Laser-Induced Controllable Porosity in Additive Manufacturing Boosts Efficiency of Electrocatalytic Water Splitting.

In laser-based additive manufacturing (AM), porosity and unmelted metal powder are typically considered undesirable and harmful. Nevertheless in this work, precisely controlling laser parameters during printing can intentionally introduce controllable porosity, yielding a porous electrode with enhanced catalytic activity for the oxygen evolution reaction (OER). This study demonstrates that deliberate introduction of porosity, typically considered a defect, leads to improved gas molecule desorption, enhanced mass transfer, and increased catalytically active sites. The optimized P-93% electrode displays superior OER performance with an overpotential of 270 mV at 20 mA cm-2. Furthermore, it exhibits remarkable long-term stability, operating continuously for over 1000 h at 10 mA cm-2 and more than 500 h at 500 mA cm-2. This study not only provides a straightforward and mass-producible method for efficient, binder-free OER catalysts but also, if optimized, underscores the potential of laser-based AM driven defect engineering as a promising strategy for industrial water splitting.

A Hydrogel Electrolyte with High Adaptability over a Wide Temperature Range and Mechanical Stress for Long-Life Flexible Zinc-Ion Batteries.

Flexible zinc-ion batteries have garnered significant attention in the realm of wearable technology. However, the instability of hydrogel electrolytes in a wide-temperature range and uncontrollable side reactions of the Zn electrode have become the main problems for practical applications. Herein, N,N-dimethylformamide (DMF) to design a binary solvent (H2O-DMF) is introduced and combined it with polyacrylamide (PAM) and ZnSO4 to synthesize a hydrogel electrolyte (denoted as PZD). The synergistic effect of DMF and PAM not only guides Zn2+ deposition on Zn(002) crystal plane and isolates H2O from the Zn anode, but also breaks the hydrogen bonding network between water to improve the wide-temperature range stability of hydrogel electrolytes. Consequently, the symmetric cell utilizing PZD can stably cycle over 5600 h at 0.5 mA cm- 2@0.5 mAh cm-2. Furthermore, the Zn//PZD//MnO2 full cell exhibits favorable wide-temperature range adaptability (for 16000 cycles at 3 A g-1 under 25 °C, 750 cycles with 98 mAh g-1 at 0.1 A g-1 under -20 °C) and outstanding mechanical properties (for lighting up the LEDs under conditions of pressure, bending, cutting, and puncture). This work proposes a useful modification for designing a high-performance hydrogel electrolyte, which provides a reference for investigating the practical flexible aqueous batteries.

Anion Storing Boron Nitride Hybrid Nanosheets for High-Performance Dual Ion and Zinc Alkaline Full Cells.

Hexagonal boron nitride (BN), a well-known member of 2D materials, has a structure similar to graphene and is often referred to as white graphene. Despite its unique physical and chemical properties for energy storage applications, there have been very few studies on how BN stores anion carriers. Herein, the hybrid architecture and anion storage mechanism of BN nanosheets for high-performance hybrid energy storage full cells based on dual-ion and Zinc (Zn) alkaline systems is demonstrated. The chemical bonding between BN and reduced graphene oxide (rGO) is attributed to the formation of the heterointerface, which facilitates the charge transfer kinetics during an OH storing process. Based on the reversible surface redox reaction of BN and rGO hybrid (BN@rGO) confirmed by computational and spectroscopic analyses, the BN@rGO electrode is applied to both Na and OH dual-ion and Zn alkaline full cells. In the dual-ion system, Ti3C2‖BN@rGO full cells extended the operating voltage range up to 1.7 V, delivering a cell capacity of 49.4 mAh g-1 at 1000 mA g-1 and retaining 80% of its initial capacity after 40 000 cycles. In the Zn alkaline system, Zn‖BN@rGO full cells achieved a cell capacity of 58.1 mAh g-1 at 1000 mA g-1 and retained 80% capacity over 90 000 cycles.

Self-Powered Disinfection Using Triboelectric, Conductive Wires of Metal-Organic Frameworks.

Efficient water disinfection is vitally needed in rural and disaster-stricken areas lacking power supplies. However, conventional water disinfection methods strongly rely on external chemical input and reliable electricity. Herein, we present a self-powered water disinfection system using synergistic hydrogen peroxide (H2O2) assisted electroporation mechanisms driven by triboelectric nanogenerators (TENGs) that harvest electricity from the flow of water. The flow-driven TENG, assisted by power management systems, generates a controlled output with aimed voltages to drive a conductive metal-organic framework nanowire array for effective H2O2 generation and electroporation. The injured bacteria caused by electroporation can be further damaged by facile diffused H2O2 molecules at high throughput. A self-powered disinfection prototype enables complete disinfection (>99.9999% removal) over a wide range of flows up to 3.0 × 104 L/(m2 h) with low water flow thresholds (200 mL/min; ∼20 rpm). This rapid, self-powered water disinfection method is promising for pathogen control.

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High-performance Aqueous Zinc-Vanadium Batteries.

A zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn-ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi-functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in-situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high-valence Al3+ plays multifunctional roles of competing with Zn2+ for solvation and forming a Zn-Al alloy layer with a homogeneous electric field to mitigate the side reactions and dendrite generation. The Al-containing cathode-electrolyte interface considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn || Zn cell with KASO exhibits an ultra-long cycle of 6000 h at 2 mA cm-2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS-KASO electrolyte showed excellent cycling stability, even at a low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm-2). This study offers a practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are regarded as promising candidates in next-generation energy storage technology; however, the electrode materials in PIBs are usually restricted by the shortcomings of large volume expansion and poor cycling stability stemming from a high resistance towards diffusion and insertion of large-sized K ions. In this study, BiSbSx nanocrystals are rationally integrated with sulfurized polyacrylonitrile (SPAN) fibres through electrospinning technology with an annealing process. Such a unique structure, in which BiSbSx nanocrystals are embedded inside the SPAN fibre, affords multiple binding sites and a short diffusion length for K+ to realize fast kinetics. In addition, the molecular structure of SPAN features robust chemical interactions for stationary diffluent discharge products. Thus, the electrode demonstrates a superior potassium storage performance with an excellent reversible capacity of 790 mAh g-1 (at 0.1 A g-1 after 50 cycles) and 472 mAh g-1 (at 1 A g-1 after 2000 cycles). It's one of the best performances for metal dichalcogenides anodes for PIBs to date. The unusual performance of the BiSbSx @SPAN composite is attributed to the synergistic effects of the judicious nanostructure engineering of BiSbSx nanocrystals as well as the chemical interaction and confinement of SPAN fibers.

In†Situ Electropolymerization Enables Ultrafast Long Cycle Life and High-Voltage Organic Cathodes for Lithium Batteries.

Organic cathode materials have attracted extensive attention because of their diverse structures, facile synthesis, and environmental friendliness. However, they often suffer from insufficient cycling stability caused by the dissolution problem, poor rate performance, and low voltages. An in situ electropolymerization method was developed to stabilize and enhance organic cathodes for lithium batteries. 4,4',4''-Tris(carbazol-9-yl)-triphenylamine (TCTA) was employed because carbazole groups can be polymerized under an electric field and they may serve as high-voltage redox-active centers. The electropolymerized TCTA electrodes demonstrated excellent electrochemical performance with a high discharge voltage of 3.95 V, ultrafast rate capability of 20 A g-1 , and a long cycle life of 5000 cycles. Our findings provide a new strategy to address the dissolution issue and they explore the molecular design of organic electrode materials for use in rechargeable batteries.

A Redox-Active 2D Metal-Organic Framework for Efficient Lithium Storage with Extraordinary High Capacity.

Metal-organic framework cathodes usually exhibit low capacity and poor electrochemical performance for Li-ion storage owing to intrinsic low conductivity and inferior redox activity. Now a redox-active 2D copper-benzoquinoid (Cu-THQ) MOF has been synthesized by a simple solvothermal method. The abundant porosity and intrinsic redox character endow the 2D Cu-THQ MOF with promising electrochemical activity. Superior performance is achieved as a Li-ion battery cathode with a high reversible capacity (387 mA h g-1 ), large specific energy density (775 Wh kg-1 ), and good cycling stability. The reaction mechanism is unveiled by comprehensive spectroscopic techniques: a three-electron redox reaction per coordination unit and one-electron redox reaction per copper ion mechanism is demonstrated. This elucidatory understanding sheds new light on future rational design of high-performance MOF-based cathode materials for efficient energy storage and conversion.

Red Phosphorus Nanoparticle@3D Interconnected Carbon Nanosheet Framework Composite for Potassium-Ion Battery Anodes.

Red phosphorus (P) has been recognized as a promising storage material for Li and Na. However, it has not been reported for K storage and the reaction mechanism remains unknown. Herein, a novel nanocomposite anode material is designed and synthesized by anchoring red P nanoparticles on a 3D carbon nanosheet framework for K-ion batteries (KIBs). The red P@CN composite demonstrates a superior electrochemical performance with a high reversible capacity of 655 mA h g-1 at 100 mA g-1 and a good rate capability remaining 323.7 mA h g-1 at 2000 mA g-1 , which outperform reported anode materials for KIBs. The transmission electron microscopy and theoretical calculation results suggest a one-electron reaction mechanism ofP + K+ + e- → KP, corresponding to a theoretical capacity of 843 mA h g-1 ,which is the highest value for anode materials investigated for KIBs. The study not only sheds light on the rational design of high performance red P anodes for KIBs but also offers a fundamental understanding of the potassium storage mechanism of red P.

Recent research progress in non-aqueous potassium-ion batteries.

Large-scale energy storage technologies are in high demand for effective utilization of intermittent electricity generations and efficient electric power transmission. The feasibility of lithium-ion batteries for large-scale energy storage is under debate due to the scarcity and uneven distribution of lithium resources in the Earth's crust. Therefore, there arises tremendous interest in pursuing alternative energy storage systems based on earth-abundant materials. Recently, non-aqueous potassium-ion batteries (KIBs) are emerging as a promising energy storage system due to the abundance of potassium and the encouraging battery performance. Here, the recent research progress in non-aqueous KIBs is summarized, including electrode materials, electrolytes, battery architectures and fundamental electrochemical processes. The challenges and future research opportunities are also briefly discussed.

Synergistic Cationic Shielding and Anionic Chemistry of Potassium Hydrogen Phthalate for Ultrastable Zn─I2 Full Batteries.

Electrolyte additives are investigated to resolve dendrite growth, hydrogen evolution reaction, and corrosion of Zn metal. In particular, the electrostatic shielding cationic strategy is considered an effective method to regulate deposition morphology. However, it is very difficult for such a simple cationic modification to avoid competitive hydrogen evolution reactions, corrosion, and interfacial pH fluctuations. Herein, multifunctional additives of potassium hydrogen phthalate (KHP) based on the synergistic design of cationic shielding and anionic chemistry for ultrastable Zn||I2 full batteries are demonstrated. K cations, acting as electrostatic shielding cations, constructed the smooth deposition morphology. HP anions can enter the first solvation shell of Zn2+ for the reduced activities of H2O, while they remain in the primary solvation shell and are finally involved in the formation of SEI, thus accelerating the charge transfer kinetics. Furthermore, by in situ monitoring the near-surface pH of the Zn electrode, the KHP additives can effectively inhibit the accumulation of OH- and the formation of by-products. Consequently, the symmetric cells achieve a high stripping-plating reversibility of over 4500 and 2600 h at 1.0 and 5 mA cm-2, respectively. The Zn||I2 full cells deliver an ultralong term stability of over 1400 cycles with a high-capacity retention of 78.5%.

Cube-like anatase TiO2 mesocrystals as effective electron-transporting materials toward high-performance perovskite solar cells.

Electron-transporting materials (ETMs) with higher carrier mobility and a suitable band gap structure play a significant role in determining the photovoltaic performance of perovskite solar cells (PSCs). Herein, cube-like mesoporous single-crystal anatase TiO2 (Meso-TiO2) nanoparticles synthesized by using a facile hydrothermal method were utilized as an efficient ETM for PSCs. The superior semiconducting properties of the Meso-TiO2 based ETM enabled the best power conversion efficiency (PCE) of 20.05% for a PSC. Moreover, the device retained 80% of its initial PCE after being stored in ambient conditions for 20 days under 25 ± 5% relative humidity. In contrast to the commercial TiO2 ETM, the Meso-TiO2 ETM based PSC showed a distinguished interface with better interfacial conditions and improved carrier extraction originating from the cube-like mesoporous single-crystal anatase TiO2 ETM.

Single-Phase Ternary Compounds with a Disordered Lattice and Liquid Metal Phase for High-Performance Li-Ion Battery Anodes.

Si is considered as the promising anode materials for lithium-ion batteries (LIBs) owing to their high capacities of 4200 mAh g-1 and natural abundancy. However, severe electrode pulverization and poor electronic and Li-ionic conductivities hinder their practical applications. To resolve the afore-mentioned problems, we first demonstrate a cation-mixed disordered lattice and unique Li storage mechanism of single-phase ternary GaSiP2 compound, where the liquid metallic Ga and highly reactive P are incorporated into Si through a ball milling method. As confirmed by experimental and theoretical analyses, the introduced Ga and P enables to achieve the stronger resistance against volume variation and metallic conductivity, respectively, while the cation-mixed lattice provides the faster Li-ionic diffusion capability than those of the parent GaP and Si phases. The resulting GaSiP2 electrodes delivered the high specific capacity of 1615 mAh g-1 and high initial Coulombic efficiency of 91%, while the graphite-modified GaSiP2 (GaSiP2@C) achieved 83% of capacity retention after 900 cycles and high-rate capacity of 800 at 10,000 mA g-1. Furthermore, the LiNi0.8Co0.1Mn0.1O2//GaSiP2@C full cells achieved the high specific capacity of 1049 mAh g-1 after 100 cycles, paving a way for the rational design of high-performance LIB anode materials.

Progressive activation of porous vanadium nitride microspheres with intercalation-conversion reactions toward high performance over a wide temperature range for zinc-ion batteries.

Rechargeable aqueous zinc-ion batteries have great promise for becoming next-generation storage systems, although the irreversible intercalation of Zn2+ and sluggish reaction kinetics impede their wide application. Therefore, it is urgent to develop highly reversible zinc-ion batteries. In this work, we modulate the morphology of vanadium nitride (VN) with different molar amounts of cetyltrimethylammonium bromide (CTAB). The optimal electrode has porous architecture and excellent electrical conductivity, which can alleviate volume expansion/contraction and allow for fast ion transmission during the Zn2+ storage process. Furthermore, the CTAB-modified VN cathode undergoes a phase transition that provides a better framework for vanadium oxide (VOx). With the same mass of VN and VOx, VN provides more active material after phase conversion due to the molar mass of the N atom being less than that of the O atom, thus increasing the capacity. As expected, the cathode displays an excellent electrochemical performance of 272 mAh g-1 at 5 A g-1, high cycling stability up to 7000 cycles, and excellent performance over a wide temperature range. This discovery creates new possibilities for the development of high-performance multivalent ion aqueous cathodes with rapid reaction mechanisms.

Adaptive Ionization-Induced Tunable Electric Double Layer for Practical Zn Metal Batteries over Wide pH and Temperature Ranges.

The violent side reactions of Zn metal in aqueous electrolyte lead to sharp local-pH fluctuations at the interface, which accelerate Zn anode breakdown; thus, the development of an optimization strategy to accommodate a wide pH range is particularly critical for improving aqueous Zn metal batteries. Herein, we report a pH-adaptive electric double layer (EDL) tuned by glycine (Gly) additive with pH-dependent ionization, which exhibits excellent capability to stabilize Zn anodes in wide-pH aqueous electrolytes. It is discovered that a Gly-ionic EDL facilitates the directed migration of charge carriers in both mildly acidic and alkaline electrolytes, leading to the successful suppression of local saturation. It is worth mentioning that the regulation effect of the additive concentration on the inner Helmholtz plane (IHP) structure of Zn electrodes is clarified in depth. It is revealed that the Gly additives without dimerization can develop orderly and dense vertical adsorption within the IHP to effectively reduce the EDL repulsive force of Zn2+ and isolate H2O from the anode surface. Consequently, they Zn anode with tunable EDL exhibits superior electrochemical performance in a wide range of pH and temperature, involving the prodigious cycle reversibility of 7000 h at Zn symmetric cells with ZnSO4-Gly electrolytes and an extended lifespan of 50 times in Zn symmetric cells with KOH-Gly electrolytes. Moreover, acidic Zn powder||MnO2 pouch cells, and alkaline high-voltage Zn||Ni0.8Co0.1Mn0.1O2 cells, and Zn||NiCo-LDH cells also deliver excellent cycling reversibility. The tunable EDL enables the ultrahigh depth of discharge (DOD) of 93%. This work elucidates the design of electrolyte additives compatible in a wide range of pH and temperature, which might cause inspiration in the fields of practical multiapplication scenarios for Zn anodes.

Rapid synthesis of layered K x MnO2 cathodes from metal-organic frameworks for potassium-ion batteries.

Layered transition metal oxides (LTMOs) are a kind of promising cathode materials for potassium-ion batteries because of their abundant raw materials and high theoretical capacities. However, their synthesis always involves long time calcination at a high temperature, leading to low synthesis efficiency and high energy consumption. Herein, an ultra-fast synthesis strategy of Mn-based LTMOs in minutes is developed directly from alkali-transition metal based-metal-organic frameworks (MOFs). The phase transformation from the MOF to LTMO is systematically investigated by thermogravimetric analysis, variable temperature optical microscopy and X-ray diffraction, and the results reveal that the uniform distribution of K and Mn ions in MOFs promotes fast phase transformation. As a cathode in potassium-ion batteries, the fast-synthesized Mn-based LTMO demonstrates an excellent electrochemical performance with 119 mA h g-1 and good cycling stability, highlighting the high production efficiency of LTMOs for future large-scale manufacturing and application of potassium-ion batteries.

Ultrafast Synthesis of Layered Transition-Metal Oxide Cathodes from Metal-Organic Frameworks for High-Capacity Sodium-Ion Batteries.

Layered transition-metal oxides are promising candidate cathode materials for sodium-ion batteries due to their abundant raw materials and high theoretical capacity. Nevertheless, a long-time high-temperature heat treatment is required in traditional preparation methods, leading to low synthesis efficiency and waste of energy. Herein, an ultrafast preparation method of layered transition-metal oxides was proposed through minute calcination of metal-organic frameworks (MOFs). The homogeneous distribution of different atoms in MOFs allows fast phase transition during the calcination process. P'2-phase layered sodium manganese oxide was successfully obtained and demonstrated excellent electrochemical performance, with a high reversible capacity of 212 mA h g-1 and a cycling performance of 84% capacity retention after 100 cycles. Furthermore, this method can be expanded to a wide variety of MOF precursors and oxide electrode materials for different types of batteries. Our findings provide an efficient and cost-effective synthesis method for high-performance layered transition-metal oxide cathodes.

High-Rate, Large Capacity, and Long Life Dendrite-Free Zn Metal Anode Enabled by Trifunctional Electrolyte Additive with a Wide Temperature Range.

Aqueous Zn-ion batteries (AZIBs) have been recognized as promising energy storage devices due to their high theoretical energy density and cost-effectiveness. However, side reactions and Zn dendrite generation during cycling limit their practical application. Herein, ammonium acetate (CH3 COONH4 ) is selected as a trifunctional electrolyte additive to enhance the electrochemical performance of AZIBs. Research findings show that NH4 + (oxygen ligand) and CH3 COO- (hydrogenligand) with preferential adsorption on the Zn electrode surface can not only hinder Zn anode directly contact with active H2 O, but also regulate the pH value of the electrolyte, thus suppressing the parasitic reactions. Additionally, the formed SEI is mainly consisted of Zn5 (CO3 )2 (OH)6 with a high Zn2+ transference number, which could achieve a dendrite-free Zn anode by homogenizing Zn deposition. Consequently, the Zn||Zn symmetric batteries with CH3 COONH4 -based electrolyte can operate steadily at an ultrahigh current density of 40 mA cm-2 with a cumulative capacity of 6880 mAh cm-2 , especially stable cycling at -10 °C. The assembled Zn||MnO2 full cell and Zn||activated carbon capacitor also deliver prominent electrochemical reversibility. This work provides unique understanding of designing multi-functional electrolyte additive and promotes a long lifespan at ultrahigh current density for AZIBs.

Soluble Organic Cathodes Enable Long Cycle Life, High Rate, and Wide-Temperature Lithium-Ion Batteries.

Organic electrode materials free of rare transition metal elements are promising for sustainable, cost-effective, and environmentally benign battery chemistries. However, severe shuttling effect caused by the dissolution of active materials in liquid electrolytes results in fast capacity decay, limiting their practical applications. Here, using a gel polymer electrolyte (GPE) that is in situ formed on Nafion-coated separators, the shuttle reaction of organic electrodes is eliminated while maintaining the electrochemical performance. The synergy of physical confinement by GPE with tunable polymer structure and charge repulsion of the Nafion-coated separator substantially prevents the soluble organic electrode materials with different molecular sizes from shuttling. A soluble small-molecule organic electrode material of 1,3,5-tri(9,10-anthraquinonyl)benzene demonstrates exceptional electrochemical performance with an ultra-long cycle life of 10 000 cycles, excellent rate capability of 203 mAh g-1 at 100 C, and a wide working temperature range from -70 to 100 °C based on the solid-liquid conversion chemistry, which outperforms all previously reported organic cathode materials. The shielding capability of GPE can be designed and tailored toward organic electrodes with different molecular sizes, thus providing a universal resolution to the shuttling effect that all soluble electrode materials suffer.

Highly Potassiophilic Carbon Nanofiber Paper Derived from Bacterial Cellulose Enables Ultra-Stable Dendrite-Free Potassium Metal Anodes.

Potassium-metal batteries are attractive candidates for low-cost and large-scale energy storage systems due to the abundance of potassium. However, K metal dendrite growth as well as volume expansion of K metal anodes on cycling have significantly hindered its practical applications. Although enhanced performance has been reported using carbon hosts with complicated structure engineering, they are not suitable for mass production. Herein, a highly potassiophilic carbon nanofiber paper with abundant oxygen-containing functional groups on the surface and a 3D interconnected network architecture is fabricated through a facile, scalable, and environmental-friendly biosynthesis method. As a host for K metal anode, uniform K nucleation and stable plating/stripping performance are demonstrated, with a stable cycling of 1400 h and a low overpotential of 45 mV, which are much better than all carbon hosts without complicated structure engineering. Moreover, full cells pairing the carbon nanofiber paper/K composite anodes with K4Fe(CN)6 cathodes exhibit excellent cycle stability and rate capability. The results provide a promising way for realizing dendrite-free K metal anodes and high-performance potassium-ion batteries.