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Staged Lithiation/Delithiation of Silicon Anode in All-Solid-State Batteries Revealed by High-Stack-Pressure Operando
Ying Jiang1, Shouquan Yao1, Hui Feng1
1Engineering Research Center for Nanophotonics & Advanced Instrument (Ministry of Education), Shanghai Key Laboratory of Magnetic Resonance, Institute of Magnetic Resonance and Molecular Imaging in Medicine, School of Physics, East China Normal University, Shanghai 200241, P. R. China.
All-solid-state lithium-ion batteries (ASSLBs) with silicon anodes show promise. Operando 7Li NMR spectroscopy under high pressure reveals a multistep reaction mechanism and temperature-dependent phase transitions in Si anodes.
Area of Science:
- Materials Science
- Electrochemistry
- Solid-State Chemistry
Background:
- All-solid-state lithium-ion batteries (ASSLBs) offer enhanced safety and energy density.
- Silicon (Si) anodes are crucial for high-performance ASSLBs but their electrochemical behavior is poorly understood.
- Existing characterization methods struggle with the amorphous phases and high pressures in solid cells.
Purpose of the Study:
- To investigate the microscopic chemical evolution of Si anodes during cycling in ASSLBs.
- To develop and apply a quantitative operando 7Li NMR spectroscopy technique compatible with high stack pressures.
- To elucidate the lithiation/delithiation mechanism and phase transitions in Si anodes.
Main Methods:
- Development of a specialized operando NMR setup for high-pressure (95 MPa) studies.
- Utilizing quantitative 7Li NMR spectroscopy to monitor Si anode electrodes in LiCoO2|Li6PS5Cl|Si full cells.
- Analysis of NMR spectra to identify lithium silicide phases and track dynamic changes.
Main Results:
- Successfully monitored lithium chemical states in Si anodes in real-time under high pressure.
- Identified three distinct lithium silicide phases (Li3.75Si, Li3.25Si, Li2.33Si) during cycling.
- Revealed a four-stage asymmetric lithiation/delithiation mechanism and quantified temperature-dependent silicide formation rates.
Conclusions:
- Operando 7Li NMR is effective for studying Si anodes in ASSLBs under operational conditions.
- The study clarifies the complex, multistep reaction pathways and phase transitions in Si anodes.
- Understanding these mechanisms provides insights into optimizing Si anode performance in solid-state batteries.
