Positive electrode material for a lithium ion accumulator

1. A compound of formula Li 1+x (Ni a Mn b Co c Al y ) 1−x O 2 wherein:

a, b and c are non-zero;

a+b+c+y=1;

1.05≦(1+x)/(1−x)≦1.25;

0.015≦y(1−x);

the atomic amount of manganese representing from 95% to 100% of the atomic amount of nickel.

2. The compound according to claim 1 , wherein the amount of manganese represents from 97% to 100% of the amount of nickel.

3. The compound according to claim 1 , wherein 0.02≦y(1−x).

4. The compound according to claim 1 , wherein 0.04≦y(1−x).

5. The compound according to claim 1 , wherein 0.09≦y(1−x).

6. The compound according to claim 1 , wherein 1.05≦(1+x)/(1−x)≦1.15.

7. The compound according to claim 1 , wherein 1.05≦(1+x)/(1−x)≦1.10.

8. The compound according to claim 1 , wherein:

a=b=0.5−z:

c=2z−y; and

0<z≦0.15.

9. The compound according to claim 8 , wherein 0<z≦0.10.

10. The compound according to claim 9 , wherein 0<z≦0.0075.

11. The compound according to claim 1 , devoid of Mn 3+ ions.

12. An electrode comprising the compound according to claim 1 .

13. A lithium-ion or lithium-polymer electrochemical generator comprising an electrode according to claim 12 .

14. The compound according to claim 2 , wherein the amount of manganese preferably represents from 98% to 100% of the amount of nickel.

15. The compound according to claim 14 , wherein the amount of manganese preferably represents from 99% to 100% of the nickel amount.