Adjustable Interlayer Spacing for Layered Titanate for Potassium Storage

Potassium-ion batteries (KIBs) are promising substitutes for lithium-ion batteries (LIBs) in grid-scale energy storage due to the Earth-abundancy of potassium [1]. Practical KIB applications, however, are hindered by slow diffusion kinetics and severe structural deterioration as the large cation is cycled in and out of the electrode, respectively leading to low specific capacity and short lifetime [2]. Herein we synthesize layered alkali titanates as electrode materials for KIBs by chemical reaction between nanoparticles and aqueous alkali hydroxides. By increasing the interlayer spacing of titanates, we show improvements in electrochemical performances in terms of specific capacity, charging rate and cycle life. Larger interlayer spacing allows quick and increased ion storage [3]. The adjustment of reaction temperature, concentration and types of hydroxides has direct effects on the interlayer spacing of these titanates. As a result, we have produced a range of alkali titanates with different interlayer spacing. Some as-prepared titanates with larger interlayer spacing deliver electrochemical performances for KIBs comparable to titanium-oxide based LIBs [4], [5]. Our work provides a method to design future energy storage electrode materials for large ions.