Doping is one of the most important ways to tailor the performance of energy materials. However, the crystal structure of doped materials is usually oversimplified as a simple substitution of dopants. Here, we characterized the doped α-Fe2O3 with different Cu cations using synchrotron X-ray diffraction, X-ray absorption, and X-ray photoelectron spectroscopy, and electrochemically evaluated it as an anode in lithium batteries. The results suggest that doping is not the simple replacement of Fe3+ sites by Cu2+ or Cu+ but induces a complex local structure change, which may be a characteristic of this class of materials. In Cu+-doped samples, Cu+ not only replaces the Fe3+ site and distorts the FeO6 octahedra, but also gives rise to oxygen vacancies in CuO6 octahedra in the bulk structure and peroxides at the surface, leading to uniform precipitation of Cu as a conductive and buffering agent. These CuO6 octahedra also facilitate homogeneous reactions (electrochemical reduction of Cu+ and Fe3+ together) and the formation of high quality solid-electrolyte interface (SEI) layers. All these factors account for its improved electrochemical performance (discharge capacity of 841(25) mAh/g against 758(21) mAh/g of undoped one, after 80 cycles at 100mA/g). In Cu2+-doped samples, Cu2+ takes both Fe3+ and empty octahedral interstitial sites, forming linear clusters of three neighboring CuO6 octahedra. Such medium-range phase separation causes electrochemical reduction to metallic Cu before the reduction of Fe3+, leading to inactive surface Cu that contributes to poor SEI layers and deteriorates its electrochemical performances. The present work allows a better understanding of how doping affects the crystallographic structures and offers insights into how this strategy can be employed to improve electrochemical performance, in contrast to the ambiguity over material properties associated with the commonly accepted model of simple atomic replacement.

cannot be sufficiently met by current commercial lithium-ion batteries (LIBs) due to the limit of their cathode materials. Most commercial cathode materials, such as the state-of-the-art LiCoO 2 and LiFePO 4 , have low specific capacity (<200 mAh g −1) or poor rate performance. [2] Compared with these commercial cathode materials, the layered vanadium pentoxide (α-V 2 O 5 , hereafter referred to as simply V 2 O 5 , space group Pnma) [3] is a promising and inexpensive cathode material for LIBs due to its high theoretical capacity of up to 440 mAh g −1 , achieved through the intercalation of three lithium ions within the host stucture. [4] However, this material exhibits low lithium diffusivity and electric conductivity, leading to poor battery performance in terms of capacity and cyclic retention, [5] thus hindering their practical applicability. Strategies to overcome these drawbacks have been explored, mainly involving morphology control, composite formation, and structural tuning by a third element. [6] Nanostructured morphologies generally have reduced dimensions to shorten the diffusion distance of lithium ions, and thus allow for high power performance. [6,7] Various nanostructures of V 2 O 5 such as nanotubes, [8] nanofibers, [9] nanobelts, [7a] and nanorods [7b] have been synthesized by different methods and do show improved power performance. Composites, mainly composed Na 0.33 V 2 O 5-type metal vanadates generally show better cycling stability than α-V 2 O 5 as a cathode in Li-ion batteries, because they contain enough crystallographic voids that allow for lithium intercalation without significant structural deformation, but metal leaching upon cycling deteriorates their capacity retention. Here a new barium vanadate Ba 0.16(1) V 2 O 5 is reported that does not undergo Ba leaching during cycling and shows a great promise for fast Li intercalation. Sr 0.15(1) V 2 O 5 is isostructural to Na 0.33 V 2 O 5 (space group C2/m), while Ba 0.16(1) V 2 O 5 adopts a new structure (space group P2 1 /c), a derivative of Na 0.33 V 2 O 5. The framework of Ba 0.16(1) V 2 O 5 consists of edge-shared VO 6 octahedral layers and the VO 5 pyramidal bridge, generating unidirectional tunnels. Unlike the in-plane arrangement of atoms in Sr 0.15(1) V 2 O 5 , the nonplanar arrangement in Ba 0.16(1) V 2 O 5 makes the host framework more flexible and creates larger voids for Ba. Compared with the combination of displacement and intercalation mechanisms in the Sr 0.15(1) V 2 O 5 cathode, Li intercalation looks dominant in the Ba 0.16(1) V 2 O 5 cathode due to its increased flexibility. Hence, Ba 0.16(1) V 2 O 5 exhibits improved cycling stability compared to Sr 0.15(1) V 2 O 5 , suggesting that lower symmetry leads to higher cyclic stability in the V 2 O 5-related compounds. This study illustrates how guest cations can tune the structural symmetry to modulate the reaction mechanism of electrode materials toward superior performances.

Advances in medical technology have increased treatment modalities for premature infants and have greatly improved their survival and clinical outcomes. However, saving the lives of extremely premature infants has become an ethical dilemma, considering the potential undesirable consequences on the baby and the family as a result of the intensive life-support efforts. The authors draw on 2 case scenarios to illustrate the limitations of advanced medical technology on extremely premature infants who experience significant morbidities and mortality. The ethical discussion concerns the doctrines of the sanctity of life and the quality of life, with emphasis on the best interest of the infant.

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Gd6FeBi2 is reported as the only one room-temperature magnet with a Curie temperature (Tc) of ca. 350 K among more than hundreds of compounds with its structural type, which makes it more attractive in potential applications. To reveal the origin of such high ordering temperature, critical behaviors, electronic structure and crystal-field effects of Gd6FeBi2 are investigated in this work. The short-range Gd-Fe ferrimagnetic interaction is supported by the non-Curie-Weiss paramagnetic behavior, crystal and electronic structure analyses, in agreement with previous DFT calculations. Unlike the strong TM-TM exchange interactions, the Gd-Fe exchange interaction shows limited influence on the critical exponents determined by long-range exchange interactions, which seems a common feature in RE-TM based alloys without TM-TM exchange interactions.However, the strong Gd-Fe hybridization reduces the influence of vibronic couplings on the shortrange exchange interaction and thus allows a high Tc. The broadening or splitting mechanism of Gd 4f-electron bands is addressed based on crystal-field analysis and likely another factor for elevated Tc in Gd6FeBi2 and Gd-based compounds with non-magnetic elements. Different magnetic behaviors among isostructural compounds, and the relationship between the band splitting and crystal-field effects is also discussed.