Electrochemical Properties of Rechargeable Organic Radical Battery with PTMA Cathode

Abstract

The electrochemical properties of the organic radical battery (ORB) having a lithium metal anode and a cathode consisting of a nitroxide radical polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) with 1M LiPF6 as an electrolyte in ethylene carbonate (EC)/dimethyl carbonate (DMC) have been evaluated at room temperature. The cell, with a thin cathode of 17 mu m thickness incorporating 40 wt.% of PTMA, exhibited the full theoretical specific capacity at current densities up to 10 C (similar to 1 mA/cm(2)). However, a decrease in the specific capacity and an increase in the ohmic resistance were observed at higher current densities. The cell performance was good even on repeated charge-discharge cycles as an excess of 85 % retention of the initial discharge capacity was observed. This was true even after 400 cycles. However, a gradual decrease in capacity, an increase in charge-discharge voltage separation, and an electrode/electrolyte interfacial resistance have been observed after a large number of cycles. The examination of the scanning electron micrographs of the cathode material revealed that prolonged cycling resulted in the agglomeration of PTMA particles. These in turn increased the resistance and decreased the capacity of the cell.