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At least 73 records · Page 4

System level electrochemical principles

The traditional electrochemical storage concepts are difficult to translate into high power, high voltage multikilowatt storage systems. The increased use of electronics, and the use of electrochemical couples that minimize the difficulties associated with the corrective measures to reduce the cell to cell capacity dispersion were adopted by battery technology. Actively cooled bipolar concepts are described which represent some attractive alternative system concepts. They are projected to have higher energy densities lower volumes than current concepts. They should be easier to scale from one capacity to another and have a closer cell to cell capacity balance. These newer storage system concepts are easier to manage since they are designed to be a fully integrated battery. These ideas are referred to as system level electrochemistry. The hydrogen-oxygen regenerative fuel cells (RFC) is probably the best example of the integrated use of these principles.

Thaller, L. H.↗

Perspective—Potential Benefit of Li-Rich Cathode Materials: Reduction of Co and Ni Content Rather than Achievement of Ultra-High Capacities

In the conventional cycling protocol for lithium and manganese rich NMC layered oxides (LMRNMC), the upper cutoff voltage V cut is extended to ~ 4.8, to achieve capacities of similar to 250 mAh g -1 . With this mode of operation, structural rearrangements result in voltage fade upon cycling. Herein, a strategy is proposed to avoid these structural rearrangements based on (a) restricting V cut to values < ~ 4.6 to shut down the bulk instabilities, and (b) application of a (preferably) semi-coherent coating that protects the surface oxygen. The potential benefit of this strategy would be to minimize Co and Ni content, compared to Ni-rich NMC.

25 ENERGY STORAGE↗

Correlating the phase evolution and anionic redox in Co-Free Ni-Rich layered oxide cathodes

Current trend of high-capacity Ni-rich layered cathode is to develop high-Ni and low-Co or Co-free oxides. The high Ni content layered oxides provide great advantages in capacity, cost and environmental benignity, similar to LiNiO 2 parent compound. But they also inherit drawbacks in structural and chemical instability at high voltages upon cycling. As such, elemental substitution plays a profound role in addressing these challenges. This work elucidates the roles of Al doping in cationic redox and anionic oxygen activity in LiAl x Ni 1-x O 2 using combined X-ray absorption spectroscopy (XAS), resonant inelastic X-ray scattering (RIXS) as well as operando differential electrochemical mass spectrometry (DEMS). Using synchrotron wide-angle X-ray scattering (WAXS), we extrapolate a general principle of phase transition and its coupling with lattice anionic oxygen redox. These findings shed light on the advancement of high-capacity, stable-cycling and safe-operating Ni-rich cathode materials for next generation Li-ion batteries.

25 ENERGY STORAGE↗

Elimination of NO Pollutant in Semi-enclosed Spaces over Sodium-promoted Cobalt Oxyhydroxide (CoOOH) by Oxidation and Adsorption Mechanism

Low concentrations of NOx accumulated in air in semi-enclosed spaces is a severe health hazard, but its efficient removal at low cost is a grand challenge. A simple method in preparing CoOOH for low-concentration NO removal at room temperature is described here. The samples are synthesized by oxidizing Co(OH)2 to CoOOH with different oxidants (Na2S2O8, O2 and H2O2). Among them, CoOOH prepared by Na2S2O8 (Co-NS) shows remarkable performance for NO abatement, while the samples synthesized by and H2O2 (Co-HO) and O2 (Co-OG) have no apparent NO removal capacity. It is found that the Co-NS material contains a higher concentration of residual Na, which contributes to the decreased crystallinity and increased concentrations of surface active species (Co2+, active oxygen) for NO storage. Following NO storage, the material can be readily regenerated by water washing. The authors from East China University of Science and Technology acknowledge support from National Basic Research Program of China (2013CB933200), National Natural Science Foundation of China (21577035, 21577034), Commission of Science and Technology of Shanghai Municipality (15DZ1205305) and 111 Project (B08021). Aiyong Wang acknowledges the China Scholarship Council for the Joint-Training Scholarship Program with the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the US DOE under contract DE-AC05-76RL01830. FG is supported by the U.S. DOE/Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office.

NOx abatement, NOx adsorber, ambient temperature, ↗

Stabilizing high-Ni cathodes with gradient surface Ti-enrichment

High-Ni cathodes are being intensely pursued worldwide for electric vehicles and other energy-dense applications due to their high capacity and low cost. However, structural instabilities during electrochemical cycling and when subjected to thermal treatment have been the major issues hindering their practical deployment. We here report a rational design of coating-integrated-into-synthesis protocol for fabricating surface Ti-enriched LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811#Ti) material. The coating to intermediates is crucial to obtain high structural ordering, both in the bulk and surface of high-Ni cathodes, and the Ti substitute has a unique tri-valence (Ti 3+ ) in a gradient surface distribution. Further, the simulations of projected density of states in the atomistic understanding further certify significantly enhanced stability of lattice oxygen for the NMC811 through such a Ti 3+ -based structure reinforcement. Consequently, the NMC811#Ti cathode delivers a high capacity up to 200mAhg -1 at 0.1 C, along with superior stabilities during air-storage and thermal treatment (up to 297°C at the fully charged state under differential scanning calorimetric measurements). The corresponding NMC811#Ti||graphite full cell exhibits a desired 83.6% capacity retention after 1000 cycles at 0.5 C in a voltage range of 2.8–4.3V. This work demonstrates a delicate surface reinforcement to stabilize high-Ni cathodes for long-life and safe lithium-ion batteries.

36 MATERIALS SCIENCE↗

Proton Storage in Metallic H 1.75 MoO 3 Nanobelts through the Grotthuss Mechanism

The proton, as the cationic form of the lightest element-H, is regarded as most ideal charge carrier in "rocking chair " batteries. However, current research on proton batteries is still at its infancy, and they usually deliver low capacity and suffer from severe acidic corrosion. In this work, electrochemically activated metallic H 1.75 MoO 3 nanobelts are developed as a stable electrode for proton storage. The electrochemically pre-intercalated protons not only bond directly with the terminal O 3 site via strong O-H bonds but also interact with the oxygens within the adjacent layers through hydrogen bonding, forming a hydrogen-bonding network in H 1.75 MoO 3 nanobelts and enabling a diffusion-free Grotthuss mechanism as a result of its ultralow activation energy of ~0.02 eV. To the best of our knowledge, this is the first reported inorganic electrode exhibiting Grotthuss mechanism-based proton storage. Additionally, the proton intercalation into MoO 3 with formation of H 1.75 MoO 3 induces strong Jahn-Teller electron-phonon coupling, rendering a metallic state. As a consequence, the H 1.75 MoO 3 shows an outstanding fast charging performance and maintains a capacity of 111 mAh/g at 2500 C, largely outperforming the state-of-art battery electrodes. More importantly, a symmetric proton ion full cell based on H 1.75 MoO 3 was assembled and delivered an energy density of 14.7 Wh/kg at an ultrahigh power density of 12.7 kW/kg, which outperforms those of fast charging supercapacitors and lead-acid batteries.

25 ENERGY STORAGE↗

Evaluation of Hydrogen Storage Quantity Limits for Safety Requirements

As hydrogen storage facilities increase in size and capacity, it may be necessary to evaluate codes and standards that regulate hydrogen, especially in relation to allowable aggregate quantities. Existing regulations for other substances with comparable hazards such as oxygen, natural gas, and petroleum were reviewed; most fuels do not have aggregate quantity limits despite sometimes having individual tank capacity restrictions or limits for certain non-industrial, indoor, or small-scale applications. This precedent suggests that specifying a hydrogen quantity limit may not be necessary. Several possible methods for identifying an appropriate limit are presented to illustrate different approaches for a limit basis. These methods are based on overall risk, or the specific consequences inflicted by a jet fire or an explosion on people and infrastructure. However, these example metrics tend to require assumptions about potential leak sizes, suggesting that a general aggregate quantity limit would be difficult to justify without more system-specific requirements.

08 HYDROGEN↗

Interplay Between Cation and Anion Redox in Ni-Based Disordered Rocksalt Cathodes

The reversibility of the redox processes plays a crucial role in the electrochemical performance of lithium-excess cation-disordered rocksalt (DRX) cathodes. Here, we report a comprehensive analysis of the redox reactions in a representative Ni-based DRX cathode. The aim of this work is to elucidate the roles of multiple cations and anions in the charge compensation mechanism that is ultimately linked to the unique electrochemical performance of Ni-based DRX cathodes. Generally, the low-voltage discharge plateau that results in the low energy efficiency and strong voltage hysteresis is associated with the low-voltage oxygen redox. However, incorporating Mo cation promotes the oxygen activity and the Mo migration between octahedral and tetrahedral sites enhances the O reduction potential as well as energy efficiency. This work highlights the important role that electrochemically inactive transition metal plays in the redox chemistry and provides useful insights into the potential pathway to further address the challenges in Ni-based DRX systems.

Yue, Yuan↗

Harbinger of hysteresis in lithium-rich oxides: Anionic activity or defect chemistry of cation migration

In this work, we present findings on the mechanisms of hysteresis in lithium-rich cathode oxides. It is generally reported that the energy inefficiency, observed during electrochemical cycling of Li-rich electrodes, is a direct result of anion redox processes. Similarly, the coupled phenomenon of cation migration has been cited as being a mere consequence of that process with no essential ramification to hysteresis. Such works, however, have only shown correlations and not causation. Specifically, studies that clearly preclude the complete absence of either anion redox or cation migration (down to defect-level concentrations) are not reported yet. Herein, we present first principles calculations and experimental data on a bespoke Li-rich system that is indubitably immune to oxygen activity but yet exhibits significant energy inefficiency. Additionally, the results directly implicate transition metal migration as the fundamental, sole process responsible for hysteresis in this material. This study is of particular importance to the design and development of new Li-rich materials aimed at eliminating the role of oxygen and enhancing the effective cationic redox contribution to the capacity and points out the essential need to develop materials devoid of transition metal migration to interstitial sites in both layered and disordered oxides alike.

25 ENERGY STORAGE↗

Composition-Nanoarchitecture-Performance Analysis of High Energy Density Electrodeposited Silicon for Lithium-Ion Battery Anodes

Electrodeposition of silicon (Si) was previously demonstrated as a promising method for fabricating 3D-structured lithium-ion battery anodes. However, the relationship between the electrochemical performance and chemical composition of the relatively impure electrodeposited silicon is not well understood. Here, we report the electrodeposition of a Si-dominant active material (EDEP-Si) onto 3D-structured nickel (Ni) scaffolds and systematically compare the electrochemical properties, elemental composition, atomistic Si coordination, and molecular structure of EDEP-Si with high-purity amorphous Si grown via static chemical vapor deposition. Despite the considerable amount of carbon (9–11 at %) and oxygen (42–44 at %) present in EDEP-Si, the cycling stability and high reversible specific capacity are remarkably similar to those of CVD-Si on a silicon basis (~2400 mA h/g-Si after 100 cycles). The primary difference is that EDEP-Si exhibits reduced cycling efficiency over the first 10–20 cycles. Reactions between carbon and, more importantly, oxygen in EDEP-Si with lithium are likely responsible for the reduced early cycle performance and lower capacity of the total deposit. Finally, our observations suggest ultrapure Si is not necessary for high electrochemical access to reversible charge storage, although limiting the presence of incorporated impurity species would improve energy density and first cycle efficiency.

25 ENERGY STORAGE↗

Understanding cation doping achieved by atomic layer deposition for high-performance Li-Ion batteries

As Li ion battery (LIB) technology develops, its nanoscale design is attracting more and more interest. Atomic layer deposition (ALD) has emerged as a promising technique to provide conformal and ultrathin coating for LIB materials. In this work, an iron oxide (FeO x ) ALD was performed on LiMn 1.5 Ni 0.5 O-5 4 (LMNO) cathode particles, followed by an annealing process. Here, Fe was doped into LMNO during the ALD process; and it was found that lattice oxygen loss and structural change of LMNO occurred at a reaction temperature of 450 °C under vacuum. Meanwhile, Fe diffused from the surface to the bulk of LMNO. After post-annealing, FeO x -coated LMNO recovered its structure and lattice oxygen under proper annealing conditions, and exhibited significant enhancement of specific capacity, rate capability, and cyclic stability.

25 ENERGY STORAGE↗

Enabling Facile Anionic Kinetics through Cationic Redox Mediator in Li-Rich Layered Cathodes

Anionic oxygen redox has aroused great interests in developing high-capacity Li-ion battery cathode materials. The fundamental understanding of this concept, compared to cationic redox, has promoted extensive studies on lithium transition metal oxides including those of 4d and 5d transition metals. Lithium ruthenium oxide has been found to exhibit a reversible anionic redox upon cycling. However, lithium-rich layered oxide with anionic redox is still facing great challenges such as sluggish kinetics. Here we investigate the effect of cationic redox on the kinetics of anionic reaction when they are strongly coupled. We report the cobalt substituted lithium ruthenium oxide, where all Ru, Co and O redox participate in the charge compensation mechanism in relatively defined voltage regions. Additionally, the improved anionic kinetics is attributed to the fast cationic Co redox process that serves as a redox mediator. Our work sheds light into the potential direction to address the commonly believed sluggish anionic kinetics in high-capacity oxygen-redox cathode materials.

25 ENERGY STORAGE↗

Fast oxygen redox enabled by flexible Al–O bonds in P2-type layered oxides for sodium batteries

Sodium-ion batteries (SIBs) exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources. Triggering lattice oxygen redox (LOR) in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes, providing high operating potential and substantial capacity. However, irreversible phase transitions associated with LOR, particularly from prisms (P-type stacking) to octahedrons (O-type stacking), lead to severe structural distortions and sluggish Na + diffusion kinetics. In this work, an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase. Furthermore, the flexible Al-O bonds accommodate asymmetric variations in their occupied states during the sodiation process, mitigating local structural distortions through Al-O bond contraction. Stabilization of the local structure ensures the maintenance of a robust Na + diffusion pathway. As a result, the Al-substituted cathode achieves a low Na + diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V, maintaining 62.5% capacity retention over 100 cycles.

36 MATERIALS SCIENCE↗

Polymer-ceramic composite electrolytes for all-solid-state lithium batteries: Ionic conductivity and chemical interaction enhanced by oxygen vacancy in ceramic nanofibers

Perovskite Li 3x La 2/3-x TiO3 (LLTO) nanofibers have been heat-treated in the hydrogen-containing atmosphere and then incorporated with the poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) polymer to form a composite electrolyte. Hydrogen treatment has created oxygen vacancies in the LLTO nanofibers, which has reduced the activation energy of Li ion transport along intra-grains and inter-grains, leading to improvement in the ion conductivity of LLTO nanofibers. Hydrogen treatment of the LLTO nanofibers has also enhanced the chemical interaction between the LLTO nanofibers and the polymer matrix in the composite electrolyte, and favored the Li ion transport at the nanofiber/polymer interface, improving the ion conductivity of the composite electrolyte to 3.4×10- 4 S/cm at room temperature. As a result, the Li|composite-electrolyte|Li half-cell exhibits good stability during lithium plating/stripping cycling at room temperature, showing an overpotential of ~91 mV at a constant current density of 0.5 mA/cm 2 . Finally, the full-cell battery with the composite electrolyte, lithium metal anode and lithium iron phosphate cathode shows excellent rate capacity and cycling performance.

25 ENERGY STORAGE↗

Multinonmetal-Doped V 2 O 5 Nanocomposites for Lithium-Ion Battery Cathodes

Lithium-ion batteries (LIBs) are critical for portable electronics and electric vehicles, demanding higher energy density to meet increasing energy storage needs. Current commercial cathode materials, such as LiFePO 4 and LiCoO 2 , are limited by a single electron transfer, restricting their energy density. Vanadium pentoxide (V 2 O 5 ) emerges as a promising high-capacity cathode due to its high theoretical capacity of 443 mA h g –1 with three Li storage capacities, significantly surpassing conventional materials. However, the practical application of V 2 O 5 is hindered by a large structural evolution and rapid capacity fading during full lithium intercalation. Here, this study introduces a multinonmetal doping (MNM) strategy to enhance V 2 O 5 cathodes by incorporating all-nonmetal dopants (B, P, and Si) and graphene (G). MNM-V 2 O 5 -G exhibits increased surface oxygen defects, improving charge transfer kinetics and thus enhancing the rate performance and cycling stability. Our results provide valuable insights into the role of surface oxygen defects in stabilizing V 2 O 5 with element doping. This research highlights the potential of multinonmetal doping to improve LIB cathode materials, offering a promising pathway for design of high-energy-density V 2 O 5 cathodes and advancing the development of next-generation energy storage solutions.

25 ENERGY STORAGE↗

Fast Proton Insertion in Layered H 2 W 2 O 7 via Selective Etching of an Aurivillius Phase

H 2 W 2 O 7 , a metastable material synthesized via selective etching of the Aurivillius-related Bi 2 W 2 O 9 , is shown as an electrode for high power proton-based energy storage. Comprehensive structural characterization is performed to obtain a high-fidelity crystal structure of H 2 W 2 O 7 using an iterative approach that combines X-ray diffraction, neutron pair distribution function, scanning transmission electron microscopy, Raman spectroscopy, and density functional theory modeling. Electrochemical characterization shows a capacity retention of ≈80% at 1000 mV s –1 (1.5-s charge/discharge time) as compared to 1 mV s –1 (≈16-min charge/discharge time) with cyclability for over 100 000 cycles. Energetics from density functional theory calculations indicate that proton storage occurs at the terminal oxygen sites within the hydrated interlayer. Last, optical micrographs collected during in situ Raman spectroscopy show reversible, multicolor electrochromism, with color changes from pale yellow to blue, purple, and last, orange as a function of proton content. These results highlight the use of selective etching of layered perovskites for the synthesis of metastable transition metal oxide materials and the use of H 2 W 2 O 7 as an anode material for proton-based energy storage or electrochromic applications.

25 ENERGY STORAGE↗

Probing Depth-Dependent Transition-Metal Redox of Lithium Nickel, Manganese, and Cobalt Oxides in Li-Ion Batteries

Layered lithium nickel, manganese, and cobalt oxides (NMC) are among the most promising commercial positive electrodes in the past decades. Understanding the detailed surface and bulk redox processes of Ni-rich NMC can provide useful insights into material design options to boost reversible capacity and cycle life. Both hard X-ray absorption (XAS) of metal K-edges and soft XAS of metal L-edges collected from charged LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) showed that the charge capacity up to removing ~0.7 Li/f.u. was accompanied with Ni oxidation in bulk and near the surface (up to 100 nm). Of significance to note is that nickel oxidation is primarily responsible for the charge capacity of NMC622 and 811 up to similar lithium removal (~0.7 Li/f.u.) albeit charged to different potentials, beyond which was followed by Ni reduction near the surface (up to 100 nm) due to oxygen release and electrolyte parasitic reactions. Overall, this observation points toward several new strategies to enhance reversible redox capacities of Ni-rich and/or Co-free electrodes for high-energy Li-ion batteries.

25 ENERGY STORAGE↗

A KMnO 4 -Generated Colloidal Electrolyte for Redox Mediation and Anode Protection in a Li–Air Battery

The rechargeable lithium-oxygen (Li-O 2 ) battery has the highest theoretical specific energy density of any rechargeable batteries and could transform energy storage systems if a practical device could be attained. However, among numerous challenges, which are all interconnected, are polarization due to sluggish kinetics, low cycle life, small capacity, and slow rates. Here, in this study, we report on use of KMnO 4 to generate a colloidal electrolyte made up of MnO 2 nanoparticles. The resulting electrolyte provides a redox mediator for reducing the charge potential and lithium anode protection to increase cycle life. This electrolyte in combination with a stable binary transition metal dichalcogenide alloy, Nb 0.5 Ta 0.5 S 2 , as the cathode enables the operation of a Li-O 2 battery at a current density of 1 mA center dot cm -2 and specific capacity ranging from 1000 to 10000 mA center dot h center dot g -1 (corresponding to 0.1-1 mA center dot h center dot cm -2 ) in a dry air environment with a cycle life of up to 150. This colloidal electrolyte provides a robust approach for advancing Li-air batteries.

25 ENERGY STORAGE↗