Elucidating the role of anionic chemistry towards high-rate intermediate-temperature Na-metal halide batteries

Journal Article · Tue Dec 31 23:00:00 EST 2019 · Energy Storage Materials

DOI:https://doi.org/10.1016/j.ensm.2019.08.021· OSTI ID:1595295

Zhan, Xiaowen ^[1]; Sepulveda, Jonathan P. ^[1]; Lu, Xiaochuan ^[1]; Bonnett, Jeff F. ^[1]; Canfield, Nathan L. ^[1]; Lemmon, Teresa L. ^[1]; Jung, Keeyoung ^[2]; Reed, David M. ^[1]; Sprenkle, Vincent L. ^[1]; Li, Guosheng ^[1]

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1. BATTELLE (PACIFIC NW LAB)
2. Research Institute of Industrial Science & Technology

Sodium (Na)-based battery technologies that are economical (because Na is abundant) and have long cycle life are gaining importance for large-scale energy storage applications. Among the widely studied Na-based battery systems, intermediate-temperature (IT) Na-metal halide (Na-MH) batteries have demonstrated several advantages over conventional high-temperature Na batteries, including superior battery safety, lower operating temperature and manufacturing cost, potentially longer cycle life, and easier assembly, etc. However, the rate performance of IT Na-MH batteries is inevitably affected by lower operating temperatures. In pursuit of faster charge-transfer reaction kinetics, we extended our studies of cathode materials beyond the extensively investigated NiCl2 to NiBr2 (NaBr/Ni) and NiI2 (NaI/Ni) compounds. We systematically investigated the synergetic effects of anion chemistry on the electrochemical properties. Surprisingly, among three tested cathodes, the NaBr/Ni cathode showed the highest energy density of 174 Wh/kg at 33.3 mA/cm2 (~0.8C), which is 2.5 and 1.9 times higher than those of NaCl/Ni and NaI/Ni cells. We explored the underlying enhancement mechanism in great detail via multiple structural characterization and electrochemical techniques. The sodium-halide salt dissolution in molten NaAlCl4 was found to be the determining factor in rate improvement. Our findings will greatly advance IT Na-MH battery technologies and pave the way towards fundamental understanding of reaction kinetics for high-temperature batteries in general.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1595295
• Report Number(s): PNNL-SA-143535
• Journal Information: Energy Storage Materials, Journal Name: Energy Storage Materials Vol. 24
• Country of Publication: United States
• Language: English