JP7344724B2 - All-solid-state lithium-ion secondary battery system and charging device for all-solid-state lithium-ion secondary battery - Google Patents

Description

The present invention relates to an all-solid-state lithium-ion secondary battery system and a charging device for an all-solid-state lithium-ion secondary battery.

In recent years, in order to combat global warming, it has been strongly desired to reduce the amount of carbon dioxide. In the automobile industry, expectations are high for reducing carbon dioxide emissions through the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and non-aqueous batteries such as secondary batteries for motor drives hold the key to their practical application. Electrolyte secondary batteries are actively being developed.

Secondary batteries for motor drives are required to have extremely high output characteristics and high energy compared to consumer lithium ion secondary batteries used in mobile phones, notebook computers, and the like. Therefore, lithium ion secondary batteries, which have the highest theoretical energy of all practical batteries, are attracting attention and are currently being rapidly developed.

Here, lithium ion secondary batteries that are currently in widespread use use a flammable organic electrolyte as an electrolyte. Such liquid-based lithium ion secondary batteries require more stringent safety measures against leakage, short circuits, overcharging, etc. than other batteries.

Therefore, in recent years, research and development on all-solid-state lithium ion secondary batteries (hereinafter also referred to as "all-solid-state batteries") using oxide-based or sulfide-based solid electrolytes have been actively conducted. A solid electrolyte is a material mainly composed of an ion conductor capable of ion conduction in a solid state. Therefore, in principle, all-solid-state lithium ion secondary batteries do not suffer from various problems caused by flammable organic electrolytes, unlike conventional liquid-based lithium ion secondary batteries. Furthermore, in general, the use of high-potential, large-capacity positive electrode materials and large-capacity negative electrode materials can significantly improve the output density and energy density of the battery. All-solid-state batteries that use sulfide-based materials as positive electrode active materials and metallic lithium or lithium-containing alloys as negative electrode active materials are promising candidates.

By the way, in a lithium ion secondary battery, the internal resistance increases as its charge/discharge cycles are repeated. When the internal resistance of a battery increases, there are problems such as it becomes difficult to draw a large current, it takes a long time to charge, and the battery becomes more likely to generate heat, which makes it easier for the battery to deteriorate. . Therefore, suppressing the increase in internal resistance of a lithium ion secondary battery is important from the viewpoint of extending the life of the battery.

In an all-solid-state battery, as a technique for suppressing an increase in internal resistance as the charge/discharge cycle progresses, Patent Document 1 describes a layered region that slowly expands as the amount of charge increases, and a layered region that expands gradually as the amount of charge increases. A charging method for an all-solid-state battery is disclosed in which a negative electrode active material having a Li ion insertion site consisting of a rapidly expanding pore region is used, and only the layered region is used during normal charging. According to Patent Document 1, the above-described configuration suppresses deterioration of contact between the negative electrode active material and the solid electrolyte during charging, thereby suppressing an increase in internal resistance as the charge/discharge cycle progresses. It is said that it is possible.

Japanese Patent Application Publication No. 2016-154104

The present inventors have diligently searched for the cause of the increase in internal resistance in all-solid-state batteries. As a result, not only the contact state between the active material and the solid electrolyte as discussed in Patent Document 1 deteriorates, but also the occurrence of minute cracks in the solid electrolyte layer and the interface between the electrode active material layer and the solid electrolyte layer. It was found that the dominant cause was an increase in ohmic resistance due to peeling.

There is a problem in that the internal resistance that has increased due to these dominant causes cannot be reduced (recovered) by the technique proposed in Patent Document 1. Furthermore, the technique disclosed in Patent Document 1 does not include a detection circuit that determines whether the Li ion insertion site used for charging belongs to a layered region or a pore region. Therefore, depending on the charging method disclosed in Patent Document 1, there is also a problem in that it is difficult to determine whether it is possible to suppress the increase in internal resistance.

An object of the present invention is to provide a means for detecting an increase in the internal resistance of an all-solid-state battery when charging the battery, and making it possible to continue charging after reducing the increased internal resistance. be.

The present inventors conducted extensive studies to solve the above problems. As a result, when charging an all-solid-state lithium-ion secondary battery, the internal resistance value of the battery is measured, and the measured internal resistance value or its rate of increase relative to the initial internal resistance value exceeds a predetermined threshold. The present inventors have discovered that the above-mentioned problem can be solved by controlling the battery to be charged with a heating current larger than the rated charging current, and have completed the present invention.

An all-solid-state lithium ion secondary battery system according to an embodiment of the present invention first includes a positive electrode including a positive electrode active material layer containing a positive electrode active material, a negative electrode including a negative electrode active material layer containing a negative electrode active material, and a negative electrode including a negative electrode active material layer containing a negative electrode active material. An all-solid-state lithium ion secondary battery including a power generation element having a positive electrode active material layer and a solid electrolyte layer interposed between the negative electrode active material layer and the negative electrode active material layer is provided. The system also includes a charger that charges the all-solid-state lithium ion secondary battery, an internal resistance measurement unit that measures the internal resistance of the all-solid-state lithium ion secondary battery, and a control unit that controls the charger. Equipped with. The control unit may be configured such that when the charger charges the all-solid-state lithium ion secondary battery, the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value is determined in advance. When the threshold value is exceeded, the charger is controlled to charge the all-solid-state lithium ion battery with a heating current that is larger than the rated charging current.

An all-solid-state lithium-ion secondary battery charging device according to another aspect of the present invention includes a charger that charges the all-solid-state lithium-ion secondary battery, and an internal battery that measures the internal resistance of the all-solid-state lithium-ion secondary battery. The battery includes a resistance measurement section and a control section that controls the charger. The control unit may be configured such that when the charger charges the all-solid-state lithium ion secondary battery, the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value is determined in advance. When the threshold value is exceeded, the charger is controlled to charge the all-solid-state lithium ion battery with a heating current that is larger than the rated charging current.

According to the present invention, when charging an all-solid-state battery, it is possible to detect an increase in the internal resistance of the battery, reduce the increased internal resistance, and then continue charging. As a result, various problems caused by an increase in internal resistance can be prevented from occurring, which can contribute to shortening charging time and extending the life of the battery.

1 is a block diagram for explaining the configuration of an all-solid-state lithium ion secondary battery system according to an embodiment of the present invention. 1 is a system schematic diagram of an electrical system of an electric vehicle equipped with an all-solid-state lithium ion secondary battery system according to an embodiment of the present invention. 5 is a flowchart showing the procedure of rapid charging processing in the secondary battery system 1. FIG. A graph for explaining an example of a method for calculating battery temperature T from the temperature T _m measured by a temperature sensor of a secondary battery (vertical axis is temperature; horizontal axis is position inside the battery where the battery temperature T to be calculated is (temperature estimation) (distance from position). FIG. 1 is a configuration diagram of a power supply circuit in an idling stop vehicle according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing the overall structure of a stacked (internal parallel connection type) all-solid-state lithium ion secondary battery (stacked secondary battery) that is an embodiment of the present invention. 1 is a cross-sectional view schematically showing a bipolar all-solid-state lithium ion secondary battery (bipolar secondary battery) according to an embodiment of the present invention. 1 is a perspective view showing the appearance of a flat lithium ion secondary battery, which is a typical embodiment of a stacked secondary battery.

Hereinafter, the embodiments of the present invention described above will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the claims and is not limited only to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

[Secondary battery system]
FIG. 1 is a block diagram for explaining the configuration of an all-solid-state lithium ion secondary battery system according to an embodiment of the present invention. FIG. 2 is a system schematic diagram of an electrical system of an electric vehicle equipped with an all-solid-state lithium ion secondary battery system according to an embodiment of the present invention.

Referring to FIG. 1, this all-solid-state lithium ion secondary battery system (hereinafter also referred to as "secondary battery system 1") is an all-solid-state lithium-ion secondary battery (hereinafter also referred to as "secondary battery 2"). Equipped with Then, charging power is supplied to the voltage sensor 3 that measures the cell voltage (voltage between terminals) of the secondary battery 2, the temperature sensor 4 that measures the outer surface temperature (environmental temperature) of the secondary battery 2, and the secondary battery 2. It includes a voltage/current adjustment section 5 , a current sensor 6 that measures the charging/discharging current of the secondary battery 2 , and a control section 7 that controls charging/discharging of the secondary battery 2 . Further, the voltage and current adjustment section 5 is connected to an external power supply 8 and receives power during charging, while discharging to the external power supply 8 side via the voltage and current adjustment section 5 during discharging (details will be described later).

Referring to FIG. 2, secondary battery 2 is normally stored in battery pack 100 in the form of secondary battery module (battery assembly) 110. The battery pack 100 is equipped with a battery management (battery control) system (BMS) 120. This BMS 120 is equipped with a voltage sensor 3, a temperature sensor 4, a current sensor 6, etc., and transmits information about the battery pack 100 and the secondary battery 2 (secondary battery module 110) to the upper control unit 7, and provides instructions therefor. and controls the battery pack 100 and the secondary battery 2 (secondary battery module 110). That is, the BMS 120 also functions as a control unit in the present invention. The battery pack 100 further includes a junction box 130 for controlling disconnection of the secondary battery module 110 from the high-voltage circuit, and this junction box 130 is controlled by the control unit 7.

The electric vehicle also includes a DC/DC junction box 200. The DC/DC junction box 200 is equipped with a DC/DC converter 210 for converting high voltage from the secondary battery 2 (secondary battery module 110) to low voltage. The DC/DC junction box 200 also includes a normal charging relay 220 for controlling disconnection of the secondary battery 2 (secondary battery module 110) to the normal charging system, and a normal charging relay 220 for controlling disconnection of the secondary battery 2 (secondary battery module 110) to the quick charging system. The device further includes a quick charging relay 230 for the purpose of charging. The normal charging relay 220 is connected to the normal charging port 222 via the on-vehicle charger 221, and the quick charging relay 230 is directly connected to the quick charging port 232.

The details of each part shown in FIG. 1 will be explained below.

The secondary battery 2 is a normal all-solid-state lithium ion secondary battery, and includes a positive electrode including a positive electrode active material layer containing a positive electrode active material, a negative electrode including a negative electrode active material layer containing a negative electrode active material, and the positive electrode. A power generation element having an active material layer and a solid electrolyte layer interposed between the negative electrode active material layer and the negative electrode active material layer is provided. Note that details of the all-solid-state lithium ion secondary battery will be described later.

The voltage sensor 3 may be, for example, a voltmeter, and measures the cell voltage (voltage between terminals) between the positive electrode and the negative electrode of the secondary battery 2. The cell voltage (voltage between terminals) measured when the secondary battery 2 is not energized is the open circuit voltage (OCV) of the secondary battery 2. On the other hand, the cell voltage (voltage between terminals) measured during charging and discharging of the secondary battery 2 is equal to the voltage drop (ΔV = ΔI × R) caused by the internal resistance (R) of the secondary battery 2 due to this open circuit. The value is changed from the voltage (OCV). That is, the voltage sensor 3 can function as an SOC detection section or an OCV detection section. The mounting position of the voltage sensor 3 is not particularly limited, and may be any position as long as it can measure the cell voltage between the positive electrode and the negative electrode within the circuit connected to the secondary battery 2.

Temperature sensor 4 measures the outer surface temperature (environmental temperature) of secondary battery 2 . The temperature sensor 4 is attached, for example, to the surface of the case (exterior body, housing) of the secondary battery 2. In this embodiment, the temperature of the secondary battery 2 is acquired by the control unit 7, which will be described later, estimating the temperature inside the secondary battery 2 from the outer surface temperature of the secondary battery 2 measured by the temperature sensor 4. do. That is, the temperature sensor 4 and the control section 7 function as a temperature detection section that detects the temperature of the secondary battery 2.

When charging the secondary battery 2, the voltage/current adjustment unit 5 adjusts the voltage and current of the power from the external power supply 8 based on a command from the control unit 7, and supplies the power to the secondary battery 2. Further, when the secondary battery 2 is discharged, the voltage/current adjustment section 5 releases the electricity discharged from the secondary battery 2 to the external power source 8 side. In this way, the voltage/current adjustment section 5, the external power supply 8, and the control section 7, which will be described later, function as a charger that charges the secondary battery 2.

Here, the external power source 8 is a power source for electric vehicles, called a so-called power grid, used for charging electric vehicles, etc., and outputs direct current. Such a power source for an electric vehicle converts commercial power (alternating current) into direct current of the voltage and current necessary for charging the secondary battery 2 and provides it. Further, the external power source 8 is equipped with a power regeneration function, and when the secondary battery 2 is discharged, the direct current can be converted to alternating current and regenerated to the commercial power source. Note that a well-known power supply with a power regeneration function may be used as a device constituting such an external power supply 8, so a detailed explanation will be omitted here (as a power supply with a power regeneration function, For example, there are those disclosed in JP-A-7-222369, JP-A-10-080067, etc.).

When the external power source 8 is not connected to an external power supply device such as a commercial power source, for example, when charging the secondary battery 2 using another externally installed secondary battery as a power source, the power discharged from the secondary battery 2 It is preferable to store the battery in another secondary battery. This can reduce energy waste.

The current sensor 6 is, for example, an ammeter. The current sensor 6 measures the current value of the power supplied from the voltage/current adjustment unit 5 to the secondary battery 2 when charging the secondary battery 2, and the current value of the power supplied from the secondary battery 2 to the voltage/current adjustment unit 5 during discharging. Measures the power current value. The mounting position of the current sensor 6 is not particularly limited, and it may be placed in a circuit that supplies power from the voltage/current adjustment unit 5 to the secondary battery 2 and can measure current values during charging and discharging. good.

The control unit 7 is a so-called computer that includes, for example, a CPU 71 and a storage unit 72. The control unit 7 controls the charger when performing the charging process on the secondary battery 2 and adjusts the conditions of the charging process, etc., according to the procedure described later. As such a control unit 7, for example, an ECU (Electronic Control Unit) or the like may be used in an electric vehicle. Note that when the secondary battery 2 is mounted on a vehicle, the secondary battery 2 and the control unit 7 may be mounted on the vehicle, and the charger may be installed outside the vehicle. Alternatively, the charger may be installed outside the vehicle, and the control unit 7 may also be mounted on the charger.

Here, the storage unit 72 includes a nonvolatile memory in addition to a RAM that the CPU 71 uses as a working area. The nonvolatile memory stores a program for controlling the charger (adjusting charging processing conditions) in this embodiment.

In addition, the storage unit 72 stores the initial internal resistance value R _{1 of the secondary battery 2 and the initial internal resistance value R 1} of the secondary battery 2, which is referred to when controlling the charger (adjusting the charging processing conditions) in this embodiment. A threshold value (R' _t ) for the rate of increase R' of the internal resistance value R with respect to the initial internal resistance value R ₁ and a threshold value (T _t ) for the battery temperature T of the secondary battery 2 are stored. Furthermore, the storage unit 72 stores a map (hereinafter also referred to as "first map") showing the relationship between the battery voltage V of the secondary battery 2 and the state of charge (SOC) of the secondary battery. There is.

[Charging process]
The procedure of charging processing in the secondary battery system 1 configured in this way will be explained.

This charging process is performed in a state where the secondary battery system 1 is connected to the external power supply 8 and charging power can be supplied to the secondary battery 2. Further, the charging process in this embodiment is controlled by a constant current (CC) charging method that is performed until the voltage of the secondary battery 2 reaches a predetermined voltage. However, the form of the charging process is not limited to this, and charging is performed using a constant current (CC) charging method, and after the voltage of the secondary battery 2 reaches a predetermined voltage, it is performed using a constant voltage (CV) charging method. A current/constant voltage (CC-CV) charging method may also be used.

In the control in this embodiment, when the charger charges the secondary battery 2 (specifically, before charging the secondary battery 2 at the rated charging current, or when charging the secondary battery 2 at the rated charging current), (during charging), it is determined whether the rate of increase of the internal resistance value measured by the internal resistance measuring section with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. Then, when the rate of increase of the internal resistance value with respect to the initial internal resistance value is equal to or higher than the threshold value, the charger is controlled to charge the secondary battery 2 with a heating current larger than the rated charging current. . Note that unless otherwise specified, this charging process (control of the charger) is performed by the control unit 7. Hereinafter, with reference to FIG. 3, the procedure of this control when performing quick charging will be explained. FIG. 3 is a flowchart showing the procedure of quick charging processing in the secondary battery system 1.

First, the control unit 7 turns on the quick charging relay 230 (step S101). Subsequently, the control unit introduces power from the external power supply 8 to the voltage/current adjustment unit 5 and applies a charging current (pulse current) to the secondary battery 2 for about several seconds (step S102). Note that the charging current (pulse current) applied at this time is applied for the purpose of calculating the internal resistance value R of the secondary battery 2. Therefore, it is not necessary to apply the current for a long time, so a pulse current may be used. Further, the value of the charging current (pulse current) is not particularly limited as long as it is a value that allows calculation of the internal resistance value R.

Next, the control unit 7 acquires the charging current I from the current sensor 6 and the battery voltage V from the voltage sensor 3. Then, the control unit 7 calculates the internal resistance value R (=V/I) of the secondary battery 2 from Ohm's law based on these acquired values, and also calculates the internal resistance value R of the secondary battery 2. An increase rate R' with respect to the initial internal resistance value _R1 is calculated (step S103). Here, the rate of increase R' is
R'=(R-R ₁ )/R ₁ ×100
It is expressed as follows.

In the present embodiment, the control unit 7 also uses a “map showing the relationship between the battery voltage V of the secondary battery 2 and the state of charge (SOC) of the secondary battery” (first map) stored in the storage unit 82. With reference to , the SOC of the secondary battery 2 is calculated and obtained based on the battery voltage V obtained from the voltage sensor 3 (step S103).

Furthermore, in this embodiment, the control unit 7 calculates and obtains the internal temperature of the secondary battery 2 (battery temperature T) from the measured temperature T _m obtained from the temperature sensor 4 (step S103). At this time, the control unit 7 controls the temperature of the secondary battery detected by the temperature sensor 4 based on the thermal resistance value (thermal conductivity) between the temperature detection position by the temperature sensor 4 and the power generation element of the secondary battery 2. Correct the measured temperature _Tm . Here, FIG. 4 is a graph for explaining an example of a method of calculating the battery temperature T from the temperature T _m measured by the temperature sensor 4 of the secondary battery 2 (the vertical axis is temperature; the horizontal axis is the battery temperature T to be calculated). (distance from the position inside the battery (temperature estimation position)). As shown in FIG. 4, the distance from the temperature estimation position to the battery surface is Δx ₁ , the distance from the battery surface to the measurement position by temperature sensor 4 (for example, the surface of the battery case) is Δx ₂ , and both sides of the battery surface are Let the temperatures of T _s1 and T _s2 (T _s1 >T _s2 ), respectively. Then, the heat transfer coefficients h ₁ and h ₂ on the surface of the battery and the surface of the battery case, which are all known parameters, the thermal conductivity λ _c in the battery, the thermal conductivity λ _M from the battery to the measurement position, and the measurement Using the temperature T _m and the outside temperature T _∞ , the heat flux J in this system is:
J=λ _c (TT _s1 )/Δx ₁
J=h ₁ (Ts ₁ - Ts ₂ )
J=λ _M (Ts ₂ - T _∞ )/Δx ₂
J=h ₂ (T _m - T _∞ )
It is expressed as follows. By solving these for T, the battery temperature T can be calculated. By performing the following control using the battery temperature T corrected in this way, more precise control becomes possible.

In the present embodiment, the control unit 7 next compares the rate of increase R' of the internal resistance value calculated above with a threshold value R' _t that is predetermined and stored in the storage unit 72, and determines R'. It is determined whether ' is greater than or equal to R' _t (step S104). Here, if it is determined that R' is smaller than R' _t (R'<R' _t ) (S104: NO), the control based on the rate of increase R' of the internal resistance value is ended and the process proceeds to the next step. move on. This is because the rate of increase R' of the internal resistance value of the secondary battery 2 (and the absolute value of the internal resistance value R) is sufficiently low, so there is a risk that various problems may occur due to the high internal resistance value. This means that it is assumed that there is no such thing. In this case, the control unit 7 introduces power from the external power supply 8 to the voltage/current adjustment unit 5, applies the rated charging current to the secondary battery 2, and starts main charging (step S105).

When main charging is started in step S105, the control unit 7 acquires the battery voltage V from the voltage sensor 3, and also refers to the first map stored in the storage unit 82 to determine the battery voltage V acquired from the voltage sensor 3. Based on V, the SOC of the secondary battery 2 is calculated and obtained (step S106). Thereafter, the control unit 7 determines whether the SOC value of the secondary battery 2 calculated in step S106 is larger than a target SOC (SOC>target SOC) that is preset as a value sufficient to finish the charging process. (Step S107). Here, if it is determined that the SOC value of the secondary battery 2 is larger than the target SOC (SOC>target SOC) (S107: YES), the control unit 7 controls the voltage and current adjustment unit 5 to charge At the same time as finishing the process, the quick charging relay is turned off (step S108).

On the other hand, if it is not determined in step S107 that the SOC value of the secondary battery 2 is larger than the target SOC (SOC>target SOC) (S107: NO), the control unit 7 repeats the control from step S103.

On the other hand, if it is determined in step S104 that the rate of increase R' of the internal resistance value R is equal to or higher than the threshold value R' _t (R'≧R' _t ) (S104: YES), the control unit 7 8 to the voltage/current adjustment unit 5 to apply a current (heating current) larger than the rated charging current to the secondary battery 2 (step S110). Generally, when a current is applied to the secondary battery 2, Joule heat calculated as Q = RI ² × t (R is the resistance value, I is the current value, and t is the time) is generated, but the heating current is Greater than the rated charging current. Therefore, when the heating current is applied, a larger amount of Joule heat is generated inside the battery than when charging with the rated charging current. As a result, the internal temperature of the battery (battery temperature T) rises, and when the internal temperature of the battery rises to near the melting point of a certain material constituting the power generation element, the material melts. In this embodiment, this fact is utilized to reduce (recover) the internal resistance of the secondary battery 2. Specifically, for example, when comparing the melting point of the solid electrolyte, which is the main constituent material of the secondary battery 2, with the melting points of the active materials of the positive and negative electrodes, it is found that the solid electrolyte composed of oxides and sulfides has a higher melting point. usually have a higher melting point. The melting point of sulfur (S), which is suitably used as a positive electrode active material, is 115.2°C, and the melting point of elemental metal lithium (Li), which is suitably used as a negative electrode active material, is 180.5°C. be. Therefore, when the internal temperature of the secondary battery 2 is raised to around the lowest melting point of sulfur (S) (115.2° C.) among these, the sulfur (S) that is the positive electrode active material melts. By melting the positive electrode active material (sulfur (S)) in this manner, fluidity is generated at the interface between the positive electrode active material layer and the solid electrolyte layer, and the contact state between these layers is improved. As a result, the ohmic resistance (interface resistance) between these layers is reduced, and as a result, the internal resistance of the secondary battery 2 is reduced (recovered). By applying the rated charging current to the secondary battery 2 whose internal resistance has been reduced (recovered) in this way and performing the main charging, there is an advantage that the charging time can be shortened.

As mentioned above, by applying the heating current, the internal temperature of the secondary battery 2 (battery temperature T) is raised to around the melting point of the constituent materials of the power generation element, but it is also raised to a value exceeding this melting point. Then, the material melts and the shape of the power generation element cannot be maintained. Therefore, when the control unit starts applying the heating current in step S110, it acquires the measured temperature _Tm from the temperature sensor 4, and calculates and acquires the battery temperature T using the same method as described above (step S110). S111). Then, the control unit 7 compares the battery temperature T obtained in this way with a threshold temperature T _t that is predetermined and stored in the storage unit 72 and determines whether T is equal to or higher than T _t . (Step S112) At this time, there is no particular restriction on the specific value of the threshold temperature _Tt , which is high enough to reduce the internal resistance value of the secondary battery 2 and within the melting point of the constituent materials of the power generation element. It may be a value sufficiently lower than the lowest value (115.2°C, which is the melting point of sulfur (S) in the above example).

Here, if it is determined that the battery temperature T is equal to or higher than the threshold temperature T _t (T≧T _t ) (S112: YES), it is assumed that the internal resistance value of the secondary battery 2 has been sufficiently reduced. I can do it. Therefore, in this case, the control unit 7 controls the voltage and current adjustment unit 5 to stop charging with the heating current by stopping the application of the heating current (step S113), and resumes the control from step S102. repeat. By setting the threshold temperature _Tt in this way and stopping charging with the heating current when the battery temperature T of the secondary battery 2 reaches or exceeds the threshold temperature _Tt , the positive electrode after application of the heating current is It is possible to prevent the maximum temperatures of the active material and the negative electrode active material from exceeding their respective melting points (below their respective melting points). As a result, melting of the active material component and accompanying destruction of the shape of the power generation element are prevented. In order to enable this control, in this embodiment, the control unit 7 controls the magnitude of the heating current and/or the application time of the heating current.

On the other hand, if it is determined in step S112 that the battery temperature T is less than the threshold temperature T _t (T<T _t ) (S112: NO), the control unit 7 repeats the control from step S111.

Although the control according to the present invention has been described in detail above, the embodiment described with reference to the drawings is merely an example, and modifications may be made as appropriate within the scope of the technical idea of the invention described in the claims. The present invention may also be implemented using the following methods. For example, in the embodiment described above, a threshold value _R't of the rate of increase R' in the internal resistance value of the battery is set, and the necessity of applying the heating current is determined based on this threshold value R't. However, without using the rate of increase as an index, a threshold value _Rt of the absolute value of the internal resistance value is set, and this is compared with the measured value R of the internal resistance value of the battery, and the heating current is applied. You may decide whether or not it is necessary. Furthermore, as described above, the dominant cause of the increase in internal resistance in all-solid-state batteries is an increase in ohmic resistance (interfacial resistance) due to interlayer separation between the electrode active material layer and the solid electrolyte layer. In measuring the internal resistance value based on Ohm's law as described above, the ohmic resistance (interface resistance) cannot be separated from the measured internal resistance value and used for control. On the other hand, by measuring the internal resistance value using electrochemical impedance measurement (EIS) and performing the control of the present invention by regarding the electrolyte resistance component calculated from the Cole-Cole plot as the internal resistance value, It becomes possible to control using a resistance value that approximates the interlayer ohmic resistance (interfacial resistance) between the electrode active material layer and the solid electrolyte layer, which is a major factor, as an index. However, the above-mentioned measurement based on Ohm's law has the advantage that on-board control is possible in vehicle-mounted secondary battery systems and the like.

Further, in the embodiment described above, the secondary battery 2 is mounted on the vehicle, and the charger charges the secondary battery 2 using power supplied from a power source (external power source 8) installed outside the vehicle. Apply heating current. According to such an embodiment, it is possible to check the state of health (SOH) of the secondary battery 2 every time it is charged, and it is also possible to constantly monitor the rate of increase in the internal resistance value, so that the internal This has the advantage that resistance can be reduced (recovered).

However, even if the secondary battery 2 is installed in the vehicle, the charger uses power supplied from another power source installed in the vehicle, not the external power source 8, to charge the secondary battery 2. A heating current may be applied to. For example, in an electric vehicle in which the secondary battery 2 shown in Fig. 2 is used as a high-voltage battery, a lead-acid battery installed as a low-voltage battery (so-called 12V battery) or a conventional non-aqueous electrolyte lithium ion secondary battery is used. It can be used as "another power source mounted on a vehicle". According to such an embodiment, even in a situation where the external power source 8 cannot be accessed, such as while driving, the health (SOH) of the secondary battery 2 is determined and the presence or absence of an increase in internal resistance is detected. It becomes possible to reduce (recover) the internal resistance of the secondary battery 2 on-board by applying a heating current from the low-voltage battery as necessary.

Further, an example of another embodiment in which a heating current is applied to the secondary battery 2 using electric power supplied from another power source mounted on the vehicle will be described with reference to FIG. 5.

FIG. 5 is a configuration diagram of a power supply circuit in an idling stop vehicle according to an embodiment of the present invention. Power supply circuit 300 is a circuit that supplies power to starter motor (SM) 240 and other electrical loads 250, and includes a main battery 310, a sub-battery 320, and a relay 330. It is assumed that the power supply circuit 300 also supplies power to a controller (not shown).

As the main battery 310, for example, a lead acid battery is used. Lead acid batteries use lead dioxide for the positive electrode, spongy lead for the negative electrode, and dilute sulfuric acid for the electrolyte. The main battery 310 is charged by regenerative power generated by the alternator (ALT) 260, and the open circuit voltage in a fully charged state is, for example, 12.7V.

The sub-battery 320 is provided to prevent the power supply voltage of the vehicle from instantaneously dropping due to a large current flowing through the starter motor (SM) 240 when restarting the engine (not shown) from idling stop. In this embodiment, the all-solid-state lithium ion secondary battery 2 is used as the sub-battery 320. The sub-battery 320 is charged by regenerative power generated by the alternator (ALT) 260, and the open circuit voltage in a fully charged state is, for example, 13.1V.

Relay 330 is a switch that connects sub-battery 320 to power supply circuit 300 or disconnects it from power supply circuit 300, and is controlled by a controller (not shown). Relay 330 is a normally open a contact, which cuts off sub-battery 320 from power supply circuit 300 when the contact is open, and connects sub-battery 320 to power supply circuit 300 when the contact is closed. Specifically, while the engine is in operation, sub-battery 320 is connected to power supply circuit 300, and sub-battery 320 is charged with electric power supplied from alternator (ALT) 260. Furthermore, when restarting the engine from idling stop, the sub-battery 320 is connected to the power supply circuit 300, and power from the sub-battery 320 is supplied to the starter motor (SM) 240. In addition, the sub-battery 320 is connected to or disconnected from the power supply circuit 300 as necessary.

In such an embodiment, for example, a lead acid battery mounted as the main battery 310 may be used as "another power source mounted on the vehicle." Furthermore, the alternator (ALT) 260 that generates regenerative power can also be used as "another power source mounted on the vehicle." According to these embodiments, even in a situation where the external power source 8 cannot be accessed, such as while driving, the health of the secondary battery 2 (SOH) is determined and the presence or absence of an increase in internal resistance is detected. It becomes possible to reduce (recover) the internal resistance of the secondary battery 2 as the sub-battery 320 on-board by applying a heating current from the main battery 310 (lead-acid battery) or alternator (ALT) 260 according to the .

In addition, according to another embodiment of the present invention, a charging device (charging device for an all-solid lithium ion secondary battery) for charging the secondary battery 2 described above is provided. A charging device for charging an all-solid-state lithium-ion secondary battery includes a charger for charging the all-solid-state lithium-ion secondary battery, an internal resistance measuring section for measuring an internal resistance of the all-solid-state lithium-ion secondary battery, When the charger charges the all-solid-state lithium ion secondary battery, when the internal resistance value measured by the internal resistance measurement unit or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. and a control unit that controls the charger to charge the all-solid-state lithium ion battery with a heating current larger than a rated charging current.

According to still another embodiment of the present invention, a secondary battery charging method for charging the above-described secondary battery 2 is also provided. A charging method for an all-solid-state lithium-ion secondary battery includes, when a charger charges the all-solid-state lithium-ion secondary battery, an internal resistance value of the all-solid-state lithium-ion secondary battery or an increase rate relative to its initial internal resistance value. is equal to or higher than a predetermined threshold, charging the all-solid-state lithium ion battery with a heating current larger than the rated charging current.

The all-solid-state lithium-ion secondary battery that constitutes the all-solid-state lithium-ion secondary battery system according to this embodiment will be described below.

FIG. 6 schematically shows the overall structure of a stacked (internal parallel connection type) all-solid-state lithium ion secondary battery (hereinafter also simply referred to as a "stacked secondary battery"), which is an embodiment of the present invention. FIG. A stacked secondary battery 10a shown in FIG. 6 has a structure in which a substantially rectangular power generation element 21 in which a charging/discharging reaction actually proceeds is sealed inside a laminate film 29 that is a battery exterior body.

As shown in FIG. 6, the power generation element 21 of the stacked secondary battery 10a of this embodiment includes a positive electrode in which positive electrode active material layers 13 are arranged on both sides of a positive electrode current collector 11', a solid electrolyte layer 17, and a negative electrode. It has a structure in which a negative electrode with negative electrode active material layers 15 arranged on both sides of a current collector 11'' is laminated. Specifically, one positive electrode active material layer 13 and the adjacent negative electrode active material layer 15 face each other with the solid electrolyte layer 17 in between, and the positive electrode, the solid electrolyte layer, and the negative electrode are stacked in this order. ing. Thereby, the adjacent positive electrode, solid electrolyte layer, and negative electrode constitute one single cell layer 19. Therefore, it can be said that the stacked secondary battery 10a shown in FIG. 6 has a configuration in which a plurality of cell layers 19 are stacked and electrically connected in parallel. Note that the positive electrode active material layer 13 is disposed on only one side of the outermost positive electrode current collectors located on both outermost layers of the power generation element 21, but active material layers may be provided on both sides. . That is, instead of using a current collector exclusively for the outermost layer with an active material layer provided on only one side, a current collector with active material layers on both sides may be used as it is as the outermost layer current collector. In addition, by reversing the arrangement of the positive electrode and negative electrode from FIG. 6, the outermost layer negative electrode current collector is located on both outermost layers of the power generation element 21, and A negative electrode active material layer may be arranged on both sides.

A positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are electrically connected to each electrode (positive electrode and negative electrode) are attached to the positive electrode current collector 11′ and the negative electrode current collector 11″, respectively. It has a structure in which it is led out to the outside of the laminate film 29 so as to be sandwiched between the two. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are connected to the positive electrode current collector 11' and the negative electrode current collector 11' of each electrode via a positive electrode terminal lead and a negative electrode terminal lead (not shown), respectively, as necessary. ' may be attached by ultrasonic welding, resistance welding, etc.

In the above description, an embodiment of an all-solid-state battery according to one aspect of the present invention has been described using a stacked (internal parallel connection type) all-solid-state lithium ion secondary battery as an example. However, the types of all-solid-state batteries to which the present invention is applicable are not particularly limited, and include a positive electrode active material layer electrically bonded to one surface of the current collector and an electrically bonded layer to the opposite surface of the current collector. It is also applicable to a bipolar type all-solid-state battery including a bipolar type electrode having a bonded negative electrode active material layer.

FIG. 7 is a cross-sectional view schematically showing a bipolar all-solid-state lithium ion secondary battery (hereinafter also simply referred to as a "bipolar secondary battery") according to an embodiment of the present invention. . A bipolar secondary battery 10b shown in FIG. 7 has a structure in which a substantially rectangular power generation element 21 in which charge and discharge reactions actually proceed is sealed inside a laminate film 29 that is a battery exterior body.

As shown in FIG. 7, the power generation element 21 of the bipolar secondary battery 10b of this embodiment has a positive electrode active material layer 13 electrically coupled to one surface of the current collector 11. It has a plurality of bipolar electrodes 23 each having an electrically coupled negative electrode active material layer 15 formed on its opposite surface. Each bipolar electrode 23 is stacked with the solid electrolyte layer 17 in between to form the power generation element 21 . Note that the solid electrolyte layer 17 has a structure in which a solid electrolyte is formed into layers. At this time, the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of another bipolar electrode 23 adjacent to the one bipolar electrode 23 are arranged to face each other with the solid electrolyte layer 17 in between. , bipolar electrodes 23 and solid electrolyte layers 17 are alternately stacked. That is, the solid electrolyte layer 17 is sandwiched between the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of another bipolar electrode 23 adjacent to the one bipolar electrode 23. has been done.

Adjacent positive electrode active material layer 13 , solid electrolyte layer 17 , and negative electrode active material layer 15 constitute one cell layer 19 . Therefore, it can be said that the bipolar secondary battery 10b has a structure in which the single cell layers 19 are stacked. Note that the positive electrode active material layer 13 is formed only on one side of the outermost layer current collector 11a on the positive electrode side located at the outermost layer of the power generation element 21. Further, the negative electrode active material layer 15 is formed only on one side of the negative electrode side outermost layer current collector 11b located at the outermost layer of the power generation element 21.

Furthermore, in the bipolar secondary battery 10b shown in FIG. 7, a positive electrode current collector plate (positive electrode tab) 25 is arranged adjacent to the outermost layer current collector 11a on the positive electrode side, and this is extended to form a battery exterior body. It is derived from the laminate film 29. On the other hand, a negative electrode current collector plate (negative electrode tab) 27 is arranged adjacent to the outermost layer current collector 11b on the negative electrode side, and is similarly extended and led out from the laminate film 29.

Note that the number of times the cell layer 19 is stacked is adjusted depending on the desired voltage. Furthermore, in the bipolar secondary battery 10b, the number of times the unit cell layers 19 are stacked may be reduced if sufficient output can be ensured even if the thickness of the battery is made as thin as possible. In the bipolar secondary battery 10b, in order to prevent external impact and environmental deterioration during use, the power generating element 21 is sealed under reduced pressure in a laminate film 29, which is the battery exterior, and the positive electrode current collector plate 25 and the negative electrode collector It is preferable to have a structure in which the electric plate 27 is taken out from the laminate film 29.

The main components of the above-described stacked secondary battery 10a will be explained below.

[Current collector]
The current collector has a function of mediating the movement of electrons from one surface in contact with the positive electrode active material layer to the other surface in contact with the negative electrode active material layer. There is no particular restriction on the material constituting the current collector. As the constituent material of the current collector, for example, metal or conductive resin may be used.

Specifically, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a cladding material of nickel and aluminum, a cladding material of copper and aluminum, etc. may be used. Alternatively, it may be a foil whose metal surface is coated with aluminum. Among these, aluminum, stainless steel, copper, and nickel are preferred from the viewpoints of electron conductivity, battery operating potential, adhesion of the negative electrode active material to the current collector by sputtering, and the like.

Furthermore, examples of the latter resin having electrical conductivity include resins in which a conductive filler is added to a non-conductive polymer material as necessary.

Examples of non-conductive polymer materials include polyethylene (PE; high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide. (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA) , polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or polystyrene (PS). Such non-conductive polymeric materials can have excellent potential or solvent resistance.

A conductive filler may be added to the above-mentioned conductive polymer material or non-conductive polymer material as necessary. In particular, when the resin serving as the base material of the current collector consists only of non-conductive polymers, a conductive filler is inevitably required to impart conductivity to the resin.

The conductive filler can be used without particular limitation as long as it is a substance that has conductivity. For example, metals, conductive carbon, and the like are examples of materials with excellent conductivity, potential resistance, or lithium ion blocking properties. The metal is not particularly limited, but includes at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or containing these metals. Preferably, it contains an alloy or a metal oxide. Furthermore, there are no particular limitations on the conductive carbon. Preferably, it is selected from the group consisting of acetylene black, Vulcan (registered trademark), Black Pearl (registered trademark), carbon nanofiber, Ketjenblack (registered trademark), carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. It contains at least one kind.

The amount of conductive filler added is not particularly limited as long as it can impart sufficient conductivity to the current collector, and is generally 5 to 80% by mass based on 100% by mass of the total mass of the current collector. It is.

Note that the current collector may have a single-layer structure made of a single material, or may have a laminated structure in which layers made of these materials are appropriately combined. From the viewpoint of reducing the weight of the current collector, it is preferable to include at least a conductive resin layer made of a resin having conductivity. Further, from the viewpoint of blocking the movement of lithium ions between the cell layers, a metal layer may be provided on a part of the current collector.

[Negative electrode active material layer]
The negative electrode active material layer contains a negative electrode active material. The negative electrode active material preferably contains elemental metal lithium (Li) or a lithium-containing alloy. The types of these negative electrode active materials are not particularly limited, but examples of Li-containing alloys include alloys of Li and at least one of In, Al, Si, and Sn. In some cases, two or more types of negative electrode active materials may be used together. Moreover, it goes without saying that negative electrode active materials other than those mentioned above may be used.

Examples of the shape of the negative electrode active material include particulate (spherical, fibrous), thin film, and the like. When the negative electrode active material has a particle shape, the average particle size (D ₅₀ ) is, for example, preferably within the range of 1 nm to 100 μm, more preferably within the range of 10 nm to 50 μm, and even more preferably 100 nm. 20 μm, particularly preferably 1 to 20 μm. Note that in this specification, the value of the average particle diameter (D ₅₀ ) of the active material can be measured by a laser diffraction scattering method.

The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but for example, it is preferably within the range of 40 to 99% by mass, and preferably within the range of 50 to 90% by mass. More preferred.

Preferably, the negative electrode active material layer further includes a solid electrolyte. By including the solid electrolyte in the negative electrode active material layer, the ionic conductivity of the negative electrode active material layer can be improved. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes, but they generally have a large effective fracture toughness value because they are not easily affected by grain boundaries (i.e., cracks caused by dendrites It is preferable that the electrolyte contains a sulfide solid electrolyte from the viewpoints of high ionic conductivity (hard to develop) and high ionic conductivity.

Examples of the sulfide solid electrolyte include LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP ₂ S ₅ , LiI-Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS _4, Li ₃ PS _4, Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiI, Li ₂ SP ₂ S ₅ - Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ S-B ₂ S ₃ , Li ₂ S-P ₂ S ₅ -Z _m S _n (where m and n are positive numbers, and Z is either Ge, Zn, or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Examples include Li ₂ S-SiS ₂ -Li _x MO _y (where x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In). . Note that the description “Li ₂ SP ₂ S ₅ ” means a sulfide solid electrolyte made using a raw material composition containing Li ₂ S and P ₂ S ₅ , and the same applies to other descriptions.

The sulfide solid electrolyte may have, for example, a Li ₃ PS ₄ skeleton, a Li ₄ P ₂ S ₇ skeleton, or a Li ₄ P ₂ S ₆ skeleton. . Examples of the sulfide solid electrolyte having a Li ₃ PS ₄ skeleton include LiI-Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS _{4, and} Li ₃ PS ₄ . Furthermore, examples of the sulfide solid electrolyte having a Li ₄ P ₂ S ₇ skeleton include a Li-P-S solid electrolyte (eg, Li ₇ P ₃ S ₁₁ ) called LPS. Further, as the sulfide solid electrolyte, for example, LGPS expressed by Li _(4-x) Ge _(1-x) P _x S ₄ (x satisfies 0<x<1) or the like may be used. Among these, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing the element P, and more preferably the sulfide solid electrolyte is a material containing Li ₂ SP ₂ S ₅ as a main component. Furthermore, the sulfide solid electrolyte may contain halogen (F, Cl, Br, I).

In addition, when the sulfide solid electrolyte is Li ₂ S-P ₂ S ₅ system, the ratio of Li ₂ S and P ₂ S ₅ is a molar ratio of Li ₂ S:P ₂ S ₅ =50:50 to 100. :0, and particularly preferably Li ₂ S:P ₂ S ₅ =70:30 to 80:20.

Further, the sulfide solid electrolyte may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid phase method. Note that sulfide glass can be obtained, for example, by performing mechanical milling (ball mill, etc.) on a raw material composition. Further, crystallized sulfide glass can be obtained, for example, by heat-treating sulfide glass at a temperature equal to or higher than the crystallization temperature. Further, the ionic conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25° C.) is preferably 1×10 ⁻⁵ S/cm or more, and 1×10 ⁻⁴ S/cm or more. More preferably, it is at least cm. Note that the ionic conductivity value of the solid electrolyte can be measured by an AC impedance method.

Examples of the oxide solid electrolyte include compounds having a NASICON type structure. Examples of compounds having a NASICON type structure include a compound represented by the general formula Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (0≦x≦2) (LAGP), and a general formula Li _1+x Al _x Ti _{2 -x} (PO ₄ ) ₃ (0≦x≦2) (LATP) and the like. In addition, other examples of oxide solid electrolytes include LiLaTiO (e.g., Li _0.34 La _0.51 TiO ₃ ), LiPON (e.g., Li _2.9 PO _3.3 N _0.46 ), LiLaZrO (e.g. , Li ₇ La ₃ Zr ₂ O ₁₂ ), and the like.

Examples of the shape of the solid electrolyte include particle shapes such as true spheres and ellipsoids, thin film shapes, and the like. When the solid electrolyte has a particle shape, its average particle diameter (D ₅₀ ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. On the other hand, the average particle diameter (D ₅₀ ) is preferably 0.01 μm or more, more preferably 0.1 μm or more.

The content of the solid electrolyte in the negative electrode active material layer is, for example, preferably in the range of 1 to 60% by mass, more preferably in the range of 10 to 50% by mass.

In addition to the above-described negative electrode active material and solid electrolyte, the negative electrode active material layer may further contain at least one of a conductive additive and a binder.

Examples of conductive aids include metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium; alloys or metal oxides containing these metals; carbon fibers (specifically, vapor-grown carbon fibers); (VGCF), polyacrylonitrile carbon fiber, pitch carbon fiber, rayon carbon fiber, activated carbon fiber, etc.), carbon nanotubes (CNT), carbon black (specifically, acetylene black, Ketjen black (registered trademark)) , furnace black, channel black, thermal lamp black, etc.), but are not limited to these. Further, a particulate ceramic material or resin material coated with the above metal material by plating or the like can also be used as a conductive aid. Among these conductive additives, from the viewpoint of electrical stability, it is preferable to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon; , silver, gold, and carbon, and more preferably carbon. These conductive aids may be used alone or in combination of two or more.

The shape of the conductive aid is preferably particulate or fibrous. When the conductive additive is in the form of particles, the shape of the particles is not particularly limited, and may be any shape such as powder, sphere, rod, needle, plate, column, irregular shape, flake, spindle, etc. I don't mind.

The average particle diameter (primary particle diameter) when the conductive additive is in the form of particles is not particularly limited, but from the viewpoint of the electrical characteristics of the battery, it is preferably 0.01 to 10 μm. In addition, in this specification, "particle diameter of a conductive aid" means the maximum distance L among the distances between arbitrary two points on the outline of a conductive aid. The value of the "average particle diameter of the conductive aid" is the particle diameter of particles observed in several to several dozen fields of view using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The value calculated as the average value shall be adopted.

When the negative electrode active material layer contains a conductive additive, the content of the conductive additive in the negative electrode active material layer is not particularly limited, but is preferably 0 to 10% by mass based on the total mass of the negative electrode active material layer. , more preferably 2 to 8% by weight, and still more preferably 4 to 7% by weight. Within this range, it becomes possible to form a stronger electron conduction path in the negative electrode active material layer, and it is possible to effectively contribute to improving battery characteristics.

On the other hand, the binder is not particularly limited, but examples include the following materials.

Polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyethernitrile, polytetrafluoroethylene, Polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and hydrogenated products thereof , thermoplastic polymers such as styrene/isoprene/styrene block copolymers and their hydrogenated products, tetrafluoroethylene/hexafluoropropylene copolymers (FEP), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymers (PFA) , fluororesins such as ethylene/tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene/chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), vinylidene fluoride- Hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based fluororubber), vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene-based fluororubber ( Examples include vinylidene fluoride-based fluororubbers such as VDF-PFMVE-TFE-based fluororubber), vinylidene fluoride-chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber), and epoxy resins. Among these, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferred.

The thickness of the negative electrode active material layer varies depending on the structure of the intended all-solid-state battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[Cathode active material layer]
The positive electrode active material layer contains a positive electrode active material. The type of positive electrode active material is not particularly limited, but elemental sulfur (S ₈ ) or a reduction product of sulfur containing lithium (any of the compounds Li ₂ S ₈ to Li ₂ S) is preferably used. For example, elemental sulfur (S ₈ ) has an extremely large theoretical capacity of about 1670 mAh/g, and has the advantage of being low cost and abundant in resources. In this case, when the all-solid-state lithium ion secondary battery is provided in a charged state, elemental sulfur (S ₈ ) is included as the positive electrode active material. In addition, when an all-solid-state lithium ion secondary battery is provided in a discharged state, a sulfur reduction product containing lithium (any of the above-mentioned Li ₂ S ₈ to Li ₂ S compounds) is used as the positive electrode active material. ).

Note that the positive electrode active material layer contains a positive electrode active material other than the above-mentioned elemental sulfur (S ₈ ) or the reduction product of sulfur containing lithium (any of the above-mentioned compounds of Li ₂ S ₈ to Li ₂ S). May include. However, the proportion of the reduction product of elemental sulfur or sulfur containing lithium in the positive electrode active material contained in the positive electrode active material layer is preferably 50 to 100% by mass, more preferably 80 to 100% by mass. , more preferably 90 to 100% by weight, even more preferably 95 to 100% by weight, particularly preferably 98 to 100% by weight, and most preferably 100% by weight.

Examples of positive electrode active materials other than simple sulfur or reduction products of sulfur containing lithium include disulfide compounds, sulfur-modified polyacrylonitrile represented by the compound described in International Publication No. 2010/044437 pamphlet, and sulfur-modified polyisoprene. , rubeanic acid (dithiooxamide), polysulfurized carbon, and the like. Further, inorganic sulfur compounds such as S-carbon composite, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , MoS ₂ and MoS ₃ can also be used. Further, as positive electrode active materials that do not contain sulfur, for example, layered rock salt active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , Li(Ni-Mn-Co)O ₂ , LiMn ₂ O ₄ , LiNi Examples include spinel-type active materials such as _0.5 Mn _1.5 O ₄ , olivine-type active materials such as LiFePO ₄ and LiMnPO ₄ , and Si-containing active materials such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ . Further, examples of oxide active materials other than those mentioned above include Li ₄ Ti ₅ O ₁₂ . In some cases, two or more types of positive electrode active materials may be used together. Note that, of course, positive electrode active materials other than those mentioned above may be used.

Examples of the shape of the positive electrode active material include particulate (spherical, fibrous), thin film, and the like. When the positive electrode active material is in the form of particles, the average particle size (D ₅₀ ) is, for example, preferably within the range of 1 nm to 100 μm, more preferably within the range of 10 nm to 50 μm, and even more preferably 100 nm. 20 μm, particularly preferably 1 to 20 μm. Note that in this specification, the value of the average particle diameter (D ₅₀ ) of the active material can be measured by a laser diffraction scattering method.

The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but for example, it is preferably within the range of 40 to 99% by mass, and preferably within the range of 50 to 90% by mass. More preferred. Note that the positive electrode active material layer may also further contain at least one of a solid electrolyte, a conductive aid, and a binder, as necessary, similarly to the negative electrode active material layer described above. Since the specific forms of these materials are the same as those described above, detailed explanations will be omitted here.

[Solid electrolyte layer]
The solid electrolyte layer of the bipolar secondary battery according to this embodiment is a layer that contains a solid electrolyte as a main component and is interposed between the above-described positive electrode active material layer and negative electrode active material layer. Since the specific form of the solid electrolyte contained in the solid electrolyte layer is the same as that described above, detailed explanation will be omitted here.

The content of the solid electrolyte in the solid electrolyte layer is, for example, preferably within the range of 10 to 100% by mass, more preferably within the range of 50 to 100% by mass, and within the range of 90 to 100% by mass. It is more preferable that

The solid electrolyte layer may further contain a binder in addition to the solid electrolyte described above. Since the specific form of the binder that can be contained in the solid electrolyte layer is the same as that described above, detailed explanation will be omitted here.

The thickness of the solid electrolyte layer varies depending on the configuration of the intended bipolar secondary battery, but for example, it is preferably within the range of 0.1 to 1000 μm, and preferably within the range of 0.1 to 300 μm. is more preferable.

[Positive current collector plate and negative current collector plate]
The material constituting the current collector plates (25, 27) is not particularly limited, and known highly conductive materials conventionally used as current collector plates for secondary batteries may be used. As the constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoints of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. Note that the positive electrode current collector plate 25 and the negative electrode current collector plate 27 may use the same material or different materials.

[Positive lead and negative lead]
Further, although not shown, the current collector 11 and the current collecting plates (25, 27) may be electrically connected via a positive electrode lead or a negative electrode lead. As constituent materials for the positive electrode and negative electrode leads, materials used in known lithium ion secondary batteries can be similarly employed. In addition, the parts taken out from the exterior are covered with heat-resistant insulating heat-shrinkable material to prevent them from contacting peripheral equipment or wiring and causing electrical leakage, which may affect products (e.g., automobile parts, especially electronic equipment, etc.). Preferably, it is covered with a tube or the like.

[Battery exterior body]
As the battery exterior body, a well-known metal can case can be used, or a bag-shaped case using a laminate film 29 containing aluminum that can cover the power generation element as shown in FIGS. 6 and 7 can be used. It can be done. The laminate film may be, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order, but is not limited thereto. A laminate film is desirable from the viewpoint that it has high output and excellent cooling performance, and can be suitably used in batteries for large equipment such as EVs and HEVs. Moreover, the exterior body is more preferably a laminate film containing aluminum because the group pressure applied to the power generation element from the outside can be easily adjusted.

FIG. 8 is a perspective view showing the appearance of a flat lithium ion secondary battery, which is a typical embodiment of a stacked secondary battery.

As shown in FIG. 8, the flat stacked secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for extracting power are pulled out from both sides of the battery. There is. The power generation element 57 is surrounded by the battery exterior body (laminate film 52) of the laminated secondary battery 50, and the periphery thereof is heat fused, and the power generation element 57 has a positive electrode tab 58 and a negative electrode tab 59 pulled out to the outside. It is sealed in a sealed condition. Here, the power generation element 57 corresponds to the power generation element 21 of the stacked secondary battery 10a shown in FIG. 6 described above.

Note that the above-mentioned lithium ion secondary battery is not limited to a flat, stacked type battery. A wound type lithium ion secondary battery may have a cylindrical shape, or may be a cylindrical battery that has been deformed into a rectangular flat shape. etc., there are no particular restrictions. The above-mentioned cylindrical shape is not particularly limited, and its exterior body may be made of a laminate film or a conventional cylindrical can (metal can). Preferably, the power generation element is packaged with an aluminum laminate film. With this form, weight reduction can be achieved.

Further, there is no particular restriction on taking out the tabs 58 and 59 shown in FIG. 8. The positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side, as shown in FIG. It is not limited to. Further, in a wound type lithium ion battery, the terminals may be formed using, for example, a cylindrical can (metal can) instead of a tab.

[Assembled battery]
A battery pack is made up of multiple batteries connected together. Specifically, it is configured by using at least two or more, serially or parallelly, or both. By connecting them in series or parallel, it becomes possible to freely adjust the capacity and voltage.

A plurality of batteries can be connected in series or in parallel to form a small detachable battery pack. By connecting multiple small, removable batteries in series or in parallel, high-capacity, large-capacity batteries suitable for vehicle drive power sources and auxiliary power sources that require high volumetric energy density and high volumetric output density can be used. It is also possible to form a battery pack with an output. How many batteries to connect to make a battery pack, and how many stages of small battery packs to stack to make a large-capacity battery pack depends on the battery capacity of the vehicle (electric vehicle) in which it will be mounted. You can decide according to the output.

When carrying out the charging method according to the present invention for an assembled battery, for example, the charging process can be performed while measuring the internal resistance value of each individual battery (single cell) that constitutes the assembled battery. With such a configuration, charging processing can be performed while separately performing control to reduce the internal resistance of each individual battery (single cell).

[vehicle]
The non-aqueous electrolyte secondary battery of this embodiment maintains its discharge capacity even after long-term use, and has good cycle characteristics. Additionally, it has a high volumetric energy density. Vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles require higher capacity, larger size, and longer lifespan than electric and portable electronic device applications. . Therefore, the non-aqueous electrolyte secondary battery can be suitably used as a vehicle power source, for example, as a vehicle drive power source or an auxiliary power source.

Specifically, a battery or a battery pack formed by combining a plurality of batteries can be mounted on the vehicle. According to the present invention, it is possible to configure a long-life battery with excellent long-term reliability and output characteristics, so when such a battery is installed, it is possible to configure a plug-in hybrid electric vehicle with a long EV mileage or an electric vehicle with a long mileage on a single charge. . Batteries or assembled batteries made by combining multiple of these can be used, for example, in the case of automobiles, such as hybrid vehicles, fuel cell vehicles, electric vehicles (all four-wheeled vehicles (passenger cars, commercial vehicles such as trucks, buses, light vehicles, etc.), etc. , two-wheeled vehicles (including motorcycles, and three-wheeled vehicles)) can provide long-life and highly reliable vehicles. However, the application is not limited to automobiles; for example, it can be applied to various power sources for other vehicles, such as trains, and on-board power sources such as uninterruptible power supplies. It is also possible to use it as

[Experiment example]
For the purpose of confirming the feasibility of implementing the present invention, a charging process was performed using a current (heating current) larger than the rated charging current, and compared with a case where the charging process was performed using the rated charging current. We conducted a simulation experiment to confirm that the time required for the battery to rise in temperature was reduced.

First, the initial internal resistance value of a commercially available all-solid-state lithium ion secondary battery (positive electrode active material: sulfur (S), negative electrode active material: metallic lithium (Li)) was measured, and the rate of increase in internal resistance was measured. The internal resistance value was calculated assuming that 80%. Then, assuming that the internal resistance value corresponds to the electrolyte resistance, the amount of heat equivalent to Joule heat calculated from the current value to be supplied was calculated.

On the other hand, the amount of heat required to raise the temperature of the battery from room temperature (20°C) to the upper limit temperature can be determined from the heat capacity of the battery determined from the constituent materials of the secondary battery and the preset upper limit temperature. Calculated. Then, assuming that all the heat equivalent to the Joule heat mentioned above is used to raise the temperature of the battery, the current is applied for the time required to raise the temperature of the battery from room temperature (20°C) to the upper limit temperature. Each current value was calculated and compared. Note that the upper limit temperature was set at 115.degree. C. in view of the fact that the melting point of metal lithium (Li), which is a material with the lowest melting point among the power generation elements of the battery, is 115.2.degree.

The above simulation experiment was conducted using a current value equivalent to normal charging (3 kW single phase 200 V), and the results are shown in Table 1 below. Note that in this experiment, the value of the charging current was set to 15A, 18A, or 22.5A.

Similarly, the above simulation experiment was conducted using a current value equivalent to quick charging (50 kW), and the results are shown in Table 2 below. Note that in this experiment, the value of the charging current was set to 125A, 150A, or 187.5A.

As can be seen from the results shown in Tables 1 and 2, it can be seen that as the value of the charging current increases, the time required to raise the temperature of the battery becomes shorter. For this reason, in the control of the secondary battery system or secondary battery charging device according to the present invention, when an increase in the internal resistance value of the battery is detected, a heating current is used to increase the temperature of the battery, and the solid electrolyte is By melting the material at the layer-electrode active material layer interface, it is expected that the internal resistance value can be reduced (recovered) in an extremely short time.

1 All-solid-state lithium ion secondary battery system,
2 All-solid-state lithium ion secondary battery,
3 voltage sensor,
4 temperature sensor,
5 voltage and current adjustment section,
6 current sensor,
7 control unit,
8 external power supply,
10a, 50 stacked secondary battery,
10b bipolar secondary battery,
11 current collector,
11′ positive electrode current collector,
11'' negative electrode current collector,
11a outermost layer current collector on the positive electrode side,
11b outermost layer current collector on the negative electrode side,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21, 57 Power generation element,
23 Bipolar electrode,
25 Positive electrode current collector plate (positive electrode tab),
27 Negative electrode current collector plate (negative electrode tab),
29, 52 laminate film,
58 Positive electrode tab,
59 negative electrode tab,
71 CPU,
72 Memory section,
100 battery pack,
110 Secondary battery module,
120 Battery Management System (BMS),
130 junction box,
200 DC/DC junction box,
210 DC/DC converter,
220 Normal charging relay,
221 On-board charger,
222 Normal charging port,
230 quick charge relay,
232 Quick charging port 240 Starter motor (SM),
250 Electrical load,
260 Alternator (ALT),
300 power supply circuit,
310 Main battery (lead acid battery),
320 sub battery (all-solid battery),
330 relay.

Claims (7)

a positive electrode including a positive electrode active material layer containing a positive electrode active material containing a reduction product of sulfur containing elemental sulfur (S ₈ ) or lithium ;
a negative electrode including a negative electrode active material layer containing a negative electrode active material;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer;
An all-solid-state lithium ion secondary battery equipped with a power generation element having
a charger for charging the all-solid-state lithium ion secondary battery;
an internal resistance measurement unit that measures the internal resistance of the all-solid-state lithium ion secondary battery;
When the charger charges the all-solid-state lithium ion secondary battery, when the internal resistance value measured by the internal resistance measurement unit or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. , by controlling the charger to charge the all-solid-state lithium ion battery with a heating current larger than the rated charging current, the interface between the positive electrode active material layer and the solid electrolyte layer is separated, resulting in ohmic a control unit that suppresses an increase in resistance ;
Equipped with
The heating current is a current that melts the elemental sulfur (S ₈ ) or the reduction product of sulfur containing lithium while maintaining its shape, and generates fluidity between it and the solid electrolyte layer. , an all-solid-state lithium-ion secondary battery system. After the all-solid-state lithium ion battery is charged with the heating current,
When the internal resistance value or the rate of increase becomes less than the threshold value, or when the battery temperature of the all-solid lithium ion battery becomes equal to or higher than a predetermined threshold temperature, the control unit controls the heating The all-solid-state lithium-ion secondary battery system according to claim 1, wherein the charger is controlled to stop charging with current and charge the all-solid-state lithium-ion battery with the rated charging current. The control unit controls the magnitude and/or application time of the heating current so that the maximum temperature of the positive electrode active material and the negative electrode active material after application of the heating current is less than their respective melting points. The all-solid-state lithium ion secondary battery system according to claim 1 or 2. The all-solid-state lithium-ion secondary battery is mounted on a vehicle, and the charger applies the heating current to the all-solid-state lithium-ion secondary battery using electric power supplied from a power source installed outside the vehicle. The all-solid-state lithium ion secondary battery system according to any one of claims 1 to 3, wherein: The all-solid-state lithium-ion secondary battery is mounted on a vehicle, and the charger supplies the heating current to the all-solid-state lithium-ion secondary battery using power supplied from another power source mounted on the vehicle. The all-solid-state lithium ion secondary battery system according to any one of claims 1 to 3, wherein: The all-solid lithium ion diode according to any one of claims 1 to 5, wherein the positive electrode active material contains elemental sulfur or a reduction product of sulfur containing lithium, and the negative electrode active material contains elemental metallic lithium. Next battery system. a positive electrode including a positive electrode active material layer containing a positive electrode active material containing a reduction product of sulfur containing elemental sulfur (S ₈ ) or lithium;
a negative electrode including a negative electrode active material layer containing a negative electrode active material;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer;
A charging device for charging an all-solid-state lithium ion secondary battery equipped with a power generation element having
a charger for charging the all-solid-state lithium ion secondary battery;
an internal resistance measurement unit that measures the internal resistance of the all-solid-state lithium ion secondary battery;
When the charger charges the all-solid-state lithium ion secondary battery, when the internal resistance value measured by the internal resistance measurement unit or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. , by controlling the charger to charge the all-solid-state lithium ion battery with a heating current larger than the rated charging current, the interface between the positive electrode active material layer and the solid electrolyte layer is separated, resulting in ohmic a control unit that suppresses an increase in resistance ;
Equipped with
The heating current is a current that melts the elemental sulfur (S ₈ ) or the reduction product of sulfur containing lithium while maintaining its shape, and generates fluidity between it and the solid electrolyte layer. , a charging device for all-solid-state lithium-ion secondary batteries.