[DESCRIPTION] CATHODE BASED UPON TWO KINDS OF COMPOUNDS AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME [TECHNICAL FIELD] 5 The present invention relates to a cathode for lithium secondary batteries comprising a combination of two specific kinds of compounds, thus exhibiting long lifespan, long-period storage properties and superior stability at ambient temperature and high temperatures. [BACKGROUND ART] 10 Technological development and increased demand for mobile equipment have led to a rapid increase in the demand for secondary batteries as energy sources. Among these secondary batteries, lithium secondary batteries having high energy density and voltage, long cyclespan and low self-discharge ratio are commercially available and widely used. 15 In addition, increased interest in environmental issues has brought about a great deal of research associated with electric vehicles (EV) and hybrid electric vehicles (HEV) as substitutes for vehicles using fossil fuels such as gasoline vehicles and diesel vehicles which are a major cause of air pollution. Nickel-metal hydride (Ni-MH) secondary batteries are generally used as power sources of electric vehicles (EV) and 20 hybrid electric vehicles (HEV). However, a great deal of study associated with use of -1- lithium secondary batteries with high energy density, discharge voltage and power stability is currently underway and some are commercially available. In particular, lithium secondary batteries used for electric vehicles should have high energy density, exert high power within a short period of time and be useful under 5 severe conditions for 10 years or longer, thus requiring considerably superior stability and long-period lifespan, as compared to conventional small lithium secondary batteries. Conventional lithium secondary batteries used for small-size batteries generally utilize lithium cobalt composite oxide having a layered structure for a cathode and a 10 graphite-based material for an anode. However, lithium cobalt composite oxide is disadvantageous in that cobalt used as a main element is extremely expensive and lithium cobalt composite oxide is unsuitable for use in an electric vehicle in terms of stability. Accordingly, lithium manganese composite oxide having a spinel crystal structure composed of manganese, which is low-cost and exhibits superior stability, 15 may be suitable as the cathode of lithium ion batteries for electric vehicles. However, when lithium manganese composite oxide is stored at a high temperature, manganese is eluted into an electrolyte, deteriorating battery properties. Accordingly, there is a need for measures to prevent this phenomenon. Further, lithium manganese composite oxide disadvantageously has a small capacity per battery 20 weight, as compared to conventional lithium cobalt composite oxides or lithium nickel composite oxides, thus limiting an increase in capacity per battery weight. Batteries to improve this limitation should be designed in order to practically apply batteries as power sources of electric vehicles. In order to solve these disadvantages, a great deal of research associated with -2- fabrication of an electrode using a mix cathode active material is conducted. For example, Japanese Patent Application Publication Nos. 2002-110253 and 2004-134245 disclose a technology using a mixture of lithium manganese composite oxide and lithium nickel cobalt manganese composite oxide in order to increase revitalization 5 power or the like, but still having disadvantages of poor cycle lifespan of lithium manganese oxide and limitation of improvement in stability. Further, Korean Patent No. 0458584 discloses a cathode active material composed of an active material compound having a nickel-based large spherical diameter with an average diameter of 7 to 25 μm and an active material compound 10 having a nickel-based small spherical diameter with an average diameter of 2 to 6 im (for example LIxMn2O4_ZXz, in which X represents F, S or P and 0.90 < x < 1.1 and 0 < X < 0.5) to increase the volume density of an electrode plate and thereby improve battery capacity. In addition, in order to improve battery capacity, lifespan and high-rate 15 discharge properties, Korean Patent No. 0570417 discloses use of lithium tetraoxide dimanganese having a spinel crystal structure as a cathode active material, Japanese Patent Application Publication No. 2002-0080448 discloses use of a cathode active material _ containing lithium manganese composite oxide and Japanese Patent Application Publication No. 2004-134245 discloses fabrication of secondary batteries 20 using a cathode active material containing lithium manganese composite oxide having a spinel crystal structure and lithium transition metal composite oxide. Secondary batteries used for electric vehicles (EV), hybrid electric vehicles (HEV) and the like require superior rate and power properties depending on operation -3- conditions of vehicles. However, in spite of the related art known to date, secondary batteries exhibiting the desired lifespan and stability have yet to be developed. [DISCLOSURE 5 [TECHNICAL, PROBLEM Therefore, the present invention has been made to solve the above problems and other technical problems that have yet to be resolved. As a result of a variety of extensive and intensive studies and experiments to solve the problems as described above, the inventors of the present invention have 10 developed a cathode for secondary batteries comprising a combination of specific two compounds such as a compound of Formula 1 and a compound of Formula 2 and discovered that in the case where a secondary battery is fabricated using such a cathode, performance such as stability and lifespan of the battery can be improved, and rate properties and power properties are superior. The present invention was completed 15 based on this discovery. [TECHNICAL, SOLUTION] Accordingly, the cathode for lithium secondary batteries according to the present invention comprises a combination of one or more compounds selected from Formula 1 and one or more compounds selected from Formula 2: 20 (1-s-t)[Li(LiaMn(l_a_x_y)NixCoy)O2]*s[Li2CO3]*t[LiOH] (1) -4- (1-u)LiFePO4*uC (2) wherein O Initial 1 week 2 3 weeks 4 5 6 weeks weeks weeks weeks Ex. 1 97.9 97.0 95.4 93.8 93.1 91.9 Ex. 2 98.2 97.2 95.0 93.3 92.6 91.5 Comp. 95.8 91.2 89.6 87.8 84.1 76.2 Ex. 1 100 Comp. 94.3 90.5 87.3 82.3 78.5 65.7 Ex. 2 Comp. 96.6 93.7 91.5 89.3 86.2 84.8 Ex. 3 15 As can be seen from Table 1 above and FIG. 1, the batteries of Examples 1 and 2 exhibited a considerable small capacity decrease, as compared to the batteries of -15- Comparative Examples 1 to 3. In particular, it can be seen that, as time passes, the difference in capacity decrease increases. Further, the battery of Comparative Example 3 composed of a layered crystal structure compound in which only LiOH is absent exhibited a considerable small capacity decrease, as compared to batteries of 5 Comparative Examples 1 and 2, but exhibited a considerably great capacity decrease, as compared to the batteries of Examples 1 and 2. [Experimental Example 2] The batteries fabricated in Examples 1 and 2 and Comparative Examples 1 to 3 were charged to 1 C and discharged to 1 C at 100 cycles and the capacity thereof was 10 measured. At 50% of state of charge (SOC), the batteries were placed in a 45°C convection oven and capacity decrease thereof was then measured at l Oth, 50"' and 100" cycles. The results are shown in Table 2 below. Initial 10t' cycle 50t' cycle 100th cycle Ex.1 100 98.8 97.8 Ex. 2 99.9 98.3 97.4 Comp. 97.5 90.3 76.7 Ex. 1 100 Comp. 96.9 89.9 65.2 Ex. 2 Comp. 98.6 94.8 88.2 Ex. 3 As can be seen from Table 2 above, the batteries of Examples 1 and 2 exhibited 15 a considerably small capacity decrease, as compared to the batteries of Comparative Examples 1 to 3. In particular, it can be seen that, as the number of cycles increases, the difference in capacity decrease increases. It can be seen that this phenomenon is the same in the battery of Comparative Example 3 composed of a layered crystal -16- structure compound in which only LiOH is absent. 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 5 scope and spirit of the invention as disclosed in the accompanying claims. [CLAIMS] [Claim 1 ] A cathode for lithium secondary batteries comprising a combination of one or more compounds selected from Formula 1 and one or more compounds selected from Formula 2: 5 (1-s-t) [Li(LiaMn(l_a_X_y)NixCoy)O2J * s [Li2CO3] *t[LiOH] (1-u)LiFePO4*uC (2) (1) wherein 0

Documents

Application Documents

#	Name	Date
1	4591-delnp-2012-Form-18-(25-05-2012).pdf	2012-05-25
2	4591-delnp-2012-Correspondence Others-(25-05-2012).pdf	2012-05-25
3	Translation-Search Report.pdf	2012-06-04
4	Priority Document.pdf	2012-06-04
5	Power of Authority.pdf	2012-06-04
8	Form-1.pdf	2012-06-04
9	Drawings.pdf	2012-06-04
10	4591-delnp-2012-Correspondence-Others-(16-07-2012).pdf	2012-07-16
11	4591-DELNP-2012-FER.pdf	2018-03-01
12	4591-DELNP-2012-Verified English translation (MANDATORY) [30-05-2018(online)].pdf	2018-05-30
13	4591-DELNP-2012-OTHERS-310518.pdf	2018-06-07
14	4591-DELNP-2012-Correspondence-310518.pdf	2018-06-07
15	4591-DELNP-2012-Proof of Right (MANDATORY) [19-07-2018(online)].pdf	2018-07-19
16	4591-DELNP-2012-PETITION UNDER RULE 137 [19-07-2018(online)].pdf	2018-07-19
17	4591-DELNP-2012-PETITION UNDER RULE 137 [19-07-2018(online)]-1.pdf	2018-07-19
18	4591-DELNP-2012-OTHERS [19-07-2018(online)].pdf	2018-07-19
19	4591-DELNP-2012-Information under section 8(2) (MANDATORY) [19-07-2018(online)].pdf	2018-07-19
20	4591-DELNP-2012-FORM 3 [19-07-2018(online)].pdf	2018-07-19
21	4591-DELNP-2012-FER_SER_REPLY [19-07-2018(online)].pdf	2018-07-19
22	4591-DELNP-2012-DRAWING [19-07-2018(online)].pdf	2018-07-19
23	4591-DELNP-2012-CLAIMS [19-07-2018(online)].pdf	2018-07-19
24	4591-DELNP-2012-OTHERS-230718.pdf	2018-07-25
25	4591-DELNP-2012-Correspondence-230718.pdf	2018-07-25
26	4591-DELNP-2012-PatentCertificate21-08-2018.pdf	2018-08-21
27	4591-DELNP-2012-IntimationOfGrant21-08-2018.pdf	2018-08-21
28	4591-DELNP-2012-RELEVANT DOCUMENTS [31-01-2019(online)].pdf	2019-01-31
29	4591-DELNP-2012-RELEVANT DOCUMENTS [21-02-2020(online)].pdf	2020-02-21
30	4591-DELNP-2012-RELEVANT DOCUMENTS [27-09-2021(online)].pdf	2021-09-27
31	4591-DELNP-2012-RELEVANT DOCUMENTS [29-09-2021(online)].pdf	2021-09-29
32	4591-DELNP-2012-RELEVANT DOCUMENTS [15-09-2022(online)].pdf	2022-09-15
33	4591-DELNP-2012-POWER OF AUTHORITY [17-11-2022(online)].pdf	2022-11-17
34	4591-DELNP-2012-FORM-16 [17-11-2022(online)].pdf	2022-11-17
35	4591-DELNP-2012-ASSIGNMENT WITH VERIFIED COPY [17-11-2022(online)].pdf	2022-11-17
36	4591-DELNP-2012-RELEVANT DOCUMENTS [23-08-2023(online)].pdf	2023-08-23

Search Strategy

1	search4591_28-02-2018.pdf