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At least 361 records · Page 20

The Microscopic Mechanism of Lithiation and Delithiation in the Ag/C Buffer Layer for Anode‐Free Solid‐State Batteries

Abstract Lithium metal solid‐state batteries (LMSSBs) have demonstrated their high energy density and cycling performance at high current densities in an anode‐free architecture, featuring a thin Ag/C composite buffer layer (BL) between the current collector (CC) and the solid electrolyte (SE). This study explains the microscopic mechanism of the Ag/C BL by using first‐principles atomistic and continuum modeling. It is shown that Ag effectively acts as a homogeneous solid‐solution beyond AgLi 2.32 and maintains a positive potential even at AgLi 25 during lithiation. Key factors underlying the working of the Ag/C BL include lower interfacial resistance at the BL/CC interface than at the BL/SE interface, leading to predominant Li deposition on BL/CC, and substantial Ag–Li volume expansion during lithiation. This, combined with stronger BL/SE adhesion, causes BL/SE separation and Ag–Li extrusion toward the CC side. During delithiation, Ag re‐precipitates as nanoparticles uniformly on the CC, with its positive lithiation potential homogenizing Li currents in subsequent cycles. Other metals are less effective due to their relatively large overpotential, premature lithiation termination, and limited volume expansions hindering movement toward the CC. The study aids the BL design, focusing on metal choice and optimization material and microstructural properties, such as the Li‐ion conductivity and interfacial resistance.

25 ENERGY STORAGE↗

Mastering the Copolymerization Behavior of Ethyl Cyanoacrylate as Gel Polymer Electrolyte for Lithium‐metal Battery Application

Polymers with strong electron-withdrawing groups (e.g., cyano-containing polymers) are attractive for a wide range of applications due to their high dielectric constant and outstanding electrochemical stability. However, the polymerization of such monomers is difficult to control with trace of water affording instant reactions, and copolymerization with other monomers without using strong acid is even more challenging. The present study demonstrates a facile approach enabling efficient and controllable copolymerization of ethyl cyanoacrylate (ECA) without adding undesired additives, achieving mechanically robust and high ion-conduction gel polymer electrolyte (GPE) for safe and long cycle-life lithium-metal batteries (LMBs). The incorporated dual-lithium salts, i.e., lithium difluoro(oxalato)borate (LiDFOB) and lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) not only facilitate radical polymerization of ECA monomers by suppressing their anionic polymerization, but also promote the formation of high-ionic conducting GPE. The incorporated methyl methacrylate (MMA) monomer accelerates the radical polymerization of ECA (confirmed by DFT calculations), achieving controlled copolymerization of ECA-based copolymers. Here, the mechanically robust polymer network made by the ECA copolymer enables LMBs with both LFP cathodes and high-voltage LCO cathodes (4.5 V) operatable at different temperatures with ultra-long cycle life at 1 C (capacity retention of 81.1 % and 83.8 %, respectively, over 1000 cycles).

Min, Weixing [Nankai University, Tianjin (China)]↗

Accessing a high‐voltage nonaqueous hybrid flow battery with a sodium‐methylphenothiazine chemistry and a sodium‐ion solid electrolyte

Abstract The development of redox flow batteries (RFBs) with nonaqueous electrolytes offers the possibility of accessing a high cell‐operation voltage (no restrain of hydrogen evolution and oxygen evolution potentials) and a low operation temperature (can be operated below the freezing point of water). Therefore, nonaqueous RFBs have recently garnered increasing attention. However, the cross‐mixing of liquid electrode/electrolyte materials has been plaguing the progress of the nonaqueous RFBs. Herein, we present a crossover‐free, high voltage nonaqueous hybrid flow battery (HFB) with a novel sodium‐methylphenothiazine (MPT) chemistry and a single‐ion solid‐electrolyte separator. The Na‐MPT redox couple delivers a high voltage of ~2.6 V when the cell was operated at a medium current density. A NASICON‐type solid electrolyte membrane (Na 3 Zr 2 Si 2 PO 12 ) could circumvent the crossover of the liquids between the positive and negative electrodes, and meanwhile could maintain a single‐ion (Na + ‐ion) conduction between the two electrodes to sustain the electrochemical reactions. Under such an electrochemical mechanism, the nonaqueous Na‐MPT HFB shows remarkable cycling performance.

Yu, Xingwen↗

A high-performance intermediate temperature reversible solid oxide cell with a new barrier layer free oxygen electrode

The best solution to address the critical durability issue of solid oxide electrolytic cells (SOECs) for high-efficiency and high-rate H 2 production is to lower the operating temperature without sacrificing the performance. Developing high performance oxygen electrodes (OEs) is a key to capitalizing this solution. Here, in this paper, we report on a highly active OE for intermediate temperature ZrO 2 -based SOECs without a CeO 2 barrier layer. The new barrier-layer-free (BLF) OE is a composite of two materials, (Bi 0.75 Y 0.25 ) 0.93 Ce 0.07 O 1.5±δ (BYC) that exhibits high oxide-ion conductivity and La 0.8 Sr 0.2 MnO 3 (LSM) that possesses a high electronic conductivity to enable fast oxygen reduction/evolution reactions (ORR/OER). Featuring a microscale porous BYC scaffold decorated with high surface area LSM nanoparticles (NPs), the new BLF-OE exhibited a low area specific resistance (ASR) of 0.10 Ω cm 2 at 650 °C in air. With 50%H 2 -50%H 2 O as a feed to hydrogen electrode (HE) and air to OE, the single cell performance achieved 588 mA cm -2 at 0.80 V in the fuel cell mode and 688 mA cm -2 at 1.30 V in the electrolytic mode at 650 °C. Our in-house testing showed that this level of performance was ~3.5x higher than the cell with the benchmark La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ -Ce 0.9 Gd 0.1 O 2-δ OE. The long-term durability testing under alternating fuel cell and electrolytic modes showed a low degradation rate of 0.10 mA cm -2 h -1 over 550 hours. These encouraging results showed the great promise of the newly developed BYC-LSM to be an excellent OE candidate for intermediate temperature SOECs.

25 ENERGY STORAGE↗

Interface stability of LiCl-rich argyrodite Li 6 PS 5 Cl with propylene carbonate boosts high-performance lithium batteries

In solid-state lithium (Li)-metal batteries (SSLMBs), sulfide-based Li-ion conductors represent one of the most popular solid electrolytes (SEs). However, the development of sulfide-based SSLMBs is significantly hampered by interfacial issues including large solid-solid contact resistance and serious side reactions at the SE/electrode interface. To address these issues, here, we demonstrated a simple and efficient strategy by using LiCl-rich argyrodite Li 6 PS 5 Cl (Li 6 PS 5 Cl-LiCl) SE and trace amount of propylene carbonate (PC) at the SE/electrode interface to facilitate the formation of stable and robust solid electrolyte interphase (SEI). Additionally, the formed SEI not only serves as a buffer layer to passivate the interfacial reactions and suppress Li dendrite growth, but also acts as a bridge for Li-ion conduction to reduce the contact resistance. As a result, the Li||Li symmetric cell exhibited long-term electrochemical cycling stability over 1000 h at a current density of 0.2 mA cm -2 . Furthermore, the assembled Li||Li 4 Ti 5 O 12 (LTO) batteries delivered a specific capacity of 175 mAh g–1 at 0.2 C, and remained an excellent specific capacity of 116 mAh g –1 after 200 cycles at a high current rate of 1 C. These features indicate a feasible strategy to enhance the interfacial property of high-performance SSLMBs.

25 ENERGY STORAGE↗

Anomalously high elastic modulus of a poly(ethylene oxide)-based composite electrolyte

The practical use of lithium metal anodes in solid-state batteries requires a polymer membrane with high lithium-ion conductivity, thermal/electrochemical stability, and mechanical strength. The primary challenge is to effectively decouple the ionic conductivity and mechanical strength of the polymer electrolytes. We report a remarkably facile single step synthetic strategy based on in-situ crosslinking of poly(ethylene oxide) (xPEO) in the presence of a woven glass fiber (GF). Such a simple method yields composite polymer electrolytes (CPE) of anomalously high elastic modulus up to 2.5 GPa over a broad temperature range (20 °C – 245 °C) that has never been previously documented. An unsupervised machine learning algorithm, K-mean clustering analysis, was implemented on the hyperspectral Raman mapping at the xPEO/GF interface. Using such a unique means, we show for the first time that the promoted mechanical strength originates from xPEO and GF interactions through dynamic hydrogen and ionic bonding. High ionic conductivity is achieved by the addition plasticizer (e.g. tetraglyme), where trifluoromethanesulfonate anions are tethered to the xPEO matrix and Li + cations are favorably transported through coordination with the plasticizer. Further, stringent galvanostatic cycling tests indicates the CPE can be stably cycled for >3000 h in a Li-metal symmetric cell at a moderate temperature (nearly 1500 Coulombs/cm 2 Li equivalents), outperforming most of the PEO-based electrolytes. The GF reinforced CPE reported here has multifunctional uses, such as solid electrolytes for all solid-state batteries and membranes for redox-flow batteries. Although the focus of this study is on lithium-based batteries, the results are equally promising for other alkali metal based batteries such as sodium and potassium.

25 ENERGY STORAGE↗

Performance of stainless steel interconnects with (Mn,Co) 3 O 4 -Based coating for solid oxide electrolysis

Mixed transition-metal oxide coatings are commonly applied to stainless steel interconnects for solid oxide cell stacks. Such coatings reduce oxidation and Cr evaporation rates, leading to improved degradation rate and stack lifetime. Here, the ChromLok™ MCO-based composition (Mn,Co) 3 O 4 is applied to Crofer 22 APU stainless steel and evaluated specifically for application in solid oxide electrolyzer stacks operating around 800 °C and utilizing oxygen-ion-conducting solid oxide cells. The MCO coating is found to decrease the stainless steel oxidation rate by about one order of magnitude, and decrease the Cr evaporation rate by fourfold. Furthermore, the coating also dramatically lowers the rate of area-specific resistance increase for stainless steel coupons oxidized for 500 h with constant current applied, from 33 mΩ*cm 2 kh -1 for an uncoated coupon to less than 4 mΩ*cm2 kh -1 for coated coupons. The coating is demonstrated on full-scale interconnects for single-cells, where the coating dramatically reduces degradation rate, and for a stack, which displays stable operation for 700 h.

08 HYDROGEN↗

Understanding the effect of organic coatings on 4-nitrostyrene hydrogenation selectivity over Pt/TiO 2 catalysts

The hydrogenation of 4-nitrostyrene was investigated over Pt/TiO 2 catalysts to understand the effects of different catalyst coatings on product selectivity and reaction rates. This reaction is a much-investigated selectivity probe due to difficulty in controlling reactivity between the nitro and vinyl groups of 4-nitrostyrene, with C=C reduction generally being more favorable. 4-Nitrostyrene hydrogenation reactions were carried out in a batch reactor using uncoated, organothiol coated, phosphonic acid (PA) coated, and ion-conducting polymer (ionomer) coated catalysts. Thiols form dense coatings on Pt surfaces, whereas PAs preferentially accumulate on TiO 2 ; ionomer binding preference is unknown for this type of catalyst. The coating densities of the thiols and PAs were varied to observe the effects of loading on catalytic activity and reaction selectivity relative to the uncoated catalyst. Changes in selectivity were observed for catalysts with all coatings, with thiol coatings shifting selectivity towards the nitro reduction product, 4-vinylaniline (4-VA), and both ionomer and PA coatings shifting towards 4-ethylnitrobenzene, the olefin hydrogenation product. It was observed that selectivity toward 4-VA increased with thiol coating density, where 1,2-benzenedithiol (BDT) coated catalysts exhibited a selectivity of >99%. These changes were attributed to the identity of the adsorption sites blocked by the different coatings: blocking of metal sites via thiols decreased the rate of C=C hydrogenation, whereas blocking of TiO 2 sites by PAs decreased the rate of nitro group hydrogenation. The changes observed for ionomer and PA coatings suggested that ionomers, like PAs, bind preferentially to the metal oxide support rather than the active metal. This work provides new support to the proposal that nitro group hydrogenation preferentially occurs on TiO 2 sites after hydrogen spillover and underscores how selection of ligand functionality can be used to tune catalyst selectivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Air oxidation of yttrium hydride as a high temperature moderator for thermal neutron spectrum fission reactors

Yttrium hydride (YH x ) is an attractive moderator material for thermal neutron spectrum fission reactors requiring a small reactor core volume and has been selected as the neutron moderator for the Transformational Challenge Reactor (TCR), an advanced gas-cooled microreactor. Before YH x can be used in this application, it is important to understand the material response to off-normal conditions. In the present study, 550–650 °C isothermal dry air oxidation was performed to simulate a depressurized loss of force circulation (DLOFC) event. The oxidation was performed using thermogravimetric analysis (TGA) on bulk crack-free YHx coupons. Oxidation studies were also performed on Y coupons to elucidate the impact of H on oxidation. Both the chemistry and distribution of processing impurities were found to strongly affect oxidization behavior on a batch-to-batch basis. Regardless of batch, YHx oxidized at a significantly lower rate than Y at all temperatures, and the lower rate was directly correlated with increased hydride content. Metallic Y exhibited complex exponential kinetics, whereas YH x also exhibited complex kinetics but gained considerably less mass. According to literature reports on protonic and native-ion conductivities of Y 2 O 3 and mass spectrometry analysis of gaseous reaction products formed during the oxidation of YH x , a mechanism for the reduced oxidation rate of yttrium hydride is suggested.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Impact of polymer additives on crack mitigation of rod-coated fuel cell cathode catalyst layers

Cracks in catalyst layers (CLs) are a potential source of long-term failure in a fuel cell membrane electrode assembly (MEA). While modifications to the CL ink formulation can affect the degree of cracking, these changes may lead to lower initial performance than their cracked analogues due to the established link between formulation and performance. In this work, we explored the use of polymeric additives to mitigate CL cracks. Small quantities of poly (acrylic acid), poly (ethylene oxide), poly (methyl methacrylate), or poly (vinyl alcohol) - 5 wt% relative to ionomer mass - were added to the ink prior to its final mixing. Poly (vinyl alcohol) resulted in crack-free CLs, whereas the other polymers resulted in CLs with similar crack percentages as the control CL. Through a combination of transmission electron microscopy, X-ray computed tomography, and infrared spectroscopy, we ascribed the crack-mitigating mechanism of poly (vinyl alcohol) to its ability to hydrogen-bond with Nafion, the ion conducting polymer binder in the catalyst ink. Initial performance of this non-cracked electrode exhibited nearly identical electrochemical behavior to its cracked counterpart, demonstrating that PVA additives successfully reduce cracks while maintaining cell initial performance.

30 DIRECT ENERGY CONVERSION↗

Simplified calculation of the area specific impedance for solid-state battery design

Simplified algebraic area specific impedance (ASI) correlations have been developed for solid-state composite battery electrodes made of a single ion conducting electrolyte, conductive additive, and intercalation active material. Two ASI expressions were developed, one for short times ( i.e. , pulsed power operation) and another for the pseudo steady state operation (i.e., sustained discharge for energy estimation). A full electrochemical model based on porous electrode theory was developed to examine the accuracy of the simplified ASI expressions. The simplified expressions agree favorably with full model results over a wide range of parameters (i.e. , electrode thicknesses, electrolyte conductivities, solid-state diffusion coefficients, specific surface areas, etc.) and conditions (i.e. , C-rates, states of charge, and pulse times). Under most conditions, the error between the full model and the correlations is well below 7 %. Higher errors were observed for the pseudo steady state expression at high/ low states of charge where the assumption of uniform reaction distributions loses validity. Here, the short time ASI has higher error at low states of charge due to the nonlinearity of the open circuit voltage equation, which is assumed linear in the formulation of the simplified algebraic expression.

25 ENERGY STORAGE↗

Quaternized poly(arylene ether benzonitrile) membranes for vanadium redox flow batteries

In this work, a series of quaternized poly (arylene ether benzonitrile)s (QAxCN; x = percent quaternization) were synthesized for the vanadium redox flow battery (VRFB) application. The presence of highly polar nitrile groups incorporated in the quaternized polymer chain provides desirable polymer properties (low water uptake, high dimensional stability and low VO 2+ permeability) without compromising ion conductivity. VRFB single cells using the aforementioned membranes showed excellent performance. As a result, the cell using a 15 μm-thick QA50CN membrane exhibited superior coulombic efficiency (98.2%) and comparable energy efficiency (86.5%) at 40 mA cm -2 compared to the single cell using Nafion-212 with a coulombic efficiency of 95.5% and an energy efficiency of 86.2%. The cell cycling stability and membrane oxidative stability data confirmed that the QAxCN membranes have the potential to replace Nafion membranes for energy storage in VRFB applications.

25 ENERGY STORAGE↗

Understanding the impact of SPMAK and PEGPEA in crosslinked PEGDA membranes: Methanol-carboxylate co-transport behavior and correlating structure-physicochemical-transport properties

Investigating multicomponent transport in dense, hydrated polymer membranes is necessary in applications such as fuel cells, electrolyzers, and desalination systems. Of particular interest are photoelectrochemical CO 2 reduction cells (PEC-CRC) which produce liquid products such as alcohols (methanol) and carboxylates (formate, acetate). Flux coupling and competitive sorption behavior of these products (solutes) have been found to affect permselectivity, thereby motivating us to investigate fundamental membrane structure-physicochemical-transport relationships. Past research has shown that systematic tuning of crosslinked cation exchange membranes (CEMs) with charge-neutral monoacrylate monomers containing alkyl and phenyl groups (i.e., poly(ethylene glycol) methacrylate (PEGMA), and poly(ethylene glycol) phenyl ether acrylate (PEGPEA)) can suppress acetate transport (permeability) in co-permeation with methanol. To further investigate this transport behavior and to enhance membrane ionic conductivities, 3-sulfopropyl methacrylate potassium (SPMAK), a sulfonated monoacrylate monomer is incorporated here. SPMAK content is varied with neutral PEGPEA and diacrylate crosslinker, poly (ethylene glycol) diacrylate (PEGDA) of two different chain lengths (n = 10 and 13) to prepare membranes of various compositions. Electrochemical and physicochemical properties including ionic conductivity, ion exchange capacity, and water uptake increase with increasing charged SPMAK content. Different states of water within hydrated membranes are probed using differential scanning calorimetry (DSC), where increasing intermediate (loosely bound) water is observed with increasing hydrophilic SPMAK content. The transport behavior of methanol and carboxylates (formate, acetate, propionate) are investigated, where permeabilities vary as methanol > formate > acetate ≈ propionate. Interestingly, permeabilities decrease with increasing PEGPEA content and are more dependent on solute diffusion than sorption. Permeabilities and diffusivities decrease while permselectivities increase with decreasing PEGDA chain length.

25 ENERGY STORAGE↗

Characterization of hot-pressed von Alpen type NASICON ceramic electrolytes

The Na-ion conducting solid electrolyte NASICON is a promising solid state electrolyte (SSE) for use in Na based electrochemical systems. The effects of particle morphology and synthesis of von Alpen type NASICON via hot-pressing were investigated. Spray dried particles were shown to improve mechanical and electrochemical properties. X-ray diffraction, scanning electron microscopy, impulse excitation measurements, Vickers hardness, and impedance spectroscopy were used to correlate relationships between phase purity, microstructure, mechanical properties, and electrochemical properties. Scanning electron microscopy showed the presence of a glass phase as between 19.08% and 28.23% area percentage and a ZrO 2 phase between 0.46% and 3.51% area percentage in the hot-pressed samples. Impulse excitation showed elastic modulus varying from 83.65 to 97.65 GPa. The first values of Poisson's ratio and shear modulus of NASICON are reported as between 0.23 and 0.26 and 33.87 to 38.79 GPa, respectively. Vickers hardness and fracture toughness measurements showed Vickers hardness ranging from 4.30 to 4.68 GPa and fracture toughness ranging from 1.05 to 1.09 MPa m ½ . Impedance spectroscopy showed grain conductivities ranging from 1.023 to 1.287 mS/cm, with grain boundary resistance percentages between 73.22 and 47.5%. Total conductivities ranged from 0.292 to 0.596 mS/cm, with 0.596 mS/cm being achieved at room temperature for the spray dried powders with lower grain boundary resistance percentages.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Solid-state polymer magnesium supercapacitor

Here, the present article focuses on the development of a highly ion-conductive, solvent-free, solid-state polymer electrolyte membrane (PEM) via photopolymerization of polyethylene glycol diacrylate (PEGDA) network from its homogeneous melt mixtures containing succinonitrile (SCN) plasticizer and magnesium bis(trifluoromethane sulfonyl) imide Mg(TFSI) 2 salt. The above solid-state Mg-PEM exhibits a Helmholtz electric double-layer capacitor (EDLC) behavior in its supercapacitive symmetric carbonaceous electrode configuration. The electrochemical stability for this PEM membrane (20/40/40 PEGDA/SCN/Mg (TFSI) 2 ) was found to be approximately 3 V from linear sweep voltammetry with a specific capacitance of about 44 F/g from cyclic voltammetry and an energy density of approximately 17 Wh/kg in the 0–2 V range from the constant current density (CCD) experiment. Of particular interest is its excellent capacity retention of over 11,200 cycles, thus tested with the Coulombic efficiency of over 87%. Moreover, the energy density after extensive cycling for 11,200 has increased to approximately 56 Wh/kg at 10 mV/s in the potential range of 0–3 V relative to 17 Wh/kg in the potential range of 0–2 V at the same scan rate, attesting the excellent electrochemical stability and long life of the present Mg-PEM supercapacitor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Glass-fiber-reinforced polymeric film as an efficient protecting layer for stable Li metal electrodes

With numerous reports on protecting films for stable lithium (Li) metal electrodes, the key attributes for how to construct these efficient layers have rarely been fully investigated. Here, we report a rationally designed hybrid protective layer (HPL) with each component aligning with one key attribute; i.e., cross-linked poly(dimethylsiloxane) (PDMS) enhances flexibility, polyethylene glycol (PEG) provides homogeneous ion-conducting channels, and glass fiber (GF) affords mechanical robustness. A significant improvement of the electrochemical performance of HPL-modified electrodes can be achieved in Li/HPL@Cu half cells, HPL@Li/HPL@Li symmetric cells, and HPL@Li/LiFePO 4 full cells. Even with an industrial standard LiFePO 4 cathode (96.8 wt % active material), the assembled cell still exhibits a capacity retention of 90% after 100 cycles at 1 C. More importantly, the functionality of each component has been studied comprehensively via electrochemical and physical experiments and simulations, which will provide useful guidance on how to construct efficient protective layers for next-generation energy storage devices.

25 ENERGY STORAGE↗

Correlating wavelength dependence in LiMn2O4 cathode photo-accelerated fast charging with deformations in local structure

The growth in electrified transportation has benefited from the massive worldwide research efforts used to discover and improve electrode materials and electrolytes. Nevertheless, lithium-ion batteries still suffer from a slow-charging limitation. Recently, it has been demonstrated that white light illumination of LiMn2O4 provokes faster charging, improving the kinetics of delithiation without the use of nanostructured active materials. In this work, we probe the mechanism of photo-accelerated fast charging and show that Mn d-d electronic transitions occurring under red light illumination are largely responsible for the increased charging rate. It is further demonstrated through X-ray absorption spectroscopy methods that LiMn2O4 Mn-Mn bond distances shorten after d-electron excitation. The shrinkage in the crystal volume beneficially contributes to delithiation kinetics by lowering the resistance to lithium-ion conduction. Advanced materials that can absorb light to modulate their structure may provide us with a new mechanistic pathway to pursue for increasing charge transfer rates.

25 ENERGY STORAGE↗