Molten-salt chemical exfoliation process for preparing two-dimensional mesoporous Si nanosheets as high-rate Li-storage anode

Two-dimensional (2D) materials have attracted enormous attention due to their functional applications in energy storage. In this work, a low-temperature molten-salt chemical exfoliation methodology is developed for producing free-standing 2D mesoporous Si through deintercalation of CaSi₂ in excess molten AlCl₃ at 195 ℃. The average dimension of these sheets is 1.5 μm, and the thickness of a single sheet is approximately 10 nm. The as-prepared 2D Si has a Brunauer–Emmett–Teller surface area of 154 m²·g^-1 and an average pore size of 5.87 nm. With this unique structure, the 2D Si exhibits superior Li-storage performance, including a reversible capacity of 2, 974 mA·h·g^-1 at 0.2 C, reversible capacities of 2, 162, 1, 947, and 1, 527 mA·h·g^-1 at 0.8, 2, and 5 C after 200 cycles, and a capacity retention of 357 mA·h·g^-1 even at 30 C (90 A·g^-1).