Redox-active organic materials (ROMs) are promising candidates as alternative electrode materials for rechargeable batteries because of their natural abundance and versatility. In particular, p-type ROMs show high redox potentials (>3.0 V vs. Li+/Li); but, it is still challenging to deliver high specific capacity because they typically possess a single redox center. In this work, we present 5,11-diethyl-5,11-dihydroindolo[3,2-b]carbazole (DEICZ) as a new p-type ROM for a cathode material. Notably, DEICZ showed two plateaus at high voltages of 3.44/4.09 V vs. Li+/Li within the stable electrolyte window to deliver a high specific capacity of 93 mAh/g at the initial cycle. To improve cycle stability and rate capability, a composite cathode of DEICZ was fabricated by intermixing with single-walled carbon nanotubes (SWNTs). The DEICZ/SWNTs electrode maintained 70.4% of its initial capacity after 300 cycles at 1 C-rate and functioned even at 100 C-rate. Furthermore, its application potential as a flexible battery was demonstrated by performing 1000 times bending test.