JP2014056811A - Molten salt battery system and method for charging and discharging the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a molten salt battery system which is a power supply device employing a molten salt battery as a secondary battery, in which energy efficiency as the entire system is heightened.SOLUTION: A molten salt battery system 200 is configured by an acting molten salt battery whose electrolyte is in a molten state and which is in an operative state as battery (a battery pack 100 of a battery unit U1) and a standby molten salt battery which is in a charged state and is standing by in a non-operative state (a battery pack 100 of a battery unit U2). When the acting molten salt battery reaches a prescribed state by being discharged (for example, when its remaining life drops below a threshold), a heating device for the standby molten salt battery is activated by using output of the acting molten salt battery and the standby molten salt battery is thereby placed into an operative state.

Description

  The present invention relates to a molten salt battery system that includes a molten salt battery using a molten salt as an electrolyte, and that can independently supply power to a load independently of an external power source, and a charge / discharge method thereof.

Recently, there is an increasing market need for a power supply device using a secondary battery to be installed in a small-scale consumer such as a home. Such a power supply device can be used, for example, as an emergency power supply during a power failure.
The secondary battery used in the power supply device is preferably a battery having an excellent energy density, such as a lithium ion battery. However, the lithium ion battery has a caution that the electrolyte is flammable. On the other hand, in recent years, as a secondary battery having a strong advantage of nonflammability in addition to high energy density, a molten salt battery using a molten salt as an electrolyte has been developed and attracts attention (Patent Document 1 and Non-Patent Document 1). (See Patent Document 1).

  The operating temperature range of the molten salt battery is 57 ° C. to 190 ° C., which is superior in that it can be used particularly in a high temperature range as compared with the operating temperature range of a lithium ion battery (−20 ° C. to 80 ° C.). Yes. Therefore, a power supply device using a molten salt battery that is nonflammable and can be used even in a high temperature region does not require equipment such as exhaust heat space or fire prevention. As a whole, a relatively compact power supply device can be obtained.

JP 2009-67644 A JP 2004-111123 A JP 2011-228211 A JP2012-134126A

"SEI WORLD" March 2011 issue (VOL. 402), Sumitomo Electric Industries, Ltd.

  However, the molten salt battery cannot be charged or discharged unless the electrolyte is in a molten state. In order to melt the electrolyte, a temperature of 57 ° C. or higher, which cannot be obtained at room temperature, is required, and in order to operate more stably, 90 ° C. or higher is desirable. Therefore, when electric power is constantly supplied to the electric heater for obtaining such temperature, the amount of electric power becomes a negative factor that lowers the energy efficiency of the power supply device.

  In view of such a problem, an object of the present invention is to improve the energy efficiency of the entire system in a molten salt battery system that is a power supply device employing a molten salt battery as a secondary battery.

  The present invention is a molten salt battery system constituted by a plurality of molten salt batteries using a molten salt as an electrolyte, the working molten salt battery in which the electrolyte is in a molten state, and a heating device for heating the working molten salt battery, A pre-molten salt battery that is charged and in which the electrolyte is solidified, a heating device that can heat the pre-molten salt battery, and when the operating molten salt battery reaches a predetermined state by discharge, A controller for operating the heating device for the pre-molten salt battery using the output of the working molten salt battery to bring the electrolyte of the pre-molten salt battery into a molten state.

  On the other hand, the present invention is a molten salt battery charging / discharging method executed by a molten salt battery system including a plurality of molten salt batteries having a molten salt as an electrolyte, and at least two sets of the molten salt batteries prepared as described above, In each set, the first step of charging in a state where the electrolyte is melted by a heating device, and for some of the molten salt batteries, some of the molten salt batteries are heated and kept warm by the heating device. The second step of maintaining the molten state, the third step of transitioning the electrolyte to a solidified state without keeping the temperature of the remaining molten salt battery, and the need to supply power to the load, A fourth step of supplying electric power from the molten salt battery, and when the partial molten salt battery reaches a predetermined state by discharge, using the output of the molten salt battery, at least one of the remaining molten salts Battery The solution electrolyte to transition into a molten state by the heating device, then, with respect to the load, and has a, a fifth step of supplying power from the molten salt battery transitioning into the molten state.

  Further, the present invention from a slightly different point of view is a molten salt battery system including a plurality of molten salt batteries using a molten salt as an electrolyte, and an operating molten salt battery in an operating state and the operating molten salt battery. A heating device that heats and retains, a preliminary molten salt battery that is not heated and kept in a non-operating state in a charged state, a heating device that can heat the preliminary molten salt battery, and the working molten salt battery A control device that operates the heating device for the pre-molten salt battery using the output of the working molten salt battery to bring the pre-molten salt battery into an operating state when the battery reaches a predetermined state by discharge. It is a thing.

  Moreover, the present invention is a molten salt battery charging / discharging method executed by a molten salt battery system including a plurality of molten salt batteries having a molten salt as an electrolyte, and at least two sets of the molten salt batteries prepared as described above, In each set, the first step of charging in a state of being heated and kept warm by the heating device, and a part of all the molten salt batteries that are heated and kept warm by the heating device to maintain the operation state The second step, the third step of waiting for the remaining molten salt batteries in a non-operating state without heating and heating, and when it becomes necessary to supply power to the load, power is supplied from the partial molten salt batteries When the fourth step and the part of the molten salt batteries reach a predetermined state by discharging, at least one of the remaining molten salt batteries is heated by the heating device using the output of the molten salt battery. Operation To transition to state, then, with respect to the load, and has a, a fifth step of supplying power from the molten salt battery transitioning into working state.

According to the molten salt battery system and the charging / discharging method thereof of the present invention, even if heating is required to bring the preliminary molten salt battery into an operating state, the standby molten salt battery that is on standby is heated and kept warm by a heating device. Since it is unnecessary, it is possible to save the power and increase the energy efficiency of the entire system.
In addition, in the case of a pre-molten salt battery that preserves electric power in a solid state of the electrolyte, heating insulation and supplementary charging by a heating device is unnecessary, so that power is saved and the energy efficiency of the entire system is improved. be able to.

1 is a schematic diagram showing in principle the basic structure of a power generation element in a molten salt battery. It is a perspective view which shows simply the lamination structure of a molten salt battery main body (main-body part as a battery). It is a cross-sectional view about the structure similar to FIG. It is a perspective view which shows the outline of the external appearance of the molten salt battery of the state accommodated in the battery container. It is a perspective view (a partial cross section is included) which shows an example of the state which arranged the molten salt battery as a unit cell in the outer box, and comprised the assembled battery. It is a block diagram which shows the circuit structure of the molten salt battery system which concerns on 1st Embodiment of this invention. It is a sequence diagram regarding charge of a molten salt battery system. It is the figure which represented the charging process of the battery unit in FIG. 7 with the flowchart. It is a sequence diagram regarding discharge of a molten salt battery system. It is the figure which represented the takeover process of the battery unit in FIG. 9 with the flowchart. It is a block diagram which shows the circuit structure of the molten salt battery system which concerns on 2nd Embodiment of this invention.

[Summary of Embodiment]
The gist of the embodiment of the present invention includes at least the following.

  (1) That is, this is a molten salt battery system constituted by a plurality of molten salt batteries using a molten salt as an electrolyte, and the working molten salt battery in which the electrolyte is in a molten state, and heating the working molten salt battery A heating device that is charged, a pre-molten salt battery in which the electrolyte is solidified, a heating device that can heat the pre-molten salt battery, and the working molten salt battery is brought into a predetermined state by discharging. And a control device for operating the heating device for the pre-molten salt battery using the output of the working molten salt battery to bring the electrolyte of the pre-molten salt battery into a molten state.

  In the molten salt battery system configured as described above, power can be supplied from the operating molten salt battery to the load when the voltage of the external power source is lost or when the external power source is not used. In addition, when the operating molten salt battery reaches a predetermined state by discharging, the heating device for the preliminary molten salt battery is operated by the output of the operating molten salt battery, and the preliminary molten salt battery is brought into a molten state. Thereby, the preliminary molten salt battery in which the electrolyte is in a solidified state can be started and power can be supplied to the load. Since the molten salt battery does not self-discharge in the solidified state, the charged (preferably fully charged) state can be maintained at room temperature for a long period of time. Thus, the molten salt battery that stores power in the solidified state of the electrolyte does not require heat insulation and supplementary charging by a heating device.

(2) Moreover, in the molten salt battery system of said (1), a predetermined state is that the charge capacity remaining capacity of an operation | movement molten salt battery becomes below a threshold value, for example.
In this case, for example, when the remaining amount of the operating molten salt battery is low, power is supplied from the first operating molten salt battery to the preliminary molten salt battery by starting the preliminary molten salt battery using the remaining amount. The battery that is the main body of the battery can be replaced. Thereby, electric power can be supplied to a load over a long time.

(3) Moreover, in the molten salt battery system of the above (2), the molten salt battery system includes a voltage sensor that detects an open voltage of the operating molten salt battery, and the control device estimates the remaining amount based on the detected open voltage. It may be.
In this case, the initial remaining amount before the start of discharge can be estimated from the open circuit voltage (OCV).

(4) The molten salt battery system according to (2) or (3) further includes a current sensor that detects a current output from the operating molten salt battery, and the control device performs integration based on the detected current. The amount of power may be calculated, and the remaining amount may be estimated based on the integrated power amount.
In this case, the remaining amount can be accurately estimated based on the actually output electric energy.

(5) Moreover, in the molten salt battery system in any one of said (1)-(4), a preliminary | backup molten salt battery contains what is mounted so that attachment or detachment is possible, and what is stored in non-mounting. be able to.
The preliminary molten salt battery in which the molten salt battery is changed from a solidified state to a molten state changes its position and becomes an operating molten salt battery. On the other hand, since the operating molten salt battery that has been operating until now is used, it can be said that the pre-molten salt battery that has been stored becomes the same as the initial state by replacing it. In other words, when the remaining amount of the operating molten salt battery decreases, the installed pre-molten salt battery is replaced with a new operating molten salt battery, and the used battery is repeatedly stored and replaced with the stored pre-molten salt battery. Power can be continuously supplied to the load for a long time according to the number.

(6) In addition, in the molten salt battery system according to any one of (1) to (5), a battery unit including an operating molten salt battery and a heating device thereof, and a battery unit including a preliminary molten salt battery and a heating device thereof. However, at least one of each may be detachably provided.
In this case, replacement with a unit including a heating device is possible, so replacement is easy.

  (7) On the other hand, as a method, a molten salt battery charging / discharging method executed by a molten salt battery system including a plurality of molten salt batteries using a molten salt as an electrolyte, wherein at least two sets of the molten salts are prepared. In each set, the battery is charged in a state where the electrolyte is melted by the heating device, and some of the molten salt batteries among all the molten salt batteries are heated and kept warm by the heating device. When the second step of maintaining the molten state of the electrolyte, the third step of transitioning the electrolyte to a solidified state without keeping the temperature of the remaining molten salt battery, and when it is necessary to supply power to the load, A fourth step of supplying electric power from a part of the molten salt batteries; and when the part of the molten salt batteries reaches a predetermined state by discharge, using the output of the molten salt battery, at least one of the remaining Two melts An electrolyte salt battery is transitioned to a molten state by the heating device, then, with respect to the load, and has a, a fifth step of supplying power from the molten salt battery transitioning into the molten state.

  In the charge / discharge method as described above, when the voltage of the external power source is lost or when the external power source is not used, power can be supplied to the load from some of the molten salt batteries that are operating. Further, when the molten salt battery reaches a predetermined state by discharge, at least one of the remaining spare molten salt batteries is operated by the output of the molten salt battery and is heated by the heating apparatus. A spare molten salt battery is brought into a molten state. As a result, it is possible to start the spare molten salt battery in which the electrolyte is in a solid state and supply power to the load. Since the molten salt battery does not self-discharge in the solidified state, the charged (preferably fully charged) state can be maintained at room temperature for a long period of time. Thus, the molten salt battery that stores power in the solidified state of the electrolyte does not require heat insulation and supplementary charging by a heating device.

(8) In the charging / discharging method of (7), the external power source is a commercial power source, the first step is performed using nighttime power, and the fourth and fifth steps are performed in the daytime. You may be made to do.
In this case, a use form of electric power that releases the electric power stored by using the night electric power in the daytime is realized, and the daytime electric power demand for the commercial power source can be reduced. If this type of power usage becomes widespread, it will contribute to the reduction of the peak value of power demand that generally shows a peak in the daytime or the leveling of power demand.

  (9) On the other hand, from a slightly different point of view, a molten salt battery system including a plurality of molten salt batteries using a molten salt as an electrolyte, the working molten salt battery in an operating state, and the working molten salt battery A heating device that heats and retains, a preliminary molten salt battery that is not heated and kept in a non-operating state in a charged state, a heating device that can heat the preliminary molten salt battery, and the working molten salt battery A control device that operates the heating device for the pre-molten salt battery using the output of the working molten salt battery to bring the pre-molten salt battery into an operating state when the battery reaches a predetermined state by discharge. It is a thing.

  In the molten salt battery system configured as described in (9) above, when the voltage of the external power source is lost or when the external power source is not used, power can be supplied from the operating molten salt battery to the load. . In addition, when the operating molten salt battery reaches a predetermined state by discharging, the heating device for the preliminarily molten salt battery is operated by the output of the operating molten salt battery, and the preliminarily molten salt battery is brought into the operating state. Thereby, a preliminary | backup molten salt battery can be started and electric power can be supplied to load.

  (10) Further, as a molten salt battery charging / discharging method executed by a molten salt battery system including a plurality of molten salt batteries using a molten salt as an electrolyte, at least two sets of the molten salt batteries prepared are Both the first step of charging while being heated and kept warm by the heating device, and the second step of keeping the operating state by heating and keeping warm for some of the molten salt batteries among the molten salt batteries. And the third step of waiting for the remaining molten salt batteries to stand by in a non-operating state without heating and heating, and the fourth step of supplying electric power from the partial molten salt batteries when it is necessary to supply electric power to the load. And when a part of the molten salt battery reaches a predetermined state by discharging, the output of the molten salt battery is used to heat and operate at least one of the remaining molten salt batteries by the heating device. Condition To transition to, then, to the load, and has a, a fifth step of supplying power from the molten salt battery transitioning into working state.

  In the charge / discharge method as described in (10) above, when the voltage of the external power source is lost or when the external power source is not used, power is supplied to the load from a part of the molten salt batteries that are operating. Can do. Further, when the molten salt battery reaches a predetermined state by discharge, at least one of the remaining spare molten salt batteries is operated by the output of the molten salt battery and is heated by the heating apparatus. The spare molten salt battery is put into operation.

[Details of the embodiment]
<Basic structure of molten salt battery>
FIG. 1 is a schematic diagram showing in principle the basic structure of a power generation element in a molten salt battery. In the figure, the power generation element includes a positive electrode 1, a negative electrode 2, and a separator 3 interposed therebetween. The positive electrode 1 is composed of a positive electrode current collector 1a and a positive electrode material 1b. The negative electrode 2 includes a negative electrode current collector 2a and a negative electrode material 2b.

The material of the positive electrode current collector 1a is, for example, an aluminum nonwoven fabric (wire diameter: 100 μm, porosity: 80%). The positive electrode material 1b is a mixture of, for example, NaCrO ₂ as a positive electrode active material, acetylene black, PVDF (polyvinylidene fluoride), and N-methyl-2-pyrrolidone at a mass ratio of 85: 10: 5: 100. It is a thing. And what was kneaded in this way is filled in the positive electrode collector 1a of an aluminum nonwoven fabric, and after drying, it presses at 100 Mpa, and it forms so that the thickness of the positive electrode 1 may be set to about 1 mm.
On the other hand, in the negative electrode 2, an Sn—Na alloy containing, for example, tin as a negative electrode active material is formed on the aluminum negative electrode current collector 2a by plating.

  The separator 3 interposed between the positive electrode 1 and the negative electrode 2 is obtained by impregnating a glass non-woven fabric (thickness 200 μm) or a polyolefin sheet (thickness 50 μm) with a molten salt as an electrolyte. This molten salt is, for example, a mixture of 56 mol% NaFSA and 44 mol% KFSA (potassium bisfluorosulfonylamide), and has a melting point of 57 ° C. At a temperature equal to or higher than the melting point, the molten salt melts and becomes an electrolytic solution in which high-concentration ions are dissolved, and touches the positive electrode 1 and the negative electrode 2. Moreover, this molten salt is nonflammable. The operating temperature range of this molten salt battery is 57 ° C to 190 ° C.

In addition, although the material, component, and numerical value of each part mentioned above are suitable examples, it is not limited to these.
For example, in addition to the above, a mixture of NaFSA and LiFSA, KFSA, RbFSA or CsFSA is also suitable as the molten salt. In addition, other salts composed of organic cations and the like may be mixed. In general, (a) a mixture containing NaFSA, (b) a mixture containing NaTFSA, and (c) a mixture containing NaFTA are suitable as the molten salt. . It is also possible to mix two or more of (a) to (c). In these cases, since the molten salt of each mixture has a relatively low melting point, a state in which high-concentration ions are dissolved with a small amount of heating can be realized, and the molten salt battery can be operated.

<Specific structure of molten salt battery>
Next, a more specific configuration of the power generation element of the molten salt battery will be described. FIG. 2 is a perspective view schematically showing a laminated structure of a molten salt battery main body (main body portion as a battery) 10, and FIG. 3 is a cross-sectional view of the same structure.
2 and 3, a plurality (six are shown) of rectangular flat plate-like negative electrodes 2 and a plurality (five are shown) of rectangles accommodated in a bag-like separator 3 respectively. The flat positive electrodes 1 are opposed to each other and are stacked in the vertical direction in FIG. 3, that is, in the stacking direction, to form a stacked structure.

  The separator 3 is interposed between the positive electrode 1 and the negative electrode 2 adjacent to each other. In other words, the positive electrode 1 and the negative electrode 2 are alternately stacked via the separator 3. For example, 20 positive electrodes 1 and 21 negative electrodes 2 and 20 separators 3 as “bags”, but 40 intervening between positive electrodes 1 and 2 are actually stacked. is there. The separator 3 is not limited to a bag shape, and may be 40 separated.

  In FIG. 3, the separator 3 and the negative electrode 2 are drawn so as to be separated from each other, but they are in close contact with each other when the molten salt battery is completed. Naturally, the positive electrode 1 is also in close contact with the separator 3. In addition, the vertical and horizontal dimensions of the positive electrode 1 are smaller than the vertical and horizontal dimensions of the negative electrode 2 in order to prevent the generation of dendrites, and the outer edge of the positive electrode 1 passes through the separator 3. Thus, it faces the peripheral edge of the negative electrode 2.

《One form of practical unit cell》
The molten salt battery main body 10 configured as described above is accommodated in a rectangular parallelepiped battery container made of, for example, an aluminum alloy, and forms a unit cell, that is, a physical individual as a battery.
FIG. 4 is a perspective view showing an outline of the appearance of the molten salt battery B in a state of being accommodated in such a battery container 11. 2 and 3, terminals (only the terminal 1t of the positive electrode 1 is shown) are drawn out of the battery container 11 from the positive electrode 1 and the negative electrode 2, respectively. In FIG. 4, a safety valve 12 for releasing the pressure when the internal atmospheric pressure rises excessively is provided at the top of the battery container 11. The inner surface of the battery container 11 is insulated. The battery container 11 is heated by, for example, a heater to be described later that is in close contact with the front and back surfaces, and as a result, the electrolyte salt becomes a molten salt electrolyte.

<< One form of practical assembled battery >>
FIG. 5 is a perspective view (including a partial cross-section) illustrating an example of a state in which the assembled battery 100 is configured by arranging a plurality of molten salt batteries B as unit cells configured as described above in the outer box 13. It is. However, illustration of details, such as a terminal of molten salt battery B, is omitted. If necessary, the battery pack 100 can be configured by a large number of molten salt batteries by arranging the molten salt batteries in a plurality of rows in a direction (depth direction) orthogonal to the direction of the arrangement.

Each molten salt battery B is connected in series or series-parallel with each other according to the required output (voltage, current). Thereby, the assembled battery 100 can be used with a desired voltage / current rating. Between each battery container 11, the planar heater 14 as a heating apparatus is mounted | worn. By heating with this heater 14, the molten salt battery B is heated so that it may become more than melting | fusing point of molten salt. Actually, the whole is heated to 90 ° C. to 95 ° C. in order to obtain a stable molten state. Thereby, molten salt will melt | dissolve and it will be in the state which can be charged and discharged.
The method of providing the heater 14 is merely an example, and various modifications such as a configuration in which one heater 14 is sandwiched between a predetermined number (a plurality) of molten salt batteries B and a configuration in which the heater is applied to the bottom surface or the side surface. Is possible.

  The outer box 13 is, for example, a substantially rectangular parallelepiped as a whole, and includes a main body portion 13a and a lid portion 13b. After accommodating the assembled battery 100 configured by arranging a large number of molten salt batteries, the lid portion 13b is fixed to the main body portion 13a with, for example, a bolt. The outer box 13 is preferably made of a material or a structure excellent in heat insulation, and the material is preferably ceramic, for example. The assembled battery 100 is housed in the outer box 13 together with the heater 14. In addition, the output line from the assembled battery 100, the power supply line to the heater 14, and the output line of the temperature sensor (not shown) are passed through the outer box 13 by providing a wall penetrating bush or the like (not shown), for example. Is done. The outer box 13 is not in a sealed state, and a constant inner and outer ventilation is possible.

Thus, by using the assembled battery 100 accommodated in the outer box 13, it is difficult for the heat generated from the heater 14 to escape to the outside of the outer box 13, and the heat retaining effect of the assembled battery 100 by the outer box 13 is obtained. . Therefore, the thermal efficiency is improved, and the molten salt can be maintained at a temperature higher than the melting point, particularly at a suitable 90 ° C. to 95 ° C. with less power.
In addition, the assembled battery 100 does not necessarily have to be accommodated in the outer box 13, and can be used in a state in which the assembled battery 100 is simply assembled without the outer box.

<< First Embodiment as Molten Salt Battery System >>
FIG. 6 is a block diagram showing a circuit configuration of the molten salt battery system according to the first embodiment of the present invention. This shows a simple form that is the basic type of the system. In the figure, the molten salt battery system 200 includes two battery units U1 and U2. Each of the battery units U1 and U2 is the same as the “thing”, but has a different role. On the other hand, the electrolyte of the molten salt battery inside is in a molten state and operates as a battery. This is referred to as an “operating molten salt battery”. The other is a state in which the electrolyte is solidified after full charge of the molten salt battery inside, and is in a dormant state where the battery does not operate. This is referred to as a “preliminary molten salt battery”. In addition, although it is preferable that a preliminary | backup molten salt battery is a full charge, it does not necessarily need to be a full charge, and should just be charged more than fixed. Here, for example, the molten salt battery of the battery unit U1 is an “operating molten salt battery”, and the molten salt battery of the battery unit U2 is a “preliminary molten salt battery”.

  The battery unit U1 includes an assembled battery 100, a temperature sensor 110, a voltage sensor 120, a heater 140, and switches SW2 and SW3, which are connected as illustrated. The assembled battery 100 is, for example, as shown in FIG. The assembled battery 100 is an example for securing a voltage / current necessary as an output, and basically a molten salt battery may be used regardless of whether it is a single body or an assembly.

  The temperature sensor 110 is attached in close contact with, for example, the battery container 11 of any molten salt battery B constituting the assembled battery 100 and detects the temperature of the battery container 11. A signal representing the detected temperature is sent to the control device 130. Since the plurality of molten salt batteries B form a group of assembled batteries 100, the temperature of any one of the battery containers 11 can be handled as the average temperature of the assembled battery 100.

  In addition to the above, there are various ways of providing the temperature sensor 110. For example, a plurality of temperature sensors may be provided so as to detect temperatures at a plurality of locations throughout the assembled battery 100, and the average or minimum value of the detected temperatures may be calculated by the control device 130. The temperature sensor 110 can also be housed inside the battery container 11.

  The voltage sensor 120 detects the voltage across the assembled battery 100 and sends a signal representing the voltage to the control device 130. The heater 140 is a general term for the heater 14 in FIG. The switches SW2 and SW3 are, for example, semiconductor switching elements, and are turned on / off in response to a drive signal from the control device 130.

On the other hand, the battery unit U2 includes an assembled battery 100, a temperature sensor 110, a voltage sensor 120, a heater 140, and switches SW4 and SW5, which are connected as illustrated. The switch symbol (symbol) is different from the battery unit U1 for convenience, but the substance is the same.
The battery units U1 and U2 can be easily attached to and detached from the circuit and casing (not shown) of the system in units.

  In addition to the battery units U1 and U2 and the control device 130, the molten salt battery system 200 includes a conversion device 150, a switch SW1, a current sensor 160, and an inverter 170 that performs DC / AC conversion for an AC load. These are connected as shown. The converter 150 converts the voltage supplied from the external power source PS into a DC voltage required in the molten salt battery system 200. The switch SW1 is, for example, a semiconductor switching element, and is normally on. However, the switch SW1 is off when performing a self-sustained operation (supplying power to the load independently from the external power source PS). The current sensor 160 uses, for example, a shunt resistor or a Hall element, detects the output current (direct current) of the molten salt battery system 200, and sends a signal representing the detected current to the control device 130.

  The molten salt battery system 200 is normally supplied with power from an external power source PS. With this electric power, the assembled battery 100 of each battery unit U1, U2 can be charged. The external power source PS is a commercial power source in this embodiment. The load L1 is an AC load and is usually directly connected to the external power source PS. However, when the external power source PS is out of power, the load L1 can be supplied with power by switching to the molten salt battery system 200. . Moreover, the molten salt battery system 200 can connect the DC load L2 as necessary.

  The control device 130 receives a voltage input by being connected to the electric circuit P to which the output voltage is applied. Based on the input voltage, the control device 130 generates a control power supply voltage such as DC5V or 12V, and provides the control power supply voltage to a device that requires the control power supply voltage in the molten salt battery system 200.

<Charging the molten salt battery system>
FIG. 7 is a sequence diagram showing exchanges between the units shown in FIG. 6 regarding charging of molten salt battery system 200. In the initial state of the switches SW1 to SW5 in FIG. 6, it is assumed that only the switch SW1 is on and the others are all off.

In FIG. 7 with reference to FIG. 6, when the external power source PS is normal in order from the top, power is directly supplied from the external power source PS to the load L1.
In the sequence in the frame F in FIG. 7, the upper stage and the lower stage from the middle dotted line are parallel processing (par) to each other, and are executed simultaneously.

  First, when the control device 130 turns on the switch SW3 in FIG. 6 on the upper side, power is supplied from the external power source PS to the heater 140 of the battery unit U1, and the assembled battery 100 of the battery unit U1 is heated. When the assembled battery 100 reaches the operating temperature (90 ° C. or higher and lower than 95 ° C.), the control device 130 turns on the switch SW2. As a result, charging power is supplied from the external power source PS to the assembled battery 100 of the battery unit U1.

  During charging, the control device 130 periodically turns off the switch SW2 for a very short time and detects the open voltage (OCV) of the assembled battery 100 by the voltage sensor 120. Based on the detected open circuit voltage, control device 130 estimates the remaining amount (state of charge (SOC)). When the open circuit voltage reaches a value corresponding to full charge, the control device 130 recognizes that the assembled battery 100 of the battery unit U1 has been fully charged and is in a fully charged state.

  On the other hand, when the control device 130 turns on the switch SW5 in FIG. 6 on the lower side, power is supplied from the external power source PS to the heater 140 of the battery unit U2, and the assembled battery 100 of the battery unit U2 is heated. When the assembled battery 100 reaches the operating temperature (90 ° C. or higher and lower than 95 ° C.), the control device 130 turns on the switch SW4. As a result, charging power is supplied from the external power source PS to the assembled battery 100 of the battery unit U2.

  During charging, the control device 130 periodically turns off the switch SW4 for a very short time and detects the open voltage (OCV) of the assembled battery 100 by the voltage sensor 120. Based on the detected open-circuit voltage, control device 130 estimates the remaining charge capacity (charge state; SOC). When the open-circuit voltage reaches a value corresponding to full charge, control device 130 recognizes that assembled battery 100 of battery unit U2 has been fully charged and has become fully charged.

Thereafter, the control device 130 turns off the switches SW4 and SW5. When the switch SW4 is turned off, the assembled battery 100 of the battery unit U2 is not charged / discharged. Further, when the switch SW5 is turned off, the heat insulation by the heater 140 is stopped. Accordingly, the temperature of the assembled battery 100 of the battery unit U2 gradually decreases and eventually reaches room temperature. When the temperature falls below 57 ° C., the molten salt electrolyte begins to solidify and is completely solidified at room temperature. Since the molten salt battery does not self-discharge in the solidified state, the fully charged state can be maintained at room temperature for a long time. That is, the assembled battery 100 is a “preliminary molten salt battery”. Since the molten salt battery that stores electric power in a solidified state of the electrolyte does not need to be kept warm by the heater 140, power consumption can be saved.
On the other hand, the assembled battery 100 of the battery unit U <b> 1 becomes a “working molten salt battery” that is heated and kept warm after that and maintains the molten state of the electrolyte.

FIG. 8 is a flowchart showing the charging process of the battery unit U2 in FIG.
The control device 130 that has started the charging process turns on the switch SW5 and heats the assembled battery 100 of the battery unit U2 by the heater 140 (step S1). Next, the control device 130 waits for the temperature T of the assembled battery 100 to reach the operating temperature (90 ° C. or higher and lower than 95 ° C.) (step S2). When the temperature T of the assembled battery 100 reaches the operating temperature, the control device 130 turns on the switch SW4 to start charging, and monitors the remaining battery level as described above (step S3). Thereafter, waiting for full charge (step S4), and after full charge, by turning off the switches SW4 and SW5, the electrolyte of each molten salt battery constituting the assembled battery 100 of the battery unit U2 is solidified. A transition is made (step S5).

《Discharge from molten salt battery system》
Next, the discharge from the molten salt battery system 200 will be described with reference to the sequence of FIG. In the initial state of the switches SW1 to SW5 in FIG. 6, the switches SW2 and SW3 are on and the switches SW1, SW4 and SW5 are off. The molten salt battery system 200 is disconnected from the external power source PS by turning off the switch SW1.

  In FIG. 9, when it is necessary to supply power to the load autonomously from the molten salt battery system 200 due to, for example, a power failure of the commercial power supply, first, the load L1 (and / or from the assembled battery 100 of the battery unit U1). Power is supplied to L2). The control device 130 monitors the remaining amount of the assembled battery 100 of the battery unit U1. The remaining amount is obtained by an operation of subtracting the actually output accumulated power amount and the power consumption amount in the heater 140 from the initial remaining amount estimated from the open voltage at the time of full charge. This integration is performed by the control device 130 based on the output current detected by the current sensor 160. By such integration, the remaining amount can be accurately estimated based on the actually output electric energy. Further, the power consumption of the heater 140 can be obtained as an approximate value by integrating the power consumption of the heater 140 by the time when both the switches SW2 and SW3 are on.

  When the remaining amount becomes less than or equal to the threshold value, the control device 130 turns on the switch SW5 and heats the assembled battery 100 of the battery unit U2 by the heater 140. The heating power is supplied from the assembled battery 100 of the battery unit U1 to the heater 140 of the battery unit U2. The control device 130 monitors the temperature of the assembled battery 100 of the battery unit U2, and turns on the switch SW4 when the operating temperature (90 ° C. or higher and lower than 95 ° C.) is reached. Thereby, electric power begins to be supplied from the assembled battery 100 of the battery unit U2 to the load L1 (and / or L2).

Thereafter, the control device 130 turns off the switches SW2 and SW3 and stops using the battery unit U1. Thus, the main body of power supply to the load is taken over from the assembled battery 100 of the battery unit U1 to the assembled battery 100 of the battery unit U2.
Note that the control device 130 continues monitoring the remaining amount and monitoring the battery pack 100 of the battery unit U2 thereafter.

FIG. 10 is a flowchart showing the battery unit takeover process in FIG.
The control device 130 periodically monitors the remaining amount of the operating molten salt battery, that is, the assembled battery 100 of the battery unit U1 (step S11), and monitors whether the remaining amount is equal to or less than the threshold value (step S12). When the remaining amount is equal to or less than the threshold value, the switch SW5 is turned on, and the preliminary molten salt battery, that is, the assembled battery 100 of the battery unit U2, is heated by the heater 140 (step S13). Thereafter, the control device 130 waits for the temperature T of the preliminary molten salt battery to reach the operating temperature (90 ° C. or more and less than 95 ° C.) (step S14). When the temperature reaches the operating temperature, the switch SW4 is turned on and then the switch SW2 and SW3 is turned off and the main body of power supply is handed over from the battery unit U1 to the battery unit U2 (step S15).

<< Summary of Operation in Molten Salt Battery System of First Embodiment >>
When the process from charging to discharging as described above is summarized as a charging / discharging method of the molten salt battery, the method includes at least the following steps.
(First step)
The two sets of molten salt batteries (the assembled battery 100) are fully charged in a state where the electrolyte is melted by the heating device 140 in each of the sets, and are preferably fully charged. In this case, it is the external power source PS that supplies power to the heating device 140 and supplies charging power. Note that the two sets are the minimum required basic type, and may be two or more sets.
(Second step)
One molten salt battery (the assembled battery 100 of the battery unit U1) is heated and kept warm by the heating device 140 to maintain the molten state of the electrolyte. That is, the molten salt battery is an active molten salt battery.

(Third step)
For the other molten salt battery (the assembled battery 100 of the battery unit U2), the electrolyte is transitioned to a solidified state without being kept warm. That is, the molten salt battery is a preliminary molten salt battery.
(4th process)
Thereafter, when it becomes necessary to supply power to the loads (L1, L2) autonomously, power is first supplied from one molten salt battery (the assembled battery 100 of the battery unit U1).
(5th process)
When one molten salt battery (the assembled battery 100 of the battery unit U1) becomes less than the threshold value due to discharge, the other molten salt is heated by the heating device 140 (battery unit U2) using the output of the molten salt battery. The electrolyte of the battery (the assembled battery 100 of the battery unit U2) is brought into a molten state. That is, at this time, the position of the molten salt battery is changed from the preliminary molten salt battery to the working molten salt battery. Thereafter, electric power can be supplied to the load from the other molten salt battery that has become an active molten salt battery.

  In addition, when there are more sets of molten salt batteries (assembled batteries) to be operated / reserved, some (at least one (one set)) of molten salt batteries are operated in a molten state, and the remaining A plurality of molten salt batteries are made to stand by in a solidified state. When the remaining amount of the operating molten salt battery becomes equal to or less than the threshold value, at least one of the remaining molten salt batteries is heated to transition to the molten state, and the role of the operating molten salt battery is taken over.

  According to the molten salt battery system 200 configured as described above and its charging / discharging method, power can be supplied from the operating molten salt battery to the load when the voltage of the external power source PS is lost due to a power failure. . In addition, when the operating molten salt battery reaches a state where the remaining amount is less than or equal to the threshold value due to discharge, the heating device for the pre-molten salt battery is operated by the output of the operating molten salt battery, and the pre-molten salt battery is brought into the molten state. To do. Thereby, the preliminary molten salt battery in which the electrolyte is in a solidified state can be started and power can be supplied to the load. Since the molten salt battery does not self-discharge in the solidified state, the state of charge completion (full charge) can be maintained at room temperature for a long time. In this way, the molten salt battery that stores power in the solidified state of the electrolyte does not require heat insulation and supplementary charging by a heating device, so that power can be saved and the energy efficiency of the entire system can be improved. Can do.

  Further, by setting an appropriate value slightly above the discharge limit as the remaining amount threshold value, it is possible to start the preliminary molten salt battery with the so-called final force of the operating molten salt battery. That is, after the first operating molten salt battery has been used for as long as possible, the battery serving as the main power supply can be replaced with the preliminary molten salt battery. Thereby, electric power can be supplied to a load over a long time.

  Further, the two battery units U1 and U2 shown in FIG. 6 are detachably mounted on the system as described above. Furthermore, the battery unit can be stored as a single spare part without being mounted. This battery unit also stores electric power, preferably because the electrolyte is solidified in a fully charged state. Then, after taking over between the two mounted battery units, when the used battery unit whose remaining amount is equal to or less than the threshold is replaced with the spare battery unit, the state of the two battery units Is substantially in the same state as the molten salt battery system immediately after the start of the self-sustaining operation.

In other words, when the remaining amount of the operating molten salt battery decreases, the installed pre-molten salt battery is replaced with a new operating molten salt battery, and the used battery is repeatedly stored and replaced with the stored pre-molten salt battery. Power can be continuously supplied to the load for a long time according to the number. If the number of storage is sufficient, it is possible to maintain power supply from the molten salt battery system to the load even during a long power outage due to an accident such as a disaster.
Moreover, the replacement in units of units can be easily performed including the heater that is usually integrated with the molten salt battery.

In addition, although the said embodiment demonstrated as a molten salt battery system which can supply electric power to a load autonomously at the time of a power failure of the external power source PS which is a commercial power supply, the external power source PS is also used other than a power failure. When not in use, the system can be used effectively.
For example, in the case where the electricity price contract with the power supply company is made separately at night and day, electricity is stored in the molten salt battery system 200 using nighttime power that is lower than daytime, and commercial power is used as much as possible during the daytime. What is necessary is just to make it supply electric power to load from the molten salt battery system 200, without using. That is, among the aforementioned steps, the first step is performed using nighttime power, and the fourth and fifth steps are performed in the daytime.

Thereby, the usage pattern of the electric power which discharge | releases the electric power stored using night electric power in the daytime is implement | achieved, and the electric power demand in the daytime with respect to a commercial power source can be reduced. If this type of power usage becomes widespread, it will contribute to the reduction of the peak value of power demand that generally shows a peak in the daytime or the leveling of power demand.
In addition, on the consumer side, it is possible to reduce the electricity bill. Although there is a loss due to the fact that the charging / discharging efficiency is not 100%, due to the difference in the electricity charge between day and night, even if the loss is expected, it is possible to reduce the electricity charge as a whole.

  In the above embodiment, as a timing for taking over the role of the operating molten salt battery to the preliminary molten salt battery, the specific example is that the remaining amount of the operating molten salt battery is equal to or less than the threshold value. In the case of electric power, it is also possible to set the timing of taking over that the operating time has reached a predetermined time.

  In the above embodiment, the external power source PS has been described as a commercial power source, but may be a power source provided from a power conditioner such as a solar power generation device or a wind power generation device. For example, in the case of solar power generation, if power is stored in the molten salt battery system 200 by surplus power obtained by subtracting the used power from daytime generated power, and the power is discharged from the molten salt battery system 200 after sunset, on a customer basis. It becomes possible to realize self-sufficiency of electricity.

<< Second Embodiment as Molten Salt Battery System >>
FIG. 6 shows the molten salt battery system as a basic type, but the number of battery units can be increased according to the required voltage and current.
FIG. 11 is a block diagram showing a circuit configuration of a molten salt battery system according to the second embodiment of the present invention. The main difference from FIG. 6 is that n battery units U11, U12,..., U1n responsible for either one of operation / spare and n battery units U21, U22,. U2n is prepared in a relationship of n parallel connections. In addition, n switches SW11, SW12,..., SW1n are provided for the plus-side electric circuits P1, P2,.

  When the current required for the load is large, the necessary current capacity can be ensured by such a parallel connection. In FIG. 11, one of the operation / standby is the battery unit U11, U12,..., U1n and the other is the battery unit U21, U22,. Other “groupings” are also possible. For example, out of a total of (2 × n) battery units, any half may be an “operating group” and the remaining half may be a “preliminary group”.

<< 3rd Embodiment as a molten salt battery system >>
In each of the above embodiments, the molten salt battery in which the electrolyte solution is solidified at room temperature has been described. For example, a mixture of NaFSA and Py13FSA (N-methyl-N-propylpyrrolidinium FSA) is from 57 ° C. Also, it can be applied as an electrolytic solution / electrolyte having a low melting point, for example, a molten state even at a room temperature of about 20 degrees. Accordingly, a molten salt battery system using a molten salt battery that can be charged / discharged even at room temperature will be described.
That is, in this case, the preliminary molten salt battery does not solidify the electrolyte even at room temperature, but in order to obtain an “operating state” that secures a practical level of charge / discharge current, for example, heating up to about 50 ° C. to 90 ° C. is necessary. On the other hand, although it is in a molten state even at room temperature, it is in a state where there is little self-discharge. Therefore, the preliminary molten salt battery is kept in a non-operating state without being heated and kept warm. Then, when the operating molten salt battery reaches a predetermined state by discharging, the heating device for the preliminary molten salt battery is operated using the output of the operating molten salt battery, and the preliminary molten salt battery is brought into an operating state.

<< Summary of Operation in Molten Salt Battery System of Third Embodiment >>
When the process from charging to discharging as described above is described as a charging / discharging method of the molten salt battery, the method includes at least the following steps.
(First step)
Two sets of molten salt batteries (assembled battery 100) are charged in a state where each set is heated and kept warm by a heating device, and preferably in a fully charged state.
(Second step)
One molten salt battery (the assembled battery 100 of the battery unit U1) is heated and kept warm. That is, the molten salt battery is an active molten salt battery.

(Third step)
The other molten salt battery (the assembled battery 100 of the battery unit U2) is kept at a normal temperature without being heated and kept in a non-operating state. That is, the molten salt battery is a preliminary molten salt battery.
(4th process)
Thereafter, when it becomes necessary to supply power to the loads (L1, L2) autonomously, power is first supplied from one molten salt battery (the assembled battery 100 of the battery unit U1).
(5th process)
When one molten salt battery (the assembled battery 100 of the battery unit U1) becomes less than the threshold value due to discharge, the other molten salt is heated by the heating device 140 (battery unit U2) using the output of the molten salt battery. The battery (the assembled battery 100 of the battery unit U2) is heated to transition to the operating state. That is, at this time, the position of the molten salt battery is changed from the preliminary molten salt battery to the working molten salt battery. Thereafter, electric power can be supplied to the load from the other molten salt battery that has become an active molten salt battery.

  If there are more or more molten salt batteries (assembled batteries) to be operated / reserved, some (at least one (one set)) of molten salt batteries are operated, and the remaining (plural). The molten salt battery is made to stand by in a non-operating state. If the remaining amount of the operating molten salt battery becomes equal to or less than the threshold value, at least one of the remaining molten salt batteries is heated to be shifted to the operating state, and the role of the operating molten salt battery is taken over.

According to the molten salt battery system 200 and the charge / discharge method thereof according to the third embodiment configured as described above, when the voltage of the external power source PS is lost due to a power failure, power is supplied from the operating molten salt battery to the load. Can be supplied. In addition, when the operating molten salt battery reaches a state where the remaining amount is less than or equal to the threshold value due to discharge, the heating device for the preliminary molten salt battery is operated by the output of the operating molten salt battery, and the preliminary molten salt battery is set to the operating state. To do. Since the preliminary molten salt battery has little self-discharge at room temperature, it can maintain a state close to the state of charge completion (full charge) at room temperature for a relatively long period of time. In addition, even if heating is necessary to put the preliminary molten salt battery into operation, the standby molten salt battery that is in standby does not need to be kept warm by a heating device, so that power is saved accordingly. The energy efficiency of the entire system can be increased.
Others are the same as those of the molten salt battery system 200 according to the first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1: positive electrode 1a: positive electrode current collector 1b: positive electrode material 1t: terminal 2: negative electrode 2a: negative electrode current collector 2b: negative electrode material 3: separator 10: molten salt battery main body 11: battery container 12: safety valve 13: outer box 14 : Heater 13a: Main body part 13b: Lid part 100: Battery pack (molten salt battery)
110: Temperature sensor 120: Voltage sensor 130: Control device 140: Heater (heating device)
150: Conversion device 160: Current sensor 170: Inverter 200: Molten salt battery system B: Molten salt battery L1, L2: Load P1 Electric circuit PS: External power source SW1 to SW1n: Switches U1, U2, U11, U12, U1n, U21 , U22, U2n: Battery unit

Claims (10)

A molten salt battery system comprising a plurality of molten salt batteries using a molten salt as an electrolyte,
An operating molten salt battery in which the electrolyte is in a molten state;
A heating device for heating the working molten salt battery;
A pre-molten salt battery that is charged and in which the electrolyte is solidified;
A heating device capable of heating the preliminary molten salt battery;
When the operating molten salt battery reaches a predetermined state by discharging, the heating device for the preliminary molten salt battery is operated using the output of the operating molten salt battery, and the electrolyte of the preliminary molten salt battery is in a molten state A molten salt battery system comprising:   The molten salt battery system according to claim 1, wherein the predetermined state is that a remaining charge capacity of the operating molten salt battery is equal to or less than a threshold value.   The molten salt battery system according to claim 2, further comprising a voltage sensor that detects an open voltage of the operating molten salt battery, wherein the control device estimates the remaining amount based on the detected open voltage.   A current sensor that detects a current output from the operating molten salt battery is provided, and the control device calculates an integrated power amount based on the detected current, and estimates the remaining amount based on the integrated power amount. The molten salt battery system according to claim 2 or 3.   The molten salt battery system according to any one of claims 1 to 4, wherein the preliminary molten salt battery includes a battery that is detachably mounted and a battery that is stored unmounted.   The battery unit including the operating molten salt battery and its heating device, and at least one battery unit including the preliminary molten salt battery and its heating device, respectively, are detachably provided. The molten salt battery system according to claim 1. A molten salt battery charging / discharging method executed by a molten salt battery system comprising a plurality of molten salt batteries having a molten salt as an electrolyte,
A first step of charging the molten salt batteries prepared in at least two sets in a state where the electrolyte is melted by a heating device in each set;
A second step of maintaining a molten state of the electrolyte by heating and maintaining a part of the molten salt batteries among all the molten salt batteries;
A third step of transitioning the electrolyte to a solidified state without heat retention for the remaining molten salt battery;
When it becomes necessary to supply power to the load, a fourth step of supplying power from the partial molten salt battery;
When some of the molten salt batteries reach a predetermined state by discharge, the output of the molten salt battery is used to transition the electrolyte of at least one of the remaining molten salt batteries to the molten state by the heating device. Then, a fifth step of supplying electric power from the molten salt battery that has transitioned to the molten state with respect to the load. The external power source is a commercial power source,
The said 1st process is performed using night electric power, The said 4th process and the said 5th process are the charging / discharging methods of the molten salt battery of Claim 7 performed in daytime. A molten salt battery system comprising a plurality of molten salt batteries using a molten salt as an electrolyte,
An operational molten salt battery in operation;
A heating device for heating and maintaining the working molten salt battery;
A pre-molten salt battery that is kept in a non-operating state without being heated and kept in a charged state, and
A heating device capable of heating the preliminary molten salt battery;
When the operating molten salt battery reaches a predetermined state by discharge, the heating device for the preliminary molten salt battery is operated using the output of the operating molten salt battery, and the preliminary molten salt battery is put into an operating state. A molten salt battery system comprising a control device. A molten salt battery charging / discharging method executed by a molten salt battery system comprising a plurality of molten salt batteries having a molten salt as an electrolyte,
A first step of charging the molten salt batteries prepared in at least two sets, each set being heated and kept warm by a heating device;
A second step of maintaining a working state by heating and maintaining the molten salt battery among all the molten salt batteries with the heating device;
For the remaining molten salt battery, a third step of waiting in a non-operating state without heating and keeping warm,
When it becomes necessary to supply power to the load, a fourth step of supplying power from the partial molten salt battery;
When some of the molten salt batteries reach a predetermined state by discharging, the output of the molten salt battery is used to heat at least one of the remaining molten salt batteries by the heating device and transition to an operating state And a fifth step of supplying electric power from the molten salt battery that has transitioned to an operating state with respect to the load.

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