Carbon encapsulated cobalt sulfide nano-particles anchored on reduced graphene oxide as high capacity anodes for sodium-ion batteries and glucose sensor

Cobalt sulfide is a promising anode material for a sodium-ion battery because of its high capacity and abundance. However, practical issues such as huge volume changes during sodiation/desodiation result in a low capacity retention during cycling, thus posing a serious challenge to practical applications. In this work, we report a rather easy, single pot microwave synthesis technique having the ability to create carbon-coated, uniformly distributed cobalt sulfide nanoparticles (20-40 nm) on reduced graphene oxide (CoS2@C-rGO). In this structure, the graphene substrate acts as a robust conductive platform to anchor cobalt sulfide, and the outer carbon encapsulation guarantees both the structural integrity and conductivity of the composite. When evaluated as an anode material in a sodium-ion battery, CoS2@CrGO exhibited a stable cycling performance and superior high-rate capability, delivering a reversible capacity as high as 794.9 mAhg−1 at 0.5 A, after 175 cycles. Furthermore, our CoS2@C-rGO electrodes can be used as enzyme-less glucose sensors that exhibit a wide linear response within a range of up to 3 mM of glucose and a low detection limit of 0.078 M.