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We studied the efficiency of different particle-sized sulfide solid electrolyte-based cathode composites. First, we prepared the Li7P2S8I solid electrolytes with different particle sizes through a high energy ball milling process and solution method. The structural details of the prepared solid electrolytes were studied by powder X-ray diffraction. The surface morphologies and particle size of the electrolytes were studied by field emission electron microscopy. The ionic conductivity of the prepared solid electrolytes was studied by the electrochemical impedance spectroscopy technique. Finally, we have prepared a LiNi0.8Co0.1Mn0.1O2 (NCM 811) based cathode composite and studied the electrochemical performance of the fabricated all-solid-state lithium batteries. The mixed particle-sized solid electrolyte-based cathode composite exhibited higher specific capacitance (127.2 mA h g−1) than the uniform-sized solid electrolyte-based cathode composite (117.1 mA h g−1). The electrochemical analysis confirmed that the sulfide solid electrolytes with mixed particle size exhibited better electrochemical performance.

We develop a new solution synthesis strategy for producing high ionic-conducting sulfide solid electrolyte using ethylenediamine (EDA) solvent. Here, we follow three simple steps: dissolve the precursor in ethylenediamine solvent to form the clear solution, then removing a solvent at 180 °C followed by heat treatment. The prepared Li5.5MPS4.5Cl1.5 electrolyte demonstrated the high ionic conductivity of 2.87 mS cm-1 at 25 °C. Further, fabricated solid battery using optimized electrolyte exhibited a high initial discharge capacity of 175.7 mAh g-1 at 0.1 C rate. Moreover, the synthesis technique is a convenient and quick process, thus facilitating mass production of solid electrolytes.

Integration of P2 and O3 phases in Na0.5Fe0.5Mn0.5O2 cathode via Li-ion substitution is proposed to enhance its electrochemical performance for sodium-ion battery applications. The formation of P2 and the combination of P2/O3 intergrowth were confirmed by X-ray diffraction refinement, high resolution transmission electron microscopy and X-ray photoelectron microscopy analyses. Various content of lithium was used to find optimum P2+O3 combinations. The optimized Li-ion substituted Na0.5(Li0.10Fe0.45Mn0.45)O2 showed a high initial discharge capacity of 146.2 mAh g−1 with improved cycling stability, whereas the pristine Na0.5Fe0.5Mn0.5O2 initially delivered a discharge capacity of 127.0 mAh g−1. In addition, the combination of P2+O3 increased its average voltage, which is important for achieving high energy density sodium-ion batteries. Overall, the prepared Na0.5(Li0.10Fe0.45Mn0.45)O2 electrode exhibited the improved cycling performance in terms of reversible capacity and rate capability compared to pristine Na0.5Fe0.5Mn0.5O2 electrode material.

The development of anode materials with high capacity and good cycling stability is one of the state-of-the-art objectives in the field of rechargeable sodium-ion batteries. In this work, we synthesized high-capacity spinel Fe2GeO4 using a facile hydrothermal method followed by calcination and investigated its electrochemical performance as an anode material for sodium-ion batteries. The Fe2GeO4 material delivered a high initial discharge capacity of 448.1 mAh g−1, but it showed gradual capacity fading with a capacity retention of 67.4% after 50 cycles. Its high initial capacity originated from the high electrochemical activity of Fe caused by its multiple oxidation reactions. To enhance the cycling stability of the Fe2GeO4, carbon was coated onto the surface of Fe2GeO4 particles. The carbon-coated Fe2GeO4 (Fe2GeO4@C) exhibited an initial discharge capacity of 423.0 mAh g−1 with good capacity retention. The sodium-ion full cell was assembled with an Fe2GeO4@C anode and a NaCo0.5Fe0.5O2 cathode, and the results showed superior cycling performance, demonstrating that the Fe2GeO4@C can be used as a promising anode material for sodium-ion batteries.

Sulfide-based lithium superionic conducting solid electrolytes for all-solid-state lithium batteries have received much attention due to their high safety, ionic conductivity, and compatibility. However, high-temperature treatment over a long time is needed to achieve high ionic conductivity. In this work, we have prepared the dual-halide-based Li7P2S8X type lithium superionic conductors by dry ball mill process and the high ionic conducting phase was achieved by low temperature (200℃) heat-treatment process. High ionic conducting halogen-halogen composition was arrived at through a series of optimization processes. Among the compositions tested, the Li7P2S8Br0.25I0.75 solid electrolyte exhibited a high ionic conductivity value of 6.16 mS cm−1, at room temperature. The ionic radius of the halogen element played an important role in the formation of the high ionic conducting phase. Further, the ionic conductivity of Li7P2S8I0.75Br0.25 solid electrolyte was improved by metal doping at P-site. The Sn-doped Li7P2S8I0.75Br0.25 solid electrolyte exhibited a high ionic conductivity value of 7.78 mS cm−1, at room temperature. The addition of large-sized Sn atoms extended the crystal lattice parameters and increased the Li-ions transport path. The partial substitution of Sn atoms at P-site was confirmed by NMR and Laser Raman analysis. The electrochemical stability of the prepared solid electrolyte was studied by cyclic voltammetry and DC charge-discharge analysis. The addition of a metal atom to the Li7P2S8Br0.25I0.75 solid electrolyte decreased the side reaction with the Li metals. Thus, low-temperature treated metal-doped Li7P2S8Br0.25I0.75 solid electrolytes are highly favourable for the fabrication of high-performance all-solid-state batteries. The fabricated all-solid-state battery using Sn doped Li7P2S8Br0.25I0.75 solid electrolyte exhibited the high specific capacity value of 170 mAh g−1 (0.1C), at room temperature.

Sodium-ion batteries (SIBs) are undoubtedly the most promising alternatives to lithium-ion batteries considering the natural abundance, distribution and cost of sodium resources. Still, SIBs face challenges in the development of suitable anode materials due to the large volume change during sodiation/de-sodiation, which results in inferior cycling stability. Herein, we synthesized a yolk–shell structured pyrrhotite (Fe1−xS)@N-doped carbon (FS@NC) through a solution-based method and investigated its electrochemical properties for use in SIBs as an anode material. The optimized yolk–shell structured FS@NC with distinctive voids and a core exhibited a high reversible capacity of 594 mA h g−1 over 100 cycles at 100 mA g−1, excellent rate capability and superior cycling performance compared to core–shell and pristine Fe1−xS materials. During the charge and discharge cycles, the synergistic effect of the porous core (Fe1−xS) with empty voids and a defective carbon shell configuration provided a large electrode/electrolyte contact area and shortened the diffusion path for electrons and sodium ions. It also mitigated the structural degradation by accommodating the volume change during continuous cycles, which was confirmed by ex situ SEM and TEM analyses. To demonstrate a practical application, we assembled a sodium-ion full cell with an O3-type NaCo0.5Fe0.5O2 cathode and a yolk–shell structured FS@NC anode, and the results showed superior energy storage performance.

Lithium solid state batteries are one of the state of the art energy storage systems due to their high safety. However, ionic conductivity in solid electrolytes is a concern, because at present it does not match the ionic conductivity of non-aqueous Li-ion batteries, thus resulting in sluggish electrochemical kinetics. In this report, we enhance the ionic conductivity of Li-argyrodites (Li6PS5Cl0.5Br0.5) through Si substitution at the P-site using a dry ball milling process. Among the silicon substitutions, Li6.2Si0.2P0.8S5Cl0.5Br0.5 exhibited the high ionic conductivity of 5.12 mS cm−1 compared to pristine Li6PS5Cl0.5Br0.5 at 4.02 mS cm−1. The Rietveld refinement analysis revealed that after silicon substitution, volume of the unit cell gets increased that allows the lithium at T2-site, that promotes the fast Li-ion transport. Moreover, the optimized solid electrolyte was utilized in a solid state battery system, and demonstrated a high initial capacity of 148.1 mAh g−1 at 0.1 C rate compared to pristine argyrodite (135.1 mAh g−1). Further, we demonstrated the interface phenomena between electrode and solid electrolyte using ex-situ XPS analysis. This confirmed the formation of interface products such as LiCl, Li2S, lithium polysulfides and P2Sx, which influence the cycling stability of the ASSLBs.

We develop a new solution synthesis strategy for producing high ionic-conducting sulfide solid electrolyte using ethylenediamine (EDA) solvent. Here, we follow three simple steps: dissolve the precursor in ethylenediamine solvent to form the clear solution, then removing a solvent at 180 °C followed by heat treatment. The prepared Li5.5PS4.5Cl1.5 electrolyte demonstrated the high ionic conductivity of 2.87 mS cm−1 at 25 °C. Further, fabricated solid battery using optimized electrolyte exhibited a high initial discharge capacity of 175.7 mAh g−1 at 0.1 C rate. Moreover, the synthesis technique is a convenient and quick process, thus facilitating mass production of solid electrolytes.

Lithium-rich antiperovskite-type (LiRAP) solid electrolytes have received a great deal of attention due to their high mobile ion occupancy rate and narrow activation barrier. Oxide-based LiRAPs are widely studied. However, almost no reports are available on the electrochemical nature of sulfide-based LiRAPs. Here, we prepared the first antiperovskite-like Li3SI – solid solution type solid electrolyte and studied its electrochemical properties. The crystalline nature of the electrolyte was evaluated by powder X-ray diffraction. Electrochemical impedance spectroscopy showed that the Li3SI solid electrolyte exhibited an ionic conductivity of 2.2 × 10−5 S cm−1 at room temperature. The electrochemical stability of the electrolyte was studied with cyclic voltammetry and DC cycle tests, which showed that the proposed electrolyte was stable up to 10 V and >100 h, respectively. An assembled all-solid-state lithium battery using the Li3SI solid electrolyte exhibited an initial discharge capacity of 96.8 mAh g−1 at a current density of 3 mA g−1.