Oxides having high energy densities

1. A composition, comprising:

an oxide, having a structure:

B i (Ni j T m Y k )O 2 ,

wherein:

i is greater than 0, j is greater than about 0.2, k is greater than about 0.2, m is less than about 0.25, and (j+k+m) is between about 0.95 and about 1.05;

T is cobalt and/or aluminum;

Y represents one or more atoms, each independently selected from the group consisting of transition metals other than cobalt, Group 13 elements other than aluminum, Group 14 elements, Group 15 elements, Group 16 elements, or magnesium;

B represents one or more atoms that are not T or Y such that at least about 90% of B i is lithium;

B has a combined valency of Z B and Y has a combined valency of Z y , (i Z B +2j+k Z Y +3m) being between about 3.8 and 4.2; and

the oxide comprises a plurality of first, repeating atomic planes comprising B and a plurality of second, repeating atomic planes comprising Ni and/or Y and/or T, the plurality of first, repeating atomic planes having less than about (22.5(⅓−m)) % by number of Ni and/or Y and/or T compared to the total number of atoms present within the plurality of first, repeating atomic planes, as determined by 6 Li NMR, wherein the oxide comprises an O3 crystal structure.

2. The composition of claim 1 , wherein the oxide has a structure:

Li i (Ni j Mn k )O 2 .

3. The composition of claim 2 , wherein (j/k) is between about 0.8 and about 1.2.

4. The composition of claim 3 , wherein (j/k) is between about 0.9 and about 1.1.

5. The composition of claim 2 , wherein the plurality of first, repeating atomic planes has less than about 4% by number of Ni and/or Y.

6. The composition of claim 5 , wherein the plurality of first, repeating atomic planes has less than about 3% by number of Ni and/or Y.

7. The composition of claim 6 , wherein the plurality of first, repeating atomic planes has less than about 2% by number of Ni and/or Y.

8. The composition of claim 7 , wherein the plurality of first, repeating atomic planes has less than about 1% by number of Ni and/or Y.

9. The composition of claim 2 , wherein the plurality of second atomic planes has less than about 4% by number of Li.

10. The composition of claim 9 , wherein the plurality of second atomic planes has less than about 3% by number of Li.

11. The composition of claim 10 , wherein the plurality of second atomic planes has less than about 2% by number of Li.

12. The composition of claim 11 , wherein the plurality of second atomic planes has less than about 1% by number of Li.

13. The composition of claim 2 , wherein the oxide, when used as a positive electrode in an electrochemical cell against a Li anode, charged to 4.6 V, gives, upon discharge to 2.5 V, a capacity of at least about 150 mA h/g at a current rate of at least 280 mA/g.

14. The composition of claim 13 , wherein the oxide has a capacity of at least about 170 mA h/g.

15. The composition of claim 14 , wherein the oxide has a capacity of at least about 200 mA h/g.

16. The composition of claim 2 , wherein the plurality of first, repeating atomic planes has at least about 95% by number of Li atoms.

17. The composition of claim 16 , wherein the plurality of first, repeating atomic planes has at least about 96% by number of Li atoms.

18. The composition of claim 17 , wherein the plurality of first, repeating atomic planes has at least about 97% by number of Li atoms.

19. The composition of claim 18 , wherein the plurality of first, repeating atomic planes has at least about 98% by number of Li atoms.

20. The composition of claim 19 , wherein the plurality of first, repeating atomic planes has at least about 99% by number of Li atoms.

21. The composition of claim 2 , wherein the oxide has a structure:

Li(Ni 0.5 Mn 0.5 )O 2 .

22. A composition, comprising:

an oxide, having a structure:

B i (Ni j T m Y k )O 2 ,

wherein:

i is greater than 0, j is greater than about 0.2, k is greater than about 0.2, m is less than about 0.25, and (j+k+m) is between about 0.95 and about 1.05;

T is cobalt and/or aluminum;

Y represents one or more atoms, each independently selected from the group consisting of transition metals other than cobalt, Group 13 elements other than aluminum, Group 14 elements, Group 15 elements, Group 16 elements, or magnesium;

B represents one or more atoms that are not T or Y such that at least about 90% of B i is lithium;

B has a combined valency of Z B and Y has a combined valency of Z y , (i Z B +2j+k Z Y +3m) being between about 3.8 and 4.2; and

the oxide comprises a plurality of first, repeating atomic planes comprising B and a plurality of second, repeating atomic planes comprising Ni and/or Y and/or T, the plurality of first, repeating atomic planes having at least about 90% by number of B atoms compared to the total number of atoms present within the first, repeating atomic planes, the oxide having a hexagonal crystal structure, and an a lattice parameter and a c lattice parameter such that c/a is greater than about 4.95, wherein the oxide comprises an O3 crystal structure.

23. A composition, comprising:

an oxide, having a structure:

B i (Ni j T m Y k )O 2 ,

wherein:

i is greater than 0, j is greater than about 0.2, k is greater than about 0.2, m is less than about 0.25, and (j+k+m) is between about 0.95 and about 1.05;

T is cobalt and/or aluminum;

Y represents one or more atoms, each independently selected from the group consisting of transition metals other than cobalt, Group 13 elements other than aluminum, Group 14 elements, Group 15 elements, Group 16 elements, or magnesium;

B represents one or more atoms that are not T or Y such that at least about 90% of B i is lithium;

B has a combined valency of Z B and Y has a combined valency of Z y , (i Z B +2j+k Z Y +3m) being between about 3.8 and 4.2; and

the oxide, when used as a positive electrode in an electrochemical cell against a Li anode, charged to 4.6 V, gives, upon discharge to 2.5 V, a capacity of at least about 120 mA h/g at a current rate of at least 280 mA/g, wherein the oxide comprises an O3 crystal structure.