High damage tolerance of electrochemically lithiated silicon

Abstract

Mechanical degradation and resultant capacity fade in high-capacity electrode materials critically hinder their use in high-performance rechargeable batteries. Despite tremendous efforts devoted to the study of the electro–chemo–mechanical behaviours of high-capacity electrode materials, their fracture properties and mechanisms remain largely unknown. Here we report a nanomechanical study on the damage tolerance of electrochemically lithiated silicon. Our in situ transmission electron microscopy experiments reveal a striking contrast of brittle fracture in pristine silicon versus ductile tensile deformation in fully lithiated silicon. Quantitative fracture toughness measurements by nanoindentation show a rapid brittle-to-ductile transition of fracture as the lithium-to-silicon molar ratio is increased to above 1.5. Molecular dynamics simulations elucidate the mechanistic underpinnings of the brittle-to-ductile transition governed by atomic bonding and lithiation-induced toughening. Our results reveal the high damage tolerance in amorphous lithium-rich silicon alloys and have important implications for the development of durable rechargeable batteries.

Fracture Toughness Characterization of Lithiated Germanium as an Anode Material for Lithium-Ion Batteries

“…Figure 6 shows a direct comparison between the fracture energy of lithiated Ge obtained in this work and the previously measured fracture energy of lithiated Si. 22 The fracture energy of pristine Si is 3 J/m 2 which is slightly higher than that of unlithiated Ge of 2.33 J/m and discharging if the concentration of Li is low. At higher levels of Li, the fracture energy of lithiated Si increases with the Li content, indicating that Si undergoes a brittle-to-ductile transition as lithiation proceeds.…”

“…In our previous work, we also combined in situ TEM study and reactive-force field molecular dynamics (MD) simulations with nanoindentation testing to gain mechanistic insights into the fracture mechanisms of lithiated Si. 22 All of the three different techniques have consistently shown that lithium-rich Si is more damage tolerant than lithium-lean Si. The interested reader is referred to there for more details.…”

“…Fracture toughness measurement by nanoindentation.-An inhouse developed nanoindentation system situated inside an argonfilled glove box 22 was employed to measure the fracture toughness of lithiated Ge electrodes. Fracture indentation tests were performed using a diamond cube-corner tip and monitored by a long working distance (WD) microscope.…”

“…In the present work, the direct measurement of the fracture toughness of lithiated Ge is performed by applying a nanoindentation method that we have previously developed. 22 Furthermore, we compare the fracture resistance of lithiated Ge with that of lithiated Si 22 and assess the suitability of the materials for use in high-performance LIBs. The quantitative fracture characteristics obtained in our work provide fundamental insights for engineering new Ge-based electrodes and optimizing the microstructures of advanced LIBs.…”

Bi-objective optimal design of a damage-tolerant multifunctional battery system

“…Consequently, several research groups have been investigating approaches to damage tolerant batteries, see e.g. [4,5]. The present study focusses on damage tolerant battery systems [6], whereby damage tolerance is imparted by (micro)-structural features of the battery pack rather than by alternations to the battery composition.…”