Preparation And Electrochemical Properties Of Two-dimensional Expanded Graphite And NiFe-LDH Intercalated Composites

The energy crisis and environmental problems have prompted people to develop renewable and sustainable energy.However,the most attractive green energy has the disadvantage of intermittent supply in nature.Therefore,the development of new energy storage technology has become a feasible way to solve this key problem.Supercapacitors and secondary batteries,as current research hotspots,play an indispensable role in the field of clean energy research.Among them,the development of cathode materials is one of the key research directions.In this paper,two-dimensional(2D)intercalated composite electrode materials were prepared by introducing guest intercalation agent into the layered 2D main bodies including carbon-based materials and bimetallic hydroxide materials,and supercapacitors and zinc ion batteries were constructed.The main results are as follows:(1)The intercalation composite product of PG/PANI was prepared by in-situ polymerization using Pristine graphite(PG)as 2D matrix and polyaniline(PANI)as intercalation agent.Comparing the XRD results of PG and PG/PANI,it was found that the lattice spacing of graphite in the(002)plane increased from 0.333 nm to 0.335 nm.According to the Electrochemical Impedance Spectroscopy(EIS),PG/PANI showed excellent ion diffusion performance.After 2500 cycles of charge-discharge tests,the capacity of PG/PANI still maintained 115.3%of its initial capacitance at a current density of 1.0 A g^-1.That was because PANI expanded the diffusion channel of the materials,and the layered space improved the structural stability of PANI.(2)Expanded graphite(EG)was prepared by using PG as 2D matrix and Cr₂O₃as oxidant.The results of XRD analysis showed that the lattice spacing of EG in the(002)plane was 0.009 nm larger than that of PG.With EG as the 2D matrix,EG/PANI was prepared at first,and then the intercalation agent in the composite was doped with organophosphate(PA-350)to obtain EG/P-PANI.The results of XRD analysis showed that the lattice spacing of EG/P-PANI was 0.012 nm larger than that of PG.In the electrochemical performance test,the voltage test window of EG/P-PANI composite increased from 2.3 V to 2.4 V.After 5000 cycles charge-discharge test,the capacity retention rate was still as high as 80.7%,showing better electrochemical performance.This was due to the fact that the hydrophilic properties of PA-350in EG/P-PANI materials could fully contact the electrolyte so as to improve the electrical conductivity of the electrode.(3)Melamine and cyanuric acid were inserted into EG to prepare EG/g-C₃N₄precursors in situ.The EG/g-C₃N₄-X composite products were obtained by heat treatment at 450 C°and 700C°,respectively.The results showed that the cyclic voltammetry curve of EG/g-C₃N₄-700electrode material sintered at 700 C°was almost rectangular,showing good electrochemical activity.In the cycle life test,the capacity retention rate of EG/g-C₃N₄-700 electrode was 89.6%after 2000 cycles,which was better than the product EG/g-C₃N₄-450(76.9%)sintered at 450C°.(4)Layered NiFe-LDH was used instead of carbon-based material,and sulfonated Polyaniline(SPAN)was used as intercalation agent to investigate the effect of intercalation agent on the structure of metal double hydroxide.The results showed that SPAN could greatly improve the capacity of the battery,that was because at the current density of 0.1 A g^-1the discharge capacity of NiFe-LDH/SPAN(333.3 m Ah g^-1)was twice as much as that of NiFe-LDH(164.7 m Ah g^-1).At the same time,it showed better stability in the cycle life test.