PAN And Metal-TCNQ Derivative As Key Materials Of Lithium Ion Battery

Owing to the environmental deterioration and energy shortage,energy storage batteries have been employed to a great variety of fields.Currently,in order to address the safety problem of commercial lithium ion batteries,all solid-state batteries become a hot research filed.Flexibility,abundant resources and electrochemical stability are the advantages of solid-state batteries,but low ionic conductivity at room temperature is the biggest obstacle toward the application of dry polymer electrolyte.The first part of this thesis is about improving the PAN-based “polymer-in-salt” electrolyte through graphene oxide?GO?nano-filler.At present,organic materials are deemed to be the substitution of traditional inorganic materials.Although organic material has many merits,such as environmental friendly,cheap price and structural diversity,it's high solubleness in liquid electrolyte and low electronic conductivity inhibit the application in lithium ion batteries.The second part of this thesis is aimed to prepare a low solubleness and high conductivity micro-nano CuTCNQ charge-transfer complex.The main works are as follows:?1?Based on PAN/LiTFSI polymer electrolyte,we make use of 2D layered GO as a nano-filler to improve the performance of polymer electrolyte.We have discussed the influence of GO on the ionic conductivity,electrochemical stability,lithium ion transference number,conductivity retention and interfacial stability.?2?The addition of GO has effectively enhanced the performance of polymer electrolyte.When the content of GO is 0.9 wt%,the best performances were acquired with an ionic conductivity of 1.1×10-4 S cm^-1,a transference number of 0.4,an oxidation potential over 4.5 V.?3?X-ray diffraction and Fourier transform infrared technologies have been employed to analyze the changes on microstructure of polymer electrolyte after the inclusion of GO.The reasons for conductivity enhancement are discussed.We think both the surface groups of GO and Li_m⁺TFSI_n^- cluster contribute to the enhanced movement of lithium ions.?4?TCNQ and Cu foil were used to synthesize CuTCNQ through solution method.We investigated the variation on structure of CuTCNQ by controlling the reaction time.Powder CuTCNQ and film CuTCNQ were used to study the electrochemical performance in lithium ion battery.For powder CuTCNQ,when the current density is 11 mA g^-1,the specific capacity comes to 40 mAh g^-1 after 50 cycles of discharge-charge process with capacity retention of 74 %?compared with the second cycle?.We found that the specific capacity is 42 and 37 mAh g^-1 while the current density is 11 and 110 mA g^-1,which means an excellent rate performance.?6?We have investigated the performance of film CuTCNQ.The result shows a good electrochemical reversibility.Obviously,film CuTCNQ shows a great potential in high-energy batteries without extra binders and conductive additive.?7?Ex-situ methods were used to demonstrate the structure reversibility during charge and discharge process.CV curves revealed a split of reduction/oxidation peaks.