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Abstract

Disclosed is a negative electrode active material which has a high capacity and good cyclability. The negative electrode active material comprises nanosize carbon particles and nanosize tin dioxide particles that are supported in a high-dispersion state on the nanosize carbon particles. The negative electrode active material has a high discharge capacity because of the reversible progress of a conversion reaction of tin dioxide (SnO₂+4Li⁺+4e⁻→2Li₂O+Sn) therein. In a charge-discharge cycle test within a voltage range of 0 to 2 V vs. an Li/Li⁺ electrode, the negative electrode active material shows a discharge capacity retention rate of about 90% even after 500 charge-discharge cycles at the rate 1 C, which indicates excellent cyclability. Therefore, the negative electrode active material can be suitably used in a lithium ion secondary battery and a hybrid capacitor.

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