Construction And Properties Of Prussian White Derivatives For High Specific Energy Lithium-Sulfur Batteries Cathode

With the demand of battery life for portable electronic devices and electric vehicles,the importance of high specific energy secondary batteries is becoming more and more prominent.Among all kinds of battery energy storage technologies,lithium-sulfur battery has become one of the most promising options for future energy storage systems due to its high theoretical energy density（2600 Wh kg-1）,abundant sulfur storage,low cost and environmental friendliness.However,the shuttle effect of lithium polysulfide and its slow redox reaction kinetics lead to problems such as poor rate performance and short cycle life,which greatly limits its commercial application.To solve the above problems,effective sulfur hosts with high electrical conductivity,strong adsorption,and high catalytic activity have been constructed used Prussia white（PW）as the template in this work.Benefiting from the fast electronic transmission rate,strong interaction between lithium polysulfide and sulfur host,and the advantages of carbon materials,the specific capacity,rate performance and cycling stability are significantly improved,which provides reliable experimental datas and theoretical guidance for advanced lithium-sulfur battery research.The main results are as follows:（1）Controllable preparation and properties of prismatic tubular Fe₃O₄/PNCT: Using PW as self-template,Fe₃O₄/PNCT sulfur host material was prepared.Based on its structural advantages and enhanced adsorption on lithium polysulfide,the cycling stability of lithium-sulfur battery was improved effectively,with 1000 cycles at 1 C/5 C,and the capacity attenuation rate of each cycle was only 0.03%.;（2）Study on the construction and properties of Fe₃O₄/Fe₃C/PNCT heterojunction: Using PW as template and one-step carbon reduction method,the in-situ carbon material embedded in Fe₃O₄/Fe3 C heterojunction was successfully prepared and used as the sulfur matrix material of batteries.Due to the synergistic effect of strong adsorption of Fe₃O₄ and high catalytic activity of Fe3 C,the rate performance of the battery can be significantly improved.The specific capacity of the battery was up to 745 m Ah g-1 under 5 C;（3）Design,preparation and properties of oxygen-rich Fe₃O₄-x/Fe P heterojunction: Fe₃O₄-x/Fe P/PNCT heterojunction was prepared by anionic doping using Fe₃O₄ as precursor.By the synergistic advantages of oxygen vacancies and heterogeneous interfaces,the rate and cycling stability of lithium-sulfur battery with S/Fe₃O₄-x/Fe P/PNCT as positive electrodes were significantly improved.The specific capacity was up to 667 m Ah g-1 after 1300 cycles at 8 C,and the capacity decay rate was only 0.03%/cycle.Even in the poor electrolyte（E/S=7 μL mg-1）,the area capacity can still maintained 7.2 mAh cm^-2.