Building Fast Ion-Conducting Pathways on 3D Metallic Scaffolds for High-Performance Sodium Metal Anodes.

Building 3D electron-conducting scaffolds has been proven to be an effective way to alleviate severe dendritic growth and infinite volume change of sodium (Na) metal anodes. However, the electroplated Na metal cannot completely fill these scaffolds, especially at high current densities. Herein, we revealed that the uniform Na plating on 3D scaffolds is strongly related with the surface Na+ conductivity. As a proof of concept, we synthesized NiF2 hollow nanobowls grown on nickel foam (NiF2@NF) to realize homogeneous Na plating on the 3D scaffold. The NiF2 can be electrochemically converted to a NaF-enriched SEI layer, which significantly reduces the diffusion barrier for Na+ ions. The NaF-enriched SEI layer generated along the Ni backbones creates 3D interconnected ion-conducting pathways and allows for the rapid Na+ transfer throughout the entire 3D scaffold to enable densely filled and dendrite-free Na metal anodes. As a result, symmetric cells composed of identical Na/NiF2@NF electrodes show durable cycle life with an exceedingly stable voltage profile and small hysteresis, particularly at a high current density of 10 mA cm-2 or a large areal capacity of 10 mAh cm-2. Moreover, the full cell assembled with a Na3V2(PO4)3 cathode exhibits a superior capacity retention of 97.8% at a high current of 5C after 300 cycles.

Integrating antimony/amorphous vanadium oxide composite structure into electrospun carbon nanofibers for synergistically enhanced lithium/sodium-ion storage.

Development of advanced anode material is highly desired in the energy storage field, not only for the current dominant lithium ion battery (LIB), but also for the sodium ion battery (SIB) with high potential in large-scale and low-cost stationary energy storage systems. Herein, we present a sea cucumber-like hybrid (Sb/VOx-CNFs) which integrates Sb and amorphous VOx composite structure into carbon fibers through electrospinning and sequential annealing treatment. With the specific structural and composition advantages brought synergistically by the Sb/VOx composite structure and the carbon fiber skeleton, the as-prepared Sb/VOx-CNFs delivers a high rate capacity and long-cycle life for both Na+ (∼337 mAh g-1 after 1000 cycles at 1 A g-1) and Li+ (∼554 mAh g-1 after 300 cycles at 0.5 A g-1) when applied as anode materials in the assembled SIB and LIB coin cells due to the improved charge transfer, enlarged active sites and enhanced structural stabilities. The practical applicability of Sb/VOx-CNFs is also demonstrated by the assembly and tests of Sb/VOx-CNFs//Na3V2(PO4)3 full cell where the commercial Na3V2(PO4)3 is employed as the cathode material. Importantly, the presented strategy with favorable synergistic effect could provide expansion opportunities for the design of composite structured nanomaterials in the energy storage fields.