Aluminothermic reduction synthesis of porous silicon nanosheets from vermiculite as high-performance anode materials for lithium-ion batteries

Designing silicon with two-dimensional (2D) micromorphology and porous nanostructure has proven to be an effective route to obtain high capacities during cycling when adopted as anode materials for lithium-ion batteries. Here, a mild and cost-efficient chemical route is developed to synthesize Si nanosheets from vermiculite via a preliminary chemical delamination assisted with low-temperature aluminothermic reduction in a eutectic molten salt system. Benefiting from the self-templating role of multilayered crystal structure of vermiculite and the high reduction efficiency of aluminothermic reaction, the as-prepared Si nanosheets possess ultrathin 2D morphology and hierarchical porous structure. As anode materials for lithium-ion batteries, Si nanosheets exhibit a high reversible capacity of 1696 mAh g−1 at a current density of 0.2 A g−1 after 100 cycles, 1269 mAh g−1 at 1.0 A g−1 after 300 cycles and excellent rate capability with desirable capacities of 1314 mAh g−1 at 4.0 A g−1. This work provides a promising technical route for the transformation of low-cost natural vermiculite to value-added high performance silicon anode materials, which can be extended to other layered silicate minerals. A mild and low-cost strategy is introduced to synthesize porous Si nanosheets from raw vermiculite via a combination of chemical delamination, acidification and aluminothermic reduction. Si nanosheets as anode active materials in LIBs exhibit remarkably improved electrochemical performances. [Display omitted] •Natural vermiculite is used as raw materials to prepare Si nanosheets for LIBs.•Si nanosheets are prepared via a low-temperature aluminothermic reduction reaction.•Si nanosheets possess ultrathin 2D morphology and well-developed hierarchical porous structure.•LIBs based on Si nanosheets as anode show excellent electrochemical performance.