Electrode for secondary battery having improved energy density and lithium secondary battery including the same

1. A positive electrode for a secondary battery, comprising:

an electrode layer having a positive electrode active material and a first conductive material; and

a positive electrode current collector,

wherein the first conductive material is one of natural graphite, artificial graphite thermally treated at 2800° C. or more, or a combination thereof, and present in an amount ranging from 0.1 wt % to 5 wt % based on a total weight of the electrode layer, and

wherein the first conductive material has an average particle diameter ranging from 3 micrometers to 20 micrometers,

wherein a specific surface area of the first conductive material is 5.0 m 2 /g to 8.0 m 2 /g,

wherein a tap density of the first conductive material is 0.8 g/ml to 1.2 g/ml,

wherein a true density of the first conductive material is 2.20 g/cc to 2.30 g/cc, and

wherein a spheroidization degree of the first conductive material is 10 to 100.

2. The positive electrode according to claim 1 , wherein the electrode active material comprises particles of positive electrode active material.

3. The positive electrode according to claim 1 , wherein the first conductive material is uniformly distributed in the electrode layer.

4. The positive electrode according to claim 1 , wherein the first conductive material is present on a surface of the electrode active material.

5. The positive electrode according to claim 1 , wherein the first conductive material has a scale shape, a spherical shape, an oval shape, a fiber shape, a spindle shape or an onion shape.

6. The positive electrode according to claim 1 , wherein the electrode active material comprises a lithium transition metal oxide represented by Formula 1 or 2 below:

Li x M y Mn 2-y O 4-z A z   (1)

wherein M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi;

A is at least one monovalent or divalent anion; and

0.9≤ x≤ 1.2, 0< y< 2, and 0≤ z< 0.2,

(1− x )LiM′O 2-y A y −x Li 2 MnO 3-y′ A y′   (2)

wherein M′ is Mn a M b ;

M is at least one selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and Period II transition metals;

A is at least one selected from the group consisting of anions such as PO 4 , BO 3 , CO 3 , F and NO 3 ; and

0< x< 1, 0< y≤ 0.02, 0< y′≤ 0.02, 0.5≤ a≤ 1.0, 0≤ b≤ 0.5, and a+b= 1.

7. The positive electrode according to claim 1 , wherein the electrode active material comprises first particles having average particle diameters (D50) of 10 nanometers to 50 nanometers and/or secondary particles, in which the first particles are agglomerated, having average particle diameters (D50) of 3 micrometers to 15 micrometers.

8. The positive electrode according to claim 1 , wherein a porosity of the electrode layer is 17% to 32%.

9. A secondary battery comprising the electrode according to claim 1 .

10. The secondary battery according to claim 9 , wherein the secondary battery is a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery.

11. A battery module comprising the secondary battery according to claim 9 as a unit cell.

12. A battery pack comprising the battery module according to claim 11 .

13. A device comprising the battery pack according to claim 12 as a power source.

14. The device according to claim 13 , wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage.

15. The positive electrode according to claim 1 , wherein the first conductive material is present in an amount ranging from 0.5 wt % to 5 wt % based on a total weight of the electrode layer.

16. The positive electrode according to claim 1 , wherein the electrode layer further comprises a second conductive material different from the first conductive material.

17. The positive electrode according to claim 16 , wherein the second conductive material is selected from the group consisting of natural graphite that is not thermally treated, artificial graphite that is not thermally treated; carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and mixtures thereof.