Understanding the Effect of Polydopamine Interlayer on the Long‐Term Cycling Performance of Silicon Anodes: A Multiphysics‐Based Model Study

Abstract

To understand the effect of a polydopamine interlayer between a copper current collector and a silicon composite electrode, a physics-based model is used to analyze the cycle performance of silicon-based lithium-ion half-cells with bare and polydopamine-treated copper current collectors. We investigate the capacity-fading mechanisms of the two cell configurations by analyzing the model parameters that change with cycling. The major capacity-fading mechanisms in the silicon-based anodes are the increase in film resistance (solid electrolyte interphase resistance and contact resistance) and the isolation of silicon active material. The polydopamine interlayer reduced the contribution of the film resistance and isolation of the silicon active material to the capacity fade by 22 % and 10 %, respectively. The insulating-nature of the polydopamine interlayer resulted in an increase in the charge transfer resistance contributing to 15 % reduction in the capacity retention. The efficacy of the physics-based model is validated with experimental data obtained from silicon-based half-cells with bare and polydopamine-treated copper current collectors.

Design of Thin-Film Interlayer between Silicon Electrode and Current Collector Using a Chemo-Mechanical Degradation Model

“…This resulted in a decrease in the rate constant for electron transfer in the BV equation. 15 Figure 4c shows the relationship between the rate constant (k p ) and number of cycles for Li/Si cells with PD-treated and bare copper foil. At the beginning of cycling, electrons tunnel through the PD-laminate, which leads to a reduction in the rate constant.…”

“…14,15,25,26 Modeling of SEI formation.-For Si-based electrodes, it has been reported that, two types of SEI are formed during the (de) lithiation processes. First is the formation of diethyl methyl 2,5dioxahexane dicarboxylate (DEDOHC) 26 during the initial stages of cycling when a mixture of ethylene carbonate/diethyl carbonate (EC: DEC) related solvents are used for the electrolyte and ethyl methyl 2, 5-dioxahexane dicarboxylate (EMDOHC) 15 when a mixture of z E-mail: mhryou@hanbat.ac.kr; yongmin.lee@dgist.ac.kr *Electrochemical Society Student Member. ethylene carbonate/ethyl methyl carbonate (EC:EMC) related solvents are used.…”

“…ethylene carbonate/ethyl methyl carbonate (EC:EMC) related solvents are used. Second is lithium ethylene dicarbonate (LiEDC) 15,26 which is formed when the lithiated Si is exposed to the electrolyte due to crack formation because of volume expansion.…”

“…Considering a step input to the system defined according to the following conditions: where the expression for the step input concentration, ( ) C N mean is determined by fitting the excess concentration of Li ions from our previous report 15 and is given as…”

“…14 A non-destructive capacity-fading analysis method was adopted identify and quantify the effect of the PD laminate on the cyclic degradation mechanisms of Li/Si cells. 15 To further understand the principles underlying the enhancement in the rate performance by the adhesive thin film laminate, a chemomechanical model considering the contact resistance and isolation of Si particles was developed to describe the various degradation mechanisms. 16 However, the chemo-mechanical model did not consider other degradation mechanisms such as the SEI formation and effect of the conductivity and design parameters of the PD laminate on the electrochemical performance.…”