Photo-assisted Rechargeable Battery Based On The Bifunctional Compatible Electrode

The excessive dependence of mankind on fossil energy induces the reduction of non-renewable energy and serious environmental pollution.Among numerous clean energy sources,solar energy has the characteristics of easy access and huge energy,is the most promising solution.The combination of solar cells and rechargeable batteries into one single integrated device–photo rechargeable battery can use solar energy efficiently for continuous power supply.However its development is far from commercialization.In addition to the limited photoelectric conversion efficiency,the major bottleneck of limiting the development of photo rechargeable batteries is the selection of bifunctional electrode,which is the prerequisite for the combination of them and the key factor of electron transmission,energy storage and stability.Improving the compatibility of bifunctional electrode is undoubtedly an effective way to solve this bottleneck.In this thesis,different bifunctional electrodes were prepared to adapt to different complete systems based on the compatibility of electrodes:?1?The bifunctional reticulated Cu₂S electrode is prepared by chemical corrosion method,which serves as both the counter electrode of the sensitized solar cell and the catalytic electrode of the semi redox flow battery.To construct a three-electrode system with good compatibility,the integrated three-electrode photo-assisted rechargeable battery utilizates CdS/CdSe co-sensitized TiO₂ as the photo electrode,reticulated Cu₂S as the bifunctional electrode,metallic sodium as the anode,and Na₂S₄ and NaClO₄ as the inorganic and organic electrolyte respectively.Through the photovoltage response measurement of photo-assisted charging,the decrement of 0.2 V charging voltage can be obtained during the charging process of the integrated device.Through photo-assisted galvanostatic measurement,the discharge capacity of photo-assisted charging is 2.5 times higher than that of dark charging.?2?The sulfur/carbon composite electrode is prepared on the substrate of nickel foam by loading sulfur and carbon nanotube which can load the active material and ensure the liquidity of the electrolyte simultaneously.As the counter electrode of dye-sensitized solar cells and the anode of lithium sulfur batteries,it has demonstrated excellent performance.Based on this bifunctional electrode,the LiTFSI electrolyte can be used as the same medium to combine dye-sensitized solar cells and lithium sulfur batteries into one well compatible three-electrode photo-assisted rechargeable battery.The integrated device has a photovoltage response of 0.65 V,which can be charged under illumination circumstances to reduce the charging voltage.In the process of galvanostatic charging,the longer time of the illumination,the higher discharge capacity is in the photo-assisted charging 1000 s,and the discharge capacity can reach 125.7 mAh g^-1.After illumination,the discharge capacity of the integrated device is increased to 91.1 mAh g^-1 even if the galvanostatic charge and discharge in the completely dark environment.?3?The Cu₂S flower-like nanoparticles synthesized by hydrothermal method can be served as the counter electrode materials of sensitized solar cells and the cathode material of lithium ion batteries.Herein we prepared a bifunctional electrode by blade coating the Cu₂S on the surface of dye-sensitized TiO₂ photoanode directly.Based on the traditional lithium ion battery structure,we combine the bifunctional electrode and the lithium metal electrode into a simple and universal two-electrode photo-assisted rechargeable battery system.By intermittent illumination,the obvious photovoltage response proves the good compatibility of the complete device,while reducing the charging voltage by 0.2 V.Compared with the discharge capacity after charging in darkness,the discharge capacity of photo-assisted charging is 16 mAh g^-1 and the discharge capacity of photo-assisted charging can reach to 209.6 mAh g^-1.