Enhanced Na⁺ pseudocapacitance in a P, S co-doped carbon anode arising from the surface modification by sulfur and phosphorus with C–S–P coupling

Abstract

Enhanced phosphorus (7.2 wt%) and sulfur (15.7 wt%) co-doped carbon (PSC) is synthesized via a one-step sintering of carbon disulfide and red phosphorus in a vacuum.

Ultrahigh Phosphorus Doping of Carbon for High‐Rate Sodium Ion Batteries Anode

“…In our previous work, it was revealed that the adsorption energy (E ads ) of Na on the surface (P site) of the 4*4*1 supercell graphite layer with only one substituted P atom was −0.38 eV. [30] Here, it is found that the E ads for Na (site I) can be further enhanced to −0.42 eV with the increase of P incorporated into the supercell (Figure 7a), indicating a stronger interaction between sodium and the double P-doped structure. This is also confirmed by the corresponding differential charge density (DCD) isosurfaces as verified in Figure 7b, where excess electrons (transferred from Na) are accumulated at the C atoms close to P atoms.…”

“…It is well known that doped P atom with less electronegativity can donate electrons to the adjacent carbon, facilitating Na + adsorption. [15,30] Thus, it is reasonable to speculate that more P(C 3 ) can be beneficial to the formation of abundant adsorption sites to accommodate sodium ions, contributing to an enhanced capacity.…”

“…[22][23][24][25][26] Compared with N and S doping, P doping can exhibit a stronger adsorption ability and display a great superiority of low discharge voltage (<1.0 V). [27][28][29][30][31][32][33] Unfortunately, the doping content of P is relatively low (<10 wt%), resulting in insufficient active sites for limited Na-storage capacity of hard carbon (<400 mAh g −1 ). The low doping levels can be attributed to following aspects: 1) The high binding energy and long bond length of PC (compared with CC) lead to severe lattice distortion when P is incorporated into the carbon skeleton, thus requiring a higher reaction energy.…”

Realizing High‐Performance Li/Na‐Ion Half/Full Batteries via the Synergistic Coupling of Nano‐Iron Sulfide and S‐doped Graphene

“…Almost 100 % coulombic efficiency was retained throughout the entire cycling process, indicating the excellent stability of the aerogel‐structure endowing efficient reversible sodiation in the electrode. In addition, the S‐doping in the composite extends the low‐voltage plateau capacity and thereby promotes interfacial charge storage via reversible reaction with Na + , thus favoring high‐rate performances [17c,41] . The inability of the pristine FeS to achieve high discharge capacities at high rates is due to the large size of FeS particles that hinders the diffusion of Na + and makes the conversion reaction incomplete.…”

Novel Approach Through the Harmonized Sulfur in Disordered Carbon Structure for High-Efficiency Sodium-Ion Exchange

“…Regarding the sodium-ion exchange mechanism, SiB anode materials are classified to insertion-, alloying- and conversion-type materials. − However, owing to the volume expansion of alloying materials and the low capacity of conversion materials, research has focused on carbon-based insertion materials, and disordered carbon materials have been reported to be more suitable for accommodating large sodium ions than traditional graphite materials. − Furthermore, as part of this vigorous development, various strategies have been introduced to redesign the internal structure of carbon materials by doping them with heteroatoms and enhancing their physical and chemical properties to improve their electrochemical performance. − Among others, sulfur can potentially participate in an additional direct reaction as well as increase the electrical conductivity. ,− Meanwhile, although many of the above-reported studies improved the electrochemical performance of SiBs, various precursors, stepwise synthesis, and redesign processes were required for incorporating the heteroatoms. In addition, studies on SiBs performance at high specific current have remained obscure.…”