2016 Fiscal Year Annual Research Report
次世代リチウムイオン電池の創成にむけたＬｉ２Ｓナノ構造電極の開発
| Project/Area Number |
16F16061
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| Research Institution | Osaka University |
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Principal Investigator |
西山 憲和 大阪大学, 基礎工学研究科, 教授 (10283730)
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| Co-Investigator(Kenkyū-buntansha) |
HU WEN 大阪大学, 基礎工学研究科, 外国人特別研究員
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| Project Period (FY) |
2016-04-22 – 2018-03-31
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| Keywords | Electrocatalyst / ORR / N-doped carbon / macro-mesopore |
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| Outline of Annual Research Achievements |
Limited by the practical reasons as described in the subsequent section, last year our research mainly focused on porous carbon preparation and application in the oxygen reduction reaction (ORR) field. With the aim of architecting an inexpensive material to afford abundant, readily accessible catalytic active sites, we rationally designed and successfully synthesized a N-doped 3D open macro/mesoporous carbon by a facile solvothermal method, wherein an in-situ polymerization-induced, N-containing resin-colloidal silica nanospheres self-assembled gelation (PIAG) methodology is adopted. This metal-free catalyst catalyzes ORR via 4e- pathway, manifesting desirable catalytic activity with relatively high onset potential (0.91 V vs. RHE), half-wave potential (0.785 V), and comparable polarization current density at 0.2 V (5 mA cm-2) to that of commercial Pt/C. This can be attributed to cooperative contributions by satisfactory graphitization for conductivity enhancement, key N species to supply abundant catalytic sites, favorable surface area (845 m2 g-1) enabling more catalytic sites being exposed, and fast mass transport through smooth open pore channels (interconnected macropores with mesopores ca. 16 nm, pore volume of 4.1 cc g-1) promising those exposed catalytic sites to be fully utilized. Moreover, this catalyst is much more stable than Pt/C and free from fuel crossover poisoning. Relevant results about this research work has now been published on Electrochemistry Communications 2017, 75, 9-12.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
We cost half of the last year to build the platform for Li-S batteries, including order and installation of glove-box, a series of apparatus for electrode preparation and coin cell assembly (film applicator, disc cutter, hydraulic crimper), 8 channel battery analyzer, and the purchase of chemicals and materials. It is noteworthy that some chemicals, like lithium plate, and all the solvents and salts necessary for electrolyte preparation can only be ordered after glove-box installation. Thus last year we mainly focused our research on porous carbon for ORR application, for which all the electrochemical devices are readily available in our laboratory. But still, during the last few months we have already started research works on Li-S batteries, and some preliminary good results are achieved.
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| Strategy for Future Research Activity |
(1) Employing the above reported solvothermal PIAG method, we also synthesized a porous Co, N-codoped carbon. When we decorate this material on the Celgard polypropylene (PP) separator for Li-S batteries, the preliminary electrochemical measurement showed that the initial discharge capacity of a simple C/S cathode (i.e. MWCNT/S-70 wt%) at 0.2 C is greatly increased to 1406 mAh g-1 from 741 mAh g-1 using bare PP separator. The interlayer seems having great capability to confine and reutilize polysulfides escaped from the cathode region. Therefore, in the coming year, we plan to characterize the morphology and structure of the as-synthesized Co-N-C in detail by XRD, FE-SEM, TEM, EDS, XPS, N2 sorption techniques. Meanwhile, systematic electrochemical analysis including CV, cycle performance at variant current densities, EIS, etc. on Co-N-C/PP and control samples will be carried out. Finally, combining the material structure with electrochemical performance, a possible mechanism to elucidate the interaction between polysulfides and Co-N-C should be proposed.
(2) In the last year, we also prepared a hierarchical N-doped carbon with 3D ordered macroporous framework (N-HOPC). Motivated by the promising result as described in Plan 1, we plan to dope Co during the synthesis of N-HOPC. Then we test the Li-S cell applying Co, N-HOPC as interlayer. The objective of this research is to testify whether Co-N moiety is the general active sites for polysufides adsorption and redox catalysis.
(3) Summarizing results, and preparing manuscripts for publication.
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