Conventional Cathode Research Articles

MoO2 Nanoclusters Embedded in Hierarchical Nitrogen Doped Carbon Nanoflower as Electrocatalytic Mediators in Aqueous Zinc-Tellurium Batteries: Enhancing Electrochemical Kinetics of Tellurium Redox Reaction.

Aqueous zinc-ion batteries (AZIBs) are considered to be one of the most promising devices for large-scale energy storage systems owing to their high theoretical capacity, environmental friendliness, and safety. However, the ionic intercalation or surface redox mechanisms in conventional cathode materials generally result in unsatisfactory capacities. Conversion-type aqueous zinc-tellurium (Zn-Te) batteries have recently gained widespread attention owing to their high theoretical specific capacities. However, it remains an enormous challenge to improve the slow kinetics of the aqueous Zn-Te batteries. Here, MoO2 nanoclusters embedded in hierarchical nitrogen-doped carbon nanoflower (MoO2 /NC) hosts are successfully synthesized and loaded with Te in aqueous Zn-Te batteries. Benefitting from the highly dispersed MoO2 nanoclusters and hierarchical nanoflower structure with a large specific surface area, the electrochemical kinetics of the Te redox reaction are significantly improved. As a result, the Te-MoO2 /NC electrode exhibits superior cycling stability and a high specific capacity of 493 mAh g-1 at 0.1 A g-1 . Meanwhile, the conversion mechanism is systematically explored using a variety of ex situ characterization methods. Therefore, this study provides a novel approach for enhancing the kinetics of the Te redox reaction in aqueous Zn-Te batteries.

Influence of applied magnetic field in an air-breathing microwave plasma cathode

The air-breathing electric propulsion concept refers to a spacecraft in very-low Earth orbit (VLEO) ingesting upper atmospheric air as propellant for an electric thruster. This compensates atmospheric drag and allows the spacecraft to maintain its orbital altitude, removing the need for on-board propellant storage and allowing an extended mission duration which is not limited by propellant exhaustion. There is a need for development of a robust, high current density and long life cathode (or neutralizer) for air-breathing electrostatic thrusters as conventional thermionic hollow cathodes are susceptible to oxygen poisoning. An Air-breathing Microwave Plasma CAThode is proposed to overcome this issue through the use of a microwave plasma discharge, producing an extracted current in the order of 1 A with 0.1 mg s−1 of air. In this paper, the effect of varying magnetic-field strength and topology is investigated by using an electromagnet coil, which reveals a significantly different behaviour for air compared to xenon. The extracted current with xenon increases by 3.9 times from the zero-field value up to a peak around 150 mT magnetic-field strength at the antenna, whereas an applied field does not increase the extracted current with air at nominal conditions. A non-zero magnetic-field with air is however beneficial for current extraction at reduced neutral densities. A distinct increase in extracted current is identified at low bias voltages with air for a field strength of around 50 mT at the internal microwave antenna, consistent across varying field topologies. The effect of a lowered magnetic-field strength in the orifice region is investigated through the use of a secondary coil, resulting in an extracted current increase of 25% for a relaxation from 6 mT to 1 mT, and demonstrating the beneficial impact of a locally reduced field strength on electron extraction.

Delocalized Lithium Ion Flux by Solid-State Electrolyte Composites Coupled with 3D Porous Nanostructures for Highly Stable Lithium Metal Batteries.

This work investigates the root cause of failure with the ultimate anode, Li metal, when employing conventional/composite separators and/or porous anodes. Then a feasible route of utilizing Li metal is presented. Our operando and microscopy studies have unveiled that Li+ flux passing through the conventional separator is not uniform, resulting in preferential Li plating/stripping. Porous anodes alone are subject to clogging with moderate- or high-loading cathodes. Here we discovered it is necessary to seek synergy from our separator and anode pair to deliver delocalized Li+ to the anode and then uniformly plate Li metal over the large surface areas of the porous anode. Our polymer composite separator containing a solid-state electrolyte (SE) can provide numerous Li+ passages through the percolated SE and pore networks. Our finite element analysis and comparative tests disclosed the synergy between the homogeneous Li+ flux and current density reduction on the anode. Our composite separators have induced compact and uniform Li plating with robust inorganic-rich solid electrolyte interphase layers. The porous anode decreased the nucleation overpotential and interfacial contact impedance during Li plating. Full cell tests with LiFePO4 and Li[Ni0.8Mn0.1Co0.1]O2 (NMC811) exhibited remarkable cycling behaviors: ∼80% capacity retention at the 750th and 235th cycle, respectively. A high-loading NMC811 (4 mAh cm-2) full cell displayed maximum cell-level energy densities of 334 Wh kg-1 and 783 Wh L-1. This work proposes a solution for raising energy density by adopting Li metal, which could be a viable option considering only incremental advancement in conventional cathodes lately.

Study of Mass Transfer Enhancement of Electrolyte Flow Field by Rotating Cathode in Through-Mask Electrochemical Micromachining.

To solve the problem of the nonuniform distribution of temperature and electrolytic products in the electrolyte flow field during through-mask electrochemical micromachining, the use of a rotating cathode with surface structures is proposed. The rotation of the cathode increases the efficiency of heat and mass transfer by the electrolyte flow. Simulations are performed to analyze the influence of the type of surface structure, the number of surface structures, and the rotational speed of the cathode on the electrolyte flow field. The results show that the use of a rotating cathode with surface structures significantly improves the mass transfer efficiency of the electrolyte flow field in comparison with a conventional cathode structure, and, in particular, a grooved rotating cathode can increase the outlet flow velocity by about 23%. An experimental demonstration of micropit array processing shows that the use of a grooved rotating cathode increases the mass transfer efficiency by 34% and the processing efficiency by nearly 40% compared with a smooth-surfaced rotating cathode. The grooved rotating cathode also gives the highest machining accuracy. Using this cathode, a uniform micropit array with an average micropit diameter of 201.83 μm, a diameter standard deviation of 3.49 μm, and a depth standard deviation of 0.87 μm is processed.

Modifying La0.5Sr0.5MnO3 with the U element leads to the formation of nanocomposites as a cathode for proton-conducting SOFCs

Sr-doped LaMnO3 (LSM) is a conventional cathode material for traditional solid oxide fuel cells (SOFCs), but its application in proton-conducting SOFCs is unsatisfactory due to the lack of catalytic activity of LSM at intermediate temperatures. Various strategies have been employed to optimize LSM performance, but no radiative element has been utilized. In this study, uranium was used to modify LSM. The U-doped LSM (LSMU) was not a pure phase but rather a mixture of LSM and SrUO4. The formation of oxygen vacancy was promoted at the LSM/SrUO4 interface, as indicated by first-principles calculations and experimental studies, potentially enhancing the oxygen reduction reaction (ORR) activity of the material. Using LSMU as the cathode, the proton-conducting SOFC (H–SOFC) reaches a peak power density of 1206 mW cm−2 at 700 °C, significantly greater than the LSM cell, which reached only 522 mW cm−2 under the same testing conditions. In addition, the current LSMU cell demonstrated the highest power output for LSM-based H–SOFCs to date, proving the LSUM to be an effective cathode for H–SOFCs. This study demonstrated a potential method for immobilizing uranium in a perovskite cathode oxide with improved performance for H–SOFCs.

Aging Property of Halide Solid Electrolyte at the Cathode Interface.

Halide solid electrolytes have recently emerged as a promising option for cathode-compatible catholytes in solid-state batteries (SSBs), owing to their superior oxidation stability at high voltage and their interfacial stability. However, their day- to month-scale aging at the cathode interface has remained unexplored until now, while its elucidation is indispensable for practical deployment. Herein, the stability of halide solid electrolytes (e.g., Li3 InCl6 ) when used with conventional layered oxide cathodes during extended calendar aging is investigated. It is found that, contrary to their well-known oxidation stability, halide solid electrolytes can be vulnerable to reductive side reactions with oxide cathodes (e.g., LiNi0.8 Co0.1 Mn0.1 O2 ) in the long term. More importantly, the calendar aging at a low state of charge or as-fabricated state causes more significant degradation than at a high state of charge, in contrast to typical lithium-ion batteries, which are more susceptible to high-state-of-charge calendar aging. This unique characteristic of halide-based SSBs is related to the reduction propensity of metal ions in halide solid electrolytes and correlated to the formation of an interphase due to the reductive decomposition triggered by the oxide cathode in a lithiated state. This understanding of the long-term aging properties provides new guidelines for the development of cathode-compatible halide solid electrolytes.

Flexible aqueous Zn–S battery based on an S-decorated Ti3C2Tx cathode

Flexible aqueous zinc-ion batteries can store energy safely and at a low cost, which benefits wearable electronic gadgets; however, currently used cathodes restrict these devices with a low specific capacity and energy density. Herein, we developed a flexible zinc-sulfur (Zn–S) battery constructed by Ti3C2Tx decorated with sulfur (S@Ti3C2Tx) as a cathode and Zn metal anode with iodine-added amphiphilic gel electrolyte (AGE). Benefiting from the confinement synergy of S@Ti3C2Tx cathode, the Zn-S battery exhibited a high storage capacity of 772.7 mAh g−1 at 300 mA g−1, which is higher than a conventional S-decorated carbon cathode (491.7 mAh g−1). More specially, the flexible device offers good cycling stability (82.7%) and excellent mechanical stability with 91% capacity retention after 90° bending (500 cycles). To demonstrate real applications, the flexible Zn–S batteries were integrated in series to power electrical gadgets (e.g., digital clock, light-emitting diode, and robot). It exhibits exceptional flexibility to sustain different deformations and maintains a steady supply of power to run the wearable electronic gadget. These findings offer a fresh starting point for flexible energy storage technologies and show the promising potential of the Zn–S battery in real-world applications.

A Mechanistic Insight into the Oxygen Redox of Li-Rich Layered Cathodes and their Related Electronic/Atomic Behaviors Upon Cycling.

Li-rich cathodes have been extensively investigated as their energy density is superior to Li stoichiometric cathode materials. In addition to the transition metal redox, this intriguing electrochemical performance originates from the redox reaction of the anionic sub-lattice. This new redox process, the so-called anionic redox or, more directly, oxygen redox in the case of oxides, almost doubles the energy density of Li-rich cathodes compared to conventional cathodes. Numerous theoretical and experimental investigations have thoroughly established the current understanding of the oxygen redox of Li-rich cathodes. However, different reports are occasionally contradictory, indicating that current knowledge remains incomplete. Moreover, several practical issues still hinder the real-world application of Li-rich cathodes. As these issues are related to phenomena resulting from the electronic to atomic evolution induced by unstable oxygen redox, a fundamental multiscale understanding is essential for solving the problem. In this review, we attempt to summarize the current mechanistic understanding of oxygen redox, the origin of the practical problems, and how current studies tackle the issues. This article is protected by copyright. All rights reserved.

Insights into Electrode Architectures and Lithium-Ion Transport in Polycrystalline V2 O5 Cathodes of Solid-State Batteries.

Polymer-based solid-state batteries (SSBs) have received increasing attentions due to the absence of interfacial problems in sulfide/oxide-type SSBs, but the lower oxidation potential of polymer-based electrolytes greatly limits the application of conventional high-voltage cathode such as LiNix Coy Mnz O2 (NCM) and lithium-rich NCM. Herein, this study reports on a lithium-free V2 O5 cathode that enables the applications of polymer-based solid-state electrolyte (SSE) with high energy density due to the microstructured transport channels and suitable operational voltage. Using a synergistic combination of structural inspection and non-destructive X-ray computed tomography (X-CT), it interprets the chemo-mechanical behavior that determines the electrochemical performance of the V2 O5 cathode. Through detailed kinetic analyses such as differential capacity and galvanostatic intermittent titration technique (GITT), it is elucidated that the hierarchical V2 O5 constructed through microstructural engineering exhibits smaller electrochemical polarization and faster Li-ion diffusion rates in polymer-based SSBs than those in the liquid lithium batteries (LLBs). By the hierarchical ion transport channels created by the nanoparticles against each other, superior cycling stability (≈91.7% capacity retention after 100 cycles at 1C) is achieved at 60 °C in polyoxyethylene (PEO)-based SSBs. The results highlight the crucial role of microstructure engineering in designing Li-free cathodes for polymer-based SSBs.

In situ construction of cubic 3D Li+ channels enabling stable electrochemical topology in a Li-rich layered solid-state oxide-based lithium-ion battery

Solid-state Li-ion batteries (SSLIBs) are expected to become the next-generation energy storage devices due to their high energy density and safe reliability. While the use of conventional cathodes in SSLIBs clearly cannot meet the increasing energy density demands of electric vehicles (EVs). A Li-rich Mn-based oxide (LRMO) has been extensively studied in liquid-state electrolytes (LEs) due to its higher capacity density (≥250 mAh g−1). However, the further application of LRMO in SSLIBs is rarely reported due to its extremely low electronic conductivity (10−11 S cm−1) and gas evolution at high voltage (≥4.3 V). This work demonstrates a novel in situ synthetic strategy for preparing enhanced cubic 3D Li+ channel buffered LRMO cathodes packaged with Li6.75La3Zr1.75Nb0.25O12 (LLZNO) solid electrolyte (SE) for use in SSLIBs. The stable electrochemical topology contributes to good initial discharge capacities (IDC, 0.1 C, 183.1 mAh g−1) and stable cycling retention (0.1 C, 300 cycles, 73.4%) at room temperature (RT, 25 °C). In situ tests analysis and first-principles calculations (DFT) results demonstrated the promising industrial prospects for using the LZM cathode in SSLIBs.

Customizing the morphology and microstructure of single-crystalline Ni-rich layered cathode materials for all-solid-state batteries

A single-crystalline Ni-rich cathode material is synthesized for high-performance all-solid-state batteries (ASSBs). We customize the morphology and microstructure of the material by optimizing the synthesis process (particle size control and post-heat treatment) and demonstrate the advantages of single-crystalline cathode materials for practical use in ASSBs. The particle density and particle hardness of single-crystalline cathode materials with a particle size of 5 μm are considerably higher than those of the conventional polycrystalline cathode materials that are composed of spherical aggregates of submicron-scale primary particles. These structural features of the single-crystalline cathode materials improve the long-term cycling performance and rate capability of an ASSB configured with an argyrodite–Li6PS5Cl solid electrolyte. This is mainly attributed to the intimate interfacial solid–solid contacts and enhanced diffusion kinetics induced by the monolithic morphology of the single-crystalline cathode materials in the electrode. Moreover, undesirable microcrack formation and particle fracture in cathode materials are effectively suppressed during cycling. The feasibility of ASSBs configured with single-crystalline Ni-rich cathode materials is examined in detail.

Prelithiation of Lithium Peroxide for Silicon Anode: Achieving a High Activation Rate.

The use of lithium peroxide (Li2O2) as a cost-effective low-weight prelithiation cathode additive was successfully demonstrated. Through a series of studies on the chemical stability of Li2O2 and the activation process of Li2O2 on the cathode, we revealed that Li2O2 is more compatible with conventional electrolyte and cathode laminate slurry than lithium oxide. Due to the significantly smaller size of commercial Li2O2, it can be used directly as a cathode additive. Moreover, the activation of Li2O2 on the cathode leads to the impedance growth of the cathode possibly resulting from the release of dioxygen and evacuation of Li2O2 inside the cathode. With the introduction of a new Li2O2 spread-coating technique on the cathode, the capacity loss was suppressed. Si||NMC full cells using Li2O2 spread-coated cathode demonstrated a highly promising activation rate of Li2O2 and significantly enhanced specific capacity and cycling stability compared to the uncoated full cells.

Sodium Rich Vanadium Oxy-Fluorophosphate - Na3.2 Ni0.2 V1.8 (PO4 )2 F2 O - as Advanced Cathode for Sodium Ion Batteries.

Conventional sodium-based layered oxide cathodes are extremely air sensitive and possess poor electrochemical performance along with safety concerns when operating at high voltage. The polyanion phosphate, Na3 V2 (PO4 )3 stands out as an excellent candidate due to its high nominal voltage, ambient air stability, and long cycle life. The caveat is that Na3 V2 (PO4 )3 can only exhibit reversible capacities in the range of 100 mAh g-1 , 20% below its theoretical capacity. Here, the synthesis and characterizations are reported for the first time of the sodium-rich vanadium oxyfluorophosphate, Na3.2 Ni0.2 V1.8 (PO4 )2 F2 O, a tailored derivative compound of Na3 V2 (PO4 )3 , with extensive electrochemical and structural analyses. Na3.2 Ni0.2 V1.8 (PO4 )2 F2 O delivers an initial reversible capacity of 117 mAh g-1 between 2.5 and 4.5V under the 1C rate at room temperature, with 85% capacity retention after 900 cycles. The cycling stability is further improved when the material is cycled at 50°C within 2.8-4.3V for 100 cycles. When paired with a presodiated hard carbon, Na3.2 Ni0.2 V1.8 (PO4 )2 F2 O cycled with a capacity retention of 85% after 500 cycles. Cosubstitution of the transition metal and fluorine in Na3.2 Ni0.2 V1.8 (PO4 )2 F2 O as well as the sodium-rich structure are the major factors behind the improvement of specific capacity and cycling stability, which paves the way for this cathode in sodium-ion batteries.

Boosting kinetics of tellurium redox reaction for high-performance aqueous zinc-tellurium batteries

Aqueous zinc-ion batteries have attracted extensive attention due to their environmental friendliness, low cost and high theoretical capacity. Among them, the conventional cathode materials mainly rely on ion intercalation or surface redox mechanisms, which usually exhibit unsatisfactory specific capacity. Currently, aqueous zinc-tellurium (Zn-Te) batteries based on conversion mechanisms have shown great potential to provide greater specific capacity. However, the sluggish electrochemical reaction kinetics limits the further development of Zn-Te batteries. Herein, the hierarchical structure was prepared by in situ growing MoS2 on N, F co-doped porous carbon nanosheets (MoS2@NFC), which served as Te hosts to construct aqueous Zn-Te batteries. Benefitting from the hierarchical structure and unique catalytic property of the MoS2@NFC, the kinetics of Te redox reaction was remarkably enhanced for aqueous Zn-Te batteries. As a result, the aqueous Zn-Te batteries based the Te-MoS2@NFC electrode exhibited high specific capacity (483 mAh g−1 at 150 mA g−1), outstanding rate performance and excellent cycling stability. Furthermore, the catalytic conversion mechanism of Zn-Te batteries was systematically explored through various ex-situ characterization methods and density functional theory (DFT) calculations. Therefore, this work provides a novel idea to design high performance conversion-type aqueous zinc-ion batteries.

Tailored interface composition improves the integrity of electrode/electrolyte interphases for high-voltage Ni-rich lithium metal batteries in a sulfolane-based electrolyte

High-voltage lithium metal batteries (LMBs) matched with Ni-rich cathodes can deliver high energy density to satisfy the rapid development of power battery systems. However, conventional solid electrolyte interphase (SEI) or cathode electrolyte interphase (CEI) composed of Li2CO3, Li2O, LiF and alkyl lithium carbonate cannot meet the requirements for high-voltage LMBs in terms of stability and mechanical performance. Herein, a sulfolane-based electrolyte assisted with co-solvent and dual-salt strategies is developed to realize tailored LiF-boride-sulfide-containing interphases on both electrodes, in which the decomposition product RSOx can combine various inorganic and organic components. The improved integrity of interphases can mitigate the continuous decomposition of the electrolyte, thereby promoting uniform and dense lithium deposition and protecting the structure of cathode materials. Thus, the prepared sulfolane-based electrolyte results in an average Coulombic efficiency of 99.1% for Li||Cu cells and enables 4.7 V Li||LiNi0.8Co0.1Mn0.1O2 cells to maintain 80.0% capacity retention after 200 cycles. Besides, Cu||LiNi0.8Co0.1Mn0.1O2 anode-free cells (3.5 mAh cm−2, capacity retention of 70.5% after 50 cycles) further confirm the practicality of the prepared electrolyte. This work offers a direct and efficient method to enhance the integrity and stability of interphases by optimizing the electrolyte composition.

A Critical Evaluation of Interfacial Stability in Li-excess Cation-disordered Rock-salt Oxide Cathode

Li-rich cation-disordered rock-salt oxides (DRXs) are promising candidates for next-generation Li-ion cathode materials due to the demonstrated high capacity (> 300 mAh g−1) by utilizing both transition metal (TM) cations and oxygen anions with a much-widened material design space as compared to conventional layered cathodes, which heavily rely on Co and Ni. However, the serious performance deterioration during long-term cycling impedes their practical applications. Although oxygen loss and associated densified surface layer are responsible for the performance deterioration, these issues are part of the scope of cathode electrolyte interface (CEI) which need further study, including its chemical composition, chemical and electrochemical stability, formation mechanism as well as the effects on battery performance. Through careful monitoring of the CEI evolution of Li1.2Mn0.4Ti0.4O2 (LMTO) in conventional carbonated-based electrolyte upon charging and discharging, we identify that the continuously growing CEI layer exhibits gradually increasing LiF as the main composition. The significant change of the CEI layer is closely related to loss of lattice oxygen (O2−), the continuous over-reduction of redox-active TMs (e.g. Mn3+, Mn 4+) from the cathode surface, severe TMs dissolution, and the release of CO2/O2, and irreversible phase transition in surface structures, which eventually cause a fast capacity degradation and voltage decay. This research provides a fundamental interpretation for understanding interfacial stability in this young class of DRX cathode materials.

Investigation on Thermal Efficiency Enhancement and Sideband Emission Suppression for Magnetron Injection Gun

At low-power operation, an approach with a capture structure is employed to absorb the trapped electrons for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{Ka}$</tex-math> </inline-formula> -band gyro-traveling wave tube (Gyro-TWT). When the power is further increased, the capture structure cannot play a role and the working current fluctuates. In subsequent experiments, the capture structure was found to have severe traces of melting. According to the position characteristics of the capture structure, the main reason for its melting is the phenomenon of sideband emission from the cathode of magnetron injection gun (MIG). In heat transfer systems of the conventional cathode, the rear electrode emits trapped electrons, which are accelerated by an electric field and bombard the capture structure. We adopted the scheme of adjusting the cathode heat transfer system. The enhanced cathode is called the isolated cathode (ISO-cathode). The test experiment proved that sideband emission is suppressed and thermal efficiency is improved. In the experiment, the cathode power decreased from 85 to 42 W when the operating temperature is at 1050 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C. In the end, the absorbed power of the capture structure is less than about 1/10 of the original power by simulation. The life and reliability of MIG are increased by ISO-cathode. The foundation is laid for further improvement on the average power by ISO-cathode.

A Mesoporous Tungsten Oxynitride Nanofibers/Graphite Felt Composite Electrode with High Catalytic Activity for the Cathode in Zn-Br Flow Battery.

High electrochemical polarization during a redox reaction in the electrode of aqueous zinc-bromine flow batteries largely limits its practical implementation as an effective energy storage system. This study demonstrates a rationally-designed composite electrode that exhibits a lower electrochemical polarization by providing a higher number of catalytically-active sites for faster bromine reaction, compared to a conventional graphite felt cathode. The composite electrode is composed of electrically-conductive graphite felt (GF) and highly active mesoporous tungsten oxynitride nanofibers (mWONNFs) that are prepared by electrospinning and simple heat treatments. Addition of the 1D mWONNFs to porous GF produces a web-like structure that significantly facilitates the reaction kinetics and ion diffusion. The cell performance achieves in this study demonstrated high energy efficiencies of 89% and 80% at current densities of 20 and 80mA cm-2 , respectively. Furthermore, the cell can also be operated at a very high current density of 160mA cm-2 , demonstrating an energy efficiency of 62%. These results demonstrate the effectiveness of the mWONNF/GF composite as the electrode material in zinc-bromine flow batteries.

High-rate deposition of ultra-thick silver film by hollow cathode magnetron sputtering

The deposition of high-performance micro-sized ultra-thick silver films is a critical issue. Hollow cathode magnetron sputtering is one of the promising techniques for depositing ultra-thick silver films. A novel cylindrical “three-dimensional magnetron sputtering” (3-DMS) magnet pack presented here was developed based on a conventional hollow cathode magnet pack to deposit high-performance ultra-thick silver film at a high rate. A stable process condition at the average power of 4 kW is realized by the new cylindrical “3-DMS” magnet pack's 137.5 mm diameter targets and a specially designed cooling well. Comparison of deposition rates with different power supplies and at different average power levels are discussed. The behavior of electrons on the target surface in this magnetic field arrangement is investigated using COMSOL Multiphysics software. The composition, topography, mechanical properties and residual stress of the ultra-thick silver film deposited by different sputtering modes (DCMS, HIPIMS, and Pulsed DCMS) are also discussed.

High-performance aqueous zinc-ion hybrid capacitors based on 3D printed metal-organic framework cathodes

The zinc-ion hybrid capacitor is a promising energy storage device, but current overall capacity is limited by the capacitance of the carbon cathode. We produced a hierarchically porous, nitrogen-doped carbon cathode with good cycling and mechanical stability by 3D printing and pyrolysis of the zinc-based metal–organic framework ZIF-8. When incorporated into a zinc-ion hybrid capacitor, we achieved an areal capacitance of 16.9 F cm−2 and energy density of 7.23 mW h cm−2, outperforming zinc-ion hybrid capacitors based on conventional cathodes.