Three-Dimensional Hierarchical Graphene-CNT@Se: A Highly Efficient Freestanding Cathode for Li-Se Batteries

A three-dimensional (3D) graphene-CNT@Se (3DG-CNT@Se) aerogel with carbon nanotube/selenium sandwiched between graphene nanosheets is realized through a facile solvothermal method. Without polymetric binders, conductive additives, or metallic current collectors, the freestanding cathode demonstrates an initial capacity of 632.7 mA h g^-1, a value close to 95% of the theoretical capacity of 675 mA h g^-1. At 1, 4, and 10 C, the cathode owns reversible specific capacities of 558.3, 436.4, and 192.9 mA h g^-1, respectively. Such record-breaking values, as compared to earlier Li-Se batteries, are attributed to the unique 3D mesoporous, conductive network offering highly efficient channels for electron transfer and ionic diffusion, as well as the hierarchical structure preventing fast dissolution of polyselenides and suppressing volume expansion of Se in charge/discharge. The work is expected to open up promising opportunities to realize the application of Li-Se batteries in portable electronics, electrical vehicles, and so forth.