Electrode active material for electrochemical element and method for producing same, electrode material for electrochemical element, electrode for electrochemical element, electrochemical element, and mobile body

Abstract

The present invention provides an electrochemical element having excellent load characteristics and charge / discharge cycle characteristics, an electrode active material that can constitute the electrochemical element, a method for producing the same, an electrode material and an electrode, and a mobile body having the electrochemical element. SOLUTION: The electrode active material for an electrochemical element of the present invention is characterized by having a monoclinic crystal structure and containing an oxide that satisfies the following general formula (1): A y M 1 αAl x-α Nb 12-x-z M 2 z O 29-δ (1) [In the general formula (1), A is at least one element selected from Li and Na; M 1 is at least one element selected from the group consisting of Fe, Mn, Zn, Cu, Ag, Mg, Ca, Sr, Ba, Co, Eu, Y, Bi, La, Ce, Nd, Sm and Gd; M 2 is a specific element, and 0

Description

[Technical Field]

[0001] The present invention relates to an electrochemical device having excellent load characteristics and charge / discharge cycle characteristics, an electrode active material that can constitute the electrochemical device, a method for producing the same, an electrode material and an electrode, and a mobile object having the electrochemical device. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, a type of electrochemical device, are used as power sources for portable electronic devices such as mobile phones and laptop personal computers, as well as electric vehicles. However, as these devices become smaller and more functional, there is a growing demand for non-aqueous electrolyte secondary batteries that are smaller, lighter, and have higher capacities and energy densities.

[0003] In current non-aqueous electrolyte secondary batteries, a lithium-containing composite oxide is typically used as the positive electrode active material, and graphite or the like is typically used as the negative electrode active material.

[0004] In addition, in order to construct a battery that can be charged and discharged at a large current value without causing an internal short circuit due to lithium deposition at the negative electrode, spinel-type lithium titanate (Li4Ti5O 12 However, lithium titanate has a theoretical capacity of 175 mAh / g (600 mAh / cm 3 ) is the theoretical capacity of graphite [372 mAh / g (830 mAh / cm 3 ) and this is where the problem lies.

[0005] For this reason, in recent years, TiNb2O7 and Ti2Nb have been used as negative electrode active materials with larger capacities than lithium titanate. 10 O 29 , AlNb 11 O 29 , Zn2Nb 34 O 87 , Cu 0.02 Ti 0.94 Nb 2.04The application of oxides of niobium and other metals, such as O7, has been investigated (Patent Documents 1 to 5, Non-Patent Documents 1 to 4, etc.). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-160365 [Patent Document 2] Japanese Patent Application Publication No. 2019-53945 [Patent Document 3] Japanese Patent Application Publication No. 2019-160729 [Patent Document 4] Patent Publication No. 2021-82420 [Patent Document 5] International Publication No. 2021 / 074592 [Non-patent literature]

[0007] [Non-Patent Document 1] Electrochemistry Communications, 2012, Vol. 25, pp. 39-42 [Non-patent document 2] ACS Applied Material Interfaces, 2019, Vol. 11, pp. 6086-6096 [Non-patent document 3] Journal of Materials ChemistryA, 2019, Vol. 7, pp. 25537-25547 [Non-patent document 4] Journal of Power Sources, 2016, vol. 328, pp. 336-344 Summary of the Invention [Problem to be solved by the invention]

[0008] Meanwhile, non-aqueous electrolyte secondary batteries are also required to have improved load characteristics and charge / discharge cycle characteristics. However, when the materials disclosed in Patent Documents 1 to 5 and Non-Patent Documents 1 to 4 are used as active materials, it is difficult to achieve both good load characteristics and good charge / discharge cycle characteristics.

[0009] The present invention has been made in consideration of the above circumstances, and its object is to provide an electrochemical element having excellent load characteristics and charge / discharge cycle characteristics, an electrode active material that can constitute the electrochemical element, a manufacturing method thereof, an electrode material and an electrode, and a mobile body having the electrochemical element. [Means for solving the problem]

[0010] The electrode active material for an electrochemical element of the present invention is characterized by being an oxide having a monoclinic crystal structure and satisfying the following general formula (1).

[0011] A y M 1 α Al x-α Nb 12-x-z M 2 z O 29-δ (1)

[0012] In the general formula (1), A is at least one element selected from Li and Na; M 1 is at least one element selected from the group consisting of Fe, Mn, Zn, Cu, Ag, Mg, Ca, Sr, Ba, Co, Eu, Y, Bi, La, Ce, Nd, Sm and Gd; M 2 is at least one element selected from the group consisting of K, Ti, Ni, Zr, V, Mo, Ta and W, and 0 <x≦1.1、0≦y≦24、0≦z≦2、-1≦δ≦2、0<α≦0.4xである。

[0013] The electrode material for an electrochemical element of the present invention is characterized by containing the electrode active material for an electrochemical element of the present invention.

[0014] Furthermore, the electrode for electrochemical devices of the present invention is characterized by containing the electrode active material for electrochemical devices of the present invention or the electrode material for electrochemical devices of the present invention.

[0015] The electrochemical element of the present invention has a positive electrode and a negative electrode, and is characterized in that one of the positive electrode and the negative electrode is the electrode for an electrochemical element of the present invention.

[0016] The mobile body of the present invention is characterized by having the electrochemical element of the present invention.

[0017] The electrode active material for electrochemical elements of the present invention can be produced through a process of firing the oxide represented by the general formula (1) or its precursor in a carbon container under a vacuum atmosphere, thereby further improving its properties. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an electrochemical element having excellent load characteristics and charge / discharge cycle characteristics, an electrode active material that can constitute the electrochemical element, a manufacturing method thereof, an electrode material and an electrode, and a mobile body having the electrochemical element. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of an electrochemical element according to one embodiment of the present invention. [Figure 2] FIG. 2 is a plan view schematically illustrating another example of an electrochemical element according to one embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view taken along line II in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described below based on embodiments.

[0021] <Electrode active materials for electrochemical devices> The electrode active material for an electrochemical element of this embodiment (hereinafter, sometimes simply referred to as "active material") is an oxide that has a monoclinic crystal structure and satisfies the following general formula (1).

[0022] A y M 1 α Al x-α Nb 12-x-z M 2 z O 29-δ (1)

[0023] In the general formula (1), A is at least one element selected from Li and Na; M 1 is at least one element selected from the group consisting of Fe, Mn, Zn, Cu, Ag, Mg, Ca, Sr, Ba, Co, Eu, Y, Bi, La, Ce, Nd, Sm and Gd; M 2 is at least one element selected from the group consisting of K, Ti, Ni, Zr, V, Mo, Ta and W, and 0 <x≦1.1、0≦y≦24、0≦z≦2、-1≦δ≦2、0<α≦0.4xである。

[0024] element M 1 is Fe(Fe 2+ ), Mn(Mn 2+ ), Zn(Zn 2+ ), Cu(Cu + , Cu 2+ ), Ag(Ag + ), Mg(Mg 2+ ), Ca(Ca 2+ ), Sr(Sr 2+ ), Ba(Ba 2+ ), Co(Co 2+ ), Eu(Eu 2+ ,EU 3+ ), Y(Y 3+ ), Bi(Bi 3+ ), La(La 3+ ), Ce(Ce 3+ , Ce 4+ ), Nd(Nd 3+ ), Sm(Sm 3+ ) and Gd(Gd 3+ ) is Nb(Nb 5+ ) and Al(Al 3+) has a larger effective ionic radius than AlNb 11 O 29 Based on Al, part of which is element M 1 By being substituted by AlNb 11 O 29 The lattice constant of the crystal is larger than that of the active material of this embodiment, and the diffusibility of the element A ions inside the crystal is increased. Therefore, the load characteristics of an electrochemical device formed using the active material of this embodiment are improved.

[0025] In addition, AlNb 11 O 29 In this case, Al has the effect of stabilizing the crystal structure, and a part of it is replaced by the element M. 1 It is thought that the substitution of SiO 2 with SiO 2 may impair the stability of the crystal structure of the oxide, which is likely to result in a greater tendency for the capacity to decrease (deterioration of charge-discharge cycle characteristics) when electrochemical elements using this oxide as an active material are repeatedly charged and discharged.

[0026] However, contrary to this expectation, as represented by the general formula (1), the element M 1 If the amount of Al substituted by AlNb is within a certain range, the capacity decrease during repeated charge and discharge in an electrochemical device configured with this oxide as the active material can be reduced by AlNb 11 O 29 The reason is that the ionic radius of Nb (Nb 5+ ) and Al(Al 3+ ) larger than element M 1 By incorporating the element A, the lattice constant of the oxide increases before the element A ions that act as carriers are inserted, and the space in which the element A ions are occluded expands, making it possible to suppress the volume change of the oxide (active material) that occurs when the element A ions are inserted and extracted during charging and discharging, and it is presumed that this makes it possible to suppress the deterioration of the electrode even when the electrochemical device is repeatedly charged and discharged.

[0027] Thus, the active material of this embodiment makes it possible to improve the load characteristics of the electrochemical device while maintaining high charge-discharge cycle characteristics.

[0028] The oxide represented by the general formula (1) contains an element M 1 The alloy may contain only one element selected from Fe, Mn, Zn, Cu, Ag, Mg, Ca, Sr, Ba, Co, Eu, Y, Bi, La, Ce, Nd, Sm, and Gd, or may contain two or more elements selected from these elements M. 1 Among these, Fe, Mn, Zn and Cu are preferred, and Zn and Cu are more preferred, since they are particularly easy to substitute for Al in terms of electron configuration and are highly effective in increasing the electron conductivity of the oxide.

[0029] The oxide represented by the general formula (1) contains the element M 1 For example, Fe 3+ / Fe 2+ and Cu 2+ / Cu + When an oxide represented by the general formula (1) contains an element having a mixed valence, such as Fe or Cu, many oxygen vacancies may occur (i.e., δ becomes greater than 0 in the general formula (1)), which further improves the electronic conductivity and ionic conductivity of the oxide represented by the general formula (1). Therefore, when the oxide represented by the general formula (1) contains Fe or Cu as the element M, further improvement in the load characteristics of the electrochemical device can be expected.

[0030] The oxide represented by the general formula (1) contains an element M which substitutes a part of Al. 1 and at least one element M selected from the group consisting of K, Ti, Ni, Zr, V, Mo, Ta and W. 2 These elements M 2 In the oxide represented by the general formula (1) having a monoclinic crystal structure, Nb is a component that does not replace a part of the Al constituting the crystal, but substitutes Nb, or is a component that is dissolved in the crystal or is contained as an impurity. The oxide represented by the general formula (1) contains the element M 2The amount z may be 0, but the element M 2 When the oxide represented by the general formula (1) contains an oxide having a content z of 2 or less, the content z does not affect the performance of the active material of this embodiment and is therefore acceptable. The oxide represented by the general formula (1) may contain water.

[0031] In the oxide represented by the general formula (1), Al is a component for enhancing the structural stability of the oxide, and the action of Al improves the reversibility of the active material during charge and discharge of the electrochemical device.

[0032] In the oxide represented by the general formula (1), as described above, a part of Al is the element M 1 The amount of Al and the element M 1 The sum of the amounts of Al and M is greater than 0. 1 In order to more effectively exert the above-mentioned functions, the content of Al and element M in the oxide is preferably 0.8 or more. 1 If the amount of Al is too large, the amount of Nb in the oxide becomes too small, and there is a risk that the effect of Nb will not be exhibited well. 1 The sum x of the amount of is 1.1 or less, and preferably 1.05 or less.

[0033] In addition, in the oxide represented by the general formula (1), the element M 1 The amount α is greater than 0, and from the viewpoint of better ensuring the effect of improving the load characteristics of the electrochemical device, it is preferable that it is 0.05 or more. However, in the oxide represented by the general formula (1), the element M 1 If the amount of element M is too large, the stability of the crystal structure decreases, and there is a risk that the charge-discharge cycle characteristics of the electrochemical device cannot be maintained at a high level. Therefore, from the viewpoint of improving the charge-discharge cycle characteristics of the electrochemical device, it is preferable that the amount of element M in the oxide represented by the general formula (1) is too large. 1 The amount α is 0.4x or less, more specifically, it is preferably 0.44 or less, and more preferably 0.4 or less.

[0034] In the oxide represented by the general formula (1), the element A is at least one of Li and Na, and is absorbed into or desorbed from the oxide by charging and discharging an electrochemical device (i.e., functions as a carrier). The oxide may or may not contain the element A. In the case of the oxide not containing the element A, for example, by charging an electrochemical device used as a negative electrode active material or by pre-doping with ions of element A before use in an electrochemical device, ions of element A are inserted, and the oxide comes to contain element A.

[0035] The amount y of the element A in the oxide represented by the general formula (1) is 0 or more and 24 or less.

[0036] In the oxide represented by the general formula (1), the amount of oxygen is originally AlNb 11 O 29 Similarly, 29, but element M 1 The value may vary depending on the presence of an element A. Specifically, in the general formula (1), δ is -1 or more and 2 or less, preferably 1.95 or less. When δ in the general formula (1) is greater than 0, oxygen deficiency occurs in the oxide. In this case, the electronic conductivity and the conductivity of element A ions of the active material containing the oxide are improved, and the use of such an active material makes it possible to further increase the energy density of the electrochemical device.

[0037] In the oxide represented by the general formula (1), δ, which relates to the amount of oxygen, is determined by the element M that forms the cation. 1 , element M 2 The amount of Nb and Al is determined by the amount of oxygen that forms the anion.

[0038] One of the more preferred embodiments of the active material of this embodiment is one in which the oxide represented by the general formula (1) satisfies the following general formula (2).

[0039] M 1 α Al1-1.5α Nb 11+0.5α O 29-δ (2)

[0040] The element M in the general formula (2) 1 is at least one of Zn and Cu, and 0<α≦0.4, 0≦δ≦0.5α. The element M in the general formula (2) 1 The amount α is preferably 0.05 or more, preferably 0.4 or less, and more preferably 0.35 or less. In addition, in the general formula (2), δ relating to the amount of oxygen is 0 or more and 0.5α or less, but as described above, 0<α≦0.4, so the value of δ is 0 or more and 0.2 or less.

[0041] The oxide represented by the general formula (1) and satisfying the general formula (2) comes to satisfy, for example, the following general formula (3) by inserting Li ions.

[0042] Li y M 1 α Al 1-1.5α Nb 11+0.5α O 29-δ (3)

[0043] In the general formula (3), the element M 1 The amount α and the amount of oxygen δ are the same as those in the general formula (2), and 0 <y≦22である。

[0044] In the active material of this embodiment, it is preferable that the oxide represented by the general formula (1) is subjected to a reduction treatment. In the oxide, Nb is usually pentavalent (Nb 5+ ), but by reduction treatment, it becomes tetravalent Nb (Nb 4+ ) will be mixed. 4+ is Nb 5+ Since the ionic radius of tetravalent Nb is larger than that of element M, the presence of tetravalent Nb in the oxide increases the lattice size of the oxide having a monoclinic crystal structure. 1Not only contains it, but also oxygen deficiency occurs due to the reduction treatment [as a result, the value of δ in the general formula (1) increases]. In the active material containing the reduced oxide, the action due to the increase in the lattice size and the action due to oxygen deficiency function synergistically, and the electron conductivity and the diffusibility of element A ions are further improved. Therefore, by using the active material containing the reduced oxide, for example, it is possible to further increase the energy density of the electrochemical element.

[0045] When the active material satisfies the following (a) or (b), it can be said that the oxide in the active material has been reduced to such an extent that the electron conductivity and the diffusibility of element A ions of the active material are further improved.

[0046] (a) The ratio Z (atomic%) of Nb in all Nb in the oxide represented by the general formula (1) contained in the active material is 3.5 ≦ Z ≦ 30. 4+ The ratio Z (atomic%) of Nb in all Nb in the oxide represented by the general formula (1) contained in the active material is 3.5 ≦ Z ≦ 30.

[0047] (b) In the active material containing the oxide, when the absorbance at a wavelength of 500 nm is A1, the absorbance at a wavelength of 600 nm is A2, and the absorbance at a wavelength of 700 nm is A3, the relationship A1 < A2 is satisfied, and the relationship A3 < A2 is satisfied.

[0048] The active material containing the oxide changes color from white to yellow to blue by being subjected to a reduction treatment. Therefore, when the above (b) is satisfied, that is, when the relationship A1 < A2 is satisfied and the relationship A3 < A2 is satisfied, it can be determined that the oxide in the active material has been reduced to such an extent that the electron conductivity and the diffusibility of element A ions of the active material are improved.

[0049] As a more specific aspect of the oxide to be subjected to the reduction treatment, for example, among those represented by the general formula (1), those in which element M 1 is at least one element selected from the group consisting of Fe, Cu, and Zn, and 0 < δ ≦ 2.

[0050] In the active material containing the oxide that has undergone the reduction treatment, the element M is present on the surface and inside. 1 The ratio of element M 1 Specifically, in the active material, the ratio of element M to Nb determined by X-ray photoelectron spectroscopy (XPS) is 1 The atomic ratio P of Nb (the ratio of the number of element M1 atoms when the number of Nb atoms is 100. The same applies to the atomic ratio Q) and the ratio of element M to Nb determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) 1 It is preferable that the atomic ratio Q of P satisfies the relationship P>Q. In this case, the effect of improving the energy density of the electrochemical device is more improved.

[0051] In the active material of this embodiment, the proportion of the oxide having a monoclinic crystal structure and represented by the general formula (1) in the total amount of the active material is preferably 20 mass % or more, more preferably 50 mass % or more, and may be 100 mass %.

[0052] The active material of this embodiment has excellent output power and is therefore less susceptible to polarization caused by Li-ion diffusion inside the active material due to the increased particle size of the active material particles. For the same reason, the primary particles of the active material may form aggregates (secondary particles). However, from the viewpoint of improving the load characteristics and charge / discharge cycle characteristics of the electrochemical device, if the primary particles of the active material are secondary particles, it is preferable that the primary particles of the active material are sintered together, and primary particles are more preferable.

[0053] <Method of manufacturing active material for electrochemical element> The method for producing the active material of this embodiment is not particularly limited. For example, Nb, Al, element M 1Niobium oxide (oxide represented by the general formula (1)) can be synthesized and produced by a solid-state reaction method in which precursors of active materials (oxides represented by the general formula (1)) such as various metal oxides are mixed and fired, or by a reaction method in which a mixture of metal compounds prepared by co-precipitating chloride salts, nitrate salts, and alkoxides of the respective metals in a liquid phase is used as a precursor.

[0054] In the solid-state reaction method, firing is preferably performed at a temperature of 800°C or higher, more preferably in the range of 900°C to 1400°C, to enhance the interdiffusion of various metal ions. The firing time is not particularly limited, but can be performed for 1 to 1000 hours. If the firing temperature exceeds 1200°C, oxygen is gradually released from the sample, resulting in the formation of crystal phases other than the monoclinic crystal phase, or the composition no longer satisfying the general formula (1). Therefore, it is more preferable to hold the sample at 1200°C or higher for 10 hours or less. The cooling rate of the sample during firing is not particularly limited as long as a monoclinic crystal phase is obtained. However, to obtain a monoclinic crystal phase that is stable at high temperatures, a cooling rate of 15°C / min to 60°C / min (including natural cooling) is preferred. Rapid cooling may be performed at a cooling rate of 1°C / sec to 1000°C / sec.

[0055] The reduction treatment can be carried out by placing the precursor in a carbon container and calcining it under a vacuum atmosphere. The calcination conditions are preferably a temperature of, for example, 800°C to 1200°C and a time of, for example, 1 to 1000 hours.

[0056] In this specification, "under a vacuum atmosphere" means that the pressure inside the firing furnace is equal to or lower than low vacuum (100 Pa to 31 kPa) in accordance with ISO 3529-1, and more preferably equal to or lower than medium vacuum (0.1 Pa to 100 Pa).

[0057] <Method for determining the composition of active material for electrochemical element> The composition of the active material of this embodiment can be analyzed, for example, by ICP-AES. If the active material of this embodiment is sintered with an oxide-based solid electrolyte, making it difficult to separate the components, and quantification using ICP-AES is difficult, the composition can also be determined by a method combining a scanning electron microscope (SEM) or a transmission electron microscope (TEM) with various elemental analysis methods such as an energy dispersive X-ray spectrometer (EDS) or a wavelength dispersive X-ray spectrometer (WDS).

[0058] The amount of oxygen vacancies δ contained in the active material of this embodiment is determined by ICP-AES analysis. 1 , element M 2 The molar amount of oxygen is determined by the sum of the molar amounts of Al and Nb using an oxygen / nitrogen analyzer (ON736 or the like) manufactured by LECO Japan LLC.

[0059] The Nb mole amount relative to the total Nb mole amount in the active material of this embodiment 4+ The molar amount Z (%) of Nb3d5 / 2 can be determined from the area ratio of the peaks assigned to Nb3d5 / 2 in the XPS spectrum.

[0060] <Method for confirming the monoclinic structure of active materials for electrochemical devices> The crystal structure of the active material of this embodiment can be determined by measuring the powder X-ray diffraction (powder XRD) pattern using a Rigaku RINT2500VPC (X-rays used: CuKα radiation) and comparing it with the Powder Diffraction File (PDF) database or by analyzing it using the Rietveld method. When comparing crystal lattice sizes between different samples, Si powder (Rigaku, a0 = 5.4308 Å at 298.1 K) is mixed as an internal reference when preparing the sample for powder XRD measurement, and the spectrum is corrected so that the peak attributable to the X-ray diffraction of the Si (111) plane is at 2θ = 28.442 degrees. The lattice constant (d 010) can be calculated by doubling the interplanar spacing determined from the peak attributable to diffraction of the (020) plane, assuming an X-ray wavelength of 1.5418 Å. When the active material of this embodiment is contained in a negative electrode as a negative electrode active material, a 1 kΩ resistor is connected and constant resistance discharge is performed for 100 hours, and then the negative electrode of an electrochemical device (battery, etc.) is removed, and the surface of the electrode opposite to the surface bonded to the current collector is processed flat so that it is parallel to the current collector, and the surface is then fixed to a sample stage for powder XRD, whereby a powder XRD pattern of the electrode can be obtained. When the active material of this embodiment is contained in a positive electrode as a positive electrode active material, the positive electrode of an electrochemical element (battery, etc.) is charged at a constant current of 10 μA under a condition of an upper limit voltage of 3 V, and then further maintained at a constant voltage of 3 V for 100 hours. Thereafter, the positive electrode is removed, and the surface of the electrode opposite to the surface joined to the current collector is processed flat so that it is parallel to the current collector, as in the case of a negative electrode, and the surface is fixed to a sample stage for powder XRD, whereby a powder XRD pattern of the electrode can be obtained.

[0061] When the active material of this embodiment is sintered with a crystalline sulfide-based solid electrolyte or an oxide-based solid electrolyte, a specimen is extracted from a sample compact containing the active material of this embodiment using focused ion beam (FIB) processing, mounted on a TEM specimen stage, and then thinned to a thickness of 100 nm or less. A selected area electron diffraction (SAD) pattern of the specimen is obtained using a TEM, and the monoclinic structure can be confirmed by analyzing the SAD pattern.

[0062] <Method for measuring absorbance of active material for electrochemical device> The absorbance of the active material of this embodiment can be obtained by dispersing 5 mg of the active material in 20 ml of water using an ultrasonic disperser, placing the suspension in a 1 cm square cuvette, and measuring the absorbance at wavelengths of 500 nm, 600 nm, and 700 nm using a near-infrared-visible spectrophotometer.

[0063] <Method for measuring P and Q in the active material for electrochemical devices> The P is the ratio of the area of ​​the peak attributed to Nb in the XPS spectrum to the area of ​​the element M 1 The Q is determined by the ratio of the area of ​​the peaks attributable to the element M to the molar amount of Nb determined by ICP-AES. 1 is the ratio of the molar amounts of

[0064] <Electrode materials for electrochemical devices> The electrode material for electrochemical devices of this embodiment (hereinafter sometimes simply referred to as "electrode material") contains the electrode active material for electrochemical devices of the above embodiment, and may contain other materials for constituting an electrode for electrochemical devices together with the active material. Such materials include conductive additives such as carbon black, binders, solid electrolytes, etc., and the electrode material may contain one or more of these together with the active material of the above embodiment, as necessary.

[0065] The electrode material may be obtained by adhering another material to the surface of the active material, or may be a mixture of the active material and another material, or may be a mixture of the active material and another material.

[0066] When the electrode material contains carbon black, examples of the carbon black include thermal black, furnace black, channel black, ketjen black, acetylene black, etc. When the electrode material contains carbon black, the content of carbon black in the electrode material can be, for example, 0.1 to 25 parts by mass per 100 parts by mass of the active material of the above embodiment.

[0067] When the electrode material contains a binder, the binder may be a fluororesin such as polyvinylidene fluoride (PVDF), etc. When the electrode material contains a binder, the content of the binder in the electrode material may be, for example, 0.1 to 25 parts by mass per 100 parts by mass of the active material of the above embodiment.

[0068] When the electrode material contains a solid electrolyte, the solid electrolyte is not particularly limited as long as it has Li-ion conductivity. For example, sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, oxide-based solid electrolytes, etc. can be used.

[0069] Examples of sulfide-based solid electrolytes include particles such as Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, Li2S-B2S3-based glasses. In recent years, thio-LISICON-type materials [Li 10 GeP2S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 etc., Li 12-12a-b+c+6d-e M 1 3+a-b-c-d M 2 b M 3 c M 4 d M 5 12-e X e (However, M 1 is Si, Ge or Sn, M 2 is P or V, M 3 is Al, Ga, Y or Sb, M 4 is Zn, Ca, or Ba, M 5 is either S or S and O, X is F, Cl, Br or I, 0≦a<3, 0≦b+c+d≦3, 0≦e≦3), or those of the argyrodite type [such as Li6PS5Cl, Li 7-f+g PS 6-x Cl x+y (However, 0.05≦f≦0.9, -3.0f+1.8≦g≦-3.0f+5.7), those represented by Li 7-h PS 6-h Cl i Br j (However, h=i+j, 0<h≦1.8, 0.1≦i / j≦10.0), etc.] can also be used.

[0070] Examples of the hydride-based solid electrolyte include, for example, LiBH4, a solid solution of LiBH4 and the following alkali metal compound (for example, those having a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1), and the like. Examples of the alkali metal compound in the solid solution include at least one selected from the group consisting of lithium halides (such as LiI, LiBr, LiF, LiCl), rubidium halides (such as RbI, RbBr, RbF, RbCl), cesium halides (such as CsI, CsBr, CsF, CsCl), lithium amide, rubidium amide, and cesium amide.

[0071] Examples of the halide-based solid electrolyte include, for example, monoclinic LiAlCl4, defective spinel-type or layered-structured LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), and the like. In addition, for example, known ones described in International Publication No. 2020 / 070958 and International Publication No. 2020 / 070955 can also be used.

[0072] Examples of the oxide-based solid electrolyte include, for example, garnet-type Li7La3Zr2O 12 , NASICON-type Li 1+O Al 1+O Ti 2-O (PO4)3, Li 1+p Al 1+p Ge 2-p (PO4)3, perovskite-type Li 3q La 2 / 3-q TiO3, and the like.

[0073] Among these solid electrolytes, sulfide-based solid electrolytes are preferred because of their high Li-ion conductivity. Sulfide-based solid electrolytes containing Li and P are more preferred. Particularly preferred are argyrodite-type sulfide-based solid electrolytes having high Li-ion conductivity and high chemical stability.

[0074] When the electrode material contains a solid electrolyte, the content of the solid electrolyte in the electrode material can be, for example, 0.1 to 500 parts by mass per 100 parts by mass of the active material of the above embodiment.

[0075] <Electrodes for electrochemical elements> The electrode for an electrochemical element of this embodiment (hereinafter sometimes simply referred to as "electrode") contains the active material of the above embodiment or the electrode material of the above embodiment, and is used as a positive electrode or a negative electrode of an electrochemical element such as a secondary battery.

[0076] Examples of the electrode of this embodiment include a molded body (such as a pellet) obtained by molding an electrode mixture containing an active material and an electrode material, and an electrode having a structure in which a layer (electrode mixture layer) made of a molded body of an electrode mixture is formed on a current collector.

[0077] When the active material of the above embodiment is used, the electrode mixture constituting the electrode contains, together with the active material, necessary materials selected from a conductive aid, a binder, a solid electrolyte, etc. Furthermore, when the electrode material of the above embodiment is used, the electrode mixture constituting the electrode can also contain, together with the electrode material, necessary materials selected from a conductive aid, a binder, a solid electrolyte, etc., but depending on the component composition of the electrode material, the electrode mixture can also be composed of the electrode material alone.

[0078] Examples of the conductive additive for the electrode mixture include carbon materials such as the various carbon blacks listed above as examples usable in electrode materials, graphite (natural graphite, artificial graphite), graphene, vapor-grown carbon fiber, carbon nanofiber, and carbon nanotubes; powders of Cu, Ni, Al, Au, and Pd, or alloys thereof, or porous bodies thereof; and these may be used alone or in combination of two or more. The content of the conductive additive in the electrode mixture (including the amount of carbon black if the electrode material used in the electrode mixture contains carbon black) is preferably 0 to 25 mass%.

[0079] The binder for the electrode mixture can be the same as the above-mentioned examples of the binder usable for the electrode material. Note that, for example, when a sulfide-based solid electrolyte is contained in the electrode mixture (including when a sulfide-based solid electrolyte is contained in the electrode material constituting the electrode mixture), if good moldability can be ensured in forming a compact of the electrode mixture without using a binder, the electrode material does not need to contain a binder.

[0080] When a binder is required in the electrode mixture, its content (including the amount of the binder if the electrode material used in the electrode mixture contains a binder) is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when the electrode mixture contains a sulfide-based solid electrolyte and therefore can be molded without a binder, its content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is contained).

[0081] The solid electrolyte for the electrode mixture can be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes listed above as examples of materials that can be used for the electrode. To improve the properties of the electrochemical element, it is desirable to contain a sulfide-based solid electrolyte, and it is more desirable to contain an argyrodite-type sulfide-based solid electrolyte.

[0082] The average particle size of the solid electrolyte is preferably 0.1 μm or more, and more preferably 0.2 μm or more, from the viewpoint of reducing grain boundary resistance, while it is preferably 10 μm or less, and more preferably 5 μm or less, from the viewpoint of forming a sufficient contact interface between the active material and the solid electrolyte.

[0083] The average particle diameter of various particles (solid electrolyte, positive electrode active material, etc.) referred to in this specification means the 50% diameter value (D50) in the volume-based integrated fraction when the integrated volume is determined from particles with small particle sizes using a particle size distribution measuring device (such as a Microtrac particle size distribution measuring device "HRA9320" manufactured by Nikkiso Co., Ltd.).

[0084] When a solid electrolyte is contained in the electrode mixture, its content (including the amount of the solid electrolyte when the electrode material used in the electrode mixture contains a solid electrolyte) is preferably 4 to 80 mass %.

[0085] The content of the active material in the electrode mixture (the amount of the active material used in the electrode mixture or the active material derived from the electrode material) is preferably 20 to 95 mass %.

[0086] When an electrode has a current collector, the following can be used for the current collector. When the electrode serves as the positive electrode of an electrochemical element, the current collector can be made of metal such as aluminum, nickel, or stainless steel foil, punched metal, mesh, expanded metal, foamed metal, or carbon sheet. When the electrode serves as the negative electrode of an electrochemical element, the current collector can be made of copper, nickel, or aluminum foil, punched metal, mesh, expanded metal, foamed metal, or carbon sheet.

[0087] The electrode mixture compact can be formed, for example, by compressing an electrode mixture prepared by mixing the active material of the above embodiment or the electrode material of the above embodiment with a conductive additive, a binder, a solid electrolyte, and the like, which are added as needed, by pressure molding or the like.

[0088] In the case of an electrode having a current collector, it can be produced by bonding a molded body of the electrode mixture formed by the above-mentioned method to the current collector by, for example, pressing.

[0089] Alternatively, the electrode mixture may be mixed with a solvent to prepare an electrode mixture-containing composition, which may then be applied to a substrate such as a current collector or a solid electrolyte layer (in the case of forming an all-solid-state battery) that faces an electrode, dried, and then pressed to form a molded body of the electrode mixture.

[0090] The solvent for the electrode mixture-containing composition can be water or an organic solvent such as N-methyl-2-pyrrolidone (NMP). When a solid electrolyte is also included in the electrode mixture-containing composition, it is preferable to select a solvent that is less likely to deteriorate the solid electrolyte. In particular, sulfide-based and hydride-based solid electrolytes undergo chemical reactions with trace amounts of water, so nonpolar aprotic solvents such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene are preferred. Ultra-dehydrated solvents with a water content of 0.001% by mass (10 ppm) or less are particularly preferred. Fluorine-based solvents such as "Vertrel®" from DuPont-Mitsui Fluorochemicals, "Zeorolla®" from Zeon Corporation, and "Novec®" from Sumitomo 3M Company, as well as nonaqueous organic solvents such as dichloromethane and diethyl ether can also be used.

[0091] The thickness of the electrode mixture compact (in the case of an electrode having a current collector, the thickness of the electrode mixture compact per side of the current collector; the same applies below) is usually 50 μm or more, but from the viewpoint of increasing the capacity of the electrochemical element, it is preferably 200 μm or more. Note that the load characteristics of an electrochemical element are generally improved by making the positive electrode or negative electrode thinner, but with the electrode of this embodiment, it is possible to improve the load characteristics even when the electrode mixture compact is as thick as 200 μm or more. Therefore, in this embodiment, the effect is more pronounced when the thickness of the electrode mixture compact is, for example, 200 μm or more. Furthermore, the thickness of the electrode mixture compact is usually 3000 μm or less.

[0092] In the case of an electrode for an electrochemical element produced by forming an electrode mixture layer on a current collector using an electrode mixture-containing composition containing a solvent, the thickness of the electrode mixture layer is preferably 50 to 1000 μm.

[0093] <Electrochemical element> The electrochemical element of the present embodiment has a positive electrode and a negative electrode, and it is sufficient that either the positive electrode or the negative electrode is the electrode for the electrochemical element of the above embodiment. There are no particular restrictions on the other configurations and structures, and various configurations and structures employed in electrochemical elements such as conventionally known secondary batteries can be applied.

[0094] The electrochemical element of this embodiment includes electrochemical elements such as secondary batteries having a separator and an electrolytic solution interposed between a positive electrode and a negative electrode, and all-solid-state secondary batteries having a solid electrolyte layer between a positive electrode and a negative electrode; and supercapacitors. However, the following will describe in detail a secondary battery, which is a representative embodiment of the electrochemical element of this embodiment.

[0095] A cross-sectional view schematically illustrating a secondary battery, which is an example of the electrochemical element of this embodiment, is shown in Fig. 1. The secondary battery 1 shown in Fig. 1 has a positive electrode 10, a negative electrode 20, a separator (a solid electrolyte layer if the secondary battery is an all-solid-state secondary battery) 30 interposed between the positive electrode 10 and the negative electrode 20, and an electrolyte solution (if the secondary battery is a secondary battery containing an electrolyte solution) sealed within an exterior body formed of an exterior can 40, a sealing can 50, and a resin gasket 60 interposed between them.

[0096] The sealing can 50 is fitted into the opening of the outer can 40 via a gasket 60, and the open end of the outer can 40 is tightened inward, causing the gasket 60 to abut against the sealing can 50, thereby sealing the opening of the outer can 40 and creating an airtight structure inside the battery.

[0097] The outer can and sealing can can be made of stainless steel or other materials. Materials such as polypropylene and nylon can be used for the gasket. If heat resistance is required for the battery's intended use, heat-resistant resins with melting points exceeding 240°C, such as fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. If the battery is intended for use in applications requiring heat resistance, a glass hermetic seal can also be used for the sealing.

[0098] 2 and 3 are diagrams schematically showing another example of a secondary battery, which is an example of the electrochemical device of this embodiment. Fig. 2 is a plan view of the secondary battery, and Fig. 3 is a cross-sectional view taken along line II in Fig. 2.

[0099] The secondary battery 100 shown in Figures 2 and 3 houses an electrode body 200 inside a laminate film casing 500 made of two metal laminate films, and the laminate film casing 500 is sealed at its outer periphery by heat-sealing the upper and lower metal laminate films.

[0100] When the secondary battery 100 is an all-solid-state secondary battery, the electrode body 200 is configured by laminating a positive electrode, a negative electrode, and a solid electrolyte layer interposed therebetween. On the other hand, when the secondary battery 100 is a secondary battery other than an all-solid-state secondary battery, the electrode body 200 is configured by laminating a positive electrode, a negative electrode, and a separator interposed therebetween, and an electrolyte (such as an electrolytic solution) is enclosed together with the electrode body 200 in the laminate film exterior body 500. At least one of the positive electrode and the negative electrode of the electrode body 200 is the electrode of the above embodiment.

[0101] In Figure 3, in order to avoid cluttering the drawing, the layers that make up the laminate film exterior body 500 and the components (positive electrode, negative electrode, etc.) that make up the electrode body 200 are not shown separately.

[0102] The positive electrode of the electrode body 200 is connected to a positive electrode external terminal 300 inside the battery 100, and although not shown, the negative electrode of the electrode body 200 is also connected to a negative electrode external terminal 400 inside the battery 100. One end of the positive electrode external terminal 300 and the negative electrode external terminal 400 is drawn out to the outside of the laminate film exterior body 500 so that they can be connected to external devices, etc.

[0103] When the secondary battery is an all-solid-state secondary battery, the electrode mixture of the above-described embodiment contains a solid electrolyte. On the other hand, when the secondary battery is a non-aqueous electrolyte secondary battery, the electrode mixture of the above-described embodiment does not need to contain a solid electrolyte.

[0104] Furthermore, when a non-aqueous electrolyte secondary battery is manufactured using an electrode containing the active material of the above embodiment as a positive electrode and a negative electrode that does not contain Li (Li ions) involved in the charge and discharge of the battery, it is necessary to introduce Li (Li ions) involved in the charge and discharge of the battery into the active material of the electrode of the above embodiment. In this case, for example, the active material of the above embodiment can be doped with Li ions in advance by a standard method (ex-situ pre-doping). Alternatively, if the non-aqueous electrolyte secondary battery has a non-aqueous electrolyte, a Li source (metallic Li foil, Li alloy foil, etc.) can be placed in a location that can contact the non-aqueous electrolyte inside the battery, and the active material of the electrode of the above embodiment can be doped with Li ions inside the battery (in-situ pre-doping). In the case of the in-situ pre-doping, for example, a pre-doping electrode can be used in which a Li source is attached to the surface of a current collector and electrically connected to the negative electrode.

[0105] <Negative electrode for secondary battery using the electrode of the above embodiment as the positive electrode> When the positive electrode of the nonaqueous electrolyte secondary battery is the electrode of the above embodiment, the negative electrode may be, for example, one consisting of only a molded body of a negative electrode mixture containing a negative electrode active material and a conductive additive, or one having a structure in which a layer (negative electrode mixture layer) consisting of a molded body of a negative electrode mixture is formed on a current collector.

[0106] The negative electrode active material may be one or a mixture of two or more carbonaceous materials capable of absorbing and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesophase carbon microbeads (MCMB), and carbon fiber. Other examples of the negative electrode active material include elements such as Al, Si, Sn, Ge, Bi, Sb, In, Zn, and P, as well as their alloys; lithium-containing nitrides and lithium-containing sulfides that can be charged and discharged at low voltages similar to those of lithium metal; and lithium metal.

[0107] The content of the negative electrode active material in the negative electrode mixture is preferably 15 to 100 mass %.

[0108] The conductive additive for the negative electrode can be the same as those exemplified above as those usable for the electrode of the above embodiment. The content of the conductive additive in the negative electrode mixture is preferably 0.1 to 15 mass %.

[0109] When the nonaqueous electrolyte secondary battery using the electrode of the above embodiment as the positive electrode is an all-solid-state secondary battery and the negative electrode active material is in particulate form, the negative electrode mixture can contain a solid electrolyte.

[0110] The solid electrolyte of the negative electrode can be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes exemplified above as usable for the electrode material of the above embodiment. To improve the battery characteristics, it is desirable to contain a sulfide-based solid electrolyte, and it is more desirable to contain an argyrodite-type sulfide-based solid electrolyte.

[0111] The content of the solid electrolyte in the negative electrode mixture is preferably 4 to 90 mass %.

[0112] The negative electrode mixture may contain a binder, or may not contain a binder if good formability can be ensured without using a binder, such as in the case of a negative electrode that also contains a sulfide-based solid electrolyte. The binder may be the same as the binder exemplified above as one that can be used in the electrode of the above embodiment.

[0113] When a binder is required in the negative electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when a binder is not required in the negative electrode mixture from the viewpoint of formability, the content thereof is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is contained).

[0114] When a current collector is used for the negative electrode, the same current collectors as those exemplified above as those usable when the electrode of the above embodiment is a negative electrode can be used as the current collector.

[0115] The compact of the negative electrode mixture can be formed, for example, by compressing a negative electrode mixture prepared by mixing a negative electrode active material with a conductive additive, a binder, a solid electrolyte, etc., which are added as needed, by pressure molding, etc. A negative electrode constituted only by a compact of the negative electrode mixture can be produced by the above-mentioned method.

[0116] In the case of a negative electrode having a current collector, it can be produced by bonding a molded body of the negative electrode mixture formed by the above-mentioned method to the current collector by, for example, pressing.

[0117] Furthermore, in the case of a negative electrode having a current collector, the negative electrode can also be produced by a method in which a negative electrode mixture-containing composition (paste, slurry, etc.) prepared by dispersing the above-mentioned negative electrode mixture in a solvent is applied to a current collector, dried, and then pressure-molded by calendering or the like as necessary to form a molded body of the negative electrode mixture (negative electrode mixture layer) on the surface of the current collector.

[0118] The solvent for the negative electrode mixture-containing composition can be water or an organic solvent such as NMP. When the negative electrode mixture-containing composition also contains a solid electrolyte, it is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte, and it is preferable to use the same solvents as those exemplified above as solvents for the electrode mixture-containing composition containing a solid electrolyte.

[0119] The thickness of the negative electrode mixture compact (in the case of a negative electrode having a current collector, the thickness of the positive electrode mixture compact per one side of the current collector; the same applies hereinafter) is usually 50 μm or more, but from the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. In addition, the thickness of the negative electrode mixture compact is usually 2000 μm or less.

[0120] In the case of a negative electrode produced by forming a negative electrode mixture layer on a current collector using a negative electrode mixture-containing composition containing a solvent, the thickness of the negative electrode mixture layer is preferably 50 to 1000 μm.

[0121] <Positive electrode for secondary battery using the electrode of the above embodiment as the negative electrode> When the negative electrode of the secondary battery is the electrode of the above embodiment, the positive electrode may be, for example, one consisting of only a molded body of a positive electrode mixture containing a positive electrode active material and a conductive additive, or one having a structure in which a layer (positive electrode mixture layer) consisting of a molded body of a positive electrode mixture is formed on a current collector.

[0122] The positive electrode active material is not particularly limited as long as it is a positive electrode active material used in conventional secondary batteries, that is, an active material capable of absorbing and releasing Li ions. Specific examples of the positive electrode active material include LiM r Mn 2-rSpinel-type lithium manganese composite oxide represented by O4 (where M is at least one element selected from the group consisting of Li, Na, K, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Zr, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, In, Nb, Ta, Mo, W, Y, Ru and Rh, and 0 ≦ r ≦ 1), Li r Mn (1-s-r) Ni s M t O (2-u) F v (where M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr and W, 0.8 ≦ r ≦ 1.2, 0 < s < 0.5, 0 ≦ t ≦ 0.5, u + v < 1, -0.1 ≦ u ≦ 0.2, 0 ≦ v ≦ 0.1) Layered compound, LiCo 1-r M r O2 (where M is at least one element selected from the group consisting of Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, and 0 ≦ r ≦ 0.5) Lithium cobalt composite oxide, LiNi 1-r M r O2 (where M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, and 0 ≦ r ≦ 0.5) Lithium nickel composite oxide, Li 1+s M 1-r N r PO4F s (where M is at least one element selected from the group consisting of Fe, Mn and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V and Ba, and 0 ≦ r ≦ 0.5, 0 ≦ s ≦ 1) Olivine-type composite oxide, Li2M 1-r N rExamples include pyrophosphate compounds represented by P2O7 (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0≦r≦0.5), and any one of these may be used alone or two or more may be used in combination.

[0123] When the secondary battery is an all-solid-state secondary battery, the average particle size of the positive electrode active material is preferably 1 μm or more, more preferably 2 μm or more, and preferably 10 μm or less, more preferably 8 μm or less. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. When a positive electrode active material having an average particle size within the above range is used, a large interface with the solid electrolyte contained in the positive electrode can be secured, thereby further improving the load characteristics of the battery.

[0124] When the secondary battery is an all-solid-state secondary battery, the positive electrode active material preferably has a reaction suppression layer on its surface to suppress reaction with the solid electrolyte contained in the positive electrode.

[0125] If the positive electrode active material and the solid electrolyte come into direct contact within the positive electrode mixture compact, the solid electrolyte may oxidize to form a resistance layer, resulting in a decrease in ionic conductivity within the compact. By providing a reaction suppression layer on the surface of the positive electrode active material that suppresses reaction with the solid electrolyte and preventing direct contact between the positive electrode active material and the solid electrolyte, it is possible to suppress a decrease in ionic conductivity within the compact due to oxidation of the solid electrolyte.

[0126] The reaction suppression layer may be made of any material that has ion conductivity and can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can form the reaction suppression layer include oxides containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti, and Zr, more specifically, Nb-containing oxides such as LiNbO3, Li3PO4, Li3BO3, Li4SiO4, Li4GeO4, LiTiO3, LiZrO3, and Li2WO4. The reaction suppression layer may contain only one of these oxides, or may contain two or more of them, or may even form a composite compound of two or more of these oxides. Among these oxides, Nb-containing oxides are preferred, and LiNbO3 is more preferred.

[0127] The reaction suppression layer is preferably present on the surface in an amount of 0.1 to 1.0 part by mass per 100 parts by mass of the positive electrode active material, which allows for effective suppression of the reaction between the positive electrode active material and the solid electrolyte.

[0128] Examples of methods for forming a reaction suppression layer on the surface of a positive electrode active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0129] The content of the positive electrode active material in the positive electrode mixture is preferably 20 to 95 mass %.

[0130] The conductive additive for the positive electrode may be the same as those exemplified above as those usable in the electrode of the above embodiment. The content of the conductive additive in the positive electrode mixture is preferably 0.1 to 15 mass %.

[0131] When the secondary battery is an all-solid-state secondary battery, the positive electrode mixture contains a solid electrolyte.

[0132] The positive electrode solid electrolyte may be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes listed above as examples of materials that can be used in the electrode materials of the above-described embodiments. To improve battery characteristics, it is desirable to include a sulfide-based solid electrolyte, and it is more desirable to include an argyrodite-type sulfide-based solid electrolyte.

[0133] The content of the solid electrolyte in the positive electrode mixture is preferably 4 to 80 mass %.

[0134] The positive electrode mixture may contain a binder, or may not contain a binder if good moldability can be ensured without using a binder, such as in the case of a positive electrode that also contains a sulfide-based solid electrolyte. The binder may be the same as the binder exemplified above as one that can be used in the electrode of the above embodiment.

[0135] When a binder is required in the positive electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when a binder is not required in the positive electrode mixture from the viewpoint of formability, the content thereof is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is contained).

[0136] When a current collector is used for the positive electrode, the same current collectors as those exemplified above as those usable when the electrode of the above embodiment is a positive electrode can be used as the current collector.

[0137] The compact of the positive electrode mixture can be formed, for example, by compressing a positive electrode mixture prepared by mixing a positive electrode active material, a conductive additive, and optionally a binder, a solid electrolyte, etc., by pressure molding, etc. A positive electrode composed only of a compact of the positive electrode mixture can be produced by the above-mentioned method.

[0138] In the case of a positive electrode having a current collector, it can be produced by bonding the green body of the positive electrode mixture formed by the above-mentioned method to the current collector by, for example, pressing.

[0139] Furthermore, in the case of a positive electrode having a current collector, the positive electrode can also be produced by a method in which a positive electrode mixture-containing composition (paste, slurry, etc.) prepared by dispersing the above-mentioned positive electrode mixture in a solvent is applied to a current collector, dried, and then pressure-molded by calendering or the like as necessary to form a molded body of the positive electrode mixture (positive electrode mixture layer) on the surface of the current collector.

[0140] The solvent for the positive electrode mixture-containing composition can be an organic solvent such as NMP. When the positive electrode mixture-containing composition also contains a solid electrolyte, it is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte, and it is preferable to use the same solvents as those exemplified above for the electrode mixture-containing composition containing the solid electrolyte.

[0141] The thickness of the positive electrode mixture compact (in the case of a positive electrode having a current collector, the thickness of the positive electrode mixture compact per one side of the current collector; the same applies hereinafter) is usually 50 μm or more, but from the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. In addition, the thickness of the positive electrode mixture compact is usually 2000 μm or less.

[0142] In the case of a positive electrode produced by forming a positive electrode mixture layer on a current collector using a positive electrode mixture-containing composition containing a solvent, the thickness of the positive electrode mixture layer is preferably 50 to 1000 μm.

[0143] (solid electrolyte layer) When the secondary battery is an all-solid-state secondary battery, the solid electrolyte in the solid electrolyte layer interposed between the positive electrode and the negative electrode can be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes previously exemplified as usable electrode materials in the above-described embodiment. However, to improve battery characteristics, it is preferable to contain a sulfide-based solid electrolyte, and it is more preferable to contain an argyrodite-type sulfide-based solid electrolyte. It is even more preferable to contain a sulfide-based solid electrolyte in all of the positive electrode, negative electrode, and solid electrolyte layer, and it is even more preferable to contain an argyrodite-type sulfide-based solid electrolyte.

[0144] The solid electrolyte layer may have a porous body such as a resin nonwoven fabric as a support.

[0145] The solid electrolyte layer can be formed by a method of compressing the solid electrolyte by pressure molding or the like; or a method of applying a solid electrolyte layer-forming composition prepared by dispersing the solid electrolyte in a solvent onto a substrate, a positive electrode, or a negative electrode, drying the composition, and, if necessary, performing pressure molding such as pressing.

[0146] It is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte as the solvent used in the solid electrolyte layer-forming composition, and it is preferable to use the same solvents as those exemplified above as the solvents for the electrode mixture-containing composition containing the solid electrolyte.

[0147] The thickness of the solid electrolyte layer is preferably 10 to 500 μm.

[0148] (separator) When the secondary battery is a battery other than an all-solid-state secondary battery, the separator interposed between the positive electrode and the negative electrode should have sufficient strength and be able to retain a large amount of non-aqueous electrolyte. From this perspective, a microporous film or nonwoven fabric containing polyethylene, polypropylene, or an ethylene-propylene copolymer, having a thickness of 10 to 50 μm and an opening ratio of 30 to 70%, is preferred.

[0149] (non-aqueous electrolyte) When the secondary battery is a battery other than an all-solid-state secondary battery, a non-aqueous liquid electrolyte (hereinafter referred to as a "nonaqueous electrolyte") is usually used as the electrolyte. The non-aqueous electrolyte is prepared by dissolving an electrolyte salt such as a lithium salt in an organic solvent. The organic solvent is not particularly limited, but examples thereof include chain esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate; cyclic esters with high dielectric constants such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; and mixed solvents of chain esters and cyclic esters. Mixed solvents of chain esters as the main solvent and cyclic esters are particularly suitable.

[0150] Examples of electrolyte salts that can be dissolved in an organic solvent to prepare a non-aqueous electrolyte include LiPF6, LiBF4, LiAsF6, LiSbF6, LiCF3SO3, LiC4F9SO3, LiCF3CO2, Li2C2F4(SO3)2, and LiC n F 2n+1 SO3 (n≧2), LiN(RfSO2)(Rf'SO2), LiC(RfSO2)3, LiN(RfOSO2)2 (where Rf and Rf' are fluoroalkyl groups), etc. may be used alone or in combination. The concentration of the electrolyte salt in the nonaqueous electrolyte is not particularly limited, but is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and is preferably 1.7 mol / L or less, more preferably 1.5 mol / L or less.

[0151] In the secondary battery, in addition to the non-aqueous electrolyte solution, a gel electrolyte obtained by gelling the non-aqueous electrolyte solution with a gelling agent made of a polymer or the like can also be used as the non-aqueous electrolyte.

[0152] (aqueous electrolyte) When the negative electrode of the secondary battery is the electrode of the above embodiment, an aqueous electrolyte can also be used. Examples of the aqueous electrolyte include a composition in which 1 mol of an alkali metal salt containing an organic anion having a fluoroalkyl group as a component is mixed with more than 4 mol to 15 mol of water.

[0153] (electrode body) The positive electrode and the negative electrode can be used in a battery in the form of a laminated electrode body in which the positive electrode and the negative electrode are laminated with a solid electrolyte layer or a separator interposed therebetween, or in the form of a wound electrode body in which this laminated electrode body is wound.

[0154] When forming an electrode body having a solid electrolyte layer, it is preferable to pressure-mold the positive electrode, negative electrode, and solid electrolyte layer in a stacked state, from the viewpoint of increasing the mechanical strength of the electrode body.

[0155] (Battery type) The secondary battery may have a configuration such as that shown in FIG. 1, which has an exterior body composed of an exterior can, a sealing can, and a gasket, i.e., a configuration generally referred to as a coin-type battery or a button-type battery, or a configuration such as that shown in FIGS. 2 and 3, which has an exterior body composed of a resin film or a metal-resin laminate film, or may have an exterior body made of metal and having a bottomed, tubular (cylindrical or rectangular) exterior can and a sealing structure that seals the opening. [Example]

[0156] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0157] Example 1 <Synthesis of active materials> Active materials were synthesized using a solid-state reaction method using various metal oxide powders (all obtained from Kojundo Chemical Co., Ltd.). Nb2O5 (purity: >99.9%), α-Al2O3 (purity: >99.99%), and ZnO (purity: >99.99%) were weighed and mixed in amounts of 14.507 g, 427.6 mg, and 80.3 mg, respectively. The mixture of starting materials was added to a 500 ml zirconia container along with 15 g of ethanol and 120 g of 5 mm diameter YSZ balls. The mixture was mixed in a planetary ball mill (Fritsch "Planetarymill Pulverisette 5") at 250 rpm for 3 hours. The zirconia balls were separated from the mixed sample, and the resulting slurry was dried to obtain the active material precursor powder. The precursor powder was transferred to an alumina crucible and heated to 1150°C at a rate of 16°C / min in an air atmosphere, then held there for 8 hours and naturally cooled to room temperature. The resulting powder was crushed in a mortar for 5 minutes and passed through a 150 μm mesh sieve to obtain a crude active material. 4 g of the crude active material was added to a zirconia container with an internal volume of 12.5 ml along with 4 g of ethanol and 30 g of 5 mm diameter YSZ balls, and crushed for 3 hours at 250 rpm in the planetary ball mill. The resulting slurry was vacuum dried overnight at 60°C to obtain Zn. 0.1 Al 0.85 Nb 11.05 O 29 The obtained Zn 0.1 Al 0.85 Nb 11.05 O 29 The powder XRD pattern of the active material was measured, and it was confirmed that the active material had a monoclinic crystal structure.

[0158] <Formation of solid electrolyte layer> A sulfide-based solid electrolyte (Li 5.4 PS 4.2 Cl 0.8 Br 0.8 ): 80 mg was added and the pressure was increased to 1000 kgf / cm using a press. 2 The solid electrolyte layer was formed by molding under a pressure of 1000 kJ / cm.

[0159] <Preparation of positive electrode> Synthesized Zn 0.1 Al 0.85 Nb 11.05 O 29 The positive electrode mixture was prepared by mixing the active material (A), the same sulfide solid electrolyte as that used in the solid electrolyte layer, and graphene (a conductive additive) in a mass ratio of 60:33:7 and thoroughly kneading the mixture. Next, 15 mg of the positive electrode mixture was placed on top of the solid electrolyte layer in the reinforced resin cylinder, and the mixture was pressed at 4000 kgf / cm using a press. 2 The positive electrode was formed from the positive electrode mixture compact on the solid electrolyte layer, thereby producing a laminate in which the positive electrode and the solid electrolyte layer were laminated.

[0160] <Assembly of sheet-type all-solid-state secondary batteries> A 10 mm diameter, 100 μm thick lithium metal plate and a 10 mm diameter, 100 μm thick indium metal plate, both fabricated by rolling, were placed on the solid electrolyte layer side of the laminated body as the negative electrode. Then, 10 mm diameter, 1 mm thick SUS discs were placed and fixed on the positive and negative electrode sides, respectively, to form a laminated electrode assembly. Using the laminated electrode assembly, a sheet-type all-solid-state battery similar to that shown in Figure 2 was fabricated. A positive electrode current collector foil (SUS foil) and a negative electrode current collector foil (SUS foil) were attached side by side with a certain gap between them to the inner surface of the aluminum laminate film that constitutes the laminated film exterior. Each current collector foil was cut to a shape with a main portion facing the positive or negative electrode surface of the laminated electrode assembly and a portion that protrudes from the main portion toward the outside of the battery to become the positive electrode external terminal 300 and the negative electrode external terminal 400.

[0161] The laminated electrode body was placed on the negative electrode current collector foil of the laminated film casing, and the laminated electrode body was wrapped in the laminated film casing so that the positive electrode current collector foil was positioned on the positive electrode of the laminated electrode body. The remaining three sides of the laminated film casing were sealed by heat fusion under vacuum to obtain a sheet-shaped all-solid-state secondary battery.

[0162] Example 2 The active material is monoclinic Zn 0.2 Al 0.7 Nb 11.1 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0163] Example 3 The active material is monoclinic Zn 0.3 Al 0.55 Nb 11.15 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0164] Example 4 The active material is monoclinic Cu 0.1 Al 0.85 Nb 11.05 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0165] Example 5 The active material is monoclinic Cu 0.2 Al 0.7 Nb 11.1 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0166] Example 6 The active material is monoclinic Cu 0.3 Al 0.55 Nb 11.15 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0167] Comparative Example 1 The active material is monoclinic AlNb 11 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0168] Comparative Example 2 The active material is monoclinic Zn 0.67 Nb 11.33 O 29 (Zn2Nb 34 O 87 ), a sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0169] Comparative Example 3 The active material is monoclinic Zn 0.566 Al 0.1 Nb 11.31 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0170] Comparative Example 4 The active material is monoclinic Ti2Nb 10 O 29 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for the above change. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0171] Comparative Example 5 Except for changing the active material to monoclinic TiNbO, a sheet-shaped all-solid-state secondary battery was fabricated in the same manner as in Example 1. It was confirmed in the same manner as in Example 1 that the active material used in the positive electrode was a monoclinic crystal.

[0172] The sheet-shaped all-solid-state secondary batteries of the Examples and Comparative Examples were evaluated as follows.

[0173] [Load characteristic evaluation] For each sheet-shaped all-solid-state secondary battery of the Examples and Comparative Examples, 1000 kg / cm 2 The batteries were pressurized and restrained at a pressure of 0.05 C, and discharged at a constant current until the voltage reached 0.38 V. Subsequently, constant voltage discharge was performed until the current reached 0.01 C, and then constant current charging was performed at a current of 0.05 C until the voltage reached 1.88 V, and the charge capacity (initial capacity) was measured. Next, for each battery, constant current discharge and constant voltage discharge and constant current charging were performed under the same conditions as for measuring the initial capacity, and constant current discharge and constant voltage discharge were performed again under the same conditions as for measuring the initial capacity, and constant current charging was performed at a current of 0.24 C until the voltage reached 1.88 V, and the charge capacity (0.24 C charge capacity) was measured. The 0.24 C charge capacity was then divided by the initial capacity to determine the capacity retention rate for each battery, and the load characteristics were evaluated based on this.

[0174] [Charge / discharge cycle characteristics] For each of the sheet-shaped all-solid-state secondary batteries in the Examples and Comparative Examples, two cycles of charge and discharge were performed under the same conditions as in the load characteristic evaluation, after which the 0.24C charge capacity was measured, the open-circuit voltage was measured for one hour, and then constant-current charging was performed at a current value of 0.1C until the voltage reached 1.88V. The open-circuit voltage was measured again for one hour, and then step charging was performed under constant-current conditions at a current value of 0.05C until the voltage reached 1.88V. The sum of all the constant-current step charge capacities at 0.24C, 0.1C, and 0.05C (0.05C charge capacity) was then calculated. The 0.05C charge capacity was then divided by the initial capacity to calculate the capacity retention rate, which was expressed as a percentage, and the charge-discharge cycle characteristics were evaluated based on this.

[0175] The evaluation results are shown in Table 1 together with the composition and physical properties of the active material. In Table 1, "α" in the active material column means the value of α in the general formula (1), and "d 010 " means the value of the interplanar spacing of the (010) plane determined by X-ray diffraction (the same applies to Table 3 below).

[0176] [Table 1]

[0177] As shown in Table 1, the sheet-shaped all-solid-state secondary batteries of Examples 1 to 6, each having a positive electrode containing an oxide represented by the general formula (1) as an active material, had a high capacity retention rate during the load characteristic evaluation and a high capacity retention rate during the charge-discharge cycle characteristic evaluation, and had excellent load characteristics and charge-discharge cycle characteristics.

[0178] In contrast, element M 1 The battery of Comparative Example 1 uses a positive electrode having an oxide not containing Al as an active material, the batteries of Comparative Examples 2, 4, and 5 use a positive electrode having an oxide not containing Al as an active material, and the battery of Comparative Examples 1, 2, 3, and 4 uses a positive electrode having an oxide not containing Al as an active material. 1 The battery of Comparative Example 3, which used a positive electrode having an oxide with an inappropriate amount as an active material, had a lower capacity retention rate during the load characteristic evaluation and a lower capacity retention rate during the charge-discharge cycle characteristic evaluation than the batteries of the Examples, and was therefore inferior in load characteristic and charge-discharge cycle characteristic.

[0179] Example 7 <Preparation of positive electrode material> 0.86 g of lithium and 38.7 g of pentaethoxyniobium were mixed in 394 g of dehydrated ethanol to prepare a coating solution for forming a reaction suppression layer. Next, 1000 g of the positive electrode active material (LiNi 0.5 Mn 1.5 The coating solution for forming a reaction suppression layer was applied to the surface of the cathode active material (LiNbO4) at a rate of 2 g per minute. The resulting powder was heat-treated at 350°C to obtain a cathode material with a reaction suppression layer formed on the surface, the reaction suppression layer being composed of 2 parts by mass of LiNbO3 per 100 parts by mass of the cathode active material.

[0180] The positive electrode material, vapor-grown carbon fiber (conductive additive), and Li 5.8 PS 4.6 Cl 1.6 A positive electrode mixture was prepared by mixing the positive electrode material, conductive additive, and sulfide-based solid electrolyte in a mass ratio of 67:4:29. 102 mg of this positive electrode mixture was placed in a powder molding die with a diameter of 7.5 mm, and a pressure of 1000 kgf / cm was applied using a press. 2The mixture was molded under a pressure of 1000 kJ / cm 2 to prepare a positive electrode mixture compact having a cylindrical shape.

[0181] <Formation of solid electrolyte layer> On top of the solid electrolyte layer in the powder molding die, 17 mg of the same sulfide-based solid electrolyte as used for the positive electrode was placed, and the mixture was pressed at 1000 kgf / cm using a press. 2 The positive electrode mixture compact was molded under a pressure of 1000 kJ / cm 2 , thereby forming a solid electrolyte layer on the positive electrode mixture compact.

[0182] <Preparation of negative electrode> Monoclinic Zn 0.1 Al 0.85 Nb 11.05 O 29 (negative electrode active material) and sulfide-based solid electrolyte (Li 5.4 PS 4.2 Cl 0.8 Br 0.8 ) and graphene (conductive additive) were mixed in a mass ratio of 60:33:7 and thoroughly kneaded to prepare a negative electrode mixture. Next, 67 mg of the negative electrode mixture was placed on top of the solid electrolyte layer in the powder molding die, and a pressure of 10,000 kgf / cm was applied using a press. 2 The mixture was molded under a pressure of 1000 MPa, and a negative electrode made of the negative electrode mixture molded body was formed on the solid electrolyte layer, thereby producing a laminated electrode body in which the positive electrode, the solid electrolyte layer, and the negative electrode were laminated.

[0183] <Assembly of all-solid-state batteries> Flexible graphite sheet "PERMA-FOIL" (product name) manufactured by Toyo Tanso Co., Ltd. (thickness: 0.1 mm, apparent density: 1.1 g / cm 3Two sheets of graphite sheet 10 were punched out to the same size as the laminated electrode body, and one of them was placed on the inner bottom surface of a stainless steel sealed can into which a polypropylene annular gasket had been fitted. Next, the laminated electrode body was placed on top of the graphite sheet with the negative electrode facing the graphite sheet side, and another graphite sheet was placed on top of that. A stainless steel outer can was then placed over the laminated electrode body, and the open end of the outer can was crimped inward to seal, thereby producing a flat all-solid-state secondary battery with a diameter of approximately 9 mm, in which the graphite sheets were placed between the inner bottom surface of the sealed can and the laminated electrode body, and between the inner bottom surface of the outer can and the laminated electrode body.

[0184] Example 8 The negative electrode active material is monoclinic Cu 0.1 Al 0.85 Nb 11.05 O 29 A flat all-solid-state secondary battery was produced in the same manner as in Example 7, except for changing the above.

[0185] Comparative Example 6 The negative electrode active material is monoclinic AlNb 11 O 29 A flat all-solid-state secondary battery was produced in the same manner as in Example 7, except for changing the above.

[0186] The flat all-solid-state secondary batteries of Examples 7 and 8 and Comparative Example 6 were evaluated as follows.

[0187] [Load characteristics] The all-solid-state batteries of Examples 7, 8, and Comparative Example 6 were subjected to constant current charging at a current value of 0.07 C until the voltage reached 3.8 V, followed by constant voltage charging at a current value of 0.005 C, and then constant current discharging at a current value of 0.07 C until the voltage reached 1.5 V, to determine the initial capacity. Constant current charging and constant voltage charging were performed again, followed by constant current step discharging, and the discharge capacity at each current value (constant current step discharge capacity) was measured. The constant current step discharging was performed by constant current discharging at a current value of 0.6 C until the voltage reached 1.5 V, then constant current discharging at a current value of 0.3 C until the voltage reached 1.5 V, and then constant current discharging at a current value of 0.1 C until the voltage reached 1.5 V. Then, the sum of all the constant current step discharge capacities from 0.6 C to 0.1 C (0.1 C discharge capacity) was calculated, and the 0.6 C discharge capacity (the same as the step discharge capacity when discharging at 0.6 C during constant current step discharge) was divided by the 0.1 C discharge capacity to evaluate the load characteristics.

[0188] [Charge / discharge cycle characteristics] The all-solid-state batteries of Examples 7, 8, and Comparative Example 6 were subjected to constant current charging at a current value of 0.07 C until the voltage reached 3.8 V, followed by constant voltage charging at a current value of 0.005 C, and then constant current discharging at a current value of 0.07 C until the voltage reached 1.5 V, and the initial capacity was determined. They were again subjected to constant current charging at a current value of 0.07 C until the voltage reached 3.8 V, followed by constant voltage charging at a current value of 0.005 C, followed by constant current step discharging, and the discharge capacity at each current value (constant current step discharge capacity) was measured. The constant current step discharge was performed by discharging the charged batteries at a constant current value of 0.6 C until the voltage reached 1.5 V, then discharging at a current value of 0.3 C until the voltage reached 1.5 V, and then discharging at a current value of 0.1 C until the voltage reached 1.5 V. The sum of all the constant current step discharge capacities from 0.6 C to 0.1 C (0.1 C discharge capacity) was then determined. Next, each battery was charged at a constant current of 0.3 C up to 3.8 V, and then charged at a constant voltage of 0.005 C. After that, constant current step discharge of 0.6 C to 0.1 C was performed under the same conditions as above, and the 0.1 C discharge capacity was measured.

[0189] Of the series of charge-discharge operations described above, the operation when the initial capacity was measured was defined as the first cycle, and the final operation of constant voltage charging at a current value of 0.3 C followed by constant current step discharge was defined as the third cycle. The 0.1 C discharge capacity of the third cycle was divided by the 0.1 C discharge capacity of the charge-discharge cycle (second cycle) in which constant current charging was performed at a current value of 0.1 C to evaluate the charge-discharge cycle characteristics.

[0190] The evaluation results for the all-solid-state batteries of Examples 7 and 8 and Comparative Example 6 are shown in Table 2 as relative values ​​when the result for the all-solid-state battery of Comparative Example 6 is set to 100.

[0191] [Table 2]

[0192] As shown in Table 2, the flat all-solid-state secondary batteries of Examples 7 and 8, which had a negative electrode containing the oxide represented by the general formula (1) as an active material, had high capacity retention rates in the load characteristic evaluation and in the charge-discharge cycle characteristic evaluation, and had excellent load characteristics and charge-discharge cycle characteristics.

[0193] In contrast, element M 1 The battery of Comparative Example 6, which used a negative electrode having an oxide not containing , as an active material, had a lower capacity retention rate in the load characteristic evaluation and a lower capacity retention rate in the charge-discharge cycle characteristic evaluation than the batteries of the Examples, and was therefore inferior in load characteristic and charge-discharge cycle characteristic.

[0194] Example 9 The active material is monoclinic Cu 0.21 Al 0.74 Nb 11.05 O 27.89 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for changing the active material to monoclinic crystals, in the same manner as in Example 1. The composition of the active material was determined by ICP-AES measurement and measurement using an oxygen / nitrogen analyzer.

[0195] Example 10 A mixture of various metal oxide powders (all obtained from Kojundo Chemical Co., Ltd.) was placed in a carbon container and reduced by firing at 1000°C for 4 hours in a vacuum atmosphere with a pressure of 100 Pa or less. 0.14 Al 0.73 Nb 11.13 O 28.00 The active material was the monoclinic Cu 0.14 Al 0.73 Nb 11.13 O 28.00 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for changing the active material to monoclinic crystals, in the same manner as in Example 1. The composition of the active material was determined by ICP-AES measurement and measurement using an oxygen / nitrogen analyzer.

[0196] Example 11 The active material is monoclinic Fe 0.20 Al 0.83 Nb 10.97 O 28.23 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for changing the active material to monoclinic crystals, in the same manner as in Example 1. The composition of the active material was determined by ICP-AES measurement and measurement using an oxygen / nitrogen analyzer.

[0197] Comparative Example 7 The active material is a monoclinic Al alloy that has been subjected to reduction treatment. 0.87 Nb 11.13 O 28.47 A sheet-shaped all-solid-state secondary battery was produced in the same manner as in Example 1, except for changing the active material to monoclinic crystals, in the same manner as in Example 1. The composition of the active material was determined by ICP-AES measurement and measurement using an oxygen / nitrogen analyzer.

[0198] For the sheet-shaped all solid state secondary batteries of Examples 9 to 11 and Comparative Example 7, the load characteristics and charge / discharge cycle characteristics were evaluated in the same manner as the battery of Example 1, except that the lower limit discharge voltage was changed to 0.18 V, and the energy density per weight of active material was calculated by dividing the battery capacity by the weight of the active material contained in the electrode.

[0199] The compositions and physical properties of the active materials of the sheet-shaped all-solid-state secondary batteries of Examples 9 to 11 and Comparative Example 7 are shown in Tables 3 and 4, and the evaluation results are shown in Table 5. In the column "Presence or Absence of Reduction Treatment" in Table 3, "◯" means that the reduction treatment was performed, and "×" means that the reduction treatment was not performed.

[0200] [Table 3]

[0201] [Table 4]

[0202] [Table 5]

[0203] As shown in Tables 3 to 5, the sheet-shaped all-solid-state secondary batteries of Examples 9 to 11, which have a positive electrode containing an oxide represented by the general formula (1) as an active material, have high capacity retention rates in the load characteristic evaluation and in the charge-discharge cycle characteristic evaluation, and have excellent load characteristics and charge-discharge cycle characteristics. 1 The battery of Comparative Example 7, which had a positive electrode using an aluminum-niobium composite oxide containing no niobium as an active material, was poor in both the capacity retention rate during the load characteristic evaluation and the capacity retention rate during the charge-discharge cycle characteristic evaluation.

[0204] Further, a reduction treatment is performed in a carbon container, and the value of Z is suitable, and the absorbances A1, A2, and A3 satisfy the relationship A1 < A2 and A3 < A2, and the atomic ratio P and the atomic ratio Q satisfy the relationship P > Q. The battery of Example 10 having a positive electrode using the oxide as an active material has a higher energy density than the batteries of Examples 9 and 11 having a positive electrode using the oxide without the reduction treatment as an active material, and the battery of Comparative Example 7 having a positive electrode using an aluminum niobium composite oxide not containing element M1 as an active material.

[0205] The present invention can also be implemented in other forms without departing from the gist thereof. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention is interpreted preferentially based on the description of the appended claims rather than the description of the above specification, and all modifications within the scope equivalent to the claims are included in the claims.

Industrial Applicability

[0206] The electrochemical element of the present invention can be applied to the same uses as conventional secondary batteries having non-aqueous electrolytes (non-aqueous electrolytic solutions or gel-like electrolytes), secondary batteries having aqueous electrolytes, all-solid-state secondary batteries, and supercapacitors. Further, the electrode for an electrochemical element of the present invention can constitute the electrochemical element of the present invention, and the active material for an electrochemical element of the present invention and the electrode material for an electrochemical element of the present invention can constitute the electrode for an electrochemical element of the present invention.

[0207] The electrochemical element of the present invention has excellent load characteristics and is therefore suitable for applications where such characteristics are often required, such as power sources for industrial equipment and mobile objects (vehicles such as electric cars, hybrid cars, and electric motorcycles, ships, submarines, radio-controlled cars, flying objects such as rockets and artificial satellites, drones, etc.). Some mobile objects, such as hybrid cars, charge their batteries using regenerative energy. In such cases, the charging current and voltage may be unstable, which can easily lead to the formation of dendrites of element A within the battery, potentially resulting in battery degradation. However, the electrochemical element of the present invention uses an oxide that is less likely to form dendrites of element A as the active material. Therefore, even when charging using regenerative energy, degradation due to dendrites of element A can be suppressed, making the element suitable for use in mobile objects that require such charging. [Explanation of symbols]

[0208] 1,100 Electrochemical element (secondary battery) 10 positive electrode 20 negative electrode 30 Solid electrolyte layer or separator 40 outer can 50 sealed cans 60 gaskets 200 Electrode body 300 Positive external terminal 400 Negative external terminal 500 Laminated film exterior

Claims

1. It has a monoclinic crystal structure and contains an oxide that satisfies the following general formula (1): The content of the oxide is 20 to 100 mass %, An electrode active material for an electrochemical element, characterized in that the ratio Z (atomic %) of Nb 4+ to the total Nb in the oxide represented by the general formula (1) satisfies the following relationship: 3.5≦Z≦30. A ｙ M １ α Al ｘ－α Nb １２－ｘ－ｚ M ２ ｚ O ２９－δ (1) [In the general formula (1), A is at least one element selected from Li and Na; M １ is Fe or Fe and at least one element selected from the group consisting of Mn, Zn, Cu, Ag, Mg, Ca, Sr, Ba, Co, Eu, Y, Bi, La, Ce, Nd, Sm, and Gd, and M ２ is at least one element selected from the group consisting of K, Ti, Ni, Zr, V, Mo, Ta, and W, and 0<x≦1.1, 0≦y≦24, 0≦z≦2, −1≦δ≦2, 0<α≦0.4x.

2. 2. The electrode active material for an electrochemical element according to claim 1, wherein in the general formula (1), 0<δ≦2.

3. 3. The electrode active material for electrochemical elements according to claim 1 or 2, wherein, when absorbance at a wavelength of 500 nm is A1, absorbance at a wavelength of 600 nm is A2, and absorbance at a wavelength of 700 nm is A3, the relationship A1 < A2 is satisfied and the relationship A3 < A2 is satisfied.

4. 4. The electrode active material for electrochemical elements according to any one of claims 1 to 3, wherein an atomic ratio P of Fe to Nb determined by X-ray photoelectron spectroscopy and an atomic ratio Q of Fe to Nb determined by inductively coupled plasma atomic emission spectroscopy satisfy the relationship P>Q.

5. A method for producing the electrode active material for an electrochemical element according to any one of claims 1 to 4, comprising: A method for producing an electrode active material for an electrochemical element, comprising calcining an oxide represented by the general formula (1) or a precursor thereof in a carbon vessel under a vacuum atmosphere.

6. An electrode material for an electrochemical element, comprising the electrode active material for an electrochemical element according to any one of claims 1 to 4.

7. 7. The electrode material for an electrochemical device according to claim 6, further comprising a solid electrolyte.

8. An electrode for an electrochemical element, comprising the electrode active material for an electrochemical element according to any one of claims 1 to 4, or the electrode material for an electrochemical element according to claim 6 or 7.

9. 9. An electrochemical element comprising a positive electrode and a negative electrode, one of which is the electrode for an electrochemical element according to claim 8.

10. A mobile object comprising the electrochemical device according to claim 9.

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