From Natural Fibers to High-Performance Anodes: Sisal Hemp Derived Hard Carbon for Na-/K-Ion Batteries and Mechanism Exploration.

Hard carbon (HC) is a promising anode material in alkali metal ion batteries owing to its cost-effectiveness, abundant sources, and low working voltage. However, challenges persist in achiving prolonged cycling stability and consistent capacity, and the sodium storage mechanism in HC is still debated. Herein, an unreported biomass precursor, "sisal," for deriving hard carbon is developed. A series of sisal hemp-derived hard carbon with natural 3D porous channels are prepared. Through phase characterization and electrochemical testing, the relationship between microstructure and sodium storage capacity is elucidated, further confirming the suitability of the "adsorption-insertion-filling" mechanism for sodium storage properties in hard carbon materials. Without the need for any additional modification strategies, this biomass-derived hard carbon demonstrates excellent electrochemical performance in both sodium-ion and potassium-ion batteries (SIBs and PIBs). The as-prepared HC-1300 demonstrates excellent ion storage capability, delivering a high reversible capacity of 345.2 mAh g-1 in SIBs and 310 mAh g-1 in PIBs at 0.1 C. Moreover, it maintains a specific capacity of 237.3 mAh g-1 over 1200 cycles at 1 C when used in SIBs. The excellent cycling stability and superior rate performance are also presented in full cells, highlighting its potential for practical applications.

Cations-Pillared and Polyaniline-Encapsulated Vanadate Cathode for High-Performance Aqueous Zinc-Ion Batteries.

Layered vanadium-based oxides have emerged as highly promising candidates for aqueous zinc-ion batteries (AZIBs) due to their open-framework layer structure and high theoretical capacity among the diverse cathode materials investigated. However, the susceptibility to structural collapse during charge-discharge cycling severely hampers their advancement. Herein, we propose an effective strategy to enhance the cycling stability of vanadium oxides. Initially, the structural integrity of the host material is significantly reinforced by incorporating bi-cations Na+ and NH4 + as "pillars" between the V2O5 layers (NaNVO). Subsequently, surface coating with polyaniline (PA) is employed to further improve the conductivity of the active material. As anticipated, the assembled Zn//NaNVO@PA cell exhibits a remarkable discharge capacity of 492 mAh g-1 at 0.1 A g-1 and exceptional capacity retention up to 89.2 % after 1000 cycles at a current density of 5 A g-1. Moreover, a series of in-situ and ex-situ characterization techniques were utilized to investigate both Zn ions insertion/extraction storage mechanism and the contribution of polyaniline protonation process towards enhancing capacity.