Preparation Of Graphene Based Composites And Study Of Zinc Ion Energy Storage Performance

A typical zinc-ion hybrid capacitors（ZIHCs）is a hybrid electrochemical energy storage device composed of capacitive cathode and battery anode（zinc）.ZIHCs based on the low-cost characteristics,high power density,and safe performance of porous carbon and zinc metals,it has gained wide attention.However,low energy density and limited stability still restrict the development of high-performance ZIHCs.Firstly,the low capacitance of the carbon cathode limits the energy density of the ZIHCs.Secondly,the stability and utilization of battery anode are also the main challenges in the development of ZIHCs with practical benefits.Therefore,to overcome the above difficulties,thesis improves the electro/ion transport dynamics of graphene cathode by optimizing the porous structure of graphene,designing additional pseudo-capacitance,and modifying zinc metal anode,so that ZIHCs has high energy density,high power density,and long cycle life characteristics.The specific research content is as follows:（1）A single-step solvothermal self-assembly method was used to fabricate bonded polyaniline grafted graphene composites.The conductivity and flexibility of graphene buffer the volume expansion/contraction of polyaniline during the charge and discharge process.Simultaneously,the-SO₃^-can provide continuous H⁺for polyaniline（PANI）under a weakly acidic environment.The Redox reaction of AQS and PANI with Zn²⁺provides additional pseudo-capacitance,and the ZIHCs with RAP as the cathode can reach the maximum capacity of 210 m Ah g^-1,achieving the energy density of 175.5 Wh kg^-1 and the power density of 15.1 k W kg^-1.Besides,after 10000 high-current charge-discharge cycles,the device’s discharge capacity can still maintain 80.1%of the initial value,and its cycle coulombic efficiency is almost 100%.（2）Porous-reduced GO composite films cathodes anchored by alizarin red（ARS）molecules were prepared by a one-step hydrothermal reaction.Due to the porous structure of PGAF-ARS and the pseudo-capacitance characteristics of ARS,the cathode film is endowed with excellent electron/ion transport dynamics.Aqueous ZIHCs can display the combination of ultra-high energy density and max high-power density,reaching 184.9Wh kg^-1 and 20.6 k W kg^-1 respectively.Meanwhile,the specific capacity can reach 230.4m Ah g^-1 under the current density of 0.3 A g^-1,and the specific capacity can be maintained at 92.6%of the initial value under 10000 cycles of 5 A g^-1,which shows the stability of its structure.The assembled button capacitors and all-solid-state flexible capacitors also show excellent electrochemical accessibility and practically.（3）N-doped graphene composite zinc metal coating Nr GO was prepared by a simple pull-out method.The parallel coating layer with nitrogen-containing functional groups can uniformly guide the orientated deposition of Zn²⁺on the（002）crystal surface,improve the diffusion kinetics of Zn²⁺and inhibiting the generation of side reactions.The Nr GO@Zn symmetric cell showed 600 dendrite-free cycles（over 1200 h）at a current density of 1 m A cm^-2.At the current density of 5 m A cm^-2,the cell showed dendrite-free growth for more than 150 h,and its overpotential was only 31.1 m V.The complete energy storage device prepared by fully matching the capacitor cathode materials can still maintain its original electrochemical characteristics and greatly improve the ZIHCs cycle performance of the battery.