Tunable electronic structure of heterosite FePO: an in-depth structural study and polaron transport.

The development of better electrode materials for lithium-ion batteries has been intensively investigated both due to their fundamental scientific aspects as well as their usefulness in technological applications. The present technological development of rechargeable batteries is hindered by fundamental challenges, such as low energy and power density, short lifespan, and sluggish charge transport kinetics. Among the various anode materials proposed, heterosite FePO (h-FP) has been found to intercalate lithium and sodium ion hosts to obtain novel rechargeable batteries.

Size dependent electronic structure of LiFePO probed using X-ray absorption and Mössbauer spectroscopy.

We present the combined Mössbauer and X-ray absorption spectroscopy investigation of the electronic structure and local site symmetry of Fe in olivine structured LiFePO (LFP) with crystallite size (CS). The lattice parameters are found to contract with a decrease in CS, monotonously, whereas the electronic structural parameters exhibit two different regions with a threshold anomaly of around ≈30 nm. Fe Mössbauer studies reveal the coexistence of Fe and Fe sites and their relative concentrations are mainly determined by CS, which provides a comprehensive insight into the electronic structure of LFP at the mesoscopic level.

Effect of crystallite size on the phase transition behavior of heterosite FePO.

For advanced lithium-ion battery technology, olivine-based cathodes are considered to be the most dominant and technologically recognized materials. The extraction of lithium ions from olivine LiFePO results in the two-phase mixture with heterosite FePO exhibiting a deintercalation potential of 3.45 V vs.

Size induced structural changes in maricite-NaFePO: an in-depth study by experiment and simulations.

Rechargeable batteries based on the most abundant elements, such as sodium and iron, have a great potential in the development of cost effective sodium ion batteries for large scale energy storage devices. We report, for the first time, crystallite size dependent structural investigations on maricite-NaFePO through X-ray diffraction, X-ray absorption spectroscopy and theoretical simulations. Rietveld refinement analysis on the X-ray diffraction data reveals that a decrease in the unit cell parameters leads to volume contraction upon reduction in the crystallite size.

Direct evidence for the influence of lithium ion vacancies on polaron transport in nanoscale LiFePO.

Improving the electronic conductivity in lithium-based compounds can considerably impact the design of rechargeable batteries. Here, we explore the influence of lithium ion vacancies on the electronic conductivity of LiFePO4, an active cathode material, by varying the crystallite sizes. We find that about 17% lithium ion vacancy concentration leads to an enhancement in electronic conductivity of about two orders of magnitude at 313 K with respect to our initial crystallite size.

Effect of surfactant concentration on textural characteristics and biomineralization behavior of mesoporous bioactive glasses.

We report mesoporous bioactive glasses (MBGs) with different pore architecture synthesized using the supramolecular chemical approach using acid assisted sol-gel method followed by evaporation induced self-assembly (EISA) process. The surfactant of non-ionic block co-polymer used in the present work act as structure directing agent (SDA) with varying amount, which brings different textural properties. As prepared glasses possess wormhole-like mesostructure with different textural characteristics and it varies with surfactant concentrations.

Mesoporous 45S5 bioactive glass: synthesis, in vitro dissolution and biomineralization behavior.

The development of a new generation of biomaterials includes a sol-gel process to obtain glass foams, which is a well established method for CaO-SiO-PO compositions, but is not yet recognized for Bioglass® containing sodium oxide. In this study, we report, for the first time, the synthesis of a mesoporous 45S5 bioactive glass with superior textural characteristics and its in vitro dissolution and biomineralization behavior. Wormhole-like bioactive mesostructured 45S5 glass has been synthesized by an acid assisted sol-gel method followed by an evaporation induced self-assembly process.

Bio-inspired synthesis of microporous bioactive glass-ceramic using CT-DNA as a template.

We report, for the first time, bio-inspired synthesis of a bioactive glass-ceramic with superior textural properties in atmospheric conditions using CT-DNA as template. The phase composition, structure, morphology, and textural properties of the bioactive glass sample were evaluated with various analytical techniques before and after in vitro tests. The BET surface area analysis of the obtained glass-ceramic sample reveals that it possesses a high surface area with a range of (micro- to meso-) pore sizes.

Particle size dependent confinement and lattice strain effects in LiFePO4.

We report the intrinsic electronic properties of LiFePO4 (LFP) with different particle sizes measured by broad-band impedance spectroscopy and diffuse reflectance spectroscopy. The electronic properties show typical size-dependent effects with decreasing particle size (up to 150 nm). However, at the nanoscale level, we observed an enhancement in the polaronic conductivity about an order of magnitude.

Alkali oxide containing mesoporous bioactive glasses: synthesis, characterization and in vitro bioactivity.

We report, for the first time, the synthesis of sodium oxide containing mesoporous bioactive quaternary glasses and compared with two different mesoporous ternary silicate systems by modified sol-gel process. With the aid of three different glass systems, a systematic analysis has been made on phosphorous-bearing (P-bearing) and phosphorous-free (P-free) mesoporous bioactive glasses to investigate the role of phosphorus on in vitro bioactivity of various silicate glasses with constant alkali oxide content. The combined use of multiple analytical techniques XRD, FTIR, SEM, nitrogen adsorption/desorption analysis before and after soaking in the SBF solution allowed us to establish strong correlation between composition, pore structure and bioactivity.

Fast interfacial ionic conduction in nanostructured glass ceramics.

The hopping movements of mobile ions in a nanostructured LiAlSiO4 glass ceramic are characterized by time-domain electrostatic force spectroscopy (TDEFS). While the macroscopic conductivity spectra are governed by a single activation energy, the nanoscopic TDEFS measurements reveal three different dynamic processes with distinct activation energies. Apart from the ion transport processes in the glassy and crystalline phases, we identify a third process with a very low activation energy, which is assigned to ionic movements at the interfaces between the crystallites and glassy phase.

Nanoscopic study of the ion dynamics in a LiAlSiO4 glass ceramic by means of electrostatic force spectroscopy.

We use time-domain electrostatic force spectroscopy (TD-EFS) for characterising the dynamics of mobile ions in a partially crystallised LiAlSiO4 glass ceramic, and we compare the results of the TD-EFS measurements to macroscopic electrical conductivity measurements. While the macroscopic conductivity spectra are determined by a single dynamic process with an activation energy of 0.72 eV, the TD-EFS measurements provide information about two distinct relaxation processes with different activation energies.