INVESTIGATION OF CARBON FIBER ANDFREE-STANDING CARBON NANOTUBEARRAY ELECTRODES FOR LITHIUM-AIR BATTERIES

Lithium-air;Lithium-oxygen;Carbon Nanotubes;Nanoparticles;Catalysts;not listed

Gonzalez, Matthew StephensWang, Chao ;

Johns Hopkins University

关键词: Lithium-air;    Lithium-oxygen;    Carbon Nanotubes;    Nanoparticles;    Catalysts;    not listed;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/39492/GONZALEZ-THESIS-2016.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

Conventional Lithium-ion battery technology is beginning to approach its practical energy density limit. As the demand for high capacity electrical energy storage increases, the need for a viable replacement to Li-ion batteries is becoming essential. Lithium-oxygen and lithium-air batteries boast a theoretically energy density of 11,140 Wh/kg (compared to gasoline: ~12,330 Wh/kg). However there are many challenges that plague Li-O2 and Li-air batteries that prevent them from being commercially practical with current technologies. Finding a suitable electrolyte, improving the poor stability of the Li anode, and implementing materials to catalyze the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the air cathode are a few examples of challenges with the technology. Here we report developing a novel method to assemble and test lithium-air batteries constructed from standard Li-ion coin cells using a free standing, pure carbon nanotube array as the porous air breathing electrode, ionic liquid as a hydrophobic electrolyte and lithium foil as the anode. We achieved a Li-air battery capable of remaining stable up to 35 cycles to a depth of 500 mAh/gCNTs over a one week with current densities as high as 250 mA/g while breathing ambient atmosphere. By sputter coating a layer of gold onto our carbon nanotube array air cathodes we achieved a 25% increase in discharge potential when compared to pure carbon nanotubes cathodes. We found that although the addition of gold slightly increased the internal resistance (Rint) of the battery it reduced the surface and charge-transfer resistance (Rs-ct) by more than 30%. Lithium anode stability still remains a major challenge that plagues our ability to test long life improvements to the air cathode. Investigation of lithium titanate (LTO) as a lithium host remained stable after 50-100 cycles, however a negative discharge voltage arises when assembled as a lithium-oxygen cell. We suspect this may arise from an undercapacity of Li available from the LTO, requiring further testing with higher material loading. We also developed a method to test our batteries under a controlled atmosphere using a pressure vessel. This will in theory mitigate the issue of anode stability, allowing us the ability to test the long-life performance of gold and other catalysts during charge and discharge of a Li-air battery in future studies.