The Entanglement of Li Capping and Deposition: An Operando Optical Microscopy Study.

Dendrite growth and low Coulombic efficiency impede the practical application of Li-metal batteries. As such, monitoring Li deposition and stripping in real-time is crucial to understanding the fundamental lithium growth kinetics. This work presents an operando optical microscopic technique that enables precise current density control and quantification of Li layer properties (i.e., thickness and porosity) to study Li growth in various electrolytes. We discover the robustness and porosity of the remaining capping layer after the Li stripping process as the critical features governing the subsequent dendrite propagation behavior, resulting in distinct capping and stacking phenomena that affect Li growth upon cycling. While dendrite propagation quickly occurs through the fracture of the fragile Li capping layer, uniform Li plating/stripping can be facilitated by the compact and robust capping layer even at high current densities. This technique can be extended to evaluate dendrite suppression treatments in various metal batteries, providing in-depth information on metal growth mechanisms.

Quantification of the Dynamic Interface Evolution in High-Efficiency Working Li-Metal Batteries.

Lithium (Li) metal has been considered a promising anode for next-generation high-energy-density batteries. However, the low reversibility and intricate Li loss hinder the widespread implementation of Li metal batteries. Herein, we quantitatively differentiate the dynamic evolution of inactive Li, and decipher the fundamental interplay among dynamic Li loss, electrolyte chemistry, and the structure of the solid electrolyte interphase (SEI). The actual dominant form in inactive Li loss is practically determined by the relative growth rates of dead Li0 and SEI Li+ because of the persistent evolution of the Li metal interface during cycling. Distinct inactive Li evolution scenarios are disclosed by ingeniously tuning the inorganic anion-derived SEI chemistry with a low amount of film-forming additive. An optimal polymeric film enabler of 1,3-dioxolane is demonstrated to derive a highly uniform multilayer SEI and decreased SEI Li+ /dead Li0 growth rates, thus achieving enhanced Li cycling reversibility.

In-Plane Lithium Growth Enabled by Artificial Nitrate-Rich Layer: Fast Deposition Kinetics and Desolvation/Adsorption Mechanism.

An artificial lithium-nitrate (LiNO3 )-rich layer (LN-RL) is developed to address dendritic lithium (Li) growth by a fusing-infusing strategy, in which LiNO3 is loaded into stainless steel mesh and a Li-metal anode (LN-RL@Li) is obtained by casting this LN-RL onto Li foil. The LN-RL enables fast Li deposition kinetics in carbonates and endows LN-RL@Li with excellent cycleability. The underneath mechanism on the contribution of LN-RL is uncovered by detailed characterizations combining with theoretical simulations. The LN-RL promotes the desolvation and capacitive adsorption of Li ions and induces in-plane Li growth along the edges of preplated Li with planar morphology. The improved cycleability of LN-RL(@Li) is demonstrated by LiǁCu cell that presents a coulombic efficiency of 97.2% after 280 cycles and LiǁLi cell that proceeds over 1000 h at 0.5 mA cm-2 in carbonates. Additionally, the LiǁLiFePO4 cell shows a capacity retention of 58% after 400 cycles at 1 C (1 C = 170 mA g-1 ), compared to the 35% after 180 cycles for the control. This work presents not only a promising strategy for practical applications of Li-metal batteries, but also a new understanding on the role of nitrate in Li plating/stripping kinetics.