Study On Electrochemical Sodium Storage Properties Of MXene-Based Composite Structures

With the growing demand for green energy in modern society,developing energy storage devices with high capacity and good cycle stability is crucial for the next generation of energy systems.Recently,sodium-ion batteries have been considered as potential alternatives to lithium-ion batteries due to their abundant resources,low cost,and environmental friendliness.However,the larger ion radius of Na⁺（1.02（?））relative to Li⁺（0.76（?））results in slower diffusion kinetics and larger volume expansion of sodium storage materials during charge and discharge,leading to limited cycle life and poor rate capability.MXene,a two-dimensional layered material with excellent electrical conductivity and large specific surface area,is a promising electrode material for sodium-ion batteries.Particularly,integrating MXene with metal-based compounds with high theoretical capacity can improve electrochemical performance by controlling the proportion and morphology of the composite.The main research objectives are as follows:（1）Metal selenides have a large specific capacity and are considered to be excellent potential anodic materials for sodium-ion batteries.However,their actual application is severely limited due to unfavorable volume expansion,inferior cycle stability,and inactive kinetics.To address these issues,we designed and synthesized the Sn Se@f-Ti₃C₂ structure via a simple one-pot solvothermal process in this study.The high-capacity 0D Sn Se quantum dots were grown in situ and uniformly distributed on the 2D conductive MXene sheet via electrostatic attraction between Sn ions and MXene.The Sn Se@f-Ti₃C₂ composite exhibited significantly increased capacity of 540 m Ah g^-1 at 0.05 A g^-1 and excellent cycle performance with a 97.79%retention ratio after 100 cycles at 0.5 A g^-1.The excellent electrochemical performance of the Sn Se@f-Ti₃C₂ hybrid was primarily attributed to the synergy between the 0D Sn Se with high capacitance and the 2D MXene sheet with superior conductivity.On one hand,the 0D Sn Se acted as pillars between MXene layers,preventing the stacking of MXene nanosheets.On the other hand,the conductive MXene skeleton provided fast electron/ion transport capability and a large specific surface area,facilitating favorable transfer kinetics and close contact in the electrolyte/electrode interface.（2）Layered double hydroxides（LDHs）have been identified as promising anode materials for sodium-ion batteries（SIBs）.However,issues such as volume expansion and slow redox kinetics still need to be addressed.In this study,we successfully designed and synthesized a heterostructured Co Sn-LDH microsphere composite embedded in the MXene network（Co Sn-LDH@MXene）using a one-step hydrothermal and sonication process.The micro-nano hierarchies and MXene networks accelerate the migration kinetics of Na⁺and mitigate volume changes,improving the electrochemical performance of SIBs.Additionally,the large specific surface area of MXene provides a large number of active sites.The composite exhibits high discharge capacity,enhanced rate capability,and superior cycling performance,with a reversible capacity of 376.8 m Ah g^-1 after 390 cycles at 0.5 A g^-1.These results demonstrate the great potential of this composite material in constructing efficient SIBs.