Lithium insertion into silicon electrodes studied by cyclic voltammetry andoperandoneutron reflectometry

Abstract

Operando neutron reflectometry measurements were carried out to study the insertion of lithium into amorphous silicon film electrodes during cyclic voltammetry (CV) experiments at a scan rate of 0.01 mV s-1. The experiments allow mapping of regions where significant amounts of Li are incorporated/released from the electrode and correlation of the results to modifications of characteristic peaks in the CV curve. High volume changes up to 390% accompanied by corresponding modifications of the neutron scattering length density (which is a measure of the average Li fraction present in the electrode) are observed during electrochemical cycling for potentials below 0.3 V (lithiation) and above 0.2 V (delithiation), leading to a hysteretic behaviour. This is attributed to result from mechanical stress as suggested in the literature. Formation and modification of a surface layer associated with the solid electrolyte interphase (SEI) were observed during cycling. Within the first lithiation cycle the SEI grows to 120 Å for potentials below 0.5 V. Afterwards a reversible and stable modification of the SEI between 70 Å (delithiated state) and 120 Å (lithiated state) takes place.

Enabling High‐Energy Solid‐State Batteries with Stable Anode Interphase by the Use of Columnar Silicon Anodes

“…The recorded EIS spectra were identical with each other from 2 to 0.25 V and therefore were neglected. This behavior is consistent as the CV measurement shows neither a peak nor a sloping at ≈ 0.20 V in the cathodic branch that can originate from SEI formation or reaction of silicon dangling bonds with Li + , [ 38 ] which can alter EIS spectra significantly.…”

“…In the cathodic scan, a‐Si exhibits three phase transformations, i.e., from a‐Si to PI phase (Li‐50 at% Si; LiSi) at 0.21 V, in parallel with the formation of PII phase (Li‐30 at% Si; Li 7 Si 3 ) from PI and formation of PIII (Li‐24 at%; Li 3.16 Si) from PII at 0.05 V. [ 38 ] In the anodic scan two peaks appear at 0.29 and 0.49 V, which are simply reverse transformation processes; PIII‐PII, PII‐I, and formation of a‐Si, respectively. [ 34 ]…”

Impact of Surface Chemistry of Silicon Nanoparticles on the Structural and Electrochemical Properties of Si/Ni3.4Sn4 Composite Anode for Li-Ion Batteries

“…This agglomeration favorizes discrete volume changes, leading to electrode cracking [19] and severe capacity decay for the bare Si R -NiSn composite, as observed in Figure 6a. [20,38,44]. The detected dQ/dV peaks for the first galvanostatic cycle in the bare SiR-NiSn composite are consistent with the coexistence of pure Si and Sn phases ( Table 2).…”

“…However, Si electrodes suffer from severe volume expansion during lithiation (up to 400%) [18]. Such swelling induces several drawbacks from the very first cycles like amorphization, delamination and capacity degradation, which are unfavorable for long term cycling [19][20][21].…”

Recent Progress in Advanced Characterization Methods for Silicon‐Based Lithium‐Ion Batteries

“…Jerliu et al constructed a homemade cell and proved the feasibility of in situ neutron reflectometry (NR) investigation on lithiation owning to its Li sensitivity. In their recent study of the lithiation mechanism in amorphous Si film electrode, the penetration of Li into amorphous Si can be effectively observed during discharge. During delithiation, the formation of a thin Li‐rich surface layer several nanometers in depth on the electrode was observed, which might be identified near the SEI.…”