Templated Carbon Anodes With In Situ Doping For High-Performance Sodium Ion Batteries

Sodium ion batteries?SIBs?is one of the most promising next-generation energy storage devices due to the abundance and wide distribution of Na.Nevertheless,SIBs suffers from low capacity,small kinetics and poor stability because of the larger radius of Na⁺than that of Li⁺.Finding and designing suitable electrodes are essential to address the above problems.Carbonaceous materials have been intensively investigated for their abundant resources,low cost and good stability.However,their further application is limited by the low capacity and poor rate capability.The thesis aims to provide two strategies to enhance the electrochemical behavior of carbon anodes in SIBs by modifying structure and composition simultaneously.?1?The in situ nitrogen-doped carbon nanotubes?N-CNTs?were synthesized by using V₂O₅ nanowires as templates and dopamine as carbon as well as nitrogen source.Benefiting from the intertwined one-dimensional hollow structure with hierarchical pores,thin walls,large interlayer distance and nitrogen doping,the N-CNTs can deliver a capacity of 91.7 mAh g^-1 even at 10 A g^-1.Further,cycling tests show that capacities of 125.5 and 104.2 mAh g^-1 can be maintained after 1000 cycles at 1 and 5A g^-1,respectively.?2?Ultrathin and in situ sulfur-doped carbon nanosheets?HSC700?were fabricated by using hydrotalcites as templates and sodium p-styrenesulfonate as carbon and sulfur precursor.Owing to the ultrathin 2D structure,high-content sulfur doping as well as large surface area together with hierarchical pores,the HSC700 can deliver capacities of 336.3 and 125.0 mAh g^-1 at 0.1 and 10 A g^-1,respectively.In addition,it also have good long-term cycling stability at 1 and 5 A g^-1.