Partial substitution of Mn/Si with V, Cr or Al in Li2MnSiO4 nanoparticle: Dependence of the physical and electrochemical properties on the substitution strategy

Constructing a Cr-Substituted Co-Free Li-Rich Ternary Cathode with a Spinel-Layered Biphase Interface

Lithium-rich manganese-based layered oxides (LRMOs) have recently attracted enormous attention on account of their remarkably big capacity and high working voltage. However, some inevitable inherent drawbacks impede their wide-scale commercial application. Herein, a kind of Cr-containing Co-free LRMO with a topical spinel phase (Li1.2Mn0.54Ni0.13Cr0.13O2) has been put forward. It has been found that the high valence of Cr6+ can reduce the Li+ ion content and induce the formation of a local spinel phase by combining more Li+ ions, which is beneficial to eliminate the phase boundary between the spinel phase and the bulk phase of the LRMO material, thus dramatically avoiding phase separation during the cycling process. In addition, the introduction of Cr can also expand the layer spacing and construct a stronger Cr-O bond compared with Mn-O, which enables to combine the transition metal (TM) slab to prevent the migration of TM ions and the transformation of the bulk phase to the spinel phase. Simultaneously, the synergistic effect of the successfully constructed spinel-layered biphase interface and the strong Cr-O bond can effectively impede the escape of lattice oxygen during the initial activation process of Li2MnO3 and provide the fast diffusion path for Li+ ion transmission, thus further reinforcing the configurable stability. Besides, Cr-LRMO presents an ultrahigh first discharge specific capacity of 310 mAh g-1, an initial Coulombic efficiency of as high as 92.09%, a good cycling stability (a capacity retention of 94.70% after 100 cycles at 1C), and a small voltage decay (3.655 mV per cycle), as well as a good rate capacity (up to 165.88 mAh g-1 at 5C).

Synthesis and Characterization of Li2Mn0.8Ni0.2SiO4/Mn3O4 Nanocomposite for Photocatalytic Degradation of Reactive Blue (RB5) Dye

This study successfully synthesized Li2MnSiO4/Mn3O4 (LMS/M3) and Li2Mn0.8Ni0.2SiO4/Mn3O4 (LMNS/M3) nanocomposites in a two-step method first, by preparing Mn3O4 (M3) nanoparticles through a hydrothermal method and second, by synthesizing Li2MnSiO4 (LMS) and Li2Mn0.8Ni0.2SiO4 (LMNS) by ethylene diamine tetra-acetic assisted sol–gel method. In the last method, the two nanoparticles are mixed by hand-milling to form nanocomposites. Synthesized nanoparticles were characterized using X-ray diffraction, Fourier-transform infrared, Raman spectra, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area, pL and UV–vis spectra measurements. The nanocomposite presents a well-developed orthorhombic crystal structure with a Pmn21 space group. BET surface area measurements indicate that all the prepared materials are mesoporous. The photocatalytic activity of M3, LMS, LMNS, (LMS/M3), and (LMNS/M3) was investigated by the photocatalytic degradation of reactive blue 5 (RB5) under UV light irradiation using a homemade photoreactor. The maximum photodegradation was achieved at optimal pH 4 and photocatalyst dose 0.005 g/50 ml dye. Higher stability for dye degradation efficiency was attained for the LMS and LMNS nanomaterials and LMS/M3 and LMNS/M3 nanocomposites than M3 to photocatalytic activity. The photocatalyst is readily recoverable and shows excellent stability even after three cycles. The photocatalytic degradation for RB5 followed first-order kinetics.

Graphical Abstract

Understanding the effects of 3D porous architectures on promoting lithium or sodium intercalation in iodine/C cathodes synthesized via a biochemistry-enabled strategy

Rechargeable sodium-iodine and lithium-iodine batteries have been demonstrated to be promising and scalable energy-storage devices, but their development has been seriously limited by challenges such as their inferior stability and the poor kinetics of iodine. Anchoring iodine to 3D porous carbon is an effective strategy to overcome these defects; however, both the external architecture and internal microstructure of the 3D porous carbon host can greatly affect the ion intercalation of iodine/C electrodes. To realize the full potential of iodine electrodes, a biochemistry-enabled route was developed to enable the controllable design of different 3D porous architectures, from hollow microspheres to 3D foam, for use in iodine/C cathodes. Two types of spores with spherical cells, i.e. Cibotium Barometz (C. Barometz) and Oetes Sinesis (O. Sinesis), are employed as bio-precursors. By carefully controlling the degree of damage on the bio-precursors, different targeted carbon hosts were fabricated. Systematic studies were carried out to clarify the structural effects on modifying the ion-intercalation capabilities of the iodine/C cathodes in lithium-iodine and sodium-iodine batteries. Our results demonstrate the profound performance improvements of both 3D bio-foam and hollow sphere because their hierarchically porous structures can strongly immobilize iodine. Notably, the 3D bio-foam based iodine composites achieve faster ion kinetics and enhanced rate capability than their hollow sphere based counterparts. This was attributed to their higher micro/mesopore volume, larger surface area and improved packing density, which result in the highly efficient adsorption of iodine species. By virtue of the thinnest slices, the iodine/bio-foam derived from C. Barometz spores achieves the best high-rate long-term cycling capability, which retains 94% and 91% of their capacities in lithium-iodine and sodium-iodine batteries after 500 cycles, respectively. With the help of the biochemistry-assisted technique, our study provides a much-needed fundamental insight for the rational design of 3D porous iodine/C composites, which will promote a significant research direction for the practical application of lithium/sodium-iodine batteries.

Exploring ion migration in Li2MnSiO4 for Li-ion batteries through strain effects

In this paper, first principles calculations were performed to investigate the effect of lattice strain on the ionic diffusion and the defect formation in Li₂MnSiO₄, which are directly related to the rate performance.

First exploration of freestanding and flexible Na2+2xFe2−x(SO4)3@porous carbon nanofiber hybrid films with superior sodium intercalation for sodium ion batteries

A freestanding Na_2+2xFe_2−x(SO₄)₃@PCNF hybrid film introduces a highly-efficient strategy for the mass-production of high-performance cathodes for SIBs.

Effects of V2O5 nanowires on the performances of Li2MnSiO4 as a cathode material for lithium-ion batteries

Effects of V₂O₅ nanowires on the performances of Li₂MnSiO₄ as cathode materials for Li-ion batteries were tested and analyzed.

The high capacity and excellent rate capability of Ti-doped Li2MnSiO4 as a cathode material for Li-ion batteries

Ti-doped Li₂Mn_1−xTixSO₄samples exhibit superior rate capability. Even at a higher rate (2 C) the samples keep a discharge capacity of around 700 mA h g⁻¹, whereas the undoped sample only delivers a discharge capacity of ca. 5 mA h g⁻¹.