[DESCRIPTION] CATHODE ACTIVE MATERIAL FOR SECONDARY BATTERIES WITH IMPROVED RATE PROPERTY [TECHNICAL FIELD] 5 The present invention relates to a cathode active material for secondary batteries with improved rate properties. More specifically, the present invention relates to a cathode active material for secondary batteries that reduces deintercalation of oxygen from a crystal structure of LiiMnOs at a high voltage of 4.3 V to 4.6V through incorporation of excess lithium in a transition metal cation layer. 10 [BACKGROUND ART] Technological developm_ent and increased demand for m.obile equipment have led to a sharp increase in the demand for secondary batteries as energy sources. Among these secondary batteries, lithium secondary batteries having high energy density and driving voltage, long lifespan and low self-discharge are commercially 15 available and widely used. In addition, in recent years, increased interest in environmental issues has brought about a great deal of research associated with electric vehicles (EVs) and hybrid Jd^ electric vehicles (HEVs) as substitutes for vehicles, such as gasoline vehicles and diesel vehicles, using fossil fuels which are major causes of air pollution. Nickel metal hydride (Ni-MH) secondary batteries or lithium secondary batteries having high energy density, high discharge voltage and power stability are 5 generally used as power sources of electric vehicles (EVs), hybrid electric vehicles (HEVs) and the like. Lithium secondary batteries used for electric vehicles should have high energy density, exert high power within a short time and last for 10 years or longer under harsh conditions, thus requiring considerably superior stability and long lifespan, as compared 10 to conventional small lithium secondary batteries. In addition, secondary batteries used for electric vehicles (EVs), hybrid electric vehicles (HEVs) and the like require rate characteristics and power characteristics according to driving conditions of vehicles. At present, as cathode active materials for lithium ion secondary batteries, 15 lithium-containing cobalt oxide having a layered structure, such as LiCoOa, lithiumcontaining nickel oxide having a layered structure, such as LiNi02, and lithiumcontaining manganese oxide having a spinel crystal structure, such as LiMn204 are used. A graphite material is generally used as an anode active material. J ^ LiCo02 is currently used owing to superior physical properties such as cycle properties, but has disadvantages of low stability, high-cost due to use of cobalt, which suffers from natural resource limitations, and restriction of mass-use as a power source for electric automobiles. LiNi02 is unsuitable for practical application to mass- 5 production at a reasonable cost due to many factors associated with preparation methods thereof On the other hand, lithium manganese oxides such as LiMnOi and LiMn204 have an advantage of use of manganese which is abundant as a raw material and is ecofriendly, thus attracting considerable attention as a cathode active material capable of 10 replacing LiCoOa. However, lithium manganese oxide also has a disadvantage of poor cycle properties. LiMn02 disadvantageously has a low initial capacity and requires scores of charge/discharge cycles so as to obtain a predetermined capacity. In addition, LiMn204 suffers rapid capacity deterioration in cycle life and, in particular, 15 disadvantageously causes sharp deterioration in cycle properties at a high temperature of 50°C or higher due to decomposition of electrolyte and elution of manganese. In this regard, Japanese Patent Application Publication No. 2003-086180 discloses a method for improving charge/discharge cycle properties by adjusting a mean ^^^ oxidation number of manganese ions to 3.03 to 3.08 through substitution of a part of oxygen of LiMnOa by a halogen element. In addition, Japanese Patent Application Publication No. 1999-307098 discloses a method for improving high-temperature cycle properties by substituting a 5 part of oxygen of LiMn204 by a fluorine element. In addition, Japanese Patent No. 3141858 discloses a method for improving power, energy density and cycle properties by coating the surface of active material particles such as LiMn02 and LiMn204 with a metal halogenized material and substituting oxygen in the particles by a halogen element to prepare a solid solution. 10 However, lithium manganese oxides such as LiMnOa and LiMn204 cannot secure a desired level of safety and have limitations as to improvement in energy density due to their crystalline structure in spite of these conventional methods. Meanwhile, the lithium-containing manganese oxide includes Li2Mn03, in addition to LiMn02 and LiMn204. LiaMnOs is unsuitable for use in a cathode active 15 material for secondary batteries due to electrochemical inertness, in spite of considerably superior structural stability. Accordingly, some conventional methods suggest solid solution treatment or mixing of Li2Mn03 with LiM02 (M = Co, Ni, Nio.sMno.s, Mn). These cathode active materials have a broad domain in a high voltage region of 4.3V to 4.6V. This broad domain is known as a range in which lithium (Li) and oxygen (0) are deintercalated (left) from a crystal structure of Li2Mn03 and lithium is inserted into an anode. The deintercalation of lithium and oxygen in the high voltage range of 4.3 V to 4.6V imparts electrochemical activity to active materials and the broad region increases 5 capacity, but decomposition of electrolyte and generation of gas may readily occur at high voltage due to oxygen gas generated in the battery, crystal structures are physically and chemically deformed during repeated charge/discharge, rate properties are deteriorated and, as a result, battery performance is disadvantageously deteriorated. In addition, the cathode active material does not contribute to capacity due to 10 lowered terminal region of discharge voltage when used for cellular phones, or it cannot practically realize high power, since it exhibits an unusable stage of charge (SOC) due to low power when used for vehicles. Accordingly, there is an increasing need for methods capable of ultimately solving these problems. 15 [DISCLOSURE] [TECHNICAL PROBLEM] Therefore, the present invention has been made to solve the above and other technical problems that have yet to be resolved. J^ As a result of a variety of extensive and intensive studies and experiments, the present inventor developed a cathode active material which exhibits improved rate properties through minimal deintercalation of oxygen from a crystal structure of LiaMnOs at a high voltage of 4.3 V to 4.6V, as described later. The present invention 5 has been completed, based on this discovery. [TECHNICAL SOLUTION] In accordance with one aspect of the present invention, provided is a cathode active material for secondary batteries having a structure in which excessive lithium is incorporated in a cation layer composed of a transition metal, thus reducing 10 deintercalation of oxygen from a crystal structure at a high voltage of 4.3 V to 4.6V, the cathode active material being represented by Formula 1: (l-x)Li(LiaM'bMi.a-b)02* xLi2M"03 (1) wherein 0 A transition metal composite precursor was synthesized by a coprecipitation method such that a ratio of transition metals was adjusted to Nio.45Mno.55, and the transition metal composite precursor was mixed with LiaCOs such that a molar ratio of 15 Li to transition metal was 1.15:1. The mixture was incorporated into an electric furnace, was slowly heated at a rate of 5°C/min from room temperature, maintained at 950°C for 7 hours, and cooled in air to synthesize 0.9Li(Lio.o56(Nio.5Mno.5)o.944)02*0.1Li2Mn03. -15- J ^ 0.9Li(Lio.ii(Nio.5Mno.5)o.89)02*0.1Li2Mn03 was synthesized in the same manner as in Example 1, except that the transition metal composite precursor was mixed with LiaCOs such that the ratio of Li to the transition metal was adjusted to 1.2:1. 5 0.9Li(Nio.5Mno.5)02*0.1Li2Mn03 was synthesized in the same manner as in Example 1, except that the transition metal composite precursor was mixed with LiaCOs such that the ratio of Li to transition metal was adjusted to 1.1:1. 10 A transition metal composite precursor was synthesized by a coprecipitation method such that a ratio of transition metals was adjusted to Nio.4Mno.6, and the transition metal composite precursor was mixed with Li2C03 such that a molar ratio of Li to transition metal was 1.25:1. The mixture was incorporated into an electric flimace, was slowly heated at a rate of 5°C/min from room temperature, maintained at 15 950°C for 7 hours, and cooled in air to synthesize 0.8Li(Lio.o625(Nio.5Mno.5)o.9375)02*0.2Li2Mn03. -16- J ^ 0.8Li(Nio.5Mno.5)02*0.2Li2Mn03 was synthesized in the same manner as in Example 1, except that the transition metal composite precursor was mixed with Li2C03 such that the ratio of Li to transition metal was adjusted to 1.2:1. 5 A transition metal composite precursor was synthesized by a coprecipitation method such that a ratio of transition metals was adjusted to Nio^Mno.sCoo.i, and the transition metal composite precursor was mixed with Li2C03 such that a molar ratio of Li to transition metal was 1.25:1. The mixture was incorporated into an electric furnace, was slowly heated at a rate of 5°C/min from room temperature, maintained at 10 950°C for 7 hours, and cooled in air to synthesize 0.9Li(Lio.o56(Nio.4Mno.5Coo. 1)0.944)02 * 0.1 Li2Mn03. 0.8Li(Nio.5Mno.5)02*0.2Li2Mn03 was synthesized in the same manner as in Example 4, except that the transition metal composite precursor was mixed with Li2C03 15 such that the ratio of Li to transition metal was adj usted to 1.2:1. A slurry was prepared using each cathode active material synthesized in Examples 1 to 4 and Comparative Examples 1 to 3 and NMP such that a ratio of -17- ^ ^ - cathode active material:conductive material:binder was 90:6:4. The slurry was coated to a thickness of 20 fim on an aluminum foil (Al-foil) to obtain a coin-type battery. An anode active material used herein was a Li-metal and an electrolyte used herein was a solution of IM LiPFe in a solvent (consisting of ethylene carbonate (EC) 5 and ethyl methyl carbonate (EMC) at a weight ratio of 3:7). Charge/discharge capacities of the coin-type batteries were measured at 0.06C and rate properties were evaluated by calculating a ratio of IC to 0.06C. C-rate was measured based on IC of 240 mAh/g. Charge/discharge was carried out at 2.0V to 4.6V and charge and discharge were measured at CC/CV and CV, 10 respectively. Charge/discharge capacity Ex. 1 Ex.2 Comp. Ex. 1 Ex.3 Comp. Ex. 2 Charge capacity at first cycle (mAh/g) 238.0 244.3 212.8 265.8 250.0 Discharge capacity at first cycle (mAh/g) 210.0 211.2 191.8 220.0 201.3 • 1 8 - Ex.4 Comp. Ex. 3 250.5 238.6 210.7 196.9 As can be seen from Table, Examples exhibited increased charge/discharge capacity as compared to corresponding Comparative Examples and Examples 1 to 3 exhibited a uniform increase in charge/discharge capacity as a content of lithium in the cathode active material increased. Example 4 exhibited a slight decrease in 5 charge/discharge capacity, as compared to Example 3, since Co was present in the transition metal precursor and a content of Mn was lower than that of Example 3. Rate property Ex. 1 Ex.2 Comp. Ex. 1 Ex.3 Comp. Ex. 2 Ex.4 Comp. Ex. 3 Second l.OC cycle / second 0.06C cycle (capacity ratio%) 80.9 83.8 70.4 84.3 75.6 83.3 78.4 As can be seen from Table 2 above, respective Examples exhibited improved rate properties, as compared to corresponding Comparative Examples, and Examples 1 10 to 3 exhibited a uniform increase in rate properties, as the content of lithium in the •19- ^k^ cathode active material increased. Example 4 exhibited a slight decrease in rate properties, as compared to Example 3, since Co was present in the transition metal precursor and a content of Mn was lower than that of Example 3. Although the preferred embodiments of the present invention have been 5 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] As apparent from the afore-going, the cathode active material according to the 10 present invention can minimize deintercalation of oxygen (O) from a crystal structure in a broad high voltage region of 4.3V to 4.6V during charge, since excessive lithium is incorporated in a transition metal cation layer. In addition, the cathode active material according to the present invention exerts superior rate properties even when Co is used in a considerably low amount or is 15 not used. Furthermore, the secondary battery according to the present invention comprises a specific cathode active material, thus advantageously minimizing deintercalation of oxygen from a crystal structure and generation of gas caused by -20- (tf| negative reaction with an electrolyte, improving safety, minimizing structural deformation, and improving lifespan properties as well as rate and power properties. -21- ORIGINAL [CLAIMS] '» *• ,^ Ott ^^ [Claim l] A cathode active material for secondary batteries for reducing deintercalation of oxygen from a crystal structure at a high voltage of 4.3V to 4.6V through incorporation of excessive lithium in a cation layer composed of a transition 5 metal, the cathode active material being represented by Formula 1: (l-x)Li(LiaM'bMi.a-b)02* xLi2M"03 (1) wherein 0

Documents

Application Documents

#	Name	Date
1	11228-delnp-2013-GPA.pdf	2014-05-20
2	11228-delnp-2013-Form-5.pdf	2014-05-20
3	11228-delnp-2013-Form-3.pdf	2014-05-20
4	11228-delnp-2013-Form-2.pdf	2014-05-20
5	11228-delnp-2013-Form-18.pdf	2014-05-20
6	11228-delnp-2013-Form-1.pdf	2014-05-20
7	11228-delnp-2013-Description (Complete).pdf	2014-05-20
8	11228-delnp-2013-Correspondence-others.pdf	2014-05-20
9	11228-delnp-2013-Claims.pdf	2014-05-20
10	11228-delnp-2013-Abstract.pdf	2014-05-20
11	11228-delnp-2013-Correspondence-Others-(18-06-2014).pdf	2014-06-18
12	11228-DELNP-2013.pdf	2016-12-15
13	11228-DELNP-2013-FER.pdf	2018-04-27
14	11228-DELNP-2013-Verified English translation (MANDATORY) [20-07-2018(online)].pdf	2018-07-20
15	11228-DELNP-2013-PETITION UNDER RULE 137 [31-08-2018(online)].pdf	2018-08-31
16	11228-DELNP-2013-OTHERS [31-08-2018(online)].pdf	2018-08-31
17	11228-DELNP-2013-FER_SER_REPLY [31-08-2018(online)].pdf	2018-08-31
18	11228-DELNP-2013-FER_SER_REPLY [31-08-2018(online)]-1.pdf	2018-08-31
19	11228-DELNP-2013-CORRESPONDENCE [31-08-2018(online)].pdf	2018-08-31
20	11228-DELNP-2013-COMPLETE SPECIFICATION [31-08-2018(online)].pdf	2018-08-31
21	11228-DELNP-2013-CLAIMS [31-08-2018(online)].pdf	2018-08-31
22	11228-DELNP-2013-ABSTRACT [31-08-2018(online)].pdf	2018-08-31
23	11228-DELNP-2013-Power of Attorney-040918.pdf	2018-09-07
24	11228-DELNP-2013-Correspondence-040918.pdf	2018-09-07
25	11228-DELNP-2013-Response to office action (Mandatory) [16-03-2019(online)].pdf	2019-03-16
26	11228-DELNP-2013-Response to office action [24-09-2020(online)].pdf	2020-09-24
27	11228-DELNP-2013-PatentCertificate26-07-2021.pdf	2021-07-26
28	11228-DELNP-2013-IntimationOfGrant26-07-2021.pdf	2021-07-26
29	11228-DELNP-2013-POWER OF AUTHORITY [30-11-2022(online)].pdf	2022-11-30
30	11228-DELNP-2013-FORM-16 [30-11-2022(online)].pdf	2022-11-30
31	11228-DELNP-2013-ASSIGNMENT WITH VERIFIED COPY [30-11-2022(online)].pdf	2022-11-30
32	11228-DELNP-2013-RELEVANT DOCUMENTS [08-09-2023(online)].pdf	2023-09-08

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