High ICE Hard Carbon Anodes for Lithium-Ion Batteries Enabled by a High Work Function

Abstract

Hard carbons (HC) derived from biomass material are most promising anodes for lithium-ion batteries (LIBs) because of their cost effectiveness and environmental friendliness. However, the low initial Coulombic efficiency (ICE) of HC anodes reduces the energy density of full cells, which seriously impedes their practical applications. Herein, we demonstrate that the ICE of HC anodes can be significantly improved by modulating the work function of a model HC derived from cotton and deliberately treated to form C−Cl bonds on its surface. By X-ray absorption near-edge structure and density functional theory (DFT) calculation studies, it is verified that the introduction of the C−Cl bond leads to the electron transfer from C to Cl and enhances the work function of the system. In addition, this Cl-doped HC anode can inhibit the reduction of solvent molecules in the electrolyte and reduce the formation of a solid electrolyte interface (SEI) film. Consequently, the ICE is improved from 64.8 to 78.1%. This study provides an effective route to reduce the formation of the SEI film and improve the ICE of hard carbon anodes for LIBs.

Zincothermic-Reduction-Enabled Harvesting of an Si/C Composite from Rice Husks for a Li-Ion Battery Anode

“…In addition to the formation of an SEI film, the irreversible capacity in the first cycle primarily resulted from a side reaction between biomass carbon and the electrolyte. To improve this initial Coulombic efficiency, appropriate strategies such as heteroatom doping, 38 metal catalyzing, 39 and prelithiation 40 could be applied. The rate performance is shown in Figure 5c; the reversible capacities of ZnR-Si/C composite were 1265, 1150, 1050, and 890 mAh g −1 at 0.2, 0.5, 1, and 2 A g −1 , respectively.…”

Carbon–based Materials for Li‐ion Battery

“…Reproduced from ref. [81] Copyright 2021, with permission from the American Chemical Society. (d) Schematic representation of the SAXS instrument used to evaluate the microcrystalline distribution in microporous HC (Top panel) and the corresponding intensity versus scattering vector curve showing the intensity observed in the large, intermediate, and low Q ranges, along with the schematic drawing of the structural, microstructural, and morphological features respectively.…”

Reappraisal of hard carbon anodes for practical lithium/sodium-ion batteries from the perspective of full-cell matters

“…In another doping work, the Cl doping enhances the intensity of all peaks in soft X-ray absorption near-edge structure (XANES) spectroscopy, which is further improved by theoretical calculation. 137 It gains electrons from the carbon matrix more easily than the solvent molecules due to its stronger electronegativity (Fig. 13d), making it more difficult for the solvent molecules to be reduced to form SEI.…”

“…(e) Initial discharge-charge curves of Cl-HC and pure HC. (d) and (e) Reproduced with permission 137. Copyright 2021, Elsevier.…”