Vacancy-Enabled O3 Phase Stabilization for Manganese-Rich Layered Sodium Cathodes
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99 GENERAL AND MISCELLANEOUS↗
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Is alpha-V2O5 a cathode material for Mg insertion batteries?
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Sa, Niya (ORCID:0000000346565851)↗
Synchrotron X-ray studies of model SOFC cathodes, part I: Thin film cathodes
In this work, we present synchrotron x-ray investigations of thin film La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) model cathodes for solid oxide fuel cells, grown on electrolyte substrates by pulse laser deposition, in situ during half-cell operations. We observed dynamic segregations of cations, such as Sr and Co, on the surfaces of the film cathodes. The effects of temperature, applied potentials, and capping layers on the segregations were investigated using a surfacesensitive technique of total external reflection x-ray fluorescence. We also studied patterned thin film LSCF cathodes using high-resolution micro-beam diffraction measurements. We find chemical expansion decreases for narrow stripes. This suggests the expansion is dominated by the bulk pathway reactions. Lastly, the chemical expansion vs. the distance from the electrode contact was measured at three temperatures and an oxygen vacancy activation energy was estimated to be ~1.4 eV.
36 MATERIALS SCIENCE↗
Li 3 Mo 4 P 5 O 24 : A Two-Electron Cathode for Lithium-Ion Batteries with Three-Dimensional Diffusion Pathways
Abstract not provided
Wen, Bohua↗
Revealing of the Activation Pathway and Cathode Electrolyte Interphase Evolution of Li-Rich 0.5Li 2 MnO 3 ·0.5LiNi 0.3 Co 0.3 Mn 0.4 O 2 Cathode by in Situ Electrochemical Quartz Crystal Microbalance
The first-cycle behavior of layered Li-rich oxides, including Li 2 MnO 3 activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the Li 2 MnO 3 activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of xLi 2 MnO 3 ·(1- x) LiNi 0.3 Co 0.3 Mn 0.4 O 2 ( x = 0, 0.5, 1) cathode materials were studied with an in situ electrochemical quartz crystal microbalance (EQCM). The results demonstrate that a synergistic effect between the layered Li 2 MnO 3 and LiNi 0.3 Co 0.3 Mn 0.4 O 2 structures can significantly affect the activation pathway of Li 1.2 Ni 0.12 Co 0.12 Mn 0.56 O 2 , leading to an extra-high capacity. It is demonstrated that Li 2 MnO 3 activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure Li 2 MnO 3 governed by chemical decomposition (Li 2 O evolution). CEI evolution is closely related to Li + extraction/insertion. Finally, the valence state variation of the metal ions (Ni, Co, Mn) in Li-rich materials can promote CEI formation. This study is of significance for understanding and designing Li-rich cathode-based batteries.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A Superior Carbonate Electrolyte for Stable Cycling Li Metal Batteries Using High Ni Cathode
Li metal batteries pairing Li metal anode with high-nickel layer structured oxide cathode are a promising energy storage technology to achieve high energy density. To obtain long cycling life for Li metal batteries, the electrolyte plays a pivotal role in stabilizing both the Li metal anode and the high-nickel cathode upon electrochemical cycling. Herein, we report a carbonate electrolyte that enables a Li||LiNi 0.8 Mn 0.1 Co 0.1 O 2 pouch cell to achieve a high gravimetric energy density of 366 Wh/kg and unprecedented cycling stability with 80% capacity retention after 335 cycles. Here, the 19 F quantitative nuclear magnetic resonance spectroscopy and interface characterization demonstrate that FEC and LiDFOB can reduce the consumption rate of each other and the electrolyte, form a robust LiF-rich SEI on Li metal anode, and improve the microstructure integrity of the high-nickel cathode.
25 ENERGY STORAGE↗
Enabling High Stability of Co-Free LiNiO 2 Cathode via a Sulfide-Enriched Cathode Electrolyte Interface
Cobalt-free lithium nickel oxide (LNO) has garnered significant interest as the end member of high-nickel layered oxide cathodes for next-generation batteries. However, its practical performance notably underperforms expectations because of the structural degradation and unstable interfacial chemistry with electrolytes during cycling. Here, in this study, we report that a durable cathode-electrolyte interface (CEI), enriched by in situ formed sulfides and borides, can inhibit LNO structural degradation and suppress Ni ion dissolution. With the CEI protection, the stability of LNO can be remarkably extended, and batteries demonstrate a capacity retention rate of 84% (30 °C) and 79% (50 °C) after 200 cycles at 1C, respectively. These results demonstrate that enriching CEI with sulfur-containing species can effectively stabilize the interfacial chemistry of LNO, particularly at an elevated temperature of 50 °C. This finding provides valuable perspectives on designing electrolytes for cobalt-free LNO and other high-Ni cathodes toward the development of next-generation high-energy-density lithium-ion batteries.
25 ENERGY STORAGE↗
High-performing commercial Fe–N–C cathode electrocatalyst for anion-exchange membrane fuel cells
Here, to reduce the cost of fuel cell stacks and systems, it is important to create commercial catalysts that are free of platinum group metals (PGMs). To do this, such catalysts must have very high activity, but also have the correct microstructure to facilitate the transport of reactants and products. Here, we show a high-performing commercial oxygen reduction catalyst that was specifically developed for operation in alkaline media and is demonstrated in the cathode of operating anion-exchange membrane fuel cells (AEMFCs). With H 2 /O 2 reacting gases, AEMFCs made with Fe–N–C cathodes achieved a peak power density exceeding 2 W cm –2 (>1 W cm –2 with H 2 /air) and operated with very good voltage durability for more than 150 h. These AEMFCs also realized an iR-corrected current density at 0.9 V of 100 mA cm –2 . Finally, in a second configuration, Fe–N–C cathodes paired with low-loading PtRu/C anodes (0.125 mg PtRu per cm 2 , 0.08 mg Pt per cm 2 ) demonstrated a specific power of 10.4 W per mg PGM (16.25 W per mg Pt).
25 ENERGY STORAGE↗
Stabilizing Cathode–Electrolyte Interphase of Nickel-Rich Single-Crystal Cathodes for Lithium-Ion Batteries
Nickel-rich single-crystal (SC) layered oxides are promising cathode candidates for next-generation lithium-ion batteries (LIBs) owing to their high energy density and structural robustness against intergranular cracking. However, their intrinsic surface reactivity with liquid electrolytes accelerates parasitic reactions at the cathode–electrolyte interphase (CEI), leading to transition-metal dissolution, gas generation, and impedance buildup. In this work, we synthesized SC-Li x Ni 0.9 Mn 0.05 Co 0.05 O 2 (NMC9055, 1 ≤ x ≤ 1.2) using a eutectic-assisted method and investigated interface stabilization strategies. A nickel-deficient Li x Ni 0.6 Mn 0.2 Co 0.2 O 2 (NMC622, 1 ≤ x ≤ 1.2) coating was applied via evaporation-based deposition to suppress CEI degradation pathways. Structural and compositional analyses confirmed uniform shell formation and preserved particle integrity. Half-cell electrochemical testing against lithium metal revealed ∼10% higher capacity retention and improved reversibility compared with pristine SC NMC9055, particularly under high-voltage operation. In conclusion, these results highlight the critical role of controlled surface chemistry in mitigating CEI instability in nickel-rich SC cathodes, offering a pathway toward enabling durable high-energy LIBs.
Coating processes↗
Surface studies of thermionic cathodes and the mechanism of operation of an impregnated tungsten cathode
The surface properties of conventional impregnated cathodes were investigated by the use of Auger spectroscopy and work function measurements, and these were compared with a synthesized barium or barium oxide coated tungsten surface. The barium and barium oxide coated surfaces were prepared by evaporating barium onto a tungsten surface that can be heated to elevated temperatures. Multilayer or monolayer coverages can be investigated using this technique. The results of this study show that the surface of an impregnated tungsten cathode is identical to that observed for a synthesized monolayer or partial monolayer of barium on partially oxidized tungsten, using the criteria of identical Auger patterns and work functions. Desorption measurements of barium from a tungsten surface were also made. These results in conjunction with Auger and work function data were interpreted to show that throughout most of its life an impregnated cathode operating in the range of 1100 C has a partial monolayer rather than a monolayer of barium on its surface.
Forman, R.↗
Identifying a descriptor for d-orbital delocalization in cathodes of Li batteries based on x-ray Compton scattering
We discuss how x-ray Compton scattering spectra can be used for investigating the evolution of electronic states in cathode materials of Li batteries under the lithiation/delithiation process. In particular, our analysis of the Compton spectra taken from polycrystalline Li{sub x}CoO{sub 2} samples shows that the spectra are dominated by the contribution of the O-2p redox orbital. We identify a distinct signature of d-orbital delocalization, which is tied directly to the conductivity of the material, providing a descriptor based on Compton spectra for monitoring the lithiation range with improved conductivity and kinetics for electrochemical operation. Our study demonstrates that Compton scattering spectroscopy can provide a window for probing complex electronic mechanisms underlying the charging and discharging processes in Li-battery materials.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
In–Depth Analysis of the Degradation Mechanisms of High–Nickel, Low/No–Cobalt Layered Oxide Cathodes for Lithium–Ion Batteries
A rational compositional design of high-nickel, cobalt-free layered oxide materials for high-energy and low-cost lithium-ion batteries would be expected to further propel the widespread adoption of electric vehicles (EVs), yet a composition with satisfactory electrochemical properties has yet to emerge. The previous work has demonstrated a promising LiNi 0.883 Mn 0.056 Al 0.061 O 2 (NMA-89) composition that outperformed high-nickel, cobalt-containing analogs in cycling stability and maintained a comparable rate performance and thermal stability. Herein, the capacity fading mechanism of NMA-89 in a pouch full cell with a 4.2 V cutoff is compared to that of its cobalt-containing analogs. The results reveal that particle cracking in LiNi 0.89 Mn 0.055 Co 0.055 O 2 (NMC-89) and LiNi 0.883 Co 0.053 Al 0.064 O 2 (NCA-89) leads to a loss of active material and an increase in surface area, thereby exacerbating structural and surface instabilities, accelerating impedance and polarization growth, and ultimately reducing their capacity retentions. LiNi 0.89 Mn 0.044 Co 0.042 Al 0.013 Mg 0.011 O 2 (NMCAM-89) and NMA-89 experience subdued surface reactions and maintain spherical particle structures, both of which are conducive to their capacity retentions during long-term cycling. Furthermore, this investigation offers insights into how specific transition-metal ions dictate the electrochemical stability of high-Ni layered oxide cathode materials, highlights the benefit of Mn-Al combination in NMA-89, and presents potential strategies to further enhance the performance of this novel class of cathode materials.
degradation mechanisms↗
Stabilizing Transition Metal Vacancy Induced Oxygen Redox by Co 2+ /Co 3+ Redox and Sodium-Site Doping for Layered Cathode Materials
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99 GENERAL AND MISCELLANEOUS↗
High-Voltage Performance of Ni-Rich NCA Cathodes: Linking Operating Voltage with Cathode Degradation
High-voltage Ni-rich cathodes have been studied as a possible way to achieve high energy density in Li-ion batteries. However, capacity fade due to structural changes at high voltages has limited their applications. In this study, we identify 4.5 V (vs. graphite) as the optimum upper cutoff voltage (UCV) for a Ni-rich NCA cathode [LiNi 0.8 Co 0.15 Al 0.05 O 2 ]. At this UCV, NCA delivers a 12 % increase in reversible capacity (when discharged to 2.5 V) and retains 92 % of its initial capacity after 100 cycles at 1C/-1C cycling when compared to 4.2 V as UCV. By increasing UCV to 4.7 V, the discharge capacity can be raised to >200 mAh/g. However, the rate of capacity fade is greater when compared to 4.5 V as UCV. This increased rate of capacity fade, at higher UCV, is related to irreversible lattice contractions that leads to structural rearrangement at charged states during high-voltage cycling. Lastly, our results show a change in transition metal oxidation states and an onset of structural ordering occurs when the UCV is 4.7 V.
36 MATERIALS SCIENCE↗
Design of Graded Cathode Catalyst Layers with Various Ionomers for Fuel Cell Application
Proton exchange membrane fuel cells (PEMFCs) powered by green hydrogen (H2) have become a promising alternative to conventional hydrocarbon-fueled power generators. Despite technological advancements, further improvements in efficiency, durability, and low-cost production are required for the widespread adoption of PEMFCs. Though numerous approaches to improve PEMFC electrodes have been reported, most strategies utilize a single material set (e.g., one combination of catalyst and ionomer) to improve performance. Alternatively, anisotropic (graded) electrode structures with locally tunable properties may yield superior electrode performance due to improved ionic and gas phase transport. In this work, graded cathode catalyst layers (CCLs) incorporating different ionomers (Nafion D2020, Aquivion D79-25BS, and HOPI) were designed and prepared. Performance screening shows that some of these graded electrode structures have comparable performance to optimized single-ionomer electrode structures (D2020) suggesting some synergistic benefit. Additionally, we show that electrodes with lower equivalent weight (EW) D79 ionomer near the membrane and D2020 ionomer near the gas diffusion media outperformed electrodes with the inverted configuration. Finally, EIS analysis shows some graded ionomer structures (e.g. D79/D2020) have better than expected H+ conductivity, generally leading to better electrode performance. However, further optimization of ionomer content and catalyst ink formulations is needed to improve overall PEMFC performance.
DIRECT ENERGY CONVERSION↗