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Lithium‐rich layered oxides (LLOs) have gained significant attention due to their high capacity of over 250 mAh g−1, which originates from the charge compensation of oxygen anions activated under high voltage. However, the charge compensation of oxygen anions is prone to over‐oxidation, leading to serious irreversible oxygen release, surface‐interface reactions, and structural evolution. These detriments make LLOs undergo fast voltage decay and capacity fading, which have hindered their practical applications for many years. Herein, this work develops a multifunctional co‐doping strategy and constructs W─O bonds with strong bonding interaction and covalence, low bond energy Li─S bonds with non‐binding electrons near the Fermi level, and continuous and homogeneous surface spinel‐like layer induced by W/S co‐doping. Their synergistic effect significantly mitigates the irreversible oxygen release and surface‐interface reactions and improves structural stability of Li‐rich layered cathodes. Thus, the designed and prepared Co‐free Li‐rich layered cathode (Li1.232Mn0.574Ni0.191W0.003O1.995S0.005) delivers superior voltage and capacity stability. Its capacity retention after 400 cycles is as large as 86%, and its voltage decay rate from the 10th to the 400th cycle is only 0.626 mV cycle−1. [ABSTRACT FROM AUTHOR]

The utilization of high‐voltage intercalation cathodes in calcium‐ion batteries (CIBs) is impeded by the substantial size and divalent character of Ca2+ ions, which result in pronounced volume alterations and sluggish ion mobility, consequently causing inferior reversibility and low energy/power densities. To tackle these issues, polyanionic K‐vacant KxVPO4F (x∼0, designated as K0VPF) is proposed as high‐voltage and ultra‐stable cathode material in CIBs. The K0VPF demonstrates a decent calcium storage capacity of 75 mAh g−1 at 10 mA g−1 and remarkable capacity retention of 84.2% over 1000 cycles. The average working voltage of the K0VPF is 3.85 V versus Ca2+/Ca, representing the highest value reported for CIB cathodes to date. The combined experimental and theoretical investigations revealed that the low volume changes and hopping diffusion barriers contribute to the extraordinary stability and high‐power capabilities, respectively, of K0VPF. The distribution of Ca ions into polyanionic frameworks with pronounced spatial separation effectively attenuates the Ca2+–Ca2+ repulsive force and thus augmenting the Ca migration kinetics. The high voltage of K0VPF is attributed to the inductive effect from the largely electronegative fluorine. In conjunction with a calcium metal anode and a compatible electrolyte, Ca metal full cells featured a record‐high energy density of ≈300 Wh kg−1. [ABSTRACT FROM AUTHOR]

van der Waals In2Se3 has attracted significant attention for its room‐temperature 2D ferroelectricity/antiferroelectricity down to monolayer thickness. However, instability and potential degradation pathway in 2D In2Se3 have not yet been adequately addressed. Using a combination of experimental and theoretical approaches, we here unravel the phase instability in both α‐ and β′‐In2Se3 originating from the relatively unstable octahedral coordination. Together with the broken bonds at the edge steps, it leads to moisture‐facilitated oxidation of In2Se3 in air to form amorphous In2Se3−3xO3x layers and Se hemisphere particles. Both O2 and H2O are required for such surface oxidation, which can be further promoted by light illumination. In addition, the self‐passivation effect from the In2Se3−3xO3x layer can effectively limit such oxidation to only a few nanometer thickness. The achieved insight paves way for better understanding and optimizing 2D In2Se3 performance for device applications. [ABSTRACT FROM AUTHOR]

A new infrared nonlinear optical quaternary sulfide, CsCd4In5S12, was successfully synthesized via a high-temperature reaction using the CsI flux. This new compound adopts the KCd4Ga5S12-type structure crystallizing in the non-centrosymmetric (NCS) space group R3 (No. 146). It features a 3D diamond-like network constructed by vertex-sharing distorted [CdS4]6− and [InS4]5− tetrahedra which are aligned along the c axis with Cs+ cations dispersing in the cavities. It possesses a direct optical band gap of 2.47 eV with a wide transparency range (0.53–25 μm) and high thermal stability up to 1061 K. Moreover, CsCd4In5S12 achieves a good balance between a high laser-induced damage threshold (LIDT, 9.3 × AgGaS2 in the size range of 150–200 μm) and strong powder second-harmonic generation (SHG, 1.1 × AgGaS2) with phase matching (PM) behavior. Theoretical calculations revealed that the band edges are mainly composed of In–S bond orbitals, which make the dominant contribution to the NLO response. [ABSTRACT FROM AUTHOR]

2M-WS2 as a new phase of transition metal dichalcogenides possesses many novel physical properties, such as superconductivity and topological surface states. The effect of n-type doping on the superconductivity of this material has been studied. However, p-type doping has not been studied, because it is difficult to implement p-type doping in metastable 2M-WS2. In this paper, p-type doping was achieved in 2M-WS2 for the first time by using Mo. With the increase of the Mo content, the carrier concentration rises slightly from 1.42 × 1021 cm−1 to 1.56 × 1021 cm−1. Meanwhile, the superconducting transition temperature decreases monotonously with the increase of Mo doping and reaches a minimum value of 4.37 K at the doping limit of x = 0.6 in W1−xMoxS2. Combining the data of n-type doped 2M-WS2 from our previous research, we summarize the carrier concentration and superconducting transition temperature in a phase diagram, which shows a typical dome-like shape. These results uncover the relationship between the carrier concentration and electronic state of 2M-WS2. [ABSTRACT FROM AUTHOR]

Two new chalcohalides La6Cd0.75Ga2Q11.5Cl2.5 (Q = S and Se) with mixed-anionic functional groups were synthesized through a high temperature reaction using LaCl3 as reaction-flux. Both compounds crystalize in the non-centrosymmetric space group P63 with highly oriented tetrahedron [GaQ4] and one-dimension chain [CdQ/Cl6] (Q = S and Se). The La6Cd0.75Ga2S11.5Cl2.5 shows a large laser-induced damage threshold (LIDT) (18.6 × AgGaS2) and strong second harmonic generation (SHG) response (0.8 × AgGaS2). These results indicate that the introduction of halogens into chalcogenides is beneficial to achieve large LIDTs and SHG response. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides and carbonitrides (TMDs and MXenes) have attracted great attention in electrochemistry due to their tunable electronic structures. Herein, a new compound of Nb2Se2C is designed as a "TMD–MXene"-like material. It exhibits better oxygen evolution reaction performance than most other reported TMDs, MXenes, and commercial electrocatalysts due to the enriched active sites and excellent conductivity. [ABSTRACT FROM AUTHOR]

A new mid-infrared nonlinear optical oxyselenide compound, Sr4Pb1.5Sb5O5Se8, was successfully synthesized by traditional solid-state reaction. It crystallizes in the noncentrosymmetric space group Cm (No. 8) of the monoclinic system. The crystal structure is composed of edge-sharing quasi-2D 2∞ [Pb1.5Sb3Se8]4− zigzag layers with Sr2+ ions and anionic 1∞ [SbO2.5]2− pseudo-chains separating the adjacent layers. The compound has good thermal stability up to approximately 1000 K which is beneficial for nonlinear optical applications. The sharp down signal of the second harmonic generation (SHG) response measured with a 2.09 μm laser in the reflection mode reveals its nonlinear optical properties. The new compound Sr4Pb1.5Sb5O5Se8 provides some guidance to design new mid-infrared nonlinear optical materials. [ABSTRACT FROM AUTHOR]

Black TiO2−x attracts enormous attention due to its large solar absorption and improved conductivity. In this work, a novel structure of TiO2−x with conductive TiO layer, performing full‐spectrum absorption, was synthesized in one step by the unforeseen dismutation reaction of titanium sub‐oxides (TinO2n−1) in ammonium halide atmosphere. For this new reaction, a possible mechanism of decomposition‐etching‐disproportionation‐rehydrolysis process was proposed. The vital intermediate reactant TiCl4, which verifies the assumption, has been captured in the form of (NH4)2TiCl6, especially where Ti2O3 is the reactant. Furthermore, this work not only can nominate TiO as an alternative for noble metals or carbon materials in the aim to improve the electron conductivity and solar absorption of black TiO2−x, which are important in electrochemistry and optoelectronics fields, but also can be a new route to synthesize special structures for other multivalent transition metals. [ABSTRACT FROM AUTHOR]

Multiband materials have received increasing attention due to their superior solar absorption properties. Here we design a new multiband compound, namely Ba5Bi2Co2S10, which crystallizes in the space group C22h-P21/m (No. 11) of the monoclinic system. Ba5Bi2Co2S10 is composed of one-dimensional 1∞[Bi2Co2S10]10− chains along the a axis. The adjacent chains are separated by Ba2+ ions. The optical band gap of the compound is 1.05 eV and 0.74 eV, presenting typical multi-absorption characteristics. First-principles calculations, which are perfectly consistent with the experimental results, show that the hybrid coupling effect between Co and S gives rise to multiband characteristics. Evident optoelectronic conversion properties were observed under visible light illumination with a photocurrent density of 4.0 mA cm−2 at 1 V. [ABSTRACT FROM AUTHOR]