Mn3O4 nano-octahedrons embedded in nitrogen-doped graphene oxide as potent anode material for lithium-ion batteries.

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. Supplementary Information: The online version contains supplementary material available at 10.1007/s11581-023-05035-6.

Influence of Chloride Ion Substitution on Lithium-Ion Conductivity and Electrochemical Stability in a Dual-Halogen Solid-State Electrolyte.

Li+ conducting halide solid-state electrolytes (SEs) are developing as an alternative to contemporary oxide and sulfide SEs for all-solid-state batteries (ASSBs) due to their high ionic conductivity, excellent chemical and electrochemical oxidation stability, and good deformability. However, the instability of halide SEs against the Li anode is still one of the key challenges that need to be addressed. Among halides, fluorides have shown a wider electrochemical stability window due to fluoride's high electronegativity and smaller ionic radius. However, the ionic conductivity of fluoride-based SEs is lower compared to other halide-based SEs. To achieve better interface stability with the Li anode, the presence of fluoride is not only advantageous for a wider potential window but also forms a stable passivation layer at the Li/SEs interface. Therefore, developing mixed halogen-based solid electrolytes, particularly fluorine and chlorine-based SEs are promising in ASSBs. Herein, we report dual halogen-based SEs, Li2ZrF6-xClx (0 ≤ x ≤ 2), synthesized via ball-milling. The X-ray diffraction results revealed that Li2ZrF6-xClx compounds crystallize in the trigonal phase (P3̅1m). Using impedance spectroscopy, an increase in Li+ conductivity with the increase in Cl content was observed for Li2ZrF6-xClx. Compared with x = 0, Li+ conductivity for the sample with x = 1 improved by ∼5 orders of magnitude. The Li+ conductivities for Li2ZrF5Cl1 at 25 and 100 °C are 5.5 × 10-7 and 2.1 × 10-5 S/cm, respectively. Moreover, Li2ZrF5Cl1 exhibits the widest electrochemical stability window and excellent Li interface stability. Our work indicates Li2ZrF6-xClx as an attractive material for optimization in the class of halide-based solid-state Li-ion conductors.

Stable Cycling Lithium-Sulfur Solid Batteries with Enhanced Li/Li10GeP2S12 Solid Electrolyte Interface Stability.

We herein explore a facile and straightforward approach to enhance the interface stability between the lithium superionic conducting Li10GeP2S12 (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 (PYR13TFSI) as the interface modifier. The results demonstrated the presence of 1 M LiTFSI/PYR13TFSI 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 cm2 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.

Stabilizing Li10SnP2S12/Li Interface via an in Situ Formed Solid Electrolyte Interphase Layer.

Despite the extremely high ionic conductivity, the commercialization of Li10GeP2S12-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 Li10SnP2S12 (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 (Pyr13TFSI) 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/Pyr13TFSI 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.

Facile hydrothermal synthesis of urchin-like cobalt manganese spinel for high-performance supercapacitor applications.

A facile hydrothermal method has been adopted to synthesize the spherical urchin-like hierarchical CoMn2O4 nanostructures on the nickel foam substrate. The as-synthesized urchins have an average diameter of ∼3-7µm with numerous self-assembled nanoneedles grown radically in all the directions from its center with a huge void space between them. For comparison, we have also studied the electrochemical as well as other physicochemical properties of parent simple Co3O4 and MnO2 materials, which were also synthesized by a similar hydrothermal method. The results show that CoMn2O4 electrode displayed significantly higher (more than two times) areal and specific capacitances compared to Co3O4 and MnO2 electrodes with excellent capacitance retention and Coulombic efficiency. Moreover, the energy and power densities obtained for CoMn2O4 electrode are also far higher than the parent Co3O4 and MnO2. Long-term cycling tests of CoMn2O4 electrode shows the improved capacitance with high rate capability up to 6000 cycles indicating their potential for high performance supercapacitor applications. The better electrochemical performance of CoMn2O4 electrode can be attributed to the smart urchin-like nanostructures, which has several advantages like, more electroactive sites for faradic reactions emerging from the two metal ions, higher electronic/ionic conductivity and fast electrolyte transportation kinetics promoted by unique morphology.

Charge storage, electrocatalytic and sensing activities of nest-like nanostructured Co3O4.

We synthesized nanostructured Co3O4 samples using anionic (SDS), cationic (CTAB) and nonionic (Triton X-100) surfactant molecules in hydrothermal conditions and subsequent calcination. This approach facilitates the synthesis of porous Co3O4 material with bundle-like-sheet, nest-like and flake-like morphologies with specific surface areas in the range of 50-77m2g-1. Among these materials, the nest-like nanostructured Co3O4 material has unique pore architecture, larger pore volume, low solution and charge transfer resistance, and found to be an active material for charge storage, electrocatalytic and sensing applications. The specific capacitance value of the nest-like Co3O4 is 404Fg-1 at a current density of 2Ag-1 with 80% specific capacitance retention. The electrocatalytic oxidation of methanol occurs at lower onset potential on this material with good electrochemical stability. It has good sensing ability for glucose with high sensitivity of 929µAcm-2mM-1, fast response time of ∼0.5s and detection limit as low as ∼1µM. These results show that the nest-like nanostructured Co3O4 material is a versatile candidate for various applications.

A Vanadium(V) Oxide Nanorod Promoted Platinum/Reduced Graphene Oxide Electrocatalyst for Alcohol Oxidation under Acidic Conditions.

A Pt-V2 O5 /rGO ternary hybrid electrocatalyst was designed by using active vanadium(V) oxide (V2 O5 ) nanorods and reduced graphene oxide (rGO) components. The V2 O5 nanorods were synthesized by a simple polyol-assisted solvothermal method and were incorporated uniformly onto rGO sheets by intermittent microwave heating. Subsequently, Pt nanoparticles (2-3 nm in size) were deposited over the V2 O5 /rGO composite by the conventional polyol reflux method. The electrocatalytic performance of the Pt-V2 O5 /rGO ternary hybrid and bare Pt/rGO catalysts towards the oxidation of simple alcohols was evaluated in acidic media. The ternary hybrid catalyst exhibited higher electrocatalytic activity than bare Pt/rGO and also showed good stability. The higher electrocatalytic activity of the Pt-V2 O5 /rGO ternary hybrid was attributed to a synergistic effect among the Pt, V2 O5 , and rGO components. In addition, oxygen-containing species, such as OH groups, were generated on V2 O5 at lower potentials. These groups were able to scavenge intermediate species such as COads on the Pt surfaces and helped to regenerate the active sites on the Pt surface more effectively for the routine alcohol oxidation reaction.

Vanadium pentoxide nanochains for high-performance electrochemical supercapacitors.

We have synthesized unique hierarchical one dimensional (1D) nanochains of V2O5 by employing simple hydrothermal method using cetyltrimethylammonium bromide (CTAB) as a soft template. The electrochemical performance of resulting V2O5 electrode materials was evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques. The V2O5 nanochains (V2O5-ctab) show maximum specific capacitance of 631 F g(-1) at a current density of 0.5 A g(-1) and retain 300 F g(-1) even at high current density of 15 A g(-1). In addition the V2O5 nanochains show good cyclic stability with 75% capacitance retention after 1200 charge-discharge cycles. The order of specific capacitance is commercial bulk-V2O5 (160 F g(-1))