A positive electrode active material for a secondary battery includes a lithium composite transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn), and a glassy coating layer formed on surfaces of particles of the lithium composite transition metal oxide, wherein, in the lithium composite transition metal oxide, an amount of the nickel (Ni) in a total amount of transition metals is 60 mol % or more, and an amount of the manganese (Mn) is greater than an amount of the cobalt (Co), and the glassy coating layer includes a glassy compound represented by Formula 1.

Li.sub.aM.sup.1.sub.bO.sub.c  [Formula 1] wherein, M.sup.1 is at least one selected from the group consisting of boron (B), aluminum (Al), silicon (Si), titanium (Ti), and phosphorus (P), and 1≤a≤4, 1≤b≤8, and 1≤c≤20.

A positive electrode active material for a secondary battery includes a lithium composite transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn), and a glassy coating layer formed on surfaces of particles of the lithium composite transition metal oxide, wherein, in the lithium composite transition metal oxide, an amount of the nickel (Ni) in a total amount of transition metals is 60 mol % or more, and an amount of the manganese (Mn) is greater than an amount of the cobalt (Co), and the glassy coating layer includes a glassy compound represented by Formula 1.

Li.sub.aM.sup.1.sub.bO.sub.c  [Formula 1] wherein, M.sup.1 is at least one selected from the group consisting of boron (B), aluminum (Al), silicon (Si), titanium (Ti), and phosphorus (P), and 1≤a≤4, 1≤b≤8, and 1≤c≤20.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

A method uses mild fluorinating agents, such as hydrofluorocarbons—HCFs, perfluorocarbons—PFCs, hydrochlorofluorocarbons HCFCs and chlorofluorocarbons—CFCs, to fine-tune the fluorination process in battery material preparation in order to obtain uniform nanometer-sized surface fluoride coated battery materials. The use of a vertical flow-type tube reactor permits a fine-tuning of the fluorination process by accurately regulating the active gas or mixture of gases flow over battery materials using mass-flow regulators, and precisely setting the temperature with vertical rube furnace. Additionally, these fluorinating agents have slightly different reactivity, decomposing and reacting with battery materials at different temperatures, and therefore, offering additional parameter of fluorination fine-tuning. The method is scalable and can be easily adapted as an industrial solution. Moreover, all these gases are non-toxic, non-corrosive and non-flammable gases at room temperatures, hence, they are more convenient to handle than highly-toxic and highly-corrosive HF and F.sub.2 gases.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.