Interface Degradation of LaCl₃-Based Solid Electrolytes Coupled with Ultrahigh-Nickel Cathodes.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Chloride solid electrolytes (SEs) offer compatibility with high-nickel cathodes in all-solid-state lithium batteries (ASSLBs).
• However, side reactions at the cathode/SE interface lead to capacity decay during ASSLB cycling.

Purpose of the Study:

• To investigate the interface failure mechanisms between an ultrahigh-nickel cathode (NCM92) and a LaCl3-based chloride SE (LLZTC).
• To elucidate the causes of capacity decay in ASSLBs using a novel three-electrode testing device.

Main Methods:

• Development of a three-electrode ASSLB testing device.
• Application of Distribution of Relaxation Time (DRT) analysis to assess interface impedance.
• Utilizing Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) for interface characterization.

Main Results:

• ASSLB degradation was observed, marked by a significant increase in NCM92/LLZTC interface impedance, especially at higher charging voltages (4.8 V).
• Analysis confirmed deterioration due to active lattice oxygen and loss of physical contact at the cathode/SE interface.
• Both electrochemical degradation and physical contact failure were identified as primary failure modes.

Conclusions:

• The study elucidates the dual mechanisms of electrochemical and physical degradation at the cathode/solid electrolyte interface in high-nickel ASSLBs.
• Understanding these failure modes is crucial for improving the cycling stability and performance of ASSLBs.
• This research provides insights into optimizing cathode-electrolyte interfaces for advanced solid-state batteries.