Positive electrode materials for high discharge capacity lithium ion batteries
View Patent ↗Positive electrode active materials are described that have a high tap density and 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 battery.
1. A method for the synthesis of a layered lithium metal oxide composition, the method comprising,
precipitating a mixed metal carbonate composition from a solution wherein the mixed metal carbonate composition has a selected composition, the precipitating step comprising the gradual combination under stirred conditions with a maintained pH from about 6.0 to about 7.45, of an aqueous metal ion solution comprising dissolved +2 metal cations and an aqueous carbonate solution comprising a dissolved carbonate composition, wherein the aqueous carbonate solution comprises sodium carbonate and ammonium hydroxide;
drying the mixed metal carbonate composition while heating in an oxygen free atmosphere for about 4 hours to about 12 hours before heating the carbonate composition to form the corresponding metal oxide composition;
mixing a lithium source in powder form comprising lithium carbonate with the mixed metal carbonate composition to form a mixture;
heating the mixture of the lithium source and the mixed metal carbonate composition in an oxygen containing atmosphere to a temperature from about 400° C. to about 800° C. to form a metal oxide composition; and
heating the metal oxide composition in an oxygen containing atmosphere to a temperature from about 700° C. to about 1200° C. to form a crystalline layered lithium metal oxide composition, which is lithium rich relative to a LiMO 2 reference composition where M represents non-lithium metal cations.
2. The method of claim 1 wherein the solution comprises acetate anions, sulfate anions, nitrate anions or combinations thereof.
3. The method of claim 1 wherein the solution further comprises lithium cations.
4. The method of claim 1 wherein the lithium metal oxide composition can be approximately represented by 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.
5. The method of claim 1 wherein the lithium metal oxide composition can be approximately represented by a formula of xLiMO 2 .(1−x)Li 2 M′O 3 , wherein M′ comprises Mn and M comprises Mn, Co and Ni.
6. The method of claim 1 wherein the lithium source further comprises lithium hydroxide powder.
7. The method of claim 1 further comprising applying a stabilization coating composition to the lithium metal oxide composition to form a positive electrode active material.
8. The method of claim 7 wherein the lithium metal oxide composition is homogenized in a coating solution that comprises the cation of the coating composition before the addition of a solution comprising the counter anion of the coating composition to deposit the coating composition onto the lithium metal oxide composition through precipitation.
9. The method of claim 7 wherein the positive electrode active material comprises from about 0.5 mole percent to about 4 mole percent metal fluoride as the stabilization coating.
10. The method of claim 7 wherein the stabilization coating comprises AlF 3 .
11. The method of claim 7 wherein the stabilization coating comprises Al 2 O 3 .
12. The method of claim 7 wherein the positive electrode active material 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.
13. The method of claim 7 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.
14. The method of claim 7 wherein positive electrode active material has a discharge capacity at a 10th discharge cycle between about 260 and about 290 mAh/g at room temperature at a discharge rate of C/3 when discharged from 4.6 volts to about 2.0 volts.
15. The method of claim 7 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.
16. The method of claim 7 wherein the positive electrode active material has a tap density of at least about 1.8 g/ml.
17. The method of claim 1 further comprising homogenizing the metal oxide composition to form a powder.
18. The method of claim 1 wherein the aqueous carbonate solution further comprises ammonium hydroxide at a concentration from about 0.25M to about 2M.