Water-based phytic acid-crosslinked supramolecular binders for lithium-sulfur batteries

Rechargeable Li-S batteries have drawn much attention because of their high theoretical energy density (2600 Wh kg(-1)) and environmental friendliness. However, Li-S batteries undergo complex phase transitions and large volume changes during the charge-discharge process, which greatly decreases the lifetimes of Li-S batteries. Here, we investigate the use of water-based phytic acid-crosslinked supramolecular binders in the sulfur cathode to prolong charge-discharge cycling of Li-S batteries. The supramolecular binder is fabricated with a mixture of phosphorylated soybean protein isolate (P-SPI), poly(ethylene oxide) (PEO), and phytic acid (PA), which is denoted by SPP. Strong adsorption of polysulfides by the SPP binder is verified by using UV-vis spectroscopy with an in situ battery. In the sulfur cathodes, the three-dimensional carbon (3DC) with the specific surface area of 2208 m(2)/g and the total pore volume of 1.64 cm(3)/g is used as sulfur hosts. The high discharge capacity of 932.8 mAh g(-1) is achieved by SPP-based Li-S batteries at a high sulfur loading of 8.9 mg cm(-2) at 0.1C. A discharge capacity at 1C is 629.7 mAh g(-1), with stable cycling over 800 charge-discharge cycles, and a capacity attenuation of only 0.0298% per cycle. The coulombic efficiency remained at 99.7%. The new type of waterbased supramolecular polymer binder has high potential for use in high-energy-density Li-S batteries.