Reversible cross-linked phosphorylate binder for recyclable lithium-sulfur batteries

The development of facile and eco-friendly recycling strategies for lithium-sulfur batteries (LSBs) is very important since they will generate a growing hazard to the environment. Herein, a hydrogen bonding cross-linked multi-functional binder (named: APL) of Lithiated polyacrylic acid-co-vinylphosphonic acid (AA-VPA) and phosphorylated soy protein (P-SPI) is explored for LSBs. Owing to the precipitation of P-SPI at the isoelectric point, hydrogen bonding cross-linking between AA-VPA and P-SPI can be readily dissociated under acidic conditions, providing a facile method to enable SC composite recycled by a convenient acid pickling. Moreover, the robust cross-linking network provides APL binder a strong bonding force and excellent mechanical properties, ensuring the structural integrity of the sulfur (S) electrode during long-term cycling. The abundant polar groups within APL polymeric network endow sulfur cathode with superior polysulfide anchoring capacity and retard the shuttle effect of LSBs. APL-based sulfur cathode rendered a high specific capacity of 940 mAh g−1 with a sulfur loading of 4.8 mg cm−2. After 250 charge/discharge cycles at a current density of 1C, the specific capacity of sulfur cathode is still as high as 805 mAh g−1. Hence, the flexible electrode remains intact after bending. This work proposes an environment-friendly and cost-effective strategy for the development of reversible cross-linked multi-functional binders for recyclable and high-energy LSBs.