RuO_(2) nanoparticles supported on Ni and N co-doped carbon nanotubes as an efficient bifunctional electrocatalyst of lithium-oxygen battery

镍和氮共掺杂碳纳米管负载RuO_(2)纳米颗粒作为锂氧电池的高效双功能电催化剂

Li_(2)O_(2),as the discharge product of Li-O_(2) batteries on cathode,is difficult to be electrochemically decomposed,which will lead to short cycling lifespan of the batteries.In this study,the cycling lifespan of Li-O_(2)battery was prolonged significantly by an efficient bifunctional catalyst.The Ni and N co-doped carbon nanotubes(Ni NCs)were synthesized firstly,and then RuO_(2) nanoparticles were deposited on Ni NCs by a hydrothermal route to synthesize RuO_(2)/Ni NC catalysts.Transmission electron microscopy and X-ray diffraction characterizations demonstrated that part of metallic Ni was converted into NiO and Ni(OH)2 after loading RuO_(2),and the existence of Ni O layer can prevent further oxidation of metallic Ni.The Li-O_(2)battery with RuO_(2)/Ni NC as the cathode catalyst exhibits an overpotential of 0.43 V,which is much lower than the value of 1.03 V measured with the Li-O_(2) battery using Ni NC as the cathode catalyst.At a rate of 200 mAg^(-1),the Li-O_(2) battery with the RuO_(2)/Ni NC cathode can maintain a reversible capacity of 500 mAhg^(-1)for 260 cycles,and 117 cycles with a higher reversible capacity of 1000 m A h g^(-1).The superior property of the RuO_(2)/NiNC bifunctional catalyst could be ascribed to the high activity of RuO_(2) and the rich carbon nanotube structure of NiNC for deposition and decomposition of Li_(2)O_(2).

氧化锂是锂-氧电池的主要放电产物,其很难电化学分解,因而导致电池的循环寿命过短.本文通过有效的双功能催化剂显著提升了锂-氧电池的循环寿命.首先,我们合成了镍和氮掺杂的碳纳米管(NiNC),然后通过水热法在Ni NC上负载二氧化钌(RuO_(2))纳米粒子合成RuO_(2)/Ni NC催化剂.透射电子显微镜和X-射线粉末衍射证明在水热负载RuO_(2)之后部分金属镍被转变成氧化镍和氢氧化镍,且氧化镍的存在缓解了金属镍的进一步氧化.以RuO_(2)/Ni NC为正极催化剂的锂氧电池的过电压仅为0.43 V,远低于使用NiNC作为正极催化剂的1.03 V.当限定充放电条件为200 m A g^(-1),500 mAhg^(-1)时循环寿命可达260次,在1000 mAhg^(-1)高比容量下的循环寿命也达到117次.RuO_(2)/NiNC催化剂优异的性能归因于RuO_(2)的高活性和NiNC材料丰富的碳纳米管结构促进了放电产物(Li_(2)O_(2))的生成和分解.