Lithium ion secondary battery

Abstract

To prevent discharge of cobalt (Co) and oxygen (O) from surfaces of positive electrode active material particles and to reduce cracks and defect of positive electrode active material particles in order to prevent segregation of cobalt to negative electrodes or separators.SOLUTION: Active material particles include lithium, metal elements M1, metal elements M2 of II-valent and / or IV-valent, and oxygen. A metal atom M1 is one or more of cobalt, manganese and nickel. The active material particles have one or more crystallites. The active material particles have a first area positioned inside and a second area positioned outside the first area. The second area uses for the secondary battery the active material particles including more metal elements M2 than the first area.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, or an electronic device. In particular, the present invention relates to a cathode active material that can be used in a secondary battery, a secondary battery, and a method for manufacturing the battery. and electronic devices having secondary batteries.

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

[0003] In 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] 2. Description of the Related Art Electronic devices that are carried by users or worn by users have been actively developed.

[0005] Electronic devices carried by users or worn by users are primary energy storage devices, which are examples of power storage devices. It operates on batteries or secondary batteries. Electronic devices carried by users are designed to be used for long periods of time. It is desirable to use a large-capacity secondary battery for this purpose. If a battery is built in, the problem is that a large-capacity secondary battery is large and heavy. Development is underway to develop small or thin, high-capacity secondary batteries that can be built into electronic devices.

[0006] In particular, lithium cobalt is used as the positive electrode active material for secondary batteries because it can produce a high voltage of 4V. Composite oxide (LiCoO2) is widely used. Plate-like particles are disclosed.

[0007] High-power, high-capacity lithium-ion secondary batteries are used in mobile phones, smartphones, and Portable information terminals such as notebook computers, portable music players, digital cameras, medical equipment , or hybrid electric vehicle (HEV), electric vehicle (EV), or plug-in hybrid Along with the development of the semiconductor industry, next-generation clean energy vehicles such as hybrid electric vehicles (PHEV) are also expected to become popular. Demand for it has expanded rapidly, and it is an essential source of rechargeable energy in today's information society. It has become indispensable.

[0008] In lithium-ion secondary batteries, deterioration occurs due to repeated charge and discharge cycles. This causes the battery discharge capacity to become smaller than the initial capacity. Depending on the ion secondary battery, the use of the device that contains the lithium ion secondary battery may be affected. There is also a safety issue, as there is a risk of fire during use or during rapid charging. If a number of problems occur, not only the secondary battery but also the This will lead to the recall of the device, resulting in huge recall costs and damage to the brand. The damage to chair manufacturers is great. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] WO2010 / 074303 Summary of the Invention [Problem to be solved by the invention]

[0010] Lithium ion secondary batteries and the positive electrode active materials used therein have various characteristics, such as cycle characteristics, capacity, Furthermore, there is still room for improvement in various aspects such as charge / discharge characteristics, reliability, safety, and cost. It is left behind.

[0011] In order to identify the cause of deterioration of lithium-ion secondary batteries, the positive electrode active material particles (lithium When observing the LiCoO2 composite oxide, multiple cracks were found in the particles. In addition, cracks that can be observed in the SEM photograph were observed within the particles. It is believed that there are many other defects as well.

[0012] The present inventors have investigated the surface of the particles, mainly through multiple cracks and defects in the particles, and have found that cobalt (Co), acid Cobalt (O) or cobalt oxide (Co+O) is released or dissolved into the electrolyte. It is speculated that this is one of the causes of deterioration of lithium-ion secondary batteries.

[0013] Furthermore, cobalt released or dissolved into the electrolyte segregates on the negative electrode, forming segregated material. It has also been observed that cobalt segregates inside the separator. It can be observed.

[0014] In light of these circumstances, in order to prevent the segregation of cobalt in the negative electrode and separator, Preventing the release of cobalt (Co) and oxygen (O) from the surface of the active material particles, positive electrode It is important to reduce the occurrence of cracks and defects in the active material particles.

[0015] One embodiment of the present invention is to use a lithium ion secondary battery to prevent deterioration in charge / discharge cycles. Another object of the present invention is to provide an active material that does not undergo oxidation. Another object of the present invention is to provide a secondary battery having excellent charge-discharge characteristics. Another object of the present invention is to provide a secondary battery having improved safety or One object is to provide a highly reliable secondary battery.

[0016] Another embodiment of the present invention provides a novel substance, an active material, a power storage device, or a manufacturing method thereof. One of our goals is to provide

[0017] The description of these problems does not preclude the existence of other problems. It is not necessary for the embodiments to solve all of these problems. It is possible to extract other problems from the description of the claim. [Means for solving the problem]

[0018] In order to achieve the above object, one aspect of the present invention is a battery having a current collector and an active material layer on the current collector. The active material layer has a plurality of active material particles in contact with the current collector, and the active material particles contain lithium, metal elements, M1, one or both of divalent and tetravalent metal elements M2, and oxygen, M1 is one or more of cobalt, manganese, and nickel, and the active material particles are one or more of The active material particles have a plurality of crystallites, and each active material particle has a first region located inside and a second region located outside the first region. and a second region located at the first region, the second region containing a larger amount of metal element M2 than the first region. The positive electrode is characterized in that

[0019] In the above structure, the metal element M2 is magnesium, calcium, silicon, and titanium. Alternatively, the metal element M2 is magnesium, calcium, and titanium. The active material particles are provided with divalent and tetravalent metal oxides, specifically magnesium oxide, in the vicinity of their surfaces. MgO X ), calcium oxide (CaO X ), silicon oxide (SiO X ) and other segregation This prevents the release of cobalt or oxygen from the particle surface. In a solid consisting of multiple elements (e.g., A, B, C), the ) is unevenly distributed. This prevents the elution of cobalt or oxygen into the electrolyte. In this way, it is possible to provide an active material that does not deteriorate during charge-discharge cycles.

[0020] In the above-mentioned configuration, the second region may further contain fluorine. The presence of fluorine in the porous particles improves corrosion resistance against hydrofluoric acid produced by decomposition of the electrolyte. This may occur.

[0021] In the above configuration, X-ray diffraction (XRD) analysis The crystallite size measured by this method is 0.5 μm or more, preferably 1 μm or more.

[0022] In the above configuration, the size of the active material particles to be measured is 1 μm or more and 50 μm or less. The particle size refers to D50 (also known as the median diameter).

[0023] Another aspect of the present invention is a secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode has a current collector and an active material layer on the current collector, and the active material layer is in contact with the current collector. The active material particles include a plurality of active material particles, each of which contains lithium, a metal element M1, a divalent element, and a tetravalent element. One or both metal elements M2 and oxygen are included, and the metal atom M1 is cobalt, manganese, and nickel, and the active material particles have one or more crystallites, The child has a first region located inside and a second region located outside the first region, The second region contains more metal element M2 than the first region, and the secondary battery is The capacity after repeated charge and discharge is 78% or more of the initial capacity.

[0024] Another aspect of the present invention is a secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode has a current collector and an active material layer on the current collector, and the active material layer is in contact with the current collector. The active material particles include a plurality of active material particles, each of which contains lithium, a metal element M1, a divalent element, and a tetravalent element. One or both metal elements M2 and oxygen are included, and the metal atom M1 is cobalt, manganese, and nickel, and the active material particles have one or more crystallites, The child has a first region located inside and a second region located outside the first region, The second region contains more metal element M2 than the first region, and the secondary battery can be The capacity after repeated charge / discharge within the range of 30 cycles or less is 98% or more of the initial capacity. be.

[0025] Another aspect of the present invention is a method for producing a divalent or tetravalent silicon dioxide using a sol-gel method. One or both of the metal elements M2 are coated on the first active material particles having defects, a first step of forming second active material particles, and a third step of forming third active material particles by heat-treating the second active material particles; a second step of obtaining active material particles; and a third step of applying a slurry containing the third active material particles onto a current collector. and a step of repairing defects contained in the first active material particles in the second step. The method for producing a positive electrode is characterized by the above.

[0026] In the above-mentioned manufacturing method, the size of the crystallites contained in the third active material particles is equal to or larger than that of the first active material particles. larger than the crystallites contained in the crystallites.

[0027] In the above-mentioned manufacturing method, the size of the crystallites contained in the third active material particles is equal to or larger than that of the first active material particles. This is more than twice the amount of crystallites contained in the crystallites.

[0028] In the above preparation method, the crystallite size is measured by XRD analysis.

[0029] In the above-mentioned manufacturing method, the second step is performed at a temperature of 600° C. or more and 1000° C. or less in an oxygen-containing atmosphere. Heating at temperatures between 600°C and 1000°C reduces cracks and defects in the particles. This makes the surface of the particles shiny and reduces the surface area. By achieving an electrically stable state, a secondary battery with high safety and reliability can be realized.

[0030] In the above-mentioned manufacturing method, the first active material particles contain lithium, a metal element M1, and oxygen. , the metal atom M1 is one or more of cobalt, manganese, and nickel.

[0031] In the present specification and the like, the layered rock salt type crystals of the composite oxide containing lithium and the metal element M1 The crystal structure has a rock-salt type ion arrangement in which cations and anions are arranged alternately, and the metal elements M1 and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It is possible for defects such as missing cations or anions to exist. Strictly speaking, the layered rock salt crystal structure is a distorted rock salt crystal lattice structure. This may be the case.

[0032] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. It is possible for there to be a deficiency of cations or anions. [Effects of the Invention]

[0033] The size of the cracks in the active material particles is reduced, and the number of cracks and defects is reduced, resulting in the cobalt and By creating a structure that prevents oxygen from eluting into the electrolyte, the stability of the crystalline structure within the active material particles is further improved. This can increase the charge / discharge cycle characteristics.

[0034] Furthermore, a secondary battery having high safety and reliability can be provided. A substance, a power storage device, or a manufacturing method thereof can be provided.

[0035] The description of these effects does not preclude the existence of other effects. The embodiment does not necessarily have to have all of these effects. , the specification, drawings, claims, etc., and It is possible to extract other effects from the claims and other descriptions. [Brief explanation of the drawings]

[0036] [Figure 1] 1A and 1B are a perspective view and a cross-sectional view of a particle illustrating one embodiment of the present invention. [Figure 2] FIG. 1 is a conceptual diagram showing changes in crystallites and cracks before and after treatment according to one embodiment of the present invention. [Figure 3] 1 is an SEM photograph showing one embodiment of the present invention. [Figure 4]1A and 1B are diagrams illustrating materials according to one embodiment of the present invention. [Figure 5] 1A to 1C are diagrams illustrating steps in one embodiment of the present invention. [Figure 6] FIG. 1 is a diagram illustrating a process flow showing one embodiment of the present invention. [Figure 7] FIG. 2 is a diagram illustrating a coin-type secondary battery. [Figure 8] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 9] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 10] FIG. 2 is a diagram illustrating a method of discharging a secondary battery. [Figure 11] FIG. 10 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive additive. [Figure 12] FIG. 2 is a diagram illustrating a cylindrical secondary battery. [Figure 13] FIG. 2 is a diagram illustrating a secondary battery. [Figure 14] FIG. 2 is a diagram illustrating a secondary battery. [Figure 15] FIG. 2 is a diagram illustrating a secondary battery. [Figure 16] FIG. 2 is a diagram illustrating a secondary battery. [Figure 17] 1A to 1C illustrate examples of electronic devices. [Figure 18] 1A to 1C illustrate examples of electronic devices. [Figure 19] 1A to 1C illustrate examples of electronic devices. [Figure 20] FIG. 1 is a diagram illustrating the crystal structure of lithium cobalt oxide. [Figure 21] 2 is a graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 22] 2 is a graph showing the rate characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 23] 2 is a graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and various modifications in form and details are possible by those skilled in the art. Furthermore, the present invention should not be construed as being limited to the description of the following embodiments. It is not something that can be done.

[0038] (Embodiment 1) FIG. 1(A1) shows an example of a perspective view of an active material particle 110 having a plurality of cracks 105. In FIG. FIG. 1(A2) shows a cross-sectional view taken along the dotted line 160 in FIG. 1(A1). The active material particles 110 are particles of a composite oxide containing lithium, a metal element M1, and oxygen. The metal element M1 is one or more of cobalt, manganese, and nickel. It is possible.

[0039] In particle 110, multiple crystallites can be seen in one particle, and as shown in Figure 1(A2), The cracks 105 are also present in the sample. The active material particles 110 shown in FIG. 1(A1) are untreated and are used as they are. When a secondary battery was fabricated using the electrode active material layer and the cycle characteristics were measured, deterioration progressed and the metal element The element M1, for example, cobalt, is deposited in the negative electrode and separator.

[0040] The surface of the active material particle 110 shown in FIG. 1(A1), particularly the cobalt or oxygen from the cracks, To prevent dissolution, the material is covered with a material containing the metal element M2 and heated at high temperatures in an oxygen-containing atmosphere. Heat treatment is carried out at a temperature between 600°C and 1000°C. As the metal element M2, one or both of divalent and tetravalent metals can be used. Specifically, one or more of magnesium, calcium, silicon, and titanium are applied. As a coating method, a sol-gel coating using an alkoxide of the metal element M2 can be used. The method can be applied.

[0041] When Ti was used as the metal element M2, a sol-gel method using Ti alkoxide was performed. After that, the material is heat-treated at a high temperature (600°C or higher and 1000°C or lower) in an atmosphere containing oxygen. By using a sol-gel method with Ti alkoxide and heat treatment, divalent and tetravalent Ti The metal element M2 moves to the surface, preventing the dissolution of cobalt or oxygen. Furthermore, by performing a heat treatment after the sol-gel method using Ti, the active material particles This makes the surface of the element smooth, reducing the surface area and making it more stable.

[0042] In the sol-gel method, an alkoxide of a metal element M2 or the like is introduced into the cracks of the active material particles 110. The cracks are repaired by heat treatment. If the heat treatment temperature is low, the cracks are repaired. If the heating temperature is too high, many oxygen vacancies are formed, and the function as a positive electrode active material is lost. In addition, if the heating temperature is too high, there is a concern that the lithium may evaporate.

[0043] Particles of a composite oxide containing lithium, a metal element M1, and oxygen, such as lithium cobalt The composite oxide (LiCoO2) has oxygen vacancies in the particles, which particularly promotes mass transfer. Therefore, the titanium oxide coated by the sol-gel method is likely to repair the cracks. Titanium oxide and titanium compounds obtained by reacting with LiCoO2 are conductive and Similarly, metal alkoxides and other metals that form non-stoichiometric oxides are also suitable. When coated with an aqueous solution of a metal salt of an organic acid, it has electrical conductivity and lithium ion conductivity. So it is preferable.

[0044] Even a small crack at the edge of a particle can cause a large crack due to stress concentration. Therefore, the sol-gel method and heat treatment, which also repairs small cracks, are important.

[0045] A perspective view of the treated active material particles 100 is shown in FIG. 1(B1). A cross-sectional view taken along dotted line 150 is shown in FIG. 1(B2).

[0046] As shown in Figure 1(B2), after the treatment, the cracks disappeared, the crystallites grew partially, and the active material The number of crystallites in the grains decreases.

[0047] Figure 2 shows an example of a model diagram of the change in crystallites within active material particles before and after treatment. Here are four examples.

[0048] There are several possible patterns of changes in crystallites due to treatment. An example of the change will be described.

[0049] First, in FIG. 2(A1), cracks 105 are generated between different crystallites in a particle 110. FIG. 2(A2) shows the particle 110 of FIG. 2(A1) after the above-mentioned treatment. By performing the treatment, the cracks 105 are repaired and the different crystallites are reunited into one. It is conceivable that crystallites may form.

[0050] Next, FIG. 2(B1) shows that a particle 110 has many small cracks 105 in one crystallite. FIG. 2(B2) shows an example in which the particle 110 in FIG. 2(B1) is subjected to the above-mentioned processing. The particle 100 after the treatment. By performing the treatment, many cracks 105 are repaired and the defects are eliminated. It is possible that crystallites may not be formed.

[0051] Next, FIG. 2(C1) shows an example where in particle 110, a crack 105 has occurred in one crystallite. FIG. 2(C2) shows particle 100 after performing the above-described treatment on particle 110 of FIG. 2(C1). By performing the treatment, a situation where the crack 105 is repaired and a defect-free crystallite is obtained can be considered.

[0052] Next, FIG. 2(D1) shows an example where in particle 110, the crystal axes of adjacent crystallites are different. FIG. 2(D2) shows particle 100 after performing the above-described treatment on particle 110 of FIG. 2(D1). By performing the treatment, a case where adjacent crystallites become one crystallite can be considered. However, it is preferable that for adjacent crystallites, the oxygen cubic close-packed structure is consistent.

[0053] Also, by the heat treatment, magnesium oxide (MgO X (0 < X)), calcium oxide (CaO X (0 < X)), silicon oxide (SiO X (0 < X)), etc. are segregated. With such a configuration, cracks are less likely to occur, and cobalt or oxygen in the active material particles does not flow out into the electrolyte.

[0054] SEM photographs of a plurality of active material particles after the treatment are shown in FIG. 3(B).

[0055] The treated active material particle 100 has a structure in which the number of cracks and defects is reduced and cobalt and oxygen do not elute into the electrolyte, and the stability of the crystal structure in the active material particles is improved, so the charge-discharge cycle characteristics are further improved. Also, the treated active material particle 100 is a new substance and can also be called a new positive electrode active material.

[0056] By using the treated active material particles 100 in the positive electrode active material layer, a safe and highly reliable secondary A battery may be provided.

[0057] (Embodiment 2) As a method for coating the cracked active material particles 110 shown in the first embodiment, a sol Liquid phase methods including gel method, solid phase method, sputtering method, evaporation method, CVD (chemical vapor deposition) Methods such as a laser deposition (LD) method and a pulsed laser deposition (PLD) method can be applied.

[0058] In this embodiment, a sol-gel method is applied, which is expected to provide a uniform coating and allows processing at atmospheric pressure. The manufacturing method will be explained with reference to FIGS.

[0059] <Sol-gel method> First, the alkoxide of the metal element M2 is dissolved in alcohol. The metal of the metal oxide is one or both of the divalent and tetravalent metals described above, specifically, magnesium. M2 can be selected from the group consisting of magnesium, calcium, silicon, and titanium. Alkali metal elements, alkaline earth metal elements, alkali metal elements and alkaline earth metal elements Various elements other than element I, such as typical metal elements and transition metal elements, may also be used.

[0060] Alkali metal elements include Li, Na, K, Rb, Cs, and Fr, and alkaline earth elements include Li, Na, K, Rb, Cs, and Fr. The metalloid elements include Be, Mg, Ca, Sr, Ba, and Ra, and the alkali metal elements include Typical metal elements other than the alkali earth metal elements I include Sc, Ti, V, Cr, M n, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Examples of transition metal elements include Hf, Ta, W, Re, Os, Ir, Pt, and Au. I, Zn, Ga, Ge, Cd, In, Sn, Sb, Hg, Ti, Pb, Bi, and Po are listed. can be done.

[0061] Figure 4(A-1) shows the general formula of the alkoxide of the metal element M2. M2 represents a tetravalent metal element, and R may be the same or different. independently, an alkyl group having 1 to 18 carbon atoms, or a substituted or unsubstituted alkyl group having 6 or more carbon atoms; The alkyl group having 1 to 18 carbon atoms includes a methyl group, an ethylene group, an aryl group, an aryl group having 1 to 13 carbon atoms, an aryl group having 1 to 18 ... ethyl group, propyl group, hexyl group, octyl group, decyl group, dodecyl group, octadecyl group and branched alkyl groups such as isopropyl, isobutyl, and t-butyl. Examples of the aryl group having 6 to 13 carbon atoms include a phenyl group, a naphthyl group, Specific examples include a biphenyl group and a fluorenyl group. Not limited to.

[0062] Figure 4(A-2) shows one of the titanium alkoxides in Figure 4(A-1) using titanium for M2. The general formula is shown below. Specific examples of titanium alkoxides include tetramethoxytitanium and tetraethoxytitanium. Titanium, tetra-n-propoxytitanium, and tetra-i-propoxytitanium (see Figure 4 (A- 3)) (Tetraisopropyl orthotitanate, Titanium isopropoxide, Titanium (sometimes written as m tetraisopropoxide, TTIP, etc.), tetra -n-butoxytitanium, tetra-i-butoxytitanium, tetra-sec-butoxytitanium , tetra-t-butoxytitanium, and the like.

[0063] As a solvent for dissolving the alkoxide of the metal element M2, alcohols are preferred, and primary alkoxides are preferred. Alcohols or secondary alcohols are particularly preferred because they have high solubility for the metal alkoxides. For example, methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, For example, ethanol can be used.

[0064] Next, a compound containing lithium and metal element M1 is added to an alcohol solution of alkoxide of metal element M2. The composite particles (active material particles 110 shown in the first embodiment) are added and stirred. By adding (HO), the hydrolysis reaction of water and titanium alkoxide occurs as shown in Figure 4(B). At the same time, an acid or a base may be added as a catalyst. A similar hydration reaction can be achieved by placing an alcohol solution of koxide in a water-containing atmosphere and stirring it. A solution reaction occurs.

[0065] Furthermore, the hydrolysis reaction shown in FIG. 4(B) is followed by a dehydration condensation reaction shown in FIG. 4(C). The hydrolysis shown in Figure 4(B) and the condensation reaction shown in Figure 4(C) occur repeatedly, resulting in the formation of the metal element M2 The sol of the oxide of the metal element M2 is produced by further proceeding the reaction. A gel is formed.

[0066] Here, the particle surface of the composite oxide containing lithium and the metal element M1 has hydroxyl groups (OH groups). It is known that lithium exists as shown in Figure 4(D-1) and Figure 4(D-2). The hydroxyl groups on the particle surface of the composite oxide containing the metal element M1 are The hydroxyl group of the metal (M2) generated by hydrolysis of the alkoxide of 2 and the By causing a dehydration condensation reaction shown in Fig. 1, a metal (M1) oxide-containing particle is formed on the surface of the particle. A sol or gel containing an oxide of genus (M2) is formed.

[0067] Thereafter, the particles 111 are recovered by filtration, and by removing the solvent, a material having the metal element M2 can be coated on the particles of the composite oxide having lithium and the metal element M1. .

[0068] Next, more specifically, a method of coating the particles 111 with titanium oxide using the sol-gel method and then obtaining the active substance particles 100 will be described using FIGS. 5 and 6.

[0069] <Mixing of the metal alkoxide solution and the particles 111 (S14 in FIG. 6)> First, TTIP 171 is dissolved in isopropanol 170, and the particles 111 are mixed therein (see FIG. 5(A)).

[0070] <Coating of the particles 111 with titanium oxide by the sol-gel method (S15 in FIG. 6)> The solution shown in FIG. 5(A) is stirred for 4 hours under the conditions of 25° C. and a humidity of 90% RH. By this treatment , using the hydrolysis and dehydration polycondensation reactions occurring between the water in the atmosphere, TTIP, and on the surface of the particles 111, the particles 111 are coated with a TiO x sol 172 (see FIG. 5(B)). The reaction is further allowed to proceed to form a TiO x gel on the particle surface.

[0071] <TiO x Recovery of the gel-coated particles 111 (S16 in FIG. 6)> In FIG. 6, the mixture after the treatment of S15 is filtered, and the residue is recovered.

[0072] <Drying of the TiOx gel (S17 in FIG. 6)> The residue recovered by the treatment of S16 in FIG. 6 is dried in vacuo at 70° C. for 1 hour to obtain a powder. Here On the particle 111, it is coated with a dry gel 173 containing titanium oxide (see Fig. 5(C)). )

[0073] <Drying of the TiOx gel (S18 in Fig. 6)> In Fig. 6, the powder obtained by the treatment of S17 is heated at 800 °C (heating rate: 200 °C / hour) for a holding time of 2 hours , under the condition that the flow rate of the atmosphere containing oxygen is 10 L / min, to obtain the active material particles 100 ( see Fig. 5(D)).

[0074] In this embodiment, an example of using titanium alkoxide as the alkoxide of the metal element M2 is shown, but it is not particularly limited, and other metal alkoxides may be used. Also, the heating conditions are not particularly limited, and the heating rate conditions and the number of heat treatment steps may be performed multiple times. Also, the slow cooling conditions after heating are not particularly limited, and the temperature reduction conditions may be adjusted as appropriate.

[0075] Note that this embodiment can be freely combined with other embodiments.

[0076] (Embodiment 3) In this embodiment, an example of the shape of a secondary battery having the active material particles 100 that function as the positive electrode active material described in the previous embodiment will be described. The materials used in the secondary battery described in this embodiment can refer to the description of the previous embodiment.

[0077] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. Fig. 7(A) is an external view of a coin-type (single-layer flat type) secondary battery, and Fig. 7(B) is a cross-sectional view thereof.

[0078] The coin-type secondary battery 300 includes a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can that also serves as a negative electrode terminal ​302 is insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode active material layer 309 .

[0079] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are each an active material. The barrier layer need only be formed on one side.

[0080] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , titanium, or alloys thereof or alloys of these with other metals (e.g. stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 304. 7 and electrically connect to each other.

[0081] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the resultant structure shown in FIG. As shown in FIG. 1, the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, and negative electrode 308 are connected to the positive electrode can 301. 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 connected with a gasket 303 interposed therebetween. Then, the laminate is pressed to form a coin-type secondary battery 300.

[0082] The positive electrode 304 is provided with the active material particles 100 that function as the positive electrode active material described in the previous embodiment. By using this, it is possible to obtain a coin-type secondary battery 300 with excellent cycle characteristics.

[0083] Here, the flow of current during charging of a secondary battery will be explained using FIG. 7(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode (positive electrode) and cathode (cathode) is switched, and the oxidation reaction and reduction reaction are switched, so the reaction potential The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. Whether charging, discharging, or applying a reverse pulse current, Even when an electric current flows through it, the positive electrode is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "positive electrode" or "+ electrode (plus electrode)". This is called the "negative electrode" or "-electrode (minus electrode)." When using the terms anode (positive electrode) and cathode (negative electrode), the following occurs during charging and discharging: This can be confusing as the anode and cathode are opposites. The term "cathode" will not be used in this specification. When using the terms cathode and positive electrode, specify whether they are charging or discharging. It will also be noted whether it corresponds to the negative pole (negative pole) or the positive pole (positive pole).

[0084] A charger is connected to the two terminals shown in FIG. 7(C) to charge the secondary battery 300. As the charging of the battery 300 progresses, the potential difference between the electrodes increases. The current flows from the external terminal of the secondary battery 300 to the positive electrode 304, and then flows into the positive electrode 30 4 to the negative electrode current collector 308, and then flows from the negative electrode to the external terminal of the secondary battery 300. The direction of the current is considered to be positive. In other words, the direction of the charging current is considered to be the direction of the current. do.

[0085] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0086] ≪CC charging≫ First, we will explain CC charging as one of the charging methods. CC charging is a method in which the battery is constantly charged for the entire charging period. This is a charging method in which a constant current flows through the secondary battery and charging stops when the voltage reaches a specified level. Assuming that the secondary battery is an equivalent circuit with internal resistance R and secondary battery capacity C as shown in Figure 8(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.

[0087] During CC charging, the switch is turned on and a constant voltage is applied, as shown in Figure 8(A). Current I flows through the secondary battery. During this time, current I is constant, so V R = R × I Ohm's Law According to the law, the voltage V across the internal resistance R R On the other hand, the voltage applied to the secondary battery capacity C is also constant. Pressure V C increases over time. Therefore, the secondary battery voltage V B As time passes, Both rise.

[0088] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, charging stops. When CC charging is stopped, the switch is turned off and the current I = 0, as shown in Figure 8(B). Therefore, the voltage V applied to the internal resistance R R Therefore, the internal resistance R The voltage drop of the secondary battery V B is decreasing.

[0089] The secondary battery voltage V during CC charging and after CC charging is stopped Band charging current An example is shown in Figure 8(C). The secondary battery voltage V B But C C It shows a slight decrease after charging is stopped.

[0090] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a charging method different from the above. First, charge the battery up to a specified voltage using CC charging, then use CV (constant voltage) charging to reduce the current that flows. This is a charging method in which charging is continued until the current becomes low, specifically until the end current value is reached.

[0091] During CC charging, as shown in Figure 9(A), the constant current power supply is switched on and the constant The voltage power supply is switched off and a constant current I flows through the secondary battery. During this time, the current I Since it is constant, V R According to Ohm's law, the voltage V applied to the internal resistance R is R Also On the other hand, the voltage V applied to the secondary battery capacity C is C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0092] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, the CC charge is switched to C During CV charging, the constant voltage power supply The switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B becomes constant On the other hand, the voltage V applied to the secondary battery capacity C C V increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R Rbecomes smaller over time. Voltage V across the internal resistance R R As becomes smaller, V R By Ohm's law, = R × I, The current I flowing through the battery also becomes smaller.

[0093] When the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all the switches are turned off as shown in Figure 9(C). The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R becomes 0V However, the voltage V applied to the internal resistance R due to CV charging R is small enough that Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends at all.

[0094] 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 9(D). Even if CCCV charging is stopped, the secondary battery voltage V B Gahoton It shows that the aircraft does not descend at all.

[0095] ≪CC discharge≫ Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is a method in which the A constant current flows from the secondary battery, and the secondary battery voltage V B becomes a certain voltage, for example 2.5V. This is a discharge method in which the discharge is stopped when

[0096] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Figure 10. According to the secondary battery voltage V B is shown to be descending.

[0097] Next, the discharge rate and charge rate will be explained. It is the relative ratio of the current during discharge and is expressed in units of C. For a battery with a rated capacity of X (Ah), In this case, the current equivalent to 1C is X(A). When discharging with a current of 2X(A), the current is 2C. If it is discharged at a current of X / 5(A), it is said to be discharged at 0.2C. The same applies to the charging rate; if you charge with a current of 2X (A), it will be charged at 2C. When charging with a current of X / 5(A), it was said to be charged at 0.2C. .

[0098] (Fourth embodiment) In this embodiment, the active material particles 10 functioning as the positive electrode active material described in the previous embodiment are Examples of materials that can be used for a secondary battery having 0 will be described. The following description will be given taking as an example a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are enclosed in an exterior body.

[0099] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0100] <Cathode active material layer> The positive electrode active material layer includes a positive electrode active material. The positive electrode active material layer also includes a conductive additive and a binder. may have

[0101] As the positive electrode active material, the active material particles 1 which function as the positive electrode active material described in the previous embodiment are used. 00 can be used. By using the particles 100, a secondary battery with high capacity and excellent cycle characteristics can be obtained. .

[0102] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, or the like can be used. A fibrous material may also be used as the conductive additive. The content of the electrical auxiliary agent is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. is more preferred.

[0103] The conductive additive can form an electrically conductive network in the active material layer. The conductive agent can maintain the electrical conduction path between the positive electrode active materials. By adding an electrical auxiliary agent, it is possible to realize an active material layer with high electrical conductivity. .

[0104] Examples of the conductive additive include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fiber. Examples of carbon fibers that can be used include mesophase pitch carbon fibers. Carbon fibers such as isotropic pitch-based carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tube can be produced by, for example, vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as graphene and fullerene can be used. Metal powders and fibers such as nickel, aluminum, silver, and gold, as well as conductive ceramic materials, etc. It can be used.

[0105] A graphene compound may also be used as the conductive additive.

[0106] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and high In addition, graphene may have excellent physical properties such as high mechanical strength. The graphene compound has a planar shape, which allows for surface contact with low contact resistance. In addition, even if they are thin, they can have very high conductivity, and even a small amount can be used to efficiently conduct electricity within the active material layer. Therefore, the 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 additive. This is preferable because it may be possible to reduce the electrical resistance. For example, graphene or multigraphene or reduced graphene O It is particularly preferred to use RGO oxide. This refers to a compound obtained by reducing graphene oxide (GO).

[0107] When using an active material with a small particle size, for example, an active material with a particle size of 1 μm or less, the specific surface area of ​​the active material is Therefore, a large amount of conductive additive is required. This tends to result in a relative decrease in the amount of active material carried. If the amount of the conductive additive decreases, the capacity of the secondary battery will decrease. When graphene compounds are used, they efficiently form conductive paths even in small amounts. This is particularly preferable because it is possible to avoid reducing the amount of the active material carried.

[0108] As an example, in the case where a graphene compound is used as a conductive additive in the active material layer 200, An example of the cross-sectional structure will be described.

[0109] 11(A) shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made up of active material particles 10 0, a graphene compound 201 as a conductive additive, and a binder (not shown). Here, for example, graphene or multi-graphene is used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet shape. The graphene compound 201 may be a multi-graphene or a graphene compound. The graphene compound 201 may be a sheet-like structure in which a plurality of multi-layers are stacked. Both the graphene and the multiple graphenes may be partially overlapped to form sheets. stomach.

[0110] In the vertical cross section of the active material layer 200, as shown in FIG. 11(A), the inside of the active material layer 200 In FIG. 11(A), the sheet-like graphene compound 201 is dispersed almost uniformly. In this figure, the graphene compound 201 is shown schematically by a thick line, but in reality, it is a single layer or The graphene compounds 201 are thin films having a thickness of multiple layers. 100, or adheres to the surface of a plurality of active material particles 100. Since they are formed as described above, they are in surface contact with each other.

[0111] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. It is possible to form a graphene sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is covered with a graphene net, the graphene net can connect the active material to each other. It can also function as a binder to bind the particles together. Therefore, the ratio of the active material to the electrode volume or weight can be reduced. In other words, the capacity of the secondary battery can be increased.

[0112] Here, graphene oxide is used as the graphene compound 201, and is mixed with an active material to form an active material. After forming the layer that will become the layer 200, it is preferable to reduce it. By using graphene oxide, which has extremely high dispersibility in polar solvents, The mixture 201 can be dispersed approximately uniformly inside the active material layer 200. The solvent is evaporated from the dispersion medium containing the dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps with each other. By dispersing the particles so that they are in surface contact with each other, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be performed by, for example, heat treatment or by using a reducing agent. It is also possible.

[0113] 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 active material particles 100 can be reduced to improve the electrical conductivity between the active material particles 100 and the graphene compound 201. Therefore, the ratio of the active material particles 100 in the active material layer 200 can be increased. This makes it possible to increase the discharge capacity of the power storage device.

[0114] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isoprene. Acrylonitrile-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene It is preferable to use a rubber material such as a propylene-diene copolymer. Fluorine rubber can be used.

[0115] As the binder, it is preferable to use, for example, a water-soluble polymer. As the molecule, for example, polysaccharides can be used. cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch These water-soluble polymers can be used in combination with the rubber materials described above. It is even better if there is one.

[0116] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. Polymethylmethacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), poly Ethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, Polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, poly Ethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylo Nitrile (PAN), Ethylene Propylene Diene Polymer, Polyvinyl Acetate, Nitrocel It is preferable to use a material such as loin.

[0117] The binder may be used in combination with two or more of the above.

[0118] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, rubber materials have excellent adhesive strength and elasticity, but it is difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, mixing with a material that has a particularly excellent viscosity adjusting effect can As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. Furthermore, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as carbohydrates. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose Carbohydrates and starches can be used.

[0119] The cellulose derivatives such as carboxymethyl cellulose are, for example, By converting cellulose into salts such as sodium salts or ammonium salts, the solubility increases, It is easier to exert its effect as a viscosity adjuster. The increased solubility makes it easier to make electrode slurry. When preparing a substrate, it is also possible to improve the dispersibility of the active material and other components. In this case, the cellulose and cellulose derivatives used as binders for electrodes include These salts are also included.

[0120] Water-soluble polymers stabilize viscosity by dissolving in water, and also act as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stably dispersed in aqueous solution. In addition, since it has functional groups, it can be easily and stably adsorbed onto the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose will For example, many materials have functional groups such as hydroxyl groups and carboxyl groups. It is expected that the polymers will interact with each other and widely cover the surface of the active material.

[0121] When the binder that covers or contacts the surface of the active material forms a film, it is called a passive film. It is expected that the passive film will also play a role in suppressing the decomposition of the electrolyte. It is a film with no or very low electrical conductivity, and for example, it is When a dynamic membrane is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film suppresses electrical conductivity while allowing lithium ions to conduct. And even more desirable.

[0122] <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. Highly conductive materials such as alloys of these can be used. It is preferable that silicon, titanium, neodymium, scavenger, etc. are not eluted at the potential of the positive electrode. Aluminum alloys containing elements such as indium and molybdenum that improve heat resistance are used. It can also be formed from a metal element that reacts with silicon to form silicide. Metal elements that react with silicon to form silicide include zirconium, titanium, and Tantalum, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten , cobalt, nickel, etc. Current collectors are available in foil, plate (sheet), mesh, and punched shapes. The current collector may be in the form of a metal, an expanded metal, or the like. It is recommended to use a thickness of 5 μm or more and 30 μm or less.

[0123] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains a conductive additive and and a binder.

[0124] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0125] As a negative electrode active material, it is possible to carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any suitable element can be used, such as silicon, tin, gallium, aluminum, Rumanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a large capacity compared to carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying and dealloying reactions with lithium. Elements capable of undergoing a reaction and compounds containing such elements are sometimes called alloy materials. do.

[0126] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to 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.

[0127] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. may be used. .

[0128] Examples of graphite include artificial graphite and natural graphite. Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the particle size, which is sometimes preferable. Examples include flake graphite and spherical natural graphite.

[0129] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), It exhibits a low potential similar to that of lithium metal (0.05V to 0.3V vs. Li / L i + 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 advantages such as higher safety compared to lithium metal.

[0130] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T i5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0131] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3) And preferable.

[0132] When a composite nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, A complex nitride of lithium and a transition metal can be used.

[0133] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. , cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the metal may be used as the negative electrode active material. Further materials that can be produced include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It also occurs with fluoride.

[0134] The conductive additive and binder that can be contained in the negative electrode active material layer are the same as those that can be contained in the positive electrode active material layer. The same materials as the conductive additive and binder can be used.

[0135] <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.

[0136] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. For example, ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyrolactone lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these Combinations and ratios may be used.

[0137] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more batteries, it is possible to prevent the internal temperature from rising due to an internal short circuit or overcharging of the storage battery. Even if the battery is damaged, it can prevent the battery from exploding or catching fire. Ionic liquids are made of cations and anions. The organic cations used in the electrolyte include quaternary cations. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations such as imidazolium cations and pyridinium cations Aromatic cations are also used as anions in electrolytes. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkylphosphate anions, etc.

[0138] The electrolyte to be dissolved in the solvent may be, for example, LiPF6, LiClO4, or LiA sF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO3 , LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2 , LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. One or more of these salts can be used in any combination and ratio. can.

[0139] The electrolyte used in the electricity storage device is free from granular waste and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). It is preferable to use a highly purified electrolyte solution with a low content of ammonium hydroxide. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably It is preferably 0.01% or less.

[0140] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene Carbonate (FEC), LiBOB, and Squishi Dinitrile compounds such as dibenzonitrile and adiponitrile may also be added. The concentration of may be, for example, 0.1 wt % to 5 wt % relative to the entire solvent.

[0141] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution. The use of electrolytes increases safety against leakage, etc. Also, the secondary battery can be made thinner and It is possible to reduce the weight.

[0142] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gel or the like can be used. Examples of polymers include polyethylene oxide (PEO ), polymers with polyalkylene oxide structure such as PVDF and polyacrylic For example, PVDF and copolymers containing them can be used. PVDF-HFP, a copolymer of hexafluoropropylene (HFP), can be used. The polymer formed may also have a porous shape.

[0143] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire pond can be solidified, there is no risk of leakage, dramatically improving safety.

[0144] [Separator] The secondary battery preferably has a separator. The separator may be made of, for example, paper. Cellulose-containing fibers, nonwoven fabrics, glass fibers, ceramics, or nanofibers, including Ilon (polyamide), Vinylon (polyvinyl alcohol fiber), polyester, acrylic Use synthetic fibers such as styrene, polyolefin, and polyurethane. The separator is made into an envelope and encases either the positive or negative electrode. It is preferable to arrange it as follows.

[0145] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a combination of these. The ceramic material can be, for example, aluminum oxide. Aluminum particles, silicon oxide particles, etc. can be used. For example, PVDF, polytetrafluoroethylene, etc. can be used. Polyamide-based materials Materials used include nylon, aramid (meta-aramid, para-aramid), etc. It is possible.

[0146] Coating with ceramic materials improves oxidation resistance, making it suitable for separators during high-voltage charging and discharging. This can suppress the deterioration of the battery and improve the reliability of the secondary battery. By coating, the separator and electrodes can be more easily attached to each other, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. Safety can be improved.

[0147] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. The surface that comes into contact with the negative electrode may be coated with a mixed material of rubber and aramid, and a fluorine-based material may be coated on the surface that comes into contact with the negative electrode. .

[0148] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the temperature can be maintained, the capacity per volume of the secondary battery can be increased.

[0149] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a highly flexible metal such as aluminum, stainless steel, copper, or nickel is A metal thin film is then formed on the metal thin film, and the outer surface of the exterior body is made of a polyamide resin or polyester. A three-layer film having an insulating synthetic resin film such as a vinyl resin can be used.

[0150] (Embodiment 5) [Cylindrical secondary battery] In this embodiment, an example of a cylindrical secondary battery will be described with reference to FIG. As shown in FIG. 12(A), the secondary battery 600 has a positive electrode cap (battery lid) 601 on the top surface. The positive electrode cap and the battery case (external case) 602 are attached to the side and bottom. The battery can (external can) 602 is insulated by a gasket (insulating packing) 610. .

[0151] Fig. 12(B) is a schematic diagram showing the cross section of a cylindrical secondary battery. Inside the can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed with a separator 605 sandwiched between them. The battery element is wound around a center pin (not shown). The battery can 602 is closed at one end and open at the other end. The material is nickel, aluminum, titanium, or other metals that are corrosion-resistant to the electrolyte, or Alloys of these and other metals (e.g., stainless steel) can be used. In addition, it is preferable to coat the electrode with nickel, aluminum, etc. to prevent corrosion by the electrolyte. A battery element in which a positive electrode, a negative electrode, and a separator are wound inside a battery can 602. The battery element is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 is filled with a non-aqueous electrolyte (not shown). A coin-type secondary battery can be used.

[0152] The positive and negative electrodes used in cylindrical storage batteries are wound, so active materials are 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 electrode A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode terminal 603. The positive terminal 60 and the positive terminal 607 can be made of a metal material such as aluminum. 3 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 Coupling) element. It is electrically connected to the positive electrode cap 601 via a stable (efficient) 611. When the internal pressure of the battery exceeds a predetermined threshold, the valve mechanism 612 closes the positive electrode cap 601 and The PTC element 611 cuts off the electrical connection with the positive electrode 604. It is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current and prevents abnormalities. It prevents heat buildup. The PTC element contains a barium titanate (BaTiO3) based semiconductor. Conductive ceramics or the like can be used.

[0153] 12(C), a plurality of secondary batteries 600 are mounted on conductive plates 613 and 614. The secondary batteries 600 may be sandwiched between the secondary batteries 600 to form a module 615. They may be connected in series, or may be connected in parallel and then connected in series. By configuring a module 615 having a plurality of secondary batteries 600, It can extract a large amount of power.

[0154] FIG. 12(D) is a top view of the module 615. For clarity of illustration, the conductive plate 613 is As shown in FIG. 12(D), the module 615 includes a plurality of secondary batteries 600. The device may have a conductive wire 616 for electrical connection. A conductive plate is provided on the conductive wire 616. Furthermore, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, the temperature control device 617 cools the secondary battery 600. If the temperature controller 617 is too cold, it can be heated. The performance of the module 615 is less affected by the outside temperature.

[0155] The positive electrode 604 is provided with the active material particles 100 that function as the positive electrode active material described in the previous embodiment. By using this, a cylindrical secondary battery 600 having a high capacity and excellent cycle characteristics can be obtained. do.

[0156] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0157] 13(A) and 13(B) are diagrams showing the external appearance of the battery pack. The circuit board 900 and the secondary battery 913 are provided. The secondary battery 913 has a terminal 951 and a terminal The battery pack has a terminal 952 and is covered with a label 910. The battery pack also has an antenna 914. You may do so.

[0158] The circuit board 900 is fixed with a seal 915. The circuit board 900 has a circuit 912. The terminal 911 is connected to the terminal 951 of the secondary battery 913 and the terminal 951 of the secondary battery 913 via the circuit board 900. The terminal 911 is electrically connected to the antenna via the circuit board 900. The terminals 911 are electrically connected to the power supply 914 and the circuit 912. Each of the terminals 911 may be used as a control signal input terminal, a power supply terminal, or the like.

[0159] The circuit 912 is, for example, a protection circuit for protecting the secondary battery 913 from overcharge, overdischarge, and overcurrent. The circuit 912 functions as a protection circuit. The antenna 914 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. In addition, flat antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, etc. The antenna 914 may be, for example, a dielectric antenna. The battery pack and the battery pack can communicate with each other via an antenna 914. As a communication method with other devices, NFC, etc., can be used between the battery pack and other devices. A response method that can do this can be applied.

[0160] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. has a function of preventing the influence of the secondary battery 913 on the electromagnetic field, for example. The layer 916 may be made of, for example, a magnetic material.

[0161] The structure of the battery pack is not limited to that shown in FIG.

[0162] For example, as shown in FIGS. 14(A-1) and 14(A-2), In the secondary battery 913 shown in (B), an antenna 918 may be provided on the other pair of opposing surfaces. FIG. 14(A-1) is an external view seen from one side of the pair of surfaces. A-2) is an external view seen from the other side of the pair of surfaces. The same parts as the battery pack shown in Fig. 13(B) are shown in Fig. 13(A) and Fig. 13(B). The description of the battery pack shown in the accompanying drawings can be used as appropriate.

[0163] As shown in FIG. 14(A-1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. As shown in FIG. 14(A-2), an antenna 914 is provided, and the pair of surfaces of the secondary battery 913 On the other hand, an antenna 918 is provided across a layer 917. The layer 917 is, for example, a secondary battery 91 The layer 917 has a function of preventing the influence of the electromagnetic field caused by the For example, a magnetic material can be used.

[0164] By adopting the above structure, two antennas are provided in the battery pack, and the antennas 914 and Both sizes of the antenna 918 can be increased.

[0165] The antenna 918 can be configured in a shape that is compatible with the antenna 914. Furthermore, the antenna 918 may be a flat conductor. This flat conductor is a conductor for electric field coupling. In other words, the capacitor has two conductors. The antenna 914 may function as a single conductor. This allows only the electromagnetic and magnetic fields to be transmitted. Instead, power can be exchanged using an electric field.

[0166] Alternatively, as shown in FIG. 14(B-1), the battery pack shown in FIG. 13(A) and FIG. 13(B) A display device 920 may be provided in the display device 920. The display device 920 is electrically connected to the terminal 911. 13(A) and 13(B) are the same as those in the battery pack shown in FIG. The explanation of the battery pack shown in FIG. 13(A) and FIG. 13(B) can be used as appropriate.

[0167] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electrophotographic display, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0168] Alternatively, as shown in FIG. 14(B-2), the secondary battery 9 shown in FIG. 13(A) and FIG. 13(B) 13 may be provided with a sensor 921. The sensor 921 is connected to a terminal 922 and a circuit board 900. 13(A) and 13(B) are electrically connected to the terminal 911. The same parts as those of the power storage device will be described with reference to the power storage device shown in FIGS. 13A and 13B. It can be used as appropriate.

[0169] The sensor 921 may be, for example, a sensor for detecting displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if it has the function of measuring volume, humidity, gradient, vibration, odor, or infrared. By providing the sensor 921, for example, data indicating the environment in which the power storage device is placed can be acquired. It is also possible to detect a signal (such as temperature) and store it in memory within the circuit 912.

[0170] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0171] The secondary battery 913 shown in FIG. 15(A) has a terminal 951 and a terminal 952 provided inside a housing 930. The winding body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. 15A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separated. Although the figure shows the winding body 950, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 955 are 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum Rubber or resin materials can be used.

[0172] As shown in FIG. 15(B), the housing 930 shown in FIG. 15(A) is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15B may be formed by a housing 930a and a housing 930b. The wound body 930 is located in the area surrounded by the housing 930a and the housing 930b. 50 are provided.

[0173] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the electric field by the housing 930a can be suppressed. An antenna such as antenna 914 may be provided inside the housing 930b. Metallic materials can be used.

[0174] Furthermore, the structure of the wound body 950 is shown in Fig. 16. The wound body 950 is made up of a negative electrode 931 and a positive electrode 932. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

[0175] The negative electrode 931 is connected to the terminal 911 shown in FIG. 13 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 91 shown in FIG. 13 via the other of the terminals 951 and 952. Connected to 1.

[0176] The positive electrode 932 is provided with the active material particles 100 that function as the positive electrode active material described in the previous embodiment. By using this, a secondary battery 913 with high capacity and excellent cycle characteristics can be obtained.

[0177] (Embodiment 6) 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.

[0178] First, as an example of an electronic device to which a secondary battery is applied, a television set (television or television) (also called revision receivers), monitors for computers, digital cameras, digital Video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices) ), portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Examples include:

[0179] Next, Fig. 17(A) and Fig. 17(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIG. 17(A) and FIG. 17(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, and a display Part 9631, display mode switch 9626, power switch 9627, power saving mode The display includes a mode changeover switch 9625, a fastener 9629, and an operation switch 9628. By using a flexible panel for the part 9631, a tablet with a wider display area can be manufactured. FIG. 17A shows a state in which the tablet terminal 9600 is opened. 17(B) shows the tablet terminal 9600 in a closed state.

[0180] 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.

[0181] A part of the display unit 9631 can be used as a touch panel area, and the user can operate the displayed operation keys. You can input data by touching the screen. You can also switch the keyboard display on the touch panel. By touching the area where the replacement button is displayed with your finger or a stylus, the display 9631 Keyboard buttons can be displayed.

[0182] A display mode changeover switch 9626 changes the display orientation between portrait and landscape. You can select between black and white and color display. The touch 9625 detects when in use by the light sensor built into the tablet terminal 9600. The display brightness can be optimized according to the amount of external light. In addition to optical sensors, other sensors such as gyros and acceleration sensors that detect tilt are also available. The device may be built-in.

[0183] FIG. 17(B) shows the tablet terminal in a closed state, and the tablet terminal includes a housing 9630 and a solar cell 96 33, a charge / discharge control circuit 9634 including a DC / DC converter 9636. As 9635, a secondary battery according to one embodiment of the present invention is used.

[0184] In addition, since the tablet terminal 9600 can be folded in half, when not in use, the housing 9630a and The housing 9630b can be folded so that the housing 9630a and the housing 9630b overlap each other. Since the display portion 9631 can be protected, the durability of the tablet terminal 9600 can be improved. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention has a high capacity and a good cycle life. The tablet terminal 9600 has excellent thermal properties, allowing it to be used for extended periods of time. We can provide it.

[0185] In addition, the tablet terminals shown in Fig. 17(A) and Fig. 17(B) can be used in various Functions that display information (still images, videos, text images, etc.), calendars, dates, or times The function to display information on the display unit, and the function to input or edit the information displayed on the display unit. It has input functions, functions to control processing using various software (programs), etc. It is possible.

[0186] The solar cell 9633 attached to the surface of the tablet terminal supplies power to the touch panel, The solar cell 9633 can be supplied to a display unit, a video signal processor, or the like. The structure can be provided on one or both sides of the power storage unit 9630, and can efficiently charge the power storage unit 9635. It can be concluded that

[0187] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 17(B) are shown in FIG. A block diagram is shown in FIG. 17C. 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, and the storage battery 9635, the DC-DC converter 9636, 17B. This corresponds to 34.

[0188] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted into a voltage for charging the storage battery 9635. The voltage is increased or decreased by a inverter 9636. When power is used from the 9633, switch SW1 is turned on and the converter 9637 The voltage is increased or decreased to the voltage required for the display unit 9631. When not displaying the display, turn SW1 off and SW2 on to charge the power storage unit 9635. The configuration may be such that electricity is supplied.

[0189] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Power storage using other power generation methods such as piezoelectric elements and thermoelectric conversion elements For example, the power may be transmitted and received wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. That's fine.

[0190] Another example of electronic equipment is shown in FIG. 18. In FIG. 18, a display device 8000 is a display device according to one embodiment of the present invention. 8 is an example of an electronic device using a secondary battery 8004 according to an embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, and a speaker unit. The secondary battery 8004 according to one embodiment of the present invention includes a housing 8003 and a secondary battery 8004. The display device 8000 is provided inside a body 8001. The display device 8000 receives power from a commercial power source. Alternatively, the power stored in the secondary battery 8004 can be used. Even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. do.

[0191] The display unit 8002 includes a liquid crystal display device, an emitting device having a light emitting element such as an organic EL element in each pixel, and Device, electrophoretic display device, DMD (Digital Micromirror Device) ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0192] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0193] In FIG. 18, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a housing 8102, a light source 8103, and a light source 8104. 18, the secondary battery 8103 is mounted in the housing 81. 8101 and a light source 8102 are installed inside a ceiling 8104. However, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can receive power from a commercial power source or can store power in a secondary battery 8103. Therefore, if the power supply from the commercial power source is interrupted due to a power outage, etc., Even when the power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0194] 18 shows an example of a lighting device 8100 that is installed on a ceiling 8104. However, the secondary battery according to one embodiment of the present invention is not limited to the ceiling 8104, but may be installed on other parts such as the side wall 8105 and the floor 8106. 106, it can be used for a fixed lighting device provided in a window 8107, etc., or it can be used for a tabletop lighting device. It can also be used in lighting devices of this type.

[0195] The light source 8102 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, fluorescent lamps and other discharge lamps, and light-emitting devices such as LEDs and organic EL elements The element is an example of the artificial light source.

[0196] In FIG. 18, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is 8 is an example of an electronic device using a secondary battery 8203 according to one embodiment of the present invention. The device 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. 8 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200. The battery 8203 may be provided in the outdoor unit 8204. Both the power supply 8201 and the power supply 8204 may be provided with a secondary battery 8203. The power supply can be supplied from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 may be equipped with secondary batteries 82 If 03 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. In addition, by using the secondary battery 8203 of one embodiment of the present invention as an uninterruptible power supply, The conditioner can be used.

[0197] In Figure 18, a separate type air conditioner consisting of an indoor unit and an outdoor unit is shown. As an example, it is an all-in-one air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used in the conditioner.

[0198] In FIG. 18, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator It has a storage compartment door 8302, a freezer compartment door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 is It can receive power from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300-capacity refrigerator.

[0199] In addition, during times when electronic devices are not in use, especially when the total amount of power that can be supplied by the commercial power supplier is low, During the time period when the ratio of the amount of electricity actually used (called the electricity usage rate) is low, By storing power in the battery, it is possible to prevent power usage rates from increasing outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low and the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores power. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. By using the secondary battery 8304 as an auxiliary power source during the daytime, the daytime power usage rate can be kept low.

[0200] In addition to the electronic devices described above, the secondary battery according to one embodiment of the present invention can be mounted in various electronic devices. According to one embodiment of the present invention, the cycle characteristics of the secondary battery can be improved. According to this aspect, a high-capacity secondary battery can be obtained, and therefore the secondary battery itself can be made small and lightweight. Therefore, the secondary battery according to one embodiment of the present invention can be By incorporating this technology into electronic devices, the electronic devices can be made lighter and have a longer lifespan. The embodiment can be implemented in appropriate combination with other embodiments.

[0201] (Embodiment 7) 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.

[0202] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), an electric vehicle (EV), or a powertrain. This will enable the realization of next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0203] 19A and 19B illustrate an example of a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. By using one aspect of the present invention, it is possible to extend the driving range. Furthermore, the automobile 8400 has a secondary battery. If many small cylindrical secondary batteries shown in Figure 12 are lined up on the floor of the car, In addition, a battery pack made up of a combination of multiple secondary batteries as shown in FIG. 20 may be attached to the floor of the vehicle. The secondary battery not only drives the electric motor 8406 but also powers the headlamp. It can supply power to light-emitting devices such as the light 8401 and room lights (not shown). .

[0204] In addition, the secondary battery is used to power the speedometer, tachometer, and other displays of the automobile 8400. The secondary battery can supply power to the navigation device of the automobile 8400. The present invention can provide power to semiconductor devices such as mobile terminals.

[0205] The automobile 8500 shown in FIG. 19(B) has a plug-in type secondary battery. It can be charged by receiving power from an external charging facility using a contactless power supply system or other methods. FIG. 19(B) shows a diagram of a charging device 8021 mounted on a ground and a charging station 8022 mounted on a vehicle 8500. The secondary battery 8024 is shown being charged via a cable 8022. For charging methods and connector specifications, please refer to the specified CHAdeMO (registered trademark) or Combo. The charging device 8021 is a charging station installed in a commercial facility. For example, plug-in technology can be used to The secondary battery 8024 installed in the automobile 8500 can be charged by the power supply. Charging is performed by converting AC power into AC power via a converter such as an AC-DC converter included in the charging device 8021. It can be converted into DC power. It also has an AC / DC converter 8025 for charging. In the case of the 8500 vehicle, charging can be performed by connecting an AC power source.

[0206] Although not shown, a power receiving device is mounted on the vehicle and power is supplied contactlessly from a power transmitting device on the ground. In this case, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be carried out not only when the vehicle is stopped but also while the vehicle is moving. This method may be used to transmit and receive power between vehicles. A solar cell may be provided to charge the secondary battery when the vehicle is stopped or running. The power can be supplied by an electromagnetic induction method or a magnetic resonance method.

[0207] 19C 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.

[0208] In addition, the scooter 8600 shown in FIG. 19(C) has a secondary battery 860 in the storage space under the seat 8604. 2 can be stored. The secondary battery 8602 can be stored even if the under-seat storage 8604 is small. The secondary battery 8602 can be stored in the under-seat storage 8604. When charging, the secondary battery 8602 is brought indoors, charged, and stored before driving. Just do that.

[0209] 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 also 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 This can contribute to reducing carbon dioxide emissions. Since the secondary battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0210] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0211] In this example, a secondary battery was fabricated using positive electrode active material particles having different coating layers, and the results were analyzed using SEM. The characteristics were analyzed using XRD and the results of comparing the properties are shown below.

[0212] <Preparation of positive electrode active material> In this example, cobalt was used as the metal element M1 and titanium was used as the metal element M2. Positive electrode active materials of Samples 11 to 14, Samples 21 to 24, and Sample 31 The preparation method for each sample was as follows:

[0213] <Sample 11> Sample 11 is a lithium cobalt oxide particle containing magnesium and fluorine, which is prepared by a sol-gel method. After forming a coating layer containing titanium by the method described above, the coating layer was heated.

[0214] In this example, a pre-synthesized magnesium- and fluorine-containing koba was used as a starting material. Specifically, the starting material was C-20F, a product of Nippon Chemical Industry Co., Ltd. It was used as a food.

[0215] 2-propanol was added so that the amount of TTIP per weight of the positive electrode active material was 0.004 ml / g. TTIP was added and dissolved. TTIP was manufactured by Kishida Chemical Co., Ltd. and had a purity of 99.0% or higher. The 2-propanol solution of TTIP was treated with a reagent containing magnesium and fluorine. Lithium cobalt oxide particles were added.

[0216] The mixture of magnesium and fluorine-containing lithium cobalt oxide particles was The mixture was stirred for 70 hours at 25°C and 90% RH using a thermostatic stirrer. This causes hydrolysis and polycondensation reactions between the water in the atmosphere and TTIP, resulting in the formation of magnesium A titanium-containing layer was formed on the surface of lithium cobalt oxide particles containing fluorine.

[0217] The mixed solution after the above treatment was filtered and the residue was collected. (No.4) was used.

[0218] The collected residue was dried at 70°C for 3 hours.

[0219] The dried powder was heated to 800°C (heating rate: 200°C / hour) for 2 hours. The flow rate of the oxygen atmosphere was set to 10 L / min.

[0220] The heated powder was cooled. The cooling time was equal to or longer than the heating time. The sieve used had a mesh size of 53 μm.

[0221] The sieved particles were used as the positive electrode active material of Sample 11.

[0222] Sample 11 has lithium cobalt oxide inside and titanium and magnesium in the surface layer. It was speculated that the positive electrode active material had a coating layer containing ZnO.

[0223] <Sample 12> Sample 12 is a comparative example, which was prepared without heating after forming and drying a titanium-containing layer. It was prepared in the same manner as Sample 11, except that heating was not performed.

[0224] Sample 12 has lithium cobalt oxide containing magnesium and fluorine inside, and A positive electrode active material having a coating layer containing titanium in the layer portion, but no magnesium segregated on the surface It was speculated that this was the case.

[0225] <Sample 13> Sample 13 was prepared as a comparative example without forming a titanium-containing layer. The sample was prepared in the same manner as Sample 11, except that no film was formed.

[0226] Sample 13 has lithium cobalt oxide inside and a coating layer containing magnesium on the surface. It was speculated that the cathode active material contained titanium but not titanium.

[0227] <Sample 14> Sample 14 is a comparative example in which no titanium-containing layer was formed and no heating was performed. Nippon Chemical Industry's C-20F was used as it was.

[0228] Sample 14 is lithium cobalt oxide containing magnesium and fluorine, but the coating layer It is a positive electrode active material that does not have

[0229] <Sample 21> Sample 21 is a lithium cobalt oxide particle containing magnesium and fluorine, which is prepared by a sol-gel method. After forming a coating layer containing titanium by the method described above, the coating layer was heated.

[0230] The amount of TTIP per positive electrode active material was 0.01 ml / g, and the atmosphere during heating was dry air. The other parts were prepared in the same manner as in Sample 11.

[0231] Sample 21 has lithium cobalt oxide inside and titanium and magnesium in the surface layer. It was speculated that the positive electrode active material had a coating layer containing ZnO.

[0232] <Sample 22> Sample 22 was prepared as a comparative example without forming a titanium-containing layer. The sample was prepared in the same manner as Sample 21, except that no film was formed.

[0233] Sample 22 has lithium cobalt oxide inside and a coating layer containing magnesium on the surface. It was speculated that the cathode active material contained titanium but not titanium.

[0234] <Sample 23> Sample 23 is a comparative example, in which titanium is added to lithium cobalt oxide particles without magnesium. After forming a layer containing fluorine, heating was performed.

[0235] The lithium cobalt oxide particles used were manufactured by Nippon Chemical Industry Co., Ltd. (product name: C-10N). Lithium cobalt oxide in which magnesium is not detected in PS, but fluorine is detected at approximately 1 atomic % It is a particle.

[0236] It was prepared in the same manner as Sample 21, except that C-10N was used as the starting material.

[0237] Sample 23 has lithium cobalt oxide inside and a coating layer containing titanium on the surface. However, it was presumed that magnesium was not segregated on the surface of the positive electrode active material.

[0238] <Sample 24> Sample 24 is a comparative example in which titanium is added to lithium cobalt oxide particles without magnesium. No layer containing fluorine was formed, and no heating was performed. It was used as is.

[0239] Sample 24 is lithium cobalt oxide without a coating layer.

[0240] <Sample 31> Sample 31 is a lithium cobalt oxide particle containing magnesium and fluorine, which is prepared by a sol-gel method. After forming a coating layer containing titanium by the method described above, the coating layer was heated.

[0241] The same preparation as Sample 11 was used except that the amount of TTIP per positive electrode active material was 0.01 ml / g. did.

[0242] Sample 31 has lithium cobalt oxide inside and titanium and magnesium in the surface layer. It was speculated that the positive electrode active material had a coating layer containing ZnO.

[0243] Preparation of Samples 11 to 14, 21 to 24, and 31 The conditions are shown in Table 1. The analysis performed on each sample is also shown below.

[0244] [Table 1]

[0245] <sem> The results of SEM observation of Samples 11 and 14 were as shown in Figure 3. By forming a layer containing titanium and then heating it, cracks and a small surface area can be formed. It was revealed that a positive electrode active material 100 having a relatively smooth surface can be produced.

[0246] <xrd> For Samples 11 to 14, the size of the crystallites inside the particles of the positive electrode active material was measured by XR The results are shown in Table 2.

[0247] [Table 2]

[0248] As shown in Table 2, sample 11, which was coated with a titanium layer and heated, was superior to the other samples. The tendency for the crystallites to become larger was observed compared to the crystal surface. Therefore, differences were observed, which were particularly noticeable on the (003) plane.

[0249] The more cracks there are, the lower the crystallinity, so the crystallite size becomes smaller and there are fewer cracks. It is considered that the higher the crystallinity, the larger the crystallite size.

[0250] It is also assumed that defects such as cracks are likely to occur along the (003) plane. Figure 20 shows a model of the crystal structure of lithium cobalt oxide (LiCoO2). The direction perpendicular to the plane is the a-axis direction, the short side of the rectangle in the figure is the b-axis direction, and the long side of the rectangle is the c-axis direction. In the figure, the (003) plane is indicated by a dotted line. As shown in Figure 20, the (003) plane has a layer structure. In lithium cobalt oxide, the bond between lithium and oxygen is Therefore, defects such as cracks occur parallel to the (003) plane. It is assumed that it is prone to stiffness.

[0251] By coating with a layer containing titanium and heating it as in this example, the (003) plane and other factors can be eliminated. It was assumed that defects such as cracks had been repaired.

[0252] <Cycle characteristics at 25℃> Using the positive electrode active materials of Samples 21 to 24, CR2032 type (diameter 20 mm) A coin-type secondary battery (3.2 mm in height) was fabricated and its cycle characteristics were evaluated.

[0253] The positive electrode contains the positive electrode active material (LCO) of Samples 21 to 24 and acetylene black. (AB) and polyvinylidene fluoride (PVDF) in a ratio of LCO:AB:PVDF=95:2. A slurry of 5:2.5 (by weight) was applied to an aluminum foil current collector. The solvent used was N-methyl-2-pyrrolidone (NMP).

[0254] The counter electrode was made of lithium metal.

[0255] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio) mixed, and vinylene carbonate (VC) was added. The material used was one containing 100% by weight of cellulose acetate.

[0256] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0257] The measurement temperature for the cycle characteristic test was 25°C. Charging was performed using CCCV, and first, The current density was 68.5 mA / g, and the upper limit voltage was 4.6 V. Then, the current density was 1.4 The charge was constant until the current density reached 6 mA / g. The measurement was carried out at a constant current of 8.5 mA / g and a lower limit voltage of 2.5V.

[0258] The conditions for CCCV charging and CC charging in this example are the same as those for the CC charging described in the second embodiment. The voltage may differ from the example given in the explanation of CV charging and CC discharging. The charging and discharging methods are the same. Charging at a higher voltage allows for a higher capacity. It may be a secondary battery.

[0259] FIG. 21 shows the results of charging the secondary batteries using the positive electrode active materials of Samples 21 to 24 to 4.6 V. The graph shows the relationship between the discharge capacity retention rate and the number of charge / discharge cycles after the initial discharge. The capacitance was calculated as 100%.

[0260] As is clear from FIG. 21, the lithium cobalt oxide particles containing magnesium and fluorine Sample 22 is a sample having no coating layer, and Sample 24 is a sample having only a coating layer containing titanium. This is because the heating of the sample 23 resulted in a decrease in the amount of magnesium. This is thought to be due to the effect of ammonium segregating to the surface layer of the lithium cobalt oxide particles.

[0261] In addition, lithium cobalt oxide particles containing magnesium and fluorine are coated with a titanium-containing coating layer. The positive electrode active material, Sample 21, exhibited extremely good cycle characteristics. , sample 22 in which magnesium was segregated in the surface layer, and sample 23 in which only a coating layer containing titanium was formed. The properties were superior to those of Sample 23.

[0262] In the cycle characteristic measurement, the discharge capacity retention rate after 10 cycles was 99%. The discharge capacity retention rate after 30 cycles was 97%.

[0263] In this way, by providing a coating layer containing titanium and magnesium, It has a better cycle than having only a coating layer or only a coating layer with magnesium. It was found that the characteristics of the SiO2 film can be obtained.

[0264] <Initial characteristics, rate characteristics, and cycle characteristics at 45°C> A secondary battery was fabricated using the positive electrode active material of Sample 31, and the initial characteristics and cycle characteristics were evaluated. It was worth it.

[0265] The positive electrode contained the positive electrode active material (LCO) of sample 31, acetylene black (AB), and poly(ethylene oxide). Polyvinylidene fluoride (PVDF) (Solvay, product name: GE51305) was used as the LCO: A slurry of AB:PVDF = 95:3:2 (weight ratio) was applied to an aluminum foil current collector. The solvent used was N-methyl-2-pyrrolidone (NMP). The amount of support on the electrode current collector is approximately 8.5 mg / cm 2 The other samples were made in the same way as samples 21 to 24. Made.

[0266] First, the initial characteristics and rate characteristics of the secondary battery using the positive electrode active material of Sample 31 were measured. Measured.

[0267] The initial charge / discharge characteristics were measured using CC / CV charging at 0.2C, 4.55V, and a 0.05C cutoff. Discharge was performed at CC, 0.2C, 3.0V cutoff. 1C=160 The measurement temperature was 25°C.

[0268] The rate capacity was measured after the first charge and discharge. Under the same conditions as discharge, 0.2C charge / 0.2C discharge, 0.2C charge / 0.5C discharge, 0.2 The measurements were taken at 25°C charge / 1.0°C discharge, and 0.2°C charge / 2.0°C discharge. The temperature was set to °C.

[0269] The results of measuring the initial characteristics and rate capacity are shown in Table 3 and FIG.

[0270] [Table 3]

[0271] Figure 22(A) is a graph of the rate capacity of Table 1. Figure 22(B) is a graph of the rate capacity of Table 3. This graph shows the rate capacity normalized by the capacity at 0.2C.

[0272] [Cycle characteristics] Cycle characteristics: CC / CV charging, 1.0C, 4.55V, 0.05C cutoff, Discharge was performed at CC, 1.0 C, and 3.0 V cutoff. The measurement temperature was 45°C. The cycle characteristics were plotted as a graph of the discharge capacity retention rate in FIG.

[0273] In the measurement of cycle characteristics, the discharge capacity retention rate after 10 cycles was 100%. The discharge capacity retention rate at the 30th cycle was 98%. The capacity retention rate was 79%.

[0274] The specific surface area of ​​the positive electrode active material of Sample 31 was measured and found to be 0.13 m 2 / g Ta.

[0275] In addition, the particle size distribution of the positive electrode active material of Sample 31 was measured, and the average particle size was 25.5 μm. 10%D was 13.5 μm, 50%D was 23.9 μm, and 90%D was 56.4 μm.

[0276] As described above, the positive electrode active material particles of Sample 31, which is one embodiment of the present invention, have extremely good initial It was found that the charge-discharge capacity, rate capacity and cycle characteristics were excellent.

[0277] From the above results, it can be seen that the positive electrode active material particles according to one embodiment of the present invention are extremely effective when used in a secondary battery. It was found that good cycle characteristics could be obtained. [Explanation of symbols]

[0278] 100 active material particles 105 Crack 110 Active material particles 111 particles 150 dotted line 170 Isopropanol 171 TTIP 172 TiOx sol 173 Dried Gel 200 Active material layer 201 Graphene Compounds 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< / xrd> < / sem>

Claims

1. a current collector and an active material layer on the current collector, the active material layer has a plurality of active material particles in contact with the current collector, the active material particles contain lithium, a metal element M1, one or both of a divalent and a tetravalent metal element M2, and oxygen; the metal atom M1 is one or more of cobalt, manganese, and nickel; the active material particles have one or more crystallites, the active material particles have a first region located inside and a second region located outside the first region, The second region contains a larger amount of the metal element M2 than the first region.

2. In claim 1, The metal element M2 is one or more of magnesium, calcium, silicon, and titanium.

3. In claim 1, The metal element M2 is magnesium, calcium, and titanium.

4. In any one of claims 1 to 3, The second region further comprises fluorine.

5. A secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, the positive electrode has a current collector and an active material layer on the current collector, the active material layer has a plurality of active material particles in contact with the current collector, the active material particles contain lithium, a metal element M1, one or both of a divalent and a tetravalent metal element M2, and oxygen; the metal atom M1 is one or more of cobalt, manganese, and nickel; the active material particles have one or more crystallites, the active material particles have a first region located inside and a second region located outside the first region, the second region contains a larger amount of the metal element M2 than the first region, The secondary battery has a capacity of 78% or more of its initial capacity after 100 cycles of repeated charging and discharging.

6. A secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, the positive electrode has a current collector and an active material layer on the current collector, the active material layer has a plurality of active material particles in contact with the current collector, the active material particles contain lithium, a metal element M1, one or both of a divalent and a tetravalent metal element M2, and oxygen; the metal atom M1 is one or more of cobalt, manganese, and nickel; the active material particles have one or more crystallites, the active material particles have a first region located inside and a second region located outside the first region, the second region contains a larger amount of the metal element M2 than the first region, The secondary battery has a capacity of 98% or more of its initial capacity after repeated charge and discharge in a range of 10 to 30 cycles.

7. a first step of coating a first active material particle having defects with one or both of a divalent and a tetravalent metal element M2 using a sol-gel method to form a second active material particle; a second step of heat-treating the second active material particles to obtain third active material particles; a third step of applying a slurry containing the third active material particles onto a current collector, The method for producing a positive electrode, wherein defects contained in the first active material particles are repaired in the second step.

8. In claim 7, The method for producing a positive electrode, wherein the size of the crystallites contained in the third active material particles is larger than the size of the crystallites contained in the first active material particles.

9. 9. The method for producing a positive electrode according to claim 7, wherein the size of the crystallites contained in the third active material particles is at least twice as large as the size of the crystallites contained in the first active material particles.

10. In any one of claims 7 to 9, The method for preparing a positive electrode, wherein the crystallite size is measured by XRD analysis.

11. In any one of claims 7 to 10, The method for producing a positive electrode, wherein the second step is carried out at a temperature of 600° C. or higher and 1000° C. or lower in an atmosphere containing oxygen.

12. In any one of claims 7 to 11, The metal element M2 is one or more of magnesium, calcium, silicon, and titanium.

13. In any one of claims 7 to 12, the first active material particles contain lithium, a metal element M1, and oxygen; The metal atom M1 is one or more of cobalt, manganese, and nickel.

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