Electrode and secondary battery including the same

Abstract

Disclosed is an electrode for secondary batteries including an electrode mixture including an electrode active material, binder and conductive material coated on a current collector wherein a conductive material is coated to a thickness of 1 to 80 μm on the current collector and the electrode mixture is coated on a coating layer of the conductive material so as to improve electrical conductivity.

Claims

1. An anode for secondary batteries comprising: a coating layer of a conductive material having a thickness of 30 to 80 μm on a current collector, and an anode mixture comprising an anode active material, a binder and the same conductive material of the coating layer, wherein the conductive material is at least one of carbon nanotube or graphene.

2. The anode according to claim 1, wherein the coating layer is coated on 40 to 90% of a total area of the current collector.

3. The anode according to claim 1, wherein the anode comprises a lithium metal oxide represented by Formula 3 below:
Li.sub.aM′.sub.bO.sub.4−cA.sub.c  (3) wherein M′ is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr; 0.1≦a≦4 and 0.2≦b≦4 in which a and b are determined according to oxidation number of M′; 0≦c≦0.2 in which c is determined according to oxidation number of A; and A is at least one monovalent or divalent anion.

4. The anode according to claim 3, wherein the lithium metal oxide is represented by Formula 4 below:
Li.sub.aTi.sub.bO.sub.4  (4) wherein 0.5≦a≦3 and 1≦b≦2.5.

5. The anode according to claim 4, wherein the lithium metal oxide is Li.sub.1.33Ti.sub.1.67O.sub.4 or LiTi.sub.2O.sub.4.

6. A secondary battery comprising the anode according to claim 1.

7. The secondary battery according to claim 6, wherein the secondary battery is a lithium secondary battery.

8. A battery module comprising the secondary battery according to claim 7 as a unit battery.

9. A battery pack comprising the battery module according to claim 8.

10. A device comprising the battery pack according to claim 9.

11. The device according to claim 10, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for storing power.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which:

(2) FIG. 1 is a graph measuring a resistance change ratio according to state of charge (SOC) when a secondary battery according to Experimental Example 1 is discharged; and

(3) FIG. 2 is a graph measuring a resistance change ratio according to state of charge (SOC) when a secondary battery according to Experimental Example 2 is charged.

MODE FOR INVENTION

(4) Now, the present invention will be described in more detail with reference to the following examples. These examples are provided only for illustration of the present invention and should not be construed as limiting the scope and spirit of the present invention.

Example 1

(5) Carbon was coated on a total area of an aluminum current collector, resulting in a of 30 μm thickness carbon layer. Thereafter, 95 wt % of lithium titanium oxide as an anode active material, 2.5 wt % of Super-P as a conductive material and 2.5 wt % of PVdF as a binder were added to NMP to manufacture an anode mixture. The anode mixture was coated on the current collector, in which a carbon layer was formed, resulting in an anode for secondary batteries.

Example 2

(6) An anode for secondary batteries was manufactured in the same manner as in Example 1, except that carbon was coated on an aluminum current collector, resulting in a 50 μm thickness carbon layer.

Comparative Example 1

(7) An anode for secondary batteries was manufactured in the same manner as in Example 1, except that a carbon layer was not formed on an aluminum current collector.

Experimental Example 1

(8) The anodes manufactured according to Examples 1 and 2 and, Comparative Example 1, cathodes coated with a cathode mixture manufactured by adding 90 wt % of LiNi.sub.0.5Mn.sub.1.5O.sub.40 as a cathode active material, 5 wt % of Super-P as a conductive material and PVdF as 5 wt % of a binder to NMP, and porous separators made of a polypropylene were used to manufacture electrode assemblies. Thereafter, after inserting the electrode assemblies into pouches and connecting lead wires, mixture solutions of ethylene carbonate (EC) and dimethyl carbonate (DMC) dissolved in 1 M LiPF.sub.6 salt in a volume ratio of 1:1 were added to electrolytes and then sealed so as to assemble lithium secondary batteries. Resistance change ratios were measured according to state of charge (SOC) during discharge of the secondary batteries. Results are shown in FIG. 1 below.

(9) As shown FIG. 1, the resistances of the batteries according to Examples 1 and 2 were reduced at SOC of 50%, when compared to that of the battery according to Comparative Example 1.

Experimental Example 2

(10) The anodes manufactured according to Examples 1 and 2, and Comparative Example 1, cathodes coated with a cathode mixture manufactured by adding 90 wt % of LiNi.sub.0.5Mn.sub.1.5O.sub.4 as a cathode active material, 5 wt % of Super-P as a conductive material and PVdF as 5 wt % of a binder to NMP, and porous separators made of a polypropylene were used to manufacture electrode assemblies. Thereafter, after inserting the electrode assemblies into pouches and connecting lead wires, solutions of ethylene carbonate (EC) and dimethyl carbonate (DMC) dissolved in 1 M LiPF.sub.6 salt in a volume ratio of 1:1 were added to electrolytes and then sealed so as to assemble lithium secondary batteries. Resistance change ratios were measured according to state of charge (SOC) during charging of the secondary batteries. Results are shown in FIG. 2 below.

(11) As shown FIG. 2, the resistances of the batteries according to Examples 1 and 2 were reduced at SOC of 50%, when compared to that of the battery according to Comparative Example 1.

(12) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

(13) As described above, an electrode for secondary batteries according to the present invention is coated with a conductive material in a predetermined thickness on a current collector, and an electrode mixture including an electrode active material, binder and conductive material are coated on the coating layer of the conductive material, whereby electrical conductivity is enhanced and the internal resistance of a battery is reduced, and, accordingly, superior rate characteristics are exhibited.