MXene-based Electrode Materials For Mg-Li Hybrid Batteries

Energy is the eternal theme of the development of human society.With the ever-decreasing fossil energy and the deep-rooted concept of"green mountains and green waters",the development and utilization of renewable energy resources are of great significance to national energy security and environmental protection.In order to strengthen the use of renewable energy sources,the development of energy storage devices?batteries?is of great significance.The problem of dendrite growth in lithium batteries has not been fundamentally solved and Magnesium battery performance is poor,so magnesium-lithium hybrid batteries have been developed to improve the performance of magnesium batteries.In this dissertation,Ti₃AlC₂ was synthesized from TiH₂,Al,TiC powders and was exfoliated to prepapated MXene?Ti₃C₂T_x?.Using the two-dimensional material MXene as the starting material,the following studies were performed:?1?The MXene was hydrothermally treated to obtain MXene/TiO₂ composites.When the hydrothermal temperature was 160°C,the maximum amount of TiO₂ was obtained on the basis of ensuring the integrity of the two-dimensional structure of MXene.The MXene/TiO₂ was silver-doped by means of hydrazine to reduce silver nitrate,obtaining MX/T/Ag electrode material.When the mass ratio of Ag⁺to MXene/TiO₂ is 8:92,the magnesium-lithium hybrid battery has superior electrochemical performance.At 100mAg^-1 Current density,specific capacity 133 mAhg^-1 maintaining after 200 cycles,increased around 21%in specific capacity over MXene/TiO₂ batteries.The reason is that TiO₂ provides high specific capacity,MXene acts as its framework,provides ion transport channels,shortens its transmission distance,and the addition of silver improves the conductivity of the composite material.?2?The MXene is hydrothermally reacted in aqueous glucose solution to obtain MXene/TiO₂@C electrode material.MXene/TiO₂@C is a carbon-coated MXene/TiO₂outer layer to form core-shell structure.The mass ratio of MXene to glucose is m?MXene?:0.4×m?glouse?=9:1,the battery performance is optimized when the hydrothermal temperature is 160°C.The initial cycle specific capacity at 100 mAg^-1 is 195 mAhg^-1,and the capacity retention rate is around 90%after 200 cycles.This specific capacity is 9.7times that of MXene and 59%higher than MXene/TiO₂.It is a very promising magnesium lithium hybrid battery electrode material.The SEM images of the TiO₂ electrode sheet before and after charging and discharging show that the reason why the capacity has been decreased is the agglomeration of TiO₂ during charge and discharge cycles.The structure of MXene/TiO₂@C not only inhibits the agglomeration of TiO₂,but also provides ion transport channels to shorten the ion transmission distance and enhance the conductivity of the electrode.It is an electrode material with potential for development of lithium-lithium hybrid batteries.