Strongly coupled sulfur nanoparticles on graphene-carbon nanotube hybrid electrode for multifunctional sodium and aluminium ion storage

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The practical utility of multiwalled carbon nanotubes in sodium and aluminium ion batteries are limited due to its low interlayer spacing of 0.34 nm. Herein, we have developed a simple approach of enhancing the interlayer spacing of multiwalled carbon nanotubes by incorporating sulfur nanoparticles into graphene-multiwalled carbon nanotube (GCNT) structure. This proof of concept is realised from its excellent specific capacity and cyclic stability for the first time in sodium and aluminium ion batteries. GCNT/S as the anode in sodium ion battery exhibits a specific capacity of about 510 mA h g−1 at a current density of 50 mA g−1 with a cyclic stability of 2500 cycles which results in about 42% enhancement in specific capacity when compared to GCNT. GCNT/S as cathode in aluminium ion battery shows a specific capacity of 507 mA h g−1 at a current density of 50 mA g−1 and a stable cyclic stability for 600 cycles. This is about 7.2 times enhancement in specific capacity when compared to GCNT. The highly durable nature is due to the small sulfur particles which offer low volume expansion and the GCNT structure acts as a buffer matrix for controlling the volume expansion. Our study provides a new and a simple strategy to enhance the specific capacity and cyclic stability of multiwalled carbon nanotubes for sodium ion batteries and aluminium ion batteries which can be a promising approach for other cost-effective battery technologies as well.