Robust and Corrosion-Resistant Overall Water Splitting Electrode Enabled by Additive Manufacturing.

Electrolysis of water has emerged as a prominent area of research in recent years. As a promising catalyst support, copper foam is widely investigated for electrolytic water, yet the insufficient mechanical strength and corrosion resistance render it less suitable for harsh working conditions. To exploit high-performance catalyst supports, various metal supports are comprehensively evaluated, and Ti6 Al4 V (Ti64) support exhibited outstanding compression and corrosion resistance. With this in mind, a 3D porous Ti64 catalyst support is fabricated using the selective laser sintering (SLM) 3D printing technology, and a conductive layer of nickel (Ni) is coated to increase the electrical conductivity and facilitate the deposition of catalysts. Subsequently, Co0.8 Ni0.2 (CO3 )0.5 (OH)·0.11H2 O (CoNiCH) nanoneedles are deposited. The resulting porous Ti64/Ni/CoNiCH electrode displayed an impressive performance in the oxygen evolution reaction (OER) and reached 30 mA cm-2 at an overpotential of only 200 mV. Remarkably, even after being compressed at 15.04 MPa, no obvious structural deformation is observed, and the attenuation of its catalytic efficiency is negligible. Based on the computational analysis, the CoNiCH catalyst demonstrated superior catalytic activity at the Ni site in comparison to the Co site. Furthermore, the electrode reached 30 mA cm-2 at 1.75 V in full water splitting conditions and showed no significant performance degradation even after 60 h of continuous operation. This study presents an innovative approach to robust and corrosion-resistant catalyst design.

Ultrathick GeP Anode To Balance the Extreme Load and Compliance for High Areal Capacity Flexible Sodium-Ion Batteries.

The ever-growing application of miniaturized electric devices calls for the manufacturing of energy storage systems with a high areal energy density. Thick electrode design is a promising strategy to acquire high areal energy density by enhancing active mass loading and minimizing inactive components. However, the sluggish reaction kinetics and poor electrode mechanical stability that are accompanied by the increased electrode thickness remain unsolved problems. Herein, for the first time, we propose a novel chemical cross-linking strategy to fabricate GeP thick electrodes with adjustable electrode thicknesses and active mass loadings for high areal capacity sodium-ion batteries (SIBs). The chemical cross-linking between carboxylic multiwalled carbon nanotubes (CNTs) and pyrolysis cellulose nanofibers (CNFs) forms a 3D network that encloses GeP nanoparticles, which guarantees fast charge transfer, efficient stress relief, and alleviated volume expansion/shrinkage of the electrode. The hierarchical porous structure generates numerous interconnected channels for unfettered Na+ diffusion, ensuring uncompromised reaction kinetics as the electrode thickness increases. As a result, the ultrathick 1031 µm GeP@C-CNTs-CNFs electrode featuring a mass loading of 18.3 mg cm-2 delivers an ultrahigh areal capacity of 10.58 mAh cm-2 accompanied by superior cycling stability, which outperforms all reported Ge-based electrodes (generally below 1.5 mAh cm-2). This work sheds insightful light on designing high areal capacity flexible thick electrodes for the applications of miniaturized electric devices.

High-Capacity Sb/Fe2S3 Sodium-Ion Battery Anodes Fabricated by a One-Step Redox Reaction, Followed by Ball Milling with Graphite.

Antimony (Sb) has been considered a promising anode for sodium-ion batteries (SIBs) owing to its high theoretical capacity (660 mA h g-1) and low redox voltage (0.2-0.9 V vs Na+/Na). However, the capacity degradation caused by the volumetric variation during battery discharge/charge hinders the practical application. Herein, guided by the DFT calculation, Sb/Fe2S3 was fabricated by annealing Fe and Sb2S3 mixed powder. Next, Sb/Fe2S3 was blended with 15 wt % graphite by ball milling, yielding nano-Sb/Fe2S3 anchored on an exfoliated graphite composite (denoted as Sb/Fe2S3-15%). When applied as an anode of SIBs, Sb/Fe2S3-15% delivered reversible capacities of 565, 542, 467, 366, 285, and 236 mA h g-1 at current rates of 1, 2, 4, 6, 8, and 10 A g-1, respectively, surpassing most of the Sb-based anodes. The co-existence of highly conductive Fe2S3 and Sb minimizes the polarization of the anode. Our experiments proved that the Sb and Fe2S3 phases were reversible during discharge/charge cycling, and the exfoliated graphite can accelerate the Na+ diffusion and e- conduction. The proposed synthesis method of this work can also be applicable to synthesize various antimony/transition metal sulfide heterostructures (Sb/M1-xS), which may be applied in a series of fields.

Polycrystalline Fe- and Sn-based sulfides for high-capacity sodium-ion battery anodes.

Nano-polycrystalline Sn2S3/Sn3S4/FeS/Fe7S8 sulfides anchored on graphene were synthesized via annealing SnS2 and Fe followed by homogeneously combining them with exfoliated graphite. When applied as an anode for a sodium-ion battery, the reversible capacity reached 863 mA h g-1 at 100 mA g-1. This facial materials synthesis method may be applied in various fields.

Manageable Bubble Release Through 3D Printed Microcapillary for Highly Efficient Overall Water Splitting.

Porous metal foams (e.g., Ni/Cu/Ti) are applied as catalyst supports extensively for water splitting due to their large specific area and excellent conductivity, however, intrinsic bubble congestion is unavoidable because of the irregular three-dimensional (3D) networks, resulting in high polarization and degraded electrocatalytic performances. To boost the H2 O decomposition kinetics, the immediate bubble removal and water supply sequential in the gas-liquid-solid interface is essential. Inspired by the high efficiency of water/nutrient transport in the capillaries plants, this work designs a graphene-based capillary array with side holes as catalyst support to manage the bubble release and water supply via a Z-axis controllable digital light processing (DLP) 3D printing technology. Like planting rice, a low-cost, high-active CoNi carbonate hydroxide (CoNiCH) is planted on support. A homemade cell can reach 10 mA cm-2 in 1.51 V, and be kept at 30 mA cm-2 for 60 h without noticeable degradation, surpassing most of the known cells. This research provides a promising avenue to design and prepare advanced catalysts in various fields, including energy applications, pollutant treatment, and chemical synthesis.

3D Printing of Multiscale Ti64-Based Lattice Electrocatalysts for Robust Oxygen Evolution Reaction.

Electrically assisted water splitting is an endurable strategy for hydrogen production, but the sluggish kinetics of oxygen evolution reaction (OER) extremely restrict the large-scale production of hydrogen. Developing highly efficient and non-precious catalytic materials is essential to accelerate the sluggish kinetics of OER. However, currently used catalyst supports, such as copper foam, suffer from inferior corrosion resistance and structural stability, resulting in the disabled functionality of 3D conductive networks. To this end, a novel 3D freestanding electrode with corrosion-resistant and robust Ti-6Al-4V titanium alloy lattice as the catalyst support is designed via a 3D printing technology of selective laser melting. After the coating of core-shell Cu(OH)2@CoNi carbonate hydroxides (CoNiCH) on the designed lattice, a unique micro/nano-sized hierarchical porous structure is formed, which endows the electrocatalyst with a promising electrocatalytic activity (a low overpotential of 355 mV at 30 mA cm-2 and Tafel slope of 125.3 mV dec-1 ). Computational results indicate that the CoNiCH exhibits optimized electron transfer and the catalytic activity of the Ni site is higher than that of the Co site in the CoNiCH. Therefore, the integration of robust catalyst supports and highly active materials opens up an avenue for reliable and high-performance OER electrocatalysts.

In-Situ Templating Growth of Homeostatic GeP Nano-Bar Corals with Fast Electron-Ion Transportation Pathways for High Performance Li-ion Batteries.

We propose an in situ template method to directionally induce the construction of germanium phosphide nanobar (GeP-nb) corals with an adjustable aspect ratio. The GeP nanobars grown onto conductive matrix with high aspect ratio expose more quickest electron-ion transportation facets for fast reaction dynamics. The customized GeP-nb electrode delivers a self-healable homeostatic behavior by reversibly stabilizing GeP crystalline structure through multi-phase reactions to maintain structural integrity and cycling stability (850 mAh g-1 at 1 A g-1 after 500 cycles). As a result, the GeP-nb presents the highest Li+ diffusion coefficient (6.21×10-11  cm2 s-1 ) among all the Ge-based anode materials studied so far, rendering an excellent rate performance (620 mAh g-1 at 5 A g-1 ) as a lithium-ion battery (LIB) anode.

Confining Nano-GeP in Nitrogenous Hollow Carbon Fibers toward Flexible and High-Performance Lithium-Ion Batteries.

Although graphite has been used as anodes of lithium-ion batteries (LiBs) for 30 years, its unsatisfactory energy density makes it insufficient toward some new electronic products such as unmanned aerial vehicles. Herein, in situ synthesis of nano-GeP confined in nitrogen-doped carbon (GeP@NC) fibers was designed and performed via coaxial electrospinning followed by a phosphating process. This way ensured the paper-like GeP@NC-x electrode with high conductivity, high flexibility, and lightweight properties, which simultaneously solved the key scientific problems of difficulty in structural design and severe volume expansion of GeP. The inner diameter and wall thickness of the nanofibers can be effectively controlled by adjusting the size of electrospinning needles. It was suggested that the fibers not only effectively inhibited the growth of GeP, resulting in the synthesis of nano-GeP with size less than 50 nm, but also alleviated the volume expansion/agglomeration and improved the diffusion kinetics of Li+ in nano-GeP during cycling. The Li+ diffusion coefficient can be improved by reducing the inner diameter and wall thickness of the fibers. As a model system, the paper-like electrode (GeP@NC-2) with a fiber diameter of 280 nm and a wall thickness of 110 nm exhibited the best electrochemical performance. When applied as anodes in LiBs, it displayed a reversible capacity of 612 mAh g-1 at the 600th cycle at 1 A g-1, while GeP@NC-0 with a solid structure only delivered 239 mAh g-1. Furthermore, the GeP@NC-2 also exhibited good long-term cycling stability at 5 A g-1, and the capacity displayed a slight difference of 221.2 and 209.0 mAh g-1 in a voltage range of 0∼3 V and 0∼1.5 V, respectively. The well-defined synthetic approach combined with unique nanostructural design provided a meaningful reference for the rational design and development of next-generation flexible and high-performance LiB anodes.

Nano Sn2 S3 Embedded in Nitrogenous-Carbon Compounds for Long-Life and High-Rate Cycling Sodium-Ion Batteries.

Metallic tin (Sn) compounds are viewed as promising candidates for sodium-ion batteries (SIB) anode materials yet suffer from large volume expansion and limited electrode kinetics. Manufacturing rational structure is a crucial factor to achieve high-efficiency sodium storage for SIBs. In this study, nano Sn2 S3 embedded in nitrogenous-carbon compounds (nano-Sn2 S3 /C) was designed for SIB anode materials via a facile three-step strategy: precipitation, heat treatment and vulcanization with no templating agent. Density functional theory calculations suggested that Sn2 S3 displayed a low Na+ diffusion energy barrier and the Sn-S bonds could be rebuilt during the sodiation/de-sodiation process. Notably, electrochemical measurements coupled with ex-situ X-ray diffraction and ex-situ transmission electron microscopy were proposed to reveal the underlying Na+ storage mechanisms. Sn2 S3 acted as a high-capacity composition, while the porous nitrogenous-carbon matrix served as a rigid-conductive frame to accommodate the volume expansion and prevented the aggregation of nano Sn2 S3 . The rationally generated architectures benefited greatly in rate capacity and structural stability. As expected, the as-prepared nano Sn2 S3 /C exhibited remarkable rate capabilities with a specific capacity of 603 and 160 mAh g-1 under typical conditions at 0.2 and 4 A g-1 , respectively. This work may trigger new enthusiasm for engineering high-performance SIB anode materials.

Nano-GeTe Embedded in a Three-Dimensional Carbon Sponge for Flexible Li-Ion and Na-Ion Battery Anodes.

Among the germanium-based compounds, GeTe is a promising anode candidate that exhibits high theoretical capacity (856 mAh g-1 vs Li+/Li and 401 mAh g-1 vs Na+/Na) and low volume expansion during an ion intercalation/deintercalation process. Nevertheless, achieving good dispersion of metal-like GeTe in anode materials remains a significant challenge. Herein, hybrid GeTe/graphene (GeTe/G) is proposed as a highly efficient anode for LiBs and SiBs by facile ball milling. Pulverized GeTe is effectively anchored on peeled graphene sheets that can accelerate Li+ transport in electrodes as predicted by theoretical calculations and thus result in improved overall electrochemical performance. For instance, GeTe/G possesses a high reversible capacity of 478 mAh g-1 under 0.1 A g-1 in the 300th cycle. Moreover, by further cross-linking the GeTe/G using carbon nanotube (CNT) and carbon nanofiber pyrolysis from cotton cellulose, the as-prepared three-dimensional (3D) flexible anode possesses macropores that acted as positive channels favorably for ion transport. Remarkably, the as-prepared flexible 3D GeTe/G/CNT electrode with a thickness of 1050 µm exhibits a high reversible capacity of 451.4 mAh g-1 (4.38 mAh cm-2) vs Li+/Li and 372.5 mAh g-1 (2.08 mAh cm-2) vs Na+/Na, respectively, in the second cycle under 0.1 A g-1. These results shed some light on the direct application of 3D flexible carbon sponge electrodes in high-performance LiBs/SiBs.

Tunable Hollow Nanoreactors for In Situ Synthesis of GeP Electrodes towards High-Performance Sodium Ion Batteries.

The practical application of germanium phosphide (GeP) in battery systems is seriously impeded referring to the sluggish reaction kinetics and severe volume change. Nanostructure design that elaborately resolves the above issues is highly desired but still remains a big challenge. Herein, unique hollow nanoreactors assembled with nitrogen-doped carbon networks for in situ synthesis of the GeP electrodes are proposed for the first time. Such nanoreactors form a self-supported conductive network, ensuring sufficient electrolyte infiltration and fast electron transport. They restrain crystal growth and accommodate the volume expansion of GeP simultaneously. Reaction kinetics and confinement effect are optimized through nanoreactor size regulation. The optimized GeP electrode has high reversible capacities and outstanding cyclability and rate performance for sodium storage, outperforming most previously reported phosphides.

Core-shell (nano-SnX/nano-Li4Ti5O12)@C spheres (X = Se,Te) with high volumetric capacity and excellent cycle stability for lithium-ion batteries.

Among binary tin chalcogenides as anode materials for lithium-ion batteries, SnSe and SnTe have attracted attention due to their high theoretical volumetric capacity. However, they suffer from sluggish dynamics and serious agglomeration during lithiation/delithiation processes, which leads to inferior cycling performance. This study reports core-shell structure (nano-SnSe/nano-Li4Ti5O12)@C and (nano-SnTe/nano-Li4Ti5O12)@C [denoted as (n-SnX/n-LTO)@C] with extraordinary lithium storage stability. Benefiting from the well-designed structural merits, the core-shell structure of (n-SnX/n-LTO)@C is well preserved over 500 cycles, suggesting its high structural integrity. The (n-SnSe/n-LTO)@C and (n-SnTe/n-LTO)@C anodes deliver high initial volumetric capacities of 3470.1 and 3885.4 mA h cm-3 at 0.2 A g-1 and maintain capacities of 2066.0 and 1975.3 mA h cm-3 even after 500 cycles, respectively. This work provides a new avenue for designing novel binary tin chalcogenide lithium-ion battery anodes with high volumetric capacity and superior long-term cycling performance.