The effect of boron-based additives on the performance of lithium anode and underlying logic for developing optimization strategies

Numerous defects in lithium (Li) metal secondary batteries are closely related to dendrite formation on the lithium metal anode (LMA). This study investigates the influence of lithium difluorooxaloborate (LiDFOB) on the apparent electrochemical performance of LMA in pyran electrolytes. Combining scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) results, a close correlation among the morphology of the deposition layer, the chemical composition of the solid electrolyte interphase (SEI), and the apparent performance of LMA is revealed. By analyzing the reaction kinetics mechanism, this study reveals that the critical step determining dendrite formation and apparent performance of LMA is the electro-crystallization step. Dendrite is a state with uneven curvature and high specific surface energy. Using AC voltammetry techniques, COMSOL Multiphysics simulations, and density functional theory (DFT) calculations, we model and analyze the regulatory effects of LiDFOB on electric double layer (EDL). Based on the above results, the underlying logic of electrolyte composition regulating crystallization kinetics is revealed as follows: chemical factors of electrolyte ∼ surface excess charge density ∼ surface (interface) tension characteristics ∼ nucleus curvature ∼ electro-crystallization kinetics behavior. This underlying logic not only explains the frequent occurrence of uneven curvature states from the perspective of thermodynamic principles but also provides fundamental guidance for developing new strategies to enhance the performance of LMA.