stacked on top of each other, and in the zigzag structure, the positive and negative electrodes are folded in a zigzag pattern.

[0177] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0178] The present technology may also be configured as follows: <1> A secondary battery comprising: a positive electrode containing a sulfur-containing polymer compound; a negative electrode containing a magnesium-containing material; and an electrolyte solution containing an electrolyte salt, wherein the sulfur-containing polymer compound contains carbon, nitrogen, and sulfur as constituent elements and has a carbon-nitrogen bond and a carbon-sulfur bond, and the electrolyte salt contains magnesium ions and lithium ions as cations and halogen ions as anions. <2> The secondary battery according to <1>, wherein the sulfur-containing polymer compound includes first and second annular portions spaced apart from each other; and connecting portions disposed between the first and second annular portions and connected to each of the first and second annular portions, wherein each of the first and second annular portions contains carbon and nitrogen as constituent elements, and the connecting portions contain sulfur as a constituent element. <3> The secondary battery according to <2>, wherein the sulfur-containing polymer compound includes a plurality of the first cyclic portions, a plurality of the second cyclic portions, and a plurality of the linking portions, wherein the plurality of first cyclic portions are condensed with each other, and the plurality of second cyclic portions are condensed with each other. <4> The secondary battery according to <2> or <3>, wherein the sulfur-containing polymer compound includes a compound represented by formula (1). (n1 is an integer of 1 or more.) <5> The secondary battery according to <1>, wherein the sulfur-containing polymer compound includes a plurality of cyclic portions condensed with each other and a linking portion linking any two of the plurality of cyclic portions, wherein each of the plurality of cyclic portions includes carbon and nitrogen as constituent elements, and the linking portion includes sulfur as a constituent element. <6> The secondary battery according to <5>, wherein the sulfur-containing polymer compound includes a compound represented by formula (2). (n2 is an integer of 1 or more.) <7> The secondary battery according to any one of <1> to <6>, wherein the halogen ions include chloride ions. <8> The secondary battery according to any one of <1> to <7>, wherein the electrolytic solution includes a solvent, and the solvent includes an ether compound. <9> The magnesium-containing material includes elemental magnesium. The secondary battery according to any one of <1> to <8>.

[0179] 21...positive electrode, 22...negative electrode

Claims

1. a positive electrode including a sulfur-containing polymer compound; a negative electrode including a magnesium-containing material; an electrolyte solution containing an electrolyte salt; Equipped with The sulfur-containing polymer compound contains carbon, nitrogen, and sulfur as constituent elements, and has a carbon-nitrogen bond and a carbon-sulfur bond, The electrolyte salt contains magnesium ions and lithium ions as cations and halogen ions as anions. Secondary battery.

2. The sulfur-containing polymer compound is a first annular portion and a second annular portion spaced apart from one another; a connecting portion disposed between the first annular portion and the second annular portion and connected to each of the first annular portion and the second annular portion; Including, each of the first annular portion and the second annular portion contains carbon and nitrogen as constituent elements; The connecting portion contains sulfur as a constituent element. The secondary battery according to claim 1 .

3. the sulfur-containing polymer compound includes a plurality of the first cyclic portions, a plurality of the second cyclic portions, and a plurality of the linking portions, the plurality of first annular portions are condensed with one another, the plurality of second annular portions are condensed with each other; The secondary battery according to claim 2 .

4. The sulfur-containing polymer compound includes a compound represented by formula (1): The secondary battery according to claim 2 . 【Chemistry 1】 (n1 is an integer of 1 or more.)

5. The sulfur-containing polymer compound is a plurality of cyclic moieties fused together; a connecting portion connected to any two of the plurality of annular portions; Including, each of the plurality of annular portions contains carbon and nitrogen as constituent elements; The connecting portion contains sulfur as a constituent element. The secondary battery according to claim 1 .

6. The sulfur-containing polymer compound includes a compound represented by formula (2): The secondary battery according to claim 5 . 【Chemistry 2】 (n2 is an integer of 1 or more.)

7. The halogen ions include chloride ions. The secondary battery according to claim 1 .

8. The electrolyte solution contains a solvent, The solvent includes an ether compound. The secondary battery according to claim 1 .

9. The magnesium-containing material includes magnesium as an elemental element. The secondary battery according to claim 1 .

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