| In order to cope with the increasingly severe world energy crisis and environmental pollution problems,while ensuring human survival and the development of social economy,exploring and developing new energy systems is the best response.Among them,nonaqueous Li-O2 batteries show immense potential and wide application foreground as next-generation energy storage facilities,with extremely high theoretical specific energy(11430 Wh kg-1),enormously precede to that of the commercial LIB(250 Wh kg-1),and it is even compare favourably with gasoline(13000 Wh kg-1).So far,great breakthroughs have been made in the comprehension of Li-O2 batteries with high-level performance.However,the disappointing actual discharge performance,poor rate/cycle performance,and inefficiency of round-trip,which severely restricts its practicality.As everyone knows,the appropriate structure and catalytic properties of the oxygen eletrode are the primary factors affecting the behavior of Li-O2 batteries.In view of this,this paper stands on the design of oxygen oxygen eletrode,and enhances battery performance by optimizing the oxygen eletrode structure.1、Bacterial cellulose has a three-dimensional network structure,strong flexibility and high structural stability.We designed and prepared a flexible and optimized bacterial cellulose based oxygen eletrode（CBC、CBC-U and CBC-KOH）with high specific surface area and high micro mesoporous structure through freeze-drying,carbonization,activation and nitrogen doping.Bacterial cellulose nanofibers interlace with each other to form a large number of micropores and mesopores,which is conducive to the transport of reactants in lithium oxygen batteries.The mesoporous of the carbonized materials is increased by activation,which can accommodate more discharge products.Doping modification can further improve the performance of the material and the ORR activity of the battery.The specific capacity of CBC-KOH oxygen eletrode is 4.15 m Ah cm-2,and the electrochemical performance of CBC-KOH oxygen eletrode is greatly improved compared with CBC oxygen eletrode.2、A three-dimensional porous tubular kapok-based oxygen eletrode（KAC-CO2-NH3）was designed with natural kapok fibers which is the most hollow among natural fibers.The oxygen eletrode is obtained by carbonization,activation,nitrogen doping and anchoring of nano-Ru particles.After activation process,the center-emptied transmission pipeline of the kapok-based oxygen eletrode is maintained well,and a large number of micropores and mesopores are evenly distributed on the tube wall.This unique structure facilitates oxygen penetration and electrolyte transmission.At the same time,a high specific surface area provides sufficient space for the storage of discharge products,overwhelmingly enlarging the solid-liquid-gas three-phase reaction interface.After loading Ru nanoparticles with high OER catalytic activity,the area specific capacity of the KAC-CO2-NH3/Ru oxygen eletrode exceeds6.41 m Ah cm-2.With a fixed capacity of 600 m Ah g-1,the KAC-CO2-NH3/Ru oxygen eletrode exhibits stable cycling behavior（233 cycles）.Furthermore,the material also unfolds high rate performance and high reversibility.3、Carbon materials will react with the electrolyte during the charging process of Li-O2batteries.Therefore,it is of great significance to find non-carbon oxygen electrodes.In order to increase the interlayer spacing and prevent the re-stacking of the layers,two types of flexible oxygen eletrodes were exploratoryly designed and prepared by using Mg O nanoparticles and urea.Respectively named E-Ti3C2Tx and P-Ti3C2Tx.The MXene material with unique lamellar structure,large specific surface area,high electronic conductivity and high electrochemical stability can provide passages for the transmission of reactants.The results show that after intercalation treatment,the stacking degree of mxene material is effectively reduced,which can provide enough storage space for discharge products,and the charge discharge capacity is significantly improved. |
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