Increase In Discharge Capacity Research Articles

Crown Ether Electrolyte Induced Li2O2 Amorphization for Low Polarization and Long Lifespan Li‐O2 Batteries

AbstractLithium‐oxygen batteries possess an extremely high theoretical energy density, rendering them a prime candidate for next‐generation secondary batteries. However, they still face multiple problems such as huge charge polarization and poor life, which lay a significant gap between laboratory research and commercial applications. In this work, we adopt 15‐crown‐5 ether (C15) as solvent to regulate the generation of discharge products in lithium‐oxygen batteries. The coronal structure endows C15 with strong affinity to Li+, firmly stabilizes the intermediate LiO2 and discharge product Li2O2. Thus, the crystalline Li2O2 is amorphized into easily decomposable amorphous products. The lithium‐oxygen batteries assembled with 0.5 M C15 electrolyte show an increased discharge capacity from 4.0 mAh cm−2 to 5.7 mAh cm−2 and a low charge overpotential of 0.88 V during the whole lifespan at 0.05 mA cm−2. The batteries with 1 M C15 electrolyte can cycle stably for 140 cycles. Furthermore, the amorphous characteristic of Li2O2 product is preserved when matched with redox mediators such as LiI, with the charge polarization further decreasing to 0.74 V over a cycle life of 190 cycles. This provides new possibilities for electrolyte design to promote Li2O2 amorphization and reduce charge overpotential in lithium‐oxygen batteries.

Crown Ether Electrolyte Induced Li2O2 Amorphization for Low Polarization and Long Lifespan Li-O2 Batteries.

Lithium-oxygen batteries possess an extremely high theoretical energy density, rendering them a prime candidate for next-generation secondary batteries. However, they still face multiple problems such as huge charge polarization and poor life, which lay a significant gap between laboratory research and commercial applications. In this work, we adopt 15-crown-5 ether (C15) as solvent to regulate the generation of discharge products in lithium-oxygen batteries. The coronal structure endows C15 with strong affinity to Li+, firmly stabilizes the intermediate LiO2 and discharge product Li2O2. Thus, the crystalline Li2O2 is amorphized into easily decomposable amorphous products. The lithium-oxygen batteries assembled with 0.5 M C15 electrolyte show an increased discharge capacity from 4.0 mAh cm-2 to 5.7 mAh cm-2 and a low charge overpotential of 0.88 V during the whole lifespan at 0.05 mA cm-2. The batteries with 1 M C15 electrolyte can cycle stably for 140 cycles. Furthermore, the amorphous characteristic of Li2O2 product is preserved when matched with redox mediators such as LiI, with the charge polarization further decreasing to 0.74 V over a cycle life of 190 cycles. This provides new possibilities for electrolyte design to promote Li2O2 amorphization and reduce charge overpotential in lithium-oxygen batteries.

An Experimental Approach to Assess Fluorine Incorporation into Disordered Rock Salt Oxide Cathodes.

Disordered rock salt oxides (DRX) have shown great promise as high-energy-density and sustainable Li-ion cathodes. While partial substitution of oxygen for fluorine in the rock salt framework has been related to increased capacity, lower charge-discharge hysteresis, and longer cycle life, fluorination is poorly characterized and controlled. This work presents a multistep method aimed at assessing fluorine incorporation into DRX cathodes, a challenging task due to the difficulty in distinguishing oxygen from fluorine using X-ray and neutron-based techniques and the presence of partially amorphous impurities in all DRX samples. This method is applied to "Li1.25Mn0.25Ti0.5O1.75F0.25" prepared by solid-state synthesis and reveals that the presence of LiF impurities in the sample and F content in the DRX phase is well below the target. Those results are used for compositional optimization, and a synthesis product with drastically reduced LiF content and a DRX stoichiometry close to the new target composition (Li1.25Mn0.225Ti0.525O1.85F0.15) is obtained, demonstrating the effectiveness of the strategy. The analytical method is also applied to "Li1.33Mn0.33Ti0.33O1.33F0.66" obtained via mechanochemical synthesis, and the results confirm that much higher fluorination levels can be achieved via ball-milling. Finally, a simple and rapid water washing procedure is developed to reduce the impurity content in as-prepared DRX samples: this procedure results in a ca. 10% increase in initial discharge capacity and a ca. 11% increase in capacity retention after 25 cycles for Li1.25Mn0.25Ti0.50O1.75F0.25. Overall, this work establishes new analytical and material processing methods that enable the development of more robust design rules for high-energy-density DRX cathodes.

Size-controlled wet-chemical synthesis of sulfide superionic conductors for high-performance all-solid-state batteries

The escalating concerns surrounding the safety issues tied to the flammability of organic liquid electrolytes in conventional lithium-ion batteries have catalyzed the evolution and advancement of all-solid-state batteries (ASSBs) integrated with solid electrolytes (SEs). Among various SE materials, sulfide-based lithium argyrodite has risen to prominence owing to its high ionic conductivity and ease of processability. Despite the wet-chemical processing method being considered advantageous for the synthesis of sulfide SEs, due to its inherent simplicity, potential scalability, and cost-effectiveness, certain challenges persist. These primarily pertain to achieving high ionic conductivity and mitigating interfacial resistance between the electrode and the SEs. Addressing these challenges, this study presents a novel, scalable, and cost-efficient wet synthesis approach to produce superionic conductive sulfide-based SEs. This method involves careful regulation of the nucleation rate and strategic substitution of elements to control particle size and enhance ionic conductivity. The resultant Li5.5PS4.5Cl1.5 SEs synthesized show a uniform size distribution (average particle diameter = 7 μm), coupled with a high ionic conductivity of 4.98 mS cm−1. This level of ionic conductivity is either comparable to or exceeds those produced through dry processes. The ability to control particle size optimizes the contact interface between the electrode and the electrolyte, reducing interfacial resistance and increasing discharge capacity. Consequently, this method paves the way for mass production of high-quality sulfide SEs. The findings of this study serve to further the development of high-performing ASSBs, making them suitable for implementation in high output power and long cruising distance electric vehicles, pushing the envelope for battery-powered transportation solutions.

F-doped Co-free LiNixMn1-xO2 (0.7 ≤ x ≤ 0.9) cathodes for ameliorating electrochemical performance of Li-ion batteries

Ni-rich LiNiCoMnO2 cathodes, which exhibit high energy densities and layered structures, have been studied For Li-ion batteries (LIBs) with high capacities and excellent stabilities. However, the high cost and price fluctuation of Co as the main element in the cathodes remain severe issues for the stable development of LIBs. Therefore, in this study, F-doped Co-free Ni-rich LiNixMn1-xO2 (0.7 ≤ x ≤ 0.9) cathodes were prepared for high-performance LIBs. With increasing Ni content, the undoped Ni-rich LiNixMn1-xO2 cathodes exhibited increased discharge capacities and decreased stabilities. In contrast, the F-doped Ni-rich LiNixMn1-xO2 cathodes delivered higher cycle retentions at 0.5 C for 100 cycles compared to the undoped cathodes. In addition, the F doping of Ni-rich LiNixMn1-xO2 cathodes can facilitate Li-ion diffusion, retaining their reversibility and high capacities at high current densities.

Improved Vanadium Redox Flow Battery Performance through a Pulsating Electrolyte Flow Regime

The increase in emissions of greenhouse gases and their environmental impact lead to a transition from primarily fossil fuel-based energy sources to renewable and eco-friendly ones, such as solar panels and wind turbines. However, these sources are intermittent, resulting in fluctuating energy production levels that require buffering, which poses significant challenges in matching production-consumption profiles. [1,2] In order to stabilise the grid and reduce dependency on fossil fuels, integrating electrical energy carriers into a smart grid to store excess energy produced during peak periods and employ it during periods of low production is a potential solution. Redox flow batteries hold promise in this regard, as the storage capacity can be decoupled from the battery size, enabling capacity to be scaled independently of power output by increasing the volume of the electrolyte. [3] In contrast to conventional secondary battery types, such as lead-acid or lithium-ion batteries, the electrolyte in a redox flow battery is non-stationary, inducing convective mass transport effects that are critical for achieving a high power output.In this work we introduced pulsations to the electrolyte flow of an all-vanadium redox flow battery, leading to a reduced stagnant boundary layer attributed to shear forces. Previously, Pérez-Gallent et al. demonstrated that the conversion can be increased by a factor of two while selectivity gains of 15-20% can be made in a electrolyser by introducing a pulsating flow. [4] Furthermore, Vranckaert et al. studied a pulsating flow combined with pillar field electrodes, using the well-known ferri-ferrocyanide redox couple, and concluded that the average limiting current density can be increased fourfold compared to working with a conventional steady state flow regime. [5] Overall, a pulsating flow behaviour yields an enhanced mass transfer of electroactive species by increasing the local velocity through pulsations. The net residence time of the reactants remains unchanged since the pulsating flow has no influence on the overall flow velocity. However, the resulting improvement of mass transfer leads to an increase in conversion. As it is clear that mass transfer enhancement strategies open the door for more efficient systems, our work will for the first time focus on the influence of a pulsating electrolyte flow on the redox flow battery performance. The results show a significant improvement: the discharge capacity at 100 mA/cm2 increased by 38.7% when applying a pulse with pulse amplitude (PA) 0.4ml and pulse frequency (PF) 2.4 Hz at a flow rate of 5 ml/min (Figure 1 A). Furthermore, this 38.7% increase in discharge capacity surpassed the performance achieved at a constant steady-state flow of 25 ml/min. Therefore, a fivefold reduction of the net flow rate is possible without performance losses, decreasing necessary pumping costs. When regarding the stability of an all-vanadium redox flow battery operated with a pulsating electrolyte flow initial fluctuations of the current efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) were recorded. However, the efficiencies became stable at 98.4%, 70.5% and 69.4% respectively, showing no decline over time (Figure 1 B). This novel and improved redox flow battery system allows to take the next step towards integrating electrical energy carriers into a smart grid suitable for renewable and green energy sources.[1] P. D. Lund, J. Lindgren, J. Mikkola, J. Salpakari, Renew. Sustain. Energy Rev. 2015, 45, 785–807.[2] H. Kondziella, T. Bruckner, Renew. Sustain. Energy Rev. 2016, 53, 10–22.[3] E. Sánchez-Díez, E. Ventosa, M. Guarnieri, A. Trovò, C. Flox, R. Marcilla, F. Soavi, P. Mazur, E. Aranzabe, R. Ferret, J. Power Sources 2021, 481, 228804.[4] E. Pérez-Gallent, C. Sánchez-Martínez, L. F. G. Geers, S. Turk, R. Latsuzbaia, E. L. V. Goetheer, Ind. Eng. Chem. Res. 2020, 59, 5648–5656.[5] M. Vranckaert, H. P. L. Gemoets, R. Dangreau, K. Van Aken, T. Breugelmans, J. Hereijgers, Electrochim. Acta 2022, 436, 141435. Figure 1

Synthesis, Electrochemical Properties and Crystal and Electronic Structure Changes in Charge/Discharge Process of Spinel Type Cathode-Materials Mg1.33-Y(V1.67-x+yMnx)O4 for Magnesium Secondary Batteries

Attention has therefore focused on rechargeable batteries using multivalent cations, which are expected to offer even higher energy densities than lithium ion batteries. One topic that has attracted attention is rechargeable batteries using Mg as a carrier. The advantage of using Mg is that it has a low electrode potential with a high capacity.Although previous research into Mg rechargeable battery cathode materials started with a report by Aurbach1) et al., and included chevrel compounds, these have had problems in terms of battery voltage and cycle properties. In spinel-type Mg1+yCo2-x-yMnxO4, charge and discharge capacities were reported to increase by substituting Mn2). V is thought to have high reversibility due to having a broad mixed atomic valence. The authors synthesized Mg1.33V1.57Ni0.1O4, and reported that the discharge capacity after 14 cycles was 160 mAh/g and the capacity retention rate was high3). Furthermore, the authors investigated the spinel solid solution αMgCo1.5Mn0.5O4-(1-α)Mg(Mg0.33V1.57Ni0.1)O4 as a new cathode material and evaluated its battery properties, and as a result found that the initial discharge capacity at α = 0.3 was 180 mAh/g with the discharge capacity maintained after 60 cycles4 ). However, the substitution products need to be investigated in order to improve the discharge potential of the Mg-V system and enhance the cycle properties.The present study investigated the synthesis of a new spinel type cathode material Mg1.33-y(V1.67-x+yMnx)O4 by substituting Mn into Mg1.33V1.67O4 and different Mg content in order to increase the charge-discharge capacity and improve the cycle properties. The crystal and electronic structures and charge-discharge properties depending on the amount of Mn substitution and Mg content, and the structural changes accompanying charging and discharging.Mg1.33-y(V1.67-x+yMnx)O4 was synthesized by a solid -phase method under high vacuum atmosphere. The product was assigned to the spinel structure with space group Fd-3m from the powder X-ray diffraction. Synthesized materials of uniform composition were confirmed from elemental mapping by STEM-EDS. Charge and discharge cycle tests showed that the deliverable discharge capacity depends on the cycle number, Mn composition, and working temperature. The charge and discharge cycle tests showed the discharge capacity increased with repeated cycles. Mg1.33V1.57Mn0.1O4 showed the largest discharge capacity of 256 mAh/g at 13th cycles while the initial capacity was only 73 mAh/g at 90°C. The local structure was analyzed based on EXAFS spectra at the V K-edge for the pristine and electrode materials, and the results suggested that Mg1.33V1.57Mn0.1O4 had the smallest lattice distortion due to Mn at 16d sites, and XAFS spectra at the V K-edge indicated the significant change in the oxidation state of V during the charge/discharge cycles. The particularly stable crystal structure and large contribution of charge compensation by V may jointly contribute to the superior charge-discharge property of Mg1.33V1.57Mn0.1O4 5).Moreover, we investigated the different Mg, Mn content sample. Mg1.25(V1.55Mn0.2)O4 showed an increase in capacity from the first discharge capacity 71mAh/g to 199mAh/g after 34 cycles at 90℃ (Fig.1). The change in crystal structure due to charging and discharging was investigated. Focusing on the magnitude of M(16d)-O6 octahedral strain, the strain after 10th discharge is significantly reduced, so it is considered that the structure was stabilized by repeating the cycles and contributed to the improvement of the cycles characteristics. The electronic structure was analyzed by MEM, which showed that the electron density between the 16d-32e sites was higher and the covalent bond was higher than that of the diffusion sites after charge and discharge. From this, it is considered that the host structure was stabilized by charge and discharge, which contributed to the increase in charge and discharge capacity. From the result of XANES, it revealed that V is trivalent to tetravalent and Mn is divalent. Furthermore, from the results of EXAFS, it was clarified that the amount of reduction was larger in Mg1.25(V1.55Mn0.2)O4, especially in charge and discharge, because the amount of change in the distance between V and O was larger. Acknowledgements This work was supported by JST ALCA-SPRING Grant Number JPMJAC1301, Japan.We are deeply grateful for the cooperation of Dr. T. Honma and Dr. H. Ofuchi of JASRI for the XAFS analyses (SPring-8, BL14B2), Dr. K. Osaka of JASRI for the measurement of the synchrotron X-ray diffraction (SPring-8, BL19B2). References 1) D. Aurbach, et al., Adv. Mater., 19, 4260 (2007).2) Y. Idemoto, et al., J. Power Sources, 482, 228920 (2021).3) Y. Idemoto, et al., J. Power Sources, 455, 227962 (2020).4) Y. Idemoto, et al, Electrochemistry, 90(2), 027002(2022).5) Y. Idemoto, et al, J. Electroanal. Chem., 928, 1107064 (2023). Figure 1

Improved Vanadium Flow Battery Performance through a Pulsating Electrolyte Flow Regime

AbstractThe interest in flow batteries as energy storage devices is growing due to the rising share of intermittent renewable energy sources. In this work, the performance of a vanadium flow battery is improved, without altering the electrochemical cell, by applying a pulsating flow. This novel flow battery flow regime aims to enhance performance by improving its mass transfer properties. Both the pulse volume and frequency have an influence on the battery performance, and lead to a 38.7 % increase in accessible discharge capacity compared to the conventional steady flow regime at values of 0.40 cm3 and 2.4 Hz in this cell, respectively. Furthermore, at these parameter settings a reduction of the mass transfer resistance by 71.4 % is achieved at 0.2 cm3/min ⋅ cm2. These results show that a pulsating flow can be beneficial in certain conditions, opening new possibilities for boosting performance in flow batteries.

Tuning phase structure and electrochemical hydrogen storage properties of A5B19-type La–Y–Ni–Mn-based superlattice alloys by partial Al substitution

Rare earth-based superlattice alloys are essential anodes for high-performance nickel-metal hydride (Ni-MH) batteries. This study aimed to improve the overall electrochemical hydrogen storage properties of (La0.33Y0.67)5Ni18.1-xMn0.9Alx alloys by adjusting the Al content. The alloys predominantly consist of the 2H–Pr5Co19 phase, with Al atoms mainly occupying the 12k2 site at the [AB5]-1/[AB5]-2 boundary and subsequently the 12k1 site at the [A2B4]/[AB5]-1 boundary. As a result, a minimum subunit volume difference of 2.08 Å3 is observed at x = 0.6. Therefore, the Al substitution is responsible for the decrease in the dehydriding plateau pressure and the increase in discharge capacity. Among them, the alloy (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 presents a discharge capacity of 361.2 mAh/g, a higher capacity retention S200 of 69.80 %, and better rate performance owning to the enhanced hydrogen diffusion rate through the multi-phase interface. This work demonstrates the potential of the (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 alloy as high-performance Ni-MH battery anode.

Effects of metal-ion substitution on the structural, morphological, and electrochemical properties of LiFexZnyMn2−x-yO4 (x, y = 0.25 or 0.75)

The oxides LiMn2O4, LiFe0.75Zn0.25MnO4, and LiFe0.25Zn0.25Mn1.5O4, referred to as LMO, LFZMO 0.75–0.25, and LFZMO 0.25–0.25, were synthesized at 800 °C using ultrasound-assisted thermal decomposition of nitrates (UA-TDN). X-ray diffraction (XRD) analyses confirmed the spinel structure (Fd3m space group) for all materials. Raman spectroscopy validated the characteristic absorption bands of the spinel phase. Energy-dispersive spectroscopy (EDS) verified the uniform distribution of Fe, Zn, Mn, and O in all samples and proved the expected stoichiometry for the different oxides. Scanning electron microscopy (SEM) images showed irregular polyhedral agglomerates in the synthesized oxides, with grain sizes ranging from approximately 600 to 800 nm. Electrochemical characterization was performed under N2 and O2 atmospheres, revealing electron-withdrawing effects with increasing iron content in the oxide composition. LFZMO 0.75–0.25, with a higher iron content, displayed better performance than LMO and LFZMO 0.25–0.25 in terms of discharge capacity and cycling performance at various rates. The greater discharge capacity of LFZMO 0.75–0.25 (47 mA h g −1) was in line with the cyclic voltammetry findings, wherein lower energy (∆GLi+/ Li0= 55.5 kJ mol−1) for lithium insertion correlated with an increased discharge capacity. Electrochemical Impedance Spectroscopy (EIS) was employed to determine diffusion constants, providing insights into Li+ insertion kinetics in the cathodic electrode and highlighting the significant influence of Zn and Fe incorporation on the lithium manganese oxide. Our findings are intriguing as the diffusion coefficient of DLi+ in LFZMO 0.75–0.25 (2.3 ×10−12 cm2 S−1) surpasses that of LMO (8.5 ×10−14 cm2 S−1) and LFZMO 0.25–0.25 (9.4 ×10−18 cm2 S−1). This observation further elucidates the more positive formal potential for Li+ insertion in LFZMO 0.75–0.25.

Unveiling the Role of Ruthenium in Layered Sodium Cobaltite Toward High‐Performance Electrode Enabled by Anionic and Cationic Redox

AbstractThe effect of Ru substitution on the structure and electrochemical properties of P2‐type Na0.67CoO2 is investigated. The first‐discharge capacities of Na0.67CoO2 and Na0.6 [Co0.78Ru0.22]O2 materials are 128 and 163 mAh g−1 (23.5 mA g−1), respectively. Furthermore, the rate capability is improved due to the electro‐conducting nature of Ru doping. Operando X‐ray diffraction analysis reveals that the Na0.67CoO2 does not undergo a phase transition; however, multiple Na+/vacancy ordered superstructures within the P2 phase appear during Na+ extraction/insertion. In contrast, the Na0.6[Co0.78Ru0.22]O2 material undergoes a P2–OP4 phase transition during desodiation, with no formation of Na+/vacancy ordering within the P2 phase. The increased discharge capacity of Na0.6[Co0.78Ru0.22]O2 is most likely associated with additional cationic Ru4+/Ru5+ redox and increased anionic O2−/(O2n−) redox participation. Combined experimental (galvanostatic cycling, X‐ray absorption spectroscopy, differential electrochemical mass spectrometry) and theoretical (density functional theory calculations) studies confirm that Ru substitution provokes the oxygen‐redox reaction and that partial O2 release from the oxide lattice is the origin of the reaction. The findings provide new insight for improving the electrode performance of cathode materials via 4d Ru substitution and motivate the development of a new strategy for the design of high‐capacity cathode materials for sodium‐ion batteries.

Electrochemical hydrogen storage in LaMO3 (M = Cr, Mn, Fe, Co, Ni) nano-perovskites

In this work, a comparative study has been demonstrated on the effect of several transition metal cations including Cr3+, Mn2+, Fe3+, Co2+, and Ni2+ in LaMO3 perovskite-type structures at its M position on their electrochemical hydrogen sorption/storage process. The nano-sized LaMO3 perovskites were synthesized using sol-gel method and then, they were calcined under the optimal experimental conditions at air atmosphere at 900 °C for 5 h. The electrochemical studies indicate that the LaFeO3 nanoparticles with uniform size and shape, in a 6 M KOH alkaline electrolyte after 15th cycles, generate the highest discharge capacity of 13,500 mAh/g compared to other nano-perovskites, which is due to their higher surface reactivity and faster electron transfer. Furthermore, after twenty cycles, this electrode displays an additional increase in discharge capacity along with superior cycling stability; hence it can be a good candidate for battery applications.

A comparative study of the effect of synthesis method on the formation of P2- and P3-Na0.67Mn0.9Mg0.1O2 cathodes

Na-ion batteries offer a way to develop large-scale energy storage necessary for the increased adoption of renewable energy sources. Layered transition metal oxide materials for electrodes can be synthesised using abundant and non-toxic materials, decreasing costs and risks compared to lithium-ion batteries. Solid state processing is commonly used for synthesis, using long calcinations at high temperatures (>800 °C). Other synthetic routes, such as biotemplating, offer the opportunity to reduce reaction temperatures and times, and can enable access to different polymorphs. Here, we compare the properties of Na0.67Mn0.9Mg0.1O2 synthesised by both solid state and biotemplating, producing both P2 and P3 polymorphs to understand the differences which arise as a result of synthesis and temperature choice. We show that biotemplated P3-Na0.67Mn0.9Mg0.1O2 offers increased discharge capacity over the more commonly reported P2 phase for 50 cycles at C/5, 103 mAh g−1 for biotemplated P3-NMMO. Furthermore, the biotemplating samples demonstrate improved capacity after 50 cycles at C/5, and higher capacity delivered at 5C in both P2 and P3 phases over conventional solid state synthesis.

Microstructural study of sonochemical synthesized belt-like Zr(MoO4)2/MoO3 composites for efficient energy storage

It is currently being widely explored as an electrode material for future storage devices that transition metal oxides can provide a synergistic effect during electrochemical reactions. We synthesized composites of Zr(MoO4)2/MoO3 with belt-like morphologies using ligand assisted Ultrasonics. Compared to other methods of synthesis, ultrasonic synthesis is less costly and easier to use, and it has the advantage of speeding up the formation process. It is possible that the duration of the sonication process can have an impact on the microstructural properties of the sample. As a result, Zr(MoO4)2/MoO3 composites were synthesized under ultrasonic probes for five, ten, and fifteen minutes, respectively. The achieved sample serves as an active material in an electrochemical energy storage system comprised of a three-electrode cell and an electrolyte containing KOH. Depending on the current density, the kinetics of the electrochemical reaction and the stability of the materials in the working electrode are affected. Nevertheless, the capacity of Zr(MoO4)2/MoO3 composites was studied at different currents of 0.5, 1, 2 and 3 mA in order to identify optimal parameters. The results indicate an increase in discharge capacity at 2 mA from the first cycle to the thirteenth cycle, from 200 to 750 mAhg−1. In contrast, applying a current of 3 mA results in a decrease in capacity and structural damage. Conversely, using lower currents of 0.5 and 1 mA results in lower capacity compared to 2 mA. In this way, belt-like Zr(MoO4)2/MoO3 composites can be utilized as potential active materials in energy storage systems, such as hydrogen storage.

Improving the electrochemical performance of ultrahigh-nickel-based layered LiNi0.95Mn0.05O2 cathode through cobalt modification for next-generation high-energy Li-ion batteries

Nickel-rich cobalt-free layered cathode materials are expected to meet the urgent demand for high-energy batteries at an adorable cost. However, as the nickel content increases and cobalt content decreases, layered cathode materials suffer from serious structure degradation and capacity fade during cycling. The large amount of residual lithium in nickel-rich materials also brings difficulties to industrial manufacturing and challenges battery safety. In this work, well-formed crystal cobalt-contained coatings with surface cobalt-doped ultrahigh-nickel-based layered LiNi0.95Mn0.05O2 cathode material is synthesized through solid solution and post-heat treatment with Co(OH)2, during which the residual lithium is significantly consumed. The optimized sample acquired at 650 ℃ shows an increased discharge capacity of 221.2 mAh g−1 from 219 mAh g−1 of the pristine one at 0.1 C and the capacity retention is enhanced from 72.6% to 83.2% for 100 cycles at 0.5 C.

Preparation of nickel and graphene modified La9CeMg80Ni5 composites and their microstructure and electrochemical properties

A La2Mg17-type alloy La9CeMg80Ni5 was prepared and mechanically crushed to powders. Ni and Graphite (GR) were added during ball milling to prepare the surface-modified La9CeMg80Ni5-GR-Ni composites. The influence of milling time and Ni content on the structure and electrochemical properties of the composite materials were investigated. After milling, the composite materials are capable of electrochemically hydriding and dehydriding at room temperature. As Ni content increases, the 40 h-milled composites show an increased discharge capacity from 219.6 to 986.2 mAh/g, HRD from 75.3% to 86.8%, and capacity retention rate of 20th cycle from 58.2% to 65.8%; the 80 h-milled composites show an increased discharge capacity from 252.6 to 1034.7 mAh/g, HRD from 80.5% to 87.9%, and capacity retention rate of 20th cycle from 47.3% to 56.2%.

ErMnO3/Er2Mn2O7/ZnO/GO multi-component nanocomposite as a promising material for hydrogen storage: Facile synthesis and comprehensive investigation of component roles

As part of this work, a multi-component nanocomposite with hydrogen storage capability was synthesized. To begin with, ErMnO3/ErMn2O5/ZnO were synthesized in-situ, and then graphene oxide (GO) was added. Oxygen-containing functional groups on the surface of GO acted as an oxidant, resulting in ErMn2O5 (Mn+3) being converted to Er2Mn2O7 (Mn+4). A secondary phase of ErMn2O5 was formed as a result of calcination temperatures lower than 1200 °C, facilitating the in-situ synthesis of three-component nanocomposite materials. An important aspect of this work is examining each component's role in changing the properties. Moreover, results showed that adding ZnO could change the magnetic property from ferromagnetism to paramagnetism, and thanks to GO, ferromagnetism was revealed once again. An electrochemical test confirmed that ZnO and GO could promote H2-storage capacity, increasing discharge capacity from 450 to 850 mAhg−1 and 1200 mAhg−1 during different steps. It can be considered that an increase in pore volume (about 10 times) is one of the factors contributing to this phenomenon.

The Double-Edged Effect of Water on Li-O2 Aprotic Batteries

Storing larger amounts of energy is becoming critical as more renewable and intermittent energy sources emerge in our society. Li-O2 batteries have the highest theoretical energy density, but there are still barriers to overcome. The presence of water in atmospheric air makes studying its effects on battery performance necessary if ambient oxygen ought to be used in such devices. This paper investigates the effect of different concentrations of water in the electrolyte of Li-O2 aprotic batteries, on deep discharge capacity and cyclability. Batteries were prepared with a metallic lithium anode, glass microfiber membrane, 0.1 M LiClO4/DMSO electrolyte with various water concentrations (15–144,000 ppm), and carbon paper cathode. An increase in discharge capacity of >300% was achieved with 550 ppm of water; however, a gradual reduction in cyclability was observed increasing water concentration. We show that it occurs due to changes in the reaction mechanism, composition, and morphology of the discharge products, incomplete decomposition, and formation of a passivating film on the metallic lithium anode. Moreover, this article elucidates the causes underlying the involved mechanism and highlights the double-edged effect of water on the electrochemical performance of Li-O2 batteries, causing improvements in deep discharge capacity at the cost of reduced cyclability.

Mechanical Structuring of Lithium‐Ion Battery Electrodes Using an Embossing Roller

Highly performing lithium‐ion batteries are essential for the electrification of the transport sector. However, the two performance criteria, high power density and high energy density, inversely correlate with each other via the mass loading of the electrodes. To achieve high charging and discharging rates at high energy densities, structuring of electrodes is a proven method. Currently, structures are mostly realized by laser ablation, which comes along with material loss and low process rates. Herein, a concept for electrode structuring through mechanical embossing in a high‐throughput roll‐to‐roll process is elaborated. Different integration options are described and the challenges are discussed. To provide a proof of concept, a hand‐operated embossing device is built and used to structure graphite anodes. In a rate capability test, an increase in discharge capacity at medium C‐rates by up to 14.3% is observed.

Numerical Study on Hydraulic Characteristics and Discharge Capacity of Modified Piano Key Weir with Various Inlet/Outlet Width Ratio

A modified piano key weir with a rounded nose and a parapet wall (MPKW) can improve the discharge capacity significantly compared to a standard piano key weir. However, the optimum of the inlet/outlet width ratio (Wi/Wo) on the discharge efficiency of MPKW is still not investigated numerically. The present work utilized the numerical modeling to investigate and analyze the effects of the inlet/outlet key width ratios on the hydraulic characteristics and discharge capacity of the MPKW. To validate the numerical model with the experimental data, the results indicate that the average relative error is 2.96%, which confirms that the numerical model is fairly well to predictthe specifications of flow over on the MPKW. Numerical simulation results indicated that the discharge capacity of the MPKW can be improved up to 8.5% by optimizing the Wi/Wo ratio ranging from 1.53 to 1.67 even if the other parameters of the MPKW keep unchanged. A big Wi/Wo ratio generally leads to an increase in discharge capacity at low heads and a little effect on the discharge efficiency at high heads. The discharge efficiency of the inlet and outlet crests increases up to 9.6% for high heads, while discharge efficiency of the lateral crest decreases up to 23.5% compared with the reference model. The findings of the study revealed that the intrinsic influencing mechanism of the Wi/Wo ratio on the discharge performance of MPKWs.