Two-Dimensional Unilamellar Cation-Deficient Metal Oxide Nanosheet Superlattices for High-Rate Sodium Ion Energy Storage

Abstract

Cation-deficient two-dimensional (2D) materials, especially atomically thin nanosheets, are highly promising electrode materials for electrochemical energy storage that undergo metal ion insertion reactions, yet they have rarely been achieved thus far. Here, we report a Tideficient 2D unilamellar lepidocrocite-type titanium oxide (Ti 0.87 O 2 ) nanosheet superlattice for sodium storage. The superlattice composed of alternately restacked defective Ti 0.87 O 2 and nitrogen-doped graphene monolayers exhibits an outstanding capacity of ∼490 mA h g −1 at 0.1 A g −1 , an ultralong cycle life of more than 10000 cycles with ∼0.00058% capacity decay per cycle, and especially superior low-temperature performance (100 mA h g −1 at 12.8 A g −1 and −5 °C), presenting the best reported performance to date. A reversible Na + ion intercalation mechanism without phase and structural change is verified by first-principles calculations and kinetics analysis. These results herald a promising strategy to utilize defective 2D materials for advanced energy storage applications.

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…During charging and discharging, sodium ions can be reversibly inserted into the Ti vacancies and interlaminar space of the superlattice. The multilayer structure without phase transition or structural change is maintained in the process of sodiation/desodiation, thus achieving excellent electrochemical performance (Figure b) . Compared with monovalent lithium ions or sodium ions, Ma et al reported that reversible Mg 2+ and Al 3+ were inserted into anatase TiO 2 , introducing a large number of Ti vacancies as insertion sites .…”

“…b) Schematic illustration of the Ti 0.87 O 2 /N‐doped graphene superlattice and the capacity retentions at different temperatures. Reproduced with permission . Copyright 2018, American Chemical Society.…”

2D Superlattices for Efficient Energy Storage and Conversion

“…Copyright 2017, AAAS. 2018) Reproduced with permission . Copyright 2018, American Chemistry Society.…”

“…A post‐calcination treatment is further introduced after the flocculation for well‐integrated superlattices with intimate interactions. Recently, a Ti 0.87 O 2 /N‐doped graphene superlattice has been reported through the calcination of superlattice of electrostatically re‐stacked Ti 0.87 O 2 and PDDA‐graphene nanosheets . A possible TiOC bonding is formed during the calcination treatment.…”

2D Titania–Carbon Superlattices Vertically Encapsulated in 3D Hollow Carbon Nanospheres Embedded with 0D TiO2 Quantum Dots for Exceptional Sodium‐Ion Storage

“…Ty pical strategies for fabricating 2D superstructures involve arduous exfoliation of bulk precursors into monolayer, subsequently,l ayer-by-layer restacking,w hich are restricted to layered bulks,a nd in particular,t hose based on van der Waals 2D interactions,w ith low throughput and limited reproducibility. [6,7] Nevertheless,2 Ds uperlattices based on non-layer structured nanomaterials have been hardly reported. Besides,t he synthesized 2D superlattices are still subjected to irreversible aggregation during synthetic and electrode fabrication processes.…”