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Despite significant efforts to fabricate high energy density (ED) lithium (Li) metal anodes, problems such as dendrite formation and the need for excess Li (leading to low N/P ratios) have hampered Li metal battery (LMB) development. Here, the use of germanium (Ge) nanowires (NWs) directly grown on copper (Cu) substrates (Cu-Ge) to induce lithiophilicity and subsequently guide Li ions for uniform Li metal deposition/stripping during electrochemical cycling is reported. The NW morphology along with the formation of the Li15Ge4 phase promotes uniform Li-ion flux and fast charge kinetic, resulting in the Cu-Ge substrate demonstrating low nucleation overpotentials of 10 mV (four times lower than planar Cu) and high Columbic efficiency (CE) efficiency during Li plating/stripping. Within a full-cell configuration, the Cu-Ge@Li – NMC cell delivered a 63.6% weight reduction at the anode level compared to a standard graphite-based anode, with impressive capacity retention and average CE of over 86.5% and 99.2% respectively. The Cu-Ge anodes are also paired with high specific capacity sulfur (S) cathodes, further demonstrating the benefits of developing surface-modified lithiophilic Cu current collectors, which can easily be integrated at the industrial scale.

We present a solution-based crystal phase engineering approach for layered transition metal disulphide nanosheets by modulating the reactivity of the molecular precursors.

We report the formation of an intermediate lamellar Cu-thiolate complex, and tuning its relative stability using alkylphosphonic acids are crucial to enabling controlled heteronucleation to form Bi(Cu

Here we report the formation of three distinct Sn-based active materials for Li-ion battery anodes, formed from the same metal–organic material (MOM) precursor sql-1-Cu-SNIFSIX. The materials were ...

Here we report the use of 1D SixGe1−x (x = 0.25, 0.5, 0.75) alloy nanowires (NWs) as anode materials for Na-ion batteries (NIBs). The strategy involves the synthesis of crystalline SixGe1−x NWs via the solution–liquid–solid (SLS) mechanism, followed by amorphization to activate the material for Na-ion cycling within a NIB. This study demonstrates the successful activation of SixGe1−x amorphous NW alloys, with a-Si0.5Ge0.5 delivering 250 mA h g−1 as compared to a-Ge NWs delivering only 107 mA h g−1 after 100 cycles. Also, amorphization proved to be a critical step, since crystalline NWs failed to activate in NIBs. However, Si NWs performed poorly during Na-ion cycling even after amorphization, and this behavior was explained by poor comparative Na-ion diffusivity. Further investigations on the impact of the relative content of Ge within the amorphized SixGe1−x NWs, Na-ion diffusivity and electrode degradation during cycling were also performed. Notably, the incorporation of Ge in the a-SixGe1−x alloy boosted Na ion diffusivity in the amorphized alloy, resulting in improved cycling performance and rate capability as compared to parent a-Si and a-Ge NWs.

Li-ion batteries (LIBs) have become critical components in the manufacture of electric vehicles (EVs) as they offer the best all-round performance compared to competing battery chemistries. However, LIB performance at low temperature (LT) extremes of EV operation (typically −40 to 0 °C) suffers from a reduced output and diminished cycle life. LT cycling increases cell impedance, diminishing Li ion diffusion through the cell, exacerbating electrode polarisation, and hindering interfacial Li+ desolvation. Herein, we present a comprehensive review of (i) the factors that influence LT Li-ion performance, (ii) outline the shortcomings of the current state-of-the-art and (iii) discuss recent findings in the field, focusing on alternative anode materials with particular emphasis on high-capacity, fast charging alternatives to the archetypal carbon (graphite) anode. Different approaches to improve LT LIB performance are outlined in an in-depth analysis of recent improvements from the anode perspective. These include electrolyte-driven enhancements, the resurgence of Li metal batteries, the impact of conductive coatings, elemental doping and nanocomposite formation, substitution of intercalating anodes with high-capacity Li alloying and Li conversion materials, and fast redox pseudocapacitance.

peer-reviewed The full text of this article will not be available until the embargo expires on the 13/10/2021 Transition metal dichalcogenides (TMDs) are increasingly of interest in the field of lithium ion batteries due to their unique structure. However, previous preparation methods have mainly focused on their growth from substrates or by exfoliation of the bulk materials. Considering colloidal synthesis has many advantages including precision control of morphology and crystal phases, there is significant scope for exploring this avenue for active material formation. Therefore, in this work, we explore the applicability of colloidal TMDs using WSe2 nanocrystals for Li ion battery anodes. By employing colloidal hotinjection protocol, we first synthesize 2D nanosheets in 2H and 1T’ crystal phases. After detailed structural and surface characterization, we investigate the performance of these nanosheets as anode materials. We find that 2H nanosheets outperformed 1T’ nanosheets exhibiting a higher specific capacity of 498 mAh g-1 with an overall capacity retention of 83.28%. Furthermore, to explore the role of morphology on battery performance 3D interconnected nanoflowers in 2H crystal phase were also investigated as an anode material. A noteworthy specific capacity of 982 mAh g-1 after 100 cycles was exhibited by these nanoflowers. The anode materials are characterized prior to cycling and after 1, 25, and 100 charge/discharge cycles, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to track the effects of cycling on the material.

Silicon nanowires (Si NWs) have been widely researched as the best alternative to graphite anodes for the next-generation of high-performance lithium-ion batteries (LIBs) owing to their high capacity and low discharge potential. However, growing binder-free Si NW anodes with adequate mass loading and stable capacity is severely limited by the low surface area of planar current collectors (CCs), and is particularly challenging to achieve on standard pure-Cu substrates due to the ubiquitous formation of Li+ inactive silicide phases. Here, the growth of densely-interwoven In-seeded Si NWs is facilitated by a thin-film of copper-silicide (CS) network in situ grown on a Cu-foil, allowing for a thin active NW layer ( 99.6% and stable performance for > 900 cycles with ≈ 88.7% capacity retention. More significantly, it delivers a volumetric capacity of ≈ 1086.1 mA h/cm3 at 5C. The full-cell versus lithium manganese oxide (LMO) cathode delivers a capacity of ≈ 1177.1 mA h/g at 1C with a stable rate capability. This electrode architecture represents significant advances toward the development of binder-free Si NW electrodes for LIB application.

Binder and conductive additive-free Si nanowires (NWs) grown directly on the current collector have shown great potential as next generation Li-ion battery anodes. However, low active material mass loadings and consequentially low areal capacities have remained a challenge in their development. Herein, we report the high-density growth of Si NWs on carbon cloth (CC) for use as Li-ion battery anodes. The NW growth reactions were carried out using a modified, glassware-based solvent vapor growth (SVG) process. Optimized growth conditions were applied to CC substrates to generate flexible Si NW anodes for Li-ion batteries. Battery testing revealed high areal charge and discharge capacities (>2 mAh/cm2) compared to Si NWs grown on stainless steel (SS) substrates (~0.3 mAh/cm2) and stable long-term cycling with 80% capacity retention after 200 cycles. The findings reported herein represent a significant advancement in the field in terms of achievable areal capacity enabled by a low-cost glassware-based system.

Herein, we demonstrate the ability of Zn to catalyze the growth of Si nanowires

Lithium (Li) metal batteries (LMBs) provide superior energy densities far beyond current Li-ion batteries (LIBs) but practical applications are hindered by uncontrolled dendrite formation and the build-up of dead Li in “hostless” Li metal anodes. To circumvent these issues, we created a 3D framework of a carbon paper (CP) substrate decorated with lithiophilic nanowires (silicon (Si), germanium (Ge), and SiGe alloy NWs) that provides a robust host for efficient stripping/plating of Li metal. The lithiophilic Li22Si5, Li22(Si0.5Ge0.5)5, and Li22Ge5 formed during rapid Li melt infiltration prevented the forma?tion of dead Li and dendrites. Li22Ge5/Li covered CP hosts delivered the best performance, with the lowest overpotentials of 40 mV (three times lower than pristine Li) when cycled at 1 mA cm−2 /1 mAh cm−2 for 1000 h and at 3 mA cm−2 /3 mAh cm−2 for 500 h. Ex situ analysis confirmed the ability of the lithiophilic Li22Ge5 decorated samples to facilitate uniform Li deposi?tion. When paired with sulfur, LiFePO4, and NMC811 cathodes, the CP-LiGe/ Li anodes delivered 200 cycles with 82%, 93%, and 90% capacity retention, respectively. The discovery of the highly stable, lithiophilic NW decorated CP hosts is a promising route toward stable cycling LMBs and provides a new design motif for hosted Li metal anodes.

Silicon nanowires (Si NWs) are a promising anode material for lithium-ion batteries (LIBs) due to their high specific capacity [1]. Achieving adequate mass loadings for binder-free Si NWs is restricted by low surface area, mechanically unstable and poorly conductive current collectors (CCs), as well as complicated/expensive fabrication routes [2][3]. Herein, a tunable mass loading and dense Si NW growth on a conductive, flexible, fire-resistant, and mechanically robust interwoven stainless-steel fiber cloth (SSFC) using a simple glassware setup is reported. The SSFC CC facilitates dense growth of Si NWs where its open structure allows a buffer space for expansion/contraction during Li-cycling. The Si NWs@SSFC anode displays a stable performance for 500 cycles with an average Coulombic efficiency of >99.5%. Galvanostatic cycling of the Si NWs@SSFC anode with a mass loading of 1.32 mg.cm−2 achieves a stable areal capacity of ≈2 mAh.cm−2 at 0.2 C after 200 cycles. Si NWs@SSFC anodes with different mass loadings are characterized before and after cycling by scanning and transmission electron microscopy to examine the effects of Li-cycling on the morphology. Notably, this approach allows the large-scale fabrication of robust and flexible binder-free Si NWs@SSFC architectures, making it viable for practical applications in high energy density LIBs. Figure 1. Areal capacity vs cycle number of Si NWs@SSFC with mass loadings 0.24 and 1.32mg.cm–2 at C/5 References [1] Y. Jin, B. Zhu, Z. Lu, N. Liu, J. Zhu, Adv. Energy Mater., 7 (2017), 1700715 [2] T. Kennedy, M. Brandon, K. M. Ryan, Adv. Mater., 28(2016), 5696 [3] T. D. Bogart, D. Oka, X. Lu, M. Gu, C. Wang, B. A. Korgel, ACS Nano, 8(2014), 915 Figure 1

peer-reviewed CuZnSe2 (CZSe) is an important ternary semiconductor comprised of earth-abundant elements with a suitable bandgap for visible light absorption and structural/stoichiometric versatility that make it a promising candidate for photovoltaic applications. Here we report the controlled synthesis of the compound copper chalcogenide in nanocrystal form using a colloidal hot injection approach. Furthermore, we demonstrate control over the crystal phase to occur as either wurtzite (WZ) or zinc blende (ZB) as a function of the presence and absence of phosphine-based ligands. A major emission peak was observed at ∼1.7 eV using low-temperature photoluminescence (PL), ranging from 30 to 200 K. Additionally, we demonstrate the ability to extend this synthetic protocol to form a polytype structure comprised of a ZB core with a WZ shell.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 16/05/2020 We report the use of assemblies of SnS nanocubes as lithium‐ion battery anodes. The particles are deposited in dense, conductive thin films with high gravimetric capacity using electrophoretic deposition, negating the requirement for binders or conductive additives. Although SnS nanocube ensembles display both alloying and conversion modes, a significant benefit to capacity retention during long‐term cycling was observed by limiting the upper cutoff voltage to 1 V. In this alloying‐only regime that is more realistic for practical use, a discharge capacity of 552 mAh g−1 was delivered with a loss of only 0.08 % per cycle observed over the 400 charge/discharge cycles. We further show that the Li2S formation that occurs in the first lithiation acts as a buffer to the expansion and contraction, though crucially this effect is optimized if this species is not cycled further (>1 V). The SnS nanocube electrodes are tested in both half‐cell (HC) and full‐cell (FC) configurations and are analyzed by using ex situ SEM and EIS analysis. Finally, the electrophoretic deposition of SnS nanocubes onto a 3D textured current collector is demonstrated to increase the mass loadings

Herein, we report the formation of core@shell nanowires (NWs) comprised of crystalline germanium NW cores with amorphous silicon shells (Ge@aSi) and their performance as a high capacity Li-ion battery anode material. The Ge NWs were synthesized directly from the current collector in a solvent vapor growth (SVG) system and used as hosts for the deposition of the Si shells via a plasma-enhanced chemical vapor deposition (PECVD) process utilizing an expanding thermal plasma (ETP) source. The secondary deposition allows for the preparation of Ge@aSi core@shell structures with tunable Ge/Si ratios (2:1 and 1:1) and superior gravimetric and areal capacities, relative to pure Ge. The binder-free anodes exhibited discharge capacities of up to 2066 mAh/g and retained capacities of 1455 mAh/g after 150 cycles (for the 1:1 ratio). The 2:1 ratio showed a minimal ∼5% fade in capacity between the 20th and 150th cycles. Ex situ microscopy revealed a complete restructuring of the active material to an interconnected Si

Calcium carbonate and carbonate-hydroxyapatite are known to form inorganic components of crystals and calcareous concretions found in many non-skeletal tissues and structures including the pineal gland. We used advanced surface analyses techniques such as polarization microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), microfocus X-ray diffraction (XRD), transmission electron microscopy with selected area electron diffraction (TEM-SAED) to investigate samples extracted from rat pineal gland after irradiation with visible light for 12 h. Single-crystal X-ray diffraction showed that the concretions were largely amorphous with the presence of some nanocrystalline phases. High resolution TEM-SAED revealed the presence of iron oxide in the form of hematite. Spectroscopy data especially Raman spectroscopy revealed a mixed nature of these concretions, which corresponded reasonably with XPS, TEM and XRD. Overall the study confirms the presence of a mixed phase of calcium carbonates including calcite, aragonite and vaterite. We note that aragonite is not a common occurrence in vertebrates and recommend further investigation to rule out any link to pathology.

Sustainability and high energy are key requirements for the next-generation lithium-ion batteries (LIBs) to match the rapidly growing electric vehicle (EV) market. On the positive electrode, lithium-rich layered oxides (LRLOs) are ideal candidates for next-generation LIBs since they are possibly free of the critical element cobalt and relatively rich in manganese. Additionally, LRLOs promise outstanding specific capacity (>250 mAh g-1), which is superior to any other cathode material reported so far. On the negative electrode side, silicon-based materials are highly interesting.1 With their very high specific capacity and slightly higher de-/lithiation potential they can overcome intrinsic challenges of graphite limiting the energy density and high-rate capability of current Li-ion cells.2 Additionally, silicon is also more abundant and – in contrast to graphite and cobalt – not listed as a critical raw material by the EU and US.3,4 Certainly, both materials still face challenges, e.g., voltage and capacity fading due to structural transformation in LRLOs, or particle cracking and excessive SEI formation in Si-based anodes, which can be possibly overcome through modifications of the materials and, especially, design of the electrolyte.5,6 Herein, we present the achievement of excellent electrochemical performance of Li-ion cells with Co-free LRLO cathodes (Li1.2Ni0.2Mn0.6O2, LRNM) offering a capacity retention of >75% after 200 cycles when paired with an a-Si-NW anode, and even 81% after 1,000 cycles in LRNM||graphite cells. In both cases a cathode pre-lithiation additive, introduced during electrode slurry processing, was successfully used as a cycle life enhancer.7 References Armand, M. et al. Lithium-ion batteries – Current state of the art and anticipated developments. J. Power Sources 479, (2020). Asenbauer, J. et al. The success story of graphite as a lithium-ion anode material – fundamentals, remaining challenges, and recent developments including silicon (oxide) composites. Sustain. Energy Fuels (2020). Bobba, S., Carrara, S., Huisman, J., Mathieux, F. & Pavel, C. Critical Raw Materials for Strategic Technologies and Sectors in the EU - a Foresight Study. European Commission (2020). Olivetti, E. A., Ceder, G., Gaustad, G. G. & Fu, X. Lithium-Ion Battery Supply Chain Considerations: Analysis of Potential Bottlenecks in Critical Metals. Joule 1, 229–243 (2017). Wu, F. et al. Reducing Capacity and Voltage Decay of Co-Free Li1.2Ni0.2Mn0.6O2 as Positive Electrode Material for Lithium Batteries Employing an Ionic Liquid-Based Electrolyte. Adv. Energy Mater. 10, (2020). Stokes, K. et al. Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte. Nano Lett. 20, 7011–7019 (2020). Solchenbach, S. et al. Lithium oxalate as capacity and cycle-life enhancer in LNMO/Graphite and LNMO/SiG full cells. J. Electrochem. Soc. 165, A512–A524 (2018).

peer-reviewed Silicon nanowires (Si NWs) are a promising anode material for lithiumion batteries (LIBs) due to their high specific capacity. Achieving adequate mass loadings for binder-free Si NWs is restricted by low surface area, mechanically unstable and poorly conductive current collectors (CCs), as well as complicated/expensive fabrication routes. Herein, a tunable mass loading and dense Si NW growth on a conductive, flexible, fire-resistant, and mechanically robust interwoven stainless-steel fiber cloth (SSFC) using a simple glassware setup is reported. The SSFC CC facilitates dense growth of Si NWs where its open structure allows a buffer space for expansion/ contraction during Li-cycling. The Si NWs@SSFC anode displays a stable performance for 500 cycles with an average Coulombic efficiency of >99.5%. Galvanostatic cycling of the Si NWs@SSFC anode with a mass loading of 1.32 mg cm−2 achieves a stable areal capacity of ≈2 mAh cm−2 at 0.2 C after 200 cycles. Si NWs@SSFC anodes with different mass loadings are characterized before and after cycling by scanning and transmission electron micros-copy to examine the effects of Li-cycling on the morphology. Notably, this approach allows the large-scale fabrication of robust and flexible binder-free Si NWs@SSFC architectures, making it viable for practical applications in high energy density LIBs.

The electrochemical performance of Ge, an alloying anode in the form of directly grown nanowires (NWs), in Li-ion full cells (vs LiCoO2) was analyzed over a wide temperature range (−40 to 40 °C). LiCoO2||Ge cells in a standard electrolyte exhibited specific capacities 30× and 50× those of LiCoO2||C cells at −20 and −40 °C, respectively. We further show that propylene carbonate addition further improved the low-temperature performance of LiCoO2||Ge cells, achieving a specific capacity of 1091 mA h g–1 after 400 cycles when charged/discharged at −20 °C. At 40 °C, an additive mixture of ethyl methyl carbonate and lithium bis(oxalato)borate stabilized the capacity fade from 0.22 to 0.07% cycle–1. Similar electrolyte additives in LiCoO2||C cells did not allow for any gains in performance. Interestingly, the capacity retention of LiCoO2||Ge improved at low temperatures due to delayed amorphization of crystalline NWs, suppressing complete lithiation and high-order Li15Ge4 phase formation. The results show that alloying anodes in suitably configured electrolytes can deliver high performance at the extremes of temperature ranges where electric vehicles operate, conditions that are currently not viable for commercial batteries without energy-inefficient temperature regulation.

Transition metal dichalcogenides (TMDs) are gaining increasing interest in the field of lithium ion batteries due to their unique structure. However, previous preparation methods have mainly focused on their growth from substrates or by exfoliation of the bulk materials. Considering colloidal synthesis has many advantages including precision control of morphology and crystal phases, there is significant scope for exploring this avenue for active material formation. Therefore, in this work, we explore the applicability of colloidal TMDs using WSe

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 10/07/2021 Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAhg-1) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR13FSI-0.3PYR13TFSI) . We show using post-mortem SEM and TEM, a distinct difference in morphologies of the active material after cycling in the presence or absence of the additives. The difference in performance is shown by post-mortem XPS analysis to arise from a notable increase in irreversible silicate formation in the absence of the carbonate additives. The composition of the solid electrolyte interphase (SEI) formed at the active material surface was further analysed using XPS as a function of the IL components revealing that the SEI was primarily made up of N, F and S containing compounds from the degradation of the TFSI and FSI anions.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 11/06/2021 Engineered two-dimensional (2D) layered materials possess unique physical properties with the potential to improve the performance and endurance of future electronic and energy devices. Here, we report the growth of complex 2D nanonetworks of crystalline tin selenide (SnSe) via liquid injection chemical vapor deposition using a single-source diselenoether precursor. Potential applications of SnSe span a wide range of technological areas, particularly in energy devices. The synthesized SnSe networks were composed of high surface area interconnected junctions of one-dimensional (1D) nanowires in a 2D plane; such complex SnSe nanonetwork structures have not previously been reported. The SnSe networks possessed an orthorhombic Pnma 62 crystal structure throughout, with the individual network branches uniformly orientated along the and directions. The width of the individual interconnected nanowire branches ranged from 120 to 250 nm with lengths ranging from 1 to 4 μm. The networks of 1D nanowires had a layer thickness of 88 ± 10 nm. A growth mechanism for the formation of these networks is proposed based on the minimization of high surface energy planes. We also highlight the potential of SnSe nanonetworks as an anode material for Li-ion batteries with galvanostatic testing showing an initial discharge capacity in excess of 1000 mAh g–1 with a 92% capacity retention after 50 cycles at a specific current of 100 mA g–1.

A solution based synthesis of well-ordered Cu-rich silicide nanoarchitectures, consisting of a pair of layered cups and stems (ρ-Cu15Si4) is demonstrated. The as-grown ρ-Cu15Si4typically exhibits distinct interconnected 1D stems, consisting of a stack of nanorods (∼300 nm in length), terminated with concave hexagonal 3D cups that evolve through a self-regulated layer-by-layer growth mechanism. Discrete-time ex situ experimental observations reveal that the ρ-Cu15Si4evolution is driven by interatomic diffusion, initially triggering the formation of binary-phase silicide islands (spheres) followed by the formation of hexagonal discs, stem growth, and lateral elongation in exactly opposite directions. It is further shown that electrochemically pregrown Cu-crystals can facilitate the direct growth of ρ-Cu15Si4in high yield with enhanced substrate coverage.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 23/07/2021 Silicon nanowires (Si NWs) have been identified as an excellent candidate material for the replacement of graphite in anodes, allowing for a significant boost in the capacity of lithium‐ion batteries (LIBs). Herein, high‐density Si NWs are grown on a novel 3D interconnected network of binary‐phase Cu‐silicide nanofoam (3D CuxSiy NF) substrate. The nanofoam facilitates the uniform distribution of well‐segregated and small‐sized catalyst seeds, leading to high‐density/single‐phase Si NW growth with an areal‐loading in excess of 1.0 mg cm−2 and a stable areal capacity of ≈2.0 mAh cm−2 after 550 cycles. The use of the 3D CuxSiy NF as a substrate is further extended for Al, Bi, Cu, In, Mn, Ni, Sb, Sn, and Zn mediated Si NW growth, demonstrating the general applicability of the anode architecture.

peer-reviewed Here we report an interesting observation on anode materials for lithium ion batteries that undergo combined conversion and alloying lithiation processes during cycling (CAMs). These materials are generating interest as low cost and high capacity alternatives to graphite. We find that common testing protocols (CTPs) are unsuitable for assessment of CAMs due to their distinct multi‐step lithiation characteristics. CTPs involve reporting total gravimetric capacity in a half‐cell configuration alone (opposite Li foil), without individual analysis of each process; energy density and the problems associated with wide discharge voltages are not addressed. Through isolating the individual lithiation processes of a model system (Cu2ZnSnS4), we determine that the conversion processes are highly unstable, whereas the alloying processes exhibit remarkable capacity retention. We demonstrate that inclusion of the conversion processes in cycling actually reduced full cell energy density when compared with alloying alone. This indicates that CTPs may well underestimate the stability of CAMs. It is apparent that the true advantage of CAMs lies in the synergistic combination of the capacity of the alloying portion, and the stability provided by the uncycling Li2S buffer material. Finally, we prescribe a set of testing protocols for a meaningful assessment of new CAMs.

We demonstrate that crystalline macroporous GeO2 inverse opals exhibit state-of-the-art capacity retention, voltage stability and a very long cycle life when tested as anode materials for Li-ion batteries. The specific capacities and capacity retention obtained from GeO2 IOs are greater than values reported for other GeO2 nanostructures and comparable to pure Ge nanostructures. Unlike pure Ge nanostructures, GeO2 IOs can be prepared in air without complex processing procedures, potentially making them far more attractive from an industrial point of view, in terms of cost and ease of production. Inverse opals are structurally and electrically interconnected, and remove the need for additives and binders. GeO2 IOs show gradual capacity fading over 250 and 1000 cycles, when cycled at specific currents of 150 and 300 mA/g, respectively, while maintaining high capacities and a stable overall cell voltage. The specific capacities after the 500th and 1000th cycles at a specific current of 300 mA/g were ~ 632 and 521 mA h/g respectively, corresponding to a capacity retention in each case of ~ 76% and 63% from the 2nd cycle. Systematic analysis of differential capacity plots obtained from galvanostatic voltage profiles over 1000 cycles offers a detailed insight into the mechanism of charge storage in GeO2 anodes over their long cycle life. Rate capability testing and asymmetric galvanostatic testing demonstrate the ability of GeO2 IO samples to deliver significantly high capacities even at high specific currents (1 A/g).

Here we report the formation of high capacity Li-ion battery anodes from Si1–xGex alloy nanowire arrays that are grown directly on stainless steel current collectors, in a single-step synthesis. The direct formation of these Si1–xGex nanowires (ranging from Si0.20Ge0.80 to Si0.67Ge0.33) 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 (Si0.67Ge0.33) sustained after 250 cycles and in full cells, against a commercial cathode, where capacities up to 1364 mAh/g (Si0.67Ge0.33) were retained after 100 cycles.

Fundamental research on Li–O2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li–O2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1–2 nm oxygen evolution reaction (OER) catalyst Ru/RuOx nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li–O2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuOx nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 31/10/2020 Herein, copper silicide (Cu15Si4) nanowires (NWs) grown in high densities from a metallic Cu substrate are utilized as nanostructured hosts for amorphous silicon (aSi) deposition. The conductive Cu15Si4 NW scaffolds offer an increased surface area, versus planar substrates, and enable the preparation of high capacity Li-ion anodes consisting of a nanostructured active material. The formation method involves a two-step process where Cu15Si4 nanowires are synthesized from a Cu substrate via a solvent vapor growth (SVG) approach followed by the plasma enhanced chemical vapor deposition (PECVD) of aSi. These binder-free anodes are investigated in half-cell (versus Li-foil) and full-cell (versus LCO) configurations with discharge capacities greater than 2000 mAh/g retained after 200 cycles (half-cell) and reversible capacities of 1870 mAh/g exhibited after 100 cycles (full-cell). Noteworthy rate capability is also attained where capacities of up to 1367 mAh/g and 1520 mAh/g are exhibited at 5C in half-cell and full-cell configurations respectively, highlighting the active material’s promise for fast charging and high power applications. The anode material is characterized prior to cycling and after 1, 25 and 100 charge/discharge cycles, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to track the effects of cycling on the material. ACCEPTED peer-reviewed

peer-reviewed Herein, textured Cu foil is presented as an attractive current collector substrate for directly grown Ge nanowire (NW) anodes. Compared to planar stainless steel (SS) current collectors, textured Cu led to an increase in achievable mass loading, removal of the requirement for a catalyst deposition step, improved adhesion of the active material and dramatically enhanced capacity retention. When SS and textured Cu foil based anodes with similar areal loadings (∼1.4 mA h cm−2) were compared, the capacity after 250 cycles for textured Cu was 2.7 times higher than the SS anode, illustrating the key role of the current collector.

peer-reviewed Herein, the electrochemical performance of directly grown Ge nanowire anodes in full-cell Li-ion configurations (using lithium cobalt oxide cathodes) are examined. The impacts of voltage window, anode/cathode balancing and anode preconditioning are assessed. The cells had a useable upper cutoff of 3.9 V, with a higher voltage cutoff of 4.2 V shown by SEM analysis to lead to Li plating on the anode surface. The rate performance of Ge NW anodes was shown to be boosted within full-cells compared to half-cells, meaning that existing studies may underestimate the rate performance of alloying mode anode materials if they are only based on half-cell investigations. The capacity retention of the full-cells is lower compared to equivalent half-cells due to progressive consumption of cyclable Li. This phenomenon is demonstrated using a parallel anode and cathode delithiation approach that could be extended to other full-cell systems. The findings stress the importance of testing promising anode materials within full-cell configurations, to identify specific capacity fade mechanisms that are not relevant to half-cells and aid the development of higher energy density storage systems.

peer-reviewed Development of cost effective and increasingly efficient sustainable materials for energy storage devices, such Li ion batteries, is of crucial future importance. Herein, the preparation of carbon nanofibers from biopolymer blends of lignin (by-product from the paper and pulp industry), with polylactic acid (PLA) and a thermoplastic elastomeric polyurethane (TPU) are described. Scanning electron microscopy (SEM) analysis shows the evolving microstructural morphology after each processing step, (electrospinning, stabilization and carbonization). Importantly, it is possible to tailor nanofiber porosity utilising miscibility/immiscibility rules between lignin and the polymer additive (PLA/TPU). PLA blends (immiscible) generate porous structures while miscible lignin/TPU blends are solid when carbonised. Electrodes produced from 50 % of PLA blends have capacity values of 611 mAhg-1 after 500 charge/discharge cycles; the highest reported to date for sustainable electrodes for Li-ion batteries. Thus, this work will promote the development of lignocelluose waste materials as high performace energy storage materials

peer-reviewed A scalable and cost-effective process is used to electroplate metallic Zn seeds on stainless steel substrates. Si and Ge nanowires (NWs) are subsequently grown by placing the electroplated substrates in the solution phase of a refluxing organic solvent at temperatures >430 °C and injecting the respective liquid precursors. The native oxide layer formed on reactive metals such as Zn can obstruct NW growth and is removed in situ by injecting the reducing agent LiBH4. The findings show that the use of Zn as a catalyst produces defect-rich Si NWs that can be extended to the synthesis of Si–Ge axial heterostructure NWs with an atomically abrupt Si–Ge interface. As an anode material, the as grown Zn seeded Si NWs yield an initial discharge capacity of 1772 mAh g−1 and a high capacity retention of 85% after 100 cycles with the active participation of both Si and Zn during cycling. Notably, the Zn seeds actively participate in the Li-cycling activities by incorporating into the Si NWs body via a Li-assisted welding process, resulting in restructuring the NWs into a highly porous network structure that maintains a stable cycling performance.

New techniques to directly grow metal oxide nanowire networks without the need for initial nanoparticle seed deposition or postsynthesis nanowire casting will bridge the gap between bottom-up formation and top-down processing for many electronic, photonic, energy storage, and conversion technologies. Whether etched top-down, or grown from catalyst nanoparticles bottom-up, nanowire growth relies on heterogeneous material seeds. Converting surface oxide films, ubiquitous in the microelectronics industry, to nanowires and nanowire networks by the incorporation of extra species through interdiffusion can provide an alternative deposition method. It is shown that solution-processed thin films of oxides can be converted and recrystallized into nanowires and networks of nanowires by solid-state interdiffusion of ionic species from a mechanically contacted donor substrate. NaVO3 nanowire networks on smooth Si/SiO2 and granular fluorine-doped tin oxide surfaces can be formed by low-temperature annealing of a Na diffusion species-containing donor glass to a solution-processed V2 O5 thin film, where recrystallization drives nanowire growth according to the crystal habit of the new oxide phase. This technique illustrates a new method for the direct formation of complex metal oxide nanowires on technologically relevant substrates, from smooth semiconductors, to transparent conducting materials and interdigitated device structures.

Herein, we report a novel approach to form axial heterostructure nanowires composed of linearly distinct Ni silicide (Ni2Si) and Si segments via a one-pot solution synthesis method. Initially, Si nanowires are grown using Au seeds deposited on a Ni substrate with the Si delivery in the solution phase using a liquid phenylsilane precursor. Ni silicide then forms axially along the wires through progressive Ni diffusion from the growth substrate, with a distinct transition between the silicide and pure Si segments. The interfacial abruptness and chemical composition of the heterostructure nanowires was analysed through transmission electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy, aberration corrected scanning transmission electron microscopy and atomically resolved electron energy loss spectroscopy. The method represents a versatile approach for the formation of complex axial NW heterostructures and could be extended to other metal silicide or analogous metal germanide systems.

peer-reviewed Here we report the first detailed investigation into the selenization mechanism of thin films of wurtzite copper zinc tin sulfide (CZTS) nanorods (NRs), giving particular emphasis to the role of the long-chain organic ligands surrounding each NR. During selenization, the NRs undergo a selenium-mediated phase change from wurtzite to kesterite, concurrent with the replacement of sulfur with selenium in the lattice and in-situ grain growth, along with the recrystallization of larger copper zinc tin selenide (CZTSe) kesterite grains on top of the existing film. By utilizing a facile ligand removal technique, we demonstrate that the formation of a large grain overlayer is achievable without the presence of ligands. In addition, we demonstrate an elegant ligand-exchange based method for controlling the thickness of the fine grain layer. This report emphasizes the key role played by ligands in determining the structural evolution of CZTS nanocrystal films during selenization, necessitating the identification of optimal ligand chemistries and processing conditions for desirable grain growth.

peer-reviewed 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.

peer-reviewed Herein, we report a novel approach to form axial heterostructure nanowires composed of linearly distinct Ni silicide (Ni2Si) and Si segments via a one-pot solution synthesis method. Initially, Si nanowires are grown using Au seeds deposited on a Ni substrate with the Si delivery in the solution phase using a liquid phenylsilane precursor. Ni silicide then forms axially along the wires through progressive Ni diffusion from the growth substrate, with a distinct transition between the silicide and pure Si segments. The interfacial abruptness and chemical composition of the heterostructure nanowires was analysed through transmission electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy, aberration corrected scanning transmission electron microscopy and atomically resolved electron energy loss spectroscopy. The method represents a versatile approach for the formation of complex axial NW heterostructures and could be extended to other metal silicide or analogous metal germanide systems.

In this report we examine the influence of electrode binder and electrolyte solvent on the electrochemical response of carbon based Li-O2 battery cathodes. Much higher discharge capacities were noted for cathodes discharged in DMSO compared to TEGDME. The increased capacities were related to the large spherical discharge products formed in DMSO. Characteristic toroids which have been noted in TEGDME electrolytes previously were not observed due to the low water content of the electrolyte. Linear voltage sweeps were used to investigate ORR in both of the solvents for each of the binder systems (PVDF, PVP, PEO and PTFE) and related to the Li2O2 formed on the cathode surfaces. Galvanostatic tests were also conducted in air as a comparison with the pure O2 environment typically used for Li-O2 battery testing. Interestingly, tests for the two electrolytes showed opposite trends in terms of discharge capacity values with capacities increased in TEGDME (compared to those seen in O2) and decreased in DMSO. The report highlights the key roles of electrolyte and cathode composition in determining the stability of Li-O2 batteries and highlights the importance of identifying more stable electrolyte/cathode pairings.