Multifunctional Application Of Biomass Carbon Material As Anode Of Potassium Ion Battery

Lithium secondary battery plays an important role in energy storage applications.As a ubiquitous energy system,lithium secondary battery has achieved great success portable electronic products and electric vehicle industry.As the use of lithium–ion batteries has increased and lithium resources have been overexploited,the rice has risen,driving research into new energy storage systems.Alkaline–metal ion batteries such as sodium and potassium ion and multi-electron transfer ion batteries such as aluminum and zinc ions are emerging.As a key part of device performance,electrode materials have always been the force of research,carbon materials have advantages of abundant production and low price,among which graphite has been successfully used in lithium ion batteries.Various types of carbon materials,such as hard-carbon and soft-carbon,also have broad prospects in different energy storage systems.However,poor cycle stability,volume expansion in the process of energy storage,low specific are the bottleneck of the new energy storage system.Biomass source is extremely rich,as precursor,its natural and stable three–dimensional structure mean more efficient conductive network.In this thesis,we mainly study anode materials of potassium ion batteries.A series of biomass carbon materials with stable structure were synthesized by simple and efficient preparation process with bamboo and balsa-wood as precursors combined with the preparation method of oxidation and sintering,and their application in the field of potassium ion battery energy storage was explored.In order to solve the problems of low specific capacity and poor stability of anode carbon material of potassium ion battery,a kind of short-range ordered amorphous carbon material was synthesized by oxidizing and sintering method using bamboo as precursor,and its electrochemical performance in the storage system of potassium ion battery was investigated.Raman spectroscopy（Raman）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）were used to analyze and characterize the microstructure.The potassium ion coin half batteries were assembled with conductive carbon black and binder,and its application was investigated.At a current density of 100 m A g^-1,three-dimensional biomass carbon（TBC）could provide a high reversible capacity of 258.3 m Ah g^-1 and a capacity retention rate of 83.8%at 300 cycles.At the same time,TBC also provides a high rate performance(150 m Ah g^-1 of specific capacity at 1000 m A g^-1 current density).In order to solve the problem of energy density decrease caused by inactive–components of potassium ion battery,a freestanding negative electrode with no inactive–components was prepared by oxidation and sintering synthesis method using balsa wood as precursor,its electrochemical performance and mechanism in potassium ion storage system were investigated.The freestanding carbon foam had a high reversible capacity of 252.7 m Ah g^-1 at 100 m A g^-1,an initial coulombic efficiency of63.7%,an excellent long-cycle stability（capacity retention rate 95.1%after 500 cycles）,and excellent rate capacity(a reversible capacity of 165 m Ah g^-1 at 2000 m A g^-1).A high Coulombic efficiency and cycle stability were maintained over the cycles of 13months.XRD,Raman,SEM,TEM and nitrogen adsorption/desorption curves were used to compare the samples at different carbonization temperatures.In order to explore the storage mechanism of potassium,the proportion of capacitive and diffusion behavior was estimated by cyclic voltammetry curves of different sweep velocities.