Analogous Confinement Effect Enables High Stability and High Capacity Ammonium Storage in Polyaniline@Poly(o-fluoroaniline)@Carbon Layer.

Rechargeable aqueous ammonium ion (NH4 +) batteries have attracted much attention due to the unique properties of NH4 +. Polyaniline (PA) with outstanding conductivity is a potential cathode material, but it can be oxidized to pernigraniline (PG) rapidly, resulting in its poor stability. In this study, polyaniline@poly(o-fluoroaniline)@carbon layer (PA@POFA@C) is prepared for excellent and durable NH4 + storage. PA@POFA@C exhibits a high capacity of 208 mAh g-1 at 0.2 A g-1 and maintains 126 mAh g-1 at 10 A g-1. More importantly, an excellent capacity retention rate of 88.24% is achieved after 2000 cycles with ≈100% coulombic efficiency. Spectroscopy studies suggest analogous confinement effect can effectively limit the escape of hydrogen in imine group, and form the hydrogen-restricted region between the PA and POFA layer which can provide H+ for the complete reduction of PG. Meanwhile, the hydrophobic effect of POFA effectively restrains the hydrolysis of PG. Interestingly, the introduction of C layer improves the hydrophilicity of electrode and shortens the activation process, serving as the outermost protective layer of the electrode. Finally, PA@POFA@C achieves desirable electrochemical performances with analogous confinement effect. This research provides ideas for the preparation of advanced polymer electrodes for aqueous NH4 + batteries.

Analogous Chelation to Boost Utilization of Sb in Sb Nanoparticles and N-doped Carbon Composites for Enhancing Potassium Storage.

Antimony (Sb) is an attractive anode material for potassium-ion batteries (PIBs), but it suffers from aggregation during the charging-discharging process, thus causing embedded active sites and collapsed structure. The analogous chelation refers to the reaction in which the central nanoparticle is linked to the matrix through multiple coordination bonds to form a stable composite. This strategy can inhibit aggregation and maintain the nanosized structure of Sb, thus activating the utilization of Sb active sites and structural stability. Given the special position of nitrogen (N) in the periodic table of elements and the strong bond energy of Sb-N, the N element can serve as an intermediate to connect Sb nanoparticles and an intrinsic N-doped carbon network via strong Sb-N-C/Sb-N═C covalent bonds using analogous chelation. Herein, a hybrid material of Sb@CTF-NC is fabricated via analogous chelation. The Sb atoms exposed on the surface of Sb nanoparticles are used to chelate with the N-doped carbon for high-performance PIBs. The mechanism underwent ex situ characterizations. The calculation of density functional theory reveals that the increase of adsorption energy and reduction of the K+ diffusion barrier accelerate the electrochemical reaction kinetics.