Polyglutamic Acid Binder for High-Performance Lithium–Sulfur Batteries

Binders play a very important part in electrodes, as they closely bind active materials, conductive agents, and current collectors together. The application of binders is critical to the electrochemical performance of Li-S batteries. Herein, a series of studies on sulfur cathodes with different binders is carried out. Compared to traditional polyvinylidene fluoride, γ-polyglutamic acid (γ-PGA) is rich in polar functional groups (amino and carboxyl groups), and the shuttle effect of lithium polysulfide can thereby be inhibited due to the secondary bond between the functional groups and polysulfide. Furthermore, the integrity of the cathode during electrochemical processes can be maintained with a γ-PGA binder. After assembly with a Li anode, a capacity retention of 62.5% is maintained after 100 cycles, which is much higher than that of batteries with traditional binders such as polyvinylidene fluoride (53.9%), polyvinylpyrrolidone (52.8%), sodium carboxymethylcellulose (40.7%), and polyacrylonitrile (51.5%).