The sulfurized polyacrylonitrile (SPAN), featuring the sulfur atoms covalently anchored with the polyacrylonitrile, gives a chance to avoid the dissolutionprecipitation mechanism of the lithium polysulfides (LiPS) in traditional Li-S batteries. However, such a solid-solid conversion in SPAN cathodes is an electrolyte-dependent behavior, and current studies lack a detailed description of the dissolution mechanism of the covalently-bonded sulfur, which is important for understanding the sulfur reduction reaction (SRR) pathway in SPAN cathodes. In this work, interestingly, we discovered that the LiPS still dissolves from the SPAN matrix in the ether-based electrolytes, which may promote the SRR kinetics. It also demonstrates that the sulfur-PAN bonds in the cathode-electrolyte interfaces are vulnerable to be attacked by the ether molecules. A selenization strategy was therefore introduced to further reinforce the bonding between the sulfur atoms and the SPAN matrix. Impressively, the as-designed cathode realizes rapid and stable lithium storage with 77% of capacity retention over 200 cycles under high mass loading of ~7 mg cm⁻², low electrolyte/sulfur ratio of ~2.9 μL mg⁻¹, and limited N/P ratio of 1.5. It is believed that the multiscale design strategy could pave a new avenue for fabricating stable organosulfur cathodes for next-generation energy storage.

Hard carbon anode has shown extraordinary potentials for sodium-ion batteries (SIBs) owing to the cost-effectiveness and advantaged microstructure. Nevertheless, the widespread application of hard carbon is still hindered by the insufficient sodium storage capacity and depressed rate property, which are mainly induced by the undesirable pseudographitic structure. Herein, we develop a molten-salt-mediated strategy to regulate the pseudographitic structure of hard carbon with suitable interlayer spacing and enlarged pseudographitic domain, which is conducive to the intercalation capacity and diffusion kinetics of sodium ions. Impressively, the optimized hard carbon anode delivers a high reversible capacity of 320 mAh·g⁻¹, along with superior rate property (138 mAh·g⁻¹ at 2 A·g⁻¹) and stable cyclability over 1800 cycles. Moreover, the in situ Raman spectroscopic study and full-cell assembly further investigate the sodium storage mechanism and practical implement of obtained hard carbon. This work pioneers a low-cost and effective route to regulate the pseudographitic structure of hard carbon materials for advanced SIBs.

Prussian blue analogs (PBAs) are effective precatalysts for the oxygen evolution reaction (OER); however, the underlying mechanism of their electrochemical activation is still not well elucidated. In this study, we designed and constructed PBA-based precatalysts to determine the electrochemical activation mechanism and achieve high-efficiency OER. The PBAs undergo in situ electrochemical transformation to form the corresponding metal (oxy)hydroxides (M(O)OH) as the true OER catalyst. More importantly, the hexacyanoferrate ligands undergo repetitive interfacial coordination/etching with/from M(O)OH during the activation process. The distinct mechanism could achieve in situ Fe doping and enable defect incorporation. The defect-enriched Fe-NiOOH derived from a well-designed NiHCF/Ni(OH)₂ precatalyst requires a low overpotential of 227 mV to reach a current density of 10 mA cm⁻² and works stably at 130 mA cm⁻² over 100 h. This study provides fundamental insights into the electrochemical activation mechanism for developing advanced precatalysts for OER.