Atomic Insights into Ti Doping on the Stability Enhancement of Truncated Octahedron LiMn2O4 Nanoparticles

Manganese Sulfate Nanocomposites Fabricated by Hot-Melt Extrusion for Chemodynamic Therapy of Colorectal Cancer

The development of metal salts-based nanocomposites is highly desired for the Fenton or Fenton-like reaction-based chemodynamic therapy of cancer. Manganese sulfate (MnSO₄)-dispersed nanoparticles (NPs) were fabricated with a hot-melt extrusion (HME) system for the chemodynamic therapy of colorectal cancer in this study. MnSO₄ was homogeneously distributed in polyethylene glycol (PEG) 6000 (as a hydrophilic polymer) with the aid of surfactants (Span 80 and Tween 80) by HME processing. Nano-size distribution was achieved after dispersing the pulverized extrudate of MnSO₄-based composite in the aqueous media. The distribution of MnSO₄ in HME extrudate and the interactions between MnSO₄ and pharmaceutical additives were elucidated by Fourier-transform infrared, X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy analyses. Hydroxyl radical generation efficiency by the Fenton-like chemistry capability of Mn²⁺ ion was also confirmed by catalytic assays. By using the intrinsic H₂O₂ in cancer cells, MnSO₄ NPs provided an elevated cellular reactive oxygen species level, apoptosis induction capability, and antiproliferation efficiency. The designed HME-processed MnSO₄ formulation can be efficiently used for the chemodynamic therapy of colorectal cancer.

In Situ Formed Core-Shell LiZnxMn2-xO4@ZnMn2O4 as Cathode for Li-Ion Batteries

Elemental doping and surface modification are commonly used strategies for improving the electrochemical performance of LiMn₂O₄, such as the rated capacity and cycling stability. In this study, in situ formed core-shell LiZn_xMn_2-xO₄@ZnMn₂O₄ cathodes are prepared by tuning the Zn-doping content. Through comprehensive microstructural analyses by the spherical aberration-corrected scanning transmission microscopy (Cs-STEM) technique, we shed light on the correlation between the microstructural configuration and the electrochemical performance of Zn-doped LiMn₂O₄. We demonstrate that part of Zn²⁺ ions dope into the spinel to form LiZn_xMn_2-xO₄ in bulk and other Zn²⁺ ions occupy the 8a sites of the spinel to form the ZnMn₂O₄ shell on the outermost surface. This in situ formed core-shell LiZn_xMn_2-xO₄@ZnMn₂O₄ contributes to better structural stabilization, presenting a superior capacity retention ratio of 95.8% after 700 cycles at 5 C at 25 °C for the optimized sample (LiZn_0.02Mn_1.98O₄), with an initial value of 80 mAh g^-1. Our investigations not only provide an effective way toward high-performance LIBs but also shed light on the fundamental interplay between the microstructural configuration and the electrochemical performance of Zn-doped spinel LiMn₂O₄.

Stimulative formation of truncated octahedral LiMn2O4 by Cr and Al co-doping for use in durable cycling Li-ion batteries

The rational design of the unique morphology of particles has been considered as the key to improving the structural stability of spinel LiMn₂O₄ cathode materials for Li-ion batteries. Herein, a facile solid-state combustion process, combined with a Cr and Al co-doping approach, is proposed to prepare various LiCr_0.01Al_xMn_1.99-xO₄ (x ≤ 0.10) cathode materials with a good crystallinity. Cr and Al co-doping facilitates the formation of a single crystal truncated octahedral morphology. This endows the as-prepared LiCr_0.01Al_xMn_1.99-xO₄ with abundant {111} planes for Mn dissolution reduction and a few {100} and {110} planes for Li⁺ ion fast diffusion channels. Moreover, the introduction of Cr and Al elements with a stable electronic configuration further boosts the structural stability of the spinel LiMn₂O₄ owing to the relatively robust Al-O and Cr-O bonds compared with the Mn-O bond. Owing to these advantages, the optimal LiCr_0.01Al_0.05Mn_1.94O₄ delivers a good electrochemical performance with a high first discharge capacity of 118.5 mA h g^-1 and a capacity retention of 70.8% after 1000 cycles at 1 C. Even at relatively high current rates of 15 and 20 C, a durable and prolonged cycling performance of up to 3000 cycles can be achieved. In addition, a high-temperature capacity retention of 72.1% is also maintained after 200 cycles at 5 C under 55 °C. This work provides potential candidates for developing long-life Li-ion batteries with a simultaneously high capacity.

Understanding the Effect of Al Doping on the Electrochemical Performance Improvement of the LiMn2O4 Cathode Material

It is well known that the electrochemical performance of spinel LiMn₂O₄ can be improved by Al doping. Herein, combining X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) with in situ electron-beam (E-beam) irradiation techniques, the influence of Al doping on the structural evolution and stability improvement of the LiMn₂O₄ cathode material is revealed. It is revealed that an appropriate concentration of Al³⁺ ions could dope into the spinel structure to form a more stable LiAl_xMn_2-xO₄ phase framework, which can effectively stabilize the surface and bulk structure by inhibiting the dissolution of Mn ions during cycling. The optimized LiAl_0.05Mn_1.95O₄ sample exhibits a superior capacity retention ratio of 80% after 1000 cycles at 10 C (1 C = 148 mA h g^-1) in the voltage range of 3.0-4.5 V, which possesses an initial discharge capacity of 90.3 mA h g^-1. Compared with the undoped LiMn₂O₄ sample, the Al-doped sample also shows superior rate performance, especially the capacity recovery performance.

Modulation of Ferroelectric and Optical Properties of La/Co-Doped KNbO3 Ceramics

The phase transition, microscopic morphology and optical and ferroelectric properties are studied in a series of La- and Co-doped KNbO₃-based ceramics. The results show that the doping induces the transformation from the orthorhombic to the cubic phase of KNbO₃, significantly reduces the optical bandgap and simultaneously evidently improves the leakage, with a slight weakening of ferroelectric polarization. Further analysis reveals that (i) the Co doping is responsible for the obvious reduction of the bandgap, whereas it is reversed for the La doping; (ii) the slight deterioration of ferroelectricity is due to the doping-induced remarkable extrinsic defect levels and intrinsic oxygen vacancies; and (iii) the La doping can optimize the defect levels and inhibit the leakage. This investigation should both provide novel insight for exploring the bandgap engineering and ferroelectric properties of KNbO₃, and suggest its potential applications, e.g., photovoltaic and multifunctional materials.

High-capacity and superior behavior of the Ni–Cu co-doped spinel LiMn2O4 cathodes rapidly prepared via microwave-induced solution flameless combustion

High-capacity and high-rate properties of the Ni–Cu co-doped spinel LiMn2O4 cathodes for Li-ion batteries.