NaCrO2-Based Batteries: Effects of Processing

Na-ion batteries (NIBs) have attracted substantial attention lately as an alternative electrochemical energy storage technology. In this study, we report the effects of processing conditions on the electrochemical properties of Na-ion batteries made of the NaCrO₂ cathode. NaCrO₂ is synthesized via solid state reactions. The as-synthesized powder is then subjected to high-energy ball milling under different conditions. The CR2032 coin cells made using the as-synthesized NaCrO₂ powder exhibit a specific capacity of 110 mAh/g in the first discharge at 0.3C rate. The specific capacity decreases gradually in the subsequent charge/discharge cycles. The observed electrochemical properties are similar to those reported previously [1,2].

High-energy ball milling has reduced the particle size drastically. However, after subjecting to high-energy ball milling the specific capacity for NaCrO₂ degrades significantly. X-ray diffraction reveals that the lattice distortion has taken place during high-energy ball milling, likely forcing some Cr ions into the tetrahedral site and thus blocking the pathway for Na intercalation and de-intercalation. This study shows that a balance between reducing the particle size and maintaining the layered structure is essential to obtain high specific capacity for the NaCrO₂ cathode.

References:

1. S. Komaba, C. Takei, T. Nakayama, A. Ogata and N. Yabuuchi, “Electrochemical intercalation activity of layered NaCrO₂ vs. LiCrO₂,” Electrochem. Commun., 12, 355-358 (2010).
2. S. Komaba, T. Nakayama, A. Ogata, T. Shimizu, C. Takei, S. Takada, A. Hokura and I. Nakai, “Electrochemically reversible sodium intercalation of layered NaNi_0.5Mn_0.5O₂ and NaCrO₂,” ECS Transactions, 16, 42, 43-55 (2009).