Surface‐Dominated Sodium Storage Towards High Capacity and Ultrastable Anode Material for Sodium‐Ion Batteries
Surface‐dominated Na storage is demonstrated on the oxygen‐functionalized graphene nanosheets with fast surface‐capacitive storage and robust structural stability. The enhanced Na storage is realized by tuning the overall oxygen content and specific C = O groups on the graphene matrix for adequate surface‐active sites, accompanying with the high electrical conductivity, high specific surface area, and optimized Na+ transport paths. Abstract The development of sodium‐ion batteries is hindered by the poor Na+ transport kinetics and structural instability of electrode materials during Na+ intercalation/deintercalation. In this work, surface‐dominated Na storage is demonstrated on the oxygen‐functionalized graphene nanosheets (FGS) with fast surface redox reaction and robust structural stability. The FGS samples with tunable oxygen contents and species are fabricated via a two‐step thermal exfoliation method from graphite oxides. The surface‐induced oxygen functional groups can serve as the surface‐redox sites for the FGS electrode, attaining a high specific capacity of 603 mAh g−1 at a current density of 0.05 A g−1, excellent rate capability (214 mAh g−1 at 10 A g−1), and ultrastable cycling stability (capacity retention close to 100% after 10 000 cycles at 5 A g−1). Even at a slow scan rate of 0.1 mV s−1 for cyclic voltammetry, about 67.7% capacity is contributed from the surface adsorption/desorption and surface‐redox reaction, suggesting surface‐dominated Na storage for the FGS‐700 (FGS sample obtained at 700 °C) electrode. The present work demonstrates that the surface oxygen functionalization is an effective strategy to develop high‐performance graphene‐based anodes due to the surface‐dominated Na storage with improved
Published in: "Advanced Functional Materials".