Lithium-lanthanum-titanium oxide sintered material, solid electrolyte containing the oxide, lithium air battery and all-solid lithium battery including the solid electrolyte, and method for producing the lithium-lanthanum-titanium oxide sintered material

Abstract

A lithium-lanthanum-titanium oxide sintered material has a lithium ion conductivity 3.010.sup.4 Scm.sup.1 or more at a measuring temperature of 27 C., the material is described by one of general formulas (1-a)La.sub.xLi.sub.2-3xTiO.sub.3-aSrTiO.sub.3, (1-a)La.sub.xLi.sub.2-3xTiO.sub.3-aLa.sub.0.5K.sub.0.5TiO.sub.3, La.sub.xLi.sub.2-3xTi.sub.1-aM.sub.aO.sub.3-a, and Sr.sub.x-1.5aLa.sub.aLi.sub.1.5-2xTi.sub.0.5Ta.sub.0.5O.sub.3 (0.55x0.59, 0a0.2, M=at least one of Al, Fe and Ga), and concentration of S is 1500 ppm or less. The material is obtained by sintering raw material powder mixture having S content amount of 2000 ppm or less in the entirety of raw material powders for mixture, that is, titanium raw material, lithium raw material, and lanthanum raw material.

Claims

1. Lithium-lanthanum-titanium oxide sintered material, wherein the material is described by one of general formulas (1-a)La.sub.xLi.sub.2-3xTiO.sub.3-aSrTiO.sub.3, (1-a)La.sub.xLi.sub.2-3xTiO.sub.3-aLa.sub.0.5K.sub.0.5TiO.sub.3, La.sub.xLi.sub.2-3xTi.sub.1-aM.sub.aO.sub.3-a, and Sr.sub.x-1.5aLa.sub.aLi.sub.1.5-2xTi.sub.0.5Ta.sub.0.5O.sub.3, and wherein 0.55x0.59, 0a0.2, M=at least one of Fe and Ga, and concentration of S is 400 ppm or less, and wherein lithium ion conductivity calculated by the following formula using an impedance analyzer in measuring frequency 5 to 13 MHz and a measuring temperature of 27 C. is 3.010.sup.4 Scm.sup.1 or more, R.sub.b () being resistance inside of particle R.sub.gb () being resistance at interface of particle, L(cm) being thickness of tabular lithium-lanthanum-titanium oxide, and S(cm.sup.2) being area of electrode,
Lithium ion conductivity (Scm.sup.1)=1/(R.sub.b+R.sub.gb)(L/S).

2. The lithium-lanthanum-titanium oxide sintered material according to claim 1, wherein x=0.57 and a0.05.

3. The lithium-lanthanum-titanium oxide sintered material according to claim 1, wherein single phase ratio is 90% or more.

4. Solid electrolyte comprising the lithium-lanthanum-titanium oxide sintered material according to claim 1.

5. Lithium air battery comprising the solid electrolyte according to claim 4.

6. The lithium air battery according to claim 5 comprising an anode active material layer, solid electrolyte and a cathode active material layer, wherein electrolytic solution is contained between the anode active material layer and the solid electrolyte, and between the cathode active material layer and the solid electrolyte.

7. All-solid lithium ion battery comprising the solid electrolyte according to claim 4.

8. A method for producing the lithium-lanthanum-titanium oxide sintered material according to claim 1, the method comprising: a mixing process in which titanium raw material, lithium raw material, lanthanum raw material, and other metal raw material if necessary are pulverized and mixed so as to obtain a powder mixture, a provisional baking process in which the powder mixture obtained in the mixing process is provisionally baked so as to obtain a provisional baked body, a pulverizing process in which the provisional baked body in the provisional baking process is pulverized so as to obtain powder, a forming process in which the powder obtained in the pulverizing process is formed so as to obtain a formed body, and a sintering process in which the formed body obtained in the forming process is sintered, wherein content amount of S in the entirety of the powder mixture is 2000 ppm or less.

9. The method for producing the lithium-lanthanum-titanium oxide sintered material according to claim 8, wherein content amount of S in the titanium raw material is 3500 ppm or less.

10. The method for producing the lithium-lanthanum-titanium oxide sintered material according to claim 8, wherein the titanium raw material is titanium oxide.

11. The method for producing the lithium-lanthanum-titanium oxide sintered material according to claim 8, wherein lithium ion conductivity is 3.010.sup.4 Scm.sup.1 or more.

12. The lithium-lanthanum-titanium oxide sintered material according to claim 1, wherein 0.05a0.2.

Description

EXAMPLES

(1) Hereinafter, the present invention is further explained by way of Examples, which are merely exemplifications, and the present invention is not limited to these Examples.

(2) 1. Evaluating Method of Lithium-Lanthanum-Titanium Oxide Sintered Material

(3) (Determining Method of x and a in Composition Formula)

(4) A lithium-lanthanum-titanium oxide sintered material, Na.sub.2O.sub.2 and NaOH were put in a zirconium crucible, heated, and melted. This was allowed to stand to cool and was dissolved by adding water and HCl. The dissolved liquid part was collected. Ti was quantified by an aluminum reduction-ammonium iron sulfate (III) titration method and the other elements were quantified by ICP emission spectrometry, the value of x and a were determined in general formulas (1-a)La.sub.xLi.sub.2-3xTiO.sub.3-aSrTiO.sub.3, (1-a)La.sub.xLi.sub.2-3xTiO.sub.3-aLa.sub.0.5K.sub.0.5TiO.sub.3, La.sub.xLi.sub.2-3xTi.sub.1-aM.sub.aO.sub.3-a, and Sr.sub.x-1.5aLa.sub.aLi.sub.1.5-2xTi.sub.0.5Ta.sub.0.5O.sub.3 (0.55x0.59, 0a0.2, M=at least one of Al, Fe and Ga).

(5) (Quantification Method S)

(6) Tabular lithium-lanthanum-titanium oxide sintered material obtained was directly placed in a cell for analysis, and qualitative and quantitative analyses of surface of the sample were performed by a wavelength dispersing type fluorescent X ray device (trade name: LIX3000 produced by Rigaku Corporation), so as to calculate concentration of S.

(7) (Measuring Method of Lithium Ion Conductivity)

(8) A surface of sample of tabular (15 mm15 mm2.5 mm) lithium-lanthanum-titanium oxide sintered material was ground by a diamond grinding stone of #150, and polished by a diamond grinding stone of #600 to finish. 1M lithium chloride water solution was absorbed in two sheets of filter paper cut in a size of 10 mm10 mm, and the tabular lithium-lanthanum-titanium oxide sintered material was adhered between the two sheets. A Cole-Cole plot was measured by using an impedance analyzer (trade name: 4192A produced by Hewlett Packard Co.) at a measuring frequency 5 Hz to 13 MHz and a measuring temperature of 27 C., and resistance values inside of a particle and at a particle interface was read based on the data measured. Lithium ion conductivity was calculated by the following formula.
Lithium ion conductivity (Scm.sup.1)=1/(R.sub.b+R.sub.gb)(L/S)

(9) R.sub.b: resistance inside of particle ()

(10) R.sub.gb: resistance at interface of particle ()

(11) L: thickness of tabular lithium-lanthanum-titanium oxide (cm)

(12) S: area of electrode (cm.sup.2)

(13) (Measuring Method of Single Phase Ratio)

(14) The lithium-lanthanum-titanium oxide sintered material obtained was pulverized in an alumina mortar to prepare a measuring sample, and the sample was measured using an X ray diffractometer (X ray source: CuK ray, trade name: X Part-ProMPD, produced by PANalytical B. V.). Single phase ratio was calculated by the formula below based on heights of the main peaks of lithium-lanthanum-titanium oxide and impurities from the diffraction pattern obtained.
Single phase ratio (%)=I/(I+S)100

(15) I: height of the strongest peak of lithium-lanthanum-titanium oxide in 2=0 to 50

(16) S: sum of heights of main peaks of all the impurities

Example 1

(17) 1. Raw Material

(18) As raw materials, lithium carbonate (produced by Sociedad Quimica y Minera de Chile S. A., purity: 99.2% or more), lanthanum oxide (produced by Yixing Xinwei Leeshing Rare Earth Co., Ltd, purity: 99.99% or more), and titanium oxide which was obtained by performing gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more, sulfur concentration: 570 ppm) were prepared. The weight of each raw material is shown in Table 1. The amount of lithium carbonate added was 7.5 mass % in excess.

(19) 2. Primary Pulverization

(20) The raw materials weighed, 200 kg of alumina media (diameter: 3 mm), 35 L of ion exchanged water and 35 L of ethanol were placed in a urethane lining ball mill (capacity 200 L), and the raw materials were pulverized and mixed for 30 minutes. They were allowed to rest for 15 hours in the ball mill, and then, they were pulverized again for 30 minutes to obtain a primary pulverized powder (raw material powder mixture). S concentration of the raw material powder mixture is shown in Table 1.

(21) 3. Primary Drying

(22) The primary pulverized powder was dried by a spray dryer to obtain the primary dried powder. The conditions of the spray drying were as follows.

(23) Amount of raw material supplied: 10 to 30 L/h

(24) Temperature at hot air inlet: 150 to 250 C.

(25) Air exhaust temperature: 90 to 120 C.

(26) Furthermore, S concentration of the primary dried powder is shown in Table 1.

(27) 4. Provisional Baking

(28) The primary dried powder was put in a sagger made of cordierite mullite material, provisionally baked in an electric furnace to obtain the provisional baked powder. The conditions of provisional baking were provisional baking temperature of 1150 C., and provisional baking time of 2 hours under an atmosphere.

(29) 5. Secondary Pulverization

(30) 70 kg of the provisional baked powder, 200 kg of zirconia media (diameter 3 mm), 60 L of ion exchanged water and 700 g of dispersing agent (ammonium polyacrylate salt) were placed in a urethane lining ball mill (capacity 200 L), and the powder was pulverized for 6 hours. After that, 4.5 kg of acrylic resin type binder was placed therein, and they are mixed for 15 minutes so as to obtain the secondary pulverized powder.

(31) 6. Secondary Drying

(32) The secondary pulverized powder was dried by spray dryer to obtain the secondary dried powder. The conditions of the spray dryer were as follows.

(33) Amount of raw material supplied: 10 to 30 L/h

(34) Temperature at hot air inlet: 200 to 250 C.

(35) Air exhaust temperature: 90 to 120 C.

(36) 7. Molding

(37) 15 g of the secondary dried powder was formed into a tabular shape of 40 mm40 mmthickness 3 mm by a mold forming (forming pressure 1000 kg/cm.sup.2), so as to obtain a molded body.

(38) 8. Sintering

(39) Primary sintering of the molded body was performed in an electric furnace at 1100 C. for 2 hours under an atmosphere, and then, secondary sintering was performed at 1460 C. for 6 hours, so as to obtain a lithium-lanthanum-titanium oxide sintered material. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 2

(40) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that weight of each raw material in Example 1 was changed as shown in Table 1. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 3

(41) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that weight of each raw material in Example 1 was changed as shown in Table 1. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 4

(42) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that the weight of each raw material in Example 1 was changed as shown in Table 1, and that 3.666 kg of SrCO.sub.3 was added. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 5

(43) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that the weight of each raw material in Example 1 was changed as shown in Table 1, and that 11.00 kg of SrCO.sub.3 was added. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 6

(44) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that the weight of each raw material in Example 1 was changed as shown in Table 1, and that 1.884 kg of Fe.sub.2O.sub.3 was added. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 7

(45) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that the weight of each raw material in Example 1 was changed as shown in Table 1, and that 5.651 kg of Fe.sub.2O.sub.3 was added. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 8

(46) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that the weight of each raw material in Example 1 was changed as shown in Table 1, and that 36.29 kg of SrCO.sub.3 and 54.86 kg of Ta.sub.2O.sub.5 were added. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 9

(47) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that weight of each raw material in Example 1 was changed as shown in Table 1, and that 25.30 kg of SrCO.sub.3 and 54.86 kg of Ta.sub.2O.sub.5 were added. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Example 10

(48) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that titanium oxide obtained by gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more) in 2. Primary pulverization was changed to titanium oxide mixture in which titanium oxide obtained by gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more) and titanium oxide obtained by a sulfuric acid method were mixed at 1:1. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 1

(49) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that titanium oxide obtained by gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more) in 1. Raw material was changed to titanium oxide obtained by a sulfuric acid method (sulfur concentration: 3850 ppm). Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 2

(50) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that 2.22 kg of H.sub.2SO.sub.4 having concentration of 20 mass % was added during performing 2. Primary pulverization. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 3

(51) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that weight of each raw material in Example 1 was changed as shown in Table 1. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 4

(52) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 1, except that weight of each raw material in Example 1 was changed as shown in Table 1. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 5

(53) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 5, except that titanium oxide obtained by gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more) in 1. Raw material was changed to titanium oxide obtained by a sulfuric acid method. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 6

(54) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 7, except that titanium oxide obtained by gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more) in 1. Raw material was changed to titanium oxide obtained by a sulfuric acid method. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

Comparative Example 7

(55) The lithium-lanthanum-titanium oxide sintered material was produced in a manner similar to that in Example 9, except that titanium oxide obtained by gas phase oxidization of titanium tetrachloride (produced by TOHO TITANIUM CO., LTD., purity: 99.99% or more) in 1. Raw material was changed to titanium oxide obtained by a sulfuric acid method. Single phase ratio, S concentration, and lithium ion conductivity of the lithium-lanthanum-titanium oxide sintered material obtained are shown in Table 2.

(56) TABLE-US-00001 TABLE 1 Added S concen- S concen- amount of tration of powder tration of Composition Li.sub.2CO.sub.3/kg TiO.sub.2/kg La.sub.2O.sub.3/kg H.sub.2SO.sub.4/kg mixture/ppm TiO.sub.2/ppm Example 1 La.sub.0.57Li.sub.0.29TiO.sub.3 5.321 36.90 42.90 0 500 570 Example 2 La.sub.0.55Li.sub.0.35TiO.sub.3 6.422 36.90 41.40 0 400 460 Example 3 La.sub.0.59Li.sub.0.23TiO.sub.3 4.220 36.90 44.41 0 500 580 Example 4 0.95La.sub.0.57Li.sub.0.29TiO.sub.30.05SrTiO.sub.3 5.055 36.90 40.76 0 400 480 Example 5 0.85La.sub.0.57Li.sub.0.29TiO.sub.30.15SrTiO.sub.3 4.523 36.90 36.47 0 500 570 Example 6 La.sub.0.57Li.sub.0.29Ti.sub.0.95Fe.sub.0.05O.sub.2.95 5.321 35.06 42.90 0 500 550 Example 7 La.sub.0.57Li.sub.0.29Ti.sub.0.85Fe.sub.0.15O.sub.2.85 5.321 31.37 42.90 0 400 520 Example 8 Sr.sub.0.495La.sub.0.05Li.sub.0.36Ti.sub.0.5Ta.sub.0.5O.sub.3 6.606 18.45 3.76 0 400 470 Example 9 Sr.sub.0.345La.sub.0.15Li.sub.0.36Ti.sub.0.5Ta.sub.0.5O.sub.3 6.606 18.45 11.29 0 400 530 Example 10 La.sub.0.57Li.sub.0.29TiO.sub.3 5.321 36.90 42.90 0 1500 2250 Comparative La.sub.0.57Li.sub.0.29TiO.sub.3 5.321 36.90 42.90 0 2500 3850 Example 1 Comparative La.sub.0.57Li.sub.0.29TiO.sub.3 5.321 36.90 42.90 2.216 2200 570 Example 2 Comparative La.sub.0.54Li.sub.0.38TiO.sub.3 6.973 36.90 40.64 0 400 570 Example 3 Comparative La.sub.0.60Li.sub.0.20TiO.sub.3 3.670 36.90 45.16 0 350 570 Example 4 Comparative 0.95La.sub.0.57Li.sub.0.29TiO.sub.30.05SrTiO.sub.3 5.055 36.90 40.76 0 2400 3800 Example 5 Comparative La.sub.0.57Li.sub.0.29Ti.sub.0.95Fe.sub.0.05O.sub.2.95 5.321 35.06 42.90 0 2500 3850 Example 6 Comparative Sr.sub.0.495La.sub.0.05Li.sub.0.36Ti.sub.0.5Ta.sub.0.5O.sub.3 6.606 18.45 3.76 0 2400 3750 Example 7

(57) TABLE-US-00002 TABLE 2 Single phase S concentra- Conductiv- Composition ratio/% tion/ppm ity/Scm.sup.1 Example 1 La.sub.0.57Li.sub.0.29TiO.sub.3 96 300 6.0 10.sup.4 Example 2 La.sub.0.55Li.sub.0.35TiO.sub.3 95 250 3.3 10.sup.4 Example 3 La.sub.0.59Li.sub.0.23TiO.sub.3 92 400 3.0 10.sup.4 Example 4 0.95La.sub.0.57Li.sub.0.29TiO.sub.30.05SrTiO.sub.3 95 300 4.4 10.sup.4 Example 5 0.85La.sub.0.57Li.sub.0.29TiO.sub.30.15SrTiO.sub.3 92 250 3.6 10.sup.4 Example 6 La.sub.0.57Li.sub.0.29Ti.sub.0.95Fe.sub.0.05O.sub.2.95 95 300 4.2 10.sup.4 Example 7 La.sub.0.57Li.sub.0.29Ti.sub.0.85Fe.sub.0.15O.sub.2.925 92 200 3.4 10.sup.4 Example 8 Sr.sub.0.495La.sub.0.05Li.sub.0.36Ti.sub.0.5Ta.sub.0.5O.sub.3 95 200 4.1 10.sup.4 Example 9 Sr.sub.0.345La.sub.0.15Li.sub.0.36Ti.sub.0.5Ta.sub.0.5O.sub.3 93 200 3.2 10.sup.4 Example 10 La.sub.0.57Li.sub.0.29TiO.sub.3 96 1200 3.3 10.sup.4 Comparative La.sub.0.57Li.sub.0.29TiO.sub.3 95 1700 1.7 10.sup.4 Example 1 Comparative La.sub.0.57Li.sub.0.29TiO.sub.3 95 1600 1.9 10.sup.4 Example 2 Comparative La.sub.0.54Li.sub.0.38TiO.sub.3 96 300 1.0 10.sup.4 Example 3 Comparative La.sub.0.60Li.sub.0.20TiO.sub.3 90 400 1.2 10.sup.4 Example 4 Comparative 0.95La.sub.0.57Li.sub.0.29TiO.sub.30.05SrTiO.sub.3 91 1800 2.3 10.sup.4 Example 5 Comparative La.sub.0.57Li.sub.0.29Ti.sub.0.95Fe.sub.0.05O.sub.2.95 91 1700 1.1 10.sup.4 Example 6 Comparative Sr.sub.0.495La.sub.0.05Li.sub.0.36Ti.sub.0.5Ta.sub.0.5O.sub.3 90 1800 1.2 10.sup.4 Example 7

(58) In Comparative Examples 1, 2, 5 to 7 in which S concentration is more than 1500 ppm, lithium ion conductivity is less than 3.010.sup.4 Scm.sup.1. Furthermore, in spite of S concentration of 1500 ppm or less, lithium ion conductivity is less than 3.010.sup.4 Scm.sup.1 in Comparative Example 3 in which La ratio is less than 0.55 and in Comparative Example 4 in which La ratio is more than 0.59.

(59) On the other hand, in all Examples 1 to 10 in which all of the values are within the range of the present invention, lithium ion conductivity is 3.010.sup.4 Scm.sup.1 or more. In particular, the conductivity was especially good in Examples 1, 5 and 7 in which La ratio in composition formula is 0.57 and S concentration is 300 ppm which is low value.

(60) Furthermore, in Comparative Examples 1, 5 to 7 in which S concentration of primary dried powder (powder mixture) is more than 2000 ppm, lithium ion conductivity is less than 3.010.sup.4 Scm.sup.1. On the other hand, in all Examples 1 to 10 in which S concentration of primary dried powder (powder mixture) is 2000 ppm or less, lithium ion conductivity is 3.010.sup.4 Scm.sup.1 or more.

(61) The present invention is promising since the lithium-lanthanum-titanium oxide sintered material can be provided, which can be used as a solid electrolyte for a lithium primary battery or a lithium secondary battery, for example, as a solid electrolyte for an all-solid lithium ion battery or a lithium air battery.