Design And Performance Of Nonmetallic Dual-ion Batteries Based On Pyr₁₄TFSI Ionic Liquid Electrolyte

Owing to their high energy density,no memory effect and low self-discharge,etc,lithium-ion batteries?LIBs?are widely used in portable electronics and electric vehicles.However,limited lithium resources,high prices and uneven distribution of lithium in the earth's crust hinder the wide applications of LIBs in the field of large-scale energy storage systems.Moreover,with the rapid development of technology,the working time of LIBs is increasingly difficult to meet people's increasing demands.Therefore,it is imperative to develop new-generation battery energy storage devices with low-cost and high-efficiency.A dual-ion battery?DIB?based on the mechanism of ion electrochemical intercalation and deintercalation has been proposed as a feasible alternative.They are expected to solve the problems of low energy density,short service time and high cost of lithium ion batteries.In this paper,we constructed the non-metallic dual-ion batteries without any metal ions participating in the electrochemical reaction using pure ionic liquid as electrolyte,and explored completely renewable electrode materials suitable for such electrolytes.At the same time,the electrochemical performances and working mechanism of the batteries were systematically performed.Main research contents are as follows:?1?A novel ionic liquid dual-graphite battery(denoted as Pyr₁₄TFSI-DGB)based on the pure Pyr₁₄TFSI ionic liquid electrolyte,using natural graphite with both oxidizing and reducing properties as active materials of positive and negative electrodes was constructed,which electrochemical performances were tested by electrochemical workstation and electrochemical testing system.Experimental results demonstrated that the Pyr₁₄TFSI-DGB delivers a discharge specific capacity of 49 mAh g^-11 and a good cycling stability over 100cycles at a current density of 50 mA g^-11 under the electrochemical window of 1.0-4.6 V.Moreover,the Pyr₁₄TFSI-DGB system exhibits a discharge platform up to about 3.7 V.The positive and negative graphites before and after cycling and in various charging and discharging states through the second cycle were characterized by X-ray diffraction?XRD?,Raman spectroscopy?Raman?and scanning electron microscope?SEM?.The results show that the reversible intercalation/de-intercalation reaction of the Pyr₁₄⁺ cations and the TFSI^-anions in the electrolyte occurred on the graphite electrodes,and show good structural stability after 100 cycles.?2?We constructed a novel coronene/graphite dual-ion battery?denoted as C/G-DIB?based on pure Pyr₁₄TFSI ionic liquid electrolyte with a polycyclic aromatic hydrocarbons?PAHs?anode and a natural graphite cathode,and tested its electrochemical performance.The electrochemical tests show that the optimum upper cut-off voltage is 4.4 V by comparing the cycle performance at different upper cut-off voltages.In the voltage range of 1.0-4.4 V,the initial discharge specific capacity of the C/G-DIB is up to 74 mAh g^-1,and discharge specific capacity of the battery remains at a high value after 500 cycles at 3 C,and the capacity retention reached 93%after 100 cycles,demonstrating an excellent cycling stability.The effects of the Pyr₁₄⁺incorporation into the coronene anode in various charging and discharging states were investigated using XRD and Fourier-transform infrared spectroscopy?FT-IR?.It is shown that the coronene anode can be inserted into the large size Pyr₁₄⁺cations to achieve energy storage and exhibits a good structural stability.