Flexible carbonized cotton covered by graphene/Co-doped SnO₂ as free-standing and binder-free anode material for lithium-ions batteries

A flexible carbonized cotton covered by graphene/Co-doped SnO₂ (CGN/SnO₂-Co) composite is prepared by in situ and subsequent microwave method, then followed by thermal annealing treatment. The SnO₂ nanoparticles with ultra-small size are uniform decorated on the CGN framework, and Co element has been successful doping into SnO₂. It is found that doping process does not affect the phase structure of SnO₂, but great influence the morphology, the electrical conductivity, and the electrochemical properties on the composites. As a free-standing and binder-free anode for lithium-ions batteries, the discharge capacity of CGN/SnO₂-Co have a high value of 549.6 mAh g⁻¹ (1996 μA cm⁻²) after 100 cycles at a current density of 100 mA g⁻¹, which is much higher than those of cotton covered by graphene/SnO₂ (CGN/SnO₂) and cotton covered by graphene/Co₃O₄ (CGN/Co₃O₄) at the same current. The improved performance of CGN/SnO₂-Co can be attributed to the highly stable and conductive CGN framework, ultra-small size of SnO₂ nanoparticles, and Co doping effect. It is reasonable to believe that this work has a great potential improve the performance of energy storage devices.