A Li–O2 battery cathode with vertical mass/charge transfer pathways

Abstract

As a candidate for next generation energy storage devices, the Li–O₂ battery (LOB) has been extensively studied in the last decade because of its ultrahigh theoretical energy density (≈3500 W h kg⁻¹) and inexhaustible “cathode material”—oxygen. Unlike other batteries with a closed configuration, the discharge/charge process of the LOB involves complicated electrochemical reactions at multi-phase interfaces. The mass/charge transfer in the oxygen cathode may limit the discharge/charge rate and capacity. Herein, a novel oxygen cathode with a rolled CNT film configuration is proposed to address the above issue. In such a configuration, the CNT film is vertically aligned, which serves as an excellent electron transfer expressway. Meanwhile, the partially wetted fluffy cotton layer between the CNT film layers endows the cathode with high ionic conductivity and oxygen diffusivity in the vertical direction. Electrons, ions and oxygen molecules may smoothly settle at both sides of the CNT film. Thus, the cathode exhibits an enhanced discharge capacity up to 13 564 mA h g⁻¹, which is 2.5 times larger than the capacity of the conventional parallel aligned CNT film. Moreover, the cycle life is also improved by 5.5 times.