Inorganic oxide powder and lithium ion secondary battery having electrode or electrolyte layer containing the same

Abstract

A material is provided that makes it possible to obtain a lithium ion secondary battery with improved power capacity under low-temperature conditions. [Solution] The above problem is solved by an inorganic oxide powder that is a glass ceramic or ceramic powder, which contains, in mass % relative to the total mass of the crystalline phase, 80.0% or more of LATP crystals and more than 0% of TiO2 crystals, and in which the a / c ratio of the LATP crystals is 0.40860 or more.

Description

[Technical Field]

[0001] The present invention relates to an inorganic oxide powder and a lithium ion secondary battery having an electrode or an electrolyte layer containing the inorganic oxide powder. [Background technology]

[0002] Lithium-ion secondary batteries, which have high energy density and can be charged and discharged, are widely used as power sources for electric vehicles and mobile phone terminals. Many of the lithium-ion secondary batteries currently available on the market use a liquid electrolyte (electrolytic solution) to achieve a high energy density. The electrolyte solution is typically a nonaqueous electrolyte solution, in which the electrolyte component, lithium salt, is dissolved in an organic solvent. A separator is typically placed between the positive and negative electrodes, and the separator is filled with the above-mentioned electrolyte solution. Furthermore, lithium-ion secondary batteries (lithium-ion polymer secondary batteries) that use a polymer compound containing the electrolyte component (lithium ion conductive polymer) as the electrolyte layer instead of the electrolyte solution have also been developed and are commercially available.

[0003] However, the charge / discharge capacity of the lithium-ion secondary battery described above tends to decrease significantly under low temperature conditions. Therefore, technological developments are being conducted to maintain a high charge / discharge capacity even under low temperature conditions.

[0004] For example, Patent Document 1 discloses a lithium ion secondary battery having a power generating element including a positive electrode including a positive electrode active material layer containing a lithium transition metal composite oxide having a predetermined composition as a positive electrode active material, a negative electrode, and an electrolyte layer containing an electrolyte solution, and the ratio D of the lithium diffusion coefficient at SOC 15% to the lithium diffusion coefficient at SOC 80% at 25°C is Li15 / D Li80 A lithium ion secondary battery (lithium ion secondary battery using a lithium-rich manganese positive electrode material) having an improved charge / discharge capacity at low temperatures, in which the value of the positive electrode charge / discharge capacity is 0.05 or more, is disclosed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-062054 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is room for further improvement in the power capacity of this lithium ion secondary battery under low temperature conditions (for example, under atmospheric conditions of -20 to 10°C), and in particular, there is room for improvement in the power capacity under low temperature conditions of lithium ion secondary batteries that have electrodes and electrolyte layers formed using specified materials.

[0007] Therefore, an object of the present invention is to provide a material that makes it possible to obtain a lithium ion secondary battery with improved power capacity under low temperature conditions. [Means for solving the problem]

[0008] To solve the above problems, the inventors conducted extensive research and found that the power capacity of lithium-ion secondary batteries under low-temperature conditions correlates with the ratio of the a-axis length to the c-axis length (a / c) of LATP crystals contained in the electrode material, as described below. Furthermore, they found that this a / c is related to the coexisting TiO crystals. Further research led to the discovery that adding glass-ceramic or ceramic powder (inorganic oxide powder) containing 80.0% or more LATP crystals and more than 0% TiO crystals, with an a / c ratio of 0.40860 or more, to the electrode or electrolyte layer material can improve the power capacity of lithium-ion secondary batteries equipped with electrodes or electrolyte layers formed using the powder. This finding led to the completion of the present invention.

[0009] That is, the present invention provides the following: <1> ~ <6> This includes embodiments of the present invention. <1> A glass-ceramic or ceramic powder, In mass % relative to the total mass of the crystalline phase, LATP crystals were 80.0% or more. TiO2 crystals exceed 0% Contains The a / c of ​​the LATP crystal is 0.40860 or more. Inorganic oxide powder. <2> The Fe content is 100.0 ppm or less. <1> The inorganic oxide powder according to claim 1. <3> The content of AlPO4 crystals is 9.7% or less by mass% relative to the total mass of the crystalline phase. <1> or <2> The inorganic oxide powder according to claim 1. <4> The a / c ratio of the LATP crystal is 0.40870 or more. <1> ~ <3> 10. The inorganic oxide powder according to claim 9, wherein the inorganic oxide powder is a powder containing 10 to 20 carbon atoms. <5> <1> ~ <4> An electrode comprising the inorganic oxide powder according to any one of the above items, and / or <1> ~ <4> 10. A lithium ion secondary battery comprising an electrolyte layer containing the inorganic oxide powder according to any one of claims 1 to 9. <6> The power capacity at -10°C is 380mWh / g or more. <5> The lithium ion secondary battery according to claim 1. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an inorganic oxide powder that can be used to obtain a lithium ion secondary battery with improved power capacity under low-temperature conditions, and to provide a lithium ion secondary battery that includes an electrode or electrolyte layer containing the inorganic oxide powder and has improved power capacity under low-temperature conditions. [Brief explanation of the drawings]

[0011] [Figure 1] 10 is a graph showing an example of calculation of the power capacity of a lithium ion secondary battery under a predetermined temperature condition. [Figure 2] 1 is a graph showing the relationship between the TiO2 crystal content (mass % relative to the total mass of the crystalline phase) and the a / c of ​​the LATP crystals contained in the inorganic oxide powders of Examples and Comparative Examples. [Figure 3]1 is a graph showing the relationship between the TiO2 crystal content (mass % relative to the total mass of the crystalline phase) and the AlPO4 crystal content (mass % relative to the total mass of the crystalline phase) in inorganic oxide powders of Examples and Comparative Examples. [Figure 4] 1 is a graph showing the results of measuring the discharge capacity (mAh / g) of a lithium ion secondary battery having a positive electrode containing the inorganic oxide powder of Example 1 or Comparative Example 2 until the voltage value reaches 3 V at −10° C. [Figure 5] 1 is a graph showing the relationship between the a / c of ​​LATP crystals contained in the inorganic oxide powder of the examples or comparative examples and the power capacity (mWh / g) at −10° C. of a lithium ion secondary battery having a positive electrode containing the inorganic oxide powder. [Figure 6] 1 is a graph showing the relationship between the Fe content (ppm) in the inorganic oxide powder of an example or a comparative example and the power capacity (mWh / g) at −10° C. of a lithium ion secondary battery having a positive electrode containing the inorganic oxide powder. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will now be described. The present invention relates to an inorganic oxide powder (hereinafter, this may be referred to as the "inorganic oxide powder of the present invention") that is a glass ceramic or ceramic powder and contains, in mass % relative to the total mass of the crystalline phase, 80.0% or more of LATP crystals and more than 0% of TiO2 crystals, and in which the a / c of ​​the LATP crystals is 0.40860 or more, and to a lithium ion secondary battery that includes an electrode containing this inorganic oxide powder and / or an electrolyte layer containing this inorganic oxide powder.

[0013] First, the components contained in the inorganic oxide powder of the present invention, the crystalline phase contained therein, its morphology, physical properties, etc. will be described in detail.

[0014] The contents of the components contained in the inorganic oxide powder of the present invention are all expressed in mass% in terms of oxide unless otherwise specified (hereinafter, when the content of a component is simply stated as %, it means mass% in terms of oxide unless otherwise specified). The contents of each component expressed in "mass% in terms of oxide" refer to the content of the oxide of each component contained in the inorganic oxide powder of the present invention, which is expressed in mass% based on the analytical values ​​obtained by analyzing the inorganic oxide powder of the present invention using ICP atomic emission spectroscopy (inductively coupled plasma atomic emission spectroscopy) for the Li component and XRF analysis (X-ray fluorescence analysis) for the other components, assuming that all of the components are oxides and the total mass is 100 mass%.

[0015] The Li2O component is an essential component for imparting lithium ion conductivity to the inorganic oxide powder of the present invention and is a constituent of the LATP crystal. From the viewpoints of lithium ion conductivity and LATP crystal formation, the lower limit of the content of this Li2O component is preferably 4.0% or more, and even more preferably 4.3% or more. The upper limit is preferably 6.0% or less, more preferably 5.7% or less, and even more preferably 5.4% or less, because this makes it easier to suppress the generation of by-products during crystallization, etc.

[0016] The Al2O3 component is a component for imparting lithium ion conductivity to the inorganic oxide powder of the present invention and can be a constituent of LATP crystals. It can also be a constituent of AlPO4 crystals. From the viewpoint of the effects of the present invention, the lower limit of the content of this Al2O3 component is preferably 3.0% or more, more preferably 4.0% or more, even more preferably 5.0% or more, even more preferably 6.0% or more, and even more preferably 6.5% or more. From the viewpoint of ease of LATP crystal formation, the upper limit is preferably 9.0% or less, even more preferably 8.7% or less.

[0017] The TiO2 component is an essential component for imparting lithium ion conductivity to the inorganic oxide powder of the present invention, and is a constituent of LATP crystals and TiO2 crystals. From the viewpoint of the effects of the present invention, the lower limit of the content of this TiO2 component is more preferably 31.0% or more, even more preferably 32.0% or more, and even more preferably 33.0% or more. The upper limit is more preferably 40.0% or less, even more preferably 38.0% or less, and even more preferably 35.0% or less, because it is easy to suppress the generation of by-products during crystallization, etc.

[0018] The P2O5 component is also an essential component for imparting lithium ion conductivity to the inorganic oxide powder of the present invention, and is a constituent of the LATP crystal. Furthermore, it is also a constituent of the AlPO4 crystal. From the viewpoint of the effects of the present invention, the lower limit of the P2O5 component content is more preferably 49.0% or more, and even more preferably 49.5% or more. The upper limit is more preferably 57.0% or less, even more preferably 56.0% or less, even more preferably 55.0% or less, even more preferably 54.0% or less, even more preferably 53.0% or less, even more preferably 52.5% or less, and even more preferably 52.0% or less, because this easily suppresses the generation of by-products during crystallization, etc.

[0019] The inorganic oxide powder of the present invention may further contain one or more components selected from the group consisting of SiO2 component, GeO2 component, ZrO2 component, SnO2 component, B2O3 component, Y2O3 component, Sc2O3 component, ZnO component, Na2O component, K2O component, and transition metal oxides such as Co, Ni, and Mn. These components will be described below.

[0020] The SiO2 component is an optional component that facilitates glass formation when the inorganic oxide powder of the present invention is used as a glass-ceramic powder. It also serves as a constituent of LATP crystals, substituting for the P site of the PO4 framework in the LATP crystals, thereby causing framework distortion and enhancing lithium ion conductivity. Furthermore, the SiO2 component can also enhance the mechanical strength of the inorganic oxide powder of the present invention. The content of the SiO2 component is preferably 5.0% or less, more preferably 4.0% or less, and even more preferably 3.0% or less. The lower limit may be greater than 0%, 0.1% or more, 0.2% or more, 0.5% or more, or 1.0% or more.

[0021] The GeO2 component is an optional component that facilitates crystal formation of the inorganic oxide powder of the present invention. It also serves as a constituent of the LATP crystal, substituting for Ti sites in the LATP crystal to increase the lithium ion content in the LATP crystal, thereby enhancing lithium ion conductivity. The GeO2 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, and even more preferably 1.0% or less.

[0022] The ZrO2 component is an optional component that can contribute to improving the chemical durability of the inorganic oxide powder of the present invention. The ZrO2 component can also enhance the water resistance of the inorganic oxide powder of the present invention. The content of the ZrO2 component is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less.

[0023] The SnO2 component is also an optional component that facilitates crystal formation in the inorganic oxide powder of the present invention. The content of the SnO2 component is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0024] The B2O3 component is also an optional component that facilitates glass formation when the inorganic oxide powder of the present invention is used to prepare a glass-ceramic powder. Furthermore, the B2O3 component can replace part of the Al2O3 component, and is also a component that can adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The content of the B2O3 component is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0025] The Sc2O3 component and the Y2O3 component are also optional components that can replace part of the Al2O3 component and adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The contents of these components are preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0026] The ZnO component is an optional component that can replace part of the TiO component and adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The content of the ZnO component is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0027] The NaO and KO components are also optional components that can adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The contents of these components are preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less.

[0028] Transition metals such as Co, Ni, and Mn are optional components that can prevent the transition metals contained in the electrode active material (particularly the positive electrode active material) from eluting into the electrolyte. The total content of these transition metals, calculated as oxides, is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less by mass. In addition, the inorganic oxide powder of the present invention preferably has an Fe content as low as possible among the transition metals, since the power capacity of the lithium-ion secondary battery can be further increased under low-temperature conditions by reducing the Fe content as much as possible in a given configuration, for example, by selecting the raw material grade or by making improvements during production. The Fe content is preferably 100.0 ppm or less, more preferably 95.0 ppm or less, even more preferably 85.0 ppm or less, even more preferably 70.0 ppm or less, even more preferably 55.0 ppm or less, even more preferably 45.0 ppm or less, even more preferably 40.0 ppm or less, even more preferably 35.0 ppm or less, even more preferably 30.0 ppm or less, even more preferably 25.0 ppm or less, even more preferably 20.0 ppm or less, even more preferably 15.0 ppm or less, and even more preferably 10.0 ppm or less. Here, "ppm" means "mg / kg," and the Fe content is the content of the Fe element measured by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0029] Furthermore, it is preferable that the inorganic oxide powder of the present invention contains as little sulfur (S) as possible (for example, less than 0.5% by mass, or even less than 0.1% by mass, calculated as oxide), and more preferably contains no sulfur. This is because reducing the S component can reduce the possibility of generating harmful gases such as hydrogen sulfide in the lithium ion secondary battery. Furthermore, it is also preferable to reduce arsenic (As), antimony (Sb), and lead (Pb) as much as possible, and more preferably not contain them, because they are harmful substances. In addition, it is also preferable to reduce bismuth (Bi) and tellurium (Te) as much as possible, and more preferably not contain them.

[0030] The inorganic oxide powder of the present invention may be a glass-ceramic powder obtained by melting raw materials at a predetermined temperature to form a glass melt, vitrifying the molten glass, and then crystallizing the molten glass by heat treatment or the like. Alternatively, it may be a ceramic powder obtained by sintering the raw materials. These powders contain at least LATP crystals and TiO crystals, and the LATP crystals account for 80.0% or more by mass of the total mass (total crystalline phase amount) of the crystalline phase contained in the inorganic oxide powder (powder aggregate) of the present invention. In other words, the LATP crystal content relative to the total crystalline phase amount is 80.0% or more. The lower limit is preferably 83.0% or more, and more preferably 85.0% or more. The upper limit is preferably 99.0% or less, more preferably 98.0% or less, even more preferably 95.0% or less, and even more preferably 92.0% or less. Furthermore, as described above, the inorganic oxide powder of the present invention contains TiO2 crystals together with the LATP crystals in a mass percentage greater than 0% relative to the total mass of the crystalline phase. By thus configuring the powder to contain a certain amount of TiO2 crystals along with a predetermined amount of LATP crystals, it becomes easier to adjust the a / c ratio of the coexisting LATP crystals to a predetermined range. The lower limit of the TiO2 crystal content is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, and even more preferably 2.0% or more. The upper limit is preferably 9.0% or less, even more preferably 7.0% or less, and even more preferably 5.0% or less.

[0031] Additionally, the inorganic oxide powder of the present invention may include some crystals other than LATP crystals and TiO crystals (e.g., other NASICON-type lithium ion conductive crystals, lithium ion conductive crystals with other structures such as LISICON-type, perovskite-type, and garnet-type, and other by-product crystals). In particular, it is preferable to include a certain amount of AlPO crystals (greater than 0%, even 1.0% or more, and even 5.0% or more by mass relative to the total mass of the crystalline phase). It is more preferable that the content of AlPO crystals is greater than the content of TiO crystals described above, and the content of AlPO crystals is preferably 9.7% or less. The AlPO crystals structurally bond particles of the LATP crystals, which are the main crystalline phase, to enhance the stability of the crystals. However, the lithium ion conductivity of the AlPO crystals themselves is low. Therefore, if the content of AlPO crystals is too high, the lithium ion conductivity may decrease.

[0032] Furthermore, the mass ratio of LATP crystals to TiO crystals contained in the inorganic oxide powder of the present invention (LATP crystals / TiO crystals) is not limited, but from the viewpoint of the effects of the present invention, it is preferably 10 or more and 100 or less. The lower limit is more preferably 12 or more, and even more preferably 15 or more. The upper limit is more preferably 80 or less, even more preferably 70 or less, even more preferably 50 or less, and even more preferably 30 or less. Furthermore, although this is not limited thereto, from the viewpoint of the effects of the present invention, the inorganic oxide powder of the present invention preferably has a total content of the above-mentioned LATP crystals, TiO2 crystals, and AlPO4 crystals (mass % of the total of these with respect to the total mass of the crystal phase) of 99.00% or more, even more preferably 99.50% or more, even more preferably 99.80% or more, and even more preferably more than 99.90%. In other words, an embodiment in which by-product crystal phases other than the above crystals are extremely small is more preferable. In this case, it is also acceptable for the powder to have a configuration in which AlPO4 crystals are substantially not included.

[0033] In the present invention, the term "LATP crystal" refers to Li1+x+y Al x Ti 2-x Si y P 3-y O 12 The NASICON-type lithium ion conductive oxide crystal is represented by the composition formula (0≦x≦0.4, 0≦y≦0.6). In this formula, from the viewpoints of the above a / c and lithium ion conductivity, the lower limit of X is preferably more than 0, more preferably 0.01 or more, even more preferably 0.05 or more, even more preferably 0.08 or more, and even more preferably 0.10 or more. The upper limit is preferably 0.35 or less, more preferably 0.30 or less. From the same viewpoint, the lower limit of Y is preferably more than 0, more preferably 0.025 or more, even more preferably 0.04 or more, and even more preferably 0.06 or more. The upper limit is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.30 or less. Furthermore, the content of each of the above crystals (mass % relative to the total mass of the crystalline phase) is a value obtained by performing X-ray diffraction (XRD) measurement on the inorganic oxide powder of the present invention under the following measurement conditions and analyzing the data. (XRD measurement conditions) Source: CuKα, 1.54060Å X-ray source: Tube voltage / current: 40kV / 40mA Goniometer radius: 250 mm Scan Type: Coupled TwoTheta / Theta Scan range: 10~60° Step width: 0.02° Entrance Soller slit: 4.1° Divergence slit: 0.5° Anti-scatter slits: 18

[0034] The glass ceramic powder described above contains a crystalline phase containing LATP crystals and TiO2 crystals (e.g., LATP crystals as the main crystalline phase and other by-product crystalline phases containing TiO2 crystals) and an amorphous phase (non-crystalline phase). In other words, it is a mixture of ceramic and glass. Furthermore, the ceramic powder described above is composed of a crystalline phase containing LATP crystals and TiO2 crystals (e.g., LATP crystals as the main crystalline phase and other by-product crystalline phases containing TiO2 crystals), and does not substantially contain an amorphous phase (non-crystalline phase).

[0035] As described above, the LATP crystals contained in the inorganic oxide powder of the present invention have an a / c ratio (the ratio of the a-axis length to the c-axis length in the unit cell of this LATP crystal) of 0.40860 or more. The inorganic oxide powder of the present invention contains a predetermined amount or more of LATP crystals in a predetermined crystal composition with an a / c ratio of 0.40860 or more. This allows for more lithium ions to be incorporated into the structure or for more paths for lithium ions to migrate. Therefore, lithium ion secondary batteries containing this in electrodes or the like have improved power capacity under low-temperature conditions (e.g., atmospheric conditions of -20 to 10°C). From the viewpoint of the effects of the present invention, this a / c ratio is more preferably 0.40870 or more, and even more preferably 0.40880 or more. The a / c ratio of the LATP crystals is determined by X-ray diffraction (XRD) measurements of the inorganic oxide powders of the present invention under the conditions described above, followed by Rietveld analysis of the resulting XRD data. This Rietveld analysis begins with a crystal structure based on literature data (ICDD database: LATP crystal data from ICDD: 00-066-0872, TiO crystal data from ICDD: 01-070-7347, and AlPO crystal data from ICDD: 01-072-7633). The crystal structure parameters are then adjusted using a profile fitting method to minimize the gap or residual between the literature data and the measured data. This analysis allows the measurement and calculation of the content (proportion of content) of LATP crystals, TiO crystals, AlPO crystals, and other by-product crystalline phases in the inorganic oxide powders of the present invention, as well as the a-axis length (Å) and c-axis length (Å) of the LATP crystal unit cell.

[0036] In the present invention, the "power capacity" of a lithium-ion secondary battery under low-temperature conditions is a value calculated from a graph showing the relationship between the discharge capacity and voltage of a lithium-ion secondary battery under a predetermined low-temperature condition (e.g., an ambient temperature of -10°C). Specifically, a lithium-ion secondary battery is first discharged from a fully charged state (SOC 100%) in a constant current manner under the predetermined low-temperature condition, and the discharge capacity (mAh / g) is measured until the battery voltage reaches 3V. Here, this discharge capacity is the discharge capacity per unit weight of positive electrode active material from a fully charged state until the end-of-discharge voltage (3V) is reached, and is calculated by dividing the product of the current and discharge time during discharge by the weight of the positive electrode active material. In this measurement, the discharge capacity is measured every 2mV (millivolts), and the battery voltage (V) during measurement is plotted on the Y-axis and the discharge capacity (mAh / g) on ​​the X-axis. The power capacity (mWh / g) of the battery is calculated by multiplying the discharge capacity (mAh / g) measured every 2 mV with the battery's voltage (V) at the time of measurement. Referring to the example calculation graph in Figure 1, the power capacity is calculated by adding up all the products of the discharge capacity measured every 2 mV from the start of discharge of the battery until it reaches 3 V and the battery's voltage at the time of measurement (essentially the area value of the region labeled "integral region" shown below the graph line in Figure 1). Therefore, this power capacity can be said to essentially indicate the amount of electrical energy that the battery can consume.

[0037] <Lithium ion conductivity> The inorganic oxide powder of the present invention is a lithium ion conductive inorganic oxide powder (lithium ion conductive inorganic material), and although not limited thereto, its lithium ion conductivity at 25°C is 1.0 × 10 -5 (1.0E-05) S / cm or more is more preferable, and 1.0 × 10 -4 (1.0E-04) S / cm or more is more preferable, and 5.0 × 10 -4 It is more preferable that the viscosity is (5.0E-04) S / cm or more. Here, this lithium ion conductivity is calculated by forming a gold electrode as a blocking electrode on the measurement object using a magnetron sputtering device, and measuring impedance using an electrochemical evaluation device under conditions of a frequency of 0.1 Hz to 7 MHz, an amplitude voltage of 10 mV, and an open circuit voltage at 25° C. In this measurement, the measurement object is a solid object before powderization (before pulverization) on whose surface a gold electrode can be formed.

[0038] <Average particle size> The inorganic oxide powder of the present invention has an average particle diameter (D 50 ) is preferably 0.1 μm or more and 2.0 μm or less from the viewpoints of the effects of the present invention and ease of use in electrodes, etc. The lower limit may be 0.2 μm or more, and the upper limit may be 1.5 μm or less, further 1.0 μm or less, further 0.7 μm or less, further 0.6 μm or less, further 0.5 μm or less, or even 0.4 μm or less. This can be adjusted by the conditions during pulverization and sieving. Here, this "average particle diameter (D 50 ) is the volume-based average particle diameter (50% volume cumulative distribution diameter (D 50 )).

[0039] The inorganic oxide powder of the present invention can be produced by a method commonly used in inorganic material production (glass ceramic production or ceramic production), such as calcination (calcination), melting, vitrification, crystallization, sintering, or a modified method thereof. To produce a glass ceramic powder, the raw material is vitrified (melted, rapidly cooled) and then crystallized by heat treatment (for example, at 900°C or higher, or even at 900°C to 1200°C, preferably at a heating rate of 10°C / min or higher), which is then cooled (cooling at a cooling rate of 10°C / min or higher is particularly preferred) to obtain glass ceramic particles, which are then crushed, finely pulverized, and passed through a classifier to produce a glass ceramic powder. Examples of such methods include, but are not limited to, vitrifying (melting, quenching) the raw material, followed by heat treatment (for example, at 900°C or higher, or even at 900°C to 1200°C, preferably at a heating rate of 10°C / min or higher). Furthermore, when producing ceramic powder, an example method is to mix and mold the raw materials, sinter them into a solid-state reaction (for example, at a temperature between 700°C and 1300°C, preferably at a heating rate of 30°C / min or more for calcination and 10°C / min or more for firing), cool them (preferably at a cooling rate of 10°C / min or more) to obtain a ceramic body, which is then crushed, finely pulverized, and pulverized through a classification device to produce ceramic powder. These methods have in common the uniformity of heating and cooling, the heating rate, the heating temperature and time, the cooling rate, the cooling temperature and time, the grinding conditions (material, amount, and diameter of the media, and in the case of a wet method, the type and amount of the solvent, the grinding time, etc.), and the grinding device, and the like, so that the inorganic oxide powder of the present invention can be obtained. The mass % (content) of TiO2 crystals relative to the total mass of the crystalline phase can be controlled, for example, by controlling the ratio of the raw material composition, the raw material mixing conditions, the crystalline system of the raw material TiO2, conditions such as the heat treatment atmosphere, the heat treatment temperature and time, or the solid-state reaction temperature and time, and in the case of glass ceramics, the crystallization temperature and time. The same applies to AlPO4 crystals, and it can also be adjusted by controlling the properties (viscosity and concentration) of the raw material H3PO4. Furthermore, by using zirconia balls as media during the above-mentioned grinding, the inclusion of Fe can be prevented.

[0040] <Lithium-ion secondary battery> Next, a lithium ion secondary battery having an electrode containing the inorganic oxide powder of the present invention and / or an electrolyte layer containing the inorganic oxide powder of the present invention will be described in detail.

[0041] As described above, this lithium ion secondary battery comprises an electrode containing the inorganic oxide powder of the present invention (an electrode containing the inorganic oxide powder of the present invention together with an electrode active material), and / or an electrolyte layer containing the inorganic oxide powder of the present invention (such as a lithium ion conductive polymer electrolyte layer containing the inorganic oxide powder of the present invention), i.e., an electrode and / or electrolyte layer formed using a material containing the inorganic oxide powder of the present invention, and has improved power capacity under low temperature conditions (for example, a power capacity of 380 mWh / g or more under atmospheric conditions of -10°C). For example, the inorganic oxide powder of the present invention can be mixed with a positive electrode material (positive electrode active material) or a negative electrode material (negative electrode active material), and optionally a conductive additive, binder, and molded to form an electrode (positive electrode or negative electrode). The electrodes (positive and negative electrodes) containing the mixture can be combined with a nonaqueous electrolyte solution containing a fluorine-containing lithium salt dissolved in an aprotic organic solvent as an electrolyte component, and a separator (disposed between the positive and negative electrodes) to form the lithium-ion secondary battery. Alternatively, at least a portion of the surface of the positive or negative electrode material can be coated with the inorganic oxide powder of the present invention, and an electrode can be formed using this. Both the mixing and coating can be performed. The inorganic oxide powder of the present invention may be contained in either the positive or negative electrode, or both may contain the inorganic oxide powder of the present invention. However, it is more preferable that at least the positive electrode contains the inorganic oxide powder of the present invention, as this will more easily achieve the effects of the present invention. The lithium ion conductive polymer electrolyte used as the electrolyte layer may also be formed by blending the inorganic oxide powder of the present invention. In this case, this may be combined with an electrode that does not contain the inorganic oxide powder of the present invention to form a lithium ion secondary battery. Generally, when a material other than an electrode active material is contained in an electrode of a lithium ion secondary battery, the power capacity tends to decrease. However, one of the major features of the inorganic oxide powder of the present invention is that even when the inorganic oxide powder is contained in an electrode of a lithium ion secondary battery together with an electrode active material, the power capacity can be improved under low temperature conditions.

[0042] The positive electrode active material of the positive electrode material can be a transition metal compound capable of absorbing and releasing lithium, such as a transition metal oxide containing at least one selected from the group consisting of manganese, cobalt, nickel, vanadium, niobium, molybdenum, iron, and titanium (specifically, LiCoO2). Examples of the negative electrode active material of the negative electrode material include lithium metal, alloys capable of absorbing and releasing lithium, such as lithium-aluminum alloys and lithium-indium alloys, transition metal oxides of titanium and vanadium, and carbon-based materials such as graphite (specifically, artificial graphite). Examples of conductive additives include carbon-based materials such as acetylene black. Examples of binders include fluororesins such as PVdF (polyvinylidene fluoride) and rubber materials such as SBR (styrene butadiene rubber). In addition, thickeners such as CMC (sodium carboxymethyl cellulose) can also be used.

[0043] The nonaqueous electrolyte is an electrolyte solution in which an electrolyte component containing a lithium salt is dissolved in a liquid nonaqueous solvent, and examples of this liquid nonaqueous solvent include aprotic organic solvents (e.g., mixed solvents of cyclic carbonates and / or chain carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate). Examples of the electrolyte component include lithium salts such as lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonimide (LiFSI). Furthermore, examples of lithium ion conductive polymer electrolytes include those in which an electrolyte component containing a lithium salt is impregnated into a polymer compound (such as a polymer gel, e.g., polyvinylidene fluoride or polyacrylonitrile). In addition, the above-mentioned liquid non-aqueous solvent may also be impregnated. Furthermore, lithium ion conductive inorganic materials may also be included.

[0044] <Power capacity under low temperature conditions> As described above, a lithium ion secondary battery having an electrode containing the inorganic oxide powder of the present invention and / or an electrolyte layer containing the inorganic oxide powder of the present invention has improved power capacity under low-temperature conditions (e.g., under atmospheric conditions of −10°C). A specific embodiment is a lithium ion secondary battery having an electrode (particularly a positive electrode) containing the inorganic oxide powder of the present invention and a nonaqueous electrolyte containing LiPF as an electrolyte component, and the power capacity at −10°C (under atmospheric conditions of −10°C) can be 380 mWh / g or more. Furthermore, this power capacity at −10°C can be 385 mWh / g or more, further 390 mWh / g or more, further 395 mWh / g or more, further 400 mWh / g or more, further 405 mWh / g or more, and even 410 mWh / g or more.

[0045] This power capacity at -10°C can be measured and calculated as follows. Specifically, a cathode composite containing 0 to 10% by mass of the inorganic oxide powder of the present invention (mass ratio relative to the total mass of the cathode composite) was applied to an Al foil cathode current collector and dried to form a cathode. Anode composite containing 0 to 10% by mass of the inorganic oxide powder of the present invention (mass ratio relative to the total mass of the cathode composite) was applied to a Cu foil anode current collector and dried to form a cathode. In other words, the inorganic oxide powder of the present invention was mixed into either or both of the cathode composite and the anode composite, and a nonaqueous electrolyte containing LiPF6 as the electrolyte component, the cathode and anode described above, and a separator were combined to form a lithium-ion secondary battery. Then, using a charge-discharge device, a known chemical conversion treatment and known aging were performed in this order, followed by the following low-temperature test. The discharge capacity (mAh / g) was measured and graphed as described above, and the power capacity (mWh / g) at −10°C was calculated. Low temperature test: A lithium-ion secondary battery with SOC 100% (fully charged) is stored at -10°C for 6 hours to stabilize the temperature, and then CC discharge (0.5C, -10°C) is performed to the discharge end voltage (3V) to check the discharge capacity and power capacity.

[0046] The embodiment described above is merely an example for facilitating understanding of the present invention, and is not intended to limit the present invention. In other words, the components and the like described above may be changed or improved without departing from the spirit of the present invention, and the present invention naturally includes equivalents thereof.

[0047] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples, and various modifications are possible within the technical concept of the present invention. [Example]

[0048] Various lithium-ion conductive inorganic oxide powders (glass ceramic powders or ceramic powders) were prepared and evaluated, and lithium-ion secondary batteries equipped with electrodes containing the powders were also evaluated.

[0049] <Preparation of lithium ion conductive glass ceramic powder> The raw materials used were LiCO3, H3PO4, TiO2, and Al(PO3)3, with optional SiO2. They were weighed and mixed uniformly to achieve the desired composition. They were then placed in a platinum pot and rapidly heated (at a rate of 200-800°C / min) in an electric furnace at 1500°C for 4 hours while stirring. The resulting molten glass was then rapidly cooled by dropping it into running water, yielding glass flakes. The glass flakes were quickly removed from the water, spread on a flat plate, and dried in a thermostatic chamber at 100°C for at least 12 hours to remove moisture. The dried glass flakes obtained above were then heated at a rate of 10 to 100°C / min, and then heat-treated at 950°C for 6 to 12 hours depending on the powder conditions, to cause crystallization. Glass ceramics were then obtained by cooling to room temperature at a rate of 10 to 20°C / min, and then crushed and sized to produce the lithium ion conductive glass ceramic powder of Example 1 or Example 3. During crushing, zirconia balls were used as the crushing media to prevent the inclusion of Fe.

[0050] <Preparation of lithium ion conductive ceramic powder> The raw materials used were LiCO3, Li3PO4, H3PO4, TiO2, and Al(PO3)3. They were weighed to achieve the desired composition and uniformly mixed. Then, pellets measuring approximately 15 mm in diameter and 5 mm thick were formed. The mixture was placed in a platinum crucible, capped with a lid made of the same material, and placed in an electric furnace. The mixture was heated at a rate of 50 °C / min and then calcined at 1000 °C for 10 hours. After cooling to room temperature, the mixture was removed, dry-ground to approximately 100 μm or less, and then pelletized again in the same manner. The crucible and lid were placed in an electric furnace, heated at a rate of 10 °C / min, and then fired (sintered) at 1200 °C for 4 hours. The mixture was then cooled to room temperature at 20 °C / min to obtain ceramics. These were then crushed and sized to produce the lithium ion conductive ceramic powders of Example 2, Comparative Example 1, and Comparative Example 2. Except for Comparative Example 2, zirconia balls were used as the grinding media to prevent the inclusion of Fe.

[0051] These lithium ion conductive glass-ceramic powders and lithium ion conductive ceramic powders (Examples 1-3, Comparative Examples 1-2) were subjected to X-ray diffraction (XRD) measurements (using an automated XRD analyzer, Bruker's "D8 DISCOVER") under the following conditions. Rietveld analysis of the XRD data was then performed. The proportions of LATP, TiO2, and AlPO4 crystals contained in these crystalline phases, as well as the a-axis length (Å) and c-axis length (Å) of the LATP crystal unit cell, were measured and calculated using profile fitting. Furthermore, the content of Fe as an impurity was confirmed using inductively coupled plasma optical emission spectroscopy (ICP-OES: an ICP optical emission spectrometer, Agilent Technologies' "ICP-OES 5900"). These results are summarized in Table 1 below. Note that "total" in Table 1 refers to the total content of LATP crystals, TiO2 crystals, and AlPO4 crystals (% by mass relative to the total mass of the crystalline phase). Furthermore, a graph showing the relationship between the content of TiO2 crystals contained therein (% by mass relative to the total mass of the crystalline phase) and the a / c of ​​LATP crystals is shown in Figure 2, and a graph showing the relationship between the content of TiO2 crystals (% by mass relative to the total mass of the crystalline phase) and the content of AlPO4 crystals (% by mass relative to the total mass of the crystalline phase) is shown in Figure 3.

[0052] (XRD measurement conditions) Source: CuKα, 1.54060Å X-ray source: Tube voltage / current: 40kV / 40mA Goniometer radius: 250 mm Scan Type: Coupled TwoTheta / Theta Scan range: 10~60° Step width: 0.02° Entrance Soller slit: 4.1° Divergence slit: 0.5° Anti-scatter slits: 18 (ICP-OES analysis conditions) Equipment: ICP optical emission spectrometer (Agilent Technologies, ICP-OES 5900) Measurement conditions: nebulizer flow rate 0.70 L / min, Fe measurement wavelength 238.204 nm

[0053] Furthermore, the lithium ion conductivity of these lithium ion conductive glass ceramic powders and lithium ion conductive ceramic powders was measured and evaluated at 25° C. The measurements were carried out as follows, and the results are also shown in Table 1 below (ionic conductivity).

[0054] [Lithium ion conductivity (S / cm) at 25°C] The samples for measuring lithium ion conductivity were crystallized flake glass in Examples 1 and 3, and sintered bodies after firing in Example 2 and Comparative Examples 1 and 2. A gold electrode was formed on each sample as a blocking electrode using a magnetron sputtering device (SC-701HMC, manufactured by Sanyu Electronics Co., Ltd.), and impedance measurements were performed at 25°C using an electrochemical evaluation device (SP300, manufactured by Biologic Co., Ltd.) under conditions of a frequency of 0.1 Hz to 7 MHz, an amplitude voltage of 10 mV, and an open circuit voltage, and the lithium ion conductivity (S / cm) was calculated.

[0055] <Tests on lithium-ion secondary batteries equipped with electrodes containing lithium-ion conductive glass ceramic powder or lithium-ion conductive ceramic powder> An electrode (positive electrode) was formed using each of the powders, and a test was conducted using a lithium ion secondary battery equipped with the electrode to confirm and evaluate the power capacity at −10° C. Specifically, the test was conducted as follows.

[0056] [Fabrication of electrodes and batteries] 1) Preparation of the positive electrode Using a planetary centrifugal mixer (Thinky Corporation, Awatori Rentaro), 98% by mass of LiCoO2 as the positive electrode active material, 1% by mass of acetylene black as a conductive additive, 1% by mass of PVdF as a binder, and 1% by mass of one of the above powders were mixed, and NMP (1-methyl-2-pyrrolidone) was added to adjust the viscosity, followed by degassing to form a paste-like slurry. This slurry was applied to a 20 μm thick Al foil using an automatic coater (Hosen Co., Ltd., HSCM20-800S) and dried at 120°C. The electrode's basis capacity (discharge capacity per unit area of ​​the active material layer applied to the substrate) was 3.6 mAh / cm. 2 This was pressed into a roll press (Hosensha, HSR-60150H) to a density of 3.5 g / cm 3 The film was pressed to a thickness of 59 μm, punched out to 30 mm x 40 mm using a press cutter (Aichi Technical Co., Ltd.), and vacuum dried at 160°C for 16 hours using a glass tube oven (Nippon Buchi Co., Ltd., B-585). 2) Preparation of the negative electrode Using a planetary centrifugal mixer (Thinky Corporation, Awatori Rentaro), 97.5% by mass of artificial graphite was mixed as the negative electrode active material, 1% by mass of CMC as a thickener, and 1.5% by mass of SBR as a binder, and ion-exchanged water was added to prepare a paste-like slurry. This slurry was applied to a 16.5 μm thick Cu foil using an automatic coater (Hosen Co., Ltd., HSCM20-800S) and dried at 65°C. The electrode had a capacity of 4.0 mAh / cm. 2 This was pressed into a roll press (Hosen Co., Ltd., HSR-60150H) to a density of 1.4 g / cm 3 The film was pressed to a thickness of 90 μm, punched out to 30.5 mm x 40.5 mm using a press cutter (Aichi Technical Co., Ltd.), and vacuum dried at 160°C for 16 hours using a glass tube oven (Nippon Buchi Co., Ltd., B-585). 3) Battery construction In a dry room (temperature 23°C, dew point temperature -50°C or lower), the positive and negative electrodes obtained in 1) and 2) above were tab-welded so that the A / C ratio (volume ratio of positive electrode active material to negative electrode active material) was 1.2, and the resultant was housed in a laminated resin film together with a separator (polypropylene, film thickness 22 μm, porosity 48%) and thermocompressed with a sealer. An electrolyte (electrolyte components: 1 mol / L LiPF6, solvent: ethylene carbonate: ethyl methyl carbonate = 3:7 VC (vinylene carbonate) 1%) was injected, impregnating the electrodes and separator, and the battery was vacuum-sealed (vacuum degassing and sealing) to prepare a battery.

[0057] [Confirming power capacity at -10℃] For all the batteries fabricated, a charge / discharge device (Asuka Electronics, ACD-M01) and a small environmental tester (Espec, SH-242) were used for temperature control, and the following chemical conversion treatment, vacuum degassing, and resealing (similar to the vacuum sealing during cell battery fabrication), followed by the following aging process, were carried out in this order. Then, the following low-temperature test was carried out, and the discharge capacity (mAh / g) was measured every 2 mV until the voltage reached 3 V. The results were then graphed to calculate the power capacity (mWh / g) under atmospheric conditions at -10°C. The results are also summarized in Table 1 below. FIG. 4 is a graph showing the above measurement results for a lithium ion secondary battery having a positive electrode containing the inorganic oxide powder of Example 1 and a lithium ion secondary battery having a positive electrode containing the inorganic oxide powder of Comparative Example 2 (some plots are omitted in FIG. 4), FIG. 5 is a graph showing the relationship between the a / c of ​​the LATP crystals contained in each of the above powders mixed into the positive electrode and the power capacity (mWh / g) at −10° C. of a lithium ion secondary battery having a positive electrode containing the same, and FIG. 6 is a graph showing the relationship between the Fe content (ppm) contained in each of the above powders mixed into the positive electrode and the power capacity (mWh / g) at −10° C. of a lithium ion secondary battery having a positive electrode containing the same. Chemical treatment: CC-CV charge (0.05C, 4.4V-0.01C cutoff, 45℃), CC discharge (0.1C, 3.0V cutoff, 45℃), CC-CV charge (0.1C, 4.4V-0.05C cutoff, 45℃), CC discharge (0.1C, 3.0V cutoff, 45℃). Aging: CC-CV charge (0.2C, 4.4V-0.05C cutoff, 25℃), CC discharge (0.2C, 3.0V cutoff, 25℃). Low temperature test: CC-CV charging (0.2C, 4.4V-0.05C cutoff, 25℃), resting (leaving) at -10℃ for 6 hours, and CC discharging (0.5C, 3.0V cutoff, -10℃) to the discharge end voltage (3V) to check the discharge capacity and power capacity.

[0058] [Table 1]

[0059] These results show that by using a lithium ion conductive glass ceramic powder or lithium ion conductive ceramic powder containing 80.0% or more LATP crystals and more than 0% TiO2 crystals, in mass % relative to the total mass of the crystalline phase, and further having an a / c ratio of the LATP crystals of 0.40860 or more, the power capacity of a lithium ion secondary battery equipped with a positive electrode containing this powder exceeded 380 mWh / g at -10°C (Examples 1 to 3). It was also shown that the higher the a / c ratio of the glass ceramic powder or ceramic powder or the lower the Fe content, the more likely the power capacity of the lithium ion secondary battery at -10°C tends to increase. On the other hand, the powders of Comparative Example 1, which did not contain TiO2 crystals, and Comparative Example 2, in which the content of LATP crystals was outside the specified range, had a power capacity of less than 380 mWh / g at -10°C of a lithium ion secondary battery equipped with a positive electrode containing these powders, and did not achieve the effects of the above examples.

Claims

1. A glass-ceramic powder comprising: In terms of oxide, mass % Li 2 O component is 4.0 to 6.0%, Al 2 O 3 component is 3.0 to 9.0%, TiO 2 component 31.0 to 40.0%, P 2 O 5 component 49.0 to 57.0%, SiO 2 content of 5.0% or less Contains In mass % relative to the total mass of the crystalline phase, LATP crystals are 80.0% or more, TiO 2 Crystals 2.0% or more Contains The a / c of the LATP crystal is 0.40880 or more; Inorganic oxide powder.

2. 2. The inorganic oxide powder according to claim 1, wherein the Fe content is 25.0 ppm or less.

3. AlPO in mass% relative to the total mass of the crystalline phase 4 3. The inorganic oxide powder according to claim 1, wherein the content of crystals is 9.7% or less.

4. A lithium ion secondary battery comprising an electrode containing the inorganic oxide powder according to claim 1 or 2, and / or an electrolyte layer containing the inorganic oxide powder according to claim 1 or 2.

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