Tortuosity in electrochemical devices: a review of calculation approaches

ABSTRACT

The tortuosity of a structure plays a vital role in the transport of mass and charge in electrochemical devices. Concentration polarisation losses at high current densities are caused by mass transport limitations and are thus a function of microstructural characteristics. As tortuosity is notoriously difficult to ascertain, a wide and diverse range of methods have been developed to extract the tortuosity of a structure. These methods differ significantly in terms of calculation approach and data preparation techniques. Here, a review of tortuosity calculation procedures applied in the field of electrochemical devices is presented to better understand the resulting values presented in the literature. Visible differences between calculation methods are observed, especially when using porosity–tortuosity relationships and when comparing geometric and flux-based tortuosity calculation approaches.

KEYWORDS:

• Tortuosity
• microstructure
• diffusion
• tomography
• modelling

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Bernhard Tjaden http://orcid.org/0000-0002-5055-5923

Dan Brett http://orcid.org/0000-0002-8545-3126

Paul Shearing http://orcid.org/0000-0002-1387-9531

Additional information

Funding

The authors acknowledge funding from the Engineering and Physical Sciences Research Council (EPSRC) (EP/K005030/1, EP/M009394/1 and EP/M014045/10), the Royal Academy of Engineering and Praxair, Inc. for the studentship of B.T. This manuscript is the result of much fruitful discussion and we thank Donal Finegan and Samuel Cooper for their helpful contributions.