Yue Qi1
Brown University1
Li metal is the preferred anode material for high energy Li batteries. However, stable plating and stripping of Li metal in both liquid and solid electrolytes remain a significant challenge, particularly at practically feasible current densities. This Li/electrolyte interface is further complicated by a complex solid electrolyte interface (SEI). The electronic, ionic, and mechanical properties of the Li/SEI interface can significantly change the Li plating and stripping morphology.<br/>A Density Functional Theory (DFT) informed phase-field method was developed to integrate electrochemistry with mesoscale plating morphology. It revealed that the Li intergranular growth in Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> solid electrolytes originated from the trapped electrons at grain boundaries and internal surfaces. This phenomenon is material specific, as several other key solid electrolytes do not trap electrons at grain boundaries or internal defects. [1]<br/>The lithium stripping process generates vacancies, which may accumulate as voids and lead to uneven current distribution and dendrite growth in the following plating cycles. A stack pressure is typically required during stripping, causing large scale lithium metal creep. Here, we captured the multiple length and time scales by combing interface interactions with DFT simulations, vacancy hopping with kinetic Monte Carlo (KMC), and plastic deformation with continuum simulations. Generally lithiophilic interface requires less stack pressure to maintain a flat surface while a higher stack pressure is needed at lithiophobic interfaces to accelerate Li vacancy diffusion into the bulk and maintain a flat surface. This critical stack pressure needs to be high enough to alter the Li forward-and-backward hopping barriers at the interface. This multiscale simulation scheme illustrates the importance of including the chemical-mechanical effects during Li stripping morphology evolution. [2,3]<br/><br/><br/>H.K. Tian et al., Chemistry of Materials 2019, 31(18) 7351-7359<br/>C.T. Yang and Y. Qi, Chemistry of Materials 2021, 33, 2814-2823<br/>M. Feng, C.T. Yang, and Y. Qi, J. Electrochem. Soc. 2022, 169 (9), 090526