In situ observation of cracking and self-healing of solid electrolyte interphases during lithium deposition

Resolving Current-Dependent Regimes of Electroplating Mechanisms for Fast Charging Lithium Metal Anodes

Poor fast-charge capabilities limit the usage of rechargeable Li metal anodes. Understanding the connection between charging rate, electroplating mechanism, and Li morphology could enable fast-charging solutions. Here, we develop a combined electroanalytical and nanoscale characterization approach to resolve the current-dependent regimes of Li plating mechanisms and morphology. Measurement of Li⁺ transport through the solid electrolyte interphase (SEI) shows that low currents induce plating at buried Li||SEI interfaces, but high currents initiate SEI-breakdown and plating at fresh Li||electrolyte interfaces. The latter pathway can induce uniform growth of {110}-faceted Li at extremely high currents, suggesting ion-transport limitations alone are insufficient to predict Li morphology. At battery relevant fast-charging rates, SEI-breakdown above a critical current density produces detrimental morphology and poor cyclability. Thus, prevention of both SEI-breakdown and slow ion-transport in the electrolyte is essential. This mechanistic insight can inform further electrolyte engineering and customization of fast-charging protocols for Li metal batteries.

Development of a Lightweight LTO/Cu Electrode as a Flexible Anode via Etching Process for Lithium-Ion Batteries

In recent years, flexible energy storage devices have attracted the growing demand for flexible electronic systems. Therefore, research on reliable electrodes with high mechanical flexibility and good electronic and lithium-ion conductivity has become critical. Carbon-coated Li₄Ti₅O₁₂ (LTO) nanostructures find essential applications in high-performance lithium-ion batteries (LiBs). Nevertheless, the conventional copper current collector with a thickness of several micrometers accounts for a large proportion of the LiB, making the low-energy density LiB with much less flexibility. Here, hundred nm-thick (LTO/Cu) copper foil-LTO nanostructures are fabricated using a scalable and straightforward process which can be assembled into a film into a flexible, lightweight electrode by etching a conventional copper foil to form an ultra-thin copper layer for LIBs (<1 μm). This process provides essential flexibility to the as-prepared electrode and provides template support for simple fabrication. The LiB cell using the novel LTO/Cu as the anode exhibits an energy capacity of 123 mA h/g during 40 charge-discharge cycles at a 0.1C rate. Besides, the coulombic efficiency of the LiB using LTO/Cu remains over 99% after 40 cycles. These results show the uses of this novel anode and its potential in high-density and flexible commercial lithium-ion batteries.

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 implement 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 solid electrolyte interphase (SEI). The actual domination form in inactive Li loss is practically determined by the relative growth rates of dead Li0 and SEI Li+ because of the persistent evolving of Li metal interface during cycling. Distinct inactive Li evolution scenarios are disclosed when ingeniously tuning the inorganic anion-derived SEI chemistry with 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 declined SEI Li+/dead Li0 growth rates, thus achieving enhanced Li cycling reversibility.

Lithium Deposition-Induced Fracture of Carbon Nanotubes and Its Implication to Solid-State Batteries

The increasing demand for safe and dense energy storage has shifted research focus from liquid electrolyte-based Li-ion batteries toward solid-state batteries (SSBs). However, the application of SSBs is impeded by uncontrollable Li dendrite growth and short circuiting, the mechanism of which remains elusive. Herein, we conceptualize a scheme to visualize Li deposition in the confined space inside carbon nanotubes (CNTs) to mimic Li deposition dynamics inside solid electrolyte (SE) cracks, where the high-strength CNT walls mimic the mechanically strong SEs. We observed that the deposited Li propagates as a creeping solid in the CNTs, presenting an effective pathway for stress relaxation. When the stress-relaxation pathway is blocked, the Li deposition-induced stress reaches the gigapascal level and causes CNT fracture. Mechanics analysis suggests that interfacial lithiophilicity critically governs Li deposition dynamics and stress relaxation. Our study offers critical strategies for suppressing Li dendritic growth and constructing high-energy-density, electrochemically and mechanically robust SSBs.