ION CONDUCTIVE CERAMIC AND METHOD FOR PREPARING SAME

Abstract

The present invention relates to a ceramic solid electrolyte, which is a key component of an all-solid-state lithium secondary battery, for improving safety, and a method for synthesizing the same. The present invention relates to an oxide-based conductive ceramic of a new NASICON structure of the chemical formula Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12 (X is Zr, Si, Sn, or Y, 0<x<2) or Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12 (X=Si, Sn, Ge, or Y, 1.5≤x≤2.3). The present invention relates to a method for manufacturing an oxide-based conductive ceramic having the above novel NASICON structure.

Claims

1. An oxide-based conductive ceramic having a NASICON structure of the following chemical formula 1,
Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12  [Chemical Formula 1] (X is Zr, Si, Sn, or Y, and 0<x<2)

2. An oxide-based conductive ceramic having a NASICON structure of the following chemical formula 2,
Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12  [Chemical Formula 2] (X=Si, Sn, Ge, or Y, and 1.5≤x≤2.3)

3. A process for synthesizing an oxide-based conductive ceramic having a NASICON structure of the following chemical formula 1 or 2, wherein the raw materials of the ceramic solid electrolyte are mixed, ball milled, and subjected to first heat treatment at 300° C. to 500° C., and secondary heat treatment at 800° C. to 1,200° C.
Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12  [Chemical Formula 1] (X is Zr, Si, Sn, or Y, and 0<x<2)
Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12  [Chemical Formula 2] (X=Si, Sn, Ge, or Y, and 1.5≤x≤2.3)

4. A process for synthesizing an oxide-based conductive ceramic having a NASICON structure of the following chemical formula 1 or 2, wherein the raw materials of the ceramic solid electrolyte are put in water, mixed by ball milling, the ball milled mixture is dried in a dryer, first heat treatment is performed at 300° C. to 500° C., and secondary heat treatment is performed at 800° C. to 1200° C.
Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12  [Chemical Formula 1] (X is Zr, Si, Sn, or Y, and 0<x<2)
Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12  [Chemical Formula 2] (X=Si, Sn, Ge, or Y, and 1.5≤x≤2.3)

5. A process for synthesizing an oxide-based conductive ceramic having a NASICON structure of the following chemical formula 1 or 2, wherein the raw materials of the ceramic solid electrolyte are put in water, mixed by ball milling, the ball milled mixture is dried first by rotary concentration or spraying, dried second in a dryer, first heat treatment is performed at 300° C. to 500° C., and secondary heat treatment is performed at 800° C. to 1200° C.
Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12  [Chemical Formula 1] (X is Zr, Si, Sn, or Y, and 0<x<2)
Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12  [Chemical Formula 2] (X=Si, Sn, Ge, or Y, and 1.5≤x≤2.3)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a SEM image of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3o.sub.12 (x=0.3), oxide-based conductive ceramics of a NASICON structure synthesized by a general solid-state method.

[0013] FIG. 2 is a SEM image of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2), oxide-based conductive ceramics of a NASICON structure synthesized by a general solid-state method.

[0014] FIG. 3 is an XRD pattern of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3), oxide-based conductive ceramics of a NASICON structure.

[0015] FIG. 4 is a SEM photograph of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3), oxide-based conductive ceramic particles of a NASICON structure.

[0016] FIG. 5 is a graph showing an ionic conductivity according to temperature of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3), oxide-based conductive ceramics of a NASICON structure.

[0017] FIG. 6 is an XRD pattern of Li.sub.1+xAl.sub.xSn.sub.2−xp.sub.3O.sub.12 (x=0.5), oxide-based conductive ceramics of a NASICON structure.

[0018] FIG. 7 is a SEM photograph of Li.sub.1+xAl.sub.xSn.sub.2−xP.sub.3O.sub.12 (x=0.5), oxide-based conductive ceramic particles of a NASICON structure.

[0019] FIG. 8 is a graph showing an ionic conductivity according to temperature of Li.sub.1+xAl.sub.xSn.sub.2−xP.sub.3O.sub.12 (x=0.5), oxide-based conductive ceramics of a NASICON structure.

[0020] FIG. 9 is XRD patterns of Li.sub.1+xAr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2) and Li.sub.1+xZr.sub.2Sn.sub.xP.sub.3−xO.sub.12 (x=2), oxide-based conductive ceramics of a NASICON structure.

[0021] FIG. 10 is a SEM photograph of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2), oxide-based conductive ceramic particles of a NASICON structure.

[0022] FIG. 11 is a graph showing an ionic conductivity according to temperature of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2), oxide-based conductive ceramics of a NASICON structure.

[0023] FIG. 12 is a SEM photograph of Li.sub.1+xZr.sub.2Sn.sub.xP.sub.3−xO.sub.12 (x=2), oxide-based conductive ceramic particles of a NASICON structure.

[0024] FIG. 13 is a photograph of particles of Li.sub.1.3Al.sub.0.3Si.sub.1.7P.sub.3O.sub.12, ceramic solid electrolytes prepared through a rotary concentration process.

[0025] FIG. 14 is a photograph of particles of Li.sub.1.3Al.sub.0.3Si.sub.1.7P.sub.3O.sub.12, ceramic solid electrolytes prepared through a spraying process.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] The specific content of the present invention will be described in more detail. However, this is to present one embodiment of the present invention as an example. The present invention is not limited by the following description and the present invention is only defined by the following claims.

[0027] The novel oxide-based conductive ceramics of NASICON structure according to the present invention may have a structure as shown in Chemical Formula 1 below.

Li.sub.1+xAl.sub.zX.sub.2−xP.sub.3O.sub.12  [Chemical Formula 1] [0028] (X=Zr, Si, Sn, or Y, and 0<x<2)

[0029] The novel oxide-based conductive ceramics of NASICON structure according to the present invention may have a structure as shown in Chemical Formula 2 below.

Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12  [Chemical Formula 2] [0030] (X is Si, Sn, Ge, or Y, and 1.5≤x≤2.3)

[0031] In one embodiment of the present invention, the raw materials of the ceramic solid electrolyte are mixed, the raw materials are sufficiently mixed by ball milling, and the mixture after ball milling is subjected to first heat treatment and secondary heat treatment to result in the conductive ceramics of Chemical Formula 1. The first heat treatment may be to calcinate the ceramic particles, and the second heat treatment may be to fire the ceramic particles.

[0032] In one embodiment of the present invention, the raw materials of the ceramic solid electrolyte are mixed using water as a solvent, the raw materials are sufficiently mixed by ball milling in a solution state, the mixture after ball milling is dried in a dryer, and is subjected to first heat treatment and secondary heat treatment to result in the conductive ceramics of Chemical Formula 1. The first heat treatment may be to calcinate the ceramic particles, and the second heat treatment may be to fire the ceramic particles.

[0033] The ball milling speed may be 150 to 350 rpm, 200 to 350 rpm, 250 to 350 rpm, and 250 to 300 rpm.

[0034] The ball milling mixing time may be 12 hours to 48 hours, 12 hours to 36 hours, and 24 hours to 36 hours.

[0035] The drying time in the dryer may be 12 hours to 36 hours, preferably 18 hours to 24 hours, and the drying temperature may be 60° C. to 100° C., preferably 70° C. to 80° C.

[0036] The first heat treatment temperature may be 300° C. to 500° C., preferably 350° C. to 450° C. The secondary heat treatment temperature may be 800° C. to 1,200° C., preferably 850° C. to 1,100° C., and more preferably 900° C. to 1,100° C. Depending on the material and conditions, 800° C. to 1,000° C. may be preferred, and 900° C. to 1,000° C. may be preferred.

[0037] The first heat treatment time and the second heat treatment time may be 2 hours to 12 hours, 2 hours to 11 hours, 2 hours to 10 hours, 2 hours to 9 hours, 2 hours to 8 hours, 2 hours to 7 hours, 2 hours to 6 hours, 2 hours to 5 hours, 2 hours to 4 hours, 3 hours to 12 hours, 3 hours to 11 hours, 3 hours to 10 hours, 3 hours to 9 hours, 3 hours to 8 hours, 3 hours to 7 hours, 3 hours to 6 hours, 3 hours to 5 hours, 3 hours to 4 hours, 4 hours to 12 hours, 4 hours to 11 hours, 4 hours to 10 hours, 4 hours to 9 hours, 4 hours to 8 hours, 4 hours to 7 hours, 4 hours to 6 hours, 4 hours to 5 hours, 5 hours to 12 hours, 5 hours to 11 hours, 5 hours to 10 hours, 5 hours to 9 hours, 5 hours to 8 hours, 5 hours to 7 hours, 5 hours to 6 hours, 6 hours to 12 hours, 6 hours to 11 hours, 6 hours to 10 hours, 6 hours to 9 hours, 6 hours to 8 hours and 6 hours to 7 hours.

[0038] In one embodiment of the present invention, the raw materials of the ceramic solid electrolyte are mixed, the raw materials are sufficiently mixed by ball milling, and the mixture after ball milling is subjected to first heat treatment and secondary heat treatment to result in the conductive ceramics of Chemical Formula 2. The first heat treatment may be to calcinate the ceramic particles, and the second heat treatment may be to fire the ceramic particles.

[0039] In one embodiment of the present invention, the raw materials of the ceramic solid electrolyte are mixed using water as a solvent, the raw materials are sufficiently mixed by ball milling in a solution state, the mixture after ball milling is dried in a dryer, and is subjected to first heat treatment and secondary heat treatment to result in the conductive ceramics of Chemical Formula 2. The first heat treatment may be to calcinate the ceramic particles, and the second heat treatment may be to fire the ceramic particles.

[0040] The ball milling mixing time may be 8 hours to 48 hours, 8 hours to 36 hours, 8 hours to 24 hours, 10 hours to 24 hours, and 10 hours to 18 hours.

[0041] The drying time in the dryer may be 12 hours to 36 hours, preferably 18 hours to 24 hours, and the drying temperature may be 60° C. to 100° C., preferably 70° C. to 80° C.

[0042] The first heat treatment temperature may be 300° C. to 500° C., preferably 350° C. to 450° C. The secondary heat treatment temperature may be 800° C. to 1,200° C., preferably 850° C. to 1,100° C., and more preferably 900° C. to 1,100° C. Depending on the material and conditions, 800° C. to 1,000° C. may be preferred, and 900° C. to 1,000° C. may be preferred.

[0043] The first heat treatment time and the second heat treatment time may be 2 hours to 13 hours, 2 hours to 12 hours, 2 hours to 11 hours, 2 hours to 10 hours, 2 hours to 9 hours, 2 hours to 8 hours, 2 hours to 7 hours, 2 hours to 6 hours, 2 hours to 5 hours, 2 hours to 4 hours, 3 hours to 13 hours, 3 hours to 12 hours, 3 hours to 11 hours, 3 hours to 10 hours, 3 hours to 9 hours, 3 hours to 8 hours, 3 hours to 7 hours, 3 hours to 6 hours, 3 hours to 5 hours, 3 hours to 4 hours, 4 hours to 13 hours, 4 hours to 12 hours, 4 hours to 11 hours, 4 hours to 10 hours, 4 hours to 9 hours, 4 hours to 8 hours, 4 hours to 7 hours, 4 hours to 6 hours, 4 hours to 5 hours, 5 hours to 13 hours, 5 hours to 12 hours, 5 hours to 11 hours, 5 hours to 10 hours, 5 hours to 9 hours, 5 hours to 8 hours, 5 hours to 7 hours, 5 hours to 6 hours, 6 hours to 13 hours, 6 hours to 12 hours, 6 hours to 11 hours, 6 hours to 10 hours, 6 hours to 9 hours, 6 hours to 8 hours, 6 hours to 7 hours, 5 hours to 13 hours, 5 hours to 12 hours, 5 hours to 11 hours, 5 hours to 10 hours, 5 hours to 9 hours, 5 hours to 8 hours, 5 hours to 7 hours, 5 hours to 6 hours, 6 hours to 13 hours, 6 hours to 12 hours, 6 hours to 11 hours, 6 hours to 10 hours, 6 hours to 9 hours, 6 hours to 8 hours and 6 hours to 7 hours.

[0044] In one embodiment of the present invention, the mixture after ball milling is firstly dried with a rotary concentration step or spray drying step, and secondly dried at 60° C. to 100° C., preferably 60° C. to 80° C., more preferably 70° C. to 80° C., the first heat treatment is performed, and the second heat treatment is performed to prepare oxide-based conductive ceramics of Chemical Formula 1 or 2. The temperature of the rotary concentration process may be 60° C. and 100° C., preferably 70° C. to 80° C. The temperature of the spray drying process may be 80° C. to 300° C., preferably 100° C. to 200° C.

EXAMPLES OF THE INVENTION

Example 1

[0045] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3)

[0046] LiCl, Al(NO.sub.3).sub.3.Math.9H.sub.2O, NH.sub.4H.sub.2PO.sub.4, and C.sub.8H.sub.20O.sub.4Si were calculated according to chemical equivalents, and then 1.3:0.3:3:1.7 moles were mixed. After that, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500 ml container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1.

[0047] The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 24 hours. After mixing with ball milling for 24 hours, the zirconia balls were removed. Thereafter, a first heat treatment was performed at 400° C. for 3 hours. After grinding the heat-treated powder in a mortar, a secondary heat treatment was performed at 900° C. for 4 hours to synthesize oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3). The SEM photograph of the conductive ceramic particles synthesized in Example 1 was shown in FIG. 1.

Example 2

[0048] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2)

[0049] Li.sub.3PO.sub.4, SiO.sub.2, and ZrO.sub.2 were calculated according to chemical equivalents, and then 1:2:2 moles were mixed. After that, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500m1 container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 10 hours. After mixing with ball milling for 10 hours, the zirconia balls were removed. Thereafter, a first heat treatment was performed at 400° C. for 5 hours. After grinding the heat-treated powder in a mortar, a secondary heat treatment was performed at 1,100° C. for 12 hours to synthesize oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2). The SEM photograph of the conductive ceramic particles synthesized in Example 2 was shown in FIG. 2.

Example 3

[0050] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3)

[0051] LiCl, Al(NO.sub.3).sub.3.Math.9H.sub.2O, NH.sub.4H.sub.2PO.sub.4, and C.sub.8H.sub.20O.sub.4Si were calculated according to chemical equivalents, and 1.3:0.3:3:1.7 moles were added to 500 ml of distilled water. After that, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500 ml container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 24 hours. After mixing with ball milling for 24 hours, the zirconia balls were removed and dried at 80° C. for 12 hours. Thereafter, a first heat treatment was performed at 400° C. for 3 hours. After grinding the heat-treated powder in a mortar, secondary heat treatment was performed at 900° C. for 4 hours to synthesize oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3).

[0052] The XRD pattern of the conductive ceramics synthesized in this way was shown in FIG. 3. The SEM photograph of the conductive ceramic particles synthesized in Example 3 was shown in FIG. 4. The ionic conductivity according to the temperature of the conductive ceramics synthesized in Example 3 was shown in FIG. 5.

[0053] The conductive ceramic of Li.sub.1+xAl.sub.xSi.sub.2−xP.sub.3O.sub.12 (x=0.3) had an ionic conductivity of 1.08×10.sup.4 S/cm at 30° C., and an average particle size of 4 μm.

Example 4

[0054] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1+xAl.sub.xSn.sub.2−xP.sub.3O.sub.12 (x=0.5)

[0055] LiCl, Al(NO.sub.3).sub.3.Math.9H.sub.2O, NH.sub.4H.sub.2PO.sub.4, and SnO.sub.2 were calculated according to chemical equivalents, and 1.5:0.5:3:1.5 moles were added to 500 ml of distilled water. After that, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500m1 container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 24 hours. After mixing with ball milling for 24 hours, the zirconia balls were removed and dried at 80° C. for 12 hours. Thereafter, a first heat treatment was performed at 400° C. for 3 hours. After grinding the heat-treated powder in a mortar, secondary heat treatment was performed at 900° C. for 4 hours to synthesize oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1+xAl.sub.xSn.sub.2−xP.sub.3O.sub.12 (x=0.5).

[0056] The XRD pattern of the conductive ceramics synthesized in this way was shown in FIG. 6. The SEM photograph of the conductive ceramic particles synthesized in Example 4 was shown in FIG. 7. The ionic conductivity according to the temperature of the conductive ceramics synthesized in Example 4 was shown in FIG. 8.

[0057] The conductive ceramic of Li.sub.1+xAl.sub.xSn.sub.2−xP.sub.3O.sub.12 (x=0.5) had an ionic conductivity of 6.07×10.sup.4 S/cm at 30° C., and an average particle size of 3 μm.

Example 5

[0058] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2)

[0059] Li.sub.3PO.sub.4, SiO.sub.2, and ZrO.sub.2 were calculated according to chemical equivalents, and 1:2:2 moles were added to 500 ml of distilled water. After that, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500 ml container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 10 hours. After mixing with ball milling for 10 hours, the zirconia balls were removed and dried at 80° C. for 12 hours. Thereafter, a first heat treatment was performed at 400° C. for 5 hours. After grinding the heat-treated powder in a mortar, secondary heat treatment was performed at 1,100° C. for 12 hours to synthesize oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2).

[0060] The XRD pattern of the conductive ceramics synthesized in this way was shown in FIG. 9. The SEM photograph of the conductive ceramic particles synthesized in Example 5 was shown in FIG. 10. The ionic conductivity according to the temperature of the conductive ceramics synthesized in Example 5 was shown in FIG. 11.

[0061] The conductive ceramic of Li.sub.1+xZr.sub.2Si.sub.xP.sub.3−xO.sub.12 (x=2) had an ionic conductivity of 7.6×10.sup.−4 S/cm at 30° C., and an average particle size of 4 μm.

Example 6

[0062] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1+xZr.sub.2Sn.sub.xP.sub.3−xO.sub.12 (x=2)

[0063] Li.sub.3PO.sub.4, SnO.sub.2, and ZrO.sub.2 were calculated according to chemical equivalents, and 1:2:2 moles were added to 500 ml of distilled water. After that, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500 ml container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 10 hours. After mixing with ball milling for 10 hours, the zirconia balls were removed and dried at 80° C. for 12 hours. Thereafter, a first heat treatment was performed at 400° C. for 5 hours. After grinding the heat-treated powder in a mortar, secondary heat treatment was performed at 1,100° C. for 12 hours to synthesize oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1+zZr.sub.2Sn.sub.xP.sub.3−xO.sub.12 (x=2).

[0064] The XRD pattern of the conductive ceramics synthesized in this way was shown in FIG. 9.

[0065] The conductive ceramic of Li.sub.1+xZr.sub.2Sn.sub.xP.sub.3−xO.sub.12 (x=2) had an ionic conductivity of 4.8×10.sup.−4 S/cm at 30° C., and an average particle size of 5 μm.

Example 7

[0066] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1.3Al.sub.0.3Si.sub.1.7P.sub.3O.sub.12

[0067] LiCl, Al(NO.sub.3).sub.3.Math.9H.sub.2O, NH.sub.4H.sub.2PO.sub.4, and SiO.sub.2 were calculated according to chemical equivalents, and 1.3:0.3:3:1.7 moles were added to 500 ml of distilled water. Thereafter, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500 ml container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 24 hours. After removing the zirconia balls, the raw materials were firstly dried by rotary concentration at 80° C. for 6 hours, put in an evaporation dish, and secondly dried sufficiently at 80° C. for 24 hours, then the dried raw materials were ground with a mortar to make into powder and subjected to heat treatment. In the first heat treatment, the sample was heated from room temperature to 400° C. for calcination, then heat treated for 4 hours, and cooled naturally until it reached 100° C. or less. Secondary heat treatment was performed at 1,000° C. for 4 hours to fire the sample. Then, it was pulverized to obtain oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1.3Al.sub.0.3Si.sub.1.7P.sub.3O.sub.12.

[0068] The photograph of the particles of the conductive ceramic synthesized in this way was shown in FIG. 13. As shown in FIG. 13, the ceramic synthesized by adding the rotary concentration process has round particles and a very even distribution. The average particle size was 2 μm.

Example 8

[0069] Synthesis of Oxide-Based Conductive Ceramics of NASICON Structure with Chemical Composition of Li.sub.1.3Al.sub.0.3Si.sub.1.7P.sub.3O.sub.12

[0070] LiCl, Al(NO.sub.3).sub.3.Math.9H.sub.2O, NH.sub.4H.sub.2PO.sub.4, and SiO.sub.2 were calculated according to chemical equivalents, and 1.3:0.3:3:1.7 moles were added to 500 ml of distilled water. Thereafter, zirconia balls of 5 mm and 10 mm diameter were prepared in a 2:1 ratio, and then put into a 500 ml container prepared so that the volume ratio of the mixed raw materials and the zirconia balls was 1:1. The rotational speed of ball milling was 200-300 RPM, and ball milling was performed for 24 hours. After removing the zirconia balls, the raw materials were firstly dried by spraying method at 170° C. for 24 hours, put in an evaporation dish, and secondly dried sufficiently at 80° C. for 24 hours, then the dried raw materials were ground with a mortar to make into powder and subjected to heat treatment. In the first heat treatment, the sample was heated from room temperature to 400° C. for calcination, then heat treated for 4 hours, and cooled naturally until it reached 100° C. or less. Secondary heat treatment was performed at 1,000° C. for 4 hours to fire the sample. Then, it was pulverized to obtain oxide-based conductive ceramics of NASICON structure with a chemical composition of Li.sub.1.3Al.sub.0.3Si.sub.1.7P.sub.3O.sub.12.

[0071] The photograph of the particles of the conductive ceramic synthesized in this way was shown in FIG. 14. As shown in FIG. 14, the ceramic synthesized by adding the spray-drying process has round particles and a very even distribution. The average particle size was 3 μm.