Scientists from Osaka Metropolitan University have successfully developed a new positive electrode material Na2FeS2, which is composed of sodium, iron and sulfur.
In the tests, the batteries using the positive electrode of Na2FeS2 had a large energy storage capacity and could be charged and discharged for more than 300 cycles.
Since Na2FeS2 consists of abundant and cheap elements, it is expected to be used in solid state sodium batteries with greater capacity and lower cost.
The demand for high energy density rechargeable batteries, such as lithium-ion batteries, is increasing every year as society moves towards carbon neutrality. Sodium-ion batteries, which have a resource advantage over lithium-ion batteries, are gaining more attention as new, inexpensive and high-performance materials continue to be developed.
A research group led by Associate Professor Atsushi Sakuda, President Masahiro Tatsumisago and Professor Akitoshi Hayashi from the Graduate School of Engineering at Osaka Metropolitan University successfully developed a new positive electrode, in Na2FeS2for solid state sodium batteries.
The batteries have a large energy storage capacity, high reversibility and use cheap and readily available elements.
In addition, batteries using Na2FeS2 as the positive electrode can be charged and discharged for more than 300 cyclesdue to the exclusive crystal structure of Na2FeS2 which gives the electrode a long service life.
Most high-capacity metal sulfide electrodes are based on conversion-type reactions, in which large rearrangements, during charging and discharging, are associated with inhomogeneous reactions and degradation.
Na2FeS2, on the other hand, achieves a high degree of reversibility during loading and unloadingby undergoing insertion-type reactions, which allow the electrode to retain its crystalline structure for many cycles.
The new Na2FeS2 positive electrodes are well balanced in terms of materials, cost and lifetime; we hope that they can be practically used in solid state sodium batteries. In the future, we will continue our research to develop cheaper solid state sodium batteries with even higher performance, looking at power input and output for fast charging, as well as manufacturing and premium anode materials test.
Atsushi Sakuda
More information: onlinelibrary.wiley.com