Hydrothermal-derived carbon as a stabilizing matrix for improved cycling performance of silicon-based anodes for lithium-ion full cells

Abstract

In this work, silicon/carbon composites are synthesized by forming an amorphous carbon matrix around silicon nanoparticles (Si-NPs) in a hydrothermal process. The intention of this material design is to combine the beneficial properties of carbon and Si, i.e., an improved specific/volumetric capacity and capacity retention compared to the single materials when applied as a negative electrode in lithium-ion batteries (LIBs). This work focuses on the influence of the Si content (up to 20 wt %) on the electrochemical performance, on the morphology and structure of the composite materials, as well as the resilience of the hydrothermal carbon against the volumetric changes of Si, in order to examine the opportunities and limitations of the applied matrix approach. Compared to a physical mixture of Si-NPs and the pure carbon matrix, the synthesized composites show a strong improvement in long-term cycling performance (capacity retention after 103 cycles: ≈55% (20 wt % Si composite) and ≈75% (10 wt % Si composite)), indicating that a homogeneous embedding of Si into the amorphous carbon matrix has a highly beneficial effect. The most promising Si/C composite is also studied in a LIB full cell vs a NMC-111 cathode; such a configuration is very seldom reported in the literature. More specifically, the influence of electrochemical prelithiation on the cycling performance in this full cell set-up is studied and compared to non-prelithiated full cells. While prelithiation is able to remarkably enhance the initial capacity of the full cell by ≈18 mAh g−1, this effect diminishes with continued cycling and only a slightly enhanced capacity of ≈5 mAh g−1 is maintained after 150 cycles.

Tailoring Electrolyte Additives with Synergistic Functional Moieties for Silicon Negative Electrode-Based Lithium Ion Batteries: A Case Study on Lactic Acid O-Carboxyanhydride

“…), the development and inclusion of advanced active materials possessing higher energy densities than present state-of-the-art active materials are believed to be the only option to achieve the aforementioned values for energy density and costs for future LIBs. − Apart from carbon/graphite as a standard negative electrode (N) material, mainly alloying-type negative electrode materials and in particular silicon (Si) are considered to be the most promising candidates to further increase the energy density of N. ,− Although already small amounts of silicon (very often as SiO x ) are added to the carbon-based N within some commercial LIBs, ,, the incorporation of higher amounts of Si, which would enable a strong boost in terms of energy density, is still hampered by the insufficient cycle life of such cells. This issue is essentially related to huge volume variations of Si upon (de-)­lithiation, going along with structural instabilities of N. ,, Mainly, the breakdown and in consequence the continuous (re-)­formation , of the solid electrolyte interphase (SEI) , at the alloy surface consume significant amounts of active lithium (Li) and electrolyte, consequently resulting in a poor cycling performance of LIBs incorporating Si-based N. − Various approaches to address those issues are reported in the literature, including nanostructuring of the Si, − using intermetallic , or carbon-based composite materials, , the application of artificial protection layers, , or prelithiation techniques − for compensating active Li losses.…”

Mechanochemical Synthesis of Fe–Si-Based Anode Materials for High-Energy Lithium Ion Full-Cells

“…A high packing density is beneficial regarding the volumetric energy of a LIB but depicts a huge challenge, in particular for nanostructured Si-based materials. In this regard, the synthesized Si–Fe materials clearly outmatch most nanosized materials, for example Si nanoparticles (tap densities of ∼0.16 g cm –3 ) or nanostructured Si–C materials, such as hydrothermal-derived Si–C composites (<0.25 g cm –3 ) that were reported by our group . Furthermore, the applied mechanochemical synthesis route yields materials with low BET specific surface areas (≤4.5 m 2 g –1 ) due to the formation of agglomerates and welded together particles (Table ).…”

Fabrication of Porous Si@C Composites with Core-Shell Structure and Their Electrochemical Performance for Li-ion Batteries

“…Nevertheless, in nano-Si/C composites prepared by the mixing of nano-Si and a carbon precursor and further carbonization (e.g., liquid phase method), the nano-Si particles are difficult to disperse evenly in the carbon matrix due to their characteristic of easy agglomeration, which worsens the electrochemical performance of nano-Si/C composites. Meanwhile, nano-Si/C composites with uniform carbon coating can be obtained via different approaches (e.g., chemical vapor deposition technique [25] and hydrothermal method [26]), but the high production cost and difficulty in large-scale production limit their commercial applications.…”