Comparative Study of Li4Ti5O12 Composites Prepared withPristine, Oxidized, and Surfactant‐Treated Multiwalled Carbon Nanotubes for High‐Power Hybrid Supercapacitors

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AbstractIn hybrid supercapacitors, lithium‐ion battery (LIB)‐type intercalation materials have slower reaction kinetics than electrical double‐layer‐capacitor‐type carbonaceous materials. Thus, it is of prime importance to improve the rate capability of LIB‐type intercalation materials to achieve high energy density as well as high power density from hybrid supercapacitors. In this study, we report Li4Ti5O12/pristine multiwalled carbon nanotube (LTO/P‐MWCNT) composites with high rate capability and demonstrate their anode application for high‐power hybrid supercapacitors. For comparison, two additional LTO composites are prepared by using oxidized MWCNTs and surfactant‐treated MWCNTs through a similar spray‐drying process. The LTO/P‐MWCNT composite shows superior rate capability over the other two composites, owing to the high electrical conductivity of pristine MWCNTs. The hybrid supercapacitor composed of a LTO/P‐MWCNT anode and an activated carbon cathode delivers an energy density of 70.9 Wh kg−1 at a power density of 0.03 kW kg−1 and a maximum power density of 21.8 kW kg−1 is achieved at an energy density of 24.3 Wh kg−1. Furthermore, the hybrid supercapacitor exhibits excellent cycling stability. These salient results provide further impetus to the use of MWCNTs in the design and synthesis of high‐rate oxide‐based composites with efficient lithium‐ion transport and high electrical conductivity for high‐power hybrid supercapacitors and high‐power LIBs.