Real‐Time Imaging of Intercalation–Conversion Li Storage in MXenes for Solid‐State Batteries

Why It Matters

Understanding the nanoscale charge‑storage mechanisms enables targeted MXene engineering, accelerating the development of high‑energy‑density solid‑state batteries for commercial applications.

Key Takeaways

• Operando STEM visualizes Li intercalation in Ti3C2Tx
• Three pathways: intercalation, Li2O conversion, electrolyte breakdown
• O‑terminated MXenes allow room‑temperature Li uptake
• F/Cl terminations need elevated temperatures for Li penetration
• Surface‑termination engineering boosts solid‑state battery performance

Pulse Analysis

Two‑dimensional transition‑metal carbides and nitrides, known as MXenes, have emerged as a versatile class of electrode materials for next‑generation energy storage. Their high electrical conductivity, tunable chemistry, and layered structure make them attractive for all‑solid‑state batteries, which promise higher safety and energy density than conventional liquid‑electrolyte cells. However, the lack of direct observation of lithium‑ion transport and redox processes inside MXene electrodes has limited the ability to rationally tailor their composition. Bridging this knowledge gap is essential for translating MXene research into commercial solid‑state technologies.

The recent operando scanning transmission electron microscopy (STEM) study provides the first real‑time nanoscale view of lithium intercalation and conversion in Ti3C2Tx MXene electrodes paired with a sulfide solid electrolyte. Three distinct pathways were captured: reversible Li intercalation within the interlayer spacing accompanied by Ti redox, partial formation and decomposition of surface Li2O, and electrochemical breakdown of the sulfide electrolyte. Crucially, the work demonstrates that surface terminations govern these mechanisms—oxygen‑terminated MXenes enable efficient Li uptake at ambient temperature, whereas fluorine or chlorine terminations require heating to achieve comparable penetration.

These insights establish surface‑termination engineering as a practical lever to boost lithium accommodation and redox utilization in solid‑state batteries. By selecting or post‑treating MXenes to favor O‑termination, manufacturers can improve capacity, rate capability, and cycle life without resorting to exotic additives. The methodology also sets a precedent for operando microscopy in other emerging electrode systems, accelerating materials‑by‑design cycles. As the solid‑state market targets automotive and grid‑scale deployments, such mechanistic clarity will be a decisive factor in achieving cost‑effective, high‑performance energy storage solutions.