Unravelling the electrochemical impedance spectroscopy of silicon half cells with commercial loading

Abstract

Silicon (Si) is an important anode material for lithium ion batteries (LIBs), and increasing the loading of Si electrodes is an important step towards commercialization. However, half cells commonly used...

New Insights into the Behaviour of Commercial Silicon Electrode MaterialsviaEmpirical Fitting of Galvanostatic Charge‐Discharge Curves

“…[32] The results of the DRT analysis at 0.07 V are shown in Figure 3c, and these show large changes in the peak at 10 3 Hz associated with the Li CE. [1,24] Over the course of the first 21 cycles this peak grows and shifts to slightly lower frequencies, but after this point the trend reverses and the peak shrinks and shifts to higher frequencies. This may be explained by crack formation in the SEI leading to reduced Li + diffusion resistance.…”

“…This shows how the EIS changes depending on the potential, with the spectrum at 0.07 V in particular showing a very large impedance loop due to the Li (CE). [1,24,31] Figure 1c shows an example of one of the C/3 cycles in Figure 1a after baseline subtraction against the potential (vs Li/Li + ). The orange line denotes the fit of Eq.…”

“…This can be elucidated by analysing the distribution of relaxation times (DRT). [1,24,32] DRT analysis is a method for deconvoluting the time constants τ of an EIS spectrum. This technique relies upon the assumption that the response of an electrochemical system to a perturbation (such as an oscillating potential) decays exponentially at a particular distribution of timescales.…”

“…Electrode slurries were prepared by high-speed stirring in a manner described previously, using SL650-SOC (Iopsilion) as the active material. [24] Electrode sheets were made by coating onto 10 mm thick copper foil using a doctor blade with a blade height of 130 mm and dried at room temperature. This yielded electrodes with a material loading of 3.27 mg/cm 2 and a thickness of 48 mm.…”

“…[6] Further, the use of lithium (Li) metal as counter electrode (CE) for studying Si has been shown to have significant effect on the results. [1,[24][25][26] Phase I (Eq. ( 4)) exists at low potentials vs Li/Li + , forming Li 3.5 Si at 0.07 V during lithiation and Li 2 Si at around 0.3 V during delithiation.…”