Mitigating Electrochemical Isolation in Ni-Rich Layered Cathodes for Durable Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• All-solid-state batteries (ASSBs) offer superior safety and energy density compared to Li-ion batteries.
• Cathode-solid electrolyte (SE) interfacial instability is a major hurdle for ASSB performance.
• Ni-rich layered oxides (NMCs) are promising cathode materials, but prone to degradation with sulfide SEs.

Purpose of the Study:

• To investigate the interfacial degradation mechanisms between Ni-rich NMCs and sulfide SEs.
• To identify strategies for mitigating interfacial instability and improving ASSB performance.
• To demonstrate the efficacy of conductive carbon additives in enhancing cathode stability.

Main Methods:

• In-depth spectroscopic analysis (e.g., XPS, Raman) to probe interfacial chemistry.
• Electrochemical testing including cycling performance, rate capability, and impedance spectroscopy.
• Materials characterization of cathode and SE interfaces before and after cycling.

Main Results:

• Uncovered electrochemical isolation of NMC particles due to rapid interfacial degradation.
• Identified polysulfide formation from SE degradation as a key driver of NMC deterioration.
• Demonstrated that functionalized conductive carbon addition suppresses SE degradation and NMC deterioration.
• Achieved high active material utilization, enhanced stability, and excellent rate capability (95% retention at 5C after 500 cycles) with high active loading (≥12 mg cm⁻²).
• Observed high Coulombic efficiency (99.8%) even during high-temperature cycling.

Conclusions:

• Electrochemical isolation and polysulfide-driven degradation are critical failure pathways for Ni-rich NMC/sulfide SE interfaces.
• Functionalized conductive carbon is a scalable and effective strategy for in situ interfacial regulation.
• This approach significantly enhances the stability, rate capability, and thermal resilience of ASSBs.