Covalently Confined Sulfur Composite with Carbonized Bacterial Cellulose as an Efficient Cathode Matrix for High-Performance Potassium–Sulfur Batteries

Abstract

Although the development of potassium−sulfur batteries (KSBs) is in the nascent stage, KSBs draw keen interest as they offer a few unique advantages over Li− and Na−sulfur battery systems, including lower cost and highest ionic mobility of K + ions. However, shuttling of intermediate polysulfides and the insulating nature of sulfur result in poor utilization of the active material and significant capacity loss during cycling. In this study, we overcome these critical issues of KSBs by developing an active cathode material as a covalently confined sulfur composite with carbon derived from a sustainable precursor (bacterial cellulose) (hereinafter referred to as CCS@CBC). The synthesis temperature of CCS@CBC is varied from 150 to 450 °C to achieve the optimal covalent fixing of sulfur in the carbon matrix verified by X-ray diffraction and infrared spectroscopy. The increase in the synthesis temperature of CCS@CBC ensures proper covalent confinement of sulfur with the carbon matrix that facilitates the relieving of the shuttle effect as revealed in the electrochemical performance of as-prepared KSBs. The CCS@CBC prepared at 450 °C delivers an impressive initial capacity of 615 mAh g −1 and retains 383 mAh g −1 after 250 cycles at a current density of 200 mA g −1 . Furthermore, the rate-capability and the self-discharge tests reveal the superior performance of CCS@CBC at 450 °C compared to lower synthesis temperature. A higher sulfur loading (2.5 mg cm −2 ) electrode is also tested to evaluate the commercial aspect. The first-principles calculations are also performed to investigate the interaction of the host material with polysulfides to better understand the experimental findings. The outcome of this study can be helpful in the future development of high-performance KSBs.

Bacterial Cellulose-Derived Self-Supported Carbon Electrodes for Stable Performance Metal–Sulfur Batteries: A Novel Approach toward Full-Cell Studies

“…This polar structure may act as a binding site for the soluble polysulfides and thus help to relieve the detrimental effect of the shuttle behavior of soluble polysulfides. In our earlier reports, we have also performed the first-principle calculations to validate this observation in LSB and KSB . Later, the half-cell and full-cell configurations were tested, as discussed in the following sections.…”

“…In our earlier reports, we have also performed the first-principle calculations to validate this observation in LSB 6 and KSB. 5 Later, the half-cell and full-cell configurations were tested, as discussed in the following sections.…”

“…In literature, carbonaceous materials have been explored as conducting cathode matrices for MSBs and have revealed remarkable electrochemical performances due to higher specific area, porous structure, and abundant functional groups. 5,6,13,14 Further, while assembling the conventional lithium−sulfur batteries (LSBs) and potassium−sulfur batteries (KSBs), conductive agents, binders, and current collectors are used for electrode fabrication. 15−17 These components are electrochemically inactive in the cell, leading to the device's decreased energy density.…”

“…Metal–sulfur batteries (MSBs) have attained enormous attention as an alternative to metal–ion batteries due to their high specific capacity and energy density. − In general, lithium–sulfur and potassium–sulfur chemistry surpass other MSBs’ chemistry due to the higher redox potential of lithium and potassium metal, which enables these systems to have higher energy density. − However, the commercialization of MSBs is plagued with several critical challenges. First, the insulating nature of sulfur results in the underutilization of active material.…”

“…Third, volume changes resulting from the conversion of the S 8 molecule to M 2 S (metal disulfide) lead to the destruction and detachment of the cathodic material from the current collector. − Therefore, a suitable matrix with efficient electronic conductivity, a porous structure, and a good specific surface area is required to avoid these challenges. In literature, carbonaceous materials have been explored as conducting cathode matrices for MSBs and have revealed remarkable electrochemical performances due to higher specific area, porous structure, and abundant functional groups. ,,, …”