Secondary battery

Abstract

To provide a positive electrode active material with high capacity and good cycle characteristics.SOLUTION: A positive electrode active material exhibits minimal change in crystal structure between the charged and discharged states. For example, a positive electrode active material that has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of about 4.6 V exhibits less change in crystal structure and volume between charge and discharge than known positive electrode active materials. When this pseudo-spinel crystal structure is present, diffraction peaks appear at 2θ=19.30±0.20° and 2θ=45.55±0.10° when analyzed by XRD.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] In addition, in this specification, the term "electronic device" refers to a device in general 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 such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have become available. In particular, lithium-ion batteries, which have high output and high energy density, are being developed. The secondary battery is used in mobile phones, smartphones, laptops, and other portable information terminals. , portable music players, digital cameras, medical equipment, next-generation clean energy vehicles (H Hybrid vehicles (HEV), electric vehicles (EV), plug-in hybrid vehicles (PHEV) Demand for rechargeable energy is rapidly expanding along with the development of the semiconductor industry. As a source of supply, it has become an indispensable part of the modern information society.

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

[0006] Therefore, we aimed to improve the cycle characteristics and capacity of lithium-ion secondary batteries by developing a positive electrode active material. Improvements to the material have been investigated (Patent Document 1, Patent Document 2 and Non-Patent Document 1). Research into the crystal structure of electrode active materials has also been conducted (Non-Patent Documents 2 to 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-164758 [Patent Document 2] Special Publication No. 2014-523840 [Non-patent literature]

[0008] [Non-Patent Document 1] Jae-Hyun Shim et al, “Characterization of Spinel LixCo2O4-Coated LiCoO2 Prepared with Post-Thermal Treatment as a Cathode Material for Lithium Ion Batteries”, CHEMISTRY OF MATERIALS, 2015, 27, pp.3273-3279 [Non-patent document 2] 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, pp.17340-17348 [Non-patent document 3] 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 4] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 Summary of the Invention [Problem to be solved by the invention]

[0009] One aspect of the present invention is a lithium ion secondary battery having a higher capacity and excellent charge-discharge cycle characteristics. Another object of the present invention is to provide a positive electrode active material for a lithium battery. By using it in ion secondary batteries, the decrease in capacity during charge / discharge cycles is suppressed. Another object of the present invention is to provide a substance for forming a high-capacity secondary battery. One object of the present invention is to provide a secondary battery having excellent charge-discharge characteristics. Another object of one embodiment of the present invention is to provide a safe or highly reliable secondary battery. One of the objectives is to provide a pond.

[0010] 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 the following.

[0011] The description of these problems does not preclude the existence of other problems. It is not necessary for the embodiments to solve all of these problems. It is possible to extract other problems from the description of the claim. [Means for solving the problem]

[0012] In order to solve the above problems, a positive electrode active material according to one embodiment of the present invention has a characteristic that It is characterized by little change in the crystal structure.

[0013] One aspect of the present invention is a secondary battery including a positive electrode and a negative electrode, and the XRD pattern of the positive electrode is When analyzed by the Rietveld method, the positive electrode has a pseudospinel crystal structure, and the pseudospinel The proportion of the type crystal structure is 60 wt % or more.

[0014] Another aspect of the present invention is a method for producing a lithium-based electrolytic capacitor comprising: lithium, cobalt, magnesium, oxygen, fluorine, and a cathode active material having the above structure, wherein the cathode active material is used in a cathode and lithium metal is used in a cathode. The current value of the lithium-ion secondary battery was measured at 25°C until the battery voltage reached 4.6V. After charging until the voltage dropped sufficiently, the positive electrode was analyzed by powder X-ray diffraction using CuKα1 radiation. Diffraction peaks at 2θ=19.30±0.20° and 2θ=45.55±0.10° The positive electrode active material has the following structure.

[0015] Another aspect of the present invention is a method for producing a lithium-based electrolytic capacitor comprising: lithium, cobalt, magnesium, oxygen, fluorine, and A positive electrode active material having a positive electrode active material with a charge depth of 0.8 or more, wherein the abundance ratio is 60w The volume per unit cell of the crystal structure with t% or more and the positive electrode active area at a charge depth of 0.06 or less The volume per unit cell of a crystal structure with an abundance ratio of 60 wt% or more in a substance, and The difference is within 2.5% for the positive electrode active material.

[0016] In the above, the positive electrode active material preferably contains at least one of Ti and Al. [Effects of the Invention]

[0017] According to one aspect of the present invention, a lithium ion secondary battery having high capacity and excellent charge / discharge cycle characteristics is provided. Furthermore, by using it in a lithium ion secondary battery, 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. Also, a secondary battery with excellent charge / discharge characteristics can be provided. Furthermore, a secondary battery with high safety and reliability can be provided. Furthermore, a novel substance, active material particles, a power storage device, or a manufacturing method thereof can be provided. do.

[0018] The description of these effects does not preclude the existence of other effects. The embodiment does not necessarily have all of these effects. Effects other than these may be included in the description, This becomes clear from the description, drawings, claims, etc. From any description, it is possible to extract effects other than these. [Brief explanation of the drawings]

[0019] [Figure 1] 1A and 1B are diagrams illustrating the depth of charge and the crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 2] 1A and 1B are diagrams illustrating the depth of charge and the crystal structure of a conventional positive electrode active material. [Figure 3] XRD pattern calculated from the crystal structure. [Figure 4] 1A and 1B are diagrams illustrating the crystal structure and magnetism of a positive electrode active material of one embodiment of the present invention. [Figure 5] 1A and 1B are diagrams illustrating the crystal structure and magnetism of a conventional positive electrode active material. [Figure 6] FIG. 10 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive additive. [Figure 7] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 8] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 9] FIG. 2 is a diagram illustrating a method of discharging a secondary battery. [Figure 10] FIG. 2 is a diagram illustrating a coin-type secondary battery. [Figure 11] FIG. 2 is a diagram illustrating a cylindrical secondary battery. [Figure 12] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 13] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 14] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 15] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 16] FIG. 1 is a diagram illustrating a laminated secondary battery. [Figure 17] FIG. 1 is a diagram illustrating a laminated secondary battery. [Figure 18] FIG. 2 is a diagram showing the appearance of a secondary battery. [Figure 19] FIG. 2 is a diagram showing the appearance of a secondary battery. [Figure 20] 1A to 1C are diagrams illustrating a method for manufacturing a secondary battery. [Figure 21] 1A and 1B are diagrams illustrating a bendable secondary battery. [Figure 22] 1A and 1B are diagrams illustrating a bendable secondary battery. [Figure 23]1A to 1C illustrate examples of electronic devices. [Figure 24] 1A to 1C illustrate examples of electronic devices. [Figure 25] 1A to 1C illustrate examples of electronic devices. [Figure 26] 1A to 1C illustrate examples of electronic devices. [Figure 27] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 28] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 29] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 30] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 31] 1 shows an XRD pattern of a positive electrode active material of a comparative example of Example 1. [Figure 32] 1 shows an XRD pattern of a positive electrode active material of a comparative example of Example 1. [Figure 33] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 34] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 35] 1 shows an XRD pattern of a positive electrode active material of a comparative example of Example 1. [Figure 36] 1 shows XRD patterns of positive electrode active materials according to an embodiment of the present invention and a comparative example of Example 1. [Figure 37] 4 is a graph showing the volume change rate of the positive electrode active material according to an embodiment of the present invention in Example 1. [Figure 38] 1 shows cycle characteristics of a secondary battery according to an embodiment of the present invention in Example 1 and a secondary battery according to a comparative example. [Figure 39] 1 shows ESR signals of positive electrode active materials according to an embodiment of the present invention and a comparative example in Example 2. [Figure 40] 1 shows ESR signals of positive electrode active materials according to an embodiment of the present invention and a comparative example in Example 2. [Figure 41] Crystal structure model used in the calculation of Example 3. [Figure 42] 10 is a graph illustrating the calculation results of Example 3. [Figure 43] 10 is a graph illustrating the calculation results of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0020] 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 various modifications in form and details are possible by those skilled in the art. Furthermore, the present invention should not be construed as being limited to the description of the following embodiments. It is not something that can be done.

[0021] In this specification, crystal planes and directions are indicated by Miller indices. In the above, numbers are usually surrounded by superscript bars in crystallography, but in this specification and other documents, due to limitations on the notation used in the application, numbers are used as superscript bars. Instead of putting a bar above the number, a minus sign (-) may be placed before the number. Also, individual orientations that indicate directions within a crystal are [ ], and collective orientations that indicate all equivalent directions are < >, individual faces that represent crystal faces are ( ), and collective faces with equivalent symmetry are {}. Express it.

[0022] 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 (such as B) is distributed spatially non-uniformly.

[0023] 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. It's called inside.

[0024] In the present specification and the like, the layered rock salt type crystal structure of a composite oxide containing lithium and a transition metal is The structure has a rock salt type ion arrangement in which cations and anions are arranged alternately, and the transition metal and lithium The lithium atoms are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It refers to a crystalline structure. It may have defects such as cation or anion deficiencies. Strictly speaking, the rock salt crystal structure is a distorted structure of the rock salt crystal. be.

[0025] 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.

[0026] In the present specification and the like, the pseudospinel type composite oxide containing lithium and a transition metal The crystal structure is in the space group R-3m, and although it is not a spinel-type crystal structure, cobalt, Ions such as magnesium ions occupy the hexa-coordinated oxygen sites, and the ion arrangement is symmetrical, similar to that of spinel. The pseudo-spinel crystal structure has a crystalline structure that is stable against light elements such as lithium. Oxygen may occupy 4-coordinated sites, and in this case the ionic arrangement also has a symmetry similar to that of the spinel type. It has.

[0027] The pseudospinel crystal structure has random Li between layers, but the CdCl2 crystal structure It can be said that this crystal structure is similar to the CdCl2 type. The structure is that when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 NiO 2) It has a similar crystal structure to pure lithium cobaltate, or a layered rock containing a large amount of cobalt. It is known that salt-type positive electrode active materials do not usually have this crystal structure.

[0028] Layered rock salt crystals and the anions in rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure) It is estimated that the anions in pseudospinel crystals also have a cubic close-packed structure. When the anions are in contact, there exists a crystal plane where the cubic close-packed structure formed by the anions is oriented in the same direction. However, the space group of layered rock salt crystals and pseudospinel crystals is R-3m, and the space group of rock salt crystals is R-3m. The crystal space groups 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 with symmetry, the mirror crystals that satisfy the above conditions The index is different between layered rock salt crystals and pseudospinel crystals and rock salt crystals. is composed of anions in layered rock salt crystals, pseudospinel crystals, and rock salt crystals. When the orientation of the resulting cubic close-packed structure is aligned, the crystal orientation is said to be roughly the same. be.

[0029] The crystal orientation of the two regions roughly coincides, as can be seen from TEM (transmission electron microscope) and STEM images. (Scanning Transmission Electron Microscope) image, HAADF-STEM (High Angle Scattering Annular Dark Field Scanning Transmission Electron Microscope) It can be judged from the images of the annular bright-field scanning transmission electron microscope (ABF-STEM), etc. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as materials for judgment. If the crystal orientation is roughly the same, cations and anions will appear linearly in a TEM image. It is observed that the difference in direction of the alternating rows is 5 degrees or less, and more preferably 2.5 degrees or less. However, light elements such as oxygen and fluorine cannot be clearly observed in TEM images. In such cases, the alignment of the orientations can be determined by the arrangement of the metal elements.

[0030] 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.

[0031] 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 defined as 0, and the depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is defined as 1. That is what I will say.

[0032] In this specification, charging refers to transferring lithium ions from the positive electrode to the negative electrode in the battery. This refers to the movement of electrons from the negative electrode to the positive electrode in an external circuit. In this case, charging refers to the process of releasing lithium ions. The positive electrode active material is referred to as a charged positive electrode active material. The positive electrode active material is referred to as a positive electrode active material charged at a high voltage. If the CoO2 is charged at 219.2mAh / g or more, the positive electrode is charged at a high voltage. The active material is lithium cobalt oxide (here, impurity element) with impurity elements of 5 at % or less. (Elements other than lithium, cobalt, and oxygen) in a 25°C environment. Charge at a constant current until the battery voltage reaches 4.6V (for lithium counter electrode), then reduce the current to 0. The positive electrode active material after constant voltage charging up to 0.1 C is also called a positive electrode active material charged at a high voltage. We will do so.

[0033] Similarly, discharging means transferring lithium ions from the negative electrode to the positive electrode within the battery and discharging them from an external circuit. The positive electrode active material is lithium. The insertion of ions is called discharging. Also, a positive electrode active material with a charge depth of 0.5 or less is called a discharged material. In addition, a positive electrode active material with a charge depth of 0.06 or less, or a high The positive electrode active material is discharged to 90% or more of its charge capacity from the charged state. This refers to the discharged positive electrode active material. For example, in LiCoO2, the charge capacity is 21 If the battery is charged at a high voltage, it is at 90% of its capacity. The positive electrode active material after discharging 197.3mAh / g or more is considered to be a fully discharged positive electrode active material. In addition, lithium cobalt oxide with impurity elements of 5 at % or less (here, the impurity element (Elements refer to elements other than lithium, cobalt, and oxygen) at 25°C The positive electrode active material after constant current discharge until the voltage drops to 3V or less (in the case of lithium counter electrode) is also sufficiently This is referred to as the discharged positive electrode active material.

[0034] (Embodiment 1) [Positive electrode active material structure] First, referring to FIGS. 1 and 2, a cathode active material 100 according to an embodiment of the present invention and a conventional cathode active material are shown. The quality of the conventional positive electrode described in this embodiment will be explained below. The electrode active material is a material that contains elements other than lithium, cobalt, and oxygen, or has cobalt added to the surface. It is a simple lithium cobalt oxide (LiCoO2) that has not been processed by coating or other methods. be.

[0035] <Conventional positive electrode active materials> An example of a conventional positive electrode active material is lithium cobalt oxide. As described in Non-Patent Documents 2 and 3, the crystal structure changes depending on the charge depth. Figure 2 shows a typical crystal structure of lithium cobalt oxide.

[0036] As shown in Figure 2, LiCoO2 at a charge depth of 0 (discharged state) is a bond of the space group R-3m. It has a region with a crystal structure, and there are three CoO2 layers in the unit cell. The crystal structure is sometimes called an O3 type crystal structure. The CoO2 layer is a layer in which oxygen is added to cobalt. This refers to a structure in which six-coordinated octahedral structures are connected on a plane with edge sharing.

[0037] At a charge depth of 1, the crystal structure has the space group P-3m1, and CoO exists in the unit cell. There is one layer of two layers. Therefore, this crystal structure is sometimes called the O1 type crystal structure.

[0038] In addition, when the charge depth is about 0.88, LiCoO2 has a crystal structure of the space group R-3m. This structure is different from the structure of CoO2, such as P-3m1(O1), and the structure of R-3m(O3). This crystal structure can be said to be a structure in which the LiCoO2 structure and the LiCoO2 structure are alternately stacked. This is sometimes called the H1-3 crystal structure. In reality, the H1-3 crystal structure is The number of cobalt atoms per cell is twice that of other structures. In this specification, the c-axis of the H1-3 type crystal structure is expressed as a unit cell to facilitate comparison with other structures. The figure will be shown as half the original.

[0039] Repeated high voltage charging and discharging to a charge depth of about 0.88 or more. LiCoO2 has a H1-3 type crystal structure and a R-3m(O3) structure in the discharged state. The crystal structure changes repeatedly during this time.

[0040] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the arrows, in the H1-3 type crystal structure, the CoO2 layer is significantly larger than the R-3m(O3). Such dynamic structural changes have a negative effect on the stability of the crystal structure. Ugh.

[0041] Furthermore, the difference in volume is large. Details will be described in Example 1, but the comparison is based on the same number of cobalt atoms. When the H1-3 crystal structure is discharged, the difference in volume between the H1-3 crystal structure and the O3 crystal structure in the discharged state is 3.5% or more. be.

[0042] 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.

[0043] 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 it becomes difficult to insert and extract lithium. It is thought that this is the case.

[0044] <Positive Electrode Active Material of One Embodiment of the Present Invention> ≪Inside≫ In contrast, the positive electrode active material 100 of one embodiment of the present invention has a sufficiently discharged state and a high voltage The difference in crystal structure and volume between the charged and uncharged materials is small.

[0045] The crystal structure of the positive electrode active material 100 before and after charging and discharging is shown in FIG. , cobalt, and oxygen. In addition to the above, it is preferable to contain magnesium. It is also preferable that the material contains halogen such as fluorine or chlorine. It is preferable to have at least one of the following:

[0046] The crystal structure at charge depth 0 (discharged state) in Figure 1 is the same as that in Figure 2, R-3m(O3). The positive electrode active material 100 according to one embodiment of the present invention has a sufficiently charged state of about 0.88. , has a crystal structure different from that shown in FIG. 2. This crystal structure of space group R-3m is referred to herein as This is called a pseudo-spinel crystal structure. In the structure, the symmetry of the cobalt atom and the symmetry of the oxygen atom are explained by the Although the illustration is omitted, in reality, lithium of about 12 atomic % relative to cobalt is present between the CoO2 layers. In both the O3 type crystal structure and the pseudospinel type crystal structure, C It is preferable for magnesium to exist in a dilute state between the oO2 layers, i.e., at the lithium site. It is also preferable that a dilute amount of halogen such as fluorine is present at the oxygen site. At least one of aluminum and titanium is present in the cobalt site. preferable.

[0047] In the positive electrode active material 100, changes in the crystal structure when lithium is released are suppressed. For example, as shown by the dotted lines in Figure 1, there is almost no misalignment of the CoO2 layers in these crystal structures. .

[0048] In addition, as will be described in detail in Example 1, the positive electrode active material 100 has an O3 type crystal structure at a charge depth of 0. The difference in volume per unit cell between the pseudospinel crystal structure with a charge depth of 0.88 and the % or less, more particularly 2.2% or less.

[0049] Therefore, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0050] The pseudospinel crystal structure has the coordinates of cobalt and oxygen in the unit cell as C It can be shown as o(0,0,0.5), O(0,0,x)(0.20≦x≦0.25). do.

[0051] Magnesium, which is present in small amounts between the CoO2 layers, has the effect of suppressing the displacement of the CoO2 layers. Therefore, when magnesium exists between the CoO2 layers, it tends to form a pseudospinel crystal structure. Therefore, it is preferable that magnesium is also distributed inside the particles of the positive electrode active material 100. In order to distribute magnesium inside the particles, the manufacturing process of the positive electrode active material 100 In this step, it is preferable to carry out a heat treatment.

[0052] However, if the heat treatment temperature is too high, cation mixing occurs and the magnesium When magnesium is present in the cobalt site, The effect of maintaining the structure of R-3m is lost. Furthermore, if the heat treatment temperature is too high, There are concerns about adverse effects such as cobalt being reduced to a divalent state and lithium evaporating. do.

[0053] Therefore, before the heat treatment for distributing magnesium inside the particles, the cobalt oxide It is preferable to add a halogen compound such as a fluorine compound to the lithium. Adding lithium cobalt oxide causes a decrease in the melting point of the cation. At a temperature where mixing is unlikely to occur, it is easy to distribute magnesium throughout the particles. Furthermore, if a fluorine compound is present, the corrosion resistance against the hydrofluoric acid produced by the decomposition of the electrolyte is improved. It can be expected to improve.

[0054] Furthermore, a small amount of titanium and aluminum is diluted on the cobalt site of the positive electrode active material 100. The presence of at least one further suppresses the change in the crystal structure.

[0055] The magnesium distributed inside the positive electrode active material 100 has the effect of suppressing the displacement of the CoO2 layer. At the same time, the cobalt around the magnesium is reduced to a divalent state to balance the charge. Therefore, if there is an excess of magnesium, the positive electrode active material 100 There is a risk that some of the particles will form a solid solution of MgO and CoO(II). In the region where oO(II) is dissolved, the route for lithium insertion and desorption disappears. Put away.

[0056] However, titanium is stable in the tetravalent state, followed by trivalent, while aluminum is stable in the trivalent state. Therefore, titanium or aluminum present in the cobalt site is unstable. Even if there is magnesium on the surrounding lithium site, it is difficult to reduce to divalent. When titanium or aluminum is present in the cobalt site, MgO and CoO(I It is thought that it is difficult for the structure to be solid-dissolved.

[0057] Furthermore, when at least one of titanium and aluminum is contained, the acid resistance is improved, particularly in a charged state. In other words, oxygen bound to titanium or aluminum becomes less active. Therefore, the catalytic effect of the oxidative decomposition of the electrolyte is reduced, and the oxidation of the electrolyte on the surface of the positive electrode active material is Decomposition becomes less likely to occur.

[0058] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100. In addition, it is more preferable that the magnesium concentration in the surface layer of the particle is higher than the average of the entire particle. The particle surface is essentially made up of crystal defects, so it is prone to instability and changes in the crystal structure begin. If the magnesium concentration in the surface layer is high, the change in the crystal structure will be more effective. Furthermore, if the magnesium concentration in the surface layer is high, the electrolyte will decompose. It is also expected that the corrosion resistance against the hydrofluoric acid generated by the process will be improved.

[0059] It is also preferable that the concentration of fluorine in the surface layer of the positive electrode active material 100 is higher than the average concentration of fluorine in the whole particle. The presence of fluorine in the surface layer, which is the area in contact with the electrolyte, improves resistance to hydrofluoric acid. It can effectively improve the palatability.

[0060] In addition, the concentration of either titanium or aluminum is higher in the surface layer than in the average of the whole particle. It is preferable that the magnesium concentration is high in the region where titanium or aluminum is added. If any one of these elements is present in large amounts, it will have a strong effect of suppressing the change in the CoO2 layer. In addition, oxidative decomposition of the electrolyte on the surface of the positive electrode active material is less likely to occur.

[0061] In this way, the surface layer of the positive electrode active material 100 contains more magnesium, fluorine, titanium, or Preferably, the inner portion has a different composition from the inner portion, with at least one portion containing a higher concentration of aluminum. It is also preferable that the composition has a stable crystal structure at room temperature. For example, at least the surface layer portion of the positive electrode active material 100 may have a different crystal structure from that of the surface layer portion. In addition, a part of the surface layer and the inside may have a rock salt type crystal structure. In this case, it is preferable that the crystal orientation of the surface layer and the crystal orientation of the interior are approximately the same.

[0062] When the positive electrode active material 100 contains magnesium and titanium, the peak of the titanium concentration It is preferable that the peak exists in a region deeper than the magnesium concentration peak. Since titanium can be trivalent or trivalent, the distance between titanium and oxygen can change depending on the valence of titanium. Therefore, the area around the titanium atom is stable even if there is variation in the distance between the metal and oxygen. For example, when the surface layer of the positive electrode active material 100 has a rock salt crystal structure, the region containing titanium This can function as a buffer region and contribute to stabilizing the internal crystal structure.

[0063] However, if the surface layer consists of only MgO or only a solid solution of MgO and CoO(II), As mentioned above, there is no route for lithium insertion and desorption. It also contains cobalt in the discharged state and lithium in the discharged state, providing a pathway for lithium insertion and desorption. It is also preferable that the concentration of cobalt is higher than that of magnesium.

[0064] ≪Grain boundary≫ The positive electrode active material 100 contains magnesium, halogen, cobalt, aluminum, or titanium. Although the ions may be present randomly and sparsely inside the grain, some of them should be segregated at the grain boundaries. is more preferred.

[0065] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is higher than that of the interior. It is preferable that the fluorine concentration is higher than that in other regions. In addition, it is preferable that either titanium or aluminum is present at or near the grain boundary. It is also preferable that the concentration of

[0066] 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, The change in the crystal structure can be more effectively suppressed. High concentrations of either titanium or aluminum have the effect of suppressing the change of the CoO2 layer. It can exert strong results.

[0067] In addition, when the magnesium and fluorine concentrations at and near the grain boundaries are high, the positive electrode active material Even if a crack occurs along the grain boundary of 100 grains, the surface The magnesium and fluorine concentrations are high near the positive electrode. The corrosion resistance of the active material to hydrofluoric acid can also be improved.

[0068] In this specification, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary. It shall be so decided.

[0069] ≪Particle size≫ If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse. On the other hand, if the size is too small, the surface of the active material layer becomes too rough. There are also problems such as difficulty in supporting the active material layer when applied to the body and excessive reaction with the electrolyte. Therefore, it is preferable that D50 (also called median diameter) is 1 μm or more and 100 μm or less. It is preferable that the thickness is 2 μm or more and 40 μm or less.

[0070] <Analysis method> A positive electrode according to one embodiment of the present invention, in which a certain material exhibits a pseudospinel crystal structure when charged at a high voltage. Whether or not the active material is 100 can be determined by examining the positive electrode charged at high voltage using XRD, electron diffraction, and neutron diffraction. This can be determined by analyzing using X-ray diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can analyze the crystalline structure of the positive electrode active material with high resolution. The height and orientation of the crystallites can be compared, and the lattice periodic distortion and crystallite size can be analyzed. It is possible to obtain sufficient accuracy by measuring the positive electrode obtained by disassembling the secondary battery. It is preferable in this respect.

[0071] As described above, the positive electrode active material 100 according to one embodiment of the present invention is in a high-voltage charged state and a discharged state. The characteristic of this battery is that the crystal structure changes little when it is in a high-voltage charging state. Materials with large crystal structures occupying 50% or more are not desirable because they cannot withstand high voltage charging and discharging. As will be explained in detail in Example 1, the desired crystal structure cannot be obtained by simply adding elements. It should be noted that there are cases where magnesium and fluorine are not included. Although they share the common feature of being lithium cobalt oxide, the pseudo-spinel crystal structure is 60 wt% or more. In some cases, the H1-3 type crystal structure accounts for 50% or more. At this voltage, the pseudo-spinel crystal structure is almost 100%. Therefore, the positive electrode active material 10 according to one embodiment of the present invention may have an H1-3 type crystal structure. To determine whether or not the crystal structure is 0, analysis of the crystal structure, including XRD, is required. be.

[0072] ≪Charging method≫ The high voltage charging required to make the above judgment is performed using a coin cell (CR2032) with a lithium counter electrode. This can be done by fabricating a 20mm diameter, 3.2mm height type.

[0073] More specifically, the positive electrode contains a positive electrode active material, acetylene black (AB), and polyfluoride. Positive electrode active material: AB: PVDF = 95:3:2 (weight ratio) The resulting slurry can be applied to a positive electrode current collector made of aluminum foil and used.

[0074] The counter electrode can be made of lithium metal. However, if a material other than lithium metal is used for the counter electrode, When the secondary battery is charged, the potential of the positive electrode is different from the potential of the secondary battery. For example, when looking at the potential of the positive electrode, Charging to 4.5 V with a graphite counter electrode is roughly equivalent to charging to 4.6 V with a lithium counter electrode. Unless otherwise specified, voltages and potentials in this specification and the like are those of the positive electrode.

[0075] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. can be used.

[0076] The separator can be made of polypropylene with a thickness of 25 μm.

[0077] The positive and negative electrode cans can be made of stainless steel (SUS). do.

[0078] 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 Charge at a constant voltage until the temperature reaches 0.01C. Here, 1C is 137mA / g. Temperature After charging in this way, disassemble the coin cell and remove the positive electrode. The positive electrode active material is then charged at a high voltage. The active material is preferably sealed in an argon atmosphere to prevent reaction with external components. For example, XRD can be performed in a sealed vessel with an argon atmosphere.

[0079] <XRD> The CuKα1 line calculated from the pseudo-spinel crystal structure and H1-3 crystal structure model The ideal powder XRD pattern obtained by this method is shown in Figure 3. For comparison, the LiCoO 2(O3) and the ideal XRD calculated from the crystal structure of CoO2(O1) at charge depth 1 The patterns of LiCoO2(O3) and CoO2(O1) are also shown. SD (Inorganic Crystal Structure Database) The model of Materials Studio (BIOVIA) was created from the crystal structure information obtained from Using Reflex Powder Diffraction, one of the modules The range of 2θ was set to 15° to 75°, the step size was 0.01, and the wavelength λ 1=1.540562×10 -10 m, λ2 are not set, Monochromator is The H1-3 type crystal structure pattern was determined as single. The pseudospinel pattern was similarly created based on the XRD pattern of the positive electrode active material of one embodiment of the present invention. From the turn, Rietveld analysis software TOPAS by Bruker AXS The crystal structure was estimated using version 3, and the XRD pattern was created in the same way as the others. The XRD pattern of the positive electrode active material of one embodiment of the present invention is shown in Example 1.

[0080] As shown in Figure 3, in the pseudospinel crystal structure, 2θ = 19.30 ± 0.20° (19. 10° or more and 19.50° or less), and 2θ=45.55±0.10° (45.45° or more) A diffraction peak appears at 2θ=19.30° (below 45.65°). ±0.10° (19.20° or more and 19.40° or less), and 2θ=45.55±0.0 A sharp diffraction peak appears at 5° (45.50° to 45.60°). No peaks appear at these positions in the type 3 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 100 according to one embodiment of the present invention This can be said to be a characteristic of

[0081] The positive electrode active material 100 according to one embodiment of the present invention has a pseudo-spinel crystal structure when charged at a high voltage. However, not all of the particles need to have a pseudospinel crystal structure. However, the XRD pattern may be When a rhottveld analysis was performed, it was found that the pseudo-spinel crystal structure was preferably 50 wt% or more. It is preferable that the content is 60 wt% or more, and more preferable that the content is 66 wt% or more. It is preferable that the pseudo-spinel crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably If the content is preferably 66 wt % or more, the positive electrode active material will have sufficiently excellent cycle characteristics. can be done.

[0082] The crystallite size of the pseudo-spinel structure of the positive electrode active material particles is The O2 (O3) content decreases to only about 1 / 10 of that of the positive electrode before charging and discharging. Even under the measurement conditions of D, a clear peak of the pseudospinel crystal structure was observed after high-voltage charging. On the other hand, in simple LiCoO2, some of the structures resembled pseudospinel crystal structures. Even if the crystallite size is small, the peak becomes broad and small. , can be determined from the half-width of the XRD peak.

[0083] The characteristics revealed from the XRD pattern are those of the internal structure of the positive electrode active material. In the case of positive electrode active materials with particle diameters (D50) of 1 μm to 100 μm, the For example, the surface layer of the positive electrode active material 100 has a very small volume, so the surface layer has a crystal structure different from that of the interior. Even if it has a structure, it is highly likely that it will not appear in the XRD pattern.

[0084] ESR In the positive electrode active material 100 having a pseudo-spinel crystal structure, as shown in FIG. 1 and FIG. 4(A), As shown in Figure 4(B), cobalt is present in the hexa-coordinated oxygen site. In cobalt, the 3d orbital is e g Orbit and t 2g The orbit is split and arranged in a direction away from the oxygen. Placed 2g Low orbital energy. Some of the cobalt atoms present in the oxygen hexacoordinated sites is t 2g Diamagnetic Co with all orbitals filled 3+ However, the oxygen hexacoordinated cobalt The other part of the cobalt present in the ion is paramagnetic Co 2+ or Co 4+ It was cobalt This paramagnetic cobalt is Co 2+ and Co 4+ In both cases there is one unpaired electron Therefore, it is not possible to distinguish them by ESR, but depending on the valence of the surrounding elements, You can also take.

[0085] On the other hand, in the conventional positive electrode active material, the surface layer is a spinel that does not contain lithium in the charged state. It has been stated that the crystal structure of the spin-type crystalline structure shown in FIG. It has a Co3O4 crystal structure.

[0086] When spinel is described by the general formula A[B2]O4, element A is tetracoordinated and element B is hexacoordinated. Therefore, in this specification, the site with 4-coordinated oxygen atoms is referred to as the A site, and the site with 6-coordinated oxygen atoms is referred to as the B site. The site is sometimes called the B site.

[0087] In the spinel-type crystal structure of Co3O4, not only the B site with 6 oxygen atoms but also the B site with 4 oxygen atoms are Cobalt also exists at the A site. As shown in Figure 5(B), in the case of cobalt with 4 oxygen coordination, Split e g Orbit and t 2g Among the orbitals, e g The orbital energy is low. Co. 2+ , Co 3+ and Co 4+ All of these have unpaired electrons and are paramagnetic. Therefore, if particles with sufficient spinel-type Co3O4 are analyzed by ESR etc., it is found that Co 2+ , Co 3+ or Co 4+ A peak due to paramagnetic cobalt should be detected. do.

[0088] However, in the positive electrode active material 100 according to one embodiment of the present invention, the paramagnetic cobalt with four oxygen atoms is In other words, compared with the conventional example, the positive peak of one embodiment of the present invention is The active material has a small peak derived from spinel-type Co3O4, which can be detected by ESR, etc. Spinel-type Co3O4 does not contribute to the charge / discharge reaction, and In addition, since it is thermally unstable, the less spinel-type Co3O4, the better. Therefore, it can be said that the positive electrode active material 100 is different from the conventional examples.

[0089] 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, the concentration of each element can be quantified for about half of the surface area. Furthermore, narrow scan analysis can be used to analyze the bonding state of elements. The quantitative accuracy of XPS is usually about ±1 atomic %, and the detection limit varies depending on the element. It depends on the material, but it is about 1 atomic %.

[0090] When XPS analysis was performed on 100% of the positive electrode active material, the cobalt concentration was set to 1. The relative value of magnesium concentration is preferably 0.4 or more and 1.5 or less, and 0.45 or more and less than 1.00. The relative value of the fluorine concentration is preferably 0.05 or more and 1.5 or less, and more preferably 0. More preferably, the concentration of either titanium or aluminum is 3 or more and 1.00 or less. The relative value of is preferably 0.05 or more and 0.4 or less, and more preferably 0.1 or more and 0.3 or less.

[0091] In addition, when the positive electrode active material 100 was analyzed by XPS, the bond energy between fluorine and other elements was The peak showing the ion exchange reaction is preferably 682 eV or more and less than 685 eV, and more preferably 684.3 eV This is about 685 eV, which is the binding energy of LiF. and the binding energy of magnesium fluoride, 686 eV. That is, when the positive electrode active material 100 contains fluorine, lithium fluoride and magnesium fluoride Preferably, the bond is other than sodium.

[0092] Furthermore, when the positive electrode active material 100 was analyzed by XPS, the bond between magnesium and other elements was The peak showing the energy is preferably 1302 eV or more and less than 1304 eV, It is more preferable that the bond energy of magnesium fluoride is about 1303 eV. This is a different value from the 1305 eV, which is the energy of the bond between the two atoms, and is close to the binding energy of MgO. That is, when the positive electrode active material 100 contains magnesium, a bond other than magnesium fluoride It is preferable that:

[0093] EDX Among EDX measurements, ED is a method of measuring while scanning an area and evaluating the area two-dimensionally. It is sometimes called EDX area analysis. Data on linear areas can be extracted from EDX area analysis and used to Evaluating the distribution of the molecular concentration within the positive electrode active material particles is sometimes called line analysis.

[0094] EDX surface analysis (e.g., elemental mapping) revealed that the Quantitative analysis of the concentration of magnesium, fluorine, titanium or aluminum in In addition, EDX analysis can be used to identify magnesium, fluorine, titanium, or aluminum. The concentration peaks of the rhamnosine can be analyzed.

[0095] When EDX analysis was performed on the positive electrode active material 100, the peak of magnesium concentration in the surface layer It is preferable that the particles are present at a depth of up to 3 nm from the surface of the positive electrode active material 100 toward the center. It is preferable that the depth of the pores is within 1 nm, and more preferable that the depth of the pores is within 0.5 nm. is more preferable.

[0096] In addition, the distribution of fluorine in the positive electrode active material 100 preferably 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 100 is located at a depth of 3 nm from the center, and the depth of 1 nm It is more preferable that the surface is present up to a depth of 0.5 nm, and even more preferable that the surface is present up to a depth of 0.5 nm. stomach.

[0097] In addition, when EDX analysis was performed, a small amount of titanium or aluminum was found in the surface layer of the positive electrode active material 100. At least one concentration peak occurs at a depth of 0.2n from the surface of the positive electrode active material 100 toward the center. Preferably, the surface is present at a depth of 0.5 nm to 3 nm. It is more preferable to do so.

[0098] Furthermore, when the positive electrode active material 100 is subjected to line analysis or area analysis, the microstructure in the vicinity of the grain boundaries is The ratio of the number of magnesium and cobalt atoms (Mg / Co) is preferably 0.020 or more and 0.50 or less. It is more preferable that the ratio is 0.025 or more and 0.30 or less. It is even more preferable that the ratio is 0.030 or more and 0. 20 or less is preferable.

[0099] [Method for producing positive electrode active material] Next, an example of a method for manufacturing the positive electrode active material 100 according to one embodiment of the present invention will be described.

[0100] <Step S11: Preparation of starting materials> First, a lithium source and a cobalt source are prepared as starting materials. A fluorine source is also preferably provided as a starting material.

[0101] As the lithium source, for example, lithium carbonate or lithium fluoride can be used. As the source of magnesium, for example, cobalt oxide can be used. For example, magnesium oxide, magnesium fluoride, magnesium hydroxide, magnesium carbonate Examples of the fluorine source include lithium fluoride and magnesium fluoride. In other words, lithium fluoride can be used as both a lithium source and a fluorine source. It can also be used.

[0102] The atomic weight of magnesium contained in the magnesium source is 0 when the atomic weight of cobalt is 1. Preferably, it is 0.001 or more and 0.1 or less, more preferably 0.005 or more and 0.02 or less, and 0 Around .01 is even more preferable.

[0103] The fluorine contained in the fluoride source is at least 1.0 times the magnesium contained in the magnesium source. The ratio is preferably 4 times or less (atomic ratio), and more preferably 1.5 times or more and 3 times or less (atomic ratio). It is even more preferable that:

[0104] <Step S12: Mixing of Starting Materials> Next, the starting materials are mixed. For example, a ball mill, a bead mill, etc. may be used for mixing. When using a ball mill, for example, zirconia balls are used as the media. It is preferable that

[0105] <Step S13: First Heat Treatment> Next, in step S12, the mixed material is heated. This step is called baking or first heating. Heating is preferably carried out at a temperature of 800°C or higher but lower than 1100°C. It is more preferable to carry out the treatment at a temperature of 00°C or higher and 1000°C or lower, and even more preferable to carry out the treatment at about 950°C. If the temperature is too low, the decomposition and melting of the starting materials may be insufficient. If the temperature is too high, Co is reduced and Li evaporates, resulting in defects where Co becomes divalent. There is a risk of this happening.

[0106] The heating time is preferably 2 hours or more and 20 hours or less. For example, heating is performed at 1000°C for 10 hours, and the temperature is increased by 20 The temperature is preferably 0°C / h and the flow rate of the dry atmosphere is preferably 10 L / min. For example, the time required to cool the material from the holding temperature to room temperature is 10 hours or more, or 50 hours or more. It is preferable to set it to 0.5 or less.

[0107] By heating in step S13, lithium cobalt oxide can be synthesized. When magnesium and fluorine are contained, the magnesium and fluorine are separated into the lithium cobalt oxide. The resulting particles are composite oxides.

[0108] In addition, lithium, cobalt, fluorine, and magnesium are synthesized as starting materials. In this case, the particles of the composite oxide containing the compound may be used. 3 can be omitted. For example, lithium cobalt oxide manufactured by Nippon Chemical Industry Co., Ltd. Particles (trade name: C-20F) can be used as one of the starting materials. The area that can be analyzed by XPS from the surface is 20 μm, and fluorine, magnesium, calcium The lithium cobalt oxide particles contain sodium, silicon, sulfur, and phosphorus.

[0109] <Step S14: Coating with material containing at least one of titanium and aluminum> Next, the surface of the lithium cobalt oxide particles is coated with at least one of titanium and aluminum. It is preferable to coat the surface with a material having the above properties. Coating methods include the sol-gel method. Liquid phase method, solid phase method, sputtering method, evaporation method, CVD (chemical vapor deposition), PLD (plane deposition) method In this embodiment, a method such as a laser deposition method can be applied. This section explains the application of the sol-gel method, which is expected to provide a good coating and allows processing at atmospheric pressure.

[0110] First, titanium alkoxide, aluminum alkoxide, or a mixture of these is used as an alkoxide. The solution is dissolved in alcohol and then lithium cobalt oxide particles are mixed.

[0111] Titanium alkoxides include, for example, titanium tetraisopropox ide (TTIP) can be used. Examples of aluminum alkoxides include Aluminum isopropoxide can be used. The alcohol solvent can be: For example, isopropanol can be used.

[0112] The amount of metal alkoxide required varies depending on the particle size of lithium cobalt oxide. When using IP, if the particle size (D50) of lithium cobalt oxide is about 20 μm, For lithium tritate particles, TTIP is 0.004 ml / g or more and 0.01 ml / g or less. When aluminum isopropoxide is used, it is preferable to add it so that the particle size is the same. Then, 0.027% of aluminum isopropoxide is added to the lithium cobalt oxide particles. It is preferable to add it so that the content is 9 g / g or more and 0.0697 g / g or less.

[0113] Next, a mixture of an alcohol solution of metal alkoxide and lithium cobalt oxide particles is heated in a steam bath. The mixture is stirred in a gas-containing atmosphere. Stirring can be performed, for example, with a magnetic stirrer. The stirring time is determined based on the time at which the water in the atmosphere and the metal alkoxide undergo hydrolysis and polycondensation reactions. Any time sufficient for this is sufficient, for example, 4 hours, 25°C, 90% RH (relative humidity). The test can be carried out under the following conditions:

[0114] By reacting water vapor in the atmosphere with metal alkoxide, the The sol-gel reaction can proceed slowly. Also, the reaction between metal alkoxide and water at room temperature can be This allows for a gentler reaction than, for example, heating at a temperature above the boiling point of the alcohol solvent. By proceeding with the sol-gel reaction slowly, A coating layer of uniform thickness and high quality can be formed.

[0115] After the above treatment, the precipitate is collected from the mixture. The collection method can be filtration, centrifugation, etc. The precipitate is dissolved in the same solvent as the metal alkoxide. It can be cleaned with alcohol.

[0116] The collected residue is then dried, for example, at 70°C for 1 hour to 4 hours, under vacuum or It can be ventilated and dried.

[0117] <Step S15: Second Heat Treatment> Next, the titanium or aluminum-coated material produced in step S14 is The lithium cobalt oxide particles are then heated. This step is sometimes called the second heat treatment. do.

[0118] The heating time is preferably 1 hour or more and 50 hours or less at the holding temperature, If the heating time is too short, magnesium and fluorine will be easily removed. If a molten metal is added, segregation in the surface layer and in the vicinity of the grain boundaries may be insufficient. However, if the heating time is too long, the titanium or aluminum coating may be damaged. There is a risk that the diffusion of metals will proceed too quickly, resulting in low concentrations in the surface layer and near the grain boundaries.

[0119] The holding temperature is preferably 500°C or higher and 1200°C or lower, and more preferably 700°C or higher and 920°C or lower. A temperature of 800°C or higher and 900°C or lower is more preferable. However, if the concentration is too high, Mg may not be distributed to the Co site. Co such as LiCoO2 3+ Not CoO, but Co 2+ becomes stable , there is a risk that the layered structure of CoO2 may not be maintained.

[0120] The second heat treatment is preferably performed in an atmosphere containing oxygen. Unless the heating temperature is lowered, there is a risk of Co being reduced.

[0121] In this embodiment, the temperature is maintained at 800°C for 2 hours, and the temperature is increased by 200°C. / h, and the oxygen flow rate is 10 L / min.

[0122] Regarding cooling after heating, it is preferable to take a long cooling time, as this makes it easier to stabilize the crystal structure. The time required for lowering the temperature from the holding temperature to room temperature is preferably 10 hours or more and 50 hours or less.

[0123] In this way, the first heating process (step S13) and the second heating process (step S15) In the first heat treatment, the starting materials are sufficiently mixed together. The melting points of Co3O4 (895°C) and Li2CO3 (723°C) are used to react. In the next heat treatment, magnesium is distributed between the CoO2 layers. In order to achieve this, the heating is performed at a temperature lower than that in the first heating treatment. 3+ Co 2+ Yo The temperature at which the material becomes stable is 920°C in air according to the Ellingham diagram. The treatment is preferably carried out at 920°C or lower.

[0124] <Step S16: Collection> The cooled particles are then collected. Preferably, the particles are then sieved. Through these steps, the positive electrode active material 100 of one embodiment of the present invention can be manufactured.

[0125] After step S16, steps S14 to S16 are repeated multiple times. Coating may be performed by a sol-gel method. The number of repetitions may be one, two or more. By repeatedly performing sol-gel processing and heat treatment, cracks form in the lithium cobalt oxide particles. If cracks occur, they can be reduced.

[0126] In addition, when the sol-gel treatment is performed multiple times, the type of metal alkoxide used may be the same. If different materials are used, for example, the first sol-gel treatment Titanium alkoxide was used in the first sol-gel treatment, and aluminum alkoxide was used in the second sol-gel treatment. It is possible.

[0127] In this embodiment, the positive electrode active material 100 contains lithium, cobalt, and oxygen. However, one embodiment of the present invention is not limited to this. For example, the positive electrode active material 100 The transition metals contained in the alloy are not limited to cobalt, but also include very small amounts of nickel and manganese. In addition to the transition metals listed above, the starting material may contain at least one of aluminum may be added.

[0128] In one embodiment of the present invention, a fully charged positive electrode active material and a fully discharged positive electrode active material are Therefore, the pseudospin as defined in this specification is sufficient as long as the change in the crystal structure is suppressed. The crystal structure does not have to be a crystalline structure, and magnesium, fluorine, titanium or aluminum may be used. It is not necessary to include elements such as ruthenium.

[0129] The positive electrode active material 100 may contain carbon, sulfur, silicon, sodium, calcium, zirconium, It may also contain other elements such as:

[0130] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0131] (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, the positive electrode, the negative electrode, and the electrolyte solution However, the following description will be given taking as an example a secondary battery enclosed in an exterior body.

[0132] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0133] <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.

[0134] The positive electrode active material 100 described in the previous embodiment can be used as the positive electrode active material. By using the positive electrode active material 100 described in the previous embodiment, it is possible to achieve high capacity and good cycle characteristics. An excellent secondary battery can be obtained.

[0135] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, or the like can be used. In addition, a fibrous material may be used as the conductive additive. The content of the electrical auxiliary agent is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. is more preferred.

[0136] The conductive additive can form an electrically conductive network in the active material layer. The conductive agent can maintain the electrical conduction path between the positive electrode active materials. By adding an electrical auxiliary agent, it is possible to realize an active material layer with high electrical conductivity. .

[0137] Examples of the conductive additive include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fiber. Examples of carbon fibers that can be used include mesophase pitch carbon fibers. Carbon fibers such as isotropic pitch-based carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tube can be produced by, for example, vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as graphene and fullerene can be used. Metal powders and fibers such as nickel, aluminum, silver, and gold, as well as conductive ceramic materials, etc. It can be used.

[0138] A graphene compound may also be used as the conductive additive.

[0139] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and high In addition, graphene may have excellent physical properties such as high mechanical strength. The graphene compound has a planar shape, which allows for surface contact with low contact resistance. In addition, even if they are thin, they can have very high conductivity, and even a small amount can be used to efficiently conduct electricity within the active material layer. Therefore, the use of graphene compounds 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 laser dryer, the entire surface of the active material is covered with graphene, which is 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, It is particularly preferable to use RGO. Here, RGO is, for example, graphene oxide (g It refers to a compound obtained by reducing ethylenediaminetetraacetic acid (GO).

[0140] 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 is Therefore, a large amount of conductive additive is required. This tends to result in a relative decrease in the amount of active material carried. If the capacity of the secondary battery decreases, the capacity of the secondary battery will decrease. When graphene compounds are used, they 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.

[0141] As an example, in the case where a graphene compound is used as a conductive additive in the active material layer 200, An example of the cross-sectional structure will be described.

[0142] 6(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. 100, a graphene compound 201 as a conductive additive, and a binder (not shown). Here, for example, graphene or multi-graphene is used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet shape. The graphene compound 201 may also be a multi-graphene or (and) a plurality of The graphene may be partially overlapped to form a sheet.

[0143] In the vertical cross section of the active material layer 200, as shown in FIG. 6(B), In FIG. 6(B), the sheet-like graphene compound 201 is dispersed almost uniformly. In this figure, the graphene compound 201 is shown schematically by a thick line, but in reality, it is a single layer or The graphene compounds 201 are thin films having a thickness of multiple layers. The active material 100 is partially covered or is attached to the surface of a plurality of granular positive electrode active materials 100. Since they are formed to be attached to each other, they are in surface contact with each other.

[0144] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. It is possible to form a graphene sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is covered with a graphene net, the graphene net can connect the active material to each other. It can also function as a binder to bind the particles together. Therefore, the ratio of the active material to the electrode volume or weight can be reduced. In other words, the capacity of the secondary battery can be increased.

[0145] 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 layer 200, it is preferable to reduce it. By using graphene oxide, which has extremely high dispersibility in polar solvents, The mixture 201 can be dispersed approximately uniformly inside the active material layer 200. The solvent is removed by evaporation from the dispersion medium containing the dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compounds 201 remaining in the active material layer 200 are partially overlapped with each other. By dispersing the particles so that they are in surface contact with each other, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be performed by, for example, heat treatment or by using a reducing agent. It is also possible.

[0146] Therefore, unlike granular conductive additives such as acetylene black, which come into point contact with the active material, graphite Since the compound 201 enables surface contact with low contact resistance, it is more effective than ordinary conductive additives. The amount of the positive electrode active material 100 is smaller than that of the graphene compound 201, and the electrical conductivity between the positive electrode active material 100 and the graphene compound 201 is improved. 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.

[0147] In addition, by using a spray dryer, the entire surface of the active material is covered with a conductive additive in advance. A graphene compound is formed as a coating, and the active material is then conductively bonded to the graphene compound. An electrical path can also be formed.

[0148] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isoprene. Acrylonitrile-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-styrene rubber It is preferable to use a rubber material such as a propylene-diene copolymer. Fluorine rubber can be used.

[0149] 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), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch These water-soluble polymers can be used in combination with the above-mentioned rubber materials. It is even better if there is one.

[0150] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. 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.

[0151] The binder may be used in combination with two or more of the above.

[0152] 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 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 calcium carbonate. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose Carbohydrates and starches can be used.

[0153] The cellulose derivatives such as carboxymethyl cellulose are, for example, By converting cellulose into salts such as sodium salts or ammonium salts, the solubility increases, It is easier to exert its effect as a viscosity adjuster. The increased solubility makes it easier to make electrode slurry. When preparing a substrate, it is also possible to improve the dispersibility of the active material and other components. In this case, the cellulose and cellulose derivatives used as binders for electrodes include These salts are also included.

[0154] Water-soluble polymers stabilize viscosity by dissolving in water, and also act as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stably dispersed in aqueous solution. In addition, since it has functional groups, it can be easily and stably adsorbed onto the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose will For example, 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.

[0155] 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 play a role in suppressing the decomposition of the electrolyte. It is a film with no gas conductivity or extremely low electrical conductivity, and is immobilized on the surface of the active material, for example. When a crystalline film is formed, decomposition of the electrolyte can be suppressed at the battery reaction potential. In addition, the passive film suppresses electrical conductivity while allowing lithium ions to conduct. Even more desirable.

[0156] <Positive electrode current collector> The positive electrode current collector may be made of metals such as stainless steel, gold, platinum, aluminum, titanium, or the like. The material used for the positive electrode current collector is a highly conductive material, such as an alloy of these. It is preferable that the material does not dissolve at the potential of the positive electrode. It uses aluminum alloys containing elements such as sulphur 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, and Niobium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, Cobalt, nickel, etc. Current collectors are available in foil, plate (sheet), mesh, and punched metal. The current collector may be in the form of a barrel, expanded metal, or the like. It is recommended to use one with a thickness of 30 μm or more.

[0157] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains a conductive additive and and a binder.

[0158] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0159] As a negative electrode active material, it is possible to carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any suitable element can be used, such as silicon, tin, gallium, aluminum, Rumanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a large capacity compared to carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying and dealloying reactions with lithium. Elements capable of undergoing a reaction and compounds containing such elements are sometimes called alloy materials. do.

[0160] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to SiO xHere, it is preferable that x has a value close to 1. For example, x is 0 A value between 0.2 and 1.5 is preferred, and a value between 0.3 and 1.2 is more preferred.

[0161] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. may be used. .

[0162] Examples of graphite include artificial graphite and natural graphite. Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the particle size, which is sometimes preferable. Examples include flake graphite and spherical natural graphite.

[0163] Graphite is formed when lithium ions are inserted into graphite (forming a lithium-graphite intercalation compound) It shows a low potential similar to that of lithium metal (0.05V to 0.3V vs. Li / Li + This allows the lithium-ion secondary battery to exhibit a high operating voltage. 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 metallic lithium.

[0164] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T i5O 12 ), lithium-graphite intercalation compound (Li xC6), niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0165] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) And preferable.

[0166] When a composite nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, A complex nitride of lithium and a transition metal can be used.

[0167] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. , cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the metal may be used as the negative electrode active material. Further materials that can be produced include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It also occurs with fluoride.

[0168] The conductive additive and binder that can be contained in the negative electrode active material layer are the same as those that can be contained in the positive electrode active material layer. The same materials as the conductive additive and binder can be used.

[0169] <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.

[0170] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. For example, ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyrolactone 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 or more of the following may be used: trihydrofuran, sulfolane, sultone, etc. Combinations and ratios may be used.

[0171] 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 batteries, the internal temperature of the secondary battery can be increased due to an internal short circuit or overcharging. Even if the battery is not fully charged, it can prevent the secondary battery from exploding or catching fire. Ionic liquids are made up of cations and anions. The organic cations used in the electrolyte include quaternary cations. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations such as imidazolium cations and pyridinium cations Aromatic cations are also used as anions in electrolytes. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkylphosphate anions, etc.

[0172] The electrolyte to be dissolved in the solvent is, for example, LiPF6, LiClO4, Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 , Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium such as LiN(C4F9SO2)(CF3SO2) and LiN(C2F5SO2)2 Use one or more of these ammonium salts in any combination and ratio. can be done.

[0173] 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 "impurities"). It is preferable to use a highly purified electrolyte solution with a low content of ammonium hydroxide. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably It is preferably 0.01% or less.

[0174] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxalate) Lithium borate (LiBOB), as well as dinitriles such as succinonitrile and adiponitrile Additives such as compounds may be added. The concentration of the added material is, for example, It should be between 0.1 wt% and 5 wt%.

[0175] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0176] The use of polymer gel electrolytes increases safety against leakage, etc. It is possible to make the device thinner and lighter.

[0177] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gel or the like can be used.

[0178] Examples of the polymer include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with a hexagonal structure, PVDF, polyacrylonitrile, etc., and their For example, a copolymer containing PVDF and hexafluoropropylene (H PVDF-HFP, a copolymer of PVDF and PVDF, can be used. The mer may have a porous shape.

[0179] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire pond can be solidified, there is no risk of leakage, dramatically improving safety.

[0180] [Separator] The secondary battery preferably has a separator. The separator may be made of, for example, paper. , nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable that the electrode be processed into a shape such that it wraps around either the positive electrode or the negative electrode.

[0181] 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. Aluminum particles, silicon oxide particles, etc. can be used. For example, PVDF, polytetrafluoroethylene, etc. can be used. Polyamide-based materials Materials used include nylon, aramid (meta-aramid, para-aramid), etc. It is possible.

[0182] Coating with ceramic materials improves oxidation resistance, making it suitable for separators during high-voltage charging and discharging. This can suppress the deterioration of the battery and improve the reliability of the secondary battery. By coating, the separator and electrodes can be more easily attached to each other, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. Safety can be improved.

[0183] 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. .

[0184] 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 temperature can be maintained, the capacity per volume of the secondary battery can be increased.

[0185] [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. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a highly flexible metal such as aluminum, stainless steel, copper, or nickel is A metal thin film is then formed on the metal thin film, and the outer surface of the exterior body is made of a polyamide resin or polyester. A three-layer film having an insulating synthetic resin film such as a vinyl resin can be used.

[0186] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0187] ≪CC charging≫ First, we will explain CC charging as one of the charging methods. CC charging is a method in which the battery is constantly charged for the entire charging period. This is a charging method in which a constant current flows through the secondary battery and charging stops when the voltage reaches a specified level. Assuming that the secondary battery is an equivalent circuit with internal resistance R and secondary battery capacity C as shown in Figure 7(A), In this case, the secondary battery voltage V B is the voltage V across the internal resistance R R and the secondary battery capacity C Applied voltage V C It is the sum of.

[0188] During CC charging, the switch is turned on and a constant voltage is applied, as shown in Figure 7(A). Current I flows through the secondary battery. During this time, current I is constant, so V R = R × I Ohm's Law According to the law, the voltage V across the internal resistance R R On the other hand, the voltage applied to the secondary battery capacity C is also constant. Pressure V C increases over time. Therefore, the secondary battery voltage V B As time passes, Both rise.

[0189] 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, as shown in Figure 7(B). Therefore, the voltage V applied to the internal resistance R R Therefore, the internal resistance R The voltage drop of the secondary battery V B is decreasing.

[0190] The secondary battery voltage V during CC charging and after CC charging is stopped B and charging current An example is shown in Figure 7(C). The secondary battery voltage V B But C C It shows a slight decrease after charging is stopped.

[0191] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a charging method different from the above. First, charge the battery up to a specified voltage using CC charging, then use CV (constant voltage) charging to reduce the current that flows. This is a charging method in which charging is continued until the current becomes low, specifically until the end current value is reached.

[0192] During CC charging, as shown in Figure 8(A), the constant current power supply is switched on and the constant The voltage power supply is switched off and a constant current I flows through the secondary battery. During this time, the current I Since it is constant, V R According to Ohm's law, the voltage V applied to the internal resistance R is R Also On the other hand, the voltage V applied to the secondary battery capacity C is C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0193] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, the CC charge is switched to C During CV charging, the constant voltage power supply The switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B becomes 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. Voltage V across the internal resistance R R As becomes smaller, V RBy Ohm's law, = R × I, The current I flowing through the battery also becomes smaller.

[0194] When the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all switches are turned off as shown in Figure 8(C). The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R becomes 0V However, the voltage V applied to the internal resistance R due to CV charging R is small enough that Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends.

[0195] 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 8(D). Even if CCCV charging is stopped, the secondary battery voltage V B Gahoton It shows that the aircraft does not descend at all.

[0196] ≪CC discharge≫ Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is a method in which the A constant current flows from the secondary battery, and the secondary battery voltage V B becomes a certain voltage, for example 2.5V. This is a discharge method in which the discharge is stopped when

[0197] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Fig. 9. Therefore, the secondary battery voltage V B is shown to be descending.

[0198] Next, the discharge rate and charge rate will be explained. It is the relative ratio of the current during discharge and is expressed in units of C. For a battery with a rated capacity of X (Ah), In this case, the current equivalent to 1C is X(A). When discharging with a current of 2X(A), the current is 2C. If it is discharged at a current of X / 5(A), it is said to be discharged at 0.2C. The same applies to the charging rate; if you charge with a current of 2X (A), it will be charged at 2C. When charging with a current of X / 5(A), it was said to be charged at 0.2C. .

[0199] (Embodiment 3) In this embodiment, the shape of the secondary battery having the positive electrode active material 100 described in the previous embodiment is The material used in the secondary battery described in this embodiment is the same as that in the previous embodiment. The description of the condition can be taken into consideration.

[0200] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. 10(B) is a cross-sectional view of the secondary battery shown in FIG.

[0201] 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. 302 is insulated and sealed by 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 306 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode active material layer 309 .

[0202] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 each have The active material layer may be formed on only one side.

[0203] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , titanium, or alloys thereof or alloys of these with 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 304. 7 and electrically connect to each other.

[0204] 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 impregnated with an electrolyte. ) the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, 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 interposed therebetween. Then, the laminate is pressed to form a coin-type secondary battery 300.

[0205] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, it is possible to achieve high capacity cycling. The coin-type secondary battery 300 can be made to have excellent characteristics.

[0206] Here, the flow of current during charging of the secondary battery will be explained using FIG. 10(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode (electrode) is switched, and the oxidation reaction and reduction reaction are switched. 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 an electric current flows through the positive electrode, it is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "negative electrode" or "-electrode (minus electrode)". When the terms anode (positive electrode) and cathode (negative electrode) are used, the difference between charging and discharging is Therefore, the anode and cathode are often used interchangeably. The term "anode" (negative electrode) is not used in this specification. When using the terms "positive electrode" or "cathode," specify whether it is charging or discharging, and It will also be noted whether it corresponds to a positive pole (positive electrode) or a negative pole (negative electrode).

[0207] A charger is connected to the two terminals shown in FIG. 10(C) to charge the secondary battery 300. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0208] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG. 11. Cylindrical secondary battery 600 As shown in FIG. 11(A), the battery 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 .

[0209] Fig. 11(B) is a schematic diagram showing the cross section of a cylindrical secondary battery. Inside the can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed with a separator 605 sandwiched between them. The battery element is wound around a center pin (not shown). The battery can 602 is closed at one end and open at the other end. The material is nickel, aluminum, titanium, or other metals that are corrosion-resistant to the electrolyte, or Alloys of these and other metals (e.g., stainless steel) can be used. In addition, to prevent corrosion by the electrolyte, the battery can 602 is coated with nickel, aluminum, etc. It is preferable that the positive electrode, the negative electrode, and the separator are wound inside the battery can 602. The battery element is sandwiched between a pair of opposing insulating plates 608 and 609. A non-aqueous electrolyte (not shown) is poured into the battery can 602 in which the battery element is provided. The non-aqueous electrolyte may be the same as that used in coin-type secondary batteries.

[0210] The positive and negative electrodes used in cylindrical secondary 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.

[0211] 11(C), a plurality of secondary batteries 600 are connected to a conductive plate 613 and a conductive plate 614. The secondary batteries 600 may be sandwiched between the secondary batteries 600 to form a module 615. They may be connected in series, or may be connected in parallel and then connected in series. By configuring a module 615 having a plurality of secondary batteries 600, It can extract a large amount of power.

[0212] FIG. 11(D) is a top view of the module 615. For clarity of illustration, the conductive plate 613 is As shown in FIG. 11(D), the module 615 includes a plurality of secondary batteries 600. The device may have a conductive wire 616 for electrical connection. A conductive plate is provided on the conductive wire 616. Furthermore, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, the temperature control device 617 cools the secondary battery 600. If the temperature controller 617 is too cold, it can be heated. The performance of the module 615 is less affected by the outside temperature. The medium is preferably insulating and non-flammable.

[0213] By using the positive electrode active material described in the above embodiment for the positive electrode 604, it is possible to achieve high capacity cycling. The cylindrical secondary battery 600 can be made to have excellent characteristics.

[0214] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0215] 12(A) and 12(B) are diagrams showing the external appearance of a secondary battery. The circuit board 900 is connected to the antenna 914 and the antenna 915. A label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. Furthermore, the secondary battery 913 is connected to a terminal 951 and a terminal 952 .

[0216] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , terminal 952, antenna 914, antenna 915, and circuit 912. A plurality of terminals 911 are provided, and each of the plurality of terminals 911 is used as a control signal input terminal, a power supply terminal, etc. may also be used.

[0217] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 915 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Alternatively, antenna 914 or antenna 915 may be used. The flat conductor may function as one of the conductors for electric field coupling. In other words, the capacitor has two conductors, one of which is an annulus. The antenna 914 or the antenna 915 may be activated. Instead, power can be exchanged using an electric field.

[0218] The line width of antenna 914 is preferably larger than the line width of antenna 915. This allows the amount of power received by the antenna 914 to be increased.

[0219] The secondary battery has a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has a function of shielding an electromagnetic field generated by the secondary battery 913, for example. The layer 916 may be made of, for example, a magnetic material.

[0220] The structure of the secondary battery is not limited to that shown in FIG.

[0221] For example, as shown in FIGS. 13(A-1) and 13(A-2), An antenna may be provided on each of a pair of opposing surfaces of a secondary battery 913 shown in (B). FIG. 13(A-1) is an external view showing one of the pair of surfaces, and FIG. 13(A-2) is a view showing the external view of the pair of surfaces. 12(A) and 12(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 12(A) and 12(B). It can be used as appropriate.

[0222] As shown in FIG. 13(A-1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. As shown in FIG. 13(A-2), an antenna 914 is provided, and the pair of surfaces of the secondary battery 913 On the other hand, an antenna 918 is provided across a layer 917. The layer 917 is, for example, a secondary battery 91 The layer 917 has a function of shielding the electromagnetic field generated by the magnetic material 3. can be used.

[0223] 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 shape that can be applied to the antenna 914, for example. A communication method between the secondary battery and other devices via the antenna 918 can be applied. For example, NFC (near field communication) can be used between secondary batteries and other devices. A response method that can be applied can be applied.

[0224] Alternatively, as shown in FIG. 13(B-1), the secondary battery 9 shown in FIG. 12(A) and FIG. 12(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. 12(A) and 12(B), the same parts as those of the secondary battery shown in FIG. 12(A) and FIG. The explanation of the secondary battery shown in FIG. 12(B) can be used as appropriate.

[0225] 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 electrophotographic display, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0226] Alternatively, as shown in FIG. 13(B-2), the secondary battery 9 shown in FIG. 12(A) and FIG. 12(B) 13 may be provided with a sensor 921. The sensor 921 is connected to the terminal 911 via a terminal 922. The secondary battery shown in FIG. 12(A) and FIG. 12(B) is electrically connected to the same part. In this regard, the description of the secondary battery shown in FIGS. 12(A) and 12(B) can be used as appropriate.

[0227] The sensor 921 may be, for example, a sensor for detecting displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if it has the function of measuring volume, 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 a signal (such as temperature) and store it in memory within the circuit 912.

[0228] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0229] The secondary battery 913 shown in FIG. 14(A) has a terminal 951 and a terminal 952 provided 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 by using an insulating material or the like. 14A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separated. Although the figure shows the winding body 950, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 955 are 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum Rubber or resin materials can be used.

[0230] As shown in FIG. 14(B), the housing 930 shown in FIG. 14(A) is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 14B may be formed by a housing 930a and a housing 930b. The wound body 930 is located in the area surrounded by the housing 930a and the housing 930b. 50 are provided.

[0231] 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 secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the electric field by the housing 930a can be suppressed. Antennas such as antenna 914 and antenna 915 may be provided inside the housing 930b. For example, a metal material can be used.

[0232] Furthermore, the structure of the wound body 950 is shown in Fig. 15. The wound body 950 is made up of a negative electrode 931 and a positive electrode 932. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

[0233] The negative electrode 931 is connected to the terminal 911 shown in FIG. 12 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 91 shown in FIG. 12 via the other of the terminals 951 and 952. Connected to 1.

[0234] By using the positive electrode active material described in the above embodiment for the positive electrode 932, it is possible to achieve high capacity cycling. The secondary battery 913 can have excellent characteristics.

[0235] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it will have at least one flexible portion. If the secondary battery is mounted in an electronic device that also has a battery, it can be bent according to the deformation of the electronic device. can.

[0236] A laminated secondary battery 980 will be described with reference to FIG. The battery 980 has a wound body 993 shown in FIG. 15, a positive electrode 995, and a separator 996. Similar to the wound body 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

[0237] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 is determined as required. The negative electrode 994 is connected to the lead electrode 997 and the lead 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 and the lead electrode 998 are connected to a positive electrode current collector (not shown).

[0238] As shown in FIG. 16(B), a film 981 that serves as an exterior body and a film 98 having a recess are 2 are bonded together by thermocompression or the like, and the above-mentioned wound body 993 is housed in the space formed. In this way, a secondary battery 980 can be fabricated as shown in FIG. 3 has lead electrodes 997 and 998, and is connected to a film 981 and a recessed portion. The inside of the film 982 is impregnated with an electrolyte.

[0239] 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 material such as a resin. If a resin material is used as the material, when external force is applied, the film 981 and the recessed portion The film 982 can be deformed to produce a flexible secondary battery. can be done.

[0240] In addition, although Fig. 16(B) and Fig. 16(C) show examples using two films, A space is formed by folding one sheet of film, and the above-mentioned wound body 99 is inserted into the space. 3 may be accommodated.

[0241] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, it is possible to achieve high capacity cycling. The secondary battery 980 can have excellent characteristics.

[0242] In addition, in FIG. 16, a secondary battery 9 having a wound body in a space formed by a film that serves as an exterior body is shown. For example, as shown in Figure 17, the shape of the outer film is It can also be used as a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes in the space formed. good.

[0243] The laminated secondary battery 500 shown in FIG. 17(A) includes a positive electrode current collector 501 and a positive electrode active material. a positive electrode 503 having a positive electrode active material layer 502, a negative electrode current collector 504 and a negative electrode active material layer 505 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 body 509. The exterior body 509 is filled with an electrolyte 508. The electrolyte solution shown in the second embodiment can be used.

[0244] In the laminated secondary battery 500 shown in FIG. 17(A), a positive electrode current collector 501 and a negative electrode current collector 502 are The electrode current collector 504 also serves as a terminal for electrical contact with the outside. The current collector 501 and the negative electrode current collector 504 are partially 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 not exposed to the outside, and the lead electrode is connected to the positive electrode current collector 501 or the negative electrode The lead electrode may be exposed to the outside by ultrasonic bonding to the current collector 504 .

[0245] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, poly A film made of propylene, polycarbonate, ionomer, polyamide, etc. is coated with an A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied, and the metal is further On the metallic thin film, an insulating synthetic resin such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A three-layer film provided with an oil film can be used.

[0246] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, in A), an example consisting of two current collectors is shown, but in reality, as shown in Figure 17(B), As shown in Figure 1, it is composed of multiple electrode layers.

[0247] In FIG. 17(B), as an example, the number of electrode layers is set to 16. However, the secondary battery 500 has flexibility. In FIG. 17(B), the negative electrode current collector 504 has eight layers. The positive electrode current collector 501 has eight layers, making a total of 16 layers. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. 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.

[0248] An example of the external appearance of a laminated secondary battery 500 is shown in FIGS. 18 and 19. 8 and 19 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.

[0249] 20(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 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. In addition, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. The area and shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. I can't.

[0250] [Method for manufacturing laminated secondary batteries] Here, an example of a method for manufacturing the laminated secondary battery shown in FIG. 18 will be described with reference to FIG. This will be explained using (B) and (C).

[0251] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The figure shows five pairs of negative electrodes 506, separators 507, and positive electrodes 503. 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 region. For example, ultrasonic welding or the like can be used for bonding. Similarly, the bonding of the tab regions of the negative electrodes 506 to each other and the bonding of the negative electrode leads to the tab region of the negative electrode on the outermost surface are also preferable. The bonded electrode 511 is then bonded.

[0252] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0253] Next, as shown in FIG. 20(C), the exterior body 509 is folded at the portion indicated by the broken line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. , so that the electrolyte 508 can be poured later, An area that is not bonded (hereinafter referred to as an inlet) is provided.

[0254] Next, electrolyte 508 (not shown) is introduced into exterior body 509 through an inlet provided in exterior body 509. The electrolyte 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the inlet is bonded. A secondary battery 500 that is a tubular secondary battery can be fabricated.

[0255] By using the positive electrode active material described in the above embodiment for the positive electrode 503, it is possible to achieve high capacity cycling. The secondary battery 500 can have excellent characteristics.

[0256] [Bendable secondary battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 21 and 22. .

[0257] FIG. 21(A) shows a schematic top view of a bendable secondary battery 250. ), (B2), and (C) are cut along the cutting lines C1-C2 and C3- C4 is a schematic cross-sectional view taken along the cutting line A1-A2. The battery has a positive electrode 211a and a negative electrode 211b housed inside an exterior body 251. A lead 212a electrically connected to the negative electrode 211a, and a lead 212b electrically connected to the negative electrode 211b. The cord 212b extends outside the exterior body 251. In addition to the positive electrode 211a and the negative electrode 211b, an electrolyte (not shown) is enclosed in the .

[0258] The positive electrode 211a and the negative electrode 211b of the secondary battery 250 will be described with reference to FIG. 22. FIG. 22(A) shows the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. FIG. 22(B) shows a perspective view of the positive electrode 211a and the negative electrode 211b, as well as a lead wire. 2 is a perspective view showing a lead 212a and a lead 212b.

[0259] As shown in FIG. 22(A), the secondary battery 250 includes a plurality of rectangular positive electrodes 211a, a plurality of short The battery has a strip-shaped negative electrode 211b 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 thereon.

[0260] The surfaces of the positive electrode 211a on which the positive electrode active material layer is not formed and the surfaces of the negative electrode 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 the porous layer is not formed are in contact with each other. will be done.

[0261] In addition, the surface on which the positive electrode active material layer of the positive electrode 211a is formed and the surface on which the negative electrode active material layer of the negative electrode 211b is formed are A separator 214 is provided between the formed surfaces. Data 214 is shown by a dotted line.

[0262] As shown in FIG. 22(B), the positive electrodes 211a and the leads 212a are connected to each other at the joints 215. The negative electrodes 211b and the leads 212b are electrically connected at the joints 211a and 212b. Electrical connection is made at 15b.

[0263] Next, the exterior body 251 will be described with reference to FIGS. 21(B1), (B2), (C), and (D). do.

[0264] 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 at the folded portion 261 and a pair of sealing portions 2 The pair of sealing portions 262 are connected to the positive electrode 211a and the negative electrode 211b. The seal portion 26 is provided on either side of the pole 211b and can also be called a side seal. 3 has a portion overlapping with the lead 212a and the lead 212b, and is also called a top seal. This can be done.

[0265] The exterior body 251 has a ridge line 271 and a valley line 272 at the portion overlapping the positive electrode 211a and the negative electrode 211b. It is preferable that the sealing portion 26 of the exterior body 251 has a wave shape in which the grooves 72 are arranged alternately. 2 and the seal portion 263 are preferably flat.

[0266] FIG. 21(B1) is a cross section cut at the part overlapping with the ridge line 271, and FIG. 21(B2) is a cross section cut at the part overlapping with the ridge line 271. The cross section is cut at the part overlapping with the valley line 272. Figures 21(B1) and (B2) are both secondary It corresponds to a cross section in the width direction of the battery 250, the positive electrode 211a, and the negative electrode 211b.

[0267] Here, the ends in the width direction 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, At this time, if the distance La is too short, the exterior body 251 and the The positive electrode 211a and the negative electrode 211b may rub against each other strongly, 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 corroded 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.

[0268] 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. .

[0269] More specifically, the stacked positive electrode 211a and negative electrode 211b and a separator (not shown) are When the total thickness of the data 214 is thickness t, the distance La is 0.8 times or more and 3.0 times or less of thickness t. times or less, preferably 0.9 times or more and 2.5 times or less, more preferably 1.0 times or more and 2.0 times or less By setting the distance La in this range, it is possible to make the device compact and easy to bend. This makes it possible to realize a highly reliable battery.

[0270] In addition, when the distance between the pair of seal portions 262 is a distance Lb, the distance Lb is and is sufficiently larger than the width of the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable. When the secondary battery 250 is repeatedly bent or deformed, Even if the positive electrode 211a and the negative electrode 211b come into contact with the exterior body 251, the positive electrode 211a and the negative electrode 211b Since a part of the electrode 211b can be shifted in the width direction, the positive electrode 211a and the negative electrode 211b This effectively prevents the exterior body 251 from rubbing against each other.

[0271] For example, the difference between the distance La between the pair of seal portions 262 and the width Wb of the negative electrode 211b is 1.6 times or more and 6.0 times or less, preferably 1.8 times, the thickness t of 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. .

[0272] 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: It's nice.

[0273]

number

[0274] 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 is between 1.0 and 2.0.

[0275] FIG. 21(C) is a cross section including the lead 212a, and shows the secondary battery 250, the positive electrode 211a, 21(C), the bending portion 211b corresponds to the cross section of the negative electrode 211b in the longitudinal direction. In the portion 261, the ends of the positive electrode 211a and the negative electrode 211b in the length direction and the outer casing 251 It is preferable to have a space 273 between them.

[0276] 21(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. 21(A).

[0277] When the secondary battery 250 is bent, a part of the exterior body 251 located on the outside of the bend stretches, and a part located on the inside More specifically, the other part positioned outside the exterior body 251 is deformed so as to shrink. The part of the outer casing 2 deforms so that the amplitude of the wave becomes smaller and the period of the wave becomes larger. The part located inside 51 is deformed 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 the stress is alleviated, the material that constitutes the exterior body 251 does not need to stretch. As a result, the exterior body 251 is not damaged and the secondary battery 250 can be bent with a small force. Cut.

[0278] Furthermore, as shown in FIG. 21(D), when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 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 folded. The deviation increases as the distance from the bent portion 261 increases. The stress applied to the positive electrode 211a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211b As a result, the positive electrode 211a and the negative electrode 211b do not need to be broken. Therefore, the secondary battery 250 can be bent without any bending.

[0279] In addition, a space 273 is provided between the positive electrode 211a and the negative electrode 211b and the exterior body 251. As a result, the positive electrode 211a and the negative electrode 211b located on the inner side when bent are attached to the exterior body 251. can be displaced relative to one another without contacting each other.

[0280] The secondary battery 250 illustrated in FIGS. 21 and 22 has a casing that can withstand repeated bending and stretching. The battery characteristics are also less likely to deteriorate. The positive electrode 211a of the secondary battery 250 has the same structure as that described in the previous embodiment. By using a positive electrode active material, a battery with even better cycle characteristics can be obtained.

[0281] (Fourth embodiment) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on an electronic device will be described. do.

[0282] First, as explained in part of the third embodiment, a bendable secondary battery is mounted on an electronic device. Examples are shown in Figures 23(A) to 23(G). Examples of devices include television sets (also called televisions or television receivers), Computer monitors, digital cameras, digital video cameras, digital photos Frame, mobile phone (also called mobile phone or mobile phone device), portable game machine, portable information Examples include terminals, audio playback devices, and large game machines such as pachinko machines.

[0283] In addition, the flexible secondary battery can be mounted on the inner or outer wall of a house or building, or on the inside or outside of a car. It is also possible to incorporate it along the curved surface of the interior or exterior of the vehicle.

[0284] FIG. 23A shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, etc. The secondary battery 7407 is a secondary battery of one embodiment of the present invention. This makes it possible to provide a lightweight, long-lasting mobile phone.

[0285] FIG. 23B shows the mobile phone 7400 in a bent state. When the entire device is deformed by an external force and curved, the secondary battery inside 7407 is also bent. At this time, the state of the bent secondary battery 7407 is shown in FIG. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is shown in the bent state. The secondary battery 7407 is fixed with a lead electrode 7 electrically connected to the current collector. For example, the current collector is copper foil, and some of it is alloyed with gallium to form a current collector. Improved adhesion between the active material layer and the body, ensuring reliability when the secondary battery 7407 is bent It has a high composition.

[0286] FIG. 23(D) shows an example of a bangle-type display device. The portable display device 7100 includes: The device includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. 23(E) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When the device is worn on the user's arm with the device attached, the housing may deform and cause damage to 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 is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature is The area is within the range of 40 mm to 150 mm, and the area is part of the main surface of the casing or the secondary battery 7104. The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more and 150 mm or less. If the thickness is within the range of 1 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment, a lightweight, long-life portable display device can be provided.

[0287] FIG. 23(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 is , a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 72 05, input / output terminal 7206, etc.

[0288] The portable information terminal 7200 is capable of carrying out mobile phone calls, e-mails, viewing and creating documents, playing music, and internet access. - It can run various applications such as internet communication and computer games. do.

[0289] 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 can be touched with a finger or a stylus. For example, the icon 72 displayed on the display unit 7202 can be operated by touching it. You can launch the application by touching 07.

[0290] 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 operation, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system installed in the portable information terminal 7200 can The function of the operation button 7205 can also be freely set using the stem.

[0291] 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 operation is possible. You can also make calls.

[0292] The portable information terminal 7200 also has an input / output terminal 7206, and a connector for connecting to other information terminals. Data can be exchanged directly via the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. It is also possible.

[0293] 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. 23E is curved inside the housing 7201. Alternatively, it can be incorporated in the band 7203 in a bendable state.

[0294] 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 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.

[0295] FIG. 23G shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 304 and includes the secondary battery of one embodiment of the present invention. The display unit 7304 may be provided with a touch sensor, and may function as a portable information terminal. It is also possible.

[0296] The display surface of the display unit 7304 is curved, and images can be 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. The situation can be changed.

[0297] 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 also possible to charge the device via the input / output terminals. The charging operation may be performed by wireless power supply without using the input / output terminals.

[0298] By using the secondary battery of one embodiment of the present invention as the secondary battery included in the display device 7300, This makes it possible to provide a display device with a long life at a low cost.

[0299] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device is shown in FIG. 23(H), and will be explained with reference to FIGS. 24 and 25.

[0300] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, the secondary battery can be lightweight and have a long life. For example, we can provide various products such as electric toothbrushes, electric shavers, and These include mobile 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 small, lightweight, stick-shaped secondary battery with a large capacity.

[0301] FIG. 23(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In 23(H), the electronic cigarette 7500 is an atomizer 7501 containing a heating element and an atomizer A secondary battery 7504 that supplies power to the MYZA, and a cart containing a liquid supply bottle, sensors, etc. To enhance safety, the secondary battery 7504 is protected from overcharging and overcharging. A protection circuit for preventing 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 504 is the tip when held, so the total length is short and the weight is light. Since the secondary battery of one embodiment of the present invention has a high capacity and good cycle characteristics, We offer a compact and lightweight e-cigarette 7500 that can be used for long periods of time. Can be provided.

[0302] Next, Fig. 24(A) and Fig. 24(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIG. 24(A) and FIG. 24(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, and a display Part 9631, display mode changeover switch 9626, switch 9627, switch 962 5, a fastener 9629, and an operation switch 9628. The display unit 9631 has a flexible By using a panel with this, it is possible to create a tablet terminal with a larger display area. FIG. 24(A) shows the tablet terminal 9600 in an open state, and FIG. 24(B) shows the tablet terminal 9600 in an open state. The tablet terminal 9600 is shown in a closed state.

[0303] The tablet terminal 9600 also includes a battery storage device inside the housing 9630a and the housing 9630b. The power storage unit 9635 is connected to the housing 9630a through the movable portion 9640. It is located across 9630b.

[0304] The entire or part of the display area 9631 can be used as a touch panel area. By touching images, text, input forms, etc. containing icons displayed in the area, data can be For example, a keyboard is provided on the entire surface of the display portion 9631 on the housing 9630a side. The button is displayed to display information such as text and images on the display unit 9631 on the housing 9630b. It may be displayed and used.

[0305] In addition, a keyboard is displayed on the display unit 9631 on the housing 9630b side, and The display portion 9631 may be used to display information such as characters and images. 31 to display the keyboard display switch button on the touch panel, and By touching the screen with a finger or a stylus, keyboard buttons are displayed on the display 9631. You may do so.

[0306] Switches 9625 to 9627 are used to operate the tablet terminal 9600. It is not only an interface for the For example, at least one of the switches 9625 to 9627 may be This 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 be The ability to switch between vertical and horizontal display, or between black and white and color display In addition, for example, at least one of the switches 9625 to 9627 may have a function of The display portion 9631 may have a function of adjusting the luminance of the display portion 9631. The brightness of the tablet terminal 9600 is measured by the external light during use, detected by the light sensor built into the tablet terminal 9600. The tablet device can be configured to optimize the brightness according to the amount of light. In addition, other detection devices such as gyro, acceleration sensor, etc. that detect tilt are also included. It may be stored.

[0307] FIG. 24(B) shows the tablet terminal 9600 in a folded state. The terminal 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. The power storage unit 9635 includes a charge / discharge control circuit including a charge / discharge control circuit 9634. A secondary battery is used.

[0308] 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 so that they overlap each other. By folding, the display portion 9631 can be protected, and therefore the durability of the tablet terminal 9600 can be improved. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can improve the It has a large capacity and good cycle characteristics, making it a tablet that can be used for a long period of time. A portable terminal 9600 can be provided.

[0309] In addition, the tablet terminal 9600 shown in FIG. 24(A) and FIG. 24(B) , functions to display various information (still images, videos, text images, etc.), calendar, date or The function to display the time, etc. on the display, and the function to touch input or edit the information displayed on the display Touch input function, function to control processing by various software (programs), etc. It can have:

[0310] The solar cell 9633 attached to the surface of the tablet terminal 9600 generates power. The solar cell 963 can be supplied to a panel, a display unit, a video signal processing unit, etc. 3 can be provided on one or both sides of the housing 9630, and the power storage unit 9635 can be efficiently charged. The power storage unit 9635 can be configured to use a lithium ion battery. This has the advantage of enabling miniaturization.

[0311] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 24(B) are shown in FIG. A block diagram is shown and described in FIG. 24(C). In FIG. 24(C), a solar cell 9633, a power storage body 963 5, a DCDC converter 9636, a converter 9637, switches SW1 to SW3, and a display section 9631 are shown. The power storage body 9635, the DCDC converter 9636, the converter 9637, and the switches SW1 to SW3 correspond to the locations corresponding to the charge-discharge control circuit 96 34 shown in FIG. 24(B).

[0312] First, an example of the operation when power is generated by the solar cell 9633 by external light will be described. The power generated by the solar cell is boosted or bucked by the DCDC converter 9636 so as to become a voltage for charging the power storage body 9635. When the power from the solar cell 9633 is used for the operation of the display section 9631, the switch SW1 is turned on, and the converter 9637 boosts or bucks to the voltage required for the display section 9631. When the display on the display section 9631 is not performed, the switch SW1 is turned off, the switch SW2 is turned on, and the power storage body 9635 can be charged. 9633 is turned on, and the converter 9637 boosts or bucks to the voltage required for the display section 9631. Also, when the display on the display section 9631 is not performed, the switch SW1 is turned off, the switch SW2 is turned on, and the power storage body 9635 can be charged. 9635 can be charged by turning off the switch SW1 and turning on the switch SW2. A configuration may be adopted such that charging of the power storage body 9635 is performed.

[0313] Note that the solar cell 9633 is shown as an example of the power generation means, but is not particularly limited, and charging of the power storage body 9635 may be performed by other power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that charges by wireless (non-contact) power transmission and reception, or a configuration that combines other charging means A configuration may be adopted such that charging of the power storage body 9635 is performed by other power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that charges by wireless (non-contact) power transmission and reception, or a configuration that combines other charging means A configuration may be adopted such that charging of the power storage body 9635 is performed by other power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that charges by wireless (non-contact) power transmission and reception, or a configuration that combines other charging means A configuration may be adopted such that charging of the power storage body 9635 is performed by other power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that charges by wireless (non-contact) power transmission and reception, or a configuration that combines other charging means may also be adopted.

[0314] FIG. 25 shows an example of another electronic device. In FIG. 25, the display device 8000 is one of the present invention 8 is an example of an electronic device using a secondary battery 8004 according to an embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, and a speaker unit. The secondary battery 8004 according to one embodiment of the present invention includes a housing 8003 and a secondary battery 8004. The display device 8000 is provided inside a body 8001. The display device 8000 receives power from a commercial power source. Alternatively, the power stored in the secondary battery 8004 can be used. Even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. do.

[0315] The display unit 8002 includes a liquid crystal display device, an emitting device having a light emitting element such as an organic EL element in each pixel, and Device, electrophoretic display device, DMD (Digital Micromirror Device) ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0316] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0317] In FIG. 25, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a housing 8102, a light source 8103, and a light source 8104. 25, the secondary battery 8103 is mounted in the housing 81. 8101 and a light source 8102 are installed inside a ceiling 8104. However, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can receive power from a commercial power source or can store power in a secondary battery 8103. Therefore, if the power supply from the commercial power source is interrupted due to a power outage, etc., Even when the 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.

[0318] 25 shows an example of a lighting device 8100 that is installed on a ceiling 8104. However, the secondary battery according to one embodiment of the present invention is not limited to the ceiling 8104, but may be installed on other parts such as the side wall 8105 and the floor 8106. 106, it can be used for a fixed lighting device provided in a window 8107, etc., or it can be used for a tabletop lighting device. It can also be used in lighting devices of this type.

[0319] The light source 8102 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, fluorescent lamps and other discharge lamps, and light-emitting devices such as LEDs and organic EL elements The element is an example of the artificial light source.

[0320] In FIG. 25, 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 according to one embodiment of the present invention. The device 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. 8 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200. The battery 8203 may be provided in the outdoor unit 8204. Both the power supply 8201 and the power supply 8204 may be provided with a secondary battery 8203. The power supply can be supplied from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 may be equipped with secondary batteries 82 If 03 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. In addition, by using the secondary battery 8203 of one embodiment of the present invention as an uninterruptible power supply, The conditioner can be used.

[0321] In Figure 25, a separate type air conditioner consisting of an indoor unit and an outdoor unit is shown. As an example, it is an all-in-one air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used in the conditioner.

[0322] In FIG. 25, 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, a refrigerator It has a storage compartment door 8302, a freezer compartment door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 is It can receive power from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300-capacity refrigerator.

[0323] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers are Equipment requires high power for a short period of time, so it supplements the power that cannot be supplied by commercial power. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for This prevents the commercial power breaker from tripping during use.

[0324] In addition, during times when electronic devices are not in use, especially when the total amount of power that can be supplied by the commercial power supplier is low, 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 battery, it is possible to prevent power usage rates from increasing outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low and the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores power. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. By using the secondary battery 8304 as an auxiliary power source during the daytime, the daytime power usage rate can be kept low.

[0325] According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability is 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 it possible to reduce the size and weight of the secondary battery itself. 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, it is possible to make the electronic device lighter and with a longer life span. The present embodiment can be implemented in appropriate combination with other embodiments.

[0326] (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.

[0327] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), an electric vehicle (EV), or a powertrain. This will enable the realization of next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0328] 26A and 26B illustrate an example of a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. The hybrid vehicle can be realized by using the secondary battery according to one embodiment of the present invention. In addition, the automobile 8400 has a secondary battery. The secondary battery is mounted on the floor of the vehicle as shown in Fig. 11(C) and Fig. 11(D). The battery modules can be arranged side by side. Also, multiple secondary batteries shown in Figure 16 can be combined. The battery pack may be installed on the floor of the vehicle. 6, as well as lighting such as headlights 8401 and room lights (not shown). The device can be powered.

[0329] In addition, the secondary battery is used to power the speedometer, tachometer, and other displays of the automobile 8400. The secondary battery can supply power to the navigation device of the automobile 8400. The present invention can provide power to semiconductor devices such as mobile terminals.

[0330] The automobile 8500 shown in FIG. 26(B) has a plug-in type secondary battery. It can be charged by receiving power from an external charging facility using a contactless power supply system or other methods. FIG. 26(B) shows a diagram of a charging device 8021 installed on a ground and a charging station 8022 installed on a vehicle 8500. The secondary batteries 8024 and 8025 are shown being charged via a cable 8022. When charging, please refer to CHAdeMO (registered trademark) or Combo for charging method and connector specifications. The charging device 8021 may be a charging station installed in a commercial facility. It can be a power station or a home power source. For example, plug-in technology can The secondary batteries 8024 and 8025 mounted on the automobile 8500 are charged by an external power supply. Charging is done by converting AC power directly into AC power via a conversion device such as an AC-DC converter. This can be done by converting it into AC power.

[0331] 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, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be carried out not only when the vehicle is stopped but also while the vehicle is moving. This method may be used to transmit and receive power between vehicles. A solar cell may be provided to charge the secondary battery when the vehicle is stopped or running. The power can be supplied by an electromagnetic induction method or a magnetic resonance method.

[0332] 26C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in (C) has a secondary battery 8602, side mirrors 8601, and a turn signal. The secondary battery 8602 can supply electricity to the direction indicator light 8603. can.

[0333] In addition, the scooter 8600 shown in FIG. 26(C) has a secondary battery 860 in the storage space under the seat 8604. 2 can be stored. The secondary battery 8602 can be stored even if the under-seat storage 8604 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 stored before driving. Just do that.

[0334] 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 body can be made smaller and lighter, it will contribute to reducing the weight of the vehicle, which will improve the driving 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 battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0335] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0336] In this example, a positive electrode active material 100 according to one embodiment of the present invention and lithium cobalt oxide as a comparative example were prepared. The results of the XRD analysis are then explained.

[0337] [Preparation of positive electrode active material] <Sample 01> As a positive electrode active material sample 01 according to one embodiment of the present invention, magnesium and fluoride were used as starting materials. The lithium cobalt oxide particles were prepared by adding the element, and then heated.

[0338] In sample 01, as described in step S11 of the first embodiment, the starting material lithium Lithium carbonate was used as the calcium source, cobalt oxide as the cobalt source, and magnesium oxide as the magnesium source. The magnesium and lithium fluoride were used as the fluorine source. 1.0 2Co 0.99 Mg 0.01 O 1.98 F 0.02 It was weighed so that

[0339] Next, in step S12, the starting materials were mixed. The mixture was mixed using a mill at 250 rpm for 2 hours.

[0340] Next, in step S13, the mixed materials are placed in a crucible made of aluminum oxide (hereinafter referred to as aluminum). The melt was heated in a muffle furnace with a dry air atmosphere of 1000 rpm. The flow rate was 10 L / min, the holding temperature was 950°C (heating rate 200°C / hour), and the holding time was 10 hours. The time required to lower the temperature from the holding temperature to room temperature was 10 hours or more and 15 hours or less.

[0341] Step S14 was not performed because no titanium or aluminum coating treatment was performed.

[0342] Next, in step S15, the magnesium and fluorine-containing zeolite synthesized in step S13 is Lithium cobalt oxide particles containing cobalt dioxide were placed in an alumina crucible and heated in a muffle furnace under oxygen. The flow rate of the atmosphere was 10 L / min, and the holding temperature was 900°C (heating rate: 200°C / hour). The time required to cool the temperature from the holding temperature to room temperature was 10 hours or more and 15 hours or less.

[0343] The mixture was then crushed by sieving. The thickness was 53 μm.

[0344] Finally, the particles were collected to obtain the positive electrode active material of Sample 01. It was found that the concentrations of magnesium and fluorine in the surface layer of the active material were higher than those in the interior. are.

[0345] <Sample 02> Sample 02 is a cathode active material containing magnesium and fluorine according to one embodiment of the present invention. The lithium cobalt oxide particles were heated to prepare the nanoparticles.

[0346] In sample 02, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) were used as the starting material. Therefore, in sample 02, the same as in the first embodiment was used. Steps S12 and S13 were omitted. The diameter (D50) is approximately 20 μm, and fluorine, magnesium, and cations are present in the region that can be analyzed by XPS. It is a lithium cobalt oxide particle containing calcium, sodium, silicon, sulfur, and phosphorus. Since no titanium or aluminum coating process was performed, step S14 was also not performed.

[0347] Next, in step S15, the lithium cobalt oxide particles were placed in an alumina crucible and heated. Using a muffle furnace, the flow rate of the dry air atmosphere was set to 5 L / min, and the temperature was maintained at 800°C (rising temperature). The temperature was set to 200°C / hour, and the holding time was 2 hours. The temperature was lowered from the holding temperature to room temperature in 10 minutes. The time was set to between 1 hour and 15 hours. After that, the sample was sieved and collected in the same manner as sample 01. The positive electrode active material prepared under the above conditions also had magnesium and fluorine concentrations in the surface layer higher than those in the interior. It is known to be higher than

[0348] <Sample 03> Sample 03 is a cathode active material containing magnesium and fluorine according to one embodiment of the present invention. The positive electrode active material was prepared by coating lithium cobalt oxide particles with titanium by the sol-gel method.

[0349] In sample 03, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) were used as the starting material. Therefore, steps S12 and S13 were omitted. Ta.

[0350] Next, in step S14, the lithium cobalt oxide particles are coated with a material containing titanium. Specifically, TTIP was dissolved in isopropanol, and the isopropanol A solution was prepared. Then, lithium cobalt oxide particles were mixed into the solution. Mix with lithium cobalt oxide containing cadmium and fluorine to make 0.004 ml / g. It met.

[0351] This mixture was stirred on a magnetic stirrer for 72 hours at 25°C and 90% RH. The mixture was stirred without a lid. This treatment allowed hydrolysis and polycondensation to occur between the water in the atmosphere and TTIP. The reaction is carried out to form titanium on the surface of lithium cobalt oxide particles containing magnesium and fluorine. A layer containing fluorine was formed.

[0352] After the above treatment, the mixture was centrifuged at 3000 rpm to collect the precipitate. The mixture was washed with isopropanol.

[0353] The collected precipitate was dried in a ventilation oven at 70°C for 3 hours.

[0354] Next, in step S15, the lithium cobalt oxide particles coated with the titanium-containing material are The mixture was placed in an alumina crucible and heated in a muffle furnace with an oxygen atmosphere at a flow rate of 10 L / min. The holding temperature was 800°C (heating rate: 200°C / hour) and the holding time was 2 hours. The temperature drop time from the sample to room temperature was 10 hours to 15 hours. The positive electrode active material prepared under the above conditions was composed of titanium and magnesium in the surface layer. It is known that the concentrations of nesium and fluorine are higher than those in the interior. It has been found that the peak of the concentration of magnesium is in a deeper region than the peak of the concentration of magnesium.

[0355] <Sample 04> Sample 04 is a cathode active material containing magnesium and fluorine according to one embodiment of the present invention. A positive electrode active material was produced by coating lithium cobalt oxide particles with aluminum using the sol-gel method. did.

[0356] In sample 04, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) were used as the starting material. Therefore, steps S12 and S13 were omitted. Ta.

[0357] Next, in step S14, a material containing aluminum is added to the lithium cobalt oxide particles. Specifically, aluminum isopropoxide was dissolved in isopropanol, A solution of aluminum isopropoxide in isopropanol was prepared. Lithium phosphate particles were mixed with aluminum isopropoxide, magnesium, and fluoride. The amount of lithium cobalt oxide containing the element was 0.0279 g / g.

[0358] The mixture was then placed on a magnetic stirrer for 8 hours at 25°C and 90% RH, with the lid closed. This treatment allowed the mixture to be heated with water and aluminum isopropoxide in the atmosphere. Lithium cobalt oxide containing magnesium and fluorine undergoes hydrolysis and polycondensation reactions. An aluminum-containing layer was formed on the surface of the particles.

[0359] The mixed solution after the above treatment was filtered and the residue was collected. (No. 4), and isopropanol was used for cleaning.

[0360] The collected residue was dried in a vacuum bell jar at 70°C for 1 hour.

[0361] Next, in step S15, lithium cobalt oxide coated with an aluminum-containing material is The particles were placed in an alumina crucible and heated in a muffle furnace with an oxygen atmosphere at a flow rate of 10 L. / min, the holding temperature was 800°C (heating rate 200°C / hour), and the holding time was 2 hours. The temperature drop time from the temperature to room temperature was 10 hours or more and 15 hours or less. The positive electrode active material prepared under the above conditions was sieved and collected in the same manner as in Example 1. It has been found that the concentrations of ammonium, magnesium, and fluorine are higher inside than inside. The aluminum concentration peak is located in a deeper region than the magnesium concentration peak. I know.

[0362] <Sample 05> Sample 05 is a comparative example of lithium cobalt oxide particles containing magnesium and fluorine. (Nippon Chemical Industry Co., Ltd., product name: C-20F) without sol-gel treatment or heating. It was used as is.

[0363] <Sample 06> Sample 06 is a comparative example of lithium cobalt oxide containing neither magnesium nor fluorine. The particles were coated with aluminum by a sol-gel method.

[0364] In sample 06, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) were used as the starting material. Therefore, steps S12 and S13 were omitted. The lithium cobalt oxide particles have a particle size (D50) of about 5 μm, and can be observed by XPS or other methods. These are lithium cobalt oxide particles with no detectable magnesium.

[0365] Next, in step S14, a material containing aluminum is added to the lithium cobalt oxide particles. Specifically, aluminum isopropoxide was dissolved in isopropanol, A solution of aluminum isopropoxide in isopropanol was prepared. Lithium phosphate particles were mixed with aluminum isopropoxide, magnesium, and fluoride. The amount of lithium cobalt oxide containing the element was 0.0917 g / g.

[0366] It was then stirred, collected and dried in the same manner as sample 04.

[0367] Next, in step S15, lithium cobalt oxide coated with an aluminum-containing material is The particles were heated, cooled, and collected. The heating temperature was set to 500°C, and the procedure was the same as for sample 04. It was made in.

[0368] The preparation conditions for Samples 01 to 06 are shown in Table 1.

[0369] [Table 1]

[0370] [Secondary battery production] Using the positive electrode active materials of Sample 01 to Sample 06 prepared above, A coin-type secondary battery (diameter 20 mm, height 3.2 mm) was fabricated.

[0371] The positive electrode was made of the positive electrode active material (LCO) prepared above, acetylene black (AB), and polycarbonate. Polyvinylidene fluoride (PVDF) was used in a ratio of LCO:AB:PVDF=95:3:2 (by weight). The mixed slurry was applied to a current collector.

[0372] The counter electrode was made of lithium metal.

[0373] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. We used the following.

[0374] The separator was made of polypropylene with a thickness of 25 μm.

[0375] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0376] [XRD after first charge] Secondary batteries using the positive electrode active materials of Samples 01 to 06 were subjected to CCCV at a specified voltage. Specifically, the battery was charged at a constant current of 0.5C up to the specified voltage, and then the current was reduced to 0.01C. The secondary battery was then placed in a glove box in an argon atmosphere. The cathode was removed by disassembly in the box, washed with DMC (dimethyl carbonate), and the electrolyte was Then, the powder XRD analysis was carried out using CuKα1 radiation. We used the Bruker AXS fully automated multipurpose X-ray diffractometer D8 ADVANCE. The XRD instrument was set up for powder samples, but the sample height was adjusted according to the requirements of the instrument. The sample was set flat without being curved.

[0377] FIG. 27 shows the positive electrode of a secondary battery using the positive electrode active material of Sample 01 after charging at 4.6 V. For comparison, the XRD patterns of the same pseudospinel crystal structure as in Figure 3 and the H1-3 crystal structure are also shown. The crystal structure pattern is also shown. When sample 01 was charged at 4.6 V, the pseudo-spin The crystal structure was a mixture of H1-3 and H1-3 types. It was estimated that the crystal structure was spinel-type at 66 wt%.

[0378] FIG. 28 shows the secondary battery using the positive electrode active material of Sample 02 at 4.1 V, 4.2 V, and 4.3 V. X of the positive electrode after charging at V, 4.4V, 4.5V, 4.6V, 4.7V, and 4.8V The RD pattern shows that sample 02, when charged at 4.6 V, has a pseudo-spinel crystal structure. It was also revealed that sample 02, when charged at 4.7 V or higher, It has a different crystal structure from pseudospinel, and the peak width is broadened, resulting in a decrease in crystallinity. was speculated.

[0379] Figure 29 shows the secondary battery using the positive electrode active material of Sample 03 at 4.1 V, 4.2 V, and 4.3 V. X of the positive electrode after charging at V, 4.4V, 4.5V, 4.6V, 4.7V, and 4.8V The RD pattern is shown. Sample 03 also has a pseudospinel crystal structure when charged at 4.6 V. It was also revealed that sample 03, charged at 4.6 V, showed a clearer pattern. The sample showed less crystalline structure other than pseudospinel than sample 02 charged at 4.6 V. It was also speculated that sample 03, when charged at 4.7 V or higher, exhibited a different behavior from pseudospinel. It was presumed that the crystal structure was different from that of the original and that the peak width was broadened, resulting in a decrease in crystallinity.

[0380] FIG. 30 shows the results of the secondary battery using the positive electrode active material of Sample 04 at 4.6 V, 4.7 V, and The XRD patterns of the positive electrode after charging at 4.8 V are shown. Sample 04 is charged at 4.6 V and 4 It was revealed that when charged to 4.7V, it has a pseudospinel crystal structure. Sample 04, when charged at 8 V, has a different crystal structure from pseudospinel and has a peak It was presumed that the width of the crystals had widened and the crystallinity had decreased.

[0381] FIG. 31 shows a secondary battery using the positive electrode active material of Sample 05 of the comparative example, at 4.1 V and 4.2 V. , after charging at 4.3V, 4.4V, 4.5V, 4.6V, 4.7V, and 4.8V The XRD pattern of the positive electrode is shown. Sample 05, a comparative example, was charged at 4.6 V or more and 4.7 V or less. When the crystal structure was analyzed, it was found that the crystal structure was not a pseudospinel type but an H1-3 type. (The peaks from 43.5° to 46° (2θ) are particularly distinctive.) It was revealed that the crystal structure changes to H1-3 type between 4.8V and 4.6V. When charged at 1000 W, sample 05 had a crystal structure different from that of pseudospinel and H1-3. It was inferred that the width of the peaks broadened and the crystallinity decreased.

[0382] FIG. 32 shows the results of the secondary battery using the positive electrode active material of Comparative Example Sample 06 after charging at 4.6 V. The XRD patterns of the positive electrodes of sample 06 and sample 06 when charged at 4.6 V are shown. It was revealed that it has a crystal structure.

[0383] [XRD after multiple charging] Next, Sample 02, Sample 03, and Comparative Example Sample 05 were measured at 4.6V. After multiple charging cycles, the battery was analyzed by XRD. Specifically, it was charged CCCV at 4.6V. The sample was charged once. After CCCV charging at 4.6V, the discharge voltage was Constant current discharge (CC discharge) to 2.5V, then CCCV charge at 4.6V The samples were charged twice. Some samples were also charged nine times.

[0384] FIG. 33 shows the results of charging a secondary battery using the positive electrode active material of Sample 02 once at 4.6 V. The XRD patterns of the positive electrode after charging twice are shown. Not only the crystal structure but also the H1-3 crystal structure and other structures are present, and the crystallinity is reduced. However, in the second charge, structures other than the pseudospinel crystal structure decreased, and It was more crystalline than the eyes.

[0385] Figure 34 shows the results of a secondary battery using the positive electrode active material of Sample 03, which was cycled once, twice, and twice at 4.6 V. The XRD patterns of the positive electrode after nine charging cycles are shown. Not only spinel type crystal structure but also H1-3 type crystal structure and other structures exist, and crystallinity is reduced. However, after the second charge, structures other than the pseudospinel crystal structure were observed. The structure was reduced, and the pseudospinel crystal structure maintained high crystallinity.

[0386] FIG. 35 shows the results of a secondary battery using the positive electrode active material of Sample 05, which is a comparative example, at 4.6 V. The XRD patterns of the positive electrode after the first and second charging cycles are shown in Fig. 1. Both the first and second charges had the H1-3 type crystal structure. 2θ), the characteristics become clear.

[0387] [XRD after multiple discharges] Next, Sample 02, Sample 03, and Comparative Sample 05 were subjected to 10 irradiations. Specifically, after CCCV charging (4.6 V), the After repeating the charge and discharge cycle (2.5V) 10 times, the secondary battery in the discharged state was disassembled and The pole was removed and analyzed by XRD.

[0388] FIG. 36 shows the results of 10 discharges for Sample 02, Sample 03, and Comparative Sample 05. For comparison, the XRD patterns of the same LiCoO2(O3) and pseudo- The patterns of the spinel crystal structure and H1-3 crystal structure are also shown. Sample 0 Sample 2, Sample 3, and Sample 5 all have the structure of LiCoO2(O3). However, in sample 05, the (0 0 3) plane and (0 The diffraction peaks from planes perpendicular to the c-axis, such as the 0 6) plane, broadened, and the crystallinity decreased. In contrast, Sample 02 and Sample 03 show high results because the CoO2 layer does not shift. It was estimated that the crystallinity was maintained and there was little deterioration after 10 charge / discharge cycles.

[0389] [Volume change] Next, the lattice constant and crystal structure of sample 03 were estimated from the XRD patterns at each charge depth. The volume per unit cell of each crystal structure was then calculated and compared with the volume before charging. To make it easier to compare with other crystal structures, the c-axis of the H1-3 crystal structure is the unit cell. The calculation was performed using half the value of the formula.

[0390] Table 2 shows the lattice constants and crystallinity estimated from the XRD patterns of Sample 03 at each charge depth. The structure is shown.

[0391] [Table 2]

[0392] When charging at 4.1V or higher and 4.5V or lower, the two-phase crystals belonging to the space group R-3m This is because the charge depth varies within or between particles of each positive electrode active material. This is thought to be due to the difference in the values ​​of R-3m(1) and R-3m(2) in Table 2. Ta.

[0393] When charged at 4.6 V, the pseudospinel crystal structure and the H1-3 crystal structure were mixed. Furthermore, Rietveld analysis revealed that the pseudospinel crystal structure is 77w It was estimated that it contained more than t%.

[0394] When charged at 4.7 V, the H1-3 crystal structure and the O1 crystal structure were mixed. It was estimated that:

[0395] The pseudo-spinel crystal structure has a volume change rate of 2.5% or less from the O3 crystal structure. In the case of the H1-3 crystal structure, the difference is 2.2% or less compared to the O3 crystal structure. The volume change rate was 3.5% or more.

[0396] The volume change rate in Table 2 is shown in Figure 37. O3: Marker indicating the depth of charge 0 Only refer to the horizontal axis at the top of the graph. Also, in Figure 37, the crystal structure is R-3m(1)(2) , pseudospinel type crystal structure, H1-3 type crystal structure, or O1 type crystal structure The individual markers indicate the items that will be used.

[0397] As is clear from Table 2 and Figure 37, the pseudospinel crystal structure is more favorable than the H1-3 crystal structure. The volume change per unit cell is also small. Sample 03, charged at 4.6 V, Because it has a pseudo-spinel crystal structure of 77 wt% or more, changes in the crystal structure and volume are suppressed. It became clear that this was the case.

[0398] [Cycle characteristics] Next, the cycle characteristics of the secondary batteries using Sample 01, Sample 03, and Sample 05 was evaluated.

[0399] Samples 01 and 03, whose cycle characteristics were evaluated, were XRD analysis samples. The batches are different and the manufacturing conditions are slightly different, so an asterisk is added in the graph. There is no significant difference in the characteristics of the positive electrode active material. The treatment was carried out at 1000°C. Sample 03 had 0.5% TTIP in the sol-gel treatment. The second heat treatment was carried out in a dry air atmosphere.

[0400] The coin cell is made of a positive electrode active material (LCO), acetylene black (AB), and polyvinyl fluoride. Lithium fluoride (PVDF) was mixed at a ratio of LCO:AB:PVDF = 95:2.5:2.5 (by weight). The rest were prepared in the same manner.

[0401] The cycle test was performed at 25°C, and charging was performed using CCCV (0.5C, 4.6V, final current 0.01 C), and discharge was CC (0.5C, 2.5V). The current value was 137 mA / g.

[0402] Figure 38(A) shows the discharge capacities of Sample 01, Sample 03, and Sample 05. B) shows the discharge capacity retention rate. Sample 05 of the comparative example maintained the discharge capacity at the 40th cycle. On the other hand, the positive electrode active material of one embodiment of the present invention had an initial capacity that was lower than that of the comparative example. At 100 cycles, sample 03 was 78.4% and sample 01 was 7 The charge retention rate was 67.5% at 0 cycles, demonstrating good cycle characteristics.

[0403] The positive electrode active material according to one embodiment of the present invention exhibits good cycle performance even when charged and discharged at a high voltage of 4.6 V. It was revealed that the characteristics were exhibited.

[0404] As described above, in Samples 01 to 04, which are positive electrode active materials according to one embodiment of the present invention, 4 It was found that the pseudo-spinel crystal structure was more than 60% when charged to 0.6V. The difference in crystal structure and volume between the discharged and discharged states of the H1-3 type crystal structure is smaller than that of the H1-3 type crystal structure. Therefore, when charged at high voltage, it becomes a pseudo-spinel. Positive electrode active materials with a crystalline structure have good cycle characteristics even when charged and discharged at high voltages. be.

[0405] In contrast, in the comparative samples 05 and 06, the pseudo-spin The H1-3 type crystal structure was mainly observed, with no or only a small amount of the Nell type crystal structure. The H1-3 type crystal structure has a large difference in crystal structure and volume from the O3 type crystal structure. Therefore, Sample 05 and Sample 06 cannot withstand high voltage charging. The discharge capacity actually decreases significantly.

[0406] The comparative sample 05 contains magnesium and fluorine, similar to the sample 01. However, when charged to 4.6V, the H1-3 crystal structure is predominant, resulting in poor cycle characteristics. As described above, the positive electrode active material of one embodiment of the present invention is characterized in that the change in crystal structure due to charge and discharge is small. It was also shown that this is a sign of ferrous metals, and that this cannot be determined solely by the elements contained. [Example]

[0407] In this example, a positive electrode active material 100 according to one embodiment of the present invention and lithium cobalt oxide as a comparative example were prepared. The results of the ESR analysis will be explained.

[0408] [Preparation of positive electrode active material] <Sample 11A and Sample 11B> The starting material was added with magnesium and fluorine and subjected to the first heat treatment, which was designated as Sample 1. The sample obtained by subjecting the sample to a second heat treatment was designated as sample 11A, and then the second heat treatment was performed to designate sample 11B.

[0409] In steps S11 and S12, the ratio of each element is Li 1.02 Co 0.99 Mg 0.01 O 1.98 F 0.02 Lithium carbonate, cobalt oxide, magnesium oxide The lithium fluoride and the ammonium fluoride were weighed and mixed. In this case, an aluminum oxide crucible was used, and the flow rate of the dry air atmosphere was set to 10 L / min. The temperature was 1000°C (heating rate: 200°C / hour) and the holding time was 10 hours. The temperature-lowering time was set to 10 hours or more and 15 hours or less. The lithium cobalt oxide particles containing magnesium and fluorine were designated as Sample 11A.

[0410] Next, the lithium cobalt oxide particles containing magnesium and fluorine of sample 11A were mixed with alumina The mixture was placed in a crucible and subjected to the second heat treatment in step S15. The flow rate of the dry air atmosphere was 10 L. / min, the holding temperature was 800°C (heating rate 200°C / hour), and the holding time was 2 hours. The time required for cooling from the temperature to room temperature was 10 hours or more and 15 hours or less. The particles thus obtained were designated as Sample 11B.

[0411] <Sample 12B> As a comparative example, the first and second heat treatments were carried out without adding magnesium and fluorine. The product thus produced was designated as Sample 12B.

[0412] Lithium carbonate and cobalt oxide were weighed so that the ratio of each element was Li1Co1O2. The other parts were prepared in the same manner as in Sample 11B.

[0413] [ESR] Samples 11A, 11B, and 12B were analyzed by ESR. The results are shown in Figures 39 and 40. Figure 39 shows the signal measured at room temperature. Figure 40 shows the signal measured at low temperature. (10K) measurement results are shown in an enlarged view to compare the sharp signal around 320 mT. do.

[0414] As shown in Figure 39, Sample 12B and Sample 11A showed a decrease in the saturation voltage from 120 mT to 150 mT. A broad signal centered at mT was detected, but in sample 11B, this signal was This signal corresponds to Co with four oxygen atoms (A site in Figure 5). Respond.

[0415] Therefore, sample 12B, which does not have magnesium and fluorine, and sample 12B, which does not have magnesium and fluorine, Sample 11A, which contains silicon and fluorine but is not subjected to the second heat treatment, has a spinel-type crystal structure. Co3O4, but magnesium and fluorine were added and a second heat treatment was performed. It was revealed that sample 11B was below the detection limit.

[0416] As shown in Figure 40, a sharp peak centered at around 320 mT was observed in all samples. This signal corresponds to Co with six oxygen atoms coordinated (B site in Figure 5).

[0417] Among these, in sample 11A of FIG. 40(B) and sample 11B of FIG. 40(C), 3 A shoulder peak was observed around 12 mT, but not in sample 12B in Figure 40(A). This peak indicates that Mg exists near Co. It was revealed that ESR can also be used to determine whether a positive electrode active material contains Mg. . [Example]

[0418] In this example, what elements should be dissolved to form a pseudo-spinel crystal structure during high voltage charging? Calculations were carried out to clarify how likely this is to occur.

[0419] As explained in Figure 2, the H1-3 type crystal structure is similar to that of CoO2 such as P-3m1(O1). The structure is made up of alternating layers of LiCoO2 such as R-3m(O3). do.

[0420] Therefore, when the number of structures belonging to P-3m1 increases to about half, the H1-3 type crystal structure is formed. Conversely, if the structure belonging to R-3m accounts for 50% or more, R It is thought that the pseudo-spinel crystal structure, which is -3m, is easily formed. The crystal structure models of m1 and R-3m were used to reproduce the positive electrode active material in the high-voltage charging state. The stabilization energies in the presence of Al or Ti were calculated.

[0421] The crystal structure model for the high-voltage charged state is R-3m(O3) as explained in Figure 2, with all Li removed. The extracted material and P-3m1(O1) were used. The two cases are when Ti or Co is inserted into the most stable position between the CoO2 layers or when it is substituted into the Co site. The sum was calculated for each.

[0422] The crystal structure model of P-3m1 when Mg, Al, or Ti is intercalated between CoO2 layers is shown in Figure 41. The crystal structure model of R-3m is shown in Figure 41(A2). The crystal structure model of P-3m1 when it is at the Co site is shown in Figure 41(B1), and the result of R-3m is shown in Figure 41(B2). The crystal structure model is shown in Figure 41(B2). Table 3 shows the calculation conditions.

[0423] [Table 3]

[0424] Energy difference ΔE (eV) between the space group P-3m1 structure and the space group R-3m structure When Mg is inserted between the CoO2 layers, the calculation is performed using the following formula: The energy of an element is the energy of a single atom.

[0425]

number

[0426] Similarly, when Mg is substituted into the Co site, the calculation was performed using the following formula.

[0427]

number

[0428] The results of similar calculations for other elements are shown in Figure 42. The results for the case without exchange and for the case with Li inserted between the CoO2 layers are also shown.

[0429] Figure 42(A) shows the stable structure when Al, Ti, Mg, or Li is inserted between the CoO2 layers. 1 is a graph showing the chemical energy ΔE. For all elements, ΔE is a negative value. This means that the structure of the space group R-3m is more stable than P-3m1. The values ​​of all elements were lower than those of Li. The active material is more likely to have the R-3m structure than simple LiCoO2, even under high voltage charging conditions. Among them, Mg was found to be the most effective among Al, Ti, and Mg. It became clear.

[0430] Figure 42(B) shows the stabilization energy when Al, Ti, or Mg is substituted at the Co site. 3 is a graph showing ΔE. For all elements, ΔE is a positive value, and the P-3m1 structure It was shown that Al and Ti are more stable than when they are not substituted (when Co is present). The values ​​of Mg were also low, but the values ​​of Mg were higher than when not substituted.

[0431] Therefore, while Mg present between the CoO2 layers is highly effective in maintaining the R-3m structure, It was revealed that Mg present at the Co site had no such effect.

[0432] Next, when all lithium is inserted, the crystal structure of R-3m(O3) in the discharged state is A Calculate whether l, Ti, or Mg is more stable by substituting into the Li site or the Co site. The calculation method was the same as in Figure 42. The results are shown in Figure 43.

[0433] Al and Ti have the same negative ΔE regardless of whether they are substituted at the Li site or the Co site. The value of ΔE was smaller for Ti. Therefore, Al and Ti were It was shown that Ti tends to dissolve easily in CoO2, and that Ti dissolves more easily in CoO2.

[0434] On the other hand, when comparing Mg at the Li site and Co site, the Li site was larger and more stable. Therefore, it was shown that Mg is more likely to enter the Li site than the Co site. In both cases, ΔE is positive, so Mg tends to be somewhat difficult to dissolve in LiCoO2. This tendency suggests that some Mg segregates in the surface layer and near the grain boundaries. It can explain the phenomenon.

[0435] From the above, when Mg exists between the CoO2 layers (Li site), a large amount of Li is extracted and a high The R-3m structure is easily maintained even when the material is charged, and the pseudo-spinel crystal structure is easily formed. Therefore, Mg, which tends to enter the Li site of LiCoO2, is removed by the second heat treatment. It is important to ensure that the Li site (not the Co site) is included in the fabrication process. can be obtained. [Explanation of symbols]

[0436] 100 Cathode active material 200 Active material layer 201 Graphene Compounds 211a positive electrode 211b negative electrode 212a Lead 212b Lead 214 Separator 215a Joint 215b Joint 217 Fixing member 250 Secondary battery 251 Exterior body 261 Bending section 262 Seal part 263 Seal part 271 Ridgeline 272 Valley Line 273 Space 300 Secondary battery 301 Positive electrode can 302 Anode can 303 Gasket 304 Positive electrode 305 Positive electrode current collector 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 lead electrode 511 Negative lead electrode 600 Secondary battery 601 Positive electrode cap 602 Battery can 603 Positive terminal 604 Positive electrode 605 Separator 606 negative electrode 607 Negative terminal 608 Insulating plate 609 Insulating board 611 PTC element 612 Safety valve mechanism 613 Conductive Plate 614 Conductive Plate 615 Module 616 Conductor 617 Temperature Control Device 900 Circuit Board 910 Label 911 terminal 912 circuits 913 Secondary battery 914 Antenna 915 Antenna 916 layers 917 layers 918 Antenna 920 Display device 921 Sensor 922 terminal 930 chassis 930a housing 930b housing 931 negative electrode 932 Positive electrode 933 Separator 950 Wound body 951 terminal 952 terminals 980 Secondary battery 981 Film 982 Film 993 Wound body 994 negative electrode 995 positive electrode 996 Separator 997 Lead Electrode 998 Lead electrode 7100 Portable display devices 7101 Housing 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Personal Digital Assistant 7201 Case 7202 Display section 7203 Band 7204 Buckle 7205 Operation button 7206 Input / output terminal 7207 Icon 7300 display device 7304 Display section 7400 mobile phone 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 7407 Secondary battery 7408 Lead electrode 7500 e-cigarettes 7501 Atomizer 7502 Cartridge 7504 Secondary battery 8000 display device 8001 Case 8002 Display section 8003 Speaker section 8004 Secondary battery 8021 Charging device 8022 cable 8024 Secondary battery 8025 Secondary battery 8100 Lighting equipment 8101 Housing 8102 Light source 8103 Secondary battery 8104 Ceiling 8105 Side wall 8106 beds 8107 Window 8200 indoor unit 8201 Housing 8202 Ventilation outlet 8203 Secondary battery 8204 Outdoor unit 8300 Electric refrigerator-freezer 8301 Housing 8302 Refrigerator door 8303 Freezer door 8304 Secondary battery 8400 Automobiles 8401 Headlight 8406 Electric motor 8500 cars 8600 Scooter 8601 Side mirror 8602 Secondary battery 8603 Turn signal light 8604 Under-seat storage 9600 tablet device 9625 Switch 9626 Switch 9627 Switch 9628 Operation Switch 9629 Fasteners 9630 chassis 9630a housing 9630b housing 9631 Display section 9633 Solar Cells 9634 Charge / Discharge Control Circuit 9635 Electricity storage unit 9636 DC / DC Converter 9637 Converter 9640 Moving parts

Claims

1. A secondary battery having a positive electrode active material containing lithium, cobalt, magnesium, oxygen, and fluorine, The volume per unit cell of the pseudo-spinel crystal structure having an abundance ratio of 60 wt% or more in the positive electrode active material with a charging depth of 0.8 or higher, The volume per unit cell of the crystal structure having an abundance ratio of 60 wt% or more in the positive electrode active material with a charging depth of 0.06 or less, A secondary battery in which the difference is within 2.5%.

2. In claim 1, The positive electrode active material is titanium, and the secondary battery is otherwise.

3. In claim 1 or claim 2, The positive electrode active material is aluminum, and the secondary battery is otherwise.

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