Nitrogen/Phosphorus Dual‐Doped Hard Carbon Anode with High Initial Coulombic Efficiency for Superior Sodium Storage

Abstract

Among anode materials for sodium-ion batteries (SIBs), hard carbon (HC) gains more attention due to its low cost, high electronic conductivity, and renewable resources. However, sluggish kinetics result in its low-rate capability and unfavorable cycle stability. Moreover, HC often presents low initial Coulombic efficiency (ICE), which also limits the utilization of the battery capacity and energy density. Herein, nitrogen and phosphorus dual-doped HC (denoted as NPHC) with network structure is synthesized by a facile interfacial polymerization method, which endows the NPHC with synergistic effects of the enlarged interlayer spacing and improved conductivity. Con-sequently, the obtained NPHC exhibits a high reversible capacity (286 mAh g À 1 at 0.1 A g À 1 ), excellent rate capability (144 mAh g À 1 at 10 A g À 1 ), high ICE (71 %), and remarkable cyclability over 2000 cycles at 1 A g À 1 . Moreover, the storage mechanism of sodium ions is examined by a series of ex-situ characterizations. Additionally, when coupled with Na 3 V 2 (PO 4 ) 2 F 3 as a cathode, the full cell delivers superior cyclability (capacity retains 90 % over 300 cycles at 1 A g À 1 ). This work may shed new insight into designing other carbon-based electrode materials for high-performance energy storage.

Boosting the Development of Hard Carbon for Sodium‐Ion Batteries: Strategies to Optimize the Initial Coulombic Efficiency

“…In general, carbonization treatment of heteroatom‐enriched biomass precursors, acid‐assisted pyrolysis of the precursors, and pyrolysis of the precursors with corresponding salts are the effective way to realize co‐doped HC. [ 122,123 ] Great efforts have been devoted in recent years to take advantage of synergistic coupling effects of multi‐heteroatoms doping and realize an optimal ICE of HCs anode. Wang et al.…”

“…In general, carbonization treatment of heteroatom-enriched biomass precursors, acid-assisted pyrolysis of the precursors, and pyrolysis of the precursors with corresponding salts are the effective way to realize co-doped HC. [122,123] Great efforts have been devoted in recent years to take advantage of synergistic coupling effects of multi-heteroatoms doping and realize an optimal ICE of HCs anode. Wang et al also designed the P/S co-doped HCs with a porous bowl-like structure, the physical characterizations displayed that S doping can increase the interlayer spacing of graphite to some extent, meanwhile, P doping was beneficial for the generation of P-O and C-S-P bonds.…”

Advanced Anode Materials for Rechargeable Sodium-Ion Batteries

“…(e) Long-term cycle performance of the NPHC and NHC electrodes at 1 A g –1 . Reprinted with permission from ref . Copyright 2023, Wiley-VCH.…”

“…Hence, nitrogen doping and nano crystallization are effective ways to improve the Na-ion storage performances of carbon-based materials. Wu et al introduced nitrogen and phosphorus into hard carbon (denoted as NPHC), in which the synergistic effect of N/P dual-doping on enlarging interlayer spacing and improving conductivity ensured high reversible specific capacity, excellent rate capability, high initial CE of 71%, and ultralong cyclability over 2000 cycles at 1.0 A g –1 (Figure e). Boron (B) has been reported in recent literature to possess good compatibility with carbon structure due to its similar diameter and electronic structure to C atom .…”

Process and Drying Behavior Toward Higher Drying Rates of Hard Carbon Anodes for Sodium‐Ion Batteries with Different Particle Sizes: An Experimental Study in Comparison to Graphite for Lithium‐Ion‐Batteries

“…The graphite anodes have an area capacity of 2.2 mAh cm À2 with a dry film thickness of %75 μm. [18] With the coating weight of the HC electrodes and an assumed practical specific capacity of about 300 mAh g À1 [1,41] (%200-400 mAh g À1 ), [1,42,43] the average area capacity for the investigated HC electrodes is also 2.2-2.3 mAh cm À2 .…”