Artificial Organo-Fluoro-Rich Anode Electrolyte Interface and Partially Sodiated Hard Carbon Anode for Improved Cycle Life and Practical Sodium-Ion Batteries

Abstract

In this work, a strategy is introduced wherein without keeping any excess cathode, a practical full-cell sodium-ion battery has been demonstrated by utilizing a hard carbon (HC) anode and sodium vanadium fluorophosphate and carbon nanotube composite (NVPF@C@CNT) cathode. A thin, robust, and durable solid electrolyte interface (SEI) is created on the surface of HC through its incubation wetted with a fluoroethylene carbonate (FEC)-rich warm electrolyte in direct contact with Na metal. During the incubation, the HC anode is partially sodiated and passivated with a thin SEI layer. The sodium-ion full cell fabricated while maintaining N/P ∼1.1 showed the first cycle Coulombic efficiency of ∼97% and delivered a stable areal capacity of 1.4 mAh cm–2 at a current rate of 0.1 mA cm–2 realized for the first time to the best of our knowledge. The full cell also showed a good rate capability, retaining 1.18 mAh cm–2 of its initial capacity even at a high current rate of 0.5 mA cm–2, and excellent cycling stability, giving a capacity of ∼1.0 mAh cm–2 after 500 cycles. The current strategy presents a practical way to make a sodium-ion full cell, utilizing no excess cathode material, significantly saving cost and time.

Spray‐coated Hard Carbon Composite Anodes for Sodium‐Ion Insertion

“…A clear increase in S a values was observed when the HC composite electrodes were cycled with FEC added to the electrolyte (404.6 � 67.6 nm). We associate this with the formation of a more inhomogeneous SEI layer [82] formed on the HC particle surface, as e. g. reported in 1 M NaClO 4 in EC/ PC(1 : 1). S a analyses were also carried out for calendared spraycoated and DB-coated HC composite electrodes and the corresponding S a values are shown in Figure S13b.…”

The Progress of Hard Carbon as an Anode Material in Sodium-Ion Batteries

“…These stable interfaces ensure the high coulombic efficiency and long-cycle stability of the hard carbon negative electrode, with a capacity of 247.9 mAh g −1 after 500 cycles and a capacity retention rate of 94.8%. Lohani et al formed a thin, dense SEI film on the surface of hard carbon by directly contacting hard carbon that was moistened with a vinyl carbonate electrolyte with sodium metal [ 111 ]. During incubation, the hard carbon negative electrode was partially passivated by a thin SEI film.…”

Water-soluble densely functionalized poly(hydroxycarbonylmethylene) binder for higher-performance hard carbon anode-based sodium-ion batteries

“…16 It has been observed that defect-rich hard carbon leads to the formation of an uneven and thick SEI with poor mechanical strength due to increased electrolyte consumption, which lowers the cycling stability and reaction kinetics. 17–22 Much research has focused on electrolytes, 23 defect optimization and introducing oxygen functional groups in HC, 24 artificial SEI, 25,26 presodiation, 27 HC/MoS 2 /NC nanocomposites 28 etc. , to obtain a stable, uniform, and thin SEI.…”