Bis-imino-acenaphthenequinone-Paraphenylene-Type Condensation Copolymer Binder for Ultralong Cyclable Lithium-Ion Rechargeable Batteries

Graphite has been the conventional lithium-ion anode for the negative electrode for the past three decades. One of the major challenges for graphite anodes is the exfoliation of graphite framework on deep cycling at a fast current rate, leading to a gradual capacity fade. In this regard, poly(vinylidene fluoride) (PVDF) has been the conventional binder widely used for stabilizing the graphite framework. Unfortunately, its nonconducting nature, slow dissolution in the electrolyte, and poor adherence to the current collector limit its utility as a robust binder for lithium-ion batteries with a long cycle life. Here, we report an n-type conjugated copolymer bis-imino-acenaphthenequinone-paraphenylene (BP) as an alternate binder material for the graphite anode. The BP binder-based anodic half-cells outperformed the PVDF-based counterpart, showing an excellent performance with a reversible capacity of 260 mA h g(-1), cyclability up to 1735 long cycles at 1 C rate, and 95% capacity retention. The superior performance of the BP binder was attributed to its ability to provide mechanical robustness to the electrode laminate, maintain electronic conductivity within the electrode, and undergo n-doping in the anodic environment, influencing the formation of a thin solid electrolyte interface with low interfacial impedance.

Automated summary

Graphite has been commonly used as the conventional lithium-ion anode, but faces challenges of exfoliation leading to capacity fade. This study introduces an n-type conjugated copolymer BP as a substitute binder for graphite anodes, showing superior performance and cycle stability.