Eliminating anion depletion region and promoting Li+ solvation via anionphilic metal organic framework for dendrite-free lithium deposition

Abstract

Lithium metal batteries (LMBs) have great potential for next-generation rechargeable batteries due to the high theoretical capacity and ideal compatibility coupled with diverse cathode materials. However, the random Li deposition associated with the large local space charge caused by the anion depletion near the surface of anode, as well as the insufficient reduction of Li+ related to the suppressed Li+ solvation process induced by the electrostatic force between anion and cation hinder the development of high-energy-density LMBs. Herein, as evidenced theoretically and experimentally, we simultaneously eliminate the anion depletion region and promote the lithium salt dissociation by employing ZIF-67 with unsaturated metal sites as anionphilic additive to regulate anion distribution and weaken its bond with Li+. As a result, the short-circuit hazard is remitted in symmetrical cell with modified electrolyte at 3 mA cm−2 under capacity of 3 mAh cm−2 for more than 2000 h. As employed for the lithium-sulfur battery with high sulfur loading of 4.5 mg cm−2, the modulated electrolyte enables the battery delivering an initial capacity of 713 mAh g−1 with decay rate of 0.05% per cycle over 100 cycles at 3 mA cm−2. This work demonstrates an efficient and scalable strategy for constructing dendrite-free LMBs via eliminating the anion depletion region and facilitating the Li+ solvation process.