JP2010192385A - Sulfur battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable highly efficient utilization of sulfur, and to enhance the preservation characteristics, charge and discharge efficiency and battery capacity, for a sulfur battery. <P>SOLUTION: An evaluation cell 10 is provided with a cathode 20 containing sulfur; an anode 16 containing alkali metals; a solid electrolyte membrane 19 arranged between the cathode 20 and the anode 16; and an electrolyte solution at least interposed between the cathode 20 and the solid electrolyte membrane 19. In a first configuration, the solid electrolyte membrane 19 contains a polymer combination body having imides. Here, the combination body shows either a copolymer or a crosslinking body. The crosslinking may be either through covalent bonding or forming an imide salt with the use of multivalent cations. Additionally, in a second configuration, the solid electrolyte membrane 19 contains polymer with borons. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sulfur battery.

  Conventionally, sulfur batteries using sulfur as a positive electrode active material are known. Sulfur has a very high theoretical capacity density of 1675 mAh / g, and therefore can be expected as a high capacity battery. However, in an electrolyte-based sulfur battery, sulfur molecules, polysulfide ions, etc. may be dissolved and diffused into the electrolyte during charge / discharge, which reacts with the negative electrode metal to cause self-discharge, resulting in storage characteristics and Charge / discharge efficiency may be degraded. Also, in all-solid electrolyte batteries, it is difficult to ensure conductivity because sulfur is an insulator, and the effective utilization rate of sulfur may decrease, and the high capacity expected for sulfur batteries cannot be obtained. was there.

  Thus, for example, Patent Document 1 proposes to appropriately select a cell configuration and an electrolyte to increase the effective utilization rate of sulfur, that is, to bring the battery capacity per unit sulfur amount closer to the theoretical capacity. For example, Patent Document 2 proposes to protect the negative electrode by forming an inorganic solid electrolyte film as a protective layer on the negative electrode metal as an intermediate between the electrolyte system and the all solid electrolyte system. Further, for example, in Patent Document 3, in a non-aqueous electrolyte lithium-sulfur battery using lithium as a negative electrode, a battery containing sulfur coated with a polymer electrolyte as a positive electrode is used, and a polymer is interposed between the positive electrode and the separator or between the negative electrode and the separator. It has been proposed that by disposing an electrolyte, self-discharge caused by diffusion of lithium polysulfide produced at the positive electrode to the negative electrode is suppressed, and charge / discharge cycle characteristics are improved.

JP-T-2001-520447 JP-T-2002-513991 JP 2003-242964 A

  However, since the battery of Patent Document 1 does not suppress diffusion of sulfur and the like to the negative electrode side, it is not sufficient for suppressing self-discharge and charge / discharge efficiency reduction. Moreover, since the battery of patent document 2 uses a brittle inorganic solid electrolyte membrane, there were problems that the electrolyte membrane was cracked or an efficient cell configuration could not be achieved. Moreover, in the battery described in Patent Document 3, lithium polysulfide is suppressed from diffusing to the negative electrode using a flexible polymer electrolyte, but this is not sufficient, for example, a charge / discharge cycle was performed. Even later, it was desired to have a higher battery capacity.

  The present invention has been made in view of such problems, and its main purpose is to provide a sulfur battery with better storage characteristics, charge / discharge efficiency, and battery capacity while enabling high-efficiency utilization of sulfur. To do.

  As a result of diligent research in order to achieve the above-described object, the present inventors have found that a solid electrolyte membrane having a polymer-bonded polymer having an imide or a solid electrolyte membrane having a polymer having boron is used in an electrolyte-based sulfur battery. It is placed between the negative electrode and the positive electrode, and by interposing an electrolyte between at least the positive electrode and the solid electrolyte, it enables high-efficiency use of sulfur, while improving storage characteristics, charge / discharge efficiency, and battery capacity. The inventors have found what can be done and have completed the present invention.

That is, the sulfur battery of the first aspect of the present invention is
A positive electrode containing sulfur;
A negative electrode containing an alkali metal;
A solid electrolyte membrane disposed between the positive electrode and the negative electrode and having a polymer conjugate with an imide;
An electrolytic solution interposed between at least the positive electrode and the solid electrolyte membrane;
It is equipped with.

In addition, the sulfur battery of the second aspect of the present invention is
A positive electrode containing sulfur;
A negative electrode containing an alkali metal;
A solid electrolyte membrane disposed between the positive electrode and the negative electrode and having a polymer with boron;
An electrolytic solution interposed between at least the positive electrode and the solid electrolyte membrane;
It is equipped with.

  With this sulfur battery, it is possible to improve the storage characteristics, charge / discharge efficiency, and battery capacity while enabling highly efficient use of sulfur. The reason why such an effect is obtained is not clear, but is presumed as follows. That is, the presence of the electrolyte solution between the positive electrode and the solid electrolyte membrane dissolves sulfur molecules and polysulfide ions generated in the positive electrode in the electrolyte solution. Therefore, the efficiency of the active material supply becomes better. For this reason, highly efficient utilization of sulfur is attained. Further, the solid electrolyte membrane of the present invention is a cation exchange membrane and therefore has a blocking ability of polysulfide ions as anions, and since it is a solid membrane, it is a neutral molecule of sulfur molecules (usually octamers). There is also the ability to suppress permeation. This prevents diffusion of polysulfide ions and sulfur molecules formed on the positive electrode by charging and discharging to the negative electrode side, thereby suppressing self-discharge on the negative electrode, storage characteristics after charging and charging and discharging efficiency, battery Capacity is good. Therefore, by combining the electrolytic solution and the solid electrolyte membrane of the present invention, it is presumed that the storage characteristics, the charge / discharge efficiency, and the battery capacity can be improved while enabling high-efficiency use of sulfur.

2 is a cross-sectional view illustrating a schematic configuration of an evaluation cell 10. FIG.

  A sulfur battery according to a first aspect of the present invention includes a positive electrode containing sulfur, a negative electrode containing an alkali metal, a solid electrolyte membrane disposed between the positive electrode and the negative electrode, and having a polymer combination having an imide. And at least an electrolyte solution interposed between the positive electrode and the solid electrolyte membrane. The sulfur battery of the second aspect of the present invention is a positive electrode containing sulfur, a negative electrode containing an alkali metal, a solid electrolyte membrane having a polymer with boron disposed between the positive electrode and the negative electrode, And at least an electrolytic solution interposed between the positive electrode and the solid electrolyte membrane. Examples of the alkali metal include lithium, sodium, and potassium, among which lithium having a high theoretical capacity density is preferable. For convenience of explanation, description will be made using lithium below. That is, a lithium sulfur battery will be described.

  In the sulfur battery of the present invention, the positive electrode is not particularly limited as long as it contains sulfur as a positive electrode active material. Sulfur may be a simple substance of sulfur or a sulfur compound such as metal polysulfide. For this positive electrode, for example, a positive electrode active material, a conductive material, and a binder are mixed, and an appropriate solvent is added to form a paste-like positive electrode material, which is applied to the surface of the current collector and dried. It may be formed by compressing to increase the electrode density. Here, the conductive material is not particularly limited as long as it is a conductive material. For example, carbon blacks such as ketjen black, acetylene black, channel black, furnace black, lamp black, and thermal black may be used. Natural graphite such as flake graphite, artificial graphite, graphite such as expanded graphite, conductive fibers such as carbon fiber and metal fiber, or metal powder such as copper, silver, nickel, and aluminum may be used. Alternatively, an organic conductive material such as a polyphenylene derivative may be used. Moreover, these may be used independently and may be used in mixture of two or more. Although it does not specifically limit as a binder, A thermoplastic resin, a thermosetting resin, etc. are mentioned. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin) , Polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrif Examples include olefin copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and ethylene-acrylic acid copolymer. . These materials may be used alone or in combination. As the current collector, a metal plate such as stainless steel, aluminum, copper, nickel, or a metal mesh can be used.

  In the sulfur battery of the present invention, the negative electrode may include a material that absorbs and releases lithium. Here, examples of the material that occludes and releases lithium include metal oxides, metal sulfides, and carbonaceous substances that occlude and release lithium in addition to metal lithium and lithium alloys. Examples of the lithium alloy include alloys of lithium with aluminum, silicon, tin, magnesium, indium, calcium, and the like. Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide. Examples of the metal sulfide include tin sulfide and titanium sulfide. Examples of the carbonaceous material that occludes and releases lithium include graphite, coke, mesophase pitch carbon fiber, spherical carbon, and resin-fired carbon. For this negative electrode, a current collector, a conductive material, and a binder can be used as appropriate as in the case of the positive electrode.

  In the sulfur battery of the present invention, the solid electrolyte membrane disposed between the positive electrode and the negative electrode has a polymer combination having an imide in the first form, and has boron in the second form. It has a polymer. The solid electrolyte membrane may have a sulfonic acid group. These solid electrolyte membranes have a common function in shielding sulfide ions, polysulfide ions, and sulfur molecules and selectively permeating lithium ions.

  In the sulfur battery according to the first aspect of the present invention, the solid electrolyte membrane has a polymer conjugate having an imide. Here, the polymer conjugate refers to a polymer in which one or more kinds of polymers are bonded by crosslinking or polymerization. Examples of such a polymer conjugate include a conjugate containing a sulfonimide such as poly (perfluoroalkylenesulfonimide). Of these, a conjugate containing poly (perfluorotrimethylenesulfonimide) (see formula (1), hereinafter also referred to as PTSI) is preferable. Here, M is a metal and is preferably an alkali metal. N is a positive number satisfying n ≧ 1. By the way, when PTSI is not a conjugate, it is highly swellable with a polar solvent and often does not form a film. In addition, if the degree of swelling is high, sulfur or sulfide ions to be blocked may be transmitted. For this reason, PTSI needs to be a conjugate. As the PTSI conjugate, a copolymer of PTSI and polysulfone is preferable, and a block copolymer is more preferable. Alternatively, a crosslinked product in which PTSI is bonded to the 1,3,5 position of the benzene skeleton (see Japanese Patent Application No. 2006-86261 (WO007 / 114406)) is preferable. The cross-linked product described above preferably has a molar ratio of 3-substituted benzene to sulfonimide of 2: 3. With such a crosslinked body, it is presumed that the degree of crosslinking is more appropriate. Examples of the crosslinking method include a method of crosslinking by covalent bond, a method of crosslinking by forming an imide salt using a polyvalent cation, and a combination thereof may be used. When cross-linking is performed using a polyvalent cation, PTSI becomes a cross-linked product by substituting M in the formula (1) with a polyvalent cation. Examples of the cation used for crosslinking include calcium, magnesium, and aluminum which have a high ionization tendency. Moreover, it is preferable that it is a bivalent cation. Among these, calcium is more preferable because it has a high ionization tendency and exists stably as ions. The polyvalent cation is preferably 15% or more of the imide exchange capacity. When 100% of the imide exchange capacity is exchanged with a polyvalent cation, it is expected that the permeation of lithium ions will be inhibited, but in reality, even if treated with a large excess of an aqueous polyvalent cation carbonate solution, all will be exchanged. There seems to be no problem. However, if the amount of the polyvalent cation is too small, the degree of cross-linking decreases, and if it is excessive, the lithium ion permeation may be inhibited. Therefore, the polyvalent cation may be about 50% of the imide exchange capacity. More preferred. When the imide before cross-linking with a polyvalent cation is present in the form of a metal salt such as Li, the cross-linked product is immersed in a predetermined amount of polyvalent ion carbonate aqueous solution after making the imide salt into a proton. It is preferable that it is obtained by the method to do. This is because the crosslinking reaction becomes better. The polymer imide-containing conjugate can be used as a free-standing film, but preferably has a structure in which the porous film is impregnated. When the porous membrane is impregnated with a polymer combination having an imide, it is preferable to impregnate the porous membrane with the polymer having an imide and then perform the above-described polymerization or crosslinking. Hereinafter, a block copolymer of PTSI and polysulfone is also referred to as PTSIPS (poly (perfluorotrimethylenesulfonimide) / polysulfone block copolymer). In addition, a porous film impregnated with PTSI and crosslinked is also referred to as FINP (filling imide network polymer). Since the characteristics of FINP vary depending on the thickness and the degree of crosslinking, the optimal one should be selected as appropriate. When the degree of crosslinking is low, the lithium ion permeability is high, but it easily swells and tends to cause a reduction in the shielding ability of polysulfide ions, sulfide ions, and sulfur molecules. On the other hand, if the film thickness is too thick or the cross-linking degree is too high, the resistance increases and it is likely to cause a voltage drop. Therefore, a structure in which a film having a high degree of crosslinking and a film having a high effect of shielding sulfur or the like may be stacked on a film having a high lithium ion permeability and a low degree of crosslinking. By doing so, it is presumed that both low resistance and high selectivity can be achieved.

  In the sulfur battery according to the second aspect of the present invention, the solid electrolyte membrane is a polymer having boron in its structure. This is because the anion is trapped by the Lewis acidity of boron, and Li transport occurs selectively. As a result, polysulfide ions and sulfide ions, which are anions, are difficult to permeate the electrolyte membrane, and it can be expected to prevent diffusion of sulfur, which is a neutral molecule, by a solid membrane. It is considered that the reaction between ions, sulfur and the negative electrode can be suppressed. The polymer having boron in the structure is preferably a polymer in which an electron withdrawing group is bonded to boron, and examples thereof include a borate ester and a borane derivative substituted with a fluorophenyl group. Specifically, as a polymer of a boric acid ester compound having a double bond as disclosed in JP-A-2008-117762, for example, poly (ethylene glycol monomethacrylate) having a boric acid ester in the ester portion of an acrylic acid polymer. ) Polyelectrolyte polymers comprising borate or poly (ethylene glycol monoacrylate borate) and a polyether polymer compound such as polyethylene glycol dimethyl ether. In addition, a borane derivative polymer having a triphenylborane structure having a trisubstituted borane structure as a pendant group bonded to the main chain at the phenyl group portion, or a borane in which perfluorophenylborane in which hydrogen of the phenyl group is substituted with fluorine is a pendant group It may be a derivative polymer. Further, it may be a structure containing boron having an anion trapping ability, and may be a boron polymer in which a borane or boric acid structure is not in the pendant group but in the main chain of the polymer. The thickness of the solid electrolyte membrane is preferably 10 μm or more and 1 mm or less, and more preferably 10 μm or more and 500 μm or less. A thickness of 10 μm or more is preferable because it is sufficient to prevent an electrical short circuit during use and pinholes are not easily generated. Moreover, if it is 500 micrometers or less, since there is little voltage drop by an electrical resistance, it is preferable.

In the sulfur battery of the present invention, the electrolytic solution is interposed at least between the positive electrode and the solid electrolyte membrane. By doing so, since polysulfide ions, sulfide ions, and sulfur molecules generated at the positive electrode are dissolved in the electrolyte, the efficiency of supplying the active material is higher than when only a solid electrolyte is used. It seems to be good. As such a configuration, for example, a configuration in which the positive electrode or the negative electrode is in contact with the solid electrolyte membrane in an impregnated state with the electrolytic solution may be employed. By doing in this way, a solid electrolyte membrane will also have a function which prevents an electrical short circuit. Moreover, it is good also as a structure which contacts a positive electrode in the state which impregnated electrolyte solution in the solid electrolyte membrane. Note that the electrolyte does not have to be interposed between the negative electrode and the solid electrolyte membrane. However, when the contact state between the solids is not good, the ionic conduction can be improved by the electrolytic solution. It is preferable that an electrolytic solution is interposed between the electrode and the solid electrolyte membrane. The electrolytic solution may be a solution in which a supporting salt is dissolved in a solvent. The supporting salt is not particularly limited as long as it is a lithium salt used in a normal lithium secondary battery. For example, Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N , LiPF ₆ , LiClO ₄ , LiBF ₄ , and other known supporting salts can be used. These may be used alone or in combination. The solvent of the electrolytic solution is not particularly limited as long as it is non-proton-donating and used in a normal lithium secondary battery, but ethers such as dimethoxyethane (DME), triglyme and tetraglyme, dioxolane (DOL), Cyclic ethers such as tetrahydrofuran and mixtures thereof are preferred. Alternatively, ionic liquids such as 1-methyl-3-propylimidazolium bis (trifluorosulfonyl) imide and 1-ethyl-3-butylimidazolium tetrafluoroborate can be used. The electrolytic solution only needs to be interposed at least between the positive electrode and the solid electrolyte membrane, and may be impregnated in a porous separator or the like, or a polymer such as polyvinylidene fluoride, polyethylene oxide, polyethylene glycol, or polyacrylonitrile. Or an saccharide such as an amino acid derivative or a sorbitol derivative may be gelled by containing an electrolyte solution containing a supporting salt. Also, in sulfur batteries, the amount of active material that can be effectively used may decrease due to the dissolution of the active material (sulfur, polysulfide ions, etc.) in the solution, so polysulfide ions, etc. are added to the electrolyte beforehand. You may keep it.

  The sulfur battery of the present invention may include a separator between the negative electrode and the positive electrode. The separator may be disposed between the positive electrode and the solid electrolyte membrane, may be disposed between the negative electrode and the solid electrolyte membrane, or both. Among these, it is preferable to dispose between the positive electrode and the solid electrolyte membrane because the electrolytic solution between the positive electrode and the solid electrolyte membrane is easily retained. The separator is not particularly limited as long as it has a composition that can withstand the use range of the secondary battery. For example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a microporous film of an olefin resin such as polyethylene or polypropylene Is mentioned. These may be used alone or in combination.

  The shape of the sulfur battery of the present invention is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, the lithium sulfur battery in which the alkali metal contained in the negative electrode is lithium has been described, but the alkali metal contained in the negative electrode may be sodium or potassium.

[Experimental example A1]
(1) Production of Solid Electrolyte Membrane (PTSIPS Membrane) First, OH-terminated poly (ether ether sulfone) serving as a hydrophobic portion of PTSIPS was synthesized as follows. Three-necked flask 500ml connected a Dean-Stark tube and a three-way stopcock, a bisphenol 8.5 g (46 mmol), bis - (4-chlorophenyl) sulfone 12 g (42 mmol), K ₂ CO ₃ and 25 g (0. 18 mol) and vacuumed for 1 hour to dry. Thereafter, 65 ml of commercially available dehydrated dimethylacetamide (DMAc) and 65 ml of toluene were added, heated at 100 ° C. for 1 hour, then heated to 165 ° C. over 3 hours, and the water produced was azeotroped with toluene. At the same time, water was removed from the reaction system. After further reacting at 165 ° C. for 3 days, an excess amount of 4.2 g (23 mmol) of bisphenol was added, and further reacted at the same temperature for 1 day. The inorganic salt precipitated after the reaction was filtered, and then the polymerization solution was reprecipitated in ethanol and vacuum-dried for 12 hours or longer to obtain the desired product (16 g, yield 88%). The synthesis method is shown below (see formula (2)). The degree of polymerization h of the obtained target product was measured by NMR and found to be 14.5. Hereinafter, this polymer is also referred to as OH-terminated PEES (h = 14.5).

  Next, K body F-Ph terminal poly (perfluorotrimethylene sulfonimide), which becomes the hydrophilic part of PTSIPS, was synthesized as follows. In a 200 ml flask, 20 g (65 mmol) of perfluorotrimethylene-1,3-disulfonamide (PTMDSA, see formula (3)), perfluorotrimethylene-1,3-disulfonyl fluoride (PTMDSF, formula (4)) 18 g (57 mmol) and 20 ml of acetonitrile were added. Next, 50 ml (0.29 mol) of diisopropylethylamine was added and heated at 80 ° C. for 48 hours. Thereafter, volatile components were distilled off, 1N NaOH aqueous solution was added, and then the organic layer was extracted with acetonitrile. The solvent was distilled off with an evaporator, 1N HCl aqueous solution was added until the solution was acidic, the solvent was removed with an evaporator, and the organic substance was extracted with acetonitrile to remove the salt. The acetonitrile extract was evaporated, dissolved in a small amount of acetonitrile, filtered through celite, and dried under reduced pressure at 80 ° C. 39 g (8.5 mmol) of this, 5.0 g (26 mmol) of 4-fluorobenzenesulfonyl chloride, and 50 ml of acetonitrile were added to a 200 ml flask. Furthermore, 30 ml (0.17 mol) of diisopropylethylamine was added and heated at 80 ° C. overnight. Thereafter, the solvent was distilled off, 1N aqueous KOH solution and a small amount of acetonitrile were added, and the aqueous layer was removed by decantation. This operation was repeated 5 times, and the organic solvent was distilled off with an evaporator. Thereafter, the salt was removed by celite filtration with acetonitrile, and the residue was dried under reduced pressure to obtain the desired product (41 g, yield 51%). The synthesis method is shown below (see formula (5)). The synthetic polymerization degree j was measured by NMR and found to be 20.5. Hereinafter, this polymer is also referred to as K-form F-Ph terminal PTSI (j = 20.5).

Using the thus obtained OH-terminated PEES (h = 14.5) and K-form F-Ph-terminated PTSI (j = 20.5), PTSIPS was synthesized as follows. In a 100 ml two-necked eggplant-shaped flask connected to a Dean-Stark tube and a three-way cock, 15 g of the OH-terminated PEES (h = 14.5) synthesized above (OH end group amount 5.1 mmol), K-form F- 19 g Ph-terminal PTSI (j = 20.5) (F-Ph end group amount 5.1 mmol), 1.4 g (10 mmol) K ₂ CO ₃ and 2.7 g (10 mmol) 18-crown-6 were added. Dry under vacuum for 1 hour. Thereafter, 300 ml of dehydrated DMAc and 250 ml of toluene were added, heated at 100 ° C. for 1 hour, gradually heated to 165 ° C., the produced water was azeotroped with toluene, and water was removed from the reaction system together with toluene. . The reaction was further carried out at 165 ° C. for 14 days. After the reaction, the polymerization solution was filtered, and the mother liquor was added to 1N HCl aqueous solution for reprecipitation. The recovered precipitate was dissolved in acetonitrile and filtered, and acetonitrile in the mother liquor was distilled off to obtain the desired product (29 g, yield 87%, ion exchange capacity EW 661 g / eq.). The synthesis scheme is shown below (Formula (6)). This was dissolved in dimethylformamide (DMF), impregnated into a porous polyethylene film until the porous material became transparent at the time of drying, and repeatedly dried by heating at 80 ° C. to obtain a PTSIPS film. This membrane was treated with a 1N aqueous hydrochloric acid solution, further treated with a 1 wt% aqueous lithium carbonate solution, washed with water and dried to obtain a Li-type PTSIPS membrane.

(2) Production of evaluation cell The positive electrode was produced as follows. First, sulfur powder (average particle diameter of 75 μm or less, purity 99.99%, manufactured by High Purity Chemical), conductive assistant carbon (ECP600JD, manufactured by Lion), and binder, polytetrafluoroethylene (PTFE), 50: The mixture was mixed at a weight ratio of 40:10, ethanol was added, kneaded until it became a bowl-like shape, molded into a sheet, and then dried. This was cut into a diameter of 12 mm to obtain a positive electrode. At this time, the weight of the positive electrode was 3 to 4 mg. As the negative electrode, metallic lithium having a thickness of 0.4 mm and a diameter of 18 mm was used. The electrolyte was 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) mixed at a volume ratio of 9: 1, and lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) was added at 1 mol / L. What was melt | dissolved so that it might become a density | concentration was used. As the solid electrolyte membrane, PTSIPS (film thickness 40 μm) obtained by the above-described method was used.

  An evaluation cell was produced using the positive electrode, negative electrode, electrolytic solution, and solid electrolyte membrane thus obtained. FIG. 1 is an explanatory view of an evaluation cell, FIG. 1 (a) is a cross-sectional view before the evaluation cell 10 is assembled, and FIG. 1 (b) is a cross-sectional view after the evaluation cell 10 is assembled. In assembling the evaluation cell 10, first, a negative electrode 16 (the above-described metal lithium having a thickness of 0.4 mm and φ18 mm is formed in a cavity 14 provided in the center of the upper surface of a stainless steel cylindrical base 12 having a thread groove on the outer peripheral surface. ), A separator 18 (microporous polyethylene membrane, manufactured by Tonen Chemical Co., Ltd.), a solid electrolyte membrane 19, a separator 18, and a positive electrode 20 (a positive electrode having a diameter of 12 mm described above) are laminated in this order. Next, after injecting about 0.1 mL of the above-described non-aqueous electrolyte into the cavity 14, a polypropylene insulating ring 29 is inserted, and then a conductive cylinder 24 liquid-tightly fixed in the hole of the insulating ring 22. Is placed on the positive electrode 20, and a conductive cup-shaped lid 26 is screwed into the cylindrical substrate 12. Further, an insulating resin ring 27 is arranged on the cylinder 24, and a pressure bolt 25 having a through hole 25a is screwed into a screw groove carved in an inner peripheral surface of an opening 26a provided at the center of the upper surface of the lid 26, The negative electrode 16, the separator 18, the solid electrolyte membrane 18, and the positive electrode 20 are pressed and adhered. In this way, the evaluation cell 10 can be manufactured. The cylinder 24 is positioned below the upper surface of the ring 22 and is in contact with the lid 26 via the insulating resin ring 27, so that the lid 26 and the cylinder 24 are not in contact with each other. Further, since the packing 28 is disposed around the cavity 14, the electrolyte injected into the cavity 14 does not leak outside. In this evaluation cell 10, the lid 26, the pressure bolt 25, and the cylindrical base 12 are integrated with the negative electrode 16, so that the whole becomes the negative electrode side, and the column 24 is integrated with the positive electrode 20 and insulated from the negative electrode 16. Therefore, it becomes the positive electrode side. The evaluation cell thus obtained was designated as Experimental Example 1.

[Experiment A2]
(1) Production of solid electrolyte membrane (highly crosslinked FINP membrane) First, benzene-1,3,5-sulfonamide (1,3,5-substituted benzene) (BTSA, see formula (7)) and PTMDSF (formula ( 4) was weighed to a molar ratio of 1: 1.5. These were stirred for 1 hour in a solution prepared such that acetonitrile and tetraethylamine (both manufactured by Wako Pure Chemical Industries, Ltd.) had a weight ratio of 4.000: 5.721 to obtain a material monomer solution. The obtained material monomer solution was impregnated into a porous polyethylene membrane (film thickness 50 μm, manufactured by DSM Soltech) in a vial bottle, irradiated with ultrasonic waves for 3 minutes, reacted at 50 ° C. for 24 hours, and further at 90 ° C. Heated for 24 hours. Thereafter, the mixture was stirred for 12 hours at room temperature in a solution composed of 15% by volume nitric acid and 85% by volume ethanol, and then stirred for 15 hours in a 15% nitric acid solution under a temperature condition of 50 ° C. (Film thickness 36 μm, ion exchange capacity ˜3 meq / g) was obtained.

(2) Production of Evaluation Cell An evaluation cell was produced in the same manner as in Experimental Example A1 except that the highly crosslinked FINP membrane thus obtained was used as a solid electrolyte membrane, and designated as Experimental Example A2.

[Experiment A3]
(1) Production of solid electrolyte membrane (FINP membrane) BTSA (see formula (7)), PTMDSF (see formula (4)), and PTMDSA (see formula (3)) are 1: 4.5: 3 Li-type FINP membrane (film thickness 40 μm, ion exchange capacity ˜3 meq / g) in the same manner as in Experimental Example A2, except that a porous polyethylene membrane having a thickness of 60 μm was used. Got.

(2) Production of Evaluation Cell An evaluation cell was produced in the same manner as in Experimental Example A1 except that the FINP membrane thus obtained was used as a solid electrolyte membrane, and designated as Experimental Example A3.

[Experiment A4]
(1) Production of Solid Electrolyte Membrane (FINP Membrane) A Li-type FINP membrane (film thickness of 30 μm, ion) was used in the same manner as in Experiment A3 except that a porous polyethylene membrane having the same thickness of 50 μm as in Experiment A2 was used. Exchange capacity ˜3 meq / g) was obtained.

(2) Production of Evaluation Cell An evaluation cell was produced in the same manner as in Experimental Example A1 except that the FINP membrane thus produced was used as a solid electrolyte membrane, and designated as Experimental Example A4.

[Experiment A5]
The FINP membrane (Li body) used in Experimental Example A4 was treated with hydrochloric acid with 1N hydrochloric acid, washed with water, and lithium was protonated, and then immersed in saturated lime water in an amount equivalent to 50% of the imide salt exchange capacity for 1 hour. Ion exchange was performed to form a crosslinked structure. At this time, the lime water has changed to neutral, and 50% of the exchange capacity has been exchanged for Ca ions. This was washed with water, dipped in a 1 wt% lithium carbonate aqueous solution, and lithium exchanged. This was dried to obtain a FINP film. An evaluation cell was produced in the same manner as in Experimental Example A1 except that the FINP membrane thus obtained was used as a solid electrolyte membrane, and this was designated as Experimental Example A5.

[Experiment A6]
The FINP membrane (Li body) used in Experimental Example A3 was treated with hydrochloric acid with 1N hydrochloric acid, washed with water, lithium was proton-substituted, and then immersed in saturated lime water in an amount equivalent to 15% of the imide salt exchange capacity for 1 hour. A FINP film was obtained in the same manner as in Experimental Example A5. An evaluation cell was prepared in the same manner as in Experimental Example A1 except that the FINP membrane thus obtained was used as a solid electrolyte membrane, and this was designated as Experimental Example A6.

[Experiment A7]
Experiments were conducted except that the FINP film (Li body) used in Experimental Example A3 was treated with hydrochloric acid with 1N hydrochloric acid, washed with water, proton-substituted lithium, and then immersed in a large excess of saturated lime water with respect to the imide salt exchange capacity for 1 hour. A FINP film was obtained in the same manner as in Example A6. An evaluation cell was prepared in the same manner as in Experimental Example A1 except that the FINP membrane thus obtained was used as a solid electrolyte membrane, and used as Experimental Example A7.

[Experiment A8]
A FINP membrane was obtained in the same manner as in Experimental Example A7, except that the FINP membrane (Li body) used in Experimental Example A7 was not proton-substituted. An evaluation cell was prepared in the same manner as in Experimental Example A1 except that the FINP membrane thus obtained was used as a solid electrolyte membrane, and used as Experimental Example A8.

[Experimental example B1]
(1) Production of Solid Electrolyte Membrane (Borate Electrolyte Membrane) According to the production method of Example 4 of Japanese Patent Application Laid-Open No. 2008-117762, borate ester electrolyte membrane (thickness 0.3 mm, σ = 5 × 10 ⁻⁴ S / cm (Room temperature)).

(2) Production of evaluation cell Polyethylene glycol containing 1M lithium bis (tetrafluoroethylsulfonyl) imide (LiBETI) as a supporting salt as an electrolyte using the borate electrolyte membrane thus obtained as a solid electrolyte membrane An evaluation cell was prepared in the same manner as in Experimental Example A1 except that dimethyl ether was used, and used as Experimental Example B1.

[Experiment B2]
A boric acid ester electrolyte membrane was prepared in the same manner as in Experimental Example B1, and this was used as a solid electrolyte membrane. As an electrolyte, 1M lithium bis (tetrafluoroethylsulfonyl) imide (LiBETI) and 3M Li ₂ S ₃ were used. An evaluation cell was prepared in the same manner as in Experimental Example A1 except that polyethylene glycol dimethyl ether contained as a supporting salt was used, and used as Experimental Example B2.

[Experimental example C1]
An evaluation cell was prepared in the same manner as in Experimental Example A1 except that no solid electrolyte membrane was used, and it was designated as Experimental Example C1.

[Experimental example C2]
(1) Production of solid electrolyte membrane (PTSI membrane) 4.3 g (14 mmol) of PTMDSA (see formula (3)) and 4.1 g (13 mmol) of PTMDSF (see formula (4)) in a 50 ml flask, 6 ml of acetonitrile was added. Thereto, 11 ml (65 mmol) of diisopropylethylamine was added and heated at 80 ° C. for 48 hours. Then, volatile components were distilled off, 1N NaOH aqueous solution was added, and then the organic layer was extracted with acetonitrile. Further, the solvent was distilled off with an evaporator, 1N HCl aqueous solution was added until the solution was acidic, the solvent was removed with an evaporator, and the organic substance was extracted with acetonitrile to remove the salt. Further, the solvent was distilled off from the acetonitrile extract, dissolved in a small amount of acetonitrile, filtered through celite, and dried under reduced pressure at 80 ° C. 8.0 g (1.0 mmol) of this, 0.84 g (4.3 mmol) of 4-fluorobenzenesulfonyl chloride, and 12 ml of acetonitrile were added to a 50 ml flask. Further, 5.4 ml (31 mmol) of diisopropylethylamine was added and heated at 80 ° C. for about 12 hours. Thereafter, volatile components were distilled off, 1N NaOH aqueous solution was added, and then the organic layer was extracted with acetonitrile. Further, the solvent was distilled off with an evaporator, 1N HCl aqueous solution was added until the solution was acidic, the solvent was removed with an evaporator, and the organic substance was extracted with acetonitrile to remove the salt. Further, the acetonitrile extract was evaporated, dissolved in a small amount of acetonitrile, filtered through celite, and dried under reduced pressure at 80 ° C. to obtain the desired product (4.6 g, yield 55%). The following figure shows the synthesis method (see formula (8)). It was 29.8 when synthetic polymerization degree j of the obtained target object was measured by NMR. An equal amount of an aqueous lithium carbonate solution was added to the aqueous solution of the polymer, converted to a Li form, and then dried by heating. This Li polymer is dissolved in ethanol and impregnated into filter paper (product number 704, thickness 0.25 mm, manufactured by Nihon Riken Kikai Co., Ltd.) and dried by heating at 60 ° C. until the porous material becomes transparent at the time of drying. Repeated. The thickness of the obtained PTSI film was about 0.5 mm. Since PTSI became oily when immersed in the electrolyte, and separated from the porous polyethylene to form droplets, which no longer functioned as a membrane, hydrophilic filter paper was used. In this way, a PTSI film was obtained.

(2) Production of Evaluation Cell An evaluation cell was produced in the same manner as in Experimental Example A1 except that the PTSI membrane thus obtained was used as a solid electrolyte membrane and impregnated in filter paper instead of porous polyethylene. Experimental Example C2 It was.

[Experiment C3]
LiTi ₂ (PO ₄ ) · AlPO ₄ (0.3 mm thickness, σ = 1 to 2 × 10 ⁻⁴ S / cm (room temperature)), which is a Li ion conductive glass ceramic solid electrolyte manufactured by OHARA, is used as the solid electrolyte membrane. An evaluation cell was produced in the same manner as in Experimental Example A1 except that the result was as Experimental Example C3.

[Evaluation]
A charge / discharge test was performed using the evaluation cell of each experimental example produced as described above. First, after discharging to a discharge end potential of 1 V (vs. Li ^/ Li ⁺ ) at a current of 0.5 mA, charging is performed to a charge end potential of 3 V (vs. Li ^/ Li ⁺ ) at a current of 0.5 mA. went. With this charge / discharge as one cycle, the charge capacity (Ah / g-S) and discharge capacity (Ah / g-S) of the fifth cycle are measured, and the charge capacity divided by the charge capacity is multiplied by 100 to charge. The discharge efficiency (%) was determined. Here, Ah / g-S indicates the capacity per weight of sulfur in the positive electrode. After the fifth cycle charge, the current is increased to 5 mA, the discharge is alternately performed up to the discharge end potential of 1 V (vs. Li ^/ Li ⁺ ), and the charge is alternately performed up to the charge end potential of 3 V (vs. Li ^/ Li ⁺ ). The charge / discharge capacity (Ah / g-S) was measured 5 times. The fifth discharge capacity (Ah / g-S) was defined as the capacity at the time of 5 mA discharge. Subsequently, the discharge and charging at 0.5 mA described above were repeated 5 times, and then the circuit was held in an open circuit state, and the open circuit voltage (V) after 10 hours was measured. Further, the charge capacity immediately before holding for 10 hours (Ah / g-S) and the discharge capacity after holding for 10 hours (Ah / g-S) were measured, and the charge / discharge efficiency (%) was determined in the same manner as described above. Moreover, the charge capacity (Ah / g-S) immediately before the 24-hour holding and the discharge capacity (Ah / g-S) after the 24-hour holding were measured, and the charge / discharge efficiency (%) was determined in the same manner as described above. Subsequently, the above charge / discharge at 0.5 mA was repeated, the charge capacity (Ah / g-S) and the discharge capacity (Ah / g-S) at the 60th cycle were measured, and the charge / discharge efficiency ( %). Further, the capacity retention rate (%) was obtained by multiplying the discharge capacity at the 60th cycle by the discharge capacity at the 5th cycle and multiplying by 100.

[Experimental result]
Table 1 shows the experimental results of Experimental Examples A1 to A8, B1, B2, and C1 to C3. Table 1 shows the discharge capacity at the fifth cycle, the charge / discharge efficiency at the fifth cycle, the open-circuit voltage after holding for 10 hours, the charge / discharge efficiency after holding for 10 hours, and the charge / discharge efficiency after holding for 24 hours. The discharge capacity at 5 mA discharge, the discharge capacity at the 60th cycle, the charge / discharge efficiency at the 60th cycle, and the capacity retention rate were summarized. Compared to the case of using a solid electrolyte membrane having a polymer copolymer or cross-linked polymer having an imide in the molecule as a solid electrolyte membrane (Experimental Examples A1 to A8) and not using a solid electrolyte membrane (Experimental Example C1) It was found that the fifth cycle discharge capacity, the fifth cycle charge / discharge efficiency, the 60th cycle discharge capacity, and the 60th cycle charge / discharge efficiency were all good, and a high battery capacity and charge / discharge efficiency were obtained. It was also found that the open voltage after 10 hours, the charge / discharge efficiency after 10 hours, and the charge / discharge efficiency after 24 hours showed high values, and the storage characteristics after charge were also good. Among them, Experimental Example A1 having a copolymer, Experimental Example A2 having a highly crosslinked product, and Experimental Example A5 having a crosslinked product having a higher degree of crosslinking by cationic crosslinking have better storage characteristics. It was. Moreover, when it has a crosslinked body, the charging / discharging efficiency of Experimental Example A2 having a crosslinked body with a high degree of crosslinking was good, and then the charging / discharging efficiency of Experimental Example A5 that was cationically crosslinked was favorable. On the other hand, Experimental Examples A3 and A4 having a low-crosslinking degree were good in discharge capacity, and then Experimental Example A5 in which the degree of crosslinking was increased by cationic crosslinking was good. In addition, when the degree of cross-linking was the same, Experimental Example A3 with a film thickness of 40 μm was equivalent or superior in all items compared to Experimental Example A4 with a film thickness of 30 μm. Moreover, when it had the crosslinked body which carried out Ca bridge | crosslinking, Experimental example A5, A6, A7 was favorable in items other than 5 mA discharge capacity, and A5 was more favorable especially. From this, it was surmised that it is preferable that Ca cross-linking is about 50% in a battery that does not require high output. Moreover, in the case of a cross-linked product obtained by Ca cross-linking, it was presumed that a Li-form of an imide salt that had been Ca-cross-linked after being proton-substituted once was preferable to one that was directly Ca-cross-linked. Even when the solid electrolyte membrane had a polymer having an imide in the molecule, the discharge capacity was extremely low when it was not a copolymer or a crosslinked product (Experimental Example C2). The PTSI membrane of Experimental Example C2 became oily when dipped in the electrolyte, and separated from porous polyethylene into droplets and did not function as a membrane. Experiments were possible by using hydrophilic filter paper to retain PTSI as a membrane, but it was found that the characteristics fluctuated greatly and did not work as a stable barrier layer. From this, when it has a polymer which has an imide in a molecule | numerator, it was guessed that this polymer should be a copolymer and a crosslinked body further.

  When using a solid electrolyte membrane having a polymer having boron in the molecule (Experimental Examples B1 and B2), compared with the case of not using a solid electrolyte membrane (Experimental Example C1), the charge / discharge efficiency at the fifth cycle, It was found that the charge / discharge efficiency at the 60th cycle was good, and high charge / discharge efficiency was obtained. At this time, it was found that in the experimental example B2 containing polysulfide ions in the electrolytic solution, the discharge capacity was improved without lowering the charge / discharge efficiency as compared with the experimental example B1 not containing. Furthermore, since Experimental Example B2 has the highest capacity retention rate after 60 cycles even when compared with Experimental Examples A1 to A8, the addition of polysulfide ions to the electrolytic solution does not depend on the type of solid electrolyte. It was estimated that the maintenance rate would improve.

  When an inorganic solid electrolyte was used as in Experimental Example C3, the discharge capacity at 5 mA discharge was 0 Ah / g-S. Moreover, when the evaluation cell was disassembled after the experiment was completed, fine cracks were generated in the solid electrolyte. This is presumed to be caused by the fact that the inorganic solid electrolyte is a brittle material.

  From the above, by providing a solid electrolyte membrane having a polymer conjugate with an imide or a solid electrolyte membrane having a polymer with boron, and an electrolytic solution interposed at least between the positive electrode and the solid electrolyte, It was presumed that storage characteristics, charge / discharge efficiency, and battery capacity would be well balanced while enabling high-efficiency utilization.

10 Evaluation Cell, 12 Cylindrical Substrate, 14 Cavity, 16 Negative Electrode, 18 Separator, 19 Solid Electrolyte Membrane, 20 Positive Electrode, 22 Ring, 24 Column, 25 Pressure Bolt, 25a Through Hole, 26 Lid, 26a Opening, 27 Insulating Resin Ring, 28 Packing, 29 Insulating ring.

Claims (6)

A positive electrode containing sulfur;
A negative electrode containing an alkali metal;
A solid electrolyte membrane disposed between the positive electrode and the negative electrode and having a polymer conjugate with an imide;
An electrolytic solution interposed between at least the positive electrode and the solid electrolyte membrane;
Sulfur battery equipped with.   2. The sulfur battery according to claim 1, wherein in the solid electrolyte membrane, the conjugate is a copolymer of a polysulfone structure and a perfluoroalkylenesulfonimide structure.   The sulfur battery according to claim 1 or 2, wherein the solid electrolyte membrane has the conjugate crosslinked with a multivalent cation. A positive electrode containing sulfur;
A negative electrode containing an alkali metal;
A solid electrolyte membrane disposed between the positive electrode and the negative electrode and having a polymer with boron;
An electrolytic solution interposed between at least the positive electrode and the solid electrolyte membrane;
Sulfur battery equipped with.   The sulfur battery according to claim 4, wherein the solid electrolyte membrane is a polymer having a borate ester.   The sulfur battery according to claim 1, wherein the electrolytic solution contains polysulfide ions.

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