Understanding and mitigating degradation mechanisms of Li-ion batteries

Application of Li-ion batteries in electric vehicles requires improved safety, increased lifetime and high charging rates. One of the most commonly used intercalation anode material for Li-ion batteries, graphite, is vulnerable to Li nucleation, a side reaction which competes with the intercalation process and leads to loss of reversible capacity of the battery, ageing and short-circuits.

In this work, which is part of the Faraday Institution Multiscale Modelling Project, we performed ONETEP DFT calculations using our new solvent, electrolyte and voltage control models, for the first time in an electrochemical cell, to study the nucleation and growth of Li clusters on graphite anodes. We find the voltage below which the nucleation becomes favourable as a function of the size of nucleated clusters, lithiation state, and site of deposition and show that the nucleation and growth is favoured on the zigzag edge termination of the graphite electrode and on the lithiated graphite. In contrast to previous simulations that have been done in vacuum and under charge rather than voltage control, our approach can be calibrated with respect to common reference electrodes such as the standard hydrogen electrode and the Li-metal electrode, which is used as a reference electrode in Li-ion batteries, to produce predictions that “use the same language” and are readily accessible to experimentalists. It opens the door to a new frontier in materials science: computational electrochemical interface design, and we expect it will lead to a significant amount of high impact research in this technologically important area.

Our analysis has profound implications for the occurrence, avoidance and control of metal dendrite growth in a battery cell through ab-initio simulation. The resulting thermodynamic parameters  represent the very first step of subsequent kinetic analyses for in-silico predictions of important results before experimental verification, leading to rapid discovery of new electrolytes and charging procedures to improve safety and lifetime of future cells.

More information can be found in this paper:

Li nucleation on the graphite anode under potential control in Li-ion batteries. A. Bhandari, C. Peng, J. Dziedzic, J.R. Owen, D. Kramer, C.-K. Skylaris, J. Mater. Chem. A, 2022,10, 11426-11436 (pdf)