Charging management system for secondary battery

Abstract

Provided is a charging management system which is for a secondary battery and has a new configuration. The present invention comprises: a secondary battery having a first battery cell and a second battery cell that are connected in series; a current measurement circuit having a function of measuring, at the time of charging the secondary battery, current flowing in the first battery cell and the second battery cell; a voltage measurement circuit having a function of measuring, at the time of charging the secondary battery, respective voltages in the first battery cell and the second battery cell; and a control circuit having a function of performing control for matching charging rates of the first battery cell and the second battery cell. The control circuit has a function of calculating data sets indicative of the respective battery characteristics for the first battery cell and the second battery cell, in accordance with data of the measured current and data of the measured voltages. The control for matching the charging rates of the first battery cell and the second battery cell is performed by controlling the charging rates through matching maximal values of the data sets indicative of the battery characteristics.

Description

Secondary battery charging management system

[0001] FIELD One embodiment of the present invention relates to a secondary battery, a charge management method for a secondary battery, and a charge management system for a secondary battery. Another embodiment of the present invention relates to a charge method for a secondary battery.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of the invention disclosed in this specification and the like relates to an object or a method. Alternatively, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a display device, a light-emitting device, a power storage device, an imaging device, a memory device, a driving method thereof, or a manufacturing method thereof.

[0003] Energy storage devices (also called batteries or secondary batteries) are now used in a wide range of fields, from small electronic devices to automobiles. As the range of applications for batteries expands, applications using multi-cell battery stacks, in which multiple battery cells are connected in series, are also increasing.

[0004] The battery storage device is equipped with a circuit for detecting abnormalities during charging and discharging, such as overcharging or overdischarging. Such a circuit acquires data such as voltage and current, and based on that data, performs control such as stopping charging and discharging or cell balancing. This allows for battery protection and control.

[0005] Patent Document 1 discloses a protection IC that functions as a battery protection circuit. Specifically, Patent Document 1 discloses a protection IC that has multiple internal comparators and compares a reference voltage with the voltage at the terminal to which the battery is connected to detect abnormalities during charging and discharging.

[0006] U.S. Patent Application Publication No. 2011-267726

[0007] Measuring the state of charge (SOC) is effective for controlling cell balancing, which equalizes the electrical quantity (also called capacity or charge capacity) of multiple battery cells. Because the SOC cannot be measured directly, it is possible to measure the open circuit voltage (OCV) and estimate it from the SOC-OCV curve. However, there is a problem in that it takes time for the battery cells to stabilize before the OCV can be accurately measured.

[0008] Furthermore, as described above, in cell balancing and other control, when equalizing the electrical charge of multiple battery cells while measuring the voltages of the terminals of multiple battery cells connected in series, it is necessary to ensure that the changes in the electrical charge of the multiple battery cells are consistent. However, because the change in voltage relative to the electrical charge of a battery cell is small, the electrical charge variation relative to the voltage variation may be large. Therefore, there is a problem in that it is difficult to detect the electrical charge variation relative to the voltage variation unless the voltage near full charge, where the change in voltage relative to the electrical charge variation is large, is confirmed.

[0009] In view of the above, an object of one embodiment of the present invention is to provide a novel secondary battery management system that is highly reliable and capable of performing cell balancing. Another object of one embodiment of the present invention is to provide a novel secondary battery management system that can perform cell balancing by estimating variations in the amounts of electricity among battery cells connected in series without waiting for the battery cells to stabilize. Another object of one embodiment of the present invention is to provide a novel secondary battery management system that can perform cell balancing by estimating a state of charge that is less affected by variations in the amounts of electricity due to variations in the voltages of multiple battery cells. Another object of one embodiment of the present invention is to provide a novel secondary battery management system.

[0010] The problems of one embodiment of the present invention are not limited to the problems listed above. The problems listed above do not preclude the existence of other problems. The other problems are problems not mentioned in this section, which will be described below. Problems not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be appropriately extracted from these descriptions. One embodiment of the present invention solves at least one of the problems listed above and / or other problems.

[0011] One aspect of the present invention is a charging management system for a secondary battery, comprising: a secondary battery having a first battery cell and a second battery cell connected in series; a current measurement circuit having a function of measuring a current flowing through the first battery cell and the second battery cell when the secondary battery is being charged; a voltage measurement circuit having a function of measuring the voltage of each of the first battery cell and the second battery cell when the secondary battery is being charged; and a control circuit having a function of performing control to align the charging rates of the first battery cell and the second battery cell, wherein the control circuit has a function of calculating data indicating battery characteristics based on measured current data and measured voltage data for each of the first battery cell and the second battery cell, and the control to align the charging rates of the first battery cell and the second battery cell is performed by controlling the charging rates to align the maximum values ​​of the data indicating the battery characteristics.

[0012] In one aspect of the present invention, the maximum value of the data indicating the battery characteristics is preferably a maximum value when dQ / dV, which represents the amount of change in electrical quantity relative to the amount of change in voltage, is plotted on the vertical axis and integrated capacity is plotted on the horizontal axis, in a charge management system for a secondary battery.

[0013] In one aspect of the present invention, the maximum value of the data indicating the battery characteristics is preferably a maximum value when dt / dV, which represents the amount of change over time with respect to the amount of change in voltage, is plotted on the vertical axis and time is plotted on the horizontal axis, in a charge management system for a secondary battery.

[0014] In one aspect of the present invention, the charge management system for a secondary battery is preferably such that the secondary battery is charged at a constant current.

[0015] Other aspects of the present invention will be described in the following embodiments and in the drawings.

[0016] According to one embodiment of the present invention, a novel secondary battery management system can be provided that is highly reliable and capable of performing cell balancing. Alternatively, according to one embodiment of the present invention, a novel secondary battery management system can be provided that can perform cell balancing by estimating the variation in the amount of electricity among battery cells connected in series without waiting for the battery cells to stabilize. Alternatively, according to one embodiment of the present invention, a novel secondary battery management system can be provided that can perform cell balancing by estimating a state of charge that is less affected by the variation in the amount of electricity among the battery cells in relation to the variation in voltage. Alternatively, according to one embodiment of the present invention, a novel secondary battery management system can be provided.

[0017] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc.

[0018] FIG. 1B is a block diagram illustrating a charge management system. FIG. 2 is a flow diagram illustrating a charge management system. FIG. 3 is a schematic diagram illustrating a charge management system. FIGS. 4A to 4C are schematic diagrams illustrating a charge management system. FIG. 5 is a flow diagram illustrating a charge management system. FIG. 6 is a schematic diagram illustrating a charge management system. FIGS. 7A to 7C are schematic diagrams illustrating a charge management system. FIG. 8 is a flow diagram illustrating a charge management system. FIGS. 9A to 9C are schematic diagrams illustrating a charge management system. FIG. 10 is a block diagram illustrating a charge management system. FIG. 11 is a block diagram illustrating a charge management system. FIG. 12 is a flow diagram illustrating a charge management system. FIG. 13A is an exploded perspective view of a coin-type secondary battery, FIG. 13B is a perspective view of the coin-type secondary battery, and FIG. 13C is a cross-sectional perspective view thereof. FIG. 14A shows an example of a cylindrical secondary battery. FIG. 14B shows an example of a cylindrical secondary battery. FIG. 14C shows an example of a plurality of cylindrical secondary batteries. FIG. 14D illustrates an example of a power storage system including a plurality of cylindrical secondary batteries. FIGS. 15A and 15B illustrate an example of a secondary battery, and FIG. 15C illustrates the internal structure of the secondary battery. FIGS. 16A to 16C illustrate an example of a secondary battery. FIGS. 17A and 17B illustrate the external appearance of a secondary battery. FIGS. 18A to 18C illustrate a manufacturing method of a secondary battery. FIGS. 19A to 19C illustrate a configuration example of a battery pack. FIG. 20A is a perspective view of a power storage module illustrating one embodiment of the present invention, FIG. 20B is a block diagram of the power storage module, and FIG. 20C is a block diagram of a vehicle including the power storage module. FIGS. 21A to 21D illustrate an example of a transportation vehicle. FIG. 21E illustrates an example of an artificial satellite. FIGS. 22A and 22B illustrate a power storage device according to one embodiment of the present invention. Fig. 23A is a diagram showing an electric bicycle, Fig. 23B is a diagram showing a secondary battery for the electric bicycle, and Fig. 23C is a diagram explaining a scooter. Figs. 24A to 24D are diagrams explaining an example of an electronic device.Fig. 25A shows an example of a wearable device, Fig. 25B shows a perspective view of a wristwatch-type device, and Fig. 25C is a diagram illustrating a side view of the wristwatch-type device. Figs. 26A and 26B are diagrams illustrating data showing the battery characteristics of a battery cell.

[0019] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes can be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0020] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and repeated explanations thereof will be omitted. Furthermore, when referring to similar functions, the same hatching pattern may be used and no particular reference numeral may be assigned.

[0021] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0022] In this specification, the ordinal numbers such as "first" and "second" are used for convenience and do not limit the number of components or the order of the components (for example, the order of processes or the order of stacking). Furthermore, an ordinal number assigned to a component in one part of this specification may not match an ordinal number assigned to the same component in another part of this specification or in the claims.

[0023] In this specification, the same symbols may be used in the drawings to designate identical elements or elements having similar functions, elements made of the same material, or elements formed at the same time, and by using the same symbols, repeated explanations may be omitted.

[0024] In addition, in top views (also called "plan views") and perspective views, some components may be omitted to make the drawings easier to understand.

[0025] Embodiment 1 In this embodiment, a charge management system for a secondary battery according to one embodiment of the present invention will be described.

[0026] 1 shows an example of a block diagram for explaining a charge management system according to one embodiment of the present invention. The charge management system 100 includes a secondary battery 10, a charge / discharge control switch 20, an integrated circuit (IC) 30, a load 80, and a charger 90. The diagram also shows a discharge switch 81 for controlling the current flowing through the load 80 and a charge switch 91 for controlling the current flowing from the charger 90.

[0027] The secondary battery 10 includes battery cells 11A to 11D connected in series. Although the charge management system 100 according to one embodiment of the present invention includes four battery cells, the number of battery cells may be two or more. When describing the content common to the battery cells 11A to 11D, the battery cells may be referred to as the battery cells 11.

[0028] The secondary battery 10 may include a heater and a temperature sensor. By including the heater and the temperature sensor, a configuration can be achieved in which control is performed according to the temperature of the secondary battery 10. The heater may be, for example, a PTC (Positive Temperature Coefficient) thermistor. The temperature sensor may be, for example, an NTC (Negative Temperature Coefficient) thermistor. However, other types of temperature sensors, such as a PTC thermistor or a thermocouple, may also be used.

[0029] The load 80 controls a discharge switch 81 to allow current to flow from the secondary battery 10. Examples of the load 80 include a CPU, memory, display, inverter, etc. in an electronic device, and a motor, light, power steering, inverter, etc. in a vehicle.

[0030] The charger 90 controls a charging switch 91 to supply current for charging the secondary battery 10. An example of the charger 90 is an AC adapter. The charger 90 may have a function of converting AC power to DC power or a function of converting voltage.

[0031] When charging using the charger 90, it is preferable that the charging condition from the start of charging to the end of charging be constant current charging. For example, even if it takes time from when the upper limit voltage is determined until charging is stopped, the upper limit voltage will not change suddenly during the constant current charging period.

[0032] The charge / discharge control switch 20 is provided in the path between the secondary battery 10 and the load 80, and in the path between the secondary battery 10 and the charger 90. The charge / discharge control switch 20 is composed of a transistor that functions as a switch and a diode for suppressing reverse current. The transistor for charge control and the transistor for discharge control may be separate transistors. The charge / discharge control switch 20 is controlled to charge or discharge by the control of the IC 30 for cell balancing.

[0033] The IC 30 includes a control unit 33 having a memory 34, a current measurement circuit 31, voltage measurement circuits 32A to 32D, and discharge units 35A to 35D. The voltage measurement circuits 32A to 32D and discharge units 35A to 35D are provided in accordance with the number of battery cells 11. Each of the discharge units 35A to 35D includes a resistive element 36 and a cell balance control switch 37.

[0034] The IC 30 has a function mainly of cell balancing. The IC 30 may also be called a cell balance control IC. The IC 30 may also have a protection function and a control function for the secondary battery 10. The protection function refers to one or more of the following protection functions for the battery cells of the secondary battery 10: overcharge protection, overdischarge protection, overcharge current protection, overdischarge current protection, and overheat protection. The control function refers to one or more of the following control functions: charge control, discharge control. In other words, the IC 30 is a battery control IC.

[0035] The IC 30 preferably functions as an MCU (Micro Controller Unit). In this case, the IC 30 has a CPU, memory, a clock generation circuit, an input unit, and an output unit. The input unit and the output unit may be collectively referred to as an I / O unit.

[0036] The current measurement circuit 31 has the function of detecting the current (charging current) flowing through the battery cells 11A to 11D. The current measurement circuit 31 is also called a current sensor or current detection element. The current measurement circuit 31 can use a Hall-type current sensor or a shunt resistor sensor. The current measurement circuit 31 can provide the measured current value (current data) to the control unit 33.

[0037] It is preferable that the current measurement circuit 31 also has a coulomb counter function. For example, by having the coulomb counter function, the current measurement circuit 31 and the control unit 33 can be used to calculate the cumulative amount of electricity in the secondary battery 10. From the calculated amount of electricity, the amount of electricity charged in the battery cells can be calculated, and cell balancing in the battery cells 11A to 11D can be controlled.

[0038] The voltage measurement circuits 32A to 32D have the function of detecting the terminal voltages (charging voltages) of the battery cells 11A to 11D, respectively. In addition to the voltages during charging, the voltage measurement circuits 32A to 32D may also have the function of measuring the terminal voltages (referred to as discharge voltages) of the battery cells 11A to 11D during discharging. To distinguish between charging voltages and discharging voltages, for example, a plus sign may be added to the charging voltage and a minus sign to the discharging voltage. Of course, a minus sign may be added to the charging voltage and a plus sign to the discharging voltage. Furthermore, when describing content common to the voltage measurement circuits 32A to 32D, they may be referred to as the voltage measurement circuit 32.

[0039] The voltage measurement circuits 32A to 32D can measure the terminal voltages at regular intervals, which can be 80 msec to 10 sec, preferably 90 msec to 1 sec. By shortening the interval, the states of the battery cells 11A to 11D can be determined with high accuracy.

[0040] The voltage measurement circuits 32A to 32D can provide the measured voltage values ​​(voltage data) to the control unit 33. If the measured voltage values ​​are analog values, the analog values ​​may be converted to digital and provided to the control unit 33. That is, the voltage measurement circuits 32A to 32D may have a circuit that converts analog values ​​to digital, and this circuit may be an analog-to-digital converter (ADC), and the ADC configuration may be a ΔΣ modulation type, a parallel comparison type (also referred to as a flash type), or a pipeline type. The ΔΣ modulation type has high resolution and is therefore suitable for voltage measurement circuits.

[0041] The discharge units 35A to 35D have the function of discharging each of the battery cells 11A to 11D. The discharge units 35A to 35D are provided so as to be connected in parallel to each of the battery cells 11A to 11D. By turning on the cell balance control switches 37 of the discharge units 35A to 35D, current flows through the resistance elements 36, thereby discharging the corresponding battery cells 11A to 11D. The discharge units 35A to 35D are controlled by the control unit 33 for cell balancing to determine whether or not to discharge. Furthermore, when describing content common to the discharge units 35A to 35D, they may be referred to as discharge units 35.

[0042] The control unit 33 stores the measured current values ​​(current data) and voltage values ​​(voltage data) in a memory 34 of the control unit 33 to control the uniformity of the amount of electricity (charging rate) charged to the multiple battery cells 11, i.e., to control cell balancing. The control unit 33 has a function to calculate data indicating battery characteristics for uniforming the amount of electricity of the battery cells 11A to 11D, using the voltage values ​​of the battery cells 11A to 11D provided by the voltage measurement circuits 32A to 32D and the current values ​​flowing through the battery cells 11A to 11D provided by the current measurement circuit 31. Specifically, the control unit 33 has a function to calculate data related to the voltage derivative (dQ / dV) of the amount of electricity.

[0043] The dQ / dV calculated by the control unit 33 can be stored as time-series data in the memory 34. The control unit 33 can analyze the stored dQ / dV time-series data. By analyzing the dQ / dV time-series data, the control unit 33 can calculate the peak voltage of dQ / dV. The control unit 33 detects the voltage values ​​of the battery cells 11A to 11D using the voltage measurement circuits 32A to 32D, and can therefore calculate the peak voltage of dQ / dV of the battery cells 11A to 11D.

[0044] In this specification, the peak voltage of dQ / dV refers to the voltage at which the dQ / dV time-series data reaches a maximum value within a certain voltage range. The voltage range may be, for example, 0.03 V, 0.01 V, or 0.001 V. The peak voltage may be calculated each time dQ / dV is calculated, or may be calculated at regular intervals.

[0045] The peak voltage of dQ / dV can detect changes in the crystalline structure of the positive electrode active material due to changes in the amount of electricity being charged. Therefore, the waveform acquired during charging can be used to understand the variation in the amount of electricity being charged among the battery cells 11A to 11D. Here, the waveform can have various shapes, such as a curve, a straight line, or a combination of a curve and a straight line. Furthermore, the waveform is not limited to a periodic wave. Examples of waveforms acquired during charging include a dQ / dV-V curve, a dQ / dV-Q curve, or a dt / dV-t curve created from data on the voltage, time, and current during charging. A charge management system according to one embodiment of the present invention detects the extreme values ​​of this waveform to estimate the variation in the amount of electricity being charged among the battery cells and control cell balancing.

[0046] When there is a variation in the amount of electricity charged to series-connected battery cells, measuring the OCV is effective for estimating the SOC. However, measuring the OCV takes time until the battery cells stabilize. Furthermore, when equalizing the amount of electricity between battery cells while measuring the voltage at each terminal of multiple battery cells connected in series, if the change in voltage relative to the amount of electricity is small, the amount of electricity varies greatly relative to the voltage variation, making it difficult to detect the variation in the amount of electricity between battery cells. One aspect of the present invention detects changes in the crystalline structure of the positive electrode active material due to changes in the amount of electricity being charged using the peak voltage of dQ / dV. This allows for estimation of the variation in the amount of electricity being charged between battery cells and cell balancing, without waiting for the battery cells to stabilize, even when the change in voltage due to the change in amount of electricity is small.

[0047] In the following description of the present specification, a configuration for performing cell balancing by estimating the variation in the amount of electricity charged among battery cells connected in series will be described, but the present invention is not limited to this. For example, the present invention can also be applied to a configuration for performing cell balancing by estimating the variation in the amount of electricity charged among battery cells connected in parallel.

[0048] The memory 34 of the control unit 33 preferably has a table linking the environmental temperature of the battery cell with the charging conditions. The memory 34 of the control unit 33 also preferably stores charging characteristics linked with the environmental temperature of the battery cell. The charging characteristics may be past measurements of the battery cell 11, measurements of other battery cells having similar characteristics, or waveforms obtained by calculation.

[0049] The control unit 33 may use the charging characteristics of the battery cell stored in the memory 34 to analyze the extreme values ​​in the differential curves of the voltage and the quantity of electricity. Here, examples of the charging characteristics that can be used include the quantity of electricity-voltage curve, the voltage-dQ / dV curve, the ΔV-t curve, and the impedance characteristics.

[0050] <Charging Method Example 1> An example of a charging method using the secondary battery charge management system 100 of one embodiment of the present invention will be described using the flow diagram shown in Fig. 2. Fig. 3 is a diagram schematically showing dQ / dV-Q curves for battery cells 11A to 11D connected in series. Figs. 4A to 4C are diagrams schematically showing changes in the amount of electricity due to cell balancing control of the battery cells 11A to 11D based on the secondary battery charge management system 100.

[0051] First, in step S000, the process starts.

[0052] Next, in step S001, constant current charging of the secondary battery is started. Note that this constant current charging is continued until charging is stopped.

[0053] Next, in step S002, the voltage measurement circuits 32A to 32D start measuring the voltages of the battery cells 11A to 11D. The control unit 33 measures time using a clock signal or the like. The current measurement circuit 31 also starts measuring the currents flowing through the battery cells 11A to 11D. The voltage measurement circuits 32A to 32D provide the measured voltage values ​​to the control unit 33. The current measurement circuit 31 provides the measured current values ​​to the control unit 33.

[0054] Next, in step S003, the control unit 33 accumulates (stores) the voltage values ​​measured by the voltage measurement circuits 32A to 32D and the current values ​​measured by the current measurement circuit 31 after step S002 as data pairs and times. The data accumulation can be performed using the memory 34 or the like included in the control unit 33. The time associated with the voltage value and the current value can be, for example, the time from the start of charging.

[0055] Next, in step S004, the control unit 33 uses the group data of voltage values, current values, and time accumulated as needed to calculate the voltage differential of the quantity of electricity for each battery cell (battery cells 11A to 11D), i.e., dQ / dV, which represents the amount of change in the quantity of electricity relative to the amount of change in voltage. Here, after group data of voltage values, current values, and time has been accumulated for a predetermined period of time in step S003, the voltage differential dQ / dV for each battery cell (battery cells 11A to 11D) may be calculated in step S004. For example, the group data may be accumulated for a period sufficient to detect extreme values.

[0056] The calculation performed in step S004 may be performed simultaneously with the accumulation (storage) of the group data performed in step S003. In other words, the calculation can be performed without using the group data of the accumulated voltage value, current value, and time. The value obtained by the calculation is stored in the memory 34 or the like of the control unit 33 for processing based on the waveform of the value. By configuring the calculated value to be stored in the memory 34, it is possible to reduce the amount of data stored in the memory 34.

[0057] For example, in a curve (hereinafter, dQ / dV-Q curve) estimated for each battery cell (battery cells 11A to 11D) shown in FIG. 3 , the horizontal axis represents the quantity of electricity Q and the vertical axis represents the voltage derivative dQ / dV of the quantity of electricity Q. The extreme values ​​(also referred to as peaks), for example, the maximum values ​​(also referred to as upwardly convex peaks) of the curve vary for each battery cell. The quantity of electricity on the horizontal axis corresponds to the quantity of electricity (integrated capacity) accumulated during charging. This variation in the quantity of electricity is due to changes in the crystalline structure of the positive electrode active material and can be confirmed by observing the change in the quantity of electricity during charging. For battery cell 11B, which reaches the second maximum value after passing the maximum value of the dQ / dV-Q curve estimated from battery cell 11A, a deviation in the quantity of electricity Q1 occurs. For battery cell 11C, which reaches the third maximum value after passing the maximum value of the dQ / dV-Q curve estimated from battery cell 11B, a deviation in the quantity of electricity Q2 occurs. In battery cell 11D, which reaches the fourth maximum value after passing the maximum value of the dQ / dV-Q curve estimated from battery cell 11C, a difference of electric quantity Q3 occurs. The difference in electric quantity between battery cell 11A and battery cell 11D is Q1 + Q2 + Q3. The difference in electric quantity between battery cell 11B and battery cell 11D is Q2 + Q3.

[0058] In the present embodiment and the like, the maximum value obtained as the extreme value is described as an upwardly convex peak, but this is not limited thereto. For example, it is sufficient if an extreme value resulting from a change in the crystal structure of the positive electrode active material is detected in a waveform acquired during charging of a battery cell. For example, in the case of a waveform of dV / dQ, which is the reciprocal of dQ / dV, a downwardly convex peak, which is a minimum value, may also be detected.

[0059] The maximum value of the dQ / dV-Q curve shown for each battery cell (battery cells 11A to 11D) in Figure 3 can be detected even when the change in battery cell voltage due to charging is small. In other words, it can be detected when the amount of electricity due to charging is small compared to the amount of electricity when the battery cell is fully charged. For example, as schematically shown in Figure 4A, it can be detected even when the change in voltage during charging is small (the hatched portion corresponds to the amount of electricity charged). In Figure 4A, the upward arrow indicates the increase in the amount of electricity due to constant current charging.

[0060] Next, in step S005, the control unit 33 determines whether the voltage of any of the battery cells has reached the end voltage (the voltage indicating a fully charged state). For example, as shown in FIG. 4B , the constant current charging is stopped when battery cell 11A (the battery cell indicated by the hatched area corresponds to the battery cell that has reached the end voltage) is detected among battery cells 11A to 11D. In the case of constant current charging, the difference in the amount of electricity between battery cell 11A that has reached the end voltage and the other battery cells 11B to 11D is the same as the difference in the amount of electricity at the time when the maximum value is detected in battery cells 11A to 11D ( FIG. 4A ). If the voltage of any of battery cells 11A to 11D has not reached the end voltage, constant current charging is continued, and the voltage and current values ​​are accumulated.

[0061] Next, in step S006, the control unit 33 performs discharge according to the difference in the amount of electricity at the time when the maximum value was detected on the dQ / dV-Q curve. Discharge is performed for each of the battery cells 11A to 11D according to the difference in the amount of electricity at which the maximum value was detected on the dQ / dV-Q curve. For example, as schematically shown in FIG. 4C , the difference in the amount of electricity between the battery cells 11A and 11D is Q1 + Q2 + Q3, so the discharger 35A is controlled to discharge the battery cell 11A so that the difference in the amount of electricity becomes Q1 + Q2 + Q3. For example, as schematically shown in FIG. 4C , the difference in the amount of electricity between the battery cells 11B and 11D is Q2 + Q3, so the discharger 35B is controlled to discharge the battery cell 11B so that the difference in the amount of electricity becomes Q2 + Q3. For example, as shown in Fig. 4C, the difference in the amount of electricity between battery cell 11C and battery cell 11D is Q3, so the discharger 35C is controlled to discharge battery cell 11C to achieve Q3. Note that in Fig. 4C, the downward arrows indicate the decrease in the amount of electricity due to discharge. By discharging and balancing the cells in this manner, the charge rates of battery cells 11A to 11C can be made to match the amount of electricity of battery cell 11D.

[0062] Next, in step S007, constant current recharging is started for the battery cells 11A to 11D for which cell balancing has been performed.

[0063] Next, in step S099, the process ends.

[0064] The secondary battery charge management system 100 detects a maximum value from data indicating the battery characteristics of each battery cell, and can adjust the discharge amount of each battery cell according to the deviation of the detected maximum value. The data indicating the battery characteristics changes according to the amount of electricity charged. The secondary battery charge management system 100 can perform cell balancing between battery cells connected in series by adjusting the discharge amount of each battery cell according to the deviation of the data indicating the battery characteristics of each battery cell.

[0065] <Second Example of Charging Method> A configuration different from the charging method in the charge management system for secondary batteries using the dQ / dV-Q curve described above will be described below.

[0066] dQ / dV can be expressed as the following equation (1).

[0067] dQ / dV=(dQ / dt)×(dt / dV) (1)

[0068] During constant current charging, dQ / dt is constant, so dQ / dV is proportional to dt / dV. Therefore, by evaluating the dt / dV characteristics during constant current charging, it is possible to obtain information similar to that of the dQ / dV characteristics.

[0069] Below, an example of evaluating the dt / dV characteristic in the region where constant current charging is performed is shown. The dt / dV characteristic can be obtained without having to obtain the current value of the secondary battery each time, and can be performed more easily than dQ / dV in some cases. Furthermore, since only two parameters, voltage and time, are required to be obtained, the calculation is simple and the circuit scale can be reduced in some cases. Furthermore, since the amount of data to be obtained can be reduced, the scale of the memory 34 can be reduced in some cases.

[0070] An example of a charging method using the secondary battery charge management system 100 according to one embodiment of the present invention will be described with reference to the flow diagram shown in Fig. 5. Fig. 6 is a diagram schematically showing dt / dV-t curves for battery cells 11A to 11D connected in series. Figs. 7A to 7C are diagrams schematically showing changes in the amount of electricity due to cell balancing control of the battery cells 11A to 11D based on the secondary battery charge management system 100.

[0071] First, in step S000, the process starts.

[0072] Next, in step S101, constant current charging of the secondary battery is started. Note that this constant current charging is continued until charging is stopped.

[0073] Next, in step S102, the voltage measurement circuits 32A to 32D start measuring the voltages of the battery cells 11A to 11D. The control unit 33 uses a clock signal or the like to measure the amount of change in voltage (dV) versus time (dt). The voltage measurement circuits 32A to 32D provide the measured voltage values ​​to the control unit 33.

[0074] Next, in step S103, the control unit 33 accumulates (stores) the voltage values ​​measured by the voltage measurement circuits 32A to 32D after step S102 as data pairs with the time. The data accumulation can be performed using the memory 34 or the like included in the control unit 33. For example, the time from the start of charging can be used as the time associated with the voltage value.

[0075] Next, in step S104, the control unit 33 uses the group data of voltage values ​​and times that are accumulated as needed to calculate the time voltage differential for each battery cell (battery cells 11A to 11D), i.e., dt / dV, which represents the amount of change in voltage over time. Here, after group data of a certain predetermined time, voltage value, and time is accumulated in step S103, the time voltage differential dt / dV for each battery cell (battery cells 11A to 11D) may be calculated in step S104. For example, the group data may be accumulated for a period sufficient to detect extreme values.

[0076] The voltage measurement in step S102 may be performed on one or more of the battery cells 11A to 11D. For example, the voltage may be measured separately for the battery cells (main battery cells) whose voltage is measured sequentially and the battery cells (subsidiary battery cells) whose voltage is measured intermittently.

[0077] The main battery cell can be selected from, for example, the battery cell with the lowest voltage or the battery cell with the highest voltage among the battery cells immediately after starting constant-current charging (step S101). By determining the main battery cell, the timing of executing step S103 (which stores voltage values ​​for each battery cell), described below, can be controlled. For example, when measuring the voltage of each battery cell in step S103, the voltage value of the main battery cell is measured. Then, when the voltage value of the main battery cell changes by 6 mV, the voltage values ​​of all the subordinate battery cells are measured, and the time differential of the voltage, i.e., dt / dV, which represents the amount of change in voltage over time, is calculated. This configuration allows the voltage values ​​of all battery cells to be measured in accordance with the change in the voltage value of the main battery cell, making it easier to compare the maximum values ​​of the time-varying waveform and improving detection accuracy.

[0078] For example, in the curves (hereinafter referred to as dt / dV-t curves) estimated for each battery cell (battery cells 11A to 11D) shown in FIG. 6 , the horizontal axis represents time t and the vertical axis represents the voltage differential dt / dV with respect to time t. The extreme values ​​(also referred to as peaks), for example, the maximum values ​​(also referred to as upwardly convex peaks) of the curves vary for each battery cell. The time on the horizontal axis corresponds to the cumulative time during charging. This variation in the quantity of electricity is due to changes in the crystalline structure of the positive electrode active material and can be confirmed by observing the change in the quantity of electricity during charging. For battery cell 11B, which reaches the second maximum value after passing the maximum value of the dt / dV-t curve estimated from battery cell 11A, a time T1 deviation occurs. For battery cell 11C, which reaches the third maximum value after passing the maximum value of the dt / dV-t curve estimated from battery cell 11B, a time T2 deviation occurs. For battery cell 11D, which is the fourth to reach the maximum value after passing the maximum value of the dt / dV-t curve estimated from battery cell 11C, a time difference of T3 occurs. The time difference between battery cell 11A and battery cell 11D is time (T1 + T2 + T3). The time difference between battery cell 11B and battery cell 11D is time (T2 + T3).

[0079] The maximum value of the dt / dV-t curve shown for each battery cell (battery cells 11A to 11D) in Figure 6 is detected when the change in battery cell voltage due to charging is small. In other words, it can be detected when the amount of electricity due to charging is small compared to the amount of electricity when the battery cell is fully charged. For example, as shown in Figure 7A, it can be detected even when the change in voltage during charging is small (the hatched area corresponds to the amount of electricity charged). In Figure 7A, the upward arrow indicates the increase in the amount of electricity due to constant current charging. Note that because constant current charging is used, the difference in the amount of electricity between battery cells can be estimated as I (current) x (T1 + T2 + T3), I (current) x (T2 + T3), and I (current) x T3, as shown in the figure.

[0080] Next, in step S105, the control unit 33 determines whether the voltage of any of the battery cells has reached the end voltage. For example, as shown in FIG. 7B , the constant current charging is stopped when battery cell 11A (the battery cell with the filled hatched area corresponds to the battery cell that has reached the end voltage) is detected among battery cells 11A to 11D. The difference in the amount of electricity between battery cell 11A that has reached the end voltage and the other battery cells 11B to 11D is the same as the difference in the amount of electricity at the time when the maximum value was detected in battery cells 11A to 11D ( FIG. 7A ). If the voltage of any of battery cells 11A to 11D has not reached the end voltage, constant current charging is continued and the voltage value is accumulated.

[0081] Next, in step S106, the control unit 33 performs discharge according to the difference in the amount of electricity at the time when the maximum value was detected on the dt / dV-t curve. Discharge is performed according to the amount of electricity corresponding to the difference in time when the maximum value was detected on the dt / dV-t curve. For example, as schematically shown in FIG. 7C , the difference in the amount of electricity between the battery cell 11A and the battery cell 11D is I×(T1+T2+T3), so the discharger 35A is controlled to discharge the battery cell 11A to I×(T1+T2+T3). For example, as schematically shown in FIG. 7C , the difference in the amount of electricity between the battery cell 11B and the battery cell 11D is I×(T2+T3), so the discharger 35B is controlled to discharge the battery cell 11B to I×(T2+T3). For example, as shown in Fig. 7C, the difference in the amount of electricity between battery cell 11C and battery cell 11D is I x T3, so the discharger 35C is controlled to discharge battery cell 11C to I x T3. Note that in Fig. 7C, the downward arrows indicate the decrease in the amount of electricity due to discharge. By discharging and balancing the cells in this manner, the charge rates of battery cells 11A to 11C can be made equal to the amount of electricity of battery cell 11D.

[0082] Next, in step S107, constant current recharging is started for the battery cells 11A to 11D for which cell balancing has been performed.

[0083] Next, in step S099, the process ends.

[0084] The secondary battery charge management system 100 detects a maximum value from data indicating the battery characteristics of each battery cell, and can adjust the discharge amount of each battery cell according to the deviation of the detected maximum value. The data indicating the battery characteristics changes according to the amount of electricity charged. The secondary battery charge management system 100 can perform cell balancing between battery cells connected in series by adjusting the discharge amount of each battery cell according to the deviation of the data indicating the battery characteristics of each battery cell.

[0085] <Charging Method Example 3> An example of a charging method using the secondary battery charge management system 100 according to one embodiment of the present invention will be described using the flow diagram shown in Fig. 8. Figs. 9A to 9C are diagrams that schematically show the control of cell balancing of the battery cells 11A to 11D based on the secondary battery charge management system 100. Note that the data showing the battery characteristics corresponding to Fig. 8 and Figs. 9A to 9C are the same as those in Fig. 6, and the above description is incorporated herein by reference.

[0086] First, in step S000, the process starts.

[0087] Next, in step S201, constant current charging of the secondary battery is started. Note that this constant current charging is continued until charging is stopped.

[0088] Next, in step S202, the voltage measurement circuits 32A to 32D start measuring the voltages of the battery cells 11A to 11D. The control unit 33 measures time using a clock signal or the like. The voltage measurement circuits 32A to 32D provide the measured voltage values ​​to the control unit 33.

[0089] Next, in step S203, the control unit 33 accumulates (stores) the voltage values ​​measured by the voltage measurement circuits 32A to 32D after step S202 as data pairs with time. The data accumulation can be performed using the memory 34 or the like included in the control unit 33. For example, the time associated with the voltage value can be the time from the start of charging.

[0090] Next, in step S204, the control unit 33 calculates the time voltage differential dt / dV for each battery cell (battery cells 11A to 11D) using the group data of voltage values ​​and time that is accumulated as needed. Here, after group data of a certain predetermined time, voltage value, and time is accumulated in step S203, the time voltage differential dt / dV for each battery cell (battery cells 11A to 11D) may be calculated in step S204. For example, the group data may be accumulated for a period sufficient to detect extreme values.

[0091] Accumulation of the voltage differential dt / dV results in a dt / dV-t curve similar to that shown in Figure 6. Therefore, as shown in Figure 9A, the difference in the amount of electricity between battery cells can be estimated similarly to that shown in Figure 7A. Specifically, the difference in the amount of electricity between battery cells can be estimated as I (current) x (T1 + T2 + T3), I (current) x (T2 + T3), and I (current) x T3, as shown in the figure.

[0092] Next, in step S205, the control unit 33 determines whether or not a maximum value has been detected in the dt / dV-t curve for all of the battery cells 11A to 11D. If a maximum value has not been detected for any of the battery cells 11A to 11D, constant current charging continues and voltage values ​​are accumulated.

[0093] Next, in step S206, the control unit 33 discharges the battery cells 11A and 11D according to the difference in the amount of electricity at the time when the maximum value was detected on the dt / dV-t curve, while continuing constant-current charging. Discharging is performed according to the amount of electricity corresponding to the difference in the time when the maximum value was detected on the dt / dV-t curve. For example, as schematically shown in FIG. 9B , the difference in the amount of electricity between the battery cells 11A and 11D is I×(T1+T2+T3), so the discharger 35A is controlled to discharge the battery cell 11A at I×(T1+T2+T3). For example, as schematically shown in FIG. 9B , the difference in the amount of electricity between the battery cells 11B and 11D is I×(T2+T3), so the discharger 35B is controlled to discharge the battery cell 11B at I×(T2+T3). For example, as shown in Fig. 9B, the difference in the amount of electricity between battery cell 11C and battery cell 11D is I x T3, so the discharger 35C is controlled to discharge battery cell 11C to achieve I x T3. In Fig. 9B, the downward arrows represent a decrease in the amount of electricity due to discharge. In Fig. 9B, the upward arrows represent an increase in the amount of electricity due to constant current charging (current I). By discharging for cell balancing while charging in this way, the charge rates of battery cells 11A to 11C can be made equal to that of battery cell 11D without waiting for any one battery cell to be fully charged.

[0094] Next, in step S207, the control unit 33 determines whether the voltage of any of the battery cells has reached the end voltage. For example, as shown in FIG. 9C , the constant current charging is stopped when battery cell 11A (the battery cell with the filled hatched area corresponds to the battery cell that has reached the end voltage) is detected among battery cells 11A to 11D. The difference in the amount of electricity between battery cell 11A that has reached the end voltage and the other battery cells 11B to 11D has been reduced by the discharging operation in step S206. If the voltage of any of battery cells 11A to 11D has not reached the end voltage, step S206 continues.

[0095] Next, in step S099, the process ends.

[0096] The secondary battery charge management system 100 detects a maximum value from data indicating the battery characteristics of each battery cell, and can adjust the discharge amount of each battery cell according to the deviation of the detected maximum value. The data indicating the battery characteristics changes according to the amount of electricity charged. The secondary battery charge management system 100 can perform cell balancing between battery cells connected in series by adjusting the discharge amount of each battery cell according to the deviation of the data indicating the battery characteristics of each battery cell.

[0097] <Charge Management System Example 2> Fig. 10 shows an example of a block diagram for explaining a charge management system according to one embodiment of the present invention. A charge management system 100A includes a secondary battery 10, a charge / discharge control switch 20, an IC (Integrated Circuit) 30, a load 80, and a charger 90. In the following description of Fig. 10 , parts that are common to the description of Fig. 1 are denoted by common reference numerals, and description thereof will be omitted.

[0098] The IC 30 includes a control unit 33 having a memory 34, a current measurement circuit 31, differentiators 38A to 38D, and discharge units 35A to 35D. The differentiators 38A to 38D and discharge units 35A to 35D are provided in accordance with the number of battery cells 11. When describing the content common to the differentiators 38A to 38D, they may be referred to as the differentiator 38.

[0099] The current measurement circuit 31 has the function of detecting the current (charging current) flowing through the battery cells 11A to 11D. The current measurement circuit 31 has a resistor 31A and an operational amplifier 31B. A shunt resistor is preferably used for the resistor 31A. The resistance value of the shunt resistor is preferably 10 mΩ to 300 mΩ, and more preferably 50 mΩ to 120 mΩ. This is preferable because the voltage drop across the resistor 31A can be amplified by the operational amplifier 31B.

[0100] The configuration of the differentiator 38 applicable to the differentiators 38A to 38D will be described with reference to FIG.

[0101] The differentiator 38 has a function of outputting a time difference, and can output the time difference when a difference occurs between the terminal voltage at time t1 and the terminal voltage at time t2, for example. In addition to the above functions, the differentiator 38 also has a function of converting an analog value into a digital value, a so-called AD converter function. Because the differentiator 38 has a voltage measurement function, the voltage measurement circuit 32 described above can be omitted.

[0102] 1 and the like is configured to convert the captured voltage using an AD converter and output the converted voltage to the control unit 33, whereas the differentiator 38 can be configured to output the captured voltage to the control unit 33 when the captured voltage has changed by a certain voltage ΔV. This allows the control unit 33 to operate intermittently between the normal state and the standby state, thereby reducing the current consumption of the control unit 33.

[0103] When the control unit 33 operates intermittently, the control unit 33 alternates between a normal state in which it controls cell balancing and a standby state in which it waits for a signal corresponding to a voltage change from the differentiator 38. The differentiator 38 sends a wake-up signal to transition the control unit 33 from the standby state to the normal state, and after transitioning the control unit 33 to the normal state, transmits information about the time dt required for the voltage to change in the battery cells 11A to 11D. After receiving this information, the control unit 33 simply transitions back to the standby state.

[0104] FIG. 11 shows the control unit 33 together with the differentiator 38. The differentiator 38 includes a sample-and-hold circuit 200, a comparator 201, a DA converter 202, a successive approximation register 203, a second control circuit 204, and a clock generation circuit 205. The differentiator 38 may include an AD converter, which may be configured as a double integral type, a successive approximation type, a ΔΣ modulation type, a parallel comparison type (also referred to as a flash type), or a pipeline type. The number of bits of the successive approximation type may be 10 to 18 bits, and the conversion speed is preferably several tens of kHz to several MHz. The number of bits of the double integral type may be 8 to 20 bits, and the conversion speed is preferably several Hz to several kHz.

[0105] The differentiator 38 can hold the acquired voltage (analog value) in the sample-and-hold circuit 200. It is preferable that the value be held in the sample-and-hold circuit 200 while the analog value is being converted into a digital value. The transistor included in the sample-and-hold circuit 200 can be an OS transistor. An OS transistor is a transistor in which an oxide semiconductor layer is applied to an active layer.

[0106] The off-state current of an OS transistor is, for example, 1 aA (1×10) per 1 μm channel width at room temperature. −１８ A) Below, 1zA (1×10 −２１ A) or less, or 1yA (1 x 10 −２４ Note that the off-state current of a Si transistor per 1 μm of channel width at room temperature can be 1 fA (1×10 −１５ A) More than 1pA (1×10 −１２ A) or less. Therefore, it can be said that the off-state current of an OS transistor is about 10 orders of magnitude lower than that of a Si transistor. A transistor with such a low off-state current is suitable for the sample-and-hold circuit 200.

[0107] The value output from the sample-and-hold circuit 200 is input to the comparator 201 and compared with the data output from the successive approximation register 203. The successive approximation register 203 divides the analog voltage value into at least two or more parts, and outputs digital data, each of which is assigned to a respective bit. Before being input to the comparator 201, the digital data is converted from digital to analog data via a DA converter 202. The comparator 201 compares the data from the sample-and-hold circuit 200 with the data from the successive approximation register 203. If the data match, a 0 is output, and if the data do not match, a 1 is output. The value 0 or 1 is output to the second control circuit 204, and if the data match, a voltage (digital) is output from the successive approximation register 203. In this way, a voltage converted into a digital value can be obtained.

[0108] Data DataA, Data B, and Data C are output from the second control circuit 204 to the control unit 33. Data DataA is, for example, a sign (+ or -) indicating charging or discharging. Data DataB is, for example, count data related to time. Data DataC is a flag in the event of an error. An error that will be flagged is when the voltage difference is assigned as 1 bit and is determined to be 2 bits or more.

[0109] The differentiator 38 can output the time between time t1 and time t2. The differentiator 38 can count based on a clock signal or the like input to the differentiator 38 and output data corresponding to the time.

[0110] The difference calculator 38 may output a positive or negative sign. The sign can be used to distinguish between a voltage during charging and a voltage during discharging. If such a distinction is not necessary, there is no need to output the sign.

[0111] FIG. 12 shows a flow diagram regarding the differential processing.

[0112] First, in step S11, differential processing is started.

[0113] Next, in step S12, an arbitrary time T ０ The analog voltage value acquired is converted into a digital value (D ０ ) can be converted into a digital value. Information about the time of acquisition is also added to the voltage value. The conversion into a digital value can be performed using, for example, the above-mentioned successive approximation type AD converter. ０ ) is used as the basis for differential processing.

[0114] Next, in step S13, T １ The analog voltage value acquired after 2 seconds is converted into a digital value (D １ ) to convert the analog voltage value into a digital signal. Information about the time at which the voltage value was acquired is also added to the voltage value. After T seconds, the interval is between 50 ms and 1 s, preferably between 100 ms and 150 ms, depending on the specifications of the management system. The analog voltage value should be acquired periodically at the intervals mentioned above.

[0115] Next, in step S14, a reference digital value (D ０ ) and the digital value after T seconds (D １ ) is subtracted and difference processing is performed.

[0116] Next, in step S15, it is determined whether the result of the subtraction process is other than 0. If it is not 0 (corresponding to No in the figure), the process proceeds. If it is 0 (corresponding to Yes in the figure), the process returns to step S13, where a new voltage value is acquired, converted into a digital value, and then converted into the digital value of the reference voltage (D ０ ) and repeat the difference process.

[0117] If it is not 0, the process proceeds to step S16, and the time difference (ΔT=T １ -T ０ ) is calculated and output.

[0118] Thereafter, the difference processing ends as shown in step S17.

[0119] Based on the time difference (ΔT), graphs relating to battery characteristics such as voltage differential waveforms can be calculated, and cell balancing can be performed as shown in FIG. 2 and the like.

[0120] The structure, method, and the like described in this embodiment can be used in appropriate combination with the structure, method, and the like described in other embodiments.

[0121] Second Embodiment In the present embodiment, elements constituting a lithium ion battery will be described as an example of a battery included in the secondary battery 10. Although not described in the present embodiment, batteries other than lithium ion batteries, such as sodium ion batteries, nickel-metal hydride batteries, and lead-acid batteries, may also be used as the secondary battery 10.

[0122] A lithium ion battery includes a negative electrode, a positive electrode, an electrolyte, a separator, and an exterior body.

[0123] [Negative Electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer has a negative electrode active material, and may further have a conductive material and a binder.

[0124] The current collector can be, for example, a metal foil. The negative electrode can be formed by applying a slurry to a metal foil and drying it. Pressing may be performed after drying. The negative electrode is formed by forming an active material layer on a current collector.

[0125] The term "slurry" refers to a material liquid used to form an active material layer on a current collector, and contains an active material, a binder, and a solvent, and preferably further contains a conductive material. The slurry is also called an electrode slurry or an active material slurry, and when forming a negative electrode active material layer, it is also called a negative electrode slurry.

[0126] <Negative Electrode Active Material> As the negative electrode active material, for example, a carbon material or an alloy-based material can be used.

[0127] Examples of carbon materials that can be used include graphite (natural graphite, artificial graphite), graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon fiber (carbon nanotube), graphene, and carbon black.

[0128] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape and is therefore preferred. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB, and this may be preferred. Examples of natural graphite include flake graphite and spherical natural graphite.

[0129] When lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed), graphite exhibits a potential as low as that of metallic lithium (0.05 V to 0.3 V vs. Li / Li ＋ This allows lithium-ion batteries using graphite to exhibit high operating voltages. Graphite is also preferred because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and greater safety compared to lithium metal.

[0130] The non-graphitizable carbon can be obtained by calcining a synthetic resin such as a phenolic resin or a plant-derived organic material. The non-graphitizable carbon contained in the negative electrode active material of the lithium-ion battery according to one embodiment of the present invention preferably has a (002) plane spacing measured by X-ray diffraction (XRD) of 0.34 nm or more and 0.50 nm or less, and more preferably 0.35 nm or more and 0.42 nm or less.

[0131] In addition, the negative electrode active material can be an element capable of undergoing a charge-discharge reaction through alloying and dealloying reactions with lithium. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. These elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Alternatively, compounds containing these elements may be used. For example, SiO, Mg ２ Si, Mg ２ Ge, SnO, SnO ２ , Mg ２ Sn, SnS ２ , V ２ Sn ３ , FeSn ２ , CoSn ２ , Ni ３ Sn ２ , Cu ６ Sn ５ , Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb ３ , LaSn ３ , La ３ Co ２ Sn ７ , CoSb ３ , InSb, SbSn, etc. Here, elements capable of undergoing charge-discharge reactions by alloying / dealloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloy-based materials.

[0132] In this specification, "SiO" refers to, for example, silicon monoxide. ｘHere, x preferably has a value of 1 or close to 1. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0133] Titanium dioxide (TiO ２ ), lithium titanium oxide (Li ４ Ti ５ O １２ ), lithium-graphite intercalation compound (Li ｘ C ６ ), niobium pentoxide (Nb ２ O ５ ), tungsten oxide (WO ２ ), molybdenum oxide (MoO ２ ) and other oxides can be used.

[0134] In addition, as the negative electrode active material, a composite nitride of lithium and a transition metal, Li ３ Li with N-type structure ３−ｘ M ｘ N (M=Co, Ni, Cu) can be used. For example, Li ２．６ Co ０．４ N ３ has a large discharge capacity (900 mAh / g, 1890 mAh / cm ３ ) and is preferred.

[0135] When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, so V, which does not contain lithium ions, can be used as the positive electrode active material. ２ O ５ , Cr ３ O ８ It is preferable that the composite nitride of lithium and a transition metal can be used as the negative electrode active material by first removing the lithium ions contained in the positive electrode active material, even when a material containing lithium ions is used as the positive electrode active material.

[0136] Furthermore, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, a transition metal oxide that does not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO), can be used as the negative electrode active material. Further examples of materials that undergo a conversion reaction include Fe２ O ３ , CuO, Cu ２ O, RuO ２ , Cr ２ O ３ oxides such as CoS ０．８９ , sulfides such as NiS and CuS, Zn ３ N ２ , Cu ３ N, Ge ３ N ４ Nitrides such as NiP ２ , FeP ２ , CoP ３ Phosphides such as FeF ３ , BiF ３ This also occurs with fluorides such as

[0137] Although one type of anode active material from among the above-described anode active materials can be used, a combination of two or more types of anode active materials can also be used, for example, a combination of a carbon material and silicon, or a combination of a carbon material and silicon monoxide.

[0138] Another example of a negative electrode is one that does not have a negative electrode active material at the end of the battery fabrication. A negative electrode that does not have a negative electrode active material can be, for example, a negative electrode that has only a negative electrode current collector at the end of the battery fabrication, in which lithium ions released from the positive electrode active material upon charging the battery are deposited as lithium metal on the negative electrode current collector to form a negative electrode active material layer. A battery using such a negative electrode is sometimes called a negative electrode-free (anode-free) battery, a negative electrode-less (anode-less) battery, or the like.

[0139] When a negative electrode without a negative electrode active material is used, a film for uniforming lithium deposition may be provided on the negative electrode current collector. For example, a solid electrolyte having lithium ion conductivity can be used as the film for uniforming lithium deposition. Examples of solid electrolytes that can be used include sulfide-based solid electrolytes, oxide-based solid electrolytes, and polymer-based solid electrolytes. Among these, polymer-based solid electrolytes are suitable as films for uniforming lithium deposition because they are relatively easy to form uniformly on the negative electrode current collector. Furthermore, for example, a metal film that forms an alloy with lithium can be used as the film for uniforming lithium deposition. For example, a magnesium metal film can be used as the metal film that forms an alloy with lithium. Lithium and magnesium form a solid solution over a wide composition range, making them suitable as films for uniforming lithium deposition.

[0140] Furthermore, when a negative electrode that does not have a negative electrode active material is used, a negative electrode current collector having projections and recesses can be used. When a negative electrode current collector having projections and recesses is used, the recesses of the negative electrode current collector become cavities into which lithium contained in the negative electrode current collector can be easily deposited, and therefore, when lithium is deposited, it is possible to prevent it from forming a dendritic shape.

[0141] <Binder> As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Furthermore, as the binder, fluororubber can be used.

[0142] Furthermore, it is preferable to use, for example, a water-soluble polymer as the binder. Examples of the water-soluble polymer that can be used include polysaccharides. Examples of the polysaccharide that can be used include cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.

[0143] Alternatively, it is preferable to use, as the binder, materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose.

[0144] The binder may be used in combination with two or more of the above.

[0145] For example, a material with a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, while rubber materials have excellent adhesive strength and elasticity, it may be difficult to adjust the viscosity when mixed with a solvent. In such cases, it is preferable to mix them with a material with a particularly excellent viscosity adjusting effect. For example, a water-soluble polymer may be used as a material with a particularly excellent viscosity adjusting effect. Furthermore, as water-soluble polymers with a particularly excellent viscosity adjusting effect, the above-mentioned polysaccharides, for example, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose, cellulose derivatives such as regenerated cellulose, or starch may be used.

[0146] In addition, the solubility of cellulose derivatives such as carboxymethyl cellulose can be increased by converting them into salts such as sodium or ammonium salts of carboxymethyl cellulose, making them more effective as viscosity adjusters. Higher solubility can also improve dispersibility with active materials or other components when preparing electrode slurries. In this specification, the cellulose and cellulose derivatives used as electrode binders also include their salts.

[0147] Water-soluble polymers stabilize viscosity by dissolving in water, allowing active materials and other materials combined as binders, such as styrene-butadiene rubber, to be stably dispersed in aqueous solutions. Furthermore, the presence of functional groups is expected to facilitate stable adsorption to the surface of active materials. Furthermore, many cellulose derivatives, such as carboxymethyl cellulose, contain functional groups such as hydroxyl or carboxyl groups, and the presence of these functional groups is expected to facilitate interactions between polymers, resulting in widespread coverage of the active material surface.

[0148] When the binder covers the surface of the active material or contacts the surface and forms a film, it is expected to function as a passive film and have the effect of suppressing decomposition of the electrolyte. Here, the "passive film" refers to a film with no electrical conductivity or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it can suppress decomposition of the electrolyte at the battery reaction potential. Furthermore, it is more desirable that the passive film suppresses electrical conductivity while still allowing lithium ions to conduct.

[0149] <Conductive Material> The conductive material is also called a conductivity imparting agent or a conductivity aid, and is made of a carbon material. By attaching the conductive material between multiple active materials, the multiple active materials are electrically connected to each other, thereby increasing the conductivity. Note that the term "attachment" does not only refer to physical adhesion between the active material and the conductive material, but also includes cases where a covalent bond is formed, bonding due to van der Waals forces, where the conductive material covers part of the surface of the active material, where the conductive material is embedded in the surface irregularities of the active material, and where the materials are electrically connected even when not in contact with each other.

[0150] The active material layers such as the positive electrode active material layer and the negative electrode active material layer preferably contain a conductive material.

[0151] As the conductive material, for example, one or more of carbon black such as acetylene black and furnace black, graphite such as artificial graphite and natural graphite, carbon fibers such as carbon nanofibers and carbon nanotubes, and graphene compounds can be used.

[0152] Examples of carbon fibers that can be used include mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers. Carbon nanofibers and carbon nanotubes can also be used as carbon fibers. Carbon nanotubes can be produced by vapor phase growth, for example.

[0153] In this specification and the like, graphene compounds include graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multi-graphene oxide, graphene quantum dots, etc. Graphene compounds contain carbon, have a shape such as a plate or sheet, and have a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by six-membered carbon rings may also be called a carbon sheet. Graphene compounds may have functional groups. Furthermore, graphene compounds preferably have a curved shape. Furthermore, graphene compounds may be rolled up to resemble carbon nanofibers.

[0154] The active material layer may also contain, as a conductive material, metal powder or metal fiber such as copper, nickel, aluminum, silver, or gold, or a conductive ceramic material.

[0155] The content of the conductive material relative to the total amount of the active material layer is preferably 1 wt % or more and 10 wt % or less, and more preferably 1 wt % or more and 5 wt % or less.

[0156] Unlike granular conductive materials such as carbon black, which make point contact with the active material, graphene compounds enable surface contact with low contact resistance, and therefore can improve the electrical conductivity between the granular active material and the graphene compound with a smaller amount than that of ordinary conductive materials. This allows the ratio of the active material in the active material layer to be increased, thereby increasing the discharge capacity of the battery.

[0157] Particulate carbon-containing compounds such as carbon black and graphite, or fibrous carbon-containing compounds such as carbon nanotubes, tend to fill microscopic spaces. Microscopic spaces refer to, for example, the spaces between multiple active materials. By combining a carbon-containing compound that easily fills microscopic spaces with a sheet-like carbon-containing compound such as graphene, which can impart conductivity across multiple particles, the density of the electrode can be increased, resulting in the formation of an excellent conductive path. The battery obtained by the manufacturing method of one embodiment of the present invention has a high capacity density per volume and is stable, making it effective as an in-vehicle battery.

[0158] <Current Collector> As the current collector, a material that has high conductivity and does not alloy with carrier ions such as lithium, such as metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, and titanium, and alloys thereof, can be used. The current collector can be appropriately shaped, such as a sheet, mesh, punched metal, or expanded metal.

[0159] Furthermore, a resin current collector can be used as the current collector, which includes, for example, a resin such as polyolefin (polypropylene, polyethylene, etc.), nylon (polyamide), polyimide, vinylon, polyester, acrylic, or polyurethane, and a particulate or fibrous conductive material (also called a conductive filler).

[0160] The conductive material contained in the resin current collector can be one or more of a conductive carbon material and a metal material such as aluminum, titanium, stainless steel, gold, platinum, zinc, iron, or copper. Examples of the conductive carbon material include carbon black such as acetylene black and furnace black, graphite such as artificial graphite and natural graphite, carbon fibers such as carbon nanofibers and carbon nanotubes, graphene, and graphene compounds. When the resin current collector is used as a positive electrode current collector, it is preferable that the resin current collector further contains an antioxidant such as a hindered phenol material.

[0161] Examples of carbon fibers that can be used include mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers. Carbon nanofibers and carbon nanotubes can also be used as carbon fibers. Carbon nanotubes can be produced by vapor phase growth, for example.

[0162] The conductive material contained in the resin current collector may have an average particle size of 10 nm or more and 10 μm or less, and preferably 30 nm or more and 5 μm or less.

[0163] The current collector preferably has a thickness of 5 μm or more and 30 μm or less.

[0164] The negative electrode current collector is preferably made of a material that does not alloy with carrier ions such as lithium.

[0165] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material and may further contain at least one of a conductive material and a binder. Note that the positive electrode current collector, conductive material, and binder may be those described in [Negative electrode].

[0166] The current collector can be, for example, a metal foil. The positive electrode can be formed by applying a slurry to a metal foil and drying it. Pressing may be performed after drying. The positive electrode is formed by forming an active material layer on a current collector.

[0167] The slurry is a material liquid used to form an active material layer on a current collector, and refers to a material containing an active material, a binder, and a solvent, preferably further mixed with a conductive material. The slurry is also called an electrode slurry or an active material slurry, and when forming a positive electrode active material layer, it is also called a positive electrode slurry.

[0168] <Positive Electrode Active Material> As the positive electrode active material, at least one of a composite oxide having a layered rock salt structure, a composite oxide having an olivine structure, and a composite oxide having a spinel structure can be used.

[0169] As the composite oxide having a layered rock salt structure, any one or more of lithium cobalt oxide, lithium nickel-cobalt-manganese oxide, lithium nickel-cobalt-aluminate, and lithium nickel-manganese-aluminate can be used. ２ (M1 is one or more selected from nickel, cobalt, manganese, and aluminum), but the coefficients of the composition formula are not limited to integers.

[0170] As the lithium cobalt oxide, for example, lithium cobalt oxide to which magnesium and fluorine are added can be used. It is also preferable to use lithium cobalt oxide to which magnesium, fluorine, aluminum and nickel are added.

[0171] As the lithium nickel-cobalt-manganese oxide, for example, lithium nickel-cobalt-manganese oxide having a ratio of nickel:cobalt:manganese = 1:1:1, nickel:cobalt:manganese = 6:2:2, nickel:cobalt:manganese = 8:1:1, nickel:cobalt:manganese = 9:0.5:0.5, etc. Furthermore, as the lithium nickel-cobalt-manganese oxide, it is preferable to use lithium nickel-cobalt-manganese oxide to which one or more of aluminum, calcium, barium, strontium, and gallium have been added.

[0172] As the composite oxide having an olivine structure, any one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, and lithium iron manganese phosphate can be used. The composition formula is LiM2PO ４ (M2 is one or more elements selected from iron, manganese, and cobalt), but the coefficients of the composition formula are not limited to integers.

[0173] Also, LiMn ２ O ４ The above-mentioned composite oxides having a spinel structure can be used.

[0174] [Electrolyte] Examples of electrolytes are described below. As one form of electrolyte, a liquid electrolyte (also called an electrolyte solution) having a solvent and an electrolyte dissolved in the solvent can be used. The electrolyte is not limited to a liquid electrolyte (electrolyte solution) that is liquid at room temperature, and a solid electrolyte can also be used. Alternatively, an electrolyte (semi-solid electrolyte) that includes both a liquid electrolyte that is liquid at room temperature and a solid electrolyte that is solid at room temperature can also be used. When a solid electrolyte or semi-solid electrolyte is used in a bendable battery, the flexibility of the battery can be maintained by having a structure in which the electrolyte is included in part of the laminate inside the battery.

[0175] When a liquid electrolyte is used in a secondary battery, for example, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. can be used in any combination and ratio.

[0176] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the electrolyte solvent, it is possible to prevent the secondary battery from exploding or catching fire even if the temperature of the internal region of the secondary battery rises due to short-circuiting or overcharging. The ionic liquid is composed of a cation and an anion, and includes an organic cation and an anion. Examples of the organic cation include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anion include monovalent amide anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkylsulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0177] The secondary battery of one embodiment of the present invention has, for example, an alkali metal ion (e.g., a lithium ion, a sodium ion, a potassium ion, or the like) or an alkaline earth metal ion (e.g., a calcium ion, a strontium ion, a barium ion, a beryllium ion, a magnesium ion, or the like) as a carrier ion.

[0178] When lithium ions are used as carrier ions, the electrolyte contains a lithium salt, for example, LiPF ６ , LiClO ４ , LiAsF ６ , LiBF ４ , LiAlCl ４ , LiSCN, LiBr, LiI, Li ２ SO ４ , Li ２ B １０ Cl １０ , Li ２ B １２ Cl １２ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiC(CF ３ SO２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiN(CF ３ SO ２ ) ２ , LiN(C ４ F ９ SO ２ ) (CF ３ SO ２ ), LiN(C ２ F ５ SO ２ ) ２ etc. can be used.

[0179] As an example, the organic solvent described in this embodiment contains ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and when the total amount of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is 100 vol%, the volume ratio of the ethylene carbonate, the ethyl methyl carbonate, and the dimethyl carbonate can be x:y:100-x-y (where 5≦x≦35 and 0<y<65). More specifically, an organic solvent containing EC, EMC, and DMC in a volume ratio of EC:EMC:DMC=30:35:35 can be used.

[0180] Furthermore, it is preferable that the electrolyte solution be highly purified, with a low content of granular dust or elements other than the constituent elements of the electrolyte solution (hereinafter simply referred to as "impurities"). Specifically, it is preferable that the weight ratio of impurities to the electrolyte solution be 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0181] Furthermore, for the purpose of improving safety, etc., an additive such as vinylene carbonate (VC), propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), or a dinitrile compound such as succinonitrile or adiponitrile may be added to the electrolyte to form a coating (solid electrolyte interface) at the interface between the electrode (active material layer) and the electrolyte. The concentration of the additive may be, for example, 0.1 wt % to 5 wt % relative to the solvent.

[0182] Furthermore, if the electrolyte contains a polymeric material that can be gelled, safety against leakage, etc. Typical examples of polymeric materials that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel.

[0183] Examples of polymeric materials that can be used include polymers having a polyalkylene oxide structure, such as polyethylene oxide (PEO), PVDF, and polyacrylonitrile, as well as copolymers containing these. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The polymers formed may also have a porous shape.

[0184] [Separator] When the electrolyte contains an electrolytic solution, a separator is disposed between the positive electrode and the negative electrode. Examples of separators that can be used include those made of cellulose-containing fibers such as paper, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers such as nylon (polyamide), vinylon (polyvinyl alcohol-based fibers), polyester, acrylic, polyolefin, and polyurethane. The separator is preferably processed into a bag shape and disposed so as to encase either the positive electrode or the negative electrode.

[0185] The separator may have a multilayer structure. For example, an organic film such as polypropylene or polyethylene may be coated with a ceramic material, a fluorine-based material, a polyamide material, or a mixture of these. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine-based materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aramid (meta-aramid, para-aramid).

[0186] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging and improving the reliability of secondary batteries. Coating with fluorine-based materials also improves adhesion between the separator and electrodes, improving output characteristics. Coating with polyamide-based materials, especially aramid, improves heat resistance, improving the safety of secondary batteries.

[0187] For example, both sides of a polypropylene film may be coated with a mixed material of aluminum oxide and aramid, or the surface of the polypropylene film that contacts the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface that contacts the negative electrode may be coated with a fluorine-based material.

[0188] When a separator with a multilayer structure is used, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, and therefore the capacity per volume of the secondary battery can be increased.

[0189] [Exterior Body] The exterior body of the secondary battery can be made of a metal material such as aluminum or a resin material. Alternatively, a film-like exterior body can be used. Examples of the film include a three-layer structure film in which a thin, flexible metal film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is further provided on the thin metal film as the outer surface of the exterior body.

[0190] The structure, method, and the like described in this embodiment can be used in appropriate combination with the structure, method, and the like described in other embodiments.

[0191] Third Embodiment In this embodiment, examples of the shape of the secondary battery 10 will be described.

[0192] [Coin-Type Secondary Battery] An example of a coin-type secondary battery will be described. Fig. 13A is an exploded perspective view of a coin-type (single-layer flat) secondary battery, Fig. 13B is an external view, and Fig. 13C is a cross-sectional view thereof. Coin-type secondary batteries are mainly used in small electronic devices.

[0193] 13A is a schematic diagram that shows the overlapping of components (upper and lower relationships and positional relationships) for ease of understanding, and therefore, FIGS. 13A and 13B are not completely identical corresponding views.

[0194] In Fig. 13A, a positive electrode 304, a separator 310, a negative electrode 307, a spacer 322, and a washer 312 are stacked. These are sealed with a negative electrode can 302 and a positive electrode can 301 by a gasket. Note that the gasket for sealing is not shown in Fig. 13A. The spacer 322 and the washer 312 are used to protect the inside or to fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together. The spacer 322 and the washer 312 are made of stainless steel or an insulating material.

[0195] A positive electrode 304 has a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305 .

[0196] FIG. 13B is a perspective view of the completed coin-type secondary battery.

[0197] In the coin-type secondary battery 300, a positive electrode can 301, which also serves as a positive electrode terminal, and a negative electrode can 302, which also serves as a negative electrode terminal, are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector. The negative electrode 307 is not limited to a laminated structure, and may be formed of lithium metal foil or a lithium-aluminum alloy foil.

[0198] It is to be noted that the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 each only need to have an active material layer formed on one side.

[0199] The positive electrode can 301 and the negative electrode can 302 can be made of a metal such as nickel, aluminum, or titanium that is corrosion-resistant to the electrolyte, or an alloy of these metals or an alloy of these metals with other metals (e.g., stainless steel). Furthermore, to prevent corrosion by the electrolyte, etc., they are preferably coated with nickel, aluminum, or the like. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0200] These negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolyte, and as shown in Fig. 13C, the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are crimped together via a gasket 303 to produce a coin-type secondary battery 300. In the coin-type secondary battery 300, the positive electrode can 301 can be called a positive electrode terminal, and the negative electrode can 302 can be called a negative electrode terminal.

[0201] By having the above-described configuration, the coin-type secondary battery 300 can have a high discharge capacity and excellent cycle characteristics.

[0202] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to Fig. 14A . As shown in Fig. 14A , a cylindrical secondary battery 616 has a positive electrode cap (battery lid) 601 on the top surface and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap 601 and the battery can (external can) 602 are insulated by a gasket (insulating packing) 610. In the cylindrical secondary battery 616, the positive electrode cap 601 can be called the positive electrode terminal, and the battery can 602 can be called the negative electrode terminal.

[0203] 14B is a schematic diagram showing a cross section of a cylindrical secondary battery. The cylindrical secondary battery shown in FIG. 14B has a positive electrode cap (battery lid) 601 on the top surface and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap and battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0204] A battery element is provided inside a hollow cylindrical battery can 602, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched between them. Although not shown, the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open. The battery can 602 can be made of a metal, such as nickel, aluminum, or titanium, or an alloy of these metals or an alloy of these metals with other metals (e.g., stainless steel), which is corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat the battery can 602 with nickel, aluminum, or the like to prevent corrosion by the electrolyte. Inside the battery can 602, the wound battery element, in which the positive electrode, negative electrode, and separator are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. A nonaqueous electrolyte (not shown) is poured into the battery can 602, in which the battery element is provided. The nonaqueous electrolyte may be the same as that used in coin-type secondary batteries.

[0205] Since the positive and negative electrodes used in a cylindrical storage battery are wound, it is preferable to form active materials on both sides of the current collector.

[0206] A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to a safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 613 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the increase in internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistor whose resistance increases as the temperature increases, and the increased resistance limits the amount of current to prevent abnormal heat generation. The PTC element is made of barium titanate (BaTiO ３ )-based semiconductor ceramics, etc. can be used.

[0207] FIG. 14C shows an example of a power storage module 615. The power storage module 615 includes multiple secondary batteries 616. The positive electrodes of each secondary battery are electrically connected to a conductor 624. The negative electrodes of each secondary battery are electrically connected to a conductor 625. Therefore, the conductor 624 can be referred to as the positive terminal of the power storage device (battery pack), and the conductor 625 can be referred to as the negative terminal of the power storage device (battery pack). The conductor 624 is electrically connected to a control circuit 620 via a wiring 623. The conductor 625 is electrically connected to the control circuit 620 via a wiring 626. The control circuit 620 may be a charge / discharge control circuit that performs charging and discharging, or a protection circuit that prevents overcharging and / or overdischarging. The control circuit 620 also includes an external terminal 629 and an external terminal 630.

[0208] FIG. 14D shows an example of a power storage module 615. The power storage module 615 includes multiple secondary batteries 616, which are sandwiched between conductive plates 628 (conductive plates 628A and 628B) and conductive plates 614 (conductive plates 614A and 614B). The multiple secondary batteries 616 are electrically connected to the conductive plates 628 and 614 by wiring 627. The multiple secondary batteries 616 may be connected in parallel, in series, or in series after being connected in parallel. Configuring the power storage module 615 with multiple secondary batteries 616 allows for the extraction of large amounts of power. The multiple secondary batteries 616 can be referred to as a power storage device or a battery pack. In this case, the conductive plate with the highest potential among the conductive plates 628 and 614 can be referred to as the positive terminal of the power storage device or the positive terminal of the battery pack. Furthermore, the conductive plate with the lowest potential among the conductive plate 628 and the conductive plate 614 can be referred to as the negative electrode terminal of the power storage device or the negative electrode terminal of the battery pack.

[0209] Furthermore, a temperature control device may be provided between the multiple secondary batteries 616. When the secondary batteries 616 are overheated, they can be cooled by the temperature control device, and when the secondary batteries 616 are too cold, they can be heated by the temperature control device. This makes it difficult for the performance of the power storage module 615 to be affected by the outside temperature.

[0210] 14D , the power storage module 615 is electrically connected to a control circuit 620 via wiring 621 and wiring 622. The wiring 621 is electrically connected to the positive electrodes of the multiple secondary batteries 616 via a conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the multiple secondary batteries 616 via a conductive plate 614. The control circuit 620 also has external terminals 629 and 630.

[0211] [Other Structural Examples of Secondary Battery] Structural examples of secondary batteries will be described with reference to FIGS. 15A to 16C.

[0212] The secondary battery 913 shown in FIG. 15A has a wound body 950 provided with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. The terminal 952 contacts the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. Note that in FIG. 15A , for convenience, the housing 930 is shown separated, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0213] 15B, the housing 930 shown in Fig. 15A may be formed from a plurality of materials. For example, the secondary battery 913 shown in Fig. 15B has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in the area surrounded by the housing 930a and the housing 930b.

[0214] The housing 930a can be made of an insulating material such as organic resin. In particular, by using a material such as organic resin on the surface on which the antenna is formed, it is possible to suppress shielding of the electric field by the secondary battery 913. Note that if the shielding of the electric field by the housing 930a is small, the antenna may be provided inside the housing 930a. The housing 930b can be made of, for example, a metal material.

[0215] 15C shows the structure of the wound body 950. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 sandwiched therebetween, and the laminated sheet is wound. Note that a plurality of layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.

[0216] Alternatively, a secondary battery 913 may be provided that has a wound body 950a as shown in Fig. 16. The wound body 950a shown in Fig. 16A has a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0217] The separator 933 has a width wider than the negative electrode active material layer 931 a and the positive electrode active material layer 932 a, and is wound so as to overlap the negative electrode active material layer 931 a and the positive electrode active material layer 932 a. From the standpoint of safety, it is preferable that the negative electrode active material layer 931 a be wider than the positive electrode active material layer 932 a. A wound body 950 a having such a shape is preferable due to its high safety and productivity.

[0218] 16B , the negative electrode 931 is electrically connected to a terminal 951 by ultrasonic bonding, welding, or crimping. The terminal 951 is electrically connected to a terminal 911a. The positive electrode 932 is electrically connected to a terminal 952 by ultrasonic bonding, welding, or crimping. The terminal 952 is electrically connected to a terminal 911b.

[0219] 16C , the wound body 950 a and the electrolyte are covered by the housing 930 to form the secondary battery 913. It is preferable to provide the housing 930 with a safety valve, an overcurrent protection element, etc. The safety valve is a valve that opens when the inside of the housing 930 reaches a predetermined internal pressure to prevent the battery from exploding.

[0220] As shown in Fig. 16B, the secondary battery 913 may have multiple wound bodies 950a. Using multiple wound bodies 950a can result in a secondary battery 913 with a larger discharge capacity. For other elements of the secondary battery 913 shown in Figs. 16A and 16B, the descriptions of the secondary battery 913 shown in Figs. 15A to 15C can be referred to.

[0221] <Laminated Secondary Battery> Next, examples of external views of an example of a laminated secondary battery are shown in Figures 17A and 17B. Figures 17A and 17B have a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511. The portion of the positive electrode lead electrode 510 that is exposed to the outside of the secondary battery can be called a positive electrode terminal, and the portion of the negative electrode lead electrode 511 that is exposed to the outside of the secondary battery can be called a negative electrode terminal.

[0222] 18A shows an external view of a positive electrode 503 and a negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The positive electrode 503 also has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a tab region). The negative electrode 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 also has a region where the negative electrode current collector 504 is partially exposed, i.e., a tab region. Note that the area or shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. 18A .

[0223] <Method of Manufacturing Laminated Secondary Battery> An example of a method of manufacturing the laminated secondary battery whose external view is shown in FIG. 17A will be described with reference to FIGS. 18B and 18C.

[0224] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. FIG. 18B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example is shown in which five pairs of negative electrodes and four pairs of positive electrodes are used. This can also be called a laminate consisting of a negative electrode, a separator, and a positive electrode. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For example, ultrasonic welding or the like may be used for joining. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0225] Next, the negative electrode 506 , the separator 507 , and the positive electrode 503 are arranged on the outer casing 509 .

[0226] Next, as shown in Fig. 18C, the exterior body 509 is folded at the portion indicated by the dashed line. Thereafter, the outer periphery of the exterior body 509 is joined. For example, thermocompression bonding may be used for joining. At this time, an area (hereinafter referred to as an inlet) that is not joined is provided in a part (or one side) of the exterior body 509 so that an electrolyte can be introduced later.

[0227] Next, the electrolyte solution is introduced into the inside of the exterior body 509 through an inlet provided in the exterior body 509. The introduction of the electrolyte solution is preferably carried out under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is joined. In this manner, the laminated secondary battery 500 can be produced.

[0228] [Example of Battery Pack] An example of a secondary battery pack according to one embodiment of the present invention, which can be wirelessly charged using an antenna, will be described with reference to FIG.

[0229] Fig. 19A is a diagram showing the appearance of secondary battery pack 531, which has a thin rectangular parallelepiped shape (also called a thick flat plate shape). Fig. 19B is a diagram illustrating the configuration of secondary battery pack 531. Secondary battery pack 531 has circuit board 540 and secondary battery 513. Label 529 is affixed to secondary battery 513. Circuit board 540 is fixed with sticker 515. Secondary battery pack 531 also has antenna 517.

[0230] The interior of the secondary battery 513 may have a structure including a wound body or a laminated body.

[0231] 19B , the secondary battery pack 531 has a control circuit 590 on a circuit board 540. The circuit board 540 is electrically connected to the terminal 514. The circuit board 540 is also electrically connected to the antenna 517, one 551 of the positive and negative leads of the secondary battery 513, and the other 552 of the positive and negative leads. The positive lead may be referred to as a positive terminal, and the negative lead may be referred to as a negative terminal.

[0232] In the secondary battery pack 531, the secondary battery 513 and the control circuit 590 can have the same configuration as the charge management system 100 described in Embodiment 1 or the like.

[0233] 19C , the semiconductor device may include a circuit system 590a provided on a circuit board 540 and a circuit system 590b electrically connected to the circuit board 540 via a terminal 514. The terminal 514 includes a plurality of terminals, and includes at least a high-potential terminal (external terminal 51 in FIG. 1B ) and a low-potential terminal (external terminal 52 in FIG. 1B ).

[0234] The antenna 517 is not limited to a coil shape and may be, for example, a wire shape or a plate shape. Furthermore, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may also be used. Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 517 may function as one of the two conductors of a capacitor. This allows power to be exchanged not only by electromagnetic fields and magnetic fields but also by electric fields.

[0235] The secondary battery pack 531 includes a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has a function of, for example, shielding an electromagnetic field generated by the secondary battery 513. The layer 519 can be formed using, for example, a magnetic material.

[0236] In this embodiment, an example of a vehicle including a secondary battery according to one embodiment of the present invention will be described. The secondary battery and the control circuit described in this embodiment can use the configuration of the charge management system 100 or the like described in Embodiment 1.

[0237] The secondary battery can be applied to a typical vehicle, such as an automobile. Examples of the automobile include next-generation clean energy automobiles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHEVs or PHVs). The secondary battery can be used as one of the power sources mounted on the automobile. The vehicle is not limited to an automobile. Examples of the vehicle include trains, monorails, ships, submersibles (deep-sea exploration vessels, unmanned submersibles), aircraft (helicopters, unmanned aerial vehicles (drones), airplanes, rockets, and artificial satellites), electric bicycles, and electric motorcycles. The secondary battery of one embodiment of the present invention can be applied to these vehicles.

[0238] The electric vehicle is equipped with first power storage devices 1301a and 1301b as main driving secondary batteries, and a second power storage device 1311 that supplies power to an inverter 1312 that starts a motor 1304. The second power storage device 1311 is also called a cranking battery (also called a starter battery). The second power storage device 1311 only needs to have high output, and does not need to have a large capacity, and the capacity of the second power storage device 1311 is smaller than that of the first power storage devices 1301a and 1301b.

[0239] The internal structure of the first power storage device 1301a may be a wound type shown in FIG. 15C or 16A or a stacked type shown in FIG. 17A or 17B. The first power storage device 1301a may include an all-solid-state battery. The use of an all-solid-state battery for the first power storage device 1301a enables a high capacity, improved safety, and reductions in size and weight.

[0240] Although this embodiment shows an example in which two first power storage devices 1301a and 1301b are connected in parallel, three or more may be connected in parallel. Furthermore, if the first power storage device 1301a can store sufficient power, the first power storage device 1301b may be omitted. A large amount of power can be extracted by configuring a battery pack having a plurality of secondary batteries as a power storage device. The plurality of secondary batteries may be connected in parallel, in series, or in series after being connected in parallel. A plurality of secondary batteries is also called a battery pack.

[0241] In addition, in the case of a secondary battery for vehicle use, in order to cut off power from multiple secondary batteries, a service plug or circuit breaker that can cut off high voltage without using tools is provided in the first power storage device 1301a.

[0242] The power of the first power storage devices 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V in-vehicle components (such as the electric power steering 1307, the heater 1308, and the defogger 1309) via the DCDC circuit 1306. When a rear motor 1317 is provided on the rear wheels, the first power storage device 1301a is also used to rotate the rear motor 1317.

[0243] The second power storage device 1311 also supplies power to 14V in-vehicle components (audio 1313, power windows 1314, lamps 1315, etc.) via the DCDC circuit 1310.

[0244] Next, the first power storage device 1301a will be described with reference to FIG. 20A.

[0245] FIG. 20A shows an example in which nine prismatic secondary batteries 1300 are used as one power storage module 1415. Furthermore, nine prismatic secondary batteries 1300 are connected in series, with one electrode fixed by a fixing portion 1413 made of an insulator and the other electrode fixed by a fixing portion 1414 made of an insulator. While this embodiment shows an example in which the batteries are fixed by the fixing portions 1413 and 1414, they may also be housed in a battery housing box (also called a casing). Because it is expected that a vehicle will be subjected to external vibrations or shaking (such as from the road surface), it is preferable to fix multiple secondary batteries by the fixing portions 1413 and 1414 or a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421. Furthermore, the other electrode is electrically connected to the control circuit unit 1320 by wiring 1422. In the first power storage device 1301a, of the electrodes connected to the wiring 1421 or the wiring 1422, the one with a higher potential can be referred to as a positive electrode terminal of the first power storage device 1301a, and the one with a lower potential can be referred to as a negative electrode terminal of the first power storage device 1301a. The control circuit 1320 includes an external connection terminal 1325 and an external connection terminal 1326.

[0246] A memory circuit including a transistor using an oxide semiconductor may be used for the control circuit portion 1320. A charge control circuit or a battery control system including a memory circuit including a transistor using an oxide semiconductor may be referred to as a battery operating system (BTOS) or a battery oxide semiconductor (BTOS).

[0247] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, a metal oxide such as In-M-Zn oxide (wherein the element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used as the metal oxide. In particular, the In-M-Zn oxide that can be used as the metal oxide is preferably a C-Axis Aligned Crystal Oxide Semiconductor (CAAC-OS) or a Cloud-Aligned Composite Oxide Semiconductor (CAC-OS). Alternatively, an In—Ga oxide or an In—Zn oxide may be used as the metal oxide. The CAAC-OS is an oxide semiconductor having multiple crystalline regions, each of which has a c-axis oriented in a specific direction. The specific direction is the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. The crystalline regions are regions in which the atomic arrangement is periodic. When the atomic arrangement is considered as a lattice arrangement, the crystalline regions are also regions in which the lattice arrangement is aligned.

[0248] Note that "CAC-OS" has a mosaic structure in which a material is separated into a first region and a second region, and the first region is distributed throughout the film (hereinafter, also referred to as a cloud structure). That is, CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed. However, it may be difficult to observe a clear boundary between the first region and the second region.

[0249] For example, in the case of CAC-OS in an In—Ga—Zn oxide, EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) can confirm that the CAC-OS has a structure in which a region containing In as a main component (first region) and a region containing Ga as a main component (second region) are unevenly distributed and mixed.

[0250] When a CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act complementarily, thereby providing the CAC-OS with a switching function (a function of turning on / off). That is, a CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and functions as a semiconductor as a whole. By separating the conductive function and the insulating function, both functions can be maximized. Therefore, by using a CAC-OS in a transistor, a high on-current (I ｏｎ ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0251] Oxide semiconductors have a variety of structures, each of which has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0252] Furthermore, since the control circuit unit 1320 can be used in high-temperature environments, it is preferable to use a transistor using an oxide semiconductor. To simplify the process, the control circuit unit 1320 may be formed using a unipolar transistor. A transistor using an oxide semiconductor for the semiconductor layer has a wider operating ambient temperature range than single-crystal Si, from −40° C. to 150° C., and its characteristics change less even when the secondary battery overheats than a single-crystal Si transistor. The off-current of a transistor using an oxide semiconductor is below the lower limit of measurement regardless of temperature, even at 150° C., whereas the off-current characteristics of a single-crystal Si transistor are highly temperature-dependent. For example, at 150° C., the off-current of a single-crystal Si transistor increases, and the current on / off ratio does not become sufficiently large. The control circuit unit 1320 can improve safety.

[0253] The control circuit unit 1320, which uses a memory circuit including transistors using oxide semiconductors, can also function as an automatic control device for the secondary battery to address causes of instability such as micro-shorts. Functions for eliminating causes of instability such as micro-shorts include overcharging prevention, overcurrent prevention, overheating control during charging, cell balancing in the battery pack, over-discharging prevention, a fuel gauge, automatic control of charging voltage and current according to temperature, control of charging current according to the degree of deterioration, detection of abnormal behavior of micro-shorts, and prediction of abnormalities related to micro-shorts. The control circuit unit 1320 has at least one of these functions. Furthermore, the automatic control device for the secondary battery can be made ultra-miniaturized.

[0254] Furthermore, a "micro-short" refers to a tiny short circuit inside a secondary battery, which is not so small that the positive and negative electrodes of the secondary battery are short-circuited and render it unable to be charged or discharged, but rather refers to a phenomenon in which a small short-circuited part allows a small amount of short-circuit current to flow. Even if the short-circuit occurs in a relatively short period of time and in a small location, a large voltage change occurs, and this abnormal voltage value may affect subsequent estimations.

[0255] One of the causes of micro-short circuits is said to be that multiple charge and discharge cycles cause uneven distribution of the positive electrode active material, resulting in localized current concentration in parts of the positive electrode and negative electrode, causing parts of the separator to stop functioning, or the generation of by-products due to side reactions, resulting in micro-short circuits.

[0256] In addition to detecting micro-shorts, the control circuit 1320 can also be said to detect the terminal voltage of the secondary battery and manage the charge / discharge state of the secondary battery. For example, to prevent overcharging, it can turn off both the output transistor and the cutoff switch of the charging circuit almost simultaneously.

[0257] Next, an example of a block diagram of the power storage module 1415 shown in FIG. 20A is shown in FIG. 20B.

[0258] The control circuit unit 1320 includes a switch unit 1324 including at least a switch for preventing overcharging and a switch for preventing overdischarging, a control circuit 1322 for controlling the switch unit 1324, a voltage measurement unit for the first power storage device 1301a, and a PTC element 1332. The control circuit unit 1320 sets upper and lower voltage limits for the secondary battery used and limits the upper limit of the current from the outside or the upper limit of the output current to the outside. The range between the lower and upper voltage limits of the secondary battery is within the recommended voltage range, and when the secondary battery falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent overcharging and / or overdischarging. For example, if the control circuit 1322 detects a voltage that could cause overcharging, it turns off the switch unit 1324 to cut off the current. A PTC element may also be provided in the charge / discharge path to provide a function for cutting off the current in response to an increase in temperature. The control circuit section 1320 also has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0259] The switch portion 1324 can be configured by combining n-channel transistors or p-channel transistors. The switch portion 1324 is not limited to a switch having a Si transistor using single crystal silicon. For example, the switch portion 1324 may be formed using a power transistor having Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), or GaOx (gallium oxide; x is a real number greater than 0). Furthermore, memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, and therefore integration can be easily achieved. Furthermore, OS transistors can be manufactured using the same manufacturing equipment as Si transistors, and therefore can be manufactured at low cost. That is, the control circuit portion 1320 using OS transistors can be stacked on the switch portion 1324 and integrated into a single chip. The volume occupied by the control circuit section 1320 can be reduced, which allows for miniaturization.

[0260] Next, an example of a block diagram of a vehicle to which the power storage module 1415 shown in FIG. 20A is applied is shown in FIG. 20C.

[0261] The first power storage devices 1301a and 1301b mainly supply power to on-board equipment of the 42V system (high voltage system), and the second power storage device 1311 supplies power to on-board equipment of the 14V system (low voltage system). Lead-acid batteries are often used as the second power storage device 1311 due to their cost advantages. Lead-acid batteries have the disadvantage of being more self-discharged than lithium-ion batteries and being prone to deterioration due to a phenomenon called sulfation. Using a lithium-ion battery as the second power storage device 1311 has the advantage of being maintenance-free, but after long-term use, for example, three years or more, there is a risk of abnormalities occurring that are difficult to identify during manufacturing. In particular, if the second power storage device 1311 that starts the inverter becomes inoperable, in order to prevent the motor from being unable to start even if the first power storage devices 1301a and 1301b have remaining capacity, if the second power storage device 1311 is a lead-acid battery, power is supplied from the first battery to the second battery, and the second battery is charged to always maintain a fully charged state.

[0262] In this embodiment, an example in which lithium ion batteries are used for both the first power storage device 1301a and the second power storage device 1311 is shown. The second power storage device 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double layer capacitor. For example, an all-solid-state battery may be used. By using an all-solid-state battery for the second power storage device 1311, high capacity, miniaturization, and weight reduction can be achieved.

[0263] Furthermore, regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and is then charged into the second power storage device 1311 via the control circuit unit 1321 from the motor controller 1303 or the battery controller 1302. Alternatively, the first power storage device 1301a is charged from the battery controller 1302 via the control circuit unit 1320. Alternatively, the first power storage device 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerative energy, it is desirable that the first power storage devices 1301a and 1301b be capable of rapid charging.

[0264] The battery controller 1302 can set the charging voltage and charging current of the first power storage devices 1301a and 1301b. The battery controller 1302 can set charging conditions in accordance with the charging characteristics of the secondary battery to be used, and can perform rapid charging.

[0265] Although not shown, when an external charger is connected, the charger's outlet or the charger's connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger is charged to the first power storage devices 1301a and 1301b via the battery controller 1302. Some chargers are provided with a control circuit, and although the function of the battery controller 1302 may not be used, it is preferable to charge the first power storage devices 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. The control circuit unit 1320 may also be provided in the connection cable or the charger's connection cable. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) provided in the electric vehicle. The CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU also includes a microcomputer. The ECU uses a CPU or a GPU.

[0266] External chargers installed at charging stations and the like include 100V-200V outlets, or three-phase 200V and 50kW. Charging can also be performed by receiving power from external charging equipment using a wireless power supply system or the like.

[0267] When rapid charging is performed, a secondary battery that can withstand high voltage charging is desired in order to charge in a short time.

[0268] Furthermore, by using graphene as a conductive material, a secondary battery with significantly improved electrical characteristics can be realized, as a synergistic effect of suppressing capacity decline and maintaining high capacity even when the electrode layer is thickened and the amount of graphene supported is increased. This is particularly effective for secondary batteries used in vehicles, and it is possible to provide a vehicle with a long driving range, specifically a driving distance of 500 km or more per charge, without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0269] Next, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described.

[0270] 14D , 16C , and 20A can be installed in a vehicle to realize next-generation clean energy automobiles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs). Furthermore, the secondary battery can also be installed in agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, ships, submarines, aircraft, rockets, artificial satellites, space probes, planetary probes, or spacecraft. The secondary battery of one embodiment of the present invention can be a high-capacity secondary battery. Therefore, the secondary battery of one embodiment of the present invention is suitable for miniaturization and weight reduction and can be suitably used in transportation vehicles.

[0271] 21A to 21D illustrate examples of transportation vehicles using one embodiment of the present invention. The automobile 2001 illustrated in FIG. 21A is an electric automobile using an electric motor as a power source for traveling. Alternatively, the automobile 2001 is a hybrid automobile that can appropriately select and use an electric motor or an engine as a power source for traveling. When a secondary battery is installed in a vehicle, an example of the secondary battery described in Embodiment 3 is installed in one or more locations. The automobile 2001 illustrated in FIG. 21A includes a battery pack 2200, which includes a power storage module to which multiple secondary batteries are connected. It is preferable that the automobile 2001 further includes a charge control device electrically connected to the power storage module.

[0272] Furthermore, the automobile 2001 can charge its secondary battery by receiving power from an external charging facility using a plug-in system, a contactless power supply system, or the like. The charging method or connector standard may be a predetermined system such as CHAdeMO (registered trademark) or Combo. The charging battery may be a charging station installed in a commercial facility or a household power source. For example, plug-in technology can be used to charge the power storage device installed in the automobile 2001 using an external power supply. Charging can be performed by converting AC power to DC power via a conversion device such as an AC-DC converter.

[0273] Although not shown, a power receiving device can be mounted on a vehicle and power can be supplied contactlessly from a ground-based power transmitting device to charge the vehicle. In the case of this contactless power supply method, by incorporating a power transmitting device into a road or an exterior wall, charging can be performed not only while the vehicle is stopped but also while the vehicle is moving. This contactless power supply method can also be used to transmit and receive power between two vehicles. Furthermore, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped or moving. For such contactless power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0274] 21B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle. The power storage module of the transport vehicle 2002 is, for example, a four-cell unit of secondary batteries with a nominal voltage of 3.0 V to 5.0 V, with 48 cells connected in series to achieve a maximum voltage of 170 V. Apart from the number of secondary batteries constituting the power storage module of the battery pack 2201, the transport vehicle 2002 has the same functions as those shown in FIG. 21A, and therefore a description thereof will be omitted.

[0275] 21C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor. The power storage module of the transport vehicle 2003 has a maximum voltage of 600 V, for example, with 100 or more secondary batteries connected in series, each having a nominal voltage of 3.0 V to 5.0 V. Therefore, secondary batteries with little variation in characteristics are required.

[0276] Fig. 21D shows, as an example, an aircraft 2004 having an engine that burns fuel. The aircraft 2004 shown in Fig. 21D has wheels for takeoff and landing, and can therefore be considered part of a transport vehicle, and has a battery pack 2203 that includes a power storage module formed by connecting multiple secondary batteries and that includes the power storage module and a charge control device.

[0277] The power storage module of the aircraft 2004 is, for example, eight 4 V secondary batteries connected in series to produce a maximum voltage of 32 V. Apart from the number of secondary batteries constituting the power storage module of the battery pack 2203, the power storage module has the same functions as those shown in Fig. 21A, and therefore a description thereof will be omitted.

[0278] 21E illustrates, as an example, a satellite 2005 equipped with a secondary battery 2204. Because the satellite 2005 is used in space at extremely low temperatures, it is preferable that the satellite 2005 be equipped with the secondary battery 2204, which is one embodiment of the present invention and has excellent low-temperature resistance. It is more preferable that the secondary battery 2204 be mounted inside the satellite 2005 while being covered with a heat-insulating member.

[0279] 22A and 22B , an example in which a secondary battery according to one embodiment of the present invention is mounted in a building will be described. The secondary battery and the control circuit described in this embodiment can use the configuration of the charge management system 100 or the like described in Embodiment 1.

[0280] The house illustrated in FIG. 22A includes a power storage device 2612 including a secondary battery of one embodiment of the present invention, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611 or the like. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The power obtained by the solar panel 2610 can be charged to the power storage device 2612. The power stored in the power storage device 2612 can be charged to a secondary battery included in the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in an underfloor space. By installing the power storage device 2612 in the underfloor space, the space above the floor can be effectively utilized. Alternatively, the power storage device 2612 may be installed on the floor.

[0281] The power stored in the power storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the power storage device 2612 of one embodiment of the present invention can be used as an uninterruptible power supply, enabling the use of electronic devices.

[0282] 22B illustrates an example of a power storage device according to one embodiment of the present invention. As illustrated in FIG. 22B , a power storage device 791 according to one embodiment of the present invention is installed in an underfloor space 796 of a building 799.

[0283] A control device 790 is installed in the power storage device 791, and the control device 790 is electrically connected to the distribution board 703, the power storage controller 705 (also called the control device), the display 706, and the router 709 by wiring.

[0284] Electric power is sent from commercial power source 701 to distribution board 703 via service line attachment portion 710. Electric power is also sent to distribution board 703 from power storage device 791 and commercial power source 701, and distribution board 703 supplies the sent electric power to general load 707 and power storage load 708 via outlets (not shown).

[0285] The general load 707 is, for example, an electronic device such as a television or a personal computer, and the power storage load 708 is, for example, an electronic device such as a microwave oven, a refrigerator, or an air conditioner.

[0286] The power storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has a function of measuring the amount of power consumed by the general load 707 and the power storage load 708 during a day (e.g., from midnight to midnight). The measurement unit 711 may also have a function of measuring the amount of power of the power storage device 791 and the amount of power supplied from the commercial power source 701. The prediction unit 712 has a function of predicting the amount of power demand to be consumed by the general load 707 and the power storage load 708 during the next day based on the amount of power consumed by the general load 707 and the power storage load 708 during the previous day. The planning unit 713 has a function of creating a plan for charging and discharging the power storage device 791 based on the amount of power demand predicted by the prediction unit 712.

[0287] The amount of power consumed by the general load 707 and the power storage load 708 measured by the measurement unit 711 can be confirmed on the display 706. It can also be confirmed on an electronic device such as a television or a personal computer via the router 709. It can also be confirmed on a mobile electronic device such as a smartphone or a tablet via the router 709. The amount of power demand for each time period (or each hour) predicted by the prediction unit 712 can also be confirmed on the display 706, the electronic device, or the mobile electronic device.

[0288] In this embodiment, as an example of mounting a secondary battery on a vehicle, a lithium-ion battery according to one embodiment of the present invention is mounted on a motorcycle or a bicycle. The configuration of the charge management system 100 or the like described in Embodiment 1 can be used in the secondary battery and the control circuit described in this embodiment.

[0289] 23A illustrates an example of an electric bicycle using the power storage device of one embodiment of the present invention. The power storage device of one embodiment of the present invention can be applied to an electric bicycle 8700 illustrated in FIG. 23A. The power storage device of one embodiment of the present invention includes, for example, a plurality of storage batteries and a protection circuit.

[0290] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 can supply electricity to a motor that assists a rider. The power storage device 8702 is portable and is shown in a state removed from the bicycle in FIG. 23B . The power storage device 8702 includes a plurality of built-in storage batteries 8701 included in the power storage device of one embodiment of the present invention, and the remaining battery charge and the like can be displayed on a display unit 8703. The power storage device 8702 also includes a control circuit 8704 that can control charging or detect an abnormality of the secondary battery, an example of which is shown in Embodiment 6. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage batteries 8701.

[0291] 23C illustrates an example of a two-wheeled vehicle using a power storage device of one embodiment of the present invention. A scooter 8600 illustrated in FIG. 23C includes a power storage device 8602, a side mirror 8601, and a turn signal light 8603. The power storage device 8602 can supply electricity to the turn signal light 8603.

[0292] 23C can store a power storage device 8602 in an under-seat storage compartment 8604. The power storage device 8602 can be stored in the under-seat storage compartment 8604 even if the under-seat storage compartment 8604 is small.

[0293] Embodiment 7 In this embodiment, an example of mounting a secondary battery according to one embodiment of the present invention in an electronic device will be described. Examples of electronic devices that mount a secondary battery include television sets (also referred to as televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game consoles, personal digital assistants, sound players, and large game consoles such as pachinko machines. Examples of personal digital assistants include notebook personal computers, tablet terminals, e-book terminals, and mobile phones. The secondary battery and control circuit described in this embodiment can use the configuration of the charge management system 100 or the like described in Embodiment 1.

[0294] 24A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into a housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also includes a secondary battery 2107.

[0295] The mobile phone 2100 can execute various applications such as mobile phone calls, e-mail, document browsing and creation, music playback, internet communication, and computer games.

[0296] The operation button 2103 can be provided with various functions such as time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, power saving mode activation / deactivation, etc. For example, the functions of the operation button 2103 can be freely set by an operating system incorporated in the mobile phone 2100.

[0297] The mobile phone 2100 is also capable of performing standardized short-range wireless communication, and can also make hands-free calls by communicating with a wirelessly enabled headset, for example.

[0298] The mobile phone 2100 also includes an external connection port 2104, and can directly exchange data with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Note that charging may be performed by wireless power supply without using the external connection port 2104.

[0299] Furthermore, the mobile phone 2100 preferably has a sensor. As the sensor, for example, a fingerprint sensor, a pulse sensor, a human body sensor such as a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like is preferably mounted.

[0300] 24B shows an unmanned aerial vehicle 2300 having multiple rotors 2302. The unmanned aerial vehicle 2300 is also called a drone. The unmanned aerial vehicle 2300 includes a secondary battery 2301 according to one embodiment of the present invention, a camera 2303, and an antenna (not shown). The unmanned aerial vehicle 2300 can be remotely controlled via the antenna.

[0301] Fig. 24C shows an example of a robot. A robot 6400 shown in Fig. 24C includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0302] The microphone 6402 has a function of detecting the user's speaking voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0303] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0304] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0305] The robot 6400 includes, in its internal area, a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or electronic component.

[0306] 24D shows an example of a cleaning robot. The cleaning robot 6300 includes a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side surfaces, a brush 6304, operation buttons 6305, a secondary battery 6306, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0307] The cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, when an object that may become entangled in the brush 6304, such as a wire, is detected by image analysis, the cleaning robot 6300 can stop rotation of the brush 6304. The cleaning robot 6300 includes a secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or electronic component in its internal area.

[0308] 25A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for a wearable device that can be charged wirelessly as well as via a wired connection with an exposed connector.

[0309] 25A , the secondary battery according to one embodiment of the present invention can be mounted on a glasses-type device 4000. The glasses-type device 4000 includes a frame 4000a and a display unit 4000b. Mounting the secondary battery on the temples of the curved frame 4000a makes it possible to provide the glasses-type device 4000 with a lightweight design, a good weight balance, and a long continuous use time.

[0310] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the headset device 4001. The headset device 4001 includes at least a microphone unit 4001a, a flexible pipe 4001b, and an earphone unit 4001c. The secondary battery can be provided in the flexible pipe 4001b or the earphone unit 4001c.

[0311] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the device 4002 that can be directly attached to the body. A secondary battery 4002b can be provided in a thin housing 4002a of the device 4002.

[0312] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the device 4003 that can be attached to clothing. A secondary battery 4003b can be provided in a thin housing 4003a of the device 4003.

[0313] Furthermore, the secondary battery of one embodiment of the present invention can be mounted on the belt-type device 4006. The belt-type device 4006 includes a belt portion 4006a and a wireless power receiving portion 4006b, and the secondary battery can be mounted in an internal region of the belt portion 4006a.

[0314] Furthermore, the secondary battery which is one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch device 4005 has a display portion 4005a and a belt portion 4005b, and the secondary battery can be provided in the display portion 4005a or the belt portion 4005b.

[0315] The display unit 4005a can display not only the time but also various other information such as incoming emails or phone calls.

[0316] Furthermore, since the wristwatch-type device 4005 is a wearable device that is worn directly on the wrist, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated to manage the user's health.

[0317] FIG. 25B shows a perspective view of the wristwatch-type device 4005 removed from the wrist.

[0318] 25C shows a side view of the display portion 4005a. Fig. 25C shows a state in which a secondary battery 913 is built in the internal region. The secondary battery 913 is the secondary battery described in Embodiment 3. The secondary battery 913 is provided in a position overlapping with the display portion 4005a, and can have high density and high capacity, and is small and lightweight.

[0319] In this example, a secondary battery was fabricated and its characteristics were evaluated.

[0320] <Preparation of Positive Electrode Active Material> A positive electrode active material was prepared.

[0321] As the lithium cobalt oxide, commercially available lithium cobalt oxide (Cellseed C-10N, manufactured by Nippon Chemical Industry Co., Ltd.) was prepared. Next, the prepared lithium cobalt oxide was heated at 850° C. for 2 hours in an oxygen atmosphere.

[0322] Lithium fluoride and magnesium fluoride were weighed and mixed in a molar ratio of lithium fluoride:magnesium fluoride = 1:3 to obtain a magnesium source. Next, magnesium in the magnesium source was weighed out so that the amount of magnesium in the lithium cobalt oxide was 1 at % of the cobalt in the lithium cobalt oxide, and the magnesium was mixed with heated lithium cobalt oxide to obtain a mixture A1.

[0323] Next, the mixture A1 was heated at 900° C. for 20 hours in an oxygen atmosphere to obtain a composite oxide B1.

[0324] Next, nickel hydroxide was prepared as the nickel source, and aluminum hydroxide was prepared as the aluminum source. Each was weighed out so that the nickel content of the nickel hydroxide was 0.5 at% of the cobalt content of the composite oxide B1, and the aluminum content of the aluminum hydroxide was 0.5 at% of the cobalt content of the composite oxide B1, and then mixed with the composite oxide B1 to obtain a mixture C1.

[0325] Next, the mixture C1 was heated at 850° C. for 10 hours in an oxygen atmosphere to prepare a sample Sa1.

[0326] <Preparation of Positive Electrode> Sample Sa1, acetylene black (AB), polyvinylidene fluoride (PVDF), and NMP were mixed to prepare a slurry, with the ratio of Sample Sa1, AB, and PVDF being Sample Sa1:AB:PVDF=95:3:2 (weight ratio).

[0327] The prepared slurry was applied to one side of an aluminum foil, and then heated at 80° C. to volatilize the NMP. After heating, the aluminum foil was pressed to obtain a positive electrode.

[0328] <Preparation of Negative Electrode> Graphite, VGCF (registered trademark), carboxymethyl cellulose sodium salt (CMC-Na), styrene-butadiene rubber (SBR), and water were mixed to prepare a slurry, where the ratio of graphite, VGCF, CMC-Na, and SBR was graphite:VGCF:CMC-Na:SBR=96:1:1:2 (weight ratio).

[0329] The prepared slurry was applied to one side of a copper foil, which was then heated at 50° C. to obtain a negative electrode.

[0330] <Preparation of Secondary Battery> A secondary battery was prepared using the positive electrode and negative electrode prepared above. The electrolyte solution used was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3:7, and lithium hexafluorophosphate (LiPF ) was used as the lithium salt. ６ ) was used, and the concentration of lithium salt in the electrolyte was 1.00 mol / L. Polypropylene was used as the separator. A film in which a polypropylene layer, an acid-modified polypropylene layer, an aluminum layer, and a nylon layer were laminated in this order was used as the film serving as the exterior body. One negative electrode having a negative electrode active material layer formed on one side and one positive electrode having a positive electrode active material layer formed on one side were prepared, and the negative electrode active material layer and the positive electrode active material layer were arranged so that they faced each other with the separator sandwiched between them.

[0331] Through the above steps, a secondary battery was fabricated.

[0332] <dQ / dV-V curve> A charging test was performed using the fabricated secondary battery as a battery cell. Four battery cells C1 to C4 connected in series were used as the secondary battery. The ambient temperature during the measurement was 27°C, and the charging conditions were constant current charging at 0.5 C and a charge cut-off voltage of 4.26 V.

[0333] Fig. 26A shows the dQ / dV-V curves of battery cells C1 to C4 during charging. Fig. 26B shows an enlarged view of the curves in the vicinity of 4.20 V in the data of Fig. 26A. During charging, the data acquisition interval was 6 mV, i.e., data was acquired when the voltage change dV was 6 mV. Voltage measurements were taken every 100 ms, and data was acquired when the voltage change dV was 6 mV.

[0334] During charging, the peaks at 4.20 V of the dQ / dV-V curves of battery cells C1 to C4 were reached in the following order: battery cell C1, battery cell C2, battery cell C3, and battery cell C4. The peak of battery cell C2 occurred 140.7 seconds after the peak of battery cell C1. The peak of battery cell C3 occurred 272.1 seconds after the peak of battery cell C1. The peak of battery cell C4 occurred 333.8 seconds after the peak of battery cell C1. Considering that charging was performed at a constant current, the difference in the amount of electricity between battery cells C1 and C2 was estimated to be 0.6036 mAh. The difference in the amount of electricity between battery cells C1 and C3 was estimated to be 1.1671 mAh. The difference in the amount of electricity between battery cells C1 and C4 was estimated to be 1.4312 mAh.

[0335] Cell balancing can be performed by discharging the other battery cells C1, C2, and C3 in accordance with the battery cell C4, which last reached its peak. The discharge amount of battery cell C1 was set to 1.4312 mAh, the discharge amount of battery cell C2 was set to 1.14312 - 0.6036 = 0.8276 mAh, and the discharge amount of battery cell C3 was set to 1.14312 - 1.1671 = 0.2641 mAh.

[0336] Thereafter, the battery cells C1 and C4 were charged by 1.4312 mAh, thereby completing full charging of the battery cells C1 to C4.

[0337] <Additional Notes Regarding the Description of the Present Specification, etc.> The following additional notes will be given regarding the above-described embodiments and the explanations of the respective configurations in the embodiments.

[0338] The configurations shown in each embodiment can be combined with the configurations shown in other embodiments as appropriate to form one aspect of the present invention. In addition, when multiple configuration examples are shown in one embodiment, the configuration examples can be combined as appropriate.

[0339] In addition, the content (or even a part of the content) described in one embodiment can be applied to, combined with, or replaced with another content (or even a part of the content) described in that embodiment, and / or the content (or even a part of the content) described in one or more other embodiments.

[0340] The contents described in the embodiments refer to the contents described in each embodiment using various figures or the contents described using text in the specification.

[0341] Furthermore, a figure (or even a part thereof) described in one embodiment can be combined with another part of that figure, another figure (or even a part thereof) described in that embodiment, and / or a figure (or even a part thereof) described in one or more other embodiments to form even more figures.

[0342] In addition, in the present specification and the like, in the block diagrams, components are classified by function and shown as independent blocks. However, in actual circuits, etc., it is difficult to separate components by function, and there may be cases where one circuit is involved in multiple functions, or where one function is involved across multiple circuits. Therefore, the blocks in the block diagrams are not limited to the components described in the specification, but may be rephrased appropriately depending on the situation.

[0343] In addition, in the drawings, the size, layer thickness, or region is shown at an arbitrary size for convenience of explanation. Therefore, it is not necessarily limited to the scale. Note that the drawings are shown schematically for clarity, and are not limited to the shapes or values ​​shown in the drawings. For example, it is possible to include variations in signal, voltage, or current due to noise, or variations in signal, voltage, or current due to timing deviations.

[0344] In this specification and the like, when describing the connection relationship of a transistor, the terms "one of the source or drain" (or first electrode or first terminal) and "the other of the source or drain" (or second electrode or second terminal) are used. This is because the source and drain of a transistor vary depending on the structure or operating conditions of the transistor. Note that the source and drain of a transistor can be appropriately referred to as source (drain) terminal, source (drain) electrode, or the like depending on the situation.

[0345] Furthermore, the terms "electrode" and "wiring" used in this specification and the like do not limit the functionality of these components. For example, an "electrode" may be used as part of a "wiring," and vice versa. Furthermore, the terms "electrode" and "wiring" also include cases where multiple "electrodes" or "wirings" are integrally formed.

[0346] Furthermore, in this specification and the like, the terms voltage and potential can be interchanged as appropriate. Voltage refers to the potential difference from a reference potential. For example, if the reference potential is a ground voltage (earth voltage), then voltage can be interchanged with potential. Ground potential does not necessarily mean 0 V. Note that potential is relative, and the potential applied to wiring, etc. may change depending on the reference potential.

[0347] In this specification and the like, terms such as "film" and "layer" can be interchangeable depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film." Or, for example, the term "insulating film" can be changed to the term "insulating layer."

[0348] In this specification, a terminal refers to a part that electrically connects a battery cell, an IC, etc., and the shape of the terminal is not particularly limited. Terminals of various shapes can be used, such as a bolt shape, a wire shape, a flat shape, a ring shape, a socket shape, a pin shape, a solder hemispherical shape used in a BGA (Ball Grid Array), a flat shape used in an LGA (Land Grid Array), a through-hole and a land (also called a pad) on a printed wiring board, etc. In some cases, a part of the battery's exterior body functions as a positive terminal or a negative terminal, and in such cases, a part of the battery's exterior body can be used as the positive terminal or the negative terminal.

[0349] In this specification, "A and B are connected" refers to an electrical connection between A and B. Here, "A and B are electrically connected" refers to a connection in which an electrical signal can be transmitted between A and B when an object (such as a switch, transistor element, or diode, or a circuit including such an object and wiring) is present between A and B. Note that "A and B are electrically connected" also includes a case in which A and B are directly connected. Here, "A and B are directly connected" refers to a connection in which an electrical signal can be transmitted between A and B via wiring (or electrodes) or the like, without passing through the object. In other words, a direct connection refers to a connection that can be regarded as the same circuit diagram when represented by an equivalent circuit.

[0350] Furthermore, in this specification and elsewhere, "parallel" refers to, for example, a state in which two straight lines are arranged at an angle of -10° or more and 10° or less. Therefore, cases in which the angle is -5° or more and 5° or less are also included. Furthermore, "perpendicular" and "orthogonal" refer to, for example, a state in which two straight lines are arranged at an angle of 80° or more and 100° or less. Therefore, cases in which the angle is 85° or more and 95° or less are also included.

[0351] In this specification and elsewhere, when referring to counting values ​​and measurement values, terms such as "identical," "same," "equal," or "uniform" are used, unless otherwise specified, and include an error of plus or minus 20%.

[0352] In this specification and the like, segregation refers to a phenomenon in which a certain element (for example, B) is spatially distributed non-uniformly in a solid composed of a plurality of elements (for example, A, B, C).

[0353] In this specification, the surface layer of a particle of active material or the like refers to a region extending from the surface to the interior, extending up to approximately 10 nm perpendicular or nearly perpendicular from the surface. Alternatively, it refers to a region within 50 nm. Alternatively, it refers to a region within 5 nm. The surface layer is synonymous with near-surface, near-surface region, or shell. Nearly perpendicular refers to an angle of 80° to 100°. Surfaces caused by cracks or fissures may also be considered the surface. The region deeper than the surface layer is referred to as the interior. In EDX line analysis, the surface of a positive electrode active material refers to the measurement point where the transition metal exhibits a measurement value closest to 50% of the average detected amount of the bulk. Alternatively, in the tangent method, it refers to the intersection of a tangent drawn to the intensity profile of the EDX line analysis of the transition metal and the depth axis. In STEM images, the surface of a positive electrode active material refers to the boundary between the region where an image derived from the crystalline structure of the positive electrode active material is observed and the region where it is not observed, and is the outermost region where atomic columns derived from the nuclei of metal elements with atomic numbers greater than that of lithium are observed. Alternatively, the surface is defined as the intersection of a tangent drawn to the brightness profile from the surface to the bulk in an STEM image and the axis in the depth direction. The surface in an STEM image or the like may be determined in conjunction with an analysis with higher spatial resolution.

[0354] In this specification, the layered rock-salt type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock-salt type ion arrangement in which cations and anions are alternately arranged, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. Defects such as cation or anion deficiencies may also be present. Furthermore, strictly speaking, the layered rock-salt type crystal structure may have a distorted rock-salt type crystal lattice structure.

[0355] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately, and it is also possible for there to be a deficiency of cations or anions.

[0356] In this specification and the like, the O3'-type crystal structure (also referred to as a pseudospinel-type crystal structure) possessed by a composite oxide containing lithium and a transition metal refers to a crystal structure that is in the space group R-3m and is not a spinel-type crystal structure, but in which ions of cobalt, magnesium, etc. occupy oxygen hexacoordination positions and in which the arrangement of cations has a symmetry similar to that of the spinel type. Note that in the O3'-type crystal structure, light elements such as lithium may occupy oxygen tetracoordination positions, and in this case, the arrangement of ions also has a symmetry similar to that of the spinel type.

[0357] The O3'-type crystal structure has random Li atoms between layers, but CdCl ２ It can be said that this crystal structure is similar to that of the CdCl type. ２ A similar crystal structure to the Li-type is lithium nickel oxide. ０．０６ NiO ２ However, it is known that pure lithium cobaltate or layered rock salt-type positive electrode active materials containing a large amount of cobalt do not usually adopt this crystal structure.

[0358] The anions in the layered rock salt crystal and the rock salt crystal have a cubic close-packed structure (face-centered cubic lattice structure). It is estimated that the anions in the O3'-type crystal also have a cubic close-packed structure. When they contact, there is a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of the layered rock salt crystal and the O3'-type crystal is R-3m, which is different from the space group of the rock salt crystal, Fm-3m (the space group of a general rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry). Therefore, the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt crystal and the O3'-type crystal and the rock salt crystal. In this specification, when the orientation of the cubic close-packed structure formed by the anions is aligned in the layered rock salt crystal, the O3'-type crystal, and the rock salt crystal, the crystal orientation may be said to be approximately aligned.

[0359] A secondary battery has, for example, a positive electrode and a negative electrode. A material constituting the positive electrode is a positive electrode active material. The positive electrode active material is, for example, a substance that undergoes a reaction that contributes to the charge / discharge capacity. Note that the positive electrode active material may partially contain a substance that does not contribute to the charge / discharge capacity.

[0360] In this specification and the like, the positive electrode active material used in one embodiment of the present invention may be referred to as a positive electrode material, a positive electrode material for a secondary battery, or the like. In this specification and the like, the positive electrode active material used in one embodiment of the present invention preferably includes a compound. In this specification and the like, the positive electrode active material used in one embodiment of the present invention preferably includes a composition. In this specification and the like, the positive electrode active material used in one embodiment of the present invention preferably includes a composite.

[0361] In this specification, Miller indices are used to represent crystal planes and crystal directions. Individual planes representing crystal planes are represented using ( ). In crystallography, crystal planes, crystal directions, and space groups are represented by a superscript bar. However, due to formatting constraints, in this specification, instead of a bar above the number, a minus sign (-) may be placed before the number. Individual orientations indicating directions within a crystal are represented using [ ], collective orientations indicating all equivalent directions are represented using < >, individual planes indicating crystal planes are represented using ( ), and collective planes with equivalent symmetry are represented using {}. Trigonal crystals represented by the space group R-3m are generally represented as a hexagonal composite hexagonal lattice for ease of understanding the structure, and Miller indices such as (hkl) and (hkil) are sometimes used. Here, i is -(h+k).

[0362] In this specification, the theoretical capacity of a positive electrode active material refers to the amount of electricity when all of the intercalable and deintercalable lithium contained in the positive electrode active material is deintercalated. ２ The theoretical capacity of LiNiO is 274 mAh / g. ２ The theoretical capacity of LiMn is 274mAh / g. ２ O ４ The theoretical capacity of the battery is 148 mAh / g.

[0363] In this specification, the depth of charge is a value that indicates how much capacity is charged based on the theoretical capacity of the positive electrode active material, in other words, how much lithium has been released from the positive electrode. For example, lithium cobalt oxide (LiCoO ２ ) and lithium nickel-cobalt-manganese oxide (LiNi ｘ Co ｙ Mn ｚO ２ In the case of a positive electrode active material having a layered rock salt structure such as (x+y+z=1), based on the theoretical capacity of 274 mAh / g, a charge depth of 0 refers to a state in which no Li has been released from the positive electrode active material, a charge depth of 0.5 refers to a state in which lithium equivalent to 137 mAh / g has been released from the positive electrode, and a charge depth of 0.8 refers to a state in which lithium equivalent to 219.2 mAh / g has been released from the positive electrode. ａ CoO ２ When expressed as (0≦a≦1), when the charge depth is 0, a is 1, LiCoO ２ When the charge depth is 0.5, a is 0.5 Li ０．５ CoO ２ When the charge depth is 0.8, a is 0.2. ０．２ CoO ２ It is written as follows.

[0364] 10: Secondary battery, 11: Battery cell, 20: Charge / discharge control switch, 31: Current measurement circuit, 32: Voltage measurement circuit, 33: Control unit, 34: Memory, 35: Discharger, 36: Resistance element, 37: Cell balance control switch, 38: Differential calculator, 80: Load, 81: Discharge switch, 90: Charger, 91: Charging switch, 100: Charging management system

Claims

1. A secondary battery having a first battery cell and a second battery cell connected in series, A current measuring circuit having the function of measuring the current flowing through the first battery cell and the second battery cell during charging of the secondary battery, A voltage measurement circuit having the function of measuring the voltage of the first battery cell and the second battery cell, respectively, during the charging of the secondary battery, The system includes a control circuit that has a function to control the charging levels of the first battery cell and the second battery cell to be equal, The control circuit has a function to calculate data indicating battery characteristics in each of the first and second battery cells, according to the measured current data and the measured voltage data. Control to equalize the charge levels of the first and second battery cells is performed by controlling the charge levels so that the maximum values ​​of the data indicating the battery characteristics are equal. The maximum value of the data showing the aforementioned battery characteristics is the maximum value when dQ / dV, which represents the change in electric quantity with respect to the change in voltage, is plotted on the vertical axis and the integrated capacity on the horizontal axis. A charging management system for secondary batteries.

2. A secondary battery having a first battery cell and a second battery cell connected in series, A current measuring circuit having the function of measuring the current flowing through the first battery cell and the second battery cell during charging of the secondary battery, A voltage measurement circuit having the function of measuring the voltage of the first battery cell and the second battery cell, respectively, during the charging of the secondary battery, The system includes a control circuit that has a function to control the charging levels of the first battery cell and the second battery cell to be equal, The control circuit has a function to calculate data indicating battery characteristics in each of the first and second battery cells, according to the measured current data and the measured voltage data. Control to equalize the charge levels of the first and second battery cells is performed by controlling the charge levels so that the maximum values ​​of the data indicating the battery characteristics are equal. The maximum value of the data showing the aforementioned battery characteristics is the maximum value when dt / dV, which represents the change in voltage over time, is plotted on the vertical axis and time on the horizontal axis. A charging management system for secondary batteries.