Integrated and heterostructured cobalt manganese sulfide nanoneedle arrays as advanced electrodes for high-performance supercapacitors

Herein, uniform cobalt manganese hydroxide (CMOH) nanoneedle arrays were firstly prepared via a low-temperature hydrothermal process using nickel (Ni) foam as a nanoneedle growth support framework. Subsequently, stable and integrated heterostructures of cobalt-manganese sulfides (CMS) with porous structures can be simultaneously formed and grown through the reaction of CMOH with Na2S during the hydrothermal anion-exchange reaction process while retaining their intrinsic nanoneedle array structure. The as-prepared CMS nanoneedle arrays as binder-free electrodes for supercapacitors exhibit a high area capacity of 0.53 mA h cm(-2) at 2 mA cm(-2) and good rate performance, as well as outstanding cycle life (only 6.3% capacity loss after 1500 cycles). Based on the unique architecture and excellent electrochemical performance of CMS nanoneedle arrays, a novel CMS-8//AC asymmetric supercapacitor with a high operating voltage of 1.7 V was fabricated using CMS nanoneedle arrays as the positive electrode and activated carbon (AC) as the negative electrode, respectively, and provided a maximum specific energy of 48.5 W h kg(-1) at a specific power of 524.5 W kg(-1). Such excellent electrochemical behaviors suggest that the CMS nanoneedle arrays are promising electrode materials for high performance supercapacitors. More-over, the present synthesis strategy can be extended to prepare other porous, integrated and heterostructured metal compounds.