Multifunctional CoO@C metasequoia arrays for enhanced lithium storage

Abstract

Cobalt oxide is a promising high-capacity anode material for lithium ion batteries (LIBs), but its development is limited by poor cycling stability due to its huge volume change happening during repeated conversion processes. In this paper, a robust and rational strategy was designed to improve the electrochemical performance of cobalt oxide (CoO) by preparing self-supported CoO@C core–shell metasequoia-like nanowire arrays on a conducting nickel foam substrate with solid adhesion. Interestingly, the present CVD process can produce onion-like graphitic carbon at a relatively low temperature (300–350°C) near the substrate due to the catalysis of nickel foam. More importantly, the direct and compact contact of cobalt oxide with the thin carbon layer and the conducting substrate provided an effective pathway for fast charge transfer and ion transport without any requirement of other ancillary materials, such as carbon black or binder, to improve the system׳s conductivity and stability. As an anode material for LIBs, the heterocomposite exhibited a larger reversible capacity, higher rate capability, and excellent cycling stability by comparison with the pristine CoO@C and Co3O4 on nickel foam due to the triple electronically conductive guarantee of carbon shells, conducting nickel foam substrate and the oriented orderly CoO nanowire arrays. The preparation of the orderly 1D nanostructures with conductive coating on conductive substrates has been proven to generate efficient electrode materials, opening up an alternate way to improve the electrochemical stability of LIBs. The present route is expected to be extended to the synthesis of other oxides as electrodes for LIBs.