Preparation,modification Of MOFs-based Porous Carbon Materials And Their Application In Solid State Capacitors

Lithium ion capacitors（LICs）are assembled by a high power density capacitive cathode and a high energy density battery type anode in an electrolyte containing lithium salts.The difference in the energy storage mechanism of electrode materials makes lithium ion capacitors show excellent Electrical performance.However,it also faces the following three problems:1)Commercial activated carbon as a capacitive cathode has a lower capacity due to a large number of ineffective pore structures,which restricts the energy density of lithium ion capacitors;2)The difference in reaction mechanism causes the cycle stability of battery anodes to be incomparable with capacitive cathodes,resulting in an imbalance in the reaction kinetics of anodes and cathodes,limiting the increase in power density and cycle life;3)Lithium ion capacitor using liquid electrolyte are prone to dangerous accidents such as explosion,combustion,and liquid leakage.In response to these three issues,this thesis relies on the self-designable characteristics of the metal organic framework（MOF）to synthesize its derived carbon materials for the research of capacitive cathodes and battery anodes.In addition,a solid gel separator prepared based on polyvinylidene fluoride-hexafluoropropylene（PVDF-HFP）is used to improve the safety and stability of lithium ion capacitors.The specific work is as follows:（1）Using fluorine-containing organic raw materials and zinc-based salts to synthesize ZTF in a simple and efficient way.Through reasonable temperature carbonization and HCl washing,ZTF-derived carbon（ZTF-C）with super large specific surface area(3132 m²·g^-1)and porous volume(3.504 cm³·g^-1)was obtained.With an appropriate degree of graphitization and oxygen doping,ZTF-C as a half-cell has a specific capacity as high as 123.4 m Ah·g^-1 and excellent cycle stability.A lithium-ion capacitor that uses it as a cathode and high-temperature carbonized sucrose hard carbon（SHC）as an anode can provide a power density of 40 k W·kg^-1and an energy density of157 Wh·kg^-1,and can be used after 4000 cycles After that,it still has a retention rate of85%.（2）ZIF-8 and ZTF were modified from the two directions of high element doping and high specific surface area respectively,and two MOFs derived from ZC&F-CNT and ZTH-C suitable for battery anodes were synthesized.Carbon materials,both show far superior specific capacity and cycle stability than graphite and hard carbon.Two kinds of carbon derived from MOFs after short-circuit pre-insertion are used as battery anodes and matched with ZTF-C to form two kinds of lithium ion capacitors with carbon derived from double MOFs.The advantages of high-performance anodes and the problems caused by insufficient prelithiation are analyzed.（3）The PVDF-HFP-based gel solid-state diaphragm is prepared by the electrospinning process to replace the diaphragm and electrolyte in the lithium-ion capacitor,and is matched with ZTF-C and SHC to form a solid-state lithium-ion capacitor.The device has a maximum energy density of 148.76 Wh·kg^-1,and even at a high power density of 33.6 k W·kg^-1,it still retains 20.6 Wh·kg^-1.In addition,after 8000 charge-discharge cycles,83.3%of the capacity is retained.It provides ideas for a new generation of"three highs"energy storage equipment with high power energy density,high cycle stability,and high safety.