Review—The Lithiation/Delithiation Behavior of Si-Based Electrodes: A Connection between Electrochemistry and Mechanics

Abstract

Silicon is a promising alternative anode material to graphite because of its high gravimetric and volumetric energy densities. However, severe capacity fading is observed in Si electrodes, and it is a result of mechanical changes of Si, such as volume changes, stress or fracture. Furthermore, these mechanical behaviors are strongly coupled with the electrochemistry of the Li–Si alloying reaction in Si-based electrodes, including both thermodynamics and kinetics. Therefore, the electrochemical properties of Si-based electrodes are strongly dependent on the control of the mechanics of Si during lithiation/delithiation. Thus, it is very important to understand the correlation between electrochemistry and mechanics. Here, we review lithiation/delithiation behaviors of various types of Si-based electrodes, applying a fundamental understanding of electrochemistry and mechanics and the correlation between them.

Understanding the Effect of Cathode Composition on the Interface and Crosstalk in NMC/Si Full Cells

“…One of the reasons would be the depth of lithiation into Si increases when upper cutoff voltage increases to 4.3 V, and the depth is generally understood as a critical factor affecting degradation of Si anode. 11 Interestingly, it is noted that the extent of the reduction differs in three systems. The Coulombic efficiency changes moderately from 93.9% in Si_NMC532_4.…”

“…On the other hand, when the upper cutoff voltage is 4.3 V, the initial lithiation capacities of each aged Si/Li half-cells rarely changed, but the initial Coulombic efficiency was reduced in all cells, showing significant irreversible capacities. One of the reasons would be the depth of lithiation into Si increases when upper cutoff voltage increases to 4.3 V, and the depth is generally understood as a critical factor affecting degradation of Si anode . Interestingly, it is noted that the extent of the reduction differs in three systems.…”

“…7−10 The SEI for the Si-containing anode should passivate the Si surface, preventing further decomposition of the electrolyte. Also, because the Si-based anode suffers large mechanical changes during charge/discharge, 11 the SEI for the Si anode should be very mechanically stable and tolerant of the volumetric changes. If not, the SEI will break, leading to rapid electrolyte decomposition and Li consumption.…”

“…However, Si faces critical issues to be a substitute for the conventional graphite anode, such as a low initial Coulombic efficiency, poor cycle life, and poor calendar life. − These issues are highly dependent on the properties of the surface chemistry of the Si anode, such as the properties of the solid electrolyte interphase (SEI). − The SEI for the Si-containing anode should passivate the Si surface, preventing further decomposition of the electrolyte. Also, because the Si-based anode suffers large mechanical changes during charge/discharge, the SEI for the Si anode should be very mechanically stable and tolerant of the volumetric changes. If not, the SEI will break, leading to rapid electrolyte decomposition and Li consumption.…”

A flexible network polyimides binder for Si/graphite composite electrode inlithium‐ionbatteries

“…The result turns out that the interaction between the C–PI–OH binder, silicon particles, and collector is stronger than that of the other two binders. The improved adhesion of C–PI–OH can be explained by the free carboxylic acid group and amide group of C–PI–OH electrodes, which form a covalent bond and hydrogen bond with the hydroxyl group of silicon and current collector surface, respectively 26 . Whereas in Si/graphite/PVDF electrode, there is only van der Waals force between PVDF and other ingredients of the electrode, so it exhibits the worst adhesion performance.…”