The Fast and the Capacious: A [Ni(Salen)]‐TEMPO Redox‐Conducting Polymer for Organic Batteries

Abstract

Redox‐active nitroxyl‐containing polymers are promising candidates as possible replacements for inorganic based energy‐storage materials, due to their high energy density and fast redox kinetics. One challenge towards the implementation of such a system is the insufficient electrical conductivity, impeding the charge collection even with highly conductive additives. Herein, the first implementation of a polymeric bis(salicylideniminato) nickel (NiSalen) conductive backbone as an active charge‐collecting wire is reported. NiSalen simultaneously serves as a charge collector for nitroxyl pendants and supports the redox capacity of the material. This novel polymer exhibits a specific capacity of up to 91.5 mAh g−1, retaining 87 % of its theoretical capacity at 800 C and more than 30 % at as high as 3000 C (66 % capacity retention after 2000 cycles). The properties of the new material upon operation was studied by means of operando electrochemical methods, UV‐Vis, and electron paramagnetic resonance spectroscopy.

6,6′-{[Ethane-1,2-diylbis(azaneylylidene)]bis(methaneylylidene)}bis[2-(hexyloxy)phenolato] Nickel(II)

“…Additionally, the ethylene bridge 4H singlet appears at 3.66 ppm, along with the 2H singlet of imine protons at 7.87 ppm and a set of aromatic signals, 2H triplet at 6.49 ppm, and two 2H doublets at 6.66 and 6.81 ppm, all with 3 JH-H = 7.9 Hz. 13 C-NMR spectrum (Figure S2) contains a set of hexyloxy peaks at 14.1, 22.6, 25.7, 27.9, 31.8, and 68.1 ppm, ethylene bridge signal at 59.0 ppm, six aryl peaks at 113.6, 115.2, 120.0, 123.5, 148.7, and 154.0 ppm, and the imine carbon signal at 163.0 ppm.…”

“…Additionally, the ethylene bridge 4H singlet appears at 3.66 ppm, along with the 2H singlet of imine protons at 7.87 ppm and a set of aromatic signals, 2H triplet at 6.49 ppm, and two 2H doublets at 6.66 and 6.81 ppm, all with 3 J H-H = 7.9 Hz. 13 C-NMR spectrum (Figure S2) contains a set of hexyloxy peaks at 14.1, 22.6, 25.7, 27.9, 31. We demonstrate the possibility for the direct alkylation of [Ni(HOSalEn)] with hexyl bromide, which provides the facile one step route to the diversity of alkoxy substituted NiSalens and the polymers obtained thereof.…”

“…UV-Vis spectra were recorded in CHCl3 solutions on Shimadzu UV-1800 double-beam spectrophotometer (Shimadzu Europa GmbH, Kyoto, Japan) in 1 cm quartz cuvettes. 1 H and 13 C-NMR spectra were acquired on a Bruker Avance 400 spectrometer (Bruker Analytische Messtechnik GmbH, Rheinstetten, Germany) at 400 and 101 MHz, respectively, in CDCl3 while using a residual solvent peak as internal standard. HRMS of the positive ions was recorded from the methanolic solution of the sample using electrospray ionization of on a Bruker micrOTOF apparatus (Bruker Analytische Messtechnik GmbH, Rheinstetten, Germany) in positive mode.…”

“…1 H-NMR (400 MHz, CDCl 3 ) δ, ppm: 7.87 (s, 2H, imine), 6.81 (d, J = 7.9 Hz, 2H, Ar), 6.66 (d, J = 7.9 Hz, 2H, Ar), 6.49 (t, J = 7.9 Hz, 2H, Ar), 4.83-4.63 (m, 4H, -OCH 2 -), 3.66 (s, 4H, bridge), 1.42-1.59 (m, 4H, alkyl), 1.28-1.42 (m, 4H, alkyl), 0.93-1.13 (m, 8H, alkyl), 0.74 (t, J = 6.8 Hz, 6H, -CH 3 ). 13 C-NMR (101 MHz, CDCl 3 ) δ, ppm: 163.0 (imine), 154.0 (Ar), 148.7 (Ar), 123.5 (Ar), 120.0 (Ar), 115.2 (Ar), 113.6 (Ar), 68.1 (-OCH 2 -), 59.0 (bridge), 31.8 (alkyl), 27.9 (alkyl), 25.7 (alkyl), 22.6 (alkyl), 14.1 (-CH 3 ). FTIR (KBr)…”

“…Nickel complexes of bis(salicylideniminato) ligands (NiSalens) have attracted significant attention in the field of catalysis [1]. The most useful are the polymeric complexes of this type [2], which are considered to be the materials for electrocatalytic [3,4] and photoelectrocatalytic [5] systems, electrochemical sensors [6,7], electrochromic [8,9], and energy storage devices [10][11][12][13].…”