Lithium-ion secondary battery

Abstract

To provide a positive electrode active material for a lithium ion secondary battery with high capacity and excellent charging and discharging cycle characteristics, a positive electrode active material in which the decrease in capacity in the charging and discharging cycle is suppressed by the use for the lithium ion secondary battery, a secondary battery with high capacity, or a secondary battery with high safety or reliability.SOLUTION: A positive electrode active material includes a first material with a first crack and a second material existing inside the first crack. The first material includes one or more selected from cobalt, manganese, and nickel, lithium, oxygen, magnesium, and fluorine. The second material includes phosphorus and oxygen.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] One aspect of the present invention relates to an article, a method, or a manufacturing method. , machine, manufacture, or composition of matter One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic device. In particular, the present invention relates to a positive electrode active material that can be used in a secondary battery. The present invention relates to a battery, a secondary battery, and an electronic device having a secondary battery.

[0002] In this specification, the term "power storage device" refers to elements and devices in general that have a power storage function. For example, lithium-ion secondary batteries and other storage batteries (also called secondary batteries) This includes lithium ion capacitors and electric double layer capacitors.

[0003] In this specification, the term "electronic device" refers to any device that has a power storage device. Electro-optical devices having a power storage device, and information terminal devices having a power storage device are all electronic devices. [Background technology]

[0004] In recent years, various types of energy storage devices have become available, including lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. The development of lithium-ion batteries, which have high output and high energy density, is particularly active. Secondary batteries are used in mobile phones, smartphones, tablets, or laptops. mobile information terminals, portable music players, digital cameras, medical equipment, next-generation clean energy Hybrid vehicles (HEVs), electric vehicles (EVs), plug-in hybrids Demand for rechargeable vehicles (PHEVs, etc.) is rapidly expanding along with the development of the semiconductor industry. As a source of energy, it has become indispensable in today's information society.

[0005] The characteristics required for lithium-ion secondary batteries are higher energy density and , improved cycle characteristics, safety in various operating environments, and improved long-term reliability.

[0006] Therefore, we developed a positive electrode with the aim of improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries. Improvements to the active material have been investigated (Patent Documents 1 and 2). There are various forms, and Patent Document 3 describes particles having cracks. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-216760 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-261132 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-18985 Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present invention is a method for producing a lithium ion secondary battery having high capacity and excellent charge / discharge cycle characteristics. It is an object of the present invention to provide a positive electrode active material and a manufacturing method thereof. Another object of the present invention is to provide a method for manufacturing a positive electrode active material. When used in lithium-ion secondary batteries, the decrease in capacity during charge / discharge cycles is suppressed. Another object of one embodiment of the present invention is to provide a positive electrode active material having a high capacity. Another object of the present invention is to provide a secondary battery having excellent charge-discharge characteristics. Another object of the present invention is to provide a secondary battery that can maintain a charged state at a high voltage for a long time. The objective of the present invention is to provide a positive electrode active material in which the elution of transition metals such as cobalt is suppressed even when the positive electrode is maintained. Another aspect of the present invention is to provide a secondary battery with high safety or reliability. This is one of the challenges.

[0009] Another embodiment of the present invention is a novel substance, active material particles, a power storage device, or a manufacturing method thereof. One of our goals is to provide a method for

[0010] The description of these problems does not preclude the existence of other problems. It is not necessary for one embodiment to solve all of these problems. It is possible to extract other problems from the claims. [Means for solving the problem]

[0011] (1) One aspect of the present invention is a method for manufacturing a semiconductor device comprising: a first substance having a first crack; and a second material located at the first material, the first material being selected from cobalt, manganese, and nickel. and one or more selected from the group consisting of lithium, oxygen, magnesium, and fluorine, and a second The material is a positive electrode active material having phosphorus and oxygen.

[0012] (2) In the above configuration (1), the phosphorus concentration of the second substance is higher than that of the first substance. The sum of the concentrations of cobalt, manganese, and nickel in the second material is lower than that in the first material. It is preferable.

[0013] (3) In the above-mentioned (1) or (2), the first substance is a layered rock salt type crystal. It is preferred that the structure be:

[0014] (4) In any one of the above (1) to (3), the first substance is in particulate form, The magnesium concentration in the surface layer of the first substance is preferably higher than that in the interior.

[0015] (5) Alternatively, one embodiment of the present invention is a positive electrode including a current collector and a positive electrode active material layer, The cathode active material layer has a first cathode active material and a second cathode active material. and at least one of the first and second positive electrode active materials is a first material having cracks and a second material located inside the cracks. and a second material disposed between the current collector and the first positive electrode active material. The positive electrode has three materials, and the third material has two or more of the elements contained in the second material. do.

[0016] (6) In the above-mentioned (5), the first substance is cobalt, manganese, and nickel. one or more selected from the group consisting of lithium, oxygen, magnesium, and fluorine; The second material preferably comprises phosphorus and oxygen.

[0017] (7) Another embodiment of the present invention is a secondary battery having a positive electrode according to any one of the above structures. be.

[0018] (8) Alternatively, one embodiment of the present invention is a method for manufacturing a semiconductor device using one or more metals selected from cobalt, manganese, and nickel. A first material having a surface, a second material having magnesium, and a third material having fluorine. A first step of mixing the raw material and the raw material to prepare a first mixture, and a second step of heating the first mixture. 2 step, the first mixture heated in the second step, and the fourth mixture having phosphorus. a third step of mixing the material with the material to form a second mixture; and a third step of heating the second mixture. and a fourth step of forming a layered rock salt-type crystal structure from the first material. is a method for producing a positive electrode having a phosphate compound.

[0019] (9) In the above-mentioned configuration (8), the number of phosphorus atoms in the fourth material is Mp. , the sum of the numbers of cobalt, manganese and nickel atoms in the first material is Mm, and M It is preferable that p is 0.01 to 0.12 times Mm. [Effects of the Invention]

[0020] According to one aspect of the present invention, a lithium ion secondary battery having high capacity and excellent charge-discharge cycle characteristics is provided. The present invention provides a positive electrode active material for a battery and a method for producing the same. It is possible to provide a method for producing an active material. Therefore, it is possible to provide a positive electrode active material that suppresses the decrease in capacity during charge / discharge cycles. In addition, a high-capacity secondary battery can be provided. In addition, a secondary battery with excellent charge / discharge characteristics can be provided. Furthermore, even if the charged state at high voltage is maintained for a long time, cobalt It is possible to provide a positive electrode active material in which the elution of transition metals such as zinc is suppressed. In addition, the present invention provides a highly reliable secondary battery. Apparatuses or methods for making them may be provided. [Brief explanation of the drawings]

[0021] [Figure 1] 1A and 1B are diagrams illustrating an example of a positive electrode active material according to one embodiment of the present invention. [Figure 2] 2A and 2B are diagrams illustrating an example of a positive electrode active material according to one embodiment of the present invention. [Figure 3] FIG. 3 illustrates an example of a positive electrode of one embodiment of the present invention. [Figure 4] FIG. 4 illustrates an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 5] FIG. 5 illustrates an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 6] FIG. 6 illustrates an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 7] FIG. 7 illustrates an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 8] FIG. 8 illustrates an example of a positive electrode of one embodiment of the present invention. [Figure 9] FIG. 9 illustrates an example of a positive electrode active material of one embodiment of the present invention. [Figure 10] 10A, 10B, and 10C are diagrams illustrating an example of a positive electrode active material of one embodiment of the present invention. [Figure 11] FIG. 11 is a diagram illustrating the depth of charge and the crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 12] FIG. 12 is a diagram illustrating the depth of charge and the crystal structure of the positive electrode active material. [Figure 13] FIG. 13 is an XRD pattern calculated from the crystal structure. [Figure 14] 14A and 14B are diagrams illustrating the crystal structure and magnetism of a positive electrode active material according to one embodiment of the present invention. [Figure 15] 15A is a diagram illustrating a crystal structure of a positive electrode active material, and FIG. 15B is a diagram illustrating the magnetism of a positive electrode active material of one embodiment of the present invention. [Figure 16]Fig. 16(A) is a diagram explaining a method for charging a secondary battery, Fig. 16(B) is a diagram explaining a method for charging a secondary battery, and Fig. 16(C) is a diagram explaining a charging curve of a secondary battery. [Figure 17] Fig. 17(A) is a diagram explaining a method for charging a secondary battery. Fig. 17(B) is a diagram explaining a method for charging a secondary battery. Fig. 17(C) is a diagram explaining a method for charging a secondary battery. Fig. 17(D) is a diagram explaining a charging curve of a secondary battery. [Figure 18] FIG. 18 is a diagram illustrating a discharge curve of a secondary battery. [Figure 19] Fig. 19(A) is a diagram illustrating a coin-type secondary battery, Fig. 19(B) is a diagram illustrating a coin-type secondary battery, and Fig. 19(C) is a diagram illustrating charging. [Figure 20] Fig. 20(A) is a diagram illustrating a cylindrical secondary battery. Fig. 20(B) is a diagram illustrating a plurality of cylindrical secondary batteries. Fig. 20(C) is a diagram illustrating a plurality of cylindrical secondary batteries. Fig. 20(D) is a diagram illustrating a plurality of cylindrical secondary batteries. [Figure 21] Fig. 21(A) is a diagram illustrating an example of a secondary battery, and Fig. 21(B) is a diagram illustrating an example of a secondary battery. [Figure 22] Fig. 22(A-1) is a diagram explaining an example of a secondary battery. Fig. 22(A-2) is a diagram explaining an example of a secondary battery. Fig. 22(B-1) is a diagram explaining an example of a secondary battery. Fig. 22(B-2) is a diagram explaining an example of a secondary battery. [Figure 23] Fig. 23(A) is a diagram illustrating an example of a secondary battery, and Fig. 23(B) is a diagram illustrating an example of a secondary battery. [Figure 24] FIG. 24 is a diagram illustrating an example of a secondary battery. [Figure 25] Figure 25(A) is a diagram illustrating a laminated secondary battery, Figure 25(B) is a diagram illustrating a laminated secondary battery, and Figure 25(C) is a diagram illustrating a laminated secondary battery. [Figure 26]Figure 26(A) is a diagram illustrating a laminated secondary battery, and Figure 26(B) is a diagram illustrating a laminated secondary battery. [Figure 27] FIG. 27 is a diagram showing the appearance of a secondary battery. [Figure 28] FIG. 28 is a diagram showing the appearance of a secondary battery. [Figure 29] Fig. 29(A) is a diagram for explaining a method for manufacturing a secondary battery, Fig. 29(B) is a diagram for explaining a method for manufacturing a secondary battery, and Fig. 29(C) is a diagram for explaining a method for manufacturing a secondary battery. [Figure 30] Fig. 30(A) is a diagram illustrating a bendable secondary battery. Fig. 30(B1) is a diagram illustrating a bendable secondary battery. Fig. 30(B2) is a diagram illustrating a bendable secondary battery. Fig. 30(C) is a diagram illustrating a bendable secondary battery. Fig. 30(D) is a diagram illustrating a bendable secondary battery. [Figure 31] Figure 31(A) is a diagram illustrating a bendable secondary battery, and Figure 31(B) is a diagram illustrating a bendable secondary battery. [Figure 32] FIG. 32(A) is a diagram illustrating an example of an electronic device. FIG. 32(B) is a diagram illustrating an example of an electronic device. FIG. 32(C) is a diagram illustrating an example of a secondary battery. FIG. 32(D) is a diagram illustrating an example of an electronic device. FIG. 32(E) is a diagram illustrating an example of a secondary battery. FIG. 32(F) is a diagram illustrating an example of an electronic device. FIG. 32(G) is a diagram illustrating an example of an electronic device. FIG. 32(H) is a diagram illustrating an example of an electronic device. [Figure 33] Fig. 33(A) is a diagram illustrating an example of an electronic device, Fig. 33(B) is a diagram illustrating an example of an electronic device, and Fig. 33(C) is a diagram illustrating an example of an electronic device. [Figure 34] FIG. 34 is a diagram illustrating an example of an electronic device. [Figure 35]Fig. 35(A) is a diagram illustrating an example of a vehicle, Fig. 35(B) is a diagram illustrating an example of a vehicle, and Fig. 35(C) is a diagram illustrating an example of a vehicle. [Figure 36] 36(A) and 36(B) show the results of cross-sectional observation of the positive electrode. [Figure 37] 37(A) and 37(B) show the results of cross-sectional observation of the positive electrode. [Figure 38] 38(A) and 38(B) show the results of cross-sectional observation of the positive electrode. [Figure 39] 39(A) and 39(B) show the results of cross-sectional observation of the positive electrode. [Figure 40] 40(A) and 40(B) show the results of cross-sectional observation of the positive electrode. [Figure 41] FIG. 41 shows the results of observing a cross section of the positive electrode. [Figure 42] FIG. 42 shows the results of observing a cross section of the positive electrode. [Figure 43] 43(A) and 43(B) show the results of EELS analysis of the positive electrode. [Figure 44] Figure 44(A) shows the results of EELS analysis of the positive electrode, and Figure 44(B) shows the results of EELS analysis of the positive electrode. [Figure 45] Figure 45(A) shows the results of EELS analysis of the positive electrode, and Figure 45(B) shows the results of EELS analysis of the positive electrode. [Figure 46] FIG. 46 shows the results of the FFT analysis. [Figure 47] 47(A) and 47(B) show charge-discharge cycle characteristics. [Figure 48] FIG. 48 shows the results of the charge tolerance test. [Figure 49] FIG. 49 shows the charge-discharge cycle characteristics. [Figure 50] Figure 50(A) shows the results of the charge tolerance test, and Figure 50(B) shows the results of the charge tolerance test. [Figure 51] 51(A) and 51(B) are diagrams showing charge and discharge curves. [Figure 52] FIG. 52 is a diagram showing cycle characteristics of a secondary battery. [Figure 53] FIG. 53 is a diagram showing the rate of crack occurrence. [Figure 54] Fig. 54(A) shows the results of TEM observation of the positive electrode. Fig. 54(B) shows the results of TEM observation of the positive electrode. Fig. 54(C) shows the results of TEM observation of the positive electrode. Fig. 54(D) shows the results of TEM observation of the positive electrode. Fig. 54(E) shows the results of TEM observation of the positive electrode. [Figure 55] Fig. 55(A) shows the results of TEM observation of the positive electrode. Fig. 55(B) shows the results of TEM observation of the positive electrode. Fig. 55(C) shows the results of TEM observation of the positive electrode. Fig. 55(D) shows the results of TEM observation of the positive electrode. Fig. 55(E) shows the results of TEM observation of the positive electrode. [Figure 56] 56(A) and 56(B) are graphs showing the cycle characteristics of a secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and it is understood by those skilled in the art that various modifications may be made to the modes and details thereof. The present invention will be easily understood by reading the following description of the embodiments. It is not something that is done.

[0023] In this specification, crystal planes and directions are expressed in Miller indices. In crystallography, numbers are usually marked with a superscript bar, but in this specification and other documents, due to limitations on the notation used in the application, numbers are marked with a superscript bar. Instead of putting a bar above the letter, a number may be expressed by putting a - (minus sign) before it. Also, individual orientations that indicate directions within a crystal are [ ], and collective orientations that indicate all equivalent directions are The symbols are < >, individual crystal faces are ( ), and collective faces with equivalent symmetry are {}. Each one expresses something.

[0024] In this specification, segregation refers to a phenomenon in which a solid consisting of multiple elements (e.g., A, B, C) This refers to the phenomenon in which a certain element (e.g., B) is distributed spatially non-uniformly.

[0025] In this specification, the surface layer of particles of active material or the like refers to the region from the surface to about 10 nm. The surface caused by cracks or fractures can also be called the surface. , called the inside.

[0026] In the present specification and the like, the layered rock salt type crystals of the composite oxide containing lithium and a transition metal The structure is a rock salt type ion arrangement in which cations and anions are arranged alternately, and The lithium atoms are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It is possible for defects such as cation or anion deficiencies to exist. Strictly speaking, the layered rock salt crystal structure is a case where the lattice of the rock salt crystal is distorted. There is.

[0027] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. It is possible for there to be a deficiency of cations or anions.

[0028] In the present specification and the like, the pseudospinel type of the composite oxide containing lithium and a transition metal The crystal structure of this is in the space group R-3m, and is not a spinel-type crystal structure, but it is a cobalt-based Ions such as magnesium ions occupy the oxygen hexacoordinated positions, and the arrangement of cations is similar to that of spinel. It refers to a crystalline structure with symmetry. The pseudospinel type crystalline structure is characterized by the absence of light elements such as lithium. The atoms may occupy the oxygen tetracoordinate positions, and in this case the ionic arrangement is similar to that of the spinel type. It has symmetry.

[0029] The pseudospinel crystal structure has random Li between layers, but the CdCl2 type It can be said that this CdCl2-type similar crystal structure is The crystal structure is shown in Fig. 1 when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 Ni O2), but pure lithium cobaltate or cobalt-rich layered It is known that rock salt type positive electrode active materials do not usually have this crystal structure.

[0030] Layered rock salt crystals and the anions of rock salt crystals are in a cubic close-packed structure (face-centered cubic lattice structure) ) It is assumed that the anions in pseudospinel crystals also have a cubic close-packed structure. When they contact, there exists a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of layered rock salt crystals and pseudospinel crystals is R-3m, and The space groups of the rock salt crystals are Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest Since the space group is different from that of rock salt crystals, which have a perfect symmetry, the crystal plane must be The Lahr index is different between layered rock salt crystals and pseudospinel crystals and between rock salt crystals. In the layered rock salt crystal, pseudospinel crystal, and rock salt crystal, When the orientation of the cubic close-packed structure is aligned, the crystal orientation is roughly the same. There is.

[0031] The crystal orientation of the two regions roughly coincides with each other, as can be seen from TEM (transmission electron microscope) images and STE M (scanning transmission electron microscope) image, HAADF-STEM (high angle annular dark field scanning transmission electron microscope) image This should be judged from images such as annular bright-field scanning transmission electron microscope (ABF-STEM) images. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as a basis for judgment. In TEM images, the arrangement of cations and anions is observed as repeated bright and dark lines. When the orientation of the cubic close-packed structure in the layered rock salt crystal and the rock salt crystal is aligned, the crystal The angle between the repeated bright and dark lines is 5 degrees or less, preferably 2.5 degrees or less. In addition, light elements such as oxygen and fluorine can be clearly observed in TEM images. In some cases, it may not be possible to determine the alignment of the metal elements. do.

[0032] In this specification, the theoretical capacity of the positive electrode active material is the capacity of the positive electrode active material that can be inserted and removed. The theoretical capacity of LiCoO2 is 27 4mAh / g, the theoretical capacity of LiNiO2 is 274mAh / g, the theoretical capacity of LiMn2O4 is 148mAh / g.

[0033] In this specification, the depth of charge when all intercalable and detachable lithium is intercalated is The depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is 0, and the depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is 1. Let's assume that this is the case.

[0034] In this specification, charging refers to transferring lithium ions from the positive electrode to the negative electrode in the battery. The positive electrode active material moves electrons from the negative electrode to the positive electrode in an external circuit. In this case, the process of releasing lithium ions is called charging. Also, when the charge depth is 0.74 or more, 0.9 or less, more specifically, a positive electrode active material with a charge depth of 0.8 to 0.83, This refers to the charged positive electrode active material. For example, in LiCoO2, 219 If the charge is 0.2mAh / g, the positive electrode active material is charged at a high voltage. In O2, under a 25°C environment, the charging voltage is set to 4.525V or more and 4.65V or less (opposite electrode lithium After that, the current value is 0.01C, or The positive electrode active material after constant voltage charging until the current value is about 1 / 5 to 1 / 100 of the high voltage This refers to the positive electrode active material charged with

[0035] Similarly, discharging involves transferring lithium ions from the negative electrode to the positive electrode within the battery and discharging them into the external circuit. The positive electrode active material is lithium. The insertion of ions is called discharging. The positive electrode active material is fully discharged from a high voltage charged state to 90% or more of its charge capacity. For example, in the case of LiCoO2, the charge capacity is 2 If it is 19.2mAh / g, it is charged at a high voltage, and from here it is 90% of the charge capacity. The positive electrode active material after discharging 197.3mAh / g or more is a fully discharged positive electrode active material. In addition, in the case of LiCoO2, the battery voltage is 3V or less (counter electrode lithium) in a 25°C environment. The positive electrode active material after constant current discharge until it becomes Let's assume that this is the case.

[0036] In this specification, a non-equilibrium phase change refers to a phenomenon that causes a non-linear change in a physical quantity. For example, the capacitance (Q) can be obtained by differentiating it with respect to the voltage (V) (dQ / dV). A non-equilibrium phase change occurs before and after the peak in the dQ / dV curve, and the crystal structure changes significantly. It is believed that this is the case.

[0037] (Embodiment 1) In this embodiment, a positive electrode active material and a positive electrode according to one embodiment of the present invention will be described. The positive electrode active material of one embodiment of the present invention can be used for the positive electrode of a secondary battery. The electrode can be used in a secondary battery.

[0038] [Cathode active material] 1(A), 1(B), 2(A) and 2(B) show cross sections of a positive electrode active material 100. show.

[0039] A positive electrode active material 100 shown in FIG.

[0040] The first substance is, for example, a particle. When the first substance is a particle, for example, the particle size is 1 The particle size is preferably between 100 nm and 100 μm. The particle size is calculated, for example, from the scattering of laser light. Alternatively, the particle size can be determined by observing the cross section of the particle and calculating the diameter of the circle from the cross section. It may be calculated as:

[0041] The positive electrode active material 100 shown in FIG. 1B includes a first substance 101. The crack 105 is sometimes referred to as a crack area. A crack may be described as a crevice, a split, or a crack, for example. For example, when observing a cross section of a material, a block may be observed as a slit-shaped region. Also, cracks are, for example, slit-shaped areas and cracks that appear when observing the cross section of a material. It may refer to the surrounding area.

[0042] When observing the cross section of a material, for example, the material is cut to expose the cut surface, and the cut surface is Just observe.

[0043] The positive electrode active material 100 may have cracks 106 as shown in FIG. 1(B). In B), the crack 106 is formed inside the first material 101 or inside the positive electrode active material 100. On the other hand, the crack 105 is located in a portion on the surface of the first substance 101 or in a positive direction. It comes into contact with the surface of the electrode active material 100 .

[0044] The positive electrode active material 100 shown in FIG. 2(A) has a structure similar to that shown in FIG. 1(B), but has a structure similar to that shown in FIG. 2B shows the area surrounded by the dashed line in FIG. An enlarged view of is shown.

[0045] The second material 102 is, for example, located inside the crack. For example, the second material 102 is surrounded by the crack. Alternatively, the second material 102 may be, for example, a crack having a first inner surface and a second inner surface. In this case, the first inner surface and the second inner surface may form a continuous surface. Alternatively, the second material 102 may be located in the gap of a crack. 102 is located in the crack area, for example.

[0046] The first substance 101 has cracks 105, and thus the first substance 101 can be prevented from cracking due to the charge and discharge of the secondary battery. The stress generated during the expansion and contraction of the first material 101 is relieved, and the crack of the first material 101 is prevented. Therefore, it is possible to prevent the deterioration of performance due to charging and discharging of the secondary battery. For example, it may be possible to suppress a decrease in capacity.

[0047] The width 108 of the crack 105 is preferably 2 μm or less, and more preferably 20 nm or more. It is more preferable that the width 108 of the crack 105 is 2 μm or less. For example, it may be difficult to prevent the crack from progressing. Measurement may be performed using a cross-sectional view of the

[0048] The second material 102 preferably has an area adjacent to the crack 105. The surface area of ​​the active material increases due to the cracks 105 in the active material 101, The reaction area with the electrolyte increases. The increase in the reaction area leads to an increase in the irreversible capacity, for example. When the second material 102 comes into contact with the crack 105, the first material 10 This is preferable because it may be possible to reduce the contact area between 1 and the electrolyte and inhibit the reaction with the electrolyte.

[0049] The second substance 102 preferably has a region in contact with the inner surface of the crack 105. In addition, it is preferable that the second substance 102 has high adhesiveness to the inner surface. has a region in contact with the inner surface of the crack 105, By suppressing the progression of the crack 105, the crack 105 can be prevented from adhering to the electrolyte. The increase in the reaction area can be suppressed.

[0050] The crack 105 is formed when the first substance 101 has a crystal structure represented by the R-3m space group. In the case of a layered rock salt crystal structure, the crystals occur on a plane roughly perpendicular to the c-axis. Alternatively, the formation of cracks 105 may expose a surface that is approximately perpendicular to the c-axis. .

[0051] FIG. 9 shows an example of a cross-sectional view of a positive electrode active material 100 according to one embodiment of the present invention. The crack 105 is formed on the surface of the first material 101. The block 105 has a second substance 102 therein.

[0052] FIG. 10A shows an example of a positive electrode active material 100 that does not include a second substance 102 as a comparative example. When the positive electrode active material 100 is used in a secondary battery, the positive electrode active material 100 is In such a case, the following actions are performed: As shown in FIG. 10(B), the crack 105 progresses, e.g., the crack 105 becomes deeper. As the crack progresses, previously unexposed surfaces become exposed, and the surface When the surface of the battery comes into contact with the electrolyte, a reaction may occur. This may increase the irreversible capacity or may result in a decrease in capacity.

[0053] As the crack 105 progresses, the first substance 101 may be broken down as shown in FIG. 10(C). The first substance 101 in particulate form is broken into two or more particles. Furthermore, the first substance 101 cracks, and the positive electrode active layer is exposed. In a positive electrode having the material 100, the positive electrode active material layer may collapse.

[0054] The progress of the cracks 105 significantly reduces the capacity of the secondary battery during charge and discharge cycles. Alternatively, a short circuit may occur between the positive and negative electrodes.

[0055] As shown in FIG. 2B, the second substance 102 is present in the deeper region of the crack 105. The cracks 105 may be separated into the area to be filled with the second substance 102 and the area to be filled with the second substance 102. For example, by having a deeper region that is not filled, the pressing process of the electrode fabrication Or, when the stress generated in the positive electrode active material 100 is relieved during charging and discharging of the secondary battery, There is.

[0056] The first substance is one or more selected from cobalt, manganese, nickel, and aluminum. The first substance preferably has a layered rock salt type crystal structure or a spinel type As the positive electrode active material, for example, a composite oxide having the following crystal structure can be used. In this case, a polyanion-based positive electrode material can be used. For example, materials having an olivine type crystal structure, Nasicon type materials, etc. As the positive electrode active material, for example, a positive electrode material containing sulfur can be used.

[0057] An example of a material with a layered rock salt crystal structure is the composite oxide represented by LiMeO2. The element Me is preferably at least one selected from Co and Ni. LiCoO2 has a large capacity, is stable in the atmosphere, and is relatively thermally stable. In addition, the element Me is more preferable than Co and Ni. In addition to one or more selected from Al and Mn, the metal oxide may also contain one or more selected from Al and Mn.

[0058] An example of a material with a spinel-type crystal structure is a composite oxide represented by LiMe2O4. It is preferable to use a material containing Mn as the element Me. For example, LiM In addition, the element Me contains Ni in addition to Mn. This is preferable because the discharge voltage of the secondary battery may be improved and the energy density may be improved. In addition, lithium-containing materials with a spinel-type crystal structure containing manganese, such as LiMn2O4, The material contains a small amount of lithium nickel oxide (LiNiO2 or LiNi 1-x Me x O2(Me=C By mixing SiO, Al, etc., the characteristics of the secondary battery can be improved, which is preferable. .

[0059] For example, a polyanion-based positive electrode material may be a mixture of oxygen, element X, metal Ae, and metal Me. The metal Me can be Fe, Mn, Co, Ni, Ti , V, Nb or more, the metal Ae is one or more of Li, Na, Mg, the element X is S, It is one or more of P, Mo, W, As, and Si.

[0060] Examples of materials having an olivine-type crystal structure include composite materials (general formula LiMePO4( Me is one or more of Fe(II), Mn(II), Co(II), and Ni(II). It is possible.

[0061] Also, the general formula Li (2-j) MeSiO4 (Me is Fe(II), Mn(II), C A composite material such as one or more of O(II), Ni(II), 0≦j≦2) can be used.

[0062] Also, Ae x M2(XO4)3(Ae=Li, Na, Mg, Me=Fe, Mn, Ti, Nasicon-type compounds represented by the general formula (V, Nb, X = S, P, Mo, W, As, Si) Nasicon-type compounds include Fe2(MnO4)3 and Fe2(SO 4)3, Li3Fe2(PO4)3, etc. Also, as a positive electrode active material, Li2MePO 4F, Li2MeP2O7, Li5MeO4 (Me = Fe, Mn) A mixture can be used.

[0063] Also, polyanionic positive electrode materials containing V can be used. LiVOPO4, β-LiVOPO4, α1-LiVOPO4, LiVPO4F, LiV PO4O, LiVP2O7, LiVOSO4, Li2VOSiO4, LiVMoO6, etc. Examples include:

[0064] A material having a layered structure is preferable because it can sometimes achieve high capacity. Materials with a layered rock salt crystal structure, for example, are prone to cracking. There may be cases where this is the case.

[0065] The second substance 102 is a compound containing an element A, and phosphorus may be used as the element A. The second substance 102 is preferably a compound having a bond between element A and oxygen. It's nice.

[0066] The second substance 102 preferably contains an element D. The element D is lithium, sodium, or the like. Iron, potassium, magnesium, zinc, cobalt, iron, manganese, nickel, aluminum and fluorine. The second material 102 may also contain nitrogen. The second material 102 may also have nitrogen and hydrogen bonds.

[0067] For example, a phosphate compound can be used as the second substance. Phosphate compounds containing element D can be used. Phosphate compounds containing hydrogen in addition to element D can also be used. Acid compounds can be used. Phosphate compounds include ammonium phosphate and An ammonium salt having element D can be used.

[0068] Phosphate compounds include lithium phosphate, sodium phosphate, potassium phosphate, and magnesium phosphate. Nesium, zinc phosphate, aluminum phosphate, ammonium phosphate, lithium dihydrogen phosphate ammonium dihydrogen phosphate, magnesium monohydrogen phosphate, lithium cobalt phosphate, The first substance may be, in particular, lithium phosphate or magnesium phosphate. It is preferable.

[0069] Here, the number of atoms of the element Me contained in the first substance is M M , the element A contained in the second substance The number of children is M A In the first substance 101, for example, M A is M M 0.01 times or more than 0. It is preferably 12 times or less, and more preferably 0.02 times or more and 0.08 times or less. If there are multiple elements Me or A, M and M A As multiple The sum of the atomic numbers of the elements is used.

[0070] For example, in a material having a layered rock salt crystal structure, phosphorus is a transition metal contained in the material. It is thought that substitution with the first substance is unlikely to occur. When a compound having phosphorus is used as the second substance, the first It is thought that the crystal structure of the material (such as lithium cobalt oxide) is unlikely to change. Therefore, it is preferable.

[0071] The concentrations of the elements contained in the first substance 101 and the second substance 102 are determined by, for example, the energy distribution. Energy Dispersive X-ray spectroscopy (EDX) rometry), electron energy loss spectroscopy (EELS) This can be evaluated using methods such as gy-loss spectroscopy.

[0072] The concentration of element A in the second substance 102 may be higher than the concentration of element A in the first substance 101. In addition, the concentration of the element Me in the second substance 102 is preferably It is preferable that the concentration is lower than that.

[0073] When the first substance 101 has a halogen element on its surface, the melting point of the second substance 102 In addition, the second substance 102 may react with the halogen, and the reaction product may be The reaction product may have a lower melting point than the second material 102. do.

[0074] By mixing lithium phosphate with lithium fluoride, the For this reason, lithium phosphate is often used in combination with other materials such as fluorine. When it coexists with halogens, its melting point may be lowered.

[0075] In a manufacturing process of a positive electrode active material according to one embodiment of the present invention, the first substance 101 has a surface containing fluorine. The first substance 101 may contain lithium fluoride, which was used in the manufacturing process. There may be cases where this is the case.

[0076] The melting point of the second substance 102 is lowered, and the fluidity of the second substance 102 is increased. This may make it easier for the object to get inside the rack 105.

[0077] [Positive electrode] 3 shows a cross section of the positive electrode 200. The positive electrode 200 has a positive electrode active material layer 203. The electrode 200 preferably has a current collector 202. The positive electrode active material layer 203 is formed on the current collector 202. The positive electrode active material layer 203 preferably has a region in contact with the current collector 202. .

[0078] The positive electrode active material layer 203 has a plurality of positive electrode active materials 100. In addition to the active material, other materials such as a coating on the surface of the active material, a conductive additive, or a binder may be included. good.

[0079] In FIG. 3, some of the positive electrode active materials 100 contained in the positive electrode active material layer 203 are Examples of the positive electrode active material include a positive electrode active material 100a, a positive electrode active material 100b, a positive electrode active material 100c, and a positive electrode active material 100d. Electrode active material 100d is shown.

[0080] The positive electrode active material layer 203 also contains a third substance 103. The third substance 103 is, for example, The third substance 103 has a particulate shape. For example, the third substance 103 has the same material as the second substance 102. For example, the third substance 103 may contain an element common to the second substance 102. It is preferable to have two or more.

[0081] In the positive electrode 200 shown in FIG. 3, the positive electrode active material 100c is composed of a first material 101c and a second material 101b. The first material 101c and the second material 102c are , a first substance 101 and a second substance 102 can be referenced.

[0082] In the positive electrode 200 shown in FIG. 3, the third material 103 is a positive electrode active material 100a and a positive electrode active material The third material 103 is located between the positive electrode active material 100a and the positive electrode active material 100b. b, the electrical conductivity of the positive electrode active material layer 203 may be increased. In addition, it is possible to suppress a decrease in the adhesiveness of the components inside the positive electrode active material layer 203 due to charge and discharge. This may be possible.

[0083] In the positive electrode 200 shown in FIG. 3, the third material 103 surrounds the positive electrode active material 100b. By this arrangement, the positive electrode active material 100b and the surrounding active materials are connected to each other via the third material 103. It may increase adhesion to

[0084] In the positive electrode 200 shown in FIG. 3, the third material 103 is a positive electrode active material 100d and a current collector 20 2, the positive electrode active material 100d and the third material 103 are interposed between the positive electrode active material 100d and the third material 103. Adhesion to the body 202 may be enhanced.

[0085] For example, when the second substance 102 and the third substance 103 contain phosphorus, the electrolyte The hydrogen fluoride generated by the solution reacts with the second substance 102 or the third substance 103. However, the hydrogen fluoride concentration in the electrolyte may decrease. In this case, hydrogen fluoride may be generated by hydrolysis. Hydrogen fluoride may be generated by the reaction of the PVDF and alkali. By reducing the hydrogen fluoride concentration in the collector, corrosion and peeling of the coating can be suppressed. It may also be possible to prevent the loss of adhesiveness caused by gelation or insolubilization of PVDF.

[0086] Note that the conductive additive and binder are not shown in FIG. The positive electrode active material 100 and the third material 103 are sandwiched between the positive electrode active material 100 and the binder 103, and the plurality of a region sandwiched between the positive electrode active material 100, a region sandwiched between the positive electrode active material 100 and the current collector 202, Located at etc.

[0087] In addition, lithium phosphate may have the conductivity of carrier ions such as lithium, When the positive electrode active material 100 contains lithium phosphate, it has the advantage of being less likely to inhibit the charging and discharging of the secondary battery. There is.

[0088] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, or the like may be used. Furthermore, a fibrous material may be used as the conductive additive. The content of the conductive additive is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. Bottom is more preferable.

[0089] The conductive additive can form an electrically conductive network in the active material layer. The auxiliary agent can maintain the electrical conduction path between the positive electrode active materials. By adding a conductive additive, it is possible to realize an active material layer with high electrical conductivity. do.

[0090] Examples of the conductive additive include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon. Examples of carbon fibers include mesophase pitch carbon fibers. Carbon fibers such as carbon fibers, isotropic pitch-based carbon fibers, etc. can be used. Carbon nanofibers, carbon nanotubes, etc. can be used. The nanotubes can be produced by, for example, a vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as silicon, graphene, and fullerene can be used. Metal powders and fibers such as nickel, aluminum, silver, and gold, as well as conductive ceramic materials can be used.

[0091] A graphene compound may also be used as the conductive additive.

[0092] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and In some cases, the graphene has excellent physical properties, such as high mechanical strength. Graphene compounds have a planar shape. Graphene compounds enable surface contact with low contact resistance. In addition, even if the material is thin, it can have very high conductivity, and a small amount can be used efficiently in the active material layer. Therefore, graphene compounds are used as conductive additives. This is preferable because it is possible to increase the contact area between the active material and the conductive additive. By using a spray-drying device, the entire surface of the active material is covered with graphene, a conductive additive. It is preferable to form the compound as a coating. In addition, electrical resistance may be reduced. Here, examples of the graphene compound include graphene, multigraphene, and the like. It is particularly preferable to use RGO, which may be, for example, graphene oxide ( This refers to a compound obtained by reducing graphene oxide (GO).

[0093] When using an active material with a small particle size, for example, an active material with a particle size of 1 μm or less, the specific surface area of ​​the active material Therefore, a large amount of conductive additive is required. This tends to result in a relatively reduced amount of active material carried. If the amount of the conductive additive decreases, the capacity of the secondary battery will decrease. When graphene compounds are used, they can efficiently form conductive paths even in small amounts. This is particularly preferable because it is possible to avoid reducing the amount of the active material carried.

[0094] As an example, a graphene compound is used as a conductive additive in the positive electrode active material layer 203. An example of the cross-sectional configuration in this case will be described.

[0095] 8 shows a vertical cross-sectional view of the positive electrode active material layer 203. The positive electrode active material layer 203 is made up of a plurality of positive electrode active materials. The material 100 (in FIG. 8, for example, the positive electrode active material 100a, the positive electrode active material 100b, the positive electrode active material a graphene compound 201 as a conductive additive; The graphene compound 201 may be, for example, a graphene compound. Here, the graphene compound 201 may be a sheet or multi-graphene. In addition, the graphene compound 201 preferably has a shape of a plurality of multi-graphs. Graphene, or (and) multiple graphenes may be partially overlapped to form a sheet. stomach.

[0096] In the vertical cross section of the positive electrode active material layer 203, the positive electrode active material layer 203 has a substantially uniform distribution. In FIG. 8, the graphene compound 201 in the form of a sheet is dispersed. 1 is shown schematically by a thick line, but in reality it is a thin film having the thickness of a single layer or multiple layers of carbon molecules. The plurality of graphene compounds 201 are arranged so as to partially cover the plurality of granular positive electrode active material particles 100. or formed so as to be stuck to the surface of a plurality of granular positive electrode active materials 100. Therefore, they are in surface contact with each other.

[0097] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. forming a graphene compound net or graphene net. When the active material is covered with a graphene net, the graphene net can Therefore, the amount of binder can be reduced. This allows for the active material to be used in a smaller amount or not in a larger amount, reducing the proportion of the active material in the electrode volume or weight. The ratio can be improved, that is, the capacity of the secondary battery can be increased.

[0098] Here, graphene oxide is used as the graphene compound 201 and mixed with an active material to form a positive electrode. After forming the layer that will become the active material layer 203, it is preferable to reduce the graphene compound 201. By using graphene oxide, which has extremely high dispersibility in polar solvents, The phenanthroline compound 201 can be dispersed approximately uniformly inside the positive electrode active material layer 203. The solvent is evaporated from the dispersion medium containing uniformly dispersed graphene oxide, and the graphene oxide is then removed. In order to reduce the graphene compound 201, the graphene compound 201 remaining in the positive electrode active material layer 203 is partially They overlap and are dispersed to the extent that they come into surface contact with each other, forming a three-dimensional conductive path. The reduction of graphene oxide may be carried out by, for example, heat treatment or by reducing It may be carried out using a base agent.

[0099] Therefore, unlike granular conductive additives such as acetylene black, which come into point contact with the active material, Since the phenyl compound 201 enables surface contact with low contact resistance, it is not necessary to use a conventional conductive additive. The electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 can be improved with a smaller amount than that of the graphene compound 201. Therefore, the ratio of the positive electrode active material 100 in the positive electrode active material layer 203 can be increased. This makes it possible to increase the discharge capacity of the secondary battery.

[0100] In addition, by using a spray dryer in advance, the entire surface of the active material is covered with the conductive additive. The graphene compound is formed as a coating, and the active material is further bonded to the graphene compound. A conductive path can also be formed.

[0101] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isopropyl Ethylene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene- It is preferable to use a rubber material such as a propylene-diene copolymer. For this purpose, fluororubber can be used.

[0102] As the binder, it is preferable to use, for example, a water-soluble polymer. As the molecule, for example, polysaccharides can be used. cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropyl Cellulose, diacetyl cellulose, regenerated cellulose and other cellulose derivatives, as well as starch In addition, these water-soluble polymers can be used in combination with the above-mentioned rubber materials. It is more preferable to use

[0103] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethacrylic acid. Methyl (Polymethyl methacrylate, PMMA), Sodium polyacrylate, Polyvinyl Polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride Polyvinyl chloride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer It is preferable to use materials such as polyvinyl acetate and nitrocellulose.

[0104] The binder may be used in combination with two or more of the above.

[0105] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, rubber materials have excellent adhesive strength and elasticity, but it is difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, mixing with a material that has a particularly excellent viscosity adjusting effect can be As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. Furthermore, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as cellulose, cellulose acetate, and the like. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxymethylcellulose Cellulose derivatives such as hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose Conductive materials and starch can be used.

[0106] The cellulose derivatives such as carboxymethyl cellulose are, for example, The solubility increases when cellulose is converted into salts such as sodium salts or ammonium salts. The increased solubility of the solubility of the electrode makes it easier to achieve the desired viscosity. It is also possible to improve the dispersibility of the active material and other components when preparing the battery. In the present invention, the cellulose and cellulose derivatives used as binders for the electrodes include: The salts thereof are also included.

[0107] Water-soluble polymers stabilize viscosity by dissolving in water, and also work well with active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stable in aqueous solution. In addition, since it has functional groups, it is easily and stably adsorbed onto the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose can be Many materials have functional groups such as hydroxyl groups and carboxyl groups. It is expected that the polymers will interact with each other and widely cover the surface of the active material.

[0108] When the binder that covers or contacts the surface of the active material forms a film, it is called a passive film. It is expected that the passive film will also act as a barrier to prevent the decomposition of the electrolyte. A film with no electrical conductivity or extremely low electrical conductivity, for example, on the surface of an active material When a passive film is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film suppresses electrical conductivity and does not allow lithium ions to be conducted. It is even more desirable to

[0109] The positive electrode current collector may be made of metals such as stainless steel, gold, platinum, aluminum, titanium, etc. Highly conductive materials such as these alloys can be used. It is preferable that the material does not dissolve at the potential of the positive electrode. Aluminum alloys with added elements such as candium and molybdenum that improve heat resistance It can also be formed from a metal element that reacts with silicon to form silicide. Metal elements that react with silicon to form silicide include zirconium, Titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungste The current collectors are available in foil, plate (sheet), mesh, punched, etc. The current collector may be in the form of a metal, an expanded metal, or the like. It is preferable to use one with a thickness of 5 μm or more and 30 μm or less.

[0110] [Method 1 for preparing positive electrode active material] First, an example of a method for producing a positive electrode active material 100 according to one embodiment of the present invention will be described with reference to FIG. Another example of a specific manufacturing method is shown in FIG.

[0111] First, a first substance is prepared. As an example, lithium, a transition metal, and oxygen are used. A case where a composite oxide having the above structure is used as the first substance will be described.

[0112] <Step S21> First, as shown in step S21 of FIG. 4, a compound having lithium, a transition metal, and oxygen is formed. As materials for the composite oxide, a lithium source and a transition metal source are prepared.

[0113] As the lithium source, for example, lithium carbonate, lithium fluoride, etc. can be used.

[0114] The transition metal may be, for example, at least one of cobalt, manganese, and nickel. can be done.

[0115] When a layered rock salt type crystal structure is used as the first substance, the ratio of the materials is The mixture ratio of cobalt, manganese, and nickel is as follows. Also, the layered rock salt type crystal structure Aluminum may be added to these transition metals within the range of .beta..

[0116] As the transition metal source, oxides, hydroxides, etc. of the above transition metals can be used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As the nickel source, manganese oxide, manganese hydroxide, etc. can be used. As the aluminum source, nickel oxide, nickel hydroxide, etc. can be used. , aluminum oxide, aluminum hydroxide, etc. can be used.

[0117] <Step S22> Next, the lithium source and the transition metal source are mixed together (step S22 in FIG. 4). The mixing can be carried out by a dry method or a wet method. For example, a ball mill, a bead mill, etc. When using a ball mill, for example, zirconia balls can be used as media. It is preferable to use

[0118] <Step S23> Next, the mixed material is heated. This process is called "sintering" to distinguish it from the subsequent heating process. This is sometimes called the first heating or the formation of the first layer. Heating can be performed at temperatures between 800°C and 1100°C. It is preferable to carry out the treatment at a temperature of 900°C or higher and 1000°C or lower, and it is even more preferable to carry out the treatment at about 950°C. If the temperature is too low, the starting materials may not be fully decomposed and melted. On the other hand, if the temperature is too high, the transition metals may be excessively reduced, or lithium may evaporate. For example, defects may occur in which cobalt becomes divalent.

[0119] The heating time is preferably 2 hours or more and 20 hours or less. The temperature should be kept low (for example, a dew point of -50°C or less, preferably -100°C or less). For example, it is preferable to heat at 1000°C for 10 hours, increase the temperature by 200°C / h, and dry The flow rate of the atmosphere is preferably 10 L / min. After that, the heated material is cooled to room temperature. For example, the temperature can be lowered from a specified temperature to room temperature in 10 to 50 hours. It is preferable to set it to below.

[0120] However, cooling to room temperature in step S23 is not essential. 24, Step S25 and Steps S31 to S34 If not, cooling may be to a temperature above room temperature.

[0121] <Steps S24 and S25> The fired material is collected (step S24 in FIG. 4) and used as the first substance 101. A composite oxide containing lithium, a transition metal, and oxygen is obtained (step S25 in FIG. 4). Specifically, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and cobalt oxide are Lithium cobalt oxide with manganese substituted in the cobalt oxide, or nickel-manganese-cobalt oxide Obtain lithium.

[0122] In step S25, a compound having lithium, a transition metal, and oxygen synthesized in advance is used. In this case, steps S21 to S25 may be performed using a composite oxide (see FIG. 5). 24 can be omitted.

[0123] When using a pre-synthesized composite oxide containing lithium, transition metal, and oxygen In this specification, lithium, transition metals, and and a composite oxide containing lithium and oxygen, and a cathode active material containing lithium, cobalt, and Nickel, manganese, aluminum and oxygen are used, and elements other than the above main components are considered impurities. For example, when analyzed by glow discharge mass spectrometry, the total impurity concentration is 10,000p It is preferably 5000 ppm wt or less, and more preferably 5000 ppm wt or less. The total impurity concentration of transition metals such as titanium and arsenic is 3000 ppm wt or less. It is preferable that the content of the hydroxybenzoate is 1500 ppm by weight or less, and more preferable that the content of the hydroxybenzoate is 1500 ppm by weight or less.

[0124] For example, as a pre-synthesized lithium cobalt oxide, Lithium cobalt oxide particles (product name: Cellseed C-10N) can be used. The average particle size (D50) of the powder was approximately 12 μm, and the particle size was measured by glow discharge mass spectrometry (GD-MS). In the impurity analysis, the magnesium concentration and fluorine concentration were 50 ppm wt or less, and Calcium concentration, aluminum concentration and silicon concentration are 100 ppm wt or less, nickel concentration is 100 ppm wt or less The concentration of arsenic is 11 ppm or less, the concentration of sulfur is 500 ppm or less, and the concentration of arsenic is 11 ppm or less. 00 ppm wt or less, and the concentration of other elements other than lithium, cobalt and oxygen is 150 It is lithium cobalt oxide, which is less than ppm wt.

[0125] Alternatively, lithium cobalt oxide particles (product name: Cellseed C- 5H) can also be used. This has an average particle size (D50) of about 6.5 μm and is In the impurity analysis by -MS, the concentration of elements other than lithium, cobalt and oxygen was C- It is lithium cobalt oxide, which is about the same as or less than 10N.

[0126] In this embodiment, cobalt is used as the transition metal, and a pre-synthesized cobalt oxide is used. Lithium particles (Cellseed C-10N manufactured by Nippon Chemical Industry Co., Ltd.) will be used (Figure 5).

[0127] The composite oxide containing lithium, a transition metal, and oxygen in step S25 is formed by removing defects and strain. It is preferable that the crystal structure of the layered rock salt type has few impurities. It is preferable that the composite oxide contains lithium, a transition metal, and oxygen. If a large amount of impurities is included, there is a high possibility that the crystal structure will have many defects or strains.

[0128] Here, the first substance 101 may have cracks. The cracks may be, for example, steps. This occurs in one or more of steps S21 to S25. , which occurs during the baking process in step S23. The number of cracks that occur may change depending on conditions such as speed. It may also occur during processes such as crushing.

[0129] In the positive electrode active material of one embodiment of the present invention, a process for producing the positive electrode active material and a process for producing the positive electrode are We focus on the cracks that occur during the welding process.

[0130] By going through steps S45 to S48 described below, the first substance 101 A compound containing element A is inserted as the second substance 102 into the cracks. Alternatively, the second substance 102 may adhere to the surface of the first substance 101. A coating including the second material 102 may be formed on the surface of the first material 101 .

[0131] Furthermore, after steps S45 to S48 described below, a compound having element A is However, if the particles are not inserted into the cracks in the first substance 101 and exist as particles, That is, the positive electrode active material 100 contains particles of a compound having element A. In this case, the particle does not enter the crack, but is present between the first materials 101 or Alternatively, the particles may be disposed between the first material 101 and the current collector. , may be observed as the third substance 103 mentioned above.

[0132] <Step S45> Next, a compound containing element A is prepared as raw material 901 (step S45 in FIG. 4). The raw material 901 is a material that is used as a raw material for the second material 102 and the third material 103 .

[0133] In step S45, the raw material 901 may be pulverized. For example, a ball mill or A bead mill or the like can be used. The powder obtained after pulverization is classified using a sieve. Good too.

[0134] The raw material 901 is a compound containing element A, and phosphorus can be used as element A. The second substance is preferably a compound having a bond between element A and oxygen.

[0135] For example, a phosphate compound can be used as the second substance. Phosphate compounds containing element D can be used. Element D can be lithium, sodium, potassium, or one selected from the group consisting of aluminum, magnesium, zinc, cobalt, iron, manganese and aluminum The above elements are also available. Phosphate compounds containing hydrogen in addition to element D can also be used. In addition, ammonium phosphate and ammonium salts containing element D are used as phosphate compounds. It can be used.

[0136] Phosphate compounds include lithium phosphate, sodium phosphate, potassium phosphate, and magnesium phosphate. Nesium, zinc phosphate, aluminum phosphate, ammonium phosphate, lithium dihydrogen phosphate Examples of the first substance include magnesium phosphate, lithium cobalt phosphate, etc. In particular, lithium phosphate and magnesium phosphate are preferably used.

[0137] In this embodiment, lithium phosphate is used as the raw material 901 (step S45 in FIG. 5). ).

[0138] <Step S46> Next, the raw material 901 obtained in step S45 and the first substance obtained in step S25 are mixed. The raw material 901 is mixed with the raw material 101 obtained in step S25 (step S46 in FIG. 4). The amount of the first substance 101 is 0.01 mol or more and 0.1 mol or less per 1 mol of the first substance 101. Preferably, the amount of the mixture is 0.02 mol or more and 0.08 mol or less. For example, a ball mill, a bead mill, etc. can be used for the mixing. Classification may also be carried out using a sieve.

[0139] <Step S47> Next, the mixed materials are heated (step S47 in FIG. 4). In some cases, this step may not be necessary. It is preferable to carry out the heating at a temperature of 550°C or higher and lower than 1200°C, and more preferable to carry out the heating at a temperature of 550°C or higher and 950°C or lower. If the temperature is too low, the starting materials may decompose and melt. On the other hand, if the temperature is too high, the transition metal may be excessively reduced, There is a risk of defects occurring due to factors such as lithium evaporation.

[0140] Heating may produce a reaction product between the first substance 101 and the raw material 901 .

[0141] The heating time is preferably 2 hours or more and 60 hours or less. The temperature should be kept low (for example, a dew point of -50°C or less, preferably -100°C or less). For example, it is preferable to heat at 1000°C for 10 hours, increase the temperature by 200°C / h, and dry The flow rate of the atmosphere is preferably 10 L / min. After that, the heated material is cooled to room temperature. For example, the temperature can be lowered from a specified temperature to room temperature in 10 to 50 hours. It is preferable to set it to below.

[0142] However, cooling to room temperature in step S47 is not essential. If there is no problem in carrying out step 48, the cooling may be to a temperature higher than room temperature.

[0143] <Step S48> The fired material is collected (step S48 in FIG. 4) to obtain the positive electrode active material 100.

[0144] [Method 2 for preparing positive electrode active material] Next, referring to FIG. 6, another example of a method for producing a positive electrode active material 100 according to an embodiment of the present invention will be described. Another example of a specific manufacturing method will be described with reference to FIG.

[0145] <Step S11> As shown in step S11 of FIG. 6, first, a fluorine source and chlorine are used as materials for the mixture 902. A halogen source such as a source of fluorine and a magnesium source are prepared. It is also preferable to prepare a lithium source. Desirable.

[0146] As the fluorine source, for example, lithium fluoride, magnesium fluoride, etc. can be used. Among these, lithium fluoride has a relatively low melting point of 848°C, and the annealing process described below It is preferable because it is easily melted. Examples of the chlorine source include lithium chloride, magnesium chloride, etc. Examples of magnesium sources that can be used include magnesium fluoride and magnesium oxide. The lithium source may be cadmium, magnesium hydroxide, magnesium carbonate, etc. For example, lithium fluoride and lithium carbonate can be used as the catalyst. Lithium can be used as both a lithium source and a fluorine source. Sium can be used as both a fluorine source and a magnesium source.

[0147] In this embodiment, lithium fluoride LiF is prepared as a fluorine source and a lithium source, Magnesium fluoride (MgF2) will be prepared as a fluorine source and magnesium source. (Step S11 in FIG. 7). Lithium fluoride LiF and magnesium fluoride MgF2 are Mixing iF:MgF2 at a molar ratio of about 65:35 has the greatest effect in lowering the melting point. On the other hand, if the amount of lithium fluoride is too large, the lithium becomes excessive and the Therefore, lithium fluoride (LiF) and magnesium fluoride (MgF) The molar ratio of LiF to MgF2 is preferably LiF:MgF2=x:1 (0≦x≦1.9). LiF:MgF2=x:1 (0.1≦x≦0.5) is more preferable, and LiF:Mg F2=x:1 (near x=0.33) is more preferable. , and a value greater than 0.9 times but less than 1.1 times that value.

[0148] If the subsequent mixing and grinding steps are to be carried out wet, a solvent is prepared. ketones such as acetone, alcohols such as ethanol and isopropanol, ethers, di- Xanthan Gum, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is more preferable to use an aprotic solvent that is less likely to react with lithium. In this embodiment, acetone is used (see step S11 in FIG. 7).

[0149] <Step S12> Next, the materials of the mixture 902 are mixed and crushed (step S in FIGS. 6 and 7). 12) Mixing can be done either dry or wet, but wet mixing allows for smaller particles to be crushed. For mixing, a ball mill, a bead mill, or the like can be used. When using a ball mill, it is preferable to use, for example, zirconia balls as media. It is preferable to thoroughly carry out this mixing and grinding process to finely pulverize the mixture 902. .

[0150] <Steps S13 and S14> The mixed and crushed materials are collected (step S13 in FIGS. 6 and 7), and the mixture 90 2 is obtained (step S14 in FIGS. 6 and 7).

[0151] The mixture 902 has an average particle diameter (D50: also called median diameter) of 600 nm. It is preferably from 1 μm to 20 μm, and more preferably from 1 μm to 10 μm. If the mixture 902 is pulverized in this way, lithium, transition metals, and When the mixture is mixed with a composite oxide having oxygen, the mixture 902 is formed on the surface of the composite oxide particles. It is easy to make the mixture 902 adhere uniformly to the surface of the composite oxide particles. After heating, halogen and magnesium are thoroughly distributed in the surface layer of the composite oxide particles. If there is a region in the surface layer that does not contain halogen and magnesium, the charging In this case, it may be difficult for the material to have a pseudospinel crystal structure in an electrically charged state, as described below.

[0152] <Steps S21 to S25> Next, through steps S21 to S25, lithium, transition metal, and oxygen are added to the Steps S21 to S25 are described in detail with reference to FIGS. 4 and 5. Please refer to the description in the above.

[0153] <Step S31> Next, the mixture 902 is mixed with a composite oxide containing lithium, a transition metal, and oxygen. (Step S31 in FIGS. 6 and 7). Transition metals TM in oxides and magnesium Mg in Mix 902Mix1 Mix1 of The atomic ratio is TM:Mg Mix1 = 1:y (0.0005≦y≦0.03) Preferably, TM:Mg Mix1 = 1:y (0.001≦y≦0.01) Preferably, TM:Mg Mix1 A ratio of about 1:0.005 is even more preferable.

[0154] The mixing in step S31 is carried out after the mixing in step S12 in order not to destroy the particles of the composite oxide. For example, it is preferable to set the rotation speed to be milder than that of the mixing in step S12. It is preferable to use conditions with less heat or shorter time. For mixing, a ball mill, a bead mill, etc. can be used. When using a ball mill, for example, zirconia balls should be used as the media. is preferred.

[0155] <Steps S32 and S33> The mixed materials are collected (step S32 in FIGS. 6 and 7) to obtain a mixture 903. (Step S33 in FIGS. 6 and 7).

[0156] In this embodiment, the mixture of lithium fluoride and magnesium fluoride is treated with an impurity Although the present invention has been described as a method of adding lithium cobalt oxide with low Instead of the mixture 903 in step S33, a starting material of lithium cobalt oxide may be used. A material containing a magnesium source and a fluorine source and then calcined may be used. The process includes steps S11 to S14 and steps S21 to S25. Since there is no need to separate the processes, it is simple and highly productive.

[0157] Alternatively, lithium cobalt oxide pre-doped with magnesium and fluorine is used. Magnesium and fluorine doped lithium cobalt oxide can be used to This is simpler and allows the steps up to step S32 to be omitted.

[0158] Furthermore, lithium cobalt oxide, to which magnesium and fluorine have been added in advance, In addition, a magnesium source and a fluorine source may be added.

[0159] <Step S34> Next, the mixture 903 is heated. This step is called annealing to distinguish it from the previous heating step. Or it may be called second heating.

[0160] The annealing is preferably carried out at a suitable temperature and time. The particle size and the size of the composite oxide having lithium, transition metal and oxygen in step S25 The temperature and composition of the particles vary depending on the conditions. Small particles require lower temperatures or Shorter times may be more preferable.

[0161] For example, if the average particle diameter (D50) of the particles in step S25 is about 12 μm, annealing The temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The annealing time is, for example, 3 hours or longer. It is preferable that the heating time is 10 hours or more, more preferable that the heating time is 60 hours or more.

[0162] On the other hand, when the average particle diameter (D50) of the particles in step S25 is about 5 μm, the annealing temperature The annealing temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The annealing time is, for example, 1 hour or higher and 10 Preferably, it is less than 1 hour, and more preferably about 2 hours.

[0163] The temperature drop time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0164] When the mixture 903 is annealed, the material with a low melting point (e.g., fluorine) in the mixture 902 is first annealed. It is thought that the lithium ion (lithium chloride, melting point 848°C) melts and is distributed in the surface layer of the composite oxide particles. The presence of this molten material then lowers the melting point of other materials, causing them to melt. For example, magnesium fluoride (melting point 1263°C) melts and turns into a composite oxide. It is thought to be distributed in the surface layer of the particles.

[0165] The elements contained in the mixture 902 distributed in the surface layer are lithium, transition metals, and oxygen. It is believed that the metal is dissolved in the composite oxide having the formula

[0166] The elements contained in the mixture 902 are diffused in the surface and the inside of the composite oxide particles rather than in the inside. Therefore, magnesium and halogens are more likely to dissolve in the surface layer and near the grain boundaries. As will be described later, the magnesium concentration in the surface layer and near the grain boundaries is higher than that in the interior. When the temperature is high, the change in the crystal structure can be more effectively suppressed.

[0167] <Step S35> The annealed material is collected to obtain the first substance 101.

[0168] <Step S45> Next, a compound containing element A is prepared as raw material 901 (steps 6 and 7). For step S45, please refer to the description of FIGS. 4 and 5.

[0169] <Step S46> Next, the raw material 901 obtained in step S45 and the first substance obtained in step S35 are mixed. The raw material 901 is mixed with the raw material 101 obtained in step S25 (step S46 in FIG. 4). The amount of the first substance 101 is 0.01 mol or more and 0.1 mol or less per 1 mol of the first substance 101. Preferably, the amount of the mixture is 0.02 mol or more and 0.08 mol or less. For example, a ball mill, a bead mill, etc. can be used for the mixing. Classification may also be carried out using a sieve.

[0170] <Steps S47 and S48> Next, steps S47 and S48 are carried out to obtain the positive electrode active material 100. For step S47 and step S48, please refer to the descriptions of FIGS. 4 and 5. .

[0171] By producing the positive electrode active material 100 using the production method shown in FIGS. Positive electrode active material 10 having a pseudospinel crystal structure when charged to a charge depth of about 0.88 0 may be obtained. The pseudospinel crystal structure will be described in detail in the embodiment described later. states:

[0172] [How to make the positive electrode] As an example, a method of preparing a slurry and applying the slurry to prepare a positive electrode. This article describes:

[0173] The solvent used for the slurry is preferably a polar solvent. For example, water, methanol, Ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF ), N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO) One or a mixture of two or more kinds can be used.

[0174] First, a positive electrode active material, a conductive additive, and a binder are mixed to prepare a mixture J. A solvent is added to the mixture J and mixed to prepare a mixture K. Here, when preparing the mixture K, Alternatively, kneading at a high viscosity may be performed.

[0175] In the mixing and kneading steps, for example, a kneader can be used.

[0176] Next, the viscosity of the mixture K is measured. After that, a solvent is added as necessary to adjust the viscosity. Through the above steps, a slurry for coating the positive electrode active material layer is obtained.

[0177] Next, a method for forming a positive electrode active material layer on a current collector using the prepared slurry will be described. Reveal.

[0178] First, the slurry is applied onto the current collector. The surface treatment may be, for example, a corona discharge treatment, a plasma treatment, or Here, undercoating is a process in which a slurry is applied to the current collector. Before coating, the positive electrode active material layer is coated with a film to reduce the interface resistance between the positive electrode active material layer and the current collector. It refers to a film formed on the current collector to improve adhesion with the current collector. It is not necessarily required to be in the form of a film, but may be formed in the form of islands. The capacity may be expressed as an active material. For example, a carbon material may be used as the undercoat. Examples of carbon materials include graphite, acetylene black, and ketjen. Carbon black such as Black (registered trademark), carbon nanotubes, etc. can be used. can.

[0179] The slurry can be applied by the slot die method, gravure method, blade method, or a combination of these methods. A continuous coating machine or the like may also be used for coating.

[0180] Next, the solvent of the slurry is evaporated to form the positive electrode active material layer 203. can.

[0181] The solvent evaporation step of the slurry is carried out at a temperature of 50°C or higher and 200°C or lower, preferably 60°C or higher and 150°C or lower. It is recommended to carry out the process at a temperature range of 100°C or less.

[0182] The thickness of the positive electrode active material layer 203 thus formed is preferably 5 μm or more, for example. It is sufficient if the thickness is 300 μm or less, and more preferably 10 μm or more and 150 μm or less.

[0183] The positive electrode active material layer 203 may be formed on both sides of the current collector, or on only one side. Alternatively, the positive electrode active material layer 203 may be formed partially on both sides. It's okay.

[0184] After the solvent is evaporated from the positive electrode active material layer 203, the positive electrode active material layer 203 is compressed by a roll press method, a flat press method, or the like. It is preferable to perform pressing by a method such as the above. Heat may be applied during pressing.

[0185] By pressing the positive electrode, the capacity per volume of the secondary battery can be improved. When the first material contains lithium cobalt oxide, for example, the density of the positive electrode active material layer is preferably Preferably, the concentration is 2.0 g / cc or more and 5.0 g / cc or less, and more preferably, 3.5 g / cc or more and 4.0 g / cc or less. It is less than 0.5g / cc.

[0186] The pressure of the press should be between 100kN / m and 3000kN / m, preferably 500kN / m or more and 2500kN / m or less.

[0187] Pressing the positive electrode may cause cracks to form in the first substance 101. In addition, the adhesion between the first substance 101 and the third substance 103 may be improved. The load on the first substance 101 due to the press can be reduced.

[0188] Here, the second material 102 and the third material 103 have a hardness lower than that of the first material 101. The low hardness makes it possible to easily press the plurality of first objects together. In some cases, a third substance 103 may easily get between the substances 101.

[0189] On the other hand, pressing the positive electrode may cause excessive cracks in the active material. By using the active material and active material layer according to one embodiment of the present invention, excessive cracks in the active material can be prevented. may be able to suppress it.

[0190] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0191] (Embodiment 2) In this embodiment, a structure and the like of a positive electrode active material of one embodiment of the present invention will be described.

[0192] 11 and 12, the positive electrode active material that can be produced by the method of the first embodiment will be described. 11 and 12, cobalt is used as the transition metal in the positive electrode active material. This section describes the cases where

[0193] [Cathode active material 1] The crystal structure of lithium cobalt oxide (LiCoO2), one of the positive electrode active materials, changes depending on the depth of charge. A typical crystal structure of lithium cobalt oxide is shown in Figure 12.

[0194] As shown in FIG. 12, lithium cobalt oxide at a charge depth of 0 (discharged state) is in the space group R It has a region with a -3m crystal structure, and there are three CoO2 layers in the unit cell. Therefore, this crystal structure is sometimes called an O3 type crystal structure. The term "octahedral structure" refers to a structure in which an octahedral structure in which oxygen atoms are six-coordinated to each other is connected on a plane in an edge-sharing state. do.

[0195] At a charge depth of 1, the crystal structure has the space group P-3m1, and there is Co in the unit cell. There is one O2 layer, so this crystal structure is sometimes called an O1-type crystal structure.

[0196] In addition, when the charge depth is about 0.88, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to the structure of CoO2, such as P-3m1(O1), and R-3m(O 3) and the structure of LiCoO2, and the structure of The crystal structure is sometimes called the H1-3 type crystal structure. has twice the number of cobalt atoms per unit cell of the other structures. In this specification, including 2, the c-axis of the H1-3 type crystal structure is It will be shown as a diagram of half of a unit cell.

[0197] Repeated high voltage charging and discharging to a charge depth of about 0.88 or more. In other words, lithium cobalt oxide has a H1-3 type crystal structure and a R-3m(O3) structure in the discharged state. The crystal structure changes repeatedly between this structure and the other structure (i.e., a non-equilibrium phase change).

[0198] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the arrows, in the H1-3 type crystal structure, the CoO2 layer is Such dynamic structural changes have a negative effect on the stability of the crystal structure. Can be given.

[0199] Furthermore, the difference in volume is large. When comparing the same number of cobalt atoms, the H1-3 type crystal The difference in volume between the structure and the O3-type crystal structure in the discharged state is more than 3.5%.

[0200] In addition, the H1-3 type crystal structure has continuous CoO2 layers such as P-3m1(O1). The resulting structure is likely to be unstable.

[0201] Therefore, repeated high-voltage charging and discharging may cause the crystal structure of lithium cobalt oxide to collapse. There is a match.

[0202] [Cathode active material 2] <Internal>

[0203] FIG. 11 shows another example of the crystal structure of the positive electrode active material before and after charge and discharge.

[0204] The crystal structure at charge depth 0 (discharged state) in Figure 12 is the same as in Figure 12, R-3m(O3). On the other hand, the positive electrode active material in Figure 11 shows the same results as in Figure 12 when the charge depth is about 0.88, which is a sufficient charge depth. This crystal structure of the space group R-3m is referred to as a pseudospin structure in this specification. The pseudo-spinel crystal structure shown in Figure 11 is called the spinel crystal structure. In the figure, the symmetry of the cobalt atom and the symmetry of the oxygen atom are explained by the lithium Although the illustration is omitted, in reality, lithium of about 12 atomic % relative to cobalt is present between the CoO2 layers. In both the O3 type crystal structure and the pseudospinel type crystal structure, C It is preferable for magnesium to exist in a dilute state between the oO2 layers, i.e., at the lithium site. It is also preferable that halogens such as fluorine are present randomly and dilutely at the oxygen sites. It's nice.

[0205] In the positive electrode active material 100, when a large amount of lithium is released by charging at a high voltage, the crystal structure For example, as shown by the dotted line in Figure 11, in these crystal structures, oThere is almost no shift in the O2 layer.

[0206] In addition, the positive electrode active material 100 has an O3 type crystal structure at a charge depth of 0 and a pseudo-O3 type crystal structure at a charge depth of 0.88. The difference in volume per unit cell of the spinel-type crystal structure is 2.5% or less, more specifically, 2. It is less than 2%.

[0207] Therefore, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0208] The pseudospinel crystal structure has the coordinates of cobalt and oxygen in the unit cell as Co( 0,0,0.5), O(0,0,x), and 0.20≦x≦0.25. Cut.

[0209] Magnesium exists randomly and dilutely between the CoO2 layers, i.e., at the lithium sites. This has the effect of suppressing the displacement of the CoO2 layers. Therefore, magnesium is a positive electrode active material 100. It is preferable that magnesium is distributed throughout the particles. In addition, in the process of manufacturing the positive electrode active material 100, heat treatment is preferably performed.

[0210] However, if the heat treatment temperature is too high, cation mixing occurs and magnesium When magnesium is present in the cobalt site, If the temperature of the heat treatment is too high, the effect of maintaining the structure of R-3m will be lost. However, there are concerns about adverse effects such as cobalt being reduced to a divalent state and lithium evaporating. can be.

[0211] Therefore, before the heat treatment to distribute magnesium throughout the particles, cobalt oxide It is preferable to add a halogen compound such as a fluorine compound to lithium. Adding substances to lithium cobalt oxide lowers its melting point. At a temperature where on-mixing is unlikely to occur, it is easy to distribute magnesium throughout the particles. Furthermore, if a fluorine compound is present, the electrolyte will have corrosion resistance to the hydrofluoric acid produced by decomposition. can be expected to improve.

[0212] It should be noted that the positive electrode active material 100 has been previously described as a composite acid containing lithium, cobalt, and oxygen. Although the case where the cobalt is a nickel oxide has been described, the cobalt may contain nickel in addition to the cobalt. In this case, the number of nickel atoms in the sum of the number of cobalt and nickel atoms (Co+Ni) is The ratio of (Ni) Ni / (Co+Ni) is preferably less than 0.1, and more preferably 0.075 More preferably, it is:

[0213] If the battery is charged at a high voltage for a long period of time, transition metals will leach out of the positive electrode active material into the electrolyte. However, by having nickel in the above ratio, the positive electrode activity It may be possible to suppress the elution of transition metals from the substance 100 .

[0214] By adding nickel, the charge / discharge voltage is reduced, so for the same capacity, the voltage is reduced. This can be achieved, which may result in suppressing the elution of transition metals and the decomposition of the electrolyte. Here, the charge / discharge voltage refers to a voltage in the range from zero charge depth to a predetermined charge depth. .

[0215] <Surface layer> It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100. In addition, it is more preferable that the magnesium concentration in the surface layer of the particle is higher than the average of the entire particle. In other words, the magnesium concentration in the particle surface measured by XPS etc. is different from that measured by ICP-MS etc. It is more preferable that the magnesium concentration on the particle surface is higher than the average magnesium concentration on the whole particle. In other words, they are all crystal defects, and when charging, lithium is released from the surface, so the internal This is the part where the lithium concentration is likely to be lower than that of the other part. If the magnesium concentration in the surface layer is high, the change in the crystal structure will be more likely to occur. Furthermore, if the magnesium concentration in the surface layer is high, the electrolyte may break down. It is also expected that the corrosion resistance against hydrofluoric acid produced by dissolution will be improved.

[0216] In addition, the concentration of halogens such as fluorine in the surface layer of the positive electrode active material 100 is higher than the average of the whole particle. The presence of halogen in the surface layer, which is the region in contact with the electrolyte, Corrosion resistance to hydrofluoric acid can be effectively improved.

[0217] In this way, the surface layer of the positive electrode active material 100 has a higher concentration of magnesium and fluorine than the inside. It is preferable that the composition is different from that of the interior, and that the composition is stable at room temperature. Therefore, the surface layer may have a different crystal structure from the interior. For example, at least a part of the surface layer of the positive electrode active material 100 has a rock salt type crystal structure. In addition, when the surface layer and the inside have different crystal structures, the crystal orientation of the surface layer and the inside may be It is preferable that the directions are roughly the same.

[0218] However, if the surface layer is only MgO or only a solid solution structure of MgO and CoO(II), Therefore, the surface layer must contain at least cobalt. In the discharged state, it must also have lithium and have a path for lithium insertion and desorption. It is also preferable that the concentration of cobalt is higher than that of magnesium.

[0219] <Grain boundary> The magnesium or halogen contained in the positive electrode active material 100 is present randomly and dilutely inside. However, it is more preferable that a portion of the metal is segregated at the grain boundaries.

[0220] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is also It is preferable that the halogen concentration at the grain boundary and its vicinity is higher than that in other regions. It is preferable that the thickness of the slit is higher than that of other areas of the slit.

[0221] Like the particle surface, the grain boundary is also a planar defect. Therefore, it is prone to instability and changes in the crystal structure. Therefore, if the magnesium concentration at and near the grain boundary is high, This makes it possible to more effectively suppress changes in the crystal structure.

[0222] In addition, when the magnesium and halogen concentrations at and near the grain boundaries are high, the positive electrode activity Even if a crack occurs along the grain boundary of a particle of material 100, the crack The magnesium and halogen concentrations are high near the surface. The corrosion resistance of the positive electrode active material against hydrofluoric acid can also be improved.

[0223] In this specification, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary. We will do so.

[0224] <Particle size> If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse. On the other hand, if the size is too small, the surface of the active material layer becomes too rough. Problems include difficulty in supporting the active material layer when coating on the body, and excessive reaction with the electrolyte. Therefore, D50 is preferably 1 μm or more and 100 μm or less, and more preferably 2 μm or more and 40 μm or less. It is more preferable that the thickness is 5 μm or less, and further more preferable that the thickness is 5 μm or more and 30 μm or less.

[0225] [Analysis method] A certain positive electrode active material exhibits a pseudospinel crystal structure when charged at a high voltage. The presence or absence of the ions was confirmed by examining the positive electrode charged at high voltage using XRD, electron diffraction, neutron diffraction, and electron scanning. This can be determined by analyzing electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. XRD can analyze the symmetry of transition metals such as cobalt contained in the positive electrode active material with high resolution. The degree of crystallinity and the orientation of the crystals can be compared. Analysis is possible, and sufficient accuracy can be obtained even when measuring the positive electrode obtained by disassembling the secondary battery. , etc., are preferable.

[0226] As mentioned above, the positive electrode active material that exhibits a pseudospinel crystal structure when charged at a high voltage is The feature of this battery is that there is little change in the crystal structure between the state when it is charged at high voltage and the state when it is discharged. A material in which the crystal structure that changes significantly from the discharged state to the charged state occupies 50 wt% or more. The material is not preferable because it cannot withstand high voltage charging and discharging. It is important to note that the desired crystal structure may not be obtained by simply adding magnesium. Although they have in common the fact that they are lithium cobalt oxides containing fluorine and fluorine, they are charged at high voltages. In this state, the pseudo-spinel crystal structure is 60 wt% or more, and the H1-3 crystal structure is In some cases, the content is 50 wt% or more. At a certain voltage, the pseudo-spinel crystal structure It becomes nearly 100 wt%, and when the voltage is further increased, the H1-3 type crystal structure is generated. Therefore, when charged at a high voltage, the positive electrode active material exhibits a pseudospinel crystal structure. To determine whether or not this is the case, analysis of the crystal structure, including XRD, is required. do.

[0227] However, when the positive electrode active material is in a high-voltage charged or discharged state, its crystalline structure changes when it comes into contact with the air. For example, the pseudo-spinel crystal structure may change to the H1-3 crystal structure. Therefore, all samples should be handled in an inert atmosphere such as argon. It is preferable to dry the mixture.

[0228] <Charging method> A certain composite oxide is a positive electrode active material that exhibits a pseudospinel crystal structure when charged at a high voltage. High voltage charging to determine whether or not a coin cell (CR20) is used with a lithium counter electrode is 32 types, diameter 20mm height 3.2mm) can be made and charged.

[0229] More specifically, the positive electrode is formed by mixing a positive electrode active material, a conductive additive, and a binder in a slurry. The above may be applied to a positive electrode current collector made of aluminum foil and used.

[0230] Lithium metal can be used for the counter electrode. When the secondary battery is in a charged state, the potential of the secondary battery is different from the potential of the positive electrode. is the potential of the positive electrode unless otherwise specified.

[0231] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. The above can be used.

[0232] The separator can be made of polypropylene with a thickness of 25 μm.

[0233] The positive and negative electrode cans can be made of stainless steel (SUS). Cut.

[0234] The coin cell prepared under the above conditions was charged at a constant current of 4.6 V and 0.5 C, and then the current value The battery is charged at a constant voltage until the temperature reaches 0.01C. Here, 1C is 137mA / g. After charging in this way, place the coin cell in a glow By disassembling it in the box and removing the positive electrode, the positive electrode active material charged at high voltage can be obtained. When various analyses are carried out after this, the container is sealed in an argon atmosphere to prevent reactions with external components. For example, XRD can be performed in a sealed container in an argon atmosphere. can.

[0235] <xrd> CuKα1 radiation calculated from the pseudospinel crystal structure and H1-3 crystal structure model The ideal powder XRD pattern of LiC at a charge depth of 0 is shown in Figure 13. The ideal X calculated from the crystal structure of oO2(O3) and CoO2(O1) at charge depth 1 The RD patterns are also shown. The patterns of LiCoO2(O3) and CoO2(O1) are ICSD(Inorganic Crystal Structure Database) e) (see Non-Patent Document 5) Reflex Powder Dif, one of the modules of io (BIOVIA) The 2θ range was from 15° to 75°, and Step s ize=0.01, wavelength λ1=1.540562×10 -10 m, λ2 are not set, Mo The nochromator was single. The H1-3 type crystal structure pattern is non-patentable. The pseudospinel pattern was similarly created from the crystal structure information described in Reference 3. The crystal structure was estimated from the XRD patterns of the positive electrode active materials, and the crystal structure was analyzed using TOPAS ver. The XRD analysis was performed using the crystal structure analysis software (Mfg., manufactured by KEKER) as well as the other XRD analyses. A pattern was created.

[0236] As shown in FIG. 13, in the pseudospinel crystal structure, 2θ=19.30±0.20° (1 9.10° to 19.50°), and 2θ = 45.55 ± 0.10° (45.45 Diffraction peaks appear at 2θ = 19. 30±0.10° (19.20° or more and 19.40° or less), and 2θ=45.55±0 A sharp diffraction peak appears at 0.05° (45.50° or more and 45.60° or less). No peaks appear at these positions in the -3 type crystal structure and CoO2 (P-3m1, O1). Therefore, when charged at high voltage, 2θ = 19.30 ± 0.20°, and 2θ The appearance of the peak at 45.55±0.10° indicates that the positive electrode active material 10 according to one embodiment of the present invention This can be said to be a characteristic of 0.

[0237] This shows the crystal structure at charge depth 0 and the crystal structure when charged at high voltage, and the diffraction peaks of the XRD More specifically, the positions where the main diffraction peaks of both are close to each other. The difference in the positions at which peaks appear is 2θ = 0.7 or less, and more preferably 2θ = 0.5 or less.

[0238] In addition, the positive electrode active material that exhibits a pseudo-spinel crystal structure when charged at a high voltage has a structure in which all of the particles The crystal structure does not have to be a pseudo-spinel type. It may contain other crystal structures, or it may be partially However, when the Rietveld analysis was performed on the XRD pattern, The pseudo-spinel crystal structure is preferably 50 wt% or more, and more preferably 60 wt% or more. It is more preferable that the content is 66 wt % or more, and further more preferable that the content is 66 wt % or more. The structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. If the positive electrode active material has the above-mentioned properties, it can have sufficiently excellent cycle characteristics.

[0239] In addition, even after more than 100 charge / discharge cycles from the start of measurement, Rietveld analysis was performed. In this case, the pseudospinel crystal structure is preferably 35 wt% or more, and more preferably 40 wt% or more. It is more preferable that the content is 43 wt % or more, and further more preferable that the content is 43 wt % or more.

[0240] In addition, the crystallite size of the pseudo-spinel structure of the positive electrode active material particles is Therefore, the same X as the positive electrode before charging and discharging is used. Even under RD measurement conditions, a clear peak of pseudospinel crystal structure was observed after high-voltage charging. On the other hand, in simple LiCoO2, some of the structure resembles a pseudospinel crystal structure. Even if it is, the crystallite size will be small and the peak will be broad and small. can be determined from the half-width of the XRD peak.

[0241] In addition, the layered rock salt structure of the particles of the positive electrode active material in the discharged state, which can be estimated from the XRD pattern, In this crystal structure, it is preferable that the lattice constant of the c-axis is small. When a foreign element substitutes for the ammonium site, or when cobalt enters the oxygen tetracoordinate site (A site), Therefore, first, the amount of Co3O4 with a different element substitution and spinel crystal structure is small. A composite oxide with a layered rock salt type crystal structure with few defects is created, and then magnesium is added. Mixing a nesium source and a fluorine source to insert magnesium into the lithium site provides good It is believed that a positive electrode active material that exhibits cycle characteristics can be produced.

[0242] The c-axis lattice constant of the crystal structure of the positive electrode active material in the discharged state is 14.06 before annealing. 0×10 -10 m or less is preferable, and 14.055 × 10 -10 m or less is more preferable, and 1 4.051×10 -10 The lattice constant of the c-axis after annealing is 14 .060×10 -10 m or less is preferable.

[0243] In order to keep the c-axis lattice constant within the above range, it is preferable to have a small amount of impurities, especially cobalt. The amount of transition metals other than manganese and nickel added is preferably small. It is preferable that the content is 1000 ppm wt or less, and more preferably 1500 ppm wt or less. In addition, cation mixing between lithium and cobalt, manganese, or nickel is less likely to occur. It is preferable not to have one.

[0244] The characteristics revealed from the XRD pattern are characteristics regarding the internal structure of the positive electrode active material. In the case of a positive electrode active material with an average particle diameter (D50) of about 1 μm to 100 μm, the inside and In comparison, the volume of the surface layer is very small, so the surface layer of the positive electrode active material 100 is different from the inside. Even if the material has a different crystal structure, it is highly likely that this will not appear in the XRD pattern.

[0245] <esr> Here, using Figures 14 and 15, the difference between the pseudo-spinel crystal structure and other crystal structures will be explained. In the pseudo-spinel crystal structure, the ESR is used to determine whether the As shown in Figure 1 and Figure 14(A), cobalt resides in a site with 6 oxygen coordination. As shown in (B), in cobalt with 6 oxygen coordination, the 3d orbitals are e g Orbit and t 2g Split into orbit and the orbital t, which avoids the direction where oxygen exists. 2g Low orbital energy. Oxygen hexacoordinate Some of the cobalt present at the site is 2g Diamagnetic Co with all orbitals filled 3+ Kobal However, the other part of the cobalt present in the oxygen hexacoordinated site is paramagnetic Co 2+ or Co 4+ This paramagnetic cobalt may be Co 2+ and Co 4 + In both cases, there is one unpaired electron, so it is impossible to distinguish by ESR. Depending on the valence of the element, either valence may be taken.

[0246] If the positive electrode active material does not exhibit a pseudospinel crystal structure when charged at a high voltage, It is said that when charged, the surface layer may have a spinel-type crystal structure that does not contain lithium. In this case, the spinel-type crystal structure shown in Figure 15(A) is Co3O4 This will result in the following:

[0247] When spinel is described by the general formula A[B2]O4, element A is oxygen tetracoordinate and element B is oxygen Therefore, in this specification, the site with 4-coordinated oxygen atoms is called the A site, and the site with 6-coordinated oxygen atoms is called the B site. The site is sometimes called the B site.

[0248] In the spinel-type crystal structure of Co3O4, not only the B site with 6 oxygen atoms but also the B site with 4 oxygen atoms As shown in Figure 15(B), cobalt is present in the A site of the tetrahedral oxygen atom. So, the split e g Orbit and t 2g Among the orbitals, e g The orbital energy is low, so oxygen 4-coordinate Co 2+ , Co 3+ and Co 4+ All of these have unpaired electrons and are paramagnetic. Therefore, if particles with sufficient spinel-type Co3O4 are analyzed by ESR, etc., the oxygen tetracoordination Co 2+ , Co 3+ or Co 4+ A peak due to paramagnetic cobalt should be detected. is.

[0249] However, when charged at a high voltage, the positive electrode active material exhibiting a pseudospinel crystal structure is acidic. The peaks due to the paramagnetic cobalt in 4-coordinate coordination are so small that they cannot be confirmed. Unlike normal spinels, pseudospinels in the literature contain a quantity of oxygen tetracoordinated that can be detected by ESR. It does not contain cobalt, so when charged at high voltage it forms a pseudo-spinel crystal structure. The positive electrode active material shown in Fig. 1 has a small peak derived from spinel-type Co3O4, which can be detected by ESR, etc. The amount of spinel-type Co3O4 may be so small that it cannot be detected. Therefore, the less spinel-type Co3O4, the better.

[0250] <xps> X-ray photoelectron spectroscopy (XPS) measures the surface to a depth of approximately 2 to 8 nm (usually approximately 5 nm). Since it is possible to analyze the area up to the surface, the concentration of each element can be determined for about half of the surface area. It is possible to quantitatively analyze the element bonding state by narrow scan analysis. The quantitative accuracy of XPS is usually about ±1 atomic %, and the lower limit of detection is It depends on the material, but is about 1 atomic percent.

[0251] XPS analysis was performed on the positive electrode active material that exhibits a pseudospinel crystal structure when charged at high voltage. When the concentration of cobalt is taken as 1, the relative value of the magnesium concentration is 0.4 or more. It is preferably 1.5 or less, and more preferably 0.45 or more but less than 1.00. The relative value of the gen concentration is preferably 0.05 or more and 1.5 or less, and more preferably 0.3 or more and 1.00 or less. preferable.

[0252] In addition, XPS analysis was performed on the positive electrode active material that exhibits a pseudospinel crystal structure when charged at a high voltage. When analyzed, the peaks showing the bond energy between fluorine and other elements were 682 eV or higher. It is preferable that the energy is less than 684.3 eV, and more preferably about 684.3 eV. is the binding energy of lithium fluoride, 685 eV, and the binding energy of magnesium fluoride, This is a different value from the combined energy of 686 eV. When the positive electrode active material exhibits a pseudo-spinel crystal structure, it contains fluorine. and magnesium fluoride bonds are preferred.

[0253] Furthermore, we have investigated the positive electrode active material that exhibits a pseudospinel crystal structure when charged at high voltages. When S was analyzed, the peak showing the bond energy between magnesium and other elements was 1302e It is preferable that the energy is 1000 V or more and less than 1304 eV, and more preferably about 1303 eV. This is a different value from the binding energy of magnesium fluoride, 1305 eV. This is close to the binding energy of magnesium oxide. When the positive electrode active material exhibits a pseudospinel crystal structure and contains magnesium, magnesium fluoride Preferably, the bond is other than sodium.

[0254] <edx> Among EDX measurements, the measurement is performed while scanning the area, and the area is evaluated two-dimensionally. It is sometimes called DX area analysis. Also, data on linear areas is extracted from EDX area analysis, Evaluating the distribution of atomic concentrations within positive electrode active material particles is sometimes called line analysis.

[0255] EDX surface analysis (e.g., elemental mapping) revealed that the The concentrations of magnesium and fluorine can be quantitatively analyzed. Line analysis allows for the analysis of magnesium and fluorine concentration peaks.

[0256] EDX analysis of positive electrode active materials that exhibit a pseudospinel-type crystal structure when charged at high voltages When charged at a high voltage, the peak of magnesium concentration in the surface layer was It is found that the crystalline structure exists within a depth of 3 nm from the surface toward the center of the positive electrode active material. Preferably, it exists to a depth of 1 nm, more preferably to a depth of 0.5 nm. It is even more preferable that

[0257] In addition, the fluorine in the positive electrode active material, which exhibits a pseudospinel crystal structure when charged at a high voltage, The distribution of magnesium should preferably overlap with that of magnesium. The peak of the fluorine concentration in the surface layer is at a depth of 3 mm from the surface of the positive electrode active material 100 toward the center. Preferably, the ions are present in the range of 1 nm to a depth of 200 nm, more preferably in the range of 1 nm to a depth of 200 nm, and It is more preferable that the thickness is up to 0.5 nm.

[0258] In addition, we have also conducted line analysis and characterization of the positive electrode active material that exhibits a pseudospinel crystal structure when charged at a high voltage. Or when surface analysis is performed, the atomic number ratio (M g / Co) of magnesium to cobalt near the grain boundaries is preferably 0.020 or more and 0.50 or less. More preferably, it is 0.025 or more and 0.3 0 or less. Even more preferably, it is 0.030 or more and 0.20 or less.

[0259] <dQ / dV vs V curve> In addition, a positive electrode active material that exhibits a spinel-like crystal structure when charged at a high voltage, after being charged at a high voltage, for example, when discharged at a low rate of 0.2C or less, a characteristic voltage change may appear near the end of discharge. This change can be clearly confirmed by the presence of at least one peak in the range of 3.5V to 3.9V in the dQ / dV vs V curve obtained from the discharge curve. In the dQ / dV vs V curve obtained from the discharge curve, at least one peak exists in the range of 3.5V to 3.9V, which can be clearly confirmed.

[0260] This embodiment can be implemented in appropriate combination with other embodiments.

[0261] (Embodiment 3) In this embodiment, a negative electrode, an electrolyte, a separator, and an exterior body that can be used in a secondary battery will be described. Also, a charge / discharge method of the secondary battery will be described.

[0262] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. Also, the negative electrode active material layer may have a conductive assistant and a binder.

[0263] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material, a carbon-based material, or the like can be used.

[0264] As the negative electrode active material, an element capable of performing a charge / discharge reaction by an alloying / dealloying reaction with lithium can be used. For example, silicon, tin, gallium, aluminum, ... Germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a higher capacity than carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. Silicon is preferably used, and compounds containing these elements may also be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag 3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, Examples include InSb and SbSn. Here, charging and discharging occurs through alloying and dealloying reactions with lithium. Elements that can undergo a reaction and compounds containing such elements are sometimes called alloy materials. be.

[0265] In this specification, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to Si O x Here, it is preferable that x has a value close to 1. For example, x can be expressed as The ratio is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0266] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. stomach.

[0267] Examples of graphite include artificial graphite and natural graphite. Examples include carbon 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, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the product, which is sometimes preferable. , flake graphite, and spherical natural graphite.

[0268] When lithium ions are inserted into graphite (the formation of lithium-graphite intercalation compounds), ) shows a low potential similar to that of lithium metal (0.05V to 0.3V vs.Li / Li + This allows lithium-ion secondary batteries to exhibit high operating voltages. Furthermore, graphite has a relatively high capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[0269] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4 Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5 ), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be done.

[0270] In addition, the negative electrode active material is a nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) And preferable.

[0271] When a nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, Nitrides of lithium and transition metals can be used.

[0272] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, lithium oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) A transition metal oxide that does not form an alloy with aluminum may be used as the negative electrode active material. Further materials that produce this include Fe2O3, CuO, Cu2O, RuO2, and Cr2O3 oxides such as CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge Nitrides such as 3N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. This also occurs with fluoride.

[0273] The conductive additive and binder that the negative electrode active material layer can have are: The same materials as the conductive additive and binder that can be used can be used.

[0274] The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0275] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. Preferably, for example, ethylene carbonate (EC), propylene carbonate (PC), Ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyro Lactone, 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 sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in combinations and ratios of:

[0276] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more, the internal temperature of the secondary battery can be prevented from rising due to an internal short circuit or overcharging. Even if the battery is heated, it can prevent explosion and fire of the secondary battery. The electrolyte solution is made of tetravalent cations and anions. ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations Aliphatic onium cations such as imidazolium cations and pyridinium cations The following aromatic cations are also used as anions in electrolytes: monovalent amide-based Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkanes perfluoroalkyl borate anion, tetrafluoroborate anion, perfluoroalkyl bo ... phosphate anion, hexafluorophosphate anion, or perfluoroalkyl phosphate hydrate anions, etc.

[0277] The electrolyte to be dissolved in the solvent is, for example, LiPF6, LiClO4, L iAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO 4. Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9S O3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2 )2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. One or more of these titanium salts may be used in any combination and ratio. This can be done.

[0278] The electrolyte used in secondary batteries is free from granular dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as " It is preferable to use a highly purified electrolyte solution with a low content of impurities. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably 1% or less. It is preferably 0.01% or less.

[0279] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxa) Lithium borate (LiBOB), succinonitrile, adiponitrile, fluorobenzene Additives such as dinitrile compounds such as benzene, cyclohexylbenzene, and biphenyl are added. The concentration of the added material is, for example, 0.1 wt% to 5 wt% of the total solvent. This can be done as follows.

[0280] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0281] The use of polymer gel electrolyte increases safety against leakage etc. The pond can be made thinner and lighter.

[0282] Gelled polymers include silicone gel, acrylic gel, and acrylonitrile gel. , polyethylene oxide gel, polypropylene oxide gel, fluorine-based polymer A gel or the like can be used.

[0283] Examples of polymers include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with side structures, PVDF, polyacrylonitrile, etc., and their For example, a copolymer containing PVDF and hexafluoropropylene ( PVDF-HFP, a copolymer of PVDF and HFP, can be used. The polymer may have a porous shape.

[0284] In addition, instead of the electrolytic solution, a solid electrolyte containing an inorganic material such as a sulfide or oxide, It is possible to use a solid electrolyte containing a polymer material such as PEO (polyethylene oxide). When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire battery can be solidified, there is no risk of leakage, dramatically improving safety.

[0285] [Separator] The secondary battery preferably has a separator. Examples of the separator include: Paper, nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (polyamide) vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable to process the electrode into a shape and place it so as to wrap either the positive electrode or the negative electrode.

[0286] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a combination of these. The ceramic material can be, for example, aluminum oxide. Examples of the fluorine-based material include aluminum particles, silicon oxide particles, etc. For example, PVDF, polytetrafluoroethylene, etc. can be used. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be done.

[0287] Coating with ceramic materials improves oxidation resistance, making it possible to use separators during high-voltage charging and discharging. This suppresses the deterioration of the battery and improves the reliability of the secondary battery. Coating the separator and electrodes makes them adhere more easily, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, making it suitable for secondary batteries. Safety can be improved.

[0288] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. The surface that comes into contact with the negative electrode may be coated with a mixed material of rubber and aramid, and a fluorine-based material may be coated on the surface that comes into contact with the negative electrode. .

[0289] When a separator with a multilayer structure is used, even if the overall thickness of the separator is thin, the safety of the secondary battery can be maintained, so that the capacity per unit volume of the secondary battery can be increased.

[0290] [Outer casing] As the outer casing of the secondary battery, for example, a metal material such as aluminum or a resin material can be used. Also, a film-shaped outer casing can be used. As the film, for example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide etc. A metal thin film excellent in flexibility such as aluminum, stainless steel, copper, nickel, etc. is provided on the film made of such materials, and further, a polyamide-based resin, polyester A three-layer film provided with an insulating synthetic resin film such as a resin film as the outer surface of the outer casing on the metal thin film can be used.

[0291] [Charging and discharging method]

[0292] The charging and discharging of the secondary battery can be performed as follows, for example.

[0292] <CC charging> First, CC charging as one of the charging methods will be described. CC charging is a charging method in which a constant current is passed through the secondary battery throughout the charging period and the charging is stopped when a predetermined voltage is reached. Assume an equivalent circuit of an internal resistance R and a secondary battery capacity C for the secondary battery as shown in Fig. 16(A). In this case, the secondary battery voltage V is the sum of the voltage V applied to the internal resistance R and the voltage V applied to the secondary battery capacity C. B is the sum of the voltage V applied to the internal resistance R and the voltage V applied to the secondary battery capacity R C. C and the voltage V applied to the secondary battery capacity C is the sum.

[0293] During CC charging, as shown in Fig. 16(A), the switch is turned on and a constant current I flows through the secondary battery. During this period, since the current I is constant, V R Ohm's law of \(V = R\times I\) According to the law, the voltage \(V\) across the internal resistance \(R\) R is also constant. On the other hand, the voltage \(V\) across the secondary battery capacity \(C\) increases over time. Therefore, the secondary battery voltage \(V\) C increases over time. B Over time it increases.

[0294] And when the secondary battery voltage \(V\) B reaches a predetermined voltage, for example, 4.3 V, the charging is stopped When the CC charging stops, as shown in FIG. 16(B), the switch turns off and the current \(I\) becomes 0. Therefore, the voltage \(V\) across the internal resistance \(R\) R becomes 0 V. Therefore, the secondary battery voltage \(V\) B decreases.

[0295] Examples of the secondary battery voltage \(V\) during CC charging and after CC charging stops B and the charging current are shown in FIG. 16(C). The secondary battery voltage \(V\) that was increasing during CC charging B is shown to slightly decrease after CC charging stops.

[0296] <CCCV charging> Next, CCCV charging, which is a charging method different from the above, will be described. CCCV charging first performs charging up to a predetermined voltage by CC charging, and then charges until the current flowing during CV (constant voltage) charging decreases, specifically, until it reaches the termination current value.

[0297] During CC charging, as shown in FIG. 17(A), the switch of the constant current power supply is on and the switch of the constant voltage power supply is off, and a constant current \(I\) flows into the secondary battery. During this period, since the current \(I\) is constant, \(V\) R According to Ohm's law, the voltage V applied to the internal resistance R is R On the other hand, the voltage V applied to the secondary battery capacity C is also constant. C increases over time Therefore, the secondary battery voltage V B increases over time.

[0298] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, the CC charge is stopped. Switch to CV charging. During CV charging, as shown in Figure 17(B), the constant voltage The power supply switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B is constant On the other hand, the voltage V applied to the secondary battery capacity C C V increases over time. B = V R +V C Therefore, the voltage V across the internal resistance R R becomes smaller over time The voltage V across the internal resistance R R As becomes smaller, V R = R × I according to Ohm's law , the current I flowing through the secondary battery also becomes smaller.

[0299] When the current I flowing through the secondary battery reaches a predetermined value, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all the switches are turned off as shown in Figure 17(C). The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R is 0V However, the voltage V applied to the internal resistance R due to CV charging R is small enough Therefore, even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly falls .

[0300] During CCCV charging and after stopping CCCV charging, the secondary battery voltage V B and An example of the charging current is shown in FIG. 17(D). Even after stopping CCCV charging, the secondary battery voltage V B hardly shows little drop.

[0301] <CC Discharge> Next, CC discharge, which is one of the discharge methods, will be described. CC discharge is a discharge method in which a constant current flows from the secondary battery throughout the discharge period, and the discharge is stopped when the secondary battery voltage V reaches a predetermined voltage, for example, 2.5V. B becomes at that time.

[0302] Examples of the secondary battery voltage V B and the discharge current during CC discharge are shown in FIG. 18. As the discharge progresses the secondary battery voltage V B shows a decreasing trend.

[0303] Next, the discharge rate and the charge rate will be described. The discharge rate is the relative ratio of the current during discharge to the battery capacity, and is expressed in units of C. In a battery with a rated capacity of X (Ah), a current equivalent to 1C is X (A). When discharging with a current of 2X (A), it is said that the discharge is performed at 2 C, and when discharging with a current of X / 5 (A), it is said that the discharge is performed at 0.2C as such. Also, the charge rate is the same. When charging with a current of 2X (A), it is said that the charge is performed at 2C and when charging with a current of X / 5 (A), it is said that the charge is performed at 0.2C as such. is said.<002188>

[0304] (Embodiment 4) In this embodiment, the form of the secondary battery having the positive electrode active material 100 described in the previous embodiment The materials used in the secondary battery described in this embodiment are the same as those in the previous embodiment. The description of the form can be taken into consideration.

[0305] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. FIG. 19(A) shows a coin-type (single-layer flat) 19(B) is a cross-sectional view of the secondary battery of the same type.

[0306] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. The can 302 is insulated and sealed with a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 30 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode current collector 308 which is set in contact with the negative electrode current collector 308. The negative electrode active material layer 309 is formed by the bonding.

[0307] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are active The material layer only needs to be formed on one side.

[0308] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. Metals such as aluminum and titanium, or alloys of these and other metals (e.g., stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 305. 07 and electrically connect to each other.

[0309] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the negative electrode 307, the positive electrode 304, and the separator 310 are then placed in a sealed container. As shown in Fig. 1B, the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, and negative electrode 307 are placed in the same container. The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are secured together with a gasket 303. The coin-type secondary battery 300 is manufactured by crimping the battery.

[0310] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, high capacity and cycle The coin-type secondary battery 300 can have excellent battery characteristics.

[0311] Here, the flow of current during charging of a secondary battery will be explained using FIG. 19(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current go in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode and the oxidation reaction are reversed, and the reaction potential is The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. In this case, even during charging, discharging, or when a reverse pulse current is applied, Even when a charging current is flowing, the positive electrode is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "+ electrode (plus The electrode is called the "negative electrode" or "-electrode (minus electrode)." The terms anode and cathode are used to describe the relationship between the two electrodes during charging and discharging. Therefore, the anode and cathode are not The term "anode" (negative electrode) will not be used in this specification. When using the terms "positive electrode" or "negative electrode," specify whether it is during charging or discharging. It will also be noted whether it corresponds to the positive pole or the negative pole.

[0312] A charger is connected to the two terminals shown in FIG. 19(C), and the secondary battery 300 is charged. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0313] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG. 20. Cylindrical secondary battery 60 FIG. 20(A) shows an external view of the cylindrical secondary battery 600. FIG. 20(B) shows a cross section of the cylindrical secondary battery 600. As shown in FIG. 20(B), the cylindrical secondary battery 600 has a It has a positive electrode cap (battery lid) 601 and a battery can (external can) 602 on the side and bottom. The positive electrode cap and the battery can (external can) 602 are connected by a gasket (insulating packing) )610.

[0314] Inside the hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed with a separator. The battery element is wound with the battery 605 sandwiched between them. The battery can 602 is closed at one end and open at the other. The battery can 602 is made of nickel, aluminum, or titanium, which is resistant to corrosion by the electrolyte. or alloys of these with other metals (e.g., stainless steel, etc.) In addition, nickel, aluminum, etc. can be used to prevent corrosion by the electrolyte. It is preferable to coat the battery can 602. Inside the battery can 602, the positive electrode, the negative electrode, and The battery element, in which the separator and the battery cell are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries. do.

[0315] The positive and negative electrodes used in cylindrical storage batteries are wound, so active material is formed on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode 603. The positive electrode terminal 607 can be made of a metal material such as aluminum. 603 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC (Positive Temperature Coefficient) element. The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via a positive electrode coefficient 611. The safety valve mechanism 612 releases the positive electrode cap 601 when the internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 cuts off the electrical connection between the positive electrode 604 and the positive electrode 604. It is a thermal resistor whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current. It prevents abnormal heat generation. The PTC element is made of barium titanate (BaTiO3) Semiconductor ceramics and the like can be used.

[0316] 20(C), a plurality of secondary batteries 600 are mounted on a conductive plate 613 and a conductive plate 61 4 to form a module 615. The plurality of secondary batteries 600 may be connected in parallel. They may be connected in series, or may be connected in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, , a large amount of power can be extracted.

[0317] 20(D) is a top view of module 615. For clarity, conductive plate 613 As shown in FIG. 20(D), the module 615 is made up of a plurality of secondary batteries 600. The conductive plate may be placed on the conductive wire 616. In addition, even if a temperature control device 617 is provided between the plurality of secondary batteries 600, When the secondary battery 600 is overheated, the temperature control device 617 cools it down. If 600 is too cold, it can be heated by the temperature control device 617. Therefore, the performance of the module 615 is less affected by the outside temperature. The heat transfer medium is preferably insulating and non-flammable.

[0318] By using the positive electrode active material described in the above embodiment for the positive electrode 604, high capacity and cycle The cylindrical secondary battery 600 can be made to have excellent battery characteristics.

[0319] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0320] 21(A) and 21(B) are diagrams showing the external appearance of the battery pack. 9, the secondary battery 913 has a circuit board 900 and a secondary battery 913. The secondary battery 913 has a label 9 21(B), the secondary battery 913 has a terminal 95 1 and terminal 952.

[0321] The circuit board 900 is fixed with a seal 915. The circuit board 900 has a circuit 912. The terminal 911 is connected to the terminal 951, the terminal 952, and the antenna 91 via the circuit board 900. 4 and the circuit 912. In addition, a plurality of terminals 911 are provided, and the plurality of terminals 911 Each of these terminals may be used as a control signal input terminal, a power supply terminal, or the like.

[0322] The circuit 912 may be provided on the back surface of the circuit board 900. The shape of the antenna is not limited to a coil, but may be, for example, a wire or a plate. Antennas such as face antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas A tena may also be used.

[0323] Alternatively, the antenna 914 may be a flat conductor. This flat conductor may be a conductor for electric field coupling. In other words, the capacitor has two conductors. The antenna 914 may function as a single conductor. This allows only the electromagnetic and magnetic fields to be transmitted. Instead, power can be exchanged using an electric field.

[0324] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. Layer 916 has a function of shielding an electromagnetic field generated by, for example, a secondary battery 913. For example, a magnetic material can be used as 6.

[0325] The structure of the secondary battery is not limited to that shown in FIG.

[0326] For example, as shown in FIGS. 22(A-1) and 22(A-2), 1(B), an antenna is provided on each of a pair of opposing surfaces of the secondary battery 913. FIG. 22(A-1) is an external view showing one of the pair of surfaces, and FIG. 22(A- 2) is an external view showing the other of the pair of surfaces. 21(A) and 21(B) are the same as those in the secondary battery shown in FIG. The explanations given above can be used as appropriate.

[0327] As shown in FIG. 22(A-1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. An antenna 914 is provided, and as shown in FIG. 22(A-2), a pair of surfaces of the secondary battery 913 An antenna 918 is provided on the other side of the layer 917. The layer 917 is, for example, a secondary battery 9 The layer 917 has a function of shielding the electromagnetic field generated by the magnetic field 13. You can use your body.

[0328] By adopting the above structure, the size of both the antenna 914 and the antenna 918 can be increased. The antenna 918 can perform data communication with an external device, for example. The antenna 918 has a function of being able to receive the signal. A method for communication between a secondary battery and other devices via an antenna 918 can be applied. The method is to use NFC (near field communication) between secondary batteries and other devices. It is possible to apply a response method that can be used.

[0329] Alternatively, as shown in FIG. 22(B-1), the secondary battery shown in FIG. 21(A) and FIG. 21(B) A display device 920 may be provided in the terminal 913. The display device 920 is electrically connected to the terminal 911. It is not necessary to provide the label 910 in the area where the display device 920 is provided. The same parts as those of the secondary battery shown in FIG. 21(A) and FIG. 21(B) are shown in FIG. The description of the secondary battery shown in FIG. 21(B) can be used as appropriate.

[0330] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electronic For example, an electroluminescence (EL) display device can be used. By using the polarizer, the power consumption of the display device 920 can be reduced.

[0331] Alternatively, as shown in FIG. 22(B-2), the secondary battery shown in FIG. 21(A) and FIG. 21(B) A sensor 921 may be provided at the terminal 913. The sensor 921 is connected to the terminal 911 via a terminal 922. 21(A) and 21(B). For this, the description of the secondary battery shown in FIGS. 21(A) and 21(B) can be used as appropriate.

[0332] The sensor 921 may be, for example, a sensor for measuring displacement, position, velocity, acceleration, angular velocity, number of rotations, distance, Light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, It is sufficient if it has the function of measuring flow rate, humidity, gradient, vibration, odor, or infrared. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It is also possible to detect data (such as temperature) and store it in memory within the circuit 912.

[0333] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0334] The secondary battery 913 shown in FIG. 23(A) has a terminal 951 and a terminal 952 inside a housing 930. The winding body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing 930 by using an insulating material or the like. It is not in contact with the housing 930. For convenience, in FIG. 23(A), the housing 930 is shown separated. However, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 952 are 52 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum). For example, a material such as aluminum or a resin material can be used.

[0335] As shown in FIG. 23(B), the housing 930 shown in FIG. 23(A) can be made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 23B may be formed by a housing 930a and a housing The area surrounded by the housing 930a and the housing 930b is where the wound body is placed. 950 is provided.

[0336] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the capacitor is formed, the electric field generated by the secondary battery 913 If the shielding of the electric field by the housing 930a is small, the housing 930a Antennas such as antenna 914 and antenna 915 may be provided inside the housing 930b. For example, a metal material can be used as the material.

[0337] Furthermore, the structure of the wound body 950 is shown in Fig. 24. The wound body 950 includes a negative electrode 931, The wound body 950 has a positive electrode 932 and a separator 933. The wound body 950 has the separator 933 sandwiched therebetween. Then, the negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. Multiple layers may be stacked.

[0338] The negative electrode 931 is connected to the terminal 911 shown in FIG. 21 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 951 shown in FIG. Connected to 11.

[0339] By using the positive electrode active material described in the above embodiment for the positive electrode 932, a high capacity and cycle life can be achieved. This makes it possible to obtain a secondary battery 913 with excellent battery characteristics.

[0340] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it can be made with fewer flexible parts. If the secondary battery is mounted in an electronic device that has some of the same characteristics, the secondary battery can be bent in accordance with the deformation of the electronic device. It is also possible.

[0341] A laminated secondary battery 980 will be described with reference to FIG. The secondary battery 980 has a wound body 993 shown in FIG. 4, a positive electrode 995, and a separator 996. The wound body 993 is the same as that described in FIG. Similar to the wound body 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

[0342] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 may be as many as necessary. The negative electrode 994 is connected to the lead electrode 997 and the lead electrode 998. The positive electrode 995 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 998. The positive electrode 997 is connected to a positive electrode current collector (not shown) via the other of the electrode 997 and the lead electrode 998. .

[0343] As shown in FIG. 25(B), a film 981 that serves as an exterior body and a film 982 having a recess are The above-mentioned wound body 993 is housed in a space formed by bonding the above-mentioned wound body 993 and the above-mentioned wound body 82 together by thermocompression bonding or the like. By doing so, a secondary battery 980 can be fabricated as shown in FIG. 93 has a lead electrode 997 and a lead electrode 998, and a film 981 and a recessed portion. The inside of the film 982 is impregnated with an electrolyte.

[0344] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a metal or resin material. If a resin material is used as the material for the recess, when an external force is applied, the film 981 and the recess The film 982 having the above structure can be deformed to produce a flexible storage battery. can be done.

[0345] In addition, although Fig. 25(B) and Fig. 25(C) show examples using two films, A space is formed by folding one film, and the above-mentioned wound body 9 is inserted into the space. 93 may also be accommodated.

[0346] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, it is possible to achieve high capacity and cycle. The secondary battery 980 can have excellent battery characteristics.

[0347] In addition, in FIG. 25, a secondary battery having a wound body in a space formed by a film that serves as an exterior body is shown. We have explained the example of 980, but as shown in Figure 26, for example, the shape is determined by the film that forms the exterior. It can also be used as a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes in the space formed. good.

[0348] The laminated secondary battery 500 shown in FIG. 26(A) includes a positive electrode current collector 501 and a positive electrode active material. A positive electrode 503 having a material layer 502 and a negative electrode current collector 504 and a negative electrode active material layer 505 are provided. The battery includes a negative electrode 506, a separator 507, an electrolyte 508, and an exterior body 509. A separator 507 is provided between a positive electrode 503 and a negative electrode 506 provided in a housing 509. The exterior body 509 is filled with an electrolyte 508. The electrolyte 508 contains The electrolyte solution shown in Embodiment Mode 2 can be used.

[0349] In the laminated secondary battery 500 shown in FIG. 26(A), a positive electrode current collector 501 and The negative electrode current collector 504 also serves as a terminal for electrical contact with the outside. A part of the electrode current collector 501 and the negative electrode current collector 504 is exposed to the outside from the outer casing 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be disposed in the outer casing 509. The lead electrode is connected to the positive electrode current collector 501 or the negative electrode current collector 502 by using the lead electrode. The lead electrode may be exposed to the outside by ultrasonic bonding to the electrode current collector 504 .

[0350] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, polypropylene, or the like. On a membrane made of a material such as polypropylene, polycarbonate, ionomer, or polyamide, A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied. On the metal thin film, an insulating composite such as polyamide resin or polyester resin is used as the outer surface of the exterior body. A laminate film having a three-layer structure provided with a resin film can be used.

[0351] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, (A) shows an example of a structure with two current collectors, but in reality, as shown in Figure 26(B ) it is composed of multiple electrode layers.

[0352] In FIG. 26(B), as an example, the number of electrode layers is set to 16. In FIG. 26(B), the negative electrode current collector 504 is made up of eight layers. 26(B) shows a structure of 16 layers in total, with 8 layers of positive electrode current collector 501. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. Of course, the number of electrode layers is not limited to 16, and may be more or less. In this case, a secondary battery having a larger capacity can be obtained. In this case, a secondary battery can be made thin and highly flexible.

[0353] An example of an external view of a laminated secondary battery 500 is shown in FIGS. 27 and 28. 27 and 28 show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead The positive electrode 510 and the negative electrode 511 are provided.

[0354] FIG. 29(A) shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is connected to the positive electrode current collector 5 01, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a tab region). The electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 is formed in a region where the negative electrode current collector 504 is partially exposed, i.e., a tab. The area and shape of the tab regions of the positive electrode and negative electrode are the same as those in the example shown in FIG. Not limited to.

[0355] [Method for manufacturing laminated secondary batteries] Here, an example of a method for manufacturing a laminated secondary battery, the external view of which is shown in FIG. 27, will be described with reference to FIG. 9(B) and (C) will be used to explain.

[0356] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The negative electrode 506, separator 507, and positive electrode 503 are shown. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tabs of the positive electrode on the outermost surface are shown. The positive electrode lead electrode 510 is bonded to the bonding region. For example, ultrasonic welding or the like is used for bonding. Similarly, the tab regions of the negative electrodes 506 are bonded to each other, and the negative electrode is bonded to the tab region of the negative electrode on the outermost surface. The lead electrode 511 is bonded.

[0357] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0358] Next, as shown in Figure 29(C), the exterior body 509 is folded at the portion indicated by the broken line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. At this time, a part (or one side) of the outer casing 509 is provided so that the electrolyte 508 can be poured therein later. A region (hereinafter referred to as an inlet) that is not joined to the substrate is provided.

[0359] Next, electrolyte 508 (not shown) is introduced into the exterior body 509 through an inlet provided in the exterior body. The electrolyte solution 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is bonded. A secondary battery 500 of this type can be fabricated.

[0360] By using the positive electrode active material described in the previous embodiment for the positive electrode 503, it is possible to achieve high capacity and cycle. The secondary battery 500 can have excellent battery characteristics.

[0361] [Bendable secondary battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 30 and 31. do.

[0362] FIG. 30(A) shows a schematic top view of a bendable secondary battery 250. 1), (B2), and (C) are cut along the cutting lines C1-C2 and C3 in FIG. 30(A), respectively. 1C-C4 is a schematic cross-sectional view taken along the line A1-A2. The positive electrode 211a and the negative electrode 211b are housed inside the exterior body 251. A lead 212a electrically connected to the negative electrode 211b. The lead 212b extends to the outside of the package 251. In addition to the positive electrode 211a and the negative electrode 211b, an electrolyte (not shown) is enclosed in the region. do.

[0363] The positive electrode 211a and the negative electrode 211b of the secondary battery 250 will be explained with reference to FIG. 31(A) shows the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. FIG. 31(B) is a perspective view illustrating a structure in which, in addition to the positive electrode 211a and the negative electrode 211b, a FIG. 2 is a perspective view showing a lead 212a and a lead 212b.

[0364] As shown in FIG. 31(A), the secondary battery 250 includes a plurality of rectangular positive electrodes 211a, a plurality of positive electrodes 211b, and a plurality of positive electrodes 211c. The negative electrode 211b has a rectangular shape and a plurality of separators 214. Each of the positive electrodes 211a and 211b has a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the surface of the negative electrode 211b except for the tab. A negative electrode active material layer is formed on the portion.

[0365] The surfaces of the positive electrodes 211a on which the positive electrode active material layer is not formed and the surfaces of the negative electrodes 211b on which the negative electrode active material layer is not formed are The positive electrode 211a and the negative electrode 211b are stacked so that the surfaces on which no material is formed are in contact with each other. will be done.

[0366] In addition, the surface on which the positive electrode active material of the positive electrode 211a is formed and the surface on which the negative electrode active material of the negative electrode 211b is formed are A separator 214 is provided between the surfaces. The data 214 is shown by a dotted line.

[0367] As shown in FIG. 31(B), the positive electrodes 211a and the leads 212a are connected to each other at the joints 21. The negative electrodes 211b and the leads 212b are electrically connected at the joints 5a. Electrical connection is made at 215b.

[0368] Next, the exterior body 251 will be described with reference to FIGS. 30(B1), (B2), (C), and (D). do.

[0369] The exterior body 251 has a film-like shape and is configured to sandwich the positive electrode 211a and the negative electrode 211b. The exterior body 251 is folded in two as shown in FIG. The pair of sealing portions 262 are connected to the positive electrode 211a and the sealing portion 263. The seal portion 2 is provided on either side of the negative electrode 211b and can also be called a side seal. 63 has a portion overlapping with the lead 212a and the lead 212b, and is also called a top seal. It is possible.

[0370] The exterior body 251 has ridge lines 271 and valley lines at the portions overlapping the positive electrode 211a and the negative electrode 211b. It is preferable that the sealing portion 272 of the exterior body 251 has a wave shape in which the sealing portions 272 are arranged alternately. 62 and the seal portion 263 are preferably flat.

[0371] FIG. 30(B1) is a cross section cut at the part overlapping with the ridge line 271, and FIG. 30(B2) is 30(B1) and (B2) are cross sections cut at the part where the valley line 272 overlaps. It corresponds to a cross section in the width direction of the secondary battery 250, the positive electrode 211a and the negative electrode 211b.

[0372] Here, the widthwise ends of the positive electrode 211a and the negative electrode 211b, i.e., the positive electrode 211a and the negative electrode 211b, The distance between the end of the negative electrode 211b and the seal portion 262 is defined as La. When deformation such as bending is applied to the positive electrode 211a and the negative electrode 211b, as will be described later, If the distance La is too short, the outer casing 251 The positive electrode 211a and the negative electrode 211b may rub strongly against each other, and the exterior body 251 may be damaged. In particular, if the metal film of the exterior body 251 is exposed, the metal film may be easily damaged by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the secondary battery 250 increases. .

[0373] In addition, the greater the total thickness of the stacked positive electrode 211a and negative electrode 211b, the greater the It is preferable to increase the distance La between the negative electrode 211a and the seal portion 262. stomach.

[0374] More specifically, the stacked positive electrode 211a, negative electrode 211b, and separator (not shown) When the total thickness of the actuator 214 is t, the distance La is 0.8 to 3.0 times the thickness t. Preferably, the ratio is 0.9 to 2.5 times, more preferably 1.0 to 2.0 times. By setting the distance La in this range, it is possible to make the device compact and resistant to bending. This makes it possible to realize a highly reliable battery.

[0375] Furthermore, when the distance between the pair of seal portions 262 is a distance Lb, the distance Lb is a and the width of the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable because it prevents the secondary battery 250 from being deformed by repeated bending or other deformation. Even if the positive electrode 211a and the negative electrode 211b come into contact with the exterior body 251, Since a part of the negative electrode 211b can be shifted in the width direction, the positive electrode 211a and the negative electrode 211 This effectively prevents the outer casing 251 from rubbing against the outer casing 251.

[0376] For example, the difference between the distance Lb between the pair of seal portions 262 and the width Wb of the negative electrode 211b is The thickness is 1.6 times or more and 6.0 times or less, preferably 1.8 times or more, the thickness t of the positive electrode 211a and the negative electrode 211b. It is preferable that the ratio is 2.0 times or more and 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less. stomach.

[0377] In other words, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula 1: I wish.

[0378]

number

[0379] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, and more preferably The value must be between 1.0 and 2.0.

[0380] 30(C) is a cross section including the lead 212a, and shows the secondary battery 250, the positive electrode 211, As shown in FIG. 30(C), the bending At the end portion 261, the ends of the positive electrode 211a and the negative electrode 211b in the length direction and the outer casing 25 It is preferable to have a space 273 between the first and second electrodes.

[0381] FIG. 30(D) shows a schematic cross-sectional view of the secondary battery 250 when bent. ) corresponds to the cross section taken along the cutting line B1-B2 in FIG. 30(A).

[0382] When the secondary battery 250 is bent, a part of the exterior body 251 located on the outside of the bend stretches, and More specifically, the other part located on the outside of the exterior body 251 is deformed so as to shrink. The part where the wave is generated is deformed so that the amplitude of the wave is small and the period of the wave is large. The part located inside 251 changes so that the wave amplitude is large and the wave period is small. In this way, the exterior body 251 is deformed, and as it is bent, Since this stress is alleviated, the material that constitutes exterior body 251 itself does not need to expand or contract. As a result, the exterior body 251 is not damaged and the secondary battery 250 can be bent with a small force. can.

[0383] Furthermore, as shown in FIG. 30(D), when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 211b are bent. At this time, the plurality of stacked positive electrodes 211a and 211b are displaced relative to each other. The negative electrode 211b is fixed at one end on the seal portion 263 side by the fixing member 217, so that it is not broken. The deviation increases as the distance gets closer to the bent portion 261. The stress applied to the positive electrode 211a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211 As a result, the positive electrode 211a and the negative electrode 211b do not need to be able to expand or contract. Therefore, the secondary battery 250 can be bent without any trouble.

[0384] In addition, a space 273 is provided between the positive electrode 211a and the negative electrode 211b and the exterior body 251. By this, the positive electrode 211a and the negative electrode 211b located on the inner side when bent are attached to the exterior body 25. It can move relative to 1 without touching it.

[0385] The secondary battery 250 illustrated in FIGS. 30 and 31 has a good external appearance even when repeatedly bent and stretched. Damage to the housing, the positive electrode 211a and the negative electrode 211b, etc., is unlikely to occur, and the battery characteristics are also unlikely to deteriorate. The secondary battery 250 has a positive electrode 211a that is not easily broken down. By using such a positive electrode active material, a battery with even better cycle characteristics can be obtained.

[0386] (Embodiment 5) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted in an electronic device will be described. Reveal.

[0387] First, as explained in part of the third embodiment, a bendable secondary battery is mounted on an electronic device. Examples of such a battery are shown in Figures 32(A) to 32(G). As a child device, for example, a television device (also called a television or television receiver) , computer monitors, digital cameras, digital video cameras, digital photo frame, mobile phone (also called mobile phone, mobile phone device), portable game machine, portable information Examples include information terminals, audio playback devices, and large game machines such as pachinko machines.

[0388] In addition, the flexible secondary battery can be attached to the inner or outer wall of a house or building, or to an automobile. It can also be incorporated into curved surfaces of the interior or exterior of a vehicle.

[0389] FIG. 32A shows an example of a mobile phone. The mobile phone 7400 includes a housing 740 1, in addition to a display unit 7402, operation buttons 7403, an external connection port 7404, The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, and the like. The secondary battery 7407 is a secondary battery of one embodiment of the present invention. This allows us to provide lightweight, long-lasting mobile phones.

[0390] FIG. 32(B) shows the mobile phone 7400 in a bent state. When the entire 00 is deformed by an external force and curved, the secondary battery installed inside The secondary battery 7407 is also bent. At this time, the state of the bent secondary battery 7407 is as shown in FIG. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is bent. The secondary battery 7407 is fixed in a state where the lead electrode is electrically connected to the current collector. For example, the current collector is made of copper foil, and some of it is alloyed with gallium to form a contact with the current collector. This improves adhesion with the active material layer, making the secondary battery 7407 highly reliable when bent. It is composed of:

[0391] FIG. 32(D) shows an example of a bangle-type display device. The portable display device 7100 is , a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. FIG. 32(E) shows the bent state of the secondary battery 7104. When the device is bent and worn on the user's arm, the housing may deform and damage part of the secondary battery 7104 or The total curvature changes. The degree of curvature at any point on the curve is expressed as the radius of the corresponding circle. The value expressed as the radius of curvature is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. A part of the main surface of the housing or secondary battery 7104 within the range of 40 mm to 150 mm in diameter The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more. If the thickness is within the range of 0 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment of the present invention, a lightweight and long-life portable display device can be provided.

[0392] FIG. 32(F) shows an example of a wristwatch-type portable information terminal. Portable information terminal 7200 The watch includes a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 7 205, an input / output terminal 7206, etc.

[0393] The portable information terminal 7200 is capable of performing functions such as mobile phone calls, e-mails, document browsing and creation, music playback, internet connection, and so on. It can run various applications such as internet communication and computer games. Cut.

[0394] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and the screen can be touched with a finger or a stylus. For example, the icon 7 displayed on the display unit 7202 can be operated by touching the You can launch the application by touching 207.

[0395] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as auto-start, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system built into the mobile information terminal 7200 can be The system also allows the functions of the operation buttons 7205 to be freely set.

[0396] In addition, the mobile information terminal 7200 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free You can also make calls.

[0397] The portable information terminal 7200 also has an input / output terminal 7206, and can be connected to other information terminals via a connector. Data can be exchanged directly through the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. You may go.

[0398] The display portion 7202 of the portable information terminal 7200 includes the secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, a lightweight and long-life portable information terminal can be provided. For example, the secondary battery 7104 shown in FIG. 32(E) is curved and inserted into the housing 7201. The flexible support 7204 may be incorporated into the band 7203 in a flexible state or may be incorporated into the band 7203 in a flexible state.

[0399] The mobile information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Human body sensors such as sensors, pulse sensors, and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors It is preferable that a sensor, etc. be installed.

[0400] FIG. 32G shows an example of a wristband-type display device. The display device 7300 has a display unit The display device 7300 includes a secondary battery 7304 according to one embodiment of the present invention. The display portion 7304 may be provided with a touch sensor, and may function as a portable information terminal. It is also possible to do so.

[0401] The display surface of the display unit 7304 is curved, and images are displayed along the curved display surface. The display device 7300 can also communicate with the display device 7300 by short-distance wireless communication according to a communication standard. You can change the situation.

[0402] The display device 7300 is also equipped with an input / output terminal, and can be directly connected to other information terminals via a connector. It is possible to exchange data and also charge via the input / output terminal. The charging operation may be performed by wireless power supply without using the input / output terminals.

[0403] When the secondary battery of one embodiment of the present invention is used as the secondary battery included in the display device 7300, A lightweight, long-life display device can be provided.

[0404] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device will be described. This will be explained using Figures 32(H), 33 and 34.

[0405] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, it is possible to achieve lighter weight and a longer life. For example, we can provide daily electronic products such as electric toothbrushes, electric shavers, Examples include electric beauty devices, and the secondary batteries for these products are designed to be easy for users to hold. Therefore, there is a demand for a secondary battery that is stick-shaped, small, lightweight, and has a large capacity.

[0406] FIG. 32(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In FIG. 32(H), the electronic cigarette 7500 includes an atomizer 7501 including a heating element and an atomizer 7502. The secondary battery 7504 supplies power to the tomizer, and the car battery contains the liquid supply bottle, sensors, etc. To enhance safety, the secondary battery 7504 is A protection circuit for preventing over-discharge may be electrically connected to the secondary battery 7504. The secondary battery 7504 has an external terminal so that it can be connected to a charging device. The 7504 is the tip when held, so the total length is short and the weight is light. It is desirable that the secondary battery according to one embodiment of the present invention has a high capacity and good cycle characteristics. The 7500 is a small and lightweight electronic cigarette that can be used for long periods of time. We can provide it.

[0407] Next, Fig. 33(A) and Fig. 33(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIGS. 33(A) and 33(B) includes a housing 963 0a, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, a table A display unit 9631 having a display unit 9631a and a display unit 9631b, switches 9625 to The display unit 9631 has a latch 9627, a fastener 9629, and an operation switch 9628. By using a flexible panel, the tablet terminal has a larger display area. FIG. 33(A) shows the tablet terminal 9600 in an open state, and FIG. (B) shows the tablet terminal 9600 in a closed state.

[0408] The tablet terminal 9600 also includes a housing 9630a and a housing 9630b. The power storage unit 9635 is connected to the housing 9630a through a movable part 9640. It is provided across the body 9630b.

[0409] The entire or a part of the display portion 9631 can be used as a touch panel. By touching images, text, input forms, etc. containing icons displayed in the area, data can be For example, the entire surface of the display portion 9631a on the housing 9630a side is covered with keys. The board buttons are displayed, and information such as characters and images is displayed on the display unit 9631b on the housing 9630b side. The information may be displayed.

[0410] In addition, a keyboard is displayed on the display unit 9631b on the housing 9630b side. The display unit 9631a on the a side may be used to display information such as characters and images. The keyboard display switch button of the touch panel is displayed in the section 9631. Touching the buttons with your finger or a stylus will display a keyboard on the display 9631. It can also be set to

[0411] In addition, the touch panel area of ​​the display unit 9631a on the housing 9630a side and the touch panel area of ​​the display unit 9631b on the housing 9630b side are It is also possible to simultaneously perform touch inputs to the touch panel area of ​​the display portion 9631b.

[0412] In addition, switches 9625 to 9627 are used to operate the tablet terminal 9600. It is not only an interface for switching between various functions, but also an interface for For example, at least one of the switches 9625 to 9627 may be an interface. The other functions as a power on / off switch for the tablet device 9600. Also, for example, at least one of the switches 9625 to 9627 may The ability to switch between portrait and landscape display, or between black and white and color display For example, at least one of the switches 9625 to 9627 may have a function of switching the At least one of the display units 9631 may have a function to adjust the brightness of the display unit 9631. The brightness of 31 is the brightness detected by the light sensor built into the tablet terminal 9600 during use. It can be optimized according to the amount of external light. In addition, other detection devices such as gyro, acceleration sensor, etc. that detect tilt are also included. It may be stored.

[0413] In FIG. 33A, a display portion 9631a on the housing 9630a side and a display portion 9631b on the housing 9630b side are 9631a and 9631b have almost the same display area. The display area of ​​each of the 9631b is not particularly limited, and one size may be different from the other. The display quality may be different, e.g. one may have a higher resolution display than the other. It may also be a display panel that can display

[0414] FIG. 33(B) shows the tablet terminal 9600 in a folded state. The portable terminal 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. In addition, a charge / discharge control circuit 9634 including a power storage unit 9635 is provided. Such a power storage unit is used.

[0415] As mentioned above, the tablet terminal 9600 can be folded in half, so when not in use, The housing 9630a and the housing 9630b can be folded together. By folding the tablet terminal 9600, the display portion 9631 can be protected. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can With its high capacity and good cycle characteristics, this tablet can be used for a long period of time. A mobile terminal 9600 can be provided.

[0416] In addition, the tablet terminal 9600 shown in FIG. 33(A) and FIG. 33(B) It has the function to display various information (still images, videos, text images, etc.), calendar, date Or a function to display the time etc. on the display, or to touch input or edit the information displayed on the display Touch input function, function to control processing by various software (programs), etc.

[0417] The tablet terminal 9600 is equipped with a solar cell 9633 on its surface, which generates power. The solar cell 96 can supply the power to the panel, the display unit, the video signal processing unit, etc. 33 can be provided on one or both sides of the housing 9630, and can efficiently charge the power storage unit 9635. The power storage unit 9635 can be configured to use a lithium ion battery. The use of such a device has the advantage of enabling miniaturization.

[0418] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. A block diagram is shown in FIG. 33(C) and will be explained. In FIG. 33(C), a solar cell 9633, a power storage unit 96 35, DC-DC converter 9636, converter 9637, switches SW1 to SW3, The display unit 9631 is shown, along with a power storage unit 9635, a DC-DC converter 9636, and a The inverter 9637 and the switches SW1 to SW3 are connected to the charge / discharge control circuit 9 shown in FIG. This corresponds to 634.

[0419] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted into a voltage to charge the storage battery 9635. The converter 9636 increases or decreases the voltage. When power is used from the battery 9633, the switch SW1 is turned on, and the converter 963 7, the voltage is increased or decreased to the voltage required for the display unit 9631. When not displaying in 1, turn SW1 off and SW2 on to turn on the power storage unit 9635. It is sufficient to configure the device so that charging is performed.

[0420] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Storage by other power generation means such as piezoelectric elements and thermoelectric conversion elements (Peltier elements) For example, the power supply 9635 may be configured to transmit and receive power wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. You may do so.

[0421] Another example of electronic equipment is shown in FIG. 34. In FIG. 34, a display device 8000 is a display device according to the present invention. 8 is an example of an electronic device using a secondary battery 8004 according to one embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker, and The secondary battery 8004 according to one embodiment of the present invention includes: The display device 8000 is provided inside a housing 8001. The display device 8000 is supplied with power from a commercial power source. It is also possible to use the power stored in the secondary battery 8004. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention can be used. The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. become.

[0422] The display unit 8002 is a display device having a light emitting element such as a liquid crystal display device or an organic EL element in each pixel. Optical devices, electrophoretic displays, DMD (Digital Micromirror Devices) ice), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0423] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. This includes all display devices for displaying information, such as:

[0424] In FIG. 34, a stationary lighting device 8100 includes a secondary battery 8 according to one embodiment of the present invention. 8103. Specifically, the lighting device 8100 includes a housing 8101, 34, the secondary battery 8103 is disposed in the housing 8. 101 and a light source 8102 are installed inside a ceiling 8104. 8, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can be supplied with power from a commercial power source or can be powered by a secondary battery 8103. The stored power can also be used. Therefore, in the event of a power outage, the power supply from the commercial power source can be reduced. Even when power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0425] In addition, FIG. 34 illustrates a lighting device 8100 of a fixed type provided on a ceiling 8104. However, in the secondary battery according to one embodiment of the present invention, the side wall 8105, the floor 8106, and the like are not included in the ceiling 8104. It can be used for a fixed lighting device provided in a window 8107 or a desk. It can also be used in upper lighting devices.

[0426] The light source 8102 can be an artificial light source that artificially obtains light using electricity. Specifically, this applies to incandescent lamps, discharge lamps such as fluorescent lamps, and light-emitting devices such as LEDs and organic EL elements. An example of the artificial light source is a light element.

[0427] In FIG. 34, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is 8 is an example of an electronic device using a secondary battery 8203 of one embodiment of the present invention. The indoor unit 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. In the example shown, the secondary battery 8203 is provided in the indoor unit 8200. The secondary battery 8203 may be provided in the outdoor unit 8204. Both the outdoor units 8204 may be provided with a secondary battery 8203. The battery can be supplied with power from a commercial power source or stored in a secondary battery 8203. In particular, both the indoor unit 8200 and the outdoor unit 8204 are equipped with secondary batteries 8 If 203 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8203 of one embodiment of the present invention as an uninterruptible power supply, Conditioner can be used.

[0428] In addition, Figure 34 shows a separate type air conditioner consisting of an indoor unit and an outdoor unit. However, it is an integrated air conditioner that has the functions of both an indoor unit and an outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used for the conditioner.

[0429] In FIG. 34, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, It has a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, etc. In FIG. A secondary battery 8304 is provided inside the housing 8301. The power can be supplied from a commercial power source or can be stored in a secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. Even in this case, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, 8300 refrigerators and freezers will be available for use.

[0430] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers The sub-devices require high power for a short period of time, so the power that cannot be supplied by the commercial power supply is supplemented. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for supporting This can prevent the commercial power breaker from tripping when using the

[0431] In addition, during times when electronic devices are not in use, the total amount of power that can be supplied by commercial power suppliers is also During the time period when the ratio of the amount of electricity actually used (called the electricity usage rate) is low, By storing power in the secondary battery, it is possible to prevent power usage rates from increasing outside the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low, the refrigerator compartment door 83 02, during the night when the freezer door 8303 is not opened or closed, power is supplied to the secondary battery 8304. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 open and close. During the daytime, when the vehicle is in operation, the secondary battery 8304 is used as an auxiliary power source, thereby reducing the power consumption during the daytime. The rate can be kept low.

[0432] According to one embodiment of the present invention, the cycle characteristics of a secondary battery can be improved, and the reliability can be improved. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. This improves the characteristics of the secondary battery, thereby making the secondary battery itself smaller and lighter. Therefore, the secondary battery according to one embodiment of the present invention can be used in the electronic devices described in this embodiment. By incorporating the above-mentioned in the electronic device, it is possible to make the electronic device lighter and with a longer life span. This embodiment can be implemented in appropriate combination with other embodiments.

[0433] (Embodiment 6) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0434] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), an electric vehicle (EV), or It will be possible to realize next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). do.

[0435] FIG. 35 illustrates a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. By using one aspect of the present invention, it is possible to improve the driving range of a hybrid vehicle. A long vehicle can be realized. The automobile 8400 also has a secondary battery. 20(C) and 20(D) are mounted on the floor of the vehicle. In addition, a battery pack consisting of multiple secondary batteries as shown in FIG. The battery may be installed on the floor of the vehicle. In addition, it also supplies power to light-emitting devices such as headlights 8401 and room lights (not shown). can be supplied.

[0436] In addition, the secondary battery is used for the displays of the car 8400, such as the speedometer and tachometer. The secondary battery can supply power to the navigation system of the automobile 8400. The power supply can be used to power semiconductor devices such as gating systems.

[0437] The car 8500 shown in FIG. 35(B) has a plug-in secondary battery. It can be charged by receiving power from an external charging facility using a method such as contactless power supply. FIG. 35(B) shows a diagram of a charging device 8021 mounted on a ground and a charging device 8022 mounted on a vehicle 8500. The secondary battery 8024 is shown being charged via a cable 8022. For charging methods and connector specifications, please refer to the specifications of CHAdeMO (registered trademark) and Combo. The charging device 8021 may be a charging station installed in a commercial facility. For example, plug-in technology can be used to The secondary battery 8024 mounted on the automobile 8500 can be charged by the power supply of Charging is performed by converting AC power to DC power via a converter such as an AC / DC converter. It is possible to do so.

[0438] Although not shown, a power receiving device is mounted on the vehicle, and power is supplied contactlessly from a power transmitting device on the ground. In this case, the power transmission device is installed on the road or on the exterior wall. By incorporating this, charging can be done not only when the vehicle is stopped but also while the vehicle is moving. The vehicle may transmit and receive power between them using the same method. A solar cell may be provided in the vehicle so that the secondary battery can be charged when the vehicle is stopped or running. To supply power in the above, an electromagnetic induction method or a magnetic field resonance method can be used.

[0439] 35C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in FIG. 5(C) includes a secondary battery 8602, side mirrors 8601, and a directional indicator. The secondary battery 8602 supplies electricity to the direction indicator light 8603. can be done.

[0440] In addition, the scooter 8600 shown in FIG. 35(C) has a secondary battery 86 in the storage under the seat 8604. The secondary battery 8602 can be stored in the under-seat storage 8604, which is small. The secondary battery 8602 can be stored in the under-seat storage 8604. When charging, the secondary battery 8602 is brought indoors, charged, and then stored away before driving. Just pay it.

[0441] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. Therefore, the secondary battery itself can be made smaller and lighter. If the battery itself can be made smaller and lighter, it will contribute to reducing the vehicle's weight, which will improve the cruising range. In addition, the secondary battery installed in the vehicle can be used as a power supply source for other purposes. In this case, for example, it is possible to avoid using commercial power sources during peak power demand periods. If we can avoid using commercial power sources during peak power demand periods, we can save energy and This can contribute to reducing carbon dioxide emissions. Since the secondary battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0442] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0443] In this example, a positive electrode of one embodiment of the present invention was fabricated and evaluated.

[0444] <Sample 1> In Sample 1, the process up to step S35 was carried out using the manufacturing method shown in FIG. Substance 101 was prepared.

[0445] First, LiF and MgF2 were weighed so that the molar ratio of LiF:MgF2 was 1:3, and then dissolved. Acetone was added as a solvent and the mixture was mixed and crushed in a wet manner. The treatment was carried out in a ball mill at 150 rpm for 1 hour. The treated material was collected and This was used as a first mixture (steps S11 to S14).

[0446] Next, we used pre-synthesized lithium cobalt oxide (CeO2) manufactured by Nippon Chemical Industry Co., Ltd. Lucido C-10N was used (step S25). Cellseed C-10N has a D50 of 12 It is lithium cobalt oxide with few impurities and a particle size of about μm.

[0447] Next, the molecular weight of lithium cobalt oxide was compared with the molecular weight of magnesium atoms contained in the mixture 902. The mixture was weighed so that the molecular weight was 0.5 atomic % and mixed in a dry state. The mixture was mixed in a ball mill at 150 rpm for 1 hour. 3 (steps S31 to S33).

[0448] Next, the mixture 903 was placed in an alumina crucible and heated at 850°C for 6 minutes in a muffle furnace in an oxygen atmosphere. The alumina crucible was covered during the annealing. The oxygen flow rate was 10 The temperature was increased at 200°C / hr and decreased over 10 hours. The processed material was designated as first substance 101 (steps S34 and S35).

[0449] Next, lithium phosphate was prepared and pulverized (step S45). The grinding was carried out in a ball mill using near balls at 400 rpm for 60 hours. The mixture was sieved through a 100 μm diameter sieve.

[0450] Next, the crushed lithium phosphate was mixed with the first substance 101 (step The amount of lithium phosphate mixed was 0.0 mol per 1 mol of the first substance 101. The amount was equivalent to 6 mol. Mixing was carried out in a ball mill using zirconia balls, and 1 The mixture was mixed at 50 rpm for 1 hour. After mixing, the mixture was sieved through a 300 μm φ sieve. The mixture was placed in an alumina crucible, covered, and annealed in an oxygen atmosphere at 750°C for 20 hours. Then, the powder was collected by sieving it through a 53 μm diameter sieve (step S47). S48), Sample 1 was obtained.

[0451] [Preparation of positive electrode] Next, a positive electrode was produced using Sample 1 produced above.

[0452] For the positive electrode, Sample 1 was used as the active material, and the mixture of AB and PVDF was used as the active material: A slurry of AB:PVDF = 95:3:2 (weight ratio) was applied to the current collector. NMP was used as the solvent for the slurry.

[0453] After the slurry was applied to the current collector, the solvent was evaporated and the electrode 1-1 (Electrode 1-1) was used as the positive electrode. Electrode 1-1) was obtained. Also, for Electrode 1-1, 210kN After applying a pressure of 1467 kN / m, a further pressure of 1467 kN / m was applied to electrode 1-2 (Elect The amount of support on Electrode 1-1 was approximately 20 mg / cm. m 2 , electrode density is approximately 2.0 g / cm 3 Electrode 1-2 support The dose is approximately 20 mg / cm 2 , electrode density is approximately 3.7 g / cm 3 It was.

[0454] [Cross-section observation] The obtained Electrode 1-1 and Electrode 1-2 were cross-sectioned. The cross section was exposed by polishing with a polishing polisher and observed under a scanning electron microscope (SEM). Observations were made using a 2000 Angular Electron Microscope.

[0455] Figure 36(A) shows Electrode 1-2, and Figure 36(B) shows Electrode 1-1 show cross-sectional SEM images, respectively.

[0456] In the cross section of Electrode 1-2 shown in FIG. 36(A), the positive electrode on the current collector 701 The cathode active material layer 702 is observed. The cathode active material 703 contained in the cathode active material layer 702, and An enlarged view of the vicinity is shown in FIG.

[0457] In FIG. 37(A), the positive electrode active material 703 has cracks 704, 705 and In the cross section of the positive electrode active material 703, cracks 704 and cracks It is suggested that a part of the crack 705 is in contact with the surface of the positive electrode active material 703. It is suggested that 6 is located inside the positive electrode active material 703.

[0458] FIG. 37(B) shows an EDX analysis corresponding to the same position as the cross-sectional SEM image shown in FIG. 37(A). The phosphorus and cobalt mapping images are shown in cracks 704 and 705. At the corresponding locations, there was a high concentration of phosphorus and no significant cobalt was detected. It was found that a substance containing phosphorus was present inside the cracks 704 and 705. It is speculated that the substance is made from lithium phosphate.

[0459] On the other hand, no significant phosphorus was detected in crack 706.

[0460] FIG. 38(A) is an enlarged view of the crack 704 and its vicinity in FIG. 37(A), and FIG. 8(B) is an enlarged view of the crack 704 and its vicinity in FIG. 37(B).

[0461] In addition, in FIG. 37(A), a substance 781 having a particulate shape was observed. B) shows that the phosphorus concentration is high and cobalt is prominent at the position corresponding to substance 781. Since substance 781 contains phosphorus, it is possible to use lithium phosphate as a raw material. It is presumed to be a substance that

[0462] In the cross section of Electrode 1-1 shown in FIG. 36(B), the positive electrode on the current collector 711 The cathode active material layer 712 is observed. The cathode active material 713 contained in the cathode active material layer 712, and An enlarged view of the vicinity is shown in FIG.

[0463] In FIG. 39(A), the positive electrode active material 713 has cracks 714. In the cross section of FIG. 13, a part of the crack 714 is in contact with the surface of the positive electrode active material 713. This suggests that...

[0464] FIG. 39(B) shows an EDX analysis corresponding to the same position as the cross-sectional SEM image shown in FIG. 39(A). This is a mapping image of phosphorus and cobalt at the position corresponding to crack 714. The concentration of phosphorus was high, and no significant cobalt was detected. It was suggested that a substance containing phosphorus exists in the part of the sintered body. It is presumed to be a substance that

[0465] FIG. 40(A) is an enlarged view of the crack 714 and its vicinity in FIG. 39(A), and FIG. 39(B) is an enlarged view of the crack 714 and its vicinity in FIG. 39(B).

[0466] [EELS, FFT] Next, the obtained Sample 1 was thinned by FIB method and then analyzed by STE. M observation and EELS measurements were performed.

[0467] Figure 41 shows the crack and its vicinity in Sample 1, and Figure 42 shows the surrounding area. The results of observing the area and the area with different contrast using HAADF-STEM. Figure 41 shows the image at a magnification of 64,000 times, and Figure 42 shows the image at a magnification of 16,000 times. In FIG. 42, the inventors observed that the area around the observation area was made of cobalt oxide. This is the area that was observed and was assumed to contain lithium. We speculated that the area with different phosphate content is the area where lithium phosphate is the main raw material.

[0468] Area 1 (area1) to Area 4 (area4) where EELS measurements were performed This is shown by a square in Figure 41. Area 5 (area 5), ​​where the EELS measurement was performed, is The measurement results for area 1, area 2, and area 5 are shown in the squares in Figure 42. The results of measurements in area 3 and area 4 are shown in Figure 43(A) and Figure 43(B), respectively. are shown in the table below.

[0469] FIG. 44(A) shows the Li-K edge and the PL edge in FIG. 43(A). FIG. 44(B) is an enlarged view of the part of FIG. 43(A) that has arrived at the OK edge. This is an enlarged view of the highlighted area.

[0470] FIG. 45(A) is an enlarged view of a portion of FIG. 43(B) focusing on the Co-M edge. 45(B) shows the OK edge and the Co-L edge in FIG. 43(B). FIG. 10 is an enlarged view of a focused portion.

[0471] Phosphorus was prominently observed in area 1 and area 2, which correspond to the inside of the crack. The presence of lithium was also suggested. On the other hand, cobalt was not significantly observed. .

[0472] In the region around the crack, i.e., in the positive electrode active material 100, a region corresponding to the first material 101 Cobalt was prominently observed in area 4, suggesting that this is the case.

[0473] In addition, in area 5 in Figure 42, which is an area with a different contrast from the surrounding area, Phosphorus was prominently observed.

[0474] Next, for the area around area2, the fast Fourier transform analysis pattern (FFT(F The Fast Fourier Transformation (FFT) pattern is shown in Figure 46. In addition, the actual measured values ​​of the positional relationship (distance, angle) of the spots in the obtained FFT pattern and the JCP The distance and angle correspond to the DS card No. 04-006-8566. The incident direction is

[0212] . As shown in Figure 46, the obtained FFT pattern is Orthorhombic crystal, PDS card no. 04-006-8566 There was a good correspondence with the structure.

[0475] From the above, it can be concluded that the substance located inside the crack in Sample 1 is lithium phosphate. It was suggested that this may be a [Example]

[0476] In this example, a positive electrode and a secondary battery according to one embodiment of the present invention were fabricated and evaluated.

[0477] <Sample 2> Sample 2 is a mixture of lithium cobalt oxide, LiF, and MgF2, and then heat treated. Steps S11 to S14 for carrying out the steps S11 to S14 are not carried out, and the lithium cobalt oxide and the lithium phosphate are mixed. The material was mixed and subjected to steps S46 to S48, which included heat treatment. In Example 2, the positive electrode active material 100 was prepared by the preparation method shown in FIG. 5. Step S4 Steps S45 to S48 and step S25 are the same as those in the first embodiment. The conditions used in 1 were used.

[0478] <Sample 3> Sample 3 is a mixture of lithium cobalt oxide, LiF, and MgF2, and then heat treated. After performing steps S11 to S14, the obtained substance and lithium phosphate are Steps S46 to S48, which involve mixing and heat treatment, were not carried out. The first substance 101 obtained in Example 1 was designated as Sample 3.

[0479] <Sample 4> As Sample 4, pre-synthesized lithium cobalt oxide was used. The lithium cobalt oxide synthesized in advance was Cellseed C-1 manufactured by Nippon Chemical Industry Co., Ltd. ON was used.

[0480] [Preparation of positive electrode] Sample 2, Sample 3 and Sample 4 were used as the active material. The active material, AB, and PVDF were mixed in a ratio of AB:PVDF=9. The slurry was mixed in a weight ratio of 5:3:2 and coated on the current collector. NMP was used as the solvent.

[0481] After the slurry was applied to the current collector, the solvent was evaporated and then a pressure of 210 kN / m was applied. After this, a further pressure of 1467 kN / m was applied to obtain a positive electrode. The positive electrode used as the active material is Electrode 2, and Sample 3 is The positive electrode was used as electrode 3-2, and Sample 4 was used as the active material. The positive electrode is designated as Electrode 4. The amount of support on Electrode 2 is Approximately 20 mg / cm 2 , electrode density is approximately 3.7 g / cm 3 Electro The loading of de 3-2 is approximately 20 mg / cm 2 , electrode density is approximately 3.9 g / cm 3 in The amount of support on Electrode 4-2 was approximately 20 mg / cm. 2 , electrode density is approximately 3.9 g / cm 3 In addition, Sample 3 was used as the active material. In the positive electrode, the slurry is applied to the current collector, the solvent is evaporated, and then the above-mentioned pre- The electrode that was not subjected to the test is designated as Electrode 3-1. The positive electrode using sample 4 as the active material was not pressed in the same way as electrode 4-. 1 (Electrode 4-1).

[0482] [Secondary battery production] The fabricated Electrode 1-2, Electrode 2, Electrode Electrode 3-2 and Electrode 4-2 were used as the positive electrodes. A coin-type secondary battery (diameter 20 mm, height 3.2 mm) was fabricated.

[0483] The counter electrode was made of lithium metal.

[0484] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. The following was used.

[0485] The separator was made of polypropylene with a thickness of 25 μm.

[0486] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0487] [Cycle characteristics] At 25°C, charge is CCCV (0.2C, final current 0.02C), discharge is CC (0.2C The graph shows the change in discharge capacity when a charge-discharge cycle was performed with the lower limit voltage set to 2.5 V. (A) shows the results when the upper limit voltage of charging is 4.5V, and (B) shows the results when the upper limit voltage of charging is The results are shown for a voltage of 4.6 V. 1 C is the current value per weight of the positive electrode active material, which is 200 mA / g. The vertical axis is the discharge capacity, and the horizontal axis is the cycle (Cy cle).

[0488] The cycle characteristics were the best in Electrode 1-2, and Ele Good results were also obtained with electrode 3-2. Electrode 4-2 showed a significant decrease in capacity with cycling. In the manufacturing process of the material, conditions using materials containing halogen, magnesium, lithium, etc. In this case, good cycle characteristics were obtained.

[0489] [Charging endurance test] The secondary battery was charged by CCCV (0.05C, 4.5V or 4.6V, Final current 0.005C, discharge CC (0.05C, 2.5V) at 25°C for 2 The cycle was measured.

[0490] Then, the battery was charged at 60°C using CCCV (0.05C). The upper limit voltage was 4.55V. Or 4.65V, and the time from when the secondary battery voltage reaches the upper limit voltage to 0 The time it takes for the voltage to drop below 0.01V (for example, 4.54V if it is 4.55V) (hereafter, When the voltage of the secondary battery falls below the upper limit voltage, for example, , there is a possibility that a phenomenon such as a short circuit may have occurred. 1C is set to 200mA / g.

[0491] Figure 48 shows the results when the upper limit voltage is 4.55V and the results when the upper limit voltage is 4.65V. Electrode 1-2 and Electrode 2 showed excellent charging resistance. In comparison, Electrode 3-2 and Electrode 4-2 The results showed that the charge resistance was low. The results showed that the charging tolerance was higher under the conditions [Example]

[0492] In this example, a secondary battery was manufactured using a positive electrode of one embodiment of the present invention and evaluated.

[0493] <Sample 5 (Sample 5) to Sample 10 (Sample 10)> Using the method for preparing Sample 1 shown in Example 1, a positive electrode active material, Sample 5 (Sa Samples 5 to 10 were prepared. The temperature of the boiler was changed from 750°C for 20 hours to 850°C for 2 hours. The amount of lithium phosphate mixed in 6 is Sam Sample 6 was 0.005 mol, Sample 7 was 0.02 mol, and Sample 8 was 0.04 mol, and Sample 9 was 0.0 In Sample 10, the amount was equivalent to 0.10 mol.

[0494] [Secondary battery production] Using Sample 3, Sample 4, Sample 5 to Sample 10 Then, a positive electrode was prepared by the method described in Example 2, and the positive electrode thus prepared was used to carry out the test described in Example 2. A secondary battery was fabricated using this method.

[0495] [Cycle characteristics] Figure 49 shows the charging at 25°C, CCCV (0.2C, upper limit voltage 4.6V, final current 0.0 2C), and discharge was CC (0.2C, lower limit voltage 2.5V). The graph shows the change in discharge capacity. 1C is the current value per weight of the positive electrode active material, which is 200mA / g. The vertical axis is the discharge capacity, and the horizontal axis is the cycle. e) is the number of times.

[0496] In the process of manufacturing the positive electrode active material, materials containing halogen, magnesium, lithium, etc. Good cycle characteristics were obtained under the conditions of using

[0497] In addition, during the manufacturing process, under any conditions in which lithium phosphate was mixed, On the other hand, as the amount of lithium phosphate added increased, the discharge The capacitance decreased because the proportion of the first material 101 in the positive electrode active material decreased. It can be said that there is.

[0498] [Charging endurance test] The secondary battery was charged by CCCV (0.05C, 4.5V or 4.6V, Final current 0.005C, discharge CC (0.5C, 2.5V) at 25°C for 2 seconds The cycle was measured.

[0499] Then, the battery was charged at 60°C using CCCV (0.05C). The upper limit voltage was 4.55V. Or 4.65V, and the time from when the secondary battery voltage reaches the upper limit voltage to 0 The time it takes for the voltage to drop below 0.01V (for example, 4.54V if it is 4.55V) (hereafter, When the voltage of the secondary battery falls below the upper limit voltage, for example, , there is a possibility that a phenomenon such as a short circuit may have occurred. 1C is set to 200mA / g.

[0500] Figure 50(A) shows the results when the upper limit voltage is 4.55V, and Figure 50(B) shows the results when the upper limit voltage is 4.6 The horizontal axis shows the results at 5 V. The horizontal axis shows the lithium phosphate mixed in step S46. 1 mol of the first substance 101.

[0501] As can be seen from Figures 50(A) and (B), the charge retention time increases as the amount of lithium phosphate added increases. On the other hand, as shown in Figure 49, the amount of lithium phosphate added It was found that the discharge capacity decreases as the amount of the secondary battery increases. To realize a battery, a sufficient amount of lithium phosphate must be added to ensure the safety of the secondary battery. It is sufficient to add it, and there is no need to add it in excess.

[0502] As the upper limit voltage of charging increases, the capacity of the secondary battery increases. Ample 4), the upper limit voltage for charging is set to 4.3V, 4.4V, 4.5V and 4. 51(A) shows the charge and discharge curves when the upper limit voltage of charging is changed from 0V to 6V. In Figure 51(B), the upper limit voltage for charging is 4.4V and 4.3V. The charge and discharge curves are shown in Fig. 1. The discharge capacity is 1.0V when the upper limit voltage of the charge is 4.3V. 154.8mAh / g at 4.4V, 169.2mAh / g at 4.5V, 186.9m Ah / g, and at 4.6V it was 220.8mAh / g.

[0503] By setting the upper limit voltage at 4.6V, a high capacity can be obtained. For example, in order to achieve both high reliability and safety, if the upper limit voltage is 4.5V, As a condition for obtaining a significantly higher capacity than that of the first substance 101, The amount of lithium phosphate added is about 0.10 mol, and the condition for obtaining a higher capacity is The amount of lithium phosphate is estimated to be about 0.06 mol. The amount of lithium phosphate to be added per liter is, for example, 0.01 mol or more and 0.12 mol or less. or 0.02 mol or more and 0.08 mol or less. [Example]

[0504] In this example, a secondary battery was manufactured using a positive electrode active material of one embodiment of the present invention. The cracks in the particles were observed.

[0505] [Preparation of positive electrode] Sample 1 (LiF and MgF2 and lithium cobalt oxide) prepared in Example 1 The mixture was prepared, heat-treated, mixed with lithium phosphate, and then heat-treated. Electrode 1-1 (not pressed) is a positive electrode using a Electrode 1-2 (pressed), and S prepared in Example 2 Ample 3 (LiF and MgF2) and lithium cobalt oxide mixtures were prepared and heat-treated. Electrode 3-1 (a material obtained by pressing) is a positive electrode. Electrode 3-1 (pressed) and Electrode 3-2 (pressed) were used to prepare four types of positive electrodes. I'm prepared.

[0506] [Secondary battery production] Next, using each of the four types of positive electrodes prepared, a CR2032 type (diameter 20 mm high) A coin-type secondary battery (thickness: 3.2 mm) was fabricated.

[0507] The counter electrode was made of lithium metal.

[0508] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. The following was used.

[0509] The separator was made of polypropylene with a thickness of 25 μm.

[0510] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0511] [Cycle characteristics] Figure 52 shows the charging at 25°C with CCCV (0.2C, upper voltage 4.6V, final current 0.02 C), discharge was performed in CC (0.2C, lower limit voltage 2.5V) charge / discharge cycle. The graph shows the change in capacitance. 1C is the current value per weight of the positive electrode active material, which is 200mA / g. The axis represents the discharge capacity, and the horizontal axis represents the cycle. ) times.

[0512] The cycle characteristics were measured using Sample 1 as the positive electrode active material. Excellent results were obtained in Electrode 1-2 and Electrode 1-1. Electrode 3-1 and Elctrode using Sample 3 as the substrate Regarding 3-2, the positive electrode was pressed, and the deterioration A more pronounced tendency was observed.

[0513] [Cross-section observation] In order to evaluate cracks in the positive electrode active material of the positive electrode, the cross-sectional observation method shown in Example 1 was used. The cross section of each positive electrode was observed using the method, and the incidence of cracks was calculated. The crack occurrence rate is the number of cracks observed by cross-sectional observation. The value was divided by the number of particles detected and multiplied by 100, and the unit was expressed as %.

[0514] FIG. 53 shows Electrode 1-1, Electrode 2-3, and Electrode 3-4 before being incorporated into a secondary battery. e Cracks in 1-2, Electrode 3-1 and Electrode 3-2 In addition to these four types of positive electrodes, the electrode prepared in Example 2 was also used. The number of cracks in e 4-1 and Electrode 4-2 is also shown. An increase in the number of cracks due to pressing was also observed in positive electrodes using electrode active materials. The number of cracks after pressing was calculated for the positive electrode using Sample 1 and the positive electrode using Sample 3. The positive electrode using Sample 4 had the lowest positive electrode activity. The phosphate compounds contained in the material may contribute significantly to reducing the number of cracks, and the positive electrode activity The magnesium and fluorine contained in the material may also contribute to reducing the number of cracks. was suggested.

[0515] [Plane observation] To evaluate changes such as cracks caused by charge / discharge cycles, the positive electrode of the secondary battery is More specifically, after a certain number of charge-discharge cycles, the secondary battery was disassembled and The positive electrodes of the secondary batteries were then observed from above, and the secondary batteries were then reassembled. The process of setting the battery up and restarting the charge / discharge cycle was repeated several times.

[0516] Figure 54(A), (B), (C), (D) and (E) show Electrode 1-2 Before, after 10 cycles, and after 30 cycles of charge and discharge cycles for a secondary battery having The planar observation results of the positive electrode after 40 cycles and 50 cycles are shown in Figure 54(A). Some of the cracks observed are indicated by arrows. Figure 54(E) shows the same cracks as Figure 54(A). Arrows point to cracks that are believed to correspond to the cracks shown.

[0517] Figure 55(A), (B), (C), (D) and (E) show Electrode 3-2 Before, after 10 cycles, and after 30 cycles of charge and discharge cycles for a secondary battery having The results of plane observation of the positive electrode after 40 cycles and 50 cycles are shown in Figure 55(A). Some of the cracks observed are indicated by arrows. Figure 55(E) shows the same cracks as Figure 55(A). Arrows point to cracks that are believed to correspond to the cracks shown.

[0518] From the observation results of Figures 54 and 55, it can be seen that in the preparation of the positive electrode active material, Electrode 1-2 does not contain phosphoric acid, while Electrode 3-2 does. This suggests that the progression of cracks during charge-discharge cycles is suppressed compared to the case of [Example]

[0519] In this example, a secondary battery using graphite for the negative electrode was fabricated, and the cycle characteristics were evaluated.

[0520] [Secondary battery production] Sample 1, Sample 3 and Sample 4 prepared in the previous examples The positive electrode was fabricated using each of these materials as the positive electrode active material. The positive electrode active material, AB, and PVDF were mixed in a ratio of 95:3:2 (weight ratio) and the slurry was applied to the current collector. The slurry was coated with NMP.

[0521] After the slurry was applied to the current collector, the solvent was evaporated and then a pressure of 178 kN / m was applied. After that, a pressure of 1248 kN / m was applied to each of the positive electrode active materials. The amount of the positive electrode active material carried was 9 mg / cm. 2 More than 11mg / cm 2 below was the value.

[0522] The negative electrode uses graphite as the active material, and is made of VGCF (registered trademark), CMC-Na, SBR, and The blend of active material: VGCF (registered trademark): CMC-Na: SBR = 96:1:1:2 (weight ratio) The slurry was mixed in a ratio of 100% by weight, and the viscosity was adjusted with pure water. The slurry was then applied to one side of the current collector, dried, and resuspended in pure water. The negative electrode was made of a material in which the solvent had been evaporated. A copper foil with a thickness of 18 μm was used as the current collector. Loading amount: 6 mg / cm 2 Over 8mg / cm 2 The values ​​were as follows:

[0523] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). A mixture of EC:DEC = 3:7 (volume ratio) was used.

[0524] The separator was made of polypropylene with a thickness of 25 μm. One positive electrode and one negative electrode were placed side by side. The active material layers were arranged facing each other, with a separator sandwiched between them.

[0525] The secondary battery produced corresponds to 15mAh / g at 0.01C for the purpose of aging. After charging the battery to the capacity required, cut off a part of the outer casing, open it, and roll it over the gas. After that, the cut part was sealed with the outer casing. After charging the battery to a capacity corresponding to 0.5mAh / g, it was kept at 40°C for 24 hours. I cut off a part of the exterior body to open it, and rolled it over to remove the gas. CCCV (0.1C, 4.4V, final current 0.01C), discharge CC(0.2C, 2.5 After charging at CCCV (0.2C, 4.4V, final current 0.02C), The battery was charged and discharged twice at CC (0.2C, 2.5V).

[0526] Next, charge at CCCV (0.2C, 4.4V or 4.45V, final current 0.02C) The charge-discharge cycle characteristics were evaluated with CC (0.2 C, 2.5 V). The results are shown in Figure 56. Figure 56(A) shows the upper limit voltage for charging at 4.4V, and Figure 56(B) shows the upper limit voltage for charging at 4. The results are for a voltage of 45V. Sample 3, and magnesium, fluorine, and phosphate in the preparation of the positive electrode active material In Sample 1 using the above, excellent results were obtained in both cycle characteristics. [Explanation of symbols]

[0527] 100: positive electrode active material, 100a: positive electrode active material, 100b: positive electrode active material, 100c: positive electrode active material material, 100d: positive electrode active material, 101: first material, 101c: first material, 102: second material 2 substance, 102c: second substance, 103: third substance, 105: crack, 106: crack rack< / edx> < / xps> < / esr> < / xrd>

Claims

1. a current collector and a positive electrode active material layer located on the current collector, the positive electrode active material layer includes a plurality of positive electrode active materials, a first phosphate compound located between the plurality of positive electrode active materials, and a plurality of graphene compounds partially covering the plurality of positive electrode active materials, the plurality of positive electrode active materials include a first positive electrode active material, the first positive electrode active material has cracks, the first positive electrode active material includes magnesium, fluorine, and lithium cobalt oxide; the first positive electrode active material has a second phosphate compound inside the cracks, a magnesium concentration in a surface layer portion of the first positive electrode active material is higher than a magnesium concentration in an interior of the first positive electrode active material; a fluorine concentration in a surface layer portion of the first positive electrode active material is higher than a fluorine concentration in an interior of the first positive electrode active material; a lithium-ion secondary battery, wherein, in an X-ray photoelectron spectroscopy analysis of the plurality of positive electrode active materials, when the concentration of cobalt is taken as 1, the concentration of magnesium is 0.45 or more and less than 1.00, and when the concentration of cobalt is taken as 1, the concentration of fluorine is 0.3 or more and less than 1.

00.

2. a current collector and a positive electrode active material layer located on the current collector, the positive electrode active material layer includes a plurality of positive electrode active materials, a first phosphate compound located between the plurality of positive electrode active materials, and a plurality of graphene compounds attached to surfaces of the plurality of positive electrode active materials, the plurality of positive electrode active materials include a first positive electrode active material, the first positive electrode active material has cracks, the first positive electrode active material includes magnesium, fluorine, and lithium cobalt oxide; the first positive electrode active material has a second phosphate compound inside the cracks, a magnesium concentration in a surface layer portion of the first positive electrode active material is higher than a magnesium concentration in an interior of the first positive electrode active material; a fluorine concentration in a surface layer portion of the first positive electrode active material is higher than a fluorine concentration in an interior of the first positive electrode active material; a lithium-ion secondary battery, wherein, in an X-ray photoelectron spectroscopy analysis of the plurality of positive electrode active materials, when the concentration of cobalt is taken as 1, the concentration of magnesium is 0.45 or more and less than 1.00, and when the concentration of cobalt is taken as 1, the concentration of fluorine is 0.3 or more and less than 1.

00.

3. In claim 1 or claim 2, A lithium ion secondary battery, wherein the first phosphate compound and the second phosphate compound each contain one or more elements selected from lithium, sodium, potassium, magnesium, zinc, cobalt, iron, manganese, and aluminum.

4. In any one of claims 1 to 3, A lithium ion secondary battery, wherein, when the first positive electrode active material is analyzed by EDX, phosphorus is found inside the cracks.

5. In any one of claims 1 to 4, the plurality of positive electrode active materials include a second positive electrode active material, a third phosphate compound is disposed between the second positive electrode active material and the current collector; Lithium-ion secondary battery.

6. In any one of claims 1 to 5, The positive electrode active material layer of the lithium ion secondary battery does not contain a binder.

7. In any one of claims 1 to 6, The graphene compound includes graphene or multi-graphene.

8. In any one of claims 1 to 7, the first positive electrode active material has a first region having a layered rock salt crystal structure and a second region having a rock salt crystal structure in a surface layer portion of the first positive electrode active material, The first region and the second region have substantially the same crystal orientation.

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