Study On Electrolyte Of High Capacity Aluminum Ion Battery

In the 21st century,human beings are facing two major challenges of energy and environment.Therefore,the development of a new generation of efficient and clean renewable energy is an inevitable requirement for the realization of efficient and sustainable development of human society.In order to develop a high-performance energy storage system,it is necessary to explore a high-performance and recyclable secondary battery,which has the characteristics of safety and environmental protection consistent with clean secondary energy.Due to the shortage of lithium resources,high cost and poor safety of lithium ion battery,the next generation of high-capacity and ultra-high life battery-aluminum ion battery(AIBs),has attracted people’s attention.Here,a series of AIBs electrolytes were synthesized by using AlCl3 as the precursor of Al complex,amide,hydrochloric acid and ammonium chloride as the cationic precursor.The electrochemical performance and energy storage mechanism of the batteries were studied and reported in detail.(1)A novel ionic liquid is prepared as electrolyte of AIBs by mixing anhydrous AlCl3 and caprolactam(CPL)according to different molar ratio,and the influence of urea on the electrochemical performance in AlCl3/CPL electrolyte is discussed,and the charging/discharging mechanism of AIBs is described.AlCl3/CPL electrolyte shows a cut-off voltage of 2.7 V,which greatly improves the specific discharge capacity of the battery compared with published papers.Also,the battery has a good cycling stability and rate performance.It is found that the specific discharge capacity of AIBs increased by 16.67-30%when a proper amount of urea was added to AlCl3/CPL electrolyte,and the electrochemical performance of AlCl3/CPL is greatly improved.The reason why urea improved the performance of the battery is found by the comparison of chemical properties,conductivity test and resistance analysis of ionic liquid.The micro properties of the electrolyte were characterized by Raman,XRD and EPMA,and the existence of AlCl4 and Al2Cl7-ions in the pristine electrolyte is indicated.The electrochemical mechanism of the intercalation/de-intercalation of AlCl4 in the process of charging/discharging of AIBs with AlCl3/CPL and AlCl3/urea/CPL systems is described,and it provides new insights for the research and development of AIBs.(2)The AIBs electrolyte is synthesized by mixing AlCl3(the precursor of Al complex)with ImidazoleHCl and pyridine hydrochloride(PC)respectively.Electrochemical properties and the charging/discharging mechanism of the battery are described.AlCl3/ImidazoleHCl and AlCl3/PC electrolyte use commercial graphite and spherical graphite as cathode respectively.The electrolyte exhibits excellent electrochemical performance,reduces the threshold of AIBs positive material,and decreases the cost of AIBs.The chemical nature of the electrolyte is characterized by Raman,which indicates that the existence of AlCl4-and Al2Cl7-in the electrolyte has a good conductivity.The intercalation/de-intercalation mechanism of AlCl4-was analyzed by characterization of XPS and EDS,and it was verified that the hydrochloric acid material was suitable for the cation precursor of AIBs electrolyte.The excellent electrochemical performance of AIC13/ImidazoleHCl and AlCl3/PC provides new ways for the synthesis of AIBs electrolyte from other hydrochloric acid salt.(3)Two novel AIBs electrolytes are synthesized by mixing AlCl3 with Benzyltrimethylammonium Chloride(BTMAC)and Benzyltriethylammonium chloride(TEBAC)respectively.The electrochemical properties of the electrolytes and the energy storage principle of AIBs are characterized with natural graphite and commercial graphite as positive cathode.AICI3/BTMAC electrolyte shows a good electrochemical performance at ultra-high current density.AlCl3/TEBAC electrolyte shows superior charging capacity at 25 A g-1,which can be fully charged in 13 seconds.In this paper,the research of aluminum electrodeposition and AIBs electrolyte is firstly combined,and the application of ionic liquid in two fields is described,which creates a new way for the research of AIBs electrolyte.AlCl3/BTMAC and AlCl3/TEBAC ionic liquids are potential electrolytes for AIBS.