Research On Bismuth/Antimony-based Materials As Anode For High Performance Potassium/sodium Ion Batteries

Rechargeable batteries have aroused much concern to fight against the deteriorating environment and tackle the ever-increasing energy demand.Among them,lithium-ion batteries have achieved great commercial success due to their high energy density and good stability.However,the high cost and scarce lithium resources have been hindering their further development in the future.Therefore,finding low cost and resourceful substitutes has become a top priority.Potassium and sodium have similar redox potentials to lithium,and they are low-cost and abundant in earth.Hence,they have the potential to replace lithium in alkaline metal batteries and have become a new research focus.Notably,electrode materials have become the key to promote the application of potassium ion batteries(PIBs)and sodium ion batteries(SIBs).Bismuth and antimony-based materials have excellent rate performance and high theoretical capacity,and have become promising candidates for future anode materials.However,there are still some problems that urgently need to be addressed,such as sluggish reaction kinetic,violent volume expansion,and poor cycling stability.Based on above discussion,long life and high-rate performance bismuth/antimony-based material for potassium/sodium ion batteries anode were obtained by specific structure design.Their potassium/sodium storage behaviors were investigated in depth via electrochemical tests,DFT calculations and et al.The main research contents of this thesis are as follows:(1)Spray drying and high-temperature calcination were utilized to prepare tremella-like porous microspheres with BiSb nanoparticles embedded in carbon matrix(BiSb@TCS).The microsphere was made up of two-dimensional carbon nanowalls and there exists M-O-C bonds between active nanoparticles and carbon matrix,providing a short ion diffusion path and excellent structural stability.When used as the anode of PIBs and SIBs,it exhibited ultra-long cycling life and excellent rate performance.In PIBs,it rendered a high reversible capacity of181 m Ah g^-1 after 5700 cycles at 2 A g^-1,and the specific capacity at 6 A g^-1 was as high as119.3 m Ah g^-1,which is better than most of the bismuth-based and antimony-based anode materials in literature at present.In SIBs,it provided a reversible capacity of 186 m Ah g^-1 after1000 cycles at 2 A g^-1,and the specific capacity was 136.2 m Ah g^-1 at 10 A g^-1.Furthermore,potassium/sodium storage mechanism,kinetics,and thermodynamic behavior of BiSb@TCS were analyzed.It is found that such an extraordinary performance is derived from the excellent structural stability of the microspheres,the shortened ion diffusion path,and the enhanced spontaneous adsorption of BiSb for alkali metal ions.In addition,kinetic analysis showed that pseudocapacitance effect also plays an important role in the excellent rate performance of the battery.(2)Spray drying and high-temperature calcination were performed to synthesize tremella-like porous microspheres with Bi₂O₃ embedded in carbon matrix(Bi₂O₃@TCS).Bi₂O₃ was applied to potassium ion batteries for the first time.The material exhibited enhanced electrochemical performance.In PIBs,it provided a specific capacity of 161 m Ah g^-1 after 200cycles at 2 A g^-1,while in SIBs,it still rendered 119 m Ah g^-1 after 1000 cycles at 2 A g^-1.CV curve revealed its possible potassium storage mechanism.Kinetic analysis showed that the contribution of pseudocapacitance has played a certain role in its good rate performance.