Cathode materials for lithium-ion secondary cells

• US 6,017,654 A
• Filed: 08/04/1997
• Issued: 01/25/2000
• Est. Priority Date: 08/04/1997
• Status: Expired due to Fees

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Kumta, Prashant Nagesh, Sriram, Mandyam Ammanjee, Chang, Chun-Chieh
• Primary Examiner(s): Nuzzolillo, Maria
• Assistant Examiner(s): Wills, Monique M.
• Application Number:
  US08/906,024
• Time in Patent Office: 904 Days
• Field of Search: 429/223, 429/221, 429/224, 429/231.1, 429/231.2, 429/231.3, 429/231.5, 429/231.95, 429/229, 429/231.6
• US Class Current: 429/231.95
• CPC Class Codes: C01G 45/1228 of the type [MnO2]n- , e.g. LiMnO2, Li[MxMn1-x]O2
• CPC Class Codes: C01G 53/42 containing alkali metals, e.g. LiNiO2
• CPC Class Codes: C01G 53/50 of the type [MnO2]n- , e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/76 by a space-group or by other symmetry indications
• CPC Class Codes: C01P 2002/77 by unit-cell parameters, atom positions or structure diagrams
• CPC Class Codes: C01P 2002/78 by stacking-plane distances or stacking sequences
• CPC Class Codes: C01P 2002/88 by thermal analysis data, e.g. TGA, DTA, DSC
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: H01M 2004/028 Positive electrodes
• CPC Class Codes: H01M 4/485 of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy H01M4/505, H01M4/525 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Crystalline lithiated transition metal oxide materials having a rhombohedral R-3m crystal structure includes divalent cations selected and added in amounts so that all or a portion of the divalent cations occupy sites in transition metal atom layers within the materials'"'"' crystal lattice. The lithiated transition metal oxides are useful as cathode materials in lithium-ion secondary cells. The materials include, but are not limited to, Li_1+x Ni_1-y M_y N_x O₂(1+x) and Li₁ Ni_1-y M_y N_x O_p, wherein M is a transition metal selected from titanium, vanadium, chromium, manganese, iron, cobalt, and aluminum, and N is a group II element selected from magnesium, calcium, strontium, barium, and zinc. The materials provide improved cyclability and high voltage capacity as cathodes in lithium-ion secondary cells. Processes for producing the divalent cation-containing lithium transition metal oxide materials of the invention are also disclosed.

Claims

1. A crystalline material comprising atoms of lithium, oxygen, and at least one transition metal, the material further comprising divalent cations on sites within atom layers of the crystalline material including said atoms of said at least one transition metal.

2. The material recited in claim 1 wherein the material has a single phase R-3m crystal structure when lacking said divalent cations.

3. The material recited in claim 2 wherein a portion of said lithium atoms may be reversibly removed from said crystal structure.

4. The material recited in claim 3 wherein said atom layers including said transition metal atoms increase the oxidation state of transition metal ions within the material.

5. The material recited in claim 3 wherein said divalent cations are present in a range of from 1 to 25 atomic percent based on the overall number of atoms in said atom layers of the material including said transition metal atoms.

6. The material recited in claim 5 wherein said range is from 3 to 15 atomic percent.

7. The material recited in claim 3 wherein said divalent cations are ions selected from the group consisting of group II elements and zinc.

8. The material recited in claim 7 wherein said divalent cations are ions of alkaline earth elements.

9. The material recited in claim 8 wherein said alkaline earth elements are selected from the group consisting of magnesium, calcium, strontium, and barium.

10. The material recited in claim 3 wherein said transition metals are at least one selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, and aluminum.

11. The material recited in claim 1 having the composition

12. The material recited in claim 1 having the composition

13. The material recited in claim 1 having the composition

16. The cathode recited in claim 1, wherein said material has the composition

17. The cathode recited in claim 1, wherein said material has the composition

30. The material recited in claim 1 having the composition

31. The material recited in claim 30, wherein 0.07≦

x≦

0.15.

32. The material recited in claim 1 having the composition

33. The material recited in claim 32, wherein 0.03≦

x≦

0.15.

34. The material recited in claim 1 having the composition

35. The material recited in claim 34, wherein 0.03≦

x≦

0.15.

36. The material recited in claim 1 having a composition selected from the group consisting of Li₁.03 Ni₀.75 Co₀.25 Mg₀.03 O₂.06, Li₁.05 Ni₀.75 Co₀.25 Mg₀.05 O₂.10, Li₁.10 Ni₀.75 Co₀.25 Mg₀.10 O₂.20, Li₁.15 NiMg₀.15 O₂.30, and LiNi₀.75 Co₀.25 Mg₀.03 O_p where 2.03≦

p≦

2.06.

14. A cathode for an electrochemical cell, the cathode comprising a crystalline material comprising atoms of lithium, oxygen, and at least one transition metal, said material further comprising divalent cations on sites within atom layers of said material including atoms of said at least one transition metal.

15. The cathode recited in claim 14, wherein said material has the composition

18. A lithium-ion secondary cell comprising:

a cathode comprising a crystalline material comprising atoms of lithium, oxygen, and at least one transition metal, said material further comprising divalent cations on sites within atom layers of said material including atoms of said at least one transition metal;

an anode that is compatible with said cathode; and

an electrolyte that is compatible with said cathode and said anode.

19. The lithium-ion secondary cell recited in claim 18, wherein said material has the composition

20. The lithium-ion secondary cell recited in claim 18, wherein said material has the composition

21. The lithium-ion secondary cell recited in claim 18, wherein said material has the composition

22. A process for producing a lithium transition metal oxide crystalline material, the process comprising:

combining at least an amount of a lithium-containing material, an amount of a transition metal-containing material, and an amount of a material containing atoms of at least one element selected from the group consisting of group II elements and zinc to yield a homogenous solid therefrom; and

heat treating said homogenous solid to produce an active crystalline lithium transition metal oxide material that contains atoms of said at least one element selected from the group consisting of group II elements and zinc, said amounts selected so that in said active material said atoms of said at least one element selected from the group consisting of group II elements and zinc occupy sites within crystal layers of said active material including transition metal atoms.

23. The process recited in claim 22 wherein said act of combining includes:

dissolving said amounts in at least one solvent to provide a homogenous solution; and

drying said homogenous solution while constantly stirring to remove said solvent from said homogenous solution and provide said homogenous solid.

24. The process recited in claim 22 wherein said act of combining includes:

dissolving said amounts in at least one solvent to provide a homogenous solution; and

spraying said homogenous solution through an atomizing nozzle into a chamber, said chamber being maintained at a temperature above the drying temperature of said solvent, to evaporate said solvent and provide said homogenous solid in a powder form.

25. The process recited in claim 22 wherein in said act of combining, said lithium-containing material comprises lithium hydroxide and wherein said act of combining includes:

dissolving said amount of lithium hydroxide and said amount of transition metal-containing material in an organic solvent to form a lithium-containing solution;

preparing an aqueous solution of said amount of material containing atoms of said at least one element selected from group II elements and zinc;

mixing together said aqueous solution and said lithium-containing solution to form a mixture;

allowing said mixture to stand until gelation occurs and a gel is provided; and

drying said gel to obtain said homogenous solid.

26. The process recited in claim 22 wherein said active crystalline lithium transition metal oxide material containing atoms of at least one element selected from the group consisting of group II elements and zinc has the composition

27. The process recited in claim 22 wherein said active crystalline lithium transition metal oxide material containing atoms of at least one element selected from the group consisting of group II elements and zinc has the composition

28. The process recited in claim 22 wherein said active crystalline lithium transition metal oxide material containing atoms of at least one element selected from the group consisting group II elements and zinc has the composition

29. A process for producing a lithium-ion secondary cell, the process comprising fabricating the cell from:

a cathode comprising a crystalline material comprising atoms of lithium, oxygen, and at least one transition metal, said material further comprising divalent cations on sites within atom layers of said material including atoms of said at least one transition metal;

an anode that is compatible with said cathode; and

an electrolyte that is compatible with said cathode.