Battery

Abstract

The positive electrode (23) contains lithium oxide that has an anti-fluorite crystal structure and in which a transition metal is solid-solved, and the electrolyte solution (29) contains a boron compound that contains at least one compound selected from the group consisting of a compound represented by formula (1) and a compound represented by formula (2). R1-R6 independently represent an alkyl group having 1-10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group in which at least one hydrogen atom is optionally substituted by a halogen atom or an alkyl group having 1-10 carbon atoms. At least one of R4-R6 may be a hydrogen atom. B (OR1) (OR2) (OR3) (1) BR4R5R6 (2)

Description

Technical Field

[0001] The present disclosure relates to batteries. Background Art

[0002] As described in Patent Document 1, the redox reaction between lithium oxide (Li2O) and lithium peroxide (Li2O2) has been known to be applicable to secondary batteries. However, one of the technical challenges is the poor electronic conductivity and high overvoltage of lithium oxide and lithium peroxide.

[0003] Patent Document 2 discloses that charge overvoltage can be reduced by forming a transition metal into a solid solution in the crystal structure of lithium oxide.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent No. 4554935

[0006] Patent Document 2: Japanese Patent No. 6179944 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In the conventional technology, there is room for improvement from the viewpoint of the cycle characteristics of batteries.

[0009] Means for solving problems

[0010] The present disclosure provides a battery comprising a positive electrode, a negative electrode, a separator and an electrolyte.

[0011] The positive electrode comprises lithium oxide having an inverse fluorite crystal structure and containing a transition metal in a solid solution as a positive electrode active material.

[0012] The electrolyte contains a boron compound,

[0013] The boron compound includes at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2).

[0014] B(OR 1 )(OR 2 )(OR 3 ) ・・・(1)

[0015] BR 4 R 5 R 6 ・・・(2)

[0016] In the formula (1), R 1 ~R 3are each independently an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group having at least one hydrogen atom optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms,

[0017] In the formula (2), R 4 ~R 6 are independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group in which at least one hydrogen atom is optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms. 4 ~R 6 Except for the case where all atoms are hydrogen.

[0018] Effects of the Invention

[0019] According to the technology disclosed herein, the cycle characteristics of a battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a cross-sectional view schematically showing the structure of a battery according to one embodiment of the present disclosure.

[0021] Figure 2 is a diagram showing the structural formula of a boron compound.

[0022] Figure 3A The figure shows the X-ray diffraction pattern of the positive electrode active material when the transition metal M1 is Co.

[0023] Figure 3B Shown is the X-ray diffraction pattern of the positive electrode active material when the transition metal M1 is Cu.

[0024] Figure 3C Shown is the X-ray diffraction pattern of the positive electrode active material when the transition metal M1 is Fe.

[0025] Figure 4A A SEM image of the positive electrode active material of Sample 3 is shown.

[0026] Figure 4B A SEM image of the positive electrode active material of Sample 17 is shown.

[0027] Figure 5 This is a graph showing the charge and discharge curves of Sample 1 and Sample 14.

[0028] Figure 6 This graph plots the calculation results of the integrated intensity ratio I2 / I1 and the integrated intensity ratio I3 / I1 of the positive electrode active materials of Samples 1 to 28. DETAILED DESCRIPTION

[0029] (Insights that form the basis of this disclosure)

[0030] By utilizing the redox reaction between lithium oxide and lithium peroxide, a battery with a higher theoretical capacity than conventional lithium-ion batteries can be obtained. The theoretical capacity is 897 mAh per 1g of lithium oxide. On the other hand, the lithium peroxide generated during charging is a peroxide and is therefore unstable and may decompose through reactions with the electrolyte. Furthermore, compared to conventional lithium-ion batteries with a charge current of 2.5V to 4.5V (vs. Li / Li + ) is charged and discharged, and in batteries using lithium oxide as the positive electrode active material, the voltage is 1.8V~3.4V (vs.Li / Li + ) for charge and discharge. This is because further increases in the charge potential generate oxygen. Specifically, the potential range used in batteries using lithium oxide as the positive electrode active material differs from that used in conventional lithium-ion batteries. Thus, lithium oxide-based positive electrode active materials have characteristics different from those used in conventional lithium-ion batteries. Consequently, detailed conditions for improving cycle characteristics, such as the composition of the electrolyte, are largely unknown.

[0031] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments.

[0032] (Implementation Method)

[0033] Figure 1 1 is a cross-sectional view showing a schematic structure of a battery 100 according to one embodiment of the present disclosure. The battery 100 includes a positive electrode 23, a negative electrode 26, an electrolyte 29, a separator 27, and an outer casing 28. The positive electrode 23 includes a positive electrode collector 21 and a positive electrode active material layer 22. The positive electrode active material layer 22 is disposed on the positive electrode collector 21. The negative electrode 26 includes a negative electrode collector 24 and a negative electrode active material layer 25. The negative electrode active material layer 25 is disposed on the negative electrode collector 24. A separator 27 is disposed between the positive electrode 23 and the negative electrode 26. The positive electrode 23 and the negative electrode 26 face each other with the separator 27 interposed therebetween. The positive electrode 23, the negative electrode 26, the separator 27, and the electrolyte 29 are housed in the outer casing 28. The battery 100 is typically a secondary battery.

[0034] The positive electrode active material layer 22 contains lithium oxide solid-dissolved (doped) with a transition metal M1 as the positive electrode active material. The lithium oxide solid-dissolved with the transition metal M1 has an inverse fluorite crystal structure. The inverse fluorite crystal structure is a structure in which the positional relationship between cations and anions in the fluorite structure is reversed (inverted). The reason why lithium oxide solid-dissolved with the transition metal M1 improves its electronic conductivity is not necessarily clear, but it is considered as follows. When the transition metal M1 is solid-dissolved in the lithium oxide, the transition metal M1 enters the lithium site, and oxygen atoms are tetrahedrally coordinated around the transition metal M1 to form an outer orbital complex. For example, in the case of cobalt, multiple unpaired electrons exist in the 3d orbital, and these unpaired electrons impart electronic conductivity to the lithium oxide. Furthermore, assuming the valence of the transition metal M1 is +3, since lithium has a valence of +1, in order to maintain charge neutrality within the crystal, two lithium atoms are released from the crystal in addition to the lithium atoms substituted with the transition metal M1, forming two vacancies. These pores serve as lithium ion conduction paths, thereby improving the ion conductivity of lithium oxide. The lithium oxide in which the transition metal M1 is solid-dissolved may be a substitutional solid solution.

[0035] The charge and discharge reaction formulas in the battery 100 are as follows.

[0036] Reaction at cathode 23: Li2O2 + 2Li + + 2e - ⇔ 2Li2O

[0037] Reaction at the negative electrode 26: Li ⇔ Li + + e -

[0038] The transition metal M1 is not particularly limited as long as it can be solid-dissolved in lithium oxide. The transition metal M1 can be, for example, an element selected from the group of elements of Groups 3 to 11 of Periods 4 and 5 of the periodic table. Specifically, the transition metal M1 can include at least one selected from Fe, Co, and Cu. The transition metal M1 can be Fe, Co, or Cu. These elements are preferred from the perspective of suppressing the increase in the charging voltage of the battery 100 and increasing the discharge capacity of the battery 100.

[0039] Lithium oxide containing a transition metal M1 solid solution in a discharged state can have the compositions represented by the following formulas (A) and (B). According to quantum science calculations, when the valence of the transition metal M1 is +3, α preferably satisfies the relationship 0.0327 ≤ α ≤ 0.1484. When the valence of the transition metal M1 is +2, α preferably satisfies the relationship 0.0490 ≤ α ≤ 0.2224.

[0040] When the valence of transition metal M1 is +3: (Li (1-3α) M1 α )2O・・・(A)

[0041] When the valence of transition metal M1 is +2: (Li (1-2α) M1 α )2O・・・(B)

[0042] The amount of lithium contained in the positive electrode active material is defined as m0 (mol). The amount of transition metal M1 contained in the positive electrode active material is defined as m1 (mol). The ratio (m1 / (m0+m1)) is, for example, not less than 0.01 and not more than 0.34. By appropriately adjusting the ratio (m1 / (m0+m1)), the increase in the charge voltage of the battery 100 can be suppressed while increasing the discharge capacity of the battery 100.

[0043] The positive electrode current collector 21 is a sheet or film made of a metal material such as aluminum, an aluminum alloy, stainless steel, titanium, or a titanium alloy. The sheet or film may be porous or non-porous. Examples of the sheet or film include metal foil and metal mesh. A carbon material may be coated on the surface of the positive electrode current collector 21 as an auxiliary conductive material.

[0044] The positive electrode active material layer 22 may contain other materials such as a conductive additive, an ion conductor, and a binder.

[0045] Conductive additives and ion conductors are used to reduce the resistance of the positive electrode 23. Examples of conductive additives include carbon materials and conductive polymer compounds. Examples of carbon materials include carbon black, graphite, acetylene black, carbon nanotubes, carbon nanofibers, graphene, fullerene, and graphite oxide. Examples of conductive polymer compounds include polyaniline, polypyrrole, and polythiophene. At least one selected from these conductive additives may be used.

[0046] Examples of ion conductors include gel electrolytes such as polymethacrylate and polymethyl methacrylate, organic solid electrolytes such as polyethylene oxide, and Li7La3Zr2O 12 Inorganic solid electrolytes such as ionic conductors and the like can be used.

[0047] The binder is used to improve the binding properties of the material constituting the negative electrode 26. Examples of the binder include polymer materials such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, styrene-butadiene copolymer rubber, polypropylene, polyethylene, and polyimide. At least one selected from these binders can be used.

[0048] The negative electrode current collector 24 is a sheet or film made of a metal material such as stainless steel, nickel, a nickel alloy, copper, or a copper alloy. The sheet or film may be porous or non-porous. Examples of the sheet or film include metal foil and metal mesh. A carbon material may be coated on the surface of the negative electrode current collector 24 as a conductive auxiliary material.

[0049] The negative electrode active material layer 25 may contain a negative electrode active material capable of absorbing and releasing lithium. Examples of negative electrode active materials capable of absorbing and releasing lithium include lithium titanate, graphite, silicon, silicon-containing oxides, zinc alloys, lithium metal, and lithium alloys. At least one selected from these negative electrode active materials may be used. As the negative electrode active material, lithium metal is more preferably used. The theoretical capacity of the positive electrode active material disclosed herein is 897 mAh per 1 g of lithium oxide, which is more than three times greater than other positive electrode active materials used in the past. Therefore, lithium metal is suitable as the negative electrode active material.

[0050] The negative electrode active material layer 25 may contain other materials such as a conductive additive, an ion conductor, and a binder. The conductive additive, ion conductor, and binder used in the positive electrode active material layer 22 may also be used in the negative electrode active material layer 25 .

[0051] The electrolyte 29 may be impregnated in the positive electrode 23, the negative electrode 26, and the separator 27. The electrolyte 29 may fill the internal space of the outer casing 28. The electrolyte 29 allows lithium ions to move between the positive electrode 23 and the negative electrode 26.

[0052] In this embodiment, the electrolyte 29 may contain a boron compound as an additive. The boron compound contains at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2). In formula (1), R 1 ~R 3 are independently an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group having at least one hydrogen atom optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms. 4 ~R 6 are independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group in which at least one hydrogen atom is optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms. 4 ~R 6 Except for the case where all atoms are hydrogen.

[0053] B(OR 1 )(OR 2 )(OR 3 ) ・・・(1)

[0054] BR4 R 5 R 6 ・・・(2)

[0055] The boron compound contained in the electrolyte 29 has the effect of improving the cycle characteristics of the battery 100. The reason for this is not necessarily clear, but it is presumed that the boron compound suppresses the dissolution of lithium peroxide generated by charging into the electrolyte 29.

[0056] In R 1 ~R 6 When an alkyl group is included, the number of carbon atoms of the alkyl group may be 1, 2 or more and 5 or less, or 2 or 3.

[0057] In formula (1), R 1 、R 2 and R 3 The boron compound having such a structure can improve the cycle characteristics of the battery 100. In addition, the boron compound having such a structure is easy to synthesize.

[0058] In formula (2), R 4 、R 5 and R 6 The boron compound having such a structure can improve the cycle characteristics of the battery 100. In addition, the boron compound having such a structure is easy to synthesize.

[0059] In R 1 ~R 6 When the boron compound contains a halogen atom, the halogen atom may be a fluorine atom. When the boron compound contains a fluorine atom, the effect of improving the cycle characteristics of the battery 100 tends to be enhanced.

[0060] The boron compound may include at least one selected from triethyl borate, tripropyl borate, triisopropyl borate, tris(2,2,2-trifluoroethyl) borate, tri(o-tolyl) borate, tris(pentafluorophenyl)borane, triphenyl borate, tris(hexafluoroisopropyl) borate, and tris(4-chlorophenyl) borate. These boron compounds can effectively improve the cycle characteristics of the battery 100.

[0061] The concentration of the boron compound in the electrolyte 29 is not particularly limited. The concentration of the boron compound in the electrolyte 29 is, for example, 0.01 mol / liter to 2.00 mol / liter, preferably 0.02 mol / liter to 0.50 mol / liter. By adjusting the concentration of the boron compound within an appropriate range, the effect of improving the cycle characteristics of the battery 100 can be sufficiently achieved.

[0062] In addition to the boron compound, the electrolyte 29 may also contain a non-aqueous solvent and a lithium salt. The boron compound is preferably dissolved in the non-aqueous solvent. This structure can easily improve the cycle characteristics of the battery 100.

[0063] As non-aqueous solvents, cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, cyclic esters, chain esters, fluorinated solvents, nitriles, etc. can be used. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of chain carbonates include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of cyclic ethers include tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane. Examples of chain ethers include 1,2-dimethoxyethane and 1,2-diethoxyethane. Examples of cyclic esters include γ-butyrolactone. Examples of chain esters include methyl acetate. Examples of fluorinated solvents include fluoroethylene carbonate, fluoromethyl propionate, fluorobenzene, fluoroethyl methyl carbonate, and fluorodimethyl carbonate. Examples of nitriles include acetonitrile. At least one selected from these non-aqueous solvents can be used.

[0064] Examples of lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(perfluoroethylsulfonyl)imide (LiN(SO2C2F5)2), LiAsF6, LiCF3SO3, and lithium difluoro(oxalato)borate. At least one selected from these lithium salts may be used.

[0065] The electrolyte 29 may include a gel electrolyte and / or an ionic liquid.

[0066] The gel electrolyte may be a material obtained by impregnating a polymer material with the electrolytic solution 29. Examples of the polymer material include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and polymers having ethylene oxide bonds.

[0067] Examples of cations constituting ionic liquids include aliphatic chain quaternary cations, aliphatic cyclic ammonium, and nitrogen-containing heterocyclic aromatic cations. Examples of aliphatic chain quaternary cations include tetraalkylammonium and tetraalkylphosphonium. Examples of aliphatic cyclic ammonium include pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium, and piperidinium. Examples of nitrogen-containing heterocyclic aromatic cations include pyridinium and imidazolium. Examples of anions constituting ionic liquids include PF6 - 、BF4 - 、SbF6 - 、AsF6 - 、SO3CF3- 、N(SO2F)2 - 、N(SO2CF3)2 - 、N(SO2C2F5)2 - 、N(SO2CF3)(SO2C4F9) - 、C(SO2CF3)3 - etc. The ionic liquid may contain a lithium salt.

[0068] The separator 27 is an electrolyte layer having lithium ion conductivity. The material of the separator 27 is not particularly limited as long as it allows lithium ions to pass through. The material of the separator 27 can be at least one selected from a solid electrolyte, a gel electrolyte, an ion exchange resin membrane, a semipermeable membrane, and a porous membrane. If the separator 27 is made of these materials, the safety of the battery 100 can be fully ensured. Examples of the solid electrolyte include sulfide solid electrolytes such as Li2S-P2S5, Li7La3Zr2O 12 (LLZ) and other oxide solid electrolytes. Examples of gel electrolytes include those containing fluororesins such as PVdF. Examples of ion exchange resin membranes include cation exchange membranes and anion exchange membranes. Examples of porous membranes include those made of polyolefin resins and those made of cellophane obtained by weaving glass fibers into nonwoven fabrics.

[0069] The outer casing 28 is made of, for example, a material obtained by laminating a metal foil such as aluminum foil with a resin film such as PET film. The outer casing 28 may be a container made of resin or metal.

[0070] The shape of the battery 100 is not limited to the laminated type, and other shapes of the battery 100 include a coin shape, a cylindrical shape, a square shape, a sheet shape, a button shape, and a flat shape.

[0071] Next, the positive electrode active material will be described in more detail.

[0072] The positive electrode active material may contain, in addition to lithium oxide containing a transition metal M1 in a solid solution, a transition metal oxide containing a transition metal M2. Including the transition metal oxide in the positive electrode active material can suppress increases in the charge voltage of the battery 100 and improve the discharge capacity of the battery 100.

[0073] The transition metal oxide containing the transition metal M2 has a crystal structure different from the crystal structure of lithium oxide in which the transition metal M1 is solid-dissolved. The transition metal oxide containing the transition metal M2 may contain a composite oxide containing lithium and the transition metal M2. The crystal structure of the composite oxide may be different from the crystal structure of lithium oxide. The transition metal oxide containing the transition metal M2 may not contain lithium. The transition metal oxide may contain a metal oxide containing only the transition metal M2 as a metal element. The transition metal oxide containing the transition metal M2 may contain at least one selected from a composite oxide containing lithium and the transition metal M2 and a metal oxide containing only the transition metal M2 as a metal element.

[0074] The transition metal M2 may be, for example, an element selected from the group of elements in Groups 3 to 11 of Periods 4 and 5 of the periodic table. The transition metal M2 may include, for example, at least one selected from Fe, Co, and Cu. The transition metal M2 may be Fe, Co, or Cu. These elements are preferred from the perspective of suppressing the increase in the charge voltage of the battery 100 and increasing the discharge capacity of the battery 100.

[0075] The transition metal M2 may be the same as or different from the transition metal M1 solid-dissolved in the crystals of lithium oxide. Typically, the transition metal M1 and the transition metal M2 are the same element or group of elements. The transition metal M1 and the transition metal M2 may be the same element. When the transition metal M1 and the transition metal M2 are the same element, it is easy to control the composition of the positive electrode active material. In addition, it has the advantages of easy manufacturing and the ability to reduce raw material costs. The transition metal oxide may be a residue of a raw material used to dissolve the transition metal M1 in lithium oxide, or it may be a by-product generated during the synthesis of the positive electrode active material.

[0076] When the positive electrode active material contains a transition metal oxide containing a transition metal M2, the amount of lithium oxide and the lithium contained in the transition metal oxide is defined as m0 (mol). The amount of transition metal M1 present in the positive electrode active material is defined as m1 (mol). The amount of transition metal M2 present in the positive electrode active material is defined as m2 (mol). The ratio (m1+m2) / (m0+m1+m2) is, for example, greater than 0.01 and less than 0.34. By appropriately adjusting the ratio (m1+m2) / (m0+m1+m2), the effect of suppressing the increase in charge voltage and the effect of increasing the discharge capacity are enhanced.

[0077] When the transition metal M1 and the transition metal M2 are the same element, the amount of substance m1 is the amount of substance of the transition metal M1 present in the positive electrode active material. The above ratio is represented by (m1 / (m0+m1)).

[0078] The presence of the transition metal oxide can be confirmed by X-ray diffraction measurement. The degree of solid solubility of the transition metal M1 in the lithium oxide and the preferred amount of the transition metal oxide can be determined based on multiple diffraction peaks attributable to the lithium oxide in which the transition metal M1 is solid-dissolved, and at least one diffraction peak attributable to the transition metal oxide.

[0079] In the X-ray diffraction pattern of the positive electrode active material measured using Cu-Kα radiation, the diffraction peak existing in the diffraction angle 2θ range of 30° to 40° is defined as the first diffraction peak. The diffraction peak existing in the diffraction angle 2θ range of 52° to 62° is defined as the second diffraction peak. The diffraction peak existing in the diffraction angle 2θ range of 40° to 50° is defined as the third diffraction peak. The first diffraction peak is a diffraction peak attributed to the (111) plane of lithium oxide. The second diffraction peak is a diffraction peak attributed to the (220) plane of lithium oxide. The third diffraction peak is a diffraction peak attributed to the crystal plane of the transition metal oxide. The integrated intensity of the first diffraction peak is defined as I1, the integrated intensity of the second diffraction peak is defined as I2, and the integrated intensity of the third diffraction peak is defined as I3. In this embodiment, the integrated intensity ratio I2 / I1 is 0.48 or greater, and the integrated intensity ratio I3 / I1 is 0.10 or greater and 1.30 or less. Meeting these conditions suppresses the increase in the charge voltage of the battery 100 and improves the discharge capacity of the battery 100. Suppressing the increase in the charge voltage is also related to suppressing the generation of oxygen.

[0080] The integrated intensity ratio I2 / I1 is an indicator of the degree of solid solubility of the transition metal M1 in lithium oxide crystals. When the valence of the transition metal M1 is +3, since lithium has a valence of +1, in addition to the lithium atoms substituted with the transition metal M1, two lithium atoms are released from the crystal to maintain charge neutrality within the crystal. The incorporation of the transition metal M1, which has a greater valence than lithium atoms, into the crystal and the release of two lithium atoms from the crystal to maintain charge neutrality induces slight strain in the crystal structure of the lithium oxide, the parent material. The greater this strain, the greater the integrated intensity ratio I2 / I1. Quantum science calculations show a proportional relationship between the amount of transition metal M1 doped in lithium oxide and the integrated intensity ratio I2 / I1. When the solid solubility of the transition metal M1 is sufficient, the effect of suppressing the charge voltage rise and increasing the discharge capacity are also enhanced. Furthermore, the theoretical integrated intensity ratio I2 / I1 for a Li2O crystal is approximately 0.33.

[0081] The integrated intensity ratio I3 / I1 is an indicator reflecting the amount of residues and / or by-products of the raw materials used to dissolve the transition metal M1 in lithium oxide. For example, when cobalt oxide or lithium cobalt oxide is used as a raw material to dissolve cobalt in lithium oxide, LiCoO2 is contained in the positive electrode active material as a residue and / or by-product. In this case, reflection from the (104) plane of LiCoO2 is observed as the third diffraction peak. As the amount of residues and / or by-products decreases, the diffraction intensity of the third diffraction peak decreases, and thus the integrated intensity ratio I3 / I1 also decreases. As the amount of residues and / or by-products increases, the diffraction intensity of the third diffraction peak increases, and thus the integrated intensity ratio I3 / I1 also increases. The composition and structure of the residues and / or by-products contained in the positive electrode active material can be judged based on the overall X-ray diffraction pattern including the third diffraction peak. When a transition metal oxide crystal is present, a diffraction peak appears within a range of a diffraction angle 2θ of 40° to 50°, regardless of the type of transition metal.

[0082] The reason why the effect of suppressing the rise of charging voltage and improving the discharge capacity is improved when the transition metal M1 is appropriately solid-dissolved in lithium oxide and the residues and / or by-products do not disappear but exist appropriately is not necessarily clear. The present inventors speculate as follows. During the charging process, lithium atoms are separated from lithium oxide, oxygen ions are oxidized and changed into peroxide ions, and lithium oxide is changed into lithium peroxide. Here, in the case where the positive electrode active material is composed only of a substance in which the transition metal M1 is completely solid-dissolved in lithium oxide, the volume shrinkage of the positive electrode active material during the charging process becomes larger, a gap is generated between the positive electrode active material and the conductive additive, the electronic resistance of the entire electrode increases, and the charging voltage rises. In contrast, according to the present disclosure, by appropriately containing residues and / or by-products containing transition metal M2 in the positive electrode active material, the charge compensation caused by the change in the valence of the transition metal M2 is utilized to suppress the volume shrinkage of the positive electrode active material during the charging process. As a result, the effect of suppressing the rise of charging voltage and the effect of improving the discharge capacity can be exerted. The acquisition of these effects is supported by the embodiments described below.

[0083] The lower limit of the integrated intensity ratio I2 / I1 may be 0.50 or 0.55. The upper limit of the integrated intensity ratio I2 / I1 is not particularly limited and may be 1.00 or 0.90. The integrated intensity ratio I2 / I1 may be 0.50 or more and 1.00 or less, 0.50 or more and 0.90 or less, 0.55 or more and 1.00 or less, or 0.55 or more and 0.90 or less.

[0084] The integrated intensity ratio I3 / I1 is preferably 0.20 or greater. The integrated intensity ratio I3 / I1 may be 1.10 or less, or 1.00 or less.

[0085] The ranges of the integrated intensity ratio I2 / I1 and the integrated intensity ratio I3 / I1 can be defined by any combination of the above values. For example, the integrated intensity ratio I2 / I1 can be set to be greater than 0.48, and the integrated intensity ratio I3 / I1 can be set to be greater than 0.20 and less than 1.10.

[0086] The integrated intensity ratio I2 / I1 can be set to 0.50 or more and 1.00 or less, and the integrated intensity ratio I3 / I1 can be set to 0.10 or more and 1.30 or less. The integrated intensity ratio I2 / I1 can be set to 0.50 or more and 1.00 or less, and the integrated intensity ratio I3 / I1 can be set to 0.20 or more and 1.10 or less. Alternatively, the integrated intensity ratio I2 / I1 can be set to 0.50 or more and 1.00 or less, and the integrated intensity ratio I3 / I1 can be set to 0.20 or more and 1.00 or less.

[0087] The integrated intensity ratio I2 / I1 can be set to be greater than or equal to 0.50 and less than or equal to 0.90, and the integrated intensity ratio I3 / I1 can be set to be greater than or equal to 0.10 and less than or equal to 1.30. The integrated intensity ratio I2 / I1 can be set to be greater than or equal to 0.50 and less than or equal to 0.90, and the integrated intensity ratio I3 / I1 can be set to be greater than or equal to 0.20 and less than or equal to 1.10. Alternatively, the integrated intensity ratio I2 / I1 can be set to be greater than or equal to 0.50 and less than or equal to 0.90, and the integrated intensity ratio I3 / I1 can be set to be greater than or equal to 0.20 and less than or equal to 1.00.

[0088] The integrated intensity ratio I2 / I1 can be set to 0.55 or more and 1.00 or less, and the integrated intensity ratio I3 / I1 can be set to 0.10 or more and 1.30 or less. The integrated intensity ratio I2 / I1 can be set to 0.55 or more and 1.00 or less, and the integrated intensity ratio I3 / I1 can be set to 0.20 or more and 1.10 or less. The integrated intensity ratio I2 / I1 can also be set to 0.55 or more and 1.00 or less, and the integrated intensity ratio I3 / I1 can be set to 0.20 or more and 1.00 or less.

[0089] The integrated intensity ratio I2 / I1 can be set to 0.55 or more and 0.90 or less, and the integrated intensity ratio I3 / I1 can be set to 0.10 or more and 1.30 or less. The integrated intensity ratio I2 / I1 can be set to 0.55 or more and 0.90 or less, and the integrated intensity ratio I3 / I1 can be set to 0.20 or more and 1.10 or less. Alternatively, the integrated intensity ratio I2 / I1 can be set to 0.55 or more and 0.90 or less, and the integrated intensity ratio I3 / I1 can be set to 0.20 or more and 1.00 or less.

[0090] The integrated intensity ratio I2 / I1 of Li2O crystals not doped with transition metal M1 is approximately 0.33. If the integrated intensity ratio I2 / I1 exceeds 0.33 while maintaining the inverse fluorite crystal structure of Li2O, it can be determined that the transition metal M1 is solid-dissolved in lithium oxide.

[0091] The positive electrode active material, for example, has a secondary particle structure composed of multiple primary particles of lithium oxide and multiple primary particles of a transition metal oxide. Positive electrode active materials having this structure can be efficiently produced using synthesis methods such as mechanochemical milling. The primary particles, for example, have a diameter in the nanometer range. The secondary particles, for example, have a diameter in the micrometer range.

[0092] The true density of the positive electrode active material is, for example, 2.0 g / cm 3 Above and 3.3g / cm 3 By appropriately adjusting the true density, the energy density of the battery 100 can be increased compared to conventional lithium secondary batteries. The true density can be measured by a pycnometer method after finely pulverizing the positive electrode active material.

[0093] The specific surface area of ​​the positive electrode active material is, for example, 1.6 m 2 / g or above and 60m 2 By appropriately adjusting the specific surface area, the energy density of the battery 100 can be increased. The specific surface area is a value obtained by the BET method.

[0094] The positive electrode active material may have a particle shape. Each particle of the positive electrode active material may have a particle size of 0.01 μm. 2 Above and 500μm 2 The following cross-sectional areas are present. By appropriately adjusting the particle size of the positive electrode active material, the cycle characteristics of the battery 100 can be improved. The cross-sectional area of ​​each particle of the positive electrode active material can be calculated using a cross-sectional SEM image of the positive electrode 23. All particles of the positive electrode active material may have a cross-sectional area within the above range, or only a portion of the particles (e.g., 90% or more by number) may have a cross-sectional area within the above range.

[0095] The positive electrode active material can be prepared, for example, by mechanochemical methods. First, lithium oxide powder and a raw material for the transition metal M1 are mixed to prepare a mixture. The ratio of lithium oxide to the raw material for the transition metal M1 can be determined so that the ratio (m1 / (m0+m1)) described above is within the desired range. Examples of the raw material for the transition metal M1 include oxides of the transition metal M1, composite oxides containing lithium and the transition metal M1, and single substances of the transition metal M1.

[0096] The synthesis of the positive electrode active material by a mechanochemical method is carried out using a device capable of exerting a mechanochemical effect, such as a ball mill or a bead mill. The atmosphere during the synthesis is not particularly limited and may be an atmospheric atmosphere, an inert atmosphere, a dry atmosphere, or a dry inert atmosphere. In order to suppress the mixing of inevitable impurities such as oxygen and water, the synthesis of the positive electrode active material is preferably carried out under a dry inert atmosphere. The inert atmosphere, for example, uses an inert gas such as nitrogen, argon, or helium.

[0097] By adjusting the rotational speed of the device, the processing time, the processing temperature, the size of the raw material particles, the composition of the raw material of the transition metal M1, the size of the pulverizing medium and other conditions, the degree of solid dissolution of the transition metal M1 into lithium oxide can be adjusted. In other words, the ratio of the integrated intensity I2 / I1 and the ratio of the integrated intensity I3 / I1 can be controlled. For example, as the rotational speed increases and the processing time increases, the solid dissolution of the transition metal M1 into lithium oxide progresses, so the ratio I2 / I1 increases and the ratio I3 / I1 decreases. By setting the manufacturing conditions so that the ratio of the integrated intensity I2 / I1 and the ratio of the integrated intensity I3 / I1 are within the desired range, a positive electrode active material that can suppress the rise in the charging voltage and increase the discharge capacity can be obtained.

[0098] (Other Implementation Methods)

[0099] (Note)

[0100] Based on the description of the above embodiments, the following technical solutions are disclosed.

[0101] (Technical Solution 1)

[0102] A battery comprising a positive electrode, a negative electrode, a separator and an electrolyte.

[0103] The positive electrode comprises lithium oxide having an inverse fluorite crystal structure and containing a transition metal in a solid solution as a positive electrode active material.

[0104] The electrolyte contains a boron compound,

[0105] The boron compound includes at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2).

[0106] B(OR 1 )(OR 2 )(OR 3 ) ・・・(1)

[0107] BR 4 R 5 R 6 ・・・(2)

[0108] In the formula (1), R 1 ~R 3are each independently an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group having at least one hydrogen atom optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms,

[0109] In the formula (2), R 4 ~R 6 are independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group in which at least one hydrogen atom is optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms. 4 ~R 6 Except for the case where all atoms are hydrogen.

[0110] According to such a technical configuration, the cycle characteristics of the battery can be improved.

[0111] (Technical Solution 2)

[0112] According to the battery of technical solution 1, in the formula (1), R 1 、R 2 and R 3 The boron compound having such a structure can sufficiently improve the cycle characteristics of the battery.

[0113] (Technical Solution 3)

[0114] According to the battery of technical solution 1 or 2, in the formula (2), R 4 、R 5 and R 6 The boron compound having such a structure can sufficiently improve the cycle characteristics of the battery.

[0115] (Technical Solution 4)

[0116] The battery according to any one of claims 1 to 3, wherein the halogen atom is a fluorine atom. When the boron compound contains a fluorine atom, the effect of improving the battery cycle characteristics tends to be enhanced.

[0117] (Technical Solution 5)

[0118] The battery according to any one of technical solutions 1 to 4, wherein the boron compound comprises at least one selected from triethyl borate, tripropyl borate, triisopropyl borate, tris(2,2,2-trifluoroethyl) borate, tri(o-tolyl) borate, tris(pentafluorophenyl)borane, triphenyl borate, tris(hexafluoroisopropyl) borate, and tris(4-chlorophenyl) borate. These boron compounds can reliably improve the cycle characteristics of the battery.

[0119] (Technical Solution 6)

[0120] According to any one of technical solutions 1 to 5, the concentration of the boron compound in the electrolyte is 0.01 mol / L or more and 2.00 mol / L or less. With this technical configuration, the effect of improving the cycle characteristics of the battery can be fully achieved.

[0121] (Technical Solution 7)

[0122] According to the battery of any one of technical solutions 1 to 6, the positive electrode active material has a particle shape, and the particles of the positive electrode active material have a diameter of 0.01 μm. 2 Above and 500μm 2 By appropriately adjusting the particle size of the positive electrode active material, the cycle characteristics of the battery can be improved.

[0123] (Technical Solution 8)

[0124] According to any one of technical solutions 1 to 7, the negative electrode contains lithium metal. With such a technical configuration, the energy density of the battery can be increased.

[0125] (Technical Solution 9)

[0126] According to any one of technical solutions 1 to 8, the positive electrode active material further comprises a transition metal oxide containing a transition metal M2, and in an X-ray diffraction pattern of the positive electrode active material measured using Cu-Kα radiation, the ratio of the integrated intensity of the second diffraction peak attributable to the (220) plane of the lithium oxide within a diffraction angle 2θ range of 52° to 62° to the integrated intensity of the first diffraction peak attributable to the (111) plane of the lithium oxide within a diffraction angle 2θ range of 30° to 40° is 0.48 or greater, and the ratio of the integrated intensity of the third diffraction peak attributable to the crystal plane of the transition metal oxide within a diffraction angle 2θ range of 40° to 50° to the integrated intensity of the first diffraction peak is 0.10 or greater and 1.30 or less. According to such a technical configuration, an increase in charge voltage can be suppressed and discharge capacity can be improved.

[0127] (Technical Solution 10)

[0128] According to the battery of claim 9, the positive electrode active material has a secondary particle structure composed of a plurality of primary particles of the lithium oxide and a plurality of primary particles of the transition metal oxide. A positive electrode active material having such a structure can be efficiently produced by various granulation methods.

[0129] Example

[0130] Each operation in preparing the positive electrode active material and battery production was performed in a dry atmosphere or an argon atmosphere. A dry atmosphere is an air atmosphere with a dew point of -40°C or less. Examples, comparative examples, and samples may include cases where the same operation was repeated multiple times to obtain a sufficient amount of sample.

[0131] [Preparation of electrolyte]

[0132] (Comparative Example 1)

[0133] Ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1:1 to obtain a mixed solvent. LiPF6 was dissolved in the mixed solvent at a concentration of 1 mol / L to obtain the electrolyte solution of Comparative Example 1.

[0134] (Examples 1 to 9)

[0135] The boron compounds shown in Table 1 were added to the electrolyte of Comparative Example 1 to obtain electrolytes of Examples 1 to 9. For boron compounds that are liquid at 20°C, the concentration of the boron compound in the electrolyte was adjusted to 5% by volume. For boron compounds that are solid at 20°C, the concentration of the boron compound in the electrolyte was adjusted to 0.050 mol / L. The structural formulas of the boron compounds shown in Table 1 are shown in FIG. Figure 2 .

[0136] Table 1

[0137]

[0138] [Production of positive electrode active material]

[0139] 1.00 g of Li₂O and 0.82 g of LiCoO₂ were ground and mixed in a mortar to obtain a mixture. This mixture, along with 45 g of zirconia balls (5 mm diameter), was placed in a planetary ball mill (Fritzsch GmbH, P-7 model, 45 mL container) and milled at 420 rpm for 100 hours. This yielded a positive electrode active material.

[0140] [Battery Production]

[0141] CR2016 coin cells were fabricated using the aforementioned positive electrode active material. The positive electrode used a positive electrode mixture containing the positive electrode active material, acetylene black, and polytetrafluoroethylene in a mass ratio of 7:2:1. Lithium metal was used as the negative electrode. A polyolefin porous membrane was used as the separator. 120 μL of the electrolytes from Examples 1 to 9 and Comparative Example 1 were used as the electrolyte.

[0142] [Charge and discharge test]

[0143] The batteries of the embodiment and comparative example were charged at a current value of 0.40 mA until the voltage reached 3.4 V. After a 20-minute pause, constant current discharge was performed at 0.40 mA until the voltage reached 1.8 V. After constant current discharge, constant voltage discharge was performed at 1.8 V until the current value reached 5 mA / g. The unit of current value "mA / g" represents the current value per 1 g of Li2O. This charge and discharge cycle was repeated 5 times. The discharge capacity of the first cycle, i.e., the initial discharge capacity, the discharge capacity of the fifth cycle, and the capacity retention rate are shown in Table 2. The capacity retention rate is the ratio of the discharge capacity of the fifth cycle to the initial discharge capacity. In Table 2, the unit of capacity "mAh / g" represents the capacity per 1 g of Li2O.

[0144] Table 2

[0145]

[0146] As shown in Table 2, the battery of Example containing the boron compound exhibited a higher capacity retention rate than the battery of Comparative Example 1 containing no boron compound.

[0147] [Dissolution test]

[0148] Ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 1 to prepare a mixed solvent. A boron compound is added to the mixed solvent at a concentration shown in Table 1 to prepare a solution containing the boron compound. A prescribed amount of lithium peroxide is added to the solution containing the boron compound and stirred, and the amount of lithium peroxide dissolved in the solution is visually observed. As a result, there is a correlation between the capacity maintenance rate shown in Table 2 and the amount of lithium peroxide dissolved. There is a tendency that the amount of lithium peroxide dissolved in the solution containing the boron compound in the embodiment showing a high capacity maintenance rate is small. Therefore, it can be understood that the higher the capacity maintenance rate shown in Table 2, the more the dissolution of lithium peroxide into the electrolyte can be suppressed.

[0149] Based on the above findings, the boron compound is preferably at least one selected from triethyl borate, tripropyl borate, triisopropyl borate, tri(2,2,2-trifluoroethyl) borate, tri(o-tolyl) borate, tri(pentafluorophenyl)borane and triphenyl borate, and more preferably at least one selected from triethyl borate, tripropyl borate and triphenyl borate.

[0150] Next, a plurality of positive electrode active materials having different production conditions and / or raw materials were prepared, and the charge voltage and discharge capacity of batteries using these positive electrode active materials were examined.

[0151] [Preparation of positive electrode active material: Co-based]

[0152] (Sample 1)

[0153] 1.00 g of Li₂O and 0.82 g of LiCoO₂ were ground and mixed in a mortar to obtain a mixture. This mixture, along with 45 g of zirconia balls (5 mm diameter), was placed in a planetary ball mill (Fritzsch GmbH, P-7 model, 45 mL container) and milled at 420 rpm for 100 hours. This yielded the positive electrode active material of Sample 1.

[0154] (Sample 2)

[0155] A positive electrode active material of Sample 2 was prepared in the same manner as Sample 1, except that the mixture was milled at 600 rpm for 36 hours.

[0156] (Sample 3)

[0157] The positive electrode active material of Sample 3 was prepared in the same manner as Sample 1, except that a planetary ball mill (manufactured by Fritsch GmbH, Model PL-7, 45 mL container) was used.

[0158] (Sample 4)

[0159] The positive electrode active material of Sample 4 was prepared at a different time using the same method as that of Sample 3. As described below, the main differences between Samples 3 and 4 are the volume ratio of vinylene carbonate in the battery electrolyte and the amount of the positive electrode mixture.

[0160] (Sample 5)

[0161] The positive electrode active material of Sample 5 was prepared in the same manner as Sample 1, except that 2.00 g of Li 2 O and 1.63 g of LiCoO 2 were used and the mixture was milled at 600 rpm for 100 hours.

[0162] (Sample 6)

[0163] The positive electrode active material for Sample 6 was prepared in the same manner as Sample 1, except that the mixture of 2.00 g of Li₂O and 1.63 g of LiCoO₂ was milled at 600 rpm for 100 hours and then heat-treated. Heat treatment was performed in an argon atmosphere at 250°C (ambient temperature) for 6 hours. The temperature was raised over a period of 1 hour, and after the heat treatment, the mixture was slowly cooled by allowing it to stand naturally.

[0164] (Sample 7)

[0165] 2.00 g of Li₂O and 1.34 g of Co₃O₄ were ground and mixed in a mortar to obtain a mixture. This mixture was placed in a planetary ball mill (Fritzsch GmbH, P-7, 45 mL container) along with 45 g of zirconia balls (5 mm diameter) and milled at 420 rpm for 100 hours. This yielded the positive electrode active material of Sample 7.

[0166] (Sample 8)

[0167] The positive electrode active material of Sample 8 was prepared in the same manner as Sample 1 except that 2.00 g of Li 2 O and 1.64 g of LiCoO 2 were used.

[0168] (Sample 9)

[0169] 5.00 g of Li₂O and 4.08 g of LiCoO₂ were ground and mixed in a mortar to obtain a mixture. This mixture, along with 98 g of zirconia balls (5 mm diameter), was placed in a planetary ball mill (PL-7, 80 mL container, manufactured by Fritsch GmbH) and milled at 420 rpm for 100 hours. This yielded the positive electrode active material of Sample 9.

[0170] (Sample 10)

[0171] The positive electrode active material of Sample 10 was prepared by the same method as Sample 9 except that the treatment time was changed to 150 hours.

[0172] (Sample 11)

[0173] The positive electrode active material of Sample 11 was prepared in the same manner as that of Sample 3. As described below, the main differences between Samples 3 and 11 are the volume ratio of vinylene carbonate in the battery electrolyte and the amount of the positive electrode mixture.

[0174] (Sample 12)

[0175] The positive electrode active material for Sample 12 was made from the same material as that for Sample 11 and was produced simultaneously. Specifically, a container for Sample 11 was placed at one position in the planetary ball mill, and a container for Sample 12 was placed at another position in the mill. As will be described later, the amount of positive electrode mixture used in the battery of Sample 12 differed from that used in the battery of Sample 11.

[0176] (Sample 13)

[0177] The positive electrode active material for Sample 13 was made from the same material as that for Sample 4 and was produced simultaneously. Specifically, a container for Sample 4 was placed at one position in the planetary ball mill, and a container for Sample 13 was placed at another position in the mill. As described later, the type of electrolyte and the amount of positive electrode mixture used in the battery of Sample 13 differed from those used in the battery of Sample 4 in terms of the type of electrolyte and the amount of positive electrode mixture.

[0178] (Sample 14)

[0179] The positive electrode active material of Sample 14 was prepared in the same manner as Sample 1, except that 2.00 g of Li 2 O and 1.64 g of LiCoO 2 were used and the treatment time was changed to 10 hours.

[0180] (Sample 15)

[0181] The positive electrode active material for Sample 15 was prepared using the same method as Sample 1, except that the mixture of 2.00 g of Li₂O and 1.63 g of LiCoO₂ was milled at 600 rpm for 100 hours and then heat-treated. Heat treatment was performed in an argon atmosphere at 350°C (ambient temperature) for 6 hours. The temperature was raised over a period of 1 hour, and after the heat treatment, the mixture was slowly cooled by allowing it to stand naturally.

[0182] (Sample 16)

[0183] The positive electrode active material for Sample 16 was prepared using the same method as Sample 1, except that the mixture of 2.00 g of Li₂O and 1.63 g of LiCoO₂ was milled at 600 μm for 100 hours and then heat-treated. Heat treatment was performed in an argon atmosphere at 450°C (ambient temperature) for 6 hours. The temperature rise took one hour, and after the heat treatment, the mixture was slowly cooled by allowing it to stand naturally.

[0184] [Production of positive electrode active material: Cu-based]

[0185] (Sample 17)

[0186] 2.00 g of Li₂O and 1.78 g of CuO were ground and mixed in a mortar to obtain a mixture. This mixture, along with 45 g of zirconia balls (5 mm diameter), was placed in a planetary ball mill (Fritzsch GmbH, P-7 model, 45 mL container) and milled at 600 rpm for 100 hours. This yielded the positive electrode active material of Sample 17.

[0187] (Sample 18)

[0188] The positive electrode active material of Sample 18 was prepared by the same method as Sample 17 except that 2.00 g of Li2O and 0.67 g of CuO were used.

[0189] (Sample 19)

[0190] The positive electrode active material of Sample 19 was prepared in the same manner as Sample 17 except that 1.99 g of Li2O and 1.14 g of CuO were used.

[0191] (Sample 20)

[0192] The positive electrode active material of Sample 20 was prepared by the same method as Sample 17 except that 2.00 g of Li2O and 1.43 g of CuO were used.

[0193] (Sample 21)

[0194] The positive electrode active material of Sample 21 was prepared by the same method as Sample 17, except that 1.99 g of Li 2 O and 0.66 g of CuO were used and the treatment time was changed to 48 hours.

[0195] (Sample 22)

[0196] The positive electrode active material of Sample 22 was prepared by the same method as Sample 17 except that 2.00 g of Li2O and 0.47 g of CuO were used.

[0197] [Production of positive electrode active material: Fe-based]

[0198] (Sample 23)

[0199] 2.00 g of Li₂O and 1.19 g of Fe₂O₃ were ground and mixed in a mortar to obtain a mixture. This mixture, along with 45 g of zirconia balls (5 mm diameter), was placed in a planetary ball mill (Fritzsch GmbH, P-7 model, 45 mL container) and milled at 600 rpm for 100 hours. This yielded the positive electrode active material of Sample 23.

[0200] (Sample 24)

[0201] The positive electrode active material of Sample 24 was prepared by the same method as Sample 23 except that 2.00 g of Li 2 O and 0.89 g of Fe 2 O 3 were used.

[0202] (Sample 25)

[0203] 2.00 g of Li₂O and 1.29 g of Fe₃O₄ were ground and mixed in a mortar to obtain a mixture. This mixture was placed in a planetary ball mill (Fritzsch GmbH, P-7, 45 mL container) along with 45 g of zirconia balls (5 mm diameter) and milled at 420 rpm for 100 hours. This yielded the positive electrode active material of Sample 25.

[0204] (Sample 26)

[0205] 5.00 g of Li₂O and 4.01 g of FeO were ground and mixed in a mortar to obtain a mixture. This mixture was placed in a planetary ball mill (PL-7, 80 mL container, manufactured by Fritsch GmbH) along with 98 g of zirconia balls (5 mm diameter) and milled at 420 rpm for 150 hours. This yielded the positive electrode active material of Sample 26.

[0206] (Sample 27)

[0207] The positive electrode active material of Sample 27 was prepared in the same manner as Sample 23 except that the mixture was milled at 420 rpm for 72 hours.

[0208] (Sample 28)

[0209] The positive electrode active material of Sample 28 was prepared in the same manner as Sample 23 except that 2.00 g of Li 2 O and 0.63 g of Fe 2 O 3 were used.

[0210] [X-ray diffraction measurement]

[0211] Powder X-ray diffraction measurement of the positive electrode active material was performed using a powder X-ray diffractometer (MiniFlex 600, manufactured by Rigaku Corporation) under the following measurement conditions.

[0212] Cu-Kα rays

[0213] Detector: HyPix400MF

[0214] Scan step: 0.02deg

[0215] Scanning speed: 2deg / min

[0216] 2θ: 10~80 degrees

[0217] The average spectrum of 8 measurements was used

[0218] Figure 3A The figure shows the X-ray diffraction pattern of the positive electrode active material when the transition metal M1 is Co. Figure 3BShown is the X-ray diffraction pattern of the positive electrode active material when the transition metal M1 is Cu. Figure 3C Shown is the X-ray diffraction pattern of the positive electrode active material when the transition metal M1 is Fe.

[0219] [Calculation of the integrated intensity ratio]

[0220] The X-ray diffraction pattern of each positive electrode active material was analyzed using analysis software (manufactured by OriginLab, OriginPro2022). That is, the integrated intensity I1 of the first diffraction peak, the integrated intensity I2 of the second diffraction peak, and the integrated intensity I3 of the third diffraction peak were calculated. When there are multiple peaks corresponding to the third diffraction peak, the Lorentz function or the Voigt function was used for peak separation. The integrated intensity of each separated peak was calculated, and their sum was regarded as the integrated intensity I3 of the third diffraction peak. For example, when Cu is used as the transition metal M1, the diffraction peak attributed to the reflection from the (013) plane of the Li2CuO2 crystal classified as the space group Immm and the diffraction peak attributed to the reflection from the (103) plane of the Li2CuO2 crystal appear in the range of diffraction angle 2θ of 40° to 50°. The sum of the integrated intensities of each peak is regarded as the integrated intensity I3 of the third diffraction peak.

[0221] The diffraction peak of Li2CuO2 (space group Immm) also appears at 49.94°, but this diffraction peak is proportional to the diffraction peak appearing in the range of 40° to 45° and its intensity is also weak. Therefore, as an indicator of the abundance ratio of Li2CuO2 to lithium oxide, only the integrated intensity of the diffraction peak appearing in the range of 40° to 45° is used in the calculation.

[0222] When Co was used as the transition metal M1, the diffraction peak attributed to reflection from the (104) plane of LiCoO2 crystals classified as space group R-3m was considered the third diffraction peak, and the integrated intensity I3 was calculated. When Fe was used as the transition metal M1, the diffraction peaks attributed to reflection from the (204) and (323) planes of Li5FeO4 were considered the third diffraction peak, and the integrated intensity I3 was calculated. The calculation results of the integrated intensity ratio I2 / I1 and the integrated intensity ratio I3 / I1 are shown in Table 3A.

[0223] LiCoO2 (space group R-3m) also has a diffraction peak at 49.77°, but this peak is proportional to the diffraction peak appearing in the 40° to 45° range and is also weaker in intensity. Therefore, as an indicator of the abundance ratio of LiCoO2 to lithium oxide, only the integrated intensity of the diffraction peak appearing in the 40° to 45° range is used in the calculation.

[0224] Table 3A

[0225]

[0226] [Observation using a scanning electron microscope (SEM)]

[0227] Figure 4A A SEM image of the positive electrode active material of Sample 3 is shown. Figure 4B The following shows an SEM image of the positive electrode active material of Sample 17. As can be seen from these SEM images, the positive electrode active materials of Samples 3 and 17 have a secondary particle structure. The positive electrode active materials of the other samples also have the same secondary particle structure.

[0228] [Determination of true density]

[0229] The true density of the positive electrode active materials of Samples 1 to 4, Sample 13, Samples 17 to 20, and Sample 22 was measured using a hydrometer method.

[0230] [Measurement of specific surface area]

[0231] The specific surface areas of the positive electrode active materials of Samples 3, 4, 11, and 12 were measured by the BET method.

[0232] [Battery Production]

[0233] CR2016 coin cell batteries were produced using the positive electrode active materials of Samples 1-28. The positive electrode used a positive electrode mixture containing the positive electrode active material, acetylene black, and polytetrafluoroethylene in a mass ratio of 7:2:1. A 0.3 mm thick lithium metal foil was used as the negative electrode. A three-layer separator consisting of non-woven fabric / polyolefin resin film / non-woven fabric was used as the separator. Samples 13-1, 13-2, and 13-3 were identical coin cell batteries using the positive electrode active material of Sample 13. The charge and discharge test conditions were different.

[0234] Electrolyte A used in the battery of Sample 1 was prepared by the following method. Ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1:1. Vinylene carbonate was added to the mixture of ethylene carbonate and diethyl carbonate at a ratio of 1% by volume to form a mixed solvent. LiPF6 was dissolved in the resulting mixed solvent at a concentration of 1 mol / L to prepare Electrolyte A.

[0235] Electrolyte B was prepared using the same method as Electrolyte A, except that the volume ratio of vinylene carbonate in the mixed solvent was changed to 5% by volume. Electrolyte C was prepared using the same method as Electrolyte A, except that the volume ratio of vinylene carbonate in the mixed solvent was changed to 10% by volume. Electrolyte D was prepared using the same method as Electrolyte A, except that vinylene carbonate was not used. Depending on the amount of vinylene carbonate, the performance of the battery will vary slightly. However, the effect brought about by vinylene carbonate reaches saturation at around 1% by volume, so the difference in battery performance caused by the amount of vinylene carbonate is small.

[0236] The types of electrolytes and the amounts of positive electrode mixtures used in the batteries of Samples 1 to 28 are shown in Table 3B.

[0237] Table 3B

[0238]

[0239] [Charge and discharge test]

[0240] (Sample 1)

[0241] The battery of Sample 1 was charged at a current of 64.7 mA / g, with the upper voltage limit set at 3.5 V and the upper limit of the charge capacity set at 647 mAh / g. The charge capacity, voltage at 500 mAh / g, and voltage at 600 mAh / g are shown in Table 4. After a 20-minute pause, the battery was discharged at a constant current of 64.7 mA / g to 1.0 V. The discharge capacities at voltages of 2.2 V, 2.0 V, 1.8 V, and 1.5 V are shown in Table 4.

[0242] The unit of capacity, "mAh / g," represents the capacity per 1g of Li2O. The unit of current value, "mA / g," represents the current value per 1g of Li2O.

[0243] (Sample 14)

[0244] The battery of Sample 14 was charged at a current of 64.7 mA / g, with the upper voltage limit set at 3.5 V and the upper limit of the charge capacity set at 647 mAh / g. The charge capacity, voltage at 500 mAh / g, and voltage at 600 mAh / g are shown in Table 4. After a 20-minute pause, the battery was discharged at a constant current of 64.7 mA / g to 1.5 V. The discharge capacities at voltages of 2.2 V, 2.0 V, 1.8 V, and 1.5 V are shown in Table 4.

[0245] Figure 5 Graphs showing charge and discharge curves of Sample 1 and Sample 14.

[0246] Table 4

[0247]

[0248] The difference between Sample 1 and Sample 14 lies in the amount of raw materials added and the grinding time. The charging voltage of the battery of Sample 14 reached 3.5V before the charging capacity reached 647mAh / g. Therefore, the discharge capacity of the battery of Sample 14 was small. In contrast, the charging voltage of the battery of Sample 1 was flat before reaching the upper limit of the charging capacity of 647mAh / g. In addition, the battery of Sample 1 showed a large discharge capacity. That is, in the battery of Sample 1, the rise in charging voltage was suppressed and the discharge capacity was improved. It is believed that the positive electrode active material of Sample 14 contains excessive raw material residues. In addition, although the amount of positive electrode mixture used in the battery of Sample 1 and the battery of Sample 14 is also different, the difference in the amount of positive electrode mixture has very little effect on the charging voltage and discharge capacity compared with the difference in the physical properties of the positive electrode active material.

[0249] Batteries of Samples 1 and 14 were repeatedly charged and discharged under the above conditions. For the batteries of Samples 1 and 14, the ratio of the discharge capacity at the second cycle to the charge capacity at the second cycle was calculated as the coulombic efficiency (unit: %). The results showed that the coulombic efficiency of the battery of Sample 1 was 99.7%. The coulombic efficiency of the battery of Sample 14 was 84.1%. The battery of Sample 1 also exhibited excellent coulombic efficiency.

[0250] (Sample 2)

[0251] The battery of Sample 2 was subjected to a charge and discharge test under the same conditions as those of Sample 1. The results are shown in Table 5.

[0252] (Sample 3)

[0253] The upper voltage limit was set at 3.4V, the upper limit of the charge capacity was set at 600mAh / g, and the battery of Sample 3 was charged at a current of 50.0mA / g. The charge capacity, voltage at 500mAh / g, and voltage at 600mAh / g are shown in Table 5. After a 20-minute pause, the battery was discharged at a constant current of 50.0mA / g to 1.8V. Then, discharge was continued at a constant voltage of 1.8V until the current reached 5mA / g. The discharge capacities at voltages of 2.2V, 2.0V, and 1.8V are shown in Table 5.

[0254] (Sample 4)

[0255] The battery of Sample 4 was charged at a current of 50.0 mA / g, with the upper voltage limit set at 3.4 V and the upper limit of the charge capacity set at 600 mAh / g. The charge capacity, voltage at 500 mAh / g, and voltage at 600 mAh / g are shown in Table 5. After a 20-minute pause, the battery was discharged at a constant current of 50.0 mA / g to 1.5 V. Then, constant voltage discharge at 1.5 V was performed for 66 hours. The discharge capacities at voltages of 2.2 V, 2.0 V, 1.8 V, and 1.5 V are shown in Table 5.

[0256] Table 5

[0257]

[0258] Sample 2 has a higher rotation speed and a shorter treatment time than Sample 1. By increasing the rotation speed, the increase in charge voltage was suppressed as in Sample 1, and the discharge capacity was increased.

[0259] Samples 3 and 4 were samples in which the model of the ball mill was different from that of Sample 1. Even with the change in the model of the ball mill, the increase in the charge voltage was suppressed and the discharge capacity was improved as in Sample 1.

[0260] The battery of Sample 2 was repeatedly charged and discharged under the above conditions. For the battery of Sample 2, the ratio of the discharge capacity at the second cycle to the charge capacity at the second cycle was calculated as the coulombic efficiency (unit: %). The coulombic efficiency of the battery of Sample 2 was 94.8%.

[0261] (Samples 5 to 7, Sample 15 and Sample 16)

[0262] The upper limit voltage was set to 3.4V, the lower limit voltage was set to 1.5V, the upper limit of the charge and discharge capacity of the first cycle was set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle was set to 400mAh / g, and the upper limit of the charge and discharge capacity of the third cycle was set to 500mAh / g. The batteries of samples 5 to 7, sample 15 and sample 16 were charged and discharged at a current value of 50.0mA / g. The pause time when migrating from the charging process to the discharging process was 20 minutes. During the discharge process, when 1.5V was reached before reaching the specified capacity, a constant voltage discharge of 1.5V was performed for 1 hour. The charge capacity of the third cycle and the voltage at 500mAh / g during the third cycle charge are shown in Table 6. The discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, 1.8V and 1.5V during the third cycle discharge is shown in Table 6.

[0263] (Sample 8)

[0264] The upper limit voltage is set to 3.4V, the lower limit voltage is set to 1.8V, the upper limit of the charge and discharge capacity of the first cycle is set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle is set to 400mAh / g, and the upper limit of the charge and discharge capacity of the third cycle is set to 500mAh / g. The battery of sample 8 is charged and discharged at a current value of 50.0mA / g. The pause time when moving from the charging process to the discharging process is 20 minutes. During the discharge process, the voltage did not reach 1.8V before reaching the specified capacity. The charging capacity of the third cycle and the voltage at 500mAh / g during the charging of the third cycle are shown in Table 6. The discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, and 1.8V during the discharge of the third cycle is shown in Table 6.

[0265] (Sample 9)

[0266] The upper limit voltage is set to 3.4V, the lower limit voltage is set to 1.8V, the upper limit of the charge and discharge capacity of the first cycle is set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle is set to 400mAh / g, and the upper limit of the charge and discharge capacity of the third cycle is set to 500mAh / g. The battery of sample 9 is charged and discharged with a current value of 50.0mA / g. The pause time when moving from the charging process to the discharge process is 20 minutes. During the discharge process, when 1.8V is reached before the specified capacity is reached, a constant voltage discharge of 1.8V is implemented and the discharge is carried out until the current value reaches a current value of 5mA / g. The charge capacity of the third cycle and the voltage at 500mAh / g during the charge of the third cycle are shown in Table 6. The discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, and 1.8V during the discharge of the third cycle is shown in Table 6.

[0267] (Sample 10)

[0268] The upper limit voltage was set to 3.4V, the lower limit voltage was set to 1.8V, the upper limit of the charge and discharge capacity of the first cycle was set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle was set to 400mAh / g, and the upper limit of the charge and discharge capacity of the third cycle was set to 500mAh / g. The battery of sample 10 was charged and discharged at a current value of 50.0mA / g. The pause time when migrating from the charging process to the discharging process was 20 minutes. During the discharge process, the voltage did not reach 1.8V before reaching the specified capacity. The charge capacity of the third cycle and the voltage at 500mAh / g during the charge of the third cycle are shown in Table 6. The discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, and 1.8V during the discharge of the third cycle is shown in Table 6.

[0269] (Samples 11 and 12)

[0270] The upper limit voltage was set to 3.4V, the lower limit voltage was set to 1.8V, the upper limit of the charge and discharge capacity of the first cycle was set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle was set to 500mAh / g, the upper limit of the charge and discharge capacity of the third cycle was set to 600mAh / g, and the upper limit of the charge and discharge capacity of the fourth cycle was set to 700mAh / g. The batteries of samples 11 and 12 were charged and discharged at a current value of 50.0mA / g. The pause time when migrating from the charging process to the discharging process was 20 minutes. During the discharge process, the voltage did not reach 1.8V before reaching the specified capacity. The charge capacity of the second cycle and the voltage at 500mAh / g during the charge of the second cycle are shown in Table 6. The discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, and 1.8V during the discharge of the second cycle is shown in Table 6.

[0271] Table 6

[0272]

[0273] The positive electrode active materials of Samples 5, 6, 15, and 16 were manufactured under identical conditions, except for the processing temperature. The battery of Sample 15 exhibited a slightly higher charge voltage and lower discharge capacity. The battery of Sample 16 exhibited both lower charge and discharge capacities. In contrast, the batteries of Samples 5 and 6 exhibited lower charge voltages and higher discharge capacities.

[0274] The battery of Sample 7 contained a positive electrode active material produced using Co₃O₄ as the raw material for the transition metal M1. The battery of Sample 8 contained a positive electrode active material produced using LiCoO₂ as the raw material for the transition metal M1. Whether using an oxide containing only Co or a composite oxide as the raw material for the transition metal M1, both achieved the effect of suppressing the increase in charge voltage and improving the discharge capacity.

[0275] Samples 9 to 12 were samples in which the model of the ball mill was different from that of Samples 5 to 8. Even with the change in the model of the ball mill, the increase in the charge voltage was suppressed and the discharge capacity was improved, similarly to Samples 5 to 8.

[0276] The ratio of the discharge capacity at the fourth cycle to the charge capacity at the fourth cycle was calculated as the coulombic efficiency (unit: %) for the batteries of Samples 11 and 12. The coulombic efficiency for both batteries of Samples 11 and 12 was 100.0%.

[0277] (Sample 13-1)

[0278] The upper voltage limit was set at 3.4V, the upper limit of the charge capacity was set at 600mAh / g, and the battery of sample 13-1 was charged at a current of 50.0mA / g. The charge capacity, the voltage at 500mAh / g, and the voltage at 600mAh / g are shown in Table 7A. After a 20-minute pause, constant current discharge was performed at a current of 50.0mA / g to 1.5V. Then, constant voltage discharge was performed at 1.5V until the voltage reached 5mA / g or 24 hours had passed. The discharge capacity at each voltage of 2.2V, 2.0V, 1.8V, and 1.5V is shown in Table 7A.

[0279] (Sample 13-2)

[0280] The upper voltage limit was set at 3.4V, the upper limit of the charge capacity was set at 647mAh / g, and the battery of sample 13-1 was charged at a current value of 64.7mA / g. The charge capacity, the voltage at 500mAh / g, and the voltage at 600mAh / g are shown in Table 7A. After a 20-minute pause, constant current discharge was performed at a current value of 50.0mA / g to 1.5V. Then, constant voltage discharge was performed at 1.5V until the voltage reached 5mA / g or 24 hours had passed. The discharge capacity at each voltage of 2.2V, 2.0V, 1.8V, and 1.5V is shown in Table 7A.

[0281] Table 7A

[0282]

[0283] The positive electrode active material used in the battery of Sample 13-1 and Sample 13-2 is the same. As shown in Table 7A, even when the charge-discharge test conditions were changed from those of Sample 13-1 to those of Sample 13-2, the increase in charge voltage was suppressed, and the discharge capacity was improved, similar to Sample 1.

[0284] (Sample 13-3)

[0285] The upper limit voltage was set to 3.4V, the lower limit voltage was set to 1.8V, the upper limit of the charge and discharge capacity of the first cycle was set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle was set to 400mAh / g, the upper limit of the charge and discharge capacity of the third cycle was set to 500mAh / g, the upper limit of the charge and discharge capacity of the fourth cycle was set to 600mAh / g, and the upper limit of the charge and discharge capacity of the fifth cycle was set to 700mAh / g. The battery of sample 13-3 was charged and discharged at a current value of 50.0mA / g. The pause time when transitioning from the charging process to the discharging process was 20 minutes. The charge capacity of the third cycle, the voltage at 500mAh / g during the charge of the third cycle, and the discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, and 1.8V during the discharge of the third cycle are shown in Table 7B. The charge capacity at the fifth cycle, the voltage at 700 mAh / g during charge at the fifth cycle, and the discharge capacity at voltages of 2.5 V, 2.2 V, 2.0 V, and 1.8 V during discharge at the fifth cycle are shown in Table 7C.

[0286] Table 7B

[0287]

[0288] Table 7C

[0289]

[0290] As shown in Table 7B and Table 7C, the battery of Sample 13-3 exhibited a low charge voltage and a large discharge capacity in both the 3rd cycle and the 5th cycle.

[0291] (Sample 21)

[0292] The upper limit voltage was set at 3.4V, the upper limit of the charge capacity was set at 533mAh / g, and the battery of Sample 20 was charged at a current value of 53.3mA / g. After a 20-minute pause, constant current discharge was performed at a current value of 53.3mA / g to 1.0V. This cycle was repeated three times. The charge capacity of the third cycle and the voltage at 200mAh / g during the third cycle of charge are shown in Table 8A. The discharge capacity at voltages of 2.2V, 2.0V, 1.8V, and 1.5V during the third cycle of discharge are shown in Table 8A.

[0293] (Samples 17 to 20 and Sample 22)

[0294] The upper limit voltage is set to 3.4V, the lower limit voltage is set to 1.5V, the upper limit of the charge and discharge capacity of the first cycle is set to 300mAh / g, the upper limit of the charge and discharge capacity of the second cycle is set to 400mAh / g, and the upper limit of the charge and discharge capacity of the third cycle is set to 500mAh / g. The batteries of samples 17 to 20 and sample 22 are charged and discharged at a current value of 50.0mA / g. The pause time when migrating from the charging process to the discharging process is 20 minutes. During the discharge process, when 1.5V is reached before the specified capacity is reached, a constant voltage discharge of 1.5V is performed for 1 hour. The charge capacity of the third cycle and the voltage at each capacity of the third cycle are shown in Table 8A. The discharge capacity at each voltage of 2.5V, 2.2V, 2.0V, 1.8V, and 1.5V during the discharge of the third cycle is shown in Table 8B.

[0295] Table 8A

[0296]

[0297] Table 8B

[0298]

[0299] The batteries of Samples 21 and 22 reached their upper voltage limit of 3.4 V at charge capacities of 240.8 mAh / g and 261.1 mAh / g, respectively. Furthermore, the discharge capacities of the batteries of Samples 21 and 22 were low. In contrast, the batteries of Samples 17 to 20 exhibited low charge voltages and large discharge capacities.

[0300] In the batteries of Sample 21 and Sample 22, the reasons for the high charge voltage and low discharge capacity can be attributed to the short treatment time and the small amount of CuO.

[0301] As shown in the results of Samples 17 to 20, when the transition metal M1 is Cu, similar to the case of Co, the effect of suppressing the increase in charge voltage and the effect of improving the discharge capacity are obtained.

[0302] (Samples 23 to 28)

[0303] The upper voltage limit was set at 3.4V, the upper limit of the charge capacity was set at 300mAh / g, and the batteries of Samples 23 to 28 were charged at a current of 50.0mA / g. The charge capacity, voltage at 200mAh / g, and voltage at 300mAh / g are shown in Table 9. After a 20-minute pause, constant-current discharge was performed at a current of 50.0mA / g to 1.5V (1.8V in Sample 26). Then, constant-voltage discharge was performed at 1.5V (1.8V in Sample 26) for 1 hour. The discharge capacities at voltages of 2.2V, 2.0V, 1.8V, and 1.5V are shown in Table 9.

[0304] Table 9

[0305]

[0306] The charging voltages of the batteries of samples 23 to 26 were lower than those of the batteries of samples 27 and 28. The discharge capacities of the batteries of samples 27 and 28 were small. In contrast, the batteries of samples 23 to 26 showed large discharge capacities.

[0307] The high charge voltage and low discharge capacity of the batteries of Samples 27 and 28 were due to the low rotation speed of the device, the short processing time, and the small amount of Fe.

[0308] As shown in the results of Samples 23 to 26, when the transition metal M1 is Fe, the effect of suppressing the charge voltage increase and improving the discharge capacity are achieved, similar to the cases of Co and Cu. Furthermore, the raw material for Fe as the transition metal M1 can be any of Fe2O3 (Samples 23 and 24), Fe3O4 (Sample 25), and FeO (Sample 26).

[0309] Figure 6 This graph plots the calculated results of the integrated intensity ratios I2 / I1 and I3 / I1 for the positive electrode active materials of samples 1 through 28. The horizontal axis represents the integrated intensity ratio I2 / I1. The vertical axis represents the integrated intensity ratio I3 / I1. The numbers "1, 2, 3, ... 28" represent samples 1 through 28, respectively. The integrated intensity ratio I2 / I1 for Li2O single crystals is approximately 0.33.

[0310] A small integrated intensity ratio I2 / I1 indicates a low degree of solid solubility of the transition metal M1. A large integrated intensity ratio I2 / I1 indicates a high degree of solid solubility of the transition metal M1. The integrated intensity ratio I2 / I1 of the batteries of samples 1 to 13, 17 to 20, and 23 to 26 was 0.48 or greater. It is believed that in these samples, the solid solubility of the transition metal M1 in the lithium oxide was sufficient, and the effect of improving electronic conductivity and ionic conductivity was fully achieved.

[0311] A small integrated intensity ratio (I3 / I1) indicates a low amount of residues and / or byproducts. A large integrated intensity ratio (I3 / I1) indicates a high amount of residues and / or byproducts. The integrated intensity ratios (I3 / I1) for batteries from samples 1 to 13, 17 to 20, and 23 to 26 were within the range of 0.10 to 1.30. This indicates that the positive electrode active materials used in these batteries contain moderate amounts of residues and / or byproducts.

[0312] Industrial availability

[0313] The technology disclosed herein can be used for batteries such as lithium secondary batteries.

Claims

1. A battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, The positive electrode comprises lithium oxide having an inverse fluorite crystal structure and containing a transition metal in a solid solution as a positive electrode active material. The electrolyte contains a boron compound, The boron compound includes at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2), B(OR 1 )(OR 2 )(OR 3 ) ・・・(1) BR 4 R 5 R 6 ・・・(2) In the formula (1), R 1 ~R 3 are each independently an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group having at least one hydrogen atom optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms, In the formula (2), R 4 ~R 6 are independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is optionally substituted by a halogen atom, or a phenyl group in which at least one hydrogen atom is optionally substituted by a halogen atom or an alkyl group having 1 to 10 carbon atoms, but R 4 ~R 6 Except for the case where all atoms are hydrogen.

2. The battery according to claim 1, In the formula (1), R 1 、R 2 and R 3 Have the same structure.

3. The battery according to claim 1, In the formula (2), R 4 、R 5 and R 6 Have the same structure.

4. The battery according to claim 1, The halogen atom is a fluorine atom.

5. The battery according to claim 1, The boron compound comprises at least one selected from triethyl borate, tripropyl borate, triisopropyl borate, tris(2,2,2-trifluoroethyl) borate, tri(o-tolyl) borate, tris(pentafluorophenyl)borane, triphenyl borate, tris(hexafluoroisopropyl) borate, and tris(4-chlorophenyl) borate.

6. The battery according to claim 1, The concentration of the boron compound in the electrolyte solution is 0.01 mol / liter or more and 2.00 mol / liter or less.

7. The battery according to claim 1, The positive electrode active material has a particle shape, The particles of the positive electrode active material have a diameter of 0.01 μm. 2 Above and 500μm 2 The following cross-sectional area.

8. The battery according to claim 1, The negative electrode includes lithium metal.

9. The battery according to claim 1, The positive electrode active material further comprises a transition metal oxide containing a transition metal M2, In the X-ray diffraction pattern of the positive electrode active material measured using Cu-Kα radiation, The ratio of the integrated intensity of the second diffraction peak attributable to the (220) plane of the lithium oxide existing in the range of the diffraction angle 2θ of 52° to 62° to the integrated intensity of the first diffraction peak attributable to the (111) plane of the lithium oxide existing in the range of the diffraction angle 2θ of 30° to 40° is 0.48 or more, A ratio of the integrated intensity of a third diffraction peak attributable to a crystal plane of the transition metal oxide existing within the diffraction angle 2θ range of 40° to 50° to the integrated intensity of the first diffraction peak is 0.10 or more and 1.30 or less.

10. The battery according to claim 9, The positive electrode active material has a secondary particle structure composed of a plurality of primary particles of the lithium oxide and a plurality of primary particles of the transition metal oxide.

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