A Physical Impedance Model of Lithium Intercalation into Graphite Electrodes for a Coin‐Cell Assembly

Abstract

Graphite electrodes are widely used in commercial metal‐ion batteries as anodes. Electrochemical impedance spectroscopy serves as one of the primary non‐destructive techniques to obtain key information about various batteries during their operation. However, interpretation of the impedance response of graphite electrodes in contact with common organic electrolytes can be complicated. It is especially challenging, particularly when utilizing the 2‐electrode configuration that is common in battery research. In this work, we elaborate on a physical impedance model capable of accurately describing the impedance spectra of a graphite|electrolyte|metallic Li system in a coin‐cell assembly during two initial charge/discharge cycles. We analyze the dependencies of the model parameters for graphite and metallic lithium as a function of the state of charge to verify the model. Additionally, we suggest that the double layer capacitance values obtained during specific intercalation stages could help to determine if the area‐normalized values align with the expected range. The data and the procedure necessary for calibration are provided.

Effect of Graphene on the Performance of Silicon–Carbon Composite Anode Materials for Lithium-Ion Batteries

“…This study demonstrated that the proposed (Si/graphite/graphene)@C promising anode material for LIBs with high energy density requirements. The presence of a straight line in electrochemical impedance spectra typically reveals lithium-ion diffusion kinetics [35,36]. The effective lithium-ion diffusion coefficient can be evaluated by the following equation [37,38]:…”

Ion Depletion Microenvironments Mapped at Active Electrochemical Interfaces with Operando Freezing Cryo-Electron Microscopy

“…Cryogenic electron microscopy (cryo-EM) has emerged as a solution to the latter problem, enabling multimodal studies of beam-sensitive electrode or electrolyte materials and their interfaces; − however, traditional cryo-EM sample preparations for battery materials are ex situ and time-consuming. Batteries must be disassembled under an inert atmosphere after electrochemical cycling, a process that takes on the order of 10 3 s and often damages or destroys solid–liquid interfaces by allowing the electrolyte to dry before freezing. ,, Even when care is taken to preserve and vitrify a layer of electrolyte for cryo-EM, , ion diffusion coefficients are in the range of 10 –6 cm 2 s –1 in typical battery liquid electrolytes and diffusion layers are expected to be 10 –6 –10 –5 m thick; , thus, operando ion concentration profiles should relax well before ex situ freezing occurs. This makes it impossible to directly visualize the local microenvironments and resulting kinetic limitations that underpin safety and stability in practical batteries by using existing characterization techniques.…”