Se–Se Bonds Involved Polyurethane-Based Binders for Enhanced Redox Kinetics in Lithium-Ion Batteries

Although the proportion of binder in batteries is tiny, it plays a significant role in maintaining the integrity of the electrode structure and ensuring the cycling stability of batteries. This study, based on the concept of “redox mediators (RMs),” involved the design and synthesis of a series of Se–Se bonds containing polyurethanes, which have been used as binders for lithium iron phosphate cathodes in lithium-ion batteries (LIBs). Se–Se contained binders as RMs not only accelerate the redox kinetics of the battery but also improve the discharge specific capacity and lithium-ion (Li+) transport rate of the battery. The synergistic movement of the hard and soft segments in the polyurethane endowed the binders with high elasticity, and the hydrogen bonding within the binders further enhanced the mechanical properties and reduced the volume change of the electrode during charging and discharging, thus improving the electrochemical cycling performance of the battery. After 500 cycles at 1 C, LIBs with PUPEG-400 as the binders boasted the highest initial discharge specific capacity of 139.77 mA h g–1, while those with PUPEG-2000 as the binders exhibited the highest capacity retention of 72.37%.