Work-Function-Induced Interfacial Electron/Ion Transport in Carbon Hosts toward Dendrite-Free Lithium Metal Anodes

Coupled electron/ion transport is a decisive feature of Li plating/stripping, wherein the compatibility of electron/ion transport rates determines the morphology of deposited Li. Local Li+ hotspots form due to inhomogeneous interfacial charge transfer and lead to uncontrolled Li deposition, which decreases the Li utilization rate and safety of Li metal anodes. Herein, we report a method to obtain dendrite-free Li metal anodes by driving electron pumping and accumulating and boosting Li ion diffusion by tuning the work function of a carbon host using cobalt-containing catalysts. The results reveal that increasing the work function provides an electron deviation from C to Co, and electron-rich Co shows favorable binding to Li+ . The Co catalysts boost Li+ diffusion on the carbon fiber scaffolds without local aggregation by reducing the Li+ migration barrier. The as-obtained dendrite-free Li metal anode exhibits a Coulombic efficiency of 99.0 %, a cycle life of over 2000 h, a Li utilization rate of 50 %, and a capacity retention of 83.4 % after 130 cycles in pouch cells at a negative/positive capacity ratio of 2.5. These findings provide a novel strategy to stabilize Li metal by regulating the work function of materials using electrocatalysts.

Reversible Solid-Solid Conversion of Sulfurized Polyacrylonitrile Cathodes in Lithium-Sulfur Batteries by Weakly Solvating Ether Electrolytes

Despite carbonate electrolytes exhibiting good stability to sulfurized polyacrylonitrile (SPAN), their chemical incompatibility with lithium (Li) metal anode leads to poor electrochemical performance of Li||SPAN full cells. While the SPAN employs conventional ether electrolytes that suffer from the shuttle effect, leading to rapid capacity fading. Here, we tailor a dilute electrolyte based on a low solvating power ether solvent that is both compatible with SPAN and Li metal. Unlike conventional ether electrolytes, the weakly solvating ether electrolyte enables SPAN to undergo reversibly "solid-solid" conversion. It features an anion-rich solvation structure that allows for the formation of a robust cathode electrolyte interphase on the SPAN, effectively blocking the dissolution of polysulfides into the bulk electrolyte and avoiding the shuttle effect. What's more, the unique electrolyte chemistry endowed Li ions with fast electroplating kinetics and induced high reversibility Li deposition/stripping process from 25 °C to -40 °C. Based on tailored electrolyte, Li||SPAN full cells matched with high loading SPAN cathodes (≈3.6 mAh cm-2 ) and 50 μm Li foil can operate stably over a wide range of temperatures. Additionally, Li||SPAN pouch cell under lean electrolyte and 5 % excess Li conditions can continuously operate stably for over a month.