Gas‐Phase Synthesis of Silicon‐Rich Silicon Nitride Nanoparticles for High Performance Lithium–Ion Batteries

Abstract

electrical vehicles. Therefore, the energy density as well as rate capability of LIBs needs to be further improved. While there are many parameters defining a battery's characteristics, the anode and cathode materials have by far the highest impact on performance.Silicon is widely recognized as the most promising component in high-capacity anode materials for next-generation LIBs, owing to its natural abundance, low working potential, and its high theoretical storage capacity of 3579 mAh g −1 . [2,3] Furthermore, enhanced rate performance compared to graphite, [4,5] environmental benignity, and low cost [6][7][8] are some of the additional advantages. However, siliconbased anodes mainly face two challenges: fracturing and pulverization of the anode, and continuous solid-electrolyte interphase (SEI) growth. These challenges arise from the large amount of Li atoms that can be inserted into silicon leading to huge volume changes of up to 300% at full lithiation, [9] resulting in severe cracking, mechanical instability, and ultimately a loss of electrical contact. Thus, parts of the active material become electrochemically inactive [10,11] and respective electrodes usually show failure after only a few cycles. This problem is generally solved by using nanomaterials such as nanowires, nanoparticles, or thin films. [12][13][14][15] Crystalline silicon nanoparticles with a diameter below a critical value of 150 nm are resilient to cracking because the generated hoop stress from anisotropic expansion during lithiation is too low to drive crack propagation. [16,17] In contrast, amorphous silicon nanoparticles show better lithiation kinetics and the critical diameter rises to almost 1 µm due to isotropic expansion. [18,19] Whereas nano structuring mitigates challenges related to fracturing and pulverization, the high specific surface area enhances irreversible capacity losses and capacity fade in the first cycles through a high volume fraction of the inactive SEI. [20,21] However, it acts as a stabilizing, passivating layer on the electrode surface during battery charging and consists of a wide variety of reduction products and varies with electrolyte composition, silicon surface groups, formation procedure, and so on. [22][23][24] During cycling, the SEI in silicon-based anodes fractures and the repetitive exposure of fresh silicon surfaces readily leads to advanced degradation through continuous SEI growth. For high cycle life silicon anodes, it is crucial to design a mechanically robust SEI, for example, by embedding the silicon nanoparticles in a matrix such as carbon, namely Si/C composites, [25][26][27] wrapping them, for example, with polyanilineThe practical application of silicon-based anodes is severely hindered by continuous capacity fade during cycling. A very promising way to stabilize silicon in lithium-ion battery (LIB) anodes is the utilization of nanostructured silicon-rich silicon nitride (SiN x ), a conversion-type anode material. Here, SiN x with structure sizes in the sub-micrometer range have been syn...

Towards a framework for evaluating and reporting Hansen solubility parameters: applications to particle dispersions

“…SiN x NPs were chosen as a technically relevant model system because of their promising use-case in Li-ion batteries to give improved long-term cyclability and stability. [37][38][39] Nanoscale Advances Accepted Manuscript…”

“…SiN x NPs were prepared by pyrolyzing SiH 4 in the presence of NH 3 in the gas phase (see supplementary methods for details of the particle synthesis), followed by dispersing the 14 sieved powder (Mesh-270, 63 µm) into twelve PLs (see Table 1 for the list of liquids used here) and finally characterized using an AC device LUMiSizer® (LUM GmbH, Berlin, Germany). The primary particle size range (30 -300 nm) 39 was large enough that no sizedependent dispersion effects were observed. 40 As-synthesized particles were "clean" without ligands or other residuals due to the high reaction temperature (900 °C), however, they might be slightly oxidized at the surface due to handling at ambient conditions.…”

“…40 As-synthesized particles were "clean" without ligands or other residuals due to the high reaction temperature (900 °C), however, they might be slightly oxidized at the surface due to handling at ambient conditions. 39 Throughout all experiments, the particles were dispersed in ultrapure liquids without the addition of ligands/surfactants. Details on the dispersion preparation and AC measurements are provided in supplementary methods.…”

Towards a Framework for Evaluating and Reporting Hansen Solubility Parameters: Applications to Nano and Micron Scale Particle Dispersions

“…SiNx NPs were chosen as a technically relevant model system because of their promising use-case in Li-ion batteries to give improved long-term cyclability and stability. [37][38][39]…”

“…SiNx NPs were prepared by pyrolyzing SiH4 in the presence of NH3 in the gas phase (see supplementary methods for details of the particle synthesis), followed by dispersing the sieved powder (Mesh-270, 63 µm) into twelve PLs (see Table 1 for the list of liquids used here) and finally characterized using an AC device LUMiSizer® (LUM GmbH, Berlin, Germany). The primary particle size range (30 -300 nm) 39 was large enough that no sizedependent dispersion effects were observed. 40 As-synthesized particles were "clean" without ligands or other residuals due to the high reaction temperature (900 °C), however, they might be slightly oxidized at the surface due to handling at ambient conditions.…”