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Herein, we describe the synthesis and evaluation of hierarchical mesoporous orthorhombic niobium oxide (T-Nb2O5) as an anode material for rechargeable lithium-ion batteries (LIB). The as-synthesized material addresses key challenges such as beneficial porous structure, poor rate capability, and cycling performance of the anode for Li-ion devices. The physicochemical characterization results reveal hierarchical porous nanostructure morphology with agglomerated particles and a 20 to 25 nm dimension range. Moreover, the sample has a high specific surface area (~65 m2 g−1) and pore volume (0.135 cm3 g−1). As for the application in Li-ion devices, the T-Nb2O5 delivered an initial discharging capacity as high as 225 mAh g−1 at 0.1 A g−1 and higher rate capability as well as remarkable cycling features (~70% capacity retention after 300 cycles at 250 mA g−1) with 98% average Coulombic efficiency (CE). Furthermore, the scan rate-dependent charge storage mechanism of the T-Nb2O5 electrode material was described, and the findings demonstrate that the electrode shows an evident and highly effective pseudocapacitive Li intercalation behaviour, which is crucial for understanding the electrode process kinetics. The origin of the improved performance of T-Nb2O5 results from the high surface area and mesoporous structure of the nanoparticles. [ABSTRACT FROM AUTHOR]

Mn3O4 nano-octahedrons embedded in N-doped graphene oxide (MNGO) nanosheets were synthesized using a simple, energy-efficient, and rapid microwave-digested hydrothermal route in a single step. The structural and morphological aspects of synthesized materials were evaluated by XRD, IR, Raman, FE-SEM, and HR-TEM techniques. Then, the composite MNGO was tested for its Li-ion storage properties and compared with reduced graphene oxide (rGO) and Mn3O4 materials. The MNGO composite exhibited superior reversible specific capacity, excellent cyclic stability, and outstanding structural integrity throughout the electrochemical studies. The MNGO composite showed a reversible capacity of 898 mA h g−1 after 100 cycles at 100 mA g−1 and Coulombic efficiency of 97.8%. Even at a higher current density of 500 mA g−1, it exhibits a higher specific capacity of 532 mA h g−1 (~1.5 times higher than commercial graphite anode). These results demonstrate that Mn3O4 nano-octahedrons embedded on N-doped GO are a highly durable and potent anode material for LIBs. [ABSTRACT FROM AUTHOR]

Mixed transition metal oxides/spinels are excellent energy storage electrode materials that can deliver sizeable specific capacitance, excellent cyclic stability, and good rate capability than their single metal oxide analogues. Synthetic methods and strategies greatly influence materials' structure, morphology, and functionality. Among several strategies employed to improve the capacitance of metal oxides, the addition of surfactant is one of the simple strategies that help profoundly increase the electrode material's surface area/active sites. This study prepared a tetragonal spinel CoMn2O4 material using a simple hydrothermal approach by a surfactant, polyvinylpyrrolidone (PVP)-based morphological strategy. Electrochemical techniques such as cyclic voltammetry (CV) and galvanostatic charge/discharge cycling (GCD) were used to investigate the active material's energy storage properties. The structural and morphological properties were studied using XRD, SEM, and TEM techniques. The obtained CoMn2O4 material has unique and beautiful Indian borage shrub-like morphology. The unique morphology of CoMn2O4 material provided excellent electrochemical properties by virtue of its enhanced physicochemical properties like pore size distribution, increased surface area, and many active sites for electrolyte ions that incurred large specific and areal capacitances. Further, the significant structural integrity provides extended cycling stability (~116% capacity retention) with high Coulombic efficiency of ~98% even after 6000 cycles without any dwindle in capacitance value. These fascinating features make CoMn2O4 a promising and optimistic pseudocapacitive electrode material. [ABSTRACT FROM AUTHOR]

Herein, we have explored performance of layered LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode material for Li ion battery applications, prepared by different preparation strategies namely co-precipitated mixed hydroxide and solid state high temperature approach combined with high-temperature calcination. The effect of crystal structure and morphology of the obtained materials were characterized by means of X-ray diffraction and scanning electron microscopy. X-ray analysis reveals that the observed lattice parameter ratio c/a is greater than 4.89 for materials with different approaches, which indicates the formation of hexagonal layered α-NaFeO2 structure. The electrochemical properties of the materials were thoroughly characterized by means of charge–discharge experiments and electrochemical impedance spectroscopy. The direct solid state synthesized NCM111 material exhibits a low retention and discharge capacity of 60 mAh g−1 at the end of 50 cycles with high irreversible capacity during cycling. The present studies have shown that the importance of material synthesis route and its sintering process, prepared at 900 °C for 8 h results low cation mixing between Li and metal ions layer in NCM111 lattice compared to other sintered samples, resulting in superior electrochemical performance. The reversible capacity of 175 mAh g−1 is noticed at C/10 rate within the voltage window of 2.5–4.4 V for 900 °C treated sample. Even at C/3 rate, a stable high reversible capacity of 145 mAh g−1 is obtained with high capacity retention of 95%. The Rietveld and EIS spectroscopic analysis conforms the existence stable layered structure and electrode, interface for NCM11 approached through co-precipitation. [ABSTRACT FROM AUTHOR]

A new type of three-dimensional (3D) oxy-phosphate materials are explored for the application of Li and Na batteries. The molybdenum tungsten oxy phosphate, MoWO3(PO4)2, was synthesized by solid-state method and evaluated for Li/Na insertion/de-insertion electrode material for the first time. The cell at charged state (vs. Li+/Li) showed a discharge capacity of 786 mAh g−1 within the voltage window of 0.3 V with amorphization of crystalline MoWO3(PO4)2 as observed from ex-situ powder XRD analysis. The structural integrity was revealed in this material, even with nearly more than 5 Li+ ions into the lattice, leading to the discharge capacity of 250 mAh g−1. The reversible charge/discharge behavior with insertion/de-insertion of 2.4 Li+ ions in the voltage range of 1.65 − 3.5 V resulted in 110 and 95 mAh g−1 at C/10 and C/5 rates, respectively. On the other hand, poor cycling performance was noticed for Na ion insertion and desertion, with a discharge capacity of 250 mAh/g within the voltage range of 0.3 − 3.5 V (vs. Na+/Na). [ABSTRACT FROM AUTHOR]

Hierarchical flower-like NiCo2O4 anchored on multiwalled carbon nanotubes (NiCo2O4-MCNTs) act as robust bifunctional electrocatalysts towards O2 (OER) and H2 (HER) evolution reactions. The NiCo2O4-MCNTs hybrid is synthesized in a facile surfactant-free hydrothermal process, and its flower-like morphology was shown to consist of 1D nanowires. The MCNT support is beneficial for enhanced reactive sites, efficient charge transfer, and durability of the composite. The material shows low overpotentials of 350 mV and 209 mV for OER and HER, respectively at 10 mAcm-2. Such values are comparable to contemporary noble-metal catalysts and even lower than reported non-precious catalysts. Moreover, this hybrid shows high current density, lower Tafel slope, and excellent stability. The synergistic coupling effects between the MCNTs and NiCo2O4 are key factors for the superior catalytic activity of these hybrid materials. [ABSTRACT FROM AUTHOR]

Spinel NiCo 2 O 4 in different morphologies is of current interest in the design and development of electrochemical supercapacitors. In this work, we synthesized two different morphologies of NiCo 2 O 4 by facile hydrothermal method employing CTAB as a soft template and urea as hydrolysis controlling agent. This study has been undertaken to determine the effect of synthesis temperature on the morphology and pseudocapacitance behavior of the NiCo 2 O 4 . We find that the temperature variation in the synthesis procedure has a strong effect on the morphology of NiCo 2 O 4 , producing urchin-like morphology at 120 °C (NiCoO-120-cal) and sheaf-like morphology at 200 °C (NiCoO-200-cal) with hierarchical porous textures. The effect of morphology on the electrochemical pseudocapacitance behavior was studied by CV, CP and EIS techniques. Both NiCo 2 O 4 samples show higher electrochemical performance than the parent NiO and Co 3 O 4 synthesized under similar conditions. The maximum specific capacitance values obtained for NiCoO-120-cal and NiCoO-200-cal are 636 and 504 F g −1 respectively, at a current density of 0.5 A g −1 . The capacitance retention of NiCoO-120-cal and NiCoO-200-cal samples, respectively, are 76% and 69% after 1000 charge–discharge cycles at a current density of 1 A g −1 . [ABSTRACT FROM AUTHOR]

We herein explore a facile and straightforward approach to enhance the interface stability between the lithium superionic conducting Li 10 GeP 2 S 12 (LGPS) solid electrolyte and Li metal by employing ionic liquid such as 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/ N-methyl- N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 13 TFSI) as the interface modifier. The results demonstrated the presence of 1 M LiTFSI/PYR 13 TFSI ionic liquid; the interface stability at the electrode/solid electrolyte (i.e., Li/LGPS) was improved remarkably by forming an in situ solid electrolyte interphase (SEI) layer. As a result, an effectively reduced interfacial resistance from 2021 to 142 Ω cm 2 and stable Li stripping/plating performance (over 1200 h at 0.038 mA cm -2 and 1000 h at 0.1 mA cm -2 ) were achieved in the Li/LGPS/Li symmetric cells. On this basis, the Li-S solid-state batteries were further architectured with one of the S@C composite [where C is the ketjen black carbon (KBC) or PBX 51-type activated carbon (PBX51C) or multiwalled carbon nanotubes (MCNTs)] cathode and the LGPS solid electrolyte. The batteries with S@KBC electrodes delivered an excellent discharge/charge performance with a high initial discharge capacity of 1017 mA h g -1 and better stability than those of the batteries with the S@PBX51C and S@MCNTs electrodes. High surface area, unique beneficial pore structure, and better particle dispersion of sulfur in the S@KBC composite facilitate high sulfur utilization and also increase the intimate contact between the electrode and LGPS solid electrolyte during the discharge/charge process.

Despite the extremely high ionic conductivity, the commercialization of Li 10 GeP 2 S 12 -type materials is hindered by the poor stability against Li metal. Herein, to address that issue, a simple strategy is proposed and demonstrated for the first time, i.e., in situ modification of the interface between Li metal and Li 10 SnP 2 S 12 (LSPS) by pretreatment with specific ionic liquid and salts. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy results reveal that a stable solid electrolyte interphase (SEI) layer instead of a mixed conducting layer is formed on Li metal by adding 1.5 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/ N-propyl- N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 13 TFSI) ionic liquid, where ionic liquid not only acts as a wetting agent but also improves the stability at the Li/LSPS interface. This stable SEI layer can prevent LSPS from directly contacting the Li metal and further decomposition, and the Li/LSPS/Li symmetric cell with 1.5 M LiTFSI/Pyr 13 TFSI attains a stable cycle life of over 1000 h with both the charge and discharge voltages reaching about 50 mV at 0.038 mA cm -2 . Furthermore, the effects of different Li salts on the interfacial modification is also compared and investigated. It is shown that lithium bis(fluorosulfonyl) imide (LiFSI) salt causes the enrichment of LiF in the SEI layer and results in a higher resistance of the cell upon a long cycling life.