Insight into the Formation and Stability of Solid Electrolyte Interphase for Nanostructured Silicon-Based Anode Electrodes Used in Li-Ion Batteries

Abstract

Silicon-based anode fabrication with nano-scale structuration improves the energy density and life cycle of Li-ion batteries. As-synthesized silicon (Si) nanowires (NWs) or nanoparticles (NPs) directly on the current collector represent a credible alternative to conventional graphite anode. However, the operating potentials of these electrodes are below the electrochemical stability window of all electrolytes used in commercial Li-ion systems. During the first charging phase of the cell, partial decomposition of the electrolyte takes place, which leads to the formation of a layer at the surface of the electrode, called Solid Electrolyte Interphase (SEI). A stable and continuous SEI layer formation is a critical factor to achieve reliable life-time stability of the battery. Once formed, the SEI acts as a passivation layer that minimizes further degradation of the electrolyte during cycling, while allowing lithium ions diffusion with their subsequent insertion into the active material and ensures reversible operation of the electrode. However, one of the major issues requiring deeper investigation is the assessment of the morphological extension of the SEI layer into the active material which is one of the main parameters affecting the anode performances. In the present study, we use electron tomography (ET) with low electron dose to retrieve three-dimensional information on the SEI layer formation and its stability around SiNWs and SiNPs. The possible mechanisms of the SEI evolution could be inferred from the interpretation and analysis of the reconstructed volumes. Significant volume variations in the SiNW and an inhomogeneous distribution of the SEI layer around the NWs are observed during cycling and provide insights of the potential mechanism leading to the generally reported SiNWs anodes capacity fading. By contrast, analysis of the reconstructed SiNPs' volume for a sample undergoing one lithiation-delithiation cycle evidence that the SEI remains homogeneously distributed around the NPs that retain their spherical morphology and points to the potential benefit of such nanoscale Si anode materials to improve their cycling lifetime.

Nanostructuring Strategies for Silicon‐based Anodes in Lithium‐ion Batteries: Tuning Areal Silicon Loading, SEI Formation/Irreversible Capacity Loss, Rate Capability Retention and Electrode Durability

“…The SiNPs size increases to 40 nm when the deposition time is increased to 10 minutes, as shown in Figure 3(c). Regarding the SiNPs localization on the CNT sidewalls, our previous studies using electron tomography technique helped us assessing their 3D localization which can reasonably be correlated to the presence of point‐defects on the external graphitic structure of the tube [28] . These defects, formed during the nanotube growth, can be considered as anchorage points for the Si precursors that nucleate into seeds and start increasing their volume to form SiNPs by continuous local SiH 4 gas decomposition.…”

“…Regarding the SiNPs localization on the CNT sidewalls, our previous studies using electron tomography technique helped us assessing their 3D localization which can reasonably be correlated to the presence of point-defects on the external graphitic structure of the tube. [28] These defects, formed during the nanotube growth, can be considered as anchorage points for the Si precursors that nucleate into seeds and start increasing their volume to form SiNPs by continuous local SiH 4 gas decomposition. This morphology evolution also induces a modification of the overall SiNPs specific surface area, which tends to decrease with the increase of the deposition time, as it is clearly evidenced by comparing the 5 minutes deposited samples with the 10 minutes deposited ones.…”

Prediction of SEI Formation in All‐Solid‐State Batteries: Computational Insights from PCL‐based Polymer Electrolyte Decomposition on Lithium‐Metal

“…However, performing multiple runs of AIMD simulations and averaging them is computationally very demanding. Our results in this study are based on the single run of AIMD simulations, as in the recent theoretical studies [69–71] . The structural stability of the electrolyte mixture is analyzed using the evolution of the total energy during the simulation time.…”

“…Our results in this study are based on the single run of AIMD simulations, as in the recent theoretical studies. [69][70][71] The structural stability of the electrolyte mixture is analyzed using the evolution of the total energy during the simulation time. Figure S2 shows the variation of the total energy versus the dynamic step in AIMD simulations at 450 K for the pure electrolyte mixture.…”

Guar Gel Binders for Silicon Nanoparticle Anodes: Relating Binder Rheology to Electrode Performance

“…Silicon is a promising alternative to conventional graphite anodes for Li-ion batteries (LIBs), as Si has a specific capacity (Li 3.75 Si, 3579 mAh g –1 ) approximately 10 times that of graphite (LiC 6 , 372 mAh g –1 ). , However, structural rearrangements upon charge–discharge cycling limit the use of Si in commercial cells . Si particles undergo volume expansions >300% at full lithiation, and mechanical stresses at such large volume expansions cause cracks and formation of a solid-electrolyte interphase (SEI) on the newly exposed Si surface, which irreversibly consumes lithium. The SEI is an electronic insulator, and recurrent cracking results in the electronic isolation of Si particles and untimely cell failure.…”