Water-Based Dual-Crosslinked Polymer Binders for High-Energy-Density Lithium-Sulfur Batteries.

High mass-loading electrodes with long-term stability has long been a great challenge for lithium sulfur batteries, since the conventional binders are unable to cope with the shuttling of lithium polysulfides and the structural damage in electrode. Here, a novel water-based polymer, polyphosphate acid crosslinked chitosan ethylamide carbamide (PACEC), is developed as the binder to construct high-energy-density sulfur cathode and flexible LSBs. With a dual-crosslinked network, the PACEC shows excellent affinity with lithium polysulfides to relieve the shuttle effect, and robust mechanical properties to stabilize the electrode. The sulfur cathode based on PACEC demonstrates a high sulfur loading of 14.8 mg cm-2, areal initial capacity of 17.5 mAh cm-2 and Coulombic efficiency of 99.3%, while the amount of electrolyte is strictly limited to be 6 μL mg-1. More importantly, robust pouch cell with an area of 6 cm2 and only 177% oversized lithium can successfully integrate energy density of 6.5 mAh/cm2 with cycling retention per cycle of 99.74% during 270 cycles) and flexibility at curvature of 3 mm. This study provides inspirations for the design of eco-friendly polymer binders, and paving new ways for the development of LSBs.