Synthesis of Poly(4-methacryloyloxy-TEMPO) via Group-Transfer Polymerization and Its Evaluation in Organic Radical Battery

Abstract

Novel group-transfer polymerization (GTP) of 4-methacryloyloxy-TEMPO for the preparation of poly(4-methacryloyloxy-TEMPO) (PTMA) has been developed. The new PTMA has been tested as an active electrode material in rechargeable organic radical battery (ORB). The advantage of the GTP method is that it affords PTMA containing the theoretical amount of nitroxide groups. Furthermore, cross-linked PTMA was prepared in the presence of small amounts of ethylene glycol dimethacrylate. Cyclic voltammetry of this PTMA showed a single, highly reversible redox couple at a potential of ca. 3.6 V (vs Li/Li+). This potential is similar to the potential of materials (e.g., LiCoO2) used for the positive electrode in lithium-ion batteries. In galvanostatic cycling experiments between 3.0 and 4.0 V in a half-cell setup vs metallic Li as counter and reference electrode a reversible specific charge of ca. 103 Ah kg-1 at current rates up to 1 C was obtained with the cross-linked PTMA. The useable charge capacity is very stable with cycling, showing only a slight decrease after 200 full charge−discharge cycles at 2 C.