Insights into the Effects of Zinc Doping on Structural Phase Transition of P2-Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries.

P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ X-ray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SS-NMR) techniques was carried out to gain a deep insight into the structural evolution of P2-Na0.66Ni0.33-xZnxMn0.67O2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na0.66Ni0.33Mn0.67O2. Zinc doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni(4+)/Ni(3+)/Ni(2+) redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.

Zero-Strain Na2FeSiO4 as Novel Cathode Material for Sodium-Ion Batteries.

A new cubic polymorph of sodium iron silicate, Na2FeSiO4, is reported for the first time as a cathode material for Na-ion batteries. It adopts an unprecedented cubic rigid tetrahedral open framework structure, i.e., F4̅3m, leading to a polyanion cathode material without apparent cell volume change during the charge/discharge processes. This cathode shows a reversible capacity of 106 mAh g(-1) and a capacity retention of 96% at 5 mA g(-1) after 20 cycles.

Enhancing the energy density of safer Li-ion batteries by combining high-voltage lithium cobalt fluorophosphate cathodes and nanostructured titania anodes.

Recently, Li-ion batteries have been heavily scrutinized because of the apparent incompatibility between safety and high energy density. This work report a high voltage full battery made with TiO2/Li3PO4/Li2CoPO4F. The Li2CoPO4F cathode and TiO2 anode materials are synthesized by a sol-gel and anodization methods, respectively. X-ray diffraction (XRD) analysis confirmed that Li2CoPO4F is well-crystallized in orthorhombic crystal structure with Pnma space group. The Li3PO4-coated anode was successfully deposited as shown by the (011) lattice fringes of anatase TiO2 and (200) of γ-Li3PO4, as detected by HRTEM. The charge profile of Li2CoPO4F versus lithium shows a plateau at 5.0 V, revealing its importance as potentially high-voltage cathode and could perfectly fit with the plateau of anatase anode (1.8-1.9 V). The full cell made with TiO2/Li3PO4/Li2CoPO4F delivered an initial reversible capacity of 150 mA h g(-1) at C rate with good cyclic performance at an average potential of 3.1-3.2 V. Thus, the full cell provides an energy density of 472 W h kg(-1). This full battery behaves better than TiO2/Li2CoPO4F. The introduction of Li3PO4 as buffer layer is expected to help the cyclability of the electrodes as it allows a rapid Li-ion transport.

Toward a stabilized lattice framework and surface structure of layered lithium-rich cathode materials with Ti modification.

Layered lithium-rich oxides have several serious shortcomings such as fast voltage fading and poor cyclic stability of energy density which greatly hinder their practical applications. Fabrication of a stable framework of layered lithium-rich oxides during charging-discharging is crucial for addressing the above problems. In this work, we show that Ti modification is a promising way to realize this target with bifunctional roles. For example, it is able to substitute Mn in the lattice framework and form a stable surface layer. It therefore leads to an improved retention of energy density of the Ti-modified Li1.2Mn0.54-xTixNi0.13Co0.13O2 (x = 0.04, 0.08, and 0.15) materials during cycling. The evolution of dQ/dV curves show that the layered/spinel phase transformation is suppressed owing to the introduction of strong Ti-O bonds in the framework. In addition, SEM, TEM, and EIS results confirm that a more uniform and stable interface layer is formed on Ti-modified Li1.2Mn0.54-xTixNi0.13Co0.13O2 (x = 0.04, 0.08, and 0.15) materials compared with the Ti-free counterpart. The stable interface layer on the lithium-rich oxides is also beneficial for further reducing side reactions, resulting in stable interface layer resistance. Therefore, the improved cycling performance of the material is due to both contribution of the more stable framework and enhanced electrode/electrolyte interface by Ti modification.

Lumbosacral epidural lipomatosis causing rapid onset cauda equina syndrome.

Spinal epidural lipomatosis (SEL) is a rare cause of cauda equina syndrome (CES), which must be diagnosed with MRI in conjunction with a high level of clinical suspicion. Most reported cases are associated with obesity, steroid use or are secondary to endocrinopathies, frequently present subacutely or chronically, and have been managed with both surgical decompression and non-operative measures. We describe an obese 55-year-old man with rapid onset CES secondary to idiopathic lumbosacral SEL which was managed successfully with surgical decompression. Although often thought to be a trivial radiological finding, it is important not to be dismissive of patients presenting with compressive neuropathy and MRI evidence of space-occupying SEL.

Ten-year follow-up of a patient with Osler-Weber-Rendu syndrome and recurrent cerebral abscess secondary to pulmonary arteriovenous fistula.

In 1998, one of us (MJM) published an article discussing several patients with Osler-Weber-Rendu Syndrome or hereditary haemorrhagic telangiectasia with secondary cerebral complications. These were intracerebral haemorrhage, ischaemic infarct and intracerebral abscess. We outlined the background of the syndrome as well as its genotype and predicted an increasingly important role for genetic testing. Our aim in this paper is to examine the progress of one of the patients as well as recommending follow-up guidelines for patients with pulmonary arteriovenous fistulae that have been treated.