One step “growth to spinning” of biaxially multilayered CNT web electrode for long cycling Li–O2 batteries

Abstract

Li–O2 batteries have attracted great attention because of their high theoretical energy density, which exceeds the highest possible value of currently used Li-ion batteries. The operation of Li–O2 batteries include the formation and decomposition of Li2O2 at the cathode, and cell degradation occurs because such discharge products accumulate on the pores and cause pore clogging. For reversible charge–discharge process, in this study, a biaxially multilayered high crystalline carbon nanotube (CNT) web was designed and fabricated by a modified direct spinning method, which was the first demonstration that realize the biaxially multilayered structure in one-step process. The high crystallinity of the CNT surface reduced its decomposition and the biaxial alignment of CNT enabled the web to be opened for O2 gas and electrolytes without pore clogging. The pore size distribution verified that effective pores were better developed in the biaxially multilayered CNT web, which facilitated the flow of O2 gas and electrolytes. The use of this specially designed CNT as a cathode improved the cyclability by 75% and dramatically reduced the overpotential. For the practical use of Li–O2 batteries, a 3D folded cell with biaxially multilayered CNT web electrode is fabricated and demonstrated 30 cycles at 100 W h/kgcell cutoff.