JP3091885B2 - High temperature secondary battery and battery module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature secondary battery used for electric power storage, an electric vehicle battery and the like, and a battery module assembled using the same.

[0002]

2. Description of the Related Art A high-temperature type secondary battery according to the present invention has an operating temperature higher than room temperature and a liquid metal cathode at the operating temperature.
A battery capable of repeatedly charging and discharging, having a solid electrolyte and a partially or entirely liquid anode. One example of such a battery is a sodium-sulfur battery. In a sodium-sulfur battery, an anode and a cathode are generally housed in a metal anode container and a cathode container, respectively, and are provided with an anode terminal and a cathode terminal for taking out current to the outside. The active material of the cathode is metallic sodium, which is liquid at battery operating temperatures. Although sulfur is used as the active material of the anode, it is used in the form of being impregnated in felt-like graphite which is a current collector because of lack of electron conductivity. Anode container and cathode container
The battery is insulated with an insulator, and the battery generally has a sealed structure. Further, inside the battery, the anode and the cathode are separated by a solid electrolyte. The solid electrolyte is a good conductor of metal ions formed at the cathode, but needs to have extremely low electron conductivity. Generally, beta alumina or the like is used. The solid electrolyte is generally formed in a tubular shape having a closed lower end in order to increase the area where a battery reaction occurs, and is formed so as to separate the active material into its outside and inside.

[0003] Such high-temperature secondary batteries are rarely used as single cells, and are often used in the form of a module in which a plurality of batteries are combined. The module is assembled so that cells are connected in series and in parallel, and charging and discharging are performed according to the voltage and current values suitable for the purpose of use. In order for the battery to operate at a high temperature, the battery module is placed in whole or in part in a heat insulation facility and operated. As a conventional example, JP-A-1-253173 is cited.

[0004]

In such a high-temperature type secondary battery, electrochemical deterioration such as generation of dentite occurs in the solid electrolyte due to inversion caused by current flowing into the battery at normal temperature. As a result, there is a problem that the solid electrolyte is damaged, and in the worst case, the entire module becomes inoperable.

[0005] The flow of current into the battery at room temperature is used to confirm the short-circuit between cells during the assembly of the module, the connection of the battery in the module, and the connection of the measurement line attached to the module. Occurs when voltage is applied to the The above conventional example does not consider this point. The former occurs when the insulation between batteries is incomplete. FIG. 5 shows batteries connected in series. Each of the batteries 14, 15, and 16 is placed on a metal mounting table 17 also serving as a heat insulating container via an insulating material pedestal 13. The batteries are connected in series by a connection line 12. In this case, if for some reason the insulation of the insulating pedestal 13 of the two batteries 14 and 16 becomes incomplete, and there is continuity between the batteries 14 and 16 and the installation base 17, the batteries 15 and 16 Short-circuits. If this is written as a circuit diagram, it will be as shown in FIG. In such a case, when the potential of the cathode of the battery 15 becomes higher than that of the anode (polarization), reverse charging occurs. In that case, sodium dendrite is generated in the solid electrolyte in the battery and the solid electrolyte is damaged, and even in a small case, the strength of the solid electrolyte is reduced. The thermal expansion difference causes the destruction of the solid electrolyte.

[0006] As for the latter, since the module has a sealed structure in which the module is placed in a heat insulating container as described above, it is necessary to check the connection of the batteries or the connection of the measurement line for measuring the voltage and current of the battery such as a megger test. , Which must be performed at room temperature before operation. On the other hand, if the operation is performed without checking these connections, if a problem occurs in the connections, it is only at the temperature at which the active material melts that is found, and then the temperature is lowered again at room temperature. Since the malfunction must be repaired, there is a problem that it takes a very long time until normal operation is performed. However, in order to protect the solid electrolyte, it is common practice to raise the temperature without confirming the connection at room temperature, assuming that it will take time, which may adversely affect the battery and its solid electrolyte at room temperature. There was no method to confirm these connections without giving.

An object of the present invention is to prevent a current from flowing into a battery at room temperature, which has a bad effect on a battery and a solid electrolyte, to be resistant to a short circuit between a plurality of batteries, and to confirm connection at room temperature. An object of the present invention is to provide a high-temperature secondary battery and a battery module that can be inspected.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an anode provided with an anode active material and a current collector which are liquid at an operating temperature, an anode container containing the anode, and a liquid metal at an operating temperature. A cathode provided with a cathode active material, a cathode container that houses the cathode and contacts the cathode, an insulator that insulates the anode container and the cathode container, and a solid electrolyte that separates the anode and the cathode. In the high-temperature secondary battery provided, between the anode container and the cathode container, at room temperature, has a lower resistance value than the internal resistance of the battery at room temperature, at the battery operating temperature than the internal resistance of the battery at that temperature It is characterized by being connected by connection means having a high resistance value. Here, in the high-temperature secondary battery, the anode active material is sulfur and / or sodium polysulfide, the cathode active material is sodium, and the solid electrolyte is β-alumina and / or β ″ -alumina. The resistance of the connection means at room temperature is not more than 1/100 of the internal resistance of the battery at room temperature, and at the operating temperature of the battery, 100 times the internal resistance of the battery at that temperature. The connection means may be a thermal switch or a positive temperature coefficient (PTC) thermistor.

According to another aspect of the present invention, there is provided a battery module for charging / discharging comprising a plurality of high temperature secondary batteries, a module container for accommodating the plurality of batteries, and a temperature increasing means for increasing the temperature of the batteries. Wherein the high-temperature secondary battery is any one of the above.

[0010]

As described above, between the anode container and the cathode container of the unit cell, at room temperature, the resistance is lower than the internal resistance of the battery at room temperature, and the operating temperature of the battery is lower than the internal resistance of the battery at that temperature. When assembling a module by connecting a substance or element having high resistance, that is, connection means, in parallel with the battery, if a voltage is applied to the module at room temperature, such as when checking the connection, the voltage applied to the module from the outside Current flows through the connection means without passing through each cell since the resistance of the substance or element is lower than the internal resistance of the battery at room temperature. Therefore, no current that adversely affects the solid electrolyte flows into the battery. Also, if a short circuit occurs in the series section of a module combining these batteries, a closed circuit is formed in each of the cells, so that no current flows into other batteries, and consequently the reverse of the battery due to reversal. No charging occurs.

On the other hand, at the battery operating temperature, since the resistance of the connection means is higher than the internal resistance of the battery, the connection means is like an open switch. In this case, current flows through the battery and the module behaves similarly to a module without connection means.

By the above-described operation, in the battery of the present invention and the module using the battery, the battery can be electrochemically destroyed without impairing the operation of the battery at the battery operating temperature. Can be prevented from flowing.

In order to ensure this effect and not to impair the good battery efficiency which is a feature of the high-temperature type secondary battery, the resistance value of the connecting means at room temperature is set to be lower than that of the battery at room temperature. It is desirable that the internal resistance be 1/100 or less of the internal resistance and that the battery operating temperature be 100 times or more the internal resistance of the battery at that temperature. The reason is that when the resistance value at room temperature is higher than 1/100 of the internal resistance of the battery at room temperature, the ratio of the current flowing into the battery increases, and depending on the externally applied voltage or the magnitude of the battery short circuit, This is because a current may flow in the battery in an amount that has an adverse electrochemical effect on the solid electrolyte. When the resistance of the connection means is smaller than 100 times the internal resistance of the battery at the battery operating temperature, the current flowing into the connection means cannot be ignored, the resistance loss of the module increases, the battery efficiency decreases, and the module performance decreases. To drop it.

[0014]

FIG. 3 is a sectional view of a sodium-sulfur battery according to the present invention. The anode 10 and the cathode 5 are generally housed in a metal anode container 9 and a cathode container 6, respectively, and are provided with an anode terminal 8 and a cathode terminal 4 for taking out current to the outside. The active material of the cathode is metallic sodium, which is liquid at battery operating temperatures. Although sulfur is used as the active material of the anode, it is used in the form of being impregnated in felt-like graphite which is a current collector because of lack of electron conductivity. The anode container 9 and the cathode container 4 are insulated by an insulator 7, and the battery generally has a sealed structure. Further, inside the battery, the anode 10 and the cathode 5 are separated by a solid electrolyte 11. Although the solid electrolyte 11 is a good conductor of metal ions formed at the cathode, it is necessary that the electron conductivity is extremely small, and beta alumina or the like is generally used. The solid electrolyte 11 is generally formed in a tubular shape having a closed lower end in order to increase the area in which a battery reaction occurs, and is formed so as to separate the active material into its outside and inside. 2 is a connection means according to the present invention, which connects between the anode container 9 and the cathode container 6 and has a lower resistance value at room temperature than the internal resistance of the battery at room temperature, It has the property of having a resistance value higher than the internal resistance of the battery at that temperature.

As described above, between the anode container 9 and the cathode container 6 of the unit cell, at room temperature, the resistance is lower than the internal resistance of the battery at room temperature, and at the battery operating temperature, the internal resistance of the battery at that temperature is lower. Connecting means 2 having a higher resistance than
A case where the battery module as shown in FIG. 4 is assembled by connecting the battery in parallel will be described. In FIG. 4, a plurality of the batteries 1 are mounted on an insulating pedestal 13 and housed in a module container 19. The container 1
A heater wire 21 is provided on the inner surface of the heater 9 via a heat insulating material 20. Reference numeral 22 denotes an exhaust pipe, and 23 denotes a blower.

FIG. 1 is a circuit diagram showing a state in which a voltage is applied to the module at normal temperature for checking connections and the like. Here, the connection means 2 is described as a closed switch because of its function. In this case, the external voltage applied to the module 3
Since the resistance of the connection means 2 is lower than the internal resistance of the battery 1 at room temperature, the current flows through the connection means 2 without passing through each cell. Therefore, no current that adversely affects the solid electrolyte 11 flows into the battery 1. Also, when a short circuit occurs in the series part of a module combining these batteries, a closed circuit is formed in each of the cells, so that no current flows into other batteries, and therefore, the battery is not reversed due to the reversal of the polarity. There is no reverse charging.

On the other hand, a circuit diagram of the battery module at the battery operating temperature is shown in FIG. Since the resistance of the connecting means 2 is higher than the internal resistance of the battery 1, the connecting means 2 is described as an open switch. In this case, the current flows via the battery 1 and the module behaves similarly to the module without the connection means 2.

In this embodiment, the arrangement of the connecting means 2 added to the battery is arranged outside the battery in parallel with the battery. However, the connecting means 2 has corrosion resistance to the battery active material and has a negative electrode. If it is not a conductor of the active material ion, it can be incorporated in the battery or be one of the components of the battery. For example, such connection means can be used as an insulator between the anode and cathode containers. Hereinafter, a specific description will be given with reference to examples.

(Embodiment 1) Eighty sodium-sulfur batteries having a capacity of 500 Wh were prepared, and a bimetal was used between each cathode vessel and anode vessel, which had conduction at room temperature and no conduction at 300 ° C. The heat switch was joined with silver solder. By arranging 8 such batteries in series and 10 in parallel, 40
A kWh battery module was prepared. Apply a voltage to both ends of the eight batteries in series with a tester to check each series connection, confirm that there is continuity, and make sure that the insulation between the measurement lines that measure the battery voltage is good. To check, a megger test was performed with a voltage of 300V. It was repeated for each series of 10 sets. The temperature was increased at a rate of 5 ° C. per hour and the module was operated at 330 ° C. No battery is damaged during the temperature rise process, and all batteries maintain sound characteristics even after charging and discharging for 250 cycles by repeating charging and discharging for 8 hours at a current of 300 A and 250 cycles. The average efficiency of the battery, that is, the ratio of the amount of discharged electricity to the amount of charged electricity was as good as 87%. Disassemble the battery taken out of the module,
Examination of the solid electrolyte beta-alumina revealed that the part that was in contact with sodium turned slightly grayish white,
No other abnormalities were observed.

(Embodiment 2) As in Embodiment 1, except that the thermal switch is replaced by about 5 Ω at room temperature and about 1 kΩ at 300 ° C.
The positive temperature coefficient thermistor was silver-brazed between the anode container and the cathode container to prepare 60 sodium-sulfur batteries. The internal resistance of this battery was 300Ω at 20 ° C. and 4 mΩ at 300 ° C. As in the case of the first embodiment, six cables were assembled into a module in a series of 10 parallel, and the connection of the series connection and the connection of the battery voltage measurement line were checked in the same manner as in the first embodiment. Example 1 of this battery module
As a result of performing the test under the same conditions as in the above, the characteristics of the battery at the end of the test were sound, and the average efficiency of the battery was 80%.

Comparative Example 1 A sodium-sulfur battery as in Example 1 except that no heat switch was added
In this way, eight series and ten parallel battery modules were made in the same manner as in Example 1. In the same manner as in Example 1, the connection of the serial connection by the tester was confirmed, and the connection of the battery voltage measurement line was confirmed by the megger test. In the process of increasing the temperature of this module at a rate of 3 ° C./hour, 23 batteries were damaged at about 110 ° C., and the battery voltage became 0 V, making it impossible to operate the entire module. After the module was cooled down, the undamaged battery was disassembled and examined. As a result, many sodium dendrites were confirmed on the anode side of the solid electrolyte. In addition, when the battery was decomposed with slight damage, the crack origin was equivalent to the sodium dendrite part, and from this, by applying a voltage to the battery at room temperature, sodium ions were generated at the interface between the solid electrolyte and the anode. It is thought that the strength of the solid electrolyte was reduced by receiving electrons from the graphite felt of the current collector and precipitated as a metal in the solid electrolyte, and it was impossible to withstand the stress generated when the anode sulfur was melted, causing damage. Can be Thus, when voltage is applied to the battery module at room temperature without taking the countermeasures as in Example 1 and Example 2, operation of the entire module becomes impossible due to battery damage due to electrochemical deterioration of the solid electrolyte. May be.

(Example 3) As in Example 1, forty sodium-sulfur batteries with a bimetallic thermal switch were prepared, and eight battery modules in series and five parallel were assembled. However, among the eight rows in one series, the two anode terminals at both ends were connected and deliberately short-circuited. With respect to this module, a continuity test and a megger test were performed by a tester in the same manner as in Example 1, and the temperature was increased and an energization experiment was performed with a current of 120 A. One of the short-circuited rows cannot be charged and discharged, and the battery efficiency of the entire module is reduced by that amount, but it does not adversely affect the other series, and even after 250 cycles of energization, Batteries maintained good characteristics. After cooling this module,
As a result of disconnecting the deliberately short-circuited wire and assembling it again into a module, heating and energizing it, the eight batteries in series that could not be charged or discharged due to the short-circuit first were charged in the same way as the other batteries. Discharge was possible and showed good characteristics. (Comparative Example 2) As in Example 3, but using 40 sodium-sulfur batteries without a thermal switch, an eight-series and five-parallel battery module was assembled. The two anode terminals were connected and intentionally short-circuited. This module was subjected to a continuity test and a megger test using a tester in the same manner as in Example 1. In this module, the second battery from the cathode side was damaged in the row of eight short-circuited batteries in the process of raising the temperature,
Driving became impossible. After the module was cooled down, the remaining seven batteries which were short-circuited were heated up one by one and tested as single cells, and three of them were damaged during the temperature rise. For the remaining four batteries, although the cause is not clear, the open circuit voltage of the batteries in the charged state was as low as about 1.8 V, and all batteries were reassembled in the module and damaged during temperature rise.

Example 4 A battery was manufactured in the same manner as in Example 2 except that a thermistor was added to the battery. However, there are three types of thermistors used, each having a resistance value of (i) 25 ° C .:
5 Ω, 300 ° C .: 10 kΩ, (ii) 25 ° C .: 100 m
Ω, 300 ° C .: 10 mΩ, (iii) 25 ° C .: 1 Ω, 30
0 ° C .: 100 Ω, and a total of 30 pieces were manufactured, 10 pieces each. The internal resistance of the battery not including the thermistor was 250 Ω at 25 ° C. and 4 mΩ at 300 ° C. These batteries were assembled into modules of 5 series and 2 parallel for each thermistor (i), (ii) and (iii). A voltage is applied to both ends of the five batteries with a tester to check each series connection, and a megger test is performed with a voltage of 1 kV to check whether insulation between the measurement lines for measuring the battery voltage is good. went. It was repeated for each series set.

In order to conduct an energization experiment on these three modules, the temperature was increased at a rate of 5 ° C./hour.
In the module made using the battery provided with the thermistor, one battery was damaged at about 110 ° C., and one series operation was impossible. In the battery module prepared by using the thermistor of (ii), there was no abnormality during temperature rise, but the efficiency during battery operation was extremely low at 55%, which made it difficult to use the module. On the other hand, (iii)
In the battery module made using the battery incorporating the thermistor, there was no battery abnormality during temperature rise, the battery efficiency was as high as 85%, and the battery characteristics were abnormal even after repeated charge / discharge cycles of 250 cycles. I couldn't.

The abnormalities in the battery modules of the thermistors (i) and (ii) can be considered as follows. That is, in the battery module of the thermistor (i), when a connection test or the like is performed at room temperature, the resistance value of the thermistor is not sufficiently large compared to the internal resistance of the battery. It is considered that the solid electrolyte was electrochemically deteriorated and the battery was damaged. Also, in the battery module of the thermistor of (ii), at the battery operating temperature, the resistance value of the thermistor is not sufficiently large compared to the internal resistance of the battery, so that a current flowing into the thermistor is generated, which is a heat energy loss. It is considered that the efficiency of the module has been reduced. As described above, it is desirable that the resistance value of the thermistor added to the battery be 1/100 or less of the internal resistance of the battery at normal temperature and 100 times or more of the internal resistance of the battery at the operating temperature of the battery.

Example 5 Nickel chloride was used for the anode and aluminum chloride-sodium chloride for the electrolyte.
In the same manner as in Example 1, twenty sodium-nickel chloride batteries having a capacity of 0 Wh and a heat switch that conducts at room temperature and does not conduct at 250 ° C. were added. These were assembled into four modules in series and five parallel, and the connection was confirmed in the same manner as in Example 1. The temperature was increased to 250 ° C. at a rate of 5 ° C./hour, and a charge / discharge test was performed at 50 A. No battery was damaged during the heating process, and no abnormalities were found in the characteristics of the individual batteries even after 100 cycles of charging and discharging.

[0027]

According to the present invention, it is possible to prevent current from flowing into a battery at room temperature, which adversely affects a battery and a solid electrolyte, in a high-temperature type secondary battery module such as a sodium-sulfur battery. Thus, a high-temperature secondary battery and a battery module that are resistant to a short circuit between a plurality of batteries and that can perform electrical inspection such as confirmation of connection at normal temperature can be obtained.

In the embodiment of the present invention, only a thermal switch and a thermistor are shown as connection means to be added to the battery. However, even if other substances or elements are used at room temperature, the internal resistance of the battery is lower than that of the battery. As long as it is sufficiently small and sufficiently smaller than the internal resistance of the battery at the battery operating temperature, it can be used similarly.

[Brief description of the drawings]

FIG. 1 is a circuit diagram when a voltage is externally applied at normal temperature to a module using a battery of the present invention.

FIG. 2 is a circuit diagram at a battery operating temperature of a module using the battery of the present invention.

FIG. 3 is a diagram showing a structure of a sodium-sulfur battery of the present invention.

FIG. 4 is a perspective view of the battery module of the present invention.

FIG. 5 is a diagram illustrating a short circuit that occurs in series-connected batteries when the insulation between the batteries is incomplete.

FIG. 6 is a circuit diagram illustrating a short circuit that occurs in series-connected batteries when the insulation between the batteries is incomplete.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 Connecting means 3 Externally applied voltage 4 Cathode terminal 5 Cathode 6 Cathode container 7 Insulation material 8 Anode terminal 9 Anode container 10 Anode 11 Solid electrolyte 12 Connection line 13 Insulator base 14 Battery 15 Battery 16 Battery 17 Battery stand 18 External resistance

Continued on the front page (72) Inventor Tetsuo Koyama 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. ) Inventor: Seiko Nishimura 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-62-110841 (JP, A) JP-A-62-1221826 (JP, A) JP Hei 1-122575 (JP, A) Actually open 57-57,254 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/39 H01M 10/42-10/44

Claims (5)

(57) [Claims] An anode provided with an anode active material and a current collector which is liquid at an operating temperature, an anode container containing the anode, a cathode provided with a cathode active material of a liquid metal at an operating temperature, and a cathode housed therein A high-temperature secondary battery comprising: a cathode container in contact with the cathode; an insulator for insulating the anode container and the cathode container; and a solid electrolyte separating the anode and the cathode. The containers are connected by a connecting means having a resistance value lower than the internal resistance of the battery at room temperature at room temperature, and having a resistance value higher than the internal resistance of the battery at the battery operating temperature at the room temperature. High temperature type secondary battery. 2. The high-temperature secondary battery according to claim 1, wherein the anode active material is sulfur and / or sodium polysulfide, the cathode active material is sodium, and the solid electrolyte is β.
A high-temperature secondary battery that is a sodium-sulfur battery composed of alumina and / or β ″ -alumina; 3. The high-temperature secondary battery according to claim 1, wherein the resistance of the connection means is 1/100 or less of the internal resistance of the battery at room temperature at room temperature, and at that temperature at the battery operating temperature. High-temperature secondary battery that is 100 times or more the internal resistance of the battery of claim 1. 4. The high-temperature secondary battery according to claim 1, wherein the connection means is a thermal switch or a positive temperature coefficient (PTC) thermistor. 5. A battery module for charging and discharging, comprising: a plurality of high-temperature secondary batteries; a module container accommodating the plurality of batteries; and a temperature raising means for increasing the temperature of the batteries. A battery module, wherein the type secondary battery is one according to any one of claims 1 to 4.