Compressible, gradient-immersion, regenerable carbon nanotube sponges as high-performance lithium–oxygen battery cathodes

Lithium–oxygen batteries promise ultrahigh energy density, yet one of the key barriers toward applications is the rapid performance decay during cycling especially at high rates, owing to the sluggish redox kinetics and severe parasitic reactions under elevated overpotentials within the cathode. In face of the above challenge, here we present a carbon nanotube sponge-based high-performance lithium–oxygen cathode by a series of approaches such as tailoring discharge product morphology to lower the overpotential, controlled sponge-compression for high mass loading to facilitate high-rate cycling, gradient electrolyte-immersion to rationally utilize its interior for efficient multiphase transport, and water treating for regenerated use. These 4 methods target different aspects of the electrochemical behavior in a Li–O2 cathode, thus constituting a complementary and integrated strategy to overcome the challenges in this field. As a result, we achieve simultaneously an ultralong cycle life (1423 cycles, 2846 h) at high rate (0.5 mA cm−2) under low overpotential (charging below 4.0 V throughout 1100 cycles), also with an areal capacity over 20 mAh cm−2 and extended 500 cycles after regeneration. Such an overall performance is much superior to recently developed 3D metal foam or carbon-based cathodes. Our designed sponge cathode represents a promising candidate for developing durable, high-energy and high-power metal–air battery systems, pushing forward their practical application.