JP2012195105A - Molten salt battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molten salt battery capable of preventing a short circuit in the molten salt battery, and ensuring safety and inhibiting performance degradation by making a separator of a resin which can be easily impregnated with a molten salt.SOLUTION: A separator 3 for a molten salt battery is composed of a resin resistant to hydrogen fluoride, such as PTFE, to prevent the corrosion of the separator even when hydrogen fluoride is evolved in the molten salt battery. Furthermore, the separator has an average pore diameter of 0.1 to 5 μm, and a thickness of 10 to 300 μm. Thus the required cycle characteristics as a molten salt battery are obtained and the reduction in the capacity of the molten salt battery during a rapid charge is inhibited while a short circuit in the molten salt battery is prevented.

Description

  The present invention relates to a molten salt battery using a molten salt as an electrolyte.

  For efficient use of electric power, a storage battery with high energy density and high efficiency is required. As such a storage battery, a sodium-sulfur battery disclosed in Patent Document 1 has been developed.

JP 2007-273297 A

Another high energy density and high efficiency storage battery is a molten salt battery. The molten salt battery is a battery using a molten salt as an electrolyte, and operates in a state where the molten salt is melted. As the molten salt, for example, NaFSA (sodium bisfluorosulfonylamide) using sodium ion as a cation and FSA (bisfluorosulfonylamide; (FSO ₂ ) ₂ N ⁻ ) as an anion is used. The molten salt battery includes a positive electrode, a negative electrode, and a separator. The separator is a sheet-like member that separates the positive electrode and the negative electrode, and holds a molten salt containing ions therein. In a conventional molten salt battery, a glass separator using a glass cloth or the like may be used.

  Usually, in a battery using an alkali metal such as Na as an active material component of the negative electrode and an organic electrolyte as an electrolyte, alkali metal dendrite growth occurs during charge and discharge due to a side reaction between the two. When dendrite growth occurs, there is a risk that the positive electrode and the negative electrode are short-circuited in the battery. In order to solve this problem, it has been discovered that in a molten salt battery using a molten salt mainly composed of inorganic molecules such as NaFSA as an electrolyte, side reaction between the electrolyte and the active material is suppressed, and dendrite growth is unlikely to occur. . On the other hand, in the lithium battery using Li metal as a negative electrode, the view that the dendrite growth of Li metal tends to be relatively decreased by increasing the operating temperature is also shown. The molten salt battery operates at a temperature of about 80 ° C. to 100 ° C., which is higher than room temperature, but it has been found that the dendritic growth of alkali metal can be further suppressed by increasing the operating temperature. Has been.

  As described above, the molten salt battery is a highly safe battery in which dendrite growth is unlikely to occur, and has an excellent feature that exhibits extremely stable charge / discharge cycle characteristics under normal operating conditions. However, even in molten salt batteries, when rapid charging is required for in-vehicle applications, etc., dendritic growth may occur especially in areas where current tends to concentrate, such as electrode edges, but as R & D progresses It has become apparent.

  In addition, the internal temperature of the molten salt battery may rise abnormally during operation due to a short circuit between a part of the positive electrode and the negative electrode. When the internal temperature of the molten salt battery rises abnormally, a part of the internal molten salt may be thermally decomposed. For example, a molten salt such as NaFSA contains fluorine atoms. When the molten salt is thermally decomposed, water contained as impurities in the molten salt battery reacts with fluorine atoms in the molten salt. Hydrogen fluoride may be generated. Since hydrogen fluoride corrodes silicon dioxide, when a glass separator is used, the separator is corroded by hydrogen fluoride. In the corroded portion of the separator, the hole diameter is enlarged, and the positive electrode and the negative electrode are easily short-circuited. When a short-circuit occurs, the internal temperature of the molten salt battery further increases. As described above, in the molten salt battery using the glass separator, there is a possibility that the thermal runaway in which the internal temperature continues to rise occurs. For this reason, it is desirable that the separator material be a substance resistant to hydrogen fluoride.

  As a substance resistant to hydrogen fluoride, there is a resin such as a fluororesin. A molten salt battery including a separator made of a resin resistant to hydrogen fluoride can prevent thermal runaway. However, since a resin such as a fluororesin is difficult for a molten salt to permeate, a separator made of resin is not easily impregnated with a molten salt. For this reason, in a molten salt battery equipped with a separator made of resin, there is a problem that ions contained in the molten salt pass through the separator and transfer charge between the positive electrode and the negative electrode is poor and the performance as a battery is low. is there.

  The present invention has been made in view of such circumstances, and the object of the present invention is to suppress a short circuit in the molten salt battery even if dendrite growth occurs, and the molten salt An object of the present invention is to provide a molten salt battery in which safety is ensured and deterioration in performance is suppressed by adjusting the pore size of a resin separator so as to be easily impregnated.

  The molten salt battery according to the present invention is a molten salt battery including a porous and sheet-like separator and using a molten salt as an electrolyte, and the separator is made of a resin having resistance to hydrogen fluoride as an average. The pore diameter is from 0.1 μm to 5 μm.

  In the present invention, by using a resin that is resistant to hydrogen fluoride as the separator material of the molten salt battery, the separator is not corroded even if hydrogen fluoride is generated in the molten salt battery. In addition, by setting the average pore diameter of the separator to 0.1 μm or more and 5 μm or less, the separator can be impregnated with molten salt, and the minimum cycle characteristics as a molten salt battery can be obtained. Here, the resistance means that there is no change in physical properties such as strength or weight after the immersion test in the molten salt containing hydrogen fluoride, and in particular, there is no change in the average pore size of the porous separator. Say.

  In the molten salt battery according to the present invention, the separator has a thickness of 10 μm or more and 300 μm or less.

  In this invention, the fall of the capacity | capacitance of the molten salt battery at the time of high-speed discharge is suppressed, preventing a short circuit by making the thickness of the separator of a molten salt battery into 10 micrometers or more and 300 micrometers or less.

  In the molten salt battery according to the present invention, the separator has an average pore diameter of 0.5 μm or more and 2 μm or less.

  In the present invention, when the average pore size of the separator of the molten salt battery is 0.5 μm or more and 2 μm or less, the separator can be more easily impregnated with the molten salt, and the molten salt battery has more practical cycle characteristics. It is done.

  In the molten salt battery according to the present invention, the separator has a thickness of 30 μm or more and 100 μm or less.

  In this invention, the fall of the capacity | capacitance of the molten salt battery at the time of high-speed discharge is suppressed more by making the thickness of the separator of a molten salt battery into 30 micrometers or more and 100 micrometers or less.

  In the molten salt battery according to the present invention, the resin is polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polymethylpentene, polyvinylidene chloride, polybutadiene, polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polyacrylonitrile, It is any one kind of resin selected from the group consisting of polymethyl methacrylate and polycarbonate, or a mixture of plural kinds of resins selected from the group.

  In the present invention, PTFE that is resistant to hydrogen fluoride and that is resistant to the molten salt at a temperature equal to or higher than the melting point of the molten salt is used as the resin as the separator material.

  The molten salt battery according to the present invention is characterized in that hydrophilicity is imparted to the separator.

  In the present invention, by imparting hydrophilicity to the separator of the molten salt battery, the wettability of the separator with respect to the molten salt is improved, and the separator can be impregnated with the molten salt.

  In the present invention, thermal runaway is prevented from occurring due to the generation of hydrogen fluoride inside the molten salt battery, and cycle characteristics that can be used as a molten salt battery are obtained. As a result, it is possible to ensure the safety of the molten salt battery and to suppress the deterioration of the performance of the molten salt battery.

It is typical sectional drawing which shows the structural example of the molten salt battery of this invention. It is a graph which shows the experimental result which investigated the relationship between the thickness and average hole diameter of a separator, and the battery characteristic of a molten salt battery.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a schematic cross-sectional view showing a configuration example of the molten salt battery of the present invention. FIG. 1 shows a schematic cross-sectional view of a molten salt battery cut longitudinally. The molten salt battery is configured such that a positive electrode 1, a separator 3, and a negative electrode 2 are arranged side by side in a rectangular parallelepiped box-shaped battery container 51 whose upper surface is open, and a lid 52 is attached to the battery container 51. The battery container 51 and the lid 52 are made of aluminum. The positive electrode 1 and the negative electrode 2 are formed in a rectangular flat plate shape, and the separator 3 is formed in a sheet shape. The separator 3 is interposed between the positive electrode 1 and the negative electrode 2 and is isolated so that the positive electrode 1 and the negative electrode 2 are not short-circuited. The positive electrode 1, the separator 3, and the negative electrode 2 are stacked and arranged vertically with respect to the bottom surface of the battery container 51.

  A spring 41 made of corrugated metal is disposed between the negative electrode 2 and the inner wall of the battery case 51. The spring 41 is made of an aluminum alloy and biases a flat plate-like presser plate 42 having inflexibility to press the negative electrode 2 toward the separator 3 and the positive electrode 1 side. The positive electrode 1 is pressed by the reaction of the spring 41 from the inner wall opposite to the spring 41 to the separator 3 and the negative electrode 2 side. The spring 41 is not limited to a metal spring or the like, and may be an elastic body such as rubber, for example. When the positive electrode 1 or the negative electrode 2 expands or contracts due to charge / discharge, the volume change of the positive electrode 1 or the negative electrode 2 is absorbed by the expansion and contraction of the spring 41.

The positive electrode 1 is formed by applying a positive electrode material 12 including a positive electrode active material such as NaCrO ₂ and a binder on a rectangular plate-shaped positive electrode current collector 11 made of aluminum. The positive electrode active material is not limited to NaCrO ₂ . In the negative electrode 2, a negative electrode material 22 containing a negative electrode active material such as tin is formed on a rectangular plate-shaped negative electrode current collector 21 made of aluminum by plating. When the negative electrode material 22 is plated on the negative electrode current collector 21, tin plating is performed after zinc is plated on the base as a zincate treatment. The negative electrode active material is not limited to tin. For example, tin may be replaced with metallic sodium, carbon, silicon, or indium. The negative electrode material 22 may be formed, for example, by applying a binder to a negative electrode active material powder and applying the powder onto the negative electrode current collector 21. Details of the separator 3 will be described later.

  In the battery container 51, the positive electrode material 12 of the positive electrode 1 and the negative electrode material 22 of the negative electrode 2 face each other, and the separator 3 is interposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1, the negative electrode 2, and the separator 3 are impregnated with an electrolyte made of a molten salt. In order to prevent a short circuit between the positive electrode 1 and the negative electrode 2, the inner surface of the battery container 51 has an insulating structure by a method such as coating with an insulating resin. A positive terminal 53 and a negative terminal 54 for connecting to the outside are provided on the outside of the lid 52. The positive electrode terminal 53 and the negative electrode terminal 54 are insulated from each other, and the portion of the lid 52 facing the inside of the battery container 51 is also insulated by an insulating film or the like. One end of the positive electrode current collector 11 is connected to the positive electrode terminal 53 with a lead wire 55, and one end portion of the negative electrode current collector 21 is connected to the negative electrode terminal 54 with a lead wire 56. The lead wire 55 and the lead wire 56 are insulated from the lid portion 52. The lid 52 is attached to the battery container 51 by welding.

The electrolyte of the molten salt battery is a molten salt that becomes a conductive liquid in a molten state. At a temperature equal to or higher than the melting point of the molten salt, the molten salt melts into an electrolytic solution, and the molten salt battery operates as a secondary battery. In order to lower the melting point, it is desirable that the electrolyte is a mixture of a plurality of types of molten salts. For example, a mixed salt of NaFSA with sodium ion as a cation and FSA as an anion and KFSA with potassium ion as a cation and FSA as an anion is used as the electrolyte. Hereinafter, this mixed salt is referred to as NaFSA-KFSA. The composition of NaFSA-KFSA is, for example, 45% by mole of NaFSA and 55% by mole of KFSA. With this composition, the melting point of NaFSA-KFSA is about 57 ° C. In addition, it can replace with this molten salt and can also use the molten salt which used F element of FSA for the fluoroalkyl group as electrolyte. Examples of the molten salt include TFSA (bistrifluoromethylsulfonylamide) which is a salt in which all F elements of FSA are substituted with CF ₃ , or a salt in which a part of F elements of FSA is substituted with CF ₃ . Furthermore, a molten salt containing a plurality of anions selected from the group in which all or part of the F element of FSA is substituted with other fluoroalkyl groups may be used as the electrolyte.

The molten salt used as the electrolyte is not limited to a molten salt having Na or K as a cation. A molten salt having one or more species selected from the group consisting of alkali metals and alkaline earth metals as cations can also be used as the electrolyte. The alkali metal can be selected from Li, Na, K, Rb and Cs. The alkaline earth metal can be selected from Mg, Ca, Sr and Ba. For example, as a single salt of a molten salt using FSA as an anion, LiFSA, NaFSA, KFSA, RbFSA, CsFSA, Mg (FSA) ₂ , Ca (FSA) ₂ , Sr (FSA) ₂ and Ba (FSA) ₂ can be mentioned. It is done. Examples of the molten salt having TFSA as an anion include LiTFSA, NaTFSA, KTFSA, RbTFSA, CsTFSA, Mg (TFSA) ₂ , Ca (TFSA) ₂ , Sr (TFSA) ₂ and Ba (TFSA) _2. It is done. These molten salts can be used as an electrolyte. A mixed salt obtained by mixing these single salts can be used as the electrolyte. The molten salt may contain other cations such as organic ions.

  Moreover, the structure of the molten salt battery shown in FIG. 1 is a schematic structure, and the molten salt battery may include other components (not shown) such as a heater for heating the inside or a temperature sensor. Good. Moreover, although the form provided with one pair of the positive electrode 1 and the negative electrode 2 was shown in FIG. 1, the molten salt battery of this invention is a form with which the some positive electrode 1 and the negative electrode 2 were piled up alternately via the separator 3. There may be.

  Next, details of the separator 3 will be described. The separator 3 is formed in a porous sheet shape using a resin resistant to hydrogen fluoride as a material. Here, the resistance to hydrogen fluoride means that there is no change in physical properties such as strength or weight after the immersion test in the molten salt containing hydrogen fluoride, and in particular, the average pore diameter of the porous separator 3. Say no change. As the resin having resistance to hydrogen fluoride, polyolefin, acrylic, polyester, polyether, fluororesin, and a composite thereof can be used. In particular, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyvinylidene chloride (PVDC), polybutadiene (BR), polyethylene terephthalate (PET) ), Polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and a resin selected from the group consisting of polycarbonate (PC), the material of separator 3 It can be used as A mixture of a plurality of types of resins selected from this group can also be used as the material for the separator 3.

  The aforementioned resin does not undergo thermal decomposition even at a temperature higher than the melting point of the molten salt, which is the operating temperature of the molten salt battery, and has resistance to the molten salt at a temperature higher than the melting point of the molten salt. The above-mentioned resin has resistance to hydrogen fluoride. For this reason, even when the internal temperature of the molten salt battery rises abnormally, the separator 3 is not corroded by the generated hydrogen fluoride, and the positive electrode 1 and the negative electrode 2 are short-circuited due to the corrosion of the separator 3. Furthermore, the internal temperature does not increase. Therefore, the occurrence of thermal runaway in the molten salt battery is prevented. Among the above-mentioned resins, PTFE has the best performance in resistance to hydrogen fluoride and heat resistance. In addition, polyethylene, polypropylene, and the like can have heat resistance of about 110 ° C., which is a temperature exceeding the normal operating temperature of the molten salt battery, by cross-linking polymerization.

  Usually, a resin resistant to hydrogen fluoride such as PTFE has low hydrophilicity and poor wettability to molten salt. Therefore, the separator 3 is subjected to a treatment for imparting hydrophilicity. Specifically, UV (ultraviolet) irradiation or plasma treatment is performed on a sheet made of a resin such as PTFE, and the separator 3 is manufactured from the sheet after UV irradiation or plasma treatment. The plasma treatment is performed, for example, by exposing a sheet made of PTFE to plasma generated by applying a high frequency voltage to a mixed gas of nitrogen gas and hydrogen gas. For example, in a PTFE sheet after UV irradiation or plasma treatment, a part of fluorine is substituted with a hydroxyl group, and hydrophilicity is increased by the action of the hydroxyl group. By producing the separator 3 from a sheet made of a resin having increased hydrophilicity, the separator 3 is imparted with hydrophilicity. Separator 3 is given hydrophilicity, so that wettability to molten salt is improved compared to PTFE and other resins that have not been treated to impart hydrophilicity, and impregnation with molten salt is a comparison. Easy.

  The separator 3 has a porous structure in order to impregnate the inside thereof with molten salt and move charge carriers between the positive electrode 1 and the negative electrode 2. When the pore diameter of the separator 3 is too small, it is difficult to impregnate the molten salt inside, and the movement of charge carriers passing through the separator 3 becomes difficult, so that the cycle characteristics of the molten salt battery are deteriorated. That is, the capacity of the molten salt battery decreases after repeating the charge and discharge cycles. In order for the molten salt to be impregnated into the separator 3 and the molten salt battery to obtain the minimum cycle characteristics, the average pore size of the separator 3 needs to be 0.1 μm or more. Further, in order for the molten salt to be more easily impregnated into the separator 3 and the molten salt battery to obtain appropriate cycle characteristics, the average pore diameter of the separator 3 is desirably 0.5 μm or more. When the pore diameter of the separator 3 is excessive, the dendrite generated in the positive electrode 1 or the negative electrode 2 is likely to penetrate the separator 3 and the risk of occurrence of a short circuit is increased. In order to prevent a short circuit, the average pore diameter of the separator 3 needs to be at least 5 μm or less. In order to reduce the frequency of occurrence of a short circuit to a practical range, the average pore diameter of the separator 3 is desirably 2 μm or less.

  The thickness of the separator 3 is related to the risk of a short circuit as with the hole diameter. When the thickness of the separator 3 is too small, the danger that a dendrite will penetrate the separator 3 and a short circuit will generate | occur | produce will increase. In order to prevent a short circuit, the thickness of the separator 3 needs to be at least 10 μm. In order to reduce the frequency of occurrence of a short circuit to a practical range, the thickness of the separator 3 is preferably 30 μm or more. Moreover, the internal resistance of a molten salt battery rises, so that the thickness of the separator 3 is large. When the thickness of the separator 3 is excessive, the capacity of the molten salt battery decreases during high-speed discharge due to an increase in internal resistance. In order to reduce the internal resistance to such an extent that the molten salt battery can operate, the thickness of the separator 3 needs to be 300 μm or less. In addition, in order to suppress a decrease in the capacity of the molten salt battery during high-speed discharge within a practical range, the thickness of the separator 3 is desirably 100 μm or less.

  FIG. 2 is a table showing the experimental results of examining the relationship between the thickness and average pore diameter of the separator 3 and the battery characteristics of the molten salt battery. Molten salt batteries using separators 3 with different specifications were prepared, and the battery characteristics were examined. FIG. 2 shows the capacity retention after 100 cycles and the 1C / 0.2C discharge capacity ratio as battery characteristics for each of the molten salt batteries using six types of separators 3 having different thicknesses, porosity and average pore diameter. The results of the investigation are shown. The capacity retention after 100 cycles is a percentage obtained by dividing the capacity of the molten salt battery after 100 cycles of charge / discharge by the capacity of the molten salt battery before use. Usually, the capacity after 100 cycles is smaller than the capacity before use, and the capacity retention after 100 cycles is less than 100%. The 1C / 0.2C discharge capacity ratio is expressed as a percentage obtained by dividing the capacity when the molten salt battery is discharged at a discharge rate of 1C by the capacity when the molten salt battery is discharged at a discharge rate of 0.2C. It is a thing. 1C is a discharge rate higher than 0.2C, and the 1C / 0.2C discharge capacity ratio indicates the ratio of the capacity decreased by increasing the discharge speed to the capacity during low-speed discharge.

  No. In the sample No. 1, the separator 3 has a thickness of 30 μm, a porosity of 63%, and an average pore diameter of 0.565 μm. The ratio is 93%. No. In the sample of No. 2, the thickness of the separator 3 is 30 μm and No. 2 is used. 1 and the efficiency is 59%. It is almost the same as 1. On the other hand, no. No. 2 has an average pore diameter of 0.149 μm. Less than 1. No. The thickness of the separator 3 in No. 2 is No. 2. No. 1 is the same as No. 1. No. 2 has a 1C / 0.2C discharge capacity ratio of 92%. It is almost the same as 1. However, no. 2 has a small average pore diameter, the capacity retention after 100 cycles is 55%. Significantly less than 1. No. If the average pore size of the separator 3 is 0.1 μm or more as in the sample of No. 2, the molten salt battery can obtain the minimum cycle characteristics. It is clear that the average pore diameter of the separator 3 is desirably 0.5 μm or more like the sample 1.

  No. In the sample of No. 3, the thickness of the separator 3 is No. 3. The molten salt battery has a 1C / 0.2C discharge capacity ratio of 96%, which enables high-speed discharge. However, the average pore diameter of the separator 3 is as very small as 0.088 μm, and the capacity retention after 100 cycles of the molten salt battery is as very low as 20%. Thus, when the average pore diameter of the separator 3 is less than 0.1 μm, it is clear that the cycle characteristics of the molten salt battery are extremely deteriorated and it is difficult to use as a storage battery.

  No. In the sample of No. 4, the average pore diameter of the separator 3 is 0.175 μm, and No. 4 2 and the capacity retention after 100 cycles of the molten salt battery was 61%. Slightly larger than 2. The separator 3 has a thickness of 50 μm and No. 2 and the 1C / 0.2C discharge capacity ratio of the molten salt battery is 85%. Less than 2. No. In the sample of No. 5, the average pore diameter of the separator 3 is 0.162 μm and 2 and the capacity retention after 100 cycles of the molten salt battery is 68%. Slightly larger than 2. The separator 3 has a thickness of 75 μm and No. The 1C / 0.2C discharge capacity ratio of the molten salt battery is 72%, which is more than twice that of No. 2. Less than 2. It is clear that when the average pore size of the separator 3 is increased, the cycle characteristics of the molten salt battery are improved, and when the thickness of the separator 3 is increased, the capacity of the molten salt battery during high-speed discharge is reduced.

  No. In the sample No. 6, the average pore size of the separator 3 is No. 6. No. 1 and 0.473 μm, and the gas efficiency is No. 1. 88% which is larger than 1. The capacity retention after 100 cycles of the molten salt battery is 80%. The cycle characteristics are almost equal to 1. No. In the sample No. 6, the thickness of the separator 3 is 100 μm. Significantly greater than one. The 1C / 0.2C discharge capacity ratio of the molten salt battery is 63%. It is significantly lower than 1. When the thickness of the separator 3 is increased, it is expected that the capacity of the molten salt battery at the time of high-speed discharge is further reduced, which is not practical. Thus, it is apparent that the thickness of the separator 3 is desirably 100 μm or less in order to suppress the decrease in the capacity of the molten salt battery during high-speed discharge to a practical range.

  As described above in detail, in the molten salt battery according to the present embodiment, since the material of the separator 3 is a resin resistant to hydrogen fluoride, heat is generated by the generation of hydrogen fluoride inside the molten salt battery. Runaway is prevented from occurring. Moreover, in this Embodiment, the cycling characteristics of a molten salt battery will be in a practical state by making the average hole diameter of the separator 3 into an appropriate value. Moreover, the fall of the capacity | capacitance of the molten salt battery at the time of high-speed discharge can be suppressed by making the thickness of the separator 3 into an appropriate value. Therefore, the molten salt battery of the present invention can suppress the deterioration in performance while preventing the occurrence of thermal runaway.

  The separator 3 provided in the molten salt battery of the present invention may have a multilayer structure. For example, the separator 3 may have a configuration in which a plurality of sheets having different hole diameters or porosity are stacked. Further, for example, the separator 3 may have a configuration in which hydrophilicity is imparted by forming a polyvinyl alcohol layer on the surface of a sheet made of a resin resistant to hydrogen fluoride. As described above, the material of the separator 3 is preferably PTFE from the viewpoint of resistance to hydrogen fluoride and heat resistance. However, if the resin is resistant to hydrogen fluoride, the material of the separator 3 is a resin other than PTFE. May be. When a resin other than PTFE is used as the material of the separator 3, the operating temperature of the molten salt battery needs to be a temperature at which the material of the separator 3 is not thermally decomposed.

  In the present embodiment, the positive electrode current collector 11 and the negative electrode current collector 21 are made of aluminum, but may be made of other conductors. Further, the shape of the molten salt battery is not limited to a rectangular parallelepiped shape, and may be other shapes. For example, the shape of the molten salt battery may be cylindrical.

DESCRIPTION OF SYMBOLS 1 Positive electrode 11 Positive electrode collector 12 Positive electrode material 2 Negative electrode 21 Negative electrode collector 22 Negative electrode material 3 Separator

Claims (6)

A molten salt battery including a porous sheet-like separator and using a molten salt as an electrolyte,
The separator is
Resin with resistance to hydrogen fluoride is used as a material,
A molten salt battery having an average pore diameter of 0.1 μm or more and 5 μm or less. The molten salt battery according to claim 1, wherein the separator has a thickness of 10 μm to 300 μm. The molten salt battery according to claim 1, wherein the separator has an average pore diameter of 0.5 μm or more and 2 μm or less. The molten salt battery according to any one of claims 1 to 3, wherein the separator has a thickness of 30 µm or more and 100 µm or less. The resin comprises polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polymethylpentene, polyvinylidene chloride, polybutadiene, polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polyacrylonitrile, polymethyl methacrylate, and polycarbonate. The molten salt battery according to any one of claims 1 to 4, wherein the molten salt battery is any one kind of resin selected from a group, or a mixture of a plurality of kinds of resins selected from the group. The molten salt battery according to claim 1, wherein hydrophilicity is imparted to the separator.

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