Co₃O₄-carbon nanotube heterostructures with bead-on-string architecture for enhanced lithium storage performance

In this report, alkylcarboxyl group-decorated carbon nanotubes (CNTs) with clustered functionalization patterns are achieved based on a modified Birch reduction in liquid ammonia. By using these functional CNTs (f-CNTs), a new type of Co₃O₄-CNT heterostructure is prepared via a simple hydrothermal method. SEM and TEM analyses reveal that the as-synthesized Co ₃O₄-CNT heterostructures exhibit bead-on-string architecture, in which the Co₃O₄ spheres are threaded with CNTs. A possible growth mechanism is proposed to explain the formation of these Co₃O₄-CNT heterostructures. The electrochemical properties of the Co₃O₄-CNT heterostructures as anode materials for lithium ion batteries are investigated. The Co₃O ₄-CNT heterostructures display high electrochemical activity, good cycle stability and improved rate performance. Such a large improvement of the electrochemical performance can be related to the robust necklace-like architectures which possess properties such as high mechanical stability, excellent electric conductivity and good strain accommodation.