Lithium-Nitrate-Containing Gel Polymer Electrolyte for Carbonate-Based Anode-Free Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Anode-free lithium metal batteries offer high energy density but face challenges with reversible lithium deposition and solid electrolyte interface (SEI) formation.
• Lithium nitrate (LiNO3) is beneficial for SEI formation but has poor solubility in conventional carbonate electrolytes.

Purpose of the Study:

• To develop a gel polymer electrolyte (GPE) that effectively incorporates LiNO3 for improved lithium metal battery performance.
• To investigate the role of polyhedral oligomeric silsesquioxane (POSS) in enhancing the GPE's ionic conductivity and SEI properties.

Main Methods:

• Fabrication of a GPE using polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) and POSS, acting as a LiNO3 reservoir.
• Electrochemical characterization including ionic conductivity measurements and cycling performance in Cu||Li cells.
• X-ray photoelectron spectroscopy (XPS) to analyze SEI composition and morphology.

Main Results:

• The POSS-containing GPE achieved an ionic conductivity of 1.011 mS cm⁻¹ at room temperature.
• The GPE facilitated robust SEI formation, mitigated electrolyte degradation, and resulted in smooth, spherical lithium morphology.
• Cu||Li cells with the GPE demonstrated a 5-fold increase in cycle life, reaching 250 cycles at 0.5 mA cm⁻².

Conclusions:

• The developed GPE effectively addresses LiNO3 solubility issues and enhances SEI formation in anode-free lithium metal batteries.
• Incorporation of POSS improves ionic conductivity and battery cyclability, paving the way for more stable and energy-dense lithium metal batteries.