Unique nanocrystalline frameworks in mesoporous tin phosphate prepared through a hydrofluoric acid assisted chemical reaction

Abstract

A mesostructured tin phosphate (SnPi) material has been prepared in the presence of an amphiphilic block copolymer (F127), tin chloride (SnCl₄), and phosphoric acid (H₃PO₄) in an ethanol–water mixed solvent medium. The mesoporous SnPi material, with a large pore diameter (7.4 nm), nanocrystalline walls, a high surface area (310 m² g⁻¹), and a unique flake-like particle shape, is successfully synthesized by a two-step heat treatment of the parent mesostructured SnPi under flowing N₂ gas followed by flowing air. Under moderate conditions (293 K and 60% relative humidity), our mesoporous SnPi shows 6.5 times more proton (H⁺) conductivity compared to its non-porous/bulk analogue (SnPi-B), due to its higher surface area and unique nanocrystalline porous structure enriched with free O–H groups. The preliminary electrochemical properties of our crystalline mesoporous SnPi as an anode for lithium-ion batteries (LIBs) have been studied as well, which exhibits good reversible specific capacity with good cycling stability and excellent capacity retention of 92%.