Lithium ion secondary battery

Abstract

To provide a positive electrode active material for a lithium ion secondary battery having high capacity and excellent charge / discharge cycle characteristics.SOLUTION: When a pattern obtained by powder X-ray diffraction using a CuK α 1 ray is subjected to Rietveld analysis, the crystal structure has a 3m of R-space group, the a-axis lattice parameter is larger than 2.814 * 10 (- 10) m and smaller than 2.817 * 10 (- 10) m, and the c-axis lattice parameter is larger than 14.05 * 10 (- 10) m and smaller than 14.07 * 10 (- 10) m, when the positive electrode active material is analyzed by X-ray photoelectron spectroscopy, the relative value of the concentration of magnesium is 1.6 or more and 6.0 or less when the concentration of cobalt is 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] One aspect of the present invention relates to an article, a method, or a manufacturing method. Process, machine, manufacture, or composition of matter One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or a semiconductor device. In particular, the present invention relates to a secondary battery that can be used in an electronic device or a method for manufacturing the same. The present invention relates to a positive electrode active material, a secondary battery, and an electronic device having the 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). Research into the crystal structure is also being conducted (Non-Patent Documents 1 to 3).

[0007] X-ray diffraction (XRD) is one of the techniques used to analyze the crystalline structure of positive electrode active materials. ICSD (Inorganic Crystal Streptavidin) introduced in Non-Patent Document 5 Analysis of XRD data using the Structure Database can be done.

[0008] Patent Document 3 describes the Jahn-Teller effect in nickel-based layered oxides. There are. [Prior art documents] [Patent documents]

[0009] [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. 2017-188466 [Non-patent literature]

[0010] [Non-Patent Document 1] Toyoki Okumura et al, “Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3-and O2-lithium cobalt oxides from first-principle calculation”, Journal of Materials Chemistry, 2012, 22, p.17340-17348 [Non-patent document 2] Motohashi, T. et al, “Electronic phase diagram of the layered cobalt oxide system LixCoO2(0.0≦x≦1.0)”, Physical Review B, 80(16);165114 [Non-patent document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-patent document 4] WE Counts et al, Journal of the American Ceramic Society,(1953) 36[1] 12-17. Fig.01471 [Non-Patent Document 5] Belsky, A. et al., “New developments in the Inorganic Crystal Structure Database (ICSD): accessibility in support of materials research and design”, Acta Cryst., (2002) B58 364-369. Summary of the Invention [Problem to be solved by the invention]

[0011] 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.

[0012] 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

[0013] 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]

[0014] One aspect of the present invention is a method for producing a lithium-based lithium-ion battery comprising lithium, cobalt, magnesium, oxygen, and fluorine. The Rietveld solution was used to calculate the pattern obtained by powder X-ray diffraction using CuKα1 radiation. When the crystal structure was analyzed, it was determined that the crystal structure had the R-3m space group and a density of 2.814 × 10 - 10 m, 2.817×10 -10 m and the c-axis lattice constant is 14.0 5×10 -10 m, 14.07 × 10 -10 m and can be detected by X-ray photoelectron spectroscopy. When the cobalt concentration is taken as 1, the relative value of the magnesium concentration is 1.6 or more. It is a positive electrode active material having a dielectric constant of .0 or less.

[0015] Alternatively, one embodiment of the present invention is a compound of lithium, cobalt, magnesium, oxygen, and fluorine. and a positive electrode active material having the above structure, wherein the positive electrode active material is used in a positive electrode and lithium metal is used in a negative electrode. For lithium-ion secondary batteries, until the battery voltage reaches 4.7V in a 25°C environment The battery was charged at a constant current, and then charged at a constant voltage until the current reached 0.01C. Then, the positive electrode was replaced with CuKα When analyzed by powder X-ray diffraction using a single line, 2θ is 19.10° or more and 19.50° or less. and a second diffraction peak having a 2θ of 45.50° or more and 45.60° or less. and a positive electrode active material having the above structure.

[0016] In any of the above configurations, the positive electrode active material is used for the positive electrode, and lithium metal is used for the negative electrode. The lithium ion secondary battery used had a battery voltage of 4.7V in a 25°C environment. After that, the positive electrode was charged at a constant current until the current value reached 0.01C. When analyzed by powder X-ray diffraction using uKα1 radiation, 2θ is 19.10° or more and 19.50° or more. The first diffraction peak is below 45.50° and the second diffraction peak is below 45.60°. It is preferable that the flexural strength has a fold peak.

[0017] In any of the above configurations, the amount of magnesium measured by X-ray photoelectron spectroscopy The concentration is preferably 1.6 or more and 6.0 or less, assuming that the concentration of cobalt is 1.

[0018] In any of the above structures, nickel, aluminum, and phosphorus are contained. It is preferable that:

[0019] Alternatively, one embodiment of the present invention is a method for producing a lithium-based fluorine-based lithium ion battery comprising mixing a lithium source, a fluorine source, and a magnesium source. a first step of preparing a first mixture, the first mixture comprising lithium, cobalt, and oxygen; a second step of mixing the composite oxide with the first mixture to prepare a second mixture; a third step of heating the mixture of step 2 to form a third mixture; and a fourth step of mixing the aluminum source with the silicon dioxide to form a fourth mixture; and heating the fourth mixture. and a fifth step of preparing a fifth mixture, In the fourth step, the number of aluminum atoms in the aluminum source is determined by the number of aluminum atoms in the third mixture. The number of cobalt atoms contained in the positive electrode active material is 0.001 times or more and 0.02 times or less. It is the law.

[0020] In the above configuration, the magnesium source in the first step The number of atoms is 0.005 times or more the number of cobalt atoms in the composite oxide in the second step. It is preferable that the ratio is 0.5 times or less. [Effects of the Invention]

[0021] 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]

[0022] [Figure 1] FIG. 1 is a diagram illustrating the depth of charge and the crystal structure of the positive electrode active material. [Figure 2] FIG. 2 is a diagram illustrating the state of charge and the crystal structure of the positive electrode active material. [Figure 3] FIG. 3 is an XRD pattern calculated from the crystal structure. [Figure 4] Figure 4(A) shows the lattice constant calculated from XRD. Figure 4(B) shows the lattice constant calculated from XRD. Figure 4(C) shows the lattice constant calculated from XRD. [Figure 5] Figure 5(A) shows the lattice constant calculated from XRD. Figure 5(B) shows the lattice constant calculated from XRD. Figure 5(C) shows the lattice constant calculated from XRD. [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 method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 9]FIG. 9 illustrates an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 10] 10(A) and 10(B) are cross-sectional views of an active material layer in which a graphene compound is used as a conductive additive. [Figure 11] Fig. 11(A) is a diagram explaining a method for charging a secondary battery, Fig. 11(B) is a diagram explaining a method for charging a secondary battery, and Fig. 11(C) is a diagram explaining a method for charging a secondary battery. [Figure 12] Fig. 12(A) is a diagram explaining a method for charging a secondary battery, Fig. 12(B) is a diagram explaining a method for charging a secondary battery, and Fig. 12(C) is a diagram explaining a method for charging a secondary battery. [Figure 13] Fig. 13(A) is a diagram illustrating a method for charging a secondary battery, and Fig. 13(B) is a diagram illustrating a method for discharging a secondary battery. [Figure 14] Fig. 14(A) is a diagram illustrating a coin-type secondary battery, Fig. 14(B) is a diagram illustrating a coin-type secondary battery, and Fig. 14(C) is a diagram illustrating current and electrons during charging. [Figure 15] Fig. 15(A) is a diagram illustrating a cylindrical secondary battery. Fig. 15(B) is a diagram illustrating a cylindrical secondary battery. Fig. 15(C) is a diagram illustrating a plurality of cylindrical secondary batteries. Fig. 15(D) is a diagram illustrating a plurality of cylindrical secondary batteries. [Figure 16] Fig. 16(A) is a diagram illustrating an example of a battery pack, and Fig. 16(B) is a diagram illustrating an example of a battery pack. [Figure 17] Fig. 17(A1) is a diagram explaining an example of a secondary battery. Fig. 17(A2) is a diagram explaining an example of a secondary battery. Fig. 17(B1) is a diagram explaining an example of a secondary battery. Fig. 17(B2) is a diagram explaining an example of a secondary battery. [Figure 18] Fig. 18(A) is a diagram illustrating an example of a secondary battery, and Fig. 18(B) is a diagram illustrating an example of a secondary battery. [Figure 19] FIG. 19 is a diagram illustrating an example of a secondary battery. [Figure 20] Fig. 20(A) is a diagram illustrating a laminated secondary battery, Fig. 20(B) is a diagram illustrating a laminated secondary battery, and Fig. 20(C) is a diagram illustrating a laminated secondary battery. [Figure 21] Figure 21(A) is a diagram illustrating a laminated secondary battery, and Figure 21(B) is a diagram illustrating a laminated secondary battery. [Figure 22] FIG. 22 is a diagram showing the appearance of a secondary battery. [Figure 23] FIG. 23 is a diagram showing the appearance of a secondary battery. [Figure 24] Fig. 24(A) is a diagram for explaining a method for manufacturing a secondary battery, Fig. 24(B) is a diagram for explaining a method for manufacturing a secondary battery, and Fig. 24(C) is a diagram for explaining a method for manufacturing a secondary battery. [Figure 25] Fig. 25(A) is a diagram illustrating a bendable secondary battery. Fig. 25(B1) is a diagram illustrating a bendable secondary battery. Fig. 25(B2) is a diagram illustrating a bendable secondary battery. Fig. 25(C) is a diagram illustrating a bendable secondary battery. Fig. 25(D) is a diagram illustrating a bendable secondary battery. [Figure 26] Figure 26(A) is a diagram illustrating a bendable secondary battery, and Figure 26(B) is a diagram illustrating a bendable secondary battery. [Figure 27] FIG. 27(A) is a diagram illustrating an example of an electronic device. FIG. 27(B) is a diagram illustrating an example of an electronic device. FIG. 27(C) is a diagram illustrating an example of an electronic device. FIG. 27(D) is a diagram illustrating an example of an electronic device. FIG. 27(E) is a diagram illustrating an example of an electronic device. FIG. 27(F) is a diagram illustrating an example of an electronic device. FIG. 27(G) is a diagram illustrating an example of an electronic device. FIG. 27(H) is a diagram illustrating an example of an electronic device. [Figure 28] Fig. 28(A) is a diagram illustrating an example of an electronic device, Fig. 28(B) is a diagram illustrating an example of an electronic device, and Fig. 28(C) is a diagram illustrating an example of an electronic device. [Figure 29] FIG. 29 is a diagram illustrating an example of an electronic device. [Figure 30] Fig. 30(A) is a diagram illustrating an example of a vehicle, Fig. 30(B) is a diagram illustrating an example of a vehicle, and Fig. 30(C) is a diagram illustrating an example of a vehicle. [Figure 31] 31(A) and 31(B) show the continuous charge tolerance of the secondary battery. [Figure 32] 32(A) and 32(B) show the continuous charge tolerance of the secondary battery. [Figure 33] 33(A) and 33(B) show the cycle characteristics of the secondary battery. [Figure 34] 34(A) and 34(B) show the results of XRD evaluation of the positive electrode. [Figure 35] 35(A) and 35(B) show the results of XRD evaluation of the positive electrode. [Figure 36] 36(A) and 36(B) show the continuous charge tolerance of the secondary battery. [Figure 37] FIG. 37 shows the cycle characteristics of the secondary battery. [Figure 38] Figure 38(A) shows the charge and discharge curve of a secondary battery, Figure 38(B) shows the charge and discharge curve of a secondary battery, and Figure 38(C) shows the charge and discharge curve of a secondary battery. [Figure 39] 39(A) shows the results of TEM observation of the positive electrode active material, and Fig. 39(B) shows the results of EDX analysis of the positive electrode active material. [Figure 40] 40(A) and 40(B) show the results of XRD evaluation of the positive electrode. DETAILED DESCRIPTION OF THE INVENTION

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 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.

[0030] The pseudospinel crystal structure has random Li between layers, but the CdCl2 type It can be said that this CdCl2-like crystal structure is similar to the CdCl2-type crystal structure. 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 0.7 or more, Positive electrode active materials with a voltage of 0.9 or less are sometimes referred to as positive electrode active materials charged at a high voltage.

[0036] 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. This refers to the positive electrode active material that has been discharged in minutes.

[0037] 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.

[0038] (Embodiment 1) In this embodiment, a positive electrode active material of one embodiment of the present invention will be described.

[0039] [Positive electrode active material structure] Materials with a layered rock-salt crystal structure, such as lithium cobalt oxide (LiCoO2), are It has a high capacitance and is known to be an excellent positive electrode active material for secondary batteries. An example of a material with a crystalline structure is a composite oxide represented by LiMO2. An example of M is one or more selected from Co and Ni. In addition to one or more selected from Co and Ni, one or more selected from Al and Mn Examples include:

[0040] The Jahn-Teller effect in transition metal compounds depends on the number of electrons in the d orbital of the transition metal: The strength of the effect is known to vary.

[0041] In compounds containing nickel, distortion is likely to occur due to the Jahn-Teller effect. Therefore, when LiNiO2 is charged and discharged at high voltage, In LiCoO2, the Jahn-Teller effect is This suggests that the effect of the ion implantation is small, and the resistance to charging and discharging at high voltages may be superior, which is preferable. It's nice.

[0042] The positive electrode active material will be described with reference to Figs. 1 and 2. The case where cobalt is used as the transition metal in the substance will be described.

[0043] <Cathode active material 1> The positive electrode active material 100C shown in FIG. 2 is prepared by the method described later. The lithium cobalt oxide (LiCoO2) shown in Figure 2 is a lithium cobalt oxide (LiCoO2) with no added cations. As described in Non-Patent Documents 1 and 2, etc., the charge depth of lithium varies depending on the The crystal structure changes.

[0044] As shown in Figure 1, 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 six oxygen atoms are coordinated to form a single octahedron, which is connected to the plane by edge-sharing. .

[0045] 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.

[0046] 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, the c-axis of the H1-3 type crystal structure is used as a unit to facilitate comparison with other structures. This will be shown in a diagram of half the size of a knit cell.

[0047] As an example, the H1-3 type crystal structure has a unit cell as described in Non-Patent Document 3. The coordinates of cobalt and oxygen in 1(0, 0, 0.27671±0.00045), O2(0, 0, 0.11535±0. 00045), where O1 and O2 are oxygen atoms. The H1-3 crystal structure is formed by a unit cell with one cobalt and two oxygen atoms. On the other hand, as will be described later, the pseudospinel crystal structure of one embodiment of the present invention is preferably is represented by a unit cell with one cobalt and one oxygen. The symmetry between cobalt and oxygen is different between the spinel structure and the H1-3 structure. The pseudospinel structure is less different from the O3 structure than the H1-3 type structure. It is more preferable to use any one of the unit cells to represent the crystal structure of the positive electrode active material. For example, the selection of GOF (good of field) in Rietveld analysis of XRD is fitness) should be selected to be smaller.

[0048] High-voltage charging where the charging voltage is 4.6V or higher based on the oxidation-reduction potential of lithium metal When the battery is repeatedly charged or discharged to a deep depth of charge of 0.8 or more, Lithium cobalt oxide has a H1-3 type crystal structure and a R-3m(O3) structure in the discharged state. The crystal structure changes (i.e., non-equilibrium phase changes) between these two states.

[0049] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the arrows and the lines, in the H1-3 type crystal structure, the CoO2 layer is larger than the R-3m(O3) layer. Such dynamic structural changes have a negative effect on the stability of the crystal structure. Yes.

[0050] 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 3.0%.

[0051] 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.

[0052] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to collapse. The breakdown of the crystal structure causes a deterioration in cycle characteristics. , the number of sites where lithium can exist stably decreases, and lithium insertion and desorption becomes difficult. This is thought to be the reason.

[0053] <Cathode active material 2> ≪Inside≫ In the positive electrode active material of one embodiment of the present invention, the CoO2 layer is displaced during repeated high-voltage charge and discharge. Furthermore, the change in volume can be reduced. The positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. The positive electrode active material according to one embodiment of the present invention can have a stable crystal structure in a charged state at a high voltage. Therefore, the positive electrode active material of one embodiment of the present invention has a short circuit resistance when maintained in a charged state at a high voltage. In such cases, safety is improved, making it preferable. .

[0054] The positive electrode active material of one embodiment of the present invention has a sufficient discharge state and a high voltage charged state. The change in the crystal structure and the difference in volume when compared per the same number of transition metal atoms in small.

[0055] The crystal structure of the positive electrode active material 100A before and after charge and discharge is shown in FIG. It is a composite oxide containing titanium, cobalt, and oxygen. It is also preferable that the compound contains a halogen such as fluorine or chlorine.

[0056] The crystal structure at charge depth 0 (discharged state) in Figure 2 is the same as that in Figure 1, R-3m(O3). On the other hand, the positive electrode active material 100A has a different crystal structure from the H1-3 type when fully charged. It has a different crystal structure. This structure is in the space group R-3m, and the spinel crystal structure is However, ions such as cobalt and magnesium occupy the oxygen hexacoordinate positions, and the coordination of cations The rows have a symmetry similar to that of the spinel type. Therefore, this structure is referred to as a pseudospinel type in this specification. In the diagram of the pseudospinel crystal structure shown in Figure 2, cobalt In order to explain the symmetry of the atom and the symmetry of the oxygen atom, the lithium is omitted. However, in reality, lithium exists between the CoO2 layers at a ratio of, for example, 20 atomic % or less relative to cobalt. In addition, in both the O3 type crystal structure and the pseudospinel type crystal structure, CoO2 It is preferable that magnesium exists dilutely between the layers, i.e., at the lithium site. It is preferable that halogen such as fluorine is present randomly and dilutely at the oxygen sites.

[0057] In addition, in the pseudospinel crystal structure, light elements such as lithium occupy the four oxygen coordination positions. In this case, the ion arrangement also has a symmetry similar to that of the spinel type.

[0058] The pseudospinel crystal structure has random Li between layers, but the CdCl2 type It can be said that this CdCl2-like crystal structure is similar to the CdCl2-type crystal structure. The crystal structure is shown in Fig. 1 when lithium nickel oxide is charged to a charge depth of 0.94 (Li0.06 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.

[0059] 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.

[0060] In the case of the positive electrode active material 100A, when a large amount of lithium is released by charging at a high voltage, the crystal structure The change in the positive electrode active material 100C is suppressed more than that in the positive electrode active material 100C. For example, as shown by the dotted line in FIG. Furthermore, there is almost no misalignment of the CoO2 layers in these crystal structures.

[0061] More specifically, the positive electrode active material 100A has a stable structure even when the charging voltage is high. For example, the positive electrode active material 100C has a high charging voltage at which the H1-3 type crystal structure is formed, e.g. For example, even at a voltage of about 4.6 V based on the potential of lithium metal, the positive electrode active material 100 In A, there is a region of charging voltage where the crystal structure of R-3m(O3) can be maintained. For example, the potential of lithium metal is about 4.65V to 4.7V. There is also a region where the pseudo-spinel crystal structure can be formed even at high voltages. In some cases, H1-3 type crystals can be observed only after the For example, when graphite is used as the negative electrode active material, the voltage of the secondary battery is 4.3V or more, and There is a charging voltage range where the crystal structure of R-3m(O3) can be maintained even below 1000V. The charging voltage is further increased, for example, above 4.35V, based on the potential of lithium metal. Even at 55V or less, there exists a region in which the pseudospinel crystal structure can be formed.

[0062] Therefore, the crystalline structure of the positive electrode active material 100A remains unchanged even after repeated charging and discharging at high voltages. It doesn't crumble easily.

[0063] The pseudospinel crystal structure has the coordinates of cobalt and oxygen in the unit cell as follows: Co (0,0,0.5), O(0,0,x), 0.20≦x≦0.25 can.

[0064] 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 A is distributed throughout the particles. Therefore, it is preferable to perform a heat treatment in the process of producing the positive electrode active material 100A.

[0065] 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.

[0066] 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.

[0067] If the magnesium concentration is increased above a desired value, the effect on stabilizing the crystal structure is reduced. In addition to the lithium site, magnesium may also be present at the cobalt site. This is thought to be because the magnesium contained in the positive electrode active material of one embodiment of the present invention also enters the matrix. The number of um atoms is preferably 0.001 times or more and 0.1 times or less the number of cobalt atoms, and more preferably 0.0 More preferably, it is greater than 1 and less than 0.04, and even more preferably about 0.02. The magnesium concentration shown in is determined by, for example, measuring the magnesium content of the entire particle of the positive electrode active material using ICP-MS or the like. It may be a value obtained by elementary analysis, or a value obtained by mixing raw materials in the process of producing the positive electrode active material. It may be based on.

[0068] Lithium cobalt oxide is added with metals other than cobalt (hereinafter referred to as metal Z), such as nickel, One or more metals selected from aluminum, manganese, titanium, vanadium and chromium They may be added, and it is particularly preferred to add one or more of nickel and aluminum. Manganese, titanium, vanadium, and chromium may easily take on a stable tetravalent state. The addition of the metal Z may contribute significantly to the stability of the positive electrode active material of one embodiment of the present invention. For example, in some materials, the crystalline structure may become more stable when charged at a high voltage. In the positive electrode active material of one embodiment of the present invention, the metal Z improves the crystallinity of the lithium cobalt oxide. It is preferable to add it at a concentration that does not change significantly. It is preferable that the amount is such that the desired effect is not exhibited.

[0069] As the magnesium concentration of the positive electrode active material of one embodiment of the present invention increases, the volume of the positive electrode active material increases. The amount of magnesium may decrease. For example, this can occur when magnesium enters the lithium site. This may reduce the amount of lithium that contributes to charging and discharging. In some cases, magnesium may produce magnesium compounds that do not contribute to charging and discharging. The positive electrode active material of one embodiment contains nickel as the metal Z in addition to magnesium. This may increase the capacity per weight and per volume. In one embodiment, the positive electrode active material contains aluminum as the metal Z in addition to magnesium. This may increase the capacity per weight and per volume. The positive electrode active material of one embodiment of the present invention contains nickel and aluminum in addition to magnesium. This may allow for higher capacity per weight and volume.

[0070] The concentrations of elements such as magnesium and metal Z contained in the positive electrode active material of one embodiment of the present invention are as follows: is expressed using the number of atoms.

[0071] The number of nickel atoms in the positive electrode active material of one embodiment of the present invention is 7.5 times the number of cobalt atoms. % or less, more preferably 0.05% or more and 4% or less, and even more preferably 0.1% or more and 2% or less. The nickel concentration shown here is more preferably determined by measuring the nickel concentration in the positive electrode active material using, for example, ICP-MS or the like. The value may be obtained by elemental analysis of the entire particle, or may be obtained by analyzing the raw materials in the process of producing the positive electrode active material. It may also be based on the value of the ingredient combination.

[0072] The number of aluminum atoms in the positive electrode active material of one embodiment of the present invention is 0.01 to the number of cobalt atoms. The range is preferably 0.05% or more and 4% or less, and more preferably 0.1% or more and 2% or less. The aluminum concentration can be determined by, for example, performing elemental analysis of the entire particle of the positive electrode active material using ICP-MS. It may be a value obtained by the calculation, or it may be a value based on the composition of raw materials in the process of producing the positive electrode active material. Good too.

[0073] The positive electrode active material of one embodiment of the present invention preferably contains an element X, and the element X is preferably phosphorus. In addition, the positive electrode active material of one embodiment of the present invention is preferably a compound containing phosphorus and oxygen. It is more preferable that the .alpha.-hydroxybenzoate has the following structure:

[0074] The positive electrode active material of one embodiment of the present invention contains a compound containing element X, and thus high-voltage charging When the state is maintained, a short circuit may be unlikely to occur.

[0075] When the positive electrode active material of one embodiment of the present invention contains phosphorus as the element X, the decomposition of the electrolyte This may cause the hydrogen fluoride generated to react with phosphorus, resulting in a decrease in the hydrogen fluoride concentration in the electrolyte. do.

[0076] If the electrolyte contains LiPF6, hydrogen fluoride may be generated due to hydrolysis. In addition, hydrogen fluoride is produced by the reaction of PVDF, which is used as a component of the positive electrode, with alkali. The decrease in hydrogen fluoride concentration in the electrolyte may cause corrosion of the current collector. In addition, it may be possible to prevent the adhesion of PVDF from gelling or becoming insoluble. It may be possible to suppress the decline.

[0077] When the positive electrode active material according to one embodiment of the present invention contains magnesium in addition to the element X, high voltage charging When element X is phosphorus, the number of phosphorus atoms is equal to that of cobalt. The ratio of the number of atoms of 1 to 20% is preferable, the ratio of 2 to 10% is more preferable, and the ratio of 3% is even more preferable. More preferably, the number of magnesium atoms is 0.01 to 8.0%. 0.1% or more and 10% or less is preferable, 0.5% or more and 5% or less is more preferable, 0.7% or more The phosphorus and magnesium concentrations shown here are, for example, those obtained by ICP- The value may be a value obtained by performing elemental analysis of the entire particle of the positive electrode active material using MS or the like, or may be a value obtained by performing elemental analysis of the entire particle of the positive electrode active material using MS or the like. It may also be based on the value of the raw material composition in the process of making the quality.

[0078] When the positive electrode active material has cracks, phosphorus, more specifically, for example, phosphorus and acid, is present inside the cracks. The presence of a compound containing an element may inhibit the progression of cracks.

[0079] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100A. In addition, it is preferable that the magnesium concentration in the surface layer of the particle is higher than the average of the whole particle. For example, the magnesium concentration in the particle surface layer measured by XPS etc. is different from that measured by ICP-MS etc. It is preferable that the magnesium concentration is higher than the average magnesium concentration of the whole particles to be treated.

[0080] In addition, the positive electrode active material 100A may contain elements other than cobalt, such as nickel, aluminum, ma In the case where the composition contains one or more metals selected from the group consisting of zinc, iron, and chromium, particles of the metal It is preferable that the concentration in the surface layer is higher than the average concentration in the whole particle. The concentration of elements other than cobalt in the particle surface layer to be measured is measured by ICP-MS etc. It is preferable that the concentration is higher than the overall average concentration of the element.

[0081] The particle surface is essentially a crystal defect, and lithium is released from the surface during charging. As the lithium concentration in the outer layer increases, it is more likely to become lower than in the inner layer. If the magnesium concentration in the surface layer is high, the crystal structure will be easily broken. This allows for more effective suppression of structural changes. It is also expected that the corrosion resistance against hydrofluoric acid produced by decomposition of the electrolyte will be improved.

[0082] In addition, the concentration of halogens such as fluorine in the surface layer of the positive electrode active material 100A is higher than the average concentration of the whole particle. The presence of halogen in the surface layer, which is the region in contact with the electrolyte, This effectively improves corrosion resistance to hydrofluoric acid.

[0083] Thus, the surface layer of the positive electrode active material 100A has a higher concentration of magnesium and fluorine than the inside. It is preferable that the composition of the outer layer is different from that of the inner layer, and that the outer layer has a high degree of crystallinity and is stable at room temperature. Therefore, even if the surface layer has a different crystal structure from the interior, For example, at least a part of the surface layer of the positive electrode active material 100A has a rock salt crystal structure. In addition, when the surface layer and the inside have different crystal structures, It is preferable that the orientations of the two are approximately the same.

[0084] 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.

[0085] Furthermore, the element X is preferably located near the surface of the particles of the positive electrode active material 100A. For example, the positive electrode active material 100A may be covered with a coating containing the element X.

[0086] ≪Grain boundary≫ The magnesium or halogen contained in the positive electrode active material 100A is randomly and dilutely distributed inside. Although they may be present, it is more preferable that some of them are segregated at the grain boundaries.

[0087] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100A is also It is preferable that the halogen concentration at the grain boundary and its vicinity is higher than that in other regions. Preferably it is higher than other areas of the interior.

[0088] 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.

[0089] 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 grain of material 100A, the crack The magnesium and halogen concentrations are high near the surface, which is why cracks occur. The corrosion resistance of the subsequent positive electrode active material to hydrofluoric acid can also be improved.

[0090] 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.

[0091] ≪Particle size≫ If the particle size of the positive electrode active material 100A is too large, it becomes difficult for lithium to diffuse. On the other hand, if the particle size is too small, the surface of the active material layer becomes too rough when the particle size is too small. Problems such as difficulty in supporting the active material layer when coating the current collector and excessive reaction with the electrolyte Therefore, the average particle size (D50: also called the median diameter) is 1 μm or more. Preferably, it is 100 μm or less, more preferably 2 μm or more and 40 μm or less, and more preferably 5 μm or less More preferably, it is not less than 30 μm.

[0092] <Analysis method> According to one aspect of the present invention, a positive electrode active material exhibits a pseudospinel crystal structure when charged at a high voltage. Whether or not the positive electrode active material 100A is of the embodiment can be determined by measuring the positive electrode charged at a high voltage using XRD, electron beam Analysis using diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can be used to determine the symmetry of transition metals such as cobalt contained in the positive electrode active material. It is possible to analyze the crystallinity with high resolution, compare the crystallinity and crystal orientation, and measure the lattice period. The positive electrode obtained by disassembling a secondary battery can be measured directly, allowing for analysis of electrical distortion and crystallite size. This is preferable in that sufficient accuracy can be obtained even if the

[0093] As described above, the positive electrode active material 100A according to one embodiment of the present invention is in a state where it is charged at a high voltage. It is characterized by the fact that there is little change in the crystal structure between the charged and discharged states. Materials with a crystal structure that exhibits large changes in the charge and discharge states, accounting for 50 wt% or more, are resistant to high-voltage charging and discharging. Furthermore, the desired crystal structure cannot be obtained by simply adding impurity elements. It should be noted that there are cases where this is not possible. For example, Although they share the common feature of being lithium valence oxide, they are pseudo-spinel-type when charged at high voltage. When the crystal structure is 60 wt% or more, and when the H1-3 type crystal structure is 50 wt% or more In addition, at a certain voltage, the pseudo-spinel crystal structure is almost 100 wt%. Furthermore, if the voltage is increased further, an H1-3 type crystal structure may occur. Therefore, in order to determine whether or not the positive electrode active material 100A of one embodiment of the present invention is a positive electrode active material 100A, it is necessary to use XRD and other methods. Analysis of the crystal structure is needed.

[0094] 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 crystal structure may change from a pseudo-spinel type to an H1-3 type. Therefore, all samples were stored in an inert atmosphere such as argon. It is preferable to use a bonding method.

[0095] ≪Charging method≫ In order to determine whether a certain composite oxide is the positive electrode active material 100A of one embodiment of the present invention, For example, high voltage charging is performed using a coin cell (CR2032 type, 20mm diameter) with a lithium counter electrode. It is possible to create a battery (3.2mm high) and charge it.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] The separator can be made of polypropylene with a thickness of 25 μm.

[0100] The positive and negative electrode cans can be made of stainless steel (SUS). Cut.

[0101] 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.

[0102] <XRD> CuKα1 calculated from the pseudospinel crystal structure and H1-3 crystal structure model An ideal powder XRD pattern using the line is shown in Figure 3. For comparison, the LiC at a charge depth of 0 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. It was similarly created from the crystal structure information described in Reference 3. The pseudospinel crystal structure pattern is The crystal structure of the positive electrode active material according to one embodiment of the present invention was estimated from the XRD pattern, and the TOPAS ve r.3 (crystal structure analysis software manufactured by Bruker) was used for fitting and comparison with other Similarly, XRD patterns were generated.

[0103] As shown in Figure 3, 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 0A.

[0104] 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.

[0105] It should be noted that the positive electrode active material 100A of one embodiment of the present invention forms a pseudo-spinel crystal when charged at a high voltage. However, not all of the particles need to have a pseudo-spinel type crystal structure. However, the XRD pattern may be When Rietveld analysis was performed, the pseudo-spinel crystal structure was 50 wt% or more. It is preferably 60 wt% or more, more preferably 66 wt% or more. It is more preferable that the pseudo-spinel type crystal structure is 50 wt% or more, more preferably 60 wt% or more. Furthermore, if the content is more preferably 66 wt % or more, it will be a positive electrode active material with sufficiently excellent cycle characteristics. It is possible.

[0106] In addition, even after more than 100 charge / discharge cycles from the start of measurement, Rietveld analysis was performed. In this case, the pseudo-spinel crystal structure is preferably 35 wt% or more, and 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.

[0107] The crystallite size of the pseudospinel crystal structure of the positive electrode active material particles varies depending on the discharge state. Therefore, the positive electrode before charging and discharging Even under the same XRD measurement conditions, the peaks of a clear pseudospinel crystal structure were not observed after high-voltage charging. On the other hand, in simple LiCoO2, some of the crystal structure resembles a pseudospinel type. Even if the structure can be obtained, the crystallite size will be small and the peak will be broad and small. The crystallite size can be determined from the half-width of the XRD peak.

[0108] As described above, in the positive electrode active material according to one embodiment of the present invention, the influence of the Jahn-Teller effect is small. The positive electrode active material of one embodiment of the present invention has a layered rock salt type crystal structure and is preferably It is preferable that the transition metal is mainly cobalt. In materials where the influence of the Jahn-Teller effect is small, other than cobalt, It may have the metal Z mentioned.

[0109] XRD analysis of the positive electrode active material suggests that the Jahn-Teller effect is small. We consider the range of lattice constants that can be used.

[0110] 4(A) and (B) show that the positive electrode active material of one embodiment of the present invention has a layered rock salt type crystal structure. However, in the case of cobalt and nickel, the lattice definition of the a-axis and c-axis was obtained using XRD. The results of the estimation of the number are shown in Fig. 4(A) for the a-axis and Fig. 4(B) for the c-axis. The XRD used to calculate the lattice constants shown in Figures 4(A) and (B) was obtained by synthesizing the positive electrode active material. The horizontal axis shows the nickel concentration, and the horizontal axis shows the cobalt concentration. The positive electrode active material is, Steps S21 to S25 are used to create the condenser. The nickel concentration was determined by adding cobalt and nickel in step S21. The figure shows the concentration of nickel when the sum of the number of atoms of nickel and nickel is 100%.

[0111] 5(A) and (B) show that the positive electrode active material of one embodiment of the present invention has a layered rock salt type crystal structure. In the case of cobalt and manganese, the a-axis and c-axis lattice were determined using XRD. The results of estimating the constants are shown below. Figure 5(A) shows the results for the a-axis, and Figure 5(B) shows the results for the c-axis. The XRD used to calculate the lattice constants shown in Figures 5(A) and (B) was used to synthesize the positive electrode active material. The manganese concentration on the horizontal axis is the same as that on the cobalt The manganese concentration is calculated based on the sum of the number of manganese and manganese atoms taken as 100%. , which is produced using steps S21 to S25 described later, and in step S21 A cobalt source and a manganese source were used. The concentration of manganese was determined by adding cobalt in step S21. The manganese concentration is shown when the sum of the number of manganese and manganese atoms is taken as 100%.

[0112] Figure 4(C) shows the lattice constants of the positive electrode active materials shown in Figures 4(A) and (B). The lattice constant of the a-axis divided by the lattice constant of the c-axis (a-axis / c-axis) is shown in Figure 5(C). For the positive electrode active material whose lattice constants are shown in Figures 5(A) and (B), the lattice constant of the a-axis The value obtained by dividing the number by the lattice constant of the c-axis (a-axis / c-axis) is shown.

[0113] Figure 4(C) shows that the a-axis / c-axis tends to change significantly when the nickel concentration is 5% or 7.5%. This distortion is thought to be due to the Jahn-Teller distortion. At nickel concentrations below 7.5%, the Jahn-Teller strain is small. This suggests that an excellent positive electrode active material can be obtained.

[0114] Next, from Figure 5(A), when the manganese concentration is 5% or more, the behavior of the change in lattice constant is This suggests that the manganese concentration is different from that of the manganese oxide and does not follow Vegard's law. This suggests that the crystal structure is different. Therefore, the manganese concentration is preferably, for example, 4% or less. It's nice.

[0115] The above ranges of nickel concentration and manganese concentration are always within the ranges in the surface layer of the particles. In other words, the surface layer of the particle may have a higher concentration than the above. There are cases where this happens.

[0116] From the above, the preferable range of the lattice constant was considered, and it was found that the positive electrode of one embodiment of the present invention In the active material, the state without charge and discharge or discharged state that can be estimated from the XRD pattern In the layered rock salt type crystal structure of the particles of the positive electrode active material in the charged state, the lattice constant of the a-axis is 2 .814×10-10 m, 2.817×10 -10 smaller than m and the grid of the c axis The child constant is 14.05 x 10 -10 m, 14.07 × 10 -10 be smaller than m It has been found that this is preferable. The state in which no charge and discharge is performed is, for example, when preparing a positive electrode for a secondary battery. It may be in a powder state before being mixed.

[0117] Alternatively, the layer structure of the particles of the positive electrode active material in a state where no charge / discharge is performed or in a discharged state may be In a rock salt crystal structure, the lattice constant of the a-axis divided by the lattice constant of the c-axis (a-axis / c-axis) is preferably greater than 0.20000 and less than 0.20049.

[0118] Alternatively, the layer structure of the particles of the positive electrode active material in a state where no charge / discharge is performed or in a discharged state may be In the rock salt crystal structure, when XRD analysis was performed, 2θ was 18.50° or more and 19.30° or less. The first peak is observed at 2θ of 38.00° or less and the second peak is observed at 2θ of 38.80° or less. A peak may be observed.

[0119] 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 it is about 1 atomic %.

[0120] When XPS analysis was performed on the positive electrode active material 100A, the cobalt concentration was set to 1. The relative value of the magnesium concentration is preferably 1.6 or more and 6.0 or less, and more preferably 1.8 or more and less than 4.0. The relative concentration of halogen such as fluorine is preferably 0.2 or more and 6.0 or less. It is preferable that the ratio is 1.2 or more and 4.0 or less.

[0121] For example, monochromated aluminum can be used as the X-ray source when performing XPS analysis. The take-off angle may be set to, for example, 45°.

[0122] In addition, when the positive electrode active material 100A was analyzed by XPS, the bond energy between fluorine and other elements was The peak showing the energy is preferably 682 eV or more and less than 685 eV, and 684.3 It is more preferable that the bond energy of lithium fluoride is about 100 eV. 685 eV, and the binding energy of magnesium fluoride, 686 eV. In other words, when the positive electrode active material 100A contains fluorine, lithium fluoride and and magnesium fluoride bonds are preferred.

[0123] Furthermore, when the positive electrode active material 100A was analyzed by XPS, the amount of magnesium and other elements was The peak showing the binding energy is preferably 1302 eV or more and less than 1304 eV. It is more preferable that the electron energy is about 1303 eV. This is a different value from the bond energy of magnesium oxide, which is 1305 eV. In other words, when the positive electrode active material 100A contains magnesium, the magnesium fluoride Preferably, the bond is other than sodium.

[0124] 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.

[0125] 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.

[0126] When EDX analysis was performed on the positive electrode active material 100A, the peak of magnesium concentration in the surface layer The gaps are present up to a depth of 3 nm from the surface toward the center of the positive electrode active material 100A. Preferably, it exists to a depth of 1 nm, more preferably to a depth of 0.5 nm. It is even more preferable that

[0127] In addition, the distribution of fluorine in the positive electrode active material 100A overlaps with the distribution of magnesium. Therefore, when EDX analysis is performed, the peak of the fluorine concentration in the surface layer is It is preferable that the surface of the substance 100A is located at a depth of 3 nm from the surface toward the center. It is more preferable that the thickness is within 1 nm, and even more preferable that the thickness is within 0.5 nm. preferable.

[0128] ≪dQ / dVvsV curve≫ Furthermore, the positive electrode active material of one embodiment of the present invention can be charged at a high voltage and then discharged at a low voltage of, for example, 0.2 C or less. When discharging at a low rate, a characteristic voltage change may appear near the end of the discharge. The dQ / dV vs V curve obtained from the discharge curve is in the range of 3.5V to 3.9V. This can be clearly seen by the presence of at least one peak.

[0129] [Method 1 for preparing positive electrode active material] Next, an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described with reference to FIGS. 6 and 7. Another example of a specific manufacturing method will be described with reference to FIGS.

[0130] <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.

[0131] 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.

[0132] 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. (As a specific example of FIG. 6, step S11 of FIG. 8) When LiF and MgF2 are mixed at a molar ratio of about 65:35, the melting point of the mixture is lowered. On the other hand, when the amount of lithium fluoride is large, the lithium There is a concern that excessive fluoride will cause deterioration of cycle characteristics. The molar ratio of F to magnesium fluoride MgF2 is LiF:MgF2 = x:1 (0≦x≦1. 9), and LiF:MgF2=x:1 (0.1≦x≦0.5) is more preferable. Preferably, LiF:MgF2=x:1 (x=approximately 0.33) is even more preferable. In writing, "nearby" means a value greater than 0.9 times and less than 1.1 times the value.

[0133] 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. 8).

[0134] <Step S12> Next, the materials of the mixture 902 are mixed and crushed (step S in FIGS. 6 and 8). 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. .

[0135] <Steps S13 and S14> The mixed and crushed materials are collected (step S13 in FIGS. 6 and 8) and mixed 90 2 is obtained (step S14 in FIGS. 6 and 8).

[0136] The mixture 902 preferably has a D50 of, for example, 600 nm or more and 20 μm or less. It is more preferable that the particle size is 1 μm or more and 10 μm or less. 2, when mixed with a composite oxide containing lithium, a transition metal, and oxygen in a later process, In addition, it is easy to uniformly attach the mixture 902 to the surface of the composite oxide particles. If the mixture 902 is uniformly attached to the surface of the composite oxide particles, the mixture 902 will leak onto the surface layer of the composite oxide particles after heating. This is preferable because it is easy to distribute halogen and magnesium in the surface layer. If there is a region that does not contain magnesium, the pseudospinel crystals described above will form in the charged state. It may be difficult to achieve the structure.

[0137] Next, through steps S21 to S25, lithium, transition metal, and oxygen are added to the A composite oxide is obtained.

[0138] <Step S21> First, as shown in step S21 of FIG. 6, 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.

[0139] As the lithium source, for example, lithium carbonate, lithium fluoride, etc. can be used.

[0140] The transition metal may be, for example, at least one of cobalt, manganese, and nickel. can be done.

[0141] When a layered rock salt type crystal structure is used as the positive electrode active material, 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..

[0142] 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.

[0143] <Step S22> Next, the lithium source and the transition metal source are mixed together (step S22 in FIG. 6). 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

[0144] <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.

[0145] 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.

[0146] 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.

[0147] The metal contained in the positive electrode active material is Some of the metals may be introduced in steps S41 to S43 described later. It can also be introduced in step S46. More specifically, in steps S22 and S46, In step S23, metal M1 (M1 is cobalt, manganese, nickel, and aluminum) In steps S41 to S46, a metal M2 is introduced. (M2 is, for example, one or more selected from manganese, nickel, and aluminum) In this way, by separating the steps of introducing metal M1 and metal M2, In some cases, it is possible to change the depth profile of the metal. For example, The concentration of metal M2 can be increased in the surface layer of all the metals. The ratio of the number of atoms of the metal M2 to the reference number is made higher in the surface layer than in the interior. This can be done.

[0148] In the positive electrode active material according to one embodiment of the present invention, preferably, cobalt is selected as the metal M1, Nickel and aluminum are selected as the metal M2.

[0149] <Steps S24 and S25> The fired material was collected (step S24 in FIG. 6) and used as the positive electrode active material 100C. A composite oxide containing lithium, a transition metal, and oxygen is obtained (Step S25 in FIG. 6). Specifically, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and cobalt Lithium cobalt oxide partially substituted with manganese, or nickel-manganese-cobalt Lithium oxide is obtained.

[0150] 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. 8). 24 can be omitted.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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 8).

[0155] 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.

[0156] Here, the positive electrode active material 100C may have cracks. This occurs in one or more of steps S21 to S25. For example, this occurs during the baking process in step S23. The number of cracks that occur may change depending on conditions such as the speed of the cracks. It may also occur during processes such as blending and grinding.

[0157] <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 8). The number of transition metal atoms in the oxide, TM, and the number of magnesium atoms in the mixture 902, MgM The ratio of ix1 is TM:MgMix1=1:y (0.005≦y≦0.05). It is preferable that TM:MgMix1=1:y (0.007≦y≦0.04). It is more preferable that TM:MgMix1=1:0.02 or so.

[0158] 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.

[0159] <Steps S32 and S33> The mixed materials are collected (step S32 in FIGS. 6 and 8) to obtain a mixture 903. (Step S33 in FIGS. 6 and 8).

[0160] 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.

[0161] 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.

[0162] 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.

[0163] <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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] The temperature drop time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0168] 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.

[0169] 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

[0170] 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.

[0171] <Steps S35 and S36> The annealed material was collected (step S35 in FIGS. 6 and 8) to obtain the positive electrode active material 10. 0A_1 is obtained (step S36 in FIGS. 6 and 8).

[0172] [Method 2 for preparing positive electrode active material] The positive electrode active material 100A_1 obtained in step S36 may be further processed. Here, a process for adding metal Z is performed. This process is performed after step S25. By doing so, the concentration of metal Z in the particle surface layer of the positive electrode active material is made higher than that in the interior. This is preferable because it may be possible to

[0173] The addition of the metal Z may be carried out, for example, by adding the metal Z together with the mixture 902 in step S31. In this case, the number of steps can be reduced and the process can be simplified. This is preferable because it can be done easily.

[0174] Alternatively, as will be described later, the addition of metal Z may be performed after steps S31 to S35. In this case, for example, a compound of magnesium with the metal Z can be suppressed. It may be possible to control it.

[0175] Through steps S41 to S53 described below, a positive electrode active material according to one embodiment of the present invention is obtained. The metal Z is added in the above process. The metal Z can be added by, for example, a liquid phase method such as a sol-gel method, Solid phase method, sputtering method, evaporation method, CVD (chemical vapor deposition) method, PLD (pulsed laser The above-mentioned metal M2 can be added by, for example, This can be done using the metal Z addition step described below.

[0176] <Step S41> As shown in FIG. 7, first, in step S41, a metal source is prepared. When the sol-gel method is applied, a solvent for the sol-gel method is prepared. The metal Z may be aluminum, a metal oxide, a metal hydroxide, a metal oxide, or the like. In this case, for example, the number of cobalt atoms in lithium cobalt oxide is 1, and the metal source is The concentration of aluminum in the metal Z should be between 0.001 and 0.02 times. In the case of Kel, for example, the number of cobalt atoms in lithium cobalt oxide is 1, and the metal source The nickel concentration in the metal Z is 0.001 times or more and 0.02 times or less. In the case of aluminum and nickel, for example, the cobalt atoms of lithium cobalt oxide The number is set to 1, and the aluminum concentration in the metal source is 0.001 times or more and 0.02 times or less, or The concentration of nickel in the metal source may be 0.001 times or more and 0.02 times or less.

[0177] As an example, a sol-gel method is used, and aluminum isopropoxide is used as a metal source. An example in which isopropanol is used as a solvent will be shown (step S41 in FIG. 9).

[0178] <Step S42> Next, aluminum alkoxide is dissolved in alcohol, and then lithium cobalt oxide is added. The particles are mixed (step S42 in FIGS. 7 and 9).

[0179] The amount of metal alkoxide required varies depending on the particle size of the lithium cobalt oxide. When aluminum isopropoxide is used, the particle size (D50) of lithium cobalt oxide is 20 If the number of cobalt atoms in lithium cobalt oxide is 1, then the number of cobalt atoms in aluminum is 1. The aluminum concentration in the isopropoxide is 0.001 to 0.02 times. It is preferable to add

[0180] Next, the mixture of the alcohol solution of metal alkoxide and the lithium cobalt oxide particles was added to water. Stirring is performed in a steam-containing atmosphere. Stirring can be performed, for example, with a magnetic stirrer. The stirring time is determined based on the time it takes for the water in the atmosphere and the metal alkoxide to undergo hydrolysis and polycondensation reactions. For example, 4 hours, 25°C, 90% RH (relative humidity). It can be done under conditions of humidity (relative humidity). and in an atmosphere that is not temperature controlled, such as the atmospheric atmosphere in a draft chamber. In such a case, it is preferable to carry out the stirring for a longer period of time. For example, it may be left at room temperature for 12 hours or more.

[0181] By reacting water vapor in the atmosphere with metal alkoxide, the reaction is more efficient than when liquid water is added. The sol-gel reaction can be carried out slowly even at room temperature. This reaction allows for a higher yield than, for example, heating at a temperature above the boiling point of the alcohol solvent. The sol-gel reaction can be carried out slowly. By carrying out the sol-gel reaction slowly, This allows the formation of a high-quality coating layer with a uniform thickness.

[0182] <Steps S43 and S44> After the above treatment, the precipitate is collected from the mixed solution (step S43 in FIGS. 7 and 9). The recovery method can be filtration, centrifugation, evaporation to dryness, etc. It can be washed with the same alcohol as the solvent used to dissolve the metal alkoxide. If evaporation to dryness is used, separation of the solvent and precipitate is not necessary in this step. For example, the precipitate may be collected in the drying step of the next step (step S44). stomach.

[0183] Next, the collected residue is dried to obtain a mixture 904 (step S44 in FIGS. 7 and 9). The drying process can be carried out, for example, at 80°C for 1 hour to 4 hours, using vacuum or ventilation. Cut.

[0184] <Step S45> Next, the resulting mixture 904 is fired (step S45 in FIGS. 7 and 9).

[0185] The firing time is preferably 1 hour to 50 hours within the specified temperature range. If the baking time is too short, the surface layer may be damaged. The crystallinity of the compound containing the metal Z may be low. Alternatively, the diffusion of the metal Z may be insufficient. Or organic matter may remain on the surface. However, if the baking time is long, If the temperature is too high, the diffusion of metal Z may proceed too much, resulting in a low concentration in the surface layer and near the grain boundaries. In addition, productivity decreases.

[0186] The specified temperature is preferably 500°C or higher and 1200°C or lower, and more preferably 700°C or higher and 920°C or lower. It is more preferable that the temperature is 800°C or higher and 900°C or lower, and it is even more preferable that the temperature is 800°C or higher and 900°C or lower. The compound having metal Z formed in the layer may have low crystallinity. Diffusion may be insufficient, or organic matter may remain on the surface.

[0187] It is also preferable that the firing is carried out in an atmosphere containing oxygen. When the oxygen partial pressure is low, the firing temperature If the temperature is not lowered, there is a risk that Co will be reduced.

[0188] In this embodiment, the specified temperature is set to 850° C. and is maintained for 2 hours. °C / h, and the oxygen flow rate is 10 L / min.

[0189] Regarding cooling after firing, it is preferable to take a long cooling time, as this makes it easier to stabilize the crystal structure. For example, it is preferable that the time required for the temperature to drop from the specified temperature to room temperature is 10 hours or more and 50 hours or less. Here, the baking temperature in step S45 is set to be lower than the baking temperature in step S34. Preferably, it is low.

[0190] <Steps S46 and S47> Next, the cooled particles are collected (step S46 in FIGS. 7 and 9). In the above process, the positive electrode active material 100A according to one embodiment of the present invention is 2 can be fabricated (step S47 in FIGS. 7 and 9).

[0191] After step S47, steps S41 to S46 are repeated. The repetition may be once, or may be two or more times.

[0192] In addition, when the treatment is repeated multiple times, the type of metal source used may be the same or different. When different materials are used, for example, an aluminum source is used in the first treatment, A nickel source can be used in the second treatment.

[0193] <Step S51> Next, a compound containing element X is prepared as a first raw material 901 (see steps in FIGS. 7 and 9). Step S51).

[0194] In step S51, the first raw material 901 may be crushed. A mill, a bead mill, etc. can be used. The powder obtained after pulverization is separated using a sieve. You may also grade.

[0195] The first raw material 901 is a compound containing an element X, and phosphorus may be used as the element X. The first raw material 901 is preferably a compound having a bond between an element X and oxygen. It's nice.

[0196] For example, a phosphate compound can be used as the first raw material 901. A phosphate compound having element D can be used as the phosphate. Element D is lithium, sodium, , potassium, magnesium, zinc, cobalt, iron, manganese and aluminum It is possible to use a phosphate compound containing hydrogen in addition to element D. In addition, ammonium phosphate and ammonium phosphate containing element D can be used as phosphate compounds. A hum salt can be used.

[0197] Phosphate compounds include lithium phosphate, sodium phosphate, potassium phosphate, and magnesium phosphate. Nesium, zinc phosphate, aluminum phosphate, ammonium phosphate, lithium dihydrogen phosphate Examples of positive electrode active materials include magnesium phosphate, magnesium monohydrogen phosphate, and lithium cobalt phosphate. In particular, lithium phosphate and magnesium phosphate are preferably used.

[0198] In this embodiment, lithium phosphate is used as the first raw material 901 (see FIGS. 7 and 9). Step S51).

[0199] <Step S52> Next, the first raw material 901 obtained in step S51 and the positive electrode The first raw material 901 is mixed with the active material 100A_2 (step S52 in FIGS. 7 and 9). is 0.01 m per 1 mol of the positive electrode active material 100A_2 obtained in step S25. 100 mol or more and 0.1 mol or less, more preferably 0.02 mol or more and 0.08 mol or less It is preferable to mix the above-mentioned ingredients in the same amount. For example, a ball mill, a bead mill, etc. may be used for mixing. The powder obtained after mixing may be classified using a sieve.

[0200] <Step S53> Next, the mixed materials are heated (step S53 in FIGS. 7 and 9). In the preparation of the 3-hydroxybenzoate, this step may not be performed. It is preferable to carry out the heating at a temperature of 00°C or higher but lower than 1200°C, and to carry out the heating at a temperature of 550°C or higher but lower than 950°C. If the temperature is too low, the starting materials may decompose and On the other hand, if the temperature is too high, the transition metals may be excessively reduced. There is a risk of defects occurring due to factors such as lithium evaporation.

[0201] Heating may produce a reaction product between positive electrode active material 100A_2 and first raw material 901. do.

[0202] 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.

[0203] However, cooling to room temperature in step S53 is not essential. If there is no problem in carrying out step 54, the cooling may be to a temperature higher than room temperature.

[0204] <Step S54> The calcined material is collected (step S54 in FIGS. 7 and 9), and a positive electrode containing element D is formed. Active material 100A_3 is obtained.

[0205] Regarding the positive electrode active material 100A_1, the positive electrode active material 100A_2, and the positive electrode active material 100A_3, For this purpose, reference can be made to the description of the positive electrode active material 100A shown in FIG. 2 and the like.

[0206] (Embodiment 2) In this embodiment, a secondary battery having the positive electrode active material 100 described in the previous embodiment is used. In this embodiment, examples of materials that can be used for the positive electrode, the negative electrode, and the electrolyte will be described. A secondary battery in which the electrolyte is enclosed in an exterior body will be described as an example.

[0207] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0208] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material. In addition, other substances such as a coating on the surface of the active material, a conductive additive, or a binder may be included.

[0209] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, it is possible to achieve high capacity and cycle characteristics. Therefore, a secondary battery having excellent properties can be obtained.

[0210] 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. Below is more preferable.

[0211] 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.

[0212] 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.

[0213] A graphene compound may also be used as the conductive additive.

[0214] 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).

[0215] 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.

[0216] In the following, as an example, a graphene compound is used as a conductive additive in the active material layer 200. An example of the cross-sectional configuration in this case will be described.

[0217] 10(A) shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of granular positive electrode active material. A material 100, a graphene compound 201 as a conductive additive, a binder (not shown), Here, the graphene compound 201 includes, for example, graphene or multigraphene. Here, the graphene compound 201 preferably has a sheet shape. Preferably, the graphene compound 201 is a multi-graphene or (and) A plurality of graphenes may be partially overlapped to form a sheet.

[0218] In the vertical cross section of the active material layer 200, as shown in FIG. 10(B), In the portion, the sheet-like graphene compound 201 is dispersed almost uniformly. In this figure, the graphene compound 201 is shown as a schematic diagram with a thick line, but in reality, it is a single layer of carbon molecules. The graphene compounds 201 are formed of a plurality of granular positive electrodes. The positive electrode active material 100 is partially covered with the positive electrode active material 100 or is spread on the surface of a plurality of granular positive electrode active materials 100. Since they are formed to adhere to each other, they are in surface contact with each other.

[0219] 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.

[0220] Here, graphene oxide is used as the graphene compound 201, and is mixed with an active material to form an active material. After forming the layer that will become the graphene compound layer 200, it is preferable to reduce the layer. By using graphene oxide, which has extremely high dispersibility in polar solvents, The compound 201 can be dispersed approximately uniformly inside the active material layer 200. The solvent is evaporated from the dispersion medium containing the graphene oxide dispersed in the solution, and the graphene oxide is reduced. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps with each other. By dispersing the particles so that they come into surface contact with each other, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be carried out by, for example, heat treatment or by using a reducing agent. You may go.

[0221] 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 active material layer 200 can be increased. This makes it possible to increase the discharge capacity of the secondary battery.

[0222] 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.

[0223] 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.

[0224] 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

[0225] 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.

[0226] The binder may be used in combination with two or more of the above.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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

[0231] <Positive electrode current collector> 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.

[0232] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. and a binder.

[0233] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0234] As a negative electrode active material, it can carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any element can be used, such as 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.

[0235] 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.

[0236] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. stomach.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. つLi 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2. 6Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 )of This is preferable.

[0241] When a composite nitride of lithium and transition metals is used, lithium ions are included in the negative electrode active material, As a positive electrode active material, materials that do not contain lithium ions, such as V2O5 and Cr3O8, are used. In addition, when a material containing lithium ions is used as the positive electrode active material, However, by first removing the lithium ions contained in the positive electrode active material, As the lithium-transition metal nitride, a complex nitride of lithium and a transition metal can be used.

[0242] 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.

[0243] 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.

[0244] <Negative electrode current collector> 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.

[0245] [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:

[0246] 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.

[0247] 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.

[0248] 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.

[0249] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxa) Lithium borate (LiBOB), as well as dinitriles such as succinonitrile and adiponitrile The concentration of the additives may be, for example, The content should be between 0.1 wt% and 5 wt%.

[0250] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0251] The use of polymer gel electrolyte increases safety against leakage etc. The pond can be made thinner and lighter.

[0252] 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.

[0253] 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.

[0254] 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.

[0255] [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.

[0256] 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.

[0257] 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.

[0258] 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. .

[0259] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the capacity per unit volume of the secondary battery can be increased,

[0260] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. , such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide On the film made of such material, a highly flexible material such as aluminum, stainless steel, copper, or nickel is applied. A metal thin film is provided, and a polyamide resin or polyester is further provided on the metal thin film as the outer surface of the exterior body. A film having a three-layer structure provided with an insulating synthetic resin film such as a terephthalate resin can be used.

[0261] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0262] ≪CC charging≫ First, we will explain CC (constant current) charging as one of the charging methods. A constant current is passed through the secondary battery throughout the entire period, and charging stops when the specified voltage is reached. This is a charging method. The secondary battery is charged with the internal resistance R and the secondary battery capacity C as shown in Figure 11(A). In this case, the secondary battery voltage V B is the voltage V across the internal resistance R R and two Voltage V applied to the next battery capacity C C It is the sum of.

[0263] During CC charging, the switch is turned on and a constant current is applied, as shown in Figure 11(A). During this time, the current I is constant, so V R = R x I in ohms According to the law, the voltage V across the internal resistance R R On the other hand, depending on the secondary battery capacity C, Voltage V C increases over time. Therefore, the secondary battery voltage V B Over time, It increases with time.

[0264] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, charging stops. When CC charging is stopped, the switch is turned off and the current I = 0. Therefore, the voltage V applied to the internal resistance RR becomes 0V. Therefore, the secondary battery Voltage V B is decreasing.

[0265] The secondary battery voltage V during CC charging and after CC charging is stopped B and charging current An example of this is shown in Figure 11(C). The secondary battery voltage V B but , it is shown that there is a slight decrease after CC charging is stopped.

[0266] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a charging method different from the above. First, charge to a specified voltage using CC charging, then use CV (constant voltage) charging to charge the current This is a charging method in which charging is performed until the current becomes low, specifically until it reaches the end current value.

[0267] During CC charging, the constant current power supply is switched on as shown in Figure 12(A). At this time, the constant voltage power supply is switched off and a constant current I flows through the secondary battery. Since 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.

[0268] 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 12(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.

[0269] 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 12(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 .

[0270] The secondary battery voltage V during CCCV charging and after CCCV charging is stopped B and An example of the charging current is shown in Figure 13(A). Even if CCCV charging is stopped, the secondary battery voltage V B Gaho It shows that the aircraft is barely descending at all.

[0271] ≪CC discharge≫ Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is A constant current flows from the secondary battery, and the secondary battery voltage V B is set to a predetermined voltage, e.g. 2.5V. This is a discharge method in which the discharge is stopped when

[0272] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Figure 13(B). As the charge progresses, the secondary battery voltage V B is shown to be descending.

[0273] Next, the discharge rate and charge rate will be explained. It is the relative ratio of the discharge current to the battery, expressed in units of C. In this case, the current equivalent to 1C is X (A). When discharging with a current of 2X (A), It is said that it was discharged at C, and when it was discharged at a current of X / 5(A), it was discharged at 0.2C. The charging rate is also the same, if you charge it with a current of 2X (A), it will be 2C. If it is charged at a current of X / 5(A), it is said to be charged at 0.2C. cormorant.

[0274] (Embodiment 3) In this embodiment, the secondary battery having the positive electrode active material 100 described in the previous embodiment is 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.

[0275] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. FIG. 14(A) shows a coin-type (single-layer flat) 14(A) and 14(B) are external views of a secondary battery of the same type, and FIG. 14(B) is a cross-sectional view thereof.

[0276] 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. 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.

[0277] 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.

[0278] 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.

[0279] 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 immersed in an electrolyte. 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.

[0280] 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.

[0281] Here, the flow of current during charging of the secondary battery will be explained using FIG. 14(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.

[0282] A charger is connected to the two terminals shown in FIG. 14(C), and the secondary battery 300 is charged. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0283] [Cylindrical secondary battery] Next, see Figures 15(A), (B), (C) and (D) for examples of cylindrical secondary batteries. The external view of a cylindrical secondary battery 600 is shown in FIG. 15(A). 15(B) is a diagram showing a cross section of a cylindrical secondary battery 600. The cylindrical secondary battery 600 has a positive electrode cap (battery lid) 601 on the top surface, and The positive electrode cap and the battery can (external can) 602 are attached to the bottom surface. It is insulated from 602 by a gasket (insulating packing) 610 .

[0284] 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.

[0285] 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.

[0286] 15(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.

[0287] 15(D) is a top view of module 615. For clarity, conductive plate 613 As shown in FIG. 15(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.

[0288] 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.

[0289] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0290] 16(A) and 16(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 16(B), the secondary battery 913 has a terminal 95 1 and terminal 952.

[0291] The circuit board 900 has a circuit 912. The terminal 911 is connected to the terminal The terminal 951 is connected to the terminal 952, the antenna 914, and the circuit 912. 1, and each of the plurality of terminals 911 is used as a control signal input terminal, a power supply terminal, etc. That's fine.

[0292] 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.

[0293] Alternatively, the antenna 914 may be a flat conductor. In other words, the capacitor can function as one of the two conductors. The antenna 914 may function as one of the conductors. Furthermore, electric power can be exchanged using an electric field.

[0294] 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.

[0295] The structure of the secondary battery is not limited to that shown in FIGS.

[0296] For example, as shown in Figs. 17(A1) and 17(A2), Figs. In the secondary battery 913 shown in FIG. 9B, an antenna may be provided on each of a pair of opposing surfaces. FIG. 17(A1) is an external view showing one of the pair of surfaces, and FIG. 17(A2) is an external view showing one of the pair of surfaces. 16(A) and 16(B) are external views showing the other of the pair of surfaces. For the same parts as the secondary battery, please refer to the description of the secondary battery shown in Figures 16(A) and 16(B). It can be used as appropriate.

[0297] As shown in FIG. 17(A1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. As shown in FIG. 17(A2), an antenna 914 is provided on both sides of the secondary battery 913. An antenna 918 is provided on the opposite side with a layer 917 sandwiched therebetween. The layer 917 is, for example, a secondary battery 913. The layer 917 has a function of shielding the electromagnetic field caused by the magnetic material. It can be used.

[0298] 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.

[0299] Alternatively, as shown in FIG. 17(B1), the secondary battery 9 shown in FIG. 16(A) and FIG. 16(B) A display device 920 may be provided in the display device 13. 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. 16(A) and 16(B), the same parts as those of the secondary battery shown in FIG. 16(A) and FIG. The explanation of the secondary battery shown in FIG. 16(B) can be used as appropriate.

[0300] 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.

[0301] Alternatively, as shown in FIG. 17(B2), the secondary battery 9 shown in FIG. 16(A) and FIG. 16(B) 13 may be provided with a sensor 921. The sensor 921 is connected to the terminal 911 via a terminal 922. It is electrically connected to the same part as the secondary battery shown in Fig. 16(A) and Fig. 16(B). In this regard, the description of the secondary battery shown in FIGS. 16(A) and 16(B) can be used as appropriate.

[0302] 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.

[0303] Furthermore, an example of the structure of the secondary battery 913 will be explained with reference to FIGS. 18(A), 18(B) and 19. Reveal.

[0304] The secondary battery 913 shown in FIG. 18(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. 18(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.

[0305] As shown in FIG. 18(B), the housing 930 shown in FIG. 18(A) can be made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 18B 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.

[0306] 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 918 may be provided inside the housing 930b. For example, a metal material can be used as the material.

[0307] Furthermore, the structure of the wound body 950 is shown in Fig. 19. 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.

[0308] The negative electrode 931 is connected to the terminal 951 or the terminal 952 as shown in FIGS. 16(A) and 16(B). The positive electrode 932 is connected to the terminal 911 shown in FIG. It is connected to the terminal 911 shown in FIGS.

[0309] 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.

[0310] [Laminated secondary battery] Next, examples of laminated secondary batteries will be described with reference to FIGS. 20(A) to 26(B). If the laminated secondary battery has a flexible structure, it can be used as a flexible battery. If the secondary battery is mounted in an electronic device having at least a part of the battery, the secondary battery can be adjusted to conform to the deformation of the electronic device. It can also be bent.

[0311] 20(A), (B), and (C), the laminated secondary battery 980 The laminated secondary battery 980 has a wound body 993 shown in FIG. The wound body 993 includes a negative electrode 994, a positive electrode 995, and a separator 996. The winding body 993 is formed by sandwiching a separator 996 between the negative electrode 991 and the negative electrode 992, similar to the winding body 950 described with reference to FIG. The positive electrode 994 and the positive electrode 995 are stacked on top of each other, and the laminated sheet is wound up.

[0312] 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. .

[0313] As shown in FIG. 20(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.

[0314] 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.

[0315] In addition, although Fig. 20(B) and Fig. 20(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.

[0316] 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.

[0317] In addition, in Fig. 20(B) and (C), the film is wound in the space formed by the outer casing. 21(A) and 21(B) are used. In this way, a plurality of rectangular positive electrodes, separators, and The secondary battery may have a cathode and an anode.

[0318] The laminated secondary battery 500 shown in FIG. 21(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.

[0319] In the laminated secondary battery 500 shown in FIG. 21(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 .

[0320] 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.

[0321] 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 21(B ) it is composed of multiple electrode layers.

[0322] In FIG. 21(B), as an example, the number of electrode layers is set to 16. In FIG. 21(B), the negative electrode current collector 504 is made up of eight layers. 21(B) shows a structure of 16 layers in total, with 8 layers of the 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.

[0323] An example of an external view of a laminated secondary battery 500 is shown in FIGS. 22 and 23. 22 and 23 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.

[0324] FIG. 24(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.

[0325] [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. 22, will be described. 4(B) and (C) will be used to explain.

[0326] 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.

[0327] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0328] Next, as shown in FIG. 24(C), the exterior body 509 is folded at the portions indicated by the broken lines. 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.

[0329] 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.

[0330] 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.

[0331] [Bendable secondary battery] Next, examples of bendable secondary batteries are shown in Figures 25(A), (B1), (B2), (C), (D), and (B) of FIG. 26 will be referred to.

[0332] Fig. 25(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. 25(A), respectively. 1C-C4 is a schematic cross-sectional view taken along the cutting 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.

[0333] The positive electrode 211a and the negative electrode 211b of the secondary battery 250 are shown in FIG. 26(A) shows a positive electrode 211a, a negative electrode 211b, and a separator. 26(B) is a perspective view illustrating the stacking order of the positive electrode 211a and the negative electrode 214. 11b, as well as leads 212a and 212b.

[0334] As shown in FIG. 26(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.

[0335] 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.

[0336] 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 parameter 214 is shown in dotted lines.

[0337] As shown in FIG. 26(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.

[0338] Next, the exterior body 251 will be described with reference to FIGS. 25(B1), (B2), (C), and (D). do.

[0339] 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.

[0340] 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.

[0341] FIG. 25(B1) is a cross section cut at the part overlapping with the ridge line 271, and FIG. 25(B2) is 25(B1) and (B2) are cross sections cut at the part overlapping with the valley line 272. It corresponds to a cross section in the width direction of the secondary battery 250, the positive electrode 211a and the negative electrode 211b.

[0342] 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. .

[0343] 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.

[0344] 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.

[0345] 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.

[0346] 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.

[0347] 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.

[0348]

number

[0349] 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.

[0350] 25(C) is a cross section including the lead 212a, and shows the secondary battery 250, the positive electrode 211, 25(C), the bending portion 211a corresponds to the cross section of the negative electrode 211b in the longitudinal direction. 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.

[0351] FIG. 25(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. 25(A).

[0352] 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.

[0353] Furthermore, as shown in FIG. 25(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 is such that the deviation amount increases as the distance approaches 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.

[0354] 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.

[0355] Examples are shown in Figures 25(A), (B1), (B2), (C), (D), and Figures 26(A) and (B). The secondary battery 250 shown in the figure was repeatedly bent and stretched without damage to the exterior body or the positive electrode 211a. In addition, the negative electrode 211b is less likely to be damaged, and the battery characteristics are less likely to deteriorate. The positive electrode 211a of the battery 250 is made of the positive electrode active material described in the previous embodiment. This makes it possible to obtain a battery with even better cycle characteristics.

[0356] (Fourth embodiment) 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.

[0357] 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 Fig. 27(A) to Fig. 27(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.

[0358] 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.

[0359] FIG. 27A shows an example of a mobile phone. The mobile phone 7400 has 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.

[0360] FIG. 27B 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:

[0361] FIG. 27(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. 27(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.

[0362] FIG. 27(F) shows an example of a wristwatch-type portable information terminal. 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.

[0363] 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.

[0364] 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.

[0365] 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.

[0366] 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.

[0367] 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.

[0368] 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. 27(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.

[0369] 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.

[0370] FIG. 27G 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.

[0371] 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.

[0372] 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.

[0373] 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.

[0374] 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 Figure 27(H), Figures 28(A), (B), (C) and Figure 29.

[0375] 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.

[0376] FIG. 27(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In FIG. 27(H), an 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.

[0377] Next, Fig. 28(A) and Fig. 28(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIGS. 28(A) and 28(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. 28(A) shows the tablet terminal 9600 in an open state, and FIG. (B) shows the tablet terminal 9600 in a closed state.

[0378] 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.

[0379] 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.

[0380] 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

[0381] 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.

[0382] 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.

[0383] In FIG. 28A, 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

[0384] FIG. 28(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.

[0385] 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.

[0386] In addition, the tablet terminal 9600 shown in FIG. 28(A) and FIG. 28(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.

[0387] 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.

[0388] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. A block diagram is shown in FIG. 28(C) and will be explained. In FIG. 28(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.

[0389] 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.

[0390] 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.

[0391] Another example of electronic equipment is shown in FIG. 29. In FIG. 29, 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.

[0392] 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.

[0393] 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:

[0394] In FIG. 29, 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, 29, 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.

[0395] In addition, FIG. 29 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.

[0396] 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.

[0397] In FIG. 29, 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.

[0398] In addition, Figure 29 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.

[0399] In FIG. 29, 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. 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.

[0400] 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

[0401] 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.

[0402] 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.

[0403] (Embodiment 5) 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.

[0404] 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.

[0405] 30(A), (B), and (C) show the results of the test using the secondary battery according to one embodiment of the present invention. An automobile 8400 shown in FIG. 30(A) uses electricity as a power source for running. It is an electric vehicle that uses a motor. Or, it uses an electric motor as a power source for driving. The present invention relates to a hybrid vehicle that can use an engine selected as needed. By using this, it is possible to realize a vehicle with a long cruising range. The secondary battery is attached to the floor of the vehicle as shown in Fig. 15(C) and Fig. 15(D). ) can be used by arranging the secondary battery modules shown in Figs. A battery pack consisting of multiple secondary batteries as shown in B) may be installed on the floor of the vehicle. The secondary battery not only drives the electric motor 8406 but also powers the headlights 8401 and Power can be supplied to a light emitting device such as a room light (not shown).

[0406] 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.

[0407] The car 8500 shown in FIG. 30(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. 30(B) shows a diagram of a charging device 8021 mounted on a ground and a charging station 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.

[0408] 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.

[0409] 30C 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. 1(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.

[0410] In addition, the scooter 8600 shown in FIG. 30(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.

[0411] 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.

[0412] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0413] In this example, a positive electrode active material containing magnesium, fluorine, and phosphorus was prepared. A secondary battery having a positive electrode using the active material is manufactured, and the continuous charge durability and cycle life of the secondary battery are measured. The properties were evaluated.

[0414] <Preparation of positive electrode active material> The positive electrode active material was prepared with reference to the flow charts of FIGS. Steps S41 to S47 were not performed.

[0415] First, a mixture 902 containing magnesium and fluorine was prepared (steps shown in FIG. 8). Steps S11 to S14) The molar ratio of LiF and MgF2 is LiF:MgF2=1: The mixture was weighed to a weight of 3, and acetone was added as a solvent, followed by wet mixing and pulverization. The powder was crushed and pulverized in a ball mill using zirconia balls at 150 rpm for 1 hour. The treated material was collected and designated as mixture 902.

[0416] Next, a positive electrode active material containing cobalt was prepared (step S25). The lithium cobalt oxide synthesized for this purpose was Cellseed C-10 manufactured by Nippon Chemical Industry Co., Ltd. CellSeed C-10N is a cobalt alloy with a D50 of approximately 12 μm and few impurities. It is lithium oxide.

[0417] Next, the mixture 902 and lithium cobalt oxide were mixed (step S31). The atomic weight of magnesium in mixture 902 is The atomic weights were conditioned. The values ​​of the conditions were approximately 0.5%, 1.0%, 2.0%, and 3. The magnets of the positive electrode active materials were weighed out so that the magnets were 0.0% and 6.0%. The atomic weight of sodium is shown in Tables 1 and 2 below. The mixture was dry mixed. The mixture was mixed in a ball mill using zirconia balls at 150 rpm for 1 hour.

[0418] Next, the treated material was collected to obtain a mixture 903 (steps S32 and S3 3).

[0419] 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 with a lid during the annealing. The oxygen flow rate was 10 L / min. The temperature rise rate was 200°C / hr, and the temperature drop rate was 10 hours or more. The material after the heat treatment is collected (step S35), sieved, and the magnesium The positive electrode active material (positive electrode active material 100A_1 shown in FIG. 8) was prepared by adjusting the amount of added aluminum. The magnesium concentration was then measured at 0.5%, 1.0%, 2.0%, and 3.0% (step S36). 0.0% and 6.0% of the positive electrode active material 100A_1, respectively, 11. Sample 12. Sample 13. Samp These are called Sample 14 and Sample 15. In the preparation, the positive electrode active material 100A_1 obtained in this step and the positive electrode active material 100B_2 obtained in the following step were used. Both the positive electrode active material that had been subjected to steps S51 to S54, which will be described later, and the positive electrode active material that had been subjected to steps S52 to S54 were used.

[0420] Thereafter, the metal addition in steps S42 to S47 shown in FIG. 9 is not performed. We proceeded to Top S51.

[0421] Next, lithium phosphate was prepared (step S51). The material 100A_1 was mixed (step S52). The amount of lithium phosphate mixed was The amount was equivalent to 0.06 mol per 1 mol of active material 100A_1. The mixture was mixed in a ball mill using ruthenium balls at 150 rpm for 1 hour. The mixture was then placed in an alumina crucible and covered with a lid. The substrate was then annealed in an oxygen atmosphere at 750° C. for 20 hours (step S53). The powder was collected by passing it through a sieve with a diameter of 1 mm (Step S54). The positive electrode active material ( The following are positive magnesium concentrations: 0.5%, 1.0%, 2.0%, 3.0% and 6.0% The electrode active materials are Sample 21 and Sample 2, respectively. 2, Sample 23, Sample 24 and Samp le(sample) 25) was obtained.

[0422] <Preparation of secondary battery> Each positive electrode was fabricated using each of the positive electrode active materials obtained above. A slurry of AB and PVDF mixed at a weight ratio of 95:3:2 was prepared. The slurry was coated on a current collector and NMP was used as the solvent for the slurry.

[0423] 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 pressure of 1467 kN / m was applied. Through these steps, a positive electrode was obtained. The electrode loading is approximately 20 mg / cm 2 It was decided.

[0424] Using the prepared positive electrode, a CR2032 type coin (diameter 20 mm, height 3.2 mm) was A secondary battery of this type was fabricated.

[0425] The counter electrode was made of lithium metal.

[0426] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). The mixture was EC:DEC = 3:7 (volume ratio). For the secondary battery, 2 wt% vinylene carbonate (VC) was added to the electrolyte. Ta.

[0427] The separator was made of polypropylene with a thickness of 25 μm.

[0428] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0429] <Continuous charging durability> Next, the continuous charge durability of each secondary battery using each of the prepared positive electrode active materials was evaluated. First, charging was performed under CCCV (0.05C, 4.5V or 4.6V, final current 0 0.005C), discharge CC (0.05C, 2.5V) and measured for 2 cycles at 25°C It was determined.

[0430] Then, the battery was charged at 60°C using CCCV (0.05C). The upper limit voltage was 4.55V. or 4.65V, and the termination condition is the secondary battery voltage minus 0.01V from the upper limit voltage. The time until the voltage dropped below 4.54V (for 4.55V) was measured. If the voltage drops below the upper limit, a short circuit or other problem may have occurred. 1C was set to 200mA / g.

[0431] The time measured for each secondary battery is shown in Tables 1 and 2. Table 1 shows the steps The results are those obtained using the positive electrode active material obtained in S36. Positive electrode active material prepared through Step S54, i.e., positive electrode active material to which a phosphorus compound is added This is the result of using quality.

[0432] [Table 1]

[0433] [Table 2]

[0434] In addition, for the results using the positive electrode active material obtained in step S36, the charging voltage was set to 4.5 Figure 31(A) shows the time-current characteristics when the charging voltage is 5V, and Figure 31(B) shows the time-current characteristics when the charging voltage is 4.65V. The time-current characteristics are shown in FIG.

[0435] In addition, the positive electrode active material produced through steps S51 to S54, i.e., phosphorus The results of using the positive electrode active material to which the compound was added were obtained by setting the charging voltage to 4.55 V. The time-current characteristics when the charging voltage is 4.65V are shown in Figure 32(A). The characteristics are shown in FIG.

[0436] By adding a phosphorus compound, the time until the voltage drop occurs is longer, and continuous charging is possible. Furthermore, when the amount of Mg added was 2%, the continuous charging It was suggested that the resistance to electricity was significantly improved.

[0437] <Cycle characteristics> Next, the cycle characteristics of the secondary batteries using each of the prepared positive electrode active materials were evaluated. First, charge was CCCV (0.05C, 4.6V, final current 0.005C), and discharge was The test was performed for two cycles at 25°C under CC (0.05C, 2.5V). At °C, charge is CCCV (0.2C, 4.6V, final current 0.02C), discharge is CC The battery was repeatedly charged and discharged at (0.2C, 2.5V) to evaluate its cycle characteristics.

[0438] In Figures 33(A) and (B), the horizontal axis represents the cycle and the vertical axis represents the discharge capacity. This is the result of using the positive electrode active material obtained in step S36, and FIG. 33(B) shows the result of using the positive electrode active material obtained in step S36. The positive electrode active material prepared through steps S51 to S54, i.e., the addition of a phosphorus compound, This is the result of using the positive electrode active material.

[0439] When we look at the rate of capacity decrease with respect to the number of cycles, we see that there is a significant difference depending on the concentration of magnesium added. No difference can be seen. On the other hand, the higher the concentration of magnesium added, the greater the decrease in initial capacity. This is because the ratio of phosphorus compounds to the weight of the active material is high, This is thought to be due to the decrease in the proportion of cobalt, which reduces the proportion of substances that contribute to the charge / discharge reaction. . [Example]

[0440] In this example, magnesium, fluorine, cobalt, and metals other than cobalt are used. A positive electrode active material is prepared, a secondary battery having a positive electrode using the positive electrode active material is prepared, and the secondary battery XRD of the positive electrode after charging, continuous charging tolerance of the secondary battery, and cycle characteristics of the secondary battery were evaluated. did.

[0441] <Preparation of positive electrode active material> Referring to the flow charts in FIGS. 8 and 9, the positive electrode active material Sample 30 Sample 35 was prepared in steps S51 to S55. No S54 was carried out.

[0442] First, regarding Sample 30 to Sample 35 A mixture 902 containing magnesium and fluorine was prepared (steps S11 to S15). LiF and MgF2 were weighed so that the molar ratio of LiF:MgF2 was 1:3. 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 using near balls at 150 rpm for 1 hour. The mixture was collected and designated as mixture 902.

[0443] Next, regarding Sample 30 to Sample 35 As a positive electrode active material containing cobalt, CellSeed C-10N manufactured by Nippon Chemical Industry Co., Ltd. was prepared (step S25).

[0444] Next, regarding Sample 30 to Sample 35 The mixture 902 and lithium cobalt oxide were mixed (step S31). The atomic weight of magnesium in Mixture 902 relative to the atomic weight of cobalt in magnesium The mixture was weighed so that the content was 2.0%. The mixture was dry mixed. The mixture was mixed using zirconia balls. The grinding was carried out in a ball mill at 150 rpm for 1 hour.

[0445] Next, regarding Sample 30 to Sample 35 The treated material was collected to obtain a mixture 903 (steps S32 and S33). .

[0446] Next, regarding Sample 30 to Sample 35 The mixture 903 was placed in an alumina crucible and heated in a muffle furnace in an oxygen atmosphere at 850°C for 60 hours. The alumina crucible was covered with a lid during the annealing (step S34). The flow rate was 10 L / min. The temperature was increased at 200°C / hr and decreased over 10 hours. The material after the heat treatment was collected and sieved (step S35), and the positive electrode active material 10 0A_1 was obtained (step S36).

[0447] Next, regarding Sample 31 to Sample 35 The processing of steps S41 to S46 was performed. In step S41 to step S46, the metal source was not added. , Sample 31 to Sample 35, The positive electrode active material 100A_1 and the metal source were mixed by the step S41. The solvents were also mixed together.

[0448] <<Aluminum addition>> For Sample 31 and Sample 32, A coating layer containing aluminum was formed on the positive electrode active material 100A_1 by a sol-gel method. Al isopropoxide was used as the raw material, and 2-propanol was used as the solvent. The atomic weight of aluminum is shown in Sample 31, where cobalt and aluminum are In Sample 32, the atomic weight of the The atomic weight of each of the titanium and aluminum was adjusted to 0.5% of the total atomic weight. The resulting mixture was then placed in an alumina crucible, covered, and heated to 850°C in an oxygen atmosphere. The powder was then sieved through a 53 μm diameter sieve and annealed for 2 hours (step S45). The positive electrode active material was collected (step S46), and the positive electrode active material was sample 31 and sample S Ample (sample) 32 was obtained.

[0449] <<Nickel addition>> For Sample 33 and Sample 34, Nickel hydroxide, which is a metal source, was mixed with the positive electrode active material 100A_1. In Sample 33, the atomic weight of cobalt is calculated as follows: In Sample 34, the cobalt and nickel atoms are The mixture was mixed so that the total amount was 0.5%. The mixture was mixed in a ball mill at 150 rpm for 1 hour. After mixing, the mixture was sieved through a 300 μm φ sieve. The resulting mixture was then placed in an alumina crucible, covered, and heated in an oxygen atmosphere for 8 hours. The mixture was annealed at 50°C for 2 hours (step S45). After that, the mixture was sieved through a 53 μm diameter sieve. The powder was collected (step S46) and used as a positive electrode active material as Sample 33. and Sample 34 was obtained.

[0450] <<Addition of aluminum and nickel>> For Sample 35, nickel hydroxide, which is the metal source, and the positive electrode active material Material 100A_1 was mixed with a ball mill, and then aluminum was added by the sol-gel method. A coating layer containing Al isopropoxide was used as the metal source and 2 The atomic weight of nickel and the atomic weight of aluminum were The total atomic weight of barium, nickel, and aluminum was 0.5%. The resulting mixture was then placed in an alumina crucible, covered with a lid, and heated in an oxygen atmosphere for 850°C. The powder was then annealed at 20°C for 2 hours (step S45). was collected (step S46), and Sample 35 was obtained as the positive electrode active material. .

[0451] <Preparation of secondary battery> Sample 30 to Sample 35 obtained above Each of these was used as the positive electrode active material to fabricate each positive electrode. The slurry of F mixed with active material, AB, and PVDF in a ratio of 95:3:2 (by weight) was applied to the current collector. NMP was used as the solvent for the slurry.

[0452] 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 pressure of 1467 kN / m was applied. Through these steps, a positive electrode was obtained. The electrode loading is approximately 20 mg / cm 2 It was decided.

[0453] Using the prepared positive electrode, a CR2032 type coin (diameter 20 mm, height 3.2 mm) was A secondary battery of this type was fabricated.

[0454] The counter electrode was made of lithium metal.

[0455] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). The mixture was EC:DEC = 3:7 (volume ratio). The secondary batteries tested contained 2 wt% vinylene carbonate (VC) in the electrolyte. did.

[0456] The separator was made of polypropylene with a thickness of 25 μm.

[0457] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0458] <XRD of positive electrode> First, before charging and discharging, the positive electrode was evaluated by XRD. shows the XRD of the positive electrode before charging and discharging. A significant peak was observed at 5°. The horizontal axis of the graphs shown in Figures 34(A) and (B) is 2θ The vertical axis is intensity.

[0459] <XRD of positive electrode after charging> Next, the fabricated secondary batteries were tested at 4.55V, 4.6V, 4.65V and 4.7V. V. Specifically, at 25°C, the battery was charged to each voltage by CCCV charging. After constant current charging at 0.2C, the battery was charged at a constant voltage until the current value reached 0.02C. The current was set to 191mA / g for 1C. The secondary battery in a charged state was placed in a globe in an argon atmosphere. The box is disassembled to remove the positive electrode, which is then washed with DMC (dimethyl carbonate) and electrolyzed. The liquid was removed, and the mixture was sealed in an airtight container under an argon atmosphere and subjected to XRD analysis.

[0460] Figures 35(A) and (B) show the results for Sample 35, respectively. The horizontal axis of the graphs shown in Figures 35(A) and (B) indicates the XRD corresponding to the charging voltage conditions. is 2θ, and the vertical axis is intensity.

[0461] Figure 35(A) shows the peak observed in the 2θ range from 18° to 20°. The peak observed at 4.55 V is thought to be due to the O3 type crystal structure. As the voltage increases, the peak position shifts to the higher angle side. In this case, in addition to the peak near 18.9°, a peak was also observed near 19.2°. In a two-phase mixture state with two crystal structures, the O3 type crystal structure and the pseudospinel type crystal structure. This suggests that the temperature is near 19.3° when the charging voltage is 4.7 V. The peak is thought to be due to the pseudospinel crystal structure.

[0462] Figure 35(B) shows the peaks observed in the 2θ range from 40° to 50°. As the voltage is increased, a peak appears at 4.7 V near 43.9°, suggesting an H1-3 type crystal structure. The arc becomes weaker and can be observed.

[0463] As described above, in the positive electrode active material of one embodiment of the present invention, as the charge voltage is increased, At 5V, it is thought that a region occurs where the O3 crystal structure changes to a pseudospinel crystal structure. Even when the voltage is increased to 4.7 V, the H1-3 type crystal structure is mixed, but the pseudo-saturated structure is the main structure. The positive electrode active material of one embodiment of the present invention is thought to have a pinel-type crystal structure and has a high charging voltage. It was also suggested that the stability was high.

[0464] <Continuous charging durability> Next, the continuous charge durability of the secondary battery was evaluated. First, Sample 3 Secondary batteries using Samples 0 to 35 as positive electrode active materials were prepared. Charge CCCV (0.05C, 4.5V or 4.6V, final current 0.005C), discharge was measured for two cycles at 25°C under CC (0.05C, 2.5V).

[0465] Then, the battery was charged at 60°C using CCCV (0.05C). The upper limit voltage was 4.55V. or 4.65V, and the termination condition is the secondary battery voltage minus 0.01V from the upper limit voltage. The time until the voltage dropped below 4.54V (for 4.55V) was measured. If the voltage drops below the upper limit, a short circuit or other problem may have occurred. 1C was set to 200mA / g.

[0466] The measured time for each secondary battery is shown in Table 3. Duplicate batteries were fabricated, and Table 3 shows the average of the two results.

[0467] [Table 3]

[0468] Also Sample 30, Sample 32, Sample The results using Sample 34 and Sample 35 were Figure 36(A) shows the time-current characteristics when the charging voltage is set to 4.55V. The time-current characteristics when V is set as V are shown in FIG.

[0469] By adding aluminum, the time until the voltage drop occurs is longer, and continuous charging is possible. It was also suggested that the resistance to nickel was improved compared to when only nickel was added. The addition of zinc and aluminum significantly improved the durability against continuous charging. Ta.

[0470] <Cycle characteristics> Next, Sample 30, Sample 32, Samp Regarding the secondary battery using Sample 34 and Sample 35 First, the charging was CCCV (0.05C, 4.6V, final voltage cut-off). Current 0.005C, discharge CC (0.05C, 2.5V) at 25°C for 2 cycles After that, the charge was measured at 25°C using CCCV (0.2C, 4.6V, cut-off current The battery was repeatedly charged and discharged at CC (0.02C, 2.5V) and discharged at CC (0.2C, 2.5V). Sex was evaluated.

[0471] The results of the cycle characteristics are shown in Figure 37. In Figure 37, the horizontal axis represents cycles and the vertical axis represents discharge capacity. Also, Figure 38(A) shows Sample 32, and Figure 38(B) shows Samp Figure 38(C) shows the first charge of Sample 34, and Figure 38(C) shows the first charge of Sample 35. The discharge curve shows that the addition of nickel improved the initial capacity (Sample (Sample) 34) In addition, by adding nickel or aluminum, It was suggested that the capacity loss was suppressed, especially under the condition that nickel and aluminum were added. Better results were obtained in (Sample 35). [Example]

[0472] In this example, the positive electrode was evaluated by measuring the DC resistance.

[0473] <Preparation of secondary battery> A positive electrode was prepared using Sample 11 shown in Example 1 as the positive electrode active material. The positive electrode active material, carbon black, and PVDF were mixed in the following order: active material: carbon black: PVDF The slurry was mixed at a weight ratio of DF=90:5:5 and coated onto the current collector. NMP was used as the solvent for the slurry.

[0474] 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 pressure of 1467 kN / m was applied. Through these steps, a positive electrode was obtained. The electrode loading is approximately 20 mg / cm 2 It was decided.

[0475] Using the prepared positive electrode, a CR2032 type coin (diameter 20 mm, height 3.2 mm) was A secondary battery of this type was fabricated.

[0476] The counter electrode was made of lithium metal.

[0477] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). The mixture was EC:DEC = 3:7 (volume ratio). For the secondary battery, 2 wt% vinylene carbonate (VC) was added to the electrolyte. Ta.

[0478] The separator was made of polypropylene with a thickness of 25 μm.

[0479] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0480] <Charge-discharge cycle test> DC resistance was measured before the charge-discharge cycle test and after 50 charge-discharge cycle tests. The charge-discharge cycle test was carried out under the conditions shown in Example 1.

[0481] <DC resistance measurement> Next, DC resistance was measured using the fabricated secondary battery. The system used was Hokuto Denko Corporation HJ1001SM8A type.

[0482] First, the battery was charged to 4.5 V at 25°C using CCCV, and then rested for 20 minutes. After CC discharge to 3.0 V, the battery was left to rest for 20 minutes. Using this as a reference, DC resistance measurements were carried out under various SOC conditions as follows.

[0483] First, the battery was charged to 4.5 V by CCCV at 25°C. Then, it was discharged and S DC resistance measurements were taken at three OC conditions: 70%, 20%, and 10%. went.

[0484] At each SOC, after the discharge capacity reaches the specified SOC, current is passed for a certain period of time. The DC resistance was measured and is shown in Table 4.

[0485]

Table 4

[0486] The smaller the SOC, the greater the tendency for the DC resistance to increase. Also, after performing the cycle test, the DC resistance was found to increase by about 1.3 to 1.4 times.

Example

[0487] In this example, cross-sectional TEM-EDX analysis of the particles of the positive electrode active material of one aspect of the present invention was performed.

[0488] After thinning each sample by FIB (Focused Ion Beam System: focused ion beam processing observation device), a TEM image was observed. Fig. 39(A) shows the cross-sectional TEM image of Sample 35 prepared in Example 2.

[0489] <TEM-EDX Analysis> In Fig. 39(A), TEM-EDX analysis was performed on the portion surrounded by the broken line. The analysis was performed linearly from the surface to the inside of the particle. The line was made to be approximately perpendicular to the surface. Fig. 39(B) shows the results of the line analysis of EDX. In the vicinity of the surface, relatively, the concentration of aluminum was high and the concentration of cobalt was low. Also, an increase in the concentration of magnesium was suggested near the surface. From this, in the particles of the positive electrode active material, aluminum, magnesium, etc. may contribute to the stabilization of the structure on the particle surface.

Example

[0490] In this example, a secondary battery including a positive electrode using the positive electrode active material of one embodiment of the present invention was manufactured. The positive electrode of the secondary battery was evaluated by XRD after charging.

[0491] Sample 30 and Sample 1 prepared in Example 2 35 to prepare positive electrodes, and secondary batteries were prepared using the positive electrodes. The positive electrode and the secondary battery were fabricated by the methods shown in Example 2.

[0492] <XRD of positive electrode after charging> Next, each secondary battery was charged to either 4.6V or 4.65V. CCV charging was performed. Specifically, at 45°C, after constant current charging at 0.2C up to each voltage, The battery was charged at a constant voltage until the current reached 0.02 C. Here, 1 C is 191 mA / g. The charged secondary battery was then disassembled in an argon atmosphere glove box to remove the positive electrode. The electrode was then removed and washed with DMC (dimethyl carbonate) to remove the electrolyte. The mixture was placed in a sealed container with a phosphate atmosphere and subjected to XRD analysis.

[0493] Figure 40(A) and (B) show the results of XRD. In (Sample) 30, in addition to the peak suggesting the H1-3 type crystal structure, The peaks around 20.9° and 36.8° are clearly observed. The peaks around the nucleus are thought to be due to CoO2, which is the result of lithium elimination and the breakdown of the crystal structure. In contrast, Sample 35 is in a pseudo-stable state. A spinel structure was suggested, suggesting stability even at high charging voltages. [Explanation of symbols]

[0494] 100: Positive electrode active material, 100A: Positive electrode active material, 100A_1: Positive electrode active material, 100A_2 : Positive electrode active material, 100A_3: Positive electrode active material, 100C: Positive electrode active material, 200: Active material layer, 201: graphene compound, 211a: positive electrode, 211b: negative electrode, 212a: lead, 21 2b: lead, 214: separator, 215a: joint, 215b: joint, 217: fixing Fixing member, 250: secondary battery, 251: exterior body, 261: folding portion, 262: sealing portion, 263: Seal portion, 271: Ridge line, 272: Valley line, 273: Space, 300: Secondary battery, 3 01: Positive electrode can, 302: Negative electrode can, 303: Gasket, 304: Positive electrode, 305: Positive electrode current collector body, 306: positive electrode active material layer, 307: negative electrode, 308: negative electrode current collector, 309: negative electrode active material layer 310: separator, 500: secondary battery, 501: positive electrode current collector, 502: positive electrode active material layer , 503: positive electrode, 504: negative electrode current collector, 505: negative electrode active material layer, 506: negative electrode, 507: Separator, 508: electrolyte, 509: exterior body, 510: positive electrode lead electrode, 511: negative electrode Lead electrode, 600: secondary battery, 601: positive electrode cap, 602: battery can, 603: positive electrode Terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: Insulating plate, 609: insulating plate, 611: PTC element, 612: safety valve mechanism, 613: conductive plate, 614: Conductive plate, 615: Module, 616: Conductive wire, 617: Temperature control device, 900: circuit board, 901: raw material, 902: mixture, 903: mixture, 904: mixture, 910: Label, 911: terminal, 912: circuit, 913: secondary battery, 914: antenna, 916: Layer, 917: Layer, 918: Antenna, 920: Display device, 921: Sensor, 922: Terminal , 930: housing, 930a: housing, 930b: housing, 931: negative electrode, 932: positive electrode, 93 3: separator, 950: wound body, 951: terminal, 952: terminal, 980: secondary battery, 9 81: Film, 982: Film, 993: Winding body, 994: Negative electrode, 995: Positive electrode, 9 96: Separator, 997: Lead electrode, 998: Lead electrode, 7100: Portable display device , 7101: Housing, 7102: Display unit, 7103: Operation buttons, 7104: Secondary battery, 7 200: Portable information terminal, 7201: Housing, 7202: Display unit, 7203: Band, 720 4: Buckle, 7205: Operation button, 7206: Input / output terminal, 7207: Icon, 7 300: display device, 7304: display unit, 7400: mobile phone, 7401: housing, 740 2: Display unit, 7403: Operation buttons, 7404: External connection port, 7405: Speaker, 7406: Microphone, 7407: Secondary battery, 7500: Electronic cigarette, 7501: Atomizer , 7502: cartridge, 7504: secondary battery, 8000: display device, 8001: housing , 8002: display unit, 8003: speaker unit, 8004: secondary battery, 8021: charging device ,8022: Cable, 8024: Secondary battery, 8100: Lighting device, 8101: Housing, 8 102: Light source, 8103: Secondary battery, 8104: Ceiling, 8105: Side wall, 8106: Floor, 8107: Window, 8200: Indoor unit, 8201: Housing, 8202: Air outlet, 8203: Secondary Battery, 8204: Outdoor unit, 8300: Electric refrigerator-freezer, 8301: Housing, 8302: Refrigeration 8303: Freezer door, 8304: Secondary battery, 8400: Automobile, 8401: Headlight, 8406: Electric motor, 8500: Automobile, 8600: Scooter, 860 1: Side mirror, 8602: Secondary battery, 8603: Turn signal light, 8604: Under-seat storage ,9600:Tablet type terminal,9625:Switch,9627:Switch,9628: Operation switch, 9629: fastener, 9630: housing, 9630a: housing, 9630b: housing body, 9631: display section, 9631a: display section, 9631b: display section, 9633: solar cell ,9634: Charge and discharge control circuit, 9635: Power storage body, 9636: DCDC converter, 96 37: Converter, 9640: Moving parts

Claims

1. A lithium-ion secondary battery having a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, The positive electrode active material contains magnesium in its surface layer, A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.7V in a 25°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed and washed with dimethyl carbonate, and then the positive electrode is XRD measured in an argon atmosphere.

2. A lithium-ion secondary battery having a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, When the positive electrode active material was subjected to XPS analysis using aluminum as the X-ray source, magnesium was detected. A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.7V in a 25°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed and washed with dimethyl carbonate, and then the positive electrode is XRD measured in an argon atmosphere.

3. A lithium-ion secondary battery comprising a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, and a negative electrode further containing silicon, The positive electrode active material contains magnesium in its surface layer, A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.7V in a 25°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed and washed with dimethyl carbonate, and then the positive electrode is XRD measured in an argon atmosphere.

4. A lithium-ion secondary battery comprising a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, and a negative electrode further containing silicon, When the positive electrode active material was subjected to XPS analysis using aluminum as the X-ray source, magnesium was detected. A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.7V in a 25°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed and washed with dimethyl carbonate, and then the positive electrode is XRD measured in an argon atmosphere.

5. A lithium-ion secondary battery having a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, The positive electrode active material contains magnesium in its surface layer, A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.6V in a 45°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed, and the positive electrode is washed with dimethyl carbonate. The positive electrode is then measured by XRD in an argon atmosphere.

6. A lithium-ion secondary battery having a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, When the positive electrode active material was subjected to XPS analysis using aluminum as the X-ray source, magnesium was detected. A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.6V in a 45°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed, and the positive electrode is washed with dimethyl carbonate. The positive electrode is then measured by XRD in an argon atmosphere.

7. A lithium-ion secondary battery comprising a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, and a negative electrode further containing silicon, The positive electrode active material contains magnesium in its surface layer, A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.6V in a 45°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed, and the positive electrode is washed with dimethyl carbonate. The positive electrode is then measured by XRD in an argon atmosphere.

8. A lithium-ion secondary battery comprising a positive electrode having a positive electrode active material containing lithium, cobalt, oxygen, magnesium, fluorine, and aluminum, and a negative electrode further containing silicon, When the positive electrode active material was subjected to XPS analysis using aluminum as the X-ray source, magnesium was detected. A lithium-ion secondary battery in which, when the positive electrode of the lithium-ion secondary battery is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has a first diffraction peak corresponding to the pseudo-spinel crystal structure of lithium cobalt oxide, with a 2θ of 19.10° to 19.50° due to CuKα1 line, and a second diffraction peak with a 2θ of 45.45° to 45.65°. XRD measurement conditions: A CR2032 type coin cell is fabricated using the positive electrode of the lithium-ion secondary battery, lithium metal as the counter electrode, and 1 mol / L lithium hexafluoride phosphate as the electrolyte of the electrolyte, where the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC), mixed in a ratio of EC:DEC = 3:7 (volume ratio). A polypropylene separator is used, and the positive electrode can and negative electrode can are made of stainless steel. The fabricated coin cell is charged at a constant current of 0.2C (1C is 191mA / g per weight of positive electrode active material) to 4.6V in a 45°C environment, then charged at a constant voltage until the current value becomes 0.02C. The coin cell after constant voltage charging is disassembled in an argon atmosphere, the positive electrode is removed, and the positive electrode is washed with dimethyl carbonate. The positive electrode is then measured by XRD in an argon atmosphere.

9. When the positive electrode is subjected to XRD measurement in a discharged state, the measured XRD pattern has a third diffraction peak with 2θ between 18.50° and 19.30°, and a fourth diffraction peak with 2θ between 38.00° and 38.80°. A lithium-ion secondary battery according to claims 1 to 8.

10. When the lattice constants of the a-axis and c-axis in the layered rock salt crystal structure of space group R-3m were determined for the positive electrode active material by XRD measurement in the discharge state, the lattice constant of the a-axis was found to be 2.814 × 10⁻¹⁴. －１０ Larger than m: 2.817 × 10 －１０ It is less than m, and the lattice constant of the c axis is 14.05 × 10⁻¹⁰. －１０ Larger than m: 14.07 x 10 －１０ Smaller than m A lithium-ion secondary battery according to claims 1 to 8.

11. Regarding the positive electrode active material, when the lattice constants of the a-axis and c-axis in the layered rock salt type crystal structure were determined by XRD measurement in the discharge state, the value obtained by dividing the lattice constant of the a-axis by the lattice constant of the c-axis (a-axis / c-axis) was greater than 0.20000 and less than 0.20049. The lithium-ion secondary battery according to claim 10.

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