Use Of Cathode Research Articles

Strong Magnetic Exchange Interactions and Delocalized Mn-O States Enable High-Voltage Capacity in the Na-Ion Cathode P2-Na0.67[Mg0.28Mn0.72]O2.

The increased capacity offered by oxygen-redox active cathode materials for rechargeable lithium- and sodium-ion batteries (LIBs and NIBs, respectively) offers a pathway to the next generation of high-gravimetric-capacity cathodes for use in devices, transportation and on the grid. Many of these materials, however, are plagued with voltage fade, voltage hysteresis and O2 loss, the origins of which can be traced back to changes in their electronic and chemical structures on cycling. Developing a detailed understanding of these changes is critical to mitigating these cathodes' poor performance. In this work, we present an analysis of the redox mechanism of P2-Na0.67[Mg0.28Mn0.72]O2, a layered NIB cathode whose high capacity has previously been attributed to trapped O2 molecules. We examine a variety of charge compensation scenarios, calculate their corresponding densities of states and spectroscopic properties, and systematically compare the results to experimental data: 25Mg and 17O nuclear magnetic resonance (NMR) spectroscopy, operando X-band and ex situ high-frequency electron paramagnetic resonance (EPR), ex situ magnetometry, and O and Mn K-edge X-ray Absorption Spectroscopy (XAS) and X-ray Absorption Near Edge Spectroscopy (XANES). Via a process of elimination, we suggest that the mechanism for O redox in this material is dominated by a process that involves the formation of strongly antiferromagnetic, delocalized Mn-O states which form after Mg2+ migration at high voltages. Our results primarily rely on noninvasive techniques that are vital to understanding the electronic structure of metastable cycled cathode samples.

Optimization of Bi2O3 Content in CuO-Bi2O3 Cathodes for Secondary Zn Alkaline Batteries Leads to Improved Capacity and Cycling

Secondary alkaline batteries pairing Zn anodes with metal oxide cathodes (MnO2, CuO, etc.) are a promising route to energy-dense, inexpensive batteries for use in grid-scale energy storage. However, the low cycle life and material stability of secondary alkaline batteries, especially when compared to competing chemistries like Li-ion batteries, must be addressed in order to further develop these technologies. In recent years, studies have shown that the addition of chemical additives like Bi2O3 to the metal oxide cathodes can significantly improve their cyclability. Further work is needed, however, to better understand the mechanism of this improvement and further optimize cathode composition and performance.In this presentation, we will present our efforts to optimize the Bi2O3 composition of a CuO-Bi2O3 cathode for use in secondary Zn-CuO alkaline batteries. Earlier reports showed that relatively large quantities of Bi2O3 additive (10 wt.%) allowed for improved cathode conductivity and promoted the electroreduction of CuOx to Cu0. However, the use of such large quantities of a heavy additive also reduced the effective capacity of the resulting cathode by up to 15%, relative to a CuO cathode without any Bi2O3. Here, we show that the use of as little as 1 wt.% Bi2O3 is sufficient to affect a similar improvement in CuO cycling performance, and that even a Bi2O3-saturated KOH electrolyte solution is sufficient to impact the cyclability of a CuO cathode. Using a variety of physical and (electro)chemical techniques, we show that at these low Bi concentrations the Bi likely cycles between a sparingly soluble BiOx/Bi(OH)4 2- reservoir contained in both the cathode and electrolyte in the charged state, and solid Bi0 that is uniformly distributed on the surface of the CuOx/Cu0 cathode in the discharged state. Various electron microscopy techniques (SEM and STEM) show that this has a notable impact on the physical morphology of the active material in the cathodes after cycling, while electrochemical impedance spectroscopy (EIS) shows how electron transfer resistance varies based on Bi2O3 concentration. On a fundamental level, our results show that changes in Bi2O3 concentration notably impact the charge-discharge behavior of the CuO cathodes and results in the suppression of metal hydroxide-related redox peaks on charge. The absence of these peaks is thus correlated with improved cyclability, suggesting that the addition of Bi and the suppression of these recharge pathways may lead to higher capacity, more stable CuO cathodes in the future.This work was supported by the U.S. Department of Energy, Office of Electricity and Sandia National Laboratories, a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Dr. Imre Gyuk, Director of Energy Storage Research, Office of Electricity is thanked for his financial support. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Effect of NMC-doping Concentration on the Structural Feature and Electrical Properties of Lithium Iron Phosphate Cathode for Use in Lithium-ion Batteries

T his study investigates the synthesis of Lithium Iron Phosphate (LFP) with NMC-doped cathode materials, aiming to enhance the performance of lithium-ion batteries. The NMC content was varied from 0.02 to 0.10wt%, and 1wt% of (NH4)3PO4 was added to all conditions to prevent phosphate loss during the calcination process. The composite powder was prepared using a straightforward mixed oxide method, with a calcination temperature of 600 °C for 5 hours under an argon gas flow. X-ray diffraction (XRD) analysis confirmed the successful formation of pure LFP with an orthorhombic crystal structure, devoid of any secondary phases. To further explore the impact of NMC doping on the structural characteristics, FTIR and Raman spectroscopy were employed. Results revealed that increasing NMC doping concentration beyond 0.02wt% led to the broadening of the PO43− symmetric stretching band at approximately 947 cm−1, indicating a higher degree of disorder in the LFP structures. This disorder was found to adversely affect electrochemical performance, resulting in decreased discharge capacity and increased impedance, as determined by electrochemical impedance spectroscopy (EIS), with higher concentrations of NMC and (NH4)3PO4. Scanning Electron Microscopy (SEM) analysis unveiled the presence of agglomerated particles ranging in size from 0.5 to 0.9 microns. Optimal conditions were identified with the addition of NMC doped at 0.02wt%, which exhibited a discharge capacity of approximately 119.41 mAh/g at 0.2 C, along with a low impedance of 200 Ohm. Moreover, the 0.02wt% sample demonstrated a promising linear trend in cycle performance, suggesting its potential for future applications in lithium-ion batteries.

Reducing Manganese Dissolution in Electrolytic Manganese Dioxide Electrodes in NaOH Electrolyte

Previous attempts to enhance the stability and performance of MnO2-based cathodes for use in aqueous alkaline electrolytes, primarily KOH-based, have relied on a range of additives. This work demonstrates that the fast capacity decay of the MnO2-based cathode materials in alkaline electrolytes is mainly due to spontaneous manganese dissolution when cycling through the second-electron reaction voltage range. Reducing relative electrolyte content and using carbon materials that have a high specific surface area suppresses manganese dissolution and thus extends the cycle life of the electrode material while reducing overall battery costs. Moreover, reducing the size of the MnO2 particles and decreasing the cycling rate are found to increase manganese dissolution and negatively impact the performance of the electrode material, indicating a sensitivity to material surface area. Lastly, Fe-MnO2-based low-cost battery chemistry was also demonstrated based on the second electron reaction of the MnO2 in an electrolyte lean environment, which could be promising for grid-level energy storage.

High‐Entropy Cubic Perovskite Oxide‐Based Solid Electrolyte in Quasi‐Solid‐State Li–S Battery

The shuttle effect of polysulfides with its corresponding capacity fading and safety issues is the major barrier in the realization of lithium–sulfur battery (LSB) technology despite having high energy density and high specific capacity. Solid ceramic electrolytes using poly(ethylene oxide) (PEO) matrix has attracted much interest due to their superior safety compared to their liquid electrolyte counterparts. However, cubic perovskite electrolytes suffer from considerable interfacial challenges with lithium metal anodes. Besides, ceramic electrolytes are difficult to process further due to their inherent brittleness. Herein, a novel high‐entropy cubic perovskite (HE‐LLZO) prepared by the ball‐milling method is designed to which PEO matrix is added along with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for use as a solid‐state electrolyte (PEO–HE–LLZO–LiTFSI) in LSB. This electrolyte gives good ionic conductivity and blocks lithium dendrite formation as well. A novel transition metal rare‐earth‐based high‐entropy oxide is incorporated into the sulfur cathode for use as a host material to ameliorate the redox kinetics. A quasi‐solid‐state LSB is designed with transition metal rare‐earth oxide carbon nanotubes incorporated into sulfur as composite cathode and PEO–HE–LLZO–LiTFSI electrolyte. This study highlights the viability of designing high‐entropy materials as a solid‐state electrolyte for next‐generation all‐solid‐state LSBs.

Cr-Doped FeC2O4 Microrods Formed Directly on AISI 420 Stainless Steel to Enhance Electrochemical NO3- Reduction to N2 at Circumneutral pH.

We synthesized low-cost cathodes for use in the electrochemical NO3- reduction reaction (NO3RR) via the simple reconstruction of AISI 420 stainless steel (SS). Thermochemical treatment of the SS in oxalic acid generated iron oxalate (FeC2O4) microrods (BL-SS), with further anodization affording Cr-doped Fe2O3 (R-SS) or FeC2O4 (G-SS). G-SS displayed supreme N2 selectivity during galvanostatic electrolysis at circumneutral pH. Electroanalysis and descriptor/scavenger analysis indicated that Fe sites were the primary active sites of NO3- adsorption, with C2O42- as the H-binding sites. The C2O42- ligands and Cr dopants altered the electronic structures of the Fe sites. A parametric study of the current density, pH, [NO3-]0, and [Cl-]0 indicated an Eley-Rideal N2 generation mechanism, with NO2- as an intermediate. Cl- elevated the N2 selectivity but reduced the NO3RR efficiency. To demonstrate the practical applicability of G-SS with a proposed regeneration strategy, its durability was examined in synthetic and real wastewater matrices. Compared with that in synthetic wastewater, G-SS displayed more stable performance in real wastewater owing to the natural buffering capacity at the cathode, which reduced the corrosion rate. Cr-doped FeC2O4 is viable for use in the low-cost, efficient electrochemical treatment of wastewater containing NO3-.

Synthesis and Thermal Evaporation Deposition of Sodium Oxychloride Solid-State Electrolyte for Sodium-Ion Batteries

Sodium-ion batteries have attracted significant attention by offering an alternative option to lithium-ion batteries. Solid-state sodium oxyhalides (Na3OX, X = Cl, Br, I) have the advantage of cost-effective synthesis from raw materials in a time-effective manner. In this study, sodium oxychloride (Na3OCl) antiperovskite was synthesized using a novel approach that allowed for facile synthesis outside of an argon glovebox. The ionic conductivity of Na3OCl pellets compressed between graphite-coated copper foil was tested in the temperature range of 160˚C and 200˚C using electrochemical impedance spectroscopy (EIS). Arrhenius plots demonstrated linear behavior in the whole temperature range with a calculated activation energy of 0.98 eV. At lower temperatures, EIS data was not available likely due to high impedance from the thickness of the electrolyte pellet, high activation energy, or slow migration of sodium ions through the Na3OCl structure. To decrease electrolyte thickness, we implement physical vapor deposition (PVD) thermal evaporation to coat thin films (<100 µm) of the electrolyte onto graphite-coated copper foil and sodium-based cathodes for use in symmetric cell and half-cell configurations. The melting and crystallization temperatures were determined using differential scanning calorimetry (DSC). The purity of as-synthesized sodium oxychloride and PVD-deposited layer was evaluated using X-ray diffraction (XRD). The results on chemical composition and crystal-to-glass phase transformations are produced from in-situ X-ray diffraction (XRD) spectroscopy in the temperature range from 25˚C up to the melting point of Na3OCl. Cross-sectional SEM images of PVD-deposited sodium oxychloride showed an even distribution of sodium, oxygen, and chlorine. However, XRD analysis of deposited layers showed that sodium oxychloride had a tendency to decompose into the precursors during deposition. This work is focused on maintaining the sodium oxychloride composition and structure during PVD thermal evaporation by optimizing the PVD deposition parameters.The authors acknowledge financial support from the NSF IUCRC program for the “Center for solid-state electric power storage” (#2052631) and support from the South Dakota Board of Regents for the “Governor’s Research Center (GRC) for electrochemical energy storage”.

Damage characterisation of tantalum ion source electrodes and reconditioning by wire- and powder-based laser metal deposition

The internal ion source of the Advanced Molecular Image Technologies (AMIT) superconducting cyclotron uses cathodes made of pure tantalum to generate high energy H− ion beams for the production of isotopes for positron emission tomography. During service, the cathodes are impacted by high-energy ions from the plasma. The resulting erosion creates craters that reduce the current density of the extracted beam. The cathodes eventually need to be replaced when the ion source can no longer be activated. This research explores the possibility of repairing the tantalum cathodes used in the AMIT cyclotron through laser metal deposition additive manufacturing. The damaged parts were first characterised by 3D imaging, scanning electron microscopy, and Vickers microhardness to understand the damage mechanisms occurring during service and quantify the extent of the damage. Different repair strategies were then tested employing both high-purity tantalum wire and powder feedstocks and the properties of the reconditioned electrodes were determined. The ability of laser metal deposition to restore the damaged cathodes for use in the AMIT cyclotron has been demonstrated.

A salt-baking ‘recipe’ of commercial nickel-molybdenum alloy foam for oxygen evolution catalysis in water splitting

Ni-based metal foam holds promise as an electrochemical water-splitting catalyst, due to its low cost, acceptable catalytic activity and superior stability. However, its catalytic activity must be improved before it can be used as an energy-saving catalyst. Here, a traditional Chinese recipe, salt-baking, was employed to surface engineering of nickel-molybdenum alloy (NiMo) foam. During salt-baking, a thin layer of FeOOH nano-flowers was assembled on the NiMo foam surface then the resultant NiMo-Fe catalytic material was evaluated for its ability to support oxygen evolution reaction (OER) activity. The NiMo-Fe foam catalyst generated an electric current density of 100 mA cm−2 that required an overpotential of only 280 mV, thus demonstrating that its performance far exceeded that of the benchmark catalyst RuO2 (375 mV). When employed as both the anode and cathode for use in alkaline water electrolysis, the NiMo-Fe foam generated a current density (j) output that was 3.5 times greater than that of NiMo. Thus, our proposed salt-baking method is a promising simple and environmentally friendly approach for surface engineering of metal foam for designing catalysts.

Advanced Concentration Gradient Cathode Material for Next-Generation Electric Vehicles

With the prevalence of electric vehicles (EVs), the use of Li-ion batteries (LIBs) in EVs presents a new set of challenges such as cost, charging behavior, driving range per charge, risk of thermal runaway, and battery life. As the performance of LIBs is largely determined by the cathode material, the development of high-performance LIBs for EVs has focused on increasing the capacity of the cathode by using Ni-rich Li[NixCoyAl1−x−y]O2 (NCA) and Li[NixCoyMn1−x−y]O2 (NCM) cathodes.1 Ni-rich core encapsulated by a shell with concentration gradients (CSG) is the only field-proven strategy that is able to tap the potential capacity of Ni-rich cathodes while providing long cycle life.2 Despite the success of CSG cathodes, concentration gradients in the hydroxide precursor are intrinsically unstable and susceptible to flattening through interdiffusion during lithiation process.3 Furthermore, excessive coarsening during lithiation destroys the aligned microstructure, which undermines the mechanical stability of the cathode against microcrack formation.3 Therefore, CSG cathodes require a narrow processing temperature window; however, this increases their manufacturing cost.Herein, it was demonstrated that the doping of a CSG cathode with an average composition of Li[Ni0.9Co0.5Mn0.5]O2 with 0.5 mol% Sb substantially improved its cycling stability while providing manufacturing flexibility. Sb doping allowed precise tailoring of the cathode microstructure through the retardation of cation migration and the inhibition of coarsening by pinning particle boundaries. The Sb-doped CSG cathode retained ~80% of its initial capacity for 2500 cycles, while the pristine CSG90 cathode showed similar capacitive deterioration over only 1500 cycles. The proposed Sb-doped CSG90 cathode for use in electric vehicles represents an ideal high-energy-density cathode with a composition engineered to maximize capacity; its modified microstructure ensures a long battery life and ease of manufacturing, enabling cost reduction. Reference s : [1] H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources, 2013, 233, 121.[2] U.-H. Kim, H.-H. Ryu, J.-H. Kim, R. Mucke, P. Kaghazchi, C. S. Yoon, Y.-K. Sun, Adv. Energy Mater. 2019, 9, 1803902.[3] G.-T. Park, H.-H Ryu, T.-C. Noh, G.-C. Kang, Y.-K. Sun, Mater. Today, 2022, 52, 9.

Fluorine‐Doping Strategy To Improve the Surface and Electrochemical Properties of LiNi0.6Co0.2Mn0.2O2 Cathodes for Use in Lithium‐Ion Batteries

AbstractThis study sought to achieve fluorine doping into the surface structure of LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes for use in lithium‐ion batteries by the atomic layer deposition method to improve structural stability and electrochemical performance. Thin‐film electrodes were used to clearly understand the fundamental effects of surface properties. Based on our observations, the oxygen vacancy that basically exists in the surface of the NCM622 thin‐film electrode triggers the additional formation of oxygen derivatives with a spinel‐like phase, leading to poor cycling stability and severe deterioration of the surface structure. Contrary, the fluorinated NCM622 thin‐film electrode exhibits improved electrochemical properties including satisfactory cycling stability, which benefits from the higher binding energy of fluorine that positively influences the stability of the surface oxygen layer by being doped into the unstable oxygen site, and thus the formation of oxygen derivative phases is successfully suppressed during electrochemical reactions.

(Digital Presentation) Lithiation/De-Lithiation of a Unique C-S Species in Amorphous FeS4/C Cathodes for Li Batteries

When paired with Li metal anodes, Fe-based conversion cathodes like iron sulfide present a promising material for creating energy dense rechargeable batteries for energy storage. While iron sulfide cathodes (e.g. FeS2) typically suffer from deleterious polysulfide formation, recent work with a class of amorphous iron sulfide-carbon composites (e.g. FeS4/C) has shown minimal evidence of polysulfide formation during lithiation and de-lithiation, and thus it may represent a pathway to stable, polysulfide-free iron sulfide batteries. Prior reports indicate that the active component of the composite is the FeS4 and that the amorphous carbon does not exhibit any electrochemical response. While studying this material, however, we have found evidence to suggest that the cycling of FeS4 alone does not fully explain the electrochemical and chemical behavior observed for the FeS4/C cathode, and that the carbon plays a significant role in the overall electrochemistry of the composite.In this presentation, we will present a study of this amorphous FeS4/C composite as a cathode for use in Li batteries and provide evidence of the electrochemical lithiation and de-lithiation of a previously unstudied and unreported C-S compound found in the composite material. Our results indicate that this C-S species is amorphous and is (electro)chemically similar to sulfurized poly(acrylonitrile) (SPAN) and carbyne polysulfide (C-PS). By coupling ex situ Raman and X-ray photoelectron spectroscopy (XPS) to galvanostatic battery cycling, we show how chemical changes in the FeS4/C cathode correspond to electrochemical features associated with the lithiation and de-lithiation of both iron sulfide and the C-S species. Our results indicate that the C-S species is electrochemically active at all stages of cycling, while the FeS4 loses activity within approximately 15-20 cycles. This differs significantly from earlier reports and suggests that the lack of polysulfide formation when testing the FeS4/C composite may in fact be due to the cycling of this C-S species rather than iron sulfide. These results serve as an initial foray into the electrochemistry of this new material and should provide a basis for additional study of this new and promising C-S based cathode material for Li batteries.This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

CO2 Turned into a Nitrogen Doped Carbon Catalyst for the Fuel Cell and Metal-Air Battery Applications

Metal-free catalysts based on nitrogen-doped carbon are among the most promising replacements for Pt-based materials on polymer electrolyte membrane fuel cell (PEMFC) cathodes due to their inherent stability (lack of metal atoms bypasses most of the degradation mechanisms encountered in metal-based non-precious metal catalysts). However, the production of carbon nanostructures that have suitable oxygen reduction reaction (ORR) activities for fuel cell cathode use can create massive amounts of CO2 as a by-product, which counteracts the environmental friendliness of fuel cells. Here, we demonstrate a new method for creating ORR catalysts directly from CO2, which can produce a catalyst with a negative carbon footprint instead of a positive one. Via a fused Li-K carbonate eutectic mixture or pure Li2CO3, CO2 was split into gaseous oxygen and solid carbon, which was then doped with nitrogen using a pyrolysis process with the presence of dicyandiamide and polyvinylpyrrolidone. A thorough physico-chemical characterization of the catalyst materials is presented alongside their electrocatalytic properties for the ORR. The reasons for the properties of the resulting carbon depending on the electrolyte mixture for CO2 electrolysis and deposition temperature are explored. The best performing material had ORR activity nearing that of Pt/C, showing the potential that this method has for creating competitive catalysts while remaining environmentally benign [1]. References Ratso, S.; Walke, P. R.; Mikli, V.; Ločs, J.; Šmits, K.; Vītola, V.; Šutka, A.; Kruusenberg, I. CO2 Turned into a Nitrogen Doped Carbon Catalyst for Fuel Cells and Metal–Air Battery Applications. Green Chem. 2021, 23 (12), 4435–4445. https://doi.org/10.1039/D1GC00659B. Figure 1

Efficient electrocatalytic nitrate reduction via boosting oxygen vacancies of TiO2 nanotube array by highly dispersed trace Cu doping

Nitrate pollution of water bodies is a serious global-scale environmental problem. The electrocatalytic nitrate reduction reaction (NO3RR) using Cu-based electrodes allows excellent nitrate removal; however, its long-term operation results in copper leaching, leading to health risks. This study proposes a strategy for efficient nitrate removal through the activation of oxygen vacancies on a highly dispersed Cu-doped TiO2 nanotube array (Cu/TNTA) cathode via electrodeposition. The mechanism underlying the activation of oxygen vacancies and enhancement in charge transfer at the cathode–pollutant interface upon trace (0.02 wt%) Cu doping is elucidated by electron paramagnetic resonance analysis, UV–visible diffuse reflection spectroscopy, and Raman spectroscopy. The Cu/TNTA-300 exhibits a nitrate removal rate of 84.3% at 12 h; the electrode activity did not decrease after 10 cycles, and no Cu2+ was detected in the solution. Electrochemical characterization and density functional theory calculations demonstrate that Cu doping promotes efficient charge transfer between nitrate and the electrode and reduces the energy barrier of the nitrate reduction reaction. This work provides a platform for novel design of cathodes for use in efficient and safe electrocatalytic nitrate reduction in environmental water bodies.

Acoustic Emission Monitoring of High-Entropy Oxyfluoride Rock-Salt Cathodes during Battery Operation

High-entropy materials with tailorable properties are receiving increasing interest for energy applications. Among them, (disordered) rock-salt oxyfluorides hold promise as next-generation cathodes for use in secondary batteries. Here, we study the degradation behavior of a high-entropy oxyfluoride cathode material in lithium cells in situ via acoustic emission (AE) monitoring. The AE signals allow acoustic events to be correlated with different processes occurring during battery operation. The initial cycle proved to be the most acoustically active due to significant chemo-mechanical degradation and gas evolution, depending on the voltage window. Irrespective of the cutoff voltage on charge, the formation and propagation of cracks in the electrode was found to be the primary source of acoustic activity. Taken together, the findings help advance our understanding of the conditions that affect the cycling performance and provide a foundation for future investigations on the topic.

Copper-iron ternary metal fluorides from multi-metallic template fluorination and their first use as cathode in solid state Li-batteries

Conversion cathodes such as metal fluorides are particularly interesting for their theoretical capacities up to 711 mAh/g when used in Li-ion batteries. However, they generally suffer from high hysteresis and/or poor cyclability. To overcome these problems, ternary metal fluorides are being explored to improve electrochemical properties compared to the usual binary fluorides: a polymer electrolyte membrane is also used to avoid undesirable cathode-electrolyte reactions and to assess the compatibility of such cathode materials with All Solid State Batteries (ASSB). Among the multi-metallic models, copper hexacyanoferrate Cu3[Fe(CN)6]2.nH2O from the Prussian blue analogue family (PBA), is fluorinated under pure fluorine gas at selected temperatures according to preliminary thermogravimetric mass spectrometry analyses. Using X-ray absorption spectroscopy and diffraction, an inverse perovskite structure [Cu(H2O)4]3·(FeF6)2 is identified at a fluorination temperature of 140 ​°C and an intimate mixture of CuF2 and FeF3 is formed at 350 ​°C. The cyclic voltammogram of the latter compared to that of a ball-milled sample of similar composition CuF2/FeF3 highlights the advantages of MMTF multi-metallic template fluorination for electrochemical properties, interpreted by the high level of homogeneous dispersion of the redox centers obtained with this method compared to the mechanical milling reference evaluated by SEM. The fluorides are also found to be compatible with the commercial solid polymer electrolyte membrane PEO-LiTFSI (Poly Ethylene Oxide impregnated with Lithium bis(trifluoromethanesulfonyl)imide), underlining the suitability of the MMTF-prepared cathodes for use in the ASSB.

Длительность пучка убегающих электронов при субнаносекундном фронте импульса напряжения

The conditions for obtaining runaway electron (RE) current pulses with a minimum duration at a subnanosecond breakdown of centimeter gaps filled with air at atmospheric pressure were studied. It is shown that the RE current pulse duration depends on many parameters, such as the cathode form, the magnitude of the interelectrode distance, the diameter of the diaphragm, which is part of the anode, as well as on the size of the receiving part of the collector. It has been established that the use of cathodes with an extended edge having a small radius of curvature, RE current pulses consisting of two peaks of picosecond duration can be recorded.

Duration of runaway electron current pulses when applying voltage pulses with a subnanosecond rise time

The conditions for obtaining runaway electron (RE) current pulses with a minimum duration at a subnanosecond breakdown of centimeter gaps filled with air at atmospheric pressure were studied. It is shown that the RE current pulse duration depends on many parameters, such as the cathode form, the magnitude of the interelectrode distance, the diameter of the diaphragm, which is part of the anode, as well as on the size of the receiving part of the collector. It has been established that the use of cathodes with an extended edge having a small radius of curvature, RE current pulses consisting of two peaks of picosecond duration can be recorded. Keywords: runaway electrons, beam current, picosecond pulse duration, subnanosecond breakdown.

High-Energy Cathodes via Precision Microstructure Tailoring for Next-Generation Electric Vehicles

With the prevalence of electric vehicles (EVs), Ni-rich layered cathodes have been extensively studied to increase their capacities. The use of a Ni-rich core encapsulated by a shell with concentration gradients (CSG) is the only field-proven strategy that is able to tap the potential capacity of Ni-rich cathodes. Herein, it was demonstrated that doping a CSG cathode with an average composition of Li[Ni0.9Co0.05Mn0.05]O2 with 0.5 mol% Sb substantially improved its cycling stability while providing manufacturing flexibility. Sb doping allowed precise tailoring of the cathode microstructure through the retardation of cation migration and the inhibition of coarsening by pinning particle boundaries. The Sb-doped CSG cathode retained ∼80% of its initial capacity for 2500 cycles, while the pristine CSG90 cathode showed similar capacitive deterioration over only 1500 cycles. The proposed Sb-doped CSG90 cathode for use in EVs represents an ideal high-energy-density cathode with a composition engineered to maximize capacity; its modified microstructure ensures a long battery life and ease of manufacturing, enabling cost reduction.

Ultra-stable cycling of multi-doped (Zr,B) Li[Ni0.885Co0.100Al0.015]O2 cathode

The Zr and B co-doped Ni-rich Li[Ni0.885Co0.100Al0.015]O2 cathode shows extraordinarily stable cycle performance. The Li[Ni0.885Co0.100Al0.015]O2 cathode doped with 0.3 mol% Zr and 1.5 mol% B exhibits remarkable long-term cycling by retaining 95% of its initial capacity even after 1000 cycles whereas the pristine Li[Ni0.885Co0.100Al0.015]O2 cathode retains only 62% after 500 cycles. The unprecedented stability performance of the co-doped Li[Ni0.885Co0.100Al0.015]O2 cathode is attributed to the microstructure modification that inhibits microcrack propagation in the deeply charged state. Although the proposed cathode may not be an ideal cathode for use in a high-end EV due to its inferior rate capability, the co-doped Li[Ni0.885Co0.100Al0.015]O2 is well suited for applications where power demand is moderate and battery life and cost are critical. Moreover, the proposed cathode suggests that appropriate microstructure modification can effectively resolve the inherent capacity fading of Ni-rich layered cathodes, providing the material design guidelines for the next generation of high-performance LIBs.