title: Multiscale Hyperporous Silicon Flake Anodes for High Initial Coulombic Efficiency and Cycle Stability.
abstract: Three-dimensional (3D) hyperporous silicon flakes (HPSFs) are prepared via the chemical reduction of natural clay minerals bearing metal oxides. Natural clays generally have 2D flake-like structures with broad size distributions in the lateral dimension and varied thicknesses depending on the first processing condition from nature. They have repeating layers of silicate and metal oxides in various ratios. When the clay mineral is subjected to a reduction reaction, metal oxide layers can perform a negative catalyst for absorbing large amounts of exothermic heat from the reduction reaction of the silicate layers with metal reductant. Selectively etching out metal oxides shows a hyperporous nanoflake structure containing 100 nm macropores and meso-/micropores on its framework. The resultant HPSFs are demonstrated as anode materials for lithium-ion batteries. Compared to conventional micro-Si anodes, HPSFs exhibit exceptionally high initial Coulombic efficiency over 92%. Furthermore, HPSF anodes show outstanding cycling performance (reversible capacity of 1619 mAh g-1at a rate of 0.5 C after 200 cycles, 95.2% retention) and rate performance (∼580 mAh g-1at a rate of 10 C) owing to their distinctive structure.
authors.affiliation: Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, South Korea.
authors.forename: Jaegeon
authors.initials: J
authors.lastname: Ryu
authors.affiliation: Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, South Korea.
authors.forename: Dongki
authors.initials: D
authors.lastname: Hong
authors.affiliation: Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, South Korea.
authors.forename: Myoungsoo
authors.initials: M
authors.lastname: Shin
authors.affiliation: Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, South Korea.
authors.forename: Soojin
authors.initials: S
authors.lastname: Park
keywords: clay materials; high initial Coulombic efficiency; hyperporous silicon flakes; lithium-ion battery anodes