Composite cathode materials having improved cycle life
Lithiated composite materials and methods of manufacture are provided that are capable of imparting excellent capacity and greatly improved cycle life in lithium-ion secondary cells. By supplementing a high nickel content lithium storage material with a transition metal oxide lithium storage material or a dopant at relatively low levels, the capacity of the high nickel content lithium storage materials is maintained while cycle life is dramatically improved. These characteristics are promoted by methods of producing the materials that intermix unlithiated precursor materials with a lithium source and sintering the materials together in a single sintering reaction. The resulting lithiated composite materials provide for the first time both high capacity and excellent cycle life to predominantly high nickel content electrodes.
1. An electrode material for a rechargeable lithium ion electrochemical cell, said electrode material comprising:
a non-lithiated high nickel content lithium storage material comprising Ni a Co b wherein a is from 81 to 99 and b is from 1 to 19 and where a+b=100;
a non-lithiated transition metal dopant material; and
a lithium source;
said non-lithiated high nickel content lithium storage material, said non-lithiated transition metal dopant material and said lithium source intermixed and sintered to form a lithiated composite material;
wherein said high nickel content lithium storage material is present as a predominant by weight relative to said transition metal dopant material; and
wherein said composite material is characterized by a longer cycle life than that of the high nickel content lithium storage material.
2. The electrode material of claim 1 wherein said dopant material is present at 10 atomic percent or less relative to said high nickel content lithium storage material.
3. The electrode material of claim 1 wherein said dopant material is present at from 0.1 to 4 atomic percent relative to said high nickel content lithium storage material.
4. The electrode material of claim 1 wherein said composite material maintains a capacity in excess of 160 milliamphours per gram at 40 cycles.
5. The electrode material of claim 1 wherein said composite material maintains a capacity in excess of 170 milliamphours per gram at 30 cycles.
6. The electrode material of claim 1 wherein said high nickel content lithium storage material comprises Ni 92 Co 8 .
7. The electrode of claim 1 wherein said high nickel content lithium storage material further comprises Mn at an atomic percentage of 10% or less.
8. The electrode material of claim 1 wherein said dopant is an oxide of a transition metal.
9. The electrode material of claim 8 wherein said transition metal is selected from the group consisting of Ti, W, Mo, or combinations thereof.
10. The electrode material of claim 1 wherein said dopant is a sulfide of a transition metal.
11. The electrode material of claim 10 wherein said transition metal is selected from the group consisting of W, Mo, or combinations thereof.
12. The electrode material of claim 1 wherein said lithium source is present at greater than stoichiometric ratio.
13. A method of making an electrode material for a rechargeable lithium ion electrochemical cell, said method comprising the steps of:
(a) providing a non-lithiated high nickel content lithium storage material comprising Ni a Co b wherein a is from 81 to 99 and b is from 1 to 19 and where a+b=100;
(b) providing a non-lithiated transition metal dopant;
(c) mixing said non-lithiated high nickel content lithium storage material and said non-lithiated transition metal dopant with a lithium source to form a lithiated composite material, wherein said high nickel content lithium storage material is present as a predominant by weight relative to said dopant; and
(d) sintering said lithiated composite material, wherein said composite material is characterized by a longer cycle life than that of the high nickel content lithium storage material.
14. The method of claim 13 wherein said dopant material is present at 5 weight percent or less relative to said non-lithiated high nickel content lithium storage material.
15. The method of claim 13 wherein said dopant material is present at from 0.1 to 4 atomic percent relative to said non-lithiated high nickel content lithium storage material.
16. The method of claim 13 wherein said lithiated composite material maintains a capacity in excess of 160 milliamphours per gram at 40 cycles.
17. The method of claim 13 wherein said lithiated composite material maintains a capacity in excess of 170 milliamphours per gram at 30 cycles.