Role of electrolyte in stabilizing hard carbon as an anode for rechargeable sodium-ion batteries with long cycle life

Abstract

Hard carbon (HC) is an attractive anode material for grid-level sodium-ion batteries (NIBs) due to the widespread availability of carbon, its high specific capacity, and low electrochemical working potential. However, the issues of low first cycle Coulombic efficiency and poor rate performance of HC need to be addressed for it to become a practical long-life solution for NIBs. These drawbacks appear to be electrolyte dependent, since ether-based electrolytes can largely improve the performance compared with carbonate electrolytes. An explanation for the mechanism behind these performance differences is critical for the rational design of highly reversible sodium storage. Combining gas chromatography, Raman spectroscopy, cryogenic transmission electron microscopy, and X-ray photoelectron spectroscopy, this work demonstrates that the solid electrolyte interphase (SEI) is the key difference between ether-and carbonated-based electrolyte, which determines the charge transfer kinetics and the extent of parasitic reactions. Although both electrolytes show no residual sodium stored in the HC bulk structure, the uniform and conformal SEI formed by the ether-based electrolyte enables improved cycle efficiency and rate performance. These findings highlight a pathway to achieve long-life grid-level NIBs using HC anodes through interfacial engineering.

Poly(benzobisthiazole-dione) Frameworks for Highly Reversible Sodium- and Potassium-Ion Storage

“…33,34 The stored Na + ions interact with the carbonyl groups (CO) of PBTD and form the C−O−Na bond as revealed from the characteristic peak at ∼537.5 eV in the O 1s spectrum (Figure 2d). 35,36 The carbonyl group is restored after charging to 3.0 V (Figure 2e), suggesting that the redox reaction of PBTD is reversible. 37 This conclusion is also evidenced by the ex situ FT-IR analysis of PBTD, which shows that the CO vibration peak at ∼1640 cm −1 almost disappears at the discharged state and recovers at the charged state (Figure 2f).…”

“…Its reverse anodic scan exhibits two oxidation peaks at ∼2.1 and ∼2.5 V, corresponding to the reversible oxidation of Na 2 PBTD back to PBTD. , The sodiation/desodiation process was further probed by ex situ X-ray photoelectron spectroscopy (XPS). At the fully discharged state, a strong peak centered at ∼1072.8 eV evolves in the Na 1s spectrum owing to the formation of sodiated Na x PBTD ( x ≤ 2) (Figure c). , The stored Na + ions interact with the carbonyl groups (CO) of PBTD and form the C–O–Na bond as revealed from the characteristic peak at ∼537.5 eV in the O 1s spectrum (Figure d). , The carbonyl group is restored after charging to 3.0 V (Figure e), suggesting that the redox reaction of PBTD is reversible . This conclusion is also evidenced by the ex situ FT-IR analysis of PBTD, which shows that the CO vibration peak at ∼1640 cm –1 almost disappears at the discharged state and recovers at the charged state (Figure f).…”

Yolk–Shell Antimony/Carbon: Scalable Synthesis and Structural Stability Study in Sodium Ion Batteries

“…It agrees with the literature that Na 2 O and Na 2 CO 3 are discovered in the SEI generated in PC‐based electrolytes. [ 25 ] The framed area shown in Figure 6i is totally amorphous, and no diffraction spots or rings could be resolved in the corresponding FFT pattern (Figure S10, Supporting Information). The crystalline domains are the critical evidence for the generation of SEI in/on the shell, but it should be pointed out that the dominant part of SEI is amorphous.…”

Fe3+-Derived Boosted Charge Transfer in an FeSi4P4 Anode for Ultradurable Li-Ion Batteries

“…More specifically, the electrode materials were carefully detached from the Cu foil and dispersed in ethanol for 0.5–1 h using a sonicator to separate the aggregated particles. Subsequently, the solution was slowly dropped on Formvar/Carbon 200 mesh Cu TEM grids (TED PELLA, INC.) and dried inside a vacuum oven (at 50 °C) for 1 h. The grids were conveyed in airtight foil/poly bags (Sigma-Aldrich) to avert unwanted reactions in air. − Continuous-wave EPR was recorded using a Bruker EMXplus spectrometer in the X band at a temperature of 4 K with a microwave frequency of 9.64 GHz, power of 1 mW, modulation frequency of 100 kHz, and modulation amplitude of 10 G. The intensities of all the samples were normalized by their mass. The g value was calculated using the following equation where h , v , β e , and B 0 denote the Planck constant, frequency, Bohr magneton, and resonance magnetic field, respectively. ,, The XPS data were collected on a K-alpha (Thermo Scientific Inc.) instrument using monochromated Al Kα radiation.…”