Electrode materials for rechargeable battery
A positive electrode is disclosed for a non-aqueous electrolyte lithium rechargeable cell or battery. The electrode comprises a lithium containing material of the formula Na y Li x Ni z Mn 1-z-z′ M z′ O d , wherein M is a metal cation, x+y>1, 0<z<0.5, 0≦z′<0.5, y+x+1 is less than d, and the value of d depends on the proportions and average oxidation states of the metallic elements, Li, Na, Mn, Ni, and M, if present, such that the combined positive charge of the metallic elements is balanced by the number of oxygen anions, d. The inventive material preferably has a spinel or spinel-like component in its structure. The value of y preferably is less than about 0.2, and M comprises one or more metal cations selected preferably from one or more monovalent, divalent, trivalent or tetravalent cations, such as Mg 2+ , Co 2+ , Co 3+ , B 3+ , Ga 3+ , Fe 2+ , Fe 3+ , Al 3+ , and Ti 4+ . The electrode material can be synthesized using an ion-exchange reaction with a lithium salt in an organic-based solvent to partially replace sodium ions of a precursor material with lithium ions.
1. A process for preparing a lithium containing material of formula
Na y Li x Ni z Mn 1-z-z′ M z′ O d , wherein M is a metal cation, x+y>1, 0<z<0.5, 0≦z′≦0.5, y+x+1 is less than d, and the value of d depends on the proportions and average oxidation states of the metallic elements, Li, Na, Mn, Ni, and M, if present, such that the combined positive charge of the metallic elements is balanced by the number of oxygen anions, d,
wherein the y is less than 0.2 and M, if present, is one or more metal cation selected from one or more monovalent, divalent, trivalent or tetravalent cations, and
wherein the Na y Li x Ni z Mn 1-z-z′ M z′ O d , contains a spinel or spinel-like component,
the process comprising:
exchanging lithium ions for sodium ions in a precursor composition of formula Na y′ Li x′ Ni z Mn 1-z-z′ M z′ O d′ wherein M is a metal cation, x′+y′>1, 0<z<0.5, 0≦z′≦0.5, y′+x′+1 is less than d′, and the value of d′ depends on the proportions and average oxidation states of the metallic elements, Li, Na, Mn, Ni, and M, if present, such that the combined positive charge of the metallic elements is balanced by the number of oxygen anions, d′; wherein the exchange of lithium ions for sodium ions is accomplished by reacting a mixture of the precursor composition with a lithium salt dissolved in an organic solvent, the precursor composition and the resulting exchanged lithium containing material being insoluble in the organic solvent.
2. The process of claim 1 wherein the lithium salt is lithium bromide and the organic solvent is hexanol.
3. The process of claim 1 wherein the mixture is refluxed in the solvent.
4. The process of claim 3 further comprising stirring the mixture at room-temperature following the refluxing step.
5. The process of claim 1 wherein the exchanged lithium containing material is isolated by filtration and optionally washing the filtered material with an alcohol.
6. The process of claim 5 wherein the alcohol is methanol.
7. The process of claim 5 wherein the isolated lithium containing material is dried at room temperature after washing with the alcohol.
8. The process of claim 1 wherein M is at least one cation selected from the group consisting of Mg 2+ , Co 2+ , Co 3+ , B 3+ , Ga 3+ , Fe 2+ , Fe 3+ , Al 3+ and Ti 4+ .
9. The process of claim 1 wherein 2<d≦3.
10. The process of claim 1 wherein the lithium containing material of formula Na y Li x Ni z Mn 1-z-z′ M z′ O d comprises a component selected from the group consisting of Na 0.02 Li 1.0 Ni 0.25 Mn 0.75 O d , Na 0.04 Li 1.24 Ni 0.25 Mn 0.75 O d , Na 0.09 Li 1.14 Ni 0.25 Mn 0.75 O d , and Na 0.02 Li 1.31 Ni 0.25 Mn 0.75 O d .
11. The process of claim 10 wherein the lithium containing material of formula Na y Li x Ni z Mn 1-z-z′ M z′ O d exhibits a high-intensity layered peak and small Li—Ni—Mn ordering peaks in the range of about 20-25° 2θ (CuKα).
12. The process of claim 1 wherein the lithium containing material of formula Na y Li x Ni z Mn 1-z-z′ M z′ O d has a morphology that comprises primary globule particles having a size in the range of about 5 nm to about 500 nm, and secondary particles having a size in the range of about 2 μm to about 20 μm.