Jeom-Soo Kim

ZrO2- and Li2ZrO3-stabilized spinel and layered electrodes for lithium batteries

Strategies for countering the solubility of LiMn{sub 2}O{sub 4} (spinel) electrodes at 500 {sup o}C and for suppressing the reactivity of layered LiMO{sub 2} (M = Co, Ni, Mn, Li) electrodes at high potentials are discussed. Surface treatment of LiMn{sub 2}O{sub 4} with colloidal zirconia (ZrO{sub 2}) dramatically improves the cycling stability of the spinel electrode at 50 {sup o}C in Li/LiMn{sub 2}O{sub 4} cells. ZrO{sub 2}-coated LiMn{sub 0.5}Ni{sub 0.5}O{sub 2} electrodes provide a superior capacity and cycling stability to uncoated electrodes when charged to a high potential (4.6 V vs Li{sup 0}). The use of Li{sub 2}ZrO{sub 3}, which is structurally more compatible with spinel and layered electrodes than ZrO{sub 2} and which can act as a Li{sup +}-ion conductor, has been evaluated in composite 0.03Li{sub 2}ZrO{sub 3} - 0.97LiMn{sub 0.5}Ni{sub 0.5}O{sub 2} electrodes; glassy Li{sub x}ZrO{sub 2 + x/2} (0

The effect of tetravalent titanium substitution in LiNi1−xTixO2 (0.025⩽x⩽0.2) system

Layered LiNi{sub 1-x}Ti{sub x}O{sub 2} (0.025 {<=} x {<=} 0.2) containing tetravalent titanium ions was prepared by solid-state reaction at 750{sup o}C under an oxygen stream. The products show highly ordered and phase-pure layered compounds. The structural integrity of the materials could be preserved by substituting Ti{sup 4+} ions to prevent impurity Ni{sup 2+} migration into lithium sites. The LiNi{sub 1-x}Ti{sub x}O{sub 2} (0.025 {<=} x {<=} 0.2) cathode exhibits high reversible capacities (up to 240 mA h/g) and excellent cyclability (over 100 cycles) in the range 4.3-2.8 V at a current density of 0.2 mA/cm{sup 2} (C/5 rate). One composition, LiNi{sub 0.975}Ti{sub 0.025}O{sub 2}, showed the highest reversible capacity and energy density of all known layered LiNiO{sub 2} or LiCoO{sub 2} materials. The novel concept of substitution of tetravalent titanium is proven to be promising.