Interfacial Stability of Phosphate-NASICON Solid Electrolytes in Ni-Rich NCM Cathode-Based Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Developing stable, low-impedance interfaces is crucial for all-solid-state batteries (ASSBs).
• Thiophosphate solid electrolytes face oxidation instability and interface resistance issues.
• NASICON-type phosphates offer high potential stability but have mechanical and grain boundary limitations.

Purpose of the Study:

• To comparatively study the interface stability and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 (NCM-811) cathodes with β-Li3PS4 (LPS) and Li1.5Al0.5Ti1.5(PO4)3 (LATP) solid electrolytes.
• To investigate the interfacial behavior under operating conditions using advanced characterization techniques.

Main Methods:

• Fabrication of ASSBs using NCM-811 cathode composites with LPS and LATP solid electrolytes.
• Assembly and operation of ASSBs in a hot-press setup at 150 °C.
• In situ electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) for interface analysis.

Main Results:

• The LATP-based cathode composite exhibited significantly suppressed interface resistance compared to the LPS-based composite.
• The chemical state of the NCM-811/LATP interface remained unchanged during cycling.
• The ASSB utilizing LATP demonstrated stable reversible cycling performance, outperforming the thiophosphate-based cell.

Conclusions:

• Li1.5Al0.5Ti1.5(PO4)3 (LATP) effectively mitigates interfacial challenges in bulk-type ASSBs.
• LATP is a promising solid electrolyte candidate for developing high-performance and stable ASSBs.
• The findings highlight LATP's potential to overcome limitations associated with traditional thiophosphate electrolytes.