Biomass Carbon For Lithium-ion Batteries Preparation And The Test Of Electrochemical Properties

Lithium-ion battery has the advantages of high working current,good cycle characteristics,large self-discharge rate and so on.At present,it has become one of the most potential energy storage power sources in the world.The anode materials of lithium batteries are mostly graphite materials.However,due to the improvement of capacity requirements,the battery capacity produced by graphite has been unable to be realized.The application of biomass materials in lithium batteries has greatly reduced the cost of raw materials,providing a green and sustainable development path for the preparation of lithium batteries.In this paper,lotus root,a new biomass material rarely reported in the field of lithium battery,is selected.Through the research on the cheap and non-toxic lotus root material,porous carbon material is obtained through activator treatment and high-temperature pyrolysis and carbonization as the cathode of lithium-ion batteries.The main research contents and results are as follows:(1)In this study,poplar catkins,pig manure,rapeseed shell,cotton straw,bamboo leaf and lotus-root were preliminarily selected as carbon sources,and then the porous biomass carbon materials were pyrolyzed by high-temperature carbonization.The surface structure and micro characteristics of the materials were explored by physical characterization methods.The results show that there is an obvious porous structure in the lotus root carbon material,and the electrolyte can be better soaked in this porous structure,which is conducive to the propagation of lithium ions and electrons.Therefore,lotus root material is selected for further research.(2)As an activator,KOH can activate biomass materials,form developed pore structure,accelerate the migration of lithium ions,and bring convenience to the charge and discharge of lithium-ion batteries.The effects of chemical activation methods on the electrochemical properties of lotus-root carbon materials were studied by comparing the effects of KOH and KOH.The results show that the lotus root carbon material obtained by KOH activation has better electrochemical performance,which is mainly due to the improvement of specific surface area and more developed pore structure of the activated carbon material,which improves the propagation efficiency of lithium ions.(3)In order to study the effect of carbonization temperature on the structural characteristics of carbon materials.The influence of high temperature on the composition and characteristics of carbon materials,lotus root was selected as carbon materials,and the lotus root materials were carbonized at three temperatures of700℃、900、1100℃.With the increase of carbonization temperature,the internal ordering degree of carbon materials changes,and the specific surface area and pore volume change significantly.When the carbonization temperature is 900℃,the maximum specific surface area and pore structure are obtained.It is found that the carbon material carbonized at 900℃ has the maximum charge discharge capacity,maximum cycle stability and magnification characteristics,which is mainly due to its good pore structure and graphitization degree.(4)The effect of SEI film on electrochemical properties was studied.The formation process of SEI film was understood from the electrochemical changes before and after discharge.The results show that lithium-ion batteries have excellent electrochemical properties,which are closely related to the stability and integrity of the films.