Anode Properties\nof NaTi₂(PO₄)₃ Prepared by Adding\nExcess Na₂CO₃ for Aqueous Sodium-Ion Batteries

Abstract

Aqueous Na-ion batteries (ASIBs) are being developed\nas one of\nthe next-generation large-scale rechargeable battery types. In the\ndevelopment of ASIBs, the further improvement of the anode properties\nof one of them, NaTi₂(PO₄)₃ (NTP),\nis important. Therefore, we tried to modify the NTP surface with a\nmaterial having Na-ion conductivity, such as a solid electrolyte interphase\nlayer. NTP was prepared with the addition of an excess amount of Na₂CO₃ and exhibited better cyclability and rate capability.\nIn particular, this NTP showed good cycle stability even with the\nuse of an aqueous electrolyte with a low salt concentration. The surfaces\nof the obtained NTPs were analyzed using S/TEM and electron energy\nloss spectroscopy measurements. The particle surface was modified\nby a Na-rich phase such as Na₃Ti₂³⁺(PO₄)₃. In addition, the prepared NTPs had\nhigh crystallinity, which is thought to contribute to the good rate\ncapability. We have found a simple method of adding excess Na₂CO₃ during NTP synthesis to improve the anode properties\nof NTPs.