Additive-Free Organic Radical Batteries Prepared through Electrochemical Polymerization of TEMPO-Decorated Terthiophene

Batteries based on organic active materials offer a promising alternative to traditional metal-based systems due to environmental issues as well as high possible charging and discharging rates. However, the established organic materials suffer from a very low intrinsic electrical conductivity, requiring the addition of conductive materials. Herein, we present an approach to overcome this problem through the application of a conductive polythiophene decorated with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) units through elec-trochemical polymerization of suitable monomers directly onto the battery electrode. We demonstrate that a terthiophene linked to one TEMPO moiety not only allows successful electropolymerization but also the construction of additive-free organic batteries. Based on electrochemical investigations in combination with quantum chemical simulations, we can evaluate the underlying redox processes at the molecular level. Cell tests demonstrate the principle functionality of the system with rate capabilities of up to 20% capacity retention at 50C and a good long-term stability with a capacity loss of only 0.03% per cycle.