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Mesoporous Co3O4-Rods-Entangled Carbonized Polyaniline Nanotubes as an Efficient Cathode Material toward Stable Lithium-air Batteries Chengxing Li, Daobin Liu, Yukun Xiao, Zixuan Liu, Li Song, and Zhipan Zhang ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.9b00291 • Publication Date (Web): 18 Mar 2019 Downloaded from http://pubs.acs.org on March 20, 2019
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ACS Applied Energy Materials
Mesoporous Co3O4-Rods-Entangled Carbonized Polyaniline Nanotubes as an Efficient Cathode Material toward Stable Lithium-air Batteries Chengxing Lia, Daobin Liub, Yukun Xiaoa ,Zixuan Liu*c ,Li Songb, and Zhipan Zhang*a
a Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081 P. R. China, *E-mail:
[email protected] b National Synchrotron Radiation Laboratory, School of Chemistry and Materials Science, CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230026 P. R. China
c Department of New Energy Technologies, Ningbo Institute of Materials Technology and Engineering ,Chinese Academy of Sciences, Zhongguan West Rd.1219, Zhenhai Dist., Ningbo City, Zhejiang Prov.315201 P. R. China, *E-mail:
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KEYWORDS : lithium-air batteries, cobalt oxide, carbonized polyaniline nanotubes, synergistic effects, electrocatalytic activities, cycling stability
ABSTRACT: Lithium-air batteries (LABs) are considered as one of the most promising next-generation energy storage devices due to their high theoretic specific energy. However, the commercialization of current LABs is considerably limited by the high overpotential in charging/discharging, low energy efficiency, and poor cyclability. To solve these problems, mesoporous Co3O4-rods-entangled carbonized polyaniline nanotubes (Co3O4-e-cPANI) have been facilely prepared through a facile hydrothermal method and their unique hierarchical architectures fully exploit the synergistic effect from the catalytically-active Co3O4 and the conductive cPANI, simultaneously facilitating the rapid oxygen diffusion, electrolyte penetration as well as unimpeded electron transportation. As a result, the LAB with the Co3O4-e-cPANI cathode shows an excellent cycling stability of 430 cycles under a reversible capacity of 500 mAh g-1 and 226 cycles under a higher capacity of 1000 mAh g-1. The current results demonstrate that optimizing the air
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ACS Applied Energy Materials
cathode structure such as constructing Co3O4-e-cPANI architecture is an important route to further improve the stability of LABs towards practical applications.
1. INTRODUCTION
The rapid development in portable electronic devices and electric vehicles has posed new challenges on high-energy-density secondary batteries. (1) While the Li-ion battery based on the intercalation mechanism has been widely implemented, its low energy density is unlikely to meet the demands of long-range electric vehicles and high-duty energy storage systems. (2) In comparison, rechargeable metal-air batteries have shown much higher specific energy densities. For instance, lithium-air batteries (LABs) feature an open cell structure where oxygen can be supplied from the atmosphere without occupying the battery volume, thus reducing the battery weight and improving their mass-specific energy density (~3500Wh kg-1 in theory).(3-6) Despite these inherent merits, LABs have suffered from low energy efficiency, high overpotential and short cycle life.(7-9) In particular, the air cathode is the core component that determines the performance of the battery, where oxygen undergoes the oxygen reduction reaction (ORR) to form Li2O2 (2Li+ + O2 + 2e− ⇋ Li2O2, 2.96 V vs. Li/Li+) during discharge and Li2O2 subsequently decomposes via the reversed oxygen evolution reaction (OER) under charging.(10) Unfortunately, the insulating Li2O2 can significantly reduce the electrical conductivity of the air cathode, simultaneously passivating active sites upon the ORR and slowing down the subsequent OER process.(11) Meanwhile, the random deposition of Li2O2 tends to block the permeation of oxygen and the diffusion of electrolyte species (such as Li+) inside the cathode, resulting in a serious decay in the capacity upon repetitive cycles.(12,13) Consequently, it is vital to optimize
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the interfacial structure of the cathode to facilitate ORR/OER, fast electron transport as well as unimpeded permeation of oxygen and electrolyte species. Due to their large surface area, high electrical conductivity and notable catalytic activity in the ORR, heteroatom-doped carbon materials are interesting candidates for applications in air cathodes.(14-19) For example, Lin et al. reported an air cathode based on a nitrogen-doped carbon composite and the fabricated LAB showed a specific capacity of 9905 mAh g-1.(16) However, the cathode exhibited a poor cycle stability of
