Superhigh Coulombic Efficiency Lithium–Sulfur Batteries Enabled by In Situ Coating Lithium Sulfide with Polymerizable Electrolyte Additive

摘要

The polysulfide shuttling and electrode structure destruction caused byheterogeneous conversion reactions are the fundamental causes of the poorreversibility of high-energy-density lithium–sulfur (Li–S) batteries. The mostdirect manifestation is the unsatisfactory low Coulombic efficiency (CE).Herein the importance of CE in evaluating Li–S batteries is highlighted anda remedy is presented for such low efficiencies by in situ coating lithiumsulfide (Li_2S), as the cathode, with polymerizable electrolyte additives, wheretrithiocyanuric acid trilithium salt (TTCA-Li) is employed for a typical demonstration.The involved reaction catalytically decreases the initial overpotentialof Li_2S, and the produced coating confines the shuttling of lithium polysulfides,thus inhibiting the redistribution of sulfur species and active sulfurloss upon cycling. The prototype full cell where the coated Li2S cathodecouples with the Li anode has an extremely high CE of over 99.5%, while,in a Li-free cell, the Li_2S cathode well matches the lithiated silicon anode ina low N/P ratio of 1.2. This approach shows its practicality and generalitythrough a pouch cell demonstration with a practically high Li_2S loading andthe extension to elemental sulfur-based batteries by injecting the TTCA-Liadditives into cycling cells.