Hierarchically porous carbon-coated SnO2@graphene foams as anodes for lithium ion storage

Abstract

Graphene-based hierarchically porous materials have exhibited enormous potentials in high-performance lithium-ion batteries. However, the electrochemical performance of these materials is hampered due to the detachment of active materials from graphene upon long-term cycling. Therefore, the interfacial design between active materials and graphene is crucial for their high performance in lithium-ion storage. In this study, a hierarchically porous architecture of spatially confining carbon-coated SnO2 nanospheres (C-SnO2 NSs) within graphene foam has been designed and fabricated by employing the H-bonding effect of sodium carboxymethyl cellulose to bridge the C-SnO2 NSs and graphene sheets in a complete encapsulation arrangement. The as-fabricated architecture not only prevents the detachment of C-SnO2 from graphene and direct exposure of them in electrolyte, but also suppresses the electrode's pulverization caused by the large volume change of SnO2 during charge/discharge processes, thus achieving SnO2 interfacial and structural stability. Moreover, benefiting from the hierarchical porosity and interconnected graphene network, electrode reaction kinetics is greatly enhanced. As a result of these merits, the as-built electrode shows extraordinary rate capability (611.1 mA h g−1 at 4.0 A g−1; 427.9 mA h g−1 at 8.0 A g−1) and robust cycling stability (1458.8 mA h g−1 remaining after 700 cycles at 1.0 A g−1).