Marine waste derived carbon materials for use as sulfur hosts for Lithium-Sulfur batteries.

Lithium-sulfur batteries are a promising alternative to lithium-ion batteries as they can potentially offer significantly increased capacities and energy densities. The ever-increasing global battery market demonstrates that there will be an ongoing demand for cost effective battery electrode materials. Materials derived from waste products can simultaneously address two of the greatest challenges of today, i.e., waste management and the requirement to develop sustainable materials. In this study, we detail the carbonisation of gelatin from blue shark and chitin from prawns, both of which are currently considered as waste biproducts of the seafood industry. The chemical and physical properties of the resulting carbons are compared through a correlation of results from structural characterisation techniques, including electron imaging, X-ray diffraction, Raman spectroscopy and nitrogen gas adsorption. We investigated the application of the resulting carbons as sulfur-hosting electrode materials for use in lithium-sulfur batteries. Through comprehensive electrochemical characterisation, we demonstrate that value added porous carbons, derived from marine waste are promising electrode materials for lithium-sulfur batteries. Both samples demonstrated impressive capacity retention when galvanostatically cycled at a rate of C/5 for 500 cycles. This study highlights the importance of looking towards waste products as sustainable feeds for battery material production.

Binder-Free Anodes for Potassium-ion Batteries Comprising Antimony Nanoparticles on Carbon Nanotubes Obtained Using Electrophoretic Deposition.

Antimony has a high theoretical capacity and suitable alloying/dealloying potentials to make it a future anode for potassium-ion batteries (PIBs); however, substantial volumetric changes, severe pulverization, and active mass delamination from the Cu foil during potassiation/depotassiation need to be overcome. Herein, we present the use of electrophoretic deposition (EPD) to fabricate binder-free electrodes consisting of Sb nanoparticles (NPs) embedded in interconnected multiwalled carbon nanotubes (MWCNTs). The anode architecture allows volume changes to be accommodated and prevents Sb delamination within the binder-free electrodes. The Sb mass ratio of the Sb/CNT nanocomposites was varied, with the optimized Sb/CNT nanocomposite delivering a high reversible capacity of 341.30 mA h g-1 (∼90% of the initial charge capacity) after 300 cycles at C/5 and 185.69 mA h g-1 after 300 cycles at 1C. Postcycling investigations reveal that the stable performance is due to the unique Sb/CNT nanocomposite structure, which can be retained over extended cycling, protecting Sb NPs from volume changes and retaining the integrity of the electrode. Our findings not only suggest a facile fabrication method for high-performance alloy-based anodes in PIBs but also encourage the development of alloying-based anodes for next-generation PIBs.

Si Nanowires: From Model System to Practical Li-Ion Anode Material and Beyond.

Nanowire (NW)-based anodes for Li-ion batteries (LIBs) have been under investigation for more than a decade, with their unique one-dimensional (1D) morphologies and ability to transform into interconnected active material networks offering potential for enhanced cycling stability with high capacity. This is particularly true for silicon (Si)-based anodes, where issues related to large volumetric expansion can be partially mitigated and the cycle life can be enhanced. In this Perspective, we highlight the trajectory of Si NWs from a model system to practical Li-ion battery anode material and future prospects for extension to beyond Li-ion batteries. The study examines key research areas related to Si NW-based anodes, including state-of-the-art (SoA) characterization approaches followed by practical anode design considerations, including NW composite anode formation and upscaling/full-cell considerations. An outlook on the practical prospects of NW-based anodes and some future directions for study are detailed.

Real-Time TEM Observation of the Role of Defects on Nickel Silicide Propagation in Silicon Nanowires.

Metal silicides have received significant attention due to their high process compatibility, low resistivity, and structural stability. In nanowire (NW) form, they have been widely prepared using metal diffusion into preformed Si NWs, enabling compositionally controlled high-quality metal silicide nanostructures. However, unlocking the full potential of metal silicide NWs for next-generation nanodevices requires an increased level of mechanistic understanding of this diffusion-driven transformation. Herein, using in situ transmission electron microscopy (TEM), we investigated the defect-controlled silicide formation dynamics in one-dimensional NWs. A solution-based synthetic route was developed to form Si NWs anchored to Ni NW stems as an optimal platform for in situ TEM studies of metal silicide formation. Multiple in situ annealing experiments led to Ni diffusion from the Ni NW stem into the Si NW, forming a nickel silicide. We observed the dynamics of Ni propagation in straight and kinked Si NWs, with some regions of the NWs acting as Ni sinks. In NWs with high defect distribution, we obtained direct evidence of nonuniform Ni diffusion and silicide retardation. The findings of this study provide insights into metal diffusion and silicide formation in complex NW structures, which are crucial from fundamental and application perspectives.

Revealing Seed-Mediated Structural Evolution of Copper-Silicide Nanostructures: Generating Structured Current Collectors for Rechargeable Batteries.

Metal silicide thin films and nanostructures typically employed in electronics have recently gained significant attention in battery technology, where they are used as active or inactive materials. However, unlike thin films, the science behind the evolution of silicide nanostructures, especially 1D nanowires (NWs), is a key missing aspect. CuxSiy nanostructures synthesized by solvent vapor growth technique are studied as a model system to gain insights into metal silicide formation. The temperature-dependent phase evolution of CuxSiy structures proceeds from Cu>Cu0.83Si0.17>Cu5Si>Cu15Si4. The role of Cu diffusion kinetics on the morphological progression of Cu silicides is studied, revealing that the growth of 1D metal silicide NWs proceeds through an in situ formed, Cu seed-mediated, self-catalytic process. The different CuxSiy morphologies synthesized are utilized as structured current collectors for K-ion battery anodes. Sb deposited by thermal evaporation upon Cu15Si4 tripod NWs and cube architectures exhibit reversible alloying capacities of 477.3 and 477.6 mAh g-1 at a C/5 rate. Furthermore, Sb deposited Cu15Si4 tripod NWs anode tested in Li-ion and Na-ion batteries demonstrate reversible capacities of ≈518 and 495 mAh g-1.

Binder-free germanium nanoparticle decorated multi-wall carbon nanotube anodes prepared via two-step electrophoretic deposition for high capacity Li-ion batteries.

Germanium (Ge) has a high theoretical specific capacity (1384 mA h g-1) and fast lithium-ion diffusivity, which makes it an attractive anode material for lithium-ion batteries (LIBs). However, large volume changes during lithiation can lead to poor capacity retention and rate capability. Here, electrophoretic deposition (EPD) is used as a facile strategy to prepare Ge nanoparticle carbon-nanotube (Ge/CNT) electrodes. The Ge and CNT mass ratio in the Ge/CNT nanocomposites can be controlled by varying the deposition time, voltage, and concentration of the Ge NP dispersion in the EPD process. The optimized Ge/CNT nanocomposite exhibited long-term cyclic stability, with a capacity of 819 mA h g-1 after 1000 cycles at C/5 and a reversible capacity of 686 mA h g-1 after 350 cycles (with a minuscule capacity loss of 0.07% per cycle) at 1C. The Ge/CNT nanocomposite electrodes delivered dramatically improved cycling stability compared to control Ge nanoparticles. This can be attributed to the synergistic effects of implanting Ge into a 3D interconnected CNT network which acts as a buffer layer to accommodate the volume expansion of Ge NPs during lithiation/delithiation, limiting cracking and/or crumbling, to retain the integrity of the Ge/CNT nanocomposite electrodes.

Cobalt Oxide 2D Nanosheets Formed at a Polarized Liquid|Liquid Interface toward High-Performance Li-Ion and Na-Ion Battery Anodes.

Cobalt oxide (Co3O4)-based nanostructures have the potential as low-cost materials for lithium-ion (Li-ion) and sodium-ion (Na-ion) battery anodes with a theoretical capacity of 890 mAh/g. Here, we demonstrate a novel method for the production of Co3O4 nanoplatelets. This involves the growth of flower-like cobalt oxyhydroxide (CoOOH) nanostructures at a polarized liquid|liquid interface, followed by conversion to flower-like Co3O4 via calcination. Finally, sonication is used to break up the flower-like Co3O4 nanostructures into two-dimensional (2D) nanoplatelets with lateral sizes of 20-100 nm. Nanoplatelets of Co3O4 can be easily mixed with carbon nanotubes to create nanocomposite anodes, which can be used for Li-ion and Na-ion battery anodes without any additional binder or conductive additive. The resultant electrodes display impressive low-rate capacities (at 125 mA/g) of 1108 and 1083 mAh/g, for Li-ion and Na-ion anodes, respectively, and stable cycling ability over >200 cycles. Detailed quantitative rate analysis clearly shows that Li-ion-storing anodes charge roughly five times faster than Na-ion-storing anodes.

Solution processable Si/Ge heterostructure NWs enabling anode mass reduction for practical full-cell Li-ion batteries.

Here, we report the solution phase synthesis of axial heterostructure Si and Ge (hSG) nanowires (NWs). The NWs were grown in a high boiling point solvent from a low-cost Sn powder to achieve a powder form product which represents an attractive route from lab-scale to commercial application. Slurry processed anodes of the NWs were investigated in half-cell (versus Li-foil) and full-cell (versus NMC811) configurations of a lithium ion battery (LIB). The hSG NW anodes yielded capacities of 1040 mA h g-1 after 150 cycles which corresponds to a 2.8 times increase compared to a standard graphite (372 mA h g-1) anode. Given the impressive specific and areal capacities of the hSG anodes, a full-cell test against a high areal capacity NMC811 cathode was examined. In full-cell configuration, use of the hSG anode resulted in a massive anode mass reduction of 50.7% compared to a standard graphite anode. The structural evolution of the hSG NW anodes into an alloyed SiGe porous mesh network was also investigated using STEM, EDX and Raman spectroscopy as a function of cycle number to fully elucidate the lithiation/delithiation mechanism of the promising anode material.

Colloidal synthesis of the mixed ionic-electronic conducting NaSbS2 nanocrystals.

Solution-based synthesis of mixed ionic and electronic conductors (MIECs) has enabled the development of novel inorganic materials with implications for a wide range of energy storage applications. However, many technologically relevant MIECs contain toxic elements (Pb) or are prepared by using traditional high-temperature solid-state synthesis. Here, we provide a simple, low-temperature and size-tunable (50-90 nm) colloidal hot injection approach for the synthesis of NaSbS2 based MIECs using widely available and non-toxic precursors. Key synthetic parameters (cationic precursor, reaction temperature, and ligand) are examined to regulate the shape and size of the NaSbS2 nanocrystals (NCs). FTIR studies revealed that ligands with carboxylate functionality are coordinated to the surface of the synthesized NaSbS2 NCs. The synthesized NaSbS2 nanocrystals have electronic and ionic conductivities of 3.31 × 10-10 (e-) and 1.9 × 10-5 (Na+) S cm-1 respectively, which are competitive with the ionic and electrical conductivities of perovskite materials generated by solid-state reactions. This research gives a mechanistic understanding and post-synthetic evaluation of parameters influencing the formation of sodium antimony chalcogenides materials.

Cu Current Collector with Binder-Free Lithiophilic Nanowire Coating for High Energy Density Lithium Metal Batteries.

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 Li15 Ge4 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.

Lithiophilic Nanowire Guided Li Deposition in Li Metal Batteries.

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 Li22 Si5 , Li22 (Si0.5 Ge0.5 )5, and Li22 Ge5 formed during rapid Li melt infiltration prevented the formation of dead Li and dendrites. Li22 Ge5 /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 Li22 Ge5 decorated samples to facilitate uniform Li deposition. 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.

Multipod Bi(Cu2-xS)n Nanocrystals formed by Dynamic Cation-Ligand Complexation and Their Use as Anodes for Potassium-Ion Batteries.

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(Cu2-xS)n heterostructures with a tunable number of Cu2-xS stems on a Bi core. The denticity of the phosphonic acid group, concentration, and chain length of alkylphosphonic acids are critical factors determining the stability of the Cu-thiolate complex. Increasing the stability of the Cu-thiolate results in single Cu2-xS stem formation, and decreased stability of the Cu-thiolate complex increases the degree of heteronucleation to form multiple Cu2-xS stems on the Bi core. Spatially separated multiple Cu2-xS stems transform into a support network to hold a fragmented Bi core when used as an anode in a K-ion battery, leading to a more stable cycling performance showing a specific capacity of ∼170 mAh·g-1 after 200 cycles compared to ∼111 mAh·g-1 for Bi-Cu2-xS single-stem heterostructures.

Temperature induced diameter variation of silicon nanowires via a liquid-solid phase transition in the Zn seed.

Herein, we demonstrate the ability of Zn to catalyze the growth of Si nanowires via reaction temperature determined, vapour-liquid-solid (VLS) or vapour-solid-solid (VSS) growth mechanisms. This is the first reported use of a type B catalyst to grow Si nanowires via the VSS mechanism to our knowledge whereby the highly faceted Zn seeds resulted in an increased NW diameter. This was used to induce diameter variations along the axial length of individual nanowires by transitioning between VLS and VSS growth.

Dense Silicon Nanowire Networks Grown on a Stainless-Steel Fiber Cloth: A Flexible and Robust Anode for Lithium-Ion Batteries.

Silicon nanowires (Si NWs) are a promising anode material for lithium-ion 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 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.

A Nanowire Nest Structure Comprising Copper Silicide and Silicon Nanowires for Lithium-Ion Battery Anodes with High Areal Loading.

High loading (>1.6 mg cm-2 ) of Si nanowires (NWs) is achieved by seeding the growth from a dense array of Cu15 Si4 NWs using tin seeds. A one-pot synthetic approach involves the direct growth of CuSi NWs on Cu foil that acts as a textured surface for Sn adhesion and Si NW nucleation. The high achievable Si NW loading is enabled by the high surface area of CuSi NWs and bolstered by secondary growth of Si NWs as branches from both Si and CuSi NW stems, forming a dense Si active layer, interconnected with an electrically conducting CuSi array (denoted Si/CuSi). When employed as Li-ion battery anodes, the Si/CuSi nest structure demonstrates impressive rate performance, reaching 4.1 mAh cm-2 at C/20, 3.1 mAh cm-2 at C/5, and 0.8 mAh cm-2 at 6C. Also, Si/CuSi shows remarkable long-term stability, delivering a stable areal capacity of 2.2 mAh cm-2 after 300 cycles. Overall, complete anode fabrication is achieved within a single reaction by employing an inexpensive Sn powder approach.

Alloying Germanium Nanowire Anodes Dramatically Outperform Graphite Anodes in Full-Cell Chemistries over a Wide Temperature Range.

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.

Direct Growth of Si, Ge, and Si-Ge Heterostructure Nanowires Using Electroplated Zn: An Inexpensive Seeding Technique for Li-Ion Alloying Anodes.

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.

Colloidal WSe2 nanocrystals as anodes for lithium-ion batteries.

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 WSe2 nanocrystals for Li ion battery anodes. By employing colloidal hot-injection 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 found that 2H nanosheets outperformed 1T' nanosheets exhibiting a higher specific capacity of 498 mA h 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. It is worth noting that a specific capacity of 982 mA h g-1 was exhibited after 100 cycles by these nanoflowers. The anode materials were 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.

Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte.

Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAh g-1) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR13FSI-0.3PYR13TFSI). We show, using postmortem 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 postmortem 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 analyzed 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.

Copper Silicide Nanowires as Hosts for Amorphous Si Deposition as a Route to Produce High Capacity Lithium-Ion Battery Anodes.

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). A 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.