ABSTRACT
A carbonophosphate compound of Li2.72Na0.31MnPO4CO3 was synthesized via ion exchange. The initial discharge capacity of Li2.72Na0.31MnPO4CO3 in 15 molal (or 15 m) LiTFSI was 110 mA h g-1 at 2 mA cm-2 (â¼0.5C). Due to the decomposition of Li2.72Na0.31MnPO4CO3, the capacity retention degraded to 64% after 100 cycles.
ABSTRACT
Correction for 'Local structure of a highly concentrated NaClO4 aqueous solution-type electrolyte for sodium ion batteries' by Ryo Sakamoto et al., Phys. Chem. Chem. Phys., 2020, 22, 26452-26458, DOI: 10.1039/D0CP04376A.
ABSTRACT
Aqueous Na-ion batteries with highly concentrated NaClO4 aq. electrolytes are drawing attention as candidates for large-scale rechargeable batteries with a high safety level. However, the detailed mechanism by which the potential window in 17 m NaClO4 aq. electrolyte was expanded remains unclear. Therefore, we investigated the local structure around a Na+ ion or a ClO4- ion using X-ray diffraction combined with empirical potential structure refinement (EPSR) modelling and Raman spectroscopy. The results showed that in 17 m NaClO4 aq. electrolyte, most of the water molecules were coordinated to Na+ ions and few free water molecules were present. The 17 m NaClO4 aq. electrolyte could be interpreted as widening the potential window because almost all water molecules participated in hydration of the Na+ ions.
ABSTRACT
The carbonophosphate Na3FePO4CO3 was synthesized by the mechanical ball milling method for the first time. The composition of the obtained sample with a higher amount of Fe2+ was Na2.66Fe2+0.66Fe3+0.34PO4CO3 as confirmed by Mössbauer analysis, owing to the good airtight properties of this method. The obtained samples in an organic electrolyte delivered an initial discharge capacity of 124 mAh/g at room temperature, and a larger discharge capacity of 159 mAh/g (1.66 Na+/mole) at 60 °C. With 17 m NaClO4 aqueous electrolyte, a discharge capacity of 161 mAh/g (1.69 Na+/mole) was delivered because of the high ionic conductivity of the concentrated aqueous electrolyte. During the charge-discharge process, the formation of Fe4+ after charging up to 4.5 V and the return of Fe2+ after discharging down to 1.5 V were detected by ex-situ X-ray absorption near edge structure (XANES) analysis.
ABSTRACT
We study the Na-ion battery characteristics of SnS as a negative electrode by first-principles calculations. From energy analyses, we clarify the discharge reaction process of the Na/SnS half-cell system. We show a phase diagram of Na-Sn-S ternary systems by constructing convex-hull curves, and show a possible reaction route considering intermediate products in discharge reactions. Voltage-capacity curves are calculated based on the Na-SnS reaction path that is obtained from the ternary phase diagram. It is found that the conversion reactions and subsequently the alloying reactions proceed in the SnS electrode, contributing to its high capacity compared with the metallic Sn electrode, in which only the alloying reactions progresses stepwise. To verify the calculated reaction process, x-ray absorption spectra (XAS) are calculated and compared with experimental XAS at S K-edge, showing meaningful XAS changes associated with Na2 S and SnS in discharged and charged states, respectively.
ABSTRACT
Sodium ion batteries meet the demand for large-scale energy storage, such as in electric vehicles, due to the material abundance of sodium. In this report, nanotube-type Na2V3O7 is proposed as a cathode material because of its fast sodium diffusivity, an important requirement for sodium ion batteries, through the investigation of ~4300 candidates via a high-throughput computation. High-rate performance was confirmed, showing ~65% capacity retention at a current density of 10C at room temperature, despite the large particle size of >5 µm. A good cycle performance of ca. 94% in capacity retention after 50 cycles was obtained owing to a small volumetric change of <0.4%.
ABSTRACT
We report a battery made from a single material using Li1.5Cr0.5Ti1.5(PO4)3 as the anode, cathode and electrolyte. A high rate capability at room temperature and very low-temperature operation (233 K) were possible as a result of the superior ionic conductivity and low interfacial resistance obtained from the single-phase cell design.
