Polyethylene Glycol Surface Modification and Polythiophene Side-Chain Chemistry: A Combined Strategy toward High-Capacity Lithium-Ion Battery Anodes

In the development of high-capacity lithium-ion batteries (LIBs), the combined optimization of active material interfaces and polymer binder chemistry plays a critical role in improving electrode performance and longevity. This work explores a dual design strategy incorporating polyethylene glycol (PEG) surface modification and carboxylated polythiophene side-chain tailoring to enhance the electrochemical behavior of magnetite (Fe₃O₄)-based anodes. PEG is employed to improve interfacial stability, while carboxylated polythiophene binders with varying alkyl side-chain lengths─poly[3-(potassium-4-butanoate)thiophene-2,5-diyl] (P3KBT), poly[3-(potassium-5-pentanoate)thiophene-2,5-diyl] (P3KPT), and poly[3-(potassium-6-hexanoate)thiophene-2,5-diyl] (P3KHT)─are used to modulate molecular interactions and ion transport. Among these three analogs, the PEG–Fe₃O₄–P3KHT electrode exhibits superior ion-transfer kinetics, the highest capacity retention, and the lowest charge-transfer resistance after extended cycling. Compared to their non-PEG analogs, PEG-coated electrodes demonstrate enhanced structural integrity and electrochemical behavior, emphasizing the synergistic effects of surface modification and side-chain chemistry. These findings highlight the importance of interfacial interactions and molecular design in achieving robust and high-performance composite anodes for next-generation LIBs.. Authors: Li, Han [Lehigh Univ., Bethlehem, PA (United States)] (ORCID:0009000318361381); Ren, Haoze [Lehigh Univ., Bethlehem, PA (United States)] (ORCID:0000000204503962); Rodriguez Campos, Armando [Stony Brook Univ., NY (United States)]; Qin, Siyu [Lehigh Univ., Bethlehem, PA (United States)] (ORCID:0000000211694437); Thorpe, Ryan [Lehigh Univ., Bethlehem, PA (United States)]. DOE Contract: SC0012673. Subjects: Fe3O4; PEG coating; charge transport; coating materials; composites; electrodes; lithium-ion battery; organic polymers; polythiophene; side-chain chemistry; surface modification