Numerical design of microporous carbon binder domains phase in composite cathodes for lithium-ion batteries

Lithium-ion battery (LIB) performance can be significantly affected by the nature of the complex electrode microstructure. The carbon binder domain (CBD) present in almost all LIB electrodes is used to enhance mechanical stability and facilitate electronic conduction, and understanding the CBD phase microstructure and how it affects the complex coupled transport processes is crucial to LIB performance optimization. In this work, the influence of microporosity in the CBD phase has been studied in detail for the first time, enabling insight into the relationships between the CBD microstructure and the battery performance. To investigate the effect of the CBD pore size distributions, a random field method is used to generate in silico a multiple-phase electrode structure, including bimodal pore size distributions seen in practice and microporous CBD with a tunable pore size and variable transport properties. The distribution of macropores and the microporous CBD phase substantially affected simulated battery performance, where battery specific capacity improved as the microporosity of the CBD phase increased

High speed 4D neutron computed tomography for quantifying water dynamics in polymer electrolyte fuel cells

In recent years, low temperature polymer electrolyte fuel cells have become an increasingly important pillar in a zero carbon strategy for curbing climate change, with their potential to power multiscale stationary and mobile applications. The performance improvement is a particular focus of research and engineering roadmaps, with water management being one of the major areas of interest for development. Appropriate characterisation tools for mapping the evolution, motion and removal of water are of high importance to tackle shortcomings. This article demonstrates the development of a 4D high speed neutron imaging technique, which enables a quantitative analysis of the local water evolution. 4D visualisation allows the time resolved studies of droplet formation in the flow fields and water quantification in various cell parts. Performance parameters for water management are identified that offer a method of cell classification, which will, in turn, support computer modelling and the engineering of next generation flow field design

4D imaging of lithium batteries using correlative neutron and X ray tomography with a virtual unrolling technique

The temporally and spatially resolved tracking of lithium intercalation and electrode degradation processes are crucial for detecting and understanding performance losses during the operation of lithium batteries. Here, high throughput X ray computed tomography has enabled the identification of mechanical degradation processes in a commercial Li MnO2 primary battery and the indirect tracking of lithium diffusion; furthermore, complementary neutron computed tomography has identified the direct lithium diffusion process and the electrode wetting by the electrolyte. Virtual electrode unrolling techniques provide a deeper view inside the electrode layers and are used to detect minor fluctuations which are difficult to observe using conventional three dimensional rendering tools. Moreover, the unrolling provides a platform for correlating multi modal image data which is expected to find wider application in battery science and engineering to study diverse effects e.g. electrode degradation or lithium diffusion blocking during battery cyclin

Roadmap on Li-ion battery manufacturing research

Growth in the Li-ion battery market continues to accelerate, driven by increasing need for economic energy storage in the electric vehicle market. Electrode manufacture is the first main step in production and in an industry dominated by slurry casting, much of the manufacturing process is based on trial and error, know-how and individual expertise. Advancing manufacturing science that underpins Li-ion battery electrode production is critical to adding value to the electrode manufacturing value chain. Overcome the current barriers in the electrode manufacturing requires advances in material innovation, manufacturing technology, in-line process metrology and data analytics to improve cell performance, quality, safety and process sustainability. In this roadmap we present where fundamental research can impact advances in each stage of the electrode manufacturing process from materials synthesis to electrode calendering. We also highlight the role of new process technology such as dry processing and advanced electrode design supported through electrode level, physics-based modelling. To compliment this, the progresses in data driven models of full manufacturing processes is reviewed. For all the processes we describe, there is a growing need process metrology, not only to aid fundamental understanding but also to enable true feedback control of the manufacturing process. It is our hope this roadmap will contribute to this rapidly growing space and provide guidance and inspiration to academia and industry

Characterization of the 3-dimensional microstructure of a graphite negative electrode from a Li-ion battery

The 3-dimensional microstructure of a porous electrode from a lithium-ion battery has been characterized for the first time. We use X-ray tomography to reconstruct a 43 x 348 x 478 mu m sample volume with voxel dimensions of 480 nm, subsequent division of the reconstructed volumes into sub-volumes of different sizes allow us to determine microstructural parameters as a function of sub-division size. We show that the minimum size for a representative volume element is about 43 x 60 x 60 mu m for volume-specific surface area, but as large as the full sample volume for porosity and tortuosity. (C) 2009 Elsevier B.V. All rights reserved

Discrete element method and electrochemical modelling of lithium ion cathode structures characterised by X-ray computed tomography

Electrode microstructure can profoundly affect the performance of lithium-ion batteries. In this work, the effect of the calendering process on electrode microstructures is investigated using the Discrete Element Method (DEM) with a bonded particle model. A comprehensive evaluation between realistic electrode structures and idealised DEM structures as characterised using X-ray computed tomography (XCT) is presented. The electrode structural and transport properties of tomography scans and DEM structures, i.e. porosity distribution, specific surface area and tortuosity factors are studied. Following consideration of the carbon binder domain (CBD) phase, electrochemical analysis is further performed. Excellent agreement between tomography and idealised structures from DEM simulations is achieved, taking into account the effect of calendering. With electrode compression battery performance is improved after calendering. This study provides a basis for using DEM and electrochemical analysis to quantitatively evaluate the battery performance in future

Multiscale tomographic analysis of the thermal failure of Na-Ion batteries

In recent years, the ability to examine the processes that cause the catastrophic failure of batteries as a result of thermal runaway has improved substantially. In this work, the effect of thermal runaway on the microstructure of the electrodes of a Na-ion battery is examined using X-ray computed tomography for the first time. The thermal failure induced via accelerating rate calorimetry enabled the examination of failed electrodes, which were subsequently compared with fresh samples. Pre- and post-mortem microstructural analysis shows changes in both electrodes as a result of the thermal runaway process at the micrometre length-scale. It is seen that the cathode shows the largest changes in structure, with the anode remaining morphologically similar post-failure at the sub-micron length-scale. The formation of a highly X-ray attenuating layer, which is proposed to be a metallic product of the thermal runaway reaction, is observed, indicating that the thermal runaway mechanisms which occur in Na-ion batteries may be similar to those reported for Li-ion systems

Core–shell TiO2@C ultralong nanotubes with enhanced adsorption of antibiotics

As materials capable of adsorbing antibiotics continue to be developed, composite adsorbents have been shown to offer advantages over mono-material adsorbents. In this work, ultralong titanium dioxide@carbon nanotubes were prepared by a simple hydrothermal treatment, followed by carbonization. The composite material is able to adsorb three different categories of antibiotics, including tetracycline (TC), ofloxacin (OFO) and norfloxacin (NFO). The adsorption results show that the adsorption properties of composite materials have been greatly improved compared with single inorganic adsorbent materials, for which the adsorption capacities are 240 mg g−1 (TC), 232 mg g−1 (OFO), and 190 mg g−1 (NFO), respectively. The adsorption mechanism is consistent with a Langmuir pseudo-first-order kinetic model