Preparation And Properties Of Biomass-based Materials For Energy Storage

Global warming and the depletion of fossil fuels are forcing people to develop new energy sources.Supercapacitors,we can also name them as electrochemical capacitors or supercapacitors,act as energy storage devices,playing an increasingly important role in the fields of information technology,electronic products and automotive energy because of their high power density,long service life and low environmental pollution.Recent advances have mainly focused on developing new electrode materials such as carbon-based electrodes,metal oxides and transition metal sulfides.Few people have focused on improving the electrochemical performance by optimizing the structure of the electrode material and the entire device without changing the chemistry of the electrode material.The excellent structural design makes full use of the active electrode material for supercapacitors and can promote the transport of ions and electrons,especially for thick electrode materials.A thick electrode with high areal mass loading is desirable in supercapacitor designs because of its advantages in enhancing the energy density of the supercapacitor device by maximizing the packing density of the electroactive cathode and anode materials while lowering the manufacturing cost by reducing the number of inactive material layers.However,for thick electrodes,the material is prone to deformation,and the transport of electrons and ions in it is difficult,making it difficult to perform in practical preparation and application.It is well known that reducing the tortuosity of a material can accelerate the ion transfer process,which can improve the rate performance of the material,especially for thick electrodes.Therefore,how to reduce the tortuosity of the material,the rapid transmission of ions and electrons,and the low deformation property are the main challenges in preparing thick electrode materials while increasing the loading of the active material.A few contents of the specific research of my paper are as follows:(1)The combination of hydro-thermal synthesis and electrodeposition is used to grow the active material on the nickel-cobalt double hydroxide(CW@LDH@LDH)as the cathode,which solves the problem of low active material loading.We used KOH to activate wood carbon(AWC)as the anode.The anode and cathode materials are derived from natural wood and have their unique anisotropic structure.Ions can pass directly through the pores,showing low tortuosity.At the same time,the large thickness,high active material loading,good electrical conductivity and layered pore structure ensure ultra-high surface capacitance and excellent rate performance.The assembly of a thick asymmetric supercapacitor exhibits a very high energy density and power density,providing a new direction for green,low cost,high load,low deformation supercapacitors.(2)Graphene is a two-dimensional carbon material which is an ideal carbon material for supercapacitors due to its high specific surface area and excellent electrical conductivity.In order to make full use of the regular structure of natural wood and its vertical pore structure,we use simple vacuum-assisted impregnation to fill graphene into the vertical channels of wood and form graphene aerogel in its pores,which greatly increased its ratio surface.And the graphene aerogel in the channel accelerates the conduction of electrons.We use KOH to activate CW@GO increases the specific surface area by nearly 100 times and maintains its original structure,breaking through the limitations of previous KOH activation only for powders.The electric double layer carbon material ensures excellent cycle stability of the capacitor.The thick electrode,good conductivity and layered pore structure ensure ultra-high surface capacitance and excellent rate performance.Assembling into a thick symmetrical supercapacitor exhibits a very high energy density and power density,providing a new direction for green,low cost,low deformation thick electric double layer supercapacitors.