Positive electrode materials for lithium ion batteries having a high specific discharge capacity and processes for the synthesis of these materials
View Patent ↗Positive electrode active materials are described that have a very high specific discharge capacity upon cycling at room temperature and at a moderate discharge rate. Some materials of interest have the formula Li 1+x Ni α Mn β CO γ O 2 , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, and γ ranges from about 0.05 to about 0.3. The materials can be coated with a metal fluoride to improve the performance of the materials especially upon cycling. Also, the coated materials can exhibit a very significant decrease in the irreversible capacity lose upon the first charge and discharge of the cell. Methods for producing these materials include, for example, a co-precipitation approach involving metal hydroxides and sol-gel approaches.
1. A positive electrode active material for a lithium ion cell having a discharge capacity at a 10th discharge cycle of at least 250 mAh/g at room temperature at a discharge rate of C/3 when discharged from 4.6 volts to 2.0 volts after the material is activated in the first cycle through a charge to 4.6V at a rate of C/10,
comprising a lithium metal oxide composition having a formula Li 1+x Ni α Mn β Co γ M δ O 2-z F z , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, γ ranges from about 0.05 to about 0.3, δ ranges from about 0 to about 0.1 and z ranges from about 0 to about 0.1, and where M is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb or combinations thereof, and a stabilizing coating,
wherein the positive electrode active material has a first cycle irreversible capacity loss at a discharge rate of C/10 of no more than about ⅔ of the first cycle irreversible capacity loss of the lithium metal oxide composition, which corresponds to the positive electrode active material without the stabilization coating.
2. The positive electrode active material of claim 1 wherein the composition can be further represented by a formula of xLiMO 2 .(1-x) Li 2 M′O 3 , where M represents one or more metal ions having an average valance of +3 and M′ represents one or more metal ions having an average valance of +4 and 0≦x≦1.
3. The positive electrode material of claim 2 wherein M′ comprises Mn and M comprises Mn, Co and Ni.
4. The positive electrode material of claim 1 wherein the composition has a formula Li 1+x Ni α Mn β Co γ O 2 , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, and γ ranges from about 0.05 to about 0.3.
5. The positive electrode material of claim 1 wherein the stabilizing coating comprises AlF 3 .
6. The positive electrode active material of claim 1 having a discharge capacity at a 10th discharge cycle of at least 255 mAh/g at room temperature at a discharge rate of C/3 when discharged from 4.6 volts to 2.0 volts.
7. The positive electrode active material of claim 1 having a discharge capacity at a 10th discharge cycle between about 260 and about 275 mAh/g at room temperature at a discharge rate of C/3 when discharged from 4.6 volts to about 2.0 volts.
8. The positive electrode active material of claim 1 wherein the stabilizing coating comprises a coating of metal fluoride.
9. A secondary lithium ion battery comprising a positive electrode comprising the positive electrode active material of claim 1 , a negative electrode comprising a lithium intercalation composition and a separator between the positive electrode and the negative electrode.
10. The positive electrode active material of claim 1 , wherein the lithium metal oxide composition comprises a layered lithium metal oxide comprising +4 metal cations, +3 metal cations and +2 metal cations within a crystalline lattice, wherein the stabilizing coating comprises a metal/metalloid fluoride, and wherein the positive electrode active material has a discharge capacity at the 20th cycle that is at least about 98% of the 5th cycle discharge capacity when discharged at room temperature at a discharge rate of C/3.
11. The positive electrode active material of claim 1 wherein the material comprises from about 0.5 mole percent to about 4 mole percent metal fluoride as the stabilizing coating.
12. The positive electrode active material of claim 11 wherein the metal fluoride comprises AlF 3 .
13. The positive electrode active material of claim 1 wherein the electrode material has a discharge capacity at the 20th cycle that is at least about 98.5% of the 5th cycle discharge capacity when discharged at room temperature with a rate of C/3.
14. The positive electrode active material of claim 1 wherein the stabilizing coating comprises Al 2 O 3 .
15. A method for the synthesis of a layered lithium metal oxide composition, the method comprising
precipitating a mixed metal hydroxide composition from a solution comprising +2 metal cations wherein the hydroxide composition has a selected composition;
heating the hydroxide composition to form a metal oxide composition; and
combining a lithium source composition to the metal oxide composition to form a lithium metal oxide precursor;
heating the lithium metal oxide precursor to form a crystalline lithium metal oxide, wherein the crystalline lithium metal oxide composition has a formula Li 1+x Ni α Mn β Co γ M δ O 2 , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, γ ranges from about 0.05 to about 0.3, and δ ranges from about 0 to about 0.1, and where M is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb or combinations thereof; and
applying a stabilizing coating to form the positive electrode active material of claim 1 .
16. The method of claim 15 wherein the solution comprises acetate anions, sulfate anions, nitrate anions or combinations thereof.
17. The method of claim 15 wherein the lithium metal oxide composition has a formula Li 1+x Ni α Mn β Co γ O 2 , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, and γ ranges from about 0.05 to about 0.3.
18. A method for the synthesis of a layered lithium metal oxide composition, the method comprising
precipitating a mixed metal hydroxide composition from a solution comprising +2 metal cations wherein the hydroxide composition has a selected composition;
adding a lithium source in powder form to the metal hydroxide composition to form a mixture;
heating the mixture to form a corresponding crystalline lithium metal oxide composition, wherein the crystalline lithium metal oxide composition has a formula Li 1+x Ni α Mn β Co γ M δ O 2 , where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, γ ranges from about 0.05 to about 0.3, and δ ranges from about 0 to about 0.1, and where M is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb or combinations thereof; and
applying a stabilizing coating to form the positive electrode active material of claim 1 .