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 m²/g and the total pore volume of 1.64 cm³/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 water-based supramolecular polymer binder has high potential for use in high-energy-density Li-S batteries.