High performance layered cathode materials for high voltage sodium-ion batteries
A cathode active material includes Na x MO 2 having at least a first phase, a second phase different from the first phase, and a third phase that is different from the first and second phases, wherein each phase is independently selected from Pm or On, where m and n are individually an integer, M is a transition metal or a mixture of transition metals, and x is greater than 0 and less than or equal to 1.
1. A cathode active material comprising integrated Na x MO 2 having at least a first phase, a second phase different from the first phase, and a third phase that is different from the first and second phases, wherein each phase is independently selected from Pm or On, where m and n are individually an integer, M is a transition metal or a mixture of transition metals, and x is greater than 0 and less than or equal to 1, wherein the cathode active material further comprises a surface coating.
2. The cathode active material of claim 1 , wherein m is 1, 2, 3, 4, 5, 6, 7, or 8; and n is 1, 2, 3, 4, 5, 6, 7, or 8.
3. The cathode active material of claim 1 , wherein M is selected from the group consisting of Fe, Co, Ni, Mn, Cr, V, Cu, Ti, and a combination of any two or more thereof.
4. The cathode active material of claim 1 further comprising a dopant such that an overall formula of the doped cathode active material is Na x M y M′ z O 2-δ F δ , wherein M′ is Li, Mg, Al, Ca, Sc, Zn, Y, Zr, Nb, Mo, Ru, Ag, Ba, Sb, or a combination of any two or more thereof; y is greater than 0 and less than or equal to 0.9; z is greater than 0 and less than or equal to 0.1; and δ is greater than 0 and less than or equal to 0.2.
5. The cathode active material of claim 1 , wherein the M is a mixture of Co, Ni, and Mn.
6. The cathode active material of claim 1 having the formula Na x NiαCoβMn γ O 2 , and α is greater than 0 and less than or equal to 1, β is greater than 0 and less than or equal to 1, and γ is greater than 0 and less than or equal to 1, where the total of α,βand γ is equal to 1.
7. The cathode active material of claim 1 , wherein the first phase is P2, the second phase is O1, and the third phase is O3.
8. The cathode active material of claim 1 , further comprising a current collector, a conductive agent, a binder, or any combination thereof.
9. The cathode active material of claim 1 , wherein the surface coating comprises a metal oxide, a metal fluoride, a metal phosphate, a conductive carbon coating, a metal oxyfluoride, or a combination of any two or more thereof.
10. The cathode active material of claim 9 , wherein the surface coating comprises a metal oxide selected from the group consisting of MgO, Al 2 O 3 , ZrO 2 , MnO 2 , CeO 2 , TiO 2 , ZnO, SiO 2 , SnO 2 , Cr 2 O 3 , and a combination of any two or more thereof.
11. The cathode active material of claim 9 , wherein the surface coating comprises a metal fluoride selected from the group consisting of AlF 3 , CaF 2 , CeF 3 , ZrF, ZrF 2 , ZrF 3 , ZrF 4 , LaF 3 , SrF 2 , and a combination of any two or more thereof.
12. The cathode active material of claim 9 , wherein the surface coating comprises a metal phosphate selected from the group consisting of AlPO 4 , YPO 4 , Li 3 PO 4 , FePO 4 , Mg 3 (PO 4 ) 2 , Zn 3 (PO 4 ) 2 , Ca 3 (PO 4 ) 2 , Co 3 (PO 4 ) 2 , Ni 3 (PO 4 ) 2 , and a combination of any two or more thereof.
13. The cathode active material of claim 9 , where the surface coating comprises a metal oxyfluoride selected from the group consisting of iron oxyfluoride, cerium oxyfluoride, magnesium oxyfluoride, zirconium oxyfluoride, aluminum oxyfluoride, vanadium oxyfluoride, silicon oxyfluoride, bismuth oxyfluoride, and a combination of any two or more thereof.