Coordination‐Chemistry‐Engineered Copolymer Binders Enables Fast‐Kinetic, Thin‐SEI SiC Anodes in Wide‐Temperature Practical Lithium‐Ion Batteries

ABSTRACT Silicon‐based anodes suffer from sluggish kinetics reaction, large volume expansion, poor structural stability due to the unstable solid electrolyte interphase (SEI). Series of functional binders are proven to regulate the formation of SEI layers. Herein, poly(vinyl alcohol‐ co ‐acrylic acid) copolymers (PVA 3 ‐ co ‐LiPAA 1 and PVA 3 ‐ co ‐NaPAA 1 ) are synthesized based on metal‐coordinated strategy, where Li + or Na + coordinate with carboxylate groups for strong interfacial anchoring and efficient ion‐transport pathways. Particularly, all the electrochemical and structural measurements are carried out on the 100 mA h SiC||LiCoO 2 full cells to verify its practical applications. It is found that coordination chemistry between alkali metal ions and polymer binders can successfully induce the growth of thin and robust interfacial layers SEI films, thus protecting structural stability, accelerating interfacial Li + ion diffusion rate, and preventing large volume expansion. Deeply, compared to Na‐coordinated binder, it is revealed that Li‐coordinated binder could further lower ionic migration barriers. As a result, 3.8 Ah SiC@graphite||LiCoO 2 pouch cells with PVA 3 ‐ co ‐LiPAA 1 enables higher 800 th capacity retention of 79% under 3 C/0.05 C and 25°C, and 300 th capacity retention of 89% under 1.5 C/0.05 C and ‐10°C. This work may provide a new strategy towards practical applications of high‐energy‐density silicon‐based anodes.