An Aqueous, Electrolyte‐Type, Rechargeable Device Utilizing a Hydrophilic Radical Polymer‐Cathode

Abstract

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 rechargeable battery based on hydrophilic radical polymer electrode and its green assessment

“…The polymers are also thermally stable. Their 10% decomposition temperatures are higher than 2008C (18,21). This is sufficiently higher than the envisioned operating temperatures of the battery.…”

“…Synthetic procedures poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl vinylether) (PTVE) 2,2,6,6-tetramethylpiperidne-N-oxyl-4-vinyl, synthesizedas the monomer, was prepared using the coupling reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidne-4-oxyl and vinyl acetate with catalyst of bis(1,5-cyclooctadiene) diiridium(I) dichloride and 3-chloroperbenzoic acid, according to a previous paper (21,22,29,30). The vinyl monomer was polymerized via cationic polymerization in dichloromethane with boron trifluoride diethyl etherate as the initiator at Á258C.…”

“…Recently, we designed a hydrophilic radical polymer, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl vinylether) (PTVE), which sufficiently functioned even in an aqueous electrolyte, and reported the following electrode performance (21,22): (i) high charging and discharging capacity of 131 mAh g (1 ascribed to the stoichiometric redox of the radical moieties; (ii) long cycle life, often exceeding 1000 cycles, derived from the chemical stability of the radicals and from the amorphous electrode structure; and (iii) high chargingÁdischarging rate performance (1200 C) resulting from the rapid electron-transfer process of the radical moiety and the high equivalent electrical conductivity of the aqueous electrolyte on the order of 10 Á2 to 10 Á3 m 2 S mol Á1 , which is 10 times higher than that of organic electrolytes (23). (The rate of 1 C is defined as the current density at which the charging or discharging of the cell takes in 1 h. Most conventional batteries function during the charging or discharging at 1Á2 C.) An important issue described in this report is that a combination of hydrophilic radical polymer and aqueous electrolyte allowed an organic electrolytefree battery design and a rapid chargingÁdischarging performance at the same time.…”

“…(The rate of 1 C is defined as the current density at which the charging or discharging of the cell takes in 1 h. Most conventional batteries function during the charging or discharging at 1Á2 C.) An important issue described in this report is that a combination of hydrophilic radical polymer and aqueous electrolyte allowed an organic electrolytefree battery design and a rapid chargingÁdischarging performance at the same time. Previous papers (21,22) have discussed only the electrode performance, without evaluating the safety of the radical polymer electrode. One could assume that such a battery configuration has inherent advantages in terms of many aspect of green chemistry.…”

Hydroalkoxylation of alkynes by a nitroxyl containing alcohol, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl: synthesis of spin-labeled enol ethers

“…In recent years a number of works (mainly patents) describing applications of 4-vinyloxy-TEMPO have appeared. For instance, polymers and copolymers based on this vinyl ether have been proposed as efficient cathode materials for greener organic radical batteries, [25][26][27][28][29][30][31][32][33][34][35] and a nano-scale memory device was constructed by nanolithographic patterning of oxidized poly(4-vinyloxy-TEMPO). 36 The first synthesis of 4-vinyloxy-TEMPO, which goes back to 1986, comprised the hydroalkoxylation of acetylene with 4-hydroxy-2,2,6,6-tetramethylpiperidine in KOH/DMSO followed by oxidation (Na 2 WO 4 as catalyst).…”