Preferential Stripping of a Lithium Protrusion Resulting in Recovery of a Planar Electrode

Abstract

Lithium metal is a high-energy-density battery electrode material, but the largely irreversible growth of lithium protrusions on an initially planar electrode during cycling makes it unsuitable for incorporation into a commercial battery. In this study, a lithium electrode with globular protrusions was stripped electrochemically, and the local morphology of the electrode as a function of time was determined by hard X-ray tomography. We demonstrate that globules are preferentially stripped compared to a planar electrode in our system, which incorporates a nanostructured block copolymer electrolyte. We report current density at the electrode as a function of micron-scale position and time. The local current density during the electrode healing process calculated from a reference frame at the electrode/electrolyte interface provides insight into the driving forces responsible for selective stripping of the globule. These results imply the possibility of discharging protocols that may return a lithium electrode to its initial planar state.

Moving beyond 99.9% Coulombic efficiency for lithium anodes in liquid electrolytes

“…Analytical expressions derived using linear stability analysis agree with these results from molecular dynamics, and further suggest that, in polymers (of which the SEI may be constituted), high stiffness 56 and surface energy can facilitate smooth Li plating 57 . On the other hand, increasing the current densities demanded during stripping can facilitate dissolution/smoothening of previously formed mossy or roughened Li, leading to a smoother Li/electrolyte interface 58,59 . This beneficial effect originates from high current densities and preferential stripping at local inhomogeneities of Li deposits due to stronger concentration gradients, helping to restore a more planar morphology 58 .…”

“…On the other hand, increasing the current densities demanded during stripping can facilitate dissolution/smoothening of previously formed mossy or roughened Li, leading to a smoother Li/electrolyte interface 58,59 . This beneficial effect originates from high current densities and preferential stripping at local inhomogeneities of Li deposits due to stronger concentration gradients, helping to restore a more planar morphology 58 . Thus, while slow plating is desired for smooth Li deposition, fast stripping may be desirable for high CE.…”

Lithium‐Metal Batteries via Suppressing Li Dendrite Growth and Improving Coulombic Efficiency

“…Based on the effect of discharge current on the Li morphology, it is even proposed that designing the discharge protocols properly may return a Li electrode to its initial planar state in LMBs. [88] 4.5.2. Pressure Pressure exists widely inside practical LMBs that can be produced by the cell assembly, SEI squeezing, and volume expansion of both electrodes during cycling.…”

“…Based on the effect of discharge current on the Li morphology, it is even proposed that designing the discharge protocols properly may return a Li electrode to its initial planar state in LMBs. [ 88 ]…”

Failure Mechanisms at the Interfaces between Lithium Metal Electrodes and a Single-Ion Conducting Polymer Gel Electrolyte

“…In principle, a sealed pouch cell is illuminated with monochromatic X-rays and a corresponding optical image is reconstructed from the radiogram using a scintillator and an optical microscope . Hard X-ray microtomography has been used to study the interface between Li and polymer electrolytes and to monitor the morphological changes upon Li plating and stripping. ,,,− The cycling experiments in these studies were conducted at temperatures well above room temperature (e.g., 90 °C). We are only aware of one X-ray microtomography study of single-ion conducting gels .…”