Irreversible additive contained in cathode material for secondary battery, cathode material including the same, and secondary battery including cathode material
An irreversible additive contained in a cathode material for a secondary battery according to one embodiment of the present disclosure, the irreversible additive being an oxide represented by the following chemical formula 1, wherein the oxide has a trigonal crystal structure, Li 2+a Ni 1−b Ti b O 2+c (1) in the above formula, −0.2≤a≤0.2, 0<b≤0.2, and 0≤c≤0.2.
1 . An irreversible additive contained in a cathode material for a secondary battery, comprising,
an oxide represented by the following chemical formula 1,
wherein the oxide has a trigonal crystal structure and belongs to a space group of P3-m1,
Li 2+a Ni 1−b Ti b O 2+c (1)
in the above formula, −0.2≤a≤0.2, 0<b≤0.2, and 0≤c≤0.2.
2 . The irreversible additive according to claim 1 , wherein:
the oxide has a crystal lattice of a=3.0964 Å, c=5.0760 Å, and γ=120.00°.
3 . The irreversible additive according to claim 1 , wherein:
the oxide is Li 2 Ni 0.97 Ti 0.03 O 2 .
4 . The irreversible additive according to claim 1 , wherein:
the oxide has an oxygen formation energy of 4.25 eV or more and 5.0 eV or less.
5 . A cathode material comprising the irreversible additive of claim 1 and a cathode active material.
6 . The cathode material according to claim 5 , wherein:
a content of the irreversible additive is 0.1% by weight to 10% by weight based on the total weight of the cathode material.
7 . A secondary battery comprising a cathode in which the cathode material of claim 5 is coated onto a cathode current collector,
wherein
the irreversible additive is converted into a monoclinic system within an operating voltage range of 4.0V or more.
8 . The secondary battery according to claim 7 , wherein:
the irreversible additive belongs to a space group of C2/m when having a monoclinic crystal structure.
9 . The secondary battery according to claim 7 , wherein:
the cathode active material comprises an oxide represented by the following chemical formula 2,
Li(Ni a Co b Mn c )O 2 (2)
in the above formula, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1.
10 . The secondary battery according to claim 7 , wherein:
the secondary battery has a structure in which an electrode assembly is built in a battery case together with an electrolyte, with the electrode assembly comprising:
the cathode;
an anode in which an anode material including an anode active material is coated onto an anode current collector; and
a separator that is interposed between the cathode and the anode.