| Under the background of the era of carbon neutralization proposed by General Secretary Xi Jinping,the development,storage and utilization of green energy will surely take the center stage.However,due to the intermittent and uncertain limitations of renewable energy sources such as solar energy,tidal energy and wind energy,the problem of how to store the energy and utilize it on demand remains to be solved.New large-scale energy storage facilities with high energy density,high safety and cost-effectiveness seem to provide an effective solution.Lithium-ion batteries have been commercialized for many years and possessed mature technological processes,but eventually,it will face the dilemma of scarcity of lithium resources and soaring upstream raw material costs,so it is imminent to develop other types of metal-ion energy storage devices.Metal-ion hybrid supercapacitors were generally regarded as potential competitors due to its combination of both high energy density of secondary batteries and high power density of supercapacitors,among which the aqueous zinc-ion hybrid supercapacitor stands out owing to its characteristics of high safety,environmental friendliness and multivalent ion storage.In addition,dual-ion batteries,due to its efficient energy storage mechanism,the anions and cations in the electrolyte respectively inserted into/extracted from the positive and negative electrodes to achieve energy storage and utilization,with the natural advantages of wide voltage window and high energy density,had been also extensively studied as alternative candidates,and among which sodium-based dual-ion batteries are also emerging due to the wide and uniform distribution of sodium resources and their cheap and easy availability.As a key part of energy storage devices,electrode materials greatly affect their energy storage performance.Commonly used zinc/sodium storage electrode materials,such as oxides or sulfides and their composites,possess significant advantages and disadvantages,high theoretical specific capacity but always accompanied with a fast capacity fading and poor cycle life,such as sulfide electrode materials usually delivered a poor cycle performance due to the volume expansion during cycling.As a classic energy storage material,full-carbonaceous materials have exceptionally stable cycle performance and long cycle life,as well as low cost,and have been widely used in various capacitors and secondary batteries.In this thesis,full-carbonanceous materials were selected as electrode materials for these above two energy storage devices,which showing more environmental friendliness while reducing the cost,in order to provide design ideas and references for the commercialization of these two energy storage devices.In this work,the density and pore structure of three-dimensional graphene was controlled by changing the removal method of water solvent,and a three-dimensional porous graphene zinc storage cathode material with dense structure was constructed,which greatly improved the volumetric energy density of zinc-ion hybrid supercapacitors with a ensured fast Zn2+ transport.Using waste walnut shells as raw materials,a sodium-storage hard carbon anode material with stable structure was prepared by carbonization.The effect of pyrolysis temperature on the sodium storage performance and sodium storage mechanism was studied,and KS6 graphite was further matched as the cathode to assemble a dual-ion battery.The specific research were as follows:（1）The graphene hydrogel was prepared by a one-step hydrothermal method,and its influence on the microstructure of three-dimensional porous graphene was studied by different drying methods.Furthermore,the pore size was directionally adjusted to balance the pore structure and density,and eventually the pore size of the prepared three-dimensional porous graphene was controlled in the range of 0.6-10 nm,which was suitable for zinc storage.At the same time,the high density of 1.38 g cm–3 ensured the high volume performance of Zn-ion hybrid capacitors,which delivered a volume specific capacitance of 299 F cm–3 at a current density of 0.1 A g–1,even at a high current density of5 A g–1,the volumetric capacitance reached 225 F cm–3,and the capacity retention was as high as 85% after 30000 cycles.Furthermore,the device exhibited satisfactory energy output,reaching an energy density of 118 Wh L–1at a power density of 116 W L–1,which was much higher than most reported zinc-ion hybrid supercapacitors.（2）A two-step carbonization method was used to prepare walnut shell-derived carbon with waste walnut shells as raw materials.The soluble organic substances such as grease were washed away by acetone,and then a series of steps such as ball milling,sieving,low temperature pyrolysis,acid washing,alkali washing,and high temperature carbonization at different temperatures were carried out to prepare walnut shell-derived carbon（WS–x,x reprenent the carbonization temperature）.The effect of different carbonization temperatures on its microscopic morphology and structure was studied,and then the drived carbon was used as a negative electrode material to assemble a sodium ion half-cell to study its sodium storage effect and sodium storage mechanism.The research results show that WS-1200 exhibited excellent sodium storage performance when used as the anode of sodium-ion half-cells,with a discharge specific capacity as high as 336.5 m Ah g–1at a current density of 0.5 A g–1,and the capacity still retained 285.9 m Ah g–1 after 1000 cycles,and the average capacity decay per cycle was only 0.015%,showing the stable microstructure of the material.Moreover,the drived carbon still delivered a specific capacity of 140 m Ah g–1 at a high current density of 10 A g–1,indicating its excellent rate performance.Based on the excellent sodium storage performance of the derived carbon,this work further matched KS6 graphite as cathode and WS–1200 as anode to assemble a sodium-based dual-ion battery to study the energy storage performance of the device.The research results show that the device exhibited a capacity of 245.6 m Ah g–1at a current density of 0.5 A g–1and remained192.6 m Ah g–1 after 3000 cycles,but also a capacity of 120.3 m Ah g–1 at a high current density of 5 A g–1,and a stable capacity around 50 m Ah g–1 after a slow deacy with a cycle life exceeds 30000 cycles.Moreover,the energy density was as high as 172.06 Wh kg–1 at a power density of 68.75 W kg–1.This work shows that through the waste utilization,the energy storage performance of the material can be improved while reducing the cost,which greatly improves the cost-effectiveness of high energy density energy storage devices. |
