Lithium-ion secondary battery comprising inorganic oxide powder and an electrode or electrolyte layer containing it.

Abstract

This invention provides a material that enables the creation of lithium-ion secondary batteries with improved power capacity under low-temperature conditions. [Solution] The above problem is solved by an inorganic oxide powder, which is a glass ceramic or ceramic powder, containing 80.0% or more of LATP crystals and more than 0% of TiO2 crystals by mass percentage relative to the total mass of the crystalline phase, and having an a / c ratio of 0.40860 or more for the LATP crystals.

Description

[Technical Field]

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

[0002] Lithium-ion rechargeable batteries, which have high energy density and can be charged and discharged, are widely used in applications such as power supplies for electric vehicles and mobile phone terminals. Most lithium-ion secondary batteries currently on the market use a liquid electrolyte to achieve high energy density. This electrolyte is typically a non-aqueous solution, such as a lithium salt dissolved in an organic solvent. The battery structure mainly consists of a separator between the positive and negative electrodes, with the electrolyte filling the cavity. Furthermore, lithium-ion secondary batteries (lithium-ion polymer secondary batteries) that use a polymer compound containing electrolyte components (lithium-ion conductive polymer) as the electrolyte layer have also been developed and are commercially available.

[0003] However, lithium-ion secondary batteries, as described above, tend to experience a significant decrease in charge and discharge capacity under low-temperature conditions. Therefore, technological development is underway to maintain high charge and discharge capacity even under low-temperature conditions.

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

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-062054 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, there is still room for improvement regarding 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 regarding the power capacity under low-temperature conditions of lithium-ion secondary batteries equipped with electrodes and electrolyte layers formed using predetermined materials.

[0007] Therefore, the present invention aims 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 diligently conducted research and found that the power capacity of a lithium-ion secondary battery under low-temperature conditions, as described later, correlates with the ratio (a / c) of the a-axis length to the c-axis length of the LATP crystals contained in the electrode and other materials. Furthermore, they found that this a / c is related to the coexisting TiO2 crystals, and through further investigation, they discovered that by incorporating glass ceramics or ceramic powder (inorganic oxide powder) containing 80.0% or more LATP crystals and more than 0% TiO2 crystals as mass percent of the total mass of the crystalline phase, and having an a / c ratio of 0.40860 or more of these LATP crystals, into the electrode or electrolyte layer material, the power capacity of a lithium-ion secondary battery equipped with an electrode or electrolyte layer formed using this material can be improved under low-temperature conditions, thus completing the present invention.

[0009] In other words, the present invention is as follows <1> ~ <6> Includes embodiments. <1> Glass ceramics or ceramic powder, In terms of mass percentage relative to the total mass of the crystalline phase, LATP crystals of 80.0% or more, TiO2 crystals exceeding 0% Contains, The a / c ratio of the LATP crystal is 0.40860 or higher. Inorganic oxide powder. <2> The Fe content is 100.0 ppm or less. <1> The inorganic oxide powder described above. <3> The AlPO4 crystal content is 9.7% or less by mass percentage relative to the total mass of the crystalline phase. <1> or <2> The inorganic oxide powder described above. <4> The a / c ratio of the LATP crystal is 0.40870 or higher. <1> ~ <3> An inorganic oxide powder as described in any one of the following. <5> <1> ~ <4> An electrode containing an inorganic oxide powder as described in any one of the following, and / or <1> ~ <4> A lithium-ion secondary battery comprising an electrolyte layer containing an inorganic oxide powder as described in any one of the following. <6> The power capacity at -10℃ is 380mWh / g or more. <5> Lithium-ion secondary batteries as described above. [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. Furthermore, it is possible to provide a lithium-ion secondary battery with improved power capacity under low-temperature conditions that includes an electrode or electrolyte layer containing this inorganic oxide powder. [Brief explanation of the drawing]

[0011] [Figure 1] This is an example graph showing the calculation of the power capacity of a lithium-ion secondary battery under specified temperature conditions. [Figure 2] This graph shows the relationship between the TiO2 crystal content (mass %) relative to the total mass of the crystalline phase and the a / c ratio of the contained LATP crystals in the inorganic oxide powders of the examples or comparative examples. [Figure 3]This is a graph showing the relationship between the TiO₂ crystal content (mass% relative to the total mass of the crystal phase) and the AlPO₄ crystal content (mass% relative to the total mass of the crystal phase) in the inorganic oxide powder of an example or comparative example. [Figure 4] This is a graph showing the measurement results of discharge capacity (mAh / g) until the voltage value reaches 3 V at -10°C for a lithium ion secondary battery comprising a positive electrode containing the inorganic oxide powder of Example 1 or Comparative Example 2. [Figure 5] This is a graph showing the relationship between the a / c ratio of LATP crystals contained in the inorganic oxide powder of an example or comparative example and the power capacity (mWh / g) at -10°C of a lithium ion secondary battery comprising a positive electrode containing said inorganic oxide powder. [Figure 6] This is a graph showing the relationship between the Fe content (ppm) in the inorganic oxide powder of an example or comparative example and the power capacity (mWh / g) at -10°C of a lithium ion secondary battery comprising a positive electrode containing said inorganic oxide powder. [[Mode for Carrying Out the Invention]]

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

[0013] First, the components contained in the inorganic oxide powder of the present invention, the crystal phase contained therein, the form and physical properties thereof, and the like will be described in detail.

[0014] The content of each component in the inorganic oxide powder of the present invention is expressed in mass % in terms of oxide unless otherwise specified (hereinafter, when simply % is mentioned regarding the content of a component, it means mass % in terms of oxide unless otherwise specified). The content of each component expressed in "mass % in terms of oxide" is determined by analyzing the inorganic oxide powder of the present invention by performing ICP emission spectroscopy (inductively coupled plasma emission spectroscopy) for the Li component and XRF analysis (X-ray fluorescence analysis) for the other components, and then expressing the oxide content of each component in the inorganic oxide powder of the present invention in mass % based on the total mass assuming that all of these components are oxides, with the total mass being 100% by 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 component of LATP crystals. The lower limit of the Li2O content is more preferably 4.0% or more, and even more preferably 4.3% or more, from the viewpoint of lithium ion conductivity and LATP crystal formation. The upper limit is more preferably 6.0% or less, even more preferably 5.7% or less, and even more preferably 5.4% or less, as this makes it easier to suppress the formation 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 component of LATP crystals. Furthermore, it can also be a component of AlPO4 crystals. From the viewpoint of the effects of the present invention, the lower limit of the Al2O3 content is more preferably 3.0% or more, even 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. The upper limit is more preferably 9.0% or less, and even more preferably 8.7% or less, considering the ease of LATP crystal formation.

[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 component of LATP crystals and TiO2 crystals. From the viewpoint of the effects of the present invention, the lower limit of the TiO2 component content 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, as this makes it easier to suppress the formation 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 component of LATP crystals. Furthermore, it is also a component of AlPO4 crystals. From the viewpoint of the effects of the present invention, the lower limit of the P2O5 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, as it makes it easier to suppress the formation 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, GeO2, ZrO2, SnO2, B2O3, Y2O3, Sc2O3, ZnO, Na2O, K2O, and transition metal oxides such as Co, Ni, and Mn. The following explains these ingredients.

[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 can also be a component of LATP crystals, substituting at the P site of the PO4 skeleton in the LATP crystal, causing skeleton distortion and potentially increasing lithium ion conductivity. Furthermore, this SiO2 component can also increase the mechanical strength of the inorganic oxide powder of the present invention. The SiO2 content 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 becomes a component of the LATP crystal, and by substituting into the Ti sites in the LATP crystal, it can increase the lithium ion content in the LATP crystal and thereby enhance 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. Furthermore, this ZrO2 component can also enhance the water resistance of the inorganic oxide powder of the present invention. The ZrO2 content 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 of the inorganic oxide powder of the present invention. The SnO2 content 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 as a glass ceramic powder. Furthermore, this B2O3 component can be substituted for a portion 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 and Y2O3 components can also be substituted for a portion of the Al2O3 component and are optional components that can adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The content of each of these components is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0026] The ZnO component can substitute for a portion of the TiO2 component and is an optional component that can adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The ZnO content is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0027] The Na2O and K2O components are also optional components that can adjust the lithium ion conductivity of the inorganic oxide powder of the present invention. The content of each of these components 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.

[0028] Transition metals such as Co, Ni, and Mn are optional components that can suppress the elution of transition metals contained in the electrode active material (especially the positive electrode active material) into the electrolyte. The total content of these transition metals 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, in terms of oxide mass percent. Furthermore, the inorganic oxide powder of the present invention can increase the power capacity of the lithium-ion secondary battery under low-temperature conditions by reducing the Fe content as much as possible in a predetermined configuration, for example by selecting the raw material grade or making improvements during manufacturing. Therefore, it is preferable that the Fe content among the transition metals be reduced as much as possible. The Fe content is more preferably 100.0 ppm or less, even 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 amount of Fe element measured by inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0029] Furthermore, the inorganic oxide powder of the present invention preferably contains as little sulfur (S) as possible (for example, less than 0.5% by mass percentage in terms of oxide, and even less than 0.1%), and more preferably no sulfur at all. This is because reducing the S component reduces the possibility of generating harmful gases such as hydrogen sulfide in the lithium-ion secondary battery. Similarly, it is preferable to reduce the content of arsenic (As), antimony (Sb), and lead (Pb) as much as possible, and more preferably no sulfur at all, because they are harmful substances. In addition, it is preferable to reduce the content of bismuth (Bi) and tellurium (Te) as much as possible, and more preferably no sulfur at all.

[0030] Furthermore, 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 it, and then crystallizing it by heat treatment or the like, or it may be a ceramic powder obtained by sintering raw materials or the like. These must contain at least LATP crystals and TiO2 crystals, and the amount of LATP crystals must be 80.0% or more by mass of the total mass of the crystalline phase (total amount of crystalline phase) contained in the inorganic oxide powder (powdered aggregate) of the present invention, that is, the LATP crystal content must be 80.0% or more relative to the total amount of crystalline phase. The lower limit is more preferably 83.0% or more, and even more preferably 85.0% or more. The upper limit is more preferably 99.0% or less, even 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 more than 0% by mass of TiO2 crystals together with the LATP crystals in relation to the total mass of the crystalline phase. By having a configuration in which a certain amount of TiO2 crystals are included together 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 more preferably 0.5% or more, even 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 more preferably 9.0% or less, even more preferably 7.0% or less, and even more preferably 5.0% or less.

[0031] In addition, the inorganic oxide powder of the present invention may also contain in part crystals other than LATP crystals and TiO2 crystals (for example, other NASICON-type lithium-ion conductive crystals, lithium-ion conductive crystals of other structures such as LISICON-type, perovskite-type, and garnet-type, and other by-product crystals). In particular, embodiments containing a certain amount of AlPO4 crystals (more than 0%, more than 1.0%, and more than 5.0% in mass percent relative to the total mass of the crystal phase) are preferred, and embodiments in which the content of these AlPO4 crystals is greater than the content of the TiO2 crystals described above are preferred, but the content of these AlPO4 crystals is preferably 9.7% or less. This is because AlPO4 crystals structurally bond the particles of the LATP crystal, which is the main crystal phase, and increase the stability of the crystal, but since the lithium-ion conductivity of AlPO4 crystals themselves is low, if the content is too high, the lithium-ion conductivity may decrease.

[0032] Furthermore, the mass ratio of LATP crystals to TiO2 crystals (LATP crystals / TiO2 crystals) in the inorganic oxide powder of the present invention is not limited, but from the viewpoint of the effects of the present invention, it is preferably 10 to 100. 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 not limited thereto, from the viewpoint of the effects of the present invention, the inorganic oxide powder of the present invention is more preferably 99.00% or more, even more preferably 99.50% or more, even more preferably 99.80% or more, and even more preferably over 99.90%. In other words, embodiments in which by-product crystalline phases other than the above-mentioned crystals are extremely small are more preferable. In this case, the AlPO4 crystals may be substantially absent.

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

[0034] Furthermore, the glass ceramic powder described above contains a crystalline phase (for example, 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 ceramics and glass. Moreover, the ceramic powder described above consists of a crystalline phase (for example, LATP crystals as the main crystalline phase and other by-product crystalline phases containing TiO2 crystals), and substantially no amorphous phase (non-crystalline phase) is included.

[0035] Furthermore, as mentioned 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 the LATP crystal) of 0.40860 or higher. In the inorganic oxide powder of the present invention, because the a / c ratio of LATP crystals contained in a predetermined amount or more in a predetermined crystal composition is 0.40860 or higher, it is possible to incorporate more lithium ions into this structure or to increase the number of pathways through which lithium ions can move. Therefore, lithium-ion secondary batteries containing this in electrodes, etc., have improved power capacity under low-temperature conditions (for example, under 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 higher, and even more preferably 0.40880 or higher. Here, the a / c ratio of the LATP crystal is a value confirmed by Rietveld analysis of the XRD measurement data obtained by performing X-ray diffraction (XRD) measurements on the inorganic oxide powder of the present invention under the measurement conditions described above. This Rietveld analysis starts the calculation using the crystal structure based on literature values ​​(ICDD database; LATP crystal data is ICDD:00-066-0872, TiO2 crystal data is ICDD:01-070-7347, and AlPO4 crystal data is ICDD:01-072-7633) as initial values, and adjusts the crystal structure parameters by profile fitting so that the gap and residuals between the literature values ​​and the measurement data are small. Through this analysis, not only the content (content ratio in the crystal phase) of LATP crystals, TiO2 crystals, AlPO4 crystals, and other by-product crystal phases contained in the inorganic oxide powder of the present invention described above can be measured and calculated, but also 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 the voltage of the lithium ion secondary battery under predetermined low-temperature conditions (e.g., under an atmospheric condition of -10°C). Specifically, first, a lithium ion secondary battery under predetermined low-temperature conditions is subjected to CC discharge from a fully charged state (SOC 100%), and the value of discharge capacity (mAh / g) until the voltage value of the battery reaches 3 V is measured. Here, this discharge capacity is the discharge capacity per unit weight of the positive electrode active material from the fully charged state until the end-of-discharge voltage (3 V) is reached, and is defined as a value obtained by dividing the product of the discharge current and the discharge time by the weight of the positive electrode active material. In this measurement, the discharge capacity is measured every 2 mV (millivolts), and plotting is performed with the voltage value (V) of the battery at the time of measurement on the Y-axis and the discharge capacity (mAh / g) on the X-axis. The sum of products of the discharge capacity (mAh / g) discharged every 2 mV and the voltage value (V) of the battery at the time of measurement is taken as the power capacity (mWh / g) of the battery. To re-explain the above with reference to the calculation example graph in Fig. 1, the total value obtained by summing all the products of the discharge capacity values measured every 2 mV and the battery voltage values at the time of measurement from the start of discharge of the battery until reaching 3 V (substantially the area value of the region described as the integration region shown below the graph line in Fig. 1) is taken as the power capacity. Therefore, it can be said that this power capacity substantially indicates 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 even more preferable, and 5.0×10 -4 (5.0E-04) S / cm or more is even more preferable. Here, the lithium-ion conductivity is calculated by forming a gold electrode as a blocking electrode on the object to be measured using a magnetron sputtering apparatus, and then measuring the impedance using an electrochemical evaluation apparatus at 25°C under the conditions of a frequency of 0.1 Hz to 7 MHz, an amplitude voltage of 10 mV, and an open-circuit voltage. In this measurement, the object to be measured is a solid material before powdering (before pulverization) on which a gold electrode can be formed on the surface.

[0038] <Average particle size> The inorganic oxide powder of the present invention has an average particle size (D 50 A particle size of 0.1 μm or more and 2.0 μm or less is preferable from the viewpoint 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, and further 0.4 μm or less. This can be adjusted by conditions during grinding or sizing. Here, this "average particle diameter (D 50 )" refers to the average particle diameter based on volume (50% diameter of the volume integrated distribution (D) measured by a laser diffraction / scattering particle size distribution analyzer. 50 )) is.

[0039] The present invention provides a method for producing inorganic oxide powders using general methods in the production of inorganic materials (glass ceramics production or ceramics production), such as calcination (pre-calcination), melting, vitrification, crystallization, and sintering, or modified methods thereof. While not limited to these methods, an example of a glass ceramics powder is obtained by vitrifying the raw material (melting, rapid cooling), then crystallizing it through heat treatment (for example, to 900°C or higher, or even 900°C to 1200°C, with a particularly favorable heating rate of 10°C / min or higher), cooling it (particularly favorable cooling at a cooling rate of 10°C / min or higher), and then further crushing, fine grinding, and pulverizing through a classification device to obtain glass ceramics powder. Furthermore, when producing ceramic powder, examples include mixing and molding the raw materials, performing solid-phase reaction sintering (for example, 700°C to 1300°C, with a heating rate of 30°C / min or more for calcination and 10°C / min or more for final calcination), cooling (a cooling rate of 10°C / min or more is particularly preferable) to obtain a ceramic body, and then further crushing, fine grinding, and classification to produce ceramic powder. Common to these methods, the inorganic oxide powder of the present invention can be obtained by appropriately adjusting the homogeneity of heating and cooling, heating rate, heating temperature and time, cooling rate, cooling temperature and time, grinding conditions (material, amount, and diameter of media, type and amount of solvent in the case of wet grinding, grinding time, etc.), and grinding equipment. The mass percentage (content) of TiO2 crystals relative to the total mass of the crystalline phase can be controlled, for example, by controlling the ratio of raw material composition, the mixing conditions of the raw materials, the crystal system of the raw material TiO2, the heat treatment atmosphere, the heat treatment temperature and time or the solid-phase 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, the inclusion of Fe can be prevented by using zirconia balls as a media during the grinding process.

[0040] <Lithium-ion rechargeable battery> Next, a lithium-ion secondary battery comprising 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 the 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), that is, an electrode and / or electrolyte layer formed using a material containing the inorganic oxide powder of the present invention, with improved power capacity under low-temperature conditions (for example, a power capacity of 380 mWh / g or more under -10°C atmospheric conditions). For example, an electrode (positive or negative electrode) can be formed by mixing and molding the inorganic oxide powder of the present invention with a positive electrode material (positive electrode active material) or a negative electrode material (negative electrode active material) and, if necessary, a conductive additive, a binder, etc., and combining the electrode (positive and negative electrode) containing this with a non-aqueous electrolyte solution in which a lithium salt containing fluorine is dissolved as an electrolyte component in an aprotic organic solvent, and a separator (placed between the positive and negative electrodes) to form the lithium-ion secondary battery described above. Alternatively, at least a portion of the surface of the positive electrode material or the negative electrode material may be coated with the inorganic oxide powder of the present invention and used to form the electrode, or both the mixing and this coating may be performed. It is also possible for only one of the positive or negative electrode to contain the inorganic oxide powder of the present invention, or for both to contain the inorganic oxide powder of the present invention, but it is more preferable that at least the positive electrode contains the inorganic oxide powder of the present invention, as this makes it easier to exhibit the effects of the present invention. Furthermore, the lithium-ion conductive polymer electrolyte used as the electrolyte layer may also be formed by incorporating the inorganic oxide powder of the present invention, and in this case, it 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, including materials other than the electrode active material in the electrodes of lithium-ion secondary batteries tends to lead to a decrease in power capacity. However, one of the major features of the inorganic oxide powder of the present invention is that it can improve the power capacity of lithium-ion secondary batteries even when included together with the electrode active material, under low-temperature conditions.

[0042] As the positive electrode active material for the positive electrode material, a transition metal compound capable of intercalating and releasing lithium can be used. For example, 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, etc.) can be used. As the negative electrode active material for the negative electrode material, examples include alloys capable of intercalating and releasing lithium, such as metallic lithium, lithium-aluminum alloys, and lithium-indium alloys, transition metal oxides such as titanium and vanadium, and carbon-based materials such as graphite (specifically, artificial graphite, etc.). Furthermore, as a conductive additive, carbon-based materials such as acetylene black can be used. Furthermore, as a binder, examples include fluororesins such as PVdF (polyvinylidene fluoride) and rubber materials such as SBR (styrene-butadiene rubber). In addition, thickeners such as CMC (carboxymethylcellulose sodium) can also be used.

[0043] Furthermore, a non-aqueous electrolyte is an electrolyte in which an electrolyte component containing a lithium salt is dissolved in a liquid non-aqueous solvent. Examples of this liquid non-aqueous solvent include aprotic organic solvents (for example, mixed solvents of cyclic carbonates and / or linear 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 hexafluoride phosphate (LiPF6) and lithium bisfluorosulfonimide (LiFSI). Furthermore, examples of lithium-ion conductive polymer electrolytes include those obtained by impregnating a polymer compound (such as a polymer gel, e.g., polyvinylidene fluororide, polyacrylonitrile, etc.) with an electrolyte component containing a lithium salt. In addition, a non-aqueous liquid solvent as described above may also be impregnated. Furthermore, lithium-ion conductive inorganic materials may be further included.

[0044] <Power capacity under low-temperature conditions> As described above, a lithium-ion secondary battery comprising 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 (for example, under an atmosphere of -10°C). A specific embodiment is a lithium-ion secondary battery comprising an electrode (particularly a positive electrode) containing the inorganic oxide powder of the present invention and a non-aqueous electrolyte containing LiPF6 as an electrolyte component, and its power capacity at -10°C (under an atmosphere of -10°C) can be 380 mWh / g or more. Furthermore, this power capacity at -10°C can be 385 mWh / g or more, 390 mWh / g or more, 395 mWh / g or more, 400 mWh / g or more, 405 mWh / g or more, and 410 mWh / g or more.

[0045] The power capacity at -10°C can be measured and calculated as follows. Specifically, first, a positive electrode composite material is prepared by coating an Al foil, which is the positive electrode current collector, with the inorganic oxide powder of the present invention in a ratio of 0 to 10% by mass (mass ratio to the total mass of the positive electrode composite material), and drying it to form the positive electrode. Similarly, a negative electrode composite material is prepared by coating a Cu foil, which is the negative electrode current collector, with the inorganic oxide powder of the present invention in a ratio of 0 to 10% by mass (mass ratio to the total mass of the negative electrode composite material), and drying it to form the negative electrode. In other words, the inorganic oxide powder of the present invention is mixed into either the positive electrode composite material or the negative electrode composite material, or both. A lithium-ion secondary battery is then manufactured by combining a non-aqueous electrolyte solution with LiPF6 as the electrolyte component, the above-mentioned positive and negative electrodes, and a separator. Then, using a charge / discharge device, known chemical treatment and known aging are performed in that order, followed by the following low-temperature test. The discharge capacity (mAh / g) is measured and graphed as described above, and the power capacity (mWh / g) at -10°C is calculated. Low-temperature test: A lithium-ion secondary battery with a state of charge (SOC) of 100% is stored at -10°C for 6 hours to allow the temperature to stabilize. Then, CC discharge (0.5C, -10°C) is performed until the discharge termination voltage (3V) is reached to confirm the discharge capacity and power capacity.

[0046] The embodiments described above are merely examples to facilitate understanding of the present invention and do not limit it. In other words, the components and the like described above can be changed or improved without departing from the spirit of the present invention, and of course, the present invention includes equivalents thereof.

[0047] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments, and various modifications are possible within the technical concept of the present invention. [Examples]

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

[0049] <Preparation of lithium-ion conductive glass ceramic powder> As raw materials, LiCO3, H3PO4, TiO2, and Al(PO3)3, along with SiO2 as needed, were weighed to achieve the desired composition and uniformly mixed. The mixture was then placed in a platinum pot and rapidly heated (at a heating rate of 200-800°C / min), and heated and melted in an electric furnace at 1500°C for 4 hours while stirring. The resulting glass melt was then rapidly cooled by dropping it into running water to obtain flake-shaped glass. This flake-shaped glass was quickly recovered from the water, spread on a flat plate, and dried in a 100°C constant temperature bath for 12 hours or more to remove moisture. The dried, flake-like glass obtained above was then heated at a rate of 10-100°C / min, followed by heat treatment at 950°C for 6-12 hours according to the conditions of each powder to induce crystallization. Furthermore, it was cooled to room temperature at a rate of 10-20°C / min to obtain glass ceramics, which were then crushed and sized to obtain the lithium-ion conductive glass ceramic powder of Example 1 or Example 3. During this crushing process, zirconia balls were used as a media to prevent the inclusion of Fe.

[0050] <Preparation of lithium-ion conductive ceramic powders> LiCO3, Li3PO4, H3PO4, TiO2, and Al(PO3)3 were used as raw materials. After weighing and uniformly mixing them to achieve the desired composition, the mixture was formed into pellets approximately 15 mm in diameter and 5 mm thick. These pellets were placed in a platinum crucible, covered with a lid made of the same material, and placed in an electric furnace. The furnace was heated at a rate of 50°C / min, followed by calcination at 1000°C for 10 hours. After cooling to room temperature, the pellets were removed, dry-ground to a size of approximately 100 μm or less, and then re-formed into pellets. The crucible and lid were then placed in an electric furnace. The furnace was heated at a rate of 10°C / min, followed by final firing (sintering) at 1200°C for 4 hours. The pellets were then cooled to room temperature at 20°C / min to obtain ceramics. These ceramics were then ground and sized to obtain the lithium-ion conductive ceramic powders of Example 2, Comparative Example 1, or Comparative Example 2. In all cases except Comparative Example 2, zirconia balls were used as a media during the grinding process to prevent the inclusion of Fe.

[0051] For these lithium-ion conductive glass ceramic powders and lithium-ion conductive ceramic powders (Examples 1-3, Comparative Examples 1-2), X-ray diffraction (XRD) measurements were performed under the following conditions (using an automated X-ray diffractometer, Bruker "D8 DISCOVER"), and Rietveld analysis of the XRD measurement data was performed. The content ratios of LATP crystals, TiO2 crystals, and AlPO4 crystals 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 the profile fitting method. Furthermore, the content of Fe contained as an impurity was confirmed by inductively coupled plasma emission spectrometry (ICP-OES: ICP emission spectrometer, Agilent Technologies "ICP-OES 5900"). These results are summarized in Table 1 below. In Table 1, "total" refers to the total content of LATP crystals, TiO2 crystals, and AlPO4 crystals (mass %) relative to the total mass of the crystalline phase. Furthermore, Figure 2 shows a graph illustrating the relationship between the TiO2 crystal content (mass %) relative to the total mass of the crystalline phase and the a / c ratio of LATP crystals, and Figure 3 shows a graph illustrating 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.

[0052] (XRD measurement conditions) Source: CuKα, 1.54060Å X-ray source: Tube voltage / tube current, 40kV / 40mA Goniometer radius: 250mm Scan type: Coupled TwoTheta / Theta Scan range: 10-60° Step width: 0.02° Incident solar slit: 4.1° Divergence slit: 0.5° Scatter prevention slits: 18 (ICP-OES analysis conditions) Equipment: ICP 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 at 25°C was measured and evaluated. The measurements were performed as described below, and the results are shown in Table 1 (ionic conductivity).

[0054] [Lithium-ion conductivity at 25°C (S / cm)] Examples 1 and 3 used samples of glass in a crystallized state from flake-like glass, while Examples 2 and Comparative Examples 1 and 2 used samples of sintered bodies after firing as samples for lithium ion conductivity measurement. Gold electrodes were formed on each sample as blocking electrodes using a magnetron sputtering apparatus (Sanyu Electronics, SC-701HMC), and impedance measurements were performed at 25°C under the 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] <Testing of lithium-ion secondary batteries equipped with electrodes containing lithium-ion conductive glass-ceramic powder or lithium-ion conductive ceramic powder> Using the above powders, electrodes (positive electrodes) were formed, and the power capacity at -10°C was confirmed and evaluated in tests using lithium-ion secondary batteries equipped with these electrodes. Specifically, the tests were conducted as follows.

[0056] [Fabrication of electrodes and batteries] 1) Preparation of the positive electrode Using a rotation-orbit mixer (Sinky Co., Ltd., Awatori Rentaro), 98% by mass of LiCoO2 was mixed 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 any of the above powders. NMP (1-methyl-2-pyrrolidone) was added to adjust the viscosity, and the mixture was degassed to obtain a paste-like slurry. This slurry was applied to a 20 μm thick aluminum foil using an automatic coating machine (Hosen Co., Ltd., HSCM20-800S) and dried at 120°C. The basis capacity of the electrode (discharge capacity per unit area of ​​the active material layer applied to the substrate) was 3.6 mAh / cm². 2 This was processed using a roll press machine (Housensha, HSR-60150H) to a density of 3.5 g / cm³. 3 The material was adjusted to a film thickness of 59 μm, pressed, punched out to 30 mm x 40 mm using a press cutter (manufactured by Aichi Technical Co., Ltd.), and vacuum dried at 160°C for 16 hours using a glass tube oven (manufactured by Nippon Buch Co., Ltd., B-585). 2) Fabrication of the negative electrode Using a rotation-orbit mixer (Sinky Co., Ltd., 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. Deionized water was added to prepare a paste-like slurry. This slurry was applied to a 16.5 μm thick Cu foil using an automatic coating machine (Hosen Co., Ltd., HSCM20-800S) and dried at 65°C. The basis capacity of the electrode was 4.0 mAh / cm². 2 This was processed using a roll press machine (Housensha, HSR-60150H) to obtain a density of 1.4 g / cm³. 3 The material was adjusted to a film thickness of 90 μm and pressed, then punched out into 30.5 mm x 40.5 mm pieces using a press cutter (manufactured by Aichi Technical Co., Ltd.), and vacuum dried at 160°C for 16 hours using a glass tube oven (manufactured by Nippon Buch Co., Ltd., B-585). 3) Making a battery In a dry room (temperature 23°C, dew point temperature below -50°C), 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. These electrodes were then placed together with a separator (polypropylene, film thickness 22 μm, porosity 48%) in a laminate resin film and heat-sealed with a sealer. An electrolyte (electrolyte component: 1 mol / L LiPF6, solvent: ethylene carbonate:ethyl methyl carbonate = 3:7 VC (vinylene carbonate) 1%) was injected to impregnate the electrodes and separator, and the battery was fabricated by vacuum sealing (vacuum degassing and sealing).

[0057] [Verification of 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. The following chemical treatment, vacuum degassing and resealing (same as the vacuum sealing during cell battery fabrication), and the following aging were performed in this order. After that, the following low-temperature test was conducted, and the discharge capacity (mAh / g) values ​​were measured at 2mV intervals until the voltage reached 3V. These values ​​were graphed, and the power capacity (mWh / g) under -10°C atmospheric conditions was calculated. These results are also summarized in Table 1 below. Furthermore, Figure 4 shows graphs (some plots are omitted in Figure 4) showing the above measurement results for the lithium-ion secondary battery equipped with the inorganic oxide powder of Example 1 and the lithium-ion secondary battery equipped with the inorganic oxide powder of Comparative Example 2. Figure 5 shows a graph showing the relationship between the a / c ratio of LATP crystals contained in each of the powders mixed in the positive electrode and the power capacity (mWh / g) at -10°C of the lithium-ion secondary battery equipped with the positive electrode containing this. Figure 6 shows a graph showing the relationship between the Fe content (ppm) contained in each of the powders mixed in the positive electrode and the power capacity (mWh / g) at -10°C of the lithium-ion secondary battery equipped with the positive electrode containing this. 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 charging (0.2C, 4.4V-0.05C cutoff, 25℃), CC discharge (0.2C, 3.0V cutoff, 25℃). Low-temperature test: A test to confirm discharge capacity and power capacity by performing CC-CV charging (0.2C, 4.4V-0.05C cutoff, 25℃), resting (leaving) at -10℃ for 6 hours, and CC discharge (0.5C, 3.0V cutoff, -10℃) up to the discharge termination voltage (3V).

[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 percentage of the total mass of the crystalline phase, and further having an a / c ratio of 0.40860 or higher for the LATP crystals, 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 1-3). 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 would be 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 LATP crystal content was outside the specified range, resulted in a lithium-ion secondary battery equipped with a positive electrode containing these powders having a power capacity of less than 380 mWh / g at -10°C, and the effects described in the above examples were not obtained.

Claims

1. Glass ceramics or ceramic powder, In terms of mass percentage relative to the total mass of the crystalline phase, LATP crystals of 80.0% or more, TiO 2 Crystals exceeding 0% Contains, The a / c ratio of the LATP crystal is 0.40860 or higher. Inorganic oxide powder.

2. The inorganic oxide powder according to claim 1, wherein the Fe content is 100.0 ppm or less.

3. In terms of mass % relative to the total mass of the crystalline phase, AlPO 4 The inorganic oxide powder according to claim 1 or 2, wherein the crystal content is 9.7% or less.

4. The inorganic oxide powder according to claim 1 or 2, wherein the a / c ratio of the LATP crystal is 0.40870 or higher.

5. A lithium-ion secondary battery comprising an electrode containing the inorganic oxide powder described in claim 1 or 2, and / or an electrolyte layer containing the inorganic oxide powder described in claim 1 or 2.

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