Polysulphides reversible faradaic reactions in supercapacitor application

Lignin-based dual component additives as effective electrode material for energy management systems

A functional PbO-lignin electrode hydrid material composite was designed and manufactured. Moreover, its connection efficiency was confirmed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We noted that the superficial layers of PbO combined with layers of the biopolymer and that oxygen atoms present in both materials had influence on the chemical environment of the neighboring compound. Hence, it can be said that the addition of PbO significantly contributes to the improvement of thermal stability of the final inorganic-organic system. In the framework of the study, the dispersive, morphological and structural characteristics were determined using scanning electron microscopy (SEM) and laser diffraction method. Electrochemical studies indicated that the PbO-lignin material exhibits better electrochemical properties compared to PbO without the addition of kraft lignin (increased capacitance, lower charge transfer resistance), as the specific capacitance after 5000 charge/discharge cycles was still at 95% of the initial value. Such promising operating parameters show that this material can be successfully used as an electrode material for energy management systems.

Achieving Rich Mixed-Valence Polysulfide/Carbon Nanotube Films toward Ultrahigh Volume Energy Density and Largely Deformable Pseudocapacitors

In this work, new insights into dependence of electrochemical performance enhancement on transition metals' rich mixed valence and their atomic ratio as well as redox active polysulfides are proposed. Especially, the influence of atomic ratio is further demonstrated by both experiments and density functional theoretical calculation where increasing Co/S leads to the enlargement of both interatom distance and hole diameter in a Mn_xCo_yS_z cell. We rationally designed and prepared novel flexible electrodes of a rich mixed-valence polysulfide Mn_xCo_yS_z/carbon nanotube film (CNTF) through acid activation of a dense CNTF into a hydrogel-like conductive matrix, growth of the Mn_xCo_y(CO₃)_0.5OH precursor on each CNT, and controlled sulfidation. Nanostructure control allows us to obtain fast electron/ion transfer and increased availability of active sites/interfaces. The optimal MnCo₉S₁₀/CNTF shows a specific capacitance reaching 450 F cm^-3 at 10 mA cm^-2, much higher than reported values for CNT-based electrodes. Also, it exhibits remarkable cycling stability with only 1.6% capacity loss after 10 000 cycles at a high current density of 80 mA cm^-2. An all-solid-state asymmetric supercapacitor (ASC) applying MnCo₉S₁₀/CNTF delivers an exceptionally high volumetric energy density of 67 mW h cm^-3 (at 10 W cm^-3). Particularly, integrated electric sources with adjustable output voltages can be obtained by connecting several ASCs in series, and there are no structural failure and capacity loss during repeated large-angle twisting and vigorous hammering. This work provides a general route to energy storage devices with ultrahigh volumetric energy density and outstanding reliability for wearable electronics.