Intercalation of Lithium into Graphite: Insights from First-Principles Simulations

Abstract

Understanding ion intercalation at electrode–electrolyte interfaces is key to the development of energy storage and water desalination. In this work, we investigate Li+ kinetics at a prototypical interface between graphite anodes and an organic electrolyte, and we elucidate key factors that determine ion transport, using first-principles methodology coupling ab initio molecular dynamics simulations with a solvation model. We show that surface chemical composition significantly influences the kinetics of ion intercalation from the liquid into graphite. We find that this is partly related to the ion desolvation process, which varies notably for different graphite surface chemical terminations. In addition, interfacial polarization is found to play an important role in determining energy barriers for ion transfer. We also discuss the impact of electrode potentials, which is often neglected in conventional first-principles calculations despite being a key factor in device configurations. Our study provides insights into the coupling of electronic and ionic effects of interfacial chemistry on ion transport at complex electrode–electrolyte interfaces.

Enabling Fast‐Charging Lithium‐Ion Battery Anodes: Influence of Spheroidization on Natural Graphite

“…Therefore, fast-charging performance can be achieved with optimization of the overall cell design and components including active and non-active materials, electrode architecture, separator and electrolyte. [2][3][4][5][6][7][8] At the electrode level, reduced mass loading generally improves the rate performance at the expense of energy density. Hence, electrode properties (such as loading, porosity, density, electric conductivity and tortuosity) need to be tailored carefully to meet both requirements of fast kinetics and high energy density.…”

“…[5] At the interface between the liquid electrolyte and the graphite, the charging process comprises of very complex intermediate steps (desolvation of the lithium ions, their migration through the solid electrolyte interface -SEI, access to the edge-planes of the graphite structure, and finally intercalation between the graphene layers into the graphite bulk), each with specific reaction kinetics. [6,7] Indeed, many studies have suggested that the lithium intercalation process and its related kinetics are the main factors determining the fast-charging ability of the whole battery system. [8][9][10] Even though the mechanism of interface reactions and the rate-determining step of the lithium intercalation reaction remain partly unclear due to their complexity, the importance of the carbon surface is well established.…”

“…Besides the intrinsic kinetics of the lithiation/de‐lithiation process of the active materials, the charging rate of a Li‐ion cell depends on many factors at different levels, encompassing all steps from the electrode manufacturing methods to the cell charging procedure. Therefore, fast‐charging performance can be achieved with optimization of the overall cell design and components including active and non‐active materials, electrode architecture, separator and electrolyte [2–8] . At the electrode level, reduced mass loading generally improves the rate performance at the expense of energy density.…”

“…When this overall process is inhibited, anode polarization occurs with consequent undesired side‐reactions (such as lithium plating and dendrite formation, and consequent safety risks) [5] . At the interface between the liquid electrolyte and the graphite, the charging process comprises of very complex intermediate steps (de‐solvation of the lithium ions, their migration through the solid electrolyte interface – SEI, access to the edge‐planes of the graphite structure, and finally intercalation between the graphene layers into the graphite bulk), each with specific reaction kinetics [6,7] . Indeed, many studies have suggested that the lithium intercalation process and its related kinetics are the main factors determining the fast‐charging ability of the whole battery system [8–10] .…”

“…Indeed, many studies have suggested that the lithium intercalation process and its related kinetics are the main factors determining the fast‐charging ability of the whole battery system [8–10] . Even though the mechanism of interface reactions and the rate‐determining step of the lithium intercalation reaction remain partly unclear due to their complexity, the importance of the carbon surface is well established [6] . The considerable advances made in the field of characterization techniques, along with the increasing quality standards required for LiB applications, led to a more nuanced understanding of the nano‐ and micro‐scale properties to target when optimizing graphite as an active material.…”