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

Abstract

The present invention provides a material capable of obtaining a lithium ion secondary battery having improved power capacity under low temperature conditions. The above technical 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 in terms of mass% with respect to the total mass of the crystalline phase, and the a / c 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 electrolyte layer comprising the powder. Background Technology

[0002] High-energy-density, rechargeable lithium-ion batteries are widely used in applications such as power supplies for electric vehicles and mobile phone terminals.

[0003] Most commercially available lithium-ion secondary batteries currently use liquid electrolytes (electrolytes) to achieve high energy density. These electrolytes typically consist of lithium salts dissolved in an organic solvent (non-aqueous electrolytes), and are usually structured with a separator between the positive and negative electrodes filled with such an electrolyte. However, lithium-ion secondary batteries (lithium-ion polymer batteries) that use a polymer compound containing electrolyte components (lithium-ion conductive polymers) as the electrolyte layer, instead of these electrolytes, have also been developed and are commercially available.

[0004] In this case, lithium-ion secondary batteries as described above tend to experience a significant decrease in charge and discharge capacity at low temperatures. Therefore, technologies are being developed to achieve high charge and discharge capacity even at low temperatures.

[0005] For example, Patent Document 1 discloses a lithium-ion secondary battery (a lithium-ion secondary battery using a lithium-rich manganese cathode material), which includes a power generation element comprising: a positive electrode containing a positive electrode active material layer, the positive electrode active material layer containing a lithium transition metal composite oxide having a predetermined composition as the positive electrode active material; a negative electrode; and an electrolyte layer containing an electrolyte solution, wherein the ratio D of the lithium diffusion coefficient of the lithium-ion secondary battery at 25°C and a state of charge (SOC) of 15% to that at a state of charge (SOC) of 80% is... Li15 / D Li80 It is above 0.05, which improves the charge and discharge capacity at low temperatures.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2024-062054 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, there is still room for improvement regarding the power capacity of the lithium-ion secondary battery under low-temperature conditions (e.g., -20 to 10°C), particularly for lithium-ion secondary batteries with electrodes or electrolyte layers formed using specified materials.

[0011] Therefore, the object of the present invention is to provide a material for a lithium-ion secondary battery that can achieve improved power capacity under low-temperature conditions.

[0012] Methods for solving technical problems

[0013] To address the aforementioned technical problems, the inventors conducted in-depth research and discovered a correlation between the power capacity of lithium-ion secondary batteries under low-temperature conditions and the ratio (a / c) of the a-axis length to the c-axis length of LATP crystals contained in the electrode materials. Furthermore, a correlation was found between this a / c ratio and the coexisting TiO2 crystals. Further research revealed that by including glass ceramics or ceramic powders (inorganic oxide powders) in the electrode or electrolyte layer materials, specifically glass ceramics or ceramic powders containing 80.0% or more of LATP crystals and greater than 0% of TiO2 crystals by mass percentage relative to the total mass of the crystalline phase, and with an a / c ratio of 0.40860 or more, the power capacity of lithium-ion secondary batteries with electrodes or electrolyte layers formed using these materials can be improved under low-temperature conditions, thus completing this invention.

[0014] In other words, the present invention includes the following embodiments <1> to <10>.

[0015] <1> An inorganic oxide powder, which is a powder of glass ceramic or ceramic, wherein,

[0016] It contains, in terms of mass percent relative to the total mass of the crystalline phase:

[0017] LATP crystals with a purity of over 80.0%

[0018] TiO2 crystals greater than 0%,

[0019] Furthermore, the a / c ratio of the LATP crystals is 0.40860 or higher.

[0020] <2> The inorganic oxide powder as described in <1>, wherein the Fe content is 100.0 ppm or less, more preferably 30.0 ppm or less.

[0021] <3> Inorganic oxide powder as described in <1> or <2>, wherein the content of AlPO4 crystals is 9.7% or less, based on the mass percentage of the total mass of the crystalline phase.

[0022] <4> The inorganic oxide powder as described in any one of <1> to <3>, wherein the a / c of ​​the LATP crystal is 0.40870 or more, more preferably 0.40880 or more to 0.41000 or less.

[0023] <5> An inorganic oxide powder as described in any one of <1> to <4>, wherein, based on the mass percentage relative to the total mass of the crystalline phase, it contains: more than 83.0% to less than 99.0% of the LATP crystals and more than 1.0% to less than 9.0% of the TiO2 crystals.

[0024] <6> The inorganic oxide powder as described in any one of <1> to <5>, wherein, based on the mass percentage of the total mass of the crystalline phase, the mass ratio of the LATP crystals to the TiO2 crystals (LATP crystals / TiO2 crystals) is 10 or more to 100 or less, more preferably 10 or more and 50 or less.

[0025] <7> The inorganic oxide powder as described in any one of <1> to <6>, wherein the total content of the LATP crystals, the TiO2 crystals and the AlPO4 crystals is 99.00% or more, more preferably 99.80% or more, based on the mass percentage of the total mass of the crystalline phase.

[0026] <8> The inorganic oxide powder as described in any one of <1> to <7>, wherein the lithium-ion conductivity at 25°C is 1.0 × 10⁻⁶. -5 S / cm or higher, more preferably 1.0×10 -4 S / cm or higher, and even more preferably 5.0×10 -4 S / cm or higher.

[0027] <9> A lithium-ion secondary battery comprising: an electrode containing inorganic oxide powder as described in any one of <1> to <8>, and / or an electrolyte layer containing inorganic oxide powder as described in any one of <1> to <8>.

[0028] <10> The lithium-ion secondary battery as described in <9>, wherein the power capacity at -10℃ is above 380mWh / g.

[0029] The effects of the invention

[0030] According to the present invention, an inorganic oxide powder can be provided for use in obtaining a lithium-ion secondary battery with improved power capacity under low-temperature conditions. Furthermore, a lithium-ion secondary battery having an electrode or electrolyte layer containing the powder, with improved power capacity under low-temperature conditions, can be provided. Attached Figure Description

[0031] Figure 1 This is a chart illustrating the calculation of the electrical capacity of a lithium-ion secondary battery under specified temperature conditions.

[0032] Figure 2 This 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 ratio of the LATP crystals contained in the inorganic oxide powder of the examples or comparative examples.

[0033] Figure 3 This is a graph showing the relationship between the TiO2 crystal content (mass %) and the AlPO4 crystal content (mass %) in the inorganic oxide powder of the examples or comparative examples.

[0034] Figure 4 This is a graph showing the measured discharge capacity (mAh / g) of a lithium-ion secondary battery having a positive electrode containing inorganic oxide powder of Example 1 or Comparative Example 2, up to a voltage of 3V at -10°C.

[0035] Figure 5 This is a graph showing the relationship between the a / c of ​​LATP crystals contained in the inorganic oxide powder of the embodiments or comparative examples and the power capacity (mWh / g) of a lithium-ion secondary battery having a positive electrode containing the inorganic oxide powder at -10°C.

[0036] Figure 6 This is a graph showing the relationship between the Fe content (ppm) in the inorganic oxide powder of the examples or comparative examples and the power capacity (mWh / g) of a lithium-ion secondary battery having a positive electrode containing the inorganic oxide powder at -10°C. Detailed Implementation

[0037] The present invention will be described.

[0038] The present invention relates to an inorganic oxide powder, which is a glass-ceramic or ceramic powder, wherein, based on the mass percentage of the total mass of the crystalline phase, it contains more than 80.0% LATP crystals and more than 0% TiO2 crystals, and the a / c ratio of the LATP crystals is more than 0.40860 (hereinafter sometimes referred to as "the inorganic oxide powder of the present invention"), and a lithium-ion secondary battery having an electrode containing the inorganic oxide powder and / or having an electrolyte layer containing the inorganic oxide powder.

[0039] First, the components, crystalline phases, morphology, and physical properties of the inorganic oxide powder of the present invention will be described in detail.

[0040] It should be noted that, unless otherwise specified, the content of the components contained in the inorganic oxide powder of the present invention is expressed as mass % converted from oxides (hereinafter, when the content of a component is only stated as % unless otherwise specified, it refers to mass % converted from oxides). This content of each component expressed as "mass % converted from oxides" means that, for the inorganic oxide powder of the present invention, the Li component is analyzed by ICP emission spectroscopy (high-frequency inductively coupled plasma emission spectroscopy), and other components are analyzed by XRF (fluorescence X-ray diffraction). When the total mass, assuming that all these components are oxides based on their analytical values, is recorded as 100% by mass, the content of each oxide component contained in the inorganic oxide powder of the present invention is expressed as mass % (%).

[0041] The Li2O component is an essential component that imparts lithium-ion conductivity to the inorganic oxide powder of the present invention, and is also a constituent component of LATP crystallization. From the viewpoint of lithium-ion conductivity and LATP crystallization formation, the lower limit of the Li2O component content is preferably 4.0% or more, more preferably 4.3% or more. The upper limit, based on the ease with which the formation of byproducts is suppressed during crystallization and other processes, is preferably 6.0% or less, more preferably 5.7% or less, and even more preferably 5.4% or less.

[0042] The Al2O3 component, which imparts lithium-ion conductivity to the inorganic oxide powder of the present invention, can be a constituent component of LATP crystals. Alternatively, it can be a constituent component of AlPO4 crystals. From the viewpoint of the effects of the present invention, the lower limit of the Al2O3 content is preferably 3.0% or more, more preferably 4.0% or more, further preferably 5.0% or more, even more preferably 6.0% or more, and still more preferably 6.5% or more. The upper limit, based on the ease of LATP crystal formation, is preferably 9.0% or less, more preferably 8.7% or less.

[0043] TiO2 is an essential component that imparts lithium-ion conductivity to the inorganic oxide powder of the present invention, and is a constituent of LATP crystallization and TiO2 crystallization. From the viewpoint of the effectiveness of the present invention, the lower limit of the TiO2 content is preferably 31.0% or more, more preferably 32.0% or more, and even more preferably 33.0% or more. The upper limit, based on the ease with which the formation of byproducts is suppressed during crystallization and other processes, is preferably 40.0% or less, more preferably 38.0% or less, and even more preferably 35.0% or less.

[0044] The P2O5 component, which is also an essential component for imparting lithium-ion conductivity to the inorganic oxide powder of the present invention, is a constituent component of LATP crystallization. Alternatively, it can be a constituent component of AlPO4 crystallization. From the viewpoint of the effectiveness of the present invention, the lower limit of the P2O5 content is preferably 49.0% or more, more preferably 49.5% or more. The upper limit, based on the ease with which the formation of byproducts is suppressed during crystallization and other processes, is preferably 57.0% or less, more preferably 56.0% or less, more preferably 55.0% or less, even more preferably 54.0% or less, even more preferably 53.0% or less, still more preferably 52.5% or less, and even more preferably 52.0% or less.

[0045] The inorganic oxide powder of the present invention may also 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.

[0046] The following is an explanation of these components.

[0047] The SiO2 component is any component that facilitates glass formation when the inorganic oxide powder of the present invention is a glass-ceramic powder. Furthermore, it can also be a constituent component of LATP crystals, replacing the P sites of the PO4 framework in LATP crystals, thereby causing framework distortion and improving lithium-ion conductivity. Moreover, this SiO2 component can also improve the mechanical strength of the inorganic oxide powder of the present invention. It should be noted that the SiO2 content is preferably 5.0% or less, more preferably 4.0% or less, and even more preferably 3.0% or less. Its lower limit can be greater than 0%, or more than 0.1%, or more than 0.2%, or more than 0.5%, and even more than 1.0%.

[0048] The GeO2 component is any component that facilitates the crystallization of the inorganic oxide powder of the present invention. Furthermore, it can also be a constituent component of LATP crystals, replacing Ti sites in LATP crystals to increase the lithium-ion content and thereby improve lithium-ion conductivity. It should be noted that the content of the GeO2 component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and even more preferably 1.0% or less.

[0049] The ZrO2 component is any component that can help improve the chemical durability of the inorganic oxide powder of the present invention. Furthermore, the ZrO2 component can also improve the water resistance of the inorganic oxide powder of the present invention. It should be noted that 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 still more preferably 0.5% or less.

[0050] SnO2 is also any component that facilitates the crystallization of the inorganic oxide powder of the present invention. It should be noted that the content of SnO2 is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0051] The B2O3 component is any component that facilitates glass formation when the inorganic oxide powder of the present invention is selected as a glass-ceramic powder. Furthermore, this B2O3 component can replace a portion of the Al2O3 component and is also a component capable of adjusting the lithium-ion conductivity of the inorganic oxide powder of the present invention. It should be noted that 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.

[0052] The Sc2O3 and Y2O3 components, which can also replace a portion of the Al2O3 component, are any components capable of adjusting the lithium-ion conductivity of the inorganic oxide powder of the present invention. It should be noted that the content of these components is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0053] ZnO can replace a portion of the TiO2 component and is any component capable of adjusting the lithium-ion conductivity of the inorganic oxide powder of the present invention. It should be noted that the ZnO content is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0054] Na2O and K2O are also arbitrary components capable of adjusting the lithium-ion conductivity of the inorganic oxide powder of the present invention. It should be noted that the content 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.

[0055] Transition metals such as Co, Ni, and Mn are any components capable of suppressing the dissolution of transition metals contained in electrode active materials (especially positive electrode active materials) into the electrolyte. It should be noted that the total content of these transition metals, expressed as a percentage by mass of oxides, is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.0% or less, and still even more preferably 0.5% or less.

[0056] It should be noted that the inorganic oxide powder of the present invention, by means of, for example, selecting raw material grades or improving manufacturing processes, can reduce the Fe content as much as possible under a specified composition, thereby further improving the power capacity of the aforementioned lithium-ion secondary battery under low-temperature conditions. Therefore, it is preferable to keep the Fe content in the transition metal as low as possible. Furthermore, the Fe content is more preferably 100.0 ppm or less, even more preferably 95.0 ppm or less, further 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 Fe element content measured by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0057] Furthermore, the inorganic oxide powder of the present invention preferably has a sulfur (S) content reduced to a minimum (e.g., less than 0.5% by mass percentage in oxide form, further less than 0.1%, etc.), and more preferably is sulfur-free. This is because reducing the S content can reduce the possibility of generating harmful gases such as hydrogen sulfide in the aforementioned lithium-ion secondary batteries. In addition, arsenic (As), antimony (Sb), and lead (Pb) are also preferably reduced to a minimum, and more preferably are not present, as they are harmful substances. Furthermore, bismuth (Bi) and tellurium (Te) are also preferably reduced to a minimum, and more preferably are not present.

[0058] Furthermore, the inorganic oxide powder of the present invention can be a glass-ceramic powder obtained by melting raw materials into a glass melt at a specified temperature, vitrifying it, and then crystallizing it through heat treatment; or it can be a ceramic powder obtained by sintering raw materials. It should contain at least LATP crystals and TiO2 crystals, and the LATP crystals should account for 80.0% by mass or more of the total mass (total crystalline phase content) of the crystalline phase contained in the inorganic oxide powder (powder aggregate) of the present invention, that is, it contains 80.0% or more of LATP crystals relative to the total crystalline phase content. The lower limit is preferably 83.0% or more, more preferably 85.0% or more. The upper limit is preferably 99.0% or less, more preferably 98.0% or less, further preferably 95.0% or less, and even more preferably 92.0% or less. In addition, the inorganic oxide powder of the present invention, as described above, together with the LATP crystals, also contains more than 0% TiO2 crystals by mass% relative to the total mass of the crystalline phase. In this way, by including a certain amount of TiO2 crystals along with a specified amount of LATP crystals, the a / c ratio of the coexisting LATP crystals can be easily adjusted to a specified range. It should be noted that 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 further preferably 2.0% or more. The upper limit is preferably 9.0% or less, more preferably 7.0% or less, and further preferably 5.0% or less.

[0059] Furthermore, the inorganic oxide powder of the present invention may also contain a portion of crystals other than LATP crystals and TiO2 crystals (e.g., other NASICON-type lithium-ion conductive crystals, LISICON-type, perovskite-type, garnet-type, and other structures of lithium-ion conductive crystals, and other by-product crystals). In particular, an embodiment containing a certain amount of AlPO4 crystals (greater than 0%, or more than 1.0%, or more than 5.0% by mass percentage relative to the total mass of the crystalline phase) is preferred, and an embodiment in which the content of AlPO4 crystals is greater than the content of TiO2 crystals described above is even more preferred, but the content of AlPO4 crystals is preferably 9.7% or less. This is because, although AlPO4 crystals can structurally connect the particles of LATP crystals, which are the main crystalline phase, to each other to improve the stability of the crystals, AlPO4 crystals themselves have low lithium-ion conductivity, so if the content is too high, it may lead to a decrease in lithium-ion conductivity.

[0060] Furthermore, while the mass ratio (LATP crystals / TiO2 crystals) of the inorganic oxide powder contained in the present invention is not limited, it is preferably 10 or more and 100 or less from the viewpoint of the effects of the present invention. The lower limit is preferably 12 or more, more preferably 15 or more. The upper limit is preferably 80 or less, more preferably 70 or less, more preferably 50 or less, and even more preferably 30 or less.

[0061] Furthermore, although not limited to this, based on the effects of the present invention, the total content (total mass %) of the LATP crystals, TiO2 crystals, and AlPO4 crystals in the inorganic oxide powder of the present invention is preferably 99.00% or more, more preferably 99.50% or more, further preferably 99.80% or more, and even more preferably greater than 99.90%. In other words, an embodiment with very few byproduct crystalline phases other than the aforementioned crystals is preferred. It should be noted that, in this case, it is also possible to configure the powder to be substantially free of AlPO4 crystals.

[0062] In this invention, "LATP crystallization" refers to the process of using Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 The chemical formula represents a NASICON-type lithium-ion conductive oxide crystal with a conductivity of (0≤x≤0.4, 0≤y≤0.6). In this formula, based on the aforementioned a / c ratio or lithium-ion conductivity, the lower limit of X is preferably greater than 0, more preferably 0.01 or more, even more preferably 0.05 or more, still more preferably 0.08 or more, and even more preferably 0.10 or more. Its upper limit is preferably 0.35 or less, more preferably 0.30 or less. Based on the same viewpoint, the lower limit of Y is preferably greater than 0, more preferably 0.025 or more, even more preferably 0.04 or more, and even more preferably 0.06 or more. Its upper limit is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.30 or less.

[0063] In addition, the content of each crystal (mass %) mentioned above is obtained by measuring the inorganic oxide powder of the present invention by X-ray diffraction (XRD) under the following measurement conditions and analyzing the data.

[0064] (XRD measurement conditions)

[0065] X-ray source: CuKα

[0066] X-ray source: tube voltage and tube current, 40kV and 40mA.

[0067] Goniometer radius: 250mm

[0068] Scan type: Coupled TwoTheta / Theta

[0069] Scanning range: 10–60°

[0070] Step size: 0.02°

[0071] Incident angle of the Sola slit: 4.1°

[0072] Diverging slit: 0.5°

[0073] Anti-scattering slit: 18

[0074] It should be noted that the aforementioned glass-ceramic powder comprises: 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. In other words, it is a mixture of ceramic and glass. Furthermore, the aforementioned ceramic powder, composed of the 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), substantially does not contain an amorphous phase.

[0075] Furthermore, the LATP crystals contained in the inorganic oxide powder of the present invention, as described above, 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 more. The inorganic oxide powder of the present invention, by having an a / c ratio of 0.40860 or more for the LATP crystals contained in a specified amount in a specified crystalline composition, can acquire more lithium ions within the structure or increase the path for lithium ion movement. Therefore, lithium-ion secondary batteries containing this powder in electrodes, etc., have improved power capacity under low-temperature conditions (e.g., under environmental conditions of -20 to 10°C). From the viewpoint of the effects of the present invention, this a / c is more preferably 0.40870 or more, and even more preferably 0.40880 or more. While not limited to a specific upper limit, it can be, for example, 0.41000 or less, or 0.40950 or less.

[0076] Here, the a / c ratio of LATP crystals is the value confirmed by Rietbelt analysis of the obtained X-ray diffraction (XRD) measurements of the inorganic oxide powder of the present invention under the measurement conditions described above. This Rietbelt analysis involves using the crystal structure based on literature values ​​(ICDD database, where 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 the initial value for calculation. The crystal structure parameters are adjusted using a spectral fitting method to reduce the difference and residual between the literature values ​​and the measured data. Through this analysis, not only can the content (proportion in the crystalline phase) of LATP crystals, TiO2 crystals, AlPO4 crystals, and other byproduct crystalline phases contained in the inorganic oxide powder of the present invention be measured and calculated, but the a-axis length of the unit cell of LATP crystals can also be measured and calculated. and c-axis length

[0077] It should be noted that, in this invention, the "power capacity" of a lithium-ion secondary battery under low-temperature conditions refers to a value calculated based on a graph showing the relationship between the discharge capacity and voltage of a lithium-ion secondary battery under specified low-temperature conditions (e.g., -10°C). Specifically, firstly, the lithium-ion secondary battery is fully charged (SOC 100%) under specified low-temperature conditions and then subjected to constant current discharge (cc discharge). The discharge capacity (mAh / g) is measured when the battery voltage reaches 3V. Here, the discharge capacity refers to the discharge capacity per unit weight of positive electrode active material from a fully charged state to the discharge termination voltage (3V), which is the product of the discharge current and the discharge time divided by the weight of the positive electrode active material. Furthermore, in this measurement, the discharge capacity is measured every 2mV, and the battery voltage (V) at the time of measurement is plotted as the Y-axis and the discharge capacity (mAh / g) as the X-axis. Then, the sum of the products of the discharge capacity (mAh / g) at every 2mV discharge interval and the battery voltage (V) at the time of measurement is taken as the battery's electrical capacity (mWh / g). (Refer to...) Figure 1 The calculation example chart further illustrates the above content. From the start of the battery's discharge until the voltage reaches 3V, the discharge capacity measured every 2mV is multiplied by the battery voltage value at the time of measurement. The sum of all products (actually...) Figure 1 The area value of the integral region shown below the graph line represents the battery's electrical capacity. Therefore, this electrical capacity can also be said to represent the total amount of electrical energy that the battery can consume.

[0078] <Lithium-ion conductivity>

[0079] The inorganic oxide powder of the present invention is a lithium-ion conductive inorganic oxide powder (lithium-ion conductive inorganic material). Although not limited, its lithium-ion conductivity at 25°C is preferably 1.0 × 10⁻⁶. -5 (1.0E-05)S / cm or higher, more preferably 1.0×10 -4 (1.0E-04)S / cm or higher, more preferably 5.0×10 -4 (5.0E-04)S / cm or higher.

[0080] Here, the lithium-ion conductivity is obtained by forming a gold electrode as a barrier electrode on the object to be measured using a magnetron sputtering device, and then measuring and calculating the impedance using an electrochemical evaluation device at 25°C under conditions of a frequency of 0.1 Hz to 7 MHz, an amplitude voltage of 10 mV, and an open-circuit voltage. Furthermore, 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.

[0081] <Average Particle Size>

[0082] Based on the effects of the present invention or its ease of use in electrodes, etc., the inorganic oxide powder of the present invention has an average particle size (D) 50 The particle size ranges from 0.1 μm to 2.0 μm. The lower limit can be above 0.2 μm, and the upper limit can be below 1.5 μm, below 1.0 μm, below 0.7 μm, below 0.6 μm, below 0.5 μm, or below 0.4 μm. This can be adjusted by the conditions during grinding or granulation.

[0083] Here, the "average particle size (D)" 50 "50% cumulative particle size distribution (D)" refers to the average particle size of a volumetric reference measured by a laser diffraction-scattering particle size distribution measuring device. 50 )).

[0084] The method for manufacturing inorganic oxide powder of the present invention can be carried out using general methods or variations thereof in inorganic material manufacturing (glass ceramic manufacturing or ceramic manufacturing), such as firing (pre-firing), melting, vitrification, crystallization, and sintering. Although not limited thereto, in the case of glass ceramic powder, the following method can be cited: after vitrifying (melting, rapid cooling) the raw material, it is crystallized by heat treatment (e.g., at 900°C or higher, further at 900°C or higher and 1200°C or lower, particularly preferably at a heating rate of 10°C / min or higher), and then cooled (particularly preferably cooled at a cooling rate of 10°C / min or higher) to obtain glass ceramic particles, which are then coarsely crushed, micro-pulverized, and pulverized by a classification device to produce glass ceramic powder. In the case of ceramic powder, the following method can be used: Raw materials are mixed and shaped, then subjected to solid-state reaction sintering (e.g., at 700°C or higher and 1300°C or lower, particularly preferably heated at a rate of 30°C / min or higher during pre-firing and 10°C / min or higher during main firing), and then cooled (particularly preferably cooled at a rate of 10°C / min or higher) to obtain a ceramic body. This body is then coarsely crushed, finely pulverized, and further pulverized using a classifying device to produce ceramic powder. Furthermore, these methods share the common feature that the inorganic oxide powder of the present invention can be obtained by appropriately adjusting the uniformity of heating and cooling, the heating rate, the heat treatment temperature and time, the cooling rate, the cooling temperature and time, the pulverizing conditions (material, quantity, and diameter of the medium; type and quantity of solvent in wet conditions; pulverizing time, etc.), and the pulverizing device. It should be noted that the mass percentage (content) of TiO2 crystals relative to the total mass of the crystalline phase can be controlled, for example, by adjusting the proportion of raw material components, the mixing conditions of the raw materials, the crystal system of the raw material TiO2, or the heat treatment atmosphere, heat treatment temperature and time, or solid-state reaction temperature and time, and in the case of glass ceramics, by adjusting the crystallization temperature and time. The same applies to AlPO4 crystallization, and it can also be adjusted by controlling the properties (viscosity or concentration) of the raw material H3PO4. Furthermore, during the above-mentioned pulverization process, using zirconia raw material spheres as a medium can prevent the incorporation of Fe.

[0085] <Lithium-ion secondary batteries>

[0086] Next, a detailed description will be given of a lithium-ion secondary battery having an electrode comprising the inorganic oxide powder of the present invention and / or an electrolyte layer comprising the inorganic oxide powder of the present invention.

[0087] 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). In other words, it is a lithium-ion secondary battery comprising an electrode and / or an electrolyte layer formed using a material containing the inorganic oxide powder of the present invention, and its power capacity under low-temperature conditions is improved (for example, the power capacity is 380 mWh / g or more under an ambient temperature of -10°C).

[0088] For example, by mixing 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 as needed with conductive additives, binders, etc., and molding, an electrode (positive electrode or negative electrode) can be formed. The electrode (positive electrode and negative electrode) containing these can be combined with a non-aqueous electrolyte in which a fluorinated lithium salt is dissolved in an aprotic organic solvent as an electrolyte component, and a separator (disposed between the positive electrode and the negative electrode) to produce the aforementioned lithium-ion secondary battery. Furthermore, the inorganic oxide powder of the present invention can be used to coat at least a portion of the surface of the positive electrode material or the negative electrode material, and this can be used to form an electrode. The mixing and coating described above can also be combined. It should be noted that either the positive electrode or the negative electrode may contain only the inorganic oxide powder of the present invention, or both may contain the inorganic oxide powder of the present invention. However, from the viewpoint that it is easier to exert the effects of the present invention, it is more preferable that at least the positive electrode contains the inorganic oxide powder of the present invention. In addition, the lithium-ion conductive polymer electrolyte used as the electrolyte layer can also be formed in conjunction with the inorganic oxide powder of the present invention. In this case, it can also be combined with an electrode that does not contain the inorganic oxide powder of the present invention to form a lithium-ion secondary battery.

[0089] It should be noted that, generally, when materials other than electrode active materials are included in the electrodes of lithium-ion secondary batteries, there is a tendency for the power capacity to decrease. However, a major feature of the inorganic oxide powder of the present invention is that, even when included in the electrodes of lithium-ion secondary batteries together with the electrode active materials, it can improve the power capacity under low-temperature conditions.

[0090] As positive electrode materials, positive electrode active materials can be transition metal compounds capable of absorbing and releasing lithium, such as transition metal oxides containing at least one selected from the group consisting of manganese, cobalt, nickel, vanadium, niobium, molybdenum, iron, and titanium (specifically, LiCoO2, etc.). As negative electrode materials, negative electrode active materials can include lithium metal or lithium-aluminum alloys, lithium-indium alloys, and other alloys capable of absorbing and releasing lithium; transition metal oxides such as titanium and vanadium; and carbon-based materials such as graphite (specifically, artificial graphite, etc.). Furthermore, carbon-based materials such as acetylene black can be used as conductive additives. Further, fluoropolymers such as PVdF (polyvinylidene fluoride) or rubber materials such as SBR (styrene-butadiene rubber) can be used as binders. Additionally, thickeners such as CMC (sodium carboxymethyl cellulose) can also be used.

[0091] In addition, non-aqueous electrolytes are electrolytes in which an electrolyte component containing lithium salts is dissolved in a non-aqueous liquid solvent. Examples of non-aqueous solvents for this liquid include: aprotic organic solvents (e.g., mixed solvents of cyclic carbonates and / or chain carbonates such as ethylene carbonate, propylene carbonate, butyl carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate). Examples of electrolyte components include: lithium salts such as lithium hexafluorophosphate (LiPF6) or lithium bis(fluorosulfonyl)imide (LiFSI).

[0092] Furthermore, examples of lithium-ion conductive polymer electrolytes include electrolytes in which a lithium salt-containing electrolyte component is impregnated into a polymer compound (such as a polymer gel, polyvinylidene fluoride, or polyacrylonitrile). Alternatively, electrolytes in which a non-aqueous solvent such as the aforementioned liquid can also be used. Furthermore, they can be further enriched with an inorganic material that is lithium-ion conductive.

[0093] <Power capacity under low temperature conditions>

[0094] As described above, lithium-ion secondary batteries comprising electrodes containing the inorganic oxide powder of the present invention and / or electrolyte layers containing the inorganic oxide powder of the present invention exhibit improved power capacity under low-temperature conditions (e.g., at an ambient temperature of -10°C). Specifically, 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 is exemplified, achieving a power capacity of 380 mWh / g or higher at -10°C (at an ambient temperature of -10°C). Furthermore, this power capacity at -10°C can reach 385 mWh / g or higher, or even 390 mWh / g or higher, 395 mWh / g or higher, 400 mWh / g or higher, 405 mWh / g or higher, or 410 mWh / g or higher.

[0095] The electrical capacity at -10℃ can be measured and calculated in the following manner.

[0096] Specifically, firstly, a positive electrode is prepared by coating a positive electrode current collector (Al foil) with a mixture of the inorganic oxide powder of the present invention at a mass ratio of 0-10% (relative to the total mass of the positive electrode mixture) and drying it. Secondly, a negative electrode is prepared by coating a negative electrode current collector (Cu foil) with a mixture of the inorganic oxide powder of the present invention at a mass ratio of 0-10% (relative to the total mass of the negative electrode mixture) and drying it. In other words, a lithium-ion secondary battery is prepared by mixing the inorganic oxide powder of the present invention into either or both of the positive and negative electrode mixtures and combining it with a non-aqueous electrolyte containing LiPF6 as the electrolyte, the aforementioned positive and negative electrodes, and a separator. Then, using a charge-discharge device, a known formation treatment and a known aging treatment are performed in sequence, and the following low-temperature test is conducted. The discharge capacity (mAh / g) is measured and plotted as described above, and the power capacity (mWh / g) at -10°C is calculated.

[0097] Low temperature test: The lithium-ion secondary battery with SOC 100% (fully charged) is stored at -10℃ for 6 hours to make the temperature constant, and then CC discharge (0.5C, -10℃) is performed until the discharge cutoff voltage (3V) to confirm the discharge capacity and power capacity.

[0098] The embodiments described above are merely examples for the purpose of facilitating understanding of the present invention and are not intended to limit the invention. That is to say, changes and modifications can be made to the components described above without departing from the spirit of the present invention, and the present invention naturally includes equivalents thereto.

[0099] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments. Various modifications can be made without departing from the technical concept of the present invention.

[0100] Example

[0101] Various inorganic oxide powders (glass-ceramic powders or ceramic powders) with lithium-ion conductivity were prepared and evaluated, and lithium-ion secondary batteries incorporating electrodes containing these powders were also evaluated.

[0102] <Preparation of Lithium-ion Conductive Glass-Ceramic Powders>

[0103] As raw materials, LiCO3, H3PO4, TiO2, and Al(PO3)3, with SiO2 added as needed, are weighed into specified components and uniformly mixed. The mixture is then placed in a platinum crucible and rapidly heated (at a heating rate of 200–800 °C / min) in an electric furnace at 1500 °C with stirring for 4 hours. The resulting molten glass is then dripped into running water for rapid cooling, yielding sheet-like glass. This sheet-like glass is immediately removed from the water, laid on a flat plate, and dried in a constant-temperature bath at 100 °C for at least 12 hours to remove moisture.

[0104] Then, the dried sheet glass obtained above is heated at a heating rate of 10-100°C / min, and then heat-treated at 950°C for 6-12 hours according to the conditions of each powder to crystallize it. Next, it is cooled to room temperature at a cooling rate of 10-20°C / min to obtain glass ceramic, which is then crushed and granulated to obtain the lithium-ion conductive glass ceramic powder of Example 1 or Example 3. It should be noted that zirconia spheres are used as a medium during this crushing process to prevent Fe from being mixed in.

[0105] <Preparation of Lithium-ion Conductive Ceramic Powder>

[0106] As raw materials, LiCO3, Li3PO4, H3PO4, TiO2, and Al(PO3)3 were weighed into specified components, uniformly mixed, and pressed into sheets approximately 15 mm in diameter and 5 mm thick. These sheets were placed in a platinum crucible, covered with a lid of the same material, and placed in an electric furnace. The furnace was heated at a rate of 50 °C / min and pre-fired at 1000 °C for 10 hours. After cooling to room temperature, the sheets were removed, dry-pulverized to approximately 100 μm or less, and pressed again into the same sheet shape. The sheets were placed in the aforementioned crucible, covered, and placed in an electric furnace. The furnace was heated at a rate of 10 °C / min and then sintered at 1200 °C for 4 hours. The mixture was then cooled to room temperature at a rate of 20 °C / min to obtain ceramic. This ceramic was then pulverized and granulated to obtain the lithium-ion conductive ceramic powder of Example 2, Comparative Example 1, or Comparative Example 2. It should be noted that, except for Comparative Example 2, zirconia spheres were used as a medium during pulverization to prevent Fe contamination.

[0107] 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 (automatic X-ray diffractometer, Bruker "D8 DISCOVER"). Rietbeld analysis was performed on the XRD data, and the proportions of LATP crystals, TiO2 crystals, and AlPO4 crystals contained in these crystalline phases, as well as the a-axis length of the LATP crystal unit cell, were measured and calculated using the spectral fitting method. and c-axis length Furthermore, the content of Fe as an impurity was confirmed by inductively coupled plasma optical emission spectrometry (ICP-OES: ICP emission spectrometer, manufactured by Agilent Technologies, “ICP-OES 5900”).

[0108] These results are summarized in Table 1 below. It should be noted that "total" in Table 1 refers to the combined content of LATP crystals, TiO2 crystals, and AlPO4 crystals (mass %) relative to the total mass of the crystalline phase. Furthermore, a graph showing the a / c relationship between the TiO2 crystal content (mass %) and the LATP crystal content is shown below. Figure 2 The graph shown below illustrates the relationship between the content of TiO2 crystals (mass %) and the content of AlPO4 crystals (mass %) relative to the total mass of the crystalline phase. Figure 3 As shown.

[0109] (XRD measurement conditions)

[0110] X-ray source: CuKα

[0111] X-ray source: tube voltage and tube current, 40kV and 40mA.

[0112] Goniometer radius: 250mm

[0113] Scan type: Coupled TwoTheta / Theta

[0114] Scanning range: 10–60°

[0115] Step size: 0.02°

[0116] Incident angle of the Sola slit: 4.1°

[0117] Diverging slit: 0.5°

[0118] Anti-scattering slit: 18

[0119] (ICP-OES analysis conditions)

[0120] Apparatus: ICP emission spectroscopy analyzer (manufactured by Agilent Technologies, ICP-OES 5900)

[0121] Measurement conditions: atomizer flow rate 0.70 L / min, Fe measurement wavelength 238.204 nm.

[0122] 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. It should be noted that the measurements were performed as follows, and the results are also shown in Table 1 below (ionic conductivity).

[0123] [Lithium-ion conductivity at 25°C (S / cm)]

[0124] Examples 1 and 3 used samples in the state of crystallized sheet-like glass, while Examples 2 and Comparative Examples 1 and 2 used samples in the state of sintered bodies after primary firing as samples for lithium-ion conductivity measurement. Then, gold electrodes were formed on each sample as blocking electrodes using a magnetron sputtering apparatus (Sanyu Electronics Co., Ltd., SC-701HMC). Impedance measurements were then performed using an electrochemical evaluation apparatus (Bio-Logic Co., Ltd., SP300) at 25°C 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.

[0125] <Tests using lithium-ion secondary batteries with electrodes containing lithium-ion conductive glass-ceramic powder or lithium-ion conductive ceramic powder>

[0126] Electrodes (positive electrodes) were formed using the powders described above, and the electrical capacity at -10°C was confirmed and evaluated through tests using lithium-ion secondary batteries equipped with these electrodes. The specific tests were conducted as shown below.

[0127] [Electrode and Battery Fabrication]

[0128] 1) Preparation of the positive electrode

[0129] Using a rotation-revolution mixer (Thinky Corporation, Awatori Rentaro), 98% by mass LiCoO2 as the positive electrode active material, 1% by mass acetylene black as a conductive additive, 1% by mass PVdF as a binder, and 1% by mass of any one of the aforementioned powders were mixed. NMP (1-methyl-2-pyrrolidone) was added to adjust the viscosity, and after defoaming, a paste-like slurry was prepared. This slurry was coated onto a 20 μm thick Al foil using an automatic coating machine (Hokusen Corporation, HSCM20-800S) and dried at 120°C. The areal density capacity (discharge capacity per unit area of ​​the active material layer coated on the substrate) of the electrode was 3.6 mAh / cm². 2 It was then adjusted and pressed using a roller press (manufactured by Baoquan Company, HSR-60150H) to a density of 3.5 g / cm³. 3The film thickness was 59μm. It was punched into 30mm×40mm pieces using a punch press (manufactured by Aichi Technology Co., Ltd.), and then vacuum dried at 160℃ for 16 hours in a glass tube oven (manufactured by Buchi Co., Ltd., Japan, B-585).

[0130] 2) Preparation of the negative electrode

[0131] Using a rotation-revolution mixer (Thinky Corporation, Awatori Rentaro), 97.5% by mass artificial graphite was mixed as the negative electrode active material, 1% by mass CMC as a thickener, and 1.5% by mass SBR as a binder. Ion-exchanged water was added to prepare a paste-like slurry. This slurry was then coated onto a 16.5 μm thick Cu foil using an automatic coating machine (Hokusen Corporation, HSCM20-800S) and dried at 65°C. The areal density capacity of the electrode was 4.0 mAh / cm³. 2 It was then adjusted and pressed using a roller press (manufactured by Baoquan Company, HSR-60150H) to a density of 1.4 g / cm³. 3 The film thickness was 90μm. It was punched into 30.5mm×40.5mm pieces using a punch press (manufactured by Aichi Technology Co., Ltd.), and then vacuum dried at 160℃ for 16 hours in a glass tube oven (manufactured by Buchi Co., Ltd., Japan, B-585).

[0132] 3) Battery manufacturing

[0133] In a drying chamber (temperature 23℃, dew point below -50℃), the positive and negative electrodes obtained in steps 1) and 2) above are welded together with tabs at an A / C ratio (capacity ratio of positive to negative active materials) of 1.2. They are then placed together with a separator (polypropylene, film thickness 22μm, porosity 48%) into a laminated resin film and sealed by hot pressing with a sealing machine. An electrolyte (electrolyte composition: 1mol / L LiPF6, solvent: ethylene carbonate: ethyl methyl carbonate = 3:7, VC (ethylene carbonate) 1%) is injected to wet the electrodes and separator. Then, vacuum sealing (vacuum degassing and sealing) is performed to produce a battery.

[0134] [Confirmation of power capacity at -10℃]

[0135] All manufactured batteries were subjected to the following formation treatment, vacuum degassing and repackaging (same as the vacuum packaging during battery preparation) and aging treatment in sequence using a charge-discharge device (ASKA Electronics Co., Ltd., ACD-M01) and a small environmental tester (ESPEC Co., Ltd., SH-242) under temperature management. After these treatments, a low-temperature test was conducted, measuring the discharge capacity (mAh / g) per 2mV up to 3V, plotting the results, and calculating the power capacity (mWh / g) under -10℃ environmental conditions. The results are summarized in Table 1 below. Furthermore, the above measurement results for a lithium-ion secondary battery with a positive electrode containing the inorganic oxide powder of Example 1 and a lithium-ion secondary battery with a positive electrode containing the inorganic oxide powder of Comparative Example 2 are shown below. Figure 4 ( Figure 4 (Part of the drawing is omitted). The relationship between the a / c ratio of LATP crystals contained in the above-mentioned powders mixed in the positive electrode and the capacity (mWh / g) of a lithium-ion secondary battery having a positive electrode containing the powders at -10°C is shown in the figure. Figure 5 The relationship between the Fe content (ppm) of each of the powders mixed in the positive electrode and the power capacity (mWh / g) of a lithium-ion secondary battery having a positive electrode containing the powders at -10°C is shown in the figure. Figure 6 .

[0136] Formation process: CC-CV charging (0.05C, 4.4V-0.01C cutoff, 45℃), CC discharging (0.1C, 3.0V cutoff, 45℃), CC-CV charging (0.1C, 4.4V-0.05C cutoff, 45℃), CC discharging (0.1C, 3.0V cutoff, 45℃).

[0137] Aging process: CC-CV charging (0.2C, 4.4V-0.05C cutoff, 25℃), CC discharging (0.2C, 3.0V cutoff, 25℃).

[0138] Low temperature test: Perform CC-CV charging (0.2C, 4.4V-0.05C cutoff, 25℃), rest (place) at -10℃ for 6 hours, and CC discharge (0.5C, 3.0V cutoff, -10℃) until the discharge cutoff voltage (3V) to confirm the discharge capacity and power capacity.

[0139] Table 1

[0140]

[0141] Based on these results, it is evident that by using lithium-ion conductive glass-ceramic powder or lithium-ion conductive ceramic powder, which contains more than 80.0% LATP crystals and more than 0% TiO2 crystals (based on the mass percentage relative to the total mass of the crystalline phase), and whose a / c ratio of the LATP crystals is more than 0.40860, the lithium-ion secondary battery equipped with a positive electrode containing this powder exhibits a power capacity greater than 380 mWh / g at -10°C (Examples 1-3). Furthermore, the results also show that the higher the a / c ratio of the aforementioned glass-ceramic powder or ceramic powder, or the lower the Fe content, the easier it is to achieve a higher power capacity of the aforementioned lithium-ion secondary battery at -10°C.

[0142] On the other hand, the powders of Comparative Example 1, which does not contain TiO2 crystals, and Comparative Example 2, whose LATP crystal content is outside the specified range, have a lithium-ion secondary battery with a positive electrode containing the powder, and the power capacity at -10°C is less than 380 mWh / g, failing to achieve the same effect as the above embodiments.

[0143] This application claims priority based on Japanese Patent Application No. 2025-029816, filed on February 27, 2025, the entire disclosure of which is incorporated herein by reference.

Claims

1. An inorganic oxide powder, which is a glass-ceramic powder, wherein, In terms of mass percentage converted from oxides, it contains: 4.0%–6.0% Li₂O content; Al2O3 content: 3.0%–9.0%; TiO2 content: 31.0%–40.0%; 49.0%–57.0% P2O5 content; and The SiO2 content is less than 5.0%, and It contains, in terms of mass% relative to the total mass of the crystalline phase: LATP crystals with a purity of over 80.0% TiO2 crystals with a content of more than 2.0% Furthermore, the a / c ratio of the LATP crystals is 0.40880 or higher.

2. The inorganic oxide powder as described in claim 1, wherein, The Fe content is below 25.00 ppm.

3. The inorganic oxide powder as described in claim 1 or 2, wherein, The content of AlPO4 crystals is less than 9.7% by mass percentage relative to the total mass of the crystalline phase.

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

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