In Situ and Operando Investigations of Failure Mechanisms of the Solid Electrolyte Interphase on Silicon Electrodes

Abstract

The lifetime of rechargeable lithium ion batteries is closely related to the formation and evolution of the solid electrolyte interphase (SEI). These passivation films undergo substantial deformations when the underlying electrode particles expand and contract during cycling. Directly probing these changes is extremely challenging. In this study, we demonstrate a new approach for applying controlled strains to SEI films with patterned Si electrodes, in conjunction with direct observations of mechanical degradation using in operando atomic force microscopy. Monitoring both strain and crack formation in SEI provides new in-depth understanding of SEI fracture. These results verify that crack formation occurs during lithiation (this has been predicted previously but not directly observed). Additional SEI formation at low potentials did not fill these cracks, which directly contradicts prior speculation. These experiments also made it possible to estimate the fracture toughness of the SEI (a key value that has not been previously measured).

Advances in Understanding Materials for Rechargeable Lithium Batteries by Atomic Force Microscopy

“…They conclude that the lateral Si expansion alters the SEI formation and tensile strains aggravate extensive cracks. This investigation enhances in‐depth understanding of the mechanical property of the surface passivation films and correlates the chemical–mechanical degradation with capacity fade in LIBs . Then, they use in situ AFM and electrochemical lithium loss measurement to compare the SEI formation and evolution of patterned silicon islands and continuous silicon thin films.…”

“…This investigation enhances in-depth understanding of the mechanical property of the surface passivation films and correlates the chemical-mechanical degradation with capacity fade in LIBs. [51] Then, they use in situ AFM and electrochemical lithium loss measurement to compare the SEI formation and evolution of patterned silicon islands and continuous silicon thin films. They plot the irreversible capacity versus strain map to determine the relationship between mechanical deformation in the SEI layer and capacity at different states of charge.…”

Challenges and Recent Progress in the Development of Si Anodes for Lithium‐Ion Battery

“…[34] Recently, in situ and operando atomic force microscopy was used for mechanical property of SEI, of which the fracture energy is estimated to be ≈13 J m −2 . [35] Although nanosized materials can achieve stable long cycling electrochemical performance by addressing materials pulverization and unstable SEI problem through elegant structure designs, there are also challenges related to nanosized materials, including low initial Coulombic efficiency, low tap density leading to low electrode mass loading and low areal capacity, and high cost. In the following sections, we will summarize [42] Copyright 2014, Nature Publishing Group.…”

Effect of Collector Roughness on Properties of Amorphous Silicon Thin‐Film Anodes

“…So the silicon anode with favorable specific capacity for high‐capacity electronic devices is expected to replace the graphite anode. However, the silicon anode materials have not been put into practical use since the huge volume expansion (up to 280 %) during the charge‐discharge process . Severe volume expansion results in the pulverization of silicon materials and separation of active materials from current collectors, which prevents the formation of the stable solid electrolyte interface film (SEI) .…”

“…However, the silicon anode materials have not been put into practical use since the huge volume expansion (up to 280 %) during the charge-discharge process. [5][6][7][8] Severe volume expansion results in the pulverization of silicon materials and separation of active materials from current collectors, which prevents the formation of the stable solid electrolyte interface film (SEI). [9][10] Since the silicon surface is in direct contact with the electrolyte, the lithium ions are consumed continuously in order to forming new SEI film, which is responsible for the rapid decrease in the reversible capacity and for the poor cycle performance.…”