| Since the commercialization of lithium-ion batteries,the batteries performance has been continuously improved and the industry has developed rapidly.However,the energy density is far from the needs of modern industries and it also has become the biggest constraint for the battery industry in the future.It has received much attention that the theoretical energy density of lithium-air batteries is 3,500 Wh/kg.Cathode plays a decisive role in the performance of lithium-air battery.In this paper,TiO2 based cathode with excellent stability is selected.In order to solve the problem of insufficient catalytic activity of TiO2 material,we improve it by self-doped,and oxygen vacancies are introduced into the crystal lattice also to improve the catalytic ability of the material.On the other hand,the semiconductor characteristics of TiO2 are utilized to assist the electrochemical process with photocatalysis,and the performance of the battery is greatly improved by the synergetic effect of electrochemical reaction and photocatalysis.TiO2-?-Ar/H2 the cathode catalysts that the non-stoichiometric ratio of?is 0.0625was prepared by hydrothermal reaction,proton exchange and heat treatment.The modified material not only decreases the band gap to 3.17 eV,but also expands the spectral response range,and makes the conductivity of the electrode greater,and increases carrier concentration to 8.73×1020 cm-3.The oxygen vacancies in the crystal lattice enhance the ability of the cathode to catalyze the electrode reaction.The discharge platea is near 2.637 V,and the charge platea is 4.590 V,when battery in no light at current density of 1 A g-1 has smaller overpotential than others.In illuminating environments,the discharge voltage was increased by 0.095 V at current density of 1 A g-1,and the charging voltage was decreased by 0.202 V.The battery was completed 100cycles at 2 A g-11 with the synergetic effect of electrochemical reaction and photocatalysis.By in-situ GC,it was found that the discharge consumed more oxygen during the illumination,and more oxygen was generated during the charging.The synergetic effect could enhance ORR and OER reaction rates.Because side reactions will affect the electrochemical performance,we use Ti nanowire array as the substrate and made the TiO2 catalytic to grow on the surface of self-supporting electrode.The core-shell structure of the all-titanium system was prepared by hydrothermal reaction and heat treatment.The carrier concentration of Ti@TiO2-?-Ar/H2 cathode is as high as 2.24×1021 cm-3,which is much higher than that of TiO2-?-Ar/H2 cathode catalysts.The surface catalytic layer of Ti@TiO2-?-Ar/H2cathode contains oxygen vacancies,and?is 0.190,which is higher than the self-doping degree of TiO2-?-Ar/H2 catalyst.Because Ti4+is more easily reduced to Ti3+.The effect of photocatalysis on the overpotential of the battery is still significant.The discharge voltage at 1 A g-1 increased of 0.068 V,and the charging voltage is also reduced by0.241 V.Analysis of the amount of oxygen escaping during charge and discharge can also be inferred that photocatalysis could improve electrochemical reaction. |
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