Locally Saturated Ether-Based Electrolytes With Oxidative Stability For Li Metal Batteries Based on Li-Rich Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Li-rich, Mn-rich (LMR) layered oxide cathodes offer high energy density and lower cost for Li metal batteries.
• The high operating potentials of LMR cathodes and Li metal anodes pose significant challenges for electrolyte stability.
• Developing robust electrolytes is crucial for realizing the potential of these advanced battery systems.

Purpose of the Study:

• To investigate the efficacy of a localized-high-concentration electrolyte (LHCE) for Li||LMR cells.
• To understand the design principles and performance mechanisms of LHCEs in high-voltage battery applications.
• To demonstrate the practical viability of LHCEs in full cell configurations.

Main Methods:

• Design and synthesis of a localized-high-concentration electrolyte (LHCE) using ether solvents.
• Electrochemical cycling of Li||LMR cells with LHCE and a carbonate control electrolyte.
• Molecular dynamics (MD) simulations to elucidate ion solvation structures.
• Surface analysis using X-ray photoelectron spectroscopy (XPS) and cryogenic transmission electron microscopy (cryo-TEM).

Main Results:

• The LHCE demonstrated excellent oxidative stability, crucial for LMR cathode performance.
• MD simulations revealed that aggregated Li+/anion solvation structures stabilize the electrolyte.
• The LHCE achieved 95.8% capacity retention after 100 cycles, outperforming the control.
• Full cells (4 mAh cm-2 LMR||2× Li) using LHCE retained 87% capacity after 80 cycles.

Conclusions:

• A properly designed LHCE can overcome electrolyte challenges in high-voltage Li||LMR batteries.
• The salt/solvent ratio is critical for LHCE oxidative stability, driven by solvation structures.
• LHCEs offer a promising pathway for developing high-energy, cost-effective Li metal batteries.