3D Graphene And MXene Based-anode Materials For Lithium/sodium-ion Batteries

Because of its high energy density,lithium-ion batteries have been employed as the principal power source for a variety of portable electronic products and electric vehicles.However,lithium-ion batteries are not ideal for large-scale electrical energy storage conversion systems due to the high cost of lithium salts and the limited and uneven distribution of lithium resources.Recently,because of its low cost,and natural availability,sodium metal has recently emerged as a possible alternative to lithium metal as anode material for next-generation energy storage systems.However,lithium and sodium ion batteries have many of the same problems,such as lower electrical conductivity and poorer capacity,limiting their rapid development.And since the radius of sodium is larger than that of lithium,most anode materials for lithium batteries are not suitable for sodium cells.Ggraphene and transition metal carbide（MXene）show great promise for high performance lithium/sodium batteries due to their adjustable layer spacing,unique structure and excellent performance.Therefore,this paper focuses on the controlled design of graphene and MXene as the substrate materials with respect to their material composition,structure and morphology,and investigates their electrochemical performance and mechanism in lithium/sodium batteries.The main research contents are as follows:1.Graphene-based Co-MOF composites for lithium/sodium ion batteries,ZIF-67@r GO composite:ZIF-67 is combined with graphene to create a highly stable anode that can improve performance even more.Subsequently,3D ZIF-67@r GO composites with excellent electron and ion-transport properties were synthesized.The as-formed 3D ZIF-67@r GO film can be directly compressed and used as a binder-free LIBs anode,delivering a superior Li storage capacity of 1421 m Ah g^-1 at 0.1 m A g^-1 and excellent rate performance of 889 m Ah g^-1 at 4A g^-1.As SIBs,excellent sodium storage capacity of 410 m Ah g^-1 is provided at 0.1 m A g^-1,and excellent magnification performance of 108 m Ah g^-1 is provided at 4A g^-1.2.Alkali-induced 3D MXene frameworks for lithium/sodium ion batteries,3D 6M-MXene framework anode materials:3D frameworks of potassium hydroxide-induced folded Ti₃C₂MXene nanosheets were prepared by simple magnetic stirring.The 3D 6M-MXene frameworks with extended interlayer spacing have excellent capacity(0.1 A g^-1,390 m Ah g^-1),excellent multiplicative capability,and long-term cycling capability（99%capacity retention after 1500cycles）as anode materials for stabilized Li-ion batteries.When used as a sodium ion anode,the electrode also achieves an extraordinary capacity of 98 m Ah g^-1 at 0.1 A g^-1 and an extraordinary capacity retention rate of 80%at a high current density of 2 A g^-1.3.MXene based Na₂Ti₃O₇ composites for Li-ion batteries,sandwich shaped Na₂Ti₃O₇nanosheet/Ti₃C₂ MXene composites:A unique sandwich-like Na₂Ti₃O₇ nanosheet/Ti₃C₂MXene composite with an expanded interlayer spacing of MXene has been fabricated by one-step simultaneous alkalization and oxidation.The NTO@MXene with a unique structure shortens ion diffusion distance and promotes electrolyte infiltration,which is favorable for high-performance rechargeable batteries.As a result,the NTO@MXene composite as an anode electrode for lithium-ion battery（LIB）,delivered exceptional rate performance(159 m Ah g^-1 at4 A g^-1)and long-life cycling performance(capacity retention of nearly 100%at 4 A g^-1 after1200 cycles).When used as a sodium-ion battery（SIB）anode,the electrode also achieved an extraordinary capacity of 103 m Ah g^-1 at 0.1 A g^-1 and exceptional capacity retention of 70%at a high current density of 2 A g^-1 after 3000 cycles.