Lithium-ion secondary battery

Abstract

To provide a positive electrode active material having high capacity and good cycle characteristics.SOLUTION: A positive electrode active material includes a crystal structure that changes little between the charged and discharged states. For example, a positive electrode active material that has a layered rock salt type crystal structure in the discharged state and a pseudo-spinel type crystal structure in the charged state at a high voltage of about 4.6 V has a smaller change in crystal structure and volume before and after charging and discharging than known positive electrode active materials. When the positive electrode active material has this pseudo-spinel type crystal structure, diffraction peaks are generated 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 positive electrode active material that can be used in a secondary battery, The present invention relates to a secondary battery and an electronic device having a secondary battery.

[0002] In this specification, the term "electricity storage device" refers to elements and devices having an electricity storage function in general. For example, lithium ion secondary batteries and other storage batteries (also called secondary batteries) These include lithium ion capacitors and electric double layer capacitors.

[0003] In addition, in this specification, the term "electronic device" refers to any device having 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 storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have become available. The development of lithium-ion batteries, which have high power and high energy density, is particularly The secondary battery is used in mobile phones, smartphones, notebook computers, 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 has expanded rapidly along with the development of the semiconductor industry. As a source of supply, it has become indispensable in today's 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 developed a positive electrode active material with the aim of improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries. 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] JP 2006-164758 A [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 and discharge characteristics. Another object of the present invention is to provide a secondary battery having high safety or reliability. 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 the objectives 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 embodiment to solve all of these problems. It is possible to extract problems other than those mentioned above 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 crystal structure.

[0013] One aspect of the present invention is a secondary battery having 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 type 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 lithium-ion battery comprising the steps of: A positive electrode active material having the above structure, the positive electrode active material being used in a positive electrode and lithium metal being used in a negative electrode. The current value of the lithium-ion secondary battery was increased until the battery voltage reached 4.6 V in a 25°C environment. After charging until the charge level was sufficiently low, 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 lithium-ion battery comprising the steps of: A positive electrode active material having a positive electrode active material with a charge depth of 0.8 or more, the abundance ratio of which is 60w The volume per unit cell of the crystal structure with t% or more and the positive electrode activity at a charge depth of 0.06 or less The volume per unit cell of a crystal structure that is present at 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. Effect of the Invention

[0017] According to one embodiment of the present invention, there is provided a lithium ion secondary battery having a high capacity and excellent charge / discharge cycle characteristics. In addition, by using the positive electrode active material 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. In addition, a secondary battery with high safety and reliability can be provided. It is also possible to provide a novel substance, active material particles, a power storage device, or a manufacturing method thereof. do.

[0018] The description of these effects does not preclude the existence of other effects. The embodiment does not need to have all of these effects. Effects other than these may be included in the description, This is self-evident from the description in the drawings, claims, etc. It is possible to extract other effects from any of the descriptions. [Brief description of the drawings]

[0019] [Figure 1] 1A and 1B are diagrams illustrating the charge depth and the crystal structure of a positive electrode active material of one embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating the charge depth and crystal structure of a conventional positive electrode active material. [Diagram 3] XRD pattern calculated from crystal structure. [Figure 4] 1A to 1C are diagrams illustrating a crystal structure and magnetic property of a positive electrode active material of one embodiment of the present invention. [Diagram 5] 1A to 1C are diagrams illustrating the crystal structure and magnetism of a conventional positive electrode active material. [Figure 6] FIG. 13 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive assistant. [Figure 7] FIG. 4 is a diagram illustrating a method of charging a secondary battery. [Figure 8] FIG. 4 is a diagram illustrating a method of charging a secondary battery. [Figure 9] 5A to 5C are diagrams 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 are diagrams illustrating examples of electronic devices. [Figure 24] 1A to 1C are diagrams illustrating examples of electronic devices. [Diagram 25] 1A to 1C are diagrams illustrating examples of electronic devices. [Figure 26] 1A to 1C are diagrams illustrating 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. [Diagram 30] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Diagram 31] 1 is an XRD pattern of a positive electrode active material of a comparative example of Example 1. [Diagram 32] 1 is an XRD pattern of a positive electrode active material of a comparative example of Example 1. [Diagram 33] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Diagram 34] 1 shows an XRD pattern of a positive electrode active material according to an embodiment of the present invention in Example 1. [Diagram 35] 1 is an XRD pattern of a positive electrode active material of a comparative example of Example 1. [Diagram 36] 1 shows XRD patterns of positive electrode active materials according to an embodiment of the present invention in Example 1 and a comparative example. [Figure 37] 4 is a graph showing the volume change rate of the positive electrode active material according to one embodiment of the present invention in Example 1. [Figure 38] 3 shows cycle characteristics of the secondary battery according to an embodiment of the present invention in Example 1 and a comparative example. [Figure 39] 4 shows ESR signals of the positive electrode active material according to an embodiment of the present invention and a comparative example of Example 2. [Diagram 40] 4 shows ESR signals of the positive electrode active material according to an embodiment of the present invention and a comparative example of Example 2. [Diagram 41] Crystal structure model used in the calculation in Example 3. [Diagram 42] 13 is a graph illustrating the calculation results of Example 3. [Diagram 43] 13 is a graph illustrating the calculation results of Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the 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. The present invention is not 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, in crystallography, the numbers are usually surrounded by 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 indicated by [ ], and a collective orientation that indicates all equivalent directions is indicated by < >, individual faces that indicate 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 a particle of an active material or the like refers to a region extending 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. The term refers to a crystal structure. It is acceptable for there to be defects such as deficiencies of cations or anions. Strictly speaking, the rock salt crystal structure is a distorted structure of the rock salt crystal lattice. be.

[0025] In the present specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. The structure may contain a deficiency of cations or anions.

[0026] In the present specification and the like, the pseudospinel type of a composite oxide containing lithium and a transition metal is The crystal structure is in the space group R-3m, and is not a spinel type crystal structure, but it does contain cobalt, Ions such as magnesium ions occupy the 6-coordinated oxygen sites, and the ion arrangement is symmetrical, similar to that of the spinel type. The pseudo-spinel type crystal structure has a crystal structure that is stable against light elements such as lithium. Oxygen may occupy 4-coordinate sites, and in this case the ionic arrangement also has a symmetry similar to that of the spinel type. has.

[0027] The pseudospinel crystal structure has random Li between layers, but CdCl 2 Formation It can be said that the crystal structure is similar to that of CdCl. 2 Crystals similar to the type The structure is that when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 NiO 2 ) crystal structure, but is similar to that of pure lithium cobalt oxide, or a layered rock rich in 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 of rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure) It is assumed that the anions of pseudospinel crystals also have a cubic close-packed structure. When the anions are in contact with each other, 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 the layered rock salt crystals and pseudospinel crystals is R-3m, and the space group of the rock salt crystals is R-3m. Crystal space groups Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest Since the space group of the crystal is different from that of the rock salt type crystals, the mirror of the crystal plane that satisfies the above conditions The -index is different between layered rock salt crystals and pseudospinel crystals and between rock salt crystals. In layered rock salt crystals, pseudospinel crystals, and rock salt crystals, the anions form When the orientation of the cubic close-packed structure is aligned, the crystal orientation is 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) This can be judged from images such as ABF-STEM (annular bright-field scanning transmission electron microscope) images. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used for judgment. If the crystal orientation is roughly the same, cations and anions will be linearly arranged in a TEM image. It is observed that the difference in the orientation 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 some 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 refers to the capacity of the positive electrode active material that can be inserted and removed. The charge when all lithium is removed is called LiCoO 2 The theoretical capacity of 4mAh / g, LiNiO 2 The theoretical capacity of LiMn is 274mAh / g. 2 O 4 Theoretical capacity of is 148mAh / g.

[0031] In the present specification, the charge depth when all the intercalable and detachable lithium is intercalated is The charge depth when all the intercalable lithium in the positive electrode active material is deintercalated is defined as 0, and the charge depth 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 a battery. The positive electrode active material is a material that moves electrons from the negative electrode to the positive electrode in an external circuit. In this case, charging refers to the process of removing lithium ions. Also, when the charge depth exceeds 0.5, The positive electrode active material is referred to as a charged positive electrode active material. The positive electrode active material is defined as a positive electrode active material charged at a high voltage. For example, Li Chief of Staff 2 If the positive electrode is charged at 219.2mAh / g or more at The active material is lithium cobalt oxide, which contains 5 at % or less of impurity elements (here, impurity (Elements other than lithium, cobalt, and oxygen) in a 25°C environment. Charge the battery at a constant current until the battery voltage reaches 4.6V (when using lithium as the counter electrode), then reduce the current to 0. The positive electrode active material after constant voltage charging up to 0.1C is also called a positive electrode active material charged at a high voltage. We have decided to do so.

[0033] Similarly, discharging means moving lithium ions from the negative electrode to the positive electrode in the battery and discharging them from an external circuit. The term refers to the transfer of electrons from the positive electrode to the negative electrode in a battery. The insertion of ions is called discharging. A positive electrode active material with a charge depth of 0.5 or less is called a discharged material. In addition, the positive electrode active material with a charge depth of 0.06 or less, or the positive electrode active material with a high The positive electrode active material that has been discharged to 90% or more of its charge capacity from the charged state is then fully charged. This is called the discharged positive electrode active material. For example, LiCoO 2 The charging capacity is 21 If the battery is charged at 9.2mAh / g, it is in a high-voltage charged state, and from this point, it is at 90% of its charge capacity. The positive electrode active material after discharging 197.3 mAh / 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 The battery voltage is measured at 25°C under the following conditions: 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 FIG. 1 and FIG. 2, a positive electrode active material 100 according to an embodiment of the present invention and a conventional positive electrode active material are shown. The quality of the conventional positive The active material is a material that contains elements other than lithium, cobalt, and oxygen, or has cobalt added to the surface. A simple lithium cobalt oxide (LiCoO 2 )in 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. A typical crystal structure of lithium cobalt oxide is shown in Figure 2.

[0036] As shown in Figure 2, LiCoO 2 is the result of the space group R-3m The unit cell has a region with a crystal structure and contains CoO 2 There are three layers. The crystal structure is sometimes called the O3 type crystal structure. 2 The layer is a layer of cobalt with oxygen This refers to a structure in which a 6-coordinate octahedral structure is connected to a plane with edge sharing.

[0037] At a charge depth of 1, the crystal structure has the space group P-3m1, and there is CoO 2 There is one layer. Therefore, this crystal structure is sometimes called the O1 type crystal structure.

[0038] Also, LiCoO at a charge depth of about 0.88 2 has a crystal structure in the space group R-3m. This structure is similar to that of CoO 2 The structure of R-3m(O3) and UnaLiCoO 2 It can be said that the structure of and the structure of are stacked alternately. The H1-3 crystal structure is sometimes called the H1-3 crystal structure. The number of cobalt atoms per cell is twice that of other structures. In this specification, the c-axis of the H1-3 crystal structure is expressed as the unit cell in order to facilitate comparison with other structures. The figure will be shown as half the original size.

[0039] Repeated high voltage charging and discharging until the charge depth reaches 0.88 or more. and LiCoO 2 The H1-3 type crystal structure and the discharged R-3m(O3) structure are The crystal structure undergoes repeated changes during this process.

[0040] However, these two crystal structures are similar to CoO 2 The layer misalignment is large. As shown by the arrows in the H1-3 crystal structure, CoO 2 The layer is larger than R-3m (O3). Such dynamic structural changes adversely affect 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 discharged state is reached, the difference in volume between the H1-3 type crystal structure and the O3 type crystal structure in the discharged state is 3.5% or more. be.

[0042] In addition, the H1-3 crystal structure has a CoO 2 The layers are continuous The resulting structure is likely to be unstable.

[0043] Therefore, the crystal structure of lithium cobalt oxide breaks down when it is repeatedly charged and discharged at high voltages. The breakdown of the crystal structure causes the deterioration of cycle characteristics. The number of sites where lithium can exist stably decreases, and it becomes difficult to insert and remove lithium. It is believed 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 lithium ions 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 above.

[0046] The crystal structure at charge depth 0 (discharged state) in Figure 1 is the same as that in Figure 2, R-3m(O3). In the case of the positive electrode active material 100 according to one embodiment of the present invention, when the charge depth is sufficiently 0.88, 2. The crystal structure of this space group R-3m is referred to herein as The pseudo-spinel crystal structure shown in Fig. 1 is called the pseudo-spinel crystal structure. In the structure, the lithium ion is used to explain the symmetry of the cobalt atom and the symmetry of the oxygen atom. Although the display is omitted, the actual CoO 2 Between the layers, about 12 atomic percent lithium is added to cobalt. In both the O3 and pseudospinel crystal structures, C oO 2 It is preferable that magnesium exists in a dilute state between the layers, i.e., at the lithium site. It is also preferable that a halogen such as fluorine is present in a dilute amount 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, the change in the crystal structure when lithium is released is suppressed. For example, as shown by the dotted lines in Fig. 1, in these crystal structures, CoO 2 There is almost no layer misalignment .

[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 pseudospinel crystal structure with a charge depth of 0.88 is 2.5 % or less, and more specifically, 2.2% or less.

[0049] Therefore, the crystal structure is not easily destroyed 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 This can be expressed as o(0,0,0.5) and O(0,0,x) (0.20≦x≦0.25). do.

[0051] Chief of Staff 2 Magnesium, which is present dilutely between the layers, is 2 Effective in preventing layer misalignment Therefore, the CoO 2 When magnesium is present between the layers, it tends to form a pseudospinel crystal structure. Therefore, it is preferable that magnesium is distributed inside the particles of the positive electrode active material 100. In order to distribute magnesium inside the particles, the process of producing the positive electrode active material 100 In the above, 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 The possibility of magnesium entering the cobalt site increases. When magnesium is present in the cobalt site, The effect of maintaining the structure of R-3m will be lost. Furthermore, if the heat treatment temperature is too high, There are also concerns about adverse effects such as cobalt being reduced to divalent and lithium evaporating. do.

[0053] Therefore, before the heat treatment for distributing magnesium inside the particles, the lithium cobaltate It is preferable to add a halogen compound such as a fluorine compound to the lithium. The addition of lithium cobalt oxide lowers the melting point of the lithium cobalt oxide. At a temperature where unmixing is unlikely to occur, it becomes easy to distribute magnesium throughout the particles. Furthermore, if fluorine compounds are present, the electrolyte will have high corrosion resistance against hydrofluoric acid produced by decomposition. It can be expected to improve.

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

[0055] Magnesium distributed inside the positive electrode active material 100 is CoO 2 The effect of suppressing layer misalignment 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 have a structure in which MgO and CoO(II) are solid-dissolved. In the region where oO(II) is dissolved, the route for lithium insertion and removal disappears. Put away.

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

[0057] In addition, when the battery contains at least one of titanium and aluminum, it is possible to prevent oxidation, 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 suppressed. 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 concentration in the whole particle. The particle surface is essentially made up of crystal defects, so it becomes unstable and the crystal structure begins to change. If the magnesium concentration in the surface layer is high, the change in the crystal structure will be more effective. In addition, if the magnesium concentration in the surface layer is high, the electrolyte will decompose and It is also expected that the corrosion resistance against the hydrofluoric acid generated by the process will be improved.

[0059] In addition, it is preferable that the concentration of fluorine in the surface layer of the positive electrode active material 100 is higher than the average concentration of 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 was higher in the surface layer than in the whole particle. It is preferable that the magnesium concentration is high in the region where titanium or aluminum is added. If there are many of any of the above, the CoO 2 It has a strong effect of suppressing layer changes. In addition, oxidative decomposition of the electrolyte on the surface of the positive electrode active material is more unlikely to occur.

[0061] In this way, the surface layer of the positive electrode active material 100 is richer in magnesium, fluorine, titanium, or It is preferable that the inner portion has a different composition from the inner portion, in which at least one concentration of aluminum is high. It is also preferable that the composition has a stable crystal structure at room temperature. For example, at least the surface layer of the positive electrode active material 100 may have a different crystal structure from that of the other surface layer. In addition, a part of the surface layer may have a rock salt type crystal structure. In the case where the crystal orientation is substantially the same in the surface layer and in the interior, it is preferable that the crystal orientation be substantially the same in the surface layer and in the interior.

[0062] In addition, 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 have a valence of 1 or 2, 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 the distance between the metal and oxygen varies. For example, when the surface layer of the positive electrode active material 100 has a rock salt type crystal structure, the region containing titanium may function as a buffer region and contribute to stabilizing the internal crystal structure.

[0063] However, if the surface layer is made of only MgO or a solid solution of MgO and CoO(II), As mentioned above, there is no route for lithium insertion and removal. It also contains cobalt in the discharged state, and lithium in the discharged state, providing a route for lithium insertion and removal. 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 exist 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 inside. It is preferable that the fluorine concentration is higher than that in other regions. Also, the fluorine concentration at the grain boundaries and their vicinity is high. In addition, it is preferable that either titanium or aluminum is present at the grain boundary and in the vicinity thereof. It is also preferable that the concentration of is high.

[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 is high at and near the grain boundaries, The change in the crystal structure can be more effectively suppressed. If the concentration of either tungsten or aluminum is high, the CoO 2 The effect of suppressing layer changes 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 within about 10 nm from the grain boundary. It is 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 the active material layer becoming difficult to support when applied to the body and excessive reaction with the electrolyte. Therefore, it is preferable that D50 (also called the 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 an 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 material is active is 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 crystal structure of the positive electrode active material with high resolution, The height and orientation of the crystallites can be compared, and the lattice periodicity distortion and crystallite size can be analyzed. It is possible to obtain sufficient accuracy by measuring the positive electrode obtained by disassembling a 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 capable of detecting the state of high voltage charging and discharging. The characteristic of this battery is that the crystal structure changes little when it is discharged. 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 have in common the fact that they are lithium cobalt oxides, the pseudo-spinel crystal structure accounts for 60 wt% or more of the total. In some cases, the H1-3 crystal structure is more than 50%. At this voltage, the pseudo-spinel crystal structure is almost 100%, and when the voltage is further increased, 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 the crystal structure is 0 or not, analysis of the crystal structure, including XRD, is required. be.

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

[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) mixed The resulting slurry can be applied to a positive electrode current collector made of aluminum foil and then 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 that of the secondary battery. For example, when we look at the potential of the positive electrode, Charging at 4.5 V with a graphite counter electrode is roughly equivalent to charging at 4.6 V with a lithium counter electrode. In this specification and the like, voltages and potentials are those of the positive electrode unless otherwise specified.

[0075] The electrolyte contained 1 mol / L lithium hexafluorophosphate (LiPF 6 ) 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 having a thickness of 25 μm.

[0077] The positive and negative electrode cans may 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 the current value was 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 take out 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 enclosed in a sealed vessel with an argon atmosphere.

[0079] <XRD> The CuKα1 line calculated from the pseudo-spinel crystal structure and the H1-3 crystal structure model. The ideal powder XRD pattern obtained by this is shown in Figure 3. For comparison, the LiCoO 2 (O3) and CoO at charge depth 1 2 Ideal XRD calculated from the crystal structure of (O1) The pattern is also shown. 2 (O3) and CoO 2 (O1) pattern is IC SD (Inorganic Crystal Structure Database) The model was created using Materials Studio (BIOVIA) from the crystal structure information obtained from Using Reflex Powder Diffraction, one of the modules The range of 2θ is from 15° to 75°, the step size is 0.01, and the wavelength is λ 1=1.540562×10 -10 m, λ2 are not set, Monochromator is The H1-3 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° to 19.50°), and 2θ=45.55±0.10° (45.45° or less) A diffraction peak appears at 2θ=19.30° (45.65° or less). ±0.10° (19.20° to 19.40°) and 2θ=45.55±0.0 A sharp diffraction peak appears at 5° (45.50° to 45.60°). Type 3 crystal structure and CoO 2 (P-3m1, O1) No peaks appear at these positions. 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 It can be said that this is 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 pseudo-spinel type crystal structure. However, the XRD pattern may be When the 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 of the cellulose ester is 60 wt% or more, more preferably 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 further preferably If the content is preferably 66 wt % or more, the positive electrode active material has sufficiently excellent cycle characteristics. can be done.

[0082] In addition, the crystallite size of the pseudo-spinel structure of the positive electrode active material particles is The XR of the positive electrode before and after charging and discharging is the same as that of the positive electrode before and after 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, the simple LiCoO 2 In the present study, some of the crystal structures resembled pseudospinel 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 characteristics of the internal structure of the positive electrode active material. In the case of the positive electrode active material with a particle size (D50) of about 1 μm to 100 μm, the inside of the For example, the volume of the surface layer is very small, so that the surface layer of the positive electrode active material 100 has a crystal structure different from that of the inside. Even if it has a structure, it is highly likely that it will not show up in the XRD pattern.

[0084] <ESR> In the case of a positive electrode active material 100 having a pseudo-spinel type crystal structure, as shown in FIG. 1 and FIG. 4(A), As shown in Figure 4(B), cobalt is present in the site with 6 oxygen coordination. In cobalt, the 3d orbitals are e g Orbit and t 2gThe orbit is split and arranged in a way that avoids the direction where oxygen exists. The t 2g The orbital has low energy. Some of the cobalt atoms are present in the oxygen hexacoordinated sites. t 2g Diamagnetic Co with all orbitals filled 3+ However, the oxygen 6-coordinated cyano group is The other part of the cobalt present in the ion exchange reaction 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, they cannot be distinguished by ESR, but depending on the valence of the surrounding elements, You may also take the following.

[0085] On the other hand, in the conventional positive electrode active material, the surface layer is a spinel that does not contain lithium when charged. It has been said that the crystal structure of the spinel shown in FIG. Co, which has a nell-type crystal structure 3 O 4 This means that

[0086] Spinel is classified into the general formula A[B 2 ]O 4 In this case, element A has 4 oxygens and element B has 6 oxygens. Therefore, in this specification, the site with 4 oxygen coordination is called the A site, and the site with 6 oxygen coordination is called the B site. The site is sometimes called the B site.

[0087] Spinel-type crystal structure Co 3 O 4 So, not only the B site with 6 oxygen atoms, but also the B site with 4 oxygen atoms Cobalt is also present 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 Of the orbitals, e gThe orbital energy is low. Therefore, the oxygen 4- Co 2+ , Co 3+ and Co 4+ All of them have unpaired electrons and are paramagnetic. Spinel type Co 3 O 4 If particles with sufficient oxygen are analyzed by ESR etc., it is possible to find Co with 4 oxygen coordination. 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 oxygen-coordinated paramagnetic cobalt is In other words, the positive peak of one embodiment of the present invention is smaller than that of the conventional example. The active material is a spinel type Co that can be detected by ESR etc. 3 O 4 The peak due to is small, Sometimes it is so small that it cannot be seen. 3 O 4 does not contribute to the charge / discharge reaction, Because of its thermal instability, spinel-type Co 3 O 4 The smaller 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 about 2 to 8 nm (usually about 5 nm). Since it is possible to analyze the area, the concentration of each element can be quantified for about half of the surface layer. In addition, 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 depends on the element. It depends on the material, but is about 1 atomic percent.

[0090] When XPS analysis was performed on 100% positive electrode active material, the cobalt concentration was set to 1. The relative value of the magnesium concentration is preferably 0.4 or more and 1.5 or less, and more preferably 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. It is more preferable that the binding energy of the LiF is about 685 eV. and magnesium fluoride, which is 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 bonds between magnesium and other elements were 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 energy of 1305 eV, which is close to the binding energy of MgO. In other words, when the positive electrode active material 100 contains magnesium, the bond other than that of magnesium fluoride It is preferable that:

[0093] <EDX> Among EDX measurements, ED is a method of measuring an area while scanning it and evaluating the area in two dimensions. Also, data on linear areas is extracted from EDX area analysis, and the original Evaluation of 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) has revealed that the To quantitatively analyze the concentration of magnesium, fluorine, titanium or aluminum in In addition, EDX analysis can be used to determine whether magnesium, fluorine, titanium, or aluminum is included. The concentration peaks of the rhamnoides 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 surface of the positive electrode active material 100 is located at a depth of up to 3 nm toward the center. Preferably, the surface is present at a depth of 1 nm, and more preferably at a depth of 0.5 nm. is more preferred.

[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 the 100 is located within a depth of 3 nm toward the center, and the depth of 1 nm More preferably, it is present 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 is located 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] In addition, when the positive electrode active material 100 was subjected to line analysis or area analysis, the microstructure in the vicinity of the grain boundaries was 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 of 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. Also, a magnesium source is prepared. And preferably a fluorine source is also provided as a starting material.

[0101] The lithium source can be, for example, lithium carbonate or lithium fluoride. As the tungsten source, for example, cobalt oxide can be used. As the magnesium source, 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, the range 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 in the fluoride source is at least 1.0 times the magnesium 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.

[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 sintering or first heating. Heating is preferably performed at a temperature of 800°C or higher and 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 a temperature of about 950°C or lower is even more preferable. If the temperature is too low, the decomposition and melting of the starting materials may be insufficient. If the temperature is too high, Co will be reduced and Li will evaporate, resulting in defects where Co becomes divalent. There is a risk of this happening.

[0106] The heating time is preferably from 2 hours to 20 hours. The firing is carried out in an atmosphere such as dry air. For example, the heating is performed at 1000°C for 10 hours, and the temperature is increased by 20 The drying temperature is preferably 10°C / h and the flow rate of the drying atmosphere is preferably 10 L / min. Cool the material to room temperature. For example, cool the material from the holding temperature to room temperature for 10 hours or more or 50 hours or more. It is preferable to set the temperature within 100° C. or less.

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

[0108] In addition, lithium, cobalt, fluorine, magnesium, etc., which are pre-synthesized as starting materials, are used. In this case, the step S12 and the step S1 3 can be omitted. For example, lithium cobalt oxide manufactured by Nippon Chemical Industry Co., Ltd. As one of the starting materials, particles (product name: C-20F) with a particle size of about The area that can be analyzed by XPS is 20 μm in diameter, and fluorine, magnesium, calcium, and 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 of the substrate with a material having the above-mentioned properties. The coating method includes the sol-gel method. The liquid phase method, solid phase method, sputtering method, deposition method, CVD (chemical vapor deposition) method, PLD (plane deposition) method, In the present embodiment, a method such as a laser deposition method can be applied. In this section, we will explain 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 The lithium cobalt oxide particles are dissolved in alcohol and then mixed with the lithium cobalt oxide particles.

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

[0112] The amount of metal alkoxide required varies depending on the particle size of lithium cobalt oxide. For example, TT When using IP, if the particle size (D50) of lithium cobalt oxide is about 20 μm, For lithium tritate particles, TTIP is set to 0.004ml / g or more and 0.01ml / g or less. It is preferable to add aluminum isopropoxide 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, the mixture of the alcohol solution of metal alkoxide and the lithium cobalt oxide particles is heated in a water vapor atmosphere. The mixture is stirred in an atmosphere containing air. Stirring can be performed, for example, by using a magnetic stirrer. The stirring time is determined based on the time when 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 performed under conditions of (relative humidity, RH).

[0114] By reacting water vapor in the atmosphere with metal alkoxide, the The sol-gel reaction can proceed slowly. Also, metal alkoxide and water react at room temperature. 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 good quality can be formed.

[0115] The precipitate is collected from the mixture after the above treatment. 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, in vacuum or It can be air-dried.

[0117] <Step S15: Second Heat Treatment> Next, the titanium or aluminum-containing material produced in step S14 is coated on the substrate. 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 dissolved. If the alloy 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 far, resulting in low concentrations in the surface layer and in the vicinity of 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. It is more preferable that the temperature is 800°C or higher and 900°C or lower. However, if the temperature is too high, Mg may not be distributed to the Co site. LiCoO 2 Like Co 3+ Not a CoO, but a Co 2+ becomes stable , CoO2 There is a risk that the layered structure of the material may not be maintained.

[0120] In addition, the second heat treatment is preferably performed in an atmosphere containing oxygen. If the heating temperature is not lowered, there is a risk of Co being reduced.

[0121] In this embodiment, the holding temperature is set to 800° C. and held 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 since this makes it easier to stabilize the crystal structure. For example, 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 heat treatment (step S13) and the second heat treatment (step S15) In the first heat treatment, the starting materials are sufficiently mixed together. Co for reaction 3 O 4 (895℃) and Li 2 CO 3 Melting point (723℃) In the next heat treatment, magnesium is converted to CoO 2 Distribute between layers In order to achieve this, the heating is performed at a temperature lower than that in the first heating process. 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 less.

[0124] <Step S16: Collection> The cooled particles are then collected. It is further preferred to sieve the particles. Through this process, 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 or more. By repeatedly performing sol-gel processing and heat treatment, the lithium cobalt oxide particles were cracked. If cracks occur, they can be reduced.

[0126] In addition, when performing the sol-gel treatment multiple times, the type of metal alkoxide used may be the same. In the case where a different one is 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. Although the materials have been described above, one embodiment of the present invention is not limited thereto. 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 also contain very small amounts of 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 It is sufficient that 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 for the material to contain elements such as ruthenium.

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

[0130] This embodiment mode can be used 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 are Here, a secondary battery enclosed in an exterior body will be taken as an example.

[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 includes at least a positive electrode active material. In addition, other substances such as a coating on the surface of the active material, a conductive aid, or a binder may be included.

[0134] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, it is possible to obtain a high capacity and good cycle characteristics. This makes it possible to produce an excellent secondary battery.

[0135] As the conductive assistant, 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 assistant. 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 assistant can form an electrical 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 having high electrical conductivity. .

[0137] Examples of the conductive assistant include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fibers. Examples of carbon fibers that can be used include mesophase pitch carbon fibers. In addition, 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, a vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as copper, nickel, and graphene can be used. Nickel, aluminum, silver, gold and other metal powders, metal fibers, conductive ceramic materials, etc. It can be used.

[0138] In addition, a graphene compound may be used as the conductive assistant.

[0139] Graphene compounds have excellent electrical properties, such as high electrical conductivity, as well as high flexibility and In addition, graphene may have excellent physical properties such as high mechanical strength. The compound has a planar shape. Graphene compounds enable surface contact with low contact resistance. In addition, even if the material is thin, it can have very high conductivity, and a small amount of the material can be used to efficiently conduct electricity within the active material layer. Therefore, the graphene compound can be used as a conductive additive. This is preferable because it is possible to increase the contact area between the active material and the conductive assistant. 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 preferred to use RGO, where RGO is, for example, graphene oxide (g This refers to a compound obtained by reducing raphene oxide (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 relatively reduced amount of active material carried. If the capacity of the secondary battery decreases, the capacity of the secondary battery decreases. 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] In the following, as an example, a graphene compound is used as a conductive assistant in the active material layer 200. An example of the cross-sectional structure will be described.

[0142] 6A 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 assistant, 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. In addition, the graphene compound 201 may 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 in bold as a schematic diagram, but in reality, it is a single layer or The graphene compound 201 is a thin film having a thickness of multiple layers. The active material 100 is partially covered, or the surface of a plurality of granular positive electrode active materials 100 is covered with the adhesive. Since the electrodes 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. The graphene compound is then bonded to the graphene sheet (hereinafter referred to as a graphene compound net or a graphene net). When the active material is covered with a graphene net, the graphene net can bond the active material to each other. It can also function as a binder to bind the material together. This allows the amount of binder to be reduced. The ratio of active material to the electrode volume or weight can be adjusted to suit the application. 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 the layer that will become the layer 200 is formed, 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, for example, by 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 and the graphene compound 201 is reduced, 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, the entire surface of the active material is covered with a conductive additive in advance using a spray dryer. 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, butadiene rubber, ethylene-styrene rubber, acrylonitrile-butadiene rubber, butadiene 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. CMC, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, regenerated cellulose, and starch These water-soluble polymers can be used in combination with the above-mentioned rubber materials. It is even better if there is a

[0150] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. Polyvinyl chloride (Polymethyl methacrylate (PMMA)), Sodium polyacrylate, Polyvinyl chloride Polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (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 of 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, it is possible to mix the material with a particularly excellent viscosity adjusting effect. As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. In addition, 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 For example, starch or starch can be used.

[0153] In addition, cellulose derivatives such as carboxymethyl cellulose are, for example, carboxymethyl The solubility of cellulose increases when it is converted into a salt such as sodium salt or ammonium salt. It is easy to exert its effect as a viscosity adjuster. The higher the solubility, the easier it is to make the electrode slurry. In the preparation of the electrode, the dispersibility of the electrode with the active material and other components can be improved. In this regard, the cellulose and cellulose derivatives used as the binder for the electrodes are as follows: These salts are also included.

[0154] Water-soluble polymers stabilize the viscosity by dissolving in water, and also serve as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stable in aqueous solution. In addition, since it has a functional group, it is easy to stably adsorb on the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose, for example, 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 preventing the decomposition of the electrolyte. A film with no gas conductivity or extremely low electrical conductivity. For example, an immobile film is formed on the surface of an active material. When the electrolyte film is formed, the 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 highly conductive, such as an alloy of these. It is preferable that the material does not dissolve at the potential of the positive electrode. The aluminum alloy contains elements such as tungsten and molybdenum that improve heat resistance. It can also be formed from a metal element that reacts with silicon to form a silicide. Metal elements that react with silicon to form silicide include zirconium, titanium, and , hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, Cobalt, nickel, etc. Current collectors are available in foil, plate (sheet), mesh, punched metal, etc. The collector may be in the form of a barrel, an expanded metal, or the like. It is recommended to use one having a particle size 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 assistant 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 / de-alloying reactions with lithium. For example, silicon, tin, gallium, aluminum, and 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 high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Compounds containing these elements may also be used. For example, SiO, Mg 2 Si, Mg 2 Ge, SnO, SnO 2 , Mg 2 Sn, SnS 2 , V 2 Sn 3 , FeSn 2 , CoSn 2 , Ni 3 Sn 2 , Cu 6 Sn 5 , Ag 3 Sn, Ag 3 Sb, Ni 2 MnSb, CeSb 3 , LaSn 3 , La 3 Co 2 Sn 7 , CoSb 3 , I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying / 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, SiO refers to, for example, silicon monoxide. Alternatively, SiO x Here, 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-based materials include graphite, 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 of artificial graphite include mesophase graphite. Carbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. 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 preferred. It is relatively easy to reduce the particle size, which may be preferable. Examples of the graphite include flake graphite and spherical natural graphite.

[0163] When lithium ions are inserted into graphite (the formation of lithium-graphite intercalation compounds), 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. In addition, graphite has a relatively high capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has the advantage of being safer than metallic lithium.

[0164] Titanium dioxide (TiO 2 ), lithium titanium oxide (Li 4 T i 5 O 12 ), lithium-graphite intercalation compound (Li x C 6 ), niobium pentoxide (Nb 2 O 5 ) , tungsten oxide (WO 2), molybdenum oxide (MoO 2 ) and other oxides can be used. can.

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

[0166] When a composite nitride of lithium and transition metals is used, the negative electrode active material contains lithium ions, V that does not contain lithium ions as the positive electrode active material 2 O 5 , Cr 3 O 8 Combined with other materials It is preferable that the positive electrode active material contains lithium ions. The lithium ions contained in the positive electrode active material are first removed to form the negative 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. For example, Lithium oxide (LiO), cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the negative electrode active material may be used. Further materials that are produced include Fe 2 O 3 ,CuO,Cu 2 O, RuO 2 , Cr 2 O 3 etc. oxide, CoS0.89 , NiS, CuS and other sulfides, Zn 3 N 2 , Cu 3 N, Ge 3 N 4 Nitrides such as NiP 2 , FeP 2 , CoP 3 Phosphides such as FeF 3 , BiF 3 etc. It also occurs with fluoride.

[0168] The conductive assistant 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 conductive additive and binder may be the same as those that 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 ethyl propionate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethylsulfur oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of trihydrofuran, sulfolane, sultone, etc., or two or more of these 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, the internal temperature of the secondary battery increases due to an internal short circuit or overcharging. Even if the battery is heated, it can prevent explosion or fire of the secondary battery. Ionic liquids are made of cations and anions. The electrolyte solution contains an organic cation and an anion. 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 perfluoroalkyl phosphate anions, etc.

[0172] The electrolyte to be dissolved in the above-mentioned solvent is, for example, LiPF 6 , LiClO 4 , Li AsF 6 , LiBF 4 , LiAlCl 4 , LiSCN, LiBr, LiI, Li 2 SO 4 , Li 2 B 10 Cl 10 , Li 2 B 12 Cl 12 , LiCF 3 SO3 , LiC 4 F 9 SO 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiN(CF 3 SO 2 ) 2 , LiN(C 4 F 9 SO 2 )(CF 3 SO 2 ), LiN(C 2 F 5 SO 2 ) 2 Richie Use one or more of these salts in any combination and ratio. can be done.

[0173] The electrolyte used in secondary batteries is free of granular waste and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "inorganic substances"). It is preferable to use a highly purified electrolyte solution with a low content of ruthenium oxide (also called "pure substance"). 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, vinylene carbonate, propane sultone (PS), and tert-butyl ether were used in the electrolyte. 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 is sufficient to set the content to 0.1wt% or more and 5wt% or less.

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

[0176] By using a polymer gel electrolyte, safety against leakage etc. is improved. It is possible to reduce the thickness and weight of the device.

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

[0178] Examples of the polymer include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with a fluororesin structure, PVDF, polyacrylonitrile, etc., and their combinations 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, 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, the installation of a separator or spacer becomes unnecessary. Since the entire pond can be solidified, there is no risk of leakage, and safety is improved dramatically.

[0180] [Separator] The secondary battery preferably has a separator. The separator may be, for example, a 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 separator is processed into a shape such that it envelops 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, fluorine, polyamide, or a combination of these. The ceramic material can be, for example, arsenic oxide. Aluminum particles, silicon oxide particles, etc. can be used. For example, PVDF, polytetrafluoroethylene, etc. can be used. Polyamide-based materials Examples of materials used include nylon and aramid (meta-aramid and para-aramid). It is possible.

[0182] Coating with ceramic materials improves oxidation resistance, making it ideal for separators during high-voltage charging and discharging. This suppresses the deterioration of the capacitor and improves the reliability of the secondary battery. By coating the electrode, the separator and the electrode are more easily adhered to each other, improving the output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. This can improve safety.

[0183] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, the surface of the polypropylene film that comes into contact with the positive electrode may be coated with aluminum oxide. Alternatively, the surface in 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. .

[0184] By using a multi-layered separator, the safety of the secondary battery can be ensured even if the overall thickness of the separator is thin. Since the capacity per unit volume of the secondary battery can be increased, the capacity per unit volume of the secondary battery can be increased.

[0185] [Exterior body] The exterior body of the secondary battery is made of, for example, a metal material such as aluminum or a resin material. Also, a film-like exterior body can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a flexible metal such as aluminum, stainless steel, copper, nickel, etc. is A thin metal film is then applied, and a polyamide resin or polyester resin is applied to the outer surface of the exterior body on the thin metal film. For example, a three-layer film having an insulating synthetic resin film such as a fluorine-based 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, which is one of the charging methods. CC charging is This is a charging method in which a constant current is passed through the secondary battery and charging is stopped when a specified voltage is reached. The secondary battery is assumed to be 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, as shown in Figure 7(A), the switch is turned on and a constant current is applied. 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 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 is stopped. 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, with the internal resistance R The voltage drop of the secondary battery V B decreases.

[0190] The secondary battery voltage V during CC charging and after CC charging is stopped B and the 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 to a specified voltage using CC charging, then use CV (constant voltage) charging to reduce the current flowing. This is a charging method in which charging is continued until the battery becomes low, specifically until the battery reaches a cut-off current value.

[0192] During CC charging, the constant current power supply is switched on and the constant current is 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 RAccording to Ohm's law, the voltage V across 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 is switched to V charging, as shown in Figure 8(B). 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 resistor R R As becomes smaller, V R By Ohm's law, = R × I, The current I flowing to the next battery also becomes smaller.

[0194] When the current I flowing through the secondary battery becomes a certain current, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all the switches are turned off as shown in FIG. The switch is turned off and the current I becomes 0. Therefore, the voltage V across 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 at all.

[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 the CCCV charging is stopped, the secondary battery voltage V B Gahoton The figure 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 at 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 The figure shows how the light descends.

[0198] Next, the discharge rate and the charge rate will be described. 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 charging rate is also the same; if you charge with a current of 2X(A), it will be charged at 2C. When the battery was charged with a current of X / 5(A), it was charged at 0.2C. .

[0199] (Embodiment 3) In this embodiment, the shape of a 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 form may be taken into consideration.

[0200] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. FIG. 10(A) shows a coin-type (single-layer flat type) 10(A) 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 contacting a negative electrode current collector 308. The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode.

[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 or aluminum, which is resistant to corrosion by the electrolyte. , titanium, 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 for covering the positive electrode 304, and the negative electrode can 302 is for covering the negative electrode 304. 7 and electrically connected 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. As shown in FIG. 1, the positive electrode can 301 is placed downward, and the positive electrode 304, the separator 310, the 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 manufacture a coin-type secondary battery 300.

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

[0206] Here, the flow of current during charging of a secondary battery will be explained with reference to FIG. When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of electric current are in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode (cathode) is switched, and the oxidation and reduction reactions are switched, so the reaction potential The electrode with the higher reaction potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. In this case, the charge / discharge current is always the same whether the battery is charging or discharging or 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 and cathode are used, the difference between charging and discharging is , which can lead to confusion. The term "cathode" is not used in this specification. When using the terms negative electrode ( ) or cathode ( ), specify whether they are charging or discharging, and positive electrode ( It will also be indicated whether it corresponds to a positive pole or a negative pole.

[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. 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 disposed on the bottom surface of the positive electrode cap and the battery can (external can). It is insulated from 602 by a gasket (insulating packing) 610 .

[0209] Fig. 11(B) is a schematic diagram showing a cross section of a cylindrical secondary battery. Inside the can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are sandwiched between a separator 605. A wound battery element is provided. Although not shown, the battery element is wound around a center pin. 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 resistant to corrosion by the electrolyte. These and their alloys with other metals (e.g., stainless steel, etc.) can be used. In addition, to prevent corrosion by the electrolyte, the battery can 602 is coated with nickel, aluminum, or the like. 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 a coin-type secondary battery.

[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 606. The positive terminal 607 may be made of a metal material such as aluminum. 03 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) The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via a capacitance 611. The safety valve mechanism 612 is a mechanism for releasing the positive electrode cap 601 when the internal pressure of the battery increases beyond 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 element whose resistance increases when the temperature rises, and the amount of current is limited by the increase in resistance. It prevents abnormal heat generation. The PTC element is made of barium titanate (BaTiO 3 )system Semiconductor ceramics and the like can be used.

[0211] 11C, a plurality of secondary batteries 600 are mounted on 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 in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, It is possible to extract a large amount of power.

[0212] FIG. 11D 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. In addition, a temperature control device 617 may be provided between the multiple 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 and cycle. 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 an antenna 914 and an antenna 915. A label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. In addition, the secondary battery 913 is connected to a terminal 951 and a terminal 952 .

[0216] The circuit board 900 includes a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , a terminal 952, an antenna 914, an antenna 915, and a 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 annulus can be used as one of the two conductors of the capacitor. In this way, the electromagnetic field, the magnetic field, and the like can be detected by the antenna 914 or the antenna 915. Alternatively, 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 secondary battery 913, and between 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 FIG. 13(A-1) and FIG. 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 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 Figs. 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 a pair of surfaces of a secondary battery 913. As shown in FIG. 13(A-2), an antenna 914 is provided on one side of the secondary battery 913. An antenna 918 is provided on the other side of the layer 917. The layer 917 is, for example, a secondary battery 91 The layer 917 has a function of blocking 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. Examples of such technologies include NFC (near field communication), which can be used between secondary batteries and other devices. It is possible to apply a response method that allows

[0224] Alternatively, as shown in FIG. 13(B-1), the secondary battery 9 shown in FIG. 12(A) and FIG. 12(B) may be used. 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 portion where the display device 920 is provided. 12(A) and 12(B), the same parts as those of the secondary battery shown in FIG. The description 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, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display device, an electrophotographic display device, 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) may be used. A sensor 921 may be provided on the sensor 13. 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 FIG. 12(A) and FIG. 12(B) can be appropriately applied.

[0227] The sensor 921 may be, for example, a sensor for detecting displacement, position, speed, acceleration, angular velocity, number of rotations, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if the device has the function of measuring the amount, humidity, gradient, vibration, odor, or infrared rays. 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] Further, a structural example of the secondary battery 913 will be described with reference to FIGS.

[0229] A secondary battery 913 shown in FIG. 14A 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. In FIG. 14A, for convenience, the housing 930 is not in contact with the 9, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 95 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum). Materials such as rubber or resin materials can be used.

[0230] As shown in FIG. 14B, the housing 930 shown in FIG. 14A is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. The wound body 930b is attached to the housing 930a. 50 are provided.

[0231] The housing 930a can be made of an insulating material such as an 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 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] The structure of the wound body 950 is shown in FIG. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked on top of each other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 are laminated together. 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, the battery can be cycled with a high capacity. 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, the flexible portion is at least If the secondary battery is mounted on an electronic device that also has a battery, the secondary battery 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 interposed therebetween. The laminated sheet is then wound.

[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 collector (not shown) via one of the lead electrodes 998. The other of the electrode 997 and the lead electrode 998 is connected to a positive electrode current collector (not shown).

[0238] As shown in FIG. 16B, 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 to form a space in which the above-mentioned wound body 993 is housed. In this way, a secondary battery 980 can be manufactured as shown in FIG. 3 has a lead electrode 997 and a lead electrode 998, a film 981, and a recess 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 resin material. If a resin material is used as the material, when an external force is applied, the film 981 and the recessed portion The film 982 having the electrode can be deformed to produce a secondary battery having flexibility. can be done.

[0240] In addition, although Fig. 16(B) and Fig. 16(C) show an example in which two films are used, A space is formed by folding one sheet of film, and the above-mentioned wound body 99 is inserted into the space. It may also accommodate 3.

[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 serving as an exterior body is shown. We have explained the example of 80, but as shown in Figure 17, the shape is determined by the film that is the exterior body. The space defined by the positive electrode layer can be used as a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes. 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 The positive electrode current collector 504 also serves as a terminal for obtaining electrical contact with the outside. A part of the current collector 501 and the negative electrode current collector 504 is exposed to the outside from the exterior body 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged in a manner similar to that described above. Instead of exposing it to the outside, a lead electrode is used to connect the lead electrode 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 a A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied. 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 having 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 FIG. 1, it is composed of multiple electrode layers.

[0247] In FIG. 17B, as an example, the number of electrode layers is 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 a structure of 8 layers, totaling 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 addition, when the number of electrode layers is small, the secondary battery can have a larger capacity. In this case, a secondary battery can be made thin and has excellent flexibility.

[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 connected to each other.

[0249] FIG. 20A shows an external view of a positive electrode 503 and a negative electrode 506. The positive electrode 503 is connected to a 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 a 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 the negative electrode are not limited to the example shown in FIG. I can't.

[0250] [Method of manufacturing laminated secondary battery] Here, an example of a method for producing a 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 laminated. The negative electrode 506, the separator 507, and the positive electrode 503 are shown. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tabs of the positive electrode on the outermost surface are shown. The positive electrode lead electrode 510 is bonded to the region. For example, ultrasonic welding or the like may be used for bonding. Similarly, the bonding between the tab regions of the negative electrodes 506 and the bonding of the negative electrode leads to the tab region of the outermost negative electrode are preferably performed. Then, the metal layer 511 is 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 dashed line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. 509, so that the electrolyte 508 can be poured in later. An area that is not joined (hereinafter referred to as an inlet) is provided.

[0254] Next, electrolyte 508 (not shown) is introduced into exterior body 509 through an inlet. The electrolyte 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert gas atmosphere. It is preferable to carry out the above steps under the condition that the lamination is not completely adhered to the substrate. Finally, the inlet is joined. It is possible to manufacture a secondary battery 500 which is a plastic type secondary battery.

[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 and cycle. 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. 21(A) and (B2) are cut along the lines C1-C2 and C3- 3C4 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 wire 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. 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 lead wire in addition to the positive electrode 211a and the negative electrode 211b. 2 is a perspective view showing the lead 212a and the lead 212b.

[0259] As shown in FIG. 22(A), the secondary battery 250 has 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 portion of the surface other than the tab, and a negative electrode 211b is formed on the portion of the surface other than 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 laminated 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. 22B, the positive electrodes 211a and the leads 212a are connected to each other through a joint 215. The negative electrodes 211b and the leads 212b are electrically connected to each other at the joints 211a. 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 arranged 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 seal portions 2 The pair of sealing parts 262 are connected to the positive electrode 211a and the negative electrode 211b. The seal portion 26 is provided on either side of the electrode 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 corrugated 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 portion overlapping with the ridge line 271, and FIG. 21(B2) is a cross section cut at the portion overlapping with the ridge line 271. The cross section is taken at the part overlapping with the valley line 272. 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 distance between the end of the negative electrode 211b and the seal portion 262 is defined as La. When the electrode 211 is bent or otherwise deformed, the positive electrode 211a and the negative electrode 211b are elongated as described below. In this case, 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 laminated positive electrodes 211a and negative electrodes 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 laminated positive electrode 211a and negative electrode 211b and a separator (not shown) are When the total thickness of the data input 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, the device can be compact and resistant to bending. 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 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 the negative electrode 211a and the negative electrode 211b It is preferable that the ratio is 2.0 to 4.0 times. .

[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 is.

[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 greater than or equal to 1.0 and less than or equal to 2.0.

[0275] FIG. 21C is a cross section including the lead 212a, and shows the secondary battery 250, the positive electrode 211a, 21(C), the bending portion 211a corresponds to a 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 exterior body 251 It is preferable to have a space 273 therebetween.

[0276] FIG. 21(D) shows a schematic cross-sectional view of the secondary battery 250 when bent. corresponds to the cross section taken along 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 located on the outside of the exterior body 251 is deformed so as to shrink. The portion 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 the exterior body 251 is bent. Since the stress is relieved, the material that constitutes the exterior body 251 does not need to expand or contract. As a result, the exterior body 251 is not damaged, and the secondary battery 250 can be bent with a small force. 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 multiple stacked positive electrodes 211a and 211b are shifted relative to each other. The negative electrode 211b is fixed at one end on the seal portion 263 side by the fixing member 217. The amount of deviation increases toward the bent portion 261. The stress applied to the positive electrode 211a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211b As a result, the positive electrode 211a and the negative electrode 211b do not need to be damaged. 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 one another.

[0280] The secondary battery 250 illustrated in FIG. 21 and FIG. 22 has a casing that can withstand repeated bending and straightening. The body, the positive electrode 211a and the negative electrode 211b, etc. are unlikely to be damaged, and the battery characteristics are unlikely to deteriorate. The secondary battery 250 has a positive electrode 211a having the same structure as described in the previous embodiment. By using a positive electrode active material, a battery having even better cycle characteristics can be obtained.

[0281] (Embodiment 4) 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 described 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 walls of houses or buildings, or on the inside or outside of automobiles. It is also possible to incorporate it along the curved surfaces of the interior or exterior of the vehicle.

[0284] FIG. 23A shows an example of a mobile phone. A mobile phone 7400 includes a housing 7401. In addition to the display unit 7402, operation buttons 7403, an external connection port 7404, 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 mobile phone with a long life.

[0285] FIG. 23B shows the mobile phone 7400 in a curved state. When the battery is deformed by applying an external force to the battery, the secondary battery installed inside the battery is released. The secondary battery 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 in a bent state. The secondary battery 7407 is fixed in place by a lead electrode 7407 electrically connected to the current collector. For example, the current collector is a copper foil, which is partially alloyed with gallium to form a current collector. Improved adhesion between the active material layer and the body, and increased reliability when the secondary battery 7407 is bent This is a highly structured product.

[0286] FIG. 23D shows an example of a bangle-type display device. The portable display device 7100 is The device includes a housing 7101 , a display unit 7102 , operation buttons 7103 , and a secondary battery 7104 . FIG. 23E shows the bent state of the secondary battery 7104. When the device is attached to the user's arm, the housing may deform and cause damage to part of the secondary battery 7104 or The total curvature changes. Note that 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 inverse of the radius of curvature is called the curvature. Within the range of 40 mm to 150 mm, a part of the main surface of the case 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. 23F 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 telephone calls, e-mails, viewing and creating documents, playing music, and using the Internet. - It can run various applications such as internet communication and computer games. do.

[0289] The display unit 7202 has a curved display surface, and displays images along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be used to input a touch signal to the screen using 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 short-distance wireless communication according to a communication standard. For example, by communicating with a wireless headset, You can also make calls.

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

[0293] A display portion 7202 of a portable information terminal 7200 includes a secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, a lightweight portable information terminal with a long life can be provided. For example, the secondary battery 7104 shown in FIG. 23E is curved inside the housing 7201. or may be incorporated in a bendable state inside the band 7203.

[0294] The portable information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Sensors for human body such as pulse sensors, body temperature sensors, touch sensors, pressure sensors, acceleration sensors It is preferable that the above-mentioned components are mounted on the vehicle.

[0295] FIG. 23G shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 The display device 7300 includes a display 304 and a secondary battery of one embodiment of the present invention. The display unit 7304 may be equipped 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 the display can be performed along the curved display surface. In addition, the display device 7300 can display a display state by short-distance wireless communication according to a communication standard. The situation can be changed.

[0297] The display device 7300 also has an input / output terminal, and can directly connect 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 going through 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, It is possible to provide a display device with a long life and low cost.

[0299] FIG. 1 shows an example in which the secondary battery having excellent cycle characteristics shown in the above embodiment is mounted on an electronic device. 23(H), FIG. 24 and FIG. 25.

[0300] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, the device can be lightweight and have a long life. For example, we can provide a wide range of products for daily electronic devices, such as electric toothbrushes, electric shavers, These include mobile beauty devices, and the secondary batteries for these products are designed to be easy for users to carry. Therefore, there is a demand for a stick-shaped secondary battery that is small, lightweight, and has 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 that includes a heating element and an atomizer A secondary battery 7504 that supplies power to the myza, and a cart including a liquid supply bottle and sensors, etc. The secondary battery 7504 is composed of a ridge 7502. 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 the 7500 electronic cigarette, which is small and lightweight and 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, housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, Part 9631, display mode changeover switch 9626, switch 9627, switch 962 5, a fastener 9629, and an operation switch 9628. The display unit 9631 is flexible. By using a panel with this feature, it is possible to create a tablet terminal with a larger display area. FIG. 24(A) shows a tablet terminal 9600 in an open state, and FIG. 24(B) shows a 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 display unit 9631 can be configured such that all or a part of the display unit 9631 is a touch panel. By touching images, text, input forms, etc., including icons displayed in the relevant area, data is 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 used by displaying it.

[0305] In addition, a keyboard is displayed on the display unit 9631 on the housing 9630b side, and The display unit 9631 may be used to display information such as text and images. 31 to display the touch panel keyboard display switch button, and By touching the display with a finger or a stylus, keyboard buttons are displayed on the display unit 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 It functions as a switch to turn the power of the tablet 9600 on and off. Also, for example, at least one of the switches 9625 to 9627 may be The ability to change the display orientation, such as horizontal or vertical, or to switch 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 determined by the external light during use detected by a light sensor built into the tablet terminal 9600. The tablet device can be configured to optimize the brightness according to the amount of light from the light sensor. In addition, it also incorporates other detection devices such as gyros, acceleration sensors, and other sensors that detect tilt. It may be stored.

[0307] FIG. 24B shows a tablet terminal 9600 folded in half. 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 according to one embodiment of the present invention. 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 as to overlap each other. By folding the tablet terminal 9600, the display portion 9631 can be protected, and therefore the durability of the tablet terminal 9600 can be improved. In addition, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can have high The tablet has a large capacity and good cycle characteristics, allowing it to 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) , the ability to display various information (still images, videos, text images, etc.), calendars, dates, or The function to display the time, etc. on the display, and to operate or edit the information displayed on the display by touch input touch input function, function to control processing by various software (programs), etc. may have the following structure:

[0310] The tablet terminal 9600 is equipped with a solar cell 9633 on its surface, which provides power to the touch screen. The solar cell 963 can supply the solar cell 963 with the panel, the display unit, or the image signal processing unit. 3 can be provided on one or both sides of the housing 9630, and can efficiently charge the power storage unit 9635. The power storage unit 9635 can be a lithium ion battery. The use of such a structure has the advantage of enabling miniaturization.

[0311] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. A block diagram is shown in FIG. 24(C) and will be described. FIG. 24(C) shows a solar cell 9633 and a power storage unit 963 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, which includes a storage battery 9635, a DC-DC converter 9636, and a The inverter 9637 and the switches SW1 to SW3 are connected to the charge / discharge control circuit 96 shown in FIG. This corresponds to 34.

[0312] First, an example of operation in which power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted to a voltage for charging the storage battery 9635 by the DCDC controller. The voltage is increased or decreased by a inverter 9636. When power from the 9633 is used, switch SW1 is turned on and the converter 9637 The voltage is increased or decreased to a voltage required for the display unit 9631. When not displaying the data, turn switch SW1 off and switch SW2 on to store the data. It is sufficient to configure the device to charge the battery 9635.

[0313] The solar cell 9633 is shown as an example of a power generating means, but is not limited thereto. Storage of electricity by other power generation means such as piezoelectric elements and thermoelectric conversion elements For example, the device may be configured to transmit and receive power wirelessly (contactlessly). It is also possible to combine it with a non-contact power transmission module that charges the battery by using a contactless power transmission method, or other charging methods. This is also fine.

[0314] FIG. 25 shows another example of electronic equipment. In FIG. 25, a display device 8000 according to one embodiment of the present invention is 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. 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 according to one embodiment of the present invention can be used. By using the secondary battery 8004 as an uninterruptible power supply, the display device 8000 can be used. do.

[0315] The display unit 8002 may be a liquid crystal display device, an emitting device having light emitting elements such as organic EL elements in each pixel, or the like. Device, electrophoretic display device, DMD (Digital Micromirror Devi ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a 3D Emission Display can be used.

[0316] In addition, display devices are used for TV broadcast reception, personal computers, advertising displays, etc. , all display devices for displaying information are included.

[0317] In FIG. 25, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a light source 8102, and a light source 8103 are used. 25, the secondary battery 8103 is disposed in the housing 81. 8102 is 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, when the power supply from the commercial power source is cut off due to a power outage, Even when the electricity cannot be received, the secondary battery 8103 according to one embodiment of the present invention is used as an uninterruptible power source. This enables the lighting device 8100 to be used.

[0318] In addition, FIG. 25 illustrates a lighting device 8100 that is installed on a ceiling 8104. However, in the secondary battery according to one embodiment of the present invention, other than the ceiling 8104, for example, the side wall 8105, the floor 8106, 106, the window 8107, etc., can be used as a fixed lighting device, or a tabletop lighting device. The present invention can also be used in lighting devices of this type.

[0319] In addition, 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, light emitting diodes and organic electroluminescence (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 as follows: 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. A secondary battery 8203 may be provided in both the power source 8202 and the power source 8204. The power supply can be provided from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, a secondary battery 82 is provided in both the indoor unit 8200 and the outdoor unit 8204. 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 according to 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, an all-in-one air conditioner that has both indoor and outdoor unit functions in a single housing. The secondary battery according to one embodiment of the present invention can also be used for 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 room door 8302, a freezer room 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 commercial power sources due to a power outage, etc. However, by using the secondary battery 8304 according to one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300 freezer refrigerator.

[0323] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens, electric rice cookers, etc. The equipment requires high power for a short period of time. Therefore, the equipment supplements the power that cannot be supplied by commercial power sources. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for It can prevent the commercial power breaker from tripping during use.

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

[0325] According to one embodiment of the present invention, the cycle characteristics of a secondary battery are improved, and the reliability is improved. Moreover, according to one aspect of the present invention, a high-capacity secondary battery can be obtained, and therefore 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 provide an electronic device with a longer life and a lighter weight. The 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), electric vehicle (EV), or powertrain. This will make it possible to realize next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0328] FIG. 26 illustrates 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 this way, a vehicle with a long driving range can be realized. The secondary battery is mounted on the floor of the vehicle interior 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 FIG. The battery pack may be installed on the floor of the vehicle. 6, as well as emitting light such as headlights 8401 and room lights (not shown). The device can be powered.

[0329] In addition, the secondary battery is used for the display of the speedometer, tachometer, etc. 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 power distribution systems.

[0330] The automobile 8500 shown in FIG. 26(B) is a secondary battery that is plugged in. The device can be charged by receiving power from an external charging facility using a contactless charging method or other methods. FIG. 26(B) shows a diagram of a charging device 8021 installed on the 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. For example, plug-in technology can be used to 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 to direct power via a conversion device such as an ACDC 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 receives power from a ground power transmitting device in a non-contact manner. In this non-contact power supply method, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be done not only when the vehicle is stopped but also while it is moving. Using this method, electric power may be transmitted between vehicles. A solar battery may be installed to charge the secondary battery when the vehicle is stopped or running. The power can be supplied using an electromagnetic induction method or a magnetic resonance method.

[0332] FIG 26(C) 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 in the under-seat storage 8604 even if it is small. The secondary battery 8602 can be removed and 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 besides the vehicle. 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 reduce secondary This can contribute to reducing carbon dioxide emissions. In addition, if the cycle characteristics are good, Since the batteries 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. EXAMPLES

[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 sample 01 of the positive electrode active material according to one embodiment of the present invention, magnesium and fluorine were used as starting materials. The lithium cobalt oxide particles were prepared by adding cations and then heating them.

[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. We prepared magnesium as a source of fluorine and lithium fluoride as a source of fluorine. The ratio of each element was Li 1.0 2 Co 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 grinding was carried out using a mill at 250 rpm for 2 hours.

[0340] Next, in step S13, the mixed material is placed in an aluminum oxide crucible (hereinafter, referred to as aluminum oxide). The crucible was heated in a muffle furnace with a dry air flow rate 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 for cooling from the holding temperature to room temperature was 10 hours or more and 15 hours or less.

[0341] Step S14 was not performed since no titanium or aluminum coating process was performed.

[0342] Next, in step S15, the magnesium and fluorine-containing zeolite synthesized in step S13 is Lithium cobalt oxide particles containing 100% uranium were placed in an alumina crucible and heated in a muffle furnace in the presence of oxygen. The flow rate of the atmosphere was 10 L / min, the holding temperature was 900°C (heating rate: 200°C / hour), and The time required to lower 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 diameter 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. is.

[0345] <Sample 02> Sample 02 is a positive electrode active material having 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 about 20 μm, and fluorine, magnesium, and calcium are present in the region that can be analyzed by XPS. The lithium cobalt oxide particles contain calcium, sodium, silicon, sulfur, and phosphorus. Since no titanium or aluminum coating process was performed, step S14 was not performed.

[0347] Next, in step S15, the lithium cobalt oxide particles were placed in an alumina crucible and heated. A muffle furnace was used, the flow rate of the dry air atmosphere was 5 L / min, and the holding temperature was 800°C (rise The temperature was 200°C / hour and the holding time was 2 hours. The temperature drop from the holding temperature to room temperature was 10 hours. The time was set to 15 hours or more. After that, the samples were 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 that.

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

[0349] Sample 03 also uses lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) 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 lithium cobalt oxide containing nesium and fluorine at 0.004ml / g. It came together.

[0351] The 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 caused hydrolysis and polycondensation by 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] The mixture after the above treatment was centrifuged to collect the precipitate. The centrifugation was performed at 3000 rpm. The mixture was washed with isopropanol.

[0353] The collected precipitate was dried in a ventilated drying 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. A muffle furnace was used, and the flow rate of the oxygen 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 to cool the sample to room temperature was 10 to 15 hours. The positive electrode active material produced under the above conditions was composed of titanium and magnesium in the surface layer. It has been found that the concentrations of nasium and fluorine are higher than in the interior. It has been found that the peak of magnesium concentration is in a deeper region than the peak of magnesium concentration.

[0355] <Sample 04> Sample 04 is a positive electrode active material having 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] Sample 04 also uses lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) 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 barium oxide particles were mixed. Aluminum isopropoxide was mixed with magnesium and fluoride. The lithium cobalt oxide containing the element was mixed at a concentration of 0.0279 g / g.

[0358] The mixture was then placed on a magnetic stirrer for 8 hours at 25°C and 90% RH, covered. This treatment resulted in the mixture being heated with water and aluminum isopropoxide in the atmosphere. Lithium cobalt oxide containing magnesium and fluorine is produced by hydrolysis and polycondensation. An aluminum-containing layer was formed on the surface of the particles.

[0359] The mixed liquid 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, the lithium cobalt oxide coated with the 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 time required for the temperature to drop 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 had a surface layer of aluminum. It has been found that the concentrations of nium, magnesium and fluorine are higher inside the 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. (manufactured by Nippon Chemical Industry Co., Ltd., product name: C-20F) without sol-gel treatment or heating. Used as is.

[0363] <Sample 06> Sample 06 is a comparative example of lithium cobalt oxide that does not contain magnesium or fluorine. The particles were coated with aluminum by a sol-gel process.

[0364] In sample 06, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd.) were used as the starting material. Product name: C-5H) was used. 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 barium oxide particles were mixed. Aluminum isopropoxide was mixed with magnesium and fluoride. The lithium cobalt oxide containing the element was mixed at a concentration of 0.0917 g / g.

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

[0367] Next, in step S15, the lithium cobalt oxide coated with the aluminum-containing material is The particles were heated, cooled, and collected. The heating temperature was set to 500°C, and the rest of 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] [Preparation of secondary battery] Using the positive electrode active materials of Sample 01 to Sample 06 prepared above, CR2032 type 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 poly Polyvinylidene fluoride (PVDF) was used in the following ratio by weight: LCO:AB:PVDF=95:3:2 The mixed slurry was applied to a current collector.

[0372] Lithium metal was used as the counter electrode.

[0373] The electrolyte contained 1 mol / L lithium hexafluorophosphate (LiPF 6 ) The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC=3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. The following was used.

[0374] The separator was made of polypropylene having 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 Sample 01 to Sample 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 and charged at a constant voltage until the battery reached a constant voltage of 0.01V. The positive electrode was removed by disassembly in the box, and the electrolyte was then removed by washing with DMC (dimethyl carbonate). The specimen was then analyzed by powder XRD using CuKα1 radiation. We used the Bruker AXS fully automated multipurpose X-ray diffraction instrument D8 ADVANCE. The XRD instrument was set for powder samples, but the height of the sample 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 and H1-3 crystal structure as in Figure 3 are also shown. The crystal structure pattern is also shown. When sample 01 was charged at 4.6 V, the pseudo-spin structure The crystal structure was a mixture of H1-3 and H1-2. It was estimated that the material had 66 wt% spinel-type crystal structure.

[0378] FIG. 28 shows a secondary battery using the positive electrode active material of Sample 02 at 4.1 V, 4.2 V, and 4.3 V. V, X of the positive pole after charging at 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, decreasing the crystallinity. was speculated.

[0379] FIG. 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. V, X of the positive pole after charging at 4.4V, 4.5V, 4.6V, 4.7V, and 4.8V The RD pattern is shown in Fig. 1. Sample 03 also has a pseudo-spinel crystal structure when charged at 4.6 V. It was also found that sample 03, charged at 4.6 V, had a clearer pattern. The sample showed less crystal 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 crystalline structure, and the peak width was broadened, resulting in a decrease in crystallinity.

[0380] FIG. 30 shows the results of a 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 at 4.6 V and 4 It was revealed that when charged to 4.7V, it has a pseudo-spinel 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 crystal structure was broadened and the crystallinity was reduced.

[0381] FIG. 31 shows a secondary battery using the positive electrode active material of Comparative Example Sample 05 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 of the comparative example was charged at 4.6V to 4.7V. When the crystal structure was examined, 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 characteristic.) It was revealed that the crystal structure changes to H1-3 type between 4.8V and 4.6V. Sample 05, when charged at 1000 Hz, has a crystal structure different from that of pseudospinel and H1-3. It was presumed that the width of the peak broadened and the crystallinity decreased.

[0382] FIG. 32 shows the charge current after charging a secondary battery using the positive electrode active material of Comparative Example Sample 06 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 tested at 4.6 V. 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 Discharged at a constant current (CC discharge) until the voltage reached 2.5V, then charged at CCCV 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 once and twice are shown. The crystallinity is reduced because not only the crystal structure but also the H1-3 crystal structure and other structures are present. However, the number of structures other than the pseudospinel crystal structure decreased during the second charge, and It was more crystalline than the eyes.

[0385] FIG. 34 shows the results of a secondary battery using the positive electrode active material of Sample 03, which was cycled once, twice, and then cycled at 4.6 V. The XRD patterns of the positive electrode after nine charging cycles are shown. Sample 03 also showed a pseudo- Not only spinel type crystal structure, but also H1-3 type crystal structure and other structures exist, and the crystallinity is reduced. However, after the second charge, structures other than the pseudo-spinel crystal structure were observed. The pseudospinel crystal structure was reduced, while the pseudospinel crystal structure maintained a 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 are shown in Fig. 1. For sample 05, the XRD patterns of the positive electrode after the first and second charging are shown in Fig. 1. Both the first and second charges had the H1-3 type crystal structure. The characteristics become clear when you pay attention to the peaks that exist up to 2θ.

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

[0388] FIG. 36 shows the results of 10 discharges for Sample 02, Sample 03, and Comparative Sample 05. The XRD patterns of the positive electrodes after the LiCoO 2 (O3), pseudo The patterns of the spinel crystal structure and the H1-3 crystal structure are also shown. Sample 0 2, Sample 03, and Sample 05 are all LiCoO 2 It has the structure (O3) However, in sample 05, LiCoO 2 (0 0 3) plane in (O3), (0 0 6) The width of the diffraction peaks from planes perpendicular to the c-axis, such as the c-axis 0 6) plane, was broadened, and the crystallinity was reduced. In contrast, Sample 02 and Sample 03 are CoO 2 No layer misalignment for high yield 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. In order to make it easier to compare with other crystal structures, the unit cell is set as the c-axis of the H1-3 crystal structure. The calculation was done using half the value of the rule.

[0390] Table 2 shows the lattice constants and crystal structure 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 more and 4.5V or less, the two-phase bonds belonging to the space group R-3m This is because the charge depth increases within or between the particles of each positive electrode active material. This is thought to be due to the difference in the amount of heat generated. In Table 2, these are indicated as R-3m(1) and R-3m(2). Ta.

[0393] When charged at 4.6 V, the pseudospinel crystal structure and the H1-3 crystal structure were mixed. It was estimated that the pseudo-spinel crystal structure was 77w by Rietveld analysis. 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] In addition, 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 charge depth 0 Refer to the horizontal axis at the top of the graph only. Also, in Figure 37, the crystal structure is R-3m(1)(2). It is estimated that the crystal structure is either a pseudospinel type, an H1-3 type, or an O1 type. The individual markers indicate what is being

[0397] As is clear from Table 2 and FIG. 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, Since it has a pseudo-spinel crystal structure of 77 wt% or more, changes in 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 the asterisks are marked 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 the amount of TTIP used in the sol-gel treatment increased to 0. The concentration was set to 0.1 ml / g, and the second heat treatment was carried out in a dry air atmosphere.

[0400] The coin cell is made of positive electrode active material (LCO), acetylene black (AB), and polyvinyl fluoride (PVF). 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 with CCCV (0.5C, 4.6V, final current 0.01 C) and CC (0.5C, 2.5V) discharge. The current value was 137 mA / g.

[0402] FIG. 38(A) shows the discharge capacities of Sample 01, Sample 03, and Sample 05. B) shows the discharge capacity retention rate. Sample 05, a comparative example, maintained its discharge capacity at 40 cycles. On the other hand, the initial capacity of the positive electrode active material according to one embodiment of the present invention was 40.9%. At the 100th cycle, sample 03 was 78.4% and sample 01 was 7 The charge retention rate was 67.5% at the 0th cycle, indicating good cycle characteristics.

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

[0404] As described above, in Sample 01 to Sample 04, which are the positive electrode active materials according to one embodiment of the present invention, It was found that the pseudo-spinel crystal structure was more than 60% when charged to .6 V. The difference in crystal structure and volume between the discharged state and the H1-3 crystal structure is smaller than that between the discharged state and the H1-3 crystal structure. Therefore, it is difficult to deteriorate even if it is repeatedly charged and discharged. 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 crystal structure of the H1-3 type was mainly observed, while the crystal structure of the H1-3 type was not observed or was very little observed. The H1-3 crystal structure has a large difference in crystal structure and volume from the O3 crystal structure. Therefore, Sample 05 and Sample 06 cannot withstand high voltage charging. The material actually reduces the discharge capacity significantly.

[0406] In addition, Sample 05, which is a comparative example, contains magnesium and fluorine like Sample 01. However, when charged at 4.6 V, 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 during charging and discharging is small. It was also shown that this is a sign of a mineral that cannot be determined solely by the elements contained. EXAMPLES

[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. We will then explain the results of the ESR analysis.

[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. The sample was designated as sample 1A, and then subjected to a second heat treatment to obtain 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 lithium fluoride were weighed and mixed. In this experiment, an aluminum oxide crucible was used, the flow rate of the dry air atmosphere was set to 10 L / min, and The temperature was 1000°C (heating rate: 200°C / hour) and the holding time was 10 hours. The temperature drop time in the first heat treatment was 10 hours or more and 15 hours or less. Magnesium and fluorine-containing lithium cobalt oxide particles were used as sample 11A.

[0410] Next, the magnesium and fluorine-containing lithium cobalt oxide particles 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 resulting particles were designated as Sample 11B.

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

[0412] The ratio of each element is Li 1 Co 1 O 2 Lithium carbonate and cobalt oxide were weighed out so that The rest was 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 enlarged to compare the sharp signals around 320mT. do.

[0414] As shown in FIG. 39, in Sample 12B and Sample 11A, the A broad signal was detected centered around mT, but in sample 11B, this signal was This signal corresponds to Co with 4 oxygen atoms (A site in Figure 5). Respond.

[0415] Therefore, sample 12B, which does not have magnesium and fluorine, and sample 12C, which does not have magnesium and fluorine, Sample 11A, which has fluorine and is not subjected to the second heat treatment, has a spinel-type crystal structure. Co 3 O 4 However, it has magnesium and fluorine and has been subjected to a second heat treatment. Sample 11B was found to be below the detection limit.

[0416] As shown in Figure 40, all samples had a sharp peak centered around 320 mT. This signal corresponds to Co with 6 oxygen atoms (B site in Figure 5).

[0417] Among these, in sample 11A in FIG. 40(B) and sample 11B in FIG. 40(C), 3 A shoulder peak was observed around 12 mT, but not observed 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. . EXAMPLES

[0418] In this embodiment, what kind of element should be dissolved to form a pseudo-spinel crystal structure during high-voltage charging? The calculations revealed how likely it is that

[0419] As explained in Figure 2, the H1-3 type crystal structure is a CoO 2 of Structure and LiCoO such as R-3m(O3) 2 The structure is a laminated structure of 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. Using the crystal structure models of m1 and R-3m, we reproduced the positive electrode active material in the high-voltage charging state, and The stabilization energies in the presence of Al or Ti were calculated.

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

[0422] Mg, Al or Ti is CoO 2 The crystal structure model of P-3m1 when it is in the interlayer is shown in Figure 41. The crystal structure model of R-3m is shown in Figure 41(A2). Mg, Al or Ti is The crystal structure model of P-3m1 when it is at the Co site is shown in Figure 41(B1), and the results of R-3m are shown. 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 MgCoO 2 When inserting between layers, the calculation is done using the following formula: Insertion / Replacement 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 according to the following formula.

[0427]

number

[0428] The results of similar calculations for other elements are shown in Figure 42. If not converted, and CoO 2 The results when Li is inserted between the layers are also shown.

[0429] Figure 42(A) shows the CoO 2 Stability when Al, Ti, Mg, or Li is inserted between layers This is a graph showing the chemical conversion energy ΔE. For all elements, ΔE is a negative value. This means that the structure in space group R-3m is more stable than P-3m1. The values ​​of all the elements were lower than those of Li. 2 Positive electrode between layers The active material is a simple LiCoO 2 It is easier to achieve the R-3m structure even in a high-voltage charging state than 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. ΔE is a graph showing the relationship between the P-3m1 structure and the ΔE of each element. 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 higher than those without substitution.

[0431] Therefore, the CoO 2 The Mg present between the layers is highly effective in maintaining the structure of R-3m, It was revealed that Mg present at the Co site had no such effect.

[0432] Next, when all the 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 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 Chief of Staff 2 It was shown that Ti tends to be easily dissolved in these metals, and that Ti is particularly easily dissolved in these metals.

[0434] On the other hand, when comparing Mg at the Li site and the 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. Since ΔE is positive for both substitutions, Mg is LiCoO 2 It tends to be somewhat difficult to dissolve in This tendency suggests that some Mg segregates in the surface layer and near the grain boundaries. This can explain the phenomenon.

[0435] From the above, CoO 2 When Mg is present between layers (Li sites), a large amount of Li is extracted, resulting in a high The R-3m structure is easily maintained even in a charged state, and the pseudo-spinel crystal structure is easily formed. Therefore, LiCoO 2 The second heat treatment is performed to add Mg that is easily inserted into the Li site. It is important to place the Li site (not the Co site) reliably during the fabrication process, including the 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 part 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 plate 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 Circuit 913 Secondary battery 914 Antenna 915 Antenna 916 layers 917 layers 918 Antenna 920 Display device 921 Sensor 922 Terminal 930 Case 930a Case 930b Case 931 negative electrode 932 Positive electrode 933 Separator 950 Wound body 951 Terminal 952 Terminal 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 Case 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Portable Information Terminal 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 Case 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Mike 7407 Secondary battery 7408 Lead electrode 7500 Electronic 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 Case 8102 Light source 8103 Secondary battery 8104 Ceiling 8105 Side wall 8106 Bed 8107 Window 8200 indoor unit 8201 Case 8202 Ventilator 8203 Secondary battery 8204 Outdoor unit 8300 Electric refrigerator-freezer 8301 Case 8302 Refrigerator door 8303 Freezer door 8304 Secondary battery 8400 Automobiles 8401 Headlight 8406 Electric Motor 8500 Automobiles 8600 Scooter 8601 Side mirror 8602 Secondary battery 8603 Turn signal light 8604 Under-seat storage 9600 Tablet PC 9625 Switch 9626 Switch 9627 Switch 9628 Operation Switch 9629 Fastener 9630 Case 9630a Case 9630b Case 9631 Display section 9633 Solar Cells 9634 Charge / discharge control circuit 9635 Electric storage unit 9636 DC-DC Converter 9637 Converter 9640 Moving parts

Claims

1. A lithium ion secondary battery having a positive electrode, The positive electrode has a positive electrode active material including lithium cobalt oxide, The positive electrode active material contains magnesium and fluorine, the positive electrode having diffraction peaks at least at 2θ=19.30±0.20° and 2θ=45.55±0.10° in an XRD pattern obtained by performing powder XRD analysis using CuKα1 radiation at a charge depth of 0.

88.

2. A lithium ion secondary battery having a positive electrode, The positive electrode has a positive electrode active material including lithium cobalt oxide, The positive electrode active material of the lithium ion secondary battery includes magnesium and fluorine. However, the positive electrode is A battery having the positive electrode, a counter electrode using lithium metal, an electrolyte solution, and a separator using polypropylene was prepared (here, the electrolyte in the electrolyte solution was 1 mol / L lithium hexafluorophosphate (LiPF 6 ), and the electrolyte solution was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a ratio of EC:DEC=3:7 (volume ratio) and 2 wt % vinylene carbonate (VC)). Thereafter, the prepared battery was charged at a constant current of 0.5 C in a 25° C. environment until the voltage reached 4.6 V (where 1 C is the current value per positive electrode active material, 137 mA / g). Thereafter, the battery that had been subjected to the constant current charging was subjected to constant voltage charging at a voltage of 4.6 V in an environment of 25° C. until the current value reached 0.01 C. Thereafter, in a glove box under an argon atmosphere, the positive electrode is removed from the battery that has been subjected to the constant voltage charging, and the removed positive electrode is sealed in an airtight container, Thereafter, the positive electrode sealed in the sealed container is subjected to powder XRD analysis using CuKα1 radiation, and the XRD pattern has diffraction peaks at least at 2θ=19.30±0.20° and 2θ=45.55±0.10°.

3. When the XRD pattern is analyzed by the Rietveld method, the proportion of a crystal structure having characteristic diffraction peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10° is 50 wt % or more. The lithium ion secondary battery according to claim 1 or 2.

4. When the XRD pattern is analyzed by the Rietveld method, the proportion of a crystal structure having characteristic diffraction peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10° is 60 wt % or more. The lithium ion secondary battery according to claim 1 or 2.

5. When the XRD pattern is analyzed by the Rietveld method, the proportion of a crystal structure having characteristic diffraction peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10° is 66 wt% or more. The lithium ion secondary battery according to claim 1 or 2.

6. The positive electrode active material is a substance having a peak showing a bond energy between magnesium and other elements at least at 1302 eV or more and less than 1304 eV when the positive electrode active material is subjected to XPS analysis. The lithium ion secondary battery according to any one of claims 1 to 5.

7. The positive electrode active material has magnesium inside the positive electrode active material. The lithium ion secondary battery according to any one of claims 1 to 6.

8. The positive electrode active material further contains aluminum, The positive electrode active material has a region in which aluminum is present at a cobalt site of the positive electrode active material. The lithium ion secondary battery according to any one of claims 1 to 7.

9. The positive electrode active material further contains titanium, The positive electrode active material has a region in which titanium is present at a cobalt site of the positive electrode active material. The lithium ion secondary battery according to any one of claims 1 to 8.

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