Sodium Metal Anodes with Self‐Correction Function Based on Fluorine‐Superdoped CNTs/Cellulose Nanofibrils Composite Paper

Abstract

Despite much efforts to stabilize sodium metal anodes for promoting their commercial applications, achieving a safe cycling process without intrinsic dendrite growth remains difficult owing to the unstable reaction interface and irregular sodium metal propagation. Herein, fluorine-superdoped carbon nanotubes with a fluorine content of 14.38 at% are achieved using a new oxidation-assisted plasma strategy, and then alternately assembled with cellulose nanofibrils to form periodical conductive/dielectric composite paper with outstanding mechanical properties. The superdoping of fluorine facilitates the construction of a NaF-dominated solid electrolyte interphase layer, while the periodical conductive/dielectric network re-homogenizes electric field distribution around irregular sodium protrusions, realizing a "bottom-up" sodium orientation deposition and the "selfcorrection" functionality during sodium plating/stripping process. Density functional theory calculations reveal that the specific oxygen species (CO/CO) and fluorine species (semi-ionic CF/covalent CF 2 ) on the surface of carbon matrix, could remarkably trap active fluorine fragments and generate NaF with sodium metal, respectively, which promotes the superdoping of fluorine and forms dendrite-free sodium anodes. This delicate structure renders the sodium anodes a low nucleation overpotential of ≈7 mV, high Coulombic efficiency of 99.5% over 300 cycles at 3 mA cm −2 , stable operation for up to 2100 h under ≈16 mV, and excellent full battery performance.

Fluorinated porous frameworks enable robust anode-less sodium metal batteries

“…S41), which is ranked among the top documented values to our knowledge (Fig. 4J and table S6) (24,25,27,30,31,35,(48)(49)(50)(51)(52)(53)(54)(55)(56)(57). Besides, a similar voltage profile and a low overpotential of 7 mV in FCTF symmetric battery are achieved under an unprecedented DOD of 100% (fig.…”

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

“…These results confirm that the electrochemical performance of the full cell using Na/NiF 2 @NF anodes is significantly improved compared with that using bare Na anodes. Moreover, a comparison for Na-ion full cells between the NVP/C-Na/NiF 2 @NF and prior reported anode materials assembled with NVP/C cathodes is listed in Figure g and Table S2 (Supporting Information), ,,− exhibiting an outstanding capacity retention and ultralong cycling lifespan at high current densities, which indicates the Na/NiF 2 @NF anodes have a promising prospect for practical applications.…”

Wide-temperature-range sodium-metal batteries: from fundamentals and obstacles to optimization

“…Clearly, the fluctuant Na + are deposited at different rates on SEI surfaces with different morphologies. 162,185 The uneven Na + deposition in plating/stripping causes an abnormal growth of dendrites, which can penetrate the separator, causing short circuits and posing serious safety hazards. 185,186 After considering the diffusion of Na + in the SEI, the local thickness, morphology and composition of the SEI is a crucial aspect of the final Na + flux.…”