Exfoliation of Na₂Ti₃O₇ into Colloidal Nanosheets with Enhanced Discharge Capacity

Sodium-ion batteries (SIBs), which are being considered as possible alternatives to lithium-ion batteries, have attracted great scientific and industrial interest because sodium is inexpensive and more abundant than lithium. Among various anode materials for SIBs, Na₂Ti₃O₇, with a layered structure, has a high potential due to its stable electrochemical sodiation/desodiation behavior. However, Na₂Ti₃O₇ has a large band-gap energy and a zigzag framework, which results in low electrical conductivity and poor sodium-ion diffusion. Thus, to circumvent such drawbacks, in this study, Na₂Ti₃O₇ was successfully exfoliated by the soft-chemical exfoliation technique via a two-step intercalation reaction. Transmission electron microscopy (TEM) studies show that the obtained exfoliated material is composed of thin nanosheets. Electrochemical sodium-ion storage tests showed that the exfoliated nanosheets had a much higher discharge capacity than bare bulk Na₂Ti₃O₇, revealing that the exfoliation process could be utilized to develop new electrode materials with enhanced energy-storage properties.