We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

We used anionic sulfate surfactants to assist the stabilization of graphene in aqueous solutions and facilitate the self-assembly of in situ grown nanocrystalline TiO2, rutile and anatase, with graphene. These nanostructured TiO2-graphene hybrid materials were used for investigation of Li-ion insertion properties. The hybrid materials showed significantly enhanced Li-ion insertion/extraction in TiO2. The specific capacity was more than doubled at high charge rates, as compared with the pure TiO2 phase. The improved capacity at high charge-discharge rate may be attributed to increased electrode conductivity in the presence of a percolated graphene network embedded into the metal oxide electrodes.

/pdf/self-assembled-tio2-graphene-hybrid-nanostructures-for-19bf2ydovk.pdf

Self-assembled TiO2-Graphene Hybrid Nanostructures for Enhanced Li-ion Insertion

Positive electrodes for Li-ion and lithium batteries (also termed “cathodes”) have been under intense scrutiny since the advent of the Li-ion cell in 1991. This is especially true in the past decade. Early on, carbonaceous materials dominated the negative electrode and hence most of the possible improvements in the cell were anticipated at the positive terminal; on the other hand, major developments in negative electrode materials made in the last portion of the decade with the introduction of nanocomposite Sn/C/Co alloys and Si−C composites have demanded higher capacity positive electrodes to match. Much of this was driven by the consumer market for small portable electronic devices. More recently, there has been a growing interest in developing Li−sulfur and Li−air batteries that have the potential for vastly increased capacity and energy density, which is needed to power large-scale systems. These require even more complex assemblies at the positive electrode in order to achieve good properties. This r...

Positive Electrode Materials for Li-Ion and Li-Batteries†

Carbon-coated Fe3O4 nanospindles are synthesized by partial reduction of monodispersed hematite nanospindles with carbon coatings, and investigated with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electrochemical experiments. The Fe3O4C nanospindles show high reversible capacity (∼745 mA h g−1 at C/5 and ∼600 mA h g−1 at C/2), high coulombic efficiency in the first cycle, as well as significantly enhanced cycling performance and high rate capability compared with bare hematite spindles and commercial magnetite particles. The improvements can be attributed to the uniform and continuous carbon coating layers, which have several functions, including: i) maintaining the integrity of particles, ii) increasing the electronic conductivity of electrodes leading to the formation of uniform and thin solid electrolyte interphase (SEI) films on the surface, and iii) stabilizing the as-formed SEI films. The results give clear evidence of the utility of carbon coatings to improve the electrochemical performance of nanostructured transition metal oxides as superior anode materials for lithium-ion batteries.

Carbon Coated Fe3O4 Nanospindles as a Superior Anode Material for Lithium-Ion Batteries

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 some recent developments in the synthesis and characterization of nanostructured cathode materials, including lithium transition metal oxides, vanadium oxides, manganese oxides, lithium phosphates, and various nanostructured composites. The major goal of this Review is to highlight some new progress in using these nanostructured materials as cathodes to develop lithium batteries with high energy density, high rate capability, and excellent cycling stability resulting from their huge surface area, short distance for mass and charge transport, and freedom for volume change in nanostructured materials.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.200702242

Developments in Nanostructured Cathode Materials for High‐Performance Lithium‐Ion Batteries

Porous, well crystalline LiFePO 4 /C composites with different amounts of carbon have been prepared by a sol-gel technique. The thickness of carbon coatings (paintings) has been determined by high-resolution transmission electron microscopy. It is shown that carbon coating thickness can be controlled by the amount of carbon and it has an impact on the obtained reversible capacity. Furthermore, it is shown that atomic ratio of nonactive Fe(III) phase (presumably Fe 3 P) in as-synthesized LiFePO 4 /C composites depends on the amount of carbon in the composite. Using Mossbauer spectroscopy, we have confirmed that the nonactive Fe(III) remains nearly unchanged in the composite during cycling. The lowest amount of carbon in LiFePO 4 /C composites obtained from citrate anion as a gelling agent was 3.2 wt % and this particular amount corresponds to the carbon coating thickness of about 1-2 nm. The reversible capacity obtained from the above-mentioned composite delivers close to 80% of the theoretical capacity at room temperature with a current density of 170 mA/g (C/1 rate).

Impact of the Carbon Coating Thickness on the Electrochemical Performance of LiFePO4 / C Composites

Porous olivine composites synthesized by sol-gel technique

To increase the power density of battery materials, without significantly affecting their main advantage of a high energy density, novel material architectures need to be developed. Using the example of LiFePO4, we demonstrate a simple, sol−gel-based route that leads to large (up to 20 μm) primary LiFePO4 particles, each of which contains hierarchically organized pores in the meso and macro range. As the pores are formed due to vigorous gas evolution (mainly CO and CO2) during degradation of a citrate precursor, they are perfectly interconnected within each particle. Elementary carbon, the other citrate-degradation product, is deposited on the walls of emerging pores. The superposition of a continuous 1−2 nm thick carbon film (electron conductor) on pores (ion conductor when filled with electrolyte) represents a unique architecture in which the electrons and ions are simultaneously supplied to the site of insertion in the particle interior. The material can operate at current rates up to 50 C while preser...

Darko Hanzel

Papers

Impact of the Carbon Coating Thickness on the Electrochemical Performance of LiFePO4 / C Composites

Porous olivine composites synthesized by sol-gel technique

Wired Porous Cathode Materials: A Novel Concept for Synthesis of LiFePO4

Impact of synthesis conditions on the structure and performance of Li2FeSiO4

Magnetic properties of novel superparamagnetic iron oxide nanoclusters and their peculiarity under annealing treatment