Shell Structure Control of PPy-Modified CuO Composite Nanoleaves for Lithium Batteries with Improved Cyclic Performance

Polypyrrole (PPy)-modified CuO nanocomposites (NCs) with various shell structures have been synthesized by controlling the polymerization time of pyrrole in the presence of leaf like CuO nanobelts (NBs) as wire templates. The synthesized CuO/PPy NCs and CuO NBs are characterized by XRD, FT-IR, TGA, SEM, TEM, STEM, and EDX line analysis/elemental mapping. The formation mechanism of CuO/PPy core shell NCs is also illustrated. Electrochemical lithium-storage properties of all the products are evaluated by using them as anode materials for Li-ion batteries (LIBs). It is found that the polymerization time of pyrrole plays a significant role in affecting the shell structures and subsequent lithium storage properties of the hybrid Cu0/PPy NCs. With the extension of polymerization time, CuO/PPy NCs gradually form typical core shell structures, where the doped PPy with increasing content is steadily and uniformly coated on the CuO surface. Correspondingly, the discharge/charge capacity and cyclic durability of CuO/PPy NCs are significantly enhanced. For the core shell NCs made by the 3 h polymerization, a greatly improved initial capacity of 1114 mAh g(-1) and a high reversible capacity of 760 mAh g(-1) are achieved, which are much better than those of the bare CuO NBs and the NCs without core shell structures. The improved performance of core shell CuO/PPy NCs can be attributed to their advantageous structure features that buffer volume variations of the rigid CuO, allow short Li-ion diffusion length, form good interface interaction between PPy and CuO for charge transfer, and avoid direct contacts between CuO and electrolytes during charge discharge processes. This study indicates that the structural tuning of polymer/metal oxide composites by controlling the polymerization time is a simple and promising way to improve the electrode performance of NCs for energy storage.