Flexible-battery management system and electronic equipment

Abstract

According to the present invention, a safe charging environment is provided for a flexible battery that can follow the movement of a housing. Provided is a flexible-battery management system or flexible-battery-equipped electronic equipment, having a sensor that detects movement of the flexible battery, and a charge control circuit that has a function of starting or stopping charging of the flexible battery on the basis of a signal from the sensor. The sensor uses the charge control circuit to start charging the flexible battery when it has been detected that the flexible battery is in an unfolded first form and when it has been detected that the flexible battery is in a curved second form.

Description

Flexible battery management system and electronic device

[0001] One aspect of the present invention relates to a flexible battery management system and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field, and relates to a semiconductor device, a display device, a light-emitting device, a recording device, a driving method thereof, or a manufacturing method thereof.

[0003] In recent years, there has been active development of wearable devices such as smart watches and head-mounted displays. To ensure comfortable wearing, the exterior of wearable devices often has a curved portion that fits comfortably to the human body, and a configuration with a curved portion has also been proposed for secondary batteries to be installed in wearable devices (see Patent Document 1).

[0004] Furthermore, mobile devices such as smartphones and tablets are equipped with flexible displays that move along with their moving housings (see Patent Document 2). [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] JP 2016-110640 A [Patent Document 2] JP 2016-075884 A [Non-Patent Document]

[0006] As flexible displays have come to be mounted on electronic devices as in Patent Document 2, there has been an increasing demand for flexible batteries that can follow the movement of the housing of the electronic device. However, in the field of secondary batteries, where safety is considered important, secondary batteries are assumed to be fixed, and there have been few reports on flexible batteries.

[0007] The secondary battery in Patent Document 1 is described as being preferably flexible in the event that the smartwatch is deformed by an external force, but the deformation is slight when the smartwatch is worn, and the secondary battery is fixed to the smartwatch together with a plate. Furthermore, the lithium-ion battery in Patent Document 2 is fixed in a position overlapping with the immovable housing.

[0008] In view of the above, an object of one embodiment of the present invention is to provide a safe charging environment for a flexible battery that can follow the movement of a housing. Another object of one embodiment of the present invention is to provide a lithium-ion battery that is suitable for the flexible battery.

[0009] 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 it is possible to extract problems other than these from the description in the specification, drawings, and claims (hereinafter referred to as the specification, etc.).

[0010] In view of the above, one aspect of the present invention is a flexible battery management system that includes a sensor that detects the movement of a flexible battery and a charge control circuit that has the function of starting or stopping charging of the flexible battery based on a signal from the sensor, and that starts charging of the flexible battery using the charge control circuit when the sensor detects that the flexible battery is in an unfolded first form and when the sensor detects that the flexible battery is in a curved second form.

[0011] In another aspect of the present invention, the charge control circuit preferably includes a voltage measurement circuit.

[0012] In another aspect of the present invention, the charge control circuit preferably includes a current measuring circuit.

[0013] In another aspect of the present invention, the charge control circuit preferably includes a temperature sensor.

[0014] Another aspect of the present invention is an electronic device that includes a housing, a flexible battery that can follow the movement of the housing, a sensor that detects the movement of the flexible battery, and a charge control circuit that stops or starts charging of the flexible battery based on a signal from the sensor, and that starts charging of the flexible battery using the charge control circuit when the sensor detects that the flexible battery is in an unfolded first form and when the sensor detects that the flexible battery is in a curved second form.

[0015] In another aspect of the present invention, it is preferable that a cover portion is located on the outside of the housing, and the flexible battery is installed inside the cover portion.

[0016] In another aspect of the present invention, the cover preferably has a sliding function relative to the housing.

[0017] In another aspect of the present invention, it is preferable that the housing has a space inside, and the sensor is installed in the space.

[0018] In another aspect of the present invention, the sensor is preferably a switch, an angular velocity sensor, or a magnetic sensor.

[0019] In another aspect of the present invention, the housing can be bent via a hinge portion, and the sensor is preferably provided at the hinge portion.

[0020] In another aspect of the present invention, the sensor preferably includes an expansion / contraction sensor.

[0021] In another aspect of the present invention, in the second embodiment, it is preferable that the radius of curvature of the flexible battery is 5 mm or more.

[0022] According to one embodiment of the present invention, a system for managing a safe charging environment for a flexible battery that can follow the movement of a housing can be provided.Furthermore, another embodiment of the present invention can provide a lithium-ion battery suitable for the flexible battery.

[0023] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc.

[0024] FIGS. 1A and 1B are perspective views of an electronic device having a flexible battery according to one embodiment of the present invention. FIGS. 2A and 2B are cross-sectional views of an electronic device having a flexible battery according to one embodiment of the present invention. FIG. 3 is a cross-sectional view of an electronic device having a flexible battery according to one embodiment of the present invention. FIGS. 4A to 4C are diagrams illustrating the radius of curvature of a flexible battery according to one embodiment of the present invention. FIGS. 5A to 5C are cross-sectional views of a flexible battery and a sensor according to one embodiment of the present invention. FIG. 6A is a perspective view of a flexible battery according to one embodiment of the present invention, FIG. 6B is a perspective view of a circuit board, and FIG. 6C is a cross-sectional view of a semiconductor element. FIGS. 7A and 7B are circuit diagrams of a flexible battery management system according to one embodiment of the present invention. FIGS. 8A and 8B are circuit diagrams of a flexible battery management system according to one embodiment of the present invention. FIG. 9 is a circuit diagram of a flexible battery management system according to one embodiment of the present invention. FIG. 10A is a top view of an electronic device having a flexible battery according to one embodiment of the present invention, and FIGS. 10B and 10C are cross-sectional views of an electronic device having a flexible battery according to one embodiment of the present invention. FIGS. 11A to 11C are perspective views of an electronic device having a flexible battery according to one embodiment of the present invention. FIGS. 12A and 12B are cross-sectional views showing a flexible battery according to one embodiment of the present invention. FIG. 13A is a cross-sectional view showing a negative electrode according to one embodiment of the present invention, and FIG. 13B is a top view showing a negative electrode according to one embodiment of the present invention. FIG. 14A is a cross-sectional view showing a positive electrode according to one embodiment of the present invention, and FIG. 14B is a top view showing a positive electrode according to one embodiment of the present invention. FIG. 15A is a plan view showing an exterior body according to one embodiment of the present invention, FIG. 15B is a view showing an exterior body according to one embodiment of the present invention, and FIGS. 15C to 15E are cross-sectional views showing an exterior body according to one embodiment of the present invention. FIGS. 16A and 16B are cross-sectional views showing an exterior body according to one embodiment of the present invention, and FIG. 16C is a diagram illustrating how to bend an exterior body according to one embodiment of the present invention. FIG. 17A is a schematic perspective view showing an exterior body according to one embodiment of the present invention, and FIG. 17B is a cross-sectional view showing an exterior body according to one embodiment of the present invention. FIGS. 18A to 18E are cross-sectional schematic views showing an exterior body according to one embodiment of the present invention. FIGS. 19A to 19E are cross-sectional schematic views showing an exterior body according to one embodiment of the present invention. 20 is a cross-sectional view illustrating an exterior package according to one embodiment of the present invention. 21A and 21B are top views illustrating an exterior package according to one embodiment of the present invention.FIGS. 22A to 22C are top views illustrating an exterior body of one embodiment of the present invention. FIGS. 23A to 23D are top views illustrating a flexible battery of one embodiment of the present invention, and FIG. 23E is a cross-sectional view illustrating a flexible battery of one embodiment of the present invention. FIGS. 24A and 24B are cross-sectional views illustrating an exterior body of one embodiment of the present invention. FIG. 25 is a flow chart illustrating a method for manufacturing a cathode active material by a coprecipitation method according to one embodiment of the present invention. FIGS. 26A to 26C are a flow chart illustrating a method for manufacturing a cathode active material by a solid-phase method according to one embodiment of the present invention. FIGS. 27A to 27D are diagrams illustrating electronic devices of one embodiment of the present invention. FIGS. 28A to 28D are diagrams illustrating electronic devices of one embodiment of the present invention. FIGS. 29A to 29C are diagrams illustrating electronic devices of one embodiment of the present invention. FIGS. 30A to 30C are diagrams illustrating electronic devices of one embodiment of the present invention.

[0025] Hereinafter, examples of embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention should not be construed as being limited to the following examples. The embodiments of the present invention can be modified within the scope of the spirit of the present invention.

[0026] In this specification, a flexible battery is a battery that has mobility, and specifically refers to a battery that can move with the moving housing when it is clamped in the housing.

[0027] In this specification and the like, the positive electrode active material refers to a compound containing a transition metal and oxygen, capable of inserting and extracting Li. The compound is sometimes called a composite oxide. Therefore, the positive electrode active material does not include carbonic acid, hydroxyl groups, and the like adsorbed after the preparation of the positive electrode active material. Furthermore, the positive electrode active material does not include electrolytes, organic solvents, binders, conductive materials, or compounds derived from these materials attached to the positive electrode active material.

[0028] In this specification, the interface between the region where a transition metal (e.g., Co, Ni, Mn, Fe) that oxidizes and reduces with the insertion and removal of Li is present and the region where it is not present is defined as the surface of the positive electrode active material. Furthermore, in this specification, the surface layer portion refers to the region extending from the surface toward the interior, within 50 nm perpendicular or approximately perpendicular from the surface. The surface layer portion is synonymous with the near-surface, near-surface region, or shell. In this specification, the region deeper than the surface layer portion of the positive electrode active material is referred to as the bulk. The bulk is synonymous with the interior or core. In this specification, the coating portion of the positive electrode active material includes a portion formed by the deposition of decomposition products of the electrolyte solution during charge and discharge, unless otherwise specified. The coating portion does not have to cover the entire positive electrode active material.

[0029] Embodiment 1 In this embodiment, an electronic device of one embodiment of the present invention will be described with reference to FIGS.

[0030] 1A , 1B , 2A , and 2B illustrate an example of an electronic device 100 of one embodiment of the present invention. The electronic device 100 of one embodiment of the present invention includes at least a housing 101, a display portion 102, a power button 103, a button 104, a speaker 105, a microphone 106, a flexible battery 107, and a sensor 109. The housing 101 can be moved using a hinge portion 119. The display portion 102 is an area where a display can be viewed and includes a display or the like.

[0031] As shown in Figures 1A and 2A, the housing 101 is in an unfolded state (referred to as a first state) using the hinge portion 119. Figure 2A is a cross-sectional view of the unfolded state, and this cross-sectional view corresponds to a portion of the microphone 106 side shown in Figure 1A. As shown in Figure 2A, when the housing 101 is unfolded, the flexible battery 107 also assumes an unfolded state following the housing 101. The flexible battery 107 shown in Figure 2A may be referred to as a straight-shaped flexible battery.

[0032] As shown in Figures 2A and 2B, the housing 101 is folded using the hinge portion 119 (referred to as a second form). Figure 2B is a cross-sectional view of the folded form, and in order to show the state of the flexible battery 107, a display and the like are omitted. When the housing 101 is folded as shown in Figure 2B, the flexible battery 107 also assumes a folded form. The flexible battery 107 shown in Figure 2B may be referred to as a curved flexible battery, a bent flexible battery, or the like.

[0033] Although not shown in Figures 1A, 1B, 2A, and 2B, the electronic device 100 of one embodiment of the present invention can grasp a transition from the first form to the second form, or a transition from the first form to the second form, by controlling the position of the housing 101. Of course, a transition from the second form to the first form, or a transition from the second form to the first form, can also be grasped. These transitional and transitional forms are distinguished from the first and second forms, and because the housing 101 has the same form, they are collectively referred to as the third form. The electronic device of the present invention has the flexible battery described above.

[0034] To ensure safety, the flexible battery 107 is charged in the first and second modes, but not in the third mode. Specifically, it is preferable that the electronic device 100 be equipped with a system that uses a sensor 109 or the like to start charging after it is confirmed that the flexible battery 107 is in the first or second mode, and stops charging when it is confirmed that it is in the third state.

[0035] That is, the electronic device 100 of one embodiment of the present invention preferably includes a system that detects the first to third modes using the sensor 109. If the sensor 109 can detect the first mode and the second mode, which are modes for starting charging, it can determine that the third mode is the other mode, and charging can be stopped. Furthermore, if the sensor 109 can detect the third mode, which is a mode for stopping charging, it can determine that the other mode is the first mode or the second mode, and charging can be started.

[0036] 1A , it is preferable to install sensor 109 in a region overlapping hinge portion 119 in a top view, as this makes it easier to grasp the movement of electronic device 100. Of course, the installation position of sensor 109 can be determined depending on the function of sensor 109, so sensor 109 does not necessarily have to be installed in a region overlapping hinge portion 119. In a cross-sectional view, sensor 109 may be installed on either housing 101 or hinge portion 119.

[0037] As shown in FIG. 2A , the electronic device 100 preferably includes a protective member 150 on the display surface side of the housing 101 so as to overlap the display unit 102. To enable viewing of the display unit 102, the protective member 150 may be light-transmissive in the area overlapping the display unit 102. A space 149 is located in the area surrounded by the housing 101 and the protective member 150. A display panel 151, an optical member 152 located on the display panel 151, and a touch sensor panel 153 located on the optical member 152 are provided in the area within the space 149 that overlaps the display unit 102. The protective member 150, the display panel 151, the optical member 152, and the touch sensor panel 153 may be fixed to one another by an adhesive layer. The optical member 152 may be a polarizing plate, a circular polarizing plate, or the like.

[0038] 2A , a part of the display panel 151 is folded back in an area outside the display unit 102, and an FPC (Flexible Printed Circuit) 158 can be connected to the folded back part. An IC 159 is preferably mounted on the FPC 158. The FPC 158 is connected to a terminal provided on a printed circuit board 160.

[0039] 1A to 2B , electronic device 100 preferably further includes, in addition to housing 101, cover unit 120 located on the outside of housing 101. Cover unit 120 may have a function (referred to as a sliding function) that allows it to be displaced relative to housing 101. For example, cover unit 120 may have a mechanism that allows it to slide in conjunction with hinge unit 119.

[0040] 2B, it is preferable that the flexible battery 107 is located inside the cover portion 120. This configuration is preferable because it allows the flexible battery 107 to easily follow the movement of the housing 101.

[0041] 3, a second battery 170 may be disposed in the space 149. The second battery 170 does not have to be a flexible battery, and may be fixed to the housing 101.

[0042] A specific example of such an electronic device 100 is a portable information terminal that can be used as a smartphone, a tablet, or the like. A specific example of the flexible battery 107 is a lithium ion battery. Lithium ion batteries have high output and high capacity, making them suitable as batteries for portable information terminals.

[0043] 1A , 1B , 2A , and 2B , the electronic device 100 of one embodiment of the present invention can be bent, specifically, at a region overlapping with a hinge portion 119 (shown by a dashed line in FIG. 1 ), and the housing 101, the display portion 102, and the flexible battery 107 can move along the hinge portion 119. Furthermore, the housing 101 can be opened and closed along the hinge portion 119, and the display portion 102 and the flexible battery 107 can follow the movement of the housing 101. Note that although components other than the flexible battery 107 are omitted in FIG. 2B , it is preferable that the flexible battery 107 be positioned inside the cover portion 120, because the flexible battery 107 can easily follow the movement of the housing 101.

[0044] As shown in Figures 1B and 2B, in the second folded form of the electronic device 100, it is preferable that the cover unit 120 slides relative to the housing 101, and the second display unit 102b can be seen from the slid portion. Even when folded in two, the user can view simple displays such as the time display or a notification display of received email on the second display unit 102b. The back surface of the display unit 102 can be used as the second display unit 102b. In other words, the second display unit 102b can be the same as the display unit 102. Of course, the second display unit 102b may be a display unit separate from the display unit 102.

[0045] 1B and 2B , the cover unit 120 is partially fixed to the housing 101, but is not fixed in the portion overlapping with the hinge unit 119 and the second display unit 102b. Specifically, it is sufficient that the cover unit 120 is fixed to a portion of the housing 101 located on the back surface of the electronic device 100, and that the cover unit 120 is held so as to be slidable relative to the housing 101 in the portion overlapping with the hinge unit 119 and the second display unit 102b. Furthermore, the cover unit 120 may be detachable from the housing 101.

[0046] The hinge portion 119, which is also referred to as a connecting portion, has a structure in which a plurality of pillars 119a overlap and are connected at the overlapping regions, as shown in FIG. 2B . The hinge portion 119 is not limited to this structure, and may have various other shapes. In particular, it is preferable that the hinge portion 119 has a mechanism that allows it to bend without expanding or contracting the display unit 102 and the flexible battery 107.

[0047] 1A, the hinge portion 119 is positioned so as to overlap the center of the flexible battery 107, but the present invention is not limited to this. For example, the hinge portion 119 may be positioned at a position offset from the center of the flexible battery 107. The flexible battery 107 can be bent in the region overlapping with the hinge portion 119.

[0048] 1A to 2B , the flexible battery 107 in the electronic device 100 of one embodiment of the present invention can also take any of the first to third modes. In the second mode, the flexible battery 107 has a curvature radius of 5 mm or more, preferably 10 mm or more, and more preferably 10 mm or more and 60 mm or less.

[0049] The radius of curvature of a surface will be described using Figure 4. In Figure 4A, on a plane 3701 obtained by cutting a curved surface 3700, a portion of a curve 3702 included in the curved surface 3700 is approximated to an arc of a circle, and the radius of the circle is taken as radius of curvature 3703, and the center of the circle is taken as center of curvature 3704. Figure 4B shows a top view of the curved surface 3700. Figure 4C shows a cross-sectional view of the curved surface 3700 cut by the plane 3701. When a curved surface is cut with a plane, the radius of curvature of the curve that appears in the cross section will differ depending on the angle of the plane with respect to the curved surface or the cutting position, but in this specification and the like, the smallest radius of curvature is taken as the radius of curvature of the flexible battery 107.

[0050] The cross-sectional shape of the flexible battery 107 is not limited to an arc shape, and may be a shape having a partial arc. Examples of a shape having a partial arc include a wave shape or an S-shape. A shape having a partial arc may have a curved surface with multiple centers of curvature. In this case, the flexible battery 107 can be bent so that the radius of curvature of the curved surface with the smallest radius of curvature at each of the multiple centers of curvature is 5 mm or more, preferably 10 mm or more, and more preferably 10 mm or more and 60 mm or less.

[0051] Again, to ensure safety, the flexible battery 107, which can follow the movement of the housing 101, is charged in the first or second form and is not charged in the third form. That is, using the sensor 109 or the like, charging starts when it is confirmed that the flexible battery 107 is in the first or second form, and charging stops when it is confirmed that it is in the third state.

[0052] The charging of such a flexible battery 107 can be controlled by a charging control circuit. By inputting a signal obtained from the sensor 109 to the charging control circuit, the charging of the flexible battery 107 can be controlled so that charging is performed in the first mode or the second mode, and charging is not performed in the third mode.

[0053] To ensure safety, the state of charge (SOC) of the flexible battery 107 may be known. Even in the second embodiment, charging may be stopped when the state of charge is 85% or higher, preferably 90% or higher. The SOC can be known by the charge control circuit.

[0054] The discharge of the flexible battery 107 that can follow the movement of the housing 101 may be performed in any of the first to third modes described above.

[0055] In this manner, one embodiment of the present invention can provide a safe charging environment for the flexible battery 107 that can follow the movement of the housing.

[0056] The display unit 102 shown in FIG. 1 can display a light using a flexible display. Specifically, a flexible display can be used for the display panel 151 shown in FIG. 2A . The flexible display has a plurality of light-emitting devices arranged in a matrix as display elements, and the plurality of light-emitting devices may be sandwiched between flexible films. As the light-emitting element, an EL device (also referred to as an EL element) such as an organic light-emitting diode (OLED) or a quantum-dot light-emitting diode (QLED) is preferably used. Examples of light-emitting materials included in the EL element include fluorescent materials that emit fluorescence, phosphorescent materials that emit phosphorescence, inorganic compounds (such as quantum dot materials), and substances that exhibit thermally activated delayed fluorescence (thermally activated delayed fluorescence: TADF materials). Furthermore, an LED such as a micro LED can also be used as the light emitting device.

[0057] The flexible display is thin, and even when it is installed in the housing 101, a sufficient space can be secured inside the housing 101. Therefore, the degree of freedom in installing the sensor 109 can be increased.

[0058] The sensor 109 may be any sensor that can detect the movement of the flexible battery 107. Although Fig. 1A illustrates an example in which the sensor 109 is installed in an area that overlaps with the hinge portion 119 when viewed from above, the sensor 109 may be installed in an area that can detect the movement of the flexible battery 107. The form of detecting the movement of the flexible battery 107 may include the first and second forms described above, and does not necessarily include the first to third forms described above.

[0059] The sensor 109 described above can be a physical switch such as a push switch. FIG. 5A shows a cross-sectional view of the electronic device 100 according to the first embodiment when a push switch 109a is used as the sensor 109. Note that FIG. 5A omits all components except the flexible battery 107 and the sensor 109a. The electronic device 100 includes the flexible battery 107 in the cover 120 and the push switch 109a in the housing 101, for example, in the space 149. The push switch 109a is preferably positioned so as to overlap the area where the flexible battery 107 bends. A signal can be obtained from the push switch 109a in response to the movement of the flexible battery 107. Specifically, as shown in FIG. 5A , if a push switch 109a that is turned on when the flexible battery 107 is not bent is used, a signal based on the on state can be obtained. When the flexible battery 107 begins to bend, the push switch 109a turns off, and a signal based on the off state can be obtained. A signal obtained from the push switch 109 a can be input to a charging control circuit or the like, and control can be performed to stop or start charging the flexible battery 107 .

[0060] Furthermore, the sensor 109 can be an angular velocity sensor 109b. When an angular velocity sensor is used, it is preferable to install angular velocity sensors 109b1 and 109b2 in the housing 101, typically in the space 149 or the cover portion 120, as shown in FIG. 5B . It is preferable to position the angular velocity sensor 109b1 so as to overlap with a first region that can be divided by the hinge portion 119, and to position the angular velocity sensor 109b2 so as to overlap with a second region that can be divided by the hinge portion 119. Since the angular velocity changes according to the movement of the flexible battery 107, this change can be input to a charge control circuit or the like, and control can be performed to stop or start charging the flexible battery 107.

[0061] Furthermore, a magnetic sensor 109c can be used as the sensor 109. When a magnetic sensor is used, it is preferable to install a magnet 109c2 inside the housing 101 and install a magnetic sensor, typically a 3D magnetic sensor 109c1, inside the cover portion 120, as shown in FIG. 5C . Furthermore, both the 3D magnetic sensor 109c1 and the magnet 109c2 may be installed in the housing 101, typically in the space 149. Since the applied magnetic field changes depending on the movement of the flexible battery 107, this change can be input to a control circuit or the like, and control can be performed to stop or start charging the flexible battery 107.

[0062] 6A shows a perspective view of the flexible battery 107. In Fig. 6A, the area overlapping with the hinge portion 119 is indicated by a dashed line in accordance with Fig. 1A. A circuit board 130 is electrically connected to the flexible battery 107, and the structure in which the flexible battery 107 and the circuit board 130 are integrated may be referred to as a battery pack.

[0063] 6B shows a perspective view of the circuit board 130. A charge control circuit 135 is installed on the circuit board 130. The charge control circuit 135 has a control circuit and the like, is electrically connected to the sensor 109, and can receive signals and the like from the sensor 109. The charge control circuit 135 has a function of stopping or starting charging of the flexible battery 107 based on signals and the like from the sensor 109. Specifically, charging can be started by turning on a switching element included in the charge control circuit 135, and can be stopped by turning off the switching element. A transistor may be used as the switching element.

[0064] 6C shows the structure of a transistor M21 that can be used as a circuit element such as a switching element included in the charge control circuit 135. The transistor M21 is formed on, for example, an insulating film 501C.

[0065] The transistor M21 has a semiconductor film 508 located on the insulating film 501C. The semiconductor film 508 can be made of, for example, a semiconductor containing a group 14 element. Specifically, the semiconductor film 508 can be made of a semiconductor containing silicon, and typically, polysilicon can be used for the semiconductor film 508. Furthermore, the semiconductor film 508 can be made of single crystal silicon.

[0066] A metal oxide, typically an oxide semiconductor, can be used for the semiconductor film 508. Specifically, an oxide semiconductor containing indium, an oxide semiconductor containing indium, gallium, and zinc, or an oxide semiconductor containing indium, gallium, zinc, and tin can be used for the semiconductor film 508.

[0067] A compound semiconductor containing silicon and oxygen, typically a SiC semiconductor, can be used for the semiconductor film 508. A compound semiconductor containing gallium and nitrogen, typically a GaN semiconductor, can be used for the semiconductor film 508.

[0068] Transistor M21 includes conductive layer 504, conductive layer 512A, and conductive layer 512B.

[0069] The conductive layer 504 has a region overlapping with a region 508C of the semiconductor film 508, and has a function of a gate. The region 508C corresponds to a channel formation region.

[0070] The conductive layer 512A has a function of either a source electrode or a drain electrode, and the conductive layer 512B has a function of the other of the source electrode or the drain electrode.

[0071] The semiconductor film 508 has regions 508A and 508B, which may be referred to as impurity regions, source regions, and drain regions. The region 508A is electrically connected to a conductive layer 512A, and the region 508B is electrically connected to a conductive layer 512B.

[0072] The insulating film 506 has a region sandwiched between the semiconductor film 508 and the conductive layer 504. The insulating film 506 functions as a gate insulating film.

[0073] In addition, an insulating layer 516 is provided to cover the conductive layer 504. The insulating layer 516 has a stacked structure of a first insulating layer 516A and a second insulating layer 516B.

[0074] Furthermore, the conductive layer 524 can be used as a back gate of a transistor, and the conductive layer 524 can be provided under the semiconductor film 508. A structure in which gates are located above and below a semiconductor film is sometimes referred to as a dual gate structure. The conductive layer 524 has a region that sandwiches the semiconductor film 508 between itself and the conductive layer 504. The conductive layer 524 functions as a gate. The insulating film 501D is sandwiched between the semiconductor film 508 and the conductive layer 524 and functions as a gate insulating film.

[0075] An insulating layer 518 is provided to cover the conductive layers 512A and 512B.

[0076] Such a charge control circuit 135 has a function of managing the charging of the flexible battery 107, and specifically, can stop or start charging. The function of stopping charging can also be used to make the charge control circuit 135 function as a protection circuit.

[0077] Furthermore, the electronic device 100 may have a plurality of batteries, and it is sufficient that at least one of the plurality of batteries is the flexible battery 107 .

[0078] 1A and 1B show an example in which the display surface of the display unit 102 is folded inward, but this is not particularly limited thereto, and a configuration in which the display surface is folded outward, unlike in FIGS. 1A and 1B, may be applied depending on the configuration of the hinge unit 119. Depending on the configuration of the hinge unit 119, a configuration in which the display surface is folded inward or outward may be applied.

[0079] The electronic device 100 equipped with such a flexible display is extremely lightweight, making it possible to realize an electronic device 100 with excellent portability. By installing the flexible battery 107 as a secondary battery for the electronic device 100, a portion of the electronic device 100 can be folded, making it possible to reduce the size of the electronic device 100. In other words, it is possible to realize an electronic device 100 with excellent portability.

[0080] <Flexible Battery Management System> The electronic device 100 according to one embodiment of the present invention may be equipped with a flexible battery management system. FIG. 7A illustrates an example of a flexible battery management system 10 according to one embodiment of the present invention. The flexible battery management system 10 includes a charge control circuit 135, a flexible battery 107, and a sensor 109. The charge control circuit 135 is electrically connected to the flexible battery 107. Specifically, the charge control circuit 135 is electrically connected to the positive and negative electrodes of the flexible battery 107. A positive electrode terminal such as a positive electrode lead or a positive electrode tab may be provided on the flexible battery 107 as the positive electrode. A negative electrode terminal such as a negative electrode lead or a negative electrode tab may be provided on the flexible battery 107 as the negative electrode. In this case, the charge control circuit 135 is electrically connected to the positive electrode terminal and the negative electrode terminal. The sensor 109 has a function of detecting the state of the flexible battery 107. Specifically, it has a function of detecting the movement of the flexible battery 107 that follows the movement of the housing. The sensor 109 is electrically connected to the charge control circuit 135.

[0081] 7A includes at least a voltage measurement circuit 15, a current measurement circuit 16, and a control circuit 18. The charge control circuit 135 further includes a first switch 35 and a second switch 36 electrically connected to the control circuit 18. The first switch 35 functions to stop charging in the event of overcharging, and the second switch 36 functions to stop discharging in the event of overdischarging. Charging of the flexible battery 107 can be stopped using the first switch 35 based on a signal from the sensor 109.

[0082] The charge control circuit 135 shown in FIG. 7B differs from that shown in FIG. 7A in that it further includes a temperature sensor 20 .

[0083] 7A and 7B, the voltage measurement circuit 15 is electrically connected to the positive and negative electrodes of the flexible battery 107. The voltage measurement circuit 15 may be electrically connected to the positive and negative terminals.

[0084] The voltage measurement circuit 15 has a function of measuring the voltage (referred to as terminal voltage) of the flexible battery 107, for example, a function of measuring the terminal voltage (referred to as charging voltage) when the flexible battery 107 is being charged. The voltage measurement circuit 15 may also have a function of measuring the terminal voltage (referred to as discharging voltage) when the flexible battery 107 is being discharged in addition to the charging voltage.

[0085] The voltage measurement circuit 15 can provide the measured voltage value to the control circuit 18. If the measured voltage value is an analog value, the analog value may be converted to digital and provided to the control circuit 18. That is, the voltage measurement circuit 15 may have a circuit that converts the analog value to digital, and this circuit can be an analog-to-digital converter (ADC). ADC configurations include a delta-sigma modulation type, a parallel comparison type (also referred to as a flash type), and a pipeline type. The delta-sigma modulation type is suitable for the voltage measurement circuit 15 because of its high resolution.

[0086] <Measurement Example 1 of Voltage Vb1> Measurement Example 1 of voltage Vb1 between the positive and negative electrodes of the flexible battery 107 will be described using Fig. 8A. Of the charge control circuit 135 in Fig. 8A, only the voltage measurement circuit 15 is shown, and the rest is omitted. The voltage measurement circuit 15 can directly measure the voltage Vb1 between the positive and negative electrodes of the flexible battery 107, as shown in Fig. 8A.

[0087] <Measurement Example 2 of Voltage Vb1> As shown in FIG. 8B, the voltage measurement circuit 15 can also measure the resistively divided voltage Vb1. In FIG. 8B, only the voltage measurement circuit 15 is shown in the charge control circuit 135; the rest is omitted. In FIG. 8B, the voltage Vb1 is divided into voltages Vb2 and Vb3 by resistive elements 122 and 123, and the voltage measurement circuit 15 can measure, for example, voltage Vb3. To be able to measure voltage Vb3, the voltage measurement circuit 15 is electrically connected between the negative electrode of the flexible battery 107 and the resistor elements 122 and 123.

[0088] When the voltage measurement circuit 15 measures the voltage obtained by resistively dividing the voltage between the positive and negative electrodes of the flexible battery 107, the voltage measurement circuit 15 or the control circuit 18 may estimate the voltage Vb1 between the positive and negative electrodes of the flexible battery 107 from the resistively divided voltage.

[0089] 7A and 7B , the current measurement circuit 16 is electrically connected to the positive electrode of the flexible battery 107, and a resistive element is located between the connection points to measure the potential difference across the resistive element. The current measurement circuit 16 may also be electrically connected to the positive electrode terminal.

[0090] The current measurement circuit 16 has a function of measuring the current flowing through the positive and negative electrodes of the flexible battery 107, and preferably has a function of measuring, for example, the current (referred to as charging current) when the flexible battery 107 is being charged. The current measurement circuit 16 may also have a function of measuring the current (referred to as discharging current) when the flexible battery 107 is being discharged in addition to the charging current.

[0091] The current measurement circuit 16 can provide the measured current value to the control circuit 18. The measured current value is an analog value, but the analog value may be converted to digital and provided to the control circuit 18, and the analog-to-digital converter (ADC) described above can be used.

[0092] 7A and 7B, the sensor 109 is electrically connected to the control circuit 18. Again, the sensor 109 has a function of detecting the state of the flexible battery 107. Specifically, the sensor 109 has a function of detecting the movement of the flexible battery 107 that follows the movement of the housing.

[0093] 7A and 7B has a function of controlling the start and stop of charging of the flexible battery 107. Furthermore, the control circuit 18 may have a calculation function, a detection function, a determination function, etc. The calculation function can calculate data indicating the battery characteristics of the flexible battery 107 from values ​​provided by the voltage measurement circuit 15, etc.

[0094] <Determination Function> The determination function of the control circuit 18 enables it to determine, based on the signal obtained from the sensor 109, when charging should be stopped.

[0095] <Stopping Charging> The control circuit 18 has a function of stopping charging based on a signal obtained from the sensor 109 .

[0096] <Charging Conditions> Constant current-constant voltage (CC-CV) charging may be used to charge the flexible battery 107. CC-CV charging involves performing constant current charging, and then, after the upper limit of the charging voltage is reached during constant current charging, performing constant voltage charging.

[0097] It is preferable that the charging condition from the start of charging to the end of charging be constant current charging. For example, during constant current charging, the voltage changes after charging is stopped and then resumed, making it easier to grasp the SOC (state of charge).

[0098] <Coulomb Counter> The charge control circuit 135 preferably has a function as a coulomb counter. For example, as a function of the coulomb counter, the charge control circuit 135 can calculate the cumulative amount of electricity of the flexible battery 107 using the current measurement circuit 16 and the control circuit 18. From the calculated amount of electricity, the charge capacity and discharge capacity of the flexible battery 107 can be calculated.

[0099] <SOC> The control circuit 18 may also have a function of analyzing the SOC using the calculated charge capacity and discharge capacity. The control circuit 18 may be a CPU (Central Processing Unit), an MCU (Micro Controller Unit), or the like.

[0100] The control circuit 18 may also include a memory circuit 19 in addition to the CPU or MCU.

[0101] 7B can measure the operating temperature of the flexible battery 107. The temperature sensor 20 only needs to be able to measure a range from low to high temperatures. The temperature sensor 20 is preferably installed so as to be in contact with the exterior body of the flexible battery 107 or the outer casing of the exterior body.

[0102] When the flexible battery 107 is used at different temperatures, such as low and high temperatures, or low and room temperatures, the information on the operating temperature obtained from the temperature sensor 20 is useful. Even when the flexible battery 107 is used in the same temperature range, if an abnormality occurs in the battery due to movement, the temperature sensor 20 can detect the abnormality.

[0103] <Secondary Battery> Details of the flexible battery 107 will be described later.

[0104] <Battery Pack> The flexible battery management system 10B shown in Figure 9 is an example in which a charge control circuit 135 is electrically connected to a battery pack, i.e., m flexible batteries 107 connected in series. Figure 9 shows an example of a flexible battery management system 10B where m is an integer greater than or equal to 4, and shows flexible battery 107(1), flexible battery 107(2), flexible battery 107(3), and flexible battery 107(m) as the first, second, third, and mth flexible batteries of the m flexible batteries 107. The charge control circuit 135 may be divided into m charge control circuits 135(m), but is preferably shared as shown in Figure 9.

[0105] Furthermore, in the flexible battery management system 10B, the voltages and the like of m flexible batteries 107 can be measured using m voltage measurement circuits 15 connected to each of them. The voltage measurement circuits 15 may be shared rather than being divided into m voltage measurement circuits 15 as shown in FIG. 9. The voltage and the like may be measured using the total voltage of the m flexible batteries 107 connected in series (for example, the voltage between the positive electrode of flexible battery 107(1) and the negative electrode of flexible battery 107(m) in FIG. 9).

[0106] The flexible battery 107 of one embodiment of the present invention can be folded in two or more ways, for example, folded in three. The battery can be folded in three by increasing the number of hinge portions 119.

[0107] The hinge portion 119 may be provided with a ratchet mechanism or a non-slip mechanism so that the bending angle can be adjusted as needed.

[0108] The flexible battery 107 of one embodiment of the present invention has high reliability against repeated deformation and can therefore be suitably used in such foldable devices.

[0109] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0110] Embodiment 2 In this embodiment, another embodiment of an electronic device according to one embodiment of the present invention will be described with reference to FIGS.

[0111] FIG. 10A is a top view of an electronic device 100A of one embodiment of the present invention, illustrating a mode (first mode) in which the display portion 102 is unfolded. FIG. 10B is a side view illustrating the structure of the electronic device 100A, with the arrow indicating the display direction. As illustrated in FIGS. 10A and 10B , the electronic device includes a first housing 101a and a second housing 101b, which are connected to each other by a hinge portion 119A. The first housing 101a and the second housing 101b can be moved by using the hinge portion 119A. FIG. 10C is a side view illustrating the hinge portion 119A illustrated in FIG. 10B .

[0112] 10A , an electronic device 100A of one embodiment of the present invention includes a display unit 102 and a computing device 410 located outside the display unit 102. The display unit 102 further includes a flexible display, a touch panel 422 that serves as an input means for detecting a user's finger and supplying an operation command, and a flexible battery 107A (shown by a dashed line). The flexible battery 107A can have a similar structure to the flexible battery 107 described in the above embodiment.

[0113] Folding information and operation commands for electronic device 100A are supplied to computing device 410, and image information based on the signals is supplied to the flexible display and displayed on display unit 102. In electronic device 100A, display unit 102 can be folded, and touch panel 422 can also be folded.

[0114] As shown in FIG. 10B , the flexible battery 107 is held by the first housing 101a, the second housing 101b, etc. As shown in FIG. 10A , hinge portions 119A are paired and installed on opposing sides. By bending such hinge portions 119A, the first housing 101a and the second housing 101b can be moved, and the flexible battery 107 can be moved in accordance with the housings. Although not shown in FIG. 10B , the flexible display and touch panel 422 can also be moved in accordance with the first housing 101a and the second housing 101b, similar to the flexible battery 107. In order to move the flexible battery 107A in accordance with the housings, it is preferable to position the flexible battery 107 in the center as viewed from the side of the electronic device 100A, as shown in FIG. 10B .

[0115] The hinge portion 119A may be a support shaft, an elastic body, or the like.

[0116] As shown in FIG. 10C, the hinge portion 119A preferably has a configuration in which an elastic body 481c is positioned between a first expansion sensor 481a and a second expansion sensor 481b. When the hinge portion 119A is bent, one of the pair of expansion sensors detects expansion and the other detects contraction, and supplies the detected signal to a charge control circuit 135 electrically connected to the flexible battery 107A. The detected signal may also be supplied to the arithmetic device 410 shown in FIG. 10A or elsewhere. By comparing these signals, bending information about the electronic device 100A can be obtained. Based on this information, charging of the flexible battery 107 can be stopped or started.

[0117] In the second embodiment, the flexible battery 107A of one embodiment of the present invention preferably has a curvature radius of 5 mm or more, preferably 10 mm or more, and more preferably 10 mm or more and 60 mm or less.

[0118] The flexible battery 107A of one embodiment of the present invention can be folded in two or more times, for example, in three. The battery can be folded in three by increasing the number of hinge portions 119A.

[0119] In addition, the hinge portion 119A may be provided with a ratchet mechanism or a non-slip mechanism so that the bending angle can be adjusted appropriately.

[0120] The flexible battery 107A of one embodiment of the present invention has high reliability against repeated deformation and can therefore be suitably used in such foldable devices.

[0121] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0122] Embodiment 3 In this embodiment, another embodiment of an electronic device according to one embodiment of the present invention will be described with reference to FIGS.

[0123] 11A is a perspective view illustrating a structure of an electronic device 100B of one embodiment of the present invention. The electronic device 100B illustrates a first mode in which the display portion 102 is unfolded. FIG. 11B illustrates a third mode in which the display portion 102 is being folded. FIG. 11C illustrates a second mode in which the display portion 102 is folded.

[0124] In this embodiment, as shown in FIG. 11A and other figures, the electronic device 100B has two sets of first and second housings 101a and 101b. The second housing 101b is positioned so as to overlap the first housing 101a, and can sandwich a flexible battery 107B and other components. The two sets of first and second housings 101a and 101b are connected to a hinge portion 119B. The hinge portion 119B allows the two sets of first and second housings 101a and 101b to move. In order to move the flexible battery 107B in accordance with the housings, the flexible battery 107B may be positioned in the center when viewed from the side of the electronic device 100B. A space is located in the area surrounded by the first and second housings 101a and 101b. A sensor can be installed in this space.

[0125] 11B and 11C , the display portion 102 is folded so that it can be seen from the outside. However, one embodiment of the present invention is not limited to this. The display portion 102 may be folded so that it can be hidden from view.

[0126] 11A to 11C includes a flexible display in addition to a flexible battery 107 on a display unit 102. The electronic device 100B further includes a first housing 101a and a second housing 101b. The first housing 101a and the second housing 101b are connected via a hinge portion 119B.

[0127] The first housing 101a and the second housing 101b are preferably made of a material less flexible than the flexible battery 107B. Furthermore, if the first housing 101a and the second housing 101b are made of a light-blocking material, the drive circuit of the electronic device 100B can be disposed therein, and external light can be prevented from irradiating the drive circuit.

[0128] The first housing 101a and the second housing 101b can be formed using materials such as plastic, metal, alloy, rubber, etc. Using plastic or rubber is preferable because it results in a support panel that is lightweight and resistant to breakage. For example, the first housing 101a and the second housing 101b can be formed using silicone rubber, stainless steel, or aluminum.

[0129] In this embodiment, the first form shown in FIG. 11A and the second form shown in FIG. 11C enable charging of the flexible battery 107, and the form shown in FIG. 11B stops charging of the flexible battery 107.

[0130] In addition, in the electronic device 100B, the flexible display can be folded either by bending it so that the display surface faces inward (inward bending) or so that the display surface faces outward (outward bending). When the electronic device 100B is not in use, bending it so that the display unit 102 faces inward can prevent scratches or dirt from being formed on the display unit 102.

[0131] In the second embodiment, the flexible battery 107B of one embodiment of the present invention preferably has a curvature radius of 5 mm or more, preferably 10 mm or more, and more preferably 10 mm or more and 60 mm or less.

[0132] The flexible battery 107B of one embodiment of the present invention can be folded in two or more times, for example, in three. The battery can be folded in three by increasing the number of hinge portions 119B.

[0133] In addition, the hinge portion 119B may be provided with a ratchet mechanism or a non-slip mechanism so that the bending angle can be adjusted appropriately.

[0134] The flexible battery 107 of one embodiment of the present invention has high reliability against repeated deformation and can therefore be suitably used in such foldable devices.

[0135] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0136] Embodiment 4 In this embodiment, a structure of a flexible battery 107 of one embodiment of the present invention will be described.

[0137] The cross-sectional view shown in FIG. 12A shows the flexible battery 107 in a straight state (first state). The cross-sectional view shown in FIG. 12B shows the flexible battery 107 in a bent state (second state or third state). The flexible battery 107 can also maintain a bent state. Furthermore, the flexible battery 107 can alternate between the straight state shown in FIG. 12A and the bent state shown in FIG. 12B. The bent state of the flexible battery 107 as shown in FIG. 12B may be referred to as having a curved portion. The bent position can be located in the center of the flexible battery 107, or can be located elsewhere.

[0138] 12A and 12B , the flexible battery 107 has a negative electrode 301 and a positive electrode 331, and has a structure in which the negative electrode 301 and the positive electrode 331 are stacked (sometimes referred to as a stacked structure or an electrode with a stacked structure). In the flexible battery 107, the number of stacked negative electrodes 301 and the number of stacked positive electrodes 331 may be the same, or the number of stacked negative electrodes 301 may be different from the number of stacked positive electrodes 331. For example, the number of stacked negative electrodes 301 may be greater than the number of stacked positive electrodes 331.

[0139] 12A shows a configuration in which the area of ​​the negative electrode 301 is equal to the area of ​​the positive electrode 331. In the flexible battery 107, the area of ​​the negative electrode 301 may be equal to the area of ​​the positive electrode 331, or the area of ​​the negative electrode 301 may be different from the area of ​​the positive electrode 331.

[0140] As shown in Figure 12B, when the flexible battery 107 is bent while one end thereof is fixed, the laminated structure of the negative electrode 301 and the positive electrode 331 is maintained, but at the other end of the flexible battery 107, the position of the end of the negative electrode 301 may shift from the position of the end of the positive electrode 13.

[0141] 12A and the bent state shown in Fig. 12B alternately, the negative electrode 301 and the positive electrode 331 move in accordance with the above-mentioned positional deviation. When they move in accordance with the above-mentioned deviation, the adjacent negative electrode 301 and positive electrode 331 may rub against each other.

[0142] The flexible battery 107 of one embodiment of the present invention includes a buffer layer 305 located at least between the adjacent negative electrode 301 and positive electrode 331 in order to reduce friction between the adjacent negative electrode 301 and positive electrode 331. Specifically, the flexible battery 107 has a structure in which the buffer layer 305 encases the active material layer of the negative electrode 301 or the active material layer of the positive electrode 331. The buffer layer 305 encases either of the active material layers, thereby reducing friction between the negative electrode 301 and the positive electrode 331. Furthermore, the flexible battery 107 preferably has a structure in which the buffer layer 305 encases the active materials and the like in the negative electrode 301 and the positive electrode 331.

[0143] A graphene compound, graphene, or carbon fiber can be used for the buffer layer 305. The above-described friction during movement can be suppressed simply by attaching a graphene compound, graphene, or carbon fiber to the active material layer. Graphene compounds and the like will be described later. The buffer layer 305 can exhibit electrical conductivity if it is made of, for example, a carbon material, and can also exhibit insulating properties depending on the proportion of oxygen and other elements contained therein.

[0144] The negative electrode 301 includes a current collector 302 (sometimes referred to as a negative electrode current collector) and an active material layer 303 (sometimes referred to as a negative electrode active material layer). The positive electrode 331 includes a current collector 332 (sometimes referred to as a positive electrode current collector) and an active material layer 333 (sometimes referred to as a positive electrode active material layer). Ordinal numbers may be assigned to distinguish the current collectors from each other.

[0145] If the buffer layer 305 is conductive, it is preferable to provide a separator in the flexible battery 107. If the buffer layer 305 is insulating, the buffer layer 305 can function as a separator, which is preferable because it makes the flexible battery 107 unnecessary to provide a separator.

[0146] <Negative Electrode> The structure of the negative electrode 301 will be described. Fig. 13A shows a cross-sectional view of the negative electrode 301, and Fig. 13B shows a top view of the negative electrode 301. The cross-sectional view in Fig. 13A corresponds to the position indicated by the dotted line in Fig. 13B.

[0147] The negative electrode 301 has a current collector 302 and an active material layer 303. As shown in FIG. 13A , the active material layer 303 may be formed on two surfaces (one surface and the other surface) of the current collector 302. Forming the active material layer 303 on two surfaces is referred to as a double-sided formed structure or a double-sided coated structure. Although not shown in FIG. 13A , the active material layer 303 may be formed on either one surface or the other surface of the current collector 302. Forming the active material layer 303 on one surface is referred to as a single-sided formed structure or a single-sided coated structure.

[0148] 12A to 13B , in the negative electrode 301, the current collector 302 and the active material layer 303 are wrapped in the buffer layer 305. In other words, the buffer layer 305 wraps the current collector 302 and the active material layer 303. The flexible battery 107 of one embodiment of the present invention including such a buffer layer 305 becomes more movable and has high safety and durability.

[0149] The buffer layer 305 is preferably flexible and easily deformable, and is expected to have increased mechanical strength in electrodes and the like where the buffer layer 305 is disposed.

[0150] <Graphene Compound> Here, graphene compounds will be explained again. First, graphene will be explained. Graphene is a single atomic layer of carbon arranged, with π bonds between the carbon atoms. In other words, graphene refers to a substance that contains carbon, has a shape such as a sheet (also referred to as a plate), and has a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by the six-membered carbon rings may be called a carbon sheet.

[0151] Furthermore, a stack of 2 to 100 graphene layers may be referred to as multilayer graphene. Graphene and multilayer graphene have, for example, a length of the longitudinal direction or major axis on a plane of 50 nm to 100 μm, preferably 800 nm to 50 μm.

[0152] Next, graphene compounds will be described. A compound having graphene or multilayer graphene as a basic skeleton is called a "graphene compound (also called a "graphene compound")." Other graphene compounds include graphene oxide, multilayer graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, graphene quantum dots, and the like, which will be described later.

[0153] A graphene compound is, for example, a compound in which graphene or multilayer graphene is modified with an atom other than carbon or an atomic group having an atom other than carbon. Alternatively, the graphene or multilayer graphene may be a compound in which graphene or multilayer graphene is modified with an atomic group mainly composed of carbon, such as an alkyl group or an alkylene group. The atomic group modifying graphene or multilayer graphene may be referred to as a substituent, a functional group, a characteristic group, or the like. In this specification and the like, "modification" refers to the introduction of an atomic group having an atom other than carbon or an atomic group having an atom other than carbon into graphene, multilayer graphene, a graphene compound, or graphene oxide (described later) by a substitution reaction, an addition reaction, or other reaction. The front and back surfaces of graphene may be modified with different atoms or atomic groups. In multilayer graphene, each layer may be modified with different atoms or atomic groups.

[0154] A graphene compound refers to, for example, a compound that contains carbon, has a shape such as a sheet, and has a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by the six-membered carbon rings may be called a carbon sheet.

[0155] <Graphene oxide> An example of graphene modified with the above-mentioned atoms or atomic groups is graphene or multilayer graphene modified with oxygen or a functional group containing oxygen. Examples of the oxygen-containing functional group include an epoxy group, a carbonyl group such as a carboxyl group, a hydroxyl group, or a lactol group. A graphene compound modified with oxygen or a functional group containing oxygen may be referred to as graphene oxide. In this specification, graphene oxide also includes multilayer graphene oxide. Graphene oxide can exhibit insulating properties.

[0156] <Fluorine Termination> Furthermore, as the graphene compound, a material in which the ends of graphene are terminated with fluorine may be used.

[0157] <Method for Producing Graphene Oxide> Next, an example of a method for producing graphene oxide will be described. Graphene oxide can be obtained by oxidizing the above-mentioned graphene or multigraphene. Alternatively, graphene oxide can be obtained by separating the layers of graphite oxide. Graphite oxide can be obtained by oxidizing graphite. Here, graphene oxide may be further modified with the above-mentioned atoms or atomic groups.

[0158] Graphene oxide can be produced by various synthesis methods, such as the Hummers method, the modified Hummers method, or oxidation of graphite.

[0159] For example, the Hummers method and the modified Hummers method are techniques for forming graphite oxide by oxidizing graphite such as flake graphite. The graphite oxide thus formed is formed by oxidizing the graphite in places, resulting in the bonding of functional groups such as carbonyl groups, carboxyl groups, hydroxyl groups, and lactol groups. This impairs the crystallinity of the graphite and increases the distance between layers. Therefore, the layers can be easily separated by ultrasonic treatment or the like to obtain graphene oxide.

[0160] Here, an example of a method for producing graphene oxide using the modified Hummers method will be described. A sulfuric acid solution of potassium permanganate or the like is added to graphite powder to cause an oxidation reaction, forming a mixed solution containing graphite oxide. Graphite oxide contains functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups due to the oxidation of carbon in graphite. Therefore, the interlayer distance of graphene oxide is longer than that of graphite. Next, ultrasonic vibration is applied to the mixed solution containing graphite oxide to cleave the graphite oxide with a long interlayer distance, allowing graphene oxide to be separated and forming a dispersion containing graphene oxide.

[0161] When graphene oxide is produced by the modified Hummers method, the obtained graphene oxide may contain elements such as sulfur and nitrogen.

[0162] The sulfur concentration in the graphene compound of one embodiment of the present invention is, for example, preferably 5% or less, more preferably 3% or less.

[0163] The graphene compound of one embodiment of the present invention may contain, for example, 10 ppm or more and 5% or less, or 100 ppm or more and 3% or less, or 0.1% or more and 3% or less of sulfur.

[0164] Here, the concentration of sulfur contained in the graphene compound can be evaluated using elemental analysis such as XPS, for example.

[0165] The graphene compound of one embodiment of the present invention may contain, for example, 0.1% to 3% nitrogen.

[0166] <Reduced Graphene Oxide> A compound obtained by reducing graphene oxide is sometimes called "RGO (Reduced Graphene Oxide)." Here, RGO may also be written as "rGO" as shown in Non-Patent Document 1. Note that in RGO, not all of the oxygen contained in graphene oxide is released, and some oxygen or atomic groups containing oxygen may remain bonded to carbon. For example, RGO may have a functional group such as an epoxy group, a carbonyl group such as a carboxyl group, or a hydroxyl group.

[0167] The reduced graphene oxide preferably has a portion having a carbon concentration of more than 80 atomic % and an oxygen concentration of 2 atomic % to 15 atomic %. By setting the carbon concentration and oxygen concentration in this range, the electrical conductivity of the reduced graphene oxide can be increased.

[0168] Furthermore, the reduced graphene oxide preferably has an intensity ratio G / D of the G band to the D band in the Raman spectrum of at least 1. Reduced graphene oxide having such an intensity ratio can have high electrical conductivity.

[0169] Note that the reduction of graphene oxide may be performed by, for example, heat treatment or by using a reducing agent.

[0170] Reduced graphene oxide refers to, for example, a material that contains carbon and oxygen, has a sheet-like shape, or the like, and has a two-dimensional structure formed of six-membered carbon rings.

[0171] <Pores> By reducing graphene oxide, pores can be formed in the graphene compound in some cases. The pores in the graphene compound can correspond to regions through which carrier ions, specifically lithium ions, can pass. The presence of such pores facilitates the insertion and desorption of carrier ions, thereby improving the rate characteristics of the battery. The pores formed in a part of the carbon sheet are sometimes called voids, defects, or gaps. In addition to carrier ions, it is also preferable that ions of alkali metals other than lithium, anions and cations used in the electrolyte, anions and cations contained in the electrolyte solution, etc., can pass through.

[0172] The graphene compound may have holes formed by a plurality of carbon atoms and one or more fluorine atoms. The plurality of carbon atoms are preferably bonded in a ring, and one or more of the ring-bonded carbon atoms are preferably terminated with the fluorine. Fluorine has a high electronegativity and is easily negatively charged. Positively charged lithium ions approach each other, which causes an interaction, stabilizing energy and lowering the barrier energy for carrier ions, specifically lithium ions, to pass through the holes. Therefore, the presence of fluorine in the holes of the graphene compound allows carrier ions to pass easily through even small holes, and the graphene compound can have excellent conductivity.

[0173] <Multi-membered ring> In addition to the six-membered ring composed of carbon, the graphene compound may have a five-membered ring composed of carbon or a seven- or more-membered ring composed of carbon. Here, a region through which ions can pass may be generated near the seven- or more-membered ring. The region through which ions can pass may be considered as the hole. One example of the ion is a carrier ion, specifically a lithium ion. Other examples of the ion include ions of alkali metals other than lithium, anions contained in the electrolyte, and cations.

[0174] <Sheet-like graphene compound> The graphene compound may be in the form of a single sheet with a plurality of graphene compounds partially overlapping each other. Alternatively, a plurality of graphene compounds may be gathered together to form a sheet. The graphene compound has a planar shape, allowing for surface contact. Such a graphene compound may be referred to as a graphene compound sheet or a graphene compound net, as described above. The graphene compound sheet has, for example, a region having a thickness of 0.33 nm or more and 100 μm or less, more preferably 0.34 nm or more and 10 μm or less.

[0175] In a graphene compound sheet, for example, a region through which ions can pass may be generated between adjacent graphene compounds. Therefore, the graphene compound sheet may have excellent ion conductivity. Alternatively, the graphene compound sheet may easily adsorb ions. Again, one example of the ions is a carrier ion, specifically, a lithium ion. Further, other examples of the above-mentioned ions include ions of alkali metals other than lithium, anions contained in an electrolyte solution, and cations.

[0176] Furthermore, it is thought that the graphene compound sheet can be deformed when an external force is applied due to sliding between graphene compounds stacked on top of each other in a plane, and may be less susceptible to cracks or the like.

[0177] Such a graphene compound sheet may be modified with an atom other than carbon, an atomic group having an atom other than carbon, or an atomic group mainly containing carbon such as an alkyl group, etc. Furthermore, each of a plurality of layers of the graphene compound sheet may be modified with a different atom or atomic group.

[0178] <Conductivity> Graphene compounds can have high conductivity even when they are thin, and the surface contact can increase the contact area between graphene compounds or between a graphene compound and an active material, thereby efficiently forming a conductive path even when the amount per volume is small.

[0179] <Insulating Properties> A graphene compound can also be used as an insulator. For example, a graphene compound sheet can be used as a sheet-like insulator. Here, for example, graphene oxide may have higher insulating properties than a non-oxidized graphene compound. Furthermore, a graphene compound modified with an atomic group may have improved insulating properties depending on the type of the modified atomic group.

[0180] <Method for Producing Graphene Compound> A graphene compound can be produced by a spray-drying method, a coating method, or the like. In this embodiment, as an example, a case where a graphene compound sheet is produced by a spray-drying method using a graphene oxide dispersion as a raw material will be described. Note that the graphene oxide contained in the graphene oxide dispersion may be multilayer graphene oxide, and the graphene oxide dispersion may contain graphene oxide, or graphene oxide and multilayer graphene oxide.

[0181] The solvent used for the graphene oxide dispersion is preferably a polar solvent, such as one or a mixture of two or more selected from water, methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), ethylene glycol, diethylene glycol, and glycerin.

[0182] A graphene compound having graphene oxides can be obtained by forming a film of multiple graphene oxides on a substrate or plate using a spray-drying method. When multiple graphene compounds are stacked on top of each other during film formation, a graphene compound sheet can also be produced. The spray-drying method can control the film thickness of the graphene compound or graphene compound sheet by adjusting the film formation time, the concentration of the dispersion, or the like, and is therefore suitable for producing the graphene compound or graphene compound sheet of one embodiment of the present invention.

[0183] <Positive Electrode> Next, Figures 14A and 14B show details of the positive electrode 331. Figure 14A shows a cross-sectional view of the positive electrode 331, and Figure 14B shows a top view of the positive electrode 331. The cross-sectional view in Figure 14A corresponds to the position indicated by the dotted line in Figure 14B.

[0184] The positive electrode 331 has a current collector 332 and an active material layer 333. As shown in FIG. 14A , the active material layer 333 may be formed on two surfaces (one surface and the other surface) of the current collector 332. Again, forming the active material layer 333 on two surfaces is referred to as a double-sided formed structure or a double-sided coated structure. Although not shown in FIG. 14A , the active material layer 333 may be formed on either one surface or the other surface of the current collector 332. Again, forming the active material layer 333 on one surface is referred to as a single-sided formed structure or a single-sided coated structure.

[0185] In the positive electrode 331, the current collector 332 and the active material layer 333 are wrapped in the buffer layer 305. In other words, the buffer layer 305 wraps the current collector 332 and the active material layer 333. With such a structure including the buffer layer 305, the flexible battery 107 of one embodiment of the present invention becomes more mobile when repeatedly bent because the buffer layer 305 reduces friction.

[0186] Furthermore, the buffer layer 305 can have the property of being flexible and easily deformable, and can increase the mechanical strength of the positive electrode and the like.

[0187] A flexible battery having a cushioning material as in this embodiment is preferable because it has high safety and durability.

[0188] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0189] Fifth Embodiment In this embodiment, a configuration example of an exterior body of a flexible battery will be described.

[0190] The surface of the exterior body is preferably wavy. A wavy shape includes a shape with unevenness on the surface, and the convexities preferably exist continuously in one direction. It is more preferable that the intervals between consecutive convexities are periodic, and it is even more preferable that the heights of consecutive convexities are uniform. When the flexible battery is bent, an exterior body having such a wavy shape can deform so that the period and height of the convexities change, thereby alleviating bending stress and preventing damage to the exterior body.

[0191] When the flexible battery is bent, it is preferable that the edge where the tab or the like is connected is fixed, and the edge of the laminated electrode in the other part, specifically the edge opposite to the one edge, is shifted. In other words, the laminated electrode bends with the position of the tab or the like as a fixed point and fulcrum, and the corrugated exterior body can deform to follow this.

[0192] Furthermore, it is preferable to provide a space between the edge of the laminated electrode and the inner wall of the exterior body, specifically inside the exterior body, on one side of the exterior body corresponding to the position where the edge of the laminated electrode is shifted. This space allows the laminated battery to shift when the flexible battery is bent, preventing the edge of the laminated electrode from contacting the inner wall of the exterior body. This space prevents the edge of the laminated electrode from contacting the inner wall of the exterior body, even when the laminated electrode is thick, preventing damage to the exterior body. For example, the flexible battery can be safely bent and stretched even when the thickness of the laminated electrode is greater than 400 μm, 500 μm or more, or 1 mm or more. Furthermore, the space prevents damage to the exterior and other components even when the thickness of the laminated electrode is extremely thin, from 1 μm to 400 μm.

[0193] In the flexible battery of one embodiment of the present invention, there is no limitation on the thickness of the electrode of the stacked structure; however, the thickness may be determined according to the required capacity of an electronic device in which the flexible battery is mounted or the space provided for mounting the battery.

[0194] In the flexible battery of one embodiment of the present invention, the thickness of the negative electrode or positive electrode is 1 mm or less, preferably 400 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. The total thickness of the negative electrode, positive electrode, and separator is, for example, 10 mm or less, preferably 5 mm or less, more preferably 4 mm or less, and even more preferably 3 mm or less.

[0195] Furthermore, in order to increase the space inside the exterior body, it is preferable that the positions of the convexities on the surface of the exterior body located above the laminated electrode and the back surface of the exterior body located below the laminated electrode are offset. Specifically, the positions of the convexities on the surface of the exterior body located above the laminated electrode and the convexities on the back surface of the exterior body located below the laminated electrode are formed so as not to overlap, i.e., to be offset. Note that the convexities on the back surface of the exterior body refer to the region protruding on the side opposite the laminated electrode. Because the convexities have periodicity, the above offset can be expressed as a 180-degree phase shift. Such a corrugated exterior body is preferable because it allows for the formation of a space at the position where the distance between the laminated electrode and the exterior body is longest.

[0196] In one aspect of the present invention, the laminated electrode can be sandwiched between two exterior bodies folded in half. When folding the exterior body in half, it is preferable to stagger the convex phases as described above. It is preferable for the convex phases to be shifted by 180 degrees. Pressure and heat can be applied to the folds of the exterior body to flatten them.

[0197] More specific configuration examples and manufacturing method examples will be described below with reference to the drawings.

[0198] Fig. 15A is a plan view of the example 10 exemplified below. Fig. 15B is a view from the direction indicated by the arrow in Fig. 15A. Figs. 15C, 15D, and 15E are schematic cross-sectional views taken along cutting lines A1-A2, B1-B2, and C1-C2 in Fig. 15A, respectively.

[0199] The flexible battery 107 includes an exterior body 11, a stacked battery 12 housed inside the exterior body 11, and current collectors 13a and 13b electrically connected to the stacked battery 12 and extending outside the exterior body 11. In addition to the stacked battery 12, an electrolyte is also enclosed inside the exterior body 11.

[0200] The exterior body 11 has a corrugated shape and is folded in two to sandwich the stacked batteries 12. The exterior body 11 has a pair of portions 31 that overlap the stacked batteries 12, a folded portion 32, and a pair of joints 33 and 34. The pair of joints 33 are strip-shaped portions that extend substantially perpendicular to the folded portion 32 and are provided with the portion 31 in between. The joints 34 are strip-shaped portions located on the opposite side of the folded portion 32 with the portion 31 in between. The portion 31 can also be described as the area surrounded by the folded portion 32, the pair of joints 33, and the joints 34. Here, Figure 15A and other figures show an example in which the joints 34 sandwich portions of the current collectors 13a and 13b.

[0201] The surface of at least portion 31 of exterior body 11 has a wave shape in which concave and convex portions are repeated in the extending direction of paired joints 33. In other words, portion 31 has a wave shape in which ridge lines 21 and valley lines 22 are alternately repeated. In Figure 15A etc., ridge lines 21 connecting the peaks of the convex portions are shown by dashed lines, and valley lines 22 connecting the bottoms of the valley portions are shown by broken lines.

[0202] In addition, in a plan view, the length of exterior body 11 in the extension direction of joint 33 is longer than the length in a direction that passes through joint 34, portion 31, and folded portion 32 and is parallel to the extension direction of joint 33. As shown in Fig. 15A, with respect to a line connecting the ends of a pair of joints 33 on the folded portion 32 side, the portion of folded portion 32 that is located closest to joint 34 is located a distance L1 toward joint 34.

[0203] The stacked battery 12 has a configuration in which at least positive electrodes and negative electrodes are alternately stacked. The stacked battery 12 may also be referred to as an electrode stack. A separator may be provided between the positive electrode and the negative electrode. Here, the greater the number of layers of the stacked battery 12, the greater the capacity of the flexible battery 107. For details of the stacked battery 12, the above-described embodiment can be referred to.

[0204] The thickness of the laminated battery 12 is, for example, 200 μm to 9 mm, preferably 400 μm to 3 mm, more preferably 500 μm to 2 mm, and typically about 1.5 mm.

[0205] 15A, 15C, and 15D, a space 25 is formed inside the exterior body 11 between the end of the stacked battery 12 and the folded portion 32. Here, the length of the space 25 in a direction parallel to the extension direction of the joint 33 is defined as distance d0. Distance d0 can also be said to be the distance between the end of the stacked battery 12 and the inner surface of the exterior body 11 located at the folded portion 32.

[0206] Furthermore, the joint 34 joins the exterior body 11 and the current collector 13a (and current collector 13b) extending inside and outside the exterior body 11. Therefore, the position of the laminated battery 12 relative to the exterior body 11 is fixed. The current collector 13a is one of the negative electrode current collector and the positive electrode current collector of the laminated battery 12, and the current collector 13b is the other of the negative electrode current collector and the positive electrode current collector. Note that the one and the other are examples and may be interpreted interchangeably. Furthermore, tabs made of metal foil or the like may be provided instead of the current collectors 13a and 13b. The exterior body 11 and the tab are joined at the joint 34, and similarly, the position of the laminated battery 12 relative to the exterior body 11 is fixed.

[0207] 15A, 15C, and 15D, it is preferable that the portion 31 of the exterior body 11 has a region in which the period of the convexities becomes longer and the height of the convexities becomes smaller closer to the bent portion 32. The flexible battery 107 is manufactured to have such an exterior body, and a space 25 is formed inside the exterior body 11.

[0208] 15C and 15D, the pair of portions 31 that overlap the stacked battery 12 should be positioned so that the convex portions are 180 degrees out of phase with each other. In other words, the exterior body 11 should be folded so that the stacked battery 12 is sandwiched between the ridge lines 21 and the valley lines 22. This allows a large space 25 to be obtained.

[0209] Next, the shape of the battery having the space 25 formed therein when bent will be described.

[0210] FIG. 16A is a schematic cross-sectional view showing a simplified portion of the configuration of the flexible battery 107.

[0211] Here, the pair of portions 31 of the exterior body 11 are distinguished and denoted as portions 31a and 31b, respectively. Similarly, the ridge lines of each portion are distinguished and denoted as ridge line 21a and ridge line 21b, and the valley lines of each portion are distinguished and denoted as valley line 22a and valley line 22b.

[0212] 16A , the stacked battery 12 has five electrodes 43 stacked on top of each other. The electrodes 43 correspond to the negative and positive electrodes in the above embodiment. Furthermore, the stacked battery 12 is fixed in position relative to the exterior body 11 at the joints 34.

[0213] A space 25 is provided inside the exterior body 11 near the bent portion 32. Here, the distance between the end of the electrode 43 on the bent portion 32 side and the inner wall of the exterior body 11 when the exterior body 11 is not bent is defined as distance d0.

[0214] The neutral plane of the flexible battery 107 is defined as neutral plane C. Here, neutral plane C is assumed to coincide with the neutral plane of the central electrode 43 among the five electrodes 43 of the stacked battery 12.

[0215] 16B is a schematic cross-sectional view of the flexible battery 107 when it is bent into an arc shape around point O. Here, the flexible battery 107 is bent so that the portion 31a faces outward and the portion 31b faces inward.

[0216] As shown in Figure 16B, the outer portion 31a deforms so that the height of the convexities becomes smaller and the period of the convexities becomes longer. That is, the distance between the ridge lines 21a and the distance between the valley lines 22b of the inner portion 31a become wider. On the other hand, the inner portion 31b deforms so that the height of the convexities becomes larger and the period of the convexities becomes shorter. That is, the distance between the ridge lines 21b and the distance between the valley lines 22b of the inner portion 31b after bending become narrower. By deforming the portions 31a and 31b in this way, the stress applied to the exterior body 11 is alleviated, and the flexible battery 107 can be bent without damaging the exterior body 11.

[0217] 16B, the stacked battery 12 deforms so that the electrodes 43 are misaligned relative to each other. This relieves the stress on the stacked battery 12, allowing the flexible battery 107 to bend without damaging the stacked battery 12. In FIG. 16B, each electrode 43 is shown as not stretching when bent. By making the thickness of the electrode 43 sufficiently small relative to the radius of curvature of the bend, the stress on each electrode 43 itself can be reduced.

[0218] Of the electrodes 43 of the laminated battery 12, the electrodes 43 located outside the neutral plane C have their ends shifted toward the joint 34. On the other hand, the electrodes 43 located inside the neutral plane C have their ends shifted toward the folded portion 32. Here, the distance between the end of the innermost electrode 43 on the folded portion 32 side and the inner wall of the exterior body 11 is reduced from distance d0 to distance d1. Here, the relative shift amount between the electrode 43 located on the neutral plane C and the innermost electrode 43 is defined as distance d2. Distance d1 is equal to the value obtained by subtracting distance d2 from distance d0.

[0219] If the distance d0 before bending is smaller than the distance d2 after bending, the electrode 43 located inside the neutral plane C of the laminated battery 12 will come into contact with the inner wall of the exterior body 11. Therefore, the necessary distance d0 will be considered below.

[0220] The following description will be made with reference to Fig. 16C, in which a curve corresponding to the neutral plane C is shown by a dashed line, and a curve corresponding to the innermost surface of the stacked battery 12 is shown by a solid line as curve B.

[0221] Curve C has a radius r ０ The curve B is an arc of radius r １ It is an arc of radius r ０ and radius r １ The difference between these is defined as t. Here, t is equal to the value obtained by multiplying the thickness of the stacked battery 12 by half. Furthermore, the lengths of the arcs of curves C and B are equal. The arc angle of curve C is defined as θ, and the arc angle of curve B is defined as θ+Δθ.

[0222] From the above relationship, the distance d2, which is the deviation of the curve B from the end of the curve C, can be calculated as follows:

[0223]

[0224] That is, the distance d2 can be estimated from the thickness of the stacked battery 12 and the bending angle, and is not dependent on the length of the stacked battery 12 or the radius of curvature of the bend.

[0225] As described above, by making the distance d0 in the space 25 greater than or equal to the distance d2, it is possible to prevent contact between the stacked battery 12 and the exterior body 11 when the flexible battery 107 is bent. Therefore, when the flexible battery 107 having the stacked battery 12 with a thickness of 2t is bent for use, if the maximum angle is the angle θ, then the distance d0 between the stacked battery 12 and the inner wall of the exterior body 11 in the space 25 should be a value equal to or greater than t × θ.

[0226] For example, when the battery is bent at 30 degrees for use, the distance d0 of the space 25 may be set to πt / 6 or more. Similarly, when the battery is bent at 60 degrees for use, d0 may be set to πt / 3 or more. When the battery is bent at 90 degrees for use, d0 may be set to πt / 2 or more. When the battery is bent at 180 degrees for use, d0 may be set to πt or more.

[0227] For example, if the flexible battery 107 is not used for applications such as winding, the maximum expected bending angle of the flexible battery 107 can be 180 degrees. Therefore, in such applications, the flexible battery 107 can be used in any device as long as the distance d0 is set to a length equal to or greater than πt, preferably a length greater than πt. For example, when the flexible battery 107 is used by bending it in two, the flexible battery 107 can be incorporated into various electronic devices that use the flexible battery 107 bent in a V-shape or a U-shape.

[0228] Furthermore, for example, when the flexible battery 107 is wound around a cylindrical shape, the distance d0 of the space 25 may be set to 2πt or more to accommodate 360-degree bending. When the flexible battery 107 is wound around more than one circumference, the distance d0 of the space 25 may be set to an appropriate value accordingly. When the flexible battery 107 is deformed into an accordion-like shape, the distance d0 of the space 25 may be set to an appropriate value depending on the direction and angle of the bending portion of the flexible battery 107 and the number of bending portions.

[0229] The above is the description of the space 25.

[0230] An example of a method for manufacturing the flexible battery 107 will be described below.

[0231] First, a flexible film that will become the exterior body 11 is prepared.

[0232] It is preferable to use a material with high water resistance and gas resistance for the film. It is also preferable to use a laminate film in which a metal film and an insulating film are laminated as the film used as the exterior body. Metals or alloys that can be used as metal foils, such as aluminum, stainless steel, nickel steel, gold, silver, copper, titanium, chromium, iron, tin, tantalum, niobium, molybdenum, zirconium, and zinc, can be used as the metal film. Furthermore, the insulating film can be a single-layer film selected from a plastic film made of an organic material, a hybrid material film containing an organic material (such as an organic resin or fiber) and an inorganic material (such as a ceramic), or a carbon-containing inorganic film (such as a carbon film or a graphite film), or a laminate film made of a plurality of these. Metal films are easy to emboss, and forming protrusions by embossing increases the surface area of ​​the film exposed to the outside air, resulting in excellent heat dissipation.

[0233] Next, the flexible film is subjected to processing such as embossing to form the exterior body 11 having a corrugated shape.

[0234] The convex and concave portions of the film can be formed by press processing (e.g., embossing). The convex and concave portions formed in the film by embossing form a closed space with a variable volume, with the film serving as part of the wall of the sealing structure. This closed space can also be said to be formed when the film has a bellows structure. Furthermore, a sealing structure using a film has waterproof and dustproof effects. Furthermore, the method is not limited to embossing, which is a type of press processing, and any method that can form a relief on a part of the film may be used. Furthermore, a combination of these methods, for example, embossing and another press processing may be performed on a single film. Furthermore, multiple embossing processes may be performed on a single film.

[0235] The convex portions of the film may be hollow semicircular, hollow semielliptical, hollow polygonal, or hollow irregular. In the case of a hollow polygonal shape, having more corners than a triangle is preferable because it is possible to reduce stress concentration at the corners.

[0236] 17A shows an example of a perspective schematic diagram of the exterior body 11 formed in this manner. The exterior body 11 has a wave shape in which multiple ridge lines 21 and valley lines 22 are alternately arranged on the surface that faces the outside of the flexible battery 107. Here, it is preferable that adjacent ridge lines 21 and adjacent valley lines 22 are arranged at equal intervals.

[0237] Next, a portion of the exterior body 11 is folded so as to sandwich the stacked battery 12 prepared in advance ( FIG. 17B ). At this time, it is preferable to adjust the length of the exterior body 11 so that the current collector 13 a or current collector 13 b connected to the stacked battery 12 is exposed to the outside. Furthermore, since the portion of the exterior body 11 extending beyond the stacked battery 12 will later become the joints 33 and 34, the width of the extending portion should be long enough to accommodate the thickness of the stacked battery 12.

[0238] 17B shows an example in which a pair of portions 31 sandwiching the stacked battery 12 are positioned so that the phases of their respective waves are shifted by 180 degrees. That is, the state in which the exterior body 11 is bent is shown so that the ridge lines 21 of the pair of portions 31 overlap each other and the valley lines 22 of the pair of portions 31 overlap each other.

[0239] Here, the position and shape of the bending portion of the exterior body 11 will be described. Fig. 18A is a diagram schematically illustrating a cross section of the exterior body 11. Figs. 18B to 18E respectively illustrate the cross-sectional shape of the bending portion 32 when points P1 to P4 shown in Fig. 18A are the bending positions. Note that, in the following, the case where the exterior body 11 is bent in the direction indicated by the arrow in Fig. 18A will be described, and the lower surface corresponds to the outer surface of the flexible battery 107. Therefore, in Fig. 18A, the portion protruding upward is shown as a valley line 22, and the portion protruding downward is shown as a ridge line 21.

[0240] 18B to 18E, a hatched pattern is applied to the area surrounded by the bent portion 32. Here, two positions where the periodicity of the waves of the exterior body 11 is disrupted are taken as boundaries, and the area sandwiched between these boundaries is taken as the bent portion 32. Note that in Figures 18B to 18E, etc., the shape of the bent portion 32 is exaggerated, and therefore its perimeter may not be drawn correctly.

[0241] Point P1 coincides with valley line 22. As shown in Fig. 18B, bending at point P1 allows bent portion 32 to have a substantially arcuate shape. In addition, bending at point P1 allows the phases of opposing waves to be shifted by 180 degrees.

[0242] Point P2 coincides with ridge line 21. As shown in Fig. 18C, bending at point P2 also allows bent portion 32 to have a substantially arc-like shape. Bending at point P2 also allows the phases of the opposing waves to be shifted by 180 degrees.

[0243] Point P3 is between ridge line 21 and valley line 22 and is closer to ridge line 21 than their midpoint. As shown in Fig. 18D , by shifting from ridge line 21 or valley line 22, the shape of bent portion 32 becomes distorted and not symmetrical. Furthermore, by bending at point P3, it is possible to bend so that the ridge lines, the valley lines, and the ridge and valley lines of the opposing waves do not coincide with each other.

[0244] Point P4 coincides with the midpoint between ridge line 21 and valley line 22. As shown in Figure 18E, when bending at point P4, the shape of bent portion 32 becomes extremely irregular. Specifically, bent portion 32 tends to protrude upward or downward. Therefore, it becomes difficult to increase the distance between stacked battery 12 and the inner wall of exterior body 11 on the side opposite the protruding portion.

[0245] 18B , 18C , and 18D have in common that they all have a single ridge 21 between the valley line 22 of the portion 31 closest to the bent portion 32 and the bent portion 32. In particular, FIG. 18B illustrates an example in which the boundary of the bent portion 32 coincides with the wave ridge 21. In this way, the exterior body 11 bends with the two wave ridges 21 or their vicinity as boundaries, thereby ensuring a wide space in the thickness direction inside the bent portion 32 and its vicinity. As described above, when bending the flexible battery 107, it is important to increase the distance between the outermost electrode of the laminate and the inner wall of the exterior body 11. Therefore, by using such a shape, this distance can be increased.

[0246] 18E, on the underside, there is no ridge line 21 between the valley line 22 of the portion 31 that is closest to the bent portion 32 and the bent portion 32. Therefore, a wide space in the thickness direction is unlikely to be formed at the bent portion 32 and its vicinity.

[0247] Here, it is preferable that the portion of exterior body 11 that will become folding portion 32 has a flat shape without a corrugated shape. For example, as shown in Fig. 19A, a portion of exterior body 11 may be flattened by clamping it between molds 91 and 92, each having a flat surface, and applying pressure or applying pressure while applying heat.

[0248] 19B is a schematic cross-sectional view of exterior body 11 that has been partially flattened in this manner. In this example, exterior body 11 is partially flattened so as to connect ridge lines 21 to each other.

[0249] 19C is a schematic cross-sectional view of exterior body 11 when it is bent at point P5 in the center of the formed flat portion. As shown in FIG. 19C, by forming flattened exterior body 11 into bent portion 32, it is possible to form a larger space than that shown in FIG. 19B.

[0250] 19D and 19E show examples in which a wider area is flattened than in Fig. 19C. Here, as in Fig. 19B, a portion of the exterior body 11 is flattened so as to connect the ridge lines 21. In this way, by flattening the exterior body 11 over an area wider than the thickness of the stacked battery 12, a wide space with a uniform thickness can be formed.

[0251] The above is an explanation of the relationship between the position of the bent portion and the shape of the bent portion.

[0252] Next, a method for processing a film that can be used for the exterior body 11 will be described.

[0253] First, a sheet made of a flexible substrate is prepared. The sheet is a laminate having a heat seal layer on one or both sides of a metal film. The adhesive layer is a heat-sealable resin film containing polypropylene or polyethylene. In this embodiment, a metal sheet having a nylon resin on the surface of an aluminum foil and an acid-resistant polypropylene film and a laminate of a polypropylene film on the back of the aluminum foil is used. This sheet is cut to prepare a film of the desired size.

[0254] Then, this film is embossed. As a result, a film having a concave-convex shape can be produced. The film has a plurality of concave-convex portions, and thus has a visible wavy pattern. Here, an example is shown in which the sheet is cut and then embossed, but the order is not particularly limited, and the sheet may be embossed before cutting and then cut. Alternatively, the sheet may be folded and thermocompressed before cutting.

[0255] Embossing, which is a type of press working, will be explained below.

[0256] Fig. 20 is a cross-sectional view showing an example of embossing. Embossing is a type of press processing, and refers to a process in which an embossing roll with an uneven surface is pressed against a film to form unevenness in the film corresponding to the unevenness of the embossing roll. The embossing roll is a roll with a pattern engraved on its surface.

[0257] 20 shows an example of embossing on both sides of a film, and a method of forming a film with convex portions having peaks on one side.

[0258] 20 shows a state in which a film 90 is sandwiched between an embossing roll 95 in contact with one side of the film and an embossing roll 96 in contact with the other side, and the film 90 is being fed in a film traveling direction 60. A pattern is formed on the film surface by pressure or heat. Alternatively, a pattern may be formed on the film surface by both pressure and heat.

[0259] As the embossing roll, a metal roll, a ceramic roll, a plastic roll, a rubber roll, an organic resin roll, a wooden roll, or the like can be used as appropriate.

[0260] In Figure 20, embossing is performed using an embossing roll 96, which is a male-pattern embossing roll, and a female-pattern embossing roll 95. The male-pattern embossing roll 96 has multiple convex portions 96a. These convex portions correspond to the convex portions to be formed on the film to be processed. The female-pattern embossing roll 95 has multiple convex portions 95a. Adjacent convex portions 95a form recesses that fit into the convex portions to be formed on the film by the convex portions 96a provided on the male-pattern embossing roll 96.

[0261] By successively performing embossing to raise a portion of the film 90 and blank pressing to depress a portion of the film 90, it is possible to continuously form convex portions and flat portions. As a result, a pattern can be formed on the film 90.

[0262] 21A and 21B are top views showing the resulting shape when embossing is performed twice, changing the direction of film 90. Embossing does not have to be performed on the thermocompression-bonded area. Specifically, film 90 is embossed in a first direction, and then embossed in a second direction rotated 90 degrees from the first direction, resulting in film 61 having the embossed shape (which can be referred to as a cross-wave shape) shown in FIGS. 21A and 21B. The cross-wave-shaped film 61 shown in FIG. 21A represents the outer shape used when fabricating a flexible battery using a single film 61, and can be folded in half along the dashed line. The multiple films (films 62 and 63) with cross-wave shapes shown in FIG. 21B represent the outer shape used when fabricating a flexible battery using two films (films 62 and 63), and films 62 and 63 can be stacked for use.

[0263] As described above, by performing processing using an embossing roll, it is possible to miniaturize the device. Furthermore, since processing can be performed without cutting the film, it is excellent in mass productivity. Note that processing is not limited to using an embossing roll, and for example, the film may be processed by pressing a pair of embossing plates with uneven surfaces against the film. In this case, one of the embossing plates may be flat, and processing may be performed in multiple steps.

[0264] In the above-described configuration example of the flexible battery, the exterior body on one side of the flexible battery and the exterior body on the other side have the same embossed shape, but the configuration of the flexible battery of one embodiment of the present invention is not limited to this. For example, the flexible battery may have an embossed shape on the exterior body on one side of the flexible battery and no embossed shape on the exterior body on the other side. Furthermore, the exterior body on one side of the flexible battery may have different embossed shapes.

[0265] 22 to 24, a flexible battery having an embossed shape on the exterior body on one side of the flexible battery and not having an embossed shape on the exterior body on the other side will be described.

[0266] First, a sheet made of a flexible substrate is prepared. The sheet is a laminate, with an adhesive layer (also called a heat seal layer) on one or both sides of a metal film. The adhesive layer is a heat-sealable resin film containing polypropylene or polyethylene. In this embodiment, a metal sheet is used, with nylon resin on the surface of aluminum foil and an acid-resistant polypropylene film and a polypropylene film laminate on the back of the aluminum foil. This sheet is cut to prepare the film 90 shown in FIG. 22A.

[0267] Then, a portion of this film 90 (film 90a) is embossed, while film 90b is not. The resulting film 61 shown in FIG. 22B is produced in this manner. As shown in FIG. 22B, a visible pattern is formed by forming irregularities on the surface of film 61a, but no irregularities are formed on the surface of film 61b. A boundary exists between film 61a, on which irregularities are formed, and film 61b, on which irregularities are not formed. In FIG. 22B, the embossed portion of film 61 is film 61a, and the unembossed portion is film 61b. The embossing of film 61a may form the same irregularities over the entire surface, or two or more different irregularities may be formed in different locations on film 61a. When two or more different irregularities are formed, a boundary exists between the different irregularities.

[0268] Alternatively, the entire surface of the film 90 in Fig. 22A may be embossed. The embossing of the film 61 may form the same unevenness over the entire surface, or may form two or more different unevennesses at different locations on the film 61. When two or more different unevennesses are formed, there is a boundary between the different unevennesses. Alternatively, as shown in Fig. 22C, a film 61a having unevenness on its surface and a film 61b having no unevenness on its surface may be prepared.

[0269] Although an example in which the sheet is cut and then embossed is shown here, the order is not particularly limited, and the sheet may be embossed before cutting and then cut to form the state shown in Fig. 22B. Alternatively, the sheet may be folded and thermocompressed before cutting.

[0270] In this embodiment, film 61 is fabricated by forming a pattern by providing projections and depressions on both sides of a portion of film 90 (film 90a), and film 61 is then folded in the center to overlap two edges, and three sides are sealed with adhesive layers. Here, film 61 is referred to as exterior body 11.

[0271] Next, the exterior body 11 (exterior body 11a and exterior body 11b) is folded along the dotted lines in Fig. 22B to obtain the state shown in Fig. 23A. Fig. 23B shows a positive electrode 52, a separator 53, and a negative electrode 54.

[0272] 23E , a stack of a positive electrode current collector 64 having a positive electrode active material layer 58 formed on a portion of its surface, a separator 65, and a negative electrode current collector 66 having a negative electrode active material layer 59 formed on a portion of its surface, which constitute a flexible battery, is prepared. Note that, for the sake of simplicity, an example is shown in which a single stacked combination of the positive electrode current collector 64 having the positive electrode active material layer 58 formed on it, the separator 65, and the negative electrode current collector 66 having the negative electrode active material layer 59 formed on it is housed in an exterior body, but multiple combinations may be stacked and housed in an exterior body to increase the capacity of the flexible battery.

[0273] Then, two lead electrodes 56 having a sealing layer 55 shown in Fig. 23C are prepared. The lead electrodes 56 are also called lead terminals and are provided to pull out the positive electrode or negative electrode of the flexible battery to the outside of the exterior film. The positive electrode lead is made of aluminum, and the negative electrode lead is made of nickel-plated copper.

[0274] Then, the positive electrode lead and the protruding portion of the positive electrode current collector 64 are electrically connected by ultrasonic welding or the like. Also, the negative electrode lead and the protruding portion of the negative electrode current collector 66 are electrically connected by ultrasonic welding or the like.

[0275] Then, two sides of the exterior body 11 are sealed by thermocompression bonding, leaving one side for the electrolyte to be placed in (hereinafter, the shape of the film in this state is also referred to as a bag-like shape). During thermocompression bonding, the sealing layer 55 provided on the lead terminal also melts, fixing the lead terminal and the exterior body 11 together. Then, under reduced pressure or in an inert atmosphere, a desired amount of electrolyte is dripped onto the inside of the bag-like exterior body 11. Finally, the remaining edge of the exterior body 11 that was not thermocompression bonded is sealed by thermocompression bonding.

[0276] In this way, the flexible battery 40 shown in FIG. 23D can be fabricated.

[0277] The resulting exterior of the flexible battery 40 has an uneven pattern on the surface of the film 90. The area between the dotted line and the end in Fig. 23D is the thermocompression bonding area 17, which also has an uneven pattern on the surface. Although the unevenness of the thermocompression bonding area 17 is smaller than that of the central area, it can alleviate the stress applied when the flexible battery is bent.

[0278] FIG. 23E shows an example of a cross section taken along the dashed line A-B in FIG. 23D.

[0279] 23E, the unevenness of exterior body 11a differs between the region overlapping with positive electrode current collector 64 and thermocompression bonded region 17. As shown in Fig. 23E, positive electrode current collector 64, positive electrode active material layer 58, separator 65, negative electrode active material layer 59, and negative electrode current collector 66 are laminated in this order and sandwiched between folded exterior body 11, and further sealed at the edges with adhesive layer 30, with electrolyte solution 50 being contained in the remaining space inside folded exterior body 11.

[0280] The volume ratio of the battery portion to the entire flexible battery is preferably 50% or more. Figures 24A and 24B show cross-sectional views C-D of the flexible battery of Figure 23D. Figure 24A shows a battery 12 with a laminated structure inside the battery, an embossed film 61a covering the upper surface of the battery, a non-embossed film 61b covering the lower surface of the battery, and an embossed film 61b. For simplicity of illustration, the laminated structure of the positive electrode current collector on which the positive electrode active material layer is formed, the separator, the negative electrode current collector on which the negative electrode active material layer is formed, and the electrolyte are collectively shown as the battery 12 with a laminated structure inside the battery. Furthermore, T is the thickness of the battery 12 with a laminated structure inside the battery, and t １ is the sum of the embossing depth and film thickness of the embossed film 61a covering the top surface of the battery, t ２ indicates the thickness of the unembossed film 61b covering the bottom surface of the battery and the sum of the embossing depth and film thickness of the embossed film 61b. In this case, the thickness of the entire flexible battery is T+t １ +t ２ Therefore, in order to make the volume ratio of the battery 12 portion of the laminated structure inside the battery to the entire flexible battery 50% or more, T>t １ +t ２ It is necessary to do this.

[0281] Although the adhesive layer 30 is only partially shown in FIG. 23E, a layer made of polypropylene is provided on the surface of the film to which the film is bonded, and only the thermocompression bonded portion becomes the adhesive layer 30.

[0282] 23E shows an example in which the lower side of the exterior body 11 is fixed and crimped. In this case, the upper side is bent significantly, forming a step. Therefore, if multiple, for example, eight or more, combinations of the above-described layers are provided between the bent exterior body 11, the step becomes large, and there is a risk of excessive stress being applied to the upper side of the exterior body 11a. This may also result in a large misalignment between the end of the upper film and the end of the lower film. In this case, a step may also be provided in the lower film to prevent misalignment at the ends, and the film may be crimped in the center to equalize the stress.

[0283] If a large misalignment occurs, there will be an area where part of the edge of one film does not overlap with the other film, and this area can be cut out to align the edge of the upper film with the edge of the lower film, thereby correcting the misalignment.

[0284] The content of this embodiment mode can be freely combined with the content of other embodiment modes.

[0285] Embodiment Mode 6 In this embodiment mode, a structure of a battery that can be applied to the above embodiment modes will be described.

[0286] [Negative Electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer has a negative electrode active material, and may further have a conductive material and a binder.

[0287] The current collector can be, for example, a metal foil. The negative electrode can be formed by applying a slurry to a metal foil and drying it. Pressing may be performed after drying. The negative electrode is formed by forming an active material layer on a current collector.

[0288] The slurry is a material liquid used to form an active material layer on a current collector, and refers to a material containing an active material, a binder, and a solvent, preferably further mixed with a conductive material. The slurry is also called an electrode slurry or an active material slurry, and when forming a negative electrode active material layer, it is also called a negative electrode slurry.

[0289] <Negative Electrode Active Material> As the negative electrode active material, for example, a carbon material or an alloy-based material can be used.

[0290] Examples of carbon materials that can be used include graphite (natural graphite, artificial graphite), graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon fiber (carbon nanotube), graphene, and carbon black.

[0291] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape and is preferred. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB, and this may be preferred. Examples of natural graphite include flake graphite and spherical natural graphite.

[0292] When lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed), graphite exhibits a potential as low as that of metallic lithium (0.05 V to 0.3 V vs. Li / Li ＋ This allows lithium-ion batteries using graphite to exhibit high operating voltages. Graphite is also preferred because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and greater safety compared to lithium metal.

[0293] The non-graphitizable carbon can be obtained by calcining a synthetic resin such as a phenolic resin or a plant-derived organic material. The non-graphitizable carbon contained in the negative electrode active material of the lithium-ion battery according to one embodiment of the present invention preferably has a (002) plane spacing measured by X-ray diffraction (XRD) of 0.34 nm or more and 0.50 nm or less, and more preferably 0.35 nm or more and 0.42 nm or less.

[0294] In addition, the negative electrode active material can be an element capable of undergoing a charge-discharge reaction through alloying and dealloying reactions with lithium. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. These elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Alternatively, compounds containing these elements may be used. For example, SiO, Mg ２ Si, Mg ２ Ge, SnO, SnO ２ , Mg ２Sn, SnS ２ , V ２ Sn ３ , FeSn ２ , CoSn ２ , Ni ３ Sn ２ , Cu ６ Sn ５ , Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb ３ , LaSn ３ , La ３ Co ２ Sn ７ , CoSb ３ , InSb, SbSn, etc. Here, elements capable of undergoing charge-discharge reactions by alloying / dealloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloy-based materials.

[0295] In this specification, "SiO" refers to, for example, silicon monoxide. ｘ Here, x preferably has a value of 1 or close to 1. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0296] 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 dioxide (WO ２ ), molybdenum dioxide (MoO ２ ) and other oxides can be used.

[0297] In addition, as the negative electrode active material, a 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 ０．４N has a large discharge capacity (900 mAh / g, 1890 mAh / cm ３ ) and is preferred.

[0298] When a nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, so V, which does not contain lithium ions, is used as the positive electrode active material. ２ O ５ , Cr ３ O ８ It is preferable that the material can be combined with a material such as the above. Even when a material containing lithium ions is used as the positive electrode active material, it is possible to use a nitride of lithium and a transition metal as the negative electrode active material by first desorbing the lithium ions contained in the positive electrode active material.

[0299] Furthermore, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, a transition metal oxide that does not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO), can be used as the negative electrode active material. Further examples of materials that undergo a conversion reaction include 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 also occurs with fluorides such as

[0300] Although one type of anode active material from among the above-described anode active materials can be used, a combination of two or more types of anode active materials can also be used, such as a combination of a carbon material and silicon, or a combination of a carbon material and silicon monoxide.

[0301] <Binder> As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Furthermore, as the binder, fluororubber can be used.

[0302] 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.

[0303] Alternatively, it is preferable to use, as the binder, materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose.

[0304] The binder may be used in combination with two or more of the above.

[0305] For example, a material with a particularly excellent viscosity adjusting effect may be used in combination with another material. For example, while rubber materials have excellent adhesive strength and elasticity, it may be difficult to adjust the viscosity when mixed with a solvent. In such cases, it is preferable to mix them with a material with a particularly excellent viscosity adjusting effect. For example, a water-soluble polymer may be used as a material with a particularly excellent viscosity adjusting effect. Furthermore, as a water-soluble polymer with a particularly excellent viscosity adjusting effect, the above-mentioned polysaccharides, for example, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose, cellulose derivatives such as regenerated cellulose, or starch may be used.

[0306] In addition, the solubility of cellulose derivatives such as carboxymethyl cellulose can be increased by converting them into salts such as sodium or ammonium salts of carboxymethyl cellulose, making them more effective as viscosity adjusters. Higher solubility can also improve dispersibility with active materials or other components when preparing electrode slurry. In this specification, cellulose and cellulose derivatives used as electrode binders also include their salts.

[0307] Water-soluble polymers stabilize viscosity by dissolving in water, allowing active materials and other materials combined as binders, such as styrene-butadiene rubber, to be stably dispersed in aqueous solutions. Furthermore, the presence of functional groups is expected to facilitate stable adsorption to the surface of active materials. Furthermore, many cellulose derivatives, such as carboxymethyl cellulose, contain functional groups such as hydroxyl or carboxyl groups, and the presence of these functional groups is expected to facilitate interactions between polymers, resulting in widespread coverage of the active material surface.

[0308] When the binder covers the surface of the active material or contacts the surface and forms a film, it is expected to function as a passive film and have the effect of suppressing decomposition of the electrolyte. Here, the "passive film" refers to a film with no electrical conductivity or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it can suppress decomposition of the electrolyte at the battery reaction potential. Furthermore, it is more desirable that the passive film suppresses electrical conductivity while still allowing lithium ions to conduct.

[0309] <Conductive Material> The conductive material is also called a conductivity imparting agent or a conductivity aid, and is made of a carbon material. By attaching the conductive material between multiple active materials, the multiple active materials are electrically connected to each other, thereby increasing the conductivity. Note that the term "attachment" does not only refer to physical adhesion between the active material and the conductive material, but also includes cases where a covalent bond is formed, bonding due to van der Waals forces, where the conductive material covers part of the surface of the active material, where the conductive material is embedded in the surface irregularities of the active material, and where the materials are electrically connected even when not in contact with each other.

[0310] The active material layers such as the positive electrode active material layer and the negative electrode active material layer preferably contain a conductive material.

[0311] As the conductive material, for example, carbon black such as acetylene black and furnace black can be used. As the conductive material, graphite such as artificial graphite and natural graphite can be used. As the conductive material, carbon fibers such as carbon nanofibers and carbon nanotubes can be used. As the conductive material, graphene or a graphene compound described in the above embodiment can be used. As the conductive material, one or a mixture of two or more of the above materials can be used.

[0312] Examples of the carbon fiber that can be used include mesophase pitch-based carbon fiber and isotropic pitch-based carbon fiber. Also, examples of the carbon fiber that can be used include carbon nanofibers and carbon nanotubes. Carbon nanofibers and carbon nanotubes can be produced by, for example, vapor deposition.

[0313] Furthermore, the conductive material may be a metal powder or metal fiber such as copper, nickel, aluminum, silver, or gold, or a conductive ceramic material.

[0314] The content of the conductive material relative to the total amount of the active material layer is preferably 1 wt % or more and 10 wt % or less, and more preferably 1 wt % or more and 5 wt % or less.

[0315] Unlike granular conductive materials such as carbon black, which make point contact with the active material, graphene or a graphene compound enables surface contact with the active material with low contact resistance, and therefore can improve the electrical conductivity between the granular active material and graphene or a graphene compound with a smaller amount than that of a typical conductive material. This allows the ratio of the active material in the active material layer to be increased, thereby increasing the discharge capacity of the battery.

[0316] Carbon black or carbon fiber easily enters into minute spaces, such as the spaces between multiple active materials. By combining carbon black or carbon fiber, which easily enters into minute spaces, with graphene or a graphene compound, which allows for surface contact, the density of the electrode can be increased and an excellent conductive path can be formed.

[0317] <Current Collector> As the current collector, a material that has high conductivity and does not alloy with carrier ions such as lithium, such as metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, and titanium, and alloys thereof, can be used. The current collector can be appropriately shaped, such as a sheet, mesh, punched metal, or expanded metal. It is preferable to use a current collector with a thickness of 5 μm or more and 30 μm or less.

[0318] The negative electrode current collector is preferably made of a material that does not alloy with carrier ions such as lithium.

[0319] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material and may further contain at least one of a conductive material and a binder. Note that the positive electrode current collector, conductive material, and binder may be those described in [Negative electrode].

[0320] The current collector can be, for example, a metal foil. The positive electrode can be formed by applying a slurry to a metal foil and drying it. Pressing may be performed after drying. The positive electrode is formed by forming an active material layer on a current collector.

[0321] The slurry is a material liquid used to form an active material layer on a current collector, and refers to a material containing an active material, a binder, and a solvent, preferably further mixed with a conductive material. The slurry is also called an electrode slurry or an active material slurry, and when forming a positive electrode active material layer, it is also called a positive electrode slurry.

[0322] <Positive Electrode Active Material> As the positive electrode active material, at least one of a composite oxide having a layered rock salt structure, a composite oxide having an olivine structure, and a composite oxide having a spinel structure can be used.

[0323] As the composite oxide having a layered rock salt structure, any one or more of lithium cobalt oxide, lithium nickel-cobalt-manganese oxide, lithium nickel-cobalt-aluminate, and lithium nickel-manganese-aluminate can be used. ２ (M1 is one or more selected from nickel, cobalt, manganese, and aluminum), but the coefficients of the composition formula are not limited to integers.

[0324] As the lithium cobalt oxide, for example, lithium cobalt oxide to which magnesium and fluorine are added can be used. It is also preferable to use lithium cobalt oxide to which magnesium, fluorine, aluminum and nickel are added.

[0325] As the lithium nickel-cobalt-manganese oxide, for example, lithium nickel-cobalt-manganese oxide having a ratio of nickel:cobalt:manganese = 1:1:1, nickel:cobalt:manganese = 6:2:2, nickel:cobalt:manganese = 8:1:1, nickel:cobalt:manganese = 9:0.5:0.5, etc. Furthermore, as the lithium nickel-cobalt-manganese oxide, it is preferable to use lithium nickel-cobalt-manganese oxide to which one or more of aluminum, calcium, barium, strontium, and gallium have been added.

[0326] As the composite oxide having an olivine structure, any one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, and lithium iron manganese phosphate can be used. ４ (M2 is one or more elements selected from iron, manganese, and cobalt), but the coefficients of the composition formula are not limited to integers.

[0327] Also, LiMn ２ O ４ The above-mentioned composite oxides having a spinel structure can be used.

[0328] [Electrolyte] Examples of electrolytes are described below. As one form of electrolyte, a liquid electrolyte (also referred to as an electrolyte solution) having a solvent and an electrolyte dissolved in the solvent can be used. The electrolyte is not limited to a liquid electrolyte (electrolyte solution) that is liquid at room temperature, and a solid electrolyte can also be used. Alternatively, an electrolyte (semi-solid electrolyte) that includes both a liquid electrolyte that is liquid at room temperature and a solid electrolyte that is solid at room temperature can also be used. When a solid electrolyte or semi-solid electrolyte is used in a bendable battery, the flexibility of the battery can be maintained by having a structure in which the electrolyte is included in a part of the laminate inside the battery.

[0329] When a liquid electrolyte, i.e., an electrolytic solution, is used in a flexible battery, any 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, etc., or any combination and ratio of two or more thereof can be used.

[0330] 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 flexible battery from exploding or catching fire even if the temperature of the internal region of the flexible battery rises due to short-circuiting or overcharging. The ionic liquid is composed of cations and anions, including organic cations and anions. Examples of organic cations 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 anions include monovalent amide anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkylsulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0331] A flexible battery according to one embodiment of the present invention has, as carrier ions, for example, alkali metal ions such as lithium ions, sodium ions, and potassium ions, and alkaline earth metal ions such as calcium ions, strontium ions, barium ions, beryllium ions, and magnesium ions.

[0332] When lithium ions are used as carrier ions, the electrolyte contains a lithium salt, for example, LiPF ６ , LiClO ４ , LiAsF ６ , LiBF ４ , LiAlCl ４ , LiSCN, LiBr, LiI, Li ２ SO ４ , Li ２ B １０ Cl １０ , Li ２ B １２ Cl １２ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiC(CF ３ 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.

[0333] As an example, the organic solvent described in this embodiment contains ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and when the total amount of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is 100 vol%, the volume ratio of the ethylene carbonate, the ethyl methyl carbonate, and the dimethyl carbonate can be x:y:100-x-y (where 5≦x≦35 and 0<y<65). More specifically, an organic solvent containing EC, EMC, and DMC in a volume ratio of EC:EMC:DMC=30:35:35 can be used.

[0334] Furthermore, the electrolyte is preferably highly purified, with a low content of granular dust or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). Specifically, the weight ratio of impurities to the electrolyte is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less.

[0335] Furthermore, for the purpose of improving safety, etc., an additive such as vinylene carbonate (VC), propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), or a dinitrile compound such as succinonitrile or adiponitrile may be added to the electrolyte to form a coating portion (solid electrolyte interface) at the interface between the electrode (active material layer) and the electrolyte. The concentration of the additive may be, for example, 0.1 wt % to 5 wt % relative to the solvent.

[0336] Furthermore, if the electrolyte contains a polymeric material that can be gelled, safety against leakage, etc. Typical examples of polymeric materials that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel.

[0337] Examples of polymeric materials that can be used include polymers having a polyalkylene oxide structure, such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and 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.

[0338] [Separator] When the electrolyte contains an electrolytic solution, a separator is placed 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), polyimide, vinylon (polyvinyl alcohol-based fibers), polyester, acrylic, polyolefin, and polyurethane. The separator is preferably processed into a bag shape and positioned so as to encase either the positive electrode or the negative electrode.

[0339] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene may be coated with a ceramic material, a fluorine-based material, a polyamide material, a polyimide 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).

[0340] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging and improving battery reliability. 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 battery safety.

[0341] 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.

[0342] By using a separator with a multilayer structure, the safety of the battery can be maintained even if the overall thickness of the separator is thin, and therefore the capacity per unit volume of the battery can be increased.

[0343] [Exterior Body] The exterior body of the battery can be made of a metal material such as aluminum, stainless steel, or titanium, or a resin material. A film-like exterior body can also be used. Examples of films that can be used include a three-layer structure in which a highly flexible metal thin film or metal foil such as aluminum, stainless steel, titanium, 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 metal thin film as the outer surface of the exterior body. Such a multilayer structure film can be called a laminate film. In this case, the laminate film may be referred to as an aluminum (aluminum) laminate film, a stainless steel laminate film, a titanium laminate film, a copper laminate film, a nickel laminate film, or the like, using the name of the material of the metal layer.

[0344] The material or thickness of the metal layer of the laminate film may affect the flexibility of the battery. For example, an aluminum laminate film having a polypropylene layer, an aluminum layer, and nylon is preferably used as an exterior body for a battery with excellent flexibility (flexibility). Here, the thickness of the aluminum layer is preferably 50 μm or less, more preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the aluminum layer is thinner than 10 μm, there is a concern that pinholes in the aluminum layer may reduce the gas barrier properties, so the thickness of the aluminum layer is preferably 10 μm or more.

[0345] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0346] Seventh Embodiment In this embodiment, a manufacturing method 1 for a positive electrode active material that can be applied to the above-described embodiments will be described with reference to Fig. 25. Note that manufacturing method 1 uses a coprecipitation method, and specifically, is characterized in that a coprecipitated precursor containing Co, Ni, and Mn is prepared using a coprecipitation apparatus, a Li salt is mixed with the coprecipitated precursor, the mixture is heated, and then a calcium compound (calcium carbonate) is added and the mixture is further heated.

[0347] As shown in FIG. 25 , a cobalt source, a nickel source, and a manganese source are prepared, an alkaline aqueous solution is prepared as aqueous solution 893, and chelating agents are prepared as aqueous solutions 892 and 894. The cobalt source, nickel source, and manganese source are mixed to prepare aqueous solution 890. Aqueous solution 890 and aqueous solution 892 are mixed to prepare mixed solution 901. Mixed solution 901, aqueous solution 893, and aqueous solution 894 are reacted to produce a compound containing at least nickel, cobalt, and manganese. This reaction may be referred to as a neutralization reaction, an acid-base reaction, or a coprecipitation reaction, and the compound containing at least nickel, cobalt, and manganese (the nickel compound in FIG. 25 ) may be referred to as a precursor of a nickel-cobalt-manganese compound. The reaction occurring by performing the process surrounded by the dashed line in FIG. 25 may also be referred to as a coprecipitation reaction.

[0348] <Cobalt aqueous solution> An aqueous cobalt solution is prepared as a cobalt source. ４ ), cobalt chloride (e.g., CoCl ２ ) or cobalt nitrate (e.g., Co(NO ３ ) ２ ), cobalt acetate (e.g., C ４ H ６ CoO ４ ), cobalt alkoxide, or organic cobalt complex, or an aqueous solution containing a hydrate thereof. Organic acids of cobalt, such as cobalt acetate, or hydrates thereof, may also be used. In this specification, the organic acid includes citric acid, oxalic acid, formic acid, and butyric acid in addition to acetic acid.

[0349] For example, an aqueous solution of these compounds in pure water can be used. The cobalt aqueous solution is acidic, so it can be referred to as an acidic aqueous solution.

[0350] <Nickel aqueous solution> A nickel aqueous solution is prepared as a nickel source. As the nickel aqueous solution, an aqueous solution of nickel sulfate, nickel chloride, nickel nitrate, or a hydrate thereof can be used. Alternatively, an aqueous solution of an organic acid salt of nickel, such as nickel acetate, or a hydrate thereof can be used. Alternatively, an aqueous solution of nickel alkoxide or an organic nickel complex can be used.

[0351] <Manganese aqueous solution> A manganese aqueous solution is prepared as a manganese source. As the manganese aqueous solution, a manganese salt such as manganese sulfate, manganese chloride, manganese nitrate, or an aqueous solution of a hydrate thereof can be used. Alternatively, an aqueous solution of an organic acid salt of manganese, such as manganese acetate, or an aqueous solution of a hydrate thereof can be used. Alternatively, an aqueous solution of a manganese alkoxide or an organic manganese complex can be used.

[0352] The above-described cobalt aqueous solution, nickel aqueous solution, and manganese aqueous solution may be prepared and then mixed to prepare the aqueous solution 890, or nickel sulfate, cobalt sulfate, and manganese sulfate may be mixed and then mixed with water to prepare the aqueous solution 890. In the present embodiment, desired amounts of nickel sulfate, cobalt sulfate, and manganese sulfate are weighed out and mixed to prepare the aqueous solution 890 containing a mixture of nickel sulfate, cobalt sulfate, and manganese sulfate.

[0353] The aqueous solution 890 is mixed with the aqueous solution 892 to prepare a mixed solution 901. The aqueous solutions 892 and 894 are aqueous solutions that function as chelating agents, but are not particularly limited thereto, and the aqueous solutions 892 and 894 may be pure water.

[0354] <Alkaline aqueous solution> An alkaline solution is prepared as the aqueous solution 893. Examples of the alkaline aqueous solution include aqueous solutions containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia. For example, an aqueous solution obtained by dissolving these in pure water can be used. An aqueous solution obtained by dissolving multiple types selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide in pure water may also be used.

[0355] <Reaction Conditions> When reacting the mixed solution 901 and the aqueous solution 893 according to the coprecipitation method, the pH of the reaction system is adjusted to 9.0 or more and 12.0 or less, preferably 10.5 or more and 11.5 or less. For example, when the aqueous solution 894 is placed in a reaction tank and the mixed solution 901 and the aqueous solution 893 are dropped into the reaction tank (also referred to as a reaction vessel), the pH of the aqueous solution in the reaction tank is preferably maintained within the above-mentioned range. The same applies when the aqueous solution 893 is placed in a reaction tank and the aqueous solution 894 and the mixed solution 901 are dropped into the reaction tank. The same applies when the mixed solution 901 is placed in a reaction tank and the aqueous solution 894 and the aqueous solution 893 are dropped into the reaction tank. The dropping rate (also referred to as the liquid delivery rate) of the aqueous solution 893, the aqueous solution 894, or the mixed solution 901 is preferably 0.1 mL / min or more and 0.8 mL / min or less, which is preferable because it makes it easier to control the pH conditions.

[0356] The aqueous solution in the reaction vessel is preferably stirred using a stirring means. The stirring means has a stirrer or stirring blades. Two to six stirring blades can be provided. For example, when four stirring blades are used, they are preferably arranged in a cross shape when viewed from above. The rotation speed of the stirring means is preferably 800 rpm to 1200 rpm.

[0357] The temperature of the reaction vessel is adjusted to be 50° C. or higher and 90° C. or lower. The dropping of the aqueous solution 893, the aqueous solution 894, or the mixed solution 901 may be started after the temperature has reached the appropriate temperature.

[0358] The inside of the reaction vessel is preferably kept in an inert atmosphere. For example, when a nitrogen atmosphere is used, nitrogen gas is preferably introduced at a flow rate of 0.5 L / min to 2 L / min.

[0359] The reactor may also be equipped with a reflux condenser, which allows nitrogen gas to escape from the reactor and water to return to the reactor.

[0360] After the above reaction, a compound containing at least nickel, cobalt, and manganese is precipitated in the reaction vessel. Filtration is performed to recover the compound containing nickel, cobalt, and manganese. It is preferable to wash the reaction product precipitated in the reaction vessel with pure water, add an organic solvent with a low boiling point (e.g., acetone), and then perform the above filtration.

[0361] The filtered compound containing at least nickel, cobalt, and manganese may be further dried. For example, the compound may be dried under vacuum or reduced pressure at 60°C to 120°C for 0.5 to 12 hours. In this manner, a compound containing nickel, cobalt, and manganese can be obtained. In Figure 25, the compound containing nickel, cobalt, and manganese is referred to as a nickel compound.

[0362] The compound containing at least nickel, cobalt, and manganese obtained by the above reaction is obtained as secondary particles formed by aggregation of primary particles. In this specification, the term "primary particle" refers to the smallest particle (clump) without grain boundaries when observed, for example, at 5000x magnification using a scanning electron microscope (SEM). In other words, the term "primary particle" refers to the smallest particle surrounded by grain boundaries. The term "secondary particle" refers to particles (particles independent from others) formed by aggregation of the primary particles so as to share part of the grain boundaries (peripheries of the primary particles) and which are not easily separated. In other words, the secondary particles may have grain boundaries.

[0363] In this embodiment, in the compound containing nickel, cobalt, and manganese obtained by the coprecipitation method, the atomic ratio of nickel, cobalt, and manganese is appropriately adjusted to Ni:Co:Mn=8:1:1 or approximately therein.

[0364] <Lithium Compound> Next, a lithium compound is prepared. As the lithium compound, lithium hydroxide (e.g., LiOH), lithium carbonate (e.g., Li ２ CO ３ (melting point 723°C)), or lithium nitrate (e.g., LiNO ３) are examples. In particular, among lithium compounds typified by lithium hydroxide (melting point 462°C), it is preferable to use a material with a low melting point. A positive electrode active material with a high proportion of nickel is more susceptible to cation mixing than lithium cobalt oxide, so the first heating must be performed at a low temperature. Therefore, it is preferable to use a material with a low melting point. The lithium concentration of the positive electrode active material 400, which will be described later, can be adjusted appropriately at this stage. In this embodiment, the molar ratio is adjusted appropriately to 1.01 with respect to the nickel compound (a compound containing nickel, cobalt, and manganese) which is the coprecipitated precursor.

[0365] In this embodiment, a compound containing nickel, cobalt, and manganese is mixed with a lithium compound to obtain the mixture 904. A mortar or a stirring mixer is used for mixing.

[0366] Next, the first heating is performed. As a firing device for performing the first heating, an electric furnace, for example, a rotary kiln furnace, can be used.

[0367] The first heating temperature is preferably higher than 400° C. and equal to or lower than 1050° C. The first heating time is preferably 1 hour or more and 20 hours or less.

[0368] The material is then crushed or pulverized in a mortar to achieve a uniform particle size, and then recovered. It may also be classified using a sieve. When recovering the material after heating, it is preferable to transfer it from the crucible to a mortar and then recover it, since this prevents impurities from being mixed into the material.

[0369] Next, the second heating is performed. As a firing apparatus for performing the second heating, an electric furnace or a rotary kiln furnace can be used.

[0370] The second heating temperature is preferably higher than 400°C and not higher than 1050°C. The second heating time is preferably 1 hour or more and 20 hours or less. The second heating is preferably performed in an oxygen atmosphere, and it is particularly preferable to perform the second heating while supplying oxygen. For example, the flow rate is 10 L / min per 1 L of the furnace volume. Specifically, the mixture 904 is preferably heated with the container containing the mixture 904 covered.

[0371] The mixture is then crushed or pulverized in a mortar to make the particle size uniform, and then recovered.Furthermore, the mixture may be classified using a sieve.

[0372] <Calcium Compound> Then, the obtained mixture 905 is mixed with a compound 910. In this embodiment, a calcium compound is used as the compound 910. Examples of calcium compounds include calcium oxide, calcium carbonate (melting point 825°C), and calcium hydroxide. In this embodiment, calcium carbonate (CaCO ３ The amount of the compound 910 is preferably such that calcium is weighed and added in a range of 0.5 atm % to 3 atm % relative to the amount of the compound containing nickel, cobalt, and manganese.

[0373] Thereafter, a third heating step is performed. The third heating temperature is at least higher than the first heating temperature, and is preferably higher than 662°C and lower than 1050°C. The third heating time is shorter than that of the second heating, and is preferably 0.5 hours or longer and 20 hours or shorter. The third heating step is preferably performed in an oxygen atmosphere, and it is particularly preferable to perform the third heating step while supplying oxygen. For example, the flow rate is 10 L / min per 1 L of the furnace volume. Specifically, the heating step is preferably performed with the container containing the mixture 905 covered.

[0374] The mixture is then crushed or pulverized in a mortar to make the particle size uniform, and then recovered.Furthermore, the mixture may be classified using a sieve.

[0375] The above steps can produce the positive electrode active material 400. The positive electrode active material 400 obtained in the above steps is an NCM, and contains calcium in the periphery of the primary particle or the periphery of the secondary particle.

[0376] 25, a process may be used in which a lithium compound and a calcium compound are mixed with a nickel compound, which is a coprecipitated precursor, and then heated. In this case, the third heating step may be unnecessary.

[0377] In the above-described production flow, heating after adding the calcium compound (calcium carbonate) is performed at a temperature at which the primary particles do not melt and at which calcium does not diffuse into the primary particles. The lower limit temperature for heating after adding the calcium compound (calcium carbonate) is preferably set to the eutectic point of 662°C. By heating at 662°C or higher after adding the calcium compound (calcium carbonate), calcium carbonate and lithium carbonate melt, resulting in the formation of molten calcium carbonate and lithium carbonate between the primary particles, and calcium diffuses and becomes scattered inside the secondary particles. In this way, calcium-doped lithium nickel-cobalt-manganese oxide can be obtained. Calcium may be present inside the nickel-cobalt-manganese oxide or may be present in a state of coating the nickel-cobalt-manganese oxide. A coated state is sometimes referred to as calcium being present in the covered portion of the nickel-cobalt-manganese oxide.

[0378] In the above-described production flow, the procedure for adding a calcium compound has been described, but an aluminum compound may be added instead of the calcium compound. The aluminum compound may be added at the same time as the calcium compound, or may be added when producing the coprecipitated precursor. In this way, aluminum-doped lithium nickel-cobalt-manganese oxide can be obtained. Aluminum may be present inside the lithium nickel-cobalt-manganese oxide, or may be present in a state that coats it. A coated state is sometimes described as a state in which the covered part of the lithium nickel-cobalt-manganese oxide has aluminum.

[0379] In the above-described production flow, an aluminum compound may be added in addition to a calcium compound. The timing of adding the aluminum compound may be the same as or different from the timing of adding the calcium compound. In the case where the timing is different, for example, the aluminum compound may be added when producing the coprecipitated precursor.

[0380] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0381] 26A to 26C , a method for manufacturing a positive electrode active material that can be applied to the above-described embodiments will be described. Note that the method for manufacturing a positive electrode active material uses a solid phase method, and specifically, is characterized by undergoing annealing and initial heating.

[0382] <Step S11> In step S11 shown in FIG. 26A, a lithium source (Li source) and a transition metal M source (M source) are prepared as starting materials for lithium and transition metal M, respectively.

[0383] As the lithium source, it is preferable to use a compound containing lithium, such as lithium carbonate, lithium hydroxide, lithium nitrate, or lithium fluoride. It is preferable that the lithium source has high purity, and it is preferable to use a material with a purity of, for example, 99.99% or higher.

[0384] The transition metal M can be selected from elements in Groups 4 to 13 of the periodic table, and for example, one or more selected from manganese, cobalt, and nickel are used. As the transition metal M, only cobalt may be used, only nickel may be used, two elements of cobalt and manganese may be used, two elements of cobalt and nickel may be used, or three elements of cobalt, manganese, and nickel may be used. When only cobalt is used, the resulting positive electrode active material has lithium cobalt oxide (LCO), and when three elements of cobalt, manganese, and nickel are used, the resulting positive electrode active material has lithium nickel-cobalt-manganese oxide (NCM).

[0385] As the transition metal M source, it is preferable to use a compound containing the transition metal M, and for example, an oxide or hydroxide of a metal exemplified as the transition metal M can be used. As a cobalt source, cobalt oxide, cobalt hydroxide, etc. can be used. As a manganese source, manganese oxide, manganese hydroxide, etc. can be used. As a nickel source, nickel oxide, nickel hydroxide, etc. can be used. As an aluminum source, aluminum oxide, aluminum hydroxide, etc. can be used.

[0386] The transition metal M source preferably has a high purity, for example, a material with a purity of 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N (99.995%) or higher, and even more preferably 5N (99.999%) or higher. By using a high-purity material, impurities in the positive electrode active material can be controlled.

[0387] In addition, the transition metal M source preferably has high crystallinity, for example, single crystal grains. The crystallinity of the transition metal M source can be evaluated using 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, etc., or by X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. Note that the above-mentioned methods for evaluating crystallinity can be applied not only to the transition metal M source but also to the evaluation of the crystallinity of other sources.

[0388] When two or more transition metal M sources are used, the two or more transition metal M sources are preferably prepared in a ratio (mixing ratio) that allows the two or more transition metal M sources to form a layered rock salt type crystal structure.

[0389] <Step S12> Next, in step S12 shown in FIG. 26A , the lithium source and the transition metal M source are pulverized and mixed to prepare a mixed material. The pulverization and mixing can be performed by either a dry or wet method. The wet method is preferred because it allows for smaller pulverization. When using the wet method, a solvent is prepared. Examples of solvents that can be used include ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, and N-methyl-2-pyrrolidone (NMP). It is more preferable to use an aprotic solvent that is less likely to react with lithium. In this embodiment, dehydrated acetone with a purity of 99.5% or higher is used. It is preferable to mix the lithium source and the transition metal M source in dehydrated acetone with a purity of 99.5% or higher, with a water content reduced to 10 ppm or less, and then pulverize and mix them. Using dehydrated acetone with the above purity can reduce potential impurities.

[0390] A ball mill, a bead mill, or the like can be used as a means for mixing, etc. When using a ball mill, aluminum oxide balls or zirconium oxide balls are preferably used as grinding media. Zirconium oxide balls are preferred because they emit less impurities. Furthermore, when using a ball mill, a bead mill, or the like, the peripheral speed is preferably set to 100 mm / s or more and 2000 mm / s or less in order to suppress contamination from the media. In this embodiment, the peripheral speed is set to 838 mm / s (rotation speed 400 rpm, ball mill diameter 40 mm).

[0391] <Step S13> Next, in step S13 shown in FIG. 26A , the mixed material is heated. The heating temperature is preferably 800°C or higher and 1100°C or lower, more preferably 900°C or higher and 1000°C or lower, and even more preferably about 950°C. If the temperature is too low, the decomposition and melting of the lithium source and the transition metal M source may be insufficient. On the other hand, if the temperature is too high, defects may occur due to lithium evaporation from the lithium source and / or excessive reduction of the metal used as the transition metal M source. For example, when cobalt is used as the transition metal M, excessive reduction can cause cobalt to change from trivalent to divalent, which can induce oxygen defects, etc.

[0392] If the heating time is too short, LiMO ２ However, if the heating time is too long, productivity decreases. For example, the heating time is preferably 1 hour or more and 100 hours or less, and more preferably 2 hours or more and 20 hours or less.

[0393] The temperature rise rate depends on the heating temperature reached, but is preferably 80° C. / h to 250° C. / h. For example, when heating at 1000° C. for 10 hours, the temperature rise rate should be 200° C. / h.

[0394] Heating is preferably carried out in an atmosphere with little water, such as dry air, for example, in an atmosphere with a dew point of -50°C or less, more preferably -80°C or less. In this embodiment, heating is carried out in an atmosphere with a dew point of -93°C. In addition, in order to suppress impurities that may be mixed into the material, the CH ４ , CO, CO ２, and H ２ The impurity concentrations of the above should be set to 5 ppb (parts per billion) or less.

[0395] Heating is preferably carried out in an atmosphere containing oxygen. For example, dry air may be continuously introduced into the reaction chamber. In this case, the flow rate of the dry air is preferably 10 L / min. The method of continuously introducing oxygen into the reaction chamber and allowing oxygen to flow through the reaction chamber is called "flow."

[0396] When heating is performed in an oxygen-containing atmosphere, a method that does not allow oxygen to flow may be used. For example, a method may be used in which the reaction chamber is depressurized and then filled with oxygen to prevent the oxygen from entering or leaving the reaction chamber, which is called purging. For example, the reaction chamber may be depressurized to -970 hPa and then filled with oxygen to 50 hPa.

[0397] After heating, the material may be cooled naturally, but it is preferable that the time required for the temperature to drop from the specified temperature to room temperature is within a range of 10 to 50 hours. However, cooling to room temperature is not necessarily required, as long as the material is cooled to a temperature acceptable for the next step.

[0398] The heating in this step may be carried out using a rotary kiln or a roller hearth kiln. Heating in a rotary kiln can be carried out while stirring, whether in a continuous or batch system.

[0399] The crucible or sheath used during heating is preferably made of a highly heat-resistant material such as alumina (aluminum oxide), mullite / cordierite, magnesia, or zirconia. Furthermore, since aluminum oxide is a material that is less susceptible to impurities, the purity of the alumina crucible or sheath is 99% or higher, preferably 99.5% or higher. In this embodiment, a crucible made of aluminum oxide with a purity of 99.9% is used. It is preferable to heat the crucible or sheath with a lid, which prevents the material from volatilizing.

[0400] After heating, the material may be crushed and sieved as necessary. When recovering the heated material, it may be transferred from the crucible to a mortar and then recovered. It is preferable to use a mortar made of aluminum oxide. A mortar made of aluminum oxide is a material that does not easily release impurities. Specifically, a mortar made of aluminum oxide or zirconium oxide with a purity of 90% or more, preferably 99% or more, is used. Heating conditions equivalent to those of step S13 can also be applied to heating steps other than step S13, which will be described later.

[0401] <Step S14> By the above steps, a composite oxide having a transition metal M (LiMO ２ The composite oxide can be obtained by ２ It is sufficient for the lithium composite oxide to have a crystal structure represented by the formula: Li:M:O = 1:1:2, and the composition is not strictly limited to Li:M:O = 1:1:2. When cobalt is used as the transition metal M, the composite oxide is called a cobalt-containing composite oxide and is represented by LiCoO2. The composition is not strictly limited to Li:Co:O = 1:1:2.

[0402] Although the example of producing the composite oxide by the solid phase method in steps S11 to S14 has been shown, the composite oxide may also be produced by a coprecipitation method or a hydrothermal method.

[0403] <Step S15> Next, in step S15 shown in Fig. 26A, the composite oxide is heated. Because this is the first heating of the composite oxide, the heating in step S15 may be called initial heating. Alternatively, because this heating is performed before step S20 described below, it may be called preheating or pretreatment.

[0404] As described above, the initial heating causes lithium to be desorbed from a portion of the surface layer of the composite oxide. It is also expected to have the effect of increasing the internal crystallinity. Furthermore, impurities may be mixed into the lithium source and / or transition metal M prepared in step S11, etc. The initial heating can reduce the amount of impurities in the composite oxide completed in step S14.

[0405] Furthermore, initial heating has the effect of smoothing the surface of the composite oxide. A smooth surface means that there are few irregularities, the composite oxide is rounded overall, and the corners are rounded. Furthermore, a smooth surface means that there is little foreign matter adhering to the surface. Foreign matter is thought to be a cause of irregularities, so it is preferable that it does not adhere to the surface.

[0406] For this initial heating, it is not necessary to prepare a lithium compound source, a source of the additional element A, or a material that functions as a flux.

[0407] If the heating time in this step is too short, sufficient effects will not be obtained, but if it is too long, productivity will decrease. For example, the heating conditions can be selected from those described in step S13. In addition to the heating conditions, the heating temperature in this step should be lower than the temperature in step S13 in order to maintain the crystalline structure of the complex oxide. Furthermore, the heating time in this step should be shorter than the time in step S13 in order to maintain the crystalline structure of the complex oxide. For example, heating at a temperature of 700°C or higher and 1000°C or lower for 2 hours or longer and 20 hours or shorter is recommended.

[0408] The effect of increasing the internal crystallinity is, for example, the effect of alleviating distortion, displacement, etc. resulting from differences in shrinkage, etc., of the composite oxide produced in step S13.

[0409] The heating in step S13 may cause a temperature difference between the surface and the interior of the composite oxide. The temperature difference may induce a contraction difference. It is also thought that the temperature difference causes a difference in fluidity between the surface and the interior, resulting in a contraction difference. The energy associated with the contraction difference causes a difference in internal stress in the composite oxide. The internal stress difference is also called strain, and this energy is sometimes called strain energy. The internal stress is removed by the initial heating in step S15; in other words, the strain energy is thought to be homogenized by the initial heating in step S15. When the strain energy is homogenized, the strain in the composite oxide is alleviated. Therefore, the surface of the composite oxide may become smoother after step S15. This is also called an improved surface. In other words, it is thought that the contraction difference that occurred in the composite oxide is alleviated after step S15, resulting in a smoother surface of the composite oxide.

[0410] Furthermore, the difference in shrinkage may cause microscopic deviations in the composite oxide, such as deviations in crystals. This step is preferably carried out in order to reduce such deviations. This step makes it possible to equalize the deviations in the composite oxide. When the deviations are equalized, the surface of the composite oxide may become smooth. This is also referred to as the alignment of crystal grains. In other words, it is believed that step S15 reduces the deviations of crystals and the like that have occurred in the composite oxide, resulting in a smooth surface of the composite oxide.

[0411] When a composite oxide with a smooth surface is used as a positive electrode active material, deterioration during charging and discharging of the flexible battery is reduced, and cracking of the positive electrode active material can be prevented.

[0412] The smooth surface of a composite oxide can be expressed as a surface roughness of at least 10 nm or less when surface irregularity information is quantified from measurement data at a cross section of the composite oxide. The cross section is, for example, a cross section obtained when observing with a scanning transmission electron microscope (STEM).

[0413] In step S14, a composite oxide containing lithium, a transition metal M, and oxygen that has been synthesized in advance may be used. In this case, steps S11 to S13 can be omitted. By performing step S15 on a composite oxide that has been synthesized in advance, a composite oxide with a smooth surface can be obtained.

[0414] It is possible that the lithium in the composite oxide is reduced by the initial heating, and the added element A, which will be explained in the next step S20, etc., may be more likely to enter the composite oxide due to the reduced lithium.

[0415] <Step S20> The additive element A may be added to a composite oxide having a smooth surface, as long as it can form a layered rock salt crystal structure. Adding the additive element A to a composite oxide having a smooth surface allows the additive element A to be added evenly. Therefore, it is preferable to add the additive element A after the initial heating. The step of adding the additive element A will be described with reference to FIGS. 26B and 26C.

[0416] 26B, a source of an additive element A (A source) to be added to the composite oxide is prepared. A lithium source may be prepared together with the additive element A source.

[0417] The additive element A can be 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. The additive element A can be one or more selected from bromine and beryllium. However, since bromine and beryllium are toxic to living organisms, it is more preferable to use the additive elements described above.

[0418] When magnesium is selected as the additional element A, the source of the additional element A can be called a magnesium source. As the magnesium source, magnesium fluoride, magnesium oxide, magnesium hydroxide, magnesium carbonate, or the like can be used. Furthermore, a plurality of the above-mentioned magnesium sources may be used.

[0419] When fluorine is selected as the additional element A, the source of the additional element A can be called a fluorine source. Examples of the fluorine source that can be used include lithium fluoride, magnesium fluoride, aluminum fluoride, titanium fluoride, cobalt fluoride, nickel fluoride, zirconium fluoride, vanadium fluoride, manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride, calcium fluoride, sodium fluoride, potassium fluoride, barium fluoride, cerium fluoride, lanthanum fluoride, and sodium aluminum hexafluoride. Among these, lithium fluoride is preferred because it has a relatively low melting point of 848°C and is easily melted in the heating step described below.

[0420] Magnesium fluoride can be used as both a fluorine source and a magnesium source, and lithium fluoride can be used as a lithium source. Another lithium source that can be used in step S21 is lithium carbonate.

[0421] The fluorine source may be a gas, such as fluorine, carbon fluoride, sulfur fluoride, or oxygen fluoride, which may be mixed into the atmosphere in the heating step described below. A plurality of the above-mentioned fluorine sources may also be used.

[0422] In this embodiment, lithium fluoride is prepared as the fluorine source, and magnesium fluoride is prepared as the fluorine source and magnesium source. Lithium fluoride and magnesium fluoride are prepared in the form of LiF:MgF ２ The effect of lowering the melting point is greatest when the molar ratio is about 65:35. On the other hand, if the amount of lithium fluoride is too high, there is a concern that the lithium will be excessive and the cycle characteristics will deteriorate. Therefore, the molar ratio of lithium fluoride to magnesium fluoride is set to LiF:MgF ２ =x:1 (0≦x≦1.9), and LiF:MgF ２ =x:1 (0.1≦x≦0.5) is more preferable, and LiF:MgF ２ = x: 1 (x = 0.33 or its vicinity) is more preferable. In this specification, "or its vicinity" refers to a value that is greater than 0.9 times and smaller than 1.1 times the value.

[0423] At the same time, the amount of magnesium added is２ Based on this, the content is preferably more than 0.1 atomic % and not more than 3 atomic %, more preferably 0.5 atomic % to 2 atomic %, and even more preferably 0.5 atomic % to 1 atomic %. When the amount of magnesium added is 0.1 atomic % or less, the initial discharge capacity is high, but the discharge capacity drops rapidly when charge / discharge cycles are repeated to increase the depth of charge. When the amount of magnesium added is more than 0.1 atomic % and not more than 3 atomic %, both the initial discharge characteristics and the charge / discharge cycle characteristics are good even when charge / discharge cycles are repeated to increase the depth of charge. On the other hand, when the amount of magnesium added exceeds 3 atomic %, both the initial discharge capacity and the charge / discharge cycle characteristics tend to gradually deteriorate.

[0424] 26B, the magnesium source and the fluorine source are pulverized and mixed. This step can be performed under pulverization and mixing conditions selected from those described in step S12.

[0425] If necessary, a heating step may be performed after step S22. The heating step can be performed under heating conditions selected from those described in step S13. The heating time is preferably 2 hours or more, and the heating temperature is preferably 800°C or higher and 1100°C or lower.

[0426] 26B, the pulverized and mixed materials are collected to obtain a source of the additional element A (A source). Note that the source of the additional element A shown in step S23 contains a plurality of starting materials and can be called a mixture.

[0427] The particle size of the mixture is preferably such that the median diameter (D50) is 600 nm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less. Even when a single material is used as the source of the additional element A, the median diameter (D50) is preferably 600 nm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less.

[0428] Such a finely powdered mixture (including cases where only one type of additive element A is present) is easy to uniformly adhere to the surface of the composite oxide when mixed with the composite oxide in a subsequent step. Uniform adhesion of the mixture to the surface of the composite oxide is preferable because it facilitates uniform distribution or diffusion of fluorine and magnesium in the surface layer portion of the composite oxide after heating. The region where fluorine and magnesium are distributed can also be referred to as the surface layer portion. If there is a region in the surface layer that does not contain fluorine and magnesium, it may be difficult to obtain the O3'-type crystal structure described below in the charged state. Note that although fluorine has been used in the description, fluorine may also be chlorine, and can be interpreted as including these and therefore as halogen. The surface layer portion where fluorine and magnesium are distributed refers to a region that extends from the surface to the interior, perpendicular or approximately perpendicular to the surface, within 50 nm, preferably within 35 nm, more preferably within 20 nm, and even more preferably within 10 nm.

[0429] <Step S21> A step different from that shown in Fig. 26B will be described with reference to Fig. 26C. In step S21 shown in Fig. 26C, four types of additive element A sources to be added to the composite oxide are prepared. That is, Fig. 26C differs from Fig. 26B in the type of additive element A source. A lithium source may be prepared together with the additive element A source.

[0430] As sources of four types of additive element A, a magnesium source (Mg source), a fluorine source (F source), a nickel source (Ni source), and an aluminum source (Al source) are prepared. The magnesium source and the fluorine source can be selected from the compounds described in FIG. 26B . Nickel oxide, nickel hydroxide, etc. can be used as the nickel source. Aluminum oxide, aluminum hydroxide, etc. can be used as the aluminum source.

[0431] <Step S22> and <Step S23> Next, step S22 and step S23 shown in FIG. 26C are the same as the steps described in FIG. 26B.

[0432] 26A , the composite oxide is mixed with a source of the additional element A. The ratio of the number of atoms M of the transition metal M in the composite oxide containing lithium, the transition metal M, and oxygen to the number of atoms Mg of magnesium in the additional element A is preferably M:Mg=100:y (0.1≦y≦6), and more preferably M:Mg=100:y (0.3≦y≦3).

[0433] The mixing in step S31 is preferably performed under conditions of a lower rotation speed or shorter time than in step S12 to avoid destroying the composite oxide. It can also be said that the dry method provides milder conditions than the wet method. For example, a ball mill, a bead mill, or the like can be used for mixing. When using a ball mill, it is preferable to use zirconium oxide balls as the medium.

[0434] In this embodiment, dry mixing is performed in a ball mill using zirconium oxide balls with a diameter of 1 mm at 150 rpm for 1 hour in a dry room with a dew point of −100° C. or higher and −10° C. or lower.

[0435] <Step S32> Next, in step S32 of Fig. 26A, the mixed materials are collected to obtain a mixture 903. When collecting the materials, they may be crushed and then sieved, if necessary.

[0436] In this embodiment, a method is described in which lithium fluoride as a fluorine source and magnesium fluoride as a magnesium source are added to the composite oxide after the initial heating. However, the present invention is not limited to the above method. In step S11, that is, in the stage of the starting materials for the composite oxide, a magnesium source, a fluorine source, etc. can be added to the lithium source and the transition metal M source. Then, in step S13, heating is performed to obtain LiMO with added magnesium and fluorine. ２ In this case, it is not necessary to separate the steps S11 to S14 from the steps S21 to S23. This method is simple and has high productivity.

[0437] Alternatively, a composite oxide to which magnesium and fluorine have been added in advance may be used. If a composite oxide to which magnesium and fluorine have been added is used, steps S11 to S32 and step S20 can be omitted. This method can be said to be simple and highly productive.

[0438] Alternatively, a magnesium source and a fluorine source, or a magnesium source, a fluorine source, a nickel source and an aluminum source may be further added to a composite oxide to which magnesium and fluorine have been added in advance in step S20.

[0439] 26A, the mixture 903 is heated. The heating conditions can be selected from those described in step S13. The heating time is preferably 2 hours or more.

[0440] Here, a supplementary note about the heating temperature will be given. The lower limit of the heating temperature in step S33 is ２ The temperature at which the reaction between the LiMO and the additive element A source proceeds must be equal to or higher than the temperature at which the reaction between the LiMO and the additive element A source proceeds. ２ The temperature may be lower than the melting point of these materials as long as it is a temperature at which mutual diffusion of elements contained in the source of the additive element A occurs. ｍ 0.757 times (Tammann temperature T ｄ ) solid-phase diffusion occurs. Therefore, the heating temperature in step S33 should be 500° C. or higher.

[0441] Of course, the reaction proceeds more easily when the temperature is equal to or higher than the temperature at which at least a part of the mixture 903 melts. ２ When LiF and MgF ２ Since the eutectic point of is around 742°C, the lower limit of the heating temperature in step S33 is preferably set to 742°C or higher.

[0442] Also, LiCoO ２ :LiF:MgF ２A mixture 903 obtained by mixing the components so that the molar ratio was 100:0.33:1 exhibits an endothermic peak at around 830° C. in differential scanning calorimetry (DSC). Therefore, the lower limit of the heating temperature is more preferably 830° C. or higher.

[0443] A higher heating temperature is preferable because the reaction proceeds more easily, the heating time is shorter, and productivity is higher.

[0444] The upper limit of heating temperature is LiMO ２ Decomposition temperature of LiCoO ２ The decomposition temperature of LiMO is less than 1130°C. At temperatures close to the decomposition temperature, a small amount of LiMO ２ Therefore, the temperature is more preferably 1000°C or lower, even more preferably 950°C or lower, and even more preferably 900°C or lower.

[0445] Taking these factors into consideration, the heating temperature in step S33 is preferably 500°C to 1130°C, more preferably 500°C to 1000°C, even more preferably 500°C to 950°C, and even more preferably 500°C to 900°C. Also, it is preferably 742°C to 1130°C, more preferably 742°C to 1000°C, even more preferably 742°C to 950°C, and even more preferably 742°C to 900°C. Also, it is preferably 800°C to 1100°C, or 830°C to 1130°C, more preferably 830°C to 1000°C, even more preferably 830°C to 950°C, and even more preferably 830°C to 900°C. The heating temperature in step S33 is preferably higher than that in step S13.

[0446] Furthermore, when the mixture 903 is heated, it is preferable to control the partial pressure of fluorine or fluoride resulting from the fluorine source or the like within an appropriate range.

[0447] In the manufacturing method described in this embodiment, some materials, for example, LiF, which is a fluorine source, may function as a flux. This function allows the heating temperature to be controlled to the temperature of the composite oxide (LiMO). ２) can be lowered to a temperature lower than the decomposition temperature, for example, 742°C or higher and 950°C or lower, and additive element A including magnesium can be distributed in the surface layer portion, thereby producing a positive electrode active material with good characteristics.

[0448] However, since LiF has a lower specific gravity in a gaseous state than oxygen, there is a possibility that LiF will volatilize when heated, and if it volatilizes, the amount of LiF in the mixture 903 will decrease. This will weaken its function as a flux. Therefore, it is necessary to heat while suppressing the volatilization of LiF. Even if LiF is not used as a fluorine source, etc., LiMO ２ There is a possibility that Li on the surface reacts with F in the fluorine source to produce LiF, which may then volatilize. Therefore, even if a fluoride with a higher melting point than LiF is used, it is still necessary to suppress volatilization.

[0449] Therefore, it is preferable to heat the mixture 903 in an atmosphere containing LiF, that is, to heat the mixture 903 in a state where the partial pressure of LiF is high in the heating furnace. By heating in this manner, it is possible to suppress the volatilization of LiF in the mixture 903.

[0450] The heating in this step is preferably performed so as not to stick together the mixture 903. If the mixture 903 sticks together during heating, the contact area with oxygen in the atmosphere decreases, and the route along which the additional element A (for example, fluorine) diffuses is blocked, which may result in a poor distribution of the additional element A (for example, magnesium and fluorine) in the surface layer portion.

[0451] It is also believed that uniform distribution of the additive element A (e.g., fluorine) in the surface layer portion results in a smooth cathode active material with few irregularities. Therefore, in order to maintain or further smooth the surface after the heating in step S15 in this process, it is preferable that the mixture 903 does not stick to itself.

[0452] Furthermore, when heating in a rotary kiln, it is preferable to control the flow rate of the oxygen-containing atmosphere in the kiln during heating. For example, it is preferable to reduce the flow rate of the oxygen-containing atmosphere, or to first purge the atmosphere and then not flow the atmosphere after introducing the oxygen atmosphere into the kiln. Flowing oxygen may cause the fluorine source to evaporate, which is undesirable in terms of maintaining surface smoothness.

[0453] When heating is performed using a roller hearth kiln, the mixture 903 can be heated in an atmosphere containing LiF by placing a lid on a container containing the mixture 903, for example.

[0454] The heating time is determined by the heating temperature, the LiMO ２ It changes depending on the size and composition of LiMO. ２ When is small, a lower temperature or shorter time may be more preferable than when is large.

[0455] The composite oxide (LiMO) in step S14 of FIG. ２ When the median diameter (D50) of the powder is about 12 μm, the heating temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The heating time is, for example, preferably 3 hours or higher, more preferably 10 hours or higher, and even more preferably 60 hours or higher. The cooling time after heating is preferably, for example, 10 hours or higher and 50 hours or lower.

[0456] On the other hand, the composite oxide (LiMO) ２ When the median diameter (D50) of the powder is about 5 μm, the heating temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The heating time is preferably, for example, 1 hour or higher and 10 hours or lower, and more preferably about 2 hours. The cooling time after heating is preferably, for example, 10 hours or higher and 50 hours or lower.

[0457] <Step S34> Next, in step S34 shown in Fig. 26A, the heated material is recovered and crushed as necessary to obtain positive electrode active material 500. At this time, it is preferable to further sieve recovered positive electrode active material 500. Through the above steps, positive electrode active material 500 according to one embodiment of the present invention can be produced. The positive electrode active material according to one embodiment of the present invention has a smooth surface.

[0458] This embodiment can be used in combination with other embodiments.

[0459] (Embodiment 9) In this embodiment, an example in which a flexible battery according to one embodiment of the present invention is mounted in an electronic device will be described. Examples of electronic devices in which a flexible battery is mounted include television sets (also referred to as televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game consoles, personal digital assistants, sound players, and large game consoles such as pachinko machines. Examples of personal digital assistants include notebook personal computers, tablet terminals, e-book readers, and mobile phones.

[0460] 27A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into a housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also includes a flexible battery 2107. The flexible battery 2107 is bendable, and therefore can be mounted in a bendable area of ​​the mobile phone 2100.

[0461] 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.

[0462] 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.

[0463] 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.

[0464] The mobile phone 2100 also includes an external connection port 2104, and can directly exchange data with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Note that charging may be performed by wireless power supply without using the external connection port 2104.

[0465] Furthermore, the mobile phone 2100 preferably has a sensor. As the sensor, for example, a fingerprint sensor, a pulse sensor, a body temperature sensor or other human body sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like is preferably mounted.

[0466] 27B shows an unmanned aerial vehicle 2300 having multiple rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 has a flexible 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. The flexible battery 2301 is bendable and can be mounted in a bendable area of ​​the unmanned aerial vehicle 2300.

[0467] Fig. 27C shows an example of a robot. The robot 6400 shown in Fig. 27C includes a flexible 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. The flexible battery 6409 is bendable and can be mounted in a bending area of ​​the robot 6400.

[0468] 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.

[0469] 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.

[0470] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0471] The robot 6400 includes a flexible battery 6409 according to one embodiment of the present invention and a semiconductor device or electronic component in its internal area.

[0472] 27D shows an example of a cleaning robot. The cleaning robot 6300 includes a display unit 6302 located on the top surface of a housing 6301, multiple cameras 6303 located on the side surfaces, a brush 6304, an operation button 6305, a flexible 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 the dust from the suction port located on the bottom surface. The flexible battery 6306 is bendable and can be mounted in a bending area of ​​the cleaning robot 6300.

[0473] The cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, when an object that may become entangled in the brush 6304, such as a wire, is detected by image analysis, the cleaning robot 6300 can stop rotation of the brush 6304. The cleaning robot 6300 includes a flexible battery 6306 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal area.

[0474] 28A shows an example of a wearable device. The wearable device uses a flexible battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for a wearable device that can be charged wirelessly as well as via a wired connection with an exposed connector.

[0475] For example, a flexible battery according to one embodiment of the present invention can be mounted on a glasses-type device 4000 as shown in FIG. 28A . The glasses-type device 4000 includes a frame 4000a and a display unit 4000b. By mounting a flexible battery on the temples of the curved frame 4000a, the glasses-type device 4000 can be lightweight, have a good weight balance, and can be used for a long time. The flexible battery can be bent, and can be mounted on the curved portion.

[0476] Furthermore, a flexible 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. A flexible battery can be provided in the flexible pipe 4001b or the earphone unit 4001c. The flexible battery can be bent and can be mounted on a curved portion.

[0477] Furthermore, a flexible 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 flexible battery 4002b can be provided inside a thin housing 4002a of the device 4002. The flexible battery can be bent and can be mounted on a curved portion.

[0478] Furthermore, the flexible battery according to one embodiment of the present invention can be mounted on a device 4003 that can be attached to clothing. A flexible battery 4003b can be provided in a thin housing 4003a of the device 4003. The flexible battery can be bent and can be mounted on a curved portion.

[0479] Furthermore, the flexible 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 flexible battery can be mounted in an internal region of the belt portion 4006a. The flexible battery can be bent and can be mounted on a curved portion.

[0480] Furthermore, the flexible battery according to one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch device 4005 has a display portion 4005a and a belt portion 4005b, and a flexible battery can be provided on the display portion 4005a or the belt portion 4005b. The flexible battery can be bent and can be mounted on a curved portion.

[0481] The display unit 4005a can display not only the time but also various other information such as incoming emails or phone calls.

[0482] Furthermore, since the wristwatch-type device 4005 is a wearable device that is worn directly on the wrist, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated to manage the user's health.

[0483] FIG. 28B shows a perspective view of the wristwatch-type device 4005 removed from the wrist.

[0484] A side view is also shown in Figure 28C. Figure 28C shows how a flexible battery 913 is built into the internal area. The flexible battery 913 is provided in a position overlapping the display unit 4005a, and can be made high density and large capacity, while being small and lightweight. The flexible battery 913 can be bent, and can be mounted on a curved portion.

[0485] 28D 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.

[0486] The main bodies 4100a and 4100b each have a driver unit 4101, an antenna 4102, and a flexible battery 4103. They may also have a display portion 4104. They preferably also 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. The flexible battery 4103 can be bent and can be mounted on a curved portion.

[0487] The case 4110 has a flexible battery 4111. It also preferably 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, etc. The flexible battery 4111 can be bent and can be mounted on a curved part.

[0488] 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 main units 4100a and 4100b to be used as, for example, a translation device.

[0489] The flexible battery 4103 of the main body 4100a can be charged from the flexible battery 4111 of the case 4110. The flexible battery 4111 and the flexible battery 4103 can be bent and can be mounted on a curved portion.

[0490] 29A to 29C show examples of eyeglass-type devices different from those described above. Fig. 29A is a perspective view of an eyeglass-type device 5000.

[0491] The glasses-type device 5000 has a function as a so-called mobile information terminal, and can execute various programs and play various contents by connecting to the Internet. For example, the glasses-type device 5000 has a function to display augmented reality content in AR mode. The glasses-type device 5000 may also have a function to display virtual reality content in VR mode. Note that the glasses-type device 5000 may also have a function to display substitutional reality (SR) or mixed reality (MR) content in addition to AR and VR.

[0492] The eyeglass-type device 5000 includes a housing 5001, an optical member 5004, a wearing device 5005, a light-shielding portion 5007, and the like. The housing 5001 preferably has a cylindrical shape. The eyeglass-type device 5000 is preferably configured to be wearable on the user's head. It is more preferable that the housing 5001 of the eyeglass-type device 5000 is worn on the user's head above the outer circumferential line of the head that passes through the eyebrows and ears. By making the housing 5001 into a cylindrical shape that curves along the user's head, the wearability of the eyeglass-type device 5000 can be improved. The housing 5001 is fixed to the optical member 5004. The optical member 5004 is fixed to the wearing device 5005 via the light-shielding portion 5007 or via the housing 5001.

[0493] The eyeglasses-type device 5000 has a display device 5021, a reflector 5022, a flexible battery 5024, and a system unit. The display device 5021, the reflector 5022, the flexible battery 5024, and the system unit are preferably provided inside a housing 5001. The system unit may be provided with a control unit, a storage unit, a communication unit, a sensor, and the like that are included in the eyeglasses-type device 5000. The system unit is also preferably provided with a charging circuit, a power supply circuit, and the like. The flexible battery 5024 is bendable and can be mounted on a curved portion.

[0494] Fig. 29B shows the components of the glasses-type device 5000 in Fig. 29A. Fig. 29B is a schematic diagram for explaining the details of the components of the glasses-type device 5000 shown in Fig. 29A.

[0495] 29B , a flexible battery 5024, a system unit 5026, and a system unit 5027 are provided along the cylinder of a cylindrical housing 5001. In addition, a system unit 5025 is provided along the flexible battery 5024 etc.

[0496] The housing 5001 preferably has a curved cylindrical shape. By providing the flexible battery 5024 along the curved cylinder, the flexible battery 5024 can be efficiently installed in the housing 5001, the space inside the housing 5001 can be used efficiently, and the volume of the flexible battery 5024 can be increased in some cases.

[0497] The housing 5001 has, for example, a cylindrical shape, and the axis of the cylinder is, for example, along a part of an approximately ellipse. Furthermore, it is preferable that the cross section of the cylinder is, for example, approximately ellipse. Alternatively, it is preferable that the cross section of the cylinder has, for example, a part of an ellipse. In particular, when the eyeglass-type device 5000 is worn on the head, it is preferable that the part of the cross section having an ellipse shape is located on the side facing the head when worn. However, one aspect of the present invention is not limited to this. For example, the cross section of the cylinder may have a part that is polygonal (triangle, square, pentagon, etc.).

[0498] The housing 5001 is formed to be curved along the forehead of the user, for example. The housing 5001 is also positioned so as to fit along the forehead, for example.

[0499] The housing 5001 may be configured by combining two or more cases. For example, it may be configured by combining an upper case and a lower case. It may also be configured by combining an inner case (the side worn by the user) and an outer case. It may also be configured by combining three or more cases.

[0500] An electrode may be provided on the housing 5001 in a portion that touches the forehead, and brain waves may be measured by the electrode. Alternatively, an electrode may be provided on the portion that touches the forehead, and information such as the user's sweat may be measured by the electrode.

[0501] A plurality of flexible batteries 5024 may be installed inside the housing 5001 .

[0502] Furthermore, the flexible battery 5024 is preferable because it can be shaped to fit the curved tube. Furthermore, the flexibility of the flexible battery allows for greater freedom of installation inside the housing. The flexible battery 5024, a system unit, and the like are installed inside the cylindrical housing. The system unit is configured, for example, on multiple circuit boards. The multiple circuit boards and the flexible battery are connected using connectors, wiring, and the like. The flexibility of the flexible battery allows for installation while avoiding connectors, wiring, and the like.

[0503] The flexible battery 5024 may be provided inside the housing 5001 as well as inside the wearing device 5005. The housing 5001 has a first part 5102 that is movable and a second part 5103 that is not movable.

[0504] 30A to 30C show examples of head-mounted devices. Figures 30A and 30B show a head-mounted device 5100 having a band-shaped attachment 5105, and the head-mounted device 5100 is connected to a terminal 5150 shown in Figure 30C via a cable 5120.

[0505] 30A shows the first portion 5102 in a closed state, and FIG. 30B shows the first portion 5102 in an open state. When closed, the first portion 5102 has a shape that covers not only the front but also the sides of the face. This can shield the user's field of vision from external light, thereby enhancing the sense of realism and immersion. For example, depending on the content displayed, this can also enhance the sense of fear felt by the user.

[0506] 30A and 30B has a band-shaped wearing device 5105. This makes it less likely to slip off than the configuration shown in Fig. 30A etc., and is therefore suitable for enjoying content that requires a relatively large amount of physical activity, such as an attraction.

[0507] A flexible battery 5107 or the like may be built into the back of the head of the wearing equipment 5105. By balancing the weight of the housing 5101 on the front of the head and the weight of the flexible battery 5107 on the back of the head, the center of gravity of the head-worn device 5100 can be adjusted, improving the wearing comfort.

[0508] Alternatively, a flexible battery 5108 having flexibility may be installed inside the band-shaped wearing device 5105. In the example shown in Fig. 30A, two flexible batteries 5108 are installed inside the wearing device 5105. Using a flexible battery having flexibility is preferable because it can be shaped to fit the curved band-like shape.

[0509] The wearing device 5105 also has a part 5106 that covers the forehead or forehead of the user. By including the part 5106, it is possible to make it less likely to slip off. Furthermore, an electrode can be provided on the part 5106 or on the part of the housing 5101 that touches the forehead, and brain waves can be measured using the electrode.

[0510] This embodiment can be implemented in appropriate combination with other embodiments. [Explanation of Symbols] 100: Electronic device, 101: Housing, 102: Display unit, 103: Power button, 104: Button, 105: Speaker, 106: Microphone, 107: Flexible battery, 109: Sensor, 119: Hinge unit, 120: Cover unit

Claims

1. a sensor that detects the movement of the flexible battery; a charging control circuit having a function of starting or stopping charging of the flexible battery based on a signal from the sensor; When the sensor detects that the flexible battery is in a first unfolded form and when the sensor detects that the flexible battery is in a second curved form, the charging control circuit starts charging the flexible battery. Flexible battery management system.

2. In claim 1, The charging control circuit includes a voltage measurement circuit. Flexible battery management system.

3. In claim 1 or claim 2, the charging control circuit includes a current measurement circuit; Flexible battery management system.

4. In claim 1 or claim 2, the charging control circuit has a temperature sensor; Flexible battery management system.

5. The housing and a flexible battery that can follow the movement of the housing; a sensor for detecting the movement of the flexible battery; a charging control circuit that stops or starts charging the flexible battery based on a signal from the sensor; When the sensor detects that the flexible battery is in a first unfolded form and when the sensor detects that the flexible battery is in a second curved form, the charging control circuit starts charging the flexible battery. electronic equipment.

6. In claim 5, a cover portion located on the outside of the housing; The flexible battery is installed within the cover portion. electronic equipment.

7. In claim 5 or claim 6, The cover portion has a function of sliding relative to the housing. electronic equipment.

8. In claim 5 or claim 6, A space is provided inside the housing, The sensor is installed in the space. electronic equipment.

9. In claim 5 or claim 6, The sensor is a switch, an angular velocity sensor, or a magnetic sensor. electronic equipment.

10. In claim 5, The housing can be folded via a hinge portion, The sensor is installed in the hinge portion. electronic equipment.

11. In claim 10, The sensor includes an expansion / contraction sensor. electronic equipment.

12. In claim 5 or claim 6, In the second embodiment, the radius of curvature of the flexible battery is 5 mm or more. electronic equipment.