Nitrogen and oxygen dual-doped hierarchical porous carbon derived from rapeseed meal for high performance lithium–sulfur batteries

N-doped CNTs wrapped sulfur-loaded hierarchical porous carbon cathode for Li-sulfur battery studies

Lithium-sulfur (Li-S) batteries are considered promising next-generation energy storage devices due to their low cost and high energy density (2600 W h kg-1). However, the practical applicability of Li-S batteries is hindered by the insulating nature of sulfur cathodes, and the high solubility of polysulfides (Li2Sx, 3 < x ≤ 8) which are formed during the electrochemical process. Integrating sulfur into the carbon host is an effective way to enhance the conductivity of the electrode which hampers the shuttling effect of the polysulfides. Here in this study, hierarchical porous carbon structures (HPC) are prepared from spent coffee waste (SCW) by the KOH activation process and are encapsulated with sulfur (SHPC) which increases the interaction between sulfur and carbon and enhances both the electronic and ionic conductivities. Further wrapping of SHPC with N-doped multi-walled carbon nanotubes (NCNTs) gives a SHPC-NCNT composite, which alleviates the shuttling of polysulfides by trapping them and ensures the required conductivity to the sulfur cathode during the Li+ reactions. When studied as a cathode material for Li-S batteries, the prepared cathode showed 664 and 532 mA h g-1 specific capacities after 150 cycles at 0.2C and 0.5C, respectively. The stable cyclability and rate capability properties of SPHCNCNT suggest that the prepared sulfur composite is suitable as a cathode material for Li+ energy storage applications.

Regeneration of Activated Sludge into SiO2-Decorated Heteroatom-Doped Porous Carbon as Advanced Electrodes for Li-S Batteries

The regeneration of harmful activated sludge into an energy source is an important strategy for municipal sludge treatment and recycling. Herein, SiO₂-modified N,S auto-doped porous carbon (NSC@SiO₂) with high conductivity (70 S m^-1) is successfully obtained through a simple calcination method of the activated sludge from wastewater treatment. Further, P-doped NSC@SiO₂ (NSPC@SiO₂) is designed to achieve a higher surface area (891 m² g^-1 vs 624 m² g^-1), a larger pore volume (0.87 cm³ g^-1 vs 0.08 cm³ g^-1), and more carbon defects. Due to its special structure, NSPC@SiO₂ is used as a sulfur host of lithium-sulfur batteries. The results of polysulfide adsorption experiments, S 2p X-ray photoelectron spectra (XPS), Li₂S nucleation experiments, polysulfide symmetric cells, measurement of the galvanostatic intermittent titration (GITT), polarization voltage difference, lithium-ion diffusion rate, and Tafel slope verified that NSPC@SiO₂ greatly improved the adsorption capacity of polysulfides, lowered the barrier to Li₂S formation and the internal resistances of cells, and accelerated Li⁺ ion diffusion and the reaction kinetics of polysulfide conversion, resulting in the excellent performance of polysulfide capture and superior rate performance and cyclic stability. By comparing NSPC@SiO₂ with NSC@SiO₂, a higher initial capacity (1377 mAh g^-1 vs 1150 mAh g^-1 at 0.1C), better rate capacity (912 mAh g^-1 vs 719 mAh g^-1 at 2C), and low capacity decay (0.094% per cycle within 200 cycles) are obtained. Our work provides direction for the treatment, disposal, and resource utilization of activated sludge.

Rambutan peel derived porous carbons for lithium sulfur battery

Porous carbons were prepared from the biomass waste rambutan peels using hydrothermal carbonization followed by the KOH activation process. Rambutan peel derived porous carbons (RPC) with high surface area of 2104 m2 g−1 and large pore volume of 1.2 cm3 g−1 were obtained at KOH/carbon ratio of 4 and activation temperature of 900 °C. The as-obtained porous carbons were capable of encapsulating sulfur with a high loading of 68.2 wt% to form RPC/S composite cathode for lithium sulfur (Li–S) battery. High specific discharge capacities of about 1275 mAh g−1 were demonstrated by the RPC/S composites at 0.1 C. After 200 cycles at 0.1 C, a high specific capacity of 936 mAh g−1 was maintained, showing an excellent capacity retention of about 73%.

Simple and Sustainable Preparation of Nonactivated Porous Carbon from Brewing Waste for High-Performance Lithium-Sulfur Batteries

The development of renewable energy sources requires the parallel development of sustainable energy storage systems because of its noncontinuous production. Even the most-used battery on the planet, the lithium-ion battery, is reaching its technological limit. In light of this, lithium-sulfur batteries have emerged as one of the most promising technologies to address this problem. The use of biomass to produce cathodes for these batteries addresses not only the aforementioned problem, but it also reduces the carbon footprint and gives added value to something normally considered waste. Here, the production, by simple and nonactivating pyrolysis, of a carbon material using the abundant "after-boiling waste" derived from beer brewing is reported. After adding a high sulfur loading (70 %) to this biowaste-derived carbon by the "melt diffusion" method, the sulfur-carbon composite is used as an effective cathode in Li-S batteries. The cathode shows excellent performance, reaching high capacity values with long-term cyclability at high current-847 mAh g^-1 at 1 C, 586 mAh g^-1 at 2 C, and even 498 mAh g^-1 at 5 C after 400 cycles-drastically reducing capacity loss to values approaching 0.01 % per cycle. This work demonstrates the possibility of obtaining low-cost, highly sustainable cathodic materials for the design of advanced energy storage systems.