Lithium diffusivity in antimony-based intermetallic and FeSb-TiC composite anodes as measured by GITT.

The diffusion coefficient of lithium is an important parameter in determining the rate capability of an electrode and its ability to deliver high power output. Galvanostatic intermittent titration technique (GITT) is a quick electrochemical method to determine diffusion coefficients in electrode materials and is applied here to antimony-based anodes for lithium-ion batteries. Like other alloy anodes, antimony suffers from large volume change and a short cycle life, so GITT is also applied to determine the effects on lithium diffusivity of antimony intermetallics and composite electrodes designed to mitigate these issues. Pure antimony is measured to have a diffusion coefficient of 4.0 × 10(-9) cm(2) s(-1), in agreement with previously measured values. The intermetallics NiSb, FeSb, and FeSb2 all demonstrate diffusivity values within an order of magnitude of antimony, while Cu2Sb shows roughly an order of magnitude improvement due to the persistence of the Cu2Sb phase during cycling. The composite electrode FeSb-TiC is shown to offer significant enhancement of the diffusion coefficient positively correlated with higher concentrations of TiC in the composite up to a maximum value of 1.9 × 10(-7) cm(2) s(-1) at 60 wt% TiC, nearly two full orders of magnitude greater than that of pure antimony.

High-performance FeSb-TiC-C nanocomposite anodes for sodium-ion batteries.

Antimony-based alloy anodes with a Fe metal support dispersed in a conductive matrix consisting of TiC and carbon have been developed by high energy mechanical milling (HEMM) for sodium-ion batteries. The samples have been characterized by X-ray diffraction before and after sodiation at different C rates and by high-resolution transmission electron microscopy before and after cycling for 100 cycles. Electrochemical charge-discharge cycling at various rates and electrochemical impedance spectroscopy measurements have been carried out with and without 2 vol% of the fluoroethylene carbonate (FEC) additive in the electrolyte. With well-defined crystalline FeSb and TiC structures, the FeSb-TiC-C nanocomposite anodes demonstrate superior rate capability with good capacity retention at 10,000 mA g(-1) for sodium-ion storage, which could be ascribed to the novel nanocomposite structure consisting of a good metal (Fe) framework and a combination of conductive TiC and carbon as a matrix. The FEC additive particularly leads to a longer cycle life with high rate capability due to the formation of a stable, thin SEI layer and a smaller charge-transfer resistance.

Crystal structures of polymerized lithium chloride and dimethyl sulfoxide in the form of {2LiCl·3DMSO} n and {LiCl·DMSO} n.

Two novel LiCl·DMSO polymer structures were created by combining dry LiCl salt with dimethyl sulfoxide (DMSO), namely, catena-poly[[chlorido-lithium(I)]-µ-(dimethyl sulfoxide)-κ2 O:O-[chlorido-lithium(I)]-di-µ-(dimethyl sulfoxide)-κ4 O:O], [Li2Cl2(C2H6OS)3] n , and catena-poly[lithium(I)-µ-chlorido-µ-(dimethyl sulfoxide)-κ2 O:O], [LiCl(C2H6OS)] n . The initial synthesized phase had very small block-shaped crystals (<0.08 mm) with monoclinic symmetry and a 2 LiCl: 3 DMSO ratio. As the solution evaporated, a second phase formed with a plate-shaped crystal morphology. After about 20 minutes, large (>0.20 mm) octa-hedron-shaped crystals formed. The plate crystals and the octa-hedron crystals are the same tetra-gonal structure with a 1 LiCl: 1 DMSO ratio. These structures are reported and compared to other known LiCl·solvent compounds.

3D Printing of Ridged FeS2 Cathodes for Improved Rate Capability and Custom-Form Lithium Batteries.

Additive manufacturing can enable the fabrication of batteries in nonconventional form factors, enabling higher practical energy density due to improved material packing efficiency of power sources in devices. Furthermore, energy density can be improved by transitioning from conventional Li-ion battery materials to lithium metal anodes and conversion cathodes. Iron disulfide (FeS2) is a prominent conversion cathode of commercial interest; however, the direct-ink-write (DIW) printing of FeS2 inks for custom-form battery applications has yet to be demonstrated or optimized. In this work, DIW printing of FeS2 inks is used to systematically investigate the impact of ink solid concentration on rheology, film shape retention on arbitrary surfaces, cathode morphology, and electrochemical cell performance. We find that cathodes with a ridged interface, produced from the filamentary extrusion of highly concentrated FeS2 inks (60-70% solids w/w%), exhibit optimal power, uniformity, and stability when cycled at higher rates (in excess of C/10). Meanwhile, cells with custom-form, wave-shaped electrodes (printed FeS2 cathodes and pressed lithium anodes) are demonstrated and shown to exhibit similar performance to comparable cells in planar configurations, demonstrating the feasibility of printing onto complex geometries. Overall, the DIW printing of FeS2 inks is shown to be a viable path toward the making of custom-form conversion lithium batteries. More broadly, ridging is found to optimize rate capability, a finding that may have a broad impact beyond FeS2 and syringe extrusion.

FeSb2-Al2O3-C nanocomposite anodes for lithium-ion batteries.

FeSb2-Al2O3-C nanocomposite synthesized by ambient-temperature high-energy mechanical milling (HEMM) of Sb2O3, Fe, Al, and C has been investigated as an anode material for lithium-ion batteries. The FeSb2-Al2O3-C nanocomposites are characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The characterization data reveal it to be composed of crystalline FeSb2 nanoparticles finely dispersed in an amorphous matrix of Al2O3 and carbon. The FeSb2-Al2O3-C nanocomposite exhibits an initial discharge (lithiation) capacity of 877 mAh g(-1) and an initial charge (delithiation) capacity of 547 mAh g(-1), yielding an initial coulombic efficiency of 62%. The extended cycling performance for this composite is far superior to that of the intermetallic FeSb2 or a similarly prepared FeSb2-C composite. FeSb2-Al2O3-C retains a specific capacity of ∼350 mAh g(-1) after 500 lithiation/delithiation cycles.