Surface protected lithium-metal-oxide electrodes
A lithium-metal-oxide positive electrode having a layered or spinel structure for a non-aqueous lithium electrochemical cell and battery is disclosed comprising electrode particles that are protected at the surface from undesirable effects, such as electrolyte oxidation, oxygen loss or dissolution by one or more lithium-metal-polyanionic compounds, such as a lithium-metal-phosphate or a lithium-metal-silicate material that can act as a solid electrolyte at or above the operating potential of the lithium-metal-oxide electrode. The surface protection significantly enhances the surface stability, rate capability and cycling stability of the lithium-metal-oxide electrodes, particularly when charged to high potentials.
1. A positive electrode for a non-aqueous lithium cell comprising coated lithium metal oxide particles, the surface of the lithium metal oxide particles comprising a coating containing Li 3 PO 4 and a lithium-metal-polyanionic material comprising at least one lithium cation, at least one other metal cation, and at least one polyvalent metal-free anion wherein the coating is deposited on the surface of the lithium metal oxide particles from an acidic sol-gel solution.
2. The electrode of claim 1 , wherein the lithium metal oxide particles comprise a spinel-type structure, a layered-type structure, or a combination thereof.
3. The electrode of claim 1 , wherein the lithium metal oxide comprises one or more compounds represented by the general formula, xLi 2 M′O 3 .(1−x)LiMO 2 , in which M′ comprises one or more metal ions with an average tetravalent oxidation state, and M comprises one or more metal ions with an average trivalent oxidation state.
4. The electrode of claim 3 , in which M′ comprises Mn, and M comprises one or more of Mn, Ni and Co.
5. The electrode of claim 1 , wherein the lithium metal oxide particles contain fluoride ions.
6. The electrode of claim 1 , wherein the lithium-metal-polyanionic material is a lithium-ion conductor that operates at or above a voltage selected from the group consisting of 4 V, 4.5 V, and 5 V, versus metallic lithium.
7. The electrode of claim 1 , wherein the lithium-metal-polyanionic material comprises one or more materials selected from the group consisting of a lithium-metal-phosphate and a lithium-metal-silicate.
8. The electrode of claim 7 , wherein the lithium-metal-polyanionic material comprises one or more material selected from the group consisting of a lithium-nickel-phosphate, a lithium-cobalt-phosphate, a lithium-magnesium-phosphate, a lithium-nickel-silicate, a lithium-cobalt-silicate, and a lithium-magnesium-silicate.
9. The electrode of claim 1 , wherein the lithium-metal-polyanionic material is amorphous or poorly crystalline.
10. The electrode of claim 1 , wherein the lithium-metal-polyanionic material comprises a stoichiometric structure, a cation-deficient structure, an anion-deficient structure, or a combination of two or more of the foregoing structures.
11. The electrode of claim 1 , wherein the lithium-metal-polyanionic material comprises an olivine material.
12. The electrode of claim 1 , wherein the lithium-metal-polyanionic material comprises a lithium-metal-phosphate in which the metal thereof is selected from a divalent metal ion, trivalent metal ion, or tetravalent metal ion.
13. The electrode of claim 12 , wherein the lithium-metal-phosphate is selected from the group consisting of (a) Li 3−x M x/2 PO 4 in which M is one or more of divalent Ni, Co, Mg and Zn, and 0<x<2 and (b) Li 3−x M x/3 PO 4 in which M is one or more of trivalent Al, Ga and La, and 0<x<3.
14. The electrode of claim 1 , wherein the lithium-metal-polyanionic material comprises a lithium-metal-silicate.
15. The electrode of claim 14 , wherein metal of the lithium-metal-silicate is one or more of Ni, Co, Mg and Zn.
16. The electrode of claim 14 , wherein the lithium-metal-silicate comprises Li 4−x M x/2 SiO 4 in which M is one or more of Ni, Co, Mg and Zn, and 0<x<2.
17. A positive electrode for a non-aqueous lithium cell comprising lithium-metal-oxide particles containing a lithium metal oxide compound, the surface of the particles including a sol-gel deposited coating comprising Li 3 PO 4 , wherein the coating optionally includes a lithium-metal-polyanionic material comprising at least one lithium cation, at least one other metal cation, and at least one polyvalent metal-free anion wherein the coating is deposited on the surface of the lithium metal oxide particles from an acidic sol-gel solution.
18. The electrode of claim 17 , wherein the electrode additionally comprises carbon particles mixed with the coated lithium metal oxide particles and held together by a binder.
19. The electrode of claim 1 , wherein the electrode additionally comprises carbon particles mixed with the coated lithium metal oxide particles and held together by a binder.