Structure Design,Synthesis Of Copper Chalcogenides And Their Aluminum Storage Mechanism

In 1991,Sony commercialized lithium-ion batteries for the first time.In the course of nearly 30 years of development,lithium-ion batteries have made great progress and occupied a large market share.However,the development of lithium-ion batteries has also encountered bottlenecks,such as difficulties in increasing energy density and higher manufacturing costs.Therefore,more and more attentions are shifting to nonlithium secondary batteries.Aluminum is the most abundant metal element on the earth,and Al3+ can transfer three electrons in the electrochemical process,which can provide the highest volume specific capacity and mass specific capacity next to lithium.Therefore,aluminum ion batteries have broad application prospects.Owing to the fact that metal aluminum has no dendrites during charging and discharging processes,it can be directly used as an anode electrode.Therefore,it is mainly the cathode material that determines the energy density of aluminum ion batteries.Recent studies have shown that transition metal chalcogenides are an ideal cathode material.In this paper,selenium and tellurium with larger radius,weaker electronegativity,and better electronic conductivity were introduced through structural design to improve the electrochemical performance of copper-sulfur compounds.Sedoped CuS and Cu1.81 Te nanorods were synthesized by a simple method,and their aluminum storage mechanism was studied.The main results are summarized as follows:(1)CuS nanosheets and CuSxSe1-x nanosheets are synthesized using S powder,Se powder,and Cu(NO3)2 as raw materials.The doping of Se can not only significantly increase the volume of CuS cell and the interplanar layer spacing,but also improve the conductivity of CuS.The specific discharge capacity of CuSxSe1-x can be reached 308 mAh g-1 in the first cycle,and it can still be stable at 90 mAh g-1 after 100 cycles.The results of Cyclic Voltammetry(CV)and Galvanostatic Intermittent Titration Technique(GITT)show that the diffusion coefficient of aluminum ions in CuSxSe1-x is improved by 2 to 3 orders of magnitude compared to CuS.In addition,ex-situ X-ray diffraction(ex-XRD)and X-ray photoelectron spectroscopy(XPS)are used to study the electrochemical mechanism of Al/CuS batteries,and it is shown that the reversible conversion between CuS and Cu,Al2S3 occurs during the charging and discharging processes.(2)Cu1.81Te nanorods were synthesized by hydrothermal method using Te powder and CuCl2 as raw materials.Cu1.81Te nanorods exhibit excellent electrochemical performance as a novel cathode material for aluminum ion batteries.At a current density of 10 mA g-1,the initial specific discharge capacity can reach 270 mAh g-1.When the current density is increased to 40 mA g-1,the initial specific discharge capacity can reach 144 mAh g-1.and it can still be stable at 50 mAh g-1 after 66 cycles.The GITT and CV results show that the diffusion coefficient of Al3+ in Cu1.81Te is much higher than that in the sulfide,which is mainly due to the low electronegativity and high conductivity of Te.In addition,ex-XRD,XPS,and 27Al nuclear magnetic resonance(NMR)were used to study the electrochemical mechanism of Al/Cu1.81 Te batteries.The results show that Al3+ ions are intercalated and de-intercalated in Cu1.81Te during charging and discharging processes.