Negative electrode material for secondary battery, negative electrode for secondary battery, and secondary battery

Abstract

To provide a negative electrode material for a secondary battery having superior functionality.SOLUTION: A negative electrode material for a secondary battery includes at least one metal oxide selected from the group consisting of tungsten oxide and molybdenum oxide.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a negative electrode material for a secondary battery, a negative electrode for a secondary battery, and a secondary battery.

Background Art

[0002] Since a lithium-ion secondary battery, which is a typical non-aqueous secondary battery, has a high voltage and a high capacity, it is widely used not only as a power source for small electronic devices such as mobile phones and notebook computers but also as a power source for automobiles such as electric vehicles and hybrid vehicles and a large stationary power source for power storage.

[0003] For example, Patent Document 1 discloses a battery including an electrode containing a negative electrode active material containing titanium oxide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of intensive studies, the present inventor has found that there is room for further improving the function of the battery including the negative electrode described in Patent Document 1.

[0006] The present disclosure has been made in view of such problems. That is, the main object of the present disclosure is to provide a negative electrode material for a secondary battery having more excellent functions. Another object of the present disclosure is to provide a negative electrode for a secondary battery including such a negative electrode material for a secondary battery and a secondary battery including the negative electrode for a secondary battery.

Means for Solving the Problems

[0007] In order to solve the above problems, the present inventors conducted extensive research and discovered that the use of a specific metal oxide as a negative electrode material makes it possible to further improve capacity and cycle characteristics, and thus completed the present disclosure.

[0008] That is, the negative electrode material for a secondary battery according to an embodiment of the present disclosure is The oxide comprises at least one metal oxide selected from the group consisting of tungsten oxide and molybdenum oxide. Moreover, the negative electrode for a secondary battery according to another embodiment is The negative electrode material for a secondary battery is comprised of the above. Furthermore, a secondary battery according to yet another embodiment includes the above-described negative electrode for secondary batteries. [Effects of the Invention]

[0009] The present disclosure can provide a negative electrode for a secondary battery having better functions. [Brief explanation of the drawings]

[0010]

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[0011] A secondary battery negative electrode material, a secondary battery negative electrode, and a secondary battery according to embodiments of the present disclosure are described in detail below. The applicant provides the following explanations and examples to enable those skilled in the art to fully understand the present disclosure, and it should be noted that these are not intended to limit the subject matter described in the claims. In other words, the present disclosure is not particularly limited to the preferred embodiments described below, and can be implemented with appropriate modifications within the scope of its intended purpose. For convenience, the present disclosure may be divided into embodiments and examples, taking into account the ease of explanation or understanding of the key points. However, partial substitution and / or combination of the configurations shown in different embodiments is possible. In describing such embodiments, to avoid unnecessary redundancy and to facilitate understanding by those skilled in the art, duplicated explanations of substantially identical features may be omitted, and only differences may be described. In particular, similar effects resulting from similar configurations may not be repeatedly mentioned in each embodiment.

[0012] The negative electrode material for a secondary battery, the negative electrode for a secondary battery, and the secondary battery according to embodiments of the present disclosure will be described with reference to the drawings as needed. The contents shown in the drawings are merely shown schematically and exemplarily for the purpose of understanding the present disclosure, and the appearance and dimensional ratios may differ from the actual objects. For example, characteristic parts of the embodiments of the present disclosure may be emphasized.

[0013] The numerical ranges referred to in this specification are intended to include the lower and upper limits themselves, unless otherwise specified by terms such as "less than" and "more / greater than". That is, taking a numerical range such as 20°C to 25°C as an example, this numerical range is interpreted as including the lower limit value "20°C" and the upper limit value "25°C". Also, terms such as "about" and "around" mean that they can include variations of a few percent (for example, ±10%) of the target numerical value.

[0014] Also, among the plurality of numerical ranges defined by the lower limit value or the upper limit value described in the specification, any numerical range defined by an arbitrary lower limit value and any numerical range defined by an arbitrary upper limit value can be combined to form a numerical range defined by the lower limit value and the upper limit value.

[0015] <First Embodiment: Negative Electrode Material for Secondary Battery> The first embodiment relates to a negative electrode material for a secondary battery. The negative electrode material for a secondary battery according to the first embodiment comprises at least one metal oxide selected from the group consisting of tungsten oxide and molybdenum oxide.

[0016] [Operating Mechanism] The negative electrode material for a secondary battery according to the first embodiment can improve the function of a secondary battery including a negative electrode comprising the same. The reason is presumed as follows. The negative electrode material for a secondary battery according to the first embodiment comprises at least one metal oxide selected from the group consisting of tungsten oxide and molybdenum oxide. Tungsten oxide and molybdenum oxide have a lower oxidation-reduction potential than titanium oxide. Therefore, when used as a negative electrode material, the electromotive force of the battery can be increased. Also, tungsten oxide and molybdenum oxide have a larger interplanar spacing of the crystal corresponding to the diffusion path of carriers than titanium oxide. For this reason, carriers (for example, Li + and Na +The occlusion and release of + and Na + ) occur more smoothly. Therefore, the negative electrode material selected from the group consisting of tungsten oxide and molybdenum oxide can further improve the function of the battery including the negative electrode containing the negative electrode material.

[0017] [The opportunity to devise the present disclosure]

[0018] The performance of a battery (especially the performance of the negative electrode) depends on how much energy represented by the product of the capacity and the voltage difference can be stored. In order to improve the performance of such a battery, the present inventor has tried to improve both characteristic values of the capacity and the voltage, that is, to improve by increasing the capacity and lowering the redox potential to a lower potential.

[0019] From the viewpoint of improving the function of the secondary battery, the present inventor has focused on the fact that tungsten oxide and molybdenum oxide as negative electrode materials are advantageous in the following three properties compared to titanium oxide used as a conventional negative electrode material. (1) Improvement of energy density due to a decrease in redox potential (2) Promotion of occlusion and release of carriers due to an increase in the lattice spacing of crystals (3) High electronic conductivity

[0020] Regarding (1), tungsten oxide undergoes a redox reaction represented by half-reaction formula (1): [Chemical formula] at a lower potential than titanium oxide. Similarly, molybdenum oxide also undergoes a redox reaction at a lower potential than titanium oxide. In short, the inventor has conceived that, since tungsten oxide and molybdenum oxide undergo redox reactions at a lower potential than titanium oxide, using tungsten oxide and molybdenum oxide as the negative electrode active material of a secondary battery can achieve a larger energy density.

[0021] (2) For easier understanding, taking the same crystal system as an example, it will be explained by comparison with titanium oxide. Fig. 1 is a plan view showing a rutile-type crystal structure. In Fig. 1, relatively large white circles indicate tungsten ions, molybdenum ions, or titanium ions, and relatively small white circles indicate oxygen ions. In titanium oxide (TiO2), the length L of the voids in the crystal is 230 pm. In contrast, for rutile-type tungsten oxide (WO2), the length of the voids in the crystal is 241 pm. In short, based on the fact that the voids in the crystal can serve as diffusion paths for carriers (e.g., Li + and Na + ), the inventor has conceived that using molybdenum oxide and tungsten oxide, which have a larger inter-lattice spacing in the crystal compared to titanium oxide, as the negative electrode material for a secondary battery can realize a larger diffusion path through which the carriers pass, which is advantageous for the insertion and extraction of carriers.

[0022] (3) Regarding this, in a battery, oxidation and reduction reactions occur simultaneously at the electrode. Therefore, not only the movement of carriers (e.g., Li + and Na + ) but also the movement of the other carrier (electrons) is important. Since tungsten oxide and molybdenum oxide have high electronic conductivity, the movement of electrons is less likely to inhibit the movement of Li + and Na + .

[0023] Based on the above technical findings and ideas, the inventor obtained the feeling that tungsten oxide and molybdenum oxide are useful as negative electrode materials. The inventors further focused on utilizing the conversion reaction for carrier occlusion in order to improve the function of the battery. That is, the idea is that high capacity can be achieved by utilizing the conversion reaction for carrier occlusion in addition to the insertion reaction. The conversion reaction refers to a reaction in which when carriers are occluded in the electrode active material (crystal) constituting the electrode, the electrode active material and the carriers each form a different crystal phase and phase separation occurs.

[0024] In conventional general technical knowledge, the conversion reaction has been regarded as something to be suppressed because it increases the volume of the electrode (negative electrode). Although it will be described in detail in the examples, the inventors actually confirmed that the merit of high capacity is greater than the increase in the volume of the electrode (negative electrode) of the battery. Such high capacity can be adjusted by the operating potential of the battery.

[0025] (Tungsten Oxide) Tungsten oxide is, for example, WO X (X is 2 or more and 3 or less). Such tungsten oxide includes WO3 (more specifically, γ-WO3 (WO3-1 and WO3-4 in the examples) and δ-WO3), WO 2.92 (W 25 O 73 ), WO 2.9 (W 10 O 29 ), WO 2.8 (W5O 14 ), WO 2.76 (W 17 O 47 ), WO 2.72 (W 18 O 49 ), WO 2.63 (W8O 21 ), and WO2. For example, WO2, WO 2.72is at least one tungsten oxide selected from the group consisting of WO3. Such chemical species can be confirmed by an X-ray diffraction spectrum measured using an X-ray diffractometer. The measurement sample may be a negative electrode material in a powder state, or a finished product (negative electrode and battery) may be disassembled to extract a specific negative electrode material for measurement. The measurement conditions are described in detail in the examples.

[0026] (Molybdenum oxide) Molybdenum oxide is, for example, МоO Y (where Y is 2 or more and 3 or less). Such molybdenum oxide is МоO3 (more specifically, α-MоO3 and β-MoO3), МоO 2.89 (Mo9O 26 ), МоO 2.88 (Mo8O 23 ), МоO 2.8 (Mо5O 14 ), МоO 2.76 (Mо 17 O 47 ), МоO 2.75 (Mo4O 11 ), and МоO2. For example, it is at least one tungsten oxide selected from the group consisting of МоO2 and МоO3. Such chemical species can be confirmed by an X-ray diffraction spectrum measured using an X-ray diffractometer. The measurement sample may be a negative electrode material in a powder state, or a finished product (negative electrode and battery) may be disassembled to extract a specific negative electrode material for measurement. The measurement conditions are described in detail in the examples.

[0027] The particle sizes (volume median diameter D 50 ) of tungsten oxide and molybdenum oxide are each independently, for example, 50 nm or more, 70 nm or more, or 90 nm or more. The particle sizes (volume median diameter D 50 ) of tungsten oxide and molybdenum oxide are each independently, for example, 50 μm or less, or 40 μm or less.Where the volume median diameter D 50The particle size of tungsten oxide represented by is the particle size of secondary particles formed by aggregation of primary particles of tungsten oxide. Similarly, the particle size of molybdenum oxide is the particle size of secondary particles formed by aggregation of primary particles of molybdenum oxide. The method for measuring the above particle size will be described in detail in the examples.

[0028] The crystallite sizes of tungsten oxide and molybdenum oxide are each independently, for example, greater than 10 nm, or greater than 20 nm. The crystallite sizes of tungsten oxide and molybdenum oxide are, for example, 150 nm or less, or 90 nm or less. The method for measuring the crystallite size will be described in detail in the examples.

[0029] The specific surface areas of tungsten oxide and molybdenum oxide are each independently, for example, 0.5 m 2 / g or more, 0.7 m 2 / g or more, or 0.9 m 2 / g or more. The specific surface areas of tungsten oxide and molybdenum oxide are each independently, for example, 100 m 2 / g or less, 50 m 2 / g or less, 30 m 2 / g or less, or 10 m 2 / g or less. This specific surface area is the specific surface area of the secondary particles of tungsten oxide and molybdenum oxide.

[0030] [Method for producing tungsten oxide and molybdenum oxide] An example of the method for producing tungsten oxide (powder) and molybdenum oxide (powder) will be described. The method for producing tungsten oxide includes, for example, firing a raw material of tungsten oxide. The firing can be carried out, for example, in an electric furnace. The firing temperature is, for example, 500 to 900 °C. The firing time is, for example, 0.5 to 5 hours. In the firing, the raw material may be reduced in a hydrogen atmosphere, or a deammoniation reaction and / or a dehydration reaction may be carried out in an air atmosphere. Examples of the raw material of tungsten oxide include ammonium paratungstate (5(NH4)2O·12WO3·5H2O), tungstic acid (WO3·H2O), and tungsten trioxide (tungsten dioxide, or tungsten oxide WO2.72 Examples of the raw materials include...

[0031] The method for producing molybdenum oxide is the same as the method for producing tungsten oxide described above, except that the raw material of tungsten oxide is changed to the raw material of molybdenum oxide. Examples of the raw material of molybdenum oxide include ammonium paramolybdate ((NH4)6Mo7O 24 ·4H2O). Also, molybdenum oxide powder may be produced by pulverizing molybdenum oxide ore. That is, the method for producing molybdenum oxide includes, for example, pulverizing molybdenum oxide ore.

[0032] <Second Embodiment: Negative Electrode for Secondary Battery> The second embodiment of the present disclosure relates to a negative electrode for a secondary battery. The negative electrode for a secondary battery according to the second embodiment includes the negative electrode material for a secondary battery according to the first embodiment. The negative electrode for a secondary battery according to the second embodiment is, for example, an alkali metal ion battery (more specifically, a lithium ion battery, a sodium ion battery, and a potassium ion battery) and an alkaline earth metal ion battery (more specifically, a magnesium ion battery). Examples of the lithium ion battery include a non-aqueous lithium ion battery and a solid electrolyte lithium ion battery. Examples of the sodium ion battery include a non-aqueous sodium ion battery.

[0033] When the negative electrode for a secondary battery is the negative electrode of a non-aqueous alkali metal ion battery and a non-aqueous alkaline earth metal ion battery, the negative electrode for a secondary battery may further include at least one selected from the group consisting of a binder, a conductive aid, and a thickener in addition to the negative electrode material according to the first embodiment. Examples of the binder include styrene-butadiene rubber. Examples of the conductive aid include acetylene black. Examples of the thickener include carboxymethyl cellulose (CMC).

[0034] When the negative electrode for a secondary battery is the negative electrode of a solid electrolyte alkali metal ion battery or a solid electrolyte alkaline earth metal ion battery, the negative electrode for a secondary battery may contain a solid electrolyte in addition to the negative electrode material according to the first embodiment. As the solid electrolyte, for example, in the case of a lithium ion battery, a lithium salt (more specifically, at least one lithium salt selected from the group consisting of lithium borate, lithium sulfate, and lithium carbonate) can be mentioned.

[0035] [Method for manufacturing a negative electrode for a secondary battery] In the method for manufacturing a negative electrode for a secondary battery according to the second embodiment, in a non-aqueous alkali metal ion battery and a non-aqueous alkaline earth metal ion battery, for example, the slurry method is used. An example of such a method for manufacturing a negative electrode for a secondary battery includes applying a slurry to a current collector (for example, a copper foil) to form a coating film, and heating the coating film.

[0036] The slurry contains, for example, the negative electrode material according to the first embodiment, a binder (for example, styrene-butadiene rubber), a conductive assistant (for example, acetylene black), a thickener (for example, carboxymethyl cellulose (CMC)), and a solvent (for example, water). The slurry can be prepared by kneading these. The heating temperature is, for example, 100 to 150 °C.

[0037] In the method for manufacturing a negative electrode for a secondary battery according to the second embodiment, in a solid electrolyte alkali metal ion battery, an alkali metal salt or an alkaline earth metal salt and the negative electrode material according to the first embodiment are mixed, and a pellet-shaped negative electrode mixture is produced by hot compression molding. Examples of the alkali metal salt (for example, Li salt and Na salt) and the alkaline earth metal salt include inorganic salts of alkali metals and alkaline earth metals (more specifically, carbonates, nitrates, and sulfates).

[0038] <Third Embodiment: Secondary Battery> The third embodiment of the present disclosure relates to a secondary battery. The secondary battery according to the third embodiment includes the negative electrode for a secondary battery according to the second embodiment.

[0039] The conversion reaction proceeds when operating at a potential of 0.5 V or less (0.3 V or more and 0.5 V or less). Therefore, in order to promote the conversion reaction in addition to the insertion reaction during the occlusion of carriers, for example, in addition to the above potential range, it is preferable to set a potential range larger than the above numerical range. Such a potential is, for example, 0.3 V or more and 3.0 V or less, 0.5 V or more and 1.5 V or less. From the viewpoint of effectively utilizing the conversion reaction, in a preferred embodiment, it is operated at a potential of 0.5 V or less.

[0040] (Negative electrode for secondary battery and application to secondary battery of tungsten oxide and molybdenum oxide) As mentioned in the first embodiment, tungsten oxide and molybdenum oxide are useful as negative electrode materials for secondary batteries because they have (1) an improvement in energy density due to a decrease in the redox potential, (2) promotion of the occlusion and release of carriers due to an increase in the lattice spacing of the crystal, and (3) high electronic conductivity. However, as a result of intensive studies by the present inventors, it has been found that there are technical problems to be overcome in applying tungsten oxide and molybdenum oxide as negative electrode materials for secondary batteries to the negative electrodes of secondary batteries. Specifically, when the negative electrode active material occludes carriers in the crystal in a secondary battery, the volume may expand, leading to battery damage. The present inventors have succeeded in improving the energy density of the battery while suppressing volume expansion under predetermined conditions (for example, the above potential range).

[0041] The secondary battery according to the third embodiment may be pre-cycled (pre-cycle treatment). Pre-cycling means performing one or more charge-discharges before using (operating) the secondary battery in this specification. The conditions for pre-cycling are, for example, a current density of 0.025 C to 0.25 C (that is, 20.9 mA / g to 209 mA / g). The lower the current density of pre-cycling (that is, the slower the insertion-desorption reaction of carriers into the electrode), the more sufficiently the insertion reaction during the use of the secondary battery can proceed, and the higher capacity can be more sufficiently exhibited.

[0042] The secondary battery according to the third embodiment includes an electrode (the negative electrode and the positive electrode for the secondary battery according to the second embodiment) and a battery container that houses the electrode. The electrode has the negative electrode for the secondary battery according to the second embodiment and the positive electrode. When the secondary battery is a non-aqueous secondary battery, it further has a separator disposed between these electrodes. When the secondary battery is a coin-type battery, the battery container is made of metal and has, for example, an upper battery container (cap), a lower battery container (case), and a gasket that electrically insulates the upper and lower battery containers. The secondary battery may further have a conductive washer and a conductive spacer between the battery and the battery container.

[0043] (Positive electrode) The positive electrode may be, for example, a metal foil (an alkali metal foil (more specifically, a lithium foil, a sodium foil, and a potassium foil), an alkaline earth metal foil (more specifically, a magnesium foil)), and an alloy foil containing these metals (more specifically, a lithium-indium foil). (Separator) Examples of the separator include a microporous membrane and a non-woven fabric, and examples of their composition include a polyester-based polymer, a polyolefin-based polymer, an ether-based polymer, and glass fiber.

[0044] (Electrolyte) The electrolyte includes an electrolyte and a solvent. The electrolyte contains an alkali metal ion (more specifically, Li + , Na + and K + ) or an alkaline earth metal ion (more specifically, Mg 2+ ) and a counter ion. Examples of the counter ion (negative ion) include PF6 - , BF4 - , ClO4 - , AsF6 - , CF3SO3 - , (CF3SO2)2N - , (C2F5SO2)2N - , and (CF3SO2)3C - .

[0045] Examples of the solvent include alkylene carbonates (more specifically, ethylene carbonate (EC)) and polyalkyl carbonates (more specifically, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC)). These solvents may be halogenated. For example, fluoroethylene carbonate (FEC).

[0046] [Method for manufacturing a secondary battery] When the secondary battery is a non-aqueous secondary battery, for example, a positive electrode and a negative electrode are laminated via a separator to form a planar laminate or wound to form a wound body (laminate). The wound body is housed in a battery container and sealed. An opening is provided during sealing, an electrolytic solution is injected, and the opening is sealed to obtain a secondary battery.

[0047] When the secondary battery is a solid electrolyte secondary battery, for example, a positive electrode and a negative electrode are laminated and formed into a pellet-shaped laminate by compression molding. This pellet-shaped laminate has, for example, a positive electrode made of a metal foil, a negative electrode mixture (a mixture of the negative electrode material according to the first embodiment and a solid electrolyte) as the negative electrode, and a solid electrolyte layer (a layer containing the solid electrolyte contained in the negative electrode mixture) disposed between the negative electrode and the positive electrode. The laminate is housed in a battery container and sealed to obtain a secondary battery.

[0048] The negative electrode material for a secondary battery, the negative electrode for a secondary battery, and the secondary battery according to the embodiments of the present disclosure include the following aspects. <1> A negative electrode material for a secondary battery comprising at least one metal oxide selected from the group consisting of tungsten oxide and molybdenum oxide. <2> The tungsten oxide is WO X (X is 2 or more and 3 or less), the negative electrode material for a secondary battery according to <1>. <3> The tungsten oxide is WO2, WO 2.72The negative electrode material for a secondary battery according to <1> or <2>, which is at least one tungsten oxide selected from the group consisting of WO3. <4> wherein the molybdenum oxide is MoO Y (Y is 2 or more and 3 or less), the negative electrode material for a secondary battery according to any one of <1> to <3>. <5> The negative electrode material for a secondary battery according to any one of <1> to <4>, wherein the molybdenum oxide is at least one molybdenum oxide selected from the group consisting of MoO2 and MoO3. <6> The negative electrode material for a secondary battery according to any one of <1> to <5>, wherein the crystallite size of the metal oxide is greater than 20 nm and 90 nm or less. <7> The specific surface area of the metal oxide is 0.5 m 2 / g or more and 100 m 2 / g or less, the negative electrode material for a secondary battery according to any one of <1> to <6>. <8> The metal oxide is included as spherical secondary particles formed by aggregation of primary particles, the volume median diameter D of the secondary particles 50 is 50 nm or more and 50 μm or less, the negative electrode material for a secondary battery according to any one of <1> to <7>. <9> A negative electrode for a secondary battery comprising the negative electrode material for a secondary battery according to any one of <1> to <8>. <10> The negative electrode for a secondary battery according to <9>, which is for a non-aqueous lithium battery, a non-aqueous sodium battery, or a lithium solid battery. <11> A secondary battery comprising the negative electrode for a secondary battery according to <9> or <10>. <12> The secondary battery according to <11>, which is operated at a potential of 0.5 V or less.

[0049] The embodiments of the present disclosure have been described above. However, the above embodiments are merely examples of the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and various design changes can be made without departing from the gist of the present disclosure. Such design changes will be easily understood by those skilled in the art.

Example

[0050] Hereinafter, the present disclosure will be described more specifically using examples. Note that the present disclosure is not limited by the following examples at all.

[0051] <1. Fabrication of battery> [1-1. Preparation of negative electrode active material (negative electrode raw material)] (Synthesis of tungsten oxide) -Synthesis Example 1 (Example 1): Synthesis of tungsten dioxide WO2- Tungsten trioxide (manufactured by Nippon Shinyaku Co., Ltd., "WO3-4") as a starting material was placed in an electric furnace and heat-treated in a hydrogen atmosphere. The conditions of this heat treatment were a heating temperature of 580 °C, a heating time of 60 minutes (holding time at a heating temperature of 580 °C), and a heating rate of about 10 °C / min. As a result, a brown powder was obtained.

[0052] -Synthesis Example 2 (Example 2): Synthesis of tungsten oxide WO 2.72 - Tungsten trioxide (manufactured by Nippon Shinyaku Co., Ltd., "WO3-4") as a starting material was placed in an electric furnace and heat-treated in a hydrogen atmosphere. The conditions of this heat treatment were a heating temperature of 750 °C, a heating time of 60 minutes (holding time at a heating temperature of 750 °C), and a heating rate of about 10 °C / min. As a result, a purple powder was obtained.

[0053] -Synthesis Example 3 (Example 3): Synthesis of tungsten trioxide WO3- Ammonium paratungstate (5(NH4)2O·12WO3·5H2O) as a starting material was placed in an electric furnace and heat-treated in an air atmosphere. The conditions of this heat treatment were a heating temperature of 800 °C, a heating time of 60 minutes (holding time at 800 °C), and a heating rate of about 10 °C / min. As a result, a green powder was obtained (this powder corresponds to "WO3-4" manufactured by Nippon Shin Metal Co., Ltd.). A green powder was obtained.

[0054] -Synthesis Example 4 (Example 4): Synthesis of Tungsten Trioxide WO3- Tungstic acid (WO3·H2O) as a starting material was placed in an electric furnace and heat-treated in an air atmosphere. The conditions of this heat treatment were a heating temperature of 750 °C, a heating time of 60 minutes (holding time at 750 °C), and a heating rate of about 10 °C / min. As a result, a yellow powder was obtained.

[0055] (Synthesis of Molybdenum Oxide) -Synthesis Example 5 (Example 5): Synthesis of Molybdenum Dioxide MoO2- Ammonium paramolybdate ((NH4)6Mo7O 24 ·4H2O) as a starting material was placed in an electric furnace and heat-treated in a hydrogen atmosphere. The conditions of this heat treatment were a heating temperature of 590 °C, a heating time of 120 minutes (holding time at 590 °C), and a heating rate of about 10 °C / min. As a result, a brown powder was obtained.

[0056] -Synthesis Example 6 (Example 6): Synthesis of Molybdenum Trioxide MoO3- MoO3 powder (manufactured by Taiyo Kogyo Co., Ltd.) was crushed by air jet milling at a compressed air pressure of 6 - 7 kg / cm 2 to obtain a white powder.

[0057] -Comparative Example 1: Preparation of Titanium Dioxide- As the powder of the comparative example, titanium dioxide ("STR-100N" manufactured by Sakai Chemical Industry Co., Ltd., white powder) was prepared.

[0058] [1-2. Fabrication of the Negative Electrode] (Negative Electrode for Non-Aqueous Alkaline Metal Ion Battery) - Preparation of Slurry - The brown powder of Synthesis Example 1 (tungsten dioxide WO2 powder), acetylene black as a conductive aid, carboxymethyl cellulose (CMC) as a thickener, and styrene-butadiene rubber as a binder were put into a container of a ball mill so that the volume ratio (black powder: conductive aid: thickener: binder) was 70:15:10:5. Further, 3 mL of pure water heated to about 100°C was put into this container. The above container was sealed to enclose the above mixture. In this state, a mixing process was performed for 30 minutes. In the mixing by the ball mill, containers and balls made of quartz (density 2.65 g / cm 3 ) were used. Thus, a slurry was obtained.

[0059] - Fabrication of Negative Electrode - The obtained slurry was applied onto a copper foil (thickness 18 μm) to form a coating film. The coating film was heat-treated under the condition of a temperature of 120°C to form a film-shaped negative electrode (coated electrode) (film thickness 15 μm, coating amount 1.5 mg / cm 2 ) on the copper foil.

[0060] (Negative Electrode for Solid-State Lithium-Ion Battery) Referring to FIG. 2, a method for manufacturing a negative electrode for a solid-state lithium-ion battery will be described. FIG. 2 is a diagram for explaining a method for manufacturing a negative electrode for a solid electrolyte lithium-ion battery. As shown in FIG. 2, lithium borate-lithium sulfate-lithium carbonate (Li3BO3-Li2SO4-Li2CO3) as a solid electrolyte 13', a mixture of lithium borate-lithium sulfate-lithium carbonate (Li3BO3-Li2SO4-Li2CO3) and the powder of Synthesis Example 1 as a negative electrode mixture 12', and a metal copper foil as a current collector 11 were sequentially introduced and laminated into the recess of a hot compression press 100. The recess of the hot compression press 100 was composed of a cylindrical die 101 having a cylindrical hollow structure and a lower punch 102 for closing the lower opening end of the hollow structure of the die 101. An upper punch 103 was fitted into the recess of the hot compression press 100, and the lower surface of the upper punch 103 was brought into contact with the upper surface of the current collector 11. Under heating conditions of 230°C, a stress (230 MPa) was applied vertically downward from the upper punch 103 for 3 hours for compression molding. The heating was performed by a heater 104. Thereby, a negative electrode 10 in which a solid electrolyte layer 13, a negative electrode mixture layer 12, and a current collector 11 were laminated was manufactured.

[0061] [1-3. Fabrication of Coin-Type Battery] The coin-type battery was fabricated in a glove box under an argon atmosphere with a dew point of -100°C or lower and an oxygen concentration of 1 ppm or lower.

[0062] (Non-Aqueous Lithium-Ion Battery) Referring to FIGS. 3 and 4, the fabrication of a non-aqueous lithium ion battery will be described. FIG. 3 is a schematic diagram showing the appearance of a non-aqueous lithium ion battery. FIG. 4 is an exploded perspective view of the non-aqueous lithium ion battery. As shown in FIGS. 3 and 4, the non-aqueous lithium ion battery 1 has a structure in which a washer 40, a spacer 50, a metal lithium foil (thickness of about 1 μm) as a counter electrode (positive electrode) 20, a glass fiber filter (Whatman's "GF / A", air permeability 4.3 s / 100 mL) as a separator 30, a coated electrode (test electrode, negative electrode) 10 prepared in 1-2 as a negative electrode, and a gasket 60 are laminated in this order and housed in a cap (battery container) 70 and a case (battery container) 80. Further, an electrolyte solution was injected to fabricate a 2032-type coin cell.

[0063] In Example 1, the electrolyte solution contained LiFSA as an electrolyte and ethylene carbonate (EC) as a solvent. The non-aqueous lithium ion battery of Example 1 was of the WO2 / LiFSA / PC system.

[0064] In Example 2, the electrolyte solution contained 1M LiPF6 as an electrolyte and a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) as solvents (volume ratio EC:DMC:EMC = 33:33:33, content of FEC: 10% by weight based on 100% by weight of the total weight of the electrolyte solution). The coated electrode was obtained by punching out the coated electrode obtained in 1-2 into a circular shape together with a copper foil. The copper foil functioned as a current collector 11. The non-aqueous lithium ion battery of Example 2 was of the WO2 / LiPF6 / EC+DMC+EMC+FEC system.

[0065] In Examples 3 to 5, non-aqueous lithium ion batteries were fabricated in the same manner as in Example 2, except that WO 2.72 , WO3(G), and WO3(Y) were used instead of WO2 as the negative electrode material. That is, the non-aqueous lithium ion batteries of Examples 3 to 5 were WO 2。72 / LiPF6 / EC + DMC + EMC + FEC system, WO3(G) / LiPF6 / EC + DMC + EMC + FEC system, and WO3(Y) / LiPF6 / EC + DMC + EMC + FEC system.

[0066] In Comparative Example 1, a non-aqueous lithium ion battery was fabricated in the same manner as in Example 2, except that TiO2 was used instead of WO2 as the negative electrode material. That is, the non-aqueous lithium ion battery of Comparative Example 1 was of the TiO2 / LiPF6 / EC + DMC + EMC + FEC system.

[0067] In Examples 6 - 7, non-aqueous lithium ion batteries were fabricated in the same manner as in Example 2, except that MoO2 and MoO3 were used instead of WO2 as the negative electrode materials, respectively. That is, the non-aqueous lithium ion batteries of Examples 6 - 7 were of the MoO2 / LiPF6 / EC + DMC + EMC + FEC system and the MoO3 / LiPF6 / EC + DMC + EMC + FEC system, respectively.

[0068] (Fabrication of non-aqueous sodium ion battery) In Example 8, a coin-shaped battery (non-aqueous sodium ion battery) was fabricated in the same manner as the non-aqueous lithium ion battery of Example 2, except that the counter electrode was changed from metallic lithium foil to metallic sodium foil, and the electrolyte was changed from an electrolyte containing 1M NaPF6 and a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC) (volume ratio EC:DMC = 50:50, content of FEC: 10% by weight based on the total weight of 100% by weight of the electrolyte) to an electrolyte containing 1M NaPF6 and a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC) (volume ratio EC:DMC = 50:50). That is, the non-aqueous sodium ion battery of Example 8 was of the WO2 / NaPF6 / EC + DMC + FEC system.

[0069] In Examples 9 - 11, WO 2.72, except that WO3(G) and WO3(Y) were used, a non-aqueous sodium ion battery was fabricated in the same manner as in Example 8. That is, the non-aqueous sodium ion batteries of Examples 9 to 11 were WO 2。72 / NaPF6 / EC+DMC+FEC system, WO3(G) / NaPF6 / EC+DMC+FEC system, and WO3(Y) / NaPF6 / EC+DMC+FEC system, respectively.

[0070] In Comparative Example 2, except that TiO2 was used instead of WO2 as the negative electrode material, a non-aqueous lithium ion battery was fabricated in the same manner as in Example 8. That is, the non-aqueous lithium ion battery of Comparative Example 2 was a TiO2 / NaPF6 / EC+DMC+FEC system.

[0071] In Examples 12 to 13, except that MoO2 and MoO3 were used instead of WO2 as the negative electrode material, respectively, non-aqueous sodium ion batteries were fabricated in the same manner as in Example 8. That is, the non-aqueous sodium ion batteries of Examples 12 to 13 were MoO2 / NaPF6 / EC+DMC+FEC system and MoO3 / NaPF6 / EC+DMC+FEC system, respectively.

[0072] (Solid Electrolyte Lithium Ion Battery) With reference to FIG. 5, the manufacturing method of the solid electrolyte lithium ion battery of Example 14 will be described. FIG. 5 is a diagram for explaining the manufacturing method of the solid electrolyte lithium ion battery. As shown in FIG. 5, the negative electrode 10 fabricated in 1-2 was placed in the recess of the compression press 110, and an indium lithium alloy (Li-In) was placed as the counter electrode (positive electrode) 20 on the negative electrode 10. The recess of the hot compression press was composed of a cylindrical die 111 having a cylindrical hollow structure and a lower punch 112 for closing the lower opening end of the hollow structure of the die 111. The die 111 was made of an insulating material. The upper punch 113 was fitted into the recess of the compression press 110, and the lower surface of the upper punch 113 was brought into contact with the upper surface of the counter electrode 20. A stress (80 MPa) was applied vertically downward from the upper punch 113 for compression molding. Thereby, a laminate in which the negative electrode 10 and the counter electrode 20 were laminated was fabricated. A coin-shaped battery was fabricated without using an electrolytic solution by replacing the counter electrode 20, separator 30, and negative electrode 10 in the non-aqueous lithium battery with the above laminate.

[0073] <2. Measurement Method> [2-1. Measurement of X-ray Diffraction Spectrum] The X-ray diffraction spectra of the powders of Synthesis Examples 1 to 6 were measured using a powder X-ray diffractometer (Rigaku Corporation's "Ultima IV", radiation source CuKα, optical system: parallel beam optical system). The measurement conditions were: divergence slit 0.5°, scattering slit 2.0°, receiving slit open, scanning step width 0.002°, scanning speed 2° / min, measurement voltage 40 kV, and measurement current 40 mA.

[0074] [2-2. Measurement of Volume Expansion Rate of Negative Electrode] The non-aqueous lithium ion battery (WO2 / LiFSA / PC system) of Example 1 was charged at a potential range of 0.3 to 1.5 V. At this time, the volume of the negative electrode of Example 1 in three scenarios was measured. The volume of the negative electrode of the battery before the battery of Example 1 was completely discharged and charged (designated as No. 1) was measured (5th charge-discharge cycle). From the state of No. 1, the volume of the negative electrode of the battery when the battery was charged and the capacity was 40 mAh / g (designated as No. 2) was measured (5th charge-discharge cycle). From the state of No. 2, the volume of the negative electrode of the battery when the battery was further charged and the capacity was 200 mAh / g (designated as No. 3) was measured (5th charge-discharge cycle). Based on the obtained volume of No. 1, the volume expansion rate (%) of each battery of No. 1 to 3 was calculated.

[0075] [2-3. Measurement of Charge-Discharge Curve] Using a coin-type battery, the charge-discharge curve was measured under the following conditions. (Non-aqueous Lithium Ion Battery) · Temperature: 30 °C · Potential range: 0.01 V to 2.5 V (vs Li / Li + ) · Current density: 1 C, 496 mAh / g (WO2), 694 mAh / g (WO3), 641 mAh / g (WO 2.72)、694 mAh / g (WO3), 836 mAh / g (MoO2), 1117 mAh / g (MoO3) (Non-aqueous sodium ion battery) · Temperature: 30 °C · Potential range: 0.01 V to 2.5 V (vs Na / Na + ) · Current density: 1 C, 5 mAh / g (WO2)

[0076] [2 - 4. Measurement of particle size] Using sodium hexametaphosphate as a dispersant, the powders obtained in Synthesis Examples 1 to 6 were independently dispersed in an aqueous solution prepared to a concentration of 1 g / L (without adding a dispersant for WO3), and the particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer ("MT3300EXII" manufactured by Microtrac). From the particle size distribution, the volume median diameter D 50 was calculated.

[0077] [2 - 5. Method for measuring crystallite size] Based on the results of the XRD spectrum measurement obtained in 2 - 1, the crystallite size was calculated using the Scherrer equation. Specifically, using analysis software ("PDXL" manufactured by Rigaku Corporation), the half-widths of the three peaks with the highest diffraction intensity were calculated from the XRD spectrum. From the obtained half-widths, the Scherrer equation was used to calculate a plurality of crystallite sizes and their average value. The obtained average value was taken as the crystallite size.

[0078] [2 - 6. Measurement of specific surface area of powder] Using a fully automatic specific surface area measurement device ("HMmodel - 1201" manufactured by Mountech Co., Ltd.), the specific surface area of the powder was measured by the BET one-point method. The measurement sample was pretreated by degassing and drying at a temperature of 200 °C for 30 minutes.

[0079] [2 - 7. Imaging method for scanning electron microscope (SEM) images] Using a field emission type scanning electron microscope (electrolytic emission type scanning electron microscope: FE-SEM) (manufactured by JEOL Ltd., model "JSM-IT800"), SEM images were taken under the measurement conditions of an acceleration voltage of 10 kV and a working distance of 10 mm.

[0080] <3. Results> [3-1. Identification by X-ray diffraction spectrum] (Tungsten oxide) - Synthesis Example 1: WO2- Figure 6 shows the X-ray diffraction (XRD) spectrum of the powder obtained in Synthesis Example 1. As shown in Figure 6, from the pattern of the XRD spectrum, it was confirmed that the powder obtained in Synthesis Example 1 is a WO2 chemical phase having a distorted rutile-type crystal structure. Figure 7 shows the distorted rutile-type crystal structure. In the powder of Synthesis Example 1, in Figure 7, the sphere 121 described by a relatively thin line represents tungsten ions (W 4+ ), and the sphere 122 described by a relatively thick line represents oxygen ions (O 2- ). The results are summarized in Table 1.

[0081]

Table 1

[0082] - Synthesis Example 2: WO 2.72 - Figure 8 shows the XRD spectrum of the powder obtained in Synthesis Example 2. As shown in Figure 8, from the pattern of the XRD spectrum, it was confirmed that the powder obtained in Synthesis Example 2 contains a WO2 chemical phase, a W8O 21 chemical phase, a W 18 O 49 (WO 2.72 ) chemical phase, and a WO3 chemical phase. Note that the powder of Synthesis Example 2 is hereinafter also referred to as "WO 2.72 " using the most abundant chemical phase (the chemical phase of the main component) representing the plurality of tungsten oxide chemical phases contained in the powder of Synthesis Example 2.

[0083] - Synthesis Example 3: WO3- Figure 9 shows the XRD spectrum of the powder obtained in Synthesis Example 3. As shown in Figure 9, from the pattern of the XRD spectrum, it was confirmed that the powder obtained in Synthesis Example 3 is a WO3 chemical phase having a distorted rhenium oxide (ReO3) type crystal structure (see Figure 10). Figure 10 shows a distorted rhenium oxide (ReO3) type crystal structure. In the powder of Synthesis Example 3, in Figure 10, sphere 123 described by a relatively thin line represents tungsten ion (W 6+ ), and sphere 124 described by a relatively thick line represents oxygen ion (O 2- ). Further, Figure 11 shows a scanning electron microscope (SEM) image of the powder obtained in Synthesis Example 3. As shown in Figure 11, the crystal system of the powder obtained in Synthesis Example 3 was a mixed crystal system of monoclinic and orthorhombic crystals. In addition, in order to distinguish it from tungsten trioxide obtained in Synthesis Example 4 described later, tungsten trioxide obtained in Synthesis Example 3 is also referred to as WO3(G) or WO3-4.

[0084] - Synthesis Example 4: WO3- Figure 12 shows the X-ray diffraction (XRD) spectrum of the powder obtained in Synthesis Example 4. As shown in Figure 12, from the pattern of the XRD spectrum, it was confirmed that the powder obtained in Synthesis Example 4 is a WO3 chemical phase having a distorted rhenium oxide (ReO3) type crystal structure (see Figure 10). In addition, in order to distinguish it from WO3(G) obtained in Synthesis Example 3 described above, tungsten trioxide obtained in Synthesis Example 4 is also referred to as WO3(Y) or WO3-1.

[0085] Further, Figure 13 shows an SEM image of the powder obtained in Synthesis Example 4. As shown in Figure 13, the crystal system of the powder obtained in Synthesis Example 4 was a mixed crystal system of monoclinic and orthorhombic crystals. The shape of the primary particles constituting the powder obtained in Synthesis Example 4 was needle-like and plate-like. The differences between the powder obtained in Synthesis Example 4 and the powder obtained in Synthesis Example 3 were color (see Table 1), the shape of the primary particles, and the particle aggregation state (see Figures 7 and 9). These differences are considered to be due to at least the different starting materials of the powders of Synthesis Examples 3 to 4.

[0086] (Molybdenum Oxide) - Synthesis Example 5: MoO2- Fig. 14 shows the X-ray diffraction (XRD) spectrum of the powder obtained in Synthesis Example 5. As shown in Fig. 14, from the pattern of the XRD spectrum, it was confirmed that the powder obtained in Synthesis Example 5 contains a MoO2 chemical phase having a distorted rutile-type crystal structure (see Fig. 7).

[0087] - Synthesis Example 6: MoO3- Fig. 15 shows the X-ray diffraction (XRD) spectrum of the powder obtained in Synthesis Example 6. As shown in Fig. 15, from the pattern of the XRD spectrum, it was confirmed that the powder obtained in Synthesis Example 6 is a MoO3 chemical phase having a distorted rhenium oxide-type crystal structure (see Fig. 10).

[0088] [3-2. Non-aqueous Lithium-ion Battery] (3-2-1. Change in Anode Reaction) - Example 1: Non-aqueous Lithium-ion Battery of WO2 / LiFSA / PC System- The change in the anode reaction will be described with reference to Figs. 16, 17 and 18. Figs. 16 to 18 show the discharge curves of a non-aqueous lithium-ion battery of the WO2 / LiFSA / PC system (anode material: WO2, electrolyte: propylene carbonate, lithium salt: lithium bis(fluorosulfonyl)imide (hereinafter also referred to as "LiFSA")). The temperature was 30 °C. The potential ranges were 0.75 to 1.5 V in Fig. 16, 0.5 to 1.5 V in Fig. 17 and 0.3 to 3.0 V in Fig. 18. Also, the current densities were 62 mAh / g in Fig. 16, 124 mAh / g in Fig. 17 and 124 mAh / g in Fig. 18.

[0089] As shown in Fig. 16, in the charge curve, the potential increased simply with the increase in capacity in the region around 25 to 45 mAh / g. On the other hand, the charge curve showed a simple decrease with the increase in capacity in the region around 5 to 30 mAh / g and further showed a plateau region. Therefore, it was found that only the insertion reaction substantially proceeded during charging in the potential range of 0.75 to 1.5 V. Also, the maximum capacity was about 70 mAh / g.

[0090] As shown in Fig. 17, in the charge curve, the potential decreased with the increase in capacity and had an inflection point (around 45 mAh / g), and in the discharge curve, it increased with the increase in capacity and had an inflection point (around 50 mAh / g). Therefore, in the potential range of 0.5 to 1.5 V, it was found that in addition to the insertion reaction during charging, the conversion reaction was also proceeding. Also, the maximum capacity was around 125 mAh / g.

[0091] As shown in Fig. 18, in the charge curve, the potential decreased with the increase in capacity and had an inflection point (around 80 mAh / g), and in the discharge curve, it increased with the increase in capacity and had an inflection point (around 50 mAh / g). Therefore, in the potential range of 0.5 to 1.5 V, in charging, in addition to the half-reaction formula (2):

Chem.

Chem.

[0092] Based on the charge-discharge curve in Fig. 16, as the lower limit of the potential was decreased to widen the potential range, an inflection point appeared in the charge-discharge curve, and it was observed that the range of the charge-discharge curve from the inflection point increased. Therefore, in the occlusion of carriers accompanying the charging of the battery, it was found that in addition to the insertion reaction, the conversion reaction was also proceeding. Furthermore, as the lower limit of the potential was decreased to widen the potential range, since the maximum capacity shown by the charge-discharge curve increased, it was found that the battery had a higher capacity due to the progress of the conversion reaction.

[0093] (3-2-2. Volume expansion rate) - Example 1: Non-aqueous lithium-ion battery of the WO2 / LiFSA / PC system - Table 2 summarizes the measurement results of the volume expansion rate. [Table 2]

[0094] As shown in Table 2, it was found that as the capacity of the battery increased, the volume expansion rate of the battery increased.

[0095] (3-2-3. Particle size distribution) The particle size distributions of the powders of Synthesis Examples 1 to 2 and 5 were measured. Fig. 19 shows the particle size distribution of the powder of Synthesis Example 1. From the particle size distribution, the volume median diameter D 50 was calculated. The results are summarized in Table 1.

[0096] (3-2-4. Charge-discharge curve) - Non-aqueous lithium-ion batteries of Examples 2 to 5 (negative electrode: tungsten oxide) - The charge-discharge curves of the non-aqueous lithium-ion batteries are shown in Figs. 20 to 23. Additionally, various physical property values are summarized in Tables 3 to 6. The inset figures in Figs. 20 to 23 indicate the number of charge-discharge cycles. The same applies hereinafter. Figs. 20 to 23 have different negative electrode active materials. Fig. 24 summarizes the charge-discharge curves of the first charge-discharge cycle of Figs. 20 to 23 and the charge-discharge curve of TiO2 of the comparative example.

[0097] [Table 3]

[0098] [Table 4]

[0099] [Table 5]

[0100] [Table 6]

[0101] As shown in FIG. 20, in Examples 2 to 5, charge-discharge curves associated with the occlusion of lithium into tungsten oxide and the release of lithium from tungsten oxide were confirmed. Also, as shown in FIG. 24, the charge-discharge curves of the non-aqueous lithium-ion batteries of Examples 2 to 5 had a larger capacity and a lower potential compared to the charge-discharge curves of the non-aqueous lithium-ion battery of Comparative Example 1. Therefore, the batteries of Examples 2 to 5 had a higher capacity and a lower potential compared to Comparative Example 1. Therefore, it was shown that tungsten oxide in Examples 2 to 5 is very promising as a negative electrode material (negative electrode active material) for secondary batteries.

[0102] -Non-aqueous lithium-ion battery (negative electrode: molybdenum oxide)- The charge-discharge curves of the non-aqueous lithium-ion battery are shown in FIGS. 25 to 26 and FIG. 23. Also, various physical property values are summarized in Tables 6 to 7. FIGS. 25 to 26 have different negative electrode active materials. FIG. 27 summarizes the charge-discharge curves of the first charge-discharge cycle in FIGS. 25 to 26 and the charge-discharge curves of TiO2 of Comparative Example 1.

[0103] [Table 7]

[0104] [Table 8]

[0105] As shown in FIGS. 25 to 26, in Examples 6 to 7, charge-discharge curves associated with the occlusion of lithium into molybdenum oxide and the release of lithium from molybdenum oxide were confirmed. Also, as shown in FIG. 27, the charge-discharge curve of Example 6 had a larger capacity and a lower potential compared to the charge-discharge curve of Comparative Example 1. Therefore, the battery of Example 6 had a higher capacity and a lower potential compared to Comparative Example 1. Furthermore, as shown in Fig. 27, the charge-discharge curve of Example 7 had the same capacity as that of Comparative Example 1, but was slightly lower in potential. Therefore, it was shown that molybdenum oxide (especially molybdenum trioxide) is promising as a negative electrode material (negative electrode active material) for a battery with high energy density.

[0106] (3-2-5. Cycle characteristics of discharge capacity) Fig. 28 is a diagram showing the relationship between the discharge capacity and the number of charge-discharge cycles. As shown in Fig. 28, Example 7 (negative electrode active material: MoO3) had a large initial capacity (initial discharge capacity), Example 6 (negative electrode active material: MoO2) had the largest capacity among Examples 2 to 7 after charge-discharge cycles, and Examples 2 to 5 (negative electrode active material: WO2, WO x , WO3(G), WO3(Y)) had a gentle attenuation of the discharge capacity. Thus, Examples 2 to 7 showed that they had cycle characteristics of various discharge curves. Therefore, the negative electrode active material according to this embodiment can select a material according to, for example, the application and required specifications, so that the degree of freedom in battery design can be increased.

[0107] (3-2-6. Charge-discharge curve: presence or absence of pre-cycle) Fig. 39 is a diagram showing the charge-discharge curves of a non-aqueous lithium-ion battery of the MnO2 / LiPF6 / (EC+DMC+EMC+FEC) system under pre-cycle treatment (current density: 0.25C, 0.1C, 0.025C). Before the measurement of charge-discharge, after performing one pre-cycle at a predetermined current density (0.25C (209 mA / g), 0.1C (83.6 mA / g), or 0.025C (20.9 mA / g)), charge-discharge measurement (measurement conditions: current density 1C (836 mA / g), potential range 0.01V to 2.5V, and temperature 30°C) was performed to obtain a charge-discharge curve. The number of charge-discharge cycles was 1. For comparison, the charge-discharge curve (current density: 0C) obtained without pre-cycle treatment was described. The (initial) discharge capacity was obtained from the obtained charge-discharge curve. The results are shown in Table 8.

[0108]

Table 9

[0109] As shown in FIG. 39 and Table 8, it was observed that the charge-discharge curve with pre-cycling tended to have a higher capacity and a lower potential compared to the charge-discharge curve without pre-cycling. Specifically regarding the capacity, it was observed that the initial discharge capacity with pre-cycling tended to increase compared to the initial discharge capacity without pre-cycling. Furthermore, it was found that the smaller the current density of the pre-cycling, the larger the initial discharge capacity. From such results, in the initial charge-discharge of the non-aqueous lithium-ion battery, the insertion reaction of Li into MnO2 + is suggested to occur efficiently by performing pre-cycling with a lower current density (that is, by allowing the insertion reaction to proceed relatively slowly). + That is, the insertion and deinsertion of Li into MnO2 occurs efficiently.

[0110] FIGS. 41 to 43 are diagrams showing the charge-discharge curves of a non-aqueous lithium-ion battery of the MoO2 / LiPF6 / (EC + DMC + EMC + FEC) system under pre-cycling treatment (any one of 0.25C (209 mA / g), 0.1C (83.6 mA / g), 0.025C (20.9 mA / g), once). For comparison, FIG. 40 shows a diagram showing the charge-discharge curve of a non-aqueous lithium-ion battery of the MoO2 / LiPF6 / (EC + DMC + EMC + FEC) system without pre-cycling treatment.

[0111] In the battery without pre-cycling treatment, as shown in FIG. 40, it was found that the charge-discharge capacity increased as the charge-discharge cycle increased (for example, from 5 cycles to 100 cycles). In contrast, in the battery with pre-cycling treatment, as shown in FIGS. 41 to 43, the amount of change in the charge-discharge capacity was smaller compared to the battery without pre-cycling treatment.

[0112] (3-2-7. Cycle characteristics of discharge capacity: With or without pre-cycling) Fig. 44 shows a diagram illustrating the relationship between the discharge capacity and the number of charge-discharge cycles in a non-aqueous lithium-ion battery under pre-cycle treatment. As shown in Fig. 44, it was confirmed that the discharge capacity (initial discharge capacity) at the first charge-discharge cycle of the battery subjected to pre-cycle treatment was larger than the initial discharge capacity of the battery not subjected to pre-cycle treatment. Also, the discharge capacity of the battery subjected to pre-cycle treatment showed a shape having a maximum value on the side of a smaller number of charge-discharge cycles compared to the discharge capacity of the battery not subjected to pre-cycle treatment.

[0113] [3-3. Non-aqueous sodium-ion battery] (3-3-1. Charge-discharge curve) - Non-aqueous sodium-ion battery (negative electrode: tungsten oxide)- Figs. 29 to 32 and Fig. 33 show the charge-discharge curves of the non-aqueous sodium-ion batteries of Examples 8 to 11. Also, various physical property values were summarized in Tables 10 to 13. In Figs. 29 to 32, the negative electrode active materials are different. Fig. 33 is a compilation of the charge-discharge curves of the first charge-discharge cycle of Figs. 29 to 32 and the charge-discharge curve of TiO2 of Comparative Example 2.

[0114]

Table 10

[0115]

Table 11

[0116]

Table 12

[0117]

Table 13

[0118] As shown in Fig. 33, in Examples 8 to 11, charge-discharge curves associated with the occlusion of sodium into tungsten oxide and the release of sodium from tungsten oxide were confirmed.

[0119] -Non-aqueous sodium-ion battery (negative electrode: tungsten oxide)- Figs. 34 to 35 and Fig. 36 show the charge-discharge curves of the non-aqueous sodium-ion batteries of Examples 12 to 13. At the same time, various physical property values are summarized in Tables 14 to 15. In Figs. 34 to 35, the negative electrode active materials are different. Fig. 36 is a summary of the charge-discharge curves of the first charge-discharge cycle in Figs. 34 to 35 and the charge-discharge curve of TiO2 of Comparative Example 2.

[0120]

Table 14

[0121]

Table 15

[0122] As shown in Fig. 36, in Examples 12 to 13, charge-discharge curves associated with the occlusion of sodium into molybdenum oxide and the release of sodium from molybdenum oxide were confirmed. Also, as shown in Fig. 36, the charge-discharge curve of Example 13 had a higher capacity and a lower potential compared to the charge-discharge curve of Comparative Example 2. Therefore, it was shown that molybdenum oxide (particularly, molybdenum trioxide) is promising as a negative electrode material (negative electrode active material) for a battery with a high energy density.

[0123] (3-3-2. Cycle characteristics of discharge capacity) Fig. 37 shows the charge-discharge cycle characteristics of the discharge capacity. Examples 8 to 13 had a plateau region compared to Comparative Example 2. Also, Example 8 showed a larger discharge capacity compared to Comparative Example 2.

[0124] [3-4. Solid electrolyte lithium-ion battery] (3-4-1. Discharge curve) Fig. 38 shows the charge-discharge curves of the solid electrolyte lithium ion battery. Also, various physical property values are summarized in Table 16.

[0125]

Table 16

[0126] As shown in Fig. 38, in Example 14, charge-discharge curves associated with the occlusion of lithium into tungsten oxide and the release of lithium from tungsten oxide were confirmed. Therefore, it was shown that tungsten oxide is promising as a negative electrode material (negative electrode active material) for a solid electrolyte lithium ion battery.

Industrial Applicability

[0127] The negative electrode material for a secondary battery of the present disclosure can be used, for example, for a negative electrode of a secondary battery. The negative electrode for a secondary battery of the present disclosure can be used, for example, for a secondary battery.

Explanation of Signs

[0128] 1 Battery 10 Negative electrode 11 Current collector 12 Negative electrode binder layer 12’ Negative electrode binder 13 Solid electrolyte layer 13’ Solid electrolyte 20 Positive electrode (counter electrode) 30 Separator 40 Washer 50 Spacer 60 Gasket 70 Cap (battery container) 80 Case (battery container) 100 Hot compression press 101 Die 102 Lower punch 103 Upper punch 104 Heater 110 Compression press 111 Die 112 Lower punch 113 Upper punch

Claims

1. A negative electrode material for a secondary battery, comprising at least one metal oxide selected from the group consisting of tungsten oxide and molybdenum oxide.

2. The tungsten oxide is WO Ｘ (X is 2 or more and 3 or less), the negative electrode material for a secondary battery according to claim 1.

3. The tungsten oxide is WO ２ , WO ２．７２ , and WO ３ The negative electrode material for a secondary battery according to claim 1 or 2, which is at least one tungsten oxide selected from the group consisting of

4. The molybdenum oxide is MoO Ｙ where Y is from 2 to 3), the negative electrode material for a secondary battery according to claim 1.

5. wherein the molybdenum oxide is at least one molybdenum oxide selected from the group consisting of MoO ２ and MoO ３ The negative electrode material for a secondary battery according to claim 1 or 4.

6. The negative electrode material for a secondary battery according to Claim 1 or 2, wherein the crystallite size of the metal oxide is greater than 20 nm and 90 nm or less.

7. The specific surface area of the metal oxide is 0.5 m ２ / g or more and 100 m ２ / g or less. The negative electrode material for a secondary battery according to claim 1.

8. The metal oxide is included as spherical secondary particles formed by aggregation of primary particles. The volume median diameter D of the secondary particles ５０ is 50 nm or more and 50 μm or less, and the negative electrode material for a secondary battery according to claim 1.

9. A negative electrode for a secondary battery, comprising the negative electrode material for a secondary battery according to Claim 1.

10. The negative electrode for a secondary battery according to Claim 9, which is for a non-aqueous lithium battery, a non-aqueous sodium battery, or a lithium solid battery.

11. A secondary battery, comprising the negative electrode for a secondary battery according to Claim 10.

12. The secondary battery according to Claim 11, which is operated at a potential of 0.5 V or less.

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