ELECTRODE INCLUDING ALTERNATELY ARRANGED ELECTRODE MIXTURE PARTS AND IRREVERSIBLE PARTS AND SECONDARY BATTERY INCLUDING THE SAME

Abstract

Disclosed herein are an electrode configured such that electrode mixture parts, each of which includes an electrode active material, and irreversible parts, each of which includes an irreversible additive, are alternately coated on one surface or both surfaces of a current collector to form an electrode pattern and a secondary battery including the same.

Claims

1. An electrode configured such that electrode mixture parts, each of which comprises an electrode active material, and irreversible parts, each of which comprises an irreversible additive, are alternately coated on one surface or both surfaces of a current collector to form an electrode pattern.

2. The electrode according to claim 1, wherein the electrode mixture parts and the irreversible parts are alternately arranged in a vertical direction or a horizontal direction on a basis of a direction in which an electrode terminal of the electrode is formed.

3. The electrode according to claim 1, wherein each of the electrode mixture parts and the irreversible parts is formed in a strip shape when viewed from above.

4. The electrode according to claim 1, wherein the electrode mixture parts and irreversible parts are alternately arranged on the opposite surfaces of the current collector, and wherein a structure in which the electrode mixture parts and the irreversible parts that are alternately arranged on one surface of the current collector and a structure in which the electrode mixture parts and the irreversible parts that are alternately arranged on the other surface of the current collector are identical to each other.

5. The electrode according to claim 1, wherein the electrode mixture parts are coated on 10 to 99% of a total area of the electrode when viewed from above.

6. The electrode according to claim 5, wherein the electrode mixture parts are coated on 50 to 99% of a total area of the electrode when viewed from above.

7. The electrode according to claim 1, wherein the electrode mixture parts are coated at predetermined intervals.

8. The electrode according to claim 1, wherein the irreversible parts are coated at predetermined intervals.

9. The electrode according to claim 1, wherein the irreversible additive has an operation voltage of 1.0 V to 2.5 V with respect to Li.

10. The electrode according to claim 1, wherein the irreversible additive exhibits higher conductivity than the electrode active material.

11. The electrode according to claim 1, wherein the electrode is a positive electrode, and wherein the irreversible additive is a lithiated lithium titanium oxide (LTO) or lithium molybdenum compound.

12. The electrode according to claim 11, wherein the irreversible additive is a lithium titanium oxide represented by Li.sub.7/3Ti.sub.5/3O.sub.4.

13. The electrode according to claim 11, wherein the irreversible additive is a lithium molybdenum sulfide represented by Formula 1 below:
Li.sub.2+xMo.sub.6−yM.sub.yS.sub.8−z   (1) where −0.1≦x≦0.5, 0≦y≦0.5, −0.1≦z≦0.5, and M is a metal or transition metal cation having an oxidation number of +2 to +4.

14. The electrode according to claim 13, wherein the lithium molybdenum sulfide is Li.sub.2.3Mo.sub.6S.sub.7.7.

15. The electrode according to claim 1, wherein the electrode is a negative electrode, and wherein the irreversible additive is a molybdenum compound.

16. The electrode according to claim 15, wherein the irreversible additive is a molybdenum sulfide represented by Formula 2 below:
Mo.sub.aS.sub.b   (2) where a ratio of a to b (a/b) is ½ to 1.

17. The electrode according to claim 16, wherein the molybdenum sulfide is Mo.sub.6S.sub.8.

18. The electrode according to claim 1, wherein the irreversible additive is provided in an amount of 80 wt % to 99 wt % with respect to a total weight of the irreversible parts.

19. The electrode according to claim 1, wherein each of the irreversible parts further comprises a binder or a binder and a conductive agent, in addition to the irreversible additive.

20. The electrode according to claim 1, wherein each of the electrode mixture parts has an aperture ratio of 5% to 40%.

21. The electrode according to claim 1, wherein each of the irreversible parts has an aperture ratio of 20% to 90%.

22. A secondary battery configured such that an electrode assembly comprising the electrode according to claim 1 is impregnated with an electrolytic solution.

23. A battery module comprising the secondary battery according to claim 22 as a unit cell.

24. A battery pack comprising the battery module according to claim 23.

25. A device comprising the battery pack according to claim 24 as a power source.

26. The device according to claim 25, wherein the device is selected from a group consisting of a mobile phone, a portable computer, a smart phone, a tablet PC, a smart pad, a netbook computer, a light electronic vehicle (LEV), an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage apparatus.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0066] 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 drawings, in which:

[0067] FIG. 1 is a plan view and a side view showing an electrode according to an embodiment of the present invention.

BEST MODE

[0068] 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 of the present invention.

EXAMPLE 1

[0069] Preparation of a Positive Electrode Mixture Part

[0070] 94 wt % of a lithium nickel-based oxide (Li(NiMnCo).sub.1/3O.sub.2) as a positive electrode active material, 3 wt % of Super-P as a conductive agent, and 3 wt % of PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing a positive electrode mixture.

[0071] Preparation of an Irreversible Part

[0072] 94 wt % of a lithium titanium oxide (Li(Li.sub.1/3Ti.sub.5/3)O.sub.4) as an irreversible additive, 3 wt % of Super-P as a conductive agent, and 3 wt % of PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing an irreversible additive mixture.

[0073] Manufacture of a Positive Electrode

[0074] The positive electrode mixture and the irreversible additive mixture were alternately coated, dried, and pressed on aluminum foil having a thickness of 15 μm, as shown in FIG. 1, thereby manufacturing a positive electrode. At this time, the positive electrode mixture part had an aperture ratio of 25%, and the irreversible part had an aperture ratio of 40%.

EXAMPLE 2

[0075] A positive electrode mixture part was prepared, an irreversible part was prepared, and a positive electrode was manufactured in the same manner as in Example 1 except that 94 wt % of a lithium molybdenum sulfide (Li.sub.2.3Mo.sub.6S.sub.7.7) was used as the irreversible additive in place of a lithium titanium oxide (Li(Li.sub.1/3Ti.sub.5/3)O.sub.4). At this time, the positive electrode mixture part had an aperture ratio of 25%, and the irreversible part had an aperture ratio of 40%.

COMPARATIVE EXAMPLE 1

[0076] 89 wt % of a lithium nickel-based oxide (Li(NiMnCo).sub.1/3O.sub.2) as a positive electrode active material, 3 wt % of Super-P as a conductive agent, 3 wt % of PVdF as a binder, and 5 wt % of a lithium molybdenum sulfide (Li.sub.2.3Mo.sub.6S.sub.7.7) as an irreversible additive were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing a positive electrode mixture. The positive electrode mixture was coated, dried, and pressed on aluminum foil having a thickness of 15 μm, thereby manufacturing a positive electrode. At this time, the positive electrode mixture layer had an aperture ratio of 25%.

COMPARATIVE EXAMPLE 2

[0077] 94 wt % of a lithium nickel-based oxide (Li(NiMnCo).sub.1/3O.sub.2) as a positive electrode active material, 3 wt % of Super-P as a conductive agent, and 3 wt % of PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing a positive electrode mixture. The positive electrode mixture was coated on aluminum foil having a thickness of 15 on. 94 wt % of a lithium molybdenum sulfide (Li.sub.2.3Mo.sub.6S.sub.7.7) as an irreversible additive, 3 wt % of Super-P as a conductive agent, and 3 wt % of PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing an irreversible additive mixture. The irreversible additive mixture was coated, dried, and pressed on the positive electrode mixture layer, which was coated on the aluminum foil, such that the irreversible additive mixture had a thickness of 5 μm, thereby manufacturing a positive electrode. At this time, the positive electrode mixture layer had an aperture ratio of 25%, and the irreversible additive layer had an aperture ratio of 40%.

COMPARATIVE EXAMPLE 3

[0078] 92 wt % of a lithium nickel-based oxide (Li(NiMnCo).sub.1/3O.sub.2) as a positive electrode active material, 3 wt % of Super-P as a conductive agent, 3 wt % of PVdF as a binder, and 2 wt % of a lithium titanium oxide (Li(Li.sub.1/3Ti.sub.5/3)O.sub.4) as an irreversible additive were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing a positive electrode mixture. The positive electrode mixture was coated, dried, and pressed on aluminum foil having a thickness of 15 μm, thereby manufacturing a positive electrode. At this time, the positive electrode mixture layer had an aperture ratio of 25%.

COMPARATIVE EXAMPLE 4

[0079] 94 wt % of a lithium nickel-based oxide (Li(NiMnCo).sub.1/3O.sub.2) as a positive electrode active material, 3 wt % of Super-P as a conductive agent, and 3 wt % of

[0080] PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing a positive electrode mixture. The positive electrode mixture was coated on aluminum foil having a thickness of 15 μm. 94 wt % of a lithium titanium oxide (Li(Li.sub.1/3Ti.sub.5/3)O.sub.4) as an irreversible additive, 3 wt % of Super-P as a conductive agent, and 3 wt % of PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent, thereby preparing an irreversible additive mixture. The irreversible additive mixture was coated, dried, and pressed on the positive electrode mixture layer, which was coated on the aluminum foil, such that the irreversible additive mixture had a thickness of 5 μm, thereby manufacturing a positive electrode. At this time, the positive electrode mixture layer had an aperture ratio of 25%, and the irreversible additive layer had an aperture ratio of 40%.

COMPARATIVE EXAMPLE 5

[0081] 94 wt % of a lithium nickel-based oxide (Li(NiMnCo).sub.1/3O.sub.2) as a positive electrode active material, 3 wt % of Super-P as a conductive agent, and 3 wt % of PVdF as a binder, were added to N-methyl-2-pyrrolidone (NMP) as a solvent, in the state in which a lithium molybdenum sulfide (Li.sub.2.3Mo.sub.6S.sub.7.7) or a lithium titanium oxide (Li(Li.sub.1/3Ti.sub.5/3)O.sub.4) was not added or coated, thereby preparing a positive electrode mixture. The positive electrode mixture was coated, dried, and pressed on aluminum foil having a thickness of 15 μm, thereby manufacturing a positive electrode. At this time, the positive electrode mixture layer had an aperture ratio of 25%. That is, the positive electrode was manufactured such that the positive electrode mixture part occupied 100% of the area of the positive electrode.

EXPERIMENTAL EXAMPLE 1

[0082] 84 wt % of artificial graphite and 10 wt % of a silicon oxide (SiO) as a negative electrode active material, 2 wt % of Super-P as a conductive agent, 3 wt % of styrene butadiene rubber (SBR) as a binder, and 1 wt % of carboxymethyl cellulose (CMC) as both a thickener and binder were added to distilled water as a solvent, thereby preparing a negative electrode mixture. The negative electrode mixture was coated on copper foil having a thickness of 10 μm, thereby manufacturing a negative electrode. The negative electrode had an irreversible efficiency of about 86% (charge capacity: 245 mAh/g).

[0083] The irreversible efficiencies of the positive electrodes manufactured according to Examples 1 and 4 and Comparative Examples 1 to 5 and the measured capacities of batteries, manufactured such that each of the batteries included the positive electrode and the negative electrode, are shown in Table 1.

TABLE-US-00001 TABLE 1 Negative electrode Positive electrode efficiency efficiency Battery capacity Example 1 86.3% 87.1% 79.0 Ah Example 2 87.0% 79.2 Ah Comparative 86.9% 79.4 Ah Example 1 Comparative 86.8% 79.4 Ah Example 2 Comparative 87.0% 79.1 Ah Example 3 Comparative 87.1% 79.0 Ah Example 4 Comparative 91.2%   75 Ah Example 5

[0084] As shown in Table 1 above, it can be seen that the differences in irreversible efficiency between the positive electrodes including the lithium molybdenum sulfide or the lithium titanium oxide as the irreversible additive according to Examples 1 and 2 and the negative electrodes are smaller than the difference in irreversible efficiency between the positive electrode not including the irreversible additive according to Comparative Example 5 and the negative electrode and that the capacities of batteries manufactured using the positive electrodes according to Examples 1 and 2 and the negative electrodes are higher than the capacity of a battery manufactured using the positive electrode according to Comparative Example 5 and the negative electrode. This means that the battery capacities are increased because the lithium, as an irreversible agent of the negative electrode, increases the irreversibility of the positive electrode.

[0085] The reason for this is that the lithium molybdenum sulfide and the lithium titanium oxide participate in reaction only during initial charging, and do not participate in reaction during discharging, because the operation voltages of the lithium molybdenum sulfide and lithium titanium oxide, which are within a range of 1.0 V to 2.5 V with respect to Li, are lower than the operation voltage of the positive electrode.

[0086] Consequently, it can be seen that, when the lithium molybdenum sulfide or the lithium titanium oxide serving as the irreversible additive was included in the positive electrode, the total capacity and the energy density per unit volume of a battery cell may be maximized by adjusting the initial irreversible efficiency of the positive electrode within a range similar to that of the negative electrode.

EXPERIMENTAL EXAMPLE 2

[0087] The positive electrodes manufactured according to Examples 1 and 2 and Comparative Examples 1 to 5 were immersed into an electrolytic solution, and the amount of time taken until the degree of impregnation reached about 80% was measured. The results are shown in Table 2 below. The degree of impregnation is the ratio of electrode weight incremental to the initial electrode weight, expressed as a percentage, when an electrode is impregnated with an electrolytic solution.

TABLE-US-00002 TABLE 2 Degree of impregnation (time, sec) Example 1 2705 Example 2 2580 Comparative Example 1 4050 Comparative Example 2 3570 Comparative Example 3 3950 Comparative Example 4 3490 Comparative Example 5 3900

[0088] As shown in Table 2 above, it can be seen that the electrodes according to Examples 1 and 2 of the present invention achieved desired degrees of impregnation within a shorter time than the electrodes according to Comparative Examples 1 and 3, in each of which the irreversible additive was simply mixed with the positive electrode mixture, the electrodes according to Comparative Examples 2 and 4, in each of which the irreversible additive layer was formed on the positive electrode mixture layer, and the electrode according to Comparative Example 5, in which only the positive electrode mixture layer, which had a low aperture ratio, was provided.

EXPERIMENTAL EXAMPLE 3

[0089] Batteries were manufactured using the positive electrodes manufactured according to Examples 1 and 2 and Comparative Examples 1 and 5 and the negative electrode manufactured according to Experimental Example 1, and 10-second discharge resistance of the batteries for each SOC were measured. The results are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Resistance (mohm) SOC5 SOC25 SOC50 SOC75 SOC95 Example 1 1.84 1.60 1.53 1.52 1.52 Example 2 1.84 1.58 1.52 1.52 1.51 Comparative 1.96 1.66 1.58 1.58 1.59 Example 1 Comparative 1.87 1.63 1.56 1.56 1.56 Example 5

[0090] Referring to Table 3, it can be seen that the batteries using the positive electrodes manufactured according to Examples 1 and 2 exhibit better output characteristics than the batteries using the positive electrodes manufactured according to Comparative Examples 1 and 5. The reason for this is that the positive electrodes manufactured according to Examples 1 and 2 are characterized in that the irreversible part, which had a high aperture ratio, is coated on the current collector together with the electrode mixture part, whereby the degree of impregnation with the electrolytic solution is increased, as can be seen from Experimental Example 2, and therefore the electrode resistance is reduced.

[0091] In the electrode according to the present invention, therefore, it is possible to easily adjust irreversible efficiency through the use of the irreversible additive. In addition, it is possible to exhibit excellent output characteristics over the entire SOC range by improving the degree of impregnation with the electrolytic solution.

[0092] Although the exemplary 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

[0093] As is apparent from the above description, an electrode according to the present invention is configured such that electrode mixture parts, each of which includes an electrode active material, and irreversible parts, each of which includes an irreversible additive, are alternately arranged. Consequently, it is possible to easily adjust irreversible efficiency based on the contents of the irreversible additive and the distribution of the irreversible parts. In addition, it is possible to improve impregnation with an electrolytic solution while exhibiting high-capacity characteristics by adjusting the aperture ratio of the electrode mixture parts and the aperture ratio of the irreversible parts. As a result, it is possible to prevent the concentration of the electrolytic solution from being polarized. Consequently, it is possible to restrain an increase in the resistance of a battery such that the battery exhibits excellent output characteristics.