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Title: Micro-structured hollow fibers for micro-tubular solid oxide fuel cells
Author: Li, Tao
ISNI:       0000 0004 7233 0105
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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Micro-tubular solid oxide fuel cells (MT-SOFCs) have received increasing research interest in the past decade. However, current development is restricted in R&D phase due to several technical challenges, such as expensive manufacturing route, which limits mass-scale production, and the difficulties in efficient current collection, especially from the small lumen of micro-tubes. In terms of fabrication, conventional routes usually consist of repetitions of coating and sintering, which is both time and cost-consuming. To tackle this problem, a phase inversion-assisted co-extrusion process has been established in this study, which dramatically simplifies the fabrication process, with improved adhesion. The phase inversion process could lead to the formation of an asymmetric structure, comprising micro-channels and a sponge-like structure. The former morphology could facilitate fuel transport, while the latter provides reactive sites for electrochemical reactions. The feasibility of the new manufacturing route has been established by fabricating anode/anode functional layer (AFL)/electrolyte triple-layer hollow fibers and the results suggest that inserting an AFL could effectively improve power density by 30% due to enlarged triple-phase boundary. As for the current collection from the lumen side, a new nickel-based current collector has been developed via co-extrusion. By controlling the fabrication parameters, a deliberate mesh-structure has been obtained with uniformly distributed entrances. Inserting this nickel-based inner layer considerably increases the electrical conductivity of anode and reduces gas diffusion resistance. After a complete cell was constructed, systematic electrochemical performance tests were undertaken. It has been illustrated that more uniform current collection has been achieved and contact loss, which is the major contributor towards ohmic loss in conventional current collectors, has been significantly reduced to less than 10% of total ohmic loss. This result indeed highlights the features of process economy and high efficiency of the new current collection design and suggests this design to be suitable for large-scale stack construction.
Supervisor: Li, Kang Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral