JPWO2017073765A1 - Lithium sodium titanium composite oxide powder for electrode of electricity storage device, active material, and electrode sheet and electricity storage device using the same - Google Patents

Abstract

Having a crystal structure belonging to the space group Cmca or space group Fmmm, the general _{formula: Li 2 + x Na 2 +} y Ti 6-z M z O 14 ( provided that at least M is selected Al, Ga, an In, V, from Nb and Ta X is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1. Provided is a lithium sodium titanium composite oxide powder for an electrode active material of an electricity storage device, comprising a lithium sodium titanium composite oxide as a main phase.

Description

  The present invention relates to a lithium sodium titanium composite oxide powder suitable as an electrode material for an electricity storage device, an active material containing the lithium sodium titanium composite oxide powder, an electrode sheet using the active material, and an electricity storage device It is about.

  In recent years, various materials have been studied as electrode materials for power storage devices. Among them, lithium-titanium composite oxides can provide an electricity storage device with excellent input / output characteristics when used as an active material for a negative electrode, and thus are attracting attention as an active material material for electricity storage devices for electric vehicles such as HEV, PHEV, and BEV. ing. Among them, lithium titanate having a spinel structure has almost no volume change associated with charge / discharge and can move three-dimensional Li ions, and is particularly excellent in charge / discharge cycle characteristics and input / output characteristics. It is promising as an active material for electricity storage devices.

However, in lithium titanate having a spinel structure (Li ₄ Ti ₅ O ₁₂ ), since the occlusion / release reaction of lithium proceeds at a high potential of about 1.55 V with respect to lithium, the operating voltage of the electricity storage device to which it is applied Becomes lower and the energy density becomes smaller.

  Therefore, as an electrode material in which the occlusion and release reaction of lithium proceeds at a relatively low potential, it has a crystal structure belonging to space group Cmca or space group Fmmm, which contains alkali metal and alkaline earth metal elements as main constituent elements. Lithium titanium composite oxides have attracted attention, and several compositions have been studied as electrode materials.

For example, Patent Document 1 discloses that Li _{2 + x} ATi ₆ O ₁₄ (where A is at least one selected from the group consisting of Na, K, Mg, Ca, Ba, and Sr) having a crystal structure in which the space group is Cmca. T is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, Ta, W, B, Al, Ga, and In. And x is 0 ≦ x ≦ 5), and Li _{2 + x} AT _{i6- y My} O ₁₄ (where A is selected from the group consisting of Na, K, Mg, Ca, Ba, and Sr) M is selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, Ta, W, B, Al, Ga, and In. At least one element, x is ≦ x ≦ 5 and y is 0 <y <6). In the composition formula, A is one or two of Mg, Ca, Ba and Sr, T is Ti, And in the composition formula containing M, M is a part of a kind of composition of Al, V, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, B, Ga, Zr and In. Is specifically disclosed, and it has been shown that a nonaqueous electrolyte battery with improved energy density can be provided.

Further, Patent Document _{2, Li 2 + n1 Na 2} -x1 K x1 Ti 6 O 14 (n1 is 0 ≦ n1 ≦ 2, x1 satisfies _{0 <x1 ≦ 1.2.),} Li 2 + n2 Na 2-x2- _{y2 K x2 Rb y2 Ti 6 O} 14 (n2 is 0 ≦ n2 ≦ 2, x2 and y2 satisfy the 0 ≦ x2 ≦ 1.2,0 <y2 ≦ 0.5 and 0 <5x2 + 12y2 ≦ 6. ), and Li _{2 + n3} Na _2-x3-y3-z3 K _x3 Rb _y3 Cs _z3 Ti ₆ O ₁₄ (n3 is 0 ≦ n3 ≦ 2, x3, y3 and z3 are 0 ≦ x3 ≦ 0.25, 0 ≦ y3 ≦ 0.05, 0 <z3 ≦ 0.05 and 0 <y3 + z3 ≦ 0.05) are described, and a part of the composition containing Na and K as essential elements contained in these compositional formulas is concrete. _disclosed, Li 4 _Ti 5 _{O 1} Substantially the same capacity retention ratio is indicated to be obtained when.

JP 2005-267940 A JP, 2014-103032, A

  However, the conventional lithium titanium composite oxide having a crystal structure belonging to the space group Cmca or the space group Fmmm as described above has poor charge / discharge cycle characteristics at high temperatures, and is excellent in charge / discharge cycle characteristics even in a high temperature environment. This is an important issue for the application to the required electric storage devices for electric vehicles. It is also an important issue to suppress gas generation in a high temperature environment.

  Accordingly, the present invention provides a lithium sodium titanium composite oxide powder that is excellent in charge / discharge cycle characteristics in a high temperature environment and that suppresses gas generation after the charge / discharge cycle in a high temperature environment, and an active material, and uses the same. It is an object of the present invention to provide an electrode sheet and an electricity storage device.

  As a result of studying the above problems, the present inventors have found that a lithium-titanium composite oxide having a crystal structure belonging to the space group Cmca or the space group Fmmm contains Na and further contains a periodic table as an element for substituting the Ti site. Lithium sodium titanium composite oxide powder containing at least one element selected from Al, Ga, In belonging to Group 13 and V, Nb, Ta belonging to Group 5 of the periodic table has a charge / discharge cycle life at high temperature. The present invention was completed by finding that the amount of gas generated after a long charge / discharge cycle under a high temperature environment was small. That is, the present invention relates to the following matters.

(1) has a crystal structure belonging to the space group Cmca or space group Fmmm, the general _{formula: Li 2 + x Na 2 +} y Ti 6-z M z O 14 ( provided that selection, M is Al, Ga, In, V, from Nb and Ta X is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1.) A lithium sodium titanium composite oxide powder for an electrode active material of an electricity storage device, comprising a lithium sodium titanium composite oxide represented by

(2) specific surface area determined by the BET method is ^{1m 2} / ^g~50m 2 / g, by X-ray diffraction, the _Li 2 _Na 2 _Ti 6 _{O 14} having a crystal structure belonging to the space group Cmca or space group Fmmm the crystallite size from the half width is calculated from the Scherrer formula peak in the range of diffraction angle 2 [Theta] = 17.6 to 18.6 ° when the _{D X,} characterized in that _{D X} is 80nm or more The lithium sodium titanium composite oxide powder for an electrode active material of the electricity storage device according to (1).

(3) The ratio D _BET / D _X (μm / μm) of D _BET and D _X is 4 or less when the specific surface area equivalent diameter calculated from the specific surface area is D _BET ( A lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device according to 1) or (2).

  (4) The total pore volume is 0.001 ml / g to 0.5 ml / g, and the lithium sodium titanium composite oxide for electrode active material of the electricity storage device according to any one of (1) to (3) Powder.

(5) Including secondary particles in which primary particles composed of the lithium sodium titanium composite oxide are aggregated, and when the volume median particle size is D50, D50 is 10 μm or more and 35 μm or less, and the ratio of D50 and D _BET D50 / D _BET (μm / μm) is 25 or more and 100 or less, The lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device according to any one of (1) to (4).

  (6) The average compressive strength of the secondary particles is 0.3 MPa or more and 7 MPa or less, and the lithium sodium titanium composite oxide for an electrode active material of an electricity storage device according to any one of (1) to (5) Powder.

  (7) The average circularity of the secondary particles is 80% or more, and the lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device according to any one of (1) to (6).

  (8) An active material containing the lithium sodium titanium composite oxide powder for an electrode of the electricity storage device according to any one of (1) to (7).

  (9) An electrode for an electricity storage device comprising the active material according to (8), at least one conductive agent selected from graphites, carbon blacks, and carbon nanotubes, and a binder. Sheet.

  (10) The electrode sheet for an electricity storage device according to (9), wherein the conductive agent includes at least carbon nanotubes.

  (11) The conductive agent contains at least one conductive agent selected from graphites and carbon blacks in addition to carbon nanotubes, and the proportion of carbon nanotubes in the total conductive agent is 1% by mass or more and 49% by mass. The electrode sheet for an electricity storage device according to (10), wherein:

  (12) The carbon nanotubes are formed by stacking 2 to 30 bell-shaped structural units having a top portion with a closed graphite net surface and a trunk portion with an open lower portion sharing a central axis. A plurality of bell-shaped structural unit aggregates, and the carbon nanotubes are formed by connecting a plurality of bell-shaped structural unit aggregates at intervals in a head-to-tail manner to form fibers. The electrode sheet for an electricity storage device according to any one of (9) to (11), wherein

  (13) An electrical storage device using the electrode sheet according to any one of (9) to (12).

  (14) An electricity storage device including a positive electrode including a material capable of inserting and extracting lithium as an active material, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. And the said negative electrode contains the electrode sheet in any one of (10)-(13), The electrical storage device characterized by the above-mentioned.

  (15) The nonaqueous electrolytic solution is obtained by dissolving an electrolyte salt in a nonaqueous solvent, and ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, and 2,3-butylene are dissolved in the nonaqueous solvent. A ratio of cyclic carbonate having at least one alkylene chain selected from propylene carbonate, 1,2-butylene carbonate and 2,3-butylene carbonate in all cyclic carbonates, including at least one cyclic carbonate selected from carbonates Is 55 volume% or more and 100 volume% or less, The electrical storage device as described in (14) characterized by the above-mentioned.

  (16) The non-aqueous electrolyte is a solution in which an electrolyte salt is dissolved in a non-aqueous solvent, and dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, It contains a chain ester having at least one methyl group selected from methyl propionate, methyl acetate and ethyl acetate, and the content of all chain esters in the non-aqueous solvent is 60% by volume or more and 90% by volume or less. The electrical storage device according to (14) or (15), which is characterized.

(17) The non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent, and includes at least LiPF ₆ as the electrolyte salt in the non-aqueous electrolyte, and further includes LiBF ₄ , LiPO ₂ F ₂ and The electrical storage according to any one of (14) to (16), wherein at least one lithium salt selected from LiN (SO ₂ F) ₂ is contained in the non-aqueous electrolyte at a concentration of 0.001M to 1M. device.

  (18) The electricity storage device according to any one of (13) to (17) is a lithium ion secondary battery, and a charging potential in a fully charged state of the negative electrode of the lithium ion secondary battery is 1 with respect to a lithium reference electrode. A lithium ion secondary battery having a voltage of 0.05 V or higher.

  (19) The lithium ion secondary battery according to (18), wherein a discharge potential of the negative electrode in a fully discharged state is 1.8 V or less with respect to a lithium reference electrode.

  (20) The lithium ion secondary battery according to (18) or (19), wherein the active material contained in the positive electrode is a composite metal oxide having a spinel structure.

  (21) The lithium ion secondary battery according to (20), wherein the composite metal oxide contains manganese.

(22) The lithium ion secondary battery according to (21), wherein the composite metal oxide is LiMn ₂ O ₄ or LiNi _0.5 Mn _1.5 O ₄ .

  According to the present invention, when applied as an electrode material for an electricity storage device, the charge / discharge cycle life at high temperatures is long, that is, the discharge capacity retention rate after charge / discharge cycles at high temperatures is large, and the gas after charge / discharge cycles It is possible to provide a lithium sodium titanium composite oxide powder with a small amount of generation, an active material containing the same, and an electricity storage device using the active material.

FIG. 1 is a diagram showing an X-ray diffraction pattern of Li ₂ Na ₂ Ti ₆ O _{14 in} the space group Cmca. FIG. 2 is a diagram showing an X-ray diffraction pattern of Li ₂ Na ₂ Ti ₆ O _{14 in} the space group Fmmm.

The lithium sodium titanium composite oxide of the present invention has a general structure: Li _{2 + x} Na _{2 + y} Ti _6-z M _z O ₁₄ (where M is Al, Ga, In , V, Nb, and Ta, x is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <Z ≦ 1.) A lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device, the main phase being a lithium sodium titanium composite oxide represented by: That is, the lithium sodium titanium composite oxide of the present invention is a lithium titanium composite oxide having a crystal structure belonging to space group Cmca or space group Fmmm, and contains substantially only Na as an alkali metal other than Li. In addition, a part of the Ti site is substituted with at least one element selected from Al, Ga, In, V, Nb, and Ta.

Here, the general formula: Li _{2 + x} Na _{2 + y} Ti _6-z M _z O ₁₄ (where M is selected from Al, Ga, In, V, Nb, and Ta) having a crystal structure belonging to the space group Cmca or the space group Fmmm X is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1.) Is a general formula: Li _{2 + x} Na _{2 + y} having a crystal structure belonging to the space group Cmca or the space group Fmmm among the peaks measured by the X-ray diffraction method. Ti _6-z M _z O ₁₄ (where M is at least one element selected from Al, Ga, In, V, Nb and Ta, x is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0 Is 1, z is 0 <z ≦ 1.) Shows an X-ray diffraction pattern similar to the diffraction angle 2θ of _Li 2 _Na 2 _Ti 6 _{O 14} having a crystal structure belonging to the space group Cmca or space group Fmmm When the diffraction intensity of the peak corresponding to the peak in the range of = 17.6 to 18.6 ° is defined as 100, the total of the main peak intensities of the other phases detected is 5 or less. The general formula: Li _{2 + x} Na _{2 + y} Ti _6-z M _z O ₁₄ (wherein M is selected from Al, Ga, In, V, Nb and Ta) having a crystal structure belonging to the space group Cmca or the space group Fmmm. X is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1. When the component is smaller, the initial discharge capacity of the electricity storage device tends to be higher. Therefore, the other phases are preferably small, and the total of the main peak intensities of the detected other phases is particularly preferably 3 or less.

Further, the general formula: Li _{2 + x} Na _{2 + y} Ti _6-z M _z O ₁₄ (where M is at least one element selected from Al, Ga, In, V, Nb and Ta, and x is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1, and the lithium sodium titanium composite oxide represented by orthorhombic crystal As the X-ray diffraction pattern, there are two types of card data, an X-ray diffraction pattern that is very similar to the case where the space group is Cmca and the case where the space group is Fmmm. 1, the X-ray diffraction pattern of _Li 2 _Na 2 _Ti 6 _{O 14} of the space group Cmca, Figure 2, the X-ray diffraction pattern of _Li 2 _Na 2 _Ti 6 _{O 14} of the space group Fmmm, respectively. As shown in FIG. 1 and FIG. 2, in any X-ray diffraction pattern, peaks with markedly large intensities are observed near 2θ = 18 ° and 2θ = 45 °. Can also be called the main peak. Therefore, in the present invention, of these two peaks, a peak around 2θ = 18 ° (2θ = 17.6 to 18.6 °) is treated as a main peak, and the relative intensity when the intensity of this peak is 100 is used. As a value, the intensity of the main peak of another crystal phase including anatase type titanium dioxide and rutile type titanium dioxide Li ₂ TiO ₃ is calculated.

Furthermore, as shown in FIGS. 1 and 2, since the X-ray diffraction pattern very similar between the case where the space group is Cmca and the case where the space group is Fmmm is given, the general formula: Li _{2 + x according} to the present invention is given. Na _{2 + y} Ti _6-z M _z O ₁₄ (where M is at least one element selected from Al, Ga, In, V, Nb and Ta, and x is −0.1 ≦ x ≦ 0.1) And y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1.) From the X-ray diffraction pattern, the lithium sodium titanium composite oxide represented by It may not always be possible to clearly define whether it belongs to Cmca or the space group Fmmm. Furthermore, according to the knowledge of the present inventors, the operational effects of the present invention are sufficiently exerted both in the case where it can be determined that it belongs to the space group Cmca and in the case where it can be determined that it belongs to the space group Fmmm. . Therefore, in the present invention, the general formula: Li _{2 + x} Na _{2 + y} Ti _6-z M _z O ₁₄ (where M is at least one element selected from Al, Ga, In, V, Nb and Ta, and x Is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1.) Any of those belonging to the space group Cmca and those belonging to the space group Fmmm can be used.

  M in the general formula is at least one element selected from Al, Ga, In, V, Nb, and Ta. From the viewpoint of improving the discharge capacity retention rate after a charge / discharge cycle at high temperature, Al or Nb is Nb is preferable and Nb is particularly preferable.

  Further, x in the general formula is −0.1 ≦ x ≦ 0.1. When x is within this range, the discharge capacity retention rate after the charge / discharge cycle at a high temperature is large, and the amount of gas generated is small. The upper limit of x in the general formula is preferably 0.08 from the viewpoint of maximizing the utilization efficiency of lithium ions of the lithium sodium titanium composite oxide and improving the discharge capacity retention rate after the charge / discharge cycle at a high temperature, More preferably, it is 0.06, Most preferably, it is 0.04. From the same viewpoint, the lower limit of x in the general formula is preferably -0.08, more preferably -0.06, and particularly preferably -0.04.

  In the above general formula, y is −0.1 ≦ y ≦ 0.1. If y is this range, the discharge capacity maintenance factor after the charge / discharge cycle at a high temperature is large, and the amount of gas generated is small. The upper limit of y is preferably 0.08, more preferably 0.06, from the viewpoint of stabilizing the crystal structure of the lithium sodium titanium composite oxide and improving the discharge capacity retention rate after the charge / discharge cycle at high temperature. Yes, most preferably 0.04. From the same viewpoint, the lower limit of y is preferably -0.08, more preferably -0.06, and most preferably -0.04.

  Moreover, z in the said general formula is 0 <z <= 1. If z is in this range, the discharge capacity retention rate after the charge / discharge cycle at a high temperature is large, and the amount of gas generated is small. The upper limit of z is preferably 0.7, more preferably 0.4, from the viewpoint of enhancing the electronic conductivity of the lithium sodium titanium composite oxide and improving the discharge capacity retention rate after the charge / discharge cycle at a high temperature. Particularly preferably 0.2. From the same viewpoint, the lower limit of z is preferably 0.001, more preferably 0.01, and particularly preferably 0.05.

<Specific surface area>
The specific surface area of the lithium sodium titanium composite oxide powder of the present invention as determined by the BET method is ^{1m 2} / ^g~50m 2 / g. When the specific surface area is in this range, high input / output characteristics can be realized without impairing the handlinability of the powder. Preferably ^{2m 2} / ^g~45m 2 / g from the above ^viewpoints, 3m ² / ^g~40m 2 / g is particularly preferred.

<Specific surface area equivalent diameter D _BET >
The specific surface area equivalent diameter D _BET of the lithium sodium titanium composite oxide powder of the present invention is a specific surface area equivalent diameter calculated from the specific surface area determined by the BET method. The specific surface area equivalent diameter D _BET of the lithium sodium titanium composite oxide powder of the present invention is preferably 0.03 μm to 0.6 μm. When D _BET is 0.03 μm to 0.6 μm, the charge / discharge capacity of the electricity storage device can be increased. Moreover, it is especially preferable that D _BET is 0.03 to 0.4 μm, and if it is within this range, the input characteristics of the electricity storage device are also improved.

<Crystallite diameter D _X >
In the present invention, the peak (Li) of diffraction angle 2θ = 17.6 to 18.6 ° of Li ₂ Na ₂ Ti ₆ O ₁₄ having a crystal structure belonging to space group Cmca or space group Fmmm, as determined by X-ray diffraction. when the crystal structure of ₂ Na ₂ Ti ₆ O ₁₄ is to belong to the space group Cmca, and the crystallite diameter _{D X} of from the half value width is calculated from the Scherrer formula of (111) peak corresponding to surface). D _X of lithium sodium titanium composite oxide powder of the present invention is preferably 80nm or more. When D _X is at 80nm or more, it is possible to minimize the effects of resistance when the lithium ions move grain boundary, deterioration in battery performance due to polarization increases caused by the grain boundaries lithium ion moves Can be suppressed. The _{D X} is preferably at 500nm or less. D _X it is possible to minimize the influence of diffusion resistance inside the particles as long as 500nm or less, it is possible to suppress the deterioration of the cell performance due to polarization increases caused by the internal particles of lithium ions to move. A method for measuring the D _X, described in detail in Example.

<D _BET / D _X (μm / μm)>
The ratio D _BET / D _X (μm / μm) of D _BET and D _X of the lithium sodium titanium composite oxide powder of the present invention is preferably 4 or less, more preferably 3 or less, and 2.5 or less. It is more preferable that it is 2 or less. The smaller D _BET / D _X is, the better the input / output characteristics of the electricity storage device to which the lithium sodium titanium composite oxide powder of the present invention is applied as the electrode material.

<Total pore volume>
The total pore volume of the lithium sodium titanium composite oxide powder of the present invention is preferably 0.001 ml / g to 0.5 ml / g. When the total pore volume of the lithium sodium titanium composite oxide powder of the present invention is within this range, the discharge capacity retention rate after a charge / discharge cycle at a high temperature becomes higher when applied to an electricity storage device. The total pore volume is preferably 0.005 ml / g or more, more preferably 0.01 ml / g or more, from the viewpoint of further improving the discharge capacity maintenance rate after the charge / discharge cycle at a high temperature, Particularly preferred is 0.015 ml / g or more. From the same viewpoint, it is preferably 0.45 ml / g or less, more preferably 0.4 ml / g or less, and particularly preferably 0.35 ml / g or less. The total pore volume of the lithium sodium titanium composite oxide powder of the present invention is the total pore volume measured by a gas adsorption method.

<Volume Median Particle Size D50>
The volume-median particle size (average particle size, hereinafter referred to as D50) of the lithium sodium titanium composite oxide powder of the present invention is preferably 0.01 μm or more and 35 μm or less, and more preferably 10 μm or more and 35 μm or less. It is particularly preferably 20 μm or more and 30 μm or less. Here, D50 means a particle size in which the cumulative volume frequency calculated by the volume fraction is 50% when integrated from the smaller particle size. The measurement method is described in [5. Particle size distribution].

<D50 / D _BET (μm / μm)>
The ratio D50 / D _BET (μm / μm) of D50 and D _BET of the lithium sodium titanium composite oxide powder of the present invention is preferably 25 or more and 100 or less. If D50 / D _BET is within this range, the discharge capacity retention rate after the high-temperature cycle of the electricity storage device to which the lithium sodium titanium composite oxide powder of the present invention is applied as an electrode material is further large, and the amount of gas generated at high temperature is further increased. Few. In addition, it is preferable that the lithium sodium titanium composite oxide powder of the present invention includes secondary particles formed by aggregating primary particles made of lithium sodium titanium composite oxide, and D50 / D _BET (μm / μm) is This is an index related to the degree of aggregation of primary particles with respect to secondary particles. D50 / D _BET (μm / μm) is more preferably 25 or more and 28 or more from the viewpoint of increasing the discharge capacity maintenance rate after the high temperature cycle of the electricity storage device and reducing the amount of gas generated at high temperature. More preferably, it is more preferably 30 or more. Further, from the viewpoint of increasing the discharge capacity maintenance rate after the high temperature cycle of the electricity storage device and reducing the amount of gas generated at high temperature, D50 / D _BET (μm / μm) is more preferably 100 or less, 80 Or less, more preferably 60 or less.

<Average compressive strength of secondary particles>
When the lithium sodium titanium composite oxide powder of the present invention contains secondary particles, the average compressive strength of the secondary particles is preferably 0.3 MPa or more and 7 MPa or less. If the average compressive strength of the secondary particles of the lithium sodium titanium composite oxide powder of the present invention is in this range, the discharge after the high-temperature cycle of the electricity storage device to which the lithium sodium titanium composite oxide powder of the present invention is applied as an electrode material The capacity maintenance rate is further increased. From the viewpoint of increasing the discharge capacity retention rate after the high temperature cycle of the electricity storage device, the average compressive strength of the secondary particles is more preferably 0.4 MPa or more, further preferably 1 MPa or more, and 1.2 MPa. The above is particularly preferable. Further, from the viewpoint of increasing the discharge capacity maintenance rate after the high-temperature cycle of the electricity storage device and reducing the amount of gas generation at high temperature, the average compressive strength of the secondary particles is more preferably 6.2 MPa or less. More preferably, it is more preferably 4.2 MPa or less. The method for measuring the average compressive strength of the secondary particles is described in [7. The average compressive strength of the secondary particles] will be described.

<Average circularity of secondary particles>
When the lithium sodium titanium composite oxide powder of the present invention contains secondary particles, the average circularity of the secondary particles is preferably 80% or more. If the average circularity of the secondary particles of the lithium sodium titanium composite oxide powder of the present invention is within this range, the discharge after the high-temperature cycle of the electricity storage device to which the lithium sodium titanium composite oxide powder of the present invention is applied as an electrode material The capacity maintenance rate is further increased. From the viewpoint of further increasing the discharge capacity retention rate after the high-temperature cycle of the electricity storage device, the average circularity of the secondary particles is more preferably 90% or more, further preferably 94% or more, and 95% or more. It is particularly preferred that The method for measuring the average circularity is described in [8. The average circularity of the secondary particles] will be described.

(Method for producing lithium sodium titanium composite oxide powder)
Hereinafter, an example of a method for producing the lithium sodium titanium composite oxide powder of the present invention will be described by dividing it into a raw material preparation step and a firing step. It is not limited.

<Raw material preparation process>
As raw materials for the lithium sodium titanium composite oxide powder of the present invention, a titanium raw material, a lithium raw material, a sodium raw material, and a raw material of M in the above general formula, that is, a raw material of an element that substitutes a part of the titanium site are used. As the titanium raw material, titanium compounds such as anatase type titanium dioxide and rutile type titanium dioxide are used. As a titanium raw material, it is preferable that it reacts easily with a lithium raw material in a short time, and the anatase type titanium dioxide is preferable from the viewpoint. In particular, complete anatase-type titanium dioxide having a rutile ratio of 0% is preferable.

  As the lithium raw material, lithium compounds such as lithium hydroxide monohydrate, lithium oxide, lithium hydrogen carbonate, and lithium carbonate are used, and lithium hydroxide monohydrate and lithium carbonate are preferable.

  As the sodium raw material, sodium compounds such as sodium hydroxide monohydrate, sodium oxide, sodium hydrogen carbonate and sodium carbonate are used, and sodium hydroxide monohydrate and sodium carbonate are preferred.

  As the raw material of M in the above general formula, that is, the raw material of the element substituting a part of the titanium site, the oxide of M, hydroxide, nitride, phosphide, sulfide, fluoride, chloride, bromide, iodine Or inorganic salts such as carbonates, sulfates, nitrates, borates and phosphates, and organic salts such as acetates. From the viewpoint of ease of synthesis, oxides, fluorides, sulfates, and acetates are preferable.

In the present invention, before firing the mixture composed of the above raw materials, the particle size distribution curve measured by a laser diffraction / scattering type particle size distribution measuring machine of the mixed powder constituting the mixture is such that D95 is 4 μm or less. It is preferable to prepare. The D95 is to increase the _{D X,} reducing the _{D BET / D X (μm /} μm), from the viewpoint of increasing the total pore volume, more preferably 3μm or less, more preferably 2μm or less, Particularly preferably, it is 1.5 μm or less. Here, D95 is a particle size in which the cumulative volume frequency calculated by the volume fraction is 95% when integrated from the smaller particle size. The mixture may be a mixed powder prepared as described above, or a granulated powder obtained by granulating the mixed powder prepared as described above. Moreover, it is good also considering the state of the mixture used for baking as the slurry form containing the above mixed powder or granulated powder. When the mixture is a granulated powder, the D95 of the granulated powder is not necessarily 4 μm or less, and is preferably a granulated powder obtained by granulating a mixed powder having a D95 of 4 μm or less.

  The titanium raw material, the lithium raw material, the sodium raw material, and the raw material of M in the above general formula, that is, the raw material of the element that substitutes a part of the titanium site are mixed. As a method for preparing a mixture of these raw materials, the following methods can be employed. The first method is a method in which the raw materials are mixed and then pulverized simultaneously with mixing. The second method is a method in which each raw material is pulverized and then mixed or mixed while lightly pulverizing. The third method is a method in which powders made of fine particles are produced from each raw material by a method such as crystallization, classified as necessary, and mixed while mixing or lightly pulverizing. Among them, in the first method, the method of pulverizing simultaneously with the mixing of the raw materials is an industrially advantageous method because it involves fewer steps.

  When the obtained mixture is a mixed powder, it can be directly used for the next firing step. In the case of a mixed slurry made of a mixed powder, the mixed slurry can be granulated and dried with a spray dryer or the like and then subjected to the next firing step.

[Baking process]
The resulting mixture is then fired. There are no particular restrictions on the firing conditions, but usually the mixture is fired at a maximum temperature (holding temperature) of 800 to 1100 ° C. and a holding time of 0.5 to 25 hours at the maximum temperature. From the viewpoint of reducing the particle size of the obtained lithium sodium titanium composite oxide powder and increasing the crystallite size, it is preferable to fire at a high temperature for a short time, and in that case, the maximum temperature during firing is 850 to 1100 ° C. The holding time at the maximum temperature during firing is preferably 12 hours or less. The maximum temperature during firing is more preferably 880 ° C., and the holding time at the maximum temperature is more preferably 10 hours or less, and particularly preferably 8 hours or less. When the maximum temperature during firing is high, a shorter holding time is selected. Similarly, from the viewpoint of reducing the particle size of the obtained lithium sodium titanium composite oxide powder and increasing the crystallite size, the residence time from 700 ° C. to the maximum temperature (holding temperature) is set in the heating process during firing. In particular, it is preferable to shorten the temperature, for example, it is preferable to set the temperature rising rate to 200 ° C./h or more.

  The firing method is not particularly limited as long as it can be fired under such conditions. Examples of the firing furnace that can be used include a fixed-bed firing furnace such as a box furnace (muffle furnace) and a tubular furnace, a roller hearth firing furnace, a mesh belt firing furnace, a fluidized bed firing furnace, and a rotary kiln firing furnace. When using a roller hearth-type firing furnace or a mesh belt-type firing furnace that contains the powder in a sagger and fires, in order to make the quality of the obtained lithium sodium titanium composite oxide powder constant, It is preferable to make the temperature distribution uniform, and it is preferable to reduce the amount of powder contained in the mortar. Although the atmosphere at the time of baking is not specifically limited, It is preferable that it is an atmosphere containing oxygen.

[Post-processing process]
In the present invention, the lithium sodium titanium composite oxide powder obtained in the firing step can be used as an active material as it is, but the powder obtained by granulating or further granulating the powder is used. It can also be used as an active material after post-treatment such as heat treatment. For example, the lithium sodium titanium composite oxide powder obtained in the firing step may be slurried using a dispersion medium such as water, and the resulting slurry may be granulated and dried by a spray dryer or the like. -You may heat-process the powder after drying. By adding such a post-treatment step, it is easy to adjust D50 / D _BET (μm / μm), average compressive strength of secondary particles, average circularity of secondary particles, and the like. For example, in order to obtain a lithium sodium titanium composite oxide powder having an average compressive strength of secondary particles of 1 MPa or more and 5 MPa or less, the lithium sodium titanium composite oxide powder obtained in the firing step is slurried and sprayed with a spray dryer or the like. After granulation and drying, heat treatment is preferably performed in a temperature range of 400 ° C to 650 ° C.

(Active material)
The active material of the present invention contains the lithium sodium titanium composite oxide powder of the present invention. One or more substances other than the lithium sodium titanium composite oxide powder of the present invention may be contained. Examples of other substances include carbon materials (pyrolytic carbons, cokes, graphites (artificial graphite, natural graphite, etc.), organic polymer compound combustion bodies, carbon fibers), tin and tin compounds, silicon and silicon compounds. Is used.

(Electrode sheet)
The electrode sheet of the present invention comprises, as an electrode mixture layer on one or both sides of a current collector, an active material of the present invention, and at least one conductive agent selected from graphites, carbon blacks, and carbon nanotubes. The electrode sheet for an electricity storage device including a binder, and is cut according to the design shape of the electricity storage device and used as a negative electrode. Examples of graphites include natural graphite (such as flake graphite), artificial graphite, and the like. Examples of carbon blacks include acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and the like. Carbon nanotubes include single-phase carbon nanotubes, multi-wall carbon nanotubes (graphite layers are multi-layer concentric cylinders) (non-fishbones), cup-stacked carbon nanotubes (fishbones), and nodal carbon nanofibers (Non-fishbone structure), platelet-type carbon nanofibers (like a playing card), and the like. These graphites, carbon blacks, and carbon nanotubes may be appropriately mixed and used. There is no particular limitation, specific surface area of the carbon blacks is preferably 30~3000m ² / g, more preferably from 50~2000m ² / g. The specific surface area of the graphite is preferably 30 to 600 m ² / g, more preferably 50 to 500 m ² / g. The aspect ratio of the carbon nanotubes is preferably 10 to 1000. With such a conductive agent, the electrode density is particularly likely to increase, and the capacity can be easily increased. The addition amount of the conductive agent is optimized depending on the specific surface area of the active material and the type and combination of the conductive agent, but is preferably 10% by mass or less, more preferably 8% by mass with respect to the entire electrode mixture layer. Or less, more preferably 6% by mass or less.

  The electrode sheet of the present invention preferably contains carbon nanotubes as the conductive agent. If carbon nanotubes are included as a conductive agent, the discharge capacity retention rate after a charge / discharge cycle at a high temperature is further increased. Among the carbon nanotubes, multi-walled carbon nanotubes (graphite layers are multi-layer concentric cylinders) (non-fish-bone-like) are preferable. In particular, a head with a closed graphite network surface described in JP 2012-46864 A or the like is used. A bell-shaped structural unit having a top portion and a body portion having an open bottom includes a plurality of bell-shaped structural unit assemblies formed by stacking 2 to 30 layers sharing a central axis, and a plurality of the bell-shaped structural units. Particularly preferred is fibrous carbon in which bell-shaped structural unit aggregates are connected in a head-to-tail manner at intervals to form fibers. If this fibrous carbon is contained as a conductive agent, the discharge capacity maintenance rate after a charge / discharge cycle at a high temperature is particularly increased.

  Furthermore, the electrode sheet of the present invention preferably contains at least one conductive agent selected from graphites and carbon blacks in addition to containing carbon nanotubes as the conductive agent. The proportion of the carbon nanotubes in it is preferably 1% by mass or more and 49% by mass or less, and more preferably 5% by mass or more and 40% by mass or less.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), a copolymer of styrene and butadiene (SBR), and a copolymer of acrylonitrile and butadiene (NBR). ), Carboxymethylcellulose (CMC) and the like. Although not particularly limited, the molecular weight of polyvinylidene fluoride is preferably 20,000 to 200,000. From the viewpoint of securing the binding property of the electrode mixture layer, it is preferably 25,000 or more, more preferably 30,000 or more, and further preferably 50,000 or more. From the viewpoint of ensuring conductivity, it is preferably 150,000 or less. In particular, when the specific surface area of the active material is 10 m ² / g or more, the molecular weight is preferably 100,000 or more.

  The amount of the binder added is optimized depending on the specific surface area of the active material and the type and combination of the conductive agent, but is usually 0.2 to 15% by mass with respect to the entire electrode mixture layer. . From the viewpoint of enhancing the binding property and increasing the strength of the mixture layer, the content is more preferably 0.5% by mass or more, further preferably 1% by mass or more, and particularly preferably 2% by mass or more. From the viewpoint of increasing the active material ratio in the mixture layer and increasing the discharge capacity of the electricity storage device per unit mass and unit volume of the mixture layer, the addition amount of the binder is preferably 10% by mass or less, More preferably, it is 5 mass% or less.

  Examples of the current collector include aluminum, stainless steel, nickel, copper, titanium, baked carbon, and those whose surfaces are coated with carbon, nickel, titanium, and silver. Moreover, the surface of these materials may be oxidized, and unevenness | corrugation may be given to the collector surface by surface treatment. Examples of the shape of the current collector include a sheet, a net, a foil, a film, a punched one, a lath body, a porous body, a foamed body, a fiber group, and a nonwoven fabric molded body.

  The electrode sheet is prepared by adding a solvent to the active material, conductive agent and binder of the present invention, mixing and kneading them, adjusting the viscosity while adding the solvent, and forming a paint. It can be obtained by coating on top, drying and compressing.

  A method for mixing the active material of the present invention, the conductive agent, and the binder in the solvent is not particularly limited, but the active material of the present invention, the conductive agent, and the binder are simultaneously mixed in the solvent. The method of mixing in the method, the method of mixing the conductive material and the binder in a solvent in advance, and then the additional mixing of the active material of the present invention, the slurry of the active material of the present invention, the conductive agent slurry and the binder solution in advance The method of producing and mixing each is mentioned. In order to make these electrode mixture layer constituent materials uniformly disperse in the mixture layer, a method in which the conductive material and the binder are previously mixed in a solvent and then the active material is additionally mixed, and the negative electrode active material slurry, A method of preparing a conductive agent slurry and a binder solution in advance and mixing them is preferable.

  As the solvent, water or an organic solvent can be used. Examples of the organic solvent include aprotic organic solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide, or a mixture of two or more kinds, preferably N-methylpyrrolidone.

  When water is used as the solvent, the binder is preferably added at the stage of finally adjusting to a desired viscosity in order not to cause the binder to aggregate. When aluminum is used as the negative electrode current collector, it is preferable to adjust pH by adding an acidic compound in order to suppress corrosion of aluminum. As the acidic compound, either an inorganic acid or an organic acid can be used. As the inorganic acid, phosphoric acid, boric acid and oxalic acid are preferable, and oxalic acid is more preferable. The organic acid is preferably an organic carboxylic acid. Further, as a method for preventing corrosion of aluminum, it is preferable to use an aluminum current collector in which the surface of the aluminum current collector is coated with an alkali-resistant material such as carbon. In the case of using an organic solvent as the solvent, it is preferable to use the binder by dissolving it in an organic solvent in advance.

  As an apparatus for mixing and kneading by adding a solvent to the active material, the conductive agent and the binder of the present invention, for example, a kneader of a type in which a stirring bar rotates while rotating in a kneading container such as a planetary mixer In addition, a twin-screw extrusion kneader, a planetary stirring and defoaming device, a bead mill, a high-speed swirling mixer, a powder suction continuous dissolution and dispersion device, and the like can be used. In addition, it is preferable to start mixing and kneading in a state where the solid content concentration is high, and adjust the viscosity of the coating material by gradually reducing the solid content concentration. It is preferable to use the mixing / kneading apparatus properly. The solid content concentration at the stage of starting mixing and kneading is preferably 60 to 90% by mass, and more preferably 70 to 90% by mass. If the solid content concentration is 60% by mass or more, sufficient shearing force can be obtained to uniformly disperse the active material of the present invention, the binder, and the conductive agent, and if it is 90% by mass or less, It is possible to avoid applying an extremely large load to the device.

(Electric storage device)
The power storage device of the present invention is a power storage device using the electrode sheet of the present invention, and stores and releases energy using intercalation and deintercalation of lithium ions to the electrode containing the active material. For example, it is a hybrid capacitor or a lithium battery. As an electricity storage device of the present invention, a positive electrode containing a material capable of occluding and releasing lithium as an active material, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte solution, It is an electrical storage device containing, Comprising: It is preferable that the said negative electrode contains the electrode sheet of this invention.

[Hybrid capacitor]
As the hybrid capacitor, active adsorption and intercalation such as active material whose capacity is formed by the physical adsorption similar to the electrode material of the electric double layer capacitor, such as activated carbon, or graphite, on the positive electrode, This is a device that uses an active material in which capacitance is formed by deintercalation, or an active material in which capacitance is formed by redox, such as a conductive polymer, and uses the active material of the present invention for the negative electrode.

[Lithium battery]
The lithium battery of the present invention is a generic term for a lithium primary battery and a lithium secondary battery. In this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.

  The lithium battery includes a positive electrode, a negative electrode, a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, and the like. Below, the structure of the positive electrode which comprises the lithium battery of this invention, a non-aqueous electrolyte, and a lithium battery is demonstrated.

<Positive electrode>
The positive electrode has a mixture layer containing a positive electrode active material, a conductive agent, and a binder on one or both surfaces of the positive electrode current collector.

As the positive electrode active material, a material capable of inserting and extracting lithium is used. For example, as the active material, a composite metal oxide with lithium containing cobalt, manganese, nickel, lithium-containing olivine-type phosphate, or the like These positive electrode active materials can be used singly or in combination of two or more. Examples of such composite metal oxides include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x <1), LiCo _1/3 Ni _1/3 Mn. _1/3 O ₂ , LiNi _1/2 Mn _3/2 O _{4 and the} like. A part of these lithium composite oxides may be substituted with other elements, and a part of cobalt, manganese, nickel may be replaced with Sn. , Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, La, etc., or a part of O is replaced with S or F Or it can coat | cover with the compound containing these other elements. Examples of the lithium-containing olivine-type phosphate include LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO ₄ , LiFe _1-x M _x PO ₄ (M is selected from Co, Ni, Mn, Cu, Zn, and Cd). At least one, and x is 0 ≦ x ≦ 0.5.

  Examples of the conductive agent and binder for the positive electrode include the same as those for the negative electrode. Examples of the positive electrode current collector include aluminum, stainless steel, nickel, titanium, calcined carbon, and aluminum or stainless steel having a surface treated with carbon, nickel, titanium, or silver. The surface of these materials may be oxidized, and the surface of the positive electrode current collector may be uneven by surface treatment. Examples of the shape of the current collector include a sheet, a net, a foil, a film, a punched one, a lath body, a porous body, a foamed body, a fiber group, and a nonwoven fabric molded body.

<Non-aqueous electrolyte>
The nonaqueous electrolytic solution is obtained by dissolving an electrolyte salt in a nonaqueous solvent. There is no restriction | limiting in particular in this non-aqueous electrolyte, A various thing can be used.

As the electrolyte salt, one that dissolves in a non-aqueous electrolyte is used. For example, an inorganic lithium salt such as LiPF ₆ , LiBF ₄ , LiPO ₂ F ₂ , LiN (SO ₂ F) ₂ , LiClO _4, or LiN (SO _{2). CF 3) 2, LiN (SO} 2 C 2 F 5) 2, LiCF 3 SO 3, LiC (SO 2 CF 3) 3, LiPF 4 (CF 3) 2, LiPF 3 (C 2 F 5) 3, LiPF 3 Lithium salts containing a chain-like fluorinated alkyl group such as (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso-C ₃ F ₇ ), and (CF ₂ ) ₂ ( SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi and other lithium salts containing cyclic fluorinated alkylene chains, bis [oxalate-O, O ′] lithium borate and diflu Examples thereof include lithium salts using an oxalate complex such as oro [oxalate-O, O ′] lithium borate as an anion. Among these, particularly preferable electrolyte salts are LiPF ₆ , LiBF ₄ , LiPO ₂ F ₂ , and LiN (SO ₂ F) ₂ , and the most preferable electrolyte salt is LiPF ₆ . These electrolyte salts can be used singly or in combination of two or more. As the preferred combination of these electrolyte salts include LiPF _6, further LiBF _4, LiPO ₂ F _2, and LiN _(SO 2 _F) at least one lithium salt selected from ₂ nonaqueous solution Is preferable.

  The concentration used by dissolving all the electrolyte salts is usually preferably 0.3 M or more, more preferably 0.5 M or more, and even more preferably 0.7 M or more with respect to the non-aqueous solvent. Moreover, the upper limit is preferably 2.5 M or less, more preferably 2.0 M or less, and even more preferably 1.5 M or less.

  On the other hand, examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, chain esters, ethers, amides, phosphate esters, sulfones, lactones, nitriles, S═O bond-containing compounds, and the like, including cyclic carbonates. Is preferred. The term “chain ester” is used as a concept including a chain carbonate and a chain carboxylic acid ester.

  Examples of the cyclic carbonate include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, and 2,3-butylene carbonate. Ethylene carbonate, propylene carbonate, 1, One or more selected from 2-butylene carbonate and 2,3-butylene carbonate are more preferable from the viewpoint of improving the 50C charge rate characteristics and reducing the amount of gas generated during high-temperature storage. Propylene carbonate, 1,2- One or more cyclic carbonates having an alkylene chain selected from butylene carbonate and 2,3-butylene carbonate are more preferred. The ratio of the cyclic carbonate having an alkylene chain in the total cyclic carbonate is preferably 55% by volume to 100% by volume, and more preferably 60% by volume to 90% by volume.

Therefore, as the non-aqueous electrolyte, a non-aqueous solvent containing one or more cyclic carbonates selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, and 2,3-butylene carbonate, LiPF ₆ , LiBF ₄ , It is preferable to use a nonaqueous electrolytic solution in which an electrolyte salt containing at least one lithium salt selected from LiPO ₂ F ₂ and LiN (SO ₂ F) ₂ is used. As the cyclic carbonate, propylene carbonate, 1, One or more cyclic carbonates having an alkylene chain selected from 2-butylene carbonate and 2,3-butylene carbonate are more preferred.

In particular, the concentration of the total electrolyte salt is 0.5 M or more and 2.0 M or less, and the electrolyte salt includes at least LiPF ₆ and further 0.001 M or more and 1 M or less of LiBF ₄ , LiPO ₂ F ₂ , and LiN. It is preferable to use a nonaqueous electrolytic solution containing at least one lithium salt selected from (SO ₂ F) ₂ . When the proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is 0.001 M or more, the effect of improving the charge / discharge cycle characteristics of the electricity storage device in a high-temperature environment and the reduction of gas generation after the charge / discharge cycle It is preferable that the effect is easily exhibited, and that it is 1.0 M or less because there is little concern that the effect of improving the charge / discharge cycle characteristics under a high temperature environment and the effect of reducing the amount of gas generated after the charge / discharge cycle are reduced. The proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is preferably 0.01 M or more, particularly preferably 0.03 M or more, and most preferably 0.04 M or more. The upper limit is preferably 0.8M or less, more preferably 0.6M or less, and particularly preferably 0.4M or less.

  The non-aqueous solvent is preferably used as a mixture in order to achieve appropriate physical properties. The combination includes, for example, a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate, a chain carbonate and a lactone, a combination of a cyclic carbonate, a chain carbonate and an ether, a cyclic carbonate, a chain carbonate and a chain ester. Combinations, combinations of cyclic carbonates, chain carbonates, and nitriles, combinations of cyclic carbonates, chain carbonates, and S═O bond-containing compounds are included.

  As the chain ester, one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate, One or more symmetrical linear carbonates selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate, pivalate esters such as methyl pivalate, ethyl pivalate, and propyl pivalate Preferable examples include one or more chain carboxylic acid esters selected from methyl propionate, ethyl propionate, propyl propionate, methyl acetate, and ethyl acetate (EA).

  Among the chain esters, chain esters having a methyl group selected from dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate, methyl acetate and ethyl acetate (EA) are preferable. In particular, a chain carbonate having a methyl group is preferred.

  Moreover, when using chain carbonate, it is preferable to use 2 or more types. Further, it is more preferable that both a symmetric chain carbonate and an asymmetric chain carbonate are contained, and it is further more preferable that the content of the symmetric chain carbonate is more than that of the asymmetric chain carbonate.

  The content of the chain ester is not particularly limited, but it is preferably used in the range of 60 to 90% by volume with respect to the total volume of the nonaqueous solvent. When the content is 60% by volume or more, the viscosity of the non-aqueous electrolyte does not become too high, and when the content is 90% by volume or less, the electrical conductivity of the non-aqueous electrolyte is decreased. The above range is preferable because there is little possibility that the effect of improving the discharge cycle characteristics and the effect of reducing the amount of gas generated after the charge / discharge cycle are reduced.

  The volume ratio of the symmetric chain carbonate in the chain carbonate is preferably 51% by volume or more, and more preferably 55% by volume or more. The upper limit is more preferably 95% by volume or less, and still more preferably 85% by volume or less. It is particularly preferred that the symmetric chain carbonate contains dimethyl carbonate. The asymmetric chain carbonate preferably has a methyl group, and methyl ethyl carbonate is particularly preferable. In the above case, it is preferable because the effect of improving the charge / discharge cycle characteristics under a higher temperature environment and the effect of reducing the amount of gas generated after the charge / discharge cycle are improved.

  The ratio of cyclic carbonate and chain ester is cyclic carbonate: chain ester (volume ratio) from the viewpoint of improving the effect of improving charge / discharge cycle characteristics in a high temperature environment and the effect of reducing the amount of gas generated after the charge / discharge cycle. Is preferably 10:90 to 45:55, more preferably 15:85 to 40:60, and particularly preferably 20:80 to 35:65.

<Structure of lithium battery>
The structure of the lithium battery of the present invention is not particularly limited, and a coin-type battery having a positive electrode, a negative electrode, and a single-layer or multi-layer separator, and a cylindrical battery and a corner having a positive electrode, a negative electrode, and a roll separator. An example is a type battery.

  As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. For example, polyethylene, polypropylene, cellulose paper, glass fiber paper, polyethylene terephthalate, polyimide microporous film and the like can be mentioned, and a multilayer film constituted by combining two or more kinds can also be used. In addition, the surfaces of these separators can be coated with resin such as PVDF, silicon resin, rubber-based resin, particles of metal oxide such as aluminum oxide, silicon dioxide, and magnesium oxide. The pore diameter of the separator may be in a range generally useful for batteries, for example, 0.01 to 10 μm. The thickness of the separator may be in a general battery range, and is, for example, 5 to 300 μm.

[Lithium ion secondary battery]
A lithium ion secondary battery of the present invention includes a positive electrode containing a material capable of inserting and extracting lithium as an active material, a negative electrode, a separator disposed between the positive electrode and the negative electrode, a non-aqueous electrolyte, It is preferable that the negative electrode includes the electrode sheet of the present invention, and a charging potential in a fully charged state of the negative electrode is 1.05 V or more with respect to a lithium reference electrode. . This is because, in the lithium ion secondary battery of the present invention, when the charge potential in the fully charged state of the negative electrode is in this range, the discharge capacity maintenance rate after the charge / discharge cycle in a high temperature environment is further increased. The charging potential of the negative electrode in a fully charged state is more preferably 1.1 V or more, and particularly preferably 1.15 V or more with respect to the lithium reference electrode. By setting it as the above range, the discharge capacity maintenance rate after the charge / discharge cycle especially in a high temperature environment becomes large. In the lithium ion secondary battery, in addition to the charge potential in the fully charged state of the negative electrode being in the above range, the discharge potential in the fully discharged state of the negative electrode is 1.8 V or less with respect to the lithium reference electrode. More preferably. In the lithium ion secondary battery of the present invention, when the charge potential in the complete discharge state of the negative electrode is within this range, the discharge capacity retention rate after the charge / discharge cycle in a high temperature environment is further increased. This is because if the discharge potential in the complete discharge state of the negative electrode is within this range, the discharge capacity retention rate after the charge / discharge cycle in a higher temperature environment is further increased. The discharge potential in the complete discharge state of the negative electrode is more preferably 1.7 V or less, and particularly preferably 1.6 V or less with respect to the lithium reference electrode. By setting it as the above range, the discharge capacity maintenance factor after the charging / discharging cycle in a high temperature environment becomes large, and the gas generation in a high temperature environment is also suppressed.

The active material contained in the positive electrode of the lithium ion secondary battery of the present invention is preferably a composite metal oxide having a spinel structure. This is because the discharge capacity retention rate after the charge / discharge cycle in a high temperature environment is increased. Here, as the composite metal oxide having a spinel structure, specifically, LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiMg _0.5 Mn _1.5 O ₄ , LiNi _0.5 Ge Examples thereof include _1.5 O ₄ , LiNiVO ₄ , LiMnVO ₄ , and LiMnVO ₄ . Among these composite metal oxides having a spinel structure, a composite metal oxide containing manganese is preferable, LiMn ₂ O ₄ or LiNi _0.5 Mn _1.5 O ₄ is more preferable, and LiMn ₂ O ₄ is Particularly preferred. In these two types, the discharge capacity maintenance rate after the charge / discharge cycle in a high temperature environment is particularly large. Note that the composite metal oxide having the spinel structure may be a composition in which a part of the constituent elements is replaced with another element.

  Next, the details of the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples, and can be easily inferred from the gist of the invention. Including any combination. In particular, it is not limited to the combination of the solvent which comprises the non-aqueous electrolyte of an Example. Details of the physical property values given in the following examples and comparative examples are described.

(Various physical property measurement methods)
[1. XRD]
As a measuring device, an X-ray diffractometer using CuKα ray (Rigaku Corporation, RINT-TTR-III type) was used. The measurement conditions of the X-ray diffraction measurement are: measurement angle range (2θ): 10 ° to 90 °, step interval: 0.02 °, measurement time: 0.25 seconds / step, radiation source: CuKα ray, tube voltage : 50 kV, current: 300 mA.

A peak corresponding to a peak in the range of diffraction angle 2θ = 17.6 to 18.6 ° of Li ₂ Na ₂ Ti ₆ O ₁₄ having a crystal structure belonging to space group Cmca or space group Fmmm (Li ₂ Na ₂ Ti ₆ O _In the case where the crystal structure of ₁₄ belongs to the space group Cmca, the intensity of the peak corresponding to the (111) plane), the main peak intensity of anatase-type titanium dioxide (diffraction angle 2θ = 24.7 to 25.7 °) (101) plane derived from the peak intensity of the inner) surface derived peak intensity ((110 in the range of diffraction angle 2 [Theta] = 27.2-27.6 °) the main peak intensity of rutile-type titanium dioxide), and _Li 2 TiO ₃ Peak intensity (diffraction angle 2θ = peak intensity derived from (−133) plane within the range of 43.5 to 43.8 °) was measured. Also the calculation of _Li 2 TiO ₃ and (-133) main peak intensity of _Li 2 TiO ₃ is multiplied by 100/80 on surface derived peak intensity ((002) intensity of the peak of the corresponding surface). The intensity of a peak corresponding to a peak in the range of diffraction angle 2θ = 17.6 to 18.6 ° of Li ₂ Na ₂ Ti ₆ O ₁₄ having a crystal structure belonging to space group Cmca or space group Fmmm is defined as 100. The relative values of the main peak intensities of the rutile titanium dioxide, anatase titanium dioxide, and Li ₂ TiO ₃ were calculated.

[2. Crystallite diameter (D _X )]
The crystallite diameter (D _X ) of the lithium sodium titanium composite oxide powder of the present invention was measured using an X-ray diffractometer using CuKα rays (RINT-TTR-III type, manufactured by Rigaku Corporation). Measurement conditions were as follows: measurement angle range (2θ): 15.8 ° to 21.0 °, step interval: 0.01 °, measurement time: 1 second / step, radiation source: CuKα ray, tube voltage: 50 kV, Current: A peak in the range of diffraction angle 2θ = 17.6 to 18.6 ° of Li ₂ Na ₂ Ti ₆ O ₁₄ having a crystal structure belonging to space group Cmca or space group Fmmm obtained as 300 mA (Li ₂ Na ₂ From the half-value width of the peak corresponding to the (111) plane when the crystal structure of Ti ₆ O ₁₄ belongs to the space group Cmca, it was obtained from the Scherrer equation, that is, the following equation (1). In calculating the half width, it is necessary to correct the line width by the optical system of the diffractometer, and silicon powder was used for this correction.
D _X = K · λ / (FW (S) · cos θ _c ) (1)
FW (S) ^ D = FWHM ^ D-FW (I) ^ D
FW (I) = f0 + f1 × (2θ) + f2 × (2θ) ²
θ _c = (t0 + t1 × (2θ) + t2 (2θ) ² ) / 2
K: Scherrer constant (0.94)
λ: wavelength of CuKα ₁ line (1.54059 mm)
FW (S): Sample-specific half-width (FWHM)
FW (I): Device-specific half-width (FWHM)
D: Deconvolution parameter (1.3)
f0 = 5.108673E-02
f1 = 1.058424E-04
f2 = 6.871481E-06
θ _c : Bragg angle correction value t0 = −3,000E-03
t1 = 5.119E-04
t2 = −3.599E-06

[3. Specific surface area (m ² / g)]
The specific surface area of the lithium sodium titanium composite oxide powder of the present invention is measured by a one-point method using liquid nitrogen using a fully automatic BET specific surface area measuring device manufactured by Mountec Co., Ltd., trade name “Macsorb HM model-1208”. did.

[4. BET diameter (D _BET )]
The BET diameter (D _BET ) of the lithium sodium titanium composite oxide powder of the present invention was obtained from the following formula (2) assuming that all particles constituting the powder were spheres having the same diameter. Here, D _BET is the BET diameter (μm), ρ _S is the true density (g / cc) of lithium sodium sodium titanium composite oxide, and S is [3. Specific surface area (m ² / g) measured by the method described in “Specific surface area (m ² / g)”.
D _BET = 6 / (ρ _S × S) (2)

[5. Particle size distribution)
The particle size distribution of the lithium sodium titanium composite oxide powder of the present invention was measured using a laser diffraction / scattering type particle size distribution analyzer (Nikkiso Co., Ltd., Microtrack MT3300EXII). For the preparation of the measurement sample, ion exchange water was used as a measurement solvent. About 50 mg of a sample was put into 50 ml of a measurement solvent, and 1 cc of 0.2% sodium hexametaphosphate aqueous solution as a surfactant was added, and the obtained measurement slurry was processed with an ultrasonic disperser. The measurement slurry subjected to the dispersion treatment was accommodated in a measurement cell, and a measurement solvent was added to adjust the slurry concentration. The particle size distribution was measured when the transmittance of the slurry was within an appropriate range. The volume median particle size D50 of the lithium sodium titanium composite oxide powder of the present invention is calculated from the results obtained by the above particle size distribution measurement, and the cumulative volume frequency calculated by the volume fraction is integrated from the smaller particle size. The particle size was 50%.

[6. Total pore volume (gas adsorption method)]
The total pore volume of the lithium sodium titanium composite oxide powder of the present invention was measured by a gas adsorption method using a fully automatic gas adsorption amount measuring apparatus AC1-iQ (manufactured by QUANTACHROME) as follows. 1 g of lithium sodium titanium composite oxide powder was accommodated in a measuring cell (large cell) having a stem diameter of 6 mm, stored in the measuring device, and deaerated under vacuum at 200 ° C. for 15 hours. With the measurement apparatus, nitrogen gas was used as the adsorption gas, and a fully automatic gas adsorption amount measurement was performed by a constant volume method to measure the total pore volume.

[7. (Average compressive strength of secondary particles)
The average compression strength of secondary particles of the lithium sodium titanium composite oxide powder of the present invention was measured using a Shimadzu micro compression tester (MCT-510) to which a test force “1 g or less measurement mode” was added. “Compression test” was selected as the test mode, and the compression strength when the particles were compressed by 10% of the measured particle diameter was defined as the compression strength of the measured secondary particles. The measurement sample dispersed on the sample stage is observed with an optical microscope at an arbitrary position, and in the field of view of the optical microscope, it can be determined that the particles do not overlap with each other and that secondary particles are clearly formed. Particles were randomly selected and measured one by one to obtain an average value of 50 points, and the average value was defined as “average compressive strength of secondary particles”. The surface detection point of the compression test data was the point where the device automatically detected the surface. The type of indenter was “FLAT50” and the length measurement mode was “single”. For particles with a compressive strength of 3 MPa or less, the “soft sample measurement” mode was used, the test force was 4.90 mN, the load speed was 0.0100 mN / sec, and the load holding time was 5 seconds. For particles with a compressive strength exceeding 3 MPa, the “soft sample measurement” mode was not used, the test force was 4.90 mN, the load speed was 0.0446 mN / sec, and the load holding time was 5 seconds.

[8. (Average circularity of secondary particles)
The circularity is an index of sphericity when a particle is projected on a two-dimensional plane, and is an index instead of sphericity. In the present invention, for the secondary particles of the lithium sodium titanium composite oxide powder of each example, the perimeter of the perfect circle having the same area as the measurement target particle is expressed as a percentage with respect to the perimeter of the measurement target particle. The value was determined as the circularity of each particle, and the average value was defined as the average circularity. The perimeter of the particles to be measured was determined by image processing of the SEM image, and the circularity was determined by the following equation (3). 50 particles were randomly selected from a plurality of SEM images measured at an arbitrary location, and the average circularity of 50 randomly selected particles was defined as the average circularity.
Circularity = (perimeter of a perfect circle having the same area as the particle to be measured) / (perimeter of the particle to be measured) × 100 (%) (3)

(Example 1-1)
<Preparation of raw materials>
Li ₂ CO ₃ (Alfa Aesar (ALF) product number: 034418) as a lithium raw material, Na ₂ CO ₃ (Alfa Aesar (ALF) product number: L13098) as a sodium raw material, anatase TiO ₂ (average grain as a titanium raw material) As shown in Table 1, Al ₂ (SO ₄ ) ₃ · 14-18 hydrate (manufactured by Wako Pure Chemical Industries, product number: 010-02125) is used as a raw material for the titanium site substitution element. The composition (Li ₂ Na ₂ Ti _5.99 Al _0.01 O ₁₄ ). In weighing, Al ₂ (SO ₄ ) ₃ · 14 to 18 hydrate was handled as Al ₂ (SO ₄ ) ₃ · 16 hydrate. The weighed powder was put into a container together with ZrO ₂ balls (diameter 2 mm), and pulverized and mixed with a ball mill until D95 of the obtained mixed powder became 1.0 μm.

<Baking>
The obtained mixed powder was filled in a high-purity alumina mortar and fired at 900 ° C. for 12 hours in air using a fixed-bed tubular furnace. The rate of temperature increase from room temperature to the maximum temperature (holding temperature) was 200 ° C./h. Thereafter, the fired product obtained was collected, sieved (mesh roughness: 45 μm), and the powder that passed through the sieve was collected to obtain a lithium sodium titanium composite oxide powder.

  The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. The physical properties of the lithium sodium titanium composite oxide powder of Example 1-1 are shown in Table 1 together with other examples and comparative examples.

(Electrochemical evaluation)
<Preparation of non-aqueous electrolyte for characteristic evaluation>
The non-aqueous electrolyte used for the battery for evaluating the characteristics was prepared as follows. A nonaqueous solvent of ethylene carbonate (EC): propylene carbonate (PC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 10: 20: 20: 50 was prepared, and LiPF was used as an electrolyte salt thereof. ₆ was dissolved to a concentration of 1M and LiPO ₂ F ₂ to a concentration of 0.05M to prepare a non-aqueous electrolyte.

<Preparation of multi-walled carbon nanotube for conductive agent>
{Synthesis of multi-walled carbon nanotubes}
In ion-exchanged water, cobalt nitrate [Co (NO ₃ ) ₂ .6H ₂ O: molecular weight 291.03], magnesium nitrate [so that the molar ratio of metal elements is Co: Mg: Al = 8: 66: 26 Mg (NO ₃ ) ₂ · 6H ₂ O: molecular weight 256.41] and aluminum nitrate [Al (NO ₃ ) ₃ · 9H ₂ O: molecular weight 375.13] were dissolved and mixed under stirring under basic conditions. Thereafter, the produced precipitate was filtered, washed and dried. After heating this to 500 degreeC and baking for 1 hour, it grind | pulverized in the mortar and the catalyst with the spinel structure by substitution solid solution was acquired. Next, a quartz wool support was provided in the quartz reaction tube, and a catalyst was sprayed thereon. After heating the temperature in the tube to 550 ° C. in a He atmosphere, a mixed gas composed of CO and H ₂ (volume ratio: CO / H ₂ = 99.0 / 1.0) is used as a raw material gas from the bottom of the reaction tube. A multi-walled carbon nanotube was obtained by flowing at a flow rate of 28 L / min for 7 hours. The obtained multi-walled carbon nanotubes had a yield of 15 times the mass of the catalyst.

{Preparation of multi-walled carbon nanotube slurry}
The obtained multi-walled carbon nanotube, carboxymethylcellulose (CMC) and ion-exchanged water were prepared and stirred so as to have a mass ratio of 1.0: 0.8: 98.2 to prepare a slurry. Using this slurry, beads made of zirconia (outer diameter: 1.0 mm) are vesseld by using a bead mill (model: PICOMILL PCM-LR type, agitator material: silicon nitride, vessel inner surface material: zirconia). The mixture was pulverized while controlling the internal pressure of the vessel to 0.06 MPa or less at an agitator peripheral speed of 8 m / sec and a slurry feed speed of 30 to 50 ml / min.

<Preparation of negative electrode sheet>
90% by mass of the lithium sodium titanium composite oxide powder of Example 1-1 as an active material, 4.5% by mass of acetylene black as a conductive agent, 0.5% by mass of multi-walled carbon nanotubes, and polyfluorinated as a binder A paint containing vinylidene at a ratio of 5% by mass was prepared as follows. After mixing polyvinylidene fluoride, acetylene black, the above-mentioned multi-walled carbon nanotube slurry, and 1-methyl-2-pyrrolidone solvent previously dissolved in a 1-methyl-2-pyrrolidone solvent in a planetary stirring deaerator, lithium Sodium titanium composite oxide powder was added, and the total solid content concentration was adjusted to 64% by mass and mixed in a planetary stirring deaerator. Further, a 1-methyl-2-pyrrolidone solvent was added to prepare a total solid content concentration of 56% by mass, and the mixture was mixed with a planetary stirring and deaerator to prepare a coating material. The obtained paint was applied to both sides of an aluminum foil and dried to prepare a negative electrode sheet.

<Preparation of positive electrode sheet>
In the same production method as in <Preparation of negative electrode sheet>, as an active material, 90% by mass of lithium manganate (LiMn ₂ O ₄ ) powder, 5% by mass of acetylene black (conductive auxiliary agent), polyvinylidene fluoride (condensation) A paint containing 5% by mass of the adhesive was prepared, applied onto an aluminum foil and dried, and then applied to the opposite surface and dried to prepare a positive electrode sheet.

<Production of laminated battery>
The negative electrode sheet was pressed to obtain a predetermined electrode density, and then punched to prepare a negative electrode having a mixture layer having a lead wire connecting portion of 4.2 cm in length and 5.2 cm in width. At this time, the thickness of the mixture layer on one side was 35 μm, and the amount of the mixture was 70 g / m ² . After pressing the positive electrode sheet, a positive electrode having a mixture layer of 4 cm in length and 5 cm in width and having lead wire connecting portions was produced. At this time, the thickness of the mixture layer on one side was 20 μm, and the amount of the mixture was 70 g / m ² . The prepared negative electrode and positive electrode, and a 1 mm thick Li metal foil punched out to 14 mmφ as a lithium reference electrode are opposed to each other through a separator made of a microporous polyethylene film, and the aluminum foil lead wire is used as a positive and negative electrode. Connect the nickel foil lead wire to the Li foil, add the non-aqueous electrolyte for characteristic evaluation to each other, and vacuum seal with an aluminum laminate, so that the gas after 45 ° C. charge-discharge cycle and charge-discharge cycle A laminate type battery for generation evaluation was produced. The capacity of this laminated battery was 200 mAh.

<Charge / discharge cycle test and measurement of gas generation amount>
Charge the laminated battery produced by the method described in <Preparation of Laminated Battery> in a constant temperature bath at 25 ° C. with a current of 40 mA until the negative electrode potential becomes 1.1 V with respect to the lithium reference electrode. In addition, after carrying out constant-current constant-voltage charging in which the charging current is 10 mA in a state where the potential of the negative electrode is 1.1 V with respect to the lithium reference electrode, 3 cycles of constant current discharge for discharging until the potential became 1.8 V with respect to the lithium reference electrode (however, charging is performed when current flows so that Li is occluded in the negative electrode. Current was set to flow between the positive and negative electrodes.) The laminate battery was taken out from the thermostat and the volume of the laminate battery (volume of the laminate battery before the cycle test) was measured by Archimedes method. Thereafter, the temperature of the thermostatic bath is set to 45 ° C., and charging is performed at a current of 200 mA until the potential of the negative electrode becomes 1.1 V with respect to the lithium reference electrode. After performing constant current and constant voltage charging in which the charging current reaches 10 mA in a state of 1 V, discharging is performed until the negative electrode potential becomes 1.8 V with respect to the lithium reference electrode at a current of 200 mA. 500 cycles of constant current discharge were performed. The discharge capacity at the first cycle was divided by the discharge capacity at the 500th cycle, and a discharge capacity retention rate after a 500 cycle charge / discharge test at 45 ° C., that is, a 500 cyc discharge capacity retention rate (45 ° C.) was calculated. Then, the temperature of the thermostat was set to 25 ° C. and stored for 1 hour. Next, the laminate battery was taken out from the thermostat, and the volume of the laminate battery (the volume of the laminate battery after storage) was measured by the Archimedes method. The volume of the laminate battery before the cycle test was subtracted from the volume of the laminate battery after the cycle test, and the amount of gas generated after the 500-cycle charge / discharge test at 45 ° C. was calculated. The gas generation amount shown in Table 1 is a relative amount with the gas generation amount in Comparative Example 1 described later as 100%.

  The characteristics evaluation results of the laminate type battery using the lithium sodium titanium composite oxide powder of Example 1-1 as an electrode sheet are described above, and the lithium sodium titanium composite oxide powders of other examples and comparative examples are used as electrode sheets. It shows in Table 1 together with the characteristic evaluation result of the used lithium ion secondary battery (laminate type battery). In Table 1, acetylene black and multi-walled carbon nanotubes used as conductive agents in this example are abbreviated as AB and CNT.

(Examples 1-2 to 1-6)
Composition of each example shown in Table 1 for each raw material (Example 1-2: Li ₂ Na ₂ Ti _5.95 Al _0.05 O ₁₄ , Example 1-3: Li ₂ Na ₂ Ti _5.9 Al _0.1 O ₁₄ , Example 1-4: Li ₂ Na ₂ Ti _5.8 Al _0.2 O ₁₄ , Example 1-5: Li ₂ Na ₂ Ti _5.5 Al _0.5 O ₁₄ , Example 1-6: Lithium sodium titanium of Examples 1-2 to 1-6 in the same manner as Example 1-1 except that it was weighed and mixed so as to be Li ₂ Na ₂ Ti ₅ Al ₁ O ₁₄ ). A composite oxide powder was produced. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powders of Examples 1-2 to 1-6 are shown in Table 1 together with other examples and comparative examples.

(Examples 1-7 to 1-10)
Nb ₂ O ₅ (Alfa Aesar (ALF) product instead of Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125) No. 011366), compositions of each example shown in Table 1 (Example 1-7: Li ₂ Na ₂ Ti _5.9 Nb _0.01 O ₁₄ , Example 1-8: Li ₂ Na ₂ Ti _5.95 Nb _0.05 O ₁₄ , Example 1-9: Li ₂ Na ₂ Ti _5.9 Nb _0.1 O ₁₄ , Example 1-10: Li ₂ Na ₂ Ti _5.8 Nb _0.2 O ₁₄ ) Lithium sodium titanium composite oxide powders of Examples 1-7 to 1-10 were produced in the same manner as in Example 1-1, except that the raw material powders were weighed and mixed. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powders of Examples 1-7 to 1-10 are shown in Table 1 together with other examples and comparative examples.

(Examples 1-11 to 1-13)
Using the lithium sodium titanium composite oxide powder of Example 1-10, a laminated battery was produced in the same manner as in Example 1-10. Example 1-1, except that the charge potential and discharge potential with respect to the lithium reference electrode of each example were changed as shown in Table 1 in the charge / discharge cycle test and the gas generation amount measurement after the charge / discharge cycle. In the same manner as above, the characteristics of the laminate type batteries of each example were evaluated. The results are shown in Table 1 together with other examples and comparative examples.

(Examples 1-14 to 1-16)
The lithium sodium titanium composite oxide powder of Example 1-10 was used as the active material of the negative electrode, except that the active material shown in Table 1 was used instead of lithium manganate as the positive active material. In the same manner as in Example 1-10, laminated batteries of Examples 1-14 to 1-16 were produced. The characteristics of the laminate type battery of each example were evaluated in the same manner as in Example 1-1. The results are shown in Table 1 together with other examples and comparative examples.

(Example 1-17)
The lithium sodium titanium composite oxide powder of Example 1-10 was used as the negative electrode active material except that only 5% by mass of acetylene black was used as the negative electrode conductive agent (no multi-walled carbon nanotubes were used). A laminated battery was prepared in the same manner as in Example 1-10. The characteristics of the laminate type battery of each example were evaluated in the same manner as in Example 1-1. The results are shown in Table 1 together with other examples and comparative examples.

(Examples 1-18 and 1-19)
Nb ₂ O ₅ (Alfa Aesar (ALF) product instead of Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125) No. 011366), compositions of each example shown in Table 1 (Example 1-18: Li ₂ Na ₂ Ti _5.5 Nb _0.5 O ₁₄ , Example 1-19: Li ₂ Na ₂ Ti ₅ Nb ₁ O ₁₄ ) The lithium sodium titanium composite oxide powders of Examples 1-18 and 1-19 were produced in the same manner as in Example 1-1, except that the raw material powder was weighed and mixed. did. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powders of Examples 1-18 and 1-19 are shown in Table 1 together with other examples and comparative examples.

(Example 1-20)
As a raw material for the titanium site substitution element, V ₂ O ₅ (manufactured by Strem Chemicals, Inc.) instead of Al ₂ (SO ₄ ) ₃ · 14-18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125) No. 93-2321), and the raw material powder was weighed and mixed so as to be the composition of Example 1-20 shown in Table 1 (Li ₂ Na ₂ Ti _5.9 V _0.1 O ₁₄ ) Produced the lithium sodium titanium composite oxide powder of Example 1-20 in the same manner as in Example 1-1. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Example 1-21 are shown in Table 1 together with other examples and comparative examples.

(Example 1-21)
As a raw material for the titanium site substitution element, Ga ₂ O ₃ (manufactured by Strem Chemicals, Inc.) instead of Al ₂ (SO ₄ ) ₃ · 14-18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125) No. 93-3106), and the raw material powder was weighed and mixed so as to be the composition of Example 1-21 (Li ₂ Na ₂ Ti _5.9 Ga _0.1 O ₁₄ ) shown in Table 1 Produced the lithium sodium titanium composite oxide powder of Example 1-21 in the same manner as in Example 1-1. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Example 1-21 are shown in Table 1 together with other examples and comparative examples.

(Example 1-22)
As a raw material for the titanium site substitution element, Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125) is replaced with In ₂ O ₃ (Chempur Feinchemalien und Forschungsbeddorf GmbH product No .: 004424-100), and the raw material powder was weighed and mixed so as to be the composition of Example 1-22 shown in Table 1 (Li ₂ Na ₂ Ti _5.9 In _0.1 O ₁₄ ) Produced the lithium sodium titanium composite oxide powder of Example 1-22 in the same manner as in Example 1-1. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. Table 1 shows the physical properties of the lithium sodium titanium composite oxide powder of Example 1-22 together with other examples and comparative examples.

(Example 1-23)
A lithium sodium titanium composite oxide powder of Example 1-23 was produced in the same manner as in Example 1-10 except that the holding time at the maximum temperature during the mixed powder firing was 24 hours. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Example 1-23 above are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 1)
Raw materials not containing raw materials for titanium site substitution elements, ie, Li ₂ CO ₃ (product number: Al3Aesar (ALF), product number: 034418), Na ₂ CO ₃ (product number: Alfa Aesar (ALF), product number: L13098), and anatase TiO ₂ (average particle size 0.6 μm) was the same as Example 1-1 except that it was weighed and mixed so as to become the composition of Comparative Example 1 (Li ₂ Na ₂ Ti ₆ O ₁₄ ) shown in Table 1. By the method, the lithium sodium titanium composite oxide powder of Comparative Example 1 was produced. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Comparative Example 1 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 2)
A comparative example shown in Table 1 was used instead of sodium raw material Na ₂ CO ₃ (product number: L13098, manufactured by Alfa Aesar (ALF)) and barium raw material BaCO ₃ (manufactured by Wako Pure Chemical Industries, product number: 028-08761). The lithium barium titanium composite oxide powder of Comparative Example 2 was produced in the same manner as in Comparative Example 1, except that the raw material powder was weighed and mixed so as to become the composition of No. ₂ (Li ₂ Ba ₂ Ti ₆ O ₁₄ ). did. The physical properties of the obtained lithium barium titanium composite oxide powder were measured by the methods described in [Methods for measuring physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium barium titanium composite oxide powder of Comparative Example 2 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 3)
In place of sodium raw material Na ₂ CO ₃ (Alfa Aesar (ALF) product number: L13098), magnesium raw material MgCO ₃ (Strem Chemicals, Inc. product number: 93-1220) was used, and the comparison shown in Table 1 The lithium magnesium titanium composite oxide powder of Comparative Example 3 was prepared in the same manner as in Comparative Example 1 except that the raw material powder was weighed and mixed so as to be the composition of Example 3 (Li ₂ Mg ₂ Ti ₆ O ₁₄ ). Manufactured. The physical properties of the obtained lithium magnesium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium magnesium titanium composite oxide powder of Comparative Example 3 are shown in Table 1 together with other Examples and Comparative Examples.

(Comparative Example 4)
In place of sodium raw material Na ₂ CO ₃ (manufactured by Alfa Aesar (ALF), product number: L13098), calcium raw material CaCO ₃ (manufactured by Chempur Feinchemien und Forschungsbedgarf GmbH, product number: 001089-1) is used for comparison shown in Table 1. The lithium calcium titanium composite oxide powder of Comparative Example 4 was prepared in the same manner as in Comparative Example 1 except that the raw material powder was weighed and mixed so as to be the composition of Example 4 (Li ₂ Ca ₂ Ti ₆ O ₁₄ ). Manufactured. The physical properties of the obtained lithium calcium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the above comparative example 4 lithium calcium titanium composite oxide powder are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 5)
As a raw material for the titanium site substitution element, instead of Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125), MnO ₂ (manufactured by Strem Chemicals, Inc., product number: 93-2510), except that the raw material powder was weighed and mixed so as to be the composition of Comparative Example 5 (Li ₂ Na ₂ Ti _5.9 Mn _0.1 O ₁₄ ) shown in Table 1. The lithium sodium titanium composite oxide powder of Comparative Example 5 was produced by the same method as -1. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Comparative Example 5 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 6)
As a raw material for the titanium site substitution element, instead of Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (manufactured by Wako Pure Chemical Industries, product number 010-02125), Co ₃ O ₄ (manufactured by Alfa Aesar (ALF) product number) Example 1 except that the raw material powder was weighed and mixed so as to be the composition of Comparative Example 6 shown in Table 1 (Li ₂ Na ₂ Ti _5.9 Co _0.1 O ₁₄ ). 1 was used to produce lithium sodium titanium composite oxide powder of Comparative Example 6. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Comparative Example 6 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 7)
A comparative example shown in Table 1 was used instead of the sodium raw material Na ₂ CO ₃ (product number: L13098, manufactured by Alfa Aesar (ALF)) and barium raw material BaCO ₃ (product number: 028-08761 manufactured by Wako Pure Chemical Industries, Ltd.). The lithium of Comparative Example 7 was the same as Example 1-1, except that the raw material powder was weighed and mixed so that the composition of No. 7 (Li ₂ Ba ₂ Ti _5.95 Al _0.05 O ₁₄ ) was obtained. Barium titanium composite oxide powder was produced. The physical properties of the obtained lithium barium titanium composite oxide powder were measured by the methods described in [Methods for measuring physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium barium titanium composite oxide powder of Comparative Example 7 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 8)
As a raw material for the titanium site substitution element, instead of Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O (manufactured by Wako Pure Chemical Industries, product number: 010-02125), In ₂ O ₃ (Chempur Feinchemikalin und Forschungsbadgarf GmbH product) No .: 004424-100), and comparison was made except that raw material powder was weighed and mixed so as to be the composition of Comparative Example 8 shown in Table 1 (Li ₂ Ba ₂ Ti _5.95 In _0.05 O ₁₄ ). In the same manner as in Example 7, lithium sodium titanium composite oxide powder of Comparative Example 8 was produced. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Comparative Example 8 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 9)
In addition to the sodium raw material Na ₂ CO ₃ (product number: L13098, manufactured by Alfa Aesar (ALF)), K ₂ CO ₃ (manufactured by Wako Pure Chemical Industries, product number: 160-03491) was used as the raw material for the sodium site substitution element. In the same manner as in Comparative Example 1, except that the raw material powder was weighed and mixed so as to be the composition of Comparative Example 9 shown in Table 1 (Li ₂ Na _1.5 K _0.5 Ti ₆ O ₁₄ ). The lithium sodium titanium composite oxide powder of Comparative Example 9 was produced. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Comparative Example 9 are shown in Table 1 together with other examples and comparative examples.

(Comparative Example 10)
In addition to the sodium raw material Na ₂ CO ₃ (manufactured by Alfa Aesar (ALF), product number: L13098), K ₂ CO ₃ (manufactured by Wako Pure Chemical Industries, product number: 160-03491) and Rb as the raw material for the sodium site substitution element _{Using 2} CO ₃ (manufactured by Combi-Blocks, product number: QA-6120), the composition of Comparative Example 10 shown in Table 1 (Li ₂ Na _1.4 K _0.25 Rb _0.35 Ti ₆ O ₁₄ ) was used. The lithium sodium titanium composite oxide powder of Comparative Example 10 was produced in the same manner as in Comparative Example 1 except that the raw material powder was weighed and mixed. The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Comparative Example 10 are shown in Table 1 together with other examples and comparative examples.

(Examples 2-1 to 2-5)
The lithium sodium titanium composite oxide powder of Example 1-10 was used as the negative electrode active material, except that the nonaqueous solvent of the nonaqueous electrolyte used in the battery for evaluating the characteristics was changed as follows. In addition, a laminated battery was produced in the same manner as in Example 1-10, and the characteristics of the laminated battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 2.
Example 2-1; ethylene carbonate (EC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 30: 20: 50
Example 2-2; ethylene carbonate (EC): propylene carbonate (PC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 15: 15: 20: 50
Example 2-3; propylene carbonate (PC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 30: 20: 50
Example 2-4; ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC) (volume ratio) = 10: 20: 70
Example 2-5; ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC) (volume ratio) = 17: 33: 50

(Examples 2-6 to 2-10)
Lithium sodium titanium of Example 1-10, except that the type of electrolyte salt of the non-aqueous electrolyte used in the battery for evaluating characteristics and the concentration of each electrolyte salt in the non-aqueous electrolyte were changed as follows: A laminated battery was produced in the same manner as in Example 1-10 including using the composite oxide powder as the negative electrode active material, and the characteristics of the laminated battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 2.
Example 2-6; LiPF _{6 at a} concentration of 1M
Example 2-7; LiPF _{6 at a} concentration of 1M and LiBF _{4 at a} concentration of 0.05M
Example 2-8; LiPF _{6 at a} concentration of 1M and lithium bisfluorosulfonylimide (LiFSI) at a concentration of 0.05M
Example 2-9; concentration 1M LiPF ₆ and concentration 0.05M lithium bisoxalate borate (LiBOB)
Example 2-10; LiPF _{6 at a} concentration of 1M and LiBF _{4 at a} concentration of 0.5M

(Examples 2-11 and 2-12)
In Example 2-11, the proportion of the conductive agent in the coating material used for preparing the negative electrode sheet was 3.0% by mass for acetylene black and 2.0% by mass for the multi-walled carbon nanotubes. In Example 2-12, acetylene black was used. Example 1 including the use of the lithium sodium titanium composite oxide powder of Example 1-10 as an active material of the negative electrode except that 2.0% by mass and 3.0% by mass of the multi-walled carbon nanotube were used. A laminated battery was produced in the same manner as in Example 10, and the characteristics of the laminated battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 2.

(Example 3-1)
The lithium sodium titanium composite oxide powder of Example 1-10 was screened using a hammer mill (Dalton, AIIW-5 type) with a screen opening of 0.5 mm, a rotation speed of 8,000 rpm, and a powder feed rate. : Crushed under conditions of 25 kg / hr. To the powder obtained by pulverization, ion-exchanged water was added and stirred so that the solid content concentration of the slurry was 30% by mass to prepare a slurry. The obtained slurry was sprayed, dried and granulated using a spray dryer (L-8i, manufactured by Okawara Chemical Co., Ltd.) at an atomizer rotational speed of 25,000 rpm and an inlet temperature of 210 ° C. Next, the powder that passed through the sieve was placed in an alumina sagger and heat-treated at 500 ° C. for 1 hour in a continuous conveyor furnace. The obtained powder was sieved (mesh roughness: 53 μm), and the powder that passed through the sieve was collected to produce the lithium sodium titanium composite oxide powder of Example 3-1.

  The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical property of the lithium sodium titanium composite oxide powder of Example 3-1 and the property evaluation result of the laminate type battery were compared with the physical property of the lithium sodium titanium composite oxide powder of Example 1-10 and the property evaluation result of the laminate type battery. Table 3 also shows.

(Examples 3-2 and 3-3)
The lithium of Example 3-2 and Example 3-3 was the same as Example 3-1, except that the heat treatment temperature was 350 ° C in Example 3-2 and 600 ° C in Example 3-3. Sodium titanium composite oxide powder was produced.

  The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Example 3-2 and Example 3-3 and the evaluation results of the characteristics of the laminate-type battery were compared with the physical properties and laminate of the lithium sodium titanium composite oxide powder of Example 1-10. It shows in Table 3 together with the characteristic evaluation result of the type battery.

(Example 3-4)
Example 3-1, except that the slurry obtained by spraying and drying the slurry of lithium sodium titanium composite oxide powder using a spray dryer and granulating the powder without performing heat treatment Similarly, lithium sodium titanium composite oxide powder of Example 3-4 was produced.

  The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical property of the lithium sodium titanium composite oxide powder of Example 3-4 and the results of the evaluation of the characteristics of the laminate type battery are the same as the physical properties of the lithium sodium titanium composite oxide powder of Example 1-10 and the results of the evaluation of the characteristics of the laminate type battery. Table 3 also shows.

(Example 3-5)
To the mixed powder obtained in the same raw material preparation step as Example 1-1, ion-exchanged water was added and stirred so that the solid content concentration of the slurry was 30% by mass to prepare a slurry. The obtained slurry was sprayed, dried and granulated using a spray dryer (L-8i, manufactured by Okawara Chemical Co., Ltd.) at an atomizer rotational speed of 25,000 rpm and an inlet temperature of 210 ° C. The obtained powder was fired in the same manner as in Example 1-1, and then sieved (mesh roughness: 53 μm), and the powder that passed through the sieve was collected to obtain the lithium sodium titanium composite of Example 3-5. An oxide powder was produced.

  The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical property of the lithium sodium titanium composite oxide powder of Example 3-5 and the property evaluation result of the laminate type battery were compared with the physical property of the lithium sodium titanium composite oxide powder of Example 1-10 and the property evaluation result of the laminate type battery. Table 3 also shows.

(Examples 3-6 and 3-7)
Implementation was carried out in the same manner as in Example 3-1, except that the holding time at the maximum temperature (900 ° C.) during firing was changed to 24 hours in Example 3-6 and 3 hours in Example 3-7. The lithium sodium titanium composite oxide powders of Example 3-6 and Example 3-7 were produced.

  The physical properties of the obtained lithium sodium titanium composite oxide powder were measured by the methods described in [Methods for measuring various physical properties]. Moreover, the laminated battery was produced by the method similar to Example 1-1, the charge / discharge cycle test and the gas generation amount measurement after a charge / discharge cycle were performed by the method similar to Example 1-1. The physical properties of the lithium sodium titanium composite oxide powder of Example 3-6 and the results of evaluation of the characteristics of the laminate type battery were compared with the physical properties of the lithium sodium titanium composite oxide powder of Example 1-10 and the results of the evaluation of the characteristics of the laminate type battery. Table 3 also shows.

(Examples 4-1 to 4-5)
Except that the nonaqueous solvent of the nonaqueous electrolyte used in the battery for evaluating the characteristics was changed as follows, the lithium sodium titanium composite oxide powder of Example 3-6 was used as the active material for the negative electrode. Including, a laminated battery was produced in the same manner as in Example 3-6, and the characteristics of the laminated battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 4.
Example 4-1; ethylene carbonate (EC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 30: 20: 50
Example 4-2; ethylene carbonate (EC): propylene carbonate (PC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 15: 15: 20: 50
Example 4-3; propylene carbonate (PC): methyl ethyl carbonate (MEC): dimethyl carbonate (DMC) (volume ratio) = 30: 20: 50
Example 4-4; ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC) (volume ratio) = 10: 20: 70
Example 4-5; ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC) (volume ratio) = 17: 33: 50

(Examples 4-6 to 4-10)
Lithium sodium titanium of Example 3-6, except that the type of electrolyte salt of the non-aqueous electrolyte used in the battery for evaluating characteristics and the concentration of each electrolyte salt in the non-aqueous electrolyte were changed as follows: A laminated battery was produced in the same manner as in Example 3-6 including using the composite oxide powder as the negative electrode active material, and the characteristics of the laminated battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 4.
Examples 4-6; LiPF _{6 at a} concentration of 1M
Examples 4-7; LiPF _{6 at a} concentration of 1M and LiBF _{4 at a} concentration of 0.05M
Examples 4-8; LiPF _{6 at a} concentration of 1M and lithium bisfluorosulfonylimide (LiFSI) at a concentration of 0.05M
Examples 4-9; LiPF _{6 at a} concentration of 1M and lithium bisoxalate borate (LiBOB) at a concentration of 0.05M
Examples 4-10; LiPF _{6 at a} concentration of 1M and LiBF _{4 at a} concentration of 0.5M

(Examples 4-11 and 4-12)
In Example 4-11, the proportion of the conductive agent in the coating material used for the production of the negative electrode sheet was 3.0% by mass for acetylene black and 2.0% by mass for multi-walled carbon nanotubes. In Example 4-12, acetylene black was used. Example 3 including using the lithium sodium titanium composite oxide powder of Example 3-6 as the active material of the negative electrode except that 2.0% by mass and 3.0% by mass of the multi-walled carbon nanotube are used. A laminated battery was produced in the same manner as in Example 6, and the characteristics of the laminated battery were evaluated in the same manner as in Example 1-1. The results are shown in Table 4.

As described above, the general formula of the present invention: Li _{2 + x} Na _{2 + y} Ti _6-z M _z O ₁₄ (where M is at least one element selected from Al, Ga, In, V, Nb and Ta, and x Is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1.) When the lithium sodium titanium composite oxide powder having a main phase of M is not containing M, when M is an element other than Al, Ga, In, V and Nb, or other alkaline metal element instead of Na Compared with the case of containing, the discharge capacity maintenance rate after a high temperature cycle was large, and the amount of gas generation at high temperature was small.

  Further, in the lithium ion secondary battery using the lithium sodium titanium titanium composite oxide powder of the present invention as an active material for a negative electrode, the non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent, The aqueous solvent contains at least one cyclic carbonate selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, and 2,3-butylene carbonate, and propylene carbonate in the total cyclic carbonate, 1,2- When the ratio of the cyclic carbonate having at least one alkylene chain selected from butylene carbonate and 2,3-butylene carbonate is 55% by volume or more and 100% by volume or less, the discharge capacity maintenance rate after the high-temperature cycle is further large, Furthermore, the amount of gas generated at high temperature was small

  Further, in the lithium ion secondary battery using the lithium sodium titanium titanium composite oxide powder of the present invention as an active material for a negative electrode, the non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent, The aqueous solvent contains a chain ester having at least one methyl group selected from dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate, methyl acetate and ethyl acetate, When the total chain ester content in the solvent was 60% by volume or more and 90% by volume or less, the discharge capacity retention rate after the high-temperature cycle was further large, and the amount of gas generated at a high temperature was small.

Further, in the lithium ion secondary battery using the lithium sodium titanium composite oxide powder of the present invention as an active material for a negative electrode, the nonaqueous electrolytic solution is obtained by dissolving an electrolyte salt in a nonaqueous solvent, and the electrolyte At least LiPF ₆ as a salt is contained in the non-aqueous electrolyte, and at least one lithium salt selected from LiBF ₄ , LiPO ₂ F ₂ and LiN (SO ₂ F) ₂ is non-aqueous at a concentration of 0.001M to 1M. When it was contained in the electrolytic solution, the discharge capacity retention rate after the high temperature cycle was further large, and the amount of gas generated at a high temperature was small.

  Further, in the lithium ion secondary battery using the lithium sodium titanium composite oxide powder of the present invention as the negative electrode active material, the negative electrode conductive agent includes at least one conductive agent selected from graphites and carbon blacks, When the ratio of the carbon nanotubes in the total conductive agent was 1% by mass or more and 49% by mass or less, the discharge capacity retention rate after the high-temperature cycle was further large, and the amount of gas generated at a high temperature was small.

Further, in the lithium sodium titanium composite oxide powder of the present invention, D50 is 10μm or 35μm or less, the ratio of D50 and _{D BET D50 / D BET (μm} / μm) is 25 or more and 100 or less, the average circularity of the secondary particles In the case where the powder physical properties were 80% or more and the average compressive strength of the secondary particles was 0.3 MPa or more and 7 MPa or less, the discharge capacity retention rate after the high-temperature cycle was further large, and the amount of gas generated at high temperature was small. In the lithium ion secondary battery using the lithium sodium titanium composite oxide powder of the present invention having this powder physical property as the negative electrode active material, when the non-aqueous electrolyte specified in paragraphs 0162 to 0164 is used, In particular, the discharge capacity retention rate after the high-temperature cycle was large, and the amount of gas generated was particularly small at high temperatures.

  When the lithium sodium titanium composite oxide powder of the present invention is used, an energy storage device having a large energy density, excellent charge / discharge cycle characteristics in a high temperature environment, and a small amount of gas generated after the charge / discharge cycle can be obtained. Therefore, the lithium sodium titanium composite oxide powder of the present invention is particularly suitable as an electrode material for an electricity storage device that is mounted on HEV, PHEV, BEV or the like and whose performance is strongly required not to deteriorate over a long period of time.

Claims (22)

Having a crystal structure belonging to the space group Cmca or space group Fmmm, the general _{formula: Li 2 + x Na 2 +} y Ti 6-z M z O 14 ( provided that at least M is selected Al, Ga, an In, V, from Nb and Ta X is −0.1 ≦ x ≦ 0.1, y is −0.1 ≦ y ≦ 0.1, and z is 0 <z ≦ 1. A lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device, comprising a lithium sodium titanium composite oxide as a main phase. Specific surface area determined by the BET method is ^{1m 2} / ^g~50m 2 / g, the diffraction angle of _Li 2 _Na 2 _Ti 6 _{O 14} having X-ray diffraction, a crystal structure belonging to the space group Cmca or space group Fmmm 2 [Theta] = 17.6 to 18.6 crystallite diameter calculated from the equation from the half width of Scherrer peaks ranging ° when the _{D x,} claim 1, wherein the _{D x} is 80nm or more A lithium sodium titanium composite oxide powder for an electrode active material of an electricity storage device according to 1. 2. The ratio D _BET / D _X (μm / μm) of D _BET and D _X is 4 or less, where D _BET is a specific surface area equivalent diameter calculated from the specific surface area. 2. Lithium sodium titanium composite oxide powder for electrode active material of electricity storage device according to 2.   4. The lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device according to claim 1, wherein the total pore volume is 0.001 ml / g to 0.5 ml / g. Including secondary particles in which primary particles composed of the lithium sodium titanium composite oxide are aggregated, and when the volume median particle size is D50, D50 is 10 μm or more and 35 μm or less, and the ratio D50 / D _BET is D50 / D _BET (micrometer / micrometer) is 25 or more and 100 or less, The lithium sodium titanium complex oxide powder for electrode active materials of the electrical storage device as described in any one of Claims 1-4 characterized by the above-mentioned.   6. The lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device according to any one of claims 1 to 5, wherein the secondary particles have an average compressive strength of 0.3 MPa or more and 7 MPa or less.   7. The lithium sodium titanium composite oxide powder for an electrode active material for an electricity storage device according to claim 1, wherein the secondary particles have an average circularity of 80% or more.   The active material material containing the lithium sodium titanium complex oxide powder for electrodes of the electrical storage device as described in any one of Claims 1-7.   An electrode sheet for an electricity storage device, comprising: the active material according to claim 8; at least one conductive agent selected from graphites, carbon blacks, and carbon nanotubes; and a binder.   The power storage device electrode sheet according to claim 9, wherein the conductive agent includes at least carbon nanotubes.   The conductive agent includes at least one conductive agent selected from graphites and carbon blacks in addition to carbon nanotubes, and the ratio of carbon nanotubes in the total conductive agent is 1% by mass or more and 49% by mass or less. The electrode sheet for an electricity storage device according to claim 10. A bell formed by stacking 2 to 30 bell-shaped structural units, each having the top of the carbon nanotubes having a closed graphite mesh surface and a trunk having an open lower portion, sharing a central axis. A plurality of structural unit assemblies,
The carbon nanotubes are configured by forming a plurality of bell-shaped structural unit assemblies connected at intervals in a head-to-tail manner to form fibers. An electrode sheet for an electricity storage device according to claim 1.   An electrical storage device using the electrode sheet according to any one of claims 9 to 12. A positive electrode including a material capable of inserting and extracting lithium as an active material, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolytic solution,
The said negative electrode contains the electrode sheet as described in any one of Claims 10-13, The electrical storage device characterized by the above-mentioned.   The non-aqueous electrolyte solution is obtained by dissolving an electrolyte salt in a non-aqueous solvent, and selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, and 2,3-butylene carbonate in the non-aqueous solvent. The ratio of the cyclic carbonate having at least one alkylene chain selected from propylene carbonate, 1,2-butylene carbonate and 2,3-butylene carbonate in the total cyclic carbonate is 55 volumes. The power storage device according to claim 14, wherein the power storage device is not less than 100% and not more than 100% by volume.   The non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent, and dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate in the non-aqueous solvent. Including a chain ester having at least one methyl group selected from methyl acetate and ethyl acetate, and the content of all chain esters in the non-aqueous solvent is 60% by volume or more and 90% by volume or less. The electricity storage device according to claim 14 or 15. The non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent, and includes at least LiPF ₆ as the electrolyte salt in the non-aqueous electrolyte, and further includes LiBF ₄ , LiPO ₂ F ₂ and LiN (SO _{2 F)} storage device as claimed in any one claims 14 to 16, characterized in that it comprises at least one lithium salt selected from ₂ in the nonaqueous electrolytic solution in 1M concentrations below or 0.001 M. The electricity storage device according to any one of claims 13 to 17 is a lithium ion secondary battery,
The lithium ion secondary battery, wherein a charging potential in a fully charged state of the negative electrode of the lithium ion secondary battery is 1.05 V or more with respect to a lithium reference electrode.   19. The lithium ion secondary battery according to claim 18, wherein a discharge potential of the negative electrode in a completely discharged state is 1.8 V or less with respect to a lithium reference electrode.   The lithium ion secondary battery according to claim 18 or 19, wherein the active material contained in the positive electrode is a composite metal oxide having a spinel structure.   21. The lithium ion secondary battery according to claim 20, wherein the composite metal oxide contains manganese. The lithium ion secondary battery according to claim 21, wherein the composite metal oxide is LiMn ₂ O ₄ or LiNi _0.5 Mn _1.5 O ₄ .

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