Controlling uniform deposition of discharge products at the nanoscale for rechargeable Na–O2 batteries

Abstract

Sodium–oxygen batteries are an attractive alternative for electrical energy storage applications because of their high-energy density and low cost. As a common challenge for all air-based battery systems, Na–O₂ batteries also suffer from inefficient reversible formation of discharge products and poor cycling performance. Here, we report the design and synthesis of a binder-free air electrode composed of three-dimensional (3D) nitrogen-doped graphene aerogels (N-GAs). In this design, nitrogen-doped graphene aerogels grow directly on the Ni foam (3D N-GA@Ni) with a well-preserved interconnected 3D architecture. The Na–O₂ cell with the 3D N-GA electrode is capable of large capacity (10 905 mA h g_carbon⁻¹ at a current density of 100 mA g_carbon⁻¹), long cycle life (over 100 cycles at 100 mA g⁻¹ with a specific capacity limit of 500 mA h g_carbon⁻¹) and high rate performance (over 50 cycles at 300 mA g_carbon⁻¹). These properties are mainly attributed to the active N-group, which controls the uniform deposition of discharge products at the nanoscale and provides active sites for decreasing overpotential. This encouraging performance also offers a brand new approach to improve the electrochemical performance of Na–O₂ batteries and other metal–air batteries.