Secondary battery material and synthesis method

Abstract

A composite Li1+xMn2−x−yMyO4 cathode material stabilized by treatment with a second transition metal oxide phase that is highly suitable for use in high power and energy density Li-ion cells and batteries. A method for treating a Li1+xMn2−x−yMyO4 cathode material utilizing a dry mixing and firing process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically depicts the powder X-ray diffraction spectra of untreated Li_1.05Mn_1.95O₄ and three Li_1.05Mn_1.95O₄ samples modified with LiCoO₂ by methods as described in Comparative Examples 1 and 2 and Example 1;

FIG. 2 graphically depicts the discharge capacity profiles at 65° C. of four LiCoO₂ modified Li_1.05Mn_1.95O₄ materials prepared by methods described in Comparative Examples 1 and 2 and Examples 1 and 2 and the unmodified Li_1.05Mn_1.95O₄ material.

FIG. 3 graphically depicts the discharge capacity profiles at 65° C. of an untreated cathode material with composition LiMn₂O₄, a treated cathode material with composition Li_1.05Mn_1.95O₄ and a LiCoO₂ modified LiMn₂O₄ cathode prepared by methods of this invention as described in Example 3.

FIG. 4 graphically depicts the normalized discharge capacity profiles at 65° C. of an untreated cathode material with composition LiMn₂O₄, a treated cathode material with composition Li_1.05Mn_1.95O₄ and a LiCoO₂ modified LiMn₂O₄ cathode prepared by methods of this invention as described in Example 3.

Claims

1. A method for treating a lithium transition metal oxide cathode material with a second lithium transition metal oxide comprising the steps of: providing a quantity of powdered lithium transition metal oxide cathode material;dry mixing the powdered lithium transition metal oxide cathode material with precursors of a second transition metal oxide phase; andfiring the mixture.

2. The method of claim 1 wherein the lithium transition metal oxide cathode material is selected from the group consisting of Li1+xMn2−x−yMyO4 where 0≦x≦0.5, 0≦y≦1 and M=Al, Ni, Co, Ti, V, Mg, Cr.

3. The method of claim 2 wherein the second transition metal oxide phase is selected from the group consisting of Li1−xCo1−yMyO2 where 0≦x≦1, 0≦y≦1 and M=Al, Mn, Ni, Ti, V, Mg, Cr.

4. The method of claim 3 wherein the precursors of the second lithium transition metal oxide phase are selected from the group consisting of lithium nitrate, lithium acetate, lithium formate, lithium hydroxide, lithium oxide, cobalt nitrate, cobalt acetate, cobalt formate, cobalt hydroxide, cobalt oxide and combinations thereof.

5. The method of claim 4 wherein the composition of the dry mix is determined to yield upon firing a final composite cathode material comprising a 1% to 6% by weight proportion of the second transition metal oxide phase.

6. The method of claim 5 wherein the lithium transition metal cathode material and precursor materials are continuously dry mixed for a period of 1-5 hours.

7. The method of claim 6 wherein the mixture of the lithium transition metal cathode material and precursor materials is fired between 300° C. and 700° C.

8. The method of claim 7 wherein the process conditions produce a composite transition metal oxide cathode material with a surface layer of heterogeneous phase composition.

9. The method of claim 1 comprising a lithium transition metal oxide cathode material selected from the group consisting of Li1+xMn2−xO4 where 0≦x≦0.5.

10. The method of claim 9 comprising a transition metal oxide surface treatment phase selected from the group consisting of Li1−xCoO2 where 0≦x≦0.5.

11. The method of claim 10 wherein the precursors of the second lithium transition metal oxide phase are selected from the group consisting of lithium nitrate, lithium acetate, lithium formate, lithium hydroxide, lithium oxide, cobalt nitrate, cobalt acetate, cobalt formate, cobalt hydroxide, cobalt oxide and combinations thereof.

12. The method of claim 11 wherein the composition of the dry mix is determined to yield upon firing a final composite cathode material comprising a 1% to 6% by weight proportion of the second transition metal oxide phase.

13. The method of claim 12 wherein the lithium transition metal cathode material and precursor materials are continuously dry mixed for a period of 1-5 hours.

14. The method of claim 13 wherein the mixture of the lithium transition metal cathode material and precursor materials is fired between 300° C. and 700° C.

15. The method of claim 14 wherein the process conditions produce a composite transition metal oxide cathode material with a surface layer of heterogeneous phase composition.

16. A cathode material for Li-ion cells comprising a core composition of Li1+xMn2−x−yMyO4 where 0≦x≦0.5, 0≦y≦1 and M=Al, Ni, Co, Ti, V, Mg, Cr and a surface layer of heterogeneous phase composition comprising the core phase and a second transitional metal oxide phase.

17. The cathode material of claim 16 wherein the second transition metal oxide phase of the surface layer is Li1−xCo1−yMyO2 where 0≦x≦1, 0≦y≦1 and M=Al, Mn, Ni, Ti, V, Mg, Cr.

18. The cathode material of claim 17 wherein the cathode material surface layer is comprised of more than 55% but less than 95% of the second transition metal oxide surface phase.

19. The cathode material of claim 17 wherein the cathode material surface layer is comprised of more than 70% but less than 90% of the second transition metal oxide surface phase.

20. A cathode material for Li-ion cells comprising a core composition of Li1+xMn2−xO4 where 0≦x≦0.5 and a surface layer comprising a heterogeneous mixture of the core phase and s second transition metal phase of composition Li1−xCo1−yO2 where 0≦x≦0.5 such that the second transition metal phase makes up more than 55% but less than 90% of the surface layer.