Amorphous GeSnSe nanoparticles as a Li-Ion battery anode with High-Capacity and long cycle performance.

A new ternary amorphous GeSnSe (GSS) nanopowder was effectively synthesized by using ball milling under inert atmosphere. Its topographical, microstructural and elemental characterizations revealed the formation of nanoparticles with undefined shape, short-range order and the tailored stoichiometry. Remarkably, this novel amorphous material demonstrates its competences as a promising Li-ion host anode, exhibiting a high cycle performance with a specific charge capacity of 963 mAh g-1 at an applied C-rate of 0.2C with a coulombic efficiency > 99.4 % after 300 cycles. Its high specific capacity, large rate capability, acceptable capacity retention and long cycle life could be attributed to a dual Li-ion storage mechanism that consists mostly of multiple reversible electrochemical processes as conversion and alloying reactions and capacitive processes. Moreover, its stable volume expansion (34 %), moderate electrode polarization (248.9 mV), reasonable charge transfer resistance (83 Ω) and apparent Li-ion diffusion coefficients between 10-9 - 10-14 cm2 s-1 could be promoted by a synergistic effect between Ge (capacity), Sn (conductivity) and Se (stability), which plays an important role on the stability and high cycle performance of the promising GSS-based anode.

Facile one-pot synthesis of lithium metal nanoparticles for superior lithium-ion anode applications.

A capable one-step method, femtosecond laser ablation of solids in liquids, was successfully applied to prepare lithium metal nanoparticles to mitigate the initial capacity loss and improve the electrochemical performance of a graphite-based electrode as a Li-host anode. Remarkably, according to the physicochemical characterization, this advanced optical method allowed to obtain uniform spheroidal and crystalline Li nanoparticles with an average particle size <20 nm. These novel ultrafine Li nanoparticles significantly decrease the initial capacity loss of a graphite-based anode, leading to reach high coulombic efficiency (>99 %), good specific charge capacity (322 mAh/g), and superior capacity retention (96 %) at an applied current density of 100 mA g-1 after 200 cycles.

Influence of the fluoroethylene carbonate on the electrochemical behavior of Bi3Ge4O12 as Lithium-ion anode.

Systematic ex-situ X-ray diffraction (XRD) characterization and electrochemical study revealed the key roles that the cut-off voltage and fluoroethylene carbonate (FEC) additive play on improving electrochemical performance of the Bi3Ge4O12-based (BGO) electrode. The ex-situ XRD analysis revealed that BGO particles suffer multiphase transitions during the (dis)charge reactions, being observed some phases as Bi2O2.33, BiLi3, Li2O, Ge4Li15, Ge2Li7, Ge3Li7, Ge5Li22, Ge4Li9, Bi2O3 and GeO2. The electrochemical evaluation exhibited that the addition of 5 v/v% of FEC in 1.0 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate and diethyl carbonate (EC: DEC) at an applied cut-off voltage (1.5 V vs Li/Li+) improves the specific capacity (29%, delivering 479 mAh g-1), capacity retention (12%) and rate capability (369 mAh g-1 at 1000 mA g-1) of the BGO-based electrode. Also, FEC promotes the formation of a stable solid-electrolyte interface (SEI) layer on the anode at a cut-off voltage of 1.5 V vs Li/Li+. It displays the lowest values of SEI and charge transfer (CT) resistances, and electrode polarization, improving the reversibility of the alloying reactions related to Ge-Li and Bi-Li and maintaining their redox activity after 100 cycles, according to dQ dV-1 data.

Double transition metal MXene (TixTa4-xC3) 2D materials as anodes for Li-ion batteries.

A bi-metallic titanium-tantalum carbide MXene, TixTa(4-x)C3 is successfully prepared via etching of Al atoms from parent TixTa(4-x)AlC3 MAX phase for the first time. X-ray diffractometer and Raman spectroscopic analysis proved the crystalline phase evolution from the MAX phase to the lamellar MXene arrangements. Also, the X-ray photoelectron spectroscopy (XPS) study confirmed that the synthesized MXene is free from Al after hydro fluoric acid (HF) etching process as well as partial oxidation of Ti and Ta. Moreover, the FE-SEM and TEM characterizations demonstrate the exfoliation process tailored by the TixTa(4-x)C3 MXene after the Al atoms from its corresponding MAX TixTa(4-x)AlC3 phase, promoting its structural delamination with an expanded interlayer d-spacing, which can allow an effective reversible Li-ion storage. The lamellar TixTa(4-x)C3 MXene demonstrated a reversible specific discharge capacity of 459 mAhg-1 at an applied C-rate of 0.5 °C with a capacity retention of 97% over 200 cycles. An excellent electrochemical redox performance is attributed to the formation of a stable, promising bi-metallic MXene material, which stores Li-ions on the surface of its layers. Furthermore, the TixTa(4-x)C3 MXene anode demonstrate a high rate capability as a result of its good electron and Li-ion transport, suggesting that it is a promising candidate as Li-ion anode material.

Engineered heat dissipation and current distribution boron nitride-graphene layer coated on polypropylene separator for high performance lithium metal battery.

Li metal as a battery anode has been intensively studied because of its high gravimetric capacity (3860 mAh g-1), a low standard electrode potential (-3.04 vs. SHE), a reasonable electronic conductivity and low density. However, lithium metal suffers from a continuous Li dendrite growth upon charge-discharge cycling, delivering a poor coulombic efficiency and consequently its early failure. Here, engineered bilayer separators demonstrate that a boron nitride-graphene (BNxGry) layer coated on one side of polypropylene (PP) membrane remarkably reduces the polarization and impedance, and significantly improve the performance and stability of Li/Cu half-cells. Moreover, Li/LiFePO4 full cell with the modified BN50Gr50/PP separator presents a remarkably stable 1000 charge-discharge cycles with a specific capacity of 114 mAh g-1 at 1C-rate. The superiority of the modified separator is orginated from an effective synergistic effect between physico-chemical properties of Gr (reducing local current density) and BN (dissipating local heat) and its enhanced structural and mechanical stability.

First-principles view of the interaction between Li and Bi4Ge3O12 anodes.

As a novel anodic electrode for Li-ion storage, the cubic Bi4Ge3O12 phase can experimentally deliver a remarkably high reversible specific capacity of 586 mA h g-1 at 200 mA h g-1 with a coulombic efficiency of 99.8% after 500 cycles, and has recently attracted attention for its stable electrochemical performance. Here we calculated its lithiation/delithiation reactions by using density functional theory studies, through the structural changes as the conversion and alloying reaction takes place during the Li-ion insertion and extraction process. The obtained theoretical capacity of Li is 48.75 mol (∼1043 mA h g-1) for 1 mol Bi4Ge3O12. The decomposed Bi2O3 (P3[combining macron]m1) and GeO2 (P3121) in the lithiation process of Bi4Ge3O12 are the active materials to react with the Li atoms via a conversion reaction. Besides Li2O with both Fm3[combining macron]m and Pnma phases, the final lithiation products of Bi4Ge3O12 should include Li3Bi (Fm3[combining macron]m) and Li4.25Ge (F4[combining macron]3m), through the alloying reactions of multi-valence elements of Bi and Ge with Li. Bi and Ge metals are also helpful in the decomposition of Li2O into Li during the delithiation process, increasing the reversibility of the conversion reactions. Our research provides theoretical support to understand the working mechanism of Bi4Ge3O12 and related mixed-metal anode materials.

Waste Biomass-Derived Carbon Anode for Enhanced Lithium Storage.

Due to increased populations, there is an increased demand for food; thus, battery electrode materials created from waste biomass provide an attractive opportunity. Unfortunately, such batteries rarely sustain capacities comparable to current state-of-the-art technologies. However, an anode synthesized from waste avocado seeds provides high cycling stability over 100 cycles and provides comparable capacity to graphite, around 315 mAh g-1 at 100 mA g-1 current density, and readily outperforms graphene in terms of both stability and capacity. This novel electrode provides such capacities as an amorphous carbon without the use of any additives or doped heteroatoms by utilizing capacitance-driven mechanisms to contribute to 54% of its lithium-ion storage. This allows the waste biomass-derived anode to overcome its low apparent diffusion coefficient of 4.38 × 10-11 cm2 s-1. By creating battery anodes from avocado seeds, waste streams can be redirected into creating valuable, renewable energy storage resources.

Reversible, stable Li-ion storage in 2 D single crystal orthorhombic α-MoO3 anodes.

Engineering two dimensional (2D) materials at atomic level is a key factor to achieve enhanced electrochemical Li-ion storage properties. This work demonstrates that single crystals of orthorhombic α-MoO3 phase can preferentially grow with a 2D nanoarchitecture via a ball-milling process, followed by heat treatment at elevated temperature. Detailed FE-SEM and TEM micrographs proved the 2D architecture of α-MoO3 nanoparticles and Raman spectroscopy evidenced the active vibration modes that correspond to the orthorhombic α-MoO3 phase. Single crystalline MoO3 belts depicted high intensity of (0 2 0) and (0 4 0) indexed planes indicating a preferential arrangement. As Li-ion host anode, the 2D α-MoO3 nanostructure delivered high reversible specific discharge capacity of ~540 mA h g-1 at 0.2 C-rate with 99.9% coulombic efficiency as well as 63% capacity retention after 200 charge-discharge cycles. An excellent reversible Li-ion storage performance (high capacity, longer cycle life and good rate capability) was attributed to the 2D α-MoO3 arrangement consists of MoO6 octahedron by corner sharing chains.

New Insight on the Formation of Sodium Titanates 1D Nanostructures and Its Application on CO2 Hydrogenation.

The aim of this work is focused on the study of a series of non-traditional catalytic nanomaterials to transform greenhouse CO2 gas into added-value products. We found encouraging results of CO2 hydrogenation activity over sodium titanates with different morphologies. The yield to methanol increases with the increase in the Na incorporated in the nanostructures confirming the proposed mechanism. Samples were prepared at different times of hydrothermal treatment (HTT) with NaOH solutions, and these materials were labeled as Ti-nR-x with x as the hours on the HTT. HRTEM initially showed sphere-shaped nanoparticles in the TiO2 commercial nanopowder, increasing the HTT resulted in morphological changes in which the structures passed from nanosheets and finally to nanorods after 30 h. The X-ray diffraction and Raman spectroscopy results indicated the formation of sodium titanates such as Na2Ti3O7 with short Ti-O bonds and that Na begins to be incorporated into the distorted TiO6 crystalline structure after 5 h of HTT (until 12 wt%). The crystalline and shape transformation resulted in a significant modification on the textural properties passing from 51 m2.g-1 to 150 m2.g-1 and from a pore volume of 0.12 cm3.g-1 to 1.03 cm3.g-1 for Ti-ref and Ti-nR-30 respectively. We also observed differences in the electronic properties as the bandgap presented a blue shift from 3.16 eV on the TiO2 reference nano-powder to 3.44 eV for the Ti-nR-30 calcined sample. This fact coincides with the presence of a more electron-rich state of the Ti4+ and the formation of negative charge layer induced by the presence of Na+ interlayer cations detected by XPS analysis, at the same this helped us to explain the catalytic activity results.

Bismuth germanate (Bi4Ge3O12), a promising high-capacity lithium-ion battery anode.

An unexplored promising lithiation-host anode material, Bi4Ge3O12, delivers a reversible specific discharge capacity of ∼586 mA h g-1 at 200 mA g-1 after 500 cycles with a coulombic efficiency of ∼99.8%. DFT calculations detected distorted [BiO6]9- octahedra, and the band structure of BGO revealed an indirect gap of 3.50 eV. A plausible reaction mechanism of storing lithium is proposed.