Li-S batteries are a promising energy storage technology due to their high theoretical capacity, but they suffer from issues such as poor cycle stability and capacity loss over time. Here, we investigate the impact of carrageenan, a polysaccharide binder derived from red algae, on the performance of Li-S batteries. Electrode slurries are prepared without the toxic solvent N-methyl-2-pyrrolidone, using only water as a solvent and dispersant, making the process potentially scalable and cost-effective. With the optimal amount of carrageenan, we observe a capacity retention of 69.1% at 4 C after 1000 charge-discharge cycles. Carrageenan-based electrodes deliver 30% higher capacity than those made with the industry-standard polyvinylidene fluoride binder. X-ray photoelectron spectroscopy analysis confirms the chemical binding of carrageenan to the sulfur active material, and transmission X-ray absorption spectroscopy reveals that carrageenan effectively traps shorter-chain lithium polysulfides, improving the overall battery performance.

In this work, we study the influence of reduced graphene oxide (rGO) on the morphology and chemistry of highly porous N,S-doped carbon cryogels. Simultaneously, we propose an easily upscalable route to prepare such carbons by adding graphene oxide (GO) in as-received suspended form to the aqueous solution of the ι-carrageenan and urea precursors. First, 1.25–5 wt% GO was incorporated into the dual-doped polymer matrix. The CO₂, CO, and H₂O emitted during the thermal treatments resulted in the multifaceted modification of the textural and chemical properties of the porous carbon. This facilitated the formation of micropores through self-activation and resulted in a substantial increase in the apparent surface area (up to 1780 m²/g) and pore volume (up to 1.72 cm³/g). However, adding 5 wt% GO led to overactivation. The incorporated rGO has an ordering effect on the carbon matrix. The evolving oxidative species influence the surface chemistry in a complex way, but sufficient N and S atoms (ca. 4 and >1 at%, respectively) were preserved in addition to the large number of developing defects. Despite the complexity of the textural and chemical changes, rGO increased the electrical conductivity monotonically. In alkaline oxygen reduction reaction (ORR) tests, the sample with 1.25 wt% GO exhibited a 4e⁻ mechanism and reasonable stability, but a higher rGO content gradually compromised the performance of the electrodes. The sample containing 5 wt% GO was the most sensitive under oxidative conditions, but after stabilization it exhibited the highest gravimetric capacitance. In Li-ion battery tests, the coulombic efficiency of all the samples was consistently above 98%, indicating the high potential of these carbons for efficient Li-ion insertion and reinsertion during the charge–discharge process, thereby providing a promising alternative for graphite-based anodes. The cell from the 1.25 wt% GO sample showed an initial discharge capacity of 313 mAh/g, 95.1% capacity retention, and 99.3% coulombic efficiency after 50 charge–discharge cycles.

Conventional Li−S battery cathode synthesis routes are time‐consuming, energy‐intensive, use toxic solvents, and yet fail to effectively confine sulfur into carbon matrices, reducing the cathode efficiency. Supercritical CO₂ (scCO₂) presents notable benefits as a “green solvent” due to its affordability, chemical inertness, recyclability, non‐flammability, and non‐toxicity. It eliminates the need for energy‐intensive post‐heat treatments, providing a more sustainable and efficient option. CO₂ in supercritical state gains unique gas‐like and liquid‐like properties that enable precise sulfur loading, uniform encapsulation, and improved sulfur‐carbon interactions, which enhance conductivity and reaction kinetics. Recent studies show that cathodes prepared using scCO₂ exhibit exceptional electrochemical performance, including long‐term cycling stability and high coulombic efficiency. The versatility of scCO₂ in infiltrating various host architectures also makes it suitable for a wide range of cathode designs. Despite its tremendous potential, this advanced synthesis technology is often overlooked in textbooks, underscoring the need for awareness within the research community. This review highlights the remarkable features of scCO₂ and examine up‐to‐date research progress, focusing on its application in developing high‐performance carbon/sulfur composite cathodes. An application‐focused audience would benefit from a summary of this review, as they reveal new Li−S cathode synthesis technologies that haven't been widely explored or discussed.

High surface area carbon was obtained from -carrageenan – urea cryogels doped with 1.25 – 5 wt% graphene oxide (GO). Incorporation of GO resulted in multifaceted modification in the textural and chemical properties of the carbon cryogel. The thermal decomposition of GO facilitated the formation of micropores resulted in a substantial increase in the apparent surface area (up to 1780 m2/g). The annealing at 1000 °C removed part of the heteroatoms but left behind a high number of defects. While the volatile thermal degradation products of GO affected the porous texture and the surface chemistry in a complex way, its reduced residue resulted in a gradually increasing electrical conductivity. The influence of GO was studied in oxygen reduction reaction (ORR) and in Li-ion storage application. GO affected the electron transfer mechanism in the ORR tests and challenged the stability of the electrodes. Even if the electrode has been stabilized under oxygen-free conditions, later may undergo destabilization processes during the ORR. The 5 wt% GO doped sample was the most sensitive under oxidative conditions, but finally it exhibited the highest capacitance. In the Li-ion battery tests the coulombic efficiency of all the samples was consistently above 98 %, indicating the great potential of such carbons for efficient Li-ion insertion and reinsertion during the charge – discharge process, thereby providing a promising alternative for graphite-based anodes. The cell from the 1.25% sample showed an initial discharge capacity of 313 mAh/g, 95.1 % capacity retention and 99.3 % coulombic efficiency after 50 charge – discharge cycles.