Crack-Free Silicon Monoxide as Anodes for Lithium-Ion Batteries

Insights into the Effect of SiO Particle Size on the Electrochemical Performance between Half and Full Cells for Li-Ion Batteries

Silicon monoxide (SiO) has attracted growing attention as one of the most promising anodes for high-energy-density lithium-ion batteries (LIBs), benefiting from relatively low volume expansion and superior cycling performance compared to bare silicon (Si). However, the size of the SiO particle for commercial application remains uncertain. Besides, the materials and concepts developed on the laboratory level in half cells are quite different from what is necessary for practical operation in full cells. Herein, we investigate the electrochemical performance of SiO with different particle sizes between half cells and full cells. The SiO with larger particle size exhibits worse electrochemical performance in the half cell, whereas it demonstrates excellent cycling stability with a high capacity retention of 91.3% after 400 cycles in the full cell. The reasons for the differences in their electrochemical performance between half cells and full cells are further explored in detail. The SiO with larger particle size possessing superior electrochemical performance in full cells benefits from consuming less electrolyte and not being easier to aggregate. It indicates that the SiO with larger particle size is recommended for commercial application and part of the information provided from half cells may not be advocated to predict the cycling performances of the anode materials. The analysis based on the electrochemical performance of the SiO between half cells and full cells gives fundamental insight into further Si-based anode research.

Operando study of mechanical integrity of high-volume expansion Li-ion battery anode materials coated by Al2O3

Group IV elements and their oxides, such as Si, Ge, Sn and SiO have much higher theoretical capacity than commercial graphite anode. However, these materials undergo large volume change during cycling, resulting in severe structural degradation and capacity fading. Al₂O₃coating is considered an approach to improve the mechanical stability of high-capacity anode materials. To understand the effect of Al₂O₃coating directly, we monitored the morphology change of coated/uncoated Sn particles during cycling using operando focused ion beam-scanning electron microscopy. The results indicate that the Al₂O₃coating provides local protection and reduces crack formation at the early stage of volume expansion. The 3 nm Al₂O₃coating layer provides better protection than the 10 and 30 nm coating layer. Nevertheless, the Al₂O₃coating is unable to prevent the pulverization at the later stage of cycling because of large volume expansion.

Weakly Solvating Solution Enables Chemical Prelithiation of Graphite-SiOx Anodes for High-Energy Li-Ion Batteries

Although often overlooked in anode research, the anode's initial Coulombic efficiency (ICE) is a crucial factor dictating the energy density of a practical Li-ion battery. For next-generation anodes, a blend of graphite and Si/SiO_x represents the most practical way to balance capacity and cycle life, but its low ICE limits its commercial viability. Here, we develop a chemical prelithiation method to maximize the ICE of the blend anodes using a reductive Li-arene complex solution of regulated solvation power, which enables a full cell to exhibit a near-ideal energy density. To prevent structural degradation of the blend during prelithiation, we investigate a solvation rule to direct the Li⁺ intercalation mechanism. Combined spectroscopy and density functional theory calculations reveal that in weakly solvating solutions, where the Li⁺-anion interaction is enhanced, free solvated-ion formation is inhibited during Li⁺ desolvation, thereby mitigating solvated-ion intercalation into graphite and allowing stable prelithiation of the blend. Given the ideal ICE of the prelithiated blend anode, a full cell exhibits an energy density of 506 Wh kg^-1 (98.6% of the ideal value), with a capacity retention after 250 cycles of 87.3%. This work highlights the promise of adopting chemical prelithiation for high-capacity anodes to achieve practical high-energy batteries.