Reliable Evaluation of Na-Ion Battery Materials: Eliminating Na-Metal Distortions

Abstract

<title>Abstract</title> Na-ion batteries are gaining momentum as a cost-effective, scalable, and sustainable energy storage solution for integrating renewable energy and promoting widespread electrification. To accelerate their development, extensive research on electrode and electrolyte materials has been conducted using half-cell configurations with a Na metal counter electrode, following a practice inherited from Li-ion battery studies. However, this routine evaluation must be critically reconsidered, because the high reactivity of Na metal drives continuous parasitic reactions with electrolytes, undermining reproducibility and distorting key electrochemical indicators such as capacity, Coulombic efficiency, cycling stability, and interphase resistance, thereby ultimately misguiding material and cell design. To overcome this severe issue, a simple and reliable evaluation protocol is established by employing NASICON (Na Super Ionic Conductor)-type counter electrodes, which effectively eliminates Na metal-induced artifacts. This work provides a foundation for standardized testing, enabling precise material screening, quantitative benchmarking, and informed advancement of Na-ion battery technologies.

Affiliated Institutions

• Kyoto University JP
• Tokyo University of Science JP
• The University of Tokyo JP
• Waseda University JP

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