CATHODE ACTIVE MATERIAL SHOWING IMPROVED CHARACTERISTICS AT HIGH VOLTAGE

PROBLEM TO BE SOLVED: To provide: a cathode active material which enables the battery activation with a high voltage and enables the increase in battery capacity while suppressing the worsening of a battery performance, the shortening of a lifetime, and the occurrence of a side reaction, such as the thermal decomposition of an electrolyte, the reaction of a lithium-containing anode with an electrolyte, the oxidation of a cathode, or the decomposition of a cathode active material; a battery arranged by use of such a cathode active material; and a lithium secondary battery.SOLUTION: A cathode active material comprises: a lithium transition metal oxide based on at least one transition metal selected from Ni, Mn and Co. The lithium transition metal oxide includes fluorine; and a major part of the fluorine, i.e. 50-99.9% of the total weight of the fluorine is present on the surface of the lithium transition metal oxide. In the cathode active material, at least one metal selected from Mg, Ti, Zr, Al and Fe, and sulfur(S) are included in the lithium transition metal oxide. In the cathode active material, the content of the fluorine is preferably 10 wt% or less to the total weight of the lithium transition metal oxide.SELECTED DRAWING: Figure 2 【課題】バッテリーの性能低下、寿命の減少、電解質の熱分解や、電解質とリチウム含有のアノード反応・カソード酸化・カソード活物の分解等の副反応の発生等を抑制しながら、高電圧でバッテリーを作動し、バッテリー容量が増加するカソード活物質及びそれを用いたバッテリ、リチウム二次電池の提供。【解決手段】Ｎｉ、Ｍｎ及びＣｏから選択される一種以上の遷移金属に基づくリチウム遷移金属酸化物を含み、そのリチウム遷移金属酸化物がフッ素を含み、フッ素の大部分、フッ素の総重量の５０〜９９．９％が、リチウム遷移金属酸化物の表面上に存在し、Ｍｇ、Ｔｉ、Ｚｒ、ＡｌとＦｅから選択される一種以上の金属、及び硫黄（Ｓ）が、前記リチウム遷移金属酸化物中に含まれるカソード活物質。好ましくは、フッ素の含有量が、前記リチウム遷移金属酸化物の総重量に対して、１０重量％以下であるカソード活物質。【選択図】図２