Introduction of as-prepared cobalt source-containing carbon nanotubes to Co1-xS@C mesoporous nanospheres for an ultrahigh lithium storage

Abstract

When a carbon-doping nanocomposite of cobalt sulfide is applied as lithium-ion battery (LIB) anodes, both the emerging of interfacial lithium storage and the carbon-enhanced reversibility of intermediate polysulfides (Li2Sn, 3 ≤ n ≤ 8) may collectively determine the high-capacity properties of these electrodes. Herein, synthetic protocol of Co1-xS@C mesoporous nanospheres (pore ∼6.67 nm, sphere ∼215.9 nm) is modified to obtain the carbon nanotubes (CNTs) doped composite of CNT-Co1-xS@C (pore ∼6.49 nm, sphere ∼210.8 nm) by substituting as-prepared CNT-Co for chemical CoCl2. Within 0.01–3.0 V vs. Li+/Li at 200 mA g−1, in each cycle CNT-Co1-xS@C delivers a much higher discharge capacity than Co1-xS@C, and the former gives an initial value of 2147.6 mAh g−1 that gradually decreases to the minimum of 1253.7 mAh g−1 in the 70th cycle and then gradually increases to an ultrahigh value of 2026.8 mAh g−1 in the 180th cycle. Upon cycling, both the gradual increase of interfacial storage capacity and the gradually decreasing anionic fraction of bulk storage capacity, as well as the plausible high-capacity mechanism of composite CNT-Co1-xS@C as LIB anodes, indicate a successful introduction of as-prepared cobalt source-containing CNTs to Co1-xS@C mesoporous nanospheres for a potential application purpose.