Improved Electrode Performance Research Articles

Improved Electrode Performance of Lithium-Excess Molybdenum Oxyfluoride: Titanium Substitution with Concentrated Electrolyte

A titanium-substituted lithium-excess molybdenum oxyfluoride, Li2.1–yTi0.2Mo0.7O2F, is synthesized by mechanical milling and tested as a positive electrode material in a conventional carbonate-based electrolyte or concentrated electrolyte. Reversibility as the electrode material is significantly improved by suppression of dissolution of the molybdenum oxyfluoride on electrochemical cycles. Li2.1–yTi0.2Mo0.7O2F delivers a reversible capacity of 265 mA h g–1 after 30 cycles at a rate of 50 mA g–1 with concentrated electrolyte. This finding contributes to the development of high-energy and long-cycle-life rechargeable lithium batteries with lithium-excess metal oxyfluorides in the future.

Effect of Passivating Shells on the Chemistry and Electrode Properties of LiMn2O4 Nanocrystal Heterostructures.

Building a stable chemical environment at the cathode/electrolyte interface is directly linked to the durability of Li-ion batteries with high energy density. Recently, colloidal chemistry methods have enabled the design of core-shell nanocrystals of Li1+ xMn2- xO4, an important battery cathode, with passivating shells rich in Al3+ through a colloidal synthetic route. These heterostructures combine the presence of redox-inactive ions on the surface to minimize undesired reactions, with the coverage of each individual particle in an epitaxial manner. Although they improve electrode performance, the exact chemistry and structure of the shell as well as the precise effect of the ratio between the shell and the active core remain to be elucidated. Correlation of these parameters to electrode properties would serve to tailor the heterostructure design toward complete shutdown of undesired reactions. These knowledge gaps are the target of this study. Li1+ xMn2- xO4 nanocrystals with Al3+-rich shells of different thicknesses were synthesized. Multimodal characterization comprehensively revealed the elemental distribution, electronic state, and crystallinity in the heterostructures, which confirmed the potential of this approach to finely tune passivating layers. All of the modified nanocrystals improved the capacity retention while retaining charge storage compared to the bare counterpart, even under harsh conditions.

Exploring the Role of Electrode Microstructure on the Performance of Non-Aqueous Redox Flow Batteries

Redox flow batteries are an emerging technology for long-duration grid energy storage, but further cost reductions are needed to accelerate adoption. Improving electrode performance within the electrochemical stack offers a pathway to reduced system cost through decreased resistance and increased power density. To date, most research efforts have focused on modifying the surface chemistry of carbon electrodes to enhance reaction kinetics, electrochemically active surface area, and wettability. Less attention has been given to electrode microstructure, which has a significant impact on reactant distribution and pressure drop within the flow cell. Here, drawing from commonly used carbon-based diffusion media (paper, felt, cloth), we systematically investigate the influence of electrode microstructure on electrochemical performance. We employ a range of techniques to characterize the microstructure, pressure drop, and electrochemically active surface area in combination with in-operando diagnostics performed in a single electrolyte flow cell using a kinetically facile redox couple dissolved in a non-aqueous electrolyte. Of the materials tested, the cloth electrode shows the best performance; the highest current density at a set overpotential accompanied by the lowest hydraulic resistance. We hypothesize that the bimodal pore size distribution and periodic, well-defined microstructure of the cloth are key to lowering mass transport resistance.

Phase transfer of oxide particles using hydroxamic acid derivatives and application for supercapacitors

Particle extraction through liquid-liquid interface (PELLI) methods are developed for the colloidal processing of ZnO, CeO2 and FeOOH particles. The direct transfer of the particles from an aqueous synthesis medium to a device processing medium allows for reduced nanoparticle agglomeration, because drying and re-dispersion processes are avoided. Different PELLI methods are developed, which are based on the use of chelating hydroxamates molecules, such as octanohydroxamic acid (OCHA) and bufexamac (BFXM) as extractors. OCHA and BFXM show strong adsorption on the ZnO, CeO2 and FeOOH particles due to chelating bonding mechanisms and allow for efficient particle extraction from water to organic solvents. Bottom–up and top-down methods are used, depending on the density of the organic solvents. OCHA shows improved extraction of particles, compared to BFXM due to the difference in the chemical structure. The unique feature of hydroxamates is related to their pH-dependent solubility and their strong adsorption on particles at high pH, despite the electrostatic repulsion of the negatively charged particles and dissociated hydroxamic acids. It is found that OCHA can be used as a capping agent for particle synthesis and an extractor for their extraction to an organic phase. The advantages of PELLI methods are demonstrated by the fabrication and testing of FeOOH-carbon nanotube electrodes for supercapacitors, which show enhanced performance and high capacitance at high active mass loading. The enhanced electrochemical performance is achieved due to reduced particle agglomeration, which allows improved particle mixing with conductive carbon nanotubes. The capacitive properties are investigated at different charge-discharge rates. The impedance spectroscopy data shows dependence of capacitance on electrode potential and provides an insight into the strategies for further improvement of electrode performance.

Superior role of MXene nanosheet as hybridization matrix over graphene in enhancing interfacial electronic coupling and functionalities of metal oxide

A superior efficiency of MXene (Ti3C2) nanosheet as a hybridization matrix over graphene is evidenced by comparative investigation on uniformly-stacked MnO2–Ti3C2 and MnO2–reduced graphene oxide (rGO) nanohybrids. Density functional theory calculation and spectroscopic analyses demonstrate a stronger interfacial electronic coupling and greater charge transfer of polar MnO2 with hydrophilic Ti3C2 nanosheet than with hydrophobic rGO one, which maximizes the hybridization effect with the conductive nanosheet. Also, hybridization with Ti3C2 nanosheet is more effective in enhancing the ion diffusivity and porosity of MnO2 than that with strongly self-stacking rGO, which is attributable to weaker self-stacking tendency of Ti3C2. Due to these hybridization effects, the MnO2–Ti3C2 nanohybrid delivers larger specific capacitance with improved rate performance than does the MnO2–rGO nanohybrid, underscoring higher efficiency of MXene hybridization in improving electrode performance. This study clearly demonstrates that exfoliated MXene nanosheet can act as a superior hybridization matrix over rGO to explore strongly-coupled nanohybrids with improved energy-related functionality.

Ethers Illume Sodium‐Based Battery Chemistry: Uniqueness, Surprise, and Challenges

AbstractSodium‐ion batteries (SIBs) have the potential to be practically applied in large‐scale energy storage markets. The rapid progress of SIBs research is primarily focused on electrodes, while electrolytes attract less attention. Indeed, the improvement of electrode performance is arguably correlated with the electrolyte optimization. In conventional lithium‐ion batteries (LIBs), ether‐based electrolytes are historically less practical owing to the insufficient passivation of both anodes and cathodes. As an important class of aprotic electrolytes, ethers have revived with the emerging lithium‐sulfur and lithium‐oxygen batteries in recent years, and are even booming in the wave of SIBs. Ether‐based electrolytes are unique to enabling these new battery chemistries in terms of producing stable ternary graphite intercalation compounds, modifying anode solid electrolyte interphases, reducing the solubility of intermediates, and decreasing polarization. Better still, ether‐based electrolytes are compatible with specific inorganic cathodes and could catalyze the assembly of full SIBs prototypes. This Research News article aims to summarize the recent critical reports on ether‐based electrolytes in sodium‐based batteries, to unveil the uniqueness of ether‐based electrolytes to advancing diverse electrode materials, and to shed light on the viability and challenges of ether‐based electrolytes in future sodium‐based battery chemistries.

Magnetic-field-induced orientation of fructose dehydrogenase on iron oxide nanoparticles for enhanced direct electron transfer

We present electrochemical evidence that magnetic interactions between the paramagnetic heme centers of fructose dehydrogenase subunit II and superparamagnetic iron oxide nanoparticles enable a suitable orientation of the enzyme molecule and enhance the rate of direct electron transfer. This enhancement of the rate of DET resulting from the appropriate orientation was examined with differential pulse voltammetry. The closer approach of the heme sites to the electrode results in a decreased fructose oxidation overpotential, a smaller Michaelis–Menten constant and an overall improvement in electrode performance in the presence of an external magnetic field.

One pot synthesis of (La,Sr)CoO3/(La,Sr)2CoO4 for IT-SOFCs cathodes

It is well known that hetero-interfaces in (La,Sr)CoO3/(La,Sr)2CoO4 (LSC113/214) are beneficial in catalyzing ORR for SOFC cathodes. This can be achieved by synthesizing the individual phases and mixing them together. In this study, so as to maximize the hetero interfaces, an alternative method was used in which one pot Pechini method was employed to synthesize a two-phase structure. LSC113/214 two phase structures from one precursors solution were successfully synthesized without the formation of any undesired third phase for the first time. It was found that a minimum temperature of 800 °C was necessary so as to obtain the fully crystallized dual phase powder. Two phase structures of molar fractions from 0.40 to 0.60 was targeted and were successfully obtained with some deviations. Impedance measurements were carried out on porous conventional symmetric cells fabricated with the synthesized dual phase powders between 400 and 700 °C. The dual phase powders had improved electrode performance as compared to single phase and physically mixed powders, but this was limited down to 500 °C.

Vertical graphene nanowalls coating of copper current collector for enhancing rate performance of graphite anode of Li ion battery: The merit of optimized interface architecture

Carbon coating has been attracting wide interests as optimum protection technology for Li ion batteries. Recently, carbon-coating has been considered as effective modification for copper/aluminum current collector. Although rate performance and lifetime of electrodes have been widely investigated, interfacial insight remains very superficial, hampering considerable improvement of electrode performance. Here we propose mechanistic models of double interfaces: one interface locates between Cu and active materials, and the other is referred to as solid electrolyte interphase (SEI) film coating on the current collector. Then vertical graphene nanowalls coated copper (VG) was prepared to reduce interfacial resistance of SEI film derived from an amorphous carbon coating layer. As a result, it exhibited a good rate performance with ∼190 mAh/g at 3 C, in contrast with ∼160 mAh/g for commercial carbon-coated copper (CC) and ∼90 mAh/g for traditional bare copper (BC).

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

Synthesis of Si-Induced MnO/Mn2SiO4@C Cuboids as High-Performance Anodes for Lithium-Ion Batteries.

The exploration of anode materials of lithium-ion batteries (LIBs) is still a great challenge because of their low electrical conductivity and poor durability. Transition-metal oxides are proposed as a potential alternative, even though their dimension and structure greatly affect their electrochemical properties. In this study, MnO/Mn2SiO4@C cuboids were prepared via the polymerization-pyrolysis process. Larger MnCO3 precursor particles embedded into a monolithic carbon framework and formed smaller nanoparticles owing to the inducing effect of Si element in phthalocyanino silicon (SiPc), giving MnO/Mn2SiO4@C cuboids. The micron-scaled cuboid composite can lead to higher tap density and greater electrical performance due to lower interparticle resistance. Therefore, the as-prepared MnO/Mn2SiO4@C electrode exhibits stable specific capacities of 585.9 and 423.9 mA h g-1 after 1000 discharge/charge cycles at 1 and 2 A g-1, respectively. Meanwhile, an excellent rate capacity of 246.3 mA h g-1 was achieved even at 30 A g-1. Additionally, this facile and economical strategy to improve electrode performance provides a commercially feasible way for the construction of high-performance LIBs.

Binder-free carbon fiber-based lithium-nickel-manganese-oxide composite cathode with improved electrochemical stability against high voltage: Effects of composition on electrode performance

A binder-free nickel-manganese-based cathode is developed using carbon fibers as current collector via a low-temperature sequential process including electrodeposition, hydrothermal reaction, and calcination. The physical and electrochemical properties of the fiber-type cathodes are found to depend significantly on the Mn:Ni molar ratio and calcination temperature. The typical cathode material exhibits flake-like morphology and is composed of spinel LiMn2O4 (LMO), LiNi0.5Mn1.5O4 (LNMO), and lithium-rich layered Li2MnO3 (LRL–LMO), forming an LMO/LNMO composite. During electrochemical evaluation under high voltage operation at 2.5–4.9 V, the fiber-type LMO/LNMO cathode shows discharge capacity of ∼140 mAh g−1 with enhanced discharge voltage and stable cycle performance with over 98% capacity retention after 50 cycles. The capacity of fiber-type LMO cathode decays from 120 mAh g−1 with cycling (2.5–4.9 V), and begins to fail at the 12th cycle. Hence, the spinel LNMO can function as a framework to stabilize the LMO/LNMO composite material against high voltage. Fiber-type LMO/LNMO cathode benefits from the integrated electrochemical characteristics of spinel LMO, LNMO, and LRL-LMO, leading to improved electrode performance.

Metaheuristics Computation-Assisted Multi-Element Doping Design in Electrode Materials for Rechargeable Batteries

Low-level doping of electrode materials is known to be a common and simple method that can be used to improve electrode performance. However, multi-element doping compositions have generally been confined to the empirical intuition of researchers via trial-and-error. Here we propose a more systematic approach to designing multi-element doping compositions for electrode materials via a non-dominated sorting genetic algorithm (NSGA-II)-based computation. LiMnPO4 was selected to demonstrate our strategy not only because of its promising features such as a high operating voltage, comparable capacity, and structural stability, but also because it is known for insufficient electrochemical performance with poor reversibility and rate capability. In this study, a NSGA-II was employed to determine the optimum multi-element doping composition at the Mn site of olivine-structured LiMnPO4 through six consecutive generations, each of which contained 25 dopant sets that finally led to the pinpointing of two potential candidates for a multi-element doped LiMnPO4. Both the doped LiMnPO4/C with selective compositions delivered a reversible capacity of about 150 mA h g˗1, and also exhibited a high rate capability at the 2C rate and a decent cyclability with 91% capacity retention during 30 cycles. This approach can be widely applied to explore local optimization of multi-element substitutions for high performance electrode materials, and further it would provide a broader view for investigating other functional materials with multiple compositions that could be locally optimized.

PDMS based multielectrode arrays for superior in-vitro retinal stimulation and recording.

Understanding of the neural response to electrical stimulation requires simultaneous recording from the various neurons of retina. Electrodes form the physical interface with the neural or retinal tissue. Successful retinal stimulation and recording demands conformal integration of these electrodes with the soft tissue to ensure establishment of proper electrical connection with the excitable tissue. Mechanical impedance of polydimethylsiloxane (PDMS) being compliant with that of retinal tissue, offers excellent potential as a substrate for metal electrodes. In this paper, Cr/Au micro electrodes with 200μm diameter were fabricated on rigid and flexible PDMS substrates under crack free condition. Spontaneous buckling of thin films over PDMS substrates improved electrode performance circumventing the fabrication issues faced over a buckled surface. Individual electrodes from the multielectrode arrays (MEAs) were examined with electrochemical impedance spectroscopy and cyclic voltammetry. Controlled fabrication process as described here generates buckles in the metal films leading to increased electrode surface area that increases the charge storage capacity and decreases the interface impedance of the metal electrodes. At 1kHz, impedance was reduced from 490 ± 27 kΩ to 246 ± 19 kΩ and charge storage capacity was increased from 0.40±0.87 mC/cm2 to 2.1±0.87 mC/cm2. Neural spikes recorded with PDMS based electrodes from isolated retina also contained less noise as indicated by signal to noise ratio analysis. The present study established that the use of PDMS as a substrate for MEAs can enhance the performance of any thin film metal electrodes without incorporation of any coating layers or nanomaterials.

Nanostructured SOFC Electrode Scaffolds Prepared via High Temperature in situ Carbon Templating of Hybrid Materials

High surface area solid oxide fuel cell (SOFC) electrode scaffold materials were prepared at traditional sintering temperatures by sintering hybrid inorganic-organic gels in argon. The prepared materials were yttria-stabilized zirconia (YSZ, 8 mol% Y2O3), gadolinia doped ceria (GDC, Ce0.8Gd0.2O3-δ) and strontium titanate (STO, SrTiO3). Gels were prepared via the citric acid (Pechini) method and the propylene oxide method. The gels were sintered between 1050oC and 1350oC in argon, creating an amorphous carbon template in situ, which preserved a ceramic scaffold nanostructure. The carbon template was removed upon heating in air to 700oC. Specific surface areas up to 83, 95, and 99 m2/g were achieved for YSZ, GDC, and STO, respectively. The carbon template concentration and resulting surface areas are tunable by modifying the gel formulations. Symmetric cathode cells were prepared with traditional and nanostructured YSZ. As expected, the gel-derived, nanostructured YSZ improved electrode performance.

Development of Binder Free Fiber-Type Li-Ni-Mn-O Cathode with High-Voltage Stability for Lithium-Ion Battery

Introduction With the advancement in electronic applications ranging from portable devices to large-scale ones, such as electric vehicles (EVs), hybrid electric vehicles (HEVs) and stationary energy storage systems for smart grid community, lithium ion batteries (LIBs) with high energy density and power density are seriously required. To meet the requirement, a battery design capable of affording more active material loading on an electrically conductive network without other additives is therefore preferred. Regarding the above issue, fiber-type electrodes, namely using carbon fibers as current collectors, have been developed to improve the battery performance. [1,2] Due to its binder-free electrode design, lithium ions can directly intercalate into and deintercalate from the host material based on an effective conductive connection, thus leading to improved electrochemical performances. To combine the advantages of carbon fiber and high-voltage active material, we develop a binder-free fiber-type cathode composed of nickel-manganese-based (LMO/LNMO) active material and evaluate its electrode performance. Experimental To prepare the fiber-type cathode, a sequential synthesis process, including electrodeposition, hydrothermal reaction and post-calcination treatment, was applied. In the first step, a carbon fiber tow aligned in the same orientation was partly immersed into a solution with nickel and manganese nitrate to carry out the electrodeposition for the formation of precursor. Secondly, the fiber precursor was rinsed, dried and then moved to an autoclave with a LiOH solution, where the hydrothermal treatment was performed under 100ºC for 20 h. After rinsing and drying, the fiber tow was calcined at 400ºC for 1 h and then a fiber-type LMO/LNMO cathode can be eventually obtained. To analyze the morphology and crystalline structure of the active material, SEM and XRD are respectively applied. For its electrochemical evaluation, a coin cell (CR2032) was used, in which the fiber-type cathode and lithium foil were used as working and counter/reference electrodes, respectively. In addition, the electrolyte was 1 M LiPF6 in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ration of 1:1. Results and Discussion Based on the SEM observation, the active materials, which are synthesized with different Mn/Ni ratio during the electrodeposition step, are found to differ in morphology. From the XRD analysis of the active materials, three crystalline phases of layered Li1.88[MnxNi(1-x)]1.12O3, spinel LiMn2O4 and LiNi0.5Mn1.5O4 crystalline phases can be identified. As for the electrochemical performance, the fiber-type LMO/LNMO cathode shows an initial discharge capacity of ca. 140 mAh/g with two plateaus at 4.7 and 4.0 V in its discharge profile. In addition, for the cycling test, the capacity retention at the 50th cycle is 98% and the coulomb efficiency for each cycle is above 90%, exhibiting a stable electrochemical behavior in the voltage range 2.5‒4.9 V. Therefore, it is suggested that the fiber-type cathode is beneficial for the reversible ion intercalation/deintercalation into and from the host structure of the active material LMO/LNMO, thus contributing to the improved electrode performance under high voltage operation.

Optimization of NiFe2O4/rGO composite electrode for lithium-ion batteries

The combination of carbon compositing and the proper choice of binders in one system offer an effective strategy for improving electrode performance for lithium ion batteries (LIBs). Here, we focus on the optimization of reduced graphene oxide content in NiFe2O4/reduced graphene oxide (abbreviated to NiFe2O4/rGO) composites and the proper choice of binders to enhance the cycling stability of the NiFe2O4 electrode. The NiFe2O4/rGO composites were fabricated by a hydrothermal-annealing method, in which the mean size of spinel NiFe2O4 nanoparticles was approximately 20nm. When tested as anode materials for LIBs, the NiFe2O4/rGO electrodes with carboxymethylcellulose (CMC) binder exhibited excellent lithium-storage performance including high reversible capacity, good cycling durability and high-rate capability. The capacity could be retained as high as 1105mAhg−1 at a current density of 100mAg−1 for over 50 cycles, even cycled at higher current density of 1000mAg−1, a capacity of 800mAhg−1can be obtained, whereas the electrode with the polyvinylidene fluoride (PVDF) binder suffered from rapid capacity decay under the same test conditions. As a result, the NiFe2O4/rGO composites with CMC binder electrode in this work are promising as anodes for high-performance LIBs, resulting from the synergistic effect of optimal graphene content and proper choice of binder.

Improvement of Na Ion Electrode Activity of Metal Oxide via Composite Formation with Metal Sulfide.

The composite formation with a conductive metal sulfide domain can provide an effective methodology to improve the Na-ion electrode functionality of metal oxide. The heat treatment of TiO2(B) under CS2 flow yields an intimately coupled TiO2(B)-TiS2 nanocomposite with intervened TiS2 domain, since the reaction between metal oxide and CS2 leads to the formation of metal sulfide and CO2. The negligible change in lattice parameters and significant enhancement of visible light absorption upon the reaction with CS2 underscore the formation of conductive metal sulfide domains. The resulting TiO2(B)-TiS2 nanocomposites deliver greater discharge capacities with better rate characteristics for electrochemical sodiation-desodiation process than does the pristine TiO2(B). The 23Na magic angle spinning nuclear magnetic resonance analysis clearly demonstrates that the electrode activities of the present nanocomposites rely on the capacitive storage of Na+ ions, and the TiS2 domains in TiO2(B)-TiS2 nanocomposites play a role as mediators for Na+ ions to and from TiO2(B) domains. According to the electrochemical impedance spectroscopy, the reaction with CS2 leads to the significant enhancement of charge transfer kinetics, which is responsible for the accompanying improvement in electrode performance. The present study provides clear evidence for the usefulness in composite formation between the semiconducting metal oxide and metal sulfide in exploring new efficient NIB electrode materials.

Is There a Benefit in Employing Graded Electrodes for Lithium-Ion Batteries?

Literature reports show both benefits and negligible impact when including graded electrodes in battery design, depending upon the exact model and conditions used. In this paper, we use two different optimization approaches for a secondary current distribution porous electrode model with nonlinear kinetics to confirm that computed solutions are correct. We use these confirmed optimal solutions to probe several ways that graded porosity can improve electrode performance. Single objective optimization such as reducing the overall electrode resistance using a graded electrode design provides a modest 4–6% reduction in resistance for typical lithium-ion battery parameters. Multiple objective optimization—for example, simultaneously considering electrode resistance and the overpotential variance and eventually the overpotential average as well—shows that multilayer designs open up a much richer feasible design space for achieving multiple goals. The ultimate answer to the value of graded electrodes will be the techno-economic analysis that links the benefits of an expanded optimal design space to the detrimental costs associated with manufacturing multilayer electrodes. An open-access executable code that can give optimal porosity distribution of any specified chemistry and detailed explanation of the two approaches can be found on the Subramanian group's website.

Resolving Electrode Morphology's Impact on Platinum Group Metal-Free Cathode Performance Using Nano-CT of 3D Hierarchical Pore and Ionomer Distribution.

This article reports on the characterization of polymer electrolyte fuel cell (PEFC) cathodes featuring a platinum group metal-free (PGM-free) catalyst using nanoscale resolution X-ray computed tomography (nano-CT) and morphological analysis. PGM-free PEFC cathodes have gained significant interest in the past decade since they have the potential to dramatically reduce PEFC costs by eliminating the large platinum (Pt) raw material cost. However, several challenges remain before they are commercially viable. Since these catalysts have lower volumetric activity, the PGM-free cathodes are thicker and subject to increased gas and proton transport resistances that reduce the performance. To better understand the efficacy of the catalyst and improve electrode performance, a detailed understanding the correlation between electrode fabrication, morphology, and performance is crucial. In this work, the pore/solid structure and the ionomer distribution was resolved in three dimensions (3D) using nano-CT for three PGM-free electrodes of varying Nafion loading. The associated transport properties were evaluated from pore/particle-scale simulations within the nano-CT-imaged structure. These characterizations are then used to elucidate the microstructural origins of the dramatic changes in fuel cell performance with varying Nafion ionomer loading. We show that this is primarily a result of distinct changes in ionomer's spatial distribution. The significant impact of electrode morphology on performance highlights the importance of PGM-free electrode development in concert with efforts to improve catalyst activity and durability.