A film of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl vinylether) coated on a current collector displayed a rapid and reversible electrochemical response in aqueous electrolytes, and allowed an ultrafast full charging of 3 mC cm(-2) in as short as 3 seconds by virtue of the combination of the hydrophilic radical polymer and the aqueous electrolyte possessing a high electrical conductivity.

Poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) was designed and synthesized as an electrode-active polymer for an organic rechargeable device containing an aqueous electrolyte. The device demonstrated a 1.2 V output voltage, exceeded 2000 charging-discharging cycles, and had a high charging rate performance within 1 min.Polyacrylamide is a well-known hydrophilic soft matter widely used in cell culture, drug delivery, and soil amendment. 1-4 Its applications have been vigorously studied in the biological, medical and agricultural fields. On the other hand, the study of the electronic energy related application has been minor and limited to polymer electrolyte fuel cells. 5 We now report a new application of polyacrylamide as an electrode-active material in organic rechargeable devices.Organic-based electrode-active materials have been paid considerable attention because of their potential to overcome the inherent disadvantages of metal-based electrodes, such as limited raw-material resource and tedious waste process. We have focused on the reversible redox reaction of radical species, such as nitroxide, phenoxyl and galvinoxyl radicals, synthesizing a series of aliphatic polymers bearing pendant radical groups (we call them "radical polymer"), and utilizing them as an electrode-active or charge-storage material in a rechargeable device. 6-13 A typical example of a radical polymer is poly(2,2,6,6tetramethylpiperidinyloy-4-yl norbornene). 10 This polymer contains 2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl (TEMPO) groups which are rapidly, reversibly, and stoichiometrically oxidized to the corresponding oxoammonium cation. The poly(TEMPOsubstituted norbornene) was used as the positive electrode (the cathode) ‡ and coupled with a lithium metal negative electrode (an anode) ‡ in a semi-organic rechargeable device containing a LiPF 6 ethylene carbonate/diethyl carbonate (1/1) solution. The device demonstrated a high charging-discharging performance, such as a 3.6 V output voltage, rapid charging within 1 min, and exceeded 1000 charging-discharging cycles. 12 In addition, a test cell composed of the poly(TEMPO-substituted norbornene) cathode, poly(galvinoxylstyrene) anode and (

A hydrophilic poly(vinyl ether)‐backbone polymer bearing a pendant TEMPO radical, poly(2,2,6,6‐tetramethylpiperidinyloxy‐4‐yl vinyl ether) (PTVE), was designed as a cathode‐active material, which displays a reversible one‐electron redox capability, even in an aqueous electrolyte. The PTVE layer coated on a current collector demonstrated a rapid charging‐discharging rate based on the combination of the redox‐active nitroxide radicals built into the hydrophilic polymer and the aqueous electrolyte that possessed a high electrical conductivity. A test cell fabricated with a PTVE cathode, a zinc anode, and an aqueous electrolyte gave an output voltage of 1.7 V and showed the ability to be recharged more than 500 times rechargeability.

A highly cross-linked polyviologen hydrogel, poly(tripyridiniomesitylene) (PTPM), has been designed as an anode-active material. It displays a reversible two-electron redox capability at -0.4 and -0.8 V vs Ag/AgCl in an aqueous electrolyte. The PTPM layer coated on a current collector by electropolymerization via a 4-cyanopyridinium electro-coupling reaction demonstrates a rapid charging-discharging reaction with a redox capacity comparable to that obtainable using the formula weight-based theoretical density, because of the combination of the redox-active viologen moieties built into the hydrogel. A test cell that has been fabricated using the developed PTPM anode, a poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm)-based cathode, and an aqueous electrolyte exhibits a discharging voltage of 1.1 and 1.5 V, and has proven its ability to be recharged more than 2000 times.

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