Abstract
Recently, materials with hierarchical nanoporous architectures have been proposed to enhance the performance of alloy-type lithium-ion battery (LIB) and sodium-ion battery (SIB) anodes. However, the origin of this enhancement has not been elucidated. The present work is aimed at identifying the fundamental mechanism behind this enhanced performance using sodium storage in antimony as a model system. We have found that the amount of sodium reversibly stored in antimony is enhanced by roughly 27% when hierarchical nanoporous antimony with bimodal porosity is used as the anode instead of nanoporous antimony with unimodal porosity. Electron microscopy analysis based on energy-dispersive X-ray spectroscopy mapping and computational analysis based on Monte Carlo simulations reveal that the difference in performance originates from mass transport limitations associated with the transfer of sodium ions from the electrolyte to the bulk of antimony. Typically, in hierarchical nanoporous antimony electrodes with bimodal porosity, the diffusion of sodium ions through the bulk of the material is very favorable, resulting in full sodiation of antimony. In contrast, under similar experimental conditions (i.e., the same charge/discharge rate) nanoporous antimony with unimodal porosity is only partially sodiated. The full sodiation of hierarchical nanoporous antimony is favored by large pores, which facilitate the penetration of the electrolyte into the bulk of antimony, reducing the overall effective diffusion length inside the material. Interestingly, in terms of cycle-life, the capacities achieved in these two types of electrode architectures start to decay after 200 cycles with the same decay trend, suggesting that the hierarchical nanoporous architecture does not contribute to the cycling stability; that is, the large pores only improve the charge storage kinetics. These insights will contribute to the development of high-performance alloy-type SIB and LIB anodes.
Original language | English |
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Pages (from-to) | 11231-11241 |
Number of pages | 11 |
Journal | ACS Applied Energy Materials |
Volume | 3 |
Issue number | 11 |
DOIs | |
State | Published - Nov 23 2020 |
Externally published | Yes |
Funding
The authors are thankful to the Vagelos Institute for Energy Science and Technology (VIEST) for the financial support through the 2018 VIEST seed grant. M.L. thanks the China Scholarship Council (CSC) for her scholarship. This work was carried out in part at the Singh Center for Nanotechnology, part of the National Nanotechnology Coordinated Infrastructure Program, which is supported by the NSF grant NNCI-1542153. The authors gratefully acknowledge use of facilities and instrumentation supported by NSF through the University of Pennsylvania Materials Research Science and Engineering Center (MRSEC) (DMR-1720530). A.M.R. acknowledges the support of the US Department of Energy, Office of Basic Energy Sciences, under grant DE-SC0019281. The authors acknowledge computational support from the National Energy Research Scientific Computing Center.
Keywords
- Antimony
- Hierarchical nanoporous architectures
- Monte Carlo simulations sodium-ion diffusion
- Sodium-ion battery anodes