JP2008130278A - Charging system, charging device, and battery pack - Google Patents

Abstract

A charging system, a charging device, and a battery pack capable of increasing a charging voltage exceeding a reference voltage are provided.
A secondary battery 141 having a porous protective film 325 between a negative electrode plate 303 and a positive electrode plate 301, and a charging voltage current supply circuit 33 for supplying a charging voltage Vb for charging the secondary battery 141. And a voltage exceeding a reference voltage that is a voltage between the negative electrode plate 303 and the positive electrode plate 301 when the negative electrode plate 303 is in a fully charged state in which the potential on the lithium reference is substantially 0V. The charging / discharging control part 211 which performs constant voltage charging by supplying the set voltage Vs to the secondary battery 141 by the charging voltage current supply circuit 33 as a charging voltage is provided.
[Selection] Figure 1

Description

  The present invention relates to a charging system for charging a secondary battery, a charging device, and a battery pack including the secondary battery.

  FIG. 10 is a graph for explaining a charge voltage and current management method according to the prior art. FIG. 10 is a graph in the case of a lithium ion battery, and shows changes in the terminal voltage α1 of the secondary battery, the charging current α2 supplied to the secondary battery, and the SOC (State Of Charge) α3.

  First, as for the terminal voltage α1, a trickle charge region is reached from the start of charging, and a small constant current I1, for example, a charging current of 50 mA, is supplied. Among the cell voltages of one or a plurality of cells, the minimum cell voltage Vmin is the trickle. This trickle charging is continued until the charging end voltage Vm, for example, 2.3 V is reached.

  When the cell voltage Vmin reaches the end voltage Vm, it switches to a constant current (CC) charging region, and a constant current I2, for example, a nominal capacity value NC is discharged at a constant current, and the level that can be discharged in 1 hour is set to 1C. A charging current obtained by multiplying 70% of the number by the number of parallel cells PN is supplied, and constant current (CC) charging is performed.

  As a result, when the terminal voltage of the charging terminal of the battery pack becomes a predetermined end voltage Vf of 4.2 V per cell (= number of series cells SN × 4.2 V, therefore, for example, in the case of three cells in series, 12.6 V). When the charging current value is decreased so as not to exceed the end voltage Vf and the charging current value decreases to the current value I3 set by the temperature, it is determined that the battery is fully charged. Thus, the supply of charging current is stopped. That is, the charging depth α3 when the charging current value decreases to the current value I3 indicates 100%. The current value I3 is a determination value for detecting full charge. Ideally, 0A is desirable to fully charge the charge capacity, but in constant voltage charge, the secondary battery approaches full charge. Since the charging current decreases and the charging becomes slow, if the current value I3 is set to 0 A, it takes a long time to increase a slight charging capacity. For this reason, the current value I3 is appropriately set depending on the balance between the charging capacity and the charging time. For example, a current value of about (0.1 A × number of parallel cells PN) is set. In this case, 0.1A is set to 1/20 CA with respect to the battery capacity C, for example.

  FIG. 11 is an explanatory diagram showing changes in the positive electrode potential Pp and the negative electrode potential Pm with respect to the lithium reference when the lithium ion battery is charged. The horizontal axis indicates the SOC, and the vertical axis indicates the potential. As shown in FIG. 11, when the lithium ion battery is charged, the positive electrode potential Pp increases and the negative electrode potential Pm decreases as the SOC increases. In this case, the terminal voltage of the lithium ion battery is the difference between the positive electrode potential Pp and the negative electrode potential Pm, and is given by Pp−Pm.

  Then, as the SOC increases, the negative electrode potential Pm decreases and the difference between the positive electrode potential Pp and the negative electrode potential Pm when the negative electrode potential Pm becomes 0 V, that is, the positive electrode potential Pp is the charge current value, temperature, positive electrode and negative electrode However, when lithium cobaltate is used as the positive electrode active material, the voltage may be approximately 4.2 V when lithium cobaltate is used as the positive electrode active material. Are known.

  Further, when the negative electrode potential Pm becomes a negative potential, lithium ions moving from the positive electrode to the negative electrode are deposited as metallic lithium on the negative electrode surface. The lithium metal deposited on the negative electrode surface grows toward the positive electrode in the form of columnar dendrites, so-called lithium dendrites, and penetrates a separator made of a resin material such as polyethylene, for example. As a result of short-circuiting, it is known that the separator melts due to a short-circuit current flowing through the lithium dendrite, and the short-circuited portion expands and the battery may be damaged.

  Therefore, lithium manganate is used as the positive electrode active material so that the terminal voltage per cell does not exceed 4.2 V when lithium cobaltate is used as the positive electrode active material so that the negative electrode potential Pm does not become a negative potential. When used, the end voltage Vf is set so as not to exceed 4.3V. For example, the final voltage Vf is 4.2 V × series cell number SN when lithium cobaltate is used as the positive electrode active material, and 4.3 V × series cell number SN when lithium manganate is used as the positive electrode active material. The charging voltage is set so as not to exceed the end voltage Vf set in this way when the secondary battery is charged.

  Further, when the negative electrode potential Pm becomes 0V, if it is charged further, metal lithium is deposited and cannot be charged. Therefore, the charged state when the negative electrode potential Pm becomes 0V is set to a fully charged state (SOC: 100 %). Hereinafter, the voltage between the negative electrode and the positive electrode when the negative electrode is in a fully charged state in which the potential on the lithium reference is substantially 0 V is referred to as a reference voltage. That is, the reference voltage when lithium cobaltate is used as the positive electrode active material is 4.2 V, and the reference voltage when lithium manganate is used as the positive electrode active material is 4.3 V.

  If the charging voltage is increased beyond the reference voltage, a lithium dendrite is formed and the negative electrode and the positive electrode are short-circuited, the short-circuit current melts the separator, and the short-circuited part expands and the battery may be damaged. Therefore, conventionally, it has been impossible to increase the charging voltage beyond the reference voltage.

  By the way, when charging the secondary battery, a voltage drop caused by the product of the charging current and the internal resistance of the secondary battery, the on-resistance of the switching element, and the like is included in the charging voltage. Since the voltage drop Vr caused by such a resistance component is proportional to the charging current, it particularly increases in the constant current charging region shown in FIG. Then, even if the charging voltage reaches the reference voltage, the open circuit voltage (OCV) of the secondary battery is lower than the charging voltage by the voltage drop Vr, and does not reach the reference voltage.

Paying attention to such points, charging methods are known in which charging time is shortened by performing constant current charging at a voltage higher than the reference voltage by a voltage drop Vr (for example, Patent Document 1 and Patent Document 1). 2). In addition, after the constant current charging is completed, charging is performed at a voltage higher than the reference voltage in a region where the charging current is large, and the charging voltage is decreased according to the decrease in the charging current, that is, according to the decrease in the voltage drop Vr. A charging method is known in which the charging time is shortened while considering that the open circuit voltage (OCV) of the secondary battery does not exceed the reference voltage (see, for example, Patent Document 3).
Japanese Patent Application Laid-Open No. 2004-282881 JP-A-9-19073 JP 2004-274874 A

  However, as described above, the technique of performing constant current charging with a voltage higher than the reference voltage by the voltage drop Vr has a disadvantage that constant voltage charging cannot be performed with a voltage exceeding the reference voltage. In addition, in the technology for increasing the charging voltage within the range of the voltage drop Vr due to the charging current after the constant current charging is completed, the charging voltage must be decreased as the charging current decreases. This is a charging method different from constant voltage charging in which charging is performed at a constant charging voltage, and there is a disadvantage that a charging voltage exceeding a reference voltage cannot be maintained.

  The present invention has been made in view of such circumstances, and by performing constant voltage charging at a charging voltage exceeding the reference voltage, at least one of shortening the charging time and increasing the battery capacity is enabled. An object of the present invention is to provide a charging system, a charging device, and a battery pack.

  A charging system according to the present invention includes a secondary battery including a heat-resistant member having heat resistance between a negative electrode and a positive electrode, a charging voltage supply unit that supplies a charging voltage for charging the secondary battery, A set voltage set to a voltage exceeding a voltage between the negative electrode and the positive electrode when the negative electrode is in a fully charged state in which the potential on the lithium reference is substantially 0 V is defined as the charge voltage. A charging control unit that performs constant voltage charging by supplying the secondary battery to the secondary battery by the charging voltage supply unit.

  According to this configuration, the charging control unit supplies the set voltage set to a voltage exceeding the reference voltage from the charging voltage supply unit to the secondary battery, thereby performing constant voltage charging. In this case, lithium dendrite may be formed and the negative electrode and the positive electrode may be short-circuited. However, since a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode, the negative electrode and the positive electrode are formed by lithium dendrite. Even if a short-circuit current flows between them, the expansion of the short-circuited portion is suppressed by the heat-resistant member. As a result, constant voltage charging can be performed with a charging voltage exceeding the reference voltage without damaging the secondary battery.

  The heat resistant member is preferably a porous protective film containing a resin binder and an inorganic oxide filler. According to this configuration, since the porous protective film has heat resistance, even when the set voltage is applied between the negative electrode and the positive electrode, the negative electrode and the positive electrode are short-circuited by lithium dendrite, and heat is generated, Since the porous protective film does not melt or deform, the possibility that the short-circuited portion expands and the secondary battery is abnormally overheated is reduced.

  The heat-resistant member may be a separator. According to this configuration, since the separator has heat resistance, even if the set voltage is applied between the negative electrode and the positive electrode and the negative electrode and the positive electrode are short-circuited by lithium dendrite to generate heat, the separator melts. The possibility that the short-circuit portion is expanded due to the deformation and the secondary battery is abnormally overheated is reduced.

Further, as the active material of the positive electrode, Li _{a Mb} Ni _c Co _d O _e (M is at least selected from the group consisting of Al, Mn, Sn, In, Fe, Cu, Mg, Ti, Zn, and Mo) It is a kind of metal, and 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, and 1.8 <e <2.2. Further, it is preferable to use b + c + d = 1 and 0.34 <c).

As an active material for the positive _electrode, at least one metal is _{Li a M b Ni c Co d} O e (M to Al, Mn, Sn, In, Fe, Cu, Mg, Ti, are selected from the group consisting of Zn, and Mo And 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, 1.8 <e <2.2, b + c + d = 1 and 0.34 <c) is used, the volume expansion of the active material due to charging is reduced, so by increasing the charging voltage beyond the reference voltage, Even when charging is performed, the possibility that the positive electrode active material expands in the container housing the electrode and the electrode buckles is reduced.

  In addition, a charging current supply unit that supplies a charging current for charging the secondary battery, and a constant current charging by supplying a predetermined constant current to the secondary battery from the charging current supply unit. And a voltage detection unit that detects a terminal voltage of the secondary battery, and the terminal voltage detected by the voltage detection unit during the execution of the constant current charge is When the voltage becomes equal to or higher than a set voltage, it is preferable that the constant current charging control unit stops the constant current charging and the charging control unit executes the constant voltage charging.

  According to this configuration, a constant current is supplied to the secondary battery, and the secondary battery is charged with a constant current until the terminal voltage of the secondary battery is equal to or higher than the set voltage exceeding the reference voltage. Constant voltage charging is performed. In this case, the period during which the constant current charging is performed can be extended as compared with the case where the constant current charging is switched to the constant voltage charging when the terminal voltage of the secondary battery is equal to or lower than the reference voltage. When switching from constant current charging to constant voltage charging, the charging current flowing in the secondary battery gradually decreases, but as described above, the charging current is maintained without being reduced by extending the period of constant current charging. As a result, the charging time is shortened. In addition, since constant voltage charging is performed with a set voltage exceeding the reference voltage as the charging voltage, the charging current flowing to the secondary battery in constant voltage charging increases as compared with the case where the voltage equal to or lower than the reference voltage is used as the charging voltage. Time is shortened.

  The charging control unit further includes a current detection unit that detects a charging current flowing through the secondary battery, and the charging control unit is preset with a charging current detected by the current detection unit during the execution of the constant voltage charging. The supply voltage to the secondary battery is stopped when the set voltage is applied to the fully charged secondary battery. It is preferable that the current value is set to be equal to or greater than the current value flowing through the.

  According to this configuration, when constant voltage charging is performed using the set voltage as a charging voltage, the charging current decreases as the SOC increases. Then, when the charging current detected by the current detection unit decreases until reaching a preset end current, the supply of the charging voltage to the secondary battery is stopped, that is, the charging of the secondary battery is ended. The end voltage is set to a current value equal to or greater than the current value flowing through the secondary battery when the set voltage is applied to the fully charged secondary battery. Charging is not further continued in a state where the potential at the reference is substantially 0 V, and the possibility that lithium is deposited on the negative electrode and the secondary battery is deteriorated can be reduced. Then, in order to charge to the same charge capacity (SOC 100%), constant voltage charging is performed at a set voltage exceeding the reference voltage, thereby shortening the charging time of the secondary battery, and lithium is deposited on the negative electrode so that the secondary battery is charged. The risk of deterioration can be reduced.

  The charging control unit further includes a current detection unit that detects a charging current flowing through the secondary battery, and the charging control unit is preset with a charging current detected by the current detection unit during the execution of the constant voltage charging. The supply voltage to the secondary battery is stopped when the set voltage is applied to the fully charged secondary battery. It may be set to the value of the current flowing through.

  According to this configuration, when constant voltage charging is performed using the set voltage as a charging voltage, the charging current decreases as the SOC increases. Then, when the charging current detected by the current detection unit decreases until reaching a preset end current, the supply of the charging voltage to the secondary battery is stopped, that is, the charging of the secondary battery is ended. In this case, the end voltage is set to a current value that flows through the secondary battery when the set voltage is applied to the fully charged secondary battery. As a result of further charging beyond the state of substantially 0V, the charging capacity of the secondary battery can be increased. Further, even when the secondary battery is further charged beyond the fully charged state as described above, a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode of the secondary battery. Even if a short-circuit current flows between the negative electrode and the positive electrode due to the dendrite, the heat-resistant member suppresses the expansion of the short-circuited portion, so that the battery can be charged without causing damage.

  Further, the charging system according to the present invention is a charging system including a battery pack and a charging device for charging the battery pack, wherein the battery pack includes a secondary battery and a lithium reference for a negative electrode of the secondary battery. The secondary battery is charged with a voltage exceeding a reference voltage, which is a voltage between the negative electrode and the positive electrode of the secondary battery when the battery is fully charged, which is a state where the potential at the battery is substantially 0V. A battery information storage unit that stores battery information indicating whether or not the charging is possible, and the charging device includes a charging voltage supply unit that supplies a charging voltage for charging the secondary battery, and the battery When battery information indicating that the secondary battery can be charged with a voltage exceeding the reference voltage is stored in the information storage unit, a voltage exceeding the reference voltage is set as a set voltage, and the battery Information storage When battery information indicating that the secondary battery can be charged with a voltage exceeding the reference voltage is not stored, a setting voltage setting processing unit that sets a voltage equal to or lower than the reference voltage as a setting voltage; A charge control unit that performs constant voltage charging by supplying the set voltage set by the set voltage setting processing unit to the secondary battery by the charge voltage supply unit as the charge voltage.

  According to this configuration, when charging a battery pack including a secondary battery that can be charged with a voltage exceeding the reference voltage, the charging device uses the battery information stored in the battery information storage unit. A voltage exceeding the reference voltage is set as the set voltage, and constant voltage charging is executed using the set voltage as the charge voltage. Therefore, the charge voltage can be increased beyond the reference voltage without damaging the secondary battery. In addition, when charging a battery pack having a secondary battery that cannot be charged with a voltage exceeding the reference voltage, the battery pack can be charged with a secondary battery at a voltage exceeding the reference voltage. Since the battery information is not stored, the charging device sets the voltage below the reference voltage as the set voltage, and the constant voltage charge is executed using this set voltage as the charge voltage. As a result, the battery is charged with a voltage exceeding the reference voltage. The risk of damaging the secondary battery by charging a secondary battery that cannot be accidentally charged with a voltage exceeding the reference voltage is reduced.

  Moreover, the charging device according to the present invention charges a connection terminal for connecting to a secondary battery provided with a heat-resistant member having heat resistance between the negative electrode and the positive electrode, and charging the secondary battery to the connection terminal. Exceeding the voltage between the negative electrode and the positive electrode when fully charged, which is a state where the potential of the negative electrode on the lithium reference is substantially 0V. A charge control unit that performs constant voltage charging by supplying the set voltage set to a voltage to the connection terminal by the charge voltage supply unit as the charge voltage.

  According to this configuration, the charging control unit supplies the set voltage set to a voltage exceeding the reference voltage from the charging voltage supply unit to the secondary battery, thereby performing constant voltage charging. In this case, lithium dendrite may be formed and the negative electrode and the positive electrode may be short-circuited. However, since a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode, the negative electrode and the positive electrode are formed by lithium dendrite. Even if a short-circuit current flows between them, the expansion of the short-circuited portion is suppressed by the heat-resistant member. As a result, constant voltage charging can be performed with a charging voltage exceeding the reference voltage without damaging the secondary battery.

  The charging device according to the present invention is a charging device for charging a battery pack including a secondary battery and a battery information storage unit that stores battery information related to the secondary battery. A charging voltage supply unit for supplying a charging voltage for charging the battery, and a state in which the potential of the negative electrode of the secondary battery on the lithium reference is substantially 0 V as information on the secondary battery in the battery information storage unit Battery information indicating that the secondary battery can be charged with a voltage exceeding a reference voltage that is a voltage between the negative electrode and the positive electrode of the secondary battery when the fully charged state is reached is stored. If it is, the voltage exceeding the reference voltage is set as a set voltage, and the battery information indicating that the secondary battery can be charged with the voltage exceeding the reference voltage is stored in the battery information storage unit. It has not been A setting voltage setting processing unit that sets a voltage equal to or lower than the reference voltage as a setting voltage, and a setting voltage set by the setting voltage setting processing unit is supplied to the secondary battery by the charging voltage supply unit as the charging voltage. And a charge control unit that performs constant voltage charging.

  According to this configuration, when charging a battery pack including a secondary battery that can be charged with a voltage exceeding the reference voltage, the battery information stored in the battery information storage unit by the set voltage setting processing unit Based on this, a voltage exceeding the reference voltage is set as the set voltage, and constant voltage charging is executed using this set voltage as the charging voltage. Therefore, the charging voltage can be increased beyond the reference voltage without damaging the secondary battery. it can. In addition, when charging a battery pack having a secondary battery that cannot be charged with a voltage exceeding the reference voltage, the battery pack can be charged with a secondary battery at a voltage exceeding the reference voltage. Since the battery information is not stored, the set voltage setting processing unit sets a voltage that is equal to or lower than the reference voltage as the set voltage, and the constant voltage charging is performed using the set voltage as the charge voltage. As a result, the voltage that exceeds the reference voltage The possibility that the secondary battery that cannot be charged with the battery is accidentally charged with a voltage exceeding the reference voltage to damage the secondary battery is reduced.

  The battery pack according to the present invention is a battery pack connected to a charging device that outputs a voltage for charging a secondary battery in accordance with an instruction from the outside, and has a heat resistance between the negative electrode and the positive electrode. A voltage exceeding the voltage between the negative electrode and the positive electrode when a fully charged state in which the potential of the negative electrode on a lithium basis is substantially 0 V is obtained. A charging control unit for performing constant voltage charging by outputting the instruction to the charging device so that the charging device supplies the secondary battery with the set voltage set to 1 as the charging voltage. .

  According to this configuration, an instruction to supply the set voltage set to a voltage exceeding the reference voltage to the secondary battery as a charge voltage is output to the charging device by the charge control unit, and the set voltage is charged. Constant voltage charging is performed. In this case, lithium dendrite may be formed and the negative electrode and the positive electrode may be short-circuited. However, since a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode, the negative electrode and the positive electrode are formed by lithium dendrite. Even if a short-circuit current flows between them, the expansion of the short-circuited portion is suppressed by the heat-resistant member. As a result, constant voltage charging can be performed with a charging voltage exceeding the reference voltage without damaging the secondary battery.

  According to the charging system having such a configuration, the charge control unit exceeds the voltage between the negative electrode and the positive electrode when the fully charged state in which the potential on the lithium reference of the negative electrode is substantially 0V. The constant voltage charging is executed by supplying the set voltage set to the voltage from the charging voltage supply unit to the secondary battery. In this case, lithium dendrite may be formed and the negative electrode and the positive electrode may be short-circuited. However, since a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode, the negative electrode and the positive electrode are formed by lithium dendrite. Even if a short-circuit current flows between them, the expansion of the short-circuited portion is suppressed by the heat-resistant member. As a result, constant voltage charging can be performed with a charging voltage exceeding the reference voltage without damaging the secondary battery.

  Further, according to the charging system having such a configuration, when charging a battery pack including a secondary battery that can be charged with a voltage exceeding the reference voltage, the charging device stores the battery pack in the battery information storage unit. Based on the battery information, the voltage exceeding the reference voltage is set as the set voltage, and constant voltage charging is executed using this set voltage as the charging voltage, so the charging voltage exceeds the reference voltage without damaging the secondary battery. Can be increased. In addition, when charging a battery pack having a secondary battery that cannot be charged with a voltage exceeding the reference voltage, the battery pack can be charged with a secondary battery at a voltage exceeding the reference voltage. Since the battery information is not stored, the charging device sets the voltage below the reference voltage as the set voltage, and the constant voltage charge is executed using this set voltage as the charge voltage. As a result, the battery is charged with a voltage exceeding the reference voltage. The risk of damaging the secondary battery by charging a secondary battery that cannot be accidentally charged with a voltage exceeding the reference voltage is reduced.

  Further, according to the charging device having such a configuration, the voltage between the negative electrode and the positive electrode when the charge control unit is in a fully charged state in which the potential on the lithium reference of the negative electrode is substantially 0V. A constant voltage charging is executed by supplying a set voltage set to a voltage exceeding 1 to the secondary battery from the charging voltage supply unit. In this case, lithium dendrite may be formed and the negative electrode and the positive electrode may be short-circuited. However, since a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode, the negative electrode and the positive electrode are formed by lithium dendrite. Even if a short-circuit current flows between them, the expansion of the short-circuited portion is suppressed by the heat-resistant member. As a result, constant voltage charging can be performed with a charging voltage exceeding the reference voltage without damaging the secondary battery.

  Further, according to the charging device having such a configuration, when charging a battery pack including a secondary battery that can be charged with a voltage exceeding the reference voltage, the battery information storage unit is set by the set voltage setting processing unit. The voltage exceeding the reference voltage is set as the set voltage based on the battery information stored in the battery, and constant voltage charging is executed using this set voltage as the charging voltage. The charging voltage can be increased. In addition, when charging a battery pack having a secondary battery that cannot be charged with a voltage exceeding the reference voltage, the battery pack can be charged with a secondary battery at a voltage exceeding the reference voltage. Since the battery information is not stored, the set voltage setting processing unit sets a voltage that is equal to or lower than the reference voltage as the set voltage, and the constant voltage charging is executed using the set voltage as the charge voltage. The possibility that the secondary battery that cannot be charged with the battery is accidentally charged with a voltage exceeding the reference voltage to damage the secondary battery is reduced.

  Further, according to the battery pack having such a configuration, the voltage between the negative electrode and the positive electrode when the charge control unit is in a fully charged state in which the potential on the lithium reference of the negative electrode is substantially 0V. An instruction to supply a set voltage set to a voltage exceeding 1 to the secondary battery as a charge voltage is output to the charging device, and constant voltage charging using the set voltage as the charge voltage is executed. In this case, lithium dendrite may be formed and the negative electrode and the positive electrode may be short-circuited. However, since a heat-resistant member having heat resistance is provided between the negative electrode and the positive electrode, the negative electrode and the positive electrode are formed by lithium dendrite. Even if a short-circuit current flows between them, the expansion of the short-circuited portion is suppressed by the heat-resistant member. As a result, constant voltage charging can be performed with a charging voltage exceeding the reference voltage without damaging the secondary battery.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a block diagram showing an example of the configuration of the charging system according to the first embodiment of the present invention. The charging system 1 includes a battery pack 2 that includes a charger 3 that charges the battery pack 2. However, even if an electronic device system is configured to further include a load device (not shown) that receives power from the battery pack 2. Good. Moreover, the charger 3 may be comprised as a part of load apparatus. In that case, although the battery pack 2 is charged from the charger 3 in FIG. 1, the battery pack 2 may be attached to the load device and charged through the load device. The battery pack 2 and the charger 3 are connected to each other by DC high-side terminals T11 and T21 that supply power, communication signal terminals T12 and T22, and GND terminals T13 and T23 for power supply and communication signals. . Similar terminals are also provided when the load device is provided.

  In the battery pack 2, the DC high-side charging path 11 extending from the terminal T11 includes FETs (Field Effect Transistors) 12 and 13 having different conductivity types for charging and discharging. The charging path 11 is connected to the high side terminal of the assembled battery 14. The low-side terminal of the assembled battery 14 is connected to the GND terminal T13 via the DC low-side charging path 15, and the charging path 15 has a current detection resistor 16 (current) that converts charging current and discharging current into voltage values. The detection unit) is interposed.

  A trickle charging circuit 25 is provided in parallel with the FET 12. The trickle charging circuit 25 is configured by connecting in parallel a series circuit composed of a current limiting resistor 26 and an FET 27 and another series circuit composed of a current limiting resistor 28 and an FET 29. The current limiting resistor 28 has a resistance value smaller than that of the current limiting resistor 26. A configuration without the current limiting resistor 28 and the FET 29 may be used.

  The assembled battery 14 is formed by connecting a plurality of secondary batteries (cells) in series and parallel. For example, three secondary batteries 141 are connected in series. The temperature of the secondary battery 141 is detected by the temperature sensor 17 and input to the analog / digital converter 19 in the control IC 18. Further, the voltage between the terminals of each secondary battery 141 is read by the voltage detection circuit 20 (voltage detection unit) and input to the analog / digital converter 19 in the control IC 18. Furthermore, the current value detected by the current detection resistor 16 is also input to the analog / digital converter 19 in the control IC 18. The analog / digital converter 19 converts each input value into a digital value and outputs the digital value to the control unit 21. Note that the secondary battery 141 may be used alone instead of the assembled battery 14.

  The control unit 21 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And a peripheral circuit and the like, and by executing a control program stored in the ROM, a charge / discharge control unit 211 (charge control unit), a constant current charge control unit 212, and a trickle charge control unit It functions as 213.

  In response to each input value from the analog / digital converter 19, the charge / discharge control unit 211 calculates a voltage value and a current value of a charging current that instructs the charger 3 to output, from the communication unit 22. It transmits to the charger 3 via terminals T12, T22; T13, T23. Further, the charge / discharge control unit 211 detects an abnormality outside the battery pack 2 such as a short circuit between the terminals T11 and T13 or an abnormal current from the charger 3 based on each input value from the analog / digital converter 19 or an assembled battery. For example, a protection operation such as blocking the FETs 12 and 13 is performed against an abnormal temperature rise of the 14.

  The trickle charge control unit 213 turns off the fast charge FET 12 while turning on the discharge FET 13 at the initial stage of charge, turns on the FET 27 in the trickle charge circuit 25, turns off the FET 29, and trickle charges the charger 3. By instructing a current output for use, the current limiting resistor 26 is used to perform trickle charging as in the prior art, and then the FET 29 is turned on and the FET 27 is turned off so that the resistance value is smaller than that of the current limiting resistor 26. The current resistor 28 is used to perform medium speed charging that supplies a current that is greater than the conventional trickle charging current. When the current limiting resistor 28 and the FET 29 are not provided, the battery pack may be a method in which the FET 27 is turned off and the FET 12 is turned on to supply a medium speed charging current on the charger side.

  The constant current charge control unit 212 turns on the FETs 12 and 13, turns off the FETs 27 and 29, and outputs an instruction to the charger 3 to supply a predetermined constant current, thereby performing constant current charging. Execute. Then, a reference voltage that is a voltage between the negative electrode and the positive electrode when a fully charged state in which the potential of the negative electrode of each secondary battery 141 included in the assembled battery 14 is substantially 0 V in terms of lithium (When lithium cobaltate is used as the positive electrode active material, the reference voltage is 4.2 V), for example, a set voltage Vs set to a voltage of about 4.25 V to 4.30 V, the voltage of each secondary battery 141 When the terminal voltage reaches and the terminal voltage Vb of the assembled battery 14 becomes equal to or higher than the set voltage Vs × the number of series cells SN, the constant current charge control unit 212 stops constant current charging, while the charge / discharge control unit 211 sets By outputting an instruction to output the voltage Vs × the number of series cells SN to the charger 3, the set voltage Vs × the number of series cells SN is applied to the assembled battery 14 to perform constant voltage charging. .

  The set voltage Vs is set to a voltage exceeding the reference voltage, but the reference voltage varies depending on the type of the positive electrode active material. Therefore, the set voltage Vs may be appropriately set to a voltage exceeding the reference voltage corresponding to the type of the positive electrode active material.

  Note that “the potential of the negative electrode of the secondary battery 141 on the basis of lithium is substantially 0 V” means not only 0 V but also the charging current value, temperature, the composition of the positive electrode active material 322 and the negative electrode active material 324, etc. This means that it includes the fluctuation range of the negative electrode potential caused by variations in the affecting conditions.

  In the charger 3, the instruction is received by the communication unit 32 as communication means in the control IC 30, and the charge control unit 31 configured by using, for example, a microcomputer is connected to the charge voltage / current supply circuit 33 (charge voltage supply unit). The charging current supply unit) is controlled to supply the charging current with the voltage value, current value, and pulse width. The charging voltage / current supply circuit 33 includes an AC-DC converter, a DC-DC converter, and the like, and converts an input voltage into a voltage value, a current value, and a pulse width instructed by the charging control unit 31, and the terminals T21, T11: Supply to charging paths 11 and 15 via T23 and T13.

  In addition, it is not restricted to the example provided with the control part 21 in the battery pack 2, You may make it provide the charger 3 in the control part 21, or make it equip the charger 3 with a part of control part 21.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the secondary battery 141. A secondary battery 141 shown in FIG. 2 is a cylindrical non-aqueous electrolyte secondary battery having a wound electrode group, for example, a lithium ion secondary battery. In the electrode plate group 312, a positive electrode plate 301 (positive electrode) including a positive electrode lead current collector 302 and a negative electrode plate 303 (negative electrode) including a negative electrode lead current collector 304 are wound in a spiral shape via a separator 305. Has a rotated structure. A porous protective film (not shown) is formed between the negative electrode plate 303 and the separator 305.

  An upper insulating plate 306 is attached to the upper portion of the electrode plate group 312, and a lower insulating plate 307 is attached to the lower portion. The electrode plate group 312 and the case 308 containing a non-aqueous electrolyte (electrolyte) (not shown) are sealed with a gasket 309, a sealing plate 310, and a positive electrode terminal 311.

  A substantially circular groove 313 is formed substantially at the center of the sealing plate 310. When gas is generated in the case 308 and the internal pressure exceeds a predetermined pressure, the groove 313 is broken and the case 308 is broken. The gas is released. Further, a convex portion for external connection is provided at a substantially central portion of the positive electrode terminal 311, and an electrode opening 314 is provided in the convex portion, and the gas released by breaking the groove 313 is supplied to the electrode opening. The unit 314 is discharged to the outside of the secondary battery 141.

  FIG. 3 is a cross-sectional view showing the configuration of the electrode plate group 312 in detail. 3 includes a negative electrode current collector 323, a negative electrode active material 324, a porous protective film 325, a separator 305, a positive electrode active material 322, and a positive electrode current collector 321 which are stacked in this order. Yes.

  A positive electrode plate 301 shown in FIG. 3 is configured by coating a positive electrode active material 322 substantially uniformly on the surface of a positive electrode current collector 321 made of a metal foil such as an aluminum foil.

The positive electrode active material 322 contains a transition metal-containing composite oxide containing lithium, for example, a transition metal-containing composite oxide such as LiCoO ₂ or LiNiO ₂ used in a non-aqueous electrolyte secondary battery as a positive electrode active material. Among these transition metal-containing composite oxides, a high end-of-charge voltage can be used, and a part of Co that can form a good-quality film by adsorbing or decomposing an additive on the surface in a high-voltage state is another element. The transition metal-containing composite oxide substituted with is preferable.

As such a transition metal-containing composite oxide, specifically, for example, a general formula Li _{a Mb} Ni _c Co _d O _e (M is Al, Mn, Sn, In, Fe, Cu, Mg, Ti, And at least one metal selected from the group consisting of Zn and Mo, and 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, In the range of 0.8 <e <2.2, and b + c + d = 1 and 0.34 <c). In particular, in the above general formula, it is preferable that M is at least one metal selected from the group consisting of Cu and Fe.

  Since the positive electrode active material 322 configured as described above has a reduced volume expansion in a charged state, the positive electrode active material 322 has a positive electrode in the case 308 even when charged beyond the fully charged state (SOC 100%) shown in FIG. The possibility that the active material 322 expands to cause the electrode plate group 312 to buckle is reduced.

In the following description, when lithium cobaltate is used as the positive electrode active material 322 (a fully charged state in which the potential of the negative electrode plate 303 of the secondary battery 141 on the basis of lithium is substantially 0 V). A case where the reference voltage which is the voltage between the negative electrode plate 303 and the positive electrode plate 301 is 4.2 V) will be described as an example. (When lithium manganate is used as the positive electrode active material 322, the reference voltage is 4.3V.)
Further, the negative electrode plate 303 shown in FIG. 3 is configured by applying a negative electrode active material 324 substantially uniformly on the surface of a negative electrode current collector 323 made of a metal foil such as an aluminum foil.

As the negative electrode active material 324, a carbon material, a lithium-containing composite oxide, a material that can be alloyed with lithium, or the like, a material capable of reversibly inserting and extracting lithium, and metallic lithium can be used. Examples of carbon materials include coke, pyrolytic carbons, natural graphite, artificial graphite, mesocarbon microbeads, graphitized mesophase microspheres, vapor-grown carbon, glassy carbons, carbon fibers (polyacrylonitrile-based, pitch-based) , Cellulose-based, vapor-grown carbon-based), amorphous carbon, and carbon materials obtained by firing organic substances. You may use these individually or in mixture of 2 or more types. Among these, carbon materials obtained by graphitizing mesophase small spheres, and graphite materials such as natural graphite and artificial graphite are preferable. Examples of materials that can be alloyed with lithium include Si alone or a compound of Si and O (SiO _x ). You may use these individually or in mixture of 2 or more types. By using the silicon-based negative electrode active material as described above, a higher capacity non-aqueous electrolyte secondary battery can be obtained.

  As the separator 305 shown in FIG. 3, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. The separator 305 is desirably based on a resin material having a melting point of 200 ° C. or less, and polyolefin is particularly preferably used. Of these, polyethylene, polypropylene, ethylene-propylene copolymer, a composite of polyethylene and polypropylene, and the like are preferable. A polyolefin separator having a melting point of 200 ° C. or less is easily melted when the battery is short-circuited due to an external factor, and the resin material is softened to block the pore structure, thereby suppressing the movement of ions. A so-called shutdown effect is obtained, and the safety of the secondary battery 141 can be improved.

  The separator 305 may be a single layer film made of one kind of polyolefin resin or a multilayer film made of two or more kinds of polyolefin resins. The thickness t1 of the separator 305 is not particularly limited, but is preferably 8 to 30 μm from the viewpoint of maintaining the design capacity of the battery.

  The porous protective film 325 (heat resistant member) shown in FIG. 3 is prepared, for example, by preparing a paint containing an inorganic oxide filler and a resin binder (hereinafter referred to as a porous film paint), and applying this to the surface of the negative electrode plate 303. It is obtained by drying the coating film. The porous film paint is obtained by mixing an inorganic oxide filler and a resin binder with a filler dispersion medium. As the dispersion medium, organic solvents such as N-methyl-2-pyrrolidone (NMP) and cyclohexanone and water are preferably used, but are not limited thereto. The filler, the resin binder, and the dispersion medium can be mixed using a double-arm stirrer such as a planetary mixer or a wet disperser such as a bead mill. Examples of the method for applying the porous film coating to the electrode surface include a comma roll method, a gravure roll method, and a die coating method.

  The porous protective film 325 may be formed on the surface of the negative electrode plate 303 as long as the fine particle slurry containing the resin binder and the inorganic oxide filler is applied to at least one of the negative electrode and the positive electrode surface. However, the present invention is not limited to this example, and it may be formed on the surface of the positive electrode plate 301 or may be formed so as to face both surfaces of the positive electrode plate 301 and the negative electrode plate 303. The thickness t2 of the porous protective film 325 is preferably in the range of 0.1 μm to 200 μm.

From the viewpoint of obtaining a porous protective film 325 having high heat resistance, the inorganic oxide filler has heat resistance of 250 ° C. or higher and is electrochemically stable within the potential window of the nonaqueous electrolyte secondary battery. It is desirable. Many inorganic oxide fillers satisfy these conditions. Among inorganic oxides, alumina, silica, zirconia, titania and the like are preferable, and in particular, alumina powder or SiO having a particle size in the range of 0.1 μm to 50 μm. It is preferable to be selected from ₂ powders (silica). An inorganic oxide filler may be used individually by 1 type, and 2 or more types may be mixed and used for it.

From the viewpoint of obtaining a porous protective film 325 having good ion conductivity, the bulk density (tap density) of the inorganic oxide filler is preferably 0.2 g / cm ³ or more and 0.8 g / cm ³ or less. When the bulk density is less than 0.2 g / cm ³ , the inorganic oxide filler becomes too bulky, and the structure of the porous protective film 325 may become fragile. On the other hand, if the bulk density exceeds 0.8 g / cm ³ , it may be difficult to form suitable voids between the filler particles. The particle size of the inorganic oxide filler is not particularly limited, but the smaller the particle size, the lower the bulk density. The particle shape of the inorganic oxide filler is not particularly limited, but it is preferably an amorphous particle in which a plurality of (for example, about 2 to 10, preferably 3 to 5) primary particles are connected and fixed. Since primary particles are usually composed of a single crystal, amorphous particles are always polycrystalline particles.

  The amount of the resin binder contained in the porous protective film 325 is preferably 1 part by weight or more and 20 parts by weight or less, more preferably 1 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the inorganic oxide filler. . When the amount of the resin binder exceeds 20 parts by weight, many of the pores of the porous protective film 325 are blocked with the resin binder, and the discharge characteristics may be deteriorated. On the other hand, when the amount of the resin binder is less than 1 part by weight, the adhesion between the porous protective film 325 and the electrode surface is lowered, and the porous protective film 325 may be peeled off.

  From the viewpoint of maintaining the thermal stability of the porous protective film 325 even when an internal short circuit occurs at a high temperature, the melting point or the thermal decomposition temperature of the resin binder is preferably 250 ° C. or higher. When the resin binder is made of a crystalline polymer, the melting point of the crystalline polymer is preferably 250 ° C. or higher. However, since the main component of the porous protective film 325 is an inorganic oxide having high heat resistance, the effect of the present invention is not greatly dependent on the heat resistance of the resin binder.

  The range of the porosity P of the porous insulating film may be determined in a range satisfying 10.10 ≦ R−P ≦ 0.30, where R is the ratio of the true volume to the apparent volume of the separator.

  The porosity P of the porous protective film can be determined by the following method. First, a coating material (hereinafter referred to as a porous membrane coating material) containing an inorganic oxide filler, a resin binder, and a dispersion medium in which the filler is dispersed is prepared. A porous film paint is applied on the metal foil and dried. A sample of the porous protective film is obtained by cutting the dried coating film together with the metal foil into an arbitrary area and removing the metal foil. From the thickness and area of the obtained sample, the apparent volume Va of the porous protective film is obtained, and the weight of the sample is further measured. Next, the true volume Vt of the porous protective film is determined using the weight of the sample and the true specific gravity of the inorganic filler and the resin binder. The porosity P is obtained from the apparent volume Va and the true volume Vt by the following formula (1).

Porosity P = (Va−Vt) / Va (1)
The porosity P can be set to a desired value by appropriately setting the size, for example, the average particle diameter and the shape of the inorganic oxide filler, and is preferably about 35 to 45%, for example.

  The ratio R of the true volume to the apparent volume of the separator 305 can be obtained by the following method. First, the apparent volume Vas of the separator 305 is calculated from the thickness and area of the separator 305, and the weight of the separator 305 is measured. Next, the true volume Vts of the separator is obtained using the weight of the separator 305 and the true specific gravity. The ratio R is obtained from the apparent volume Vas and the true volume Vts according to the following formula (2).

Ratio R = Vts / Vas (2)
The inorganic oxide filler can be made into a dendritic shape, a cocoon shape, a tuft shape or the like by making the inorganic oxide filler into polycrystalline particles. Polycrystalline particles having such a shape are suitable for forming moderate voids because it is difficult to form an excessively dense packed structure in the porous protective film. The polycrystalline particles include, for example, particles in which about 2 to 10 primary particles are connected by melting, particles in which about 2 to 10 crystal growing particles come into contact with each other, and the like.

  The average particle diameter of the polycrystalline particles (volume-based median diameter: D50) can be measured by, for example, a wet laser particle size distribution measuring device manufactured by Microtrack. When the average particle size of the polycrystalline particles is less than twice the average particle size of the primary particles, the porous protective film may have an excessively dense packing structure. When the average particle size exceeds 10 μm, the porosity of the porous protective film May become excessive and the structure of the porous protective film may become brittle.

  The method for obtaining polycrystalline particles is not particularly limited, but for example, it can be obtained by sintering an inorganic oxide to form a lump and then crushing the lump appropriately. In addition, polycrystalline particles can also be obtained directly by bringing particles in crystal growth into contact with each other without going through a pulverization step.

  For example, when α-alumina is sintered to form a lump, and the lump is appropriately pulverized to obtain polycrystalline particles, the sintering temperature is preferably 800 to 1300 ° C., and the sintering time is preferably 3 to 30 minutes. . Moreover, when crushing a lump, it can grind | pulverize using wet equipment, such as a ball mill, and dry equipment, such as a jet mill and a jaw crusher. In that case, those skilled in the art can control the polycrystalline particles to an arbitrary average particle size by appropriately adjusting the pulverization conditions.

  In addition, without using the separator 305, for example, as in the electrode plate group 312a shown in FIG. 4, by setting the porosity P, the thickness t2, or the curvature and other characteristics of the porous protective film 325a as appropriate, the separator Instead of 305, a structure using a porous protective film 325a may be used.

  Further, instead of providing the porous protective film 325, for example, a heat-resistant separator 305a (heat-resistant member) may be used as in the electrode plate group 312b shown in FIG. The heat-resistant separator 305a shown in FIG. 5 includes an aramid resin layer 356, which is a heat-resistant material, on the surface of a polyethylene substrate 355, for example. The thickness t6 of the polyethylene substrate 355 is about 14 μm, for example, and the thickness t7 of the aramid resin layer 356 is about 3 to 4 μm, for example.

  Next, the operation of the charging system 1 configured as described above will be described. FIG. 6 is an explanatory diagram showing an example of the operation of the charging system 1 according to the embodiment of the present invention. Moreover, FIG. 7 is a flowchart which shows an example of operation | movement of the charging system 1 which concerns on one Embodiment of this invention.

  First, trickle charge control unit 213 requests trickle charge current to charge control unit 31 via communication units 22 and 32, FETs 13 and 27 are turned on, FETs 12 and 29 are turned off, and current limiting resistor 26 is used. Trickle charging is started with a small and constant current I11, for example, a charging current of 50 mA (step S1, timing T1).

  Next, the trickle charge control unit 213 confirms the terminal voltage of each secondary battery 141 detected by the voltage detection circuit 20 (step S2), and the minimum voltage among the terminal voltages is the switching voltage Vma, for example, 1.. When the voltage exceeds 0 V (YES in step S2), the process proceeds to step S3 to perform medium-speed current charging.

  Next, in step S3, the trickle charge controller 213 turns on the FET 29, turns off the FET 27, and uses the current limiting resistor 28 having a smaller resistance value than the current limiting resistor 26, so that the charging current is changed from the current I11 to the current I12. (Timing T2). The current I12 is set to a current value obtained by multiplying the number of parallel cells PN by 10 to 50%, for example, by setting the level at which the nominal capacity value NC is discharged at a constant current and can be discharged in 1 hour to 1C (for example, NC = 2000 mAh, and when two are in parallel, 10% is 400 mA).

  Then, the trickle charge control unit 213 confirms the terminal voltage of each secondary battery 141 detected by the voltage detection circuit 20 (step S4), and the minimum voltage among the terminal voltages is the end voltage Vm, for example 2.3V. (YES in step S4), that is, when all of the terminal voltages of one or more secondary batteries 141 exceed the same trickle charge end voltage Vm as before, trickle charge is terminated and constant current charge is started. If necessary, the process proceeds to step S5.

  That is, the end voltage Vm of the trickle charge remains the same as the conventional one, and the conventional trickle charge region is divided into the first half region where the charge is performed with the current value I11 of the conventional trickle charge and another current value I11 larger than the conventional current value I11. It is divided into a second half region where charging is performed with the current value I12, and trickle charging with the conventional current value I11 is rounded up early, and the second half of the trickle charging period (region) is defined as a medium speed current charging region from the current value I11. The battery is charged with a current value I12 that is greater than Thereby, the charging current in the medium-speed current charging region can be increased, and the charging time of the assembled battery 14 can be shortened.

  Next, in step S5, the constant current charge control unit 212 turns the FETs 12 and 13 on, the FETs 27 and 29 off, and supplies a large charge current I13, for example, to the charge control unit 31 via the communication units 22 and 32. The level that can be discharged in 1 hour is set to 1C, and the current value obtained by multiplying 80% to 200% by the number of parallel cells PN (for example, NC = 2000 mAh, when two are in parallel, 100%, 4000 mA) is set. An instruction to do so is output. Then, the charging current Ic set to the current value of the charging current I13 is output from the charging voltage / current supply circuit 33 in accordance with the control signal from the charging control unit 31, and constant current charging is performed (timing T3).

  Then, the terminal voltage Vb of the assembled battery 14 detected by the voltage detection circuit 20 is confirmed by the constant current charge control unit 212 (step S6), and when the terminal voltage Vb becomes equal to or higher than the set voltage Vs × the number of series cells SN ( In step S6, YES, the constant current charge control unit 212 stops the constant current charge and proceeds to step S7 to start the constant voltage charge.

  In this case, the set voltage Vs is between the negative electrode plate 303 and the positive electrode plate 301 when the fully charged state is reached, in which the potential on the lithium reference of the negative electrode plate 303 of each secondary battery 141 is substantially 0V. Is set to a voltage exceeding the reference voltage (4.2V), for example, 4.3V. Then, when the terminal voltage Vb becomes equal to or higher than the set voltage Vs × the number of series cells SN, it means that the terminal voltage of each secondary battery 141 becomes equal to or higher than the set voltage Vs in principle. Then, the lithium reference potential of the negative electrode plate 303 of the secondary battery 141 is substantially lower than 0 V, and metallic lithium begins to deposit on the surface of the negative electrode active material 324.

  Here, in the case of a conventional secondary battery that does not include a heat-resistant member such as the porous protective films 325 and 325a shown in FIGS. 3 and 4 and the separator 305a shown in FIG. 5, metallic lithium is deposited on the negative electrode surface. Then, the deposited metal lithium becomes lithium dendrite and grows toward the positive electrode, and as a result of short-circuiting between the negative electrode and the positive electrode through a separator made of a resin material such as polyethylene, a short circuit flows through the lithium dendrite. There is a possibility that the separator melts due to the electric current, the short-circuited portion expands, and the battery is damaged. Therefore, in the conventional secondary battery, in order not to deposit lithium on the negative electrode, in order to prevent the terminal voltage of the secondary battery from exceeding the reference voltage, for example, in the secondary battery using lithium cobaltate as the positive electrode active material, 4. The set voltage Vs was set to a voltage of 4.2 V or less so as not to exceed 2 V. Therefore, in the conventional secondary battery, the constant current charge can be performed only until the timing T4 when the terminal voltage Vb reaches 4.2V × the number of series cells SN.

  However, in the secondary battery 141, lithium dendrite is formed by providing the porous protective films 325 and 325 a shown in FIGS. 3 and 4 and the heat-resistant member such as the separator 305 a shown in FIG. Even if the negative electrode plate 303 is short-circuited, expansion of the short-circuited portion due to melting of the separator is suppressed, so the set voltage Vs is set to 4.25V to exceed the reference voltage (4.2V). 4. It can be set to 30V. As a result, the constant voltage charging can be performed until the timing T5 when the terminal voltage Vb reaches the set voltage Vs (4.30 V) × the number of series cells SN. As a result, the terminal voltage Vb is larger for a longer period than when charging the conventional secondary battery. Since the constant current charging can be continued with the charging current, the charging time can be shortened.

  Next, in step S <b> 7, the charge / discharge control unit 211 outputs an instruction to output the set voltage Vs × the number of series cells SN to the charge control unit 31 via the communication units 22 and 32. Then, according to the control signal from the charging control unit 31, the charging voltage / current supply circuit 33 outputs the set voltage Vs × the voltage of the number of series cells SN, that is, 4.3V × 3 = 12.9V, and the assembled battery 14 The terminal voltage Vb is set to 12.9 V and constant voltage charging is performed.

  When charging a conventional secondary battery that does not have a heat-resistant member such as the porous protective films 325 and 325a shown in FIGS. 3 and 4 and the separator 305a shown in FIG. 5, deposition of lithium on the negative electrode is avoided. In order to do so, it was necessary to perform constant voltage charging at a voltage of 4.2 V × the number of series cells SN or less. However, since the secondary battery 141 can be charged at a voltage of 4.30V × the number of series cells SN in step S7, the charging current of the constant voltage charging can be increased to increase the charging current. It becomes possible to shorten the charging time.

  Then, the charging / discharging control unit 211 confirms the charging current Ic detected by the current detection resistor 16 (step S8). When the charging current Ic becomes equal to or lower than the preset end current I14 (YES in step S8), charging / discharging is performed. The discharge control unit 211 proceeds to step S9 to end the charging.

  The termination current I14 is set to a current value that flows through the secondary battery 141 when the set voltage Vs is applied to the fully charged secondary battery 141, and is appropriately set according to the temperature. For example, (0.5 A × A current value such as the number of parallel cells PN) is used. In this case, 0.5 A is set to a current value of, for example, about 1/4 CA with respect to the battery capacity C.

  Further, as shown in FIG. 11, the fully charged state means a charged state (SOC: 100%) when the negative electrode potential Pm becomes 0 V. Therefore, in step S8, the charging current Ic is changed to the end current I14. The coincidence (timing T6) means that the SOC of the secondary battery 141 reaches 100% and the terminal voltage becomes 4.2 V (reference voltage).

  Then, the termination current I14 for determining the full charge state is set to a current value (for example, 0.5 A × 0.5) that is larger than the current value I3 (for example, 0.1 A × number of parallel cells PN) in the case of constant voltage charging according to the background art. Since the secondary battery 141 is almost fully charged and the charging current Ic decreases and the charging progress is slowed down, the charging time with poor charging efficiency is shortened, and the background technology is used. It can charge to the same charge capacity (SOC100%) as the case where it charges by the constant voltage charge which concerns, and can shorten charging time significantly. For example, the charging time for full charge in constant voltage charging according to the background art (equivalent to setting voltage Vs of 4.2 V, end current I14 of 0.1 A × number of parallel cells PN) is about 120 minutes. What is necessary can be fully charged in about 85 minutes, for example, by performing constant voltage charging with the setting voltage Vs being 4.30 V and the termination current I14 being 0.5 A × the number of parallel cells PN.

  If the end current I14 is set to the value of the current flowing through the secondary battery 141 when the set voltage Vs is applied to the fully charged secondary battery 141, the charge current Ic is changed to the end current I14 in step S8. At the coincidence timing T6, the SOC of the secondary battery 141 reaches 100% and the terminal voltage becomes 4.2V (reference voltage). Therefore, the charging voltage in constant voltage charging exceeds 4.2V (reference voltage). Although 4.3 V is applied, the open-circuit voltage (OCV) of the secondary battery 141 is basically constant voltage charging when the voltage reaches 4.2 V (reference voltage). It can be suppressed that the open circuit voltage (OCV) of 141 exceeds 4.2 V (reference voltage), and the deterioration of the secondary battery 141 is promoted.

  Next, in step S9, the charge / discharge control unit 211 outputs an instruction to set the charging voltage to zero to the charging control unit 31, and the charging control unit 31 sets the output voltage of the charging voltage / current supply circuit 33 to zero. Stop charging.

  Note that the termination current I14 is not limited to the example of setting the current value that flows through the secondary battery 141 when the set voltage Vs is applied to the fully charged secondary battery 141. For example, as shown in FIG. The current I14 is the same as the current value smaller than the current value flowing through the secondary battery 141 when the set voltage Vs is applied to the fully charged secondary battery 141, for example, the constant voltage charging end current I3 shown in FIG. If it is set to 0.1A × number of parallel cells PN), the SOC of the secondary battery 141 exceeds 100% at the timing T7 when the charging current Ic matches the end current I14 in step S8. That is, the assembled battery 14 can be charged exceeding SOC 100%, and the charge capacity (discharge capacity) of the assembled battery 14 can be increased.

  Further, since the positive electrode active material 322 configured as described above has reduced volume expansion in a charged state, the case 308 is used even when the secondary battery 141 is charged until the SOC exceeds 100%. The risk that the positive electrode active material 322 expands and the electrode plate group 312 buckles is reduced.

(Second Embodiment)
Next, a charging system 1a according to a second embodiment of the present invention will be described. FIG. 9 is a block diagram showing an example of the configuration of the charging system 1a according to the second embodiment of the present invention. The charging system 1a shown in FIG. 9 is different from the charging system 1 shown in FIG. 1 in the following points. That is, the charging system 1a shown in FIG. 9 includes a charger 3a and a battery pack 2a.

  The battery pack 2a differs from the battery pack 2 shown in FIG. 1 in that the control unit 21a does not include the charge / discharge control unit 211, the constant current charge control unit 212, and the trickle charge control unit 213, and the battery information storage unit The difference is that 23 is provided. The battery information storage unit 23 is configured using a nonvolatile storage element such as an EEPROM (Electrically Erasable and Programmable Read Only Memory), a setting switch such as a jumper pin, and the like. The battery information storage unit 23 stores information indicating whether or not the secondary battery 141 can be charged with a voltage exceeding the reference voltage. Now, since the secondary battery 141 includes a heat-resistant member between the negative electrode and the positive electrode, information indicating that the secondary battery 141 can be charged at a voltage exceeding the reference voltage is stored in the battery information storage unit 23. . Similarly, in the case of a battery pack including a secondary battery that does not include a heat-resistant member, information indicating that charging cannot be performed at a voltage exceeding the reference voltage is stored in the battery information storage unit 23. Note that a battery pack including a secondary battery that does not include a heat-resistant member may be configured not to include the battery information storage unit 23.

  The battery information storage unit 23 further stores positive electrode information indicating the type of the positive electrode active material such as whether the positive electrode active material used in the secondary battery is lithium cobaltate or lithium manganate. Has been.

  The control unit 21a is configured using, for example, a microcomputer, and the terminal voltage Vb obtained by the analog / digital converter 19, each terminal voltage of the secondary battery 141, the temperature of the secondary battery 141, and the charging current Ic. The battery information and the positive electrode information stored in the battery information storage unit 23 are transmitted to the charger 3a via the communication unit 22 and the terminal T12, or received by the communication unit 22 from the charger 3a via the terminal T12. The FETs 12, 13, 26, and 27 are turned on and off in response to the control instruction.

  The charger 3a includes a control unit 34 configured using, for example, a microcomputer, and the control unit 34 executes a predetermined control program, whereby the charge control unit 31, the charge / discharge control unit 211a, and the constant current charge control unit. The battery charger 3 is different from the charger 3 shown in FIG. 1 in that it functions as a trickle charge control unit 213a and a set voltage setting processing unit 214.

  The set voltage setting processing unit 214 sets the set voltage Vs and the end current I14 based on the battery information and the positive electrode information transmitted from the control unit 21a. Specifically, when the set voltage setting processing unit 214 indicates that the battery information can be charged at a voltage exceeding the reference voltage, and the positive electrode active material is lithium cobalt oxide, For example, 4.25 V to 4.30 V is set as the set voltage Vs, and (0.5 A × number of parallel cells PN) is set as the end current I14. The set voltage setting processing unit 214 indicates that the battery information can be charged with a voltage exceeding the reference voltage, and if the positive electrode active material is lithium manganate, For example, 4.35 V to 4.40 V is set as Vs, and (0.5 A × number of parallel cells PN) is set as the end current I14. The set voltage setting processing unit 214 indicates that the battery information cannot be charged with a voltage exceeding the reference voltage, and if the positive electrode active material is lithium cobalt oxide, the set voltage Vs is set as the set voltage Vs. For example, 4.2 V is set, and (0.1 A × number of parallel cells PN) is set as the end current I14. The set voltage setting processing unit 214 indicates that the battery information cannot be charged with a voltage exceeding the reference voltage, and indicates that the positive electrode active material is lithium manganate as the set voltage Vs. For example, 4.3 V is set, and (0.1 A × number of parallel cells PN) is set as the end current I14.

  When the battery information cannot be acquired because the battery pack does not include the battery information storage unit 23, the set voltage setting processing unit 214 sets, for example, 4.2V as the set voltage Vs, and sets it as the end current I14. (0.1A × number of parallel cells PN) may be set.

  The charge / discharge control unit 211a, the constant current charge control unit 212a, and the trickle charge control unit 213a use the set voltage Vs set by the set voltage setting processing unit 214, the terminal voltage Vb, and each terminal of the secondary battery 141. Information on the voltage, the temperature of the secondary battery 141, the charging current Ic, etc. is acquired from the control unit 21a via the communication units 22 and 32, and a control instruction is transmitted to the control unit 21a via the communication units 22 and 32 By doing so, the charge / discharge control unit 211, the constant current charge control unit 212, and the trickle charge control unit 213 operate in the same manner except that the on / off control of the FETs 12, 13, 26, and 27 is controlled.

  Thereby, the charger 3a acquires information about the secondary battery from the battery pack 2a, and automatically sets the set voltage Vs and the termination current I14 according to the type of the secondary battery, thereby reducing the charging time. It can be shortened or the charging capacity can be increased.

  The present invention relates to a charging system used as a battery-mounted device such as an electronic device such as a portable personal computer or a digital camera, a vehicle such as an electric vehicle or a hybrid car, a battery pack used as a power source for these battery-mounted devices, and It can utilize suitably as a charging device which charges such a battery pack.

It is a block diagram which shows an example of a structure of the charging system which concerns on the 1st Embodiment of this invention. It is a schematic sectional drawing which shows an example of a structure of the secondary battery shown in FIG. It is sectional drawing which shows an example of a structure of the electrode group shown in FIG. 2 in detail. It is sectional drawing which shows in detail another example of a structure of the electrode group shown in FIG. It is sectional drawing which shows in detail another example of a structure of the electrode group shown in FIG. It is explanatory drawing which shows an example of operation | movement of the charging system which concerns on one Embodiment of this invention. It is a flowchart which shows an example of operation | movement of the charging system which concerns on one Embodiment of this invention. It is explanatory drawing which shows another example of operation | movement of the charging system which concerns on one Embodiment of this invention. It is a block diagram which shows an example of a structure of the charging system which concerns on the 2nd Embodiment of this invention. It is a graph for demonstrating the general management method of the charge voltage and electric current at the time of charge of the secondary battery which concerns on background art. It is explanatory drawing which shows the change of a positive electrode electric potential and a negative electrode electric potential with respect to the lithium reference | standard at the time of charging a lithium ion battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a Charging system 2,2a Battery pack 3,3a Charger 14 Assembly battery 16 Current detection resistor 17 Temperature sensor 19 Analog / digital converter 20 Voltage detection circuit 21,21a Control part 22,32
23 battery information storage unit 25 trickle charge circuit 26, 28 current limiting resistor 31 charge control unit 33 charge voltage / current supply circuit 34 control unit 141 secondary battery 211, 211a charge / discharge control unit 212, 212a constant current charge control unit 213, 213a Trickle charge control unit 214 Setting voltage setting processing unit 301 Positive electrode plate 303 Negative electrode plate 305, 305a Separator 312, 312a, 312b Electrode plate group 322 Positive electrode active material 324 Negative electrode active material 325, 325a Porous protective film 355 Substrate 356 Aramid resin layer I14 End current Pm Negative electrode potential Pp Positive electrode potential Vs Setting voltage

Claims (11)

A secondary battery including a heat-resistant member having heat resistance between the negative electrode and the positive electrode;
A charging voltage supply unit for supplying a charging voltage for charging the secondary battery;
A set voltage set to a voltage exceeding a voltage between the negative electrode and the positive electrode when the negative electrode is in a fully charged state in which the potential on the lithium reference is substantially 0 V is defined as the charge voltage. A charging system comprising: a charging control unit that performs constant voltage charging by supplying the secondary battery to the secondary battery by the charging voltage supply unit. The charging system according to claim 1, wherein the heat-resistant member is a porous protective film containing a resin binder and an inorganic oxide filler. The charging system according to claim 1, wherein the heat-resistant member is a separator. As the active material of the positive electrode, Li _{a Mb} Ni _c Co _d O _e (M is at least one selected from the group consisting of Al, Mn, Sn, In, Fe, Cu, Mg, Ti, Zn, and Mo) The range is 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, 1.8 <e <2.2, Furthermore, b + c + d = 1 and it is 0.34 <c) The charging system of any one of Claims 1-3 characterized by the above-mentioned. A charging current supply unit for supplying a charging current for charging the secondary battery;
A constant current charging control unit that performs constant current charging by supplying a constant current set in advance to the secondary battery from the charging current supply unit;
A voltage detection unit for detecting a terminal voltage of the secondary battery,
When the terminal voltage detected by the voltage detection unit becomes equal to or higher than the set voltage during the constant current charge execution period, the constant current charge control unit stops the constant current charge and the charge control The charging unit according to claim 1, wherein the unit performs the constant voltage charging. A current detection unit for detecting a charging current flowing in the secondary battery;
When the charging control unit decreases during the execution of the constant voltage charging until the charging current detected by the current detection unit reaches a preset end current, the charging control unit supplies the charging voltage to the secondary battery. Stop,
The end current is set to a current value that is equal to or greater than a current value that flows to the secondary battery when the set voltage is applied to the fully charged secondary battery. The charging system according to any one of the above. A current detection unit for detecting a charging current flowing in the secondary battery;
When the charging control unit decreases during the execution of the constant voltage charging until the charging current detected by the current detection unit reaches a preset end current, the charging control unit supplies the charging voltage to the secondary battery. Stop,
The end current is set to a current value that flows through the secondary battery when the set voltage is applied to the fully charged secondary battery. The charging system according to item. A charging system comprising a battery pack and a charging device for charging the battery pack,
The battery pack is
A secondary battery,
A voltage exceeding a reference voltage, which is a voltage between the negative electrode and the positive electrode of the secondary battery, when the fully charged state in which the potential on the lithium reference of the negative electrode of the secondary battery is substantially 0 V And a battery information storage unit that stores battery information indicating whether or not the secondary battery can be charged.
The charging device is:
A charging voltage supply unit for supplying a charging voltage for charging the secondary battery;
When battery information indicating that the secondary battery can be charged with a voltage exceeding the reference voltage is stored in the battery information storage unit, a voltage exceeding the reference voltage is set as a set voltage, When battery information indicating that the secondary battery can be charged at a voltage exceeding the reference voltage is not stored in the battery information storage unit, a setting for setting a voltage equal to or lower than the reference voltage as a set voltage A voltage setting processing unit;
A charge control unit that performs constant voltage charging by supplying the set voltage set by the set voltage setting processing unit as the charge voltage to the secondary battery by the charge voltage supply unit. system. Between the negative electrode and the positive electrode, a connection terminal for connecting to a secondary battery provided with a heat-resistant member having heat resistance,
A charging voltage supply unit for supplying a charging voltage for charging the secondary battery to the connection terminal;
A set voltage set to a voltage exceeding a voltage between the negative electrode and the positive electrode when the negative electrode is in a fully charged state in which the potential on the lithium reference is substantially 0 V is defined as the charge voltage. A charging control unit that performs constant voltage charging by being supplied to the connection terminal by the charging voltage supply unit. A charging device for charging a battery pack including a secondary battery and a battery information storage unit that stores battery information related to the secondary battery,
A charging voltage supply unit for supplying a charging voltage for charging the secondary battery;
In the battery information storage unit, as information about the secondary battery, the secondary battery has a fully charged state in which the potential of the negative electrode of the secondary battery on the lithium reference is substantially 0 V. When battery information indicating that the secondary battery can be charged with a voltage exceeding a reference voltage, which is a voltage between the negative electrode and the positive electrode, is stored, a voltage exceeding the reference voltage is set as a set voltage. When battery information indicating that the secondary battery can be charged with a voltage exceeding the reference voltage is not stored in the battery information storage unit, a voltage equal to or lower than the reference voltage is set as a set voltage. A set voltage setting processing unit,
A charge control unit configured to perform constant voltage charging by supplying the set voltage set by the set voltage setting processing unit as the charge voltage to the secondary battery by the charge voltage supply unit. apparatus. A battery pack connected to a charging device that outputs a voltage for charging a secondary battery according to an instruction from the outside,
A secondary battery including a heat-resistant member having heat resistance between the negative electrode and the positive electrode;
A set voltage that is set to a voltage that exceeds the voltage between the negative electrode and the positive electrode when the negative electrode is in a fully charged state in which the potential on the lithium reference is substantially 0 V is defined as the charging voltage. A battery pack comprising: a charging control unit that performs constant voltage charging by outputting the instruction to the charging device so that the charging device supplies the secondary battery.

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