Gradient H-Bonding Supports Highly Adaptable and Rapidly Self-Healing Composite Binders with High Ionic Conductivity for Silicon Anodes in Lithium-Ion Batteries.

Abstract

An ideal binder for high-energy-density lithium-ion batteries (LIBs) should effectively inhibit volume effects, exhibit specific functional properties (e.g., self-repair capabilities and high ionic conductivity), and require low-cost, environmentally friendly mass production processes. This study adopts a synergistic strategy involving gradient (strong-weak) hydrogen bonding to construct a hard/soft polymer composite binder with self-healing abilities and high battery cell environments adaptability in LIBs. The meticulously designed 3D network structure comprising continuous electron transport pathways buffers the mechanical stresses caused by changes in silicon volume and improves the overall stability of the solid electrolyte interphase film. The Si-based anode with a polymer composite binder poly(acrylic acid-g-ureido pyrimidinone5% )/polyethylene oxide (Si/PAA-UPy5% /PEO) achieves a reversible capacity of 1245 mAh g-1 after 200 cycles at 0.5 C, which is 6.6 times higher than that of the Si/PAA anode. After 200 cycles at 0.2 A g-1 , a half-cell comprising Si/C anode with a polymer composite binder (Si/C/PAA-UPy5% /PEO) has a remaining specific capacity of 420 mAh g-1 and a capacity retention rate of 79%. The corresponding full cell with a Li-based cathode (LiFePO4 /Si/C/PAA-UPy5% /PEO) has an initial area capacity of 0.96 mAh cm-2 and retains an area capacity of 0.90 mAh cm-2 (capacity retention rate = 93%) after 100 cycles at 0.2 A g-1 .