J. J. Schneider

Bio: J. J. Schneider is an academic researcher from Technische Universität Darmstadt. The author has contributed to research in topics: Carbon nanotube & Field electron emission. The author has an hindex of 10, co-authored 25 publications receiving 371 citations.

Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites based on three dimensional carbon architecture

Abstract: Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO4, M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO4, LiCoPO4) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport.

A powder diffraction study of the phase transition in LaAlO3

Abstract: The structure of LaAlO3 has been investigated around the phase transition at T(c) ≃ 800 K by neutron powder diffraction in vacuum and by X-ray powder diffraction under nitrogen atmosphere as well as by a very high resolution synchrotron experiment in air. The results were analysed in frame of the Landau theory using the fluctuation-dissipation theorem to relate the susceptibility to the atomic displacement parameters. The room temperature structure is a rhombohedrally distorted perovskite structure, space group R3c, which undergoes a transition to the ideal perovskite structure, space group Pm3m, at high temperatures. The order parameter is a rotation of the O6-octahedron described by one χ(O)-parameter. This parameter and the spontaneous strain (c/a - √6), as well as the relevant atomic displacement parameter U(op) 11(O) in the order parameter system, show a critical behaviour in agreement with a second order phase transition. Although the critical exponents of the order parameter and strain show the expected coupling behaviour, there is a striking difference of the transition temperature: the metric becomes cubic roughly 30 K below the proper T(c). This is related to spontaneous formation of domains imposing the average cubic symmetry via internal stresses.

Graphene electrodes for stimulation of neuronal cells

Abstract: Graphene has the ability to improve the electrical interface between neuronal cells and electrodes used for recording and stimulation purposes. It provides a biocompatible coating for common electrode materials such as gold and improves the electrode properties. Graphene electrodes are also prepared on SiO2 substrate to benefit from its optical properties like transparency. We perform electrochemical and Raman characterization of gold electrodes with graphene coating and compare them with graphene on SiO2 substrate. It was found that the substrate plays an important role in the performance of graphene and show that graphene on SiO2 substrate is a very promising material combination for stimulation electrodes.

Vertically aligned multiwalled carbon nanotubes for pressure, tactile and vibration sensing

Abstract: We report a simple method for the micro–nano integration of flexible, vertically aligned multiwalled CNT arrays sandwiched between a top and bottom carbon layer via a porous alumina (Al2O3) template approach. The electromechanical properties of the flexible CNT arrays have been investigated under mechanical stress conditions. First experiments show highly sensitive piezoresistive sensors with a resistance decrease of up to ∼35% and a spatial resolution of <1 mm. The results indicate that these CNT structures can be utilized for tactile sensing components. They also confirm the feasibility of accessing and utilizing nanoscopic CNT bundles via lithographic processing. The method involves room-temperature processing steps and standard microfabrication techniques.

Inscribing Wettability Gradients Onto Superhydrophobic Carbon Nanotube Surfaces

Abstract: Tunable wettability of carbon nanotube (CNT) arrays on the nanoscale is the key to move water droplets on such surfaces on a macroscopic scale. A novel type of superhydrophobic CNT surface for guided droplet transport, a key issue for future microfluidic systems, is demonstrated. It is accomplished by tailoring the required surface roughness using a process employing CNT regrowth, chemical passivation, and corona discharge.

25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress

Abstract: Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

Towards establishing standard performance metrics for batteries, supercapacitors and beyond.

Abstract: Over the past decade, electrochemical energy storage (EES) devices have greatly improved, as a wide variety of advanced electrode active materials and new device architectures have been developed. These new materials and devices should be evaluated against clear and rigorous metrics, primarily based on the evidence of real performances. A series of criteria are commonly used to characterize and report performance of EES systems in the literature. However, as advanced EES systems are becoming more and more sophisticated, the methodologies to reliably evaluate the performance of the electrode active materials and EES devices need to be refined to realize the true promise as well as the limitations of these fast-moving technologies, and target areas for further development. In the absence of a commonly accepted core group of metrics, inconsistencies may arise between the values attributed to the materials or devices and their real performances. Herein, we provide an overview of the energy storage devices from conventional capacitors to supercapacitors to hybrid systems and ultimately to batteries. The metrics for evaluation of energy storage systems are described, although the focus is kept on capacitive and hybrid energy storage systems. In addition, we discuss the challenges that still need to be addressed for establishing more sophisticated criteria for evaluating EES systems. We hope this effort will foster ongoing dialog and promote greater understanding of these metrics to develop an international protocol for accurate assessment of EES systems.

Olivine LiFePO4: the remaining challenges for future energy storage

Abstract: Rechargeable batteries can effectively store electrical energy as chemical energy, and release it when needed, providing a good choice for applications in electric vehicles (EVs). Naturally, safety concerns are the key issue for the application of battery technology in EVs. Olivine LiFePO4 is considered to be the most promising cathode material for lithium-ion batteries due to its environmental friendliness, high cycling performance and safety characteristics. Some important breakthroughs in recent years have allowed its successful commercialization. However, in spite of its success, the commercial application of LiFePO4 batteries in EVs is still hindered by some technological obstacles. Herein, we provide an update on our previous review, and overview the most significant advances in the remaining challenges for this promising battery material. New research directions and future trends have also been discussed.

A three-dimensional porous LiFePO4 cathode material modified with a nitrogen-doped graphene aerogel for high-power lithium ion batteries

Abstract: A composite cathode material consisting of (010) facet-oriented LiFePO4 nanoplatelets wrapped in a nitrogen-doped graphene aerogel is reported. Such a composite possesses a 3D porous structure with a BET surface area as high as 199.3 m2 g−1. In this composite, the nitrogen-doped graphene aerogel combined with its interconnected porous networks provides pathways for rapid electron transfer and ion transport, while the thin LFP nanoplatelets with large (010) surface area enhance the active sites and shorten the Li+ diffusion distances. As a result, a high rate capability (78 mA h g−1 at 100 C) as well as a long life cycling stability (89% capacity retention over 1000 cycles at 10 C) are achieved.