JP7163010B2 - Positive electrode active material, positive electrode, and secondary battery - Google Patents

Description

One aspect of the present invention relates to an article, method, or manufacturing method. Alternatively, the invention relates to a process, machine, manufacture, or composition of matter. One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. 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.

Note that in this specification, a power storage device generally refers to elements and devices having a power storage function. For example, storage batteries such as lithium ion secondary batteries (also referred to as secondary batteries), lithium ion capacitors, electric double layer capacitors, and the like are included.

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

In recent years, various power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air batteries have been actively developed. In particular, lithium-ion secondary batteries, which have high output and high energy density, are used in portable information terminals such as mobile phones, smart phones, tablets, or notebook computers, portable music players, digital cameras, medical equipment, or hybrid vehicles (HEV). , electric vehicles (EV), and next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEV). It has become an indispensable part of the modernized society.

Characteristics required for lithium-ion secondary batteries include further increase in energy density, improvement in cycle characteristics, safety in various operating environments, and improvement in long-term reliability.

To increase the energy density, it is effective to increase the amount of the positive electrode active material supported on the positive electrode. For example, attempts have been made as described in Patent Documents 1 to 4 below.

Japanese Patent Application Laid-Open No. 2003-217582 JP 2005-276609 A JP-A-2006-318926 JP 2013-214493 A

An object of one embodiment of the present invention is to provide a positive electrode for a lithium-ion secondary battery that has excellent charge-discharge cycle characteristics. Another object is to provide a secondary battery with high energy density. Another object is to provide a secondary battery with excellent charge/discharge characteristics. Another object of one embodiment of the present invention is to provide a secondary battery with high safety or reliability.

To achieve the above object, in one embodiment of the present invention, a positive electrode is manufactured using a substantially spherical positive electrode active material with a smooth surface. A substantially spherical positive electrode active material with a smooth surface is less susceptible to stress concentration even if its volume changes during charging and discharging. Therefore, cracks and breaks are less likely to occur. By using the positive electrode active material, a secondary battery with good cycle characteristics can be provided. In addition, when particles having different particle diameters are mixed and used for the positive electrode, the supported amount can be increased, and a secondary battery with high energy density can be provided.

One embodiment of the present invention includes a positive electrode active material and a current collector, the positive electrode active material has a substantially spherical shape, has a smooth surface, and is less likely to crack even when pressurized during a manufacturing process, Alternatively, cracks are unlikely to occur even after repeated discharge and discharge, and the positive electrode active material can be arranged at high density on the current collector, and the positive electrode active material has lithium fluoride in the surface layer and is heated during the manufacturing process. Adjacent particles are not easily sintered even when sintered, or even if sintered, they are easily pulverized.

In the above, the positive electrode active material is preferably a positive electrode active material having a uniform size with a standard deviation of the arithmetic mean particle size of 0.2 or less.

In the above, the positive electrode active material is a positive electrode active material having a smooth surface in which the ratio _AR / _{Ai of the ideal specific surface area Ai obtained from the median diameter D50 and the actual specific surface area AR is 2} or less. is preferred.

In the above, the positive electrode active material preferably has a surface fluorine binding energy peak position of more than 684.4 eV and less than 686.0 eV as measured by X-ray photoelectron spectroscopy.

In the above, the positive electrode active material has first particles and second particles, and the median diameter of the second particles is 0.66 times or less the median diameter of the first particles. is preferred.

Another aspect of the present invention is a method for manufacturing a positive electrode active material, the method including at least a first step, a second step, and a third step, wherein the first step includes transition It is a step of processing a metal oxide or a transition metal hydroxide into a substantially spherical shape to produce a first material, and a second step is a step of mixing the first material and a lithium source to form a first material. 1 is a step of preparing the mixture, and the third step is a step of heating the first mixture.

In the above, the heating temperature in the second step is preferably 700° C. or higher and 900° C. or lower.

Another aspect of the present invention is a positive electrode active material, wherein the standard deviation of the arithmetic mean particle diameter is 0.2 or less, and the ideal specific surface area A _i obtained from the median diameter D50 and the actual ratio The positive electrode active material has a surface area A _R ratio of A _R /A _i of 2 or less, and a surface fluorine binding energy peak position of more than 684.4 eV and less than 686.0 eV as measured by X-ray photoelectron spectroscopy. It is matter.

Another embodiment of the present invention is a secondary battery including the above positive electrode and negative electrode.

According to one embodiment of the present invention, it is possible to provide a positive electrode for a lithium ion secondary battery with excellent charge-discharge cycle characteristics. Alternatively, a secondary battery with high energy density can be provided. Alternatively, a secondary battery with excellent charge/discharge characteristics can be provided. Alternatively, a secondary battery with high safety or reliability can be provided.

1A and 1B are cross-sectional views of a positive electrode of one embodiment of the present invention; 1A and 1B are schematic diagrams of a positive electrode active material of one embodiment of the present invention; 4A and 4B illustrate a method for manufacturing a positive electrode active material of one embodiment of the present invention; 4A and 4B are diagrams for explaining a charging method of a secondary battery; FIG. 4A and 4B are diagrams for explaining a charging method of a secondary battery; FIG. 4A and 4B are diagrams for explaining a method of discharging a secondary battery; FIG. 4A and 4B illustrate a coin-type secondary battery; FIG. 3 is a diagram for explaining a cylindrical secondary battery; The figure explaining a secondary battery module and a vehicle. 4A and 4B are diagrams for explaining an example of a secondary battery pack; FIG. 4A and 4B are diagrams for explaining an example of a secondary battery pack; FIG. 1A and 1B illustrate examples of electronic devices; 1A and 1B are diagrams illustrating examples of an electronic device and a power storage system;

Embodiments of the present invention will be described in detail below with reference to the drawings. However, those skilled in the art will easily understand that the present invention is not limited to the following description, and that the forms and details thereof can be variously changed. Moreover, the present invention should not be construed as being limited to the description of the embodiments shown below.

In this specification and the like, the surface layer portion of a particle such as an active material refers to a region from the surface to about 10 nm. A surface caused by a crack or crack can also be called a surface. A region deeper than the surface layer is called the inside.

In the configuration of the invention to be described below, the same reference numerals are used in common for the same parts or parts having similar functions in different drawings, and repeated description thereof will be omitted. Moreover, when referring to similar functions, the hatch patterns may be the same and no particular reference numerals may be attached.

In each drawing described in this specification, the size, layer thickness, or region of each configuration may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale.

Note that ordinal numbers such as “first” and “second” in this specification and the like are used to avoid confusion of constituent elements, and are not numerically limited.

A transistor is a type of semiconductor element, and can achieve current or voltage amplification, switching operation for controlling conduction or non-conduction, and the like. A transistor in this specification includes an IGFET (Insulated Gate Field Effect Transistor) and a thin film transistor (TFT).

In this specification and the like, a metal oxide is a metal oxide in broad terms. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as oxide semiconductors or simply OSs), and the like. For example, when a metal oxide is used for a semiconductor layer of a transistor, the metal oxide is sometimes called an oxide semiconductor. That is, when a metal oxide has at least one of an amplifying action, a rectifying action, and a switching action, the metal oxide can be called a metal oxide semiconductor, abbreviated as an OS. In the case of describing an OS FET, it can also be referred to as a transistor including a metal oxide or an oxide semiconductor.

(Embodiment 1)
[Positive electrode and positive electrode active material]
An example of a positive electrode active material 100 and a positive electrode 120 including the positive electrode active material 100, which is one embodiment of the present invention, will be described with reference to FIGS.

FIG. 1A is a cross-sectional view of the positive electrode 120. FIG. Further, FIG. 1B is an enlarged view of the dashed line portion in FIG. 1A. The positive electrode 120 has a positive electrode active material 100 and a current collector 110 . Furthermore, the positive electrode 120 preferably has a binder (not shown) that binds the positive electrode active materials 100 together and a conductive aid 111 .

For example, as shown in FIG. 1C, the positive electrode 120 can be manufactured by providing a frame 121 over a current collector 110 and pouring a slurry containing a positive electrode active material 100, a binder, and a conductive aid 111 into the frame. can.

The positive electrode active material 100 preferably has a substantially spherical shape with a primary particle median diameter D50 of 500 nm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less. The term "substantially spherical" as used herein does not necessarily mean an ideal sphere, and includes an elliptical sphere, a partially chipped sphere, a distorted sphere, and a sphere with an uneven surface.

Moreover, the standard deviation of the arithmetic mean diameter of the positive electrode active material 100 is preferably 0.2 or less, more preferably 0.19 or less. Such a substantially spherical shape with a uniform particle diameter makes it difficult for stress concentration to occur even if charging and discharging are repeated. In addition, even if the positive electrode 120 is pressurized during the manufacturing process, the pressure is less likely to be concentrated. Therefore, the positive electrode active material 100 is less likely to crack.

When the positive electrode active material 100 is cracked, the surface area is excessively increased, which causes deterioration such as decomposition of the electrolyte solution or loss of oxygen or transition metal contained in the positive electrode active material. Therefore, by using the positive electrode active material 100 that is hard to break, a secondary battery with excellent cycle characteristics can be obtained. In addition, since the substantially spherical shape is a shape with little friction, it is highly fluid and is preferable because it facilitates an increase in the supported amount without applying high pressure in the production process.

Moreover, the positive electrode active material 100 preferably has a smooth surface. Since the positive electrode active material 100 with a smooth surface has few cracks, it is less likely to crack even if its volume changes due to charging and discharging. As an index of smoothness, for example, the ratio of the actual specific surface area A _R measured by the constant volume gas adsorption method to the ideal specific surface area A _i can be used. The ideal specific surface area A _i is obtained by calculation assuming that all particles have the same diameter as D50, the same weight, and an ideal sphere shape. A _R /A _i is preferably 2 or less.

The median diameter D50 can be measured with a particle size distribution meter or the like using a laser diffraction/scattering method. The specific surface area can be measured, for example, by a specific surface area measuring device using a gas adsorption method based on a constant volume method.

In addition, the particles of the positive electrode active material 100 are preferably in contact with other particles of the positive electrode active material 100 at a plurality of points. When the positive electrode active material 100 is substantially spherical with uniform shape and particle size, it becomes easier to contact other particles at a plurality of points. When the particles of the positive electrode active material 100 are in contact with the particles of the other positive electrode active material 100, the conductivity between the particles of the positive electrode active material 100 can be maintained even if the conductive additive 111 is reduced as shown in FIG. Therefore, the amount of the positive electrode active material 100 supported on the positive electrode 120 can be increased.

Whether or not the particles of the positive electrode active material 100 are in contact with other particles can be determined by cross-sectional SEM (scanning electron microscope), surface SEM, cross-sectional TEM (transmission electron microscope) observation, or the like.

Alternatively, graphene 112 may be used together with the conductive additive 111 or instead of the conductive additive 111 as shown in FIG. Since the graphene 112 has higher conductivity than acetylene black, which is often used as the conductive aid 111, and spreads two-dimensionally, the conductivity can be ensured with a small amount. Therefore, the amount of the positive electrode active material 100 supported on the positive electrode 120 can be increased.

Further, the positive electrode active material 100 may have particles with different sizes like the first particles 100a and the second particles 100b shown in FIG. 2C. At this time, when the median diameter (D50) of the second particles 100b is 0.66 times or less the median diameter (D50) of the first particles, the amount of the positive electrode active material 100 supported on the positive electrode 120 can be increased. preferable.

In addition, although FIG. 2C shows an example in which two types of particles with different sizes are included, three or more types of particles with different sizes may be included.

Furthermore, the positive electrode active material 100 preferably has a large amount of material with a low melting point or a material with a low Young's modulus in the surface layer. When a large amount of material with a low melting point or a soft material with a low Young's modulus is present in the surface layer, even if a plurality of particles are aggregated or adjacent particles are sintered, crushing is easy. Note that if the entire surface layer of the positive electrode active material 100 is made of a material with a low melting point or a material with a low Young's modulus, the resistance during charging and discharging may increase. Therefore, it is preferable that the surface layer portion of the positive electrode active material 100 is a mixture of a material with a low melting point or a material with a low Young's modulus and the same material as the inside.

The material having a low melting point here is a material having a melting point lower than that of the material inside the positive electrode active material 100 . For example, when the material inside the positive electrode active material 100 is lithium cobalt oxide (melting point: about 1140° C.), materials with a lower melting point include lithium fluoride (melting point: 848° C.), lithium carbonate (melting point: 723° C.), and fluoride. sodium chloride (melting point 993°C), lithium chloride (melting point 613°C), sodium chloride (melting point 800°C), and the like.

A material with a low Young's modulus here is a material with a lower Young's modulus than the material inside the positive electrode active material 100 . For example, when the material inside the positive electrode active material 100 is lithium cobalt oxide (Young's modulus of about 100 GPa), materials with a lower Young's modulus include lithium fluoride (Young's modulus of 65 GPa), sodium fluoride (Young's modulus of 79 GPa), chloride sodium (Young's modulus 40 GPa), and the like.

Whether or not a material with a low melting point or a material with a low Young's modulus exists in the surface layer of the positive electrode active material 100 can be determined by analysis using, for example, X-ray photoelectron spectroscopy (XPS). For example, when the peak position of fluorine binding energy on the surface of the positive electrode active material 100 exceeds 684.4 eV and is less than 686.0 eV, it is found that the surface layer portion has lithium fluoride. Therefore, it can be determined that lithium fluoride is used as a material with a low melting point or a low Young's modulus.

<Material of positive electrode active material>
Various composite oxides can be used as the material inside the positive electrode active material 100 . For example, a composite oxide having a layered rock salt crystal structure, a spinel crystal structure, or the like can be used. A polyanionic positive electrode material can also be used. Examples of polyanionic positive electrode materials include materials having an olivine-type crystal structure, Nasicon-type materials, and the like. In addition, the material is not limited to the composite oxide, and a material containing no oxygen, such as a positive electrode material containing sulfur, may be used.

For example, a composite oxide represented by LiMO ₂ can be used as a material having a layered rock salt crystal structure. Element M is preferably one or more selected from Co, Ni, and Mn. LiCoO ₂ is preferable because of its advantages such as large capacity, stability in the atmosphere, and relative thermal stability. Furthermore, as the element M, in addition to one or more selected from Co, Ni, and Mn, Al may be included.

For example, _{LiNixMnyCozOw} (where _x , _y , _z and w are, for example, x=y=z=1/3 or therearound, w=2 or thereabout) can be used. Also, for example, _{LiNixMnyCozOw} ( _x , _y , _z and w are each, for example, x=0.8 or its vicinity, y=0.1 or its vicinity, z=0.1 or its vicinity, w=2 or thereabouts) can be used. Also, for example, _{LiNixMnyCozOw} (where _x , _y , _z and w are each, for example, x=0.5 or its vicinity, y=0.3 or its vicinity, z=0.2 or its vicinity, w=2 or thereabouts) can be used. Further, for example, _{LiNixMnyCozOw} ( _x , _y , _z and w are each, for example, x=0.6 or its vicinity, y=0.2 or its vicinity, z=0.2 or its vicinity, w=2 or thereabouts) can be used. Further, for example, _{LiNixMnyCozOw} ( _x , _y , _z and w are each, for example, x=0.4 or its vicinity, y=0.4 or its vicinity, z=0.2 or its vicinity, w=2 or thereabouts) can be used.

A neighborhood is, for example, a value greater than 0.9 times and less than 1.1 times the value.

In addition, a material in which at least part of the transition metal or lithium contained in the positive electrode active material is replaced with one or more elements selected from Li, Fe, Co, Ni, Cr, Al, Mg, etc.; A material doped with one or more elements selected from Ni, Cr, Al, Mg, etc. may be used as the positive electrode active material. For example, LiFeO ₂ , Li ₂ MnO ₃ and the like can also be used.

Among composite oxides having a layered rocksalt crystal structure, it is particularly preferable to use a material having a pseudospinel crystal structure when charged at a high voltage. In such a positive electrode active material, changes in the crystal structure and volume between the charged state and the discharged state are suppressed, so that the crystal structure is less likely to collapse even when charging and discharging are repeated at high voltage. Therefore, it is a positive electrode active material with good cycle characteristics.

The pseudo-spinel type crystal structure has a space group R-3m, and although it is not a spinel type crystal structure, a transition metal such as cobalt occupies six oxygen-coordinated positions, and the arrangement of cations is symmetrical similar to that of the spinel type. It refers to a crystal structure having properties. In the pseudo-spinel crystal structure, the coordinates of cobalt and oxygen in the unit cell are Co (0, 0, 0.5), O (0, 0, x), within the range of 0.20 ≤ x ≤ 0.25 can be shown. Further, when a positive electrode active material having a pseudospinel crystal structure is analyzed using powder XRD using CuKα1 rays, 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ =45.55±0.10° (45.45° to 45.65°). More specifically, 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less) and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less) A sharp diffraction peak appears at .

Charging at a high voltage here means, for example, constant-current charging until the battery voltage reaches 4.6 V (in the case of counter electrode lithium), and then constant-voltage charging until the current value reaches 0.01C.

A composite oxide having a pseudospinel-type crystal structure when charged at a high voltage can be obtained, for example, by synthesizing a composite oxide having a layered rocksalt-type crystal structure with few impurities, followed by adding fluorine such as lithium fluoride and magnesium fluoride. It can be made by mixing the source and the magnesium source and heating at the appropriate temperature and time. The appropriate temperature is, for example, 600° C. or higher and 950° C. or lower, more preferably 700° C. or higher and 900° C. or lower. Appropriate time is 1 hour or more and 100 hours or less, more preferably 2 hours or more and 60 hours or less.

Furthermore, a solid solution obtained by combining a plurality of composite oxides can be used as the positive electrode material. For example, a solid solution of _{LiNixMnyCozO2} ( _x , _y , _z >0, x+y+z= ₁ ) and _Li2MnO3 can be used as the positive electrode active material.

For example, a composite oxide represented by LiM ₂ O ₄ can be used as the material having a spinel crystal structure. It is preferred to have Mn as the element M. For example, _{LiMn2O4 can} be used. Further, by including Ni in addition to Mn as the element M, the discharge voltage of the secondary battery may be improved and the energy density may be improved, which is preferable. In addition, 50 mol % or less of lithium nickel oxide (LiNiO ₂ or LiNi _1-x M _x O ₂ (M=Co, Al, etc.) is added to a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn ₂ O ₄ . )) is preferable because the characteristics of the secondary battery can be improved.

For example, a composite oxide containing oxygen, element X, metal A, and metal M can be used as the polyanionic positive electrode material. Metal M is one or more of Fe, Mn, Co, Ni, Ti, V, and Nb, Metal A is one or more of Li, Na, and Mg, and Element X is S, P, Mo, W, As, and Si. is one or more of

As a material having an olivine-type crystal structure, for example, a composite material (general formula LiMPO ₄ (M is one or more of Fe(II), Mn(II), Co(II), and Ni(II))) can be used. can. Representative _examples of the _{general formula LiMPO4 include LiFePO4} , _{LiNiPO4 , LiCoPO4 , LiMnPO4} , _LiFeaNibPO4 , _LiFeaCobPO4 , _{LiFeaMnbPO4 , LiNiaCobPO4 , LiNiaMnbPO4 (} a+ _b is 1 or less, 0<a< ₁ , 0 _{< b < 1 )} , _{LiFecNidCoePO4 , LiFecNidMnePO4 , LiNicCodMnePO 4} (c+d+e is 1 or less, 0<c<1, 0<d<1, 0<e<1), _{LiFefNigCohMniPO4} ( _f + _g + _h + _i is 1 or less, 0<f<1, 0< Lithium compounds such as g<1, 0<h<1, 0<i<1) can be used.

In particular, LiFePO ₄ is preferable because it satisfies well-balanced requirements for a positive electrode active material, such as safety, stability, high capacity density, and the presence of lithium ions that can be extracted during initial oxidation (charging).

In addition, a composite material of the general formula Li _(2-j) MSiO ₄ (M is one or more of Fe(II), Mn(II), Co(II), Ni(II), 0≤j≤2), etc. can be used. Representative examples of the general formula Li _(2-j) MSiO ₄ include Li _(2-j) FeSiO ₄ , Li _(2-j) NiSiO ₄ , Li _(2-j) CoSiO ₄ , Li _(2-j) MnSiO ₄ , Li _{(2-j) Fek} Ni _l SiO ₄ , Li _{(2-j) Fek} Co _l SiO ₄ , Li _{(2-j) Fek} Mn _l SiO ₄ , Li _(2-j) Ni _k Co _l SiO ₄ , Li _(2-j) Ni _k Mn _l SiO ₄ (k+l is 1 or less, 0 < k < 1, 0 < l < 1), Li _(2-j) Fe _{m N} in Co _q SiO ₄ , Li _(2-j) Fe _{m N n} Mn _q SiO ₄ , Li _(2-j) Ni _m Co _n Mn _q SiO ₄ (m+n+q is 1 or less, 0<m<1, 0<n<1, 0<q <1), Li _{(2-j) FerNisCotMnuSiO4} ( _r + _s + _t + _u is 1 or less, 0<r<1, 0<s<1, 0<t<1, 0<u<1) Lithium compounds such as can be used as materials.

Further, in the general formula of A _x M ₂ (XO ₄ ) ₃ (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb, X = S, P, Mo, W, As, Si) Nasicon-type compounds represented can be used. Nasicon-type compounds include Fe ₂ (MnO ₄ ) ₃ , Fe ₂ (SO ₄ ) ₃ , Li ₃ Fe ₂ (PO ₄ ) ₃ and the like. Further, compounds represented by the general formulas Li ₂ MPO ₄ F, Li ₂ MP ₂ O ₇ and Li ₅ MO ₄ (M=Fe, Mn) can be used as materials for the positive electrode active material.

Further, as a material for the positive electrode active material, _a lithium-manganese composite oxide represented by the composition _{formula LiaMnbMcOd} can be used _. Here, the element M is preferably a metal element other than lithium and manganese, silicon, or phosphorus, and more preferably nickel. Further, when measuring the whole particles of the lithium-manganese composite oxide, it is possible to satisfy 0<a/(b+c)<2, c>0, and 0.26≦(b+c)/d<0.5 during discharge. preferable. In order to develop a high capacity, it is preferable to use a lithium-manganese composite oxide having regions in which the crystal structure, crystal orientation, or oxygen content differs between the surface layer portion and the central portion. In order to obtain such a lithium-manganese composite oxide, it is preferable to satisfy, for example, 1.6≦a≦1.848, 0.19≦c/b≦0.935, and 2.5≦d≦3. Furthermore, it is particularly preferable to use a lithium _- manganese composite oxide represented _by the composition _{formula Li1.68Mn0.8062Ni0.318O3 .} In this specification and the like, the lithium manganese composite oxide represented by the composition formula of Li _1.68 Mn _0.8062 Ni _0.318 O ₃ means that the ratio (molar ratio) of the amount of the raw material is Li ₂ CO ₃ :MnCO ₃ :NiO=0.84:0.8062:0.318. Therefore, the lithium _- manganese composite oxide is represented by the compositional formula _{Li1.68Mn0.8062Ni0.318O3 , but} the composition may deviate from this formula.

In addition, as positive electrode materials, perovskite type fluorides such as _NaFeF3 and _FeF3 , metal chalcogenides (sulfides, selenides, tellurides) such as _TiS2 and MoS2, and _{inverse spinel} crystal structures such as LiMVO4. Materials such as oxides, _vanadium oxides _{( V2O5} , _{V6O13 , LiV3O8} , etc.), manganese oxides, and organic sulfur compounds can be used.

Moreover, a lithium-containing metal sulfide can be used as the positive electrode material. Examples include Li ₂ TiS ₃ and Li ₃ NbS ₄ .

As the positive electrode material, a borate-based positive electrode material represented by the general formula LiMBO ₃ (M is Fe(II), Mn(II), Co(II)) can be used.

A conductive material such as a carbon layer may be provided on the surface of the positive electrode active material. By providing a conductive material such as a carbon layer, the conductivity of the electrode can be improved. For example, the coating of the carbon layer on the positive electrode active material can be formed by mixing a carbohydrate such as glucose when baking the positive electrode active material. Alternatively, graphene, multi-graphene, graphene oxide (GO), or reduced graphene oxide (RGO) can be used as the conductive material. Here, RGO refers to a compound obtained by reducing graphene oxide (GO), for example.

The composition of metal, silicon, phosphorus, etc. in the entire particles of the lithium-manganese composite oxide can be measured using, for example, an ICP-MS (inductively coupled plasma mass spectrometer). Also, the oxygen composition of the entire lithium-manganese composite oxide particles can be measured using, for example, EDX (energy dispersive X-ray spectroscopy). Further, it can be determined by using valence evaluation of molten gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. The lithium-manganese composite oxide is an oxide containing at least lithium and manganese, and includes chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and at least one element selected from the group consisting of phosphorus and the like.

When the carrier ions are alkali metal ions other than lithium ions or alkaline earth metal ions, the positive electrode active material may be alkali metals (e.g., sodium, potassium, etc.) or alkaline earth metals (e.g., sodium or potassium) instead of lithium. , calcium, strontium, barium, beryllium, magnesium, etc.) may be used. For example, a sodium-containing layered oxide can be used.

Examples of materials containing sodium include NaFeO ₂ , Na _2/3 [Fe _1/2 Mn _1/2 ]O ₂ , Na _2/3 [Ni _1/3 Mn _2/3 ]O ₂ , Na ₂ Fe ₂ ( _SO4 ) ₃ , _Na3V2 (PO4) ₃ , _Na2FePO4F , _NaVPO4F , _{NaMPO4 (} M is Fe _{( II} ), Mn(II), Co(II), Ni(II) ), Na ₂ FePO ₄ F, Na ₄ Co ₃ (PO ₄ ) ₂ P ₂ O ₇ , and other sodium-containing oxides can be used as materials for the positive electrode active material.

These materials for the positive electrode active material 100 can be synthesized by the methods described above or known methods.

[Method for preparing positive electrode active material]
Next, an example of a method of processing the material of the positive electrode active material 100 into a spherical shape having a smooth surface and having a uniform shape and particle diameter will be described. The term "spheroidizing" as used herein refers to processing into a substantially spherical shape, and does not necessarily have to be processed into an ideal sphere.

<Physical polishing method>
First, referring to FIG. 3, a method of physically polishing the material of the positive electrode active material to process it into a spherical shape will be described. In this method, the material of the positive electrode active material 100 described above is polished using a polishing device, and then classified using a classifier 210 capable of classifying particles according to their size to obtain a substantially spherical positive electrode active material 100. .

It is preferable to use a plurality of polishing devices because the surface can be made smoother. For example, as shown in FIG. 3, it is preferable to sequentially use a polishing device 201a for rough grinding, a polishing device 201b for intermediate grinding, and a polishing device 201c for final polishing. Each polishing device has a motor 202, a first disk 203a and a second disk 203b. The material of the positive electrode active material is put between the first disk 203a and the second disk 203b, and one or both of the first disk 203a and the second disk 203b are rotated, so that the material of the positive electrode active material Physically grind.

Classification can be performed by sieving, dry classification, wet classification, or the like. It is preferable to use a classifier using a centrifugal force field such as a wet cyclone because high classification accuracy can be obtained. If a wet cyclone is used, oversized particles 221 are preferably collected using dust collector 220 .

This physical polishing method is highly productive because it can process a large amount of material with small equipment. It is also preferable that the temperature rise is less than other methods described later.

<High frequency induction thermal plasma method>
Further, the material of the positive electrode active material described above may be heated with thermal plasma to be spherical. For example, plasma gas is converted to thermal plasma of about 10,000 degrees by high-frequency induction, and the positive electrode active material is introduced into the plasma. The spherical particles after the thermal plasma treatment may be classified with a wet cyclone or the like.

If some elements such as lithium are lost due to the high heat of the thermal plasma, it is preferable to mix with the material having the lost elements after the thermal plasma treatment. For example, it is preferable to mix with a lithium source such as lithium fluoride, lithium carbonate, or lithium chloride after high-frequency induction thermal plasma treatment. If a material with a low melting point or a material with a low Young's modulus is used for the lithium source, the surface layer portion of the positive electrode active material 100 can contain a large amount of material with a low melting point or a low Young's modulus, which is more preferable.

This high-frequency induction thermal plasma method is preferable in that it can produce the positive electrode active material 100 that is nearly spherical. Moreover, since the particles can be oxidized, reduced, nitrided, or carbonized by the plasma gas, it can also serve as the surface modification step of the positive electrode active material 100 .

A part of the raw material of the positive electrode active material, for example, a transition metal oxide or hydroxide may be processed into a spherical shape by a high-frequency induction thermal plasma method. For example, it is known that the particle size of lithium cobaltate is affected by the particle size of raw material cobalt oxide or cobalt hydroxide. Therefore, the substantially spherical positive electrode active material 100 can also be produced by mixing and baking a lithium source and a transition metal oxide or hydroxide processed into a spherical shape by a high-frequency induction thermal plasma method. There is

For example, when cobalt oxide is used as the raw material of the positive electrode active material and lithium fluoride is used as the lithium source, cobalt oxide is first processed into a spherical shape by a high-frequency induction thermal plasma method. Next, spherically processed cobalt oxide and lithium fluoride are mixed. The mixture is fired at, for example, 900° C. or higher and 1100° C. or lower for 10 hours. In some cases, the approximately spherical positive electrode active material 100 can be produced through such a process as well.

<Gas burner method>
Alternatively, the material of the positive electrode active material 100 described above may be put into a high-temperature oxygen burner flame to be melted and spheroidized. The spheroidized particles after the treatment may be classified with a wet cyclone or the like.

This gas burner method is also preferable in that it can produce the positive electrode active material 100 that is nearly spherical.

Also, when some elements such as lithium are lost due to the high heat of the oxygen burner flame, it is preferable to mix with a material having the lost elements, as in the high-frequency induction thermal plasma method.

Furthermore, like the high-frequency induction thermal plasma method, part of the raw material of the positive electrode active material, for example, transition metal oxides or hydroxides, may be processed into spheres by the gas burner method.

The structure described in this embodiment can be combined as appropriate with any other structure described in this embodiment or any structure described in any other embodiment.

(Embodiment 2)
In this embodiment, examples of materials that can be used for a secondary battery including the positive electrode active material 100 described in the above embodiment will be described. In this embodiment, a secondary battery in which a positive electrode, a negative electrode, and an electrolytic solution are wrapped in an outer package will be described as an example.

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

<Positive electrode active material layer>
The positive electrode active material layer has at least a positive electrode active material. In addition to the positive electrode active material, the positive electrode active material layer may also contain other substances such as a film on the surface of the active material, a conductive aid, or a binder.

As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the above embodiment, a secondary battery with high capacity and excellent cycle characteristics can be obtained.

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

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

Examples of conductive aids that can be used include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fiber. As carbon fibers, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. As the carbon fiber, carbon nanofiber, carbon nanotube, or the like can be used. Carbon nanotubes can be produced, for example, by vapor deposition. Further, as the conductive aid, carbon materials such as carbon black (acetylene black (AB), etc.), graphite (black lead) particles, graphene, fullerene, etc. can be used. Also, for example, powders of metals such as copper, nickel, aluminum, silver, and gold, metal fibers, conductive ceramics materials, and the like can be used.

Alternatively, a graphene compound may be used as the conductive aid.

Graphene compounds may have excellent electrical properties of having high electrical conductivity and excellent physical properties of having high flexibility and high mechanical strength. Also, the graphene compound has a planar shape. Graphene compounds enable surface contact with low contact resistance. Moreover, even if it is thin, it may have very high conductivity, and a small amount can efficiently form a conductive path in the active material layer. Therefore, it is preferable to use a graphene compound as a conductive aid because the contact area between the active material and the conductive aid can be increased. By using a spray drying apparatus, it is preferable to form a film of a graphene compound, which is a conductive additive, covering the entire surface of the active material. Moreover, it is preferable because the electrical resistance can be reduced in some cases. Here, it is particularly preferable to use, for example, graphene or multi-graphene or RGO as the graphene compound. Here, RGO refers to a compound obtained by reducing graphene oxide (GO), for example.

When using an active material with a small particle size, for example, an active material with a particle size of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of conductive aid tends to increase, and the amount of supported active material tends to decrease relatively. When the supported amount of the active material is reduced, the capacity of the secondary battery is reduced. In such a case, it is particularly preferable to use a graphene compound as a conductive aid, since even a small amount of the graphene compound can efficiently form a conductive path, so that the supported amount of the active material does not decrease.

In addition, by using a spray drying apparatus in advance, the entire surface of the active material is covered with a graphene compound that is a conductive additive, and a conductive path can be formed with the graphene compound between the active materials. .

As the binder, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene-propylene-diene copolymer. Fluororubber can also be used as the binder.

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

Alternatively, binders include polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, and polytetrafluoro. Using materials such as ethylene, polyethylene, polypropylene, isobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyvinyl chloride, ethylene propylene diene polymer, polyvinyl acetate, polymethyl methacrylate, nitrocellulose, etc. is preferred.

You may use a binder combining two or more among the above.

For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with another material. For example, although rubber materials and the like are excellent in adhesive strength and elasticity, it may be difficult to adjust the viscosity when they are 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. For example, a water-soluble polymer may be used as a material having a particularly excellent viscosity-adjusting effect. Further, as the water-soluble polymer particularly excellent in the viscosity adjusting effect, the aforementioned polysaccharides such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, cellulose derivatives such as regenerated cellulose, and starch are used. be able to.

The solubility of cellulose derivatives such as carboxymethyl cellulose can be increased by using a salt such as a sodium salt or an ammonium salt of carboxymethyl cellulose, and the effect as a viscosity modifier can be easily exhibited. When the solubility is increased, the dispersibility with the active material and other constituents can be enhanced when the electrode slurry is prepared. In this specification, cellulose and cellulose derivatives used as binders for electrodes also include salts thereof.

By dissolving the water-soluble polymer in water, it becomes a viscosity suitable for mixing and dispersion, and the active material and other materials combined as a binder, such as styrene-butadiene rubber, can be uniformly dispersed in the aqueous solution. Moreover, since it has a functional group, it is expected to be easily adsorbed on the surface of the active material. In addition, many cellulose derivatives such as carboxymethyl cellulose are materials having functional groups such as hydroxyl groups and carboxyl groups, and due to the presence of functional groups, the macromolecules interact with each other, and the surface of the active material is widely covered. There is expected.

When the binder that covers or contacts the surface of the active material forms a film, it is expected to function as a passivation film to suppress the decomposition of the electrolytic solution. Here, the passive film is a film with no electron conductivity or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, at the battery reaction potential Decomposition of the electrolytic solution can be suppressed. It is further desirable that the passivation film suppresses electrical conductivity and allows lithium ions to conduct.

<Positive collector>
As the positive electrode current collector, highly conductive materials such as metals such as stainless steel, gold, platinum, aluminum and titanium, and alloys thereof can be used. Moreover, it is preferable that the material used for the positive electrode current collector does not elute at the potential of the positive electrode. Alternatively, an aluminum alloy added with an element that improves heat resistance, such as silicon, titanium, neodymium, scandium, or molybdenum, can be used. Alternatively, a metal element that forms silicide by reacting with silicon may be used. Metal elements that react with silicon to form silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The shape of the current collector may be foil, plate (sheet), mesh, punching metal, expanded metal, or the like. A current collector having a thickness of 5 μm or more and 30 μm or less is preferably used.

[Negative electrode]
The negative electrode has a negative electrode active material layer and a negative electrode current collector. Moreover, the negative electrode active material layer may have a conductive aid 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 charge-discharge reaction by alloying/dealloying reaction with lithium can be used. For example, materials containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. Such an element has 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 for the negative electrode active material. Compounds containing these elements may also be used. For example, SiO, _Mg2Si , _Mg2Ge , SnO, _SnO2 , _Mg2Sn , _SnS2 , _V2Sn3 , _{FeSn2 , CoSn2} , _Ni3Sn2 , _{Cu6Sn5 , Ag3Sn} , _{Ag 3} Sb, Ni ₂ MnSb, CeSb ₃ , LaSn ₃ , La ₃ Co ₂ Sn ₇ , CoSb ₃ , InSb, SbSn and the like. Here, elements capable of undergoing charge-discharge reactions by alloying/dealloying reactions with lithium, compounds containing such elements, and the like are sometimes referred to as alloy-based materials.

In this specification and the like, SiO refers to silicon monoxide, for example. Alternatively, SiO can be represented as SiO _x . Here x preferably has a value close to one. For example, x is preferably 0.2 or more and 1.5 or less, more preferably 0.3 or more and 1.2 or less.

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

Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Spherical graphite having a spherical shape can be used here as the artificial graphite. For example, MCMB may have a spherical shape and are preferred. MCMB is also relatively easy to reduce its surface area and may be preferred. Examples of natural graphite include flake graphite and spherical natural graphite.

Graphite exhibits a potential as low as lithium metal when lithium ions are intercalated into graphite (at the time of formation of a lithium-graphite intercalation compound) (0.05 V or more and 0.3 V or less vs. Li/Li ⁺ ). This allows the lithium ion secondary battery to exhibit a high operating voltage. Furthermore, graphite is preferable because it has advantages such as relatively high capacity per unit volume, relatively small volume expansion, low cost, and high safety compared to lithium metal.

Further, as negative electrode active materials, titanium dioxide (TiO ₂ ), lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ), lithium-graphite intercalation compound (Li _x C ₆ ), niobium pentoxide (Nb ₂ O ₅ ), oxide Oxides such as tungsten (WO ₂ ) and molybdenum oxide (MoO ₂ ) can be used.

Also, Li _3-x M _x N (M=Co, Ni, Cu) having a Li ₃ N-type structure, which is a composite nitride of lithium and a transition metal, can be used as the negative electrode active material. For example, Li _2.6 Co _0.4 N ₃ exhibits a large charge/discharge capacity (900 mAh/g, 1890 mAh/cm ³ ) and is preferable.

When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, so that it can be combined with materials such as V ₂ O ₅ and Cr ₃ O ₈ that do not contain lithium ions as the positive electrode active material, which is preferable. . Note that even when a material containing lithium ions is used as the positive electrode active material, a composite nitride of lithium and a transition metal can be used as the negative electrode active material by preliminarily desorbing the lithium ions contained in the positive electrode active material.

A material that causes a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) that do not form an alloy with lithium may be used as the negative electrode active material. Further, as materials in which a conversion reaction occurs, oxides such as _{Fe2O3 , CuO} , _Cu2O , _RuO2 and _Cr2O3 , sulfides such as _CoS0.89 , _NiS and CuS, and _Zn3N2 , Cu ₃ N, Ge ₃ N ₄ and other nitrides, NiP ₂ , FeP ₂ and CoP ₃ and other phosphides, and FeF ₃ and BiF ₃ and other fluorides.

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

<Negative electrode current collector>
A material similar to that of the positive electrode current collector can be used for the negative electrode current collector. For the negative electrode current collector, it is preferable to use a material that does not alloy with carrier ions such as lithium.

[Electrolyte]
The electrolytic solution has a solvent and an electrolyte. As the solvent for the electrolytic solution, aprotic organic solvents are preferred, such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, and 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 - one of dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these in any combination and ratio be able to.

In addition, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, the internal temperature of the secondary battery rises due to internal short circuits, overcharging, etc. However, it is possible to prevent the secondary battery from exploding or catching fire. Ionic liquids consist of cations and anions, including organic cations and anions. Organic cations 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. Anions used in the electrolytic solution include monovalent amide anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkylsulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, and hexafluorophosphate anions. , or perfluoroalkyl phosphate anions.

Examples of electrolytes dissolved in the above solvents include LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiAlCl ₄ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ and Li ₂ B ₁₂ . _Cl12 , _LiCF3SO3 , _LiC4F9SO3 , _{LiC ( CF3SO2} ) ₃ , _{LiC ( C2F5SO2} ) _{3 ,} LiN _{( CF3SO2} ) ₂ , _{LiN ( C4F9} SO ₂ )(CF ₃ SO ₂ ), LiN(C ₂ F ₅ SO ₂ ) ₂ or the like can be used alone, or two or more of them can be used in any combination and ratio.

The electrolytic solution used in the secondary battery is preferably a highly purified electrolytic solution containing little particulate matter and elements other than 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.

Additives such as vinylene carbonate, propanesultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), LiBOB, and dinitrile compounds such as succinonitrile and adiponitrile may also be added to the electrolytic solution. good. 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.

A polymer gel electrolyte obtained by swelling a polymer with an electrolytic solution may also be used.

By using the polymer gel electrolyte, the safety against leakage and the like is enhanced. Also, the thickness and weight of the secondary battery can be reduced.

As the polymer to be gelled, silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, fluorine polymer gel, and the like can be used.

As the polymer, for example, a polymer having a polyalkylene oxide structure such as polyethylene oxide (PEO), 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. The polymer formed may also have a porous geometry.

Further, instead of the electrolytic solution, a solid electrolyte containing an inorganic material such as a sulfide system or an oxide system, or a solid electrolyte containing a polymer material such as a PEO (polyethylene oxide) system can be used. When a solid electrolyte is used, installation of separators and spacers becomes unnecessary. In addition, since the entire battery can be made solid, the risk of liquid leakage is eliminated and safety is dramatically improved.

[Separator]
Also, the secondary battery preferably has a separator. As the separator, for example, paper, non-woven fabric, glass fiber, ceramics, nylon (polyamide), vinylon (polyvinyl alcohol fiber), polyester, acrylic, polyolefin, synthetic fiber using polyurethane, etc. can be used. can be done. It is preferable that the separator is processed into an envelope shape and arranged so as to enclose either the positive electrode or the negative electrode.

The separator may have a multilayer 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, or the like can be used. For example, PVDF, polytetrafluoroethylene, or the like can be used as the fluorine-based material. Examples of polyamide materials that can be used include nylon and aramid (meta-aramid and para-aramid).

Coating with a ceramic-based material improves oxidation resistance, so deterioration of the separator during high-voltage charging and discharging can be suppressed, and the reliability of the secondary battery can be improved. In addition, when coated with a fluorine-based material, the separator and the electrode are more likely to adhere to each other, and the output characteristics can be improved. Coating with a polyamide-based material, particularly aramid, improves the heat resistance, so that the safety of the secondary battery can be improved.

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

When a separator having a multilayer 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 unit volume of the secondary battery can be increased.

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

[Charging and discharging method]
Charging and discharging of the secondary battery can be performed, for example, as follows.

≪CC charging≫
First, CC charging will be described as one of charging methods. CC charging is a charging method in which a constant current is passed through the secondary battery throughout the charging period and charging is stopped when a predetermined voltage is reached. Assume that the secondary battery 350 is an equivalent circuit of internal resistance R and secondary battery capacity C as shown in FIG. In this case, the secondary battery voltage VB is the sum of the voltage V _R across the internal resistance _R and the voltage V _C across the secondary battery capacity C.

During CC charging, the switch is turned on and a constant current I flows through the secondary battery 350, as shown in FIG. Since the current I is constant during this period, the voltage V _R applied to the internal resistance R is also constant according to Ohm's law of V _R =R×I. On the other hand, the voltage V _C applied to the secondary battery capacity C increases with time. Therefore, the secondary battery voltage _VB increases over time.

Then, when the secondary battery voltage _VB reaches a predetermined voltage, for example 4.3V, charging is stopped. When CC charging is stopped, the switch is turned off and current I=0 as shown in FIG. 4(B). Therefore, the voltage VR applied to the internal resistance _R becomes 0V. Therefore, the voltage drop across the internal resistance _R is eliminated, and the secondary battery voltage VB drops accordingly.

FIG. 4C shows an example of the secondary battery voltage _VB and charging current during CC charging and after CC charging is stopped. It shows that the secondary battery voltage _VB , which increased during CC charging, slightly drops after CC charging is stopped.

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

During CC charging, as shown in FIG. 5A, the switch of the constant current power supply 351 is turned on, the switch of the constant voltage power supply 352 is turned off, and a constant current I flows through the secondary battery. Since the current I is constant during this period, the voltage V _R applied to the internal resistance R is also constant according to Ohm's law of V _R =R×I. On the other hand, the voltage V _C applied to the secondary battery capacity C increases with time. Therefore, the secondary battery voltage _VB increases over time.

Then, when the secondary battery voltage _VB reaches a predetermined voltage, for example, 4.3 V, the CC charging is switched to the CV charging. During CV charging, as shown in FIG. _5B , the switch of the constant-voltage power supply is turned on, the switch of the constant-current power supply is turned off, and the secondary battery voltage VB becomes constant. On the other hand, the voltage V _C applied to the secondary battery capacity C rises with time. Since V _B =V _R +V _C , the voltage V _R across the internal resistance R decreases over time. As the voltage V _R applied to the internal resistance R decreases, the current I flowing through the secondary battery also decreases according to Ohm's law of V _R =R×I.

Then, when the current I flowing through the secondary battery reaches a predetermined current, for example, a current corresponding to 0.01 C, all the switches are turned off to stop charging. When CCCV charging is stopped, the current I becomes 0 as shown in FIG. 5(C). Therefore, the voltage VR applied to the internal resistance _R becomes 0V. However, since the voltage VR applied to the internal resistance _R is sufficiently reduced by CV charging, the secondary battery voltage VB hardly drops even if the voltage drop across the internal resistance _R disappears.

FIG. 5D shows an example of the secondary battery voltage _VB and charging current during CCCV charging and after CCCV charging is stopped. It shows that the secondary battery voltage _VB hardly drops even if 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 supplied from the secondary battery throughout the discharge period, and discharge is stopped when the secondary battery voltage _VB reaches a predetermined voltage, for example, 2.5V.

FIG. 6 shows an example of the secondary battery voltage _VB and the discharge current during CC discharge. It shows how the secondary battery voltage _VB drops as the discharge progresses.

Next, the discharge rate and charge rate will be explained. Discharge rate is the relative ratio of current during discharge to battery capacity and is expressed in units of C. In a battery with a rated capacity of X (Ah), the current corresponding to 1C is X (A). When discharged at a current of 2X (A), it is said to be discharged at 2C, and when discharged at a current of X/5 (A), it is said to be discharged at 0.2C. In addition, the charging rate is the same. When charging at a current of 2X (A), it is said to charge at 2C, and when charging at a current of X/5 (A), it is said to charge at 0.2C. It is said that

(Embodiment 3)
In this embodiment, an example of the shape of a secondary battery including the positive electrode active material 100 described in the above embodiment will be described. The description of the above embodiment can be referred to for materials used for the secondary battery described in this embodiment.

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

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

Note that the active material layers of the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 may be formed only on one side.

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 electrolyte, alloys thereof, and alloys of these and other metals (for example, stainless steel) can be used. can. Also, in order to prevent corrosion due to the electrolyte, it is preferable to coat with nickel, aluminum, or the like. The positive electrode can 301 and the negative electrode can 302 are electrically connected to the positive electrode 304 and the negative electrode 307, respectively.

The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and as shown in FIG. , the positive electrode can 301 and the negative electrode can 302 are pressure-bonded via a gasket 303 to manufacture a coin-shaped secondary battery 300 .

By using the positive electrode active material described in the above embodiment for the positive electrode 304, the coin-shaped secondary battery 300 with high capacity and excellent cycle characteristics can be obtained.

Here, the flow of current during charging of the secondary battery will be described with reference to FIG. 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 secondary batteries using lithium, the anode (anode) and the cathode (cathode) are switched between charging and discharging, and the oxidation reaction and the reduction reaction are switched, so the electrode with a high reaction potential is called a positive electrode. An electrode with a low reaction potential is called a negative electrode. Therefore, in this specification, the positive electrode is referred to as the “positive electrode” or the “+ electrode (positive electrode)”, and the negative electrode is referred to as the “negative electrode” or the “− electrode (minus pole)”. The use of the terms anode and cathode in relation to oxidation and reduction reactions can be confusing as they are reversed during charging and discharging. Accordingly, the terms anode and cathode are not used herein.

A charger is connected to two terminals shown in FIG. 7C to charge the secondary battery 300 . As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[Cylindrical secondary battery]
Next, an example of a cylindrical secondary battery will be described with reference to FIG. As shown in FIG. 8A, a cylindrical secondary battery 400 has a positive electrode cap (battery cover) 401 on its top surface and battery cans (armor cans) 402 on its side and bottom surfaces. The positive electrode cap 401 and the battery can (outer can) 402 are insulated by a gasket (insulating packing) 410 .

FIG. 8B is a diagram schematically showing a cross section of a cylindrical secondary battery 400. FIG. Only the bottom surface of the battery can 402 is shown for explaining the internal structure. A battery element in which a strip-shaped positive electrode 404 and a strip-shaped negative electrode 406 are wound with a separator 405 interposed therebetween is provided inside a hollow columnar battery can 402 . The battery can 402 can be made of metals such as nickel, aluminum, titanium, etc., which are corrosion-resistant to the electrolyte, alloys thereof, and alloys of these and other metals (for example, stainless steel). . Also, in order to prevent corrosion due to the electrolyte, it is preferable to coat with nickel, aluminum, or the like. A non-aqueous electrolyte (not shown) is filled inside the battery can 402 in which the battery element is provided. The same non-aqueous electrolyte as used in coin-type secondary batteries can be used.

Since the positive electrode and the negative electrode used in a cylindrical secondary battery are wound, it is preferable to form the active material on both sides of the current collector. A positive electrode terminal (positive collector lead) 403 is connected to the positive electrode 404 , and a negative electrode terminal (negative collector lead) 407 is connected to the negative electrode 406 . A metal material such as aluminum can be used for both the positive terminal 403 and the negative terminal 407 . A negative terminal 407 is welded to the bottom of the battery can 402 . Positive electrode terminal 403 is welded to conductive plate 419 and electrically connected to positive electrode cap 401 via explosion-proof plate 412 and PTC element (Positive Temperature Coefficient) 411 . The PTC element 411 is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current to prevent abnormal heat generation. Barium titanate (BaTiO ₃ ) semiconductor ceramics or the like can be used for the PTC element.

Alternatively, a module 415 may be formed by sandwiching a plurality of secondary batteries 400 between conductive plates 413 and 414 as shown in FIG. 8C. Multiple secondary batteries 400 are electrically connected to conductive plate 413 and conductive plate 414 by wires 416 . The plurality of secondary batteries 400 may be connected in parallel, may be connected in series, or may be connected in series after being connected in parallel. A large amount of electric power can be extracted by configuring the module 415 having a plurality of secondary batteries 400 .

FIG. 8D is a top view of the module 415. FIG. The conductive plate 413 is shown in dashed lines for clarity of illustration. A temperature control device 417 may be provided between a plurality of secondary batteries 400 as shown in FIG. 8D. When the secondary battery 400 is overheated, it can be cooled by the temperature control device 417, and when the secondary battery 400 is too cold, it can be heated by the temperature control device 417. FIG. Therefore, the performance of the module 415 is less affected by the outside temperature. A buffer material 418 can be provided between the plurality of secondary batteries 400 and between the temperature control device 417 and the secondary battery 400 . By providing the buffer material 418 , it is possible to prevent the secondary batteries 400 from contacting each other or the temperature control device 417 and the secondary battery 400 from contacting each other and damaging the battery can 402 , the temperature control device 417 , and the like.

By using the positive electrode active material described in the above embodiment for the positive electrode 404, the cylindrical secondary battery 400 with high capacity and excellent cycle characteristics can be obtained.

8(C) and 8(D) described an example of a module 415 having 24 secondary batteries 400, but a module 420 having more secondary batteries 400 as shown in FIG. 9(A) may be A plurality of secondary batteries 400 , conductive plate 413 and conductive plate 414 included in module 420 are preferably arranged in housing 423 . Module 420 also preferably has a positive terminal 421 and a negative terminal 422 electrically connected to conductive plate 413 or conductive plate 414 . It also preferably has a temperature control device 417 and a cushioning material 418 .

Although the module 420 having the cylindrical secondary battery 400 has been described with reference to FIG. 9A, the module is not limited to this. good.

Further, as shown in FIG. 9B, a larger module 430 having multiple modules 420 may be provided. By installing the module 430 in a vehicle 440 as shown in FIG. 9C, for example, a next-generation clean energy vehicle such as a hybrid vehicle (HEV), an electric vehicle (EV), or a plug-in hybrid vehicle (PHEV) can be realized. realizable.

A vehicle 440 shown in FIG. 9C is an electric vehicle that uses an electric motor as a power source for running. Alternatively, it is a hybrid vehicle in which an electric motor and an engine can be appropriately selected and used as power sources for running. By using one aspect of the present invention, a vehicle with a long cruising range can be realized.

The secondary battery can not only drive an electric motor (not shown), but also can supply power to light-emitting devices such as headlights and room lights. In addition, the secondary battery can supply power to a display device such as a speedometer, a tachometer, a navigation system, etc., and a semiconductor device of the vehicle 440 .

The vehicle 440 can charge the secondary battery of the module 430 by receiving power from an external charging facility by a plug-in system, a contactless power supply system, or the like. FIG. 9C shows a state in which charging is performed via a cable 452 from a charging device 451 installed on the ground. When charging, the charging method, the standard of the connector, etc. may be appropriately performed by a predetermined method such as CHAdeMO (registered trademark) or Combo. The charging device 451 may be a charging station provided in a commercial facility, or may be a household power source. For example, plug-in technology allows the module 430 mounted on the vehicle 440 to be charged by an external power supply. Charging can be performed by converting AC power into DC power via a conversion device such as an ACDC converter.

Also, although not shown, the power receiving device can be mounted on a vehicle, and power can be supplied from a power transmission device on the ground in a non-contact manner for charging. In the case of this non-contact power supply system, it is possible to charge the battery not only while the vehicle is stopped but also while the vehicle is running by installing a power transmission device on the road or on the outer wall. In addition, electric power may be transmitted and received between vehicles using this contactless power supply method. Furthermore, a solar battery may be provided on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped or running. An electromagnetic induction method or a magnetic resonance method can be used for such contactless power supply.

FIG. 9D illustrates an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. A scooter 460 shown in FIG. The secondary battery 462 can supply electricity to a motor (not shown), headlights (not shown), turn signal lights 464, and the like.

The scooter 460 can store a secondary battery 462 in the under-seat storage. Since the secondary battery 462 has a high energy density, it can be stored even if the storage space under the seat is small. The secondary battery 462 is removable, and when charging, the secondary battery 462 can be carried indoors, charged, and stored before traveling.

According to one embodiment 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 size and weight of the secondary battery itself can be reduced. If the size and weight of the secondary battery itself can be reduced, the cruising distance can be improved because it contributes to the weight reduction of the vehicle. A secondary battery mounted on a 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. If it is possible to avoid using a commercial power supply during peak power demand, it can contribute to energy conservation and reduction of carbon dioxide emissions. Moreover, if the cycle characteristics are good, the secondary battery can be used for a long period of time, so the amount of rare metals such as cobalt used can be reduced.

[Secondary battery pack]
Next, an example of a battery pack having a secondary battery and a function of protecting or controlling the secondary battery will be described with reference to FIGS. 10 and 11. FIG.

FIG. 10A is a diagram showing the appearance of the secondary battery pack 530. FIG. FIG. 10B is a diagram illustrating the configuration of the secondary battery pack 530. FIG. The secondary battery pack 530 has a circuit board 500 and secondary batteries 513 . A label 510 is attached to the secondary battery 513 . Circuit board 500 is secured by seal 515 . The secondary battery pack 530 also has an antenna 514 .

A circuit board 500 has a circuit 512 having a function of protecting or controlling a secondary battery 513 . Circuit board 500 is also electrically connected to terminal 511 . Circuit board 500 is also electrically connected to antenna 514 , one of positive and negative leads 551 and the other of positive and negative leads 552 of secondary battery 513 .

Note that the antenna 514 is not limited to a coil shape, and may have a linear shape or a plate shape, for example. Further, antennas such as planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas may be used. Alternatively, antenna 914 may be a planar conductor. This flat conductor can function as one of conductors for electric field coupling. In other words, 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 electromagnetic fields and magnetic fields, but also by electric fields.

Secondary battery pack 530 has layer 516 between antenna 514 and secondary battery 513 . The layer 516 has a function of preventing the influence of the secondary battery 513 on the electromagnetic field, for example. A magnetic material, for example, can be used as the layer 516 .

The secondary battery 513 has a wound battery element 593 as shown in FIG. 10C. The battery element 593 has a negative electrode 594 , a positive electrode 595 and a separator 596 . A battery element 593 is obtained by laminating a negative electrode 594 and a positive electrode 595 with a separator 596 interposed therebetween, and winding the laminated sheet.

Note that the structure of the secondary battery is not limited to that shown in FIG.

For example, as shown in FIGS. 11A-1 and 11A-2, antennas may be provided on each of a pair of opposing surfaces of the secondary battery pack 530 . FIG. 11A-1 is an external view of the pair of surfaces viewed from one side, and FIG. 11A-2 is an external view of the pair of surfaces viewed from the other side.

As shown in FIG. 11A-1, an antenna 514 is provided on one of a pair of surfaces of a secondary battery pack 530 with a layer 516 interposed therebetween, and as shown in FIG. An antenna 518 is provided on the other side of the layer 517 . The layer 517 has a function of preventing the influence of the secondary battery 513 on the electromagnetic field, for example. A magnetic material, for example, can be used as the layer 517 .

With the above structure, the size of both antenna 514 and antenna 518 can be increased. The antenna 518 has a function of performing data communication with an external device, for example. For the antenna 518, for example, an antenna having a shape applicable to the antenna 514 can be applied. As a communication method between the secondary battery and another device via the antenna 518, a response method such as NFC that can be used between the secondary battery and another device can be applied.

Alternatively, the display device 520 may be provided in the secondary battery pack 530 as illustrated in FIG. 11B-1. The display device 520 is electrically connected to the terminals 511 . Note that the label 510 may not be provided in the portion where the display device 520 is provided.

The display device 520 may display, for example, an image indicating whether or not the battery is being charged, an image indicating the amount of stored electricity, and the like. As the display device 520, electronic paper, a liquid crystal display device, an electroluminescence (also referred to as EL) display device, or the like can be used, for example. For example, by using electronic paper, power consumption of the display device 520 can be reduced.

Alternatively, a sensor 521 may be provided in the secondary battery pack 530 as illustrated in FIG. 11B-2. Sensor 521 is electrically connected to terminal 911 via terminal 522 .

Sensors 521 include, for example, displacement, position, speed, acceleration, angular velocity, number of revolutions, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate , humidity, gradient, vibration, smell, or infrared rays. By providing the sensor 521 , for example, data (such as temperature) indicating the environment in which the secondary battery is placed can be detected and stored in the memory within the circuit 512 .

[Electronics]
Next, an example of mounting a secondary battery that is one embodiment of the present invention in an electronic device will be described with reference to FIGS.

FIG. 12A shows an example of a mobile phone. A mobile phone 600 includes a display unit 602 incorporated in a housing 601, operation buttons 603, an external connection port 604, a speaker 605, a microphone 606, and the like. Note that the mobile phone 600 has a secondary battery 607 . By using the secondary battery of one embodiment of the present invention for the secondary battery 607, a lightweight mobile phone with a long life can be provided.

The mobile phone 600 can run various applications such as mobile phone, e-mail, text reading and writing, music playback, Internet communication, computer games, and the like.

The operation button 603 can have various functions such as time setting, power on/off operation, wireless communication on/off operation, manner mode execution/cancellation, and power saving mode execution/cancellation. . For example, the operating system installed in the mobile phone 600 can freely set the functions of the operation buttons 603 .

In addition, mobile phone 600 is capable of performing short-range wireless communication that conforms to communication standards. For example, by intercommunicating with a headset capable of wireless communication, hands-free communication is also possible.

Also, the mobile phone 600 has an external connection port 604 and can directly exchange data with another information terminal via a connector. Also, charging can be performed via the external connection port 604 . Note that the charging operation may be performed by wireless power supply without using the external connection port 604 .

Mobile phone 600 preferably has a sensor. As sensors, for example, it is preferable to mount a human body sensor such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, and the like.

FIGS. 12B1 and 12B2 illustrate examples of electronic devices having foldable display portions. An electronic device 610 has a foldable display unit 611 incorporated in a housing 612 , an external connection port 613 , an external connection port 614 , and a secondary battery 615 . By using the secondary battery of one embodiment of the present invention as the secondary battery 615, a lightweight and long-life electronic device can be provided.

By including the foldable display portion 611, it is possible to achieve both improved visibility and improved portability due to the wide display portion. As the display unit 611, for example, an EL display device can be used. At least part of the display unit 611 has a touch panel function.

The electronic device 610 may also have a display portion 616 on the back surface of the display portion 611 as illustrated in FIG. 12B2.

FIG. 12C shows an example of an electronic book terminal. The electronic book terminal 620 has a display unit 621 , a circuit board 622 , a secondary battery 623 , a power button 624 and operation buttons 625 . By pressing the operation button 625, operations such as page turning can be performed. By using the secondary battery of one embodiment of the present invention for the secondary battery 623, a lightweight and long-life e-book reader can be provided.

Circuit board 622 has control circuitry and memory. A transistor in which a metal oxide is used for a channel formation region can be applied to the control circuit and the memory. Since a transistor using a metal oxide for a channel formation region has extremely low off-state current, the e-book reader 620 can have low power consumption.

By arranging main parts such as the circuit board 622 and the secondary battery 623 off the center of the electronic book terminal 620, the center of gravity is shifted to one side, and the electronic book terminal 620 can be easily held with one hand.

FIGS. 13A1 and 13A2 are diagrams showing an example of an earphone type computer. The earbud computer preferably has two devices, eg, a first device 650a and a second device 650b, for wearing on the left and right ears. Both the first device 650 a and the second device 650 b have a speaker 651 , a control circuit 652 , a secondary battery 653 and a microphone 654 . Also, both the first device 650a and the second device 650b preferably have an acceleration sensor and a communication antenna. Moreover, it is preferable to carry GPS.

The first device 650a and the second device 650b, for example, convert sound into an electrical signal with the microphone 654, analyze the signal with the control circuit 7602, and recognize the voice if it is voice. If the language of the voice is not the language specified by the user, it can be translated into the language specified by the user, and the translation result can be output from the speaker 651 .

A transistor including a metal oxide for a channel formation region can be used for the control circuit 652 . Since a transistor in which a metal oxide is used for a channel formation region has extremely low off-state current, the first device 650a and the second device 650b with low power consumption can be obtained.

The voice recognition function and translation function of control circuit 652 can use the result of learning using a neural network technique such as RNN (Recurrent Neural Network), for example.

In addition, if the first device 650a and the second device 650b have GPS and communication antennas, position information can be acquired, which can be used for sports such as running.

Further, first device 650a and second device 650b may be used in cooperation with other electronic devices via wireless communication. For example, in cooperation with the hands-free function of the mobile phone, call sound can be output from the speaker 651 of the first device 650a or the second device 650b.

A case 655 that can accommodate the first device 650 a and the second device 650 b preferably has a secondary battery 656 and a display section 657 . With the secondary battery 7611, the secondary batteries 653 included in the first device 650a and the second device 650b can be charged. The display unit 657 can display the charging states of the first device 650a, the second device 650b, and the case 655. FIG. Moreover, you may confirm a more detailed charge state with other electronic devices linked.

By using the secondary battery of one embodiment of the present invention as a secondary battery in a daily electronic device, a product that is lightweight and has a long life can be provided. For example, daily electronic devices include electric toothbrushes, electric shavers, electric beauty devices, and the like, and secondary batteries for these products are stick-shaped, compact, and lightweight, in consideration of ease of holding by the user. , and a large-capacity secondary battery is desired.

FIG. 13(B) is a perspective view of a device also called a cigarette containing smoking device (electronic cigarette). In FIG. 13(H), an electronic cigarette 640 is composed of an atomizer 641 including a heating element, a secondary battery 644 for supplying power to the atomizer, and a cartridge 642 including a liquid supply bottle, sensor and the like. In order to improve safety, a protection circuit that prevents overcharging and overdischarging of the secondary battery 644 may be electrically connected to the secondary battery 644 . A secondary battery 644 illustrated in FIG. 13B has an external terminal so that it can be connected to a charging device. Since the secondary battery 644 becomes a tip part when held, it is desirable that the total length is short and the weight is light. Since the secondary battery of one embodiment of the present invention has high capacity and good cycle characteristics, a small and lightweight electronic cigarette 640 that can be used for a long time can be provided.

FIG. 13C is a diagram illustrating the power storage system 700. FIG. The power storage system 700 has a power generation device 702 and a power storage device 701 . As the power generator, a power generator using solar power, wind power, wave power, ocean current power, tidal power, or the like can be used. By using the secondary battery of one embodiment of the present invention for the power storage device 701, the power storage device 701 can have high capacity and a long life.

The structure described in this embodiment can be combined as appropriate with any other structure described in this embodiment or any structure described in any other embodiment.

100 Positive electrode active material 100a Particles 100b Particles 110 Current collector 111 Conductive agent 112 Graphene 120 Positive electrode 121 Frame 201a Polishing device 201b Polishing device 201c Polishing device 210 Classifying device 220 Dust collector 221 Particles 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 350 Secondary battery 351 Constant current power supply 352 Constant voltage power supply 310 Separator 400 Secondary battery 401 Positive electrode cap 402 Battery can 403 Positive electrode Terminal 404 Positive electrode 405 Separator 406 Negative electrode 407 Negative electrode terminal 411 PTC element 412 Explosion-proof plate 413 Conductive plate 414 Conductive plate 415 Module 416 Wire 417 Temperature controller 418 Cushioning material 419 Conductive plate 420 Module 421 Positive electrode terminal 422 Negative terminal 423 Housing 430 Module 440 Vehicle 451 Charging Device 452 Cable 460 Scooter 461 Side Mirror 462 Secondary Battery 464 Turn Signal Light 500 Circuit Board 510 Label 511 Terminal 512 Circuit 513 Secondary Battery 514 Antenna 515 Seal 516 Layer 517 Layer 518 Antenna 520 Display Device 521 Sensor 522 Terminal 530 Secondary battery pack 551 One side 552 Other side 593 Battery element 594 Negative electrode 595 Positive electrode 596 Separator 600 Mobile phone 601 Case 602 Display unit 603 Operation button 604 External connection port 605 Speaker 606 Microphone 607 Secondary battery 610 Electronic device 611 Display unit 612 Case 613 External connection port 614 External connection port 615 Secondary battery 616 Display unit 620 Electronic book terminal 621 Display unit 622 Circuit board 623 Secondary battery 624 Power button 625 Operation button 640 Electronic cigarette 641 Atomizer 642 Cartridge 644 Secondary battery 650a Device 650b Device 651 speaker 652 control circuit 653 secondary battery 654 microphone 655 case 656 secondary battery 657 display unit 700 power storage system 701 power storage device 702 power generation device 911 terminal 914 antenna 7602 control circuit 7611 secondary battery

Claims (7)

having a positive electrode active material and a current collector,
The positive electrode active material has a substantially spherical shape and has a smooth surface such that the ratio _AR / _{Ai of the ideal specific surface area Ai obtained from the median diameter D50 to the actual specific surface area AR is 2} or less. and
Cracks are less likely to occur even if pressure is applied during the manufacturing process, or cracks are less likely to occur even if discharge and discharge are repeated,
The positive electrode active material can be arranged at high density on the current collector,
The positive electrode active material has lithium fluoride in the surface layer,
The positive electrode active material contains magnesium,
Adjacent particles are difficult to sinter even when heated during the production process, and even if sintered, they are easily crushed,
The positive electrode active material is a composite oxide having a layered rock salt crystal structure, and is charged at a constant current until the battery voltage reaches 4.6 V (in the case of lithium as the counter electrode), and then the current value reaches 0.01C. It has a pseudo-spinel crystal structure when charged at a constant voltage up to
The pseudospinel crystal structure exhibits a crystal structure of space group R-3m, and when analyzed using powder XRD with CuKα1 radiation, 2θ=19.30±0.20° and 2θ=45. A positive electrode having a diffraction peak at 55±0.10° . In claim 1,
The positive electrode, wherein the positive electrode active material is a positive electrode active material with a standard deviation of an arithmetic mean particle size of 0.2 or less. In either claim 1 or claim 2,
The positive electrode active material has a surface fluorine binding energy peak position of more than 684.4 eV and less than 686.0 eV as measured by X-ray photoelectron spectroscopy. In any one of claims 1 to 3,
The positive electrode active material has first particles and second particles,
The positive electrode, wherein the median diameter of the second particles is 0.66 times or less the median diameter of the first particles. A positive electrode according to any one of claims 1 to 4 ;
A secondary battery having a negative electrode. A positive electrode active material, the positive electrode active material comprising:
The standard deviation of the arithmetic mean particle size is 0.2 or less,
A ratio A _R /A _i between the ideal specific surface area A _i obtained from the median diameter D50 and the actual specific surface area A _R is 2 or less,
The peak position of the binding energy of fluorine on the surface, as measured by X-ray photoelectron spectroscopy, is greater than 684.4 eV and less than 686.0 eV,
It has lithium fluoride on the surface layer,
has magnesium,
The positive electrode active material is a composite oxide having a layered rock salt crystal structure, and is charged at a constant current until the battery voltage reaches 4.6 V (in the case of lithium as the counter electrode), and then the current value reaches 0.01C. It has a pseudo-spinel crystal structure when charged at a constant voltage up to
The pseudospinel crystal structure exhibits a crystal structure of space group R-3m, and when analyzed using powder XRD with CuKα1 radiation, 2θ=19.30±0.20° and 2θ=45. A cathode active material having a diffraction peak at 55±0.10° . A positive electrode having the positive electrode active material according to claim 6 , a conductive aid, and a current collector;
a negative electrode;
A secondary battery having

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