Fabrication of High-Energy Li-Ion Cells with Li4 Ti5 O12 Microspheres as Anode and 0.5 Li2 MnO3 ⋅0.5 LiNi0.4 Co0.2 Mn0.4 O2 Microspheres as Cathode

Important Impact of the Slurry Mixing Speed on Water-Processed Li4Ti5O12 Lithium-Ion Anodes in the Presence of H3PO4 as the Processing Additive

The aqueous processing of lithium transition metal oxides into battery electrodes is attracting a lot of attention as it would allow for avoiding the use of harmful N-methyl-2-pyrrolidone (NMP) from the cell fabrication process and, thus, render it more sustainable. The addition of slurry additives, for instance phosphoric acid (PA), has been proven to be highly effective for overcoming the corresponding challenges such as aluminum current collector corrosion and stabilization of the active material particle. Herein, a comprehensive investigation of the effect of the ball-milling speed on the effectiveness of PA as a slurry additive is reported using Li₄Ti₅O₁₂ (LTO) as an exemplary lithium transition metal oxide. Interestingly, at elevated ball-milling speeds, rod-shaped lithium phosphate particles are formed, which remain absent at lower ball-milling speeds. A detailed surface characterization by means of SEM, EDX, HRTEM, STEM-EDX, XPS, and EIS revealed that in the latter case, a thin protective phosphate layer is formed on the LTO particles, leading to an improved electrochemical performance. As a result, the corresponding lithium-ion cells comprising LTO anodes and LiNi_0.5Mn_0.3Co_0.2O₂ (NMC₅₃₂) cathodes reveal greater long-term cycling stability and higher capacity retention after more than 800 cycles. This superior performance originates from the less resistive electrode-electrolyte interphase evolving upon cycling, owing to the interface-stabilizing effect of the lithium phosphate coating formed during electrode preparation. The results highlight the importance of commonly neglected─frequently not even reported─electrode preparation parameters.

Insights into interfacial chemistry of Ni-rich cathodes and sulphide-based electrolytes in all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs) have attracted increasing attention recently because they are more safe and have higher energy densities than conventional lithium-ion batteries. In particular, ASSLBs composed of Ni-rich cathodes, sulphide-based solid-state electrolytes (SSEs) and lithium metal anodes have been regarded as the most competitive candidates. Ni-rich cathodes possess high operating potential, high specific energy and low cost, and sulphide-based SSEs have excellent ionic conductivity comparable to that of liquid electrolytes. However, severe parasitic reactions and chemo-mechanical issues hinder their practical application. Herein, the structure, ionic conductivity, chemical or electrochemical stability and mechanical property of sulphide-based SSEs are introduced. Critical interfacial problems between Ni-rich cathodes and sulphide-based SSEs, including chemical or electrochemical parasitic reactions, space charge layer effect, mechanical stress and contact loss, are summarised. The corresponding solutions including coating layer construction and structure design are expounded. Finally, the remaining challenges are discussed, and perspectives are outlined to provide guidelines for the future development of ASSLBs.

Spray-Drying of Electrode Materials for Lithium- and Sodium-Ion Batteries

The performance of electrode materials in lithium-ion (Li-ion), sodium-ion (Na-ion) and related batteries depends not only on their chemical composition but also on their microstructure. The choice of a synthesis method is therefore of paramount importance. Amongst the wide variety of synthesis or shaping routes reported for an ever-increasing panel of compositions, spray-drying stands out as a versatile tool offering demonstrated potential for up-scaling to industrial quantities. In this review, we provide an overview of the rapidly increasing literature including both spray-drying of solutions and spray-drying of suspensions. We focus, in particular, on the chemical aspects of the formulation of the solution/suspension to be spray-dried. We also consider the post-processing of the spray-dried precursors and the resulting morphologies of granules. The review references more than 300 publications in tables where entries are listed based on final compound composition, starting materials, sources of carbon etc.

Li4 Ti5 O12 Anode: Structural Design from Material to Electrode and the Construction of Energy Storage Devices

Spinel Li₄ Ti₅ O₁₂ , known as a zero-strain material, is capable to be a competent anode material for promising applications in state-of-art electrochemical energy storage devices (EESDs). Compared with commercial graphite, spinel Li₄ Ti₅ O₁₂ offers a high operating potential of ∼1.55 V vs Li/Li⁺ , negligible volume expansion during Li⁺ intercalation process and excellent thermal stability, leading to high safety and favorable cyclability. Despite the merits of Li₄ Ti₅ O₁₂ been presented, there still remains the issue of Li₄ Ti₅ O₁₂ suffering from poor electronic conductivity, manifesting disadvantageous rate performance. Typically, a material modification process of Li₄ Ti₅ O₁₂ will be proposed to overcome such an issue. However, the previous reports have made few investigations and achievements to analyze the subsequent processes after a material modification process. In this review, we attempt to put considerable interest in complete device design and assembly process with its material structure design (or modification process), electrode structure design and device construction design. Moreover, we have systematically concluded a series of representative design schemes, which can be divided into three major categories involving: (1) nanostructures design, conductive material coating process and doping process on material level; (2) self-supporting or flexible electrode structure design on electrode level; (3) rational assembling of lithium ion full cell or lithium ion capacitor on device level. We believe that these rational designs can give an advanced performance for Li₄ Ti₅ O₁₂ -based energy storage device and deliver a deep inspiration.

Free-Standing Sandwich-Structured Flexible Film Electrode Composed of Na2Ti3O7 Nanowires@CNT and Reduced Graphene Oxide for Advanced Sodium-Ion Batteries

A free-standing flexible anode material for sodium storage with sandwich-structured characteristics was fabricated by modified vacuum filtration, consisting of stacked layers of Na₂Ti₃O₇ nanowires@carbon nanotubes (NTO NW@CNT) and graphene oxide. The NTO NWs have a larger specific surface area for Na⁺ insertion/extraction with shortened ion diffusion pathways, accelerating the charge transfer/collection kinetics. The added CNTs both facilitate the uniform dispersion of the nanowires and nanotubes and also contribute to the connectivity of the nanowires, improving their conductivity. More importantly, the unique sandwichlike layered-structured film not only provides large numbers of electron-transfer channels and promotes the reaction kinetics during the charging and discharging process but also ensures the structural stability of the NTO NWs and the electrode. Electrochemical measurements suggest that this rationally designed structure endows the electrode with a high specific capacity and excellent cycling performance. A satisfactory reversible capacity as high as 92.5 mA h g^-1 was achieved after 100 cycles at 2C; subsequently, the electrode also delivered 59.9 mA h g^-1 after a further 100 cycles at 5C. Furthermore, after the rate performance test, the electrode could be continuously cycled for 100 cycles at a current density of 0.2C, which demonstrated that durable cyclic capacity with a high reversible capacity of 114.1 mA h g^-1 was retained. This novel and low-cost fabrication procedure is readily scalable and provides a promising avenue for potential industrial applications.

Identification of Host Micro RNAs That Differentiate HIV-1 and HIV-2 Infection Using Genome Expression Profiling Techniques

While human immunodeficiency virus type 1 and 2 (HIV-1 and HIV-2) share many similar traits, major differences in pathogenesis and clinical outcomes exist between the two viruses. The differential expression of host factors like microRNAs (miRNAs) in response to HIV-1 and HIV-2 infections are thought to influence the clinical outcomes presented by the two viruses. MicroRNAs are small non-coding RNA molecules which function in transcriptional and post-transcriptional regulation of gene expression. MiRNAs play a critical role in many key biological processes and could serve as putative biomarker(s) for infection. Identification of miRNAs that modulate viral life cycle, disease progression, and cellular responses to infection with HIV-1 and HIV-2 could reveal important insights into viral pathogenesis and provide new tools that could serve as prognostic markers and targets for therapeutic intervention. The aim of this study was to elucidate the differential expression profiles of host miRNAs in cells infected with HIV-1 and HIV-2 in order to identify potential differences in virus-host interactions between HIV-1 and HIV-2. Differential expression of host miRNA expression profiles was analyzed using the miRNA profiling polymerase chain reaction (PCR) arrays. Differentially expressed miRNAs were identified and their putative functional targets identified. The results indicate that hsa-miR 541-3p, hsa-miR 518f-3p, and hsa-miR 195-3p were consistently up-regulated only in HIV-1 infected cells. The expression of hsa-miR 1225-5p, hsa-miR 18a* and hsa-miR 335 were down modulated in HIV-1 and HIV-2 infected cells. Putative functional targets of these miRNAs include genes involved in signal transduction, metabolism, development and cell death.