Preparation And Electrochemical Properties Of Perovskite Fluoride Materials

Nowadays,it has entered an era of rapid energy development,nonaqueous or organic Li-ion energy storage systems,including Li-ion batteries?LIBs?,Li-Air or Li-O₂ batteries,Li-S batteries,Li-ion capacitors?LICs?,dual-ion batteries?DIBs?,etc,have been considered as very important renewable and green energy resources to resolve the evergrowing shortage of burning fossil fuels and global environmental pollution.Two new perovskite fluoride electrode materials are synthesized,which are nickel-cobalt fluoride and zinc-manganese fluoride,it is used as an energy storage device to study their electrochemical properties.The specific work and content are as follows:1.Among the nine samples of K-Ni-Co-F?KNCF for short?synthesized by solvent thermal method in the experiment,the electrochemical test showed that the sample KNCF?1-6?electrode material had the best comprehensive performance.KNCF?1-6?electrode material has typical surface transformation reaction mechanism in charge transfer process.When KNCF?1-6?is used as a negative electrode to assemble LIC with activated carbon?AC?,the LIC of KNCF?1-6?with negative precharged shows higher energy/power density and cycling stability than that of unprecharged lithium ion capacitors.Moreover,after precharged,KNCF?1-6?//AC performs better than LIC of other electrode materials.When we mix LiFePO₄?LFP?with AC at a mass ratio of 1:1,the specific capacity of the mixed positive single electrode is increased,the reconstructed LIC of KNCF?1-6?//AC+LiFePO₄?LFP??1:1?shows better performance than that of KNCF?1-6?//AC.In order to further improve the performance,KNCF?1-6?anode was prelithium treated and AC cathode was prefilled to assemble LIC.The experiment showed that KNCF?1-6?//AC could be improved correspondingly.Finally,KNCF?1-6?is used as the negative electrode of double-ion battery,the positive electrode is graphite 918;918+AC?mass ratio 1:1?;DIB is assembled according to the positive electrode of 918+LFP?mass ratio:1:1?and 918+AC+LFP?mass ratio:1:1:1?,tests show that KNCF?1-6?//918 dual-ion battery has better performance.2.Zn-Mn fluoride is synthesized by one-step solvent heating method K-Zn-Mn-F?Zn:Mn=1:0,3:1,1:1,1:3,0:1?.Five samples of synthetic sample K-Zn-Mn-F?abbreviated as KZMF??Zn:Mn=1:0,3:1,1:1,1:3,0:1?,the results of multiple and cyclic electrochemical tests show that when Zn:Mn=1:3,the electrochemical performance is optimized,The specific capacity is as high as116.9-40.8 mAh g^-1 at the current density of 0.1-3.2 A g^-1;The 1000 cycles at 2 A g^-11 showed an upward trend with a maximum specific capacity of 173.9 mAh g^-1.The reaction mechanism of Zn-Mn fluoride is speculated to be the mixed reaction mechanism of alloy and transformation.We precharged the KZMF?1-3?,construction of KZMF?1-3?//AC lithium ion capacitor,lithium ion battery KZMF?1-3?//LFP and dual ion battery KZMF?1-3?//918,these devices are selected for the appropriate voltage window and the appropriate current density for circulation.