POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND MANUFACTURING METHOD THEREOF

To provide a positive electrode active material containing Li2RuO3 as Li transition metal composite oxide, which can achieve a high capacity and which has a high-level cycle characteristic.SOLUTION: The present invention relates to a positive electrode active material for a Li ion secondary battery, which comprises an Li2RuO3 composite oxide having a layered rock salt-type crystal structure. The Li2RuO3 composite oxide to which the invention is applied has the following two requirements: (i) a diffraction peak of (003)-plane of an ilmenite type structure arises in an X-ray diffraction pattern after an initial full-charge operation; and (ii) after an initial full-charge operation, Ru ions of 20% up to 50% of Ru ions involved in the Li2RuO3 composite oxide transfer to Li ion sites. Suitable transfer of the Ru ions contributes to keeping of an interlayer distance allows a Li ion secondary battery to exhibit a high-level cycle characteristic. The Ru ion transfer is revealed from crystal structure analysis on X-ray diffraction patterns in respective stages in an initial charge process.SELECTED DRAWING: Figure 10 【課題】Ｌｉ遷移金属複合酸化物としてＬｉ２ＲｕＯ３を含む正極活物質であって、高容量化と高サイクル性を有するものを提供する。【解決手段】本発明は、層状岩塩型結晶構造を有するＬｉ２ＲｕＯ３複合酸化物からなるＬｉイオン二次電池用正極活物質に関する。本発明で適用されるＬｉ２ＲｕＯ３複合酸化物は、（ｉ）初回満充電後のＸ線回折パターンに、イルメナイト型構造の（００３）面の回折ピークが発現すること、（ｉｉ）初回満充電後において前記Ｌｉ２ＲｕＯ３複合酸化物を構成するＲｕイオンの２０％以上５０％以下のＲｕイオンがＬｉイオンサイトへ移動すること、の２つの条件を具備する。前記のＲｕイオンの好適な移動が層間距離の維持に寄与し、高サイクル性を発揮させる。このＲｕイオンの移動は、初回充電過程における各段階のＸ線回折パターンに基づく結晶構造解析から明らかにされる。【選択図】図１０