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Raman spectroscopy together with density functional calculations were used to study lattice dynamics in a layered honeycomb cobaltite Na3Co2SbO6, which can host a field-induced phase related with the Kitaev physics. We show that there develops an additional mode well above Neel temperature (at K) at 525 cm–1, which origin can be related to electronic excitation to one of doublets. Moreover, our theoretical calculations demonstrate that the highest frequency intensive mode related to the oxygen vibrations is very sensitive to type of the magnetic order. Thus, we propose to use the softening of this mode as a hallmark of the transition to a fully polarized regime, which is stabilized in Kitaev materials in strong magnetic fields. [ABSTRACT FROM AUTHOR]

Raman spectroscopy together with density functional calculations were used to study lattice dynamics in a layered honeycomb cobaltite Na3Co2SbO6, which can host a field-induced phase related with the Kitaev physics. We show that there develops an additional mode well above Neel temperature (at K) at 525 cm–1, which origin can be related to electronic excitation to one of doublets. Moreover, our theoretical calculations demonstrate that the highest frequency intensive mode related to the oxygen vibrations is very sensitive to type of the magnetic order. Thus, we propose to use the softening of this mode as a hallmark of the transition to a fully polarized regime, which is stabilized in Kitaev materials in strong magnetic fields. [ABSTRACT FROM AUTHOR]

A highly viable alternative to lithium-ion batteries for stationary electrochemical energy-storage systems is the potassium dual-ion hybrid capacitor (PIHC), especially toward fast-charging capability. However, the sluggish reaction kinetics of negative electrode materials seriously impedes their practical implementation. In this paper, a new negative electrode Bi@RPC (Nano-bismuth confined in nitrogen- and oxygen-doped carbon with rationally designed pores, evidenced by advanced characterization) is developed, leading to a remarkable electrochemical performance. PIHCs building with the active carbon YP50F positive electrode result in a high operation voltage (0.1-4 V), and remarkably well-retained energy density at a high-power density (11107 W kg -1 at 98 Wh kg -1 ). After 5000 cycles the proposed PHICs still show a superior capacity retention of 92.6%. Moreover, a reversible mechanism of "absorption-alloying" of the Bi@RPC nanocomposite is revealed by operando synchrotron X-ray diffraction and Raman spectroscopy. With the synergistic potassium ions storage mechanism arising from the presence of well-structured pores and nano-sized bismuth, the Bi@RPC electrode exhibits an astonishingly rapid kinetics and high energy density. The results demonstrate that PIHCs with Bi@RPC-based negative electrode is the promising option for simultaneously high-capacity and fast-charging energy storage devices., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Cellulose microspheres have a wide range of applications due to their unique properties and versatility. Various preparation methods have been explored to tailor these microspheres for specific applications. Among these methods, the acetate method using cellulose acetate is well known. However, replacement of the acetate group through the butyrate group significantly extends the variety of morphological properties. In the present work, microspheres based on cellulose acetate butyrate are being developed with modified characteristics in terms of particle size, porosity, surface morphology and the inner structure of the microspheres. While the inner structure of cellulose acetate microspheres is predominantly porous, microspheres prepared from cellulose acetate butyrate are mainly filled or contain several smaller microspheres. Carbon materials from cellulose acetate butyrate microspheres exhibit a high specific surface area of 567 m 2 g -1 , even without further activation. Activation processes can further increase the specific surface area, accompanied by an adaptation of the pore structure. The prepared carbons show promising results in symmetrical supercapacitors with aqueous 6 M KOH electrolytes. Activated carbons derived from cellulose acetate butyrate microspheres demonstrate an energy density of 12 Wh kg -1 at a power density of 0.9 kW kg -1 .

Rechargeable aqueous zinc batteries are potential candidates for sustainable energy storage systems at a grid scale, owing to their high safety and low cost. However, the existing cathode chemistries exhibit restricted energy density, which hinders their extensive applications. Here, a tellurium redox-amphoteric conversion cathode chemistry is presented for aqueous zinc batteries, which delivers a specific capacity of 1223.9 mAh g Te -1 and a high energy density of 1028.0 Wh kg Te -1 . A highly concentrated electrolyte (30 mol kg -1 ZnCl 2 ) is revealed crucial for initiating the Te redox-amphoteric conversion as it suppresses the H 2 O reactivity and inhibits undesirable hydrolysis of the Te 4+ product. By carrying out multiple operando/ex situ characterizations, the reversible six-electron Te 2- /Te 0 /Te 4+ conversion with TeCl 4 is identified as the fully charged product and ZnTe as the fully discharged product. This finding not only enriches the conversion-type battery chemistries but also establishes a critical step in exploring redox-amphoteric materials for aqueous zinc batteries and beyond., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Biomass-based materials have emerged as a promising alternative to the conventional graphite anode in Li-ion batteries due to their renewability, low cost, and environmental friendliness. Therefore, a facile synthesis method for porous hard carbons based on cellulose acetate microspheres and bead cellulose is used, and their application as anode materials in Li-ion batteries is discussed. The resulting porous carbons exhibit promising electrochemical characteristics, including a reversible capacity of about 300 mAh g -1 at 0.1 C (37 mA g -1 ) after 50 cycles, and stable capacities up to 210 mAh g -1 over 1000 cycles at 1 C (372 mA g -1 ) in half-cells for cellulose acetate microspheres carbonised at 1200 °C. Moreover, at 60 °C cellulose-derived carbons show higher specific capacities than graphite (300 mAh g -1 vs 240 mAh g -1 at 1 C after 500 cycles), indicating their potential for use in high-temperature applications. The different charge storage mechanisms of the prepared hard carbon materials and graphite are observed. While capacity of graphite is mainly controlled by the Faradaic redox process, the cellulose-derived carbons combine Faradaic intercalation and capacitive charge adsorption., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)