Synthesis And Electrochemical Performance Of Self-supporting Carbon-tubes-based Cathode Catalyst For Lithium-oxygen Batteries

Recahrgeable lithium-air batteries are considered to be a promising next-generation energy storage devices due to their ultra hige energy density rivaling that of gasoline.Till now,the practical application of Li-air batteries is constrained by their low colombic effiency,poor rate capability,and especially short cycle life.The rational design of cathode with proper structure and high effiency catalysts are of practicular importance for promoting the practical application of Li-air batteries.This work focous on carbon-tube-based self-supporting cathode materials for Li-air batteries.The relationship between the carbon-tubes structure and the electrochemical performance has been explored.The following is the main contents and results.?1?Hydroquinone resin was used to grow carbon nanotubes directly on Ni foam.The composites were prepared via a simple carbonization method,which avoids using explosive gaseous carbon precursors that usually applied in chemical vapor deposition method.When evaluated as cathode for Li-O₂ batteries,the binder-free structure show enhanced ORR/OER activities thus giving high rate capability(12690 mAh g^-1 at200 mA g^-1 and 3999 mAh g^-1 at 2000 mA g^-1)and outstanding long term cycling stability(capacity limited 2000 mAh g^-1,110 cycles at 200 mA g^-1).The excellent battery performance provides new insights into design low cost and high efficiency cathode for Li-O₂ batteries.?2?A composite of carbon-wrapped Mo₂C nanoparticles and carbon nanotubes was prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin.The Mo₂C nanoparticles with well-controlled particle size act as a highly active ORR/OER catalyst.The carbon coating can prevent the aggregation of the Mo₂C nanoparticles.The even distribution of Mo₂C nanoparticles results in the homogenous formation of discharge products.The skeleton of porous carbon with carbon nanotubes protruded from the composite resulting in extra voids when it was applied as a cathode for Li-O₂ batteries.The batteries delivered high discharge capacity of approximately 10400 mAh g^-1 and low average charge voltage of⁴.0V at 200 mA g^-1.With a cutoff capacity of 1000 mAh g^-1,the Li-O₂batteries exhibited excellent charge-discharge cycling stability for over300 cycles.?3?Non-woven fabrics was used as support materials for the growth of carbon tubes.Through a simple carbonization process,the 3D structure non-woven fabrics were transformed into carbon cloth.Meanwhile,carbon tubes were catalyst gowth by FeCl₃.With a cutoff capacity of 500 mAh g^-1,the Li-O₂ batteries exhibited excellent charge-discharge cycling stability for over 110 cycles.?4?A composite of N-doped carbon tubes with embedded MoFeNi and MoC nanoparticles was prepared via a simple floating catalyst chemical vapour deposition?FCCVD?method.The composite shows high CO₂reduction and evolution activities.When used as a binder-free cathode for Li-CO₂ batteries,low overpotential and long cycleability which are comparable with those of Li-O₂ batteries are achieved.The composite produced in this work show promise as a binder-free cathode for lithium-air batteries operated in the presence of O₂ and CO₂.