Simple and Scalable Synthesis Method of γ-NaTiOPO4 for Sodium Ion Batteries in Aqueous and Non-Aqueous Electrolytes
Authors: Kim Doyoub , Park Heetaek , Avdeev Maxim , Kim Minkyung , Kang Byoungwoo 
Published: September 2023

Lithium-ion batteries have been considered a suitable battery technology for energy storage systems. However, its scarcity and high cost pose challenges to the availability of lithium for mass adoption in large applications such as energy storage. Due to their natural abundance and economic feasibility, sodium-ion batteries (SIBs) have proven to be a promising alternative for large-scale applications.1

Most anode materials for research on SIBs have focused on carbonaceous materials, oxides and polyanionic compounds of the anode, like that of lithium-ion battery research on anode materials Polyanionic compounds, especially phosphates, are of particular interest due to their structural, thermal properties and, more importantly, for avoiding undesirable sodium plating.2 Contrary to lithium counterparts, SIBs have fewer alternatives for safe anode materials applicable for both non-aqueous and aqueous rechargeable SIBs.3

Various NaTiOPO4 polymorphs have previously been reported, and these materials required a synthesis process that was extremely time-consuming and a highly pressured synthesis atmosphere. However, the methods reported still produced very small amounts of synthesized material.4-8 Due to these limitations, only the β-NaTiOPO4 phase among polymorphs was studied as an anode for SIBs in a non-aqueous electrolyte.7-8 In this study, we first report a simple and scalable solid-state synthesis method for γ-NaTiOPO4, which incorporates a high-temperature quenching process to stabilize metastable γ-NaTiOPO4 with stability. It is a promising anode for SIBs in non-aqueous and aqueous electrolytes, with a capacity of roughly 120mAh/g, voltages of 1.7V and 1.5V vs Na/Na +, and a Coulombic efficiency of up to 99.9% for up to 500 cycles at 0.5C in non-aqueous electrolyte and excellent capacity retention in a full cell of NaMn0.44O2//γ-NaTiOPO4 for up to 175 cycles in aqueous electrolyte.9

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