Design and characterization of silicon-based composites in lithium-ion batteries: An overview of material structures and corresponding wet-chemical routes

Abstract

As the market share of electric vehicles (EVs) is expected to rise immensely over the next decades, the demand for improved energy storage technologies is currently at an all-time high. Silicon is regarded as a promising anode material due to its extremely high capacity and high energy density, but suffers from drastic volume changes during cycling. These cyclic volume changes lead to structural degradation of the electrode, including fracturing and loss of contact with the current collector. Importantly, the solid electrolyte interphase (SEI) formed at the surface of the Si particles has to be reformed after each cycle, which ultimately leads to capacity fading and poor cycling performance. A proposed strategy to minimize these issues is to incorporate Si nanostructures inside a (porous) composite matrix, which can reversibly accommodate the volume expansion during lithiation while also stabilizing the SEI layer. Typically, this matrix is carbon-based (amorphous, hard carbon and/or graphitic) due to its excellent conductive properties and mechanical rigidity. A number of designs such as nanoparticles, core-shell/yolk-shell structures, and more advanced architectures are reviewed and discussed, with a focus on (easily upscalable) wet-chemical routes. Furthermore, some attention is given to the chemical and morphological characterization of these structures and their interfaces, as these are critical to the stability and cycle life of the anode coating.