All-Organic Battery Based on Deep Eutectic Solvent and Redox-Active Polymers.

Sustainable battery concepts are of great importance for the energy storage demands of the future. Organic batteries based on redox-active polymers are one class of promising storage systems to meet these demands, in particular when combined with environmentally friendly and safe electrolytes. Deep Eutectic Solvents (DESs) represent a class of electrolytes that can be produced from sustainable sources and exhibit in most cases no or only a small environmental impact. Because of their non-flammability, DESs are safe, while providing an electrochemical stability window almost comparable to established battery electrolytes and much broader than typical aqueous electrolytes. Here, we report the first all-organic battery cell based on a DES electrolyte, which in this case is composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and N-methylacetamide (NMA) alongside the electrode active materials poly(2,2,6,6-tetramethylpiperidin-1-yl-oxyl methacrylate) (PTMA) and crosslinked poly(vinylbenzylviologen) (X-PVBV2+ ). The resulting cell shows two voltage plateaus at 1.07 V and 1.58 V and achieves Coulombic efficiencies of 98 %. Surprisingly, the X-PVBV/X-PVBV+ redox couple turned out to be much more stable in NaTFSI : NMA 1 : 6 than the X-PVBV+ /X-PVBV2+ couple, leading to asymmetric capacity fading during cycling tests.

Anion-Rocking Chair Batteries with Tuneable Voltage using Viologen- and Phenothiazine Polymer-based Electrodes.

Organic battery electrode materials offer the unique opportunity for full cells to operate in an anion-rocking chair mode. For this configuration a pair of p-type redox-active electrode materials is required with a substantial potential gap between their redox processes. We herein investigate viologen-functionalized polystyrenes as negative electrode paired with a phenothiazine polymer as positive electrode in all-organic full cells. The 10 % crosslinked viologen polymer X10 -PVBV gave better performance than the linear PVBV and was employed in a full cell as negative electrode with cross-linked poly(3-vinyl-N-methylphenothiazine) (X-PVMPT) as positive electrode. Three cell configurations regarding the voltage range were investigated, of which one with an operating potential of 0.9 V gave the highest performance. The full cell delivered a specific discharge capacity of 64 mA h g-1 (of X-PVMPT) in the first cycle and a capacity retention of 79 % after 100 cycles. This is one of only few reported anion rocking chair all-organic cells and the first employing a phenothiazine-based positive electrode material.

Environmentally Friendly, Photochemical Access to [ N ∧ C ∧ N ]AuIII Pincer Complexes By Oxidative Addition.

Starting from commercially available DMSAuCl and diazonium salts, cationic [ N ∧ C ∧ N ]AuIII complexes were synthesized in a selective, photosensitizer-free, photochemical reaction by irradiation with blue LED light. This new protocol represents the first easy synthesis of these types of pincer complexes in moderate to excellent yield starting from a readily available gold(I) precursor with nitrogen as the only by-product. Owing to the disadvantages of known protocols, especially the toxicity in the case of a transmetalation with mercury or the necessity for a mostly twofold excess of a gold precursor, this method offers an attractive alternative towards this kind of gold(III) complexes. In addition, the first arylated [ N ∧ C ∧ N ]Au(III) pincer complex was synthesized by using this technology.