Sizing of cracks embedded in sub-cladding using the ultrasonic synthetic aperture focusing technique (SAFT)

This paper deals with the experimental work carried out to demonstrate the feasibility of the ultrasonic Synthetic Aperture Focusing Technique (SAFT) to obtain improved detection and sizing of vertical/inclined (10° and 15° simulated cracks underneath different claddings. Crack heights ranging from 1.68 mm to 19.04 mm underneath stainless steel, Inconel and ferritic steel cladding were sized with an accuracy of ±0.1 to ±0.3 mm. The problems encountered in TOFD with regard to sizing of near-surface cracks was successfully overcome by SAFT. Mis-oriented (inclined) defects embedded below the cladding suffer added disadvantage for ultrasonic detection due to loss of reflected energy due to mis-orientation. Using SAFT even these defects could be sized accurately

Status and outlook for lithium-ion battery cathode material synthesis and the application of mechanistic modeling

This work reviews different techniques available for the synthesis and modification of cathode active material (CAM) particles used in Li-ion batteries. The synthesis techniques are analyzed in terms of processes involved and product particle structure. The knowledge gap in the process-particle structure relationship is identified. Many of these processes are employed in other similar industries; hence, parallel insights and knowledge transfer can be applied to battery materials. Here, we discuss examples of applications of different mechanistic models outside the battery literature and identify similar potential applications for the synthesis of CAMs. We propose that the widespread implementation of such mechanistic models will increase the understanding of the process-particle structure relationship. Such understanding will provide better control over the CAM synthesis technique and open doors to the precise tailoring of product particle morphologies favorable for enhanced electrochemical performance

Roadmap on Li-ion battery manufacturing research

Growth in the Li-ion battery market continues to accelerate, driven primarily by the increasing need for economic energy storage for electric vehicles. Electrode manufacture by slurry casting is the first main step in cell production but much of the manufacturing optimisation 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 to the electrode manufacturing value chain. Overcoming the current barriers in electrode manufacturing requires advances in materials, manufacturing technology, in-line process metrology and data analytics, and can enable improvements in cell performance, quality, safety and process sustainability. In this roadmap we explore the research opportunities to improve each stage of the electrode manufacturing process, from materials synthesis through to electrode calendering. We highlight the role of new process technology, such as dry processing, and advanced electrode design supported through electrode level, physics-based modelling. Progress in data driven models of electrode manufacturing processes is also considered. We conclude there is a growing need for innovations in process metrology to aid fundamental understanding and to enable feedback control, an opportunity for electrode design to reduce trial and error, and an urgent imperative to improve the sustainability of manufacture

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

Carbon binder domain networks and electrical conductivity in lithium-ion battery electrodes : a critical review

In a drive to increase Li-ion battery energy density, as well as support faster charge discharge speeds, electronic conductivity networks require increasingly efficient transport pathways whilst using ever decreasing proportions of conductive additive. Comprehensive understanding of the complexities of electronic conduction in lithium-ion battery electrodes is lacking in the literature. In this work we show higher electronic conductivities do not necessarily lead to higher capacities at high C-rates due to the complex interrelation between the electronically conducting carbon binder domain (CBD) and the ionic diffusion within electrodes. A wide body of literature is reviewed, encompassing the current maxims of percolation theory and conductive additives as well as the relationships between processing steps at each stage of electrode manufacturing and formation of electronic conduction pathways. The state-of-the-art in electrode characterisation techniques are reviewed in the context of providing a holistic and accurate understanding of electronic conductivity. Literature regarding the simulation of electrode structures and their electronic properties is also reviewed. This review presents the first comprehensive survey of the formation of electronic conductivity networks throughout the CBD in battery electrodes, and demonstrates a lack of understanding regarding the most optimum arrangement of the CBD in the literature. This is further explored in relation to the long-range and short-range electrical contacts within a battery electrode which represent the micron level percolation network and the submicron connection of CBD to active material respectively. A guide to future investigations into CBD including specific characterisation experiments and simulation approaches is suggested. We conclude with suggestions on reporting important metrics such as robust electrical characterisation and the provision of metrics to allow comparison between studies such as aerial current density. Future advances in characterisation, simulation and experimentation will be able to provide a more complete understanding if research can be quantitatively compared

Time of flight diffraction and synthetic aperture focusing technique for NDT of weldments

The limits of anomaly detection by use of nondestructive testing (NDT) methods are based on the interaction of the material with the applied probing medium. Various methods are employed for detection of anomalies in weldments. Investigations using the radiographic, ultrasonic pulse/echo, time of flight diffraction, and synthetic aperture focusing techniques were carried out on a carbon steel weld pad (thickness 18 mm) with natural anomalies introduced at predetermined locations. The anomalies were first imaged by radiography. The pulse/echo technique, using different parameters, could detect almost all the planar anomalies except a cluster of porosity. Although time of flight diffraction could recognize most of the anomalies, it was not possible to clearly resolve and characterize the cluster of pores and group of cracks. Cracks with cleft edges were almost impossible to identify. The experimental results revealed that time of flight diffraction at a minimum meets code requirements for detection of anomalies. Sizing of length and through-wall extent can be carried out using the initial time of flight diffraction data. Using the synthetic aperture focusing technique, it was possible to resolve and characterize all the anomalies on par with the radiographic information. In addition, two clusters of porosity were distinctly seen, separated by 7 mm. Hence, the reporting criteria of the "ASME Boiler and Pressure Vessel Code" (ASME, 2004) can be satisfied using ultrasonic imaging techniques such as time of flight diffraction and synthetic aperture focusing for detection, sizing and characterization of anomalies in weldments in lieu of radiography. Destructive tests were also employed at a later stage to corroborate and validate the findings of anomalies by NDT methods