Preparation of long-term cycling stable ni-rich concentration–gradient NCMA cathode materials for li-ion batteries

Nickel-rich (Ni > 90 %) cathodes are regarded as one of the most attractive because of their high energy density, despite their poor stability and cycle life. To improve their performance, in this study we synthesized a double concentration-gradient layered Li[Ni0.90Co0.04Mn0.03Al0.03]O2 oxide (CG-NCMA) using a continuous co-precipitation Taylor–Couette cylindrical reactor (TCCR) with a Ni-rich-core, an Mn-rich surface, and Al on top. The concentration-gradient morphology was confirmed through cross-sectional EDX line scanning. The as-synthesized sample exhibited excellent electrochemical performance at high rates (5C/10C), as well as cyclability (91.5 % after 100 cycles and 70.3 % after 500 cycles at 1C), superior to that (83.4 % and 47.6 %) of its non-concentration-gradient counterpart (UC-NCMA). The Mn-rich surface and presence of Al helped the material stay structurally robust, even after 500 cycles, while also suppressing side reactions between the electrode and electrolyte, resulting in better overall electrochemical performance. These enhancements in performance were studied using TEM, SEM, in-situ-XRD, XPS, CV, EIS and post-mortem analyses. This synthetic method enables the highly scalable production of CG-NCMA samples with two concentration-gradient structures for practical applications in Li-ion batteries

Fluorescence of functionalized graphene quantum dots prepared from infrared-assisted pyrolysis of citric acid and urea

Abstract(#br)This paper reports an efficient fabrication of N-doped graphene quantum dots (GQDs) showing controllable chemical and fluorescence (FL) properties through infrared carbonization (IRC) of citric acid and urea. The GQDs prefer to form an equilibrium shapes of circle with an average particle size ranged from 5 to 10 nm. The N/C atomic ratio in GQDs can be precisely tailored in a range from 21.6 to 49.6 at.% by simply controlling the weight ratio of citric acid to urea. With increasing the urea content, the GQDs not only contain N-doped graphene but also incorporate with crystalline cyanuric acid, forming a binary crystallinity. The quantum yield of 22.2% is achieved by N-doped GQDs, prepared from the IRC synthesis of chemical precursor at the citric acid/urea at 3:1. Excessive N and cyanuric acid can lead to FL quenching, red shift and wide spectral distribution. The design of GQDs possesses a multiple chromophoric band-gap structure, originated from the presence of cyanuric acid, defect-related emissive traps, and functional group distributions. This work offers an effective and inspiring approach to engineering both chemical compositions and unique crystalline structures of GQDs, and will therefore facilitate their fundamental research and applications to optical, sensing, energy and biological fields

ZIF-8-Based Quasi-Solid-State Electrolyte for Lithium Batteries.

The quasi-solid-state electrolytes (QSSEs) with an inorganic skeleton, a solid-liquid composite material combining their respective merits, exhibit high ionic conductivity and mechanical strength. However, most quasi-solid electrolytes prepared by immobilizing ionic liquid (IL) or organic liquid electrolyte in inorganic scaffold generally have poor interface compatibility and low lithium ion migration number, which limits its application. Herein, we design and prepare a ZIF-8-based QSSE (ZIF-8 QSSE) in which the ZIF-8 has a special cage structure and interaction with the guest electrolyte to form a composite electrolyte with good ionic conductivity about 1.05 × 10-4 S cm-1 and a higher lithium-ion transference number of about 0.52. With the ZIF-8 QSSE, a protype lithium battery coupled with LiCoO2 cathode shows good electrochemical performances with an initial discharge capacity of 135 mAh g-1 at 50 mA g-1 and a remaining capacity of 119 mAh g-1 after 100 cycles, only 0.119% capacity degradation per cycle. It is worth noting that the ZIF-8-based QSSEs have good thermal stability up to 350 °C that does not show thermal runaway, which is significantly higher than that of a conventional organic liquid battery system

Recent Configurational Advances for Solid-State Lithium Batteries Featuring Conversion-Type Cathodes

Solid-state lithium metal batteries offer superior energy density, longer lifespan, and enhanced safety compared to traditional liquid-electrolyte batteries. Their development has the potential to revolutionize battery technology, including the creation of electric vehicles with extended ranges and smaller more efficient portable devices. The employment of metallic lithium as the negative electrode allows the use of Li-free positive electrode materials, expanding the range of cathode choices and increasing the diversity of solid-state battery design options. In this review, we present recent developments in the configuration of solid-state lithium batteries with conversion-type cathodes, which cannot be paired with conventional graphite or advanced silicon anodes due to the lack of active lithium. Recent advancements in electrode and cell configuration have resulted in significant improvements in solid-state batteries with chalcogen, chalcogenide, and halide cathodes, including improved energy density, better rate capability, longer cycle life, and other notable benefits. To fully leverage the benefits of lithium metal anodes in solid-state batteries, high-capacity conversion-type cathodes are necessary. While challenges remain in optimizing the interface between solid-state electrolytes and conversion-type cathodes, this area of research presents significant opportunities for the development of improved battery systems and will require continued efforts to overcome these challenges

Ionic Liquid-Modified Copper Phosphate Electrodes for the Detection of α-Amino Acids in a Weakly Alkaline Solution

The effect of ionic liquid (IL) coating on the electrochemical properties of preoxidized Cu3(PO4)2 (ox-Cu3(PO4)2) electrodes was explored in pH-varied Na2HPO4 solutions. The IL of N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMPyTFSI) was found to stabilize the redox properties of ox-Cu3(PO4)2 electrodes in weakly acid and alkaline solutions. Furthermore, the amperometric response of the PMPy-TFSI/ox-Cu3(PO4)2 electrodes presented good linearity in the range of 91–500 μM for most α-amino acids (AAs). The PMPy-TFSI/ox-Cu3(PO4)2 electrodes are equipped with a high performance liquid chromatography system to perform the good selectively and specific detection of AAs. The PMPy-TFSI coating shows promise for the wider application of ox-Cu3(PO4)2 electrodes in acidic and alkaline solutions for the detection of electroactive and nonelectroacitve AAs. © 2016 The Electrochemical Society. [DOI: 10.1149/2.1381614jes] All rights reserved

Physicochemical and electrochemical properties of the (fluorosulfonyl) (trifluoromethylsulfonyl)amide ionic liquid for Na secondary batteries

In this study, thermal, physical, and electrochemical properties of the ionic liquid electrolyte system, Na[FTA]-[C(3)C(1)pyrr][FTA], (FTA(-) = (fluorosulfonyl) (trifluoromethylsulfonyl)amide and C(3)C(1)pyrr(+) = N-methyl-N-pro-pylpyrrolidinium) have been investigated for Na secondary batteries. The asymmetric FTA. structure provides a wide liquid-phase temperature range, especially at low x(Na[FTA]) (x(Na[FTA]) = molar fraction of Na[FTA]) and low temperature range. Glass transition at 170-209 K is the only observed thermal behavior in the x(Na [FTA]) of 0.0-0.4. Temperature dependence of viscosity and ionic conductivity obeys the Vogel-Tammann-Fulcher equation, and the correlation between molar conductivity and viscosity follows the fractional Walden rule. The anodic potential limits are above 5 V vs. Na+/Na at 298 and 363 K. The noticeable effects of x(Na [FTA]) are observed in the electrochemical performance of Na metal and hard carbon electrodes. In both cases, a moderate concentration, x(Na[FTA]) of 0.2-0.3, enables favorable charge-discharge behavior. At 363 K, the discharge capacities of the hard carbon electrode at x(Na[FTA]) of 0.3 are 260 and 236 mAh g(-1) at the current densities of 20 and 200 mA g(-1), respectively. The optimum cycling performance occurs at x(Na[FTA]) = 0.3, providing satisfactory capacity retention and high average Coulombic efficiency

Copolymers Based on Indole-6-Carboxylic Acid and 3,4-Ethylenedioxythiophene as Platinum Catalyst Support for Methanol Oxidation

Indole-6-carboxylic acid (ICA) and 3,4-ethylenedioxythiophene (EDOT) are copolymerized electrochemically on a stainless steel (SS) electrode to obtain poly(indole-6-carboxylic acid-co-3,4-ethylenedioxythiophene)s (P(ICA-co-EDOT))s. The morphology of P(ICA-co-EDOT)s is checked using scanning electron microscopy (SEM), and the SEM images reveal that these films are composed of highly porous fibers when the feed molar ratio of ICA/EDOT is greater than 3/2. Platinum particles can be electrochemically deposited into the P(ICA-co-EDOT)s and PICA films to obtain P(ICA-co-EDOT)s-Pt and PICA-Pt composite electrodes, respectively. These composite electrodes are further characterized using X-ray photoelectron spectroscopy (XPS), SEM, X-ray diffraction analysis (XRD), and cyclic voltammetry (CV). The SEM result indicates that Pt particles disperse more uniformly into the highly porous P(ICA3-co-EDOT2) fibers (feed molar ratio of ICA/EDOT = 3/2). The P(ICA3-co-EDOT2)-Pt nanocomposite electrode exhibited excellent catalytic activity for the electrooxidation of methanol in these electrodes, which reveals that P(ICA3-co-EDOT2)-Pt nanocomposite electrodes are more promising for application in an electrocatalyst as a support material

Improvement of the Electrochemical Characteristics of Lithium and Manganese Rich Layered Cathode Materials: Effect of Surface Coating

Surface coating with electrochemically inert materials are found to be fruitful to improve the cycleability and rate capability characteristics of lithium and manganese rich composite cathode materials. In order to understand the structure-property relation between the nature of coating and the electrochemical performance, surface modification of composite cathodes was carried out either by a thin layer of carbon or zirconia particles. Zirconia coating helps to sustain 86% capacity retention after 50 cycles as compared to bare composite which exhibits 68% capacity retention when cycled at 10 mAg(-1). Among 1 wt%, 2.5 wt% and 5 wt% zirconia coated cathode materials, 2.5 wt% zirconia coating exhibits best rate capability. We have demonstrated that the porous particulate ZrO2 coating improved the capacity retention of the composite cathodes by suppressing the impedance growth at the electrodes-electrolyte interface. (C) 2015 The Electrochemical Society