Lithium secondary battery with natural graphite anode
A lithium secondary battery includes a cathode, an anode and a non-aqueous electrolyte. The anode includes an anode active material which includes a natural graphite, an average particle diameter (D 50 ) of the natural graphite being in a range from 9 μm to 14 μm, and an expansion rate of the anode represented is 17% or less.
1. A lithium secondary battery, comprising:
a cathode;
an anode; and
a non-aqueous electrolyte,
wherein the anode comprises an anode active material comprising a natural graphite, and an average particle diameter (D 50 ) of the natural graphite is in a range from 9 μm to 14 μm, and the amount of the natural graphite is 90 weight percent or more based on a total weight of the anode active material; and
the anode has an expansion ratio of 17% or less, and the expansion ratio is represented by Equation 3:
Expansion ratio of the anode (%)=100×( T 2 −T 1 )/( T 1 ) [Equation 3]
wherein, in the Equation 3, T 1 denotes a thickness of the anode before charging, and T 2 denotes a thickness of the anode after a full charging,
a change ratio of particle density, represented by Equation 1, of the natural graphite is 0.06 or less:
Change ratio of particle density=( Da−Db )/( a−b ) [Equation 1]
wherein, in the Equation 1, Da indicates a particle density (g/cc) measured when 2.5 g of the natural graphite is put in a hole having a radius of 1 cm and a pressure of 8 kN is applied for 5 seconds, Db indicates a particle density measured when a pressure of 1 kN is applied for 5 seconds, a is 8 kN, and b is 1 kN.
2. The lithium secondary battery of claim 1 , wherein the average particle diameter of the natural graphite is in a range from 10 μm to 12 μm.
3. The lithium secondary battery of claim 1 , wherein the change ratio of particle density of the natural graphite is 0.04 or less.
4. The lithium secondary battery of claim 1 , wherein a half value width in a particle size distribution of the natural graphite is 10 μm or less.
5. The lithium secondary battery of claim 1 , wherein a half value width in a particle size distribution of the natural graphite is 9 μm or less.
6. The lithium secondary battery according to claim 1 , wherein the natural graphite is at least partially coated with a carbide layer, the carbide layer having a crystallinity less than that of the natural graphite.
7. The lithium secondary battery according to claim 1 , wherein a discharge capacity of the lithium secondary battery at a 500th cycle is 96.5% or more, relative to a discharge capacity at a first cycle.