Sustainable Solid-State Sodium-Ion Batteries Featuring Ferroelectric Electrolytes.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Solid-state batteries promise enhanced safety and energy density but face significant challenges.
• Complexity necessitates studying simplified models to understand fundamental operating principles.
• This research focuses on cells without traditional electrodes to build foundational knowledge.

Purpose of the Study:

• To investigate the electrochemical behavior of simplified solid-state cell configurations.
• To understand the role of current collectors and electrolytes in open-circuit voltage.
• To explore sodium deposition phenomena under different conditions.

Main Methods:

• Fabrication and electrochemical testing of pouch cells with composite electrolytes and dissimilar current collectors (Cu/Zn).
• Open-circuit voltage (OCV) measurements over extended periods.
• Incorporation of carbon felt to assess its impact on cell performance.
• Ab initio simulations of heterojunctions to model interfacial phenomena.

Main Results:

• A Cu/Na_2.99Ba_0.005ClO composite in a cellulose/Zn pouch cell exhibited an initial OCV of 1.10 V, increasing to 1.13 V after 120 days.
• Adding carbon felt altered the OCV to 0.85 V, which later rose to 1.20 V after 95 days.
• Ab initio simulations and experiments confirmed dipole formation and sodium deposition on the zinc current collector during discharge at room temperature, but not at 40 °C.

Conclusions:

• Simplified solid-state cell models demonstrate complex electrochemical behaviors, including unexpected voltage increases.
• Sodium deposition on the negative current collector is a key process during discharge at room temperature.
• These foundational studies are crucial for guiding the design of functional solid-state batteries.