Electrode material used to enhance all-solid-state sodium batteries

A research group led by Associate Professor Atsushi Sakuda, President Masahiro Tatsumisago, and Professor Akitoshi Hayashi at Osaka Metropolitan University have developed a new positive electrode made of Na2FeS2 for all-solid-state sodium batteries. The batteries have a high energy storage capacity and high reversibility, and use inexpensive elements that are readily available. The researchers published their findings in the journal Small.

The batteries using the Na2FeS2 as a positive electrode can be charged and discharged for more than 300 cycles, due to the unique crystal structure of the Na2FeS2 that gives the electrode a long lifespan. Most high-capacity metal sulfide electrodes rely on conversion-type reactions, during which large rearrangements — during charging and discharging — are associated with inhomogeneous reactions and degradation. The Na2FeS2, on the other hand, achieves a high degree of reversibility during charging and discharging, by undergoing insertion-type reactions, which allow the electrode to retain its crystal structure over many cycles.

Sodium-ion batteries — which have a resource advantage over lithium-ion batteries — are attracting attention as cheaper, high-performance materials continue to be developed. “The new Na2FeS2 positive electrodes are well balanced in terms of materials, cost and lifetime; we expect them to be put to practical use in all-solid-state sodium batteries. In the future, we will continue our research to develop cheaper all-solid-state sodium batteries with even higher performance, by examining high input and output for rapid recharging, as well as making and testing of superior anode materials,” Sakuda said.

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