SnS,a well-known van der Waals chalcogenide,is susceptible to oxidation in high-temperature or highhumidity environments,significantly impacting its functional performance and device stability.Conversely,oxidation can...SnS,a well-known van der Waals chalcogenide,is susceptible to oxidation in high-temperature or highhumidity environments,significantly impacting its functional performance and device stability.Conversely,oxidation can be used as an effective strategy for surface engineering,allowing for structure modulation or design,property tuning and application exploration.However,there is currently a gap in understanding the relationship between the oxidation behavior of SnS,the structure of its oxidized surface,and the dependence on oxidation temperature.In this study,we systematically investigated the evolution of SnS surfaces under thermal oxidation using electron microscopy.The microstructure evolution(e.g.,surface structures,phases,defects,and interface)of SnS during high-temperature oxidation has been fully characterized and studied based on cross-sectional samples.Various surface heterostructures were constructed,including SnO_(2)/SnS,SnO_(2)/SnS_(2)/SnS,and SnO_(2)/Sn_(2)S_(3)/SnS,offering significant potential for the surface functionalization of SnS-based systems.Accordingly,oxidation mechanisms at different stages were elucidated based on the detailed and clear picture of microstructures.This research not only deepens our understanding of the fundamental science of SnS oxidation but also provides valuable insights for preventing and developing surface oxidation engineering in SnS and other van der Waals chalcogenides/materials.展开更多
Conversion electrodes typically have high theoretical specific capacity,but mostly suffer large structural changes during charge/discharge and result in poor cycling stability.The optimization of the polycrystalline m...Conversion electrodes typically have high theoretical specific capacity,but mostly suffer large structural changes during charge/discharge and result in poor cycling stability.The optimization of the polycrystalline materials is the mostly used strategy,however,these polycrystalline materials are intrinsically vulnerable to grain-boundary(intergranular)fracture caused by the anisotropic volume change during sodiation/desodiation,resulting in rapid impedance growth and capacity decay.Herein,we propose an alternative pathway to design single-crystal materials as potential conversion anodes.As an example,SnO_(2)with different crystallinities is successfully synthesized via solvothermal methods and compared to determine the implications of different crystallinity for the electrochemical properties of conversion anodes.It is demonstrated that the single-crystal SnO_(2)not only has faster Na+diffusion dynamics but also maintains structural stability via topotactic reaction.Further optimization of the electron conduction and structural robustness is realized by uniformly covering a graphitic carbon shell on the surface of single-crystal SnO_(2)nanosheets.The modified singlecrystal SnO_(2)exhibits a high reversible capacity of 436.2 mA h g^(-1)and maintains a high capacity of 257.1 mA h g−1 and remarkable capacity retention of about 98.9%after 9000 cycles at 5000 mA g−1.The deep understandings of the topotactic reaction in single crystal conversion anode in this work provide a theoretical foundation and new direction for further developing electrode materials with excellent electrochemical performance,especially high rate capabilities,and long cyclability.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.11904039,52125103,52071041,U21A2054 and 12104071)。
文摘SnS,a well-known van der Waals chalcogenide,is susceptible to oxidation in high-temperature or highhumidity environments,significantly impacting its functional performance and device stability.Conversely,oxidation can be used as an effective strategy for surface engineering,allowing for structure modulation or design,property tuning and application exploration.However,there is currently a gap in understanding the relationship between the oxidation behavior of SnS,the structure of its oxidized surface,and the dependence on oxidation temperature.In this study,we systematically investigated the evolution of SnS surfaces under thermal oxidation using electron microscopy.The microstructure evolution(e.g.,surface structures,phases,defects,and interface)of SnS during high-temperature oxidation has been fully characterized and studied based on cross-sectional samples.Various surface heterostructures were constructed,including SnO_(2)/SnS,SnO_(2)/SnS_(2)/SnS,and SnO_(2)/Sn_(2)S_(3)/SnS,offering significant potential for the surface functionalization of SnS-based systems.Accordingly,oxidation mechanisms at different stages were elucidated based on the detailed and clear picture of microstructures.This research not only deepens our understanding of the fundamental science of SnS oxidation but also provides valuable insights for preventing and developing surface oxidation engineering in SnS and other van der Waals chalcogenides/materials.
基金supported by the National Natural Science Foundation of China(No.51971065)the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-07-E00028)The authors would like to thank SCI-GO(www.sci-go.com)for the XPS analysis.
文摘Conversion electrodes typically have high theoretical specific capacity,but mostly suffer large structural changes during charge/discharge and result in poor cycling stability.The optimization of the polycrystalline materials is the mostly used strategy,however,these polycrystalline materials are intrinsically vulnerable to grain-boundary(intergranular)fracture caused by the anisotropic volume change during sodiation/desodiation,resulting in rapid impedance growth and capacity decay.Herein,we propose an alternative pathway to design single-crystal materials as potential conversion anodes.As an example,SnO_(2)with different crystallinities is successfully synthesized via solvothermal methods and compared to determine the implications of different crystallinity for the electrochemical properties of conversion anodes.It is demonstrated that the single-crystal SnO_(2)not only has faster Na+diffusion dynamics but also maintains structural stability via topotactic reaction.Further optimization of the electron conduction and structural robustness is realized by uniformly covering a graphitic carbon shell on the surface of single-crystal SnO_(2)nanosheets.The modified singlecrystal SnO_(2)exhibits a high reversible capacity of 436.2 mA h g^(-1)and maintains a high capacity of 257.1 mA h g−1 and remarkable capacity retention of about 98.9%after 9000 cycles at 5000 mA g−1.The deep understandings of the topotactic reaction in single crystal conversion anode in this work provide a theoretical foundation and new direction for further developing electrode materials with excellent electrochemical performance,especially high rate capabilities,and long cyclability.
