Understanding the Mechanism of Stress Mitigation in Selenium-Doped Germanium Electrodes

Abstract

This paper aims to investigate the mechanism of stress mitigation in micrometer (μm) sized Selenium (Se)-doped Germanium (Ge) electrode, which includes a self-forming inactive Li-Ge-Se network enveloping multiple nanometer-sized crystalline Ge (c-Ge) particles. Considering the electrode system contains multiply active particles, models based on single-particle are unable to fully understand elusive underpinning mechanism. Hence, a phase-field model is employed to investigate the effect of the Li-Ge-Se network on the particle-particle interaction, and the stress variation of the electrode upon lithiation. The amorphous Li-Ge-Se network provides an effective Li diffusion path for inter-particle diffusion, reducing stress difference between the surfaces of neighboring particles. Furthermore, the constraint between the adjacent particles induces a higher compressive stress at the reaction front impeding the mobile Li insertion during lithiation. Though small c-Ge nano-particle in the Ge 0.9 Se 0.1 microparticle is lithiated quickly, the compressive stress is generated at its center for stress equilibrim causing more retardation effect. Meanwhile, the size difference between adjacent particles increases the principle and shear stresses in the inactive Li-Ge-Se, which could potentially lead to mechanical failure and debonding of the amorphous network. We believe that the results of this investigation can shed some light on the optimization design of electrodes.

Blade-Type Reaction Front in Micrometer-Sized Germanium Particles during Lithiation

“…The two-phase transport with a core–shell structure has also been discovered in nanometer-sized Ge, such as Ge nanoparticles and Ge nanowires . In recent years, computational studies using the two-phase Li transport model with a core–shell structure have been conducted to understand Li transport behavior and stress/strain generation in Si and Ge particles with both micrometer and nanometer sizes during battery cycling. ,− Although the two-phase core–shell model has been used in micrometer (μm)-sized alloy particles, there is no experimental evidence to validate it because of the sample size requirement for in situ TEM characterizations. In addition to the core–shell structure with a sharp boundary, a finger-type Li transport process has been discovered in a two-dimensional (2D) NiO nanosheet during the lithiation process .…”

Design Principles for Dendrite Suppression with Porous Polymer/Aqueous Solution Hybrid Electrolyte for Zn Metal Anodes

“…Phase-field simulations have been widely adopted to understand the morphological evolution during electrodeposition for metal anodes and to unveil the kinetics and underlying physics of the electrodeposition process, particularly related to the dendrite growth mechanisms, − as well as the coupling of the electrodeposition kinetics with specific mechanical properties. − In this work, we extend the previously developed nonlinear grand potential-based phase-field model , to incorporate a mechanical equilibrium equation to study the influence of the mechanical properties of the hybrid electrolyte system on the electrodeposition kinetics. Herein, we theoretically analyze the design space of one formulation of the hybrid electrolyte concept in a porous polymer/aqueous ZnSO 4 solution mixed electrolyte system which utilizes both the high conductivity of the liquid aqueous electrolyte and the mechanical suppression effect from the solid polymer framework.…”