Study on the Novel Anode for Anode for Advanced Lithium Secondary Batteries

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Ultrafine SnSb_<0.14>, SnO and SiO powders as hosts for lithium insertion show high irreversibility in the first cycle. A combination of the tin-containing hosts with Li_<2.6>Co_<0.4>N has been examined for composite anodes in lithium ion batteries. The new anode systems reduce or eliminate the first irreversible capacity and improve the cycle performances.The first lithiation capacity is ca. 90 mAh/g for Li_<2.6>Co_<0.4>N electrode and its delithiation capacity is ca. 900 mAh/g, mostly at the potential plateau of 1 V vs. Li. After the first cycle, Li_<2.6>Co_<0.4>N phase structure changes from crystalline to amorphous state, but a cycle capacity over 800 mAh/g can still be kept. For ultrafine SnSb_x, SnO and SiO, the first cycle efficiency is generally below 65 % in spite of their high reversible capacities from 550 to 1300 mAh/g. When the two different hosts are mixed to form a composite electrode, the first cycle efficiency becomes adjustable by controlling the ratio of the two hosts. The composite electrodes show a better cycle stability than the alloy and oxides, because a dispersion of Li_<2.6>Co_<0.4>N in the electrodes alleviates the volume change effect due to its small volume expansion. The composite electrodes can be used not only in liquid electrolytes, but also in solid polymer electrolytes.