Effect of Nitrogen Dopant Agents in the Performance of Graphene-Based Cathodes for Li-S Batteries.

Lithium-sulphur (Li-S) batteries offer high energy density compared to lithium-ion batteries, emerging as a promising technology for the next generation of energy storage systems. The ongoing challenge is to improve their electrochemical performance, extend their useful life and mitigate some problems that persist in this technology, by the investigation in materials with diverse properties. This work seeks to elucidate the importance and repercussions associated with functionalisation of graphene-based materials through nitrogen incorporation (more than 9 wt.% N), employing different chemical agents such as ethylenediamine and ammonia. Herein, differences in both the textural properties and the chemical environment of nitrogen within the carbonaceous network are identified, resulting in distinct electrochemical behaviours. The electrochemical performance of electrodes prepared from ammonia-functionalised samples surpasses that of ethylenediamine-functionalised samples in terms of both efficiency and rate performance. Conversely, the ethylenediamine-functionalised samples excel in stability, showing exceptional values in capacity retention per cycle. The outcomes exceeded expectations in energy performance, allowing the Li-S cells to be subjected to ultra-high rate cycling while maintaining appropriate capacity values.

Prussian Blue Analogues as Positive Electrodes for Mg Batteries: Insights into Mg2+ Intercalation.

Potassium manganese hexacianoferrate has been prepared by co-precipitation from manganese (II) chloride and potassium citrate, with chemical analysis yielding the formula K1.72 Mn[Fe(CN)6 ]0.92 □0.08 ⋅ 1.1H2 O (KMnHCF). Its X-ray diffraction pattern is consistent with a monoclinic structure (space group P 21 /n, no. 14) with cell parameters a=10.1202(6)Å, b=7.2890(5)Å, c=7.0193(4)Å, and ß=89.90(1)°. Its redox behavior has been studied in magnesium containing electrolytes. Both K+ ions deintercalated from the structure upon oxidation and contamination with Na+ ions coming from the separator were found to interfere in the electrochemical response. In the absence of alkaline ions, pre-oxidized manganese hexacianoferrate showed reversible magnesium intercalation, and the process has been studied by operando synchrotron X-ray diffraction. The location of Mg2+ ions in the crystal structure was not possible with the available experimental data. Still, density functional theory simulations indicated that the most favorable position for Mg2+ intercalation is at 32f sites (considering a pseudo cubic F m-3m phase), which are located between 8c and Mn sites.

ß-V2O5 as Magnesium Intercalation Cathode.

Magnesium batteries have attracted great attention as an alternative to Li-ion batteries but still suffer from limited choice of positive electrode materials. V2O5 exhibits high theoretical capacities, but previous studies have been mostly limited to α-V2O5. Herein, we report on the ß-V2O5 polymorph as a Mg intercalation electrode. The structural changes associated with the Mg2+ (de-) intercalation were analyzed by a combination of several characterization techniques: in situ high resolution X-ray diffraction, scanning transmission electron microscopy, electron energy-loss spectroscopy, and X-ray absorption spectroscopy. The reversible capacity reached 361 mAh g-1, the highest value found at room temperature for V2O5 polymorphs.

Electrochemical Methods for Lithium Recovery: A Comprehensive and Critical Review.

Due to the ubiquitous presence of lithium-ion batteries in portable applications, and their implementation in the transportation and large-scale energy sectors, the future cost and availability of lithium is currently under debate. Lithium demand is expected to grow in the near future, up to 900 ktons per year in 2025. Lithium utilization would depend on a strong increase in production. However, the currently most extended lithium extraction method, the lime-soda evaporation process, requires a period of time in the range of 1-2 years and depends on weather conditions. The actual global production of lithium by this technology will soon be far exceeded by market demand. Alternative production methods have recently attracted great attention. Among them, electrochemical lithium recovery, based on electrochemical ion-pumping technology, offers higher capacity production, it does not require the use of chemicals for the regeneration of the materials, reduces the consumption of water and the production of chemical wastes, and allows the production rate to be controlled, attending to the market demand. Here, this technology is analyzed with a special focus on the methodology, materials employed, and reactor designs. The state-of-the-art is reevaluated from a critical perspective and the viability of the different proposed methodologies analyzed.

Effect of Pt and Au current collector in LiMn2O4 thin film for micro-batteries.

The crystal orientation and morphology of sputtered LiMn2O4 thin films is strongly affected by the current collector. By substituting Pt with Au, it is possible to observe in the x-ray diffraction pattern of LiMn2O4 a change in the preferential orientation of the grains from (111) to (400). In addition, LiMn2O4 thin films deposited on Au show a higher porosity than films deposited on Pt. These structural differences cause an improvement in the electrochemical performances of the thin films deposited on Au, with up to 50% more specific charge. Aqueous cells using thin film based on LiMn2O4 sputtered on Au or Pt as the cathode electrode present a similar retention of specific charge, delivering 85% and 100%, respectively, of the initial values after 100 cycles. The critical role of the nature of the substrate used in the morphology and electrochemical behaviour observed could permit the exploration of similar effects for other lithium intercalation electrodes.

Revealing the electronic character of the positive electrode/electrolyte interface in lithium-ion batteries.

High voltage operating active materials are among the most promising components for positive electrodes of future high energy lithium-ion batteries. However, the operating potential range of such materials often exceeds anodically the thermodynamic stability window of the electrolyte. A surface layer is therefore formed, which is supposed to be one of the reasons for the high irreversible charge loss of these electrodes. The electronic character of such a surface layer formed at the electrode/electrolyte interface of LiNi0.5Mn1.5O4 (LNM), stoichiometric (x = 0) and overlithiated (x = 0.1) Li1+x(Ni1/3Mn1/3Co1/3)1-xO2 (NMC) based paste electrodes was investigated in situ using feedback-mode scanning electrochemical microscopy (SECM). The role in the formation of an electronically insulating layer of a conductive carbon additive-based electrode and of the Al current collector was explored as well. The surface layers formed on all oxide based paste electrodes and on conductive carbon additive based electrodes showed unexpectedly an electronic conducting behavior, while the Al current collector formed an electronically insulating layer which was found to be influenced by the electrolyte.

High Specific Power Dual-Metal-Ion Rechargeable Microbatteries Based on LiMn2O4 and Zinc for Miniaturized Applications.

Miniaturized rechargeable batteries with high specific power are required for substitution of the large sized primary batteries currently prevalent in integrated systems since important implications in dimensions and power are expected in future miniaturized applications. Commercially available secondary microbatteries are based on lithium metal which suffers from several well-known safety and manufacturing issues and low specific power when compared to (super) capacitors. A high specific power and novel dual-metal-ion microbattery based on LiMn2O4, zinc, and an aqueous electrolyte is presented in this work. Specific power densities similar to the ones exhibited by typical electrochemical supercapacitors (3400 W kg-1) while maintaining specific energies in the range of typical Li-ion batteries are measured (∼100 Wh kg-1). Excellent stability with very limited degradation (99.94% capacity retention per cycle) after 300 cycles is also presented. All of these features, together with the intrinsically safe nature of the technology, allow anticipation of this alternative micro power source to have high impact, particularly in the high demand field of newly miniaturized applications.

Ultrafast Dischargeable LiMn2O4 Thin-Film Electrodes with Pseudocapacitive Properties for Microbatteries.

LiMn2O4 (LMO) thin films are deposited on Si-based substrates with Pt current collector via multi-layer pulsed-laser-deposition technique. The LMO thin films feature unique kinetics that yield outstanding electrochemical cycling performance in an aqueous environment. At extremely high current densities of up to 1880 µA cm-2 (≈ 348 C), a reversible capacity of 2.6 µAh cm-2 is reached. Furthermore, the electrochemical cycling remains very stable for over 3500 cycles with a remarkable capacity retention of 99.996% per cycle. We provide evidence of significant nondiffusion-controlled, pseudocapacitive-like storage contribution of the LMO electrode.

Lithium recovery by means of electrochemical ion pumping: a comparison between salt capturing and selective exchange.

Currently, lithium carbonate is mainly produced through evaporation of lithium-rich brines, which are located in South American countries such as Bolivia, Chile, and Argentina. The most commonly used process, the lime-soda evaporation, requires a long time and several purification steps, which produces a considerable amount of chemical waste. Recently, several alternative electrochemical methods, based on LiFePO4 as a selective lithium capturing electrode and differing for the reaction at the counter electrode, have been proposed. In this work a comparison between the salt capturing method, based on silver / silver chloride reaction, and the selective exchange method, based on ion intercalation reaction in a Prussian Blue derivative, is performed in terms of energy consumption. In particular, the energy consumption is divided in thermodynamic and kinetic contribution, and the theoretical calculations are compared with the experimental results. The experimental results show a good agreement with the theoretical calculation. The selective exchange method shows superior performances to the salt exchange in terms of purity and efficiency, however the energy consumption is higher.

An aqueous zinc-ion battery based on copper hexacyanoferrate.

A new zinc-ion battery based on copper hexacyanoferrate and zinc foil in a 20 mM solution of zinc sulfate, which is a nontoxic and noncorrosive electrolyte, at pH 6 is reported. The voltage of this novel battery system is as high as 1.73 V. The system shows cyclability, rate capability, and specific energy values near to those of lithium-ion organic batteries based on Li4 Ti5 O12 and LiFePO4 at 10 C. The effects of Zn(2+) intercalation and H2 evolution on the performance of the battery are discussed in detail. In particular, it has been observed that hydrogen evolution can cause a shift in pH near the surface of the zinc electrode, and favor the stabilization of zinc oxide, which decreases the performance of the battery. This mechanism is hindered when the surface of zinc becomes rougher.

Selectivity of a lithium-recovery process based on LiFePO4.

The demand for lithium will increase in the near future to 713,000 tonnes per year. Although lake brines contribute to 80% of the production, existing methods for purification of lithium from this source are expensive, slow, and inefficient. A novel electrochemical process with low energy consumption and the ability to increase the purity of a brine solution to close to 98% with a single-stage galvanostatic cycle is presented.

Carcinoma escamocelular de seio frontal esquerdo: abordagem interdisciplinar em cirurgia crânio-maxilo-facial

Objetivo: As neoplasias de mucosa de seios paranasais costumam ser um desafio diagnóstico por exigir alto grau de suspeição do médico e desafio terapêutico pela anatomia topográfica com estruturas nobres como o cérebro e os globos oculares. O carcinoma escamocelular como apresentação histológica nos seios paranasais costuma estar associado a neoplasias de pele que infiltram o seio da face. Este trabalho demostra caso clínico de tumor de seio frontal com invasão de base de crânio e órbita e seu tratamento cirúrgico. Método: Este é um relato de caso de tratamento interdisciplinar de carcinoma escamocelular de seio frontal clinicamente avançado. Relato de caso: J.A.S., sexo masculino, 46 anos, natural e procedente de Cruz das Almas, Bahia. Paciente atendido no Hospital Aristides Maltez, em outubro de 2007, com diagnóstico prévio, feito por biópsia endonasal, de Carcinoma Escamocelular de seio frontal. A tomografia computadorizada de crânio e face mostrou lesão envolvendo etmóide, órbita, seio frontal e íntimo contato com meninge de lobo frontal à esquerda, estadiado como T4N0M0. Ressonância magnética de crânio demostrou formação expansiva, sugerindo processo neoplásico acometendo o seio frontal à esquerda e as células etmoidais homolaterais, com sinais de extensão intracraniana, porém sem nítida definição de infiltração do parênquima cerebral. O paciente foi submetido a abordagem bicoronal como remoção completa do osso frontal, exanteração de órbita e etmóide esquerdos com remoção de dura-máter em toda extensão de lobo frontal à esquerda e reconstrução desta com enxerto de gálea aponeurótica do escalpe de pericrânio direto, em janeiro de 2008. O paciente foi submetido a radioterapia e quimioterapia pós-cirúrgica em razão da extensão da doença com boa evolução clínica sem complicações até o momento. Conclusão: Os tumores de seios da face agregam mais dificuldade cirúrgica quando avançam seja para a base do crânio, seja para o SNC...