Energy Storage Device Management System

Abstract

Provided are a power storage device management system and management method using AI, and a computer program. A management system for power storage devices, which has an electronic apparatus having a power storage device, and a server device, such that: the power storage device has a control unit and a storage battery; the control unit has a first function of creating second data by using first data of a first time point, and a second function of transmitting the second data to the server device; the server device has a third function of creating first data of a second time point by using the second data, and a fourth function of transmitting the first data of the second time point to the control unit; and, the first, second, third, and fourth functions are repeatedly performed.

Description

Electricity storage device management system and electronic device

[0001] One embodiment of the present invention relates to a power storage device, an electronic device, a server device, a computer program, and a power storage device management system.

[0002] Another embodiment of the present invention relates to a neural network and a management system for a power storage device using the neural network.Another embodiment of the present invention relates to a vehicle using the neural network.Another embodiment of the present invention relates to an electronic device using the neural network.Another embodiment of the present invention relates to a management system for a power storage device that is not limited to vehicles but can also be applied to a power storage device for storing power obtained from a power generation facility such as a solar power generation panel installed on a structure or the like.

[0003] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof.

[0004] In this specification and the like, a semiconductor device refers to an element, circuit, device, or the like that can function by utilizing semiconductor characteristics. As one example, a semiconductor element such as a transistor or a diode is a semiconductor device. As another example, a circuit having a semiconductor element is a semiconductor device. As yet another example, a device including a circuit having a semiconductor element is a semiconductor device.

[0005] 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.

[0006] In this specification, the term "power storage device" refers to all elements and devices having a power storage function, including, for example, power storage devices such as lithium ion secondary batteries (also called secondary batteries), lithium ion capacitors, and electric double layer capacitors.

[0007] In recent years, various types of power storage devices have been actively developed, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. In particular, demand for high-power, high-energy-density lithium-ion secondary batteries has rapidly expanded in conjunction with the development of the semiconductor industry, and they are now indispensable in the modern information society as a rechargeable energy source, as they are used in portable information terminals such as mobile phones, smartphones, and notebook computers, portable music players, digital cameras, medical devices, and next-generation clean-energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs).

[0008] Lithium-ion batteries are highly useful, but despite their high output and energy density, they are known to pose high safety risks due to overcharging and overdischarging. Therefore, when using lithium-ion secondary batteries in devices, it is necessary to accurately grasp and manage their internal states, such as their state of charge and internal resistance. Known methods for estimating the internal state of lithium-ion batteries include the coulomb counter method, the open circuit voltage (OCV) method, and a Kalman filter (see Patent Document 1). In state estimation methods such as the Kalman filter, it is important to have highly accurate data, such as the SOC (State of Charge)-OCV (Open Circuit Voltage) characteristics and the FCC (Full Charge Capacity) of the power storage device to be estimated.

[0009] WO2019 / 193471 Brochure

[0010] With conventional methods, repeated charging and discharging over a long period of operation can cause deterioration of the power storage device and accumulation of measurement errors, which can significantly reduce the accuracy of data such as SOC-OCV characteristics and FCC. Furthermore, managing the power storage device with low data accuracy can accelerate the deterioration of the power storage device or put the power storage device in a dangerous state.

[0011] Furthermore, it is desirable for the SOC-OCV characteristic data to have a large number of data points and high accuracy, but there is a risk that such data, when used by the control unit of the power storage device, may end up with a data volume that exceeds the processing capacity of the control unit.

[0012] Furthermore, when new SOC-OCV characteristic data is to be created, the control unit of the power storage device may lack the computing power required to create the data.

[0013] Furthermore, if the capacity of a secondary battery can be estimated with high accuracy, it would be possible to detect abnormalities based on that value. Another objective is to provide a new method for detecting abnormalities in secondary batteries.

[0014] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these can be extracted from the description in the specification, drawings, and claims.

[0015] One embodiment of the present invention is a power storage device management system that includes an electronic device having a power storage device and a server device, wherein the power storage device includes a control unit and a storage battery, the control unit has a first function of creating second data using first data at a first point in time and a second function of transmitting the second data to the server device, and the server device has a third function of creating first data at a second point in time using the second data and a fourth function of transmitting the first data at the second point in time to the control unit, and the first function, the second function, the third function, and the fourth function are repeatedly performed.

[0016] Another aspect of the present invention is the above-mentioned energy storage device management system, in which the third function of the server device includes a first algorithm, the first function of the control unit includes a second algorithm, the control unit has a plurality of SOC-OCV characteristic data, the server device has a function of creating at least one of the plurality of SOC-OCV characteristic data by using the second data and the first algorithm, and the control unit has a function of selecting, from the plurality of SOC-OCV characteristic data, a first SOC-OCV characteristic data that is closest to a state of the storage battery by using the second algorithm.

[0017] Another embodiment of the present invention is the power storage device management system described in any one of the above, in which the electronic device has a fifth function of creating second SOC-OCV characteristic data based on the first SOC-OCV characteristic data and an estimated load of the electronic device, and the OCV value at which the SOC value is 0% in the second SOC-OCV characteristic data is higher than the OCV value at which the SOC value is 0% in the first SOC-OCV characteristic data.

[0018] Another aspect of the present invention is a power storage device management system described in any one of the above, wherein each of the multiple SOC-OCV characteristic data is composed of a combination of first bit data corresponding to an SOC value and second bit data corresponding to an OCV value, and the number of bits of the first bit data is equal to the number of bits of the second bit data.

[0019] Another aspect of the present invention is the energy storage device management system described in any one of the above, wherein the third function of the server device has a third algorithm, the first function of the control unit has a fourth algorithm, the first data has an FCC value, and the second data has an R (internal resistance) value, the server device has a function of estimating the FCC value by using the second data and the third algorithm, and the control unit has a function of calculating the R value by using the first data and the fourth algorithm.

[0020] Another aspect of the present invention is a power storage device management system described in any one of the above, wherein the control unit has a coulomb counter that measures the accumulated charge amount of the storage battery, and each time the accumulated charge amount reaches an FCC value, the accumulated charge amount is reset and the second function is performed.

[0021] Another embodiment of the present invention is an electronic device including a power storage device. The power storage device includes a control unit and a storage battery. The control unit has a plurality of SOC-OCV characteristic data. The control unit has a function of selecting data that is closest to a state of the storage battery from the plurality of SOC-OCV characteristic data.

[0022] Another embodiment of the present invention is an electronic device including a power storage device. The power storage device includes a control unit and a storage battery. The control unit has a plurality of SOC-OCV characteristic data. The control unit has a function of selecting data closest to a state of the storage battery from the plurality of SOC-OCV characteristic data. Each of the plurality of SOC-OCV characteristic data is formed by a combination of first bit data corresponding to an SOC value and second bit data corresponding to an OCV value. The number of bits of the first bit data is equal to the number of bits of the second bit data.

[0023] The server device estimates the SOC-OCV characteristic data and FCC value that indicate the current state of the power storage device at regular intervals and feeds the data back to the control unit of the power storage device, thereby enabling highly accurate management of the power storage device. By using a method in which the control unit of the power storage device selects SOC-OCV characteristic data that is closest to the current state of the power storage device from among multiple pieces of SOC-OCV characteristic data transmitted from the server device, it is possible to manage the power storage device using highly accurate SOC-OCV characteristic data with a small amount of calculation.

[0024] It is possible to provide a method for estimating the state of a secondary battery with high estimation accuracy even when the secondary battery has deteriorated. It is also possible to provide a state measurement system for a secondary battery that estimates the SOC with high accuracy in a short time and at low cost. It is also possible to provide a new method for detecting an abnormality in a secondary battery.

[0025] FIG. 1 is a conceptual diagram of an energy storage device management system illustrating one embodiment of the present invention. FIG. 2 is a diagram illustrating a processing function of the energy storage device management system related to SOC-OCV characteristic data. FIG. 3 is a diagram illustrating a data description method for SOC-OCV characteristic data. FIG. 4 is a diagram illustrating a processing function of the energy storage device management system related to FCC and internal resistance. FIG. 5 is a diagram illustrating a method for estimating an R value. FIG. 6A is a top view of a positive electrode active material according to one embodiment of the present invention, and FIGS. 6B and 6C are cross-sectional views of the positive electrode active material according to one embodiment of the present invention. FIG. 7 is a diagram illustrating a crystal structure of a positive electrode active material according to one embodiment of the present invention. FIG. 8 is an XRD pattern calculated from the crystal structure. FIG. 9 is a diagram illustrating the crystal structure of a positive electrode active material according to a comparative example. FIG. 10 is an XRD pattern calculated from the crystal structure. FIG. 11A is an exploded perspective view of a coin-type secondary battery, FIG. 11B is a perspective view of the coin-type secondary battery, and FIG. 11C is a cross-sectional perspective view thereof. FIG. 12A illustrates an example of a cylindrical secondary battery. FIG. 12B shows an example of a cylindrical secondary battery. FIG. 12C shows an example of a plurality of cylindrical secondary batteries. FIG. 12D shows an example of a power storage system including a plurality of cylindrical secondary batteries. FIGS. 13A and 13B are diagrams illustrating an example of a secondary battery, and FIG. 13C is a diagram illustrating the internal state of the secondary battery. FIGS. 14A to 14C are diagrams illustrating an example of a secondary battery. FIGS. 15A and 15B are diagrams illustrating the appearance of a secondary battery. FIGS. 16A to 16C are diagrams illustrating a manufacturing method of a secondary battery. FIGS. 17A to 17C are diagrams illustrating an example of a battery pack. FIGS. 18A and 18B are diagrams illustrating an example of a secondary battery. FIGS. 19A to 19C are diagrams illustrating an example of a secondary battery. FIGS. 20A and 20B are diagrams illustrating an example of a secondary battery. FIG. 21A is a perspective view of a battery pack illustrating one embodiment of the present invention, FIG. 21B is a block diagram of the battery pack, and FIG. 21C is a block diagram of a vehicle having a motor. 22A to 22D are diagrams illustrating an example of a transportation vehicle. 23A and 23B are diagrams illustrating a power storage device according to one embodiment of the present invention. 24A is a diagram illustrating an electric bicycle, 24B is a diagram illustrating a secondary battery for the electric bicycle, and 24C is a diagram illustrating an electric motorcycle. 25A to 25D are diagrams illustrating examples of electronic devices.Fig. 26A shows an example of a wearable device, Fig. 26B shows a perspective view of a wristwatch-type device, Fig. 26C is a diagram illustrating a side view of the wristwatch-type device, and Fig. 26D is a diagram illustrating an example of a wireless earphone.

[0026] 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.

[0027] Embodiment 1 In this embodiment, an example of a power storage device management system according to one embodiment of the present invention will be described with reference to FIGS.

[0028] Fig. 1 is a conceptual diagram of a power storage device management system. As shown in Fig. 1, the power storage device management system includes a server device 1 and an electronic device 2 including a power storage device 3. The power storage device management system has an algorithm including a neural network, and can be said to be a power storage device management system having artificial intelligence (AI).

[0029] In the present embodiment, an example of a system in which the server device 1 manages one electronic device 2 is shown, but the server device 1 can also manage multiple electronic devices 2. When the server device 1 manages multiple electronic devices 2, it is preferable that the server device 1 be capable of high-speed arithmetic processing, and therefore it is preferable that the server device 1 has a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit) as an arithmetic processing device. Note that when the server device 1 manages multiple electronic devices 2, it is preferable that the multiple electronic devices 2 and the power storage devices 3 possessed by the multiple electronic devices 2 have unique identifiers (also referred to as unique IDs). From the viewpoint of traceability, it is preferable that the identifiers be set in association with the serial numbers of the electronic devices 2 and the power storage devices 3 possessed by the electronic devices 2.

[0030] The server device 1 and the electronic device 2 can transmit and receive data via a communication network 7. The data includes first data 11 sent from the server device 1 to the electronic device 2 and second data 12 sent from the electronic device 2 to the server device 1. As shown in FIG. 5 , the power storage device 3 includes a control unit 4 and a storage battery 5. The first data 11 includes an FCC value related to the storage battery 5 and SOC-OCV characteristic data related to the storage battery 5. The second data 12 includes the SOC-OCV characteristic data currently used by the control unit 4 of the power storage device 3, an R value related to the storage battery 5, and an integrated charge amount of the storage battery 5. The integrated charge amount of the storage battery 5 is either or both of the integrated charge amount since the power storage device 3 was installed in the electronic device 2 and the integrated charge amount since the previous data transmission. In the case of both, there are two pieces of data indicating the integrated charge amount of the storage battery 5. The second data 12 may also include error data between the SOC-OCV characteristic data currently used by the control unit 4 of the power storage device 3 and the actual SOC-OCV characteristic of the storage battery 5. The error data regarding the SOC-OCV characteristic may include an array of open circuit voltage differences (ΔV) at each SOC, or may include a single value obtained by integrating the open circuit voltage differences (ΔV) at each SOC.

[0031] The timing of data communication between the server device 1 and the electronic device 2 via the communication network 7 may be any timing, but is preferably when the power storage device 3 is charging, because the power used for data communication can be covered by external power. While the power storage device 3 is charging, the timing of data communication may be, for example, when an accumulated charge amount corresponding to the FCC value of the storage battery 5 of the storage device 3 has been charged since the last data communication. The server device 1 has a function of estimating the FCC value of the first data based on the accumulated charge amount of the storage battery 5 contained in the second data and a capacity degradation table contained in the server device 1. Here, performing data communication at the timings shown above is preferable because it allows the accumulated charge amount to be calculated based on the number of communications.

[0032] [Processing Functions Related to SOC-OCV Characteristic Data] FIG. 2 is a diagram illustrating the creation of SOC-OCV characteristic data in the server device 1 and the selection of SOC-OCV characteristic data in the electronic device 2 or the control unit 4, with respect to the SOC-OCV characteristic data included in the first data 11 and the second data 12. A functional configuration related to the creation and selection of SOC-OCV characteristic data in the power storage device management system will be described using FIG. 2 . Note that FIG. 2 schematically illustrates data communication (data transmission and reception) between the server device 1 and the electronic device 2. However, in this embodiment, data communication is not limited to one-to-one direct data communication, and data communication may be performed via other electronic devices, an Internet line, a communication relay device, a communication base station, or the like. Wired communication or wireless communication may be used as the data communication method. When wireless communication is used, wireless communication conforming to a communication standard such as a fourth-generation mobile communication system (4G) or a fifth-generation mobile communication system (5G) may be used. The signal frequency of wireless communication can be, for example, any of the following frequencies: submillimeter waves of 300 GHz to 3 THz, millimeter waves of 30 GHz to 300 GHz, microwaves of 3 GHz to 30 GHz, ultra-short waves of 300 MHz to 3 GHz, ultra-short waves of 30 MHz to 300 MHz, short waves of 3 MHz to 30 MHz, medium waves of 300 kHz to 3 MHz, long waves of 30 kHz to 300 kHz, and ultra-long waves of 3 kHz to 30 kHz.

[0033] The server device 1 has a first algorithm 21. The first algorithm 21 has a function of creating first SOC-OCV characteristic data 62 using the second data 12 as input data. The first algorithm 21 preferably has a first neural network 31. The server device 1 also has a function of transmitting the first SOC-OCV characteristic data 62 to the electronic device 2 as part of the first data 11. The first SOC-OCV characteristic data 62 transmitted to the electronic device 2 is added as part of an SOC-OCV characteristic data list 61 held by the electronic device 2 or the control unit 4.

[0034] The electronic device 2 or the control unit 4 has a second algorithm 22. The second algorithm 22 has a function of selecting second SOC-OCV characteristic data 63 using the SOC-OCV characteristic data list 61 and the voltage, current, temperature, and capacity values ​​of the storage battery 5 stored in the control unit 4 as input data. The second SOC-OCV characteristic data 63 is selected to be closest to the state of the storage battery 5 at the time of selection. "Closest" means that the difference from the entire range of the SOC-OCV characteristics of the storage battery 5 is smallest. Because it is difficult to actually measure the entire range of the SOC-OCV characteristics of the storage battery 5 used in the electronic device 2, the second algorithm 22 needs to select the second SOC-OCV characteristic data 63 based on limited input data. For this reason, the second algorithm 22 preferably has a second neural network 32. The second algorithm 22 includes the second neural network 32, and thus can select the second SOC-OCV characteristic data 63 that is closest to the state of the storage battery 5 using limited input data. In addition, the electronic device 2 or the control unit 4 has a function of transmitting the second SOC-OCV characteristic data 63 to the server device 1 as part of the second data 12.

[0035] The first neural network 31 may be, for example, any one of a FFNN (Feedforward Neural Network), a CNN (Convolutional Neural Network), an RNN (Recurrent Neural Network), and an LSTM (Long Short-Term Memory).

[0036] For example, any one of a Feedforward Neural Network (FFNN), a Convolutional Neural Network (CNN), a Recurrent Neural Network (RNN), and a Long Short-Term Memory (LSTM) can be used as the second neural network 32. In addition, the second neural network 32 may select the second SOC-OCV characteristic data 63 from the SOC-OCV characteristic data list 61 using a decision tree as a classification problem.

[0037] Next, a data description method for the first SOC-OCV characteristic data 62 will be described with reference to FIG. 3 . A power storage device management system according to one embodiment of the present invention can use, for example, a data description method in which SOC data and OCV data are assigned as specific bit data, as shown in FIG. 3 . As for the SOC data, FIG. 3 shows the relationship between bit data and corresponding SOC. As for the OCV data, FIG. 3 also shows the relationship between bit data and corresponding voltage. When specific bit data in the SOC data is, for example, 0011, the corresponding SOC is 40%, and the corresponding voltage in the OCV data is 3.30 V. Under normal usage conditions, the power storage device 3 is used with an SOC in the range of 0% to 100%. However, if the power storage device 3 is not used for a long period of time, it may enter an overdischarge state of 0% or less. Furthermore, during charging, overcharging, i.e., charging to 100% or more, is a potential risk that must be addressed. Therefore, as shown in FIG. 3 , the SOC data desirably corresponds to an SOC range below 0% and an SOC range above 100%. The OCV data is data paired with the SOC data, and the OCV value of the storage battery 5 corresponding to each SOC value is assigned as the OCV data.

[0038] FIG. 3 also illustrates an example of a data description method for the first SOC-OCV characteristic data 62, in which more bit data is allocated in an SOC range close to 100%. In a lithium-ion battery, an overcharged state in which the SOC exceeds 100% can potentially lead to a decrease in the safety of the storage battery 5 and a decrease in battery life. Therefore, it is desirable to allocate more bit data in an SOC range close to 100%. The SOC range close to 100% is preferably 90% to 110%, more preferably 95% to 105%, and it is desirable to allocate more bit data in this range than in other ranges. The allocation of bit data can be performed by the server device 1. While FIG. 3 illustrates an example in which more bit data is allocated in an SOC range close to 100%, it is also possible to allocate more bit data in an SOC range close to 0%. Allocating more bit data in an SOC range close to 0% is preferable because it facilitates preventing sudden shutdown of the electronic device 2 having the power storage device 3. As in the example shown above, by allocating a large amount of bit data to a portion of the SOC range, it is possible to form sufficient SOC-OCV characteristic data even with a small number of bits, thereby achieving the effect of reducing the weight of data communication between the server device 1 and the storage device 3 and the weight of data stored within the storage device 3.

[0039] While FIG. 3 illustrates an example using 4 bits for the sake of explanation, the data may be described using a larger number of bits, such as 8 bits, 16 bits, 32 bits, or 64 bits. When using large bit data, it may not be necessary to allocate many bits to the partial range of SOC described above. This is because, when a large number of bits are allocated to the SOC-OCV characteristic data, the entire range of SOC can be described in detail, not just a partial range of SOC. Note that the number of bits of the SOC data and the number of bits of the OCV data do not necessarily need to match, but it is preferable if the number of bits of the SOC data and the number of bits of the OCV data match, as this facilitates calculation processing in the first neural network and / or the second neural network.

[0040] 3 shows an example of a data description method for the first SOC-OCV characteristic data 62 in which, in addition to the allocation of SOC data and OCV data, State A to State D representing the state of the power storage device 3 are allocated to surplus bit data. State A to State D representing the state of the power storage device 3 can be allocated as data indicating a dangerous state such as an internal short circuit of the storage battery 5, for example.

[0041] As described above, the data processing function related to the SOC-OCV characteristic data included in the power storage device management system of one embodiment of the present invention can improve the accuracy of estimating the remaining capacity of the storage battery 5. Furthermore, the server device 1 reduces the amount of data (reduction in data volume) of the SOC-OCV characteristic data and makes it suitable for neural network processing, thereby enabling lower power consumption by a control unit included in the power storage device 3.

[0042] [Processing Functions Related to FCC and Internal Resistance] Fig. 4 is a diagram illustrating the estimation of the FCC value in the server device 1 and the estimation of the R value in the electronic device 2 or the control unit 4, with respect to the FCC value included in the first data 11 and the R value included in the second data. The functional configuration of the power storage device management system related to the estimation of the FCC value and the R value will be described using Fig. 4. Note that the communication method described in Fig. 2 can be used for data communication (data transmission and reception) between the server device 1 and the electronic device 2.

[0043] The server device 1 has a third algorithm 23. The third algorithm 23 uses the R value 71a calculated by the power storage device (R data from a certain point in time before estimated by the power storage device: R ｎ−１ ) as input data to estimate the FCC 72. The third algorithm 23 preferably includes a third neural network 33. The server device 1 also has a function of transmitting the FCC 72 to the electronic device 2 as part of the first data 11.

[0044] The electronic device 2 or the control unit 4 has a fourth algorithm 24. The fourth algorithm 24 uses the FCC 72, the second SOC-OCV characteristic data 63, and the voltage value, current value, temperature, and capacity value of the storage battery 5 stored in the control unit 4 as input data, and calculates an R value 71b of the storage battery 5 (R data estimated by the power storage device: R ｎ ) is estimated. The fourth algorithm 24 preferably includes a fourth neural network 34. The electronic device 2 or the control unit 4 also has a function of estimating the R value 71 (R ｎ ) to the server device 1 as part of the second data 12.

[0045] The third neural network 33 may be, for example, any one of a FFNN (Feedforward Neural Network), a CNN (Convolutional Neural Network), an RNN (Recurrent Neural Network), and an LSTM (Long Short-Term Memory).

[0046] The fourth neural network 34 may be, for example, any one of a FFNN (Feedforward Neural Network), a CNN (Convolutional Neural Network), an RNN (Recurrent Neural Network), and an LSTM (Long Short-Term Memory).

[0047] Next, a method for estimating the R value 71 will be described with reference to Fig. 5. Fig. 5 shows the function of a fourth algorithm 24 included in the electronic device 2 or the control unit 4. The R value 71 is estimated by inputting the first SOC-OCV characteristic data 62, the FCC 72, and internal measurement values ​​of the power storage device 3 into the fourth algorithm 24. The SOC-OCV characteristic data 62 desirably has the data format described with reference to Fig. 3. The internal measurement values ​​of the power storage device 3 include the voltage value V of the storage battery 5, the current value I flowing through the storage battery 5, the temperature T of the storage battery 5, and the capacity value Q measured by the coulomb counter 6 included in the control unit 4.

[0048] As described above, the function related to estimating the FCC value and the R value included in the power storage device management system of one embodiment of the present invention enables to improve the accuracy of estimating the FCC value and the R value of the storage battery 5. Furthermore, by using lighter SOC-OCV characteristic data (reduced data amount) for estimating the R value, the data is optimized for neural network processing, and power consumption of a control unit included in the power storage device 3 can be reduced.

[0049] Furthermore, the power storage device 3 included in the electronic device 2 may have third SOC-OCV characteristic data in addition to the SOC-OCV characteristic data list 61 and the second SOC-OCV characteristic data 63. The third SOC-OCV characteristic data can be created based on the second SOC-OCV characteristic data 63 and an estimated load of the electronic device 2. The average current consumption value of the electronic device 2 can be used as the estimated load of the electronic device 2. Compared to the second SOC-OCV characteristic data 63, the third SOC-OCV characteristic data sets a voltage corresponding to a low SOC range in the OCV data higher in accordance with the estimated load of the electronic device 2. As a simplified example, for example, an SOC of 10% in the second SOC-OCV characteristic data 63 is recorded as an SOC of 0% in the third SOC-OCV characteristic data. In this example, the OCV at which the SOC becomes 0% in the third SOC-OCV characteristic data is higher than the OCV at which the SOC becomes 0% in the second SOC-OCV characteristic data 63. Using the third SOC-OCV characteristic data to display the status of the electronic device 2 to a user can be preferable in some cases because it can prevent the electronic device 2 from suddenly shutting down.

[0050] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0051] Embodiment 2 In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described.

[0052] In this specification, the theoretical capacity of a positive electrode active material refers to the amount of electricity when all of the intercalable and deintercalable lithium contained in the positive electrode active material is deintercalated. For example, LiFePO ４ The theoretical capacity of LiCoO is 170 mAh / g. ２ The theoretical capacity of LiNiO is 274 mAh / g. ２ The theoretical capacity of LiMn is 275mAh / g. ２ O ４ The theoretical capacity of the battery is 148 mAh / g.

[0053] The amount of lithium remaining in the positive electrode active material that can be inserted or removed can be determined by x in the composition formula, for example, Li ｘ CoO２ x in, or Li ｘ MO ２ In this specification, Li ｘ CoO ２ Li as appropriate ｘ M1O ２ x can be considered as an occupancy rate, and in the case of a positive electrode active material in a secondary battery, x may be expressed as x = (theoretical capacity - charging capacity) / theoretical capacity. For example, LiCoO ２ When a secondary battery using as a positive electrode active material is charged at 219.2 mAh / g, Li ０．２ CoO ２ Or we can say x = 0.2. ｘ CoO ２ The small value of x in the formula means, for example, 0.1<x≦0.24.

[0054] When the lithium cobalt oxide satisfies the stoichiometric ratio, LiCoO ２ The occupancy rate of Li on the lithium site is x = 1. Also, the secondary battery after discharge is also LiCoO ２ In this case, x = 1. The end of discharge here refers to the state where the voltage is 2.5 V (lithium counter electrode) or less at a current of 100 mA / g, for example. In a lithium ion secondary battery, when the occupancy rate of lithium in the lithium site reaches x = 1 and no more lithium can enter, the voltage drops sharply. At this point, discharge can be said to be complete. Generally, LiCoO ２ In the case of a lithium ion secondary battery using the above method, the discharge voltage drops rapidly until it reaches 2.5 V, so it is assumed that the discharge is completed under the above conditions.

[0055] In this specification and the like, the depth of charge when all intercalable and deintercalable lithium in the positive electrode active material is intercalated may be referred to as 0, and the depth of charge when all intercalable and deintercalable lithium in the positive electrode active material is deintercalated may be referred to as 1. For example, Li ｘ MO ２ When x=1, the charge depth is 0; when x=0, the charge depth is 1; and when x=0.2, the charge depth is 0.8.

[0056] <Configuration Example of Secondary Battery> Hereinafter, a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are enclosed in an exterior body will be described as an example.

[0057] [Positive Electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer has a positive electrode active material, and may also have a conductive material and a binder, which will be described later.

[0058] [Negative Electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer has a negative electrode active material, and may also have a conductive material described below and the binder described above.

[0059] [Current Collector] The positive electrode current collector and the negative electrode current collector can be made of a material that has high conductivity and does not alloy with carrier ions such as lithium, such as metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, and titanium, and alloys thereof. The current collector can be appropriately shaped, such as a sheet, mesh, punched metal, or expanded metal. The current collector should preferably have a thickness of 10 μm or more and 30 μm or less.

[0060] The negative electrode current collector is preferably made of a material that does not alloy with carrier ions such as lithium.

[0061] A titanium compound may be provided as a current collector by being laminated on the metals listed above. Examples of titanium compounds include titanium nitride, titanium oxide, titanium nitride in which part of the nitrogen is substituted with oxygen, titanium oxide in which part of the oxygen is substituted with nitrogen, and titanium oxynitride (TiO ｘ N ｙ, 0 < x < 2, 0 < y < 1), or a mixture or stack of two or more of these can be used. Among these, titanium nitride is particularly preferred because of its high conductivity and excellent oxidation suppression function. By providing a titanium compound on the surface of the current collector, for example, reaction between the metal and the material contained in the active material layer formed on the current collector can be suppressed. When the active material layer contains an oxygen-containing compound, oxidation reaction between the metal and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide (described later), oxidation reaction between oxygen contained in graphene oxide and aluminum is a concern. In such a case, providing a titanium compound on aluminum can suppress oxidation reaction between the current collector and graphene oxide.

[0062] [Conductive Material] The conductive material, also called a conductivity imparting agent or a conductivity aid, is made of a carbon material. By attaching the conductive material between multiple active materials, the multiple active materials are electrically connected to each other, thereby increasing the conductivity. Note that the term "attachment" does not only refer to physical adhesion between the active material and the conductive material, but also includes cases where a covalent bond is formed, bonding due to van der Waals forces, where the conductive material covers part of the surface of the active material, where the conductive material is embedded in the surface irregularities of the active material, and where the materials are electrically connected even when not in contact with each other.

[0063] The active material layers such as the positive electrode active material layer and the negative electrode active material layer preferably contain a conductive material.

[0064] As the conductive material, for example, one or more of carbon black such as acetylene black and furnace black, graphite such as artificial graphite and natural graphite, carbon fibers such as carbon nanofibers and carbon nanotubes, and graphene compounds can be used.

[0065] Examples of carbon fibers that can be used include mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers. Carbon nanofibers and carbon nanotubes can also be used as carbon fibers. Carbon nanotubes can be produced by vapor phase growth, for example.

[0066] The active material layer may also contain, as a conductive material, metal powder or metal fiber such as copper, nickel, aluminum, silver, or gold, or a conductive ceramic material.

[0067] The content of the conductive additive relative to the total amount of the active material layer is preferably 1 wt % or more and 10 wt % or less, and more preferably 1 wt % or more and 5 wt % or less.

[0068] Unlike granular conductive materials such as carbon black, which make point contact with the active material, graphene compounds enable surface contact with low contact resistance, and therefore can improve the electrical conductivity between the granular active material and the graphene compound with a smaller amount than that of ordinary conductive materials. This allows the ratio of the active material in the active material layer to be increased, thereby increasing the discharge capacity of the secondary battery.

[0069] Particulate carbon-containing compounds such as carbon black and graphite, or fibrous carbon-containing compounds such as carbon nanotubes, can easily enter tiny spaces. For example, tiny spaces refer to the regions between multiple active materials. By combining a carbon-containing compound that easily enters tiny spaces with a sheet-like carbon-containing compound such as graphene, which can impart conductivity across multiple particles, the density of the electrode can be increased, and an excellent conductive path can be formed.

[0070] [Binder] The active material layer preferably contains a binder. The binder binds or fixes, for example, the electrolyte and the active material. The binder can also bind or fix the electrolyte and a carbon-based material, the active material and another carbon-based material, multiple active materials together, multiple carbon-based materials, etc.

[0071] As the binder, it is preferable to use a material such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, or nitrocellulose.

[0072] Polyimide has excellent thermal, mechanical and chemical stability.

[0073] A fluorine-containing polymer material, such as a fluoropolymer, can be used. PVDF is a resin with a melting point in the range of 134°C to 169°C, and is a material with excellent thermal stability.

[0074] As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. As the binder, fluororubber can also be used.

[0075] Furthermore, it is preferable to use, for example, a water-soluble polymer as the binder. Examples of the water-soluble polymer that can be used include polysaccharides. Examples of the polysaccharide that can be used include cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.

[0076] The binder may be used in combination with two or more of the above.

[0077] <Graphene Compound> In this specification and the like, graphene compounds include graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multi-graphene oxide, graphene quantum dots, and the like. Graphene compounds contain carbon, have a shape such as a plate or sheet, and have a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by six-membered carbon rings may also be referred to as a carbon sheet. Graphene compounds may have functional groups. Furthermore, graphene compounds preferably have a curved shape. Furthermore, graphene compounds may be rolled up to resemble carbon nanofibers.

[0078] In this specification and the like, graphene oxide refers to, for example, a material that contains carbon and oxygen, has a sheet-like shape, and has a functional group, in particular, an epoxy group, a carboxy group, or a hydroxy group.

[0079] In this specification, reduced graphene oxide refers to, for example, a material containing carbon and oxygen, having a sheet-like shape, and having a two-dimensional structure formed by six-membered carbon rings. It may also be called a carbon sheet. A single reduced graphene oxide can function, but multiple sheets may be stacked. Reduced graphene oxide preferably has a portion where the carbon concentration is greater than 80 atomic % and the oxygen concentration is 2 atomic % or more and 15 atomic % or less. By achieving these carbon and oxygen concentrations, reduced graphene oxide can function as a highly conductive material even in small amounts. Furthermore, reduced graphene oxide preferably has an intensity ratio G / D of the G band to the D band in a Raman spectrum of 1 or more. Reduced graphene oxide with such an intensity ratio can function as a highly conductive material even in small amounts.

[0080] By reducing graphene oxide, it may be possible to provide holes in the graphene compound.

[0081] Alternatively, a material in which the ends of graphene are terminated with fluorine may be used.

[0082] In the longitudinal section of the active material layer, the sheet-like graphene compound is dispersed substantially uniformly in the inner region of the active material layer. The plurality of graphene compounds are formed so as to partially cover the plurality of granular active material particles or to be attached to the surfaces of the plurality of granular active material particles, and are in surface contact with each other.

[0083] Here, a mesh-like graphene compound sheet (hereinafter referred to as a graphene compound net or graphene net) can be formed by bonding multiple graphene compounds together. When an active material is covered with a graphene net, the graphene net can also function as a binder that bonds the active materials together. Therefore, the amount of binder can be reduced or no binder can be used, thereby improving the ratio of the active material to the electrode volume or weight. In other words, the charge / discharge capacity of a secondary battery can be increased.

[0084] Here, it is preferable to use graphene oxide as the graphene compound, mix it with an active material to form a layer that will become an active material layer, and then reduce it. That is, the completed active material layer preferably contains reduced graphene oxide. By using graphene oxide, which has extremely high dispersibility in a polar solvent, to form the graphene compound, it is possible to substantially uniformly disperse the graphene compound in the internal region of the active material layer. Since the solvent is volatilized and removed from the dispersion medium containing the uniformly dispersed graphene oxide and the graphene oxide is reduced, the graphene compound remaining in the active material layer partially overlaps and is dispersed to such an extent that it is in surface contact with each other, thereby forming a three-dimensional conductive path. Note that the reduction of graphene oxide may be performed, for example, by heat treatment or using a reducing agent.

[0085] Furthermore, by using a spray dryer in advance, a graphene compound, which is a conductive material, can be formed as a coating that covers the entire surface of the active material, and further, the active material can be electrically connected to each other by the graphene compound to form a conductive path.

[0086] Furthermore, a material used in forming the graphene compound may be mixed with the graphene compound and used in the active material layer. For example, particles used as a catalyst in forming the graphene compound may be mixed with the graphene compound. Examples of catalysts used in forming the graphene compound include silicon oxide (SiO ２ , SiO ｘ (x<2)), aluminum oxide, iron, nickel, ruthenium, iridium, platinum, copper, germanium, etc. The particles preferably have an average particle diameter (D50: also referred to as median diameter) of 1 μm or less, more preferably 100 nm or less.

[0087] [Separator] A separator is disposed between the positive electrode and the negative electrode. Examples of separators that can be used include those made of cellulose-containing fibers such as paper, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers such as nylon (polyamide), vinylon (polyvinyl alcohol-based fibers), polyester, acrylic, polyolefin, and polyurethane. The separator is preferably processed into a bag shape and disposed so as to encase either the positive electrode or the negative electrode.

[0088] The separator is a porous material having pores with a diameter of about 20 nm, preferably pores with a diameter of 6.5 nm or more, and more preferably pores with a diameter of at least 2 nm.

[0089] The separator may have a multilayer structure. For example, an organic film such as polypropylene or polyethylene may be coated with a ceramic material, a fluorine-based material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine-based materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aramid (meta-aramid, para-aramid).

[0090] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging and improving the reliability of secondary batteries. Coating with fluorine-based materials also improves adhesion between the separator and electrodes, improving output characteristics. Coating with polyamide materials, especially aramid, improves heat resistance, improving the safety of secondary batteries.

[0091] For example, both sides of a polypropylene film may be coated with a mixed material of aluminum oxide and aramid, or the surface of the polypropylene film that contacts the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface that contacts the negative electrode may be coated with a fluorine-based material.

[0092] When a separator with a multilayer structure is used, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, and therefore the capacity per volume of the secondary battery can be increased.

[0093] [Electrolyte] When a liquid electrolyte is used in a secondary battery, for example, the electrolyte may be one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, and the like, or two or more of these may be used in any combination and ratio.

[0094] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the electrolyte solvent, it is possible to prevent the secondary battery from exploding or catching fire even if the temperature of the internal region of the secondary battery rises due to a short circuit in the internal region or overcharging. The ionic liquid is composed of a cation and an anion, and includes an organic cation and an anion. Examples of the organic cation include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anion include monovalent amide anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkylsulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0095] In particular, in the case where silicon is used as the second active material in the negative electrode of the secondary battery of one embodiment of the present invention, a liquid electrolyte containing an ionic liquid is preferably used.

[0096] The secondary battery of one embodiment of the present invention includes, as carrier ions, alkali metal ions such as sodium ions and potassium ions, or alkaline earth metal ions such as calcium ions, strontium ions, barium ions, beryllium ions, and magnesium ions.

[0097] When lithium ions are used as carrier ions, the electrolyte contains a lithium salt, for example, LiPF ６ , LiClO ４ , LiAsF ６ , LiBF ４ , LiAlCl ４ , LiSCN, LiBr, LiI, Li ２ SO ４ , Li ２ B １０ Cl １０ , Li ２ B １２ Cl １２ , LiCF ３ SO３ , LiC ４ F ９ SO ３ , LiC(CF ３ SO ２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiN(CF ３ SO ２ ) ２ , LiN(C ４ F ９ SO ２ ) (CF ３ SO ２ ), LiN(C ２ F ５ SO ２ ) ２ etc. can be used.

[0098] The electrolyte preferably contains fluorine. For example, an electrolyte containing one or more fluorinated cyclic carbonates and lithium ions can be used as the fluorine-containing electrolyte. The fluorinated cyclic carbonate improves non-flammability and can enhance the safety of the lithium ion secondary battery.

[0099] Examples of fluorinated cyclic carbonates that can be used include fluorinated ethylene carbonate, such as monofluoroethylene carbonate (fluoroethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), and tetrafluoroethylene carbonate (F4EC). DFEC includes isomers such as cis-4,5 and trans-4,5. For low-temperature operation, it is important to use one or more fluorinated cyclic carbonates as an electrolyte to solvate lithium ions and transport them within the electrolyte contained in the electrode during charging and discharging. Using a fluorinated cyclic carbonate not as a small amount of additive but contributing to the transport of lithium ions during charging and discharging enables low-temperature operation. Within a secondary battery, lithium ions move in clusters of several to several tens of ions.

[0100] The use of a fluorinated cyclic carbonate in the electrolyte reduces the desolvation energy required for lithium ions solvated in the electrolyte contained in the electrode to enter active material particles. Reducing this desolvation energy facilitates insertion and desorption of lithium ions into active material particles, even at low temperatures. While lithium ions may migrate in a solvated state, a hopping phenomenon, in which the coordinated solvent molecules switch positions, may also occur. When lithium ions are more easily desolvated, they may be more susceptible to migration via the hopping phenomenon, which may facilitate lithium ion migration. There is a concern that electrolyte decomposition products cling to the surface of the active material during charging and discharging of secondary batteries, causing deterioration of the secondary battery. However, when the electrolyte contains fluorine, the electrolyte is smooth, making it difficult for electrolyte decomposition products to adhere to the surface of the active material. This reduces secondary battery degradation.

[0101] A plurality of solvated lithium ions may form clusters in the electrolyte and move within the negative electrode, between the positive electrode and the negative electrode, within the positive electrode, etc.

[0102] In this specification, the term "electrolyte" is a general term that includes solid, liquid, or semi-solid materials.

[0103] Deterioration is likely to occur at interfaces present in secondary batteries, such as the interface between the active material and the electrolyte. In a secondary battery according to one embodiment of the present invention, the presence of a fluorine-containing electrolyte can prevent deterioration that may occur at the interface between the active material and the electrolyte, typically, electrolyte alteration or increased viscosity. Furthermore, a binder, graphene compound, or the like may be attached to or retained by the fluorine-containing electrolyte. This configuration can maintain a reduced viscosity of the electrolyte, in other words, a smooth electrolyte, thereby improving the reliability of the secondary battery. DFEC, which has two fluorine atoms, and F4EC, which has four fluorine atoms, have lower viscosity and smoother texture than FEC, which has one fluorine atom, and their coordination bond with lithium is weaker. Therefore, adhesion of viscous decomposition products to active material particles can be reduced. Adhesion or adhesion of viscous decomposition products to active material particles hinders lithium ion migration at the interface between the active material particles. A fluorine-containing electrolyte reduces the formation of decomposition products on the surface of the active material (positive electrode active material or negative electrode active material) by solvation. Furthermore, by using an electrolyte containing fluorine, it is possible to prevent the adhesion of decomposition products, thereby preventing the generation and growth of dendrites.

[0104] Another feature is that a fluorine-containing electrolyte is used as the main component, and the fluorine-containing electrolyte is 5% by volume or more, 10% by volume or more, preferably 30% by volume or more and 100% by volume or less.

[0105] In this specification, the term "main component of the electrolyte" refers to 5% by volume or more of the total electrolyte of the secondary battery. Furthermore, "5% by volume or more of the total electrolyte of the secondary battery" refers to the percentage of the total electrolyte measured during the manufacture of the secondary battery. Furthermore, when disassembling a secondary battery after fabrication, it is difficult to quantify the percentage of each of multiple types of electrolytes, but it is possible to determine whether a certain type of organic compound accounts for 5% by volume or more of the total electrolyte.

[0106] By using an electrolyte containing fluorine, a secondary battery that can operate over a wide temperature range, specifically, from -40°C to 150°C, preferably from -40°C to 85°C, can be realized.

[0107] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), lithium bis(oxalato)borate (LiBOB), or dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be, for example, 0.1% by volume or more and less than 5% by volume with respect to the total volume of the electrolyte.

[0108] In addition to the above, the electrolyte may contain one or more aprotic organic solvents such as γ-butyrolactone, acetonitrile, dimethoxyethane, and tetrahydrofuran.

[0109] Furthermore, the use of a gelling polymer material in the electrolyte increases safety against leakage, etc. Typical examples of gelling polymer materials include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel.

[0110] Examples of polymeric materials that can be used include polymers having a polyalkylene oxide structure, such as polyethylene oxide (PEO), PVDF, and polyacrylonitrile, as well as copolymers containing these. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The polymers formed may also have a porous shape.

[0111] Although the above configuration shows an example of a secondary battery using a liquid electrolyte, it is not particularly limited. For example, semi-solid batteries and all-solid batteries can also be produced.

[0112] In this specification, the layer disposed between the positive electrode and the negative electrode is referred to as the electrolyte layer in both the case of a secondary battery using a liquid electrolyte and the case of a semi-solid battery. The electrolyte layer of a semi-solid battery can be said to be a layer formed by film formation, and can be distinguished from a liquid electrolyte layer.

[0113] In addition, in this specification, a semi-solid battery refers to a battery having a semi-solid material in at least one of the electrolyte layer, positive electrode, and negative electrode. Here, semi-solid does not mean that the ratio of solid material is 50%. Semi-solid means that while having solid properties such as small volume change, it also has some liquid-like properties such as flexibility. As long as these properties are met, the battery may be made of a single material or multiple materials. For example, a porous solid material may be impregnated with a liquid material.

[0114] In this specification, a polymer electrolyte secondary battery refers to a secondary battery having a polymer in the electrolyte layer between a positive electrode and a negative electrode. Polymer electrolyte secondary batteries include dry (or intrinsic) polymer electrolyte batteries and polymer gel electrolyte batteries.

[0115] The electrolyte comprises a lithium ion conductive polymer and a lithium salt.

[0116] In this specification, the lithium ion conductive polymer is a polymer that has conductivity for cations such as lithium. More specifically, it is a polymer compound having a polar group to which a cation can be coordinated. The polar group preferably has an ether group, an ester group, a nitrile group, a carbonyl group, a siloxane group, or the like.

[0117] Examples of the lithium ion conductive polymer that can be used include polyethylene oxide (PEO), derivatives having polyethylene oxide as the main chain, polypropylene oxide, polyacrylic acid ester, polymethacrylic acid ester, polysiloxane, and polyphosphazene.

[0118] The lithium ion conductive polymer may be branched or crosslinked, or may be a copolymer. The molecular weight is preferably 10,000 or more, and more preferably 100,000 or more.

[0119] In lithium ion conductive polymers, lithium ions move while changing the polar groups they interact with due to the partial motion (also called segmental motion) of the polymer chain. For example, in the case of PEO, lithium ions move while changing the oxygen they interact with due to the segmental motion of the ether chain. When the temperature is close to or higher than the melting point or softening point of the lithium ion conductive polymer, the crystalline regions dissolve, the amorphous regions increase, and the motion of the ether chains becomes more active, resulting in higher ionic conductivity. Therefore, when using PEO as a lithium ion conductive polymer, it is preferable to charge and discharge at 60°C or higher.

[0120] According to Shannon's ionic radius (Shannon et al., Acta A 32 (1976) 751.), the radius of a monovalent lithium ion is 0.590 × 10 when it is four-coordinated. −１ nm, 0.76 × 10 for 6 coordinations −１ nm, 0.92 × 10 for 8 coordinations −１ The radius of a divalent oxygen ion is 1.35 × 10 −１ nm, 1.36 × 10 for three-coordinate −１ nm, 1.38 × 10 for 4 coordinations −１ nm, 1.40 × 10 for 6 coordinations −１ nm, 1.42 × 10 for 8 coordinations −１ The distance between the polar groups of adjacent lithium ion conductive polymer chains is preferably at least the distance at which the lithium ions and the anions of the polar groups can stably exist while maintaining the ionic radius as described above. It is also preferable that the distance be such that sufficient interaction occurs between the lithium ions and the polar groups. However, as described above, segmental motion occurs, so it is not necessary to maintain a constant distance at all times. It is sufficient to maintain a distance that is appropriate for the lithium ions to pass through.

[0121] As the lithium salt, for example, a compound containing lithium and at least one of phosphorus, fluorine, nitrogen, sulfur, oxygen, chlorine, arsenic, boron, aluminum, bromine, and iodine can be used. For example, LiPF ６ , LiN(FSO ２ ) ２(lithium bis(fluorosulfonyl)imide, LiFSI), LiClO ４ , LiAsF ６ , LiBF ４ , LiAlCl ４ , LiSCN, LiBr, LiI, Li ２ SO ４ , Li ２ B １０ Cl １０ , Li ２ B １２ Cl １２ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiC(CF ３ SO ２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiN(CF ３ SO ２ ) ２ , LiN(C ４ F ９ SO ２ ) (CF ３ SO ２ ), LiN(C ２ F ５ SO ２ ) ２ , lithium bis(oxalato)borate (LiBOB), or the like, can be used alone or in any combination and ratio of two or more of these.

[0122] In particular, the use of LiFSI is preferable because it provides good low-temperature properties. Furthermore, LiFSI and LiTFSA are less reactive with water than LiPF6 and other compounds. This facilitates dew point control when fabricating electrodes and electrolyte layers using LiFSI. For example, LiFSI can be used in an inert atmosphere such as argon, where moisture is minimized, or in a dry room with a controlled dew point, as well as in normal air. This improves productivity and is therefore preferable. Furthermore, the use of highly dissociable and plasticizing Li salts such as LiFSI and LiTFSA is particularly preferable when using lithium conduction utilizing the segmental motion of ether chains, because they can be used over a wide temperature range.

[0123] The absence or very small amount of organic solvents makes it possible to produce a secondary battery that is less likely to catch fire or ignite, which is preferable because it improves safety. Furthermore, if the electrolyte contains no or very little organic solvent, the electrolyte layer has sufficient strength even without a separator, and it is possible to electrically insulate the positive electrode and the negative electrode. Since a separator is not required, a secondary battery with high productivity can be produced. If the electrolyte layer contains an electrolyte and an inorganic filler, the strength is further increased, and a secondary battery with higher safety can be produced.

[0124] [Exterior Body] Exterior bodies of secondary batteries can be made of metal materials such as aluminum and resin materials. Film-like exterior bodies can also be used. Examples of films that can be used include a three-layer structure in which a thin, flexible metal film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is further provided on the thin metal film as the outer surface of the exterior body. It is also preferable to use a fluororesin film as the film. Fluororesin films have high stability against acids, alkalis, organic solvents, etc., and can suppress side reactions, corrosion, etc. associated with secondary battery reactions, thereby achieving excellent secondary batteries. Examples of fluororesin films include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane: a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), FEP (perfluoroethylene propene copolymer: a copolymer of tetrafluoroethylene and hexafluoropropylene), and ETFE (ethylene tetrafluoroethylene copolymer: a copolymer of tetrafluoroethylene and ethylene).

[0125] <Example of Negative Electrode Active Material> As the negative electrode active material, it is preferable to use a material capable of reacting with carrier ions of a secondary battery, a material capable of inserting and desorbing carrier ions, a material capable of alloying with a metal that becomes a carrier ion, a material capable of dissolving and precipitating a metal that becomes a carrier ion, or the like.

[0126] An example of the negative electrode active material will be described below.

[0127] As the negative electrode active material, a metal or a compound containing one or more elements selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium can be used. Examples of alloy compounds using such elements include Mg ２ Si, Mg ２ Ge, Mg ２ Sn, SnS ２ , V２ Sn ３ , FeSn ２ , CoSn ２ , Ni ３ Sn ２ , Cu ６ Sn ５ , Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb ３ , LaSn ３ , La ３ Co ２ Sn ７ , CoSb ３ , InSb, SbSn, etc.

[0128] Furthermore, materials with low resistance obtained by adding impurity elements such as phosphorus, arsenic, boron, aluminum, and gallium to silicon may also be used. Silicon materials pre-doped with lithium may also be used. Pre-doping methods include mixing silicon with lithium fluoride, lithium carbonate, and the like and annealing the mixture, or mechanical alloying of lithium metal and silicon. Furthermore, after forming an electrode containing silicon (silicon electrode), it can be combined with an electrode such as lithium metal to dope (pre-dope) lithium through a charge-discharge reaction. The doped silicon electrode may then be combined with a counter electrode (e.g., a positive electrode for the pre-doped negative electrode) to produce a secondary battery.

[0129] For example, silicon nanoparticles can be used as the negative electrode active material. The silicon nanoparticles preferably have an average particle diameter D50 of 5 nm or more and less than 1 μm, more preferably 10 nm or more and 300 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0130] The silicon nanoparticles may be crystalline, or may have a crystalline region and an amorphous region.

[0131] Examples of silicon-containing materials include SiO ｘ (x is preferably smaller than 2, more preferably 0.5 or more and 1.6 or less) can be used.

[0132] As the negative electrode active material, for example, carbon-based materials such as graphite, graphitizable carbon, non-graphitizable carbon, carbon nanotubes, carbon black, and graphene compounds can be used.

[0133] Furthermore, as the negative electrode active material, for example, an oxide containing one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0134] As the negative electrode active material, a combination of the above-mentioned metals, materials, compounds, etc. can be used.

[0135] Examples of the negative electrode active material include SnO, SnO ２ , titanium dioxide (TiO ２ ), lithium titanium oxide (Li ４ Ti ５ O １２ ), lithium-graphite intercalation compound (Li ｘ C ６ ), niobium pentoxide (Nb ２ O ５ ), tungsten oxide (WO ２ ), molybdenum oxide (MoO ２ ) and other oxides can be used.

[0136] In addition, as the negative electrode active material, a composite nitride of lithium and a transition metal, Li ３ Li with N-type structure ３−ｘ M ｘ N (M=Co, Ni, Cu) can be used. For example, Li ２．６ Co ０．４ N ３ exhibits a large charge / discharge capacity (900 mAh / g) and is therefore preferred.

[0137] When a composite nitride of lithium and transition metals is used as the negative electrode material, V containing no lithium ions can be used as the positive electrode material. ２ O ５ , Cr ３ O ８It is preferable that the composite nitride of lithium and a transition metal be used as the negative electrode material, even when a material containing lithium ions is used as the positive electrode material, by first removing the lithium ions contained in the positive electrode material.

[0138] Furthermore, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, a transition metal oxide that does not undergo an alloying reaction with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO), can be used as the negative electrode active material. Further examples of materials that undergo a conversion reaction include Fe ２ O ３ ,CuO,Cu ２ O, RuO ２ , Cr ２ O ３ oxides such as CoS ０．８９ , sulfides such as NiS and CuS, Zn ３ N ２ , Cu ３ N, Ge ３ N ４ Nitrides such as NiP ２ , FeP ２ , CoP ３ Phosphides such as FeF ３ , BiF ３ This phenomenon also occurs with fluorides such as those listed above. Since the potential of the fluorides is high, they may also be used as positive electrode materials.

[0139] Lithium can also be used as the negative electrode active material. When lithium is used as the negative electrode active material, foil-shaped lithium can be provided on the negative electrode current collector. Lithium can also be provided on the negative electrode current collector by a gas phase method such as vapor deposition or sputtering. Lithium can also be electrochemically deposited on the negative electrode current collector in a solution containing lithium ions.

[0140] The conductive material and binder that can be contained in the negative electrode active material layer can be the same as the conductive material and binder that can be contained in the positive electrode active material layer.

[0141] In addition to the same materials as the positive electrode current collector, copper etc. can also be used as the current collector. It is preferable to use a material that does not alloy with carrier ions such as lithium for the negative electrode current collector.

[0142] As another embodiment of the negative electrode of the present invention, a negative electrode having no negative electrode active material can be used. In a secondary battery using a negative electrode having no negative electrode active material, lithium is deposited on the negative electrode current collector during charging, and the lithium on the negative electrode current collector can be eluted during discharging. Therefore, except in a fully discharged state, lithium is present on the negative electrode current collector.

[0143] When a negative electrode having no negative electrode active material is used, a film for uniformly depositing lithium may be provided on the negative electrode current collector. For example, a solid electrolyte having lithium ion conductivity can be used as the film for uniformly depositing lithium. Examples of solid electrolytes that can be used include sulfide-based solid electrolytes, oxide-based solid electrolytes, and polymer-based solid electrolytes. Among these, polymer-based solid electrolytes are suitable as a film for uniformly depositing lithium because they can be formed uniformly on the negative electrode current collector with relative ease.

[0144] Furthermore, when a negative electrode that does not have a negative electrode active material is used, a negative electrode current collector having projections and recesses can be used. When a negative electrode current collector having projections and recesses is used, the recesses of the negative electrode current collector become cavities into which lithium contained in the negative electrode current collector can be easily deposited, and therefore, when lithium is deposited, it is possible to prevent it from forming a dendritic shape.

[0145] <Example of Positive Electrode Active Material> Examples of the positive electrode active material include lithium-containing composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure.

[0146] As the positive electrode active material of one embodiment of the present invention, a positive electrode active material having a layered crystal structure is preferably used.

[0147] An example of a layered crystal structure is a layered rock salt type crystal structure. An example of a lithium-containing composite oxide having a layered rock salt type crystal structure is LiM ｘ O ｙ(x>0 and y>0, more specifically, for example, y=2 and 0.8<x<1.2) can be used. Here, M is a metal element, preferably one or more selected from cobalt, manganese, nickel, and iron. Alternatively, M is, for example, two or more selected from cobalt, manganese, nickel, iron, aluminum, titanium, zirconium, lanthanum, copper, and zinc.

[0148] LiM ｘ O ｙ As a composite oxide having lithium represented by the formula: ２ , LiNiO ２ , LiMnO ２ Also, LiNi ｘ Co １−ｘ O ２ NiCo-based compounds represented by (0<x<1), LiM ｘ O ｙ Examples of composite oxides containing lithium represented by the formula: LiNi ｘ Mn １−ｘ O ２ NiMn-based alloys represented by (0<x<1), etc.

[0149] Also, LiMO ２ Examples of composite oxides containing lithium represented by the formula: LiNi ｘ Co ｙ Mn ｚ O ２Examples include NiCoMn-based alloys (also referred to as NCM) represented by the formula (x > 0, y > 0, 0.8 < x + y + z < 1.2). Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, it is preferable that x, y, and z satisfy x:y:z = 1:1:1 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 5:2:3 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 8:1:1 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 9:0.5:0.5 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 6:2:2 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 1:4:1 or a value thereabout.

[0150] In addition, the NiCoMn-based alloys described above preferably contain at least one element selected from aluminum, magnesium, titanium, and boron in an amount of 0.1 mol % to 3 mol %.

[0151] Furthermore, examples of lithium-containing composite oxides having a layered rock salt crystal structure include Li ２ MnO ３ , Li ２ MnO ３ -LiMeO ２ (Me is Co, Ni, Mn), etc.

[0152] The use of a cathode active material having a layered crystalline structure, such as the lithium-containing composite oxide, can sometimes realize a secondary battery with a high lithium content per volume and a high capacity per volume. Such cathode active materials also exhibit a large amount of lithium elimination per volume during charging, and stabilization of the crystalline structure after elimination is required for stable charging and discharging. Furthermore, the collapse of the crystalline structure during charging and discharging can sometimes impede high-speed charging or discharging.

[0153] LiMn as the positive electrode active material ２ O ４Lithium-containing materials having a spinel-type crystal structure containing manganese, such as lithium nickel oxide (LiNiO ２ or LiNi １−ｘ M ｘ O ２ It is preferable to mix (0<x<1) (M=Co, Al, etc.) This configuration can improve the characteristics of the secondary battery.

[0154] In addition, as the positive electrode active material, ａ Mn ｂ M ｃ O ｄ A lithium-manganese composite oxide that can be expressed by the formula (1) can be used. Here, element M is preferably a metal element selected from among lithium and manganese, or silicon or phosphorus, and more preferably nickel. Furthermore, when measuring the entire lithium-manganese composite oxide particle, it is preferable that 0<a / (b+c)<2, c>0, and 0.26≦(b+c) / d<0.5 are satisfied during discharge. The composition of metals, silicon, phosphorus, etc. in the entire lithium-manganese composite oxide particle can be measured, for example, using an inductively coupled plasma mass spectrometer (ICP-MS). The oxygen composition in the entire lithium-manganese composite oxide particle can be measured, for example, using energy dispersive X-ray spectroscopy (EDX). Furthermore, the composition can be determined by using valence evaluation of fused gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICPMS analysis. The lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, phosphorus, and the like.

[0155] [Structure of Positive Electrode Active Material] Positive electrode active materials of embodiments of the present invention will be described with reference to FIGS.

[0156] Fig. 6A is a schematic top view of a positive electrode active material 100 according to one embodiment of the present invention. Fig. 6B shows a schematic cross-sectional view taken along line A-B in Fig. 6A. Fig. 6C shows a schematic cross-sectional view taken along region C in Fig. 6A.

[0157] <Contained Elements and Distribution> The positive electrode active material 100 contains lithium, a transition metal M1, oxygen, and an additional element X. The positive electrode active material 100 is LiM1O ２ It can be said that the additive element X is added to a composite oxide represented by the formula (M1 is one or more selected from Fe, Ni, Co, and Mn).

[0158] The transition metal M1 contained in the positive electrode active material 100 is preferably a metal capable of forming a layered rock-salt composite oxide belonging to the space group R-3m with lithium. For example, at least one of manganese, cobalt, and nickel can be used as the transition metal M1. That is, the positive electrode active material 100 may contain only cobalt, only nickel, a combination of cobalt and manganese, or a combination of cobalt and nickel, or three of cobalt, manganese, and nickel. That is, the positive electrode active material 100 may contain a composite oxide containing lithium and a transition metal, such as lithium cobalt oxide, lithium nickel oxide, lithium cobalt oxide in which some of the cobalt is replaced with manganese, lithium cobalt oxide in which some of the cobalt is replaced with nickel, or nickel-manganese-lithium cobalt oxide. Including nickel in addition to cobalt as a transition metal may result in a more stable crystal structure in a deep charge state where the charge depth is 0.8 or greater (x = less than 0.2), which is preferable.

[0159] The additive element X contained in the positive electrode active material 100 is preferably one or more selected from nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic. These elements may further stabilize the crystalline structure of the positive electrode active material 100. That is, the positive electrode active material 100 may contain lithium cobalt oxide containing magnesium and fluorine, lithium cobalt oxide containing magnesium, fluorine, and titanium, lithium nickel-cobalt oxide containing magnesium and fluorine, lithium cobalt-aluminate containing magnesium and fluorine, nickel-cobalt-aluminate, lithium nickel-cobalt-aluminate, lithium nickel-cobalt-aluminate containing magnesium and fluorine, or lithium nickel-manganese-cobalt oxide containing magnesium and fluorine. In this specification and the like, the additive element X may be referred to as a mixture, a part of a raw material, or the like.

[0160] As shown in FIG. 6B , the positive electrode active material 100 has a surface layer portion 100a and an interior portion 100b. The surface layer portion 100a preferably has a higher concentration of the additive element X than the interior portion 100b. Furthermore, as shown by the gradation in FIG. 6B , the additive element X preferably has a concentration gradient that increases from the interior toward the surface. In this specification and the like, the surface layer portion 100a refers to a region extending from the surface of the positive electrode active material 100 to a depth of approximately 10 nm. Surfaces formed by cracks and / or fissures may also be referred to as the surface, and as shown in FIG. 6C , the region extending from the surface to a depth of approximately 10 nm is referred to as the surface layer portion 100c. Furthermore, the region deeper than the surface layer portion 100a and the surface layer portion 100c of the positive electrode active material 100 is referred to as the interior portion 100b.

[0161] In the positive electrode active material 100 according to one embodiment of the present invention, even when lithium is released from the positive electrode active material 100 due to charging, the surface layer portion 100 a having a high concentration of the additive element X, i.e., the outer periphery of the particle, is reinforced so as not to destroy the layered structure formed of octahedra of cobalt and oxygen.

[0162] Furthermore, it is preferable that the concentration gradient of the additive element X is uniformly distributed throughout the entire surface layer 100a of the positive electrode active material 100. Even if a portion of the surface layer 100a is reinforced, if there is a portion without reinforcement, stress may be concentrated in the unreinforced portion, which is undesirable. If stress is concentrated in a portion of the particle, defects such as cracks may occur there, which may lead to breakage of the positive electrode active material and a decrease in charge / discharge capacity.

[0163] Magnesium is divalent and is more stable at the lithium site than at the transition metal site in the layered rock-salt crystal structure, and therefore more likely to enter the lithium site. The presence of magnesium at an appropriate concentration at the lithium site in the surface layer 100a facilitates the maintenance of the layered rock-salt crystal structure. Furthermore, magnesium has a strong bond with oxygen, which can suppress the desorption of oxygen around the magnesium. At an appropriate concentration, magnesium is preferable because it does not adversely affect the intercalation and deintercalation of lithium during charge and discharge. However, excessive magnesium may adversely affect the intercalation and deintercalation of lithium.

[0164] Aluminum is trivalent and can exist at the transition metal site in the layered rock salt crystal structure. Aluminum can suppress the elution of surrounding cobalt. Furthermore, aluminum has a strong bond with oxygen, so it can suppress the desorption of oxygen from around the aluminum. Therefore, if aluminum is included as the additive element X, it is possible to obtain a positive electrode active material 100 whose crystal structure is resistant to collapse even after repeated charge and discharge.

[0165] Fluorine is a monovalent anion, and when a portion of the oxygen in the surface layer portion 100a is substituted with fluorine, the lithium desorption energy is reduced. This is because the change in valence of cobalt ions accompanying lithium desorption differs depending on whether or not fluorine is present. For example, the oxidation-reduction potential of cobalt ions differs, from trivalent to tetravalent in the absence of fluorine, and from divalent to trivalent in the presence of fluorine. Therefore, when a portion of the oxygen in the surface layer portion 100a of the positive electrode active material 100 is substituted with fluorine, it can be said that desorption and insertion of lithium ions near the fluorine is more likely to occur smoothly. Therefore, when used in a secondary battery, charge / discharge characteristics, rate characteristics, etc. are improved, which is preferable.

[0166] Titanium oxide is known to have superhydrophilic properties. Therefore, by forming the cathode active material 100 with titanium oxide in the surface layer portion 100a, it is possible that the cathode active material 100 has good wettability with highly polar solvents. When formed into a secondary battery, it is possible that the interface between the cathode active material 100 and a highly polar electrolyte solution will have good contact, thereby suppressing an increase in resistance. In this specification and the like, the electrolyte solution corresponds to a liquid electrolyte.

[0167] As the charging voltage of a secondary battery increases, the voltage of the positive electrode generally increases. The positive electrode active material of one embodiment of the present invention has a stable crystal structure even at high voltages. The stable crystal structure of the positive electrode active material in a charged state can suppress a decrease in capacity due to repeated charge and discharge.

[0168] Furthermore, a short circuit in a secondary battery not only causes problems in the charging and / or discharging operations of the secondary battery, but may also lead to heat generation and fire. To achieve a safe secondary battery, it is preferable that a short circuit current be suppressed even at a high charging voltage. The positive electrode active material 100 of one embodiment of the present invention suppresses a short circuit current even at a high charging voltage. Therefore, a secondary battery that achieves both high capacity and safety can be obtained.

[0169] A secondary battery using the positive electrode active material 100 of one embodiment of the present invention preferably simultaneously satisfies high capacity, excellent charge / discharge cycle characteristics, and safety.

[0170] The concentration gradient of the added element X can be evaluated, for example, by using energy dispersive X-ray spectroscopy (EDX). Among EDX measurements, measuring while scanning an area and evaluating the area two-dimensionally is sometimes called EDX area analysis. Extracting data of a linear area from EDX area analysis and evaluating the distribution of atomic concentration within the positive electrode active material particles is sometimes called line analysis.

[0171] EDX area analysis (e.g., element mapping) can quantitatively analyze the concentration of the additive element X in the surface layer portion 100a, the interior 100b, and the vicinity of the grain boundaries of the positive electrode active material 100. Furthermore, EDX ray analysis can analyze the distribution of the concentration of the additive element X.

[0172] When EDX-ray analysis is performed on the positive electrode active material 100, the peak of the magnesium concentration (the position where the concentration is maximum) in the surface layer portion 100a is preferably present at a depth of up to 3 nm from the surface toward the center of the positive electrode active material 100, more preferably at a depth of up to 1 nm, and even more preferably at a depth of up to 0.5 nm.

[0173] Furthermore, the fluorine distribution in the positive electrode active material 100 preferably overlaps with the magnesium distribution, and therefore, when EDX-ray analysis is performed, the peak of the fluorine concentration (the position where the concentration is maximum) in the surface layer portion 100 a is preferably present at a depth of up to 3 nm from the surface of the positive electrode active material 100 toward the center, more preferably at a depth of up to 1 nm, and even more preferably at a depth of up to 0.5 nm.

[0174] It should be noted that not all of the additive elements X need have the same concentration distribution. For example, when the positive electrode active material 100 contains aluminum as the additive element X, it is preferable that the distribution is slightly different from that of magnesium and fluorine. For example, when EDX-ray analysis is performed, it is preferable that the magnesium concentration peak is closer to the surface than the aluminum concentration peak in the surface layer portion 100a. For example, the aluminum concentration peak is preferably present at a depth of 0.5 nm to 20 nm from the surface toward the center of the positive electrode active material 100, and more preferably at a depth of 1 nm to 5 nm.

[0175] Furthermore, when EDX ray analysis or EDX area analysis is performed on the positive electrode active material 100, the ratio of the number of atoms of the additive element X to the number of atoms of the transition metal M1 (X / M1) in the vicinity of the grain boundaries is preferably 0.020 or more and 0.50 or less. More preferably, it is 0.025 or more and 0.30 or less. Even more preferably, it is 0.030 or more and 0.20 or less. For example, when the additive element X is magnesium and the transition metal M1 is cobalt, the ratio of the number of magnesium atoms to the number of cobalt atoms in the vicinity of the grain boundaries (Mg / Co) is preferably 0.020 or more and 0.50 or less. Even more preferably, it is 0.025 or more and 0.30 or less. Even more preferably, it is 0.030 or more and 0.20 or less.

[0176] As described above, an excess of the additive element contained in the positive electrode active material 100 may adversely affect the insertion and desorption of lithium. Furthermore, when used in a secondary battery, this may result in an increase in resistance and a decrease in capacity. On the other hand, an insufficient amount of the additive element may not be distributed throughout the entire surface layer portion 100a, resulting in an insufficient effect of maintaining the crystalline structure. In this way, the additive element X is adjusted to an appropriate concentration in the positive electrode active material 100.

[0177] Therefore, for example, the positive electrode active material 100 may have a region where excess additive element X is unevenly distributed. The presence of such a region allows excess additive element X to be removed from other regions, and an appropriate concentration of additive element X can be achieved in the interior and most of the surface layer portion of the positive electrode active material 100. By achieving an appropriate concentration of additive element X in the interior and most of the surface layer portion of the positive electrode active material 100, an increase in resistance and a decrease in capacity when the positive electrode active material 100 is used as a secondary battery can be suppressed. The ability to suppress an increase in resistance of a secondary battery is an extremely desirable characteristic, particularly in high-rate charge / discharge.

[0178] Furthermore, in the positive electrode active material 100 having a region where the excess additive element X is unevenly distributed, it is permissible to mix a certain amount of excess additive element X in the manufacturing process, which is preferable because it widens the margin in production.

[0179] In this specification and the like, uneven distribution refers to the difference in concentration of a certain element between a certain region A and a certain region B. It may also be referred to as segregation, precipitation, non-uniformity, deviation, high concentration or low concentration, etc.

[0180] <Crystal structure> Lithium cobalt oxide (LiCoO ２ Materials having a layered rock salt type crystal structure, such as LiM1O2, have a high discharge capacity and are known to be excellent as positive electrode active materials for secondary batteries. ２ (M1 is one or more selected from Fe, Ni, Co, and Mn).

[0181] It is known that the strength of the Jahn-Teller effect in transition metal compounds varies depending on the number of electrons in the d orbital of the transition metal.

[0182] In compounds containing nickel, distortion may easily occur due to the Jahn-Teller effect. ２ When LiCoO is repeatedly charged and discharged to a deep depth of charge of 0.8 or more (x=less than 0.2), there is a concern that the crystal structure may be destroyed due to distortion. ２ It is suggested that the influence of the Jahn-Teller effect is small in this case, and the durability when deep charging and discharging to a charge depth of 0.8 or more (x=less than 0.2) is repeated may be better, which is preferable.

[0183] The positive electrode active material will be described with reference to Fig. 7 to Fig. 10. Fig. 7 to Fig. 10 describe the case where cobalt is used as the transition metal contained in the positive electrode active material.

[0184] <Conventional Positive Electrode Active Material> The positive electrode active material shown in FIG. 9 is lithium cobalt oxide (LiCoO ２ , LCO). The crystal structure of the lithium cobalt oxide shown in FIG. 9 changes depending on the charge depth. In other words, LixCoO ２ In this case, the crystal structure changes depending on the occupancy rate x of lithium at the lithium site.

[0185] As shown in FIG. 9, lithium cobalt oxide in the state of x=1 (discharged state) has a region having a crystal structure of the space group R-3m, and CoO ２There are three layers. Therefore, this crystal structure is sometimes called an O3 type crystal structure. ２ The layer refers to a structure in which octahedral structures in which cobalt is six-coordinated with oxygen atoms are continuous in the plane direction with edge sharing.

[0186] It is also known that conventional lithium cobalt oxide has a crystal structure that has high lithium symmetry when x is about 0.5 and belongs to the monoclinic space group P2 / m. This structure has CoO ２ Therefore, it is sometimes called a monoclinic O1 type crystal structure. When x = 0, it has a crystal structure of the trigonal space group P-3m1, and there is one CoO ２ There is one layer. Therefore, this crystal structure is sometimes called a trigonal O1 type crystal structure.

[0187] When x is about 0.12, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to CoO such as P-3m1(O1). ２ and LiCoO such as R-3m(O3). ２ It can also be said that this crystal structure is a structure in which the structure of and the structure of are stacked alternately. For this reason, this crystal structure is sometimes called an H1-3 crystal structure. Because unevenness can occur in the insertion and desorption of lithium, an H1-3 crystal structure is experimentally observed from approximately x = 0.25. In reality, the number of cobalt atoms per unit cell in the H1-3 crystal structure is twice that of other structures. However, in Figure 9 and other parts of this specification, to make it easier to compare with other structures, the c-axis of the H1-3 crystal structure is shown as half the unit cell.

[0188] As an example, the coordinates of cobalt and oxygen in the unit cell of the H1-3 crystal structure can be expressed as Co(0,0,0.42150±0.00016), O1(0,0,0.27671±0.00045), and O2(0,0,0.11535±0.00045). O1 and O2 are each an oxygen atom. In this way, the H1-3 crystal structure is expressed by a unit cell using one cobalt and two oxygen atoms. On the other hand, as described below, the O3' crystal structure of one embodiment of the present invention is preferably expressed by a unit cell using one cobalt and one oxygen atom. This indicates that the symmetry between cobalt and oxygen differs between the O3' crystal structure and the H1-3 structure, and that the O3' crystal structure changes less from the O3 structure than the H1-3 structure. The unit cell that is more preferably used to represent the crystal structure of the positive electrode active material may be selected, for example, so that the GOF (goodness of fit) value becomes smaller in Rietveld analysis of the XRD pattern.

[0189] When lithium cobalt oxide is repeatedly charged at a high voltage of 4.6 V or higher based on the redox potential of lithium metal, or when it is deeply charged to a depth of x of 0.24 or lower, and then discharged, the crystal structure of the lithium cobalt oxide repeatedly changes (i.e., undergoes a non-equilibrium phase change) between the H1-3 crystal structure and the R-3m(O3) structure in the discharged state.

[0190] However, these two crystal structures are different from CoO ２ As shown by the dotted lines and arrows in FIG. 9, in the H1-3 type crystal structure, CoO ２ The layers deviate significantly from R-3m(O3). Such dynamic structural changes can adversely affect the stability of the crystal structure.

[0191] Furthermore, the difference in volume is large: when compared per the same number of cobalt atoms, the difference in volume between the H1-3 type crystal structure and the O3 type crystal structure in a discharged state is 3.0% or more.

[0192] In addition, the H1-3 type crystal structure has CoO such as P-3m1(O1). ２ A structure with continuous layers is likely to be unstable.

[0193] Therefore, when lithium cobalt oxide is repeatedly charged and discharged to a depth of charge of 0.8 or more (less than x = 0.2), its crystal structure collapses. This collapse of the crystal structure causes a deterioration in cycle performance. This is thought to be because the collapse of the crystal structure reduces the number of sites where lithium can exist stably and makes it difficult for lithium to be inserted and extracted.

[0194] <Positive Electrode Active Material of One Embodiment of the Present Invention> <Interior> The positive electrode active material 100 of one embodiment of the present invention is characterized in that, upon repeated deep charging to a charge depth of 0.8 or more and discharging, the CoO ２ The layer misalignment can be reduced. Furthermore, the change in volume can be reduced. Therefore, the positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. Furthermore, the positive electrode active material of one embodiment of the present invention can have a stable crystal structure in a deeply charged state where the depth of charge is 0.8 or more. Therefore, the positive electrode active material of one embodiment of the present invention may be less likely to cause a short circuit when maintained in a deeply charged state where the depth of charge is 0.8 or more. In such cases, safety is further improved, which is preferable.

[0195] In the positive electrode active material of one embodiment of the present invention, the change in crystal structure and the difference in volume per the same number of transition metal atoms between a fully discharged state and a deeply charged state where the charge depth is 0.8 or more are small.

[0196] The crystal structure of the positive electrode active material 100 before and after charge and discharge is shown in Figure 7. The positive electrode active material 100 is a composite oxide containing lithium, cobalt as a transition metal, and oxygen. In addition to the above, it is preferable that the positive electrode active material 100 contains magnesium as the additional element X. It is also preferable that the additional element X further contains a halogen such as fluorine or chlorine.

[0197] The crystal structure of Figure 7 when x = 1 (discharged state) is the same as that of Figure 9, R-3m(O3). On the other hand, the positive electrode active material 100 of one embodiment of the present invention has a crystal structure different from the H1-3 type crystal structure when in a fully charged state. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium ions occupy the oxygen hexacoordination positions. In addition, CoO in this structure ２ The symmetry of the layers is the same as that of the O3 type. Therefore, this structure is referred to as an O3' type crystal structure in this specification. In the diagram of the O3' type crystal structure shown in FIG. 7, lithium is omitted in order to explain the symmetry of the cobalt atom and the symmetry of the oxygen atom. However, in reality, CoO ２ Between the layers, for example, 20 atomic % or less of lithium is present relative to cobalt. In both the O3 type crystal structure and the O3' type crystal structure, CoO ２ It is preferable that magnesium is present in a dilute form between the layers, i.e., at the lithium sites, and it is also preferable that halogen such as fluorine is present randomly and dilutely at the oxygen sites.

[0198] In the O3' type crystal structure, a light element such as lithium may occupy the oxygen tetracoordination position.

[0199] The O3' type crystal structure has random lithium between layers, but it can also be said to be a crystal structure similar to the CdCl2 type crystal structure. ２ A crystal structure similar to the type was formed when lithium nickel oxide was charged to x = 0.06 (Li ０．０６ NiO ２ ), but it is known that pure lithium cobaltate or layered rock salt-type positive electrode active materials containing a large amount of cobalt do not usually adopt this crystal structure.

[0200] In the positive electrode active material 100 according to one embodiment of the present invention, when a large amount of lithium is released by charging to a deep depth of charge of 0.8 or more, the change in the crystal structure is suppressed more than in conventional positive electrode active materials. For example, as shown by the dotted line in FIG. 7, in these crystal structures, CoO ２ There is almost no layer misalignment.

[0201] More specifically, the cathode active material 100 of one embodiment of the present invention has high structural stability even at high charge voltages. For example, in conventional cathode active materials, there exists a charge voltage region where the R-3m(O3) crystal structure can be maintained even at a charge voltage where the H1-3 crystal structure is formed, for example, at a voltage of about 4.6 V relative to the potential of lithium metal. Furthermore, there exists a region where the O3' crystal structure can be formed even at a higher charge voltage, for example, at a voltage of about 4.65 V to 4.7 V relative to the potential of lithium metal. Furthermore, there exists a region where the H1-3 crystal structure can be formed even at a higher charge voltage, for example, at a voltage of about 4.65 V to 4.7 V relative to the potential of lithium metal. Furthermore, there exists a region where the H1-3 crystal can be formed even at a higher charge voltage, for example, at a voltage of 4.3 V or higher and 4.5 V or lower relative to the potential of lithium metal.

[0202] Therefore, in the positive electrode active material 100 of one embodiment of the present invention, the crystal structure is unlikely to be destroyed even when deep charging to a depth of charge of 0.8 or more and discharging are repeated.

[0203] In the positive electrode active material 100, the difference in volume per unit cell between the O3 type crystal structure where x=1 and the O3' type crystal structure where x=0.2 is 2.5% or less, more specifically 2.2% or less.

[0204] In the O3' type crystal structure, the coordinates of cobalt and oxygen in the unit cell can be expressed within the range of Co(0,0,0.5), O(0,0,x), 0.20≦x≦0.25.

[0205] The additive element X, for example, magnesium, which is randomly and dilutely present between the CoO2 layers, i.e., at the lithium site, has the effect of suppressing the displacement of the CoO2 layers. ２When magnesium is present between layers, the O3'-type crystal structure is likely to be formed. Therefore, magnesium is preferably distributed in at least a part of the surface layer portion of the particle of the positive electrode active material 100 of one embodiment of the present invention, and more preferably distributed throughout the surface layer portion of the particle of the positive electrode active material 100. In order to distribute magnesium throughout the surface layer portion of the particle of the positive electrode active material 100, heat treatment is preferably performed in the process of manufacturing the positive electrode active material 100 of one embodiment of the present invention.

[0206] However, if the heat treatment temperature is too high, cation mixing occurs, increasing the possibility that the additive element X, such as magnesium, will enter the cobalt site. Magnesium present at the cobalt site is ineffective in maintaining the R-3m structure under high-voltage charging. Furthermore, if the heat treatment temperature is too high, there are concerns about adverse effects such as cobalt being reduced to divalent and lithium being evaporated or sublimated.

[0207] Therefore, it is preferable to add a halogen compound such as a fluorine compound to the lithium cobalt oxide before the heat treatment for distributing magnesium throughout the surface layer of the particles of the positive electrode active material 100. The addition of the halogen compound lowers the melting point of the lithium cobalt oxide. Lowering the melting point makes it easier to distribute magnesium throughout the surface layer of the particles of the positive electrode active material 100 at a temperature where cation mixing is unlikely to occur. Furthermore, the presence of a fluorine compound is expected to improve corrosion resistance to hydrofluoric acid produced by decomposition of the electrolyte.

[0208] Note that if the magnesium concentration is increased above a desired value, the effect on stabilizing the crystal structure may be reduced. This is thought to be because magnesium enters the cobalt site in addition to the lithium site. The number of magnesium atoms in the positive electrode active material of one embodiment of the present invention is preferably 0.001 to 0.1 times the number of atoms of the transition metal, such as cobalt, more preferably more than 0.01 to less than 0.04 times, and even more preferably about 0.02 times. The magnesium concentration shown here may be, for example, a value obtained by performing elemental analysis of the entire positive electrode active material using ICP-MS or the like, or may be based on the value of the raw material composition in the process of producing the positive electrode active material 100.

[0209] Lithium cobalt oxide may contain one or more metals selected from nickel, aluminum, manganese, titanium, vanadium, and chromium as a metal other than cobalt (hereinafter, "additive element X"). Addition of nickel and aluminum is particularly preferred. Manganese, titanium, vanadium, and chromium may be stable due to their tetravalent nature, and may contribute significantly to structural stability. Addition of the additive element X may further stabilize the crystal structure in a deeply charged state, such as a charge depth of 0.8 or greater. In the positive electrode active material of one embodiment of the present invention, the additive element X is preferably added at a concentration that does not significantly change the crystallinity of the lithium cobalt oxide. For example, the amount is preferably such that the aforementioned Jahn-Teller effect or the like is not exhibited.

[0210] The transition metals, such as nickel and manganese, and aluminum are preferably present at the cobalt site, but may be partially present at the lithium site. Magnesium is preferably present at the lithium site. Oxygen may be partially substituted with fluorine.

[0211] As the magnesium concentration in the positive electrode active material of one embodiment of the present invention increases, the capacity of the positive electrode active material may decrease. One possible cause of this is the incorporation of magnesium into the lithium site, which may reduce the amount of lithium contributing to charge and discharge. When the positive electrode active material of one embodiment of the present invention contains nickel in addition to magnesium as the additive element X, the charge and discharge cycle characteristics may be improved. Furthermore, when the positive electrode active material of one embodiment of the present invention contains aluminum in addition to magnesium as the additive element X, the charge and discharge cycle characteristics may be improved. Furthermore, when the positive electrode active material of one embodiment of the present invention contains magnesium, nickel, and aluminum as the additive element X, the charge and discharge cycle characteristics may be improved.

[0212] The element concentrations of a positive electrode active material according to one embodiment of the present invention, which contains magnesium, nickel, and aluminum as the additional element X, will be discussed below.

[0213] The number of nickel atoms in the positive electrode active material of one embodiment of the present invention is preferably 10% or less of the number of cobalt atoms, more preferably 7.5% or less, even more preferably 0.05% or more and 4% or less, and particularly preferably 0.1% or more and 2% or less. The nickel concentration shown here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS or the like, or may be based on a value obtained by mixing raw materials in the process of producing the positive electrode active material.

[0214] If the battery is charged to a deep depth of charge of 0.8 or more and maintained in this state for a long period of time, the constituent elements of the positive electrode active material may leach into the electrolyte, causing the crystal structure to collapse. However, by containing nickel in the above proportions, it may be possible to suppress the leach-out of the constituent elements from the positive electrode active material 100.

[0215] The number of aluminum atoms in the positive electrode active material of one embodiment of the present invention is preferably 0.05% to 4%, and more preferably 0.1% to 2%, of the number of cobalt atoms. The aluminum concentration shown here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS or the like, or may be based on a value obtained by mixing raw materials in the process of producing the positive electrode active material.

[0216] In addition, the positive electrode active material of one embodiment of the present invention including an additional element X preferably uses phosphorus as the additional element X. In addition, the positive electrode active material of one embodiment of the present invention more preferably includes a compound containing phosphorus and oxygen.

[0217] When the positive electrode active material of one embodiment of the present invention includes a compound containing phosphorus as the additional element X, a short circuit may be less likely to occur even when a high-temperature, deeply charged state in which the charge depth is 0.8 or more is maintained for a long period of time.

[0218] When the positive electrode active material of one embodiment of the present invention contains phosphorus as the additional element X, hydrogen fluoride generated by decomposition of the electrolyte solution may react with phosphorus, resulting in a decrease in the hydrogen fluoride concentration in the electrolyte solution.

[0219] The electrolyte is LiPF as a lithium salt. ６In the case where the electrolyte contains PVDF, hydrogen fluoride may be generated by hydrolysis. Hydrogen fluoride may also be generated by the reaction of PVDF, which is used as a component of the positive electrode, with an alkali. By reducing the hydrogen fluoride concentration in the electrolyte, corrosion of the current collector and / or peeling of the coating may be suppressed. Furthermore, gelation and / or insolubilization of PVDF may be suppressed, which may result in a decrease in adhesion.

[0220] When the cathode active material 100 of one embodiment of the present invention contains phosphorus and magnesium as the additive element X, the stability is extremely high in a deep charged state, such as a state of charge of 0.8 or more. When the additive element X contains phosphorus and magnesium, the number of phosphorus atoms is preferably 1% to 20% of the number of cobalt atoms, more preferably 2% to 10%, and even more preferably 3% to 8%. In addition, the number of magnesium atoms is preferably 0.1% to 10% of the number of cobalt atoms, more preferably 0.5% to 5%, and even more preferably 0.7% to 4%. The concentrations of phosphorus and magnesium shown here may be values ​​obtained by performing elemental analysis of the entire cathode active material 100 using, for example, ICP-MS or the like, or may be based on values ​​of the composition of raw materials in the process of producing the cathode active material 100.

[0221] When the positive electrode active material 100 has cracks, the presence of phosphorus, more specifically, a compound containing phosphorus and oxygen, inside the cracks may inhibit the progression of the cracks.

[0222] As shown in Figure 7, the symmetry of oxygen atoms is slightly different between the O3 type crystal structure and the O3' type crystal structure. Specifically, in the O3 type crystal structure, oxygen atoms are aligned along the dotted line, whereas in the O3' type crystal structure, oxygen atoms are not aligned strictly. This is because in the O3' type crystal structure, as lithium decreases, tetravalent cobalt increases, causing Jahn-Teller distortion to increase, resulting in CoO ６ This is because the octahedral structure of CoO is distorted. ２ Another factor is the increased repulsion between oxygen atoms in the layers.

[0223] <Surface Layer 100a> Magnesium is preferably distributed throughout the entire surface layer 100a of the particle of the positive electrode active material 100 of one embodiment of the present invention, and in addition, the magnesium concentration in the surface layer 100a is preferably higher than the overall average. For example, the magnesium concentration in the surface layer 100a measured by XPS or the like is preferably higher than the overall average magnesium concentration measured by ICP-MS or the like.

[0224] Furthermore, when the positive electrode active material 100 of one embodiment of the present invention contains an element other than cobalt, for example, one or more metals selected from nickel, aluminum, manganese, iron, and chromium, the concentration of the metal near the particle surface is preferably higher than the overall average. For example, the concentration of the element other than cobalt in the surface layer 100 a measured by XPS or the like is preferably higher than the concentration of the element in the entire particle measured by ICP-MS or the like.

[0225] The surface layer 100a of the positive electrode active material 100 is, so to speak, entirely composed of crystal defects. Furthermore, because lithium is removed from the surface during charging, this portion is prone to have a lower lithium concentration than the interior. This makes the surface unstable and prone to collapse of the crystal structure. A high magnesium concentration in the surface layer 100a can more effectively suppress changes in the crystal structure. Furthermore, a high magnesium concentration in the surface layer 100a can be expected to improve corrosion resistance to hydrofluoric acid produced by decomposition of the electrolyte.

[0226] Furthermore, the concentration of halogen such as fluorine in the surface layer portion 100 a of the positive electrode active material 100 of one embodiment of the present invention is preferably higher than the overall average. The presence of halogen in the surface layer portion 100 a, which is the region in contact with the electrolyte, can effectively improve corrosion resistance to hydrofluoric acid.

[0227] As described above, the surface layer portion 100a of the positive electrode active material 100 of one embodiment of the present invention preferably has a different composition from the inner portion 100b, i.e., a higher concentration of additive elements, such as magnesium and fluorine, than the inner portion 100b. Furthermore, the composition preferably has a stable crystal structure at room temperature. Therefore, the surface layer portion 100a may have a different crystal structure from the inner portion 100b. For example, at least a portion of the surface layer portion 100a of the positive electrode active material 100 of one embodiment of the present invention may have a rock salt crystal structure. Furthermore, when the surface layer portion 100a and the inner portion 100b have different crystal structures, it is preferable that the crystal orientations of the surface layer portion 100a and the inner portion 100b approximately match.

[0228] Layered rock salt crystals and the anions in rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure). It is presumed that the anions in O3'-type crystals also have a cubic close-packed structure. In this specification, if the anions have a structure in which three layers are stacked with a skewed relationship, such as ABCABC, it is referred to as a cubic close-packed structure. Therefore, the anions do not necessarily have to be strictly cubic lattices. At the same time, because real crystals always have defects, the analysis results do not necessarily conform to theory. For example, in electron diffraction or FFT (fast Fourier transform) of TEM images, etc., spots may appear at positions slightly different from the theoretical positions. For example, if the orientation from the theoretical positions is 5 degrees or less, or 2.5 degrees or less, it can be said to have a cubic close-packed structure.

[0229] When layered rock salt crystals come into contact with each other, there are crystal faces where the cubic close-packed structures formed by anions are oriented in the same direction.

[0230] Alternatively, it can be explained as follows: Anions on the (111) plane of the cubic crystal structure have a triangular arrangement. The layered rock salt type has a space group R-3m and a rhombohedral structure, but to make the structure easier to understand, it is generally expressed as a compound hexagonal lattice, and the (0001) plane of the layered rock salt type has a hexagonal lattice. The triangular lattice of the cubic (111) has the same atomic arrangement as the hexagonal lattice of the (0001) plane of the layered rock salt type. The compatibility of the two lattices can be said to be the alignment of the cubic close-packed structure.

[0231] However, the space group of the layered rock salt type crystal and the O3' type crystal is R-3m, which is different from the space group of the rock salt type crystal, Fm-3m (the space group of a general rock salt type crystal) and Fd-3m (the space group of a rock salt type crystal having the simplest symmetry), and therefore the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt type crystal and the O3' type crystal and the rock salt type crystal. In this specification, when the orientations of the cubic close-packed structures formed by anions are aligned in the layered rock salt type crystal, the O3' type crystal, and the rock salt type crystal, it may be said that the crystal orientations are approximately the same.

[0232] The fact that the crystal orientations of the two regions roughly coincide can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, electron diffraction, FFT of TEM images, etc. X-ray diffraction (XRD), neutron diffraction, etc. can also be used as materials for determination.

[0233] <Grain Boundary> The additional element X contained in the positive electrode active material 100 of one embodiment of the present invention may be present randomly and dilutely inside the positive electrode active material 100, but it is more preferable that a portion of the additional element X segregates at the grain boundary.

[0234] In other words, the concentration of the additional element X in and near the grain boundaries of the positive electrode active material 100 of one embodiment of the present invention is preferably higher than that in other regions inside the grain boundaries.

[0235] The grain boundaries can be considered as planar defects. Therefore, like the particle surfaces, they are easily unstable and tend to initiate changes in the crystal structure. Therefore, if the concentration of the added element X at and near the grain boundaries is high, the change in the crystal structure can be more effectively suppressed.

[0236] Furthermore, when the concentration of the additive element X is high at and near the grain boundaries, even if cracks occur along the grain boundaries of particles of the positive electrode active material 100 of one embodiment of the present invention, the concentration of the additive element X becomes high near the surface formed by the cracks. Therefore, the corrosion resistance to hydrofluoric acid can be improved even in the positive electrode active material after the cracks occur.

[0237] In this specification and the like, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary.

[0238] <Particle size> If the particle size of the positive electrode active material 100 of one embodiment of the present invention is too large, problems such as difficulty in diffusing lithium or excessive roughness of the surface of the active material layer when applied to a current collector occur. On the other hand, if the particle size is too small, problems such as difficulty in supporting the active material layer when applied to a current collector or excessive reaction with the electrolyte solution occur. Therefore, the average particle size D50 is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less.

[0239] <Analysis Method> Whether or not a certain positive electrode active material is the positive electrode active material 100 of one embodiment of the present invention that exhibits an O3'-type crystal structure when charged to a deep depth of charge of 0.8 or more can be determined by analyzing the positive electrode charged to a deep depth of charge of 0.8 or more using XRD, electron diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. XRD is particularly preferred in that it can analyze the symmetry of transition metals such as cobalt contained in the positive electrode active material with high resolution, can compare the level of crystallinity and crystal orientation, can analyze lattice periodic distortion and crystallite size, and can provide sufficient accuracy even when measuring a positive electrode obtained by disassembling a secondary battery.

[0240] As described above, the positive electrode active material 100 of one embodiment of the present invention is characterized by minimal change in crystal structure between a state charged to a deep depth of charge (SOC) of 0.8 or greater and a discharged state. Materials in which a crystal structure that exhibits a significant change from a discharged state when charged to a deep depth of charge (SOC) of 0.8 or greater accounts for 50 wt % or greater are undesirable because they cannot withstand deep charging and discharging when charged to a deep depth of charge (SOC) of 0.8 or greater. It should be noted that the desired crystal structure may not be achieved simply by adding an additive element. For example, even if both materials share the common feature of being lithium cobalt oxide containing magnesium and fluorine, when charged to a deep depth of charge (SOC) of 0.8 or greater, the O3'-type crystal structure may account for 60 wt % or greater, or the H1-3-type crystal structure may account for 50 wt % or greater. Furthermore, at a certain voltage, the O3'-type crystal structure may account for nearly 100 wt %, and further increasing the certain voltage may result in the H1-3-type crystal structure. Therefore, to determine whether or not the positive electrode active material 100 is one embodiment of the present invention, analysis of the crystal structure, such as XRD, is necessary.

[0241] However, when a positive electrode active material is charged to a deep charge depth of 0.8 or higher or discharged, its crystal structure may change when exposed to air. For example, it may change from an O3'-type crystal structure to an H1-3-type crystal structure. Therefore, it is preferable to handle all samples in an inert atmosphere such as an argon atmosphere.

[0242] <Charging Method> Deep charging to a depth of charge of 0.8 or more, which is used to determine whether a certain composite oxide is the positive electrode active material 100 of one embodiment of the present invention, can be performed by preparing a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) using a lithium counter electrode, for example, and charging the coin cell.

[0243] More specifically, the positive electrode may be prepared by coating a positive electrode current collector made of aluminum foil with a slurry containing a positive electrode active material, a conductive material, and a binder.

[0244] Lithium metal can be used for the counter electrode. When a material other than lithium metal is used for the counter electrode, the potential of the secondary battery differs from the potential of the positive electrode. Unless otherwise specified, voltages and potentials in this specification refer to the potential of the positive electrode.

[0245] The electrolyte contained in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6), and the electrolytic solution may be a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of EC:DEC = 3:7, with 2 wt% vinylene carbonate (VC).

[0246] The separator can be made of polypropylene having a thickness of 25 μm.

[0247] The positive electrode can and the negative electrode can may be made of stainless steel (SUS).

[0248] The coin cell prepared under the above conditions was charged at a constant current of 4.6 V and 0.5 C, followed by constant voltage charging until the current reached 0.01 C. Here, 1 C corresponds to 137 mA / g. The temperature was 25°C. After charging in this manner, the coin cell was disassembled in an argon-atmosphere glove box and the positive electrode was removed, yielding a positive electrode active material charged to a depth of charge of 0.8 or greater. When various analyses were subsequently performed, it was preferable to seal the cell in an argon atmosphere to prevent reactions with external components. For example, XRD could be performed by sealing the cell in a sealed container in an argon atmosphere.

[0249] <XRD> Figure 8 shows an ideal powder XRD pattern calculated from a model of the O3' type crystal structure using CuKα1 radiation. For comparison, LiCoO ２ The ideal XRD pattern calculated from the crystal structure of LiCoO3 is also shown. Figure 10 shows the ideal powder XRD pattern calculated from the model of the H1-3 type crystal structure using CuKα1 radiation. For comparison, the ideal powder XRD pattern calculated from the model of LiCoO3 with x = 1 is also shown. ２ (O3) and CoO with x = 0 ２ The ideal XRD pattern calculated from the crystal structure of LiCoO (O1) is also shown. ２ (O3) and CoO２ The (O1) pattern was created using Reflex Powder Diffraction, a module of Materials Studio (BIOVIA), from crystal structure information obtained from ICSD (Inorganic Crystal Structure Database). The 2θ range was set to 15° to 75°, with a step size of 0.01, a wavelength of λ1 = 1.540562 × 10 m, no λ2 setting, and a single monochromator. The O3'-type crystal structure pattern was estimated from the XRD pattern of the positive electrode active material of one embodiment of the present invention, and fitted using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker). Similarly to the other patterns, an XRD pattern was created.

[0250] As shown in Figure 8, in the O3' type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° to 19.50°) and 2θ = 45.55 ± 0.10° (45.45° to 45.65°). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° to 19.40°) and 2θ = 45.55 ± 0.05° (45.50° to 45.60°). However, as shown in Figure 10, in the H1-3 type crystal structure and CoO ２ In the case of (P-3m1, O1), no peaks appear at these positions. Therefore, it can be said that the appearance of peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10° in a state where the battery is charged to a deep depth of charge of 0.8 or more is a characteristic of the positive electrode active material 100 of one embodiment of the present invention.

[0251] This means that the positions at which the XRD diffraction peaks appear are close between the crystal structure with x = 1 and the crystal structure in the high-voltage charging state. More specifically, the difference in the positions at which two or more, preferably three or more, of the main diffraction peaks of both structures appear is 2θ = 0.7° or less, more preferably 2θ = 0.5° or less.

[0252] Note that the positive electrode active material 100 of one embodiment of the present invention has an O3'-type crystal structure when charged to a deep depth of charge of 0.8 or more. However, the entire positive electrode active material 100 does not necessarily have to have an O3'-type crystal structure. It may contain other crystal structures, or may be partially amorphous. However, when Rietveld analysis is performed on the XRD pattern, the O3'-type crystal structure is preferably 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. When the O3'-type crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more, it is possible to obtain a positive electrode active material with sufficiently excellent cycle characteristics.

[0253] Furthermore, even after 100 or more charge / discharge cycles from the start of measurement, when Rietveld analysis is performed, the O3' type crystal structure is preferably 35 wt% or more, more preferably 40 wt% or more, and even more preferably 43 wt% or more.

[0254] The crystallite size of the O3'-type crystal structure of the positive electrode active material particles is ２ Therefore, even under the same XRD measurement conditions as the positive electrode before charging and discharging, a clear peak of the O3' type crystal structure can be confirmed in the high voltage charging state. ２ In this case, even if a part of the crystal structure resembles the O3'-type crystal structure, the crystallite size will be small and the peak will be broad and small. The crystallite size can be determined from the half-width of the XRD peak.

[0255] As described above, the positive electrode active material of one embodiment of the present invention preferably has a small influence of the Jahn-Teller effect. The positive electrode active material of one embodiment of the present invention preferably has a layered rock salt crystal structure and contains cobalt as a transition metal. Furthermore, the positive electrode active material of one embodiment of the present invention may contain the aforementioned additional element X in addition to cobalt, as long as the influence of the Jahn-Teller effect is small.

[0256] Consideration of preferred ranges of the lattice constants revealed that, in a positive electrode active material according to one embodiment of the present invention, the particles of the positive electrode active material in a discharged state or in a non-charged or discharged state, which can be estimated from an XRD pattern, preferably have a layered rock-salt crystal structure in which the a-axis lattice constant is greater than 2.814 × 10 m and less than 2.817 × 10 m, and the c-axis lattice constant is greater than 14.05 × 10 m and less than 14.07 × 10 m. The non-charged or discharged state may be, for example, a powder state prior to fabrication of a positive electrode for a secondary battery.

[0257] Alternatively, in the layered rock-salt crystal structure of the particles of the positive electrode active material in a state where no charge or discharge is performed or in a discharged state, it is preferable that the value obtained by dividing the lattice constant of the a-axis by the lattice constant of the c-axis (a-axis / c-axis) is greater than 0.20000 and smaller than 0.20049.

[0258] Alternatively, when XRD analysis is performed on a layered rock salt type crystal structure possessed by particles of a positive electrode active material in a state where no charge / discharge is performed or in a discharged state, a first peak may be observed at 2θ of not less than 18.50° and not more than 19.30°, and a second peak may be observed at 2θ of not less than 38.00° and not more than 38.80°.

[0259] The peaks appearing in the powder XRD pattern reflect the crystalline structure of the interior 100b of the positive electrode active material 100, which occupies the majority of the volume of the positive electrode active material 100. The crystalline structure of the surface layer 100a and the like can be analyzed by electron diffraction or the like of a cross section of the positive electrode active material 100.

[0260] <XPS> X-ray photoelectron spectroscopy (XPS) can analyze a region from the surface to a depth of about 2 to 8 nm (usually about 5 nm), so the concentration of each element can be quantitatively analyzed for about half of the surface layer 100a. Furthermore, narrow scan analysis can be used to analyze the bonding state of elements. The quantitative accuracy of XPS is often about ±1 atomic %, and the lower detection limit is about 1 atomic %, depending on the element.

[0261] When XPS analysis is performed on the positive electrode active material 100 of one embodiment of the present invention, the number of atoms of the additive element X is preferably 1.6 to 6.0 times, and more preferably 1.8 to less than 4.0 times, the number of atoms of the transition metal. When the additive element X is magnesium and the transition metal M1 is cobalt, the number of atoms of magnesium is preferably 1.6 to 6.0 times, and more preferably 1.8 to less than 4.0 times, the number of atoms of cobalt. Furthermore, the number of atoms of halogen such as fluorine is preferably 0.2 to 6.0 times, and more preferably 1.2 to 4.0 times, the number of atoms of the transition metal.

[0262] When XPS analysis is performed, for example, monochromated aluminum can be used as the X-ray source, and the take-off angle can be set to, for example, 45°.

[0263] Furthermore, when the positive electrode active material 100 of one embodiment of the present invention is subjected to XPS analysis, the peak representing the bond energy between fluorine and another element is preferably equal to or greater than 682 eV and less than 685 eV, and more preferably about 684.3 eV. This value is different from both the bond energy of lithium fluoride (685 eV) and the bond energy of magnesium fluoride (686 eV). In other words, when the positive electrode active material 100 of one embodiment of the present invention contains fluorine, the bond is preferably other than that of lithium fluoride or magnesium fluoride.

[0264] Furthermore, when the positive electrode active material 100 of one embodiment of the present invention is subjected to XPS analysis, the peak representing the bond energy between magnesium and another element is preferably equal to or greater than 1302 eV and less than 1304 eV, and more preferably about 1303 eV. This value is different from the bond energy of magnesium fluoride, 1305 eV, and is close to the bond energy of magnesium oxide. In other words, when the positive electrode active material 100 of one embodiment of the present invention contains magnesium, the bond is preferably other than that of magnesium fluoride.

[0265] The concentration of the additive element X, such as magnesium and aluminum, which is preferably present in large amounts in the surface layer portion 100a, measured by XPS or the like is preferably higher than the concentration measured by ICP-MS (inductively coupled plasma mass spectrometry) or GD-MS (glow discharge mass spectrometry).

[0266] When a cross section of magnesium and aluminum is exposed by processing and analyzed using TEM-EDX, the concentration of the surface layer 100 a is preferably higher than the concentration of the inner portion 100 b. The processing can be performed using, for example, FIB.

[0267] In an XPS (X-ray photoelectron spectroscopy) analysis, the number of magnesium atoms is preferably 0.4 to 1.5 times the number of cobalt atoms, while in an ICP-MS analysis, the ratio of the number of magnesium atoms, Mg / Co, is preferably 0.001 to 0.06.

[0268] On the other hand, it is preferable that nickel contained in the transition metal is not unevenly distributed in the surface layer portion 100a but is distributed throughout the positive electrode active material 100. However, this does not apply when there is a region where the excess additional element X described above is unevenly distributed.

[0269] <Surface Roughness and Specific Surface Area> The positive electrode active material 100 of one embodiment of the present invention preferably has a smooth surface with few irregularities. A smooth surface with few irregularities is one factor indicating that the distribution of the additive element X in the surface layer portion 100a is good. Note that, in the process of producing the positive electrode active material 100, if the lithium cobalt oxide or the lithium nickel-cobalt-manganese oxide before the addition of the additive element X is initially heated, the positive electrode active material 100 is particularly preferred because it has significantly excellent characteristics in terms of repeated charging and discharging to a deep depth of charge of 0.8 or more.

[0270] Furthermore, since the surface of the positive electrode active material 100 is smooth and has few irregularities, the stability of the surface of the positive electrode active material 100 is improved, and it is possible to suppress the occurrence of pits.

[0271] Whether the surface is smooth and has few irregularities can be determined from, for example, a cross-sectional SEM image or cross-sectional TEM image of the positive electrode active material 100, the specific surface area of ​​the positive electrode active material 100, or the like.

[0272] For example, the surface smoothness can be quantified from a cross-sectional SEM image of the positive electrode active material 100 as follows.

[0273] First, the cathode active material 100 is processed using an FIB or the like to expose a cross section. At this time, it is preferable to cover the cathode active material 100 with a protective film, protective agent, or the like. Next, an SEM image of the interface between the protective film or the like and the cathode active material 100 is taken. The SEM image is subjected to noise processing using image processing software. For example, Gaussian blurring (σ = 2) is performed, followed by binarization. Interface extraction is then performed using image processing software. The interface line between the protective film or the like and the cathode active material 100 is then selected using a magic hand tool or the like, and the data is extracted into a spreadsheet software or the like. Using the functions of the spreadsheet software or the like, correction is performed from the regression curve (quadratic regression), and parameters for calculating roughness are obtained from the data after slope correction, and the root mean square (RMS) surface roughness is calculated from the standard deviation. Furthermore, this surface roughness is the surface roughness at least within 400 nm of the outer periphery of the particle of the cathode active material.

[0274] On the particle surfaces of the positive electrode active material 100 of the present embodiment, the root mean square (RMS) surface roughness, which is an index of roughness, is preferably 10 nm or less, less than 3 nm, preferably less than 1 nm, and more preferably less than 0.5 nm.

[0275] The image processing software used for noise processing, boundary extraction, etc. is not particularly limited, but for example, "ImageJ" can be used. The spreadsheet software is also not particularly limited, but for example, Microsoft Office Excel can be used.

[0276] Furthermore, for example, the surface smoothness of the positive electrode active material 100 can also be quantified from the ratio between the actual specific surface area AR measured by a constant volume gas adsorption method and the ideal specific surface area Ai.

[0277] The ideal specific surface area Ai is calculated assuming that all particles have the same diameter as D50, the same weight, and an ideal spherical shape.

[0278] The median diameter D50 can be measured by a particle size distribution analyzer using a laser diffraction / scattering method, etc. The specific surface area can be measured by a specific surface area measuring device using a gas adsorption method based on a constant volume method, for example.

[0279] In the positive electrode active material 100 of one embodiment of the present invention, the ratio AR / Ai of the ideal specific surface area Ai calculated from the median diameter D50 to the actual specific surface area AR is preferably 2 or less.

[0280] [Cathode Active Material Composite] Alternatively, the cathode active material 100 of one embodiment of the present invention may be a cathode active material composite having a coating layer that covers at least a part of the cathode active material 100. Examples of the coating layer include glass, oxide, and LiM2PO4. ４ (M2 is one or more selected from Fe, Ni, Co, and Mn).

[0281] The glass contained in the coating layer of the positive electrode active material composite can be a material having an amorphous portion. Examples of the material having an amorphous portion include SiO ２ , SiO, Al ２ O ３ , TiO ２ , Li ４ SiO ４ , Li ３ P.O. ４ , Li ２ S, SiS ２ , B ２ S ３ , GeS ４ , AgI, Ag ２ O, Li ２ O, P ２ O ５ , B ２ O ３ , and V ２ O ５ A material having one or more selected from the group consisting of Li, ７ P ３ S １１ , or Li １＋ｘ＋ｙ Al ｘ Ti２−ｘ Si ｙ P ３−ｙ O １２ (0<x<2, 0<y<3, etc.) can be used. A material having an amorphous portion can be used in an amorphous state as a whole, or in a partially crystallized state as crystallized glass (also called glass ceramics). The glass desirably has lithium ion conductivity. Lithium ion conductivity can also be said to have lithium ion diffusibility and lithium ion penetration. The glass preferably has a melting point of 800°C or less, more preferably 500°C or less. The glass preferably has electronic conductivity. The glass preferably has a softening point of 800°C or less, for example, Li ２ O-B ２ O ３ -SiO ２ Glasses containing fluorine can be used.

[0282] Examples of oxides contained in the coating layer of the positive electrode active material composite include aluminum oxide, zirconium oxide, hafnium oxide, and niobium oxide. ４ (M2 is one or more selected from Fe, Ni, Co, and Mn) ４ , LiNiPO ４ , LiCoPO ４ , LiMnPO ４ , LiFe ａ Ni ｂ P.O. ４ , LiFe ａ Co ｂ P.O. ４ , LiFe ａ Mn ｂ P.O. ４ , LiNi ａ Co ｂ P.O. ４ , LiNi ａ Mn ｂ P.O. ４ (a+b is 1 or less, 0<a<1, 0<b<1), LiFe ｃ Ni ｄ Co ｅ P.O. ４ , LiFe ｃ Niｄ Mn ｅ P.O. ４ , LiNi ｃ Co ｄ Mn ｅ P.O. ４ (c+d+e is 1 or less, 0<c<1, 0<d<1, 0<e<1), LiFe ｆ Ni ｇ Co ｈ Mn ｉ P.O. ４ (f+g+h+i is 1 or less, 0<f<1, 0<g<1, 0<h<1, 0<i<1), etc.

[0283] A composite treatment can be used to prepare the coating layer of the positive electrode active material composite. Examples of the composite treatment include one or more of the following: composite treatments using mechanical energy, such as mechanochemical, mechanofusion, and ball milling; composite treatments using liquid-phase reactions, such as coprecipitation, hydrothermal, and sol-gel; and composite treatments using gas-phase reactions, such as barrel sputtering, atomic layer deposition (ALD), vapor deposition, and chemical vapor deposition (CVD). For example, Picobond, manufactured by Hosokawa Micron, can be used as a composite treatment using mechanical energy. Furthermore, it is preferable to perform a heat treatment once or multiple times during the composite treatment.

[0284] The positive electrode active material composite reduces contact of the positive electrode active material with the electrolyte solution and the like, thereby suppressing deterioration of the secondary battery.

[0285] The content of this embodiment mode can be freely combined with the content of other embodiment modes.

[0286] Embodiment Mode 3 In this embodiment mode, examples of various shapes of secondary batteries each having a positive electrode or a negative electrode manufactured by the manufacturing method described in the previous embodiment will be described.

[0287] [Coin-Type Secondary Battery] An example of a coin-type secondary battery will be described. Fig. 11A is an exploded perspective view of a coin-type (single-layer flat) secondary battery, Fig. 11B is an external view, and Fig. 11C is a cross-sectional view thereof. Coin-type secondary batteries are mainly used in small electronic devices. In this specification, coin-type batteries include button-type batteries.

[0288] 11A is a schematic diagram that shows the overlapping of components (upper and lower relationships and positional relationships) for ease of understanding, and therefore, FIGS. 11A and 11B are not completely identical corresponding views.

[0289] In Fig. 11A, a positive electrode 304, a separator 310, a negative electrode 307, a spacer 322, and a washer 312 are stacked. These are sealed by a negative electrode can 302 and a positive electrode can 301. Note that a gasket for sealing is not shown in Fig. 11A. The spacer 322 and the washer 312 are used to protect the inside or to fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together. The spacer 322 and the washer 312 are made of stainless steel or an insulating material.

[0290] A positive electrode 304 has a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305 .

[0291] To prevent short-circuiting between the positive electrode and the negative electrode, a separator 310 and a ring-shaped insulator 313 are arranged so as to cover the side and top surfaces of the positive electrode 304. The separator 310 has a larger planar area than the positive electrode 304.

[0292] FIG. 11B is a perspective view of the completed coin-type secondary battery.

[0293] In the coin-type secondary battery 300, a positive electrode can 301, which also serves as a positive electrode terminal, and a negative electrode can 302, which also serves as a negative electrode terminal, are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector. The negative electrode 307 is not limited to a laminated structure, and may be formed of lithium metal foil or a lithium-aluminum alloy foil.

[0294] 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.

[0295] The positive electrode can 301 and the negative electrode can 302 can be made of a metal such as nickel, aluminum, or titanium that is corrosion-resistant to the electrolyte, or an alloy of these metals, or an alloy of these metals with other metals (e.g., stainless steel). Furthermore, to prevent corrosion by the electrolyte, etc., it is preferable to coat them with nickel, aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0296] These negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolyte solution, and as shown in FIG. 11C , 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 a gasket 303, thereby producing a coin-shaped secondary battery 300.

[0297] The above-described configuration allows the coin-type secondary battery 300 to have a high capacity, a high charge / discharge capacity, and excellent cycle characteristics. Note that, when a solid electrolyte layer is provided between the negative electrode 307 and the positive electrode 304, the separator 310 may be unnecessary.

[0298] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to Fig. 12A. As shown in Fig. 12A, a cylindrical secondary battery 616 has a positive electrode cap (battery lid) 601 on the top surface and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap 601 and the battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0299] 12B is a schematic diagram showing a cross section of a cylindrical secondary battery. The cylindrical secondary battery shown in FIG. 12B 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.

[0300] A battery element is provided inside a hollow cylindrical battery can 602, which includes a strip-shaped positive electrode 604 and a negative electrode 606 wound with a separator 605 sandwiched between them. Although not shown, the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open. The battery can 602 can be made of a metal, such as nickel, aluminum, or titanium, or an alloy of these metals or alloys of these metals with other metals (e.g., stainless steel), which are corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat the battery can 602 with nickel, aluminum, or the like to prevent corrosion by the electrolyte. Inside the battery can 602, the wound battery element, which includes 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, which contains the battery element. The nonaqueous electrolyte may be the same as that used in coin-type secondary batteries.

[0301] Since the positive and negative electrodes used in a cylindrical storage battery are wound, it is preferable to form active materials on both sides of the current collector. While the secondary battery 616 shown in Figures 12A to 12D has a cylinder whose height is greater than its diameter, this is not limiting. A secondary battery whose diameter is greater than its height may also be used. This configuration, for example, can reduce the size of the secondary battery.

[0302] By using the positive electrode active material 100 obtained in the above embodiment for the positive electrode 604, a cylindrical secondary battery 616 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0303] A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to a safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 613 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the increase in internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistor whose resistance increases as the temperature increases, and the increased resistance limits the amount of current to prevent abnormal heat generation. The PTC element can be made of barium titanate (BaTiO3) based semiconductor ceramics or the like.

[0304] 12C shows an example of a power storage system 615. The power storage system 615 has a plurality of secondary batteries 616. The positive electrodes of the respective secondary batteries are in contact with and electrically connected to conductors 624 separated by insulators 625. The conductors 624 are electrically connected to a control circuit 620 via wiring 623. The negative electrodes of the respective secondary batteries are electrically connected to the control circuit 620 via wiring 626. A protection circuit or the like that prevents overcharging or overdischarging can be used as the control circuit 620.

[0305] 12D shows an example of a power storage system 615. The power storage system 615 has a plurality of secondary batteries 616, which are sandwiched between a conductive plate 628 and a conductive plate 614. The plurality of secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by wiring 627. The plurality of secondary batteries 616 may be connected in parallel or in series. By configuring the power storage system 615 to have a plurality of secondary batteries 616, it is possible to extract a large amount of power.

[0306] A plurality of secondary batteries 616 may be connected in parallel and then further connected in series.

[0307] A temperature control device may be provided between the multiple secondary batteries 616. When the secondary batteries 616 are overheated, they can be cooled by the temperature control device, and when the secondary batteries 616 are too cold, they can be heated by the temperature control device. This makes it difficult for the performance of the power storage system 615 to be affected by the outside air temperature.

[0308] 12D , the power storage system 615 is electrically connected to a control circuit 620 via wiring 621 and wiring 622. The wiring 621 is electrically connected to the positive electrodes of the plurality of secondary batteries 616 via a conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the plurality of secondary batteries 616 via a conductive plate 614.

[0309] The control circuit 620 preferably has the second and fourth algorithms described in the first embodiment.

[0310] [Another Example of Secondary Battery Structure] An example of the structure of a secondary battery will be described with reference to FIGS. 13 and 14. FIG.

[0311] The secondary battery 913 shown in FIG. 13A has a wound body 950 provided with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. The terminal 952 contacts the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. Note that in FIG. 13A , for convenience, the housing 930 is shown separated, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0312] 13B, the housing 930 shown in Fig. 13A may be formed of a plurality of materials. For example, the secondary battery 913 shown in Fig. 13B has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in the area surrounded by the housing 930a and the housing 930b.

[0313] The housing 930a can be made of an insulating material such as organic resin. In particular, by using a material such as organic resin on the surface on which the antenna is formed, it is possible to suppress shielding of the electric field by the secondary battery 913. Note that if the shielding of the electric field by the housing 930a is small, the antenna may be provided inside the housing 930a. The housing 930b can be made of, for example, a metal material.

[0314] 13C shows the structure of the wound body 950. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 sandwiched therebetween, and the laminated sheet is wound. Note that multiple layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.

[0315] 14A to 14C may be used as a secondary battery 913 having a wound body 950a. The wound body 950a shown in Fig. 14A includes a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 includes a negative electrode active material layer 931a. The positive electrode 932 includes a positive electrode active material layer 932a.

[0316] By using the positive electrode active material 100 obtained in the above embodiment for the positive electrode 932, the secondary battery 913 can have a high capacity, a high charge / discharge capacity, and excellent cycle characteristics.

[0317] The separator 933 has a width wider than the negative electrode active material layer 931 a and the positive electrode active material layer 932 a, and is wound so as to overlap the negative electrode active material layer 931 a and the positive electrode active material layer 932 a. From the standpoint of safety, it is preferable that the negative electrode active material layer 931 a be wider than the positive electrode active material layer 932 a. A wound body 950 a having such a shape is preferable due to its high safety and productivity.

[0318] 14B, the negative electrode 931 is electrically connected to a terminal 951. The terminal 951 is electrically connected to a terminal 911a. The positive electrode 932 is electrically connected to a terminal 952. The terminal 952 is electrically connected to a terminal 911b.

[0319] 14C , wound body 950 a and the electrolyte are covered by casing 930 to form secondary battery 913. It is preferable to provide casing 930 with a safety valve, an overcurrent protection element, etc. The safety valve is a valve that opens when the inside of casing 930 reaches a predetermined internal pressure to prevent the battery from exploding.

[0320] As shown in Fig. 14B, the secondary battery 913 may have multiple wound bodies 950a. Using multiple wound bodies 950a can result in a secondary battery 913 with a larger charge / discharge capacity. For other elements of the secondary battery 913 shown in Figs. 14A and 14B, the descriptions of the secondary battery 913 shown in Figs. 13A to 13C can be referred to.

[0321] 15A and 15B show examples of external views of a laminated secondary battery, which includes a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0322] 16A shows an external view of a positive electrode 503 and a negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The positive electrode 503 also has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a tab region). The negative electrode 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 also has a region where the negative electrode current collector 504 is partially exposed, i.e., a tab region. The areas and shapes of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. 16A .

[0323] <Method of Manufacturing Laminated Secondary Battery> Here, an example of a method of manufacturing the laminated secondary battery whose external view is shown in FIG. 15A will be described with reference to FIGS. 16B and 16C.

[0324] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. FIG. 16B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example is shown in which five pairs of negative electrodes and four pairs of positive electrodes are used. This can also be called a laminate consisting of a negative electrode, a separator, and a positive electrode. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For example, ultrasonic welding or the like may be used for joining. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0325] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are arranged on the outer casing 509 .

[0326] Next, as shown in Fig. 16C, the exterior body 509 is folded at the portion indicated by the dashed line. Thereafter, the outer periphery of the exterior body 509 is joined. For example, thermocompression bonding may be used for joining. At this time, an area (hereinafter referred to as an inlet) that is not joined is provided in a part (or one side) of the exterior body 509 so that an electrolyte can be introduced later.

[0327] Next, the electrolyte solution is introduced into the inside of the exterior body 509 through an inlet provided in the exterior body 509. The introduction of the electrolyte solution is preferably carried out under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is joined. In this manner, the laminated secondary battery 500 can be produced.

[0328] By using the positive electrode active material 100 obtained in the above-described embodiment for the positive electrode 503, a secondary battery 500 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0329] [Example of Battery Pack] An example of a secondary battery pack according to one embodiment of the present invention that can be wirelessly charged using an antenna will be described with reference to FIGS. 17A to 17C. FIG.

[0330] Fig. 17A is a diagram showing the appearance of secondary battery pack 531, which has a thin rectangular parallelepiped shape (also called a thick flat plate shape). Fig. 17B is a diagram illustrating the configuration of secondary battery pack 531. Secondary battery pack 531 has circuit board 540 and secondary battery 513. Label 529 is affixed to secondary battery 513. Circuit board 540 is fixed with sticker 515. Secondary battery pack 531 also has antenna 517.

[0331] The interior of the secondary battery 513 may have a structure including a wound body or a laminated body.

[0332] 17B , the secondary battery pack 531 has a control circuit 590 on a circuit board 540. The circuit board 540 is electrically connected to the terminals 514. The circuit board 540 is also electrically connected to the antenna 517, one 551 of the positive and negative leads of the secondary battery 513, and the other 552 of the positive and negative leads.

[0333] Alternatively, as shown in FIG. 17C, the device may have a circuit system 590 a provided on a circuit board 540 and a circuit system 590 b electrically connected to the circuit board 540 via a terminal 514 .

[0334] The circuit board 540 or the circuit system 590b preferably has the second and fourth algorithms described in the first embodiment.

[0335] The antenna 517 is not limited to a coil shape and may be, for example, a wire shape or a plate shape. Furthermore, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may also be used. Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 517 may function as one of the two conductors of a capacitor. This allows power to be exchanged not only by electromagnetic fields and magnetic fields but also by electric fields.

[0336] The secondary battery pack 531 includes a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has a function of, for example, shielding an electromagnetic field generated by the secondary battery 513. The layer 519 can be formed using, for example, a magnetic material.

[0337] The content of this embodiment mode can be freely combined with the content of other embodiment modes.

[0338] Embodiment 4 In this embodiment, an example of fabricating an all-solid-state battery using the positive electrode active material 100 obtained in the above-described embodiment will be described.

[0339] As shown in FIG. 18A , a secondary battery 400 of one embodiment of the present invention includes a positive electrode 410 , a solid electrolyte layer 420 , and a negative electrode 430 .

[0340] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 includes a positive electrode active material 411 and a solid electrolyte 421. The positive electrode active material 100 obtained in the above-described embodiment is used for the positive electrode active material 411. The positive electrode active material layer 414 may also include a conductive material and a binder.

[0341] Solid electrolyte layer 420 has solid electrolyte 421. Solid electrolyte layer 420 is located between positive electrode 410 and negative electrode 430, and is a region that has neither positive electrode active material 411 nor negative electrode active material 431.

[0342] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 includes a negative electrode active material 431 and a solid electrolyte 421. The negative electrode active material layer 434 may also include a conductive material and a binder. When metallic lithium is used as the negative electrode active material 431, it is not necessary to form the material into particles, and therefore, as shown in FIG. 18B , the negative electrode 430 can be free of the solid electrolyte 421. Using metallic lithium for the negative electrode 430 is preferable because it can improve the energy density of the secondary battery 400.

[0343] The solid electrolyte 421 of the solid electrolyte layer 420 may be, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a halide-based solid electrolyte.

[0344] The sulfide-based solid electrolytes include thiolithium-based (Li １０ GeP ２ S １２ , Li ３．２５ Ge ０．２５ P ０．７５ S ４ etc.), sulfide glass (70Li ２ S・30P ２ S ５ , 30Li ２ S・26B ２ S ３ ・44LiI, 63Li ２ S・36SiS ２ ・1Li ３ P.O. ４ , 57Li ２ S・38SiS ２ ・5Li ４ SiO ４ , 50Li ２ S・50GeS ２ etc.), sulfide crystallized glass (Li ７ P ３ S １１ , Li ３．２５ P ０．９５ S ４ Sulfide-based solid electrolytes have the advantages of being highly conductive, being able to be synthesized at low temperatures, and being relatively soft, which makes it easy to maintain conductive paths even after charging and discharging.

[0345] The oxide-based solid electrolyte includes a material having a perovskite crystal structure (La ２／３−ｘ Li ３ｘ TiO ３ etc.), materials having a NASICON type crystal structure (Li １−Ｙ Al Ｙ Ti ２−Ｙ (P.O. ４ ) ３ etc.), materials having a garnet-type crystal structure (Li ７ La ３ Zr ２ O １２ etc.), materials having a LISICON type crystal structure (Li １４ ZnGe ４ O １６ etc.), LLZO (Li ７ La ３ Zr ２ O １２ ), oxide glass (Li ３ P.O. ４ -Li ４ SiO ４ , 50Li ４ SiO ４ ・50Li ３ BO ３ etc.), oxide crystallized glass (Li １．０７ Al ０．６９ Ti １．４６ (P.O. ４ ) ３ , Li １．５ Al ０．５ Ge １．５ (P.O. ４ ) ３ Oxide-based solid electrolytes have the advantage of being stable in the atmosphere.

[0346] Halide-based solid electrolytes include LiAlCl ４ , Li ３ InBr ６ , LiF, LiCl, LiBr, LiI, etc. Composite materials in which these halide-based solid electrolytes are filled into the pores of porous aluminum oxide or porous silica can also be used as the solid electrolyte.

[0347] Also, different solid electrolytes may be mixed and used.

[0348] Among them, Li having a NASICON type crystal structure １＋ｘ Al ｘ Ti ２−ｘ (P.O. ４ ) ３ (0<x<1) (hereinafter, LATP) is preferable because it contains aluminum and titanium, elements that may be contained in the positive electrode active material used in the secondary battery 400 of one embodiment of the present invention, and therefore a synergistic effect can be expected in improving cycle characteristics. In addition, productivity can be expected to be improved by reducing the number of steps. Note that in this specification and the like, the NASICON-type crystal structure refers to a structure having a NASICON-type crystal structure, which is a structure having a NASICON-type crystal structure, and which is ... ２ (XO ４ ) ３ (M: transition metal, X: S, P, As, Mo, W, etc.), ６ Octahedron and XO ４ It refers to a structure in which tetrahedrons are arranged three-dimensionally with their vertices shared.

[0349] [Exterior Body and Shape of Secondary Battery] Various materials and shapes can be used for the exterior body of the secondary battery 400 of one embodiment of the present invention, but it is preferable that the exterior body has a function of applying pressure to the positive electrode, the solid electrolyte layer, and the negative electrode.

[0350] For example, FIG. 19 shows an example of a cell for evaluating materials for an all-solid-state battery.

[0351] 19A is a cross-sectional schematic diagram of the evaluation cell, which has a lower member 761, an upper member 762, and a fixing screw or wing nut 764 that fixes them together, and the electrode plate 753 is pressed to fix the evaluation material by rotating a holding screw 763. An insulator 766 is provided between the lower member 761 and the upper member 762, both made of stainless steel. An O-ring 765 is also provided between the upper member 762 and the holding screw 763 to provide a tight seal.

[0352] The evaluation material is placed on electrode plate 751, surrounded by insulating tube 752, and pressed from above by electrode plate 753. An enlarged perspective view of the evaluation material and its surroundings is shown in Figure 19B.

[0353] The evaluation material is an example of a laminate of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c, and its cross-sectional view is shown in Fig. 19C. Note that the same reference numerals are used for the same parts in Figs. 19A to 19C.

[0354] The electrode plate 751 and the lower member 761, which are electrically connected to the positive electrode 750a, can be said to correspond to a positive electrode terminal. The electrode plate 753 and the upper member 762, which are electrically connected to the negative electrode 750c, can be said to correspond to a negative electrode terminal. Electrical resistance and the like can be measured by applying pressure to the evaluation material via the electrode plate 751 and the electrode plate 753.

[0355] The secondary battery of one embodiment of the present invention preferably uses an airtight package for its exterior. For example, a ceramic package or a resin package can be used. Furthermore, the exterior is preferably sealed in a sealed atmosphere, such as in a glove box, while blocking external air.

[0356] Fig. 20A is a perspective view of a secondary battery of one embodiment of the present invention, which has an exterior body and a shape different from those in Fig. 19. The secondary battery in Fig. 20A has external electrodes 771 and 772 and is sealed in an exterior body having a plurality of package members.

[0357] 20B shows an example of a cross section taken along the dashed line in FIG. 20A. A stack including a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is enclosed and sealed by a package member 770a having a flat plate with an electrode layer 773a, a frame-shaped package member 770b, and a package member 770c having a flat plate with an electrode layer 773b. The package members 770a, 770b, and 770c can be made of insulating materials, such as resin materials and ceramics.

[0358] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a and functions as a positive electrode terminal, while the external electrode 772 is electrically connected to the negative electrode 750c via the electrode layer 773b and functions as a negative electrode terminal.

[0359] By using the positive electrode active material 100 obtained in the above-described embodiment, an all-solid-state secondary battery having high energy density and good output characteristics can be realized.

[0360] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0361] Embodiment Mode 5 In this embodiment mode, an example in which a secondary battery different from the cylindrical secondary battery shown in FIG. 12D is applied to an electric vehicle (EV) will be described with reference to FIG. 21C.

[0362] The electric vehicle is equipped with first batteries 1301a and 1301b as main driving secondary batteries, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304. The second battery 1311 is also called a cranking battery (also called a starter battery). The second battery 1311 only needs to have high output, and does not need to have a large capacity, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0363] The internal structure of the first battery 1301a may be a wound type shown in Fig. 13A or 14C or a stacked type shown in Fig. 15A or 15B. The first battery 1301a may use the all-solid-state battery of Embodiment 4. By using the all-solid-state battery of Embodiment 4 for the first battery 1301a, a high capacity can be achieved, safety can be improved, and the battery can be made smaller and lighter.

[0364] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more batteries may be connected in parallel. Furthermore, if the first battery 1301a can store sufficient power, the first battery 1301b may be omitted. By configuring a battery pack having multiple secondary batteries, it is possible to extract large amounts of power. The multiple 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.

[0365] In addition, in a secondary battery for vehicle use, a service plug or circuit breaker that can cut off high voltage without using tools is provided in the first battery 1301a in order to cut off power from multiple secondary batteries.

[0366] The power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V in-vehicle components (such as an electric power steering (power steering) 1307, a heater 1308, and a defogger 1309) via a DCDC circuit 1306. When a rear motor 1317 is provided on the rear wheels, the first battery 1301a is also used to rotate the rear motor 1317.

[0367] In addition, the second battery 1311 supplies power to 14V in-vehicle components (audio 1313, power windows 1314, lamps 1315, etc.) via the DCDC circuit 1310.

[0368] The first battery 1301a will be described with reference to FIG. 21A.

[0369] FIG. 21A shows an example in which nine prismatic secondary batteries 1300 are combined into one battery pack 1415. Furthermore, nine prismatic secondary batteries 1300 are connected in series, with one electrode fixed by a fixing portion 1413 made of an insulator and the other electrode fixed by a fixing portion 1414 made of an insulator. While this embodiment shows an example in which the batteries are fixed by the fixing portions 1413 and 1414, they may also be housed in a battery housing box (also called a casing). Because it is expected that a vehicle will be subjected to external vibrations or shaking (such as from the road surface), it is preferable to fix multiple secondary batteries using the fixing portions 1413 and 1414 and the battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421. The other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0370] The control circuit section 1320 preferably has the second and fourth algorithms described in the first embodiment.

[0371] A memory circuit including a transistor using an oxide semiconductor may be used for the control circuit portion 1320. A charge control circuit or a battery control system including a memory circuit including a transistor using an oxide semiconductor may be referred to as a battery operating system (BTOS) or a battery oxide semiconductor (BTOS).

[0372] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, a metal oxide such as In-M-Zn oxide (wherein element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used as the oxide. In particular, the In-M-Zn oxide that can be used as the oxide is preferably a C-Axis Aligned Crystal Oxide Semiconductor (CAAC-OS) or a Cloud-Aligned Composite Oxide Semiconductor (CAC-OS). Alternatively, an In—Ga oxide or an In—Zn oxide may be used as the oxide. A CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction refers to the thickness direction of the CAAC-OS film, the normal direction to the surface where the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region is also a region with a uniform lattice arrangement. Furthermore, a CAAC-OS has a region where multiple crystalline regions are connected in the a-b plane direction, and the region may have distortion. Note that distortion refers to a portion where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with another uniform lattice arrangement in a region where multiple crystalline regions are connected. In other words, a CAAC-OS is an oxide semiconductor with a c-axis aligned and no clear orientation in the a-b plane direction. CAC-OS is a material in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof. Note that hereinafter, a state in which one or more metal elements are unevenly distributed in a metal oxide and regions containing the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof, is also referred to as a mosaic or patch state.

[0373] Furthermore, the CAC-OS has a mosaic structure in which a material is separated into a first region and a second region, and the first region is distributed throughout the film (hereinafter also referred to as a cloud structure). That is, the CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed.

[0374] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In—Ga—Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In—Ga—Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0375] Specifically, the first region is a region whose main component is indium oxide, indium zinc oxide, or the like. The second region is a region whose main component is gallium oxide, gallium zinc oxide, or the like. In other words, the first region can be referred to as a region whose main component is In. The second region can be referred to as a region whose main component is Ga.

[0376] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0377] For example, in the case of CAC-OS in an In—Ga—Zn oxide, EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) can confirm that the CAC-OS has a structure in which a region containing In as a main component (first region) and a region containing Ga as a main component (second region) are unevenly distributed and mixed.

[0378] When a CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act complementarily, thereby imparting a switching function (on / off function) to the CAC-OS. That is, a CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and the entire material functions as a semiconductor. By separating the conductive function and the insulating function, both functions can be maximized. Therefore, by using a CAC-OS in a transistor, a high on-state current (Ion), a high field-effect mobility (μ), and good switching operation can be achieved.

[0379] Oxide semiconductors have a variety of structures, each of which has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0380] Furthermore, because the control circuit unit 1320 can be used in high-temperature environments, it is preferable to use a transistor using an oxide semiconductor. To simplify the process, the control circuit unit 1320 may be formed using a unipolar transistor. Transistors using an oxide semiconductor in the semiconductor layer have a wider operating ambient temperature range than single-crystal Si transistors, from −40° C. to 150° C., and their characteristics change less even when the secondary battery overheats than single-crystal Si transistors. The off-current of a transistor using an oxide semiconductor is below the lower limit of measurement even at 150° C., whereas the off-current characteristics of single-crystal Si transistors are highly temperature-dependent. For example, at 150° C., the off-current of a single-crystal Si transistor increases, and the current on / off ratio is not sufficiently large. The control circuit unit 1320 can improve safety. Furthermore, combining the cathode active material 100 obtained in the above-described embodiment with a secondary battery using the cathode as the cathode can provide a synergistic effect in terms of safety.

[0381] The control circuit unit 1320, which uses a memory circuit including transistors using oxide semiconductors, can also function as an automatic control device for the secondary battery to address causes of instability such as micro-short circuits. Functions for eliminating causes of secondary battery instability include overcharging prevention, overcurrent prevention, overheating control during charging, cell balancing in the battery pack, over-discharging prevention, a fuel gauge, automatic control of charging voltage and current according to temperature, control of charging current according to the degree of deterioration, detection of abnormal behavior of micro-short circuits, and prediction of abnormalities related to micro-short circuits, and the control circuit unit 1320 has at least one of these functions. Furthermore, the automatic control device for the secondary battery can be made ultra-miniaturized.

[0382] A micro-short circuit refers to a tiny short circuit inside a secondary battery, which is not so small that the positive and negative electrodes of the secondary battery are short-circuited and the battery is unable to be charged or discharged, but rather a small short-circuit current flows through the tiny short circuit.Even if the short circuit occurs in a relatively short period of time and in a small location, a large voltage change occurs, and this abnormal voltage value may affect subsequent estimations.

[0383] One of the causes of micro-short circuits is said to be that multiple charge and discharge cycles cause uneven distribution of the positive electrode active material, resulting in localized current concentration in parts of the positive electrode and negative electrode, causing parts of the separator to stop functioning, or the generation of by-products due to side reactions, resulting in micro-short circuits.

[0384] In addition to detecting micro-shorts, the control circuit 1320 can also be said to detect the terminal voltage of the secondary battery and manage the charge / discharge state of the secondary battery. For example, to prevent overcharging, it can turn off both the output transistor and the cutoff switch of the charging circuit almost simultaneously.

[0385] FIG. 21B shows an example of a block diagram of the battery pack 1415 shown in FIG. 21A.

[0386] The control circuit 1320 includes a switch unit 1324 including at least a switch for preventing overcharging and a switch for preventing overdischarging, a control circuit 1322 for controlling the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit 1320 sets upper and lower voltage limits for the secondary battery used and limits the upper limit of the external current and the upper limit of the output current. The range between the lower and upper voltage limits of the secondary battery is within the recommended voltage range, and when the secondary battery falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent overcharging and overdischarging. For example, if the control circuit 1322 detects a voltage that could cause overcharging, it turns off the switch unit 1324 to cut off the current. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function for cutting off the current in response to an increase in temperature. The control circuit section 1320 also has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0387] The switch portion 1324 can be configured by combining n-channel transistors and p-channel transistors. The switch portion 1324 is not limited to a switch having a Si transistor using single crystal silicon. For example, the switch portion 1324 may be formed using a power transistor having Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), or GaOx (gallium oxide; x is a real number greater than 0). Furthermore, memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, for example, and thus can be easily integrated. Furthermore, OS transistors can be manufactured using the same manufacturing equipment as Si transistors, and therefore can be manufactured at low cost. That is, the control circuit portion 1320 using OS transistors can be stacked on the switch portion 1324 and integrated into a single chip. The volume occupied by the control circuit section 1320 can be reduced, which allows for miniaturization.

[0388] The first batteries 1301a and 1301b mainly supply power to in-vehicle devices of the 42V system (high voltage system), and the second battery 1311 supplies power to in-vehicle devices of the 14V system (low voltage system).

[0389] In this embodiment, an example in which lithium ion secondary batteries are used for both the first battery 1301a and the second battery 1311 is shown. A lead-acid battery, an all-solid-state battery, or an electric double layer capacitor may be used for the second battery 1311. For example, the all-solid-state battery of Embodiment 4 may be used. By using the all-solid-state battery of Embodiment 4 for the second battery 1311, high capacity can be achieved, and reductions in size and weight can be achieved.

[0390] Furthermore, regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and is then charged into the second battery 1311 from the motor controller 1303 and the battery controller 1302 via the control circuit unit 1321. Alternatively, the first battery 1301a is charged from the battery controller 1302 via the control circuit unit 1320. Alternatively, the first battery 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b be capable of rapid charging.

[0391] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 can set charging conditions in accordance with the charging characteristics of the secondary battery used, and can perform rapid charging.

[0392] Although not shown, when an external charger is connected, the charger's outlet or charger connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger is charged to the first batteries 1301a and 1301b via the battery controller 1302. Some chargers are provided with a control circuit, and although the functions of the battery controller 1302 may not be used, it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. The charger's outlet or the charger connection cable may also be provided with a control circuit. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) provided in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU includes a microcomputer. The ECU uses a CPU or a GPU.

[0393] External chargers installed at charging stations and the like come in a variety of types, including 100V outlets, 200V outlets, and three-phase 200V and 50kW outlets. Charging can also be performed by receiving power from external charging equipment using a wireless power supply system or the like.

[0394] When rapid charging is performed, a secondary battery that can withstand high voltage charging is desired in order to charge in a short time.

[0395] The secondary battery of the present embodiment described above uses the positive electrode active material 100 obtained in the above-described embodiment. Furthermore, by using graphene as a conductive material, a secondary battery with significantly improved electrical characteristics can be realized, as a synergistic effect of suppressing capacity reduction and maintaining high capacity even when the electrode layer is thickened and the loading amount is increased. This is particularly effective for secondary batteries used in vehicles, and a vehicle with a long cruising range, specifically a cruising range of 500 km or more per charge, can be provided without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0396] In particular, the secondary battery of the present embodiment described above can increase the operating voltage of the secondary battery by using the cathode active material 100 described in the above embodiment, and can increase the usable capacity as the charging voltage increases. Furthermore, by using the cathode active material 100 described in the above embodiment for the cathode, a secondary battery for vehicles with excellent cycle characteristics can be provided.

[0397] Next, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described.

[0398] 12D, 14C, and 21A can be installed in a vehicle to realize next-generation clean energy automobiles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs). Furthermore, the secondary battery can also be installed in transportation vehicles, such as agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space probes, planetary probes, and spacecraft. The secondary battery of one embodiment of the present invention can be a high-capacity secondary battery. Therefore, the secondary battery of one embodiment of the present invention is suitable for miniaturization and weight reduction and can be suitably used in transportation vehicles.

[0399] 22A to 22D illustrate a transportation vehicle as an example of a moving object using one embodiment of the present invention. The automobile 2001 illustrated in FIG. 22A is an electric automobile using an electric motor as a power source for traveling. Alternatively, the automobile 2001 is a hybrid automobile that can appropriately select and use an electric motor or an engine as a power source for traveling. When a secondary battery is installed in a vehicle, an example of the secondary battery described in Embodiment 3 is installed in one or more locations. The automobile 2001 illustrated in FIG. 22A includes a battery pack 2200, which includes a secondary battery module to which multiple secondary batteries are connected. The automobile 2001 preferably further includes a charge control device electrically connected to the secondary battery module, and the charge control device preferably includes the second algorithm and the fourth algorithm described in Embodiment 1.

[0400] Furthermore, the automobile 2001 can charge its secondary battery by receiving power from an external charging facility using a plug-in system, a contactless power supply system, or the like. Charging can be performed using a predetermined charging method and connector standards, such as CHAdeMO (registered trademark) or Combo, as appropriate. The secondary battery may be charged at a charging station installed in a commercial facility or from a household power source. For example, plug-in technology can be used to charge an electric storage device installed in the automobile 2001 using an external power supply. Charging can be performed by converting AC power to DC power via a conversion device, such as an AC-DC converter.

[0401] Although not shown, a power receiving device can be mounted on a vehicle and power can be supplied contactlessly from a ground-based power transmitting device to charge the vehicle. In the case of this contactless power supply method, by incorporating a power transmitting device into a road or an exterior wall, charging can be performed not only while the vehicle is stopped but also while the vehicle is moving. This contactless power supply method can also be used to transmit and receive power between two vehicles. Furthermore, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped and while moving. For such contactless power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0402] 22B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 is, for example, a four-cell unit of secondary batteries with a nominal voltage of 3.0 V to 5.0 V, with 48 cells connected in series for a maximum voltage of 170 V. Apart from the number of secondary batteries constituting the secondary battery module of the battery pack 2201, the transport vehicle 2002 has the same functions as those shown in FIG. 22A, and therefore a description thereof will be omitted.

[0403] FIG. 22C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has, for example, a maximum voltage of 600 V, with one hundred or more secondary batteries connected in series, each having a nominal voltage of 3.0 V or more and 5.0 V or less. By using a secondary battery whose positive electrode is the positive electrode active material 100 described in the above embodiment, a secondary battery with excellent rate characteristics and charge / discharge cycle characteristics can be manufactured, contributing to improved performance and a longer life of the transport vehicle 2003. Furthermore, except for the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the same functions as those of FIG. 22A are provided, and therefore further description will be omitted.

[0404] Fig. 22D shows, as an example, an aircraft 2004 having an engine that burns fuel. Since the aircraft 2004 shown in Fig. 22D has wheels for takeoff and landing, it can also be considered a type of transport vehicle, and has a battery pack 2203 that includes a secondary battery module formed by connecting multiple secondary batteries and the secondary battery module and a charge control device.

[0405] The secondary battery module of the aircraft 2004 is, for example, eight 4 V secondary batteries connected in series to produce a maximum voltage of 32 V. Other than the number of secondary batteries constituting the secondary battery module of the battery pack 2203, the secondary battery module has the same functions as those shown in Fig. 22A, and therefore a description thereof will be omitted.

[0406] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0407] Embodiment 6 In this embodiment, an example in which a secondary battery which is one embodiment of the present invention is mounted in a building will be described with reference to FIGS. 23A and 23B.

[0408] The house illustrated in FIG. 23A includes a power storage device 2612 including a secondary battery of one embodiment of the present invention, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611 or the like. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The power obtained by the solar panel 2610 can be charged to the power storage device 2612. The power stored in the power storage device 2612 can be charged to a secondary battery included in the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in an underfloor space. By installing the power storage device 2612 in the underfloor space, the space above the floor can be effectively utilized. Alternatively, the power storage device 2612 may be installed on the floor.

[0409] The power stored in the power storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the power storage device 2612 of one embodiment of the present invention can be used as an uninterruptible power supply, enabling the use of electronic devices.

[0410] 23B illustrates an example of a power storage device according to one embodiment of the present invention. As illustrated in FIG. 23B , a power storage device 791 according to one embodiment of the present invention is installed in an underfloor space 796 of a building 799. The control circuit described in Embodiment 5 may be provided in the power storage device 791. The power storage device 791 can have a long lifetime by using a secondary battery in which the positive electrode active material 100 obtained in the above embodiment is used for its positive electrode.

[0411] The power storage device 791 is provided with a control device 790, which is electrically connected by wiring to a distribution board 703, a power storage controller 705 (also referred to as a control device), a display 706, and a router 709. The control device 790 preferably has the second algorithm and the fourth algorithm described in Embodiment 1.

[0412] Electric power is sent from commercial power source 701 to distribution board 703 via service line attachment portion 710. Electric power is also sent to distribution board 703 from power storage device 791 and commercial power source 701, and distribution board 703 supplies the sent electric power to general load 707 and power storage load 708 via outlets (not shown).

[0413] The general load 707 is, for example, an electrical appliance such as a television or a personal computer, and the power storage load 708 is, for example, an electrical appliance such as a microwave oven, a refrigerator, or an air conditioner.

[0414] The power storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has a function of measuring the amount of power consumed by the general load 707 and the power storage load 708 during a day (e.g., from midnight to midnight). The measurement unit 711 may also have a function of measuring the amount of power of the power storage device 791 and the amount of power supplied from the commercial power source 701. The prediction unit 712 has a function of predicting the amount of power demand to be consumed by the general load 707 and the power storage load 708 during the next day based on the amount of power consumed by the general load 707 and the power storage load 708 during the previous day. The planning unit 713 has a function of creating a plan for charging and discharging the power storage device 791 based on the amount of power demand predicted by the prediction unit 712.

[0415] The amount of power consumed by the general load 707 and the power storage load 708 measured by the measurement unit 711 can be confirmed on the display 706. It can also be confirmed on electrical appliances such as televisions and personal computers via the router 709. It can also be confirmed on portable electronic devices such as smartphones and tablets via the router 709. The amount of power demand for each time period (or each hour) predicted by the prediction unit 712 can also be confirmed on the display 706, the electrical appliances, and the portable electronic devices.

[0416] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0417] Embodiment 7 In this embodiment, an example in which a power storage device according to one embodiment of the present invention is mounted on a motorcycle or a bicycle will be described.

[0418] 24A illustrates an example of an electric bicycle using the power storage device of one embodiment of the present invention. The power storage device of one embodiment of the present invention can be applied to an electric bicycle 8700 illustrated in FIG. 24A. The power storage device of one embodiment of the present invention includes, for example, a plurality of storage batteries and a protection circuit.

[0419] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 can supply electricity to a motor that assists a rider. The power storage device 8702 is portable and is shown in a state detached from the bicycle in FIG. 24B . The power storage device 8702 includes a plurality of built-in storage batteries 8701, which are included in the power storage device of one embodiment of the present invention, and the remaining battery charge and the like can be displayed on a display unit 8703. The power storage device 8702 also includes a control circuit 8704 that can control charging or detect an abnormality of the secondary battery, an example of which is shown in Embodiment 5. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701. The control circuit 8704 preferably includes the second and fourth algorithms described in Embodiment 1. The control circuit 8704 may be provided with the small solid-state secondary battery shown in FIGS. 20A and 20B . 20A and 20B in the control circuit 8704, power can be supplied to retain data in a memory circuit of the control circuit 8704 for a long period of time. Furthermore, a synergistic effect in terms of safety can be obtained by combining the control circuit 8704 with a secondary battery using the positive electrode active material 100 obtained in the above-described embodiment as a positive electrode. The control circuit 8704 and the secondary battery using the positive electrode active material 100 obtained in the above-described embodiment as a positive electrode can greatly contribute to eliminating accidents, such as fires, caused by secondary batteries.

[0420] 24C is an example of a two-wheeled vehicle using the power storage device of one embodiment of the present invention. A scooter 8600 shown in FIG. 24C includes a power storage device 8602, a side mirror 8601, and a turn signal light 8603. The power storage device 8602 can supply electricity to the turn signal light 8603. The power storage device 8602, which includes a plurality of secondary batteries each using the positive electrode active material 100 obtained in the above embodiment for its positive electrode, can have a high capacity and contribute to miniaturization.

[0421] 24C can store a power storage device 8602 in an under-seat storage compartment 8604. The power storage device 8602 can be stored in the under-seat storage compartment 8604 even if the under-seat storage compartment 8604 is small.

[0422] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0423] Embodiment 8 In this embodiment, an example of mounting a secondary battery according to one embodiment of the present invention in an electronic device will be described. Examples of electronic devices mounting a secondary battery include television sets (also referred to as televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game consoles, personal digital assistants, sound players, and large game consoles such as pachinko machines. Examples of personal digital assistants include notebook personal computers, tablet devices, e-book readers, and mobile phones.

[0424] 25A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into a housing 2101, operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also includes a secondary battery 2107. By including the secondary battery 2107 using the positive electrode active material 100 described in the above embodiment as a positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0425] 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.

[0426] The operation button 2103 can be provided with various functions such as time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, power saving mode activation / deactivation, etc. For example, the functions of the operation button 2103 can be freely set by an operating system incorporated in the mobile phone 2100.

[0427] 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.

[0428] The mobile phone 2100 also includes 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. Note that charging may be performed by wireless power supply without using the external connection port 2104.

[0429] The mobile phone 2100 preferably has a sensor, such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like.

[0430] FIG. 25B illustrates an unmanned aerial vehicle 2300 having a plurality of rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 includes a secondary battery 2301 according to one embodiment of the present invention, a camera 2303, and an antenna (not shown). The unmanned aerial vehicle 2300 can be remotely controlled via the antenna. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time. Therefore, the secondary battery is suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0431] Fig. 25C shows an example of a robot. A robot 6400 shown in Fig. 25C includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0432] The microphone 6402 has a function of detecting the user's speaking voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0433] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0434] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. Furthermore, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0435] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal region. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time. Therefore, the secondary battery is suitable as the secondary battery 6409 to be mounted on the robot 6400.

[0436] 25D shows an example of a cleaning robot. The cleaning robot 6300 includes a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side surfaces, a brush 6304, operation buttons 6305, a secondary battery 6306, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0437] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, if an object that may become entangled in the brush 6304, such as a wire, is detected through image analysis, the cleaning robot 6300 can stop the rotation of the brush 6304. The cleaning robot 6300 includes a secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal region. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time. Therefore, the secondary battery 6306 is suitable for use in the cleaning robot 6300.

[0438] 26A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used in daily life or outdoors, there is a demand for a wearable device that can be charged wirelessly as well as via a wired connection with an exposed connector.

[0439] For example, a secondary battery according to one embodiment of the present invention can be mounted on an eyeglasses-type device 4000 as shown in FIG. 26A . The eyeglasses-type device 4000 includes a frame 4000 a and a display unit 4000 b. Mounting a secondary battery on temples of the curved frame 4000 a makes it possible to provide the eyeglasses-type device 4000 with a lightweight design, a good weight balance, and a long continuous use time. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as its positive electrode has a high energy density and can realize a configuration that can accommodate space saving associated with a smaller housing.

[0440] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a headset device 4001. The headset device 4001 includes at least a microphone unit 4001a, a flexible pipe 4001b, and an earphone unit 4001c. The secondary battery can be provided in the flexible pipe 4001b or the earphone unit 4001c. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has a high energy density and can realize a configuration that can accommodate space saving associated with a miniaturized housing.

[0441] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 4002 that can be directly attached to the body. A secondary battery 4002b can be provided in a thin housing 4002a of the device 4002. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density, and a configuration that can accommodate space saving associated with a miniaturized housing can be realized.

[0442] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 4003 that can be attached to clothing. A secondary battery 4003b can be provided in a thin housing 4003a of the device 4003. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density, and a configuration that can accommodate space saving associated with a miniaturized housing can be realized.

[0443] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the belt-type device 4006. The belt-type device 4006 includes a belt portion 4006a and a wireless power receiving portion 4006b, and the secondary battery can be mounted in an internal region of the belt portion 4006a. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has a high energy density and can realize a configuration that can accommodate space saving associated with a miniaturized housing.

[0444] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch device 4005 includes a display portion 4005a and a belt portion 4005b, and the secondary battery can be provided in the display portion 4005a or the belt portion 4005b. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has high energy density, and a configuration that can accommodate space saving associated with miniaturization of the housing can be realized.

[0445] The display unit 4005a can display not only the time but also various other information such as incoming emails and phone calls.

[0446] Furthermore, since the wristwatch device 4005 is a wearable device that is worn directly on the arm, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated to manage the user's health.

[0447] FIG. 26B shows a perspective view of the wristwatch-type device 4005 removed from the wrist.

[0448] 26C shows a side view of the display portion 4005a. Fig. 26C shows a state in which a secondary battery 913 is built in the internal region. The secondary battery 913 is the secondary battery described in Embodiment 3. The secondary battery 913 is provided in a position overlapping with the display portion 4005a, and can have high density and high capacity, and is small and lightweight.

[0449] Since the wristwatch-type device 4005 is required to be small and lightweight, by using the positive electrode active material 100 obtained in the above-described embodiment as the positive electrode of the secondary battery 913, it is possible to obtain a high-energy density and small-sized secondary battery 913.

[0450] 26D shows an example of a wireless earphone. Here, the wireless earphone is shown having a pair of main bodies 4100a and 4100b, but this does not necessarily have to be a pair.

[0451] The main bodies 4100a and 4100b each have a driver unit 4101, an antenna 4102, and a secondary battery 4103. They may also have a display unit 4104. They also preferably have a substrate on which a circuit such as a wireless IC is mounted, a charging terminal, and the like. They may also have a microphone.

[0452] The case 4110 has a secondary battery 4111. It is preferable that the case 4110 also has a board on which circuits such as a wireless IC and a charge control IC are mounted, and a charging terminal. It may also have a display unit, buttons, and the like.

[0453] The main units 4100a and 4100b can wirelessly communicate with other electronic devices such as smartphones. This allows sound data and the like sent from other electronic devices to be played back on the main units 4100a and 4100b. If the main units 4100a and 4100b have microphones, the sound picked up by the microphones can be sent to the other electronic device, and the sound data after processing by the electronic device can be sent back to the main units 4100a and 4100b for playback. This allows the devices to be used as, for example, translation devices.

[0454] Furthermore, the secondary battery 4103 included in the main body 4100a can be charged from the secondary battery 4111 included in the case 4110. The coin-type secondary battery, the cylindrical secondary battery, or the like described in the above embodiment can be used as the secondary battery 4111 and the secondary battery 4103. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has high energy density, and by using the secondary battery 4103 and the secondary battery 4111 as the positive electrode, a configuration that can accommodate space saving associated with miniaturization of wireless earphones can be realized.

[0455] 25A to 25D preferably include a control unit having the second algorithm and the fourth algorithm described in Embodiment 1. Alternatively, the electronic device itself may have the second algorithm and the fourth algorithm described in Embodiment 1.

[0456] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0457] 1: Server device, 2: Electronic device, 3: Power storage device, 4: Control unit, 5: Storage battery, 6: Coulomb counter, 7: Communication network, 11: First data, 12: Second data, 21: First algorithm, 22: Second algorithm, 23: Third algorithm, 24: Fourth algorithm, 31: First neural network, 32: Second neural network, 33: Third neural network, 34: Fourth neural network, 61: SOC-OCV characteristic data list, 62: First SOC-OCV characteristic data, 63: Second SOC-OCV characteristic data, 71: R value estimated by power storage device, 71a: R value at one point in time estimated by power storage device, 71b: R value estimated by power storage device, 72: FCC estimated by server device

Claims

1. The electronic device includes a power storage device and a server device, The power storage device includes a control unit and a storage battery. the control unit has a first function of creating second data by using first data at a first time point, and a second function of transmitting the second data to the server device; the server device has a third function of creating first data at a second time point by using the second data, and a fourth function of transmitting the first data at the second time point to the control unit; the first function, the second function, the third function, and the fourth function are repeatedly performed; The third function of the server device includes a first algorithm, The first function of the control unit includes a second algorithm, The control unit has a plurality of SOC-OCV characteristic data, the server device has a function of creating at least one of the plurality of SOC-OCV characteristic data by using the second data and the first algorithm; The control unit has a function of using the second algorithm to select, from the plurality of SOC-OCV characteristic data, a first SOC-OCV characteristic data that is closest to a state of the storage battery.

2. The power storage device management system according to claim 1 , the electronic device has a fifth function of generating second SOC-OCV characteristic data based on the first SOC-OCV characteristic data and an estimated load of the electronic device; an OCV value at which the SOC value becomes 0% in the second SOC-OCV characteristic data is higher than an OCV value at which the SOC value becomes 0% in the first SOC-OCV characteristic data.

3. The power storage device management system according to claim 1 or 2, Each of the plurality of SOC-OCV characteristic data is configured by a combination of first bit data corresponding to an SOC value and second bit data corresponding to an OCV value, A power storage device management system, in which the number of bits of the first bit data is equal to the number of bits of the second bit data.

4. The power storage device management system according to any one of claims 1 to 3, The third function of the server device includes a third algorithm; The first function of the control unit has a fourth algorithm, the first data having an FCC value; the second data having an R value; the server device has a function of estimating the FCC value by using the second data and the third algorithm; The control unit has a function of calculating the R value by using the first data and the fourth algorithm.

5. The power storage device management system according to any one of claims 1 to 4, The control unit has a coulomb counter that measures an integrated charge amount of the storage battery, the integrated charge amount is reset and the second function is performed every time the integrated charge amount reaches the FCC value.