Gradient cathode material for lithium rechargeable batteries
A composition suitable for use as a cathode material of a lithium battery includes a core material having an empirical formula Li x M′ z Ni 1−y M″ y O 2 . “x” is equal to or greater than about 0.1 and equal to or less than about 1.3. “y” is greater than about 0.0 and equal to or less than about 0.5. “z” is greater than about 0.0 and equal to or less than about 0.2. M′ is at least one member of the group consisting of sodium, potassium, nickel, calcium, magnesium and strontium. M″ is at least one member of the group consisting of cobalt, iron, manganese, chromium, vanadium, titanium, magnesium, silicon, boron, aluminum and gallium. A coating on the core has a greater ratio of cobalt to nickel than the core. The coating and, optionally, the core can be a material having an empirical formula Li x1 A x2 Ni 1−y1−z1 Co y1 B z1 O a . “x1” is greater than about 0.1 a equal to or less than about 1.3. “x2,” “y1” and “z1” each is greater than about 0.0 and equal to or less than about 0.2. “a” is greater than 1.5 and less than about 2.1. “A” is at least one element selected from the group consisting of barium, magnesium, calcium and strontium. “B” is at least one element selected from the group consisting of boron, aluminum, gallium, manganese, titanium, vanadium and zirconium.
1. A composition, comprising:
a) a core having an empirical formula
Li x M′ z Ni 1−y M″ y O 2
wherein: x is greater than 0.1 and equal to or less than 1.3,
y is greater than 0.0 and equal to or less than 0.5,
z is greater than 0.0 and equal to or less than 0.2,
M′ includes magnesium, and
M″ includes cobalt and boron; and
b) a coating on the core having a greater ratio of cobalt to nickel than the core.
2. The composition of claim 1 , wherein y is in a range of between about 0.1 and about 0.5.
3. The composition of claim 1 , wherein y is about 0.1.
4. The composition of claim 1 , wherein y is about 0.2.
5. The composition of claim 1 , wherein the sum of x and z equals about one.
6. The composition of claim 1 , wherein the ratio of cobalt to nickel increases as a gradient from the core to an outer surface of the coating.
7. A composition, comprising:
a) a core having an empirical formula
Li x Mg 2 Ni 1−y Co y Q v O 2
wherein: x is greater than 0.1 and equal to or less than 1.3.
y is greater than 0.0 and equal to or less than 0.4,
z is greater than 0.0 and equal to or less than 0.2,
v is greater than 0.0 and equal to or less than 0.4,
Q is at least one member of the group consisting of manganese, boron, aluminum and gallium; and
b) a coating on the core having a greater ratio of cobalt to nickel than the core.