Here we report the rational design of a high-capacity Li-ion anode material comprising Ge nanowires with Si branches. The unique structure provides an electrode material with tunable properties, allowing the performance to be tailored for either high capacity or high rate capability by controlling the mass ratio of Si to Ge. The binder free Si-Ge branched nanowire heterostructures are grown directly from the current collector and exhibit high capacities of up to ∼1800 mAh/g. Rate capability testing revealed that increasing the Ge content within the material boosted the performance of the anode at fast cycling rates, whereas a higher Si content was optimal at slower rates of charge and discharge. Using ex-situ electron microscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy mapping, the composition of the material is shown to be transient in nature, transforming from a heterostructure to a Si-Ge alloy as a consequence of repeated lithiation and delithiation.

Here we report the formation of high capacity Li-ion battery anodes from SiGe alloy nanowire arrays that are grown directly on stainless steel current collectors, in a single-step synthesis. The direct formation of these SiGe nanowires (ranging from SiGe to SiGe) represents a simple and efficient processing route for the production of Li-ion battery anodes possessing the benefits of both Si (high capacity) and Ge (improved rate performance and capacity retention). The nanowires were characterized through SEM, TEM, XRD and ex situ HRSEM/HRTEM. Electrochemical analysis was conducted on these nanowires, in half-cell configurations, with capacities of up to 1360 mAh/g (SiGe) sustained after 250 cycles and in full cells, against a commercial cathode, where capacities up to 1364 mAh/g (SiGe) were retained after 100 cycles.

Here, we report the application of axially heterostructured nanowires consisting of alternating segments of silicon and germanium with a tin seed as lithium-ion battery anodes. During repeated lithiation and delithiation, the heterostructures completely rearrange into a porous network of homogeneously alloyed SiGe ligaments. The transformation was characterized through ex situ TEM, STEM, and Raman spectroscopy. Electrochemical analysis was conducted on the heterostructure nanowires with discharge capacities in excess of 1180 mAh/g for 400 cycles (C/5) and capacities of up to 613 mAh/g exhibited at a rate of 10 C.

Li-ion batteries containing cost-effective, environmentally benign cathode materials with high specific capacities are in critical demand to deliver the energy density requirements of electric vehicles and next-generation electronic devices. Here, the phase-controlled synthesis of copper sulfide (Cu x S) composites by the temperature-controlled sulfurization of a prototypal Cu metal-organic framework (MOF), HKUST-1 is reported. The tunable formation of different Cu x S phases within a carbon network represents a simple method for the production of effective composite cathode materials for Li-ion batteries. A direct link between the sulfurization temperature of the MOF and the resultant Cu x S phase formed with more Cu-rich phases favored at higher temperatures is further shown. The Cu x S/C samples are characterized through X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDX) in addition to testing as Li-ion cathodes. It is shown that the performance is dependent on both the Cu x S phase and the crystal morphology with the Cu 1.8 S/C-500 material as a nanowire composite exhibiting the best performance, showing a specific capacity of 220 mAh g −1 after 200 charge/discharge cycles.

Highly aligned copper zinc tin sulfide nanorods electrophoretically deposited directly on the current collector are tested for suitability as Li-ion battery anodes in both half-cell (HC) and full-cell (FC) configurations. This facile fabrication process offers several advantages for high-performance nanostructured battery electrodes, notably the formation of a dense, conductive carbon and binder-free film maximizing active material content. High initial capacities of 1611 and 1369 mA h g −1 are achieved for the HC and FC, respectively. The capacity trends and degradation mechanisms for this combined alloying and conversion material are analyzed in detail using differential capacity plots and electrochemical impedance spectroscopy, and it is determined that an evolution in the electrode resistance (instead of typical material pulverization/delamination) is the major driver of an initial capacity fade followed by a dramatic capacity recovery. Differences in capacity retention trends between HCs and FCs are highlighted, emphasizing the importance of extended testing in commercial style setups for complete material evaluation.