High-Temperature Thermal Reactivity and Interface Evolution of the NMC-LATP-Carbon Composite Cathode.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Temperature-assisted densification is crucial for oxide solid-state batteries to reduce interface resistance.
• Chemical reactivity between cathode components (catholyte, conducting additive, electroactive material) poses a processing challenge.

Purpose of the Study:

• To investigate the impact of temperature and heating atmosphere on the LiNi0.6Mn0.2Co0.2O2 (NMC), Li1+xAlxTi2-xP3O12 (LATP), and Ketjenblack (KB) system.
• To elucidate the chemical reactions occurring between NMC, LATP, and KB during thermal processing.

Main Methods:

• Utilized a combination of bulk and surface characterization techniques.
• Evaluated the influence of varying temperatures and heating atmospheres (air, oxygen, inert gases).

Main Results:

• Identified cation redistribution within the NMC cathode material.
• Observed lithium and oxygen loss from the NMC lattice, enhanced by LATP and KB acting as sinks.
• Formation of degradation products initiated at the surface, leading to capacity decay above 400 °C.
• Demonstrated that the reaction mechanism and degradation threshold temperature are dependent on the heating atmosphere.

Conclusions:

• Air atmosphere processing is more favorable for mitigating degradation compared to oxygen or inert gases.
• Understanding and controlling interfacial chemistry is critical for high-temperature processing of NMC-based solid-state battery cathodes.