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 at a rate of 0.5 C after 200 cycles, 95.2% retention) and rate performance (∼580 mAh g at a rate of 10 C) owing to their distinctive structure.

Research Frontiers in Energy‐Related Materials and Applications for 2020–2030

“…However, its relatively low theoretical capacity of 372 mA h g −1 offers room to develop novel high energy density negative electrodes. [49] To better accommodate the volumetric changes of the material and enable the commercial application of Si-based anodes, research is being conducted on the production of nanostructured [51] and core-shell Si electrodes. [46][47][48] • Another strategy to improve the energy density and to reduce the costs of Li-ion batteries is to develop silicon or metallic lithium anodes.…”

Fundamental Understanding of Nanostructured Si Electrodes: Preparation and Characterization

“…In terms of controlling the reaction kinetics, salt crystals (e. g., sodium chloride, potassium chloride or these of mixture) – which have higher melting points than metal reductants – play a crucial role as heat scavengers ,. After proper acid leaching, the Si produced in this manner has a mesoporous structure with a broad distribution of pore sizes that can fall into the range of mesopores or sometimes even macropores .…”

“…After proper acid leaching, the Si produced in this manner has a mesoporous structure with a broad distribution of pore sizes that can fall into the range of mesopores or sometimes even macropores . The developed pores provide a high surface‐area‐to‐volume ratio that can speed up lithiation/delithiation kinetics and accommodate volume changes that arise from the formation of lithium silicide, thereby reducing the surface stress ,…”

Recent Progress in Synthesis and Application of Low-Dimensional Silicon Based Anode Material for Lithium Ion Battery

“…Magnesiothermic reduction method is a widely used approach to synthesize silicon based anode materials [68][69][70][71]. For instance, Xie et al reported a porous silicon nanoparticle formation through magnesiothermic reduction synthesis by using the monodisperse silica sphere as stating material [72].…”