Lithium manganese-based composite oxide and method for preparing the same

Abstract

The present invention provides a lithium manganese-based composite oxide represented by the compositional formula: Li1+x(Mnl-m-nFemTin)1-xO2, wherein 0

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram depicting a crystal phase of layered rock-salt type structure in the crystal phases of the lithium manganese-based composite oxide according to the invention.

FIG. 2 is a schematic diagram depicting a crystal phase of cubic rock-salt type structure in the crystal phases of the lithium manganese-based composite oxide according to the invention.

FIG. 3 is a graph showing the X-ray diffraction patterns of samples according to Example 1 and Comparative Example 1.

FIGS. 4 (a), (a)′ and 4 (b), (b)′ are electronic image-processed electron micrographs of iron- and titanium-containing Li₂MnO₃ according to Example 1 and iron-containing Li₂MnO₃ according to Comparative Example 1, respectively.

FIG. 5 is a graph illustrating the initial charge/discharge characteristics of coin-type lithium cells each using a sample according to Example 1 or Comparative Example 1 as positive electrode materials measured at 60° C.

FIG. 6 is a graph illustrating the charge/discharge cycle number dependence of the discharge capacity of coin-type lithium cells each using a sample according to Example 1 or Comparative Example 1 as positive electrode materials.

FIG. 7 is a graph showing the X-ray diffraction patterns of samples according to Examples 2 to 6 and Comparative Example 2.

FIGS. 8 (a), (b), (c), (d), (e) and (f) are electronic image-processed electron micrographs of iron- and titanium-containing Li₂MnO₃ according to Examples 2 to 6 and iron-containing Li₂MnO₃ according to Comparative Example 2.

FIG. 9 is a graph showing the initial charge/discharge characteristics of coin-type lithium cells each using a sample according to Examples 2, 3, 4 or Comparative Example 2 as positive electrode materials measured at 60° C. and a current density of 42.5 mA/g between 2.0-4.8 V.

FIG. 10 is a graph illustrating the initial charge/discharge characteristics of a coin-type lithium cell using a sample according to Example 4 as a positive electrode material measured at 60° C. and a current density of 8.5 mA/g between 1.5-4.8 V.

FIG. 11 (a) is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 4 or Comparative Example 2 as positive electrode materials which were measured at 30, 0 and −20° C. and a current density of 42.5 mA/g after charging to 4.8 V at 30° C.; and FIG. 11 (b) is a graph illustrating the initial discharge characteristics of a coin-type lithium cell of each of the aforementioned types measured at −20° C. and a current density of 8.5 mA/g to 2.0 V.

FIG. 12 is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 4 or Comparative Example 2 as positive electrode materials which were measured by charging to 4.8 V at 30° C. and 42.5 mA/g, and then discharging to 2.0 V at current densities varied to a maximum of 10 C.

FIG. 13 is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 4 or Comparative Example 2 as positive electrode materials which were measured by charging to 4.8 V at 30° C. and 42.5 mA/g, and then discharging to 2.0 V at varying current densities of 20, 30 and 60 C.

FIG. 14 (a) is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 5 or Comparative Example 2 as positive electrode materials which were measured at temperatures of 30 and 0° C. after charging to 4.8 V at 30° C.; and FIG. 14 (b) is a graph illustrating the initial discharge characteristics of a coin-type lithium cell of each of the aforementioned types measured to 2.0 V at −20° C.

FIG. 15 (a) is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 6 or Comparative Example 2 as positive electrode materials which were measured at 30 and 0° C. and a current density of 42.5 mA/g after charging to 4.8 V at 30° C.; and FIG. 15 (b) is a graph illustrating the initial discharge characteristics of a coin-type lithium cell of each of the aforementioned types measured to 2.0 V at −20° C. and a current density of 8.5 mA/g.

FIG. 16 is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 6 or Comparative Example 2 as positive electrode materials which were measured by charging to 4.8 V at 30° C. and a current density of 42.5 mA/g and then discharging to 2.0 V at current densities varied to a maximum of 10 C.

FIG. 17 is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 6 or Comparative Example 2 as positive electrode materials which were measured by charging to 4.8 V at 30° C. and 42.5 mA/g, and then discharging to 2.0 V at varying current densities of 20, 30 and 60 C.

FIG. 18 is a graph showing the X-ray diffraction patterns of samples according to Example 7 and Comparative Example 3.

FIG. 19 (a) is a graph illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 7 or Comparative Example 3 as positive electrode materials which were measured at 30, 0 and −20° C. and a current density of 42.5 mA/g after charging to 4.8 V at 30° C.; and FIG. 19 (b) is a graph illustrating the initial discharge characteristics of a coin-type lithium cell of each of the aforementioned types measured to 2.0 V at −20° C. and a current density of 8.5 mA/g.

FIGS. 20 (a) and (b) are graphs illustrating the initial discharge characteristics of coin-type lithium cells each using a sample according to Example 7 or Comparative Example 3 as positive electrode materials which were measured by charging to 4.8 V at 30° C. and 42.5 mA/g, and then discharging to 2.0 V at current densities varied to a maximum of 60 C.

FIG. 21 is a graph showing the X-ray diffraction pattern of a sample according to Comparative Example 4.

Claims

1. A lithium manganese-based composite oxide represented by the compositional formula: Li1+x(Mnl-m-nFemTin)1−xO2

2. The lithium manganese-based composite oxide according to claim 1, wherein 0.01≦n≦0.5 in the compositional formula: Li1+x(Mnl-m-nFemTin)1−xO2.

3. The lithium manganese-based composite oxide according to claim 1, wherein 0<x<⅓, 0.05≦m≦0.75, 0.01≦n≦0.75, and 0.06≦m+n<1 in the compositional formula: Li1+x(Mnl-m-nFemTin)1−xO2.

4. The lithium manganese-based composite oxide according to claim 1, comprising a crystal phase of layered rock-salt type structure and a crystal phase of cubic rock-salt type structure.

5. A method for preparing a lithium manganese-based composite oxide as defined in claim 1, comprising forming a precipitate by alkalizing an aqueous solution containing a manganese compound, a titanium compound, and an iron compound; hydrothermally treating the precipitate along with an oxidizing agent and a water-soluble lithium compound under alkaline conditions; and firing the hydrothermally treated product in the presence of a lithium compound.

6. A positive electrode material for a lithium-ion battery, comprising a lithium manganese-based composite oxide represented by the compositional formula: Li1+x(Mnl-m-nFemTin)1−xO2

7. A lithium-ion battery, comprising a positive electrode material comprising a lithium manganese-based composite oxide represented by the compositional formula: Li1+x(Mnl-m-nFemTin)1−xO2

8. The lithium manganese-based composite oxide according to claim 2, wherein 0<x<⅓, 0.05≦m≦0.75, 0.01≦n≦0.75, and 0.06≦m+n<1 in the compositional formula: Li1+x(Mnl-m-nFemTin)1−xO2.

9. The lithium manganese-based composite oxide according to claim 2, comprising a crystal phase of layered rock-salt type structure and a crystal phase of cubic rock-salt type structure.

10. The lithium manganese-based composite oxide according to claim 3, comprising a crystal phase of layered rock-salt type structure and a crystal phase of cubic rock-salt type structure.