Secondary Battery Module

Abstract

To prevent a secondary battery from being charged with an excessive charging current value due to deterioration of the secondary battery, to extend the life of the secondary battery, in view of the problem in which the secondary battery deteriorates as it repeats charging / discharging, causing a decrease in battery voltage and battery capacity, that is to say, to extend the life of the secondary battery by performing charging control while taking into account a degree of deterioration of the secondary battery.SOLUTION: When charging a secondary battery, a charging control circuit controls a preset current value. Furthermore, a charging current control circuit (to be concrete, a circuit including an error amplifier) of a protection circuit determines a current value that flows to the secondary battery. That is, a current value that flows to the secondary battery is controlled by both the charging control circuit and a charging current control circuit being a part of the protection circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, a manufacture, or a composition of matter. Another embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Another embodiment of the present invention relates to a vehicle or an electronic device for a vehicle. In particular, the present invention relates to a protection circuit for a secondary battery, a charging control method for a secondary battery, an abnormality detection system for a secondary battery, and an electronic device having a secondary battery.

[0002] In this specification, the term "power storage device" refers to elements and devices in general that have a power storage function, including, for example, secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, all-solid-state batteries, and electric double layer capacitors. [Background technology]

[0003] In recent years, there has been active development of various types of power storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. Demand for high-power, high-energy-density lithium-ion secondary batteries, in particular, has rapidly expanded alongside the development of the semiconductor industry, and they are now essential to the modern information society as a rechargeable energy source, thanks to their high output and high energy density, and are used in a variety of applications, including mobile phones, smartphones, tablets, and notebook computers, as well as portable music players, digital cameras, medical devices, and next-generation clean-energy vehicles, such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs).

[0004] In portable information terminals, electric vehicles, etc., multiple secondary batteries are connected in series or parallel and equipped with a protection circuit (also called a protection IC) to be used as a battery pack (also called a battery assembly). The protection IC is appropriately equipped with circuits to detect overcharge voltage, overdischarge voltage, charging overcurrent, discharge overcurrent, and short circuits.

[0005] A battery pack is a device in which multiple secondary batteries are housed inside a container (metal can, film exterior) along with a specified circuit to facilitate handling of the secondary batteries. The battery pack is equipped with an ECU (Electronic Control Unit) to manage its operating status.

[0006] Secondary batteries used in electric and hybrid vehicles deteriorate depending on the number of charges, depth of discharge, charging current, charging environment (temperature changes), etc. Deterioration also depends on how the user uses the battery, and factors such as the temperature during charging, frequency of quick charging, amount of charge by regenerative braking, and timing of charging by regenerative braking may also affect the deterioration.

[0007] Although secondary batteries gradually deteriorate with repeated use, they are still being charged at the same current as before the deterioration. Conventionally, when the remaining charge of a secondary battery is low, CC charging is first performed, and once a predetermined voltage is reached, the charging is switched to CV charging.

[0008] Patent Document 1 discloses a coulomb counter including a transistor using an oxide semiconductor for measuring the capacity of a secondary battery. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent Publication No. 2014 / 0184314 Summary of the Invention [Problem to be solved by the invention]

[0010] Secondary batteries installed in portable information terminals and other devices face challenges such as preventing deterioration, providing long-term power supply, miniaturization, and low cost.

[0011] Conventionally, protection ICs have been implemented with simple circuit configurations without fully resolving these issues. Conventional protection ICs often detect uniquely determined overcharge voltages (currents) and overdischarge voltages (currents), and only control the passage or blocking of battery charge and discharge currents. Therefore, one of the objectives of this specification is to provide a control circuit that enables precise charge control of voltage and current.

[0012] Furthermore, secondary batteries suffer from degradation over repeated charge and discharge, resulting in a decrease in battery voltage and capacity. One of the objectives is to prevent secondary batteries from being charged with an excessive charging current due to their degradation, thereby extending their lifespan.

[0013] Another object of the present invention is to extend the life of the secondary battery by controlling charging in consideration of the degree of deterioration of the secondary battery.

[0014] Another objective is to ensure safety by detecting abnormalities in the secondary battery, for example, by detecting phenomena that reduce the safety of the secondary battery at an early stage, and warning the user or changing the charging conditions of the secondary battery. [Means for solving the problem]

[0015] A protection circuit is realized that has at least the function of detecting the degree of deterioration of a secondary battery and the function of adjusting the current flowing through the secondary battery. This protection circuit makes it possible to arbitrarily vary the amount of current during charging, allowing charging to be performed under detailed conditions without significantly increasing the circuit size.

[0016] When charging a secondary battery, a charging control circuit controls a preset current value, and a charging current control circuit (specifically, a circuit including an error amplifier) ​​in the protection circuit determines the current value flowing through the secondary battery. In other words, the current value flowing through the secondary battery is controlled by both the charging control circuit and the charging current control circuit, which is part of the protection circuit. The error amplifier, also known as an error amplifier, is an operational amplifier that outputs a voltage obtained by amplifying the voltage difference between two input terminals.

[0017] One of the configurations of the invention disclosed in this specification is a protection circuit having a charge control transistor connected in series with a discharge control transistor and an error amplifier, in which a first input terminal that receives a reference voltage of the error amplifier is electrically connected to a secondary battery, and a second input terminal that receives a feedback signal of the error amplifier is electrically connected to a wiring that connects the resistor and the discharge control transistor.

[0018] The present invention also provides a secondary battery module in which a protection circuit is provided for a secondary battery, the secondary battery module comprising at least a secondary battery, an overcharge detection circuit electrically connected to the secondary battery, an overdischarge detection circuit electrically connected to the secondary battery, a discharge control transistor electrically connected to the secondary battery, and a charge control transistor connected in series with the transistor, the gate of the charge control transistor being connected to the output terminal of an error amplifier, the output terminal of the error amplifier being electrically connected to the overcharge detection circuit, the gate of the discharge control transistor being electrically connected to the overdischarge detection circuit, a resistor being present between the secondary battery and the discharge control transistor, a first input terminal receiving a reference voltage of the error amplifier being electrically connected to the secondary battery, and a second input terminal receiving a feedback signal of the error amplifier being electrically connected to wiring connecting the resistor and the discharge control transistor.

[0019] In the above configuration, the charging current value set in the error amplifier is controlled according to the voltage of the DA converter in the main control circuit. The main control circuit constitutes part of the protection circuit and can be implemented using a microcomputer. The main control circuit can also be implemented using a normally-off CPU (Noff-CPU). Note that a normally-off CPU is an integrated circuit including a normally-off transistor that is in a non-conducting state (also referred to as an off state) even when the gate voltage is 0 V. A normally-off transistor can be implemented by using an oxide semiconductor for a semiconductor layer.

[0020] In the above configuration, the protection circuit may further include a comparator, a delay detection logic circuit, an oscillator circuit, a fuel gauge circuit, and a temperature detection and calculation circuit.

[0021] Conventionally, only the charge control circuit controls charging of a secondary battery module in which a protection circuit is provided for the secondary battery. Therefore, there is a possibility that users of devices powered by secondary batteries may control charging in a way that leads to deterioration of the secondary battery.

[0022] The charge control circuit uses two charging methods, specifically constant current charging and constant voltage charging, for CCCV charging, i.e., it initially performs constant current charging, switches at a certain voltage value, and then performs constant voltage charging. The charge control circuit also has the function of detecting the voltage of the secondary battery and controlling the power transistor (also called power MOS) to stop charging so that it does not exceed a certain maximum voltage value. Traditionally, power MOS has been used as a battery disconnection switch.

[0023] One aspect of the present invention is that the power MOS is not only used as a battery disconnection switch, but also as a charge current control circuit (specifically, a circuit including an error amplifier) ​​that determines the value of the current flowing to the secondary battery.

[0024] Silicon is primarily used for power devices such as power MOS, and N-channel MOSFETs and P-channel MOSFETs can be constructed using other materials such as SiC and GaN. Oxide semiconductor materials containing In, Ga, and Zn can also be used.

[0025] Furthermore, when an oxide semiconductor material is used for the power MOS, the current value flowing through the secondary battery can be controlled in an analog manner.

[0026] A circuit for controlling charging or a battery control system having 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.

[0027] Furthermore, the charging control circuit can set a predetermined threshold current and detect sudden abnormalities, specifically micro-shorts, based on the detected current value. When a micro-short occurs, the internal resistance decreases, so the amount of current flowing through a healthy secondary battery becomes relatively small, and a large current flows through a secondary battery with an abnormality, which is dangerous. The charging control circuit maintains a controlled current value and can also monitor the current value. By detecting micro-shorts and other abnormalities, secondary battery abnormalities can be detected early.

[0028] A micro-short circuit refers to a tiny short circuit within a secondary battery that does not short the positive and negative electrodes of the secondary battery to the point that charging and discharging is impossible, but rather refers to a phenomenon in which short-circuit current flows for a short period of time at the tiny short-circuited part.The cause of a micro-short circuit is thought to be that deterioration occurs due to repeated charging and discharging, and metal elements such as lithium and cobalt precipitate inside the battery.As the precipitate grows, local current concentration occurs in parts of the positive electrode and negative electrode, causing parts of the separator to stop functioning or generating by-products.

[0029] Figure 14 shows an example of a charging curve that suggests a micro-short circuit during charging. The horizontal axis of Figure 14 is the charge capacity Cb of the secondary battery, and the vertical axis is the voltage Vb of the secondary battery. A micro-short circuit is suggested in the area circled by the dashed line. [Effects of the Invention]

[0030] By performing charge control that adjusts the charge current while monitoring the degree of deterioration of the secondary battery, the overall life of the charge control system can be extended.

[0031] Furthermore, by detecting micro-shorts and the like, it is possible to detect abnormalities in the secondary battery at an early stage, and to change to safe charging conditions or stop charging. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a block diagram showing one embodiment of the present invention. [Figure 2] FIG. 2 is an example of a circuit diagram illustrating one embodiment of the present invention. [Figure 3] 3A, 3B, and 3C are diagrams illustrating a method for charging a secondary battery. [Figure 4] 4A, 4B, and 4C are diagrams illustrating a method for charging a secondary battery. [Figure 5] 5A and 5B show the charge curve and discharge curve of the secondary battery. [Figure 6] 6A, 6B, and 6C are diagrams illustrating a coin-type secondary battery. [Figure 7] 7A, 7B, 7C, and 7D are diagrams illustrating a cylindrical secondary battery. [Figure 8] 8A and 8B are diagrams illustrating an example of a secondary battery. [Figure 9] 9A, 9B, and 9C are diagrams illustrating examples of secondary batteries. [Figure 10] 10A, 10B, and 10C are diagrams illustrating a laminated secondary battery. [Figure 11]11A and 11B are diagrams illustrating a laminated secondary battery. [Figure 12] 12A, 12B, 12C, 12D, and 12E illustrate examples of small-sized electronic devices and vehicles including a secondary battery module of one embodiment of the present invention. [Figure 13] 13A, 13B, and 13C are diagrams illustrating examples of a vehicle and a house including a secondary battery module according to one embodiment of the present invention. [Figure 14] FIG. 14 is a diagram illustrating a charging curve. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, embodiments of the present invention 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 modifications can be made to the embodiments and details. Furthermore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0034] (Embodiment 1) A protection circuit 13 according to this embodiment will be described with reference to FIG.

[0035] In this embodiment, an example is shown in which the protection circuit 13 is electrically connected to a secondary battery as one protection IC. An example is shown in which a secondary battery module in which a protection IC is mounted on a secondary battery is installed as a main power source in a portable information terminal or the like.

[0036] A charge control circuit is connected to the secondary battery, and the charge control circuit has the function of detecting the voltage of the secondary battery and controlling the power MOS 12 to stop charging so that the voltage does not exceed a certain maximum voltage value.

[0037] The power MOS 12 is composed of two transistors, a charge control transistor and a discharge control transistor, connected in series. In this embodiment, the power MOS 12 and the protection circuit 13 are separate ICs. The overcharge detection circuit 15 and the gate of the charge control transistor are electrically connected, and when overcharge is detected, a gate voltage is applied to turn the charge control transistor off, thereby cutting off the current. The overdischarge detection circuit 17 and the gate of the discharge control transistor are electrically connected, and when overdischarge is detected, a gate voltage is applied to turn the discharge control transistor off, thereby cutting off the current.

[0038] The main control circuit 16 can also be considered a circuit board on which a microcomputer including a CPU (Central Processing Unit), memory, an AD converter, a DA converter, etc. is mounted. The main control circuit 16 can estimate the degree of deterioration of the secondary battery during charging. Furthermore, if a normally-off CPU is used as the main control circuit 16, it can be kept off except when charging, minimizing power consumption.

[0039] The main control circuit 16 monitors the current, voltage, temperature, etc. of the secondary battery and can estimate the degree of battery deterioration using a battery model, etc. For example, it estimates the internal state of the battery (internal resistance, SOC, etc.) using a regression model, such as a Kalman filter, and estimates the degree of battery deterioration from the estimated internal resistance value, etc. It calculates a charging current value according to the degree of deterioration and the internal state (internal resistance, SOC, temperature, etc.) and sets this value in the charging current control circuit 18.

[0040] The Kalman filter is a type of infinite impulse response filter. Multiple regression analysis is a type of multivariate analysis in which multiple independent variables are used in regression analysis. Examples of multiple regression analysis include the least squares method. While regression analysis requires a large number of time series of observed values, the Kalman filter has the advantage of being able to sequentially obtain optimal correction coefficients as long as a certain amount of data has been accumulated. The Kalman filter can also be applied to non-stationary time series.

[0041] A nonlinear Kalman filter (specifically, an unscented Kalman filter (UKF)) can be used to estimate the internal resistance and state of charge (SOC) of a secondary battery. An extended Kalman filter (EKF) can also be used.

[0042] The internal resistance and SOC of the secondary battery can be estimated using a Kalman filter. When estimating the internal resistance and SOC of the secondary battery, the post-state estimated value can be used as the output.

[0043] The charging current control circuit 18 is not particularly limited, but an error amplifier or the like can be used. The error amplifier receives a reference voltage Vref input to a non-inverting terminal and a feedback voltage Vfb input to an inverting terminal. The power supply voltage Vdd of the error amplifier is generated by, for example, the CPU of the main control circuit 16.

[0044] The charge current control circuit 18 is connected to the gate of one of the transistors of the power MOS 12, i.e., the transistor for the charge control circuit, and can adjust the amount of current flowing to the secondary battery by adjusting the gate voltage applied to that gate. This control method of adjusting the amount of current flowing to the secondary battery using the power MOS 12 is also called analog control of the power MOS 12.

[0045] The configuration shown in Figure 1 makes it possible to realize a secondary battery control system that automatically controls the amount of current during charging according to the degree of deterioration of the secondary battery. Note that "automatic control" here refers to automatic control without using software pre-stored or downloaded to the mobile information terminal's main memory or flash memory. Control using software to control the secondary battery requires securing memory capacity to run the software, which strains the mobile information terminal's functionality and may slow down the processing speed when the user performs other tasks while the mobile information terminal is charging. Using flash memory, there is a risk of high power consumption due to the need to rewrite data in the flash memory according to deterioration of the secondary battery and maintain the written data values.

[0046] The charge control circuit 14 may be mounted on the main board, or may be provided as a separate IC or microcomputer. The charge control circuit 14 is designed to charge under predetermined charging conditions according to the charge and discharge characteristics of the connected secondary battery. Even if the secondary battery deteriorates, the charging conditions are controlled by a system including the protection circuit 13 without any changes to the charge control circuit 14. By using a system including the protection circuit 13, it is possible to control the charging current according to the deterioration of the secondary battery when it has deteriorated to a certain extent.

[0047] Furthermore, the power MOS 12 can be mounted on the same substrate as the protection circuit 13 to form a single protection IC. Alternatively, a hybrid device in which an oxide semiconductor is used as the semiconductor layer of the power MOS 12 and is stacked or mixed on a Si LSI may be used as the protection IC.

[0048] Also, the resistor 11 and the protection circuit 13 can be mounted on the same substrate as one protection IC.

[0049] (Embodiment 2) In this embodiment, an example of a protection circuit is shown in FIG.

[0050] The protection circuit shown in FIG. 2 has a VC terminal and a VSS terminal.

[0051] The VC terminal is electrically connected to one terminal of the secondary battery, and is also connected to an overcharge detection circuit 25 and an overdischarge detection circuit 27 .

[0052] The overcharge detection circuit 25 includes at least a hysteresis comparator and a transistor whose gate is electrically connected to the output terminal of the hysteresis comparator.

[0053] The over-discharge detection circuit 27 is configured to include at least a hysteresis comparator. The hysteresis comparator is a circuit characterized by having two threshold values ​​for comparing potentials.

[0054] The VSS terminal is connected in series with a power MOS 22 and a resistor 21, and is electrically connected to the other terminal of the secondary battery.

[0055] In this embodiment, an example is shown in which the charging current control circuit is configured with an error amplifier 28. The error amplifier 28 receives a reference voltage Vref input to a non-inverting terminal and a feedback voltage Vfb input to an inverting terminal. The power supply voltage Vdd of the error amplifier 28 is generated, for example, by the CPU of the main control circuit 26. The output of the error amplifier 28 is connected to the gate of the transistor for controlling charging of the power MOS 22.

[0056] The main control circuit 26 is composed of a CPU, memory (RAM (Random Access Memory), ROM, flash memory, etc.), an AD converter, and a DA converter. The AD converter measures the battery voltage, current, and temperature, and the CPU estimates (calculates) the battery's deterioration level and calculates the charging current value according to the deterioration level and internal state (internal resistance, SOC, temperature, etc.). Instead of a CPU, the main control circuit 26 may be implemented as a single IC chip integrated with a GPU (Graphics Processing Unit), PMU (Power Management Unit), etc. Alternatively, the main control circuit 26 may be implemented as an FPGA (Field-Programmable Gate Array) device.

[0057] The main control circuit 26 controls the error amplifier 28 to prevent the charging current from exceeding a set current value. The error amplifier 28 controls the charging current according to the output voltage of the DA converter of the main control circuit 26.

[0058] For example, if the protection circuit shown in FIG. 2 is used, when the secondary battery has deteriorated to a certain extent, the charging current can be controlled in accordance with the deterioration.

[0059] During the initial CC charging after charging begins, if the current that the charge control circuit connected to terminal VC or terminal VSS attempts to pass to the secondary battery approaches the current value set by the main control circuit 26, the current will converge to the set value through feedback control by the charge current control circuit (error amplifier 28), the voltage will rise sharply, and the charge control circuit will enter CV charging mode. Note that the transition to CV charging before the voltage reaches the point at which charging switches from CC charging to CV charging is referred to as CV charging mode. CV charging mode can be arbitrarily varied by the protection circuit, making intermittent charging possible.

[0060] CC charging and CV charging will be explained below.

[0061] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0062] First, we will explain CC charging as one of the charging methods. CC charging is a charging method in which a constant current flows through the secondary battery throughout the entire charging period, and charging stops when a predetermined voltage is reached. The secondary battery is assumed to be an equivalent circuit with an internal resistance R and a secondary battery capacity C, as shown in Figure 3A. In this case, the secondary battery voltage V B is the voltage V across the internal resistance R R and the voltage V applied to the secondary battery capacity C C It is the sum of.

[0063] During CC charging, as shown in Figure 3A, the switch is turned on and a constant current I flows through the secondary battery. During this time, the current I is constant, so V R According to Ohm's law, the voltage V applied to the internal resistance R is R On the other hand, the voltage V applied to the secondary battery capacity C is also constant. C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0064] and the secondary battery voltage V B When the current reaches a predetermined voltage, for example, 4.3 V, charging stops. When CC charging stops, the switch turns off and the current I becomes 0, as shown in Figure 3B. Therefore, the voltage V across the internal resistance R R becomes 0V. Therefore, the secondary battery voltage V B is decreasing.

[0065] The secondary battery voltage V during CC charging and after CC charging is stopped B An example of the charging current is shown in Figure 3C. The secondary battery voltage V B However, it is shown that the value decreases slightly after CC charging is stopped.

[0066] Next, we will explain CCCV charging, which is a different charging method from the above. CCCV charging is a charging method in which the battery is first charged to a predetermined voltage using CC charging, and then the battery is charged using CV charging until the current decreases, specifically until the current reaches the cut-off value.

[0067] During CC charging, as shown in Figure 4A, the constant current power supply is switched on and the constant voltage power supply is switched off, and a constant current I flows through the secondary battery. During this time, the current I is constant, so V R According to Ohm's law, the voltage V applied to the internal resistance R is R On the other hand, the voltage V applied to the secondary battery capacity C is also constant. C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0068] and the secondary battery voltage V B When the secondary battery voltage V reaches a predetermined voltage, for example, 4.3 V, the charging mode is switched from CC to CV. During CV charging, as shown in FIG. 4B, the constant voltage power supply is switched on and the constant current power supply is switched off, and the secondary battery voltage V B On the other hand, the voltage V applied to the secondary battery capacity C is constant. C V increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R R The voltage V across the internal resistance R decreases over time. R As becomes smaller, V R According to Ohm's law, the current I flowing through the secondary battery also becomes smaller.

[0069] When the current I flowing through the secondary battery reaches a predetermined value, for example, a current equivalent to 0.01 C, charging is stopped. When CCCV charging is stopped, all switches are turned off and the current I becomes 0, as shown in Figure 4C. Therefore, the voltage V across the internal resistance R R However, the voltage V applied to the internal resistance R due to CV charging Ris small enough that even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends at all.

[0070] The secondary battery voltage V during CCCV charging and after CCCV charging is stopped B An example of the charge current and the secondary battery voltage V B It is shown that there is almost no descent.

[0071] Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is a method in which a constant current flows from the secondary battery throughout the entire discharge period, and the secondary battery voltage V B This is a discharge method in which discharge stops when the voltage reaches a predetermined value, for example, 2.5V.

[0072] The secondary battery voltage V during CC discharge B An example of the discharge current and the secondary battery voltage V B is shown to be descending.

[0073] Next, we will explain the discharge rate and charge rate. The discharge rate is the relative ratio of the current during discharge to the battery capacity, and is expressed in units of C. For a battery with a rated capacity of X (Ah), the current equivalent to 1C is X (A). When a battery is discharged at a current of 2X (A), it is said to have been discharged at 2C, and when a battery is discharged at a current of X / 5 (A), it is said to have been discharged at 0.2C. The same is true for the charge rate; when a battery is charged at a current of 2X (A), it is said to have been charged at 2C, and when a battery is charged at a current of X / 5 (A), it is said to have been charged at 0.2C.

[0074] This embodiment mode can be freely combined with Embodiment Mode 1.

[0075] (Embodiment 3) An example of a coin-type secondary battery will be described below: Fig. 6A is an external view of a coin-type (single-layer flat) secondary battery, and Fig. 6B is a cross-sectional view thereof.

[0076] In a 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.

[0077] 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.

[0078] Positive electrode can 301 and 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, it is preferable to coat them with nickel, aluminum, or the like. Positive electrode can 301 is electrically connected to positive electrode 304, and negative electrode can 302 is electrically connected to negative electrode 307.

[0079] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with an electrolyte, and as shown in FIG. 6B, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order with the positive electrode can 301 facing downwards, and the positive electrode can 301 and the negative electrode can 302 are crimped together via gasket 303 to produce a coin-type secondary battery 300.

[0080] Here, we will use Figure 6C to explain the flow of current during charging of a secondary battery. When a lithium-based secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In lithium-based secondary batteries, the anode (positive electrode) and cathode (negative electrode) are interchanged during charging and discharging, and the oxidation and reduction reactions are alternated. Therefore, the electrode with the higher reaction potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. Therefore, in this specification, whether during charging, discharging, when a reverse pulse current is applied, or when a charging current is applied, the positive electrode will be called the "positive electrode" or "+ electrode," and the negative electrode will be called the "negative electrode" or "- electrode." Using the terms anode (positive electrode) and cathode (negative electrode), which are related to oxidation and reduction reactions, could lead to confusion because their meanings are reversed during charging and discharging. Therefore, the terms anode (positive electrode) and cathode (negative electrode) will not be used in this specification. If the terms anode and cathode are used, it should be clearly stated whether they are used during charging or discharging, and whether they correspond to the positive or negative pole.

[0081] A charger is connected to the two terminals shown in Fig. 6C to charge the secondary battery 300. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0082] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to Fig. 7. As shown in Fig. 7A, a cylindrical secondary battery 600 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.

[0083] FIG. 7B is a schematic diagram showing the cross section of a cylindrical secondary battery. Inside a hollow cylindrical battery can 602, a battery element is provided, 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 center pin. 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 that is corrosion-resistant to the electrolyte, such as nickel, aluminum, or titanium, or an alloy of these metals or alloys of these metals with other metals (e.g., stainless steel). Furthermore, a coating of nickel, aluminum, or the like is preferable 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 non-aqueous electrolyte may be the same as that used in coin-type secondary batteries.

[0084] Because the positive and negative electrodes used in cylindrical storage batteries are wound, it is preferable to form active materials on both sides of the current collector. 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 612, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 612 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistor whose resistance increases as the temperature rises, and the increased resistance limits the amount of current to prevent abnormal heat generation. Barium titanate (BaTiO3) based semiconductor ceramics or the like can be used for the PTC element.

[0085] 7C , a module 615 may be configured by sandwiching a plurality of secondary batteries 600 between conductive plates 613 and 614. The plurality of secondary batteries 600 may be connected in parallel, in series, or in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted.

[0086] FIG. 7D is a top view of the module 615. For clarity, the conductive plate 613 is shown with a dotted line. As shown in FIG. 7D, the module 615 may have conductive wires 616 that electrically connect the multiple secondary batteries 600. A conductive plate can be superimposed on the conductive wires 616. A temperature control device 617 may also be provided between the multiple secondary batteries 600. When the secondary batteries 600 overheat, they can be cooled by the temperature control device 617, and when the secondary batteries 600 are too cold, they can be heated by the temperature control device 617. This makes the performance of the module 615 less susceptible to the influence of the outside air temperature. The heat medium in the temperature control device 617 is preferably insulating and non-flammable.

[0087] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0088] 8A and 8B are diagrams showing the external appearance of a secondary battery. The secondary battery has a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. 8B, the secondary battery has a terminal 951, a terminal 952, an antenna 914, and an antenna 915.

[0089] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951, a terminal 952, an antenna 914, an antenna 915, and the circuit 912. Note that a plurality of terminals 911 may be provided, and each of the plurality of terminals 911 may be used as a control signal input terminal, a power supply terminal, a temperature detection terminal (also referred to as a T terminal), or the like.

[0090] Circuit 912 is a protection circuit that includes an overcharge detection circuit, an overdischarge detection circuit, or a power MOS. Circuit board 900 on which the protection circuit is mounted may also be provided with a diode, resistor, thermistor (temperature sensor, etc.). Circuit 912 is designed to detect the resistance value of the thermistor, which changes with temperature, and to stop charging when the resistance value exceeds a threshold value (charging temperature range).

[0091] The circuit 912 may be provided on the back surface of the circuit board 900. The antennas 914 and 915 are not limited to being coil-shaped, and may be, for example, wire-shaped or plate-shaped. Also, 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 be used. Alternatively, the antenna 914 or 915 may be a flat-plate conductor. This flat-plate conductor can function as one of the conductors for electric field coupling. In other words, the antenna 914 or 915 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.

[0092] The line width of the antenna 914 is preferably larger than the line width of the antenna 915. This allows the amount of power received by the antenna 914 to be increased.

[0093] The secondary battery has a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has a function of preventing, for example, the influence of the secondary battery 913 on an electromagnetic field. The layer 916 can be made of, for example, a magnetic material.

[0094] The structure of the secondary battery is not limited to that shown in FIG.

[0095] An example of the structure of the secondary battery 913 will be described with reference to FIG.

[0096] A laminated secondary battery 980 will be described using Fig. 9. The laminated secondary battery 980 has a wound body 993 shown in Fig. 9A. The wound body 993 has a negative electrode 994, a positive electrode 995, and a separator 996. The wound body 993 is formed by stacking the negative electrode 994 and the positive electrode 995 on top of each other with the separator 996 sandwiched therebetween, and winding the laminated sheet.

[0097] As shown in Fig. 9B, a film 981 serving as an exterior body and a film 982 having a recess are bonded together by thermocompression or the like to form a space, and the above-described wound body 993 is stored in the space, thereby producing a secondary battery 980 as shown in Fig. 9C. The wound body 993 has lead electrodes 997 and 998, and is impregnated with an electrolyte solution between the film 981 and the film 982 having a recess.

[0098] For example, a metal material such as aluminum or a resin material can be used for film 981 and film 982 having recesses. If a resin material is used as the material for film 981 and film 982 having recesses, film 981 and film 982 having recesses can be deformed when an external force is applied, and a flexible storage battery can be produced.

[0099] Although FIGS. 9B and 9C show an example in which two films are used for sealing, a space may be formed by folding one film, and the wound body 993 described above may be housed in that space.

[0100] Furthermore, although Figure 9 describes an example of a secondary battery 980 having a wound body in a space formed by a film that serves as an outer casing, it may also be a secondary battery having multiple positive electrodes, separators, and negative electrodes in a space formed by a film that serves as an outer casing, as shown in Figure 10, for example.

[0101] 10A shows a positive electrode having an L-shaped positive electrode current collector 701 and a positive electrode active material layer 702. The positive electrode also has a region where the positive electrode current collector 701 is partially exposed (hereinafter referred to as a tab region). FIG. 10B shows a negative electrode having an L-shaped negative electrode current collector 704 and a negative electrode active material layer 705. The negative electrode has a region where the negative electrode current collector 704 is partially exposed, i.e., a tab region.

[0102] 10C shows a perspective view of four layers of positive electrodes 703 and four layers of negative electrodes 706. For simplicity, the separator provided between the positive electrodes 703 and the negative electrodes 706 is shown by dotted lines in FIG.

[0103] 11A includes a positive electrode 703 having an L-shaped positive electrode current collector 701 and a positive electrode active material layer 702, a negative electrode 706 having an L-shaped negative electrode current collector 704 and a negative electrode active material layer 705, a separator 707, an electrolyte 708, and an exterior body 709. The separator 707 is disposed between the positive electrode 703 and the negative electrode 706 provided within the exterior body 709. The interior of the exterior body 709 is filled with the electrolyte 708.

[0104] 11A, the positive electrode current collector 701 and the negative electrode current collector 704 also serve as terminals for electrical contact with the outside. Therefore, the positive electrode current collector 701 and the negative electrode current collector 704 may be arranged so as to be partially exposed to the outside from the exterior body 709. Alternatively, the positive electrode current collector 701 and the negative electrode current collector 704 may not be exposed to the outside from the exterior body 709, but may be exposed to the outside by using a lead electrode and ultrasonically bonding the lead electrode to the positive electrode current collector 701 or the negative electrode current collector 704.

[0105] In a laminated secondary battery, the exterior body 709 can be a three-layer laminate film having a highly flexible metal thin film made of aluminum, stainless steel, copper, nickel, or the like on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and further having an insulating synthetic resin film made of polyamide-based resin, polyester-based resin, or the like on the metal thin film as the outer surface of the exterior body.

[0106] An example of the cross-sectional structure of a laminated secondary battery is shown in Fig. 11B. Although omitted in Fig. 11A for simplicity, the battery is actually made up of multiple electrode layers.

[0107] In FIG. 11B, the number of electrode layers is 16 as an example. FIG. 11B shows a structure with a total of 16 layers, including eight layers of negative electrode current collectors 704 and eight layers of positive electrode current collectors 701. Note that FIG. 11B shows a cross section of the positive electrode lead-out portion cut along the chain line in FIG. 11A, in which eight layers of negative electrode current collectors 704 are ultrasonically bonded. Of course, the number of electrode layers is not limited to 16 and may be more or less. When the number of electrode layers is large, a secondary battery with a larger capacity can be obtained. Furthermore, when the number of electrode layers is small, the battery can be made thinner.

[0108] (Fourth embodiment) In this embodiment, an example in which the secondary battery module described in the previous embodiment is mounted on an electronic device will be described with reference to Figures 12 and 13. The secondary battery module includes at least a secondary battery and a protection circuit.

[0109] First, an example in which a secondary battery module according to one embodiment of the present invention is mounted on a small electronic device will be described with reference to FIGS. 12A to 12C.

[0110] 12A shows an example of a mobile phone. Mobile phone 2100 includes a display unit 2102 built into housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, and a microphone 2106. Mobile phone 2100 also includes a secondary battery module 2107.

[0111] 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.

[0112] 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 built into the mobile phone 2100.

[0113] 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.

[0114] The mobile phone 2100 also has an external connection port 2104, which allows direct data exchange with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Charging may also be performed by wireless power supply without using the external connection port 2104.

[0115] The mobile phone 2100 preferably has a sensor, such as a fingerprint sensor, a pulse sensor, a body temperature sensor, or other human body sensor, a touch sensor, a pressure sensor, or an acceleration sensor.

[0116] FIG. 12B is a perspective view of a device also known as a tobacco-holding smoking device (electronic cigarette). In FIG. 12B, electronic cigarette 2200 includes heating element 2201 and secondary battery module 2204 that supplies power to heating element 2201. When stick 2202 is inserted into electronic cigarette 2200, stick 2202 is heated by heating element 2201. To enhance safety, a protection circuit that prevents overcharging and over-discharging of secondary battery module 2204 may be electrically connected to secondary battery module 2204. Secondary battery module 2204 shown in FIG. 12B has external terminals that enable connection to a charging device. Because secondary battery module 2204 forms the tip when held, it is desirable that its total length be short and its weight be light. Because the secondary battery module of one embodiment of the present invention is highly safe, a compact and lightweight electronic cigarette 2200 that can be used safely for long periods of time can be provided.

[0117] 12C shows unmanned aerial vehicle 2300 having multiple rotors 2302. Unmanned aerial vehicle 2300 includes secondary battery module 2301 according to one embodiment of the present invention, camera 2303, and an antenna (not shown). Unmanned aerial vehicle 2300 can be remotely controlled via the antenna. The secondary battery module according to one embodiment of the present invention is highly safe and can be used safely for a long period of time, making it suitable as a secondary battery module to be installed in unmanned aerial vehicle 2300.

[0118] Next, an example in which the secondary battery module of one embodiment of the present invention is mounted on a vehicle will be described with reference to FIGS. 12D, 12E, and 13. FIG.

[0119] 12D shows an electric motorcycle 2400 using a secondary battery module according to one embodiment of the present invention. The electric motorcycle 2400 includes a secondary battery module 2401 according to one embodiment of the present invention, a display unit 2402, and a handlebar 2403. The secondary battery module 2401 can supply electricity to a motor that serves as power. The display unit 2402 can display the remaining charge of the secondary battery module 2401, the speed of the electric motorcycle 2400, its horizontal state, and the like.

[0120] 12E shows an example of an electric bicycle using the secondary battery module of one embodiment of the present invention. The electric bicycle 2500 includes a battery pack 2502. The battery pack 2502 includes the secondary battery module of one embodiment of the present invention.

[0121] Battery pack 2502 can supply electricity to a motor that assists the rider. Battery pack 2502 can be detached from electric bicycle 2500 and carried around. Battery pack 2502 and electric bicycle 2500 may also have a display unit that can display the remaining battery power, etc.

[0122] As shown in FIG. 13A, a secondary battery module 2602 including a plurality of secondary batteries 2601 of one embodiment of the present invention may be mounted in a hybrid electric vehicle (HEV), an electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV), or other electronic devices.

[0123] FIG. 13B shows an example of a vehicle equipped with a secondary battery module 2602. The vehicle 2603 is an electric vehicle that uses an electric motor as a power source for traveling. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor or an engine as a power source for traveling. The vehicle 2603 using an electric motor has multiple ECUs (Electronic Control Units), and the ECUs perform engine control and the like. The ECUs include a microcomputer. The ECUs are connected to a Controller Area Network (CAN) provided in the electric vehicle. CAN is one of the serial communication standards used for in-vehicle LANs. By using one embodiment of the present invention, a vehicle with high safety and a long cruising range can be realized.

[0124] The secondary battery can not only drive an electric motor (not shown) but also supply power to light-emitting devices such as headlights, room lights, etc. The secondary battery can also supply power to display devices and semiconductor devices such as a speedometer, a tachometer, and a navigation system of the vehicle 2603.

[0125] The vehicle 2603 can charge the secondary battery of the secondary battery module 2602 by receiving power supply from an external charging facility using a plug-in system, a contactless power supply system, or the like.

[0126] FIG. 13C shows a state in which a vehicle 2603 is being charged via a cable from a ground-mounted charging device 2604. The charging method and connector specifications may be appropriately determined using a predetermined method such as CHAdeMO (registered trademark) or Combo. For example, plug-in technology can be used to charge a secondary battery module 2602 mounted on the vehicle 2603 using external power supply. Charging can be performed by converting AC power to DC power via a converter such as an AC-DC converter. The charging device 2604 may be installed in a home as shown in FIG. 13C, or may be a charging station installed in a commercial facility.

[0127] Although not shown, a power receiving device can be mounted on a vehicle and power can be supplied contactlessly from a ground 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 vehicles. Furthermore, a solar cell 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.

[0128] 13C includes a power storage system 2612 including a secondary battery module of one embodiment of the present invention, and a solar panel 2610. The power storage system 2612 is electrically connected to the solar panel 2610 via wiring 2611 or the like. The power storage system 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 system 2612. The power stored in the power storage system 2612 can be charged to a secondary battery module 2602 included in a vehicle 2603 via the charging device 2604.

[0129] The power stored in the power storage system 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 system 2612 of one embodiment of the present invention can be used as an uninterruptible power supply, enabling the use of electronic devices.

[0130] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Explanation of symbols]

[0131] 11: Resistor, 12: Power MOS, 13: Protection circuit, 14: Charge control circuit, 15: Overcharge detection circuit, 16: Main control circuit, 17: Overdischarge detection circuit, 18: Charging current control circuit, 21: Resistor, 22: Power MOS, 25: Overcharge detection circuit, 26: Main control circuit, 27: Overdischarge detection circuit, 28: Error amplifier, 300: Secondary battery, 301: Positive electrode can, 302: Negative electrode can, 303: Gasket, 304: Positive electrode, 305: Positive electrode current collector, 306: Positive electrode active material layer, 307: Negative electrode, 308: Negative electrode current collector, 309: Negative electrode active material layer, 310: Separator, 6 00: secondary battery, 601: positive electrode cap, 602: battery can, 603: positive electrode terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: insulating plate, 609: insulating plate, 611: PTC element, 612: safety valve mechanism, 613: conductive plate, 614: conductive plate, 615: module, 616: conducting wire, 617: temperature control device, 701: positive electrode current collector, 702: positive electrode active material layer, 703: positive electrode, 704: negative electrode current collector, 705: negative electrode active material layer, 706: negative electrode, 707: separator, 708: electrolyte, 709: exterior body, 900: circuit board Circuit board, 910: label, 911: terminal, 912: circuit, 913: secondary battery, 914: antenna, 915: antenna, 916: layer, 951: terminal, 952: terminal, 980: secondary battery, 981: film, 982: film, 993: wound body, 994: negative electrode, 995: positive electrode, 996: separator, 997: lead electrode, 998: lead electrode, 2100: mobile phone, 2101: housing, 2102: display unit, 2103: operation button, 2104: external connection port, 2105: speaker, 2106: microphone, 2107: secondary battery module 2200: electronic cigarette, 2201: heating element, 2202: stick, 2204: secondary battery module, 2300: unmanned aerial vehicle, 2301: secondary battery module, 2302: rotor, 2303: camera, 2400: electric motorcycle, 2401: secondary battery module, 2402: display unit, 2403: handle, 2500: electric bicycle, 2502: battery pack, 2601: secondary battery, 2602: secondary battery module, 2603: vehicle, 2604: charging device, 2610: solar panel, 2611: wiring, 2612: power storage system

Claims

1. A secondary battery; an overcharge detection circuit electrically connected to the secondary battery; an over-discharge detection circuit electrically connected to the secondary battery; a first transistor for discharge control electrically connected to the secondary battery; a second transistor for charge control connected in series with the first transistor; a resistor between the secondary battery and the first transistor; An error amplifier, a main control circuit having a third transistor, estimating an internal resistance and an SOC of the secondary battery using a Kalman filter, and estimating a deterioration level of the secondary battery; a gate of the second transistor is connected to an output terminal of the error amplifier; an output terminal of the error amplifier is electrically connected to the overcharge detection circuit; a gate of the first transistor electrically connected to the over-discharge detection circuit; a first input terminal for receiving a reference voltage of the error amplifier is electrically connected to the secondary battery; a second input terminal that receives a feedback signal from the error amplifier is electrically connected to a wiring that connects the resistor and the first transistor; A secondary battery module in which a charging current value set in the error amplifier is controlled in accordance with an output voltage of a DA converter of the main control circuit.

2. A secondary battery; an overcharge detection circuit electrically connected to the secondary battery; an over-discharge detection circuit electrically connected to the secondary battery; a first transistor for discharge control electrically connected to the secondary battery; a second transistor for charge control connected in series with the first transistor; a resistor between the secondary battery and the first transistor; An error amplifier, a main control circuit having a third transistor and estimating an internal resistance and an SOC of the secondary battery using a Kalman filter; a gate of the second transistor is connected to an output terminal of the error amplifier; an output terminal of the error amplifier is electrically connected to the overcharge detection circuit; a gate of the first transistor electrically connected to the over-discharge detection circuit; a first input terminal for receiving a reference voltage of the error amplifier is electrically connected to the secondary battery; a second input terminal that receives a feedback signal from the error amplifier is electrically connected to a wiring that connects the resistor and the first transistor; A secondary battery module in which a charging current value set in the error amplifier is controlled in accordance with an output voltage of a DA converter of the main control circuit.

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