Zn2+–Imidazole Coordination Crosslinks for Elastic Polymeric Binders in High‐Capacity Silicon Electrodes

• Published in: Advanced science 2021-05, Vol.8 (9), p.2004290-n/a
• Main Authors: Kim, Jaemin, Park, Kiho, Cho, Yunshik, Shin, Hyuksoo, Kim, Sungchan, Char, Kookheon, Choi, Jang Wook
• Format: Article
• Language: English
• Subjects: carboxymethyl cellulose; Design; dynamic crosslinking; elastic binders; Electrodes; Electrolytes; in situ crosslinking; Ligands; metal–ligand coordination; NMR; Nuclear magnetic resonance; Polymers; silicon/carbon composite; supramolecular chemistry; Viscosity
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202004290

Recent research has built a consensus that the binder plays a key role in the performance of high‐capacity silicon anodes in lithium‐ion batteries. These anodes necessitate the use of a binder to maintain the electrode integrity during the immense volume change of silicon during cycling. Here, Zn2+–imidazole coordination crosslinks that are formed to carboxymethyl cellulose backbones in situ during electrode fabrication are reported. The recoverable nature of Zn2+–imidazole coordination bonds and the flexibility of the poly(ethylene glycol) chains are jointly responsible for the high elasticity of the binder network. The high elasticity tightens interparticle contacts and sustains the electrode integrity, both of which are beneficial for long‐term cyclability. These electrodes, with their commercial levels of areal capacities, exhibit superior cycle life in full‐cells paired with LiNi0.8Co0.15Al0.05O2 cathodes. The present study underlines the importance of highly reversible metal ion‐ligand coordination chemistries for binders intended for high capacity alloying‐based electrodes. Zn2+–imidazole coordination bonds, crosslinked with carboxymethyl cellulose in situ during electrode fabrication, are introduced as a polymeric binder for high‐capacity silicon anodes. The reversible metal–ligand bonds impart high elasticity to the binder network for keeping the electrode's integrity. The robust cycling performance under commercial levels of areal capacity highlights the usefulness of high elasticity involving metal–ligand bonds.