Surface-Conducting Lithium Superionic Conductors for Solid-State Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Bulk lithium superionic conductors face limitations like grain boundary disruption and porosity, hindering energy density in solid-state batteries.
• High densification is often required, which can compromise the gravimetric energy density of solid-state batteries.

Purpose of the Study:

• To discover and develop a new class of surface-conducting lithium superionic conductors.
• To overcome the limitations of bulk conductors by utilizing surface chemisorption for enhanced lithium-ion transport.
• To create ultralight and highly conductive solid-state electrolytes for high-energy-density batteries.

Main Methods:

• Surface chemisorption of ligands onto inert substrates (e.g., TiO2 nanosheets) to create lithium-ion binding and hopping sites.
• Characterization of surface Li+ diffusion using electrochemical techniques.
• Fabrication of an ultralight oxide aerogel solid-state electrolyte.
• Assembly and testing of a LiFePO4-based solid-state battery.

Main Results:

• Achieved a high surface ion mobility of 3.61 × 10^-7 cm^2·V^-1·s^-1 on ethylene glycolate-chemisorbed TiO2, a 600% improvement over bulk Li7La3Zr2O12.
• Developed an ultralight oxide aerogel electrolyte with a density of 0.29 g·cm^-3.
• Demonstrated a LiFePO4-based solid-state battery with an energy density of ~295 Wh·kg^-1, 160% higher than a Li7La3Zr2O12-based battery.
• Showcased the generalizability of the surface-conducting design for diverse cations and substrates.

Conclusions:

• Surface chemisorption is a viable strategy for creating novel surface-conducting lithium superionic conductors.
• This approach enables the development of ultralight, highly conductive solid-state electrolytes.
• The findings promise significant advancements in solid-state battery technology and other applications requiring efficient ion transport.