Coated active material, positive electrode material, positive electrode, and battery

Abstract

A coated active material 100 according to the present disclosure comprises a positive electrode active material 101 and a coating layer 102 that covers at least a part of the surface of the positive electrode active material 101. The coating layer 102 contains a compound containing Li, M, and F, and in the compound, M is at least one element selected from the group consisting of metal elements other than Li and metalloid elements. The amount of F in the compound per unit surface area of the positive electrode active material 101 is 10 mg / m2 to 280 mg / m2, inclusive.

Description

Coated active material, positive electrode material, positive electrode, and battery

[0001] The present disclosure relates to coated active materials, positive electrode materials, positive electrodes, and batteries.

[0002] Patent Document 1 discloses a method for producing a composite active material by coating a positive electrode active material with an oxide solid electrolyte and further coating the coated material with a sulfide solid electrolyte, and a battery using the composite active material.

[0003] JP 2016-18735 A

[0004] The present disclosure provides a coated active material that can reduce the internal resistance of a battery.

[0005] The present disclosure provides a cathode active material comprising: a cathode active material; and a coating layer that coats at least a portion of a surface of the cathode active material, wherein the coating layer contains a compound containing Li, M, and F, wherein the M in the compound is at least one element selected from the group consisting of metal elements and semi-metal elements other than Li, and the amount of F in the compound per unit surface area of ​​the cathode active material is 10 mg / m 2 or more and 280 mg / m 2 The present invention provides a coated active material comprising:

[0006] According to the present disclosure, it is possible to provide a coated active material that can reduce the internal resistance of a battery.

[0007] Fig. 1 is a cross-sectional view showing a schematic configuration of a coated active material according to embodiment 1. Fig. 2 is a cross-sectional view showing a schematic configuration of a positive electrode material according to embodiment 2. Fig. 3 is a cross-sectional view showing a schematic configuration of a battery according to embodiment 3.

[0008] (Findings that Form the Basis of the Present Disclosure) The present inventors conducted extensive research into the internal resistance of lithium-ion batteries and the factors that increase that resistance. As a result, they discovered that a product produced by the oxidation reaction of the electrolyte functions as a resistive layer, which increases the internal resistance of the battery. Furthermore, the present inventors discovered that fluorine compounds are effective in suppressing such electrolyte oxidation reactions. However, fluorine compounds themselves generally have high resistance. Therefore, as a result of further extensive research, the present inventors discovered that the resistance of lithium-ion batteries can be reduced by coating the surface of the positive electrode active material with an appropriate amount of fluorine compound.

[0009] From these findings, the inventors have come up with the technique of the present disclosure.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] (Embodiment 1) Fig. 1 is a cross-sectional view showing a schematic configuration of a coated active material according to embodiment 1. The coated active material 100 includes a positive electrode active material 101 and a coating layer 102. The coating layer 102 includes a compound containing Li, M, and F. In the compound, M is at least one element selected from the group consisting of metal elements and semi-metal elements other than Li. The coating layer 102 coats at least a portion of the surface of the positive electrode active material 101. The coating layer 102 may coat the entire surface of the positive electrode active material 101, or may coat only a portion of the surface of the positive electrode active material 101.

[0012] In the coated active material 100 according to the first embodiment, the amount of F of the compound per unit surface area of ​​the positive electrode active material 101 is 10 mg / m 2 or more and 280 mg / m 2 The following is the result.

[0013] "Metalloid elements" include B, Si, Ge, As, Sb, and Te.

[0014] The term "metal element" includes all elements included in Groups 1 to 12 of the periodic table excluding hydrogen, and all elements included in Groups 13 to 16 of the periodic table excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, metal elements are a group of elements that can become cations when forming inorganic compounds with halogen elements.

[0015] Hereinafter, the compound containing Li, M, and F may be simply referred to as a "fluorine compound." Furthermore, the amount of F in the coating compound per unit surface area of ​​the positive electrode active material 101 may be simply referred to as an "F amount."

[0016] Fluorine compounds have excellent oxidation resistance. Therefore, by coating the positive electrode active material 101 with a fluorine compound, oxidation of the electrolyte contained in the positive electrode including the coated active material 100 can be suppressed. This allows the internal resistance of a battery including a positive electrode including the coated active material 100 to be reduced.

[0017] In the coated active material 100, the amount of F is 10 mg / m 2 By setting the F amount to 280 mg / m or more, the positive electrode active material 101 is covered with a fluorine compound having a sufficient thickness, and therefore the oxidation reaction of the electrolyte can be sufficiently suppressed. 2 When the F amount is 10 mg / m or less, the positive electrode including the coated active material 100 can have sufficient electronic conductivity. 2 or more and 280 mg / m 2 According to the coated active material 100 described below, the internal resistance of the battery can be reduced.

[0018] In addition, the amount of F is 10 mg / m 2 or more and 280 mg / m 2 According to the coated active material 100 described below, the durability of the battery can also be improved.

[0019] Here, in the coated active material 100 according to the first embodiment, the surface area of ​​the positive electrode active material 101 is calculated by the specific surface area (m ) calculated by the following formula (A) using the area average diameter (diameter) obtained from the particle size distribution of the positive electrode active material 101 obtained by image analysis. 2 / g).

[0020] Specific surface area (m 2 / g) = 6÷(area average diameter (μm) x density (g / cm 3 )) ...Formula (A)

[0021] The image of the positive electrode active material 101 used in determining the particle size distribution of the positive electrode active material 101 may be, for example, a dynamic image obtained by continuously photographing flowing particles (wet or dry) of the positive electrode active material 101 with, for example, a CCD camera, or may be an electron microscope image obtained by photographing with an electron microscope a cross section of the coated active material 100 or a cross section of a positive electrode including the coated active material 100. At least 3,000 particles of the positive electrode active material 101 are used to measure the particle size distribution of the positive electrode active material 101.

[0022] The particle size distribution and area average diameter of the positive electrode active material 101 obtained by image analysis can be measured, for example, by an image particle size distribution measuring device.

[0023] An example of the measurement method will be described. The positive electrode active material 101 is placed in ethanol and dispersed using an ultrasonic homogenizer to prepare a measurement sample. Using a dynamic image analysis particle size analysis system (e.g., Particle Size Analysis System XPT manufactured by PSprozesstechnik), the measurement sample is introduced into the device and observed with a CCD camera, whereby the particle size distribution and area average diameter can be measured.

[0024] For example, a pycnometer method is used to measure the density of the positive electrode active material 101. A gas pycnometer that measures by gas substitution may also be used.

[0025] The amount of fluorine element in the fluorine compound contained in the coating layer 102 is measured, for example, by combustion ion chromatography. Specifically, the coated active material 100 is mixed with a combustion improver (e.g., WO3) and combusted. The combustion gas is collected with an absorbent and quantitatively analyzed by ion chromatography to determine the amount of fluorine element. For the coated active material 100 contained in the positive electrode, the coated active material 100 is removed from the positive electrode, and the amount of fluorine element is determined using combustion ion chromatography. An appropriate method for removing the coated active material 100 from the positive electrode can be selected, taking into account the characteristics of the material constituting the positive electrode. If it is difficult to remove the coated active material 100 from the positive electrode, an elemental map of the cross section of the positive electrode can be obtained using energy dispersive X-ray spectroscopy (STEM-EDX) in combination with a scanning transmission electron microscope, and the amount of fluorine element in the fluorine compound contained in the coating layer 102 can be determined using the elemental map.

[0026] The amount of F is 19 mg / m 2 or more, and 2 or more, and 2 or more, and 2 or more, and 2 The amount of F may be 275 mg / m or more. 2 or less, 240 mg / m 2 or less, 237 mg / m 2 or less, and 2 or less, 143 mg / m 2 The upper and lower limits of the amount of F may be defined by any combination selected from the above numerical values.

[0027] The amount of F is 19 mg / m 2 or more and 275 mg / m 2 or less, and 2 or more and 240 mg / m 2 or less, and 2 or more and 237 mg / m 2 or less, and 2or more and 150 mg / m 2 or less, and 2 or more and 143 mg / m 2 The F content in the coated active material 100 may be within the above range, thereby further reducing the internal resistance of the battery. Furthermore, the F content in the coated active material 100 may be within the above range, thereby achieving both a reduction in the internal resistance of the battery and improved durability of the battery.

[0028] The coating layer 102 may contain a fluorine compound containing Li, M, and F as a main component, or may contain only the fluorine compound. "Main component" refers to the component that is contained in the largest amount by mass. "Containing only a fluorine compound" means that, with the exception of inevitable impurities, no materials other than the fluorine compound are intentionally added. For example, the raw materials for the fluorine compound and by-products generated when producing the fluorine compound are included as inevitable impurities. The mass ratio of the inevitable impurities to the total mass of the coating layer 102 may be 5% or less, 3% or less, 1% or less, or 0.5% or less.

[0029] In the fluorine compound contained in the coating layer 102, M may contain at least one selected from the group consisting of Al, Ti, Zr, Si, Y, Ca, Mg, Nb, Ta, Mo, W, Ni, and Zn. When the fluorine compound contains these elements, the coated active material 100 can be expected to be highly effective in various aspects, such as improving ionic conductivity and changing mechanical properties.

[0030] In addition to the above-mentioned fluorine compound, the coating layer 102 may further contain at least one selected from the group consisting of lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesium oxide.

[0031] The ratio of the amount of substance of F to the total amount of substance of the anions constituting the fluorine compound contained in the coating layer 102 may be 0.5 or more and 1.0 or less. This configuration can improve the oxidation resistance of the coated active material 100. The fluorine compound may contain, for example, O (oxygen) as an anion constituting the fluorine compound.

[0032] The ratio of the amount of substance of F to the total amount of substance of the anions constituting the fluorine compound may be 1.0. That is, the anion constituting the fluorine compound may be only F. This configuration can further improve the oxidation resistance of the coated active material 100.

[0033] In the fluorine compound contained in the coating layer 102, the ratio of the amount of substance of Li to the total amount of substances of cations other than Li may be 2.3 or more and 6 or less. With this configuration, the coated active material 100 can further reduce the internal resistance of the battery.

[0034] The fluorine compound contained in the coating layer 102 may be represented by the following composition formula (1): Li 6-αy (Me 1-x Al x ) y F6 ... composition formula (1) Here, in composition formula (1), Me is at least one element selected from the group consisting of metal elements and semimetal elements other than Li and Al, and α is (Me 1-x Al x ) is the average valence of 0<x≦1 and 0<y≦1.5.

[0035] The fluorine compound contained in the coating layer 102 may contain a crystalline phase represented by the above composition formula (1).

[0036] When the fluorine compound contained in the coating layer 102 is a compound represented by the above composition formula (1), the coated active material 100 can further reduce the internal resistance of the battery.

[0037] In the composition formula (1), Me may be at least one selected from the group consisting of Ti and Zr.

[0038] For example, when Me in the composition formula (1) is at least one selected from the group consisting of Ti and Zr, the fluorine compound contained in the coating layer 102 may include a compound represented by the following composition formula (2): Li 6-(4-x) y (Me 1-x Al x ) y F6...composition formula (2)

[0039] The fluorine compound contained in the coating layer 102 may contain a crystalline phase represented by the above composition formula (2).

[0040] When the fluorine compound contained in the coating layer 102 includes a compound represented by the above composition formula (2), the coated active material 100 can further reduce the internal resistance of the battery and further improve the durability of the battery.

[0041] The positive electrode active material 101 includes a material having the property of absorbing and releasing metal ions (e.g., lithium ions). Examples of the positive electrode active material 101 that can be used include lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. In particular, when a lithium-containing transition metal oxide is used as the positive electrode active material 101, the manufacturing cost of the battery can be reduced and the average discharge voltage can be increased.

[0042] The positive electrode active material 101 may include a lithium-nickel-containing oxide containing Li and Ni and having a layered rock salt structure. This configuration allows the coated active material 100 to further reduce the internal resistance of the battery. In this case, the ratio of the amount of Ni to the total amount of cations other than Li in the positive electrode active material 101 may be 0.6 or greater. This configuration is expected to result in a battery with high capacity and low resistance. Furthermore, because the density of the lithium-nickel-containing oxide with a Ni-containing layered rock salt structure does not change significantly even when replaced with a replaceable element, a typical value of 4.7 may be used.

[0043] Positive electrode active material 101 may contain a material that can be used as an active material for a lithium ion battery, in addition to the lithium nickel-containing oxide described above.

[0044] Examples of materials that can be used as active materials in lithium ion batteries include LiCoO2, LiNi x Co 1-x O2 (0<x<0.5), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, heteroelement-substituted Li-Mn spinel (e.g., LiMn 1.5 Ni 0.5 O4, LiMn 1.5 A l0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4 or LiM n1.5 Zn 0.5 O4), lithium titanate (e.g., Li4Ti5O 12 ), lithium metal phosphates (e.g., LiFePO4, LiMnPO4, LiCoPO4, or LiNiPO4), transition metal oxides (e.g., VO5, MoO3).

[0045] Among the above materials, LiCoO2, LiNi x Co 1-x O2 (0<x<0.5), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Lithium-containing composite oxides selected from O2, LiMnO2, heteroelement-substituted Li-Mn spinel, lithium metal phosphate, and the like are preferred.

[0046] The positive electrode active material 101 has, for example, a particle shape. There are no particular limitations on the shape of the particles of the positive electrode active material 101. The shape of the particles of the positive electrode active material 101 may be spherical, oval, scaly, or fibrous.

[0047] The specific surface area of ​​the positive electrode active material 101 is 0.05 m 2 / g or more and 1.00m 2 / g or less, and 2 / g or more and 0.50m 2As described above, in this specification, the specific surface area of ​​the positive electrode active material 101 is the specific surface area calculated by the above formula (A) using the area average diameter calculated from the particle size distribution of the positive electrode active material 101 obtained by image analysis.

[0048] The fluorine compound contained in the coating layer 102 may be produced, for example, by the following method.

[0049] Raw material powders are prepared and mixed to obtain the desired composition.

[0050] As an example, when the target composition is LiAlF, LiF and AlF are mixed in a molar ratio of about 3: 1. The raw material powders may be mixed in a pre-adjusted molar ratio to offset composition changes that may occur during the synthesis process.

[0051] The raw material powders are reacted with each other mechanochemically (i.e., using a mechanochemical milling method) in a mixing device such as a planetary ball mill to obtain a reactant. The reactant may be fired in a vacuum or in an inert atmosphere. Alternatively, a mixture of the raw material powders may be fired in a vacuum or in an inert atmosphere to obtain a reactant. The firing is carried out, for example, at a temperature of 100°C or higher and 400°C or lower for one hour or longer. To suppress compositional changes during firing, the raw material powders may be fired in a sealed container such as a quartz tube.

[0052] The coated active material 100 can be produced by the following method.

[0053] A powder of the positive electrode active material 101 and a powder of the material for the coating layer 102 are mixed in an appropriate ratio to obtain a mixture. The mixture is then milled to impart mechanical energy to the mixture. A mixing device such as a ball mill can be used for the milling process. To suppress oxidation of the materials, the milling process may be performed in a dry and inert atmosphere.

[0054] The coated active material 100 may be manufactured by a dry particle compounding method. The treatment by the dry particle compounding method includes applying at least one mechanical energy selected from the group consisting of impact, compression, and shear to the positive electrode active material 101 and the material of the coating layer 102. The positive electrode active material 101 and the material of the coating layer 102 are mixed in an appropriate ratio.

[0055] The device used in producing the coated active material 100 is not particularly limited, and may be a device that can apply mechanical energy of impact, compression, and shear to a mixture of the positive electrode active material 101 and the material of the coating layer 102. Examples of devices that can apply mechanical energy include a ball mill and a compression shear processing device (particle composite device) such as "Mechanofusion" (manufactured by Hosokawa Micron Corporation) or "Nobilta" (manufactured by Hosokawa Micron Corporation).

[0056] "Mechanofusion" is a particle compounding device that uses a dry mechanical compounding technology by applying strong mechanical energy to multiple different raw material powders. In mechanofusion, raw material powders are placed between a rotating container and a press head, and mechanical energy of compression, shear, and friction is applied to them. This causes the particles to compound.

[0057] "Nobilta" is a particle compounding device that uses dry mechanical compounding technology, an advanced form of particle compounding technology, to compound nanoparticles as raw materials. Nobilta produces composite particles by applying mechanical energy of impact, compression, and shear to multiple types of raw material powders.

[0058] In the Nobilta, a rotor positioned to have a predetermined gap between itself and the inner wall of a horizontal cylindrical mixing vessel rotates at high speed, forcing the raw material powder through the gap, a process that is repeated multiple times. This applies impact, compression, and shear forces to the mixture, allowing composite particles of the positive electrode active material 101 and the material of the coating layer 102 to be produced. By adjusting conditions such as the rotor rotation speed, processing time, and feed amount, the thickness of the coating layer 102, the coverage of the positive electrode active material 101 by the material of the coating layer 102, and the like can be controlled.

[0059] However, processing using the above-mentioned equipment is not required. The coated active material 100 may be produced by mixing the positive electrode active material 101 and the material for the coating layer 102 using a mortar, mixer, or the like. The material for the coating layer 102 may be deposited on the surface of the positive electrode active material 101 by various methods, such as spraying, spray-dry coating, electrodeposition, immersion, or mechanical mixing using a disperser. A lithium-nickel-containing oxide having a layered rock salt structure is characterized by its tendency to react with water as the Ni ratio increases. For example, a reaction layer is likely to form on the surface of the active material particles upon reaction with water, which then becomes a resistive layer during charge and discharge, resulting in a decrease in battery performance. Therefore, when a lithium-nickel-containing oxide having a layered rock salt structure with a high Ni ratio is used as the material for the coating layer 102, a coating method that does not use water is desirable, although it is not a required condition.

[0060] (Embodiment 2) Fig. 2 is a cross-sectional view showing a schematic configuration of a cathode material according to embodiment 2. The cathode material 200 includes a coated active material 100 and a first solid electrolyte 201. The coated active material 100 is the coated active material 100 described in embodiment 1. As described in embodiment 1, the coated active material 100 can reduce the internal resistance of a battery. As a result, the cathode material 200 can reduce the internal resistance of a battery.

[0061] In the positive electrode material 200, the first solid electrolyte 201 and the coated active material 100 may be in contact with each other. In this case, the coating layer 102 and the first solid electrolyte 201 are in contact with each other. The positive electrode material 200 may include a plurality of particles of the first solid electrolyte 201 and a plurality of particles of the coated active material 100.

[0062] The median diameter of the coated active material 100 may be 0.1 μm or more and 100 μm or less. When the median diameter of the coated active material 100 is 0.1 μm or more, the coated active material 100 and the first solid electrolyte 201 can form a well-dispersed state in the positive electrode material 200. As a result, the charge / discharge characteristics of the battery are improved. Furthermore, when the median diameter of the coated active material 100 is 100 μm or less, the diffusion rate of lithium within the coated active material 100 is sufficiently ensured. This enables the battery 300 to operate at high power.

[0063] The median diameter of coated active material 100 may be larger than the median diameter of first solid electrolyte 201. This allows positive electrode active material 101 and first solid electrolyte 201 to form a well-dispersed state.

[0064] In the present disclosure, the term "median diameter" refers to the particle size at which the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction measurement device or an image analysis device.

[0065] Note that the coated active material 100, the positive electrode active material 101, and the coating layer 102 are as described in Embodiment 1, and therefore detailed description thereof will be omitted here. The first solid electrolyte 201, other materials contained in the positive electrode material 200, and a method for manufacturing the positive electrode material 200 will be described below.

[0066] The first solid electrolyte 201 may include at least one selected from the group consisting of a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte.

[0067] The halide solid electrolyte may be a compound represented by the following composition formula (3): Li α M1 β X1 γ ...Composition formula (3) where α, β, and γ are values ​​greater than 0. M1 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li. X1 is at least one element selected from the group consisting of F, Cl, Br, and I.

[0068] As the first solid electrolyte 201, for example, Li3YX16, Li2MgX14, Li2FeX14, Li(Al, Ga, In)X14, Li3(Al, Ga, In)X16, etc. can be used.

[0069] In the present disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0070] According to the above configuration, the resistance of the battery can be reduced, thereby improving the charge / discharge characteristics of the battery.

[0071] The composition formula (3) may satisfy 2.5≦α≦3, 1≦β≦1.1, and γ=6.

[0072] In the composition formula (3), X1 may include at least one selected from the group consisting of Cl and Br.

[0073] In the composition formula (3), M1 may contain yttrium (Y).

[0074] As the solid electrolyte containing Y, for example, Li a M1' b Y c The compound may be a compound represented by the composition formula X16, where a + mb + 3c = 6 and c > 0. M1' is at least one element selected from the group consisting of metal elements and metalloid elements other than Li and Y. m represents the valence of M1'.

[0075] As M1′, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb may be used.

[0076] Specific examples of solid electrolytes containing Y include Li3YF6, Li3YCl6, Li3YBr6, Li3YI6, Li3YBrCl5, Li3YBr3Cl3, Li3YBr5Cl, Li3YBr5I, Li3YBr3I3, Li3YBrI5, Li3YClI5, Li3YCl3I3, Li3YCl5I, Li3YBr2Cl2I2, Li3YBrCl4I, Li 2.7 Y 1.1 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 Y 0.3 Zr 0.7 Cl6, etc. may be used.

[0077] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge0.25 P 0.75 S4, Li 10 GeP2S 12 These include LiX, LiO, and M'O. q , Li p MO q In this case, X in "LiX" is at least one selected from the group consisting of F, Cl, Br, and I. q " and "Li p MO q " The element M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q " and "Li p MO q In the above formula, p and q are independent natural numbers.

[0078] The oxide solid electrolyte is a solid electrolyte containing oxygen. The oxide solid electrolyte may further contain anions other than sulfur and halogen elements as anions other than oxygen.

[0079] Examples of oxide solid electrolytes include NASICON-type solid electrolytes, such as LiTi2(PO4)3 and its elemental substitution products, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGeO 16 , Li4SiO4, LiGeO4 and their element substitution products, LiSiCON type solid electrolytes, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those substituted with these elements, LiPO and its N-substituted compounds, and glass or glass ceramics containing a base material containing a Li-B-O compound such as LiBO or LiBO to which a material such as LiSO or LiCO is added can be used.

[0080] The polymer solid electrolyte may be, for example, a compound of a polymer compound and a lithium salt. The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure may contain a large amount of lithium salt. This can further increase ionic conductivity. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2CF2F5)2, LiN(SO2CF3)(SO2CF4F9), and LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.

[0081] Examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI and LiBH4-P2S5.

[0082] The first solid electrolyte 201 may contain, for example, Li and S. In other words, the first solid electrolyte 201 may contain a sulfide solid electrolyte. The sulfide solid electrolyte has high ionic conductivity and can improve the charge / discharge efficiency of the battery. On the other hand, although the sulfide solid electrolyte has poor oxidation resistance, applying the technology of the present disclosure can provide a high effect.

[0083] The first solid electrolyte 201 may contain inevitable impurities such as starting materials, by-products, decomposition products, etc. used in synthesizing the solid electrolyte. This also applies to the first solid electrolyte.

[0084] The shape of the first solid electrolyte 201 is not particularly limited, and may be, for example, needle-like, spherical, oval-spherical, etc. For example, the shape of the first solid electrolyte 201 may be particulate.

[0085] For example, when first solid electrolyte 201 is in the form of particles (for example, spheres), the median diameter may be 100 μm or less.

[0086] When the median diameter of the first solid electrolyte 201 is 100 μm or less, the coated active material 100 and the first solid electrolyte 201 can be well dispersed in the positive electrode material 200. This improves the charge / discharge characteristics of the battery.

[0087] The median diameter of first solid electrolyte 201 may be 10 μm or less.

[0088] According to the above configuration, the coated active material 100 and the first solid electrolyte 201 can be well dispersed in the positive electrode material 200 .

[0089] In the positive electrode material 200 of the first embodiment, the content of the first solid electrolyte 201 and the content of the coated active material 100 may be the same as or different from each other.

[0090] The positive electrode material 200 may contain a binder to improve adhesion between particles. The binder is used to improve the binding properties of the materials constituting the positive electrode. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, polyvinyl acetate, polyvinylpyrrolidone, polyether, polycarbonate, polyethersulfone, polyetherketone, polyetheretherketone, polyphenylene sulfide, hexafluoropolypropylene, styrene-butadiene rubber, carboxymethyl cellulose, and ethyl cellulose. Also usable are copolymers of two or more monomers selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, butadiene, styrene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid ester, acrylic acid, and hexadiene. One selected from these may be used alone, or two or more may be used in combination.

[0091] The binder may be an elastomer because it has excellent binding properties. An elastomer is a polymer having rubber elasticity. The elastomer used as the binder may be a thermoplastic elastomer or a thermosetting elastomer. The binder may contain a thermoplastic elastomer. Examples of thermoplastic elastomers include styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), butylene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butylene rubber (SBR), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), hydrogenated styrene-butylene rubber (HSBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), etc. One selected from these may be used alone, or two or more may be used in combination.

[0092] The positive electrode material 200 may contain a conductive additive for the purpose of enhancing electronic conductivity. Examples of the conductive additive include graphites such as natural graphite or artificial graphite, carbon blacks such as acetylene black and ketjen black, conductive fibers such as carbon fiber or metal fiber, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. Using a carbon conductive additive can reduce costs.

[0093] <Method for manufacturing the positive electrode material> The positive electrode material 200 is obtained by mixing the coated active material 100 and the first solid electrolyte 201. The method for mixing the coated active material 100 and the first solid electrolyte 201 is not particularly limited. The coated active material 100 and the first solid electrolyte 201 may be mixed using a tool such as a mortar, or may be mixed using a mixing device such as a ball mill. Furthermore, the coated active material 100 and the first solid electrolyte 201 may be mixed in a solvent when preparing the positive electrode slurry using a mixing device such as a homogenizer.

[0094] (Embodiment 3) Fig. 3 is a cross-sectional view showing a schematic configuration of a battery according to embodiment 3. The battery 300 includes a positive electrode 301, an electrolyte layer 302, and a negative electrode 303. The electrolyte layer 302 is disposed between the positive electrode 301 and the negative electrode 303. The positive electrode 301 includes the positive electrode material 200 described in embodiment 2. This configuration allows the internal resistance of the battery 300 to be reduced. The battery 300 according to embodiment 3 may be, for example, a solid-state battery.

[0095] The volume ratio "v1:100-v1" of the coated active material 100 and the first solid electrolyte 201 contained in the positive electrode 301 may satisfy 30≦v1≦95. When 30≦v1 is satisfied, the energy density of the battery 300 is sufficiently ensured. Furthermore, when v1≦95 is satisfied, high-power operation is possible.

[0096] The thickness of the positive electrode 301 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 301 is 10 μm or more, the energy density of the battery 300 is sufficiently ensured. When the thickness of the positive electrode 301 is 500 μm or less, high-power operation is possible.

[0097] The electrolyte layer 302 is a layer containing an electrolyte material. The electrolyte material is, for example, a solid electrolyte. That is, the electrolyte layer 302 may be a solid electrolyte layer. The electrolyte layer 302 may contain at least one solid electrolyte selected from the group consisting of a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte. Details of each solid electrolyte are as described in the second embodiment. The electrolyte layer 302 may contain a solid electrolyte having the same composition as the first solid electrolyte 201 contained in the cathode material 200. The electrolyte layer 302 may contain a solid electrolyte having a composition different from the composition of the first solid electrolyte 201 contained in the cathode material 200.

[0098] According to the above configuration, the resistance of the battery 300 can be further reduced.

[0099] The electrolyte layer 302 may include a solid electrolyte containing Li and S, that is, a sulfide solid electrolyte.

[0100] The electrolyte layer 302 may contain only one solid electrolyte selected from the above-described group of solid electrolytes, or may contain two or more solid electrolytes selected from the above-described group of solid electrolytes. The multiple solid electrolytes have different compositions. For example, the electrolyte layer 302 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0101] The thickness of the electrolyte layer 302 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 302 is 1 μm or more, the positive electrode 301 and the negative electrode 303 can be more reliably separated. When the thickness of the electrolyte layer 302 is 300 μm or less, the battery 300 can operate at high power.

[0102] The negative electrode 303 contains, as a negative electrode active material, a material that has the property of absorbing and releasing metal ions (for example, lithium ions).

[0103] Examples of the negative electrode active material that can be used include metal materials, carbon materials, oxides, nitrides, tin compounds, and silicon compounds. The metal material may be a single metal. Alternatively, the metal material may be an alloy. Examples of the metal material include lithium metal and lithium alloys. Examples of the carbon material include natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. From the viewpoint of capacity density, silicon (Si), tin (Sn), silicon compounds, and tin compounds can be preferably used.

[0104] The median diameter of the particles of the negative electrode active material may be 0.1 μm or more and 100 μm or less.

[0105] The negative electrode 303 may contain other materials such as a solid electrolyte. As the solid electrolyte, the materials described in the second embodiment can be used.

[0106] The above configuration increases the lithium ion conductivity inside the negative electrode 303, enabling high-power operation. The solid electrolyte may be any of the materials exemplified in the second embodiment. That is, the negative electrode 303 may contain a solid electrolyte having the same composition as the first solid electrolyte 201 contained in the positive electrode material 200.

[0107] When the median diameter of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can be well dispersed, which improves the charge / discharge characteristics of the battery.

[0108] Furthermore, when the median diameter of the negative electrode active material is 100 μm or less, the diffusion rate of lithium within the negative electrode active material is sufficiently ensured, thereby enabling the battery to operate at high power output.

[0109] The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte, thereby enabling the negative electrode active material and the solid electrolyte to be well dispersed.

[0110] The volume ratio "v2:100-v2" of the negative electrode active material and the solid electrolyte contained in the negative electrode 303 may satisfy 30≦v2≦95. When 30≦v2 is satisfied, the energy density of the battery 300 is sufficiently ensured. Furthermore, when v2≦95 is satisfied, high-power operation is possible.

[0111] The thickness of the negative electrode 303 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 303 is 10 μm or more, the energy density of the battery 300 is sufficiently ensured. When the thickness of the negative electrode 303 is 500 μm or less, high-power operation is possible.

[0112] At least one selected from the group consisting of the electrolyte layer 302 and the negative electrode 303 may contain a binder for the purpose of improving adhesion between particles. As the binder that can be used for the electrolyte layer 302 and the negative electrode 303, the materials exemplified as the binder that can be contained in the positive electrode material 200 in the second embodiment can be used.

[0113] The negative electrode 303 may contain a conductive additive for the purpose of increasing electronic conductivity. The conductive additive usable for the negative electrode 303 may be any of the materials exemplified as the conductive additive that can be contained in the positive electrode material 200 in Embodiment 2.

[0114] The battery in the third embodiment can be configured as batteries of various shapes, such as coin type, cylindrical type, square type, sheet type, button type, flat type, and laminate type.

[0115] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0116] (Technology 1) A cathode active material comprising: a cathode active material; and a coating layer that coats at least a portion of a surface of the cathode active material, wherein the coating layer contains a compound containing Li, M, and F, wherein the M in the compound is at least one element selected from the group consisting of metal elements and semi-metal elements other than Li, and the amount of F in the compound per unit surface area of ​​the cathode active material is 10 mg / m 2 or more and 280 mg / m 2 The coated active material is as follows:

[0117] This configuration can reduce the internal resistance of the battery.

[0118] (Technology 2) The coated active material according to Technology 1, wherein the M includes at least one selected from the group consisting of Al, Ti, Zr, Si, Y, Ca, Mg, Nb, Ta, Mo, W, Ni, and Zn.

[0119] With this configuration, the coated active material of Technology 2 can be expected to be highly effective in various aspects, such as improving ionic conductivity and changing mechanical properties.

[0120] (Technology 3) The amount of F of the compound per unit surface area of ​​the positive electrode active material is 50 mg / m 2 or more and 240 mg / m 2 The coated active material according to Technology 1 or 2, which is:

[0121] This configuration is expected to achieve both a reduction in the internal resistance of the battery and an increase in the durability of the battery.

[0122] (Technology 4) The amount of F of the compound per unit surface area of ​​the positive electrode active material is 70 mg / m 2 or more and 150 mg / m 2 The coated active material according to Technology 3, which is as follows:

[0123] This configuration is expected to achieve both a reduction in the internal resistance of the battery and an increase in the durability of the battery.

[0124] (Technology 5) The coated active material according to any one of Technologies 1 to 4, wherein the ratio of the amount of substance of F to the total amount of substance of anions constituting the compound is 0.5 or more and 1.0 or less.

[0125] According to this configuration, the oxidation resistance of the coated active material can be improved.

[0126] (Technology 6) The coated active material according to any one of Technologies 1 to 5, wherein in the compound, the ratio of the amount of substance of Li to the total amount of substance of cations other than Li is 2.3 or more and 6 or less.

[0127] This configuration can further reduce the internal resistance of the battery.

[0128] (Technology 7) The compound is represented by the following composition formula (1): Li 6-αy (Me 1-x Al x ) y F6 ... composition formula (1) Here, in the composition formula (1), Me is at least one element selected from the group consisting of metal elements and semimetal elements other than Li and Al, and α is (Me 1-x Al x 7. The coated active material according to any one of claims 1 to 6, wherein x is an average valence of x and y, and 0<x≦1 and 0<y≦1.5 are satisfied.

[0129] This configuration can further reduce the internal resistance of the battery.

[0130] (Technology 8) The coated active material according to Technology 7, wherein in the composition formula (1), the Me is at least one selected from the group consisting of Ti and Zr.

[0131] This configuration can further reduce the internal resistance of the battery and improve the durability of the battery.

[0132] (Technology 9) The coated active material according to any one of Technologies 1 to 8, wherein the positive electrode active material contains a lithium-nickel-containing oxide that contains Li and Ni and has a layered rock salt structure.

[0133] This configuration can further reduce the internal resistance of the battery.

[0134] (Technology 10) The coated active material according to Technology 9, wherein in the positive electrode active material, the ratio of the amount of Ni to the total amount of cations other than Li is 0.6 or more.

[0135] This configuration can further reduce the internal resistance of the battery.

[0136] (Technology 11) A positive electrode material comprising the coated active material according to any one of technologies 1 to 10.

[0137] This configuration can reduce the internal resistance of the battery.

[0138] (Technology 12) A positive electrode comprising the positive electrode material according to Technology 11.

[0139] This configuration can reduce the internal resistance of the battery.

[0140] (Technology 13) A battery comprising the positive electrode according to Technology 12.

[0141] This configuration can reduce the internal resistance of the battery.

[0142] (Technology 14) The battery according to Technology 13, wherein the battery is a solid-state battery.

[0143] This configuration makes it possible to realize a solid-state battery with reduced internal resistance.

[0144] (Technology 15) The battery according to Technology 14, comprising a solid electrolyte containing Li and S.

[0145] This configuration makes it possible to realize a solid-state battery with reduced internal resistance.

[0146] Hereinafter, the present disclosure will be described in detail using examples and comparative examples. Note that the electrodes and batteries of the present disclosure are not limited to the following examples.

[0147] Example 1 Preparation of Fluorine Compound Contained in Coating Layer The target composition of the fluorine compound was Li3AlF6 (hereinafter referred to as LAF). In an argon atmosphere with a dew point of −60°C or lower (hereinafter referred to as a “dry argon atmosphere”), raw material powders of LiF and AlF3 were prepared in a molar ratio of LiF:AlF3 = 3:1. These raw material powders were loaded into a 45 cc planetary ball mill pod along with 1 mm diameter balls (25 g). Gamma-butyrolactone (GBL) was added dropwise to the pod to achieve a solids ratio of 30%. The solids ratio was calculated as {(mass of input raw materials) / (mass of input raw materials + mass of input solvent)} × 100. Milling was performed for 12 hours at 500 rpm using a planetary ball mill. After milling, the balls were separated to obtain a slurry. The obtained slurry was dried using a mantle heater under a nitrogen flow at 270° C. for 1 hour. The obtained solid was pulverized in a mortar to obtain a powder of LAF, which is the fluorine compound according to Example 1.

[0148] [Preparation of Coated Active Material] Powder of Li(NiCoAl)O2 (hereinafter referred to as "NCA") was prepared as the positive electrode active material. The NCA was added to ethanol and dispersed using an ultrasonic homogenizer to prepare a measurement sample. The area-average diameter of the NCA was measured by image-based particle size distribution analysis using a dynamic image analysis particle size analysis system (e.g., Particle Size Analysis System XPT manufactured by PSprozesstechnik) as an image-based particle size distribution measurement device. The area-average diameter of the NCA was 5.37 μm. Hereinafter, this positive electrode active material will be referred to as NCA5.37. The true density of Li(NiCoAl)O2 is 4.7 g / cc. Therefore, when NCA5.37 is calculated using the above formula (A), the specific surface area is 0.238 m 2 / g (= 1.12 m 2 / cc).

[0149] A coating layer made of LAF was formed on the surface of NCA5.37. The coating layer was formed by compressive shear treatment using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, NCA5.37 and LAF were weighed out to a volume ratio of 98.9:1.1, and treated under the following conditions: blade clearance: 2 mm, rotation speed: 8000 rpm, and treatment time: 30 min. This resulted in the production of the coated active material of Example 1.

[0150] The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 0.45% by mass. The specific surface area of ​​the positive electrode active material was 0.238 m 2 / g, so the amount of F is 19 mg / m 2 It was.

[0151] [Preparation of First Solid Electrolyte] In an argon glove box with a dew point of −60°C or less, raw material powders LiS and PS were weighed out to a molar ratio of LiS:PS = 75:25. These were pulverized and mixed in a mortar to obtain a mixture. The mixture was then milled for 10 hours at 510 rpm using a planetary ball mill (Fritsch, P-7). This resulted in a glassy solid electrolyte. The glassy solid electrolyte was then heat-treated in an inert atmosphere at 270°C for 2 hours. This resulted in a glass-ceramic sulfide solid electrolyte, LiS-PS (hereinafter referred to as "LPS"), being obtained as the first solid electrolyte.

[0152] [Preparation of Positive Electrode] In an argon glove box, the coated active material of Example 1 and LPS were weighed and mixed so that the volume ratio of NCA5.37 to the first solid electrolyte was 6:4. Furthermore, a binder, a solvent, and a conductive additive were mixed and dispersed using a homogenizer to prepare a positive electrode slurry. The prepared slurry was applied to a current collector and dried on a hot plate to prepare a positive electrode.

[0153] [Fabrication of Battery] Li4Ti5O was used as the negative electrode active material. 12(hereinafter referred to as LTO) was used. In an argon glove box with a dew point of -60°C or less, a binder, a solvent, a conductive additive, and LPS were mixed and dispersed using a homogenizer. This resulted in a mixture of binder, solvent, conductive additive, and LPS. LTO was added to the mixture, mixed, and dispersed using a homogenizer to prepare a slurry of the negative electrode material. The prepared slurry was applied to a current collector and dried on a hot plate to prepare a negative electrode. The mixing ratio of LTO and LPS was 65:35 by volume.

[0154] LPS, binder, and solvent were mixed and dispersed using a homogenizer to prepare a slurry containing LPS. The slurry was then applied to a substrate and dried on a hot plate to prepare an electrolyte layer.

[0155] The prepared negative electrode and electrolyte layer were laminated and pressure-molded while heated, and then the substrate was removed from the electrolyte layer. Next, a positive electrode was laminated on the opposite side of the obtained molded body from the negative electrode so that the electrolyte layer and the positive electrode were in contact with each other, and the molded body was pressure-molded while heated. After attaching a current collecting lead to the obtained molded body, it was placed in a laminate packaging material and the packaging material was sealed. This produced a battery.

[0156] [Battery Performance Evaluation] The battery was placed in a thermostatic chamber at 25°C. (i) The battery was charged at a constant current of 0.4 mA, which corresponds to a 0.3 C rate (3.3 hour rate) relative to the theoretical capacity of the battery, to a voltage of 2.7 V. It was then charged at a constant voltage of 2.7 V and terminated at a current of 0.013 mA, which corresponds to a 0.01 C rate. It was then similarly discharged at a constant current of 0.3 C (10 hour rate) to a voltage of 1.5 V. (ii) The battery was then again charged at a constant current of 0.3 C (3.3 hour rate) to a voltage of 2.7 V, and then charged at a constant voltage of 0.01 C. It was then discharged at a constant current of 0.3 C to 2.25 V, corresponding to an SOC (State of Charge) of 50, and discharged at a constant voltage of 2.25 V, which was terminated at a 0.01 C rate. (iii) After the rest, constant current discharge was performed at a rate of 10 C (0.1 hour rate) for 1 second, and the voltage after 0.1 second was measured.

[0157] The DC resistance of a battery obtained from the following formula (B) is called DCR: DCR = (Vo - V) x S / I (B) In the above formula (B), Vo is the voltage before 1 second of discharge, V is the voltage after 0.1 second of discharge, S is the area where the positive electrode and electrolyte layer are in contact, and I is the current at a 10C rate.

[0158] The DCR of the battery of Example 1 was 15.5 Ω cm 2 It was.

[0159] <<Examples 2 to 8>> The same procedures as in Example 1 are omitted.

[0160] [Preparation of Coated Active Material] Example 2 NCA5.37 and LAF were weighed out to a volume ratio of 96.9:3.1, and a coating layer made of LAF was formed on the surface of NCA5.37 using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation) in the same manner as in Example 1. This resulted in the production of the coated active material of Example 2. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 1.26 mass%. In the prepared coated active material, the amount of F was 54 mg / m 2 It was.

[0161] Example 3 NCA5.37 and LAF were weighed out to a volume ratio of 96.4:3.6, and a particle compositing device (NOB-MINI, manufactured by Hosokawa Micron Corporation) was used in the same manner as in Example 1 to form a coating layer made of LAF on the surface of NCA5.37 in the same manner as in Example 1. This resulted in the production of a coated active material of Example 3. The amount of elemental fluorine in the produced coated active material was measured by combustion ion chromatography. The amount of elemental fluorine was 1.46% by mass. In the produced coated active material, the amount of F was 63 mg / m 2 It was.

[0162] Example 4 NCA5.37 and LAF were weighed out to a volume ratio of 95.9:4.1, and a particle compositing device (NOB-MINI, manufactured by Hosokawa Micron Corporation) was used in the same manner as in Example 1 to form a coating layer made of LAF on the surface of NCA5.37. This resulted in the production of a coated active material of Example 4. The amount of fluorine element in the produced coated active material was measured by combustion ion chromatography. The amount of fluorine element was 1.67% by mass. In the produced coated active material, the amount of F was 71 mg / m 2 It was.

[0163] Example 5 NCA5.37 and LAF were weighed out to a volume ratio of 95.4:4.6, and a particle compositing device (NOB-MINI, manufactured by Hosokawa Micron Corporation) was used in the same manner as in Example 1 to form a coating layer made of LAF on the surface of NCA5.37. This resulted in the production of a coated active material of Example 5. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 1.87% by mass. In the prepared coated active material, the amount of F was 80 mg / m 2 It was.

[0164] Example 6 NCA5.37 and LAF were weighed out to a volume ratio of 94.4:5.6, and a particle compositing device (NOB-MINI, manufactured by Hosokawa Micron Corporation) was used in the same manner as in Example 1 to form a coating layer made of LAF on the surface of NCA5.37. This resulted in the production of a coated active material of Example 6. The amount of fluorine element in the produced coated active material was measured by combustion ion chromatography. The amount of fluorine element was 2.28% by mass. In the produced coated active material, the amount of F was 98 mg / m 2 It was.

[0165] Example 7 NCA5.37 and LAF were weighed out to a volume ratio of 91.9:8.1, and a particle compositing device (NOB-MINI, manufactured by Hosokawa Micron Corporation) was used in the same manner as in Example 1 to form a coating layer made of LAF on the surface of NCA5.37. This resulted in the production of a coated active material of Example 7. The amount of fluorine element in the produced coated active material was measured by combustion ion chromatography. The amount of fluorine element was 3.29 mass%. In the produced coated active material, the amount of F was 143 mg / m 2 It was.

[0166] Example 8 NCA5.37 and LAF were weighed out to a volume ratio of 84.9:15.1, and a coating layer made of LAF was formed on the surface of NCA5.37 using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation) in the same manner as in Example 1. This resulted in the production of a coated active material of Example 8. The amount of fluorine element in the produced coated active material was measured by combustion ion chromatography. The amount of fluorine element was 6.14 mass%. In the produced coated active material, the amount of F was 275 mg / m 2 It was.

[0167] <<Examples 9 to 18>> The same procedures as in Example 1 are omitted.

[0168] Example 9 [Preparation of Fluorine Compound Contained in Coating Layer] The target composition of the fluorine compound was 2.7 Ti 0.3 Al 0.7F6 (hereinafter referred to as LTAF). In a dry argon atmosphere, LiF, TiF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:TiF4:AlF3 = 2.7:0.3:0.7. These raw material powders, along with 25 g of 1 mm diameter balls, were loaded into a 45 cc planetary ball mill pod. γ-butyrolactone (GBL) was added dropwise to the pod as an organic solvent to achieve a solids content of 30%. The solids content was calculated as {(mass of input raw materials) / (mass of input raw materials + mass of input solvent)} × 100. The mixture was milled for 12 hours at 500 rpm using a planetary ball mill. After milling, the balls were separated to obtain a slurry. The resulting slurry was dried at 270°C for 1 hour under a nitrogen flow using a mantle heater. The obtained solid was pulverized in a mortar to obtain a powder of LTAF, which is a fluorine compound according to Example 9.

[0169] [Preparation of Coated Active Material] Powder of Li(NiCoAl)O2 (NCA) was prepared as the positive electrode active material. The NCA was added to ethanol and dispersed using an ultrasonic homogenizer to prepare a measurement sample. Using the same device as in Example 1, the area-average diameter of the NCA was measured by image particle size distribution. The area-average diameter of the NCA was 6.38 μm. Hereinafter, this positive electrode active material will be referred to as NCA6.38. The true density of Li(NiCoAl)O2 is 4.7 g / cc. Therefore, when NCA6.38 is calculated using the above formula (A), the specific surface area is 0.200 m 2 / g (=0.94m 2 / cc).

[0170] A coating layer made of LTAF was formed on the surface of NCA6.38. The coating layer was formed by compressive shear treatment using a particle compositer (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, NCA6.38 and LTAF were weighed out to a volume ratio of 95.4:4.6, and treated under the following conditions: blade clearance: 2 mm, rotation speed: 8000 rpm, and treatment time: 30 min. This resulted in the production of the coated active material of Example 9.

[0171] The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 1.79% by mass. The specific surface area of ​​the positive electrode active material was 0.200 m 2 / gm 2 / g, so the amount of F is 91 mg / m 2 It was.

[0172] Example 10 Preparation of Coated Active Material NCA5.37 and LTAF were weighed out to a volume ratio of 95.4:4.6, and a coating layer made of LTAF was formed on the surface of NCA5.37 using a particle composite device in the same manner as in Example 9. This resulted in the production of the coated active material of Example 10. The F content of the prepared coated active material was 77 mg / m 2 It was.

[0173] Example 11 Preparation of Coated Active Material Powder (NCA) of Li(NiCoAl)O2 was prepared as a positive electrode active material. The NCA was added to ethanol and dispersed using an ultrasonic homogenizer to prepare a measurement sample. The area-average diameter of the NCA was measured by image particle size distribution using the same device as in Example 1. The area-average diameter of the NCA was 4.09 μm. Hereinafter, this positive electrode active material will be referred to as NCA4.09. The true density of Li(NiCoAl)O2 is 4.7 g / cc. Therefore, when NCA4.09 is calculated using the above formula (A), the specific surface area is 0.312 m 2 / g (= 1.47 m 2 / cc).

[0174] A coating layer made of LTAF was formed on the surface of NCA4.09. The coating layer was formed by compressive shear treatment using a particle compositer (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, NCA4.09 and LTAF were weighed out to a volume ratio of 94.0:6.0, and treated under the following conditions: blade clearance: 2 mm, rotation speed: 8000 rpm, and treatment time: 30 min. This resulted in the production of the coated active material of Example 11.

[0175] The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 2.33 mass%. The specific surface area of ​​the positive electrode active material was 0.312 m2 / gm 2 / g, so the amount of F is 76 mg / m 2 It was.

[0176] Example 12 Preparation of Coated Active Material NCA4.09 and LTAF were weighed out to a volume ratio of 92.3:7.7, and a coating layer made of LTAF was formed on the surface of NCA4.09 using a particle composite device in the same manner as in Example 11. This resulted in the production of the coated active material of Example 12. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 2.99% by mass. In the prepared coated active material, the amount of F was 99 mg / m 2 It was.

[0177] Example 13 Preparation of Coated Active Material NCA4.09 and LTAF were weighed out to a volume ratio of 90.8:9.2, and a coating layer made of LTAF was formed on the surface of NCA4.09 using a particle composite device in the same manner as in Example 11. This resulted in the production of the coated active material of Example 13. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 3.58 mass%. In the prepared coated active material, the amount of F was 119 mg / m 2 It was.

[0178] Example 14 Preparation of Coated Active Material Powder of Li(NiCoMn)O2 (NCM) was prepared as the positive electrode active material. The NCM was added to ethanol and dispersed using an ultrasonic homogenizer to prepare a measurement sample. Using the same device as in Example 1, the area-average diameter of the NCM was measured by image particle size distribution. The area-average diameter of the NCM was 6.46 μm. Hereinafter, this positive electrode active material will be referred to as NCM6.46. The true density of Li(NiCoMn)O2 is 4.7 g / cc. Therefore, when NCM6.46 is calculated using the above formula (A), the specific surface area is 0.198 m 2 / g (=0.93m 2 / cc).

[0179] A coating layer made of LTAF was formed on the surface of NCM6.46. The coating layer was formed by compressive shear treatment using a particle compositer (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, NCM6.46 and LTAF were weighed out to a volume ratio of 95.4:4.6, and treated under the following conditions: blade clearance: 2 mm, rotation speed: 8000 rpm, and treatment time: 30 min. This resulted in the production of the coated active material of Example 14.

[0180] The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 1.79% by mass. The specific surface area of ​​the positive electrode active material was 0.198 m 2 / gm 2 / g, so the amount of F is 92 mg / m 2 It was.

[0181] Example 15 Preparation of Coated Active Material NCM6.46 and LTAF were weighed out to a volume ratio of 94.2:5.8, and a coating layer made of LTAF was formed on the surface of NCM6.46 using a particle composite device in the same manner as in Example 14. This resulted in the production of the coated active material of Example 15. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 2.25 mass%. In the prepared coated active material, the amount of F was 117 mg / m 2 It was.

[0182] Example 16 Preparation of Coated Active Material NCM6.46 and LTAF were weighed out to a volume ratio of 93.1:6.9, and a coating layer made of LTAF was formed on the surface of NCM6.46 using a particle composite device in the same manner as in Example 14. This resulted in the production of the coated active material of Example 16. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 2.68 mass%. In the prepared coated active material, the amount of F was 139 mg / m 2 It was.

[0183] Example 17 Preparation of Coated Active Material NCM6.46 and LTAF were weighed out to a volume ratio of 90.8:9.2, and a coating layer made of LTAF was formed on the surface of NCM6.46 using a particle composite device in the same manner as in Example 14. This resulted in the production of the coated active material of Example 17. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 3.58 mass%. In the prepared coated active material, the amount of F was 188 mg / m 2 It was.

[0184] Example 18 Preparation of Coated Active Material NCM6.46 and LTAF were weighed out to a volume ratio of 88.5:11.5, and a coating layer made of LTAF was formed on the surface of NCM6.46 using a particle composite device in the same manner as in Example 14. This resulted in the production of the coated active material of Example 18. The amount of fluorine element in the prepared coated active material was measured by combustion ion chromatography. The amount of fluorine element was 4.47% by mass. In the prepared coated active material, the amount of F was 237 mg / m 2 It was.

[0185] Comparative Example Procedures similar to those in Example 1 are omitted as appropriate.

[0186] As the positive electrode active material, powder of NCA5.37 was prepared. After that, batteries were produced and evaluated in the same manner as above, without carrying out the coating treatment.

[0187] The evaluation results for Examples 1 to 18 and Comparative Example are shown in Tables 1 and 2.

[0188]

[0189]

[0190] <<Discussion>> From the results shown in Tables 1 and 2, the DCR can be reduced by coating the NCM and NCA active materials with a fluorine compound. On the other hand, comparing Examples 1 to 8, it can be seen that the DCR varies depending on the amount of F, and that there is an optimum value where either too much or too little is not good. This is because if the amount is too little, the coating area on the active material surface becomes low, and if the amount is too much, the coating layer becomes too thick, and the lithium ion conduction path and electron conduction path to the active material surface are blocked by the fluorine compound contained in the coating layer. In other words, it is essentially not a simple amount of fluorine compound, but the amount of fluorine compound per surface area of ​​the active material, and the amount of F normalized by the surface area of ​​the active material is 10 mg / m 2 or more and 280 mg / m 2 When the specific surface area and type of the active material and the type of fluorine compound used in the coating layer are different, a battery with a low DCR can be obtained within the above range. As shown in Examples 9 to 18, even if the specific surface area and type of the active material and the type of fluorine compound used in the coating layer are different, a battery with a sufficiently low DCR can be obtained within the above range. Comparing Example 5 with Example 10, Example 10, which is coated with LTAF, has a lower DCR. This is because LTAF has better lithium ion conductivity than LAF. Note that, in order to improve the lithium ion conductivity of a fluorine compound material, it is desirable to contain both lithium and at least one element selected from the group consisting of metal elements and semimetal elements. For example, lithium fluoride has extremely low lithium ion conductivity.

[0191] The technology of the present disclosure is useful, for example, in all-solid-state lithium secondary batteries.

Claims

1. A cathode active material and a coating layer that coats at least a portion of a surface of the cathode active material, the coating layer containing a compound containing Li, M, and F, the M being at least one element selected from the group consisting of metal elements and semi-metal elements other than Li, and the amount of F in the compound per unit surface area of ​​the cathode active material being 10 mg / m 2 or more and 280 mg / m 2 A coated active material, which is:

2. The coated active material according to claim 1, wherein M includes at least one selected from the group consisting of Al, Ti, Zr, Si, Y, Ca, Mg, Nb, Ta, Mo, W, Ni, and Zn.

3. The amount of F of the compound per unit surface area of ​​the positive electrode active material is 50 mg / m 2 or more and 240 mg / m 2 The coated active material according to claim 1 , wherein:

4. The amount of F of the compound per unit surface area of ​​the positive electrode active material is 70 mg / m 2 or more and 150 mg / m 2 The coated active material according to claim 3 , wherein:

5. The coated active material according to claim 1, wherein the ratio of the amount of substance of F to the total amount of substances of the anions constituting the compound is 0.5 or more and 1.0 or less.

6. The coated active material according to claim 1, wherein in said compound, the ratio of the amount of substance of Li to the total amount of substances of cations other than Li is 2.3 or more and 6 or less.

7. The compound is represented by the following composition formula (1): Li 6-αy (Me 1-x A x ) y F6 ... composition formula (1) Here, in the composition formula (1), Me is at least one element selected from the group consisting of metal elements and semimetal elements other than Li and Al, and α is (Me 1-x A x 2. The coated active material according to claim 1 , wherein x≦1 and y≦1.5 are satisfied.

8. The coated active material according to claim 7, wherein in said composition formula (1), said Me is at least one selected from the group consisting of Ti and Zr.

9. The coated active material according to claim 1, wherein the positive electrode active material comprises a lithium nickel-containing oxide that contains Li and Ni and has a layered rock salt structure.

10. The coated active material according to claim 9, wherein in the positive electrode active material, the ratio of the amount of Ni to the total amount of cations other than Li is 0.6 or more.

11. A positive electrode material comprising the coated active material according to any one of claims 1 to 10.

12. A positive electrode comprising the positive electrode material according to claim 11.

13. A battery comprising the positive electrode according to claim 12.

14. The battery of claim 13, wherein the battery is a solid-state battery.

15. The battery of claim 14, comprising a solid electrolyte comprising Li and S.