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Silicon is considered an important anode material for solid-state batteries (SSBs) because of its unique properties in addressing key challenges associated with Li metal anodes such as dendrite formation and morphological instability. Despite many exciting results from previous reports on solid-state Si anodes, the initial Coulombic efficiency (ICE), a critical parameter that characterizes the electrochemical reversibility for the first cycle and directly influences the energy density of the battery, has not been well considered. Here we study the electrochemical stability between Si and three representative solid electrolytes (SEs), including a typical sulfide (75Li 2 S-25P 2 S 5 , LPS), an iodide-substituted sulfide (70(0.75Li 2 S-0.25P 2 S 5 )-60LiI, LPSI), and a hydride-based SE (3LiBH 4 -LiI, LBHI), to improve the ICE of solid-state Si anodes. Combining first-principles computations, electrochemical measurements, ex situ XPS characterizations, and mechanical measurements, we report that LBHI demonstrates superior electrochemical and chemical stability with Si anodes compared with sulfide-based SEs, enabling a high-performance solid-state Si anode with a record high ICE of 96.2% among all Si anodes reported to date. The excellent stability of LBHI with Si anode was also demonstrated in solid-state full cells with nickel-rich layered oxide cathodes. The research provides novel insights into developing high-performance Si anodes for practical applications.
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Unveiling the Mechanical and Electrochemical Evolution of Nanosilicon Composite Anodes in Sulfide‐Based All‐Solid‐State Batteries
Abstract The utilization of silicon anodes in all‐solid‐state lithium batteries provides good prospects for facilitating high energy density. However, the compatibility of sulfide solid‐state electrolytes (SEs) with Si and carbon is often questioned due to potential decomposition. Herein, operando X‐ray absorption near‐edge structure (XANES) spectroscopy, ex situ scanning electron microscopy (SEM), and ex situ X‐ray nanotomography (XnT) are utilized to investigate the chemistry and structure evolution of nano‐Si composite anodes. Results from XANES demonstrate a partial decomposition of SEs during the first lithiation stage, which is intensified by the presence of carbon. Nevertheless, the performances of first three cycles in Si–SE–C are stable, which proves that the generated media is ionically conductive. XnT and SEM results show that the addition of SEs and carbon improves the structural stability of the anode, with fewer pores and voids. A chemo‐elasto‐plastic model reveals that SEs and carbon buffer the volume expansion of Si, thus enhancing mechanical stability. The balance between the pros and cons of SEs and carbon in enhancing reaction kinetics and structural stability enables the Si composite anode to demonstrate the highest Si utilization with higher specific capacities and a better rate than pure Si and Si composite anodes with only SEs.
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- Award ID(s):
- 1924534
- PAR ID:
- 10406687
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 13
- Issue:
- 14
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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