Investigation of Mn and Fe Substitution Effects on the Characteristics of High-Voltage LiCo1–xMxPO4 (x=0.1, 0.4) Cathodes Prepared by Sol–gel Route

Herein, we provide a fundamental study revealing the substantial changes promoted by manganese and iron substitution for cobalt in a high-voltage LiCoPO4 olivine cathode. Therefore, LiCoPO4, LiCo0.9Fe0.1PO4, LiCo0.6Fe0.4PO4, LiCo0.9Mn0.1PO4, and LiCo0.6Mn0.4PO4 are synthesized by a sol–gel pathway and comparatively investigated in terms of structure, morphology, and electrochemical features in lithium battery. Besides the observed effects on structure, particle size, and metals distribution, the work reveals a gradually enhancing electrode reaction by increasing the Fe content in LiCo0.9Fe0.1PO4 and LiCo0.6Fe0.4PO4, with Co3+/Co2+ and Fe3+/Fe2+ signatures at 4.8 and 3.5 V vs Li+/Li, respectively. On the other hand, the introduction of Mn leads to a progressive electrode deactivation in LiCo0.9Mn0.1PO4 and LiCo0.6Mn0.4PO4 due to an intrinsic hindering of the Mn3+/Mn2+ process at 4.1 V vs Li+/Li. The reasons accounting for such an intriguing behavior are investigated in detail using electrochemical impedance spectroscopy within the potential range of the redox processes. The study reveals that manganese and iron substitutions in the high-voltage olivine have opposite effects on the charge transfer resistance, i.e., detrimental for the former while beneficial for the latter, with remarkable enhancement of the reversible capacity, the Coulombic efficiency, and the cycle life. Such results provide to the scientific community useful information on possible strategies to enhance the emerging LiCoPO4 high-voltage electrode by transition metal substitution

Making Free Trade Fair

Philosophers have done very little work on what makes trade fair. Perhaps the most extensive discussion is Malgorzata Kurjanska and Mathias Risse’s article, “Fairness in Trade II: export subsidies and the fair trade movement.”2 In their article, Kurjanska and Risse consider the case for trade subsidies and the Fair Trade movement. They suggest that it is not permissible for developed countries to give their producers subsidies because doing so does not strike an appropriate balance between meeting the needs of the global poor and protecting domestic workers (Kurjanska and Risse, 2008: 34). Kurjanska and Risse also argue that the case for Fair Trade hinges, primarily, on whether or not it is part of the best development strategy for poor countries. They do not think Fair Trade is part of the best development strategy and, so, they believe purchasing Fair Trade certified goods is only acceptable because doing so does not constitute a large share of the market in traded goods. This chapter argues that the case against subsidies and Fair Trade Kurjanska and Risse present is much weaker than they make out. To the contrary, it argues that giving some subsidies and purchasing some Fair Trade certified goods may even be necessary to make trade fair. Section 11.2 starts by saying a few words about the normative framework Kurjanska and Risse adopt

Degradation of Layered Oxide Cathode in a Sodium Battery: A Detailed Investigation by X-Ray Tomography at the Nanoscale

The degradation mechanism in a sodium cell of a layered Na0.48Al0.03Co0.18Ni0.18Mn0.47O2 (NCAM) cathode with P3/P2 structure is investigated by revealing the changes in microstructure and composition upon cycling. The work aims to rationalize the gradual performance decay and the alteration of the electrochemical response in terms of polarization, voltage signature, and capacity loss. Spatial reconstructions of the electrode by X-ray computed tomography at the nanoscale supported by quantitative and qualitative analyses show fractures and deformations in the cycled layered metal-oxide particles, as well as inorganic side compounds deposited on the material. These irreversible morphological modifications reflect structural heterogeneities across the cathode particles due to formation of various domains with different Na+ intercalation degrees. Besides, X-ray photoelectron spectroscopy data suggest that the latter inorganic species in the cycled electrode are mainly composed of NaF, Na2O, and NaCO3 formed by parasitic electrolyte decomposition. The precipitation of these insulating compounds at the electrode/electrolyte interphase and the related structural stresses induced in the material lead to a decrease in cathode particle size and partial loss of electrochemical activity. The retention of the NCAM phase after cycling suggests that electrolyte upgrade may improve the performance of the cathode to achieve practical application for sustainable energy storage

Analysis of Bidirectional Associative Memory using SCSNA and Statistical Neurodynamics

Bidirectional associative memory (BAM) is a kind of an artificial neural network used to memorize and retrieve heterogeneous pattern pairs. Many efforts have been made to improve BAM from the the viewpoint of computer application, and few theoretical studies have been done. We investigated the theoretical characteristics of BAM using a framework of statistical-mechanical analysis. To investigate the equilibrium state of BAM, we applied self-consistent signal to noise analysis (SCSNA) and obtained a macroscopic parameter equations and relative capacity. Moreover, to investigate not only the equilibrium state but also the retrieval process of reaching the equilibrium state, we applied statistical neurodynamics to the update rule of BAM and obtained evolution equations for the macroscopic parameters. These evolution equations are consistent with the results of SCSNA in the equilibrium state.Comment: 13 pages, 4 figure

The role of synthesis pathway on the microstructural characteristics of sulfur-carbon composites: X-ray imaging and electrochemistry in lithium battery

Two synthesis pathways are adopted to tune the microstructural characteristics of sulfur-carbon (S-C) composites for application in lithium-sulfur (Li-S) batteries. Both methods include intimate mixing of either carbon black or multiwalled carbon nanotubes with elemental sulfur, molten according to the first approach while dispersed in alcohol and heated according to the second one. Nano- and micro-scale X-ray computed tomography supported by X-ray diffraction and electron microscopy shows materials consisting of crystalline sulfur clusters (70 wt%) with size ranging from about 5 to 50 μm, surrounded by carbon. The sulfur cluster size appears limited by direct mixing of molten sulfur and carbons, in particular when carbon black is employed, whilst it is increased by exploiting the alcohol dispersion. Electrochemistry reveals that small sulfur particles lead to an improved rate capability in Li-S cells, whereas large active material domains may favor the capacity retention. The composites using carbon black nanoparticles exhibit the highest reversible capacity, with a maximum value exceeding 1500 mAh gS−1, whereas the composites involving multiwalled carbon nanotubes show the best capacity retention, with values approaching 70% over 150 cycles. Our multi-disciplinary approach will shed light on significant aspects aiming to enhance the Li-S battery and favor a practical application

Electrochemical features of LiMnPO₄ olivine prepared by sol-gel pathway

LiMnPO₄ is a potential cathode for lithium-ion battery of high thermal stability, low cost, environmental sustainability and high theoretical energy density. However, this intriguing olivine material suffers from intrinsic sluggish kinetics of lithium (de-)insertion, which limits the reversible reaction in practical lithium cells. Herein we report a careful study of the impedance features of LiMnPO₄ during electrochemical reaction in lithium cell. The LiMnPO₄ material is prepared by sol-gel method and fully characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The material shows suitable galvanostatic cycling with a working voltage of about 4.1 V, which is higher than the 3.5 V value expected from the most common olivine material, i.e., LiFePO₄. Hence, electrochemical impedance spectroscopy (EIS) is used to study the lithium (de-)insertion within the LiMnPO₄ structure. The results indicate an impedance behavior depending on the state of charge and a lithium diffusion coefficient trend slightly decreasing during cell operation within the 10⁻¹⁴ – 10⁻¹³ cm² s⁻¹ range. The electrochemical study in lithium cell reveals remarkable enhancement of the electrode kinetics at 70 °C, which suggests preferred application of LiMnPO₄ materials at the higher temperatures

Current status and future perspectives of lithium metal batteries

With the lithium-ion technology approaching its intrinsic limit with graphite-based anodes, Li metal is recently receiving renewed interest from the battery community as potential high capacity anode for next-generation rechargeable batteries. In this focus paper, we review the main advances in this field since the first attempts in the mid-1970s. Strategies for enabling reversible cycling and avoiding dendrite growth are thoroughly discussed, including specific applications in all-solid-state (inorganic and polymeric), Lithium–Sulfur (Li–S) and Lithium-O2 (air) batteries. A particular attention is paid to recent developments of these battery technologies and their current state with respect to the 2030 targets of the EU Integrated Strategic Energy Technology Plan (SET-Plan) Action 7