A Green Recycle Of Spent Lithium Batteries To Prepare Fe₂O₃/CoPi For Photoelectric Catalytic Materials

In recent decades,energy shortage and environmental pollution have made people realize the necessity and urgency of developing clean renewable energy to replace fossil energy.Lithium-ion batteries are widely used because they show great advantages in sustainable energy conversion and storage.However,a large number of waste batteries are discarded into the environment,will cause serious environmental pollution and waste.Recycling these used batteries for renewable batteries or other functional materials can both reduce the environmental burden and provide new energy storage/conversion devices.Therefore,this paper studied an effective electrochemical recovery method,a new method of producing high-performance hematite/cobalt phosphate?CoPi?photoanode from waste LiFePO₄ and LiCoO₂ batteries,and used for photoelectricity decomposition of water to produce hydrogen.The research mainly includes the following three aspects:1.Using a chemical leaching technology,oxalic acid was selected to extract iron from waste LiFePO₄,in which the better conditions were obtained by changing the ratio of oxalic acid to LiFePO₄,leaching temperature and other factors.Subsequently,the electrochemical cathode deposition technique was used to obtain Fe films on the FTO conductive substrate at constant potential?-1.1?-0.8 V vs.RHE?.Further at 680?-800?can be converted to hematite film.In this process,the conditions are optimized by changing the concentration,deposition voltage,deposition time,annealing temperature and time of the leachate.The prepared iron oxide film has uniform nanoparticles?about 80nm?,controllable thickness?about 58nm?,and the photocurrent of oxidized water under 1.23v vs RHE can reach 1.31m A/cm².2.In addition,the Co from waste LiCoO₂ was extracted into the solution by hydrothermal method with citric acid.CoPi catalyst films were prepared by anodic electrodeposition.The effects of the molar ratio,hydrothermal temperature and time of LiCoO₂ citric acid were studied.Finally,the leaching rate of cobalt ion in the solution was>95%.In the electrochemical deposition of CoPi film,amorphous oxygen evolution catalyst was obtained by controlling the concentration,deposition potential and time of electrolyte.Its performance was 1.60v vs RHE,and the current density was up to 2.75mA/cm².3.Furthermore,CoPi catalyst was electrochemically deposited on the prepared iron oxide film in a similar manner to obtain hematite/CoPi photoanode.Its oxidized water performance is up to 2.36 mA/cm² at 1.23v vs RHE time current,which is twice as high as that of iron oxide photoanode alone.Through the transient surface photovoltage TSPV spectrum,electrochemical impedance spectrum and cyclic voltammetry curve test,we found that the addition of CoPi catalyst may lead to the increase of surface storage charge,accelerate the charge separation and inhibit the surface charge composite reaction,and finally promote the photoelectric decomposition of water process.In summary,we have successfully converted LiFePO₄ and LiCoO₂ batteries into high-performance hematite/CoPi photoanode in a simple,green and environmentally friendly way for water photodecomposition.It not only realizes the efficient recovery of the waste lithium battery,but also provides an efficient photoanode for hydrogen production by water decomposition driven by solar energy.