Synthesis and Electrochemical Performance of π-Conjugated Molecule Bridged Silicon Quantum Dot Cluster as Anode Material for Lithium-Ion Batteries

Abstract

π-Conjugated molecule bridged silicon quantum dots (Si QDs) cluster was prepared by Sonogashira C−C cross-coupling reaction between 4-bromostyryl and octyl co-capped Si QDs (4-Bs/Oct Si QDs) and 1,4-diethynylbenzene. The surface chemical structure, morphology, and chemical composition of the Si QD cluster were confirmed by Fourier transform infrared spectroscopy, field emission transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Lithiumion batteries were fabricated using 4-Bs/Oct Si QD and Si QD clusters as anode materials to investigate the effect of QD clustering on the electrochemical performance. Compared with the 4-Bs/Oct Si QD electrode, the Si QD cluster exhibits improved electrochemical performance, such as a high initial discharge capacity of ∼1957 mAh/g and good cycling stability with ∼63% capacity retention following 100 cycles at a current rate of 200 mA/g when tested at the voltage window of 0.01−2.5 V. The improved electrochemical performance of the Si QD cluster is attributed to the π-conjugated molecules between the Si QDs and on the surface of Si QD cluster, which serve as a buffer layer to alleviate the mechanical stresses arising from the alloying reaction of Si with lithium and maintain the electrical conduits in the anode system.

Recent Advances in Silicon‐Based Electrodes: From Fundamental Research toward Practical Applications

“…While presenting several advantages, a notable challenge for hollow morphologies is that, because of their intimate contact with the electrolyte, a thick SEI can form. [ 217 ] Minimizing the SEI, optimizing electronic transfer kinetics, and improving the cycling stability are key for future application of hollow Si electrodes.…”

Development of a MATLAB Algorithm for Calculating Reorganization Energy Utilizing Rectilinear Normal Mode Displacements: Investigation of the Effect of Substituents on Electron and Hole Reorganization Energies of Styryl‐Capped Silicon Quantum Dots

“…The reason for choosing the styryl group as the anchoring group was that the reorganization energy of Si QDs can be adjusted by replacing the hydrogen atom at the para position of the phenyl group with various functional groups. Moreover, the styryl capped Si QDs can be successfully synthesized by catalyzed/thermal hydrosilylation reactions between hydride‐terminated Si QDs and ethynylbenzene as an unsaturated group 14,24 . Consideration was given to how to reduce the charge transfer reorganization energies for the Si QD with a fixed diameter.…”

“…Hence, in this work, we specifically investigated the effect of the electron donating or withdrawing nature of various substituents, namely, OH, OCH 3 , CH 3 , F, Br, Cl, COOH, CN, and NO 2 groups, bonded to styryl group attached to the Si QD on its reorganization energy. The styryl group was chosen as an anchoring group because it can be realized experimentally for surface passivation by catalytic or thermal hydrosilylation reactions between hydride‐terminated Si QD and ethynylbenzene 14,23,24 …”

Influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot nanocomposite anode materials for lithium-ion batteries

“…Assembly into a hierarchical architecture, with NPs as the basic structural unit, is an efficient strategy for fabricating high-performance porous materials for LIBs. 18,19,24–29 In recent years, NP assemblies have come under the spotlight as high-performance anode materials for LIBs owing to their lower interfacial area compared to that of NPs, which can significantly reduce the interparticle resistance and mitigate the risk of side reactions. 25,26 In addition, their high tap density results in thinner electrodes at the same mass loading, which allows shorter electron pathways and increases the volumetric specific capacity of the whole cell.…”