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Owing to the advantages of high operating voltage, environmental benignity, and low cost, potassium-based dual-ion batteries (KDIBs) have been considered as a potential candidate for large-scale energy storage. However, KDIBs generally suffer from poor cycling performance and unsatisfied capacity, and inactive components of conductive agents, binders, and current collector further lower their overall capacity. Herein, we prepare coral-like carbon nanowires (CCNWs) doped with nitrogen as a binder-free anode material for K+-ion storage, in which the unique coral-like porous nanostructure and amorphous/short-range-ordered composite feature are conducive to enhancing the structural stability, to facilitating the ion transfer and to boosting the full utilization of active sites during potassiation/de-potassiation process. As a result, the CCNW anode possesses a hybrid K+-storage mechanism of diffusive behavior and capacitive adsorption, and stably delivers a high capacity of 276 mAh g-1 at 50 mA g-1, good rate capability up to 2 A g-1, and long-term cycling stability with 93 % capacity retention after 2000 cycles at 1 A g-1. Further, assembling this CCNW anode with an environmentally benign expanded graphite (EG) cathode yields a proof-of-concept KDIB, which shows a high specific capacity of 134.4 mAh g-1 at 100 mA g-1, excellent rate capability of 106.5 mAh g-1 at 1 A g-1, and long-term cycling stability over 1000 cycles without negligible capacity loss. This study provides a feasible approach to developing high-performance anodes for potassium-based energy storage devices.

Energy conversion technologies like fuel cells and metal-air batteries require oxygen reduction reaction (ORR) electrocatalysts with low cost and high catalytic activity. Herein, N-doped carbon spheres (N-CS) with rich micropore structure have been synthesized by a facile two-step method, which includes the polymerization of pyrrole and formaldehyde and followed by a facile pyrolysis process. During the preparation, zinc chloride (ZnCl2) was utilized as a catalyst to promote polymerization and provide a hypersaline environment. In addition, the morphology, defect content and activity area of the resultant N-CS catalysts could be regulated by controlling the content of ZnCl2. The optimum N-CS-1 catalyst demonstrated much better catalytic activity and durability towards ORR in alkaline conditions than commercial 20 wt% Pt/C catalysts, of which the half-wave potential reached 0.844 V vs. RHE. When applied in the Zn-air batteries as cathode catalysts, N-CS-1 showed a maximum power density of 175 mW cm-2 and long-term discharging stability of over 150 h at 10 mA cm-2, which outperformed 20 wt% Pt/C. The excellent performance could be due to its ultrahigh specific surface area of 1757 m2 g-1 and rich micropore channels structure. Meanwhile, this work provides an efficient method to synthesize an ultrahigh surface porous carbon material, especially for catalyst application.

The results of a study of the processes involved in the production of indium oxide In2O3 powder, which is widely used to create transparent and electrically conducting ceramics, are described. The powder was produced in a flow of rare gas (argon or helium) at atmospheric pressure under conditions for the formation of metal-containing plasma in a non-arc discharge mode. The discharge operated in pulsed mode with a pulse repetition rate of 70 kHz and pulse duration of 12 μs. The discharge current was 670 mA and discharge voltages were 180 V and 250 V when the working gases were argon and helium, respectively. These parameters ensure a mode in which the indium cap of a molybdenum cathode suffers thermal erosion. The morphology and elemental and phase composition of the erosion products were studied using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. It was shown that the structure of the synthesized powder particles corresponded to a phase of indium oxide (III) with a body-centered cubic (bcc) lattice with lattice parameter a = 1.013 nm. The powder particles, regardless of the working gas (Ar or He), consisted of non-stoichiometric indium oxide In2O3 with a nanocrystalline structure. The average particle diameter was = 13–16 nm.

Rechargeable magnesium batteries (RMBs), as one of the most promising candidates for efficient energy storage devices with high energy, power density and high safety, have attracted increasing attention. However, searching for suitable cathode materials with fast diffusion kinetics and exploring their magnesium storage mechanisms remains a great challenge. CuS submicron spheres, made by a facile low-temperature synthesis strategy, were applied as the high-performance cathode for RMBs in this work, which can deliver a high specific capacity of 396 mAh g−1 at 20 mA g−1 and a remarkable rate capacity of 250 mAh g−1 at 1000 mA g−1. The excellent rate performance can be assigned to the nano needle-like particles on the surface of CuS submicron spheres, which can facilitate the diffusion kinetics of Mg2+. Further storage mechanism investigations illustrate that the CuS cathodes experience a two-step conversion reaction controlled by diffusion during the electrochemical reaction process. This work could make a contribution to the study of the enhancement of diffusion kinetics of Mg2+ and the reaction mechanism of RMBs.

In General, a larger number of experimental data would be required for optimizing the performance efficiency of the electrodes in solid oxide fuel cells (SOFC), as it was likely to involve many complex chemical and physical reactions. Therefore, in this study, we have attempted the artificial intelligence (AI) technique for analyzing the performance of the anode and cathode electrodes of SOFC under various key parameters that normally influences the efficiency of the electrodes. Since the cost of SOFC elements is expensive, computational trials with the aid of AI would not only be curtailing the preparation cost but also ensures less time consumption. Among the variety of AI methods available in the literature, the Support Vector Machine (SVM) appears to be one of the excellent and effective machine learning techniques. Hence, we have developed a SVM model and predicted the maximum current density and power density of Nickel oxide-samarium-doped ceria (NiO-SDC) composite anode and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode electrodes of SOFC. The input parameters such as stack temperature, supply voltage were supplied to the SVM model and obtained maximum current density and power density as output and it decides the working performance of the electrodes. We have also predicted that the maximum current density and power density of 1160 mA cm2 and 225 mW cm2 respectively at 800 °C. To validate the results as predicted from SVM, we have experimented using Yttrium stabilized zirconia electrolyte-supported single cell with our prepared NiO-SDC anode and LSCF cathode which exhibited a maximum current and power density of 1170 mA cm2 and 227 mW cm2 at 800 °C using H2 as fuel. It has been found that that the theoretical predicted data current and power densities of the electrodes from the SVM approach reasonably agrees well with the experimental results.

This article presents a process for producing LiNi1-xAlxO2 (0 1-xAlxO2 (0 2 with LiOH and Al(OH)3, followed by lithiation at temperature range of 650–710 °C, after which any residual lithium from lithiation is washed from the particle surfaces. Electrochemical performance was studied within full-cell and half-cell application; in addition, different material characterization methods were carried out to explain structure changes when certain amount of aluminum is introduced in the LiNi1-xAlxO2 structure. Surface analyses were carried out to demonstrate how washing process changes the chemical environment of the LiNi1-xAlxO2 secondary particle surface. The results demonstrate how Al doping, lithiation temperature, and the washing process affect the performance of the LiNi1-xAlxO2 cathode material.

In this work, we have prepared the hierarchically nanostructured core–shell NiCo layered double hydroxide (NiCo-LDH) nanosheets- and ZnFe2O4 nanocubes-decorated polyacrylonitrile (PAN)/pitch-based carbon nanofibers (PPCNs) webs (NiCo-LDH@PPCNs as cathode and ZnFe2O4@PPCNs as anode materials) with the bonded network structure by a facile and scalable hydrothemal method. Herein, the low-cost pitch with lower softening point (∼90 °C) as co-precursor was utilized to produce the PAN/pitch-based carbon nanofibers (PPCNs) with enhanced electrical conductivity. The obtained PPCNs with pitch content of 30% (PP30CNs) electrode material delivered higher specific capacitance (∼67 F g−1) than that (∼48 F g−1) of the PAN-based carbon nanofibers (PCNs) at 1 A g−1, due to the increased electrical conductivity and lower interfacial charge transfer resistance (RCT) of ∼0.16 Ω. Further, the NiCo-LDH-decorated PP30CNs (NiCo-LDH@PP30CNs) as cathode material showed superior specific capacitance of 1162 F g−1 at 1.0 A g−1 and ultra-high retention rate of 91.56% at 10 A g−1. The ZnFe2O4@PP30CNs as anode material also showed higher specific capacitance of 282 F g−1 at 1 A g−1 and good rate capability with capacitance retention of 56.73% at 10 A g−1. The as-fabricated asymmetric NiCo-LDH@PP30CNs//ZnFe2O4@PP30CNs hybrid supercapacitor device delivered a specific capacitance of ∼98 F g−1 at 1 A g−1 and excellent capacitance retention of ∼88% after 5000 charge–discharge cycles.

Due to stringent environmental regulations and the limited resources of fossil-based fuels, there is an urgent demand for clean and eco-friendly energy conversion devices. These criteria appear to be met by hydrogen proton exchange membrane fuel cells (PEMFCs). PEMFCs have attracted tremendous attention on account of their excellent performance with tunable operability and good portability. Nonetheless, their practical applications are hugely influenced by the scarcity and high cost of platinum (Pt) used as electrocatalysts at both cathode and anode. Pt is also susceptible to easy catalyst poisoning. Herein, this paper reviews the progress of the research regarding the development of electrocatalysts practically used in hydrogen PEMFCs, where the corner-stone reactions are cathodic oxygen reduction reaction (ORR) and anodic hydrogen oxidation reaction (HOR). To reduce the costs of PEMFCs, lessening or eliminating the use of Pt is of prime importance. For current and forthcoming laboratory/large-scale PEMFCs, there is much interest in developing substitute catalysts based on cheaper materials. As such are non-platinum (non-Pt), non-platinum group metals (non-PGMs), metal oxides, and non-metal electrocatalysts. Hence, high-performance, state-of-the-art, and novel structured electrocatalysts as replacements for Pt are needed.

As a promising cathode material, Na3V2(PO4)2F3 (NVPF) has attracted wide attention for sodium-ion batteries (SIBs) because of its high operating voltage and high structural stability. However, the low intrinsic electronic conductivity and insufficient Na ion mobility of NVPF limit its development. Herein, K-doping NVPF is prepared through a facile ball-milling combined calcination method. The effects of K-doping on the crystal structure, kinetic properties and electrochemical performance are investigated. The results demonstrate that the Na2.90K0.10V2(PO4)3F3 (K0.10-NVPF) exhibits a high capacity (120.8 mAh g−1 at 0.1 C), high rate capability (66 mAh g−1 at 30 C) and excellent cycling performance (a capacity retention of 97.5% at 1 C over 500 cycles). Also, the occupation site of K ions in the lattice, electronic band structure and Na-ion transport kinetic property in K-doped NVPF are investigated by density functional theory (DFT) calculations, which reveals that the K-doped NVPF exhibits improved electronic and ionic conductivities, and located K+ ions in the lattice to contribute to high reversible capacity, rate capability and cycling stability. Therefore, the K-doped NVPF serves as a promising cathode material for high-energy and high-power SIBs.

A mechanically strong binder with polar functional groups could overcome the dilemma of the large volume change during charge/discharge processes and poor cyclability of lithium-sulfur batteries (LSBs). In this work, for the first time, we report the use of poly(thiourea triethylene glycol) (PTTG) as a multifunctional binder for sulfur cathodes to enhance the performance of LSBs. As expected, the PTTG binder facilitates the high performance and stability delivered by the Sulfur-PTTG cathode, including a higher reversible capacity of 825 mAh g−1 at 0.2 C after 80 cycles, a lower capacity fading (0.123% per cycle) over 350 cycles at 0.5 C, a higher areal capacity of 2.5 mAh cm−2 at 0.25 mA cm−2, and better rate capability of 587 mAh g−1 at 2 C. Such superior electrochemical performances could be attributed to PTTG's strong chemical adsorption towards polysulfides which may avoid the lithium polysulfide shuttle effect and excellent mechanical characteristics which prevents electrode collapse during cycling and allows the Sulfur-PTTG electrode to maintain robust electron and ion migration pathways for accelerated redox reaction kinetics.

Solid oxide fuel cells (SOFCs) are an all-solid energy conversion device from the chemical energy of fuels to electric energy at intermediate and high temperatures. Up to now, massive efforts have been made in developing different components of solid oxide fuel cells, including electrolyte, anode, cathode and interconnect materials. Rare earth elements play an indispensable role in different components of SOFCs which have been extensively studied in the recent decades. In this review, we concentrate upon the rare earth application and recent advances in SOFCs and related materials. Materials structure involved perovskites, Ruddlesden-Popper, fluorite, spinel, pyrochlore, apatite and so on. Moreover, the effects of rare earth based oxides as matrix or dopants in different components are also discussed. Structures and properties of the materials are related to the element type, valence, coordination and ion radius. This article will provide a comprehensive research direction towards SOFCs components for their composition, structural design and mechanisms research.

To explore the natural resources as sustainable precursors offers a family of green materials. The use of bio-waste precursors especially the remaining from food processing is a scalable, highly abundant, and cost-effective strategy. Exploring waste materials is highly important especially for new materials discovery in emerging energy storage technologies such as lithium sulfur batteries (LSBs). Herein, waste milk powder is carbonized and constructed as the sulfur host with the hollow micro-/mesoporous framework, and the resulting carbonized milk powder and sulfur (CMP/S) composites are employed as cathodes for LSBs. It is revealed that the hollow micro-/mesoporous CMP/S framework can not only accommodate the volume expansion but also endow smooth pathways for the fast diffusion of electrons and Li-ions, leading to both high capacity and long cycling stability. The CMP/S composite electrode with 56 wt.% loaded sulfur exhibits a remarkable initial capacity of 1596 mAh g−1 at 0.1 C, corresponding to 95% of the theoretical capacity. Even at a rate of 1 C, it maintains a high capacity of 730 mAh g−1 with a capacity retention of 72.6% after 500 cycles, demonstrating a very low capacity fading of only 0.05% per cycle. Importantly, the Coulombic efficiency is always higher than 96% during all the cycles. The only used source material is expired waste milk powders in our proposal. We believe that this “trash to treasure” approach will open up a new way for the utilization of waste material as environmentally safe and high performance electrodes for advanced LSBs.

Bimetallic PtPd nanowires are produced by the centrifugal electrospinning method and their application as electrocatalysts in the cathode of a proton exchange membrane fuel cell (PEMFC) is evaluated. The effects of system parameters on the morphology of PtPd nanowires after calcination are explored including the rotation speed of spinneret, applied electric field, and atomic ratio of Pt and Pd in the composition. Cyclic voltammetry tests are conducted to characterize the electrochemical property and the produced PtPd nanowires are employed to fabricate the cathode catalyst layer in a PEMFC. The cell performance is measured and compared with commercial Pt/C electrocatalysts. Results show that bimetallic PtPd nanowires can be produced successfully with minimum mean diameter of 79 ± 24 nm and maximum electrochemical active surface area (ECSA) of 10.29 m 2 g − 1 at the atomic ratio Pt:Pd = 3:1. By the accelerated degradation tests, the PtPd nanowires demonstrate better durability than Pt/C. The present results reveal that the centrifugal electrospinning method can successfully fabricate PtPd nanowires which have great potential to be utilized in PEMFCs.

Funding Information: This work has been supported by the China Scholarship Council (CSC), No. 201706250038 , the Jane and Aatos Erkko Foundation ASPIRE project (Finland), Aalto University School of Science Project T30404 , and the Start-up Package of T10108 Professorship offered by Aalto University to Prof. Yongdan Li. Publisher Copyright: © 2021 The Authors Anodic TiO2 nanotube (TNT) arrays have been intensively investigated as anodes in water splitting (WS) cells because of their excellent chemical stability. However, anodic TNT is seldom considered as a cathode for the hydrogen evolution reaction (HER) in an electrochemical WS cell. This study shows that a reduced TNT (R-TNT) sample prepared with a cathodic reduction technique without loading any co-catalyst can achieve remarkable HER performance. At − 1.0 V vs reversible hydrogen electrode in 1 M NaOH in dark, R-TNT achieved a current of − 221 mA, which is 17000-times of that achieved when using TNT and 5-times of that with Ti-foil as cathode. Chronopotentiometry tests were carried out sequentially at @ −100, − 50 and − 10 mA for 24 h and decay rates of 1.3%, 5.2% and 18.4% were measured, which indicate a good stability of the R-TNT sample.

Thin films were deposited using a vacuum arc with a refractory anode. The arc was sustained between a water cooled Zr cathode and a graphite anode. Both electrodes with diameter 32 mm and 30 mm length, with a gap of 10 mm between them. The distance from the arc axis to the substrate was 110 mm. The arc was operated either 40 or 60 s before a glass substrate was exposed to the plasma for 15 s. The film thickness was measured by profilometry. The deposition rate was obtained from the film thickness and exposition time. The visual radiation emitted by the plasma plume was photographed with a digital camera. The highest measured deposition rate was 0.71 μm/min, for an arc current of 225 A and time before exposure of 60 s.

Nowadays, Li–S batteries are considered as one of the most promising alternatives to Li-ion technology in the near future, thanks to their high specific capacity and their significantly lower environmental impact and production costs. Consequently, many efforts have been directed to tackle with the inherent issues that affect Li–S batteries. One of the main problems is the so-called shuttle effect, which basically entails the unwanted migration of lithium polysulfides (LiPSs) from the cathode to the anode side, causing the degradation of the cell. Here, we report an effective strategy to restrain the shuttle effect and increase the kinetics at the cathode of the lithium–sulfur (Li–S) battery. A functional layer including high entropy oxides (HEO) coated onto the sulfur cathode allows to exploit the HEOs capability as promoter catalysts for the conversion of LiPSs. Pure HEO powders are synthesized by fast, highly efficient microwave irradiation, followed by heat treatment at 930 °C. The formation of highly crystalline HEO is confirmed by X-ray diffraction analysis. The LiPSs adsorption capability of HEO is evaluated by UV–vis and X-ray photoelectron spectroscopy analyses. The effect of the HEO-coated sulfur cathode on the electrochemical performance of the Li–S battery is studied by cyclic voltammetry and galvanostatic charge/discharge. The cell with double-coated cathode delivers an initial discharge capacity of 1173 mAh/g at C/10 with 45% capacity retention over 500 cycles at C/5, approaching ~ 99% coulombic efficiency. Graphical abstract

Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P2O74− is selected to substitute the PO43− in Na3V2(PO4)3 (NVP) lattice and regulate the ratio of polyanion groups to prepare Na3+xV2(PO4)3−x(P2O7)x (NVPPx, 0 ≤ x ≤ 0.15) materials. The optimal Na3.1V2(PO4)2.9(P2O7)0.1 (NVPP0.1) material can deliver remarkably elevated specific capacity (104 mAh g−1 at 0.1 C, 60 mAh g−1 at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP0.1 exhibits outstanding cyclic stability (91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+ migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.

Pd modified electrodes possess problems such as easy agglomeration and low electrolytic ability, and the use of manganese dioxide (MnO2) to facilitate Pd reduction of organic pollutants is just started. However, there is still a limited understanding of how to match the Pd load and MnO2 to realize optimal dechlorination efficiency at minimum cost. Here, a Pd/MnO2/Ni foam cathode was successfully fabricated and applied for the efficient electrochemical dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP). The optimal electrocatalytic hydrodechlorination (ECH) performance with 2,4,6-TCP dechlorination efficiency (92.58% in 180 min) was obtained when the concentration of PdCl2 precipitation was 1 mmol/L, the deposition time of MnO2 was 300 s and cathode potential was −0.8 V. Performance influenced by the exogenous factors (e.g., initial pH and coexisted ions) were further investigated. It was found that the neutral pH was the most favorable for ECH and a reduction in dechlorination efficiency (6% ∼ 47.6%) was observed in presence of 5 mmol/L of NO 2 − , NO 3 − , S2− or SO 3 2 − . Cyclic voltammetry (CV) and quenching experiments verified the existence of three hydrogen species on Pd surface, including adsorbed atomic hydrogen (H*ads), absorbed atomic hydrogen (H*abs), and molecular hydrogen (H2). And the introduction of MnO2 promoted the generation of atomic H*. Only adsorbed atomic hydrogen (H*ads) was confirmed that it truly facilitated the ECH process. Besides H*ads induced reduction, the direct reduction by cathode electrons also participated in the 2,4,6-TCP dechlorination process. Pd/MnO2/Ni foam cathode shows excellent dechlorination performance, fine stability and recyclable potential, which provides strategies for the effective degradation of persistent halogenated organic pollutants in groundwater.

Lithium–sulfur (Li–S) battery is labeled as a promising high-energy-density battery system, but some inherent drawbacks of sulfur cathode materials using relatively complicated techniques impair the practical applications. Herein, an integrated approach is proposed to fabricate the high-performance rGO/VS4/S cathode composites through a simple one-step solvothermal method, where nano sulfur and VS4 particles are uniformly distributed on the conductive rGO matrix. rGO and sulfiphilic VS4 provide electron transfer skeleton and physical/chemical anchor for soluble lithium polysulfides (LiPS). Meanwhile, VS4 could also act as an electrochemical mediator to efficiently enhance the utilization and reversible conversion of LiPS. Correspondingly, the rGO/VS4/S composites maintain a high reversible capacity of 969 mAh/g at 0.2 C after 100 cycles, with a capacity retention rate of 82.3%. The capacity fade rate could lower to 0.0374% per cycle at 1 C. Moreover, capacity still sustains 795 mAh g–1 after 100 cycles in the relatively high-sulfur-loading battery (6.5 mg/cm2). Thus, the suggested method in configuring the sulfur-based composites is demonstrated a simple and efficient strategy to construct the high-performance Li–S batteries.

To improve performance of membrane electrode assembly (MEA) at large current density region, efficient mass transfer at the cathode is desired, for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon. But the high loading may induce unwanted particle aggregation. In this work, H-PtNi/C with 33% (mass) Pt loading on carbon and monodisperse distribution of 3.55 nm PtNi nanoparticles, was prepared by a bimodal-pore route. In electrocatalytic oxygen reduction reaction (ORR), H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C (13.3% (mass)) in the half-cell. While in H2-O2 MEA, H-PtNi/C delivers the peak power density of 1.51 W·cm−2 and the mass transfer limiting current density of 4.4 A·cm−2, being 21% and 16% higher than those of L-PtNi/C (1.25 W·cm−2, 3.8 A·cm−2) respectively, which can be ascribed to enhanced mass transfer brought by the thinner catalyst layer in the former. In addition, the same method can be used to prepare PtFe alloy catalyst with a high-Pt loading of 36% (mass). This work may lead to a range of catalyst materials for the large current density applications, such as fuel cell vehicles.

With the advancement of secondary batteries, interfacial properties of electrode materials have been recognized as essential factors to their electrochemical performance. However, the majority of investigations are devoted into advanced electrode materials synthesis, while there is insufficient attention paid to regulate their interfaces. In this regard, the solid electrolyte interphase (SEI) at anode part has been studied for 40 years, already achieving remarkable outcomes on improving the stability of anode candidates. Unfortunately, the study on the cathode electrolyte interfaces (CEI) remains in infancy, which constitutes a potential restriction to the capacity contribution, stability and safety of cathodes. In fact, the native CEI generally possesses unfavorable characteristics against structural and compositional stability that requires demanding optimization strategies. Meanwhile, an in–depth understanding of the CEI is of great significance to guide the optimization principles in terms of composition, structure, growth mechanism, and electrochemical properties. In this literature, recent progress and advances of the CEI characterization methods and optimization protocols are summarized, and meanwhile the mutually–reinforced mechanisms between detection and modification are explained. The criteria and the potential development of the CEI characterization are proposed with insights of novel optimization directions.

A gas diffusion electrode was used to implement depolarization of the cathodic process with atmospheric oxygen to improve the production of sodium hypochlorite by electrolysis of an aqueous solution of sodium chloride. As materials for the implementation of depolarization of the cathode process on a porous cathode from the grid, we selected: manganese oxides, cobalt oxides, ruthenium oxides. These oxides are characterized by low overvoltage of the oxygen reaction. Oxides of selected metals were applied to a mesh current lead by thermal decomposition of coating solutionsю. The gas diffusion electrode consisted of a lined titanium current lead, a dispersant of gas made of porous graphite, and an external mesh working element, on which cathodic reactions occurred. The preparation of a catalytically active layer of oxide-metal coatings was carried out by thermal decomposition of coating solutions. This method fully complies with the requirements for oxide-metal electrodes for the electrolysis of aqueous solutions of sodium chloride: the ability to control the composition of the composite coating in a wide range of component concentrations. On the current-voltage cyclic dependences of the cathodic process, for all the materials studied, certain areas of oxygen reduction and combined oxygen reduction and hydrogen evolution are observed. The first section of oxygen reduction is observed to the equilibrium potentials of the hydrogen reaction (approximately –0.42 V). The oxygen reduction rate is small and amounts to 3...5 mA/cm2. There is no difference in the current-voltage dependence due to the high potential sweep speed, which does not lead to oxygen depletion in the case of cathode operation without air supply. In the second section (at potentials, more negative equilibrium potentials of the hydrogen reaction), a significant increase in the rate of the cathodic reaction due to hydrogen evolution is observed. Oxygen, in this case, is reduced at the limiting current density. In the third section (more than –1.5 V), the speed of the cathodic process is almost completely determined by the rate of hydrogen evolution. The effect of air supply to the gas diffusion cathode is observed when comparing the reverse stroke of cyclic current–voltage dependences. On the surface of the steel mesh, an increase in the reverse current is observed in the potential range –1.0 to 0 V. Which indicates an increase in adsorbed particles involved in the cathodic process. As shown earlier, this range of potentials corresponds to the 1st and 2nd sections of the obtained dependences in which the predominant oxygen reduction occurs. Therefore, an increase in the reverse current, with potentials more positive than 1.0 V, can be explained by the effect of oxygen adsorption on the surface of gas-permeable mesh steel cathodes when air is supplied. The addition of hypochlorite ion has practically no effect on the current density in the first and second sections of the current – voltage dependences. A decrease in the cathodic current density is observed at potentials more negative from the equilibrium potential of the hydrogen reaction. This indicates a certain inhibition of the process of hydrogen evolution. In the third section, the current density also decreases. This indicates that 0.08 mol∙dm3 hypochlorite ions do not participate in cathodic reduction. Recommended current density for the studied design of the gas diffusion cathode is 15 mA/cm2 at a temperature of 291...293 K. The cathodic recovery of hypochlorite ions, under these conditions, is reduced by 55...60 %.

In this article, it is intended to evaluate the performances of previously synthesized different nanometric compounds as SOFC components under real conditions. For this purpose, anodic supports SOFCs have been manufactured in different configurations. The compounds NiO-(Y2O3)0.08(ZrO2)0.92 (NiO–YSZ), (Y2O3)0.08(ZrO2)0.92 (YSZ), Sm0.2Ce0.8O1.9 (SDC), La0.6Sr0.4FeO3 (LSF) and LaNi0.6Fe0.4O3 (LNF) were used as anode support, electrolyte, barrier, cathode and contact layer, respectively. To obtain the cells, the anode supports were produced by uniaxial pressing and the remaining layers were added using the airbrush technique, assembling them by different sintering processes. The cells developed have been electrochemically tested in a temperature range between 750 and 865 °C. Additionally, degradation tests have been carried out under constant current. Moreover, to characterize the microstructure of the cells, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) analyzer has been used. The results obtained show that the incorporation of cathode and contact layers increases the power densities and decreases the total resistances of the cells with respect to the cell without cathode, especially with the addition of the LNF contact layer. Despite the improvement obtained, more tests have to be carried out in order to optimize the performance of SOFC devices in degradation tests.

Considering that cathode of microbial electrochemical system (MES) is a good electrons source for methane production via direct/indirect electron transfer to electroactive microorganisms, and that Fe(0) is also a confirmed electron donor for some electroactive microorganisms through metal-microbe direct electron transfer (DET), Fe(0)-cathode was equipped into an MES digester to enhance cathodic methane production. The results of this study indicated that the potential DET participator, Clostridium possibly obtained electrons directly from Fe(0)-cathode via metal-microbe electrons transfer, then transferred electrons directly to the definite DET participators, Methanosarcina/Methanothrix via microbe-microbe electrons transfer for CH4 production. In addition, Methanobacterium is another specially enriched methanogen on Fe(0)-cathode, which might obtain electrons directly from Fe(0)-cathode to produce CH4 via metal/electrode-microbe DET. The increment of conductivity of cathodic sludge in Fe(0)-cathode MES digester (R1) further confirmed the enrichment of electroactive microorganisms participating in DET process. As a consequence, a higher CH4 production (1205-1508 mL/d) and chemical oxygen demand (COD) removal (79.0%-93.8%) were achieved in R1 compared with graphite-cathode MES digester (R2, 720-1090 mL/d and 63.6%-85.6%) and the conventional anaerobic digester (R3, 384-428 mL/d and 35.2%-41.0%). In addition, energy efficiency calculated indicated that the output energy of CH4 production was 8.16 folds of electricity input in Fe(0)-cathode MES digester.

Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy, was investigated in 0.6 M NaCl solution and 0.6 M Na2SO4 solution by scanning electron microscopy (SEM) observations, scanning Kelvin probe force microscopy (SKPFM) analysis, hydrogen evolution, weight loss measurement, and electrochemical techniques. It is confirmed that the second phase of cast WE43 alloy is more active than Mg matrix and exhibits an anodic role in the micro-galvanic corrosion with α-Mg matrix as cathode and dissolves preferentially in Na2SO4 solution, in contrast to the situation in NaCl solution. The corrosion rate of cast WE43 alloy in Na2SO4 solution is much higher than that in NaCl solution, which is different from the conventional wisdom and could be attributed to the different role of the second phase in the micro-galvanic corrosion in two solutions.

The lithium-ion battery is the most advanced battery technology widely available. Lithium rechargeable batteries have recently been used in transportation (for example, electric cars) and energy storage systems that need a lot of energy and power on a large scale. LiNi0.6Mn0.2Co0.2O2 (NMC622) is a cathode material that has a high energy density. Doping in lithium-ion battery cathode materials has become a topic of interest worldwide. In this study, NMC622 cathode synthesis was conducted with transition metal doping using co-precipitation. The co-precipitation approach was chosen for the material's production (LiNi0.6Mn0.2Co0.2O2)1-xMx (M = Fe, Ti, Zn, Ce, and Cu) because of its ability to produce particles with a high degree of atomic uniformity. Due to the high energy metal oxygen bond dissociation, Fe, Ti, Zn, Ce, and Cu were utilized as doping materials in this work. Oxalic acid was used as a precipitation agent, and ammonia was used as a chelating agent. The doping metal used was precipitated using oxalic acid. NMC622 which has been precipitated into NMC622 precursor and doped metal that has been precipitated is mixed for later solid-state processing. Under the flow of air, the obtained oxalate precursor is heated. The characterization of metal-doped NMC622 was carried out. The x-ray diffraction pattern depicts the hexagonal layered material's structure. FTIR analysis confirmed the missing C-O bonds of the obtained product. SEM (scanning electron microscope) studies show a polyhedral morphology of the material. A charge-discharge test at 1/10 C between 2.6 and 4.3 V was used to achieve the electrochemical performance. Ce doping resulted in the best specific capacity and could be compared with non-doped materials.

DC deep-well grounding electrode (DWGE) has become a new type of grounding configuration due to its small area requirement. However, gas produced by DWGE during electrolysis may causes more severe exhaust problem than conventional electrode. To investigate the influence of different electrode materials on DWGEs gas evolution, an innovative U-shaped experimental platform was proposed to collect cathode and anode gases separately. The metalelectrolyte contact interface in a DWGE project was simulated to perform gas evolution experiments on three typical grounding electrode material. The gas evolution speeds of the materials when used as the cathode and anode were obtained. The polarization curves were used to analyze the order of corrosion speeds, and the effect of the materials on the order of the gas evolution speed. The results revealed that when operated as an anode, MMO and high silicon cast iron produce oxygen, whereas carbon steel does not. Furthermore, the evolution of O2 in MMO is faster than that in high silicon cast iron. When operated as cathode, the three materials generate hydrogen, and carbon steel exhibits the slowest H2 evolution speed. The current from the power supply consist of the reaction current of metal corrosion and gas generation.

The selection and development of cathode of alkaline zinc batteries (AZBs) is still hindered and often leads to poor rate capability and short cycle life. Here, amorphous hollow nickel-cobalt-based sulfides nanocages with nanosheet arrays (AM-NCS) are designed and constructed with ZIF-67 as the self-template to exchange with Ni2+ and S2− by using a two-step ion exchange method. The synthesized AM-NCS possess the high specific capacity (160 mAh/g at 2 A/g), and the assembled battery has excellent rate performance (146 mAh/g reversible capacity at 5 A/g). The assembled device has excellent rate performance (155 mAh/g at 2 A/g) and long cycling stability (7000 cycles, 62.5% of initial capacity). The excellent electrochemical properties of the electrode materials are mainly attributed to the unique structure, in particular, polyhedron structure with hollow structure can improve the cyclic stability, and the amorphous structure can expose more reactive sites on the surfaces of nickel, cobalt and sulfur. This work provides a new strategy for the design and fabrication of high performance cathode materials for AZBs.

Aqueous rechargeable multiple metal-ion storage battery (ARSB) has a large potential in energy storage devices due to their safe usage, low cost and high rate capability. Nevertheless, the performance of practical ARSB is largely restricted by low capacity and limited cathode materials. Herein, we demonstrate an efficient cathode material based on CoNi-layered double hydroxide (LDH) nanosheets arrays with abundant hydrogen vacancy induced by electrochemical activation process for high performance of cations storage. Consequently, the electrochemical activated CoNi-LDH (ECA-CoNi-LDH) nanosheets arrays exhibit high metal ion (Li+, Na+, Zn2+, Mg2+ and Ca2+) storage capacities, which is 9 times and 3 times higher that of unactivated CoNi-LDH arrays and ECA-CoNi-LDH without hierarchical structure, respectively. Moreover, the ECA-CoFe-LDH also shows the possibility for practical applications in actual batteries. By coupling with a Fe2O3/C anode, the assembled aqueous battery delivered a large energy density of 184.4 Wh kg−1 at power density of 4 Wh kg−1 in high voltage range of 0 ∼ 2 V. To our best knowledge, such high energy density and large working window of our assembled aqueous battery is exceeded other LDH-based aqueous battery or supercapacitor, and the energy density almost comparable than that of commercial Li-ion batteries. Moreover, almost no measurable capacitance losses can be detected even after 10000 cycles. In addition, this work also provides a strategy to develop a high energy density cathode for multiple metal-ion storage batteries.

Aprotic Li-CO2 batteries have attracted growing interest due to their high theoretical energy density and its ability to use green house gas CO2 for energy storage. However, the poor ability of activating CO2 in organic electrolyte often leads to the premature termination of CO2 reduction reaction (CO2RR) directly. Here in this work, cetyl trimethyl ammonium bromide (CTAB) was introduced into a dimethyl sulfoxide (DMSO) based Li-CO2 battery for the first time to enhance the CO2RR. Significantly improved electrochemical performances, including reduced discharge over-potential and increased discharge capacity, can be achieved with the addition of CTAB. Ab initio molecular dynamics (AIMD) simulations show that quaternary ammonium group CTA+ can accelerate CO2 reduction process by forming more stable contact ion pair (CIP) with CO2–, reducing the energy barrier for CO2RR, thus improving the CO2 reduction process. In addition, adding CTA+ is also favorable for the solution-phase growth of discharge products because of the improved migration ability of stable CTA+-CO2– CIP in the electrolyte, which is beneficial for improving the utilization ratio of cathode. This work could facilitate the development of CO2RR by providing a novel understanding of CO2RR mechanism in organic system.

NASICON-type Na3V2(PO4)3 is a promising electrode material for developing advanced sodium-ion batteries. Preparing Na3V2(PO4)3 with good performance by a cost-effective and large-scale method is significant for industrial applications. In this work, a porous Na3V2(PO4)3/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method. The Na3V2(PO4)3/C cathode displayed specific capacities of 113.4 mAh·g−1, 107.0 mAh·g−1 and 87.1 mAh·g−1 at 0.1 C, 1 C and 10 C, respectively. For the first time, the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na3V2(PO4)3/C electrodes are successfully fabricated. The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83% at 0 °C owing to the rapid sodium ion migration ability and structural stability of Na3V2(PO4)3/C. Moreover, the thermal runaway features are revealed by accelerating rate calorimetry (ARC) test for the first time. Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries. Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na3V2(PO4)3/C have a prospect of practical application in high safety requirement fields.

Introduction: Goal. Synthesize, characterize, and implement rotationally disoriented graphene (turbostratic graphene) as a cost effective cathode material in the Al-ion battery cell for enhanced performance compared to graphite and orderly-stacked graphene cathodes. Turbostratic graphene has promising conductivity and larger interplanar spacing.

This work shows the technical feasibility to obtain uranium tetrafluoride through an electrochemical mercury cell. This technique represents a custom scaling-up methodology from our previous studies to obtain UF4 using the dropping mercury electrode cell. The UF4 products were obtained from natural UF6 gas, which was hydrolyzed to obtain a 50 g/L UO2F2 solution. The electrolysis cell was made using a mercury reservoir, to reach UF4 production rates of 1 Kg UF4/day. This custom design allowed a stable UF4 production thanks to the mercury cathode, which do not permit the accumulation of solid products in its surface. The cell was tested using current densities from 5.000 to 17.500 A/m2 and temperatures from 25 to 65 °C. The maximum current efficiency achieved under these conditions was 80%. The UF4 powders possessed spherical morphology, with diameters between 20 – 80 μm. Compared to the SnCl2 precipitation, this process did not allow preferential growth of the precipitates. This improved the compaction of the UF4 – Mg powders mixtures, with densities between 3.0 – 3.5 g/cm3. The purity of the UF4 products was over 98%.

In practical pouch cell, LiNi0.5Mn0.3Co0.2O2/artificial graphite lithium ion battery using single-crystal LiNi0.5Mn0.3Co0.2O2 (S-NMC532) as cathode can have excellent cycle performance. However, single-crystal LiNi0.5Mn0.3Co0.2O2 inevitably suffers poor rate capability compared to the polycrystalline materials. Here, we systematically studied the relationship between microstructural characteristics and the practical rate performance, as well as explored the impedance change during the cycling process in the pouch cell. This work shows that the (001) plane microtexture of the electrode surface structure is a critical barrier for rate capability. Electron backscatter diffraction (EBSD), electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) are conducted on the cathodes. These analyses allow to conclude on the influence of the (001) plane microtexture on the electrode surface, which illustrates a diffusion resistance of lithium ions, and then, leading a high interfacial resistance. Thus, this work confirms the main cause of the inferior rate capability of S-NMC532 and offers guidance for developing a battery with high rate and ultralong cycling life.

We herein proposed a sample introduction technique based on solution cathode glow discharge (SCGD) of a portable design for inductively coupled plasma-optical emission spectrometry (ICP-OES) and its application in sensitive determination of mercury. The products from SCGD containing mercury vapor, were transported by an Ar flow to ICP spectrometer for detection. A gas liquid separator (GLS) and a dryer were used to condense and remove most of the accompanying moisture, which greatly improved both the stability and sensitivity of the signal. The detection limit (DL) acquired by this developed method was 0.22 μg/L (194.1 nm), which was nearly 82 times lower than that obtained by pneumatic nebulization (PN). The relative standard deviation (RSD) was 1.4% (n = 14) for a 50 μg/L standard. Blank solution (HNO3, pH 1) can effectively elute mercury residue. Its accuracy and practicality were also demonstrated by the determination of GBW10029 (fish) certified reference material, shrimp, crawfish, soil and human hair samples. The results showed good consistency with the certified values and the values obtained using inductively coupled plasma−mass spectrometry.

Applying mixed oxygen ionic and electronic conducting (MIEC) oxides as the cathode offers a promising solution to enhance the performance of solid oxide fuel cells (SOFCs). However, the phase instability in CO2-containing air and sluggish oxygen reduction activity of MIEC cathodes remain a long-term challenge for optimizing the electrochemical performance of SOFCs. Herein, a heterovalent co-doping strategy is proposed to enhance the oxygen reduction activity and CO2 tolerance of SOFCs cathodes, which can be demonstrated by developing a novel BaCo0.6Fe0.4O3-δ (BCF)-based MIEC oxide, BaCo0.6Fe0.2Sn0.1Y0.1O3-δ (BCFSY). In addition to improving the stability of BCF-based perovskites, this strategy achieves an optimized balance of ionic mobility and oxygen vacancies due to the synergies between the effects of the co-dopants. Compared with single-doped materials, BCFSY exhibits improved CO2 tolerance and considerably higher ORR activity, which is reflected in a significantly lower polarization resistance of 0.15 Ω cm2 at 600°C. The results of this work provide an efficient tactic for designing electrode materials for SOFCs.

Here we demonstrate a theory-driven, novel dual-shell coating system of Li2SrSiO4 and Al2O3, achieved via a facile and scalable sol-gel technique on LiCoO2 electrode particles. The optimal thickness of each coating can lead to increased specific capacity (∼185 mAh/g at 0.5 C-rate) at a cut-off potential of 4.5 V, and greater cycling stability at very high C rates (up to 10 C) in half-cells with lithium metal. The mechanism of this superior performance was investigated using a combination of X-ray and electron characterization methods. It shows that the results of this investigation can inform future studies to identify still better dual-shell coating schemes, achieved by such industrially feasible techniques, for application on similar, nickel-rich cathode materials.

Among the large energy storage batteries, the sodium ion batteries (SIBs) are attracted huge interest due to the fact of its abundant raw materials and low cost, and has become the most promising secondary battery. Tunnel-type sodium manganese oxides (TMOs) are industrialized cathode materials because of their simple synthesis method and proficient electrochemical performance. Na0.44MnO2 (NMO) is considered the best candidate material for all tunnel-type structural materials. In this paper, the research progress in charge and discharge of cathode materials for tunnel-type structural SIBs is reviewed, the redox mechanism and all sorts of synthesis methods and different coating methods lead to different morphology and electrochemical properties of materials and the classification of electrolytes and non-aqueous electrolytes. The development and utility of aqueous solutions are discussed, and the mechanism is analyzed. Summarized the cationic potential of the transition metal oxide for tunnel structure, plays a vital role in predicting and designing the cathode material of this structure. In addition, the future opportunities and challenges for such tunnel-type SIBs in this field are described in detail.

LiMnyFe1−yPO4 is considered a promising cathode material for next-generation lithium-ion batteries (LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the capacity loss during cycling. However, in this study, we find that the energy density degradation mainly roots in voltage decay. We have synthesized a series of LiMnyFe1−yPO4/C (0.5≤y≤0.8) and find this voltage decay is correlated with the Mn content. A high amount Mn leads to a heavier voltage decay. In-situ X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) reveal the nature of this effect, which show a mismatch along the b-axis of −2.68% (charge) and +3.4% (discharge), a volume misfit of −4.41% (charge) and +4.54% (discharge) between LixMnyFe1−yPO4 and MnyFe1−yPO4 during phase transitions. The resultant misfit strains during Li+ insertion compared to extraction result in structural degradations, such as amorphization and impurity (MnF3) accumulation after cycling. The voltage decay can be alleviated by kinetic relaxations and recovered by a wild reannealing. This work demonstrates effective strategies to improve the energy density and cycling performance of LiMnyFe1−yPO4/C, providing good references for other LIB cathodes, such as the Li-rich cathodes.

Ion-exchange reactions are commonly used to develop novel metastable electrode materials for alkali-ion batteries that cannot be synthesized using direct chemical reactions. In this study, the electrochemical K to Na ion-exchange reaction mechanisms in a layered KxCoO2 cathode as a model system were investigated using operando and ex situ structure characterization techniques. Some level of K ions was observed to remain in the layered structure during the electrochemical ion-exchange reactions. Interestingly, the K ions are well separated from the Na-rich phases in the discharged state, and they form an intermediate phase in which K and Na ions are mixed at the top of charge. We discovered that such residual K ions prevent the collapse of the layered structure in the high-voltage regime, thereby improving the cycling stability in a Na-battery system.

Short circuit failure mode (SCFM) of IGCT under extreme failure is of vital importance in MMC-HVDC system. Due to the sealing housing package of IGCT, the short circuit mechanism is hard to be clarified. Considering this limitation, the current density changes in IGCT with different failure modes are studied in a built integrated test system with placed magnetic sensor array and thermal couple array. Then the short circuit mechanism of failed IGCT is proposed based on the experiment results. IGCT with turn off failure performs self-triggering effect due to the focused short current and increased temperature in the intial destruction area, which is usually located in a single position of the outer cathode rings. While IGCT with surge current failure shares the short current among multiple initial destruction areas, which are usually distributed evenly. SEM picture and EDX analysis show that the formed conducting alloy has spread into the molybdenum plate deeply and the phenomenon of atom diffusion (molybdenum, silicon and aluminium) near the interface is observed. Finally, long term short circuit tests of more than 12h with both turn off failure and surge current failure under 3000A prove the stable short circuit failure mode of IGCT.

Aqueous rechargeable magnesium ion batteries (ARMBs) have obtained more attention due to the two-electrons transfer nature, low cost and safety. However, the scarcity of cathode materials seriously hinders the development of ARMBs because of the unfavorable strong interaction between Mg2+ and cathode material. Herein, we choose a pre-treated spinel Mn3O4 cathode for aqueous Mg2+ storage. The pre-treatment in Na2SO4 solution induces the grain refinement decorated with tortuous amorphous ion diffusion channels, facilitating the production of electrochemical reaction active sites and the diffusion of Mg2+, respectively, which achieve a (sub-)surface pseudocapacitance reaction between Mn (II) and Mn (III). As a result, the pre-treated Mn3O4 cathode exhibits a package of optimal performances, i.e., a capacity of 98.9 mAh g−1 and a high capacity retention rate of 99.4% after 2000 cycles. To the best of our knowledge, our work not only provides a new reaction mechanism of spinel Mn3O4 in aqueous batteries system, but also affords a high cycle stability electrode material for rechargeable Mg2+ energy storage.

In this study, the Ti/SnO2-RuO2 electrodes with different Yb contents were prepared by sol-gel method and thermal decomposition method, and the surface morphology and crystal structure of the electrodes were characterized by scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD), the electrochemical properties of the electrodes were tested by linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The electrochemical oxidation device was constructed with Yb-doped Ti/SnO2-RuO2 electrode as the anode and titanium plate as the cathode, and the electrochemical oxidation effect and product changes of the anode on coking wastewater were investigated. The results show that the surface of the electrode is flat with high crystallinity of SnO2 and RuO2 crystals at 1.5% Yb doping, and the LSV and CV curves indicate that the rare earth doping of 1.5% increases the oxygen precipitation potential and electrocatalytic oxidation activity of the electrode. When the electrode with rare earth doping of 1.5% is the anode with current density of 10mA/cm2 electrochemical oxidation time of 30min, the electrode can remove COD up to 85.06%, TOC up to 60.59% and UV254 from 1.594 to 0.507 for coking wastewater. GC-MS, UV-vis and three-dimensional fluorescence results of coking wastewater before and after treatment show that large toxic substances in coking wastewater are degraded to low toxic organic substances, and most soluble organic substances are degraded and transformed. This study provides the possibility of basic research for the engineering practice of electrochemical oxidation for the treatment of coking wastewater.

Zinc-ion batteries (ZIBs), in particular quasi-solid-state ZIBs, occupy a crucial position in the field of energy storage devices owing to the superiorities of abundant zinc reserve, low cost, high safety and high theoretical capacity of zinc anode. However, as divalent Zn2+ ions experience strong electrostatic interactions when intercalating into the cathode materials, which poses challenges to the structural stability and higher demand in Zn2+ ions diffusion kinetics of the cathode materials. Here, a microwave-assisted hydrothermal method is adopted to prepare pre-potassiated hydrated vanadium pentoxide (K0.52V2O5•0.29H2O, abbreviated as KHVO) cathode material, in which the potassium ions pre-inserted into the interlayers can act as “pillars” to stabilize the lamellar structure, and crystal water can act as “lubricant” to improve the diffusion efficiency of Zn2+ ions. Consequently, the KHVO displays high electrochemical properties with high capacity (∼ 300 mAh/g), superior rate capability (69 mAh/g at 5 A/g) and ultralong cycling performance (>1500 cycles at 2 A/g) in quasi-solid-state ZIBs. These superior Zn storage properties result from the large diffusion coefficient and highly stable and reversible Zn2+ (de)intercalation reaction of KHVO.

While the sulfur conversion reaction kinetics in Li–S batteries is nowadays improved by the use of appropriate electrocatalysts, it remains a challenge for the batteries to perform well under the lean electrolyte condition where polysulfide shuttle, electrode passivation and the loss of electrolyte due to side reactions, are aggravated. These challenges are addressed in this study by the tandem use of a polysulfide conversion catalyst and a redox–targeting mediator in a gel sulfur cathode. Specifically, the gel cathode reduces the polysulfide mobility and hence the polysulfide shuttle and the passivation of the lithium anode by the crossover polysulfides. The redox mediator restrains the deposition of inactive sulfur species in the cathode thereby enabling the Fe–N and Co–N co–doped carbon catalyst to prolong its catalytic activity. Consequently, the integrated catalytic system is able to increase the discharge capacity of high–loading (6.8 mg cm–2) lean–electrolyte (4.0 µL mg–1) Li–S batteries from ∼630 to ∼1316 mAh g–1, concurrently with an improvement of the cycle life (600 cycles with 46% capacity retention at 1.0 mA cm−2). Redox mediator assisted catalysis in a gel cathode is therefore an effective strategy to extend the application of the sulfur conversion catalyst in lean electrolyte Li–S batteries.

Zinc-ion batteries (ZIBs) possess great advantages in terms of high safety and low cost, and are regarded as promising alternatives to lithium-ion batteries (LIBs). However, limited by the electrochemical kinetics and structural stability of the typical cathode materials, it is still difficult to simultaneously achieve high rates and high cycling stability for ZIBs. Herein, we present a manganese oxide (SnxMnO2/SnO2) material that is dual-modified by SnO2/MnO2 heterostructures and pre-intercalated Sn4+ cations as the cathode material for ZIBs. Such modification provides sufficient hetero-interfaces and expanded interlayer spacing in the material, which greatly facilitates the insertion/extraction of Zn2+. Meanwhile, the “structural pillars” of Sn4+ cations and the “pinning effect” of SnO2 also structurally stabilizes the MnO2 species during the repeated Zn2+ insertion/extraction, leading to ultra-high cycling stability. Due to these merits, the SnxMnO2/SnO2 cathode exhibits a high reversible capacity of 316.1 mAh g−1 at 0.3 A g−1, superior rate capability of 179.4 mAh g−1 at 2 A g−1, and 92.4% capacity retention after 2000 cycles. Consequently, this work would provide a promising yet efficient strategy by combining heterostructures and cations pre-intercalation to obtain high-performance cathodes for ZIBs.

Due to high ionic conductivity and wide electrochemical window, the garnet solid electrolyte is considered as the most promising candidate electrolyte for solid-state lithium metal batteries. However, the high contact impedance between metallic lithium and the garnet solid electrolyte surface seriously hampers its further application. In this work, a Li-(ZnO)x anode is prepared by the reaction of zinc oxide with metallic lithium and in situ coated on the surface of Li6.8La3Zr1.8Ta0.2O12(LLZTO). The anode can be perfectly bound to the surface of LLZTO solid electrolyte, and the anode/electrolyte interfacial resistance was reduced from 2319 to 33.75 Ω·cm2. The Li-(ZnO)0.15|LLZTO|Li-(ZnO)0.15 symmetric battery exhibits a stable Li striping/plating process during charge-discharging at a constant current density of 0.1 mA·cm−2 for 100 h at room temperature. Moreover, a Li-(ZnO)0.15|LLZTO-SPE|LFP full battery, comprised of a polyethylene oxide-based solid polymer electrolyte (SPE) film as an interlayer between LiFePO4 (LFP) cathode and LLZTO solid electrolyte, presents an excellent performance at 60 ℃. The discharge capacity of the full battery reaches 140 mAh·g−1 at 0.1 C and the capacity attenuation is less than 3% after 50 cycles. © 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd.. All rights reserved.

High-voltage and low-cost manganese-based P2-type oxides show real promise as promising cathode for sodium-ion batteries (SIBs). But the P2−O2 phase transformation and Na+/vacancy ordering results in the inferior structural stability and Na+ diffusion coefficient, which further leads to rapid decay of capacity and poor rate capability. Herein, in consideration of the synergetic effects of dual cationic doping, electrochemically inactive Li+ and active Co3+ co-doping are proposed to solve the above issues. The novel two-step doping strategy, Co doping during synthesis of precursors via co-precipitation reaction followed by Li doping during solid-state reaction, are rationally developed. As anticipated, the Li, Co co-doped P2-type oxide exhibits the absence of P2−O2 phase transformation and Na+/vacancy disordering, which gives rise to an outstanding cycling stability (86.7% capacity retention within 100 cycles at 0.1C) and high-rate capability (reversible capacity of 109 mAh g−1 even at 10C). In addition, the full-cells composed of the co-doped P2-type positive and hard carbon negative show high energy-density, good lifespan and high-rate property. This proposed cationic co-doping provides an effective and scalable tactics for modulating the structural properties of high-voltage P2-type cathodes for advanced SIBs.

In recent years, the pursuit of high-efficiency electrochemical storage technology, the multivalent metal-ion batteries (MIBs) based on aqueous electrolytes have been widely explored by researchers because of their safety, environmental friendliness, abundant reserves and low price, and especially the merits in energy and power densities. This review firstly expounds on the problems existing in the electrode materials of aqueous multivalent MIBs (Zn2+, Mg2+, Al3+, Ca2+), from the classical inorganic materials to the emerging organic compounds, and then summarizes the design strategies in bulk and interface structure of electrodes with favorable kinetics and stable cycling performance, especially laying the emphasis on the charge storage mechanism of cathode materials and dendrite-free Zinc anode from the aspect of electrolyte optimization strategies, which can be extended to other aqueous multivalent MIBs. Ultimately, the possible development directions of the aqueous multivalent MIBs in the future are provided, anticipating to provide a meaningful guideline for researchers in this area.