Lithium ion secondary battery

Abstract

To provide a lithium ion secondary battery capable of increasing discharge capacity and energy density, and a method for manufacturing the lithium ion secondary battery.SOLUTION: A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer provided over the positive electrode current collector. The positive electrode active material layer includes a plurality of lithium-containing composite oxides each of which is expressed by general formula: LiMPO4 (M is one or more of Fe (II), Mn (II), Co (II), and Ni (II)). The lithium-containing composite oxide is a single crystal particle with a flat shape in which the length in the b-axis direction is shorter than each of the lengths in the a-axis direction and the c-axis direction. The lithium-containing composite oxide is provided over the positive electrode current collector so that the b-axis direction of the single crystal particle intersects with the surface of the positive electrode current collector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lithium ion secondary battery and a method for producing the same. [Background technology]

[0002] In recent years, lithium-ion secondary batteries have been developed. LiFePO4,L, which has an olivine structure, is used as the positive electrode active material for lithium-ion secondary batteries. Lithium-containing composite oxides such as iMnPO4, LiCoPO4, and LiNiPO4 are expected to be The transition metal element (Fe) contained in the lithium-containing composite oxide with an olivine structure , Mn, Co, Ni) are divalent.

[0003] There are several methods for producing lithium-containing composite oxides with an olivine structure, including the solid-state method, hydrothermal method, and sol-gel method. The discharge capacity and To increase the energy density, an active material layer is used to insert and extract ions, which act as carriers. Attempts have been made to reduce the particle size of the active material constituting the electrode and to narrow the width of the particle size distribution. Therefore, as a method for producing a lithium-containing composite oxide having a narrow particle size distribution and a small particle size, Therefore, the hydrothermal method is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 08 / 077447 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a lithium-ion secondary battery using a lithium-containing composite oxide, The high resistance of the composite oxides limits the improvement of discharge capacity and energy density. .

[0006] Therefore, in one aspect of the present invention, a lithium battery capable of increasing discharge capacity and energy density is provided. An object of the present invention is to provide a lithium-ion secondary battery and a method for manufacturing the same. [Means for solving the problem]

[0007] One aspect of the present invention is a lithium ion battery having a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. a lithium ion secondary battery, the positive electrode of which comprises a positive electrode current collector and a positive electrode provided on the positive electrode current collector; The positive electrode active material layer has a plurality of lithium-containing composite oxides. The composite oxides are of the general formula LiMPO4 (where M is Fe(II), Mn(II), Co(I) The lithium-containing composite oxide is represented by one or more of Ni(I), Ni(II). The flattened single crystal grains have a length in the b-axis direction and a length in the a-axis direction. The length in the b-axis direction is typically 5 nm or more and 50 nm or less. In addition, the b-axis of the single crystal grain of the lithium-containing composite oxide forms an arbitrary angle with the surface of the positive electrode current collector. The b-axis of the single crystal grain is in contact with the positive electrode current collector. The b-axis of the single crystal grain is typically aligned along the positive electrode current collector so as to intersect with the surface. It intersects with the surface of the electrode current collector at an angle of 60 degrees or more and 90 degrees or less.

[0008] The lithium-containing composite oxide has an olivine structure. belongs to the orthorhombic space group Pnma(62). The lengths of the particles in the a-axis direction and the c-axis direction are longer than the length of the particles in the b-axis direction. In this case, the lithium-containing composite oxide may be laminated.

[0009] Another embodiment of the present invention is a single crystal grain having a flat shape, wherein the length of the single crystal grain in the b-axis direction is A slurry containing a lithium-containing composite oxide having a particle size of 5 nm or more and 50 nm or less is applied to a positive electrode current collector. After applying pressure or vibration to the slurry containing the lithium-containing composite oxide, The b-axis of the silicon-containing composite oxide has an arbitrary angle with the surface of the positive electrode current collector, and the b-plane of the composite oxide is The lithium-containing composite oxide is provided on a positive electrode current collector so as to be in contact with the current collector. That is, lithium is deposited on the positive electrode current collector so that the b-axis direction of the single crystal grains intersects with the surface of the positive electrode current collector. The present invention is characterized in that a sulphur-containing composite oxide is provided.

[0010] The positive electrode of the lithium ion secondary battery according to one embodiment of the present invention is a flat single crystal grain having a b-axis direction. Lithium-containing composites with an olivine structure in which the length in the a-axis direction is shorter than the lengths in the a-axis and c-axis directions. The positive electrode active material layer has a surface (b surface) including the a-axis and the c-axis. The b-axis is in contact with the positive electrode current collector and has an arbitrary angle with the positive electrode current collector. This allows for easy movement of lithium ions between the current collector and the electrolyte. By having a positive electrode active material layer of this structure in the positive electrode, This reduces the internal resistance and enables higher output. [Effects of the Invention]

[0011] According to one embodiment of the present invention, the discharge capacity of a lithium-ion secondary battery can be increased, It is possible to increase the output of lithium-ion secondary batteries. In addition, the discharge capacity is high, making it possible to increase the output. This makes it possible to fabricate a lithium ion secondary battery that can be used for a variety of purposes. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view illustrating a positive electrode of a lithium ion secondary battery. [Figure 2] 1 is a diagram for explaining the crystal structure of olivine-type LiFePO4. FIG. [Figure 3] FIG. 1 is a perspective view illustrating a method for producing a positive electrode of a lithium ion secondary battery. [Figure 4] FIG. 1 is a cross-sectional view illustrating a lithium-ion secondary battery. [Figure 5] FIG. 1 is a perspective view of an application of a lithium ion secondary battery. [Figure 6] FIG. 1 is a diagram illustrating an example of the configuration of a wireless power supply system. [Figure 7] FIG. 1 is a diagram illustrating an example of the configuration of a wireless power supply system. DETAILED DESCRIPTION OF THE INVENTION

[0013] An example of an embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to the above description, and the embodiments and details thereof may be modified without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications can be made to the above. The present invention should not be construed as being limited to the description of the embodiments. When referring to the drawings, the same reference numerals may be used in common between different drawings. Also, when referring to similar objects, the same hatch pattern is used and when no special symbol is added, There is.

[0014] (Embodiment 1) In this embodiment, a positive electrode of a lithium-ion secondary battery according to one embodiment of the present invention and a manufacturing method thereof will be described. The method will be explained with reference to FIGS.

[0015] FIG. 1 is a perspective view of a positive electrode of a lithium ion secondary battery.

[0016] As shown in FIG. 1(A), a lithium-containing composite acid, which is a positive electrode active material, is deposited on a positive electrode current collector 101. A compound 103 is provided.

[0017] FIG. 1B shows a cathode current collector 101 on which a lithium-containing composite oxide 103a, which is a cathode active material, is deposited. , 103b are stacked.

[0018] Note that on the positive electrode current collector 101, a region containing a plurality of positive electrode active materials is referred to as a positive electrode active material layer. The positive electrode active material layer may contain a conductive additive, a binder, etc., although not shown. The term "material" refers to a substance involved in the insertion and desorption of carrier ions. The composite oxide is the positive electrode active material, but the carbon layer, conductive additive, binder, and solvent are the active materials. is not included.

[0019] The positive electrode current collector 101 is made of a highly conductive material such as platinum, aluminum, copper, titanium, or stainless steel. The positive electrode current collector 101 may be formed in a foil, plate, mesh, or other suitable shape. It can be used.

[0020] The thickness of the positive electrode active material layer is selected from the range of 20 μm to 100 μm. It is preferable to appropriately adjust the thickness of the positive electrode active material layer so as to prevent cracks and peeling. .

[0021] The lithium-containing composite oxide contained in the positive electrode active material layer is a single crystal grain with an olivine structure. Olivine-type lithium-containing composite oxides (general formula LiMPO4 (M is one or more of Fe(II), Mn( II), Co(II), Ni(II))) include, as representative examples, LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4, LiMn a Co b PO4 (a + b is 1 or less, 0 < a < 1, 0 < b < 1), LiF e c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e PO 4 (c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g C o h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 <i < 1), etc.

[0022] Note that the lithium-containing composite oxide may be covered with a carbon layer having a thickness of 10 nm or less, preferably 1 nm or more and 10 nm or less on the surface.

[0023] Here, the shape of the lithium-containing composite oxide, which is the positive electrode active material, will be described using FIG. 1(C). Explain.

[0024] The lithium-containing composite oxide 103 is an orthorhombic crystal and belongs to the space group Pnma(62). The composite oxide 103 has a shorter length in the b-axis direction than the lengths in the a-axis direction and the c-axis direction. In the olivine structure, the lithium ions are aligned along the b axis. In order to diffuse in the b-axis direction, the length in the b-axis direction is set to 5 nm or more and 50 nm or less, preferably 5 nm or more. A thickness of 20 nm or less is preferable because it facilitates the diffusion of lithium ions. and the ratio of the length in the c-axis direction is 0.5 or more and 1.5 or less, preferably 0.8 or more and 1.2 or less, i.e. That is, when the shape on the b-plane is a square or approximately a square, a lithium-containing film is formed on the positive electrode current collector 101. This is preferable because the composite oxide 103 can be densely arranged.

[0025] In addition, the lithium-containing composite oxide has a surface including the a-axis and the c-axis, that is, a b-surface, which is in contact with the positive electrode current collector 10. 1, and the b-axis direction has an arbitrary angle with respect to the surface of the positive electrode current collector 101. The b-axis direction of the crystal grains intersects with the surface of the positive electrode current collector 101. In contrast, the b-axis of the lithium-containing composite oxide typically intersects with the α-axis at an angle of 60 degrees or more and 90 degrees or less. In the olivine structure, lithium ions diffuse in the b-axis direction, so the positive electrode current collector 1 When the b-axis direction intersects with the surface of O1 at an angle between 60 and 90 degrees, more lithium ions are formed. The b-axis direction is preferably perpendicular to the surface of the positive electrode current collector 101. This means that the b-axis has an intersection with the surface of the positive electrode current collector 101. The state in which the b-axis does not intersect with the surface of the positive electrode current collector 101 means that the b-axis does not intersect with the surface of the positive electrode current collector 101. It means that it is parallel to the surface.

[0026] It should be noted that the lithium-containing composite oxide 103 has a length in the b-axis direction compared to the length in the a-axis direction and the c-axis direction. The flat single crystal grains with short lengths in the axial direction were confirmed by scanning electron microscope (SEM) and scanning electron microscope (SEM). Transmission electron microscopy (STEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) For example, the lithium-containing composite oxide 103 It was confirmed by X-ray diffraction (XRD) that the b-axis direction of the single crystal grains intersects with the surface of the positive electrode current collector 101. ) can be determined by measuring the amount of the lithium-containing composite oxide 103. This means that the dark-field image of a transmission electron microscope (TEM) shows uniform contrast and graininess. The world can be judged by its lack of recognition.

[0027] Here, the olivine structure will be explained. Figure 2 shows an olivine-type lithium-containing composite oxide. The unit cell 301 of lithium iron phosphate (LiFePO4), an example of olivine type Lithium iron phosphate has an orthorhombic crystal structure, and the unit cell contains four lithium iron phosphates in the composition formula. (LiFePO4). The olivine structure is a hexagonal close-packed structure of oxide ions. It has a basic skeleton, with lithium, iron, and phosphorus located in the gaps between the closest packed structures.

[0028] In addition, olivine-type lithium iron phosphate (LiFePO4) has tetrahedral sites and two types of octahedral sites. The tetrahedral site has four oxygen atoms at the vertices. The octahedral site has four oxygen atoms at the vertices. The tetrahedral site has six oxygen atoms at the points. The phosphorus 307 is located at the center of the tetrahedral site, and the octahedral site has six oxygen atoms at the points. Lithium 303 or iron 305 is placed at the center of the The octahedral site is called the M1 site, and the octahedral site with iron 305 at the center is called the M2 site. The M1 site is arranged one-dimensionally in the b-axis direction. That is, lithium 303 is arranged one-dimensionally in the <010> direction. For convenience, the lithium 303 and other ions, Or, bonds to atoms are not shown with lines.

[0029] In addition, iron 305 at the adjacent M2 site is bonded in a zigzag pattern with oxygen 309 in between. In addition, oxygen 309, which is bonded between iron 305 at the adjacent M2 site, is located in the tetrahedral site. It is also bonded to phosphorus 307 in the iron-oxygen-phosphorus complex. This results in a continuous iron-oxygen-phosphorus bond.

[0030] The olivine-type lithium iron phosphate may have distortion. In this case, the composition ratio of lithium, iron, phosphorus, and oxygen is not limited to 1:1:1:4. In addition, lithium ions are used as the transition metal (M) in lithium transition metal phosphate (LiMPO4). Transition metals with larger ionic radii, such as manganese, cobalt, or nickel, It may be used.

[0031] As shown in Figure 2, the olivine-type lithium iron phosphate has a stable structure even when it becomes iron phosphate. Therefore, all lithium ions can be inserted and extracted. Lithium iron has thermal stability. Lithium iron phosphate with olivine structure has a high thermal stability. The ions are arranged one-dimensionally in the b-axis direction, and the lithium ions diffuse in the b-axis direction. Therefore, by shortening the length of the single crystal grain in the b-axis direction, the diffusion of lithium ions becomes easier. It is possible.

[0032] The positive electrode shown in this embodiment is a flat single crystal grain, and the b-axis is larger than the a-axis and c-axis. The positive electrode active material layer contains an olivine-type lithium-containing composite oxide having a short length in the a direction. The plane including the axis and the c axis, i.e., the b plane, is in contact with the positive electrode current collector, and in the olivine structure, the lithium The b-axis direction, which is the ion diffusion path, crosses the surface of the positive electrode current collector. The amount of lithium ions diffusing between the electrode and the electrolyte can be increased. The lithium-containing composite oxide shown in the above embodiment can be used as a positive electrode active material for a lithium ion secondary battery. This reduces the internal resistance of the lithium-ion secondary battery, making it possible to achieve high output. In this specification, the discharge capacity of lithium can be increased to the theoretical discharge capacity. It contains a material in which lithium ions exist stably, and is capable of transporting lithium ions, which are carrier ions. For example, a material (solute) in which lithium ions exist stably is called an electrolyte. It contains an electrolyte dissolved in a liquid solvent and a material (solute) in which lithium ions exist stably. The electrolyte includes a solid electrolyte containing a solid electrolyte.

[0033] As shown in FIG. 1(B), in the positive electrode active material layer, a plurality of lithium-containing composite oxides are The stacking structure further increases the discharge capacity of the lithium-ion secondary battery compared to Figure 1(A). can be increased.

[0034] Next, the method for producing the positive electrode of the lithium ion secondary battery shown in Figure 1 will be explained using Figure 3. I will explain.

[0035] A slurry 105 containing a lithium-containing composite oxide 103 is applied onto a positive electrode current collector 101. Thereafter, the slurry containing the lithium-containing composite oxide 103 is applied using a squeegee, a blade, or the like. It is preferable to make the thickness of the slurry 105 approximately uniform. The viscosity of the slurry 105 may be increased by drying. As shown in FIG. 3(A), the lithium-containing composite oxide 103 is randomly deposited on the positive electrode current collector 101. The lithium-containing composite oxide is applied to the surface of the film, and the a-axis, b-axis, and The c-axis direction intersects with the surface of the positive electrode current collector 101. It is a flat single crystal grain with a shorter b-axis length than the axial and c-axis lengths. Therefore, when the a-axis direction or the c-axis direction intersects with the surface of the positive electrode current collector 101, When the a-plane or c-plane of the lithium-containing composite oxide 103 is in contact with the positive electrode current collector 101, As shown in the lithium-containing composite oxide 103c, the lithium-containing composite oxide is distributed on the positive electrode current collector 101 in a high state. Be scattered.

[0036] The lithium-containing composite oxide-containing slurry 105 is a mixture of a lithium-containing composite oxide, a binder, 3(A) and 3(B), the lithium-containing composite The oxide-containing slurry 105 is shown by the dashed line.

[0037] The lithium-containing composite oxide can be produced by a suitable method such as a solid phase method, a hydrothermal method, or a spray pyrolysis method. In addition, the particle size distribution and particle size are small, and the ratio of the length in the a-axis direction and the length in the c-axis direction is In comparison, the hydrothermal method is preferred as a method for producing flat single crystal grains with a short length in the b-axis direction. I wish.

[0038] Binders include starch, carboxymethyl cellulose, and hydroxypropyl cellulose. Polysaccharides such as cellulose, regenerated cellulose, and diacetyl cellulose, as well as polyvinyl chloride, poly Vinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene , polypropylene, polyvinyl alcohol, EPDM (Ethylene Propyl Ethylene Diene Monomer) rubber, sulfonated EPDM rubber, styrene butadiene vinyl polymers such as ethylene rubber, butadiene rubber, and fluororubber, polyethylene oxide, etc. Which polyethers etc.

[0039] As a conductive additive, the material itself is an electronic conductor and is used in lithium-ion secondary batteries. Any material that does not undergo chemical reactions with the substance is acceptable. For example, graphite, carbon fiber, carbon brush Carbon materials such as black, acetylene black, and VGCF (registered trademark), copper, nickel, and aluminum Powders and fibers of metallic materials such as aluminum or silver, or mixtures of these, are examples of this. A conductive additive is a substance that helps the conductivity between active materials, and it is used to connect active materials that are separated from each other. It is a material that is filled to provide electrical conductivity between active materials.

[0040] The lithium-containing composite oxide, binder, and conductive additive are dispersed or dissolved in the slurry. To achieve this, a solvent may be used as appropriate.

[0041] It should be noted that lithium-containing composite oxides with small particle sizes tend to aggregate and are difficult to disperse uniformly in the slurry. Therefore, in order to uniformly disperse the lithium-containing composite oxide in the slurry, It is preferable to use an agent and a dispersion medium appropriately.

[0042] Dispersants include polymer dispersants, surfactant dispersants (low molecular weight dispersants), and inorganic dispersants. Dispersants and dispersion media include alcohol, water, etc. Dispersants and dispersion media are lithium It may be selected appropriately depending on the composite oxide contained.

[0043] Next, physical pressure is applied to the slurry 105 containing the lithium-containing composite oxide 103. As a method for applying physical pressure to the slurry 105 containing the thium-containing composite oxide 103, On the slurry 105 containing the lithium-containing composite oxide 103, a roller, a squeegee, a blade Instead of applying physical pressure, a lithium-containing Ultrasonic vibration may be applied to the slurry containing the lithium-containing composite oxide. In the slurry 105 containing the oxide 103, the a-axis direction or the c-axis direction is the positive electrode current collector 10 The lithium-containing composite oxide 103c intersecting the surface of the positive electrode 101, i.e., the a-plane or the c-plane The lithium-containing composite oxide 103c in contact with the current collector 101 falls over, as shown in FIG. 3(B). The b-axis direction of the lithium-containing composite oxide 103 intersects with the surface of the positive electrode current collector 101. In addition, the surface b of the lithium-containing composite oxide 103 can be made into a positive electrode current collector 10 That is, the lithium-containing composite in the positive electrode current collector 101 can be brought into contact with the The contact area of the oxide 103 can be increased.

[0044] Thereafter, the slurry 105 containing the lithium-containing composite oxide 103 is heated to remove the solvent. At the same time, the lithium-containing composite oxide 103 is fixed with a binder, and the positive electrode active material layer 109 is formed. (See Figure 3(C)). The binder becomes porous and fibrous when heated. , the lithium-containing composite oxide is exposed in the gaps. In FIG. 3(C), the positive electrode active material layer 109 is indicated by a dashed line.

[0045] Through the above steps, a positive electrode for a lithium ion secondary battery can be produced.

[0046] The positive electrode shown in this embodiment is a flat single crystal grain, and the b-axis is larger than the a-axis and c-axis. The positive electrode active material layer contains an olivine-type lithium-containing composite oxide having a short length in the a direction. The plane including the a-axis and the c-axis, i.e., the b-plane, is in contact with the positive electrode current collector and is the diffusion path for lithium ions. The b-axis direction intersects with the surface of the positive electrode current collector. In addition, the positive electrode shown in this embodiment can be used as a lithium ion positive electrode. By using it in lithium-ion secondary batteries, the internal resistance of the battery is reduced and high Furthermore, the discharge capacity can be increased up to the theoretical discharge capacity.

[0047] (Embodiment 2) In this embodiment, a method for forming a positive electrode active material layer containing a solid electrolyte on a positive electrode current collector is described. Here, the first embodiment will be used for the explanation.

[0048] In this embodiment, in the positive electrode active material layer shown in Embodiment 1, lithium is used as the binder. The present invention is characterized by containing a solute for the electrolyte of an ion secondary battery.

[0049] The solute of the electrolyte is capable of transporting lithium ions, which are carrier ions, and A material in which lithium ions exist stably is used. A typical example of an electrolyte solute is LiCl. Lithium such as O4, LiAsF6, LiBF4, LiPF6, and Li(C2F5SO2)2N There is mu salt.

[0050] In addition, a solvent may be used appropriately to disperse or dissolve the electrolyte solute in the slurry. .

[0051] As shown in FIG. 3(A), similarly to the first embodiment, a lithium-containing A slurry 11 containing a composite oxide 103, a binder, and a conductive additive, as well as an electrolyte solute. After that, a process for making the thickness of the slurry 115 uniform and a process for making the thickness of the slurry 115 uniform are performed. A treatment for drying the solvent may be carried out. The slurry 115 containing the lithium-containing composite oxide is shown by the dashed line.

[0052] Next, similarly to the first embodiment, a lithium-containing composite oxide 103 and a binder material were mixed. Alternatively, a physical pressure is applied to the slurry 115 containing the lithium-containing composite oxide 103. Ultrasonic vibration may be applied to the slurry 115. As a result, as shown in FIG. The b-axis direction of the lithium-containing composite oxide 103 intersects with the surface of the positive electrode current collector 101. In addition, the b-side of the lithium-containing composite oxide 103 is attached to the positive electrode current collector 101. It can be in a contact state.

[0053] Thereafter, in the same manner as in the first embodiment, the slurry 115 containing the lithium-containing composite oxide 103 was The solvent is removed by heating, and the lithium-containing composite oxide 103 is fixed with a binder. Then, a positive electrode active material layer filled with a solid electrolyte is formed (see FIG. 3(C)). ), the positive electrode active material layer 119 is indicated by a dashed line.

[0054] According to this embodiment, a cathode having a cathode active material layer filled with a solid electrolyte on a cathode current collector is provided. This allows for the creation of a thin film electrode, which reduces the resistance at the interface between the electrode and the electrolyte. As a result, by using the positive electrode described in this embodiment, The internal resistance is further reduced, and high output and high speed charging and discharging are possible, and the discharge capacity is The capacitance can be increased.

[0055] (Embodiment 3) In this embodiment, a lithium ion secondary battery and a manufacturing method thereof will be described.

[0056] One embodiment of the lithium ion secondary battery of this embodiment will be described with reference to FIG. The cross-sectional structure of a lithium ion secondary battery will be described below.

[0057] FIG. 4 is a cross-sectional view of a lithium ion secondary battery.

[0058] The lithium ion secondary battery 400 is composed of a negative electrode current collector 407 and a negative electrode active material layer 409. a negative electrode 411 formed of a positive electrode current collector 401 and a positive electrode active material layer 403; The separator 413 is sandwiched between the negative electrode 411 and the positive electrode 405. The negative electrode current collector 407 is connected to an external terminal 419. The positive electrode current collector 401 is connected to an external terminal 417. The end of the external terminal 419 is connected to a gasket. That is, the external terminals 417 and 419 are embedded in the gasket 421. It is insulated.

[0059] The negative electrode current collector 407 is made of a highly conductive material such as copper, stainless steel, iron, or nickel. The negative electrode current collector 407 may be in the form of a foil, a plate, a mesh, or the like. Cut.

[0060] The negative electrode active material layer 409 is made of a material capable of absorbing and releasing lithium ions. Lithium, aluminum, graphite, silicon, tin, germanium, etc. are used for the cathode. The negative electrode active material layer 409 may be used alone as a negative electrode without using the negative electrode current collector 407. By comparison, the theoretical lithium storage capacities of germanium, silicon, lithium, and aluminum are If the storage capacity is large, charging and discharging is possible even with a small area, and it functions as a negative electrode. This leads to cost reduction and miniaturization of lithium-ion secondary batteries. The volume of lithium-ion batteries increases by about four times, making the material itself brittle. You need to be very careful.

[0061] The negative electrode active material layer 409 may be pre-doped with lithium. As a method, a lithium layer may be formed on the surface of the negative electrode active material layer 409 by a sputtering method. Alternatively, by providing a lithium foil on the surface of the negative electrode active material layer 409, 09 can be pre-doped with lithium.

[0062] The thickness of the negative electrode active material layer 409 is selected from the range of 20 μm to 100 μm. .

[0063] The negative electrode active material layer 409 may contain a binder and a conductive additive. The binder and conductive additive contained in the positive electrode active material layer shown in embodiment 1 are used as appropriate for the conductive additive. It is possible.

[0064] The positive electrode current collector 401 and the positive electrode active material layer 403 are the same as those of the positive electrode current collector 1 shown in Embodiment 1. 01 and the positive electrode active material layer 109 can be used as appropriate.

[0065] An insulating porous body is used for the separator 413. A typical example of the separator 413 is Examples include cellulose (paper), polyethylene, and polypropylene.

[0066] The solute of the electrolyte 415 is lithium ions, which are carrier ions, as shown in the second embodiment. A material that can transport lithium ions and in which lithium ions are present stably is used appropriately.

[0067] The solvent of the electrolyte 415 is a material that can transport lithium ions. As the solvent for the substance 415, an aprotic organic solvent is preferable. Examples include ethylene carbonate, propylene carbonate, and dimethyl carbonate. , diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetramethylpropional tetrahydrofuran, etc., and one or more of these can be used. By using a polymer material that gels as a solvent for the substance 415, safety, including leakage, is improved. Furthermore, the lithium ion secondary battery 400 can be made thinner and lighter. Typical examples of polymeric materials that are used include silicone gel, acrylic gel, and acrylonitrile gel. Examples include polyethylene oxide, polypropylene oxide, and fluorine-based polymers.

[0068] Furthermore, a solid electrolyte such as Li3PO4 can be used as the electrolyte 415. When a solid electrolyte is used as the electrolyte 415, the separator 413 is not necessary.

[0069] Alternatively, as shown in the second embodiment, a positive electrode active material filled with a solid electrolyte is applied to a positive electrode current collector. A layer may be provided.

[0070] The external terminals 417 and 419 are made of metal such as stainless steel or aluminum. It is possible.

[0071] In this embodiment, the lithium ion secondary battery 400 is a coin-type lithium ion battery. The figure shows a sealed lithium-ion secondary battery, a cylindrical lithium-ion secondary battery, and The lithium ion secondary battery can be formed into various shapes such as a rectangular lithium ion secondary battery. In addition, there are also structures in which a plurality of positive electrodes, negative electrodes, and separators are stacked, and structures in which a plurality of positive electrodes, negative electrodes, and separators are stacked. The structure may be such that the motor is wound around the core.

[0072] Lithium-ion secondary batteries have high energy density and large capacity. These features make it possible to reduce the size and weight of the battery. The positive electrode active material layer has little wear, can be used for a long period of time, and can reduce costs. Olivine is a flattened single crystal grain with a shorter length in the b-axis direction than in the a-axis and c-axis directions. By using this type of lithium-containing composite oxide, the discharge capacity of lithium-ion secondary batteries can be increased. This allows for high output.

[0073] Next, a method for manufacturing the lithium ion secondary battery 400 according to this embodiment will be described.

[0074] First, a method for producing the negative electrode 411 will be described.

[0075] On the negative electrode current collector 407, a negative electrode active material layer 40 is formed by coating, sputtering, vapor deposition, or the like. 9, the negative electrode 411 can be fabricated. Lithium, aluminum, graphite, and silicon foils, plates, or meshes can be used as negative electrodes. Here, the negative electrode is made by pre-doping graphite with lithium.

[0076] Next, the positive electrode 405 is formed by the method for forming a positive electrode described in Embodiment 1 as appropriate.

[0077] Next, the negative electrode 411, the separator 413, and the positive electrode 405 are impregnated with the electrolyte 415. 4, an external terminal 417, a positive electrode 405, a separator 413, a gasket 421, and a negative electrode 411 and external terminal 419 are stacked in this order, and external terminal 417 and external terminal 419 are fastened together by a "coin crimping machine." 419 can be crimped to produce a coin-type lithium ion secondary battery.

[0078] Between the external terminal 417 and the positive electrode 405, or between the external terminal 419 and the negative electrode 411 , spacers, and washers are inserted, and the external terminal 417 and the positive electrode 405 are connected, and the external The connection between the terminal 419 and the negative electrode 411 may be higher.

[0079] (Fourth embodiment) In this embodiment, the application of the lithium ion secondary battery described in the third embodiment is This will be explained using Figure 5.

[0080] The lithium ion secondary battery described in the third embodiment is used in digital cameras, video cameras, etc. Cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), It can be used in electronic devices such as portable game machines, personal digital assistants, and sound players. , electric vehicles, hybrid vehicles, electric rail vehicles, work vehicles, carts, electric wheelchairs, etc. An electric propulsion vehicle can be used, and an example of an electric propulsion vehicle will be described here.

[0081] FIG. 5A shows the configuration of a four-wheeled automobile 500, which is one type of electric propulsion vehicle. 0 is an electric or hybrid vehicle. Car 500 has a lithium-ion battery in its bottom. 5 shows an example in which a lithium-ion secondary battery 502 is provided. In order to clarify the position of the lithium-ion secondary battery 502, only the outline of the battery is shown in FIG. A car 500 and a lithium ion secondary battery 502 mounted in the bottom of the car 500 are shown. The lithium ion secondary battery described in the third embodiment is used as the lithium ion secondary battery 502. The lithium ion secondary battery 502 can be used in plug-in technology and wireless power supply systems. It can be charged by external power supply via the system.

[0082] (Embodiment 5) In this embodiment, a lithium-ion secondary battery according to one embodiment of the present invention is used in a wireless power supply system. (hereinafter referred to as an RF power supply system) is shown in the block diagrams of FIGS. Each block diagram shows the functions of the components in the power receiving device and the power supply device. Although the components are classified by function and shown as independent blocks, the actual components are It is difficult to completely separate these components, and one component may be involved in multiple functions. obtain.

[0083] First, the RF power supply system will be described with reference to FIG.

[0084] The power receiving device 600 is an electronic device or an electric propulsion device that is driven by the power supplied from the power supply device 700. The present invention is applicable to other electric vehicles as well as other devices that are driven by electricity. Examples of such items include cameras such as digital cameras and video cameras, digital photo frames, and mobile phones. Mobile phones, portable game machines, personal digital assistants, sound players, display devices, computers, etc. Representative examples of electric propulsion vehicles include electric vehicles, hybrid vehicles, and railway vehicles. The power supply device 700 may be an electric vehicle, a work vehicle, a cart, an electric wheelchair, etc. It has the function of supplying power to 00.

[0085] 6, the power receiving device 600 includes a power receiving device section 601 and a power load section 610. The power receiving device section 601 includes a power receiving device antenna circuit 602, a signal processing circuit 603, and a lithium The power supply device 700 includes at least a power supply device adapter and a power supply device 602. The device includes at least an antenna circuit 701 and a signal processing circuit 702 .

[0086] The antenna circuit 602 for the power receiving device receives a signal transmitted from the antenna circuit 701 for the power feeding device. or transmits a signal to the power supply device antenna circuit 701. The control circuit 603 processes the signal received by the antenna circuit 602 for the power receiving device and converts the lithium ion Charging the lithium ion secondary battery 604, supplying power from the lithium ion secondary battery 604 to the power supply load unit 610 The signal processing circuit 603 controls the operation of the power receiving device antenna circuit 602. That is, the strength and frequency of the signal transmitted from the power receiving device antenna circuit 602 are controlled. The power supply load unit 610 can control the following: It is a driving unit that receives power and drives the power receiving device 600. A typical example of the power load unit 610 is Examples of power sources include motors, drive circuits, etc., but also include other devices that receive power and drive power receiving devices. The antenna circuit for the power feeding device 701 can be used as appropriate. The power receiving device antenna circuit 602 transmits a signal to the power receiving device antenna circuit 602 or receives a signal from the power receiving device antenna circuit 602. The signal processing circuit 702 receives the signal from the antenna circuit 701 for the power feeding device. The signal processing circuit 702 controls the operation of the power supply device antenna circuit 701. That is, the strength, frequency, etc. of the signal transmitted from the power supply device antenna circuit 701 are controlled. It is possible to control things like:

[0087] The lithium ion secondary battery according to one embodiment of the present invention is used in the RF power supply system described with reference to FIG. The battery is used as the lithium ion secondary battery 604 of the power receiving device 600 in the power receiving device 600.

[0088] By using a lithium ion secondary battery according to one aspect of the present invention in an RF power supply system, Increase the discharge capacity or charge capacity (also called the amount of stored electricity) compared to conventional lithium-ion secondary batteries Therefore, the time interval between wireless power supply can be extended (reducing the hassle of power supplying multiple times). can be omitted).

[0089] In addition, the lithium ion secondary battery according to one embodiment of the present invention can be used in an RF power supply system. Therefore, if the discharge capacity or charge capacity that can drive the power supply load unit 610 is the same as that of the conventional This allows the power receiving device 600 to be made smaller and lighter, thereby reducing the total cost. It is possible.

[0090] Next, another example of an RF power supply system will be described with reference to FIG.

[0091] 7, the power receiving device 600 includes a power receiving device section 601 and a power load section 610. The power receiving device section 601 includes a power receiving device antenna circuit 602, a signal processing circuit 603, and a lithium A lithium ion secondary battery 604, a rectifier circuit 605, a modulation circuit 606, and a power supply circuit 607 are included. The power supply device 700 includes at least a power supply device antenna circuit 701 and a signal A processing circuit 702, a rectifier circuit 703, a modulation circuit 704, a demodulation circuit 705, and an oscillation circuit 706 and at least

[0092] The antenna circuit 602 for the power receiving device receives a signal transmitted from the antenna circuit 701 for the power feeding device. or transmits a signal to the power supply device antenna circuit 701. When receiving a signal transmitted from the power receiving device antenna circuit 701, the rectifier circuit 605 The signal processing circuit 602 generates a DC voltage from the received signal. 03 processes the signal received by the antenna circuit 602 for the power receiving device, and 604 and controls the supply of power from the lithium ion secondary battery 604 to the power supply circuit 607 The power supply circuit 607 supplies the power stored in the lithium ion secondary battery 604. The modulation circuit 606 serves to convert the voltage required by the power supply load unit 610. This is used when transmitting some kind of response from the power supply device 600 to the power supply device 700.

[0093] By including the power supply circuit 607, it is possible to control the power supplied to the power supply load unit 610. Therefore, it is possible to reduce the application of an overvoltage to the power supply load unit 610. This can reduce deterioration and damage to the power receiving device 600.

[0094] Furthermore, by including the modulation circuit 606, a signal can be transmitted from the power receiving device 600 to the power supply device 700. Therefore, it is possible to determine the amount of charge in the power receiving device 600 and ensure that a certain amount of charge is performed. When the power receiving device 600 receives the signal, the power receiving device 600 transmits a signal to the power supplying device 700, and the power supplying device 700 The power supply to the power receiving device 600 can be stopped. As a result, the lithium ion secondary battery By not setting the charge amount of the lithium ion secondary battery 604 to 100%, the number of times the lithium ion secondary battery 604 can be charged is It is possible to increase it.

[0095] The antenna circuit 701 for the power supply device transmits a signal to the antenna circuit 602 for the power receiving device. Alternatively, it has a role of receiving a signal from the power receiving device antenna circuit 602. When a signal is sent to the antenna circuit 602, the signal processing circuit 702 The oscillator circuit 706 is a circuit that generates a signal of a constant frequency. The tuning circuit 704 mixes the signal generated by the signal processing circuit 702 with the constant frequency generated by the oscillation circuit 706. The power supply device antenna circuit 701 has a role of applying a voltage to the power supply device antenna circuit 701 in accordance with a signal of the frequency By doing so, a signal is output from the antenna circuit 701 for the power supply device. When a signal is received from the stationary antenna circuit 602, the rectifier circuit 703 rectifies the received signal. The demodulation circuit 705 demodulates the signal rectified by the rectifier circuit 703 into the power receiving device 6. The signal processing circuit 702 extracts the signal sent from the power supply device 700 to the demodulation circuit 705. Therefore, it plays a role in analyzing the extracted signal.

[0096] Any circuit may be provided between the circuits as long as it can supply RF power. For example, After the power receiving device 600 receives the signal and generates a DC voltage in the rectifier circuit 605, A constant voltage is generated by a circuit such as a DC-DC converter or regulator. By doing so, it is possible to prevent an overvoltage from being applied inside the power receiving device 600. can be done.

[0097] The lithium ion secondary battery according to one embodiment of the present invention is used in the RF power supply system described with reference to FIG. The battery is used as the lithium ion secondary battery 604 of the power receiving device 600 in the power receiving device 600.

[0098] By using a lithium ion secondary battery according to one aspect of the present invention in an RF power supply system, Compared to conventional lithium-ion secondary batteries, the discharge capacity or charge capacity can be increased, The time interval between wireless power transfers can be extended (reducing the need to transfer power multiple times).

[0099] In addition, the lithium ion secondary battery according to one embodiment of the present invention can be used in an RF power supply system. Therefore, if the discharge capacity or charge capacity that can drive the power supply load unit 610 is the same as that of the conventional This allows the power receiving device 600 to be made smaller and lighter, thereby reducing the total cost. It is possible.

[0100] The lithium ion secondary battery according to one embodiment of the present invention is used in the RF power supply system. When the device antenna circuit 602 and the lithium ion secondary battery 604 are stacked, The deformation of the lithium ion secondary battery 604 due to charging and discharging of the lithium ion secondary battery 604 and the The impedance of the antenna circuit 602 for the power receiving device changes due to the change in the shape of the antenna. It is preferable to keep the impedance of the antenna constant. This is because there is a possibility that sufficient power may not be supplied. For example, lithium-ion secondary batteries 604 can be mounted in a battery pack made of metal or ceramic. At this time, the antenna circuit 602 for the power receiving device and the battery pack are often spaced apart by several tens of micrometers or more. desirable.

[0101] In this embodiment, there is no particular limitation on the frequency of the charging signal, and any frequency at which power can be transmitted is acceptable. Any frequency band is acceptable. For example, the charging signal is 135 kHz. It can be in the LF band (long wave), or the HF band (short wave) at 13.56MHz, or 900MHz. It can be in the UHF band (ultra-high frequency) from 1000 to 1 GHz, or in the microwave band of 2.45 GHz. stomach.

[0102] In addition, signal transmission methods include electromagnetic coupling, electromagnetic induction, resonance, and microwave. However, if the surface is wet with rain or mud, In order to reduce energy loss due to the environment, it is necessary to use low frequency bands, specifically short waves. 3MHz to 30MHz, medium wave 300kHz to 3MHz, long wave 30kHz to Electromagnetic induction method using frequencies of 300kHz and ultra-long waves of 3kHz to 30kHz It is desirable to use a resonance method.

[0103] This embodiment mode can be implemented in combination with the above embodiment modes.

Claims

1. a positive electrode current collector; and a positive electrode active material layer on the positive electrode current collector, the positive electrode active material layer has a plurality of lithium-containing composite oxides, The lithium-containing composite oxide is LiFe ｆ Ni ｇ Co ｈ Mn ｉ P.O. ４ (f+g+h+i is equal to or less than 1, 0<f<1, 0<g<1, 0<h<1, 0<i<1), the lithium-containing composite oxide is a single crystal grain having a flat shape in which the length in the b-axis direction is shorter than the lengths in each of the a-axis direction and the c-axis direction, a b-plane of the single crystal grain contacts the positive electrode current collector.

2. In claim 1, The length of the single crystal grain in the b-axis direction is 5 nm or more and 50 nm or less.

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