Coated positive electrode materials for lithium ion batteries
High specific capacity lithium rich lithium metal oxide materials are coated with inorganic compositions, such as metal fluorides, to improve the performance of the materials as a positive electrode active material. The resulting coated material can exhibit an increased specific capacity, and the material can also exhibit improved cycling. The materials can be formed while maintaining a desired relatively high average voltage such that the materials are suitable for the formation of commercial batteries. Suitable processes are described for the synthesis of the desired coated compositions that can be adapted for commercial production.
1. A lithium ion battery positive electrode material comprising an active composition coated with an inorganic coating composition,
wherein the coating composition comprises a metal/metalloid fluoride and has an average thickness from about 0.5 nanometers (nm) to about 12 nm,
wherein the active composition can be approximately represented by a formula Li 1+x Ni α Mn β Co γ A 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 to about 0.3, and δ ranges from about 0 to about 0.1, and where A is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations,
wherein the material exhibits an average voltage that is no more than about 2 percent less than the average voltage of the same active composition without the coating, when cycled from 2V to 4.6V against lithium at a rate of C/10, and
wherein the material comprises substantially spherically shaped particles with relatively homogenous size.
2. The positive electrode material of claim 1 wherein the coating composition comprises AlF 3 , MgF 2 , CaF 2 , SrF 2 or BaF 2 .
3. The positive electrode material of claim 1 wherein the coating has an average thickness no more than about 8 nm.
4. The positive electrode material of claim 1 wherein the coating has an average thickness from about 1 nm to about 8 nm.
5. The positive electrode material of claim 1 wherein the active composition can be approximately represented by a formula of bLiM′O 2 .(1−b) 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<b<1.
6. The positive electrode material of claim 5 wherein M″ is Mn and M′ is a combination of Ni, Co, and Mn.
7. The positive electrode material of claim 1 wherein the active composition can be approximately represented by 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 0.3 to about 0.65, and γ ranges from about 0.05 to about 0.4.
8. The positive electrode material of claim 1 having a specific capacity of at least about 245 mAh/g with a discharge rate of C/3 when discharged from 4.6V to 2.0 V at room temperature.
9. A battery comprising the positive electrode material of claim 1 and a non-aqueous electrolyte comprising lithium ions.
10. A lithium ion battery comprising a positive electrode, a negative electrode comprising a lithium incorporation composition, a separator between the positive electrode and the negative electrode and an electrolyte comprising lithium ions,
wherein the positive electrode comprises the positive electrode active material of claim 1 having a discharge specific capacity of at least about 190 mAh/g with a discharge rate of 2 C from 4.6 volts to 2.0 volts at room temperature for the fifteenth charge/discharge cycle, distinct electrically conductive powders and a polymer binder.
11. The lithium ion battery of claim 10 wherein the negative electrode comprises graphitic carbon.
12. The lithium ion battery of claim 10 wherein the irreversible capacity loss is reduced by at least about 10% relative to the irreversible capacity loss of an equivalent battery formed with the uncoated active composition.
13. The positive electrode material of claim 1 having a tap density of at least about 1.3 g/mL.
14. The positive electrode material of claim 1 having a discharge specific capacity of at least about 245 mAh/g, an average voltage of at least about 3.55 volts and a capacity at the 40th cycle that is at least about 90% of the capacity at the 10th cycle with a discharge rate of C/3 from 4.6 volts to 2.0 volts at room temperature.
15. The positive electrode material of claim 1 having a specific capacity of at least about 250 mAh/g with a discharge rate of C/3 from 4.6 volts to 2.0 volts at room temperature.
16. The positive electrode material of claim 1 having a capacity at 40 cycles that is at least about 95% of the capacity at the 10th cycle with a discharge rate of C/3 from 4.6 volts to 2.0 volts at room temperature.
17. The positive electrode material of claim 1 wherein the sum x+α+β+γ approximately equals to 1.0.