JP2021120957A - Lithium ion secondary battery - Google Patents

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

The homogeneity of the present invention relates to a product, a method, or a manufacturing method. Alternatively, the present invention is a process,
Regarding machines, manufactures, or compositions (composition of matter).
One aspect of the present invention relates to a method for manufacturing a semiconductor device, a display device, a light emitting device, a power storage device, a lighting device, or an electronic device. In particular, the present invention relates to a positive electrode active material that can be used for a secondary battery, a secondary battery, and an electronic device having the secondary battery.

In addition, in this specification, a power storage device refers to an element having a power storage function and a device in general. For example, it includes a storage battery (also referred to as a secondary battery) such as a lithium ion secondary battery, a lithium ion capacitor, an electric double layer capacitor, and the like.

In the present specification, the electronic device refers to all devices having a power storage device, and the electro-optical device having the power storage device, the information terminal device having the power storage device, and the like are all electronic devices.

Electronic devices carried by users and electronic devices worn by users are being actively developed.

The electronic device carried by the user and the electronic device worn by the user operate using a primary battery or a secondary battery, which is an example of a power storage device, as a power source. It is desirable that the electronic device carried by the user be used for a long time, and for that purpose, a large-capacity secondary battery may be used. If a large-capacity secondary battery is built in an electronic device, the large-capacity secondary battery is large and has a problem of increasing weight. Therefore, the development of small, thin, and large-capacity secondary batteries that can be built into portable electronic devices is underway.

In particular, since a high voltage of 4V class can be obtained, lithium cobalt composite oxide (LiCoO ₂ ) is widely used as a positive electrode active material for a secondary battery. Further, Patent Document 1 discloses plate-like particles of a positive electrode active material.

High-output, high-capacity lithium-ion secondary batteries are portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, hybrid electric vehicles (HEVs), and electric vehicles (HEVs). Demand for next-generation clean energy vehicles such as EV) or plug-in hybrid electric vehicles (PHEV) is expanding rapidly with the development of the semiconductor industry, and it is indispensable for the modern information society as a source of rechargeable energy. It has become something like that.

The lithium ion secondary battery has a drawback that it deteriorates by repeating the charge / discharge cycle and becomes smaller than the initial battery discharge capacity. Further, depending on the lithium ion secondary battery, there is a risk of ignition during use of the device containing the lithium ion secondary battery or due to quick charging, and safety is also a problem. When many problems leading to ignition occur, not only the secondary battery but also the device equipped with the secondary battery will be collected, resulting in enormous collection cost and brand deterioration. The damage done to the manufacturing company is great.

WO2010 / 074303

Lithium-ion secondary batteries and the positive electrode active materials used in them have cycle characteristics, capacities, and
Furthermore, there is still room for improvement in various aspects such as charge / discharge characteristics, reliability, safety, or cost.

_{When observing the particles (lithium cobalt composite oxide (LiCoO 2} )), which is the positive electrode active material, in order to identify the cause of deterioration of the lithium ion secondary battery, multiple cracks (including cracks, cracks, etc.) were confirmed in the particles. Was done. In addition, it is considered that the particles contain many defects in addition to the cracks that can be observed in the SEM photograph.

The present inventors may release or dissolve cobalt (Co), oxygen (O), or cobalt oxide (Co + O) into the electrolytic solution from the surface of the particles, mainly from multiple cracks or defects of the particles. , It is presumed to be one of the causes of deterioration of the lithium ion secondary battery.

Furthermore, it has also been observed that the cobalt released or dissolved in the electrolytic solution segregates on the negative electrode, and the segregated product grows. It has also been observed that cobalt segregates inside the separator.

Based on these circumstances, in order to prevent the segregation of cobalt from the negative electrode and the separator, it is necessary to prevent the release of cobalt (Co) and oxygen (O) from the surface of the positive electrode active material particles, and to prevent the positive electrode active material particles from being released. It is important to reduce the occurrence of cracks and defects.

One aspect of the present invention is to provide an active material that does not deteriorate in a charge / discharge cycle by being used in a lithium ion secondary battery. Alternatively, one aspect of the present invention is to provide a high-capacity secondary battery. Alternatively, one aspect of the present invention is to provide a secondary battery having excellent charge / discharge characteristics. Alternatively, one aspect of the present invention is to provide a secondary battery having high safety or reliability.

Alternatively, one aspect of the present invention is to provide a novel substance, an active material, a power storage device, or a method for producing the same.

The description of these issues does not prevent the existence of other issues. It should be noted that one aspect of the present invention does not need to solve all of these problems. It is possible to extract problems other than these from the description, drawings, and claims.

In order to achieve the above object, one aspect of the present invention has a current collector and an active material layer on the current collector, and the active material layer has a plurality of active material particles in contact with the current collector. , The active material particle contains lithium, metal element M1, one or both metal elements M2 of II and IV valences, and oxygen, and the metal atom M1 is one or more of cobalt, manganese, and nickel, and the active material. The particle has one or more crystallites, and the active particle has a first region located inside and a second region located outside the first region, and the second region. Is a positive electrode characterized in that it contains more metal element M2 than the first region.

In the above configuration, the metal element M2 is one or more of magnesium, calcium, silicon, and titanium. Alternatively, the metal element M2 is magnesium, calcium, and titanium. II-valent and IV-valent metal oxide in the vicinity of the surface of the active material particles, magnesium oxide in particular _(MgO X), calcium oxide _(CaO X), silicon oxide (SiO _X) is from the particle surface segregated Prevents the release of cobalt or oxygen. In the present specification and the like, segregation is an element (for example, B) in a solid composed of a plurality of elements (for example, A, B, C).
) Is unevenly distributed. By preventing the elution of cobalt or oxygen into the electrolytic solution, it is possible to provide an active material that does not deteriorate in the charge / discharge cycle.

In the above configuration, the second region may further contain fluorine. Further, the presence of fluorine in the positive electrode active material particles may improve the corrosion resistance to hydrofluoric acid generated by the decomposition of the electrolytic solution.

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

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 referred to as median diameter).

Further, the configuration of another invention is a secondary battery having a positive electrode, a negative electrode, an electrolytic solution, and a separator, and 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, and the active material particles contain lithium, one or both metal elements M2 of metal elements M1, II and IV valences, and oxygen, and are metal. The atom M1 is one or more of cobalt, manganese, and nickel, the active material particle has one or more crystallites, and the active material particle has a first region located inside and a first region. Has a second region located on the outside of
The second region contains more metal element M2 than the first region, and the capacity of the secondary battery after 100 cycles of repeated charging and discharging is 78% or more of the initial capacity.

Further, the configuration of another invention is a secondary battery having a positive electrode, a negative electrode, an electrolytic solution, and a separator, and 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, and the active material particles contain lithium, one or both metal elements M2 of metal elements M1, II and IV valences, and oxygen, and are metal. The atom M1 is one or more of cobalt, manganese, and nickel, the active material particle has one or more crystallites, and the active material particle has a first region located inside and a first region. Has a second region located on the outside of
The second region contains more metal element M2 than the first region, and the capacity of the secondary battery after repeated charging and discharging in the range of 10 cycles or more and 30 cycles or less is 98% or more of the initial capacity. be.

In addition, the constitution of another invention relating to the production method is that the metal element M2 of either one or both of the II valence and the IV valence is coated on the first active material particle having a defect by using the sol-gel method. The first step of forming the second active material particles, the second step of heat-treating the second active material particles to obtain the third active material particles, and the slurry containing the third active material particles. The third coating on the current collector
It is a method for producing a positive electrode, which comprises the above-mentioned steps and is characterized in that defects contained in the first active material particles are repaired in the second step.

In the above-mentioned production method, the size of the crystallites contained in the third active material particles is larger than that of the crystallites contained in the first active material particles.

In the above-mentioned production method, the size of the crystallites contained in the third active material particles is more than twice the size of the crystallites contained in the first active material particles.

In the above production method, the crystallite size is measured by XRD analysis.

In the above production method, the second step is performed at 600 ° C. or higher and 1000 ° C. or lower in an atmosphere containing oxygen. By heating at 600 ° C. or higher and 1000 ° C. or lower, cracks and defects of the particles can be reduced, the surface of the particles can be glossy, and the surface area can be reduced. By reducing the surface area and making it energetically stable, a secondary battery with high safety or reliability can be realized.

In the above production method, the first active material particle contains lithium, a metal element M1, and oxygen, and the metal atom M1 is one or more of cobalt, manganese, and nickel.

In the present specification and the like, the layered rock salt type crystal structure of the composite oxide containing lithium and the metal element M1 has a rock salt type ion arrangement in which cations and anions are alternately arranged, and the metal element M1 and the like. A crystal structure in which lithium can be diffused in two dimensions because lithium is regularly arranged to form a two-dimensional plane. There may be defects such as cation or anion deficiency.
Strictly speaking, the layered rock salt crystal structure may have a distorted lattice of rock salt crystals.

Further, in the present specification and the like, the rock salt type crystal structure means a structure in which cations and anions are alternately arranged. There may be a cation or anion deficiency.

By reducing the size of cracks in the active material particles and reducing the number of cracks and defects so that cobalt and oxygen do not elute into the electrolytic solution, the stability of the crystal structure in the active material particles can be further improved. It can be done, and the charge / discharge cycle characteristics are further improved.

Further, it is possible to provide a secondary battery having high safety or reliability. Further, it is possible to provide a novel substance, an active material, a power storage device, or a method for producing the same.

The description of these effects does not preclude the existence of other effects. It should be noted that one aspect of the present invention does not necessarily have to have all of these effects. It should be noted that the effects other than these are naturally clarified from the description of the description, drawings, claims, etc., and it is possible to extract the effects other than these from the description of the description, drawings, claims, etc. Is.

It is a perspective view and sectional view of the particle which shows one aspect of this invention. It is a conceptual diagram which shows the change of a crystallite and a crack before and after a process which shows one aspect of this invention. It is an SEM photograph which shows one aspect of this invention. It is a figure which shows the material which shows one aspect of this invention. It is a figure which shows the process which shows one aspect of this invention. It is a figure which shows the process flow which shows one aspect of this invention. The figure explaining the coin type secondary battery. The figure explaining the charging method of a secondary battery. The figure explaining the charging method of a secondary battery. The figure explaining the discharge method of a secondary battery. FIG. 6 is a cross-sectional view of an active material layer when a graphene compound is used as a conductive auxiliary agent. The figure explaining the cylindrical secondary battery. The figure explaining the secondary battery. The figure explaining the secondary battery. The figure explaining the secondary battery. The figure explaining the secondary battery. The figure explaining the example of the electronic device. The figure explaining the example of the electronic device. The figure explaining the example of the electronic device. The figure explaining the crystal structure of lithium cobalt oxide. The graph which shows the cycle characteristic of the secondary battery using the positive electrode active material of Example 1. FIG. The graph which shows the rate characteristic of the secondary battery using the positive electrode active material of Example 1. FIG. The graph which shows the cycle characteristic of the secondary battery using the positive electrode active material of Example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that the form and details thereof can be changed in various ways. Further, the present invention is not construed as being limited to the description contents of the embodiments shown below.

(Embodiment 1)
FIG. 1 (A1) shows an example of a perspective view of the active material particles 110 having a plurality of cracks 105.
Note that FIG. 1 (A2) shows a cross-sectional view when the cross section is cut 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. As the metal element M1, one or more of cobalt, manganese, and nickel can be applied.

In the particle 110, a plurality of crystallites can be confirmed in one particle, and as shown in FIG. 1 (A2), the particle 110 also has a crack 105 in the cross section. The SEM photograph corresponding to FIG. 1 (A1) is shown in FIG.
Shown in (A). The active material particles 110 shown in FIG. 1 (A1) are untreated, and when a secondary battery is manufactured by using it as it is for the positive electrode active material layer and the cycle characteristics are measured, deterioration progresses and the metal element M1, for example, cobalt, is used. Precipitates in the negative electrode and separator.

In order to prevent the elution of cobalt or oxygen from the surface of the active material particles 110 shown in FIG. 1 (A1), particularly cracks, the surface is coated with a material having a metal element M2, and in an atmosphere containing oxygen, a high temperature (600 ° C. or higher) is obtained. Heat treatment at 1000 ° C or lower). The heat treatment may be called annealing. As the metal element M2, one or both valences of II and IV are applied. Specifically, one or more of magnesium, calcium, silicon, and titanium can be applied. As a coating method, a sol-gel method using an alkoxide of the metal element M2 can be applied.

When Ti is applied as the metal element M2, a sol-gel method using Ti alkoxide is performed, and then heat treatment is performed at a high temperature (600 ° C. or higher and 1000 ° C. or lower) in an atmosphere containing oxygen.
By performing heat treatment together with the sol-gel method using Ti alkoxide, one or both of the II-valent and IV-valent metal elements M2 are moved to the vicinity of the surface to prevent elution of cobalt or oxygen. Further, by performing a heat treatment after the sol-gel method using Ti, the surface of the active material particles can be smoothed, the surface area can be reduced, and a stable state can be obtained.

In the sol-gel method, the alkoxide of the metal element M2 or the like invades the cracks of the active material particles 110, and the cracks are repaired by heat treatment. If the temperature of the heat treatment is low, cracks are difficult to repair, and if the heating temperature is too high, many oxygen deficiencies are formed, resulting in impairing the function as the positive electrode active material. In addition, if the heating temperature is too high, there is concern about evaporation of lithium.

Particles of composite oxides containing lithium, metal element M1 and oxygen, such as lithium cobalt composite oxide (LiCoO ₂ ), are particularly susceptible to mass transfer due to the lack of oxygen in the particles. Therefore, the titanium oxide coated by the sol-gel method can easily repair cracks. The titanium compound obtained by reacting with titanium oxide and LiCoO ₂ is suitable because it has conductivity and does not interfere with the diffusion of lithium. Similarly, coating with a metal alkoxide as an indefinite ratio oxide or an aqueous metal salt solution of an organic acid is preferable because it has electrical conductivity and lithium ion conductivity.

Even small cracks at the particle ends cause large cracks due to stress concentration, so the sol-gel method and heat treatment, in which small cracks are also repaired, are important.

A perspective view of the active material particles 100 after the treatment is shown in FIG. 1 (B1). Further, FIG. 1 (B2) shows a cross-sectional view of the treated active material particles when the cross section is cut along the dotted line 150.

As shown in FIG. 1 (B2), the crack disappears after the treatment, the crystallites partially grow, and the number of crystallites in the active material particles decreases.

FIG. 2 shows an example of a model diagram of changes in crystallites in the active material particles before and after the treatment. Figure 2
Shows four types of examples.

There are several possible patterns of changes in crystallites due to treatment. An example of the change in the crystallite will be described with reference to FIG.

First, FIG. 2 (A1) shows an example in which cracks 105 are generated between different crystallites in the particles 110. FIG. 2 (A2) shows the particles 100 after the above-mentioned treatment is applied to the particles 110 of FIG. 2 (A1). By performing the treatment, it is conceivable that the crack 105 is repaired and different crystallites become one crystallite.

Next, FIG. 2 (B1) shows a large number of small cracks 105 in one crystallite in the particle 110.
Is an example of this occurring. FIG. 2 (B2) shows the particles 100 after the above-mentioned treatment is applied to the particles 110 of FIG. 2 (B1). By performing the treatment, it is conceivable that a large number of cracks 105 may be repaired to form defect-free crystallites.

Next, FIG. 2 (C1) shows an example in which a crack 105 is generated in one crystallite in the particle 110. FIG. 2 (C2) shows the particle 1 after the above-mentioned treatment is applied to the particle 110 of FIG. 2 (C1).
It is 00. By performing the treatment, the crack 105 may be repaired to form a crystallite without defects.

Next, FIG. 2 (D1) shows an example in which the crystal axes of adjacent crystallites are different in the particles 110. FIG. 2 (D2) shows the particles 100 after the above-mentioned treatment is applied to the particles 110 of FIG. 2 (D1).
Is. By performing the treatment, it is conceivable that adjacent crystallites become one crystallite. However, it is preferable that the cubic closest packed structures of oxygen are the same for adjacent crystals.

Further, by heat treatment, magnesium oxide outside the second region _{(MgO X (0 <X)} ),
Calcium oxide (CaO _X (0 <X)), silicon oxide (SiO _X (0 <X)) and the like are segregated. With such a configuration, cracks are unlikely to occur, and cobalt or oxygen in the active material particles does not flow out to the electrolytic solution.

The SEM photographs of the plurality of active material particles after the treatment are shown in FIG. 3 (B).

The treated active material particles 100 have a structure in which cobalt and oxygen do not elute into the electrolytic solution by reducing the number of cracks and defects, and the stability of the crystal structure in the active material particles is improved. The characteristics are further improved. Further, the active material particles 100 after the treatment are new substances, and are
It can also be called a new positive electrode active material.

By using the treated active material particles 100 in the positive electrode active material layer, a secondary battery having high safety or reliability can be provided.

(Embodiment 2)
Examples of the method for coating the active material particles 110 having cracks shown in the first embodiment include a liquid phase method including a sol-gel method, a solid phase method, a sputtering method, a vapor deposition method, and a CVD (chemical vapor deposition) method. A method such as the PLD (pulse laser deposition) method can be applied.

In the present embodiment, the sol-gel method, which can be expected to have a uniform coating and can be treated at atmospheric pressure, is applied. The production method will be described with reference to FIGS. 4, 5, and 6.

<Sol-gel method>
First, the alkoxide of the metal element M2 is dissolved in alcohol. As the metal of the alkoxide of the metal element M2, one or both of the above-mentioned II and IV valence metals, specifically magnesium, calcium, silicon, and titanium can be used. Further, as M2, various elements such as an alkali metal element, an alkaline earth metal element, an alkali metal element and an alkaline earth metal element other than Italy, a typical metal element, and a transition metal element may be used.

Examples of the alkali metal element include Li, Na, K, Rb, Cs and Fr, and examples of the alkaline earth metal element include Be, Mg, Ca, Sr, Ba and Ra. The alkali metal element and alkaline soil. Metallic elements Typical metal elements other than Italy include Sc, Ti, V, Cr, and M.
n, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag,
Examples include Hf, Ta, W, Re, Os, Ir, Pt, and Au, and the transition metal element is A.
Examples thereof include l, Zn, Ga, Ge, Cd, In, Sn, Sb, Hg, TI, Pb, Bi and Po.

FIG. 4 (A-1) shows a general formula of the alkoxide of the metal element M2. In the formula of FIG. 4 (A-1), M2 represents an IV-valent metal element, and R may be the same or different. Each R independently represents an alkyl group having 1 to 18 carbon atoms or an aryl group having 6 to 13 substituted or unsubstituted carbon atoms. Examples of the alkyl group having 1 to 18 carbon atoms include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group and an octadecyl group, an isopropyl group, an isobutyl group and t. Examples of the branched alkyl group such as a butyl group include a phenyl group, a naphthyl group, and an aryl group having 6 to 13 carbon atoms.
Specific examples include a biphenyl group and a fluorenyl group. R is not limited to the above.

FIG. 4 (A-2) shows a general formula of titanium alkoxide using titanium for M2 in FIG. 4 (A-1). As specific examples of titanium alkoxide, tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetra-i-propoxytitanium (in FIG. 4 (A-).
3)) (Tetraisopropyl orthotitanium, titanium isopropoxide, Titanium
It may also be referred to as m tetraisopropoxide, TTIP, etc.), tetra-n-butoxytitanium, tetra-i-butoxytitanium, tetra-sec-butoxytitanium, tetra-t-butoxytitanium, and the like.

Alcohols are preferable as the solvent for dissolving the alkoxide of the metal element M2, and primary alcohols or secondary alcohols are particularly preferable because of the high solubility of the metal alkoxide.
For example, methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol and the like can be used.

Next, particles of a composite oxide containing lithium and the metal element M1 (active material particles 110 shown in the first embodiment) are added to an alcohol solution of the alkoxide of the metal element M2, and the mixture is stirred. By adding water (H ₂ O) here, a hydrolysis reaction between water and titanium alkoxide occurs as shown in FIG. 4 (B). At the same time, an acid or a base may be added as a catalyst. Further, the same hydrolysis reaction occurs by placing an alcohol solution of the alkoxide of the metal element M2 in an atmosphere containing water and stirring the mixture.

Further, following the hydrolysis reaction of FIG. 4 (B), the dehydration condensation reaction of FIG. 4 (C) occurs. Figure 4 (
By repeating the hydrolysis shown in B) and the condensation reaction shown in FIG. 4 (C), the metal element M2
A sol of the oxide of the metal element M2 is formed, and by further advancing the reaction, a gel of the oxide of the metal element M2 is formed.

Here, it is known that a hydroxyl group (OH group) is present on the particle surface of the composite oxide containing lithium and the metal element M1. As shown in FIGS. 4 (D-1) and 4 (D-2), the hydroxyl group on the particle surface of the composite oxide containing lithium and the metal element M1 is the metal element M shown in FIG. 4 (B).
The hydroxyl group of the metal (M2) generated by hydrolysis from the alkoxide of 2 and FIG. 4 (C).
By causing the dehydration condensation reaction shown in (1), a sol or gel containing an oxide of a metal (M2) different from M1 is formed on the particles containing the metal (M1) oxide.

Then, by recovering the particles 111 by filtration and removing the solvent, the material having the metal element M2 can be coated on the particles of the composite oxide having lithium and the metal element M1.

Next, a method of coating the particles 111 with titanium oxide by the sol-gel method and then obtaining the active material particles 100 will be described with reference to FIGS. 5 and 6.

<Mixing of metal alkoxide solution and particles 111 (S14 in FIG. 6)>
First, TTIP171 is dissolved in isopropanol 170, and particles 111 are mixed therein (see FIG. 5 (A)).

<Coating of particles 111 with titanium oxide by the sol-gel method (S15 in FIG. 6)>
The solution shown in FIG. 5 (A) is stirred under the conditions of 25 ° C. and 90% humidity RH for 4 hours. This treatment utilizes the water and TTIP in the atmosphere and the hydrolysis and dehydration polycondensation reactions that occur on the surface of the particles 111 to coat the particles 111 with _{TiO x sol 172 (see FIG. 5B).}
The reaction is further advanced to form a TiO _x gel on the particle surface.

< _{Recovery of TiO x} gel-coated particles 111 (S16 in FIG. 6)>
In FIG. 6, the mixed solution after the treatment of S15 is filtered, and the residue is recovered.

<Drying of TiOx gel (S17 in FIG. 6)>
In FIG. 6, the residue recovered by the treatment of S16 is vacuum dried at 70 ° C. for 1 hour to obtain a powder. Here, the particles 111 are coated with a dry gel 173 containing a Ti oxide (see FIG. 5C).

<Drying of TiOx gel (S18 in FIG. 6)>
In FIG. 6, the powder obtained by the treatment of S17 is heated at 800 ° C. (temperature rise 200 ° C./hour), a holding time of 2 hours, and a flow rate of an atmosphere containing oxygen at 10 L / min to obtain active material particles 100. obtain(
See FIG. 5 (D)).

In the present embodiment, an example in which a titanium alkoxide is used as the alkoxide of the metal element M2 is shown, but the present invention is not particularly limited, and other metal alkoxides may be used. Further, the heating conditions are not particularly limited, and a plurality of heating conditions and the number of heat treatments may be performed. Further, the slow cooling condition after heating is not particularly limited, and the temperature lowering condition may be appropriately adjusted.

In addition, this embodiment can be freely combined with other embodiments.

(Embodiment 3)
In the present embodiment, the active material particles 10 that function as the positive electrode active material described in the previous embodiment.
An example of the shape of the secondary battery having 0 will be described. As the material used for the secondary battery described in the present embodiment, the description of the previous embodiment can be taken into consideration.

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

In the coin-type secondary battery 300, a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal are insulated and sealed with a gasket 303 that is made of polypropylene or the like.
The positive electrode 304 is a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305.
Is formed by. Further, the negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector 308.

The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 may have an active material layer formed on only one side thereof.

For the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, and titanium that are corrosion resistant to the electrolytic solution, or alloys thereof or alloys of these and other metals (for example, stainless steel) may be used. can. Further, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum or the like. The positive electrode can 301 is the positive electrode 304, and the negative electrode can 302 is the negative electrode 30.
Electrically connect to 7 respectively.

The electrolyte is impregnated with the negative electrode 307, the positive electrode 304, and the separator 310, and FIG. 7B is shown.
As shown in the above, the positive electrode 304, the separator 310, the negative electrode 307, and the negative electrode can 302 are laminated in this order with the positive electrode can 301 facing down, and the positive electrode can 301 and the negative electrode can 302 are crimped via the gasket 303 to form a coin shape. The secondary battery 300 of the above is manufactured.

By using the active material particles 100 that function as the positive electrode active material described in the previous embodiment for the positive electrode 304, a coin-type secondary battery 300 having excellent cycle characteristics can be obtained.

Here, the flow of current when charging the secondary battery will be described with reference to FIG. 7 (C). When a secondary battery using lithium is regarded as one closed circuit, the movement of lithium ions and the flow of current are in the same direction. In a secondary battery using lithium, the anode (anode) and the cathode (cathode) are exchanged by charging and discharging, and the oxidation reaction and the reduction reaction are exchanged. Therefore, an electrode having a high reaction potential is called a positive electrode. An electrode having a low reaction potential is called a negative electrode. Therefore, in the present specification, the positive electrode is the "positive electrode" or "positive electrode" regardless of whether the battery is being charged, discharged, a reverse pulse current is applied, or a charging current is applied. The negative electrode is referred to as the "positive electrode" and the negative electrode is referred to as the "negative electrode" or the "-pole (negative electrode)". Using the terms anode (anode) and cathode (cathode) related to oxidation and reduction reactions, there is a difference between charging and discharging.
The opposite can be confusing. Therefore, the terms anode (anode) and cathode (cathode) are not used herein. Temporarily anode (anode)
When the terms "cathode" and "cathode" are used, it is specified whether the battery is being charged or discharged, and whether it corresponds to the positive electrode (positive electrode) or the negative electrode (negative electrode) is also described.

A charger is connected to the two terminals shown in FIG. 7C, and the secondary battery 300 is charged. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases. In FIG. 7 (F), the secondary battery 3
It flows from the external terminal of 00 toward the positive electrode 304, and in the secondary battery 300, the positive electrode 30
The direction of the current flowing from No. 4 toward the negative electrode current collector 308 and flowing from the negative electrode toward the external terminal of the secondary battery 300 is the positive direction. That is, the direction in which the charging current flows is the direction of the current.

[Charging / discharging method]
The secondary battery can be charged and discharged as follows, for example.

≪CC charging≫
First, CC charging will be described as one of the charging methods. CC charging is a charging method in which a constant current is passed through a secondary battery during the entire charging period, and charging is stopped when a predetermined voltage is reached. It is assumed that the secondary battery is an equivalent circuit of the internal resistance R and the secondary battery capacity C as shown in FIG. 8 (A). In this case, the secondary battery voltage V _B is the sum of the voltage V _C applied to the voltage V _R and the secondary battery capacity C according to the internal resistance R.

During CC charging, as shown in FIG. 8A, the switch is turned on and a constant current I flows through the secondary battery. During this time, since a current I is constant, the Ohm's law V R _{= R} × I, a voltage V _R is also constant according to the internal resistance R. On the other hand, the voltage V _C applied to the secondary battery capacity C increases with time. Therefore, the secondary battery voltage V _B rises with the passage of time.

Then, when the secondary battery voltage V _B reaches a predetermined voltage, for example, 4.3 V, charging is stopped. When CC charging is stopped, the switch is turned off and the current I = 0, as shown in FIG. 8 (B).
Will be. Therefore, the voltage _{V R} applied to the internal resistance R becomes 0V. _{Therefore, the secondary battery voltage V B} drops by the amount that the voltage drop in the internal resistance R disappears.

FIG. 8C shows an example of the _{secondary battery voltage V B} and the charging current during CC charging and after CC charging is stopped. _{The secondary battery voltage V B} , which had risen during CC charging, changed to C.
C It is shown that the charge is slightly reduced after the charging is stopped.

≪CCCV charging≫
Next, CCCV charging, which is a charging method different from the above, will be described. CCCV charging is a charging method in which first charging is performed to a predetermined voltage by CC charging, and then charging is performed until the current flowing by CV (constant voltage) charging decreases, specifically, until the final current value is reached. ..

During CC charging, as shown in FIG. 9A, the constant current power supply switch is turned on, the constant voltage power supply switch is turned off, and a constant current I flows through the secondary battery. During this time, since a current I is constant, the Ohm's law V R _{= R} × I, a voltage V _R is also constant according to the internal resistance R. On the other hand, the voltage V _C applied to the secondary battery capacity C increases with time. Therefore, the secondary battery voltage V _B rises with the passage of time.

Then, when the secondary battery voltage V _B becomes a predetermined voltage, for example, 4.3 V, the CC charge is changed to C.
Switch to V charging. During CV charging, as shown in FIG. 9B, the constant voltage power supply 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 _C applied to the secondary battery capacity C increases with time. _{V B} = V _R
Since a + _{V C,} the voltage _{V R} applied to the internal resistance R becomes smaller with time. According voltage V _R becomes smaller according to the internal resistance R, by Ohm's law of V R _{= R} × I, also decreases the current I flowing through the secondary battery.

Then, when the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01 C, charging is stopped. When the CCCV charging is stopped, as shown in FIG. 9C, all the switches are turned off and the current I = 0. Therefore, the voltage _{V R} applied to the internal resistance R becomes 0V. However, since the voltage V _R applied to the internal resistance R by CV charging is sufficiently small, even run out of the voltage drop at the internal resistance R, the secondary battery voltage V _B is hardly lowered.

FIG. 9 (D) shows an example of the _{secondary battery voltage V B} and the charging current during the CCCV charging and after the CCCV charging is stopped. It is shown that the _{secondary battery voltage V B} hardly drops even when the CCCV charging is stopped.

≪CC discharge≫
Next, CC discharge, which is one of the discharge methods, will be described. CC discharge is a discharge method in which a constant current is passed from a secondary battery during the entire discharge period, _{and the discharge is stopped when the secondary battery voltage V B} reaches a predetermined voltage, for example, 2.5 V.

An example of the secondary battery voltage V _{B and the discharge current during CC discharge is shown in FIG.} It is shown that the secondary battery voltage V _{B drops as the discharge progresses.}

Next, the discharge rate and the charge rate will be described. The discharge rate is a relative ratio of the current at the time of discharge to the battery capacity, and is expressed in the unit C. In a battery having a rated capacity of X (Ah), the current corresponding to 1C is X (A). When discharged with a current of 2X (A), 2C
It is said that it was discharged at 0.2C when it was discharged with a current of X / 5 (A). The charging rate is also the same. When charged with a current of 2X (A), it is said to be charged with 2C, and when charged with a current of X / 5 (A), it is charged with 0.2C. It is said that

(Embodiment 4)
In the present embodiment, the active material particles 10 that function as the positive electrode active material described in the previous embodiment.
An example of a material that can be used for a secondary battery having 0 will be described. In the present embodiment, a secondary battery in which the positive electrode, the negative electrode, and the electrolytic solution are wrapped in an exterior body will be described as an example.

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

<Cathode active material layer>
The positive electrode active material layer has a positive electrode active material. Further, the positive electrode active material layer may have a conductive auxiliary agent and a binder.

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

As the conductive auxiliary agent, a carbon material, a metal material, a conductive ceramic material, or the like can be used. Further, a fibrous material may be used as the conductive auxiliary agent. The content of the conductive auxiliary agent with respect to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less.

The conductive auxiliary agent can form a network of electrical conduction in the active material layer. The conductive auxiliary agent can maintain the path of electrical conduction between the positive electrode active materials. By adding a conductive additive to the active material layer, an active material layer having high electrical conductivity can be realized.

As the conductive auxiliary agent, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fiber, or the like can be used. As the carbon fibers, for example, carbon fibers such as mesophase pitch carbon fibers and isotropic pitch carbon fibers can be used. Further, as the carbon fiber, carbon nanofiber, carbon nanotube, or the like can be used. The carbon nanotubes can be produced by, for example, a vapor phase growth method. Further, as the conductive auxiliary agent, for example, a carbon material such as carbon black (acetylene black (AB) or the like), graphite (graphite) particles, graphene, fullerene or the like can be used. Further, for example, metal powders such as copper, nickel, aluminum, silver and gold, metal fibers, conductive ceramic materials and the like can be used.

Further, a graphene compound may be used as the conductive auxiliary agent.

Graphene compounds may have excellent electrical properties such as high conductivity and excellent physical properties such as high flexibility and high mechanical strength. In addition, the graphene compound has a planar shape. Graphene compounds enable surface contact with low contact resistance. Further, even if it is thin, the conductivity may be very high, and a conductive path can be efficiently formed in the active material layer with a small amount. Therefore, it is preferable to use the graphene compound as the conductive auxiliary agent because the contact area between the active material and the conductive auxiliary agent can be increased. It is also preferable because the electrical resistance may be reduced. Here, as the graphene compound, for example, graphene or multigraphene or redened Graphene O
It is particularly preferable to use xide (hereinafter, RGO). Here, RGO refers to, for example, a compound obtained by reducing graphene oxide (GO).

When an active material having a small particle size, for example, an active material having a particle size of 1 μm or less is used, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive auxiliary agent tends to increase, and the amount of the active material supported tends to decrease relatively. When the amount of active material supported decreases, the capacity of the secondary battery decreases. In such a case, when a graphene compound is used as the conductive auxiliary agent, the graphene compound can efficiently form a conductive path even in a small amount, so that it is not necessary to reduce the amount of the active material supported, which is particularly preferable.

Hereinafter, as an example, a cross-sectional configuration example in the case where a graphene compound is used as the conductive auxiliary agent in the active material layer 200 will be described.

FIG. 11A shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is formed by the active material particles 10.
Includes 0, graphene compound 201 as a conductive aid, and binder (not shown).
Here, for example, graphene or multigraphene may be used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet-like shape.
Further, the graphene compound 201 may be formed into a sheet by partially overlapping a plurality of multigraphenes or a plurality of graphenes. Further, in the graphene compound 201, both the plurality of multigraphenes and the plurality of graphenes may be partially overlapped to form a sheet.

In the vertical cross section of the active material layer 200, as shown in FIG. 11A, the sheet-shaped graphene compound 201 is dispersed substantially uniformly inside the active material layer 200. In FIG. 11A, the graphene compound 201 is schematically represented by a thick line, but it is actually a thin film having a thickness of a single layer or multiple layers of carbon molecules. Since the plurality of graphene compounds 201 are formed so as to wrap, cover, or stick to the surface of the plurality of active material particles 100, they are in surface contact with each other.

Here, a network-like graphene compound sheet (hereinafter referred to as graphene compound net or graphene net) can be formed by binding a plurality of graphene compounds to each other. When the active material is covered with graphene net, the graphene net can also function as a binder that binds the active materials to each other. Therefore, since the amount of the binder can be reduced or not used, the ratio of the active material to the electrode volume and the electrode weight can be improved. That is, the capacity of the secondary battery can be increased.

Here, it is preferable to use graphene oxide as the graphene compound 201, mix it with the active material to form a layer to be the active material layer 200, and then reduce the layer. By using graphene oxide having extremely high dispersibility in a polar solvent for forming the graphene compound 201, the graphene compound 201 can be dispersed substantially uniformly inside the active material layer 200. In order to volatilize and remove the solvent from the uniformly dispersed graphene oxide-containing dispersion medium and reduce the graphene oxide, the graphene compound 201 remaining in the active material layer 200 partially overlaps and is dispersed to such an extent that it comes into surface contact with each other. By doing so, a three-dimensional conductive path can be formed.
The graphene oxide may be reduced, for example, by heat treatment or by using a reducing agent.

Therefore, unlike granular conductive auxiliaries such as acetylene black that make point contact with the active material, graphene compound 201 enables surface contact with low contact resistance, so that the amount of the active material is smaller than that of ordinary conductive auxiliaries. The electrical conductivity between the particles 100 and the graphene compound 201 can be improved. Therefore, the ratio of the active material particles 100 in the active material layer 200 can be increased. As a result, the discharge capacity of the power storage device can be increased.

As the binder, for example, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer. Further, fluororubber can be used as the binder.

Further, as the binder, for example, it is preferable to use a water-soluble polymer. As the water-soluble polymer, for example, a polysaccharide or the like can be used. As the polysaccharide, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose and regenerated cellulose, starch and the like can be used. Further, it is more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.

Alternatively, as the binder, polystyrene, methyl polyacrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, etc.
It is preferable to use materials such as polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose.

The binder may be used in combination of a plurality of the above.

For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with another material. For example, a rubber material or the like has excellent adhesive strength and elastic strength, but it may be difficult to adjust the viscosity when mixed with a solvent. In such a case, for example, it is preferable to mix with a material having a particularly excellent viscosity adjusting effect. As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer may be used. Further, as the water-soluble polymer having a particularly excellent viscosity adjusting effect, the above-mentioned polysaccharides such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and cellulose derivatives such as diacetyl cellulose and regenerated cellulose, and starch are used. be able to.

In addition, the solubility of a cellulose derivative such as carboxymethyl cellulose is increased by using a salt such as a sodium salt or an ammonium salt of carboxymethyl cellulose, for example.
It becomes easier to exert the effect as a viscosity modifier. By increasing the solubility, it is possible to improve the dispersibility with the active material and other components when preparing the electrode slurry. In the present specification, the cellulose and the cellulose derivative used as the binder of the electrode include salts thereof.

The water-soluble polymer stabilizes its viscosity by being dissolved in water, and can stably disperse an active material and other materials to be combined as a binder, such as styrene-butadiene rubber, in an aqueous solution. Further, since it has a functional group, it is expected that it can be easily stably adsorbed on the surface of the active material. In addition, cellulose derivatives such as carboxymethyl cellulose are
For example, many materials have a functional group such as a hydroxyl group or a carboxyl group, and since they have a functional group, it is expected that the polymers interact with each other and widely cover the surface of the active material.

When the binder that covers the surface of the active material or is in contact with the surface forms a film, it is expected to play a role as a passivation film and suppress the decomposition of the electrolytic solution. Here, the immobile film is a film having no electron conductivity or a film having extremely low electrical conductivity. For example, when a immobile film is formed on the surface of an active material, the battery reaction potential may be changed. Decomposition of the electrolytic solution can be suppressed. Further, it is more desirable that the passivation membrane suppresses the conductivity of electricity and can conduct lithium ions.

<Positive current collector>
As the positive electrode current collector, a material having high conductivity such as metals such as stainless steel, gold, platinum, aluminum and titanium, and alloys thereof can be used. Further, it is preferable that the material used for the positive electrode current collector does not elute at the potential of the positive electrode. Further, an aluminum alloy to which an element for improving heat resistance such as silicon, titanium, neodymium, scandium, and molybdenum is added can be used. Further, it may be formed of a metal element that reacts with silicon to form VDD. Examples of metal elements that react with silicon to form silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel and the like. As the current collector, a foil-like shape, a plate-like shape (sheet-like shape), a net-like shape, a punching metal-like shape, an expanded metal-like shape, or the like can be appropriately used. It is preferable to use a current collector having a thickness of 5 μm or more and 30 μm or less.

[Negative electrode]
The negative electrode has a negative electrode active material layer and a negative electrode current collector. Further, the negative electrode active material layer may have a conductive auxiliary agent and a binder.

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

As the negative electrode active material, an element capable of performing a charge / discharge reaction by an alloying / dealloying reaction with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium and the like can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Moreover, you may use the compound which has these elements. For example, SiO, Mg ₂ Si, Mg ₂ Ge, SnO, SnO ₂ , Mg ₂ Sn, SnS ₂ , V
₂ Sn ₃ , FeSn ₂ , CoSn ₂ , Ni ₃ Sn ₂ , Cu ₆ Sn ₅ , Ag ₃ Sn, Ag ₃
Sb, Ni ₂ MnSb, CeSb ₃ , LaSn ₃ , La ₃ Co ₂ Sn ₇ , CoSb ₃ , I
There are nSb, SbSn and the like. Here, an element capable of performing a charge / discharge reaction by an alloying / dealloying reaction with lithium, a compound having the element, and the like may be referred to as an alloy-based material.

In the present specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO is SiO
It can also be expressed as _x. Here, x preferably has a value in the vicinity of 1. For example, x is 0
.. It is preferably 2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

As the carbon-based material, graphite, graphitizable carbon (soft carbon), graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black and the like may be used.

Examples of graphite include artificial graphite and natural graphite. Examples of the artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite and the like. Here, as the artificial graphite, spheroidal graphite having a spherical shape can be used. For example, MCMB may have a spherical shape, which is preferable. In addition, MCMB is relatively easy to reduce its surface area and may be preferable. As natural graphite, for example
Examples include scaly graphite and spheroidized natural graphite.

Graphite shows a potential as low as lithium metal when lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed) (0.05 V or more and 0.3 V or less vs. Li / L).
i ⁺ ). As a result, the lithium ion secondary battery can exhibit a high operating voltage. Further, graphite is preferable because it has advantages such as relatively high capacity per unit volume, relatively small volume expansion, low cost, and high safety as compared with lithium metal.

Further, as the negative electrode active material, titanium dioxide (TiO ₂ ) and lithium titanium oxide (Li ₄ T) are used.
i ₅ O ₁₂ ), Lithium-graphite intercalation compound (Li _x C ₆ ), Niobium pentoxide (Nb ₂ O ₅ )
, Tungsten oxide (WO ₂ ), molybdenum oxide (MoO ₂ ) and other oxides can be used.

_{Further, as the negative electrode active material, Li 3-x} M _x N (M = Co, Ni, Cu) having _{a Li 3} N type structure, which is a compound nitride of lithium and a transition metal, can be used. For example, Li _2.6
Co _0.4 N ₃ shows a large charge / discharge capacity (900 mAh / g, 1890 mAh / cm ³ ) and is preferable.

When lithium and transition metal compound nitrides are used, lithium ions are contained in the negative electrode active material.
As the positive electrode active material, it is preferable because it can be combined with materials such as _{V 2} O ₅ and Cr ₃ O _{8 which do not contain lithium ions.} Even when a material containing lithium ions is used as the positive electrode active material, a double nitride of lithium and a transition metal can be used as the negative electrode active material by desorbing the lithium ions contained in the positive electrode active material in advance.

Further, a material that causes a conversion reaction can also be used as the negative electrode active material. For example, a transition metal oxide that does not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), may be used as the negative electrode active material. Materials that cause a conversion reaction include oxides such as Fe ₂ O ₃ , CuO, Cu ₂ O, RuO ₂ , Cr ₂ O ₃ , sulfides such as CoS _0.89 , NiS, and CuS, and Zn ₃ N _2. , Cu ₃ N, Ge ₃
Nitrides N ₄ or the _{like, NiP 2, FeP 2, CoP} 3 etc. _phosphide, also at the FeF 3, BiF _3, etc. fluoride.

As the conductive auxiliary agent and the binder that the negative electrode active material layer can have, the same material as the conductive auxiliary agent and the binder that the positive electrode active material layer can have can be used.

<Negative electrode current collector>
The same material as the positive electrode current collector can be used for the negative electrode current collector. The negative electrode current collector preferably uses a material that does not alloy with carrier ions such as lithium.

[Electrolytic solution]
The electrolytic solution has a solvent and an electrolyte. The solvent of the electrolytic solution is preferably an aprotonic organic solvent, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, 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 sulfoxide, diethyl ether, methyl diglime, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sulton, etc., or two or more of them. Can be used in any combination and ratio.

Further, by using one or more flame-retardant and flame-retardant ionic liquids (normal temperature molten salt) as the solvent of the electrolytic solution, the internal temperature rises due to an internal short circuit of the power storage device, overcharging, or the like. However, it is possible to prevent the power storage device from exploding or catching fire. Ionic liquids consist of cations and anions, including organic cations and anions. Examples of the organic cation used in the electrolytic solution include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations. Further, as anions used in the electrolytic solution, monovalent amide anion, monovalent methide anion, fluorosulfonic anion, perfluoroalkyl sulfonic acid anion, tetrafluoroborate anion, perfluoroalkyl borate anion, hexafluorophosphate anion. , Or perfluoroalkyl phosphate anion and the like.

Further, as the electrolyte to be dissolved in the above solvent, for example, LiPF ₆ , LiClO ₄ , LiA
sF ₆ , LiBF ₄ , LiAlCl ₄ , LiSCN, LiBr, LiI, Li ₂ SO ₄ ,
Li ₂ B ₁₀ Cl ₁₀ , Li ₂ B ₁₂ Cl ₁₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃
, LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂
, LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ), LiN (C ₂ F ₅ SO ₂ ) _{2 and} other lithium salts are used, or two or more of them are used in any combination and ratio. be able to.

As the electrolytic solution used in the power storage device, it is preferable to use a highly purified electrolytic solution having a small content of elements other than granular dust and constituent elements of the electrolytic solution (hereinafter, also simply referred to as “impurities”). Specifically, the weight ratio of impurities to the electrolytic solution is preferably 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

Further, vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), LiBOB, and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolytic solution. The concentration of the material to be added may be, for example, 0.1 wt% or more and 5 wt% or less with respect to the entire solvent.

Alternatively, a polymer gel electrolyte obtained by swelling the polymer with an electrolytic solution may be used. By using the polymer gel electrolyte, the safety against liquid leakage and the like is enhanced. In addition, the secondary battery can be made thinner and lighter.

As polymers to be gelled, silicone gel, acrylic gel, acrylonitrile gel,
A polyethylene oxide-based gel, a polypropylene oxide-based gel, a fluorine-based polymer gel, or the like can be used. Examples of the polymer include polyethylene oxide (PEO).
), A polymer having a polyalkylene oxide structure, PVDF, polyacrylonitrile, etc., and a copolymer containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Further, the polymer to be formed may have a porous shape.

Further, instead of the electrolytic solution, a solid electrolyte having an inorganic material such as a sulfide type or an oxide type, or P.
A solid electrolyte having a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, it is not necessary to install a separator or a spacer. In addition, since the entire battery can be solidified, there is no risk of liquid leakage and safety is dramatically improved.

[Separator]
Further, the secondary battery preferably has a separator. Examples of the separator include fibers having cellulose such as paper, non-woven fabrics, glass fibers, ceramics, or synthetic fibers using nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, and polyurethane. It is possible to use the one formed by. It is preferable that the separator is processed into an envelope shape and arranged so as to wrap either the positive electrode or the negative electrode.

The separator may have a multi-layer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof. As the ceramic material, for example, aluminum oxide particles, silicon oxide particles and the like can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene and the like can be used. As the polyamide-based material, for example, nylon, aramid (meth-based aramid, para-based aramid) and the like can be used.

Since the oxidation resistance is improved by coating with a ceramic material, deterioration of the separator during high voltage charging / discharging can be suppressed, and the reliability of the secondary battery can be improved. Further, when a fluorine-based material is coated, the separator and the electrode are easily brought into close contact with each other, and the output characteristics can be improved.
Coating a polyamide-based material, particularly aramid, improves heat resistance and thus can improve the safety of the secondary battery.

For example, a mixed material of aluminum oxide and aramid may be coated on both sides of a polypropylene film. Further, the surface of the polypropylene film in contact with the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface in contact with the negative electrode may be coated with a fluorine-based material.

When a separator having a multi-layer structure is used, the safety of the secondary battery can be maintained even if the thickness of the entire separator is thin, so that the capacity per volume of the secondary battery can be increased.

[Exterior body]
As the exterior body of the secondary battery, for example, a metal material such as aluminum or a resin material can be used. Further, a film-like exterior body can also be used. As a film,
For example, a metal thin film having excellent flexibility such as aluminum, stainless steel, copper, and nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, and polyamide, and further, as an outer surface of an exterior body on the metal thin film. A film having a three-layer structure provided with an insulating synthetic resin film such as a polyamide resin or a polyester resin can be used.

(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. 12A, the cylindrical secondary battery 600 has a positive electrode cap (battery lid) 601 on the upper surface and a battery can (exterior can) 602 on the side surface and the bottom surface. The positive electrode cap and the battery can (outer can) 602 are insulated by a gasket (insulating packing) 610.

FIG. 12B is a diagram schematically showing a cross section of a cylindrical secondary battery. Inside the hollow cylindrical battery can 602, a battery element in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched between them is provided. Although not shown, the battery element is wound around the center pin. One end of the battery can 602 is closed and the other end is open. For the battery can 602, a metal such as nickel, aluminum, or titanium having corrosion resistance to an electrolytic solution, or an alloy thereof or an alloy between these and another metal (for example, stainless steel or the like) can be used. .. Further, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum or the like. Inside the battery can 602, the battery element in which the positive electrode, the negative electrode, and the separator are wound is sandwiched between a pair of insulating plates 608 and 609 facing each other. Further, a non-aqueous electrolytic solution (not shown) is injected into the inside of the battery can 602 provided with the battery element. Non-aqueous electrolyte is
A coin-type secondary battery can be used.

Since the positive electrode and the negative electrode used in the cylindrical storage battery are wound, it is preferable to form active materials 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 terminal (negative electrode current collecting lead) 607 is connected to the negative electrode 606. A metal material such as aluminum can be used for both the positive electrode terminal 603 and the negative electrode terminal 607. Positive electrode terminal 60
Reference numeral 3 is resistance welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC element (Positive Temperature Co).
It is electrically connected to the positive electrode cap 601 via the effective) 611. The safety valve mechanism 612 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the increase in the internal pressure of the battery exceeds a predetermined threshold value. Further, the PTC element 611 is a heat-sensitive resistance element whose resistance increases when the temperature rises, and the amount of current is limited by the increase in resistance to prevent abnormal heat generation. Barium titanate (BaTIO ₃ ) -based semiconductor ceramics or the like can be used as the PTC element.

Further, as shown in FIG. 12C, a plurality of secondary batteries 600 are used in the conductive plate 613 and the conductive plate 614.
The module 615 may be configured by sandwiching it between. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By configuring the module 615 having a plurality of secondary batteries 600,
A large amount of electric power can be taken out.

FIG. 12D is a top view of the module 615. The conductive plate 613 is shown by a dotted line for clarity. As shown in FIG. 12D, the module 615 may have conductors 616 that electrically connect a plurality of secondary batteries 600. A conductive plate can be superposed on the conducting wire 616. Further, the temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, it is cooled by the temperature control device 617, and the secondary battery 6 is cooled.
When 00 is too cold, it can be heated by the temperature control device 617. Therefore, the performance of the module 615 is less affected by the outside air temperature.

By using the active material particles 100 that function as the positive electrode active material described in the previous embodiment for the positive electrode 604, a cylindrical secondary battery 600 having a high capacity and excellent cycle characteristics can be obtained.

[Structural example of secondary battery]
Another structural example of the secondary battery will be described with reference to FIGS. 13 to 16.

13 (A) and 13 (B) are views showing an external view of the battery pack. The battery pack is
It has a circuit board 900 and a secondary battery 913. The secondary battery 913 has a terminal 951 and a terminal 952, and is covered with a label 910. The battery pack may also have an antenna 914.

The circuit board 900 is fixed with a seal 915. The circuit board 900 has a circuit 912. The terminal 911 is electrically connected to the terminals 951 and 952 of the secondary battery 913 via the circuit board 900. Further, the terminal 911 is electrically connected to the antenna 914 and the circuit 912 via the circuit board 900. A plurality of terminals 911 may be provided, and each of the plurality of terminals 911 may be used as a control signal input terminal, a power supply terminal, or the like.

The circuit 912 functions as a protection circuit that protects the secondary battery 913 from, for example, overcharging, overdischarging, and overcurrent. The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 914 is not limited to a coil shape, and may be, for example, a linear shape or a plate shape. Further, antennas such as a flat antenna, an open surface antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may be used. The antenna 914 has a function capable of performing data communication with, for example, an external device. As a communication method between the battery pack and other devices via the antenna 914, a response method that can be used between the battery pack and other devices such as NFC can be applied.

The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. Layer 916
Has a function capable of preventing the influence of the secondary battery 913 on the electromagnetic field, for example.
As the layer 916, for example, a magnetic material can be used.

The structure of the battery pack is not limited to FIG.

For example, as shown in FIGS. 14 (A-1) and 14 (A-2), FIGS. 13 (A) and 13 (A-2).
The antenna 918 may be provided on the other pair of facing surfaces of the secondary battery 913 shown in (B). FIG. 14 (A-1) is an external view of the pair of surfaces viewed from one side, and FIG. 14 (A-1) is a view.
A-2) is an external view of the pair of surfaces viewed from the other side. For the same parts as the battery pack shown in FIGS. 13 (A) and 13 (B), the description of the battery pack shown in FIGS. 13 (A) and 13 (B) can be appropriately incorporated.

As shown in FIG. 14 (A-1), an antenna 914 is provided on one of the pair of surfaces of the secondary battery 913 with the layer 916 interposed therebetween, and as shown in FIG. 14 (A-2), the secondary battery 913 is provided. The antenna 918 is provided on the other side of the pair of surfaces with the layer 917 interposed therebetween. Layer 917 is, for example, a secondary battery 91.
It has a function that can prevent the influence of 3 on the electromagnetic field. As the layer 917, for example, a magnetic material can be used.

With the above structure, two antennas can be provided in the battery pack, and the sizes of both the antenna 914 and the antenna 918 can be increased.

As the antenna 918, an antenna having a shape applicable to the antenna 914 can be applied. Further, the antenna 918 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. That is, the antenna 914 may function as one of the two conductors of the capacitor. As a result, electric power can be exchanged not only by an electromagnetic field and a magnetic field but also by an electric field.

Alternatively, as shown in FIG. 14 (B-1), the display device 920 may be provided in the battery pack shown in FIGS. 13 (A) and 13 (B). The display device 920 is electrically connected to the terminal 911. The same parts as the battery pack shown in FIGS. 13 (A) and 13 (B) are shown in FIG.
The description of the battery pack shown in (A) and FIG. 13 (B) can be appropriately incorporated.

The display device 920 may display, for example, an image showing whether or not charging is in progress, an image showing the amount of stored electricity, and the like. As the display device 920, for example, an electronic paper, a liquid crystal display device, an electroluminescence (also referred to as EL) display device, or the like can be used. For example, the power consumption of the display device 920 can be reduced by using electronic paper.

Alternatively, as shown in FIG. 14 (B-2), the secondary battery 9 shown in FIGS. 13 (A) and 13 (B).
Sensor 921 may be provided in 13. The sensor 921 includes a terminal 922 and a circuit board 900.
It is electrically connected to the terminal 911 via. For the same parts as the power storage device shown in FIGS. 13 (A) and 13 (B), the description of the power storage device shown in FIGS. 13 (A) and 13 (B) can be appropriately incorporated.

Examples of the sensor 921 include displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, voice, time, hardness, electric field, current, voltage, power, radiation, and flow rate. , Humidity, inclination, vibration, odor, or infrared rays may be measured. By providing the sensor 921, for example, data (temperature or the like) indicating the environment in which the power storage device is placed can be detected and stored in the memory in the circuit 912.

Further, a structural example of the secondary battery 913 will be described with reference to FIGS. 15 and 16.

The secondary battery 913 shown in FIG. 15A has a winding body 950 in which terminals 951 and 952 are provided inside the housing 930. The wound body 950 is impregnated with the electrolytic solution inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In FIG. 15A, the housing 930 is shown separately for convenience, but in reality, the winding body 950 is covered with the housing 930, and the terminals 951 and 95
2 extends outside the housing 930. As the housing 930, a metal material (for example, aluminum) or a resin material can be used.

As shown in FIG. 15 (B), the housing 930 shown in FIG. 15 (A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15B has a housing 930a and a housing 9.
30b is bonded to each other, and the winding body 9 is formed in the area surrounded by the housing 930a and the housing 930b.
50 is provided.

As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface on which the antenna is formed, it is possible to suppress the shielding of the electric field by the secondary battery 913. If the shielding of the electric field by the housing 930a is small, an antenna such as an antenna 914 may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used.

Further, the structure of the wound body 950 is shown in FIG. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are overlapped and laminated with the separator 933 interposed therebetween, and the laminated sheet is wound. A plurality of layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated.

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

By using the active material particles 100 that function as the positive electrode active material described in the previous embodiment for the positive electrode 932, a secondary battery 913 having a high capacity and excellent cycle characteristics can be obtained.

(Embodiment 6)
In the present embodiment, an example of mounting the secondary battery, which is one aspect of the present invention, in an electronic device will be described.

First, as electronic devices to which a secondary battery is applied, for example, television devices (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (mobile phones). (Also referred to as a telephone or a mobile phone device), a portable game machine, a mobile information terminal, a sound reproduction device, a large game machine such as a pachinko machine, and the like.

Next, FIGS. 17 (A) and 17 (B) show an example of a tablet terminal that can be folded in half. The tablet terminal 9600 shown in FIGS. 17 (A) and 17 (B) has a housing 9630.
a, housing 9630b, movable part 9640 connecting housing 9630a and housing 9630b, display unit 9631, display mode changeover switch 9626, power switch 9627, power saving mode changeover switch 9625, fastener 9629, operation switch 9628. Have. By using a flexible panel for the display unit 9631, a tablet terminal having a wider display unit can be obtained. FIG. 17A shows a state in which the tablet terminal 9600 is open, and FIG. 17B shows a state in which the tablet terminal 9600 is closed.

Further, the tablet terminal 9600 has a power storage body 9635 inside the housing 9630a and the housing 9630b. The power storage body 9635 passes through the movable portion 9640 and is provided over the housing 9630a and the housing 9630b.

A part of the display unit 9631 can be used as a touch panel area, and data can be input by touching the displayed operation keys. Further, the keyboard button can be displayed on the display unit 9631 by touching the position where the keyboard display switching button on the touch panel is displayed with a finger or a stylus.

Further, the display mode changeover switch 9626 can switch the display direction such as vertical display or horizontal display, and can select switching between black and white display and color display. The power saving mode changeover switch 9625 can optimize the brightness of the display according to the amount of external light during use detected by the optical sensor built in the tablet terminal 9600. The tablet terminal may incorporate not only an optical sensor but also another detection device such as a gyro, an acceleration sensor, or other sensor for detecting inclination.

FIG. 17B shows a closed state, and the tablet-type terminal has a housing 9630 and a solar cell 96.
33. It has a charge / discharge control circuit 9634 including a DCDC converter 9636. Further, as the power storage body 9635, a secondary battery according to one aspect of the present invention is used.

Since the tablet terminal 9600 can be folded in two, it can be folded so that the housing 9630a and the housing 9630b overlap each other when not in use. By folding
Since the display unit 9631 can be protected, the durability of the tablet terminal 9600 can be improved. Further, since the power storage body 9635 using the secondary battery of one aspect of the present invention has a high capacity and good cycle characteristics, it is possible to provide a tablet terminal 9600 that can be used for a long time over a long period of time.

In addition to this, the tablet-type terminal shown in FIGS. 17 (A) and 17 (B) has a function of displaying various information (still images, moving images, text images, etc.), a calendar, a date, a time, and the like. It can have a function of displaying on a display unit, a touch input function of performing a touch input operation or editing information displayed on the display unit, a function of controlling processing by various software (programs), and the like.

Power is applied to the touch panel by the solar cell 9633 mounted on the surface of the tablet terminal.
It can be supplied to a display unit, a video signal processing unit, or the like. The solar cell 9633 can be provided on one side or both sides of the housing 9630, and can be configured to efficiently charge the power storage body 9635.

Further, the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 17B will be described in FIG. 17 (B).
A block diagram will be shown in C) for explanation. FIG. 17C shows a solar cell 9633 and a power storage body 963.
5. The DCDC converter 9636, the converter 9637, the switches SW1 to SW3, and the display unit 9631 are shown, and the storage body 9635, the DCDC converter 9636, the converter 9637, and the switches SW1 to SW3 are the charge / discharge control circuits shown in FIG. 17B. 96
This is the part corresponding to 34.

First, an example of operation when power is generated by the solar cell 9633 by external light will be described.
The electric power generated by the solar cell is stepped up or down by the DCDC converter 9636 so as to be a voltage for charging the storage body 9635. Then, when the electric power from the solar cell 9633 is used for the operation of the display unit 9631, the switch SW1 is turned on and the converter 9637.
The voltage required for the display unit 9631 is stepped up or down. In addition, the display unit 9631
When the display is not performed, SW1 may be turned off and SW2 may be turned on to charge the power storage body 9635.

The solar cell 9633 is shown as an example of the power generation means, but is not particularly limited, and the storage body 9635 is charged by another power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). It may be. For example, a non-contact power transmission module that wirelessly (non-contactly) transmits and receives power for charging, or a configuration in which other charging means are combined may be used.

FIG. 18 shows an example of another electronic device. In FIG. 18, the display device 8000 is an example of an electronic device using the secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 800
0 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, and the like. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with electric power from a commercial power source, or can use the electric power stored in the secondary battery 8004. Therefore, even when the power cannot be supplied from the commercial power supply due to a power failure or the like, the display device 8000 can be used by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply.

The display unit 8002 includes a liquid crystal display device, a light emitting device equipped with a light emitting element such as an organic EL element in each pixel, an electrophoresis display device, and a DMD (Digital Micromirror Device).
ce), PDP (Plasma Display Panel), FED (Field)
A semiconductor display device such as an Emission Display) can be used.

The display device includes all information display devices such as those for receiving TV broadcasts, those for personal computers, and those for displaying advertisements.

In FIG. 18, the stationary lighting device 8100 is a secondary battery 81 according to an aspect of the present invention.
This is an example of an electronic device using 03. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, and the like. In FIG. 18, the secondary battery 8103 is the housing 81.
Although the case where the 01 and the light source 8102 are provided inside the ceiling 8104 where the light source 8102 is installed is illustrated, the secondary battery 8103 may be provided inside the housing 8101. The lighting device 8100 can be supplied with electric power from a commercial power source, or can use the electric power stored in the secondary battery 8103. Therefore, even when the power cannot be supplied from the commercial power supply due to a power failure or the like, the lighting device 8100 can be used by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power supply.

Although FIG. 18 illustrates the stationary lighting device 8100 provided on the ceiling 8104, the secondary battery according to one aspect of the present invention includes other than the ceiling 8104, for example, the side wall 8105 and the floor 8.
It can be used for a stationary lighting device provided in 106, a window 8107, or the like, or it can be used for a desktop lighting device or the like.

Further, as the light source 8102, an artificial light source that artificially obtains light by using electric power can be used. Specifically, incandescent lamps, discharge lamps such as fluorescent lamps, and light emitting elements such as LEDs and organic EL elements are examples of the artificial light sources.

In FIG. 18, the air conditioner having the indoor unit 8200 and the outdoor unit 8204 is
This is an example of an electronic device using the secondary battery 8203 according to one aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. Although FIG. 18 illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can be supplied with electric power from a commercial power source, or can use the electric power stored in the secondary battery 8203. In particular, the secondary battery 82 is used in both the indoor unit 8200 and the outdoor unit 8204.
When 03 is provided, the air conditioner can be used by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply even when power cannot be supplied from the commercial power supply due to a power failure or the like. It becomes.

Although FIG. 18 illustrates a separate type air conditioner composed of an indoor unit and an outdoor unit, the integrated air conditioner having the functions of the indoor unit and the outdoor unit in one housing may be used. , A secondary battery according to one aspect of the present invention can also be used.

In FIG. 18, the electric refrigerator / freezer 8300 is an example of an electronic device using the secondary battery 8304 according to one aspect of the present invention. Specifically, the electric freezer / refrigerator 8300 has a housing 8301, a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, and the like. In FIG. 18, the secondary battery 8304 is provided inside the housing 8301. Electric freezer refrigerator 8300
The electric power can be supplied from a commercial power source, or the electric power stored in the secondary battery 8304 can be used. Therefore, even when the power cannot be supplied from the commercial power source due to a power failure or the like, the electric refrigerator-freezer 8300 can be used by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply.

In addition, during times when electronic devices are not used, especially during times when the ratio of the amount of power actually used (called the power usage rate) to the total amount of power that can be supplied by the supply source of commercial power is low. By storing power in the next battery, it is possible to suppress an increase in the power usage rate outside the above time zone. For example, in the case of the electric refrigerator / freezer 8300, the temperature is low and the refrigerator door 830
2. Electric power is stored in the secondary battery 8304 at night when the freezer door 8303 is not opened and closed. Then, in the daytime when the temperature rises and the refrigerating room door 8302 and the freezing room door 8303 are opened and closed, the power usage rate in the daytime can be suppressed low by using the secondary battery 8304 as an auxiliary power source.

In addition to the above-mentioned electronic devices, the secondary battery of one aspect of the present invention can be mounted on any electronic device. According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved. Further, according to one aspect of the present invention, a high-capacity secondary battery can be obtained, and thus the secondary battery itself can be made smaller and lighter. Therefore, by mounting the secondary battery, which is one aspect of the present invention, in the electronic device described in the present embodiment, it is possible to obtain an electronic device having a longer life and a lighter weight. This embodiment can be implemented in combination with other embodiments as appropriate.

(Embodiment 7)
In the present embodiment, an example in which a secondary battery, which is one aspect of the present invention, is mounted on a vehicle is shown.

When a secondary battery is mounted on a vehicle, a next-generation clean energy vehicle such as a hybrid electric vehicle (HEV), an electric vehicle (EV), or a plug-in hybrid vehicle (PHEV) can be realized.

FIG. 19 illustrates a vehicle using a secondary battery, which is one aspect of the present invention. FIG. 19 (A)
The automobile 8400 shown in the above is an electric vehicle that uses an electric motor as a power source for traveling. Alternatively, it is a hybrid vehicle in which an electric motor and an engine can be appropriately selected and used as a power source for driving. By using one aspect of the present invention, a vehicle having a long cruising range can be realized. In addition, the automobile 8400 has a secondary battery. As the secondary battery, many small cylindrical secondary batteries shown in FIG. 12 may be used side by side with respect to the floor portion in the vehicle. Further, a battery pack in which a plurality of secondary batteries shown in FIG. 20 are combined may be installed on the floor portion in the vehicle. The secondary battery can not only drive the electric motor 8406, but also supply electric power to a light emitting device such as a headlight 8401 and a room light (not shown).

In addition, the secondary battery can supply electric power to display devices such as a speedometer and a tachometer included in the automobile 8400. In addition, the secondary battery can supply electric power to a semiconductor device such as a navigation system included in the automobile 8400.

The automobile 8500 shown in FIG. 19B can charge the secondary battery of the automobile 8500 by receiving electric power from an external charging facility by a plug-in method, a non-contact power supply method, or the like. FIG. 19B shows a state in which the secondary battery 8024 mounted on the automobile 8500 is being charged from the ground-mounted charging device 8021 via the cable 8022. When charging, the charging method, connector specifications, etc. may be appropriately performed by a predetermined method such as CHAdeMO (registered trademark) or combo. The charging device 8021 may be a charging station provided in a commercial facility or a household power source. For example, the plug-in technology can charge the secondary battery 8024 mounted on the automobile 8500 by supplying electric power from the outside.
Charging can be performed by converting AC power into DC power via a conversion device such as an ACDC converter included in the charging device 8021. Further, in the case of the automobile 8500 equipped with the charging ACDC converter 8025, charging can be performed even if an AC power supply is connected.

Further, although not shown, it is also possible to mount a power receiving device on the vehicle and supply electric power from a ground power transmission device in a non-contact manner to charge the vehicle. In the case of this non-contact power supply system, by incorporating a power transmission device on the road or the outer wall, it is possible to charge the battery not only while the vehicle is stopped but also while the vehicle is running. Further, the non-contact power feeding method may be used to transmit and receive electric power between vehicles. Further, a solar cell may be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or running. An electromagnetic induction method or a magnetic field resonance method can be used for such non-contact power supply.

Further, FIG. 19C is an example of a two-wheeled vehicle using the secondary battery of one aspect of the present invention. FIG. 19
The scooter 8600 shown in (C) includes a secondary battery 8602, a side mirror 8601, and a turn signal 8603. The secondary battery 8602 can supply electricity to the turn signal 8603.

Further, the scooter 8600 shown in FIG. 19C has a secondary battery 860 in the storage under the seat 8604.
2 can be stored. The secondary battery 8602 can be stored in the under-seat storage 8604 even if the under-seat storage 8604 is small. The secondary battery 8602 is removable, and when charging, the secondary battery 8602 may be carried indoors, charged, and stored before traveling.

According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery can be increased. Therefore, the secondary battery itself can be made smaller and lighter. If the secondary battery itself can be made smaller and lighter, it will contribute to the weight reduction of the vehicle, and thus the cruising range can be improved. Further, the secondary battery mounted on the vehicle can also be used as a power supply source other than the vehicle. In this case, for example, it is possible to avoid using a commercial power source during peak power demand. Avoiding the use of commercial power during peak power demand can contribute to energy savings and reduction of carbon dioxide emissions. Further, if the cycle characteristics are good, the secondary battery can be used for a long period of time, so that the amount of rare metals such as cobalt used can be reduced.

This embodiment can be implemented in combination with other embodiments as appropriate.

In this embodiment, a secondary battery using positive electrode active material particles having different coating layers is produced, and SEM is used.
The characteristics are analyzed using and XRD, and the results of comparing the characteristics are shown.

<Preparation of positive electrode active material>
In this example, the positive electrode active materials of Samples 11 to 14, Samples 21 to Sample 24, and Sample 31 using cobalt as the metal element M1 and titanium as the metal element M2 were prepared. The preparation method of each sample was as follows.

≪Sample 11≫
Sample 11 was prepared by forming a coating layer containing titanium on lithium cobalt oxide particles having magnesium and fluorine by a sol-gel method, and then heating the particles.

In this example, lithium cobalt oxide particles having magnesium and fluorine pre-synthesized as a starting material were used. Specifically, a product name manufactured by Nippon Chemical Industrial Co., Ltd .; C-20F was used as a starting material.

To 2-propanol, TTIP was added and dissolved so that the TTIP per weight of the positive electrode active material was 0.004 ml / g. For TTIP, a reagent manufactured by Kishida Chemical Co., Ltd. with a purity of 99.0% or higher was used. Lithium cobalt oxide particles having magnesium and fluorine were added to this 2-propanol solution of TTIP.

The mixed solution of the magnesium and fluorine-containing lithium cobalt oxide particles was stirred with a magnetic stirrer for 70 hours at 25 ° C. and 90% humidity RH. By this treatment, hydrolysis and polycondensation reaction were caused by TTIP with water in the atmosphere, and a layer containing titanium was formed on the surface of lithium cobalt oxide particles having magnesium and fluorine.

The mixed solution after the above treatment was filtered, and the residue was recovered. Kiriyama filter paper (No. 4) was used as the filter for filtration.

The recovered residue was dried at 70 ° C. for 3 hours.

The dried powder was heated. The heating was performed at 800 ° C. (heating temperature of 200 ° C./hour), holding time of 2 hours, and a flow rate of oxygen atmosphere of 10 L / min.

The heated powder was cooled. Cooling was carried out over a period of time equal to or longer than that of raising the temperature. After that, it was sifted. A sieve having an opening of 53 μm was used.

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

It was presumed that Sample 11 was a positive electrode active material having lithium cobalt oxide inside and a coating layer containing titanium and magnesium on the surface layer.

≪Sample 12≫
As a comparative example, Sample 12 was prepared without heating after forming a layer containing titanium and drying it. It was prepared in the same manner as in Sample 11 except that it was not heated.

It was presumed that Sample 12 was a cathode active material having lithium cobalt oxide containing magnesium and fluorine inside and a coating layer containing titanium on the surface layer, but magnesium was not segregated on the surface.

≪Sample 13≫
Sample 13 was prepared as a comparative example without forming a layer containing titanium. It was prepared in the same manner as in Sample 11 except that the layer containing titanium was not formed.

It was presumed that sample 13 was a cathode active material having lithium cobalt oxide inside and a coating layer containing magnesium on the surface layer, but not titanium.

≪Sample 14≫
As a comparative example, sample 14 did not form a layer containing titanium and was not heated. Specifically, C-20F manufactured by Nippon Chemical Industrial Co., Ltd. was used as it was.

Sample 14 is a positive electrode active material containing lithium cobalt oxide containing magnesium and fluorine, but without a coating layer.

≪Sample 21≫
Sample 21 was prepared by forming a coating layer containing titanium on lithium cobalt oxide particles having magnesium and fluorine by a sol-gel method, and then heating the particles.

It was prepared in the same manner as in Sample 11 except that the TTIP per positive electrode active material was 0.01 ml / g and the atmosphere during heating was dry air.

It was presumed that Sample 21 was a positive electrode active material having lithium cobalt oxide inside and a coating layer containing titanium and magnesium on the surface layer.

≪Sample 22≫
Sample 22 was prepared as a comparative example without forming a layer containing titanium. It was prepared in the same manner as in Sample 21 except that the layer containing titanium was not formed.

It was presumed that sample 22 was a cathode active material having lithium cobalt oxide inside and a coating layer containing magnesium on the surface layer, but not titanium.

≪Sample 23≫
As a comparative example, Sample 23 was prepared by forming a layer containing titanium on lithium cobalt oxide particles having no magnesium and then heating the particles.

As the lithium cobalt oxide particles, those manufactured by Nippon Chemical Industrial Co., Ltd. (product name; C-10N) were used. This is X
These are lithium cobalt oxide particles in which magnesium is not detected in PS and fluorine is detected in about 1 atomic%.

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

It was presumed that the sample 23 was a cathode active material having lithium cobalt oxide inside and a coating layer containing titanium on the surface layer, but magnesium was not segregated on the surface.

≪Sample 24≫
As a comparative example, sample 24 did not form a layer containing titanium on the magnesium-free lithium cobalt oxide particles and did not heat the particles. Specifically, C-10N manufactured by Nippon Chemical Industrial Co., Ltd. was used as it was.

Sample 24 is lithium cobalt oxide having no coating layer.

≪Sample 31≫
Sample 31 was prepared by forming a coating layer containing titanium on lithium cobalt oxide particles having magnesium and fluorine by a sol-gel method and then heating the particles.

It was prepared in the same manner as in Sample 11 except that the TTIP per positive electrode active material was 0.01 ml / g.

It was presumed that Sample 31 was a positive electrode active material having lithium cobalt oxide inside and a coating layer containing titanium and magnesium on the surface layer.

Table 1 shows the preparation conditions for Samples 11 to 14, Samples 21 to 24, and Sample 31. In addition, the analysis performed for each sample, which will be described later, is also shown.

<SEM>
The results of observing Samples 11 and 14 using SEM are as described in FIG. It has been clarified that the positive electrode active material 100 having a relatively smooth surface with few cracks and a surface area can be produced by forming a layer containing titanium and heating it.

<XRD>
For Samples 11 to 14, the size of the crystallite inside the particles of the positive electrode active material is determined by XR.
Analysis was performed using D. The results are shown in Table 2.

As shown in Table 2, the sample 11 coated with the titanium layer and heated showed a tendency for the crystallites to be larger than those of the other samples. The tendency for the crystallites to increase was different depending on the crystal plane, and was remarkable on the (003) plane and the like.

It is considered that the larger the number of cracks, the lower the crystallinity and therefore the smaller the crystallinity size, and the smaller the number of cracks, the higher the crystallinity and therefore the larger the crystallinity size.

Further, it is presumed that defects such as cracks are likely to occur along the (003) plane and the like. FIG. 20 is a model diagram of the crystal structure of lithium cobalt oxide (LiCoO _2). The direction perpendicular to the paper surface 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 shown by a dotted line. As shown in FIG. 20, the (003) plane shows the characteristics of the layer structure. In lithium cobalt oxide, the bond between lithium and oxygen is weaker than the bond between cobalt and oxygen. Therefore, it is presumed that defects such as cracks are likely to occur in parallel with the (003) plane.

It was presumed that defects such as cracks caused by the (003) surface and the like were repaired by coating the layer having titanium and heating as in this example.

<Cycle characteristics at 25 ° C>
CR2032 type (diameter 20 mm) using the positive electrode active material of Samples 21 to 24
A coin-shaped secondary battery with a height of 3.2 mm) was produced and its cycle characteristics were evaluated.

For the positive electrode, the positive electrode active material (LCO) of Samples 21 to 24, acetylene black (AB), and polyvinylidene fluoride (PVDF) were used as LCO: AB: PVDF = 95: 2.
A slurry mixed at a ratio of 5: 2.5 (weight ratio) was applied to a current collector of aluminum foil and used. N-Methyl-2-pyrrolidone (NMP) was used as the solvent.

Lithium metal was used as the counter electrode.

1 mol / L lithium hexafluorophosphate (LiPF ₆ ) was used as the electrolyte contained in the electrolytic solution, and ethylene carbonate (EC) and diethyl carbonate (DEC) were used as the electrolytic solution.
2 vinylene carbonate (VC) was added to the mixture of C: DEC = 3: 7 (volume ratio).
The one added by weight% was used.

As the positive electrode can and the negative electrode can, those made of stainless steel (SUS) were used.

The measurement temperature of the cycle characteristic test was 25 ° C. Charging is performed by CCCV, first with a constant current with a current density of 68.5 mA / g per active material weight and an upper limit voltage of 4.6 V, and then with a current density of 1.4.
Constant voltage charging was performed until the value reached mA / g. The discharge is CC, and the current density per active material weight is 6
It was carried out at a constant current of 8.5 mA / g and a lower limit voltage of 2.5 V.

The conditions for CCCV charging and CC charging in this embodiment are the CCs described in the second embodiment.
Although it may be different from the voltage illustrated in the description of CV charging and CC discharging, the charging method and discharging are the same except for the voltage. By charging with a high voltage, it can be made into a high-capacity secondary battery.

FIG. 21 shows a graph of the discharge capacity retention rate and the number of charge / discharge cycles during 4.6 V charging of the secondary battery using the positive electrode active materials of Samples 21 to 24. The discharge capacity retention rate was determined with the initial discharge capacity as 100%.

As is clear from FIG. 21, sample 22, which is lithium cobalt oxide particles having magnesium and fluorine, is better than sample 24 having no coating layer and sample 23 having only a coating layer containing titanium. The cycle characteristics were shown. This is considered to be the effect of magnesium segregating on the surface layer of the lithium cobalt oxide particles due to heating.

Further, the sample 21, which is a positive electrode active material in which a coating layer containing titanium is formed on lithium cobalt oxide particles having magnesium and fluorine, showed extremely good cycle characteristics. This was a characteristic superior to the sample 22 in which magnesium was segregated on the surface layer and the sample 23 in which only the coating layer containing titanium was formed.

In the cycle characteristic measurement, the discharge capacity retention rate at 10 cycles was 99%. The discharge capacity retention rate at 30 cycles was 97%.

As described above, it has been clarified that by providing the coating layer having titanium and magnesium, better cycle characteristics can be obtained as compared with the case where only the coating layer having titanium or only the coating layer having magnesium is provided.

<Initial characteristics, rate characteristics and cycle characteristics at 45 ° C>
A secondary battery was prepared using the positive electrode active material of Sample 31, and the initial characteristics and cycle characteristics were evaluated.

For the positive electrode, the positive electrode active material (LCO) of sample 31, acetylene black (AB), and polyvinylidene fluoride (PVDF) (manufactured by Solvay, product name; GE51305) are used as LCO:
A slurry prepared by mixing AB: PVDF = 95: 3: 2 (weight ratio) was applied to a current collector of aluminum foil. N-Methyl-2-pyrrolidone (NMP) was used as the solvent. The amount supported on the positive electrode current collector was about 8.5 mg / cm ² . Others were prepared in the same manner as in Samples 21 to 24.

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

The initial charge / discharge characteristics were measured by charging at CC / CV, 0.2C, 4.55V, and 0.05C cutoffs. Discharge was performed with CC, 0.2C, 3.0V cutoff. 1C = 160
It was set to mAh / g. The measurement temperature was 25 ° C.

The rate capacity was measured after the first charge and discharge. Change the discharge rate, except for the discharge rate, under the same conditions as the initial charge / discharge, 0.2C charge / 0.2C discharge, 0.2C charge / 0.5C discharge, 0.2
The measurement was performed in the order of C charge / 1.0 C discharge and 0.2 C charge / 2.0 C discharge. The measurement temperature is 25
The temperature was set to ° C.

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

FIG. 22 (A) is a graph of the rate capacities in Table 1. FIG. 22B is a graph showing the rate capacitance standardized with the capacitance of 0.2C in Table 3.

[Cycle characteristics]
In the cycle characteristics, charging is CC / CV, 1.0C, 4.55V, 0.05C cutoff,
Discharge was performed with CC, 1.0C, 3.0V cutoff. The measurement temperature was 45 ° C. FIG. 23 shows a graph of the measured cycle characteristics in terms of discharge capacity retention rate.

In the cycle characteristic measurement, the discharge capacity retention rate at 10 cycles was 100%. The discharge capacity retention rate at 30 cycles was 98%. The discharge capacity retention rate at 100 cycles was 79%.

The result of measuring the specific surface area of the positive electrode active material of Sample 31 was 0.13 m ² / g.

Further, as a result of measuring the particle size distribution of the positive electrode active material of the sample 31, 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.

As described above, it has been clarified that the positive electrode active material particles of the sample 31, which is one aspect of the present invention, exhibit extremely good initial charge / discharge capacity, rate capacity, and cycle characteristics.

From the above results, it was clarified that the cathode active material particles, which is one aspect of the present invention, can obtain extremely good cycle characteristics when used in a secondary battery.

100 Active Material Particle 105 Crack 110 Active Material Particle 111 Particle 150 Dotted Line 170 Isopropanol 171 TTIP
172 TiOx sol 173 Dry gel 200 Active material layer 201 Graphene compound 300 Secondary battery 301 Positive electrode can 302 Negative electrode 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

Claims (13)

It 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, and has a plurality of active material particles.
The active material particles contain lithium, one or both of the metal elements M1, II and IV valences, and oxygen.
The metal atom M1 is one or more of cobalt, manganese, and nickel.
The active material particles have one or more crystallites and
The active material particles have a first region located inside and a second region located outside the first region.
The second region contains more of the metal element M2 than the first region.
A positive electrode characterized by that. In claim 1,
The metal element M2 is one or more of magnesium, calcium, silicon, and titanium.
A positive electrode characterized by that. In claim 1,
The metal element M2 is magnesium, calcium, and titanium.
A positive electrode characterized by that. In any one of claims 1 to 3,
The second region further contains fluorine,
A positive electrode characterized by that. A secondary battery having a positive electrode, a negative electrode, an electrolytic solution, 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, and has a plurality of active material particles.
The active material particles contain lithium, one or both of the metal elements M1, II and IV valences, and oxygen.
The metal atom M1 is one or more of cobalt, manganese, and nickel.
The active material particles have one or more crystallites and
The active material particles have a first region located inside and a second region located outside the first region.
The second region contains more of the metal element M2 than the first region.
The capacity of the secondary battery after being repeatedly charged and discharged for 100 cycles is 78% or more of the initial capacity.
A secondary battery characterized by that. A secondary battery having a positive electrode, a negative electrode, an electrolytic solution, 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, and has a plurality of active material particles.
The active material particles contain lithium, one or both of the metal elements M1, II and IV valences, and oxygen.
The metal atom M1 is one or more of cobalt, manganese, and nickel.
The active material particles have one or more crystallites and
The active material particles have a first region located inside and a second region located outside the first region.
The second region contains more of the metal element M2 than the first region.
The capacity of the secondary battery after repeated charging and discharging in the range of 10 cycles or more and 30 cycles or less is 98% or more of the initial capacity.
A secondary battery characterized by that. A first step of forming a second active material particle by coating a defective first active material particle with one or both of the II and IV valence metal elements M2 using the sol-gel method. When,
The second step of heat-treating the second active material particles to obtain the third active material particles, and
It has a third step of applying the slurry containing the third active material particles onto the current collector.
A method for producing a positive electrode, characterized in that defects contained in the first active material particles are repaired in the second step. In claim 7,
The size of the crystallites contained in the third active material particles is larger than that of the crystallites contained in the first active material particles.
A method for producing a positive electrode. In claim 7 or 8, the size of the crystallites contained in the third active material particles is at least twice the size of the crystallites contained in the first active material particles.
A method for producing a positive electrode. In any one of claims 7 to 9,
A method for producing a positive electrode, characterized in that the size of the crystallite is measured by XRD analysis. In any one of claims 7 to 10,
The second step is carried out at 600 ° C. or higher and 1000 ° C. or lower in an atmosphere containing oxygen.
A method for producing a positive electrode. In any one of claims 7 to 11,
The metal element M2 is one or more of magnesium, calcium, silicon, and titanium.
A method for producing a positive electrode. In any one of claims 7 to 12,
The first active material particle contains lithium, a metal element M1, and oxygen.
The metal atom M1 is one or more of cobalt, manganese, and nickel.
A method for producing a positive electrode.

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