Boron–Phosphorus Codoped Coral-like Hard Carbon Anodes for Sodium Ion Storage

Abstract

Hard carbon materials have the advantages of low price, environmental friendliness, and good electrical conductivity but have the disadvantages of unsatisfactory sodium storage capacity and low long-cycle stability. The use of heteroatom doping and structural design can significantly improve the sodium storage properties of carbon materials. In this paper, a boron–phosphorus doped hard carbon material (CABP) was designed by using citric acid as the carbon source. The rich pore structure of CABP also provides fast transport channels for Na+, while the efficient doping of B and P atoms can distort the graphitic layer and generate more active sites and defects. The CABP carbon material therefore exhibits excellent electrochemical properties. It can obtain pretty good capacities of 246.8 mA h g–1 after 400 cycles at 0.1 A g–1. Moreover, it was able to maintain 161.9 mA h g–1 after 5000 cycles at 5 A g–1. This work provides a new route for the facile preparation of high-performance heteroatom-doped carbon materials and an idea for the preparation of diatom-doped materials for energy storage.

Flexible Precursor Modulation toward Selective Heteroatom Doping in a Hard-Carbon Anode for Sodium-Ion Batteries

“…In the first cycle, all samples have a cathode peak at about 1 V, which indicates the irreversible decomposition of the electrolyte and the formation of a solid electrolyte interface layer on the carbon surface. Moreover, the cathode peak located close to 0 V and the corresponding anode peak located close to 0.25 V indicate the sodiation/desodiation behavior of sodium ions in the disordered microcrystalline structure of hard carbon . In the subsequent two or three cycles, the CV curves show excellent reversibility.…”

“…Moreover, the cathode peak located close to 0 V and the corresponding anode peak located close to 0.25 V indicate the sodiation/ desodiation behavior of sodium ions in the disordered microcrystalline structure of hard carbon. 39 In the subsequent two or three cycles, the CV curves show excellent reversibility. Compared with HC and N-HC, the CV curves of N/S-HC show stronger redox peaks, suggesting higher Na + storage capability, which is consistent with the results of the charge/ discharge test results in Figure 3b−d.…”

Recent Progress in Hard Carbon Anodes for Sodium‐Ion Batteries

“…Therefore, researchers have also investigated the modulation of the hard carbon materials by multi‐atom doping, and the study showed that the co‐doping of heteroatoms is beneficial to improving the electrochemical performance of hard carbon. Zhang et al [ 100 ] reported a boron‐phosphorus co‐doped hard carbon material with a reversible capacity of 246.8 mAh g −1 at 0.1 A g −1 , and 119.5 mAh g −1 at 10 A g −1 , which proved its excellent rate performance. After 5,000 cycles at a high current of 5 A g −1 , the capacity was still maintained at the level of 161.9 mAh g −1, which is attributed to the synergistic effect synthesized by the elements of phosphorus and boron to add more active sites in the hard carbon structure.…”

An effective model for sodium insertion in hard carbons

“…Both the 2-level model and the 3-level model ignored the defect Na, but the defect Na should not be neglected for 2 reasons: on the one hand, the heteroatom defects always appear in HCs, 23 and on the other hand, some experimental studies use heteroatom doping defects to increase the capacity. 30–33…”

“…Both the 2-level model and the 3-level model ignored the defect Na, but the defect Na should not be neglected for 2 reasons: on the one hand, the heteroatom defects always appear in HCs, 23 and on the other hand, some experimental studies use heteroatom doping defects to increase the capacity. [30][31][32][33] Moreover, these models investigated the generic case of Na insertion in HCs, while experiments proved that the properties of Na insertion in HCs depends strongly on the specific material properties of HCs. [34][35][36][37] Bommier et al predicted Na capacity based on the pore volume and surface area of HCs; however, the mechanism of Na insertion in HCs is not considered in their study.…”