High-energy asymmetric supercapacitors based on free-standing hierarchical Co–Mo–S nanosheets with enhanced cycling stability

Abstract

Layered transition metal sulfides (TMS) are emerging as advanced materials for energy storage and conversion applications. In this work, we report a facile and cost-effective anion exchange technique to fabricate a layered, multifaceted, free standing, ultra-thin ternary cobalt molybdenum sulfide nanosheet (Co-Mo-S NS) architecture grown on a 3D porous Ni foam substrate. The unique Co-Mo layered double hydroxides are first synthesized as precursors and consequently transformed into ultra-thin Co-Mo-S NS. When employed as an electrode for supercapacitors, the Co-Mo-S NS delivered an ultra-high specific capacitance of 2343 F g at a current density of 1 mA cm with tremendous rate capability and extraordinary cycling performance (96.6% capacitance retention after 20 000 cycles). Furthermore, assembled Co-Mo-S/nitrogen doped graphene nanosheets (NGNS) in an asymmetric supercapacitor (ASC) device delivered an excellent energy density of 89.6 Wh kg, an amazing power density of 20.07 kW kg, and superior cycling performance (86.8% capacitance retention after 50 000 cycles). Such exceptional electrochemical performance of Co-Mo-S NS is ascribed to the good electrical contact with the 3D Ni foam, ultra-high contact area with the electrolyte, and enhanced architectural softening during the charging/discharging process. It is expected that the fabricated, unique, ultra-thin Co-Mo-S NS have great potential for future energy storage devices.

Freestanding Needle Flower Structure CuCo2S4 on Carbon Cloth for Flexible High Energy Supercapacitors With the Gel Electrolyte

“…And, the capacitance contribution of blank-CC is negligible. Figure 4C shows typical CV curves for CuCo 2 S 4 /CC at 0-0.6 V. Each curve shows a significant redox peak, indicating that the Cu(Co)-S-O/Cu(Co)-S-OH-related faraday reaction was carried out (Jayaraman et al, 2017). As the scan rate increased, the redox peak appeared to shift due to the presence of polarization (Ratha et al, 2017).…”

“…Through the above observations, the growth mechanism of flowerlike CuCo 2 S 4 on carbon cloth can be preliminarily obtained. First, in an alkaline environment, Cu 2+ and Co 2+ ions form a CuCo(OH) x precursor Jayaraman et al, 2017). At this time, the solution becomes a supersaturated solution with a large amount of Cu-Co precursor particles.…”

Hierarchical NiMoS and NiFeS Nanosheets with Ultrahigh Energy Density for Flexible All Solid‐State Supercapacitors

“…Metal sulfides (MSs) such as CuS, Co 9 S 8 , Ni 3 S 2 , FeS 2 , WS 2 , and MoS 2 have recently been considered as a new class of pseudocapacitive electrode/electrode materials in SCs with enhanced specific capacitance/capacity, energy and power densities as an alternative for metal oxides due to their high electrical conductivity, marvelous redox reversibility, low electronegativity, and high catalytic activity . Among the reported MSs, MoS 2 and FeS 2 received specific attention in electrode materials for SCs due to their excellent electrical conductivity, high catalytic activity, wide operating potential window, multiple oxidation states for redox kinetics, and cost‐effectiveness .…”

Recent Progress in Two‐Dimensional Layered Double Hydroxides and Their Derivatives for Supercapacitors

“…Compared with the Ni 4 V LDH electrode, the Ni 4 V−S electrode exhibits a higher specific capacitance, lower charge‐transfer resistance, and remarkable cycling stability. CoMo−S ultrathin nanosheets were grown on a 3D NF derived from CoMo LDH precursor . The CoMo−S nanosheets form an open structure supported on the NF skeleton.…”

“…CoMoÀSu ltrathin nanosheets were grown on a3 DN Fd erived from CoMo LDH precursor. [82] The CoMoÀSn anosheets form an open structure supported on the NF skeleton. They possess an ultrahighs pecific surface area of about 368 m 2 g À1 .T he unique mesoporousn etwork architecture and multivalence of Mo lead to an ultrahigh specific capacitance of 2343Fg À1 at 1mAcm À2 , with an extraordinary cycling stability( 96.6 %c apacitance retention over 20 000 cycles).…”