Dendrite-Free Li Metal Anodes and the Formation of Plating Textures with a High Transference Number Modified Separator.

The application of Li metal anodes is currently hindered by the uncontrolled growth of Li dendrites. Herein, the effects of a modified separator with a high Li+ transference number (t+ ) on the structure and electrochemical performance of Li metal anodes are reported. Stable and dendrite-free plating/stripping cycles are achieved under current densities up to 5 mA cm-2 and areal capacities up to 20 mAh cm-2 . The uniformly grown Li grains under the high t+ environment also exhibit well-defined textures (preferred orientations). At a low plating capacity, epitaxial growth takes place on the {100} textures already existing in the rolled Li foils and the uniform Li+ flux strengthens this preferred orientation. Increasing the plating capacity to 20 mAh cm-2 , the later-grown textures change to {110} due to the reduced space charges and alleviated transport limits of Li+ under the high t+ environment, which favor the exposure of the close-packed {110} planes. Compression-induced <111> fiber textures are also resolved and the content increases with the plating capacity. Identification of the textures is meaningful for the exploration of advanced epitaxial substrates beyond Cu foils for high-energy-density Li metal batteries. LiS pouch cells are finally evaluated for the potential application of the modified separator.

Promoted Deposition of Three-Dimensional Li2S on Catalytic Co Phthalocyanine Nanorods for Stable High-Loading Lithium-Sulfur Batteries.

The sulfur redox in Li-S batteries involves a complex sequence of solid-liquid-solid conversions, and reaction catalysis has recently become a focused area for further advancement. The deposition of solid Li2S from liquid Li2S4 contributes to three-quarters of the total theoretical capacity and is therefore of great significance over the entire cathode reaction. This study demonstrates a cathode material composed of carbon nanofibers decorated with catalytic Co phthalocyanine nanorods (CoPc@CNF), which are highly effective in promoting the deposition of Li2S in three-dimensional (3D) fine particles rather than 2D thin films. This significantly alleviates cathode passivation during cell charge and discharge, leading to obviously improved sulfur utilization and cycling stability for high loading cathodes. DFT calculations indicate that the promoted 3D deposition of Li2S is related to the facilitated migration of deposition precursors (Li2S4 and Li-ions) to migrate on the CoPc nanorods. Lithium-sulfur (Li-S) pouch cells were prepared with high specific (954 mAh g-1), areal (4.8 mAh cm-2), and total (235 mAh) capacities achieved at 0.5 C under high sulfur content. As metal phthalocyanines possess a high structural variability, this study provides opportunities to the design of a new class of Li-S cathode materials.