A universal synthetic route to carbon nanotube/transition metal oxide nano-composites for lithium ion batteries and electrochemical capacitors

We report a simple synthetic approach to coaxially grow transition metal oxide (TMO) nanostructures on carbon nanotubes (CNT) with ready control of phase and morphology. A thin (~4 nm) sulfonated-polystyrene (SPS) pre-coating is essential for the deposition of transition metal based materials. This layer has abundant sulfonic groups (−SO 3 − ) that can effectively attract Ni 2+ , Co 2+ , Zn 2+ ions through electrostatic interaction and induce them via hydrolysis, dehydration and recrystallization to form coaxial (NiO, Co 3 O 4 , NiCoO 2 and ZnCo 2 O 4 ) shells and a nanosheet-like morphology around CNT. These structures possess a large active surface and enhanced structural robustness when used as electrode materials for lithium-ion batteries (LIBs) and electrochemical capacitors (ECs). As electrodes for LIBs, the ZnCo 2 O 4 @ CNT material shows extremely stable cycling performance with a discharge capacity of 1068 mAh g −1 after 100 cycles at a current density of 400 mAg −1 . For EC applications, the NiCoO 2 @ CNT exhibits a high capacitance of 1360 Fg −1 at current densities of 10 Ag −1 after 3000 cycles and an overall capacitance loss of only 1.4%. These results demonstrate the potential of such hybrid materials meeting the crucial requirements of cycling stability and high rate capability for energy conversion and storage devices.