Probing the Mechanically Stable Solid Electrolyte Interphase and the Implications in Design Strategies

Abstract

The inevitable volume expansion of secondary battery anodes during cycling imposes forces on the solid electrolyte interphase (SEI). The battery performance is closely related to the capability of SEI to maintain intact under the cyclic loading conditions, which basically boils down to the mechanical properties of SEI. The volatile and complex nature of SEI as well as its nanoscale thickness and environmental sensitivity make the interpretation of its mechanical behavior many roadblocks. Widely varied approaches are adopted to investigate the mechanical properties of SEI, and diverse opinions are generated. The lack of consensus at both technical and theoretical levels has hindered the development of effective design strategies to maximize the mechanical stability of SEIs. Here, the essential and desirable mechanical properties of SEI, the available mechanical characterization methods, and important issues meriting attention for higher test accuracy are outlined. Previous attempts to optimize battery performance by tuning SEI mechanical properties are also scrutinized, inconsistencies in these efforts are elucidated, and the underlying causes are explored. Finally, a set of research protocols is proposed to accelerate the achievement of superior battery cycling performance by improving the mechanical stability of SEI.

Approaching Microsized Alloy Anodes via Solid Electrolyte Interphase Design for Advanced Rechargeable Batteries

“…Tip-enhanced Raman spectroscopy (TERS) has enabled a sampling depth of <5 nm and lateral resolution of <10 nm. [85,112] Nanda et al [85] adopted the TERS technique to acquire nanoscale topography and chemical mapping of SEI layer generated on an amorphous Si anode (Figure 2j). Recently, Gajan et al [86] investigated the dynamic composition variation in the electrode/electrolyte interphase using shell-isolated nanoparticle-enhanced Raman spectroscopy conditions, revealing the origin of the irreversible capacity of Sn electrodes in LIBs.…”

“…Mechanical Properties and Ionic Conductivity: The mechanical test of SEI has been thoroughly reviewed in previous work. [112] As it is challenging to prepare a freestanding SEI layer, AFM-based nanoindentation is the most test to examine the mechanical properties of SEI layer. [9,119,120] As illustrated in Figure 2l, Gao et al [9] optimized and designed a two-step AFM-based nanoindentation test to separately analyze elastic and plastic features of SEI layer.…”

The Critical Role of Fillers in Composite Polymer Electrolytes for Lithium Battery

“…The interfacial stability is determined by poor electrolyte–electrode contact, lithium dendrite growth and high-pressure decomposition [ 27 ]. To solve these problems, CPEs with the advantages of two components (organic and inorganic) become popular in recent years [ 158 , 159 ].…”

Structural Toughness of Fluorinated–Nitrided Interphase Passivation Layers for Lithium-Ion Batteries: A Reactive Molecular Dynamics Study

“…The proliferation of portable electronic devices and growing popularity of electric vehicles have reinvigorated efforts at improving Li-ion batteries (LIBs). , Among them, Li metal batteries (LMBs) have garnered significant recognition owing to the ultrahigh theoretical specific capacity and extremely low electrochemical redox potential of the Li metal anode. , However, performance degradation and safety concerns owing to instability of the solid electrolyte interphase (SEI) continue to limit the widespread applicability of LMBs. − The SEI is a passivation layer formed from the decomposition of electrolytes upon contact with the electrode. − As a surface film, it naturally plays a significant role in the stabilization of the electrode/electrolyte interface. For that, the SEI needs to be selective in nature: it should be electronically insulating while allowing Li + ion to diffuse, and it must be structurally stable with intrinsic resistance to mechanical fracture. − Hence, careful control of the SEI composition is crucial for optimizing the performance and lifespan of LIBs.…”