| Lithium carbon dioxide(Li-CO2)battery is a new renewable energy storage and conversion system.It not only has a high energy density,but also can capture the greenhouse gas carbon dioxide(CO2)while providing electricity under special conditions such as Mars exploration.It is considered to be the most promising nextgeneration battery system and has attracted widespread attention from scientific researchers.However,there are many thorny problems to be solved before the practical application of Li-CO2 batteries.Among them,the most important problem is that discharge product with very poor insulation and conductivity is produced during the operation of the battery:lithium carbonate(Li2CO3),which is a substance with stable chemical properties and low reactivity.During the battery cycle,LiCO3 gradually accumulates on the surface of the cathode and is difficult to decompose,which leads to an increase in battery over-potential and affects the battery’s dynamics and service life.Therefore,the development of a cathode catalyst that can efficiently decompose Li2CO3 is the key to improving the overall performance of the battery.This paper takes precious metal oxides(RuO2)and transition metal chalcogenides(CoSe2)as the starting point,successfully prepared cathode materials through reasonable design experiments and systematically studied their influence on the electrochemical performance of Li-CO2 batteries.The main research contents are as follows:1.TiO2 nanowire array modified with RuO2 nanoparticles was prepared on carbon cloth fibers(RuO2-TiO2 NAs/CT)by a combination of hydrothermal strategy and light deposition technology.When the material is directly used as the cathode of Li-CO2 battery,it shows excellent electrochemical performance.Under the conditions of a current density of 250 mA g-1 and a limited capacity of 1000 mAh g-1,the Li-CO2 battery can be continuously discharged and charged for 238 cycles,with an overpotential as low as 1.05 V;When the current density is 250 mA g-1,the specific discharge capacity of the battery is as high as 16727 mAh g-1.The experimental results combined with first-principles calculations(DFT)show that the addition of RuO2 nanoparticles allows the discharge product to grow on the surface of the cathode in a solvation-mediated way,which makes there always exist active sites that are not covered by the discharge product during the discharge process,thereby increasing the specific discharge capacity and extending battery cycle life.In addition,due to the flexibility of the prepared cathode,the assembled Li-CO2 battery can maintain the stable electrochemical performance of the battery under various deformation conditions.Finally,due to the excellent photocatalytic performance of TiO2,light can simultaneously optimize the discharge and charge over-potential of LiCO2 batteries.2.CoO nanofibers are prepared on a carbon cloth substrate(CoO/CT)by a hydrothermal strategy,and then CoSe2 nanoarray is synthesized by a selenization reaction(CoSe2/CT),which is used as a cathode material to assemble LiCO2 battery directly.In view of the ultra-thin nanosheet morphology of the CoSe2 nanoarray,it can provide more electrode/electrolyte contact interface,reduce the diffusion path of lithium ions(Li+),electron(e-)and CO2,thereby improving the electrochemical reaction kinetics of Li-CO2 batteries.In addition,CoSe2 has excellent electrical conductivity,which is conducive to the rapid transmission of e-,and Se atoms have stronger metallic properties and higher activity than O atoms.Based on the above advantages,the electrochemical performance of Li-CO2 batteries assembled with CoSe2/CT as the cathode catalyst has been significantly improved,including lower over-potential(over-potential reduced by 1.21 V,compared to pure carbon cloth cathode),longer cycle life(Under the conditions that a current density is 200 mA g-1 and a limited capacity is 1000 mAh g-1,the battery is cycled for 246 cycles,about 2460 hours)and higher discharge specific capacity(when the current density is 200 mA g-1,the discharge specific capacity is 16490.5 mAh g-1). |
