Preparation and Performance of Tantalum Micro-Arc Oxidation Battery Anode
Lithium-ion batteries are involved in almost every field,especially mobile consumer electronics,because of their outstand-ing advantages such as high operating voltage,long cycle life and high energy density.As an important part of lithium-ion batteries,anode directly determines the performance of lithium-ion batteries.Traditional anode preparation process for lithium-ion batteries is complex and time-consuming,and the binder hinders lithium ion diffusion channel and affects the electrochemical performance.In the acidic electrolyte,the tantalum surface undergoes reaction to form a stable anodic oxide coating.The oxide tantalum pentoxide(Ta2O5)has a theoretical specific capacity of up to 482 mAh·g-1.Micro-arc oxidation is a technology that uses plasma discharge in the electro-lyte to form a ceramic coating layer in situ on the surface of valve metals such as aluminium,magnesium,titanium,and others.Micro-arc oxidation technology offers several advantages,including simple operation,high efficiency,short processing time,low cost,low requirements for the experimental environment,etc.It can be completed at room temperature and normal pressure without the need for post-treatment.Currently,micro-arc oxidation technology has been widely used to improve the wear resistance,biocompatibility,and resistance to high-temperature oxidation of materials.However,its application in the field of energy batteries is still relatively limited.Therefore,the aim of this paper was to grow a porous coating layer with Ta2O5 as the primary crystalline phase on the surface of tanta-lum sheet in-situ through the micro-arc oxidation process.This coating could be directly used as the anode of lithium-ion batteries due to its high-capacity electrochemical performance,and it held promising potential for further development.Through the micro-arc oxida-tion reaction,the porous Ta2O5 coating layer was grown in-situ on the tantalum sheet.The abundant pore structure facilitated the diffu-sion of the electrolyte and accelerated the movement of lithium ions to the electrode surface.The experimental operations were as fol-lows:Ta sheet was pre-treated before the experiment,and the metal surface was mechanically polished using SiC sandpaper to remove the oxide layer until the surface was smooth and flat.Subsequently,the surface was washed and air-dried in anhydrous ethanol.In the silicate electrolyte system,the polished and cleaned tantalum sheet was immersed as the anode,while a stainless steel tank served as the cathode.The experimental parameters were configured to carry out the micro-arc oxidation reaction.Taking the tantalum sheet that had reacted,cleaning the residual electrolyte on the surface and drying it to obtain Ta2O5 coating layer.The coating layer was used as the anode of the lithium-ion battery,and the lithium sheet functioned as the counter electrode to assemble the battery.The cell assem-bly of cut specimens was conducted in a glove box(H2O＜0.1×10-6,O2＜0.1×10-6)in an argon atmosphere,following the order as:posi-tive shell,negative material,electrolyte,diaphragm,electrolyte,lithium sheet,gaskets,shrapnel,and negative cover.X-ray diffrac-tometer(XRD)and scanning electron microscope(SEM)were used to characterize the phase composition of the coating layer and the surface phase appearance.In the study of electrochemical performance,the constant current charge/discharge performance of lithium-ion battery was tested within the voltage range of 0.01～3 V.Cyclic voltammetry(CV)was carried out in the same voltage range but with different scan rates.Electrochemical impedance spectroscopy(EIS)of the battery was investigated using an electrochemical work-station with a frequency of 100 kHz to 0.01 Hz.XRD results showed that the micro-arc oxidation technique could be used to grow in-si-tu on the tantalum surface with Ta2O5 as the main crystalline phase.This coating layer could provide a theoretical capacity of up to 482 mAh·g-1,surpassing that of graphite anode and some conventional oxides.Thus,it had potential applications in electrochemical ener-gy storage.According to SEM images,it could be seen that the substance was uniformly distributed on the surface of the tantalum sheet.The pore distribution was uniform,the binding was good,and a large number of micropores provided high activity for the speci-men.Charge-discharge cycles were performed on the assembled battery at a current density of 100 μA·cm-2.The first-turn discharge specific capacity was 3877.0 mAh·cm-3,reaching 98.1％of the theoretical discharge specific capacity of Ta2O5,which demonstrated a high specific capacity and suggests potential applications in electrochemical energy storage.In EIS test,Ta2O5 anode material had the advantages of lower charge transfer resistance and faster lithium ion diffusion,which was beneficial for long-range electron conduc-tion,ultimately reducing ohmic polarization.In the present study,lithium-ion battery anode was prepared on the surface of tantalum metal using a simple synthesis method,achieving high efficiency and excellent performance.The micro-arc oxidation technique could efficiently prepare porous,binder-free Ta2O5 anode materials,and its high-capacity electrochemical performance had promising appli-cation prospects.
tantalummicro-arc oxidationlithium-ion batteriesnegative electrode material
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