Multifunctional radical polymers-enabled rapid charge/discharge and high capacity for flexible self-standing LiFePO4/PETM/SWNT hybrid electrodes

The combination of high output and high energy storage performance at the same time is a long-standing and formidable challenge in electrode technology. Herein, a multifunctional radical polymer binder, poly (ethylene-alt-TEMPO maleate) (PETM) is first introduced to construct flexible self-standing organic/inorganic hybrid electrodes, PETM/lithium iron phosphate (LFP)/single-walled carbon nanotubes (SWNT). Notably, PETM plays multifunctional roles in the PETM/LFP/SWNT electrodes as a polymer binder, electrochemical mediator, and auxiliary active material. First, PETM provides strong adhesive strength to generate robust structural integrity, allowing a three-dimensional hierarchical consecutive structure. Second, together with the electrochemical mediation of PETM, the hybrid structure greatly expedites electron/ion transportation, thus bringing fast redox reaction kinetics and high output. Third, PETM offer additional energy storage owing to the electro-activeness of radical groups. Coupled with the self-supporting property of the electrode without any redundant electro-inactive components, the electrode energy density can be substantially improved. Profiting from those advantages, the formed electrode achieves exceptional rate performance (97.5 mA h/g at 20 C), extraordinary specific/areal capacity (173 mA h g−1/8.2 mA h cm−2 at 0.1 C), and ultralong-life cycle under ultrahigh rate (over 2000 cycles at 20 C). More importantly, the electrode can be utilized as a flexible cathode in flexible batteries.