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P2-Na0.67Ni0.33Mn0.67O2 is a promising cathode for sodium-ion batteries in large-scale energy storage applications due to their advantages of low cost, high energy density, superior sodium ion conductivity, and good air stability, whereas their structural rearrangement at high voltage above 4.2 V and the appearance of Na+/vacancy ordering result in fast capacity decay and poor rate capability, which lead to unsatisfactory performance that fails to meet practical demands. In this paper, we propose a dual-ion doping strategy coupling both cations and anions. Thanks to their collaborative effect, the optimized cathode material P2-Na0.67Ni0.33Mn0.57Ti0.1O1.95F0.05 exhibits greatly improved stability in the voltage range of 2.3–4.3 V at a high rate. Specifically, it retains 79.59% of its initial capacity after 500 cycles at 5C, in contrast to 19.91% of the undoped material. Experimental and theoretical investigations on working mechanisms illustrate that Ti4+ and F− dual-ion doping effectively suppresses the P2–O2 phase transition and facilitates sodium ion diffusion kinetics. Moreover, a P2-Na0.67Ni0.33Mn0.57Ti0.1O1.95F0.05//hard carbon full cell delivers a high reversible capacity of 122 mA h g−1 with a high energy density of 365 W h kg−1 based on the mass of the cathode material. This study provides an efficient strategy to promote the application of layered oxide cathodes in practical sodium-ion batteries. [ABSTRACT FROM AUTHOR]

We report the first example of a perovskite sulfate [Na3(H2O)]Fe(SO4)3. Further structure modulation, by dimensional reduction or ligand extension, has resulted in two related layered perovskite-like compounds Na6Fe(SO4)4 and Na12Fe3(SO4)6F8. Taken together, these results open up a more general strategy for the future design of more complex perovskite-related materials. [ABSTRACT FROM AUTHOR]

In the title compound, the oxalate ligand simultaneously bridges both Mn-centred and Na-centred octahedra to produce a unique 'doubly-interpenetrated' perovskite-like lattice with an unconventional octahedral tilt system. In turn, the coordination requirements of the oxalate ligand lead to a rare 'twisted' conformation. [ABSTRACT FROM AUTHOR]

Potassium storage systems are attracting more and more attention for large scale energy storage owing to the great abundance of potassium in the earth. The development of potassium-based devices has so far been hindered by the lack of appropriate potassium-host materials since the large radius of potassium has put forward the requirement of more rigid frameworks and larger channels for K ion migration, in comparison with lithium and sodium-based devices. In this study, we report an iron-based oxalate as a positive electrode for K-ion storage. KLi3Fe(C2O4)3@C delivered a stable capacity of 140 mA h g−1 at 120 mA g−1, and showed a 91% capacity retention after 200 cycles. By combining cyclic voltammetry analysis and synchrotron X-ray absorption spectroscopy, the K storage mechanism is demonstrated to be a combined Fe2+/Fe3+ redox reaction and pseudocapacitive process. Remarkably, it displays a stable capacity of ∼130 mA h g−1 and little attenuation over 5000 cycles at 240 mA g−1 in the lifespan test. A K-based full cell was successfully constructed via pairing this cathode with a soft carbon anode and exhibited good rate capability together with a capacity retention of ∼90% for 200 cycles, indicating its promising prospect as an environment friendly and stable K-storage cathode. [ABSTRACT FROM AUTHOR]

KLi3Fe(C2O4)3 adopts a perovskite-like structure with 1 : 3 ordering of (Li,Fe) on the B-site and (K,vacancy) on the A-site; there are no previous examples of this type of cation ordering in conventional perovskites. [ABSTRACT FROM AUTHOR]

In the title compound, the oxalate ligand simultaneously bridges both Mn-centred and Na-centred octahedra to produce a unique 'doubly-interpenetrated' perovskite-like lattice with an unconventional octahedral tilt system. In turn, the coordination requirements of the oxalate ligand lead to a rare 'twisted' conformation. [ABSTRACT FROM AUTHOR]

In the title compound, the oxalate ligand simultaneously bridges both Mn-centred and Na-centred octahedra to produce a unique 'doubly-interpenetrated' perovskite-like lattice with an unconventional octahedral tilt system. In turn, the coordination requirements of the oxalate ligand lead to a rare 'twisted' conformation.

KLi 3 Fe(C 2 O 4 ) 3 adopts a perovskite-like structure with 1 : 3 ordering of (Li,Fe) on the B-site and (K,vacancy) on the A-site; there are no previous examples of this type of cation ordering in conventional perovskites.

A very rare area negative thermal expansion phenomenon is observed in a newly discovered alkali beryllium borate LiBeBO3, which is characterized by [BeBO3]∞ double layers intraconnected by edge-sharing BeO4 tetrahedra. This unusual thermal behavior is attributed to the combined vibrational effects of the abnormal Be-O structures and Li(+) cations.

The first all-alkaline-earth beryllium borate with fluorine anions, Ca3Be6B5O16F, was synthesized by a spontaneous crystallization flux method using LiF-B2O3 as the flux. The structural framework of Ca3Be6B5O16F is composed of the inter-connected [Be6B3O16] and [BO3] fundamental building blocks, with [CaO7F] distorted polyhedra located in the interstitial sites. The [Be6B3O16] group is discovered for the first time in beryllium borates. The UV-Vis-NIR diffuse-reflectance spectrum demonstrates that its UV cutoff edge is below 200 nm, and this is confirmed by first-principles studies. Thermal analysis reveals an incongruent feature at 1321 K. IR spectroscopy measurements are consistent with the crystallographic study. These data reveal that the crystal could have an application as a deep-ultraviolet optical material.