Mesoscale Anatomy of Dead Lithium Formation

Abstract

Lithium metal anodes are an attractive option for next-generation batteries because of high gravimetric and volumetric energy densities. The formation of dendritic morphology of electrodeposition during charging, however, poses safety concerns, which, in particular, have been a focus of intense research. The formation of “dead lithium” with successive cycling, on the other hand, has been relatively unexplored as the deterioration in performance is gradual. Dead lithium is the fragment of lithium that is detached from the lithium electrode during electrodissolution or stripping. In this study, the mesoscale underpinnings of dead lithium formation via a synergistic computational and experimental approach are presented. The mechanistic focus centers on the morphological evolution of the lithium electrode–electrolyte interface and the relative quantification of dead lithium formation under a range of operating temperatures and currents. This study reveals that the amount of dead lithium formed during stripping increases with decreasing current and increasing temperatures. This finding is in direct contrast to the operating conditions that lead to dendritic deposition during charging, i.e., at higher currents and lower temperatures. During stripping, more dead lithium is formed when the interface has thin narrow structures. The ionic diffusion and self-diffusion of lithium at the interface play a key role in the evolution of narrow structures at the interface. Therefore, more dead lithium is formed when diffusive processes are facilitated compared to the oxidative reaction at the interface.

Strategies towards enabling lithium metal in batteries: interphases and electrodes

“…29 More dead lithium remains for lower stripping current densities. 30,31 stainless steel more smoothly and became flatter and slightly larger, which agrees nicely with the prediction from nucleation theory based on the increased surface energy. 33 Nucleation is closely linked to defect sites as lithium deposits nucleate heterogeneously.…”

“…2d. 30,31 Tewari et al argued that with low overpotentials during stripping, the process is reaction limited, leading to lithium stripping at preferential points, disconnecting other parts from the current collector. 30,31 Thus, the plating as well as the stripping current density strongly influences the evolution of the lithium morphology during cycling.…”

“…30,31 Tewari et al argued that with low overpotentials during stripping, the process is reaction limited, leading to lithium stripping at preferential points, disconnecting other parts from the current collector. 30,31 Thus, the plating as well as the stripping current density strongly influences the evolution of the lithium morphology during cycling. For lithium foils, there is a need for strategies to realize 2D plating with as few structurerelated inefficiencies as possible to meet the requirements for practical lithium metal batteries of average Coulombic efficiencies well above 99.8%.…”

Review of Emerging Concepts in SEI Analysis and Artificial SEI Membranes for Lithium, Sodium, and Potassium Metal Battery Anodes

“…In addition, progressively more studies recognize the critical role of surface ion diffusivity in inhibiting dendrite and "dead Li" formation. [62,63] For example, how dead Li affects ion diffusion and the plating-stripping process was examined by Dasgupta and co-workers. [59] Recently, Meng and co-workers [50] established an analytical method of titration gas chromatography to quantify the contribution of unreacted metallic Li 0 in dead Li to the total amount of inactive lithium, which is otherwise tied up as Li + in various compounds.…”

“…In addition, progressively more studies recognize the critical role of surface ion diffusivity in inhibiting dendrite and “dead Li” formation. [ 62,63 ] For example, how dead Li affects ion diffusion and the plating–stripping process was examined by Dasgupta and co‐workers. [ 59 ]…”