Polydopamine-Modified Carboxymethyl Cellulose as Advanced Polysulfide Trapping Binder

Abstract

The search for a high-energy-density alternative to lithium-ion batteries has led to great interest in the lithium sulfur battery (LSB). However, poor cycle lifetimes and coulombic efficiencies (CEs) due to detrimental lithium polysulfide (LiPS) shuttling has hindered its widespread adoption. To address this challenge, a modified sodium carboxymethyl cellulose (CMC) polymer with integrated dopamine moieties and polydopamine nanoparticles was created through a facile one-pot dopamine (DOP) amidation reaction to strengthen noncovalent interactions with LiPSs and mitigate the shuttling effect. The resulting CMC-DOP binder improved electrode wettability, adhesion, and electrochemical performance. Compared to LSBs with a standard CMC binder, CMC-DOP 5:1 (with a 5:1 weight ratio of CMC to dopamine precursor) improves the specific capacity at cycle 100 by 38% to 552 mAh g−1 and CE from 96.8 to 98.9%. LSBs show good stability, even after 500 cycles. Post-mortem electrochemical impedance spectroscopy (EIS) and energy-dispersive spectroscopy (EDS) studies confirmed the effectiveness of the CMC-DOP in confining LiPS in the cathode. This simple but effective nature-inspired strategy promises to enhance the viability of LSBs without using harmful chemicals or adding excess bulk.