Migration Barrier Estimation of Carbon in Lead for Lead–Acid Battery Applications: A Density Functional Theory Approach

Recent efforts towards developing novel lead electrodes involving carbon and lead composites have shown potential for increasing the cycle life of lead–acid (LA) batteries used to store energy in various applications. In this study, first-principles calculations are used to examine the structural stability, defect formation energy, and migration barrier of C in Pb for LA batteries. Density functional theory with the GGA-PBE functional performed the best out of various functionals used for structural stability calculations. Furthermore, with the complete incorporation of C in the Pb matrix, the results show that C is energetically preferred to be at the octahedral interstitial (CiOcta) site in the FCC structure of Pb. Additionally, climbing-image nudged elastic band calculations show a minimum energy pathway for C diffusing from a stable octahedral site to the adjacent octahedral site assisted by a tetrahedral intermediate site. Therefore, the minimum energy pathway for C migration is envisioned to be CiOcta→ CiTetra→CiOcta, where the total energy barrier is observed to be ~90% and more than 100% lower than the CiTetra→CiTetra and CiOcta→CiOcta barriers, respectively.