Abstract
Li-powder anodes have been proposed as an alternative to Li-foil electrodes, as their high-surface area is expected to reduce the local current density and consequently hinder dendrite formation, which is at the origin of several drawbacks in Li metal batteries. In this work, a comprehensive theoretical/experimental approach is proposed to elucidate how the interplay of several parameters such as effective surface, porosity, and permeability of cold-pressed Li-powder electrodes evolve with the compaction pressure and how these features ultimately affect the electrochemical performance of a porous electrode. The theoretical calculations indicate that maintaining high porosity is crucial, and there is also the need to maintain particle size within an optimal range. This balance is essential to achieving a compromise between maximizing effective surface area and ensuring adequate permeability of the porous electrode. Experimentally, only Li-powder electrodes compacted at low pressure (1 MPa) are permeable enough to allow the penetration of the electrolyte into the porosity of the electrode. Interestingly, the Li-powder electrode compacted at 1 MPa is also the only porous electrode to perform better than Li-foil electrodes in electrochemical tests. Post mortem analyses after cycling reveal that the morphology of lithium electrodeposition on this specific electrode is significantly distinct from the other ones. The main findings highlight that even though Li powder can present a specific surface area a hundred times higher than that of a Li foil, this surface must be electrochemically available to result in outstanding electrochemical properties. Therefore, the particle size and the compaction pressure applied to shaping Li-powder electrodes with an optimized morphology are critical parameters to be considered for their preparation.