Elucidating the Mechanism of Fast Na Storage Kinetics in Ether Electrolytes for Hard Carbon Anodes

Abstract

The sodium storage performance of a hard carbon (HC) anode in ether electrolytes exhibits a higher initial Coulombic efficiency (ICE) and better rate performance compared to conventional ester electrolytes. However, the mechanism behind faster Na storage kinetics for HC in ether electrolytes remains unclear. Herein, a unique solvated Na+ and Na+ co‐intercalation mechanism in ether electrolytes is reported using designed monodispersed HC nanospheres. In addition, a thin solid electrolyte interphase film with a high inorganic proportion formed in an ether electrolyte is visualized by cryo transmission electron microscopy and depth‐profiling X‐ray photoelectron spectroscopy, which facilitates Na+ transportation, and results in a high ICE. Furthermore, the fast solvated Na+ diffusion kinetics in ether electrolytes are also revealed via molecular dynamics simulation. Owing to the contribution of the ether electrolytes, an excellent rate performance (214 mAh g−1 at 10 A g−1 with an ultrahigh plateau capacity of 120 mAh g−1) and a high ICE (84.93% at 1 A g−1) are observed in a half cell; in a full cell, an attractive specific capacity of 110.3 mAh g−1 is achieved after 1000 cycles at 1 A g−1.

Enabling Fast Na+ Transfer Kinetics in the Whole‐Voltage‐Region of Hard‐Carbon Anodes for Ultrahigh‐Rate Sodium Storage

“…HCM-1300-ZBE presents an ultrahigh rate performance with reversible capacity of 230.4 mAh g -1 at 20 A g -1 , and 107 mAh g -1 at 50 A g -1 , outperforming the stateof-the-art HCs (Figure 2c, Figure S18 and Table S13, Supporting Information). [15,23,37,[44][45][46][47][48][49][50][51][52] The long-term cycling performance of HCM-1300-ZBE was tested at high rate of 2 A g -1 , which delivers a reversible capacity of 344 mAh g -1 after 3000 cycles with a decay rate of 0.002% per cycle, signifying an excellent cycling stability (Figure 2d). The illustration in Figure 2d shows the charge and discharge curves of different cycles (including the 3000th cycle), revealing the excellent voltage stability performance during repeated Na + insertion/removal processes.…”

3D Ordered Porous Hybrid of ZnSe/N‐doped Carbon with Anomalously High Na+ Mobility and Ultrathin Solid Electrolyte Interphase for Sodium‐Ion Batteries

“…Due to the difference in the SEI film formed during the reduction process of different electrolytes, the optimization of electrolytes is helpful to form ultrathin and stable SEI film to further improve the diffusion rate of sodium ions and reduce the apparent activation energy. [12,[59][60][61] Therefore, to better explore the reasons for better performance of 3DOHP ZnSe@N,C hybrid when using NaOTf electrolyte, the microstructure and composition of the SEI film on its surface with three electrolytes were investigated by ex situ TEM and XPS after three cycles (Figure 8).…”

Defect‐Selectivity and “Order‐in‐Disorder” Engineering in Carbon for Durable and Fast Potassium Storage

“…Defect engineering in carbon matrix has been demonstrated to be an efficient strategy to break through the capacity limitation. [15][16][17][18][19][20] The C-C sp 3 defects enable efficient K + diffusion pathways, [21,22] while the active surface/edge sites and nanopores contributes to capacity by adsorbing K + . [23−27] Besides, the heteroatom doping in carbon lattice framework can also boost the potassium storage activity by tuning the electronic structure.…”