Two-Stage Growth of Solid Electrolyte Interphase on Copper: Imaging and Quantification by Operando Atomic Force...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• The solid electrolyte interphase (SEI) significantly impacts lithium-ion battery aging.
• Accurate SEI growth models are essential for developing longer-lasting batteries, but quantitative measurements are challenging due to nanoscale heterogeneity and environmental sensitivity.

Purpose of the Study:

• To quantitatively track SEI growth dynamics on copper electrodes in carbonate electrolytes using operando electrochemical atomic force microscopy.
• To differentiate and characterize the distinct growth regimes of the SEI and their impact on battery performance.

Main Methods:

• Utilized operando electrochemical atomic force microscopy to monitor SEI thickness and irreversible capacity in real-time.
• Analyzed the relationship between SEI thickness, charge passed, and electrochemical capacity loss to quantify SEI compactness.

Main Results:

• Observed two distinct SEI growth regimes: an early-stage primary SEI and a later-stage secondary SEI.
• The primary SEI is approximately ten times more electrochemically compact than the secondary SEI.
• Nanoscale substrate defects influence SEI morphology, indicating initial growth is not solely transport-limited.
• Primary SEI contributes significantly to irreversible capacity loss despite its thinness.

Conclusions:

• SEI growth occurs in two modes: initial reaction-limited nucleation and growth of a dense primary SEI, followed by diffusion-limited growth of a porous secondary SEI.
• The primary SEI passivates the electrode surface, governing subsequent growth.
• Understanding these dual growth mechanisms is key to engineering improved battery electrode materials and enhancing battery lifespan.