Alkali metal-containing oxide, electrode, and battery

Abstract

The present disclosure provides an alkali metal-containing oxide which contains an alkali metal element and a metal element M other than an alkali metal element, wherein: the ratio X / Y of the substance amount X of the alkali metal element contained in the alkali metal-containing oxide to the substance amount Y of the metal element M contained in the alkali metal-containing oxide is 1.2 to 2.0; and the metal element M includes two or more metal elements MS, each of which have such a valence that the absolute value of the difference between the average valence of the same element and an integer closest to the average valence is 0.1 to 0.5.

Description

Alkali metal-containing oxide, electrode and battery

[0001] The present disclosure relates to an alkali metal-containing oxide, an electrode, and a battery.

[0002] Secondary batteries are known that charge and discharge by the movement of alkali metal ions between a positive electrode and a negative electrode. Among these secondary batteries, lithium-ion secondary batteries are representative and have already been put to practical use as small power sources for devices such as mobile phones and laptops. Furthermore, demand for lithium-ion secondary batteries is increasing because they can be used as large-scale power sources for vehicles such as electric vehicles and hybrid vehicles, as well as for distributed power storage.

[0003] As an attempt to improve the capacity of lithium ion secondary batteries, Patent Document 1 discloses a lithium-excess positive electrode material with a high lithium composition ratio. Non-Patent Document 1 discloses a lithium-excess positive electrode material having a disordered rock salt structure, Li １．２ Mn ０．４ Ti ０．４ O ２ etc. have been reported.

[0004] JP 2008-98154 A

[0005] nature communications 7, article number: 13814 (2016)

[0006] However, existing lithium-rich cathode materials suffer from voltage hysteresis during charging and discharging, and there is still room for improvement in energy efficiency.

[0007] The present disclosure has been made in view of the above circumstances, and has an object to provide an alkali metal-containing oxide with high energy efficiency, and an electrode and a battery using the same.

[0008] The present disclosure includes the following exemplary embodiments: [1] An alkali metal-containing oxide containing an alkali metal element and a metal element M other than an alkali metal element, wherein a ratio X / Y of an amount of substance X of the alkali metal element contained in the alkali metal-containing oxide to an amount of substance Y of the metal element M is greater than 1.0 and not more than 2.0, and the metal element M has a valence such that the absolute value of the difference between the average valence of the same element and the integer closest to the average valence is 0.1 to 0.5. Ｓ [2] An alkali metal-containing oxide containing two or more of the metal elements M Ｓ [3] The alkali metal-containing oxide according to [1], wherein the metal element M contains V and Mn. Ｓ is an alkali metal-containing oxide according to [1] or [2], which contains a combination of two metal elements whose difference in average valence has an absolute value of 1 or more. [4] An alkali metal-containing oxide containing an alkali metal element and a metal element M other than an alkali metal element, wherein a ratio X / Y of the amount of substance X of the alkali metal element contained in the alkali metal-containing oxide to the amount of substance Y of the metal element M is greater than 1.0 and 2.0 or less, and the metal element M is １ and metal element M ２ and the metal element M １ the average valence of the same element is a non-integer, and the metal element M ２ The average valence of the same element is 4 or more, and the difference is: {(the metal element M ２ the average valence of the metal element M １ [5] The metal element M １ contains Mn, and the metal element M ２contains V. [6] The alkali metal-containing oxide according to any one of [1] to [5], which has a crystalline phase of a disordered rock-salt structure. [7] The alkali metal-containing oxide according to any one of [1] to [6], which has an amorphous phase. [8] The alkali metal-containing oxide according to any one of [1] to [7], which has a half-width of a peak observed in a 2θ range of 42 to 46 degrees in powder X-ray diffraction measurement using CuKα radiation at 25°C, of ​​0.5 to 5 degrees. [9] The alkali metal-containing oxide according to any one of [1] to [7], which has a half-width of a peak observed in a 2θ range of 42 to 46 degrees in powder X-ray diffraction measurement using CuKα radiation at 25°C ｘ Mn ａ M' ｂ V ｃ O ２＋ｙ An alkali metal-containing oxide according to any one of [1] to [8], represented by the formula: (wherein 1<x≦2.0, 0.3≦a≦0.8, 0≦b≦0.3, 0.3≦c≦0.6, 0≦y≦1.0, A is an alkali metal element, and M′ contains at least one element selected from the group consisting of Cr, Fe, Co, Ni, and Cu.)

[10] An electrode comprising the alkali metal-containing oxide according to any one of [1] to [9].

[11] A battery comprising the electrode according to

[10] .

[0009] According to the present disclosure, it is possible to provide an alkali metal-containing oxide with high energy efficiency, as well as an electrode and a battery using the same.

[0010] FIG. 1 is an X-ray diffraction chart of each lithium-containing oxide of Examples and Comparative Examples. FIG. 2 is a diagram showing the results of a charge / discharge test of Example 1. FIG. 3 is a diagram showing the results of a charge / discharge test of Example 2. FIG. 4 is a diagram showing the results of a charge / discharge test of Example 3. FIG. 5 is a diagram showing the results of a charge / discharge test of Example 4. FIG. 6 is a diagram showing the results of a charge / discharge test of Comparative Example 1. FIG. 7 is a scanning transmission electron microscope image of a sample of Example 2. FIG. 8 is an enlarged view of the scanning transmission electron microscope image of FIG. 7. FIG. 9 is a scanning transmission electron microscope image of a sample of Example 2. FIG. 10 is a selected area electron diffraction pattern of a sample of Example 2. FIG. 11 is an electron energy loss spectrum of a sample of Example 2. FIG. 12 is an electron energy loss spectrum of a sample of Example 2. FIG. 13 is a scanning transmission electron microscope image of a sample of Comparative Example 1. FIG. 14 is an electron energy loss spectrum of a sample of Comparative Example 1. FIG. 15 is an electron energy loss spectrum of a sample of Comparative Example 1.

[0011] The alkali metal-containing oxide according to this embodiment may be any alkali metal oxide containing an alkali metal element and a metal element M other than an alkali metal element, in which the ratio X / Y of the amount of substance X of the alkali metal element contained in the alkali metal-containing oxide to the amount of substance Y of the metal element M is greater than 1.0 and is 2.0 or less, and which satisfies the following conditions (1) and (2). The alkali metal-containing oxide according to the present disclosure satisfies at least one of conditions (1) and (2), but may also satisfy both. The alkali metal-containing oxide may contain an alkali metal element and a metal element M other than an alkali metal element as constituent elements. (1) The metal element M is a metal element M having a valence in which the absolute value of the difference between the average valence of the same element and the integer closest to the average valence is 0.1 to 0.5. Ｓ (2) The metal element M is a metal element M １ and metal element M ２ and a metal element M １ The average valence of the same element is a non-integer, and the metal element M ２ The average valence of the same element is 4 or more, and the difference is: {(the metal element M ２ the average valence of the metal element M１ The average valence of each of the groups is 1 or more.

[0012] Hereinafter, when referring to the alkali metal-containing oxides satisfying the above conditions (1) and (2), the alkali metal oxide satisfying the condition (1) will be referred to as the "first alkali metal-containing oxide," and the alkali metal oxide satisfying the condition (2) will be referred to as the "second alkali metal-containing oxide." Furthermore, when referring to the alkali metal-containing oxides satisfying the conditions (1) and (2) without any particular distinction, they will also be referred to as the alkali metal-containing oxide of this embodiment.

[0013] The alkali metal-containing oxide according to this embodiment contains a metal element having a non-integer average valence. The inventors of the present invention believe that the reason why such an alkali metal-containing oxide has excellent energy efficiency is as follows.

[0014] First, one of the factors related to charge / discharge efficiency is the electrical resistance of the positive electrode active material. ４＋ When ions without valence electrons (ions with an integer valence) such as these are used as elements of the positive electrode active material, the electronic conductivity of the positive electrode active material tends to decrease and the electrical resistance tends to increase. On the other hand, when metal elements other than alkali metals have non-integer valence electrons, the electronic conductivity of the positive electrode active material improves, which is thought to contribute to improving energy efficiency.

[0015] Furthermore, an oxide containing an excess amount of alkali metal, in which the amount of alkali metal element in the alkali metal-containing oxide is greater than the amount of metal element M other than the alkali metal element, has the characteristic that the oxidation-reduction reaction of oxygen contributes to the charge-discharge capacity during charge and discharge, and the oxidation-reduction reaction of oxygen generally exhibits a large voltage hysteresis.

[0016] In the first alkali metal-containing oxide, the metal element M is a metal element M having a predetermined average valence in the present invention. Ｓ By containing two or more kinds of metal elements, the conductivity can be improved, and therefore the charge / discharge capacity derived from the oxidation-reduction reaction of the metal elements increases. ２ Even if the average valence of the metal element M １The difference in average valence between the metal element M and １ This results in a relative decrease in the capacity derived from the oxidation-reduction reaction of oxygen, lowering dependency and improving energy efficiency.

[0017] In this specification, unless otherwise specified, the "average valence" of a metal element refers to the sum of the integer valence value and the abundance rate of the element having that integer valence for atoms of the same element. The integer closest to the average valence is the integer with the smallest absolute difference from the average valence, and may be either an integer larger or smaller than the average valence depending on the value of the average valence. Furthermore, when the average valence is a half integer, the integer closest to the average valence may be either an integer larger or smaller than the half integer, in which case the absolute difference is 0.5. For example, when the average valence is 2.5, the integer closest to the average valence may be either 3 or 2. The average valence of a metal element can be calculated from the valence ratio of each atom of the same element by electron energy loss spectroscopy.

[0018] In the alkali metal-containing oxide of the present embodiment, the alkali metal element is not particularly limited, but may contain at least one selected from the group consisting of Li, Na, K, Rb, and Cs, may contain at least one selected from the group consisting of Li, Na, and K, may contain at least one of Li and Na, or may contain Li.

[0019] Of the total amount of alkali metal elements contained in the alkali metal-containing oxide of this embodiment, the content of one alkali metal element may be, for example, 90 mol% or more, 95 mol% or more, 98 mol% or more, 99 mol% or more, or 99.9 mol% or more, or may contain substantially only one alkali metal element (i.e., the content of alkali metal elements other than the one alkali metal element is substantially 0 mol%. It can also be said that the content of the one alkali metal element is 100 mol%). The content of the one alkali metal element may be adjusted within the above-mentioned range and may be, for example, 90 to 100 mol% of the total amount of alkali metal elements contained in the alkali metal-containing oxide of this embodiment. The one alkali metal element may be Li, Na, or K, or may be Li, Na, or Li.

[0020] In the alkali metal-containing oxide of this embodiment, the content of the alkali metal element may be, for example, 6 to 15 mass %, 7 to 13 mass %, or 8 to 12 mass % relative to the total amount of the alkali metal-containing oxide.

[0021] The metal element M in the alkali metal-containing oxide of this embodiment is a metal element other than an alkali metal element. The metal element M may include a transition metal element and an element of the zinc group (group 12), or may include a transition metal element. The transition metal element may include an element of the fourth period. The transition metal element may include an element of groups 4 (titanium group) to 11 (copper group) of the periodic table. The transition metal element may include an element of groups 4 (titanium group) to 11 (copper group) and the fourth period of the periodic table, that is, at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu.

[0022] The content of the metal element M in the alkali metal-containing oxide of this embodiment may be, for example, 40 to 65 mass%, 45 to 60 mass%, or 48 to 58 mass%, relative to the total amount of the alkali metal-containing oxide. The content of the transition metal element in the alkali metal-containing oxide of this embodiment may be, for example, 40 to 65 mass%, 45 to 60 mass%, or 48 to 58 mass%, relative to the total amount of the alkali metal-containing oxide.

[0023] The first alkali metal-containing oxide contains a metal element M Ｓ The metal element M Ｓ is a metal element having a valence where the absolute value of the difference between the average valence of the same element and the integer closest to the average valence is 0.1 to 0.5. Ｓ The average valence of is a non-integer.

[0024] Metal element M Ｓ may contain a transition metal element and a zinc group element, and may contain a transition metal element. Ｓ The transition metal element may include an element of the fourth period. Ｓ The transition metal element as may include those from Groups 4 (titanium group) to 11 (copper group) of the periodic table. Ｓ The transition metal element may include elements of Groups 4 (titanium group) to 11 (copper group) of the periodic table and the fourth period.

[0025] In the first alkali metal-containing oxide, the metal element M Ｓ may contain at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, may contain at least one of V and Mn, or may contain V and Mn.

[0026] Metal element M in the first alkali metal-containing oxide Ｓ The content of may be, for example, 40 to 65 mass %, 45 to 60 mass %, or 48 to 58 mass % relative to the total amount of the first alkali metal-containing oxide.

[0027] Metal element M Ｓ may include a combination of two metal elements in which the absolute value of the difference in average valence is 1 or more. The absolute value of the difference may be, for example, 1 to 3, 1.1 to 3, 1.2 to 2.8, 1.5 to 2.7, or 1.7 to 2.6. Examples of such combinations of metal elements include the metal element M Ｓ１ One of the types and M Ｓ２ and may be a combination of Mn and V.

[0028] In the first alkali metal-containing oxide, the metal element MＳ The absolute value of the difference between the average valence and the integer closest to the average valence may be, for example, 0.15 to 0.5, 0.2 to 0.5, 0.25 to 0.5, 0.3 to 0.5, or 0.35 to 0.5.

[0029] In the first alkali metal-containing oxide, the metal element M Ｓ is a metal element M having an average valence of 2 to 4 (not including integers). Ｓ１ and a metal element M having a valence of 4 to 6 (not including integers). Ｓ２ In the alkali metal-containing oxide, the metal element M Ｓ１ and metal element M Ｓ２ is a different element.

[0030] In the first alkali metal-containing oxide, the metal element M Ｓ１ may contain at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, and may contain Mn.

[0031] Metal element M Ｓ１ The absolute value of the difference between the average valence of the metal element M and the integer closest to the average valence may be, for example, 0.15 to 0.5, 0.2 to 0.5, 0.25 to 0.5, 0.3 to 0.5, or 0.35 to 0.5. Ｓ１ The average valence of may be, for example, 2 to 3.5 (not including integer values), greater than 2 and less than 3, 2.1 to 2.9, 2.2 to 2.8, or 2.3 to 2.75.

[0032] Metal element M in the first alkali metal-containing oxide Ｓ１ The content of may be, for example, 15 to 40 mass %, or 20 to 35 mass %, based on the total amount of the first alkali metal-containing oxide.

[0033] Metal element M Ｓ１ may contain metal elements in at least one of a divalent and a trivalent state for the same element.

[0034] In the first alkali metal-containing oxide, the content of the divalent metal element in the divalent state may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of the same metal element as the divalent metal element. Ｓ１ is Mn ２＋ In this case, Mn ２＋ The content of may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of Mn contained in the alkali metal-containing oxide.

[0035] In the first alkali metal-containing oxide, the content of the trivalent metal element in the trivalent state may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of the same metal element as the trivalent metal element. Ｓ１ is Mn ３＋ In this case, Mn ３＋ The content of may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of Mn contained in the first alkali metal-containing oxide.

[0036] In addition, the metal element M Ｓ１ When the metal element M includes both divalent and trivalent states for the same element, the content of the metal element in the divalent or trivalent state among the metal elements may be a value relative to the total amount of the metal elements in the divalent and trivalent states among the metal elements, instead of the total amount of the metal elements including both the divalent and trivalent states. Ｓ１ When the metal element M contains a metal element in at least one of a divalent and a trivalent state, the total amount of the divalent and trivalent metal elements relative to the total amount of the metal element identical to the metal element in at least one of a divalent and a trivalent state in the first alkali metal-containing oxide may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more. Ｓ１ is Mn ２＋ and Mn ３＋When the first alkali metal-containing oxide contains at least one of the above, the ratio of Mn to the total amount of Mn is ２＋ and Mn ３＋ The total amount may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more.

[0037] In the first alkali metal-containing oxide, the metal element M Ｓ２ may contain at least one selected from the group consisting of Ti, V, Cr, Mn, and Fe, and may contain V.

[0038] Metal element M Ｓ２ The absolute value of the difference between the average valence of the metal element M and the integer closest to the average valence may be, for example, 0.2 to 0.5, 0.25 to 0.5, 0.3 to 0.48, or 0.35 to 0.47. Ｓ２ The average valence of may be, for example, 4 to 5.5 (not including integer values), greater than 4 and less than 5, 4.1 to 4.9, 4.2 to 4.8, 4.3 to 4.75, or 4.4 to 4.7.

[0039] Metal element M in the first alkali metal-containing oxide Ｓ２ The content of may be, for example, 15 to 40 mass %, or 20 to 35 mass %, based on the total amount of the first alkali metal-containing oxide.

[0040] Metal element M Ｓ２ may contain metal elements in at least one of a tetravalent and a pentavalent state for the same element.

[0041] In the first alkali metal-containing oxide, the content of the tetravalent metal element in the metal element having a tetravalent state may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of the metal element identical to the tetravalent metal element. Ｓ２ is V ４＋ In this case, V ４＋ The content of may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of V contained in the alkali metal-containing oxide.

[0042] In the first alkali metal-containing oxide, the content of the pentavalent metal element in the pentavalent state may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of the same metal element as the pentavalent metal element. Ｓ２ is V ５＋ In this case, V ５＋ The content of may be, for example, 20 to 80 mol %, 25 to 75 mol %, 30 to 70 mol %, or 40 to 60 mol % relative to the total amount of V contained in the alkali metal-containing oxide.

[0043] In addition, the metal element M Ｓ２ When the metal element M includes both tetravalent and pentavalent states for the same element, the content of the tetravalent or pentavalent metal element among the metal elements may be a value relative to the total amount of the metal elements in the tetravalent and pentavalent states among the metal elements, instead of the total amount of the metal elements including both the tetravalent and pentavalent states. Ｓ２ When the metal element M contains a metal element in at least one of a tetravalent and a pentavalent state, the total amount of the tetravalent and pentavalent metal elements relative to the total amount of the same metal element as the metal element in at least one of a tetravalent and a pentavalent state in the first alkali metal-containing oxide may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more. Ｓ２ V ４＋ and V ５＋ When the first alkali metal-containing oxide contains at least one of the above, the ratio of V to the total amount of V is ４＋ and V ５＋ The total amount may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more.

[0044] In the first alkali metal-containing oxide, the metal element M Ｓ may account for 70 mol % or more, 80 mol % or more, 85 mol % or more, or 90 mol % or more of the total amount of atoms contained in the metal element M.

[0045] When the first alkali metal-containing oxide contains V and Mn, the metal element M may further contain a transition metal element other than V and Mn. Such a transition metal element (other transition metal element) may be at least one element selected from the group consisting of Cr, Fe, Co, Ni, and Cu, and may be at least one of Ni and Cr. In this case, the metal element M Ｓ１ is Mn, and the metal element M Ｓ２ may be V.

[0046] In the first alkali metal-containing oxide, the content of the other transition metal element may be 30 mol % or less, 0.1 to 20 mol %, 1 to 15 mol %, or 5 to 10 mol % of the total amount of atoms contained in the metal element M. Furthermore, the content of the other transition metal element in the alkali metal-containing oxide may be, for example, 15 mass % or less, 1 to 10 mass %, or 2 to 8 mass % with respect to the total amount of the alkali metal-containing oxide.

[0047] The second alkali metal-containing oxide contains a metal element M １ and metal element M ２ The metal element M １ is a metal element whose average valence for the same element is not an integer. ２ is a metal element whose average valence for the same element is 4 or more.

[0048] In the second alkali metal-containing oxide, the metal element M １ may contain a transition metal element and a zinc group element, and may contain a transition metal element. １ The transition metal element may include an element of the fourth period. １ The transition metal element as may include those from Groups 4 (titanium group) to 11 (copper group) of the periodic table. １ The transition metal element may include elements of Groups 4 (titanium group) to 11 (copper group) of the periodic table and the fourth period.

[0049] In the second alkali metal-containing oxide, the metal element M １may contain at least one selected from the group consisting of Ti, V, Cr and Mn, may contain Mn, or may be Mn.

[0050] Metal element M １ The absolute value of the difference between the average valence and the integer closest to the average valence may be, for example, 0.1 to 0.5, 0.2 to 0.5, 0.25 to 0.5, 0.3 to 0.48, or 0.35 to 0.47.

[0051] Metal element M １ The average valence of may be, for example, greater than 2 and less than 3, 2.1 to 2.9, 2.2 to 2.8, or 2.3 to 2.75.

[0052] Metal element M in the second alkali metal-containing oxide １ The content of may be, for example, 15 to 40 mass %, or 20 to 35 mass %, based on the total amount of the second alkali metal-containing oxide.

[0053] Metal element M １ may contain metal elements in at least one of a divalent and a trivalent state for the same element.

[0054] In the second alkali metal-containing oxide, the content of the divalent metal element in the metal element having a divalent state may be, for example, 15 to 80 mol %, 20 to 60 mol %, 25 to 55 mol %, or 30 to 45 mol % relative to the total amount of the metal element identical to the divalent metal element. １ is Mn ２＋ In this case, Mn ２＋ The content of may be, for example, 15 to 80 mol %, 20 to 60 mol %, 25 to 55 mol %, or 30 to 45 mol % relative to the total amount of Mn contained in the alkali metal-containing oxide.

[0055] In the second alkali metal-containing oxide, the content of the trivalent metal element may be, for example, 20 to 85 mol %, 40 to 80 mol %, 45 to 75 mol %, or 55 to 70 mol % relative to the total amount of the metal element. １ is Mn ３＋ In this case, Mn ３＋The content of may be, for example, 20 to 85 mol %, 40 to 80 mol %, 45 to 75 mol %, or 55 to 70 mol % relative to the total amount of Mn contained in the alkali metal-containing oxide.

[0056] In addition, the metal element M １ When the metal element M includes both divalent and trivalent states for the same element, the content of the metal element in the divalent or trivalent state among the metal elements may be a value relative to the total amount of the metal elements in the divalent and trivalent states among the metal elements, instead of the total amount of the metal elements including both the divalent and trivalent states. １ When the metal element M contains a metal element in at least one of a divalent and a trivalent state, the total amount of the divalent and trivalent metal elements relative to the total amount of the metal element identical to the metal element in at least one of a divalent and a trivalent state in the second alkali metal-containing oxide may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more. １ is Mn ２＋ and Mn ３＋ When the second alkali metal-containing oxide contains at least one of the above, the ratio of Mn to the total amount of Mn is ２＋ and Mn ３＋ The total amount may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more.

[0057] In the second alkali metal-containing oxide, the metal element M ２ may contain a transition metal element and a zinc group element, and may contain a transition metal element. ２ The transition metal element may include an element of the fourth period. ２ The transition metal element as may include those from Groups 4 (titanium group) to 11 (copper group) of the periodic table. ２ The transition metal element may include elements of Groups 4 (titanium group) to 11 (copper group) of the periodic table and the fourth period.

[0058] In the second alkali metal-containing oxide, the metal element M ２may contain at least one selected from the group consisting of Ti, V, Cr and Mn, and may contain or be V.

[0059] Metal element M ２ The average valence of may be, for example, 4.1 to 5.9, 4.2 to 5.8, 4.5 to 5.5, 4.4 to 5.4, or 4.7 to 5.4.

[0060] Metal element M in the second alkali metal-containing oxide ２ The content of may be, for example, 15 to 40 mass %, or 20 to 35 mass %, based on the total amount of the second alkali metal-containing oxide.

[0061] Metal element M in the second alkali metal-containing oxide １ and M ２ The total content of the second alkali metal-containing oxide may be, for example, 40 to 65 mass %, 45 to 60 mass %, or 48 to 58 mass % relative to the total amount of the second alkali metal-containing oxide.

[0062] In the second alkali metal-containing oxide, the metal element M １ and M ２ The total of the atoms contained in the metal element M may account for, for example, 70 mol % or more, 80 mol % or more, 85 mol % or more, or 90 mol % or more of the total amount of atoms contained in the metal element M. １ and M ２ The total of the atoms contained in the metal element M may be, for example, 100 mol % or less of the total amount of atoms contained in the metal element M. １ and M ２ The total of may be adjusted within the above range, and may be, for example, 70 to 100 mol % of the total amount of atoms contained in the metal element M.

[0063] When the second alkali metal-containing oxide contains V and Mn, the metal element M may further contain a transition metal element other than V and Mn. Such a transition metal element (other transition metal element) may be at least one element selected from the group consisting of Ti, Cr, Fe, Co, Ni, and Cu, and may be at least one of Cr and Ni. In this case, the metal element M １is Mn, and the metal element M ２ may be V.

[0064] In the second alkali metal-containing oxide, the content of the other transition metal element may be, for example, 30 mol % or less, 0.1 to 30 mol %, 0.1 to 20 mol %, 1 to 15 mol %, or 5 to 10 mol % of the total amount of atoms contained in the metal element M.

[0065] The content of other transition metal elements in the alkali metal-containing oxide may be, for example, 15 mass% or less, 1 to 15 mass%, 1 to 10 mass%, or 2 to 8 mass% relative to the total amount of the alkali metal-containing oxide.

[0066] Metal element M ２ may contain metal elements in at least one of a tetravalent and a pentavalent state for the same element.

[0067] In the second alkali metal-containing oxide, the content of the tetravalent metal element in the metal element having a tetravalent state may be, for example, 60 mol % or less, 50 mol % or less, 35 mol % or less, 30 mol % or less, 20 mol % or less, or 10 mol % or less relative to the total amount of the metal element identical to the tetravalent metal element. ２ About V ４＋ The content of may be, for example, 60 mol % or less, 50 mol % or less, 35 mol % or less, 30 mol % or less, 20 mol % or less, or 10 mol % or less relative to the total amount of V contained in the alkali metal-containing oxide.

[0068] In the second alkali metal-containing oxide, the content of the pentavalent metal element in the pentavalent state may be, for example, 40 mol% or more, 50 mol% or more, 65 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more relative to the total amount of the same metal element as the pentavalent metal element. ２ is V ５＋ In this case, V ５＋ The content of may be, for example, 40 mol% or more, 50 mol% or more, 65 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more relative to the total amount of V contained in the alkali metal-containing oxide.

[0069] In addition, the metal element M ２ When the metal element M includes both tetravalent and pentavalent states for the same element, the content of the metal element in the tetravalent or pentavalent state among the metal elements may be a value relative to the total amount of the metal elements in the tetravalent and pentavalent states among the metal elements, instead of the total amount of the metal elements including both the tetravalent and pentavalent states. ２ When the metal element M contains a metal element in at least one of a tetravalent and a pentavalent state, the total amount of the tetravalent and pentavalent metal elements relative to the total amount of the same metal element as the metal element in at least one of a tetravalent and a pentavalent state in the second alkali metal-containing oxide may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more. ２ V ４＋ and V ５＋ When the second alkali metal-containing oxide contains at least one of the above, the ratio of V to the total amount of V is ４＋ and V ５＋ The total amount may be, for example, 80 mol % or more, 90 mol % or more, 95 mol % or more, or 99 mol % or more.

[0070] In the second alkali metal-containing oxide, the metal element M ２ The average valence of the metal element M １ The difference is 1 or more times greater than the average valence of the metal element M ２ Average valence of metal element M １ (average valence of each of the groups)} may be, for example, 1 to 3, 1.1 to 3, 1.2 to 2.8, 1.5 to 2.7, or 1.7 to 2.6.

[0071] In the alkali metal-containing oxide of this embodiment, the ratio X / Y may be, for example, 1.1 to 2.0, 1.2 to 2.0, 1.2 to 1.8, or 1.2 to 1.6.

[0072] The oxygen content in the alkali metal-containing oxide of this embodiment may be, for example, 25 to 48 mass %, or 30 to 45 mass %.

[0073] The alkali metal-containing oxide of the present embodiment is represented by the general formula: A ｘ Mn ａ M' ｂV ｃ O ２＋ｙ (In the above general formula, 1<x≦2.0, 0.3≦a≦0.8, 0≦b≦0.3, 0.3≦c≦0.6, 0≦y≦1.0, A is an alkali metal element, and M′ contains at least one element selected from the group consisting of Ti, Cr, Fe, Co, Ni, and Cu.)

[0074] In the above general formula, x may be, for example, 1.1 to 1.8, or 1.2 to 1.6. In the above general formula, a may be, for example, 0.3 to 0.6. In the above general formula, b may be, for example, 0 to 0.25, 0.01 to 0.25, or 0.03 to 0.2. In the above general formula, c may be, for example, 0.3 to 0.6.

[0075] The alkali metal-containing oxide of this embodiment may have a crystalline phase. The crystalline phase may be a crystalline phase with a disordered rock salt structure. The alkali metal-containing oxide of this embodiment may have an amorphous phase, or may have an amorphous phase and a crystalline phase.

[0076] When the alkali metal-containing oxide of this embodiment is subjected to powder X-ray diffraction measurement using CuKα radiation at 25°C, a peak having a half-width of 0.5 to 5° may be observed within a 2θ range of 42 to 46°.

[0077] The half width of the peak may be, for example, 0.6 to 4°, 0.7 to 3°, or 1 to 2.5°. In this specification, the half width refers to the full width at half maximum.

[0078] The method for producing the alkali metal-containing oxide of this embodiment is not particularly limited, but may include a method in which raw materials are mixed in a ball mill.

[0079] The raw material is not particularly limited, but for example, a low-valence metal element M Ｓ or M １ and an oxide containing a valence metal element M Ｓ or M ２ and oxides containing a low-valent metal element M Ｓ or M １ The oxide containing a divalent metal element MＳ or M １ Examples of oxides containing high valence metal elements include MnO, VO, and CrO. Ｓ or M ２ The oxides containing tetravalent to heptavalent metal elements M Ｓ For example, the oxide may be an oxide containing V ５＋ , Cr ４＋ , Cr ５＋ , Cr ６＋ , Mn ５＋ , Mn ６＋ , Mn ７＋ , or Ni ４＋ The alkali metal source may contain low-valence and high-valence metal elements M Ｓ (or M １ Or M ２ ), and the high valence metal element M Ｓ or M ２ may be contained in an oxide containing

[0080] The conditions for the ball mill are not particularly limited. The rotation speed of the ball mill may be, for example, 100 to 700 rpm. The mixing time using the ball mill may be, for example, 0.5 to 72 hours, or 10 to 60 hours. The mixing time using the ball mill may be, for example, 20 to 72 hours, or 30 to 60 hours.

[0081] The alkali metal-containing oxide of this embodiment can be used as a material for batteries (such as lithium ion batteries and sodium ion batteries that generate current as alkali metal ions move). That is, the battery of this embodiment contains the alkali metal-containing oxide. The battery may be a primary battery or a secondary battery. The battery may also be a nonaqueous secondary battery. In the battery, the lithium-containing oxide may be contained in an electrode.

[0082] The battery of this embodiment has a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode.

[0083] The positive electrode of this embodiment includes a current collector and a positive electrode mixture carried on the current collector. The positive electrode mixture may form a positive electrode mixture layer on the current collector.

[0084] The positive electrode mixture may contain the alkali metal-containing oxide of this embodiment and may also contain a conductive material (conductive additive), a binder, etc., as necessary. That is, the alkali metal-containing oxide of this embodiment may be contained in the positive electrode active material. The positive electrode active material may contain at least one of a first alkali metal-containing oxide and a second alkali metal-containing oxide.

[0085] Examples of conductive materials include carbon materials such as natural graphite, artificial graphite, cokes, carbon black, and acetylene black. Examples of binders include thermoplastic resins, specifically fluororesins such as polyvinylidene fluoride (hereinafter also referred to as "PVDF"), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers, hexafluoropropylene-vinylidene fluoride copolymers, and tetrafluoroethylene-perfluorovinyl ether copolymers; and polyolefin resins such as polyethylene and polypropylene. Examples of current collectors that can be used include Al, Ni, stainless steel, and the like.

[0086] Examples of methods for supporting the positive electrode mixture on the current collector include pressure molding, forming a paste from the electrode mixture using an organic solvent or the like, applying the paste to the current collector, drying, and then pressing to adhere the paste to the current collector. When forming a paste, for example, a slurry containing the positive electrode active material, a conductive material, a binder, and an organic solvent is prepared. Examples of organic solvents include amine-based solvents such as N,N-dimethylaminopropylamine and diethyltriamine; ether-based solvents such as ethylene oxide and tetrahydrofuran; ketone-based solvents such as methyl ethyl ketone; ester-based solvents such as methyl acetate; and aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Examples of methods for applying the electrode mixture to the current collector include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spray coating.

[0087] The negative electrode of the battery is not particularly limited and may contain a negative electrode active material and, as necessary, a conductive additive, a binder, etc. Examples of negative electrode active materials for lithium ion batteries include simple elements such as Li, Si, P, Sn, Si—Mn, Si—Co, Si—Ni, In, and Au, alloys or composites containing these elements, carbon materials such as graphite, and materials in which lithium ions are inserted between the layers of the carbon material. In the case of a negative electrode of a sodium ion battery, a material in which the Li in the material listed as a negative electrode material for a lithium ion battery is replaced with Na can be used as the negative electrode material.

[0088] The electrolyte of the battery is not particularly limited, and an electrolytic solution in which an alkali metal salt is dissolved in an organic solvent can be used. Alternatively, the electrolyte may be a solid electrolyte. Examples of the alkali metal salt include iodide salts, tetrafluoroborate salts, hexafluorophosphate salts, bis(fluorosulfonyl)imide salts, and bis(trifluoromethylsulfonyl)imide salts.

[0089] The organic solvent contained in the electrolytic solution is not particularly limited, but examples thereof include non-aqueous solvents such as cyclic carbonate esters such as ethylene carbonate (EC) or propylene carbonate (PC), linear carbonate esters such as dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethyl methyl carbonate (EMC), or sultones. The solvents may be used alone or in combination of two or more.

[0090] (Example 1) Raw material Li ３ VO ４ The powder was produced as follows: Lithium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and vanadium (V) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed in a molar ratio of 3:1 and calcined in air at 650°C for 12 hours to obtain Li ３ VO ４ A powder of 1000 ppm was obtained.

[0091] MnO powder (Sigma-Aldrich) and Li obtained as above ３ VO ４The powder was mixed at a molar ratio of 0.6:0.4, and the mixed powder was introduced into a zirconia ball mill container with 4 mm diameter zirconia balls at a mass ratio of 65:1. The ball mill container was introduced into a planetary ball mill (PM200, manufactured by Retsch), and ball milling was carried out at a rotation speed of 500 rpm for 48 hours to obtain a lithium-containing oxide.

[0092] (Example 2) MnO powder and Li ３ VO ４ A lithium-containing oxide was produced in the same manner as in Example 1 except that the molar ratio of the lithium-containing oxide to the powder was 0.5:0.5.

[0093] (Example 3) MnO powder (manufactured by Sigma-Aldrich), NiO powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and Li ３ VO ４ A lithium-containing oxide was produced in the same manner as in Example 1, except that the molar ratio of the powder was 0.4:0.1:0.5.

[0094] Example 4: MnO powder (Sigma-Aldrich) and Cr ２ O ３ Powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and Li ３ VO ４ A lithium-containing oxide was produced in the same manner as in Example 1, except that the molar ratio of the powder was 0.4:0.1:0.5.

[0095] Comparative Example 1 Lithium carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), manganese (III) oxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), manganese (IV) oxide, and TiO ２ (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out to a molar ratio of 6:2:1:3, and mixed in a wet ball mill together with ethanol and zirconia balls with a diameter of 8 mm. The mixed powder after filtration and drying was calcined at 900°C for 12 hours in an argon atmosphere to obtain Li １．２ Mn ０．５ Ti ０．３ O ２ obtained.

[0096] <X-ray Diffraction> Powder X-ray diffraction measurements were performed on each of the lithium-containing oxides in the Examples and Comparative Examples using a powder X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation). The measurements were performed at room temperature (25°C). The lithium-containing oxide was filled into a cavity in a glass plate, and the glass plate on which the sample was placed was sealed in an airtight sample stage with a beryllium window to prevent air and moisture from entering, and the measurements were performed without exposure to the atmosphere. Using a CuKα radiation source, the measurements were performed at an output of 40 kV and 40 mA, over a diffraction angle 2θ range of 10° to 90° in 0.02° steps at a rate of 2° / min. Figure 1 shows the X-ray diffraction charts of each lithium-containing oxide.

[0097] <Charge-Discharge Test> (1) Preparation of Positive Electrode The lithium-containing oxides (positive electrode active materials) of Examples 1 to 4 and Comparative Example 1, acetylene black (product name: HS-100, manufactured by Denka Co., Ltd.) as a conductive material, and polytetrafluoroethylene (PTFE, product number: 6-J, manufactured by Mitsui Chemours Fluoro Products Co., Ltd.) as a binder were weighed out to a composition of positive electrode active material: conductive material: binder = 70:20:10 (mass ratio). First, the positive electrode active material and conductive material were thoroughly mixed in an agate mortar, and the binder was added and further mixed. 7 mg of the mixture was weighed out and stretched into a circle on the mortar. The stretched mixture was pressed onto a 110 μm thick aluminum mesh (100 mesh, manufactured by Nilaco Corporation) as a current collector to obtain a positive electrode containing the positive electrode active material.

[0098] (2) Preparation and Evaluation of Li Half Cells The above-mentioned positive electrode, a polyethylene porous film (thickness 16 μm) as a separator, and 1 M LiPF as a non-aqueous electrolyte were used. ６ A coin-type battery (CR2032 type) was assembled using a solution (a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 30:35:35) and metallic lithium as a counter electrode. The battery assembly was carried out in a glove box under an argon atmosphere.

[0099] Using the produced coin-type batteries, charge / discharge tests were carried out under the following conditions at 25°C and in the voltage range of 1.5 to 4.8 V. The results of measuring the initial energy efficiency (energy during discharge / energy during charge) are shown in Table 1. Figures 2 to 6 show the results of each charge / discharge test for Examples 1 to 4 and Comparative Example 1. Charge conditions: Constant current-constant voltage charge (CC-CV) was performed at 30 mA / g, with a cutoff condition of 6 mA / g. Discharge conditions: Constant current (CC) discharge was performed at 30 mA / g.

[0100] <Observation by Scanning Transmission Electron Microscope (STEM)> Observation by a scanning transmission electron microscope (STEM) was carried out under the following measurement conditions. In addition to the STEM observation, electron loss energy spectroscopy (EELS) measurements were also carried out using an EELS spectrometer (trade name: GIF Quantum, manufactured by GATAN). Apparatus: Analytical electron microscope ARM200F manufactured by JEOL Ltd. Measurement conditions: Acceleration voltage 200 kV Sample preparation: A sample was prepared for the lithium-containing oxide of Example 2 by a dry dispersion method under an inert atmosphere.

[0101] Fig. 7 shows a scanning transmission electron microscope (STEM) image of the sample of Example 2. Fig. 7 is a bright-field STEM image. Fig. 8 shows an enlarged view of the scanning transmission electron microscope image of Fig. 7. Fig. 8 shows that a crystalline phase and an amorphous phase are mixed.

[0102] Figure 9 shows a bright-field STEM image of the sample of Example 2. Figure 10 shows a selected-area electron diffraction pattern. The circle on the bright-field STEM image in Figure 9 indicates the insertion position of the objective aperture (aperture) when measuring the selected-area electron diffraction pattern in Figure 10. The image in the lower right of Figure 10 is an image with changed contrast. As can be seen from Figure 10, a halo ring and a ring of diffraction spots are observed in the sample of Example 2, indicating that it contains both an amorphous phase and a crystalline phase. The radius of the ring of diffraction spots is 4.10 nm from the inside. －１ ((111) plane), 4.72nm －１ ((200) plane), 6.66nm －１ ((220) plane). Halo rings and rings of diffraction spots were also observed in the samples of Examples 1, 3 and 4.

[0103] 11 and 12 show the EELS spectra of the sample of Example 2. In FIG. 11, the (L ２ , L ３ ) spectrum of vanadium in the EELS spectrum. ２ , L ３ The region containing the Mn EELS spectrum is shown. The background has been removed from the EELS spectra of the sample of Example 2 in Figures 11 and 12. Figures 11 and 12 also show the fitting curves obtained by linear least squares fitting. Figure 11 shows the Mn ２＋ , Mn ３＋ , and Mn ４＋ MnCO as a standard compound containing ３ , Mn ２ O ３ and MnO ２ The EELS spectra of V and V are also shown in Fig. 12. ３＋ , V ４＋ , and V ５＋ V as a standard compound containing ２ O ３ , V.O. ２ and V ２ O ５ The EELS spectrum of the sample of Example 2 is also shown. From the analysis results of the EELS spectrum, two types of valence of V, tetravalent and pentavalent, and two types of valence of Mn, divalent and trivalent, were detected in the sample of Example 2. For V and Mn, atoms of valences other than the above two types were not detected.

[0104] The same measurements and analyses were carried out for the lithium-containing oxides of Examples 1, 3, and 4, and Comparative Example 1. Table 1 shows the average valence of V and V ４＋ and V ５＋ and the average valence of Mn and Mn ２＋ and Mn ３＋ The ratio is shown.

[0105] Fig. 13 shows a scanning transmission electron microscope image of the sample of Comparative Example 1. Fig. 13 is a bright-field STEM image. Figs. 14 and 15 show EELS spectra of the sample of Comparative Example 1. Fig. 14 shows a region including the (L2, L3) spectrum of manganese in the EELS spectrum. Fig. 15 shows a region including the (L2, L3) spectrum of titanium in the EELS spectrum. As in Example 2, the average valences of Mn and Ti were determined from the spectra.

[0106]

Claims

1. An alkali metal-containing oxide containing an alkali metal element and a metal element M other than an alkali metal element, wherein the ratio X / Y of the amount of substance X of the alkali metal element contained in the alkali metal-containing oxide to the amount of substance Y of the metal element M is greater than 1.0 and less than 2.0, and the metal element M has a valence such that the absolute value of the difference between the average valence for the same element and the integer closest to the average valence is 0.1 to 0.

5. Ｓ An alkali metal-containing oxide comprising two or more of the above.

2. The metal element M Ｓ The alkali metal-containing oxide according to claim 1 , wherein contains V and Mn.

3. The metal element M Ｓ The alkali metal-containing oxide according to claim 1 or 2, wherein the absolute value of the difference between the average valences of two metal elements is 1 or more.

4. An alkali metal-containing oxide containing an alkali metal element and a metal element M other than an alkali metal element, wherein the ratio X / Y of the amount of substance X of the alkali metal element contained in the alkali metal-containing oxide to the amount of substance Y of the metal element M is greater than 1.0 and less than or equal to 2.0, and the metal element M is １ and metal element M ２ The metal element M １ The average valence of the same element of the metal element M ２ The average valence of the same element is 4 or more, and the difference is: {(the metal element M ２ The average valence of the metal element M １ The alkali metal-containing oxide, wherein the average valence of each of the above groups is 1 or more.

5. The metal element M １ contains Mn, and the metal element M ２ The alkali metal-containing oxide according to claim 4 , wherein 6. The alkali metal-containing oxide according to claim 1 or 4, having a crystal phase of a disordered rock-salt structure.

7. The alkali metal-containing oxide according to claim 1 or 4, having an amorphous phase.

8. General formula: A ｘ Mn ａ M' ｂ V ｃ O ２＋ｙ The alkali metal-containing oxide according to claim 1 or 4, represented by the formula: (wherein 1<x≦2.0, 0.3≦a≦0.8, 0≦b≦0.3, 0.3≦c≦0.6, 0≦y≦1.0, A is an alkali metal element, and M′ contains at least one element selected from the group consisting of Cr, Fe, Co, Ni, and Cu).

9. The alkali metal-containing oxide according to claim 1 or 4, in which, when powder X-ray diffraction measurement is performed at 25° C. using CuKα radiation, a peak having a half-width of 0.5 to 5° is observed within a 2θ range of 42 to 46°.

10. An electrode comprising the alkali metal-containing oxide according to claim 1 or 4.

11. A battery comprising the electrode according to claim 10.

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