Liquid phase delamination of non-van der Waal two-dimensional sheets of tin monoxide for flexible and long lifespan sodium-ion batteries

Sodium-ion batteries are attractive alternatives to Li-ion batteries, but typically suffer from slow redox kinetics and short cycle life. These problems arise mainly from the much larger radius of the sodium ion, which results in slow diffusion and causes a large volume change during operation. Using the two-dimensional (2D) sheet form of redox-active materials with an increased number of exposed reactive sites on the surface could mitigate volume expansion while improving rate capabilities. Based on our recently developed strategy where we used a physical calendering method to weaken non-van der Waals (vdW) interactions, in this work we demonstrate liquid phase delamination of SnO to enable facile mass production of few-layer sheets. The 2D morphology allowed highly reversible redox reactions due to the greater exposure of Sn atoms. Thus, free-standing films formed from SnO sheets infiltrated with carbon nanotubes as conductive fillers exhibited excellent rate capabilities (620 and 432 mAh g −1 at 115 and 1150 mA g −1 respectively) and long cycle-life performance (77% of the initial capacity after 2000 cycles at 1150 mA g −1 ). Pouch full-cells assembled with Na 0.61 Fe[Fe(CN) 6 ] 0.94 cathode successfully powered electronic devices, e.g. light emitting diode lamps, even when bent or folded. This work thus proposes a new way to the mass production of non-vdW SnO sheets and highlights the potential of thinned non-vdW materials for electrochemical energy storage.