Amorphous Titanium Dioxide Nanosheet:Fabrication And Lithium/Sodium Storage

With the continuous iterations of various electronic products and the rapid development of electric vehicles,People have higher demands for battery performance,including energy power density,cycle time,safety and stability.Developing a new safe and reliable negative electrode material with high cycling stability and excellent rate performance is the key to improving the performance of lithium/sodium-ion batteries.Titanium dioxide,as a typical titanium-based oxide,possesses many advantages,such as suitable theoretical capacity(335 mAh g^-1),small volume change during charge and discharge（<4%）,high cycling stability,safety and environmental friendliness,etc,making it highly promising for applications in lithium/sodium-ion batteries.However,traditional titanium dioxide crystalline materials have poor rate performance.To realize the application of such materials in high-power electronic devices,it is necessary to improve the ion diffusion rate.The introduction of amorphization and two-dimensional porous morphology regulation are expected to achieve this goal and improve rate performance of battery.Amorphous materials with isotropic characteristics can facilitate ion storage and migration through the activation of open channels.Furthermore,two-dimensional porous nano-materials exhibit a larger specific surface area,promoting electrolyte wetting and maintaining ion affinity.Therefore,in this work,we developed two methods for preparing amorphous titanium dioxide nanosheets using the salt template method and peroxotitanium acid freeze-drying method.The corresponding materials exhibited excellent lithium/sodium storage capacity.1.Amorphous titanium dioxide nanosheets were prepared by using potassium chloride as a salt template,exploiting the interface strain between the salt and titanium dioxide to suppress the transition of amorphous-to-crystalline phase.These nanosheets possess a high specific surface area of 210 m² g^-1 and exhibit a open atomic arrangement structure,facilitating extensive contact with the electrolyte and reducing the ion diffusion distance.This promotes surface interface capacitive storage and enhances the lithium/sodium storage capacity of the electrode material at high rates.In lithium-ion batteries rate test at current density of 10 A g^-1,the amorphous titanium dioxide nanosheets demonstrate a high specific capacity of 138 mAh g^-1.Even after 1000 cycles at a current density of 6 A g^-1,a high specific capacity of 175 mAh g^-1 is maintained.In sodium-ion batteries rate test at current density of 10 A g^-1,the nanosheets achieve a specific capacity of 115 mAh g^-1.Even after 1000 cycles,the specific capacity remains at 84 mAh g^-1.2.To address the low yield issue in-the synthesis of amorphous titanium dioxide nanosheets,the peroxotitanium acid freeze-drying method was employed.This approach demonstrated a scalable synthesis of amorphous nanosheets on the kilogram scale and the negative electrode material achieved high-performance lithium/sodium-ion batteries.In lithium-ion batteries,after 3000 cycles at a current density of 10 A g^-1,the nanosheets exhibited a specific capacity of 130 mAh g^-1,and even after 6000 cycles,the specific capacity remained at 105.2 mAh g^-1,with a capacity retention rate of 81%.In sodium-ion batteries,after 1000 cycles at a current density of 10 A g^-1,the nanosheets exhibited a specific capacity of 82.7 mAh g^-1.