Charging control system

Abstract

One aspect of the present invention provides a charging control system that is capable of effectively using regenerative electric power without wasting the regenerative electric power. Generated regenerative electric power is efficiently stored in a second secondary battery and then stored in a main first secondary battery. Charging from the second secondary battery to the first secondary battery is performed via a DC-DC converter. The charge state of the first secondary battery and the charge state of the second secondary battery are controlled. When the first secondary battery is close to full charge and is likely to deteriorate, it is possible to perform charging from the first secondary battery to the second secondary battery.

Description

Charging Control System

[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. One embodiment of the present invention relates to a power storage device including a secondary battery, a semiconductor device, a display device, a light-emitting device, a lighting device, an electronic device, or a manufacturing method thereof.

[0002] In this specification, the term "electronic device" refers to any device having a power storage device, and includes electro-optical devices having a power storage device, information terminal devices having a power storage device, and the like.

[0003] In this specification, the term "electricity storage device" refers to elements and devices in general that have an electricity storage function, including, for example, lithium ion secondary battery electricity storage devices (also called secondary batteries), lithium ion capacitors, and electric double layer capacitors.

[0004] In recent years, the development of various power storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries, has been actively pursued. Demand for high-power, high-energy-density lithium-ion secondary batteries has been rapidly expanding in conjunction with the development of portable information terminals, such as mobile phones, smartphones, and notebook computers, portable music players, digital cameras, medical devices, next-generation clean-energy automobiles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs), and the semiconductor industry. These batteries have become indispensable in the modern information society as a rechargeable energy source.

[0005] Furthermore, next-generation clean energy vehicles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs), are equipped with a motor (a DC motor or an AC motor) for driving, and are powered by a supply of power from lithium-ion secondary batteries.

[0006] Electric vehicles may be configured to perform so-called regenerative charging, in which the drive motor is used as a generator when the accelerator pedal is released, or when the accelerator pedal is released and the brakes are applied, and the generated electricity is charged into a secondary battery.

[0007] Among lithium-ion secondary batteries, secondary batteries using sulfur-containing materials as the positive electrode active material have attracted attention. Sulfur has a high theoretical capacity of approximately 1670 mAh / g and is known to be a promising positive electrode active material in terms of energy density.

[0008] Furthermore, materials containing elemental sulfur are abundant resources, so they have the advantage of being cheaper than rare metals such as cobalt.

[0009] For example, research is being conducted on sulfur-based secondary batteries using sulfur and graphene sponge (3DGS) (Non-Patent Document 1).

[0010] Chao Lin et al. , “A facile synthesis of three dimensional graphene sponge composited with sulfur nanoparticles for flexible Li-S cathodes”, Phys. Chem. Chem. Phys. ,2016,18,22146-22153

[0011] There are various methods for using regenerative charging, depending on the manufacturer or model of the electric vehicle. Regenerative charging cannot be performed anytime and anywhere, and is limited by a charging control circuit. For example, when the secondary battery is fully charged, charging control is often performed to stop regenerative charging to prevent overcharging.

[0012] Furthermore, when the motor is decelerated at a constant torque, the regenerative power takes on a sawtooth waveform, and even if the regenerative power increases suddenly depending on the driving conditions, charging control is often performed to limit the amount of regeneration to a constant value.

[0013] In this way, because charging control is performed, energy is not fully utilized. Therefore, one of the objectives is to provide a charging control system that can effectively utilize regenerative power without wasting it.

[0014] The secondary batteries disclosed in this specification are a plurality of different types of secondary batteries, in which a first secondary battery is used as a main battery and has a larger capacity than a second secondary battery used as a sub battery.

[0015] The secondary battery charging control system disclosed in this specification includes a first secondary battery, a second secondary battery made of a different material from the first secondary battery, a control circuit that controls the first secondary battery and the second secondary battery, a power generation device that performs regenerative power generation when the electric vehicle decelerates, an inverter and a first DC-DC converter between the power generation device and the second secondary battery, a first DC-DC converter and a second DC-DC converter between the first secondary battery and the second secondary battery, and third DC-DC converters between a charging inlet and the first secondary battery and between the charging inlet and the second secondary battery, and the control circuit charges the second secondary battery with power from the first secondary battery via the first and second DC-DC converters.

[0016] In the above configuration, the first secondary battery is a lithium-ion secondary battery containing sulfur, and the second secondary battery is a lithium-ion secondary battery with a cobalt-containing oxide as a positive electrode active material. Alternatively, the first secondary battery may be a lithium-ion secondary battery containing sulfur, and the second secondary battery may be a lithium-ion capacitor or an electric double layer capacitor. The second secondary battery is capable of rapid charging and discharging, can be used to absorb large power fluctuations, and can perform efficient regeneration.

[0017] When the first secondary battery is fully charged, the regenerated power is charged into the second secondary battery. By reducing the capacity of the first secondary battery, overcharging can be prevented and the life of the first secondary battery can be extended.

[0018] In the above configuration, the power generation device that generates regenerative power when the electric vehicle decelerates is also called a generator. The electric power regenerated by the power generation device that generates regenerative power when the electric vehicle decelerates is preferably generated by a motor generator that uses a driving motor.

[0019] In the above configuration, the first DC-DC converter can convert high-voltage power supplied from the motor generator into a predetermined low voltage and output (supply) it to the second secondary battery.

[0020] In the above configuration, the second DC-DC converter can convert the power supplied from the first secondary battery to a predetermined voltage and output (supply) it to the motor generator.

[0021] In the above configuration, the third DC-DC converter can convert high-voltage power supplied from the outside into a predetermined low voltage when a charging cable is connected to the charging inlet from the outside and output (supply) it to the first secondary battery.

[0022] In the above configuration, the control circuit can charge the first secondary battery with power from the second secondary battery via the third DC-DC converter. Rather than directly charging the first secondary battery with power generated by the power generation device (also called regenerative power), the control circuit charges the second secondary battery and then charges the first secondary battery with power from the second secondary battery via the third DC-DC converter, thereby making it possible to effectively utilize the regenerative power without wasting it.

[0023] In the above configuration, the control circuit includes at least a charge / discharge control circuit (also called a battery controller), which is also called an ECU (Electronic Control Unit).

[0024] Secondary batteries have various parameters. For example, the chargeable battery capacity (capacity value in a fully charged state, so-called full charge capacity (FCC)) varies depending on the positive electrode material or negative electrode material used. Different types of secondary batteries have different usable temperature ranges, output current values, output voltage values, or internal resistances. Furthermore, optimal charging conditions (typically, charge rate) or discharge conditions (typically, discharge rate) also vary depending on the type. Note that FCC (full charge capacity, also called total capacity) is the rated capacity at room temperature of 25°C.

[0025] In order to prevent deterioration of a secondary battery, it is desirable to charge it at an optimum charge rate and use it at an optimum discharge rate. The discharge rate and charge rate are controlled using a charge / discharge control circuit.

[0026] 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 1 C 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 applies to 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.

[0027] Lithium-ion secondary batteries are not set to use the full range of the design capacity (DC), i.e., the state of charge (SOC), which is the percentage of the remaining capacity (RC) of the battery to the fully charged capacity (FCC), from 0% to 100%. To prevent over-discharge, a margin of about 5% (or 10%) is provided from 0%. Also, to prevent over-charging, a margin of about 5% (or 10%) is provided from 100%. As a result, it is said that the battery is used within the range of 5% to 95% (or 10% to 90%) of the design capacity. In practice, the upper limit voltage V ｍａｘ and the lower limit voltage V ｍｉｎBy setting the voltage range, the battery can be used within the range of 5% to 95% (or 10% to 90%) of the design capacity.

[0028] Therefore, in this specification, a fully charged secondary battery refers to 90% or 95% of the designed capacity.

[0029] The charging control system allows the generated regenerative power to be efficiently stored in the second secondary battery and then stored in the main first secondary battery. Charging from the second secondary battery to the first secondary battery is performed via a DC-DC converter. The charging states of the first secondary battery and the second secondary battery are controlled, and when the first secondary battery is close to full charge and is likely to deteriorate, charging can be performed from the first secondary battery to the second secondary battery. The control circuit monitors the first secondary battery and the second secondary battery and adjusts the amount of power to be stored, thereby extending the life of the main first secondary battery.

[0030] FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a block diagram showing one embodiment of the present invention. FIG. 3 is a block diagram showing one embodiment of the present invention. FIG. 4 is a block diagram showing one embodiment of the present invention. FIG. 5A is a block diagram showing one embodiment of the present invention, and FIG. 5B is a perspective view of a module. FIG. 6A is a perspective view showing an example of a secondary battery, and FIG. 6B is a diagram illustrating the structure of FIG. 6A. FIGS. 7A and 7B are perspective views showing an example of an electric vehicle.

[0031] 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.

[0032] Embodiment 1 In this embodiment, a charging control system according to one embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, and 4. In this embodiment, an example of a charging control system mounted on an electric vehicle will be described.

[0033] The electric vehicle is equipped with a first secondary battery 301 as a main driving secondary battery, and has a sub-second secondary battery 311. The sub-second secondary battery 311 is a secondary battery mainly used to charge regenerative current, and has a smaller capacity than the large-capacity first secondary battery 301.

[0034] The large-capacity first secondary battery 301 can extract large amounts of power by configuring a battery pack having a plurality of secondary batteries. 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. In this embodiment, a secondary battery having a positive electrode using sulfur (also called a lithium-sulfur battery or Li-S battery) is used as the first secondary battery 301.

[0035] In secondary batteries that use a material containing elemental sulfur as a positive electrode active material, lithium metal is used as an example of a negative electrode active material. During discharge, lithium metal dissolves in the electrolyte at the negative electrode to become ions, which react with sulfur at the positive electrode to be oxidized, resulting in the formation of an intermediate reaction product, lithium polysulfide (Li ２ S ｎ (2<n<8)) and then lithium sulfide (Li ２ S).

[0036] Secondary batteries that use a material containing elemental sulfur as the positive electrode active material use a positive electrode in which a carbon material coated with a film of sulfur or a sulfur compound is applied to a positive electrode current collector. Because elemental sulfur is an insulator, it is preferable to attach sulfur to the carbon material or to partially apply a thin film. Examples of sulfur compounds (also called sulfides) include metal sulfides and sulfates. Examples of metal sulfides include lithium sulfide and polysulfides (also called polysulfides).

[0037] In addition, an electrolytic solution or solid electrolyte is provided between the positive electrode and the negative electrode. When a solid electrolyte is used, an all-solid-state battery can be formed. Since an all-solid-state battery does not require the use of an organic electrolyte, problems such as leakage or battery expansion caused by the organic electrolyte decomposing into gas can be solved. In addition, an ionic liquid can be used instead of an electrolytic solution. When an electrolytic solution or an ionic liquid is used, a separator is provided between the positive electrode and the negative electrode to prevent short circuits.

[0038] Secondary batteries that use a material containing elemental sulfur as a positive electrode active material are also called lithium-sulfur batteries, and are not limited to secondary batteries that use lithium metal for the negative electrode, but also include secondary batteries that use silicon or carbon materials for the negative electrode. Typical carbon materials used for the negative electrode include graphite, graphene, graphene oxide, reduced graphene oxide, and carbon nanotubes.

[0039] Furthermore, secondary batteries that use a material containing elemental sulfur as a positive electrode active material are not limited to lithium ions, but also include secondary batteries that use sodium ions or potassium ions instead of lithium ions.

[0040] A secondary battery that uses sulfur in the positive electrode and lithium metal in the negative electrode can be a lightweight, high-capacity secondary battery.

[0041] The second secondary battery 311 uses lithium cobalt oxide (LiMO) as a positive electrode material. ２ ) and uses a lithium ion secondary battery. The second secondary battery 311 uses LiNi as a positive electrode material. ｘ Co ｙ Mn ｚ O ２ The second secondary battery 311 can be made of a NiCoMn-based material (also called NCM) represented by (x>0, y>0, z>0, 0.8<x+y+z<1.2). The second secondary battery 311 can be made of lithium iron phosphate (LiFePO ４ In this embodiment, cobalt (Co) is used as the transition metal M.

[0042] Furthermore, in order to cut off power from multiple secondary batteries in an in-vehicle secondary battery, a service plug or circuit breaker that can cut off high voltage without using tools is provided on the first secondary battery 301. For safety reasons, the main first secondary battery 301 is electrically disconnected when the system is off.

[0043] 1 also shows a battery controller 302 for controlling the charging and discharging of the first secondary battery 301 or the second secondary battery 311, a charging inlet 332 for connecting an external charging cable, and a motor generator 304 serving as a drive source. The motor generator 304 functions both as a motor and as a generator, and the motor rotation speed is controlled by a motor controller 303. When the driver depresses an accelerator 330, the motor rotation speed is controlled by the motor controller. When the motor generator 304 rotates, force is transmitted to a gear 305, causing the tire 316 to rotate.

[0044] Furthermore, when the driver applies the brake 331 while the vehicle is running, the motor generator 304 generates regenerative power. The generated regenerative power is charged into the second secondary battery 311 via the inverter 312 and the first DC-DC converter 310a. The inverter 312 is a circuit that converts AC power into DC power.

[0045] In addition, a first DC-DC converter 310a and a second DC-DC converter 310b are provided between the first secondary battery 301 and the second secondary battery 311. In addition, a third DC-DC converter 310c is provided between the first secondary battery 301 and the charging inlet 332.

[0046] The battery controller 302 is sometimes called an ECU. The ECU is connected to a Controller Area Network (CAN) provided in the electric vehicle. The CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU includes a microcomputer. The ECU also uses a CPU or a GPU.

[0047] FIG. 2 also shows an operating mode in which regenerative power is generated by braking while the vehicle is running. The block diagrams in FIGS. 1 and 2 are almost the same. In FIG. 1, the flow of regenerative power is indicated by dotted arrows. Also, the flow of operating the motor generator 304 using power from the first secondary battery 301 is indicated by arrows in FIG. 1. FIG. 2 also shows, with dotted arrows, the flow of regenerative power in regenerative mode and the flow of power from the first secondary battery 301 to the second secondary battery 311. FIG. 2 also shows the flow of power from the second secondary battery 311 to the second secondary battery 311, conceptually representing the circular supply of energy.

[0048] <Regeneration Mode> Situations in which the vehicle switches to the regeneration mode are assumed to occur when the vehicle goes down a slope without depressing the accelerator 330, or when the vehicle depresses the brake 331 while traveling.

[0049] During deceleration, the motor generator 304 and the motor controller 303 operate to generate regenerative power. The generated regenerative power is charged into the second secondary battery 311 via the inverter 312 and the first DC-DC converter 310a. In order to efficiently charge the regenerative energy, it is desirable that the second secondary battery 311 be capable of rapid charging.

[0050] Furthermore, even if the regenerative power increases suddenly depending on the driving conditions, it is preferable to control charging so that the amount of regeneration is not limited to a certain amount by the battery controller 302. This allows the regenerative power to be used to the maximum extent possible.

[0051] Furthermore, once the second secondary battery 311 has been charged, the first secondary battery 301 may be charged via the third DC-DC converter 310c by the battery controller 302. Furthermore, when the first secondary battery 301 is nearly fully charged, power may be returned to the second secondary battery 301 via the second DC-DC converter 310b and the first DC-DC converter 310a in order to prevent deterioration of the first secondary battery 301.

[0052] In this way, the battery controller 302 can relay power in the following order: starting from the second secondary battery 311, the third DC-DC converter 310c, the first secondary battery 301, the second DC-DC converter 310b, the first DC-DC converter 310a, and then back to the second secondary battery 311.

[0053] In order to prevent overcharging of the first secondary battery 301, rather than using a resistor to convert power into heat, three DCDC converters and the second secondary battery 311 are used to prevent overcharging and disperse heat. Also, in order to prevent overcharging of the second secondary battery 311, three DCDC converters and the first secondary battery 301 are used to prevent overcharging and disperse heat.

[0054] By forming a circular charging path in this way, it is possible to maintain an optimal charging state for the first secondary battery 301 and the second secondary battery 311. Furthermore, because the three DC-DC converters also function as switches, equalization that would naturally eliminate the potential difference between the first secondary battery 301 and the second secondary battery 311 does not occur.

[0055] <External Charging Mode> In Fig. 3, when charging from an external source while the vehicle is stopped, the flow of power supplied from the external source is indicated by dotted arrows. A charging cable from a charging stand is connected to the charging inlet 332, and charging is performed on the first secondary battery 301 or the second secondary battery 311 via the third DC-DC converter 310c. This charging is controlled by the charging stand or the battery controller 302.

[0056] The charging stand stops supplying power when the first secondary battery 301 is fully charged. Once stopped, charging will not be restarted even if the capacity of the first secondary battery 301 decreases. In this embodiment, when the first secondary battery 301 is fully charged, the second secondary battery 311 is charged using the power of the first secondary battery 301 to prevent deterioration of the first secondary battery 301.

[0057] <Normal Running Mode> Figure 4 shows a schematic diagram of the flow of power (energy) supply during normal running, using arrows. The driver operates the accelerator 330 to drive the motor generator 304 via the motor controller, and the torque generated by the motor generator 304 is transmitted to the tires 316 via gears 305. Power for driving the motor generator 304 is supplied from the first secondary battery 301. Power is supplied from the first secondary battery 301 to the motor generator 304 via the second DC-DC converter 310b and the inverter 312. The inverter 312 converts the DC output from the first secondary battery 301 into three-phase AC. When the first secondary battery 301 is discharging, the second DC-DC converter 310b boosts the voltage to the intended voltage at a boost rate corresponding to the voltage of the secondary battery.

[0058] Furthermore, if it is desired to further add power to the motor generator 304, power can also be supplied from the second secondary battery 311. Power is supplied to the motor generator 304 from the second secondary battery 311 via the first DC-DC converter 310a and the inverter 312. The discharge of the first secondary battery 301 and the second secondary battery 311 is controlled by the battery controller 302.

[0059] Furthermore, even if the first secondary battery 301 becomes unusable for some reason, the vehicle can be moved by using the second secondary battery 311. Furthermore, if the battery controller 302 detects an abnormality in the first secondary battery 301, charging of the first secondary battery 301 may be stopped and the power of the first secondary battery 301 may be transferred to the first secondary battery 301 to avoid danger. To ensure safety at all times, it is desirable from a fail-safe perspective to discharge and reduce the capacity stored in the large-capacity first secondary battery 301.

[0060] <Low temperature start mode> When the temperature is low, such as 0°C or below, the first secondary battery 301 may not be able to demonstrate its original capacity. In this case, a small amount of power is used when starting the vehicle, and power is relayed starting from the second secondary battery 311, through the third DCDC converter 310c, the first secondary battery 301, the second DCDC converter 310b, the first DCDC converter 310a, and then back to the second secondary battery 311, in this order, thereby raising the temperature of the first secondary battery 301. By raising the temperature of the first secondary battery 301, the first secondary battery 301 can be allowed to demonstrate its original capacity.

[0061] Although this embodiment shows an example in which two different types of secondary batteries are used, this is not particularly limited, and three or more different types of secondary batteries may be used. Although a third secondary battery for starting the inverter 312 is not shown in FIG. 1 , a lead-acid battery or an all-solid-state battery may be used. This third secondary battery is also controlled by the battery controller 302.

[0062] Second Embodiment In the first embodiment, an example of a front-wheel drive electric vehicle is shown, but in this embodiment, an example in which a generator 333 is provided on the rear wheels is shown.

[0063] 5A is almost the same as FIG. 1 except for the generator 333 and the inverter 332, so the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description of the same parts will be omitted.

[0064] As the vehicle travels, the generator 333 generates power, and the generated power is charged into the second secondary battery 311 via the inverter 322 and the third DC-DC converter 310c. In Fig. 5A, the flow of regenerated power is indicated by dotted arrows. The flow of operating the motor generator 304 using power from the first secondary battery 301 is also indicated by arrows in Fig. 5A. Charging of the second secondary battery 311 is controlled by the battery controller 302.

[0065] In order to simplify the component configuration, the generator 333 may be connected to the inverter 312 and the first DC-DC converter 310a for common use, without providing the inverter 322. The second secondary battery 311 is capable of rapid charging and discharging, can be used to absorb large power fluctuations, and can perform efficient regeneration.

[0066] The second secondary battery 311 is composed of multiple secondary batteries. For example, cylindrical secondary batteries 600 are used. As shown in FIG. 5B , a module may be configured by sandwiching the cylindrical secondary batteries 600 between conductive plates 613 and 614. Switches between the secondary batteries are not shown in FIG. 5B . The multiple secondary batteries 600 may be connected in parallel, in series, or in series after being connected in parallel. By configuring a module having multiple secondary batteries 600, large amounts of power can be extracted. Furthermore, the second secondary battery 311 is not limited to a lithium-ion secondary battery using lithium cobalt oxide as a positive electrode material, but may also be a lithium-ion capacitor or an electric double layer capacitor.

[0067] In electric vehicles, multiple secondary batteries are connected in series or parallel, equipped with a protection circuit, and used as a battery pack (also called a battery assembly). A battery pack refers to a battery module consisting of multiple secondary batteries housed inside a container (metal can, film exterior) along with a specified circuit to facilitate handling of the secondary batteries. The battery pack has an ECU (Electronic Control Unit) to manage its operating state. If the multiple secondary batteries constituting the battery pack (battery assembly) have different characteristics, an imbalance will occur. When an imbalance occurs, some secondary batteries will be overcharged or will not be fully charged, resulting in a decrease in the apparent capacity overall. A cell balance circuit may be provided to prevent variations in the characteristics of the multiple secondary batteries.

[0068] This embodiment mode can be freely combined with other embodiment modes.

[0069] (Embodiment 3) An example of a cylindrical secondary battery will be described with reference to Figures 6A and 6B. As shown in Figure 6A, 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.

[0070] FIG. 6B 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, consisting of a strip-shaped positive electrode 604 and negative electrode 606 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 such as nickel, aluminum, or titanium, or an alloy of these metals or alloys of these metals with other metals (e.g., stainless steel), which are corrosion-resistant to electrolyte. 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, consisting of the positive electrode, negative electrode, and separator, is sandwiched between a pair of opposing insulating plates 608 and 609. A nonaqueous electrolyte (not shown) is poured into the battery can 602, containing the battery element. The secondary battery is lithium cobalt oxide (LiCoO ２ ) or lithium iron phosphate (LiFePO ４ The positive electrode contains an active material such as ethylene carbonate, diethyl carbonate, or the like, and the negative electrode is made of a carbon material such as graphite that can absorb and release lithium ions. The negative electrode is made of an organic solvent such as ethylene carbonate or diethyl carbonate, and the negative electrode contains LiBF ４ or LiPF ６ The lithium salt may be a non-aqueous electrolyte solution.

[0071] Because the positive and negative electrodes used in cylindrical storage batteries are wound, it is preferable to form active material 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 when the temperature rises, and the increase in resistance limits the amount of current to prevent abnormal heat generation. ３ )-based semiconductor ceramics, etc. can be used.

[0072] In this embodiment, an example of a lithium ion secondary battery is shown, but the present invention is not limited to lithium ion secondary batteries, and a material containing element A, element X, and oxygen can be used as a positive electrode material for a secondary battery. Element A is preferably one or more selected from elements of Group 1 and elements of Group 2. As elements of Group 1, for example, alkali metals such as lithium, sodium, and potassium can be used. Furthermore, as elements of Group 2, for example, calcium, beryllium, and magnesium can be used. As element X, for example, one or more selected from metal elements, silicon, and phosphorus can be used. Furthermore, element X is preferably one or more selected from cobalt, nickel, manganese, iron, and vanadium. Representative examples include lithium-cobalt composite oxide (LiCoO ２ ), or lithium iron phosphate (LiFePO ４ ) are listed.

[0073] The negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also include a conductive additive and a binder.

[0074] The negative electrode active material may be an element capable of undergoing charge-discharge reactions 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, and indium may be used. These elements have a larger capacity than carbon, and silicon, in particular, has a theoretical capacity of 4,200 mAh / g.

[0075] The secondary battery preferably has a separator, which may be made of, for example, cellulose-containing fibers such as paper, nonwoven fabric, glass fiber, ceramics, or synthetic fibers such as nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, or polyurethane.

[0076] This embodiment mode can be freely combined with other embodiment modes.

[0077] Embodiment 4 In this embodiment, an example in which a charging system for a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0078] By installing a secondary battery in a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized.

[0079] FIG. 7A illustrates an example of a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 illustrated in FIG. 7A is an electric automobile using an electric motor 8406 as a power source for traveling. Alternatively, it is a hybrid automobile that can appropriately select and use the electric motor 8406 and an engine as a power source for traveling. By using one embodiment of the present invention, a vehicle that can efficiently recover regenerative charge by charging a second secondary battery 8403 with regenerative current can be realized. The automobile 8400 also includes a first secondary battery 8402 and a second secondary battery 8403. The second secondary battery 8403 may be a lithium-ion capacitor or an electric double-layer capacitor. The second secondary battery can be rapidly charged and discharged, can be used to absorb large power fluctuations, and can efficiently regenerate power. The first secondary battery 8402 is a different type of battery and has a larger capacity than the second secondary battery 8403. The first secondary battery 8402 has a large capacity and therefore occupies a part of the total volume inside the vehicle, but for example, a module of the first secondary battery 8402 can be placed on the floor of the vehicle. The first secondary battery 8402 not only drives the electric motor 8406 but also supplies power to light-emitting devices such as headlights 8401 and room lights (not shown). Note that the voltage supplied to the inverter for driving the electric motor 8406 differs from the voltage of light-emitting devices such as the headlights 8401 and room lights, and therefore different DC-DC converters are used for each.

[0080] The first secondary battery 8402 can supply power to display devices such as a speedometer and a tachometer included in the automobile 8400. The first secondary battery 8402 can also supply power to semiconductor devices such as a navigation system included in the automobile 8400.

[0081] The automobile 8500 shown in FIG. 7B can charge the first secondary battery 8024 of the automobile 8500 by receiving power from an external charging facility using a plug-in system and / or a wireless power supply system. FIG. 7B shows a state in which the first secondary battery 8024 installed in the automobile 8500 is being charged from a ground-mounted charging device 8021 via a charging cable 8022. The charging method and connector specifications may be appropriately determined using a predetermined system such as CHAdeMO (registered trademark) or Combo. The charging device 8021 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 first secondary battery 8024 installed in the automobile 8500 using external power supply. Charging can be performed by converting AC power to DC power using a conversion device such as an AC-DC converter.

[0082] The automobile 8500 also has a second secondary battery 8025 for regenerative charging. When rapid charging at a high charge rate is performed using external charging equipment, the standard stipulates that charging be stopped at 80% of the full charge of the first secondary battery 8024 for safety reasons. Furthermore, when normal charging at a low charge rate is performed, the first secondary battery 8024 can be fully charged, but even if regenerative charging is obtained by driving, the first secondary battery 8024 cannot be charged. However, the automobile 8500 shown in FIG. 7B can be charged because it has a second secondary battery 8025. The second secondary battery 8025 can also function as an auxiliary battery.

[0083] Furthermore, when normal charging with a low charge rate is performed, the first secondary battery 8024 can be fully charged, but leaving it in a fully charged state for a long period of time may accelerate deterioration of the first secondary battery 8024. Therefore, if the vehicle is not being driven after the first secondary battery 8024 is fully charged, power can be transferred to the second secondary battery 8025, and the life of the first secondary battery 8024 can be extended.

[0084] 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 the road and / or 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, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped and / or moving. Electromagnetic induction and / or magnetic resonance methods can be used for such contactless power supply.

[0085] According to one aspect of the present invention, the secondary battery can be made lighter and the discharge capacity of the secondary battery can be increased. Therefore, the capacity per unit weight can be increased, allowing the secondary battery itself to be made smaller and lighter. Reducing the weight of the secondary battery itself contributes to reducing the weight of the vehicle, thereby improving the cruising range. Furthermore, the secondary battery mounted on the vehicle can also be used as a power supply source for purposes other than the vehicle. In this case, for example, it is possible to avoid using a commercial power source during peak power demand periods. Avoiding the use of a commercial power source during peak power demand periods can contribute to energy conservation and reduction of carbon dioxide emissions.

[0086] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0087] 301: First secondary battery, 302: Battery controller, 303: Motor controller, 304: Motor generator, 305: Gear, 310a: First DC-DC converter, 310b: Second DC-DC converter, 310c: Third DC-DC converter, 311: Second secondary battery, 312: Inverter, 322: Inverter, 316: Tire, 330: Accelerator, 331: Brake, 332: Charging inlet, 333: Generator, 600: 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, 8021: charging device, 8022: charging cable, 8024: first secondary battery, 8025: second secondary battery, 8400: automobile, 8401: headlight, 8402: first secondary battery, 8403: second secondary battery, 8406: electric motor, 8500: automobile

Claims

A first secondary battery; a second secondary battery made of a different material than the first secondary battery; a control circuit that controls the first secondary battery and the second secondary battery; a power generation device that generates regenerative power when the electric vehicle decelerates; an inverter and a first DC-DC converter between the power generation device and the second secondary battery; the first DC-DC converter and the second DC-DC converter are disposed between the first secondary battery and the second secondary battery; a third DC-DC converter between a charging inlet and the first secondary battery and between the charging inlet and the second secondary battery; The control circuit is a charging control system that charges the second secondary battery with power from the first secondary battery via the first and second DCDC converters.

2. The charging control system according to claim 1, wherein when the first secondary battery is in a fully charged state, the regeneratively generated electric power is charged into the second secondary battery.

2. The charging control system according to claim 1, wherein the control circuit charges the first secondary battery with power from the second secondary battery via the third DC-DC converter.

2. The charging control system according to claim 1, wherein the first secondary battery is a lithium ion secondary battery containing sulfur, and the second secondary battery is a lithium ion secondary battery having an oxide containing cobalt as a positive electrode active material.

2. The charge control system according to claim 1, wherein the first secondary battery is a lithium ion secondary battery containing sulfur, and the second secondary battery is a lithium ion capacitor.

2. The charge control system according to claim 1, wherein the first secondary battery has a larger capacity than the second secondary battery.

2. The charging control system according to claim 1, wherein the regeneratively generated electric power is generated by utilizing a motor.

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