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Lattice-oxygen redox (l-OR) has become an essential companion to the traditional transition-metal (TM) redox charge compensation to achieve high capacity in Li-rich cathode oxides. However, the understanding of l-OR chemistry remains elusive, and a critical question is the structural effect on the stability of l-OR reactions. Herein, the coupling between l-OR and structure dimensionality is studied. We reveal that the evolution of the oxygen-lattice structure upon l-OR in Li-rich TM oxides which have a three-dimensional (3D)-disordered cation framework is relatively stable, which is in direct contrast to the clearly distorted oxygen-lattice framework in Li-rich oxides which have a two-dimensional (2D)/3D-ordered cation structure. Our results highlight the role of structure dimensionality in stabilizing the oxygen lattice in reversible l-OR, which broadens the horizon for designing high-energy-density Li-rich cathode oxides with stable l-OR chemistry.

Li‐rich cation‐disordered rock‐salt (DRX) materials have emerged as promising candidates for high‐capacity oxide cathodes. Their fluorinated variants have shown improved cycling stability with effectively suppressed oxygen loss. However, a comprehensive understanding of how fluorination impacts the multiscale structure and lithium transportation in DRX remains elusive in experiments. Herein, the neutron total scattering technique in conjunction with the advanced reverse Monte Carlo (RMC) fitting method is employed to characterize the intricate structure of Li1.16Ti0.37Ni0.37Nb0.1O2 (LTNNO) and the fluorinated Li1.2Ti0.35Ni0.35Nb0.1O1.8F0.2 (LTNNOF). Through rigorous statistical analysis, the multiscale structural evolution upon fluorination is quantified from atomic (≤5 Å) to long‐range scale (≈100 Å). The local Li‐rich environments around F induce a modest 2.4% increment in the number of fast Li 0TM (transition metal) channels. Crucially, at a broader scale, the proportion of 0TM channels participating in percolation increases significantly from 2.9% in LTNNO to 8.7% in LTNNOF. Fluorination improves the capacity release mainly through merging isolated fast Li channels into the percolation network. This work experimentally unravels the multiscale mechanism of fluorination‐induced performance improvement in DRX materials and highlights the necessity of adopting an advanced RMC fitting method to obtain a full view of the complex structural features in developing high‐capacity DRX cathodes. [ABSTRACT FROM AUTHOR]

Abstract: Sodium ion batteries have attracted much attention in recent years, due to the higher abundance and lower cost of sodium, as an alternative to lithium ion batteries. However, a major challenge is their lower energy density. In this work, we report a novel multi‐electron cathode material, KVOPO4, for sodium ion batteries. Due to the unique polyhedral framework, the V3+ ↔ V4+ ↔ V5+ redox couple was for the first time fully activated by sodium ions in a vanadyl phosphate phase. The KVOPO4 based cathode delivered reversible multiple sodium (i.e. maximum 1.66 Na+ per formula unit) storage capability, which leads to a high specific capacity of 235 Ah kg−1. Combining an average voltage of 2.56 V vs. Na/Na+, a high practical energy density of over 600 Wh kg−1 was achieved, the highest yet reported for any sodium cathode material. The cathode exhibits a very small volume change upon cycling (1.4% for 0.64 sodium and 8.0% for 1.66 sodium ions). Density functional theory (DFT) calculations indicate that the KVOPO4 framework is a 3D ionic conductor with a reasonably, low Na+ migration energy barrier of ≈450 meV, in line with the good rate capability obtained. [ABSTRACT FROM AUTHOR]

The new title compound is synthesized by decomposition (350 °C, 6 h) of a gel obtained from an aqueous mixture of MoO3, NH4H2PO4, Li2CO3, and oxalic acid, followed by heating the product twice at 650 and 750 °C for 2 h. [ABSTRACT FROM AUTHOR]

Na2Fe2P3O9N is prepared by reaction of NaPO3, Fe2O3, and (NH4)2HPO4 in a NH3 stream (quartz boat, 625 °C, 40 h). [ABSTRACT FROM AUTHOR]

The thermal stability of chargedcathode materials is one of thecritical properties affecting the safety characteristics of lithium-ionbatteries. New findings on the thermal-stability and thermal-decompositionpathways related to the oxygen release are discovered for the high-voltagespinel LixNi0.5Mn1.5O4(LNMO) with ordered (o-) and disordered(d-) structures at the fully delithiated (charged)state using a combination of in situ time-resolved X-ray diffraction(TR-XRD) coupled with mass spectroscopy (MS) and X-ray absorptionspectroscopy (XAS) during heating. Both o- and d- LixNi0.5Mn1.5O4, at their fully charged states, start oxygen-releasingstructural changes at temperatures below 300 °C, which is insharp contrast to the good thermal stability of the 4V-spinel LixMn2O4with no oxygenbeing released up to 375 °C. This is mainly caused by the presenceof Ni4+in LNMO, which undergoes dramatic reduction duringthe thermal decomposition. In addition, charged o-LNMO shows better thermal stability than the d-LNMOcounterpart, due to the Ni/Mn ordering and smaller amount of the rock-saltimpurity phase in o-LNMO. Two newly identified thermal-decompositionpathways from the initial LixNi0.5Mn1.5O4spinel to the final NiMn2O4-type spinel structure with and without the intermediatephases (NiMnO3and α-Mn2O3)are found to play key roles in thermal stability and oxygen releaseof LNMO during thermal decomposition. [ABSTRACT FROM AUTHOR]

Scalable and sustainable production of high voltage cathodes is required to meet the increasing demands for Li-ion batteries. Additionally, the anticipated scarcity of critical materials like cobalt necessitates demonstration of Co-free alternatives that can match the performance metrics of conventional cathodes. Herein, a hydrothermal synthesis route for production of a new class of high-capacity, cobalt-free cathode material, LiNi 0.9 Mn 0.05 Al 0.05 O 2 (NMA9055) for next-generation Li-ion batteries is reported. The synthesized cathode material shows high crystallinity and purity with monodispersed spherical morphology. Extensive electrochemical, structural, and post-mortem characterization of this novel NMA material is carried out. NMA-Li half cells show an initial discharge capacity of 200 mAh/g with a 96% capacity retention over 100 cycles when cycled between 3.0 and 4.4 V. On the other hand, NMA full cells with Li 4 Ti 5 O 12 (LTO) electrodes as the anode, show an initial discharge capacity of 186 mAh/g with 81% capacity retention over 200 cycles. Post-mortem structural and morphological characterization show that the NMA morphology and crystal structure do not degrade significantly over 200 charge/discharge cycles. This new class of cobalt free cathode material containing nickel, manganese and aluminum synthesized by an ammonia-free synthesis route is expected to provide a facile solution towards sustainable cathode production. • Hydrothermal method to synthesize LiNi 0.9 Mn 0.05 Al 0.05 O 2 (NMA) cobalt-free cathode. • High crystallinity and spherical morphology achieved by ammonia-free process. • NMA half cells show 200 mAh g−1 capacity with 96% capacity over 100 cycles. • NMA-LTO full cells shows capacity of 186 mAh g−1 with 81% retention over 200 cycles. • Extensive in-situ and ex-situ characterization performed to study the material. [ABSTRACT FROM AUTHOR]